Reproduction

ELKINGTON, J. S. H.; BLACKSHAW, A. W.

doi: 10.1530/jrf.0.0230001pmid: 5472443

Summary.A factorial experiment, using injections of oestradiol, testosterone and pregnant mare serum gonadotrophin (pmsg), has been used to show the main effects and the interactions of these hormones on the rat testis. Oestradiol caused a decrease in testis and seminal vesicle weight, seminiferous tubule diameter, lactate (LDH) and glucose-6-phosphate (G-6-PDH) dehydrogenase activity in the interstitial tissue, and cessation of spermatogenesis at the pachytene primary spermatocyte stage. Testosterone and pmsg antagonized most of these effects, but testosterone alone caused a decrease in activity of LDH and G-6-PDH in the interstitial tissue, and pmsg did not influence the effect of oestradiol on the seminal vesicle weight.Oestradiol significantly decreased the activity of the unusual isoenzyme of LDH (LDH-X) in the rat testis, and it seems likely that the induction of LDH-X synthesis occurs during the pachytene primary spermatocyte stage of spermatogenesis. Testosterone and pmsg stimulated LDH-X synthesis when combined with oestradiol, while testosterone, but not pmsg, caused stimulation of LDH-X synthesis when injected alone.

KRZANOWSKI, MACIEJ

doi: 10.1530/jrf.0.0230011pmid: 5472431

Summary.Bull semen was separated by sedimentation in milk, with egg-yolk and powdered milk added. The sex ratio (SR) of the progeny of 2866 cows inseminated with sedimented spermatozoa was compared to that of 2171 cows inseminated with unsedimented semen from the same sires. After insemination with the more rapidly sedimenting spermatozoa, a statistically significant preponderance of females was born compared to the number born after insemination with the remaining fractions of the sedimented semen. The percentage of males born after insemination with the slower sedimenting spermatozoa, however, was not higher than that in the control series. After insemination of sedimented semen, there was an increase in abortion and a deviation of the SR to the disadvantage of the numbers of males born, probably due to a more frequent abortion of male foetuses. The differentiation in the SR of the progeny, depending on the fraction used for insemination, remained, even allowing for correction as to the supposed sex of the aborted foetuses.It is suggested that the more rapid sedimentation of spermatozoa with an X chromosome was caused by their greater ability to agglomerate.

RUSSO, J.

doi: 10.1530/jrf.0.0230021pmid: 5472444

Summary.The lysosomal enzyme, acid phosphatase, presents a circadian rhythm in the mouse testis. The content of protein, water and dry matter does not change during the 24-hr period, but there is an increase in the activity of the enzyme to midday and a decrease between 12.00 and 20.00 hours.The function of this enzyme and its inverse relationship to the availability of lh are discussed.

TYNDALE-BISCOE, C. H.

doi: 10.1530/jrf.0.0230025pmid: 5472445

Summary.Pregnant tammars were ovariectomized during anoestrus or on Day 8 of the reproductive cycle that follows removal of the pouch young. Quiescent and Day-8 blastocysts were transferred to the uteri of anoestrous or Day-8 non-pregnant recipients, some of which were ovariectomized at the time of transfer.Blastocysts did not develop after ovariectomy performed during anoestrus or after transfer to anoestrous recipients. Pregnancy continued normally after ovariectomy on Day 8 and both quiescent and Day-8 blastocysts developed in the uteri of intact and ovariectomized recipients.These results indicate that the uterus by Day 8 is competent to nourish an embryo to full term without further ovarian stimulation. They also show that the quiescent blastocyst can resume development without the direct stimulus of ovarian hormones. The hypothesis most in accord with the results is that blastocyst development is inhibited during lactation by a principle of the uterus, which is inactivated during the first 8 days by corpus luteum secretions, and that these secretions also induce the endometrial changes upon which subsequent embryonic development depends.

HARMAN, S. M.; TALBERT, G. B.

doi: 10.1530/jrf.0.0230033pmid: 5528679

Summary.C57B1 female mice aged 4 to 7 months (controls) and 8 to 9, 10 to 11, 12 to 13, and 14 to 15 months were mated and killed at 12 hr, 60 hr or 7½ days post coitum (p.c.). Corpora lutea were counted and evaluated in serially sectioned ovaries. Implantation sites were counted in the animals killed 7½ days p.c. The mean number of implantations in 10- to 11-month-old mice was less than in the control animals. This decrease was closely associated with morphological degeneration of corpora lutea of pregnancy. By 12 to 13 months of age most animals had neither implantation sites nor recognizable corpora lutea of pregnancy 7½ days after mating. These two changes were highly correlated and were not due to a decrease in the number of ovulations as determined by examination of the ovaries of animals killed 12 or 60 hr p.c.It was concluded that the initial decline in fertility with increased maternal age in this strain of mouse may be due to failure of luteal support of the uterus.

O'DONNELL, J. M.; SYMONS, D. B. A.

doi: 10.1530/jrf.0.0230041pmid: 5472446

Summary.Bull spermatozoa were centrifuged on various density gradients in a zonal centrifuge rotor. Depending on the relative osmolality and viscosity of the gradients, the rates of sedimentation of the spermatozoa varied, but the distribution of the cells in all gradients followed a similar pattern. The distributions showed a single mode and a skewness towards faster-sedimenting cells. The morphology of cell fractions separated by centrifugation was examined by immunofluoresence microscopy. A significantly greater proportion of cells had lost the acrosome in faster, as compared with slower, fractions. Acrosome degeneration and loss are known to be indicators of cell senescence. Therefore, it is considered that centrifugation of bull spermatozoa on density gradients results in a distribution which reflects the age of the cells. The natural heterogeneity in samples of ejaculated spermatozoa was reduced by treatment with detergent. Detergent treatment of spermatozoa altered the centrifugation pattern to a near normal distribution.

LAND, R. B.

doi: 10.1530/jrf.0.0230049pmid: 5472447

Summary.The litter size of Finnish Landrace sheep was found to be positively correlated with the duration of oestrus at the time of mating. The within-year regression of litter size on duration of oestrus was 0·011 lambs/hr and the correlation between the two traits 0·18 (1% > P > 0·1%).Data from Finnish Landrace × Blackface, Blackface and Merino × Blackface females, indicated that the correlation was mediated through ovulation rate, and that it was not limited to the Finnish Landrace.

KLEIMAN, DEVRA G.

doi: 10.1530/jrf.0.0230055pmid: 5528680

Summary.The green acouchi, Myoprocta pratti Pocock, in common with many other South American hystricomorph rodents (= Caviomorpha), possesses a vaginal closure membrane which becomes fully perforate only at oestrus and parturition. Partial perforation occurs at other times but does not prevent its use to define cyclical activity. The oestrous cycle, about 40 days, and gestation length, about 99 days, are long, relative to the size of the animal, but are within the range of those of related species. Sexual maturity is reached between 8 and 12 months of age. One or two offspring are born at any time of year although a slight birth peak is seen during the summer months. There is no difference in the growth rate of males and females, but acouchis weaned before 2 weeks of age are retarded in growth. In captivity, breeding success is greatest when a female is housed with a single adult male.

BLOM, E.; BIRCH-ANDERSEN, A.

doi: 10.1530/jrf.0.0230067pmid: 5528681

Summary.Attempts to study the ultrastructure of the `decapitated sperm defect' in ejaculates from sterile Guernsey bulls have so far been a failure because of difficulties in fixation of the separated heads and tails. Fixation of testis and epididymis tissue from a recent typical case, however, gave better results and have confirmed that in the testis most of the heads and tails are still in close contact with each other. The separation takes place in the caput epididymidis. The cause of the defect seems to be localized to structures belonging to the base of the sperm head, especially the implantation groove and the basal plate.

BREED, W. G.; HILLIARD, JESSAMINE

doi: 10.1530/jrf.0.0230073pmid: 5472448

Summary.Ovarian function was studied in thirty-eight does suckling at least four, and usually six to eight, young each. A balanced pellet diet was available at all times. Under these conditions, ripe follicles were present in the ovaries but the corpora lutea regressed rapidly following parturition and the size of the ovaries and uterus decreased as suckling continued. A basal progesterone output could not be quantified but the release of 20α-hydroxypregn-4-en-3-one, expressed as μg/g ovary/hr, tended to rise throughout lactation. In six of the seven suckled does which were allowed to mate post partum, pregnancy was maintained, indicating that sufficient oestrogen was produced by the follicles to maintain luteal function. The results support the concept that neither lactation nor the suckling stimulus suppresses fsh and lh release, since the presumed oestrogen production continues when adequate nourishment is available.