Estradiol-induced adult anovulatory syndrome in female C57BL/6J mice: age-like neuroendocrine, but not ovarian, impairments

Long-term effects of elevated plasma estradiol (E2) on ovarian and neuroendocrine functions were examined in 4-month-old cycling female C57BL/6J mice injected s.c. with 0.2 or 0.05 mg estradiol valerate (EV), or oil. Within 7 days, EV-injected mice became permanently acyclic, exhibiting the persistent vaginal cornification (PVC) characteristic of reproductive senescence in rodents. Four months after injection, ovaries from EV-injected mice exhibited no corpora lutea, but ovulated in response to an injection of human chorionic gonadotropin (hCG) (as do older, spontaneously PVC mice). When grafted into young mice, ovaries from EV-injected mice supported as many estrous cycles as ovaries from oil-injected controls. EV did not alter the suppression of luteinizing hormone (LH) by E2, LH response to injected LH releasing hormone (LHRH), or plasma prolactin (Prl). However, EV-injected mice exhibited impairments in LH regulation similar to those seen in old, acyclic mice. Plasma LH 30 days after ovariectomy was 40% lower, and E2-induced LH surges were 60% lower, in EV-injected mice versus controls. Furthermore, EV-injected mice were unable to support estrous cycles given young ovarian grafts, in contrast to controls. Effects of sustained but physiological levels (15-20 pg/ml) of plasma E2, were examined in intact cycling mice given sham or E2 implants. Six weeks after implantation, the implants were removed; only 50% of the E2-implanted mice subsequently exhibited estrous cycles, compared with 100% of sham-implanted controls. Furthermore, those E2-implanted mice which did cycle had fewer cycles than controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Delayed anovulatory syndrome induced by estradiol in female C57BL/6J mice: age-like neuroendocrine, but not ovarian, impairments

These studies describe induction of a delayed anovulatory syndrome (DAS) by estradiol (E2) in female C57BL/6J mice. Six days after birth, female mice were injected s.c. with 0.1 micrograms estradiol benzoate or oil. Over 90% of the oil-injected controls exhibited estrous cycles from 2 to 9 mo of age. In contrast, 60% of the E2-injected mice exhibited estrous cycles at 2 mo of age but were acyclic by 9 mo; these mice were considered to have exhibited a DAS, and had longer cycles than controls. At 12 mo, ovarian impairments were assessed by examining 1) ovulation after s.c. injection of 5 IU human chorionic gonadotropin (hCG), and 2) estrous cycles after grafting into young (3-mo-old) hosts. Simultaneously, neuroendocrine impairments were assessed by examining 1) the surge of luteinizing hormone (LH) induced by E2 implants after ovariectomy, and 2) estrous cycles after receiving ovarian grafts from 3-mo-old mice. Ovaries from DAS and control mice ovulated equally in response to hCG. Ovaries from DAS mice grafted into young ovariectomized hosts supported 30% more cycles, of shorter period, compared with ovaries from control donors. However, the E2-induced LH surge was 50% smaller in DAS mice than in controls. Ovariectomized DAS hosts with ovarian grafts from young mice supported 70% fewer estrous cycles, of longer period, compared with ovariectomized control hosts with young grafts. We conclude that the E2-induced DAS in female mice is not due to ovarian impairments, but seems to result from neuroendocrine impairments.     

Prolongation and cessation of estrous cycles in aging C57BL/6J mice are differentially regulated events

The relative contributions of ovarian failure and hypothalamic-pituitary dysfunction to the prolongation and cessation of estrous cycles were assessed by measuring the ability of acutely ovariectomized (OVX) middle-aged (12 mo) mice to cycle after receiving grafts (under the renal capsule) of ovaries from young (2 mo) mice. The potentially disruptive effect of the acyclic state on the cycling response to grafted, young ovaries was avoided restricting grafting to middle-aged hosts that were still cycling. The effect of chronic exposure to ovarian secretions before the cessation of cyclicity on age-related hypothalamic-pituitary dysfunction was also assessed. The cycling ability of long-term OVX middle-aged mice (i.e., OVX at 3 mo) bearing grafts of young ovaries was compared to that of age-matched acutely OVX controls. Grafted young ovaries extended the cycling lifespan of acutely OVX middle-aged hosts by 60%. The length of this extended cycling lifespan, however, was only 80% of that achieved by young hosts bearing grafts of young ovaries. Young ovaries in middle-aged mice markedly lowered the incidence of long cycles (greater than 5 days), shifting the modal cycle length to 5 days. However, young ovaries in middle-aged mice failed to increase the incidence of 4-day cycles, the modal cycle of young controls. Middle-aged ovaries grafted into young hosts lengthened their cycles and shortened their cycling lifespan to middle-aged values. Long-term ovariectomy failed to increase the cycling lifespan of middle-aged hosts bearing grafts of young ovaries beyond that achieved in acutely OVX mice. Long-term ovariectomy did shorten the modal cycle length of middle-aged mice to 4 days, although the duration of 4-day cycling was only one-third (2 mo) that of young controls. These results indicate that the relative contributions of ovarian and neuroendocrine factors to three major events of reproductive aging vary with each event. Whereas the hypothalamic-pituitary unit appears to play an important role in the initial shift from 4- to 5-day cycles, the aging ovary plays the major role in the subsequent shift to longer cycles and in the ultimate cessation of cyclicity. Although chronic exposure to ovarian secretions during the period of cyclicity does not play a major role in the cessation of cyclicity, it appears to contribute to the hypothalamic-pituitary changes responsible for the initial shift from 4- to 5-day cycles.     

Oral administration of estradiol to young C57BL/6J mice induces age-like neuroendocrine dysfunctions in the regulation of estrous cycles

Exogenous estradiol (E2) can accelerate the onset of acyclicity and other age-related neuroendocrine changes in rodents. The present study demonstrates that chronic oral administration of E2 (850 micrograms/kg body wt/day) induces premature acyclicity in intact C57BL/6J mice. After 6 wk of E2, mice regained cyclicity but ceased cycling prematurely, whereas 12 wk of E2 caused permanent acyclicity in all mice. The acyclicity after 12 wk of E2 was not reversed by ovarian replacement from young donors, which implies extra-ovarian (neuroendocrine) lesions. The above studies with intact mice can not identify the contributions from exogenous E2 and endogenous ovarian sections and the possible impact of oral E2 on the ovary. Therefore, mice were ovariectomized (OVX) to remove ovarian contributions, treated for 12 wk with oral E2, and then were given young ovarian grafts and assayed for neuroendocrine functions. Approximately 50% of the E2-treated and grafted mice were permanently acyclic, whereas controls cycled well. Thus, oral E2 causes irreversible neuroendocrine damage. However, the presence of the ovary during E2 treatment increases the loss of cyclicity, implying a dose effect. We conclude that the induction of acyclicity is dependent on the dose and duration of E2 exposure.     

Deletion of self-reactive T cells in nude mice grafted with neonatal allogeneic thymus

The cellular basis of tolerance induction has been investigated in BALB/c(H-2d, thy 1.2, M1s1b2a) nude mice grafted with thymus of neonatal AKR/J mice(H-2k,Thy1.1,M1s1a2b). The spleen cells from nude mice grafted with AKR/J thymus showed a significantly decreased level of primary cytotoxic T cell response when stimulated with AKR/J cells, although these cells lysed well target cells of a third party C57BL/6 when stimulated with C57BL/6 cells. Consistent with CTL responses, T cells bearing V beta 6, that is important for recognizing M1s1a-encoded products of the thymic phenotype, were virtually abolished in the spleen and lymph node cells of nude mice 8 wk after grafting with AKR/J thymus. However, a substantial number of V beta 6-bearing T cells were detected in the peripheral organs of nude mice 23 wk after grafting with AKR/J thymus and in those of nude mice grafted with AKR/J fetal thymus depleted of macrophages/dendritic cells by incubating with 2'-deoxyguanosine in vitro before grafting. On the other hand, T cells bearing V beta 3, which are selectively related to M1s2a-encoded products of the host phenotype, were expressed neither on the peripheral T cells of nude mice grafted with AKR/J thymus at any stage after grafting nor on those of nude mice grafted with 2'-deoxyguanosine-treated AKR/J thymus. These data suggested that both V beta 6 and V beta 3 T cells were eliminated in the thymus of nude mice grafted with AKR/J thymus, presumably on the basis of interaction with both of graft-derived persisting and host-derived hemopoietic cells in the thymus and that thymic epithelium appears to have little capacity to eliminate T cells reactive to minor lymphocyte stimulating-encoded products.     

Sequential appearance of host-derived T cell subsets during differentiation in nude mice grafted with rat fetal thymus

To elucidate the abnormality of T cell differentiation in nude mice grafted with rat fetal thymus that develop multiple-organ-localized autoimmune diseases, we examined sequential appearance of T cell subsets and expression of TCR genes in BALB/c nude mice after grafting with fetal F344 rat thymus. We observed progressive expression of TCR gamma/delta-alpha/beta genes in the lymph node (LN) cells from 8 to 12 wk after grafting. An appreciable number of CD4+ T cells but few CD8+ T cells were detected in the LN at 8 wk after grafting. CD8+ T cells increased slowly in number by 12 wk after grafting but remained at a low level in comparison with those in nude mice 12 wk after grafting with BALB/c thymus. In correlation with an increase in the number of T cells expressing TCR alpha/beta genes, alloreactivity as assessed by MLR was increased to a normal level. However, CTL activity against alloantigens remained at a low level in the LN cells at 12 wk. At this stage, organ-specific autoimmune diseases and a high level of anti-DNA autoantibodies were detected. In these mice host-reactive T cells such as V beta 3- or V beta 11-bearing T cells were virtually eliminated in the peripheral mature T cell pool, whereas T cells maturing in the fetal rat thymus significantly proliferated in response to donor-rat stimulator cells. These results suggest that the development of the autoimmune diseases may be ascribed to an impaired maturation of CD8+ T cells but not to failure in clonal elimination of host-reactive T cells in nude mice grafted with rat thymus.     

Spermatogenesis and germ cell transgene expression in xenografted bovine testicular tissue

The present study was conducted to evaluate the development of spermatogenesis and utility of using electroporation to stably transfect germ cells with the beta-galactosidase gene in neonatal bovine testicular tissue ectopically xenografted onto the backs of recipient nude mice. Bull testicular tissue from 4-wk donor calves, which contains a germ cell population consisting solely of gonocytes or undifferentiated spermatogonia, was grafted onto the backs of castrated adult recipient nude mice. Testicular grafts significantly increased in weight throughout the grafting period and the timing of germ cell differentiation in grafted tissue was consistent with postnatal testis development in vivo relative to the bull. Seminiferous tubule diameter also significantly increased with advancing time after grafting. At 1 wk after grafting, gonocytes in the seminiferous cords completed migration to the basement membrane and differentiated germ cell types could be observed 24 wk after grafting. The presence of elongating spermatids at 24 wk confirmed that germ cell differentiation occurred in the bovine tissue. Leydig cells in the grafted bovine tissue were also capable of producing testosterone in the castrated recipient mice from 4 wk to 24 wk after grafting at concentrations that were similar to levels in intact, nongrafted control mice. The testicular tissue that had been electroporated with a beta-galactosidase expression vector showed tubule-specific transgene expression 24 wk after grafting. Histological analysis showed that transgene expression was present in both Sertoli and differentiated germ cells but not in interstitial cells. The system reported here has the potential to be used for generation of transgenic bovine spermatozoa.     

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.     

Establishment of spermatogenesis in neonatal bovine testicular tissue following ectopic xenografting varies with donor age

Ectopic testicular xenografting can be used to investigate spermatogenesis and as an alternative means for generating transgenic spermatozoa in many species. Improving the efficiency of spermatogenesis in xenografted testicular tissue will aid in the application of using this approach. The present study was conducted to evaluate age-related differences in the establishment of spermatogenesis in grafted testicular tissue from bulls between 2 and 16 wk of life. Testicular tissue was ectopically xenografted under the skin on the backs of castrated nude mice and subsequently evaluated for growth, testosterone production, and establishment of spermatogenesis 24 wk after grafting. The greatest weight increases occurred in donor tissue from calves of the ages 2, 4, and 8 wk compared with the ages of 12 and 16 wk. Recipient mouse serum testosterone concentration was at normal physiological levels 24 wk after grafting and no significant differences were detected between recipients grafted with testicular tissue from bull calves of different ages. The development of germ cells to elongated spermatids were observed in seminiferous tubules of grafts from donor calves of the ages 4, 8, 12, and 16 wk but not observed in grafts from 2-wk donors, which contained round spermatids as the most advanced germ cell stage. Grafts from 8-wk donors contained a significantly higher (10-fold) average percentage of seminiferous tubules with elongated spermatids than all other donor ages. These data demonstrate differences in the ability of testicular tissue from donor animals of different ages to establish spermatogenesis following ectopic testicular xenografting.     

Rabbit trochlear model of osteochondral allograft transplantation

Allografting and autografting of osteochondral tissues is a promising strategy to treat articular cartilage lesions in damaged joints. We developed a new model of fresh osteochondral allografting using the entire rabbit trochlea. The objective of the current study was to demonstrate that this model would achieve reproducible graft-host healing and maintain normal articular cartilage histologic, immunolocalization, and biochemical characteristics after transplantation under diverse storage and transplantation conditions. New Zealand white (n = 8) and Dutch belted (n = 8) rabbits underwent a 2-stage transplantation operation using osteochondral grafts that had been stored for 2 or 4 wk. Trochlear grafts harvested from the left knee were transplanted to the right knee as either autografts or allografts. Grafts were fixed with 22-gauge steel wire or 3-0 nylon suture. Rabbits were euthanized for evaluation at 1, 2, 4, 6, and 12 wk after transplantation. All grafts that remained in vivo for at least 4 wk demonstrated 100% interface healing by microCT. Trabecular bridging was present at the host-graft interface starting at 2 wk after transplantation, with no significant difference in cartilage histology between the various groups. The combined histology scores indicated minimal evidence of osteoarthritis. Immunostaining revealed that superficial zone protein was localized at the surface of all transplants. The rabbit trochlear model met our criteria for a successful model in regard to the ease of the procedure, low rate of surgical complications, relatively large articular cartilage surface area, and amount of host-graft bone interface available for analysis.     

Age of ovary determines remaining life expectancy in old ovariectomized mice

We investigated the capacity of young ovaries, transplanted into old ovariectomized CBA mice, to improve remaining life expectancy of the hosts. Donor females were sexually mature 2-month-olds; recipients were prepubertally ovariectomized at 3 weeks and received transplants at 5, 8 or 11 months of age. Relative to ovariectomized control females, life expectancy at 11 months was increased by 60% in 11-month recipient females and by 40% relative to intact control females. Only 20% of the 11-month transplant females died in the 300-day period following ovarian transplantation, whereas nearly 65% of the ovariectomized control females died during this same period. The 11-month-old recipient females resumed oestrus and continued to cycle up to several months beyond the age of control female reproductive senescence. Across the three recipient age groups, transplantation of young ovaries increased life expectancy in proportion to the relative youth of the ovary. Our results relate to recent findings on the gonadal input upon aging in Caenorhabditis elegans and may suggest how the mammalian gonad, including that of humans, could regulate aging and determine longevity.     

Transfer of granulomatous inflammation with nonviable preparations of schistosome granulomas in naive mice

Hepatic granulomas of euthymic (nu/+) mice infected with Schistosoma mansoni were freeze-dried or freeze-thawed 3 times and transplanted subcutaneously into naive nu/+ and athymic (nu/nu) mice. The grafted sites, studied histologically, showed formation of organized granulomas in nu/+ mice similar to donor granulomas as observed after grafting of freshly isolated granulomas. On the other hand, in nu/nu mice, the nonviable transplants elicited small and disorganized granulomas, like hepatic granulomas in nu/nu mice with schistosomiasis, but different from fresh nu/+ transplants in nu/nu skin. The findings indicate viable cells are not required for transfer of granulomatous reactions, but T cells are needed for full expression.     

The response of transplants of cultured fetal mouse ovaries in kidneys of ovariectomized adult mice

Whole ovaries from 16-day fetal mice were cultured for 6 to 20 days and then transplanted to the kidneys of ovariectomized adult mice where they remained for one to four weeks. After three weeks in the host's kidneys, many follicles developed within the transplants and became vesiculated. Many of the oocytes within these follicles had formed the first metaphase spindle of meiosis and several had completed the first polar body. Host mice bearing transplants that contained vesiculated follicles showed uterine stimulation and keratinization of their vaginae. However, ovaries that had been in culture for more than ten days before transplantation showed a limited response to the gonadotropins and never matured sufficiently to stimulate the host's reproductive tract. No ovulations occurred in any of the transplants.     

Ovarian reproductive function after exposure to diethylstilbestrol in neonatal life

Inbred and random-bred NMRI mice were treated with diethylstilbestrol (DES, 5 micrograms per day) or vehicle (olive oil) on Days 1-5 after birth. At the age of 8 wk, females were treated with saline or eCG and hCG to induce ovulation. Ova never occurred in the ampulla of the uterine tube of saline-treated, DES-treated females when these mice were not mated. After gonadotropin treatment, ova were found in the ampulla of all olive oil-treated females and in approximately 80% of DES-treated females. The number of ovulated ova was similar in both groups. Twenty percent of gonadotropin-treated, DES-treated females had ova in the ampulla and a vaginal plug after being caged with males but none became pregnant. Ovaries from inbred control or DES-treated females were grafted to the ovarian bursa of control or DES-treated ovariectomized hosts. DES-treated hosts, carrying control or DES-exposed ovaries, never became pregnant. Control females, with control ovaries or DES-exposed ovaries, became pregnant; pregnancy rate and litter size were similar for control mice regardless of whether they were supporting DES-exposed or control ovaries. Oocytes from ovaries exposed neonatally to DES can thus give rise to apparently normal offspring. The results also indicate DES-induced nonovarian disturbances, e.g. tubal and/or endometrial function, both of which are important for fertility. In the grafting experiments, a high mortality rate was found in inbred DES-exposed females caged with males. All deaths were associated with vaginal concrements (vaginal stones) and intestinal complications.     

Effects of hyperprolactinemia on activities of 17-hydroxylase, 17 beta-ol-dehydrogenase and 5 alpha-reductase in neonatally grafted and host testes in mice

Male and female (WB X C57BL/6)F1 hybrid mice were used. Two pituitaries from 60-80-day-old female mice were grafted under the capsule of the left kidney of 60-80-day-old male mice. One week after grafting, 2 testes from neonatal mice were grafted under the capsule of the right kidney of the grafted mice and 70-90-day-old intact male mice. The grafted and host testes, in groups of 10-26, were removed 15, 30, 40, 60 and 120 days after transplantation of the neonatal testes. Testicular homogenates were incubated with [3H]progesterone or [14C]4-androstene-3,17-dione, and enzyme activities per g tissue were estimated. Significantly elevated prolactin levels, slightly lower LH levels and normal testosterone levels were found in the mice with pituitary grafts, compared with those in the mice without pituitary grafts. Activities of 17-hydroxylase and 17 beta-ol-dehydrogenase increased clearly with age in the grafted testes in the mice without pituitary grafts, though the increases were inhibited significantly by the pituitary grafts. However, the pituitary grafts had no significant effect on activities of 17-hydroxylase and 17 beta-ol-dehydrogenase in the host testes under similar gonadotrophic stimulation. 5 alpha-Reductase activities in the grafted and host testes were unaffected by the pituitary grafts. These results show that hyperprolactinemia may directly inhibit increases in activities of 17-hydroxylase and 17 beta-ol-dehydrogenase with testicular age in neonatally grafted testes in mice.     

Age-related changes in ovarian responsiveness to gonadotropins in normal and neonatally estrogenized mice

Young ovariectomized mice were transplanted with ovaries obtained from either neonatally estrogenized or normal mice at different ages. Cyclic estrus ensued in 71% of the mice receiving ovarian grafts from 3-month-old normal donors. If donors were 12, 15 and 20 months old, cyclic estrus took place in 15, 10 and 0% of the recipients, respectively. By contrast, after transplantation of ovaries from neonatally estrogenized mice, and 3, 12 or 15 months, cyclic estrus occurred in about 42-48% of the recipients regardless of the age of donors. Three of 17 recipients receiving ovarian grafts from 20-month-old neonatally estrogenized donors still showed cyclic estrus. Therefore, in neonatally estrogenized mice, decline of ovarian responsiveness to circulating gonadotropins appears to be inhibited or delayed until at least 15 months of age.     

Spontaneous regeneration of older dystrophic muscle does not reflect its regenerative capacity

Young dystrophic (dy) murine muscle is capable of "spontaneous" regeneration (i.e., regeneration in the absence of external trauma); however, by the time the mice are 8 weeks old, this regeneration ceases. It has been suggested that the cessation of regeneration in dystrophic muscle may be due to exhaustion of the mitotic capability of myosatellite cells during the early stages of the disease. To test this hypothesis, orthotopic transplantation of bupivacaine treated, whole extensor digitorum longus muscles has been performed on 14 to 16-week-old 129 ReJ/++ and 129 ReJ/dydy mice. The grafted dystrophic muscle is able to produce and maintain for 100 days post-transplantation 356 +/- 22 myofibers, a number similar to that found in age-matched dystrophic muscle. The ability of old dystrophic muscle to regenerate subsequent to extreme trauma indicates that the cessation of "spontaneous" regeneration is due to factor(s) other than the exhaustion of mitotic capability of myosatellite cells. Moreover, there is no significant difference in myosatellite cell frequencies between grafted normal and dystrophic muscles (100 days post-transplantation). Myosatellite cell frequencies in grafted muscles are similar to those in age-matched, untraumatized muscles. While grafting of young dystrophic muscle modifies the phenotypic expression of histopathological changes usually associated with murine dystrophy, grafts of older dystrophic muscle show extensive connective-tissue infiltration and significantly fewer myofibers than do grafts of age-matched normal muscle. As early as 14 days post-transplantation, it is possible to distinguish between grafts of old, normal and dystrophic muscles. It is suggested that the connective tissue stroma, present in the dystrophic muscle at the time of transplantation, may survive the grafting procedure.     

Transplantation of young ovaries restored cardioprotective influence in postreproductive-aged mice

The female cardioprotective advantage, present in mammals of a reproductively competent age, is lost during the transition to a postreproductive state. The role of reproductive hormones in this transition is most evident in women with premature ovarian failure, where reduced estrogen production has been associated with an increased incidence of early death from cardiovascular disease. Previously, we reported that postreproductive-aged mice that received young ovaries displayed an increased life span. Subsequent histopathological analysis suggested the presence of a cardioprotective effect associated with the restoration of ovarian influence. This restoration in postreproductive-aged mice produced a sharp decrease in evidence of significant cardiomyopathy at death, compared with sham-transplanted mice (36.0% vs. 73.3%, respectively). Within the intact transplant group, evidence of cardiomyopathy at death was decreased in mice that were reproductively cycling at the time of transplant, compared with acyclic mice (26.7% vs. 50.0%, respectively). This observation reflects the importance of timing in restoration of ovarian influence in this study. Transplantation of young ovaries to intact, postreproductive-aged female mice provided significant, long-term restoration of a cardioprotective benefit, similar to that previously present during a reproductively competent age. In these mice, restoration of ovarian influence through ovarian transplantation may, in effect, have postponed the advance of age-associated cardiomyopathy to a point where the disease did not reach a clinically relevant threshold during the lifetime of the recipients. These results offer support for previous clinical observations suggesting that hormone replacement therapy can produce divergent results if initiated during the perimenopausal period, compared with the postmenopausal ages.     

Compensation for an increase in body fat caused by donor transplants into mice

Rodents tend to compensate for experimental obesity in which both adipocyte size and number are increased. In contrast, it was recently reported that Siberian hamsters do not compensate for dorsal subcutaneous transplants of fat, which increase body fat without changing the size of adipocytes. In the first experiment described here we tested whether mice changed the size of their endogenous fat stores 2 or 5 wk after donor fat was added as subcutaneous transplants. Each epididymal fat pad from donor mice was cut in half and placed ventrally in recipient mice, increasing body fat by approximately 10%. After 2 wk, there was no effect of the transplants on the size of endogenous fat depots or the size of adipocytes in epididymal fat depots. There was a substantial decrease in mass and adipocyte size in transplanted fat. Five weeks after surgery the endogenous epididymal and retroperitoneal fat depots of recipient mice were significantly decreased, serum leptin was reduced, and the size of adipocytes in endogenous epididymal fat was significantly reduced, although cell number had not changed. The size of transplanted cells was the same as at 2 wk. In a second experiment, epididymal fat was placed as either dorsal or ventral subcutaneous fat transplants. Five weeks after surgery the endogenous fat depots were decreased in all recipient mice but none of the differences reached statistical significance. These results suggest that mice have mechanisms to maintain total body fat mass that respond to an increase in the number of fat cells present.     

冻融小鼠卵巢移植后细胞凋亡及血管内皮生长因子表达的变化及意义研究

目的:探讨冻融小鼠卵巢同种异体移植后细胞凋亡及血管内皮生长因子表达的变化及意义。方法:收集C57BL/6j雌鼠和BALB/c雄鼠杂交后F1代4周龄小鼠卵巢,慢冻速融后移植至杂交后F1代8～12周雄鼠的肾被膜下,分别于移植后1d(24h)、2d(48h)和7d回收移植物,将冻融以及移植后不同时间段的卵巢组织进行HE染色、全卵巢卵泡计数、电镜观察、免疫组织化学分析细胞凋亡及RT-PCR检测VEGF基因表达。结果:冻融小鼠卵巢移植后随着时间的推移、各级卵泡数和卵泡存活率逐渐下降;移植后48h内细胞凋亡指数最高;电镜观察发现小鼠卵巢组织移植后损伤主要发生在移植后48h内;移植后VEGF的表达有上升的趋势,至第7d仍维持较高水平;移植后48hVEGF120mRNA和VEGF188mRNA水平明显升高(P0.05),至7d下降恢复至移植前水平,而VEGF164mRNA水平移植后无明显变化(P0.05)。结论:小鼠卵巢组织移植后48h内细胞凋亡最为严重,移植后引起大量卵泡的丢失;在移植后血管化的过程中VEGFmRNA表达量增加,VEGF120mRNA和VEGF188mRNA可能参与卵巢移植后早期血管化过程。