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. Other cells were fixed and the biotinylated GnRH coupled to avidin-gold (20 nm particles), which was subsequently silver-enhanced (70 nm particles) and examined with light and scanning electron microscopy (SEM). To enhance the location of receptor sites for quantitation, a back-scattering electron detector was employed with the SEM. Gonadotropes from all three age groups ranged in size from 3 to 13 microns in diameter. The largest gonadotropes in each age group displayed the highest number of GnRH receptors, but the concentration/surface area (microns2) was less than for smaller cells. Smaller gonadotropes (3-6 microns diameter) from 14- and 23-25-month-old mice contained more GnRH receptor sites/microns2 (p < .001) than those from 6-month-old mice; the percentage of these gonadotropes was markedly higher for 14-(65%) and 25-(52%) versus 6-month-old (5%) mice. The number of receptor sites in larger gonadotropes (6.1-13 microns diameter) did not decline with the increasing age of the mouse. Decreased secretory activity in gonadotropes of 25-month-old mice may result from age-related changes in pituitary peptide processing or release, but it is not due to a lack of GnRH receptors or the inability of GnRH to bind to its receptor site.

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. In dy/dy mice testicular weight was diminished and a deficient transduction of the gonadotropic signal is present in vivo, accompanied by reduced efficiency of 17-hydroxylase and 17-hydroxysteroid dehydrogenase. In dy2J/dy2J mice the signal transduction is normal and the reduction in enzyme efficiency is limited to 17-hydroxysteroid dehydrogenase. The in vitro HCG-induced increases in production of testosterone (T) and estradiol (E2) were reduced in dy/dy/mice, and the data indicate a reduction of enzyme activity rather than in efficiency. In dy21/dy21/mice, HCG-induced T synthesis was increased, HCG-induced E2 synthesis was normal, but basal media E2 levels were reduced, with the in vitro efficiency of aromatase being suppressed under both basal and HCG-stimulated conditions, when compared to their normal littermates.

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. Gonadotropes were identified as a result of the labeling procedure, measured for size, and the number of GnRH receptor sites counted. Gonadotropes ranged from 3 to 13 microns in diameter and contained from 23.2 +/- 3.3 to 338.4 +/- 25.2 sites per cell depending upon the size of the cell and the ligand employed. The methods described should be applicable for studying the topographical distribution of a variety of cellular receptors.

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. The levels of plasma alpha-inhibin and estradiol (E2) decreased with age. The number of follicles present in ovaries of middle-aged mice was comparable to those of 6-mo-old mice, yet plasma levels of FSH were significantly higher than those of 6-mo-old mice. This may be due to an age-related loss in the sensitivity of the hypothalamus and/or pituitary of middle-aged mice to ovarian hormones. In contrast, ovaries of 23-25-mo-old mice contained few antral follicles and consequently produced little alpha-inhibin. There appeared to be little negative feedback regulation of FSH secretion in 23-25-mo-old mice as a result of age-related ovarian impairments. This study supports an earlier hypothesis from our laboratory [Biol Reprod 1985; 32:989-997] that the primary defect(s) limiting age-related reproductive performance in mice appears to reside within the hypothalamo-hypophyseal axis, whereas secondary defects arise from the ovary.

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. Nine had intact ovaries (Gr. INT), and 17 were ovariectomized 3 weeks before they were killed. Nine of the ovariectomized rats received estradiol benzoate (EB) (Gr. EB) and the other 8 received peanut oil (Gr. OVX) prior to the decapitation. A beta-EP radioimmunoassay was used to analyze homogenates of the hypothalamus and anterior pituitary, and peripheral blood. In the hypothalamus, beta-EP levels were significantly lower in Gr. INT and Gr. EB than in Gr. OVX. In the pituitary gland and peripheral blood, beta-EP levels were significantly higher in Gr. INT than in Gr. OVX. Pituitary beta-EP levels did not vary between Gr. OVX and Gr. EB, although beta-EP levels in peripheral blood were significantly higher in Gr. EB than in Gr. OVX. No significant correlations were noted in beta-EP levels between the hypothalamus, pituitary gland, and peripheral blood in either Gr. INT, Gr. OVX, or Gr. EB. It appears that EB exerts different effects on beta-EP levels in the hypothalamus, anterior pituitary gland, and peripheral blood, and that beta-EP levels in these regions may be independent of one another.

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. The first hour of the response, unaffected by cycloheximide, was similar in 5-6-month-old (mature), 12-13-month-old (declining litters) and 16-18-month-old (irregularly cycling) mice. The remaining protein synthesis-dependent part of the response was reduced in the 16-18 and 22-24-month-old (anestrus) mice. The role of estradiol (E2) in AP aging was further tested as AP from ovariectomized (OVXed) mice, deprived of E2 since puberty, responded as well as the mature proestrous group. In contrast, aged mice subjected to long-term E2 exposure (cycling or OVXed plus E2 replacement) failed to produce the dual response pattern. Since alterations in LH response occurred during the protein-dependent phase, synthetic processes that involve packaging and transport of stored LH, or the production of new LH, may be affected by age. Furthermore, E2 is a major factor in altering LH function and appears to act before middle 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.B 'variant', or mMT/bGH fusion genes. In males, the expression of the hGH.B gene was associated with a reduction in pituitary prolactin release in vitro and an increase in LH response to LHRH stimulation, while the bGH transgene did not affect any of the examined parameters of LH and prolactin release. Median-eminence norepinephrine turnover was increased in each of the three lines of transgenic males, while median-eminence dopamine turnover was reduced only in animals expressing the hGH.B gene. In ovariectomized females, plasma LH was suppressed by hGH variant expression, while median-eminence norepinephrine turnover was suppressed in both hGH.B and bGH animals. The turnover of dopamine was increased in the median eminence of females expressing either of the human genes (hGH or gHG.B) and reduced in the median eminence of ovariectomized bGH females. We conclude that the hGH.B gene is weakly lactogenic in mice, and that the chronic stimulation of either GH receptors (by bGH) or both GH and prolactin receptors (by hGH or hGH.B) can lead to profound alterations in the metabolism of hypothalamic neurotransmitters and pituitary hormone release.

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 LH secretion and pituitary LH content were higher in the intact transgenic mice than in intact controls, while there was no significant difference in pituitary LH levels and in vitro LH secretion between the 2 groups of castrate animals. Intact transgenic mice exhibited a greater median eminence (ME) norepinephrine (NE) turnover than control animals, but ME NE turnover did not increase after castration in the transgenic animals as was the case in control mice. Castrate mice expressing the hGH gene had plasma levels of prolactin (PRL) similar to those seen in castrate controls, which was unexpected based on a previous study showing greatly attenuated PRL levels in intact hGH mice when compared to intact controls from the same line. Dopamine (DA) turnover in the ME was not significantly affected by the presence of the hGH gene, suggesting that the difference in plasma PRL levels between normal and transgenic mice is mediated through changes in PRL-regulating factors other than DA. In conclusion, the expression of the mMT-1/hGH hybrid gene in male mice leads to major alterations in LH secretion and lesser changes in PRL secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

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. Fertil., 18:544-545, '69), previously formulated to fertilize Syrian hamster ova in vitro. Spermatozoa incubated in this medium in a concentrated state overnight (14 hr) and then diluted (1 hr) fertilized 39% of the ova. Similar results (40%) were obtained with this medium by adding 20% human follicular fluid to fresh concentrated sperm for 30 min and then diluting the sperm for 2-3 hr prior to the addition of ova. Ova fertilized in vitro cleaved to the two-cell stage but failed to develop any further in culture. Two-cell embryos recovered from mated hamsters and cultured did not undergo additional cleavage. Four-cell embryos collected from mated females and cultured cleaved to the six- to eight-cell stage and stopped. Techniques and media used for fertilizing large numbers of Syrian and Chinese hamster ova in vitro will have to be modified to achieve the same degree of success in the Siberian hamster.

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. Stromal cells immediately adjacent to the implantation chamber began to enlarge and accumulate glycogen. By day 7 the mural trophoblast penetrated the luminal epithelium in discrete area. The trophoblast appeared to phagocytize uterine epithelial cells, although epithelium adjoining the points of penetration was normal. In other areas nascent apical protrusions from the uterine epithelium indented the surface of the trophoblast. The epiblast had enlarged and both visceral and parietal endoderm cells were present. The well-developed decidual cells were epithelioid and completely surrounded the implantation chamber. On day 8 the uterine epithelium had disappeared along the mural surface of the embryo. The embryonic cell mass was elongated and filled the yolk sac cavity. Reichert's membrane was well developed. The uterine epithelial basal lamina was largely disrupted, and the trophoblast was in direct contact with decidual cells. Primary and secondary giant trophoblast cells were present and in contact with extravasated maternal blood. The mural trophoblast formed channels in which blood cells were found in close proximity to Reichert's membrane. Decidual cells were in contact with capillary epithelium and in some cases formed part of the vessel wall. Structural changes occurring in the embryo and endometrium during implantation in the Chinese hamster are described for the first time in this report and are compared to those described for some other myomorph rodents.

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. This group of mice had the lowest number of spermatozoa in the cauda epididymidis (3.2 +/- 0.4 x 10(5)/mg tissue) with fewer motile spermatozoa (22.3 +/- 5.1%) than younger males. The percentage of spermatozoa retaining their acrosome after 3 h in culture was higher in aged males which had not mated when compared to younger males that had mated. After 4 h in culture, however, the number of spermatozoa that had lost their acrosome was almost identical in the two groups. Superovulated mice which were artificially inseminated with spermatozoa from 25-month-old mice that had not mated did not become pregnant. Testosterone concentrations were lowest in aged mice not mating. These concentrations may explain the poor behavioural response of these males, but whether they account for the inability of spermatozoa to fertilize ova in vitro or in vivo after artificial insemination is not known.

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.c.), maintained pregnancy, suggesting that the sterility of these animals is due to inadequate luteal function. In ovariectomized female transgenic mice, median eminence (ME) turnover of dopamine (DA) was increased, and plasma prolactin (PRL) levels were reduced, presumably because of the known lactogenic activity of hGH in rodents. From these observations we suspected that either 1) the corpora lutea of these animals are unresponsive to lactogenic hormones, or 2) hGH by stimulating tuberoinfundibular dopaminergic (TIDA) neurons interferes with the increase in PRL release that normally follows mating and this, in turn, leads to luteal failure. To distinguish between these possibilities, transgenic females were treated with PRL-secreting ectopic pituitary transplants from normal females of the same strain on day 1 p.c. Eight of ten treated females became pregnant and delivered litters. We conclude that infertility of transgenic female mice with hGH expression is due to activation of the TIDA system, suppression of endogenous PRL release, and luteal deficiency.

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. When early embryos that developed into morulae and early blastocyts in culture were transferred to surrogate females, eight normal young were born.

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. There was no evidence of aneuploidy in 10-day-old embryos sired from males of either age group. Aged males that failed to mate had lower body weight, a lower hematocrit, hypertrophied adrenal glands and seminal vesicles, decreased fructose levels in seminal vesicle fluid, atrophied testes with fewer sperm that were less motile, lower testosterone levels, and a greater percentage of degenerating epithelium lining seminiferous tubules. The latter group of aged mice, while appearing and acting as vigorous as aged mice that had mated, may have been experiencing disease processes associated with aging which subsequently impaired reproduction.

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. Animals with pituitary grafts had markedly increased plasma concentrations of prolactin, LH and FSH and enlarged seminal vesicles, whereas testicular and pituitary weights were not affected. Content of LHRH receptors and activity of aromatase in the pituitary, as well as dopamine-beta-hydroxylase activity in the hypothalamus were nearly identical in pituitary-grafted and sham-operated males. Biosynthesis of dopamine and turnover of noradrenaline in the median eminence were significantly increased in grafted males. We suggest that the increase in the activity of hypothalamic noradrenergic neurones may mediate stimulatory action of hyperprolactinaemia on LH and FSH release in the mouse. Comparison of these results with those obtained previously in the rat suggests that species differences in the effects of prolactin on gonadotrophin release may be related to its divergent effects on noradrenaline turnover.

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. Tfm/y mice were also characterized by significantly elevated circulating LH, FSH and PRL levels. Administration of hCG decreased testicular LH-R concentration in little (lit/lit) mice, whereas it had no effect in hypothyroid (hyt/hyt) and normal mice. Treatment with hCG elevated plasma T levels in all animals, but this increase was smaller in lit/lit than in Lit/- mice, while being greater in hyt/hyt than in Hyt/- mice. The present results suggest that the Tfm locus in the mouse is involved in the regulation of testicular LH-R. The only effect of GH deficiency on the parameters studied is on hCG-stimulated testicular steroidogenesis. The lack of negative autoregulation of LH-R by hCG in hyt/hyt mice may indicate a more active testicular LH-R metabolism, perhaps as a consequence of the chronic elevation of plasma TSH levels.

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 10.00, 16.00 and 18.00 h; LD 14:10; lights on at 05.00 h CST) at a dosage of 5 mEq/kg b. wt. led to a significant (P less than 0.01) suppression of the LH surge that normally occurs in the evening of proestrus at 21.00 h. Chronic administration of lithium, on the other hand, resulted in a complete disruption in the regularity of the estrous cycle. This was characterized by an increasing number of mice showing a continuous diestrous vaginal smear during the first week of exposure to lithium, after which all of the lithium-treated mice completely stopped cycling and entered into constant diestrus. These results represent for the first time that lithium has significant adverse effects on the reproductive function in the female, especially in regard to the proestrous LH surge and estrous cyclicity in mice. Since these adverse effects were manifested under conditions when plasma lithium concentrations were within or around the therapeutic range, our results provide important conceptual information concerning possible adverse effects of lithium on the reproductive function in the human female.

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. However, 72 h after injection of intermediate doses of hCG, a decrease in hCG binding also was observed in diabetic mice. Plasma testosterone was elevated 24 h after hCG injection in all types of mice studied, but the increase in diabetic mice was smaller than in normal animals. However, 72 h after treatment with hCG, plasma testosterone was still elevated in diabetic mice, but not in normal males. In vitro, hCG stimulated testicular testosterone synthesis in all groups of mice, but the observed increase was smaller in diabetic and obese than in normal animals. Plasma LH levels were higher in diabetic than in normal mice, whereas plasma FSH and prolactin levels were lower in obese mice than in normal animals. All parameters (i.e., LH receptors and circulating hormone levels) measured in yellow (Ay/a) mice were similar to those in normal (a/a) mice. The present study indicates that in these models for noninsulin-dependent diabetes, the testicular metabolism of LH receptors and capacity to secrete steroids is altered.

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. Four study groups were established; (1) Left orchiectomy only, (2) sham surgery (scrotal incision), (3) 720 degrees left testicular torsion with left orchiectomy 24 hours later, (4) 720 degrees torsion of left testicle with detorsion after 24 hours. The initial procedure was performed at 1 month of age with subsequent biopsies of the contralateral testicle at 1 week, 1 month, and 6 months after the initial procedure. Testicular tissue was examined for immunofluorescent activity using fluorescent labeled goat anti-hamster IgG. Positive controls were established by rabbit immunization (rabbit anti-hamster immunoglobulin) which was subsequently combined with fluorescent labeled goat antirabbit IgG. There was no appreciable difference in immunologic activity between control and experimental animals. Representative sections were examined histologically and no tubular damage was demonstrated and active spermatogenesis was noted at 6 months in all groups. We believe that our results support the premise that testicular torsion in the prepubertal period has no effect on the contralateral testicle.

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%. Some of the fetuses derived from matings of the above mice were dissociated and their cells prepared for chromosomal smears. No evidence of aneuploidy or mosaicism was found in fetuses derived from ovaries of young or aged mice. Aged ovaries, transferred to either young or aged recipients, were found to have fewer developing follicles and lower weight, which was most apparent in recipients that failed to mate or to get pregnant. Concentrations of luteinizing hormone, follicle-stimulating hormone (FSH), and prolactin in plasma from each of the pregnant recipients were analyzed by radioimmunoassay. The only statistical differences found between the transfer groups occurred in FSH concentrations. Plasma FSH was markedly elevated (P less than 0.005) in young recipients with ovaries transplanted from aged donors, in comparison to young recipients with ovaries from young donors. These data indicate that the aging ovary and uterus play a secondary role in reproductive failure and that the aging hypothalamic-hypophyseal complex is primarily responsible for the loss of fecundity in older female C57BL/6J mice.