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Biomedical subjects

Y Richard

Publications and source records attributed to Y Richard.

At least 37 records · Page 2Linked to original sources
PubMed1999

Identification by 16S rDNA fragment amplification and determination of genetic diversity by random amplified polymorphic DNA analysis of Pasteurella pneumotropica isolated from laboratory rodents.

Pasteurella pneumotropica is an opportunistic bacterium frequently isolated from colonies of various laboratory rodents. Identification of this species, including its differentiation into two distinct biotypes (Jawetz and Heyl), is usually based on the use of conventional bacteriologic methods. In this study, a 16S rDNA fragment amplification procedure was developed for use as an alternative method for identification and differentiation of P. pneumotropica. Polymerase chain reaction (PCR) products were two distinctive fragments of 937 and 564 bp specific for biotypes Jawetz and Heyl, respectively. Specificity of PCR products could be achieved by EcoRI cleavage, leading to 596 plus 341-bp and 346 plus 218-bp fragments for each of the amplification products. Use of this procedure confirmed identification of 34 field isolates and allowed definitive identification of some strains that could not have been done by use of bacteriologic examinations. Field isolates subjected to random amplified polymorphic DNA (RAPD) analysis had high genetic diversity among biotype Jawetz strains in contrast to biotype Heyl strains. In conclusion, RAPD could represent an additional means for identification of ambiguous strains of biotype Heyl and a valuable epidemiologic tool for identification of biotype Jawetz strains of P. pneumotropica.

Animals↗
PubMed1998

B cell-driven HIV type 1 expression in T cells: an essential role of CD86 costimulatory molecule.

During HIV-1 infection, HIV-1 is sequestered and actively replicates within lymphoid organs, mainly in areas essential for antigen-specific T-B interactions. We investigated whether cognate T-B interactions not only drive humoral response to HIV-1 but also enhance viral replication. Costimulation of in vitro HIV-1-infected tonsillar T cells with autologous or allogeneic activated B cells increased both viral replication and T cell proliferation. Addition of CD86 MAb to cocultures inhibited most p24 (84 +/- 12%, n = 13) and IL-2 (99 +/- 2%, n = 6) production, decreased T cell proliferation by 46 +/- 15% (n = 13), and decreased TNF-alpha and IFN-gamma production by 67 +/- 17% (n = 6) and 53 +/- 6% (n = 6), respectively. In contrast, CD80 MAb, which strongly inhibited IL-2 production (77 +/- 10%, n = 6), moderately downregulated p24 and TNF-alpha production (29 +/- 21%, n = 13 and 34 +/- 10%, n = 6, respectively) and did not decrease T cell proliferation (8 +/- 10%, n = 13) or IFN-gamma production (14 +/- 13%, n = 6). We thus showed that B cells deliver a potent CD86/CD28 costimulatory signal that induces T cell proliferation and simultaneously enhances HIV-1 replication. CD86+ B cells, mainly localized within the light zone of germinal centers, might thus favor active in situ replication of HIV-1 in response to each new challenge by T-dependent antigens.

Antigens, CD↗
PubMed1998

Exoprotein and slime production by coagulase-negative staphylococci isolated from goats' milk.

Milk from mastitis-free goats from French herds was examined for the presence of coagulase-negative staphylococci (CNS), and 165 positive isolates were evaluated for their capacity to produce exoproteins. Most isolates were identified as Staphylococcus caprae (N = 91) or S. xylosus (N = 36), but members of at least nine other species were present. Overall, some 57% of isolates produced toxins with phenotypic properties of alpha-hemolysin, and 75% produced toxins resembling S. aureus beta and/or delta-hemolysins. Thermostable desoxyribonuclease (TNAse) was secreted by 29% of isolates and thermolabile DNAse by 66%. Slime was produced by 42% of our cultures and, although none of them showed activity to insoluble elastase, over 70% lysed the soluble substrate. No clinical consequences were observed to correlate with exoprotein production, which proved to be inconstant within individual CNS species.

Animals↗
PubMed1998

Behaviour and enterotoxin production by Staphylococcus aureus during the manufacture and ripening of raw goats' milk lactic cheeses.

To study the possible presence of staphylococcal enterotoxin A in raw goats' milk lactic cheese, milk was inoculated with an enterotoxigenic Staphylococcus aureus strain to a final concentration of 4, 5 and 6 log(cfu/ml). Cheese was prepared following industrial specifications and ripened for 42 d. Detection of the enterotoxins was by the Vidas Staph enterotoxin test (BioMérieux) and by an indirect double-sandwich ELISA technique using anti-enterotoxin monoclonal antibodies. Staphylococcal counts declined markedly after draining, and by the end of ripening they had disappeared from some cheeses. In contrast, aerobic mesophilic organisms grew well. The level of staphylococcal enterotoxin A recovered varied from 1 to 2.5 ng/g cheese made with an initial population of 10(5) or 10(6) cfu/ml. Only traces of enterotoxin A (0.5 ng/g) were detected in cheeses made with the lowest Staph. aureus inoculum used in this study. Enterotoxin A was also detected in cheeses from which Staph. aureus had disappeared.

Animals↗
PubMed1998

CD80 expression is decreased in hyperplastic lymph nodes of HIV+ patients.

A centrofollicular hyperplasia is present within secondary lymphoid organs during all the asymptomatic phase of the HIV disease. Although this hyperplasia has been well characterized by histological studies, the nature of the phenotypic alterations in B cell populations occurring within HIV+ lymphoid organs remains to be established. By immunohistochemistry, we thus investigated whether a particular germinal center (GC) B cell population was increased during HIV-induced hyperplasia and whether any phenotypic change was specific to HIV-1 infection. As compared to normal tonsils (three cases) and HIV- hyperplastic lymph nodes (eight patients), we observed a loss of GC polarization in all HIV+ sections (11 patients), with no more delineation between dark and light zones, as shown by Ki67, CD10, CD77, CD95 and CD86 staining. In contrast to CD86 expression which remained as intensive in HIV+ as in HIV- lymph nodes, CD80 staining was strongly decreased in GC of HIV+ lymph nodes but not in their extrafollicular zones. The loss of CD80 expression from CD19+ B cells was also observed by cytometric analysis of cell suspensions of three HIV+ patients. Although we found no evidence of an increase in a particular GC B cell subset in HIV-1-induced hyperplasia, the strong GC disorganization observed may induce impaired cell-cell interactions and thus participate in the loss of CD80 antigen. In contrast to HIV- situations where CD80 and CD86 was similarly expressed on B cells, the lower level of CD80 expression in HIV+ GC may favor Th2 T cell responses through CD86-CD28 interactions.

Adult↗
PubMed1998

Evaluation of the VIDAS methodology for detection of Escherichia coli O157 in food samples.

An automated enzyme-linked fluorescence immunoassay (ELFA), the VIDAS E. coli O157 method, was compared with immunomagnetic separation (IMS) followed by culture on cefixime tellurite sorbitol MacConkey agar (CT-SMAC) for detecting Escherichia coli O157 in artificially and naturally contaminated food samples including raw milk cheeses, poultry, raw sausages, and ground beef retail samples. Confirmation of the samples positive according to the ELFA was performed by use of an automated immunoconcentration system, VIDAS ICE, which allows selective capture and release of target organisms. A total of 496 retail food samples were examined. Seventeen food samples gave positive values with the ELFA method, and among them 9 food samples were confirmed by the ICE method. Eight were shown to contain sorbitol-positive, O157-positive, H7-negative, motile, non-verotoxin-producing E. coli. The ninth positive sample contained an O157-positive, H7-negative, sorbitol-negative, non-verotoxin-producing E. coli. The IMS technique only allowed confirmation of this sorbitol-negative, non-verotoxin-producing E. coli O157.

Escherichia coli O157↗
PubMed1997

Moraxella boevrei sp. nov., a new Moraxella species found in goats.

Six Moraxella-like strains that formed a phenotypically homogeneous group were isolated from the nasal flora of healthy goats. Total genomic DNA-DNA hybridization, rRNA gene restriction pattern, DNA base composition, and genetic transformation studies were performed to determine the relationships of these bacteria to species belonging to the genus Moraxella and other fastidious gram-negative species. The new group of isolates was very homogeneous, as shown by rRNA gene restriction fragment length patterns (ribotyping), and these organisms displayed high relative binding ratios (RBRs) to each other in DNA-DNA hybridization experiments (RBRs, > or = 58%) but distinctly lower levels of DNA homology with all other species investigated. However, the RBRs obtained with species of the genus Moraxella were higher than the RBRs obtained with all other gram-negative strains examined. Although the new strains had most of the Moraxella bovis phenotypic characteristics except nitrate reduction, quantitative and qualitative genetic transformation data led to the conclusion that they belong to a distinct new cluster in the genus Moraxella. The results of this study, combined with the general morphological and phenotypic profiles of the new strains, are consistent with the creation of a new Moraxella species, for which the name Moraxella boevrei is proposed. Strain 88365 (= ATCG 700022 = CCUG 35435 = NCTC 12925 = CIP 104716) is the type strain of M. boevrei.

Animals↗
PubMed1997

Molecular and phenotypic features of aeromonads isolated from snails (Helix aspersa) affected with a new summer disease.

Forty-four aeromonads were isolated during the summer of 1994 from snails (Helix aspersa) affected or not by a newly described disease. Snta 1 rRNA gene restriction patterns (ribotyping) and nine selected conventional phenotypic tests were performed to retrospectively determine relationships among these isolates regarding the disease. Results from ribotyping were found highly discriminant in strain differentiation and suggest the possible existence of a group of Aeromonas associated with the disease. Biochemical and molecular characterizations indicated that most of these disease-associated aeromonads could belong to the phenospecies A. hydrophila. Phenospecies of aeromonads from healthy snails were distinct from those isolated from diseased snails and could be identified as A. caviae or remained undetermined. To the authors' knowledge, this is the first report of a probable pathogenic aeromonad found in snails, extending the host-pathogen spectrum of Aeromonas.

Aeromonas↗
PubMed1997

Isolation and identification of Salmonella species from chelonians using combined selective media, serotyping and ribotyping.

Thirty-two faecal samples from various pet chelonians were bacteriologically examined using various combinations of selective media for Salmonella detection. Strains identified as Salmonella were clustered by rRNA gene restriction pattern (ribotyping) analysis prior to serological typing. The combination of selenite broth and Rambach or Salmonella-Shigella agars gave the maximum rate of Salmonella recovery. Of the 32 samples examined, 13 (40%), were positive for Salmonella. Five serovars were identified, Muenchen, Rubislaw, Newport, Ferruch and a non-motile O:4,5,12, with Salmonella Muenchen the most common. This result indicates that biochemical characterization combined with ribotyping prior to serotyping can contribute to Salmonella detection on a large scale.

Animals↗
PubMed1997

Detection of Escherichia cole O157 in French food samples using an immunomagnetic separation method and the VIDAS E. coli O157.

Two commercially available screening methods, an automated enzyme-linked fluorescent immunoassay (VIDAS E. coli O157) and an immunomagnetic separation followed by culture onto cefixime tellurite sorbitol MacConkey agar (CT-SMAC), were compared for detection of Escherichia coli O157 in naturally and artificially contaminated food samples. A total of 250 naturally contaminated food samples, including raw milk cheeses, poultry, raw sausages and ground beef retail samples, were examined. Four poultry, one raw sausage and one ground beef sample were found to be positive for E. coli O157 by both methods. Of the six positive samples, five were shown to contain sorbitol-positive, O157-positive, H7-negative, motile and non-verotoxin-producing E. coli.

Cheese↗
PubMed1997

Data collection and information presentation for optimal decision making by clinical managers--the Autocontrol Project.

The Autocontrol methodology has been developed in order to support the optimisation of decision-making and the use of resources in the context of a clinical unit. The theoretical basis relates to quality assurance and information systems and is influenced by management and cognitive research in the health domain. The methodology uses population rather than individual decision making and because of its dynamic feedback design promises to have rapid and profound effect on practice. Most importantly the health care professional is the principle user of the Autocontrol system. In this methodology we distinguish three types of evidence necessary for practice change: practice based or internal evidence, best evidence derived from the literature or external evidence concerning the practice in question, and process based evidence on how to optimise the process of practice change. The software used by the system is of the executive decision support type which facilitates interrogation of large databases. The Autocontrol system is designed to interrogate the data of the patient medical record however the latter often lacks data on concomitant resource use and this must be supplemented. This paper reviews the Autocontrol methodology and gives examples from current studies.

Blood Gas Analysis↗
PubMed1996

IL4 and IL13 receptors share the gamma c chain and activate STAT6, STAT3 and STAT5 proteins in normal human B cells.

IL13 induces the same biological effects as IL4 in normal human B cells. We show that as in the IL4R complex, both IL4R alpha and IL2R gamma c are components of the IL13R and that both cytokines induced STAT6, STAT3 and STAT5 activation in B cells. In spite of this similar downstream signalling, IL4 and IL13 used a different set of Janus kinases: IL13 is unable to activate JAK1 and JAK3.

Antigens, CD↗
PubMed1996

CD40/CD40L interactions and cytokines regulate HIV replication in B cells in vitro.

Using our in vitro model of normal B cell infection, we investigated whether cellular interactions and/or cytokines directing the B cell response also regulate HIV replication. Phorbol esters and CD40 Ab plus IL4, added prior to infection, substantially increased subsequent viral replication. Postinfection, IL2 with or without IL4 and, to a lesser extent, CD40/CD40L interactions enhanced viral replication. In contrast, IL10 down-regulated HIV replication induced by cytokines, without affecting spontaneous or CD40 Ab-induced replication. Both enhancing and inhibitory effects of cytokines on viral replication were independent of their ability to modulate B cell proliferation. Thus, these two phenomena seem to be independently regulated in human B cells.

Animals↗
PubMed1996

Mechanisms of opsonized HIV entry in normal B lymphocytes.

Using our in vitro model of normal B cell infection that functions with low doses of HIV but requires virus opsonization by seropositive patient serum, and complement, we analyzed what receptors allowed virus entry. Here, we show that HIV infection of B cells occurs through 2 major receptors: the CD4 antigen and the CR1/CR2 complex. These 2 pathways work independently since a complete inhibition of virus entry requires both CD4 and CD21/CD35 blockade on CD4dim tonsillar B cells whereas only the latter is critical on CD4-negative B cells.

Antibodies, Monoclonal↗
PubMed1996

Regulation of platelet-activating factor receptor expression in human B cells and B cell lines.

We extended our previous data regarding the modulation of human platelet-activating factor receptor (hPAF-R) expression on human B cell lines as well as normal B cells. First, we showed that hPAF-R mRNA was present in B cell lines expressing membrane hPAF-R, but was absent from cell lines devoid of hPAF-R. Second, enhanced hPAF-R membrane expression induced in IM9 line by IL4 was preceeded by hPAF-R mRNA accumulation that was detectable by 8 h and which peaked at 24 h. Similar results were observed for 10 nM platelet-activating factor treatment, which increased hPAF-R mRNA content up to 120% at 48 h, whereas hPAF-R membrane expression was up-regulated by 130%. Third, our data indicate that functional hPAF-R are expressed on resting, as well as on activated, B cells and that B cell activation is required for maintaining hPAF-R membrane and mRNA expression. Thus, in normal B cells, as well as in B cell lines, transcriptional regulation and/or messenger stability control hPAF-R expression.

B-Lymphocytes↗
PubMed1996

Cytokine response of B lymphocytes from splenic lymphoma with villous lymphocytes: correlation with TNF-RII (p75) and CD11c expression.

We studied the immunophenotype and the functional reactivity to cytokines of blood cells from eight patients with Splenic Lymphoma with Villous Lymphocytes (SLVL). Cells from all cases exhibited moderate to high levels of membrane immunoglobulin, CD22 and CD40 antigens and light chain restriction (kappa/lambda: 1.7/1). CD44, CD54 and CD11b expression was detected in all cases whereas CD11c was expressed in only four cases (50%). CD11c+ cells lacked CD21 and CD23 expression whereas CD11c cells expressed both these antigens. Cells from most patients (7/8) responded to IL2 whereas only four responded to IL4 and three to TNF alpha. The response to TNF alpha correlated with spontaneous TNF-RII and CD11c expression. Although two days of culture induced the TNF-RII expression in CD11c cells, they remained unresponsive to TNF alpha. These two groups of SLVL patients also differed by IL10 mRNA content: the former (CD11c+, TNF-RII+) contained TNF alpha and IL10 mRNA whereas the latter (CD11c, TNF-RII) lacked IL10 mRNA, even after two days of culture. There were thus two groups of SLVL patients: CD11c+ and CD11c, exhibiting different patterns of cytokine response and production. These groups may correspond to different cell origins or different progression stages of the disease.

Aged↗
PubMed1995

JAK3 associates with the human interleukin 4 receptor and is tyrosine phosphorylated following receptor triggering.

In human B cells, interleukin 4 (IL4) acts in regulating proliferation, antigen expression, isotype switching and differentiation. These different effects are mediated through the IL4R complex including the IL2R gamma chain (gamma c) and a specific p130/140 binding unit referred below as human Interleukin 4 Receptor (IL4-R). Here, we studied the signal transduction events following IL4R activation and leading to CD23 expression on resting B cells. We demonstrate that IL4R triggering induced the tyrosine phosphorylation of JAK3 and of a p170 protein. Coimmunoprecipitation of JAK3 with the IL4R suggests a physical association which exists prior to IL4R complex stimulation. Orthovanadate treatment, while having no effect on IL4-induced p130 phosphorylation, leads to the hyperphosphorylation of the p170 and inhibits IL4-induced CD23 expression. These suggest that two mandatory steps exist in early IL4 signaling: one controlled by JAK3 activation and the other by the p170 phosphoprotein.

B-Lymphocytes↗