Photoperiod-driven changes in reproductive function in male rhesus monkeys.

Environmental lighting, which regulates seasonal breeding in many animal species, has not been examined as a regulator of reproduction or puberty in man or nonhuman primates. In this study we examined the effects of controlled alternating long and short daily photoperiods, independent of other environmental variables, on testicular size and function in rhesus monkeys. Sixteen animals, some pubertal, others prepubertal, were individually caged indoors in light-controlled rooms. They were subjected to a 32-week "year" with alternating 16-week cycles of long (16 h of light and 8 h of darkness) or short (8 h of light and 16 h of darkness) days. Animals were examined every 2 weeks over four 32-week "years". Body weight, testicular diameter, and testicular volume were measured, and blood was collected for testosterone and PRL determinations. We found that although short days did not trigger testicular development in prepubertal animals, testicular growth was markedly enhanced by short days in postpubertal animals, accompanied by increased plasma testosterone levels and reduced PRL levels. In long days, testes regressed, testosterone levels fell, and PRL levels rose. The periodicity of testicular size, as determined by spectral analysis, showed a strong signal at a cycle length of 31 +/- 13 weeks, but no signal at intervals close to the natural 52-week year, indicating that the observed periodicity is induced by the changes in lighting, rather than by circannual changes in other variables. These studies establish that changes in photo-period alone can modulate reproductive function in a higher primate and suggest that the onset of puberty is not directly driven by seasonal fluctuations in day length.

Dietary restriction and aging: the initiation of a primate study.

Juvenile (1 yr) and adult (3-5 yr) male rhesus monkeys (Macaca mulatta) and juvenile (1-4 yr) and adult (5-10 yr) male squirrel monkeys (Saimiri sciureus) were fed a diet at or near ad libitum levels based on recommended caloric intake for age and body weight or fed 30% less of the same diet with this restriction gradually introduced over a 3-mo period. Analysis of body weights among these respective control and experimental groups from the first year of the study indicated that the monkeys undergoing dietary restriction were gaining weight at a markedly slower rate compared to control values. Actual food intake among diet-restricted groups had been reduced 22-24% below control levels. Periodic analysis of hematology and blood chemistry measurements over the first year of the study detected few significant differences between control and experimental groups to indicate that diet restriction was not detrimental to general health. When values obtained from hematology and blood chemistry measurements of juvenile and adult groups (control and experimental groups combined) were compared to ad libitum fed old monkeys from each species (greater than 18 yr for rhesus; greater than 10 yr for squirrel monkeys), many significant age differences were noted. Among the largest and most consistent findings in both species were age-related decreases in concentrations of lymphocytes, serum glutamic oxalacetic transaminase, serum glutamic pyruvic transaminase, alkaline phosphatase, and phosphates as well as the albumin/globulin ratio and the blood urea nitrogen/creatinine ratio. Age-related increases in serum globulin and creatinine concentrations were also found. These parameters as well as many others being implemented in the study will be monitored further to determine if diet restriction affects the rate of development as well as aging as observed in numerous rodent studies applying such nutritional manipulations.

Differences in mineral metabolism among nonhuman primates receiving diets with only vitamin D3 or only vitamin D2.

We tested for differences in aspects of mineral metabolism during the administration of diets with only vitamin D3 or only vitamin D2 in four nonhuman anthropoid primate species [two catarrhini, Macaca fascicularis (crab-eating macaque) and Macaca mulatta (rhesus macaque), and two platyrrhini, Saimiri sciureus (squirrel monkey) and Aotus vociferans (night monkey)]. All four species maintained approximately 2- to 3-fold higher serum 25-hydroxyvitamin D (25OHD) level while receiving vitamin D3 than while receiving similar amounts of vitamin D2. Serum 25OHD in M. mulatta receiving the standard primate dietary supplement of vitamin D3 was high enough (360 +/- 60 vs. 70 +/- 25 nM in vitamin D-supplemented humans; P less than 0.0001) to suggest that this widely used level of vitamin D3 supplementation is excessive for some M. mulatta. Serum 24,25-dihydroxyvitamin D [24,25-(OH)2D] in A. vociferans was uniquely high [P less than 0.01; species mean, 19 +/- 5, 95 +/- 12, and 27 +/- 5 nM in groups receiving diets with 1.5 IU vitamin D3/g, 6.6 IU vitamin D3/g, and 15 IU vitamin D2/g, respectively; mean 24,25-(OH)2D from the other three species pooled across three diets was 7 +/- 5 nM]. We confirmed relative resistance to 1,25-(OH)2D in S. sciureus, manifested by osteomalacia and moderately high serum 1,25-(OH)2D. Serum 1,25-(OH)2D in S. sciureus increased 4-fold (P less than 0.05) when the precursor in serum was changed from 250HD3 to 250HD2, suggesting that this species shows more severe resistance to 1,25-(OH)2D2 than to 1,25-(OH)2D3. In conclusion, we found many differences in vitamin D metabolism among four nonhuman anthropoid primate species. The striking feature in A. vociferans (high, 24,25-(OH)2D without high 25OHD in serum independent of whether diet contained only vitamin D3 or only vitamin D2) should allow determination of whether 24,25-(OH)2D functions as a unique agonist or an inactive metabolite in this species.

The apparent reversal of a wasting syndrome by nutritional intervention in Saguinus mystax.

One hundred eighty sexually mature Saguinus mystax were imported from Peru in six lots over a period of 1 year. Within 1 year after arrival, the mortality was 60% and the majority of the tamarins showed signs similar to "wasting marmoset syndrome" (WMS). In an effort to improve the survival rate, an open formula diet replaced the commercial closed formula diet that had been fed since arrival of the tamarins. The open formula diet contained 26.2% crude protein, 12.3% ether extract, 43.3% nitrogen free extract and 5.9% crude fiber on a dry matter basis. The diet was evaluated on the basis of palatability, weight gain, mortality, digestibility, nitrogen balance, serum biochemical parameters and blood counts. The mean daily consumption on an as-is basis was 44.8g or 335 Kcal gross energy/Kg of body wt./day. During the 3 month open formula diet evaluation period average weight increased by 56g (p less than .05), mortality decreased demonstratively, and alopecia and chronic diarrhea were nearly eliminated. Mean daily gross energy intake for S. mystax (335 Kcal/Kg of body wt/day) was substantially greater than previously reported values for callitrichids. WMS signs observed in the S. mystax colony were controlled by providing what appears to be an adequate diet.

Zoonoses acquired from pet primates.

Laws regulating the importation of primates have drastically reduced the number of primates seen as pets and, thus, the hazard both to the potential owner and veterinarian. Active disease and latent carrier states in primates potentially have severe consequences for the contact person. This potential for human transmission makes it imperative that medical and veterinary professionals collaborate to educate the public on the danger of the primate as a pet.

Selected biohazards of naturally infected nonhuman primates.

The nonhuman primate is susceptible to a great number of microbiological hazards. Two groups of organisms, campylobacter and atypical mycobacteria, are important as examples of naturally occurring primate biohazards. This paper attempts to define these organism groups and their potential for problems in primates housed in natural environments. Efficient, continuous, and specific husbandry and veterinary management techniques must be employed to avoid potential disease outbreaks.

The progesterone antagonist RU 486. A potential new contraceptive agent.

Since progesterone supports endometrial nidation of the fertilized ovum, a progesterone antagonist would theoretically block this process and thus have contraceptive potential. We have explored the ability of RU 486, a newly developed competitive progesterone antagonist, to function as a contraceptive agent. A single oral dose of 10 mg per kilogram of body weight given in the midluteal phase consistently induced menses within 72 hours in women with normal cycles and no risk of pregnancy. Bleeding was not prevented by administration of human chorionic gonadotropin in the midluteal phase. This suggested that giving a single dose of RU 486 late in the menstrual cycle might be an effective contraceptive strategy. This concept was tested in monkeys. When given to rhesus females on day 25 of the cycle, a single intramuscular dose of RU 486 (5 mg per kilogram) prevented pregnancy. The vehicle-treated control animals had a 28 percent pregnancy rate (P less than 0.05 by chi-square analysis). No side effects were noted in women or monkeys. These data suggest that a progesterone antagonist such as RU 486 has the potential to be an effective, safe, and convenient contraceptive agent. Further work will be necessary to assess the safety of long-term monthly administration and to define the optimal dose and time of administration in women.

The new world primates as animal models of glucocorticoid resistance.

Many New World primate species have greatly increased plasma cortisol concentrations, decreased plasma cortisol binding globulin capacity and affinity, marked resistance of the hypothalamic-pituitary-adrenal axis to suppression by dexamethasone, and no biological evidence of glucocorticoid excess. These primates also have high levels of circulating progesterone, estrogen, mineralocorticoid, androgen and vitamin D. The glucocorticoid target tissues that have been examined (circulating mononuclear lymphocytes and cultured skin fibroblasts) have normal concentrations of glucocorticoid receptors with decreased affinity for dexamethasone. Transformation of B-lymphocytes with the Epstein-Barr virus leads to glucocorticoid receptor induction that is less than that observed with cells from Old World primates. The receptor in these cells has a low affinity for dexamethasone. The low affinity leads to an increased loss of specific bound ligand during thermal activation. Meroreceptor generation is normal. The molecular weight of the receptor, determined by SDS-PAGE, is similar to that of Old World primates (approximately 92,000) and the activation pattern per se, examined in vitro by heating cytosol and performing phosphocellulose chromatography, appears similar to that of human controls. The ratios of nuclear to cytosolic hormone-receptor-complexes and of cytosolic activated to unactivated receptor complexes in intact cells are similar to Old World primates. Results from mixing studies do not support the hypothesis that a binding inhibitor(s) or a deficient cytosolic positive modifier(s) of binding underlies the findings in these primates. The New World primates, unlike men with the syndrome of primary cortisol resistance, have compensated for their condition with intra-adrenal and mineralocorticoid receptor adaptations. Thus, unlike Old World primates, cortisol in New World primates has only weak sodium-retaining potency because the aldosterone receptor has a low affinity for cortisol. The common element that would explain the apparent resistance to six steroid hormones in New World primates remains unknown.

Adaptation of the mineralocorticoid target tissues to the high circulating cortisol and progesterone plasma levels in the squirrel monkey.

Many New World primate species have elevated circulating free plasma cortisol concentrations, target tissue resistance to cortisol, and no evidence of sodium retention. A representative New World primate, the squirrel monkey (Saimiri sciureus), has plasma cortisol concentrations above those necessary to cause complete suppression of the renin-angiotensin-aldosterone axis in an Old World primate, the cynomolgus monkey (Macaca fascicularis). Despite this, the arterial blood pressure as well as the plasma sodium, potassium, and bicarbonate levels of the squirrel monkey are similar to those of the cynomolgus monkey, and its plasma aldosterone concentrations are approximately 2-fold higher. These findings suggest that cortisol has minimal sodium-retaining effects in this species. Renal cytosol aldosterone receptor concentrations are about 2- to 3-fold lower in the squirrel monkey than in the cynomolgus, whereas the receptor affinities for [3H]aldosterone are similar in the two monkeys. Higher concentrations of cortisol are needed to displace [3H]aldosterone from the mineralocorticoid receptor in the squirrel monkey than from the renal receptor in the cynomolgus [apparent equilibrium dissociation constant (Ki) = 7.8 X 10(-7) vs. 2.9 X 10(-8) M, respectively]. In addition, in contrast to man and presumably other Old World primates, plasma aldosterone concentrations in the female squirrel monkey do not increase during the reproductive cycle or pregnancy when progesterone concentrations are 10- to 20-fold higher than those of the male or the reproductively quiescent female. This suggests that progesterone is a poor aldosterone antagonist in this species. We conclude that a low concentration of mineralocorticoid receptors in New World Primates is compensated for by higher aldosterone levels, with a concomitant increase in receptor occupancy. The salt-retaining potency of cortisol is low, presumably because of a decrease in the affinity of the aldosterone receptor for glucocorticoids in New World primates.

Effects of the luteinizing hormone-releasing hormone (LHRH) analog D-Trp6-Pro9-NEt-LHRH on the pituitary-gonadal axis of prepubertal rhesus monkeys.

To elucidate whether the luteinizing hormone-releasing hormone (LHRH) analog D-Trp6-Pro9-NEt-LHRH (LHRHa) decreases plasma testosterone levels in male primates solely by inhibiting gonadotropin secretion or, in addition, by inhibiting testicular testosterone biosynthesis, we have investigated the effects of this drug on 6 infant male rhesus monkeys. Three animals received LHRHa (12 micrograms . kg . day s.c., experimental group), and 3 animals received saline injections (control group) during the first 2 mo of life. Mean plasma testosterone was significantly lower in the experimental group compared to the control group (54 +/- 7 ng/dl vs. 501 +/- 52 ng/dl, P less than 0.001). The experimental group also had significantly lower mean follicle-stimulating hormone (FSH; 5.1 +/- 0.2 microgram/ml vs. 9.6 +/- 0.7 microgram/ml, P less than 0.001), and bioactive luteinizing hormone (LH; 2.0 +/- 0.08 microgram/ml vs. 3.5 +/- 0.2 microgram/ml, P less than 0.001). To study whether LHRHa influences testicular function directly, all animals were treated with human chorionic gonadotropin (hCG; 100 mIU . kg . day i.m.) for 28 days beginning at 8 mo of age. During Days 15 through 28 we administered LHRHa 12 micrograms . kg . day s.c. to the experimental animals and saline injections to the control group. Plasma testosterone increased to 5827 +/- 557 ng/dl in the experimental group and 4440 +/- 897 ng/dl in the control group after 14 days of hCG treatment. Plasma testosterone concentrations decreased in both groups of animals from Days 15 to 28 fo the study. All steroid intermediates were similar in both groups of animals on Days 14 and 28.(ABSTRACT TRUNCATED AT 250 WORDS)

Uterine estrogen and progesterone receptors in an estrogen- and progesterone- "resistant" primate.

The squirrel monkey, a New World primate, has elevated plasma estradiol and progesterone concentrations compared to those in the cynomolgus macaque, an Old World primate. We previously reported that uterine progesterone receptor concentrations examined in ovariectomized squirrel monkeys 2 days after estrogen treatment were about one eighth those in identically treated cynomolgus macaques. To examine this in greater detail, we gave estradiol (10 micrograms/kg X day) to ovariectomized squirrel and cynomolgus monkeys for various lengths of time (0, 2, 4, 7, and 14 days), followed by measurement of uterine estrogen and progesterone receptors and assessment of endometrial histology (including glycogen and peroxidase strains), vaginal histology, and cytology. Endometrial and vaginal morphologies showed adequate estrogen effects, as did glycogen and peroxidase stains. Two days of treatment were sufficient to induce both estrogen and progesterone receptors to maximal binding of [3H]moxestrol and [3H]R5020, respectively, in both species. Squirrel monkeys had about one third and one eighth the estrogen and progesterone uterine receptor concentrations, respectively, of cynomolgus monkeys. Receptor affinities in both species were similar. Neither [3H]moxestrol nor [3H]R5020 bound to uterine cytosols from untreated monkeys. We conclude that the increased plasma concentrations of estradiol and progesterone in the squirrel monkey compensate for the decreased estrogen and progesterone receptors in this species.

Hemodynamic and endocrine parameters in the anesthetized cynomolgus monkey: a primate model.

Hemodynamic and endocrine parameters were determined in nine anesthetized adult male cynomolgus monkeys. Simultaneous phasic and mean pressures were measured in the right atrium, pulmonary artery, and abdominal aorta. Intermittent pulmonary artery wedge pressures and mean cardiac output measured by the thermal dilution method were used to calculate stroke volume, systemic vascular resistance, and pulmonary vascular resistance. Plasma adrenocorticotropic hormone (ACTH), cortisol, and plasma renin activity were measured throughout the procedure. Technical aspects, data in the anesthetized monkey, and comparison with previously reported data are presented.

The squirrel monkey: receptor-mediated end-organ resistance to progesterone?

Fertile females of a New World primate species, the squirrel monkey (Saimiri sciureus), have plasma progesterone concentrations that vary between 57 and 510 ng/ml during the reproductive cycle and are 10- to 20-fold higher than those seen in cynomolgus monkeys (Macaca fascicularis) and other Old World primates, including man. The plasma progesterone level during pregnancy is high and varies between 140 and 490 ng/ml. Estradiol levels during the reproductive cycle and pregnancy are also higher than those of cynomolgus monkeys. After 2-day treatment of ovariectomized monkeys with estradiol in oil, the progesterone receptor content in the uterine cytosol of the squirrel monkey is one eighth that in similarly treated cynomolgus monkeys [60.4 +/- 6.5 fmol R5020 bound/mg protein vs. 496 +/- 55 (mean +/- SE); n = 8]. The receptor affinity for R5020 is the same in both species. Thus, the elevated plasma progesterone levels in squirrel monkeys appear to be a compensatory response to a receptor-mediated decrease in sensitivity to progesterone. The squirrel monkey may be a model for the study of the mechanism of action and regulation of secretion of progesterone.

Glucocorticoid hormone resistance during primate evolution: receptor-mediated mechanisms.

The concentrations of total and protein-unbound plasma cortisol of New World monkeys are higher than those of Old World primates and prosimians. The urinary free-cortisol excretion also is increased markedly. However, there is no physiologic evidence of increased cortisol effect. These findings suggest end-organ resistance to glucocorticoids. This was confirmed by showing that the hypothalamic-pituitary adrenal axis is resistant to suppression by dexamethasone. To study this phenomenon, glucocorticoid receptors were examined in circulating mononuclear leukocytes and cultured skin fibroblasts from both New and Old World species. The receptor content is the same in all species, but the New World monkeys have a markedly decreased binding affinity for dexamethasone. Thus, the resistance of these species to the action of cortisol is due to the decreased binding affinity of the glucocorticoid receptor. This presumed mutation must have occurred after the bifurcation of Old and New World primates (approximately 60 x 10(6) yr ago) and before the diversion of the New World primates from each other (approximately 15 x 10(6) yr ago).