Biomedical subjects

D L Hess

Publications and source records attributed to D L Hess.

At least 91 records · Page 5Linked to original sources

PubMed1989

Endogenous opiates regulate the nocturnal reduction in luteinizing hormone pulse frequency during the luteal phase of the macaque menstrual cycle.

Twenty-four-hour pulsatile patterns of bioactive luteinizing hormone (LH) and immunoactive estradiol (E2) and progesterone (P4) were measured during the mid-follicular (FP, Days 5, 6, or 7) and mid-luteal (LP, Days 7, 8, 9, or 10) phases of the menstrual cycle in six intact and in four ovariectomized (OVX) rhesus monkeys. Blood samples were collected remotely at 7.5-min (FP) and 15-min (LP, OVX) intervals via catheters in freely moving, vested monkeys. Hormonal patterns were analyzed by the MUNRO computer program. A significant coupling of LH and E2 pulses was observed during the FP and between the LH and P4 pulses during the LP. No diurnal rhythm of LH pulse frequency was observed during the FP or in OVX monkeys. In contrast, day/night differences in frequency were seen during the luteal phases (0.35 +/- 0.03 vs. 0.24 +/- 0.05 pulses/h, day vs. night, p less than 0.05). Naloxone (NAL), an opiate antagonist, was continuously infused (2 mg/h.i.v.) for 12 h at night during the LP. NAL treatment increased nighttime LH pulse frequency to 0.33 +/- 0.07 pulses/h, which was not different from the daytime LH pulse frequency, thereby abolishing the normal diurnal pattern. Interestingly, NAL treatment did not achieve the approximately 1 pulse/h frequency seen in the FP or OVX condition. These results support the hypothesis that P4 modulates the activity of an opioid system that is responsible both for a slowing of LH pulse frequency during the LP and for an additional nightly reduction in hypothalamic LH pulse-generating activity.

Animals↗

PubMed1989

Suppression of mediobasal hypothalamic gonadotropin-releasing hormone and plasma luteinizing hormone pulsatile patterns by phentolamine in ovariectomized rhesus macaques.

In gonadectomized animals, pulses of LH are secreted concurrently with pulsatile hypothalamic GnRH and it is hypothesized that pulses of GnRH are either driven or modulated by episodes of catecholamine release. The objective of this study was to determine if the alpha-adrenergic antagonist phentolamine (PHEN) can simultaneously block the release of GnRH and LH in ovariectomized (OVX) rhesus macaques. In Exp 1, simultaneous peripheral blood and mediobasal hypothalamic push-pull perfusion (PPP) samples were collected remotely at 10-min intervals for 24 h via a swivel/tether device in eight conscious, freely moving OVX rhesus monkeys. Phentolamine was continuously infused iv for 6 h at the rate of 4 mg/kg BW.h in five animals and 20 mg/kg BW.h in three animals. Infusion started at 6 h after the commencement of PPP. Sampling of PPP and blood continued for 12 h after the cessation of PHEN infusion. Exp 2 was carried out to determine if PHEN affects pituitary responsiveness to exogenous GnRH under conditions similar to those in Exp 1. Exogenous GnRH (5 micrograms, iv) was injected as a single bolus at 10-h intervals before, during, and after either a saline (4 ml/h for 6 h) infusion or, 3 weeks later, a PHEN infusion (4 mg/kgBW.h for 6 h) in three OVX females. The results of Exp 1 show that pulsatile patterns of hypothalamic GnRH and LH were either dampened or abolished by PHEN infusion. During the recovery period after PHEN infusion, pulse amplitudes of LH were enhanced, but pulse amplitudes of endogenous GnRH did not differ, as compared to those of corresponding LH and GnRH before infusion of PHEN. Data from Exp 2 suggested that the alpha-adrenergic blocking agent had no effect on the pituitary LH response to exogenous GnRH administration. These results directly support the hypothesis that adrenergic neuronal activities are critical for the pulsatile release of hypothalamic GnRH which governs the pulsatile release of LH in gonadectomized animals.

Animals↗

PubMed1989

Absence of regular pulsatile gonadotropin secretion during implantation in the rhesus macaque.

The secretory response of the primate corpus luteum (CL) to CG after implantation suggests that gonadotropin receptors are not depleted despite increasing CG production and continuous elevated tropic stimulation. Such continuous stimulation is known to cause down-regulation of receptors in other tissues. To determine if CG secretion is intermittent during the initial stages of CL rescue, we assessed the secretory pattern of CG during the periimplantation period by collecting frequent (4/h) blood samples in two studies (for 4 h on 3 separate days between days 8-13, or for 2 separate 13-h sequences between days 10-15 postovulation) in 13 chair-adapted females. Day 0 of gestation was defined as the day of ovulation, as estimated by peak urinary estrone conjugate excretion in females mated on days 9, 11, and 13 of the menstrual cycle. Hormone concentrations were measured by either RIA [irFSH; estradiol and progesterone (P)] or Leydig cell bioassay (bioLH or bioCG). In the first study, 4 of 6 females conceived, and the mean for bioLH was not significantly elevated until days 12-13. In the second study, 5 of 7 females conceived, and the episodic secretory pattern of circulating pituitary bioLH typically observed in cycling females (2.7 +/- 0.3 peaks/13 h) was replaced by a relatively nonpulsatile, but steadily increasing profile during days 12-15 of gestation (1.5 +/- 0.4 peaks/13 h). Although occasional large fluctuations in bioLH/CG and P were noted, the bioLH/P peaks were less congruent than those in nonfertile cycles, and there was no diurnal pattern in the secretion of either hormone. In contrast, irFSH concentrations did not fluctuate and were similar in the two groups of females [2.93 +/- 0.28 vs. 2.34 +/- 1.7 ng/ml (mean +/- SEM)]. These data demonstrate that 1) a steady, gradually increasing secretory pattern of CG is associated with rescue of the CL; 2) the circulating profile of CG during the periimplantation interval is not consistently episodic and does not support the hypothesis that intermittent CG release prevents LH/CG receptor down-regulation in the CL during early pregnancy; 3) increased bioLH/CG levels during conceptive cycles in rhesus monkeys are not detected until days 12-13 after the midcycle bioLH peak; 4) irFSH patterns on pooled aliquots appear to be uninformative with regard to gonadotropin dynamics in early pregnancy; and 5) urinary estrone conjugate measurements provide a practical method for the precise timing of infrequent events, such as implantation, in the laboratory macaque.

Animals↗

PubMed1988

Embryonic epsilon and gamma globin genes of a prosimian primate (Galago crassicaudatus). Nucleotide and amino acid sequences, developmental regulation and phylogenetic footprints.

Sequence analysis of epsilon and gamma genes and encoded globins and high-pressure liquid chromatography analysis of globin compositions in blood hemolysates obtained from embryos, fetuses and adults show that the prosimian primate Galago crassicaudatus expresses its epsilon and gamma genes only embryonically. Since rabbit, mouse and galago all have embryonic gamma genes but simian primates have fetal gamma genes, we conclude that gamma E evolved into gamma F in stem-simians. An elevated non-synonymous substitution rate characterizes this transition. The alignment of epsilon and gamma nucleotide sequences and the parsimoniously reconstructed evolutionary history of these sequences identify several anciently conserved cis-regulatory elements (phylogenetic footprints) important for gamma expression in primates and also cis-mutations which may have been involved in the recruitment of the gamma gene to a fetal program in simian primates.

Amino Acid Sequence↗

PubMed1988

Effects of estrogen on hypothalamic gonadotropin-releasing hormone release in castrated male rhesus macaques.

The evidence that hypothalamic gonadotropin-releasing hormone (GnRH) release increases during the estrogen-induced luteinizing hormone (LH) surge in castrated female macaques and that estrogen induces a similar LH surge in the male suggests that either sexual differentiation of GnRH secretion does not exist or that changes in brain GnRH are not critical for ovulation. We tested this hypothesis by using the push-pull perfusion (PPP) technique to monitor GnRH release in the mediobasal hypothalamus continuously from 10 h before to 50 h after estrogen injection in 9 castrated male rhesus macaques. Blood sampling and PPP were performed with monkeys freely moving in their own cage by using a specially designed swivel/tethering system. PPP samples were collected every 10 min and analyzed for GnRH concentration by radioimmunoassay. Blood samples were collected every hour and plasma LH was measured by bioassay. Estradiol benzoate (EB, 42 micrograms/kg, b. wt.) was subcutaneously injected after 10 h of initial PPP. The PPP was continued for 10 h after EB in 4 and 50 h after EB in 5 monkeys. Hypothalamic GnRH patterns were analyzed by the Pulsar algorithms. The results show that during the 10 h after EB, plasma LH declined rapidly, reaching low or non-detectable levels by 7-9 h, while hypothalamic GnRH releasing patterns did not change during this period (n = 9). In contrast, estrogen enhanced GnRH level and pulse amplitude, but not pulse frequency, several hours before mean peripheral plasma LH increased from suppressed values (n = 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

The development of the sexually indifferent gonad in the prosimian, Galago crassicaudatus crassicaudatus.

The morphogenesis of the sexually indifferent gonad of the primate Galago crassicaudatus crassicaudatus was studied by high-resolution light microscopy and electron microscopy in 15 embryos aged 26 to 33 days. Onset of gonadal development follows the morphogenesis of the mesonephros by a conspicuous interval and is identified as the time when the first primordial germinal cells arrive in the region ventral to the central third of the mesonephros; this is followed by intense proliferation of the coelomic mesothelial cells lining the area. They become organized into short piles that deepen in the underlying mesenchyme, enclosing the germinal cells in the process. Rapidly, the piles become confluent forming a compact mass, the gonadal blastema, which is soon cleaved into gonadal cords by stroma and vascular lacunae. The mesonephros becomes involved in the morphogenesis of the gonad only in late stages of development when anatomic continuities become established between the capsules of its regressing glomeruli and the elongating gonadal rete cords. These observations show that in the Galago the somatic cells of the gonadal blastema, i.e., the precursors of the definitive testicular and ovarian sustentacular cells, derive from the coelomic mesothelium in contrast to other mammals, e.g., ruminants and rodents, where they are of mesonephric derivation. This important point is discussed in light of the differences that exist among species with regard to the structural complexity, functionality, and stages of differentiation/involution of their mesonephroi on the one hand, and the time of gonadal development on the other.

Animals↗

PubMed1988

Luteal function following ovarian stimulation in rhesus monkeys for in vitro fertilization: atypical response to human chorionic gonadotropin treatment simulating early pregnancy.

This study determined if corpora lutea of hyperstimulated cycles in rhesus monkeys could be "rescued" by the pregnancy signal, chorionic gonadotropin (CG), given at the typical time of implantation. At menses, female monkeys received human follicle-stimulating hormone (hFSH, 60 IU, days 1 to 6) followed by human menopausal gonadotropin (hMG, 60 IU hFSH/60 IU luteinizing hormone [hLH], days 7 to 9). On day 10, human chorionic gonadotropin (hCG) was given to mimic the LH surge. Nine days later, a regimen of daily increasing doses of hCG (15 to 360 IU twice a day) was initiated to simulate rescue of the corpus luteum in early pregnancy. Serum levels of progesterone (P) increased through day 5 of the luteal phase but then declined. Circulating levels of bioactive LH were significantly less on days 7 to 9 of the luteal phase than at this stage in the natural cycle. The hCG regimen extended (P less than 0.05) the luteal phase in five of six animals. The hCG treatment elicited a persistent increase (P less than 0.05) in circulating P levels, rather than a transient rise typical of normal or simulated pregnancy in natural cycles. The authors conclude that (1) corpora lutea of hyperstimulated cycles can respond to CG, but (2) there are differences in luteal function during both the luteal phase and simulated early pregnancy that may be due to inadequate luteal development or the abnormal gonadotropin milieu existing after ovulation or both.

Animals↗

PubMed1988

Pulsatile patterns of gonadotropins and ovarian steroids during estrus and pseudopregnancy in the rabbit.

Consecutive daily plasma levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol-17 beta (E2), progesterone (P4) and 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OHP) were monitored in estrous rabbits and in these same doses during pseudopregnancy (PSP); these daily hormone levels, as well as the immediate post-coital changes in gonadotropin secretion, were similar to those in previous reports. To examine the pulsatile patterns of the gonadotropins and ovarian steroids, sequential, 10-min plasma samples were collected for 6 h from estrous does and on Days 3, 10, and 17 of PSP. All five hormones were measured in the serial samples from estrous and PSP Day 10 does; LH and FSH only were assayed in the remaining sequential samples. The amplitude and frequency of FSH pulses did not differ between any of these stages. In marked contrast, LH pulse amplitudes, and even pulse frequencies in Day 17 does, were profoundly increased during PSP above those in estrous does. Progestin secretions, both P4 and 20 alpha-OHP, also were sharply elevated in PSP Day 10 does as compared with those in estrous rabbits; the pulse amplitudes of both progestins were severalfold higher during PSP. P4 pulse frequencies were also increased at this time. Conversely, the parameters of E2 secretion did not differ between estrous and PSP Day 10 animals. In PSP Day 10 does, high amplitude pulses of both P4 and 20 alpha-OHP occurred simultaneously with high amplitude LH pulses. Simultaneous E2 and P4 pulses were evident in these same sequential plasma samples, and this E2-P4 pulse association was greater than that of 20 alpha-OHP pulses with E2 pulses. Our findings failed to identify conclusively the trophic stimulus for the progestin pulse patterns, but the mechanism may involve the coordinated action of LH and E2. The results do demonstrate that each gonadotropin and ovarian steroid is secreted in a pulsatile manner in both estrous and pseudopregnant rabbits. There are altered profiles in LH and progestin pulses, without major changes in FSH and E2 patterns, between the stages of estrus and PSP. The causes and consequences of these divergent endocrine shifts cannot be deduced from these data.

20-alpha-Dihydroprogesterone↗

PubMed1988

Serum concentrations of oestradiol and progesterone, and sexual behaviour during the normal oestrous cycle in the leopard (Panthera pardus).

Three mature nulliparous female leopards were studied for 5 years. During three separate 6-month periods serum oestradiol and progesterone concentrations were measured at weekly intervals. Oestradiol was elevated over 21 pg/ml for 54 weeks during these 3 periods, and 36 oestradiol peaks (65.8 +/- 6.3 pg/ml (mean +/- s.e.m.), range 21-172 pg/ml) were identified. Daily frequency of feline reproductive behaviours averaged over each week increased from 1.9 +/- 0.2 (n = 93) during weeks with low serum oestradiol concentrations (less than 21 pg/ml) to 5.3 +/- 0.6 (n = 54) during weeks when serum oestradiol concentrations (greater than 21 pg/ml) were high. Increased serum progesterone concentrations (13-98 n/gml) were observed on 5 occasions in 2 leopards housed together. These presumptive luteal phases lasted from 1 to 5 weeks. Baseline progesterone values were 1.6 +/- 0.4 ng/ml (n = 131). No progesterone increments were observed in isolated animals, and serum concentrations remained at baseline levels. These limited observations suggest that female leopards do not require intromission to induce ovulation and luteal function. The average interval between oestradiol peaks for cycles with no progesterone increment was 3.4 weeks (range 1-6 weeks). The interval for the 3 complete cycles associated with elevated progesterone concentrations was 7.3 weeks. Analysis of sexual behaviours over the 5-year study period revealed no evidence of seasonality in these captive leopards.

Animals↗

PubMed1987

Comparison of serum estradiol to urinary estrone conjugates in the rhesus macaque (Macaca mulatta).

Paired urine and serum samples were collected daily during fourteen nonconceptive (7 females) and ten conceptive (9 females) ovarian cycles from a total of 12 female rhesus monkeys (Macaca mulatta). Daily urine samples were analyzed for concentrations of estrone conjugates (Ei Conj). Serum samples were evaluated for concentrations of estradiol (E2) and progesterone (P) by radioimmunoassay (RIA), and bioactive luteinizing hormone (bLH) and monkey chorionic gonadotropin (mCG) were analyzed by a mouse Leydig cell bioassay. Linear correlation (r) between urinary E1 Conj and serum E2 (r range = -0.176-0.948) during nonconceptive cycles aligned by the preovulatory E1 Conj peak (Day 0) improved when daily hormone values were realigned to account for an approximately 24-h delay in the excretion of hormonal metabolites in urine (r range = 0.465-0.967). Similarly, correlation between urinary E1 Conj and serum E2 during conceptive cycles aligned by Day 0 (r range = 0.300-0.824) improved when values were offset by 24 h (r range = 0.408-0.876). When conceptive cycles were compared to nonconceptive cycles, serum P levels were significantly elevated over nonconceptive levels by Day +12 (p less than 0.001), and urinary E1 Conj levels by Day +13 (p less than 0.02), whereas serum E2 and bLH were both significantly elevated by Day +14 (p less than 0.0006 and p less than 0.01, respectively). In both nonconceptive and conceptive cycles, urinary E1 Conj paralleled serum E2 and demonstrated incremental increases above baseline levels, which were greater than for serum E2.

Animals↗

PubMed1987

Opiatergic inhibition of pulsatile luteinizing hormone release during the menstrual cycle of rhesus macaques.

The endogenous opioid peptides (EOPs) may inhibit the rate of hypothalamic gonadotropin-releasing hormone (GnRH) release and hence the frequency of pulsatile luteinizing hormone (LH) release, particularly in the luteal phase of the menstrual cycle. Our objectives were to compare the effects of an opiate antagonist, naloxone (NAL), on the patterns of LH, estradiol-17 beta (E2), and progesterone (P4) secretion during the follicular and luteal phases of the macaque menstrual cycle. Plasma levels of E2, P4, and bioactive LH were measured in serial, 15-min blood samples during 8-hr infusions of NAL (2 mg/hr) or saline, either on Days 5 or 6 of the follicular phase (FN and FS, n = 5 and 4, respectively) or on Days 8, 9, or 10 of the luteal phase (LN and LS, n = 5 each) of a menstrual cycle. The pulsatile parameters of each hormone were determined by PULSAR analysis and the correspondence of steroid pulses with those of LH were analyzed for each cycle stage in each animal. As expected, LH mean levels and pulse frequencies in LS monkeys were only about one-third of those values in FS animals. NAL had no effects on pulsatile LH, E2, or P4 release during the follicular phase. In contrast, luteal phase NAL infusions increased both LH mean levels and pulse frequencies to values which were indistinguishable from those in FS animals. LH pulse amplitudes did not differ among the four groups. Mean levels and pulse frequencies of P4 secretion in LS monkeys were about 4- and 14-fold greater than those values in FS animals. Mean levels and pulse amplitudes of P4 release in LN animals were greater than those values in all other groups. LH and E2 pulses were not closely correlated in follicular phase animals, and this pulse association was not altered by NAL. In FS monkeys, LH and P4 pulses were not correlated; however, NAL increased this LH-p4 pulse correspondence. LH and P4 pulses were closely correlated in luteal phase animals and this association was not affected by NAL. Our data suggest that the EOPs inhibit the frequency of pulsatile LH secretion in the presence of luteal phase levels of P4. During the midfollicular phase when LH pulses occur every 60 to 90 min, the opioid antagonist NAL alters neither the pulsatile pattern of LH release nor E2 secretion, but NAL may directly affect P4-secreting cells.

Animals↗

PubMed1986

Release rates of catecholamines, GABA and beta-endorphin in the preoptic area and the mediobasal hypothalamus of the rhesus monkey in push-pull perfusates: correlation with blood hormone levels.

Push-pull cannulae were implanted into the preoptic area and into the mediobasal hypothalamic median eminence complex of ovariectomized rhesus monkeys. After recovery, perfusion of the implanted areas was performed over a period of 56 h before and following estradiol benzoate treatment. This treatment results in a drop of LH levels followed by an increase. Catecholamine (norepinephrine, epinephrine and dopamine) concentrations in perfusates collected at 15 min intervals fluctuated tremendously prior to treatment with the estrogen. These fluctuations were largely reduced in perfusates of both structures following the estrogen treatment. They reoccurred at the time of increasing LH levels. beta-endorphin and GABA concentrations were also measured in the perfusates of both structures. Occasional secretory bursts were observed without any obvious relation to the estrogen treatment. It is concluded that catecholamine release in the preoptic area and in the mediobasal hypothalamic median eminence complex is of a pulsatile nature in ovariectomized rhesus monkeys. This pulsatility is largely reduced or abolished following estrogen treatment. The reduced pulsatility may bear a signal character for the release of LH.

Animals↗

PubMed1986

Differential suppression of progesterone receptors by progesterone in the reproductive tract of female macaques.

Ovariectomized cynomolgus macaques were treated with implants of estradiol (E2) for 14 days. Some animals then received an additional implant of progesterone (P) for 7-14 more days. After treatment with either E2 alone or with E2 plus P we removed the reproductive tracts and measured nuclear and cytosolic P receptors by exchange assay. In addition we used steroid radioimmunoassays(RIA) to measure levels of E2 and P in parallel aliquots of the nuclear and cytosolic fractions. P treatment reduced the concentrations of E2 in nuclear and cytosolic fractions in the cervix, endometrium, myometrium and oviduct compared to the amounts present after 14 days of E2; these data are consistent with many reports that P treatment significantly lowers the amount of nuclear and cytosolic estrogen receptors in all of these tissues. In the oviduct, myometrium and cervix both cytosolic and nuclear P receptor levels were lowered during P action. In the endometrium, however, P treatment reduced the amount of P receptor only in the cytosolic but not the nuclear fraction. RIA determinations of the amount of P retained in nuclear fractions of the P-treated animals indicate that P levels were significantly elevated only in the nuclei obtained from endometrium. This specific increase in the retention of P by endometrial nuclei during P action is consistent with the specific retention of P receptor by endometrial nuclei. These results lead to the unexpected conclusion that the stimulatory effects of P as expressed in the maintenance of the progestational state in the primate endometrium may require higher levels of occupied nuclear P receptor than do the suppressive effects of P as expressed in oviductal atrophy, diminished cervical secretion and myometrial quieting.

Animals↗

PubMed1986

Alterations in sex steroid-binding protein (SBP), corticosteroid-binding globulin (CBG), and steroid hormone concentrations during pregnancy in rhesus macaques.

Temporal relationships between concentrations of sex steroid-binding protein (SBP), corticosteroid-binding globulin (CBG), total and free estradiol, total and free testosterone, cortisol, and progesterone were studied in plasma obtained at 1- to 3-day intervals throughout gestation in six rhesus macaques. Concentrations of SBP and CBG were measured by diethylaminoethyl cellulose filter assays. Total and free steroids were estimated by radioimmunoassay and ultrafiltration dialysis, respectively. We found that SBP was elevated between days 30 and 50 and CBG between days 60 and 140; both then declined until term (167 days). Estradiol increased gradually throughout gestation. Testosterone was elevated between days 10 and 40, then declined, and rose slightly in late gestation until approximately 15 days before delivery, when it increased markedly. Free estradiol and testosterone increased dramatically before parturition. Progesterone was elevated between days 25 and 45 and declined to relatively constant levels thereafter. Cortisol was essentially unchanged throughout gestation. Our data show that in the pregnant rhesus, levels of SBP and CBG vary independently of one another, but both decline before term; concentrations of both total and free estradiol and testosterone increase markedly before parturition; in late gestation, elevated estrogen is not associated with increased levels of SBP or CBG (as it is in human females).

Animals↗

PubMed1986

Feedback effects of ovarian steroids on the hypothalamic-hypophyseal axis in the rabbit.

The feedback effects of two ovarian steroids, estradiol-17 beta (E2) and 20 alpha-hydroxypregn-4-en-3-one (20 alpha OH), were examined in both intact (INT) and ovariectomized (OVEX) does. We measured steroid-induced alterations in endogenous gonadotropin-releasing hormone (GnRH) from sequential 10-min samples of hypothalamic perfusates, simultaneous changes in peripheral plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and the modification of pituitary responsiveness, i.e., increments in plasma LH (delta LH) and plasma FSH (delta FSH), after 50 ng, 250 ng, and 1 microgram of exogenous GnRH in individual does of 6 treatment groups. The groups were: INT does, OVEX does, OVEX does receiving either one (1 E2) or two (2 E2) E2-filled Silastic capsules, OVEX does receiving a 20 alpha OH-filled capsule (20 alpha OH), and OVEX does receiving both capsules of E2 and 20 alpha OH (1 E2 + 20 alpha OH). Ovariectomy enhanced the pulsatile release of hypothalamic GnRH and pituitary LH and FSH, and increased the LH response (delta LH) to exogenous GnRH (OVEX vs. INT, p less than 0.05). Replacement of E2 at the time of ovariectomy prevented the increased GnRH and gonadotropin secretion as well as the enhanced delta LH that were observed in untreated OVEX does. The release of hypothalamic GnRH in the 20 alpha OH group was lower (p less than 0.05) than that in the OVEX group and not different from that in the INT group. The release of pituitary LH and FSH and the delta LH in the 20 alpha OH group was not different from that in the OVEX group, but these parameters were greater (p less than 0.05) than those in the INT group. The hypothalamic GnRH pulse frequency in the 1 E2 + 20 alpha OH group was lower (p less than 0.05) than that in either the 1 E2 or the 20 alpha OH group, but the delta LH in the 1 E2 + 20 alpha OH group was not different from that in either the 1 E2 or the 20 alpha OH group. The highest dose (1 microgram) of exogenous GnRH stimulated a modest increase in FSH in the OVEX, 20 alpha OH, 1 E2 + 20 alpha OH, and 1 E2 groups; but a steroid effect on delta FSH among these 4 groups was not apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

20-alpha-Dihydroprogesterone↗

PubMed1986

The androgen status of aging male rhesus macaques.

Whether the rhesus male experiences changes in the dynamics of testosterone (T) and LH secretion with age was investigated in six young (6-8 yr old; 7-12 kg) and six aged (22+ yr old; 9-11 kg) intact rhesus males. Each male was fitted with an indwelling jugular catheter, which was attached to a cranial platform and stainless steel cable tether. Catheters passed from a swivel device at the top of each cage through a wall to an adjoining room. On four occasions, 1.0-ml blood samples were obtained from each male every 20 min for 24 h for plasma T RIA and plasma LH bioassay. Plasma T and LH data were analyzed by the PULSAR program to detect hormone peaks. Mean 24-h plasma T levels were similar in young and aged males as were the pulse amplitudes of T; however, the pulsatile pattern of T concentrations was different between young and aged males. Young males displayed a marked nocturnal increase in both T concentration and number of T pulses. Aged males demonstrated a significant nocturnal elevation of plasma T concentration, but displayed a significant nocturnal diminution in both concentration and numbers of T pulses compared with young males at night. Although LH concentrations and the total number of LH pulses per 24 h were similar in young and aged males, marked age-related alterations were evident in the pulsatile pattern of LH levels. Unlike young males, aged males failed to display a daytime reduction in the number of LH pulses. Our data point to coexistent changes in hypothalamic sensitivity to the negative feedback effects of T and testicular responsiveness to LH as a function of age in the rhesus macaque.

Aging↗

PubMed1986

Persistence of fetal zone function in the infant rhesus monkey adrenal gland.

Plasma dehydroepiandrosterone sulfate (DHAS) concentrations increase markedly in the rhesus monkey fetus at the end of gestation. A further increase occurs in the infant. To determine whether the changes in plasma concentration between the fetus and infant represent maintenance of DHAS production by the infant adrenal gland, we measured the t1/2, distribution volume (VD), MCR, and production rate of DHAS in the late gestation rhesus monkey fetus (129-155 days gestation; term is 165 days) and infant (14-42 days of age). A single bolus dose of [3H]DHAS was injected into five fetuses and four infants, and blood samples were collected serially from 5 min to 24 h after the injection. The amount of [3H]DHAS in the circulation was measured after solvolysis, extraction, and Celite chromatography. The concentration of DHAS in each sample was measured by RIA. DHAS was cleared significantly more rapidly in the fetus than in the infant [MCR in fetus, 2.4 +/- 0.4 (+/- SE); MCR in infant, 0.6 +/- 0.2 liters day-1 kg-1]. The t1/2 of DHAS was shorter in the fetus than in the infant (1.0 +/- 0.1 vs. 3.3 +/- 0.7 h). Absolute VD values were larger in the fetus than in the infant (231 +/- 29 and 143.8 +/- 11.6 ml kg-1); however, they were similar when the fetal VD was calculated including placental weight as a component of fetal weight. The production rate of DHAS, calculated as the product of MCR and integrated plasma DHAS concentration for the duration of the experiment, was not significantly different between the fetus and the infant (1.0 +/- 0.2 and 3.3 +/- 1.2 mg kg-1 day-1) in spite of the marked differences in plasma DHAS concentrations (445.8 +/- 103.8 ng ml-1 in the fetus and 5165 +/- 1296 ng ml-1 in the infant). These results indicate that the adrenal of the infant rhesus monkey continues to secrete DHAS at a rate at least as high as that in the late gestation fetus. Since the infant maintains DHAS production similar to that of the fetus in the absence of the placenta, a corollary of these studies is that the elevated DHAS secretion in the rhesus infant is independent of the placenta or the hormonal milieu of pregnancy. The maintenance of a functional fetal zone in the adrenal gland makes the rhesus infant a suitable model to use in studying the regulation of DHAS secretion and fetal zone morphology.

Adrenal Glands↗

PubMed1984

Testosterone and dihydrotestosterone concentrations in elephant serum and temporal gland secretions.

Serum and temporal gland secretions (TGS) were obtained from mature wild African (Loxodonta africana) and captive Asian elephants (Elephas maximus). Samples were obtained from five cows and eight bulls culled for management purposes in Kruger National Park, South Africa, and from four females and two males residing at the Washington Park Zoo, Portland, Oregon. Our purpose was to describe the levels of the androgens, testosterone (T), and dihydrotestosterone (DHT), and to correlate these observations with sex, species and behavioral status. Male-female differences in serum T were pronounced in the Asian species, whereas male and female concentrations overlapped in the African elephant serum. Serum T concentrations in African females were greater than in Asian females. Serum DHT reflected T levels, except that the striking elevation of testosterone in Asian bulls during musth was not paralleled by equal increases in DHT levels. A species difference observed among males was higher serum T levels in nonmusth Asian bulls (1.84-5.35 ng/ml) compared to the levels in African bulls (0.38-0.68 ng/ml), except for one dominant African bull (6.64 ng/ml). This single African value was still considerably lower than the serum T values of the Asian males during musth. These musth values were the highest serum androgen concentrations: T was between 19 and 40 ng/ml (average 26.10 ng/ml). The TSG values of T and DHT were much higher than serum levels except in the Asian female. T/DHT ratios in TGS were more similar than in serum. One dominant African bull had a T TGS value of 78 ng/ml, which was much higher than the rest of the African males or females, but considerably lower than as Asian bull in musth (547 ng/ml). It seems apparent that a change in androgen status as reflected in serum and TGS levels of T and DHT precedes or is concomitant with overt alteration in behavior in the Asian male. The temporal gland appears to actively concentrate androgens in both African males and females, but in the Asian male the gland secretes only during musth when the greatest concentration of both T and DHT were observed. The apparent difference in the degree of temporal gland secretory activity between the two species suggests a more specific communicative function within the Asian male.

Animals↗