Search PubMed⌕ Search

Biomedical subjects

A F Clark

Publications and source records attributed to A F Clark.

At least 109 records · Page 6Linked to original sources
PubMed1980

Characterization of separated prostatic and phosphatase forms in normal and castrated rats.

We have investigated the effects of castration and androgen replacement on the kinetic characteristics of rat prostatic acid phosphatases (AP). Chromatography on DEAE-cellulose DE-23 and on Sephacryl S-200 allowed the separation of lysosomal (S-1) and secretory (S-3) forms of AP. In addition, these techniques revealed a third enzymic form (S-2), which eluted in the void volume of the Sephacryl S-200 column and which occurred in significant amounts only 15 days after castration. The S-2 form was extremely resistant (Ki 1500 microM) to L-tartrate inhibition in the 15-day post-castration rat which is in contrast to the behaviour of S-2 (Ki 145 microM) in control animals. The appearance of this unidentified AP form can explain the dramatic drop in the per cent inhibition of total rat AP observed between 7 and 15 days post-castration.

Acid Phosphatase↗
PubMed1980

Plasma C19-delta 5-steroid levels during normal human pregnancy.

Plasma levels of dehydroepiandrosterone sulfate, dehydroepiandrosterone and delta 5-androstenediol were measured in several women throughout pregnancy. The levels of both dehydroepiandrosterone and its sulfate decreased while those of delta 5-androstenediol did not. The levels of binding of the latter steroid to plasma proteins increased.

Adult↗
PubMed1979

An objective look at acid phosphatase determinations: a comparison of biochemical and immunological methods.

Measurements of serum and bone marrow acid phosphatase were made by 3 enzymatic methods, alpha-naphthyl phosphate, beta-glycerol phosphate, and thymolphthalein monophosphate, and ocmpared to a double antibody radioimmunoassay. Serum and bone marrow acid phosphatase levels were studied in 46 controls with histologically proven benign prostatic hyperplasia and in 135 patients with various stages of prostatic carcinoma. In the control group the upper limit for bone marrow acid phosphatase was found to be significantly higher than the corresponding serum limit with respect to the enzymatic assays studied. The radioimmunoassay was the only method suitable for the analysis of the prostatic acid phosphatase content of bone marrow. A larger number of elevations were noted in patients with extracapsular and metastatic disease when prostatic acid phosphatase measurement was carried out by radioimmunoassay as compared to enzymatic methods. However, only 8% of the patients with intracapsular disease had elevations of prostatic acid phosphatase as measured by radioimmunoassay. Additional standardisation of immunological methods and clinical trials is required before comparison can be made of results from various centres using immunological methods for the measurement of prostatic acid phosphatase and a true assessment made of the usefulness of this procedure.

Acid Phosphatase↗
PubMed1979

Multiple molecular forms of arylsulfatase A in different forms of metachromatic leukodystrophy (MLD).

Arylsulfatase A (ARA) can be separated into six to eight individual enzymatic bands of activity by isoelectric focusing on cellulose acetate membranes. The residual ARA activity in juvenile metachromatic leukodystrophy (MLD) has a single band of activity with apI of 5.5, whereas the residual ARA in the late infantile form of MLD has three bands of activity with pI range of from 5.4 to 5.8. The technique of isoelectric focusing on cellulose acetate membranes demonstrates enzymatic differences which can be correlated with the clinical form of the disease.

Cerebroside-Sulfatase↗
PubMed1978

Multiple molecular forms of certain lysosomal enzymes separated by isoelectric focusing on cellulose acetate membranes.

Analytical isoelectric focusing on cellulose acetate membranes offers greater resolution of the enzyme pattern than does standard electrophoresis and offers numerous advantages over other support media in isoelectric focusing. A series of lysosomal enzymes, deficiencies of which cause lethal storage diseases in infants and children, can be shown to exist as multiple molecular forms by analytical isoelectrical focusing on cellulose acetate membranes. This analytical technique should be a valuable tool in the investigation of enzyme polymorphism and genetically determined enzyme deficiency diseases.

Acetates↗
PubMed1978

The effect of Mycoplasma contamination on the in vitro assay of pyruvate dehydrogenase activity in cultured fibroblasts.

Cultured fibroblasts contaminated with mycoplasma were shown to have increased in levels of apparent pyruvate dehydrogenase and pyruvate dehydrogenase complex enzyme activity. The apparent pyruvate dehydrogenase specific activity was about 1000-fold greater in cultured Mycoplasma pneumoniae than in cultured fibroblasts. Several acid hydrolytic enzyme activities were also shown to be present in M. pneumoniae though a lower apparent specific activity than in cultured fibroblasts.

Cell Line↗
PubMed1978

Kinetics of testosterone metabolism in normal postmenopausal women and women with breast cancer.

The constant infusion and single injection techniques were utilized to study the kinetics of 3H-testosterone (T) metabolism in posmenopausal women with and without breast cancer. The metabolic clearance rates (mean +/- SEM) for normal postmenopausal women were 578 +/- 82 and 644 +/- 128 1/24 has obtained by the constant infusion and single injection techniques, respectively. The corresponding results for the women with breast cancer (patients) are 644 +/- 25 and 617 +/- 106 1/24 h. The single injection technique yielded values for rate constants (units) and volumes of distribution (1); K1 = 37.5 +/- 1.6 for the normals and 34.5 +/- 1.9 for the patients, K = 76.6 +/- 5.1 for the normals and 71.1 +/- 1.6 for the patients, V1 = 7.9 +/- 2.2 for the normals and 8.7 +/- 1.4 for the patients and V2 = 7.0 +/- 1.5 for the normals and 6.4 +/- 1.2 for the patients. The constant infusion technique yielded values for the conversion ratios for the transformation of T to several products; 4-androstene-3,17-dione/T of 0.02 +/- 0.003 for normals and 0.03 +/- 0.002 for patients, 5alpha-dihydrotestosterone/T of 0.02 +/- 0.002 for normals and 0.03 +/- 0.002 for patients, estrone/T of 0.04 +/- 0.01 for normals and 0.04 +/- 0.01 for patients, estradiol-17beta/T of 0.02 +/- 0.005 for normals and 0.03 +/- 0.005 for patients and estrone sulfate/T of 0.16 +/- 0.02 for normals and 0.24 +/- 0.06 for patients. The T plasma concentrations and production rates were similar for the two groups of subjects. Hence there were no significant differences between the normals and the patients for all the kinetic parameters. It was determined that all the estradiol being produced in postmenopausal women could be coming from circulating T.

Aged↗
PubMed1978

Dehydroepiandrosterone: kinetics of metabolism in normal men and women.

The single injection and constant infusion techniques were utilized to study the kinetics of dehydroepiandrosterone (DHEA) metabolism and its peripheral conversion to several other C19-steroids including C19-steroid sulfates. The MCRs (mean +/- SEM) for normal men and normal women were 1866 +/- 144 and 1901 +/- 87 liters/24 h, respectively. The single injection technique yielded values for rate constants (units) and volumes of distribution (1) as follows: K1, 42.6 +/- 7.7 for men and 37.1 +/- 5.0 for women; K2, 64.3 +/- 11.2 for men and 55.5 +/- 5.0 for women; K2, 64.3 +/- 11.2 for men and 55.5 +/- 5.0 for women; V1, 38.5 +/- 6.0 for men and 33.7 +/- 2.5 for women; V2, 30.4 +/- 7.3 for men and 27.5 +/- 9.9 for women. The constant infusion technique yielded values for the conversion ratios for the transformation of DHEA to several products: delta 5-androstene-3 beta, 17 beta-diol to DHEA of 0.10 +/- 0.01 for men and 0.16 +/- 0.03 for women, delta 4-androstenedione to DHEA of 0.04 +/- 0.01 for men and 0.07 +/- 0.02 for women, DHEA sulfate (DHEAS) to DHEA of 6.36 +/- 0.81 for men and 10.09 +/- 0.87 for women, delta 5-androstene-3 beta, 17 beta-diol sulfate to DHEA of 0.42 +/- 0.06 for men and 0.50 +/- 0.04 for women, and androsterone sulfate to DHEA of 1.11 +/- 0.13 for men and 2.06 +/- 0.18 for women. The ratios for the conversion to DHEA sulfate and androsterone sulfate were significantly higher for women than men. The plasma concentrations of DHEA were 8.50 +/- 0.95 and 8.75 +/- 1.01 ng/ml for men and women, respectively. The calculated production rates for DHEA were 16.34 +/- 2.66 and 16.19 +/- 1.78 mg/24 h for men and women, respectively. There was no sex difference in the binding of DHEA to plasma proteins and this is reflected in the lack of sex difference in the MCRs. Calculations indicate that DHEA is a major precursor of circulating delta 5-diol.

Adolescent↗
PubMed1977

Effects of androgen and estradiol administration on the weight of the ventral prostate, seminal vesicles, and testes of immature rats.

This study was designed to investigate the effects of pharmacologic doses of estradiol on th biologic actions of testosterone and 5alpha-dihydrotestosterone when administered to immature (21 to 28 of age) male rats. The weights of the prostate, seminal vesicles, and testes were used as the indicators of androgen effects. Estradiol had no effects on the testosterone- or 5alpha-dihydrotestosterone-induced increases in prostate weight over the 12 days after the androgen injection. Estradiol acted synergistically with testosterone but not 5alpha-dihydrotestosterone on the increases in seminal vesicle weight. Estradiol had no effect, by itself, on the rate of testes growth. Both androgens resulted in a decreased rate of testicular growth and this was not infuenced by estradiol.

Animals↗
PubMed1976

Acid phosphatases: androgen dependent markers of rat prostate.

Our investigations on acid phosphatase (AP) were aimed at finding a biochemical assay marker for androgen actions in the rat prostrate. We quantitatively examined the effects of l-tartrate or formaldehyde on AP activity in tissue filtrates from nine adult male rat tissues, plasma and hemolysed red blood cells (HRBC). There was significant inhibition of AP activity in all instances with the exception of HRBC with tartrate. The prostate inhibition results were not different from those for seminal vesicles and adrenals but were different from the other tissues studied. Ten days following castration the inhibition by tartrate was less in all tissues studied except plasma and HRBC; the formaldehyde inhibition percentages were not altered.

Acid Phosphatase↗
PubMed1976

Delta5-androstenediol: kinetics of metabolism and binding to plasma proteins in normal men and women.

Using the constant fusion and single injection technique the metabolic clearance rates (mean +/- SEM) for delta5-androstene-3beta, 17beta-diol (delta5-idol) were measured for 19 normal men (1311 +/- 67 1/24 h) and 10 normal women (858 +/- 63 1/24 h). The constant infusion technique yielded values for the conversation ratios for the transformation of delta5-diol to several products: dehydroepiandrosterone (DHEA)/delta5-diol of 0.06+/-0.01 for men and 0.05 +/- 0.01 for women, of delta5-diol sulfate/delta5-diol of 0.45 +/- 0.04 for men and 0.52 +/- 0.03 for women and of DHEA sulfate/delta5-diol of 5.53 +/- 0.26 for men and 5.02 +/- 0.42 for women. The single injection technique yielded rate constants (units) and volumes of distribution (liters) for delta5-diol; Ki = 34.3 +/- 4.3 for men and 35.0 +/- 3.9 for women, K2 = 63.7 +/- 4.1 for men and 75.1 +/- 4.2 for women, V1 = 23.1 +/- 3.2 for men and 11.9 +/- 2.3 for women, V2 = 14.8 +/- 3.7 for men and 9.2 +/- 3.2 for women. The mean delta5-diol plasma concentration was 1.08 +/- 0.10 ng/ml for 12 men and 1.17 +/- 0.16 ng/ml for 9 women. (he calculated blood production rates for delta5-diol were 1357 +/- 117 mug/24 h for 12 men and 969 +/- 131 mug/24 h for 9 women. The per cent binding (equilibrium dialysis) was higher for women (94.9 +/- 0.3) than for men (93.0 +/- 0.2). Paper electrophoresis showed that significant fractions of 3H-delta5-diol migrated with both the beta-globulin and albumin fractions. Estrogen administration to two normal men increased the per cent binding of delta5-diol to plasma proteins and decreased the metabolic clearance rate towards the values found for normal women.

Adult↗
PubMed1975

Increase in dissociation rate constants of cardiotonic steroid-brain (Na+ + K+)-ATPase complexes by reduction of the unsaturated lactone.

Several cardiotonic steroids have been modified by reduction of the unsaturated lactone and their interactions with the sodium- and potassium-activated ATPase ((Na+ + K+)-ATPase) have been investigated. Reduction of the unsaturated lactone results in a decrease in binding affinity due primarily to an increase in the dissociation rate constant concomitant with a decrease in the activation free energy of dissociation. This decrease in activation free energy is about 2 to 4 kcal, which is approximately equal to the energy of one hydrogen bond. It is suggested that the increase in dissociation rate due to reduction of the unsaturated lactone may make possible the use of these compounds as affinity ligands for purification of the (Na+ + K+)-ATPase or an ouabain-binding fragment.

Adenosine Triphosphatases↗
PubMed1975

Absence of pyruvate decarboxylase activity in man: a cause of congenital lactic acidosis.

A complete deficiency in the pyruvate dehydrogenase system activity contributed to the death of a 6-month-old infant with congenital lactic acidosis. The enzymatic block could be isolated to the first component, pyruvate decarboxylase (E1) of the pyruvate dehydrogenase complex. This enzymatic deficiency allowed a demonstration of an "intercomplex" exchange of the components of the mammalian pyruvate dehydrogenase system and indicated that the first component is normally present in an apparent excess.

Acidosis↗