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Biomedical subjects

R Mathis

Publications and source records attributed to R Mathis.

At least 19 recordsLinked to original sources
PubMed2006

[Orthodontics founded on "proof" or therapeutic decision making based on the literature].

Faced to an abundant literature and to various clinical situations, practitioners are nowadays invited to implement an evidence based approach. This methodology, initially developed in Canada in the 80's, is getting widely used and is perfectly suited for Orthodontics and particularly for the evaluation of interceptive treatments. It is defined as the conscentious, explicit and judicious use of current best evidence in making decisions about the care of individual patients. This approach, which requires four different steps, will initially be presented. A methodological guide that allows to grade the evidence among different research protocols, will then be introduced. At the top of the hierarchy, randomized clinical trials have shown to be the best tools available to evaluate treatment efficiency. Different research designs are finally put forward to evaluate interceptive treatments.

Databases, Bibliographic↗
PubMed2000

The presence of GSI-like genes in higher plants: support for the paralogous evolution of GSI and GSII genes.

Glutamine synthetase type I (GSI) genes have previously been described only in prokaryotes except that the fungus Emericella nidulans contains a gene (fluG) which encodes a protein with a large N-terminal domain linked to a C-terminal GSI-like domain. Eukaryotes generally contain the type II (GSII) genes which have been shown to occur also in some prokaryotes. The question of whether GSI and GSII genes are orthologues or paralogues remains a point of controversy. In this article we show that GSI-like genes are widespread in higher plants and have characterized one of the genes from the legume Medicago truncatula. This gene is part of a small gene family and is expressed in many organs of the plant. It encodes a protein similar in size and with between 36 and 46% amino acid sequence similarity to prokaryotic GS proteins used in the analyses, whereas it is larger and with less than 25% similarity to GSII proteins, including those from the same plant species. Phylogenetic analyses suggest that this protein is most similar to putative proteins encoded by expressed sequence tags of other higher plant species (including dicots and a monocot) and forms a cluster with FluG as the most divergent of the GSI sequences. The discovery of GSI-like genes in higher plants supports the paralogous evolution of GSI and GSII genes, which has implications for the use of GS in molecular studies on evolution.

Amino Acid Sequence↗
PubMed1999

The early nodulin gene MtN6 is a novel marker for events preceding infection of Medicago truncatula roots by Sinorhizobium meliloti.

MtN6 belongs to a series of cDNA clones representing Medicago truncatula genes transcriptionally activated during nodulation by Sinorhizobium meliloti (P. Gamas, F. de Carvalho Niebel, N. Lescure, and J. V. Cullimore, Mol. Plant-Microbe Interact. 9:233-242, 1996). We show here by in situ hybridization that MtN6 transcripts specifically accumulate first at very localized regions in the outer root cell layers, corresponding to outer cortical cells containing preinfection threads. At later stages, MtN6 expression is observed ahead of growing infection threads, including in the infection zone of mature root nodules. Interestingly, regulation of MtN6 is clearly distinct from that of other early nodulins expressed in the same region of the nodule, in terms of response to bacterial symbiotic mutants and to purified Nod factors. We thus suggest that MtN6 represents the first specific marker of a pathway involved in preparation to infection, which is at least partly controlled by Nod factors. Finally, we discuss the intriguing sequence homology shown by MtN6 to a protein from Emericella (Aspergillus) nidulans, FluG, that plays a key role in controlling the organogenesis of conidiophores (B. N. Lee and T. H. Adams, Genes Dev. 8:641-651, 1994).

Amino Acid Sequence↗
PubMed1996

Leuconostoc mesenteroides subsp. mesenteroides FR52 synthesizes two distinct bacteriocins.

Mesenterocin 52, a bacteriocin produced by Leuconostoc mesenteroides subsp. mesenteroides FR52, was purified from producing cells by the adsorption-desorption method, combined with reverse-phase high-performance liquid chromatography. The elution profile revealed the presence of two inhibitory peaks of activity, each displaying different inhibitory spectra. Mesenterocin 52A possessed a broad inhibitory spectrum, including anti-Listeria activity, while Mesenterocin 52B was only active against Leuconostoc spp. The amino acid sequence and M(r) of Mesenterocin 52A appeared identical to the previously described Mesentericin Y105. In contrast, Mesenterocin 52B possessed a M(r) of 3446 Da, corresponding to 32 amino acids and a sequence that shared no homology with known bacteriocins: NH2-KGVLGWLSMASSALTGPQQPNSPWLAKIKNHK.

Amino Acid Sequence↗
PubMed1993

Asymmetric synthesis and biological evaluation of beta-L-(2R,5S)- and alpha-L-(2R,5R)-1,3-oxathiolane-pyrimidine and -purine nucleosides as potential anti-HIV agents.

In order to study the structure-activity relationships of L-oxathiolanyl nucleosides as potential anti-HIV agents, a series of enantiomerically pure L-oxathiolanyl pyrimidine and purine nucleosides were synthesized and evaluated for anti-HIV-1 activity in human peripheral blood mononuclear (PBM) cells. The key intermediate 8 was synthesized starting from L-gulose via 1,6-thioanhydro-L-gulopyranose. The acetate 8 was condensed with thymine, 5-substituted uracils and cytosines, 6-chloropurine, and 6-chloro-2-fluoropurine to give pyrimidine and purine nucleosides. Upon evaluation of these final nucleosides, the 5-fluorocytosine derivative 51 was found to be the most potent compound among those tested. In the case of 5-substituted cytosine analogues, the antiviral potency was found to be in the following decreasing order: cytosine (beta-isomer) > 5-iodocytosine (beta-isomer) > 5-fluorocytosine (alpha-isomer) > 5-methylcytosine (alpha-isomer) > 5-methylcytosine (beta-isomer) > 5-bromocytosine (beta-isomer) > 5-chlorocytosine (beta-isomer). Among the thymine, uracil, and 5-substituted uracil derivatives, thymine (alpha-isomer) and uracil (beta-isomer) derivatives exhibited moderate anti-HIV activity. In the purine series, the antiviral potency is found to be in the following decreasing order: adenine (beta-isomer) > 6-chloropurine (beta-isomer) > 6-chloropurine (alpha-isomer) > 2-NH2-6-Cl-purine (beta-isomer) > guanine (beta-isomer) > N6-methyladenine (alpha-isomer) > N6-methyladenine (beta-isomer). The cytotoxicity was also determined in human PBM cells as well as Vero cells. None of the synthesized nucleosides was toxic up to 100 microM in PBM cells.

Antiviral Agents↗
PubMed1992

Selective inhibition of human immunodeficiency viruses by racemates and enantiomers of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine.

2',3'-Dideoxy-5-fluoro-3'-thiacytidine (FTC) has been shown to be a potent and selective compound against human immunodeficiency virus type 1 in acutely infected primary human lymphocytes. FTC is also active against human immunodeficiency virus type 2, simian immunodeficiency virus, and feline immunodeficiency virus in various cell culture systems, including human monocytes. The antiviral activity can be prevented by 2'-deoxycytidine, but not by other natural nucleosides, suggesting that FTC must be phosphorylated to be active and 2'-deoxycytidine kinase is responsible for the phosphorylation. By using chiral columns or enzymatic techniques, the two enantiomers of FTC were separated. The (-)-beta-enantiomer of FTC was about 20-fold more potent than the (+)-beta-enantiomer against human immunodeficiency virus type 1 in peripheral blood mononuclear cells and was also effective in thymidine kinase-deficient CEM cells. Racemic FTC and its enantiomers were nontoxic to human lymphocytes and other cell lines at concentrations of up to 100 microM. Studies with human bone marrow cells indicated that racemic FTC and its (-)-enantiomer had a median inhibitory concentration of > 30 microM. The (+)-enantiomer was significantly more toxic than the (-)-enantiomer to myeloid progenitor cells. The susceptibilities to FTC of pretherapy isolates in comparison with those of posttherapy 3'-azido-3'-deoxythymidine-resistant viruses in human lymphocytes were not substantially different. Similar results were obtained with well-defined 2',3'-dideoxyinosine- and nevirapine-resistant viruses. (-)-FTC-5'-triphosphate competitively inhibited human immunodeficiency virus type 1 reverse transcriptase, with an inhibition constant of 2.9 microM, when a poly(I)n.oligo(dC)19-24 template primer was used. These results suggest that further development of the (-)-Beta-enantiomer of FTC is warranted as an antiviral agent for infections caused by human immunodeficiency viruses.

Antiviral Agents↗
PubMed1992

Activities of the four optical isomers of 2',3'-dideoxy-3'-thiacytidine (BCH-189) against human immunodeficiency virus type 1 in human lymphocytes.

Four different isomers of 2',3'-dideoxy-3'-thiacytidine [beta-DL-(+-)-BCH-189] were evaluated in primary human lymphocytes infected with human immunodeficiency virus type 1. The beta-L-(-) isomer was the most potent enantiomer, with a median effective concentration of 1.8 nM and no discernible cytotoxicity up to 100 microM. The relative order of potencies for the isomers was beta-L-(-) greater than beta-DL-(+-) racemic greater than beta-D-(+) greater than alpha-L-(+) greater than alpha-D-(-). The beta-L-(-) enantiomer was as potent as 3'-azido-3'-deoxythymidine.

Antiviral Agents↗
PubMed1988

One-Step Purification of a Lipolytic Enzyme from Bacillus pumilus by Mild Hydrophobic Interaction Chromatography on Polyoxyalkylene Glycol-Bound Sepharose 6B.

An esterase from Bacillus pumilus was obtained in a highly purified form, starting from a crude extract, by a new chromatographic technique requiring no detergent during the elution step. The stationary phase involved was mildly hydrophobic and was prepared by covalent immobilization of a polyoxyalkylene glycol onto Sepharose 6B.

Journal Article↗
PubMed1987

Association of lipid-laden alveolar macrophages and gastroesophageal reflux in children.

The association of lipid-laden alveolar macrophages (LLAM) and gastroesophageal reflux (GER) was investigated prospectively in 115 patients in two groups. Group 1 included 74 children with chronic respiratory tract disorders and documented GER by prolonged esophageal pH monitoring, barium esophagram, and esophagoscopy; group 2 included 41 children with chronic respiratory tract disorders without GER. LLAM were present in 63 (85%) and eight (19%) children from groups 1 and 2, respectively (P less than 0.0001). Thus a strong association between the presence of LLAM and GER in children with chronic respiratory tract disorders was established. We suggest that LLAM from bronchial lavage may be a useful marker for tracheal aspiration in children with GER in whom chronic lung disease may subsequently develop.

Child↗
PubMed1984

[Steinert disease and pregnancy].

Steinert's syndrome and pregnancy with delivery are rarely associated. It is a dominant autosome disease. Certain signs in pregnancy may suggest that the fetus is affected. One case made it possible to demonstrate these facts. Hydramnios with infrequent fetal movements and a slow fetal heart rate may lead to a suspicion of fetal involvement. This is always serious. The presence of the disease in the mother should be sought if it is not already known. If there is already a known family history the patient should see a geneticist so long as early amniocentesis has not yet been performed.

Adult↗