Effect of tetracycline group antibiotics on the barrier properties of the small intestine epithelium]

The effect of 5 tetracyclines on the barrier and transport properties of the small intestine epithelium was studied. The barrier properties were estimated by a change in the ionic selectivity and conductivity of the epithelium, as well as by enterocyte linkage. The current of the short circuit served the characteristics of the Na transport system state. Dimethylchlortetracycline, methacycline and oxytetracycline in concentrations of 10(-7) g/ml decreased the epithelium conductivity and increased the cell linkage. Tetracycline and methacycline in concentrations of 10(-9) g/ml had an analogous effect. The effect was observed 10--20 minutes after the start of incubation with the substance. No effect on the current of the short circuit was observed within the concentrations of 10(-4) to 10(-9) g/ml. It is suggested that the decreased conductivity and increased linkage are due to adsorption of the tetracycline molecules in the region of close cell contacts.     

Seasonal Trophodynamics of the Upper Epipelagic Nekton Community in the Western Bering Sea

Journal of Ichthyology - Complex ecosystem analysis which includes total abundance estimation of its members as well as their quantitative trophic relationships gives an insight to ecosystem...     

The influence of electromagnetic radiation of industrial frequency on Daphnia magna (Straus)

The influence of electromagnetic radiation of industrial frequency on survival, efficiency, physiological parameters of Daphnia magna (Straus) was investigated. The electromagnetic field with intensity of a magnetic component 15 microTl and an electrical one 12 kV/m was generated. The researches were carried out in acute and chronic experiments. The experimental group was exposed to electromagnetic radiation for 8 hours daily for 30 days. As a result of the study it was revealed that the influence of electromagnetic radiation with the given parameters did not have the lethal effect on the test objects. It was found that electromagnetic radiation negatively affected Daphnia fertility. On the average, a real fertility of the Daphnia in the experimental unit was 26.32% compared to the control. The age of puberty in the experiment increased twice in comparison with the control.     

Adaptive ultrastructural changes in soil-resident Yersinia pseudotuberculosis bacteria

After the prolonged residence (from 1 month to 2 years) in flow soil columns at 6 - 8 degrees C and 18 - 20 degrees C a complex of ultrastructural changes was detected in Y. pseudotuberculosis bacteria, depending on temperature, the duration of residence in the soil and, to a definite extent, on the strain. They were manifested in the form of cell-wall changes, the formation of the capsule and intercellular slime, changes in the ribosomal saturation of cytoplasm and the conformation state of DNA in the nucleoid zone. As the result of adaptation to nutritional deficit storage substances were accumulated in the form of electron-dense inclusions (polyphosphates) and pseudovacuoles (poly-beta-oxibutyric acid). Temperature influenced the process of mitotic division and the state of chromatin in bacteria. The described ultrastructural changes Y. pseudotuberculosis may be regarded as natural adaptive reaction to the altered conditions of their residence.     

Microbiological characterization of Listeria monocytogenes isolated from different sources in the Primorsky Territory

The results of the bacteriological study of material, taken from humans, rodents, hydro-bios and environmental objects (including foodstuffs) in the Primorsky Territory, for the presence of L. monocytogenes bacteria are given. 83 bacterial strains of the genus Listeria were isolated. As revealed in this study, 25 of these strains belonged to L. monocytogenes (30.12%), 8 strains--to L. innocua (9.6%), 6 strains--to L. seeligeri (7.2%) and 2 strains--to L. ivanovii (2.4%). The greatest number of L. monocytogenes was isolated from foodstuffs and environmental objects. Some biological properties of L. monocytogenes were studied, the degree of their pathogenicity and sensitivity to antimicrobial preparations were determined.     

Investigation of relationships between marine diatoms and the bacterium Listeria monocytogenes

Relationships between marine diatoms and the bacterium Listeria monocytogenes have been studied by routine algological methods and high-resolution video-enhanced differential interference contrast light microscopy. The study showed that the relationship between the listeria and the benthic diatom Navicula sp. has a parasitic character, whereas the relationship between the listeria and the planktonic diatom Phaeodactylum tricornutum is protocooperative.     

Influence of extrametabolites of marine microalgae on the reproduction of the bacterium <Emphasis Type="Italic">Listeria monocytogenes</Emphasis>

The biological potency of extrametabolites produced by marine microalgae against reproductive forms of Listeria monocytogenes is examined. Extrametabolites of marine microalgae in exponential growth phase had no effect on L. monocytogenes. In the middle steady-state growth phase, extrametabolites of algal cultures boosted the reproduction of Listeria. An exception was Skeletonema costatum: extrametabolites of this alga in the middle steady-state growth phase showed an antibacterial effect against L. monocytogenes.     

Pathogenetic significance of the psychrophilia of Yersinia pseudotuberculosis

The work presents the data indicating that the temperature of Y. pseudotuberculosis cultivation is very important in regulating the activity of pathogenicity factors, necessary for the initiation of the pathogenic process in the cells of the macroorganism. Low temperature (8-10 degrees C), necessary for the growth of Y. pseudotuberculosis, facilitates the activation of invasive and toxic pathogenicity factors. At a growth temperature of 37 degrees C the inhibition of such necessary attributes of virulence as adhesion and invasion into epithelial cells occurs in Y. pseudotuberculosis, which decreases the capacity of these bacteria for inducing the infectious process. The virulence of Y. pseudotuberculosis population, lost as the result of its cultivation in synthetic culture media at a temperature of 37 degrees C, has been found to be restored at low temperature.