Search PubMed⌕ Search

Biomedical subjects

S Paris

Publications and source records attributed to S Paris.

At least 109 records · Page 6Linked to original sources
PubMed1987

Ecogenetics of Parkinson's disease: prevalence and environmental aspects in rural areas.

We make use of the unique combination of a homogeneous genetic and racial origin in the rural population of Quebec and the facilities of free and universal access to medical care, to study the distribution of the prevalence of Parkinson's disease in the 9 rural hydrographic regions of the Province. Through 3 different methods of ascertainment, confirmed by two control probes, we demonstrate that the prevalence of Parkinson's disease is of uneven distribution within rural areas. We further investigated the characteristics of the regions of high prevalence. These regions which are predominantly agricultural and areas of intensive market gardening were also the areas with the highest use of pesticides.

Geography↗
PubMed1986

Growth factors activate the bumetanide-sensitive Na+/K+/Cl-cotransport in hamster fibroblasts.

alpha-Thrombin, a potent mitogen for the hamster fibroblast cell line CCL 39, stimulates by approximately 3-fold 86Rb+ uptake in a mutant lacking the Na+/H+ antiport activity (PS 120). The major component of this stimulated 86Rb+ (K+) uptake is a bumetanide-sensitive flux (IC50 = 0.4 microM), which accounts for 50% of total K+ uptake in Go-arrested cells and is approximately 4-fold stimulated by maximal thrombin concentrations (EC50 = 5 X 10(-4) units/ml). This bumetanide-sensitive 86Rb+ uptake represents a Na+/K+/Cl- cotransport, as indicated by its dependence on extracellular Na+ and Cl- and by the existence in PS 120 cells of a bumetanide-sensitive K+-dependent 22Na+ uptake. The stimulation reaches its maximum within 2 min, is reduced at acidic intracellular pH values (half-maximal at pHi = 6.8), and can also be induced, to a lesser extent, by EGF and the phorbol ester 12-O-tetradecanoylphorbol 13-acetate, the effects of which are nearly additive. In contrast, preincubation with 12-O-tetradecanoylphorbol 13-acetate results in inhibition of thrombin- and EGF-induced stimulations, suggesting that activated protein kinase C might exert a feedback inhibitory control. This study clearly demonstrates that the growth factor-induced activation of the Na+/K+/Cl- cotransport is separated from the activation of the Na+/H+ antiport. However, activation of this cotransporter does not seem to play a major role in the mitogenic signaling pathway since its complete inhibition with bumetanide reduces only by 25-30% reinitiation of DNA synthesis.

Animals↗
PubMed1986

Pertussis toxin inhibits thrombin-induced activation of phosphoinositide hydrolysis and Na+/H+ exchange in hamster fibroblasts.

Prior treatment with pertussis toxin of G0-arrested hamster fibroblasts (CCL39) results in a dose-dependent inhibition of two early events of the mitogenic response elicited by alpha-thrombin: accumulation of inositol phosphates in Li+-treated cells, and activation of the Na+/H+ antiport, measured either by the amiloride-sensitive 22Na+ influx or by the increase in intracellular pH. At 10(-1) U/ml of alpha-thrombin, the maximal inhibition was approximately 50% for these two early cellular responses, but the pertussis toxin effect was more pronounced at lower thrombin concentrations. In contrast, pertussis toxin does not affect the Na+/H+ antiport activation induced by phorbol esters or EGF, the action of which is not mediated by the phosphoinositide-metabolizing pathway in CCL39 cells. Therefore, our data suggest the following. A GTP-binding regulatory protein is probably involved in signal transduction between thrombin receptors and the phosphatidylinositol 4,5-bisphosphate-specific phospholipase C. This regulation does not seem to be exerted via modulations of cyclic AMP levels. The thrombin-induced activation of Na+/H+ antiport is, at least in part, mediated by the protein kinase C, as a consequence of stimulation of phosphatidylinositol turnover.

Animals↗
PubMed1986

Alpha-thrombin-induced inositol phosphate formation in G0-arrested and cycling hamster lung fibroblasts: evidence for a protein kinase C-mediated desensitization response.

In resting Chinese hamster fibroblasts (CCL39) alpha-thrombin rapidly induces the breakdown of phosphoinositides. Accumulation of inositol phosphates (IP), measured in the presence of Li+, is detectable within 5s (seconds) of thrombin stimulation. Formation of inositol tris- and bisphosphates slightly precedes that of inositol monophosphate, indicating that thrombin activates primarily the phospholipase C-mediated generation of inositol trisphosphate from phosphatidylinositol 4,5-bisphosphate. Initial rates of IP production increase with thrombin concentration, with no apparent saturability over the range 10(-4)-10 U/ml. Thrombin-induced phosphoinositide hydrolysis rapidly desensitizes (t1/2 less than 5 min), but a residual activity, corresponding to about 10% of the initial stimulation is sustained for at least 9 h, in contrast with the undetectable activity of G0-arrested cells. This apparent desensitization may be due to a feedback regulation by protein kinase C, since pretreatment with the phorbol ester 12-O-tetradecanoyl phorbol 13-acetate (TPA) markedly inhibits (by up to 70%) subsequent thrombin-induced inositol phosphate formation. Conversely, growth factor deprivation of CCL39 cells results in a progressive increase of thrombin-induced phosphoinositide hydrolysis, from the very low level of exponentially growing cells to the maximal level of G0-arrested cells. This "up regulation" was found maximal in A51, a very well growth-arrested CCL39 derivative, and reduced or virtually abolished in two tumoral and growth factor-relaxed derivatives of CCL39. Although preliminary, this observation suggests that a persistent activation of phosphatidyl inositol breakdown might operate in variants selected for autonomous growth.

Animals↗
PubMed1985

Ecogenetics of Parkinson's disease: 4-hydroxylation of debrisoquine.

It is postulated that Parkinson's disease is the result of environmental factors acting on genetically susceptible individuals against a background of normal ageing. Many potentially neurotoxic xenobiotics are detoxified by hepatic cytochrome P450. The function of one such system was studied in forty patients with Parkinson's disease and forty normal control subjects. Significantly more parkinsonian than control subjects had partially or totally defective 4-hydroxylation of debrisoquine. Poor metabolisers of debrisoquine tended to have had earlier onset of disease.

Adult↗
PubMed1985

Cytoplasmic pH, a key determinant of growth factor-induced DNA synthesis in quiescent fibroblasts.

In response to growth factors, quiescent fibroblast mutants lacking Na+/H+ exchange activity fail to elevate their cytoplasmic pH (pHi) and to reinitiate DNA synthesis at neutral and acidic pHo. A pHi threshold of approximately 7.2 exists, below which growth factors cannot set in motion the Go to S phase transition. Restoration of the pHi defect in mutant cells restores the wild-type phenotype. These findings, combined with the properties of another class of mutants able to grow at very low pHo, demonstrate that pHi, modulated by growth factor activation of the Na+/H+ antiporter, plays a determinant role in growth control.

Animals↗
PubMed1985

Role of a Na+-dependent Cl-/HCO3- exchange in regulation of intracellular pH in fibroblasts.

We previously reported that, in a HCO3(-)-free medium, cytoplasmic pH (pHi) of hamster fibroblasts (CCL39) is primarily regulated by an amiloride-sensitive Na+/H+ antiport (L'Allemain, G., Paris, S., and Pouysségur, J. (1984) J. Biol. Chem. 259, 5809-5815). Here we demonstrate the existence of an additional pHi-regulating mechanism in CCL39 cells, namely a Na+-dependent HCO3-/Cl- exchange. Evidence for this system is based on 36Cl- influx studies and on pHi measurements in PS120, a CCL39-derived mutant lacking the Na+/H+ antiport activity. 36Cl- influx rate is a saturable function of external [Cl-] (apparent Km approximately equal to 7 mM), is competitively inhibited by external HCO3- (KI approximately equal to 3 mM), and by stilbene derivatives (KI approximately equal to 20 microM for 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid). Measurements of pHi recovery after an acute acid load indicate that PS120 cells possess an acid-extruding mechanism dependent on external HCO3-, which is inhibited by stilbene derivatives and requires external Na+. Since 22Na+ influx is stimulated upon addition of HCO3- to acid-loaded cells and this effect is completely abolished by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, we conclude that Na+ is co-transported with HCO3-, in exchange for intracellular Cl-. In a HCO3(-)-containing medium, this pHi-regulating mechanism appears to have two essential physiological functions for the Na+/H+ antiport-deficient mutant: protection of the cells against excessive cytoplasmic acidification and establishment of a steady-state pHi permissive for growth, at neutral or slightly acidic pHo values (6.6-7.2).

Amiloride↗
PubMed1985

alpha-Thrombin-induced early mitogenic signalling events and G0 to S-phase transition of fibroblasts require continual external stimulation.

In resting Chinese hamster fibroblasts (CCL39) alpha-thrombin rapidly stimulates several biochemical events implicated in the mitogenic response, including the breakdown of inositol phospholipids, activation of a plasma membrane Na+/H+ antiporter, phosphorylation of ribosomal protein S6 and increased expression of the proto-oncogene c-myc. Complete removal of the growth factor during cellular G0/G1 transit precludes the re-initiation of DNA synthesis. The present study was designed to examine the fate of alpha-thrombin-activated early events following growth factor inactivation. In cells stimulated for 30 min with alpha-thrombin, neutralization of the growth factor results in: (i) immediate arrest of inositol phosphate formation, (ii) rapid inactivation of Na+/H+ exchange, (iii) deactivation of the S6 phosphorylating system and (iv) strong reduction of c-myc mRNA level. Our findings that commitment for DNA synthesis as well as persistent activation of 'early' cellular events requires continual growth factor stimulation suggest that: (i) growth factor-induced transmembrane signals have a short life and (ii) the generation of these signals during the 8 h of the pre-replicative phase is required for G0-arrested cells to enter the S phase.

Animals↗
PubMed1985

Nutritional studies on Paracoccidioides brasiliensis: the role of organic sulfur in dimorphism.

The nutritional requirements of the mycelial and yeast-like phases of the dimorphic fungus Paracoccidioides brasiliensis, a human pathogen, were investigated. For all nine isolates tested, mycelial cells were prototrophic, whereas yeast-like cells required a sulfur-containing amino acid for growth. Moreover, changing the source of nitrogen greatly affected the morphology of the yeast-like cells.

Amino Acids, Sulfur↗
PubMed1984

Growth factors activate the Na+/H+ antiporter in quiescent fibroblasts by increasing its affinity for intracellular H+.

Growth factors (alpha-thrombin and insulin) activate a Na+/H+ antiport in G0/G1-arrested Chinese hamster lung fibroblasts (CCL39). In this report, we have examined the influence of intracellular pH on this exchange activity, measured by initial rates of amiloride-sensitive 22Na+ uptake, in the absence and presence of growth factors. Our results indicate the following. 1) In quiescent as in mitogen-stimulated cells, Na+/H+ antiport is regulated by internal H+ in an allosteric way, whereas, in contrast, interactions with external H+ and Na+ obey simple saturation kinetics. 2) The growth factor-induced activation of Na+/H+ exchange, which, under physiological conditions, is responsible for a sustained cytoplasmic alkalinization, is due to an increased affinity for internal H+ (the apparent pK is shifted by approximately 0.3 pH unit towards alkaline pH values). Therefore, we propose that growth factors promote a conformational change of the Na+/H+ antiporter, possibly at the level of an internal modifier site(s).

Amiloride↗
PubMed1984

Growth factor action and intracellular pH regulation in fibroblasts. Evidence for a major role of the Na+/H+ antiport.

Chinese hamster lung fibroblasts (CCl39) possess in their plasma membrane an amiloride-sensitive Na+/H+ antiport, activated by growth factors. Measurements of intracellular pH (pHi), using equilibrium distribution of benzoic acid, provide evidence for a major role of this antiport in 1) regulation of cytoplasmic pH, in response to an acute acid load or to varying external pH values, and 2) the increase in cytoplasmic pH (by 0.2-0.3 pH unit) upon addition of growth factors (alpha-thrombin and insulin) to G0/G1-arrested cells. Indeed, these two processes are Na+-dependent and amiloride-sensitive; furthermore, CCl39-derived mutant cells, lacking the Na+/H+ exchange activity, are greatly impaired in pHi regulation and present no cytoplasmic alkalinization upon growth factor addition. In wild type G0-arrested cells, the amplitude of the mitogen-induced alkalinization reflects directly the activity of the Na+/H+ antiport, and is tightly correlated with the magnitude of DNA synthesis stimulation. Therefore, we conclude that cytoplasmic pH, regulated by the Na+/H+ antiport, is of crucial importance in the mitogenic response.

Amiloride↗
PubMed1984

Lysosomal enzymes in ataxia: discovery of two new cases of late onset hexosaminidase A and B deficiency (adult Sandhoff disease) in French Canadians.

We have measured in leukocytes the following lysosomal enzymes in 11 Friedreich disease cases, 11 "atypical" recessive ataxias, 13 neurological controls and 16 normal controls: hexosaminidase A and B; beta-galactosidase and neuraminidase (labile and cold stable, or A and B). The lysosomal enzyme deficiencies known to produce certain forms of spinocerebellar degeneration were not present in Friedreich's disease or the Charlevoix-Saguenay syndrome. The very small scale survey of "atypical" recessive ataxias revealed 3 cases of severe deficiencies in hexosaminidase activity. Two adult brothers presenting with the clinical phenotype of Kugelberg-Welander disease (one also with ataxia), were shown to have a severe deficiency of both HEX A and HEX B activity (Sandhoff biochemical pattern). This is the first such report. A further adult female patient, unrelated to the others, had a severe isolated deficiency of HEX B and presented with a very slowly progressive and mild ataxia with severe internal strabismus. These patients and their families are being studied clinically and biochemically in greater detail and will be reported elsewhere. However these preliminary findings justify screening for such lysosomal defects in all cases of "atypical" recessive ataxia.

Adult↗
PubMed1984

Hair trace elements in Friedreich's disease.

Concentrations of zinc, copper, manganese, chromium, cobalt and selenium were measured in the hair obtained from subjects with Friedreich's disease, other inherited ataxias and neurological control patients. Although zinc and copper concentrations were significantly higher in Friedreich than in the two control groups, the mean values for all groups were well within the normal range. No major deficiency in zinc or selenium was demonstrated in Friedreich's disease using the approach. This does not, however, indicate that there is no defect in zinc and selenium metabolism, availability or transport in this disorder.

Adult↗
PubMed1984

A specific mutation abolishing Na+/H+ antiport activity in hamster fibroblasts precludes growth at neutral and acidic pH.

A H+-suicide technique based on the reversibility of Na+/H+ antiport was developed for the selection of mutants deficient in this membrane-bound activity. The strategy was to use the Na+/H+ antiporter as a H+-vector killing device. Chinese hamster lung fibroblasts (CCL39) were loaded with LiCl and incubated in Na+-, Li+-free choline Cl saline solution (pH 5.5). Under these conditions, intracellular pH dropped in 5 min from 7.1 to 4.8, leading to a rapid loss of cell viability (less than 0.1% survival after 30 min). Cytoplasmic acidification and cell death were prevented by treatment with 5-N,N-dimethylamiloride, a potent inhibitor of Na+/H+ antiport. Of the H+-suicide resistant clones that survived two cycles of selection, 90% were found deficient in Na+/H+ antiport activity. One class of mutants (PS10, PS12) fully resistant to the H+-suicide test, does not acidify the cell interior in response to an outward-directed Li+ gradient and has no detectable amiloride-sensitive Na+ influx measured either in Li+- or H+-loaded cells. Growth of these fibroblast clones lacking Na+/H+ antiport was found to be pH conditional in HCO3(-)-free medium. Whereas wild-type cells can grow over a wide range of external pHs (6.6-8.2), PS mutants cannot grow at neutral and acidic pHs (pH less than 7.2); their optimal growth occurs at alkaline pH values (pH 8-8.3). These findings strongly suggest that the Na+/H+ antiport activity through regulation of intracellular pH plays a crucial role in growth control.

Acid-Base Equilibrium↗