Relationship of single-nucleotide polymorphism rs11562975 in thermo-sensitive ion channel TRPM8 gene with human sensitivity to cold and menthol

The examination of people belonging to the Russian ethnic group revealed that 20.3% of subjects had heterozygous genotype, containing the C-allele in single nucleotide polymorphism rs11562975, located in exon 7 of the gene encoding the temperature-sensitive ion channel TRPM8. Functional differences, associated with sensitivity to cold and menthol were identified between subjects with different genotypes of the polymorphism rs11562975 (GG and GC). Subjects with heterozygous genotype GC were characterized by increased sensitivity to cold and reduced sensitivity to menthol, agonist of the ion channel TRPM8, compared with subjects with homozygous genotype GG.     

Morphological and functional abnormalities in neuromuscular junctions of Drosophila melanogaster induced by the expression of human APP gene

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the loss of neurocortical and hippocampal synapses that precedes amyloidosis and neurodegeneration and closely correlates with memory impairment. Mutations in the amyloid precursor protein (APP) cause familial AD and result in the increased production of amyloid-beta-protein (Abeta). To gain insights into synaptic effects of APP, we expressed APP, mutant form APP-Swedish and BACE in the motor neurons of fly larvae. We have shown that targeted expression of APP (APP-Swedish) in Drosophila larval motor neurons causes significant morphological and functional changes in neuromuscular junctions (NMJs): a dramatic increase in the number of synaptic buttons and changes in exocytosis as revealed by incorporation of the styryl dye FM4-64. Analysis of the number and distribution of mitochondria showed that motor neurons overexpressing APP (APP-Swedish) had a significant reduction of functional mitochondria in the presynaptic terminal. Significant synaptic abnormalities were observed for APP (APP-Swedish) and human beta-secretase (BACE) resulting in secretion of amyloid beta protein (Abeta). We suggest that APP participates in regulation of synaptic functions and its elevated expression leads to synaptic pathology independently from neurotoxic effects of Abeta.     

An evaluation of the analysis system of video transects used to sample subtidal epibiota

Two popular methods of benthic cover estimation (the point intercept technique with two sets of position points, and digital interactive color segmentation) were compared with an alternative method of digital cover estimation using Bezier curves as a tool for outlining the objects on an images and AutoCAD® software for the final evaluation of abundance. The comparison was done using still video images obtained from two 10-m transects on subtidal rocks off the Rimsky-Korsakov islands in the Sea of Japan (Russia). Ten rectangular sectors (1×0.4 m each) selected randomly within both video transects were analyzed. One-way ANOVA for repeated measurements was used to test the differences between methods. The point intercept technique differed significantly from both methods of digital estimation and had an essential positive bias. The Tukey multiple comparison test revealed the differences among digital estimation methods in the species, which have the complicated color with many contrast spots. The proposed approach using Bezier curves has an advantage over the interactive color segmentation if the objects under selection are lit at different levels or have a contrast coloration or are hidden by canopy organisms. Besides, estimation of cover in the field of AutoCAD® software is more precise and takes less time than that obtained using a scaled grid, available for automatically segmented species. The results showed that digital cover estimation using Bezier curves and AutoCAD® software is a convenient method for analyzing benthic samples at large spatial scales.     

Global stability in discrete population models with delayed-density dependence

We address the global stability issue for some discrete population models with delayed-density dependence. Applying a new approach based on the concept of the generalized Yorke conditions, we establish several criteria for the convergence of all solutions to the unique positive steady state. Our results support the conjecture stated by Levin and May in 1976 affirming that the local asymptotic stability of the equilibrium of some delay difference equations (including Ricker's and Pielou's equations) implies its global stability. We also discuss the robustness of the obtained results with respect to perturbations of the model.     

Effects of native and oxidized apolipoprotein A-I on lipid bilayer microviscosity of erythrocyte plasma membrane

Using a pyrene as a fluorescent probe, we investigated the influence of native and oxidized apolipoprotein A-I (apo A-I) and their complexes with tetrahydrocortisol (THC) on the microviscosity of the erythrocyte plasma membrane. The addition of THC to isolated membranes led to a 17% increase in the membrane microviscosity. In contrast, native apo A-I reduced the microviscosity (i.e., increased the fluidity) of the membranes by 15%. A more pronounced increase (by 25%) in the membrane fluidity was found in the presence of the complex of apo A-I with THC. Unlike native apo A-I, oxidized apo A-I and its complex with THC did not change the membrane viscosity. In view of the fact that apo A-I plays an important role in the binding of membrane cholesterol we suggest that the observed increase in the membrane fluidity under the influence of the native apo A-I is associated with the cholesterol efflux from plasma membrane. Oxidative modification of apo A-I likely disturbs the mechanisms of the cholesterol efflux and prevents the decrease in the membrane microviscosity.     

Interaction of alcohol dehydrogenase with tert-butylhydroperoxide: stimulation of the horse liver and inhibition of the yeast enzymes

Preincubation of horse liver alcohol dehydrogenase (HLADH) with the oxidative agent, tert-butyl hydroperoxide (tBOOH) results in a twofold stimulation of the ethanol dehydrogenase activity of this enzyme. This stimulation was dependent on tBOOH concentration up to 100 mM; above this concentration tBOOH did not further stimulate ethanol oxidation by HLADH. Active-site-directed reagents and classical ADH binary complexes were used to probe the possible mechanism of this activating effect. The rate and extent of stimulation by tBOOH is strongly reduced by binary complexes with NAD(+) or NADH, whose pyrophosphate groups bind to Arg-47 and Arg-369. In contrast stimulation by tBOOH was not prevented by AMP or the sulfhydryl reagents dithiothreitol and glutathione, suggesting, respectively, a lack of role for Lys-228 and sulfhydryl group oxidation in the stimulation by tBOOH. In contrast to the liver enzyme, treatment of yeast ADH (YADH) with tBOOH irreversibly inhibited its ethanol dehydrogenase activity. Inhibition of YADH by tBOOH approximated first-order rate kinetics with respect to enzyme at fixed concentrations of tBOOH between 0.5 to 300 mM. Four -SH groups per molecule of YADH were modified by tBOOH, whereas only two -SH groups were modified in HLADH. The stimulation of HLADH by tBOOH is suggested to be due to destabilization of the catalytic Zn-coordination sphere and amino acids associated with coenzyme binding in the active site, while inactivation of YADH appears to be associated with -SH group oxidation by the peroxide.     

Alternative Mechanisms for the Interaction of the Cell-Penetrating Peptides Penetratin and the TAT Peptide with Lipid Bilayers

Cell-penetrating peptides (CPPs) have recently attracted much interest due to their apparent ability to penetrate cell membranes in an energy-independent manner. Here molecular-dynamics simulation techniques were used to study the interaction of two CPPs: penetratin and the TAT peptide with 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) phospolipid bilayers shed light on alternative mechanisms by which these peptides might cross biological membranes. In contrast to previous simulation studies of charged peptides interacting with lipid bilayers, no spontaneous formation of transmembrane pores was observed. Instead, the simulations suggest that the peptides may enter the cell by micropinocytosis, whereby the peptides induce curvature in the membrane, ultimately leading to the formation of small vesicles within the cell that encapsulate the peptides. Specifically, multiple peptides were observed to induce large deformations in the lipid bilayer that persisted throughout the timescale of the simulations (hundreds of nanoseconds). Pore formation could be induced in simulations in which an external potential was used to pull a single penetratin or TAT peptide into the membrane. With the use of umbrella-sampling techniques, the free energy of inserting a single penetratin peptide into a DPPC bilayer was estimated to be ∼75 kJmol⁻¹, which suggests that the spontaneous penetration of single peptides would require a timescale of at least seconds to minutes. This work also illustrates the extent to which the results of such simulations can depend on the initial conditions, the extent of equilibration, the size of the system, and the conditions under which the simulations are performed. The implications of this with respect to the current systems and to simulations of membrane-peptide interactions in general are discussed.