Antireproductive effects of a potent gonadotropin-releasing hormone antagonist in the male rat

Administration of a potent antagonist of gondadotropin-releasing hormone (GnRH) antagonist [Ac-dehydro-Pro1, pCl-D-Phe2, D-Trp3,6]-N alpha-MeLeu7-GnRH to adult male rats for 2 weeks resulted in decreased testosterone production and sexual organ weights and in disrupted spermatogenesis. The results demonstrate the essential role of gonadotropin-releasing hormone in the maintenance of reproductive functions and have implications for the regulation of male fertility.     

Changing sensitivity of the pubertal gonadal hypothalamic feedback mechanism in man

Clomiphene citrate in doses which stimulate gonadotropin production in the adult suppresses urinary follicle stimulating hormone (FSH) excretion and plasma testosterone concentration in prepubertal children. Such results indicate that feedback between gonad and hypothalamus is operative and highly sensitive in prepubertal humans. Puberty in man, as in the rat, is accompanied by a decrease in the sensitivity of the feedback mechanism.     

Gonadotropin-releasing hormone: regulation of adenosine 3',5'-monophosphate in ovarian granulosa cells

The antigonadal effects of gonadotropin-releasing hormone in ovarian granulosa cells are due to attenuation of the adenosine 3',5'-monophosphate (cyclic AMP) response to follicle-stimulating hormone. Agonists of gonadotropin-releasing hormone progressively inhibit adenylate cyclase and stimulate phosphodiesterase activities in cultured granulosa cells, indicating that blockade of gonadotropin action is attributable to the combined effects of decreased production and increased degradation of cyclic AMP.     

Control of the rhesus monkey menstrual cycle: permissive role of hypothalamic gonadotropin-releasing hormone

In rhesus monkeys with hypothalamic lesions (which appear to abolish the endogenous production of gonadotropin-releasing hormone), normal ovulatory mestrual cycles were reestablished by an unvarying, long-term replacement regimen consisting of one intravenous pulse of synthetic gonadotropic-releasing hormone per hour. This finding is in accord with the hypothesis that the pattern of pituitary gonadotropin secretion throughout the menstrual cycle (basal secretion interrupted, once every 28 days on the average, by a preovulatory surge) is not directed by alterations in hypothalamic gonadotropin-releasing hormone secretion but by the ebb and flow of ovarian estrogens acting directly on the pituitary gland.     

Expression of beta-nerve growth factor receptor mRNA in Sertoli cells downregulated by testosterone

Nerve growth factor (NGF) is synthesized in male germ cells. The NGF receptor (NGFR) mRNA was found in the Sertoli cells of rat testis. Hypophysectomy increased both NGFR mRNA in testis and the number of NGFR hybridizing cells in seminiferous tubules. This was suppressed by treatment with chorionic gonadotropin or testosterone, but not with follicle-stimulating hormone. The NGFR mRNA also increased after destruction of Leydig cells or blocking of the androgen receptor. This suggests that NGF produced by male germ cells regulates testicular function in an androgen-modulated fashion by mediating an interaction germ and Sertoli cells.     

生殖激素对龟类生殖调控的研究进展

迄今为止,已发现有11种生殖激素参与龟类生殖调控。雌二醇和睾酮在促性腺激素释放激素、卵泡刺激素和黄体生成素的调控下主导调控龟类性腺发育、配子生成、交配、产卵及子代性别决定等重要生殖环节。孕酮、前列腺素、精氨酸催产素、皮质酮、甲状腺素和褪黑激素协同调节龟类生殖活动。在人工繁殖方面,使用GnRH等有助于克服龟类繁殖障碍,提高繁殖效率。对生殖激素对龟类生殖活动的调控作用与机理及其应用的研究进展进行了综述。     

Stimulation of gonadotropin release by a non-GnRH peptide sequence of the GnRH precursor

The human gonadotropin-releasing hormone (GnRH) precursor comprises the GnRH sequence followed by an extension of 59 amino acids. Basic amino acid residues in the carboxyl terminal extension may represent sites of processing to biologically active peptides. A synthetic peptide comprising the first 13 amino acids (H X Asp-Ala-Glu-Asn-Leu-Ile-Asp-Ser-Phe-Gln-Glu-Ile-Val X OH) of the 59-amino acid peptide was found to stimulate the release of gonadotropic hormones from human and baboon anterior pituitary cells in culture. The peptide did not affect thyrotropin or prolactin secretion. A GnRH antagonist did not inhibit gonadotropin stimulation by the peptide, and the peptide did not compete with GnRH for GnRH pituitary receptors, indicating that the action of the peptide is independent of the GnRH receptor. The GnRH precursor contains two distinct peptide sequences capable of stimulating gonadotropin release from human and baboon pituitary cells.     

Endothelin stimulation of cytosolic calcium and gonadotropin secretion in anterior pituitary cells

The presence of endothelin, a vasoconstrictor peptide, in the hypothalamus and posterior pituitary suggests that it also regulates neural and other nonvascular target cells. In pituitary gonadotrophs, low doses of endothelin evoked oscillations in the intracellular calcium concentration, and high doses induced a biphasic calcium response. Mobilization of intracellular calcium predominated during the spike phase of the calcium response to endothelin, whereas calcium entry through dihydropyridine-sensitive channels contributed to both the spike and plateau phases of the calcium response. Endothelin was a potent as hypothalamic gonadotropin-releasing hormone (GnRH) in stimulation of gonadotropin release in perifused pituitary cells. Endothelin bound specifically to pituitary cells with a dissociation constant of 70 picomolar, and induced rapid formation of inositol trisphosphate and diacyglycerol. Although intracellular calcium concentration and gonadotropin secretory responses to endothelin were independent to the GnRH receptor, endothelin and GnRH appeared to have a common signal transduction mechanism. These observations suggest that endothelin can act as a neuropeptide to regulate anterior pituitary function.     

Annual Change of the Testosterone Hormone in Male White Goats

In this research, changes of testosterone hormone in the blood serum of 9 male (3 of age 2 and 6 of age 4) White goats have been studied for a duration of one year. Analyses performed show that the general monthly averages of the testosterone hormone of the male White goats in the period of 12 months starting in January were (2.11±0.73), (2.22±0.52), (2.44±0.59),(2.10±0.41),(2.35±1.00), (3.42±1.48), (4.77±1.32), (5.61±1.40), (7.91±1.24), (10.84±1.59), (7.82±1.60), and (2.63±0.61) ng mL-1,respectively (P<0.05). The effect of the age factor on the testosterone production in White goats (age 2 and 4) was generally significant (P<0.05) for differences among months in each age group, but not significant for differences between age groups in each month. The testosterone hormone levels of male White goats encountered significant changes (P<0.05)with respect to the season.     

Pheromone-induced changes in the acidophil concentration of mouse pituitary glands

Pituitaries of female mice in anestrus resulting from colony housing were characterized by a 58.0-percent (acidophil content. Subsequent exposure to restrained male mice for one and two nights failed to evoke significant acidophilic degranulation and resulted in pituitary acidophil values of 57.4 and 55.1 percent respectively. Exposure to released males on the third night produced marked acidophilic degranulation resulting in a significant decline in pituitary acidophils to 38.0 percent. These findings support the view that female pheromone suppresses and male pheromone favors the secretion of follicle-stimulating hormone and indicate that luteotrophic hormone is secreted at its assigned time in the sequence of cyclic ovarian events initiated by the secretion of follicle-stimulating hormone.     

甲基睾丸素对中华鳖外部性征诱导作用的研究

采用甲基睾丸素处理不同发育时期的中华鳖胚胎和给孵出后３ｄ的稚鳖拌饲甲基睾丸素来观察外源性激素的诱导作用,结果表明：试验组与对照组的孵化率无显著差异。说明孵化率不受生激素处理的影响,经雄性激素处理过的所有个体外部雄性副性征明显,其尾巴长,露出背板的裙边,且好咬斗,这充分证明外源雄性激素对稚鳖的外部性征及胃较大的诱导作用。     

Detection of a gonadotropin in rabbit blastocyst before implantation

A gonadotropin similar to human chorionic gonadotropin or luteinizing hormone has been demonstrated in rabbit blastocyst prior to implantation. The gonadotropin has been detected by a radioreceptor assay for human chorionic gonadotropin with the use of the plasma membranes of bovine corpora lutea obtained during the first trimester of pregnancy. The concentrations of the human chorionic gonadotropin or luteinizing hormone per milliliter of blastocyst fluid were tenfold higher than those in the blood of pregnant rabbits on days 5 and 6 after mating.     

A parathyroid hormone inhibitor in vivo: design and biological evaluation of a hormone analog

A synthetic analog of bovine parathyroid hormone (bPTH), [tyrosine-34] bPTH-(7-34)NH2, was found to inhibit parathyroid hormone action in vivo. When the analog and parathyroid hormone were infused simultaneously to rats at a molar ratio of 200 to 1, the analog inhibited the excretion of urinary phosphate and adenosine 3',5'-monophosphate. When infused alone at the same dose rate, the analog was devoid of agonist activity. The compound was prepared by following design principles developed for inhibitors of parathyroid hormone, and is believed to be the first antagonist of parathyroid hormone that is effective in vivo.     

肉仔鸡血清蛋白质、钙、磷和睾酮含量与生长发育的关系

本文通过对不同品种肉鸡进行饲养观察,初步认定罗曼鸡生长发育最快。其饲料转化率、适应性、抗病力等明显优于AA和星布罗肉鸡。从理论上阐述了影响肉鸡生长发育的生理因素。试验分析表明,血清中总蛋白质含量与生长速度成正相关;血清钙和无机磷含量,在不同肉鸡品种之间差异不大;公鸡血清睾酮含量对肉鸡生长发育有一定促进作用,睾酮含量多的肉鸡生长发育快,一般表现出体重与血清睾酮之间有明显的相关。     

β-酪啡肽对公山羊血清FSH、LH和T水平的影响

给公山羊瘤胃灌注β－酪啡肽（β－CM）,在灌注前后采取外周血样,用放射免疫分析法测定血清促卵泡素（FSH）、促共体生成素（LH）和睾酮（T）水平,旨在研究β－酪啡肽对公山羊生殖内分泌的影响。结果表明,瘤胃灌注β－CM后,公山羊血清LH和T水平明显降低（P＜0．01或P＜0．05）,且此效应可被阿片受体拮抗内络酮（naloxon）逆转,而β－CM灌注,对公山羊血清FSH水平未昂明显影响（P＞0．05）。     

鱼体内性类固醇激素水平与催产药物相关性研究

研究怀卵大鳞副泥鳅(Paramisgurnus dabryanus)用药后亲鱼血清、卵液性激素含量变化,探讨了药物组合和变化间的相关性。结果表明,GnRH-A及其配伍注射后,泥鳅血清中雌雄激素、卵液中孕激素含量在排卵前增加,呈明显的组合—效应关系;表明催产药物可引起血清、卵液性激素含量变化,并且这一变化有一定的规律性,可能会成为繁殖药物筛选的重要指标。     

Soldier determination in ants: new role for juvenile hormone

Topical application of juvenile hormone analog induces soldier development in the ant Pheidole bicarinata. Soldier induction takes place if the juvenile hormone analog is present during a period of sensitivity that occurs during the last larval instar. Control of worker dimorphism seems to be accomplished through control of timing of metamorphosis. The smallest size at which metamorphosis can be initiated is shifted upwardfrom 1.2 to 1.7 millimeters by exposure to the juvenile hormone analog during the sensitive period.     

MUSCLE AND BLOOD HEMOGLOBIN IN THE DOLPHIN

The sex organs of the male are more resistant to dietary deficiencies, the animals showing only retrogression along with a significant loss in weight. Testosterone and gonadotropic hormone (of pregnant mare serum) produce a small but definite restorative effect. Oral administration of estrin to females depresses the food intake, while testosterone, and less so the gonadotropic hormone in males produces the opposite effect. This effect can be regarded as evidence of the dietary significance of these two hormones. The expenses of the present investigation were defrayed by the U. S. Vitamin Corporation, of New York City.     

Synthetic polypeptide antagonists of the hypothalamic luteinizing hormone releasing factor

Two analogs of the hypothalamic luteinizing hormone releasing factor modified at the histidine-2 position were tested for biological activity (secretion of luteinizing hormone) in cultures of dispersed rat anterior pituitary cells. The analog in which glycine was substituted for histidine at position 2, [Gly(2)]LRF, behaves as a partial agonist releasing less than 50 percent of the luteinizing hormone secreted at maximum concentrations of the releasing factor, while the analog in which histidine at position 2 is deleted has no significant agonist activity at any of the doses tested. When added to the cultured cells at molar ratios 10(3) to 10(4) times that of the luteinizing hormone releasing factor, both analogs decrease the amount of luteinizing hormone secreted in response to the releasing factor.     

Follicle-stimulating hormone and the regulation of testosterone secretion in rabbit testes

Regulation of testosterone secretion is presumably mediated by interstitial cell-stimulating hormone (ICSH). However, there is little information on the actions of other chemical messengers in regulating testosterone secretion. We have shown that follicle-stimulating hormone augments testosterone secretion stimuated by ICSH in rabbit testes perfused in vitro with an artificial medium.