Reproduction

Young, R. J.; Cooper, G. W.

doi: 10.1530/jrf.0.0690001pmid: 6887130

Summary. Primary amines, pyridoxal and thiols induced separation of the mammalian sperm head and tail at specific sites across the head—tail junction. Primary amines and pyridoxal induced head detachment by allowing separation of the inner and outer nuclear envelope membranes adjacent to the tail basal plates. This detachment was prevented by prior reduction with sodium cyanoborohydride. The chemistry of amine-induced head separation and the similar action of pyridoxal indicate that the head and tail are joined by Schiff bases formed between proteins within the nuclear membranes. Head detachment with thiols occurred at two sites: across the connecting filaments linking the basal plate and the capitulum of the tail—neck complex and between the inner nuclear membrane and the nuclear chromatin. Mammalian epididymal spermatozoa exhibited species differences in susceptibility to head detachment induced by hydromechanical shear. The heads of mouse epididymal spermatozoa readily separated from the tails during vortexing whereas those from the vas deferens were resistant to shear. Head separation occurred at the same site as induced by primary amines. Rabbit spermatozoa from all parts of the epididymis were resistant to mechanical shear. Species differences in the mechanical stability of the head—tail junction suggest that the intermolecular Schiff bases linking the head and tail can be formed before or during sperm transport in the epididymis and that their formation probably occurs after the appearance of the periodic structures which bridge the inner and outer membranes of the nucleus in the region of the tail basal plate.

Henderson, K. M.; Willcox, D. L.; Bruce, N. W.

doi: 10.1530/jrf.0.0690011pmid: 6350568

Summary. Prostacyclin (PGI-2), 6-keto-PGF-1α and PGF-2α were infused continuously for 6 h into the dorsal aorta of rats 8 days pregnant. PGF-2α (10 μg/h) significantly reduced plasma progesterone concentrations by 66% and luteal tissue concentrations of pregnenolone and progesterone by 78% and 95% respectively. Plasma concentrations of 20α-dihydroprogesterone remained unchanged whilst luteal tissue concentrations rose 2-fold. Plasma progesterone concentrations were significantly reduced to 50% by PGI-2 (10 μg/h) but were unaffected by 6-keto-PGF-1α (10 or 100 μg/h). Neither PGI-2 (10μg/h) nor 6-keto PGF-1α (10 or 100 μg/h) had any significant effect on plasma concentrations of 20α-dihydroprogesterone or on luteal tissue concentrations of pregnenolone, progesterone or 20α-dihydroprogesterone. Arterial blood pressure was unaffected by PGF-2α and 6-keto-PGF-1α, but was significantly reduced by PGI-2 at infusion rates ≥ 60 μg/h.

Rachman, Flore; Casimiri, V.; Psychoyos, A.; Bernard, O.

doi: 10.1530/jrf.0.0690017pmid: 6350569

Summary. The distribution of IgA, IgG and IgM was studied by an immunoperoxidase technique on sections of mouse uteri at each stage of the oestrous cycle. Staining for IgG and IgA was highest at pro-oestrus, declined at oestrus and was very low during the other stages. At pro-oestrus IgG was found throughout the stroma, in the uterine lumen, and in 10% of glandular lumina; very few IgG-containing plasma cells were present. At pro-oestrus, IgA was found in the uterine lumen, and in most of the uterine glands, both in the lumen and in the epithelium; little IgA was present in the stroma. IgA-plasma cells were detected at each stage of the cycle and were particularly numerous at pro-oestrus and oestrus. These results suggest that IgA is secreted locally from plasma cells into the uterine gland through the glandular epithelium, but that IgG enters the stroma from the local capillaries. The obvious increase in IgG and IgA secretion at pro-oestrus, when plasma oestradiol levels are highest, supports the hypothesis that, during the oestrous cycle, the humoral immune response is regulated in the uterus by ovarian hormones.

Page, R. D.; Kirkpatrick-Keller, Diana; Butcher, R. L.

doi: 10.1530/jrf.0.0690023pmid: 6684160

Summary. Zygotes were transferred, on the day of fertilization, from young and old rats with 4- or 6-day oestrous cycles into the ovarian bursa of young recipients with 4-day cycles, and zygotes from young rats with 4-day cycles were transferred into young and old recipients with 4- or 6-day cycles. Young rats with 4-day cycles served as controls for both donors and recipients. An increase in length of cycle or maternal age of donor caused an increase in unfertilized and/or abnormal eggs at the pronuclear stage (nontransferred zygotes). Increased age of donor or length of cycle decreased the implantation rate observed on Day 11 of pregnancy. Likewise, increased age of recipient or length of cycle decreased implantation rate observed on Day 11 of pregnancy. The increase in both age and length of cycle of donor or recipient caused the greatest decline in implantation rate and percentage of normal embryos observed on Day 11 of pregnancy.

Shille, V. M.; Munrot, Coralie; Farmer, Susan Walker; Papkoff, H.; Stabenfeld, G. H.

doi: 10.1530/jrf.0.0690029pmid: 6684161

Summary. LH release leading to ovulation was induced in 17 of 29 oestrous periods. The time of ovulation after coitus was determined by histological examination or by observation at laparotomy of ovaries in situ. Histological methods revealed that ovulation was complete in most follicles (9 of 13) at 32 h post coitum and in all follicles that were involved in the ovulatory process by 36 h. When laparotomy was used, no signs of preovulatory change were noted at the first observation time, 22 h post coitum, but in 4 cycles in which the entire process of ovulation was observed, the ovulatory process occurred between 23 and 28 h (3 follicles), 23 and 27 h (2 follicles), 25 and 28 h (3 follicles), and 25 and 29 h (3 follicles)post coitum. The first ovulatory process noted was complete at 25 h post coitum.In cats, LH release continued over a 16-h period before returning to baseline (long surge), values being 616 ± 180 ng/ml at ½ h and 941 ± 154 ng/ml at 2 h post coitum. In 6 cats the LH release pattern was limited to a 4-h period (short surge), values being 537 ± 218 ng/ml at ½ h and 353 ± 245 ng/ml plasma at 2 h and basal (49 ± 18 ng/ml) by 4 h post coitum. Decreased secretion of oestrogen by follicles in animals undergoing ovulation was first observed at 16 h post coitum.It is concluded that coitus induces LH release within minutes in the cat and that ovulation begins about 24 h later and finishes by about 32 h post coitum. Only one coital input can cause LH release for as long as 16–20 h although shorter periods of LH release (4 h or less) can result in ovulation.

Worthy, Karen; Haresign, W.

doi: 10.1530/jrf.0.0690041pmid: 6684163

Summary. Nine ewes of each of two breeds, Dorset Horn (long breeding season) and Welsh Mountain (short breeding season), were ovariectomized after insertion of subcutaneous implants containing oestradiol-17β. A further 9 ewes of each breed were left entire. All of the ewes were placed in an artificial photoperiod of 8L: 16D on 12 December 1980. After 5 weeks half of the ewes of each breed and physiological state were abruptly changed into a long-day photoperiod (16L:8D) while the rest remained in short days. The time of onset of seasonal anoestrus in entire animals was significantly advanced in ewes changed to long days, with the end of the breeding season coming at the normal time of year in ewes maintained in short days. These differences in oestrous cycle activity were reflected by differences in the time at which LH concentrations in ovariectomized, oestrogen-treated ewes on the two light treatments fell to basal values. Prolactin concentrations showed an immediate and sustained rise in ewes changed to long days, but remained low in ewes maintained in short days. Since the onset of seasonal anoestrus occurred in the absence of high levels of prolactin (in short-day ewes), it is concluded that prolactin is not the major vehicle by which seasonal changes in hypothalamic responsiveness to the negative feedback effects of oestradiol are produced. The results suggest that anoestrus may be due to photorefractoriness.

Ahuja, K. K.; Bolwell, G. P.

doi: 10.1530/jrf.0.0690049pmid: 6350575

Summary. The distribution of the sperm-, lectin- and antibody-binding components was examined on isolated fragments of the hamster zona pellucida. In all three studies, binding was much stronger on the outer than on the inner surface of the zona pellucida. Fab antibody-binding sites were different from those for various lectins since there appeared to be no competition for binding. Multiple components are obviously exposed on the surfaces of the zona pellucida because the sperm receptor sites are also inaccessible to Fab fragments. We conclude that although the components may be present throughout the zona they are asymmetrically arranged in relation to both surfaces.Microdisc PAGE of zonae from ovulated eggs revealed three major components of molecular weight 240 000, 150 000 and 80 000. These are probably glycoproteins and thus resemble the glycoprotein composition of the mouse zona.

Carter, D. A.; Lakhani, S.; Whitehead, Saffron A.

doi: 10.1530/jrf.0.0690057pmid: 6350576

Summary. The time-course of the inhibitory effect of hyperprolactinaemia on LH secretion was delineated. Hyperprolactinaemia was induced in ovariectomized rats with injections of domperidone or ovine prolactin and circulating LH levels were measured from 1 h to 9 days after the treatment. Inhibition of LH secretion occurred within 2–4 h after treatment, and was maintained (provided that serum prolactin remained elevated) for a period of 6 days only. Thereafter LH levels increased to become insignificantly different from control levels on Day 9. A reduction in pituitary responsiveness was not associated with the acute or sub-chronic inhibition of LH secretion, although a significant fall in responsiveness was observed simultaneously with the return of serum LH levels to control values. No changes in hypothalamic LH-RH content was found. It is concluded that an impairment of pituitary function is not responsible for the inhibitory action of prolactin on LH secretion.

Edwards, S.; Roche, J. F.; Niswender, G. D.

doi: 10.1530/jrf.0.0690065pmid: 6350577

Summary. Treatment of 97 suckling beef cows at about 30 days post partum with doses of 0·25, 0·5, 1·0, 2·5, 3·0, or 5·0 μg Gn-RH/pulse for period of 2–4 days at 1-h or 2-h intervals in three different experiments did not increase the number of cows ovulating when compared to untreated controls. Treatment with 0·25 or 0·5 μg Gn-RH/pulse resulted in little or no LH release, whereas higher doses gave discernible LH releases after each Gn-RH pulse. Pretreatment with progesterone did not affect the ovulatory or LH responses.These data indicate that pulsatile injections of Gn-RH, at the dose levels and frequencies used, cannot reactivate ovarian cyclicity in a majority of cows. We suggest that the degree of follicular development at the time of treatment is a major factor determining the ovulatory response to such pulsatile Gn-RH regimens.

Hillbrand, F. W.; Elsaesser, F.

doi: 10.1530/jrf.0.0690073pmid: 6887142

Summary. Small samples of backfat were taken daily during one oestrous cycle and more frequently after ovariectomy from 12 gilts by means of a simple biopsy technique and the levels of progesterone were determined. Compared to the levels of progesterone in peripheral plasma changes in backfat levels during the oestrous cycle were delayed by 1–2 days. Maximal levels with 89·7 ± 9·2 (mean ± s.e.m.) ng progesterone/100 mg backfat were recorded on Day 15 of the oestrous cycle. It was estimated that, on this day, a total amount of about 36 mg progesterone is stored in the adipose tissue, which is approximately 200 times that present in total blood and corresponds to the daily production of the corpora lutea of the sow on Day 11.Initial half-life of progesterone in backfat after ovariectomy was estimated to be about 34 h compared to an initial half-life of plasma progesterone of about 120 min. The exact calculation of half-lives was, however, confounded by an obvious effect of anaesthesia or surgery on progesterone levels. Changes in backfat or plasma progesterone concentrations were not affected by the fat-to-lean ratio of the gilts.Fat progesterone levels determined in 44 additional pregnant and non-pregnant sows 17 or 20 days after mating indicated that reliable diagnosis of non-pregnant sows was possible on Day 20.It is concluded that the endocrinology of the oestrous cycle in pigs is related to the enormous storage of progesterone in the fat.