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B Lacour

Publications and source records attributed to B Lacour.

At least 73 records · Page 4Linked to original sources
PubMed1997

Validation by image analysis of a turbidimetric method to study calcium oxalate crystallization.

Numerous studies of calcium oxalate crystal formation have been carried out in the past two decades. In the present study, experiments were carried out to validate a turbidimetric method allowing to assess the calcium oxalate crystallization process. This method is quick and reproducible and can be used to quantify the inhibition of calcium oxalate crystal growth by various compounds. An experimental method of validation has been developed, which consisted in filtering solutions pure or containing modifiers at given crystallization times, photographing the filters used on scanning electron microscopy and analyzing the images using mathematical methodology. The results obtained through image analysis, namely crystal density (mean particle number per unit volume) and mean area, were correlated with the turbidimetric parameters. This finding was consistent with the qualitative examination of the photographs. Moreover, the morphological differences in crystals observed on the photographs were confirmed by the calculated length/width ratio. One can therefore assume that inhibition of calcium oxalate crystal growth is at least, partly explained by surface adsorption phenomena, which may add to complex formation.

Calcium Oxalate↗
PubMed1997

[Stimulation of ileal transport of calcium by sorbitol in in situ perfused loop in rats].

OBJECTIVES: The aim of this study was to study the effect of sorbitol on sodium, water and calcium fluxes in rat ileum in situ perfused loop. METHODS: Net water, sodium and calcium fluxes, and one-way calcium fluxes were measured in situ in a perfused rat ileal loop in the presence of varying concentrations of sorbital. RESULTS: High concentrations of sorbitol in perfused ileal solution induced a decrease of sodium and water fluxes and a concomitant increase of lumen to mucosa calcium flux associated with an increase of net calcium flux, using a solution containing either 8.0 or 1.25 mM calcium. These effects were independent of absolute initial values of water and sodium fluxes. They were observed in the presence of 25 mM glucose, 10 mM theophyllin or after treatment of rats with dexamethasone. CONCLUSION: These effects of sorbitol on calcium flux are not compatible with a stimulation of paracellular pathway. By contrast, they can be explained by a stimulation of transcellular calcium pathway in ileum associated with the hyperpolarisation of the cells induced by the decrease of luminal sodium concentration necessary in the presence of sorbitol to maintain unchanged osmolarity of perfusate.

Animals↗
PubMed1996

Renal effects of angiotensin I-receptor blockade and angiotensin convertase inhibition in man.

1. The objective was to compare two means of inhibition of the renin-angiotensin system [angiotensin-converting enzyme inhibition and selective antagonism of angiotensin II subtype 1 (AT1) receptor] on renal function in 10 healthy normotensive volunteers on a normal sodium diet. Since mechanisms of action may differ between both drugs, a synergistic action was further studied by combining the two drugs. 2. The design was a double-blind randomized acute administration of either placebo or a single oral dose of enalapril, 20 mg, followed in each case by administration of the AT1 selective antagonist losartan potassium, 50 mg orally. 3. The methods included measurements of hormones (plasma renin activity, plasma aldosterone), blood pressure and renal function from 45 to 135 min after administration of placebo or enalapril, and from 45 to 135 min after losartan and placebo or losartan and enalapril. Renal function was studied using clearance of sodium, lithium, uric acid, inulin and para-aminohippuric acid. To examine further the determinants of glomerular filtration at the microcirculation level, fractional clearance of neutral dextran was determined and sieving curves were applied on a hydrodynamic model of ultrafiltration. 4. Losartan did not change plasma renin activity, blood pressure or glomerular filtration rate, but increased significantly renal plasma flow and urinary excretion of sodium and uric acid. Enalapril increased plasma renin activity and renal plasma flow, and decreased blood pressure without natriuretic, lithiuretic or uricosuric effects. The renal vasodilatation was potentiated when losartan and enalapril were combined, despite a further rise in plasma renin. In contrast to enalapril, losartan either alone or in combination with enalapril significantly depressed fractional clearances of dextran of small radii (34-42 A). These changes in fractional clearances of dextran were presumably related to the rise in glomerular plasma flow since the other major determinants of filtration, i.e. transcapillary glomerular pressure gradient, ultrafiltration coefficient and membrane property, were computed as unchanged by either losartan, enalapril or a combination of both. 5. In conclusion, these findings suggest that in normal sodium-repleted man the renal, hormonal and blood pressure effects of AT1 antagonism and angiotensin-converting enzyme inhibition are not strictly similar and could be synergistic.

Adult↗
PubMed1996

A phase II trial of partially incompatible bone marrow transplantation for high-risk acute lymphoblastic leukaemia in children: prevention of graft rejection with anti-LFA-1 and anti-CD2 antibodies. Société Française de Greffe de Moelle Osseuse.

Bone marrow transplantation (BMT) from matched sibling donors has been useful for the treatment of acute lymphoblastic leukaemia in children with a poor prognosis but is not available to more than two-thirds of patients who do not have a matched allogeneic donor. This study was undertaken to assess one strategy of marrow graft rejection prevention when alternative marrow sources such as HLA-phenoidentical unrelated volunteers and HLA-partially incompatible relatives were used. Results have been compared with two matched groups of children with the same risks factors and disease status who underwent HLA-genoidentical or autologous BMT. The conditioning regimen was the same for the three groups of patients; in the study group anti-LFA-1 and anti-CD2 monoclonal antibodies combined with T-cell depletion of the marrow was added to prevent graft rejection and graft-versus-host disease. Nineteen patients were included and followed for a median of 25 months (14 months to 3 years). Bone marrow engraftment occurred in 83% of the evaluable patients. Post-transplantation infectious diseases were the most frequent causes of death in the study group, occurring in 31% of patients. No fatal infections occurred in the two control groups. Post-transplantation relapse of leukaemia occurred in 26% of study group's patients, in 58% of autologous BMT control group's patients and 5% of HLA-genoidentical allogeneic group's patients. The event-free survival was 83% in the HLA-genoidentical control group, and 30% and 24% in the study group and in the autologous control group, respectively. In conclusion, a high rate of engraftment was achieved by the use of anti-LFA-1 and anti CD2 antibodies. Occurrence of a long-lasting immunodeficiency, however, led to a high incidence of lethal infections and relapses. Combined approaches are therefore to be investigated accelerating immune reconstitution after transplantations of T-depleted HLA partially incompatible marrow.

Adolescent↗
PubMed1996

Fourier transform infrared microscopy identification of crystal deposits in tissues: clinical importance in various pathologies.

The presence of crystal deposits in tissues is associated with various pathologies. Sometimes their identification is useful for understanding the etiology or the mechanism of the disorder. The authors applied Fourier transform infrared microscopy (FTIRM) to the molecular characterization of crystal deposits in tissue and compared the results with those provided by histologic studies using polarized light microscope and histochemical reactions. Twenty-five biopsies were investigated. In 10 cases, the results were in good agreement. In 15 cases only FTIRM could precisely identify the crystals. In three cases, this technique allowed to characterize dihydroxyadenine crystals revealing an adenine phosphoribosyltransferase deficiency previously undiagnosed in patients presenting severe chronic renal failure. In three cases, crystal deposition was related to drug therapy. In other cases, crystal identification was useful to understand the mechanism of the pathology responsible for tissue damage and crystal deposition.

Adenine↗
PubMed1996

Angiotensin converting enzyme inhibition and chronic cyclosporine-induced renal dysfunction in type 1 diabetes.

AIM: This study was designed to evaluate whether the angiotensin converting enzyme inhibitor enalapril could prevent cyclosporine-induced renal dysfunction in diabetic patients treated with CsA in monotherapy. DESIGN: Twenty-four recent onset insulin-dependent diabetic patients without prior renal involvement were randomized to receive a 3 month course of either cyclosporine (CsA) alone (7.5 mg/kg. b.i.d. in olive oil) or CsA+enalapril (20mg p.o. oad.). END POINTS: were mean arterial pressure, plasma creatinine, GFR, renal plasma flow, renal vascular resistance, sodium and lithium clearances measured before and after 3 months of treatment. RESULTS: Baseline values were identical in both groups except for mean arterial pressure which was slightly higher in the subjects subsequently receiving CsA + enalapril. Three month treatment with CsA increased significantly mean arterial pressure and renal vascular resistance by 9 and 24% respectively, while decreasing significantly glomerular filtration rate and renal plasma flow by 17 and 14% respectively. Enalapril was able to prevent the decline in GFR and the increase in blood pressure induced by CsA. This effect was demonstrated despite a similar increase in renal vascular resistance suggesting a dissociation between changes in glomerular filtration rate and renal vascular resistance during angiotensin converting-enzyme inhibition. CONCLUSION: Chronic angiotensin converting-enzyme inhibition could afford some degree of protection against CsA-induced renal dysfunction. Whether these results can be extrapolated to transplant recipients in whom CsA is usually associated to treatment by glucocorticosteroids deserves further evaluation.

Adult↗
PubMed1996

Proteins and bioprosthetic calcification in the rat model.

BACKGROUND AND AIM OF THE STUDY: The mechanism of valvular bioprostheses calcification is still unknown, but early studies showed increased Gla-protein content in calcified valves. Using an experimental model, which reproduces the clinical process, we therefore analyzed the role of minerals and proteins in bioprosthetic valvular calcification. METHODS: Glutaraldehyde pretreated porcine valves were studied before and after implantation in rats by X-ray, calcium (Ca) and phosphorus (P) measurement, Fourier Transform Infrared (FTIR) spectroscopy, SDS-PAGE and 45Ca ligand blotting of the extracted proteins. RESULTS: Before implantation, there was no X-ray calcification with very little Ca and P content. After implantation, X-ray calcifications appeared on day seven with increased Ca and P up to day 35 (p < 0.05, ANOVA). FTIR revealed structural proteins alone before implantation, plus minor proportions of lipids on day two, which always preceded Ca and P appearance. Ca and P increased up to day 35, first as amorphous and changed in carbapatite over time. SDS-PAGE before implantation revealed two proteins (66-kD and 54-kD) alone, which were sustained up to day 35. The 66-kD had 45Ca affinity. On day two, many other proteins appeared on SDS-PAGE, four of which (52, 45, 14 and below 14-kD) with 45Ca affinity. Protein pattern did not change from day two to 35. CONCLUSIONS: Valvular bioprosthesis calcification is associated with progressive increase in Ca and P content and at least five calcium-binding proteins: one intrinsic valvular protein, pre-existing to implantation, plus four other, extrinsic valvular proteins adsorbed within the tissue after implantation.

Animals↗
PubMed1996

Effects of new vitamin D analogues on parathyroid function in chronically uraemic rats with secondary hyperparathyroidism.

BACKGROUND: Treatment with calcitriol or its analogue, alfacalcidol often leads to hypercalcaemia, hyperphosphataemia or both in patients which chronic renal failure and advanced secondary hyperparathyroidism. We tested three new vitamin D analogues (CB 1093, EB 1213, GS 1725) in an attempt to identify potentially non hypercalcaemic compounds, capable of decreasing plasma parathyroid hormone (PTH) concentration. METHODS: Male Wistar AF rats aged 12-14 weeks were fed a synthetic, phosphate-rich diet and underwent either sham surgery (control) or a standard two-step 5/6th nephrectomy. Four weeks later, renal function was mildly decreased in the latter. Chronic renal failure rats were then divided into six groups, with 8-10 rats in each group. They received daily 1.p. injections, from days 0 to 4, of either placebo, calcitriol, or one of the following three active vitamin D analogues: CB1093, 0.25 micrograms; EB1213, 0.25 or 1.25 micrograms; and GS1725, 0.025 micrograms/kg body weight per day, respectively. Sham-operated rats received no drug. On day 5, arterial blood was sampled and rats were sacrificed. RESULTS: At predefined dosage schedules, all three compounds significantly decreased plasma immunoreactive PTH levels (except EB1213 at low dose). The decrement was somewhat less marked than that obtained with calcitriol, at the dose of 0.25 micrograms/kg b.w. per day. However, calcitriol induced a marked increase in plasma calcium and phosphate concentrations at that dose, whereas vitamin D analogues led to a more modest increase in plasma calcium level, and none to a worsening of hyperphosphataemia. CB1093 treatment was even associated with a significant decrease in plasma phosphate level. CONCLUSION: All three calcitriol analogues tested are promising as non-hypercalcaemic agents in the treatment of uraemic secondary hyperparathyroidism. However, more prolonged administration to uraemic rats of calcitriol analogues with slightly modified dosage schedules and of calcitriol with lower non-hypercalcaemic dose is required for an optimal comparison before considering clinical trials.

Animals↗
PubMed1996

[Uronic-acid-rich protein: a new glycoprotein inhibiting the crystallization of calcium oxalate in vitro].

During about ten years, nephrocalcin was considered the main calcium oxalate crystal growth inhibitor. Today, it appears only a urinary protein inhibitor among other ones such as non polymerized Tamm-Horsfall protein, uropontin or crystal matrix protein (CMP), a protein derived from prothrombin. All these molecules are able to inhibit either crystal growth or aggregation of calcium oxalate in urine. Another protein, named renal lithostathine, was also reported to be a potent inhibitor of secondary nucleation and growth of calcium carbonate crystals. A new urinary inhibitor of calcium oxalate formation was isolated from the urine of healthy subjects using chromatographic procedures. It is a macromolecule with a molecular weight (MW) of approximately 35 kDa as estimated by polyacrylamide gel electrophoresis. Its carbohydrate content represents an average of 8.5% of its MW. Glutamic and aspartic acids represent 24% of total amino acids. This protein is called Uronic-Acid-rich Protein (UAP) because of its uronic acid content. The same protein isolated from the urine of stone formers showed less inhibitory activity than that purified from the urine of healthy subjects. Structural modifications may explain this diminution of its inhibitory activity. This protein was also purified from rat urine using same procedures. Human and rat UAP exhibit similar biochemical characteristics and strongly inhibit calcium oxalate crystallization in vitro. Partial amino acid sequence analysis showed a homology with inter-alpha-trypsin inhibitor (ITI), confirmed by the immunological results on Western blot. Nevertheless, various chemical and enzymic treatments revealed that UAP and ITI are not identical molecules. Consequently, urine contains several macromolecular substances belonging to ITI superfamily which are involved in the inhibition of calcium oxalate crystallization. UAP takes place among the most efficient macromolecular substances known as inhibitors in calcium oxalate nephrolithiasis.

Animals↗
PubMed1996

[Method selected for the determination of creatinine in plasma or serum. Choice of optimal conditions of measurement].

The method selected by the SFBC (Société française de biologie clinique) is derived from the colorimetric reaction of creatinine with alkaline picrate, measured kinetically, without any pretreatment step. The key parameters of the reaction determining the quality of the results are studied, with special regard to samples including known interferents. The aims of the study were to gain an optimal analytical sensitivity and to reduce main interferences (acetoacetate, bilirubine, glucose, protein) which plague the Jaffé reaction, through a comprehensive study of the reagents, of their concentrations and of the analytical procedures. The selected concentrations (in the test) are: 150 mmol/L sodium hydroxide, 10 mmol/L picric acid and 2 g/L sodium dodecyl sulfate. Ten millilitres of a BRIJ solution (30% volvol) are added to the reagent. The operating procedures are as follow: sample ratio 0.07 to 0.08; wavelength 505 to 510 nm; temperature 37 degrees C; incubation of the specimen with the alkaline reagent 5 mn (at least), before starting the reaction with picric acid. A seric calibrator is recommended. The first measurement is taken 20 to 40 s after starting the reaction. Total measurement time is 120 to 150 seconds.

Blood Chemical Analysis↗
PubMed1996

[Validation and study of the transferability of the selected technique by SFBC for the determination of creatinine in plasma].

A selected method for the determination of creatinine in plasma, using the reaction with alkaline picrate without prior pretreatment has been proposed by the Commission 'Validation de techniques' in the SFBC (Société Française de biologie clinique). The transferability step was conducted in seven laboratories, equipped with different automatic analyzers, using analytical procedures derived from the recommended method. Its goal was to test whether the original analytical performances could be maintained and consistent results obtained. The validation step was designed to evaluate the linearity limits of the analytical range, the detection limit, to assess accuracy as compared to a high performance liquid chromatography and to investigate the effect of the main interferents. Linearity limits are 15 and 2000 mumol/L. The detection limit is 3 to 8 mumol/L according to the analytical systems. The selected method can fulfil the set imprecision goals: intralaboratory CV minus than 2% (within-run), minus than 4% (run-to-run), interlaboratory CV minus than 5% (for 100 mumol/L creatinine). Inaccuracy evaluated for the chosen control sera is 1 to 15% as compared to the chromatographic method, according to the sera and to the analytical systems. The results obtained with the selected method are more consistent with the HPLC than are those obtained with an alkaline picrate method without SDS or with an enzymatic method. No interference could be demonstrated for acetoacetate (up to 8 mmol/L), hemoglobin (up to 210 mumol/L), unconjugated bilirubin (up to 250 mumol/L), glucose (up to 30 mmol/L), IgG (up to 45 g/L), albumin (up to 60 g/L). The effect of cephalosporins depends on the molecule. The reagents are stable for at least 6 months when stored in closed vials at +20 degrees C. The alkaline reagent is stable 30 days at +4 degrees C. Reference limits (0.025 and 0.975 fractiles) have been established for healthy adults. They are respectively 73 to 126 mumol/L for men and 59 to 100 mumol/L for females.

Adult↗
PubMed1995

Haematogenous dissemination of prostatic epithelial cells during radical prostatectomy.

Radical prostatectomy is one treatment for organ-confined prostatic adenocarcinoma. Dissemination of malignant prostatic cells after radical prostatectomy could be partly due to prostate manipulation during dissection. We confirmed by assay of prostate-specific membrane antigen by reverse-transcription nested PCR that prostate manipulation seeded prostatic epithelial cells in the general circulation in 12 of 14 consecutive patients operated on for organ-confined prostate adenocarcinoma. Our results suggest that surgeons should approach radical prostatectomy with care to avoid seeding from the prostate gland. Antiandrogen therapy might reduce the haematogenous spread of prostatic cells during radical prostatectomy.

Adenocarcinoma↗
PubMed1995

[Evaluation of the lithogenic risk in renal lithiasis. Value of urine density measurement].

OBJECTIVE: Measuring specific gravity of urine is a simple means of self-monitoring for urolithiasis patients. METHODS: We evaluated the reliability of two test strips (N-Multistix and Combur-Stix) and determined the relationship between urine specific gravity and crystal formation in first morning urine in 179 patients with calcium oxalate lithiasis. Urine hydrometry was used as the reference method. RESULTS: There was a good correlation between urine density read on the test strips and hydrometry (r = 0.733 for N-Multistix and 0.697 for Combur-Stix). Hydrometry showed little pH effect but the test strips gave results correlated with urine pH (r = 0.764 and 0.813 respectively). When urine pH was below 6.5, the specific gravity of the urine was overestimated; inversely for pH > 7, it was underestimated. Correction factors were obtained by comparing test strip values with specific gravity measurements for pH level between 4.5 and 8. There were crystals in 66% of the urine samples with a density > or = 1012 g/l. In contrast, 75% of the samples below this value were crystal free. There was a close relationship between 24-hour urine volume and specific gravity (n = 124; r = 0.778): a specific gravity of 1.012 corresponded to 2100 ml urine output. For 24% of the patients, specific gravity of the morning urine was > or = 1.012 despite a 24-h urine output > or = 2100 ml, indicating insufficient urine dilution during the night. CONCLUSION: Measurement of specific gravity with test strips with correction for pH can be a simple way to measure the specific gravity of urine and assess whether urine dilution is sufficient to reduce the risk of crystal formation, the main risk factor in urolithiasis patients.

Humans↗
PubMed1995

Sex- and age-related composition of 10 617 calculi analyzed by infrared spectroscopy.

A series of 10 617 calculi were analyzed by stereomicroscopy and infrared spectroscopy. This first study of French calculi was compared with large series in the literature. That the frequency of pure calculi was the lowest ever observed can be related to the methodology routinely used in our laboratory, which includes microsampling. We described more than 70 components among the 10 617 calculi. The overall sex ratio male to female patients was high (2.27) and increased over the period 1981-1993. Calcium oxalate was the most frequent component (86.48%), followed by calcium phosphate (79.75%) and purines (18.64%). We found a low occurrence of "infection" stones. The sex ratio was related to stone composition and differed according to the main component. For instance, calcium oxalate dihydrate (COD) was more frequent in men than in women, with a sex ratio of 4.97 versus 2.57 for calcium oxalate monohydrate (COM). On the contrary, calcium phosphate was more frequent in female patients (sex ratio 0.72 versus overall ratio). The high frequency of COD calculi (23.17%) suggests that hypercalciuria is particularly frequent in French patients susceptible to stone formation. For each main component, a specific profile was observed in relation to the sex and age of the patients with stones.

Adult↗
PubMed1995

Mechanism of the enhancing effect of sorbitol on ileal Ca uptake in rat enterocytes.

The effect of sorbitol on Ca uptake by isolated ileal epithelial cells was investigated. Intestinal cells were isolated from rat ileum by mechanical vibration. 45Ca uptake was approximately 2 times higher in cells exposed to 200 mM sorbitol of D-alanine than in control cells. This enhancing effect of sorbitol on percentage Ca uptake decreased with increasing Ca concentrations in the incubation medium suggesting an effect on Ca entry velocity. The addition of 10 microM nifedipine or 200 microM verapamil to the incubation medium was devoid of any effect on Ca uptake in ileal cells, whereas 100 microM trifluoperazine or chlorpromazine abolished the stimulatory effect of sorbitol. Finally, the effect of sorbitol on isolated cells was independent of a measurable change of cellular ATP content. In conclusion, the stimulatory effect of sorbitol on ileal Ca uptake is probably exerted through mechanisms other than an increase in intracellular ATP concentration. Sorbitol may enhance enterocyte Ca transport via a direct interaction with calmodulin and/or the Ca pump. It may also exert its effect through an inhibition of the basolateral Na Ca exchanger.

Adenosine Triphosphate↗
PubMed1995

Alterations of cytosolic calcium in platelets and erythrocytes of Lyon hypertensive rats.

Platelet cytosolic free calcium concentration ([Ca2+]i) and intracellular pH (pHi) (including their responses to thrombin), as well as erythrocyte [Ca2+]i and 45Ca2+ influx, were studied in Lyon hypertensive (LH) and normotensive (LN) rats aged 3 months. Platelets of LH rats were characterized by substantially elevated basal [Ca2+]i values, higher [Ca2+]i levels after thrombin stimulation, and enhanced initial rate of thrombin-induced Mn2+ entry through receptor-operated Ca2+ channels. Basal platelet pHi values were not significantly different in LH and LN animals but thrombin elicited a significant alkalinization only in LH platelets. Erythrocytes of LH rats had an enhanced initial rate of 45Ca2+ and tended to elevated [Ca2+]i levels. Our data indicate profound alterations in cell Ca2+ handling in platelets and erythrocytes of LH rats, similar to those previously described in spontaneously hypertensive rats of the Okamoto-Aoki strain. The analysis of the relations between blood pressure, plasma lipids, and cell Ca2+ handling suggested that triglycerides, but not cholesterol, might be involved in altered platelet Ca2+ handling in LH rats.

Animals↗
PubMed1995

[Handicaps in the perinatal period. I. Perinatal pathology and difficulties in school].

BACKGROUND: Major handicaps are closely related to perinatal events. However, relationship of these events with other moderate disabilities such as school problems are still unclear. POPULATION AND METHODS: A representative sample of 1,408 children at school age and born in Lorraine in 1984 was studied. Two hundred and fifty children with problems were compared with 602 controls without school problems, using a multivariate analysis. RESULTS: The incidence of school difficulties among 6-year old children (in the last year of nursery school) is 17.8%. Children are at higher risk of school problems if their parents are not (odds ratio [OR] = 7.9) or are poor school graduate (OR = 2.7), if they are boys (OR = 2.0), if they are born at the end of the year (OR = 1.1) and also if they are preterm (OR = 2.7) or small for gestational age (OR = 2.5). Preterm delivery and intra-uterine growth retardation accounted for 9.6% of school difficulties. CONCLUSION: The relationship between perinatal events and school difficulties warrants to continue with prevention during pregnancy, especially among groups with multiple risk factors.

Child, Preschool↗