Biophysical and medical and biological aspects of use of polyene antibiotics in combination with dimethylsulfoxide

Modern conceptions of the physicochemical properties of dimethylsulfoxide and polyene antibiotics are reviewed. The results of investigations of independent and mutual effects of polyene antibiotics and dimethylsulfoxide on membrane permeability were analysed. The own experimental data of radioprotective and antitumour action of complex dimethylsulfoxide-polyene antibiotics are presented, and the perspectives of their use in medicine are described.     

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.     

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.     

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.