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Biomedical subjects

A Ray

Publications and source records attributed to A Ray.

At least 253 records · Page 14Linked to original sources
PubMed1987

Adrenergic modulation of gastric stress pathology in rats: a cholinergic link.

The effects of some adrenergic drugs were evaluated on cold restraint-induced gastric ulcers in rats. The beta-adrenergic antagonist, (+/-)-propranolol (1 and 10 mg/kg), as well as the beta-agonist, isoproterenol (0.05 and 0.5 mg/kg) potentiated the gastric pathology. On the other hand, the alpha-agonist, clonidine (0.5 mg/kg) attenuated and the alpha-antagonist, yohimbine (1 mg/kg) aggravated stress ulcer development. The anticholinergic agent, atropine methylnitrate (1 mg/kg), reduced both the frequency and severity of stress ulcers and also antagonized the potentiating effects of (+/-)-propranolol, isoproterenol and yohimbine. The results suggest a cholinergic role in the adrenergic modulation of gastric stress pathology.

Animals↗
PubMed1987

Protein and 28S ribosomal RNA fractional turnover rates in the rat heart after abdominal aortic stenosis.

The rate of synthesis of myocardial proteins and ribosomal ribonucleic acid (rRNA) was measured during the development of cardiac hypertrophy in rats using a continuous intracardiac infusion of 14C-tyrosine and 3H-uridine in unanaesthetised animals. Cardiac overload was induced by abdominal aortic stenosis. Left ventricular weight and total myocardial RNA concentration were significantly increased on day 4 after aortic stenosis (+19% and +18% respectively). On day 8 left ventricular weight reached +52% whereas RNA concentration had not increased further (+13%). The fractional turnover rates were calculated using the specific activities of intracellular free tyrosine and free uracil nucleotides (precursors) and those of protein bound tyrosine and 28S rRNA bound uridine monophosphate (products) respectively. The fractional rate of synthesis of proteins and rRNA (expressed as percentage per day) increased from 24% to 45% for proteins and from 25% to 34% for rRNA and peaked by day 2. The RNA activity, expressed as gram of protein synthesised per day and per gram of total RNA, was unchanged on day 1 and reached a maximal value on day 2 (+107%). These results suggest that the pre-existing ribosomal RNA could be underutilized under control conditions and that the boosting of RNA transcription, associated with that of protein translation, is a complementary process rather than a prerequisite for the transition period leading to hypertrophy.

Animals↗
PubMed1987

Replication and packaging of choleraphage phi 149 DNA.

The intercellular replication of the circularly permuted DNA of choleraphage phi 149 involves a concatemeric DNA structure with a size equivalent to six genome lengths. The synthesis of both monomeric and concatemeric DNAs during replication of phi 149 occurred in the cytoplasm. The concatemers served as the substrate for the synthesis of mature phage DNA, which was eventually packaged by a headful mechanism starting from a unique pac site in the concatemeric DNA. Packaging of DNA into phage heads involved binding of concatemeric DNA to the cell membrane. A scheme involving sequential packaging of five headfuls proceeding in the counterclockwise direction from the pac site is proposed. After infection under high-phosphate conditions, the concatemeric DNA intermediates were not formed, although synthesis of monomeric molecules was unaffected.

Bacterial Proteins↗
PubMed1987

Quantitative structure-activity relationship study on amsacrine derivatives.

Various biological activities of amsacrine derivatives were analyzed in relation to various physico-chemical parameters. The in vitro activity parameters like DNA-binding and cell inhibition constants were found to have significant correlations but with varying physico-chemical parameters. DNA-binding constants were found to be the function of van der Waals volume and the cell inhibition constant to be the function of the hydrophobic parameter. But the in vivo antitumor activity parameters like optimal dose administered intraperitoneally in mice injected with P388 leukemia cells and the percentage increase in life span of treated animals over that of control animals were not found to be related with any property of the molecules.

Amsacrine↗
PubMed1986

An F-derived conjugative cosmid: analysis of tra polypeptides in cosmid-infected cells.

The genes involved in the conjugational transfer of F plasmid DNA are organized into three closely linked operons spanning an overall length of approximately 33 kilobase pairs of F. The entire transfer (tra) region comprising all three operons has been cloned into the cosmid vector pHC79 by in vitro recombination and packaging techniques. The transfer-proficient chimeric cosmid pRS2405 was packaged into lambda capsids, and uv-irradiated E. coli cells were infected with these DNA-filled particles. A number of polypeptides programmed by the infecting DNA were identified as tra-specified products; a traJ90 mutation on pRS2405 resulted in the significant reduction of synthesis of all detectable pRS2405-specified tra polypeptides, with the exception of TraTp.

Bacterial Proteins↗
PubMed1986

Expression of F plasmid traT: independence of traY----Z promoter and traJ control.

We have shown, using an F-derived Tra+ cosmid in conjunction with the infected-cell translational system and a time-course study, that one of the surface exclusion genes, traT, can be expressed independently of the promoter of the traY----Z operon, PYZ, and in the absence of a normal quantity of traJ gene product. Studies with deleted derivatives of the cosmid pRS2405 confirmed this independence and also indicated that expression of traD can be independent of PYZ. We propose that the expression of traT by these deleted plasmids is directed from a traJ-independent promoter, PT, located adjacent to traT.

Bacterial Proteins↗
PubMed1986

The in vivo mutagenic frequency and specificity of O6-methylguanine in phi X174 replicative form DNA.

A bacteriophage phi X174-based site-specific mutagenesis system for the study of the in vivo mutagenic frequency and specificity of carcinogen-induced modification in DNA is presented. A (-)-strand primer containing O6-methylguanine in a specific site was hybridized to a single-stranded region in gene G of phi X gapped duplex DNA. The hybrid was enzymatically converted to replicative form DNA and was used to transform Escherichia coli cells. All gene G mutants generated by the modification were rescued by genetic complementation. An amber mutation in lysis gene E of the (+) strand of the replicative form DNA prevented lytic growth of wild-type phage derived from this strand. In each mutant-containing infective center produced from the transformed cells, gene G mutant phage were present in a 3:1 ratio compared to wild type. Thus, in vivo, O6-methylguanine in replicating phi X DNA has a mutagenic frequency of 75%. When repair of O6 methylguanine occurred, it was prereplicative. The mutations were due exclusively to the misincorporation of thymine.

Bacteriophage phi X 174↗
PubMed1986

Tissue cholinesterase inhibition by propranolol and related drugs.

The effect of (+/-)-propranolol and some related drugs have been investigated on the cholinesterase (ChE) enzyme activity of heart and brain tissues of the rat. Brain homogenates hydrolysed more methacholine than benzoylcholine and the reverse was true for the heart tissue. In-vitro, (+/-)-, (+)- and (-)-propranolol, as well as its quaternary analogue, UM-272, all significantly inhibited heart and brain ChE. Timolol and sotalol, however, were less potent. In-vivo, (+/-)-propranolol (30 mumol kg-1) significantly inhibited brain ChE activity in rats when compared with saline controls. It is inferred that propranolol inhibits brain and heart ChE enzyme in a non-stereoselective manner and that this cholinomimetic action could be involved in the mediation of some of its therapeutic effects.

Animals↗
PubMed1986

Autonomic regulation involved in the ocular hypotensive action of beta-adrenergic blocking agents.

The effects of racemic propranolol and some related drugs on the intraocular pressure (IOP) were studied after topical application in rabbits. These drugs produced a significant reduction in IOP with the following order of potency: (-)-propranolol greater than timolol greater than (+/-)-propranolol greater than sotalol greater than (+)-propranolol greater than pranolium. Pretreatment of rabbit eyes with atropine significantly antagonized the ocular hypotensive action of (+/-)-propranolol, timolol and pranolium. Both (+/-)-propranolol and timolol produced a significant increase in pupil diameter in the presence of a submydriatic dose of atropine. The activities of monoamine oxidase and carbonic anhydrase were unaffected by (+/-)-propranolol, timolol and pranolium in-vitro. It is concluded from the results that both cholinergic and adrenergic mechanisms may be involved in the ocular hypotensive effects of the drugs.

Adrenergic beta-Antagonists↗
PubMed1986

Nonstereoselective aspects of propranolol pharmacodynamics.

Twenty years after its discovery, the beta-adrenergic blocking agent propranolol continues to interest pharmacologists and clinicians. Its therapeutic profile has extended to areas beyond the purview of the cardiovascular system, and its ocular and central nervous system effects have been well documented. In addition, it still remains a very good pharmacological tool to map out the adrenergic beta-receptors in the body, and stereoisomers of propranolol and other beta-blockers serve as valuable agents to distinguish between the effects related to beta-adrenoceptors and those which are not. The primary purpose of this review is to summarize the evidence indicating that beta-adrenergic blocking agents lack stereoselectivity in some of their effects, including several of considerable therapeutic importance. Because many pharmacological actions of propranolol followed a nonsteroselective pattern, the involvement of beta-adrenoceptors in them was questioned and this led to the search for alternate mechanisms to explain these effects. Studies with propranolol and some related drugs indicated the involvement of a cholinergic mechanism in their antiarrhythmic, ocular hypotensive and some central effects. Also, a presynaptic inhibitory effect at the skeletal neuromuscular junction has been suggested to explain the benefical effect of propranolol and other beta-blockers in tremor. Biochemical studies with these drugs revealed their inhibitory action on the cholinesterase enzyme in blood and other tissues like myocardium and brain. It is thus hypothesized that modulation of cholinergic neurotransmission by propranolol could explain some of its nonstereoselective actions and open new vistas in propranolol pharmacodynamics.

Animals↗
PubMed1986

Effect of molecular size on the activity of adriamycin analogues: a quantitative structure-activity relationship study.

The in vitro anti-tumor activity (inhibition of human lymphoblastic leukemia cells) of some adriamycin analogues is found to be significantly correlated with the van Waals volume (VW) of the substituents. Activity is also found to be well correlated with first-order valence molecular connectivity index (1 chi V) but no correlation is found to exist between it and the hydrophobic parameter, log P (P: octanol-water partition coefficient). On the basis of these findings, it is suggested that the activity would be affected by the steric influence and to some extent by the electronic character of the substituents. From the correlating equations, it is observed that the size of C-7 glycoside ring and that of NHR2 group at its third position would greatly affect the activity. The size of C-14-R1 however, is not found to have much effect on the activity.

Antineoplastic Agents↗