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Biomedical subjects

A D'Mello

Publications and source records attributed to A D'Mello.

14 recordsLinked to original sources
PubMed1988

Evaluation of mono- and dibenzoyl esters of dopamine as potential pro-drugs for dopamine in the central nervous system.

In this study, two ester pro-drugs of dopamine (DA) were synthesized and evaluated. These derivatives were the monobenzoyl (MBDA) and dibenzoyl (DBDA) esters of DA. MBDA was 300-fold and DBDA was 20,000-fold more lipophilic than DA itself. The half-lives of hydrolysis for MBDA and DBDA at physiologic pH and temperature were 15 and 420 min respectively. These compounds were radiolabelled and their uptake into brain measured. 14C-DBDA penetrated the brain rapidly; 0.28% of the dose injected was taken up per gram of brain tissue at 5 min. However DBDA did not produce measurable increases in DA levels in the brain. 14C-MBDA was found not to penetrate the brain. However, when MBDA was administered intracerebroventricularly (i.c.v.) to rats, it caused DOPAC levels to increase significantly both in the striatum and in the rest of the brain. The increase in the amount of DOPAC measured in the striatum was 3 to 10-fold greater than that seen in the rest of the brain. In rats that were pretreated with the MAO inhibitor, pargyline, MBDA given i.c.v. caused increases in DA levels in both the striatum and in the rest of the brain. The increased DA levels in striatum were considerably greater than those seen in the rest of the brain. From these results, it is inferred that MBDA is being hydrolyzed in vivo in the brain to form DA which is then taken up into dopaminergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The action of sodium deoxycholate on Escherichia coli.

Sodium deoxycholate is used in a number of bacteriological media for the isolation and classification of gram-negative bacteria from food and the environment. Initial experiments to study the effect of deoxycholate on the growth parameters of Escherichia coli showed an increase in the lag time constant and generation time and a decrease in the growth rate constant and total cell yield of this microorganism. Cell fractionation studies indicated that sodium deoxycholate at levels used in bacteriological media interferes with the incorporation of [U-14C]glucose into the cold-trichloroacetic acid-soluble, ethanol-soluble, and trypsin-soluble cellular fractions of E. coli. Finally, sodium deoxycholate interfered with the flagellation and motility of Proteus mirabilis and E. coli. It would appear then that further improvement of the deoxycholate medium may be in order.

Culture Media↗
PubMed1982

Effects of chronic administration of bronchodilators on microshock in sensitized guinea-pigs.

In conscious guinea-pigs isoprenaline, adrenaline and salbutamol protected the animals against egg albumin and histamine microshock in a dose-dependent manner. Chronic aerosol pretreatment three times daily with adrenaline or isoprenaline, but not with salbutamol, enhanced the acute dose protection against egg albumin microshock, but there was no enhancement when the bronchodilators were given six times daily. Aminophylline when administered three times daily enhanced the protective effect of an acute dose of adrenaline. With histamine microshock, desensitization occurred to adrenaline, when given three and six times daily, and to isoprenaline, when given six times daily, but not to salbutamol. Cross-desensitization could be induced to adrenaline by isoprenaline but not by salbutamol. The data indicate that, depending on the experimental conditions, enhancement of or desensitization to the effects of bronchodilators could be shown in conscious guinea-pigs.

Aerosols↗
PubMed1979

Responses of isolated human internal anal sphincter to drugs and electrical field stimulation.

The effects of drugs and electrical field stimulation on muscle strips from the human internal anal sphincter have been examined to provide information about the receptors and nerves that might be involved in the relaxation of the muscle in vivo. Acetylcholine and bethanechol usually relaxed muscle strips; this effect was abolished by hyoscine and antagonized to a varying degree by tetrodotoxin. Hexamethonium in concentrations sufficient to block relaxations to 1,1-dimethyl-4-phenylpiperazinium iodide or nicotine had no effect on relaxations due to acetylcholine, thereby indicating that acetylcholine was acting on muscarinic receptors. The nerves stimulated by acetylcholine released an unknown transmitter. Both 1,1-dimethyl-4-phenylpiperazinium iodide and nicotine relaxed muscle strips, possibly by releasing an adrenergic neurotransmitter which, because the responses to nicotinic receptor-stimulation were blocked by propranolol, stimulated beta-adrenergic inhibitory receptors. Sphincter muscle was also relaxed by electrical field stimulation of intrinsic nerves; this response was blocked by tetrodotoxin but unaffected by hexamethonium, hyposcine, or propranolol. The nerves responding to electrical field stimulation were therefore post-ganglionic, noncholinergic, and nonadrenergic. Compounds discounted as possible neurotransmitters of the noncholinergic, nonadrenergic inhibitory nerves were prostaglandin E2 and F2 alpha, histamine, 5-hydroxytryptamine, and dopamine. Some evidence allows vasoactive intestinal peptide and adenosine triphosphate to be considered as possible neurotransmitters; this could not be confirmed because selective antagonists are not yet available.

Adenosine Triphosphate↗
PubMed1971

Destruction of chlorpromazine during absorption in the rat in vivo and in vitro.

1. Concentrations of total radioactivity in plasma of rats given intravenous and oral (35)S-chlorpromazine, were similar. Concentrations of unchanged drug, however, were lower after oral doses.2. Chlorpromazine circulated in solution through isolated loops of rat intestine was rapidly absorbed by the tissue. Measurements of glucose transport and histological examination indicated that the tissue was intact. In these in vitro experiments some of the chlorpromazine was converted to products, which together with unchanged drug, were partly retained in the intestinal wall and partly transferred to the serosal side of the tissue. Observations at three concentrations supported the hypothesis that transfer of unchanged drug occurred by passive diffusion.3. Conversion of chlorpromazine to metabolites in the intestine in vivo, would account for the differences in concentrations of chlorpromazine and total radio-activity in plasma after oral doses.

Administration, Oral↗