GnRH receptor site increase on the surface of cultured gonadotropes of senescent C57BL/6NNia mice.

Anterior pituitary cells were cultured for 2 days from 6-, 14-, and 23-25-month-old C57BL/6NNia mice. The cells were then stimulated with one of three biotinylated GnRHs [biotinyl-Lys6]-[D-Lys6]GnRH, [biotinyl-Ser4]-[D-Lys6]GnRH, [biotinyl-Ser4]-[D-Trp6, des-Gly10]GnRH) at 4 degrees C for 1 h. Some of these cells were processed unfixed, attaching avidin-fluorescein and examined with fluorescent microscopy.

Differential effects of two alleles of the dy locus on the pituitary-testicular axis of mice.

Testicular function was studied in vivo and in vitro in adult male dy/dy and dy2J/dy2J dystrophic mice. The results demonstrate that testicular function in dy/dy mice is more affected. The basal levels of pituitary hormones measured were normal in dystrophic mice, except for the presence of hyperprolactinemia in dy/dy mice.

Topographical mapping of GnRH receptors on dispersed mouse pituitary cells by backscattered electron imaging.

Mouse anterior pituitary cells cultured for 2 days were stimulated with one of three biotinylated-GnRH probes ([biotinyl-Lys6]-[D-Lys6]GnRH, [biotinyl-Ser4]-[D-Lys6]GnRH, [biotinyl-Ser4]-[D-Trp6, des-Gly10]GnRH) in the cold (4 degrees C) for 1 hr. These cells were subsequently fixed and an avidin-gold complex was conjugated to the bound GnRH. After a second fixation, the gold label was silver-enhanced for viewing with a scanning electron microscope.

Levels of alpha-inhibin in aging female mice.

alpha-inhibin was immunocytochemically localized in granulosa cells of different stages of developing follicles, freshly formed corpora lutea, and scattered interstitial cells (pigmented or ceroid cells) in ovaries of 6-, 14-, and 23-25-mo-old C57BL/6NNia mice. Developing follicles exhibited the greatest amount of staining. Quantitation of the stain using an image analysis system indicated the staining intensity within ovarian follicles of 14-mo-old mice was greater than that in 23-25-mo-old mice.

Effect of ovariectomy and estrogen replacement on hypothalamic, pituitary and peripheral blood beta-endorphin levels in the rat.

This study was initiated to detect possible changes in beta-endorphin (beta-EP) levels of the hypothalamus, anterior pituitary gland, and peripheral blood of rats after ovariectomy and estrogen administration. Attempts were also made to determine the correlation between peripheral and central levels of beta-EP. Twenty-six Sprague-Dawley rats were decapitated.

Exposure to estradiol impairs luteinizing hormone function during aging.

The loss of ovulatory cyclicity in many mammals is caused by changes in the hypothalamic-pituitary (H-P) control of the preovulatory luteinizing hormone (LH) surge. This work evaluated the anterior pituitary (AP) component of the H-P axis by determining the ability of perifused AP to release LH following sustained but pulsatile LHRH stimulation. The normal dual discharge profile of LH was affected by age.

Effects of heterologous growth hormones on hypothalamic and pituitary function in transgenic mice.

The expression of the mouse metallothionein-I (mMT) promoter/human growth hormone (hGH) fusion gene in transgenic mice leads to female sterility and major alterations in the function of the hypothalamic-adenohypophyseal system. These alterations include increases in median-eminence norepinephrine turnover and plasma LH levels, and a decrease in plasma prolactin levels in intact males, and an increase in median-eminence dopamine turnover combined with the suppression of plasma prolactin levels in ovariectomized females. To further characterize these changes and to determine whether they are due to the lactogenic or somatotropic activity of hGH, we have studied hypothalamic and pituitary function in transgenic mice expressing mMT/hGH, mMT/hGH.

Neuroendocrine function in transgenic male mice with human growth hormone expression.

The neuroendocrine effects of human growth hormone (hGH) secretion were studied in adult male mice into which an hGH gene fused with mouse metallothionein 1 (mMT-1) promoter had been introduced. Intact transgenic mice had significantly greater plasma luteinizing hormone (LH) levels than did normal littermate controls. Castration increased LH levels in normal mice but was without effect on plasma LH levels in the transgenic mice.

In vitro fertilization of Siberian hamster oocytes.

Siberian hamsters were superovulated and various media were tested in an effort to fertilize the recovered oocytes in vitro. The highest percentage of fertilized ova was achieved by using a modified Tyrode's medium, designated MT (Bavister, J. Reprod.

Blastocyst implantation in the Chinese hamster (Cricetulus griseus).

Embryonic development of the Chinese hamster (Cricetulus griseus) was studied from the onset of implantation to the formation of the parietal yolk sac placenta. Implantation began on day 6 of pregnancy, when the embryo became fixed to the uterine luminal epithelium. At this time there was no zona pellucida, and microvilli of the trophoblast and uterine epithelium were closely apposed.

Fertilizing ability of spermatozoa from aged C57BL/6NNia mice.

Spermatozoa from C57BL/6NNia mice (7- and 25-month-old males that produced offspring and 25-month-old males incapable of producing offspring which either mated or did not mate after being paired for 1 month with proven-fertile females) were tested in in-vitro fertilization studies. The 7-month-old males fertilized the largest number of oocytes (80-86%) in vitro and 79% of them subsequently developed into blastocysts in culture. Aged males which failed to mate fertilized the lowest number of oocytes (11-19%) with 48% developing to blastocysts.

Infertility in transgenic female mice with human growth hormone expression: evidence for luteal failure.

Introduction of the human growth hormone (hGH) gene fused with mouse metallothionein I promoter into domestic mice leads to ectopic synthesis of hGH, marked stimulation of somatic growth, and female sterility. Transgenic females (produced by mating transgenic males to normal females) mated but failed to become pregnant or pseudopregnant as evidenced by the recurrence of vaginal plugs every 5-7 days. Daily injections of 1 mg progesterone, starting on day 1 postcoitum (p.

Fertilization of Chinese hamster ova in vitro and in vivo and their subsequent development in culture.

Oocytes from superovulated Chinese hamsters can be fertilized in vitro using the culture medium BWW (70% of 112 ova) or a modified BWW designated as MBWW (76% of 122 ova) when either medium is supplemented with 4 mg/ml of bovine serum albumin. Ova fertilized in vitro will also cleave to the 2-cell stage in either medium (52% in BWW, 87% in MBWW), but fail to develop any further in culture. Oocytes fertilized in vivo and recovered at the late 2-cell or early 4-cell stages from females on Day 3 of pregnancy have the capacity to develop into expanded blastocysts in MBWW.

Paternal age and its effects on reproduction in C57BL/6NNia mice.

The reproductive capabilities of 6- and 24-month-old C57BL/6NNia male mice were compared after being paired for one month with a 4-month-old proven-fertile female. All of the younger males mated, with 96% yielding a litter; only 42% of aged males mated, with 65% siring young. There were no statistical differences in the litter sizes, nor any congenital defects noted in offspring from either age group.

Neuroendocrine studies in hyperprolactinaemic male mice.

In several species, including man and the rat, hyperprolactinaemia is associated with suppression of gonadotrophin release and male sexual behaviour. However, in the hyperprolactinaemic male mouse, plasma LH and FSH levels and copulatory behaviour are increased rather than suppressed. In an attempt to identify mechanism(s) which may be responsible for these effects of hyperprolactinaemia in the mouse, we have examined the effects of two ectopic pituitary isografts on several indices of hypothalamic and pituitary function in adult DBA/2J males.

Testicular LH receptors and circulating hormone levels in three mouse models for inherited diseases (Tfm/y, lit/lit and hyt/hyt).

In mice with testicular feminization (Tfm/y), the concentration of LH receptors (LH-R) in the testes was greatly elevated, when compared to their normal controls (Ta/y). The administration of hCG caused, 24 hours later, a much greater decrease in the number of testicular LH-R in Tfm/y than in Ta/y mice. However, whereas in Ta/y mice, the decrease in LH-R was accompanied by a greater than 20 fold increase in plasma testosterone (T) levels, the same dose of hCG failed to alter plasma T levels in Tfm/y mice.

Acute lithium treatment suppresses the proestrous LH surge in mice: chronic lithium leads to constant diestrus.

Although the therapeutic usefulness of lithium in manic-depressive psychosis is now well-established, a number of basic and clinical studies in recent years have shown that the administration of this anti-manic drug produces a wide range of adverse endocrine and metabolic effects. The present study was undertaken in order to examine (a) what effects acute lithium administration might have on the preovulatory surge of luteinizing hormone (LH) during proestrus, and (b) whether chronic lithium administration has any adverse effect on the estrous cycle in C57BL/6 mice. Acute injections of lithium on the day of proestrus (at 10.

Hormonal regulation of testicular human chorionic gonadotropin binding and steroidogenesis in adult mice with different forms of hereditary diabetes and obesity.

The regulation of testicular hCG binding and steroidogenesis in adult mutant mice with hereditary diabetes and obesity was studied. Low doses of hCG caused no change in hCG binding in obese (ob/ob) mice, whereas, in diabetic (db/db) mice, the increase in binding measured 24 h after hCG administration was not as great as in normal males. Intermediate doses of hCG caused a decrease in hCG binding in obese and normal mice, but not in diabetic animals.

The effect of unilateral testicular torsion on the contralateral testicle in prepubertal Chinese hamsters.

Recent studies of experimental testicular torsion in rats, rabbits, and guinea pigs have demonstrated conflicting evidence regarding contralateral testicular damage. Those studies in which cellular damage has been found are postulated to result from an immunological mechanism whereby the blood-testis barrier is disrupted with subsequent autoantibody formation. In this study, the histologic and immunologic effects of testicular torsion on the contralateral testicle were investigated in prepubertal Chinese hamsters.

Orthotopic ovarian transplantations in young and aged C57BL/6J mice.

Orthotopic ovarian transplantations were done between young (6-wk-old) and aged (17-mo-old) C57BL/6J mice. The percentages of mice mating following surgery from the four possible ovarian transfer combinations were as follows: young into young, 83%; young into aged, 46%; aged into young, 83%; and aged into aged, 36%. The percentages of these mice that were pregnant 10 days following the presence of a vaginal sperm plug were as follows: young into young, 58%; young into aged, 9%; aged into young, 50%; and aged into aged, 0%.

Concentrations of prostaglandins in plasma, seminal vesicles, and ovaries of aging C57BL/6NNia mice.

Concentrations of prostaglandin E1 (PGE1), and prostaglandin E2 (PGE2) (combined in the same radioimmunoassay) and prostaglandin F2 alpha (PGF2 alpha) were analyzed in circulating plasma and seminal vesicles of 3- and 26 to 27-month-old males and in circulating plasma and ovaries of 3-, 6-, 14 to 18- and 26 to 30-month-old female C57BL/6NNia mice. The amount of PGE declined in the plasma (P less than 0.05) and seminal vesicles (P less than 0.

Effect of treatment with different doses of bromocriptine on plasma profiles of prolactin, gonadotrophins and testosterone in mature male rats and mice.

The influence of different doses of bromocriptine (CB-154) on plasma levels of prolactin (Prl), FSH, LH and testosterone (T) in mature male rats and mice was studied. Daily subcutaneous administration of 360 micrograms of CB-154 in sesame oil was sufficient to induce maximal suppression of plasma Prl levels in mature male rats whilst subcutaneous implantation of two pellets of CB-154 and cholesterol, each containing approximately 6 mg CB-154, was effective in suppressing serum Prl levels in mature rats for at least four weeks. This was accompanied by a significant elevation of plasma levels of LH and FSH.

Autoregulation of testicular luteinizing hormone receptors in hypogonadal (hpg/hpg) mice.

The autoregulation of testicular luteinizing hormone (LH) receptors was studied in hypogonadal (hpg/hpg) and normal mice. The basal concentration of LH receptors was more than three-fold higher in hpg/hpg than in normal mice. After injection of hCG, hpg/hpg mice showed a decrease in LH receptor levels which was not observed in normal mice.

Adrenomedullary catecholaminergic activity increases with age in male laboratory rodents.

In this report, we have examined the effects of aging on adrenomedullary catecholaminergic activity by evaluating the levels of activity of adrenal dopamine-beta-hydroxylase (DBH) in three species of laboratory rodents. Groups of male Fischer 344 rats (3-, 18-, and 28-month-old), Chinese hamsters (4- and 30-month-old), and Mongolian gerbils (3- and 26-month-old) were killed, and their adrenal DBH activities were measured by a sensitive radioenzymatic method. The results indicated that adrenomedullary DBH activities showed a progressive age-related increase in all three species investigated.

Plasma and pituitary concentrations of LH, FSH and prolactin in aging Mongolian gerbils.

Samples of plasma and pituitary homogenates collected from female Mongolian gerbils (3-4, 11-13 and 20-25 month-old) at various stages of the estrous cycle were analyzed by radioimmunoassay for luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (Prl). Plasma and pituitary LH concentrations were similar in all three age groups. Plasma FSH concentrations tended to increase with age while plasma Prl concentrations remained unchanged.