The induction of auxotrophic mutations for riboflavin by the integration of plasmid pLRS33 into the chromosome of Bacillus subtilis

The transformation of Bacillus subtilis Lys- strains with plasmid pLRS33 containing pBR322 and the Bac. subtilis chromosomal fragment carrying the genes for lysin biosynthesis and the riboflavin operon regulatory operator region (ribO) leads to the appearance of Rib- mutants. It was shown that these mutants contained long deletions covering a great portion of the riboflavin operon.     

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.     

DELAYED URIC ACID ACCUMULATION IN PLASMA PROVIDES ADDITIONAL ANTI-OXIDANT PROTECTION AGAINST IRON-TRIGGERED OXIDATIVE STRESS AFTER A WINGATE TEST

Reactive oxygen species are produced during anaerobic exercise mostly by Fe ions released into plasma and endothelial/muscle xanthine oxidase activation that generates uric acid (UA) as the endpoint metabolite. Paradoxically, UA is considered a major antioxidant by virtue of being able to chelate pro-oxidative iron ions. This work aimed to evaluate the relationship between UA and plasma markers of oxidative stress following the exhaustive Wingate test. Plasma samples of 17 male undergraduate students were collected before, 5 and 60 min after maximal anaerobic effort for the measurement of total iron, haem iron, UA, ferric-reducing antioxidant activity in plasma (FRAP), and malondialdehyde (MDA, biomarker of lipoperoxidation). Iron and FRAP showed similar kinetics in plasma, demonstrating an adequate pro-/antioxidant balance immediately after exercise and during the recovery period (5–60 min). Slight variations of haem iron concentrations did not support a relevant contribution of rhabdomyolysis or haemolysis for iron overload following exercise. UA concentration did not vary immediately after exercise but rather increased 29% during the recovery period. Unaltered MDA levels were concomitantly measured. We propose that delayed UA accumulation in plasma is an auxiliary antioxidant response to post-exercise (iron-mediated) oxidative stress, and the high correlation between total UA and FRAP in plasma (R-Square = 0.636; p = 0.00582) supports this hypothesis.     

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.     

Involvement of Recovery Processes in the Effects of Radioprotectors at the Cellular and Organismal Levels

Biology Bulletin - A correlation between the effectiveness of the radioprotective action of cysteamine with the radiosensitivity of cells and their ability to recover from radiation damage was...     

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.