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Biomedical subjects

M Rossignol

Publications and source records attributed to M Rossignol.

At least 109 records · Page 6Linked to original sources
PubMed1992

The evolution of compensated occupational spinal injuries. A three-year follow-up study.

This study was undertaken to follow up an incidence rate study of spinal injuries carried out from a cross-sectional random sample consisting of 2,342 workers who were compensated at least once in the year 1981 by the Quebec Worker's Compensation Board (QWCB) for an absence from work. These workers were followed for 3 years using the QWCB information system to record any recurrence of compensated absence from work. A total of 850 (36.3%) had at least one recurrence, and had longer episodes of absence than those without a recurrence (P less than 0.0001). Of these 850 workers, 824 (96.9%) had less than five recurrences and showed a systematic trend of gradual increasing duration of absence on each subsequent recurrence (P less than 0.05 in a repeated measures analysis of variance). A positive relationship was found between the duration of the initial episode of absence from work and the subsequent history of absence from work, both in terms of risk of recurrence (P less than 0.001) and of cumulated absence from work (P less than 0.0001), after controlling for age, sex, and site of symptoms. The computed instantaneous risk of entering a recurrence in a 31 year-old man experiencing lumbar symptoms, was 19.9% (95% confidence interval = 19.8-19.9) in the year following an initial episode of one day duration, and 26.7% (95% confidence interval = 24.3-29.3) after an initial episode of 6 months.

Absenteeism↗
PubMed1988

Binding of the phytotoxin zinniol stimulates the entry of calcium into plant protoplasts.

Zinniol [1,2-bis(hydroxymethyl)-3-methoxy-4-methyl-5-(3-methyl-2-butenyloxy)benzene], a toxin produced by fungi of the Alternaria group, causes symptoms in plants that resemble those induced by the fungi. The phytotoxin binds to carrot protoplasts and isolated membranes in a saturable and reversible manner. Receptor occupancy stimulates entry of calcium into protoplasts. Zinniol can partially reverse the effects and binding of the calcium-channel blockers desmethoxyverapamil and bepridil. Selected cell lines that are insensitive to zinniol lose part of their binding capacity and sensitivity to the action of the agonist-like compound but are still able to bind calcium-channel blockers. We conclude that zinniol acts on calcium entry but that the targets of the toxin and of calcium-channel blockers are dissimilar, suggesting the occurrence of sites affected both by zinniol and by channel blockers and of sites affected only by zinniol.

Journal Article↗
PubMed1988

Functional reconstitution of a proton-translocating system responsive to fusicoccin.

Crude fusicoccin binding proteins and a partially purified plasma membrane H+-transporting ATPase (EC 3.6.1.34), both solubilized from maize tissues, were simultaneously inserted into liposomes by the freeze-thaw method. ATP-driven intravesicular acidification in the proteoliposomes, measured by the fluorescence quenching of the dye 9-amino-6-chloro-2-methoxyacridine, markedly increased upon addition of fusicoccin to the reconstituted system. This effect could not be observed when binding sites and ATPase preparations were separately reconstituted into the proteoliposomes, thus demonstrating that fusicoccin binding to its receptor is a prerequisite for ATPase stimulation.

Aminoacridines↗
PubMed1988

Cercospora beticola Toxin Inhibits Vanadate-Sensitive H Transport in Corn Root Membrane Vesicles.

The effect of Cercospora beticola toxin on the transport of protons by vanadate-sensitive ATPase was studied with corn (Zea mays) root microsomal vesicles prepared by differential centrifugation, sedimentation through a sucrose cushion, and washing with Triton X-100 plus KBr. In these preparations, addition of ATP induced intravesicular H(+)-accumulation as evidenced by a rapid quenching of the fluorescence of 9-amino-6-chloro-2-methoxy acridine. This quenching was relatively unaffected by inhibitors of mitochondrial and tonoplast-type ATPases, but was strongly reduced by inhibitors of plasma membrane H(+)-ATPase. C. beticola toxin markedly inhibited ATP dependent H(+)-transport, and this effect increased with the length of preincubation with the toxin. The same observations were made concerning ATPase activity. Inhibition of H(+)-transport was greater at pH 7.3 than at pH 5.7. Lineweaver-Burk plot analysis showed that inhibition kinetics were competitive with respect to ATP. These data suggest a direct effect of C. beticola toxin on vanadate-sensitive ATPase presumed to be associated with the plasma membrane.

Journal Article↗
PubMed1988

Risk of recurrence of occupational back pain over three year follow up.

A random sample including 2342 cases representative of all occupational back injuries in Quebec (1981) was followed up prospectively over three years to assess the recurrence rate of back problems (lumbar, thoracic, and cervical). Each medical and accident report was reviewed to obtain the site of symptoms and occupation. Age, sex, industrial sector, and number of episodes of absence from work were abstracted from the computerised Quebec Compensation Board files. The recurrence rate was 20.0% at one year follow up and 36.3% at three years. A multivariate analysis using a Poisson regression, was performed to model the risk of recurrence over time. Men had a higher chance of recurrence (risk ratio = 1.85, 95% CI = 1.50-2.27) but among recurrent cases, the average total number of episodes was comparable between men and women. Age showed a protective effect on the probability of recurrence (10 years: RR = 0.93, 95% CI = 0.88-0.98) due to the lower recurrence rate in the 45-64 year old group (31.8%). Cervical and lumbar symptoms had identical recurrence profiles whereas thoracic symptoms had a significantly lower recurrence rate. Drivers had the highest recurrence rate (42.1%) and nurses had the highest average number of recurrences (2.03) among recurrent cases. Both occupations had statistically significant excesses after controlling for the other variables.

Adolescent↗
PubMed1988

Working disability due to occupational back pain: three-year follow-up of 2,300 compensated workers in Quebec.

A cohort of 2,342 cases constituting a random sample of all occupational back injuries compensated in Quebec (Canada) during 1981 was observed prospectively for 3 years to study associations between cumulative duration of absence from work and sex, age, site of symptoms (cervical, thoracic, and lumbar), and occupation. Of the cohort members, 227 (9.7%) cumulated 6 months of absence or more. A logistic regression model showed age and site of symptoms to be the two most important risk factors associated with absences of 6 months or more. No association was found with sex or occupation. The results showed discrepancies between measures of frequency distribution of back injuries and duration of absence from work, an important finding in terms of identifying health priorities.

Absenteeism↗
PubMed1987

Radioimmunoassay of the phytotoxic compound zinniol.

The phytotoxic compound zinniol, produced by phytopathogenic fungi such as Alternaria spp. and Phoma macdonaldii was conjugated to bovine serum albumine by the mixed anhydride method. Antiserum against zinniol was obtained by injection at multiple intradermal sites of rabbits. Sensitivity of the R.I.A. was 0.14 ng/tube, the within and between-assay coefficient of variation were less than 10 and 14% respectively. Negligible binding occurred when analogs of zinniol were tested for cross reactivity. The excellent accuracy of this R.I.A., applied to ethanolic extracts of plants, might allow to determine the production of toxin by the parasite during the infection process.

Alternaria↗
PubMed1985

Antibody against rat adipose tissue lipoprotein lipase.

To facilitate detailed studies of rat adipose tissue lipoprotein lipase regulation, a high titre polyclonal antibody was raised against purified rat adipose tissue lipoprotein lipase (in a goat). The first stage of the purification of the lipoprotein lipase was carried out with heparin-Sepharose affinity chromatography. In the second stage we took advantage of the binding property of lipoprotein lipase to ampholytes. These ampholytes, used during this second step, do not have to be eliminated prior to injecting the enzyme preparation into the animal. They have neither toxic nor antigenic effects on the animal; moreover, their presence does not affect the antigenic potency of the lipoprotein lipase. When pre-incubated with a constant amount of adipose tissue lipoprotein lipase (8 mU/75 microliter), an equal volume of the antiserum raised either pure or diluted up to 1/50 resulted in complete inhibition of enzyme activity, and half maximal inhibition was observed at a dilution of 1/800. The antibody was effective in inhibiting rat heart lipoprotein lipase but not salt-resistant hepatic lipase. Immunodiffusion revealed a single line of precipitation between this antibody and the adipose tissue lipoprotein lipase.

Adipose Tissue↗
PubMed1985

Relationship between fluidity and ionic permeability of bilayers from natural mixtures of phospholipids.

Proton and calcium permeability coefficients of large unilamellar vesicles made from natural complex mixtures of phospholipids were measured in various conditions and related to membrane fluidity. Permeability coefficients at neutral pH and 25 degrees C were in the range of 10(-4) cm sec-1 and 2.5 X 10(-11) cm sec-1 for protons and calcium, respectively. With the exception of two cases, (H+) greater than 10(-4) M and (Ca2+) greater than 10(-3) M, fluidity increases correspond to permeability increases. Theoretical analysis shows that, for both ions, the measured values of permeability coefficients imply that the permeation process is controlled by the product D1D2 of the diffusion coefficient from the medium into the membrane (D1) by the diffusion coefficient in the membrane (D2). Further analysis of D1 values deduced from combined use of permeability and fluidity data shows that the solubilization should occur in a medium of dielectric constant of about 12, suggesting the involvement of the hydration water of membranes. High proton concentrations, although having virtually no effect on fluidity, trigger the appearance of lateral heterogeneity in membranes, as seen by 31P NMR, and large permeability increases. It is proposed that the main effect of fluidity and/or lateral heterogeneity on permeability may be via the membrane hydration control. We conclude that the current assumption that permeability is controlled by fluidity should be regarded with caution, at least in the case of ions and natural mixtures of phospholipids.

Calcium↗
PubMed1982

Proton permeability of liposomes from natural phospholipid mixtures.

A method to determine the proton permeability coefficient of phospholipid membrane with the fluorescent probe pyranine is described. Very high proton permeability coefficients of liposomes from natural extracts are measured with great accuracy. The proton permeability appears to be linearly related to the fluidity of the bilayers. This relation as well as the comparison of the activation energies of proton permeability and fluidity support the hypothesis (Nichols J.W. and Deamer D.W. (1980) Proc. Natl. Acad. Sci. USA 77, 2038--2042) of a transfer process along a network of hydrogen bonded water molecules. It is suggested that the common lipid characteristics of biological membranes (net surface charge and unsaturation) favor a high proton permeability.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1982

Effect of temperature and ions on the microviscosity of bilayers from natural phospholipid mixtures.

The thermotropic behaviour of two natural extracts of phospholipids differing by their content in saturated fatty acids and acidic polar heads were studied with the aid of the fluorescent probes : perylene and diphenylhexatriene. The main results are that the bilayers are in a fluid state in the range from -- 5 to 50 degrees C, in the presence as well as in the absence of calcium, and that misleading conclusions may be derived with the perylene probe. The effects of pH and Ca2+/H+ interaction on the microviscosity were studied. In the absence of calcium pH increase fluidizes the bilayers ; when Ca2+ is present the microviscosity is constant over a large pH range. Calculations using the Gouy-Chapman theory suggest that the pH-induced microviscosity changes are controlled by the content in phosphadidylserine, diphosphatidylglycerol and phosphatidic acid of the extracts. Similarly the rigidifying effect of Ca2+ seems to be related to the content in these phospholipids. These hypothesis were confirmed by modifying the content of the extracts in these phospholipids. It is proposed that the behaviour of the two studied extracts results from the high insaturation of their fatty acids, which is typical of biological membranes.

Calcium↗
PubMed1981

Post-heparin lipolytic activity with no hepatic triacylglycerol lipase involved in a mammalian species.

It was found that lipolytic activity in bovine post-heparin plasma differed from that of other mammalian species by the fact that intravenous heparin induced the release of lipoprotein lipase but not hepatic triacylglycerol lipase. Initially, this fact was strongly suspected when no remaining lipolytic activity could be found after whole bovine post-heparin plasma had been tested with either 1 M NaCl or antiserum against lipoprotein lipase. This was further confirmed by using heparin-Sepharose affinity chromatography when the entire lipolytic activity was eluted with 1.5 M NaCl but none with 0.4 or 0.7 M NaCl. The active fraction had lipoprotein lipase characteristics, i.e. it required serum activators to produce optimum activity and was fully inhibited by NaCl of high molarity and by anti-lipoprotein lipase antiserum. Neither the different doses of heparin nor the various times of sampling altered the results. This raises the question whether hepatic triacylglycerol lipase is absent from the bovine liver or whether this enzyme is present but cannot be released by heparin.

Animals↗
PubMed1981

Control of exocytotic processes: cytological and physiological studies of trichocyst mutants in Paramecium tetraurelia.

The trichocysts of Paramecium tetraurelia constitute a favorable system for studying secretory process because of the numerous available mutations that block, at various stages, the development of these secretory vesicles, their migration towards and interaction with the cell surface, and their exocytosis. Previous studies of several mutants provided information (a) on the assembly and function of the intramembranous particles arrays in the plasma membrane at trichocyst attachment sites, (b) on the autonomous motility of trichocysts, required for attachment to the cortex, and (c) on a diffusible cytoplasmic factor whose interaction with both trichocyst and plasma membrane is required for exocytosis to take place. We describe here the properties of four more mutants deficient in exocytosis ability, nd6, nd7, tam38, and tam6, which were analyzed by freeze-fracture, microinjection of trichocysts, and assay for repair of the mutational defect through cell-cell interaction during conjugation with wild-type cells. As well as providing confirmation of previous conclusions, our observations show that the mutations nd6 and tam6 (which display striking abnormalities in their plasma membrane particle arrays and are reparable through cell-cell contact but not by microinjection of cytoplasm) affect two distinct properties of the plasma membrane, whereas the other two mutations affect different properties of the trichocysts. Altogether, the mutants so far analyzed now provide a rather comprehensive view of the steps and functions involved in secretory processes in Paramecium and demonstrate that two steps of these processes, trichocyst attachment to the plasma membrane and exocytosis, depend upon specific properties of both the secretory vesicle and the plasma membrane.

Animals↗
PubMed1980

Control of membrane fusion in exocytosis. Physiological studies on a Paramecium mutant blocked in the final step of the trichocyst extrusion process.

Previous studies on exocytosis in Paramecium using mutants affecting trichocyst extrusion permitted us to analyze the assembly and function of three intramembrane particle arrays ("ring" and "rosette" in the plasma membrane, "annulus" in the trichocyst membrane) involved in the interaction between these two membranes. Using a conditional mutation, nd9, which blocks rosette assembly and prevents exocytosis at the nonpermissive temperature, we have analyzed the effect of temperature on the secretory capacity of nd9 cells. By combining several techniques (physiological studies, microinjections, inhibition of fatty acid synthesis, and freeze-fracture analysis) we demonstrate (a) that the product of the mutated allele nd9 is not thermolabile but that its activity is dependent upon temperature-induced changes in the membrane lipid composition and (b) that the product of the nd9 locus is a diffusible cytoplasmic component whose interaction with both plasma membrane and trichocyst membrane is required for rosette assembly and exocytosis. The data provide physiological evidence for the existence of a molecular complex(es) linking the two membranes and involved in the control of membrane fusion; we discuss the possible nature and function of these links.

Animals↗