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J Bienvenu

Publications and source records attributed to J Bienvenu.

124 records · Page 7Linked to original sources
PubMedDate not supplied

[Capillary electrophoresis: principles and practice in clinical laboratory].

Capillary electrophoresis represents a relatively new analytical technique. This methodology has diversified and given rise to various modes such as capillary zone electrophoresis, capillary gel electrophoresis, micellar electrokinetic capillary chromatography, capillary isoelectric focusing and capillary isotachophoresis. If capillary electrophoresis was first introduced in research laboratories, this technique is now making an entrance to the clinical laboratory. This is due to its rapid and high-efficiency separation power, its potential applications and its possible automation. Thus, capillary electrophoresis represents an attractive alternative to some time-consuming techniques. Thanks to its versatility, the use of capillary electrophoresis has been proposed for the separation and quantification of a wide spectrum of biological components ranging from macromolecules (proteins, lipoproteins, nucleic acids) to small analytes (amino acids, organic acids or drugs). This paper illustrates the potential of capillary electrophoresis which should rapidly become a major technology for a modern clinical laboratory.

Alcoholic Intoxication↗
PubMedDate not supplied

[Quality specifications and allowable standards for validation of methods used in clinical biochemistry].

The purpose of this work is to provide, for a large number of analysis in the field of clinical biochemistry, appropriate criteria for the evaluation of the performance of in vitro diagnostic methods. Based on a first set of data established in 1986 and the experience cumulated by organisers in charge of internal and external quality assessment surveys, an expert group has proposed acceptable limits for a large list of analysis (n = 116). Data are reported and presented in tables divided into 7 chapters including: general biochemistry, enzymes, proteins, tumour markers, hormones, drugs (and toxic), and urinary analysis. For each analysis are given: analytical and reference ranges, three concentration levels for control specimens to be used during evaluations and the range of values within which they can be chosen, reproducibility and repeatability limits expressed as CV%. Maximal tolerable systematic error and inaccuracy are given for control and biological specimens and compared to those obtained using a reference or validated method. These data are essential for evaluations using the protocol designed by the SFBC and can serve as quality criteria for the choice and validation of in vitro diagnostic systems.

Biochemistry↗
PubMedDate not supplied

[Standardization and automation of HLA B27 typing by flow cytometry: validation and comparison with microlymphocytotoxicity].

One of the strongest known association between human leukocyte antigen (HLA) phenotype and disease is that of ankylosing spondylitis and HLA-B27. Thus, the determination of HLA-B27 status is an useful tool in the diagnosis of ankylosing spondylitis. To date, the 2 reference methods for HLA typing (microlymphocytotoxicity and molecular biology techniques), are costly in terms of both technician time and materials, and require a great deal of experience. In total, these techniques are not well-suited for routine application in clinical immunology laboratories. Use of flow cytometry has recently been applied for HLA-B27 typing. Nevertheless, it requires an extensive validation protocol. We developed a flow cytometry technique as standardized as possible (whole blood, automated lysing system, automated photomultiplier voltage calibration, definition of thresholds stable with time) and validated our results by comparison with microlymphocytotoxicity. In total, 326 samples were analyzed. We found 99% of concordant results between the 2 techniques, and neither false positive results nor false negative results with flow cytometry could be observed. These results illustrate the reliability of the protocol. It should be remembered that reference technique remains necessary to confirm the few results (< 1%) found in "grey zone" by flow cytometry. Standardization of flow cytometry techniques, as described in this work for HLA B27, seems to be a reasonable goal for the next decade in clinical immunology laboratories.

Automation↗
PubMedDate not supplied

Drug-induced urticaria.

The occurrence of acute urticaria during treatment with drugs is a frequent event which poses two problems: 1) is the urticaria connected with the drug administration or with the underlying pathology which led to the prescription of the drug; 2) is the urticaria allergic in origin, i.e. due to specific immunity triggers, in particular IgE directed against the drug, or is the urticaria pseudo-allergic in origin, i.e. due to non-specific activation of mastocytes [1]? This question is of major importance because allergic events caused by IgE are potentially fatal while pseudo-allergic events are only rarely life-threatening. In this article we will not deal with contact urticaria where the cause is easily identifiable [2].

Acute Disease↗
PubMedDate not supplied

[Preliminary results in standardization of flow cytometry protocols for monocytic HLA-DR measurement and their application in the follow up of septic shock].

In septic shock, the diminished HLA-DR expression on monocytes has been proposed as a marker of immunoparalysis that correlates with an increased risk for fatal outcome. The present study was designed to determine whether some differences in protocol procedures could lead to discrepant results in HLA-DR measurement. After establishing a reliable protocol, the second objective was to illustrate the immunoparalysis in patients with septic shock. HLA-DR measurement on monocytes was determined by means of flow cytometry in 54 healthy donors and 16 patients with septic shock. We demonstrated that storage temperature, storage duration before staining and red cells lysis constitute crucial steps in HLA-DR measurement. The precision results with coefficients of variation below 5%, were quite convincing for a manual immunoassay. At 48 hours after diagnosis of septic shock, we found severely decreased percentages of monocytes expressing HLA-DR in septic patients (24 +/- 4%, mean +/- SEM) in comparison with healthy donors (90 +/- 1%), p < 0.001). Furthermore, the persistence of a low level of monocytic HLA-DR (less than 50 %) at day 9 after admittance was associated with patients who died. This study illustrates the state of immunoparalysis in patients with septic shock and supports the potential interest in measuring HLA-DR expression on monocytes. However, multicenter studies are now needed to validate this parameter. Based on our analytical results, we conclude that a critical issue in such studies will be the capacity in each center to perform standardized measurement of HLA-DR. It should be remembered that this determination requires the definition of a common analytical procedure between laboratories participating in the trial.

Female↗
PubMedDate not supplied

[Interest and limit of a free light chain immunoassay in serum and urine for the diagnosis and the follow-up of monoclonal dysglobulinemia].

This work aims to define the interest and the limits of free light chain (FLC) determination in serum and urine for the investigation of monoclonal gammopathies. Based on the study of nine typical cases extracted from laboratory practice, the authors demonstrate the interest of this determination for the diagnosis and the monitoring of FLC and non secretory myelomas. This test is also useful for the evaluation of response to chemotherapy and the early detection of relapses in intact immunoglobulin multiple myelomas. These results are discussed in the light of the literature with a special emphasis on AL amyloidosis and monoclonal gammapathy of undetermined significance (MGUS). Finally the authors underline some limitations leading to an overestimation of the results in certain patients together with the difficulty to interpret data when a renal damage is associated.

Aged↗
PubMedDate not supplied

Serum IL-2 level in rheumatoid arthritis: correlation with joint destruction and disease progression.

Understanding of T cell dysfunctions in rheumatoid arthritis (RA) may help to elucidate the pathophysiology of this disease. Cytokines determinations may be a promising approach and could represent a simple mean of quantifying RA immunological dysfunctions. In this study, interleukin-2 (IL-2) measurements were performed in sera of 74 RA patients to evaluate the potential use of this method to monitor "disease activity" and/or prognosis. Although the serum IL-2 levels of patients in active disease stage proved to be somewhat lower than those from patients with inactive disease, the difference was not significant. In our study, however, the serum IL-2 concentration was correlated with the circulating immune complexes level. In addition, patients with the highest serum IL-2 levels exhibited the poorest radiological stages and these same patients were often not receiving any disease modifying antirheumatic drugs (DMARD). Our results demonstrate that serum IL-2 level may be elevated in certain RA conditions. A better understanding of this phenomenon, especially the consequences of disease duration, could be of interest in the follow up and the prognosis of the disease.

Antigen-Antibody Complex↗
PubMedDate not supplied

[Non specific immunity of children with selective IgA deficiency. Aggravating role of abnormal phenotype of alpha-1-antitrypsin (author's transl)].

Among 998 children with recurrent respiratory diseases 26 children with selective IgA deficiency were found. Three groups were considered according to IgA level in serum: group I with IgA under 0.05 g per litre; group II with IgA between 0.05 and 0.3 g per litre; group III with IgA above 0.3 and under 1 g per litre. Non specific immunity was studied in these patients including immunoglobulin levels, alpha-1-antitrypsin (A.A.T.) phenotypes, phagocytosis of staphylococcus aureus by PMN, lysozyme level, complement system. Cellular immunity was evaluated by IDR tests and rosette forming cells (RE). Only non specific immune systems were disturbed in some patients and appeared as aggravating factors in IgA deficient patients. We found: Abnormal phenotypes of ATT in 11 cases; deficiencies of engulfment in 6 cases, of bactericidal activities of PMN in 7 cases out of 16 studied; decrease of lysozyme level in 4 cases out of 17 studied; increase of IgE level in 9 cases with atopic symptoms in 7 patients. In our experience the chief aggravating factor in IgA deficient patients is abnormal phenotype of AAT.

Adolescent↗
PubMedDate not supplied

[The normal protein profile in newborn infants].

The authors report the results of the immunonephelometric determination of 9 proteins in the serum of 74 newborns: CRP, orosomucoid, haptoglobin, alpha-1-antitrypsin, C3, C4, transferrin, prealbumin and apo B have been studied. The influence of gestational and postnatal ages are shown. Results are compared with those of the literature. The respective role of the transfer of plasma proteins from mother to foetus and of foetal synthesis in the concentration of a protein in the serum of a neonate is discussed.

Apolipoproteins B↗
PubMedDate not supplied

[Course of inflammatory and nutrition proteins in bacterial infections in newborn infants].

A study of 214 neonates (with 87 premature infants) reveals that C-reactive protein (CRP), orosomucoid and prealbumin are the most interesting proteins for the diagnosis of neonatal sepsis and for studying its follow-up. Orosomucoid is high in 85% of bacterial infections and CRP in 75%. Early type strep B infections give often false negative results. The evolution of CRP and of prealbumin corresponds to the effects of treatment and the evolution of orosomucoid is parallel to the healing of the patients. The ratio orosomucoid/prealbumin allows an earlier appreciation of the healing.

Bacterial Infections↗
PubMedDate not supplied

Mechanisms of action of the tumor necrosis factor and lymphotoxin ligand-receptor system.

In the past few years, a number of experimental observations have provided more insight into the mechanisms of action of tumor necrosis factor (TNF)/lymphotoxin (LT) ligand-receptor system. This system consists of three ligands, TNF, LT alpha (LT alpha) and LT beta (LT beta), and three membrane-associated receptors, p55, p75 and LT beta-receptor (LT beta-R). Like TNF, LT alpha is a secreted protein which in solution forms a homotrimer molecule, with a conformation similar to that of TNF. LT beta is a transmembrane protein that provides the membrane anchor for the attachment to the cell surface of the heteromeric complex of LT alpha and LT beta. This complex retains a structure related to TNF and LT alpha homotrimers, with the homology regions interacting in a heterotypic fashion. The LT alpha 1:LT beta 2 heteromer has been found to be a predominant form of surface LT. The biological effects of TNF and LT alpha homotrimers are mediated by p55 and p75 receptors, while the heteromeric complex of LT alpha/LT beta transduces its cellular signal via LT beta-R. Membrane-associated receptor affinities as well as final biological effects of TNF/LT can be modulated by the influence of naturally occurring soluble receptors, derived from the cell surface by proteolytic cleavage. The multimerization of receptor cytoplasmic domains upon TNF/LT ligation is postulated to activate the intracellular signal-transduction pathways. One of them is the activation of phospholipase A2 (PL-A2) resulting in the production of arachidonic acid (AA) and other metabolites, including leukotriens, phosphatidycholine-specific phospholipase C (PC-PLC) with subsequent production of diacylglycerol (DAG) and activation of protein kinase C (PKC). As a third signaling pathway, TNF/LT employ the sphingomyelinase (SMase)-mediated hydrolysis of membrane sphingomyelin (SM) to ceramide. The final link in the TNF/LT signaling is activation of nuclear transcription factors, such as NF-kappa B, AP-1, interferon regulatory factors-1 and -2 (IRF-1, IRF-2), and NF-GMa. Since induction of AP-1, IRF-1 and IRF-2 as well as NF-GMa proceeds through translational event, the posttranslational TNF/LT-driven activation of NF-kappa B remains the only cellular event identified so far that serves as a direct target in their signaling cascade.

Animals↗
PubMedDate not supplied

Analytical performances of commercial ELISA-kits for IL-2, IL-6 and TNF-alpha. A WHO study.

The determination of cytokine levels in biological fluids by accurate and sensitive methods is an absolute need to be able to define the involvement of these mediators in various clinical situations. To test if this goal was achieved with ELISA kits, a comparative study was undertaken using various commercial kits (6 for IL-2, 8 for IL-6 and 9 for TNF-alpha). The major aims of the work were to critically analyze the analytical performances of the kits and to illustrate some of the pitfalls the users may face. Substantial differences were noted in terms of sensitivity and behaviour of commercial standards versus international reference preparations. These results clearly illustrate the urgent need for a real standardization of immunoassays for cytokine quantitation.

Enzyme-Linked Immunosorbent Assay↗
PubMedDate not supplied

[Improvements from the reference material CRM 470 in the standardization of the determination of serum proteins].

The introduction of the CRM 470 in 1993 (certified reference material for 14 serum proteins) and its utilization by industrial companies for cross-calibrating their commercial standards has been an important break-through in protein standardization. This improvement has been clearly illustrated by the last national quality control survey performed in France in may 1995. At this time, about 60% of the 1,870 participants have already adopted the new standardization. The between-run precision (interlaboratory and intertechnique) has been considerably improved by the use of the new international standard (5.8 to 12.2% versus 10 to 24.1% before standardization); the same is true for accuracy. These results should convince the last reluctant laboratories to adopt the new standardization. Thus, it seems now possible to define reference ranges for serum proteins: this is the new task assigned to the Committee for Plasma Protein Standardization of the IFCC.

Blood Proteins↗