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Biomedical subjects

K J Ryan

Publications and source records attributed to K J Ryan.

At least 163 records · Page 9Linked to original sources
PubMed1977

Aromatase activity of isolated and recombined hamster granulosa cells and theca.

The major synthesis of estrogen by the follicle is postulated to require both theca and granulosa cells. Theca in this scheme provide androgens to the major aromatizing site in the follicle, and the granulosa cell. One aspect of this theory was tested here. We investigated the comparative ability of isolated granulosa and theca, alone and in recombination to aromatize androgen in vitro. We found that the granulosa aromatize [14C]substrate more efficiently than do theca, and compare with the recombined system in their ability to aromatize [14C]androgen. The data therefore substantiates one aspect of the theory regarding the nature of the synergism, i.e., that the granulosa cells, at least in vitro, are the major site of aromatization of the preovulatory follicle.

Androstenedione↗
PubMed1977

Antitumor septacidin analogues.

In the first approach by total synthesis to the structure of the antitumor antibiotic septacidin, analogues have been obtained which show similar inhibition of RNA-DNA synthesis in cultured leukemia L1210 cells and similar activity against transplanted leukemia P388 in mice. In these analogues, the natural aminoheptose moiety is replaced by 4-amino-4-deoxy-and 4-amino-4,6-dideoxy-L-glucose, to retain the natural configuration of the pyranose ring. Also retained is the lipophilic fatty acid-amino acid side chain attached to the 4-amino group and glycosylation at the 6-NH2 of adenine. If the fatty acid chain was shortened from C16 to C6, if the fatty chain was shifted to the glycine unit, or if the glycine unit was omitted, activity was completely lost. However, activity was retained if the C16 chain was shortened only to C12 or if the glycine unit was extended to beta-alanine. Both active and inactive analogues were nonbinding to DNA and nonmutagenic to Salmonella strains. The synthetic approach was to start with a suitably protected sugar (L-fucose and L-galactose), construct the adenine moiety at C-1 introduce a 4-amino group, and finally attach the preformed side chain.

Animals↗
PubMed1977

Evidence for interaction between granulosa cells and theca in early progesterone synthesis.

The temporal characteristics of steroidogenesis in vitro by hamster preovulatory follicles, were compared to granulosa cells and theca incubated separately. Gonadotropin-stimulated intact follicles or recombined granulosa cells and theca synthesized increased amounts of progesterone by 30-120 minutes of incubation. The granulosa cells and theca, when incubated separately, did not begin to accumulate progesterone until 4 to 6 hours. The relatively rapid rise in follicular progesterone synthesis after in vitro gonadotropin stimulation follows the same time course as the rapid rise in vivo of hamster and rat preovulatory progesterone after the gonadotropin surge. The sharp differences in the temporal characteristics of progesterone synthesis between follicles and separated follicular cell types suggest an interaction between granulosa cells and theca in at least one phase of progesterone synthesis.

Animals↗
PubMed1977

Evaluation of a simple device for bacteriological sampling of respirator-generated aerosols.

The Aerotest sampler (Olympic Medical Corp., Seattle, Wash.) is designed to detect bacterial contamination of respirator-generated aerosols in a simple one-step process. The sampler was evaluated by controlled contamination of Bennett AP-5, PR-2, and MA-1 respirators with Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter. Bacteria present as viable 1.4 to 3.5-mum particles in each of 77 aerosols were quantitated by using the Andersen viable-particle sampler, and the results were compared with those of colonies obtained from 10-s or 15-cycle Aerotest samples. All aerosols containing counts greater than expected in hospital air were detected by the Aerotest method. Thirteen of 14 aerosols containing less than 20 bacteria/0.028 m3 showed fewer than 5 colonies, whereas all aerosols containing greater than 1,000 bacteria/0.028 m3 showed at least 40 colonies. Aerosols with intermediate counts fell in between. Under the conditions described here, the Aerotest sampler was able to discriminate between the low levels of bacteria commonly found in hospital air and the bacterial contamination associated with nosocomial pneumonia. The Aerotest sampler provides a practical method for surveillance sampling of respirator nebulizers.

Acinetobacter↗
PubMed1977

The aromatization of androgens by primary monolayer cultures of fetal rat hypothalamus.

Aromatization of [3H]androstenedione and [3H]19-hydroxyandrostenedione to [3H]estrone has been demonstrated to occur in one to two week old primary monolayer cultures of fetal rat hypothalamus. Three times more estrone is produced from 19-hydroxyandrostenedione than from androstenedione in four day incubations. Cultures treated with cytosine arabinoside have 50% less cellular protein and produce three times more estrone from either substrate than untreated cultures. Time course experiments using cultures treated with cytosine arabinoside indicate that aromatization of 19-hydroxyandrostenedione is linear for three days and can be quantitatively measured within the first two to eight hours of incubation.

Androstenedione↗
PubMed1977

Identification of aromatase in the reptilian brain.

The present study tests the hypothesis that brain aromatase is an "ancient" property of nervous tissue and may be identified in homologues of the limbic system in a non-mammalian vertebrate, the turtle Chrysemys picta. Tissue homogenates (180 mg wet weight/2 ml) were incubated with [7 alpha-3H]androstenedione and cofactors for 60 min at 37 C. Estrone (E1) was isolated and characterized by thin layer chromatography, methylation and recrystallization to constant specific activity. No estradiol-17 beta was detected. Aromatase was found only in the forebrain but was diffusely distributed throughout this major brain division. No other neural or non-neural tissues, including mid- and hindbrain structures, testis, and ovary, synthesized detectable quantities of E1 in our system. The strio-amygdaloid complex of both sexes synthesized more E1 per unit weight than the preoptic-hypothalamic area (POA-HTH) or other forebrain structures. It is possible that the conversion of androgen to estrogen has biological significance in this species since the reaction occurred throughout the physiological temperature range experienced during activity in nature and sex differences in brain aromatase activity during the breeding season were apparent. These experiments in Chrysemys demonstrate that the synthesis of estrogen from androgen by the brain is not limited to mammals, but also occurs at a more primitive level of phylogenetic development. Restriction of aromatase to forebrain structures of the turtle is consistent with the neuroanatomic distribution of enzyme activity in the limbic system of mammals. Estrogen yield from adult turtle brain incubates (3.2-22.6 pmol/g) is more like that reported for fetal (2.7-33 pmol/g) than for adult (0.1-1.9 pmol/g) mammals. We suggest that the in situ synthesis of estrogen by the central nervous system has its orgins early in vertebrate evolution and may be a primitive characteristic of brain-steroid interactions that regulate physiological and behavioral sex in vertebrates.

Amygdala↗
PubMed1977

Presence of corticotropin in human placenta: demonstration of in vitro synthesis.

Immunoassayable (I) and bioassayable (B) ACTH activity is present in extracts of extensively washed human placental tissue and dispersed viable trophoblasts (Tr). Similar concentrations (I) (1.7-2.7 ng/g) are present in term placentas from elective cesarian section or vaginal delivery and from plancentas obtained by prostaglandin-induced abortion at 12, 15 and 18 weeks of gestation. Oral dexamethasone (8-12 mg) administered over an 8-48 h period prior to delivery does not significantly alter placental ACTH content. B-ACTH concentrations are 31-40% of I-ACTH. Sephadex G-50 filtration of term placental homogenates demonstrates two I-ACTH peaks, one eluting in the void volume and the other eluting in the region of synthetic hACTH1-39. When Tr are incubated in tissue culture medium, ACTH content of cells and of medium is significantly greater than pre-incubation levels.

Adrenocorticotropic Hormone↗
PubMed1977

Danazol inhibits steroidogenesis in the rat testis in vitro.

The effects of danazol on steroidogenesis in vitro in the rat testis were examined by studying: 1) androgen synthesis in rat Leydig cells cultured with danazol, 2) danazol binding to rat testis microsomal cytochrome P-450, and 3) enzyme kinetics of danazol inhibition of the microsomal enzymes of testicular steroidogenesis. Concentrations of danazol as low as 1 micrometer suppressed LH-stimulated testosterone and androstenedione production in cultured Leydig cells. The addition of danazol to a preparation of testicular microsomes elicited a type I cytochrome P-450 binding spectrum, with an apparent spectral dissociation constant (Ks) of 4.8 micrometer. Danazol inhibited progesterone and 17alpha-hydroxy-progesterone binding to microsomal P-450 with apparent spectral inhibition constants of 2.4 micrometer and 2.8 micrometer, respectively. Danazol competitively inhibited 3beta-hydroxy-delta5-steroid dehydrogenase-isomerase (apparent enzymatic inhibition constant, KI = 5.8 micrometer), 17alpha-hydroxylase (KI = 2.4 micrometer), 17,20 lyase (KI = 1.9 micrometer), and 17beta-hydroxysteroid dehydrogenase (KI = 4.4 micrometer). These findings indicate that low concentrations of danazol directly inhibit steroidogenesis in the rat testis in vitro.

Androgens↗
PubMed1977

Danazol inhibits steroidogenesis.

Danazol was found to inhibit multiple enzymes of steroidogenesis directly in the pregnant mare serum (PMS)-treated hamster ovary and the rat testis and adrenal in vitro. In the PMS-treated hamster ovary, danazol inhibited 17alpha-hydroxylase, 17,20-lyase, and 3beta-hydroxysteroid dehydrogenase. In the rat testis, danazol inhibited 17alpha-hydroxylase, 17,20-lyase, 3beta-hydroxysteroid dehydrogenase, and 17beta-hydroxysteroid dehydrogenase. In the rat adrenal, danazol inhibited 3beta-hydroxysteroid dehydrogenase, 21-hydroxylase, and 11beta-hydroxylase. Two hours after a subcutaneous injection of 5 mg/kg of danazol to adult male rats, serum luteinizing hormone levels were significantly increased and serum testosterone levels were significantly suppressed. These findings suggest that in the rodent one of danazol's major pharmacologic effects is the direct inhibition of steroidogenesis.

Adrenal Glands↗
PubMed1977

Vaginal absorption of estrone and 17beta-estradiol.

In order to study estrogen absorption from the vagina, 0.5 mg of unconjugated estrone (E1) or 17beta-estradiol (E2) was administered vaginally to 10 postmenopausal patients. A 29-fold increase in plasma E2 and a 4-fold increase in plasma E1 concentrations were observed 1 hour following the vaginal deposition of 0.5 mg of E2. Maximal decreases of 25% and 37% in plasma levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), respectively, were observed at 5 hours following treatment. One hour after vaginal administration of 0.5 mg of E1, a 24-fold increase in plasma E1 and a 3.7-fold increase in E2 were observed. These increases were associated with a 30% decrease in plasma FSH and LH. These data indicate that the vaginal administration of E2 or E1 may be used to achieve physiologic blood levels of these estrogens. They further suggest that vaginal estrogens not be used in patients in whom systemic estrogen therapy is contraindicated.

Aged↗
PubMed1976

Spontaneous maturation of oocytes isolated from ovaries of immature hypophysectomized rats.

Oocytes were collected from preantral follicles (200-300 mu in diameter) from 30-day-old immature rats 7 days after hypophysectomy. The ova were cultured in vitro for 17 hrs in a chemically defined medium and scored cytologically for meiotic maturation. Of 534 oocytes that were cultured 89% resumed meiosis; however, 98% of these oocytes arrested in either metaphase or anaphase I. In contrast, 82% of the oocytes isolated from preovulatory follicles (approximately 600 mu in diameter) of adult proestrus rats progressed to metaphase II. These results are discussed in terms of functional FSH and LH receptors on the granulosa cells.

Animals↗