Biomedical subjects

R M Fleming

Publications and source records attributed to R M Fleming.

At least 37 records · Page 2Linked to original sources

PubMed1984

Extraction of ceftazidime in bone.

The extraction of ceftazidime has been measured in bone by means of the outflow dilution technique following injection into the perfused nutrient artery of the canine tibia. The instantaneous extraction was found to be 0.71 +/- 0.18 and the net extraction was 0.55 +/- 0.25 (mean +/- S.D. n = 5). The extraction of this antibiotic is relatively high and this experiment demonstrates the fact that antibiotics leave capillaries in bone and pass into the fluid spaces where they can act on pathogenic organisms.

Animals↗

PubMed1984

Cannabinoid inhibition of adenylate cyclase. Pharmacology of the response in neuroblastoma cell membranes.

Adenylate cyclase in plasma membranes was inhibited by micromolar concentrations of delta 8-tetrahydrocannabinol and delta 9-tetrahydrocannabinol and by levonantradol and desacetyllevonantradol. This inhibition was noncompetitive for stimulation of the enzyme at the prostanoid receptor by prostaglandin E1 or prostacyclin, or at the peptide receptor by secretin or vasoactive intestinal peptide. Forskolin-activated adenylate cyclase was also inhibited by cannabimimetic agents. Inhibition by cannabinoid compounds was neither synergistic nor additive with muscarinic or alpha-adrenergic agents when each was present at maximally inhibitory concentrations. Cannabinoid inhibition was not blocked by atropine, yohimbine, or naloxone, suggesting that muscarinic, alpha 2-adrenergic and certain opiate receptors may not be required for the response. The inhibition of adenylate cyclase was specific for psychoactive cannabinoids, since cannabinol and cannabidiol produced minimal or no response. Inhibition was also stereoselective, since dextronantradol did not produce the response. A biphasic log dose-response curve was observed for each of the cannabinoid drugs, such that reversal of the inhibition occurred at 3-10 microM. Possible mechanisms for the effects of cannabinoid drugs on adenylate cyclase activity are discussed.

Adenylyl Cyclase Inhibitors↗

PubMed1982

Differences in characteristics preferred by college students for academic advisors, vocational counselors, and psychotherapists: a preliminary report.

144 college students rated an academic advisor, a vocational counselor, or a psychotherapist on 10 characteristics and subsequently rated each of the three types of counseling situations on how "personal" they perceived each to be. Sex of experimenter and sex of subject were varied systematically. Female subjects when tested by a male experiment preferred a psychotherapist be more religious than an academic advisor or vocational counselor. Subjects viewed psychotherapy as a more personal situation than academic advising or vocational counseling.

Adult↗

PubMed1975

A new, highly sensitive and specific assay for chymotrypsin.

1. A simple, highly sensitive, specific fluorometric method for the determination of chymotrypsin is described. 2. The new substrate utilized in this assay, N-glutaryl-glycyl-glycyl-l-phenylalanine beta-naphthylamide (GGPNA), is readily soluble in water, stable and highly specific for chymotrypsin. It is not degraded by a large excess of carboxypeptidase B, elastase, thrombin or plasmin and is virtually resistant to trypsin. 3. GGPNA is extremely sensitive to the action of chymotrypsin and permits detection of enzyme concentrations as low as 1 ng/ml. Linearity between enzyme concentration and fluorescence produced is maintained up to at least 3000 ng/ml. 4. alpha2-Macroglobulin-bound chymotrypsin hydrolyzes GGPNA at a rate about 2/3 of that exhibited by the free enzyme. 5. Bile pigments in amounts normally found in duodenal juice or traces of blood do not interfere with the assay. 6. GG PNA which releases beta-naphthylamine upon hydrolysis is suitable also for colorimetric and histological determination of chymotrypsin.

Bilirubin↗

PubMed1975

Effect of alpha2 macroglobulin on some kinetic parameters of trypsin.

1. Complex formation of trypsin with alpha2 macroglobulin results in marked changes of the Michaelis-Menten constant, pH optimum and sensitivity to ionic strength in a system using N-carbobenzoxy-glycylglycyl-L-arginine-2-naphthylamide as substrate. 2. In contrasts to the inhibition (50%) observed when alpha2 macroglobulin-bound trypsin is assayed under conditions optimal for the free enzyme, there is minimal reduction of activity when determinations are performed at a substrate concentration and pH optimal for the bound enzyme. 3. The changes in substrate concentration and ionic environment required for maximum activity of alpha2 macroglobulin-bound trypsin are similar to those observed with enzymes embedded in polyelectrolyte matrices and may reflect alterations in the microenvironment of the enzyme resulting from conformational changes of the macromolecule during interaction with trypsin. 4. Enzymatic activity of trypsin towards casein is greatly reduced by alpha2 macroglobulin, even under assay conditions optimal for the bound enzyme, confirming previous findings that access to the active center for high-molecular weight substrates is sterically hindered by alpha2 macroglobulin.

Arginine↗

PubMed1974