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Summary. Dwarf mice (DW/J; dw/dw) which exhibit a deficiency of prolactin and GH secretion were treated for 8 days with ovine prolactin and/or human GH (10 or 20 μg/day) and the effect on hepatic and testicular prolactin receptors was investigated. In both sexes there was a significant increase in body weight after all hormone treatments, but an increment in testicular weight was observed only after prolactin administration. Prolactin treatment increased the specific binding % of prolactin in liver membranes in females but not males, and in testicular homogenates (together with an increase in LH receptors). The results suggest that lack of prolactin but not of GH retards sexual development in these mice. Treatment with prolactin partly counteracts this deficiency, and the effect may be mediated by the induction of hepatic and testicular prolactin and LH receptors.

Summary. In rats that were allowed to eat the placentae after parturition concentrations of serum prolactin were elevated on Day 1 but concentrations of serum progesterone were depressed on Days 6 and 8 post partum when compared to those of rats prevented from eating the placentae. In rats treated with PMSG to induce superovulation serum prolactin and progesterone values were significantly (P < 0·05) elevated on Days 3 and 5 respectively, after being fed 2 g rat placenta/ day for 2 days. However, feeding each rat 4 g placenta/day significantly (P < 0·02) lowered serum progesterone on Day 5. Oestrogen injections or bovine or human placenta in the diet had no effect. The organic phase of a petroleum ether extract of rat placenta (2 g-equivalents/day) lowered peripheral concentrations of progesterone on Day 5, but other extracts were ineffective. We conclude that the rat placenta contains orally-active substance(s) which modify blood levels of pituitary and ovarian hormones.

Summary. Measurement of the serum concentrations of ovine chorionic sommatomammotrophin (oCS) showed that the values could be used to distinguish non-pregnant (100%) and pregnant (97%) ewes from Day 64 after mating. Values of oCS in non-pregnant ewes were <5ng/ml.

Summary. The ability of ovine placental lactogen (oPL) to stimulate progesterone secretion by the ovary as well as its ability to protect the corpus luteum against the luteolytic action of PGF-2α was investigated. When oPL was infused alone into the ovary for 2 h on Day 12 of an induced cycle at rates of 0·6, 6·0, 30·0 or 60·0 μg/h there was no significant increase in progesterone secretion by the autotransplanted ovary in 7 sheep. An extension of the infusion of oPL did not prevent luteal regression during the administration of PGF-2α given either continuously (10 μg/h for 6 h, 5 sheep) or as 5 pulses each lasting 1 h and of increasing concentration in 25 h (2 sheep). We conclude that oPL does not (a) stimulate progesterone secretion when infused directly into the arterial supply of the ovary or (b) have any direct protective effect against the luteolytic action of PGF-2α on the ovine CL.

Summary. Using the most sensitive immunocytochemical method available, on ultrathin frozen sections, the results in this paper demonstrate that bovine placental lactogen (bPL) is present in the earliest fetal binucleate cells found at 21 days post coitum in the trophectoderm. A second protein, the SBU-3 antigen, which is absent in the early stages of pregnancy appears abruptly in the binucleate cell granules at 30 days post coitum coincident with the start of villus development. Subsequently, the granules contain both bPL and the SBU-3 antigen. This sequential production of unlike proteins indicates that the binucleate cell has different functions depending on the stage of pregnancy and has important roles to play both at implantation and in villus development.

Keywords: immunology; ultrastructure; proteins; early pregnancy; cow

Summary. Sections of Days 12 to 55 sheep chorion, embedded at low temperature in glycol methacrylate, were exposed to rabbit anti-ovine chorionic somatomammotrophin (oCS) to ascertain the distribution of oCS. This hormone was first detectable on Day 14, when the cytoplasm of each chorionic cell displayed a low level of fluorescence surrounding droplets which were shown to be lipid containing. At this time, all chorionic cells were uninucleate. By Day 28, binucleate chorionic cells had appeared but showed no binding of the oCS antiserum which was confined to a significant proportion of the uninucleate chorionic cells surrounding lipid droplets, as at Day 14. The same pattern of hormone distribution, although with reduced fluorescence intensity, was observed on Day 55; fluorescence indicative of antibody binding was seen only in some of the uninucleate chorionic cells. Hence, oCS was detected in chorionic tissue before the differentiation of binucleate cells (Day 14) and, at all stages, it was confined to the cytoplasm of specific uninucleate chorionic cells in close association with lipid droplets.