Cyto B dependent and ouabain insensitive regulatory volume decrease in bicellular mouse embryo

Mouse single-cell embryos exhibit robust Regulatory Volume Decrease (RVD). In what manner the very early mammalian embryo following zygote stage is appreciably altered by the anisotonic extracellular solution is, as yet, totally unclear. Little attention was paid to this direction since there was no way to determine the blastomere volume. This work has served to quantitatively investigate the osmotic response of bicellular mouse embryos employing Laser Scanning Microtomography (LSM) followed with three-dimensional reconstruction (3 DR). We have shown that bicellular mouse embryos in hypotonic Dulbecco's experience RVD. Embryonic cells subjected to hyposmolar exhibit rapid osmotic swelling followed by gradual shrinking back toward their original volume. The van't Hoff law defines swelling phase with the effective hydraulic conductivity of 0.3 micron x min(-1) x atm(-1). Water release during RVD in bicellular mouse embryos is abolished by Cytochalasin B (Cyto B) and the volume recovery is insensitive to ouabain treatment.     

Eltor cholera in Latin America

Cholera epidemics in South and Central America in the period 1991-1999 are characterized. The mechanisms of existence of Vibrio eltor in environmental objects have been substantiated. The causes and conditions of endemic foci formation which determine the infection spread not only within the countries of the subcontinent, but also far beyond its borders are shown. The effectiveness of cholera control interventions is evaluated.     

Comparative study of various methods for determining Vibrio cholerae toxigenicity

Testing of 138 Vibrio cholerae strains for gene determinants responsible for the production of cholera enterotoxin by the polymerase chain reaction (PCR) and gene probing using molecular CT-probe showed good correlation of the results of different methods and correlation of these data with studies of V. cholerae strain virulence in vivo and in hemolytic activity test. The advantages of PCR in rapid assessment of the toxigenicity and epidemic significance of V. cholerae strains are demonstrated.     

Analysis of elemental composition (Na/K/Ca) of muscle cells in ischemia in a model of the perfused heart

It has been hypothesized that cardiac ischaemia induces some changes in the cardiac myocyte element. In the present study we analysed whether the imbalance of potassium, sodium and calcium in cardiomyocyte may be coupled with ischaemic conditions, using a perfused heard as a model. Electron Probe Microanalysis (EPMA) of papillary muscle cryosection was employed to examine the intracellular content of elements. Following a 30 min acute ischaemia the intracellular potassium was not changed and sodium was reduced. During a prolonged ischaemia (45 min) [K] loss was shown and [Na] concentration was seen reestablished. These results demonstrate that the active transport of potassium and sodium is possible at the beginning of ischaemia. This suggests that under abaerobic conditions Na-K-ATPase may be functionally coupled with an ATP-sensitive K channel through intracellular messenger, possibly ATP.     

Cytochalasin B induces changes in cytoplasmic Na+/K+ balance of two-cell mouse embryos

Changes in intracellular elemental (Na, K) concentrations caused by cytochalasin B were measured by electron probe microanalysis. Cytochalasin B is applied to transfer somatic cell nuclei into early embryo cells. This chemical causes a cytoskeleton rearrangement that may activate potassium channels, which, in turn, results in a cytoplasmic Na⁺/K⁺ imbalance. Our study showed that cytochalasin B reduced the intracellular sodium concentration. After the exposure of the mouse embryo with Dulbecco’s solution free from chemical, the Na⁺/K⁺ balance in cytoplasm reached the initial level. Possible mechanisms of registered changes in intracellular Na⁺ concentration are discussed.     

Cytochalasin B induced changes in cytoplasmic Na+/K+ balance in 2-cell mouse embryo

This work was performed to study changes in intracellular elemental (Na/K) concentrations caused by Cytochalasin B in two-cell mouse embryo using Electron Probe Microanalysis. The presence of Cytochalasin B is required to transfer a somatic cell nuclear into an early embryo cell. The direct effect of this chemical is cytoskeleton transformation, which would be able to cause the increase of potassium channel activity resulting in cytoplasmic Na/K imbalance. In our study Cytochalasin B was shown to decrease the intracellular sodium concentration. The Na/K balance in the cytoplasm of mouse embryos reverted to its intact level after treatment them with Cytochalasin B free Dulbecco's solution. Possible mechanisms responsible for the changes in the intracellular sodium concentration observed in the embryo cells are discussed.     

Potassium deficiency in rat cardiomyocytes after whole-body hyperthermia

Potassium distribution and content were studied in different compartments of rat heart papillary muscle by X-ray microanalysis. A higher concentration of potassium was measured in normal rat as compared to that in animals treated with high physiological temperature (45 degrees C), to be 120 and 80 mM, respectively.     

The Role of “Dormant” Mechanisms in Regulation of K/Na Balance in the Rat Cardiac Muscle Cell during Hypoxia

Using the electron probe microanalysis, potassium and sodium concentrations were measured in Wistar rat cardiac muscle cells. Hypoxic conditions were modeled according to the protocol of global ischemia in the absence of perfusion or via anoxic perfusion without glucose. It was shown that depending on the scheme of realization of hypoxia the change with time of the intracellular potassium and sodium balance had different character. Based on the obtained data, the sequence of activation of the hypoxia-specific mechanisms of ion transport on the cardiomyocyte membrane is considered.     

Cytoplasmic K/Na balance in heart muscle cells of young and old rats under oxygen and substrate deficiency

Age-related changes in the content of the major cellular cations of potassium and sodium in heart muscle cells of Wistar rats have been studied. The cytoplasmic concentration of potassium and sodium was determined by the electron probe microanalysis. The results revealed differences in both the concentration of the elements in young and old control animals and the responses of a cardiomyocyte to the state of acute hypoxic deenergization modelled on a perfused heart. The data are consistent with the hypothesis about the presence of genetically-related age changes in the conductance of potassium channels, which in old animals are realized against the background of deficient supply of tissues with oxygen and substrate.