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Biomedical subjects

M Mondon

Publications and source records attributed to M Mondon.

10 recordsLinked to original sources
PubMed2003

Genetic characterization of the nitrate reducing community based on narG nucleotide sequence analysis.

The ability of facultative anerobes to respire nitrate has been ascribed mainly to the activity of a membrane-bound nitrate reductase encoded by the narGHJI operon. Respiratory nitrate reduction is the first step of the denitrification pathway, which is considered as an important soil process since it contributes to the global cycling of nitrogen. In this study, we employed direct PCR, cloning, and sequencing of narG gene fragments to determine the diversity of nitrate-reducing bacteria occurring in soil and in the maize rhizosphere. Libraries containing 727 clones in total were screened by restriction fragment analysis. Phylogenetic analysis of 128 narG sequences separated the clone families into two main groups that represent the Gram-positive and Gram-negative nitrate-reducing bacteria. Novel narG lineages that branch distinctly from all currently known membrane bound nitrate-reductase encoding genes were detected within the Gram-negative branch. All together, our results revealed a more complex nitrate-reducing community than did previous culture-based studies. A significant and consistent shift in the relative abundance of the nitrate-reducing groups within this functional community was detected in the maize rhizosphere. Thus a substantially higher abundance of the dominant clone family and a lower diversity index were observed in the rhizosphere compared to the unplanted soil, suggesting that a bacterial group has been specifically selected within the nitrate-reducing community. Furthermore, restriction fragment length polymorphism analysis of cloned narG gene fragments proved to be a powerful tool in evaluating the structure and the diversity of the nitrate-reducing community and community shifts therein.

Bacteria, Anaerobic↗
PubMed2003

Scanning-force techniques to monitor time-dependent changes in topography and adhesion force of proteins on surfaces.

Scanning-force microscopy (SFM) investigations were conducted to probe the influences of the interactions of proteins with surfaces relevant in medicine. These interactions are an important feature in the area of biofilm formation. The adsorption of proteins leads to changes in topography, which was monitored for the build up of protein layers of hen egg-white lysozyme and bovine serum albumin (BSA) on mica in real time in phosphate-buffered aqueous solution over a time period of 10 min. Phase imaging was additionally applied to compare material contrasts and to evaluate this method for further application in this field. The adhesion forces that develop on a time scale below 20 s between a protein-modified SFM tip and titanium surfaces (TiO(2), TiAl6V4 and TiAl6Nb7) were investigated. The influences of the parameters loading force and interaction time between the protein and the surface were monitored as well as the influence of protein structure. The interaction time dependency of the adhesion force could be described with a kinetic model of two consecutive first-order reactions. For the maximal adhesion force a correlation to the ratio of the amino acids cysteine, proline and glycine has been proposed.

Adhesiveness↗
PubMed2002

Protein adsorption on surfaces: dynamic contact-angle (DCA) and quartz-crystal microbalance (QCM) measurements.

Adsorption of the protein bovine serum albumin (BSA) on gold has been tested at various concentrations in aqueous solution by dynamic contact-angle analysis (DCA) and quartz-crystal microbalance (QCM) measurements. With the Wilhelmy plate technique advancing and receding contact angles and the corresponding hysteresis were measured and correlated with the hydrophilicity and the homogeneity of the surface. With electrical admittance measurements of a gold-coated piezoelectrical quartz crystal, layer mass and viscoelastic contributions to the resonator's frequency shift during adsorption could be separated. A correlation was found between the adsorbed mass and the homogeneity and hydrophilicity of the adsorbed film.

Adsorption↗
PubMed2002

[Aseptic meningitis ornidazole-induced in the course of infectious endocarditis].

INTRODUCTION: Drug-induced aseptic meningitis (DIAM) has been reported as an uncommon adverse reaction to treatment, nonsteroidal anti-inflammatory drugs (NAIDS) stand for most of the published cases. EXEGIS: Our observation reports the first case of a meningeal syndrome with fever, after the administration of ornidazole, with biological aseptic meningitis with lymphocyte prodominance. Spontaneous recovery occurred within a few days and without sequelae. It involved a patient with endocarditis and revealing an intramucous sigmoid adenocarcinoma. The rest of the infection tests was negative. CONCLUSION: We concluded that we were in the presence of a DIAM, with ornidazole as the most probable implicated agent. This diagnosis is suggested in front of a recurring meningeal syndrome without any other apparent etiology, hence the importance of the questioning of the patient. Pending objective evidence usually provided by rechallenge, an antibiotic therapy is necessary, because it is, above all, a diagnosis of exclusion.

Aged↗
PubMed2000

Release of the cyano moiety in the crystal structure of N-cyanomethyl-N-(2-methoxyethyl)-daunomycin complexed with d(CGATCG).

Doxorubicin is among the most widely used anthracycline in cancer chemotherapy. In an attempt to avoid the cardiotoxicity and drug resistance of doxorubicin therapy, several analogues were synthesized. The cyanomorpholinyl derivative is the most cytotoxic. They differ greatly from their parent compound in their biological and pharmacological properties, inducing cross-links in drug DNA complexes. The present study concerns N-cyanomethyl-N-(2-methoxyethyl)-daunomycin (CMDa), a synthetic analogue of cyanomorpholino-daunomycin. Compared to doxorubicin, CMDa displays a cytotoxic activity on L1210 leukemia cells at higher concentration but is effective on doxorubicin resistant cells. The results of fluorescence quenching experiments as well as the melting temperature (DeltaTm = 7.5 degrees C) studies are consistent with a drug molecule which intercalates between the DNA base pairs and stabilizes the DNA double helix. The crystal structure of CMDa complexed to the hexanucleotide d(CGATCG) has been determined at 1.5 A resolution. The complex crystallizes in the space group P41212 and is similar to other anthracycline-hexanucleotide complexes. In the crystal state, the observed densities indicate the formation of N-hydroxymethyl-N-(2-methoxyethyl)-daunomycin (HMDa) with the release of the cyano moiety without DNA alkylation. The formation of this degradation compound is discussed in relation with other drug modifications when binding to DNA. Comparison with two other drug-DNA crystal structures suggests a correlation between a slight change in DNA conformation and the nature of the amino sugar substituents at the N3' position located in the minor groove.

Animals↗
PubMed1998

Prodrugs of anthracyclines for use in antibody-directed enzyme prodrug therapy.

A series of new prodrugs of daunorubicin and doxorubicin which are candidates for antibody-directed enzyme prodrug therapy (ADEPT) is reported. These compounds (25a,b,c and 32a,b,c) have been designed to generate cytotoxic drugs after activation with beta-glucuronidase. As expected, recovery of the active drug was observed after enzymatic cleavage by Escherichia coli beta-glucuronidase as well as by a fusion protein which has been obtained from human beta-glucuronidase and humanized CEA-specific binding region. The six prodrugs are highly stable and are more than 100-fold less cytotoxic than doxorubicin against murine L1210 cell lines. The ortho-substituted phenyl carbamates 25a,b,c are better substrates for beta-glucuronidase than the corresponding para-substituted analogues. After taking into account additional factors such as stability in plasma and kinetics of enzymatic cleavage, we selected the o-nitro prodrug 25c for clinical trials.

Animals↗
PubMed1994

Prodrugs of anthracyclines for chemotherapy via enzyme-monoclonal antibody conjugates.

New prodrugs of daunorubicin, 1c, 1e and 2c, including a galactopyranosyl residue linked to the N-3' of the daunosaminyl moiety through substituted o- or p-benzyloxycarbonyl groups were synthesized. Their low cytotoxicity and high stability in plasma fulfil the conditions for antibody-directed enzyme prodrug therapy (ADEPT). Enzymatic hydrolysis using alpha-D-galactosidase gives rise to daunorubicin by subsequent self-elimination of the spacers. However, elimination clearly depends on the aromatic substitution pattern, as demonstrated especially by comparison with non-substituted analogues.

Animals↗