Tet2 and a decrease in the histone deacetylase Hdac1. These gene expression changes may be of key importance during the early period of readaptation since they could lead to an increase in the expression of target genes.To analyze the effect of gravity on the structure of germinal tissues, we examined tissues of the testes and duct deferens of mice that were exposed to space flight conditions for 21–24 days . We evaluated the levels of cytoskeletal proteins, sperm-specific proteins, and epigenetic events; in particular, we evaluated levels of 5-hydroxymethylcytosine and of enzymes that regulate DNA methylation/demethylation. We did not detect changes in the levels of cytoskeletal proteins, sperm-specific proteins, DNA-methylases, DNA demethylases, DNA acetylases, or histone deacetylases. However, there were changes at the gene expression level. In particular, there was an increase in the demethylase  On the other hand, the preimplantation development and early stages of gastrulation may be more sensitive to changes in external mechanical stress. For example, pregnancy was not achieved in mice during space flight conditions, which researchers attributed to the lack of implantation and, as a result, the abortion of the preimplantation embryos7.It is known that the exposure of female rats to zero gravity in the second half of pregnancy does not cause significant changes in embryos9; although, for the sperm of sea urchin in space flight , FP130 protein phosphorylation, which is associated with the activation of motility, occurred 3–4 times faster than in conditions of 1 g10. Additionally, the expression of genes encoding pro-apoptotic proteins increased11, the differentiation potential of progenitor cells changed12, and the efficiency of spermatogenesis decreased14. However, the causes of such changes in sperm are not at all clear.In addition, there is every reason to believe that germ cells can change their structure in microgravity conditions. For male germ cells, it is known that the speed of the movement of the mouse spermatozoa decreases after a 7-day antiorthostatic hanging, which simulates the effects of weightlessness15. It is known that the external mechanical field plays an important role in establishing the patterns of expression of various genes, primarily those encoding cytoskeletal proteins and the associated signaling cascades, in different cell types, including stem cells22. However, how an external signal that the mechanical field has changed is transduced and leads to a change in gene expression remains completely unclear.Our previous data suggested that after a 30-day antiorthostatic suspension, changes in the patterns of cytoskeletal proteins in mouse spermatozoa and testes were not observed, although the relative mRNA levels of the corresponding genes changed23, hypomethylation was observed in human T lymphocytes24, and in lymphoblastoid cells, there was a change in the methylation level and in the hydroxymethylation level25. The data from our previous study showed that in space flight conditions, the total level of DNA methylation in the heart and lung tissues of mice increased by 21% and 32%, respectively, which correlated with changes in gene expression levels26.In higher mammals, there are a large number of methods for regulating gene expression, such as various posttranslational modifications of histones, chromatin remodeling, RNA interference, and DNA methylation, but most of these processes have hardly been studied under microgravity conditions. Few and partially contradictory data are associated with the determination of the methylation levels in different cell types in conditions of microgravity: hypermethylation took place in rice germs under space flight conditionsTherefore, the purpose of our work was to evaluate the levels of the cytoskeletal proteins and the mRNA levels of the genes that encode them in the testes and duct deferens of mice whose tissues were fixed in space flight conditions. In addition, we sought to evaluate epigenetic events, in particular, the levels of 5-hydroxymethylcytosine and of the enzymes that regulate DNA methylation/demethylation.Actn1 mRNA level was 47% lower than that of the control group (p < 0.05).In the testes Fig.  and the Kdm5B mRNA level, which in the flight group in the testes , spermatids (PRM1) and mature spermatozoa SPACA3) did not differ in any of the study groups , there were practically no changes in the levels of cytoskeletal proteins, although there were significantly more changes in the mRNA levels26. The latter may be because in the early stages of space flight, the heart and lungs are subjected to an increase of external mechanical stress due to a volume shift in the cranial direction, unlike the testes and the duct deferens. However, it should be noted that testes tissues have high levels of cellular heterogeneity, which does not allow for the identification of the contributions of individual cell types to the results that we obtained. Therefore, we decided to examine the relative content of proteins and mRNA which expression correlates with different degrees of sperm maturity, both in the duct deferens and in the testes.The results suggested that there was no change in the levels of the studied cytoskeletal proteins  in the flight group, although there was a decrease in 27. In the duct deferens, we did not observe changes in the protein levels and mRNA levels of the encoding gene, Kdm5B. However, in the testes, despite the absence of a change in the protein level, the mRNA level of this gene increased in the flight group, which may indicate a decrease in the differentiation potential and, accordingly, in the mature forms of sperm. We observed a similar effect after a 30-day antiorthostatic suspension, where a decrease in the number of the mature forms of sperm correlated with an increase in the mRNA level of the Kdm5B gene15. However, in this case, we did not note changes in the levels of protamines, the expression of which is highest in spermatids28, as well as sperm lysozyme-like protein 1 , which is localized to the acrosome of mature spermatozoa29. Perhaps this is because more mature forms of sperm are localized in the caudal epididymis, which was not available for analysis.KDM5B (a histone demethylase that demethylates ‘Lys-4’ of histone H3) was chosen as a marker for early spermatogonia, since their differentiation into spermatocytes requires inactivation of this geneThus, despite the absence of changes in the levels of cytoskeletal and sperm-specific proteins, changes in the expression of some proteins were observed.26 and may indicate a change in the efficiency of translation and/or proteolysis. Earlier, we proposed the role of actin-binding proteins in the cell mechanosensitivity at early stages of microgravity30. One of them, alpha-actinin-1 interacts with phospholipase D in the cortical cytoskeleton, and it may regulate efficiency of translation31.On the one hand, this situation correlates with our previous data after Rodent Research-1 missionOn the other hand, the question remains: what caused the changes in the observed gene expression? The reasons for the changes in expression could be associated with a wide range of factors, such as histone modifications, but for higher mammals, it is most likely because of a change in the DNA methylation levels of CpG-islands in the promoter regions of genes.In this study, we attempted to analyze the total DNA methylation level by restriction analysis and, accordingly, CG-islands in the promoter regions of the cytoskeletal genes were studied; however, the isolated genomic DNA was not of a high enough quality to conduct such an analysis.32. There were no changes in the 5-hydroxymethylcytosine levels in the testes or duct deferens. It should be noted that in the ovaries of mice after 23 days of antiorthostatic suspension, there were also no changes in the 5hmC levels, although we noted a change in the expression of the gene encoding one of the TET-family demethylases, TET2. Therefore, in this work, we also decided to examine the content and expression of genes encoding key methylases/demethylases.Nevertheless, we were able to evaluate the level of 5-hydroxymethylcytosine (5hmC), which is an intermediate product between the fully methylated and fully demethylated statesde novo methylase DNMT3a, and demethylases of the TET family  of the flight group both in the testes and duct deferens remained at the same level as the control group. However, the gene expression changed in some cases. For example, the expression of the Dnmt1 gene decreased in the testes, and the expression of Tet2 increased both in the testes and in the duct deferens, and in the previous experiment that examined the ovaries of mice after antiorthostatic suspension33. Since the DNMT1 methylase and proteins of the TET family are part of a complex that interacts with DNA34, it can be assumed that a decrease in the expression of one of the participants of the complex could lead to a decrease in the number of active complexes and, as a consequence, to a decrease in the DNA demethylation level. On the other hand, the acetylation of TET leads to an increase in its demethylation activity, and the deacetylation of HDAC1/2 proteins leads to the inhibition of their activity involving demethylases34. Interestingly, as previously observed33, an increase in Tet2 expression in the flight group correlated with a decrease in Hdac1 deacetylase expression. At the same time, a decrease in Dnmt1 methylase expression was accompanied by an increase in Hat1 histone acetylase expression in the testes of mice of the flight group.The protein content of the S-phase methylase DNMT1, Hdac1 deacetylase gene was reduced in the duct deferens, while the mRNA levels of the acetylase Hat1 remained constant; and in the testes, while the expression of the deacetylase was reduced, the expression of the acetylase was increased. Histone acetylation can regulate the efficiency of transcriptional activation both by directly changing the charge35 and causing chromatin remodeling and by the recruitment of transcriptional activators38. Therefore, in a case where the expression level of the acetylases/deacetylases changed at the translational level, we could expect to see a greater change in the expression of other genes, such as those encoding cytoskeletal proteins.In summary, the expression of the In general, in this study of the duct deferens and testes tissues of mice that were euthanized under weightless conditions, we did not detect changes in the levels of cytoskeletal proteins, sperm-specific proteins, DNA methylases, DNA demethylases, DNA acetylases and histone deacetylases. This may indicate that during 3 weeks of space flight, an adaptive protein profile formed in the germinative tissues of male mice.Tet2 demethylase (an increase) and of the histone deacetylase Hdac1 (a decrease). An increase of mechanical stress, such as the increase that is associated with a return to Earth’s gravity conditions, can trigger the realization of this pattern at the protein level and subsequent changes of cells structure and functions. That is why further detailed research is required to develop effective strategies to protect human health during the early period of readaptation to varying gravity after spending a long period under weightless conditions.However, we did observe changes in the gene expression, especially of ad libitum. All description of transport container and habitat with animal welfare were provided by Ronca A.E. et al.39.In the “Rodent Research-4” (RR-4) experiment, C57BL/6J mice obtained from the Jackson Laboratory  that were 9–12 weeks old at the time of launch were used. The animals were placed in a transport container on February 18, 2017. For four days, the transport container remained in the capsule of the Dragon SV on the launch pad. The SpaceX-10 spacecraft was launched on February 23, 2017. The animals were transferred from the transport container into an animal habitat unit onboard the ISS on February 25, 2017. During flight conditions, the animals received food and water The animals in the flight group (F) were kept in microgravity for 21–24 days, after which they were euthanized. Euthanasia was made by cardiac puncture and blood collection with pre-made anesthesia. Then, the carcasses were wrapped in two layers of foil and placed in plastic bags (so that each carcass was completely surrounded by ice), which were inserted into piles for storage at low temperature. The period between euthanasia and freezing of the carcass was approximately 2 minutes. The carcasses were stored in the MELFI freezer until returning to Earth.ad libitum. The animals in the ground control group (G) were euthanized in the laboratory after staying in microgravity conditions while being recorded with a camera , simulating the same environmental conditions as on the ISS.The animals in the basal control group (B) were euthanized in normal laboratory conditions shortly after the launch of SpaceX-10. Animals of the vivarium control group (V) were kept in standard vivarium conditions and received water and food The schedule for working with the animals of groups B, V and G corresponded to the schedule for working with group F.All animal procedures were approved by the Ames Institutional Animal Care and Use Committee .Organs were isolated from the frozen carcasses on Earth. The right testis  and duct deferens  were frozen in liquid nitrogen for determination of protein content; the left testis  and duct deferens  were placed in the RNAlater Stabilization Solution  for future work with nucleic acids. For each group of animals, we examined the biomaterial of a minimum of 6 animals.The samples, in accordance with the NASA-Roskosmos protocol “Utilization Sharing Plan on-board ISS” , were delivered to Russia on dry ice without defrosting, which was ensured by the use of temperature sensors.et al.40.Isolation of total protein from the frozen tissues and denaturing electrophoresis were performed according to the Laemmle method using a Bio-Rad system (USA). The protein concentration of each sample was measured, and the same amount of protein was loaded into each well. Transfer to the nitrocellulose membrane was performed according to Towbin de novo methylase DNMT3a (1: 2000), 5-methylcytosine hydroxylase (demethylase) TET1 (2 µg/ml), TET2 (1: 1000), TET3 (1: 1000), histone acetylase KAT1/HAT1 (1: 1000), and histone deacetylase HDAC1 (1: 1000) ; JARID1B (KDM5B) (1: 100) ; protamine (1: 250) ; and SPACA3 (1: 1000) . Biotinylated goat antibodies against mouse IgG   and rabbit IgG   were used as secondary antibodies. Further, all membranes were treated with a solution of streptavidin conjugated with horseradish peroxidase  at a dilution of 1:10,000. Protein bands were detected using 3,3′-diaminobenzidine , and the data were analyzed using ImageJ.To identify each protein, specific antibodies were used at the dilution recommended by the respective manufacturer. Specific antibodies raised in mice were used to examine the cytoskeletal proteins: beta-actin (at a dilution of 1: 500), gamma-actin (1: 200), alpha-actinin-1 (1: 200), alpha-actinin-4 (1: 200), beta-tubulin (1: 200), and desmin (1: 200) . Specific antibodies raised in rabbits for the listed proteins were used at the following dilutions: S-phase methylase DNMT1 (1: 1000), 15 as a primer and 500 ng of RNA. The relative mRNA content of the studied genes was estimated using real-time PCR with primers selected by the Primer3Plus program  according to the manufacturer’s instructions. Reverse transcription was performed using d (T)To determine the methylation levels, total DNA was isolated from the tissues, stained in the RNAlater Stabilization Solution, using a DNA extraction kit  based on the phenol/chloroform method according to the manufacturer’s instructions. The isolated DNA was applied to a nitrocellulose membrane, for the preliminarily measurement of the concentration and for denaturing (+95 °С for 5 min and then +4 °С for 3 min), at three dilutions −1 μg, 500 ng, and 200 ng. The membranes were air-dried, welded to the membrane using ultraviolet light and incubated in 4% skim milk overnight at +4 °C.To evaluate the 5hmC content, specific antibodies raised in rabbits  were used at a dilution of 0.5 μg/ml in accordance with the manufacturer’s instructions. Biotinylated goat anti-rabbit IgG antibodies  were used as secondary antibodies at a dilution of 1:10,000. Then, the membranes were treated with a streptavidin solution that was conjugated with horseradish peroxidase  at a dilution of 1:10,000. Dots were detected using 3,3′-diaminobenzidine . ImageJ was used to analyze the data.The results obtained were analyzed by ANOVA, using a post hoc t-test with significance level p < 0.05 to assess the significance of the differences between the groups. The data are presented as M ± SE, where M is the arithmetic average and SE is the error of the mean.All methods were performed in accordance with the relevant guidelines and regulations.


This increased performance of NH3 treated sample can be linked to the enhanced surface area of the composite, thereby improved adsorption and associated interaction with that of the analyte molecules at the electrodes. Further comparison of the electrode with that of commercial Dropsens electrodes provided the confirmation for the efficiency of the NH3/MWCNTs, thereby suggesting for the potentiality of applying the NH3 modified electrode towards electrochemical applications.In the present work, we described the post-treatment effects of applying different plasma atmosphere conditions on the electrochemical performances of the multiwalled carbon nanotubes (MWCNTs). For the study, a composite of MWCNTs/Co/Ti was successfully grown on the silicon substrate and then pre-treated with ammonia, oxygen and hydrogen plasma. The composite was characterized by making use of field emission scanning electron microscopy (FESEM) for the surface morphology and Raman spectroscopy for the functionalization. Further, the electrochemical measurements were performed with the use of the cyclic voltammetry (CV) applied in the 0.01 M potassium ferricyanide in 0.1 M KCl solution. On testing, the results indicated that the NH Nanofabrication comprises the manufacturing and utilization of materials and devices with dimensions in the range of 1–100 nm and because of having diverse applications, the nanomaterials research represents an advanced developing area of nanotechnology. The nanosized materials have commanded for the better features and functions in multiple different fields including the include solar cells and electronics, energy conversion and storage, construction and engineering, biomedical, automobile, consumer goods and so forth . The outThe nanofabrication method making use of the plasma enhanced chemical vapor deposition (PECVD) technique called the “bottom–up” approach where the processes are elaborated for the creation of nanoscale structures and well-organized geometries. The bottom–up approach is pursued to obligate the molecular or atomic components built up into more complex nanoscale assemblies or directed self-assembly that can be found in composite technologies . This teThe various modifications onto the surface of CNTs have been developed and become commercially available in recent years such as air oxidation , ozone o2-hybridized graphite-like carbon (C=C) bonds within the CNT lattice thereby creating the defects  [3), hydrogen (H2) and oxygen (O2) gases in order to create defects on the surface with an aim to enhance the electrochemical performances of the MWCNTs. Plasma surface treatment in general employs different gases for the study, such as oxygen, nitrogen, hydrogen and ammonia. When exposed to the plasma treatment, the excited species, radicals, electrons, ions, or UV light within the plasma interacts strongly with the surface of nanotubes leading to the breaking of spe sites) . In thise sites) . Mishra e sites)  reportede sites)  demonstr−3 mbar and temperature of 42 °C. The thickness of Ti and Co layer was measured in accordance with the previous work by Haniff et al. [2H2  used as the precursor gas was added to the chamber and maintained the pressure of 1000 mTorr, 700 °C for 10 min to facilitate the growth of MWCNTs. The working site of MWCNTs-based electrode has the same diameter with Dropsens C101 which is 0.36 mm.In this study, different samples of untreated and different plasma treated MWCNTs were prepared. Each category of different treatment samples was made in triplicate. First, by making use of the magnetron sputtering technique thin film of Titanium  as the conducting layer and Cobalt  as the catalyst for growing the CNTs were deposited onto a Si(100) substrate maintained at the reaction chamber pressure of ~10f et al. . In the 2 (C=C) bonds [3, H2 and O2 , where we maintained a flow rate of 50 sccm, pressure of 1000 mTorr, temperature of 200 °C, radio frequency power of 20 W and for a total period of 120 s.In the post-treatment study, each individual sample of MWCNTs was subjected to different plasma treatment so as to see the effects of surface properties with respect to the applied parameters. During the treatment, the MWCNTs were subjected to ion bombardment in the chamber which further expected to activate the surface electronic properties of the CNTs by breaking the spC) bonds . The samThe surface morphology of all the pristine and modified CNTs was characterized by using a field emission scanning electron microscopy system . The quality of the CNTs was evaluated by Raman spectroscopy . For the analysis, a 473 nm air-cooled laser was focused on a diffraction limited resolution of 250 nm and the samples were run for an acquisition time of 5 min.2+/Fe3+ redox reactions at the surface of CNTs was studied in 0.1 M KCl solution containing 0.01 M potassium ferricyanide (K3Fe(CN)6) at different scan rates in the range of 10–100 mV s−1. The K3Fe(CN)6 was selected as a benchmark redox system due to its surface sensitivity towards the electrochemical response, mainly for the carbon materials [2. In each electrochemical study which involves the effects of sensitivity, scan rate and NH3/MWCNT electrode performances were repeated three times.The electrochemical characterization of the electrodes was investigated by using potentiostatic system of cyclic voltammetry (CV). The electrochemical behavior of the Featerials . All theFor the electrochemical studies, the statistical analysis was performed by using one-way analysis of variance (ANOVA) and Bonferroni’s method for multiple comparisons. 3 treated (b), H2 treated (c) and O2 treated ones (d). From the figure, it confirms for the formation of all MWCNTs in a tube like structure and in addition, there are no significant changes appearing to the morphology of samples that are being treated with plasma  provides the information on the relative amounts of structural defects (degree of perfection) of the nanotubes. In general, the larger ratio indicates for a reduction in the degree of perfection due to the increase of structural defects introduced by the plasma treatment [R calculated for the MWCNTs before and the plasma treatment are tabulated in R ratio increases for the plasma treated MWCNTs as compared against the MWCNTs without any treatment, and this is a primary indication of the formation of electron deficient moieties at the MWCNTs surface due to the plasma treatment [2 treated ones has the highest defect as the value of R ratio observed to be 1.089, followed by NH3 (R = 1.034) and H2 (R = 1.017). The slight increase in the R ratio for the plasma treated MWCNTs indicate for the importance of having the necessary functionalities at the surface that are able to integrate with the lattice of nanotubes. However, the low defect ratio for the as-grown MWCNTs is due to the absence of any defective surface moieties and thereby indicating the need for the incorporation of surface groups so as to enhance the conducting properties [reatment . The valreatment . Among aoperties .3/MWCNTs, H2/MWCNTs and O2/MWCNTs in 0.01 M ferricyanide (Fe(CN)63−/4−) solution containing 0.1 M KCl (scan rate of 100 mV s−1) and the corresponding peak currents are tabulated in 2/MWCNTs seems to exhibit a lower redox peak current with reductions of 2.02 and 1.97 folds of anodic and cathodic reactions as compared to the unmodified MWCNTs. Also, there seems to be a significant enhancement in the redox peak currents for the other plasma treatments, that is, the H2/MWCNTs and NH3/MWCNTs were having increments by 1.35 and 1.5 folds for anodic peak current (ipa), while the cathodic peak current (ipc) shows the increments of 1.65 and 1.66 folds, respectively. Here, the improvement of the current signals is correlated to the increment of the diffusion rate of K3Fe(CN)6 and larger effective surface area that improved the sensitivity of the nanotubes’ surfaces [3 plasma treatment is said to have the best sensing characteristics as compared to the bare and other treatments.The sensitivity and reversibility studies were investigated by making use of the electrochemical technique so as to observe the effect of different plasma atmosphere on the electrochemical performances of MWCNTs. surfaces . Thus, fp), as against the square root of scan rates (mVs½), are illustrated in p towards mVs½ when performed in the range of 10–100 mVs−1 thereby proposing a diffusion controlled process of reactants on the electrode surface. The results obtained are used to calculate the electroactive surface area (cm2) using Randles-Sevcik equation (1) and the values are tabulated in 2), D is the diffusion coefficient of the molecules in solution (cm2/s), C is the concentration in the bulk solution (mol/mL), v is the square root of scan rate (mVs½) and ip is the peak current (mA).The influence of scan rates on the redox reactions for the pristine and modified MWCNTs were investigated and is shown in 3/MWCNTs to be the highest signal followed by H2/MWCNTs, bare MWCNTs and O2/MWCNTs. The observation of such order in the peak currents can further be linked to the electroactive surface areas of MWCNTs which is exactly same as the electrochemical response.According to Equation (1), the electroactive surface area of a material is directly proportional to the peak current and thus with an increase in the surface area of the MWCNTs in our case, the peak current should be increased. From the analysis, we observed the peak current of NH3 plasma alone on MWCNTs thin film was conducted. In order to govern the electron-transfer property of the species in a given environment, the peak separation of different scan rates was calculated. 3/MWCNTs, where the peak potential difference versus 1/square root of the scan rate was calculated. From the figure, the peak separation is getting increased with the decrease of 1/√V/s (increased scan rates), that is, the lower scan rates are having a reversible redox couple and faster electron transfer rate. Meanwhile, the greater peak separation in higher scan rates specifies a quasi-reversible reaction. In addition, multiple cycles of CV measurements were run on NH3/MWCNTs sample to observe the stability of the electrode. 3/MWCNTs in 0.1 M KCl containing 0.01 M ferricyanide (Fe(CN)63−/4−) solution that was run up to 120 cycles. From the figure, it has clearly shown for the virtual constant of either peak potential or the peak separation for the redox reactions of the ferrycyanide solution. This evidenced that the modified MWCNTs with that of NH3 are stable towards the detection and can be reusable for different kinds of applications.Further study on the activation of NH3/MWCNTs sample. In addition, we observed from the analysis that the values did not change much when we repeated the analysis for multiple times. The observation of the highest peak current for the NH3/MWCNTs as compared to all other samples significantly demonstrates that the plasma system upgraded the surface performance by means of enhancing the adsorption and interaction of the target analytes on the apparent of CNTs. Hence, the detection of analytes in the electrochemical system will be suggestively developed.In addition, a comparative study with that of the commercial Dropsens was carried out to inspect the sensitivity performance of the electrodes and the results are shown in 3, H2 and O2) proved that the ammonia plasma significantly improved the sensitivity of the electrodes up to 0.48 mA by means of increasing the effective surface area of working electrode (~0.497333 cm2) as compared against the bare electrode. Further, the NH3/MWCNTs electrode confirmed to have a better performance than the commercially available Dropsens electrodes and thereby suggesting for the potential applications of the prepared electrode towards electrochemical related studies. This improved performance of the synthesized electrode can be attributed to the increase in the surface area linked adsorption and associated electrical conductivity by means of reducing the internal resistance in the composite material. Also, the study provides information about the selection of right medium (NH3) as against the other two mediums (H2 and O2) for the composite where the hydrophilic and hydrophilic properties can be switched, in addition to improving the interaction with the analyte and all these factors contributes to achieve the highest efficiency of the electrode system.In conclusion, we proved here for the importance of having the modified surface so as to improve the electrical conductivity of the MWCNTs. For the study, the MWCNTs were successfully grown on the silicon substrate via catalytic PECVD technique followed by its characterization using the SEM and Raman spectroscopy. The modification strategies of the MWCNTs plasma treatment using different atmospheres (NH


Fifth generation ethylendiamine-core poly(amidoamine) (PAMAM G5) is presented as an efficient capping agent for the preparation of metal and semiconductor nanoparticles by ps laser ablation in water. In particular, we describe results obtained with the fundamental, second and third harmonic of a ps Nd:YAG laser and the influence of laser wavelength and pulse energy on gold particle production and subsequent photofragmentation. In this framework, the role of the dendrimer and, in particular, its interactions with gold clusters and cations are accounted. Dendrimers are monodisperse polymers characterized by a well defined structure that resembles a tree, a multifunctional surface and internal cavities . Many poN-(2-aminoethyl)propionamide) units attached regularly around the core and several end groups that are generally amino groups for a full generation dendrimer, or carboxylate groups for the half-generations. Among the different applications of PAMAM, an interesting one is its use as stabilizer for noble metal nanoparticles. Indeed, nanoparticles of noble metals are of great interest because of their potentialities into several rapidly developing fields, including tailor-made nanostructured materials for medicine and biosciences, drug delivery, in vivo cellular Raman spectroscopy and, thanks to their characteristic plasmon resonances, for photonics and information technology [The most widely known class of dendrimers are the PolyAMidoAMines (PAMAM). They are characterized by three distinct features: an ammonia or ethylendiamine core, several multifunctional repeating  or semiconductor (CdSe) nanoparticles (NPs) obtained by ps laser ablation of a target in water solutions. In particular, it is dedicated to extensive report of the results, which we have recently obtained on the preparation and characterization of PAMAM G5-capped AuNPs: i) We discuss the role of laser wavelength and energy per pulse in the ablation of the gold target; ii) we show that it is possible to control the size of the NPs by irradiating pre-formed NPs suspensions with green or UV laser pulses, thanks to the onset of photofragmentation and iii) we study the fluorescence of different NPs suspensions in order to evidence the contribution of Au quantum dots to their emission. We also show how the methods developed for preparation of PAMAM G5-capped AuNPs and the potentialities of the dendrimer as a particle stabilizer can be transferred to other systems. For this purpose, we illustrate preliminary experimental results, which we have very recently obtained in the case of laser ablation of Ag or CdSe targets in PAMAM G5/water solutions.The mechanism of laser ablation of a metallic target and its dependence on laser wavelength and pulse duration is not clear yet. In general, it is determined by different competing effects, such as multiphoton absorption, thermoionic emission and melting, whose relative importance is difficult to establish. However, once the material is extracted from the target, particle formation and growth in liquid environment can be explained in terms of the dynamic mechanism first proposed by Mafunè and co-workers . A plasmWe prepared AuNPs by ablating a gold target in PAMAM G5 aqueous solutions with 1,064, 532 and 355 nm pulses. In all cases we obtained stable, wine-red samples containing AuNPs. d electrons, which are promoted to s-p orbitals and collective oscillations of conduction electrons, i.e., dipolar plasmon resonances. The first contribution dominates at high energy, namely above 3 eV , while the second one is responsible of the absorption band in the green region of the spectrum [The absorption spectrum of AuNPs-containing suspensions, in the case of sufficiently small (below 30-40 nm radius) and non-interacting spherical particles, is the result of two contributions: interband absorption of spectrum . For thiNP appears only when RNP is sufficiently large (radius RNP > 0.5 nm). Its intensity is proportional to the particle volume, while the width broadens and tends to be swallowed by the interband contribution to the electronic spectrum in the case of particles approaching nm size. In the case of many identical and non interacting particles, the final absorption is obtained by multiplying the single particle contribution by the concentration.According to Mie’s theory , the pla2), the absorbance at 400 nm is negligible for the sample obtained with IR pulses and 16 times smaller than that obtained with 532 nm pulses, suggesting a very small Au concentration in the sample, namely a very inefficient ablation process. As a matter of fact, we have found that the energy of 5 mJ per pulse is very close to ablation threshold for 1,064 nm light in the ps time regime [2 at 532 nm and 0.15 J/cm2 at 355 nm), we observe that the most striking difference regards the visibility of the plasmon band. The poor visibility of the plasmon obtained with UV ablation suggests reduced dimensions of the nanoparticles, while the strong absorption at 400 nm suggests the presence of a high concentration of sub-nanoclusters. Such considerations permit a first interpretation of the spectral differences observed in NP = 5.2 nm and a distribution characterized by half widths σ+ = 3.7 nm and σ- = 1.6 nm. In the 532 nm case  AuNPs having dimensions and statistical distribution obtained by TEM analysis (green curves) and ii) sub-nanoclusters (red curves). In all cases the first contribution alone is not sufficient to obtain a satisfactory fit of the spectroscopic features. NP = 1.1 × 1013 cm-3, and a total density of atoms belonging to sub-nanoclusters Nat = 1.9 × 1016 cm-3. Sixteen min post irradiation of the suspension of NP = 3.2 × 1013 cm-3) and that of the atoms belonging to sub-nanoclusters Nat = 3 × 1016 cm-3. The dielectric constant of PAMAM G5 also changes to a lower value, namely 2.2, suggesting the onset of a photodegradation process of the molecule. Post irradiation with the same total energy (48 J) but with more energetic pulses (10 mJ) led to a more dramatic change in the spectral characteristics and in the density of AuNPs (NNP = 8 × 1013 cm-3) and background atoms pertaining to sub-nanoclusters (Nat = 4 × 1016 cm-3), while the dielectric constant of PAMAM G5 turned out to be again 2.2 . The gold cations complex with the PAMAM molecule and cannot reaggregate to form new nanoparticles, thus favoring the oxidation of the dendrimer and leading to an enhancement of the UV absorption. The photodegradation effect upon irradiation is further confirmed by the change of PAMAM dielectric constant, as obtained from the fit of UV-Vis spectra of A band at 285 nm also appears under spontaneous reduction of HAuClested in ,25. The endrimer ,24,25,262 fluence, that are values well above threshold for all wavelengths, differently from the case reported in In the light of the previous considerations on the formation of sub-nm clusters or gold cations, which is observed particularly with 532 nm and 355 nm pulses, it is possible to explain another big difference among the three ablating wavelengths, which is already partially suggested by When ablation is performed with 532 nm pulses  and represent an intermediate state of the matter, between the atomic and the bulk one. Among the properties of QDs, fluorescence seems a particularly interesting one. Indeed, there are reports in the literature describing the fluorescence properties of gold QDs and claiming that such systems exhibit a high quantum yield and good resistance to bleaching ,28. In p3+ ions produced during the fragmentation.There is a more than 10-fold enhancement of the overall fluorescence for excitation at 350 or 400 nm and a 2-fold reduction of the overall fluorescence for excitation with 300 nm;There is a redistribution of the relative weight of the bands, depending on the excitation wavelength, but no evidence of new bands, which could be attributed to AuQDs;The most efficient excitation is observed with 350 nm. In particular, at this wavelength, the emission band at 470 nm is quenched, while the emission concentrates into a band at 454 nm, whose intensity was negligible in the case of Au-free PAMAM G5 solutions;For excitation at 400 mn the emission concentrates into the band at 470 nm, which is intensified by a factor of 300 with respect to the case of Au-free PAMAM G5 solutions.3+ cations during the fragmentation of the AuNPs. Indeed, as we already noticed previously, Au3+ cations are trapped and stabilized by the dendrimer, acting as catalizers and favouring the oxidation of the molecule, as evidenced by the growth of the UV absorption around 290 nm. According to what is reported in , the fluIn the light of such considerations, we can exclude a direct contribution of AuQDs to the fluorescence signal, which is to be assigned thoroughly to the dendrimer. As a matter of facts, it is still unclear which part of the molecule acts as colour centre, i.e., the terminal groups or the inner cavities. According to ref. 32, PAMAM fluorescence must be attributed mainly to the interior of the molecule even if, on the basis of fluorescence life time spectroscopy, the authors do not exclude the existence of either more than one fluorescent moiety, or a single emitter into two distinct structural microenvironments. Such hypothesis could reasonably explain the rearrangement of the relative intensity of PAMAM G5 emission bands and the different enhancement factors, which we observed in the presence of gold. NP = 6 nm, with statistical distribution σ+ = σ- = 4 nm. As in the case of gold, particles are mostly spherical. However, some of them exhibit irregular shapes, as the one shown in the inset of The same procedure adopted for preparation of PAMAM G5-capped AuNPs can be used in the case of silver. There are few reports in the literature on the preparation of CdSe QDs by laser ablation. Indeed such systems, which are of great interest for several different applications, ranging from biology, to nanomedicine to photovoltaics , could tWe started by ablation with both 355 and 532 nm pulses, in methanol or pure deionized water. In all cases we could observe formation of pale yellow suspensions, which thoroughly precipitated within a few hours. The addition of PAMAM G5 to the initial solution permitted to obtain stable yellow-orange suspensions in the case of 532 nm ablation and aqueous environment. In contrast, either 355 nm pulses in PAMAM G5/water or 532 nm pulses in PAMAM G5/methanol did not allow to prepare stable samples. The results obtained by 532 nm ablation with 10 mJ pulses and three hours irradiation are reported in Fluorescence spectra of the samples are illustrated by 2. The target was placed in a 1cmx1cm quartz cuvette and was kept 2 cm in front of the focal plane of the laser beam. We used 2 mL of stabilizing solution for ablation and 1 or 2 mL for post-irradiation tests. Nanoparticles were prepared by laser ablation of metallic or semiconductor targets in water. We used the fundamental , second (532 nm) or third harmonic (355 nm) of a mode-locked Nd-YAG laser . We post irradiated the obtained suspensions by using the same laser, namely the third harmonic or the second harmonic. The pulse energy was varied from 4 to 20 mJ and the ablation or post-irradiation time from few minutes to several hours. When not otherwise specified, the focussing conditions of the laser beam were maintained constant and the diameter of the laser spot on the target was fixed at 1.4 mm. The fluence on target was varied from 0.1 to 2 J/cm. The sampling beam was perpendicular to the ps laser beam and crossed the quartz cuvette 0.5 cm above the bottom of the cell.The ablation process and the subsequent photofragmentation of nanoparticles were monitored by measuring on-line the visible spectra with an Ocean Optics fiber spectrophotometer and a tungsten lamp.cm @ 25 °C) of 22.2% or 6.37% aqueous solution of PAMAM G5 purchased from Dendritech®. According to tabulated values provided by the producer, PAMAM G5 is a monodisperse compound, having a molecular diameter of 5.4 nm. The gold and silver targets were purchased from Goodfellow and the crystalline CdSe target was purchased from Cradley Crystals. As declared by the producer, the crystal was not exactly stechiometric, but contained an excess of Cd, corresponding to 1016-1017 atoms/cm3.We prepared AuNPs suspensions in solutions of PAMAM G5 in water. The solutions were 3.8 mM with regards to superficial amino groups and were obtained by dilution with ultrapure water (18.2 MΩWe recorded UV-Vis spectra one day after the preparation of the suspensions with a double beam spectrophotometer (Perkin Elmer mod. Lambda19) and fluorescence spectra with a Jasco FP-750 spectrofluorimeter. The particles’ mean diameter and dispersivity were determined by TEM analysis. TEM samples were obtained by dipping carbon-coated copper grids in the suspensions and the images were recorded with a HRTEM JEOL2010, 200KV.We have reviewed our experimental results concerning the use of dendrimer PAMAM G5 as a stabilizing agent in the production of Au, Ag and CdSe nanoparticles obtained by ps laser ablation of a solid target in liquid environment. Indeed, to our knowledge, this molecule, which is extensively employed to cap metal nanoparticles obtained by chemical reduction methods, has never been used in other laboratories for laser ablation tests. The chemical characteristics of PAMAM G5 permit efficient stabilization of the obtained samples. In particular, in the case of CdSe, we have shown for the first time that the presence of the dendrimer in the solution permits preparation of stable and fluorescent samples, corresponding to the zincblend phase of the material. 3+ is evidenced by the growth of a LMCT band in the UV region of the absorption spectrum. Moreover, the formation of Au3+, and its interaction with the dendrimer, causes an impressive increase of PAMAM G5 fluorescence. Although it is still unclear which part of the molecule acts as colour centre, we believe that the emission of our samples does not originate from gold, but it is to be thoroughly assigned to PAMAM through its Au3+–catalized oxidation. Concerning preparation of PAMAM G5 capped AuNPs, we have discussed the role of ablating wavelength and pulse energy. We have shown that the use of the dendrimer permits stabilization of the different products formed by the interaction of the laser pulse with the target or with pre-formed nanoparticles, thus providing a deep insight into the ablation process. In particular, the presence of PAMAM G5 in AuNPs suspensions allows trapping and immobilization of sub-nanoclusters and cations and consequent monitoring of the fragmentation caused by irradiation of AnNPs with 532 and 355 nm pulses. While the presence of sub-nanoclusters can be demonstrated by proper fitting of the UV-Vis spectra of the suspensions, the presence of AuLastly, the stabilizing properties of PAMAM G5 permit reshaping of AuNPs by post-irradiation methods, that is tailoring of their average size and dispersivity. This effect can be observed also in the case of Ag. Indeed, we have shown that AgNPs can also be efficiently stabilized by the dendrimer and that, under proper conditions, they can undergo a photofragmentation process, which permits preparation of stable suspensions of nano or sub-nano particles with reduced dimensions.


In this paper, the mechanical properties of 36 aluminum alloy specimens subjected to repeated tensile loading were tested. The failure characteristics, stress-strain hysteresis curves and its corresponding skeleton curves, stress cycle characteristics, and hysteretic energy of specimens were analyzed in detail. Furthermore, the finite element model of aluminum alloy specimens under low-cycle fatigue loading was established and compared with the experimental results. The effects of specimen parallel length, parallel diameter, and repeated loading patterns on the mechanical properties of aluminum alloys were discussed. The results show that when the specimen is monotonously stretched to fracture, the failure result from shearing break. When the specimen is repeatedly stretched to failure, the fracture of the specimen is a result of the combined action of tensile stress and plastic fatigue damage. The AA6061, AA7075, and AA6063 aluminum alloys all show cyclic softening characteristics under repeated loading. When the initial stress amplitude of repeated loading is greater than 2.5%, the repeated tensile loading has a detrimental effect on the deformability of the aluminum alloy. Finally, based on experiment research as well as the results of the numerical analysis, the calculation method for the tensile strength of aluminum alloys under low-cycle fatigue loading was proposed. Aluminum alloys have the advantages of low weight, high strength, ease of processing, low-temperature resistance, corrosion resistance, and low maintenance. They are widely used in machinery manufacturing, shipbuilding, aerospace, and chemical industries. In recent years, with the continuous promotion and application of fabricated buildings in the field of civil engineering, aluminum alloys have gradually become one of the most extensively used building materials for the main stressed members in construction engineering. Concerning the large-span aluminum alloy reticulated shell structures used in construction, Guo et al. ,2 used tAt present, scholars have carried out fatigue performance tests under low-cycle fatigue loading on different types of aluminum alloys, both at home and abroad. Shaha et al. and Huang et al. ,6 conducIn summary, different types of aluminum alloys are quite different in the mechanical properties including strength, ductility, and stiffness. At present, there are few studies on the mechanical properties of extensively used aluminum alloys in construction engineering. In this study, AA6061, AA7075, and AA6063 aluminum alloys, which are extensively used in construction engineering, were selected as research objects. The mechanical properties of these three types of aluminum alloys under low-cycle fatigue loading are discussed. The work schedule in this study is carried out as follows: (a) Carrying out the mechanical property testing of aluminum alloys under repeated tension, analyzing the failure characteristics, stress-strain hysteresis curves and its corresponding skeleton curves, stress cycle characteristics, and hysteretic energy of specimens. (b) Conducting numerical simulations of the material property tests under repeated tension and comparing with test results to verify the accuracy of the finite element model. (c) Analyzing the parameters of the mechanical properties of aluminum alloys under low-cycle fatigue loading and obtaining the influence of the main parameters on the mechanical properties of aluminum alloys. (d) Based on the results of experimental study and numerical analyses, the strength design formula of aluminum alloys is proposed to provide reference data for the application of aluminum alloys in seismic engineering.Lc is 60 mm and the diameter do is 10 mm; the length of the clamping section at both ends is 35 mm, and the diameter is 16 mm; the radius R of the transition section is 40 mm. In this study, aluminum alloy specimens were directly processed by the use of the computer numerical control (CNC) grinding method for surface finishing, and the value of surface roughness (Ra) of the specimens is 0.5 μm. Based on the material type of the aluminum alloys, the specimens were divided into three groups. The design parameters of the specimens are shown in According to the ISO 6892-1: 2016 Metallic materials-Tensile testing-Part 1: Method of test at room temperature , specimeL0 was 50 mm; the tension and pressure ranges of the extensometer were both 25%. A total of 12 loading patterns were used in the test, and the loading process was process controlled by the displacement; the test loading speed was 0.8 mm/min. The loading scheme is shown in The experiment was carried out using a CMT5105 electronic universal testing machine at the Structural Laboratory of the Huaqiao University . The loading device is shown in Specimens form different fracture morphologies under uniaxial tension and repeated loading, that is, two failure modes are produced. When the specimen is monotonously stretched to breaking, the fracture of the specimen is tensile, which is the first failure mode, as shown in When the specimen is subjected to repeated tension, it produced fatigue damage, as shown in The stress-strain curves of the specimens were extracted, and the influences of material type and loading pattern on the mechanical properties of the specimen were analyzed. In this paper, σ is the force at any moment during the test divided by the original cross-sectional area.The stress-strain curves of three different types of aluminum alloy specimens under loading patterns NM1, NM3-1, NM4-3, and NM5-2 were selected for comparative analysis, as shown in The stress-strain curves of the three groups were selected and compared under the partial loading pattern, as shown in In order to analyze the stress cycle characteristics of aluminum alloys during repeated loading, the stress-time curves of three groups of specimens under the partial loading pattern were extracted and analyzed, as shown in fu and its corresponding strain εu, hysteresis energy E, and elongation rate δ are extracted, as summarized in The test results of the maximum tensile stress The hysteretic energy diagrams of three different types of aluminum alloy specimens in the partial loading pattern are selected for analysis, as shown in The hysteretic energy maps of the three groups of specimens under different loading patterns are selected for analysis, as shown in Based on the design parameters of the aluminum alloys, ANSYS 16.0 is used to establish the finite element model of the specimen. The finite element model is simulated by the eight-node hexahedral solid element SOLID185. Meshing directly affects analysis speed and accuracy of analysis results in finite element simulation. Through adjusting on computer, the element size of intermediate parallel section is 1 mm; the element size of transition section and clamping section is 1.5 mm, 15372 elements can be generated by sweeping. A line displacement constraint is applied to the clamping sections at both ends, and the junction of the upper clamping section is applied according to the loading displacement corresponding to the loading strain. The finite element model is shown in The failure morphology and finite element simulation results of the B-3-3 specimen are extracted as shown in To further verify the accuracy of the finite element model, the stress-strain curves of the three groups of specimens are compared, as shown in In order to further explore the influence of specimen size and loading pattern on the mechanical properties of aluminum alloy specimens, a total of 42 specimens are designed for the numerical analysis. The design parameters of the specimens are shown in ε is the average strain of the parallel sections, and the ordinate σ is the average stress of the parallel sections. It can be seen from To investigate the influence of the specimen size on the mechanical properties, the hysteresis curves of specimens with different sizes under the NM6 loading pattern are selected, as shown in The skeleton curves of the specimens with different parallel section lengths subjected to the NM6 loading pattern are analyzed, as shown in The skeleton curves of the specimens with different parallel section diameters subjected to the NM6 loading pattern are analyzed, as shown in The skeleton curves of three different aluminum alloy specimens are analyzed under different loading patterns, as shown in Ki is:σi is the peak stress of the skeleton curve at the ith loading during low-cycle fatigue loading; εi is the strain value corresponding to σi.In order to study the stiffness degradation law of aluminum alloys under low-cycle fatigue loading the secant stiffness is used to quantitatively analyze the stiffness degradation. The calculation formula of the secant stiffness The secant stiffness of the three aluminum alloy specimens under the action of NM6, NM8-1, and NM9-1 loading patterns is analyzed, as shown in The secant stiffness of the specimens with different parallel section lengths under the NM6 loading pattern is analyzed, as shown in The secant stiffness of the specimens with different parallel section diameters under the NM6 loading pattern is analyzed, as shown in fu of aluminum alloys under low-cycle fatigue loading:εy is the yield strain measured by uniaxial tension, fy is the yield strength measured by uniaxial tension, εmax is the maximum load strain value experienced during low-cycle fatigue loading, and fu is the tensile capacity under low-cycle fatigue loading. α and β are parameters related to the length and diameter of the parallel section of the specimen and the number of loading cycles. Based on the given parameters of the aluminum alloy materials, 1stOpt is used to determine α and β parameters. In the repeated tensile loading pattern, α = (−0.000051 − 0.003035L − 0.000506D − 0.001646N); β = (2.7387 + 0.09794L + 0.2825D + 0.000075N). In the repeated tension-compression loading patterns, α = (−0.7966 + 0.1553 L − 0.9601 D + 0.08113 N); β = (11.1786 − 0.2137 L + 1.3808 D − 0.1099 N). L is the parallel section length, D is the parallel section diameter, and N is the total number of loading cycles.Due to the complexity of the material testing and finite element simulation under low-cycle fatigue loading, it is not easy to directly estimate the tensile strength of the specimen under low-cycle fatigue loading. In order to facilitate the application of aluminum alloys in seismic engineering, based on the experimental research and numerical analysis results, this study proposes a formula for calculating the tensile strength fu of the specimen under low-cycle fatigue loading is calculated using formula (2) and compared with results of the test and the finite element analysis, as shown in The tensile strength To investigate the mechanical properties of aluminum alloys under low-cycle fatigue loading, the mechanical properties of such aluminum alloys were tested under repeated tensile loads. The finite element models of aluminum alloy specimens subjected to low-cycle fatigue loading were established and compared with the experimental results. Furthermore, the mechanical properties of aluminum alloys under low-cycle fatigue loading were analyzed. The main findings of this study are as follows:(1) When the specimen is monotonously stretched to breaking, the fracture surface is dark gray in color and has irregular fibers, and the fracture surface is rough; the fracture cross section and tensile stress direction are at an angle of 45°, which indicates a shear fracture. When the specimen is repeatedly stretched, the fracture surface is dark gray and uneven, the inner ring of the fracture cross section is perpendicular to the tensile stress, and the outer ring and tensile stress direction are at an angle of 45°. The failure of the specimen is the result of the combined action of tensile stress and plastic fatigue damage, which is a mixed fracture of tensile fracture and fatigue fracture.(2) The AA6061, AA7075, and AA6063 aluminum alloys show cyclic softening characteristics under repeated loading. They show rapid softening in the initial stage of repeated loading, while the softening rate slows down in the later stage. (3) When the initial stress amplitude of repeated loading is greater than 2.5%, the repeated tensile loading has a detrimental effect on the deformability of the aluminum alloy.(4) Compared with the repeated tensile loading pattern, the effect of the number of loading cycles on the skeleton curve is more significant in the repeated tension-compression loading pattern; and with the increase in the number of loading cycles, the bearing capacity and stiffness of the specimen will decrease.(5) For the aluminum alloy specimens, when the parallel section length is greater than 40 mm, its influence on the skeleton curve is significant. When the parallel section diameter is less than 12 mm, the influence of the parallel section diameter on the skeleton curve is significant. Reducing the parallel section length or increasing the parallel section diameter can improve the energy dissipation capability and plastic deformation ability of the aluminum alloy.(6) Based on the results of experimental research and numerical analysis, a formula for calculating the tensile strength of aluminum alloys under low-cycle fatigue loading is proposed.


P ≤ 1.56E-03) allelic frequencies and genotype distributions in many study markers in comparison with African, European, American and Asian populations. Based on FST values, the Amerindian population was also the most distinct (mean FST = 0.09917). These data highlight the unique genetic profile of the indigenous population from the Brazilian Amazon region, which is potentially important from a pharmacogenetic viewpoint. Understanding the diversity of ADME- related genetic markers is crucial to the implementation of individualized pharmacogenomic treatment protocols in Amerindian populations, as well as populations with a high degree of admixture with this ethnic group, such as the general Brazilian population.The variation in the allelic frequencies of polymorphic pharmacogenes among different ethnic groups may be responsible for severe adverse reactions to or altered efficacy of a wide variety of drugs. Amazonian Amerindian populations have a unique genetic profile that may have a fundamental on the efficacy and safety of certain drugs. The genetic characteristics of these populations are poorly known, which can negatively impact the systematic application of treatments guided by pharmacogenomic guidelines. We investigated the diversity of 32 polymorphisms in genes responsible for drug Absorption, Distribution, Metabolism and Excretion (ADME) in Amazonian Amerindians, and compared the findings with populations from other continents available in the 1000 Genomes database. We found significantly different ( Much of this inter-individual variability is related to polymorphisms in the genes involved in the Absorption, Distribution, Metabolism, and Excretion (the ADME process) of drugs or the mechanisms that determine their action in the body3.Inter-individual variability plays a fundamental role in the tolerance of and response to a number of different treatments that are widely used in clinical practice6. The principal determinant of this interethnic variability is the allelic frequencies of the polymorphisms found in pharmacogenes, which may vary considerably among different ethnic groups9.The discovery that the response to and tolerance of drugs may vary not only among individuals, but systematically among populations, in particular among different ethnic groups, had a fundamental impact on pharmacogenetic studies, leading to the development of the field of Pharmacoethnicity10, being formed by three principal ancestral groups: European settlers, African slaves, and Amerindians (Native Americans). Five centuries of miscegenation of these groups have resulted in an extremely heterogeneous genetic makeup, and a considerable challenge for pharmacogenetic studies in Brazil13.The Brazilian population is characterized by its high degree of ethnic admixture14 the Amerindian population of Brazil numbers 896 917, representing 0.47% of the country’s population. While this population is genetically distinct, few data are available on the incorporation of modern habits  into its traditional lifestyles. It nevertheless seems likely that distinct patterns of toxicity and response to pharmacological therapies will be found in this ethnic group in comparison with other populations16. However, genomic studies of pharmacogenetic biomarkers are extremely rare in Amazonian Amerindian populations.According to the most recent census (2010) of the Brazilian Institute of Geography and Statistics17.The general lack of pharmacogenomic data for these Amerindian populations represents a major obstacle to the incorporation of Pharmacogenomics (PGx) into the development of individualized treatment protocols designed to maximize the efficacy of therapies in this ethnic group. In this context, the identification of genetic polymorphisms and molecular markers of clinical significance in these populations will be essential for the development of effective treatment protocols not only for this ethnic group, but also for the populations that are admixed with this group, such as the Brazilian oneIn this context, the present study investigated a set of 32 molecular ADME markers in a combined Amazonian Amerindian population, and compared the results with populations representing five continents, obtained from the 1000 Genomes database.The study population was composed of 146 healthy individuals from three Amerindian groups located in the Amazon region of Brazil, selected from a sample database of an epidemiological study of indigenous populations of Pará State. This group included 61 individuals from the Asurini do Trocará group, 25 from the Asurini do Koatinemo group, and 60 from the Kayapó-Xicrin group. The study was approved by the National Committee for Ethics in Research (CONEP), with CAAE number 20654313.6.0000.5172. The informed consent was obtained from each study participant and all research methods in this study were performed in accordance with the approved guidelines.http://www.1000genomes.org), composed of 661 individuals from Africa (AFR), 503For the analyses, these three populations were combined in a single group, denominated IND. For comparison with populations from other continents, we used data obtained from the 1000 Genomes, phase 3 release (available at from Europe (EUR), 347 from the Americas (AMR), 504 from East Asia (EAS), and 489 from South Asia (SAS).www.pharmgkb.org), or it has been pointed in the specific literature as an important biomarker (www.ncbi.nlm.nih.gov/pubmed), and (3) it should also be among the PGx biomarkers recommended for drug dosage adjustment by global drug regulatory agencies.Thirty-two polymorphisms of 16 pharmacogenes were selected based on three main criteria: (1) the marker must be involved in any of the steps of the ADME process; (2) the PGx biomarker should also have high-level clinical annotations or related VIPs in the public database of the PharmGKB , according to the manufacture’s recommendations. The concentration and purity of the DNA were measured with a NanoDrop 1000 spectrophotometer .The polymorphisms of the ADME-related genes were genotyped by allelic discrimination using the TaqMan OpenArray Genotyping technology, with a set of 32 customized assays, which were run in a QuantStudio™ 12 K Flex Real-Time PCR system , according to the manufacturer’s protocol. The Taqman Genotyper software was used for data analysis and to verify the accuracy of the genotype readings, as well as the quality of the genotyping. The data were then filtered for SNPs that deviated from Hardy–Weinberg equilibrium (HWE).The allele frequencies of the Amerindian population were obtained directly by gene counting, and compared with the other study populations . The distribution of the genotypes among the six populations was analyzed using Fisher’s exact test. Pairwise comparisons between populations were also based on Fisher’s exact test, with the p-value being adjusted by the Bonferroni correction, with a critical p-value of 1.56E-03 being considered in all cases.ST). We ran a multidimensional scaling analysis of the FST values to provide a graphical representation of the genetic differentiation of the Amerindian population in comparison with each of the five study populations. The analyses were run in SPSS v.12.0  and Arlequin v.3.518.The inter-population variability of the ADME SNPs was assessed using Wright’s fixation index . The allele frequencies were determined for a total of 32 markers  for the comparisons of allele and genotype frequencies, and the FST values for each pairwise comparison revealed the similarities and differences in the 26 SNPs related to the ADME drug process  analysis of the Fess Fig. ; Table 2The 26 SNPs were also analyzed in pairwise comparisons between the IND population and the mean values for the five 1000 Genomes populations (ALL), as well as each of these populations individually, in order to characterize the unique aspects of the genetic profile of the Amerindian population, in comparison with those of the other populations Table .Table 3PABCB1, ABCC2, ABCC4, ABCG2, SLC22A7, and SLC29A1 genes. In the case of the phase I genes, there were two groups, the CYP2A6 and the DPYD genes with six significantly different polymorphisms. We also observed significantly different distributions in six polymorphisms in six other genes involved in the ADME processing of drug: the ITGB5, MTHFR, RRM1, TP53, TYMP and UMPS genes.In the comparison between the IND and the AFR populations, the distribution of 20 polymorphisms of 14 genes was significantly different between populations. Eight of the polymorphisms involved six transporter genes: the ABCG2, SLC22A7 and SLC29A1. Five polymorphisms were found in the phase I genes, CYP2A6 and DPYD. Four polymorphisms of four other ADME genes were also significantly different, that is, the ITGB5, MTHFR, RRM1 and UMPS genes.By contrast, we identified only 12 polymorphisms of nine genes that varied significantly between the IND and the AMR populations. These included one polymorphism in each of the three transporter genes: ABCC2, ABCG2, SLC22A7, and SLC29A1 genes. Significant differences were also found in the two phase I genes, CYP2A6 and DPYD. A significant level of variation was also found in a further five polymorphisms, of five genes, the FPGS, ITGB5, MTHFR, TP53 and UMPS.In the comparison between the IND and the EAS populations, 16 polymorphisms of 11 genes had a significantly different distribution. These included five polymorphisms of four transporter genes: the ABCC2, ABCC4, ABCG2, SLC22A7 and SLC29A1. In the phase I genes, significant differences were found in one polymorphism of the CYP2A6 gene and in four polymorphisms of the DPYD gene. The analysis also demonstrated significant differences in seven polymorphisms in five other genes related to the ADME: the ITGB5, MTHFR, RRM1, TYMP, and UMPS genes.Pairwise comparisons between the IND and the EUR populations revealed significant differences in 18 polymorphisms in 12 genes. Six of these polymorphisms involved five transporter genes: ABCB1, ABCG2, SLC22A7, and SLC29A1. Six of the variants were also found in the phase I genes, CYP2A6 and DPYD. The five other markers were identified in four other ADME-related genes, ITGB5, MTHFR, TP53 and UMPS.Finally, significant differences were identified between the IND and SAS populations in 16 polymorphisms present in 10 genes. Five of these polymorphisms were present in four transporter genes: 19. High rates of hospitalization due to ADRs are caused, in part, by the standardization of drug doses, which overlooks the variability among patients in factors such as the symptoms of the disease, environmental and genetic characteristics, and ethnicity21.Adverse Drug Reactions (ADRs) are one of the principal causes of morbidity in developed countries22. The main challenge to achieve maximum effectiveness of a drug is also the interindividual variability in drug response. Drug mechanisms focused on targets with genetic support would succeed twice as often as those without it, reducing the clinical trial’s phases due to lower rates of failure caused by lack of efficacy during clinical development23.Another important factor to be considered during treatment choice is drug efficacy, the ability of a drug to achieve the desired effect25. There have been relatively few studies of molecular biomarkers in Amerindian populations, highlighted by the fact that they are absent from the 1000 Genomes database, the largest available collection of data on human genetic variability.Most pharmacogenetic studies focus on Caucasian populations, which cannot necessarily be extrapolated reliably to the application of PGx in other ethnic groups, such as Amerindian, which may have a unique genetic profile resulting from prolonged geographic isolation and inbreedingThis emphasizes the need for the investigation in other ethnic groups, in particular Amerindians, of predictive molecular biomarkers known to play a role in specific treatments or other, as yet undiscovered markers, in order to understand the genetic variability of these populations and to use the knowledge to delineate personalized treatment protocols, in order to improve drug security in Amerindian populations from the Amazon region, as well as in other populations with a high degree of admixture with this ethnic group.ST indices indicate that the Amerindian and African populations were the most distinct genetically, which is consistent with the history of the world’s human populations, in which the Amerindian and African groups represent the extremes of the evolutionary process26.In the present study, we compared the genetic variability of Amerindian populations from the Amazon region with five populations from the 1000 Genomes Project, analyzing 26 genes responsible for the absorption, distribution, metabolization, and excretion of drugs. The FST analysis, the lower values of genetic differences with the Amazonian Amerindians is observed on the East Asian population , which is mainly composed of Chinese and Japanese individuals. This outcome corroborates with the “Bering Strait” hypothesis, which discusses that the settlement of the Americas and the formation of the first Native Americans are due the migrations of Asians populations that occurred less than 15,000 years ago through a land extension known as the Bering land bridge, which joined Northeast Asia and North America27.Still regarding the FST analysis concomitant with the pairwise comparisons analysis, the Amerindian population is genetically most similar to the American population, with significant differences being found in only 12 polymorphisms, and an FST value of 0.06042. The American samples from the 1000 Genomes database includes Colombian (CLM), Puerto Rican (PUR), Peruvian individuals (PEL), and Californian residents of Mexican descent (MXL), who are representative of the different populations of Latin America, which implies a certain degree of genetic similarity with the ancestral populations of South and Central America28.Relying up on the F29. This genetic admixture originated during the European colonization of the New World, when native Americans came into contact with European immigrants arriving on the continent from 1492 onward, and with African immigrants, from 1502 onward30.In fact, high levels of interethnic admixture have already been shown in populations from the Americas, and in particular, from Latin Americaet al. (2012) investigated the exome of the Colombian, Mexican and Puerto Rican populations from the 1000 Genomes database and estimated the contributions of African, European, and Native American ancestors to these populations. The findings of the study indicated that Amerindians contributed 12.8% of the PUR exome, 25.6% of that from CLM, and 47.6% from MXL31. There are still no studies that evaluate the ancestry of Peruvian samples in the 1000 Genomes database, however, Homburger et al. (2015) evaluated 119 individuals from Peru and determined that they had an Amerindian ancestry of 68.3%32.Gravel The profile of the genomic ancestry of Latin American countries thus indicates considerable heterogeneity in terms of the contribution of Amerindians, resulting from the varied history of the formation of these populations, and their degree of interethnic admixture. The study of ADME polymorphisms in native American populations is, therefore, fundamentally importance to ensure the optimal implementation of healthcare programs that include genomic information on both Latin and Amerindian populations.ABCB1, CYP2A6 and DPYD– whose profiles in the Amerindian population were significantly different from the other study populations. The impact on the enzyme activity caused by the allelic variants analysed is described at Supplementary Table 33.Here, we discuss specifically the data on three of the genes – ABCB1 gene (P-glycoprotein encoding [P-gp]) belongs to the ATP-binding cassete (ABC) superfamily of human carriers, and plays a key role in the absorption, distribution, and elimination of drugs within the organism, being considered one of the major determinants of drug resistance34. The rs1128503 and rs1045642 polymorphisms of the ABCB1 gene have been identified as have a potential role in the response to and toxicity of a number of different drugs, including imatinib, opioids and treatments for epilepsy37.The ABCB1 gene and Aliskiren (Rasilez HCT®), an antihypertensive drug. The EMA identifies ABCB1 as the principal efflux system involved in the intestinal absorption and biliary excretion of the drug and contraindicates the concomitant administration of Aliskiren and medications that may influence ABCB1 gene action38. The HCSC also refers to the role of the ABCB1 gene in the Aliskiren efflux system in its drug labelling, contraindicating the use of different glycoprotein inhibitors and other drugs during treatment with Aliskiren39. Polymorphisms on the ABCB1 gene also may cause a polymorphic enzyme of P-gp with diminished activity40, therefore, should also be considered as an influence factor of Aliskiren efficacy.The European and Canadian drug regulatory authorities require the inclusion of pharmacokinetic information on their drug labels on the interaction between the ABCB1 variants (of at least 40%) in the Amerindian populations from the Amazon Region. These variants may reduce glycoprotein activity and thus alter the metabolization of antihypertensive drugs, such as Aliskiren, affecting its efficacy in the treatment of Amerindian populations.In the present study, we found high allele frequencies of the CYP2 genes on chromossome 19 includes six families, one of which is the CYP2A family, with three genes, the CYP2A6, CYP2A7, and CYP2A13. The CYP2A6 gene is highly polymorphic, and its protein product represents one of the principal liver enzymes responsible for the metabolism of drugs and xenobiotics41.The cluster of CYP2A6 gene on its Letrozole label. Letrozole is a chemotherapeutic drug used to treat breast cancer. In vitro studies have shown that it is metabolized primarily in its inactive form in liver microsomes through the action of the CYP2A6 gene42.The Japanese Pharmaceutical Regulatory Agency (PMDA) includes pharmacogenetic information on the CYP2A6 polymorphisms, which modify enzyme activity, may suffer either an increased toxicity profile or treatment shortcomings. There is a wide range of functional activity data for the described variants of CYP2A6, leading to either differences in enzyme activity or mRNA expression and, consequently, protein levels43. Patients with specific polymorphic variants or a combination of CYP2A6 polymorphisms that define them as poor metabolizers may present a twofold increase in their plasmatic concentrations of Letrozole when compared with extensive metabolizers42.Patients identified as poor or normal metabolizers based on their CYP2A6*9 (rs28399433), which was extremely frequent (46%) in the Amerindian population, and much higher than in the other populations, in which the mean frequency is 13%. This indicates that the Amerindian population from the Amazon region has an abnormally high proportion of poor metabolizers, due to the frequency of the CYP2A6*9 variant, which may determine adverse toxic reactions during treatment with Letrozole, and other drugs that are metabolized by the CYP2A subfamily.One of the markers associated with the poor metabolizer profile is DPYD gene is composed of 23 exons at the 1p22 chromosomal locus. This gene encodes the enzyme dihydropyrimidine dehydrogenase (DPD), which accounts for about 85% of the hepatic catabolism of 5-fluorouracil to its inactive metabolic form, 5- fluoro-5,6-dihydrofluorouracil44. Because this is an essential enzyme in the metabolism of 5-fluorouracil, patients with low DPD enzyme activity have a higher risk of developing severe and even lethal toxicities during standard chemotherapeutic treatment with this drug45.The DPYD genotypes as the major non-functional variants of this gene: *2 A (rs3918290), *13 (rs55886062), and rs67376798. The CPIC guidelines characterize phenotypes based on each of these three variants, and strongly recommend the use of alternative drugs or the reduction of the standard 5-Fluorouracil dose by 50% for patients who are either homozygous or heterozygous for any of these three variants46.The guidelines of the Clinical Pharmacogenetics Implementation Consortium (CPIC) indicate three DPYD gene in their pharmacogenetic drug labels. Capecitabine is one of the major 5- Fluorouracil prodrugs used to treatment various types of solid neoplasias. The FDA includes a warning note in its label for this drug (XELODA®), advising patients who have genotypes associated with an absence or reduced activity of DPD that they are at a higher risk of developing severe or potentially lethal adverse reactions47.A number of national drug regulatory authorities include information on the 49.The FDA also includes pharmacogenetic information labels on the potential for severe toxicity in patients with DPD deficiency during treatment with Fluorouracil, describing the different types of adverse reaction presented by patients with homozygous or heterozygous mutations resulting from a partial or total deficiency of the DPD enzyme. The FDA recommends discontinuing permanently the use of Fluorouracil based on the severity of the toxicities observed in patients treated by the 5- FU regimeDPYD gene were identified in our Amerindian population. The allele frequencies of the rs17116806, rs1801159 and rs4970722 markers were all higher than 40%, contrasting with the much lower frequencies found in all other populations around the world. Two of three deleterious polymorphisms mentioned in the CPIC guidelines were identified in our Amerindian population. The frequency of the rs3918290 marker was 1%, similar to that of most other populations, in particular those from Asia. The rs55886062 marker had a frequency of 2%, however, which is relatively high in comparison with the other populations, in which it did not exceed 1%, when present.Nine polymorphic variants of the In our Amerindian population, the frequency of the rs1801133 mutation was consistent with that found in the other study populations (mean = 23%), whereas the rs1801131 polymorphism had a low frequency (9%) compared to the other populations (mean = 25%). This indicates a lower risk of developing serious adverse effects in Amerindian women, associated with the use of contraceptives based on norelgestromin and ethinylestradiol.Up until now, there has been no systematic assessment of the potential response of Amerindian ethnic groups from the Amazon basin to treatment with drugs known to be influenced by genetic polymorphisms. Our study evaluated the unique features in the genetic profile of 26 ADME-related genes in an Amazonian Amerindian population comparing with others continental populations, which may reflect a distinct therapeutic profile in relation to the efficacy and toxicity of drugs marketed widely for the treatment of a range of diseases. Given this, there is a clear need for the understanding of the individual genetic profiles of Amerindians, and the application of this knowledge to the design of specific pharmacogenomic-guided treatment protocols for indigenous Amazon ethnic groups. This approach would also be valid for populations, such as that of Brazil, which present a high degree of miscegenation with this indigenous group. As future perspectives of our research group regarding this study, data on other clinically better known ADME polymorphisms will further be reported in a separate paper.Table SI. Functional Activity of the allelic variants of ABCB1, CYP2A6 and DPYD gene.


A complete itemization of corrections is as follows: (1) the number of authors who received payments and the percentage of payments accounted for by corresponding authors in the Key Points; (2) the number of authors who received payments, the percentage of payments accounted for by corresponding authors, and the payment value in the abstract; (3) the number of authors who received payments, the percentage of payments accounted for by corresponding authors, and the payment value in the Results section; (4) the percentage of authors who received payments, the percentage of payments accounted for by corresponding authors, and the payment value in the Discussion section; (5) the number of authors who received payments in the Conclusions section; (6) the payment value and the number of authors who received payments in Table 2; and (7) the payment value and the number of authors who received payments in Table 3. This article has been corrected.1In the Original Investigation titled “Payments From Pharmaceutical Companies to Authors Involved in the Valsartan Scandal in Japan,”


Computers are used as a means of social communication, for work and other purposes. However, patients with spinal cord injuries may have a higher risk than normal individuals with musculoskeletal problems when using computers owing to their inability to control respective postures due to problems in motor and sensory functioning.  This study is aimed at identifying the effect of computer desk heights on musculoskeletal discomforts of the neck and upper extremities and EMG activities in patients with spinal cord (C6) and upper thoracic spinal cord injuries.  Participants of the present study were the patients diagnosed with ASIA A or B. The patients were divided into two groups according to their spinal cord injuries: C6 group and T2-T6 group. The level of the desk was set at 5 cm below the elbow, at the elbow level, and 5 cm above the elbow level. Electromyography was used to measure the duration of typing task EMG(%RVC) of the cervical erector spinae, upper trapezius, anterior deltoid, and wrist extensor. Subjective musculoskeletal discomfort (Borg-RPE) was measured at the end of the experiment. p < .05). Postanalysis revealed the C6 group had decreased RPE as the level of computer desk increased, whereas the subjects in the T2-T6 group had decreased RPE values in accordance with the decreasing level of computer desk (p < .05). In EMG, both groups had no significant differences (p > .05). However, in terms of the interaction between the muscles and the level of computer desk in both groups, the differences in the interactions of the upper trapezius and wrist extensor with each level of the desk were found (p < .05).  The two groups showed differences in terms of RPE corresponding to each level of the computer desk ( This study is meaningful in that it confirms computer work posture and preference of spinal cord-injured individuals. The global incidence of spinal cord injury shows an increasing trend every year. Approximately one-third of patients with spinal cord injuries also have tetraplegia, wherein approximately 50% of the patients have complete injuries , 2. The The number of working environments involving interfaces with computers has been increasing recently, wherein the majority of employees spend an average of 7 hours a day working at the interfaces to complete their work . IndividTherefore, the present study is aimed at identifying the effects of computer desk heights on musculoskeletal discomfort of the neck and upper extremities and EMG (electromyography) activities of patients with spinal cord (C6) and upper thoracic spinal cord injuries (T2-T6).A total of 12 patients admitted to the Y-rehabilitation Hospital located in Gyeonggi-do province from January 17 to January 26, 2018, were included in the present study. They were divided into the following two groups according to the level of spinal cord injury: C6 group (six patients) and T2-T6 groups (six patients).The inclusion criteria were as follows: (1) patients diagnosed as having complete injuries of motor function of the types of either ASIA A or B defined by the American Spinal Injury Association (ASIA) without cerebral injuries and complications such as bone fracture or bedsores –17; (2) The study protocol was approved by the IRB of Hallym University no. HIRB-2017-064) and adhered to the ethical principles of the Declaration of Helsinki. The computer used for the study had a 21-inch monitor with adjustable levels, wherein the top of the monitor was set at the patient's eye level. The distance from the monitor to the eyes of the patients was set at 70 cm, rather than the recommended range of 63 to 93 cm, in consideration of the patients' physical characteristics as subjects and their positions were each monitored into account . Keyboar17-064 anDuring the task, EMG measurement was performed using a wireless EMG system  . Adhesivα = 0.05. The postanalytic Dunn-Bonferroni procedure was used to perform multiple comparisons of the variables found to be statistically and significantly different.The PASW 22.0  for Windows was used for the statistical analyses. The patients' general characteristics, such as the age, height, weight, sitting eye level, and sitting elbow height, were expressed in mean values and standard deviations, whereas the date of onset of spinal cord injury, ASIA scale, and level of injuries were expressed in percentage. An ANOVA was carried out to analyze the musculoskeletal discomfort corresponding to the different levels of the computer desk to determine the correct level of computer desk corresponding to each level of injury. Values of %RVC for the four muscles of subjects which corresponded to each level of the computer desk were analyzed by conducting a two-way ANOVA for repetitive measurements. The significance level was set at The details of the general characteristics of the subjects are summarized in p < .05) (p < .05), whereas, in the T2-T6 group, the RPE value decreased when the computer desk height was decreased (p < .05). In particular, the RPE values of the T2-T6 group were significantly different in the following computer desk levels: (1) between the 5 cm below the elbow level and elbow level and (2) between the 5 cm above the elbow level and 5 cm below the elbow level (p < .05). However, the RPE values in the computer desk level between the level of the elbow and 5 cm above the elbow level had no significant difference (p > .05)  . The RPEp > .05) .p > .05)  .p < .05)  .In the present study, we investigated the effects of the varied keyboard positions and computer desk heights on musculoskeletal discomforts and EMG activities of patients with spinal injuries who were asked to perform a typing task on a computer, with the goal of identifying the proper keyboard position and computer desk level for these patients to prevent the occurrence of musculoskeletal problems.Factors that affect the neck and shoulder muscle tension when handling the tasks involving the use of the keyboard include: first, the incline of the thoracic spine and lumbar spine; second, the posture of the cervical vertebrae; third, the posture of the upper arm; fourth, the position of the keyboard and design; and fifth, computer-working skills and break between the work . In partThe results of the study showed that the significant differences are found between the RPE values and the varied computer desk levels in both patient groups. Our results were similar to the findings of a previous study involving patients with upper thoracic spinal cord injury who were using wheelchairs which sought to identify subjective preference and degree of fatigue when working on computers with various desk heights similar to ours. Their patients preferred the desk height level of 5 cm below the elbow level , 28. TheIn the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI), the seriousness of the injury is described by using ASIA Impairment Scale. The most severe grade AISA A is considered AISA A because the sensory or motor function is not maintained in the spinal cord S4-5 because the sensor is completely lost . In partMoreover, the effects of the different keyboard positions on EMG activities of patients with spinal cord injuries during the typing task were explored. No significant differences were found between the varied keyboard positions and EMG activities. The Occupational Safety and Health Administration (OSHA) of the United States of America recommends that the appropriate keyboard position should be from 70° to 135° of elbow flexion. However, these recommended levels are only applicable in healthy individuals; hence, studies investigating the effects of computer desk level of work table on the upper extremities, necks, and shoulders of patients with spinal cord injuries using wheelchairs are warranted . FurtherThe population of disabled people in Korea was estimated to be approximately 2,510,000 in 2014, wherein the individuals with spinal cord injuries account for 4.9% of the population with limb and body disabilities . In partThe study had several limitations. First, the study has a small sample size. Second, the representativeness of the included patients was difficult to secure despite the homogeneity of the patient's general characteristics to avoid selection bias in the study participants. Third, the typing task was a simplified short-run task, which was remarkably different from the actual work performed in computers. Thus, future studies with a large sample size and varied computer task to examine EMG activities are warranted.The RPE values, which represent the subjective measurement of musculoskeletal problems of the upper extremities of the patients in the C6 group, decreased at the computer desk level of 5 cm above the elbow level, whereas the patients in the T2-T6 group had decreased RPE values at the computer desk level of 5 cm below the elbow. Moreover, the subjects in both groups commonly exhibited no significant differences in EMG activities corresponding to the different levels of the keyboard. However, the upper trapezius and wrist extensor, among the four muscles, were found to be associated with the varied computer desk levels in both groups.The appropriate computer working conditions should be customized according to the need of the individual with a disability.