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Biomedical subjects

R Horton

Publications and source records attributed to R Horton.

At least 343 records · Page 19Linked to original sources
PubMed1975

A simple radioimmunoassay for unconjugated estriol in pregnancy plasma.

A simple and specific radioimmunoassay (RIA) for the measurement of plasma or serum unconjugated estriol (E3) in pregnancy is described for general laboratory use. Two different antibodies utilized had low cross-reaction to estrone (E1) and estradiol-17 beta (E2). With either of these antibody reagents, a method was designed that requires only an extraction step using a specific solvent mixture of ethyl acetate and n-hexane (3:2, v/v), one-hour incubation with working antibody, and separation of bound from free E3 by ammonium sulfate. Standard curves useful in the range of 0 to 2,000 pg. were obtained. This assay, requiring only 0.05 ml. of plasma, can be completed within 4 hours. The sensitivity of this RIA was 10 pg. The intra- and interassay coefficients of variation (CV) were 5.0 and 9.4 per cent, respectively. When E3 determinations by this method are compared with RIA values by a more complicated technique using Celite column chromatography, the results are not significantly different. There was a good correlation between our RIA and a standard urine E3 determination (n = 137, r = 0.82, p less than 0.001). Using our simplified method, the mean plasma E3 during pregnancy were 1.0 +/- 0.6 ng. per milliliter at 10 weeks, 2.3 +/- 0.6 ng. per milliliter at 20 weeks, 6.5 +/- 1.4 ng. per milliliter at 30 weeks, and 16.5 +/- 5.1 ng. per milliliter at term. Since the serum RIA reflects changes in free E3 which has a shorter half-life than conjugated E3, this rapid and simple method is attractive as an approach to monitor fetal-placental function.

Estriol↗
PubMed1975

Studies of renin and aldosterone in cirrhotic patients with ascites.

Plasma renin activity and aldosterone metabolism were investigated in patients with cirrhosis and refractory ascites. All patients initially showed marked elevations of plasma and renin activity and plasma aldosterone. Although metabolic clearance of aldosterone was reduced, increased secretion rate was the major factor leading to elevated plasma levels. The elevated plasma renin activity and plasma aldosterone were only minimally affected by posture, dietary sodium restriction, and diuretic administration, suggesting a near-maximal degree of secondary aldosteronism. In most patients plasma renin activity and plasma aldosterone returned to normal when spontaneous natriuresis appeared. However, in 2 patients during spontaneous diuresis and in all 3 given aminoglutethimide, sodium excretion was poorly correlated with plasma renin activity and plasma aldosterone, suggesting that other tubular and/or vascular factors are important in the intense sodium reabsorption found with cirrhosis and ascites.

Aldosterone↗
PubMed1975

Parallel radioimmunoassay for plasma cortisol and 11-deoxycortisol.

We describe a direct, rapid, and specific procedure for the parallel radioimmunoassay for cortisol and 11-deoxycortisol in plasma. The plasma sample is used directly, after heat inactivation of the natural cortisol-binding protein. The radioimmunoassay utilizes antibodies generated in rabbits by steroids congugated at their 3-oxo position to thyroglobulin. Ammonium sulfate is used to separate bound and free steroids. Our cortisol antibody and an 11-deoxycortisol antibody obtained elsewhere cross reacted negligibly with each other or with other steroids that might be present in plasma. Radioimmunoassays were therefore developed for both steroids in only 1.25 mul of plasma. The intra- and inter-assay coefficients of variation for both steroids were less than 10%, with a sensitivyt of 4 mug/liter. Steroid values obtained by a competitive protein binding method were consistently higher than those of the present method, suggesting that the former is measuring total corticosteroids. This simple approach requires only 4 h for the specific measurement of both cortisol and 11-deoxycortisol in 20 samples of plasma.

17-Hydroxycorticosteroids↗
PubMed1974

3Alpha-androstanediol kinetics in man.

Kinetics of 5alpha-androstane-3alpha, 17beta-diol (3alpha-diol) were studied in man. Clearance rates were determined by both the constant infusion and single injection techniques. Production rates were calculated as the product of clearance rate data and plasma values in the a.m. obtained by a radioimmunoassay specific for 3alpha-diol. Mean metabolic clearance rates were 1,776+/-492 (SD) liters/day in males and 1,297+/-219 (SD) liters/day in females. Metabolic clearance rates by single injection were similar. Calculated production rates are 208+/-26 (SD) mug/day in males and 35+/-11 mug/day in females, which are significantly different. Hepatic extraction of 3alpha-diol determined by hepatic vein catheterization during constant infusion was 76% which was greater than expected from information on in vitro binding in plasma. The kinetic data is of interest since 3alpha-diol has a calculated inner pool (V(1)) volume of 12-14 liters, similar to 17beta-hydroxyandrost-4-en-3-one (testosterone) and 5alpha-androstan-17beta-ol-3-one (dihydrotestosterone), but the calculated outer pool (V(2)) of 33.5 liters is very large as are the metabolic rate and transfer constant. In contrast to testosterone and dihydrotestosterone, 3alpha-diol, although bound to sex hormone binding globulin, has a high metabolic clearance of which a large fraction represents extrahepatic (splanchnic) metabolism. A production rate of 3alpha-diol similar to dihydrotestosterone together with rather unique kinetic characteristics encourages further investigation of the biological role of this potent androgen.

Abdomen↗