During the course of evolution, species have increased in complexity, and their nervous systems have evolved correspondingly with an increase in the diversity of their capabilities to respond. Part of that diversity has resulted from an increase in cell types and numbers and their interconnections. In addition, much of it comes from the panoply of neurotransmitters available, of which the neuropeptides represent a major portion. The application of the techniques of molecular biology to the nervous system has led to an appreciation of some of the genetic means by which such diversity can be generated. The cloning and sequencing of peptide precursor genes has shown the existence of gene families, genes with duplications of internal sequences, and genes evolutionarily related to one another, suggesting that one response to the increasing complexity of the organism has been a genetic diversification of the precursor population for peptides. As the precursor genes evolved and thereby provided increasing numbers of peptides, the receptor genes may have evolved simultaneously to provide diversification in the responses to these peptides (for example, the opioid peptide precursors) (Comb et al 1983). The precursor sequences obtained have led not only to the predictions of new peptides but also to the discovery of alternative methods of generating diversity from a single gene. At one extreme, the gene is translated into a polyprotein containing several peptides, which are produced in and released from the same cell. At the other extreme, the nuclear transcript of the gene is differentially spliced such that one peptide is expressed in one tissue and another in a different tissue (Calcitonin-CGRP), or one peptide may be expressed with or without a second peptide in different cells (substance P-substance K). The net result is either one neuron producing a multiplicity of responses to several co-released peptides derived from a polyprotein (POMC or PE) or a tissue- or cell-specificity in terms of which peptide is produced and released. Numerous applications have been made utilizing the cDNA probes generated from the cloning of neuropeptide precursors. Hybridization analyses, including in vitro transcription run-off, have demonstrated that the transcription of neuropeptide genes is regulated by transsynaptic activation of transmitter receptors located in the neuronal membrane, or by hormones, or by as yet unveiled mechanisms. Hybridization techniques have allowed assessment of the dynamic state of neuropeptides functioning as neuromodulators.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

DNA amplification is a pervasive phenomenon in continuous cell lines and in tumours. It can occur in many different parts of the genome with high frequency, and a very large amount of DNA, probably including many genes, is often involved in a single amplification event. In tumours, it is likely that a common mechanism underlies the amplification of genes which confer drug resistance and genes which give a growth advantage to the tumour. DNA amplification may be caused by defects in the regulation of DNA replication, and similar defects may lead to other chromosomal abnormalities such as translocations, inversions and heteroploidy. Two recent observations should facilitate identification and study of the underlying defects: agents or treatments which damage DNA can increase the rate of amplification, and mutant cell lines can be selected which amplify their DNA at a greatly increased frequency.

The studies described in this report suggest a rather complex, albeit incomplete, sequence of molecular events that we believe form part of the cascade of reactions through which a series of hormones, via cAMP, regulates the expression of specific gene products. The majority of our own studies relate to cAMP-mediated induction of LDH. Some, if not all, of the molecular steps discussed in this paper may ultimately be recognized as part of a universal mechanism by which cAMP controls gene expression in higher eukaryotes. The idea of a functional role for cAMP-dependent protein kinase subunits in cAMP-mediated gene control has already had experimental support, but our identification of the regulatory subunit RII as a topoisomerase now more firmly points to a complex function for the kinase in regulating gene function at the DNA level. We look forward to the elucidation of the function of those nuclear proteins that serve as substrate for the catalytic subunit of cAMP-dependent protein kinase. Further studies related to the molecular interaction of RII with chromosomal DNA should be a fruitful area for future research.

This report summarizes our studies, in context with the results of other laboratories, of the molecular mechanisms of glucocorticoid hormone action. The receptors for these steroids are comprised of single polypeptide chains of about 90,000 molecular weight. Binding of agonist steroids to the receptor induces a conformational change to an active receptor form that is followed by a second change in the glucocorticoid-receptor complex, termed activation, that alters the charge of the complex and results in its binding to specific sites on the DNA termed glucocorticoid regulatory elements (GREs). The GRE on the human metallothionein-IIA gene is located in the 5'-flanking DNA. It can function independently of the gene's promoter, and when ligated upstream from the herpes simplex virus (HSV) thymidine kinase (TK) gene promoter, can activate it. The binding of the glucocorticoid-receptor complex to the GRE probably alters chromatin structure over a limited span to facilitate RNA polymerase action. The regulation by glucocorticoids of growth hormone gene expression is more complex. The steroid appears to elicit both transcriptional and posttranscriptional influences that are also affected by thyroid hormone. Also the glucocorticoid influences appear to be exerted in part through DNA structures located downstream from the transcriptional initiation site. A GRE has been defined in intron A of the hGH gene through gene transfer and DNA binding experiments. Finally, gene transfer experiments suggest that pituitary-specific factors influence the ability of glucocorticoids to affect GH gene expression.

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.

No one in tumor biology can now be unaware of the overlap between growth factors and oncogenes. Many if not all oncogenes are now perceived as functional components of a mitogenic cascade which is normally controlled by growth factors. Some oncogenes function at the onset of this cascade by directing the synthesis of an automitogenic growth factor. Others function in the interior of the cascade by directing synthesis of a growth factor receptor or a structurally altered receptor derivative. Still other oncogenes appear to be mutated or rearranged homologues of genes the expression of which is normally induced by growth factors. Those of us working with platelet-derived growth factor (PDGF) take particular satisfaction in this new conceptual framework. It is within the molecular biology of PDGF that the overlap between growth factors and oncogenes is illustrated to its fullest and most tangible extent. An oncogene termed c-sis directs synthesis of a functional PDGF subunit. The PDGF receptor protein is in all probability encoded by a member of the src family of oncogenes. Formation of the PDGF:receptor complex stimulates expression of the c-myc and c-fos protooncogenes. My associates and I have devoted the past 10 years to the molecular biology of PDGF. Our studies on the control of the 3T3 cell cycle by PDGF contributed a pair of new jargon terms to the oncology literature--"competence" and "progression." We also had some input into the bottom end of the "oncogene hierarchy" displayed in Chart 1. The effort that we invested paid a pleasant dividend for me when, in the spring of 1984, the American Association for Cancer Research honored me with the Rhoads Memorial Award. What follows is an overview of the PDGF literature which is more anecdotal than comprehensive. My object is to show how the PDGF field moved from the level of whole animal biology, through biochemistry, down to molecular genetics in just 10 years time.

Human T-lymphotropic virus type III is susceptible to attack at various sites during its replicative cycle. Inhibitors of reverse transcriptase activity, including suramin, antimoniotungstate (HPA-23), and trisodium phosphonoformate, have shown in-vitro activity against the virus in early clinical trials. Other significant antiviral agents are recombinant interferon alpha-A, ribavirin, and ansamycin. Double-blind, placebo-controlled clinical trials of interferon alpha, which inhibits viral replication at easily achievable serum levels, are underway. The development of optimal therapeutic regimens will require carefully controlled, multicenter collaborative trials with standardized criteria for evaluating responses. Prolonged treatment with combinations of antiviral and immunomodulating agents may be necessary for control of HTLV-III replication and for effective treatment of the acquired immunodeficiency syndrome.

Corticosteroids appear capable of exerting an impressive array of effects on the metabolism of neural tissues. The diversity of these effects is perhaps not surprising given the wide variety of biochemically and morphologically distinguishable cell types present in the combined central and peripheral nervous systems. In conclusion, it seems useful to summarize the state of knowledge in some of the most critical research areas discussed in this review and to predict what major advances are probably forthcoming in the next few years.