Relation of the biosynthesis of intracellular and export proteins in rat liver cells during induction of proliferation by cycloheximide

After a single injection of a sublethal dose of cycloheximide (CHI) the biosynthesis of extracellular proteins in rat hepatocytes was rapidly suppressed, the reconstitution being very slow. On the contrast, the biosynthesis of intracellular proteins (e.g., histones, and other acid-soluble liver proteins) was more resistant to CHI. The activation of biosynthesis of acid-soluble and acid-insoluble proteins was found to occur stepwise. It was assumed that the activation of synthesis and accumulation of intracellular proteins after CHI release accompanied by a decreased synthesis of extracellular proteins is one of possible causes of stimulation of DNA synthesis in the hepatocytes following a single injection of CHI.     

Permeability of bilayer lipid membranes in phase transition. The significance of intermolecular phosphate-phosphate hydrogen bonding

The effect of pH on the phase transition temperature of 1,2-dipalmitoyl-sn-glycero-3-phosphate (DPPA) and 1,2-dipalmitoyl-sn-glycero-3-thionphosphate (thion-DPPA) has been investigated. The phase transition was detected using the jump like increase effect in the conductance of the planar bilayer membrane. It is shown that the steepness of pH-dependence of the phase transition temperature differs for these two kinds of lipids in the pH range of 3.5-8. This result is explained in terms of decreased intermolecular hydrogen bonding between the head groups of thion-DPPA. Calculations taking into account the ability of DPPA molecules to intermolecular phosphate-phosphate hydrogen bonding were made. The results of calculations are in good agreement with the experimental data obtained in this study.     

Change in the activity of calcium ions during illumination of a suspension of visual cell outer segment fragments]

Changes in the activity of calcium ions in the medium containing outer fragments suspension of bovine eye retina rods have been studied by the method of calcium-selective electrodes. Illumination of the suspension increases calcium ion activity in the incubation medium. Photoinduced yield of calcium ions depends on Ca+2 concentration: it equals 0.11+/-0.015 M Ca2+/1m rodopsin in the medium containing 0.1 mM CaCl2 and 0.046+/-0.002Ca2+/1M rodopsin in the medium containing 0.05 mM CaCl2. In the medium containing more than 10(-4) M CaCl2 both an increase and a decrease of Ca2+ ions have been observed.     

Causes of the resistance of Chlorella strains to physical and chemical environmental factors

Factors have been studied which are responsible for the resistance of cells of several strains of Chlorella to physical and chemical stresses; measurements have been made of the effects of UV and x irradiation, heat treatment, detergents, cadmium salts, and insecticides. Cells which were resistant to the effects of physical factors were also resistant to chemical intoxication. A positive correlation was found between the resistance of cells to the described factors and the level of endogenous thiols in the cells, as well as the free radical content. This in turn is due to an increased number of reaction centers in the electron-transport chain.     

Correlation between the rate of protein and nucleic acid synthesis and the intensity of various glucose metabolic pathways in rat liver cells

A sharp and strong suppression of protein synthesis by cycloheximide in liver cells of starving rats is paralleled with activation of RNA synthesis and glucose-6-phosphate dehydrogenase production. Subsequent reconstitution and stimulation of protein synthesis (6-12 hrs after cycloheximide injection) result in activation of hexokinase. Upon stimulation of DNA synthesis (48-60 hrs after cycloheximide injection) the activity of both enzymes is very low. Since glucose-6-phosphate dehydrogenase appears to be the limiting step of glucose decay via the pentose phosphate pathway, and hexokinase is the limiting step of glycolysis, it was assumed that RNA synthesis predominantly occurs via the pentose phosphate pathway, while that of proteins via glycolysis.     

Inversion Polymorphism and the Divergence of Two Cryptic Forms of Anopheles messeae(Diptera, Culicidae) at the Level of Genomic DNA Repeats

Genomic DNA of samples from several populations of malaria mosquito Anopheles messeaebelonging to the macullipennis Paleoarctic complex was examined using digestion with ten restriction enzymes and electrophoresis in polyacrylamide gel. The patterns of DNA repeat fractions in the EcoRI hydrolysate in two cryptic forms of An. messeaecharacterized by common inversion polymorphism were shown to be different. The genomic differences in mixed sympatric groups and those between geographically remote populations of the different forms were identical. No interindividual, intrafamilial, inter- and intrapopulation variation was revealed in either form. The electrophoregrams of individuals belonging to the same form but having different combinations of inversion chromosomal variants in the karyotypes were identical. Analysis of taxonprints in the forms showed that individuals with the same karyotype may belong to different forms. These results coupled with evidence on the ecological features of and assortative mating inAn. messeaepopulations demonstrated that the examined forms are not conspecific. Our results indicate that taxonprint analysis is the most reliable and precise test for the presence of conspecific forms in a large sympatric zone.