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C Thibault

Publications and source records attributed to C Thibault.

At least 19 recordsLinked to original sources
PubMed1992

Altered expression of G-protein mRNA in spontaneously hypertensive rats.

We have recently demonstrated that the decreased ability of hormones, forskolin and GTP to stimulate adenylate cyclase in heart and aorta from spontaneously hypertensive rats (SHR), as compared to their age-matched Wistar-Kyoto control rats (WKY), was associated with enhanced levels of Gi- and not with Gs-regulatory proteins. In the present studies we have investigated the expression of Gi-regulatory proteins at the mRNA level by Northern blotting. Total RNA of heart ventricle and aorta from WKY and SHR was probed with radiolabeled cDNA inserts encoding Gi alpha-2 and Gi alpha-3. The Gi alpha-2 and Gi alpha-3 probes detected a message of 2-3 and 3-5 kb, respectively, in both WKY and SHR, however, the message was significantly enhanced in SHR, as compared by WKY. On the other hand the cDNA probe encoding Gs alpha detected a message of 1.8 kb in heart and aorta from both WKY and SHR, however, no difference in the levels of Gs alpha mRNA was detected in SHR and WKY tissues. These results indicate that the mRNA levels of Gi alpha-2 and Gi alpha-3 and not of Gs are overexpressed in heart and aorta from SHR, which may be responsible for the increased levels of Gi as shown earlier by immunoblotting techniques. It may be suggested that the enhanced vascular tone and impaired cardiac contractility in hypertension may partly be the consequences of increased levels of Gi in heart and aorta.

Animals↗
PubMed1992

Effect of prolonged in vivo glucose infusion on insulin secretion in rats with previous glucose intolerance.

This work was designed to investigate the effect of an additional hyperglycemia on the subsequent in vivo insulin secretion in rats with various degrees of glucose intolerance. Four groups of rats received a unique injection of a low concentration of streptozotocin (STZ): 20, 27, 30, or 35 mg/kg corresponding, respectively, to STZ 20, STZ 27, STZ 30, or STZ 35 rats. Control rats were injected with citrate buffer. In all STZ groups, impaired glucose tolerance and insulin secretion were observed. These defects were roughly proportional to STZ concentration. Three weeks after STZ administration, hyperglycemia (17 mM) was produced by a 48-h glucose infusion via an indwelling catheter. Insulin secretion in response to glucose was investigated 3 h after stopping glucose infusion, by performing iv glucose tolerance tests. Insulin secretion in response to glucose doubled in control rats previously submitted to glucose infusion, and still more in rats with mild glucose intolerance (three and four times higher in STZ 20 and STZ 27 rats, respectively). By contrast, glucose infusion increased insulin secretion only slightly in STZ 30 rats and it was unchanged in STZ 35 rats. These data show that prolonged hyperglycemia has an improving effect on insulin secretion in rats with mild glucose intolerance, whereas the potentiating effect of previous hyperglycemia is lost in rats with more severe glucose intolerance.

Animals↗
PubMed1992

[Endoscopic retrograde cholangiopancreatography in the context of cholecystectomy under celioscopy].

This descriptive cohort study documents the results of endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic sphincterotomy (ES) in the perioperative period of laparoscopic cholecystectomy (LC). Of 630 consecutive patients undergoing LC, 83 (13.2%) sustained 96 ERCP, of which 65 were performed preoperatively (67.7%) and 31 postoperatively (32.3%). The common bile duct cannulation rate was 96.9% after the first attempt and 100% after the second in three patients. Common duct stones were found in 40 patients (6.3%) and three other anomalies were demonstrated ES was performed in 42 patients and 100% clearance of the common bile duct was achieved after 45 extraction procedures. Six patients (1%) were found at follow-up with unsuspected common duct stones and were all successfully treated with ES. At present time, the morbidity of ERCP and ES (7.2% and 11.9%) make them worthwhile adjuncts to perative cholangiography for the diagnosis and treatment of common bile duct stones found during the perioperative period of LC.

Adolescent↗
PubMed1992

Laparoscopic splenectomy: operative technique and preliminary report.

A technique of laparoscopic splenectomy was developed on animal models and subsequently applied in two human patients. After creation of a 15 mm Hg pneumoperitoneum, five trocars, two with 12-mm diameters, were introduced into the upper abdomen. The spleen was approached directly by dissection of the gastrosplenic ligament. The short gastric vessels and hilar vessels were individually ligated with metallic clips or a surgical stapler, depending on their size. A plastic bag was then introduced into the abdominal cavity and the spleen slipped inside. An umbilical incision measuring 2 to 3 cm was used for extraction after finger fracture of the spleen. After laboratory experience with seven animals, we used this operation on two patients. The first procedure had to be converted to open surgery because of hemorrhage; the second was successfully performed within 4 h. Knowledge of anatomic variations and meticulous surgical technique are necessary for the successful completion of splenic laparoscopic surgery.

Adolescent↗
PubMed1991

Altered expression of inhibitory guanine nucleotide regulatory proteins (Gi alpha) in spontaneously hypertensive rats.

We have recently shown that the stimulatory effects of guanine nucleotides and some agonists on adenylate cyclase activity were diminished in aorta and heart sarcolemma (SL) of spontaneously hypertensive rats (SHR). In the present studies we have examined the activity of GTP-binding proteins (G-proteins) at ADP-ribosylation level, by using pertussis toxin (PT) and cholera toxin (CT) at protein level, by using specific antibodies against Gi (inhibitory) and at mRNA level, by using cDNA probes encoding G-proteins. The labeling of Gi by PT was significantly increased in the aorta and heart SL from SHR as compared to their Wistar-Kyoto control rats (WKY). However, no change in the labeling of Gs (stimulatory) by CT was observed in SHR. Furthermore, immunoblotting experiments using AS/7 antibody which reacts with both Gi alpha-1 and showed an increased immunoprecipitation of Gi alpha-2 in heart SL from SHR. In addition, when the expression of G-proteins was probed at the mRNA levels by Northern blot analysis using cDNA probes, the mRNA levels of Gi2 alpha and Gi3 alpha were significantly enhanced in aorta and heart from SHR. However, the mRNA levels of Gs alpha were not altered in SHR. These results indicate that the gene of Gi and not of Gs is overexpressed in heart and aorta from SHR.

Adenylate Cyclase Toxin↗
PubMed1991

[Anti-infective prophylactic measures in cesareans].

Septic complications remain important in obstetrical surgery due to the serious threat they pose to life and the sequelae which they may leave. The authors have therefore attempted to identify which of the anti-infectious prophylactic treatments used in cesareans were the most effective. This analysis was based on cases in their unit seen from 1984 to 1988 and on a review of the literature. Of the patients who underwent a cesarean (9.4 percent out of 7,855 deliveries), 2 percent were infected, with and incidence of 0.65 percent serious infections (0.4 percent septicemia). On the basis of the literature, the following risk factors were identified: 1st cesarean, cesarean during labor, rupture of the membranes, surgical problem, anemia, obesity and low socio-economic level. The local fundamental and systemic prophylactic measures taken were special antibiotic prophylaxis in the patients with a risk of infection only. The short protocol, with a single injection of penicillin A or a first generation cephalosporin, after clamping the umbilical was preferable and, according to all the studies, had the advantage of avoiding the selection of resistance.

Adult↗
PubMed1990

Atrial natriuretic factor increases cyclic GMP and cyclic AMP levels in a directly photosensitive pineal organ.

Atrial natriuretic factor (ANF) stimulates accumulation of cyclic GMP in a photosensitive organ, as evidenced for the first time in cultured trout pineals. Stimulation was rapid (within a few min), dose-dependent, and stronger in organs cultured in darkness than in those cultured under light. After 30 min in the dark, (i) cyclic AMP levels were slightly increased at 10(-7) mole/l of ANF, (ii) cyclic GMP and cyclic AMP increased dramatically after inhibition of the phosphodiesterases by isobutylmethylxanthine (IBMX), (iii) ANF and IBMX effects were more than additive on cyclic GMP, (iv) pertussis toxin decreased the cyclic GMP response to ANF. These responses were affected by light. The possibility that cyclic GMP might be a second messenger of both light and chemical (ANF) inputs, in pineal photoreceptor cells, is hypothetized.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Evaluation of bull semen fertility by homologous in vitro fertilization tests.

In vitro fertilization assays were performed to investigate their validity in evaluating artificial insemination (AI) bull fertility. A total of 1,532 oocytes, collected from ovaries at the abattoir, were subsequently used in a 4 x 6 x 2 factorial design: 4 doses of heparin added into the capacitation and fertilization medium (0; 0.05; 0.1 and 0.2 micrograms/ml), 6 different bulls with known on-field non-return (NR) rates (range: 64.6-75.3%) and 2 different ejaculates for each bull, collected within a approximately 1-month interval. Oocytes were considered fertilized when 2 pronuclei (or more) were seen in the ooplasm. Both the heparin dose and bull exerted a highly significant effect on the in vitro fertilization (IVF) rates which ranged, per oocyte group, from 30-80%; bull x dose of heparin interaction was significant (P less than 0.001). The 0.05 micrograms/ml dose of heparin was optimal for discriminating individual bulls. At that dose, the correlation coefficients between the bulls, NR rates and the IVF rates from each ejaculate (within-bull or the mean of two ejaculates), were highly significant (r = 0.83). The rates of polyspermy were also significantly influenced by bull and heparin dose, but there was no interaction. In conclusion, capacitation and fertilization in a modified Tyrode medium containing 0.05 micrograms/ml of heparin may be a valuable tool for evaluating AI bull fertility.

Animals↗
PubMed1989

In vitro culture of bovine egg fertilized either in vivo or in vitro.

Three-quarters of in vivo and one-third of in vitro fertilized bovine eggs reached blastocyst stage when cultured on tubal cell monolayers (TCM), but no hatching occurred in B2 medium supplemented with estrous cow serum. When after 3 days of culture on TCM, morulae were transferred on endometrial cell monolayers (UCM), the same proportion of blastocysts was obtained and one-third of them hatched. Histological studies of hatched blastocysts showed that the number of inner cells was significantly lower than in hatched blastocysts recovered in vivo 8-8.5 days after ovulation. Moreover, the number of pycnotic cells was higher than normal, although mitosis were present. On the contrary, there was no difference in either the number or the appearance of trophoblastic cells between blastocysts obtained in vitro and in vivo. The addition of transforming growth factor (TGF-beta) to either TCM or UCM co-cultures at the very beginning of blastocyst formation specifically stimulated growth of the inner cell mass (ICM). The number of cells at hatching was about double (120) and significantly higher than that found in 8-8.5-day blastocysts in vivo. Moreover, hatching percentages were similar to the controls, even when eggs were cultured for 8 days only on TCM. However the proportion of pycnotic cells remained higher than normal, although many mitotic cells were unevenly distributed in ICM) In vivo during hatching, there were always pycnotic cells in ICM, but their number was limited and approximately similar to the number of mitosis. The uterine factors which control both mitosis and pycnosis in ICM remain to be discovered.

Animals↗
PubMed1988

Ovulation.

Three events lead to the ovulation of a normal oocyte: cytological and biochemical changes in the follicle wall, disintegration of the follicle apex and oocyte maturation. The remodelling of the follicle wall results from plasmin and collagenase activities. The thinning of the follicular apex, in addition to these enzymes, involves hydrolases liberated by dying ovarian epithelial cells. PGF2 alpha and histamine are also involved but it is not known precisely how they contribute to the apical dissociation. The nuclear and cytoplasmic maturation of the oocyte is highly dependent on the synthetic activities of granulosa cells which are regulated by LH and FSH. The pulsatile secretion of these gonadotrophins is not necessary for the final phase of Graafian follicle growth and rupture. Why high levels of gonadotrophins, normally reached during the preovulatory surge, completely change the structure and the biochemical activities of all follicular compartments remains unknown and in fact has never been studied. Moreover, there is very little information concerning the mechanisms involved both in the increase of blood flow during the LH surge and later in the blood stasis at the follicular apex. Steroids, whatever their levels and ratio, are of little if any concern in follicle rupture and nuclear maturation. However, their importance has been clearly demonstrated in the cytoplasmic maturation of the oocyte of some species.

Animals↗
PubMed1987

Catecholamines within the rabbit oviduct at fertilization time.

Dopamine, norepinephrine and epinephrine levels of rabbit oviductal fluids were measured in order to establish whether the ampullary segment contained higher concentrations correlating with the sperm hyperactivity observed in the ampulla of different mammals. In this study, we found no statistically significant differences between flushings from the ampulla or the isthmus at oestrus, ovulation or 72 h post-coitum (p.c.). However, after correcting for the volume secreted, the concentrations of catecholamines are always lower in the ampulla than in the isthmus. In all cases the levels of biogenic amines were highest at oestrus then fell at ovulation. Individual variation of these levels at the time of ovulation was observed only in the ampulla, probably due to some contribution from follicular fluid. During the early luteal phase (72 h p.c.) the catecholamine levels again increase slightly, especially in the isthmus. We conclude that whiplash motility cannot be explained by a higher level of catecholamines in the ampulla.

Animals↗
PubMed1985

[Mechanisms regulating ovulation rate and oocyte maturation. Maturation induction and superovulation].

The follicular growth takes longer in most mammals than it does in rodents: (4 to 15 days between the antral stage and ovulation in rodents, versus 65 days in women). The ovulation rates typical of animal species are mainly regulated during two critical periods: antrum formation and a few days before ovulation. The FSH level appears to be determinant, but in the animal species or races whose ovulation rate is near one, a dominant follicle is involved in the atresia of others. Increasing the level of gonadotrophins, especially of FSH, results in superovulation. However, the results are often irregular, with prolonged maturations and ovulations and oocytes of uncertain quality. Using pituitary gonadotrophins instead of placental or urinary hormones considerably increases the number of oocytes available and improves the development of embryos if the FSH/LH ratio of pituitary gonadotrophins is adjusted to the species involved. Thus, the main problem concerns the quality of the oocyte. At the present time, no criterion allows a prediction of the quality of the oocyte, and the complexity of the mechanisms involved in its intrafollicular maturation do not foreshadow a simple and rapid solution. However, appreciable improvements in our techniques are possible on the basis of current knowledge.

Animals↗
PubMed1985

Variation of astigmatism with accommodation and its relationship with dark focus.

The refraction of 122 eyes was measured for five distances of fixation with an objective Canon Auto Refractor. The cylindrical component was found to vary, but by a small amount. We found no evidence of a deliberate reduction in astigmatism with accommodation, in accord with other studies. The axis was also found to vary by at least 5 degrees in about half of the subjects tested, which is also in good accord with other investigations. The dark focus of 31 eyes was not found to correlate with a minimum astigmatic distance, since this only occurred in 11 out of the 31 eyes. For these 11 eyes, the correlation of dark focus and the dioptric distance where astigmatism was minimum was equal to + 0.54. It implied that for those eyes (about one-third of all types) there was a tendency to yield the best optical quality at the dark focus.

Accommodation, Ocular↗
PubMed1976

[Culture of the bovine graafian follicle in a continuous liquid and gas flow system].

The culture of 3-5 mm calf follicles in a new glass perfusion cell is compared to the organotypic grid culture using the same synthetic medium and a gas mixture of 55% O2 + 40% N2 and 5% CO2 Amino acid consumption is 3 to 39 times higher in the perfusion cell culture and the mitotic rate is also higher. Moreover, the cytological aspect of granulosa and cumulus cells looks similar to that of non-atresic ovarian follicles. Meiosis resumes up to metaphase 1 or metaphase 2. No pyknotic cells are observed.

Air↗