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Biomedical subjects

D C Collins

Publications and source records attributed to D C Collins.

At least 91 records · Page 5Linked to original sources
PubMed1984

Influence of anti-oestrogens on gonadotrophin secretion in control and ACTH-infused immature rats.

The objective of this study was to determine whether anti-oestrogens (nafoxidine, MER-25) would block the suppressive effects of ACTH on gonadotrophin secretion in immature rats. Female rats were castrated at 25-26 days of age, and an Alzet osmotic minipump containing ACTH (1-24) or saline was implanted in each animal. ACTH was administered at a rate of 1 IU/day by constant infusion. Beginning on the day of surgery, animals were injected daily for 5 days with 0.25, 5 or 25 micrograms/100 g body weight of nafoxidine or 5 mg MER-25 and sacrificed on the sixth day following castration. ACTH lowered serum LH concentrations and increased pituitary LH levels. Serum androstenedione concentrations were more than two times greater in ACTH-infused than in control rats, but serum oestrone levels were not affected. Serum testosterone and oestradiol concentrations in ACTH-infused rats remained below levels of detection. Administration of 0.25 micrograms of nafoxidine prevented the suppressive effects of ACTH on serum LH. Serum levels of LH in these animals were comparable to saline-treated controls (418 +/- 94 vs 443 +/- 73 ng/ml). The two higher doses of nafoxidine and MER-25 were ineffective in suppressing the actions of ACTH on serum LH. MER-25 reduced serum LH values in both controls and ACTH-infused rats. Serum FSH concentrations were not altered by ACTH or nafoxidine treatment. MER-25 elevated pituitary FSH concentrations in both control and ACTH-infused rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1984

Timing of sexual maturity in female rhesus monkeys (Macaca mulatta) housed outdoors.

A comparison of the age and season at first parturition was made for spring-born female rhesus monkeys and for females born in the fall to mothers who had been laboratory-housed before being transferred outdoors. Females (N = 9) born during the fall had first parturition during the spring and summer, as did all spring-born females (N = 68), and not during the fall as would be predicted if age were the determining factor. A separate analysis of post-menarchial, spring-born females (N = 5) beginning in September at 29 months of age revealed that the ensuing 12 months were characterized by low serum levels of oestradiol (less than 50 pg/ml), progesterone (less than 1.0 ng/ml), LH (less than 7.0 ng/ml), and FSH (less than 5.50 micrograms/ml). First ovulation subsequently occurred in the fall in all subjects at a mean age of 41.9 +/- 0.1 months, and was preceded by significant elevations in basal LH and FSH, coincident in time with the transition of summer to fall (September). Female copulatory behaviour was restricted to the period surrounding first ovulation, beginning some 2 weeks before and ceasing within 3 days after the oestradiol peak. The most rapid gain in weight occurred during the summer months before first ovulation, and was associated with significant elevations in serum GH and prolactin. These data suggest that season may influence the timing of sexual maturation in rhesus monkeys kept outside in such a way that the occurrence of first ovulation is restricted to the fall and winter months.

Animals↗
PubMed1984

The relationship of exercise to anovulatory cycles in female athletes: hormonal and physical characteristics.

The objective of this study was to examine the mechanisms by which physical activity affects the menstrual cycle. Women with high, medium, and low levels of physical activity were compared for menstrual function, physical characteristics, and urinary and serum levels of luteinizing hormone, follicle-stimulating hormone, prolactin, estradiol-17 beta, and 2-hydroxyestrone. None of the physical characteristics other than age and muscle area were significantly different in the three groups. The percentage of body fat did not appear to be a factor in the amenorrhea induced by strenuous exercise, as the percent of body fat in all three groups was less than 22%. The group of athletes under strenuous exercise which correlated with oligomenorrhea had decreased serum levels of luteinizing hormone, prolactin, and estradiol-17 beta but elevated levels of 2-hydroxyestrone. These data suggest that anovulatory cycles are correlated with the amount of exercise and increased levels of catechol estrogens. Catecholamines and beta-endorphin elevated by exercise may interact to suppress luteinizing hormone release at the hypothalamic pituitary axis.

Adolescent↗
PubMed1984

Luteinizing hormone and gonadal steroid levels during the menstrual cycle of orangutans.

Serum luteinizing hormone (LH), progesterone, 17 beta-estradiol, and testosterone were measured during a single cycle each of five female orangutans, and urinary LH was measured in four of those cycles. Midcycle peaks in LH and luteal phase elevations in progesterone (5.7-13.8 ng/ml) suggested that the cycles were ovulatory. 17 beta-Estradiol was elevated at midcycle (163-318 pg/ml) and during the luteal phase (56-136 pg/ml) and testosterone was also elevated at midcycle (143-580 pg/ml). These hormone patterns in the orangutans closely resemble those for chimpanzees, gorillas, and human females.

Animals↗
PubMed1983

Menstrual cycle patterns of hormones and sexual behavior in gorillas.

Oppositely sexed pairs of gorillas were tested behaviorally during the menstrual cycle to determine the relationship between hormone concentrations of the female and the frequency of sexual activity by the pair. Five females were tested individually during two cycles with each of two males, but serum samples for hormone assay were obtained from each female only during the first cycle of testing. There was no clear relationship between hormones and behavior for the single cycle in which the serum samples were obtained, with the exception that no copulations occurred after the early luteal phase, when progesterone was greater than 5 ng/ml. Normalized behavioral data from all four test cycles for all pairs suggested that female-solicited copulations were restricted primarily to the periovulatory period. Male sexual initiative (by one of the males) accounted for most copulations temporally dissociated from the periovulatory period. Normalized hormone data for all of the females suggested that (1) attractivity was associated with estradiol concentrations during the follicular phase, (2) proceptivity with estradiol and testosterone at midcycle, whereas (3) receptivity was not associated with hormone patterns or cycle phase. The data suggest that hormones are one of several variables that contribute to the regulation of sexual behavior in gorillas.

Animals↗
PubMed1983

Developmental patterns of serum luteinizing hormone, gonadal and adrenal steroids in the sooty mangabey (Cercocebus atys).

Serum levels of luteinizing hormone (LH), testosterone, dehydroepiandrosterone sulfate (DHAS), androstenedione and cortisol were determined in multiple samples from 86 sooty mangabeys of varying ages (0-17 years). Testosterone, androstenedione, DHAS and cortisol were measured by radioimmunoassay; LH was determined by in vitro bioassay. Serum LH concentrations were elevated in neonates (less than 6 months) and in animals older than 72 months of age. The higher LH levels were associated with increased circulating concentrations of testosterone in males but not females. The pubertal rise in serum testosterone at approximately 55-60 months of age in males was coincident with rapid body growth. No pubertal growth spurt was observed in females. Serum levels of androstenedione and DHAS were highest during early postnatal life (less than 6 months) with androstenedione exceeding 600 ng/dl in males and 250 micrograms/dl in females, but declined rapidly in both sexes to a baseline of 150 ng/dl by 19 months of age. Serum androstenedione did not fluctuate significantly in adult animals. The pattern of age-related changes in serum DHAS paralleled those of serum androstenedione, whereas serum cortisol values did not change significantly with age. Developmental changes in serum LH, testosterone and body weight suggest that the sooty mangabey matures substantially later than the rhesus monkey. The pattern of serum gonadal and adrenal steroids during sexual maturation is similar to that seen in the baboon with no evidence of an adrenarche.

Aging↗
PubMed1983

Release of progesterone from perifused, highly luteinized ovarian cells of rats: effects of luteinizing hormone and bovine serum albumin.

Release of progesterone from enzymatically dispersed luteal cells of superovulated rats was studied using a multi-channeled perifusion system. Cells were perifused with protein-free medium for up to 5 h. Basal release of progesterone showed a steady decline during the first h of perifusion to a stable baseline where it remained throughout the experiment. A 30-min exposure of the luteal cells to increasing amounts of luteinizing hormone (LH) stimulated a dose-dependent increase in progesterone release. Similar results were observed when luteal cells were exposed to 0.2 or 1.0 mM dibutyryl (Bu)2 cAMP for 30 min. Exposure of the cells to 0, 1, 10, and 100 ng LH/ml protein-free medium for 230 min showed increased release of progesterone, although the dispersed cells perifused with 100 ng LH/ml protein-free medium were unable to maintain the maximal levels of progesterone release. The effect of bovine serum albumin (BSA) in the perifusion medium on the basal and LH-stimulated progesterone release was examined. Low concentrations of BSA (0.05%) had no effect, but 0.5% and 2.0% BSA significantly increased the basal release of progesterone. However, the addition of 0.05% BSA to the medium resulted in an increased progesterone release in response to 10 ng LH/ml medium. These results suggest that the in vitro perifusion system maintains physiologically viable cells which are responsive to either LH or (Bu)2 cAMP for at least 5 h. The effect of protein in the perifusion medium or progesterone release was demonstrated by the addition of BSA.

Animals↗
PubMed1983

Effect of estradiol-treated females on all-female groups of rhesus monkeys during the transition between the nonbreeding and breeding seasons.

Behavior, sex steroid levels and sex skin color were monitored in 2 out-door-housed all-female groups of rhesus monkeys during the nonbreeding season and into the breeding period. Each group contained gonadally intact and ovariectomized (OVX) females. In one group, 2 OVX females were implanted with estradiol benzoate pellets. Female-to-female sexual behavior, sex skin redness and endocrine indices of ovulation (in intact females) all increased as the breeding season approached. The two groups did not differ with regard to these measures. This lack of difference suggests that the presence of males may be required to mediate socially facilitated out-of-season breeding by females. No strong relationships were detected between steroid levels of intact females and sex skin color or female-to-female sexual behavior in all-female groups.

Animals↗
PubMed1983

Presence of the "Beaumont" protein in serum of oral contraceptive users.

The level of the "Beaumont" protein present in serum was measured by a population of 223 black and 76 Caucasian women with different exposures to oral contraceptives (OCs). No differences were found in the values in nonusers, past users, current users, or new users of OCs. The values were higher in black nonusers and users than in comparable Caucasian groups, suggesting a racial difference. A group of 55 thrombotic women were subclassified by type of thrombosis and exposure to OC therapy. No significant difference was seen between the values in thrombotic women exposed or not exposed to OCs. A similar result was obtained when the types of thrombosis (arterial or venous) were compared. These results do not confirm Beaumont's hypothesis that antibodies are induced by contraceptive steroids in a subgroup of women on OC therapy.

Adult↗
PubMed1982

Age differences in Copulatory behavior and serum 17 beta-estradiol in female rhesus monkeys.

Young, sexually mature female rhesus monkeys housed in outdoor groups have been found to exhibit significantly longer mating periods associated with first conception compared with the duration of the annual period exhibited by older, multiparous females. An analysis of the sexual behavior and corresponding serum concentration of 17 beta-estradiol (E2) a progesterone, (P) in two age groups of rhesus females revealed that young females copulated on significantly more days prior to the E2, ovulatory peak than did older females. Serum concentrations of E2 were significantly higher from -30 to Day- 10 prior to the E2 peak (Day 0) in young females. Estradiol concentrations were similar for both age groups during the remaining follicular and periovulatory period. No age differences in serum P were observed between the two groups. Serum E2 levels associated with the onset of mating were similar in the two age groups with levels rising from 73.5 +/- 4.0 pg/ml prior to mating to 97.2 +/- 4.6 pg/ml. Thus the hormonal profile associated with the onset of mating is similar for both age groups, and the earlier occurrence of mating behavior prior to ovulation in young females is accounted for by an earlier rise in serum E2.

Aging↗
PubMed1982

Effect of low density and high density lipoproteins on progesterone secretion by dispersed corpora luteal cells from rats treated with aminopyrazolo-(3,4-d)pyrimidine.

Immature female rats, superovulated and treated daily for 3 days with 4-aminopyrazolo-(3,4-d)pyrimidine (APP), showed a marked reduction in plasma cholesterol levels, which is reflected by reduced levels of very low density, low density (LDL), and high density (HDL) lipoproteins. Luteal cells from non-APP-treated rats released 2444 +/- 212 ng progesterone/mg protein in 4 h, which slowly increased to 2806 +/- 327 after 20 h. Luteal cells from APP-treated animals showed a similar pattern at about half the level of progesterone production. In the presence of 100 ng LH/ml, progesterone levels were stimulated 2-fold in both APP-treated and nontreated controls. The addition of either human HDL or LDL to any of the preparations markedly increased the progesterone level. These results support the hypothesis that APP treatment reduces the ability of dispersed luteal cells to secret progesterone. This effect is partially overcome by the addition of either HDL or LDL to the incubation media in vitro, suggesting that rat luteal tissue can use either human HDL or LDL as a source of cholesterol. However, about 5 times as much human LDL-derived cholesterol was required to stimulate equivalent increases in progesterone compared to human HDL cholesterol.

Adenine↗
PubMed1979

Urinary excretion of estrone glucosiduronate, 17 beta-estradiol-17-glucosiduronate, and estriol-16 alpha-glucosiduronate. Significance of proportionate differences during the menstrual cycle.

The urinary excretion of estrone glucosiduronate, 17 beta-estradiol-17-glucosiduronate, and estriol-16 alpha-glucosiduronate in men and throughout the menstrual cycle in women was measured by specific radioimmunoassay. In 9 men the mean +/- SE excretion of these conjugates was 15.9 +/- 1.4, 2.7 +/- 0.3, and 3.2 +/- 0.2 microgram/24 h respectively. In 15 women studied in the midfollicular phase (day 8) of the menstrual cycle, the excretion was 19.4 +/- 1.7, 2.9 +/- 0.2, and 5.4 +/- 1.3 micrograms/24 h. Excretion of each conjugate was significantly (P less than 0.01) elevated in the midluteal phase (day 22) to 41.9 +/- 3.9, 6.3 +/- 0.8, and 12.2 +/- 1.5 micrograms/24 h respectively (n = 14). The mean excretion of estriol-16 alpha-glucosiduronate was greater than that of 17 beta-estradiol-17-glucosiduronate in the luteal phase (P less than 0.05) but not in the follicular phase or in men (P greater than 0.05). The excretion of each of these specific conjugates measured throughout the menstrual cycle in 7 women was characterized by a sharp midcycle peak and a lower, broader luteal phase peak. The ratios of estriol-16 alpha-glucosiduronate to 17 beta-estradiol-17-glucosiduronate, estrone glucosiduronate to 17 beta-estradiol-17-glucosiduronate, and estriol-16 alpha-glucosiduronate to estrone glucosiduronate throughout the menstrual cycle were analyzed. When the mean ratio during the follicular phase was set at 1, a significant increase (P less than 0.01) occurred in the mean luteal phase ratio in each case: 1.00 +/- 0.03 to 1.66 +/- 0.09, 1.00 +/- 0.04 to 1.30 +/- 0.04, and 1.00 +/- 0.03 to 1.24 +/- 0.04 (mean +/- SE) respectively. The marked alteration in the proportions of these urinary estrogen conjugates may be due to altered metabolism of 17 beta-estradiol, but it more likely reflects a change in the pattern of estrogen secretion or production between the two phases of the menstrual cycle.

Adult↗
PubMed1979

Extrasplanchnic effect of sulfobromophthalein (BSP) on plasma estrogen levels in the dog.

The effect of the drug sulfobromophthalein (BSP) on plasma estrogens in the dog were studied during intravenous infusions of 3H-labeled estrogens. During [3H]estrone infusion, BSP administration caused a marked increase in arterial plasma levels of the radioactive conjugated estrogens, estrone glucosiduronate, estradiol-17 beta glucosiduronate(s), and estrone sulfate. Levels of the unconjugated estrogens, estrone and estradiol-17 beta, were substantially unaltered. Possible mechanisms were investigated. Splanchnic extraction of the conjugates did not change significantly during BSP administration, and renal excretion rose promptly in proportion to the plasma levels, thus virtually excluding decreased biliary or renal excretion. There was no net discharge of estrogen glucosiduronate radioactivity from adipose tissue or muscle following BSP. During [3H]estrone glucosiduronate infusion, BSP again caused an increase in plasma estrone glucosiduronate, thus excluding increased formation (of this conjugate, at least). BSP caused decreased extraction of estrone glucosiduronate by the hindlimb, indicating that decreased metabolism was the probable cause of the elevated plasma levels. BSP also caused decreased formation of unconjugated estrogens by the lungs, indicating that the decreased metabolism includes decreased hydrolysis of estrogen glucosiduronates.

Animals↗