Ovarian hormones and food intake in female guinea pigs and rhesus monkeys

Food intake was measured during ovarian cycles of female guinea pigs and rhesus monkeys. In both species, the period of lowest food intake occurred around the expected time of ovulation. Feeding levels were lowest in the guinea pig during the time of estrus, estrus being estimated on the basis of vaginal membrane changes. Minimum food intake in the rhesus occurred prior to the midpoint of the menstrual cycle, on Day 13, approximately 15–16 days before the next menstruation. In ovariectomized females of both species, either multiple or single estradiol injections significantly lowered food intake. Single progesterone injections to such females were found to have no significant effect on levels of feeding.     

Food preference of young rhesus monkeys fed marginally zinc deficient diets

Zinc deprivation has been shown to produce hypogeusia in rhesus monkeys but the possible consequences of altered taste sensitivity for food preference and selection is not known. We studied 13 rhesus monkeys (2.5 to 3 years of age) for food preference in a structured choice situation. These animals were fed two levels of dietary zinc: marginally zinc deprived (fed 4 μg zinc/g diet from conception and throughout development;N=6), or control (fed a 100 μg zinc/g diet throughout the study;N=7). Preference for familiar vs unfamiliar food items, order of food preferences, persistence in retrieval of preferred and nonpreferred foods, and preference under four deprivation periods were examined. Animals were offered a choice of two food items, both containing minimal zinc levels, and food choice and latency of choice were measured. Results indicate that animals fed the marginal zinc diets had reduced preference for unfamiliar foods relative to controls and different patterns of food preference. These results may be relevant to maintenance of appropriate food selection in marginally zinc deprived populations.     

Reproductive capacity of rhesus monkeys following bilateral ovarian x-irradiation.

The effect of ovarian X-irradiation of the rhesus monkey upon menstrual cycle length, duration of menstrual bleeding, excretion of gonadotrophin in the urine, concentration of gonadotrophin in the pituitary gland, ovarian histology, and breeding performance was investigated. Doses below 4000 R had no significant effect upon the above criteria. By contrast, doses of 4000 to 7000 R rapidly induced amenorrhoea in most animals, but unexpectedly these animals did not excrete greater than normal amounts of gonadotrophin. The pituitary content of gonadotrophin in cyclic and non-cyclic animals was not significantly different. Some births occurred in the animals which had been X-irradiated.     

Self-agency in rhesus monkeys

Rhesus monkeys (Macaca mulatta) have shown the ability to monitor their own mental states, but fail the mirror self-recognition test. In humans, the sense of self-agency is closely related to self-awareness, and results from monitoring the relationship between intentional, sensorimotor and perceptual information. Humans and rhesus monkeys were trained to move a computer icon with a joystick while a distractor icon partially matched their movements. Both humans and monkeys were able to monitor and identify the icon they were controlling, suggesting they have some understanding of self-agency.     

Salmon calcitonin reduces food intake through changes in meal sizes in male rhesus monkeys

Amylinergic mechanisms are believed to be involved in the control of appetite. This study examined the effects of the amylin agonist, salmon calcitonin, on food intake and meal patterns in adult male rhesus monkeys. Fifteen minutes before the onset of their 6-h daily feeding period, monkeys received intramuscular injections of various doses of salmon calcitonin (0.032, 0.056, 0.1, 0.32, and 1 microg/kg) or saline. Salmon calcitonin dose dependently reduced total daily and hourly food intake, with significant decreases at the 0.1, 0.32, and 1 microg/kg doses. Daily food intake was reduced by approximately 35%, 62%, and 96%, at these doses, respectively. An analysis of meal patterns revealed that size of the first meal was significantly reduced across the dose range of 0.056 to 1 microg/kg, while average meal size was reduced with the 0.32 and 1 microg/kg doses. Meal number was only affected at the 1 microg/kg dose. Repeated 5-day administration of the 0.1 microg/kg dose resulted in a reduction in daily food intake only on injection day 2, while significant reductions in food intake were observed on all five injection days with a 0.32 microg/kg dose. Daily food intake was also reduced for 1 day after the termination of the 5-day injections of the 0.32 microg/kg salmon calcitonin dose. These sustained reductions in intake were expressed through decreases in meal size. These data demonstrate that salmon calcitonin acutely and consistently decreases food intake mainly through reductions in meal sizes in nonhuman primates.     

Malignant uterine mesotheliomas in squirrel monkeys following diethylstilbestrol administration

10 adult female squirrel monkeys were implanted subcutaneously with 4 60 mg pellets of diethylstilbestrol (DES); 4 animals were implanted with cholesterol pellets to serve as controls. Animals were killed at 5, 9, 11, and 14 months after insertion of pellets. All animals implanted with DES had evidence of extreme estrogenic stimulation, including marked edema of the labia, heavy vaginal cornification, and enlargement of the uterine corpus. There were several stages of uterine lesions, in general in proportion to the duration of treatment. The less advanced lesions were restricted to hyperplasia and hyperthrophy of the serosal cells. In more advanced lesions the myometrium was infiltrated; in the most advanced cases there was invasion of the endometrium. The 7 most advanced uterine tumors were classified as malignant mesotheliomas. Cholesterol-treated controls did not have any significant lesions. These observations indicate that DES is carcinogenic in the squirrel monkey, as it has been demonstrated to be in other lower mammalian species.     

Caudate electrochemical response following amphetamine administration in pigtail monkeys

In vivo electrochemical and heart rate (HR) recordings following amphetamine (AMPH) (0.8 mg/kg) and saline administration were made from caudate in four young adult pigtail (M. nemestrina) monkeys using linear sweep voltammetry. One hour following drug injection, two familiar humans served as test stimuli, and were visually exposed to the animals for 15-minute epochs each. One was threatening to the animals, and one was not. AMPH produced a significant increase in height of the electrochemical peak thought to represent oxidation of dopamine and its metabolites. Heart rate (HR) decreased during the time the peak height was increasing. HR and peak height increased during presentation of both humans under both AMPH and saline conditions. However, peak height increase under AMPH, but not saline, conditions discriminated the negative from neutral stimulus. The findings demonstrate that AMPH administration induces a significant increase in the height of a major electroactive peak in the caudate nucleus of pigtail monkeys, and further that such amphetamine-induced increases can be manipulated by altering the affective and/or emotional state of the animal.     

Changes in the behavior of laboratory-reared rhesus monkeys following the threat of separation

Four heterosexual pairs of three-year-old rhesus monkeys were either repeatedly separated from each other for 30-min or not separated. Prior to each separation, a transfer cage was displayed at the front of the cage to serve as a cue that the pair would be separated. After only a few trials, the animals displayed disturbance, particularly in the form of stereotyped pacingprior to the separation. Practical considerations related to laboratory methodology, a theoretical discussion concerning the fear of separation in monkeys and man, and the need for attention to individual differences in response to separation were emphasized.Supported by NIH grants MH22253, HD04335, and RR00169, to Dr.Gary Mitchell; whose assistance is gratefully acknowledged.     

Menopause in female rhesus monkeys

Fifteen female rhesus monkeys (Macaca mulatto), ranging in age from 8 to 34 years, were studied for one year to characterize the endocrine and menstrual changes associated with menopause in this species. Five monkeys were premenopausal; these younger monkeys, ages 8–11 years, menstruated and showed cyclic ovarian activity during the 12–month study period, as evidenced by menses and periodic elevations of serum estradiol (E₂) and luteinizing hormone (LH) concentrations. Four females, ages 24–26 years, were in transition to menopause. Two of these perimenopausal females menstruated and secreted E₂ and LH in a periodic fashion; the other two females showed elevated LH concentrations, consistently low E₂ levels, and no evidence of menstruation. Six females, ages 27–34 years, were clearly postmenopausal; LH concentrations were high, whereas E₂ concentrations were uniformly low. There was a significant inverse correlation between basal E₂ concentrations and age, and a significant positive correlation between age and LH concentrations across all 15 animals. Hormonal changes indicative of ovulation, when they occurred, were generally restricted to the winter and early spring months. Histological analysis of ovaries from four postmenopausal females revealed little or no evidence of active folliculogenesis. These data indicate that menopause in female rhesus monkeys does not occur until the second half of thethird decade of life. © 1995 Wiley-Liss, Inc.     

Plasma cortisol and catecholamine responses to intracerebroventricular administration of CRF to rhesus monkeys

Synthetic ovine corticotropin releasing factor (CRF) was administered directly into the 4th ventricle of rhesus monkeys. A dose dependent increase in plasma cortisol was observed following 10 μg/kg, 20 μg/kg, and 60 μg/kg of CRF. Increases in plasma epinephrine were also evident following the highest dose of CRF. Plasma norepinephrine, mean arterial pressure, and heart rate did not increase significantly following CRF administration. These data suggest that in the rhesus monkey, central administration of ovine CRF leads to activation of the pituitary-adrenocortical axis at doses that do not raise plasma catecholamines.     

Induction of immunodeficiency virus-specific immune responses in rhesus monkeys following gene gun-mediated DNA vaccination

Abstract: The Accell® gene delivery system (gene gun) was used to deliver gold particles coated with HIV-1_LAI and SIV_mac239 expression constructs into the epidermis of rhesus macaques, resulting in the elicitation of env- and gag-specific humoral responses. One microgram of vector DNA per dose was sufficient to induce immune responses in monkeys using SIV_mac239 gp160 and gp120 vectors driven by the CMV-intron A promoter. Several parameters, including the identity of the vector, the length of the rest period between immunizations, the number of immunizations, and the amount of DNA per immunization, are all important in designing an optimal DNA immunization regimen. In addition, gene gun-based DNA immunization using low efficiency expression vectors is an effective means of priming for the induction of vigorous antibody responses in macaques following boosting with recombinant subunits.     

Immunogenetic studies of rhesus monkeys

To assay for transplacental immunization in rhesus monkeys, sera from 253 postpartum females, 31 virgin females, and 40 males were tested for erythrocyte agglutinins. Nineteen percent of the mothers exhibited antibodies, but less than three percent of the virgin females or males did so. Antibodies were detected in 26 percent of the mothers who bore blood group-incompatible infants, in contrast to only eight percent of the mothers with compatible offspring. Thus, blood group incompatibility may lead to transplacental alloimmunization of the rhesus female. Unlike the situation in humans, hemolytic disease was not observed, even when the erythrocytes of the newborn rhesus were coated with maternal antibodies.     

Immunogenetic studies of rhesus monkeys

Five alloimmune rhesus monkey blood typing reagents have been produced which define two new blood group loci inMacaca mulatto. Three of these reagents detect blood group factors at theM locus; the other two detect factors at theN locus. By typing over 1900 pedigreed monkeys we have established that these two loci are independent of each other and of any of our previously defined blood group systems.