Progesterone and oestrone levels in the gonads and pyloric caeca of the male sea star Asterias rubens: A comparison with the corresponding levels in the female sea star

1. 1. Levels of progesterone and oestrone were estimated by means of RIA in the gonads and pyloric caeca of male specimens of Asterias rubens throughout the reproductive cycle. 2. 2. The patterns obtained appeared to be sex-specific on comparison with those of female specimens of A. rubens and it was concluded that progesterone and oestrone in the testes are involved in the regulation of gametogenesis. 3. 3. The levels of progesterone in the pyloric caeca were about ten times higher than those in the testes; in the same sequence levels of oestrone were only slightly higher. 4. 4. The onset of a new reproductive cycle, taking the abrupt decrease of the pyloric caeca-index as a marker, coincides with a strong decrease of the progesterone level (P < 0.001) and an increase of the oestrone level (P < 0.01) in the pyloric caeca. 5. 5. It is supposed that progesterone and oestrone in the pyloric caeca are concerned with making available the materials required for gametogenesis

Radioimmunoassays to determine the presence of progesterone and estrone in the starfish Asterias rubens

RIA's have been made for progesterone and estrone with the antisera S74B7 and 7604-7 40, respectively, which will be described. The characteristics of the RIA for progesterone resemble those of other reported RIA's. The antiserum for the RIA of estrone is highly specific, with main cross-reactions of 0.32%, 0.27% and 0.13% for estradiol-17β, estradiol-17α and oestriol, respectively. The RIA for estrone is sensitive (affinity constant: 28.2 × 109 1/mol), with a standard curve in the range from 1 to 10 pg. Accuracy and precision were reliable, as proved by the significant correlation between steroid added and steroid estimated. With the use of these RIA's, progesterone and estrone were demonstrated in the ovaries and pyloric ceca of single specimens of Asterias rubens. Progesterone was also present in the perivisceral fluid, but estrone appeared to be absent. The progesterone level was lower and the estrone level higher in the ovaries than in the pyloric ceca. The significance of the presence of these steroids in the ovaries and pyloric ceca of Asterias rubens, and of the differences in the steroid levels between both organs will be discussed

Superovulation of cows with PMSG: Variation in plasma concentrations of progesterone, oestradiol, LH, cortisol, prolactin and PMSG and in number of preovulatory follicles

Forty-two heifers, exhibiting normal oestrous cycles, were treated with 2500 I.U. PMSG and 2 ml prostaglandin (PG) at day 10 and 12 of the oestrous cycle, respectively. In ten heifers progesterone, oestradiol, LH, prolactin, cortisol and PMSG levels were estimated until 10 days after the initiation of superovulation. In 32 heifers the occurrence of the LH surge was determined with a rapid radioimmunoassay, and 22–30 h after the LH surge the heifers were ovariectomized. The numbers of large follicles (> 10 mm) and ovulations on the collected ovaries were counted and the levels of progesterone, oestradiol, PMSG and LH in the peripheral blood where estimated. The sum of large follicles and ovulations was assumed to represent the number of preovulatory follicles. In 16.7% of the heifers no LH surge was detected. This failure of the LH surge after superovulation appeared not to be caused by significantly different levels of cortisol, prolactin and PMSG as compared to those of cows responding with an LH surge. There was quite some variability in the interval between the PG injection and the maximum of the LH surge. The mean interval was 43.9 ± 1.5 h (SEM; n = 28). This interval PG-LH was negatively correlated with the number of preovulatory follicles (r= −0.483; P < 0.01). The interval between the onset of oestrus and the maximum of the LH surge was 1.96 ± 0.54 h (n = 22). The oestradiol concentration during the preovulatory LH surge and the number of preovulatory follicles were positively correlated (r= 0.732; P < 0.01). Progesterone levels were significantly increased after the initiation of superovulation. There was no significant correlation between the progesterone level before or after the administration of PMSG and the number of preovulatory follicles. This number was also not correlated with the concentration of PMSG in the peripheral blood shortly after injection of PMSG or shortly after injection of PG. The results indicate that the marked variability in response to PMSG/PG superovulation is not due to variations of hormone concentrations during the stages of preovulatory follicular development

Effect of chronic treatment with bromocryptine on the corpus luteum function of the cow

Six heifers received an intramuscular injection of 15 mg bromocryptine twice daily from day 1 (the day of standing oestrus was defined as day 0) until 50 h after the start of luteal regression. The overall mean level of prolactin was 0.22 ±0.01 μg/l (SEM; N=6) in the bromocryptine-treated group and 10.7±2.7 μg/1 (SEM; N=6) in the control group. No significant differences in the overall mean level of progesterone and LH, the mean length of the early-luteal phase, the luteal phase and the period of luteal regression were measured between the two groups. The results provide strong evidence that prolactin has no luteotrophic properties in the cow during the oestrous cycle

A tradeoff between immunocompetence and sexual ornamentation in domestic fowl

Females often select their mates on the basis of the size or intensity of sexual ornaments, and it is thought that such traits are reliable indicators of male quality because the costliness of these traits prevents cheating. The immunocompetence handicap hypothesis is a recently proposed mechanistic explanation of these costs and states that males carry ornaments at the expense of their resistance to disease and parasites. The tradeoff between immunocompetence and sexual ornamentation was hypothesized to arise as a consequence of the dual effect of androgens on ornamentation (1) and immune function (2). To test this hypothesis, we compared comb size between male domestic chickens Gallus domesticus of lines divergently selected for antibody responses to sheep erythrocytes (three lines: selected for low response or high response and a control line). The importance of comb size in inter- and intrasexual selection is well established, and comb size is strongly dependent on testosterone level. Comb size was larger in the males of the low line than in the high line, and comb size of control males was intermediate, indicating a tradeoff between ornamentation and immunocompetence. Testosterone (T) levels varied in a similar fashion (TLow > TControl > THigh), suggesting that this hormone could mediate the tradeoff between ornamentation and immunocompetence. These results support the idea that a tradeoff with immune function may constrain the expression of secondary sexual ornaments.

Validation of a new method of visual oestrus detection on the farm

Since visual observation is the most commonly used way of detecting oestrus and is supposed to be as effective as detection with technical devices, we evaluated a recently developed oestrus detection scoring system in daily dairy practice. In this scoring system nine signs of oestrus are scored with points, ranging 3 to 100. Twenty-one dairy farmers used the scoring system during a period of 3 weeks. All cows that were more than 30 days post partum and not confirmed pregnant were monitored, using the scoring system, by the herd owners. Oestrus was confirmed by measuring progesterone concentrations in milk. With the scoring system a detection rate of 47% was achieved. This was lower than expected, because in an earlier control period, the detection rate was 64%. We concluded that this new method might be too complicated to introduce to normal herd management, because in daily practice it is too demanding to watch cows twice a day for 30 minutes, especially if the cows show only vague and infrequent symptoms of oestrus. It also appeared to be too complicated to watch the herd at the most appropriate time. However, if the scoring system is included in the daily routine, meaning that farmers are trained to watch for other symptoms than standing heat only and are able to recognize their different values, it can be a valuable aid to oestrus detection

Plasma prolactin, progesterone and oestradiol-17β concentrations around parturition in the pig

Plasma concentrations of prolactin, progesterone and oestradiol-17β were measured by radioimmunoassay in samples taken from 2–15 days before until 1–4 days after spontaneous parturition in four sows and in one sow around prostaglandin F2α-induced parturition. Between Days −15 and −2 (Day 0 = parturition), prolactin concentrations in daily samples fluctuated somewhat, but exceeded 10 ng/ml only exceptionally. Plasma progesterone levels gradually declined or remained high until about 2 days before parturition. A final decrease of the progesterone concentrations coincided with distinct increases of the prolactin levels during the last 40 h of pregnancy. Maximal prolactin concentrations were measured before the onset of delivery of the piglets. Oestradiol-17β reached peak values around delivery. Prostaglandin F2α injection caused an immediate sharp increase of the prolactin concentration which lasted for about 6 h. During this period progesterone and oestradiol-17β concentrations did not change. A second elevation of prolactin levels was measured when progesterone finally decreased. Changes of prolactin concentrations found in this study were compared with those found in other domestic animals at the same reproductive stage

On the influence of orciprenaline on uterine motility and on plasma levels of estradiol-17β in pregnant and parturient sheep

Orciprenaline infusions in laboring ewes suppressed uterine activity. A complete inhibition of uterine activity could only be obtained in the empty uterine horn of laboring ewes. During late pregnancy a complete inhibition of the pregnant horn could be established with orciprenaline doses much lower than those necessary during parturition. In all treated ewes, aberrant patterns of plasma estradiol-17β levels were observed: very high maternal estradiol-17β levels were detected after treatment with orciprenaline. It is suggested that orciprenaline influences fetal adrenocortical functioning