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Biomedical subjects

M H Richard

Publications and source records attributed to M H Richard.

At least 19 recordsLinked to original sources
PubMed2000

[The French pharmacovigilance system: structure and missions].

THE NETWORK: The French pharmacovigilance system is composed of a network of 31 regional pharmacovigilance centers located in convenient proximity to health care professionals. CAUSALITY ASSESSMENT: A causality assessment method is compulsory for all persons involved in pharmacovigilance in order to assess the causal relationship between an adverse effect and one or more drugs. PHARMACOEPIDEMIOLOGY: If necessary, an additional evaluation of the causal relationship is performed using pharmacoepidemiology methods. THE NATIONAL COMMISSION: A technical committee and a National Commission of Pharmacovigilance centralizes at the Agence Françiase de Sécurité Sanitaire (or AFSSAPS) and assesses all data in order to provide consensual advise to the relevant authorities on necessary measures, to prevent or reduce a drug-related adverse effect.

Adverse Drug Reaction Reporting Systems↗
PubMed1997

Interferon gamma-induced PNA-binding glycoproteins as markers of human keratinocyte differentiation: biological evidence using protein kinase C agonists, antagonists and retinoic acid.

Membrane glycoproteins (gps) play an important role in cell-cell interactions during epidermal maturation, and we have previously shown an up-regulation of PNA-binding gps in cultured human keratinocytes treated with interferon gamma (IFN-gamma). The protein kinase C (PKC) pathway is known to play a key role in the regulation of proliferation and differentiation of keratinocytes and is also reported to be involved in some IFN-gamma-mediated effects. In order to evaluate the cellular mechanisms and whether PNA-binding gp expression is related to the differentiative activity of the lymphokine, we studied the effects of PKC agonists and antagonists and the role of retinoic acid (RA), in the induction of these gps in cultured human keratinocytes stimulated with IFN-gamma and processed for protein analysis. The expression of PNA-binding gps was revealed by incubation of SDS-polyacrylamide gels with 125I-PNA. The PKC antagonists (H7, sphingosine) as well as RA downregulated the IFN-gamma-induced PNA-reactive gps, whereas staurosporine and TPA upregulated their expression. These results provide evidence that PNA-reactive gps are late highly IFN-gamma-sensitive markers of keratinocyte differentiation, drastically modulated through selective isoforms of PKC.

Agglutinins↗
PubMed1994

Induction of intercellular adhesion molecule 1 expression on normal human keratinocytes by retinoic acid: comparison of cultured keratinocytes and skin explants.

As retinoic acid (RA, all trans) induces irritant reactions when applied topically to skin, we wondered whether it may be involved in the activation state of keratinocytes through ICAM-1 induction. Human skin explants and cultured keratinocytes were treated by RA and/or interferon-gamma (IFN gamma) at different concentrations during 24, 48 and 72 h. ICAM-1 expression was examined and quantified by immunohistochemistry, in situ, on cutaneous frozen sections and in cultured keratinocytes by flow cytometry analysis. Expression of mRNA was checked by Northern blot hybridizations using an oligonucleotide probe. Our results indicate: (1) the absence of spontaneous ICAM-1 expression by normal human keratinocytes both in skin explants and in cultures; (2) an ICAM-1-induced expression after 48 h of treatment by RA concentrations > 10(-6) M; this induction is dose- and time-dependent; in skin explants, ICAM-1 is occasionally observed on foci of epidermal cells; this protein induction is correlated with transcript expression in cultured keratinocytes; and (3) a synergistic effect of RA and IFN gamma (5 IU/ml) on the percentage of ICAM-1-positive cells and the level of expression of the protein. These findings indicate that RA, in a therapeutical range of concentrations can induce or stimulate ICAM-1 expression in normal human keratinocytes. This may in part explain the erythematous reaction observed in vivo after topical applications of RA which may be considered as a mediator of keratinocyte activation.

Adult↗
PubMed1993

Gamma interferon potently induces tryptophanyl-tRNA synthetase expression in human keratinocytes.

Incubation of human keratinocytes with gamma interferon (gamma-IFN) induces the synthesis of a 53-kDa protein of unknown nature and function. We report the identification of this protein through amino acid microsequencing. The NH2-terminal amino acid sequence of the 53-kDa antigen demonstrated that this protein was tryptophanyl-tRNA synthetase (Frolova et al, Gene 109:291-296, 1991, Genbank accession number 61715). This result was validated by the sequencing of tryptic peptides. Identification of the 53-kDa gamma-IFN-induced protein was confirmed by immunoblotting with an antiserum directed against beef pancreas tryptophanyl-tRNA synthetase. Northern blot analysis using a synthetic oligonucleotidic 32P-labeled probe evidenced a 3.1-kb transcript in gamma-IFN-treated cells indicating that the gene was regulated at the pre-translational level. These data show that gamma-IFN potently induces in keratinocytes the expression of an enzyme directly involved in protein biosynthesis. Elevated levels of tryptophanyl-tRNA synthetase in treated cultured keratinocytes might be involved in the cell-growth-inhibitory activity of gamma interferon.

Amino Acid Sequence↗
PubMed1993

Effects of retinoic acid on interleukin-1 alpha and -1 beta expression by normal human keratinocytes cultured in defined medium.

In human epidermis, basal keratinocytes are the main source of interleukin-1 (IL-1), and IL-1 alpha is the predominant form, whereas IL-1 beta appears to exist predominantly in cultured keratinocytes. We investigated the effects of retinoic acid (RA) treatments on IL-1 alpha and -beta protein and mRNA expression of normal human keratinocytes cultured in low-calcium defined medium with or without hydrocortisone. Radioimmunoassay showed that after stimulation by RA, the IL-1 beta intracellular level is predominantly increased, with no significant modification of IL-1 alpha expression. The addition of hydrocortisone in the culture medium resulted in a decrease in RA-induced IL-1 beta overexpression, without notable modifications in untreated cultures. Release of both IL-1 alpha and -beta in culture supernatants was detectable only after RA treatment and in the absence of hydrocortisone. The overexpression of IL-1 beta in control and RA-treated cultures mainly concerned the 52- and 31- to 36-kD biologically inactive precursor forms. Northern blot using specific IL-1 alpha and -beta oligonucleotide probes showed that IL-1 beta mRNA predominate over IL-1 alpha mRNA and reach a maximal level 6 h before the IL-1 beta protein peak. These findings indicate that in cultured keratinocytes intracellular IL-1 beta is preferentially increased by RA but in its immature forms. The significance of this overexpression remains to be elucidated.

Adult↗
PubMed1990

Vimentin expression in normal human keratinocytes grown in serum-free defined MCDB 153 medium.

We have shown that subcultured keratinocytes derived from normal human skin and grown on plastic in serum-free defined medium (MCDB 153, with 0.1 mM Ca2+ concentration) synthesize vimentin. A fibrillar vimentin expression was observed in the cell cytoplasm by immunohistochemistry with different monoclonal antibodies to vimentin in a high proportion of cultured cells. Two dimensional gel electrophoresis of cytoskeletal proteins from keratinocyte subcultures and immunoblotting reaction with different monoclonal antibodies to vimentin showed a specific reaction in a position corresponding to vimentin. No cross-reaction with keratin polypeptides was obtained. This expression of vimentin may be related to the adaptation of cells to in vitro growth conditions.

Animals↗
PubMed1979

Latex fetuin spheres as probes for influenza virus neuraminidase in productively and abortively infected cells.

Fetuin bound latex spheres do not adhere to the membranes of non-infected cells but adhere to those of cells productively infected by fowl plague virus (FPV Dobson strain). In contrast, asialo fetuin spheres do not attach to the membranes of productively infected cells. Moreover latex fetuin spheres incubated with extracts of productively infected cells and extensively washed are specifically enriched in neuraminidase activity without any trace of haemagglutinin. These observations suggest that viral neuraminidase in the membrane is the site of attachment of the sialic acid moieties of fetuin spheres. These neuraminidase sites are detectable when L cells are productively infected by a mammalian cell adapted mutant of the Dobson strain (FPV-B) but are not detectable on L cells abortively infected by wild type (FPV+). However, even in the abortive system, neuraminidase is synthesised de novo as shown by its labelling with 14C-glucosamine and by its isolation from labelled extracts of infected cells by latex fetuin spheres. These results show that misintegration of viral neuraminidase in the plasma membrane of L cells is a feature of abortive infection of these cells by the Dobson strain of FPV. However the relationship (if any) of this misintegration to abortive infection remains to be established.

Cell Line↗
PubMed1972

Composition and size of Shope fibroma virus deoxyribonucleic acid.

Deoxyribonucleic acid (DNA) extracted from purified virions of Shope fibroma virus (SFV) (by using DNA from Microccocus lysodeikticus as marker) had a buoyant density of 1.6996 +/- 0.0003 g/ml), hence a guanine plus cytosine (G + C) content of 40.4 +/- 0.3%, which is close to the G + C content of the DNA of susceptible rabbit cells (40.9 +/- 0.4%) and different from that of vaccinia virus DNA (35.5 +/- 0.4%). For the determination of the molecular weight of DNA, SFV and vaccinia purified virions, treated with Pronase and detergent, were cosedimented in sucrose density gradients. Results showed that SFV-DNA has a molecular weight of about 153 x 10(6) daltons. By electron microscopy, only one molecule corresponding to this value was observed (its length was 80.3 mum). The others had a median size of 49.8 mum +/- 0.9.

Animals↗