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Summary. Treatment of rats with anti-PMSG and anti-hCG for 5 days from Days 6,11 or 16 of pregnancy caused variable necrosis of fetal tissue, the extent of which increased from the chorionic cells to the inner trophoblastic layers with the increase in dose from 4 to 10 mg anti-PMSG. At 10 mg/day, fetal death and resorption were invariable in early to mid-pregnancy, whilst in late pregnancy some litters were carried to term. The main histological change in the corpora lutea was hyperaemia in the anti-PMSG-treated rats. Immunofluorescence studies with conjugates of anti-hCG and anti-PMSG showed sharp localization in the giant and chorionic cell layer at the feto-maternal junction.

We conclude that an hCG/PMSG-like substance is produced by rat chorionic cells and that it plays an immunosuppressive role during pregnancy.

Summary.

Gonadal progestins from fetal, juvenile, pregnant and non-pregnant Masai giraffe (Giraffa camelopardalis) were extracted, purified by TLC and measured by GLC or by competitive protein-binding assay. Progesterone was found in fetal ovaries and in a fibrotic CL from a nearterm fetus as well as in CL from juvenile animals. In pregnant animals, luteal progesterone probably increased with the duration of gestation.

The values of 20β-hydroxyprogesterone were higher in juvenile giraffes than in the fetus or during early pregnancy. No 20β-hydroxyprogesterone was detectable in a CL from late pregnancy or a CL from a non-pregnant giraffe. The values tended to be inversely related to the progesterone levels.

Detectable levels of 17α-hydroxyprogesterone were present in the fetal ovary, juvenile CL and in one pregnant animal with an early preimplantation blastocyst. In the later stages of gestation, the hormone levels were too low to be detected by TLC.

Thus, it seems that the CL present in the ovaries of fetal and juvenile giraffes are endocrinologically active and similar in function to the CL of adult female giraffes.

The breeding seasons of camels vary geographically (see Novoa, 1970), suggesting that environmental factors affect the temporal pattern of reproduction in these species. Gomes, Butler & Johnson (1971) found that a high ambient temperature had the effect of reducing testosterone production in the ram and it therefore seemed possible that the effect of the environment in the reproductive cycle of the camel was a consequence of thermal stress. In the present study the ambient temperature (20–30°C) was only moderate but the concomitant high humidity would have increased the thermal stress for an animal whose normal habitat is a hot arid environment.

Department of Veterinary Physiology, P.O. Box 30197, Nairobi, Kenya

(Received 6th November 1974)

The detergents at present in use for the separation of mammalian sperm acrosomes have unwanted side effects on the spermatozoa or on the acrosomes themselves. The present study was undertaken in an attempt to obtain a more satisfactory agent. Fresh unfermented coconut milk (CME), obtained from mature coconuts, was boiled and filtered into sterile Erlenmeyer flasks. After cooling, dihydrostreptomycin sulphate (1 mg/ml) was added. Half of the CME was mixed with an equal volume of 0·2 M-phosphate buffer, pH 7·4 (neutral pH CME) and the other half was mixed with an equal volume of 0·2 M-phosphate buffer, pH 5·9 (low pH CME). The buffered solutions were stored in a refrigerator at 2 to 4°C and used as sperm diluents within the week.

A commercial mixed liquid detergent solution (LD), comprising sodium tetrapropylene benzene sulphonate (NaTBS), sodium lauryl

Summary. The interhaemal membrane consisted of only two cellular elements: a single layer of cellular trophoblast and the fetal capillary endothelium. The hyrax is therefore one of the few mammals known to possess the cellular haemomonochorial type of placenta. The trophospongium was also cellular while the basal trophoblastic cells were strongly phagocytic. The giant multinucleate cells at the feto—maternal junction were ultrastructurally different from the trophoblast cells and showed no signs of degeneration. Their appearance suggests that they are of maternal rather than fetal origin.

Summary. In 2 prepubertal bulls 10-min blood samples collected during a 24-h period showed that gonadotrophin and testosterone peaks occurred regularly at intervals of 6 h in one animal and 8 h in the other. There was a clear relationship between the LH, FSH and testosterone peaks. The increase of gonadotrophin levels was followed 20 ± 6 (s.d.) min later by an increase of testosterone; the interval between the peak values was 61±9 (s.d.) min. The pattern of prolactin concentrations differed; there were two prolonged elevations rather than regular peaks.

Summary.

Histological studies of adenohypophyses of male Friesian and Ayrshire calves, aged 1 to 2 months, and measurements of plasma or serum LH by solid phase radioimmunoassay in Angus, Holstein, Guernsey and Jersey bulls, ranging in age from 7 months to 2 years were carried out to determine factors influencing gonadotrophin secretion. The gonadotrophin-secreting delta cells constituted 3% of the cell population of the cortical region of the adenohypophyses at 1 month of age and 4% at 2 months of age. Considerable quantities of LH (3·7±0·3 ng/ml) were present in plasma samples of Angus bulls at 7 to 9 months of age. The levels rose to 4·3±1·1 ng/ml at 12 to 14 months and, at 2 or more years of age, basal LH values were of the order of 7 to 10 ng/ml plasma or serum. No breed differences were noted either in pituitary histology or LH concentrations.

Teasing and ejaculations caused no increase in serum LH values for up to 3 hr after sexual excitement, irrespective of whether a bull or an oestrous cow was the teaser. Large irregularly occurring daily fluctuations in serum LH (0 to 50 ng/ml) were found in 6-year-old Holstein bulls. Similar but smaller variations (1 to 16 ng/ml plasma) were found in the younger Angus bulls aged 7 to 14 months. A distinct 24-hr variation in serum LH was found in two Holstein and two Guernsey bulls aged 1½ to 2 years. The diurnal serum LH values were twice the nocturnal values, an abrupt change-over occurring at 18.00 hours when most of the bulls were lying down. Hourly variations were small and insignificant during the morning and afternoon.