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Biomedical subjects

L Milewich

Publications and source records attributed to L Milewich.

At least 91 records · Page 5Linked to original sources
PubMed1978

Aromatase activity in the developing rabbit brain.

The formation of 17beta-[3H]estradiol from [1,2,6,7-3H]testosterone was assessed in placenta and central nervous system tissues from rabbit embryos that varied in age from 13-28 days of gestation. In the fetal brain, significant rates of aromatase activity were limited exclusively to the forebrain, and the highest rates of activity (approximately 0.5 pmol/h/mg protein) were found in the diencephalon both male and female embryos between days 19 and 25 of gestation. These rates of aromatase activity are second only to the fetal ovary when expressed per mg protein; moreover, forebrain is the only tissue in the male embryo capable of synthesizing significant amounts of estrogens in vitro. When projected to the whole organ, the capacity of the diencephalon for aromatization exceeds the capacity of the fetal ovary approximately 9-fold. Placental aromatase activity was high (2.1 pmol/h/mg protein) on day 13 but fell to a level approximately 20-fold lower by day 19 of gestation. These findings indicate the potential importance of the forebrain as a source of estrogens during embryogenesis.

Androstenedione↗
PubMed1978

Regulation by plasma lipoproteins of progesterone biosynthesis and 3-hydroxy-3-methyl glutaryl coenzyme a reductase activity in cultured human choriocarcinoma cells.

The regulation of both the activity of 3-hydroxy-3-methyl glutaryl coenzyme A (HMG CoA) reductase [mevalonate-NADP+ oxidoreductase (CoA-acylating) EC 1.1.1.34] and the secretion of progesterone by human plasma lipoproteins has been investigated in human choriocarcinoma cells in culture. HMG CoA reductase activity was computed from the rate of formation of [14C]mevalonolactone from [14C]HMG CoA. The activity of HMG CoA reductase was expressed as nanomoles of mevalonolactone formed/min . mg solubilized cell protein. An inverse relationship was found between the presence of lipoprotein in the culture medium and the activity of HMG CoA reductase in these cells. In cells maintained in the presence of lipoprotein-enriched culture medium containing 840 micrograms cholesterol/ml, the average activity of HMG CoA reductase was 0.25 nmol/min . mg protein. After removal of lipoprotein, the activity of HMG CoA reductase increased to 1.3 nmol/min . mg protein. The average activity of HMG CoA reductase in cells maintained in lipoprotein-deficient culture medium was 1.5 nmol/min . mg protein but fell to 0.3 nmol/min . mg protein after addition of lipoprotein to the medium. When cells were maintained in the presence of lipoprotein, the rates of section of progesterone and pregnenolone into the culture medium were 2-8 times greater than the rates of secretion of these steroids by cells maintained in the absence of lipoprotein. On the basis of these results, it is concluded that lipoproteins control the rate of cholesterol biosynthesis in cultured choriocarcinoma cells by regulating the activity of HMG CoA reductase, and control the rate of synthesis of progesterone by providing the precursor, cholesterol. We suggest that progesterone synthesis by the trophoblast of the human placenta may also be regulated by the uptake of lipoprotein from maternal blood.

Cells, Cultured↗
PubMed1978

Initiation of human parturition. IX. Progesterone metabolism by placentas of early and late human gestation.

In in vitro studies it was found that, in the presence of added NADPH, the human placenta metabolizes progesterone to 20alpha-hydroxy-4-pregnen-3-one at increasing rates as pregnancy advances. A fivefold increase in 20alpha-hydroxysteroid oxidoreductase activity is observed in term placentas compared with the enzymic activity of placentas of 12 to 20 weeks' gestation (368 +/- 53 pmoles/mg protein/hr vs 71 +/- 8 pmoles/mg protein/hr). The 5alpha-reductase and 3beta-hydroxysteroid oxidoreductase activities were similar in placentas obtained from early and late human pregnancies.

20-Hydroxysteroid Dehydrogenases↗
PubMed1977

Estrogen formation by the ovary of the rabbit embryo.

The conversion of [1,2,6,7-3H]- testosterone to radioactive estradiol was assessed in tissue slices of 18 different tissues from rabbit embryos that varied in age from 16 to 29 days gestation. Significant rates of estradiol synthesis were demonstrated only in ovaries [4.2 +/- 0.7 (mean +/- SEM) pmol/h/mg) protein], placenta (0.7 +/- 0.2 pmol/h/mg protein) and brain (0.3 +/- 0.1 pmol/h/mg protein). Estradiol formation was undetectable in day 16 gonads of both sexes and in tests at all ages examined, but by day 18 it was demonstrable in ovaries and rose rapidly to reach a level of 6 pmol/h/mg protein by day 19. The time of appearance of the enzymatic capacity to convert testosterone to estradiol in the ovary is similar to the onset of the enzymatic capacity to form testosterone by the fetal testis, suggesting that the acquisition of the enzymatic activies that allow specific endocrine function by these two tissues may be regulated by the same or similar factors during embryonic development.

Androstenedione↗
PubMed1977

Initiation of human parturition. VI. Identification and quantification of progesterone metabolites produced by the components of human fetal membranes.

The fetal membranes play a central role in the initiation of human parturition, a role that may be subserved in part by quantitative changes in progesterone metabolism. In order to identify and to quantify the metabolites of progesterone produced by the components of the human fetal membranes, amnion and chorion laeve tissues and homogenates were incubated with [3H]progesterone in the presence of added NADPH. The radioactive metabolites, 20alpha-hydroxy-4-pregnen-3-one, 5alpha-pregnane-3,20-dione and 3beta-hydroxy-5alpha-pregnan-20-one, were isolated and identified by derivative formation, a combination of chromatographic techniques, and by crystallization to constant specific activity after addition of authentic standards. A simplified technique of metabolite quantification was developed that involves one thin layer chromatographic procedure and liquid scintillation assay of radioactivity. The accuracy of this method was established by comparison with data obtained using classical techniques. This study demonstrates the presence of human fetal membranes 5alpha-reductase, 20alpha-hydroxysteroid oxidoreductase, and 3beta-hydroxy-steroid oxidoreductase, and a qualitative difference between amnion and chorion laeve.

20-alpha-Dihydroprogesterone↗
PubMed1977

Progesterone and 5alpha-pregnane-3,20-dione in peripheral blood of normal young women: Daily measurements throughout the menstrual cycle.

The peripheral plasma concentrations of progesterone and 5alpha-pregnane-3,20-dione were measured daily throughout the ovarian cycle of five presumptively ovulatory women. The concentrations of progesterone and 5alpha-pregnane-3,20-dione during the follicular phase were 0.11 +/- 0.02 ng/ml (mean +/- SE) and 0.16 +/- 0.01 ng/ml, respectively. In four of these women the concentrations of both progesterone and 5alpha-pregnane-3,20-dione began to rise immediately after the luteinizing hormone (LH) peak and reached maximal concentrations five to eight days later (progesterone: 8.6 to 19.9 ng/ml; 5alpha-pregnane-3,20-dione: 1.4 to 2.8 ng/ml). The luteal phases in these women, measured from the day of the LH peak to the onset of the next menses, varied from 13 to 18 days. In the other woman with a late LH surge (day 27 of the cycle) the peak concentrations of progesterone and 5alpha-pregnane-3,20-dione were reached four days after the LH peak (8.9 ng/ml and 0.8 ng/ml, respectively). The luteal phase in this woman was 11 days. From the results of this study, it appears that the concentrations of 5alpha-pregnane-3,20-dione in peripheral blood during the luteal phase are proportional to the availability of progesterone as substrate for the 5alpha-reductase enzyme system.

Female↗
PubMed1977

Radioiodinated derivatives for steroid radioimmunoassay. Application to the radioimmunoassay of cortisol.

Gamma-emitting steroid tracers for use in the radioimmunoassay of steroids have a number of advantages over the more common tritiated tracers. The steroid derivatives aldosterone3-(p-hydroxybenzoyl) hydrazone, aldosterone-3-(p-hydroxyphenylpropionyl)hydrazone, deoxycorticosterone-3-(p-hydroxyphenylpropionyl)hydrazone, and cortisol-3-(p-hydroxyphenylpropionyl)hydrazone were synthesized by a one-step procedure and iodinated ([125I]). To illustrate the usefulness of these derivatives, we describe the details of a cortisol radioimmunoassay. The use of the radioiodinated tracer appeared to increase the specificity of the antigen-antibody reaction when compared with [3H]cortisol. The methodology involved in the preparation of the steroid derivatives described above can be extended to other 3-oxo-4-ene-containing steroids, with the advantages of economy, simplicity, and versatility.

Aldosterone↗
PubMed1976

Aromatization of androstenedione by cultured human fibroblasts.

The conversion of (1, 2, 6, 7-3H)androstenedione to (3H)estrone was measured in fibroblast monolayers grown from biopsies of genital and nongenital skins obtained from 15 control subjects, 9 males with developmental defects of the urogenital tract, and 8 patients with hereditary male pseudohermaphroditism. Under the standardized conditions utilized in this study, the rate of estrone formation in the fibroblasts from normal controls varied from less than 0.2 to 5.5 pmol/100 mg protein/h, and these rates were enhanced by incubation of intact monolayers with choleragen, theophylline, or dexamethasone. Rates of estrone formation were higher in some foreskin strains grown from subjects with developmental defects of the urogenital tract and in strains from scrotum and foreskin of patients with familial incomplete male pseudohermaphroditism, types 1 and 2 than in normal strains or strains from patients with testicular feminization. The meaning of these apparent high rates of estrone formation is unclear.

Adolescent↗
PubMed1976

Mineralocorticoid activity of 16beta-hydroxydehydroepiandrosterone and related steroids.

16beta-Hydroxydehydroepiandrosterone (16beta-OH-DHEA) and related C19-steroids have recently been reported to be etiologic in low-renin essential hypertension. The mineralocorticoid potency of 16beta-OH-DHEA and several C19-steroids (16-oxo-A-diol, 16-oxo-testosterone, 16beta-OH-epiandrosterone, 5-androstene-3beta, 16beta,17beta-triol, 19beta-OH-testosterone, 18-OH-DHEA, and 16alpha-OH-DHEA) were investigated in two different rat bioassay systems under a variety of experimental conditions. In all but one instance, only negligible mineralocorticoid activity was observed, usually less than 0.1 per cent that of aldosterone. Since 16beta-OH-DHEA has negligible mineralocorticoid activity in the rat bioassay and the toad bladder assay (as reported by others), does not cause hypertension when injected chronically into the rat, and does not displace aldosterone from its renal receptors, it appears unlikely to be etiologic in low-renin essential hypertension. On the other hand, when 16-oxo-testosterone was injected intraperitoneally instead of subcutaneously, it demonstrated a slight increase in mineralocorticoid activity (from less than 0.1 per cent to 0.2 per cent) which equaled that of 18-hydroxydeoxycorticosterone (18-OH-DOC) injected subcutaneously. Thus, the possibility remains that 16-oxo-testosterone or a closely related metabolite may have sufficient mineralocorticoid activity to be involved in certain forms of hypertension in man.

Animals↗
PubMed1976

Initiation of human parturition. V. Progesterone binding substance in fetal membranes.

This study was undertaken as part of an investigation of the potential role of progesterone metabolism within fetal membranes in the initiation of human labor. The results of this study provide evidence that a progesterone binding substance is present in amnion and chorion laeve during the last few days of pregnancy. This substance binds progesterone, cortisol, and 5alpha-dihydroprogesterone but does not bind 20alpha-hydroxy-4-pregnen-3-one, R 5020, or dexamethasone. We conclude that this is a previously undescribed progesterone binding substance and propose a possible mechanism by which this substance may be involved in the initiation of human parturition.

17-alpha-Hydroxypregnenolone↗
PubMed1975

Aromatization of androstenedione by isolated human hairs.

The formation of (3-H) estrone has been demonstrated in human anagen scalp hair roots incubated with (1, 2, 6, 7-3H) androstenedione, and approximate rates of formation of 0.2 pmol of estrone/mg DNA/h were observed. Thus, hair is a potential site for the extraglandular formation of estrogen in man.

Adult↗
PubMed1975

Isolation and characterization of 5alpha-pregnane-3,20-dione and progesterone in pepipheral blood of pregnant women. measurement throughout pregnancy.

5alpha-Pregnane-3,20-dione and progesterone were isolated from a pregnancy plasma pool and were identified by using a combination of chromatographic techniques and mass spectrometry. Antibodies to progesterone were obtained in rabbits by immunization with progesterone-1alpha-carboxyethyl-thioether-thyroglobulin. The raised antibodies were of high affinity and one of them cross-reacted (137%) with 5alpha-pregnane-3,20-dione. This property was used to develop radioimmunoassays for measuring circulating levels of both progesterone and 5alpha-pregnane-3,20-dione in pregnancy plasma. The levels of both progesterone and 5alpha-pregnane-3,20-dione increase throughout pregnancy, but a highly significant increase is observed only after the 32nd week of gestation.

Animals↗