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C Clair

Publications and source records attributed to C Clair.

15 recordsLinked to original sources
PubMed2003

Ca2+ oscillations in hepatocytes do not require the modulation of InsP3 3-kinase activity by Ca2+.

Receptor-mediated production of inositol 1,4,5-trisphosphate (InsP(3)) initiates Ca(2+) release and is responsible for cytosolic Ca(2+) oscillations. InsP(3) oscillations have also been observed in some cells. One of the enzymes controlling InsP(3) catabolism, the InsP(3) 3-kinase, is stimulated by Ca(2+); this regulation is presumably part of the reason for InsP(3) oscillations that have been observed in some cells. Here, we investigate the possible role of Ca(2+)-activated InsP(3) catabolism on the characteristics of the InsP(3)-induced Ca(2+) oscillations. Numerical simulations show that if it is assumed that the Ca(2+)-independent InsP(3) catabolism is predominant, Ca(2+) oscillations remain qualitatively unchanged although the relative amplitude of the oscillations in InsP(3) concentrations becomes minimal. We tested this prediction in hepatocytes by masking the Ca(2+)-dependent InsP(3) catabolism by 3-kinase through the injection of massive amounts of InsP(3) 5-phosphatase, which is not stimulated by Ca(2+). We find that in such injected hepatocytes, Ca(2+) oscillations generated by modest agonist levels are suppressed, presumably because of the decreased dose in InsP(3), but that at higher doses of agonist, oscillations reappear, with characteristics similar to those of untreated cells at low agonist doses. Altogether, these results suggest that oscillations in InsP(3) concentration due to Ca(2+)-stimulated InsP(3) catabolism do not play a major role for the oscillations in Ca(2+) concentration.

Animals↗
PubMed2003

[Fluid-fluid level in an intra-osseous ganglion cyst of the talus].

The author report a very rare case of fluid-fluid level in an intra-osseous ganglion cyst of the talus that was detected on CT and MR imaging. Pre-operative diagnosis was suggested by the presence of a communication between the talo-cuboid joint and the cyst, as shown at MR Arthrography.

Adult↗
PubMed2002

[CT guided neurolysis of the sphenopalatine ganglion for management of refractory trigeminal neuralgia].

The authors present the case of a patient with recurrent trigeminal neuralgia, refractory to medical treatment and ablation of the trigeminal ganglion, who underwent three separate CT guided injections for pterygopalatine ganglion ablation over a two year period. Ablation of the pterygopalatine ganglion may be an effective technique for pain management in patients suffering from atypical facial pain syndrome, cluster headache, or neuritis. The technique used for CT guided ablation using alcohol or radiofrequency is described. The advantages and pitfalls of this technique are reviewed.

Adult↗
PubMed2001

Investigation of the roles of Ca(2+) and InsP(3) diffusion in the coordination of Ca(2+) signals between connected hepatocytes.

Glycogenolytic agonists induce coordinated Ca(2+) oscillations in multicellular rat hepatocyte systems as well as in the intact liver. The coordination of intercellular Ca(2+) signals requires functional gap-junction coupling. The mechanisms ensuring this coordination are not precisely known. We investigated possible roles of Ca(2+) or inositol 1,4,5-trisphosphate (InsP(3)) as a coordinating messengers for Ca(2+) spiking among connected hepatocytes. Application of ionomycin or of supra-maximal concentrations of agonists show that Ca(2+) does not significantly diffuse between connected hepatocytes, although gap junctions ensure the passage of small signaling molecules, as demonstrated by FRAP experiments. By contrast, coordination of Ca(2+) spiking among connected hepatocytes can be favored by a rise in the level of InsP(3), via the increase of agonist concentrations, or by a shift in the affinity of InsP(3) receptor for InsP(3). In the same line, coordination cannot be achieved if the InsP(3) is rapidly metabolized by InsP(3)-phosphatase in one cell of the multiplet. These results demonstrate that even if small amounts of Ca(2+) diffuse across gap junctions, they most probably do not play a significant role in inducing a coordinated Ca(2+) signal among connected hepatocytes. By contrast, coordination of Ca(2+) oscillations is fully dependent on the diffusion of InsP(3) between neighboring cells.

Animals↗
PubMed2001

[Stellate ganglion radiofrequency neurolysis. Report of a case followed over a 3-year period].

We present the case of a patient who experienced residual ischemic symptoms and invalidating chronic pain after an injury where three fingers of his left hand were sliced off by a chain saw. He underwent 5 stellate ganglion RF neurolysis over a two year period, followed by progressive and complete pain relief. We will underscore the value of CT guidance during needle placement and the efficacy of RF neurolysis.

Adult↗
PubMed2001

[Thoracic aortic coarctation: MRI evaluation and follow-up].

PURPOSE: Report our experience in the evaluation and follow-up of thoracic aortic coarctation with MRI and describe its role to estimate trans-stenotic flow. MATERIAL AND METHODS: 43 MR examinations were performed in 30 patients (age range 15 days to 73 years) referred to our institution in the last 7 years. RESULTS: MRI visualized the ascending, horizontal and descending portions of the aorta and the supra-aortic vessels in 42/43 patients. MRI clearly identified preoperatively an aortic coarctation in 11/12 cases confirmed by surgery. Postoperatively MRI depicted 4 restenosis and one aneurysm. In 5 patients MRI demonstrated pseudo-coarctation. A significant correlation was established between the maximal trans-stenotic pressure gradient when measured by Doppler US or angiography and the size of the signal void measured on cine-MR images (r=0.72; p<0.01). CONCLUSION: MRI is a reliable non invasive investigation method for the diagnosis and semi-quantitative evaluation of aortic coarctation particularly when colour Doppler US is not satisfactory.

Adolescent↗
PubMed2000

Hierarchical organization of calcium signals in hepatocytes: from experiments to models.

The proper working of the liver largely depends on the fine tuning of the level of cytosolic Ca(2+) in hepatocytes. Thanks to the development of imaging techniques, our understanding of the spatio-temporal organization of intracellular Ca(2+) in this - and other - cell types has much improved. Many of these signals are mediated by a rise in the level of inositol 1,4,5-trisphosphate (InsP(3)), a second messenger which can activate the release of Ca(2+) from the endoplasmic reticulum. Besides the now well-known hepatic Ca(2+) oscillations induced by hormonal stimulation, intra- and intercellular Ca(2+) waves have also been observed. More recently, subcellular Ca(2+) increases associated with the coordinated opening of a few Ca(2+) channels have been reported. Given the complexity of the regulations involved in the generation of such processes and the variety of time and length scales necessary to describe those phenomena, theoretical models have been largely used to gain a precise and quantitative understanding of the dynamics of intracellular Ca(2+). Here, we review the various aspects of the spatio-temporal organization of cytosolic Ca(2+) in hepatocytes from the dual point of view provided by experiments and modeling. We first focus on the description and the mechanism of intracellular Ca(2+) oscillations and waves. Second, we investigate in which manner these repetitive Ca(2+) increases are coordinated among a set of hepatocytes coupled by gap junctions, a phenomenon known as 'intercellular Ca(2+) waves'. Finally, we focus on the so-called elementary Ca(2+) signals induced by low InsP(3) concentrations, leading to Ca(2+) rises having a spatial extent of a few microns. Although these small-scale events have been mainly studied in other cell types, we theoretically infer general properties of these localized intracellular Ca(2+) rises that could also apply to hepatocytes.

Animals↗
PubMed2000

MR diagnosis of a congenital abnormality of the thoracic aorta with an aneurysm of the right subclavian artery presenting as a Horner's syndrome in an adult.

Congenital abnormality of the aortic arch is a diagnosis made most of the time incidentally in childhood, unless dysphagia or respiratory disorders occur before. A case of a complex aortic arch anomaly with an aneurysm of the right subclavian artery presenting as an isolated Horner's syndrome in an adult is reported herein. Magnetic resonance imaging led to this very unusual diagnosis.

Adult↗
PubMed2000

Mechanism of receptor-oriented intercellular calcium wave propagation in hepatocytes.

Intercellular calcium signals are propagated in multicellular hepatocyte systems as well as in the intact liver. The stimulation of connected hepatocytes by glycogenolytic agonists induces reproducible sequences of intracellular calcium concentration increases, resulting in unidirectional intercellular calcium waves. Hepatocytes are characterized by a gradient of vasopressin binding sites from the periportal to perivenous areas of the cell plate in hepatic lobules. Also, coordination of calcium signals between neighboring cells requires the presence of the agonist at each cell surface as well as gap junction permeability. We present a model based on the junctional coupling of several hepatocytes differing in sensitivity to the agonist and thus in the intrinsic period of calcium oscillations. In this model, each hepatocyte displays repetitive calcium spikes with a slight phase shift with respect to neighboring cells, giving rise to a phase wave. The orientation of the apparent calcium wave is imposed by the direction of the gradient of hormonal sensitivity. Calcium spikes are coordinated by the diffusion across junctions of small amounts of inositol 1,4, 5-trisphosphate (InsP(3)). Theoretical predictions from this model are confirmed experimentally. Thus, major physiological insights may be gained from this model for coordination and spatial orientation of intercellular signals.-Dupont, G., Tordjmann, T., Clair, C., Swillens, S., Claret, M., Combettes, L. Mechanism of receptor-oriented intercellular calcium wave propagation in hepatocytes.

Animals↗
PubMed1998

Receptor-oriented intercellular calcium waves evoked by vasopressin in rat hepatocytes.

Agonist-induced intracellular calcium signals may propagate as intercellular Ca2+ waves in multicellular systems as well as in intact organs. The mechanisms initiating intercellular Ca2+ waves in one cell and determining their direction are unknown. We investigated these mechanisms directly on fura2-loaded multicellular systems of rat hepatocytes and on cell populations issued from peripheral (periportal) and central (perivenous) parts of the hepatic lobule. There was a gradient in vasopressin sensitivity along connected cells as demonstrated by low vasopressin concentration challenge. Interestingly, the intercellular sensitivity gradient was abolished either when D-myo-inositol 1,4, 5-trisphosphate (InsP3) receptor was directly stimulated after flash photolysis of caged InsP3 or when G proteins were directly stimulated with AlF4-. The gradient in vasopressin sensitivity in multiplets was correlated with a heterogeneity of vasopressin sensitivity in the hepatic lobule. There were more vasopressin-binding sites, vasopressin-induced InsP3 production and V1a vasopressin receptor mRNAs in perivenous than in periportal cells. Therefore, we propose that hormone receptor density determines the cellular sensitivity gradient from the peripheral to the central zones of the liver cell plate, thus the starting cell and the direction of intercellular Ca2+ waves, leading to directional activation of Ca2+-dependent processes.

Animals↗
PubMed1997

[Imaging of abdominal trauma].

Imaging technique strategies in abdominal traumas should be aimed at determining the best strategy allowing a reliable and quick diagnosis of a potential surgical lesion. The introduction and development of modern imaging methods including CT and US thus nowadays, have a clear impact on the diagnosis and treatment of abdominal traumas.

Abdominal Injuries↗
PubMedDate not supplied

CT of small bowel obstruction in adults.

The increasing use of computed tomography in evaluating patients with acute abdominal pain has revolutionized the diagnosis of small bowel obstruction in adults. Computed tomography is incontestably the most useful and powerful tool to make positive, topographic, and etiologic diagnoses of small bowel obstruction. Good knowledge of some key signs and rigorous analysis of computed tomographic images by radiologists should lead to improved diagnosis and appropriate treatment.

Abdominal Pain↗
PubMedDate not supplied

Intradural disc herniation with cranial migration of an excluded fragment.

Intradural herniation is a rare complication of the intervertebral disc disease. The history and present clinical findings may suggest the diagnosis. Although the myelographic signs are well known, intradural hernias have seldom been illustrated by magnetic resonance imaging (MRI). We present the case of an intradural disc hernia with cranial migration of a sequestrated fragment illustrated by both myelography and MRI. To our knowledge, such a case has never been reported in the literature so far.

Cauda Equina↗