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Biomedical subjects

R Todd

Publications and source records attributed to R Todd.

At least 73 records · Page 4Linked to original sources
PubMed1987

Immunohistochemical localization of aromatase cytochrome P-450 and estradiol dehydrogenase in the syncytiotrophoblast of the human placenta.

Immunohistochemistry employing immunoglobulin G fractions raised against aromatase cytochrome P-450 and antiserum against 17 beta-estradiol dehydrogenase was used to localize these two steroid-converting enzymes in the human placenta. Immunostaining for both enzymes was found exclusively in the syncytiotrophoblast, while the underlying cytotrophoblast and the villus core did not stain. Ultrastructural examination of aromatase cytochrome P-450- and 17 beta-estradiol dehydrogenase-labeled sections disclosed immunoreactive product in the membranes of the endoplasmic reticulum; the nucleus, mitochondria, Golgi apparatus, and secretory granules were free of staining. These findings suggest that the syncytiotrophoblast is actively involved in the synthesis and metabolism of estrogens and in their role in placental endocrine function.

17-Hydroxysteroid Dehydrogenases↗
PubMed1985

Effects of adrenocorticotropic hormone, human chorionic gonadotropin, and insulin on steroid production by human adrenocortical carcinoma cells in culture.

Adrenocortical carcinoma tissue removed from a mildly hirsute 16-year-old girl was cultured in order to assess steroidogenesis and responsiveness of the cells to adrenocorticotropic hormone (ACTH), human chorionic gonadotropin (HCG), and insulin. The cells in culture produced large amounts of androstenedione and testosterone; however, production of cortisol, which was initially high, decreased with time. No aldosterone, estrone, or estradiol was produced in vitro. Both monolayer cells maintained for 6 weeks and organ culture explants maintained for over 3 days responded to ACTH (10(-7) M) with increased production of androgens (testosterone, androstenedione, dehydroepiandrosterone) but decreased production of cortisol as measured by radioimmunoassay of steroids in the culture media. Concomitant with decreased cortisol production was the enhanced formation of 11-deoxycortisol in cells exposed to ACTH, suggesting impaired 11 beta-hydroxylation. Tissue exposed to HCG (10(-7) M) in organ culture showed an increase in androgen production over control levels, but no significant effect of HCG on glucocorticoid production was found. Tumor cells differed in their androgen response to ACTH and HCG, with enhanced adrenal androgens in the presence of ACTH and more gonadal-type androgens after exposure to HCG. Insulin exposure had no effect on production of either androgen or glucocorticoid by tumor tissue in organ culture. Thus, this adrenocortical carcinoma showed marked androgen production in culture which was enhanced in different ways by ACTH and HCG. 11 beta-Hydroxylation was impaired with time in culture. No specific effect of insulin on steroidogenesis was noted.

Adolescent↗
PubMed1984

Plasma histamine and hemodynamic responses following administration of nalbuphine and morphine.

A comparative study of plasma histamine levels following administration or morphine and nalbuphine in pentobarbital anesthetized dogs was performed. Two concentrations, 3 mg/kg and 0.3 mg/kg of these drugs were investigated. High dose morphine caused an immediate marked increase in plasma histamine from 5.0 +/- 0.4 to 340 +/- 72 ng/ml. Simultaneous with this increase in plasma histamine was a marked decrease in mean arterial blood pressure within the first minute. In contrast significant alterations in plasma histamine levels were not observed with high or low doses of nalbuphine. A low dose of morphine (0.3 mg/kg) did not increase plasma histamine levels. Heart rate was not changed by any drug treatment. The use of compound 48/80 a specific mast cell degranulating agent allowed for the identification of a specific pool of mast cells capable of responding to morphine. In vitro exposure of purified dog leukocytes to high doses of morphine did not result in histamine release. These results indicate that nalbuphine does not increase plasma histamine, while morphine does, and that the source of the increase in plasma histamine is from tissue mast cells.

Anesthesia↗
PubMed1980

Apparent immunologic nonidentity of human placental and endometrial 17beta-estradiol dehydrogenase.

Immunohistochemical techniques were used to search for the presence of 17beta-estradiol dehydrogenase activity in human endometrial and placental tissues, with the use of antibodies raised against highly purified human placental 17beta-estradiol dehydrogenase. Sensitivity and specificity of the antibodies were documented by radioimmunoassay and immunodiffusion on cellulose acetate. Although staining was consistently demonstrated in the syncytiotrophoblast layer of term placentas, in both cytoplasm and nuclei, no immunohistochemical reaction was observed in endometrial samples. These results support the contention that placental 17beta-estradiol dehydrogenase is immunologically dissimilar from the endometrial enzyme.

17-Hydroxysteroid Dehydrogenases↗
PubMed1979

Gonadotropin profiles in fed and fasted obese women.

Five obese women were studied before and at the end of a prolonged fast to determine the effect on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) and on the response to luteinizing hormone--releasing factor (LRF). Although baseline serum LH values declined from a mean value of 9.1 to 6.5 m.I.U. per milliliter measured at the end of the fast, these changes in mean serum level were not statistically significant. However, the integrated LH secretion did decline when measured at the end of the fasts (p less than 0.05). FSH secretion did not change. LRF-stimulated LH and FSH values showed augmented stimulation at the end of the fast. Pulsatile gonadotropin secretion patterns remained normal. Prolonged fasting appears to alter the baseline LH secretion and the pituitary response to exogenous LRF.

Adult↗
PubMed1979

Gonadotropin, estradiol, and testosterone profiles in homosexual men.

The authors evaluated the gonadotropin-testosterone-estradiol profiles of four homosexual men and four heterosexual men by a multiple-sampling technique. Although there was extensive overlap between the two groups, the homosexual subjects had higher estradiol levels than the heterosexuals (70.3 +/- 19.8 versus 56.8 +/- 10.7 pg/ml) and lower FSH values (5.1 +/- 1.0 versus 13.2 +/- 3.4 mIU/ml). Testosterone and luteinizing hormone levels were comparable in the two groups. These observations suggest that there may be subtle differences in gonadotropin and estradiol secretion in homosexual subjects that can be detected only by repeated sampling.

Adult↗
PubMed1977

Microtechnique for most-probable-number analysis.

A microtechnique based on the most-probable-number (MPN) method has been developed for the enumeration of the ammonium-oxidizing population in soil samples. An MPN table for a research design ([8 by 12] i.e., 12 dilutions, 8 replicates per dilution) is presented. A correlation of 0.68 was found between MPNs determined by the microtechnique and the standard tube technique. Higher MPNs were obtained with the microtechnique with increased accuracy in endpoint determinations being a possible cause. Considerable savings of time, space, equipment, and reagents are observed using this method. The microtechnique described may be adapted to other microbial populations using various types of media and endpoint determinations.

Journal Article↗