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P. G. McDONALD and M. T. CLEGG

Summary.

Circulating levels of lh have been determined in intact and ovariectomized ewes before, during and after progesterone treatment. Neither 20 nor 40 mg progesterone daily for 10 days decreased the serum lh concentration during treatment. Following withdrawal, elevated levels of lh occurred on Days 4 to 6 in both intact non-cycling and ovariectomized ewes. Intact ewes treated during the initiation of the breeding season showed depressed levels of lh and failed to respond to progesterone treatment. The injection of 40 mg of progesterone daily did not delay the time of occurrence of the peak in lh activity.

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L. L. DOYLE and M. T. CLEGG

Summary.

Sixteen mature female rats were injected subcutaneously with 10 mg of progesterone daily for 14 days. After 7 days from start of treatment, all animals showed persistent dioestrous vaginal smears. By the 3rd day after withdrawal, most animals showed a pro-oestrous smear. When placed with males at this time, twelve of the sixteen treated females mated as indicated by the presence of spermatozoa in the vaginal smear or by the presence of normally cleaved ova, as compared to only one of five of the oil-injected controls. These results, when compared to the mating percentage of normal colony animals, indicate a significant improvement of mating following withdrawal of progesterone treatment.

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E. J. CLEGG and T. M. FARLEY

Summary.

  1. The effects of 'Ultandren' on seminal vesicle, coagulating gland and epididymis weights, and citric acid and fructose production in the former two organs, are described and compared.
  2. The regressions of seminal vesicle and coagulating gland weights on log dose are linear, and that of citric acid content is apparently so. The regression of epididymis weight, while probably linear, does not differ significantly from zero and that of fructose content is probably not linear.
  3. The importance of these findings with regard to the bioassay of 'Ultandren' is discussed.

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E. J. CLEGG and T. M. FARLEY

Summary.

  1. The relative potency of parenterally administered 'Ultandren' compared with testosterone propionate is approximately 1 when seminal vesicle weight is used as an index of androgenic activity.
  2. Coagulating gland weight is not a suitable indicator of male sex hormone activity for use in the bioassay of 'Ultandren'.

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DONALD J. DIERSCHKE and M. T. CLEGG

Observed reductions in the pituitary content of follicle stimulating hormone (fsh) and luteinizing hormone (lh) preceding ovulation in sheep (Santolucito, Clegg & Cole, 1960; Robertson & Hutchinson, 1962; Dierschke & Clegg, 1965; Robertson & Rakha, 1966) clearly imply that both hormones are involved in bringing about this event. These observations regarding pituitary content would seem to provide acceptable criteria for hormone release, but determination of the precise time and interval of gonadotrophin release must be confirmed by quantitative analysis of blood fsh and lh. This communication reports an attempt to accomplish that confirmation utilizing a technique for collecting pituitary effluent blood from the cavernous sinus of sheep (McFarland, Clegg & Ganong, 1960) and the highly sensitive biological assay of Parlow (1961) for lh. Assay of pituitary fsh was done by the method of Steelman