The alpha7 nicotinic acetylcholine receptor: molecular modelling, electrostatics, and energetics

The structure of a homopentameric alpha7 nicotinic acetylcholine receptor is modelled by combining structural information from two sources: the X-ray structure of a water soluble acetylcholine binding protein from Lymnea stagnalis, and the electron microscopy derived structure of the transmembrane domain of the Torpedo nicotinic receptor. The alpha7 nicotinic receptor model is generated by simultaneously optimising: (i) chain connectivity, (ii) avoidance of stereochemically unfavourable contacts, and (iii) contact between the beta1-beta2 and M2-M3 loops that have been suggested to be involved in transmission of conformational change between the extracellular and transmembrane domains. A Gaussian network model was used to predict patterns of residue mobility in the alpha7 model. The results of these calculations suggested a flexibility gradient along the transmembrane domain, with the extracellular end of the domain more flexible that the intracellular end. Poisson-Boltzmann (PB) energy calculations and atomistic (molecular dynamics) simulations were used to estimate the free energy profile of a Na+ ion as a function of position along the axis of the pore-lining M2 helix bundle of the transmembrane domain. Both types of calculation suggested a significant energy barrier to exist in the centre of the (closed) pore, consistent with a "hydrophobic gating" model. Estimations of the PB energy profile as a function of ionic strength suggest a role of the extracellular domain in determining the cation selectivity of the alpha7 nicotinic receptor. These studies illustrate how molecular models of members of the nicotinic receptor superfamily of channels may be used to study structure-function relationships.     

The effect of methanol on photosynthetic parameters of bean (Phaseolus vulgaris L.) under water deficit

Water availability is the main factor limiting crop growth and productivity in dry regions. This study was carried out in order to determine the effect of spraying methanol solution on the photosynthetic characteristics of bean plants. The main aim of our experiment was to improve plant performance under stress caused by water shortage. Two factors were involved: water-deficit stress, such as severe stress (25% of field capacity), mild stress (75% of field capacity), and no stress (100% of field capacity), and application of methanol solution spray at four concentrations: control (without spraying), 10, 20, and 30%. Methanol was applied three times at different growth stages (seedling, flowering, and podding stage) in 10-d intervals. The treatment with 20% methanol at the seedling stage resulted in increased net photosynthesis (P_N), intercellular CO₂ concentration (C_i), and decreased transpiration rate (E) under no stress and mild stress conditions. Under severe stress, 10 and 20%-methanol treatments resulted in increased C_i, maximal quantum yield of PSII photochemistry, and decreased E. At the flowering stage, methanol treatments resulted in decreased E and increased C_i under mild and severe stress. At the podding stage, 10 and 20%-methanol treatments resulted in increased P_N, C_i, and total chlorophyll content under mild stress. In conclusion, we suggested that foliar application of methanol had a positive role in enhancing photosynthetic performance.     

Effect of vermicompost fertilizer on photosynthetic characteristics of chickpea (Cicer arietinum L.) under drought stress

Water availability is an important factor for plant growth in arid environments. In recent decades, vermicompost (VC) fertilizer has been used in agriculture as a safe and effective fertilizer with high water-holding capacity. The aim of the present study was to characterize effects of VC fertilizer on photosynthetic activity of chickpea (Cicer arietinum L. cv. Karaj) under drought conditions at three different growth stages. Tests were carried out with four volumetric ratios of VC to soil, i.e., 0:100, 10:90, 20:80, and 30:70, and three levels of drought stress, i.e., no stress (NS), moderate drought (MS), and severe drought (SS) (100, 75, and 25% of field capacity, respectively). Evaluations were performed at the seedling, flowering, and podding stage. We found that the VC treatment under NS conditions significantly increased total chlorophyll content [Chl (a+b)], intercellular CO₂ concentration (C_i), net photosynthetic rate (P_N), transpiration rate (E), and maximal quantum yield of PSII photochemistry (F_v/F_m) at all three stages. The VC addition of 10 and 20% significantly enhanced the Chl content and F_v/F_m under MS and F_v/F_m, C_i, and P_N under SS at the flowering stage. In conclusion, our results proved a positive effect of the VC fertilizer on photosynthesis of chickpea under NS conditions, but it was not found under MS and SS.     

Sublethal concentration of H<Subscript>2</Subscript>O<Subscript>2</Subscript> enhances the protective effect of mesenchymal stem cells in rat model of spinal cord injury

Objective

To investigate the effect of H₂O₂ on the migration and antioxidant defense of mesenchymal stem cells (MSCs) and the neurotrophic effects of H₂O₂-treated MSCs on spinal cord injury (SCI).

Results

Sublethal concentrations of H₂O₂ decreased cell migration and expression of CXCR4 and CCR2 as well as Nrf2 expression in MSCs. In the second phase, transplantation of treated and untreated MSCs to SCI caused minor changes in locomotor dysfunction. There was a significantly difference between cell-treated and spinal cord injury groups in expression of BDNF (brain-derived neurotrophic factor). Transplantation of H₂O₂-treated cells caused an increase in BDNF expression compared to non-treated cells.

Conclusion

Transplantation of H₂O₂-treated stem cells may have protective effects against SCI through by increasing neurotrophic factors.

     

Schistosoma mansoni: cell-specific expression and secretion of a serine protease during development of cercariae.

Eukaryotic serine proteases are an important family of enzymes whose functions include fertilization, tissue degradation by neutrophils, and host invasion by parasites. To avoid damaging the cells or organisms that produced them, serine proteases must be tightly regulated and sequestered. This study elucidates how the parasitic blood fluke Schistosoma mansoni synthesizes, stores, and releases a serine protease during differentiation of its invasive larvae. In situ hybridization with a cDNA probe localized the protease mRNA to acetabular cells, the first morphologically distinguishable parasite cells that differentiate from the embryonic cell masses present in the intermediate host snail. The acetabular cells contained vimentin but not cytokeratins, consistent with a mesenchymal, not epithelial, origin. Antiprotease antibodies, localized by immunoperoxidase, showed that the protease progressively accumulated in these cells and was packaged in vesicles of three morphologic types. Extension of cytoplasmic processes containing protease vesicles formed "ducts" which reached the anterior end of fully differentiated larvae. During invasion of human skin, groups of intact vesicles were released through the acetabular cytoplasmic processes and ruptured within the host tissue. Ruptured protease vesicles were noted adjacent to degraded epidermal cells and dermal-epidermal basement membrane, as well as along the surface of the penetrating larvae themselves. These observations are consistent with the proposed dual role for the enzyme in facilitating invasion of host skin by larvae and helping to release the larval surface glycocalyx during metamorphosis to the next stage of the parasite.     

HIV,HBV and HCV Coinfection Prevalence in Iran - A Systematic Review and Meta-Analysis

Background

worldwide, hepatitis C and B virus infections (HCV and HCV), are the two most common coinfections with human immunodeficiency virus (HIV) and has become a major threat to the survival of HIV-infected persons. The review aimed to estimate the prevalence of HIV, HBV, HCV, HIV/HCV and HIV/HBV and triple coinfections in different subpopulations in Iran.

Method

Following PRISMA guidelines, we conducted a systematic review and meta-analysis of reports on prevalence of HIV, HBV, HCV and HIV coinfections in different subpopulations in Iran. We systematically reviewed the literature to identify eligible studies from January 1996 to March 2012 in English or Persian/Farsi databases. We extracted the prevalence of HIV antibodies (diagnosed by Elisa confirmed with Western Blot test), HCV antibodies and HBsAg (with confirmatory laboratory test) as the main primary outcome. We reported the prevalence of the three infections and coinfections as point and 95% confidence intervals.

Findings

HIV prevalence varied from %0.00 (95% CI: 0.00–0.003) in the general population to %17.25 (95% CI: 2.94–31.57) in people who inject drugs (PWID). HBV prevalence ranged from % 0.00 (95% CI: 0.00–7.87) in health care workers to % 30.9 (95% CI: 27.88–33.92) in PWID. HCV prevalence ranged from %0.19 (95% CI: 0.00–0.66) in health care workers to %51.46 (95% CI: 34.30–68.62) in PWID. The coinfection of HIV/HBV and also HIV/HCV in the general population and in health care workers was zero, while the most common coinfections were HIV/HCV (10.95%), HIV/HBV (1.88%) and triple infections (1.25%) in PWID.

Conclusions

We found that PWID are severely and disproportionately affected by HIV and the other two infections, HCV and HBV. Screenings of such coinfections need to be reinforced to prevent new infections and also reduce further transmission in their community and to others.     

A Theoretical Study on the Influence of Carrier Generation on Drain-Source Current of Graphene Nanoscroll Transistors

Plasmonics - A novel approach is presented in order to study the effects of carrier generation on the drain-source current of graphene nanoscroll field effect transistors (GNSFET). In this method,...     

Induction of multipotency in umbilical cord-derived mesenchymal stem cells cultivated under suspension conditions

Due to the limitations in the clinical application of embryonic stem cells (ESC) and induced pluripotent stem cells, mesenchymal stem cells (MSCs) are now much more interesting for cell-based therapy. Although MSCs have several advantages, they are not capable of differentiating to all three embryonic layers (three germ layers) without cultivation under specific induction media. Hence, improvement of MSCs for cell therapy purposes is under intensive study now. In this study, we isolated MSCs from umbilical cord tissue at the single-cell level, by treatment with trypsin, followed by cultivation under suspension conditions to form a colony. These colonies were trypsin resistant, capable of self-renewal differentiation to the three germ layers without any induction, and they were somewhat similar to ESC colonies. The cells were able to grow in both adherent and suspension culture conditions, expressed both the MSCs markers, especially CD105, and the multipotency markers, i.e., SSEA-3, and had a limited lifespan. The cells were expanded under simple culture conditions at the single-cell level and were homogenous. Further and complementary studies are required to understand how trypsin-tolerant mesenchymal stem cells are established. However, our study suggested non-embryonic resources for future cell-based therapy.     

Serum Levels of Antioxidants (Zn, Cu, Se) in Healthy Volunteers Living in Tehran

Zinc (Zn), copper (Cu), and selenium (Se) are well-known as essential trace elements. These elements attract a great interest, not only in the scientific world, but also in the public option. The aim of this study was to evaluate the serum Zn, Cu, and Se levels in healthy volunteers (60 females and 55 males) living in Tehran. The age (6–62 years) and sex of the subjects, as well as drug and tobacco consumption, were registered. The concentrations of these elements were determined by atomic absorption spectrometry. The serum levels of Zn, Cu, and Se in the normal population of Tehran was 0.89?±?0.16 mg/L, 0.95?±?0.20 mg/L, and 99.10?±?21.78 μg/L, respectively. There was no significant gender-related difference in serum Zn concentration (p?<?0.15). However, a significant difference (p?<?0.05) in both Cu and Se levels was observed between males and females.     

Triploidy induction in the Caspian salmon, Salmo trutta caspius, by heat shock

Induction of triploidy was attempted in the Caspian salmon, Salmo trutta caspius, using heat shocks. The optimal temperature level (26, 28 and 30°C), initiation time [5, 10, 20 and 40 min post-fertilization (PF)] and duration of thermal shock (5, 10 and 20 min) required for effective induction of triploidy were investigated. Incidence of triploid fry was determined by surface and volume measurements of erythrocytes as well as from flow-cytometric analysis of some blood samples. Survival from fertilization to swim-up, triploid rates and triploid yields were in the range of 0–70%, 0–97% and 0–57%, respectively. The highest triploid yield was obtained with a shock treatment at 26°C for 10 min duration initiated 40 min PF.