The eye and the brain are prototypical tissues manifesting immune privilege (IP) in which immune responses to foreign antigens, particularly alloantigens are suppressed, and even completely inhibited. Explanations for this phenomenon are numerous and mostly reflect our evolving understanding of the molecular and cellular processes underpinning immunological responses generally. IP is now viewed as a property of many tissues and the level of expression of IP varies not only with the tissue but with the nature of the foreign antigen and changes in the limited conditions under which privilege can operate as a mechanism of immunological tolerance. As a result, IP functions normally as a homeostatic mechanism preserving normal function in tissues, particularly those with highly specialized function and limited capacity for renewal such as the eye and brain. However, IP is relatively easily bypassed in the face of a sufficiently strong immunological response, and the privileged tissues may be at greater risk of collateral damage because its natural defenses are more easily breached than in a fully immunocompetent tissue which rapidly rejects foreign antigen and restores integrity. This two-edged sword cuts its swathe through the eye: under most circumstances, IP mechanisms such as blood–ocular barriers, intraocular immune modulators, induction of T regulatory cells, lack of lymphatics, and other properties maintain tissue integrity; however, when these are breached, various degrees of tissue damage occur from severe tissue destruction in retinal viral infections and other forms of uveoretinal inflammation, to less severe inflammatory responses in conditions such as macular degeneration. Conversely, ocular IP and tumor-related IP can combine to permit extensive tumor growth and increased risk of metastasis thus threatening the survival of the host. The first Ophthalmology textbook in English, written in the first half of the nineteenth century, contained a description of sympathetic ophthalmia (SO), an intraocular inflammatory disease which develops in the fellow eye several months after penetrating injury to the first eye . SO was de novo in accepted vascularized grafts (+ T regulatory cells (Tregs) –- infectious tolerance; The concept of IP has since been extended and is now regarded as a relative term, not unique to the eye or brain; it is a property of many tissues, develops d grafts  and consd grafts . Ocular Box 1).Despite ocular IP, autoimmune and immune-mediated diseases of the eye occur with demoralizing frequency; for instance, 5 year survival rates of corneal allografts in humans are lower than those of solid organ grafts , althougTerminology for Uveitis is confusing and as a result the condition has been somewhat neglected as a global cause of blindness (thus it is a “Cinderella” syndrome) mainly because clinicians have had difficulty reaching agreement as to what constitutes uveitis. However, a recent initiative is aimed at developing international criteria for the various entities that come under the umbrella of uveitis . However, the triggering antigens  can be located in any of the tissues, including the uveal tract itself. The most potent autoantigens have been identified in the retinal photoreceptors. Accordingly, uveitis (uveoretinitis) is also classified under the term “Intraocular Inflammation,” and sub-classified as to whether it affects the anterior segment of the eye  in which it is restricted to the cornea, anterior chamber, iris, ciliary body, and lens, or it selectively affects the posterior segment, which includes the pars plana region of the ciliary body (pars planitis), the vitreous gel (vitritis), the retina (retinitis), the retinal vessels , the choroid (choroiditis), or the optic nerve .The term “Uveitis” is a misnomer since it suggests that the focus of inflammation is the uvea. Discrete parts of the uvea can be affected separately: the iris (iritis), ciliary body , choroid (choroiditis), or entire uvea .Uveitis according to the SUN criteria is classified by its underlying cause and then according to its anatomic location , contain rich networks of innate immune cells  which, together with the parenchymal cells, secrete a wide range of mediators which underpin IP  rims of the retina contain a small population of DCIR+ MHC Class IIhi DCs, as does the corneal periphery , the cornea, the conjunctiva, and periocular fascia  are separated from the blood and lymphatic circulations by the blood–aqueous barrier and the blood–retinal barrier . The epithelial cells of the ciliary body maintain the intraocular pressure by pumping fluid which drains through the porous trabecular meshwork of the anterior chamber into the blood and lymphatic vessels of the episclera . The sclera itself, like the central cornea, is avascular.Blood–aqueous barrier has two components – tight junctions between the endothelial cells of the ciliary blood vessels and similar junctions between the lining epithelial cells . The RPE is a terminally differentiated layer of neuroectoderm-derived cells formed embryologically by cells of the developing outer layer of the optic cup  contain lymphatics, the intraocular compartment of the eye lacks traditional lymphatics. Aqueous fluid from the anterior chamber, presumably containing soluble antigen shed physiologically, drains via episcleral blood vessels (aqueous veins) through the venous circulation to thymus, liver, and spleen . There is also a site-specific eye-draining lymph node (DLN) which receives soluble and cell-associated antigenic material from the eye . CD8 T cells have a unique role in maintaining HSV latency at the trigeminal ganglion  and pathogen recognition receptors . Conceptual shifts in the self/non-self paradigm underpinning adaptive immunity have emerged from evidence that innate immune recognition of foreign antigens has some degree of specificity . This irs PRRs; , and to rs PRRs; . While tAt its core, IP is a form of tolerance expressed through tissue-specific properties (see above), is shown to be inducible toward foreign and alloantigens, and is assumed to underpin tolerance to ocular self-antigens. As a general hypothesis therefore, we can consider tissue-centered immunological tolerance as additional to the well-established central and peripheral tolerance mechanisms . Tissue-+ professional antigen presenting cells , lack of lymphatics, absence of MHC Class IIls APCs; .in vitro, to exert T cell suppressive activity  and RDH8 (retinol dehydrogenase 8) are liable to retinal degeneration, particularly that induced by light  required for metabolizing retinal (vitamin A) to RA, and all-trans retinal itself has recently been shown to induce Tregs in vitro . Howeverby light . Howeverby light . Indeed by light . Inductiby light  probablyby light .Aire required for negative selection of certain tissue-specific antigens presented by mTECs) develop mild to moderate ocular inflammation as part of a multiple autoimmune diathesis  and clearance of cell debris by resident tissue scavenger cells. However, if the initial encounter with antigen involves cell necrosis and/or “adjuvant” effects of microorganisms chanisms , an activia Fas/FasL  administration for inducing tolerance: intravenous (iv), subcutaneous (s/c), mucosal , intraperitoneal (ip), and intraocular (io). Io injection involves antigen uptake by APC  and induFas/FasL . SystemiFas/FasL . This reFas/FasL . The tolFas/FasL , and by Fas/FasL , from miFas/FasL .Trafficking studies using tagged molecules in mice injected io, or after application to the abraded cornea, indicate that soluble antigen rapidly reaches the eye-DLN within 30 min , 2006 an+ Tregs from mice injected io with antigen. The nature of the APC which promotes this tolerance is unclear, but mice deficient in cells expressing the macrophage surface marker F4/80, fail to generate tolerance after io injection , enter stration . Since tmponents , a possivia the blood or after a first pass through the DLN and thence to the spleen via the LN conduit system, high endothelial venules (HEV) and efferent lymphatics (via DLN to the spleen). Models which suggest that TGFβ-treated F4/80+ peritoneal macrophages preferentially mirror ocular IP overstate the case  vs cell-associated antigen (hours) trafficking from the eye or indeed from any LN drainage site is important in the context of induction of tolerance vs immunity. LN resident APC, which will preferentially capture fast-tracking soluble antigen as it percolates along the conduits, present low levels of specific antigenic peptide–MHC Class II (p-MHCII) complexes, while migratory DCs entering the DLN several hours later present high levels of p-MHCII . Both rein vitro studies, through mediators such as NO, PGE2, and retinoids . Direct infectious uveitis is less common while non-infectious uveitis is presumed to be (auto)immune in character. Despite their low expression on ocular cells, certain forms of uveitis have strong links with MHC Class I antigens  in humans and mice  have been suggested to underpin breakdown of tolerance in this model . InteresImmune privilege appears not to afford much protection against the damaging effects of uveitis possibly because IP works at the level of tissue homeostasis, mainly keeping healthy tissue free of random migrants which might provoke inflammation. However, when faced with a serious challenge, IP dismally fails to prevent severe destruction: in uncontrolled sight-threatening uveitis, both infection and the immune response to infection, can cause permanent structural damage. Therapies such as anti-TNFα disable the destructive effects of inflammation while permitting harmless monocytes to traverse the tissues without causing damage , scleral, and retinal grafts. However, IP does not protect against allograft rejection: even artificial corneas constructed from pig collagen, are rejected chanisms .+ macrophages and peripheral lymphatics . It is too early to decide whether these approaches are fanciful, but systemic immunosuppression is required to delay rejection of such grafts even for a short time, and accepted grafts do not appear to integrate with retinal neuronal circuits .Toxoplasma gondii and herpes simplex virus, reside latently in privileged sites such as the eye and brain bacterial, parasitic, and fungal infections such as trachoma, onchocerca, toxoplasmosis, herpes stromal keratitis in which there can be extensive tissue damage), is caused by a robust or even exaggerated immune response. Thus although the host survives, blindness may be the cost. The corollary is also true, as evidenced by the failure of IP in an aging immune system to protect against the re-awakening of latent infectious disease, much of which was contracted in the neonatal and early childhood years. Interestingly, those rare fatal cases of CNS HSV infection in children appear to be linked to a mutation in TLR3, providing an example from Nature in which defective innate immunity tips the balance in this precarious struggle between immunity and infection .It is clear from the above that ocular IP is a finely judged act which can readily tip. This applies to many physiological processes and Figure 4A), in part due to impaired complement Factor H binding to sulfated glycosaminoglycans  assist in clearing drusen . RPE cells normally produce anti-angiogenic factors , but can switch to produce pro-inflammatory factors such as VEGF, which promote wet AMD  macrophages associated with IP. Thus IP can be breached not only by severe overwhelming inflammatory disease, but by chronic, low grade angiogenesis-associated inflammation as in chronic uveitis and AMD. Moreover, pathological subretinal neovascularization can be reversed by utilizing IP-promoting properties of FasL  through aging and chronic disease (disabled IP) to fulminant (infectious) retinal necrosis (absent IP). Much of this activity is considered “auto-inflammatory” involving activation of innate immune receptors on various subsets of macrophages, but an adaptive immune response in AMD, involving lipid or proteolipid antigen and CD1a may also contribute to AMD-like disease . This haFigure 1) and may initiate an inflammatory response  is the fourth commonest cause of world-wide blindness, potentially increasing as the epidemic of diabetes expands . DR is aukocytes . Trappedukocytes , and actukocytes  but alsoukocytes  which haukocytes . The ocuukocytes . PDR in An interesting convergence of dysregulated metabolism and activation of immune cells has emerged through the discovery of the succinate receptor . In contrast, in other ocular tumors, at least experimentally, pro-inflammatory macrophages promote tumor regression . Primary intraocular lymphoma is grouped with CNS lymphoma, a rare extra-nodal variant of non-Hodgkin’s lymphoma  in some tumors of the head and neck is clearly demonstrated by the development of tertiary lymphoid structures (TLS) surrounding the tumor. TLS express intense immunoregulatory activity directed toward reducing chronic inflammation, a recognized poor prognostic sign, and have been likened to sites of induced IP. Constitutive IP in the eye may behave like a “TLS” to protect the host in cases of intraocular lymphomas but is a dangerous strategy .However, due to the rarity of primary intraocular lymphoma, their biology is poorly understood and animal models have not been very informative so far, thus the call for multicenter studies to investigate these tumors is timely .Another experiment of Nature is revealed by cancer-associated retinopathy (CAR). Retinal antigens aberrantly expressed in extra-ocular tumors induce serum antibodies and T cell responses, invoking a para-neoplastic syndrome of progressive retinal degeneration and eventual blindness . Early sCancer-associated retinopathy also provides insight into the nature of ocular IP and supports the notion of immunological ignorance (antigen sequestration) as one form of IP. However, the discussion above clearly shows that “all roads lead to Rome” and that ocular IP, just like immunological tolerance generally, is subject to many checkpoints. It is not intrinsically diff-erent from other forms of immune tolerance .via central and peripheral mechanisms. However, there is an evolving understanding that the target tissue and its microenvironment can also modify the immune response (Immune regulation/tolerance induction occurs primarily response  and how The ocular immune response encapsulates the full range of classical and non-classical immune responses and demonstrates many features which are reflected in other tissues, but eye tissues by modifying these responses reveal unexpected and novel features, which are relevant to immune responses generally. In addition, IP involves many recognized immunoregulatory processes, including induction of Tregs, and is inducible and transferable. This has therapeutic potential, particularly for devising ways to restore tolerance in ocular inflammatory disease, and for preventing rejection of cells and tissues, such as stem cells, currently being considered for treatment of world-wide blinding diseases such as AMD.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.The authors thank Drs Mariapia Degli-Esposti and Matt Wikstrom for critical reading of the manuscript. Original research by the authors referenced in this article was supported by the Development Trust of the University of Aberdeen and Action Medical Research, UK. We also thank Mr. Gordon Stables for the design and preparation of the figures.


Escherichia coli (STEC) may cause bloody diarrhea and hemorrhagic colitis (HC), with subsequent systemic disease. Since genes coding for Shiga toxins (stx genes) are located on lambdoid prophages, their effective production occurs only after prophage induction. Such induction and subsequent lytic development of Shiga toxin-converting bacteriophages results not only in production of toxic proteins, but also in the lysis  of the host cell. Therefore, one may ask the question: what is the benefit for bacteria to produce the toxin if they die due to phage production and subsequent cell lysis? Recently, a hypothesis was proposed (simultaneously but independently by two research groups) that STEC may benefit from Shiga toxin production as a result of toxin-dependent killing of eukaryotic cells such as unicellular predators or human leukocytes. This hypothesis could make sense only if we assume that prophage induction (and production of the toxin) occurs only in a small fraction of bacterial cells, thus, a few members of the population are sacrificed for the benefit of the rest, providing an example of “bacterial altruism.” However, various reports indicating that the frequency of spontaneous induction of Shiga toxin-converting prophages is higher than that of other lambdoid prophages might seem to contradict the for-mentioned model. On the other hand, analysis of recently published results, discussed here, indicated that the efficiency of prophage excision under conditions that may likely occur in the natural habitat of STEC is sufficiently low to ensure survival of a large fraction of the bacterial host. A molecular mechanism by which partial prophage induction may occur is proposed. We conclude that the published data supports the proposed model of bacterial “altruism” where prophage induction occurs at a low enough frequency to render toxin production a positive selective force on the general STEC population.Shiga toxin-producing  Escherichia coli is a Gram-negative bacterium, commonly known as an intestinal commensal of mammals including humans. However, some E. coli strains are pathogenic to humans. These include the Shiga toxin-producing E. coli (STEC), particularly a subset of strains classified as enterohemorrhagic E. coli (EHEC). The development of severe diseases such as the hemolytic uremic syndrome (HUS) and hemorrhagic colitis (HC) by these strains, including the most intensively studied serotype O157:H7, depends on production of Shiga toxins  and EHEC . The C-terminal part of the A-subunit is anchored to the B-subunit pentamer  are not of E. coli chromosome origin, but are part of lambdoid prophages  is strongly inhibited in the prophage state, due to the activity of the cI repressor  a hypothesis explaining how STEC might benefit from Shiga toxin production  of Shiga toxin-converting prophages is significantly more frequent than that of other known lambdoid prophages , the actual frequency of the switch from lysogenic to lytic development in an untreated bacterial host is still low  revealed that H2O2 is significantly less effective in both laboratory E. coli strains , induction occurs at most in a small percentage of cells  induces lytic development in about 10–30% of lysogenic cells in the culture  can provoke prophage induction at low frequencies. As previously discussed, adding chelating compounds, such as EDTA, to STEC cultures promotes phage induction and results in high titers of Shiga toxin-converting phage , they may be at risk interacting with T. pyriformis or T. thermophila (predators). Interestingly, Carruthers et al.  the mammalian immunological system. However, are there other benefits to bacteria possible?in vitro that the stx2 mutant of a STEC strain was less effective in adherence to epithelial cells than its wild-type counterpart. Moreover, the mutant revealed a lower capacity to colonize mouse intestine. Therefore, it was concluded that Shiga toxin promotes intestinal colonization, possibly also in humans . In fact, studies on bacteriophage λ, a close relative to Shiga toxin-converting phages, demonstrated that induction of the prophage by H2O2 is over 2 orders of magnitude more efficient in E. coli oxyR mutants than in wild-type hosts  is a transcription regulator and a major regulatory factor stimulated during oxidative stress  (for the description of the immunity analysis of Shiga toxin-encoding bacteriophages see Allison et al., E. coli strains present in the intestine or further propagation of bacteriophages on such strains if lytic development of phages is chosen after infection of sensitive bacteria. The latter scenario could also result in production of larger amounts of Shiga toxin, which would provide an additional benefit for STEC. Although it was demonstrated that there are multiple integrations sites for Shiga toxin-converting phages in E. coli genomes, and that superinfection of E. coli lysogenized by isogenic phages bearing stx genes can occur, such superinfection leads to lysogeny rather than lysis (Fogg et al., E. coli susceptible to Shiga toxin-converting phage infection.Recently, two research groups proposed independently a hypothesis that can explain the bacterial benefit from producing Shiga toxins, even if production is coupled with prophage induction and subsequent bacterial cell death (Łoś et al., 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.


Inverse associations between allergic disease and having pets or siblings are commonly attributed to the hygiene hypothesis. As an extension, one could posit that a less diverse gut microbiome in the infant, also linked with the development of allergic disease, would be a function of fewer microbes in the home environment. Piglet studies, however, indicate that greater microbe diversity in the environment actually leads to reduced diversity of the gut microbiota. In this study, we characterize the infant gut microbiota in relation to environmental factors traditionally associated with the hygiene hypothesis.The study comprised a small sub-sample of 24 infants from the Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort. Birth mode was obtained from medical records, and mothers reported on pets, siblings, and breastfeeding. Fecal samples were collected at age 4 months, and microbiota composition was characterized by high-throughput 16S rRNA sequencing.As reported by others, breastfed infants had lower microbiota richness and diversity compared to formula-fed infants. Microbiota richness and diversity were increased in infants living with pets, whereas these measures were decreased in infants with older siblings. Infants living with pets exhibited under-representation of Bifidobacteriaceae and over-representation of Peptostreptococcaceae; infants with older siblings exhibited under-representation of Peptostreptococcaceae.Two traditionally protective “hygiene hypothesis” factors have opposite effects on infant gut microbiota diversity, while apparently selecting for distinct combinations of intestinal microbes. This suggests that microbiota composition, rather than diversity, may be the more important driver of the “microflora hypothesis” of allergic disease.


Plant secondary metabolites play a key role in plant-insect interactions, whether constitutive or induced, C- or N-based. Anti-herbivore defences against insects can act as repellents, deterrents, growth inhibitors or cause direct mortality. In turn, insects have evolved a variety of strategies to act against plant toxins, e.g., avoidance, excretion, sequestration and degradation of the toxin, eventually leading to a co-evolutionary arms race between insects and plants and to co-diversification. Anti-herbivore defences also negatively impact mutualistic partners, possibly leading to an ecological cost of toxin production. However, in other cases toxins can also be used by plants involved in mutualistic interactions to exclude inadequate partners and to modify the cost/benefit ratio of mutualism to their advantage. When considering the whole community, toxins have an effect at many trophic levels. Aposematic insects sequester toxins to defend themselves against predators. Depending on the ecological context, toxins can either increase insects’ vulnerability to parasitoids and entomopathogens or protect them, eventually leading to self-medication. We conclude that studying the community-level impacts of plant toxins can provide new insights into the synthesis between community and evolutionary ecology. Plants have evolved a whole arsenal of defence strategies against herbivores, including the synthesis of a tremendous variety of chemical compounds. Chemical defence products may range from low molecular weight compounds, called secondary metabolites, to peptides and proteins that are active against insects . SecondaThe insecticidal properties of these compounds  are diverse: they may act as repellents or feeding deterrents, or induce direct toxicity leading to symptoms ranging from the inhibition of larvae or insect growth to death. In some cases, recent advances in molecular biology have made it possible to accurately identify the cellular or molecular targets of these toxins. Another active field of investigation is the elucidation of the plastic nature of such defence responses, modulated both by phytophagous (and pathogens) attacks and abiotic factors including nutrient availability , light  and drouBrassica sp. confirmed the latter hypothesis, but only when the plant was not in competition with neighbouring plants [Both constitutive and induced resistance have been shown to generate costs, described as allocation costs, resource-based trade offs between resistance and fitness, or as ecological costs, decreases in fitness resulting from interactions with other species .vs. repellence by plant odors have led to pioneering studies in the domain of plant-insect interactions, and current investigations are now focusing on identifying the numerous volatiles emitted by plant flowers or other organs and their additive and synergistic effects. Using genetically modified plants without scent bouquets, linalool, a monoterpene alcohol emitted by flowers of Phlox paniculata has been identified as the major repellent against the ant Nasius niger [Lonicera maackii were proffered to the generalist insect Spodoptera exigua, only apigenin appeared effective in deterring feeding whilst the related flavone luteolin had no effect [Brassica oleracea, Newton et al. [Brevicoryne brassicae consistently preferred plants producing progoitrin. At population level, protogoin production positively correlated with B. brassicae infection whilst sinigrin production negatively correlated with damage inflicted by the whitefly Aleyrodes proletella. Differential selection by herbivores influences the maintenance of large inter and intra-population variation in glucosinolate chemotypes in natural wild cabbage populations.Field and laboratory observations of insect attraction us niger . Repelleo effect . The conn et al.  have shoS. exigua caterpillars [i.e., specialisation). Many plant compounds act as insect growth inhibitors and depending on the dose ingested, their effect can range from delayed development to a substantial reduction in fecundity and death. For example, the ingestion of luteolin flavone caused severe deleterious effects on rpillars , althougrpillars . A 2 g/LOrgyia leucostigma, can be directly attributed to the tannins or to oxidative stress. It is also likely that hydrolysable tannins, whose hydrolysis is facilitated in the insect digestive tract, will act differently from the less biodegradable condensed tannins [The role of tannins as plant defence compounds, due to their ability to complex proteins, has been extensively investigated, but contrary to early theories  and to w tannins . Deterre tannins ).Utetheisa ornatrix [Insects have evolved multiple strategies to overcome the diverse toxins produced by plants, including contact/ingestion avoidance, excretion, sequestration, toxin degradation, and target-site insensitivity (reviewed in ). In theornatrix . Larvae Aristolochia produce aristolochic acids, which are sequestered by specialist Troidini butterflies, while derived species produce labdanoic acids which negatively affect the specialist butterflies. In milkweeds (Asclepias), cardenolides, which are sequestered by specialist monarch butterflies, show a phylogenetic decrease, while phenolic compounds, which are not sequestered, show a phylogenetic escalation [i.e., plant tolerance rather than chemical defence appears to be selected during the course of co-evolution [Over the last 50 years, plant defence theories have been formulated to explain the impressive variation in abundance, distribution, and diversity of plant secondary compounds and other defensive traits. Traditional theories of enemy-driven evolutionary dynamics (or antagonistic co-evolution) have hypothesised that defensive traits escalate through a co-diversification process. Applied to plant-insect interactions, this co-evolutionary arms race theory predicts a never ending race between plants innovating to produce new insecticidal toxins (and many other anti-insect weapons) and insects evolving resistance traits . In thiscalation . Interesvolution . TherefoPlant toxins, by definition, affect other organisms negatively, so toxins are expected to be involved only in conflictual relationships between species. However, they are not restricted to purely antagonistic interactions and also play an important role in mutualistic interactions. Indeed, conflicts are widespread in mutualisms because interacting species tend to limit their costs and increase their benefits at the expense of their partners. Plants can use toxins to alter the balance between costs and benefits to their advantage using several mechanisms that we will describe here in detail. To date, research in this area has focused on plant-pollinator interactions, but the mechanisms also apply to other mutualisms e.g., plant-seed dispersers.Aloe vryheidensis contains phenolics, whose bitter taste repels unwanted honey bees and sunbird nectarivores and whose dark colour attracts suitable frugivorous and insectivorous bird pollinators [Gelsemium sempervirens) contains the indole alkaloid gelsemine, a secondary metabolite toxic to vertebrates, which is highly distasteful and a deterrent for most pollinators [Bombus impatiens and B. bimaculatus. In both examples, the toxins simultaneously attract suitable pollinators and repel those less well suited. In the extreme case of nectar robbing, it has also been shown that toxic nectars deter thieves but not legitimate pollinators [Plants can exclude species that are too costly and/or that do not provide them enough benefits by means of a wide variety of barriers, including toxins. Indeed, insecticidal toxins are very often produced in nectar, pollen, and seeds or fruits . Baker  found thlinators . The neclinators , but whilinators ,52. In slinators . Like helinators  and SectTo date, most studies on toxic nectar have focused on single plant species, but the community-level consequences of toxic nectar should also be considered. Indeed, it has been shown that different experimental “ecological” contexts, such as the presence of alternative non-toxic nectar sources, influence pollinator deterrence due to alkaloids in floral nectar . In natuTrollius europaeus allows the plant to limit seed predation costs inflicted by its specific pollinator’s larvae Chiastocheta spp. [Chiastocheta flies, and thereby favoured the evolution of flower morphological specialisation for those flies [Nicotiana attenuata optimises the number of flower visitors per volume of nectar produced, allowing plants to keep their nectar volumes small and thereby reduce the costs of mutualism [Even suitable partners are tightly controlled in order to limit the costs and maintain the benefits of mutualism. For example, a physiological control mechanism has been described in plants pollinated by insects whose larvae develop on seeds, where selective fruit abortion of over-infested fruits limits plant costs and makes it possible to control the partner . Similareta spp. ,57. The se flies . In thisutualism , while pGelsemium sempervirens toxic nectar was shown to encourage pollinators to leave plants after visiting only a few flowers, thus reducing self-pollen transfer by about half [Partner control through toxins can also occur at a fine mechanistic, behavioural level. For example, the cycasin toxin of cycads is more abundant in female than in male cones, forcing their herbivore pollinating beetles to concentrate in male cones, which might prevent seed predation and ensure pollen export . In Gelsout half . Howeverout half ,58. ThisDalechampsia vines first evolved toxic triterpen in resins to protect staminate flowers against pollen feeders, which later became a reward for resin-collecting bees [Dalechampsia vines is a “transfer” exaptation in that it is captured by the reward function at the expense of the defence function, but in other systems the toxins impact simultaneously on antagonists and mutualists. In the globeflower Trollius europaeus, the flavonoid adonivernith is particularly abundant in the sepals forming the globose corolla [Plant traits evolve in response to the selection pressures exerted by many agents, abiotic conditions, competitors, herbivores and mutualists. In the case of toxic secondary compounds, the major selection pressure is the presence of herbivores. Under this scenario, toxins first arise as an anti-herbivore defence and subsequently impact on the interactions with mutualists. For example, ing bees ,60. In sing bees . The res corolla , which i corolla .i.e., an ecological cost of anti-herbivore defence.Toxins linked with anti-herbivore defence sometimes impact on mutualistic interactions in a positive way for the plant, as in the two examples above, but they can also have a negative impact, as it has been hypothesised for toxic nectars, which might simply be a by-product of the presence of toxins in other parts of the plant . In thisPlant insecticidal toxins do not only affect insects (herbivores and pollinators), but also can have positive or negative effects on their natural enemies. Natural enemies of insects include macropredators (invertebrate and vertebrate predators) and micropredators . Heliconius butterflies from the tropics of the New World that are able to sequester cyanoglucosides from Passiflora host-plants to varying degrees [Heliconius species and on the chemical characteristics of the Passiflora plants exploited, the butterflies are more or less toxic, but they all benefit from the same protective aposematic pattern. Many insects sequester plant insecticidal toxins that are then used as protection against predators, sometimes throughout all the ontogenetic stages see  above. T degrees . These bJunonia coenia , which sequesters iridoid glycosides from its host plants and uses them as anti-predator defences, larvae feeding on diets with high concentrations of iridoid glycosides are more likely to have lower immune response than those feeding on diets with high concentrations of these compounds. This suggests that larvae feeding on plants with high toxin concentrations might be less well defended against parasitoids, whilst at the same time being better defended against predators [Plant insecticidal toxins can have a positive impact on insect natural enemies in several ways. Insecticidal toxins may slow down insect growth rate, extending the timeframe during which the herbivore is vulnerable to parasitism or predation by its natural enemies. Toxins may also weaken host immune responses, rendering them more susceptible to parasitism. For example, the ingestion of certain plant secondary metabolites  can diminish the immune response by directly interfering with melanisation , or moreredators . Bacillus thuringiensis kurskaki (Btk) for the cabbage looper Trichoplusia ni was shown to increase on tomato relative to cucumber and pepper leaves [Heliothis zea [T. ni collected in tomato greenhouses [The toxicity of the natural entomopathogen r leaves . The chethis zea . As Btk enhouses . Parasemia plantaginis (Arctiidae) caterpillars to encapsulate a foreign object varies according to the amount of antioxidant compounds  present in the host plant species [Hyposoter exiguae has been demonstrated and adding nicotine to the diet of the tobacco hornworm induced higher larval mortality in its specialist parasitoid Cotesia congregata  induces increased mortality when ingested with salicin (a phenolic glycoside present in aspen foliage), but decreased mortality in the presence of tannins, another common group of plant phenolic compounds [Different plant compounds have been shown to have both positive and negative effects on entomoviruses . For exaompounds . There is overwhelming evidence that the impact of pathogens can be mitigated by the insect’s diet. The mixed diet adopted by polyphagous insects might indicate a compromise between the negative impact of some plant toxins on herbivore and their positive effects on natural enemies . Pharmacophagy is the active collection of plant substances for the purposes of protection against pathogens rather than nutrition: toxic plants are preferentially foraged even if it implies a fitness cost , because it confers protection against predators or pathogens . SeveralPlatyprepiavirginalis caterpillars preferentially consumed hemlock instead of lupine, their primary host plant, in field choice experiments; unparasitised caterpillars were more likely to survive to adulthood when feeding on lupine, whereas parasitised caterpillars were more likely to survive on poison hemlock [Grammia incorrupta (Arctiidae) improve their survival by selectively feeding on diets rich in pyrrolizidine alkaloids that confer resistance against tachinid flies, while excessive ingestion of these toxins reduces the survival of unparasitised caterpillars [Furthermore, there is increasing evidence that infected insects change their diet foraging behaviour and actively seek plants rich in secondary metabolites inducing a lower growth rate rather than a nutrient-rich but toxin-poor plant diet (self-medication). For example, parasitoid-infested  hemlock . Host-plrpillars . Howeverrpillars . VariatiInsects harbour a large diversity of symbionts, including gut microbiota and bacteria found inside the insects’ cells (endosymbionts). Of the many roles played by symbionts in insect biology, they have a key role in insect nutritional ecology by helping with digestion and providing nutrients that are limited or lacking in the diet  strategies. Optimal IPM strategies should take into account not only the target insect pest throughout its development, but also the whole ecological context, including the plant allelochemicals, and the insect’s competitors, predators, pathogens and symbionts.


The magnitude of the breast cancer problem implores researchers to aggressively investigate prevention strategies. However, several barriers currently reduce the feasibility of breast cancer prevention. These barriers include the inability to accurately predict future breast cancer diagnosis at the individual level, the need for improved understanding of when to implement interventions, uncertainty with respect to optimal duration of treatment, and negative side effects associated with currently approved chemoprevention therapies. None-the-less, the unique biology of the mammary gland, with its postnatal development and conditional terminal differentiation, may permit the resolution of many of these barriers. Specifically, lifecycle-specific windows of breast cancer risk have been identified that may be amenable to risk-reducing strategies. Here, we argue for prevention research focused on two of these lifecycle windows of risk: postpartum mammary gland involution and peri-menopause. We provide evidence that these windows are highly amenable to targeted, limited duration treatments. Such approaches could result in the prevention of postpartum and postmenopausal breast cancers, correspondingly. The field of cancer prevention was formalized in the 1970s and coincided with the recognition that most cancers develop through a multi-step process with long latency . Breast Conceptually, there are multiple strategies for breast cancer prevention. Primary prevention is focused on blocking tumor cell initiation by minimizing carcinogen exposure or enhancing detoxification. Examples include avoiding the use of ionizing radiation on developing breast tissue, limiting exogenous estrogen exposure, and supplementation with dietary agents such as the cruciferous isothiocyanates, which activate the p450 carcinogen metabolism pathway . UnfortuBreast cancer was the first malignancy where targeted drug treatment trials in the adjuvant setting demonstrated a concomitant secondary prevention benefit for subsequent contralateral disease. An average 50% reduction in new primary breast cancers was identified among women treated for 5 years with the SERM, tamoxifen . More reGiven the clinical success of anti-hormone based chemoprevention, it is surprising that of the more than 2 million high-risk women in the US alone, the number of women using tamoxifen for prevention is declining, with reports of 120,000 in 2000 to 20,500 in 2010 . SimilarThe toxicity profile and therapeutic index of SERM therapy is a clearly identified detractor to the drug’s acceptance among women ,7. When An additional limitation to women embracing breast cancer chemoprevention strategies is that many women may not be informed of their increased risk and thus do not know they are candidates for preventive strategies. While several models are currently utilized to predict a woman’s breast cancer risk and guide indication for chemoprevention, a comprehensive model that incorporates all known risk factors does not exist. The Breast Cancer Risk Assessment Tool (BCRAT), also known as the GAIL model, is commonly used to define high-risk women by predicting 5-year and lifetime breast cancer risks. To predict breast cancer risk, the GAIL model uses current age, age at menarche, age at first birth, number of first degree relatives with breast cancer, number of previous breast biopsies, and any pre-malignant histology results, with age being the most heavily weighted factor . Anotherneu positive and triple negative breast cancer subtypes remains unmet.Finally, an additional limitation of endocrine based chemoprevention agents is their selection against only ER positive breast cancers. Thus, SERM therapy is predicted to prevent only 38% of breast cancers during the time of treatment and would, therefore, be ineffective for the majority of women . The neeThe ideal chemoprevention agent would be highly effective at eliminating breast cancer with few off-target effects, required for a limited duration of time, and inexpensive. The SERMs meet each of these ideals only partially, as discussed above. None-the-less, tamoxifen is a success story for chemoprevention when compared to other agents tested against lung and prostate cancer, and important lessons learned from these studies need to guide further prevention research. For example, data from epidemiological and preclinical animal-model studies suggest that there are key components of the diet that are cancer-protective. These data led to a number of vitamin-based intervention trials, where, unfortunately, the results were not as expected. For example, not only did vitamin E fail to decrease risk of prostate cancer in high-risk men , and vitObservational studies have addressed the potential for use of non-steroidal anti-inflammatory drugs (NSAIDs) as breast cancer preventive agents, with mixed results. In prospective outcome studies, use of the non-selective COX-2 inhibitors aspirin and ibuprofen was associated with decreased recurrence and breast cancer related death ,18. HoweIn addition to the NSAID observational studies, evidence is increasing that COX-2 is causally involved in early stage breast cancer and thus a viable target for prevention. Thea Tlsty and colleagues have studied COX-2 expression in early malignant human tissues and shown that ductal carcinoma in situ (DCIS) lesions, along with normal breast epithelium adjacent to DCIS, express high levels of COX-2. In their cohort, expression was highest in the normal tissue adjacent to DCIS, implicating the upregulation of COX-2 in the very earliest stages of transformation . FurtherBased on experience gained to date, it is clear that several barriers significantly reduce both the feasibility of breast cancer prevention and patient confidence in these strategies. As described above, barriers include the inability to accurately predict at the individual level an impending or future breast cancer, the need to understand when in a woman’s life to implement the intervention, uncertainties regarding optimal duration of treatment, and negative side effects associated with current drugs. None-the-less, the unique biology of the mammary gland will likely permit the resolution of many of these barriers, making breast cancer prevention a viable objective. Not only does the majority of mammary gland development occur postnatally, but terminal differentiation is conditional and developmentally plastic. While these features may contribute to the high susceptibility of the breast to transformation, these feature have also permitted the identification of lifecycle-specific windows of breast cancer risk that may be amenable to therapeutic interventions .The unique biology of the breast begins in utero with breast ductal anlagen development . After bPivotal epidemiologic studies established that lifecycle events predict breast cancer risk, including age at puberty, the number of menstrual cycles across a lifetime, age at first birth, multiparity, and age at menopause ,39. Impoincrease in risk for breast cancer that occurs after each childbirth, regardless of the woman’s age [Multiple, large population studies demonstrate a transient an’s age –45. Albran’s age . Data shan’s age ,45. Furtan’s age ,46–48.To prevent the incidence of postpartum breast cancer, we must first understand how this unique life window promotes breast cancer. While pregnancy hormones are obvious candidates, the postpartum window also includes the unique process of mammary gland involution, which contributes to breast cancer progression in rodent models . During The identification of the mechanisms by which the postpartum involuting breast may promote breast cancer has opened the potential for specific chemoprevention strategies that target this at-risk population. The increase in COX-2 expression during involution provides support for targeting the COX-2 pathway and proof of concept was shown using a preclinical model of postpartum breast cancer. In this model, inhibition of COX-2, via NSAID administration during the two week period of murine postpartum involution, reduced mammary gland collagen deposition, decreased tumor COX-2 expression, and blocked tumor cell growth and invasion . ImportaAge related involution that occurs with menopause has been identified as marker of breast cancer risk; however the mechanism remains unknown . MenopauMenopause is a difficult time period to study in women due to the inability to readily identify its onset combined with wide inter-individual variation in the length of time (2–5 years) in which this process occurs. The use of pre-clinical models, however, has allowed researchers to study the impact of loss of ovarian function on breast cancer. The most commonly used model of menopause is surgical ovariectomy (OVX). Similar to humans, obesity has little effect on mammary tumor incidence in rodents prior to OVX . In contGiven that an impaired metabolic response to OVX-induced weight gain appears critical to the emergence of obesity-associated tumor promotion, the window of menopausal weight gain may provide a narrowed window during which interventions that improve metabolic control could be used to target mammary tumor growth. Metformin, a commonly prescribed anti-diabetic drug, is known to improve metabolic control. When administered to obese tumor-bearing rats during the period of OVX-induced weight gain, metformin significantly decreased tumor burden after 4 weeks . ImportaDevelopment of the mammary gland occurs in discrete and identifiable lifecycle windows that coincide with ‘hot-spots’ for breast cancer risk. These developmental windows are characterized by stromal–epithelial interactions that likely drive cancer progression. Postpartum breast involution and peri-menopause represent two lifecycle windows that are highly amenable to intervention. While additional studies are certainly necessary to confirm these approaches, current data suggest that targeting these ‘tissue-remodeling’ windows could provide the opportunity to increase treatment efficacy while decreasing the negative side effects associated with long term treatments, thereby improving effectiveness and patient acceptance of breast cancer prevention strategies.


Most cells in mammalian tissues usually contain a diploid complement of chromosomes. However, numerous studies have demonstrated a major role of “diploid-polyploid conversion” during physiopathological processes in several tissues. In the liver parenchyma, progressive polyploidization of hepatocytes takes place during postnatal growth. Indeed, at the suckling-weaning transition, cytokinesis failure events induce the genesis of binucleated tetraploid liver cells. Insulin signalling, through regulation of the PI3K/Akt signalling pathway, is essential in the establishment of liver tetraploidization by controlling cytoskeletal organisation and consequently mitosis progression. Liver cell polyploidy is generally considered to indicate terminal differentiation and senescence, and both lead to a progressive loss of cell pluripotency associated to a markedly decreased replication capacity. Although adult liver is a quiescent organ, it retains a capacity to proliferate and to modulate its ploidy in response to various stimuli or aggression , oxidative stress, toxic insult, and chronic hepatitis etc.). Here we review the mechanisms and functional consequences of hepatocytes polyploidization during normal and pathological liver growth. Polyploidy, the state of having an increase in the number of chromosomes sets, is a widespread physiological phenomenon observed particularly in plants, fungi, insects, fishes, and amphibians . The addcell-cell fusion, genesis of polyploid cells may occur independently of cell proliferation, as it has been observed during physiological development in osteoclasts [Several mechanisms have been involved in the physiopathological emergence of polyploid cells in mammals. During eoclasts  and skeleoclasts  or aftereoclasts . In thisOther mechanisms are directly associated with proliferative state of the cells.During this process, cells alternate S (DNA replication) and G phases, without performing mitosis and give rise to the genesis of autopolyploid cells .Cells can reach metaphase or anaphase A, but nuclear (karyokinesis) and cytoplasmic (cytokinesis) divisions are never observed; the best-studied example being polyploid megakaryocytes . These cDuring this pathological process, cells present an altered Spindle-Assembly-Checkpoint (SAC). The SAC prolongs mitosis until all kinetochores are stably attached to spindle microtubules; when the SAC cannot be satisfied, cells exit mitosis without undergoing anaphase or cytokinesis (genesis of mononucleated tetraploid cells). Mitotic slippage has been observed for example in cells after prolonged mitotic arrest in response to spindle toxins  or in APThis process has been extensively described during pathological division and leads to the genesis of binucleated tetraploid cells. These cells can appear following dysfunction of any of a large number of different proteins controlling cytokinesis process . In addiHepatic polyploidy is a characteristic feature of mammalian liver and accompanies late fetal development and postnatal maturation , 37. In Interestingly, in the adult liver, the genesis of polyploid cells can be reinduced following a variety of signals see .Indeed, after two-thirds hepatectomy, mitogenic signals  induce In adult rodents, DNA synthesis induced by chemical compounds is associated with modifications of polyploid status in the liver. For example, lead nitrate induces the genesis of binucleated hepatocytes . AdjunctHepatic polyploidy can be also modified by pathological overload that induce liver lesions. Different studies have described that liver of Long-Evans Cinnamon (LEC) rat , which exhibits abnormal hepatic copper and iron concentration due to the deletion of the p-type copper transport ATPase gene (Atp7b), possesses a feature of increase in polyploidy (enlarged hepatocytes with huge nuclei) and a delay in mitotic progression. Interestingly, injection of irondextran in normal mice induces liver polyploidization; this effect is inhibited by the oral intake of iron chelator , 61.Hepatocytes submitted to oxidative stressors develop pronounced increase in their polyploid status. Gorla et al. have demonstrated that subsequent to radiation, hepatocytes exhibit evidence for oxidative injury with deletion of intracellular antioxidants  and for increase of polyploidy . FurtherAll together, these results underline an extensive correlation between the generation of polyploid hepatocytes and a variety of cellular stress in the adult liver; however, cellular and molecular mechanisms involved in ploidization modification during pathological state are not well characterized.Our team has focused on the understanding of polyploidy hepatocytes lineage. We previously unveiled that during postnatal development and more precisely after weaning, diploid hepatocytes (mononucleated 2N) can engage either into a normal cell cycle and give rise to two diploid hepatocytes or follow an adaptive cell cycle with incomplete cytokinesis and give rise to one tetraploid hepatocyte (binucleated 2 × 2n) , 33. In In the heart, incomplete cytokinesis has been also implicated in the genesis of binucleated tetraploid cardiomyocytes. In mammals, the growth of embryonic heart results in proliferation of cardiomyocytes (hyperplasia) . After bInterestingly, even if failed cytokinesis is the major event for liver polyploidization during postnatal development, some studies reveal that under certain circumstances, cell fusion can also contribute to this process. Experiments on stem cells and therapeutic applications have discovered that polyploid hepatocytes can be generated following cell fusion between exogenous bone marrow cells and mature hepatocytes , 76. FurRecently, we discovered that the suckling-to-weaning transition strictly controls the establishment of the cytokinesis failure process in the liver. Using a specific immunocytochemistry approach to detect mitotic events in liver tissue, we showed that cytokinesis failure events never occurred in 19-day-old suckling rat (<3%); whereas in 19-day-old rats weaned early (at 15 days), such events were frequent (>35%), and numerous binucleated tetraploid hepatocytes were generated. It is interesting to note that while suckling is prolonged to 25 days, hepatocytes mostly enter into complete cytokinesis events (>95%—data not published). Moreover, we reported there was a new wave of proliferation in the liver associated with the establishment of these specific adaptive cell cycles , 78. We Interestingly, a role of PI3 K-Akt pathway has been also described during a pathological polyploidization process. By overexpressing Akt1, Hixon et al. have demonstrated that VSMCs are able to override the activity of the mitotic spindle checkpoint, facilitating unscheduled degradation of cyclin B, cell-cycle reentry (endoreduplication), and polyploidization process. The same results were obtained by incubating VSMCs isolated from normotensive animals with angiotensin II , which is a key activator of Akt1 in VSMCs. These results demonstrate that Akt1 regulates ploidy levels in VSMCs and contributes to vascular smooth muscle polyploidization and hypertrophy during hypertension .Saccharomyces cerevisiae, polyploidization alters the expression profile of specific genes and regulates certain aspects of physiology and cell morphology [Many examples from the literature illustrate that the acquisition of a polyploid status confers specific biological properties of cells. In the yeast rphology . In planrphology . In mammrphology . Indeed,rphology .In the liver our understanding of the consequences for hepatocytes polyploidization still remains enigmatic. (1) Polyploidy could protect hepatocytes of genotoxic damage by increasing the number of copies of functional genes; this might be especially important for the liver that has a primary function in metabolizing and eliminating toxic compounds. (2) Polyploidy could be an economical solution to growth problems that occur when an organ work within its capabilities, avoiding the great demand in energy that represents cell division. (3) Finally, polyploidy could alter the expression profile of specific genes. Recently, two studies using multitest approach of modular biology underline alteration in a wide range of functional gene groups between diploid and polyploidy hepatocytes. The authors suggest a link between genome multiplication and emergence of specific pathways (increase in metabolic plasticity and for the protection of replicating DNA from oxidative damage) that could promote hepatocyte cell survival and tissue regeneration under stressful conditions , 89.Cellular polyploidization is now well known to be correlated to chromosomal instability appearance and carcinogenesis process development. Indeed, in some tumor types, there is direct evidence for the development of aneuploidy from a transient 4n state . However


Stress initiates adaptive processes that allow the organism to physiologically cope with prolonged or intermittent exposure to real or perceived threats. A major component of this response is repeated activation of glucocorticoid secretion by the hypothalamo-pituitary-adrenocortical (HPA) axis, which promotes redistribution of energy in a wide range of organ systems, including the brain. Prolonged or cumulative increases in glucocorticoid secretion can reduce benefits afforded by enhanced stress reactivity and eventually become maladaptive. The long-term impact of stress is kept in check by the process of habituation, which reduces HPA axis responses upon repeated exposure to homotypic stressors and likely limits deleterious actions of prolonged glucocorticoid secretion. Habituation is regulated by limbic stress-regulatory sites, and is at least in part glucocorticoid feedback-dependent. Chronic stress also sensitizes reactivity to new stimuli. While sensitization may be important in maintaining response flexibility in response to new threats, it may also add to the cumulative impact of glucocorticoids on the brain and body. Finally, unpredictable or severe stress exposure may cause long-term and lasting dysregulation of the HPA axis, likely due to altered limbic control of stress effector pathways. Stress-related disorders, such as depression and PTSD, are accompanied by glucocorticoid imbalances and structural/ functional alterations in limbic circuits that resemble those seen following chronic stress, suggesting that inappropriate processing of stressful information may be part of the pathological process. The organismal response to stress  promotes survival via adjustments to ongoing physiological processes and behavior. The activation of multiple interacting processes, including the behavioral, autonomic, endocrine, and immune systems, produces an integrated stress response. While initially adaptive, prolonged activation of molecular pathways engaged by these systems can cause pronounced changes in physiology and behavior that have long-term deleterious implications for survival and well-being. In essence, prolonged or chronic stress changes the rules under which the body regulates homeostasis, requiring new strategies for successful adaptation. This concept lies at the heart of Selye's initial description of the “general adaptation syndrome,” where after an initial “alarm” stress reaction, the organism is able to successfully manage prolonged stress for substantial periods. Only when homeostatic pressure becomes too great does the individual enter into a state of frank distress, with attendant morbidity and mortality Selye, . ImportaThe literature is replete with examples of the impact of stress on physiologic systems and behavior. For example, our group finds that exposure to a prolonged, unpredictable and non-habituating stress regimen  causes marked increases in cumulative glucocorticoid secretion, sensitization of hypothalamo-pituitary-adrenocortical (HPA) responses to new stressors, decreased heart rate variability, reduced weight gain, decreased sucrose preference and increased immobility in the forced swim test  is often described as an “inverted-U” shaped curve, wherein an optimal level of glucocorticoid signaling is required to produce the most effective organismal response . These neurons synthesize ACTH secretagogues [the most prominent of which are corticotropin-releasing hormone (CRH) and arginine vasopression (AVP)] that are released into the hypophysial portal circulation (median eminence) and transported to the anterior pituitary gland. Corticotropes respond to CRH and AVP by releasing ACTH, which is released into the systemic circulation and causes synthesis and release of glucocorticoids at the level of the adrenal gland. Glucocorticoid secretion is self-limited, undergoing end-product feedback inhibition via binding GRs in multiple brain regions as well as the pituitary gland  signaling is subject to modulation by other proteins, which may affect function in the context of stress. For example, the GR-binding factor FK506 binding protein 51  reduces glucocorticoid binding affinity and GR nuclear translocation Binder, . In PFC,Chronic stress causes a marked reorganization of the central components of the HPA axis. Numerous studies document increases in CRH and AVP expression in parvocellular PVN neurons  and hippocampus  is increased under conditions of chronic stress or glucocorticoid excess  with time. Animals can generally habituate to repeated stressors  in habituation of the HPA axis stress response. The PVT is a midline thalamic nucleus that interconnects with several limbic stress-regulatory regions, including the medial PFC, basolateral amygdala and bed nucleus of the stria terminalis. Lesions of the PVT block habituation of HPA axis responses to repeated restraint , suggesting that habituation may be in part due to reduced strength or salience of perceived sensory cues  result in long-term changes in CNS stress circuits, including up-regulation of CRH expression in the PVN, even in the context of reduced corticosterone responses to individual restraint sessions. As noted above, despite habituation to homotypic stressors, novel stressors will induce a disproportionately large HPA axis stress response relative to acutely stressed controls Figure  Akana e. IncreasThe PVT may mediate sensitization (facilitation) of responses to novel stressors in animals habituated to a homotypic stressor. The PVT is one of a handful of brain regions showing enhanced Fos induction following repeated stressor exposure   and/or nucleus of the solitary tract (NTS). In cortex, repeated stress exposure sensitizes norepinephrine (NE) release following novel stressors  vs. non-habituating (CVS) models, as the latter exhibits a more severe HPA axis “phenotype,” in terms of baseline corticosterone secretion, adrenal hypertrophy and thymic involution  can protect against the development of helplessness behavior, social inhibition and behavioral withdrawal seen following inescapable stress  is confronted with environmental or physical adversity. In human depressives, the link with “actual” stress is less evident, raising the possibility that processes underlying the disorder essentially permit stress related behaviors and physical reactions to occur in the absence of threat. In depressed patients, the prefrontal cortex and amygdala, two critical components of stress circuitry, show abnormal activation patterns without any clear threat present Drevets, , suggestConsiderable progress has been made in understanding neural circuits and processes responsible for chronic stress habituation, sensitization and pathology. However, the neural trigger that differentiates successful from unsuccessful coping remains elusive. Uncovering processes underlying the transition from adaptation and pathology bears consideration of what constitutes “adaptation” and “pathology,” as many responses and behaviors that may appear “maladaptive” make perfect sense in the appropriate context. Indeed, context-inappropriate physiological and emotional responses are hallmarks of stress-related disorders . Moving forward, animal models will need to incorporate an appreciation of the relevance of physiologic and behavioral endpoints to the normal repertoire of the organism under conditions of challenge, and develop testing conditions that can more clearly query how chronic stress can generate situationally inappropriate responses reminiscent of human pathology.The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Remote ischemic preconditioning (RIPC) is the application of a transient and brief ischemic stimulus to a distant site from the organ or tissue that is afterward exposed to injury ischemia, and has been found to reduce ischemia–reperfusion injury (IRI) in various animal models. RIPC appears to offer two distinct phases of endothelial IRI protection, which are presumably mediated through neuronal and humoral pathways.We conducted a comprehensive literature review on the available published data about the potential effect of RIPC in patients undergoing IRI in one or more vital organs.Our search highlighted 24 randomized clinical trials about the effect of RIPC on variable clinical settings . Most of the trials focused on postoperative cardiac or renal function after RIPC with conflicting results. Preconditioning protocols, age limits, comorbidities, and concomitant drug use varied significantly across trials, and therefore no firm conclusions can be drawn using the available data. However, no severe local adverse events were observed in any patient undergoing limb or arm preconditioning.RIPC is a safe and well-tolerated procedure that may constitute a potentially promising innovative treatment in atherosclerotic diseases. Large, multicenter, randomized clinical trials are required to determine an optimal protocol for the RIPC procedure, and to evaluate further the potential benefits of RIPC in human ischemic injury. Transient, brief periods of ischemia are considered to trigger pathways that confer protection against a subsequent, more prolonged ischemia in the same tissue. This phenomenon is known as ischemic preconditioning (IPC). When the precedent ischemic stimulus is applied to a distant site from the organ or tissue that is afterward exposed to injury ischemia, the preconditioning is remote, and thus the procedure is named as remote ischemic preconditioning (RIPC) , adenosine, bradykinin, catecholamines, heat-shock proteins, heme oxygenase, tumor necrosis factor a (TNF-a), angiotensin, and prostaglandins) have been suggested to have a key role in the transduction of the preconditioning stimulus to the remote tissue that is exposed to ischemic injury , a metabolite generated by cells under conditions of ischemia, has similar properties with NO  and thus could be another possible mediator of the RIPC stimulus  were lower in patients who had two sequential 10-min periods of alternate lower limb ischemia immediately after induction of anesthesia and urinary catheterization. However, the rates of adverse major cardiac outcomes, renal impairment, and serum troponin elevation were similar between the preconditioned and control groups  and lung injury (airway resistance)  by Gunaydin et al. , precondThielmann et al.  used theIn a single-blind, randomized clinical trial of 120 patients undergoing elective cardiac surgery , Zimmerman et al.  found thTable Using the same preconditioning protocol in a larger randomized clinical trial of 242 patients undergoing PCI, Hoole et al.  found thSubsequently, Munk et al.  in theirPreconditioning with four cycles of 5-min upper arm ischemia followed by 5-min reperfusion was found to ameliorate contrast medium-induced kidney injury after elective coronary angiography in a randomized control trial of 100 patients with primarily impaired renal function , as well as an optimal protocol for the procedure, need to be further determined in large-scale multicenter RCTs.


Current research efforts are centered on delineating the novel health benefits of naturally derived saccharides, including growing interest in their abilities to influence neurologic health. We performed a comprehensive review of the literature to consolidate all controlled studies assessing various roles of exogenous saccharide compounds and polysaccharide-rich extracts from plants, fungi, and other natural sources on brain function, with a significant focus on benefits derived from oral intake.Studies were identified by conducting electronic searches on PubMed and Google Scholar. Reference lists of articles were also reviewed for additional relevant studies. Only articles published in English were included in this review.in vitro studies have demonstrated the ability of individual saccharide compounds and polysaccharide-rich extracts to modify behavior, enhance synaptic plasticity, and provide neuroprotective effects.Six randomized, double-blind, placebo-controlled clinical studies were identified in which consumption of a blend of plant-derived polysaccharides showed positive effects on cognitive function and mood in healthy adults. A separate controlled clinical study observed improvements in well-being with ingestion of a yeast beta-glucan. Numerous animal and Although the mechanisms by which exogenous saccharides can influence brain function are not well understood at this time, the literature suggests that certain naturally occurring compounds and polysaccharide-rich extracts show promise, when taken orally, in supporting neurologic health and function. Additional well-controlled clinical studies on larger populations are necessary, however, before specific recommendations can be made. According to a recent survey, 21% of American adults with common neurologic conditions  use biologically based therapies, consisting primarily of herbal remedies.2 Traditional Chinese, Ayurvedic, and African medicines have utilized an assortment of plants and herbal extracts to treat various central nervous system (CNS) dysfunctions.3 Effective compounds from well-known neurobiologically active plants include flavonoids from Gingko biloba and Hypericum perforatum (St John's wort) as well as alkaloids, quinones, tannins, and other phenolic compounds. To date, very little attention has been given, however, to exploring the efficacy of naturally derived complex carbohydrate compounds. The increasing prevalence of debilitating neurodevelopmental, psychiatric, and neurodegenerative diseases continues to be of significant concern for the developed world.4 Saccharides can also be used as a source for energy and neurotransmitter production.5 An early review highlighted the potential role and impact of saccharides in both simple and complex glycoconjugated form for supporting brain and cognitive function.6 Indeed, exogenously applied small sugar molecules, specifically monosaccharides, have been shown to impact functions within the brain related to cognitive benefits in human and animal studies. For example, consumption of glucose, a monosaccharide with well-established effects on brain function, has significant impacts on mood and cognition in human subjects.7 Systemic and intracranial application of l-fucose have been shown to influence glycoprotein synthesis and enhance memory behavior and synaptic plasticity in rodents,9 whereas sialic acid, another monosaccharide component of glycoproteins, has been shown to improve learning and memory following oral administration to piglets.10 Given the high concentrations of sialic acid in both the brain and human breast milk, it has been hypothesized that this monosaccharide may be an important nutrient for infant brain development.11Saccharide molecules play a number of fundamentally important roles in the brain, where they are largely glycoconjugated to proteins or lipids to assist in structural development, synaptogenesis, and synaptic transmission.in vitro and in human and animal studies following oral, systemic, and localized administration. To better understand the efficacy and possible mechanisms of action by which complex saccharides influence CNS function, we thus conducted this review of the available literature. It is anticipated that this information may be useful for guiding future research that will eventually provide a clear understanding of safe and effective dietary complex saccharides for specific neurologic health applications.The exogenous application of more complex sugar compounds has also been studied with respect to impacts on the brain. However, there remains a limited understanding of the potential mechanisms by which complex saccharide molecules may be influencing neurologic function. Saccharides derived from natural sources are structurally heterogeneous, come in neutral and acidic varieties, and can contain as much as 10 different monosaccharide sugars. The diversity of saccharides in both form and source provides potential for applied research into the occurrence, structure, and health properties of saccharides. In particular, varieties of saccharide compounds have been shown to improve brain function ®; Biothera, Eagan, MN, USA) for 4 weeks improved various measures of well-being in healthy adult marathon runners compared with placebo.12 Specifically, profile of mood state scores of tension, fatigue, anger, and confusion were significantly decreased and scores of vigor were significantly increased following supplementation. Significant improvements in cognitive function and mood have also been found in healthy middle-aged adults with a mixed polysaccharide product . In a recent study, individuals supplemented their diets for 12 weeks with placebo or a blend of saccharide-rich extracts from plants including Aloe vera, Astragalus gummifer, and Anogeissus latifolia. When compared with placebo, those subjects who consumed the blend of plant polysaccharides performed significantly better on tasks of recall and recognition memory and reported significantly reduced scores for tension and low mood .13A number of preliminary randomized, double-blind, placebo-controlled clinical trials have indicated that consumption of naturally sourced polysaccharides can benefit brain function in healthy young and middle-aged adults Table . Supplem® complex administered to healthy, middle-aged adults has been recently shown to improve recognition memory and working memory despite conditions of mental fatigue.14 In this study, blood glucose-mediated effects on cognitive function were ruled out since no changes in blood glucose levels were observed before or during testing, at 30 and 105 minutes post-treatment, respectively. Earlier research in middle-aged adults showed that a single dose of Ambrotose® complex had a tendency towards positive effects on memory tasks; however, these differences were not statistically significant, which may have been due to methodological differences in dose and time between supplementation and testing (10 minutes).15 Two studies of young adults demonstrated improved performance on tasks of visual discrimination and working memory at 45 minutes following intake of Ambrotose® complex.16 The exact mechanisms of action behind these acute improvements in cognitive function and mood are unclear. However, in a separate study of young male adults, significant increases in electroencephalogram-recorded brain wave frequencies during focused attention were seen 30 minutes after consumption of Ambrotose® complex relative to placebo.17 The specific changes in brain wave frequencies observed are commonly associated with abilities such as concentration and arousal. Overall, supplementation with a blend of plant polysaccharides seems to benefit various aspects of neurologic function and suggests functional benefits in healthy young and middle-aged adults. It is important to note, however, that these clinical studies, although well-controlled, were performed on relatively small populations; larger study groups are needed to confirm the validity of these results.Interestingly, acute effects on brain function have also been observed following intake of plant polysaccharides. A single dose of AmbrotoseCetrariella islandica, to ethanol-fed mice was able to reverse the ethanol-induced impairment in memory acquisition assessed by passive avoidance tests.18 Furthermore, an attenuation of spatial memory deficits during testing in the Morris water maze were observed with isolichenan ingestion in rats exposed to beta-amyloid peptide (A-beta), a small protein associated with the neurologic deterioration of Alzheimer's disease. It is important to note that in both studies, naive animals – those unexposed to either ethanol or A-beta – did not display memory enhancements with isolichenan treatment.Given the mechanistic limitations associated with clinical research, rodent models are commonly utilized to study the effects of therapeutic interventions on the CNS. A variety of rodent behavioral tests can be significant indicators of human cognitive function, which, when combined with experimentation on tissues from specific brain regions, can help elucidate possible mechanisms of action. For studies looking at behavioral and neurobiological effects of natural saccharides, animals with neurologic impairments have been utilized, which serves to both study the efficacy for protection against impairment-induced functional deficits and increase the likelihood of observing positive results Table . For exa19 Although cellulose also falls within the complex saccharide category, this study was concerned with comparing the immunological benefits of soluble (pectin) versus insoluble (cellulose) dietary fiber. Their results suggest that effects within the gastrointestinal tract following consumption of soluble, fermentable carbohydrates may be important for the neuroimmune recovery from LPS. Gastrointestinal fermentation effects were also proposed as one possible mechanism by which orally administered arabinoxylan from the yeast Triticum aestivum and beta-glucan from barley were able to preserve memory in a mouse model of vascular dementia.20A recent study looking at the effects of dietary fiber on sickness behavior demonstrated faster recovery from lipopolysaccharide (LPS)-induced social withdrawal with a pectin diet compared with a cellulose diet.Panax ginseng), a traditional Chinese medicine and popular natural product with touted cognitive health benefits, is typically attributed to its ginsenoside saponin content.21 However, some research suggests that ginseng's saccharide components may also play a role. A polysaccharide fraction of P. ginseng administered by daily intraperitoneal injections for 10 days seemed to enhance learning in healthy adult rats.22 Possible mechanisms of action were not addressed by the authors of this study. Fu Zi, a preparation of the daughter root from the plant Aconitum carmichaeli Debeaux (Chinese Monkshood), is another traditional Chinese medicine that has been used for centuries to treat mood disorders. Intraperitoneal injections of an alpha-glucan isolated from Fu Zi (FPS) showed antidepressant-like effects in the forced swim test, similar to the tricyclic antidepressant imipramine, in healthy mice.23 Surprisingly, FPS was also able to reverse the social avoidance behavior of defeated mice, a model of chronic stress, within just 2 weeks of intraperitoneal administration, whereas the effects of imipramine treatment were only observed after 4 weeks. The authors attributed these behavioral effects to increased brain-derived neurotrophic factor (BDNF) signaling and neurogenesis within the hippocampus, both known to be associated with an antidepressant-like response.24Neurologic effects of polysaccharide-rich plant extracts have also been observed in rodents following systemic injection Table . The bioin vivo electrophysiological recordings of LTP, performed on anesthetized rabbits, were of the responses of hippocampal dentate gyrus neurons receiving synaptic inputs from the entorhinal cortex.25The hippocampus is an important brain structure that helps regulate many behaviors, including memory and mood, and contains one of only a few sites of adult neurogenesis, the dentate gyrus. Owing to its organized neuronal circuitry, the hippocampus is commonly utilized to measure various types of synaptic transmission, including a form of synaptic plasticity – long-term potentiation (LTP) – that is believed to be the cellular basis for learning and memory. LTP is observed as an activity-dependent increase in synaptic strength that takes place when repeated presynaptic neurotransmitter release immediately precedes the generation of an action potential by the postsynaptic neuron, rendering the postsynaptic neuron hypersensitive to subsequent stimulation. It is thought that this repeated stimulation represents learning during exposure to a novel stimulus, which then strengthens specific synaptic connections for encoding long-term memories. Some of the first Parmelia caperata and Flavoparmelia baltimorensis, respectively, enhanced the magnitude of LTP induction when administered either orally or intravenously.27 Intravenous administration of another lichen-derived alpha-glucan, isolichenan from Cetariella islandica, also enhanced synaptic plasticity in the dentate gyrus.18 In this case, these results correlated somewhat with isolichenan's ability to reduce memory impairments following oral administration  may also play a role, since intracranial ventricular injection of IL-1R antagonist prior to intravenous PB-2 application was shown to enhance the alpha-glucan's effects on LTP.28Utilizing a similar method of recording hippocampal LTP in rats, a number of studies have found significant effects of lichen- and fungal-derived glucans on synaptic plasticity Table . Acute eLentinula edodes, and oral administration of Hoelen, a beta-glucan from the fungus Poria cocos Wolf, resulted in increased magnitudes of LTP.31 Altogether, there is a fair amount of in vivo evidence suggesting alpha- and beta-glucan consumption can lead to positive effects on synaptic activity in the dentate gyrus of the hippocampus. Additional research is needed to determine whether these saccharide-induced changes in synaptic plasticity convincingly lead to cognitive outcomes, and whether these functional and behavioral effects are mediated by norepinephrine or IL-1 receptor activation in the hippocampus.Like alpha-glucans, beta-glucans also appear to modulate synaptic plasticity Table . Oral anin vitro studies have demonstrated neuroprotective effects of plant-derived saccharides and saccharide-rich extracts  toxicity. In an MPTP-exposed mouse model of Parkinson's, daily intraperitoneal injections of Laminaria fucoidan reduced locomotor deficits, prevented striatal depletion of dopamine, enhanced brain antioxidant activity, and protected against the loss of dopaminergic neurons in the substantia nigra.35 In acutely dissociated rat basal forebrain neurons from the diagonal band of Broca, treatment with fucoidan from Fucus vesiculosus (Bladderwrack) protected cells from A-beta-induced apoptosis.36 Preliminary research suggests that fucoidan may also protect against brain damage associated with ischemic stroke. Compared with control animals, rats receiving intravenous infusion of Bladderwrack fucoidan for 7 days following intracerebral hemorrhage induction showed improved motor function and memory retention in a passive avoidance test, despite an increase in hematoma size.37 The authors hypothesized that these effects were due to fucoidan's anti-inflammation or hemodilation activities, although these possible mechanisms of action were not investigated in this study. Bladderwrack fucoidan, when administered through intraperitoneal injection, was also able to attenuate the extent of hypoxia-ischemia-induced neural damage in the rat cortex, hippocampus, and striatum.38The polysaccharide fucoidan may be another candidate for neurodegenerative disease therapies. In an in vitro studies have examined possible neuroprotective effects of crude plant extracts rich in complex saccharides (Table Nerium indicum (Oleander) reduced A-beta peptide-induced apoptosis of primary rat cortical neurons, whereas three of the extract fractions also improved survival during serum-deprivation.40 Similar protection against A-beta toxicity occurred in cultured cortical neurons treated with various polysaccharide-rich extracts of Lycium barbarum (Wolfberry).43 Polysaccharide fractions from Wolfberry also reduced the amount of glutamate excitotoxicity and homocysteine-induced cell death in cortical cultures.45 Finally, an aqueous extract of Verbena officinalis Linn. (Verbena), containing 30% w/w carbohydrates, protected primary rat cortical neurons from the cytotoxic effects of A-beta and dithiothreitol. The verbena extract had no protective effects against tunicamycin, hydrogen peroxide, or ultraviolet-radiation, leading the authors to speculate that components of this extract may act as antioxidants and/or bind directly to putative cell surface receptors that can detect extracellular A-beta.46 In this collection of studies of saccharide-rich extracts, treatments appeared to improve neuronal survival by either inhibiting intracellular signaling molecules involved in cell death or activating survival pathways.Additional es Table . Four diGiven the wide range of sugar compositions and structures of the saccharide compounds discussed in this review, common mechanisms of action that take place within the brain following oral consumption can be difficult to ascertain. Direct effects on the CNS would have to overcome the significant barriers of entry for complex carbohydrates that exist between the gastrointestinal tract and blood stream and then across the blood–brain barrier. Although such direct mechanisms cannot be ruled out, it is perhaps more likely that initial changes are occurring peripherally or within the digestive tract itself that ultimately result in cognitive outcomes. To elucidate possible mechanisms of action that allow ingested saccharides to affect brain function, one must have an understanding of how these compounds are processed in the gut.47 Here, we have presented animal and in vitro studies suggesting trehalose may be a viable dietary candidate for treatment of neurodegenerative disorders associated with protein misfolding (tauopathies), although no relevant testing has yet been performed on human subjects. A comparative study of the effects of trehalose versus glucose in a mouse model of Huntington's disease appeared to rule out the possibility that trehalose provides protective benefits via an increase in blood glucose levels, since trehalose was found present within the brain and glucose administration did not show the same effects.32 Additional research is needed to completely rule out whether changes in blood glucose levels are occurring following consumption of trehalose or other naturally derived complex saccharides and whether these changes are responsible for the observed alterations in brain function. Recent noteworthy evidence from a human intervention study with the mixed polysaccharide supplement, Ambrotose® complex, demonstrated beneficial effects of acute saccharide treatment on brain function, in terms of memory and cognitively demanding tasks, independent of any change in blood glucose response.14Human enzymes capable of digesting carbohydrates are largely limited to alpha-amylases that are able to hydrolyze the glycosidic bonds found in starches and certain disaccharides such as maltose and sucrose. Glucose and other monosaccharide subunits are then released and absorbed into the bloodstream, with general consensus that the majority of these monosaccharides travel on to the liver to be used as energy. The disaccharide trehalose can also be hydrolyzed into its two glucose subunits by the enzyme trehalase expressed in cells along the brush border of the small intestine.in vitro and animal studies of beta-glucan and Ambrotose® complex.49 New and exciting research has begun to demonstrate how alterations in gut bacteria can affect animal behaviors, such as anxiety and stress-induced changes in learning and memory, as well as hippocampal BDNF levels.53 Therefore, it seems plausible that consumption of complex saccharides may bring about alterations in intestinal bacteria that result in cognitive benefits. Complex interactions between the digestive, immune, and nervous systems may be responsible for some of the mechanisms by which this can occur.When consumed, the vast majority of plant-derived, non-starch complex carbohydrates are considered indigestible by human enzymes and will either pass through the digestive tract intact or may be broken down and fermented by species of colonic bacteria. Many are known to have prebiotic effects, meaning they can stimulate the growth and/or activity of beneficial bacteria that reside in the digestive tract. For example, beneficial alterations in intestinal bacteria have been demonstrated in 54 For example, various beta-glucans demonstrate immune stimulating effects,55 whereas saccharides such as those found in Ambrotose® complex show anti-inflammatory effects within the gut.56 In the study of dietary pectin on endotoxin-induced social withdrawal presented in Table 19 Once thought to be ‘immune’ to systemic inflammatory responses, it is now being discovered that the brain can be influenced by even low levels of peripherally circulating cytokines.57 Neuroinflammation can lead to cognitive dysfunction and is thought to be involved in the etiology of many neurologic disorders, including Alzheimer's, multiple sclerosis, and depression.58 Therefore, the effects of saccharide consumption on mood and cognitive function presented here may conceivably be attributed to immune signaling. Additional studies are needed, however, to determine whether immunomodulating effects of oral polysaccharides are in any way responsible for their influence on neurologic function.Many plant-derived polysaccharides have been shown to regulate the immune system as they pass through the intestinal tract.59 For example, the transport of indigestible fibers through the colon is largely controlled by the vagus nerve, which projects directly from the viscera to the brain stem and can indirectly activate limbic and cortical regions of the brain involved in regulating mood and cognition. Vagus nerve stimulation has been proven as a successful therapy for a wide variety of neurologic disorders, including epilepsy, depression, and dementia.60 Interestingly, activation of vagal afferents in rats has been shown to enhance LTP in the dentate gyrus61 and increase norepinephrine levels in the hippocampus,62 which was one suggested underlying mechanism for the effects of ingested alpha-glucans on hippocampal synaptic plasticity.29 Repeating some of the oral studies presented in this review on vagotomized animals or human subjects may help elucidate the involvement of the vagus nerve in dietary saccharide-induced neurologic effects.Dietary polysaccharides may also impact brain function via the digestive tract due to the activation of parasympathetic nerve fibers, hormonal signaling, or additional brain–gut axis pathways.in vitro before going on to show benefits following oral administration. Heparin-derived, low-molecular weight glycosaminoglycans, which are mixtures of polysulfated oligosaccharides, have indeed shown neuroprotective effects both in vitro and in animal studies.63 Interestingly, some evidence exists that such compounds may pass through the blood–brain barrier when administered peripherally. Del Bigio et al.37 speculated that systemically applied fucoidan, a sulfated heteropolysaccharide, may provide protection against stroke-induced neurologic damage in part through its anti-inflammatory effects, which have been observed following fucoidan ingestion in animal studies.54 Future research is needed to explore whether fucoidan and other natural sulfated sugar molecules can provide neuroprotective and other cognitive benefits following oral administration.Up to this point, no studies have focused on the neuroprotective effects of consuming fucoidan or any of the other polysaccharide-rich plant extracts discussed in Table 54 Before recommendations can be made regarding their specific beneficial, preventative, or therapeutic applications, more robust well-controlled clinical trials are needed. Additional basic research is also warranted to better understand the range of effects of dietary glycans on brain function and behavior and to help elucidate the mechanisms behind which they may be occurring.There is growing evidence that naturally derived saccharides have beneficial effects on brain function, demonstrated as both cellular and functional effects in terms of neuroprotection and improvements in cognition and mood. The purpose of this review was to consolidate studies on the brain-specific effects of these sugar compounds to help foster research in the area of natural complex carbohydrates and neurologic function. At present, an understanding of the efficacy and mechanisms of action for specific saccharides and saccharide-rich extracts is limited. The most promising human clinical research indicates that supplementation with a blend of plant polysaccharides can have beneficial effects on brain function related to cognitive performance and mood. In animals, various alpha-glucans have shown the most significant effects on behavior and synaptic plasticity, whereas trehalose shows significant promise for neuroprotective benefits. Encouragingly, the general safety profiles of many of these dietary polysaccharides for human consumption are positive, with few reported adverse side effects.


Accurate measurement of resource use is required for economic evaluations alongside clinical trials. Despite patient questionnaires commonly being employed, concerns over data quality persist, and there is little certainty about best practices. This review aims to collate the evidence concerning the validity and reliability of resource-use measures based on patient recall and to aid health economists in developing better measures.A search strategy incorporating terms covering healthcare resources, utilisation, patient-reported measures and validation/reliability concepts was applied to the MEDLINE, EMBASE and PsycINFO bibliographic databases. Studies were included if they concerned original research to inform costing studies, and were about patient (or proxy) self-reports of healthcare-related resource use in which a comparator  was specified. Data on study and population characteristics, type of instrument, recall period, sample size, care setting and administration method were extracted.13367 abstracts were identified as potentially relevant. Following abstract and full-text screening, 77 articles published between 1976 and 2011 were deemed relevant. The majority focused on adults (n=58), and nearly half of the articles originated from the US (n=37). Emerging themes suggest that better accuracy is achieved when patients are younger, more highly educated and healthier and are answering questions about inpatient and specialist care.There is only a limited amount of validity and reliability information available to inform best practice for resource-use measurement in clinical trials. This ongoing review will identify the gaps, giving a clearer view of where research efforts should be concentrated.