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 γ-irradiation, X-rays and accelerated carbon ions (195 MeV/u, LET 16.6 keV/μm) 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.     

The role of recipient cells in the mechanism of pathological calcification of heart valve transplants

It was found using the model of subcutaneous implantation in rats that the calcification of the aorta wall occurs by two mechanisms of which one is dependent on, and the other independent of the migration of recipient cells to the transplant.     

Calcium-induced calcium release mediates all-or-nothing responses of mesenchymal stromal cells to noradrenaline

By using Ca²⁺ imaging and Fluo-4 dye, we examined the capability of certain agonists of G-protein coupled receptors to stimulate Ca²⁺ signaling in cultured mesenchymal stromal cells (MSC) derived from the human adipose tissue. In particular, a small subpopulation (～5%) MSC was found to respond to noradrenaline with Ca²⁺ transients. The all-or-nothing fashion was characteristic of adrenergic Ca²⁺ signaling in MSC, that is, while at low concentrations noradrenaline stimulated undetectable Ca²⁺ transients, virtually maximal responses were elicited by this agonist at any concentration above the threshold of 100–200 nM. In some experiments, MSC were loaded with the photosensitive Ca²⁺ chelator NP-EGTA to produce local or global jumps in cytosolic Ca²⁺ concentration by virtue of Ca²⁺ uncaging. Global uncaging eliciting a high enough Ca²⁺ jump triggered a Ca²⁺ transient in the MSC cytoplasm, which was similar to a noradrenaline response kinetically and by magnitude. When Ca²⁺ uncaging was produced locally, it initiated a Ca²⁺ signal that traveled along a cell with a speed that exceeded an expected one by two orders of magnitude, should Ca²⁺ signal transfer be mediated merely by passive Ca²⁺ diffusion in the presence of Ca²⁺ buffer. These findings implicated Ca²⁺-induced Ca²⁺ release (CICR) as a mechanism amplifying local Ca²⁺ signals in MSC. Of Ca²⁺ targets involved in CICR, the ryanodine receptor and IP₃ receptor are only known. The inhibitory analysis revealed IP₃ receptors to be principally responsible for CICR in MSC, whereas a contribution of ryanodine receptors was negligible. Altogether, our results suggest that an initial noradrenaline-dependent rise in cytosolic Ca²⁺ stimulates, should it reach the threshold level, IP₃ receptors, thereby triggering an avalanche-like Ca²⁺ release from Ca²⁺ stores and underlying the all-or-nothing dependence of cellular responses on the agonist concentration.     

Finding of Molars of the Archaic Vole Lasiopodomys (Stenocranius) Gregaloides (Hinton, 1923) (Mammalia,Rodentia, Cricetidae) in the Late Pleistocene of the Southern Urals

Doklady Biological Sciences - A total of 1250 lower first molars (m1) of voles (Arvicolini) were studied from Late Pleistocene deposits (the radiocarbon dates from rodent bones: 17?100 ±...     

The use of the microdot immunoenzyme method for determining antibodies to Mycobacterium tuberculosis antigens

The microdot enzyme immunoassay (EIA) has been used for the determination of antibodies to M. tuberculosis protein fractions, crude antigenic preparations, PPD and old tuberculin in tuberculosis patients and healthy persons. Purified protein fractions have been found to possess the highest sensitivity and specificity in microdot EIA. The determination of antibodies to these fractions has permitted the differentiation of persons infected with M. tuberculosis from healthy ones. The use of M. tuberculosis protein fractions permits the determination of IgA and IgC in the sera of tuberculosis patients.     

The problem of enhancing the biological action of ionizing radiations. Glucose as an agent for increasing the radiosensitivity of Ehrlich ascitic carcinoma cells in vitro

The effect of short-term incubation of Ehrlich ascites tumor cells in a medium containing excess glucose on their radiosensitivity was studied with a reference to the growth of tumors of ascitic and solid forms. It was shown that the incubation of cells with glucose, being accompanied by a change in pH of the suspension, caused, by itself, only a slight increase in the duration of the latent period of solid tumor formation and in the life-span of mice with ascitic tumors but increased considerably the lethal effect of radiation, as was estimated by the above mentioned criteria and the percentage of inoculated tumors.     

Immune response of CBA mice in postnatal ontogeny

Changes in the pattern of immune response of the CBA mice during postnatal ontogenesis were studied on the models of cellular and humoral immunity. The functions mediated by the amplifier cells were shown to undergo the most significant changes. This was confirmed by a decrease in the activity of antigen-nonspecific T-suppressors, as estimated in a semisyngeneic system, an increase in the capacity of spleen lymphoid cells to induce the "graft versus host" reaction with the age and preservation of the function of hypersensitivity effectors of delayed type at the same level (after the age of 3-4 months). It is suggested that these changes might cause an age decrease in the suppressor activity of T-cells in a response to insoluble antigens.