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Biomedical subjects

M Dechaux

Publications and source records attributed to M Dechaux.

15 recordsLinked to original sources
PubMed1992

Protein kinase C activation causes inhibition of Na/K-ATPase activity in Madin-Darby canine kidney epithelial (MDCK) cells.

To evaluate the influence of protein kinase C (PKC) activation on Na/K-ATPase activity in MDCK cells, we studied the effect of phorbol myristate acetate (PMA) and two diacylglycerol analogues, oleoylacetylglycerol and dioctanoylglycerol, on the enzyme activity. Na/K-ATPase activity was determined by cytochemistry. PMA induced a time- and dose-dependent inhibition of Na/K-ATPase activity and at 100 ng/ml decreased the enzyme activity by 55% of the initial value. These effects were mimicked by oleoylacetylglycerol and dioctanoylglycerol, and were abolished by two inhibitors of PKC, 1-(5-isoquinolinylsulphonyl)-2-methylpiperazine (H7) and sphingosine. A phorbol ester that does not activate PKC, 4 alpha-phorbol 12,13-didecanoate, did not inhibit Na/K-ATPase activity. PMA inhibition persisted in the presence of cycloheximide and actinomycin D but not in the presence of amiloride. Dopamine (10 microM) inhibition of Na/K-ATPase activity was abolished in a dose-dependent manner by sphingosine. Results suggest that in MDCK cells Na/K-ATPase is an effector protein for PKC and that dopamine inhibition of its activity may be mediated by PKC.

Amiloride↗
PubMed1992

Primary distal tubular acidosis in childhood: clinical study and long-term follow-up of 28 patients.

The long-term follow-up of 28 patients with congenital primary tubular acidosis is described. Ten patients had affected siblings but no history of similar symptoms in the preceding generation. Deafness was associated in 14 patients and developed before 12 years of age. Deafness was present in all familial cases, and patients without deafness showed no familial incidence, suggesting the existence of two different entities. All patients had growth retardation, which was more severe in the older patients and was always markedly improved by alkaline therapy. Rickets was found in some patients but seemed related to vitamin D deficiency. Catch-up growth was limited to the first 2 years of therapy in patients treated before 2 years of age, but sometimes lasted longer in older patients. Of the 12 patients who reached adulthood, those without rickets achieved a normal height but the others did not. We believe that therapy should be continued throughout life because of the risk of nephrocalcinosis.

Acidosis, Renal Tubular↗
PubMed1992

Renal effects of angiotensin II in normotensive subjects on short-term cilazapril treatment.

In 13 normotensive subjects on a normal sodium diet, we studied renal vascular, blood pressure, and hormonal changes induced by infusion of exogenous angiotensin II (Ang II) (5 ng/kg/min) during baseline conditions and after 5 days of cilazapril administration. In both conditions, Ang II elicited a slight pressor response accompanied by renal hemodynamic and hormonal changes that were similar. This suggests that hourly changes in Ang II concentrations and/or in Ang II receptor density after short-term administration of the angiotensin-converting enzyme (ACE) inhibitor cilazapril does not significantly affect renal vascular reactivity. In addition, these results also indirectly suggest that most of the renal effects of ACE inhibition are mediated through suppression of Ang II formation.

Adult↗
PubMed1992

Evaluation of capillaries for ionized calcium measurements.

Commercially available capillaries containing calcium-titrated heparinate as an anticoagulant designed specifically for ionized calcium measurements in blood were tested with four serum pools with ionized calcium concentrations adjusted to 0.75, 1.25, 1.50 and 2.50 mmol/L. Although this is the best available anticoagulant for this purpose, the use of these capillaries induced a +/- 1% alteration of the original concentration around the titration level and changes of -2 to +10% at pathological values. The amount of heparinate released exceeded the recommended limit of 50 IU/mL of specimen with some variability (6% to 20%). Increasing the amount of anticoagulant with the objective of avoiding magnetic mixing did not seem to be a valid approach. Finally, Radiometer, IL and AVL capillaries gave the best available and acceptable results in terms of alterations in ionized calcium.

Blood Specimen Collection↗
PubMed1992

Effects of prolactin on Na+K(+)-ATPase activity in the nephron during maturation in the rat.

The effect of prolactin (PRL) on renal Na+K(+)-ATPase was investigated in 7-d-old neonatal rats. Animals were treated by bromocriptine (Br; a blocker of endogenous PRL secretion), and the enzyme activity was compared with that of untreated controls. Na+K(+)-ATPase was determined in renal sections in the medullary thick ascending limb of Henle's loop and in the distal tubule by cytochemistry. In the distal tubule, Na+K(+)-ATPase activity was significantly lower in Br-treated animals than in controls (330 +/- 169 versus 558 +/- 146 pmol inorganic phosphate/mm/h, respectively); values did not differ in the medullary thick ascending limb of Henle's loop between Br-treated and control animals (132 +/- 74 versus 165 +/- 113 pmol inorganic phosphate/mm/h, respectively). In vitro effects of PRL were investigated by determining the enzyme activity after incubation of renal sections from Br-treated and untreated animals with different concentrations of PRL. Results suggest that PRL may affect renal Na+K(+)-ATPase activity in the distal tubule in the neonatal period but do not support a major role of PRL in the enzyme maturation.

Animals↗
PubMed1991

Increased monocyte-dependent suppression of polyclonal activation of B lymphocytes from cystinotic children.

In infantile cystinosis the amino acid cystine preferentially accumulates in phagocytic cells, polymorphonuclear leucocytes (PMN) and monocytes, rather than in lymphocytes. We previously described functional abnormalities in the oxidative metabolism and locomotion of cystinotic PMN and monocytes. The present study shows an abnormal lymphocyte polyclonal activation as evidenced by a decreased immunoglobulin (Ig) production and generation of Ig-containing cells (ICC) in cultures of peripheral blood mononuclear cells (PBMC) from cystinotic children upon stimulation with pokeweed mitogen and Staphylococcus aureus Cowan I. However, monocyte depletion from cystinotic PBMC fully reconstituted Ig production and ICC generation, indicating: (1) the presence of an increased monocyte-dependent suppression on lymphocyte polyclonal activation, and (2) that the intrinsic ability of cystinotic lymphocytes to respond to polyclonal stimulation was preserved. The increased cystinotic monocyte-dependent suppressive effect was not mediated by prostaglandin E2 (PGE2) since its production by cystinotic PBMC upon polyclonal activation was not different from that of controls. In addition, the sensitivity of cystinotic lymphocytes to the immunosuppressive effect of varying concentrations of exogenous PGE2 was similar to that of controls. Finally, indomethacin and 2-mercaptoethanol, two agents able to scavenge hydroxyl (.OH) radicals, restored Ig production by cystinotic PBMC, suggesting a role for reactive oxygen species in the increased cystinotic monocyte-dependent suppression.

Adolescent↗
PubMed1991

Preanalytical errors in ionized calcium measurements induced by the use of liquid heparin.

The use of heparin in a liquid form to measure ionized calcium (Ca++) in plasma or whole blood can induce preanalytical errors by dilution and by changing the original Ca++ value by binding or by re-equilibration with calcium in the anticoagulant solution. To quantify these errors, Ca++ was measured on serum pools under different sampling conditions. Incomplete syringe filling and specimen volume/syringe nominal volume ratio effects were tested. Syringes were rinsed with saline to yield pure dilution effects, with sodium heparinate to study binding and with calcium-titrated heparinate to evaluate 'calcium-distortion'. Detailed tables provide percentage error values for all sampling conditions. Dilution errors could reach -5% and binding was always important (-14 to -50%). Distortion was minimal around 1.25 mmol/L but could reach -4% for high and +8% for low Ca++ values. Errors increased when syringes were not filled to their nominal volume, especially with small-sized specimens.

Anticoagulants↗
PubMed1991

In vitro evaluation of a heparinized blood sampler for ionized calcium measurement.

When ionized calcium measurements are needed urgently blood has to be sampled with an anticoagulant to allow rapid specimen processing. Heparinate salts cause a decrease in ionized calcium by binding which is clinically significant when the concentration exceeds 15 IU/mL of whole blood. The use of an anticoagulant in an aqueous state induces 'solution-dilution' errors. To avoid these two types of error the use of calcium-titrated sodium heparinate in a dry state has been proposed. However, in this situation the actual calcium concentration could be modified if its value were different from the titration level. This possibility has been studied using a commercially available sampler (Radiometer B-129). When the sampler was used as recommended, errors were non-significant around 1.25 mmol/L. There was a +3% increase for low (0.75 mmol/L) values and a -2% decrease for high (2.50 mmol/L) values. Incomplete syringe filling increased these errors.

Calcium↗
PubMed1991

Use of calcium-titrated sodium heparinate for ionized calcium determination on plasma and whole blood (heparinized blood sampler B-129 Radiometer).

We report modifications of ionized calcium as observed on specimens collected in a commercially available sampling device (Radiometer B-129). When the sampler is used as recommended, errors are non-significant around 1.25 mmol l-1. There is a +3% increase for low (0.75 mmol l-1) values and a -2% decrease for high (2.50 mmol l-1) values. Incomplete syringe-filling increases these errors.

Blood Specimen Collection↗
PubMed1991

[Atrial natriuretic factor in hemodialyzed children].

Indirect evidence suggest that volume overload is the major determinant of plasma atrial natriuretic factor (ANF) elevation in hemodialysis patients. Correlations between plasma ANF levels and extracellular volume (ECV) were investigated by simultaneously measuring both parameters in 30 pediatric hemodialysis patients (aged 1 to 17.5 years; 18 M, 12 F) 24 hours after a dialysis session. Plasma ANF was determined using a commercially available RIA (Amersham) after plasma extraction (SEP-Pack C18); ECV was estimated by determining the volume of distribution of inulin and expressing the result as the % of body weight. In hemodialysis children, ANF levels ranged from 43 to 427 pg/ml (versus 30-70 pmoles/ml in age-matched controls) and EVC ranged from 17 to 33% BW. A significant positive correlation was found between plasma ANF levels and ECV (r = 0.66; p less than 0.001). Patients who exhibited falls in blood pressure during the dialysis session had lower mean ANF and ECV values (133 +/- 90 pg/ml and 23 +/- 3% BW, respectively) than those who did not (211 +/- 123 pg/ml and 26 +/- 4% BW, respectively). Conversely, patients who needed chronic antihypertensive therapy had higher mean plasma ANF and ECV values (204 +/- 122 pg/ml and 26 +/- 4% BW, respectively) than those who did not (149 +/- 100 pg/ml and 23. 5 +/- 4.5% BW, respectively). In a small subgroup of patients who had repeated determinations, individual plasma ANF and ECV changes were closely matched and both parameters were well correlated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1979

Micro determination of plasma renin activity in normal infants and children of capillary and venous blood.

Plasma renin activity (PRA) has been measured by microassay on capillary and venous blood sampled simultaneously in 21 subjects; there is no significant difference between these two groups of PRA values. PRA values in normal infants, children and adults have been measured with this microassay and the results are similar to those previously published by authors using different radioimmunological assays.

Adult↗
PubMed1978

[Plasma creatinine, and clearance and urinary excretion of creatinine in children].

The 24 hour clearance of endogenous creatinine was compared with that of inulin in 112 children aged between 15 months and 17 years. The children had a variety of kidney disorders with renal function than ranged from normal to terminal renal failure. When the inulin clearance was less than 10 ml/min/1.73 m2 it was on average 75% of the value of the creatinine clearance. Between 10 and 60 ml/min/1.73 m2 the relationship of the inulin clearance to that of creatinine was similar (77%) but above 60 ml/min/1.73 m2 the ratio of the inulin clearance to that of creatinine was 1.05 with a wide scatter. With increasing degrees of renal failure the plasma creatinine increased less in the children under 2 years old than in those over this age so it is poor index of glomerular function in infants. In renal failure the urinary excretion of creatinine in 24 hours was reduced. When the clearance was less than 10 ml/min/1.73 m2, the urinary creatinine excretion for children under the age of 2 was 58% of the normal for the age and for children over 2, it was 86% of the expected mean.

Adolescent↗
PubMed1977

[Electrometric determination of urinary ammonia using a continuous-flow automatic method].

A critical study has been designed to evaluate the application of an electrometric method to the assay of ammonia in urine. The use of NH3-gaz permeable membrane electrode with a continuous flow system seems to have solved most of the problems evoked by former studies. The results obtained show that the method is reliable for the use in clinical routine. The simplification of the ammonia measurement procedure thus achieved will allow an important increase in the number of renal function tests that a clinical routine laboratory can handle in a hospital.

Ammonia↗
PubMedDate not supplied

Zinc bone loss in chronic renal failure and chronic metabolic acidosis.

The effects of chronic metabolic acidosis (CMA) on zinc (Zn) bone content and urinary excretion were examined in the presence of normal or reduced renal function together with some aspects of calcium (Ca) metabolism. Four groups of rats were compared. All were fed a 30% protein and 9 mg Zn/100 g diet. Two were uremic (U): The first developed acidosis (UA), which was suppressed in the other (UNA) by NaHCO3 supplement. Two other groups had normal renal function: One was normal (CNA), and the other had NH4Cl in the drinking water and acidosis (CA). Femur total Zn and Ca content was markedly reduced by CMA and was not affected by uremia. Zn urinary excretion was increased by CMA and unaltered by uremia. Ca urinary excretion was markedly reduced in uremic rats, but was enhanced in both acidotic conditions. Urinary Ca and Zn showed a strong correlation in uremic and in control rats. Plasma parathormone and 1,25(OH)2D3 were unchanged by CMA. These data are in agreement with a direct primary effect of CMA on bone in releasing buffers. CMA induces bone resorption and a parallel decrease of mineral bone components, such as Ca and Zn, with little or no role of PTH, 1,25(OH)2D3 and of uremia itself.

Acidosis↗