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C Marchand

Publications and source records attributed to C Marchand.

At least 19 recordsLinked to original sources
PubMed2001

Photoproduction of the rho(0) meson on the proton at large momentum transfer.

The differential cross section, d sigma/dt, for rho(0) meson photoproduction on the proton above the resonance region was measured up to a momentum transfer -t = 5 GeV2 using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The rho(0) channel was extracted from the measured two charged-pion cross sections by fitting the pi(+)pi(-) and p pi(+) invariant masses. The low momentum transfer region shows the typical diffractive pattern expected from Reggeon exchange. The flatter behavior at large -t cannot be explained solely in terms of QCD-inspired two-gluon exchange models. The data indicate that other processes, like quark interchange, are important to fully describe rho photoproduction.

Journal Article↗
PubMed2001

Catechol derivatives of aminopyrazine and cell protection against UVB-induced mortality.

A series of 5-aryl- and 3,5-bis-aryl-2-amino-1,4-pyrazine derivatives 4 and 6, and related imidazolopyrazinones 7, has been synthesized, the aryl groups of which are catechol and/or phenol substituents. These compounds, tested against human keratinocyte cells stressed by UVB irradiation, showed high antioxidative properties. One compound (6f) was more active than EGCG/ECG (green tea extract) in reducing cell mortality.

Antioxidants↗
PubMed2001

Structure-activity of inhibition of HIV-1 integrase and virus replication by G-quartet oligonucleotides.

As novel anti-HIV agents, the G-tetrad-forming oligonucleotides have been explored for their structure-activity relations with regard to inhibition of integrase (IN) (N. Jing, Expert Opin. Investig. Drugs (2000) 9, 1777-1785). We have now developed two families of G-quartet oligonucleotides: T40217-T40222, with potential formation of a tail-to-tail G-quartet dimer, and T40224-T40227, with phosphorothioate (PT) linkages in the guanine loops. The results obtained from biophysical measurements and the assays of the inhibition of HIV-1 IN and virus replication demonstrated that an increase in the length of the G-quartet structure from a monomer (15A) to a tail-to-tail dimer (47A) does not distinctly disrupt the inhibition of HIV-1 IN activity or the inhibition of HIV-1 replication in cell cultures. G-quartet oligonucleotides were observed to induce molecular aggregation of HIV-1 IN and interrupt the binding of viral DNA to HIV-1 IN. Also, PT substitutions did not confer any advantages compared with the regular phosphodiesters for the inhibition of HIV-1 replication by intramolecular G-quartets. The G-quartet motif is the primary requirement for the remarkable nuclease resistance and pronounced biological efficacy of these oligonucleotides.

Cell Line↗
PubMed2000

Mutations in the HIV type 1 integrase of patients receiving long-term dideoxynucleoside therapy do not confer resistance to zidovudine.

Metabolites of AZT can inhibit HIV-1 integrase in vitro (Mazumder A, et al., Proc Natl Acad Sci USA 1994;91:5771-5775). To determine if long-term dideoxynucleoside therapy can lead to the emergence of HIV-1 AZT-resistant variants containing mutations in the integrase, we have sequenced the proviral DNA encoding the HIV-1 integrase of nine HIV-1-infected patients at different time points during treatment. Four of the nine patients developed mutations during the course of treatment. Although most mutations occurred at nonconserved amino acids, one patient developed a mutation at codon (R166T), a residue that is conserved among all integrases from known HIV-1 isolates. This mutation was introduced in the recombinant HIV-1 integrase protein to determine if it could confer resistance to AZT in vitro. We show that the R166T integrase mutant is still proficient at carrying 3'-processing and 3' end-joining but that the enzyme is not resistant to AZT-TP. Our results suggest that it is unlikely that integrase inhibition contributes to the antiviral activity of AZT.

Amino Acid Sequence↗
PubMed2000

Mechanism of inhibition of HIV-1 integrase by G-tetrad-forming oligonucleotides in Vitro.

The G-tetrad-forming oligonucleotides and have been identified as potent inhibitors of human immunodeficiency virus type 1 integrase (HIV-1 IN) activity (Rando, R. F., Ojwang, J., Elbaggari, A., Reyes, G. R., Tinder, R., McGrath, M. S., and Hogan, M. E. (1995) J. Biol. Chem. 270, 1754-1760; Mazumder, A., Neamati, N., Ojwang, J. O., Sunder, S., Rando, R. F., and Pommier, Y. (1996) Biochemistry 35, 13762-13771; Jing, N., and Hogan, M. E. (1998) J. Biol. Chem. 273, 34992-34999). To understand the inhibition of HIV-1 IN activity by the G-quartet inhibitors, we have designed the oligonucleotides and, composed of three and four G-quartets with stem lengths of 19 and 24 A, respectively. The fact that increasing the G-quartet stem length from 15 to 24 A kept inhibition of HIV-1 IN activity unchanged suggests that the binding interaction occurs between a GTGT loop domain of the G-quartet inhibitors and a catalytic site of HIV-1 IN, referred to as a face-to-face interaction. Docking the NMR structure of (Jing and Hogan (1998)) into the x-ray structure of the core domain of HIV-1 IN, HIV-1 IN-(51-209) (Maignan, S., Guilloteau, J.-P. , Qing, Z.-L., Clement-Mella, C., and Mikol, V. (1998) J. Mol. Biol. 282, 359-368), was performed using the GRAMM program. The statistical distributions of hydrogen bonding between HIV-1 IN and were obtained from the analyses of 1000 random docking structures. The docking results show a high probability of interaction between the GTGT loop residues of the G-quartet inhibitors and the catalytic site of HIV-1 IN, in agreement with the experimental observation.

Base Composition↗
PubMed2000

A new family of sequence-specific DNA-cleaving agents directed by triple-helical structures: benzopyridoindole-EDTA conjugates.

Sequence-specific DNA recognition can be achieved by oligonucleotides that bind to the major groove of oligopyrimidine x oligopurine sequences. These intermolecular structures could be used to modulate gene expression and to create new tools for molecular biology. Here we report the synthesis and biochemical characterization of triple helix-specific DNA cleaving reagents. It is based on the previously reported triplex-specific ligands, benzo[e]pyridoindole (BePI) and benzo[g]pyridoindole (BgPI), covalently attached to ethylenediaminotetraacetic acid (EDTA). In the presence of iron, a reducing agent and molecular oxygen, BgPI-EDTA x FeII but not BePI-EDTA x FeII induced a double-stranded cut in a plasmid DNA at the single site where a triplex-forming oligonucleotide binds. At single nucleotide resolution, it was found that upon triplex formation BePI-EDTA x FeII led to cleavage of the pyrimidine strand and protection of the purine strand. BgPI-EDTA x FeII cleaved both strands with similar efficiency. The difference in cleavage efficiency between the two conjugates was rationalized by the location of the EDTA x FeII moiety with respect to the grooves of DNA (major groove: BePI-EDTA x FeII, minor groove: BgPI-EDTA x FeII). This work paves the way to the development of a new class of triple helix directed DNA cleaving reagents. Such molecules will be of interest for sequence-specific DNA cleavage and for investigating triple-helical structures, such as H-DNA, which could play an important role in the control of gene expression in vivo.

DNA↗
PubMed2000

Retroviral integrase inhibitors year 2000: update and perspectives.

HIV-1 integrase is an essential enzyme for retroviral replication and a rational target for the design of anti-AIDS drugs. A number of inhibitors have been reported in the past 8 years. This review focuses on the recent developments in the past 2 years. There are now several inhibitors with known sites of actions and antiviral activity. The challenge is to convert these leads into drugs that will selectively target integrase in vivo, and can be added to our antiviral armamentarium.

Anti-HIV Agents↗
PubMed2000

Emergency interruption of the inferior vena cava: a debatable issue.

In spite of improvements in the diagnosis and treatment of thromboembolic disease, pulmonary embolism continues to be a major cause of morbidity and mortality. Anticoagulation remains the preferred therapy for deep venous thrombosis; however, this form of treatment is either ineffective or contraindicated for some patients. For these patients, partial interruption of the inferior vena cava via percutaneous filter placement has become the procedure of choice to protect against fatal pulmonary embolism. We described in this paper results obtained with the available permanent filters and complications of these filters described in the literature. We highlighted the interest of temporary filters in patients whose thromboembolic risk is temporary, finally we insist on recognised indications for vena cava filters when anticoagulation is contraindicated or ineffective.

Contraindications↗
PubMed2000

Viral entry as the primary target for the anti-HIV activity of chicoric acid and its tetra-acetyl esters.

The antiviral activity of L-chicoric acid against HIV-1 has been attributed previously to the inhibition of HIV-1 integration. This conclusion was based on the inhibition of integrase activity in enzymatic assays and the isolation of a resistant HIV strain with a mutation (G140S) in the integrase gene. Here we show that the primary antiviral target of L-CA and its analogs in cell culture is viral entry. L- and D-chicoric acid (L-CA and D-CA) and their respective tetra-acetyl esters inhibit the replication of HIV-1 (III(B) and NL4.3) and HIV-2 (ROD) in MT-4 cells at a 50% effective concentration (EC(50)) ranging from 1.7 to 70.6 microM. In a time-of-addition experiment, L-CA, D-CA, L-CATA, and D-CATA were found to interfere with an early event in the viral replication cycle. Moreover, L-CA, D-CA, and their analogs did not inhibit the replication of virus strains that were resistant toward polyanionic and polycationic compounds at subtoxic concentrations. Furthermore, HIV-1 strains resistant to L-CA and D-CA were selected in the presence of L-CA and D-CA, respectively. Mutations were found in the V2, V3, and V4 loop region of the envelope glycoprotein gp120 of the L-CA and D-CA-resistant NL4.3 strains that were not present in the wild-type NL4.3 strain. Recombination of the gp120 gene of the L-CA and D-CA resistant strain in a NL4.3 wild-type molecular clone fully rescued the phenotypic resistance toward L-CA and D-CA. No significant mutations were detected in the integrase gene of the drug-resistant virus strains. Although inhibition of HIV integrase activity by L-CA and its derivatives was confirmed in an oligonucleotide-driven assay, integrase carrying the G140S mutation was inhibited to the same extent as the wild-type integrase.

Anti-HIV Agents↗
PubMed1999

Interleukin 1beta mediates the effect of high D-glucose on the secretion of TNF-alpha by mouse uterine epithelial cells.

Previous observations have shown that tumour necrosis factor alpha (TNF-alpha) synthesis is increased in the uterus of diabetic rats and that the epithelial layer lining the uterine lumen is the major site of TNF-alpha over-production. In the present study, TNF-alpha secretion was found to be stimulated by high D-glucose levels in primary cultures of mouse uterine luminal cells but not in cultures of the mouse uterine epithelial WEG-1 cell line. Experiments were performed to investigate the possibility that non-epithelial cells may mediate the influence of high D-glucose on TNF-alpha production by uterine epithelial cells. Immunocytochemical analysis revealed the reproducible presence of a small proportion of macrophages in primary cultures. Macrophages of the RAW 264.7 cell line were found to secrete more interleukin (IL)-1beta (but not TNF-alpha) when cultured in high D-glucose. TNF-alpha production in WEG-1 cells was increased upon exposure to IL-1beta and both protein kinase-C and tyrosine kinase pathways appeared to be involved in TNF-alpha stimulation. Addition of IL-1 receptor antagonist to primary cultures partially abrogated the effect of high D-glucose. Since WEG-1 cells do not produce IL-1beta, the data lend support to the hypothesis that uterine epithelial cells synthesize high levels of TNF-alpha in response to hyperglycaemia via an increase in IL-1beta secretion by stromal macrophages.

Animals↗
PubMed1999

Design of a triple-helix-specific cleaving reagent.

BACKGROUND: Double-helical DNA can be recognized sequence specifically by oligonucleotides that bind in the major groove, forming a local triple helix. Triplex-forming oligonucleotides are new tools in molecular and cellular biology and their development as gene-targeting drugs is under intensive study. Intramolecular triple-helical structures (H-DNA) are expected to play an important role in the control of gene expression. There are currently no good probes available for investigating triple-helical structures. We previously reported that a pentacyclic benzoquinoquinoxaline derivative (BQQ) can strongly stabilize triple helices. RESULTS: We have designed and synthesized the first triple-helix-specific DNA cleaving reagent by covalently attaching BQQ to ethylenediaminetetraacetic acid (EDTA). The intercalative binding of BQQ should position EDTA in the minor groove of the triple helix. In the presence of Fe(2+) and a reducing agent, the BQQ-EDTA conjugate can selectively cleave an 80 base pair (bp) DNA fragment at the site where an oligonucleotide binds to form a local triple helix. The selectivity of the BQQ-EDTA conjugate for a triplex structure was sufficiently high to induce oligonucleotide-directed DNA cleavage at a single site on a 2718 bp plasmid DNA. CONCLUSIONS: This new class of structure-directed DNA cleaving reagents could be useful for cleaving DNA at specific sequences in the presence of a site-specific, triple-helix-forming oligonucleotide and also for investigating triple-helical structures, such as H-DNA, which could play an important role in the control of gene expression in vivo.

Base Pairing↗
PubMed1999

[Carotid surgery under loco-regional anesthesia. Early results of 100 recent cases].

A prospective single-centre study was performed to evaluate the safety and efficacy of carotid revascularisation under local anesthesia. Between November 1, 1996 and March 30, 1998, 92 patients underwent surgery for 100 carotid artery stenoses under local cervical block anesthesia. Fifty-eight stenoses were asymptomatic and 42 were symptomatic. Duplex ultrasound scanning showed a tight (n = 17) or very tight carotid artery stenosis (n = 83); angiography showed 19 contralateral carotid artery stenosis and 30 hemodynamically significant stenosis of vertebral and/or subclavian arteries. Cerebral Magnetic Resonance Imaging (MRI) (N = 87) with circle of Willis Magnetic Resonance Angiogram (MRA) (n = 83) detected 29 ischemic defects (33%). Fifteen ischemic defects were found in 58 asymptomatic patients (26%). Circle of Willis was incomplete in 41%. Anesthesia was performed using superficial cervical block (n = 100). Endarterectomy was the most commonly used revascularisation technique in 86 cases with 5 eversion endarterectomies; carotid vein or prosthetic graft was used in 14%. In this study, there was no mortality, and no cardiac or neurologic complications, during the first postoperative month. Twelve patients experienced neurologic intolerance to carotid clamping. This clamping-related ischemia required 4 shunts. All patients with clamping intolerance had a good clinical outcome after revascularisation with no objective or MRI sequelae. Incomplete circle of Willis on MRA was a significant predictive test of clamping intolerance (p < 0.0001). Carotid artery surgery under local anesthesia reduces the cumulative mortality and morbidity rate (TCMM) to a very low level: 0% in this study. These recent results are the modern reference for current carotid artery surgery evaluation.

Adult↗
PubMed1998

Optimization of alternate-strand triple helix formation at the 5'CpG3' and 5'GpC3' junction steps.

Oligonucleotide-directed triple helix formation normally requires a long tract of oligopyrimidine.oligopurine sequence. This limitation can be partially overcome by alternate-strand triple helix (or switch triple helix) formation which enables recognition of alternating oligopurine/oligopyrimidine sequences. The present work is devoted to the optimization of switch triple helix formation at the 5'CpG3' and 5'GpC3' junction steps by combination of base triplets in Hoogsteen and in reverse Hoogsteen configurations. Rational design by molecular mechanics was first carried out to study the geometrical constraints at different junction steps and to propose a "switch code" which would optimize the interactions at junctions. These predictions were further checked and validated experimentally by gel retardation and DNase I footprinting assays. It was shown that the choice of an appropriate linker nucleotide in the switching third strand plays an important role in the interaction between oligonucleotides and alternating oligopurine/oligopyrimidine target sequences at different junctions: (i) the addition of a cytosine at the junction level in the oligonucleotide optimizes the crossover at the 5'CpG3' junction, whereas (ii) the best crossover at the 5'GpC3' junction step is achieved without any additional nucleotide. These results provide a useful guideline to extend double-stranded DNA sequence recognition by switch triple helix formation.

Base Composition↗
PubMed1997

[Relationship between iron status and diet in 410 hyperlipidemic patients].

In order to examine the influence of a low-fat diet on iron status, we carried out a study which involved 410 out-patients with hyperlipidaemia, i.e. 256 men and 154 women. Serum iron was positively correlated with protein intake (p = 0.11; p < 0.05) and transferrin saturation was inversely correlated with fat intake (p = - 0.12; p < 0.05). A positive iron balance (serum iron > 27 mumol/l and transferrin saturation > 45%) was found in 1.6% of the male subjects, a frequency which could be explained by the presence of the hemochromatosis genes. A negative iron balance (serum iron < 10 mumol/l and tranferrin saturation < 15%) was found in 13.7% for women aged 21-49 yr, 3.7% for women aged 50-77 yr and 3.5% for men aged 21-77 yr. We found no association between low-fat diet and iron deficiency. Men with iron deficiency had 12% decrease in total calorie intake compared to the Recommended Dietary Allowance. Our results do not provide evidence that hypolipidemic diet is associated with a high frequency of iron deficiency.

Adult↗