Instability of a three-dimnsional linear vortex in a simple model of a heterogenous excitable medium

We studied the dynamics of three-dimensional linear vortex in a heterogeneous excitable medium. Using the Aliev-Panfilov model we showed that even a small heterogeneity in excitation threshold can lead to drastic deformations of the vortex filament and an instability in its behavior.     

Effect of potential fluctuations on the activity of sinoatrial node cells

The effect of fluctuations of the transmembrane potential on the generation of the action potential is studied by simulating the rabbit sinoatrial node (SAN) pacemaker. It is shown that the effect of fluctuations is enhanced with an increase in the concentration of acetylcholine and becomes most pronounced at the border of spontaneous activity loss and after it. When applying and washing off acetylcholine, the hysteretic effect is observed.     

Disorder of gamma-motor neuronal activity in experimental thyrotoxicosis]

The activity of gamma-motor neurons was studied in the anesthetized rats following per os administration of thyroidin for 3 weeks. In experimental thyrotoxicosis against the backgrounds of an increased amount of mute filaments isolated from the stem of the n. gastrocnemius there was an increase in the frequency of discharge of the flexors and extensors of the gamma-motor neurons. A high frequency not peculiar to that of intact animals was recorded in the flexors of the gamma-motor neurons of the animals receiving thyroidin.     

Activity of Membrane-Associated Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase during Development of the Inner Membrane System in Potato Chloroplasts

Membranes of etioplasts and chloroplasts from potato plants (Solanum tuberosumL., cv. Zhu-kovskii) were fractionated by centrifugation in a sucrose gradient, and the fractions of primary membranes, fretlike structures, and frets and granal thylakoids were isolated. The carboxylase and oxygenase activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) were measured in these fractions. The membrane-bound Rubisco (mRubisco) was reconstructed in the artificial system from the primary membranes and the soluble form of Rubisco (sRubisco), both isolated from the chloroplasts. The higher carboxylase and lower oxygenase activities were found to be characteristic of this reconstructed mRubisco as compared to sRubisco. The degree of sRubisco association with primary membranes depended on the Mg²⁺concentration. The data suggested that the association of sRubisco with primary membranes occurred at the early stages of membrane formation. The biological role of mRubisco is assumed to consist in controlling the ratio between photosynthesis and photorespiration at the membrane level in plants of various physiological states.     

Radioprotective and antineoplastic activity of polyene antibiotics combined with dimethyl sulfoxide]

Radioprotective and antineoplastic activity of polyene, its derivatives and combinations with dimethyl sulfoxide (DMSO) was studied. The most potent radioprotective effect was demonstrated by methylated levorin, original levorin and by its isomer--isolevorin. Survival rate of the animals on 12th day after X-ray exposure was 100, 60, 60 per cent, at the control group 33.6, 20 and 0 per cent consequently. Levorin and alkyl derivatives of amphotericin B--methamphocin and buthamphocin inhibited growth of ascites and solid tumors to 46.3-79.0 per cent when compared to control group. Polyen antibiotics combined with DMSO also demonstrated antineoplastic activity at the animals treated with carcinogenic agent--diethyl nitrosoamine (DENA). 5-month survival of the animals was 76 per cent at nystatin and levorin group and 35.7 per cent at the control group (animals treated with DENA only).     

Haloalkaliphilic actinomycetes in soils of Mongolian desert steppes

The abundance of actinomycetes isolated from the soils of Mongolian desert steppes varies from several thousand to hundreds of thousands of CFU/g soil, depending on soil type and isolation medium. Eight actinomycete genera have been found in these soils: Streptomyces, Micromonospora, Saccharopolyspora, Actinomadura, Microtetraspora, Thermomonospora, Nocardia, and Dactylosporangium. The streptomycete complexes of brown desert-steppe and gray-brown desert alkaline soils include halophilic, alkaliphilic, and haloalkaliphilic species that grow most successfully on the media with a salt concentration of 5% and pH 8–9.     

Nucleic acid oxidation in Alzheimer disease

Increasing evidence suggests that oxidative stress is intimately associated with Alzheimer disease pathophysiology. Nucleic acids (nuclear DNA, mitochondrial DNA, and RNA) are one of the several cellular macromolecules damaged by reactive oxygen species, particularly the hydroxyl radical. Because neurons are irreplaceable and survive as long as the organism does, they need elaborate defense mechanisms to ensure their longevity. In Alzheimer disease, however, an accumulation of nucleic acid oxidation is observed, indicating an increased level of oxidative stress and/or a decreased capacity to repair the nucleic acid damage. In this review, we present data supporting the notion that mitochondrial and metal abnormalities are key sources of oxidative stress in Alzheimer disease. Furthermore, we outline the mechanisms of nucleic acid oxidation and repair. Finally, evidence showing the occurrence of nucleic acid oxidation in Alzheimer disease will be discussed.     

Expression, purification and structural analysis of the Pyrococcus abyssi RNA binding protein PAB1135

Background

Epistatic interactions of multiple single nucleotide polymorphisms (SNPs) are now believed to affect individual susceptibility to common diseases. The detection of such interactions, however, is a challenging task in large scale association studies. Ant colony optimization (ACO) algorithms have been shown to be useful in detecting epistatic interactions.

Findings

AntEpiSeeker, a new two-stage ant colony optimization algorithm, has been developed for detecting epistasis in a case-control design. Based on some practical epistatic models, AntEpiSeeker has performed very well.

Conclusions

AntEpiSeeker is a powerful and efficient tool for large-scale association studies and can be downloaded from http://nce.ads.uga.edu/~romdhane/AntEpiSeeker/index.html.     

Changes in conditioned reflex activity during adaptation of the rat to pressure-chamber and high-altitude hypoxia

A group of rats with a stereotype of conditioned reflexes was preliminarily trained to hypoxia effects during 30 days (at the "altitude" of 6000 m, time of exhibition--from 10 to 60 min, for 18 days--only 60 min). Adaptive changes in the process of training consisted in a weakening of differentiation inhibition, partial amnesia of the conditioned reaction of active avoidance and appearance of phasic states (equalization and paradoxical phases) in the cerebral cortex. The following adaptation of hypoxia "trained" rats to new natural conditions of Alpine altitude (3200 m) proceeded favourably, without disturbance of differentiation inhibition and without phasic states. Rats without preliminary training to altitude chamber hypoxia, in mountains (3200 m) were subjected to moderate tension resulting in protective inhibition, partial amnesia and transient disturbance of differentiation inhibition.     

Comparison of techniques for the measurement of skin temperature during exercise in a hot,humid environment

Exercising or working in a hot, humid environment can results in the onset of heat-related illness when an individual''s temperature is not carefully monitored. The purpose of the present study was to compare three techniques (data loggers, thermal imaging, and wired electrodes) for the measurement of peripheral (bicep) and central (abdominal) skin temperature. Young men and women (N = 30) were recruited to complete the present study. The three skin temperature measurements were made at 0 and every 10-min during 40-min (60% VO₂max) of cycling in a hot (39±2°C), humid (45±5% RH) environment. Data was statistically analyzed using the Bland-Altman method and correlation analysis. For abdominal skin temperature, the Bland-Altman limits of agreement indicated that data loggers (1.5) were a better index of wired than was thermal imaging (3.5), For the bicep skin temperature the limits of agreement was similar between data loggers (1.9) and thermal (1.9), suggesting the both were suitable measurements. We also found that when skin temperature exceeded 35°C, we observed progressively better prediction between data loggers, thermal imaging, and wired skin sensors. This report describes the potential for the use of data loggers and thermal imaging to be used as alternative measures of skin temperature in exercising, human subjects.