Timing of the luteal-placental shift in the baboon (Papio cynocephalus)

Normally cycling female baboons (Papio cynocephalus) were mated with males of proven fertility during the periovulatory period. After pregnancy was confirmed, the corpus luteum-bearing ovary was removed (CL-OVX) at day 18 (n = 1), day 20 (n = 4), day 25 (n = 3), or day 30 (n = 4) of gestation. Upon CL-OVX at day 18 or 20, there was an immediate decline in plasma progesterone to basal levels, and pregnancy was not maintained. After CL-OVX on days 25 or 30, there was a transient, small decline in plasma progesterone levels which recovered rapidly to levels found in pregnant controls, and pregnancy was maintained. Only one baboon failed to maintain pregnancy after CL-OVX on day 30, but progesterone levels remained elevated for 3 days before the termination of pregnancy suggesting that causes other than CL-OVX were responsible. In another group of three baboons, depot medroxyprogesterone acetate was administered before CL-OVX at day 20 of gestation and again at days 23 and 26. Progesterone declined sharply after CL-OVX to near basal levels but increased between days 22 and 24, and pregnancy was maintained in all cases. Estradiol levels did not decline as sharply as those of progesterone in any group, which indicates an exclusively luteal source for progesterone while estradiol comes from both the luteal and nonluteal ovaries. There is a placental increase in estradiol production which occurs much later than does the production of progesterone. The luteal-placental shift occurs between day 20 and 25 of gestation in the baboon, earlier than in women but later than in rhesus monkeys.     

Metabolizable energy intake during long-term calorie restriction in rhesus monkeys

Calorie restriction (CR) is a dietary intervention shown to increase maximum life-span. The aim of this study was to compare the metabolizable energy of the pelleted semi-purified diet with estimated energy intake from food weight. Energy density of diet, urine and feces were measured by bomb calorimetry in rhesus monkeys (23-29 years old) on CR (CR, n=11) and control (C, n=9). Food moisture was measured to be 2-fold higher (9+/-1%) than indicated on the label (approximately 5%). The measured gross energy of diet was 4.4 kcal/g dry weight of CR and 4.5 kcal/g dry weight of C diets. In a two-day trial, food intake (mean+/-SD) was 112+/-20 g and 136+/-26 g of dry mass/d in the CR and C monkeys, respectively (p=0.003). The fraction of the diet absorbed (CR=0.91; C=0.95) was different (p<0.001) between CR and C monkeys. Using these coefficients, the metabolizable energy intake averaged over 6 months was 450+/-53 and 534+/-97 kcal/d in CR and C monkeys, respectively (Diff=16%; p=0.03). These values were compared with energy expenditure (EE), as measured annually by indirect calorimetry (490+/-61 kcal/d in CR and 532+/-62 kcal/d in C monkeys). Adjusted for changes in body composition (2+/-10 kcal/d in CR and -7+/-12 kcal/d in C), energy balance was not different from zero in CR (-42+/-42 kcal/d) and C (9+/-61 kcal/d) monkeys. Use of diet weight is a reasonable estimate of the level of CR when food waste is assessed.     

Frequency dependence of dead space during high-frequency ventilation in rhesus monkeys

A rotary valve ventilator, designed to allow the direct measurement of expired gas volume and composition, was used to maintain gas exchange in anesthetized, paralyzed, rhesus monkey at ventilatory frequencies up to 20 Hz. A total of five studies were carried out on three animals. Determinations of the minute ventilation required to maintain a normal steady-state PCO2, together with the FECO2 and arterial PO2, PCO2, and pH, were made at a number of frequencies. The results so obtained were used to calculate the Bohr (physiological) dead space. Dead space remained approximately constant at close to the value determined during spontaneous ventilation for each individual animal in the range of ventilatory frequencies from below 1 to around 5 Hz, but decreased somewhat with increasing frequency above 5 Hz. The calculated physiological dead space at 15 Hz was about 70% of the value at normal respiratory frequencies. These findings in primates, obtained using a ventilator system which allows very accurate determinations of expired gas volume and content, when compared with those from our previous studies in rabbits and dogs, provide further evidence that the relationship between efficiency of gas exchange and ventilatory frequency during HFV is highly species-specific.     

Regulation of ovarian steroid biosynthesis by estrogen during proestrus in the rat

Studies were performed to test the hypothesis that the rapid decline in estradiol (E2) levels on proestrus before ovulation was due to a reduction in androgen substrate for aromatase, and that this decline in androgen was regulated by an estrogen receptor-mediated mechanism. Aromatase activity, concentrations of E2, androstenedione (A), testosterone (T), and progesterone (P4) in follicular, corpora lutea, and ovarian homogenates as well as peripheral E2, A, P4, and LH were measured in cycling rats from 1400-2000 h on proestrus. These parameters were also recorded after the expected E2 surge in animals treated at 1900 h on diestrous day 2 with the antiestrogen keoxifene (20 mg/kg), with or without an ovulatory dose of PMSG at 1600 h on proestrus. In a second experiment, P-450-17 alpha-hydroxylase/C17,20-lyase (P-450(17 alpha] activity was measured in a group of control rats at 1500, 1700, and 1900 h. Aromatase activity remained unchanged, even though serum and ovarian E2 levels were reduced from peak values at 1500 h to basal values at 1800 h (P less than 0.01). Peripheral A as well as ovarian androgens (specifically follicular but not luteal) A and T were also reduced over this time period (P less than 0.01). Although total ovarian P4 remained unchanged, follicular levels rose from 1400-2000 h (P less than 0.01). These reductions in androgens and E2 levels coincided with a marked reduction in follicular P-450(17 alpha) activity. Treatment with keoxifene with or without PMSG prevented the fall in peripheral E2 and A and the increase in peripheral P4 seen in controls. Ovarian and follicular E2, A, and to a lesser extent T were also remained at values similar to those during the E2 surge. Follicular P4 was reduced by both treatments. Neither treatment had any effect on aromatase. These results indicate that the fall in peripheral and ovarian E2 levels before ovulation was due to a decline in aromatizable androgen, through an inhibition of follicular P-450(17 alpha) enzyme activity, which appears to be mediated by an estrogen receptor-regulated mechanism.     

Calorie restriction in rhesus monkeys

Calorie restriction (CR) extends lifespan and reduces the incidence and age of onset of age-related disease in several animal models. To determine if this nutritional intervention has similar actions in a long-lived primate species, the National Institute on Aging (NIA) initiated a study in 1987 to investigate the effects of a 30% CR in male and female rhesus macaques (Macaca mulatta) of a broad age range. We have observed physiological effects of CR that parallel rodent studies and may be predictive of an increased lifespan. Specifically, results from the NIA study have demonstrated that CR decreases body weight and fat mass, improves glucoregulatory function, decreases blood pressure and blood lipids, and decreases body temperature. Juvenile males exhibited delayed skeletal and sexual maturation. Adult bone mass was not affected by CR in females nor were several reproductive hormones or menstrual cycling. CR attenuated the age-associated decline in both dehydroepiandrosterone (DHEA) and melatonin in males. Although 81% of the monkeys in the study are still alive, preliminary evidence suggests that CR will have beneficial effects on morbidity and mortality. We are now preparing a battery of measures to provide a thorough and relevant analysis of the effectiveness of CR at delaying the onset of age-related disease and maintaining function later into life.     

Defective lipid disposal mechanisms during bacterial infection in rhesus monkeys.

Mechanisms producing hypertriglyceridemia during bacterial sepsis have not been well defined. In this study lipid disposal mechanisms were assessed in 76 infected and 19 control male rhesus monkeys by the ability to dispose of triglycerides after: (1) oral lipid loading; (2) intravenous lipid loading; and (3) by lipolytic enzyme activity tests as measured by postheparin lipolytic activity (PHLA). Studies were performed both before and 48 hr after intravenous inoculation with either Salmonella typhimurium or Diplococcus pneumoniae when illness was uniformly severe and fasting serum triglyceride elevations were increased maximally. S. typhimurium-infected monkeys demonstrated significant fasting hypertriglyceridemia (p is less than 0.001), reduced clearance of orally and intravenously administered lipid and markedly reduced PHLA. During this gram-negative sepsis, mild lethargy, slight diarrhea, and a 2% mortality were observed. During D. pneumoniae sepsis, average fasting triglyceride concentrations were slightly, but not significantly elevated. While oral lipid clearance was impaired, intravenous lipid clearance was unimpaired, and PHLA was slightly reduced. Marked lethargy, agitation, and a 20% mortality were present during this gram-positive infection. Results of this study support the concept that an impairment of lipid disposal mechanisms, particularly during gram-negative sepsis with S. typhimurium, may significantly contribute to the observed hypertriglyceridemia.     

Levels of adrenal and gonadal hormones in rhesus monkeys during chronic hypokinesia

The purpose of this study was to evaluate the effect of chronic immobilization on the hypophysial-adrenal and hypophysial-gonadal axes of adult male rhesus monkeys and the effect such manipulation has on the ability of these axes to respond to exogenous corticotropin, gonadotropin, and GnRH administration. A comparison was also made of the effects of immobilization on testosterone secretion at periods of low (April) and high (November) gonadal activity in this animal. Adult male rhesus monkeys were immobilized in a horizontal position for periods of up to 20 days during March/April. The function of the hypophysial-adrenal and hypophysial-gonadal axes was studied by monitoring plasma levels of cortisol, 17-hydroxylated precursors, 11 deoxycortisol, and testosterone during the period of restraint. Groups of immobilized and control animals also received iv injections of ACTH, FSH, and LH or LHRH on day 18 of the experiment. An additional group of animals was immobilized for 20 days, but did not receive exogenous hormone treatment. This group was used for comparison of seasonal differences in testosterone secretion with another group of animals subjected to the same treatment in November. During the first 3 h of immobilization, levels of cortisol, 17-hydroxylated precursors, and 11-deoxycortisol increased markedly from initial levels. Cortisol levels remained elevated for 3 days, whereas levels of the other three adrenal hormones declined to near-initial levels within 24 h. Testosterone levels declined steadily during the first 6 h of immobilization in males studied at a time of high testicular activity (November), while an increase during the first hour of restraint followed by a decline during the next 3 days were observed in males studied during a period of low testicular activity (April). Animals injected with ACTH on day 18 of immobilization had cortisol levels similar to those of control animals, but other groups of animals restrained for a similar period exhibited a lower level of plasma testosterone than controls after the injection of FSH and LH or LHRH. These data suggest that adaptation to stress results in a reduced demand for corticosteroid production and that the adrenals of chronically stressed animals are capable of responding to exogenous corticotropin, or alternatively, the immobilization imposed was stressful for only a limited time, and after a few days, animals no longer reacted as in response to stress. Also, secretion of testosterone in male monkeys is markedly influenced by the functional state of the gonads at the time of stress initiation.     

Humoral immune response of normal rhesus monkeys during primaquine administration.

Humoral immune response of normal rhesus monkeys was studied after giving a standard dose of primaquine. The drug did not effect the level of complement (C3) and its haemolytic activity. Levels of Immunoglobulin i.e. IgG, IgM & IgA and number of immunoglobulin secreting cells also remained unaffected. Results of this study suggested that primaquine did not suppress the immune status of the host and could be given safely to the malaria patients.     

Glucose and alanine metabolism during bacterial infections in rats and rhesus monkeys

To investigate the effects of bacterial infection on glucose and alanine metabolism, a variety of studies were carried out in rat and monkey models. These included glucose turnover by a pulse-dose technique in infected rats; alanine and glucose production and utilization in control and septic monkeys; in vivo measurement of gluconeogenesis in rats, with and without an alanine load; the in vitro rate of glucose formation from various substrates by isolated liver perfusion and hepatic cells; and in vivo rates of oxidation of glucose labeled with ¹⁴C at the 1 or 6 carbon position. In rats, glucose turnover was markedly accelerated 24 hr after inoculation of either 10⁴ or 10⁷Streptococcus pneumoniae. Glucose utilization and production were also accelerated during illness and early recovery from a pneumococcal infection in monkeys. The rates of gluconeogenesis as measured by either a pulse technique in rats or continuous infusion of labeled alanine in monkey were significantly elevated during pneumococcal septicemia. During the agonal stages (10⁷) of the pneumococcal infection in rat, an alanine load resulted in a decreased rate of labeled glucose production and an increase in plasma glucose when compared to values of fasted control rats. However, early illness caused similar or increased rates of glucose production from alanine in vivo. Similar reduced rates of glucose formation were observed when the isolated livers or hepatocytes from rats during the agonal stages of infection were perfused with excess quantities of gluconeogenic substrates. Thus, in the rat, gluconeogenic capacity (ability to form glucose from excess substrates) appears to decrease only during the agonal stages of pneumococcal infection. During acute pneumococcal sepsis in the rhesus monkey, alanine production and utilization were significantly elevated and it was estimated that over 90% of the newly produced alanine was utilized for glucose synthesis. When arterial-venous differences were measured across the hindquarters, significantly more alanine was released, presumably from skeletal muscle of the septic monkey, compared to the recovery period or in the control groups. Thus, the increase in glucose synthesis in both rat and monkey appears to be correlated with substrate availability and kinetic rate, rather than gluconeogenic capacity of the liver. The major increase in glucose utilization during both S. pneumoniae and Francisella tularensis live vaccine strain (LVS) infections in rat was a progressive elevation in the rate of oxidation via the pentose phosphate shunt in the rat. Further, the rate of oxidation appeared to be correlated with the magnitude of the bacteremia, which is an indication of the severity of the infection. Therefore, since glucose oxidation is necessary for a number of metabolic processes of various cells (such as phagocytosis and RNA synthesis), the increased glucose production during pneumococcal sepsis in the rat or rhesus monkey may not represent functional wastage to remove the excess alanine produced in skeletal muscle but a necessary process in the host defense mechanism against infectious disease.     

Moderate alcohol during pregnancy: learning and behavior in adolescent rhesus monkeys

BACKGROUND: Although high-dose prenatal alcohol exposure is related to cognitive and behavioral impairments in children and adolescents with fetal alcohol syndrome, there is relatively little research on the effects of moderate drinking during pregnancy. We examined learning, memory, and behavior in adolescent rhesus monkeys prenatally exposed to moderate levels of alcohol, psychological stress, or both alcohol and stress. METHODS: Forty adolescent rhesus monkey subjects were derived from four groups of female rhesus monkeys that (1) consumed alcohol throughout gestation; (2) experienced prenatal stress; (3) experienced prenatal stress and alcohol consumption; or (4) control group (no alcohol, no stress). The subjects were assessed for number of trials required to reach 90% criterion of correct responses on nonmatching-to-sample task (NMS), followed by trials with delays of 30, 60, or 120 sec. Ratings of behavior during testing were made after each session. RESULTS: Subjects exposed to moderate prenatal alcohol required significantly more trials to reach criterion on the acquisition phase of the NMS task but had no difficulty with delays. Prenatally stressed monkeys showed lower response inhibition or less behavioral restraint, whereas prenatal alcohol plus stress monkeys showed higher activity level and stereotypies compared with controls. High scores on neonatal measures of orientation (attending to novel stimuli) and motor maturity and low scores on irritability, activity, stereotypies, and impulsivity during acquisition were correlated with fewer trials to criterion on acquisition of NMS. CONCLUSIONS: NMS trials required to reach criterion and behavior during testing are sensitive to moderate-level prenatal alcohol exposure in monkeys. The most adverse behavioral outcomes (hyperactivity and stereotypies) were associated with prenatal alcohol plus stress, raising concerns that environmental stress might provide the context within which fetal alcohol exposure could promote adverse behavioral outcomes. These effects occurred in the absence of either facial deformities or retarded physical growth.     

The lepromin test in rhesus monkeys

The lepromin test was studied in rhesus monkeys. Six control monkeys which had not been inoculated with Mycobacterium leprae, six monkeys with experimentally induced leprosy, and nine monkeys which had been inoculated with M. leprae but had not developed leprosy were evaluated with 1X, 10X, and 15X lepromin A, with 1X and 10X lepromin M (mangabey monkey derived), with 1X and 25X purified inactivated M. leprae, and with an armadillo mock lepromin. We found that the lepromin test is useful in rhesus monkeys, but that a higher concentration of antigen than is used in humans is required to induce a response in monkeys. Control monkeys appear to be lepromin negative. Animals which have been inoculated and which develop lepromatous leprosy are also negative. Monkeys which are experimentally inoculated with M. leprae and do not develop leprosy become lepromin positive. Monkeys with indeterminate leprosy have reactions intermediate between lepromatous and resistant animals. No monkeys reacted to armadillo tissue. Our results indicate that 10X lepromin A is a useful preparation for the lepromin testing of rhesus monkeys.     

Auditory looming perception in rhesus monkeys

The detection of approaching objects can be crucial to the survival of an organism. The perception of looming has been studied extensively in the visual system, but remains largely unexplored in audition. Here we show a behavioral bias in rhesus monkeys orienting to "looming" sounds. As in humans, the bias occurred for harmonic tones (which can reliably indicate single sources), but not for broadband noise. These response biases to looming sounds are consistent with an evolved neural mechanism that processes approaching objects with priority.     

Gonadal steroid modulation of the limbic-hypothalamic- pituitary-adrenal (LHPA) axis is influenced by social status in female rhesus monkeys

Chronic stress can have a deleterious effect on the reproductive axis that, for females, is manifested in an increased incidence of infertility. However, gonadal steroids may, in turn, affect a female’s response to stress as measured by activity within the limbic-hypothalamic-pituitary-adrenal (LHPA) axis. What is not clear is whether a history of exposure to stress modifies the effect of gonadal steroids on LHPA responsivity. Rhesus monkeys present a unique opportunity to assess LHPA responsivity when housed socially in groups. Under these situations, monkeys exhibit a rich network of affiliation and have established social status hierarchies. Previous work indicates that socially subordinate macaque females are hypercortisolemic due to diminished glucocorticoid negative feedback. The present study tested the hypothesis that estradiol (E₂) would decrease glucocorticoid negative feedback, assessed from a dexamethasone (DEX) suppression test, and increase the response to corticotropin releasing factor (CRF) and that these effects would be attenuated by co-treatment with P₄. In addition, we also determined whether E₂ and P₄ would differentially affect LHPA responsiveness to pharmacological challenge in socially dominant compared with subordinate females. Endogenous gonadal hormone secretion in female rhesus monkeys (n=7) was suppressed by continuous treatment with a sustained release formulation of the GnRH analog leuprolide acetate (Lupron Depot). The response to a combined DEX suppression-CRF stimulation test was assessed using a counterbalanced design during a placebo (control) treatment condition and during E₂, P₄, and E₂ + P₄ replacement therapy. Females who were members of a large breeding group of 140 adults and juveniles of both sexes, were classified as dominant (n=4) or subordinate (n=3) based on the relative social dominance positions within the group. Plasma levels of cortisol were significantly higher during E₂ replacement compared to the other treatment conditions following DEX suppression and stimulation with CRF. Escape from glucocorticoid negative feedback, assessed as the increase in cortisol following maximum suppression by DEX and prior to stimulation by CRF, was enhanced by E₂. Plasma ACTH was also significantly higher during E₂ replacement following DEX suppression, an effect that was attenuated by co-treatment with P₄. The evaluation of the influence of social status indicated that the decrease in glucocorticoid negative feedback on cortisol and ACTH release induced by E₂ was exacerbated in socially subordinate females. Overall, cortisol and ACTH decreased less in response to DEX and increased more in response to CRF in socially subordinate females compared with dominant females. Taken together, these data indicate that E₂ increases the responsiveness of the LHPA axis in female rhesus monkeys and this response in enhanced by social subordination.     

Experimental immune mediated arthritis in rhesus monkeys

Summary The induction of experimental arthritis in rhesus monkeys was studied by intradermal immunization of bovine type II collagen and antigens derived fromMycobacterium tuberculosis, Streptococcus pyogenes, andEubacterium aerofaciens. The tested bacterial antigens proved to be not arthritogenic. Bovine type II collagen induced clinical arthritis in 50% of the rhesus monkeys. Type II collagen induced arthritis in rhesus monkeys proved to be a potential model to study clinical, serological, histological, genetic, and immunologic features associated with human RA.