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Biomedical subjects

P Laroche

Publications and source records attributed to P Laroche.

At least 19 recordsLinked to original sources
PubMed2005

Multiplexed immunoassay for detection of rheumatoid factors by FIDISTM technology.

Our objective was to (i) compare FIDIS Rheuma, a new multiplexed immunoassay designed for simultaneous detection of IgM class rheumatoid factors (RF) directed against Fc determinants of IgG from humans and animals, with agglutination and ELISA (conventional methods) and (ii) evaluate the clinical sensitivity and specificity of biological markers for rheumatoid arthritis (RA). To do this, FIDIS technology was employed using the Luminex system. It consists of distinct color-coded microsphere sets, a flow cytometer, and digital signal processing hardware and software. Agglutination and ELISA tests were performed with commercial kits. The study included 134 samples from RA patients and 105 from healthy blood donors. For human specificity, we compared FIDIS with latex agglutination and ELISA. Relative sensitivities were 98.9% and 88.5% and specificities were 90.2% and 94.6%, respectively. For animal specificity, we compared FIDIS with Waaler-Rose and ELISA. The results were 84.9% and 71.9% for the sensitivities and 97.5% and 98.4% for the specificities, respectively. Detection of IgG anti-CCP by ELISA and IgG antikeratin by immunofluorescence was also determined in order to compare their clinical sensitivity and specificity with IgM-RF, according to the method used. The results were: IgG anti-CCP 72.3%, 97.2%; IgG antikeratin 36.6%, 100%; latex agglutination 66.4%, 97.2%; Waaler-Rose 55.9%, 96.3%; FIDIS human 73.9%, 92.1%; FIDIS animal 49.2%, 97.2%; ELISA human 93.2%, 95.5%; and ELISA animal 74.6%, 91.3%. The results showed the efficiency of FIDIS with analytical performance equivalent to the conventional methods, but having the advantage of giving quantitative results (IU/mL).

Agglutination Tests↗
PubMed2003

Characterisation and dissolution of depleted uranium aerosols produced during impacts of kinetic energy penetrators against a tank.

Aerosols produced during impacts of depleted uranium (DU) penetrators against the glacis (sloping armour) and the turret of a tank were sampled. The concentration and size distribution were determined. Activity median aerodynamic diameters were 1 microm (geometric standard deviation, sigma(g) = 3.7) and 2 microm (sigma(g) = 2.5), respectively, for glacis and turret. The mean air concentration was 120 Bq m(-3), i.e. 8.5 mg m(-3) of DU. Filters analysed by scanning electron microscopy (SEM) and X ray diffraction showed two types of particles (fine particles and large molten particles) composed mainly of a mixture of uranium and aluminium. The uranium oxides were mostly U3O8, UO2.25 and probably UO3.01 and a mixed compound of U and Al. The kinetics of dissolution in three media (HCO3-, HCl and Gamble's solution) were determined using in-vitro tests. The slow dissolution rates were respectively slow, and intermediate between slow and moderate, and the rapid dissolution fractions were mostly intermediate between moderate and fast. According to the in-vitro results for Gamble's solution, and based on a hypothetical single acute inhalation of 90 Bq, effective doses integrated up to 1 y after incorporation were 0.54 and 0.56 mSv, respectively, for aerosols from glacis and turret. In comparison, the ICRP limits are 20 mSv y(-1) for workers and 1 mSv y(-1) for members of the public. A kidney concentration of approximately 0.1 microg U g(-1) was predicted and should not, in this case, lead to kidney damage.

Aerosols↗
PubMed2001

Gingival bleeding, epistaxis and haematoma three days after gastroenteritis: the haemorrhagic lupus anticoagulant syndrome.

UNLABELLED: A 3 year and 9 month-old girl presented with gingival bleeding, epistaxis, and multiple haematomas 3 days after an acute episode of gastroenteritis. Prothrombin time and activated partial thromboplastin time were prolonged with reduced clotting activity of factor II (< 10%), VIII (<1%), IX (3%), XII (10%) and evidence of a high titre inhibitor. Prothrombin (factor II) level was below the detection limit, both in a functional and immunological assay. It did not increase after administration of vitamin K or fresh frozen plasma. Further studies revealed presence of a strong lupus anticoagulant and a specific IgG antibody against prothrombin. Factor VIII antigen levels also were reduced (31%), but to a lesser extent than functionally determined factor VIII (<1%). Blood coagulation normalised following clinical recovery 6 weeks after admission. The pathophysiology of this acquired inhibitor phenomenon (accelerated clearance of complexes of clotting factors and phospholipids) is discussed. CONCLUSION: The haemorrhagic lupus anticoagulant syndrome (acquired hypoprothrombinaemia lupus anticoagulant syndrome) is a rare presentation of acquired bleeding diathesis in childhood. Since most cases in post-infectious children are asymptomatic, it might be underdiagnosed. In children with newly appearing bleeding symptoms or unclear prolonged prothrombin time or activated partial thromboplastin time, one has to consider this syndrome which could lead to relevant bleeding.

Blood Coagulation Disorders↗
PubMed1999

[Reduction of renal uranium uptake by acetazolamide: the importance of urinary elimination of bicarbonate].

Acetazolamide was compared with bicarbonate for the treatment of contamination with uranium. Uranium was injected peritoneally in rats, and its distribution was investigated. Acetazolamide was three times more efficient than bicarbonate in reducing the renal content of uranium. On the other hand, it had no effect on hepatic or skeletal content. In this study, renal physiology provides the basis for understanding the mode of action of acetazolamide and bicarbonate. In this context, it is of interest to determine the alkalinity of the urine, with the aim of knowing whether bicarbonate is present to mobilize uranium.

Acetazolamide↗
PubMed1999

[Percutaneous absorption of metallic cations: uranium particulates].

Washing is usually used to reduce the risk of a skin contamination. Skin biopsies were used and contaminations were realised with 1) soluble radioactive calcium 2) insoluble particles of uranium. The result obtained with different wash liquids are presented here. Water and soap had no effect but hypertonic DTPA was the better therapy to remove uranium from skin.

Calcium Radioisotopes↗
PubMed1998

[Thorium: analysis and dosimetry of thorium welding electrodes].

The use of thoriated tungsten electrodes may be at the origin of a potential hazard for the personnel involved in the use of electrodes, as well as the general population. To assess this hazard, the electrode radioactivity measurements by alpha and beta counting has been conducted. The radioelements were identified by alpha and gamma spectromety. It appeared that there was a radioactive disequilibrium between thorium-232 (Th-232) and it daughters atoms. Additionally, some thorium 230 (Th-230) belonging to the uranium chain, was present. The chemical separation and the milling processing had affected the radioactive composition and the thorium in the electrodes, doesn't exactly corresponds to natural thorium. Radiation doses were also assessed: film and photoluminescence dosimetry were undertaken. Finally smears method showed a alpha removable area contamination. Even if the hazard is weak. As a matter of fact, it must not be neglected because it was complex, for the thorium was always accompanied by Th-232 progeny, alpha emitters but also beta and gamma emitters.

Humans↗
PubMed1997

[Modeling of cutaneous radio-contamination: effects of washings by soap and by solutions of DTPA].

Some neutral chirurgical soap, a solution of diethylen penta acetic acid (DTPA) at 1% and a solution at 25% of monocalcic trisodium salt of DTPA in serum have been studied on models of cutaneous contamination. Cesium 137 (137Cs) and Plutonium 239 (239Pu) have been used for the contamination. This research gives a protocol for external cutaneous decontamination which could be used in reception units for radiocontaminated wounded. Even the radioelement is unknown, DTPA at 25% represents a good solution for the treatment of general contamination, which is not the case for DTPA at 1%. A soap in which DTPA at 1% has been added is adapted for large cutaneous contamination. The treatment of ocular contamination is also studied in this article.

Burns, Chemical↗
PubMed1996

Technical report: effect of cryopreservation on chromosomal aberration yield in irradiated lymphocytes.

Cryopreservation is the usual method to store cells before analysis or use, for instance for biological dosimetry purposes. Some investigations have shown that thawing following freezing may induce cell injury but few studies have been made of the effect of cryopreservation on cells containing radiation-induced unstable chromosomal aberrations. In this work, lymphocytes were irradiated with 1 to 4 Gy gamma rays and stored in liquid nitrogen. The dicentric and centric ring yields were analysed after storage periods of 1 week, 1 month and 3 months. No difference in aberration frequency from control, unfrozen samples was observed over this period. Lymphocytes stored at -196 degrees C for up to at least 3 months may therefore be used for chromosome aberration scoring when over-exposure to ionizing radiation is suspected.

Chromosome Aberrations↗
PubMed1996

Advantage of using both anionic and zwitterionic phospholipid antigens for the detection of antiphospholipid antibodies.

To investigate the benefit of assaying for antiphospholipid antibodies (aPA) with different antigenic specificities, sera from 141 patients suspected of having aPA were tested by ELISA for IgG and IgM antibodies directed against the following phospholipids (PL) coated individually or together: cardiolipin, phosphatidylinositol, phosphatidylserine and phosphatidylethanolamine. Nonspecific background optical density (OD) was systematically subtracted from the test OD value. Positive reactions were defined as having an OD greater than the 97th percentile OD distribution obtained with sera from 100 healthy individuals. Although the majority of the 79 detected aPA (89% IgG and 77% IgM) were polyspecific, 11 reacted with a single PL and, moreover, belonged to only one isotype. Seven of these 11 patients presented recurrent fetal losses or thrombotic events. These results suggest that routine use of a mixture of both anionic and zwitterionic PL antigens to coat ELISA plates would better detect aPA involved in suggestive pathologies and enhance the ability to identify patients with these mono- or polyspecific antibodies directed or not against cardiolipin, the current standard.

Antibodies, Antiphospholipid↗
PubMed1996

High prevalence of antiphospholipid antibodies in precapillary pulmonary hypertension.

OBJECTIVE: To assess prevalence and clinical associations of various antiphospholipid antibodies (aPL) in patients with primary and secondary pulmonary hypertension. METHODS: A prospective trial of aPL in 38 consecutive patients with pulmonary hypertension. Nine patients had primary pulmonary hypertension. Twenty-nine patients had pulmonary hypertension secondary to different etiologies: left heart failure, 8; congenital heart defect, 11; various lung diseases, 10. The search for aPL directed against 4 phospholipids (cardiolipin, phosphatidylserine, inositol, ethanolamine) was by ELISA. RESULTS: Eleven patients (29%) had aPL, with various phospholipid specificities. Mean pulmonary artery pressure and mean pulmonary vascular resistance of aPL positive patients were not different from those of aPL negative patients. Mean pulmonary wedge pressure was significantly lower in aPL positive patients than those without aPL. Positive aPL were detected only in patients with precapillary pulmonary hypertension (11/30; 36.6%). The prevalence of aPL in primary (4/9; 44%) was not significantly different from aPL in secondary (7/29; 24%) pulmonary hypertension. There was no association between the presence of aPL and prior thrombosis or recurrent fetal losses. CONCLUSION: The frequent positivity of aPL in precapillary pulmonary hypertension, irrespective of its cause and severity, suggests the existence of an associated endothelial disease. These antibodies might play a role in the initiation and/or progression of in situ thromboses frequently observed in precapillary pulmonary hypertension. Our results reinforce the necessity of longterm anticoagulant treatment in these patients.

Adolescent↗
PubMed1994

[Conclusions of the first French workshop of standardization of anticardiolipin antibody determination associated with autoimmune pathology].

Anticardiolipine antibodies are a marker of the antiphospholipid syndrome. They are detected by Elisa. Despite its simplicity, the results obtained by this assay are not always reproducible despite several worldwide standardizations and the distribution of calibration sera by EN Harris. On 4 December 1992, the First French Anticardiolipin Antibodies Standardization Workshop was held in Paris. Eight coded standards were sent to 33 laboratories in France, one in Switzerland and one in Luxembourg. Some of them used several assays. Agreement between qualitative results was good for samples with high and moderate level of antibodies. But the results expressed in IgG antiphospholipid units were scattered, the interlaboratory coefficient of variation for each of the eight standards was higher than 70%, though the within-run coefficient of variation had a median value of 10%. Assays using bovine serum for the blocking buffer and for the dilution buffer seemed to give more reproducible results than assays using purified bovine serum albumin (p < 0.001). For only nine assays out of 38 which expressed results quantitatively, was a linear regression observed between the dilutions of a sample and the results expressed in IgG antiphospholipid units. Absence of linearity is an obstacle which must be overcome if we wish to compare quantitative results obtained by different laboratories.

Antibodies, Anticardiolipin↗
PubMed1992

Microparticle-enhanced nephelometric immunoassay for human C-reactive protein.

Polyfunctional hydrophilic microspheres of 125-nm diameter can be produced by copolymerization of acrylic monomers. Purified c-reactive protein (CRP) was covalently bound to these new micropheres, and the conjugate obtained was used as reagent in a microparticle-enhanced nephelometric immunoassay for human CRP. This assay was based on the measure, with a specially designed nephelometer, of the light scattered by aggregates formed during the immunoagglutination of the conjugate with anti-CRP antiserum. Sensitive inhibition of this agglutination by free CRP (6 ng/ml) allowed CRP quantitation in highly diluted serum samples (1/500-1/2,000), excluding any interference or sample pretreatment. The CRP assay was easy to perform (no washing or phase separation), reliable (coefficients of variation ranged from 1.3% to 9.3% for within-run and between-run determinations), and accurate (mean percentage of recovery: 104%; correlation coefficients with accepted analytical methods greater than or equal to 0.97) over a large range of concentrations. The inhibition mode excluded errors in the antigen excess zone and provided total security at high concentrations.

C-Reactive Protein↗
PubMed1992

Measurement of eleven serum proteins by microparticle-enhanced nephelometric immunoassay.

Eleven proteins (immunoglobulins IgG, IgA, IgM, orosomucoid, alpha 1-antiproteinase, haptoglobin, ceruloplasmin, C-reactive protein, transferrin, prealbumin and alpha 2-macroglobulin) in human serum were quantitated by a new microparticle-enhanced nephelometric immunoassay. This is a one step competitive assay, based on the nephelometric measurement of light scattered by clusters of protein-coated microparticles specially synthesized for that use. Statistical evaluation (precision, recovery and method comparison) shows that the determination of serum proteins is reliable and accurate for wide ranges of concentration and that the method is quite adequate for strongly increased concentrations. This microparticle-enhanced nephelometric immunoassay appears to offer an alternative method for routine measurement of a great variety of serum proteins at high and intermediate concentrations, which are usually quantified by radial immunodiffusion or conventional immunonephelometry. On account of its sensitivity, it can also be used for the determination of relatively low concentrations of analytes.

Blood Proteins↗
PubMed1991

Polyacrylic microspheres as a solid phase for microparticle enhanced nephelometric immunoassay (NEPHELIA (R)) of transferrin.

Polyfunctional hydrophilic microspheres (MS) can be produced by copolymerisation with gamma-irradiation of acrylic monomers. Transferrin (TRF) can be covalently bound to these MS by reaction between aldehyde groups of the MS and primary amino groups of the protein. MS-TRF conjugates thus obtained are agglutinated by specific antiserum and this agglutination is inhibited by free TRF. Agglutination and inhibition are quantified by measurement of the light scattered by MS-TRF conjugate clusters with a specially designed nephelometer, a process designated as microparticle enhanced nephelometric immunoassay (NEPHELIA (R)) for TRF. Recovery, correlation and reproducibility studies, simultaneously performed in three different laboratories, show that this TRF immunoassay is accurate for a large concentration range. NEPHELIA (R) may appear as an alternative method for a large variety of molecules.

Humans↗
PubMed1991

Microparticle-enhanced nephelometric immunoassay (Nephelia) for immunoglobulins G, A, and M.

Covalent binding of gamma chains of IgG, whole IgA, and mu chains of IgM on polyfunctional hydrophilic microspheres (MS) yields MS-Ig conjugates, usable as reagents in new microparticle-enhanced nephelometric immunoassays (Nephelia). The principle of the assays is inhibition by free analyte (IgG, IgA, and IgM) of agglutination of the MS-Ig conjugate with specific antiserum, the light scattered by the aggregates being measured with a nephelometer. The immunoglobulin assays developed are easy to perform (single-step assays, no washing or phase separation) and sensitive (high dilution of biological samples to exclude interferences and pretreatment). Analytical recovery results (95.4-101.2%) and correlations with generally used commercial assays (r = 0.86-0.98) indicate that the assays are accurate for large concentration ranges of immunoglobulins. Precision study gives CVs = 2.8-9.6%. Nephelia appears to be useful for quantifying a large variety of biological molecules.

Humans↗
PubMed1990

Obesity, hypertension, hyperuricemia and diabetes mellitus among the Cree and Inuit of northern Québec.

In the last thirty years, sociocultural and political changes have profoundly affected the way of life of the Cree and Inuit of Northern Québec. Their health status profile has also changed. This study presents the main results of a health survey performed among the Cree and Inuit in 1982-1984 by a multidisciplinary team. Obesity, arterial hypertension, hyperuricemia and diabetes mellitus while almost unknown in the past, have now been added to the list of Cree and Inuit health problems. Crees have the highest risk for obesity, hypertension and diabetes mellitus. Hyperuricemia for unknown reasons seems more prevalent among the Inuit. Our findings suggest that further in-depth studies of chronic conditions in these communities are needed.

Adolescent↗