Search PubMed⌕ Search

Biomedical subjects

S Paris

Publications and source records attributed to S Paris.

At least 127 records · Page 7Linked to original sources
PubMed1983

Biochemical characterization of the amiloride-sensitive Na+/H+ antiport in Chinese hamster lung fibroblasts.

Net H+ fluxes across the plasma membrane of Chinese hamster lung fibroblasts (CC139) were monitored by pH-stat titration. Na+-depleted cells release H+ upon addition of Na+. Conversely Na+- or Li+-loaded cells take up H+ from the medium when shifted to a Na+,Li+-free medium. This reversible Na+ (or Li+)-dependent H+ flux is inhibited by amiloride and does not occur in digitonin-permeabilized cells. A similar Na+/H+ exchanger was identified in vascular smooth muscle cells, corneal and aortic endothelial cells, lens epithelial cells of bovine origin, and human platelets. Kinetic studies carried out with CC139 cells indicate the following properties: 1) half-saturation of the system is observed at pH = 7.8, in the absence of Na+; 2) external Na+ stimulates H+ release and inhibits H+ uptake in a competitive manner (Ki = 2-3 mM); 3) amiloride is a competitive inhibitor for Na+ (Ki congruent to 1 microM) and a noncompetitive inhibitor for H+; 4) a coupling ratio of 1.3 +/- 0.3 for the H+/Li+ exchange suggests a stoichiometry of 1:1. We conclude that CC139 cells possess in their plasma membrane a reversible, electroneutral, and amiloride-sensitive Na+/H+ antiporter, with two distinct and mutually exclusive binding sites for Na+ and H+. The rapid stimulation of the Na+/H+ antiporter in G0/G1-arrested CC139 cells upon addition of growth factors, together with the fact that intracellular H+ concentration is, under physiological conditions, around the apparent K0.5 of the system, strongly suggests a key role of this antiport in pHi regulation and mitogen action.

Amiloride↗
PubMed1982

Cyclic AMP stimulation of Na-K pump activity in quiescent swiss 3T3 cells.

Recently, we have found that an increase in the intracellular level of cAMP acts as a mitogenic signal for Swiss 3T3 cells (Rozengurt et al., Proc. Natl. Acad, Sci. USA, 78:4392, 1981). The results presented in this paper demonstrate that addition of cAMP-elevating agents to confluent and quiescent cultures of Swiss 3T# causes a marked increase in the rate of 86Rb+ uptake but has no effect on the rate of cation efflux. The stimulation of ion uptake is mediated by the Na-K pump as shown by the ouabain sensitivity of the 86Rb+ fluxes. The increase in Na-K pump activity occurs whether cAMP is generated endogenously by stimulation of adenylate cyclase activity by cholera toxin, adenosine agonists, or PGE1 or added exogenously as 8BrcAMP. The stimulatory effect of these compounds on 86Rb+ uptake is potentiated by inhibitors of cyclic nucleotide phosphodiesterase activity. Cholera toxin stimulates the Na-K pump in a dose-dependent manner; half-maximal effect is achieved at 0.7 ng/ml. The stimulation of ouabain-sensitive 86Rb+ uptake by cAMP-elevating agents reaches a maximum after 2-3 h of incubation. This contrasts with the rapid (within minutes) stimulation of the Na-K pump caused by serum and other mitogenic agents. Further, cAMP-elevating agents fail to increase Na+ influx into 3T3 cells whereas serum causes a marked increase in Na+ influx, under identical experimental conditions. These findings suggest that the stimulation of Na-K pump activity caused by increased cAMP levels contrasts mechanistically with the rapid control of pump activity by serum which is primarily mediated by increased Na+ entry into the cells.

1-Methyl-3-isobutylxanthine↗
PubMed1982

Growth factor activation of an amiloride-sensitive Na+/H+ exchange system in quiescent fibroblasts: coupling to ribosomal protein S6 phosphorylation.

Chinese hamster lung fibroblast cells (CCl39) enter the G0/G1 nonproliferative state after serum deprivation. In this report, we show that reinitiation of DNA synthesis by serum or the combination of purified human thrombin and insulin (1-10 microgram/ml) is preceded by very early stimulation of ionic fluxes (Na+/Rb+) and protein phosphorylation (27,000 daltons, 62,000 daltons, and the ribosomal S6 proteins). The potentiating action of insulin on thrombin-stimulated DNA synthesis is also observed on thrombin-stimulated Na+ influx, Rb+ influx, and protein S6 phosphorylation. Moreover, we demonstrate that CCl39 cells possess a Na+/H+ exchange system sensitive to amiloride. Half-maximal inhibition of growth factor-activated Na+ influx and Na+-dependent H+ efflux is obtained with 3-10 microM amiloride. Two lines of evidence indicate that the extrusion of H+ via the activation of the Na+/H+ exchanger is coupled to protein S6 phosphorylation: serum-stimulated phosphorylation is blocked by (i) amiloride at a concentration that abolishes serum-stimulated Na+ influx and (ii) protonophores that acidify the cell interior. The present data support the idea that the regulation of intracellular pH is a key event in the mechanism of growth factor action.

Amiloride↗
PubMed1980

Sugar transport in chick embryo cardiac cells in culture: analysis by countertransport, relationship to phosphorylation and effect of glucose starvation.

Embryonic chick heart cells in culture transport 2-deoxy-D-glucose and 3-O-methyl-D-glucose very rapidly. By direct measurements of uptake, it was not possible to estimate accurately transport rates, nor, with 2-deoxyglucose, to discriminate clearly between its transport and phosphorylation. In contrast, the technique of countertransport made it possible to determine precisely initial transport velocity and to make the following observations: (1) phosphorylation, and not transport, is rate-limiting in 2-deoxyglucose uptake; (2) hexose transport is stimulated 5-fold by removal of glucose from culture medium; and (3) this stimulation is followed by an increase in phosphorylation, but the effect is much less pronounced (2-fold stimulation only). In conclusion, the adaptative regulation of glucose transport described in many fibroblast cell lines exists also in cardiac cells.

Animals↗
PubMed1980

Amino acid and glucose transport in sarcolemmal vesicles from chick embryo heart.

Purified plasma membranes from chick embryo heart are shown to retain several functional properties of intact cardiac cells. (1) Muscarinic cholinergic receptors copurify with previously used cell-surface markers, i.e., (K+-dependent) p-nitrophenylphosphatase and insulin receptors (Paris, S., Fosset, M., Samuel, D. and Ailhaud, G. (1977) J. Mol. Cell. Cardiol. 9, 161-174). (2) Neutral amino acids (L-alanine and alpha-aminoisobutyric acid) are actively transported into these osmotically active vesicles when an Na+ electrochemical gradient is imposed. The affinity and specificity for amino acids are similar to those described for intact cardiac cells. (3) D-Glucose is taken up more rapidly than L-glucose. The sterospecific transport system is saturable and Na+-independent. The Km value is close to that observed in intact cells with glucose analogues.

Alanine↗
PubMed1979

Uptake of fatty acids by cultured cardiac cells from chick embryo: evidence for a facilitation process without energy dependence.

Cultured heart cells from chick embryo accumulate fatty acids up to 50 fold at a steady-state level under defined conditions [ref.1]. Studies of fatty acid uptake as a function of different cellular parameters (intracellular ATP and pH, membrane potential and electrochemical gradients for monovalent and divalent cations) show the lack of effect of these factors. The rate of uptake is temperature-dependent. The maximum velocity V is affected with no change in the Km value of the saturable component; the activation energies were found to be 35.5 kJ.mol-1 for palmitate and 42 kJ.mol-1 for oleate. The results are in favour of a facilitation process which leads to an accumulation of fatty acids without energy dependence. The accumulation of fatty acids could be due to their association to intracellular membraneous and/or cytosolic components.

Acetates↗
PubMed1978

The role of serum albumin in the uptake of fatty acids by cultured cardiac cells from chick embryo.

Fatty acids enter the cultured cardiac cells from chicken embryo through two mechanisms, one involving a saturable process, the other resembling passive diffusion. Studies of the saturable component, at fixed concentrations of palmitate or of oleate and at increasing concentrations of albumin, show that this protein increases the rate of palmitate uptake with a maximum at palmitate/albumin molar ratios between 7 and 10 while it decreases the rate of oleate uptake under all conditions. Albumin cannot be replaced by other serum proteins; its effect is specific to saturated fatty acids, can be mimicked by the detergent Tween 40 and involves the binding of the fatty acid to the protein, prior to its delivery to the cell. Both with labelled saturated and unsaturated fatty acids the presence of albumin lowers the proportion of unesterified fatty acids and enhances the proportion of esterified fatty acids recovered in the cardiac cell after uptake. A similar effect of albumin was also found with hepatocytes and permanent cell lines. A specific role for serum albumin is presented, which assumes a 'dispersing' effect of this protein towards dimers (or higher aggregates) of saturated fatty acids and the entry of fatty acids into the cell as monomers.

Animals↗
PubMed1976

Uptake and metabolism of fatty acids and analogues by cultured cardiac cells from chick embryo.

Cultured heart cells from chick embryo, present as a confluent monolayer in a minimal medium, take up labelled fatty acids (from C6 to C22) bound to serum albumin with a rapid incorporation into neutral and complex lipids (visible at 15 s), while beta-oxidation is delayed (visible at 15 min). Fatty acids enter the cardiac cells through two mechanisms, one involving a readily saturable process, the other resembling passive diffusion. The saturable transport system recognizes fatty acids with a high affinity, Km from 4.5 to 16 muM. The V is from 0.03 to 0.3 nmol of fatty acid incorporated min-1 (10(6) cells)-1. Competitive inhibition occurs between fatty acids while glucose, aminoacids and lactate do not compete with palmitate for the entry into the cells. The analysis of unesterified fatty acids from the usual culture medium and from the cells show a gradient of concentration up to 54-fold; moreover experiments performed in minimal medium at 20 degrees C show that fatty acids accumulate up to 28-fold in the cells. Efflux rates can be measured after loading the cells at 20 degrees C; the curves are bimodal and the pseudo first-order rate constants thus determined are in the order of 0.5 min-1, as opposed to 2.5 to 5.0 min-1 for the passive-diffusion component calculated for the influx rates. Studies on the role of serum albumin at constant and at variable fatty acid-albumin molar ratios indicate that the rate of uptake is controlled by the total fatty acid concentration and not solely by the concentration of unbound fatty acids. No labelled fatty acid was found to be bound to the cytoplasmic fraction supposed to contain the fatty acids-binding protein; our results are in favour of the presence of a specific transport system for fatty acids either at the level of subcellular organelles or more likely at the surface of cardiac cells.

Animals↗
PubMed1972

Isolation and Characterization of Mutants of Escherichia coli with Cellular Division Selectively Affected by Growth on Fatty Acids.

Isolation and characterization of mutants of Escherichia coli that beta-oxidize fatty acids at normal rates, but which divide very slowly when grown on fatty acids, are described. These mutants grow normally on other carbon sources. By growth on oleate, experiments with radioactive precursors showed that the rates of incorporation into ribonucleic acid, protein, and cell wall were comparable to those observed with the parent, whereas the rate of incorporation into phospholipids was slightly decreased. Under these conditions the rate of incorporation of (32)P-orthophosphate into deoxyribonucleic acid was low. On the other hand, by growth on oleate, neither gross mass increase in the different macromolecules nor loss of viability was observed, whereas in the presence of inducer the derepression of the lac operon enzymes occurred. Therefore, extensive turnover of the macromolecules is involved when these mutants are grown on fatty acids. Studies of the crypticity and of the binding of 1-anilino-8-naphthalene sulfonate show differences in membrane structure between the mutants and the constitutive parent. Properties of these mutants, which are affected in the process of cellular division, are discussed.

Journal Article↗
PubMedDate not supplied

Two growth factor signalling pathways in fibroblasts distinguished by pertussis toxin.

The primary action of a family of mitogens including bombesin, bradykinin, vasopressin and alpha-thrombin is to activate the hydrolysis of polyphosphoinositides. Hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) by phospholipase C is mediated through coupling of surface receptors to a GTP-binding protein (Gp protein) which, in some cells, is inactivated by the toxin of Bordetella pertussis. It is not known whether this signalling pathway is involved in initiating DNA replication, whereas it has been firmly established that reinitiation of DNA synthesis can be triggered without activation of PtdIns(4,5)P2 hydrolysis by, for example, EGF (epidermal growth factor), FGF (fibroblast growth factor) and insulin/IGF-I (insulin-like growth factor-I), members of a class of mitogens known to activate receptor tyrosine kinases. Taking advantage of the fact that Chinese hamster lung fibroblasts respond to either class of mitogens and that their Gp protein appears to be sensitive to pertussis toxin, we have now analysed the toxin's effect on reinitiation of DNA synthesis and find that it inhibits up to 95% of thrombin-induced mitogenicity without affecting EGF- or FGF-induced DNA synthesis and proliferation. These findings strongly suggest that activation of PtdIns(4,5)P2-phospholipase C has a determinant function in growth control, and confirm the existence of alternative growth factor-signalling pathways independent of polyphosphoinositide breakdown.

Adenosine Diphosphate Ribose↗
PubMedDate not supplied

CT-guided intraarticular corticosteroid injection into the sacroiliac joints in patients with spondyloarthropathy: indication and follow-up with contrast-enhanced MRI.

PURPOSE: Our goal was to prospectively study the therapeutic efficacy of CT-guided intraarticular corticosteroid instillation of inflamed sacroiliac joints (SIJs) in patients with spondyloarthropathies and to evaluate the role of MRI as a procedure for establishing the indication and for therapeutic follow-up. METHOD: A total of 103 CT-guided corticosteroid injections of the SIJs were performed in 66 patients with inflammatory back pain (IBP): 37 bilateral, 29 unilateral. All patients did not respond to an immediately preceding 4 week nonsteroidal antiinflammatory therapy. Forty milligrams of a crystalline long-acting corticoid was instilled in each joint. All 66 patients underwent continuous clinical follow-up at 10 to 12 week intervals after corticosteroid injection to a maximum of 18 months. The degree of subjective complaints before and after the intervention was recorded using a analogue scale (0 = no pain, 10 = unbearable pain). Dynamic contrast-enhanced (Gd-DTPA, 0.1 mmol/kg body wt) MRI with quantitative determination of contrast enhancement was performed in all patients before the therapeutic intervention and in 38 patients at 8 +/- 4 months. RESULTS: Sixty-one of the 66 study patients (92.5%) showed a statistically significant abatement of subjective complaints from 8.8 +/- 1.3 to 3.3 +/- 2.3 (p < 0.01) at 1.7 +/- 1.1 weeks after intervention, and this improvement lasted for 10 +/- 5 months. The percentage contrast enhancement at dynamic MRI likewise showed a significant reduction from 100.3 +/- 48% before to 44.3 +/- 36.1% after intraarticular cortisone administration (p < 0.01). CONCLUSION: CT-guided intraarticular corticosteroid instillation in the SIJs may be regarded as an effective therapy for florid sacroiliitis. The severity of inflammation and the response to therapy can be determined quantitatively by dynamic MRI.

Adult↗
PubMedDate not supplied

Prenatal diagnosis of right lung agenesis using color Doppler and magnetic resonance imaging.

Unilateral lung agenesis should be suspected in fetuses presenting mediastinal shifting and absence of evidence of diaphragmatic hernia. Confirmation of diagnosis is not possible until birth as other more common lung anomalies may have a similar appearance. We present a case with right lung agenesis diagnosed at 34 weeks of gestation. Important for precise diagnosis was the color Doppler procedure, which revealed the absence of right pulmonary vessels. This is the first case in which unilateral lung agenesis has been recognized prenatally by nonvisualization of the corresponding lung vessels. The prenatally performed magnetic resonance sonography did not offer any advantages over sonography. Postnatally, the diagnosis was confirmed, and sinus venosus defect was also found. To prevent recurrent cardiopulmonary crisis, which could be caused by mediastinal shift, a tissue expander was implanted successfully at 3 months of age.

Adult↗
PubMedDate not supplied

[Purification of a protein characteristic of pathogenic strains of "Beauveria tenella" (author's transl)].

Purification of the protein which in immunoelectrophoresis is responsible for the precipitation are characteristic of the pathogenic strains, can easily be obtained by isoelectrofocalisation: two protein fractions are isolated. These differ in their isoelectric points and in their relative electrophoretic migration coefficients in polyacrylamide gel, but exhibit the same antigenic specificity.

Animals↗