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C Marchand

Publications and source records attributed to C Marchand.

At least 37 records · Page 2Linked to original sources
PubMed1996

Stabilization of triple helical DNA by a benzopyridoquinoxaline intercalator.

Biophysical, footprinting, and chemical probing experiments are described which characterize the triple helix-stabilizing effects of a benzo[f]pyridoquinoxaline derivative BfPQ-4,3 structurally related to the previously reported benzo[f]pyridoindole compound BePI [Mergny et al. (1992) Science 256, 1681-1684]. Two parallel triple helix model systems have been investigated; one in which the third strand matched perfectly a 27 base pair purine-pyrimidine motif in target DNA and another in which the third strand was one nucleotide longer, i.e., a 28-mer. In the latter system, the pairing of the (Y)28 third strand to the (Y.R)27 target induces the formation of a bulge containing at least one unpaired base, which can be evidenced by chemical probing experiments with osmium tetroxide. BPQ, which uinwinds a duplex DNA by 17 degrees as judged by viscometric experiments and otherwise behaves as a typical nonspecific intercalculating drug, promotes the formation of Y.R.Y parallel triple helix containing both T.A.T and C.G.C+ triplets. Both DNase I and MPE.FeII footprinting experiments concur that triplex formation with the target (Y.R)27 sequence can be detected in the presence of BPQ at about 10-fold lower oligonucleotide concentrations than are required to produce an equivalent footprint in the absence of the drug. In addition, BPQ will promote binding to the polypurine-polypyrimidine target sequence by the longer mismatched oligonucleotide, providing significant stabilization of the parallel bulge-containing(Y.R)27,(Y)28 triplex with nearly the same efficiency as the bulge-free (Y.R)27.(Y)28 triplex. Thus in vivo BPQ might enhance the formation of both undesired and desired DNA triplexes. By performing an MPE*FeII probing reaction with a 5'-32 P-labeled oligonucleotide third strand, we have obtained evidence that BPQ is actually bound to the triplex region and may distort in a sequence-specific fashion.

Base Sequence↗
PubMed1995

Localized chemical reactivity in double-stranded DNA associated with the intercalative binding of benzo[e]pyridoindole and benzo[g]pyridoindole triple-helix-stabilizing ligands.

Footprinting with methidiumpropyl-EDTA.FeII has been used to map the binding sites on duplex DNA of two closely related benzopyridoindole derivatives which selectively stabilize triple-helical DNA-oligonucleotide complexes. Both ligands bind to many sites, including certain oligopurine.oligopyrimidine tracts, with a weak preference for some (but not all) sequences rich in A.T base pairs. This indifference to primary sequence, with evidence of binding to the commonly disfavoured (A)n.(T)ntracts, may at least partially explain why the ligands stabilize triplex structures composed of T.A.T pairings. Neither 3-methoxy-7H-8-methyl-11- [(3'amino)propylamino]benzo[e]pyrido[4, 3-b]indole (BePI) nor 3- methoxy-7-[3'-diethylamino)propylamino]-10-methyl-11H- benzo[g]pyrido[4,3-b]indole (BgPI) affect the reaction of dimethyl sulphate or potassium tetrachloropalladinate with the N7 of purines in the major groove, but both enhance the reactivity of purines (mostly adenine residues) towards diethylpyrocarbonate, both proximal and distal to their identified binding sites. With potassium permanganate and osmium tetroxide/pyridine, probes for the accessibility of the 5,6 double bond of pyrimidine residues, BgPI has a more potent effect than BePI and, generally, the reaction with KMnO4 is more pronounced than that with OsO4. BgPI conspicuously potentiates the oxidation of pyrimidines in the triplet sequences 3'-ATA, 3'-GTA and 3'-GCA, whereas BePI enhances the reactivity of OsO4 towards thymine in sequences 3'-ATYR, with no effect on cytosine residues. Thus, despite their structural homology and common lack of specific sequence preferences, the two benzopyridoindole derivatives induce distinct conformational changes in duplex DNA, not just within the sites where footprints can be detected.

Animals↗
PubMed1995

Safety and feasibility of a self-monitored, home-based phase II exercise program for high risk patients after cardiac surgery.

OBJECTIVE: To determine the safety and effectiveness of a self-monitored, home-based phase II exercise program for high risk patients after cardiac surgery. METHODS: High risk patients were defined as those presenting with severe left ventricular dysfunction with an ejection fraction less than 35%, severe ventricular arrhythmias, incomplete revascularization, abnormal response to a standard walking test or significant (grade 3/4) valvular regurgitation persisting postoperatively. Eighty patients (mean age 58.5 +/- 8.9 years) were randomly assigned to two groups. The experimental group (n = 37) received a home program of aerobic training with an intensity gradually increasing from 1.5 to 4.0 multiples of resting oxygen consumption (METs). This program was started at discharge from the hospital and lasted eight weeks. The control group (n = 43) received general guidelines for progressive increase of their activity level. Functional capacity was measured at discharge by the 6 min walking test and between the sixth and eighth week following discharge by a symptom-limited exercise test, according to the Naughton protocol. RESULTS: No cardiovascular complications occurred during the training program. At the final evaluation, there was no significant difference between the experimental and control groups regarding aerobic capacity (5.1 +/- 1.8 versus 4.9 +/- 1.6 METs respectively, P = 0.61), nor peak rate-pressure product (22.8 +/- 4.9 versus 23.6 +/- 5.2 beats/min x mmHg x 10(3) respectively, P = 0.54).

Aged↗
PubMed1992

The 2-amino group of guanine is absolutely required for specific binding of the anti-cancer antibiotic echinomycin to DNA.

The 2-amino group of guanine is believed to be a critical determinant of potential DNA binding sites for echinomycin and related quinoxaline antibiotics. In order to probe its importance directly we have studied the interaction between echinomycin and DNA species in which guanine N(2) is deleted by virtue of substitution of inosine for guanosine residues. The polymerase chain reaction was used to prepare inosine-substituted DNA. Binding of echinomycin, assessed by DNAse I footprinting, was practically abolished by incorporation of inosine into one or both strands of DNA. We conclude that both the purines in the preferred CpG binding site need to bear a 2-amino group to interact with echinomycin.

Base Sequence↗
PubMed1990

Evidence for diversity of Plasmodium falciparum sporozoite surface antigens derived from analysis of antibodies elicited in humans.

We have compared the reactivities of antibodies developed by individuals frequently exposed to Plasmodium falciparum infections with the epitopes contained within the repeats of the circumsporozoite (CS) protein and their reactivities with the epitopes of a native molecule(s) accessible on the sporozoite surface. Results of direct-binding assays and competition assays between artificial and native molecules or between human antibodies and anti-CS monoclonal antibodies suggest that humans respond preferentially to epitopes not contained within the repeats of the CS protein and probably not contained in the whole CS protein. Human monoclonal antibodies reactive with P. falciparum sporozoite surface antigens were produced by Epstein-Barr virus transformation of human lymphocytes. Their pattern of reactivity with sporozoites from a number of different isolates indicates the existence of several distinct epitopes on the parasite surface. Differences between isolates and between sporozoites within a given sample were observed. No single human monoclonal antibody capable of detecting an epitope expressed in all the parasites studied was found.

Animals↗
PubMed1990

How to select Plasmodium falciparum pre-erythrocytic antigens in an expression library without defined probe.

The restricted access to Plasmodium falciparum liver stages has greatly limited the analysis of the antigenic content of that stage. Due to the lack of material to perform immunochemical studies, of access to mRNA, and of monoclonal probes, we decided to screen a genomic library with stage-restricted human antibodies. This strategy led to the identification of a large number of DNA fragments encoding both sporozoite specific as well as liver-stage specific epitopes. Following the initial characterization of one liver-stage antigen, further screening was performed by using additional selective human antibodies. These were defined as having a high degree of reactivity with native antigens on either of the two stages while being negative with the already known molecules of the two stages. From this second screening and the study of cross-reactions, several subsets of DNA clones expressing antigens present on the surface of sporozoites, or in liver stages, or in both, could be identified. In exposed individuals a high prevalence of antibodies to several of these antigens was found.

Animals↗
PubMed1990

[Oral hairy leukoplakia in AIDS. Histologic and ultrastructural study of 8 cases].

Oral hairy leukoplakia is a disease of the oral mucosa occurring almost exclusively in HIV-infected (mostly AIDS) patients and due to the opportunistic development of Epstein-Barr virus (EBV) within the oral epithelium. Clinically, it shows as whitish patches with a shaggy surface occurring on the lateral margins of the tongue, less frequently the buccal and labial mucosa or the soft palate. Histologically, it comprises parakeratotic hyperkeratosis, acanthosis and numerous koilocytoid cells within the stratum spinosum, i. e. cells with a pycnotic nucleus surrounded by a clear halo and pale-staining cytoplasm. Electronmicroscopy readily shows abundant Herpes-group viral particles within the upper epithelial layers. By immunohistochemistry, in situ molecular hybridization and Southern-blot EBV antigens and DNA have been demonstrated within the lesions whereas HPV and HIV are generally undetectable. In the present work we studied by light- and electronmicroscopy lesions from 8 HIV-seropositive individuals that fulfilled the clinical and histological criteria of OHL. Ultrastructural examination showed the presence in all cases of Herpes-type virions, which, in two of the cases studied by immunohistochemistry, proved to belong to the EBV. It is concluded that electronmicroscopy is a sufficiently sensitive examination to confirm the diagnosis of OHL suggested in the presence of an appropriate clinico-histological setting.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Crossover study of thalidomide vs placebo in severe recurrent aphthous stomatitis.

A multicentric crossover randomized trial of 100 mg of thalidomide vs placebo each for 2 months was conducted in patients with severe aphthous stomatitis of more than 6 months' duration. Seventy-three patients were included. Complete remission was obtained in 32 patients who received thalidomide and in 6 patients who received placebo. The confidence interval of the difference between the two treatments ranged from 25% to 53%. Most of the patients who did not achieve a complete remission had a dramatic improvement with regard to the number of aphthae when they were receiving thalidomide. Thirteen of 17 patients who had a complete remission while they were receiving thalidomide had a recurrence with placebo, 19 +/- 9 (mean +/- SD) days after stopping this drug. Side effects were significantly more frequent with thalidomide, especially drowsiness and constipation. We concluded that thalidomide in a dosage of 100 mg/d is an effective treatment of severe aphthous stomatitis but is not without some risk.

Adult↗