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E. C. MATHER and H. E. DALE

Summary.

Bovine spermatozoa, washed or in seminal plasma, were incubated alone or in combination with oestrogenic and progestational endometrial preparations; oxygen consumption was determined for 1 hr.

Oxygen uptake by combinations of washed spermatozoa and endometrial preparations could be predicted by addition of the respiratory activity of the isolated tissues. When diluted whole semen was substituted for washed spermatozoa, oxygen uptake by the combined tissues was significantly less than that predicted by addition. The factor in seminal plasma responsible for the depression of respiratory activity was not identified.

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E. C. MATHER and H. E. DALE

Summary.

The oxygen uptake of bovine endometrium was less when perfused with seminal plasma than when perfused with Krebs-Ringer phosphate buffer solution. Dialysing the seminal plasma against Krebs-Ringer phosphate buffer solution did not alter the depressant action of the seminal plasma. The depressant substance was shown to be partially heat labile.

Variable mineral concentrations were not responsible for the respiratory depression of the endometrium. It was found, however, that calcium is contributed to the seminal plasma in various amounts and that this contribution is made in conjunction with or associated with the non-dialysable depressant substance. Calcium does not appear to be tightly bound to the non-dialysable material and its removal does not alter the depressant action.

It was shown that the degree of respiratory depression is related to the dry weight of non-dialysable seminal plasma.

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R. L. DOAK, ALLEN HALL and H. E. DALE

Summary.

Survival of spermatozoa in the reproductive tract of the bitch was studied by examination of the female genitalia at measured intervals after copulation. Motile spermatozoa were found in the lumen of the uterus in undiminished concentrations for 4 to 6 days after copulation; numbers progressively declined but motile spermatozoa were observed as late as 268 hr after copulation. Clusters of spermatozoa were observed in a high percentage of the uterine glands. The disappearance of spermatozoa was associated with the onset of metoestrus, not with time in the uterus. Bitches bred late in oestrus and examined in metroestrus had few spermatozoa compared with bitches examined in oestrus at a comparable time after copulation. Large numbers of spermatozoa were never found in the oviducts or ovarian bursae; they were consistently found here between 20 and 40 hr after copulation, a single observation showed spermatozoa in the oviducts at 168 hours. Tubal ova were recovered from eight bitches in metoestrus, in five cleavage had begun; tubal ova were recovered from four bitches in oestrus, none had undergone cleavage. Examination of the ovaries indicated that ovulation most commonly occurred within 48 hr after the onset of oestrus.

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W. R. THRELFALL, C. E. MARTIN, H. E. DALE, R. R. ANDERSON and G. F. KRAUSE

Summary.

Pituitaries of slaughtered sows were assayed for prolactin with the intradermal pigeon crop gland technique. Sows were classified into three groups—follicular, early postovulatory and luteal—after gross inspection of the ovaries. Pituitary prolactin was lowest in the postovulatory group (57·6±2·4 i.u.) and highest in the luteal group (87·0±12·9 i.u.). This study indicated that the pituitary prolactin content in the sow was comparable with that reported for dairy cows and refutes previous reports of small quantities present in the swine pituitary.