Progesterone Concentrations In Females Research Articles

Copulatory behaviors and body condition predict post-mating female hormone concentrations, fertilization success, and primary sex ratios in Japanese quail

Environmental cues and social interactions are known to influence reproductive physiology and behavior in vertebrates. In female birds, male courtship displays can result in the growth of ovarian follicles, the production of reproductive hormones, and stimulation of oviduct development, all of which have the potential to influence maternal investment. Male Japanese quail follow a typical sequence of copulatory behaviors during a mating interaction and often force copulations with unreceptive females. We hypothesized that female Japanese quail could adjust maternal investment in response to male copulatory behaviors during a single mating interaction. We investigated the relationships between 1) male copulatory behaviors and post-mating concentrations of steroids in the female, 2) female steroid concentrations and fertilization success of inseminations and 3) female steroid concentrations and the offspring sex ratio. We found that male condition and copulatory behaviors predicted female steroid concentrations and maternal investment in eggs laid after a mating trial. The body condition of one or both mates was a significant predictor of the changes in female corticosterone and testosterone concentrations after mating, whereas specific male copulatory behaviors significantly predicted changes in female progesterone concentrations. Male and female body condition, male neck grabs and post-mating concentrations of female corticosterone, progesterone, and testosterone were all significant predictors of egg fertilization rates. Female body condition, male copulation efficiency, and female testosterone concentrations were significant predictors of offspring sex ratios. Our results show that phenotypic and behavioral characteristics of male Japanese quail modulate female steroid concentrations and result in changes in maternal investment.

Evaluation of adrenocortical function in Florida manatees (Trichechus manatus latirostris)

The study objectives were to determine the predominant manatee glucocorticoid; validate assays to measure this glucocorticoid and adrenocorticotropic hormone (ACTH); determine diagnostic thresholds to distinguish physiological vs. pathological concentrations; identify differences associated with sex, age class, female reproductive status, capture time, and lactate; and determine the best methods for manatee biologists and clinicians to diagnose stress. Cortisol is the predominant manatee glucocorticoid. IMMULITE 1000 assays for cortisol and ACTH were validated. Precision yielded intra- and inter-assay coefficients of variation for serum cortisol: ≤23.5 and ≤16.7%; and ACTH: ≤6.9 and ≤8.5%. Accuracy resulted in a mean adjusted R(2)≥0.87 for serum cortisol and ≥0.96 for ACTH. Assay analytical sensitivities for cortisol (0.1 µg/dl) and ACTH (10.0 pg/ml) were verified. Methods were highly correlated with another IMMULITE 1000 for serum cortisol (r=0.97) and ACTH (r=0.98). There was no significant variation in cortisol or ACTH with sex or age class and no correlation with female progesterone concentrations. Cortisol concentrations were highest in unhealthy manatees, chronically stressed by disease or injury. ACTH was greatest in healthy free-ranging or short-term rehabilitating individuals, peracutely stressed by capture and handling. Cortisol concentrations ≥1.0 µg/dl were diagnostic of chronic stress; ACTH concentrations ≥87.5 pg/ml were diagnostic of peracute stress. In healthy long-term captive manatees, cortisol (0.4±0.2 µg/dl) and ACTH (47.7±15.9 pg/ml) concentrations were lower than healthy free-ranging, short-term rehabilitated or unhealthy manatees. Capture time was not significantly correlated with cortisol; ACTH correlation was borderline significant. Cortisol and ACTH were positively correlated with lactate.

The relationship between plasma steroid hormone concentrations and the reproductive cycle in the Northern Pacific rattlesnake, Crotalus oreganus

We describe the reproductive cycle of Northern Pacific rattlesnakes ( Crotalus oreganus) by quantifying steroid hormone concentrations and observing reproductive behaviors in free-ranging individuals. Additionally, we examined reproductive tissues from museum specimens. Plasma steroid hormone concentrations were quantified for both male and female snakes throughout the active season (March–October). We measured testosterone (T), 5α-dihydrotestosterone (DHT), and corticosterone (B) concentrations in both sexes and 17β-estradiol (E2) and progesterone (P) in females only. We observed reproductive behaviors (e.g., consortship, courtship, and copulation) in the field and measured testis and follicle size in male and female snakes from museum collections to relate steroid hormone concentrations to the timing of reproductive events. Our study revealed that C. oreganus in central California exhibits a bimodal pattern of breeding, with most mating behavior occurring in the spring and some incidences of mating behavior observed in late summer/fall. Each breeding period corresponded with elevated androgen (T or DHT) levels in males. Testes were regressed in the spring when the majority of reproductive behavior was observed in this population, and they reached peak volume in August and September during spermatogenesis. Although we did not detect seasonal variation in female hormone concentrations, some females had high E2 in the spring and fall, coincident with mating and with increased follicle size (indicating vitellogenesis) in museum specimens. Females with high E2 concentrations also had high T and DHT concentrations. Corticosterone concentrations in males and females were not related either to time of year or to concentrations of any other hormones quantified. Progesterone concentrations in females also did not vary seasonally, but this likely reflected sampling bias as females tended to be underground, and thus unobtainable, in summer months when P would be expected to be elevated during gestation. In females, P was positively correlated with T and DHT, and E2 was positively correlated with T.

Sexually dimorphic response of the hypothalamo–pituitary–adrenal axis to chronic alcohol consumption and withdrawal

In males, long-term alcohol consumption provokes neurochemical changes in the medial parvocellular division of the PVN (PVNmp) that are partially reversed by withdrawal. Because gonadal steroids modulate the activity of the hypothalamo–pituitary–adrenal axis, we analyzed the possibility that the repercussions of chronic alcohol consumption and withdrawal on the anatomy and neurochemistry of the PVNmp might differ between the sexes. Male and female Wistar rats were examined after ingesting a 20% alcohol solution for 6 months or after 2 months of withdrawal from 6 months of alcohol consumption. The levels of gonadal steroids and the basal concentrations of corticosterone were also evaluated. Chronic alcohol consumption and withdrawal did not alter the global cytoarchitectonic features of the PVNmp in rats of both sexes. However, alcohol consumption was associated with a decrease in the number of vasopressin (VP) neurons only in females and of corticotropin releasing hormone (CRH) neurons in males and females. Further, the response to withdrawal was sexually dimorphic because in males there was a partial recovery of the number of CRH neurons whereas in females there was a further loss of VP and CRH neurons. Corticosterone levels were unchanged by alcohol consumption, but they were decreased by withdrawal in females. Alcohol consumption and withdrawal did not alter estrogen and progesterone concentrations in females, but decreased testosterone levels in males. These findings show that the response of CRH and VP neurons to excess alcohol is gender-specific, with females being more vulnerable during alcohol consumption and, most notably, after withdrawal.

Reproductive seasonality in the Tete veld rat (Aethomys ineptus) (Rodentia: Muridae) from southern Africa

AbstractVery little is known about the reproductive biology of the recently recognized Tete veld rat Aethomys ineptus. In the present study, we investigated the seasonality of reproduction in this newly recognized rodent using a number of histological and endocrinological parameters. Body mass, reproductive tract morphometrics, gonadal histology, and plasma testosterone concentrations in males and plasma oestradiol‐17β and progesterone concentrations in females were assessed from a population in the north‐central part of South Africa over a 12‐month period in order to ascertain the pattern of reproduction in the species. Seminiferous tubule diameters in 59 males were significantly larger between September and February relative to between March and August. Although spermatogenesis was prevalent in the southern hemisphere winter (June–August), the number of spermatozoa in the epididymides decreased in the southern hemisphere spring (September–November), summer (December–February) and autumn (March–May). Testicular mass relative to body mass and testicular volume regressed between May and September but exhibited recrudescence between September and April, whereas plasma testosterone concentrations increased significantly between September and February relative to between March and August. Ovarian histology of 67 females showed corpora lutea to be present throughout the year, but decreased in number during winter, whereas mean plasma progesterone concentration increased significantly between August and November and again between February and April. This bimodal pattern of progesterone concentration suggests that up to two litters per breeding season may be raised by the Tete veld rat. Gravid females were found between October and April, whereas gravid or lactating females were conspicuously absent between May and September. Collation of all these data suggests that the Tete veld rat is a seasonal breeder with reproduction confined predominantly to summer and autumn months of the southern hemisphere. However, the presence of follicular development in females and the presence of corpora lutea outside the breeding season imply that the Tete veld rat may undergo spontaneous ovulation.

ESTIMATION OF PREGNANCY RATES AND REPRODUCTIVE FAILURE IN NEW ZEALAND FUR SEALS (ARCTOCEPHALUS FORSTERI)

Progesterone concentrations after implantation and the observation of live births were used to investigate the reproductive performance and timing of reproductive failure in New Zealand fur seals (Arctocephalus forsteri). Progesterone concentrations in females that gave birth were relatively low during early active gestation (8.6 6 0.9 ng/ml) and increased significantly toward the end of the 1st trimester (14.9 6 0.9 ng/ml). In contrast, progesterone concentrations in females that did not give birth remained low. Estimated pregnancy rates and live births varied significantly between years. In 2000, the overall reproductive success of mature females was low (25.7%) and 42.3% of reproductive failure occurred at or before implantation. In 2001 and 2002, reproductive rates were higher (56.5% and 63.5%, respectively) and reproductive failure was greatest (70% and 89.5%, respectively) in mid- to late active gestation. Reproductive failure during active gestation appears to be the most significant stage in determining reproductive success; however, in years of low reproductive success, failure before or at implantation also contributed significantly to reduced reproductive rates. The finding that significant fetal mortality occurs in late gestation reinforces the caution that the use of pregnancy rates, without consideration for the stage of gestation at which measurements were taken, can positively bias estimates of reproductive rates.

Reproductive traits in the spur-thighed tortoise ( Testudo graeca terrestris): new tools for the enhancement of reproductive success and survivorship

The Mediterranean tortoise ( Testudo graeca) is listed as “Vulnerable” on the IUCN Red List. Reproductive characteristics and means to increase offspring production were studied in T. graeca terrestris in a semi-natural environment. Courtship and mating occurred during early spring for about 4 weeks, followed by a laying season of approximately 2 months, with a second, shorter mating period in the fall. During the first mating, calcified eggs were already present in the uterus; we inferred that sperm from both mating seasons were stored in the oviduct for fertilization of eggs of the second laying cycle and of the following year. Average egg production was 3.8±0.3 eggs/year. Most females laid all of their eggs in a single clutch, but 18% laid in a second clutch, 11–21 days later. X-ray radiography revealed calcified eggs in the uterus about 4 weeks before oviposition. All eggs in the uterus were calcified simultaneously and were laid in a single clutch; if a second clutch developed, those eggs were also calcified simultaneously. Based on endoscopic examinations, ovaries were active throughout the entire year. Plasma progesterone concentrations in females were very low and were detected only soon after oviposition (440±141 pg/ml). Plasma estradiol concentrations in females varied from 4.1±1.5 pg/ml to 70.2±29.4 pg/ml, with no clear seasonal pattern. Maintaining tortoises at a low environmental temperature (9±1 °C versus 28±1 °C) reduced plasma estradiol concentrations. Giving 2 mg/kg tamoxifen (TAM) increased plasma estradiol to 220±33 pg/ml when treatment was given in September but not in late October, winter or spring. Treatment with TAM increased the number of eggs laid during the following laying season to 7.3±1.0 eggs/year, laid in one to three clutches. In males, plasma testosterone concentrations had a seasonal pattern with the onset of a rise in July from 2 to >4 ng/ml, a continued increase to a peak of 12.8±5.3 ng/ml during November and a decline thereafter. Artificial incubation in sand at 29±1 °C shortened the natural incubation time of 103±3.1 days to 83.5±1.3 days, increased hatching rate from 28 to 53%, and increased survival rate from 51 to 71% at 40 weeks of age. In summary, this study provides options for increasing reproductive performance, hatchability and offspring survival in captive Mediterranean tortoises, and may offer new tools for conservation of animals that are on the verge of extinction.