Abstract: The objective of this study was to investigate the seasonal changes in melatonin profiles based on frequently collected samples in adult rams maintained under simulated natural photoperiod. In a group of six rams, the seasonal changes of melatonin were characterized in samples collected at 10‐min intervals for an equal period before and after the median of the scotophase during the spring (March) and the autumn (September) equinoxes, and also during the summer (June) and the winter (December) solstices. In an additional two rams, the rapid changes in melatonin concentrations were investigated in samples drawn at 2‐min intervals for a 2‐hr period before and after the median of the scotophase, but only during the summer and the winter solstices. The results show that in adult rams there is a distinct seasonal variation in the nightly rise of melatonin (P < 0.01). Mean concentrations in June and September were higher than in March or December (P < 0.05). There was no difference between the means in June or September. However, the means in March were lower than in December (P < 0.05). Rapid changes in melatonin concentrations occurred in samples collected either at 10‐min or 2‐min intervals. In rams sampled at 2‐min intervals, mean melatonin values in June were also higher than in December (P < 0.01). The results suggest that there are distinct seasonal changes in melatonin concentrations in the ram and that rapid changes in melatonin concentrations reflect pulsatile secretion.

The daily mean of serum progesterone in cyclic ewes (N = 5) as well as the profile characteristics of progesterone and cortisol in response to an acute single dose (5 i.u./kg liveweight 0.75) of adrenocorticotrophic hormone (ACTH) into ovariectomized ewes (N = 4) was investigated during exposure to a constant thermoneutral temperature of 18 +/- 1 degree C or to a daily cyclic heat stress temperature of 18 degrees C-35 degrees C-18 degrees C, in an environmental chamber. Serum collected daily from the cyclic ewes was assayed for progesterone, while serum collected more frequently for 10 h, on the 14th day of exposure to the respective temperature, from the ovariectomized ewes was assayed for progesterone and cortisol by RIAs. In cyclic ewes, heat stress increased the area under the daily progesterone curve (P less than 0.09) but had no effect on progesterone concentration after the regression of the CL. In ovariectomized ewes, ACTH significantly elevated the response of both cortisol and progesterone (r = 0.75, P less than 0.001) within 10-15 min of injection. In the ovariectomized ewes and during heat stress, the responses of progesterone and cortisol to ACTH were characterized by an initial acute rise, a transient drop, a steep elevation and a gradual but prolonged decline. During thermoneutral temperatures, this biphasic response pattern was not observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between four steroids, determined by radio-immunoassay of whole saliva, and clinical and bacteriological parameters were studied in 90 subjects: males, menstruating females, and pregnant females. Pocket depths and both plaque and gingival bleeding scores were recorded. Total counts and percentages of Gram-negative organisms Bacteroides and B. intermedius were determined from anaerobic cultures of subgingival plaque from 9-14 subjects in each group. None of the clinical parameters for the pregnant females differed significantly from those of non-pregnant females, nor did these parameters show any significant correlation with progression of pregnancy. No correlations were detected between bacterial and clinical parameters in the pregnant group. There were no statistically significant differences between the total bacterial counts from the three groups, yet males had significantly higher proportions of Gram-negative bacteria, Bacteroides, and B. intermedius, than did pregnant and non-pregnant females. Proportions of B. intermedius did not differ significantly between the two female groups, nor was there any correlation with progression of pregnancy. While some steroids appeared to affect some clinical or bacteriological parameters in some groups, no obvious patterns consistent with different steroid levels were detected. The results do not indicate that increased hormone levels cause more severe periodontal disease in pregnant women, nor that high salivary steroid levels result in increased recovery of B. intermedius from subgingival plaque.

Four male pygmy goats were used in a study designed to determine the effects of season on serum hormone (luteinizing hormone, follicle stimulating hormone, prolactin, testosterone, and cortisol) levels, testis size and libido, and the effects of mating on serum hormone profiles. Seasonal peaks were observed for prolactin in July, luteinizing hormone and follicle stimulating hormone in September, and testosterone in October. Luteinizing hormone peak frequency was greatest in September and was increased by mating activity in the months immediately preceding the breeding season. Scrotal circumference did not vary with season and libido showed no consistent seasonal pattern. Mating appeared to raise all hormone levels except during the months when these hormones were seasonally elevated. When episodic releases of luteinizing hormone occurred, they were associated with subsequent rises in serum testosterone levels. On some mating days, when episodic releases of luteinizing hormone were absent, changes in testosterone levels were highly correlated with changes in cortisol levels. It was concluded that both season and mating influence reproductive hormone levels in male pygmy goats.

Pituitary and testicular endocrine responses to exogenous gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH), respectively, were assessed for adult rams in an investigation of the regulation of seasonal changes in the patterns of episodic LH and testosterone secretion. Concurrent variations in testis size and in circulating levels of follicle stimulating hormone (FSH) and prolactin (PRL) were also examined. On 10 occasions throughout the year, serum hormone levels were assessed over 6- to 8-h periods during which time rams were left untreated (day 1) or were injected (iv) with single doses of either 10 micrograms synthetic GnRH (day 2) or 30 micrograms NIH-LH-S18 (day 3); blood samples were collected from the jugular vein at 10- to 20-min intervals. Testicular redevelopment during the summer, as indicated by increasing testis diameter measurements, was associated with increases in mean FSH level and was preceded by a springtime rise in mean PRL level; "spontaneously" occurring LH pulses and those produced in response to GnRH treatment were relatively large during this period. Increases in the magnitude of testosterone elevations in response to both endogenously and exogenously produced LH pulses occurred in August. Mean testosterone levels were elevated fourfold in the fall as a consequence of relatively frequent and small LH pulses stimulating a more responsive testis to produce more frequent and larger testosterone elevations; endogenous LH pulses, however, did not appear to stimulate the testes maximally at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Circulating levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin (PRL) were assessed in four long-term castrate rams at monthly intervals for 1 year beginning in March. Each month, rams were bled from the jugular vein at 10-min intervals for an 8-h period; 10 micrograms synthetic gonadotropin releasing hormone (GnRH) was injected into the jugular vein following 6 h of sampling. Changes in natural daylength were associated with seasonal variations in mean serum levels of LH (r = 0.57, P less than 0.05) and PRL (r = 0.94, P less than 0.01). LH levels declined 55% between June and October as LH peaks became more frequent and progressively smaller in magnitude, and base-line levels decreased; these trends were reversed by December. In comparison, FSH levels increased 40% between June and September and then returned to relatively low values in October. Seasonal variations in the magnitude of endogenous LH pulses were not associated with definitive changes in the LH response of the pituitary to exogenous GnRH. Although LH and FSH levels in the castrate rams were typically high, many of the seasonal-directional changes in the secretory characteristics of these hormones (i.e., LH peak frequency and magnitude, and mean FSH level) were similar to those reported for the intact ram. Data indicate that photoperiodic regulation of hypothalamic function of rams is in part via direct or steroid-independent means.

The effect of a single injection of dihydrotestosterone, testosterone, testosterone propionate, estradiol-17β or estradiol benzoate on serum levels of luteinizing hormone, follicle stimulating hormone and prolactin was studied in ovariectomized ewes. Luteinizing hormone levels increased following treatment with E, EB or TP, prolactin levels increased following treatment with E, EB, T or TP while FSH levels decreased after treatment with either E or EB. Free steroids appeared to produce earlier responses in hormone levels than the corresponding esters. Key words: Androgens, estrogens, gonadotropins, prolactin, ewes.

The influence of photoperiod on serum prolactin levels and prolactin release induced by thyrotropin releasing hormone (TRH) was determined in ewes maintained under the following lighting regimes: Room 1, lighting mimicked natural changes in photoperiod; Room 2, annual photoperiod changes condensed into 6 mo with short days in June; Room 3, same as Room 2 except photoperiod changed abruptly from 16.5 to 8.0 h on 21 Mar. and back to 16.5 h on 21 June; Room 4, constant light. Weekly blood samples were obtained from February to August. Additionally, blood samples were collected before and after treatment with 10 μg TRH on 19 May, 13 June, 27 June and 19 July. Prolactin levels were elevated in ewes exposed to long days or constant light. The mean of all pre-TRH samples was significantly correlated with stress-induced elevations in prolactin (highest pre-TRH value) (r = 0.72) and area under the TRH-induced release curve (r = 0.56). The prolactin release in response to TRH was greatest in ewes exposed to long days or constant light. Abrupt increase of day length elevated pretreatment prolactin levels (P < 0.01) and increased area under the response curve (P < 0.05). Key words: Photoperiod, TRH, prolactin, ewes

Two experiments were conducted to investigate the relationship between circulating estrogen and testosterone levels in the adult ram. Experiment 1 involved assessing the mean concentration of these hormones in blood collected from eight rams during 8-h periods of both sexual inactivity and mating with estrus-induced ewes prior to and during the fall breeding season (early August, mid-September, early November and mid-December). Rams were bled at 20-min intervals by venipuncture of the jugular vein during all periods. Serum estrogen concentration increased approximately 40% to an average (± SE) of 11.2 ± 0.8 pg/mL between August and November, and in direct relation to testosterone concentration (r = 0.88); estrogen values were generally less than 0.2% of testosterone values. Mating activity was associated with increments in circulating estrogen in September only, while testosterone levels increased in both August and September. Frequency of mating (ejaculation) was highly and positively correlated with serum estrogen concentration among rams in August (r = 0.86) and within rams across months (r = 0.78). In exp. 2, the relationship between hour-to-hour fluctuations in estrogen and testosterone levels was examined for six rams in early winter. Rams were bled as in exp. 1 for 7 h, and two of the rams were given frequent intravenous injections of NIH-LH-S14 following the first 2 h of bleeding. Short-term variations in serum estrogen concentration were not consistently related to those in testosterone. Key words: Estrogen, season, mating, ram, testosterone, circulation

Whole saliva was collected daily by four women during one menstrual cycle and twice weekly by three women during their third trimester of pregnancy. Follicular-phase saliva progesterone concentrations, as measured by radioimmunoassay, generally remained below 50 pg/mL. However, progesterone rose to a peak of 400 +/- 107 pg/mL (mean +/- SE) between days 17 and 25, after which it declined to 143 +/- 67 pg/mL by one day prior to menses. The third trimester of pregnancy was characterized by steadily increasing concentrations of saliva progesterone until 1--3 weeks prior to parturition; concentrations following parturition were similar to those of the follicular phase.

Possible age and breed differences in circulating levels of luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone in the ram were investigated. In exp. 1, blood was collected from a group of 28 rams of various ages and breeds by venepuncture from the jugular vein at 20-min intervals for an 8-h period (May). Comparison of mean serum hormone concentrations for postpubertal Finnish Landrace (Finn), Suffolk and Managra Synthetic (Line M) rams did not reveal significant (P > 0.10) breed differences. However, when rams of the three breeds were categorized by age, the mean (±SE) LH levels in lambs (n = 8), yearling (n = 12) and adult (n = 8) animals were 2.1 ± 0.4, 1.1 ± 0.2 and 0.5 ± 0.1 ng/mL, respectively; the significant decrease (P < 0.05) in LH levels in adult vs. yearling rams was due to fewer and smaller LH releases. Mean testosterone levels averaged 1.3 ± 0.2, 2.8 ± 0.4 and 2.4 ± 0.3 ng/mL for the lamb, yearling and adult ram groups, respectively. FSH levels were similar for all age groups. In exp. 2, a series of blood samples were collected from 3-mo-old Finn (n = 6) and Suffolk/Line-M crossbred (n = 6) rams in October. In comparison with crossbred rams, rams of the more prolific Finn breed exhibited substantially higher mean levels of LH (1.0 ± 0.2 vs. 0.4 ± 0.2 ng/mL; P < 0.10), FSH (250 ± 26 vs. 121 ± 16 ng/mL; P < 0.01) and testosterone (2.8 ± 0.9 vs. 0.4 ± 0.1 ng/mL; P < 0.05); higher LH and testosterone in Finn rams were associated with larger and/or more frequent elevations in the level of these hormones during the 8-h bleeding period. Results of this study seem to indicate (1) age-associated differences in the pattern of LH release in adult rams in the spring; and (2) that breed differences in blood reproductive hormone levels in postpubertal rams are not significant in the spring, but levels in 3-mo-old rams differ during the fall months according to genotype. Key words: Age, breed, gonadotropins, testosterone, serum, ram

Intact (experiment 1) or castrated (experiment 2) male rats were either fed or fasted for 24 hours. Half of each group received 75 mg 2-deoxy-D-glucose/100 gm body weight, intraperitoneally. Assays of sera from blood samples obtained from intact rats 4 hr after the injection revealed that 2-deoxy-D-glucose suppressed serum testosterone levels (P < 0.05) while 2-deoxy-D-glucose plus fasting was most effective in suppressing LH and FSH. In castrates LH was suppressed by 2-deoxy-D-glucose and FSH by fasting (P < 0.01 and P < 0.05). Serum glucose was elevated 3-5 fold by 2-deoxy-D-glucose (P < 0.01). Experiments with female rats revealed that treatment with 2-deoxy-D-glucose had no effect on the rise in serum LH that followed GnRH treatment in ovariectomized, steroid-primed animals. However, progesterone-induced LH release in estrogen-primed ovariectomized rats was blocked by 2-deoxy-D-glucose. Collectively, these results suggest that glucoprivation impairs hypothalamic control of gonadotropin secretion.

The rise in serum luteinizing hormone concentration after treatment with gonadotropin-releasing hormone was less in diabetic castrated male rats than control castrates. In intact male rats, gonadotropin-releasing hormone treatment resulted in higher serum luteinizing hormone concentrations in diabetic than in control rats.

Four male pygmy goats were 9 months of age when assigned to this experiment. They were maintained for 1 year beginning in June 1975 under natural photoperiod changes characteristic of southern Canada and ambient barn temperatures ranging from 5 to 25 C. During the third week of each month, bucks were bled from a jugular vein by venipuncture at 30-min intervals for either 12 or 24 hr (August, November, February and May). Sera were assayed for luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL) and testosterone (T) by radioimmunoassay. Both LH and T were secreted episodically, and increases in serum LH were generally followed by increased serum T concentrations which peaked within 60 minutes. Mean serum LH, T and PRL concentrations fluctuated considerably over the 24-hr periods with peak PRL concentrations generally occurring during the dark period. However, serum FSH concentrations did not show a pulsatile profile and variations over the 24-hr were minimal. Serum LH and T increased with decreasing daylength and attained maximum mean values (± SE) in October of 1.9 ± .5 ng NIH-LH-S14/ml and 15.4 ± .9 ng/ml, respectively. These increases were a result of higher baseline levels and peak frequencies. Lowest mean serum concentrations of LH (.4 ± ,1 ng/ml) and T (2.3 ± .5 ng/ml) occurred in November and June, respectively. Serum FSH increased slightly in September, but the highest concentration occurred in April (67.8 ± 4.4 ng NIH-FSH-S6/ml). Changes in serum PRL concentration paralleled changes in daylength (r = .58, P<.05). Seasonal changes in serum concentrations of LH, PRL, and T in the male pygmy goat follow closely the changes that have been reported for rams, which are also a seasonal breeder under temperate climatic conditions.