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Biomedical subjects

M Dechaux

Publications and source records attributed to M Dechaux.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1990

Quantification of renal Na-K-ATPase activity by image analysing system.

The localisation of renal Na-K-ATPase activity along the rat nephron by a cytochemical method, and its quantification by an image analysis system, are described in this paper. Frozen kidney sections were exposed to a trapping agent, the lead ammoniac-citrate-acetate complex (LACA), and to all the substrates necessary to the enzyme activity. The absorbance of the histochemical reaction product (precipitated in situ), proportional to the enzymatic activity, was then measured through the analysis of the grey levels of the transmitted image of the kidney section. This method was both sufficiently sensitive and technically simple to permit measurements of the enzyme in large numbers of tubules and to determine its activity in each region of the nephron. The Na-K-ATPase activity has been determined in the proximal convoluted tubule (PCT), the medullary thick ascending limb of the Henle's loop (mTAL), and the distal convoluted tubules (DCT) of the rat nephron. The Na-K-ATPase distribution shows an activity per millimeter tubule length higher in the DCT than in the mTAL and the PCT: 1,406 +/- 33, 823 +/- 64, and 350 +/- 71 pmoles Pi/tubule mm/h, respectively. In conclusion, the described method allows the segmental quantification of Na-K-ATPase activity at a cellular level and offers a precise approach to the analysis of this enzyme along the length of nephrons.

Animals↗
PubMed1990

Glomerular function and microalbuminuria in children with insulin-dependent diabetes.

Renal function has been evaluated in 45 diabetic children (age 12.5 +/- 4 years) with a mean diabetes duration of 4.9 +/- 3.5 years. Glomerular filtration rate (GFR; inulin and creatinine clearances), renal plasma flow (RPF; PAH clearance), resting urinary albumin excretion (UAE) were measured and compared with indexes of metabolic control: Hb A1C and blood glucose values (mean, post-prandial and maximal excursion) on the same day. GFR (inulin clearance) and RPF were significantly increased in the diabetic group (171 +/- 31 and 778 +/- 172 ml/min per 1.73 m2) compared with controls (124 +/- 18 and 631 +/- 128 ml/min per 1.73 m2). Both parameters were strongly correlated (r = 0.73; P less than 0.001). Creatinine clearance was not correlated to inulin clearance. Hyperfiltration (inulin clearance above 160 ml/min per 1.73 m2) was noted in 61% of the patients and was independent of diabetes duration. Five diabetic children had a UAE level above 15 micrograms/min. No relationship could be established between UAE and any of the metabolic indexes; GFR was weakly correlated to HbA1C (r = 0.35; P less than 0.05), to mean (r = 0.37; P less than 0.05) and post-prandial blood glucose (r = 0.37; P less than 0.05). In contrast, there was a strong correlation between GFR and the maximal blood excursion (r = 0.62; P less than 0.001). The study shows that renal abnormalities can be detected with a high frequency in diabetic subjects characterized by both an early onset and a short duration of diabetes and suggests the need for a more systematic evaluation of renal parameters in this population.

Adolescent↗
PubMed1990

Renal functional reserve in children with reduced renal mass: study by two dietary periods.

It has been suggested that the "renal functional reserve" (RFR) defined by the rise in glomerular filtration rate (GFR) after a protein load could disappear in patients with severe nephron loss but with a normal GFR. This study compared, in 17 children, inulin clearance (Cin) measured by the plasma inulin plateau at the end of two 14-day randomized periods differing in protein intake: 100% (low protein, LP), or 200% (high protein, HP) of recommended dietary allowances (RDA). Diets were aimed at maintaining food habits and energy intake. Compliance was assessed by records of the last 3-4 days, an interview with the dietician and by urinary nitrogen measurements. Mean actual protein intake was 109% (56%-139%) RDA for the LP period and 220% (163%-319%) RDA for the HP period. Cin did not change in 14 children with GFR below (n = 7) or within (n = 7) the normal range. Cin was higher in the HP period than in the LP period (+32, 50, 63%) in 3 children who had a 50% (single kidneys) or a 25% (sclerosed glomeruli) nephron loss. Non-responding children had a GFR below 105 ml/min per 1.73 m2. Nephron loss (70% sclerosed glomeruli) was estimated in only 1 child with no RFR. The results suggest that GFR measurement after prolonged dietary stimulation could help in evaluating the severity of nephron loss in children with normal or borderline GFR. The prognostic value of this test has to be confirmed by long-term follow-up.

Adolescent↗
PubMed1990

Effects of acute cisplatin administration on renal ATPase activities and magnesium excretion of rats.

Male Wistar rats were killed 1, 2, or 4 days after a single intraperitoneal injection of cisplatin (5 mg/kg). Functional renal indices, enzymatic activities, and morphological variables were studied. One day after the injection, the treated group showed an increase in the magnesium and phosphate fractional urinary excretion (FE) vs the control group (FE Mg = 5.2 +/- SEM 0.5% vs 13.0 +/- 1.7%; P less than 0.01; and FE P = 4.7 +/- 0.7% vs 14.0 +/- 1.9%; P less than 0.01). Two days after cisplatin administration, a decrease in creatinine clearance of treated animals was found, to 0.33 +/- 0.03 vs 0.51 +/- 0.03 ml/min; P less than 0.05. Na-K-ATPase and ouabain-insensitive ATPase activities were studied in the proximal convoluted tubule, the medullary thick ascending limb of the Henle's loop (mTAL), and the distal convoluted tubule. Only in mTAL one day after the cisplatin injection was there a decrease in Na-K-ATPase activity in the treated group vs controls (1103 +/- 145 vs 1734 +/- 189 pmol Pi/mm.h; P less than 0.05). Morphological studies showed a decrease in mTAL diameters on day 1, and an increase in proximal convoluted tuble diameters at day 2 of treated rats vs controls, at 27.8 +/- 0.6 vs 31.4 +/- 0.7 microns; P less than 0.05, and 50.4 +/- 1.2 vs 47.4 +/- 0.2 microns; P less than 0.05 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1990

[Kidney functional reserve. Studies in humans].

The glomerular filtration rate (GF) of each nephron can vary, with increases being caused by stimuli such as nephron reduction and ingestion of proteins. This "functional reserve" (FR), detectable by protein load tests, may be lost in extensive renal destruction where the remaining nephrons are in a permanent state of maximal stimulation. If this hypothesis is true, FR determinations would be of greater value than baseline GFR measurements for evaluating the condition of the remaining parenchyma. A very large number of studies have addressed the FR in normal subjects and have used either diets containing variable amounts of proteins or acute loads given orally (approximately 1 g/kg cooked meat) or intravenously (amino acids). All these studies have evidenced increases in the GFR after the load, regardless of its type, but with major variations across studies and patients. Subjects with a single healthy kidney seem to retain a FR whose magnitude is equal to or smaller than the FR in normal subjects. Conflicting data have been reported in more extensive destruction of the parenchyma, where the FR has been shown to either disappear or persist with no change in percentage. Thus, the practical value of GFR determinations after protein loads has not as yet been established and should be specified using better standardized methods that do not rely on creatinine clearance, at least during oral load tests where serum creatinine levels increases and is no longer stable.

Child↗
PubMed1990

[Evaluation of new markers of bone metabolism in renal osteodystrophy in children].

Serum intact parathormone (PTH 1.84) and osteocalcin levels were evaluated as early markers for secondary hyperparathyroidism in a group of pediatric patient treated with chronic hemodialysis. PTH 1.84 levels which were more closely related with alkaline phosphatase levels than PTH 53.84 levels, allowed to identify a group of children without biologic or roentgenographic evidence of hyperparathyroidism and with a normal residual hormone level. PTH 1.84 levels seem to be a reliable indicator of parathormone secretion than conventional assays and may be used as a routine test for monitoring children under chronic hemodialysis. Conversely, the plasma osteocalcin level measured by radioimmunoassay was increased in all studied patients regardless of parathyroid status and seemed to be of little value for monitoring renal osteodystrophia. Lumbar vertebral plate bone density studies disclosed abnormalities of bone mineralization in half the children with renal failure. Dialyzed or non dialyzed. Patients with decreased bone mineralization presented, in most of cases, a history of previous steroid treatment. A group of children with very severe renal failure had increased bone mineralization. The interpretation of this abnormality remains to be determined.

Bone and Bones↗
PubMed1989

Enalapril does not alter renal function in normotensive, normoalbuminuric, hyperfiltering type 1 (insulin-dependent) diabetic children.

Using a prospective randomised double-blind crossover design, the effect of the angiotensin converting enzyme inhibitor enalapril compared to a placebo was studied in 18 normotensive, normoalbuminuric Type 1 (insulin-dependent) diabetic children. Each patient had a high normal or clearly elevated glomerular filtration rate (145 ml.min-1.1.73 m2 or higher) in the 6 months prior to the study. Enalapril, 0.5 mg.kg-1.day-1, was given for 4 weeks followed by placebo for 4 weeks, or vice versa. At the end of each period, glomerular filtration rate, renal plasma flow, blood pressure, plasma renin activity, and converting enzyme activity were determined. Enalapril caused significant reduction (p = less than 0.001) in blood pressure and converting enzyme activity and a rise in plasma renin activity. A slight but not significant rise in glomerular filtration rate and renal plasma flow without change in filtration fraction was observed. These data suggest that the renin angiotensin system is not involved in the glomerular hyperfiltration of Type 1 diabetes, and can be interpreted as showing no evidence for the presence of intraglomerular hypertension in these patients.

Adolescent↗
PubMed1989

Comparison of plasma renin and prorenin in healthy infants and children as determined with an enzymatic method and a new direct immunoradiometric assay.

We compared plasma active and inactive renin (prorenin) concentrations and activities in infants and children, as measured with a newly available direct immunoradiometric assay kit for active renin and a widely used enzymatic renin assay (plasma renin activity). The study was performed in 57 healthy infants and children under steady-state conditions and in eight subjects after orthostatic stimulation. Our study; (i) reports concentrations for active and inactive renin determined by the immunoradiometric assay in normal infants and children; (ii) confirms, by use of the immunoradiometric assay, the previously described decrease in plasma active and inactive renin, as measured by the enzymatic assay, with increasing age; and (iii) shows close correlations between the results obtained by immunoradiometric and enzymatic assays for active and inactive renin in normal infants and children.

Adolescent↗
PubMed1989

Persisting glomerular hyperfiltration in short-term diabetic children without microalbuminuria.

The renal function in a group of diabetic children (n=29;age;4-17 yr; IDDM duration: 1,5-13 yr) was studied with a 3 year interval. At the first evaluation glomerular filtration rate (GFR) as assessed by inulin clearance was significantly increased compared to control values (167 +/- 32 vs. 124 +/- 18 ml/min/1.73 m2; pl less than 0.01). Eighteen out of 29 children exhibited a glomerular hyperfiltration (GFR greater than 160). Three years later mean GFR was identical (169 +/- 25 ml/min/1.73 m2) and 16 children were hyperfiltrating. Among them, 11 have had a persisting glomerular hyperfiltration over the 3-year period. Renal plasma flow (RPF) was positively correlated to GFR (r=0.7; p less than 0.01) and remained elevated at both evaluations (794 +/- 163 and 812 +/- 157 ml/min/1.73 m2, p greater than 0.01 vs, control values). When the children were separated into 3 groups according to IDDM duration no significant differences were observed in the results for GFR and RPF, Mean urinary albumin excretion was comparable at the 3-year interval, and not significantly different from the control values (5.2 +/- 3.7 and 8.2 +/- 6.6 respectively vs. 8.65 +/- 4 microgram/min). None of the children demonstrated a persistent microalbuminuria. This study reveals a high proportion of diabetic children with a persisting glomerular hyperfiltration, without any other symptom of incipiens nephropathy, If elevated GFR plays an important role in the development of diabetic nephropathy, this study emphasizes the value of regular evaluation of renal function in diabetic children.

Adolescent↗
PubMed1989

Anomalies in pH 7.40 correction in ionised calcium analysers.

As a preliminary step in a study of the effects of calcium ligands on the pH standardisation of ionised calcium (Ca2+) measurement in blood, the change in Ca2+ induced by Pco2 variation was investigated in 12 serum pools on three different instruments. This type of study should yield a log Ca2+ = f(pH) linear relationship in a pH range around pH 7.40 with a slope characterising the pH-sensitive calcium buffer capacity of the specimen. The pH 7.40 correction line should be horizontal. This was the case for an ICA2 analyser but not for an ICA1 or a Nova 8 analyser. The difference was due to an incorrect setting of the built-in slope correction factor in the ICA2: fortuitously its value was close to the effective slopes of the serum pools used for the test. Thus the anomalous behaviour of the ICA1 and the Nova 8 was due to a discrepancy between the standard built-in algorithm and the characteristics of our serum pools. These findings led us to question the use of a constant correction factor to normalise actual ionised calcium values.

Autoanalysis↗
PubMed1989

Inadequate algorithm: a cause for 'incorrect pH 7.40 correction' in ionized calcium analysers.

As a preliminary step in a study of the effects of calcium ligands on the pH standardization of ionized calcium (Ca2+) measurements in blood, the slope of logCa2+ = f(pH) linear relationship characterizing the pH-sensitive calcium buffer capacity of the specimen was investigated in 12 serum pools on three different instruments. The pH 7.40 correction line should be horizontal. This was the case for the ICA-2 but not for the ICA-1 and the NOVA-8. The discrepancy was caused by an incorrect setting of the built-in slope correction factor in the ICA-2; coincidentally, its value was close to the effective slopes of the serum pools used in the study. Thus, the 'abnormal' behaviour of the ICA-1 and the NOVA-8 was caused by an inadequacy of the built-in algorithm to the characteristics of our serum pools. These findings lead us to reconsider the use of a fixed and constant correction factor to normalize actual ionized calcium values.

Algorithms↗
PubMed1989

Anticoagulant-induced preanalytical errors in ionized calcium determination on blood.

When anticoagulated blood is necessary for ionized calcium (Ca2+) measurements especially in urgent circumstances, the type (sodium or 'calcium-titrated' heparinate) as well as the form (aqueous or dry) of anticoagulant induce preanalytical errors. To quantify these modifications Ca2+ was measured in three aqueous solutions and in three serum pools in different 'sampling' conditions. Incomplete syringe filling and specimen volume/syringe nominal volume ratio effects were tested. Syringes were rinsed (i) with saline to yield 'pure' dilution effect ('solution-dilution'); (ii) with sodium heparinate to study binding; (iii) with calcium-titrated heparinate to evaluate 'calcium-distortion'. All types of errors increased when syringes were not filled to their nominal volume, especially on small-sized specimens. Detailed tables provide percentage error values for all sampling conditions. Thus, 'solution-dilution' can reach -5%; binding is always important (-15 to -50%). 'Calcium-distortion' is minimal, around 1.25 mmol/l Ca2+, but can reach -7% for high Ca2+ and +10% for low Ca2+.

Anticoagulants↗
PubMed1987

Effects of prolactin on Na-K-ATPase activity along the rat nephron.

To test prolactin (PRL) action on osmoregulation in mammals, we evaluated in the rat the effect of this hormone on a major enzyme in renal regulation of water and electrolyte: renal Na-K-ATPase. Enzyme activity was determined by cytochemistry in medullary ascending limb (MAL) and distal convoluted tubule (DCT) from rats treated either by bromocriptine, or by PRL. Three hours after a bromocriptine injection (0.1 mg/100 g IP) a significant decrease of Na-K-ATPase activity is observed in both MAL (80% of control values, p less than 0.001) and DCT (78% p less than 0.01). Reciprocally, a significant (p less than 0.001) increase in enzyme activity is induced 3 h after a single PRL injection (140 micrograms/100 g IM), in both segments (MAL: 165%, DCT: 172% of control activities) and persists 6 h after the injection (MAL: 130%, DCT: 118%). Na-K-ATPase activity was correlated to plasma PRL levels (r = 0.78 in DCT, r = 0.89 in MAL). A direct effect of PRL on the tubule is suggested by results from experiments in which PRL, at various concentrations, is added in vitro on renal slices before Na-K-ATPase activity measurements. The increase in Na-K-ATPase activity exhibits a log-dose dependency with PRL concentration (p less than 0.01) and is still observed when AVP antagonist is added before PRL incubation, ruling out the possible role of AVP contamination of PRL. These results suggest a direct effect of PRL on renal Na-K-ATPase in MAL and DCT.

Aldosterone↗
PubMed1985

[Diffuse arterial calcified elastopathy].

Diffuse arterial calcified elastopathy was observed in 6 pediatric patients presenting with severe renovascular hypertension. Renal ultrasonography showed a characteristic pattern, the dotted corticomedullary junction, related to the increased echogenicity of the interlobar and/or arcuate arteries. Superficial temporal artery biopsy demonstrated the presence and the extension of the calcifying process involving the elastic layers of the muscular arteries. This clinicopathological syndrome may be heterogeneous from an etiological point of view: etiologic investigations led to the diagnosis of pseudoxanthoma elasticum in 2 patients; no etiology could be found in the others.

Arteries↗
PubMed1984

Inactive renin in infants and children: evidence for its physiological response to orthostasis in children.

The aim of this work was to investigate the presence of inactive renin (IR) in plasma of normal infants and children and nephrectomized children and to study the plasma IR response to stimulation of the renin-angiotensin system (orthostasis) in children. The study was performed in 10 normal infants (2 days to 1 yr old), 28 normal children (1-15 yr old), 8 nephrectomized children (8-14 yr old), and 7 normal adults (20-40 yr old). IR was calculated as the difference in renin activity in trypsin-treated (1500 micrograms/ml) plasma, e.g. total renin (TR), and in untreated plasma, e.g. active renin (AR). IR was not detectable in most infants in the supine position, but their AR values were high (8.8-30 ng/ml X h). Moreover, in some of these infants, trypsin appeared to degrade renin activity, since TR values were lower than AR values. IR was detectable in 3 infants and 27 children, but their AR values were in a lower range (0.3-10 ng/ml X h). Trypsin degradation of renin activity was not found in either children or adults. With increasing age (2 days to 40 yr), AR decreased while IR and the IR to TR ratio increased significantly (P less than 0.001). A significant (P less than 0.001) inverse relationship was found between the IR and AR values of subjects 2 days to 40 yr old. IR was detectable in all nephrectomized children and represented 25% of normal values, while AR was undetectable (less than 0.1 ng/ml X h). In children in the upright position, IR decreased and AR increased significantly (P less than 0.001) in a reciprocal manner. TR did not change. These data suggest 1) that trypsin degradation of renin activity and absence of trypsin-activated IR are specific to infants with high AR levels, and 2) that IR might be activated in vivo into AR, especially after changes in position in children. IR could be a prorenin playing a physiological role in children.

Adolescent↗