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Biomedical subjects

E Vincent

Publications and source records attributed to E Vincent.

At least 19 recordsLinked to original sources
PubMed2000

The Arabidopsis AtEPR1 extensin-like gene is specifically expressed in endosperm during seed germination.

Screening of 10 000 Arabidopsis transgenic lines carrying a gene-trap (GUS) construct has been undertaken to identify markers of seed germination. One of these lines showed GUS activity restricted to the endosperm, at the micropylar end of the germinating seed. The genomic DNA flanking the T-DNA insert was cloned by walking PCR and the insertion was shown to be located 70 bp upstream of a 2285 bp open reading frame (AtEPR1) sharing strong similarities with extensins. The AtEPR1 open reading frame consists of 40 proline-rich repeats and is expressed in both wild-type and mutant lines. The expression of the AtEPR1 gene appears to be under positive control of gibberellic acid, but is not downregulated by abscisic acid during seed germination. No expression was detected in organs other than endosperm during seed germination. The putative role of AtEPR1 is discussed in the light of its specific expression in relation to seed germination.

Amino Acid Sequence↗
PubMed1999

Membrane topography of the renal phosphate carrier NaPi-2: limited proteolysis studies.

The rat sodium/phosphate cotransporter NaPi-2 is a 70 kDa polypeptide (p70) for which eight transmembrane segments have been predicted. We have shown that p70 exists predominantly as p45 and p40 fragments which are linked by disulfide bonds. In this work, the p40 fragment, corresponding to the C-terminus of NaPi-2, was purified from renal brush-border membranes using non-reducing and then reducing column electrophoresis followed by enzymatic deglycosylation and SDS-PAGE. The N-terminal sequence obtained for this fragment, VEAIG, indicates that the formation of p45 and p40 arises from the cleavage of p70 between arginine-319 and valine-320. In order to determine the membrane topography of NaPi-2, brush-border membrane vesicles were digested with various proteases and the transporter-derived proteolytic peptides were subsequently identified by Western blotting using N- and C-terminal-directed antibodies. Our results lead us to propose an alternative topographical model in which p45 and p40 possess three transmembrane domains each and indicate that the processing site of p70 for the generation of p45 and p40 is localized in a large protein core facing the extracellular milieu. This localization of the cleavage site indicated that NaPi-2 could either be processed intracellularly by vesicular proteases or extracellularly by secretory proteases or by brush-border membrane ectoenzymes.

Animals↗
PubMed1999

[Ataxic hemiparesis due to lacunar infarct].

Ataxic hemiparesis is a syndrome in which pyramidal and cerebellar signs occur on the same side. Few authors have suggested that signs or symptoms can orientate toward a supratentorial or toward an infratentorial lesion. We have studied the risk factors and the clinical symptoms of 61 patients consecutively admitted for an ataxic hemiparesis due to a lacunar infarct diagnosed with MRI. The MRI was normal in 2 cases. A tandem lacunar infarct was found in 9 cases (pons and internal capsule in 5 cases, pons and corona radiata in 4 cases) and a clinico-radiological correlation was performed in 50 cases. The comparison of risk factors did not show any difference between the infratentorial (n = 10) and the supratentorial groups (n = 40) excepting for the history of coronary disease. The history of coronary disease was statistically more frequent in the infratentorial group. No difference was found for clinical findings between the 2 groups.

Aged↗
PubMed1999

[Angina-like chest pain and exertional esophageal ph monitoring].

OBJECTIVES: Spontaneous chest pain attacks are uncommon during 24-hour esophageal pH monitoring in patients suffering from angina-like chest pain suspected to be acid-related. The aim of this study was to assess the diagnostic value of exertional esophageal pH monitoring and to prove that exercise testing induces chest pain and gastro-esophageal reflux and therefore improves symptomatic correlation study. METHODS: Forty three patients suffering from angina-like chest pain underwent treadmill exercise testing during a 24-hour esophageal pH monitoring. Symptom analysis was made using the symptom-association probability described by Weusten. RESULTS: During the 24-hour pH monitoring, 10 patients (23%) had a pathologic esophageal acid exposure, 20 (46%) experienced chest pain and 3 (7%) had a symptom association probability > 95%. During the exercise testing on a treadmill, 19 patients (44%) had gastro-esophageal reflux, and 14 (32%) experienced chest pain, coinciding with a gastro-esophageal reflux in 8 (19%). After exercise testing, the symptom-association probability analysis was significantly changed in 9 patients (21%), > 95% in 6 patients (14%). CONCLUSION: Exercise testing on a treadmill induces chest pain episodes during a 24-hour esophageal pH monitoring and therefore improves symptomatic correlation study in patients suffering from angina-like chest pain.

Adult↗
PubMed1997

Insolation cycles as a major control of equatorial indian ocean primary production

Analysis of a continuous sedimentary record taken in the Maldives indicates that strong primary production fluctuations (70 to 390 grams of carbon per square meter per year) have occurred in the equatorial Indian Ocean during the past 910,000 years. The record of primary production is coherent and in phase with the February equatorial insolation, whereas it shows diverse phase behavior with delta18O, depending on the orbital frequency (eccentricity, obliquity, or precession) examined. These observations imply a direct control of productivity in the equatorial oceanic system by insolation. In the equatorial Indian Ocean, productivity is driven by the wind intensity of westerlies, which is related to the Southern Oscillation; therefore, it is suggested that a precession forcing on the Southern Oscillation is responsible for the observed paleoproductivity dynamics.

Journal Article↗
PubMed1997

Involvement of disulphide bonds in the renal sodium/phosphate co-transporter NaPi-2.

The rat renal brush border membrane sodium/phosphate co-transporter NaPi-2 was analysed in Western blots with polyclonal antibodies raised against its N-terminal and C-terminal segments. Under reducing conditions, proteins of 45-49 and 70-90 kDa (p45 and p70) were detected with N-terminal antibodies, and proteins of 40 and 70-90 kDa (p40 and p70) were detected with C-terminal antibodies. p40 and p45 apparently result from a post-translational cleavage of NaPi-2 but remain linked through one or more disulphide bonds. Glycosidase digestion showed that both polypeptides are glycosylated; the cleavage site could thus be located between Asn-298 and Asn-328, which have been shown to constitute the only two N-glycosylated residues in NaPi-2. In the absence of reducing agents, both N-terminal and C-terminal antibodies detected p70 and a protein of 180 kDa (p180), suggesting the presence of p70 dimers. Much higher concentrations of beta-mercaptoethanol were required to produce a given effect in intact membrane vesicles than in solubilized proteins, indicating that the affected disulphide bonds are not exposed at the surface of the co-transporter. Phosphate transport activity decreased with increasing concentrations of reducing agents [beta-mercaptoethanol, dithiothreitol and tris-(2-carboxyethyl)phosphine] and was linearly correlated with the amount of p180 detected. The target sizes estimated from the radiation-induced loss of intensity of p40, p70 and p180 were all approx. 190 kDa, suggesting that NaPi-2 exists as an oligomeric protein in which the subunits are sufficiently close to one another to allow substantial energy transfer between the monomers. When protein samples were pretreated with beta-mercaptoethanol [2.5% and 5% (v/v) to optimize the detection of p40 and p70] before irradiation, target sizes estimated from the radiation-induced loss of intensity of p40 and p70 were 74 and 92 kDa respectively, showing the presence of disulphide bridges in the molecular structure of NaPi-2.

Animals↗
PubMed1996

Phosphate deprivation induces overexpression of two proteins related to the rat renal phosphate cotransporter NaPi-2.

Polyclonal antibodies were raised in rabbits against the C-terminal portion of the rat renal brush-border membrane sodium/phosphate cotransporter NaPi-2. Antibody specificity and molecular sizes of proteins related to NaPi-2 were assayed by Western blot analysis. Proteins of 40 and 70-75 kDa (p40 and p70) were immunodetected in rat and mouse brush-border membranes and proteins of 72 and 82 kDa were detected in rabbit. The absence or presence of beta-EtSH in the samples before electrophoresis greatly influenced the immunodetection profile of the rat proteins. Since the 40 kDa protein (p40) can only be detected under reducing conditions, it probably originates from reduction of disulfide bonds in p70. Tryptic cleavage of p40 and p70 revealed identical protein fragments showing the close structural identity of those proteins. Both proteins were more abundant in the outer cortex portion of the rat kidney than in the juxtamedullary portion. Furthermore, rats fed a low-phosphate diet for 24 h showed a 20- and 14-fold increase in the amount of p40 and p70, respectively, compared to control rats, showing that the adaptation to P(i) deprivation by increasing renal phosphate reabsorption is not only the result of overproduction of p70, as previously shown, but is also due to the novel p40 which most probably derives from p70.

Amino Acid Sequence↗
PubMed1996

Inhibition of Na+/H+ exchanger activity by an alkyl-lysophospholipid analogue in a human breast cancer cell line.

The mechanisms by which ET-18-OCH3 (1-O-octadecyl-2-O-methyl-sn-glycero-3 -phosphocholine) and other analogues of alkyl-lysophospholipids exert their antineoplastic effects are not yet fully elucidated. Possible interference with mechanisms involving intracellular pH (pHi) regulation was examined by measuring the effect of ET-18-OCH3 on the activity of the Na+/H+ exchanger in the breast cancer-derived cell line MCF-7. When ET-18-OCH3 was added to culture medium at 10 muM (determined as a noncytotoxic but cytostatic concentration), it led to an intracellular acidification (0.15 pH unit). It also decreased the rate of pHi recovery by Na+/H+ exchange following artificial acidification. Kinetic parameters of the exchange indicated that this was due to a decrease in the affinity of the exchanger for both transported ions, rather than to a decrease in the number of exchanger proteins in the membrane (same maximal efflux rate for treated and untreated cells). These results suggest that Na+/H+ exchanger inhibition and subsequent cytoplasmic acidification participate in the mode of action of ET-18-OCH3, and could be used for modulation of tumor-cell chemosensitivity or their subsequent commitment into programmed cell death.

Antineoplastic Agents↗
PubMed1995

Personal name anomia: a single case study.

A case presenting an anomia specific for person proper names but no naming impairment either for other types of proper names or for common names is reported. The deficit was equally present both in face-naming and in naming upon definition and was not affected by the descriptiveness of the labels borne by the individuals. The patient had no semantic processing impairment either for faces or names. The results are discussed in terms of impaired access to intact phonological representations.

Anomia↗
PubMed1990

[Tumor markers in liver metastases of colorectal carcinoma].

Colorectal cancer is a potentially curable tumour when diagnosed in the early stages. In order to improve the results obtained up to now, we propose application of a diagnostic program among patients who undergo curative resection for colorectal adenocarcinoma, which would consist of using a panel of tumor markers, in combination with endoscopic, histologic and ultrasonographic diagnostic methods. For this study we studied 105 patients, divided into two groups: A) Group 1: 30 control patients. B) Group 2: 75 patients diagnosed as having colorectal cancer. We performed the preoperative determination of a series of tumor markers (CEA, CA 19.9, GGT and PHI), endoscopy/biopsy and hepatic ultrasonography on these patients. Our results suggest that the design of the preoperative diagnostic program makes early detection of hepatic metastases possible. The tumor marker panel combination provided a visible increase in sensitivity for detecting hepatic metastases.

Adenocarcinoma↗