Search Results

You are looking at 1 - 10 of 22 items for

  • Author: J. C. SMITH x
Clear All Modify Search
Free access

J. R. W. Walkley and C. Smith

Summary. The objective was to quantify and compare the genetic responses by direct selection on litter size, by indirect selection through a physiological trait and by combined selection, combining litter size and the physiological trait in a selection index. Three kinds of physiological trait were considered, male sex-limited (e.g. testes size), female sex-limited (ovulation rate) and traits measurable in both sexes (gonadotrophin levels).

The results are presented graphically and cover a wide range of possible situations and show the size of the responses for different parameters of the physiological trait. There is usually scope for improvement in the rate of response with combined selection, and also in special cases (high heritability and genetic correlation) with indirect selection. The increases in predicted response may range from zero to two or three times the direct response, depending on the genetic parameters. However, the need for reliable estimates of the genetic parameters is stressed, because the predicted responses might otherwise be overestimated and the selection effort misplaced.

Free access

C. J. EPSTEIN, C. W. SMITH and LILLIAN W. KWOK

Previous studies have indicated that the glucose-6-phosphate dehydrogenase (G6PD) contained within mouse ova is synthesized before ovulation and is under the genetic control of the X-chromosome (Epstein, Wegienka & Smith, 1969; Epstein, 1969). As such, it is different from the autosomally controlled hexose-6-phosphate dehydrogenase (H6PD) or glucose dehydrogenase found in liver microsomes but not in erythrocytes (Beutler & Morrison, 1967). To establish the applicability of these genetic results with ova to other tissues of the mouse, G6PD from ova has been characterized and compared with erythrocyte G6PD. Ova and pre-implantation embryos were obtained from Swiss albino mice (Mus musculus) by superovulation. For microspectrophotometric assay of enzyme activity, they were lysed by freezing and thawing in 0·05 m-tris buffer, pH 7·5, containing 0·05% bovine serum albumin (BSA) (Epstein et al., 1969). For polyacrylamide disc
Free access

S. E. Smith, W. C. Cullen and J. D. Godkin

Summary. Stereological techniques were used to quantify ultrastructural changes in the caruncular epithelium during the pre- (Day 13), peri- (Day 16) and post- (Days 19 and 22) attachment periods of placentation. Tissues from Day-13 non-pregnant ewes were used as controls. Uteri for stereological evaluation were perfused via the uterine artery with 3% glutaraldehyde and separated into proximal, middle and distal regions. Tissues from caruncular areas were processed for electron microscopy. Volume fractions (Vv) of nuclei, mitochondria, lipid and cytoplasmic granules were estimated by point-counting volumetry. Surface areas per unit tissue volume (Sv) of mitochondrial membranes and cristae, Golgi, plasmalemma, endoplasmic reticulum and nuclear membranes were estimated by line-intersection counting.

The only significant difference between pregnant and non-pregnant uterine epithelium at Day 13, a time before attachment, was a lower Sv of smooth endoplasmic reticulum (SER) in tissue from pregnant ewes. This value returned to control (non-pregnant Day 13) levels at Day 16, and was again significantly reduced at Days 19 and 22. The Vv of lipid decreased significantly at Day 16 and remained at reduced levels thereafter. These changes may reflect the effects of conceptus products on lipid storage and mobilization. The Sv of rough endoplasmic reticulum (RER) significantly increased on Day 16 of gestation, and remained elevated on Day 19. These results may reflect increased synthesis of protein for export at these times. In general, several of the values measured which may be indicative of cellular metabolism were reduced at Day 22 of pregnancy, perhaps suggesting diminished metabolism by the uterine epithelium after attachment of the trophoblast.

Large cytoplasmic granules were not observed in uterine epithelium at the pre- and early peri-attachment stage (Days 13 and 16); they were first observed at Day 19 and their Vv increased dramatically at Day 22. At this time, the Sv of uterine cellular organelles associated with protein synthesis (Golgi complex, RER, SER) was either unaltered or declining. These results support the concept that the large secretory granules may be derived from an extrauterine epithelial source such as the trophoblast.

Keywords: sheep; early pregnancy; uterine epithelium; ultrastructure; stereology

Free access

L. C. Smith, I. Wilmut and J. D. West

Summary. Karyoplasts derived from mouse embryos at the initial and final stages of the first or second mitotic interphase were fused to early and late enucleated 1-cell embryos. The time of cleavage of reconstituted and control embryos was recorded at 1-h or 8-h intervals after manipulation. This enabled assessment of nuclear and cytoplasmic control over the mitotic apparatus of the 1-cell embryo. Early nuclei from 1- or 2-cell embryos fused to late enucleated embryos delayed cleavage but for only a few hours. However, late nuclei fused to early enucleated embryos were unable to advance the cytoplasmic timing of the next cleavage division. Furthermore, these reconstituted embryos stayed in interphase longer than did controls and many embryos with nuclei derived from late 2-cell embryos failed to cleave. These findings suggest that, allowing for a short period, early nuclei can synchronize with late cytoplasm with no major damage to the cleavage apparatus. It is proposed that this period is required for the completion of DNA synthesis by the early nuclei. However, late nuclei cannot induce mitosis before the expected cytoplasmic time, and, with 2-cell karyoplasts, this interaction causes many embryos to 'block' in interphase, without cleaving, suggesting incompatible nucleo-cytoplasmic interactions between late 2-cell karyoplast and early 1-cell stage cytoplasm.

Keywords: embryo; nuclear transfer; cleavage; mouse

Free access

G. E. Webley, M. C. Richardson, C. A. Smith, G. M. Masson and J. P. Hearn

Summary. The size distribution of marmoset luteal cells was determined on Days 6, 14 and 20 after ovulation in non-pregnant cycles and in early pregnancy. Image analysis was used to estimate the cell diameter of dispersed cells prepared from the marmoset corpus luteum (CL). Steroidogenic cells showed a size distribution consistent with one population of cells. There was a significant increase in mean cell diameter (P < 0·05) from Day 6 to Day 14 in pregnant and non-pregnant animals with no further increase on Day 20. Micrographs of marmoset luteal tissue showed cells of > 10 μm containing the organelles typical of steroid-producing cells, and smaller non-steroidogenic cells surrounding the steroid-producing cells. On the basis of microscopy, there were no areas within the CL where cell composition was noticeably different. In contrast, micrographs of human luteal tissue showed two types of steroidogenic cell; most cells were similar to those in the marmoset CL but a smaller population of smaller cells could be distinguished around the periphery and along vascular septa. It is likely that these smaller and larger types of steroidogenic cells are of theca and granulosa cell origin respectively, the two cell populations differing in the degree of electron density and amount of rough endoplasmic reticulum. A distinguishing feature between marmoset and human luteal cells was the shape of the mitochondrian which were considerably rounder in marmoset luteal cells. The origin of steroidogenic cells in the marmoset CL is unclear, although in marmosets and man the luteal cell types display morphological characteristics distinct from the large and small luteal cells described for CL of the domestic ungulates.

Keywords: luteal cell; size distribution; morphology; marmoset monkey; man

Free access

C Fergani, J E Routly, D N Jones, L C Pickavance, R F Smith and H Dobson

In the ewe, steroid hormones act on the hypothalamic arcuate nucleus (ARC) to initiate the GnRH/LH surge. Within the ARC, steroid signal transduction may be mediated by estrogen receptive dopamine-, β-endorphin- or neuropeptide Y (NPY)-expressing cells, as well as those co-localising kisspeptin, neurokinin B (NKB) and dynorphin (termed KNDy). We investigated the time during the follicular phase when these cells become activated (i.e., co-localise c-Fos) relative to the timing of the LH surge onset and may therefore be involved in the surge generating mechanism. Furthermore, we aimed to elucidate whether these activation patterns are altered after lipopolysaccharide (LPS) administration, which is known to inhibit the LH surge. Follicular phases of ewes were synchronised by progesterone withdrawal and blood samples were collected every 2 h. Hypothalamic tissue was retrieved at various times during the follicular phase with or without the administration of LPS (100 ng/kg). The percentage of activated dopamine cells decreased before the onset of sexual behaviour, whereas activation of β-endorphin decreased and NPY activation tended to increase during the LH surge. These patterns were not disturbed by LPS administration. Maximal co-expression of c-Fos in dynorphin immunoreactive neurons was observed earlier during the follicular phase, compared to kisspeptin and NKB, which were maximally activated during the surge. This indicates a distinct role for ARC dynorphin in the LH surge generation mechanism. Acute LPS decreased the percentage of activated dynorphin and kisspeptin immunoreactive cells. Thus, in the ovary-intact ewe, KNDy neurones are activated prior to the LH surge onset and this pattern is inhibited by the administration of LPS.

Free access

A. M. Schmidt, D. L. Hess, M. J. Schmidt, R. C. Smith and C. R. Lewis

Summary. Three mature nulliparous female leopards were studied for 5 years. During three separate 6-month periods serum oestradiol and progesterone concentrations were measured at weekly intervals. Oestradiol was elevated over 21 pg/ml for 54 weeks during these 3 periods, and 36 oestradiol peaks (65·8 ± 6·3 pg/ml (mean ± s.e.m.), range 21–172 pg/ml) were identified. Daily frequency of feline reproductive behaviours averaged over each week increased from 1·9 ± 0·2 (n = 93) during weeks with low serum oestradiol concentrations (<21 pg/ml) to 5·3 ± 0·6 (n = 54) during weeks when serum oestradiol concentrations (>21 pg/ml) were high.

Increased serum progesterone concentrations (13–98 n/gml) were observed on 5 occasions in 2 leopards housed together. These presumptive luteal phases lasted from 1 to 5 weeks. Baseline progesterone values were 1·6 ± 0·4 ng/ml (n = 131). No progesterone increments were observed in isolated animals, and serum concentrations remained at baseline levels. These limited observations suggest that female leopards do not require intromission to induce ovulation and luteal function.

The average interval between oestradiol peaks for cycles with no progesterone increment was 3·4 weeks (range 1–6 weeks). The interval for the 3 complete cycles associated with elevated progesterone concentrations was 7·3 weeks. Analysis of sexual behaviours over the 5-year study period revealed no evidence of seasonality in these captive leopards.

Keywords: oestradiol; progesterone; behaviour; leopard; oestrous cycle

Free access

G. W. Asher, M. W. Fisher, J. F. Smith, H. N. Jabbour and C. J. Morrow

Summary. A study was conducted to determine the timing of ovulation relative to the onset of oestrus and the preovulatory LH surge in fallow deer. Mature fallow does were randomly allocated to two treatments (N = 10 per treatment) designed to synchronize oestrus on or about 17 May. Does assigned to Group 1 (prostaglandin-induced oestrus) each initially received single intravaginal CIDR [Controlled Internal Drug Release] devices for 13 days followed by an i.m. injection of 750 mg cloprostenol on Day 12(15 May) of the subsequent luteal cycle. Does assigned to Group 2 (progesterone-induced oestrus) each received CIDR devices for 13 days, with withdrawal occurring on 15 May. All does were run with crayon-harnessed bucks (10:1 ratio) from the start of synchronization (18:00 h 15 May). Ten does (5 per group) were blood sampled via indwelling jugular cannulae every 2 h for 72 h from cloprostenol injection or CIDR device withdrawal and the plasma was analysed for concentrations of progesterone and LH by radioimmunoassay. Does within each treatment were randomly allocated to an ovarian examination time of 12, 16, 20 or 24 h after the onset of oestrus. Laparoscopy was repeated at 12-h intervals until ovulation was recorded. The ovaries of does failing to exhibit oestrus were examined 72 and 86 h after cloprostenol injection or CIDR device withdrawal. A total of 17 does were observed to exhibit oestrus at a mean (±s.e.m.) interval from treatment of 44·6 ± 3·6 h for Group 1 (N = 9) and 34·1 ± 2·5 h for Group 2 (N = 8). The incidence of ovulation from 34 laparoscopic examinations was 0% for intervals <20 h, 50% at 24 h and 100% for intervals >28 h. There was no difference between animals in Groups 1 and 2. The onset of the preovulatory LH surge (n = 8 observations) occurred at the onset of oestrus, with maximum LH surge concentrations (30 ng/ml) occurring 6 h later. Of 3 does not exhibiting oestrus, 2 (Group 2) possessed active corpora lutea at CIDR device withdrawal and 1 (Group 1) possessed a large unruptured follicle 72 and 86 h after cloprostenol injection.

The data indicate that ovulation in fallow deer occurs ∼24 h after the onset of oestrus and ∼ 18 h after the peak of the preovulatory LH surge.

Keywords: fallow deer; reproduction; oestrus; ovulation; progesterone; LH

Free access

H. N. Jabbour, G. W. Asher, J. F. Smith and C. J. Morrow

Summary. Eighteen ovariectomized fallow deer does and two adult bucks were used to investigate the effect of exogenous progesterone and oestradiol benzoate on oestrous behaviour and secretion of luteinizing hormone (LH). In Expts 1 and 2, conducted during the breeding season (April–September), does were treated with intravaginal Controlled Internal Drug Release (CIDR) devices (0·3 g progesterone per device) for 12 days and differing doses of oestradiol benzoate administered 24 h after removal of the CIDR device. The dose had a significant effect on the proportion of does that exhibited oestrus within the breeding season (P < 0·001), the incidence of oestrus being 100% with 1·0, 0·1 and 0·05 mg, 42% for 0·01 mg and 0% for 0·002 mg oestradiol benzoate. There was a significant log–linear effect of dose on the log duration of oestrus, which was 6–20, 2–14, 2–12 and 2 h after treatment with 1, 0·1, 0·05 and 0·01 mg of oestradiol benzoate, respectively. Dose had a significant effect on the peak plasma LH concentration (P < 0·01), mean (±s.e.m.) surge peaks of 27·7 ± 2·3, 25·9 ± 1·8 and 18·6 ± 3·4 ng/ml being observed following treatment with 1, 0·1 and 0·01 mg oestradiol benzoate respectively. In Expt 3, also conducted during the breeding season, progesterone treatment (0 vs. 6–12 days) before the administration of 0·05mg oestradiol benzoate had a significant effect on the incidence of oestrus (0/6 vs. 10/12, P < 0·05), but not on LH secretion. The duration of progesterone treatment (6 vs. 12 days) had no effect on oestrus. In Expt 4, conducted in the nonbreeding season (October–March), control does were largely unresponsive to treatment with 0·1 mg oestradiol benzoate. This was manifest in a lower proportion of does exhibiting oestrous behaviour and LH surges. Melatonin treatment, with implants administered on four occasions at intervals of 28–30 days starting from 24 October, significantly increased the proportion of does that exhibited oestrus in February, during the later phase of the nonbreeding season (7/8 vs. 1/8, P < 0·05). Melatonin-treated does also exhibited significantly higher basal plasma LH concentrations after removal of CIDR devices in February (5·8 ± 0·5 vs. 2·1 ± 0·4 ng/ml, P < 0·01). While only one control doe had an LH surge, with a peak of 13·8 ng/ml, all melatonin-treated does exhibited LH surges, with a mean peak concentration of 58·0 ± 8·4 ng/ml.

Keywords: fallow deer; progesterone; oestradiol benzoate; oestrus; luteinizing hormone

Free access

G. J. R. HOVELL, G. M. ARDRAN, D. M. ESSENHIGH and J. C. SMITH

Summary.

Observations on the urogenital tract were made radiologically in six rams. Contrast medium was first introduced to the urethra or vas deferens before electrical stimulation was applied per rectum and later to the vas during a series of stimuli to induce ejaculation.

Without stimulation, contrast medium reaching the pelvic urethra from either the penile urethra or the ampulla was generally expelled in a retrograde manner to the bladder, while residual material in the penile urethra was voided.

Ejaculation took place only during pauses between stimuli, fluid being discharged from the ampulla straight through into the penile urethra. This main discharge was followed by some reflux of fluid from the pelvic urethra to the bladder. At rest, no fluid remained in either the pelvic or the penile urethra.