PubMed Health⌕ Search

Biomedical subjects

M Froissart

Publications and source records attributed to M Froissart.

At least 19 recordsLinked to original sources
PubMed1992

Plasma membrane Na(+)-H+ antiporter and H(+)-ATPase in the medullary thick ascending limb of rat kidney.

To characterize H+ transport mechanisms in a fresh suspension of rat medullary thick ascending limb (MTAL) tubules, we have monitored intracellular pH (pHi) with use of the fluorescent probe 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein. First, a Na(+)-H+ antiporter was identified in bicarbonate-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)-buffered media at 25 degrees C. pHi recovery of Na-depleted acidified cells was dependent on extracellular sodium concentration, which was inhibited by amiloride in a manner consistent with simple competitive interaction with one external transport site (amiloride Ki = 1.5-2.1 x 10(-5) M); Na-induced pHi recovery of acidified cells was electroneutral since it was not affected by 5 or 100 mM extracellular potassium in the presence or absence of valinomycin. Second, at 37 degrees C, pHi recovery after acute intracellular acidification caused by 40 mM acetate addition to cell suspension was inhibited 36% by 200-400 nM bafilomycin A1, a macrolide antibiotic that specifically inhibits vacuolar-type H(+)-ATPase at submicromolar concentrations. In addition, amiloride-insensitive pHi recovery was inhibited by bafilomycin A1, 10(-3) M N-ethylmaleimide, and 10(-4) M preactivated omeprazole but not by 10(-5) M vanadate, 10(-4) M SCH 28080, or removal of extracellular potassium. Also, metabolic inhibition by absence of substrate, 10(-4) M KCN, or 5 x 10(-4) M iodoacetic acid inhibited amiloride-insensitive pHi recovery. The inhibitory effects of absence of metabolic substrate and iodoacetic acid were removed by reexposure to glucose and L-leucine and by exogenous ATP, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗
PubMed1991

Mechanisms of H+/HCO3- transport in the medullary thick ascending limb of rat kidney.

The rat MTAL secretes protons into the tubular fluid and thus absorbs bicarbonate at substantial rates. Yet the cellular mechanisms of H+/HCO3- transport in the rat MTAL remain largely unsettled. We have performed intracellular pH recovery studies with use of the fluorescent probe BCECF in suspensions of rat MTAL fragments. Luminal H+ secretion occurs by two mechanisms (each responsible for 50% of the normal pHi recovery rate): (1) an electroneutral Na+/H+ antiporter that has an Na-Km of about 11 mM and is inhibited by amiloride (Ki = 2.8 x 10(-5) M); (2) a primary H+ pump that is inhibited by 10(-4) M NEM and 10(-4) M omeprazole, but not by 10(-4) M vanadate or removal of external K. These results suggest the presence of a vacuolar H(+)-ATPase rather than a H(+)-K(+)-ATPase. Basolateral HCO3 exit occurs predominantly by a Cl(-)- and Na(+)-independent electroneutral K+/HCO3- symporter, that has an HCO3-Km of about 17 mM, and is partially inhibited by 10(-4) M DIDS. Basolateral HCO3- efflux was not accompanied by variations of membrane potential monitored with the Em-sensitive fluorescent probe DIS-C3-5, and was not affected by maneuvers that depolarize the cells. It was strongly inhibited by cellular K depletion and dependent on transmembrane K gradient. We conclude that the rat MTAL should secrete protons through both Na+/H+ antiporter and H(+)-ATPase, and that basolateral HCO3- exit should occur through an electroneutral K+/HCO3- symporter.

Bicarbonates↗
PubMed1991

[Comparative study of three assays for serum IgA against Chlamydia trachomatis].

This study was undertaken to evaluate the diagnostic value of detection and titration of specific IgA antibodies against Chlamydia trachomatis in active infections of the upper genital tract. Three different techniques using L2 serovar antigens were compared: immunofluorescence on cells infected with Chlamydia trachomatis, microimmunofluorescence as described by Wang and Grauston, and an indirect immunoperoxidase method on infected cells. Good correlations were found between the three techniques. Results demonstrated that the cutoff level should be 1/16.

Chlamydia Infections↗
PubMed1979

[Associated myasthenia and disseminated lupus erythematosus. A report on two cases and complete review of the published literature (author's transl)].

Two patients aged 47 and 48 years respectively were found to have associated immunity disorders: myasthenia and DLE in the first case, and erythroblastic anemia, myasthenia, a lupus syndrome, and a thymoma in the second case. The association of myasthenia and DLE has been reported 39 times in the published literature (20 times only if stricter biological criteria are applied). The association does not increase the severity of the patient's condition and a thymoma is not present more frequently. Studies on the major histocompatibility complex and lymphocyte levels are still insufficient in this context: the haplotype was HLA A1 B8 in three cases out of seven. The physiopathological data available cannot confirm the possibility of a common pathogenesis in which the thymus and lymphocytes could play a determining role.

Antibodies↗
PubMed1979

[Value of extra-intracranial anastomosis: based on a series of 65 cases].

The authors describe the results obtained in a series of 65 patients following extra-intracranial cortical anastomosis. The best indications for this procedure are transitory ischemic accidents which cannot be approached by the direct cervical route. Cases of prolonged or definitive vascular accidents and more especially localized lesions also gave valuable results but these depend upon the condition of the cerebral parenchyma which must be carefully evaluated.

Brain Ischemia↗