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Biomedical subjects

M E Beker

Publications and source records attributed to M E Beker.

At least 19 recordsLinked to original sources
PubMedDate not supplied

[Stability to the extreme influences and significance of internal pH of Saccharomyces cerevisiae depending on the density of cellular suspensions].

The resistance of a Saccharomyces cerevisiae population against gamma-irradiation (400 krd), heating (60 degrees C), repeated freezing--thawing and rehydration of dehydrated cells was shown to depend on the density of a cell suspension. The percentage of damaged cells (stained with primulin) was found to increase in a suspension with decreasing cell concentrations. The effect was also exerted in an oxygen-free medium. The percentage of undamaged cells increased in populations with a lower cell concentration when a more viscous medium (0.2% agar) was used. The intracellular pH dropped down in a denser intact yeast suspension and rose with an increase in the concentration of dehydrated-rehydrated cells.

Freezing↗
PubMedDate not supplied

[Distribution of trehalose between the cells and the rehydration medium in dehydrated Saccharomyces cerevisiae].

The work was concerned with studying the balance of trehalose distribution between the rehydration medium and Saccharomyces cerevisiae cells grown in a chemically defined medium and dehydrated using the convective technique. A direct linear correlation between the viability of populations and the overall residual trehalose content in the cells and in the medium after the rehydration of dry yeast cells was shown to be most important. An inverse correlation was established between the viability of yeast cells and the amount of trehalose mobilised by the cells in the process of rehydration.

Culture Media↗
PubMedDate not supplied

[Relationship between the content of some fractions of high molecular weight polyphosphates and total nucleic acids upon dehydration of the yeast Saccharomyces cerevisiae].

Essential redistribution of various polyphosphate fractions was shown during dehydration and subsequent reactivation of Saccharomyces cerevisiae 14. Dehydration no matter what method was used, was followed by an increase in the content of acid soluble polyphosphates (fraction Poly P1) and a decrease of that of salt soluble polyphosphates (fraction Poly P2). Reactivation of dehydrated yeast was, on the contrary, accompanied by a decrease in the PP 1 and an increase in the Poly P2 content. A direct correlation between the Poly P2 fraction and total nucleic acids was demonstrated under various conditions of dehydration and subsequent reactivation. An inverse correlation between the content of the Poly P2, fraction and nucleic acids, on the one hand, and that of the Poly P1 fraction, on the other, was observed. Study of activities of polyphosphatases, tripolyphosphatase, pyrophosphatase and ATPase in dehydrated yeast showed values similar to those in original cells.

DNA↗
PubMedDate not supplied

[Lipid inclusions in cells and their changes during the desiccation and reactivation of yeast organisms].

The formation of lipid granules in Saccharomyces cerevisiae cells was shown to begin in the exponential phase of the culture growth and to be associated with the activity of the endoplasmic reticulum. Lipid granules can be formed (1) when the endoplasmic reticulum cisterns extend and (2) when the endoplasmic reticulum membranes separate relatively small regions of the cell cytoplasm. Yeast cells contain spherosomes which differ in their structure. Lipid granules merge together upon dehydration of yeast cells. The authors discuss possible participation of these granules in the reparation of damages of the intracellular membranes.

Cytoplasmic Granules↗
PubMedDate not supplied

[Degradation of ribonucleic acids in yeast cells during desiccation].

From 26 to 43% of RNA undergoes degradation in yeast cells when they pass into the state of anabiosis. Most of the degradation was found to occur at the first stage of cell dehydration when free water was removed from the cells. The mechanism of RNA degradation is supposed to involve enzyme-catalysed processes which are realised in the cell at the early stages of its dehydration.

Desiccation↗
PubMedDate not supplied

[Dehydration effect on the fatty acid composition of lipids in baker's yeast Saccharomyces cerevisiae 14].

The effect of dehydration on the fatty acid composition of lipids in baker's yeast Saccharomyces cerevisiae 14 cultivated on the ethanol (1.5%) containing medium in the presence or absence of glutamic acid and biotin or on molasses (2%) was studied. In spite of a relatively low drying temperature (35 degrees C), the correlation between saturated and non-saturated fatty acids may vary within 40--60 min.

Biotin↗
PubMedDate not supplied

[Biochemical and morphological characteristics of Endomycopsis fibuliger growing on media containing ethanol or starch].

Differences in growth and glucoamylase synthesis were studied with Endomycopsis fibuliger R-574 growing on media containing ethanol or starch under conditions of periodic or continuous cultivation. The activity of certain enzymes involved in the metabolism of carbon sources was studied as well as the pathways of starch and ethanol metabolism. The morphology and ultrastructure of the cells were investigated during their growth in the media containing starch or ethanol.

Ascomycota↗
PubMedDate not supplied

[Effect of saccharose and lactose on the resistance of Saccharomyces cerevisiae yeast to desiccation].

Incubation of Saccharomyces cerevisiae cells in solutions containing different sucrose or lactose concentrations (0.25 to 1.0 M) makes the organism more resistant to dehydration. The effect is increased when the cells are incubated for longer periods of time. Apparently, certain intracellular reactions making the yeast survive upon dehydration are initiated under these conditions.

Desiccation↗
PubMedDate not supplied

[Increased permeability of the intracellular membranes in the dehydration and rehydration of Saccharomyces cerevisiae yeasts].

A considerable quantity of potassium and magnesium ions was found to be released from Saccharomyces cerevisiae cells being in the state of anabiosis upon their rehydration. The nearly maximal (for each of the experiments) quantity of ions was released as early as when cells dehydrated to a residual humidity of ca. 20% were rehydrated. A further decrease of the residual humidity down to 8-10% did not increase the leakage of the ions when the cells were rehydrated. It was concluded that the permeability of the cytoplasmic and vacuolar membranes for the ions increased when the cells were dehydrated and that this phenomenon should be attributed to the removal of free water from the cells.

Cell Membrane Permeability↗