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Biomedical subjects

G Young

Publications and source records attributed to G Young.

At least 235 records · Page 13Linked to original sources
PubMed1983

Immunocytochemical identification of thyrotropin (TSH)-producing cells in pituitary glands of several species of teleosts with antiserum to human TSH beta subunit.

A rabbit antiserum raised against human thyrotropin (TSH) beta subunit (anti-human beta-TSH) was used to identify TSH cells in the pituitaries of five species of teleosts by means of the unlabeled antibody peroxidase-antiperoxidase (PAP) technique. The anti-human beta-TSH reacted only with polygonal basophils located in the rostral pars distalis (RPD) in the pituitaries of sexually immature eel (Anguilla japonica). In the pituitaries of medaka (Oryzias latipes) and white-edged rockfish (Sebastes taczanowskii), this serum reacted specifically with only one cell-type located in the antero-dorsal proximal pars distalis (PPD) and antero-ventral PPD, respectively. In the pituitaries of two species of salmonids, sexually immature rainbow trout (Salmo gairdneri) and sexually mature chum salmon (Oncorhynchus keta), the anti-human beta-TSH bound to the polygonal basophils in the ventral PPD adjacent to the RPD. Thus, the present immunocytochemical study identified polygonal basophils located in the RPD or PPD as TSH cells in five species of teleosts.

Anguilla↗
PubMed1983

Relative in vitro effectiveness of 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one and other pregnene derivatives on germinal vesicle breakdown in oocytes of ayu (Plecoglossus altivelis), amago salmon (Oncorhynchus rhodurus), rainbow trout (Salmo gairdneri), and goldfish (Carassius auratus).

The relative effectiveness of several pregnene derivatives, which had previously been identified in the ovaries of ayu (Plecoglossus altivelis), on germinal vesicle breakdown (GVBD) was investigated in vitro using folliculated oocytes of four species of teleosts, ayu, amago salmon (Oncorhynchus rhodurus), rainbow trout (Salmo gairdneri), and goldfish (Carassius auratus). Although some species differences existed in the relative effectiveness of each steroid on GVBD, 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17 alpha, 20 beta-diOHprog) was consistently the most potent inducer of final oocyte maturation. Both progesterone and 17 alpha-hydroxyprogesterone were effective at relatively high concentrations. Of the 5 beta-reduced metabolites, 17 alpha, 20 beta-dihydroxy-5 beta-pregnan-3-one was almost as effective as 17 alpha, 20 beta-diOHprog in oocytes of amago salmon and rainbow trout, while the other 5 beta-reduced compounds (3 alpha-hydroxy-5 beta-pregnan-20-one, 17 alpha-hydroxy-5 beta-pregnane-3,20-dione, 3 alpha, 17 alpha-dihydroxy-5 beta-pregnan-20-one, 5 beta-pregnane-3 alpha, 17 alpha, 20 beta-triol, and 5 beta-pregnane-3 beta, 17 alpha, 20 beta-triol) were almost or totally ineffective at the concentrations tested (1-0.001 micrograms/ml). These bioassay results, together with previous findings on the capacity of the ovary to produce 17 alpha, 20 beta-diOHprog, indicate that 17 alpha, 20 beta-diOHprog is the natural maturation-inducing steroid hormone common to three species of Salmoniformes, ayu, amago salmon, and rainbow trout. These results, however, only suggest that 17 alpha, 20 beta-diOHprog is involved in maturation of goldfish oocytes, since supportive physiological and biochemical data are lacking. Possible regulatory roles of 5 beta-reduced metabolites on steroid-induced oocyte maturation are discussed.

Animals↗
PubMed1983

Ultrastructural changes in the adenohypophysis during the ovarian cycle of the viviparous teleost Poecilia latipinna. II. The thyrotrophic cells and the thyroid gland.

Electron microscopical observations were made on the thyrotrophic (TSH) cells during the monthly cycle of oocyte development and pregnancy in female sailfin mollies. Parallel light microscopic studies were made on the thyroid gland. By morphological criteria, TSH secretion and thyroid activity run in parallel, and the findings indicate that TSH secretion and thyroid hormone output are higher during vitellogenic oocyte growth than during earlier oocyte development and during pregnancy. Measurements of TSH cell area and nuclear area and of thyroid epithelial cell height confirm this pattern. The results are discussed in the light of what is known of thyroid hormone involvement in teleostean ovarian physiology.

Animals↗
PubMed1983

Plasma 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one levels during sexual maturation of amago salmon (Oncorhynchus rhodurus): correlation with plasma gonadotropin and in vitro production by ovarian follicles.

Plasma gonadotropin (GtH) and 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17 alpha, 20 beta-diOH-prog) levels were assessed by radioimmunoassay during the sexual maturation of female amago salmon (Oncorhynchus rhodurus). Both GtH and 17 alpha, 20 beta-diOHprog levels were low in vitellogenic females (June to September) and in those with full-grown immature oocytes and were elevated in mature and ovulated females to 40 ng/ml for GtH and 50-70 ng/ml for 17 alpha, 20 beta-diOHprog. In vitro production of 17 alpha, 20 beta-diOHprog by ovarian follicles and its stimulation by partially purified chinook salmon gonadotropin (SG-G100) was examined monthly using 18 hr incubations. In June and July, levels were too low to detect (less than 30 pg/ml) in media from all treatment groups. In August and September, SG-G100 at a concentration of 1 microgram/ml stimulated low levels of production (0.2-0.3 ng/ml). Full-grown, immature follicles in October showed a dose-response production of 17 alpha, 20 beta-diOHprog, averaging over 10 ng/ml when incubated with 1 microgram/ml SG-G100. Postovulatory follicles (1-2 days after ovulation) produced large amounts of 17 alpha, 20 beta-diOHprog, averaging over 100 ng/ml with 1 microgram/ml SG-G100. These results are discussed in relation to previous work on amago salmon and other species and together indicate that 17 alpha, 20 beta-diOHprog is the major steroid responsible for oocyte maturation in amago salmon, produced as the follicular mediator of gonadotropin.

Animals↗
PubMed1983

17 alpha,20 beta-dihydroxy-4-pregnen-3-one: plasma levels during sexual maturation and in vitro production by the testes of amago salmon (Oncorhynchus rhodurus) and rainbow trout (Salmo gairdneri).

The present study investigated seasonal changes in plasma 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOHprog) levels in precociously mature and fully grown mature male amago salmon (Oncorhynchus rhodurus) and in vitro 17 alpha,20 beta-diOHprog production by the testes of amago salmon and rainbow trout (Salmo gairdneri) in response to chum salmon gonadotropin. Plasma 17 alpha,20 beta-diOHprog levels were very low from June to September, and rapidly increased in October at the beginning of the spawning season in both precociously mature and fully grown mature male amago salmon. High levels of 17 alpha,20 beta-diOHprog were maintained during the period of active spermiation in precociously mature males, and quickly declined in mid-November. Incubation of testicular fragments from spermiating rainbow trout with chum salmon gonadotropin or 17 alpha-hydroxyprogesterone resulted in a highly significant increase in 17 alpha,20 beta-diOHprog levels in the incubation medium. The chum salmon gonadotropin was also effective in stimulating 17 alpha,20 beta-diOHprog production by testicular fragments obtained from amago salmon after the breeding season. These findings are discussed in relation to the possible involvement of 17 alpha,20 beta-diOHprog in spermiation of salmonids.

Animals↗
PubMed1983

Secretory activity of Poecilia latipinna (Teleostei) pituitary in vitro: rostral pars distalis and proximal pars distalis.

The ultrastructure of each adenohypophysial secretory cell type was examined in pituitaries of adult female mollies (Poecilia latipinna) after various periods in vitro, and with varied medium osmotic pressure (OP), Na+, and Ca2+ concentrations. Prolactin (PRL) cells were markedly activated by 18 hr, and after 7 or 14 days were almost totally degranulated, with massive arrays of Golgi and RER. Reduction in OP, but not Na+ or Ca2+, caused an additional activation of PRL cells after periods of 18 hr or longer. Corticotroph (ACTH) cells became noticeably activated by 4 hr, and were possibly affected by OP, but not Na+ or Ca2+. Growth hormone (GH) cells were activated by 6 hr, and after 18 hr were quite degranulated with extensive arrays of RER. OP had no effect on GH cells before 3 days, when reduced OP appeared to cause an additional activation, with the appearance of large irregular secretory granule (SG)-like inclusions. Na+ and Ca2+ again had no effect. Gonadotrophic (GtH) cells appeared to be little affected by in vitro incubation; however, the very active cells from vitellogenic fish underwent a reduction in dilated RER after prolonged culture. Thyrotrophic (TSH) cells gradually became activated in vitro, but the response again varied with the sexual condition of the fish. Neither GtH nor TSH cells were affected by OP, Na+, or Ca2+. The findings are discussed in relation to hypothalamic control, via releasing/inhibiting factors, of adenohypophysial cell activity.

Adrenocorticotropic Hormone↗
PubMed1983

Estradiol-17 beta and 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one production by isolated ovarian follicles of amago salmon (Oncorhynchus rhodurus) in response to mammalian pituitary and placental hormones and salmon gonadotropin.

The effects of mammalian pituitary and placental hormones and dibutyryl cyclic AMP (cAMP) on the production of estradiol-17 beta and 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17 alpha, 20 beta-diOHprog) by amago salmon (Oncorhynchus rhodurus) ovarian follicles in vitro were compared with partially purified chum salmon (Oncorhynchus keta) gonadotropin (SGA). Estradiol-17 beta production was examined using midvitellogenic ovarian follicles; SGA was the most effective hormone tested; at a dose of 1 microgram/ml it stimulated the production of approximately 4 ng/ml estradiol-17 beta. Ovine LH (o-LH) was about 0.5% as effective as SGA. Taking into account the relative purity of the preparations used, ovine FSH (o-FSH) was almost as effective as o-LH. Both HCG and bovine TSH (b-TSH) stimulated estradiol-17 beta production at high doses. Porcine ACTH (p-ACTH), ovine GH (o-GH), and ovine PRL (o-PRL) induced very modest increases in estradiol-17 beta; cAMP was highly effective. 17 alpha, 20 beta-DiOHprog production was examined using full-grown immature oocytes which were capable of maturing in vitro in response to 1 microgram/ml SGA. o-LH was about 0.5% as effective as SGA. o-FSH, b-TSH, and HCG appeared to be less effective in stimulating 17 alpha, 20 beta-diOHprog production, compared to estradiol-17 beta. o-GH and o-PRL induced marginal increases in production and p-ACTH had a very modest inverse dose-response effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1983

Ultrastructural changes in the adenohypophysis during the ovarian cycle of the viviparous teleost Poecilia latipinna. III. The growth hormone, adrenocorticotrophic, and prolactin cells and the pars intermedia.

During the monthly cycle of vitellogenesis, intraovarian gestation, and parturition, the pituitary growth hormone (GH) cells show ultrastructural changes indicative of an increase in secretory activity related to vitellogenesis. In contrast, the pituitary adrenocorticotrophic (ACTH) cells are relatively inactive during vitellogenesis, but become active during late pregnancy in the few days before parturition. The prolactin cells and the two cell types of the pars intermedia do not appear to change their secretory activity during the cycle. In discussing these findings it is suggested that GH may play a metabolic role related to vitellogenesis, and that corticosteroids, secreted in response to elevated output of ACTH, may facilitate follicular rupture and/or the expulsion of the brood at the end of pregnancy.

Adrenocorticotropic Hormone↗
PubMed1983

Relationship between seasonal plasma estradiol-17 beta and testosterone levels and in vitro production by ovarian follicles of amago salmon (Oncorhynchus rhodurus).

Plasma estradiol-17 beta and testosterone levels were assessed by radioimmunoassay during the sexual maturation of female amago salmon (Oncorhynchus rhodurus). Estradiol-17 beta levels gradually increased during vitellogenesis (June to September), reached a peak in September (about 16 ng/ml) and rapidly decreased in mature and ovulated fish (about 3-4 ng/ml) in October. The seasonal pattern of plasma testosterone levels lagged behind and followed that of estradiol-17 beta during vitellogenesis, but levels remained high in mature and ovulated fish (90-110 ng/ml). Estradiol-17 beta levels and the gonadosomatic index (GSI) values correlated well during vitellogenesis: GSI values showed a linear increase, and reached a peak (29.9 +/- 1.4) in October. Values were extremely low in ovulated fish (1.2 +/- 0.2). In vitro production of estradiol-17 beta and testosterone by ovarian follicles in response to partially purified chinook salmon gonadotropin (SG-G100) was examined monthly using 18-h incubations. Throughout the vitellogenic period SG-G100 stimulated both estradiol-17 beta and testosterone production: the steroidogenic response of follicles increased from June (about 2 ng/ml estradiol-17 beta; 0.1 ng/ml testosterone) to September (about 10 and 14 ng/ml, respectively). In October full-grown immature follicles which could be induced to mature in vitro by hormone treatment produced large amounts of testosterone (about 130 ng/ml) but not estradiol-17 beta. Postovulatory follicles also produced testosterone but the values were low (10 ng/ml) compared with full-grown immature follicles. Very low levels of estradiol-17 beta were produced by postovulatory follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Evidence for a decrease in aromatase activity in the ovarian granulosa cells of amago salmon (Oncorhynchus rhodurus) associated with final oocyte maturation.

Aromatase activity in the isolated granulosa layers of amago salmon (Oncorhynchus rhodurus) ovarian follicles was examined during the course of vitellogenesis and final oocyte maturation and ovulation. Estradiol-17 beta production by isolated granulosa layers incubated with exogenous testosterone increased during the period of vitellogenesis to reach a peak in late vitellogenesis, and then declined rapidly, in association with the ability of the oocyte to mature in response to partially purified salmon gonadotropin (SG-G100). Extremely low levels of estradiol-17 beta were produced by granulosa layers from follicles which had undergone final oocyte maturation in vivo and by post-ovulatory follicles. SG-G100 had no discernible effect on estradiol-17 beta production. These results are discussed in relation to other studies on the endocrine control of steroidogenesis in this species.

Animals↗
PubMed1982

Oocyte maturation in the amago salmon (Oncorhynchus rhodurus): in vitro effects of salmon gonadotropin, steroids, and cyanoketone (an inhibitor of 3 beta-hydroxy-delta 5-steroid dehydrogenase).

The effect of partially purified chinook salmon gonadotropin (SG-G100) and a number of steroids on the induction of germinal vesicle breakdown (GVBD) in amago salmon (Oncorhynchus rhodurus) oocytes (with intact follicle layers) was investigated in vitro. SG-G100 was effective only at the highest concentration tested (1 microgram/ml). 17 alpha,20 beta-Dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOHprog) was the most potent maturation-inducing steroid tested, followed by 17 alpha-hydroxyprogesterone. Testosterone or deoxycorticosterone (DOC) enhanced the rate of GVBD in response to SG-G100. DOC also enhanced the response to 17 alpha,20 beta-diOHprog but testosterone was without effect, suggesting that DOC has a direct action on the oocyte while testosterone probably acts at the level of the follicle. Estradiol-17 beta had no effect on GVBD in response to SG-G100 or 17 alpha,20 beta-diOHprog. The action of SG-G100 was shown to be dependent on the synthesis of a second delta 4 steroidal mediator of maturation since cyanoketone, a specific inhibitor of 3 beta-hydroxy-delta 5-steroid dehydrogenase, completely abolished the maturational effects of the gonadotropin and pregnenolone but not delta 4 steroids. Radioimmunoassay of media in which oocytes were induced to mature in vitro with SG-G100 revealed significantly elevated levels of progesterone and 17 alpha,20 beta-diOHprog. Estradiol-17 beta levels, high in control media, were only elevated twofold by SG-G100. Levels of the two progestogens were extremely low or nondetectable in media in which oocytes were incubated with cyanoketone, while estradiol-17 beta levels remained high. These results are discussed in relation to other evidence indicating that 17 alpha,20 beta-diOHprog is the naturally occurring maturation-inducing steroid of amago salmon. The role of other steroid hormones, particularly the possible involvement of corticosteroids, in the control of final oocyte maturation in teleosts is explored.

17-alpha-Hydroxyprogesterone↗
PubMed1982

Characteristics of invasiveness of human nasopharyngeal carcinoma cells in organ culture, as observed by scanning electron microscopy.

Cells of a human nasopharyngeal carcinoma (CNE) were cultured in contact with embryonal mouse heart fragments wrapped in a fibrous kidney capsule as biological permeable membrane. The culture was terminated at different intervals and processed for scanning electron microscopy. Carcinoma cells showed abundant microvilli and filopodia in contact with superficial cells of the heart fragments. Cancer cells appeared firmly attached to the surface of the tissue fragments. Subsequently, malignant cells extended pseudopodia into intercellular spaces of the supporting tissue particle, and beyond the third day of cultivation, cancer cells were also found in deeper parts of the organ. The cancer cells on the surface of the specimen had apparently lost the ability to invade. After a while, microvilli and filopodia decreased in number or adhered to each other. The plasma membrane exhibited signs of degeneration.

Animals↗