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M Vial

Publications and source records attributed to M Vial.

At least 37 records · Page 2Linked to original sources
PubMed1996

[Experimental radiosurgery in rats using gamma a "gamma knife". Description of a stereotactic device for small laboratory animals].

To allow the experimental use in rats of a Gamma Knife Radiosurgical Unit, a stereotactic device adapted from the conventional Kopf's device was developed. To control the accuracy of the coordinate system based on the De Groot's rat stereotactic atlas, experimental radiosurgical lesions were made on the left striatum. The isodose curve distribution of the 4 mm collimator was calculated with the dose planning software used in Gamma Knife and superimposed on the left striatum target. Doses of 200 Gy were administered to the left striatum in six rats. The results were evaluated 21, 34 and 47 days later. At 34 and 47 days necrotic lesions were exactly as targeted. In a second group of 48 rats receiving a doses of 100 Gy, no lesions were observed after 7, 15, 24, 31, 45 days. However, in all rats sacrificed 59, 72 and 90 days after day radiation, a necrotic lesion was always present and confirmed that at each time the lesions were precisely targeted. This apparatus allows precise and reproducible gamma irradiation lesion in rat brain without expensive and time consuming imaging techniques. This device provides a useful system to observe the experimental effects of radiosurgery on the central nervous system in rats.

Animals↗
PubMed1995

Hexose accumulation by enterocytes from the jejunum and rectum of chickens adapted to high and low NaCl intake.

We have studied the effects of adaptation to low NaCl intakes on hexose transport using suspensions of enterocytes isolated from the jejunum and the rectum of the chicken. Animals (12-13 weeks old) were kept for 11 days on either a high-Na+ (HS) or a low Na+ (LS) diet. On day 11, mean serum aldosterone concentration was 46 pg/ml in HS birds and 236 pg/ml in LS birds. Results of transport studies show that: (1) adaptation to a LS diet reduces the cellular 3-oxymethyl-D-glucose cumulative capacity by 40% in the jejunum and is virtually abolished in the rectum; (2) LS adaptation reduces initial alpha-methyl-D-glucoside influx (1 mmol/l) by 22% in the jejunum and by 54% in the rectum; (3) the influx of the membrane potential sensor tetraphenyl-phosphonium (TPP+) in enterocytes strongly suggests that rectal cells of LS birds are significantly depolarized; (4) the presence of 0.1 mmol/l amiloride increases the capacity of the rectal cells of LS birds to establish a sugar gradient across the membrane; (5) incubation of enterocytes with cytochalasin B increases sugar cumulative capacity of the jejunal cells of both HS and LS birds, and has no effect on the rectal cells of LS birds. We conclude that the effects of LS adaptation on sugar transport may involve a reduction in the membrane electrical potential.

Amiloride↗
PubMed1994

Effects of ion channel blockers and phorbol ester treatments on [3H]dopamine release and neurotensin facilitation of [3H]dopamine release from rat mesencephalic cells in primary culture.

In this work, we tested the effect of ion channel blockers and of phorbol ester treatments on [3H]dopamine ([3H]DA) release and neurotensin (NT)-induced facilitation of [3H]DA release from cultures of rat fetal mesencephalic cells. The potassium channel blockers tetraethylammonium and 4-aminopyridine increased basal [3H]DA release and decreased K(+)-evoked [3H]DA release, whereas apamin was without effect. K(+)-evoked [3H]DA release was decreased by omega-conotoxin and nifedipine, totally suppressed by cadmium, and unaffected by amiloride. These results show the differential sensitivity of [3H]DA release to blockade of various ion channels and suggest the involvement of N-type, L-type, and non-L-non-N-type, but not T-type, voltage-sensitive calcium channels in K(+)-evoked release. Phorbol 12-myristate 13-acetate increased both spontaneous and K(+)-evoked [3H]DA release, suggesting a modulatory action of protein kinase C on DA release in this system. Unexpectedly, however, the effects of the phorbol ester were not counteracted by the protein kinase C inhibitors H7, staurosporine, or polymyxin B. NT-induced facilitation of K(+)-evoked [3H]DA release was insensitive to most of the ion channel blockers, except cadmium (64% decrease in NT effect), suggesting that the corresponding potassium and calcium channels were not involved in the effect of NT on [3H]DA release in this system. The NT effect was totally suppressed by phorbol ester treatments, indicating a possible desensitization of the corresponding transduction mechanisms after protein kinase C activation.

4-Aminopyridine↗
PubMed1993

Potent cocaine analogs inhibit [3H]dopamine uptake in rat mesencephalic cells in primary cultures: pharmacological selectivity of embryonic cocaine sites.

The cellular localization of the cocaine binding sites in primary cultures of embryonic rat mesencephalic cells was previously reported to differ from that observed in adult rat brain. In order to know whether this different localization was associated with a different pharmacological selectivity, we tested the effect of new cocaine analogs on tritiated dopamine ([3H]DA) uptake in primary cultures of rat embryonic mesencephalic cells. In these cultures, [3H]DA was taken up by a nomifensine-sensitive, but desipramine and fluoxetine-insensitive process, reflecting selective uptake by the dopaminergic transporter. 3 beta-(4-Chlorophenyl)tropan-2 beta-carboxylic acid methyl ester (RTI-COC-31) was by far the most potent inhibitor of the [3H]DA uptake, presenting an IC50 of 3.8 nM, while the corresponding analog with an unsubstituted phenyl ring (WIN 35,065-2) was 38 times less potent. The enantiomer of WIN 35,065-2, namely WIN 35,065-3, was 30 times less potent than the former. A similar pattern was found for the relative ability of these compounds to inhibit binding of the radiolabeled cocaine derivative [125I]RTI-55 to membranes prepared from mesencephalic cultures. The order of potencies found for the three cocaine analogs on mesencephalic cultures was similar to that previously obtained in [3H] WIN 35,428 binding experiments and [3H]DA uptake inhibition in adult rat striatum, suggesting that the pharmacological selectivity of cocaine sites functionally related to the DA transporter in cultured embryonic neurons does not differ from that obtained in adult rat brain.

Animals↗
PubMed1993

Magnetic resonance imaging of the fetus: a study of 20 cases performed without curarization.

Twenty patients underwent magnetic resonance imaging (MRI) at a mean gestational age of 32 weeks. There were 12 patients with suspected fetal brain abnormality and four with intrauterine growth retardation (IUGR), while the remaining four cases were studied for other reasons. The MRI examinations were performed on a 0.5 Tesla machine, with surface coils. One minute acquisition time T1 sequences were used. All the studies were performed without fetal curarization, and only under maternal sedation using flunitrazepam given per os 1 h before MRI examination. Three examinations were incomplete because of fetal movement artefacts. In the remaining cases, MRI allowed the examination of fetal brain anatomy. In five cases, it helped to differentiate isolated hydrocephalus and corpus callosum agenesis. Sub-ependymal nodules were depicted in a case of fetal tuberous sclerosis. One suspected arachnoid cyst was proved to be an ultrasound artefact. Decreased fetal fat on MR images was correlated with low birth weight in cases of IUGR. Due to its better spatial resolution, ultrasonography was more accurate for the diagnosis of facial and lumbar anomalies. Fetal MRI may be performed without curarization. Surface coils allow the detailed analysis of brain parenchyma, and thus MRI is especially useful in the difficult prenatal diagnosis of fetal brain abnormalities.

Adipose Tissue↗
PubMed1993

Biochemical characterization and autoradiographic localization of [125I]endothelin-1 binding sites on trophoblast and blood vessels of human placenta.

The presence of endothelin binding sites in the human placenta raises the question of the precise localization of these receptors on well defined placental constituents. In order to find an answer to this problem various approaches were used. Specific binding sites for [125I] endothelin-1 (ET-1) were identified on human term placenta, not only on membranes of smooth muscles stem villi vessels, but also on trophoblastic plasma membranes prepared from trophoblast in culture. Scatchard analysis of binding data revealed a single class of high affinity binding sites with Kd values of 26 +/- 4 pmol/L for stem villi vessels and 126 +/- 4 pmol/L for trophoblast in culture, with maximum binding capacities of 681 +/- 61 and 224 +/- 53 fmol/mg protein, respectively. The anatomical localization of these binding sites was determined by in vitro autoradiography. Autoradiograms obtained from placental sections incubated with [125I]ET-1 indicate that [125I]ET-1 high affinity binding sites exist on placental stem villi vessels and on the trophoblastic layer of the villi. The latter localization was also found on autoradiograms of trophoblast in culture. The human placental syncytiotrophoblast is a polarized epithelium with the microvillous membrane, facing maternal blood space and the basal plasma membrane, facing fetal circulation. [125I]ET-1 high affinity binding sites are present on both membranes but the number of binding sites is higher on the basal plasma membrane. These findings lead to the suggestion that ET-1 may be involved in the regulation of the feto-placental circulation and may subserve specific trophoblastic functions.

Arteries↗
PubMed1993

[Immigrants facing retirement: to stay or to return?].

"Nowadays 75% of foreigners living in Switzerland have a permanent residence permit. A new phenomenon goes along with this stabilisation: the aging of this resident foreign population, especially Italians and Spaniards who arrived in Switzerland in the fifties and sixties. This trend will have definite consequences on the costs of Swiss social security benefits. Our research project aims at clarifying which factors influence those immigrants who are near retirement to decide whether to stay or go back to their home countries." (SUMMARY IN ENG AND GER)

Behavior↗
PubMed1992

Bilirubin uridine diphosphate glucuronosyltransferase hepatic activity in jaundice associated with congenital hypothyroidism.

Hepatic bilirubin uridine diphosphate glucuronosyltransferase activity was assayed in an infant with prolonged jaundice and congenital hypothyroidism before thyroid therapy. This activity was nil, suggesting a possible delayed maturation of the enzyme. Although further studies will be necessary to confirm this hypothesis, prolonged jaundice associated with congenital hypothyroidism may be due to a delayed maturation of the hepatic glucuronidation of bilirubin.

Bilirubin↗
PubMed1992

Mesencephalic dopaminergic neurons in primary cultures express functional neurotensin receptors.

The cellular distribution and functional aspects of neurotensin (NT) binding sites in rat mesencephalic cells in primary culture were investigated by an original approach combining anatomical and biochemical studies. Using a double-labeling protocol combining 125I-NT receptor radioautography and tyrosine hydroxylase (TH) immunocytochemistry, we obtained the first direct visualization of NT binding sites on TH-immunoreactive neurons. Eighty percent of the TH neurons were endowed with NT binding sites, which can be observed on both cell bodies and processes. TH-immunoreactive neurons were characterized as dopaminergic neurons by their ability to take up dopamine in a benztropine- and nomifensine-sensitive manner. In the mesencephalic cultures, NT increased potassium-evoked release of tritiated dopamine, and the relative potencies of various NT-related peptides to increase dopamine release were in good agreement with their abilities to bind to NT sites. These results show for the first time that cultured rat mesencephalic dopaminergic cells express functional NT receptors. Finally, the specificity and distribution of NT receptors on dopaminergic neurons in primary culture are quite similar to what was observed in the adult rat brain using pharmacological and radioautographic approaches. These data indicate that NT can influence the activity of dopaminergic neurons at very early stages of the rat brain development.

Animals↗
PubMed1992

Labor induction in women at term with mifepristone (RU 486): a double-blind, randomized, placebo-controlled study.

OBJECTIVE: To determine the efficacy and safety of mifepristone as an induction agent for the initiation of labor or as a cervical ripening agent in women at term. METHODS: Our study group contained 120 women at term (after 37.5 weeks' amenorrhea) who had clear clinical indications for labor induction. They were randomized to receive either 200 mg of mifepristone or placebo on days 1 and 2 of a 4-day observation period, with labor induction planned for day 4. Eight patients, three treated with mifepristone and five receiving placebo, had to be excluded from the survey because they required cesareans for medical reasons (fetal distress or maternal complications) less than 12 hours after taking the first tablet. RESULTS: Forty-one subjects entered spontaneous labor, 31 treated with mifepristone and ten in the control group (P < .001). Forty-five needed cervical maturation with prostaglandins on day 4, 13 of whom had received mifepristone and 32 of whom had been given placebo (P < .001). Thirteen women treated with mifepristone and 13 who had taken placebo had mature cervices sufficient for classic labor induction with oxytocin and amniotomy. Patients who delivered vaginally needed a much lower amount of oxytocin when mifepristone had been given, and the mean time interval between day 1 of the survey and the onset of labor was also significantly shorter in this group. CONCLUSION: Although more studies are needed, we have found mifepristone to be a safe, efficient, and suitable induction agent for initiation of labor in women at term.

Adult↗
PubMed1991

Characterization of neurotensin binding sites on rat mesencephalic cells in primary culture.

Many studies have reported the presence of high amounts of neurotensin (NT) binding sites in the mesencephalon of adult rat, and their possible role in mediating the effects of the peptide on the activity of mesencephalic dopaminergic neurons. In the present study, we demonstrate the presence of NT sites in primary cultures of embryonic rat mesencephalic cells. On these cells, a single class of high affinity 125I-NT binding sites was observed. The value of the apparent affinity constant (0.3 nM) did not show any significant change throughout time, from 3 to 14 days in culture. The number of sites, however, increased until day 11 and decreased thereafter. Acetylneurotensin (8-13), NT and neuromedin N were potent competitors of 125I-NT binding, while NT (1-10), NT (1-11) and levocabastine were uneffective. These results indicate that the sites detected in the mesencephalic cultures share common binding properties with the high-affinity NT sites already described in adult rat brain. The neuronal localization of the NT sites was suggested by their presence in neuron-enriched serum-free cultures and their absence in glial cultures. Autoradiographic studies confirmed the cellular localization of NT sites and indicated that, under our experimental conditions, cells labeled by 125I-NT represented 0.14% of the initially plated cell number. Taken together, these results show that the development of mesencephalic neurons in primary culture is associated with an increased expression of NT binding sites. Since such cultures have been shown previously to contain functional dopaminergic neurons, we suggest that they could provide a good model to investigate the modulation of the activity of these neurons by NT.

Animals↗
PubMed1991

The effect of vasoactive intestinal peptide (VIP) on the contractile activity of human uterine smooth muscle.

1. In the present study we examined the in vitro effect of vasoactive intestinal peptide (VIP) on spontaneous contractions in both inner and outer layers of non-pregnant human myometrium. A dose-dependent relaxation was observed, but with a marked difference in sensitivity to VIP between the two layers, with an IC50 value of 1 x 10(-8) and 1 x 10(-5) mol L in the outer and inner layers, respectively. 2. We also established that VIP did not directly stimulate the adenylate cyclase activity. The only slight stimulations were observed in non-initial rate conditions. The maximal response of this indirect effect was obtained for VIP concentrations between 1 x 10(-9) and 1 x 10(-8) mol/L and this occurred to the same extent (an approximately 1.4-fold increase) in both layers. However this response is specific, since structurally related peptides such as glucagon, gastric inhibitory polypeptide (GIP), secretin, or human growth hormone-releasing factor (hGRF) had no effect in our preparations. 3. Autoradiographic studies revealed that specific VIP binding sites were located on the vascularization of the intermediate vascular layer and on arterioles and venules distributed in the inner and outer myometrial layers. They were also present in the endometrium, but not on smooth muscle cells of either layer. 4. Such observations could provide evidence for another signal transduction pathway to mediate the biological effect of VIP. An additional intermediate step on the vascularization distributed in all of the muscle cannot be excluded.

Adenylyl Cyclases↗