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B Colas

Publications and source records attributed to B Colas.

At least 19 recordsLinked to original sources
PubMed2004

[Phosphotyrosine phosphatase SHP-1, somatostatin and prostate cancer].

We review the mechanisms involved in prostatic growth based on androgens and product of neuroendocrine secretion, with special reference to the role of somatostatin (SS) in the inhibition of neoplastic growth. Our contributions in the field confirm the antiproliferative effect of SS on the prostate is mediated by phosphotyrosine phosphatase SHP-1, that is present in human prostate. This enzyme plays a role in the control of prostatic cell proliferation and in the progression of prostate cancer. Besides, we consider its presence may determine the therapeutic potential of SS in the control of prostate cancer.

Biomedical Research↗
PubMed2004

Fine-scale genetic structure and gene dispersal in Centaurea corymbosa (Asteraceae) I. Pattern of pollen dispersal.

Pollen dispersal was characterized within a population of the narrowly endemic perennial herb, Centaurea corymbosa, using exclusion-based and likelihood-based paternity analyses carried out on microsatellite data. Data were used to fit a model of pollen dispersal and to estimate the rates of pollen flow and mutation/genotyping error, by developing a new method. Selfing was rare (1.6%). Pollen dispersed isotropically around each flowering plant following a leptokurtic distribution, with 50% of mating pairs separated by less than 11 m, but 22% by more than 40 m. Estimates of pollen flow lacked precision (0-25%), partially because mutations and/or genotyping errors (0.03-1%) could also explain the occurrence of offspring without a compatible candidate father. However, the pollen pool that fertilized these offspring was little differentiated from the adults of the population whereas strongly differentiated from the other populations, suggesting that pollen flow rate among populations was low. Our results suggest that pollen dispersal is too extended to allow differentiation by local adaptation within a population. However, among populations, gene flow might be low enough for such processes to occur.

Centaurea↗
PubMed2003

Improvement of rheological properties of firm acid gels by skim milk heating is conserved after stirring.

The enhancement of the strength of set acid gels by heating milk was related to rheological parameters (water retention capacity, storage modulus) of corresponding stirred gels. To obtain accurate rheological data from stirred gel it was necessary to maintain a constant granulometry of gel particles and to recognize time after stirring as a contributing factor. Two hours after stirring, the gel exhibited a higher storage modulus when milk was heated above 80 degrees C. A measurement of viscosity of just-stirred yoghurt was sufficient to predict correctly the quality of a stirred gel analysed by viscoelastic measurements. Increased resistance to syneresis of just-stirred gels was related to higher viscosity. The quantity of beta-lactoglobulin (beta-Ig) bound to casein micelles explains the improvement of these gel qualities. We have considered that the structure of the initial firm gel (mesostructure level) was conserved in fragments within the stirred gel. Consequently, the explanation given by various authors for the effect of heating milk on the properties of set gels can also be applied to stirred gels. The same mechanism, described in literature for structure formation of set gels from acidified milk is purposed to explain the role of heating milk on the recovery of gel structure after stirring. The beta-Ig association with casein micelles during heating favoured micelle connections during the acidification. It also favoured the association of gel fragments after stirring during the recovery in gel structure.

Animals↗
PubMed2002

Effect of linsidomine on the human radial artery.

The response of the human radial artery to a direct NO donor, linsidomine or 3-morpholino-sydnonimine (Sin 1), in the therapeutic management of peri-operative spasm may increase the patency rates of these grafts in the short, medium and long term. Evaluation of the effects of Sin 1 on the human radial artery is of even greater interest as it has not been published previously. Ninety-six human radial artery rings were studied with two protocols. Rings were mounted in an isolated organ bath between two stainless steel metallic rods connected to stress gauges. Protocol 1 studied the vasorelaxant effect of Sin 1 and nitroglycerin (TNT). Protocol 2 studied the reactivity of the radial artery to the vasoconstrictor agents arginine vasopressin (AVP) and angiotensin II (ANG II). The vasorelaxant effect of Sin 1 on the human radial artery was comparable with that of TNT, but with no tolerance effect. After Sin 1 pre-incubation, the vasoconstrictor effect of ANG II was abolished, whereas AVP induced maximum vasoconstriction similar to that of the control (not statistically significant), but with a shift in the EC50 to higher concentrations, EC50=15+/-20 nM. Sin 1 vasorelaxation of rings precontracted by ANG II was maximal, whereas after contraction by AVP, relaxation remained less than 70%; Sin 1 is a potent vasorelaxant on the human radial artery, which does not exhibit cross-tolerance with nitrates. This compound may be used pre- or post-operatively, and would undoubtedly be of benefit in the peri-operative preparation bath.

Angiotensin II↗
PubMed2001

Synthesis of beta-D-glucosyl- and beta-D-fucosyl-glucoses using beta-glycosidase from Thermus thermophilus.

The thermostable beta-glycosidase from Thermus thermophilus, cloned and overexpressed in Escherichia coli was used to catalyze the transfer of beta-D-glucosyl and beta-D-fucosyl from the corresponding p-nitrophenyl-beta-D-glycopyranosides to a hydroxyl group of glucose in the synthesis of beta-D-glucosyl-D-glucopyranoses and beta-D-fucosyl-D-glucopyranoses. The yields in disaccharides produced under conditions of non-initial velocity were very attractive and the formation of the beta(1-3) linked disaccharides was largely favored. The enzyme could constitute a valuable biocatalyst for the synthesis of disaccharides involving such structures as, for example, Bifidus factors.

Disaccharides↗
PubMed2001

Direct vascular actions of methyclothiazide in remodeled mesenteric arteries from hypertensive patients.

In vitro experiments were designed to assess the inhibitory effect of the thiazide diuretic methyclothiazide (MCTZ) on contractile responses to norepinephrine (NE) of mesenteric rings from hypertensive patients and normotensive controls. Arteries were taken from portions of mesocolon from 24 patients: 13 hypertensives and 11 normotensives. Changes in the tension of mesenteric ring preparations were measured isometrically. Histologic studies showed that the arteries from hypertensive patients exhibited 1) a greater media thickness-to-lumen diameter ratio, 2) a smaller lumen diameter, and 3) identical media cross-sectional area as those of normotensive controls. At the physiologic level, the hypertensive and normotensive arteries display similar contractile responses to KCl and NE. Furthermore, our results indicate that MCTZ induces concentration-dependent inhibition of the vasoconstrictor responses to NE. This study provides evidence that hypertension is associated with the remodeling of the human mesenteric artery and that MCTZ is as efficient in inhibiting the contractile response induced by NE on hypertensive than on normotensive arteries.

Adult↗
PubMed2000

Mechanisms of methyclothiazide-induced inhibition of contractile responses in rat aorta.

Methyclothiazide (MCTZ), a thiazide diuretic, inhibits the contractile response induced by norepinephrine in aortic rings from 12-week-old spontaneously hypertensive rats (SHR). Although not modified by indomethacin, this inhibition was attenuated by either mechanical removal of the endothelium or N omega-nitro-L-arginine (NOLA) treatment. These results suggest that the MCTZ effects on the norepinephrine-evoked vascular response are mediated by an endothelium-dependent mechanism involving endothelium-dependent relaxing factor (EDRF)/nitric oxide (NO) release. MCTZ was also found to alter the contractile response induced by the addition of Ca(2+) to a depolarizing solution, and this inhibitory effect was partially abolished by NOLA application. Our data led us to propose that MCTZ relaxes aortic rings, resulting in an endothelium-dependent relaxation phenomenon that could even be reinforced under high-K(+) depolarizing conditions.

Animals↗
PubMed2000

Kinetic study of a thermostable beta-glycosidase of Thermus thermophilus. Effects of temperature and glucose on hydrolysis and transglycosylation reactions.

A beta-glycosidase of a thermophile, Thermus thermophilus, belonging to the glycoside hydrolase family 1, was cloned and overexpressed in Escherichia coli. The purified enzyme (Ttbetagly) has a broad substrate specificity towards beta-D-glucoside, beta-D-galactoside and beta-D-fucoside derivatives. The thermostability of Ttbetagly was exploited to study its kinetic properties within the range 25-80 degreesC. Whatever the temperature, except around 60 degreesC, the enzyme displayed non-Michaelian kinetic behavior. Ttbetagly was inhibited by high concentrations of substrate below 60 degreesC and was activated by high concentrations of substrate above 60 degreesC. The apparent kinetic parameters (kcat and Km) were calculated at different temperatures. Both kcat and Km increased with an increase in temperature, but up to 75 degreesC the values of kcat increased much more rapidly than the values of Km. The observed kinetics might be due to a combination of factors including inhibition by excess substrate and stimulation due to transglycosylation reactions. Our results show that the substrate could act not only as a glycosyl donor but also as a glycosyl acceptor. In addition, when the glucose was added to reaction mixtures, inhibition or activation was observed depending on both substrate concentration and temperature. A reaction model is proposed to explain the kinetic behavior of Ttbetagly. The scheme integrates the inhibition observed at high concentrations of substrate and the activation due to transglycosylation reactions implicating the existence of a transfer subsite.

Enzyme Stability↗
PubMed2000

[Effect of methyclothiazide on the entry of calcium into vascular smooth muscle cells].

The possible involvement of calcium and potassium channels in mediating the vascular actions of methyclothiazide (MCTZ), a thiazide diuretic, was investigated in isolated aortic rings from 12 week-old hypertensive rats. MCTZ (10(-4) M) inhibits the contractile response induced by addition of Ca2+ to a depolarizing solution, the maximal contracture is reduced by 87.16 +/- 6.4%. Furthermore this inhibitory effect was unaffected by charybdotoxine a selective blocker of calcium-activated K+ channels (Kca). This suggesting that MCTZ inhibits voltage-gated Ca2+ channels and blunts the Ca2+ entry into vascular smooth muscle cells. This inhibition was partially attenuated by either mechanical removal of the endothelium or N omega-nitro-L-arginine (NOLA) treatment, suggesting that MCTZ effects are also mediated by an endothelium-dependent mechanism involving endothelium-dependent relaxing factor (EDRF)/nitric oxide (NO) release. Taken together, these observations could point to a role of voltage-gated Ca2+ channels and endothelial release of EDRF/NO in the antihypertensive action of MCTZ.

Animals↗
PubMed1999

A novel endopeptidase with a strict specificity for threonine residues at the P1' position.

An endopeptidase was purified from Archachatina ventricosa by chromatography on columns of gel filtration, DEAE-Sepharose and phenyl-Sepharose. The preparation was shown to be homogeneous by polyacrylamide gel electrophoresis and capillary electrophoresis. The purified enzyme displayed two protein bands on SDS-polyacrylamide gel electrophoresis with estimated molecular weights of 90,000 and 121,000. The protease exhibited maximum proteolytic activity at 55 degrees C and at pH 8.0, but it retained more than 85% of its activity in the pH range 7.5 to 8.5. It was completely inactivated by the chelating agents EDTA and 1,10-phenanthroline which are metalloprotease inhibitors. Studies on substrate specificity showed that only the amide bonds of peptide substrates having a threonine residue at the P1' position were hydrolyzed by the purified protease. This endopeptidase constitutes a novel tool for the study of proteins in view of its narrow and unique substrate specificity.

Animals↗
PubMed1999

Cloning and expression of a beta-glycosidase gene from Thermus thermophilus. Sequence and biochemical characterization of the encoded enzyme.

A 3.2 kilobase pair DNA fragment from Thermus thermophilus HB27 coding for a beta-galactosidase activity was cloned and sequenced. A gene and a truncated open reading frame orf1 encoding respectively a beta-glycosidase (ttbeta-gly) and probably a sugar permease were located directly adjacent to each other. The deduced aminoacid sequence of the enzyme Ttbeta-gly showed strong identity with those of beta-glycosidases belonging to the glycosyl hydrolase family 1. The enzyme was overexpressed in Escherichia coli and was purified by a two-step purification procedure. The recombinant enzyme is monomeric with a molecular mass of 49-kDa. It catalyzes the hydrolysis of beta-D-galactoside, beta-D-glucoside and beta-D-fucoside derivatives. However, the kcat/Km ratio is much higher for p-nitrophenyl-beta-D-glucoside and p-nitrophenyl-beta-D-fucoside than for p-nitrophenyl-beta-D-galactoside. The specificity towards linkage positions of the disaccharides tested decreased in the following order: beta1-3 (100%) > beta1-2 (71%) > beta1-4 (40%) > beta1-6 (10%). Ttbeta-gly is a thermostable enzyme displaying an optimum temperature of 88 degrees C and a half life of 10 min at 90 degrees C. It performs transglycosylation reactions at high temperature with a yield exceeding 63% for transfucosylation reactions. On the basis of this work, the enzyme appears to be an attractive tool in the synthesis of fucosyl adducts and fucosyl sugars.

Amino Acid Sequence↗
PubMed1997

Characterization of a strictly specific acid beta-galactosidase from Achatina achatina.

An acid beta-galactosidase was isolated from the digestive juice of Achatina achatina and purified to homogeneity by anion exchange, gel-filtration and hydroxyapatite chromatographies. This enzyme is soluble, as are the cytosolic beta-galactosidases, functions at acid pH like the lysosomal enzymes but differs from the other soluble animal beta-galactosidases in that it is highly specific for the beta-D-galactosyl residue. In addition, it cleaves the beta1-4 linkage much faster than the beta1-3 and beta1-6 linkages. The enzyme is a monomeric glycoprotein with a molecular mass of 120-125 kDa and the carbohydrate moiety makes up approximately 6% (w/w) of the protein. The amino acid composition displays an important amount of acidic/amide and hydroxy amino acid residues and a low content of basic residues. The enzyme activity is markedly affected by the ionic strength of the medium and the rate-pH curve was shifted towards higher pH values in the presence of added salt. Acid beta-galactosidase is capable of catalysing transgalactosylation reactions. The yields of galactosylation of hydroxy amino acid derivatives, catalysed by the enzyme in the presence of lactose as the glycosyl donor, were higher than those reported previously with conventional sources of beta-galactosidases. In addition, the pH optimum is different for the hydrolysis (pH 3.2) and transgalactosylation (pH 5.0) reactions. On the basis of this work, the enzyme could be used as a tool in the structural analysis of D-galactose-containing oligosaccharide chains, as well as for the synthesis of glycoconjugates.

Amino Acids↗
PubMed1997

Centaurea corymbosa, a cliff-dwelling species tottering on the brink of extinction: a demographic and genetic study.

Centaurea corymbosa (Asteraceae) is endemic to a small area (< or = 3 km2), and < 500 individuals reproduce in any given year. Nevertheless, enzyme polymorphism was found within and among the six local extant populations, the most distant at 2.3 km. Levels of gene flow among populations and seed and pollen dispersal data indicated very low dispersal capacity. Rarity of long distance dispersal events coupled with traits such as prolonged juvenile period, monocarpy, and self-incompatibility precludes the establishment of new populations and thus the evolution toward colonization ability through increased dispersal rate, polycarpy, or self-compatibility. The species thus appears to be trapped on an evolutionary dead-end toward extinction, even though, from a preliminary introduction experiment, we conclude that several nearby unoccupied sites would be suitable for the species.

Biological Evolution↗
PubMed1996

Different sites of action of arachidonic acid on steroidogenesis in rat Leydig cells.

The present study in purified rat Leydig cells shows that arachidonic acid may act as an intratesticular factor regulating LH-mediated testicular steroidogenesis. Arachidonic acid decreased, in a dose-dependent manner, the LH-stimulated cAMP and testosterone levels, over 2 h incubation. Incubation of Leydig cells with arachidonic acid did not modify 125I-hCG binding to the cells as compared to control, showing that the action of arachidonic acid is not related to a decrease of hCG binding to the cells. Forskolin-stimulated cAMP and testosterone production were inhibited by 51.65 and 70.9%, respectively, in the presence of arachidonic acid (100 microM), although the ED50 for the diterpene was not changed. When isobutyl-methyl-xanthine was added to the incubation medium, the same percentage of inhibition was found indicating that arachidonic acid inhibition of cAMP production is not due to stimulation of Leydig cell phosphodiesterase activity. Pretreatment of the cells with pertussis toxin, to inactivate Gi, was also without effect on arachidonic acid inhibition of LH-stimulated cAMP production, but pertussis toxin abolished the inhibitory effects of arachidonic acid when adenylate cyclase was stimulated with forskolin. However, arachidonic acid addition resulted in inhibition of LH- and forskolin-stimulated testosterone production, even if the cells were pretreated with pertussis toxin. It can be concluded that: (1) The inhibitory effect of arachidonic acid is neither due to a decrease of hCG binding to Leydig cells nor to a stimulation of cell phosphodiesterase activity; (2) arachidonic acid modulates cAMP production at two different levels, either by activation of Gi protein and by inhibition of Gs protein or adenylate cyclase; (3) the effect of arachidonic acid on steroidogenesis is also beyond cAMP formation.

1-Methyl-3-isobutylxanthine↗
PubMed1996

Purification, kinetical and molecular characterizations of a serine collagenolytic protease from greenshore crag (Carcinus maenas) digestive gland.

A serine collagenolytic protease was purified from a water soluble fraction of greenshore crab digestive gland by acidic precipitation, gel filtration on a Sephadex G-50 column, ion-exchange chromatography on a Fractogel TSK DEAE column, immobilized metal ion affinity chromatography (IMAC) on IDA (Cu2+) Sepharose 6B and ion-exchange chromatography on Hyper D column. The molecular mass of the monomeric Carcinus serine collagenase (CSC) was estimated to be 23,000 by SDS PAGE and its isoelectric point was found to be 4.0. The CSC is optimally active at pH 7 and 30 degrees C and is stable over a month at room temperature. The CSC activity is strongly inhibited by PMSF, 3,4-DCI, soybean trypsin inhibitor, alpha 1 proteinase inhibitor and elastatinal. The CSC hydrolyzes native collagen (Type I and III). CSC N-terminal sequence is similar to shrimp chymotrypsin-like protease and crab collagenolytic protease sequences. Kinetic parameters of the CSC were determined using some peptidyl-p-nitroanilides. The catalytic efficiency (kcat/Km) is Leu > Phe > Ala.

Amino Acid Sequence↗
PubMed1996

Electrostatic interactions of the butyrylcholinesterase dimer of mucosal cells of rat intestine with glycosaminoglycans.

The G2 form of butyrylcholinesterase (BChE) of mucosal cells of rat intestine is a rare amphiphilic species, which is related to class II of acetylcholinesterase. Preliminary work indicated that the enzyme can bind heparin and suggested particular properties as compared to other BChEs. Ionic properties of the G2 form BChE were studied with different ionic exchangers. Heparin-Sepharose chromatography, nondenaturing electrophoresis and sucrose gradient centrifugation were used to study heparin interaction with the G2 form BChE. The enzyme structure was modified with reagents that react specifically with amino groups (p-hydroxyphenylglyoxal and 2,4,6-trinitrobenzene sulfonic acid). The G2 form was not retained by DEAE-cellulose which was generally used to isolate BChE from human serum, but was completely bound by strong cation exchanger (Dowex 50). Heparin-Sepharose quantitatively retained the enzyme which was partially eluted only by charged compounds. Nondenaturing gel electrophoresis showed a reduction in enzyme migration with increasing concentrations of heparin and chondroitin sulfate, but not with heparan sulfate. Triton X-100 dissociated the G2 form into monomers but failed to reverse the association between the enzyme and heparin. Reagents specific to amino groups indicated that arginine and lysine residues were involved in this association. In summary, these studies demonstrate that the ionic properties of the G2 form BChE are involved in the binding with heparin. Our results rule out the possibility of amphiphilic interactions in the formation of heparin-enzyme complex and indicate that amino groups are predominately involved in this association.

Animals↗
PubMed1996

Ultrastructural localization of butyrylcholinesterase in epithelial cells of rat intestine.

The present study reports the histochemical detection, at the ultrastructural level, of butyrylcholinesterase (BChE) in the epithelial cells of rat intestine. The enzyme activity was observed in the crypt cells as well as in the mature cells of the villi. Inside the enterocytes, BChE was seen in the reticulum cisternae, Golgi apparatus and lipid droplets. BChE was also detected in the Grünhagen spaces, associated with chylomicrons. In the intercellular spaces, at the level of the upper part of the cryptic epithelium, the enzyme was found from the base to the apex of the cells. The precise localization of BChE in the cellular structures noted suggests that its function could be related to lipid metabolism and/or cell renewal.

Animals↗