The dynamics of distribution of 125I- and 131I-bilignost in intact rats has been studied in experimental pathological condition of the liver. It has been shown that the cholecystographic radiographic contrast agent (RCA) bilignost is absorbed and accumulated mainly by the liver. This indicates that the preparation elicits a selective action with respect to the liver. Administration of 125I-bilignost in conjunction with the unlabeled cholecystographic agents bilignost and endografin induces competition for absorption by the liver, which distinguishes these preparations from the urographic agent cardiotrast decreasing accumulation of the label by the kidneys. Acute CCl4 poisoning of the animals results in a sharp decrease in the liver capacity for accumulation of 131I-bilignost and to a slight rise in the preparation kidney level. Three-day administration of phenobarbital to rats produces a considerable drop in 125I-bilignost level in all the organs tested, suggesting an enhanced RCA excretion from the body.

Activity of microsomal enzymes and the patterns of cholesterol metabolism were studied in mice of WSR/y strain, characterized by spontaneous development of atherosclerosis within the later periods of life, after early postnatal administration of an inductor of the enzymes 3-acetate-16 alpha-isothiocyanopregnenolone (ATCP). Administration of ATCP into newborn mice of SWR/y strain, from the 2nd up to 16th day after birth, led to a stable increase in activity of arylhydrocarbonate hydroxylase (an enzyme participating in unspecific metabolism of drugs), which was observed during the whole experimental period (4 months). The treatment with ATCP caused also a distinct increase in activity of cholesterol-7 alpha-hydroxylase (a key enzyme of cholesterol biotransformation and elimination) as well as a considerable decrease in content of cholesterol and lipoprotein atherogenic fractions in blood serum. The rate of cholesterol biosynthesis was similar both in mice treated with ATCP and in the control animals.

Gel filtration and equilibrium dialysis demonstrated that the hyaloplasmic fraction of the liver of B1-deficient rats does not practically bind C-TDP in vitro. An addition of the excess of non-labelled coenzyme does not increase the transketolase activity. The data obtained suggest that transketolase activation in the hyaloplasmic fraction of the liver of B1-deficient rats after administration of thiamine in vivo is due to stimulation of the additional synthesis of the enzyme protein rather than to the saturation of the free apoenzyme with newly-formed TDP. In vivo and in vitro studies suggest that the hyaloplasmic fraction of the liver of B1-deficient rats contains no free apoenzyme of transketolase.

The rat hepatocytes during chemical carcinogenesis (3'-MDAB), as well as the cells of chemically-induced primary rat hepatomas preserved their response to partial hepatectomy by stimulation of the 3H-thymidine incorporation into DNA; as in the normal liver this process is inhibited by dexamethason. No impairment in the inducibility of tyrosine aminotranspherase (EC.2.6.1.5) by the hormone was observed, whereas the hormonal induction of tryptophane pyrrolase (EC.1.13.11.11) in primary hepatomas was lost completely. The problem of the adequacy of the model of chemical carcinogenesis of the organ without consideration of the cell populations heterogeneity is discussed.

When Bacillus subtilis produces alpha-amylase in the course of continuous cultivation, it is difficult to maintain the activity at a constant level. This may be due to the formation of nonproductive mutants. Individual cells in the population have been analysed in the course of the continuous process. The composition of the population changes depending on time and the composition of the growth medium. Semisynthetic media cause selection of mutants which synthesize the enzyme at a low rate. In contrast, complex media which are more enriched in the sources of carbon and nitrogen induce accumulation of mutants with a high activity.

Various metal ions have different effect on the lipolytic activity of Rhizopus microsporus in the course of cultivation on nutrient media having diverse composition. The fungus particulary requires metal ions for the production of lipase on a mineral medium. Additional introduction of microelements into a medium containing maize extract has no significant effect on the lipolytic activity. Active biosynthesis of lipase by the culture requires zinc.

The effect of glucose, sucrose, fructose, maltose, alpha-methyl glucoside, glycerol, nonmetabolizing glucose analog--2-deoxy-D-glucose, and cyclic 3',5'-adenosine monophosphate (cAMP) on the glucoamylase biosynthesis by the yeast Endomycopsis fibuligera 20-9 was investigated. The sugars tested induced repression of the enzyme synthesis. The repressive effect of glucose, sucrose and maltose was reversed partially or completely by cAMP. The strongest derepressive effect of cAMP was noted in the presence of 2-deoxy-D-glucose. The transport of glucose and 2-deoxy-D-glucose in yeast cells was also investigated. Those compounds were found to compete for the entry into the cell. It is concluded that glucoamylase synthesis in Endomycopsis fibuligera 20-9 was susceptible to catabolite repression. Its possible mechanism discussed.

The effect of the di-N-oxide quinoxaline on the activity and biosynthesis of DNA-ase and plasmocoagulating properties of the Staphylococcus aureus, strain Zhaev, was studied. The highest action in respect to DNA-ase of the Staphylococcus is shown to display dioxydine (1,4-di-N-oxide of 2,3-dioxymethylquinoxaline). Under its effect there takes place a significant fall of the DNA-ase activity and the plasmocoagulating properties of the staphylococcus. In cultures treated with dioxydine or its biologically active analogues the ability to biosynthetize DNA-ase with subsequent cultivationon on a medium containing no compounds is not restored. A possible mechanism of action produced by the study drugs is suggested.

Acetylcholine (10(-6)--10(-3) M) added to the rat brain homogenate increased that activity of microsomal Na, K-ATPase and (14C)-amino acid incorporation in microsomal proteins. Actinomicin D (5.10(-5) M) eliminated the effect of acetylcholine. It is concluded that acetylcholine induced the synthesis of either Na, K-ATPase itself or some other proteins involved in the enzyme activity regulation.

The effect of certain metabolites of Penicillium brevi-compactum on the biosynthesis of exocellular ribonucleases and phosphomonoesterase was studied. Their synthesis was found to be inhibited by RNA and AMP, as well as by high concentrations of these enzymes in the medium. The mechanism which regulates the biosynthesis of exocellular phosphohydrolases by both phosphate and the enzymes is discussed.

In vitro estimation of synthesis of inducible tyrosine aminotransferase isoenzyme, directed by poly-A-containing RNA from liver of intact and corticol treated rats, is carried out. Total poly-A-containing RNA from liver polyribosomes of intact and induced rats was translated in cell-free system from wheat germs. Two antibodies immunoprecipitation was used to identify the translocation product (tyrosine aminotransferase). It was found that a synthesis of a specific protein product, precipitated by antibodies to tyrosine aminotransferase, takes place in cell-free system under translation of polysomic poly-A-containing liver RNA. The amount of immunoprecipitated product indicates, that the content of individual poly-A-containing mRNA for inducible tyrosine aminotransferase isoenzyme in liver of cortisol-induced rats is considerably higher than in intact animals.

Bacillus mesentericus was found to assimilate nucleic acids as a source of nitrogen and phosphorus. Nucleic acids added to the medium as a source of nitrogen or phosphorus stimulated synthesis of ribonuclease. When washed bacterial cells were incubated for a short period of time in a fresh nutrient medium containing RNA, synthesis of RNAase was also induced. Synthesis of the enzyme was inhibited by high concentrations of chloramphenicol and actinomycin D, and stimulated by low concentrations of actinomycin D. Therefore, alkaline RNAase is an inducible enzyme which participates in the nutrition processes of bacteria.

Acetic acid was found to repress cholinesterase synthesis in the cells of Arthrobacter simplex var. cholinesterasus even at very low concentrations (0.1%). The repression is very stable. It is not eliminated by glucose or an organic acid of the Krebs cycle being added to the medium with acetic acid. The combination of acetic and butyric acids decreases the repression but does not eliminate it. The kinetics of cholinesterase synthesis was different in the cells grown on the medium with acetic acid and the cells cultivated on the medium with acetic acid and glucose, then washed and transferred to a fresh growth medium with glucose and acetylcholine as the sources of carbon.

beta-Lactamases of Proteus and their role in the mechanism of the microbe resistance to penicillins and ceporin were studied. It was found that the beta-lactamase of Proteus had low activity and were produced by both beta-lactamide resistant and sensitive clinical strains of Proteus. The resistant cultures of Proteus produced enzymes more frequently (3.4--5 times) than the sensitive ones. The synthesis of beta-lactamase in the clinical Proteus strains was inducable. The high induction coefficient was achieved only in the presence of high concentrations of the inductor. No significant dependence of the culture sensitivity level of ampicillin and ceporin on the induction level was observed. The most significant part of the constitutive enzyme in Proteus was intracellular, while that of the inducable enzyme was extracellular. No correlative dependence between the culture resistance levels to penicillins and ceporin and the enzyme activity was noted. The beta-lactamase activity was not found in the transconjugants with the in vitro acquired R-factor controlling the ampicillin and ceporin resistance, as well as in the resistant mutants selected on the media with increasing concentrations of the above antibiotics. Induction of beta-lactamase synthesis was not found in these strains either. The ability of Proteus to synthesize beta-lactamase can be lost on the strain storage under laboratory conditions which was not always accompanied by reduction of the culture sensitivity to ampicillin and ceporin. The enzymatic destruction of beta-lactamides was not the main mechanism of Proteus resistance to the above antibiotics.