Season determines timing of first ovulation in rhesus monkeys (Macaca mulatta) housed outdoors

In order to determine the relative importance of age and season on the occurrence of first ovulation in rhesus monkeys, the timing of puberty in spring-born females (Group S, N = 13) was compared to that of fall (N = 3) and winter-born (N = 5) females (Group W). All females were housed outdoors and were studied from 12 months of age through first ovulation. Menarche occurred at a similar age but significantly earlier in the year for Group W (31.2 +/- 0.7 months; 25 August +/- 19.5 days) than for Group S females (31.2 +/- 0.7 months; 14 November +/- 17.1 days). First ovulation, as assessed from twice weekly serum progesterone determinations, occurred exclusively in the fall or winter in a bimodal age distribution for all females. For Group W females, 6/8 ovulated during the 3rd year at 35.8 +/- 0.7 months while 2/8 ovulated during the 4th year at 45.3 +/- 0.1 months. In contrast, only 3/13 Group S females ovulated during the 3rd year and at a significantly younger age of 31.4 +/- 0.4 months compared to Group W. The remaining Group S females (10/13) ovulated the following autumn at 43.2 +/- 0.2 months, significantly younger than the later ovulating Group W females. In addition to this pattern of first ovulation, serum concentrations of prolactin varied seasonally, rather than with age, in both groups of females with higher levels in the summer and low levels in the winter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproductive inhibition in the Cape porcupine, Hystrix africaeaustralis

Sexually mature female Cape porcupines kept under natural conditions of illumination and temperature did not conceive while housed within their natal groups. Before removal from their natal groups the sexually mature offspring copulated and experienced cyclic ovarian activity, but conception occurred only 70-120 days after dispersal. Mean oestrous cycle length of these females (36.9 +/- 11.5 days; n = 34) was similar to that of breeding females (33.0 +/- 11.64 days; n = 16), but mean peak plasma progesterone concentration (6.45 +/- 6.03 ng/ml; n = 34) was significantly (P less than 0.01) lower than that of cyclic breeding females (13.58 +/- 6.98 ng/ml; n = 16). Mean progesterone concentration at oestrus in non-breeding females (0.72 +/- 0.45 ng/ml; n = 34) was also significantly (P less than 0.01) lower than that of non-pregnant breeding females (4.21 +/- 2.44 ng/ml; n = 16). Reproductive inhibition within natal groups, in which only one female reproduces, therefore cannot be ascribed to a failure to copulate, but may be due to some factor inhibiting full expression of luteal activity or affecting ovulation.     

Fecal steroid analysis for monitoring reproduction in the sun bear (Helarctos malayanus)

Fecal steroid analyses were conducted on captive (n = 10) and free-ranging (n = 2) sun bears (Helarctos malayanus) in order to establish a noninvasive technique for monitoring endocrine profiles during the estrous cycle and pregnancy. Secondly, the effect of the contraceptive porcine zona pellucida protein (PZP) on reproductive function was studied. Finally, we investigated whether the sun bear, naturally living in the aseasonal tropical forests of Southeast Asia, is a seasonal breeder. Fecal samples were collected over periods of 7-48 months in captive untreated (n = 8) and PZP-treated (n = 2) female sun bears. In addition samples were collected over a period of 12 months from radio-collared free-ranging females (n = 2) in their natural habitat in Indonesian Borneo. Androgens, precursors of estrogens, were found to be reliable indicators of the follicular phase, whereas estrogens were found unsuitable. Pregnanediol assay was found to be a reliable indicator of luteal function. Results indicate that sun bears are polyestrous, nonseasonal breeders. Interestrus intervals in nonpregnant animals (n = 2), which were monitored for 27 months, were between 140 and 216 days. Luteal phases (89.6 +/- 3.7 days; n = 9) were preceded by androgen peaks of 15.2 +/- 1.0 days (n = 10). Hormonal profiles of two females treated with PZP indicated missing ovarian activity in one, and persistent follicular and luteal activity in another animal. However, extended periods of missing ovarian, and persistent follicular and luteal activity were also observed in other sun bears studied.     

Gender differences in deep venous thrombosis in a rat model: a preliminary study

The purpose of this study was to determine whether gender differences have an effect on inflammation and thrombosis in a rat model of venous thrombosis. A thrombus was created in mature female (n = 12) and male (n = 12) Sprague Dawley rats (Rattus norvegicus) by ligating the inferior vena cava (IVC). The IVC containing the thrombus was harvested at 1 and 3 days postligation, weighed, measured, and submitted for immunohistochemical analysis. In addition, hematology was performed at selected time points. There were no statistically significant differences in thrombus mass (mean +/- 1 standard deviation) between female and male rats at 1 (683 +/- 47.7 x 10(-4) versus 660 +/- 112.0 x 10(-4) g/cm) or 3 (683 +/- 83.3 x 10(-4) versus 580 +/- 86.0 x 10(-4) g/cm) days post-ligation. Females had significantly more platelets than did males on day 1 (741 +/- 37.2 versus 523 +/- 55.1 K/microL, P < 0.01). Day 3 males showed significant increases in vein wall neutrophils (18.0 +/- 2.30 versus 11.2 +/- 1.38, P < 0.05), ED-1-positive monocytes (54.4 +/- 16.0 versus 18.7 +/- 5.63, P < 0.05), and circulating white blood cells (15.4 +/- 0.947 x 10(3) versus 10.9 +/- 0.714 x 10(3)/microL, P < 0.01) at post-thrombosis when compared with females. We conclude that although female rats had greater thrombus mass, the male rats demonstrated more inflammatory cells in circulation and in their vein walls. This finding suggests that inflammation plays a role in thrombus resolution.     

The use of steroid hormones in superovulation of Nelore donors at different stages of estrous cycle

The objective of the present study was to evaluate the superovulatory response and ova/embryo recovery from Nelore donors following treatment with a controlled internal drug releasing device and estradiol benzoate (CIDR-B program) at different stages of the estrous cycle. The control group (TI; n=40) received a standard superovulation protocol with females of this group being between days 9 and 12 of the estrous cycle (estrus = day 0). The donors that received a CIDR-B program containing 1.9 g progesterone and an intramuscular injection of estradiol benzoate (2 mg) were at day 0 (TII; n=30), between days 2 and 6 (TIII; n=30), days 7 and 12 (TIV; n=30), days 13 and 16 (TV; n=30) and days 17 and 20 (TVI; n=30) of the estrous cycle. Superovulation was induced with 400 IU of p-FSH, divided into eight decreasing doses (80/80; 60/60; 40/40; 20/20) at intervals of 12h. The donors received PGF2alpha (Cloprostenol) 48 h after beginning the treatment and CIDRs were removed 12h later. Artificial inseminations (AI) were performed 12 and 22 h after the initiation of estrus and embryos were collected 7 days after AI. The mean numbers (+/-S.E.M.) of total ova and embryos, viable (transferable) and degenerated embryos were 14.2+/-11.3, 7.4+/-6.9 and 3.2+/-3.5 (TI), 13.3+/-10.4, 7.1+/-6.2 and 3.3+/-4.3 (TII), 13.5+/-7.0, 8.1+/-6.7 and 2.3+/-3.0 (TIII), 17.4+/-9.9, 9.4+/-6.9 and 4.0+/-4.4 (TIV), 16.9+/-8.8, 9.8+/-8.1 and 2.7+/-2.5 (TV) and 13.0+/-7.8, 7.2+/-6.9 and 2.3+/-2.5 (TVI), with no significant differences (P>/=0.05) among groups. Pregnancy rates of 67.1% (TI; n=86/128), 60.8% (TII; n=59/97), 62.5% (TIII; n=73/115), 64.1% (TIV; n=84/131), 72.3% (TV; n=81/112) and 60.6% (TVI; n=63/104) were obtained with embryos transferred from these collections and did not differ significantly (P>/=0.05) among groups. The results of the present study allow us to conclude that a combination of steroid hormones may be used prior to superovulation in Nelore donors, at any stage of the estrous cycle without affecting the efficiency of embryo transfer programs.     

Seasonal effects on the endocrine pattern of semi-captive female Asian elephants (Elephas maximus): timing of the anovulatory luteinizing hormone surge determines the length of the estrous cycle

Better breeding strategies for captive Asian elephants in range countries are needed to increase populations; this requires a thorough understanding of their reproductive physiology and factors affecting ovarian activity. Weekly blood samples were collected for 3.9 years from 22 semi-captive female Asian elephants in Thai elephant camps to characterize LH and progestin patterns throughout the estrous cycle. The duration of the estrous cycle was 14.6+/-0.2 weeks (mean+/-S.E.M.; n=71), with follicular and luteal phases of 6.1+/-0.2 and 8.5+/-0.2 weeks, respectively. Season had no significant effect on the overall length of the estrous cycle. However, follicular and luteal phase lengths varied among seasons and were negatively correlated (r=-0.658; P<0.01). During the follicular phase, the interval between the decrease in progestin concentrations to baseline and the anovulatory LH (anLH) surge varied in duration (average 25.9+/-2.0 days, range 7-41, n=23), and was longer in the rainy season (33.4+/-1.8 days, n=10) than in both the winter (22.2+/-4.5 days, n=5; P<0.05) and summer (18.9+/-2.6 days, n=8; P<0.05). By contrast, the interval between the anLH and ovulatory LH (ovLH) surge was more consistent (19.0+/-0.1 days, range 18-20, n=14). Thus, seasonal variation in estrous cycle characteristics were mediated by endocrine events during the early follicular phase, specifically related to timing of the anLH surge. Overall reproductive hormone patterns in Thai camp elephants were not markedly different from those in western zoos. However, this study was the first to more closely examine how timing of the LH surges impacted estrous cycle length in Asian elephants. These findings, and the ability to monitor reproductive hormones in range countries (and potentially in the field), should improve breeding management of captive and semi-wild elephants.     

Seasonal variation in the endocrine-testicular function of captive jaguars (Panthera onca)

Captive adult male jaguars (Panthera onca) from two locations in southeast Brazil were studied to evaluate the effects of season on endocrine and testicular function. For assessment of testicular steroidogenic activity, androgen metabolite concentrations were measured in fecal samples collected one to three times per week over 14 ( n=14 ), 9 ( n=1 ) or 7 months ( n=1 ). To assess seasonality, data were grouped by season (summer: December-February; autumn: March-May; winter: June-August; spring: September-November). Additionally, samples collected in the dry season (March-August) were compared with those collected in the wet season (September-February). There were no differences ( P>0.05 ) in fecal androgen concentrations in samples collected in spring, summer, autumn, and winter ( 480.8+/-50.4 ng/g, 486.4+/-42.0 ng/g, 335.4+/-37.7 ng/g, and 418.6+/-40.4 ng/g dry feces). However, there were differences ( P<0.05 ) in fecal androgen concentrations between the dry and wet seasons ( 380.5+/-28.0 ng/g versus 483.9+/-32.3 ng/g dry feces). Sperm samples, collected from all males twice (approximately 6 months apart) were similar; mean (+/-S.E.M.) motility, concentration and morphology were 57.0 %4.5%, 6.3+/-2.4 x 10(6) ml(-1), and 60.8+/-3.1 %, respectively. In conclusion, androgen metabolite concentrations in the captive male jaguar were not affected by season, but there was a difference between the wet and dry periods. Further research is needed to verify these results.     

Seasonal analysis of semen characteristics,serum testosterone and fecal androgens in the ocelot (Leopardus pardalis), margay (L. wiedii) and tigrina (L. tigrinus)

Captive adult male ocelots (Leopardus pardalis, n = 3), margays (L. wiedii, n = 3) and tigrinas (L. tigrinus, n = 4) in two locations in southern Brazil were studied for 14 consecutive months to evaluate the effect of season on testicular function. Reproductive evaluations, including testicular measurements, electroejaculation and blood collection were conducted monthly. Fecal samples were collected weekly for androgen metabolite analysis to assess testicular steroidogenic activity. Ocelots had the highest number of motile spermatozoa in the ejaculate (114.7+/-15.8 x 10(6); P < 0.05), the highest percentage of morphologically normal spermatozoa (82.4+/-1.2%; P < 0.05) and the highest concentration of fecal androgens (1.71 vs. 0.14 microg/g; P < 0.05). Margays and tigrinas had lower numbers of motile spermatozoa (23.4+/-2.8 x 10(6), 74.2+/-8.9 x 10(6), respectively), lower percentages of morphologically normal spermatozoa (57.4+/-2.8, 59.2+/-3.5%, respectively), and lower fecal androgen concentrations (0.15+/-0.01, 0.23+/-0.01 microg/g, respectively). Serum testosterone concentrations were similar among the three species. Fecal androgen concentrations were not affected by season, with the exception of the ocelot where concentrations were higher (P < 0.05) in the summer. Ejaculates were collected throughout the year; however, peaks in average sperm production were observed during the summer for all species. In summary, this study has identified several species differences in male testicular traits among ocelots, margays and tigrinas. Results of longitudinal reproductive assessments suggest males of each species are capable of breeding throughout the year.     

Breeding of African green monkeys (Cercopithecus aethiops) under indoor individually-caged conditions.

This paper reports the results of reproduction with 45 wild African green monkeys (Cercopithecus aethiops) (36 females and 9 males) during the nine years from 1981 to 1989 under indoor individually-caged conditions. In 206 cases of menstruation observed, menstrual discharge lasted for 2.5 +/- 1.2 days in cycles of 22-48 days, and the length of each menstrual cycle was 31.2 +/- 6.5 days. Females who had regular menstrual cycles were subjected to "one-to-one timed mating"; females and males were put together on a one-to-one basis daily only for a certain period of time on and after the day of ovulation. Females who had irregular menstrual cycles or had no menstruation were subjected to "every-other-day mating"; females and males were put together on a one-to-one basis every other day for at least 16 weeks. The pregnancy rate (No. of pregnant females/No. of mated females) by one-to-one timed mating was 48.9% (116/237); 2.0 mating trials were needed to obtain one case of pregnancy. On the other hand, the pregnancy rate (No. of pregnant females/No. of mating trials) by every-other-day mating was 96% (48/50). Females who delivered normally totaled 129. The mean gestation period was 165 days when males, weighing 343 g on average at birth, were delivered, and 166 days when females, weighing 318 g on average at birth, were delivered. The male and female newborns were nursed for 131 and 138 days, respectively, on average. Details are summarized in Table 3. This paper also reports 23 cases of abortion, 6 stillbirths, and 6 cases of Caesarean section, by which three live fetuses and three dead fetuses were obtained.     

Development from birth to sexual maturity in a semi-free-ranging colony of mandrills (Mandrillus sphinx) in Gabon.

This report presents information collected over 7 years (1983-1990) in Gabon, on a breeding group of 14, increasing to 45, mandrills maintained in a rainforest enclosure. Under these conditions, a seasonal cycle of mating (June-October) and birth (January-May) occurred. Females began to exhibit sexual skin swellings at age 2.75-4.5 years (3.6 +/- 0.6 years, mean +/- SD; n = 10) and first delivered offspring when 3.25-5.5 years old (4.4 +/- 0.8 years; n = 9). Gestation periods ranged from 152 to 176 days (167 +/- 9 days; n = 6 accurately dated pregnancies) and interbirth intervals from 11 to 15 months (12.4 +/- 1.3 months; n = 15). Females could reproduce 2 years before attaining adult body weight (10-15 kg) and complete dental eruption by 5.0-5.5 years. Males, by contrast, developed more slowly, reaching adult body weight (30-35 kg) and testicular volume (volume of left testis: 25-30 ml) at 8 years. Consistently high circulating testosterone concentrations (8.17 +/- 2.0 ng ml-1) could be measured by 9 years of age. Fully developed males exhibited fatting of the rump and flanks, as well as striking sexual skin coloration and an active sternal cutaneous gland; little expression of these features was evident during pubertal development. Marked individual age differences occurred with regard to the onset and complete development of these features, suggesting possible interactions between social environment and physical maturation.     

Observations on thermoregulatory ontogeny of mink (Mustela vison)

(1) We measured cooling rate for neonatal mink during a 10min coldroom (3.9 degrees C) exposure and subsequent warming rate during a 20min incubator (37.2 degrees C) exposure, the behaviour of the kits and the changes in their pelage between 1 and 46d of age, in an attempt to monitor the ontogeny of their thermoregulatory capacity. (2) Body weight of the 1d old kits averaged only 12.8+/-2.3g (n=4), but they gained weight rapidly reaching 226.1+/-28.3g (males, n=4) and 207.6+/-16.1g (females, n=4) at 30-31d of age, and 562.3+/-43.2g (males, n=3) and 435.7+/-35.5g (females, n=4) at 45-46d of age. (3) Body cooling rate (C(rate) ( degrees C/min); n=80) was affected by the age (between 1 and 31d), BW, initial rectal temperature (T(r0)), and sex of the kits, in addition to their body posture (P(cold), 1=extended, 2=curled-up) during coldroom exposure. C(rate) ( degrees C/min)=-0.34-0.02age-0.002BW+0.05T(r0)-0.06sex-0.20P(cold) (R(2)=0.75). (4) Body warming rate (W(rate) ( degrees C/min); n=80) was influenced by the age(2) and rectal temperature of the kit after the coldroom exposure (T(r10)). W(rate)( degrees C/min)=1.24+0.0002age(2)-0.04T(r10) (R(2)=0.76). (5) Kit fur fibre length increased from 5.45+/-0.63mm (males, n=2) and 6.20+/-0.20mm (females, n=3) at 22-23d of age to 9.43+/-1.44mm (males, n=4) and 8.70+/-1.89mm (females, n=4) at 30-31d of age, and to 12.93+/-0.47mm (males, n=3) and 11.38+/-0.41mm (females, n=4) at 45-46d of age, the growth averaging about 0.26mm per day. (6) Under normal circumstances newborn mink kits are hypothermic.Their thermoregulation develops only gradually and is dependent on increase in body mass, insulation and behavioural thermoregulation. Their strategy of survival is based on the ability to withstand hypothermia and on the nutrition and warmth provided by the dam.     

Ovarian function in the elephant: luteinizing hormone and progesterone cycles in African and Asian elephants

Serum samples were collected weekly for 3 yr from two female African elephants, for 18 mo from two other female African elephants, and for 2 yr from two female Asian elephants. Animals were not sedated at the time of blood collection. Ovarian cycles, characterized by changes in progesterone and immunoreactive luteinizing hormone (ILH) concentrations, averaged 15.9 +/- 0.6 wk (N = 25) for African females and 14.7 +/- 0.5 wk for Asian females (N = 10). The length of the active luteal phase averaged 10.0 +/- 0.3 wk for African elephants (range 8-14 wk) and 10.6 +/- 0.6 wk for Asian females (range 9-13 wk). Interluteal phases were 5.9 +/- 0.6 wk for African females and 4.2 +/- 0.5 wk for Asian females. One African female (Maliaca) had two extended interluteal phases, both occurring between the months of February and May. Excluding these two periods, there were no differences in the length of the ovarian cycle or the length of the luteal phase between species of elephant. Serum progesterone in both species ranged from less than 50 pg/ml to 933 pg/ml. Average progesterone concentrations during the luteal phase were significantly lower in African elephants compared with Asian elephants (328 +/- 13, N = 30 cycles vs. 456 +/- 23, N = 14 cycles; p less than 0.001). ILH ranged from nondetectable to 11.6 ng/ml. These data suggest that the length of the ovarian cycle in the African elephant is about 16 wk and confirm that the length of the ovarian cycle in the Asian elephant is about 15 wk.     

Androgen receptors in brain and pituitary of female rats: cyclic changes and comparisons with the male

The in vitro binding of a synthetic androgen, methyltrienolone ([3H]-R1881), to brain and pituitary (PIT) cytosol and nuclear extracts was determined in male and female rats. Purified cytosol was prepared from PIT or hypothalamic-preoptic area-amygdala (HPA) and incubated in the presence of 0.1 to 10 nM [3H]-R1881. Scatchard analysis revealed the presence of a single, saturable, high-affinity binding site in PIT cytosol with a dissociation constant (Kd) of 0.42 X 10(-10) M in females and 0.95 X 10(-10) M in intact males. The Kd of HPA cytosol was much less in castrated males [0.47 +/- 0.05 (SEM) X 10(-10)M, n = 7] and females (0.63 +/- 0.1 X 10(-10) M, n = 4) than in intact males (5.8 +/- 1.1 X 10(-10) M, n = 8). Treatment of castrated males with dihydrotestosterone (DHT) for 24 h (250 micrograms/100 g of body weight) increased the Kd of HPA cytosol only slightly (1.6 X 10(-10) M, mean of two replicates). Scatchard analysis of salt-extracted nuclear androgen receptor (ARn) showed a single, high-affinity binding site with similar Kd values in PIT and HPA of intact and castrated, DHT-treated male rats (PIT Kd = 7.3 X 10(-10) M, 9.3 X 10(-10) M; HPA Kd = 1.5 X 10(-9) M, 1.3 X 10(-9) M, respectively). Competition studies involving a range of several radioinert steroids revealed that the binding of [3H]-R1881 to cytosol (ARc) and nuclear extract was specific for androgen receptor when triamcinolone acetonide (10 microM) was added. The ARc and ARn levels were quantified in PIT, preoptic area (POA), hypothalamus (HT), amygdala, hippocampus, and cortex by single point estimation. Significantly (p less than 0.01) greater amounts of ARc were detected in PIT of ovariectomized females (32.7 +/- 2.9 fmol/mg of protein) than in that of orchidectomized males (22.33 +/- 1.6 fmol/mg of protein). The highest levels in the brain were seen in HT and POA. Pituitary ARc in females varied throughout the estrous cycle. Significantly (p less than 0.01) greater amounts were detected on estrus (45.8 +/- 2.2 fmol/mg of protein) and proestrus (39.0 +/- 1.9 fmol/mg of protein) than on diestrus (29.2 +/- 1.5 fmol/mg of protein). These data confirm the existence of specific receptors for androgen in male and female brain and PIT, and suggest an important role for androgen in the control of PIT hormone secretion in the female.     

Acute local subcutaneous VEGF165 injection for augmentation of skin flap viability: efficacy and mechanism

Distal skin ischemic necrosis is a common complication in skin flap surgery. The pathogenesis of skin flap ischemic necrosis is unclear, and there is no clinical treatment available. Here, we used the 4 x 10 cm rat dorsal skin flap model to test our hypothesis that subcutaneous injection of vascular endothelial growth factor 165 (VEGF165) in skin flaps at the time of surgery is effective in augmentation of skin flap viability, which is associated with an increase in nitric oxide (NO) production, and the mechanism involves 1) an increase in skin flap blood flow in the early stage after surgery and 2) enhanced angiogenesis subsequently to sustain increased skin flap blood flow and viability. We observed that subcutaneous injection of VEGF165 in skin flaps at the time of surgery increased skin flap viability in a dose-dependent manner. Subcutaneous injection of VEGF165 at the dose of 2 microg/flap increased skin flap viability by 28% (P < 0.05; n = 8). Over 80% of this effect was blocked by intramuscular injection of the NO synthase (NOS) inhibitor Nomega-nitro-L-arginine (13 mg/kg) 45 min before surgery (P < 0.05; n = 8). The VEGF165 treatment also increased skin flap blood flow (2.68 +/- 0.63 ml x min(-1) x 100 g(-1)) compared with the control (1.26 +/- 0.10 ml x min(-1) x 100 g(-1); P < 0.05, n = 6) assessed 6 h postoperatively. There was no change in skin flap capillary density at this time point. VEGF165-induced increase in capillary density (32.2 +/- 1.1 capillaries/mm2; P < 0.05, n = 7) compared with control (24.6 +/- 1.4 capillaries/mm2) was seen 7 days postoperatively. There was also evidence to indicate that VEGF165-induced NO production in skin flaps was stimulated by activation of NOS activity followed by upregulation of NOS protein expression. These observations support our hypothesis and for the first time provide an important insight into the mechanism of acute local VEGF165 protein therapy in mitigation of skin flap ischemic necrosis.     

Uterine steroid hormone receptors during the estrous cycle and during hibernation in the Turkish hamster (Mesocricetus brandti)

The Turkish hamster is a long-day breeder that hibernates for 4-5 mo if exposed to a short-day, cold environment. The objective of this study was to assess the uterine responsiveness of the hibernating animal to ovarian steroids. Our approach was 1) to characterize and determine uterine estrogen (E) and progesterone (P) receptors (R) during hibernation as compared to the levels observed in cycling females that had terminated hibernation, and 2) to assess the responsiveness of the uterus to E during hibernation by its ability to induce uterine P receptor. Females were exposed to short days (10L:14D) for 2 mo and then were placed in a cold-room (10L: 14D, 6 +/- 1 degrees C). After 2 or 4 mo in the cold, hibernating animals were killed and uterine steroid receptors were determined by 3H-steroid binding assay. Uterine receptors were also determined in cycling Turkish hamsters on each morning of the estrous cycle. Values for uterine receptors (pmol/g tissue, n = 4-6) during the estrous cycle (estrus, diestrus I, diestrus II, proestrus) were: 4.3 +/- 0.78, 3.9 +/- 0.19, 4.1 +/- 0.25, 3.7 +/- 0.5 for cytosolic ER; 36.6 +/- 5.8, 32.2 +/- 6.8, 36.3 +/- 1.5, 54.4 +/- 1.9 for cytosolic PR; 0.59 +/- 0.11, 0.54 +/- 0.07, 1.06 +/- 0.05, 1.42 +/- 0.17 for nuclear ER. Hibernating (torpid) animals sampled after 2 mo in the cold showed a significant (p less than 0.05) depression of cytosolic ER (2.6 +/- 0.12, n = 5) and cytosolic PR (19.0 +/- 2.6, n = 8) as compared to any day of the estrous cycle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Seasonal reproductive characteristics of female and male Jackson's hartebeest (Alcelaphus buselaphus jacksoni)

This project examined reproductive characteristics of female and male Jackson's hartebeest (Alcelaphus buselaphus jacksoni), a subspecies that originates in Africa and is currently a model for studies of endangered hartebeest subspecies. Progestagen concentrations were measured in fecal samples collected thrice weekly for 1 year from three non-pregnant, adult females, in the Northern Hemisphere (31 degrees 37'N, 81 degrees 09'W). When their ovaries were active, the females exhibited regular luteal cycles with an overall mean (+/-S.D.) cycle length of 21.4+/-4.1 days (n=31 luteal phases). Peak luteal progestagen concentration was 1.73+/-0.63mug/g, with a nadir concentration of 0.79+/-0.24mug/g. Cyclic activity ceased from 6 April to 28 June, 7 April to 8 July, and from 18 February to 20 August, for the three females, respectively. During this acyclic period, mean progestagen concentration was 0.90+/-0.23mug/g. Ejaculates were collected by electroejaculation from seven males throughout all seasons, with mean (+/- S.D.) 40+/-18% motility, 4.1+/-0.19 progressive motility (scale, 0-5), 1373+/-826x10(6)sperm/mL, and 42+/-28% morphologically normal sperm. These data characterized basic reproductive traits for Jackson's hartebeest and established the females as spontaneously ovulating and seasonally polyestrous when housed in the Northern Hemisphere, whereas males produced apparently viable sperm throughout the year.     

Prenatal androgens and the timing of seasonal reproductive transitions in sheep.

Both the onset of puberty in the lamb and the annual resumption of reproductive activity in adult male and female sheep are characterized by increased secretion of LH due to reduced responsiveness to steroid inhibition. However, the timing of puberty is sexually differentiated, for males undergo a reduction in sensitivity to steroid feedback at 10 wk of age, whereas females remain highly responsive to steroid inhibition until 30 wk. This sex difference is determined by androgens in utero. The present study was conducted to determine whether a sex difference exists in the timing of seasonal transitions in adult males and females. We compared serum LH in gonadectomized, estradiol-treated males (n = 7), females (n = 6), and androgenized females (n = 5) from blood samples collected twice weekly for one year. As determined by changes in the pattern of LH secretion, the onset and termination of the autumn breeding season were not different between males, females, and androgenized females (termination: 1 February +/- 4 days, mean +/- SE all groups; onset: males, 22 August +/- 4 days; females, 5 September +/- 18 days; androgenized females, 16 September +/- 10.5 days). However, there was a transient increase in LH (20 May to 23 June) in males, but not in females or androgenized females. Although no effects of prenatal testosterone were evident in the control of LH secretion in adult androgenized females, LH secretion in androgenized males was elevated throughout the nonbreeding season in 3 of 5 animals, indicating that exogenous testosterone may reduce seasonal increases in responsiveness to steroid inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Erythropoiesis in women during 11 days at 4,300 m is not affected by menstrual cycle phase.

Because the ovarian steroid hormones, progesterone and estrogen, have higher blood levels in the luteal (L) than in the follicular (F) phase of the menstrual cycle, and because of their known effects on ventilation and hematopoiesis, we hypothesized that less hypoxemia and less erythropoiesis would occur in the L than the F phase of the cycle after arrival at altitude. We examined erythropoiesis with menstrual cycle phase in 16 women (age 22.6 +/- 0.6 yr). At sea level, 11 of 16 women were studied during both menstrual cycle phases, and, where comparison within women was available, cycle phase did not alter erythropoietin (n = 5), reticulocyte count (n = 10), and red cell volume (n = 9). When all 16 women were taken for 11 days to 4,300-m altitude (barometric pressure = 462 mmHg), paired comparisons within women showed no differences in ovarian hormone concentrations at sea level vs. altitude on menstrual cycle day 3 or 10 for either the F (n = 11) or the L (n = 5) phase groups. Arterial oxygen saturation did not differ between the F and L groups at altitude. There were no differences by cycle phase on day 11 at 4,300 m for erythropoietin [22.9 +/- 4.7 (L) vs. 18.8 +/- 3.4 mU/ml (F)], percent reticulocytes [1.9 +/- 0.1 (L) vs. 2.1 +/- 0.3% (F)], hemoglobin [13.5 +/- 0.3 (L) vs. 13.7 +/- 0.3 g/100 ml (F)], percent hematocrit [40.6 +/- 1.4 (L) vs. 40.7 +/- 1.0% (F)], red cell volume [31.1 +/- 3.6 (L) vs. 33.0 +/- 1.6 ml/kg (F)], and blood ferritin [8.9 +/- 1.7 (L) vs. 10.2 +/- 0.9 microg/l (F)]. Blood level of erythropoietin was related (r = 0.77) to arterial oxygen saturation but not to the levels of progesterone or estradiol. We conclude that erythropoiesis was not altered by menstrual cycle phase during the first days at 4,300-m altitude.     

The ovulation rate in anoestrous female goats managed under grazing conditions and exposed to the male effect is increased by nutritional supplementation

This experiment was conducted to determine if feed supplementation before exposure of anoestrous does to males increases ovulation rate. Does (n=50) grazing natural vegetation were divided into two groups (n=25). One group received no feed supplementation, while the other was supplemented daily, with a mixture of 950 g of alfalfa hay, 290 g of rolled corn and 140 g of soy bean per animal for 7 days before exposure to bucks. On April 7, all females were exposed to four adult sexually active bucks (two per group) for 15 days. The ovulation rate at the ovulation detected within 5 days of exposure to males, assessed by transrectal ultrasonography, was greater (P<0.05) in supplemented (1.6+/-0.2) than in non-supplemented females (1.0+/-0.2). In contrast, ovulation rate at the subsequent ovulation, detected between days 6 and 15 of contact with males, was not different (P>0.05) between supplemented (1.3+/-0.1) and non-supplemented females (1.3+/-0.2). Feed supplementation 7 days before exposure to sexually active bucks of females managed under grazing conditions increased their ovulation rate at the first male-induced ovulation but the stimulatory effect of supplementation did not persist and was not observed at the subsequent ovulation.     

Inhibition of estrus and corpora lutea function with Norgestomet

Forty-five nonpregnant, nonlactating, Angus and Brangus cows were utilized to determine how long a Norgestomet ear implant would inhibit estrus when administered at various stages of an estrous cycle. All cows completed a nontreated estrous cycle to ensure normal cyclicity. At the second observed estrus (estrus = Day 1), cows were randomly allotted to be treated at metestrus (Day 3 or Day 4, n = 15); at diestrus (Day 9 or Day 10, n = 14); or at proestrus (Day 15 or Day 16, n = 16). All cows received a 2-ml intramuscular injection of 3 mg of Norgestomet accompanied by a 6-mg Norgestomet ear implant, which remained in situ for 21 days, or until individual cows were observed in estrus. Estrus was inhibited for a mean (+/- SEM) of 18.7 +/- 0.7, 19.9 +/- 0.8, and 17.0 +/- 0.8 days, respectively, when cows were treated at metestrus, diestrus, and proestrus (metestrus and diestrus vs proestrus; P < 0.05). Estrus was inhibited for an entire 21-day implantation period in 27, 50, and 38% of cows treated at metestrus, diestrus, and proestrus, respectively (P > 0.10). Norgestomet inhibited estrus in all cows for 11, 17, and 11 days after implantation when treatment was initiated at metestrus, diestrus, and proestrus, respectively (P > 0.10). These data indicate that a 6-mg Norgestomet ear implant effectively inhibits estrus in all cows for a maximum of 11 days, with some cows exhibiting estrus by Day 12 with the Norgestomet implant in situ.