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M Roux

Publications and source records attributed to M Roux.

At least 37 records · Page 2Linked to original sources
PubMed1991

GTP hydrolysis mechanisms in ras p21 and in the ras-GAP complex studied by fluorescence measurements on tryptophan mutants.

We have substituted leucine 56 or tyrosine 64 of p21 ras with a tryptophan. The intrinsic fluorescence of this tryptophan was used as an internal conformational probe for time-resolved biochemical studies of the ras protein. The slow intrinsic GTPase, GDP/GTP exchange induced by the SDC25 "exchange factor", and the fast GTP hydrolysis induced by GAP were studied. Tryptophan fluorescence of mutated ras is very sensitive to magnesium binding, GDP/GTP exchange, and GTP hydrolysis (changes in tyrosine fluorescence of wild-type ras are also observed but with a lower sensitivity). Nucleotide affinities, exchange kinetics, and intrinsic GTPase rates of the mutated ras could be measured by this method and were found to be close to those of wild-type ras. The SDC25 gene product enhances GDP/GTP exchange in both mutants. In both mutants, a slow fluorescence change follows the binding of GTP gamma S; its kinetics are close to those of the intrinsic GTPase, suggesting that a slow conformational change precedes the GTPase and is the rate-limiting step, as proposed by Neal et al. (1990) (Proc. Natl. Acad. Sci. U.S.A. 87, 3562-3565). GAP interacts with both mutant ras proteins and accelerates the GTPase of (L56W)ras but not that of (Y64W)ras, suggesting a role for tyrosine 64 in GAP-induced GTP hydrolysis. However, GAP does not accelerate the slow conformational change following GTP gamma S binding in either of the mutated ras proteins. This suggests that the fast GAP-induced catalysis of GTP hydrolysis that is observed with (L56W)ras bypasses the slow conformational change associated with the intrinsic GTPase and therefore might proceed by a different mechanism.

Amino Acid Sequence↗
PubMed1991

31P-NMR study of pig intestinal brush-border membrane structure: effect of zinc and cadmium ions.

31P-NMR experiments on intact pig small intestine brush-border membrane vesicles (BBMV) and detergent-solubilized membranes gave direct insights into the organization of the phospholipids (PL) and their interaction with zinc and cadmium ions. Various endogenous PL were identified from well resolved BBM micelle spectra. These experiments revealed a strong interaction of Zn2+ and Cd2+ with the negatively charged phosphatidylinositol and phosphatidylserine. In BBM micelles, a progressive time-dependent PL degradation occurred in the absence of ions and indicated the presence of active phospholipases. The presence of zinc inhibited the degradation process whereas cadmium had the opposite influence. 31P spectra of BBMV were carefully characterized. Neither zinc nor cadmium affected the PL bilayer structural organization. A degradation of PL, monitored by the increase of the inorganic phosphate (Pi) signal, also occurred in vesicles but to a lesser extent than in micelles. A 2/3 internal, 1/3 external PL asymmetry was observed in the absence and presence of ions.

Animals↗
PubMed1991

Calcium binding by phosphatidylserine headgroups. Deuterium NMR study.

The binding of calcium to headgroup deuterated 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphoserine (POPS) was investigated by using deuterium magnetic resonance in pure POPS membranes and in mixed 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphocholine (POPC)/POPS 5:1 (m:m) bilayers. Addition of CaCl2 to pure POPS bilayers led to two component spectra attributed, respectively, to liquid-crystallin POPS (less than 15 kHz) and POPS molecules in the calcium-induced dehydrated phase (cochleate) (approximately 120 kHz). The liquid-crystalline component has nearly disappeared at a Ca2+ to POPS ratio of 0.5, indicating that, under such conditions, most of the POPS molecules are in the precipitated cochleate phase. After dilution of the POPS molecules in zwitterionic POPC membranes (POPC/POPS 5:1 m:m), single component spectra characteristic of POPS in the liquid-crystalline state were observed in the presence of Molar concentrations of calcium ions (Ca2+ to POPS ratio greater than 50), showing that the amount of dehydrated cochleate PS-Ca2+ phase, if any, was low (less than 5%) under such conditions. Deuterium NMR data obtained in the 15-50 degrees C temperature range with the mixed PC/PS membranes, either in the absence or the presence of Ca2+ ions, indicate that the serine headgroup undergoes a temperature-induced conformational change, independent of the presence of Ca2+. This is discussed in relation to other headgroup perturbations such as that observed upon change of the membrane surface charge density.

Calcium↗
PubMed1991

Influence of beta-blockade on circulating plasma levels of 3-methoxy-4-hydroxy phenylethylene glycol (MHPG) during exercise in moderate hypertension.

1. The effect of exercise testing and beta-blockade on plasma norepinephrine (PNE), and secretion of its metabolite 3-methoxy-4-hydroxyphenylethylene glycol (MHPG), was assessed in 28 mild-to-moderate hypertensives before and after the administration of dilevalol, a new beta-blocker with beta 2-agonism. 2. This double blind, placebo-controlled study consisted of two successive submaximal exercise tests before and after the administration of a single oral dose of dilevalol (200 mg, 400 mg or 600 mg). Plasma norepinephrine levels were determined at rest, at 100 watts step of exercise and at maximal effort (Emax). 3. During the control test, mean PNE levels increased from 1.73 +/- 0.52 nmol/L (resting value) to 8.01 +/- 4.01 nmol/L at Emax (P less than 0.01) as MHPG levels increased from 11.18 +/- 1.33 nmol/L (rest) to 17.50 +/- 1.15 nmol/L (Emax, P less than 0.01). After dilevalol, PNE increased significantly as compared to controls (P less than 0.05), from 2.32 +/- 0.99 to 12.42 +/- 5.97 nmol/L (P less than 0.01). PNE and MHPG levels were correlated, both at rest and during exercise. PNE levels after beta-blockade were linearly related to the dose of beta-blocker administered. MHPG levels were unaltered by the administration of dilevalol, both before and after exercise. 4. The increase in MHPG that occurs during bicycle exercise is largely generated from an increase in central nervous system noradrenergic activity. While dilevalol increases the peripheral sympathetic nervous system, both at rest and during exercise (which is reflected by increases in PNE levels) the drug does not alter resting central nervous system noradrenergic activity nor amplify the increase in central noradrenergic activity that occurs during exercise.

Adrenergic beta-Antagonists↗
PubMed1990

Ca2+, Mg2+, Li+, Na+, and K+ distributions in the headgroup region of binary membranes of phosphatidylcholine and phosphatidylserine as seen by deuterium NMR.

The binding of calcium, magnesium, lithium, potassium, and sodium to membrane bilayers of 5 to 1 (M/M) 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and 1-palmitoyl- 2-oleoylphosphatidylserine (POPS) was investigated by using deuterium nuclear magnetic resonance (2H NMR). Both lipids were deuteriated on their polar headgroups, and spectra were obtained at 25 degrees C in the liquid-crystalline phase as a function of salt concentration. The spectra obtained with calcium were correlated with 45CaCl2 binding studies to determine the effective membrane-bound calcium at low calcium binding, up to 0.78 calcium per POPS. Deuterium quadrupolar splittings of both POPC and POPS headgroups were shown to be very sensitive to calcium binding. The behavior of these two headgroups over a wide range of CaCl2 concentrations suggests that Ca2+ binding occurs in at least two steps, the first step being achieved with 0.5 M CaCl2, with a stoichiometry of 0.5 Ca2+ per POPS. Correlations of the deuterium Ca2+ binding data with related data obtained after incorporation of a cationic integral peptide showed that the effects of these two cationic molecules of the POPS headgroup are qualitatively similar, and provided further support for two-step Ca2+ binding to the POPC/POPS 5:1 membranes. The corresponding data obtained with magnesium, lithium, and potassium indicate that these cations interact with both the choline and serine headgroups. The amplitudes of headgroup perturbations could be partly correlated to the relative affinities of the metallic cations for the lipid membrane. The two-step binding described with Ca2+ appears to be relevant to the Mg2+ data, and in certain limits to the Li+ data. The data were interpreted in terms of conformational changes of the lipid headgroups induced by an electric field due to the charges of the membrane-bound metallic cations. A conformational change of the serine headgroup induced by the membrane-bound charges is proposed. We propose that the metallic cations can be differentiated on the basis of their respective spatial distribution functions relative to the choline and serine headgroups. According to this interpretation, the divalent cations Ca2+ and Mg2+ are more deeply buried in the membrane than monovalent Na+ and K+, the case of Li+ being intermediate of the latter two. This conclusion is discussed in relation to fundamental theories of the spatial distribution of ions near the interface between water and smooth charged solid surfaces.

Binding Sites↗
PubMed1990

Autoradiographic localization of [3H]oestradiol in epididymis, seminal vesicles and prostate of the fetal guinea-pig.

The selective uptake and localization of radioactivity in the fetal male reproductive organs (epididymis, seminal vesicles and prostate) of the guinea-pig (50-60 days of gestation) after in-vivo and in-situ subcutaneous injection of [3H]oestradiol was investigated by autoradiography. In 50-day-old fetuses, the different areas of the epididymis showed selective retention of radioactivity in the nuclei of peritubular and stromal cells surrounding the epididymal duct; no retention was observed in the epididymal epithelium. A similar distribution of silver grains was observed in the 60-day-old fetus. Seminal vesicles and prostate sections from both 50- and 60-day-old fetuses showed concentration and retention of radioactivity only in stromal cells, whereas the epithelium did not exhibit silver grains. In all the tissues studied, the nuclear labelling was abolished after injection of [3H]oestradiol plus a 100-fold excess of non-labelled oestradiol. As the mesenchyme surrounding the epithelia of the epididymis, seminal vesicles and prostate were labelled selectively with [3H]oestradiol, it is suggested that during fetal life of the guinea-pig the mesenchymal stroma of these fetal male reproductive organs may be considered as a target tissue for oestrogen.

Animals↗
PubMed1990

[Evaluation of the placebo effect on blood pressure profile during exercise in patients with mild uncomplicated hypertension].

UNLABELLED: The administration of placebo (pharmacologically inactive substance) is justified in clinical trials of antihypertensive drugs, in order to avoid the inclusion of placebo-responders. The evaluation of antihypertensive treatments during exercise is an interesting end point, since aerobic exercising is part of antihypertensive treatment. The aims of this study are to determine the placebo impact on blood pressure, heart rate and catecholamine secretion profiles during exercise testing. METHOD: 10 untreated essential mild to moderate hypertensives participated to a single blind study comprising two successive submaximal exercise testings (85% of maximal theoretical heart rate), separated by a single oral administration of placebo. Blood pressure and heart rate were measured after 10 minutes of resting position and at the end of each effort step (2 mm, 20 Watts), both before and after placebo. Blood samples (5 ml) were collected at rest and during maximal exercise before and after placebo, in order to determine the effect of placebo on circulating catecholamines. RESULTS: there was no significant variations between the "control" and exercise testings after placebo, neither on blood pressure or heart rate profiles, nor in values of circulating catecholamines [Noradrenaline at rest: 1.88 +/- 0.96, exercise: 6.43 +/- 1.93 nm/l before placebo, 1.65 +/- 0.83 nm/l and 5.71 +/- 2.12 nm/l after placebo respectively (NS)]. CONCLUSION: the placebo, which effect is generally determined on blood pressure at rest by sphygmomanometry, seems devoid of any activity on blood pressure, heart rate or catecholamine profile during exercise, in essential moderate hypertensives. Thus, antihypertensive treatments at exercise can be evaluated by comparison to baseline cardiovascular parameters without placebo groups.

Adult↗
PubMed1989

Conformational changes of phospholipid headgroups induced by a cationic integral membrane peptide as seen by deuterium magnetic resonance.

Deuterium nuclear magnetic resonance (2H NMR) was used to study the interaction of a cationic amphiphilic peptide with pure DMPC membranes and with mixed bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylserine (DMPS). The choline and serine headgroups were selectively deuteriated at the alpha and beta positions. The amphiphilic peptide, with 20 leucine residues in the hydrophobic core and two cationic hydrophilic lysine residues at each end, spanned the lipid bilayer. Although 2H NMR experiments using DMPC with perdeuteriated fatty acyl chains showed that the average order parameter of the hydrophobic region was not significantly modified by the incorporation of the amphiphilic peptide, for either DMPC or DMPC/DMPS (5:1) bilayers, large perturbations of the quadrupolar splittings of the choline and serine headgroups were observed. The results obtained with the DMPC headgroup suggest that the incorporation of the cationic peptide in both DMPC and DMPC/DMPS (5:1) bilayers leads to a structural perturbation directly related to the net charge on the membrane surface. The magnitude of the observed effect seems to be similar to those observed previously with other cationic molecules [Seelig, J., MacDonald, P.M., & Scherer, P.G. (1987) Biochemistry 26, 7535-7541]. Two of the three quadrupolar splittings of the PS headgroup exhibited large variations in the presence of the amphiphilic peptide, while the third one remained unchanged. Our data have led us to propose a model describing the influence of membrane surface charges on headgroup conformation. In this model, the surface charge is represented as a uniform charge distribution. The electric field due to the charges produces a torque which rotates the polar headgroups.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1989

Triggering of the alternative pathway of human T cell activation involves members of the T 200 family of glycoproteins.

The present report describes functional characteristics of a monoclonal antibody (mAb), TA/211, which is reactive with a common determinant of the human CD45 molecules. When added to purified testing human T cells, TA/211, which is itself not mitogenic, leads to a strong proliferative response in combination with submitogenic concentrations of anti-T11(2) plus anti-T11(3) mAb. Interestingly, while amplifying anti-CD2-mediated immune responses, T cell activation induced through triggering of the CD3 molecule is not enhanced by TA/211, indicating that the triggering signal provided through CD45 is restricted to alternative pathway activation. Employing T cell subsets negatively selected for the expression of CD45R molecules defined by the mAb anti-2H4 or UCHL1, respectively, it is demonstrated that resting T cells expressing the 2H4 molecules proliferate much stronger to TA/211 than the UCHL1+ T cell subset. Together with the finding that the 2H4+ T cell subset can be activated by the concomitant binding of anti-CD2 antibodies plus anti-2H4, these data strongly suggest that the high molecular weight species of CD45 expressed by unprimed T cells are themselves involved in T cell activation via the alternative pathway.

Adjuvants, Immunologic↗
PubMed1989

Treatment of duodenal ulcer with rioprostil: a randomized multicentre double-blind study.

The effectiveness of rioprostil, 300 micrograms b.d. is evaluated in evolutive duodenal ulcer in a double-blind study in five French and North African centres. A total of 115 patients are included in the study (57 in the rioprostil group and 58 in the placebo group). After a 4-week treatment period, a significantly higher endoscopic healing rate is observed in the rioprostil group (57%) compared with the placebo group (33%) (p less than 0.01). The mean time with abdominal pain is significantly lower in the rioprostil group (5.6 +/- 4.4 days) compared to the placebo group (12.7 +/- 5 days) (p less than 0.001). Clinical and biological tolerance is excellent. The only side effect is diarrhoea (3.5% in the rioprostil group). In only one case does diarrhoea necessitate cessation of treatment. Rioprostil, 300 micrograms b.d., is thus effective in the treatment of developing duodenal ulcer.

Anti-Ulcer Agents↗
PubMed1988

Mechanisms of membrane protein insertion into liposomes during reconstitution procedures involving the use of detergents. 1. Solubilization of large unilamellar liposomes (prepared by reverse-phase evaporation) by triton X-100, octyl glucoside, and sodium cholate.

The mechanisms governing the solubilization by Triton X-100, octyl glucoside, and sodium cholate of large unilamellar liposomes prepared by reverse-phase evaporation were investigated. The solubilization process is described by the three-stage model previously proposed for these detergents [Lichtenberg, D., Robson, R.J., & Dennis, E.A.(1983) Biochim. Biophys. Acta 737, 285-304]. In stage I, detergent monomers are incorporated into the phospholipid bilayers until they saturate the liposomes. At that point, i.e., stage II, mixed phospholipid-detergent micelles begin to form. By stage III, the lamellar to micellar transition is complete and all the phospholipids are present as mixed micelles. The turbidity of liposome preparations was systematically measured as a function of the amount of detergent added for a wide range of phospholipid concentrations (from 0.25 to 20 mM phospholipid). The results allowed a quantitative determination of RSat, the effective detergent to lipid molar ratios in the saturated liposomes, which were 0.64, 1.3, and 0.30 for Triton X-100, octyl glucoside, and sodium cholate, respectively. The corresponding ratios in the mixed micelles, RSol, were 2.5, 3.8, and 0.9 mol of detergent/mol of phospholipid. The monomer concentrations of the three detergents in the aqueous phase were also determined at the lamellar to micellar transitions (0.18, 17, and 2.8 mM, respectively). These transitions were also investigated by 31P NMR spectroscopy, and complete agreement was found with turbidity measurements. Freeze-fracture electron microscopy and permeability studies in the sublytic range of detergent concentrations indicated that during stage I of solubilization detergent partitioning between the aqueous phase and the lipid bilayer greatly affects the basic permeability of the liposomes without significantly changing the morphology of the preparations. A rough approximation of the partition coefficients was derived from the turbidity and permeability data (K = 3.5, 0.09, and 0.11 mM-1 for Triton X-100, octyl glucoside, and sodium cholate, respectively). It is concluded that when performed systematically, turbidity measurements constitute a very convenient and powerful technique for the quantitative study of the liposome solubilization process by detergents.

Bacteriorhodopsins↗
PubMed1988

2H and 31P NMR study of pentalysine interaction with headgroup deuterated phosphatidylcholine and phosphatidylserine.

The interaction of cationic pentalysine with phospholipid membranes was studied by using phosphorus and deuterium Nuclear Magnetic Resonance (NMR) of headgroup deuterated dimyristoyl phosphatidylcholine (DMPC) and dimyristoyl phosphatidylserine (DMPS). In the absence of pentalysine, some of the deuterium and phosphorus spectra of DMPC/DMPS 5:1 (m:m) membranes gave lineshapes similar to those of partially-oriented bilayers with the planes of the bilayers being parallel to the magnetic field. The deuterium NMR data show that the quadrupolar splittings of the deuterated methylenes of the DMPC headgroup are not affected by adsorption of pentalysine on the PC/PS membranes. By contrast, the pentalysine produces significant changes in the quadrupolar splittings of the negatively charged DMPS headgroup. The results are discussed in relation to previous 2H NMR investigations of phospholipid headgroup perturbations arising from bilayer interaction with cationic molecules.

Deuterium↗
PubMed1988

Effect of estradiol on the progesterone receptor and on morphological ultrastructures in the fetal and newborn uterus and ovary of the rat.

The effect provoked by estradiol after administration to pregnant rats (1 mg per day) was studied in fetal and newborn uteri and ovary. Estrogen receptors are found in the fetuses of non-treated animals. Their number (in fmol/mg DNA, +/- SD) in the fetal uterus (total sites, cytosol + nuclei) was at the age of 18 days: 63 +/- 15; at 20 days 101 +/- 13; and in the 24-h-old newborn; 415 +/- 120. The respective values in the ovary were: 105 +/- 25; 520 +/- 60 and 410 +/- 190. Estradiol stimulated significantly the progesterone receptor in the fetal uterus at 20 days old. The progesterone receptor (in fmol/mg DNA, +/- SD) which was 97 +/- 17 in the non-treated animals, increased to 790 +/- 90 in the E2-primed animals. Newborns, 24-h-old, had no detectable progesterone receptor, but in the E2-treated animals the value increased to 1210 +/- 120. In the fetal ovary of non-treated animals, progesterone receptor at the age of 18 days is: 90 +/- 19; at 20 days 132 +/- 47, and in the newborns 260 +/- 67; in the E2-treated animals, the values are respectively 330 +/- 49; 865 +/- 78 and 1280 +/- 307. In the fetal uteri of E2-treated animals, histological and ultrastructural studies showed an increase in the size of the uterine horn, the height of the epithelial cells, and stromal cell differentiation. It is suggested that, as was extensively demonstrated in the fetal compartment of the guinea-pig, the machinery for estrogen responses operates also during fetal development of the rat.

Animals↗
PubMed1987

Orientation and vertical fluctuations of spin-labeled analogues of cholesterol and androstanol in phospholipid bilayers.

We have used ESR and NMR linewidth broadening by spin-labels to determine the overall orientation of spin-labeled analogues of cholesterol and androstanol in egg lecithin bilayers. While the cholesterol analogues were found to have a single orientation in each monolayer, with the acyl chain pointing towards the center of the bilayer, the androstanol analogue appeared, at least in sonicated vesicles, to experience two opposite orientations in the same monolayer, very likely with a rapid reorientation. The possibility of rapid vertical fluctuations of the sterol molecules within the phospholipid bilayer is also discussed.

Androstanols↗
PubMed1987

Proconflict and electrocorticographic effects of drugs modulating GABAergic neurotransmission.

Proconflict and electrocorticographic effects of drugs acting on the benzodiazepine (BDZ)/GABA/chloride-ionophore receptor complex were studied in rats in an attempt to correlate their anxiogenic and epileptogenic activities. Evidence for proconflict activity was assessed by means of an operant conflict procedure based on the simultaneous reward and punishment of a conditioned task, while epileptogenic properties were assessed by monitoring the electrocorticogram (ECoG) of free-moving rats. Pentylenetetrazole and picrotoxin, which act through a site on the chloride channel, and the benzodiazepine (BDZ) inverse agonist FG 7142 showed epileptogenic alterations in the ECoG at doses, respectively, 8, 2 and 3 times higher than those eliciting a significant proconflict effect. For the partial inverse agonist CGS 8216, a ratio of about 60 was found while the BDZ antagonist Ro 15-1788 showed neither epileptogenic nor proconflict activity, except at the highest tested dose for the latter effect (40 mg X kg-1 PO). Inhibition of GABA transmission may mediate both anxiogenic and epileptogenic actions, and a link between these properties may exist as a continuous spectrum of negative intrinsic efficacy at the central BDZ/GABA/chloride-ionophore receptor complex.

Animals↗