PubMed Health⌕ Search

Biomedical subjects

H Mathieu

Publications and source records attributed to H Mathieu.

At least 19 recordsLinked to original sources
PubMed2003

OTDR fiber-optical chemical sensor system for detection and location of hydrocarbon leakage.

A distributed sensing system for apolar hydrocarbons is presented which is built from a polymer-clad silica fiber adapted to an optical time domain reflectometer (OTDR) set-up. OTDR measurements allow locating and detecting chemicals by measuring the time delay between short light pulses entering the fiber and discrete changes in the backscatter signals that are caused by local extraction of hydrocarbons into the fiber cladding. The light guiding properties of the fiber are affected by interaction of the extracted chemicals with the evanescent wave light field extending into the fiber cladding. Distributed sensing of pure liquid hydrocarbons (HC) and aqueous HC solutions with a commercially available mini-OTDR adapted to sensing fibers of up to 1km length could be demonstrated. A pulsed laser diode emitting at the 850 nm telecommunication wavelength was applied in the mini-OTDR to locate the HCs by analyzing the step drop (light loss) in the backscatter signal, which is induced by local refractive index (RI) increase in the silicone cladding due to the extracted HC. The prototype instrument can be applied for monitoring hydrocarbon leakage in large technical installations, such as tanks, chemical pipelines or chemical waste disposal containments.

Environmental Monitoring↗
PubMed1999

CYP2D6 polymorphism in a Gabonese population: contribution of the CYP2D6*2 and CYP2D6*17 alleles to the high prevalence of the intermediate metabolic phenotype.

AIMS: To determine the molecular basis of the intermediate extensive metaboliser (EM) CYP2D6 phenotype in healthy Gabonese subjects. METHODS: The CYP2D6 phenotype of 154 healthy Gabonese subjects was assessed by giving the subject a single dose of 30 mg dextromethorphan, and collecting their urine for the next 8 h. The CYP2D6 genotype was determined for 50 individuals of the EM phenotypic group by Southern blotting and various PCR-based procedures aimed at identifying different CYP2D6 alleles. RESULTS: We found that in the studied Gabonese population, as compared with a French population, there is significantly higher frequency of intermediate EM phenotype having lower frequency of CYP2D6 PM alleles. To clarify this discrepancy phenotype-genotype relationship was studied. We found that the CYP2D6*17 and CYP2D6*2 alleles, prevalent in this black population, are characterised by their low capacity for dextromethorphan demethylation. Our data also show that the CYP2D6*1 allele is associated with the highest in vivo activity followed by the CYP2D6*2 allele and then the CYP2D6*17 allele. CONCLUSIONS: The higher frequencies of the CYP2D6*2 and CYP2D6*17 alleles than the CYP2D6*1 allele account for the high frequency of the intermediate EM phenotype in this black population. The polymorphism of the CYP2D6 enzyme activity in African populations could have important implications for use of drugs that are substrates for CYP2D6 and have a narrow therapeutic window.

Alleles↗
PubMed1993

Cell- and stage-specific expression of vitamin D receptor and calbindin genes in rat incisor: regulation by 1,25-dihydroxyvitamin D3.

To investigate the extent of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] action and its relationships to calbindin gene expression in mineralized tissues, we have analyzed rat incisors with different probes, including a vitamin D receptor (VDR) antibody and specific cDNAs to rat calbindin-D9K and calbindin-D28K. Developmental and hormonal controls of calbindin gene expression were investigated by Northern blot analysis of ameloblast and odontoblast mRNA. Distribution and hormone-induced changes of VDR were also studied by light microscopic immunocytochemistry. A differential tissue- and stage-specific expression of the calbindin genes was observed in microdissected portions of the continuously erupting incisor. The two calbindins were expressed in ameloblasts, whereas only calbindin-D28K was expressed in odontoblasts. Moreover, in ameloblasts, expression of calbindin-D28K preceded that of calbindin-D9K. Immunoreactivity for VDR was present in all progenitor cells and progressively decreased during the differentiation process, whereas, in differentiated tissues, a hormonal upregulation was restricted to hard tissue-forming cells, i.e., ameloblasts and odontoblasts. Furthermore, calbindin gene expression appeared to be regulated by 1,25(OH)2D3. Taken together, these data indicate that ameloblasts and odontoblasts are target cells for 1,25(OH)2D3 and provide the first insights into the hormonal control of tooth genes during development.

Animals↗
PubMed1993

Distribution and subcellular immunolocalization of 1,25-dihydroxyvitamin D3 receptors in rat epiphyseal cartilage.

The distribution and subcellular localization of the 1,25-dihydroxyvitamin D3 receptor (VDR) in the epiphyseal cartilage of normal weaning rats were examined immunocytochemically at the light and electron microscope level using a monoclonal anti-VDR antibody (9A7 gamma). VDR immunoreactivity was detected in the nuclei of chondrocytes in all zones of the epiphyseal plate cartilage from the resting to calcifying chondrocytes, and at much lower concentrations, in the cytoplasms. Perichondrial mesenchymal cells contained no VDR immunoreactivity. VDR immunoreactivity developed in the nuclei of cells in the lateral margin area as they acquired the chondroblast phenotype. VDR immunoreactivity was also found over the nucleoli of chondrocytes in all cells zones of the epiphyseal plate and appeared in the nucleoli of the cells in the lateral margin area before immunostaining of the nuclei, as the mesenchymal cells differentiated into chondroblasts. Electron microscopy showed that the immunoreactivity for 1,25(OH)2D3 receptor, indicated by gold particles, was associated with scattered clumps of compact chromatin and small clumps of dispersed chromatin. But the nuclei immunostaining patterns before and after mitosis were different in proliferative chondrocytes. The heterochromatin along the nuclear envelope was immunonegative in interphase chondrocytes, but there was VDR immunostaining over the rim of the perinuclear chromatin just after mitosis. In the nucleoli, the dense fibrillar component was immunostained, but the fibrillar centers and the perinuclear chromatin were not. This distribution of VDR immunoreactivity suggests that the hormone is directly involved in differentiation, proliferation and maturation of cartilage cells, and also with extracellular calcification in epiphyseal cartilage. The presence of immunoreactive VDR receptors in nucleoli of chondrocytes, particularly the fibrillar component, suggests that 1,25(OH)2D3 may be involved in regulation of ribosomal genes.

Animals↗
PubMed1992

Molecular analysis provides evidence for the endogenous origin of bacteremia and meningitis due to Enterobacter cloacae in an infant.

We analyzed the restriction fragment length polymorphism (RFLP) of total DNA and of ribosomal DNA regions (ribotyping) to document the occurrence of endogenous, systemic bacteremia and meningitis due to Enterobacter cloacae in a newborn. Five strains of E. cloacae were isolated from this newborn. Three of these strains were recovered from stool at counts of 10(8), 10(9), and 10(9) organisms/g of feces, respectively; one strain was isolated from blood; and one strain was isolated from cerebrospinal fluid. In addition, five epidemiologically unrelated strains of E. cloacae were studied for comparison. Our study clearly shows the genetic relatedness of the strains isolated sequentially from cultures of stool, blood, and cerebrospinal fluid. RFLP analysis of total DNA and ribotyping seem particularly well suited to the study of the epidemiology of nosocomial E. cloacae strains.

Bacteremia↗