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Biomedical subjects

M Richard

Publications and source records attributed to M Richard.

At least 55 records · Page 3Linked to original sources
PubMed1997

Homologous junctions formed between a vector and human genomic repetitive LINE-1 elements as a result of one-sided invasion.

Studies on homologous recombination in mammalian cells between an exogenous DNA molecule containing a double-strand break and a homologous genomic sequence have indicated that there were at least two distinct types of homologous recombination processes, one that involved the formation of two homologous junctions and another that involved the formation of one homologous junction and one illegitimate junction. Both types of events are produced in gene targeting experiments. We have proposed a model to account for the later process called one-sided invasion. One-sided invasion has now been reported in numerous species belonging to different phyla and appears to be a universal mechanism. It has also been observed in normal human germ cells. The role of one-sided invasion is still unknown. Using a recombination assay between LINE-1 elements from the human genome and exogenous LINE-1 sequences, we have characterized the process of homologous junction formation in one-sided invasion. We found that at each of the homologous junctions, variable lengths of the vector L1 sequences had been replaced by genomic L1 sequences. We also found a homologous junction that involved three partners, suggesting that the homologous end could be released and become available for a second round of interaction.

Base Sequence↗
PubMed1997

Calcitonin inhibits phospholipase A2 and collagenase activity of human osteoarthritic chondrocytes.

Calcitonin (CT) is a known potent inhibitor of bone resorption but its effect on cartilage enzymatic degradation has been incompletely studied. Salmon CT, at a concentration of 0, 0.1, 0.25, 0.5, 2.5 and 50 ng/ml, was added at 24 or 72 h to the culture medium of chondrocytes from human osteoarthritic hips and knees. The spontaneous collagenolytic activity, measured using a radiolabeled type II collagen, was inhibited by CT in a dose-dependent manner. However, CT had no effect on the total collagenolytic activity assayed after APMA activation. Stromelysin and plasmin activity, measured by degradation of casein and a synthetic substrate, were also unaffected by CT. Chondrocyte phospholipase A2 activity, assayed using a labeled specific substrate, was decreased by CT. Chondrocyte pre-incubation with CT significantly decreased the cell binding of labeled TNF alpha, but did not affect IL-1 beta cell binding. Attachment of chondrocytes on fibronectin was markedly stimulated by CT, while attachment to type II collagen was not. Significant effects were obtained using at least 2 or 5 ng/ml of CT. CT appears to decrease collagenolytic activity by decreasing its activation and/or increasing its inhibition by tissue inhibitors of metalloproteinases (TIMP). CT might act on osteoarthritic chondrocyte activation via mechanisms such as phospholipase A2 activity, human necrosis factor-alpha or fibronectin receptor expression.

Calcitonin↗
PubMed1997

The enzyme involved in sulfation of the turgorin, gallic acid 4-O-(beta-D-glucopyranosyl-6'-sulfate) is pulvini-localized in Mimosa pudica.

A sulfotransferase (ST) which catalyzes the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to gallic acid glucoside was characterized from microsomal preparations of Mimosa pudica. The product of the reaction was found to co-elute on HPLC with the periodic leaf movement factor 1 (PLMF-1)(gallic acid beta-D-gluco-pyranosyl-6'-sulfate). The distribution of the enzyme activity was restricted to plasma membrane preparations from primary, secondary and tertiary pulvini. The M. pudica ST activity was inhibited in a dose-dependent manner in the presence of an antibody raised against the flavonol 3-sulfotransferase of Flaveria chloraefolia, suggesting structural similarities between the two proteins. Western blot analysis of M. pudica protein extracts using these antibodies indicated the presence of a cross-reactive polypeptide with an apparent molecular mass of 42,000 Da whose distribution correlates with the presence of the gallic acid glucoside ST activity. Indirect immunogold labeling of resin-embedded sections from tertiary pulvini showed a specific localization of gold particles on the sieve-tube plasma membranes. The label distribution was uniform and other cellular organelles and membrane systems displayed little or no labeling. The results of the Western blot and immunocytochemical studies are consistent with the detection of the gallic acid glucoside ST activity in plasma membrane preparations of M. pudica pulvini cells. The specific tissue distribution of the ST in motor organ phloem cells suggests that this is the site of synthesis and/or accumulation of PLMF-1 and supports the proposed hypothesis that PLMF-1 may be acting as a chemical signal during the seismonastic response of M. pudica.

Catalysis↗
PubMed1997

Sulfation and sulfotransferases 6: Biochemistry and molecular biology of plant sulfotransferases.

It is now well established that, in mammals, sulfate conjugation constitutes an important reaction in the transformation of xenobiotics and in the modulation of the biological activity of steroid hormones and neurotransmitter. The presence of a sulfate group on some molecules can also be a prerequisite for their biological function. For example, it is well known that the sulfate groups are directly involved in the molecular interaction between heparin and antithrombin III. In plants, sulfation also seems to play an important role in the intermolecular recognition and signaling processes, as indicated by the requirement of a sulfate moiety for the biological activity of gallic acid glucoside sulfate in the seismonastic and gravitropic movements of plants, and of Nod RM1 in the cortical cell division during early nodule initiation in Rhizobium meliloti-alfalfa interaction. In addition, recent studies indicate that flavonoid conjugates, including the sulfate esters, may play a role in the regulation of plant growth by strongly binding the naphthylphthalamic acid receptor, thus blocking the quercetin-stimulated accumulation of the auxin phytohormone. Although several sulfated metabolites are known to accumulate in a variety of plant species, the study of enzymes that catalyze the sulfation reaction in plants lagged considerably compared to those conducted with their mammalian homologs. This apparent lack of interest may have been because the function of plant-sulfated metabolites is difficult to predict, since their accumulation is often restricted to a limited number of species. Despite this limitation, several plant sulfotransferases (STs) have been characterized at the biochemical level, and the cDNA clones encoding six plant STs have been isolated. Based on sequence homology, the plant ST coding sequences are grouped under the SULT3 family, also known as the flavonol ST family. This review summarizes our current knowledge of the plant STs and focuses on the functional significance of the sulfate conjugation in plant growth, development, and adaptation to stress.

Amino Acid Sequence↗
PubMed1997

Interlaboratory evaluation of short tandem repeat triplex CTT.

An interlaboratory comparison of typing results for Short Tandem Repeats (STRs) at the GenBank loci HUMCSF1PO, HUMTPOX, HUMTH01, and HUMVWFA31 using the "CTT triplex" and "CTTv quadruplex" has been evaluated. These STRs all have a nominal four basepair (bp) repeat. Seven different samples were distributed to 41 laboratories. The 34 laboratories that returned results used a wide variety of analytical systems. Comparable results were obtained for all samples at all loci when results were reported as an allelic name. Raw sizing results obtained from internal-lane sizing standards differed by nearly five bp at some loci. Many different factors contribute to this observed sizing variability, including choice of sizing standards and matrix composition. Although sizing results can be made more comparable by locus-specific offsets or calibration to a comprehensive set of alleles at each locus, samples typed to the allelic name can now be validly compared regardless of analytical method. Interlaboratory comparison of raw allelic size remains problematic.

Algorithms↗
PubMed1997

Moving health care education into the community.

The A+ Asthma Club, an educational program developed for elementary school children in inner-city schools, is offered through a series of six sessions during school hours with an additional three booster sessions. This article describes how the program was designed, its theoretical basis, the curriculum and its staffing.

Asthma↗
PubMed1996

Routine determination of flumequine in kidney tissue of pig using automated liquid chromatography.

A high-performance liquid chromatographic assay is described as a routine analytical method for the determination of flumequine (FLU) and its hydroxylated metabolite (OH-FLU) in pig kidney tissue. Kidney samples (2 g) containing FLU and OH-FLU were extracted by liquid-liquid extraction with ethyl acetate (10 ml). Analytical separations were performed by reversed-phase HPLC with fluorometric detection at 252 nm excitation and 356 nm emission under gradient conditions. The mobile phase was acetonitrile-2.7.10(-3) M oxalic acid in water (pH 2.5). The assay is specific and reproducible within the flumequine range of 0.050-2.5 micrograms/g and recovery at 0.050 microgram/g was 94.8%.

Administration, Oral↗
PubMed1996

Phylogenetic inferences from chloroplast chlB gene sequences of Nephrolepis exaltata (Filicopsida), Ephedra altissima (Gnetopsida), and diverse land plants.

The chloroplast chlB gene, involved in light-independent protochlorophyllide reduction, has been reported present in algae, in one bryophyte and some gymnosperms, but absent from various angiosperms. In this study, the complete or nearly complete chlB gene sequences from the fern Nephrolepis exaltata and the seed plant Ephedra altissima were determined. Comparison of five available land plant chlB sequences with a similar set of rbcL sequences, encoding the large subunit of ribulose 1,5-bisphosphate carboxylase, showed that the chlB rate of nonsynonymous substitution was about fourfold higher than for rbcL, while the chlB phylogeny resulted in a better resolution of the clades surveyed. The presence of chlB in other lineages of land plants was determined by amplification and sequencing of a chlB internal fragment, which was recovered from all the nonangiosperm taxa surveyed except Psilotum and Gnetum. The phylogenies derived from 23 land plant chlB sequences were largely congruent with the relationships inferred from other analyses. Neighbor-joining analysis supported the view that bryophytes are paraphyletic, with mosses as sister group to vascular plants. Within lycopodiophytes, Selaginella clustered with Lycopodium, but Isoetes was located basally to the other land plants. The various ferns surveyed were found to form a coherent group which derived after horsetails and which was sister group to seed plants. Our results strongly supported monophyly of the conifers-Ginkgo-cycads clade, where conifers were sister group to Ginkgo and cycads. The various phylogenies suggested an early divergence of the seed plant lineage leading to Ephedra.

Algal Proteins↗
PubMed1996

Assessment of urinary hydroxypyridinium cross-links measurement in osteoarthritis.

The aim of this study is to re-evaluate urinary collagen cross-links, previously proposed as markers of osteoarthritis (OA). The urinary excretion of collagen cross-links, pyridinoline (PYD) and deoxypyridinoline (DPD), was measured using high-performance liquid chromatography (HPLC) in 114 patients with OA, 19 patients with rheumatoid arthritis (RA) and 40 healthy subjects. An increase in PYD and DPD, expressed per millimole of creatinine, was confirmed in RA. However, PYD and DPD in patients with hip OA, knee OA and polyOA were similar, and did not differ from controls. In patients with radiographic end-stage OA, PYD and DPD were significantly higher than in patients with an early OA, but not significantly higher than in controls. The PYD/DPD ratio did not vary with the OA stage. Thus, urinary collagen cross-links are not elevated in OA, but could reflect bone sclerosis and/or erosion in late OA.

Adult↗
PubMed1996

Tc-99m MIBI brain SPECT of cerebellopontine angle tumors.

To prospectively evaluate the imaging feasibility of Tc-99m sestamibi brain SPECT of cerebellopontine angle (CPA) tumors, seven patients with CPA lesions seen on CT or MRI and five normal control subjects underwent brain SPECT using a triple-headed camera. Five of these patients had acoustic neuromas, one had a meningloma, and the other had a vascular loop. Subsequently, four patients underwent surgery. In normal control subjects and patients with CPA lesions, there was Tc-99m sestamibi activity in the pituitary gland, choroid plexi, and extraocular muscles. The uptake in these structures, especially the choroid plexi could not be blocked by the oral administration of potassium perchlorate in two normal subjects. Four of seven patients with CPA lesions larger than 1.0 cm in diameter showed tumor uptake (3 acoustic schwannomas, 1 meningloma). Two small ( > 1.0 cm in diameter) intracanalicular type acoustic neuromas failed to show uptake, despite additional attenuation correction for the petrous bone. There was no abnormal uptake in the patient with a vascular loop in the CPA. Preliminary data suggest that, with the exception of small intracanalicular neuromas, CPA tumors can be imaged using Tc-99m sestamibi brain SPECT.

Adult↗
PubMed1996

[Torsades de pointes in a patient under long-term maprotiline therapy. Apropos of a case].

The authors report the case of a patient who presented with wave burst arrhythmia related to long-term treatment with maprotiline. This case is interesting, as few cases of this type of complication have been reported in patients receiving long-term tetracyclic antidepressants, and the development of such a complication indicates the need for regular electrocardiographie surveillance of patients treated with heterocyclic antidepressants. Lastly, prolonged intensive care monitoring is required in the case of maprotiline-induced wave burst arrhythmia.

Aged↗
PubMed1995

Determination of fumagillin in muscle tissue of rainbow trout using automated ion-pairing liquid chromatography.

A high-performance liquid chromatographic assay is described as a routine analytical method for the determination of fumagillin in rainbow trout muscle tissue. Muscle tissue samples (1 g) containing fumagillin were deproteinized with 8 ml of an acetonitrile-water mixture (2:6, v/v). The extracts were purified with a Bond Elut Octyl C8 cartridge column, washed with a water-methanol mixture (95:5, v/v; 4 ml) and fumagillin was eluted with acetonitrile (1 ml). Analytical separations were performed by reversed-phase HPLC with UV detection at 351 nm under gradient conditions. The mobile phase was acetonitrile-0.005 M tetrabutyl ammonium phosphate in water (pH 7.8). The assay is specific and reproducible within the fumagillin range of 20-1000 ng/g and recovery at 20 ng/g was 69.2%. Sample preparation involves the use of a robotic sample preparation system. Gravimetric validation of all operations enabled Good Laboratory Practices to be observed.

Animals↗
PubMed1995

Mutational analyses of Tay-Sachs disease: studies on Tay-Sachs carriers of French Canadian background living in New England.

Tay-Sachs disease (TSD) results from mutations in HEXA that cause Hex A deficiency. Heterozygote-screening programs have been applied in groups with an increased TSD incidence, such as Ashkenazi Jews and French Canadians in Quebec. These programs are complicated by benign mutations that cause apparent Hex A deficiency but not TSD. Benign mutations account for only approximately 2% of Jewish and approximately 36% of non-Jewish enzyme-defined carriers. A carrier frequency of 1/53 (n = 1,434) was found in an ongoing prospective analysis of persons of French Canadian background living in New England by using an enzyme-based assay. DNA from enzyme-defined carriers from this population was analyzed to determine the molecular basis of Hex A deficiency. Samples (36) were tested for common mutations, and samples that were negative for these were screened for uncommon or novel mutations by using SSCP analysis. Exons showing mobility shifts were sequenced, and most mutations were confirmed by restriction enzyme digestion. Known disease-causing mutations were found in nine samples (four had a 7.6-kb deletion found in 80% of French Canadian TSD alleles), and known benign mutations were found in four samples. Seven novel changes were identified, including G748A in four samples. The molecular basis of Hex A deficiency in this carrier population differs from that of French Canadian TSD patients. Screening centers should be aware of the presence of benign mutations among U.S. French Canadians or Franco-Americans.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1995

[Pulmonary embolism associated with right auricular thrombus. Apropos of 2 cases].

The authors report two cases of serious pulmonary embolism, derived from venous thrombus (inferior vena cava in one case, superficial femoral vein in the other), associated with mobile thrombus of the right auricle, with a very rapidly favourable course after intravenous fibrinolysis. This treatment was extremely effective, allowing rapid haemodynamic improvement and resolution of the thrombus in less than 24 hours. No major haemorrhagic complications or recurrent emboli were observed. Fibrinolysis, in serious pulmonary embolism associated with thrombus of the right auricle, therefore appears to be a useful treatment, particularly in patients admitted to centres in which emergency embolectomy cannot be performed.

Aged↗
PubMed1995

Gangliosides from normal and osteoarthritic joints.

A decrease in all major gangliosides, contrasting with a marked increase in the GM3 third band (3B-GM3), has been demonstrated in osteoarthritic fibrillated cartilage. We found the 3B-GM3 in osteoarthritic fibrillated, grossly intact and osteophytic human cartilage, but it was undetectable in pig and bovine cartilage, bone, synovium, synovial fluid white cells, erythrocytes, and various extracellular tissues. We made a similar finding with lactosyl ceramide, the GM3 neutral glycolipid precursor. The search for an antibody against the 3B-GM3, as a possible specific antigenic marker of osteoarthritis (OA), was unsuccessful. However, an antibody against a molecule very close to 3B-GM3 on high performance thin layer chromatography, which will probably be identified as a glycosylphosphatidylinositol, was found in the serum of some patients with OA.

Animals↗