Kenneth G. Gould

A Longitudinal Study of Leptin During Development in the Male Rhesus Monkey: The Effect of Body Composition and Season on Circulating Leptin Levels

Abstract The objective of this study was to examine longitudinal changes in serum leptin concentrations during development and to correlate those changes with sexual development in male rhesus monkeys housed under natural environmental conditions. Blood samples were drawn from 8 control animals approximately every other month from 10 to 30 mo of age and thereafter monthly through 80 mo of age. Leptin levels declined through the juvenile period until the onset of puberty and were negatively correlated with body weight. Seven of the eight animals became sexually mature during the breeding season of their fourth year of life. Puberty was delayed in the other animal until the subsequent breeding season. There were no significant fluctuations in leptin levels prior to or in association with the pubertal rise in LH and testosterone (T) secretion. During the peripubertal period, levels of leptin varied between 2 and 3 ng/ml. The animal that exhibited delayed puberty had the lowest body weight and highest leptin levels during this period. With the achievement of sexual maturity, leptin levels varied seasonally, with peak levels in the late winter (Jan–Mar) and a nadir in the late summer (Aug–Sept). A late winter rise in leptin was also evident in most of the animals during Years 2 and 3, but not during Year 4. In the fall of Years 5 and 6, the seasonal rise in leptin concentrations lagged 3–4 mo behind the seasonal increase in LH and T. In the fall of Year 5, but not thereafter, leptin levels were positively related to percent body fat and negatively correlated with lean body mass. The data do not support the hypothesis that increasing leptin concentrations trigger the onset of puberty in the male rhesus monkey. During the juvenile period and after sexual maturation, but not during the peripubertal period, leptin secretion varied with season in the animals; but the environmental factors that cue or drive this rhythm remain to be determined.

Menstrual Cycles Continue into Advanced Old Age in the Common Chimpanzee (Pan troglodytes)

Abstract A long postreproductive lifespan may distinguish women from all other female primates. A long-held consensus among reproductive scientists has been that our closest living relative, the chimpanzee (Pan troglodytes), experiences menstrual cycles until death. However, a recent study of biannual assessments of gonadotropins, but lacking observations of menstruation, concluded that menopause occurs in chimpanzees between 35 and 40 yr of age. A separate report, but on wild chimpanzees, documented fertility through the 40–44 age range in all populations studied. These contradictory reports pose questions about differences between wild and captive populations and about assessments of menopause. The present study revisits this controversy by analyzing longitudinal records of anogenital swelling and menstruation in 89 female chimpanzees aged 6 to 59 yr (n = 2386 records on cycle length), monitored for most of their adult lives at the Yerkes National Primate Research Center. Twenty of these chimpanzees were observed past 39 yr of age; all 20 displayed menstrual cycles beyond this age, as confirmed by at least two observations of menses about 35 days apart. Three of these were older than 50 yr and still displayed menstrual cycles. Only the oldest female appeared menopausal, with cycles of anogenital swelling ceasing 2 yr prior to her death at age 59. Random-effects statistical modeling reveals a slight decrease in cycle length until 20 yr of age and a slight lengthening thereafter. Mean cycle length across the lifespan is 35.4 days. Our findings, based upon actual observations of menstrual cycles, suggest that menopause in the chimpanzee is rare, occurring near the end of the lifespan.

Permeability of the rhesus monkey oocyte membrane to water and common cryoprotectants

Successful cryopreservation of oocytes of the rhesus monkey (Macaca mulatta) would facilitate the use of this valuable animal model in research on reproduction and development, while providing a stepping stone towards human oocyte cryopreservation and the conservation of endangered primate species. To enable rational design of cryopreservation techniques for rhesus monkey oocytes, we have determined their osmotic and permeability characteristics in the presence of dimethylsulfoxide (DMSO), ethylene glycol (EG), and propylene glycol (PROH), three widely used cryoprotectants. Using nonlinear regression to fit a membrane transport model to measurements of dynamic cell volume changes, we estimated the hydraulic conductivity (Lp) and cryoprotectant permeability (Ps) of mature and immature oocytes at 23.5°C. Mature oocyte membranes were most permeable to PROH (Psu2009=u20090.56u2009±u20090.05 µm/sec) and least permeable to DMSO (Psu2009=u20090.24u2009±u20090.02 µm/sec); the permeability to EG was 0.34u2009±u20090.07 µm/sec. In the absence of penetrating cryoprotectants, mature oocytes had Lpu2009=u20090.55u2009±u20090.05 µm/min/atm, whereas the hydraulic conductivity increased to 1.01u2009±u20090.10, 0.61u2009±u20090.07, or 0.86u2009±u20090.06 µm/min/atm when mature oocytes were exposed to DMSO, EG, or PROH, respectively. The osmotically inactive volume (Vb) in mature oocytes was 19.7u2009±u20092.4% of the isotonic cell volume. The only statistically significant difference between mature and immature oocytes was a larger hydraulic conductivity in immature oocytes that were exposed to DMSO. The biophysical parameters measured in this study were used to demonstrate the design of cryoprotectant loading and dilution protocols by computer‐aided optimization. Mol. Reprod. Dev. 76: 321–333, 2009.

Acquisition of Fertilizing Capacity by Chimpanzee Sperm

Etude du potentiel fertilisant du sperme «active» de chimpanze. Cette etude sinteresse au sperme trouve dans differentes regions de lepididyme. Les tests sont effectues in vitro ou par le test de la zone libre de penetration du sperme chez le hamster

Reduced Growth Hormone Secretion Prolongs Puberty But Does Not Delay the Developmental Increase in Luteinizing Hormone in the Absence of Gonadal Negative Feedback

Abstract Previous studies have shown that the growth hormone (GH) axis is important for timing the later stages of puberty in female monkeys. However, it is not clear whether these growth-related signals are important for the initiation of puberty and early pubertal events. The present study, using female rhesus monkeys, used two approaches to answer this question. Experiment 1 tested the hypothesis that reduced GH secretion would blunt the rise in nocturnal LH secretion in young (17 mo; n = 7) but not older adolescent ovariectomized females (29 mo; n = 6). Reduced GH secretion was induced by treating females with the sustained release somatostatin analogue formulation, Sandostatin LAR (625 μg/kg). Morning (0900–0930 h) and evening (2200–2230 h) concentrations of bioactive LH were higher in older adolescent compared to young adolescent females. However, diurnal concentrations were not affected by the inhibition of GH secretion in either age group when compared to the placebo-treated, control condition. Experiment 2 tested the hypothesis that reduced GH secretion induced in young juvenile females would delay the initial increase in nocturnal LH secretion and subsequent early signs of puberty. In order to examine this hypothesis, puberty in control females (n = 7) was compared to those in which puberty had been experimentally arrested until a late adolescent age (29 mo) by the use of a depot GnRH analogue, Lupron (750 μg kg−1 mo−1; n = 7). Once the analogue treatment was discontinued, the progression of puberty was compared to a group treated in a similar fashion but made GH deficient by continuous treatment with Sandostatin LAR (n = 6). Puberty occurred as expected in control females with the initial rise in evening LH at 21 mo, menarche at 22 mo, and first ovulation at 30 mo. As expected, Lupron arrested reproductive maturation, but elevations in morning and evening LH and menarche occurred within 2 mo of the cessation of Lupron in both Lupron and Lupron-GH-suppressed females. In contrast, first ovulation was delayed significantly in the Lupron-GH-suppressed females (41 mo) compared to the Lupron-only females (36 mo). These data indicate that within this experimental model, reduced GH secretion does not perturb the early stages of puberty but supports previous observations that the GH axis is important for timing the later stages of puberty and attainment of fertility. Taken together, the data indicate that factors that reduce GH secretion may have a deleterious effect on the completion of puberty.

Effect of neonatal treatment with a gonadotropin releasing hormone antagonist on developmental changes in circulating lymphocyte subsets: a longitudinal study in male rhesus monkeys

We have examined changes in circulating lymphocyte subsets from the neonatal period until adulthood (4 months until 5.5 years of age) in male rhesus monkeys, and the impact of neonatal treatment with a GnRH antagonist (Ant) or Ant and androgen (Ant/And) on these parameters. Absolute numbers of lymphocytes, B cells, total T lymphocytes, and CD4+ T cells decreased, neutrophils increased, and CD8+ T cells did not change with age. WBC counts increased between 4 mo and 2 years of age and then fell to neonatal levels over the next two years. The decline of CD4 + T cells in association with stable CD8+ T cell levels resulted in an age-related decrease in the CD4+/CD8+ T cell ratio. At 4 months of age, WBCs, lymphocytes, total T cells, CD8+ T cells and B cells were lower in Ant- and Ant/And-treated animals compared to controls. With the exception of WBC counts, these values had normalized by 2 years of age. Reduced WBC levels in treated animals persisted through adulthood. CD4+ T cell levels tended to be lower in Ant-treated and higher in Ant/And-treated animals than in controls at 4 months of age. CD4+ T cells remained lower in Ant- than in Ant/And-treated animals at most ages. The higher CD4 + T cell counts in Ant/And-treated animals resulted in an elevated CD4 + /CD8 + T cell ratio that persisted until the onset of year 5. During years 5 and 6, seasonal fluctuations in WBCs and neutrophils were observed with counts being higher in the breeding (fall) than in the nonbreeding (summer) season. The data document that developmental changes in circulating immune cells in the rhesus monkey are qualitatively similar to those reported in humans, and provide further evidence that neonatal treatment of male rhesus monkeys with Ant or Ant/And may alter early programming of the immune system.

Germline transmission in transgenic Huntington’s disease monkeys

Transgenic nonhuman primate models are an increasingly popular model for neurologic and neurodegenerative disease because their brain functions and neural anatomies closely resemble those of humans. Transgenic Huntingtons disease monkeys (HD monkeys) developed clinical features similar to those seen in HD patients, making the monkeys suitable for a preclinical study of HD. However, until HD monkey colonies can be readily expanded, their use in preclinical studies will be limited. In the present study, we confirmed germline transmission of the mutant huntingtin (mHTT) transgene in both embryonic stem cells generated from three male HD monkey founders (F0) and in second-generation offspring (F1) produced via artificial insemination by using intrauterine insemination technique. A total of five offspring were produced from 15 females that were inseminated by intrauterine insemination using semen collected from the three HD founders (5 of 15, 33%). Thus far, sperm collected from the HD founder (rHD8) has led to two F1 transgenic HD monkeys with germline transmission rate at 100% (2 of 2). mHTT expression was confirmed by quantitative real-time polymerase chain reaction using skin fibroblasts from the F1 HD monkeys and induced pluripotent stem cells established from one of the F1 HD monkeys (rHD8-2). Here, we report the stable germline transmission and expression of the mHTT transgene in HD monkeys, which suggest possible expansion of HD monkey colonies for preclinical and biomedical research studies.