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  • Author: E. M. TUCKER x
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Experiments are described which were designed to examine the possibility that death of the goat × sheep hybrid foetus is due to the passage of haemolytic antibody from mother to foetus. 'Naturally occurring' haemolytic antibodies to sheep red cells were found in the sera of some goats with normal or hybrid pregnancies. 'Heterologous' anti-bodies, considered to be of the immune type, were found in some but not all goats with hybrid foetuses; these 'heterologous' antibodies were not found in goats carrying goat foetuses. No immune globulins of maternal or foetal origin were found in foetal plasma or in allantoic or amniotic fluids. No real evidence was obtained for the presence of immune globulins on the red cells of hybrids whether or not their mothers had anti-sheep haemolysins in their sera. It is concluded that haemolytic antibodies are not responsible for the death of the goat× sheep hybrid foetus.

The electrophoretic pattern of hybrid haemoglobin was examined.

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K. Leung, V. Padmanabhan, L. J. Spicer, H. A. Tucker, R. E. Short and E. M. Convey

Summary. Thirty primiparous suckling beef cows were slaughtered on Day 7, 14, 28,42 or 56 after parturition. Some had resumed oestrous cyclicity by the time they were slaughtered on Days 42 and 56. Amongst acyclic cows between Days 7 and 42, pituitary LH concentrations and basal and GnRH-induced release of LH from pituitary explants doubled. Pituitary FSH concentration and basal release in FSH increased only by 15–20%, while GnRH-induced release of FSH in vitro was unchanged. During post-partum anoestrus, overall mean concentrations of serum FSH did not change, whereas overall mean concentrations and pulse amplitudes of serum LH increased. Numbers and affinity constants of GnRH-binding sites in pituitary glands remained constant during the post-partum period studied. We conclude that, under these experimental conditions, numbers and affinity constants of GnRH-binding sites in the pituitary gland of post-partum beef cows do not limit the ability of the anterior pituitary gland to release gonadotrophins.

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C. B. Fehilly, S. M. Willadsen, A. R. Dain and E. M. Tucker

Summary. Aggregation chimaeras were composed of quarter (or 1 cell) contributions from 4-cell blastocysts of sheep or goats, or of an 8-cell blastocyst of one species enveloped in three 8-cell blastocysts of the other. Gestation was in sheep or goat recipient females. Of the 10 living animals born, 3 were identified as interspecific chimaeras by body conformation and coat type among the 7 quarter/quarter aggregations and 1 among the 3 giant aggregates. Interspecific chimaerism was identified by cytogenetic study of umbilicus and blood lymphocytes respectively of 2 of these, one from each type of aggregate. Intraspecific sex chimaerism was found in 3 other animals; 2 were of giant aggregate origin, but the 1 of quarter/quarter origin must have acquired it by placental anastomosis with a twin conceptus. Tests using species-specific monoclonal antibodies and electrophoretic separation of haemoglobins and isoenzymes demonstrated sheep and goat erythrocytes in one giant aggregate chimaera; their relative proportions and those of the blood lymphocytes changed over a period of 31 months from approximately 60% goat and 40% sheep to more than 90% sheep. The plasma transferrins and amylases did not show similar relative changes from their predominantly goat-like character and, by implication, neither did their tissues of origin.