Proliferation of primary human keratinocytes during histogenesis in culture

We studied formation of epithelial cysts during cultivation of the primary keratinocytes in a collagen gel. Two stages--epithelial spheroid and cysts--can be recognized in the histogenesis process. Keratinocyte migration prevails at the initial stages of morphogenesis. The stage of spheroid can be described by active cell proliferation. Stratification of spheroid epithelium takes place at the stage of epithelial cysts, while the rate of keratinocytes proliferation decreases. Formation of epithelial cysts is induced by morphogene(s) of mesenchymal origin. The obtained data indicate partial dissociation of keratinocyte proliferation and migration during cytogenesis.     

Results of ambulatory care and serodiagnosis of leptospirosis in reconvalescents in the Kuban region

The importance of the medical checkup of leptospirosis reconvalscents is shown. In 18.9% of persons having had leptospirosis and placed under medical surveillance the presence of pathological changes has been established after clinical convalescence. Recommendations concerning the prolongation of the period of medical surveillance on leptospirosis reconvalescents with less frequent checkups are given.     

Nonisotonic spontaneous contraction waves in isolated single cardiomyocytes

One-dimensional contraction bands propagating spontaneously in a cardiomyocyte are studied theoretically for three experimental situations: isotonic (zero load) regime, isometric regime, and a strong adhesive contact between the cell and a supporting surface. Possible role of such a contact in the development of the cell damage is discussed.     

Effect of hydrophobic compounds on rRNA synthesis in intact cells and isolated nuclei

Papaverine, cycloheximide, 2,4-dinitrophenol (DNP) and actinomycin D at low concentration have been shown to suppress selectively rRNA synthesis in Ehrlich ascite carcinoma cells. rRNA synthesis in isolated nuclei is not sensible to wide range of concentration of papaverine (0,005-0,1 mM), cycloheximide (0,5-100 micrograms/ml) and DNP (5-500 microM). Actinomycin D at low concentration does not act on the rRNA synthesis in vitro either. To suppress rRNA synthesis in this system much higher concentration of this agent (10 micrograms/ml) producing inhibition of all classes of rRNA synthesis in intact cells is required. Selective sensitivity of rRNA synthesis in the cells to papaverine, cycloheximide, DNP and low concentration of actinomycin D does not connect with their direct action on the apparatus of rRNA synthesis.     

Mathematical model of activation wave propagation in an isolated cardiomyocyte

In order to describe spontaneous wave-like contractions of a single isolated cardiomyocyte a mathematical model is proposed, which relates this phenomenon to propagation of calcium ion concentration wave along the cell. Free diffusion of Ca2+ ions as well as their reversible binding to regulatory proteins in contractile apparatus, Ca2+ accumulation in sarcoplasmic reticulum, and Ca-induced Ca2+ release are included in the governing equations. The model agrees with some observations. It predicts also some effects which may by a subject of future experimental research.     

Effect of one-time and chronic low-intensity irradiation on cathepsin L activity in rat brain

The effect of the total single and chronic roentgen irradiation in the dose of 0.25 Gy on the rats to alteration dynamics in lysosomal cysteine cathepsin L [CE 3.4.22.15] level in different brain regions (cortex, cerebellum, middle brain, varolian, hippocampus, striatum) was studied as a result of 1, 12, 24, 120 and 168 hours of exposure. The data obtained displayed the opposite consequences of chronic effect of 0.01 Gy during 25 days if compare with the single irradiation by 0.25 Gy that led to the cathepsin L changes different in directivity and activity level in dependence on brain region and post-irradiation period.     

Sensitivity of soil bacteria isolated from the alienated zone around the Chernobyl Nuclear Power Plant to various stress factors

Seventy strains of chemoorganotrophic bacteria isolated by our group in 1993-1994 from soil sampled in the zone around the Chernobyl Nuclear Power Plant (ChNPP) were studied with respect to their sensitivity to various stress factors damaging DNA. Bacillus subtilis, B. cereus (both spores and vegetative cells), Methylobacterium extorquens, M. mesophilicum, and unidentified pigmented bacteria were found to be the most resistant to ultraviolet (UV) radiation, exhibiting LD90 values of 40 to more than 211 J/m2. The same bacteria, as well as Bacillus polymyxa, were tolerant to hydrogen peroxide (lethal concentrations of H2O2 ranged from 0.3 to 1.0 M); i.e., UV-resistant strains were also tolerant to hydrogen peroxide and vice versa. Fluorescent pseudomonads were the most sensitive to both UV radiation and H2O2, showing LD90 from 6 to 18 J/m2 and a lethal concentration of H2O2 lower than 0.1 M. All of the soil samples collected in the alienated zone around the ChNPP, where the radioactivity of the soil had decreased from 1000 to 2 microCi/kg soil over the period from 1987 to 1995, contained not only resistant bacteria but also a small number of bacteria sensitive to UV radiation and H2O2.     

Ultraviolet irradiation of soil samples as a model of the effect of stress factors on bacterial diversity in soil ecosystem

UV irradiation is proposed for use in studying the effect of radioactive irradiation, since radioresistant bacteria are, as a rule, resistant to UV, and the mechanisms of repair of cell damage induced by UV and ionizing radiation are similar. It was found that the total number of bacteria and the number of dominant species in soil samples exposed to UV radiation decreased, indicating the unfavorable effect of UV radiation on bacterial diversity in soil ecosystems. The percentage of cells of bacteria belonging to dominant species varied significantly depending on the intensity of UV irradiation. It can be inferred that long-term irradiation of soils must impair the stability of soil ecosystems, a phenomenon that was indeed observed in the zone around the Chernobyl Nuclear Power Plant. At the same time, the UV irradiation of soil samples made it possible to reveal minor species, primarily UV-resistant pigmented bacteria. UV irradiation can probably be used as a selective factor for the isolation of radioresistant species.