Restoration of tyrosinamine transferase (TAT) with cortisol in the rat hepatocytes after the cessation of prolonged (for many days) administration of this hormone was investigated. The effect of the liver regeneration and insulin administration on this process was also studied. In single cortisol administration the TAT activity rose 5-fold; the induction response decreased after 21 days of daily administration. The TAT induction in response to cortisol administration was restored completely only on the 25th--30th day after the cessation of this hormone injection. A three-day insulin administration led to the restoration of TAT induction in response to cortisol administration. The process of the liver regeneration during the first 24 hours after partial hepatectomy induced TAT in the cells of both control animals and those given cortisol for prolonged periods; besides, it aided restoration of the induction response to cortisol administration.

Oospora lactis was found to use Tweens 20, 40, 60 and 80 as a source of carbon in a nutrient medium for lipase biosynthesis. The highest production of lipase was registered in the medium with Tween-80. The lipase activity of the culture increased if even small quantities of Tweens 40, 60 and, particularly, 80 (0.05--1.0%) were added to the medium containing cottonseed oil. All the tested Tweens stimulating the biosynthesis of lipase were also, at a particular concentration, the inhibitors of this enzyme.

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.