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Biomedical subjects

E D Bransome

Publications and source records attributed to E D Bransome.

At least 37 records · Page 2Linked to original sources
PubMed1979

Effect of pH on the binding of theophylline to serum proteins.

The binding of theophylline to serum protein within the pH range of 7.0 to 7.8 was determined by equilibrium dialysis using serum from 8 healthy adult volunteers. The percentage of theophylline bound was independent of the total concentration of the drug, but was directly related to pH. Because changes in the free fraction of theophylline may alter the therapeutic response, toxic effects, and pharmacokinetics, any future studies of the pharmacology of theophylline should include assessment of the acid-base status of the patients and measurements of free as well as total theophylline concentrations.

Adult↗
PubMed1977

Measurement of antidiabetic sulfonylureas in serum by gas chromatography with electron-capture detection.

A method is described for measurement of chlorpropamide, tolbutamide, and the tolbutamide metabolites hydroxymethyltolbutamide and carbotytolbutamide in blood. It consists of formation of the thermally stable methyl-trifluoroacetyl derivatives of chlorpropamide and tolbutamide, and the methyl-heptafluorobutyryl derivatives of hydroxymethyltolbutamide and carboxytolbutamide, which are then analyzed by electron-capture gas chromatography. Measurements of blood levels of the compounds with this method have been verified by quantitation of the same samples using gas chromatography-mass spectrometry in the mass fragmentography mode. Blood level values and beta-phase half-time disappearance rates of chlorpropamide, tolbutamide, hydroxymethyltolbutamide, and carboxytolbutamide were measured in normal volunteers following an oral dose of chlorpropamide or tolbutamide. Blood levels of the four compounds were also determined in a few diabetics receiving continuous daily treatment.

Chemical Phenomena↗
PubMed1976

Human placental 3beta-hydroxysteroid dehydrogenase: delta5-isomerase. Demonstration of an intermediate in the conversion of 3beta-hydroxypregn-5-en-20-one to pregn-4-ene-3,20-dione.

3beta-Hydroxypregn-5-en-20-one (pregnenolone) and NAD+ were incubated with a solubilized preparation of the coupled enzyme 3beta-hydroxysteroid:NAD(P) oxidoreductase-3-ketosteroid delta4,delta5-isomerase (3beta-hydroxysteroid dehydrogenase: delta5-isomerase) from the mitochondrial fraction of human placenta. Unconverted pregnenolone, pregn-4-ene-3,20-dione (rogesterone), and a small but detectable amount of pregn-5-ene-3,20-dione were isolated from the medium by Sephadex LH-20 chromomatography. The identification of pregn-5-ene-3,20-dione, confirmed by mass fragmentography, has provided the first direct evidence for the formation of the hypothetical delta5,3-ketone intermediate in the conversion of pregnenolone to progesterone. When tritium-labeled pregnenolone and [4-14C]pregnenolone were incubated simultaneously the 3H:14C ratio in isolated pregn-5-ene-3,20-dione was 4.6 times greater than in isolated progesterone and pregnenolone, indicating a kinetic isotope effect in the enzymatic isomerization of tritium-labeled pregn-5-ene-3,20-dione. Exposure of the enzyme to two steroids which inhibit the overall enzyme reaction, 2alpha-cyano-17beta-hydroxy-4,4,17alpha-trimethylandrost-5-en-3-one (cyanoketone) and 3-hydroxyestra-1,3,5(10),6,8-pentaen-17-one (equilenin), increased the relative yield of labeled pregn-5-ene-3,20-dione as well as the recovery of radioactivity remaining as unconverted pregnenolone, suggesting that both the dehydrogenase and isomerase activities were inhibited. Exposure of the enzyme to equilenin increased the ratio of isolated pregn-5-ene-3,20-dione radioactivity to progesterone radioactivity as progesterone synthesis was inhibited. Equilenin also diminished the tritium isotope effect on the isomerase reaction. Both findings suggest that it is possible to inhibit the isomerase to a greater extent than the dehydrogenase. In order to measure the rate of progesterone produced by the coupled enzymes, we have modified a radiochemical method which involves precipitation of pregnenolone by digitonin. Digitonin precipitation proved to be effective in separating unconverted pregnenolone from the steroid products of both enzyme reactions, progesterone and pregn-5-ene-3,20-dione. Neither the steroidal inhibitors nor the kinetic isotope effect altered the accuracy of the method for routine measurement of the overall rate of conversion of delta5,3beta-hydroxysteroid to delta4,3-ketosteroid.

Female↗
PubMed1976

Primary culture and maintenance of steroid-secreting human placenatal monolayers.

A simple method is described for primary culture and for maintenance of hormone-producing cells from normal human placenta. A consistent yield of cells was obtained and an average survival of 3 to 4 months in culture using 1 mm3 explants from the most vascular area of the placentas. These explants were placed in a variety of culture media in 30 ml flasks and incubated at 37 degrees C in an atmosphere of 5% CO2 and 95% air. The best yields in terms of cell growth were observed with Eagle's MEM (minimum essential medium) with supplements of horse serum and fetal calf serum or human cord serum. (Ham's F-10 with supplement of horse serum and fetal calf serum supports growth for the longest period and media containing human cord serum had the best yield of steroids.

Cell Survival↗