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Biomedical subjects

S Richard

Publications and source records attributed to S Richard.

At least 91 records · Page 5Linked to original sources
PubMed1999

Long polymerase chain reaction in detection of germline deletions in the von Hippel-Lindau tumour suppressor gene.

Experimental conditions for detection of germline deletions of the von Hippel-Lindau (VHL) gene by means of long polymerase chain reaction have been established. Primers were designed to analyse the VHL gene in three overlapping fragments: 12.5 kb in length containing promoter and exons 1 and 2; 8.7kb in length containing exons 2 and 3; and 16kb in length containing exons 2 and 3 and the 3' untranslated region. Using the described procedure, it was possible to detect large deletions in four of five cases with such mutations previously detected by Southern blotting and in 5 of 11 unrelated Polish VHL patients in whom constitutional VHL gene mutations were not found by sequencing.

Base Sequence↗
PubMed1999

Saccharomyces cerevisiae viability is strongly dependant on rehydration kinetics and the temperature of dried cells.

The effects of rehydration kinetics and temperature on the viability of Saccharomyces cerevisiae dehydrated by drying were studied. During rehydration, a water activity range of 0.117-0.455 must be crossed slowly in order to maintain cell viability. If this range is crossed rapidly, cell viability can be preserved if rehydration takes place at 50 degrees C. Several hypotheses have been proposed to explain previous results. One hypothesis, which relates cell mortality after rapid rehydration to water flow through the membrane in phase transition, is the more plausible and requires further investigation.

Colony Count, Microbial↗
PubMed1999

Radiographic assessment of hip and knee osteoarthritis. Recommendations: recommended guidelines.

Pathological lesions of osteoarthritis, demonstrated by conventional radiography, can be assessed by scoring systems and/or measurement with a quite acceptable reproducibility. Scores are recommended for a rough staging of osteoarthritis and of bone changes. Measurement is recommended for assessment of joint space narrowing progression. A good assessment of progression implicates a perfect reproducibility of the radiographic image of the joint. Accuracy of standard radiograph is improved by some views such as the hip profile and the schuss view.

Humans↗
PubMed1999

A role for the GSG domain in localizing Sam68 to novel nuclear structures in cancer cell lines.

The GSG (GRP33, Sam68, GLD-1) domain is a protein module found in an expanding family of RNA-binding proteins. The numerous missense mutations identified genetically in the GSG domain support its physiological role. Although the exact function of the GSG domain is not known, it has been shown to be required for RNA binding and oligomerization. Here it is shown that the Sam68 GSG domain plays a role in protein localization. We show that Sam68 concentrates into novel nuclear structures that are predominantly found in transformed cells. These Sam68 nuclear bodies (SNBs) are distinct from coiled bodies, gems, and promyelocytic nuclear bodies. Electron microscopic studies show that SNBs are distinct structures that are enriched in phosphorus and nitrogen, indicating the presence of nucleic acids. A GFP-Sam68 fusion protein had a similar localization as endogenous Sam68 in HeLa cells, diffusely nuclear with two to five SNBs. Two other GSG proteins, the Sam68-like mammalian proteins SLM-1 and SLM-2, colocalized with endogenous Sam68 in SNBs. Different GSG domain missense mutations were investigated for Sam68 protein localization. Six separate classes of cellular patterns were obtained, including exclusive SNB localization and association with microtubules. These findings demonstrate that the GSG domain is involved in protein localization and define a new compartment for Sam68, SLM-1, and SLM-2 in cancer cell lines.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Influence of light intensity on methanotrophic bacterial activity in Petit Saut Reservoir, French Guiana.

One year after impoundment in January 1994, methanotrophic bacteria in Petit Saut Reservoir (French Guiana) were active at the oxic-anoxic interface. This activity was revealed by the sudden extinction of diffusive methane emission (600 metric tons of CH4. day-1 for the whole lake surface area, i.e., 360 km2). Lifting of inhibition was suspected. After reviewing the potential inhibitors of this physiological guild (O2, NH4+, sulfides) and considering the similarities with nitrifiers, we suggest that sunlight influenced the methanotrophic bacteria. On the basis of phospholipid analysis, only a type II methanotrophic community was identified in the lake. Both growth and methanotrophic activity of an enriched culture, obtained in the laboratory, were largely inhibited by illumination over 150 microeinsteins. m-2. s-1. These results were confirmed on a pure culture of Methylosinus trichosporium OB3B. In situ conditions showed that water transparency was quite stable in 1994 and 1995 and that the oxycline moved steadily deeper until January 1995. Considering the mean illumination profile during this period, we showed that removal of methanotrophic growth inhibition could only occur below a 2-m depth. The oxycline reached this level in October 1994, allowing methanotrophic bacteria to develop and to consume the entire methane emission 4 months later.

Journal Article↗
PubMed1999

Pharmacological manipulation of Ins(1,4,5)P3 signaling mimics preconditioning in rabbit heart.

Recent evidence revealed biphasic alterations in myocardial concentrations of the second messenger inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3] with ischemic preconditioning (PC), i.e., increase during brief PC ischemia and decrease early during sustained test occlusion. Our aim was to determine whether an agonist and an antagonist of Ins(1,4,5)P(3) signaling (D-myo-inositol-1,4,5-trisphosphate hexasodium salt [D-myo-Ins(1,4, 5)P3] and 2-aminoethoxydiphenyl borate (2-APB), respectively), given such that they mimic this biphasic profile, would mimic infarct size reduction with PC. To test this concept, isolated, buffer-perfused rabbit hearts received no intervention (control), ischemic PC, D-myo-Ins(1,4,5)P3, D-myo-Ins(1,4,5)P(3) + PC, 2-APB, or 2-APB + PC. All hearts then underwent 30-min coronary occlusion and 2 h reflow, and infarct size was delineated by tetrazolium staining. In addition, the effects of D-myo-Ins(1,4,5)P3 and 2-APB on Ins(1,4,5)P3 signaling were evaluated in isolated fura 2-loaded rat cardiomyocytes. Mean infarct size was reduced with PC and in all D-myo-Ins(1,4,5)P3- and 2-APB-treated groups versus control (59 and 42-55%, respectively, vs. 80% of myocardium at risk, P < 0.05). Thus pharmacological manipulation of Ins(1,4,5)P3 signaling mimics the cardioprotection achieved with ischemic PC in rabbit heart.

Animals↗
PubMed1999

Pharmacological properties of trimebutine and N-monodesmethyltrimebutine.

Trimebutine [2-dimethylamino-2-phenylbutyl-3,4,5-trimethoxybenzoate hydrogen maleate (TMB)] has been demonstrated to be active for relieving abdominal pain in humans. To better understand its mechanism of action, we have tested TMB; nor-TMB, its main metabolite in humans; and their respective stereoisomers for their affinity toward sodium channels labeled by [3H]batrachotoxin, their effect on sodium, potassium, and calcium currents in rat dorsal root ganglia neurons, and their effect on veratridine-induced glutamate release from rat spinal cord slices. TMB has also been tested in an animal model of local anesthesia. TMB (Ki = 2.66 +/- 0.15 microM) and nor-TMB (Ki = 0.73 +/- 0.02 microM) displaced [3H]batrachotoxin from its binding site with affinities similar to that of bupivacaine (Ki = 7.1 +/- 0.9 microM). nor-TMB was found to block veratridine-induced glutamate release with an IC50 value of 8.5 microM, which is very similar to that of bupivacaine (IC50 = 8.2 microM); the effect of TMB was limited to 50% inhibition at 100 microM. TMB and nor-TMB blocked sodium currents in sensory neurons from rat dorsal root ganglia (IC50 = 0.83 +/- 0.09 and 1.23 +/- 0.19 microM, respectively), whereas no effect was observed on calcium currents at the same concentrations. A limited effect was observed on potassium currents (IC50 = 23 +/- 6 at 10 microM) for TMB. In vivo, when tested in the rabbit corneal reflex, TMB displayed a local anesthetic activity 17-fold more potent than that of lidocaine.

Animals↗
PubMed1999

[Apoptosis and gamma rays].

Gamma radiation can induce cell death in lymphocytes. Apoptosis is characterized by numerous morphological, biochemical and molecular modifications measurable using various methods. Some radioprotectors have antioxidant properties and are able to inhibit radiation-induced DNA fragmentation and caspase activation. There are several caspases that cleave proteolytically many proteins and trigger phosphatidylserine externalization recognized by phagocytes. Three main proteins are involved in the regulation of radiation-induced apoptosis: p53, Fas and Bcl-2. The pharmacological regulation of cell death is discussed in order to investigate the subsequent effects related to cell regeneration following radiation injury.

Animals↗
PubMed1999

[Renal cell carcinoma in a 14-year-old girl with Von Hippel Lindau disease].

We report a new case of renal cancer in the context of Von Hippel Lindau (VHL) disease in a 14-year-old girl. To our knowledge, this is the youngest case reported in the literature. VHL disease is now well known and its prognosis is related to renal cancer, which occurs very early in the patient's life, requiring adequate surveillance of patients carrying the VHL gene to ensure early diagnosis of the cancer, screening of family members and treatment, preferably conservative when permitted by the size and number of tumours, in these patients who are predisposed to developing other renal tumours, in order to delay bilateral nephrectomy and the need for dialysis or even transplantation, to a maximum.

Adolescent↗
PubMed1998

Mouse 5-HT2B receptor-mediated serotonin trophic functions.

5-HT2B receptors, in addition to phospholipase C stimulation, are able to trigger activation of the proto-oncogene product p21ras. During mouse embryogenesis, a peak of 5-HT2B receptor expression is detected at the neurulation stage; we localized the 5-HT2B expression in neural crest cells, heart myocardium, and somites. The requirement for functional 5-HT2B receptors shortly after gastrulation, is supported by culture of embryos exposed to 5-HT2B-high affinity antagonist such as ritanserin, which induces morphological defects in the cephalic region, heart and neural tube. Functional 5-HT2B receptors are also expressed during the serotonergic differentiation of the mouse F9 teratocarcinoma-derived clonal cell line 1C11. Upon 2 days of induction by cAMP, 5-HT2B receptors become functional, and on day 4, the appearance of 5-HT2A receptors coincides with the onset of active serotonin transporter by these cells. Active serotonin uptake is modulated by serotonin suggesting autoreceptor functions for 5-HT2B receptors.

Animals↗
PubMed1998

The identification of two Drosophila K homology domain proteins. Kep1 and SAM are members of the Sam68 family of GSG domain proteins.

Sam68 is a member of a growing family of RNA-binding proteins that contains an extended K homology (KH) domain embedded in a larger domain called the GSG (GRP33, Sam68, GLD1) domain. To identify GSG domain family members, we searched data bases for expressed sequence tags encoding related portions of the Sam68 KH domain. Here we report the identification of two novel Drosophila KH domain proteins, which we termed KEP1 (KH encompassing protein) and SAM. SAM bears sequence identity with mammalian Sam68 and may be the Drosophila Sam68 homolog. We demonstrate that SAM, KEP1, and the recently identified Drosophila Who/How are RNA-binding proteins that are able to self-associate into homomultimers. The GSG domain of KEP1 and SAM was necessary to mediate the RNA binding and self-association. To elucidate the cellular roles of these proteins, SAM, KEP1, and Who/How were expressed in mammalian and Drosophila S2 cells. KEP1 and Who/How were nuclear and SAM was cytoplasmic. The expression of KEP1 and SAM, but not Who/How, activated apoptotic pathways in Drosophila S2 cells. The identification of KEP1 and SAM implies that a large GSG domain protein family exists and helps redefine the boundaries of the GSG domain. Taken together, our data suggest that KEP1 and SAM may play a role in the activation or regulation of apoptosis and further implicate the GSG domain in RNA binding and oligomerization.

Alternative Splicing↗
PubMed1998

Mexoryl SX: a broad absorption UVA filter protects human skin from the effects of repeated suberythemal doses of UVA.

There is now considerable evidence that chronic UVA exposure induces damage in animal and human skin; however, little is known about UVA protection of human skin. The aim of this study is to evaluate the efficacy of Mexoryl SX, a broad UVA absorber (lamada max = 345 nm) against UVA-induced changes in human skin. The regimen of UVA exposure (13 weeks with increasing suberythemal doses) induces intense pigmentation with no erythema. Skin hydration and elasticity decrease, whereas total skin thickness, assessed by echography, remains unchanged. Irradiated epidermis reveals a significant thickening of the stratum corneum, an absence of hyperplasia and an increase in the expression of the protective iron-storage protein ferritin. No significant alterations are seen using antisera against type IV collagen or laminin, suggesting that the dermal-epidermal junction (DEJ) is mainly preserved. In dermis, enhanced expression of tenascin is seen just below the DEJ but type I procollagen, which is localized at the same site, is unaltered. Although we are unable to visualize any changes in elastic network organization using Luna staining or specific antiserum directed against human elastin, we notice an increased deposition of lysozyme or alpha-1 antitrypsin on elastin fibres. Mexoryl SX (5%) efficiently prevents these alterations. Thus, these results suggest that UVA photoprotection can prevent early putative alterations leading to photoageing.

Adult↗
PubMed1998

Protein hydration in solution: experimental observation by x-ray and neutron scattering.

The structure of the protein-solvent interface is the subject of controversy in theoretical studies and requires direct experimental characterization. Three proteins with known atomic resolution crystal structure (lysozyme, Escherichia coli thioredoxin reductase, and protein R1 of E. coli ribonucleotide reductase) were investigated in parallel by x-ray and neutron scattering in H2O and D2O solutions. The analysis of the protein-solvent interface is based on the significantly different contrasts for the protein and for the hydration shell. The results point to the existence of a first hydration shell with an average density approximately 10% larger than that of the bulk solvent in the conditions studied. Comparisons with the results of other studies suggest that this may be a general property of aqueous interfaces.

Escherichia coli↗
PubMed1998

Germline mutation profile of the VHL gene in von Hippel-Lindau disease and in sporadic hemangioblastoma.

von Hippel-Lindau (VHL) disease is a dominantly inherited disorder predisposing those afflicted to hemangioblastomas of the central nervous system and the retina, renal cell carcinomas, pheochromocytomas, and pancreatic tumors. The disease has been associated with mutations of the VHL gene. The screening of 92 unrelated patients with VHL disease for point mutations in this gene revealed 61 DNA variants. In addition, a search for EcoR1 rearrangements revealed germline anomalies in 5 patients. The 61 variants could be subdivided in 20 mutations predicted to alter the open reading frame (8 nonsense mutations, 8 frame shift mutations, and 4 mutations in consensus splicing sites) and 43 DNA sequence variants of a priori unknown biological consequence (4 in-frame insertions or deletions, 36 missense mutations, and 3 apparently silent variations). The 3' end of the coding sequence of the VHL gene, which encodes the Elongin binding domain was the site of 5 of 20 truncating mutations (25%) and of 18 of 41 DNA variants (44%) causing uncertain functional impairment. A similar screening in 18 patients with sporadic hemangioblastoma revealed 2 missense DNA variants. In order to corroborate this latter observation, a systematic screening for germline alteration of the VHL gene might be performed in a larger series of sporadic hemangioblastoma. If this preliminary result is confirmed, more than 10% of sporadic hemangioblastoma might be related to a mild VHL disease, thus a follow-up program similar to that recommended in cases of VHL disease should probably be discussed in the corresponding families.

Adult↗
PubMed1998

Heart rate as a determinant of L-type Ca2+ channel activity: mechanisms and implication in force-frequency relation.

Early studies in enzymatically isolated animal cardiomyocytes indicated that voltage-gated "L-type" Ca2+ currents (ICaL) can be upregulated following an increase of the frequency of activation. Recently, we evidenced a similar regulation of ICaL in human cardiomyocytes from both left and right ventricles and atria over a physiopathological range of stimulations (between 0.5 and 5 Hz). This regulation, enhanced by the beta-adrenergic stimulation, may be involved in the frequency-dependent potentiation of cardiac contractile force in the human healthy myocardium. We show here that the frequency-dependent regulation of ICaL is controlled by the level of phosphorylation, as well as dephosphorylation, of the Ca2+ channels. It was enhanced following activation of the protein kinase A activated by intracellular cyclic AMP (cAMP). Therefore, we anticipate that all agents stimulating cAMP production will favor this process, which was demonstrated here by activating 5HT-4 receptors using serotonin. Alternatively, it was also enhanced by the phosphatase inhibitor okadaic acid which prevents Ca2+ channels dephosphorylation. Alteration or abnormal modulation by beta-adrenergic receptor stimulation of the frequency-dependent facilitation of ICaL may partly explain the altered force-frequency relation described in heart failure.

Biomechanical Phenomena↗