A new method for determination of the activity of phenanthrene-9,10-epoxidase, one of the monoxygenases of the system of drug metabolism, in rat liver microsomes was developed. The method includes the use of phenanthrene as substrate. The rate of the substrate epoxidation is measured with the help of HPLC reverse phase in accordance with the method of the internal standard (1-naphthol) by 9,10-dihydroxy-9,10-dihydrophenanthrene, a product of the intermediate epoxide hydrolysis. For rapid quantitative conversion of the formed 9,10-epoxy-9,10-dihydrophenanthrene endogenic epoxide hydrolase is used after selective termination of the monoxygenase reaction. The time of the assay by HPLC is 4.5 minutes. Phenobarbital is a more strong and selective inductor of this form of cytochrome P-450 than 3-methylcholanthrene. The simultaneous use of the two inductors does not result in additive increasing of the enzyme activity.

Karyological analysis was made of G-banded chromosomes in the cells of three independent CHO-K1 clones stably resistant to colchicine (Clch) selected for resistance to Clch at the concentration 0.1 mkg/ml (the first step of selection), and of one clone with higher but unstable level of resistance (2 mkg/ml--the second level of resistance). The results obtained revealed a morphological instability of the P-shoulder of chromosome Z6: more often an additional genetical material (AGM) at the distal end (Z6+), or rarely deletions (Z6-). In cells of the stable resistant clones of the first step of selection the length of AGM and their morphological structures were shown to be constant, but differed among the clones. In cells of the higher resistant unstable clone the length of AGM and their morphological structure were different in different cells within the clone. The AGMs in the Clch-resistant cells are discussed in terms of possible amplification of gene(s) responsible for the Clch resistance. In the cell population of clone selected for the resistance to 2 mkg/ml of Clch the frequency of rearranged chromosomes was shown to increase. In cells of all the analysed resistant clones the chromosome Z16 was found to lose its p-shoulder.

Simple and informative method for the elucidation of de novo synthesized forms of microsomal cytochrome P-448 induced by 3-methylcholanthrene and 2,3,7,8-tetrachlordibenzo-p-dioxine has been developed. The method is based on gel fluorography upon electrophoretic separation of microsomal proteins obtained from the liver of rats pre-treated with the inducers of monooxygenase system components and then with 14C-leucine. At least two forms of cytochrome P-448 (with molecular weight of 56000 and 53000) were shown to be de novo synthesized under the influence of 3-methylcholanthrene and 2,3,7,8-tetrachlodbibenzo-p-dioxine.

Xenobiotic metabolism in the fish liver has been investigated with a view of developing test-system for biomonitoring based on multienzyme membrane-bound complexes. Extraction methods of xenobiotics from harmful pollutants and some biological tissue have been described using various sorbents and solvents. The own and literary data on the study of mutagenic effect of this contaminants and carcinogens in the Ames test-system in the presence of postmitochondrial fraction S9 from fish liver with 3-methylcholanthrene induced by microsomal oxidation system have been demonstrated.

Single oral administration of sovol (mixture of polychlorinated diphenyls) caused a significant induction of the liver monooxygenase system (MOS) in rats. The inducing effect persisted for 5 months. Liver MOS responses were similar in repeated and primary sovol administrations. Differences in the morphological liver changes have been detected following single and repeated administrations of sovol.

Different aspects of the interaction of polypeptide growth factors with their receptors are reviewed. The problem of structural and functional interactions of the normal and transforming growth factors as well as the protein products of oncogenes during transmittance of a mitogenic signal and the proliferation regulation of normal and tumour cells is discussed.

A transfer function derepressed mutant of the F-like plasmid pAP18-1 (Tc, ColV) was induced with the help of N-methyl-N'-nitro-N-nitrozoguanidine. The mutant plasmid pAP18-1drd belongs to the FVII incompatibility group of the F-like plasmids. The plasmid pAP18-1drd is characterized by the loss of the capacity for inhibiting the tra-genes functions of the Flac plasmid and is sensitive to the Tra-function inhibitors of the reference plasmids of the FinV and FinW groups.

Mouse L-cell lines (B-82, tk-) were obtained using the stepwise selection method, their aminopterin (AP) resistance being 10(3)-5 X 10(4) times higher than that of parental cells. This resistance increase results from dihydrofolate reductase (DHFR) gene amplification which was determined from the 15-120-fold rise of the enzyme activity and with the cytogenetical techniques. The development and loss of AP resistance have been studied and karyological analysis of the lines obtained carried out. Two types of karyological changes were found in stable DM and HSR cells which correspond to extrachromosomal and intrachromosomal forms of the amplified material organization. Localization of the DHFR gene in HSR was proved using the in situ hybridization technique. Extrachromosomal localization of the amplified genes in DM providing unstable AP resistance is dominant at the early stages of the development of resistance and for a long time. It was demonstrated that DM and HSR can exist in one cell during the prolonged period. DHFR gene copy number in such cells is regulated by a change in the DM number, whereas the HSR size and localization are highly stable. HSR covers 1.7-1.9% of the genome length and 38-40% of the marker chromosome length. The genes localized in HSR provide stable AP resistance. Evidence on some intermediate, relative stabilization of the resistance has been obtained. This stabilization is mediated by temporary integration of DHFR copies into other chromosomal sites, in addition to HSR.

The activity of cytochrome P-450 dependent monooxygenase system from rat liver microsomes after induction by phenobarbital and 3-methylcholantrene in early neonatal period (3-16 days after birth) was studied. It was found that the total amount of cytochrome P-450 increases after injection of these inducers in neonatal rats of all age groups. In parallel, in the case of 3-methylcholantrene induction the benz(a)pyrene hydroxylase and 7-ethoxyresorufin deethylase activities increase; phenobarbital induction causes a rise in the benzphetamine-N-demethylase and benz(a)pyrene hydroxylase activities. Immunochemical analysis involving the use of antibodies specifically directed against cytochrome P-450 of adult rats revealed that the level of cytochrome P-450 in the case of 3-methylcholantrene induction increases from 5 to 50%, whereas that of cytochrome P-450 upon phenobarbital induction increases from 5 to 40% in liver microsomes of 3- and 16-day-old rats. The mode of inhibition of various substrates metabolism by antibodies in neonatal rat microsomes suggests that the 3-methylcholantrene-induced cytochrome P-448, like in adult rats, participates in the hydroxylation of benz(a)pyrene and O-deethylation of 7-etoxyresorufin. The participation of phenobarbital-induced cytochrome P-450 in the metabolism of benzphetamine and aldrin in neonatal rats is much lower than in the adult ones. The metabolism of benz(a)pyrene in phenobarbital-induced neonatal rat microsomes in all age groups is not inhibited by antibodies. The age-dependent differences in inhibition of metabolism and the increase in the benz(a)pyrene hydroxylase activity in phenobarbital-induced rats suggest that the spectrum of inducible forms of cytochrome P-450 in neonatal rats differ from that in adult animals.

Introduction of the plasmid containing the methotrexate-resistant (Mtx-r) bacterial gene of dihydrofolate reductase (DHFR) under the control of the early promoter of SV 40 into the donor bone cells of the mouse with subsequent transplantation of the cells into lethally irradiated mice results in the increase in the life span of mice under conditions of methotrexate selection. It is due to the stable transformation of the bone marrow colony-forming cells with the plasmic DNA and the synthesis of the bacterial Mtx-r DHFR in the spleen and bone marrow of the recipient mouse.

Influence of oestron, tetracycline, reopyrine and phenobarbital on acetylation of sulphadimidine was studied in white female rats. Administration of the above-mentioned drugs caused an increase in the rate of acetylation, which reached the maximal values within the 2-5 days after the last day of administration.

Activity of enzymes participating iH metabolism of xenobiotics was studied after their induction by means of phenobarbital in rats of Wistar strain within first weeks of life. After administration of phenobarbital into the neonatal rats content of cytochrome P-450 and activity of NADPH-cytochrome c reductase were increased in liver microsomes. The rates of N-demethylation of benzphetamine and benz(alpha)pyrene hydroxylation were also increased after administration of the inducing agent. Immunochemical studies with antibodies towards some forms of cytochrome P-450 showed that enzymatic forms of cytochrome P-450 PB were induced; this enzymatic form is predominant in adult animals treated with phenobarbital. When the metabolism of benzphetamine and benz(alpha)pyrene was inhibited by antibodies, several forms of cytochrome P-450, involved in these metabolic reactions were found in neonatal rats, whereas in the adult animals only one form of the enzyme exhibited activity towards these substrates.

After a single administration of polychlorinated diphenyls (sovol) at a dose of 50 mg/kg content of hemoproteins was increased simultaneously with an increase in the rate of N- and O-demethylation in rat liver microsomes. Repeated administrations of a synthetic antioxidant 2,6-ditret-butyl-4-methylphenol (ionol) at a dose of 500 mg/kg stimulated also the liver tissue monooxygenase system; in this case, an increase in content of cytochromes P-450 and b5 was accompanied by a distinct acceleration in oxidation of the first and second types of substrates in microsomes. A combined effect of sovol and ionol maintained the rate of microsomal enzymes induction, which exceeded markedly the values caused by individual effects of the compounds.

Administration of galactose into young rats within an early postnatal period led to alteration in activity of some enzymes involved in utilization of galactose (galactose-1-phosphaturidyl transferase, galactose-6-phosphate dehydrogenase etc) for a long period of the animals life. This stable alteration in activity of adaptive enzymes was characterized as the enzymatic imprinting. After administration of galactose into neonatal animals synthesis of RNA, matrix activity of chromatin, activities of DNA-dependent RNA polymerase and RNA-dependent DNA polymerase were shown to increase in liver tissue of these animals. These alterations are considered as a possible basis for the stable alterations in the genes expression. The elevated activities of DNA-dependent RNA-polymerase and reverse transcriptase were maintained within a long period of the animals life.