The cluster method in conducting epidemiological research

The Expanded Programme on Immunization (EPI) whose goal is to reduce morbidity and mortality by providing children with immunizations against diphtheria, pertussis, tetanus, poliomyelitis, measles, and tuberculosis continually faces the problem of documenting immunization coverage rates. Therefore the EPI seeks simple, effective, and inexpensive methods of evaluation which could be implemented in different countries. An example of such a method is a simplified cluster sampling technique of estimation of immunization coverage through the examination of 210 children, selected randomly as 30 groups of 7 children each. In 1978-1984 more than 1000 immunization coverage surveys were performed all over the world, mainly in developing countries. In a modified way this method is also used to collect data on morbidity and mortality of certain EPI target diseases as well as diarrhoeal diseases.     

The arrangement of substrate and organophosphorus-inhibitor leaving groups in acetylcholinesterase active site.

The leaving groups of serine esterase substrates and organophosphorus inhibitors bind to different loci at the enzyme active site. Kinetic proof of this general conclusion is presented in the case of acetylcholinesterase reactions. The proposed model for acetylcholinesterase active site provides a new stereochemical mechanism for the phosphorylated enzyme reactivation.     

An N-terminal, 830 residues intrinsically disordered region of the cytoskeleton-regulatory protein supervillin contains Myosin II- and F-actin-binding sites

Supervillin, the largest member of the villin/gelsolin family, is a cytoskeleton regulating, peripheral membrane protein. Supervillin increases cell motility and promotes invasive activity in tumors. Major cytoskeletal interactors, including filamentous actin and myosin II, bind within the unique supervillin amino terminus, amino acids 1–830. The structural features of this key region of the supervillin polypeptide are unknown. Here, we utilize circular dichroism and bioinformatics sequence analysis to demonstrate that the N-terminal part of supervillin forms an extended intrinsically disordered region (IDR). Our combined data indicate that the N-terminus of human and bovine supervillin sequences (positions 1–830) represents an IDR, which is the largest IDR known to date in the villin/gelsolin family. Moreover, this result suggests a potentially novel mechanism of regulation of myosin II and F-actin via the intrinsically disordered N-terminal region of hub protein supervillin.     

pH modulation of large conductance potassium channel from adrenal chromaffin granules

We report here that large conductance K⁺ selective channel in adrenal chromaffin granules is controlled by pH. We measured electrogenic influx of ⁸⁶Rb⁺ into chromaffin granules prepared from bovine adrenal gland medulla. The ⁸⁶Rb⁺ influx was inhibited by acidic pH. Purified chromaffin granule membranes were also fused with planar lipid bilayer. A potassium channel with conductance of 432±9 pS in symmetric 450 mM KCl was observed after reconstitution into lipid bilayer. The channel activity was unaffected by charybdotoxin, a blocker of the Ca²⁺-activated K⁺ channel of large conductance. It was observed that acidification to pH 6.4 cis side of the membrane lowered the channel open probability and single channel conductance. Whereas only weak influence on the single channel current amplitude and open probability were observed upon lowering of the pH at the trans side. We conclude that a pH-sensitive large conductance potassium channel operates in the chromaffin granule membrane.     

The central role of selenium in the biochemistry and ecology of the harmful pelagophyte,Aureococcus anophagefferens

The trace element selenium (Se) is required for the biosynthesis of selenocysteine (Sec), the 21st amino acid in the genetic code, but its role in the ecology of harmful algal blooms (HABs) is unknown. Here, we examined the role of Se in the biology and ecology of the harmful pelagophyte, Aureococcus anophagefferens, through cell culture, genomic analyses, and ecosystem studies. This organism has the largest and the most diverse selenoproteome identified to date that consists of at least 59 selenoproteins, including known eukaryotic selenoproteins, selenoproteins previously only detected in bacteria, and novel selenoproteins. The A. anophagefferens selenoproteome was dominated by the thioredoxin fold proteins and oxidoreductase functions were assigned to the majority of detected selenoproteins. Insertion of Sec in these proteins was supported by a unique Sec insertion sequence. Se was required for the growth of A. anophagefferens as cultures grew maximally at nanomolar Se concentrations. In a coastal ecosystem, dissolved Se concentrations were elevated before and after A. anophagefferens blooms, but were reduced by >95% during the peak of blooms to 0.05 nℳ. Consistent with this pattern, enrichment of seawater with selenite before and after a bloom did not affect the growth of A. anophagefferens, but enrichment during the peak of the bloom significantly increased population growth rates. These findings demonstrate that Se inventories, which can be anthropogenically enriched, can support proliferation of HABs, such as A. anophagefferens through its synthesis of a large arsenal of Se-dependent oxidoreductases that fine-tune cellular redox homeostasis.     

Emergence of acetylcholine resistance and loss of rhythmic activity associated with the development of hypertension,obesity, and type 2 diabetes

The aim of this work was to study the influence of aging, obesity, metabolic syndrome (MS), hypertension (HT), and type 2 diabetes (T2D) on the endogenous rhythmic activity and the development acetylcholine resistance in aorta rings of male rats. T2D was produced by a free access to fat (lard). It was shown that phenylephrine (PE) or 5-hydroxytryptamine (5-HT) induces two types of rhythmic contractions: with periods T ₁ = 3–10 s and T ₂ = 50–70 s and amplitudes A ₁ = 1–5% and A ₂ = 20–40% of the maximal contraction force (F _max), respectively. Such periodic modes can be caused by the operation of two known positive feedback loops (PFL) based on the Ca²⁺-induced activation of IP3 receptor (IP3R) or phospholipase C PFL1 and PFL2, respectively, and are not eliminated by L-NAME. Slow rhythmic activity induced by acetylcholine (Ach) with period T ₃ = 7–20 min and amplitude A ₃ = 20–30% of F _max was observed only in young animals (under 6 months) and can be determined by the operation of PFL3, involving Ca²⁺, NO, kinase G, cADP-ribose, and the ryanodine receptor (RyR). Fast mode of contractions (T ₁, A ₁) is maintained regardless of age and the presence of MS and HT (140 mm Hg and higher) and disappears only at later stages of the T2D development. Probability of intermediate mode of contractions (T ₂, A ₂) decreases to 0.20–0.25 at the age of 14–16 months or during the development of HT and MS. In these circumstances, Ach could cause relaxation of preconstricted rings only to 40 and 60% of F _max, respectively. At the stages of the T2D development characterized by high values of arterial pressure (above 150 mm Hg) and of the glucose (10–12 mM), ammonium (120–180 μM), and blood lipid levels, as well as by liver dysfunction (fibrosis/cirrhosis), the rhythmic activity of any type is lost and dysfunction of the initial part of the signaling cascade with the participation of PFL3 is manifested by the absence of responses to Ach or L-NAME. Coenzyme NAD (agonist of the P2Y receptors, К⁺ channel activator and a precursor of cADP-ribose) can exert a partial relaxation of aorta rings from healthy animals and animals with MS. Nicotinamide (product and an inhibitor of ADP-ribosyl cyclase) and SNP (donor of NO) produce an effective relaxation of aorta rings from healthy animals and animals with T2D. Relaxing effect of nicotinamide may suggest a tandem operation of IP3R and RyR in the control of intracellular Ca²⁺ stores in vascular cells.     

Analysis of seasonal fluctuations in the Lotka-Volterra model

A modification of the Lotka-Volterra model was proposed. The modification takes into account the factor of seasonal fluctuations in a "predator-prey" model. In this modification, interactions between species in summer are described by the Lotka-Volterra equations; in winter, individuals of both species extinct. This generalization makes the classic model unrough, which substantially extends the field of its application. The results of numerical simulation illustrate the statement formulated above.     

The effect of electric field on the spatial-time patterns in the reaction-diffusion system

A model of electrodiffusion processes in the vicinity of cell membrane was developed. The model takes into account chemical reactions, Coulomb interactions between charged particles and the effect of external electric field. It was concluded that the applied electric field can change the characteristics of space-time patterns in the system. Dissipative structures slowly move and this is accompanied by a change in the number of structure elements. The characteristic equation includes odd powers of the wavenumber, which can lead to the appearance of soliton-like structures. The dissipative structures can appear not only due to the Turing diffusion instability but due to the disperse instability under electric field the applied.