Mesozoic marine reptiles and modern marine mammals are often considered ecological analogs, but the extent of their similarity is largely unknown. Particularly important is the presence/absence of deep-diving suction feeders among Mesozoic marine reptiles because this would indicate the establishment of mesopelagic cephalopod and fish communities in the Mesozoic. A recent study suggested that diverse suction feeders, resembling the extant beaked whales, evolved among ichthyosaurs in the Triassic. However, this hypothesis has not been tested quantitatively. We examined four osteological features of jawed vertebrates that are closely linked to the mechanism of suction feeding, namely hyoid corpus ossification/calcification, hyobranchial apparatus robustness, mandibular bluntness, and mandibular pressure concentration index. Measurements were taken from 18 species of Triassic and Early Jurassic ichthyosaurs, including the presumed suction feeders. Statistical comparisons with extant sharks and marine mammals of known diets suggest that ichthyosaurian hyobranchial bones are significantly more slender than in suction-feeding sharks or cetaceans but similar to those of ram-feeding sharks. Most importantly, an ossified hyoid corpus to which hyoid retractor muscles attach is unknown in all but one ichthyosaur, whereas a strong integration of the ossified corpus and cornua of the hyobranchial apparatus has been identified in the literature as an important feature of suction feeders. Also, ichthyosaurian mandibles do not narrow rapidly to allow high suction pressure concentration within the oral cavity, unlike in beaked whales or sperm whales. In conclusion, it is most likely that Triassic and Early Jurassic ichthyosaurs were ‘ram-feeders’, without any beaked-whale-like suction feeder among them. When combined with the inferred inability for dim-light vision in relevant Triassic ichthyosaurs, the fossil record of ichthyosaurs does not suggest the establishment of modern-style mesopelagic animal communities in the Triassic. This new interpretation matches the fossil record of coleoids, which indicates the absence of soft-bodied deepwater species in the Triassic. Many large predators in the modern marine ecosystem are mammals. A similar role was probably played by marine reptiles in the Mesozoic, until their last members became extinct 65.5 million years ago during the end-Cretaceous mass extinction Ichthyopterygia must be considered when comparing modern marine mammals with Mesozoic marine reptiles because they were the Mesozoic analog of cetaceans. Being derived from four-legged reptiles, they evolved a fish-shaped body profile about 200 million years before cetaceans. Also, their fossil record is more complete than that of other marine reptile groups Shonisaurus sikanniensis, was a suction feeder analogous to beaked whales. If true, the feeding mode interpretation would have many ecological implications. Most importantly, it raises a question of whether a suitable environment for beaked-whale-type predators, including their prey community in the meso-/bathypelagic zones, was available in the Triassic. This question has remained unaddressed until now. Prior to these two studies, suggestions of suction feeding among Mesozoic marine reptiles were made for various stem sauropterygians including the placodont HenodusDinocephalosaurusHenodus is known only from the Upper Triassic of Germany in a lagoonal setting, whereas Dinocephalosaurus is a coastal species that is known only from the Middle Triassic of China. The other species are also coastal dwellers , Eurhinosaurus longirostris , Guanlingsaurus liangae , Guizhouichthyosaurus tangae , Hauffiopteryx typicus (SMNS 81962), Ichthyosaurus communis , Leptonectes moorei (NHMUK R14370), L. tenuirostris (NHMUK 24300), Mixosaurus cornalianus , Qianichthyosaurus zhoui , Shastasaurus alexandrae , Shonisaurus sikanniensis , Stenopterygius quadriscussus (SMNS 50165), St. triscissus (SMNS 55074), Suevoleviathan integer (SMNS 4652), Temnodontosaurus platyodon , Te. trigonodon (SMNS 50000), and Toretocnemus zitteli (UCMP 8099). All but one specimen were in the existing collection of each institution and studied on-site in respective collections with permission. AGM CH-628-22 was excavated by a joint team of AGM, Peking University, University of California, Davis, and Università degli studi di Milano, with permits from the Ministry of Land and Resources of the People's Republic of China. The current study did not involve any purchase, loan, or donation of a specimen. Of the 18 specimens, mandibular width could reasonably be estimated in 15, and mandibular length in 12 specimens  and shoulder girdle posteriorly (M. sternohyoideus and M. omohyoideus), as in many extant reptiles sensu stricto is applied only to those aquatic gnathostomes that draw prey closer by suction prior to capture. In contrast, those predators that capture their prey mainly by moving their body toward prey are called ‘ram feeders’ Despite the prevalence of suction feeding among aquatic vertebrates Suction is usually used in combination with various degrees of ram feeding sensu stricto as defined above, as well as feeding where prey is captured by ram, followed by intraoral transpiration of prey for swallowing with help from subambient pressure induced by tongue movements Suction feeding in the literature on whales has been defined less strictly: it variously contains suction feeding Kogia sima and K. breviceps) and bottlenose dolphin (Tursiops truncatus) found that Kogia was a suction feeder and Tursiops a ‘ram feeder’ based on RSI Tursiops . Also, an analysis of the feeding kinematics of three species of cetaceans, namely the beluga whale (Delphinapterus leucas), Pacific white-sided dolphin (Lagenorhynchus obliquidens), and long-finned pilot whale  found that all were capable of drawing prey toward them through suction by about 2.8 to 4.1 cm, whereas these cetaceans also used various degrees of ‘ram feeding’ in combination with suction Delphinapterus had feeding sequences that qualified as suction feeding, although many of the feeding sequences of the same species represented ‘ram feeding’.Recent kinematic studies are shedding light on the status of cetacean suction feeding in comparison to that in other major vertebrate groups. A study of the feeding kinematics of the pygmy and dwarf sperm whales , whitespotted bamboo shark (Chiloscyllium plagiosum), and the planktivorous whale shark (Rhincodon typus) Tasmacetus), mysticetes, and in Monodon, whose suction feeding has not been directly observed . The two cetacean genera for which strict suction feeding has directly been established through kinematic studies (Kogia and some feeding sequences of Delphinapterus) have multiple pairs of teeth at least in the lower jaws. Furthermore, filter feeding mysticetes also exhibit completely reduced dentition; however only one mysticete, the gray whale Eschrichtius robustus, is a reported suction feeder Tooth reduction is another feature that has been discussed in the literature on whales Shonisaurus sikanniensis, which seems to have a small second pair of bones Hauffiopteryx from the Toarcian (Lower Jurassic), in which a bone exists in front of the pair of CB1  but not between those of ‘ram-feeding’ sharks and ichthyosaurs . ‘Ram-feeding’ cetaceans have more robust suspensory hyobranchial elements than do ‘ram-feeding’ sharks or ichthyosaurs , sharks , and cetaceans ; Fig. 5AEurhinosaurus , but not between those of ‘ram-feeding’ marine mammals and ichthyosaurs .The MPCI of ichthyosaurs has a small variation, but it fits in the range of ‘ram-feeding’ marine mammals, with one exception of nosaurus . This obQianichthyosaurus and Guanlingsaurus, have mandibular bluntness of about 0.42 or lower. These low bluntness values are found only in some beaked whales among suction-feeding odontocetes, whereas all others have much higher bluntness  lacked an ossified hyoid corpus, whereas robust integration between ossified hyoid corpus and cornua has been identified as essential for amniote suction feeders as pointed out earlier. Even in H. typicus, such a robust integration is questionable , whales , and sharks   , and 5. Lack of variation in the slenderness of the CB1 in ichthyosaurs is noteworthy. The ceratohyals of sharks show a broad range of slenderness depending on their prey capture ecology . The conEurhinosaurus that is discussed later. Second, ichthyosaurian mandibles are much more elongated than those of odontocete cetaceans on average .A previous study Guanlingsaurus. Because of this posterior location, ichthyosaurs are destined to have more elongated mandibles than cetaceans even when the snout lengths are similar. Also, this design leads to posterior location of the coronoid region in ichthyosaurs, which is usually found at the level of the occipital condyle. Thus, the region is too far away from the snout to function as the gape-shortening apparatus–note that the precoronoid crest of beaked whales is located at the posterior part of the snout. This apparent constraint from the jaw-joint location is not applicable to basal Ichthyopterygia, so it may be possible to find a suction feeder among basal members of the clade in the future.A part of the reason why suction feeding did not evolve in ichthyosaurs may be the basic skull design of the Ichthyosauria, which is a clade within the Ichthyopterygia Eurhinosaurus merits a separate discussion because of its uniquely low MPCI value. There is an anatomical reason why this taxon exhibits an anomalous value in this index. The genus is known for extreme shortening of the mandible, leading to an extensive overbite that is analogous to that seen in swordfish Eurhinosaurus is slender as in other ichthyosaurs and that its hyoid corpus is unossified, it lacked the ‘equipment’ to generate suction. Therefore, it was most likely a ‘ram feeder’ as with other ichthyosaurs.Delphinapterus, which use suction feeding during shallower benthic foraging Suction feeders among extant air-breathing marine vertebrates have a limited range of feeding ecology. This is partly because suction is only effective over a short distance Evidence for the presence of deep-water coleoid communities in the Triassic is scant, although its possibility cannot be completely excluded. The time period predates the common ancestor of extant decabrachian coleoids in the Late Jurassic or Early Cretaceous Hypothetically, it may be possible that some slow moving, soft-bodied coleoids, comparable to today's deepwater forms, inhabited shallow waters in the Triassic and could have served as potential prey for suction feeding marine reptiles. However, such a form has not been recognized to date, despite the fact that the fossil record of shallow water cephalopods is much richer than that of their deepwater counterparts. Absence of such slow moving forms in shallow water may be reasonable because the slowness of extant deepwater coleoids has been linked to the relaxed visually mediated predator/prey interactions in light-limited environments Another question is whether Triassic ichthyosaurs were capable of deep diving. Deep diving ability has been suggested for ichthyosaurs in the past but only for more derived ichthyosaurs in the Jurassic Hypothetically, it may be possible that some slow-moving, soft-bodied coleoids, comparable to today's deepwater forms, inhabited shallow waters in the Triassic, providing a viable prey source for suction feeders. However, such a form has not been recognized to date, even though shallow water fossils are far more abundant than their deepwater counterparts. Absence of such shallow water forms may be reasonable because the slowness of extant deepwater coleoids has been linked to the paucity of nutrients in deep sea layers Temnodontosaurus and its possible predators, whereas deep diving was suggested for Ophthalmosaurus and possibly other thunnosaurs that are more derived than TemnodontosaurusTemnodontosaurus, when it first appeared in the Hettangian (earliest Jurassic), was by far the largest of the coeval marine reptiles despite the claim of Rhomaleosaurus that Temnodontosaurus but was much smaller in gape size than the latter, is known from the Toarcian A recent study suggested that ichthyosaurian eyes evolved in response to large predators rather than deep diving Ophthalmosaurus, may predate that of the common ancestors of the Decabrachia Ophthalmosaurus included vertical migrants Ophthalmosaurus, namely Cylindrotheuthis, is thought to have been capable of withstanding shallow mesopelagic water pressure Vampyroteuthis infernalis, is a mesopelagic inhabitant.The appearance of deep-diving ichthyosaurs, such as Ophthalmosaurus, the postulated deep diving ichthyosaur, emerged. Hyobranchial morphology of marine reptiles has been largely understudied, despite its importance in inferring feeding ecology of these animals. It will be important to study it further, to understand the early evolution of modern marine ecosystems in the Mesozoic. Such a study is underway.Triassic and Early Jurassic ichthyosaurs were most likely ‘ram-feeders’ based on functional inference from hyobranchial and mandibular morphology. Together with the inferred lack of deep-diving ability and dim-light vision in suspected suction feeders among Triassic ichthyosaurs, it is unlikely that these ichthyosaurs were meso-/bathypelagic feeders resembling beaked whales. Therefore, the evolutionary history of ichthyosaurs does not necessitate the formation of deepwater soft-bodied coleoid and fish communities in the Triassic. The coleoid fossil record also suggests the lack of deepwater coleoids with soft bodies in the Triassic. Such communities may have been available by the time


Although mast cells are best known for their role in mediating allergic diseases, recent studies have highlighted the important role that these cells play in the protection against infection with a variety of organisms.2 and leukotriene C4 (LTC4). Finally, over the course of hours, the transcriptional up-regulation of cytokines and chemokines, including TNF-α and interleukin-4, can be observed. Importantly, each of these responses may occur alone or in combination depending on the stimulus. Because of their location, their plasticity, and the various mediators they produce, mast cells are important immune effector and modulatory cells that help link innate and adaptive immunity in the fight against pathogens.Mast cells are leukocytes that are derived from haematopoietic progenitor cells. They circulate in the blood in an immature form before migrating to vascularised tissues, where they undergo final differentiation and maturation with the help of stem-cell factor and other cytokines secreted by endothelial cells and fibroblasts. Mast cells are found in most tissues of the body, particularly in locations that are in close contact with the external environment, such as skin, airways, and intestines. They are, therefore, ideally placed to participate in the early recognition of pathogens. Activation of mast cells results in the release of a variety of soluble factors. Within seconds of stimulation, mast cells can undergo degranulation, rapidly releasing pre-formed mediators present within cytoplasmic granules, including histamine, the proteases tryptase and chymase, and pre-formed tumour necrosis factor-alpha  receptor FcεRI , including the Toll-like receptors (TLRs), Nod-like receptors, C-type lectins such as Dectin-1, and the glycosylphosphatidylinositol-anchored protein CD48. Selective engagement of PRRs is also an important mechanism in governing the type of mast cell response. For example, while peptidoglycan stimulation of bone marrow-derived mast cells via TLR2 leads to both cytokine release and degranulation, lipopolysaccharide (LPS) stimulation through TLR4 results in cytokine release alone Mast cells are well placed to serve as immune sentinel cells to both respond directly to pathogens and send signals to other tissues to modulate both innate and adaptive immune responses .Mast cells can participate in direct killing of organisms by phagocytosis and reactive oxygen species production Mast cells can modulate host innate immune responses through the release of granular and secreted mediators (reviewed in + T cells. In addition, mast cell products can enhance the maturation of immature DCs, and up-regulate antigen presentation and the expression of co-stimulatory molecules. Interestingly, while mast cell–derived histamine was observed to favour the polarization of naive T cells towards a Th2 phenotype by reducing DC production of IL-12 and increasing IL-10 secretion in response to LPS Mast cell products have also been implicated in the regulation of adaptive immune responses (reviewed in Importantly, while mast cell responses may act to increase host defence locally at the site of infection, it is also possible that mast cell–mediated enhancement of inflammation could induce damage of host tissues and worsen outcome during some infections. In support of this hypothesis, a recent study observed that while intraperitoneal mast cells were found to be protective in a model of experimental polymicrobial intra-abdominal sepsis, extraperitoneal mast cells in the same system produced pro-inflammatory IL-6, which was associated with increased mortality Recent studies have demonstrated that mast cells play a protective role against many pathogens. Significant advances have been made using mast cell–deficient mice, although the specific mechanisms by which mast cells inhibit most pathogens remain relatively undefined.Trichinella spiralis and Strongyloides infection have found that mast cells mediate gut expulsion of nematodes and limit the parasite tissue burden. Moreover, mast cell–deficient mice develop increased parasite burden and larger lesions during infection with Leishmania major in association with a reduction in inflammation and IL-12 production at the site of infection. Finally, a critical role for mast cell–derived TNF in limiting parasitaemia in a murine model of malaria has been demonstrated by reconstituting mast cell–deficient mice with mast cells derived from wild-type and TNF-deficient mice The first evidence supporting the protective role of mast cells against pathogens came from studies of parasitic infections including helminths, nematodes, and protozoa (reviewed in Klebsiella pneumoniaeMycoplasma pneumoniae; Pseudomonas aeruginosa and GAS skin infection; Haemophilus influenzae otitis media; and E. coli peritoneal and urinary infections, as well as polymicrobial intra-abdominal sepsis More recently, the contributions of mast cells to antibacterial immunity have also been established, particularly with respect to gram-negative bacteria (reviewed in + T cells to the site of infection that was absent in mast cell–deficient mice Evidence that mast cells mediate antiviral immunity is more limited. Mast cell activation by synthetic viral dsRNA led to the recruitment of CD84 in response to zymosan, a Saccharomyces cerevisiae cell wall preparation Aspergillus fumigatus hyphae induced degranulation of mast cells via an IgE-independent mechanism The role of mast cells in the pathogenesis of fungal infection is even less well understood. In vitro studies have found that mast cells released LTCIn allergic diseases, mast cells are seen as harmful triggers of chronic inflammation, and mast cell stabilizing agents and inhibitors are frequently used as treatment. However, emerging data suggest that mast cells are crucial in protecting the host from many infections. Although substantial effort has been directed towards defining and reversing the effects of corticosteroids and other immunosuppressive agents on neutrophil, macrophage, and dendritic cell function, similar studies are lacking for mast cells. Failure of mast cells to function as immune sentinels early in infection may play an important role in mediating susceptibility to infection in patients receiving corticosteroids or other mast cell–suppressing agents. Future studies will be required to understand the effects of these agents on specific aspects of mast cell function and subsequent susceptibility to specific infections. New strategies focused on enhancing the beneficial roles of mast cells may facilitate the early response to pathogens when the microbial burden is low.


Cancer cells, unlike normal cells, show selective dependency on certain nutrient substrates. These cells exhibit an addiction to glucose or glutamine, and a lack of flexibility in using a full spectrum of nutrient substrates. This dependency varies widely among different cancer cell types and depends on specific mutations in oncogenes and tumor suppressors, the cellular context in which these mutations occur and epigenetic factors. These wide variations in metabolic states have implications for cancer cell responses to therapy.To date, methods to analyze cellular substrate metabolism have required either the use of radioactive or stable isotope labeled substrate and/or large quantity of cells, may be labor intensive and have low throughput. Stable isotope labeling coupled with Mass Spectrum and NMR analysis has provided highly detailed information about substrate metabolism, but is relatively inaccessible techniques for a majority of researchers and they require special skills and expertise. We have devised several alternative easier and more rapid experimental methods to analyze substrate flux and metabolic states of cancer cells in a microplate. They have allowed us to analyze substrate flux including glucose, glutamine, and fatty acids, and to interrogate their bioenergetic machineries, glyclolysis and mitochondrial oxidative phosphorylation. These methods measure oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) of living cells, and can determine their dynamic responses to pathway perturbations in real-time allowing substrate flux analysis. Essentially, a large number of cell types (lines) can be analyzed using only small quantities of materials and over a short time periods (1-3 hrs) in a microplate using the XF Extracelllar Flux analyzer.In proof-of-principle experiments, we investigated substrate flux and the metabolic state of a syngenic pair of human glioblastoma cells, SF188s (slowly dividing) and SF188f (fast dividing) cells. We found that SF188f cells exhibited a substrate shift, away from glycolysis toward glutamine and fatty acid oxidation, in contrast to SF188s cells. The mitochondrial respiratory capacity and basal respiration of SF188f cells were markedly increased, but the ATP production-coupled respiration was greatly reduced. Further, the leaked respiration was also increased compared with the SF188s cells. That is, a large fraction of SF188f cells’ mitochondrial respiration was not devoted to ATP production. We suggest that cancer cells can decouple the TCA cycle from oxidative phosphorylation on an “on demand” basis. This decoupling provides a mechanism by which cancer cells can overcome the metabolic control imposed on the TCA cycle by oxidative phosphorylation, enabling them to meet their extra demand for building block synthesis in addition to energy. This also provides an explanation for the excessive rate of oxygen consumption observed in SF188f cells. In these studies, we also demonstrated that the metabolic state of SF188s and SF188f cells, e.g., glycolysis relative to glutamine oxidation, correlates with their selective susceptibility to inhibitors of glycolysis, 2-deoxyglucose, and glutamine oxidation, aminooxyacetate respectively. Therefore, these methods provide valuable tools for rapid analysis of substrate flux and bioeneregetic machineries in cancer or non-cancer cells. They can also enhance understanding the genetic and epigenetic regulation of cancer metabolism in cancer development.


Compromised pregnancies such as those associated with gestational diabetes mellitus, intrauterine growth retardation, preeclampsia, maternal undernutrition, and maternal stress may negatively affect fetal development. Such pregnancies may induce oxidative stress to the fetus and alter fetal development through the epigenetic process that may affect development at a later stage. Melatonin is an oxidant scavenger that reverses oxidative stress during the prenatal period. Moreover, the role of melatonin in epigenetic modifications in the field of developmental programming has been studied extensively. Here, we describe the physiological function of melatonin in pregnancy and discuss the roles of melatonin in fetal programming in compromised pregnancies, focusing on its involvement in redox and epigenetic mechanisms. AGEAdvanced glycation end productCREBcAMP response element-binding proteinDNMT1DNA (cytosine-5)-methyltransferase 1GDMgestational diabetis mellitusGRglucocorticoid receptorIUGRintrauterine growth retardationMeCP2methyl CpG binding protein 2mGlumetabotropic glutamate receptorMTmelatonin receptorNF-E2-related factornuclear factor erythroid 2-related factor 2NF-κBnuclear factor kappa-light-chain-enhancer of activated B cellsPdx-1pancreatic and duodenal homeobox 1Per1period circadian protein homolog 1PPARperoxisome proliferator-activated receptorROSreactive oxygen speciesREMrapid eye movementSCNsuprachiasmatic nucleusN-acetyl-5-methoxytryptamine), an endogenously produced indoleamine of the pineal gland, is an antioxidant, free radical scavenger, anti-inflammatory molecule, and is produced and secreted in a circadian fashion [et al. in the pineal gland [Melatonin  of the hypothalamus . An indiN-acetyltransferase is considered the rate-limiting enzyme. The half-life of melatonin in serum varies between less than 30 min and 60 min. Seventy percent of serum melatonin is bound to albumin, and the remaining 30% diffuses in the surrounding tissues [Melatonin is synthesized primarily in the pineal gland from the amino acid precursor tryptophan. At least four enzymes are involved in melatonin biosynthesis, among which serotonin  tissues . It is m tissues . Melaton tissues ,24.Two types of membrane-associated melatonin receptors have been cloned in mammals ; these rMelatonin has pleiotropic bioactivities and is involved in the regulation of the circadian rhythm, reproductive physiology, anti-inflammation, sleep promotion, and body temperature regulation ,3. In ad2O2), singlet oxygen (1O2), hypochlorous acid (HClO), peroxynitrite anion (ONOO−), and/or peroxynitrous acid (ONOOH) [Oxidative stress is defined as an imbalance between prooxidant and antioxidant forces leading to an overall prooxidant insult. Melatonin and its byproducts are capable of scavenging both ROS and reactive nitrogen species (RNS), including the hydroxyl radical (•OH), hydrogen peroxide (H (ONOOH) . Melaton (ONOOH) ,27.Melatonin also acts as a potent endogenous antioxidant by scavenging free radicals and upregulating antioxidant pathways. The activity and expression of antioxidant enzymes such as superoxide dismutase, glutathione, catalase, glutathione peroxidase, and glutathione reductase are increased by melatonin, which supports data concerning its indirect antioxidant action . NotablyN1-acetyl-N2-formyl-5-methoxykynuramine and N1-acetyl-5-methoxykynuramine [Melatonin is a much more potent antioxidant than many traditionally used antioxidants and has two unique features. First, melatonin does not undergo redox cycling and once oxidized, cannot be regenerated to its reduced form . Second,nuramine . These mnuramine .Mitochondria produce high amounts of ROS during their biogenesis. Mitochondria, which are characterized by a double membrane, contain several hundreds of proteins and 2–10 copies of mitochondrial DNA in the matrix enclosed by the mitochondrial inner membrane. Mitochondria play a critical role in generating energy in most eukaryotic cells. In this context, melatonin can stimulate mitochondrial biogenesis and increase the efficiency of the electron transport chain, thereby limiting electron leakage and free radical generation. In addition, the antioxidant effect of melatonin and its ability to increase mitochondrial glutathione levels is of great importance for mitochondrial physiology .Nrf2 gene and suppresses that of NF-κB through epigenetic processes [Epigenetic modifications refer to stable and heritable gene expression changes that are not mediated by DNA sequence alterations. Unlike genetic information, which is stable, epigenetic modifications occur in response to early environmental signals and instantly respond to transient stimuli, resulting in modified gene expression patterns and phenotypes later in life. Melatonin may regulate antioxidant gene and enzyme expression through epigenetic mechanisms . Melatonrocesses . In addirocesses .et al. had found the association of melatonin and spontaneous abortion which was presumed to be due to melatonin’s role in diminishing uterine contractions by decreasing the production of prostaglandins and in prevention of the immunologic rejection of trophoblast by stimulating the progesterone production [et al. showed that alleviation of the embryo death might be achieved by administration of melatonin in mice [Melatonin plays an important role in pregnancy and parturition ,19. Mateoduction . Further in mice . Moreove in mice .In rodents, melatonin-binding sites are observed in the fetal pituitary gland by gestational day 15 and in the SCN by gestational day 18 ,35. MelaPredicting the upcoming seasons to adapt physiological and behavioral functions is important for the survival of individuals and the perpetuity of species. Information about day length and circadian phase is transferred to the fetus prenatally . MaternaDuring pregnancy, circadian variations in melatonin levels in the maternal circulation have been reported in sheep ,42 and ret al. reported that maternal melatonin decreased cortisol production in the fetal adrenal gland of the capuchin monkey [Torres-Farfan n monkey . In a sun monkey . The lacn monkey . In addin monkey . Taken t−1·day−1) from gestational days 6–19 did not adversely affect the development of rat pups [et al., high-dose melatonin had no apparent effect on fetal or maternal well-being, and it did not affect myometrial activity during late gestation [There is general agreement that melatonin therapy has a remarkably benign safety profile. Melatonin has shown no obvious detrimental effects on mouse and rat embryo development in toxicity tests ,50. In prat pups . In a stestation . Howeverestation .The plasticity of the developmental process allows the organism to respond to the surrounding environment. Programming is defined as the induction, silencing, or restriction of the development of somatic structures or a physiological system, which results in long-term effects. Human epidemiological studies have provided convincing support for the concept of developmental programming by showing a strong association between low birth weight and an increased risk of adverse outcomes in adulthood, such as coronary heart disease, stroke, high blood pressure, and type 2 diabetes .Perturbations of the developmental adaptation process can also have adverse consequences on organ function and disease risk later in life. The placenta plays a critical role in fetal programming. Maternal complications of pregnancy such as gestational diabetes mellitus (GDM), intrauterine growth restriction (IUGR), preeclampsia, maternal undernutrition, and maternal stress are associated with an increased risk of brain dysfunction, cardiovascular disease, and metabolic syndrome in the offspring through fetal programming mechanisms –60. It iSeveral mechanisms contribute to fetal programming. In this review, we discuss two important mechanisms underlying fetal programming, redox and epigenetic alterations –60. DetaROS are produced within the follicle; these play a physiological role in the process of ovulation . PregnanExtensive increases in oxidative stress have been observed in association with various conditions, including smoking, diabetes, hypertension, and hypoxia, which are not uncommon in pregnant women. These conditions can cause increased oxidative stress either in the mother or the fetus, which may result in the programming of diseases in the offspring at a later stage ,66.Epigenetic modifications refer to stable and heritable gene expression changes without alterations of the DNA sequence. The mechanisms of epigenetic change include posttranslational histone modifications and DNA methylation, imprinting, and small-RNA mediated controls. Epigenetic modifications perceive the effect of early environmental signals and play a role in programming.in utero might produce long-term consequences through the epigenetic mechanism [In the first stages of placental vascular development, endothelial specialization and blood vessel formation are controlled by epigenetic mechanisms . Moreoveechanism .Increased levels of ROS are important in epigenetic modification of DNA or chromatin and influences gene expression and cell differentiation ,73. The Human follicular fluid contains high concentrations of melatonin . MelatonShift work is common during pregnancy and may disrupt the maternal melatonin rhythm. Epidemiological studies in women show that shift work increases the risk of premature delivery and the incidence of low birth weight ,78, whicPer1 and Npas2 are caused by increased occupancy of H3K14 at the histone acetylase sites in the Npas2 promoter; these alterations suggested that melatonin plays a role in epigenetic programming [Exposure of dams to a high-fat diet has been shown to increase fetal liver lipid accumulation and to increase the expression of genes involved in the liver gluconeogenic pathway ,81. Altegramming ,81.et al.[et al.[Nrf2 gene induction by acetylation and recruiting the basal transcriptional machinery to the promoter region of Nrf2-related genes. Therefore, melatonin may play a role in epigenetic modifications in fetal programming through the regulation of antioxidant enzymes [Melatonin has been suggested to regulate the expression of antioxidant genes and enzymes through epigenetic mechanisms . Sun et et al. showed tl.[et al. demonstr enzymes .Pregnancy is a physiological state accompanied by a high metabolic demand and elevated requirements for oxygen and hence prone to oxidative stress-induced organ damage. Furthermore, the placenta is a major source of oxidative stress because it is rich in polyunsaturated fatty acids. As gestation progresses, there is a gradual favoring of antioxidant activity over oxidant activity. In parallel, maternal plasma melatonin levels increase during pregnancy, reaching a maximum at term.Fetal organs, especially the SCN, are vulnerable to environmental insults via the mother ,46,84. IGDM is a syndrome characterized by glucose intolerance leading to maternal hyperglycemia, endothelial dysfunction, and abnormal regulation of vascular tone . Dependiet al. reported that hyperglycemia may result in the non-enzymatic glycation of proteins called advanced glycation end products (AGEs), which can interfere with signal transduction and thus change the soluble levels of cytokines, hormones, and free radicals, and these proteins can alter the function of the glycated proteins [Hyperglycemia increases the activity of the polyol pathway, which decreases antioxidant defenses and increases oxidative stress . Oxidatiproteins .MTNR1B gene, a functional melatonin receptor, have been reported to be associated with gestational glucose intolerance in the Chinese population [In addition to its function as a ROS scavenger involving the amelioration of oxidative damage and the proinflammatory state present in high-risk pregnancies, recent studies have shown that melatonin also plays an important role in the regulation of body weight and adiposity, which could be related to its involvement in the control of the circadian rhythm ,99. Morepulation . TherefoPdx-1 gene and a subsequent blunting of its transcription, and the development of diabetes during adulthood, explaining an epigenetic mechanism for fetal programming. Recently, Miehle et al. conducted a human study to find an association between the percentage of DNA methylation of the leptin gene in the placenta and glycemia using the 2 h post-oral glucose tolerance test at 24–28 weeks of pregnancy [GDM may predispose offspring to many disorders such as obesity, type 2 diabetes mellitus, and cardiorenal metabolic syndrome. The underlying pathophysiology may include epigenetic modifications and alterations in the balance between glucose, insulin, and other regulatory hormones involved in glucose homeostasis during intrauterine and perinatal life . In fetaregnancy . In the regnancy . HoweverIUGR is defined as a condition in which the fetus has an estimated body weight and/or length below the 10th percentile for gestational age . IUGR afet al. showed that melatonin might negate the consequences of IUGR in the presence of specific abnormalities in umbilical blood flow as long as sufficient uterine blood perfusion is maintained during pregnancy [Women diagnosed with IUGR show increased values of the indices of oxidative stress in the serum, suggesting the presence of oxidative stress ,109. Durregnancy . TherefoIUGR has been shown to induce epigenetic modification of selected genes in the placenta , as wellPreeclampsia is a multisystem disorder that is unique to human pregnancy, occurring in 5%–10% of pregnancies and is a leading cause of maternal and neonatal mortality and morbidity . There iIn women with preeclampsia, lipid peroxide levels in maternal blood and placental tissue are significantly increased. In addition, total antioxidant activities are decreased. Hence, preeclampsia might be considered as an oxidative stress disorder during pregnancy . Endogenet al. reported increased concentrations of unmethylated maspin concentrations in the plasma of women with preeclampsia compared with that of healthy pregnant controls [Maternal adversities leading to dysregulation of placental development originated from preimplantation affecting the course of pregnancy were shown in both animal and human studies to alter the epigenetic process  and result in preeclampsia and dismal fetal outcomes ,69. A recontrols . HoweverAdequate nutrition during gestation is essential for fetal growth and development. Maternal undernutrition can significantly affect fetal growth and intrauterine programming. The placenta may act as a nutrient sensor, modifying nutrient and hormone availability to feto-placental tissues in relation to environmental challenges. There is growing evidence linking slow fetal growth with the developmental programming of cardiovascular and metabolic diseases and neuropsychiatric disorders .Maternal undernutrition during pregnancy can result in asymmetric growth retardation and is associated with increased oxidative stress. In humans, fetal undernutrition is associated with significant oxidative stress in small-for-gestational-age neonates born at term to malnourished mothers . MelatonPOMC) gene expression in the fetal hypothalamus and contributes to fetal programming. The consequences of maternal undernutrition include altered regulation of food intake, energy expenditure, and glucose homeostasis later in life [Maternal undernutrition can have long-lasting effects on gene expression in the fetus and therefore can extensively affect the phenotypic outcome of the progeny. Maternal undernutrition can result in marked epigenetic changes affecting the GR and proopiomelanocortin , total sleep, and an increase in slow-wave sleep during the dark phase [et al. showed reduced duration of slow-wave sleep, increased duration of REM sleep, increased number of REM sleep events, and increased motor activity before the beginning of the dark phase of the light/dark cycle in adult offspring of mothers exposed to stress [The maternal milieu may perturb the development of the fetal circadian clock through its effect on glucocorticoid receptors, which are already present in the SCN during early development . Dugovicrk phase . Agomelao stress . This reo stress . Stress o stress , which ao stress ,146. In et al. demonstrated that agomelatine could correct all biochemical, cellular, and behavioral abnormalities displayed by maternal stress rats in adult life [The effect of maternal stress on fetal programming may be mediated by epigenetic mechanisms, with resulting behavioral modifications and altered biological rhythms in adult offspring . Morley-ult life . These ault life . Interesult life , suggestMelatonin is a potent free radical scavenger, a broad-spectrum antioxidant, and an epigenetic modification agent. The role of melatonin in pregnancy and parturition is well established. Melatonin readily crosses the placenta and the fetal blood-brain barrier and plays a key role in the regulation of development of fetal organs to extrauterine life. Compromised pregnancies result in oxidative stress to the fetus and alter fetal development through the epigenetic process. In this regard, melatonin is beneficial for reversing the adverse programming effects associated with compromised pregnancies via a redox mechanism; however, the potential role of melatonin in epigenetic modifications requires further study. Additional studies exploring the role of melatonin as a target for other pregnancy-related diseases are warranted.


Rates of infection with antibiotic-resistant bacteria have increased precipitously over the past several decades, with far-reaching healthcare and societal costs. Recent evidence has established a link between antibiotic resistance genes in human pathogens and those found in non-pathogenic, commensal, and environmental organisms, prompting deeper investigation of natural and human-associated reservoirs of antibiotic resistance. Functional metagenomic selections, in which shotgun-cloned DNA fragments are selected for their ability to confer survival to an indicator host, have been increasingly applied to the characterization of many antibiotic resistance reservoirs. These experiments have demonstrated that antibiotic resistance genes are highly diverse and widely distributed, many times bearing little to no similarity to known sequences. Through unbiased selections for survival to antibiotic exposure, functional metagenomics can improve annotations by reducing the discovery of false-positive resistance and by allowing for the identification of previously unrecognizable resistance genes. In this review, we summarize the novel resistance functions uncovered using functional metagenomic investigations of natural and human-impacted resistance reservoirs. Examples of novel antibiotic resistance genes include those highly divergent from known sequences, those for which sequence is entirely unable to predict resistance function, bifunctional resistance genes, and those with unconventional, atypical resistance mechanisms. Overcoming antibiotic resistance in the clinic will require a better understanding of existing resistance reservoirs and the dissemination networks that govern horizontal gene exchange, informing best practices to limit the spread of resistance-conferring genes to human pathogens. It is estimated that infection with antibiotic-resistant pathogens incurs over $25 billion in societal and healthcare costs annually in the United States CDC, . More thde novo mutation or the acquisition of resistance-conferring genes on mobile genetic elements   Walsh, . The ant) Walsh, . As near) Walsh, , the exc) Walsh, . This re) Walsh, , 2003:  vs. those that function via chemical modification. The β-lactamases are characterized by their ability to cleave the four-membered ring present in all β-lactam antibiotics and are some of the best-studied and widely-distributed antibiotic resistance genes  . The resulting transformants are then selected for the desired function , and metagenomic DNA fragments are sequenced and annotated to identify causal survival-conferring genes s] are difficult to identify via PCR because of their high sequence diversity -based annotation provides a sensitive, statistically sound analysis method capable of identifying remote homologs, these models still rely on underlying multiple sequences alignments of previously characterized proteins. In addition, current profile HMM databases provide high-level classification of antibiotic resistance genes , providing little functional information about the gene and its potential resistance profile. Therefore, while these techniques have the potential to identify genes that have low sequence identity to known resistance genes, in the absence of additional functional confirmation, they cannot identify novel resistance mechanisms or verify that sequence variants are functional.tet(37)  inactivates tetracycline, making it one of only three tetracycline resistance proteins to utilize this mechanism  resembles flavoproteins, oxidoreductases, and NAD(P)-requiring enzymes in sequence and conserved motifs, but has no identity to tet(X), the first tetracycline-inactivating gene identified. It is therefore unlikely that computational annotation would have identified it as a resistance gene  reductases but not dhfr, the target of trimethoprim  to other drug resistance transporters, including any known chloramphenicol exporters -Ib-cr is the only bifunctional resistance enzyme identified capable of conferring resistance to two different structural classes of antibiotics, aminoglycosides and fluoroquinolones , prohibiting functional metagenomic selections in this host from identifying antibiotic resistance genes active against these classes. Development of a Gram-positive indicator host will represent a major step forward for the field  or target the pathogen  have been explored with some success (Planson et al., For instance, recent studies have suggested engineered bacteriophage as an adjuvant to enhance the bactericidal activity of antibiotics and avoid evolution of resistance to either (Lu and Collins, Several permeabilizing products capable of disturbing the cell membrane have been identified, thus allowing antibiotics to penetrate the cells more efficiently. One such product is the low molecular-weight oligosaccharide nanomedicine OligoG, which is able to disturb multidrug-resistant bacteria (Khan et al., Drug efflux pumps, both specific and multidrug-resistant, may be inhibited through a variety of strategies. These include interfering with the expression of a functional transporter at different stages between transcription and final assembly, interfering with the assembly of channel proteins, designing inhibitors that compete with the antibiotic for efflux, disrupting the energy source, and blocking the efflux channel (Pages and Amaral, Functional metagenomic selections are a powerful technique for high-throughput characterization of the transferable resistome encoded by environmental and human-associated microbial communities, which have the potential to provide human pathogens with resistance genes through HGT. The advantages of this technique over traditional culture- and sequence-based screens are underlined when considering novel resistance mechanisms. Because resistance genes are selected on the basis of function regardless of sequence, the functional metagenomic selections reviewed above identified numerous genes with sequences highly divergent from other members of their class, as well as novel resistance mechanisms that would not have been recognized as resistance genes based on sequence alone. Conversely, they confirm antibiotic resistance function in putative drug transporters, which are frequently annotated as such regardless of true resistance ability, and permit the accurate annotation of resistance genes typically associated with other cellular functions. They have also led to the discovery of confirmed bifunctional enzymes, with broad resistance spectrums resulting from the fusion of two resistance genes. By providing a broader understanding of the resistance mechanisms currently in existence, functional metagenomic selections will aid the production of new antibiotics less susceptible to existing resistance mechanisms, as well as alternative strategies for combating antibiotic resistance.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Needlestick injuries frequently occur among healthcare workers, introducing high risk of bloodborne pathogen infection for surgeons, assistants, and nurses. This systematic review aims to explore the impact of both educational training and safeguard interventions to reduce needlestick injuries. Several databases were searched including MEDLINE, PsycINFO, SCOPUS, CINAHL and Sciencedirect. Studies were selected if the intervention contained a study group and a control group and were published between 2000 and 2010. Of the fourteen studies reviewed, nine evaluated a double-gloving method, one evaluated the effectiveness of blunt needle, and one evaluated a bloodborne pathogen educational training program. Ten studies reported an overall reduction in glove perforations for the intervention group. In conclusion, this review suggests that both safeguard interventions and educational training programs are effective in reducing the risk of having needlestick injuries. However, more studies using a combination of both safeguards and educational interventions in surgical and nonsurgical settings are needed. Needle-stick injuries are an important and common occupational injury among healthcare workers. In a UK report, 37% of nurses reported that they have sustained a needle-stick injury at some stage during their career . In AustAccording to the policy of the NHS in the UK, it is compulsory when staff sustain a needle-stick injury to report the incident . HoweverNeedle-stick injuries have been widely recognised as a source of exposure to bloodborne pathogens for workers in healthcare occupations . There aDue to the recognised risk of needle-stick injuries, safeguards have been put in place to attempt to lessen the risk of injury. These include the policy of universal precautions and needleless systems to connect with intravenous tubing . SeveralNevertheless, the health technology supply industry has not successfully developed cost-effective devices by which to protect the healthcare worker and so are not routinely used in the developing countries such as China despite the higher prevalence of bloodborne pathogens . Using nGenerally, interventions around healthcare occupational injuries fall into two major categories, those using double-gloving or blunt needles and those providing educational messages. Interventions using double-gloving or blunt needles are often implemented in different hospital departments or in different operations. Evaluations are generally designed as randomised control trials, and target surgical departments or emergency medical departments. In contrast, educational interventions provide information about the negative consequences of healthcare occupational injuries or provide strategies to change attitudes to the occupational injuries. These programs are generally targeted at students and evaluated in before-and-after designs. Both types of intervention have costs associated with them, particularly in the interventions using new devices such as double gloving and blunt needles that need more funding . Along wThe purpose of this paper is to conduct a rigorous and integrative review of interventions designed to decrease healthcare occupational injuries. To our knowledge, this is the first integrative review of the effectiveness of interventions on healthcare occupational injuries during the past 10 years. The previous review found a decrease in glove perforations when double gloves or combinations of gloves were used . The impUsing an integrative approach to literature searching, searches were conducted in five different databases, that is, MEDLINE, PsycINFO, SCOPUS, CINAHL, and Sciencedirect. The terms “glove perforation,” “Needle-stick injuries,” “reducing percutaneous injuries,” “gloving tears,” “reducing sharp injuries,” and “occupational exposure in healthcare” were used in the initial search in all databases. All of the six terms were valid in MEDLINE, the first four terms were valid in Sciencedirect, and glove perforation produced different results in SCOPUS in addition to the results obtained from the other databases. “Needle-stick injuries,” “percutaneous injuries,” and “occupational exposure” were valid in PsycINFO, and “glove perforation” and “needle-stick injuries” in CINAHL. Six thousand nine hundred and fifty-six articles were screened for inclusion  and behaviour (P = .002) in the group who received the bloodborne pathogens training. The self-reported needle-stick injuries were significantly lower for the bloodborne pathogens training group though they were not observed to practice universal precautions significantly more frequently than those in the control group [This quasiexperimental study examined the impact of structured training on prevention of occupational exposure to bloodborne pathogens on knowledge, behaviour, and incidence of needle-stick injuries among student nurses . It repool group .The reviewed interventions on needle-stick injuries includes components of double gloving, using blunt needles and educational training, and demonstrates there are significant reductions in needle-stick injuries following interventions as measured by glove perforations and changes in bloodborne pathogen knowledge. Results showed that interventions that use safeguard devices (double gloving and blunt needles) lead to a reduction in needle-stick injuries among healthcare workers. Knowledge regarding bloodborne pathogens was a major outcome measure in just one study  and resuThe results of this review are consistent with a much earlier review of interventions to prevent needle-stick injuries . In thisThe fourteen studies differed in a variety of ways, including the surgical procedures, the type of intervention, the location of the intervention , the time period of the study, and the number of participants. Most studies reported relatively serious methodological flaws such as study procedure (13 studies), randomisation methods (5 studies), and statistical tests (10 studies). In addition, thirteen studies failed to report drop-out rate, blinding procedures, consent rate, and exact number of participants which may bias results , 26–28. Of the fourteen studies, only one examined the impact of a structured educational training program on prevention of occupational exposure to bloodborne pathogens on knowledge and behaviour among student nurses . AlthougAll the reviewed studies in this paper contained an experimental group and a control group, and most had proper randomised controlled procedures. However, it may raise ethical issues if interventions are designed in a randomised controlled manner which may put the healthcare workers at a high risk of incurring needle-stick injuries in the control group. The healthcare workers in the control group may have increased risk of experiencing needle-stick injuries compared to the healthcare workers randomised to the experimental group. Thus, such possible ethical issues need to be considered in order to minimise the risk for healthcare workers.More studies are needed to evaluate interventions in nonsurgical settings, such as departments of nursing and other hospital units and among other healthcare personnel such as nurses. The current evidence suggests that both safeguard interventions and educational training programs are effective in reducing the risk of having needle-stick injuries. However, there are insufficient studies using a combination of both safeguards and educational interventions in surgical and nonsurgical settings. In future research, evaluations of these two types of interventions in both randomised controlled trials and in studies utilising other designs are needed.


To compare the diagnostic performances of computer tomography angiography (CTA) and magnetic resonance angiography (MRA) for detection and assessment of stenosis in patients with autologuous hemodialysis access.Search of PubMed, MEDLINE, EMBASE and Cochrane Library database from January 1984 to May 2013 for studies comparing CTA or MRA with DSA or surgery for autologuous hemodialysis access. Eligible studies were in English language, aimed to detect more than 50% stenosis or occlusion of autologuous vascular access in hemodialysis patients with CTA and MRA technology and provided sufficient data about diagnosis performance. Methodological quality was assessed by the Quality Assessment of Diagnostic Studies (QUADAS) instrument. Sensitivities (SEN), specificities (SPE), positive likelihood ratio (PLR), negative likelihood values (NLR), diagnostic odds ratio (DOR) and areas under the receiver operator characteristic curve (AUC) were pooled statistically. Potential threshold effect, heterogeneity and publication bias was evaluated. The clinical utility of CTA and MRA in detection of stenosis was also investigated.Sixteen eligible studies were included, with a total of 500 patients. Both CTA and MRA were accurate modality  for hemodialysis vascular access. No significant difference was detected between the diagnostic performance of CTA  and MRA . Meta-regression analyses and subgroup analyses revealed no statistical difference. The Deek’s funnel plots suggested a publication bias.Diagnostic performance of CTA and MRA for detecting stenosis of hemodialysis vascular access had no statistical difference. Both techniques may function as an alternative or an important complement to conventional digital subtraction angiography (DSA) and may be able to help guide medical management. With increasing numbers of patients who suffered from end-stage renal disease and under long-term hemodialysis, the functioning vascular access related to better prognosis and quality of life is essential. NowadaySeveral imaging modality has been published in detection and depiction of the vascular access stenosis such as color Doppler ultrasonography (CDUS), computed tomography angiography (CTA), magnetic resonance angiography (MRA) and digital subtraction angiography (DSA) in recent years. Digital subtraction angiography (DSA) is a standard technique combined with the diagnosis and treatment for AVF or AVG dysfunctions currently . HoweverConsidering that these controversial results, we performed this meta-analysis in an attempt to derive a more precise, comprehensive assessment for the overall diagnostic value of CTA and MRA in evaluation of vascular access in hemodialysis patients. To the best of our knowledge, this is the first meta-analysis on CTA and MRA in evaluation of vascular access in hemodialysis patients.Pubmed, MEDLINE, EMBASE, Cochrane Library database were all searched . The following terms were used in searching: (vascular access or arteriovenous fistula or arteriovenous graft) and  and (computed tomography angiography or magnetic resonance angiography or CT angiography or MR angiography or CTA or MRA). All the searched studies were retrieved, and their references were checked as well for other relevant publications. We also review articles to find additional eligible studies.Studies meeting the following selection criteria were included in this meta-analysis: (1) evaluation of the diagnostic performance of CTA or MRA for detecting or evaluating stenosis , (2) On per-segment or per-patient statistical basis, presentation of information for true-positive(TP), false-positive(FP), true-negative(TN) and false-negative(FN) results either found or calculated from data in the original published study, (3) Articles were published in English, (4) DSA or surgery should be the reference standards. Studies were excluded if not relevant to CTA or MRA for detecting or evaluating stenosis or without sufficient data obtained or duplicate publications. Relevant studies were examined by two independent observers (Bin Li and Qiong Li) with the Quality Assessment of Diagnostic Studies (QUADAS)  tool spe2) test and the inconsistency index (I2) [2 >50% suggested heterogeneity; A random effects model was for the meta-analysis to obtain a summary accuracy parameter if heterogeneity was identified; otherwise a fixed effects model was used.Diagnostic performance estimates for detecting more than 50% stenosis, such as sensitivity, specificity and likelihood ratio were calculated and pooled on a per-segment or per-patient basis. Using random-effects or fixed-effects model depends on the presence of statistical heterogeneity. Heterogeneity was explored by likelihood Chi-square Value (χdex (I2) . P-valueOne of main causes of heterogeneity is threshold effect in test accuracy studies. The threshold effect arises owing to different thresholds or cut-offs used in different studies to define a positive (or negative) test result . If threApart from the threshold effect, in test accuracy studies, several other factors can contribute to heterogeneity. If there was no threshold effect but significant heterogeneity, a regression meta-analysis and subgroup analysis was performed because assessment should only be attempted within homogeneous subgroup.Publication biases were assessed by Deeks's funnel plots.All the statistical computations were performed using the Meta-Disc software version 1.4  and the Our search strategy identified 333 primary studies. After ruling out the obviously irrelevant abstracts, 26 studies were left and their full texts were obtained. The details about the data acquisitions of CTA and MRA are summarized in Spearman correlation coefficient was determined to be 0.071 (P=0.867) and -0.677 (P=0.071) for CTA and MRA respectively, which indicated absence of threshold effect that could cause variations in accuracy estimates among the individual studies. 2 value are summarized in There was substantial between-study heterogeneity (P < 0.05 and I2 > 50%) for specificity, PLR and DOR in MRA imaging studies. To explore possible explanations for the heterogeneity, we firstly applied meta-regression analysis by adding the number of patients, year of publication, MR field strength, CT slice thickness, whether using contrast enhancement, access type, calculating stenosis number by patient or vascular access segment as variates. No apparent relationships were found (P > 0.05).Subgroup analyses were then conducted based on the type of access (AVF and AVF versus AVF), MR field (>1T versus ≤1T), lesion calculating( numbers per patient versus numbers per access segment) for MRA studies. Still, no significant difference was found (P > 0.05). The results of Deeks’ funnel plot asymmetry test (P =0.035) showed strong evidence for publication bias for MRA studies but no publication bias was indicated for CTA studies. Scattergram of the positive likelihood ratio and negative likelihood ratio is shown in Hemodialysis vascular access is considered to be critically important for patients with end-stage renal disease, especially arteriovenous grafts (AVGs) and arteriovenous fistulas (AVFs) mainly including the brachiocephalic, brachiobasilic and radiocephalic arteriovenous fistula . The autCTA and MRA can also diagnose vascular impairment other than stenosis, such as aneurysm, thrombosis and pseudoaneurysms, provides excellent preoperative and postoperative evaluation of patients with AVF malfunction and generated a “road map” for therapy planning -30. Both CTA and MRA for autologuous hemodialysis access have some advantages and disadvantages.Apart from two studies ,23 aboutNSF, which is regarded initially as possible complication of MRA, is a systemic disorder. It is an illness described in patients with kidney disease who present with firm, erythematous, and indurated plaques of the skin associated with subcutaneous edema. Primarily it involves the extremities and may result in flexion contractures with limited range of motion, pain, paresthesias, and/or severe pruritus. It may also involve other organs, including the lungs, heart, diaphragm, liver, and kidneys, resulting in variable end organ damage and even death . The risThere are contraindications and side effects for both CTA and MRA. The pregnant, children and patients with renal insufficiency should be suggested to avoid CTA examine because CTA examine exposes the patient to ionizing radiation and iodinated contrast agent . The preFrom a cost standpoint, it might be worthwhile to consider performing CTA or MRA before DSA in all patients with failing hemodialysis access fistulas and grafts. Doelman  revealedAs far as contrastload is concerned, it might be recommend considering MRA. Even at the higher dose of 0.3 mmol/kg, the MR contrast volume is still less than half that of the iodinated contrast required for CTA. Radiation dose might limit the practical application of CTA for the evaluation of dysfunctional hemodialysis fistulas, since multiple CTA could be effective for surveillance of patency rates but multiple CTA would expose the patient to additional radiation. Data about patient radiation dose are available in only one study  includedOur meta- analysis, including data from 500 patients with autologuous hemodialysis access, showed that CTA and MRA were accurate modalities for detecting stenosis and both had similar diagnostic performance, which was in agreement with most previous literature that suggested MDCT and MR angiography as alternatives diagnostic techniques to DSA in the analysis of hemodialysis fistula and graft stenosis. Both CTA and MRA had high sensitivity, specificity, positive likelihood ratio, negative likelihood ratio and diagnostic OR. There was no significant difference between the performance of CTA and MRA for stenosis detecting.Homogeneity test indicated that there’s no significant heterogeneity for CTA studies included but substantial heterogeneity existed in MRA studies for specificity, PLR and DOR. Meta-regression analyses showed that number of patients, year of publication, MR field strength, CT slice thickness, access type, calculating stenosis number by patient or vascular access segment had no significant influence on the between- study heterogeneity. Subgroup analyses were performed based on the type of access (AVF and AVF versus AVF), MR field (>1T versus ≤1T), lesion calculating( numbers per patient versus numbers per access segment) for MRA studies, No statistical difference was detected as well. Deek’s Funnel plots with marked asymmetry suggested a publication bias for MRA.Therefore, conclusions of published studies in detecting and evaluating hemodialysis access stenosis using MRA may be overestimated, as studies with positive and favorable results are more likely to be accepted and published.However, we could not ascribe all the heterogeneity to publication bias. Because significant disease may be detected by MRA and CTA and which allow 3-dimensional assessment but be unrecognized by the 2-dimensional DSA, it may lead to so called false-positive results from a professional and clinical standpoint. Furthermore, in 8 included studies, Planken et al reported a considerably low specificity (SPE=20%) for detection of significant stenosis, which had significant difference with others. We thought this study might have relationship with the above reason and result in between-study heterogeneity of our meta-analysis. Their large number of false-positive lesions detected with contrast- enhanced MR angiography also may be caused by a limited spatial resolution, which resulted in stenosis overestimation. Moreover, because of the use of a rectangular surface coil, no information could be obtained about the venous outflow of the upper arm.One limitation of our study is that we could not present the exact reasons for heterogeneity which was observed for pooled specificity, PLR, DOR of MRA. Except for those discussed above, there are still many variables which differed among studies regarding patient position during examination, patient characteristics, acquisition protocol, image analysis technique, indication for imaging, interobserver variability, and quality of studies, especially patient position. So meta-regression analyses we performed to detect heterogeneity were still insufficient. But these factors were not taken into account and the effect of these variables could not be examined because of variation in data presentation or incomplete reporting of data. Besides that, the number of studies on non-contrast enhancement MRA included in this meta-analysis was not enough to enable us perform a reliable subgroup analysis. It was thought that Gd-enhanced MRA is more likely to avoid stenosis overestimation than non-contrast enhancement MRA. Unlike conventional MRA techniques (TOF and phase contrast), which rely on velocity-dependent inflow or phase-shift effects, employing gadolinium does not depend upon blood motion. Unfortunately, the effect cannot be explored. More studies should emphasize on non-contrast enhancement MRA evaluating hemodialysis access in the future. The second limitation is that there are differences of the field of view (FOV) between contrast enhancement MRA and non-contrast enhancement MRA. The FOV of contrast enhancement MRA is similar to that of CTA, which included the complete vascular tree comprising feeding artery, anastomosis, draining vein and central venous outflow up to the level of the superior vena cava. But the FOV of non-contrast enhancement MRA could not include the central venous outflow. Depiction of the central venous outflow is important because subclavian vein stenoses are frequently present in dialysis patients.The third limitation stemmed from the fact that, for practical reasons, we included only studies that were written in English. Although certain less-qualified studies would be neglected by limiting publication language to English, it might invoke the so-called Tower of Babel bias . The funIn conclusion, despite the limitations of the present meta-analysis, results available indicate that CTA and MRA had similar, excellent accuracy for detecting stenosis of hemodialysis vascular access. There is no statistical difference between the diagnostic performance of CTA and MRA. Both techniques may function as an alternative or an important complement to conventional digital subtraction angiography and may be able to help guide medical management.Table S1Summary of details about the data acquisitions of CTA and MRA.(DOC)Click here for additional data file.Checklist S1PRISMA Checklist.(DOC)Click here for additional data file.


Degeneration of cardiac tissues is considered a major cause of mortality in the western world and is expected to be a greater problem in the forthcoming decades. Cardiac damage is associated with dysfunction and irreversible loss of cardiomyocytes. Stem cell therapy for ischemic heart failure is very promising approach in cardiovascular medicine. Initial trials have indicated the ability of cardiomyocytes to regenerate after myocardial injury. These preliminary trials aim to translate cardiac regeneration strategies into clinical practice. In spite of advances, current therapeutic strategies to ischemic heart failure remain very limited. Moreover, major obstacles still need to be solved before stem cell therapy can be fully applied. This review addresses the current state of research and experimental data regarding embryonic stem cells (ESCs), myoblast transplantation, histological and functional analysis of transplantation of co-cultured myoblasts and mesenchymal stem cells, as well as comparison between mononuclear and mesenchymal stem cells in a model of myocardium infarction. We also discuss how research with stem cell transplantation could translate to improvement of cardiac function. The ability of hESCs to differentiate into mature somatic cells was demonstrated using spontaneous and directed in vitro differentiation systems. So far, hESCs have been shown to differentiate into neuronal tissue [In contrast to adult stem cells, embryonic stem cells (ESCs) have the potential to differentiate into tissue derivatives of all three embryonic germ layers and therefore are termed pluripotent. Cardiomyocytes (CMCs) have been obtained by all three types of murine embryo-derived stem cells: embryonic carcinoma (EC), embryonic stem (ES), and embryonic germ (EG) cells. In this chapter, we focus our attention on human ESCs (hESCs), due to their potential clinical application. hESC lines, isolated from the inner cell mass (ICM) of embryos can be propagated continuously in the undifferentiated state when grown on top of a mouse embryonic fibroblast (MEF) feeder layer. When removed from these conditions and grown in suspension, they begin to generate three-dimensional differentiating cell aggregates termed embryoid bodies (EBs). This l tissue , ß isletl tissue , hematopl tissue , endothel tissue  and cardl tissue ,6. Interl tissue -9.1) [1). Given the versatility of hESCs and the possibility of obtaining beating CMCs from them,  ,10 they 1)  . On this issue, Kehat et al. [In the following sections, we will discuss briefly, but critically, the obstacles on the path to hESC-based cardiac therapy. A possible strategy for cell-replacement therapy would be to initially allow spontaneous differentiation of ESCs into multiple lineages t et al.  show that et al. . However, this is a relatively inefficient and haphazard process. We have to highlight that research on the exploitation of hESCs for cell-replacement therapy is still in its infancy, but the complex technical/technological problems are well worth overcoming when contemplating the benefits that this procedure may bring. Promising data has been obtained so far; hESC-based cell therapy will revolutionize medicine in the near future, offering therapeutical alternatives for treatment of severe degenerative disorders.In point of fact, several obstacles still remain unsolved: The yield of CMC production has to be dramatically improved. It is fundamental to work on the “ideal” culture conditions for CMCs differentiation. Unfortunately, the definition of strategies useful to the aim is not easy. The inherent differences between hESCs and their murine counterpart ,12,13 nein vitro in a cardiac stringent specific way. This speculation is supported by the fact that when in their natural milieu, cardiomyogenic differentiation of stem cells probably involves multiple signaling pathways. This may be mimicked in vitro with a combination of various methods that achieve a synergistic effect. In fact, in vitro derived prevascularized scaffold-free cardiac tissue patches from co-culture of cardiomyocytes, endothelial cells and fibroblasts were found to greatly improve cell viability post transplantation [Stimuli useful for directing hESC through the cardiac lineage are still only being investigated -23 A metantation .in vitro protocols for cardiomyogenic differentiation of stem cells, that utilize chemically defined culture media supplemented with recombinant cytokines and growth factors. The main drawback of the actual xenosupport system is the risk of cross-transfer of animal pathogens that might hamper future clinical applications. It was recently shown that non-human sialic acid Neu5Gc, against which many humans have circulating antibodies, is incorporated into hES cells grown on mouse feeder layers [in vitro up-scaling of clinical grade cell products essentially free of xenogenic products in compliance with good manufacturing practice (GMP) remains a significant hurdle [Culture media. For clinical applications, it is imperative to develop well-defined and efficient r layers . The user layers  and dever layers  and animr layers  or foresr layers  may provt hurdle . UniversCompetency of derived CMCs in terms of excitation-contraction coupling. Another important issue is to what extent these cells can be considered mature CMCs in terms of excitation-contraction coupling. Indeed, heterogenous electrophysiological properties have been demonstrated in CMCs derived from separate differentiation methods within the same group . This quImmune rejection has to be blocked. Upon differentiation, ES cells express molecules of the major histocompatibility complex (MHC), in particular MHC I, while MHC II expression levels are low or absent . Thus, d                            On this issue, recent high-profile reports of the derivation of human embryonic stem cells from human blastocysts produced by somatic cell nuclear transfer (SCNT) ,33,34 haCurrently, the use of SCNT is under investigation from several points of view  and has a promising potential for treatment of a variety of degenerative diseases. Furthermore, with the advent of other techniques such as xeno-free ,37 and d6.Tumorigenicity may be a problem, even when terminally differentiated CMCs are used for cell replacement. Implantation of undifferentiated ES cells leads to the formation of benign teratomas in the recipients ,35,39,40                            et al. [et al. [As discussed by Authors ,42, an Eet al.  have, fo [et al.  showed t [et al.  or cardi [et al.  and othe [et al.  would fuMost studies with cell transplantation have been performed in animal models and patients with ischemic cardiomyopathy. Although results are promising, the most appropriate cell for this therapy is still a matter of discussion. Skeletal myoblasts transplantation has been shown effective in experimental -52 and cet al [Manasché et al  demonstret al  in a fib2). Histological evaluation was made by Gomori’s Trichrome and identified cells with morphological characteristics of skeletal muscular fibers that colonize the region of fibrosis. The formation of new blood vessels was also identified in this region however, the presence of neither muscle nor blood vessels was visualized in the region of myocardial fibrosis in control group .We performed one study  in a modin vitro interaction as reported previously [2). Histological evaluation was made by hematoxylin eosin and identified cells with morphological characteristics of skeletal muscular fibers that colonize the injured myocardium .Whether these same effects can be seen in other cardiomyopathies is still not known, so we performed one study on model of Chagasic cardiomyopathy . We empheviously . The optThis effect on ventricular remodelling seems to be more related to the pathology and the way cells are transplanted into the heart than to the transplanted cell. Nevertheless, transplantation of co-cultured myoblasts and mesenchymal stem cells to a rat model of post-infarction ventricular dysfunction didn’t prevent ventricular remodelling despite of improvement in ventricular function . Cells win vitro. There was difference in baseline LVEF and LVEDV between all groups. After one month, LVEF decreased in the control group and remained unchanged in MoSC and MeSC groups. The myocardium was remodeled in all of the groups (Tables 3 and 4). Thus functional effectiveness was not demonstrated with both cell type therapy: MoSC and MeSC, when LVEF was analyzed by echocardiogram in this post-infarction dysfunctional model. Although we observed the stabilization of the MeSC therapy and no effects have been demonstrated to affect the ventricular dilatation. In spite of the fact that there was no improvement of the functional effects, the potential myocardial perfusion may warrant further analysis [Experimental studies suggest that cardiac bone marrow stem cells (SC) transplantation can has a favorable impact on tissue perfusion. The strategy to repair the myocardial scar after infarction with SC has been proposed based on its capacity to differentiate according to the environment and could give a new perspective for myocardial regeneration 55,62-64-6462-64.analysis .5), while in the new vessels formed after the MeSC transplant , there was also the presence of smooth muscle. The latter was demonstrated by the presence of muscle in new vessel stained by anti-desmin with immunoflurescence in the myocardial scar. The control demonstrated only the scar with collagen deposit: fibrosis. This new vessel resulted from MeSC transplantation could have more physiological potential for vasomotor response, but the potential effect on myocardial perfusion may have great significance in cardiac recovery. Thus both cell type therapies: MoSC and MeSC have angiogenic capacity. The new vessel formed by MeSC transplant from the histopathological point of view, was complete and characterized for the presence of smooth muscle with endothelial cells and lumen [The histopathological analysis demonstrated new vessels in both cell type therapy, but with morphological differences. The new vessel formed in the scar after MoSC transplant is constituted of endothelial cells and lumen . Transplantation of totipotent stem cell types, including bone marrow derived stem cells, into a fibrous postinfarction scar may result in their differentiation into fibroblasts [Congestive heart failure caused by myocardial infarction continues to be a major clinical problem despite recent therapeutic advances. Formation of a fibrotic scar that replaces viable myocardium leads to decreased systolic function, left ventricular remodeling, aneurysm formation and subsequently to the progression of congestive heart failure. Unfortunately, cardiac transplantation may be an option only in selected end-stage heart failure patients, mainly due to organ shortage. Restoration of the total amount of contractile cells within the necrotic tissue as a result of cell transplantation into myocardium have been widely studied in both experimental and clinical conditions  Among varoblasts -73, therNumerous studies have explored different delivery techniques. As skeletal myoblasts do not extravasate, their potential application in myocardial regeneration requires direct cell injection into the area of damaged myocardium. Therefore surgical approach (open-chest surgery) and several catheter-based methods had been proposed. The initial clinical experience with autologous skeletal myoblast transplantation during open chest cardiac surgery was obtained by Ph. Menasché et.al., followed by phase one clinical trials performed both in Paris and in Poznan ,74,75. Bet al. [A US-based multicenter phase one clinical trial aimed at evaluation of myoblast transplantation during CABG has also been reported . Eleven et al. , suggestCell transplantations during cardiac surgery has certain advantages, including easy access and good visualization of the target site as well as possible delivery of big amount of cells per unit area. However, direct transepicardial approach may cause additional risk related to the surgery. It must be underlined that possible candidates for cell transplantation usually have a history of multiple infarctions, with significant LV dysfunction and clinical symptoms of severe heart failure, being high-risk candidates for open-chest surgery. Furthermore open-chest approach does not give free access to septal wall which is frequently inflicted by postinfarction injury. Clear interpretation of clinical data obtained from trials evaluating cell transplantation during CABG is not possible. The effect of CABG and cellular transplantation performed at the same time cannot be easily distinguished. Despite the use of careful inclusion criteria aimed at selection of patients with no viable myocardium within the target postinfarction area, the possible effect of skeletal myoblast transplantation may be enhanced by myocardial revascularization. Large on-going and future clinical trials evaluating efficacy of myoblast injections during CABG may allow evaluating of the cell effect independently on restoration of blood flow. Nevertheless, a recently concluded randomized, placebo-controlled study of 97 patients, the myoblast autologous grafting in ischemic cardiomyopahty (MAGIC) trial failed to show improved LV function at 6 months after myoblast transplantation . Myoblast transplantations, performed as a sole therapy during percutaneous procedures, may allow the evaluation of the cellular effect independent of revascularization. In addition, it may enable repeated injections in patients with severe myocardial injury, since excessive numbers of transplanted cells in a single injection may result in a small percentage of survived and grafted cells. Initial experience has been obtained with cell injection into myocardium with the use of both endoventricular catheter systems  and tranThe efficacy of cell transplantation may be very much dependent on the design of catheter system used ,83. CurrAnother catheter-based endovascular system for direct myocardial injection using IVUS guided needle punctures via the coronary venous system  has been recently developed ,85. The The POZNAN trial  was perfet al. [Smits et al.  used traet al.  have shoet al.  decribesMyocardial and skeletal muscle tissues differ significantly in their electromechanical properties. Cardiac cells, having special cell-cell junctions, even though separated one from another, act together synchronically. Junctions contain adherins and gap junctions for mechanical and electrical coupling. Cardiac tissue gap junctions contain connexin-43 transmembrane protein by which electrical current can be fast and freely conducted ,88. It iThere is evidence that this positive effect of skeletal myoblasts on myocardial contractility seems to last over time and is correlated with the number of implanted cells . Experimet al [It is speculated that the inability of skeletal myoblasts to transdifferentiate to cardiomyocytes and to form junctions with neighboring cells may be a substrate for ventricular re-entry arrhythmia. Indeed, current experimental and clinical data suggest a possibility of increased risk of arrhythmogenicity. In their first clinical series, Menasché at al.  implanteet al  Later duet al . On the et al ,83. Based on published data from clinical studies, it could be speculated that the possible arrhythmogenic effect of myoblast transplantation is noticed only in the initial weeks after the procedure. The possible arrhythmogenic effect of myoblast transplantation is more probably related to its mechanics, including myocardial puncture and the inflammatory response to transplanted cells, some of which die after injection, than to possible problems with electromechanical coupling between newly developed myocytes and cardiomyocytes. Possible electromechanical coupling problems would result in late arrhythmia as cells differentiate (downregulation of connexin-43 and N-cadherin), a situation that has not been observed in clinical trials so far. At the current stage, only moderate numbers of patients that have undergone autologous skeletal myoblast transplantations, it is difficult to predict whether skeletal myoblasts are really arrhythmogenic, especially that patients with ischemic LV dysfunction frequently develop ventricular arrhythmia. Indeed, the experience of MAGIC trial  reflecte


The recent establishment and adaptation of microfluidic-based in vitro devices (μFIVDs) of lung airways have enabled a wide range of developments in modern respiratory physiology. In this paper, we address recent efforts over the past decade aimed at advancing in vitro models of lung structure and airways using microfluidic technology and discuss their applications. We specifically focus on μFIVDs covering four major areas of respiratory physiology, namely, artificial lungs (AL), the air-liquid interface (ALI), liquid plugs and cellular injury, and the alveolar-capillary barrier (ACB).Our current understanding of respiratory physiology and pathophysiological mechanisms of lung diseases is often limited by challenges in developing  The. TheμFIV devices . In contμFIVDs towards engineering an artificial lung is of high value. Although significant improvements are still required both in the design and manufacturing of ALs, microfluidic devices are contributing toward future clinical applications of respiratory support.Without a doubt, the impact of μm in the trachea, to 2.5 μm in the bronchi and finally 0.1 to 0.2 μm in the peripheral airways [in vitro airway models mimicking physiological aspects of ALI.The luminal surface of the lungs is populated with a confluent, uninterrupted epithelial cell sheet that exists as a continuum across the airway tree, from the larynx down to the alveoli . Airway  airways . For a d airways –25. Beloin vitro experimental setups have been conducted using isolated cells under submerged conditions [in vitro models are composed of cell populations fully immersed in a culture medium. However, in the specific case of pulmonary cells, these submerged in vitro conditions only loosely reflect the actual physiological environment characterizing the alveolar epithelium , nterface . In theiin vitro), parallel efforts have characterized at length growth requirements under constant perfusion for a monolayer of human alveolar epithelial cells  in a microfluidic platform [To create a stable and viable ALI over long durations , physiological changes in the thin liquid film are known to cause acute lung injury and epithelium damage. The origins of such alterations arise from abnormal physical forces, due to mechanical ventilation or fluid shear stresses, as well as from surfactant dysfunction  . In partAs mentioned earlier, pulmonary surfactant in the alveolated region of the lungs reduces dramatically surface tension at the air-liquid interface, that is, with magnitudes found between near-zero values (at end-expiration) and approximately 25 mN/m (at end-inspiration), well below values for a simple air-water interface, that is, ~70 mN/m . Howeverin vivo animal and computational models, respectively, suggest that abnormal shear stresses developed as a result of fluid mechanical stresses during the airway reopening can potentially injure the epithelial cells and lead to a variety of respiratory complications [The formation of liquid plugs in small airways can also result from clinical therapies such as mechanical ventilation (MV) and surfactant replacement therapy (SRT) . Yet, thications –51.in vitro airway models. These efforts include several bench-top models mimicking physiologically-realistic airways and address specifically the characteristics of airway closure and reopening upon the passage of a liquid plug. For instance, thin-walled polyethylene tubes of different radii using lining fluids of different surface tensions and viscosities were used as a model airway to measure the relationship between airway opening velocity and the applied airway reopening pressure [To explore the fundamental fluid mechanics of liquid plug propagation and its damaging effects on respiratory airway walls, experimental investigations have been initiated through the development of pressure . Furtherpressure . Eventuapressure . In parapressure , 54, 55.pressure . While tpressure .in vivo airway environment. To begin, one of the major differences lies in the lack of mechanical flexibility  featured in the experimental models. Moreover, such experimental models are devoid of a collagen substrate beneath the epithelial cells. This latter point is of importance since the pressure exerted during airway reopening could be buffered by collagen proteins, owing to its flexible nature, under in vivo conditions [in vivo airway anatomy. Altogether, these limitations and others have motivated researchers to explore new experimental strategies to integrate more physiologically-realistic airway environments.Given such shortcomings, more advanced platforms of idealized model airways have recently surfaced, including a parallel-plate flow chamber that features channels lined with monolayers of fetal rat lung epithelial cells (CCL-149) . There, nditions . FinallyμFIVDs have shown great potential towards creating in vitro airway models that combine the generation and transport of liquid plugs with cell cultures, all integrated within a single platform [in vivo pressures can provide a better understanding of the fluid shear stress-induced lung injury. Furthermore, μFIVDs have been utilized to investigate the effect of wall flexibility on the plug propagation and the resulting wall stresses in flexible microchannels that closely mimic human small airways [platform , 39. Recplatform . Outcomeplatform , a microplatform . This de airways .in vitro network of the airway tree was thought to be a difficult task to perform using conventional “large-scale” approaches. However, μFIVDs have opened the possibility of creating an airway tree network and generating air-liquid interfaces within an integrated single platform [in vitro models of lung airways that can be useful for exploring liquid plug propagation, lung injury, and wound healing while circumventing many of the limitations seen in conventional large-scale systems.In the past, the development of an platform , 36. Forplatform . While tplatform . This stplatform . Altogetμm [The functional efficiency of the lung is primarily characterized by the delicate structure that separates alveolar air from capillary blood . This thμm ) is compμm . Besidesμm , 63. Sinμm . Barrierμm . Due to μm . The thiμm , 66, incμm  as well μm  and injuμm .μm) and the large surface to volume ratio available for air, alveoli are inherently unstable structures since surface tension forces at the ALI have a natural tendency to collapse the lung airspace [With its large surface area and close juxtaposition with underlying capillaries, alveoli are considered the functional units of the lung . Due to airspace . The thiairspace .in vivo  approaches [in vitro model system that can mimic the in vivo barrier conditions remains a challenging task. The need for developing such model platforms is motivated by the intricate and delicate nature of alveoli that creates hurdles in understanding cell-cell interactions between different cell types, as well as answering other cell-biology-related questions with reference to the physical barrier itself [in vitro ACB models to study quantitatively both (i) drug absorption phenomena and (ii) aerosol translocation processes across the ACB. Although ex vivo approaches  have been considered useful models for examining lung injury, barrier permeability, and alveolar fluid clearance, the precise determination of cellular processes leading to barrier permeability, particle translocation, and drug absorption mechanisms lies widely out of reach using such methods. Therefore, there is a need for convenient, reliable, and robust in vitro cell-based models that not only possess a realistic ACB anatomy, but can also facilitate the study of such physiological processes.While the crucial role of the ACB in various physiological processes has been addressed quite extensively in the past using proaches –70, dever itself . In addiin vitro ACB studies [in situ. However, the major problem with A549 cells is their incapacity of forming functional tight junctions, that is, tight monolayers of polarized cells. Therefore, primary cultures of lung epithelial cells, in conjunction with pulmonary microvascular endothelial cells (PMEC), are recommended in order to reconstruct a more complete alveolar-capillary barrier. Since there are limited sources of human lung tissues, as well as ethical considerations related to the use of human lung and pulmonary microvascular tissues, the majority of studies have been conducted on cells isolated from the lungs of animals, including rat, mouse, rabbit and pig [A growing number of cell lines derived from different parts of the airways are available for  studies . Example studies . The mor and pig . However and pig .in vitro cellular models using instead lung epithelial cells and endothelial cells of human origin. For instance, a coculture system of human distal lung epithelial cells (NCI H441) and human pulmonary microvascular endothelial cells (HPMEC) using a filter membrane was developed to study cellular interactions of the ACB epithelium and endothelium in both pathogenesis and recovery from acute lung injury [As a result, several research groups have established g injury . A compag injury . Similarg injury . Most reg injury . In spitIn vitro cellular models based on microfluidic technology have been envisioned to address the limitations of traditional coculture approaches and mimic the structural, functional, and mechanical properties of human ACB. For example, a multistage μFIVD integrated with a suspended porous membrane was recently designed in order to recreate the alveolar-capillary membrane [in vivo structure of ACB, such as coculturing pulmonary epithelial and endothelial cells on opposite sides of the membrane. Despite such limitations, the microfluidic study characterized optimal growth conditions for alveolar epithelial cells cultured at ALI. Most recently, a more sophisticated microfluidic-based model was designed to mimic the critical functional aspects of human ACB [membrane . The funuman ACB  and simuμFIVD revealed that cyclic mechanical strain accentuates toxic and inflammatory responses of the luminal surface to silica nanoparticles. Alveolar epithelial cells exposed to ultrafine (12 nm) silica nanoparticles in the absence of mechanical strain showed little or no reactive oxygen species (ROS) production; in contrast, the intracellular formation of ROS was significantly increased in the presence of mechanical distortion. Similarly, the intracellular levels of ROS in the underlying endothelium were also found to be significantly elevated in the presence of cyclic strain. Moreover, mechanical strain enhances epithelial and endothelial uptake of nanoparticulates and stimulates their transport into the underlying microvascular channel .The pioneering microfluidic ACB model of Huh et al.  was alsoin vitro pulmonary airway studies; μFIVDs are able to successfully replicate the delicate structure of the native lung while incorporating critical respiratory functions. The novel technologies reviewed here have deeply contributed towards understanding cellular behavior and physiological processes at the alveolar level. While the use of μFIVDs is rapidly rising in popularity, these platforms will need, in the future, to incorporate additional cell types  in an effort to mimic regulatory and immune processes characteristic of the alveolar-capillary barrier. In addition, although significant research is still required before clinical applications of an artificial lung can be commercially available and replace current technologies, microfluidic systems have shown feasibility and demonstrated excessive advancement in the efficiency of artificial respiratory support. Overall, respiratory physiology on a chip is a noteworthy technology towards research and development of clinical applications in human respiratory disciplines.Developing anatomically and physiologically accurate models of the human respiratory system is of high importance towards applications for lung assist development as well as cytotoxicity and lung injury studies at the alveolar level. For these purposes, microfluidic systems hold great potential for use as a platform in