Progesterone and the initiation of parturition in the goat

The corpora lutea were surgically removed from 6 goats between 134 and 136 days of pregnancy and progesterone was administered daily. Pregnancy was prolonged past normal term in 4 goats receiving 25 mgs. of progesterone daily as a split dose. However, eventual delivery following progesterone withdrawal was abnormal and foetal mortality high.The progesterone therapy regime maintained maternal jugular plasma concentrations of progesterone in excess of 3 ng/ml. In normal untreated goats, maternal plasma concentrations of progesterone declined over the last 6 days of gestation. In treated goats, plasma concentrations of progesterone fell only after the cessation of therapy. Maternal plasma concentrations of estrogen rose within 24 hours of parturition in normal untreated goats. In the 4 goats in which pregnancy was prolonged, by progesterone administration, maternal plasma concentrations of estrogen were elevated for several days in the period before eventual foetal delivery.     

An efficient cyanide-degrading Bacillus pumilus strain

A Gram-positive, aerobic, endospore-forming bacterium was isolated by an enrichment technique for the ability to degrade cyanide and was identified as a Bacillus pumilus strain. The bacterium rapidly degraded 100 mg l-1 of free cyanide in the absence of added inorganic and organic substances. The ability to degrade cyanide was linked to the growth phase and was not exhibited before late exponential/early stationary phase. Cyanide-degrading activity could not be induced before this time by the addition of 20 mg cyanide l-1. Production of the cyanide-degrading activity required 0.01 mg Mn2+ l-1 and did not occur at Mn2+ concentrations below 0.002 mg l-1. Cyanide-degrading activity was intracellular and cell-free extracts rapidly degraded cyanide.     

Effects of time after ovariectomy, season and oestradiol on luteinizing hormone and follicle-stimulating hormone secretion in ovariectomized ewes.

During the breeding season, five groups of three ewes were implanted at ovariectomy with 0.36, 0.5, 1.0 and 6.0 cm oestradiol implants or implants containing no steroid. Eleven days after receiving implants, blood samples were taken every 10 min for 6 h; implants were then removed. Treatments were repeated three times during each of two consecutive breeding seasons and four times during the intervening anoestrus. In ovariectomized ewes without steroid treatment, luteinizing hormone (LH) pulse frequency increased from early to mid-breeding season, decreased to a minimum at mid-anoestrus and increased to reach a maximum at the mid-point of the second breeding season, subsequently declining. LH pulse amplitude was inversely related to frequency. Basal serum LH concentrations decreased gradually from the first breeding season to reach a minimum at mid-anoestrus and gradually increased to reach a maximum at the end of the second breeding season. Mean serum LH and follicle-stimulating hormone (FSH) concentrations were higher at the end of the second breeding season compared with the beginning of the first breeding season. All parameters of gonadotrophin secretion were decreased much more by oestradiol during the anoestrus than during the breeding season. LH pulse frequency was decreased during anoestrus and at high oestradiol concentrations during the first breeding season. Apart from LH pulse amplitude, the decreases in all parameters of gonadotrophin secretion were less during the second compared with the first breeding season. The minimum effective dose of oestradiol required to decrease mean and basal serum concentrations of LH during anoestrus was lower than in the breeding season. The minimum effective dose of oestradiol required to decrease mean serum concentrations of FSH was lower in the first compared with the second breeding season. Oestradiol depression of LH pulse amplitude and mean serum concentrations of LH and FSH showed a dose dependency during the breeding season. During anoestrus dose dependency was seen for basal concentrations of LH and mean serum concentrations of LH and FSH. We conclude that significant chronic changes in gonadotrophin secretion occur in the ewe with time after ovariectomy. Sensitivity to oestradiol also changes, and the effects of oestradiol are not always dose dependent. We suggest that the circannual pattern of LH pulse frequency and basal LH secretion are directly linked to the circannual cycle of photoperiod.(ABSTRACT TRUNCATED AT 400 WORDS)