Search

Background The biological response (heart-rate variability; HRV) to an acute psychological stressor, as well as cognitive changes in anxiety and coping style following tai chi (TC) in healthy male college students, has not been investigated in the literature. Objectives The purpose of this study was to examine the effects of TC on: (1) HRV biomarkers of acute psychological stress, (2) state anxiety, and (3) coping style in healthy male college students. Methods The study was an RCT, in which the experimental group (n=9) received TC (twice a week for 8 weeks) and the control (C) group (n=11) did not receive treatment. Reactions to an acute psychological stressor were measured by the HRV's standard deviation of normal to normal intervals (SDNN), and Spielberger's State–Trait Anxiety Inventory (STAI). Four ‘trials’ (baseline; stressor; recovery 1 and recovery 2) were conducted, with pre-tests/post-tests performed for both study groups. The Problem-Focused Styles of Coping (PFSOC) questionnaire was used to examine coping styles pre-test/post-test for both groups. Results Significant differences were found: (1) for group, test, and trial, the interaction of trial by group, and the interaction of test by trial for SDNN, P

Stress research has gained popularity due to the increased acknowledgement of chronic stress on personal health. With this increased interest, researchers need to assure that the public receives quality, evidence-based solutions. Improvements following a stress reduction intervention are generally assessed by a self-survey pre-post rather than objective biomarkers of stress. There is a need in the literature for a research paradigm utilizing two different stressors to prevent any alteration in post-intervention results due to habituation of the stressor. The Trier Social Stress Test (TSST) and the Beilock Stress Test (BST) are two different stress protocols published in the literature. The present study has three objectives: 1) to compare the efficacy of two different previously documented psychological stressors, the TSST and the BST; 2) to compare an invasive measure, serum cortisol, to a non-invasive measure, the galvanic skin response (GSR); and 3) to examine the effects of sex on the response. Fifty-seven college age males (n = 31) and females (n = 26) completed both protocols. Blood samples were collected every 10 min for 110 minutes. Baseline, stressor, and recovery 1, 2, and 3 were averaged for a 20 min period. A 2 (test: BST or TSST) by 2 (sex: male or female) by 5 (trials: baseline, stressor, and recovery 1, 2, and 3) Mixed Plot ANCOVA with repeated measures on test and trial was used to analyze the data. There was not a significant main effect for test or sex for cortisol or the GSR. There was a significant difference for trial for both biomarkers: cortisol F(4,208) = 39.41; and GSR F(4,216) = 15.18. There was also a significant interaction term for sex × trial × test, F(4,208) = 4.51 and for test × trial, F(4,208) = 14.31 for cortisol. The conclusion is that the TSST and the BST can be used as pretest posttest stressors in translational studies assessing the effectiveness of a stress reduction technique if slight modifications are made in the statistical design.

The Mindfulness-Based Stress Reduction program (MBSR) of Kabat-Zinn includes a combination of sitting meditation, yoga, and walking; thus, movement is not emphasized primarily to induce a state of awareness. The purpose of this study was to investigate the effects of a Mindfulness-Based Movement Program (MBM) in women on parameters of stress and coping; that is, in contrast to MBSR, MBM primarily emphasized yoga to cultivate awareness. This study investigated: (a) an objective measure of stress (the cortisol response to a laboratory stressor) following an 8-week MBM in year 1 participants only (n = 17; MBM group = 9; Control group = 8); (b) subjective measures of stress following an 8-week MBM in years 1 and 2 (n = 32; MBM = 16; C = 16); and (c) changes in coping style following an 8- week MBM in years 1 and 2 (n = 32; MBM = 16; C = 16). A mixed plot 2 (Group: TC or MBM) by 5 (Trial: Baseline, Stressor, Recovery 1, Recovery 2, and Recovery 3) repeated measures ANOVA was run for cortisol. Preliminary results indicated a strong trend towards a lowered cortisol response for the MBM group compared to the control group. A mixed plot 2 (Group: TC or MBM) by 2 (Time: Pretest, Post-test) repeated measures ANOVA was run for Spielberg's State Anxiety, the Perceived Stress Scale, and the Problem Focused Style of Coping Scale for the Suppressive, Reflective, and the Reactive Coping Style. There were significant main effects for time, group, and an interaction of time and group for Spielberg's State Anxiety and the Perceived Stress Scale. Significant differences were also found for time and the interaction of time and group for the Problem Focused Style of Coping for the Reflective Coping Style (p < 0.05). In conclusion, results indicate positive effects of the MBM program on perceived measures of stress and coping style in women.

Neuroendocrine adaptive responses to psychological stress include activation of the hypothalamic-pituitary-adrenal (HPA) axis and sometimes suppression of the hypothalamic-pituitary-gonadal (HPG) axis. In women who experience chronic stress, these responses are probably responsible for disturbances in the menstrual cycle. In the present experiment, we investigated the effect of an acutely stressful situation on the physiological and neuroendocrine responses in college age women. We hypothesized that females who are experiencing some degree of abnormal menstrual function or women who have less-robust cycles (oligomenorrheic females) would exhibit differences in gonadotropin secretion from eumenorrheic females when exposed to psychological stressors. Fifteen women completed this study: eumenorrheic (n = 5) and oligomenorrheic women (n = 5) who experienced a series of psychological stressors, and eumenorrheic controls (n = 5). Blood samples were taken at 10 min intervals for 8 h (09:00-17:00) in each woman during the mid-follicular phase of the menstrual cycle. The psychological stressors were administered for 1 h beginning at 13:00 h. Luteinizing hormone (LH), growth hormone (GH) and cortisol were measured in each sample to assess the effect of stress on secretion of these hormones. Deconvolution analysis was used to analyze pulsatile hormone secretion and the approximate entropy (ApEn) statistic analyzed the regularity of release of each hormone. Although, there were significant changes in heart rate (HR), skin resistance (SR) and cortisol levels in the stressed women during the psychological stressor compared to resting baseline values but not in the controls, there was no difference in either LH or GH secretion between women who experienced stress and those who did not. Furthermore, there were no differences in the LH or GH secretion patterns in the oligomenorrheic and eumenorrheic women exposed to the psychological stressor.

When energy intake is restricted in mammals, there are neuroendocrine adjustments in the secretion of reproductive and metabolic hormones to reallocate energy for vital functions. In the present study, we investigated whether there were differences in the luteinising hormone (LH), growth hormone (GH) and cortisol responses to a 48-h fast in adult gonad-intact male and female rhesus macaques. In both male and female macaques, blood glucose levels were significantly lower in fasted than in control studies, and levels were higher in males than in females. Male rhesus monkeys had significantly lower (P < 0.01) mean serum LH levels after a 48-h fast than under fed conditions and this was attributable primarily to a decrease in the amount of LH released during each secretory episode. In fasted females, serum LH levels were significantly greater (P < 0.05) than during the fed conditions but no differences were found in pulse amplitude or in the number of pulses. Almost twice as many GH pulses were observed in both males and females during fasting but there was no difference in either mean serum GH levels or pulse amplitude between control and fasted studies. A typical diurnal profile in cortisol levels was observed in both sexes and both experimental conditions. Under control conditions, male macaques released less cortisol than females, and although fasting increased mean cortisol levels in both males and females, only the males shown a significant rise over levels observed in control studies. The changes in plasma LH and cortisol levels in fasted rhesus macaques are similar to those observed in humans and suggest that gonadotrophin and corticotrophin secretion are more resistant to short-term energy deprivation in female than in male primates.

The first objective of this study was to determine whether insulin-induced hypoglycemia (IIH) inhibits LH secretion in unrestrained female macaques during the follicular phase of the menstrual cycle. There was a consistent inhibitory effect of hypoglycemia on LH secretion within 3 h in these females. This inhibition was likely an indirect effect since low glucose levels did not inhibit GnRH secretion from GT1-1 neurones in vitro. We next investigated whether administration of a vasopressin antagonist (AVPa) either alone, or with naloxone could reverse the IIH-induced inhibition of LH release. Females were studied in the follicular phase during 10 h periods with blood samples collected every 10 min. Experimental groups were IIH (n=6), IIH+AVPa (n=5) and IIH+AVPa+naloxone (n=4). The first 5 h of each study served as a control and hypoglycemia was then induced with insulin. The AVPa was given as a bolus (180 microg) just before the insulin and was followed by a continuous infusion (180 microg/h) for 5 h. Naloxone (5 mg/kg) was given with the AVPa and followed by a continuous infusion (5 mg/kg/h) for 5 h. In the IIH group, LH reached its lowest value 3-4 h after insulin. Neither AVPa nor AVPa+naloxone infusion reversed the inhibitory action of hypoglycemia on LH release. These data suggest that if there are inhibitory actions of vasopressin and endogenous opioids on GnRH release induced by hypoglycemia, they are not sufficient to explain the suppression of GnRH/LH release in intact female primates.

The first objective of this study was to investigate whether the inhibitory effect of insulin-induced hypoglycemia (IIH) on luteinizing hormone (LH) secretion was the same in unrestrained adult male rhesus macaques as has been previously reported in restrained female macaques. Since IIH did inhibit pulsatile LH secretion in adult male macaques, and some previous studies have implicated arginine vasopressin (AVP) as a central mediator of this inhibition, the second objective was to investigate whether antagonism of AVP action could reverse the IIH-induced inhibition of LH release in males. Ten adult male rhesus macaques (Macaca mulatta) were studied during 15-h periods (07.00-22.00 h), with blood samples collected every 15-min. There were three experimental groups; controls (n=5), IIH (n=6) and IIH plus vasopressin antagonist (AVPa; n=6). During the hypoglycemia studies, the first 5 h served as a control for that occasion and an insulin bolus of 1 U/kg was administered intravenously at 12.00 h. During the IIH plus AVPa, the vasopressin antagonist was infused intravenously from 12.00 h to 17.00 h. LH and testosterone decreased progressively after the insulin bolus in the IIH group reaching a minimum value at 4 h after the infusion. However, compared to the preinfusion levels, secretion of LH and testosterone was not suppressed by hypoglycemia in the group treated with the AVP antagonist. The present study shows that in male macaques not subjected to the psychological stress of restraint, IIH suppresses LH and testosterone secretion. This inhibition of LH release can be blocked in some animals by antagonism of central vasopressin receptors, suggesting that vasopressin is involved in the suppression of gonadotropin releasing hormone/LH release induced by hypoglycemia.

Fasting inhibits the gonadotropic axis and stimulates the corticotropic and somatotropic axes. Since leptin is a product of fat cells that has been implicated in the control of both reproduction and metabolism, we hypothesized that the decrease in leptin observed during fasting was responsible for these effects on reproductive and metabolic hormones. Recombinant rhesus leptin (rrhLep) produced in our laboratory was infused (100 microgram/h) into fasted adult male rhesus macaques (6-9 kg) beginning at midnight after the first missed meal and continuing until the end of the study. Bioactive luteinizing hormone (LH), testosterone, cortisol and growth hormone (GH) were measured in plasma from samples collected at 15-min intervals for the last 15 h (42-57 h) of the fast. We analyzed pulsatile LH and GH secretion by deconvolution analysis and the orderliness of pulsatile LH and GH release by the approximate entropy (ApEn) statistic. There was no difference in LH pulse frequency between control and fasted groups, but there was a significant decrease in the mean concentration of LH released (7.6 +/- 1.4 ng/ml control vs. 2.7 +/- 0.65 ng/ml fasted) that was not relieved with rrhLep infusions (2.8 +/- 0.83 ng/ml). Model-free Cluster analysis confirmed these inferences and also indicated that the peak height was lower in the fasted (4.6 +/- 1.0 ng/ml) and the fasted + rrhLep (2.85 +/- 1.0 ng/ml) groups compared to controls (16. 3 +/- 1.4 ng/ml). Testosterone levels reflected those of LH. Fasting resulted in an increase in GH secretory pulse frequency (5.3 +/- 0. 95 pulses/15 h control vs. 12.8 +/- 1.4 pulses/15 h fasted) and this increase was not affected by rrhLep infusion (12.5 +/- 1.4 pulses/15 h). In addition, fasting also increased the ApEn (decreased the orderliness) of pulsatile GH secretion, and this characteristic was not relieved with rrhLep infusions. Cortisol levels in fasted animals were 2- to 3-fold higher than those observed in control studies, and this increase was particularly pronounced at the time when the animals expected their first meal of the day. The increase in circulating cortisol observed in fasted animals was not affected by rrhLep infusion. Glucose levels at the end of the sampling period were 80 mg/dl in controls, 48 mg/dl in fasted animals and 58 mg/dl in the fasted + rrhLep group. Circulating leptin levels averaged 1.2 +/- 0.37 ng/ml in control animals, 0.7 +/- 0.2 ng/ml in fasted animals and 10.1 +/- 5.6 ng/ml in fasted animals infused with rrhLep. These studies suggest that intravenous replacement with homologous leptin does not reverse the acute changes in GH, LH and cortisol secretion observed with fasting in the adult male macaque.

OBJECTIVE: Because glucocorticoids stimulate leptin release and, at least in vitro, leptin inhibits cortisol secretion, a feedback system between glucocorticoids and leptin has been proposed. However, in humans and non-human primates there are no in vivo studies to support any role for leptin in the control of the hypothalamic-pituitary-adrenal axis. In this study, we investigated the effect of leptin on (i) ACTH-stimulated secretion of cortisol in six male rhesus monkeys and (ii) basal and forskolin (FSK)-stimulated cortisol secretion by the human adrenal carcinoma cell H295R in vitro. DESIGN AND METHODS: In vivo studies: after suppression of endogenous ACTH with either dexamethasone (n=6) or a corticotropin-releasing factor (CRF) antagonist (d-Phe CRF(12-41)) (n=3), 1 microg bolus of human ACTH(1-24) was administered to stimulate adrenal cortisol release. Blood samples were collected every 15 min for 3 h. Leptin (1 mg) was infused over 4 h, starting 1 h before ACTH bolus. In vitro studies: NCI-H295R cells were incubated for 6, 12, 24 and 48 h in the absence or presence of 20 micromol/l FSK in combination with leptin (100 ng/ml medium). Cortisol levels in serum and medium were measured by solid phase radioimmunoassay. RESULTS: Acute leptin infusion to rhesus monkeys did not change basal cortisol levels, peak cortisol levels after ACTH(1-24) or the area under the curve when compared with studies in which leptin was not given. FSK increased cortisol levels in medium at 24 and 48 h, but leptin did not change cortisol release in either control or FSK-stimulated cells. CONCLUSIONS: Short-term leptin infusion affected neither the cortisol response to ACTH in non-human primates in vivo nor cortisol release (basal or FSK stimulated) by H295R cells, in vitro. These data suggest that leptin may not be an acute regulator of primate adrenal cortisol secretion.

OBJECTIVES Although the adipocyte protein leptin has been implicated in the control of reproductive function in rodents, its role in primate reproductive physiology is poorly understood. Because primates in puberty show nighttime LH secretion and there is considerable evidence that the fertile state requires adequate nutrition, we reasoned that animals on the verge of reproductive competence would respond to leptin infusions by secreting LH. Food restriction reduces circulating leptin levels and slows or stops the GnRH pulse generator. Therefore, we examined the endocrine effects of leptin infusions in food-restricted male pubertal primates during the night when they normally secrete LH. In addition, we investigated the effect of leptin on in vitro testosterone production by Leydig cells. SUBJECTS Four pubertal male rhesus macaques (Macaca mulatta), 4–5.5 kg in weight (2.5–4-year-old) were examined in this study. Leydig cells from adult male rats were to investigate in vitro effects of leptin. DESIGN To document that animals had entered puberty, blood samples were collected from each of the four animals at 15-minute intervals for 15 h both during the day and at night. Since at this age animals secrete LH mainly at night, blood samples were collected at 15-minute intervals from each of the four animals on two separate occasions for 15 h between 1500 and 0600h. During the experiment, animals were feeding from 0800 to 0830h, cages were completely cleaned of food at 0900h and the afternoon meal was not given to individual animals on the day they were studied. One of the studies served as the control (food restricted group) and during the other, 2 mg (n = 4) or 0.3 mg (n = 3) of recombinant human leptin was administered intravenously during 2000–0100h (food restricted plus leptin group). Blood samples (1 ml) were collected through the indwelling catheter and immediately transferred from the plastic syringe into chilled glass tubes containing 10 μl 14% EDTA. The samples were centrifuged at 5-h intervals and the plasma withdrawn and stored frozen at − 20°C in polypropylene vials until assays were performed. MEASUREMENTS Bioactive LH was determined and testosterone, cortisol and leptin were measured by radioimmunoassay. RESULTS During daytime experiments in these animals, LH pulses were sometimes observed late in the day and generally continued for 12–15 h. Food-restricted pubertal males showed delayed or absent LH pulses. Short-term leptin administration to food-restricted male rhesus macaques had no effect on LH, testosterone, or cortisol levels either during or after the infusion. Leptin also had no direct effect on basal or LH-stimulated testosterone production in Leydig cells. CONCLUSIONS Our data support the notion that leptin is not the missing signal for the acute suppression of reproductive hormones secretion in food-restricted primates.

Measures of performance, mortality, adrenal weights, plasma glucocorticoid concentration, and selected immune measures were collected in an attempt to define space needs of laboratory mice. Six replications of 3 C57BL/6 male mice per cage were examined while housed on bedding at 5, 10, 15, or 20 in(2) (32.2, 64.5, 96.8, or 129 cm(2)) per mouse. Body weights were not influenced by treatment; however, mice in smaller spaces (5 in(2) per mouse) consumed or wasted more feed and water than mice given greater space allowances. Mice given the least amount of space (5 in(2) per mouse) had greater lymphocyte proliferation in response to the T-cell mitogen PHA than mice given more space. Mice provided 10 in(2) per mouse had greater natural killer cytotoxicity than mice given greater or less space. Mouse mortality was greater as more space was provided. In contrast, adrenal weights and plasma glucocorticoid concentrations were progressively greater with lower space allowances. The National Research Council 1996 recommendation of 15 in(2) per mouse, for this strain and sex of mice, would result in greater mortality and reduced activity of some immune measures. Socially housed male C57BL/6 mice will benefit from less space than recommended by the National Research Council in 1996.

We have previously demonstrated that corticotropin-releasing hormone (CRH) treatment of MA-10 mouse Leydig tumor cells results in a dose-dependent stimulation of progesterone production. In view of this observation we wished to determine the effects of CRH on the synthesis of the steroidogenic acute regulatory (StAR) protein in these cells. StAR is a steroidogenic tissue-specific, hormone-induced, rapidly synthesized protein previously shown to be involved in the acute regulation of steroidogenesis, probably by promoting the transfer of cholesterol to the inner mitochondrial membrane and the cytochrome P450 side-chain cleavage enzyme. Treatment of MA-10 cells with the cAMP analogue dibutyryl cAMP (dbcAMP) resulted in a dose- and time-dependent increase in the levels of StAR protein that reached a maximum at 800 microM dbcAMP and within a time period of 6 h. Further, treatment of MA-10 cells with CRH also resulted in a dose-dependent increase in the synthesis of the StAR protein with a maximal response observed at 1 microM. Slightly different from that observed with dbcAMP, the maximal response to 1 microM CRH was seen at 4 h following stimulation. These results indicate that the observed increase in steroid production in response to CRH in MA-10 Leydig tumor cells is similar to that previously seen with trophic hormone stimulation acting through the cAMP second messenger pathway, and that it occurs as a result of an increase in the synthesis of the StAR protein.

The lack of regular, cyclic menstruation in reproductive-aged women in whom there is no organic or anatomic cause is called functional hypothalamic amenorrhea (FHA). The cause of this malfunction in the hypothalamic-pituitary-ovarian axis is generally attributed to psychological, physical, or nutritional stress, and the underlying deficit is the suppression of gonadotropin-releasing hormone release by the hypothalamus. The diagnosis of FHA is reached by the exclusion of all other factors and conditions that could cause amenorrhea. FHA, by definition, is a chronic condition and can have serious health consequences if not treated. Since the underlying causes of the FHA are thought to be either low energy availability or dysfunctional attitudes and behaviors that result in stimulation of the hypothalamic-pituitary-adrenal axis and/or suppression of thyroid function, cognitive behavioral therapy and hypnotherapy are the best potential approaches for ameliorating this condition. Finally, increasing food intake and reducing stressful activities can be very effective in restoring menstruation.

Regular menstrual cycles are the result of predictable cyclic changes in reproductive hormones produced by the pituitary and ovary. A few neurons at the base of the brain in the hypothalamus provide the ongoing stimulus, GnRH pulses, for the synthesis and secretion of LH and FSH which, in turn, stimulate the ovaries to produce the steroids estrogen and progesterone and the small peptides inhibin and activin. It is the feedback relationships between the pituitary and ovarian hormones that provide the basis for the cyclic function of the reproductive system. If fertilization occurs, there is the possibility of a pregnancy which will suppress menstrual cycles for the duration of the pregnancy. Nursing or lactation can also suppress the ovarian cycles, but should not be relied on for birth control. The negative feedback relationship between the ovarian steroids and pituitary gonadotropins is the basis by which hormonal birth control works. Synthetic steroid hormones that can be administered orally suppress the secretion of LH and FSH and thus interrupt the growth and development of ovarian follicles.

During the lifespan of women, there are dramatic and life-changing transitions associated with the beginning and cessation of reproductive function. These transitions, puberty and menopause, result in dramatic changes in the anatomy, physiology, and cognitive function of females and are caused by fluctuating levels of estrogen and progesterone. Regular menstruation is the result of cyclic release of reproductive hormones and is a sign that all is going well. When a woman approaches menopause, menstruation usually becomes more irregular and eventually ceases because hormones from the ovary are too low to stimulate the lining of the uterus. Because the life expectancy for women is now approaching 80 years and menopause occurs at about 50 years of age, the average female will live approximately 30 years after her ovaries have ceased to produce estrogen. This has serious physical and mental health implications in the aging population, which will increase dramatically in the next few decades. Hormone replacement therapy relieves some of the uncomfortable aspects of menopause, such as hot flashes and sleep disturbances, and protects against osteoporosis. However, recent evidence suggests there may be an increased risk of certain cancers and stroke with hormone therapy. Additional research is needed to unravel the complex actions of hormone replacement formulations so that women can have a healthier life after menopause.

Relevant for female athletes in general and especially in adolescent female athletes are the long-term consequences of insufficient energy intake that results in menstrual cycle disturbances and low bone mineral density. Prolonged exercise as practiced by elite athletes can lead to serious, long-term health problems if diet is not adjusted to compensate for energy expenditure. A good barometer of how energy intake matches energy expenditure in female athletes is menstrual function. Eumenorrhea is the term used to describe normal length, regular menstrual cycles. Oligomenorrhea refers to infrequent menses or menstrual cycles that occur inconsistently at intervals of 39–90 days. Amenorrhea is the absence of menstrual cycles in a nonpregnant, sexually mature woman. When menstrual cycles become disordered as a result of prolonged or excessive exercise, there very well may be an issue related to insufficient energy intake, and consultation of a health care provider knowledgeable in sports medicine is strongly advised to correct the situation. The standard curriculum for high school and college coaches of female athletes should include the health consequences of exercise-induced menstrual function and specific methods of prevention and treatment.

Prolonged exercise requires increased utilization of blood glucose and adjustment of glucoregulatory hormones. Estrogen can reduce hepatic gluconeogenesis which could affect insulin concentrations. Amylin is co-secreted with insulin and controls influx of glucose into the blood. To determine the effect of menstrual cycle stage on glucose, leptin, and pancreatic hormone responses to prolonged (90 min) exercise. Five healthy, eumenorrheic women (24.6 ± 5.1 years; 67.4 ± 1 kg) were monitored for 3 months to determine menstrual cycle length. Subjects completed a preliminary session to determine exercise workloads and, in a fasted condition, completed two randomized 90-min treadmill exercise trials at 60 % VO2max during the early follicular (EFX) and mid-luteal phase (MLX) of their menstrual cycle. Blood samples were analyzed for glucose, insulin, C-peptide, amylin, glucagon, leptin, and cortisol concentrations at rest (−30 and 0 min), during exercise (18, 36, 54, 72, and 90 min) and after 20 min of recovery. No changes in amylin, leptin, or cortisol occurred for EFX and MLX trials. A significant (p

The actions of corticotropin-releasing hormone (CRH) on steroidogenesis in enriched preparations of mouse and rat Leydig cells were investigated. Primary cultures of purified Leydig cells as well as a Leydig tumor cell line were used in these studies. CRH had a stimulatory effect on steroid production in both isolated preparations of mouse Leydig cells (80-90% Leydig cells) and MA-10 cells (a mouse Leydig tumor cell line). In primary cultures of mouse Leydig cells, CRH was effective over a range of 1 nM-100 nM, while MA-10 cells were responsive over a wider range (10 nM-100 microM). When a submaximal dosage of CRH was given together with a maximal dosage of hCG, steroid production was stimulated even more highly in MA-10 cells. However, when primary cultures of mouse Leydig cells were treated with CRH and hCG, no similar response was observed. In addition, a CRH antagonist, alpha-helical CRH9-41, reversed the CRH stimulatory effect on steroidogenesis in both mouse Leydig cells and MA-10 cells. The accumulation of intracellular cAMP after CRH treatment was dose-responsive to CRH in both cell types, a finding similar to the results described above for steroid production. CRH had no effect on steroidogenesis in rat Leydig cells (60-80% Leydig cells) in the present study. These results indicate that mouse Leydig cells respond to CRH through specific receptors with increased production of cAMP and steroids.

It is generally accepted that corticotropin-releasing hormone (CRH) is the central mediator of stress-activated changes in the pituitary-adrenal axis because it results in the release of ACTH and ultimately increases the systemic levels of cortisol. And, because in some situations CRH also inhibits the hypothalamic release of GnRH, it has been presumed that it plays the central role in stress-related reduction in pituitary-gonadal function as well. We previously have shown that 6 h of restraint stress in intact female rhesus macaques suppresses plasma levels of LH in the follicular but not the luteal phase of the menstrual cycle and that this effect lasts beyond the period of restraint. Since CRH inhibits both the GnRH pulse generator and LH release in ovariectomized macaques and is generally thought to be the central mediator of stress-induced inhibition of gonadotropin release, we investigated the influence of CRH administration on LH in undisturbed intact female rhesus macaques. Blood samples were collected at 15-min intervals for 15 h from a remote site from female macaques in both the follicular and luteal phase. During this time, each animal received a 4-h infusion of CRH (100-Lg bolus followed by 100 pg/h for 4 h) through an indwelling jugular catheter. Blood samples were collected for an additional 8 h after cessation of the CRH infusion. Cortisol levels were significantly elevated during and after the CRH infusion and were comparable to levels observed in animals that experienced restraint. However, CRH did not suppress LH levels in either the follicular or the luteal phase. These data suggest that CRH is not the only mediator of stress-induced inhibition of gonadotropin release in primates.

The present study investigated the question of how restraint affects the hypothalamo-pituitary adrenocortical axis and the hypothalamo-pituitary gonadal axis in intact, adult female rhesus macaques in both the follicular and luteal phases of the menstrual cycle. Restraint was chosen because it is not physically harmful to the animal but rather serves primarily as a psychological stressor. Blood samples were collected from a remote site at 15-min intervals beginning at 0700 h from tethered adult female rhesus macaques. Each animal was subjected to 6 h of chair restraint after a 3-h control period in the animal's home cage. Samples were collected for an additional 6 h after the end of the restraint period, when each animal was returned to its home cage. Brief anesthesia with ketamine (administered through indwelling catheter) facilitated transfer of the animals to and from the chair. Blood samples were also collected from undisturbed females in both the follicular and luteal phases to document LH, cortisol, and progesterone secretion throughout the day. Plasma ACTH and cortisol, measured as indices of stress, were elevated within 15 min after initiation of restraint and remained elevated after the animals were returned to their cages. In animals sampled in the follicular phase, mean plasma LH levels were lower during restraint and remained suppressed for several hours after the animals were removed from restraint. LH levels were not significantly inhibited by restraint in the luteal phase. When the opiate receptor antagonist naloxone (Nx; 5 mg bolus plus 5 mg/h) was given beginning 2 h after the initiation of restraint, LH levels were elevated compared to prerestraint levels in both phases of the menstrual cycle. These data indicate that restraint is a potent activator of the pituitary-adrenal axis and that at least in the follicular phase of the menstrual cycle, restraint inhibits pituitary LH release. This inhibition of gonadotropin release may involve endogenous opiate suppression of GnRH release, since Nx reversed the effect of restraint.

We previously have shown that 6 h of restraint stress in intact male rhesus macaques (Macaca mulatta) suppresses plasma levels of both LH and testosterone and that this effect lasts beyond the period of restraint. Since corticotropin-releasing hormone (CRH) inhibits both the GnRH pulse generator and LH release in ovariectomized macaques and is generally thought to be the central mediator of stress-induced inhibition of gonadotropin release, we investigated the influence of CRH administration on LH and testosterone in unrestrained intact male rhesus macaques. Blood samples were collected from 5 intact male macaques at 15-min intervals for 15 h from a remote site. During this time, each animal received a 4-h infusion of CRH (100-micrograms bolus followed by 100 micrograms/h for 4 h) through an indwelling jugular catheter. Blood samples were collected for an additional 8 h after cessation of the CRH infusion. ACTH and cortisol levels were significantly elevated during and after the CRH infusion and were comparable to levels observed during restraint. Although LH levels appeared lower in animals given CRH, they were not different from those in untreated control males. In some animals, CRH appeared to stimulate or prolong LH release. Testosterone levels in CRH-treated animals were significantly lower than in controls both during and after CRH administration. In some instances, increases in plasma LH were not accompanied by a rise in testosterone. This would suggest that as was observed in restrained animals, stress exerts either a direct or an indirect inhibition of testicular testosterone secretion. The present data indicate that this effect may be mediated by CRH.

Crossbred pigs were used to evaluate the effects of shipping stress on natural killer (NK) cell activity, leukocyte numbers, plasma cortisol, and BW changes. In the first study, pigs were bled at a commercial farm and, after shipping, resident and shipped pigs were bled again. Plasma cortisol concen- trations were not different (P > .lo) because of large variation in cortisol concentrations. Furthermore, NK cytotoxicity was nondetectable among all pigs. A second study showed that plasma cortisol concentra- tion rose by approximately 2.6 ng/mL (P = .018) for each minute after pigs were aroused. In the third, more controlled study, pigs were housed in pens of three pigs each. Video recordings were made during the first 24 h pigs were grouped to identify socially dominant, intermediate, and submissive pigs. At time zero (before shipping), resident pigs and those to be shipped had similar plasma cortisol concentrations. However, after the 4-h shipping experience, shipped pigs had elevated (P < .05) plasma cortisol compared with resident control pigs. Shipped pigs lost 5.1% of their BW (P < .05) compared with resident pigs, which gained .02% of their BW. Body weight change during shipping and plasma cortisol were negatively

Three experiments were performed to determine the effect of stress on the neuroendocrine-immune system in nonhuman primates. In Experiment 1 the diurnal variation in cell and hormone levels was determined. The percentages of neutrophils, monocytes, and eosinophils fluctuated throughout the 24-hr period, while white blood cell (WBC), neutrophil-to-lymphocyte ratio (N:L), hemoglobin (Hgb), natural killer cell cytotoxicity (NK activity) and beta-endorphin levels did not. Experiment 2 investigated the effects of ketamine and restraint on behavior. Scratching was increased in control monkeys and animals receiving ketamine, whereas passivity was increased in chair-restrained animals. In Experiment 3, eight adult male rhesus monkeys were restrained in primate chairs at 0600h. Behavior was filmed for 3 hr and blood samples were collected at 0700, 0800, and 0900. Whole blood was analyzed for total WBC and percentage of each leukocyte type. NK activity was also measured. Plasma levels of cortisol and beta-endorphin were determined and behavior was quantitated from video-records. WBC and the percentage of neutrophils increased during the restraint period, while the percent lymphocytes and monocytes decreased. NK activity also decreased over time after restraint whereas plasma cortisol and beta-endorphin levels increased significantly. Although after the 3 hr of restraint stress, changes were found in hormone levels, behavior, and NK activity, there were no significant correlations between the parameters measured. Thus, our results indicate that there is not a common neuroendocrine response or single neuroendocrine mediator that results in predictable behavioral changes and immune suppression following stress.

The present study investigates how restraint affects the hypothalamo-hypophysial adreno-cortical axis and the hypothalamo-hypophysial gonadal axis in intact, adult male rhesus macaques. Restraint was chosen because it is not physically painful or harmful to the animal, but rather serves both as a physical and psychological stressor. Blood samples were collected from a remote site at 15-min intervals beginning at 07.00 h from tethered adult male rhesus macaques. Each of 4 animals was subjected to 6 h of chair restraint after a 3-hour control period in the animals' home cage. Samples were collected for an additional 6 h at the end of the restraint period when the animal was returned to its home cage. Brief anesthesia with ketamine (administered through the indwelling catheter) facilitated transfer of the animals to and from the chair. Blood samples were collected from 4 undisturbed males to document LH and testosterone secretion throughout the day. Plasma ACTH and cortisol, measured as indexes of stress, were elevated within 15 min after initiation of restraint and remained elevated for most of the restraint period. Conversely, LH and testosterone began to fall immediately after restraint and remained suppressed for several hours after the animals were removed from restraint and returned to their home cage. Testosterone levels were more consistently inhibited than were LH levels, a reflection of the fact that in some animals, testosterone remained low after the return of pulsatile LH secretion. In studies with naloxone (Nx), the opiate receptor antagonist (5 mg bolus plus 5 mg/h) was given beginning either at the initiation of restraint (n = 2) or 2 h thereafter (n = 2), and continued until the end of the restraint period. With Nx treatment of the restrained animals, both ACTH and cortisol were elevated as in the controls and LH and testosterone secretion were significantly increased within 1-2 h. However, after the Nx treatment was terminated and the animals were returned to their home cages, plasma levels of LH and testosterone were not different from levels in restrained animals and were significantly less than levels in untreated animals. These data show that restraint is a potent stimulus for activation of the HPAC axis and inhibits both LH and testosterone release. The pathway through which restraint inhibits LH release probably includes endogenous opiate suppression of hypothalamic GnRH release since Nx partially blocks the effect of stress.

Central release of CRH has recently been implicated in modulating natural killer cell (NK) activity independent of its role in activation of the hypothalamic-pituitary-adrenal axis. In the present study, NK- and interleukin-2 (IL-2)-activated NK cytotoxicity against K-562 target cells was examined in porcine lymphocytes cultured in vitro with ACTH or pig lymphocytes after iv or im ACTH administration. Physiological concentrations of porcine ACTH (10(-8)-10(-11) M) added to the culture medium had no direct influence on NK- or IL-2-stimulated NK cytotoxicity. In a second experiment four unrestrained pigs with indwelling catheters given an iv bolus of vehicle or ACTH (1 IU/kg BW) at 0800 h showed significantly elevated cortisol levels for 3 h after ACTH. Although serum cortisol had returned to baseline by 4 h after ACTH treatment, NK- and IL-2-stimulated NK cytotoxicity was dramatically elevated (P less than 0.01) compared to that in saline-injected controls. NK cytotoxicity in control pigs followed a diurnal pattern, with low morning and high evening cytotoxicity. Exogenous ACTH, given by bolus in the morning, prevented the normal morning decline in NK cytotoxicity. Because of this unexpected dramatic increase in NK- and IL-2-stimulated NK cytotoxicity in animals given ACTH, the experiment was replicated in two subsequent studies using 16 pigs (8 controls and 8 experimental) in each. Pigs were injected im with either ACTH (1 IU/kg BW) or an equivalent volume of saline at 0600 h. Two hours later, blood was collected by venipuncture to determine NK cytotoxicity and measure the cortisol response. As was observed in the previous study, NK- and IL-2-stimulated NK cytotoxicity was significantly greater (P less than 0.01) than that in saline-injected controls. In the final experiment pigs were given either ACTH (1 IU/kg BW) or an equivalent volume of saline at 1800 h. Two hours later, blood was collected by venipuncture to determine NK cytotoxicity and cortisol response. ACTH administered in the evening increased NK cytotoxicity, but the effect was only marginally significant and far less dramatic than in previous studies. Because ACTH had little effect on NK- and IL-2-stimulated NK activity in vitro, we hypothesize that the stimulatory effect of exogenous ACTH is mediated through an indirect mechanism, possibly through the suppression of central CRH as a result of elevated cortisol. This effect is more pronounced when the stimulatory dose of ACTH is given at a time in the circadian cycle when NK cytotoxicity is normally low.

After completing this chapter, you should have an understanding of the following: • The definition of functional hypothalamic amenorrhea (FHA). • The causes of FHA. • The importance of seeking medical attention for this condition. • The long-term medical consequences of low estrogen levels.

The association of fertility with fatness is an ancient concept. Artifacts from France and Austria thought to be at least twenty thousand years old and considered to be representations of fertility goddesses (Schneider and Wade, 2000) depict women who would be considered obese by today standards. Although generous stores of body fat in women is associated with fertility, obese mice (Zhang et al., 1994) and humans (Montague et al., 1997; Strobel et al., 1998) who suffer from a mutation in the gene that codes for either the adipocyte hormone leptin, or for its receptor, are infertile. This suggests that a circulating signal from fat might be important for both appetite control and for fertility.

Leptin is a circulating protein produced by adipocytes that has been implicated in control of body weight through appetite regulation and control of reproduction, most likely through an effect on the central nervous system. From studies in mice, it is clear that the genetic background of the animal on which the mutation in the leptin gene is placed can influence how that mutation is expressed. Although the effects of leptin have been more thoroughly documented in nonprimate species than in primates, a few human families with genetic mutations of the gene for leptin or the leptin receptor show obesity and impaired fertility. There is conflicting evidence regarding the effects of leptin in male primates, but it appears that the metabolic and reproductive effects of low leptin levels caused by reduced energy intake in adult animals can be more readily alleviated by administration of energy substrates than by administration of leptin.

In male mammals, the neuroendocrine responses to fasting include increased GH and cortisol secretion and suppressed LH and T levels. Because blood glucose levels fall during fasting, we hypothesized that this modest, but consistent, change in blood glucose was a metabolic signal for the neuroendocrine adjustments of reproductive and metabolic hormones. Glucose (d-dextrose, 480 kcal/d) was infused into fasted (48 h) adult male rhesus macaques; and LH, cortisol, and GH were measured in plasma from samples collected at 15-min intervals for the last 15 h of the fast. We analyzed hormone secretion by deconvolution analysis, and the orderliness of release patterns by the approximate entropy statistic. Circulating blood glucose was 76 ± 7 mg/dl in the fed control group, significantly higher (P < 0.01) than the level of 56 ± 3 mg/dl in the fasted group. The increase in GH pulsatility and the 2-fold elevation in cortisol levels observed in the fasted male macaques were prevented by parenteral glucose delivery. The suppression of LH in fasted animals was not relieved by glucose infusions but seemed to be partially prevented in three of the animals. These findings are consistent with the hypothesis that glucose serves as a signal of nutritional status controlling adaptive neuroendocrine responses to fasting in the primate.

Measures of performance, mortality, adrenal weights, plasma glucocorticoid concentration, and selected immune measures were collected in an attempt to define space needs of laboratory mice. Six replications of 3 C57BL/6 male mice per cage were examined while housed on bedding at 5, 10, 15, or 20 in(2) (32.2, 64.5, 96.8, or 129 cm(2)) per mouse. Body weights were not influenced by treatment; however, mice in smaller spaces (5 in(2) per mouse) consumed or wasted more feed and water than mice given greater space allowances. Mice given the least amount of space (5 in(2) per mouse) had greater lymphocyte proliferation in response to the T-cell mitogen PHA than mice given more space. Mice provided 10 in(2) per mouse had greater natural killer cytotoxicity than mice given greater or less space. Mouse mortality was greater as more space was provided. In contrast, adrenal weights and plasma glucocorticoid concentrations were progressively greater with lower space allowances. The National Research Council 1996 recommendation of 15 in(2) per mouse, for this strain and sex of mice, would result in greater mortality and reduced activity of some immune measures. Socially housed male C57BL/6 mice will benefit from less space than recommended by the National Research Council in 1996.

During puberty, primates begin to secrete LH, and presumably GnRH, at night and then eventually throughout the day as they mature. We examined the role of vasopressin, a putative inhibitor of the GnRH pulse generator, on LH secretion in pubertal male macaques both during the day when the GnRH pulse generator was not active and during the night when pulsatile LH secretion was observed. As has been found in other primates, LH and testosterone levels were low during the day and elevated at night. A potent vasopressin receptor antagonist (VPa) was administered during the middle 5 h of a 15-hour daytime or nighttime blood collection period to determine the effects on LH, testosterone and cortisol secretion. Both during the day and night, cortisol secretion was elevated during VPa infusion, suggesting that this V1a receptor antagonist has agonist activity on the V1b receptor in the pituitary involved in vasopressin-stimulated corticotropin release. Mean LH levels during VPa infusion were not different from the control period for that group during the day when LH secretion was absent. Mean LH levels were significantly higher (p < 0.05) than pre-VPa LH levels at night when pulsatile LH secretion was observed. However, LH levels at night during VPa were not higher than levels in untreated animals at the same time. The results of these studies demonstrate that LH and testosterone profiles are similar to those observed in human males during the pubertal transition and suggest that the absence of daytime gonadotropin release during puberty is not due to inhibitory vasopressinergic tone on the GnRH pulse generator.

The effects of intracerebroventricular (icv) administration of porcine corticotropin-releasing hormone (pCRH) and cortisol on the immune system and behavior were examined in domestic pigs. In Experiment 1, 50 micrograms of pCRH in 200 microliters of saline or 200 microliters of vehicle was administered i.c.v. at 0600 h. Blood samples were obtained at 0600 (prior to injection), 0700, and 0800 h. Plasma cortisol concentrations were higher at 1 and 2 h after pCRH than after saline. Generally, pCRH failed to effect NK cytotoxicity or lymphocyte proliferation in response to phytohemagluttin (PHA). However, 1 h postinjection, pigs administered pCRH i.c.v. had marginally lower NK activity than control pigs. Pigs injected with pCRH had substantially lower neutrophil chemotaxis (CHTX) than the control pigs at 1 and 2 h postinjection. As blood cortisol concentration increased, neutrophil CHTX decreased. Pigs injected i.c.v. with pCRH had higher neutrophil numbers and neutrophil:lymphocyte ratios than control pigs. Percentage of lymphocytes was higher among control than treated pigs. Central pCRH increased overall activity, particularly walking, standing, licking, rooting, and increased activity-related sequences (e.g., sit, walk and stand, walk), but reduced complex oral/nasal sequences (e.g., root, lick). In Experiment 2, pigs were injected i.c.v. with 10 micrograms of cortisol in 200 microliters of saline or with vehicle at 0600 h. Administration of cortisol failed to effect NK cytotoxicity, lymphocyte proliferation, CHTX, or leukocyte distribution. Pigs given cortisol had no apparent change in behavior. These data indicate leukocyte distribution and specific neutrophil function in pigs were significantly modulated by stress-related hormones of the hypothalamic-pituitary-adrenal axis and complexity of behavioral sequences (pigs repeating certain behavioral sequences) associated with increased activity was reduced. Oral/nasal stereotypies (as seen among confined sows) were not elevated among pigs given i.c.v. pCRH. CRH given by i.c.v. administration may serve as a better model for acute rather than chronic stress.

Our recent observations (1) that there is a difference in circadian patterns of plasma cortisol levels between male and female macaques and (2) that after gonadectomy these differences in the patterns and in the levels of cortisol were reduced prompted us to investigate how 17 beta-estradiol (E2) and progesterone affect cortisol secretion in orchidectomized male rhesus macaques. Five male macaques, castrated as adults, were implanted subcutaneously with segments of silastic tubing filled with E2 and with progesterone in a manner such that the levels and the sequence of these hormones mimicked those that occur during the menstrual cycle of intact female macaques. Since previous studies had shown that the difference in cortisol patterns was due to higher levels in females during the day, these studies were conducted from 0800 to 2000 hours. Blood samples were collected in an adjacent room at 15-minute intervals. Separate trials were conducted 2 weeks after E2 was implanted and levels were 110 +/- 14 pg/ml and again 2 weeks later after progesterone was implanted and E2 levels were 59 +/- 15 pg/ml; progesterone levels averaged 4.0 +/- 0.65 ng/ml. Mean plasma concentrations of cortisol (microgram/100 ml) for the 12-hour period were three-fold higher in orchidectomized males treated with E2 (17.2) and with E2 + progesterone (18.0) than in intact males (4.9). Levels in males treated with ovarian steroids were double that (8.5 micrograms/100 ml) observed for intact females.(ABSTRACT TRUNCATED AT 250 WORDS)

Weanling pigs (n = 132) were used to investigate the effects of three common stressors (and a control) and differing social status on behavior, immunity, plasma cortisol, blood chemical, and performance measures. Eleven blocks of 12 pigs each were evaluated. Each pen contained three pigs of dominant (DOM), intermediate (INT), or submissive (SUB) social status. Two weeks later, random pens of pigs experienced either a control treatment (CON) or they were stressed for 4 h by shipping (SHIP), heat-stressed (HEAT) with overhead heat lamps in their home pens, or cold-stressed (COLD) by direct application of water and an air current. Treatments did not influence body weights; however, percentage weight loss during SHIP was greater than for other treatments. Body weights were heavier for DOM pigs than for INT and SUB pigs. Social status had large effects on plasma cortisol, globulin, acute-phase proteins, body weight, and weight changes. Only acute shipping stress resulted in weight loss. Many immune and blood measures were not changed among acutely stressed pigs; however, the relationship between social status and mitogen-induced lymphocyte proliferation and natural killer cell cytotoxicity was disrupted during acute stress. Pig behavior was significantly changed by each stress treatment in a unique manner. During acute stress, behavioral changes seem to be the most consistent and reliable indicators.

Porcine natural killer (NK) cell cytotoxicity, plasma cortisol, total white blood cells (WBC), neutrophil:lymphocyte ratio (N:L), and circulating blood leukocytes were examined from pigs injected i.v. with either saline, ACTH, cortisol, or treated with metyrapone. Plasma cortisol increased (P.05) after ACTH and cortisol treatments and decreased (P.05) after metyrapone treatment; thus, treatments had the intended effects on in vivo cortisol concentrations. In Exp. 1, pigs were injected with either saline or ACTH at 0600 after the initial blood samples were taken (time 0). The ACTH had no effect (P.10) on NK cytotoxicity. Pigs injected i.v. with ACTH had fewer lymphocytes and more neutrophils (P.05) than control pigs. The N:L ratio was greater (P.05) among ACTH-injected than among control pigs. In Exp. 2, pigs were injected i.v. with either saline or 40 or 400 micrograms of cortisol at 0600 after the initial blood samples were obtained (time 0). Cortisol at 40 micrograms had no effect (P.10) on NK cytotoxicity. However, a 400-micrograms bolus of cortisol reduced (P.05) NK cytotoxicity (control = 39.5, cortisol = 28.3% cytotoxicity, SEM = 3.7). Each dose of cortisol reduced (P.05) circulating blood lymphocyte numbers. In Exp. 3, pigs were fed 1 g of metyrapone or no metyrapone the night before sampling. Blood samples were obtained at 0600, 0700, and 0800. Metyrapone reduced (P.05) NK cytotoxicity (control = 28.6, metyrapone = 11.8%, SEM = 1.9). Pigs treated with metyrapone had greater (P.05) numbers of neutrophils than control pigs. Numbers of lymphocytes were greater (P.05) among control than among treated pigs. Pigs treated with metyrapone had a greater (P.05) N:L ratio than control pigs. In conclusion, normal physiological concentrations or moderately increased blood cortisol concentrations did not influence NK activity, although leukocyte distributions were changed. We conclude that greatly increased or greatly decreased circulating concentrations of cortisol reduced NK cytotoxicity.

The possibility that serotonin plays a role in prolactin secretion after electrical stimulation of the rhesus medial basal hypothalamus (MBH) was investigated. Prolactin responses to electrical stimulation and intravenous injection of 0.5 and 1.0 micrograms of thyrotropin-releasing hormone (TRH) were evaluated before and after administration of methysergide (MES), a serotonin receptor blocker (2 mg orally every 12 h for 48 h), and bromocriptine (CB-154), a dopamine agonist (2.5 mg orally every 12 h for 48 h). Both electrical stimulation and TRH caused prompt increases in serum prolactin. Prestimulation (basal) prolactin levels in both drug-treated groups were not significantly lower than basal levels in control groups. Pretreatment with MES significantly attenuated the electrically induced release of prolactin but had no effect on the TRH-induced release; CB-154 blocked prolactin release induced by both types of stimulation. The study reported here has provided evidence of a possible role for hypothalamic serotinin in releasing pituitary prolactin.

The secretion of LH, PRL, and cortisol was investigated in 4 sexually mature female rhesus macaques with cardiac catheters protected by tethers. Based on endocrine parameters, all 4 of the animals ovulated within 2 months from the time they were tethered, and regular menstrual cycles of 24-34 days were observed. The catheters remained patent for 6-12 months without reposition or repair. Plasma levels of 2 stress-labile hormones, PRL and cortisol, showed diurnal fluctuations comparable to those observed in untethered animals. The frequency of LH secretory episodes was determined by measuring bioactive LH in blood samples collected at 10-min intervals in the follicular phase and at 15-min intervals in the luteal phase of the menstrual cycle. In 10 trials during the follicular phase, we estimated that an average of between 14 and 15 LH pulses occurred every 12 h. The interpulse interval ranged between 20-80 min and averaged 50 min. No change in pulse frequency was observed across the follicular phase. The number of LH pulses decreased after ovulation, and by the end of the luteal phase, the interpulse interval was 4-6 h. One example during the preovulatory LH surge revealed the high frequency, high amplitude nature of LH secretion at that time. Our experience indicates that tethered animals with cardiac catheters show no hormonal indications of stress and represent the best available model for studies requiring frequent and prolonged access to the vascular system. Our data suggest that peripheral LH fluctuations in rhesus monkeys, as in other mammals, are pulsatile, and the frequency of these pulsatile episodes changes with different phases of the menstrual cycle, presumedly in response to varying stimuli to the pituitary from the brain.

Since male hamsters castrated as adults respond to exogenous estradiol-1 713 (E2) treatment by displaying female-like behavior, we wondered whether males, like females, would release gonadotropin following E2 treatment. To determine this, we performed 2 experiments. In experiment 1, blood samples from adult gonadectomized hamsters of both sexes were collected at 3 h intervals for 48 h starting the day after a midaftemoon injection of estradiol benzoate (EB). Serum levelsof E2, LH and FSH were quantified by radioimmunoassay. Males injected with either 50 or 200 �g of EB showed no LH or FSH surge at any time during the ensuing 2 days. Females, on the other hand, showed midafternoon peaks of LH on both days following the EB injection. In experiment 2,gonadectomized hamsters of both sexes were pretreatedwith E2 -containing implants that elevated serum E2 levels to 170 ± 20 pg/mi (mean ± SEM). The injection of 5Opg ES 1 week later induced a midafternoon surge of both gonadotropins in females but not in males. These experiments show that in hamsters the response of CNS centers that control gonadotropin release to E2 are sexually dimorphic. Furthermore, they suggest that the CNS structures that mediate gonadotropin release in males are more sensitive to masculinizing effects of prenatal androgens than those thatmediate sexual behavior.

In rhesus macaques, the concentration of immunoreactive prolactin in the amniotic fluid remains low during most of the first trimester of pregnancy and then increases abruptly at 60-80 days of gestation. During the second half of pregnancy, large amounts of prolactin accumulate in the amniotic fluid. Much of this amniotic fluid prolactin may originate from the superficial endometrium (decidua). This hypothesis is supported by the increasing amounts of decidual prolactin (dPRL) measured in endometrium obtained at early (50 days), mid-(80 days), and late (greater than or equal to 150 days) gestation. In culture, late pregnancy endometrium released more dPRL than did early pregnancy endometrium. When tissues were cultured in medium without progesterone, the amounts of dPRL measured in the medium declined steadily over 6 days, regardless of the gestational age of the endometrium. dPRL was consistently measured in medium harvested from cultures that received either progesterone or medroxyprogesterone; however, progesterone did not induce an increase in the amounts of dPRL released by cultures prepared from early pregnancy endometrium. This suggests that factors in addition to progesterone may stimulate the increase in dPRL that occurs at midgestation in rhesus macaques.

Elevations in peripheral estradiol (E2) levels inhibit the pulsatile release of pituitary gonadotropins in ovariectomized rhesus monkeys. Efforts to determine the locus of E2 action [i.e. the medial basal hypothalamus (MBH) or the anterior pituitary gland (AP)] have been plagued by the diffusion of crystalline E2 from an implantation site within the MBH to the pituitary portal vasculature and, therefore, to the AP (implantation paradox). With an Alzet osmotic minipump, we delivered 10 ng E2/h to either the third ventricle or the AP of ovariectomized rhesus monkeys for a duration of 18 h, while monitoring changes in the peripheral gonadotropin concentrations. We also infused [3H]E2 into either site to determine the extent of [3H]-E2H]-E2 diffusion by the end of the infusion period. After infusion of [3H]E2 into the third ventricle for 18 h, only trace amounts of [3H]E2 were recovered from the AP. A small amount of [3H]E2 was recovered from the MBH after 18 h of delivery directly to the AP. Infusion of E2 i...

Circadian and ultradian patterns of plasma cortisol were assessed in four intact female rhesus macaques during both the late follicular (days 9-10) and midluteal (days 21-22) phases of the menstrual cycle and compared to patterns in four ovariectomized macaques. Blood samples were drawn from a remote site at 15-min intervals for 24 h via an indwelling catheter. Measures of estrogen and progesterone were obtained for each subject. For purposes of data analyses, group cortisol measurements were collapsed across hourly intervals and submitted to analysis of variance. Pulsatile characteristics of cortisol release were determined for each subject using the PULSAR computer program. Circadian cortisol patterns, present in all three groups, were characterized by a progressive rise during early morning hours (0300-0600 h), followed by a decline of short duration. All groups then displayed an unexpected midday peak (0900-1400 h), at which time cortisol levels reached their daily zenith. In each of the three groups, cortisol levels reached a nadir during late afternoon hours shortly after the light phase ended. The amplitude of circadian changes and daily mean levels of cortisol were significantly reduced by ovariectomy, without alterations in pulsatile characteristics of cortisol secretion. Daily mean cortisol levels decreased from approximately 8 micrograms/100 ml in intact subjects to 4.5 micrograms/100 ml after ovariectomy. No significant differences in the circadian/ultradian periodicity of cortisol secretion were detected between the follicular and luteal groups. When data in the intact female groups were combined and compared to those previously obtained from gonadally intact adult male macaques, similar 24-h patterns of cortisol secretion were detected. Surprisingly, amplitude changes in cortisol concentrations after ovariectomy were temporally and quantitatively similar to those in orchidectomized males. In both male and female animals, circadian patterns of cortisol secretion were reduced by gonadectomy. These results are discussed in terms of the activational influence of gonadal steroids on hypothalamic-pituitary-adrenocortical function.

In utero regulation of primate fetal adrenal glands and their role in steroidogenesis were studied between days 125-143 of gestation (term, 167 days) in chronically catheterized rhesus monkeys. Changes in fetal and maternal plasma cortisol, progesterone, estrone, estradiol, and PRL were determined in response to infusion of dexamethasone into mothers and ACTH, TRH, PRL, hCG, or α-MSH into fetuses. Significant, (P 0.05). Despite continued supp...