Cytoplasmic potassium-sodium balance in the cardiac muscle cell of young and old rats in oxygen-substrate deficiency

Age-related changes in the concentrations of the main cations potassium and sodium in the cardiac muscle cell of Wistar rats were studied. The cytoplasmic concentrations of potassium and sodium were measured by electron probe microanalysis. The results obtained showed differences both in concentrations of the cations between young and old reference animals, and in the cardiomyocyte response to the state of acute hypoxic deenergization modeled on a perfused heart. The data obtained are consistent with the hypothesis of the presence of genetically determined age-related changes in the conductance of potassium channels, which occur in old animals against the background of short supply of oxygen and substrate to tissues.     

PCR-detection of markers for epidemiologically-significant strains of Vibrio cholerae 0139, isolated in Siberia]

Fourteen V. cholerae 0139 strains were isolated in 1996-1999 in Siberia from the Ob river (Novosibirsk) and bogs and lakes (Irkutsk). The strains were tested in PCR for the key virulence determinants (ctx AB, tcp, acf). The genomes lacked these elements, and therefore the strains were acknowledged avirulent. The results correlate completely with the data of phenotypical analysis, characterizing the pathogenic characteristics of isolated strains.     

Destruction of a Bacterial Biofilm with an Electrochemically Activated Solution

Biophysics - The action of electrochemically activated water on the fine structure of biofilms formed by the plankton forms of lactic acid bacteria and E. coli was investigated. Bacterial biofilms...     

Ultrastructural localization of potassium and calcium in an insect ommatidium as demonstrated by X-ray microanalysis

Summary Ultrastructural localization of potassium and calcium in the ommatidium of the house-cricketGryllus domeslicus L. was studied by X-ray microprobe analysis using samples prepared as thin sections (2 or 5 m) of freeze-dried and embedded tissue. Real resolution was limited by the size of ice crystals (Fig. 2) and estimated as about 1 m.Average values for potassium, calcium, sodium and phosphorus in different cells of the compound eye are given in Table 1.Striking non-uniformity in distribution of these elements over the cells and their compartments was found by probe scanning (Figs. 3, 4, 5). The highest potassium and calcium concentrations were measured in the pigmented zones of photoreceptors and pigment cells. The pigment granules are thought to be the ionic depots of the eye.Potassium and sodium are fully accessible to water in sections of embedded tissue, whereas all the calcium and half of the phosphorus are not.The functional significance of the non-uniformity discovered is briefly discussed.     

Electron Probe Microanalysis of potassium and phosphorus in mouse oocytes and zygotes

Intracellular concentrations of potassium and phosphorus were determined by Electron Probe Microanalysis in mouse mature oocytes and zygotes. The oocytes were characterized by insignificant variations in the concentrations of these elements in the cytoplasm: 60 ± 4 and 103 ± 6 mM, respectively. In zygotes, on the contrary, significant variations were observed: 64 ± 16 and 84 ± 14 mM, respectively. Changes in the potassium homeostasis during the first cell cycle have been discussed.__________Translated from Ontogenez, Vol. 36, No. 2, 2005, pp. 123–127.Original Russian Text Copyright © 2005 by Pogorelov, Smolyaninova, Pogorelova, Goldstein.     

Electron probe microanalysis of potassium and phosphorus in mouse oocytes and zygotes

Intracellular concentrations of potassium and phosphorus were determined by Electron Probe Microanalysis in mouse mature oocytes and zygotes. The oocytes were characterized by insignificant variations in the concentrations of these elements in the cytoplasm: 60 +/- 4 and 103 +/- 6 mM, respectively. In zygotes, on the contrary, significant variations were observed: 64 +/- 16 and 84 +/- 14 mM, respectively. Changes in the potassium homeostasis during the first cell cycle have been discussed.     

Ultracytochemical localization and microprobe quantitation of calcium stores in the insect oocyte

Summary Detection of calcium in the follicles of Galleria mellonella (Lepidoptera) was performed using two cytochemical methods. Calcium precipitation was obtained either with ammonium oxalate (AO) or with N,N-naphtaloyl-hydroxylamine (NHA). In both cases the X-ray on line analysis monitored the presence of calcium in the oocytes, which was correlated with the accumulation of yolk spheres. concentration of calcium in oocytes filled with yolk and treated with AO amounted to 9 mmoles per 1,000 g tissue we weight. This value is similar to that calculated previously for follicles untreated with any reagent and prepared for the analysis by the freeze-drying technique (Przelcka et al. 1980).Examination of the ultrastructure of oocytes treated with NHA revealed calcium precipitate at the follicular epithelium/oocyte interface, in endocytotic canaliculi and vesicles formed by the oocyte plasma membrane, in ooplasm, and in yolk spheres. In oocytes treated with AO, the calcium-precipitate intermingled with the precipitate produced by the osmium alone. The presumed cause of this phenomenon is discussed.     

Local x-ray spectral microanalysis in cell biology. The study of sections of hydrated biological tissues

Rules required for fixation of tissues are considered aimed for a further localization of chemical elements in these tissue by means of local X-ray microanalysis. In addition, difficulties involved in fixation of diffusible elements, such as potassium or sodium, are mentioned. Physical bases of preparation of hydrated tissues for X-ray analysis are discussed.     

A cancer mutation promotes EphA4 oligomerization and signaling by altering the conformation of the SAM domain

The Eph receptor tyrosine kinases and their ephrin ligands regulate many physiological and pathological processes. EphA4 plays important roles in nervous system development and adult homeostasis, while aberrant EphA4 signaling has been implicated in neurodegeneration. EphA4 may also affect cancer malignancy, but the regulation and effects of EphA4 signaling in cancer are poorly understood. A correlation between decreased patient survival and high EphA4 mRNA expression in melanoma tumors that also highly express ephrinA ligands suggests that enhanced EphA4 signaling may contribute to melanoma progression. A search for EphA4 gain-of-function mutations in melanoma uncovered a mutation of the highly conserved leucine 920 in the EphA4 sterile alpha motif (SAM) domain. We found that mutation of L920 to phenylalanine (L920F) potentiates EphA4 autophosphorylation and signaling, making it the first documented EphA4 cancer mutation that increases kinase activity. Quantitative Föster resonance energy transfer and fluorescence intensity fluctuation (FIF) analyses revealed that the L920F mutation induces a switch in EphA4 oligomer size, from a dimer to a trimer. We propose this switch in oligomer size as a novel mechanism underlying EphA4-linked tumorigenesis. Molecular dynamics simulations suggest that the L920F mutation alters EphA4 SAM domain conformation, leading to the formation of EphA4 trimers that assemble through two aberrant SAM domain interfaces. Accordingly, EphA4 wild-type and the L920F mutant are affected differently by the SAM domain and are differentially regulated by ephrin ligand stimulation. The increased EphA4 activation induced by the L920F mutation, through the novel mechanism we uncovered, supports a functional role for EphA4 in promoting pathogenesis.