[Impedance technique for the determination of the antimicrobial activity of dental materials].

The authors propose a procedure to determine the antimicrobial activity of dental materials, by applying the principles of impedance technology. The procedure is based on the determination of the growth inhibition of test culture microorganisms by the study materials. The following parameters: the type of a test; the parameters of measurement; the qualitative and quantitative composition of culture media; the working cell concentration in the inoculum; the temperature and time of a test, were optimized.

[Cytogenetic effects of low dose radiation with different LET in human peripheral blood lymphocytes and possible mechanisms of their realization].

The induction of chromosome damage by the exposure to low doses of gamma-(60)Co and accelerated carbon ions 12C in peripheral blood lymphocytes of different donors was investigated. The complex nonlinear dose-effect dependence at the range from 1 to 50-70 cGy was observed. At the doses of 1-5 cGy the cells show the highest radiosensitivity (hypersensitivity), mainly due to the chromatid-type aberration, which is typical to those spontaneously generated in the cell and believed not to be induced by the irradiation of unstimulated lymphocytes according to the classical theory of aberration formation. With the increasing dose the frequency of the aberrations decreases significantly, in some cases up to the control level. At the doses over 50-70 cGy the dose-effect curve becomes linear. The possible role of the oxidative stress, caused by radiation-induced increase in mitochondrial reactive oxigen species (ROS) release in the phenomenon of hypersensitivity (HS) at low doses is discussed as well as cytoprotective mechanisms causing the increased radioresistance at higher doses.

[Induction of chromosome aberrations and micronuclei in human peripheral blood lymphocytes at low dose of radiation].

The chromosome damage induced by the doses of y-irradiation 6)Co in peripheral blood lymphocytes was studied using different cytogenetic assays. Isolated lymphocytes were exposed to 0.01-1.0 Gy, stimulated by PHA, and analysed for chromosome aberrations at 48 h postirradiation by metaphase method, at 49 h--by the anaphase method, at 58 h by micronucleus assay with cytochalasin B and, additionally, micronuclei were counted at 48 h on the slides prepared for the metaphase analysis without cytochalasin B. Despite of the quantitative differences in the amount of chromosome damage revealed by different methods all of them demonstrated complex nonlinear dose dependence of the frequency of aberrant cells and aberrations. At the dose range from 0.01 Gy to 0.05-0.07 Gy the cells had the highest radiosensitivity mainly due to chromatid-type aberration induction. With dose increasing the frequency of the aberrant cells and aberrations decreased significantly (in some cases to the control level). At the doses up to 0.5-0.7 Gy the dose-effect curves have become linear with the decreased slope compare to initial one (by factor of 5 to 10 for different criteria) reflecting the higher radioresistance of cells. These data confirm the idea that the direct linear extrapolation of high dose effect to low dose range--the procedure routinelly used to estimate genetic risk of low dose irradiation--cannot be effective and may lead to underestimation of chromosome damage produced by low radiation doses. Preferences and disadvantages of used cytogenetic assays and possible mechanisms of low ionising radiation doses action were discussed.

Cytogenetic effects of low-dose radiation with different LET in human peripheral blood lymphocytes.

Chromosome damage and the spectrum of aberrations induced by low doses of gamma-irradiation, X-rays and accelerated carbon ions (195 MeV/u, LET 16.6 keV/microm) in peripheral blood lymphocytes of four donors were studied. G0-lymphocytes were exposed to 1-100 cGy, stimulated by PHA, and analyzed for chromosome aberrations at 48 h post-irradiation by the metaphase method. A complex nonlinear dose-effect dependence was observed over the range of 1 to 50 cGy. At 1-7 cGy, the cells showed the highest radiosensitivity per unit dose (hypersensitivity, HRS), which was mainly due to chromatid-type aberration. According to the classical theory of aberration formation, chromatid-type aberrations should not be induced by irradiation of unstimulated lymphocytes. With increasing dose, the frequency of aberrations decreased significantly, and in some cases it even reached the control level. At above 50 cGy the dose-effect curves became linear. In this dose range, the frequency of chromatid aberrations remained at a low constant level, while the chromosome-type aberrations increased linearly with dose. The high yield of chromatid-type aberrations observed in our experiments at low doses confirms the idea that the molecular mechanisms which underlie the HRS phenotype may differ from the classical mechanisms of radiation-induced aberration formation. The data presented, as well as recent literature data on bystander effects and genetic instability expressed as chromatid-type aberrations on a chromosomal level, are discussed with respect to possible common mechanisms underlying all low-dose phenomena.

[Evaluation of the consequences of stress factors on plant seeds growing in a 30-km zone of Balakovo AES]. / Otsenka posledstvii vliianiia stressovykh faktorov na semena rastenii, proizrastaiushchikh v 30-kilometrovoi zone Balakovskoi AES.

The effect of stress factors (small doses of radiation and maximum temperatures in the econiche of the tested plants (tmax)) as well as aging on pea seeds, both acting independently and in combination, is estimated. Here we evaluate the influence of oxidizing stress on pea seeds in the laboratory (gamma-irradiated with 7 cGy at 0.3-19.1 cGy/h, tmax approximately 30-32 degrees C) and on natural plantain seeds collected in a 30-km zone of NPP (radiation exposure approximately 15 R/h, tmax approximately 38-40 degrees C). We have mathematically modeled CAs frequencies in root seedlings meristeme by invoking an enhancing factor transmitted from cell to cell. It is shown under the stress conditions: 1) CA frequency decreases whereas the fraction of inviable seeds (IS) increases, the dependence of IS on CA frequency being inversed; 2) a stimulation of proliferation of cell was observed; 3) a bystander effect appears; 4) antioxidative status (AOS) of seeds influences on adaptation on the all levels of the organization; 5) IS increases up to 73-80% under the combined effect of radiation and heat stresses.

[The detection of the influenza virus in the small intestine in diarrhea in piglets]. / Obnaruzhenie virusa grippa v tonkoi kishke pri diaree porosiat.

Electron microscopy used for examinations of small intestine suspensions of piglets in the prenatal and postnatal periods allowed influenza virions to be identified in virus population. An attempt was made to preserve the discovered population in alternating animal--cell culture--animal passages. Serological examinations of the swine herd confirmed the circulation of influenza viruses in the herd.

[Identification by electron microscopy of a corona-like virus inducing diarrhea in piglets]. / Identifikatsiia metodom élektronnoi mikroskopii koronapodobnogo virusa, vyzvaiushchego diareiu porosiat.

The results of identification by means of electron microscopy and immune electron microscopy of a corona-like virus isolated in diarrhea of pigs during the first weeks of life are presented. Morphological forms, diameter of particles, the length of external processes, and the buoyant density of virions were determined.