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Summary.
The effect of spermatozoa within the cervix and of spermatozoa within the uterus on the infiltration of polymorphonuclear leucocytes (polymorphs) into the lumen of the genital tract at oestrus was examined in ewes. Ligation of the cranial end of the cervix resulted in an accumulation of polymorphs in the lumen of the uterus and of fewer polymorphs in the lumen of the cervix. In genital tracts so ligated, spermatozoa within either the cervix or the uterus had no material effect on the number of polymorphs found in the cervix. The presence of spermatozoa in ligated uterine horns caused an increase in the number of polymorphs migrating into the lumina of the horns, the response being manifest within 5 hr. The results indicate that drainage of polymorphs from the uterus into and through the cervix is a normal occurrence in ruminants which may reduce the incidence of phagocytosis of spermatozoa in the uterus.
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Bull spermatozoa survived at extremely low cell concentrations (10 to 470 cells/μl) at 37° C in either cervical mucus or gel obtained by centrifugation of the mucus, but became immotile almost immediately after being suspended at 500 cells/μl in isotonic saline. Spermatozoa were adversely affected by suspension at low cell concentration in supernatant obtained by centrifuging mucus, or in mucus that had been liquefied by maceration. Although spermatozoa were slightly more resistant to the lethal effects of dilution in saline after passage through mucus, the resistance was quickly lost. The results suggest that the structural and physical properties of the mucus are responsible for the absence of the dilution effect on spermatozoa in cervical mucus.
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Quantitative studies were made of the distribution of spermatozoa and leucocytes in the female genital tract of mated goats and cows near the time of ovulation and of the leucocytes in the genital tract of unmated goat does at a similar time. In both species, the cervix appeared to act as a reservoir for spermatozoa. Spermatozoa were not uniformly distributed through the lumen of the cervix but tended to be aggregated in the vicinity of the cervical mucosa.
The presence of spermatozoa in the genital tract resulted in an increased number of leucocytes in the lumen of the uterus and cervix. In the cervix, the majority of the leucocytes occurred in the central mass of the mucus, this being consistent with the main invasion of the cervical mucus by the leucocytes taking place from the uterus. The resulting separation of spermatozoa and leucocytes in the cervix is probably an important factor in the survival of an adequate population of spermatozoa in the cervix of ruminants after mating.
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It is well known that in many mammalian species, including the sheep (Sundaram & Stob, 1967), unilateral ovariectomy leads to compensatory hypertrophy in the remaining ovary and an ovulation rate equal to that of the two ovaries in the control animals (Parkes, 1966). However, it has not been conclusively established that analogous compensatory changes occur in the remaining testis following unilateral orchidectomy. Although it has been shown in the hemicastrated adult rat that the remaining testis enlarges (Grant, 1957) and the epididymal sperm reserve increases to that of the two epididymides in the intact animals (Smelser, 1933), observations on the hemicastrated rabbit (Edwards, 1940) and other species (see Parkes, 1966) are conflicting. Previous studies were limited because of the lack of a technique for accurately assessing production
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Summary. Vessels with histological features characteristic of arterio–venous anastomoses were found in the stroma but not in CL. In 5 conscious ewes at the mid-luteal stage of the oestrous cycle, ovarian blood flow was significantly greater (P < 0·025) with microspheres of 50 than of 15 μm diameter in ovaries without CL (0·23 ± 0·04 (s.e.m.) and 0·11 ± 0·02 ml/min, respectively), but not in ovaries with CL (4·42 ± 0·86 and 3·73 ± 0·70 ml/min, respectively). In 5 similar but anaesthetized ewes, the portion of each ovarian artery within the ovarian vascular pedicle was bypassed with re-entrant catheters through which microspheres were perfused. A greater proportion (P < 0·01) of 50 than of 15 μm microspheres was retained in ovaries with (90 and 79%) or without (82 and 45%) a CL.
It is concluded that functional arterio–venous anastomoses are present in sheep ovaries.
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Summary. Two groups, each of 7 crossbred beef cows, which were suckling or not suckling calves, were fed a high quality food ad libitum for 3 months post partum. The non-suckling cows experienced regular ovarian cycles from 10–33 days post partum while the suckling cows did not do so until at least 14 weeks post partum. There was little difference between the groups in growth rate or in plasma glucose concentration. The plasma prolactin concentrations in the non-suckling cows showed a seasonal trend which paralleled ambient temperature and daylight hours; in the suckling cows this trend was less evident. Plasma LH concentrations were lower in suckling cows before Day 30 post partum but were similar thereafter. Most suckling cows also failed to experience oestrus or to exhibit LH release in response to an injection of oestradiol benzoate at about 6 weeks post partum. This failure, together with the earlier lower levels of LH in the suckling cows, is considered to be indicative of malfunction of the hypothalamic mechanism normally responsible for the establishment and maintenance of cyclic ovarian function.
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Summary. Changes in the mean velocity of ovarian arterial blood flow during the oestrous cycle were monitored in 5 ewes by the use of Doppler ultrasonic transducers chronically implanted around the ovarian arteries. In arteries supplying ovaries with a corpus luteum (CL), the velocity was minimal from Day −1 to Day 2 inclusive (Day 0 = day of oestrus), increased steadily until Day 13 (−4) and then declined precipitously. In contralateral arteries supplying ovaries without a CL, the velocity remained at a consistently low level throughout the oestrous cycle.
In each ewe, arterial blood velocity to the ovary with a CL and progesterone levels in peripheral plasma were highly correlated; within-individual correlations falling between r = 0·830 (P < 0·001, n = 15) and r = 0·936 (P < 0·001, n = 15). The changes in the velocity of the arterial supply to the ovulatory ovary and the plasma progesterone levels during the luteal stage of the cycle followed a similar pattern to that for weight of luteal tissue in similar ewes.
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Summary. Two experiments were conducted to examine the effects of mouse epidermal growth factor (EGF) on the concentrations of testosterone, LH and FSH in jugular blood plasma and on the pituitary responsiveness to LHRH. In 20 rams treated with subcutaneous doses of EGF at rates of 85, 98 or 113 μg/kg fleece-free body weight, mean plasma LH and testosterone concentrations were significantly reduced (P < 0·05) at 6 h after treatment but not at 24 h. EGF treatment at 130 μg/kg fleece-free body weight suppressed the plasma content of these hormones for up to 48 h. Mean plasma FSH concentrations decreased significantly (P < 0·05) for up to 48 h after EGF treatment, the effect being most pronounced in rams with mean pretreatment FSH values >0·5 ng/ml. Intravenous injections of 1·0 μg LHRH given to each of 5 rams before and at 6 h, 24 h and 72 h after EGF treatment produced LH and testosterone release patterns which paralleled those obtained in 5 control rams similarly treated with LHRH.
These results suggest that, in rams, depilatory doses of mouse EGF temporarily impair gonadotrophin and androgen secretion by inhibiting LHRH release from the hypothalamus. Such treatment appears to have no effect on the responsiveness of the pituitary to LHRH.
Keywords: testosterone; gonadotrophins; sheep; EGF; LH; FSH