Ageing of the unfertilized cow egg in vivo: how soon is fertility compromised?
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Animals↗
Biomedical subjects
R H Hunter
Publications and source records attributed to R H Hunter.
Luteinizing hormone response to an oestradiol challenge in 5 intersex pigs possessing ovotestes.
After challenge with oestradiol benzoate, the mean maximum LH concentration in 5 XX intersex pigs possessing ovarian and testicular tissue, or only testicular tissue, was 2.10 (+/- 0.41) ng/ml compared with 8.9 ng/ml in mature domestic gilts. These results indicate that exposure of the pig brain to testosterone before Day 30 of gestation is important, or that early testicular secretions other than testosterone are involved in the determination of brain gender. The observation that some intersex pigs show normal oestrous cycles implies that the response to these prenatal factors is primarily quantitative rather than qualitative.
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Low incidence of fertilisation in superovulated cows: a physiological explanation.
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Animals↗
Electrophysiological properties of the follicle wall in the pig ovary.
The transmural potential difference and short-circuit current of the porcine Graafian follicle have been measured in an attempt to test whether antral fluid accumulates as a result of active transport of salt. The values obtained by mounting explants of follicle wall in Ussing chambers were close to zero and the specific electrical resistance was only 59 delta.cm2. The elemental composition of the follicular fluid was similar to that of ovarian venous plasma with the exception of follicular Na+ which was slightly more abundant. Bicarbonate concentrations were slightly lower in follicular fluids. These findings were interpreted as evidence that the follicular wall is a leaky epithelium and, therefore, any charge resulting from net ion transport will be shunted along low resistance paracellular pathways.
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Capacitation potential of the fallopian tube: a study involving surgical insemination and the subsequent incidence of polyspermy.
In an attempt to demonstrate limitations in the capacitating potential of the Fallopian tube, ejaculated boar spermatozoa were introduced directly into the isthmus at varying intervals before ovulation. The incidence and degree of polyspermy subsequently observed were taken as indicators of the population of capacitated spermatozoa confronting the newly ovulated eggs: the more extensive the condition of polyspermy, the greater the number of capacitated spermatozoa presumed to have been available at the site of fertilization. Results are based on 673 eggs from 53 animals. When suspensions containing 2.21-3.87 x 10(8) sperm per ml were introduced 36-40 hours and 26-30 hours before ovulation, 85% and 61% respectively of the eggs were polyspermic, such eggs exhibiting mainly dispermy and trispermy. By contrast, when comparable sperm suspensions from the same boar were instilled 17-18 hours before ovulation, 70% of the eggs were polyspermic but the degree of polyspermy had increased dramatically: most eggs contained 40 or more sperm heads in the vitellus, invariably forming swollen chromatin aggregates rather than male pronuclei. Surgical insemination at times closer to ovulation significantly reduced the incidence and degree of polyspermy, reaching a low of 2% with insemination 1-2 hours before ovulation. These results therefore support the concept of a limited capacitation potential of the Fallopian tube. In a separate series of observations, mating animals shortly before surgical insemination with sperm suspensions from the same boar markedly reduced the incidence of polyspermy. This latter observation may be of clinical significance in procedures of laparoscopic or transcervical insemination into the tubes to alleviate human infertility. The manner whereby myosalpingeal physiology could be modified in response to coital stimulation is discussed.
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Physiological factors underlying the formation of ovarian follicular fluid.
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Animals↗
Influence of cell cycle stage at nuclear transplantation on the development in vitro of mouse embryos.
Nuclei were transplanted from embryos of mice at different stages of the 1st and 2nd cell cycle to oocytes enucleated at various times after fertilization. After transfer of pronuclei, a greater proportion of embryos developed to blastocysts if donor and recipient embryos were at the same stage of the cell cycle (synchronous transfer = 94%, asynchronous transfer = 76%). By contrast, when 2-cell blastomere nuclei were fused to the cytoplasm of enucleated zygotes, there was a significant effect of both cytoplast and karyoplast cell cycle stage on the development of the reconstituted embryos. Karyoplasts and cytoplasts derived from embryos at later stages of the cell cycle had greater potential to support development to blastocysts in vitro. It is suggested that the secretion of stage-specific messengers and the timing of nuclear membrane breakdown are the main factors causing the karyoplast and cytoplast effects, respectively.
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Pre- and peri-ovulatory distribution of viable spermatozoa in the pig oviduct: a scanning electron microscope study.
Using sexually mature animals, the distribution of spermatozoa has been examined at the utero-tubal junction and in the distal and proximal portions of the oviduct isthmus. Mating occurred during early oestrus and, with one exception, specimens were prepared shortly before or after ovulation. Distinct reservoirs of spermatozoa were identified in furrows between the terminal folds of the isthmus, and particularly within the troughs and transverse ridges of this region. The density of spermatozoa diminished steeply from the utero-tubal junction towards the isthmus, especially in the pre-ovulatory specimens. The membranes of most spermatozoa in the isthmus were intact up to the time of ovulation, suggesting that the acrosome reaction is a peri- or post-ovulatory event. Whilst the flagella of spermatozoa in the reservoirs were usually straight or only slightly curved, those on the surface of the epithelial folds were undulating (S-shaped). Specific microenvironments may therefore exist in the distal portion of the isthmus to regulate sperm motility; droplets of secretion were a notable feature in this region. In specimens prepared 24 hr after ovulation, spermatozoa were almost absent from the utero-tubal junction and isthmus. However, denuded eggs were observed in the proximal portion of the isthmus in this animal, and they had spermatozoa associated with the zona pellucida. Arguments are presented for a peri-ovulatory endocrine regulation of sperm redistribution and capacitation.
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Simple measures of progress and outcome in the evaluation of mental health services.
There is a tautology regarding the use of progress and outcome measures. Such measures are easy to use in a reliable and valid fashion if the language of the measures is used as an integral part of (a) treatment planning and progress review, (b) clinical supervision, and (c) program management. The paper describes example guidelines and uses of measures in each of these functions. Also included are listings of scales with documented reliability and validity (by target population) and some sources for finding computer software for scoring some of the scales.
Evaluation Studies as Topic↗
Human fertilization in vivo, with special reference to progression, storage and release of competent spermatozoa.
Whilst very large numbers of spermatozoa accumulate in the cervical mucus and crypts in the hours following coitus, evidence is offered from species with comparable gonadotrophin surge-to-ovulation intervals to suggest that the cervix is not the site of the functional sperm reservoir in women. On the contrary, human spermatozoa involved in the events of fertilization may spend the greater part of the pre-ovulatory interval in the distal portion of the Fallopian tube, that is in the intra-mural segment. This would enable spermatozoa to be arrested within reach of the site of fertilization in the ampullary region of the tube, and to be activated and released close to the time of ovulation by means of a local transfer of high concentrations of ovarian follicular hormones. The clinical importance of confirming this proposed role for the intra-mural segment of the tube is stressed, as is the possibility of specific micro-environments within the lumen of the duct.
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Distribution of spermatozoa in the mare's oviduct.
The morphology of the uterotubal junction (UTJ) and caudal isthmus during the peri-ovulatory period, and the distribution of spermatozoa within the region, were studied in 10 Pony mares. The proximal tip of the uterine horn and caudal 1-2 cm of the isthmus were removed during oestrus or shortly after ovulation from animals mated or artificially inseminated within the previous 24 h. The tissues were incised longitudinally and fixed for scanning electron microscopy. Analysis of micrographs showed deep longitudinal and oedematous folds in the preovulatory samples. After ovulation, much of the folding and oedema disappeared. There was a regional arrangement of ciliated and nonciliated cells and the cilia showed evidence of directional orientation. Occasional spermatozoa were seen in some specimens deep in furrows between folds of the UTJ.
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Cumulus oophorus mucification during resumption of meiosis in the pig. A scanning electron microscope study.
The process of cumulus mucification in pig preovulatory follicles was examined by scanning electron microscopy. The localization of extracellular material and changes in the granulosa cell surface were observed at 0, 16, 20 and 40 h after hCG injection. At 0 h the pig oocyte cumulus complex was closely attached to the parietal layer of granulosa cells. Cumulus and parietal granulosa cells had microvilli and cytoplasmic projections connecting neighbouring cells. The network of extracellular amorphous material was observed for the first time at 16 h after hCG around the cells that formed a stalk between the parietal granulosa and the cumulus oophorus. At 20 h after hCG, the intercellular matrix was thicker and extended to almost all the cumulus oophorus surface; when visible, cells were often covered by blebs and ruffling membranes. All oocytes examined by light microscopy at 16 and 20 h after hCG were at the germinal vesicle stage with condensing bivalents. Therefore, it was concluded that oocyte nuclear maturation started at the same time that a mucified peduncle was forming between the cumulus oophorus and the parietal granulosa. Shortly before ovulation (40 h after hCG) the matrix material filled all intercellular spaces and mucification had extended to the corona cell layer and the zona pellucida surface.
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A preovulatory temperature gradient between the isthmus and ampulla of pig oviducts during the phase of sperm storage.
Fine thermistor probes positioned in each end of the same oviduct and connected to the same scale were used to measure temperature gradients in the lumen before and after spontaneous ovulation in normally-cyclic gilts. Readings were taken after full surgical closure of a mid-ventral incision and a subsequent period of stabilization, but whilst animals remained under general anaesthesia. A small but consistent difference in temperature was recorded between the proximal ampulla and distal isthmus of the same oviduct in each of 20 preovulatory gilts. In 10 of these animals that had not mated, the isthmus was a mean of 0.43 degree C cooler than the ampulla (range 0.2-0.7 degree C) whereas in 10 mated animals the isthmus was 0.69 degree C cooler (range 0.2-1.6 degree C); 3 animals in the latter group had within-oviduct differences of greater than or equal to 1 degrees C. By contrast, in 12 animals that had recently ovulated, the isthmus was a mean of only 0.1 degree C cooler than the ampulla; there was no measurable temperature gradient in 3 of the animals, whilst the isthmus was 0.1 degree C warmer in 2 animals. The preovulatory temperature differences are thought primarily to reflect the extent and activity of the vascular and lymphatic beds in the oviduct tissues and, together with specific chemical microenvironments, may facilitate the relatively prolonged period of sperm storage in the distal portion of the isthmus.
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Experimental studies of sperm transport in sheep, cows and pigs.
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Animals↗
Massive spontaneous superovulation in a sexually mature pig.
Ovulation of 97 follicles was recorded in a gilt that had not received any hormonal treatment, and circumstantial evidence adduced for a rapidly proliferating tumour of the adenohypophysis. A lesser degree of superovulation had occurred in the previous oestrous cycle, whilst the rate of follicular development in the current cycle was exceptional. None of the 93 eggs recovered from the oviducts was a primary oocyte, but three were polyspermic pronucleate eggs. The most advanced stage of embryonic development was that of 4-cells. Such a degree of spontaneous superovulation has never been observed before during careful examination of more than 1200 pairs of ovaries from gilts in the same herd.
Animals↗
Ovarian follicular fluid concentrations of prostaglandins E2, F2 alpha and I2 during the pre-ovulatory period in pigs.
The concentrations of prostaglandin (PG) E2, PGF2 alpha and PGI2 (measured as 6-oxo-PGF1 alpha) in follicular fluid collected from the ovaries of mature, cycling pigs during the immediate pre-ovulatory period have been estimated by radioimmunoassay. The concentrations of all three prostaglandins were low 24-32 hrs before the expected time of ovulation, with the ratio of the mean concentrations of PGE2, PGF2 alpha and 6-oxo-PGF1 alpha being 0.7:1.1:1.0. The concentration of PGE2 showed a small increase during the next 22 hrs but, in the 2 hr period before the expected time of ovulation, the mean concentrations of PGE2, PGF2 alpha and 6-oxo-PGF1 alpha increased 119-, 11- and 5-fold, respectively, which produced a ratio of these mean concentrations of 14.8:2.2:1.0. One sample of follicular fluid contained the highest concentration of 6-oxo-PGF1 alpha (54.4 ng/ml) yet reported for any tissue from any species, but this concentration was still lower than those of PGE2 (529 ng/ml) and PGF2 alpha (94.6 ng/ml). These results show that prostaglandin concentrations increase in the follicular fluid of mature, cycling pigs in the immediate preovulatory period, with PGE2 being the predominant prostaglandin produced. In "preovulatory" follicles which failed to ovulate, prostaglandin concentrations were at baseline values. The findings in this study are consistent with follicular prostaglandins being essential for ovulation in the pig.
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Intersexuality in five pigs, with particular reference to oestrous cycles, the ovotestis, steroid hormone secretion and potential fertility.
Reproductive tissues, steroid hormone secretion, and sexual behaviour have been examined in five gilts, in each of which the right gonad was an ovotestis. Although from different females, these animals were sired by the same boar and each possessed an XX sex chromosome constitution as determined by karyotype analysis of blood cells. Despite variable amounts of testicular tissue in the ovotestis and unilateral development of a prominent epididymis, four of the animals had oestrous cycles of normal duration (20-22 days) and extended periods of standing oestrus (3-6 days). The fifth animal did not have detectable oestrous cycles but was extremely aggressive in the presence of a mature boar. Two of the gilts were mated, and there were small numbers of embryos in each uterine horn 23 and 26 days later. Removal of the ovary did not prompt compensatory hypertrophy in the ovarian portion of the ovotestis, nor did injection of pregnant mare serum gonadotrophin stimulate detectable follicular growth in ovarian tissue adjoining testicular tissue. Concerning the aetiology of this intersex condition, the unilateral appearance of an ovotestis precludes any simple involvement of a translocated portion of the Y chromosome or systemic effects of unusual titres of the putative H-Y antigen. However, bearing in mind a predisposition to gonadal asymmetry in eutherian mammals, a case is advanced for apposition or incorporation of adrenocortical tissue in the right embryonic ovary. The resultant virilization of neighbouring reproductive tissues would stem from adrenocortical androgen synthesis.
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Sperm transport into the oviducts of heifers mated early in oestrus.
An estimate has been made of the time required for a population of spermatozoa capable of fertilizing the egg to be established in the oviducts of heifers mated early in oestrus. During a general or local anaesthetic, the caudal isthmus of the oviduct was ligated and sectioned 6, 8, 10 or 12 hr after mating. The proportion of eggs fertilized as judged 2-4 days later was very low if ligation was carried out after 6 hr (1 of 11) and only approached normal levels of 85% or more following ligation at 12 hr (7 of 10). These results suggest that the population of spermatozoa capable of fertilisation is established in the oviduct over a period of not less than 6 hours and probably more than 12 hr. These results contrast with reports of rapid transport of spermatozoa to the oviduct in a period of minutes.
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