[Effect of low-intensity magnetic fields on the development of satellite muscle cells of a newborn rat in the primary culture].

The influence of Earth magnetic field shielded down to 0.3 microT and static magnetic field (60-160 microT) on the proliferation and differentiation of satellite muscle cells in the primary culture has been investigated. A stimulatory effect of static magnetic fields on the rate of the formation of massive multinucleated myotubes and an increase in the intracellular calcium concentration ([Ca2+]i) have been detected for magnetic fields of the microtesla range. On the other hand, it was shown that the reduction of earth magnetic fields to 0.3 microT leads to the inhibition of proliferation and differentiation of skeletal muscle cells in the primary culture. Since the formation of contractile myotubes during in vitro experiments is similar to the regeneration of skeletal muscle fibers under muscle damage in vivo, it may be concluded that weak magnetic fields have a strong effect on intracellular processes by influencing all phases of muscle fiber formation. It is necessary to take this fact into consideration when forecasting probable complications of skeletal muscle regeneration during long-term exposure of man to low-intensity magnetic fields and also for the potential use of low static magnetic fields as a tool to recover the affected myogenesis.

[Slow calcium waves in cultured postnatal rat skeletal myocytes].

A variety of active agents increasing [Ca2+]i in cultivated skeletal myocytes have been investigated. It was shown that, out of the agents such as noradrenaline, carbacholine, caffeine, cyclopiazonic acid, and potassium solution, only the last caused the formation of slow calcium waves in skeletal myocytes. These waves propagated not only near the location of the cell nucleus but also along the whole length of myocytes. It is supposed that this wave process can be related to the modulation of excitation-relaxation processes in skeletal muscles.

[Disturbances in the function of cardiomyocyte ryanodine receptors of spontaneously hypertensive rats revealed by 4-chloro-m-cresol].

The rates of Ca2+ release from sarcoplasmic reticulum in response to the activation of ryanodine receptors by 4-chloro-m-cresol in cardiomyocytes of three rat lines: spontaneously hypertensive (SHR) and normotensive WKY, and Wistar rats during five weeks of their growth and development have been studied to reveal differences in the function of ryanodine receptors at different stages of hypertension. Whereas the efflux of Ca2+ from sarcoplasmic reticulum in Wistar and WKY rat cardiomyocytes decreased in response to 4-chloro-m-cresol, an abrupt rise in the rate of [Ca2+]i increase was observed in myocytes of spontaneously hypertensive rats after 17 days of development. A correlation between this phenomenon and the occurrence of genetic defect of ryanodine receptors in SHR seems improbable because we did not register any differences in the rates of Ca2+ release from sarcoplasmic reticulum by the action of 4-chloro-m-cresol in concentrations 0.5-2.0 mM in the cardiomyocytes of newborn WKY and spontaneously hypertensive rats. On the other hand, pathological changes in the function of ryanodine receptors may become apparent later during ontogenesis. The connection of this phenomenon with an increase in the role of ryanodine receptors during the excitation-contraction coupling in muscle cell and an increase in the calpain expression by the age of 3 weeks in spontaneously hypertensive, but not in WKY rats, is discussed. It is supposed that the disintegration of the subunit of ryanodine receptors by calpain notably intensifies the Ca2+ release from sarcoplasmic reticulum after the activation of ryanodine receptors without affecting the characteristics of receptor binding.

[Damaging impacts at the critical time periods of prenatal ontogenesis as a factor modifying the cerebral structural development and postnatal behavior reactions]. / Povrezhdaiushchie vozdeistviia v kriticheskie periody prenatal'nogo ontogeneza kak faktor, modifitsiruiushchii strukturnoe razvitie golovnogo mozga i povedencheskie reaktsii posle rozhdeniia.

Results of a study of the nature of changes in the rat neocortex, which were observed during an early postnatal period (postnatal days 1 to 10) and which were induced by a single prenatal hypoxia on the 16th or 19th embrionic day (E16, E19), are presented in the paper. Acute hypoxia, administered on E16, was shown to result in an underdevelopment of cortical layers as well in damage to cell orientation and differentiation, i.e. it disturbed the histogenic processes (proliferation, migration and differentiation), which are most active at this time period. An immunohistochemical examination of the brain made during the postnatal period after an intrauterine hypoxia suggests that damage to proliferation and differentiation occurred in glial cells. Hypoxia administered on E19, when the level of proliferation in the brain was lower, had a less pronounced damaging effect. Deviations in the neocortical structure and in the animal's behavior found during the postnatal period could be caused by the heterochromic and heteromorphous development of brain regions in the fetus.

[The effect of synthetic protein fragments on humoral immune response]. / Vliianie sinteticheskikh fragmentov belkov na gumoral'nyi immunnyi otbet.

Effect of some protein and immunopeptide synthetic fragments on the humoral immune response has been studied. Some investigated peptides are shown to influence the antibody genesis at the secondary immune response to T-dependent antigen (bovine serum albumin) in mice. The serum antibody level specific for the bovine serum albumin is measured by enzyme-linked immunosorbent assays (ELISA). Possible mechanisms of the influence of such peptide fragments on the immune system is discussed.

[DNA replication in HeLa cells after gamma irradiation. II. The periodicity of DNA replication in the process of giant cell formation]. / Replikatsiia DNK v kletkakh HeLa posle gamma-oblucheniia. II. Periodichnost' replikatsii DNK v protsesse obrazovaniia gigantskikh kletok.

HeLa G-63 cells irradiated by 5 krads of 6 degrees Co gamma-rays 1.5--2 hours after mitosis (G1-phase) were incubated in growth medium during 9 days. The number of proliferating and eliminated cells, the content of DNA per cell nucleus, and kinetics of the labeled cell fraction upon 3H-TdR continuous incubation were studied. It has been concluded that: during the giant cell growth the nuclear DNA is replicated periodically without following mitoses; 90% of cells are involved in such a cycle; the duration of the period of DNA synthesis in giant cells is the same as that in non-irradiated cells; the duration of the gap between two successive S-periods in giant cells is 2--6 times as long as the sum of G2+M+G1 periods in the normal non-irradiated cells.

[DNA replication in HeLa cells after gamma irradiation. I. The period of DNA replicative synthesis after the irradiation of cells in the G1 phase with gamma rays in large doses]. / Replikatsiia DNK v kletkakh HeLa posle gamma-oblucheniia. I. Period replikativnogo sinteza DNK posle oblucheniia kletok v faze G1 gamma-luchami v bol'shikh dozakh.

HeLa G-63 cells irradiated by 5 krads of 60 Co-gamma-rays during their G1-period pass through the S-period of the same interphase just as do non-irradiated cells: the kinetics of labeled cells upon a 30 min incubation with 3H-TdR (radioautography) is the same for both irradiated and non-irradiated cell populations; the rate of 3H-thymidine incorporation during the S-period upon a 3H-TdR continuous incubation is the same for both the cell populations; the mean DNA content per nucleus of irradiated cell is doubled after the S-period (cytophotometry). With increasing the radiation dose (from 10 to 30 krads), the rate of 3H-TdR incorporation into cells falls, and the S-period is prolonged.