The resistance to tetracycline decreased in Escherichia coli C600 cells containing plasmid RP4 and grown under the conditions of continuous cultivation. The population of cells containing plasmid RP4 is heterogeneous in the trait of tetracycline resistance, and most cells cannot grow in a selective medium with tetracycline at a concentration of 20 micrograms/ml. The decreased resistance to tetracycline was most pronounced for a glucose-limited chemostat culture and also in the presence of two plasmids, RP4 and pBS94 , in the cells. No decrease was found in the resistance to other drugs determined by plasmid genes.

This work was aimed at studying the interactions during the growth of Actinomyces rimosus producing proteases and Actinomyces violocinereus which did not synthesize secreted proteolytic enzymes. The production of proteases in the association of the actinomycetes was shown to be stimulated by metabolic products released by A. violocinereus into the surrounding medium. The stimulating agent from the cultural broth of this culture accelerated differentiation of the mycelium of the first hyphal generation in A. rimosus, decelerated spore formation of the second hyphal generation, inhibited the growth rate, and increased the rate of protease accumulation as well as the productivity of the synthesis.

The effects of the glucocorticoid hydrocortisone on the synthesis of specific template RNA coding tyrosine aminotransferase (TAT) in rat liver during hormonal induction were studied. Using hybridization of complementary DNA (cDNA-TAT) with polysomal liver poly-A-mRNA, the content of specific mRNA-TAT in liver polysomes during and after hormonal induction, i. e. 4 and 16 hrs after hydrocortisone injection, respectively, was estimated. It was shown that 4 hrs after the hormone injection that mRNA-TAT content in liver polysomes is increased 3-4-fold, showing a return to the initial level after 16 hrs. Thus, transcription is the main link in the realization of glucocorticoid induction.

It has been shown that endogenous lipid peroxidation (LPO) is an effective mechanism participating in the destruction of endoplasmic reticulum membranes (cytochrome P450) in liver. Antioxidants are able to control the rate of degradation of cytochrome P450 in vivo. Stock of the constitutive cytochrome P450 as compared with induced P450 is more resistive to LPO in vivo and in vitro. Spontaneous as well as induced by Fe2+--ADP+ +NADPH system destruction of cytochrome P450 due to accumulation of LPO products malonic dialdehyde (MDA) occurs during incubation of isolated rats hepatocytes. The LPO inhibitors (4-methyl-2,6- ditretbutilphenol , pyrogallol) stabilize cytochrome P450 preventing accumulation MDA hepatocytes. Degradation of cytochrome P450 in microsomes during trypsin proteolysis has been found to be enhanced by PLO induction. Efficiency of proteolysis depends on the way of induction and decreases in such an order: NADPH-- HNDH --ascorbate-dependent LPO. LPO may be considered as a trigger mechanism that makes some forms of cytochrome P450 available for endogenous proteases.

A method is developed for studies of differences in peptide structure of native membrane-bound monooxygenases using limited proteolysis of liver microsomal hemoproteins. Analysis of peptide maps was carried out in constitutive and induced by 3 methylcholanthrene and 2, 3, 7, 8-tetrachlorodibenzodioxin enzyme forms, responsible for metabolic and biological activation of polycyclic aromatic hydrocarbons.

A strain of Bacillus sp. was isolated which is an active producer of levan. The dynamics of the polysaccharide biosynthesis was studied depending on concentrations of sucrose in the medium. The amount of the synthesized levan was proportional to the concentration of sucrose ranging from 0.2 to 6%, being a maximum of 28.2 mg/ml in the medium containing 12% of sucrose. The presence of urea or ammonium sulfate in the medium stimulates the levan biosynthesis. A medium with pH 6.0--6.8 is optimal for the polysaccharide formation. Levan, synthesized by Bacillus sp., is a polysaccharide with the molecular weight more than 2 mln. Levansucrase is an induced enzyme, whose inductors are sucrose and raffinose.

A combined administration of cis-dichlorodiaminoplatinum (DDP) and phenobarbital increases the activity of nonspecific oxidases, decreases the toxic effect of DDP especially its nephrotoxic action, but does not decrease the antiblastic action of DDP in rats. On the basis of experimental data the optimum regime of DDP repeated administrations is suggested.

Since most cancers eventually become refractory to chemotherapy, the development of drug resistance within tumour populations remains a major concern in the cancer treatment. The development of drug resistance is often correlated with specific chromosomal modifications. Though chromosomal aberrations are generally much more frequent in cancer than in normal cells, there are no qualitative differences between the aberrations in cancer and in normal cells. At present the genetic basis of drug resistance may be induced by gene amplification, which can be alternatively associated with chromosomal homogeneously stained regions or with double microchromosomes. The both phenomena are essentially the same: they reflect the mechanism for the amplification of genes stimulating tumour viability under unfavourable conditions.

Phenobarbital administration during 7 weeks after partial hepatectomy is shown to be a sufficient promoting factor for induction of hyperplastic nodules in the rat liver initiated by the single DENA injection to pregnant rats. Histochemical distribution of gamma-glutamyltranspeptidase was a marker for identification of hyperplastic nodules.

The effect of various carbon sources and cAMP on the glucoamylase synthesis in Aspergillus niger was studied to find carbon sources repressed the enzyme synthesis and conditions for the selection of catabolite stable mutants. Maltose at a concentration of 0.5% stimulated the glucoamylase synthesis, but at a concentration of 4% it repressed not only the enzyme synthesis but the growth of the parental strain on the agar medium. The more active mutant 66 was obtained as a result of treatment of Asp. niger st 6 with NG. This mutant is able to grow on the Czapek's medium containing maltose at concentrations 4 or 6%. The mutant 66 produced about 2.9 times more glucoamylase than its parent when maltose was added at 0.5% concentration to the medium. The glucoamylase synthesis in the parental strain was completely repressed under repressing conditions, while the level of the mutant strain activity was 35% from the level of enzyme activity on the medium without the repressor. The addition of cAMP (5.10(-5] resulted in a partial release of maltose (4%) repression of the glucoamylase synthesis in both strains. The results obtained indicate a possibility to select Asp niger mutants with the partially derepressed glucoamylase synthesis. Other regulation mechanisms in addition to catabolite repression may be involved in the regulation of the glucoamylase synthesis.

The production of extracellular 1,3-, 1,6-beta-glucanases and chitinase was studied during submerged cultivation of a Trichoderma viride strain 3/78 on various carbon sources: glycerol, glucose, lactose, sucrose, laminaran, starch, pustulan, chitin, and Agaricus bisporus fruit bodies. The synthesis of these enzymes and cellulase was studied also under the conditions of depression at low concentrations (10(-2) and 10(-3)M) of the first five aforementioned carbon sources as well as cellobiose, gentiobiose, N-acetyl-beta-D-glucosamine and 0.1% chitooligosaccharides and A. bisporus cell walls. The experiments were conducted with the washed mycelium of this strain grown for 2 days in a medium with glycerol as a carbon source. The results indicated that 1,3- and 1,6-beta-glucanases of the strain were of the constitutive nature and were repressed by such carbon sources as glycerol and glucose. Chitinase and cellulase were shown to be inducible enzymes. Chitinase was induced by N-acetyl-beta-D-glucosamine, chitooligosaccharides and A. bisporus cell walls as well as by lactose when the fungus was grown on this carbon source. Cellulase biosynthesis was induced by lactose, cellobiose and gentiobiose.

A factor stimulating the production of exoproteases by Aspergillus kanagawaensis both in a single culture and during combined cultivation with Aspergillus wentii was isolated from the cultural broth of a component in the microbial association according to our scheme. The factor is a pigment of the hydroxyanthraquinone nature. It made the enzyme biosynthesis increase 3.7 times. Its effect on the biosynthesis was compared to that produced by other anthraquinone pigments, viz. alizarin, rubomycin and cinerubins. The compounds stimulated the biosynthesis only 2 to 2.5 times.

Amino acids and proteins were found to produce different effect on the synthesis of bacitracin and exoprotease by Bacillus licheniformis 28 KA depending on the age of the cells. The enzyme synthesis was induced by amino acids and proteins only in the cells at the exponential growth phase. No correlation could be established between the antibiotic and proteolytic activities. The optimal protease synthesis was found in a medium with isoleucine whereas the antibiotic synthesis was optimal in a medium containing no amino acids.