Search Results

You are looking at 1 - 10 of 13 items for

  • Author: C Richard x
Clear All Modify Search
Free access

GORDON W. DUNCAN, RICHARD L. JOHNSTON and STANLEY C. LYSTER

Summary.

U-11634 effectively inhibits pregnancy in rats and mice following either parenteral or oral administration. A single dose administered to rats on Day 4 was as effective as treatment for the first 7 days of pregnancy; however, a single dose on other days of pregnancy was not effective. Pregnancy could not be inhibited in hamsters. At therapeutic doses this compound did not exhibit uterotrophic, anti-oestrogenic, androgenic, gonadotrophic-inhibiting, blastolytic or foetal toxicity activities.

Deciduomata formation in rats was inhibited by the compound. This effect was not reversed by progesterone or oestradiol administered simultaneously with U-11634 in ovariectomized, pseudopregnant rats with traumatized uterine horns. Inhibition of nidatory processes may be involved in the observed anti-fertility efficacy. The effects and the unique biological spectrum of this compound relative to other inhibitors of implantation are discussed.

Free access

MUHAMMAD ARSLAN, RICHARD C. WOLF, ROLAND K. MEYER and M. R. N. PRASAD

Summary.

Twelve immature female monkeys were treated with varying amounts of pregnant mare's serum gonadotrophin (pmsg). Seven of these monkeys responded to pmsg treatment as shown by sex skin development, ovarian enlargement and withdrawal bleeding. These animals reached menarche between 23 and 26 months of age, almost 1 year earlier than untreated control monkeys. Five other animals did not show an initial response to pmsg treatment and attained puberty simultaneously with the untreated animals. It is suggested that increased production of oestrogen by the pmsg-stimulated ovaries may affect the hypothalamo-hypophysial axis in such a way that puberty is accelerated.

Free access

Marina C Peluffo, Leonardo Bussmann, Richard L Stouffer and Marta Tesone

Apoptosis is associated with the regression of the corpus luteum (CL) in many species. Since caspases play a central role in apoptosis, we studied several initiators (-2, -8, and -9) and the main effector (-3) caspase in the CL during the estrous cycle of the rat. Two different populations of CL (old and new) were identified on ovaries at estrus and diestrus II (DII). Diminished (P < 0.05) luteal progesterone content and P450scc levels suggested that functional luteolysis occurred between the new CL at DII and old CL at estrus, whereas the decline (P < 0.05) in luteal weight indicated that structural regression was occurring between old CL at estrus to DII. Immunostaining for caspase-2 in luteal and endothelial cells appeared to increase as the luteal phase progressed, peaking at DII in the old CL. However, caspase-8 and -9 immunostaining showed little change with a slight increase at estrus in the old population. Notably, caspase-3 staining appeared to peak at DII in the new CL. Enzyme activity of caspase-9 increased (P < 0.05) in the new CL at DII, followed by that of caspase-2 and -3 in old CL at estrus. Caspase-8 activity did not change at any stage. The number of apoptotic cells increased at DII in the old CL. These results suggest an important role for this protease family during early events of luteolysis in the rat estrous cycle.

Free access

M Tamassia, Y Heyman, Y Lavergne, C Richard, V Gelin, JP Renard and S Chastant-Maillard

There have been few studies on a possible maternal influence on in vitro embryo production in cows. The objective of this study was to evaluate the maternal influence on oocyte production and in vitro blastocyst formation rate using repeated ovum pick-up and in vitro fertilization. Six contemporary cows raised on the same farm and with varied genetic origins were submitted to 42 weeks of ovum pick-up organized into four series. Collected oocytes were fertilized in vitro with spermatozoa from a different bull for each series. In total, 1933 oocytes were recovered from 3936 follicles with a recovery rate of 57.2% and a mean oocyte collection of 4.6+/-0.2 (mean+/-SEM) per animal per session. Animals were ranked according to their oocyte production. The best oocyte donor was the same female in all four series. No relationship was identified between oocyte production and blastocyst production rate (r=-0.08). The mean blastocyst rate was 28.8% with significant variation among animals. The best and the worst blastocyst producers were always the same animals independent of the semen used. The results of the present study support the hypothesis that in cattle, the oocyte donor influences the production of blastocysts. Furthermore, they demonstrate that oocyte and embryo production are independent factors. Further studies are necessary to identify the maternal or oocyte factors responsible for such differences.

Free access

Emma C L Bleach, Richard G Glencross and Philip G Knight

Ovarian follicle development continues in a wave-like manner during the bovine oestrous cycle giving rise to variation in the duration of ovulatory follicle development. The objectives of the present study were to determine whether a relationship exists between the duration of ovulatory follicle development and pregnancy rates following artificial insemination (AI) in dairy cows undergoing spontaneous oestrous cycles, and to identify factors influencing follicle turnover and pregnancy rate and the relationship between these two variables. Follicle development was monitored by daily transrectal ultrasonography from 10 days after oestrus until the subsequent oestrus in 158 lactating dairy cows. The cows were artificially inseminated following the second observed oestrus and pregnancy was diagnosed 35 days later. The predominant pattern of follicle development was two follicle waves (74.7%) with three follicle waves in 22.1% of oestrous cycles and four or more follicle waves in 3.2% of oestrous cycles. The interval from ovulatory follicle emergence to oestrus (EOI) was 3 days longer (P < 0.0001) in cows with two follicle waves than in those with three waves. Ovulatory follicles from two-wave oestrous cycles grew more slowly but were approximately 2 mm larger (P < 0.0001) on the day of oestrus.

Twin ovulations were observed in 14.2% of oestrous cycles and occurred more frequently (P < 0.001) in three-wave oestrous cycles; consequently EOI was shorter in cows with twin ovulations. Overall, 57.0% of the cows were diagnosed pregnant 35 days after AI. Linear logistic regression analysis revealed an inverse relationship between EOI and the proportion of cows diagnosed pregnant, among all cows (n = 158; P < 0.01) and amongst those with single ovulations (n = 145; P < 0.05). Mean EOI was approximately 1 day shorter (P < 0.01) in cows that became pregnant than in non-pregnant cows; however, pregnancy rates did not differ significantly among cows with different patterns of follicle development. These findings confirm and extend previous observations in pharmacologically manipulated cattle and show, for the first time, that in dairy cows undergoing spontaneous oestrous cycles, natural variation in the duration of post-emergence ovulatory follicle development has a significant effect on pregnancy rate, presumably reflecting variation in oocyte developmental competence.

Open access

Catherine E Forristal, Kate L Wright, Neil A Hanley, Richard O C Oreffo and Franchesca D Houghton

Human embryonic stem (hES) cells are routinely cultured under atmospheric, 20% oxygen tensions but are derived from embryos which reside in a 3–5% oxygen (hypoxic) environment. Maintenance of oxygen homeostasis is critical to ensure sufficient levels for oxygen-dependent processes. This study investigates the importance of specific hypoxia inducible factors (HIFs) in regulating the hypoxic responses of hES cells. We report that culture at 20% oxygen decreased hES cell proliferation and resulted in a significantly reduced expression of SOX2, NANOG and POU5F1 (OCT4) mRNA as well as POU5F1 protein compared with hypoxic conditions. HIF1A protein was not expressed at 20% oxygen and displayed only a transient, nuclear localisation at 5% oxygen. HIF2A (EPAS1) and HIF3A displayed a cytoplasmic localisation during initial hypoxic culture but translocated to the nucleus following long-term culture at 5% oxygen and were significantly upregulated compared with cells cultured at 20% oxygen. Silencing of HIF2A resulted in a significant decrease in both hES cell proliferation and POU5F1, SOX2 and NANOG protein expression while the early differentiation marker, SSEA1, was concomitantly increased. HIF3A upregulated HIF2A and prevented HIF1A expression with the knockdown of HIF3A resulting in the reappearance of HIF1A protein. In summary, these data demonstrate that a low oxygen tension is preferential for the maintenance of a highly proliferative, pluripotent population of hES cells. While HIF3A was found to regulate the expression of both HIF1A and HIF2A, it is HIF2A which regulates hES cell pluripotency as well as proliferation under hypoxic conditions.

Free access

Clay A Lents, Neely L Heidorn, C Richard Barb and J Joe Ford

It is well established that kisspeptin signaling is necessary for the onset of puberty in laboratory animals. However, the role that kisspeptin may have in regulating puberty in large domestic animals is unknown. We tested the hypothesis that either central or peripheral infusion of kisspeptin would stimulate gonadotropin and GH secretion in prepubertal gilts. In experiment 1, prepubertal gilts were fitted with i.c.v. cannula and indwelling jugular catheters. Animals were randomly assigned to receive 0, 10, or 100 μg kisspeptin in saline. In experiment 2, prepubertal gilts, fitted with indwelling jugular catheters, randomly received 0, 1, 2.5, or 5 mg kisspeptin in saline intravenously. Serial blood samples were collected every 15 min for 3 h before and 5 h after infusions, and serum concentrations of LH, FSH, and GH were determined. Mean concentrations of LH and FSH remained at basal levels for control animals but were increased (P<0.001) for animals receiving i.c.v. infusion of kisspeptin. Area under the LH and FSH curves following i.c.v. infusion of kisspeptin increased (P<0.001) in a dose-dependent manner. Concentrations of GH were unaffected by i.c.v. treatment. Peripheral administration of kisspeptin increased (P<0.05) serum concentrations of LH but not FSH or GH. Thus, kisspeptin can activate gonadotropic but not somatotropic hormone secretion in prepubertal gilts. The present data support the concept that kisspeptin plays a role in the mechanism involved in initiating puberty in swine.

Free access

C Richard Barb, Robert R Kraeling, George B Rampacek and Gary J Hausman

Two experiments (EXP) were conducted in ovariectomized prepubertal gilts to test the hypothesis that neuropeptide Y (NPY) stimulates appetite and modulates LH and GH secretion, and that leptin modifies such acute effects of NPY on feeding behavior and LH and GH secretion. In EXP I, gilts received intracerebroventricular (ICV) injections of 0.9% saline (saline; n=6), or 10 μg (n=7), 50 μg (n=5) or 100 μg (n=7) NPY in saline and blood samples were collected. In EXP II, gilts received ICV injections of S (n=4), or 50 μg leptin (n=4), or 100 μg NPY (n=4) or 100 μg NPY +50 μg leptin (n=4) in saline, and feed intake was measured at 4, 20 and 44 h after feed presentation and blood samples collected. In EXP I, NPY suppressed LH secretion and the 100 μg dose stimulated GH secretion. In EXP II, NPY reversed the inhibitory effect of leptin on feed intake and suppressed LH secretion, but serum GH concentrations were unaffected. These results support the hypothesis that NPY modulates feed intake, and LH and GH secretion and may serve as a neural link between metabolic state and the reproductive and growth axis in the pig.

Free access

E Mourier, A Tarrade, J Duan, C Richard, C Bertholdt, M Beaumont, O Morel and P Chavatte-Palmer

In human obstetrics, placental vascularisation impairment is frequent as well as linked to severe pathological events (preeclampsia and intrauterine growth restriction), and there is a need for reliable methods allowing non-invasive evaluation of placental blood flow. Uteroplacental vascularisation is complex, and animal models are essential for the technical development and safety assessment of these imaging tools for human clinical use; however, these techniques can also be applied in the veterinary context. This paper reviews how ultrasound-based imaging methods such as 2D and 3D Doppler can provide valuable insight for the exploration of placental blood flow both in humans and animals and how new approaches such as the use of ultrasound contrast agents or ultrafast Doppler may allow to discriminate between maternal (non-pulsatile) and foetal (pulsatile) blood flow in the placenta. Finally, functional magnetic resonance imaging could also be used to evaluate placental blood flow, as indicated by studies in animal models, but its safety in human pregnancy still requires to be confirmed.

Free access

S Chastant-Maillard, H Quinton, J Lauffenburger, N Cordonnier-Lefort, C Richard, J Marchal, P Mormede and JP Renard

The purpose of this study was to evaluate the impact of repeated follicular puncture used in the ovum pick-up technique on the welfare of cows. The evaluation relies on the physiological measurement of stress, milk production criteria, immune status, and the histological examination of ovaries. Two groups of five Holstein cows were submitted to epidural anaesthesia and genital palpation with insertion of an intravaginal ultrasound probe for transvaginal puncture (the puncture was not performed in the control group). Animals were manipulated twice a week for 8 weeks (16 manipulation sessions). The blood cortisol concentrations increased after each session; however, the concentrations were the same in both the control and the punctured groups. Two adrenocorticotrophic hormone challenge tests, performed before the first session and after the last session, showed an unchanged adrenal sensitivity through repeated puncture sessions. The transvaginal puncture did not affect milk production, or blood and milk somatic cell counts. Ovariectomies were performed on another group of four Holstein cows at various intervals (0 to 30 days) after five similar puncture sessions. Histological examination of the ovaries 4 days after puncture revealed blood-filled follicles and haemorrhagic foci in ovarian stroma, but the examination 30 days after the last puncture session demonstrated very limited, if any, fibrosis. On the basis of the criteria chosen for this study, repeated transvaginal follicular puncture on its own does not impact adversely on the welfare of cows.