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Biomedical subjects

P Martineau

Publications and source records attributed to P Martineau.

At least 19 recordsLinked to original sources
PubMed2006

Effect of individualizing starting doses of a statin according to baseline LDL-cholesterol levels on achieving cholesterol targets: the achieve cholesterol targets fast with atorvastatin stratified titration (ACTFAST) study.

AIMS: To investigate whether selecting the starting dose of atorvastatin according to baseline and target (<2.6 mmol/L) LDL-cholesterol (LDL-C) values would allow high-risk subjects to achieve target LDL-C concentration within 12 weeks, with the initial dose or a single uptitration. METHODS AND RESULTS: Twelve-week, prospective, open-label trial that enrolled 2117 high-risk subjects (statin-free [SF] or statin-treated [ST]). Subjects with LDL-C >2.6 mmol/L (100mg/dL) but <or=5.7 mmol/L (220 mg/dL) were assigned a starting dose of atorvastatin (10, 20, 40 or 80 mg/day) based on LDL-C and status of statin use at baseline, with a single uptitration at 6 weeks, if required. There was no washout for ST subjects. At study end, 80% of SF (82%, 82%, 83% and 72% with 10, 20, 40 and 80 mg, respectively) and 59% of ST (60%, 61% and 51% with 20, 40 and 80 mg, respectively) subjects reached LDL-C target. In the ST group, an additional 21-41% reduction in LDL-C was observed over the statin used at baseline. Atorvastatin was well tolerated. CONCLUSION: This study confirms that individualizing the starting dose of atorvastatin according to baseline and target LDL-C values (i.e. the required LDL-C reduction), allows a large majority of high-risk subjects to achieve target safely, within 12 weeks, with the initial dose or with a single titration.

Aged↗
PubMed2003

Potentiation of ionising radiation by targeting tumour necrosis factor alpha using a bispecific antibody in human pancreatic cancer.

The aim of this study was to treat carcinoembryonic antigen (CEA)-expressing pancreatic carcinoma cells with tumour necrosis factor alpha (TNFalpha) and simultaneous radiation therapy (RT), using a bispecific antibody (BAb) anti-TNFalpha/anti-CEA. TNFalpha used alone produced a dose-dependent inhibition of the clonogenic capacity of the cultured cells. Flow cytometry analysis of cell cycle progression confirmed the accumulation of cells in G(1) phase after exposure to TNFalpha. When TNFalpha was added 12 h before RT, the surviving fraction at 2 Gy was 60% lower than that obtained with irradiation alone (0.29 vs 0.73, respectively, P<0.00001). In combination treatment, cell cycle analysis demonstrated that TNFalpha reduced the number of cells in radiation-induced G(2) arrest, blocked irreversibly the cells in G(1) phase, and showed an additive decrease of the number of cells in S phase. In mice, RT as a single agent slowed tumour progression as compared with the control group (P<0.00001). BAb+TNFalpha+RT combination enhanced the delay for the tumour to reach 1500 mm(3) as compared with RT alone or with RT+TNFalpha (P=0.0011). Median delays were 90, 93, and 142 days for RT alone, RT+TNFalpha, and RT+BAb+TNFalpha groups, respectively. These results suggest that TNFalpha in combination with BAb and RT may be beneficial for the treatment of pancreatic cancer in locally advanced or adjuvant settings.

Adenocarcinoma↗
PubMed2003

Hydrogen incorporation in diamond: the nitrogen-vacancy-hydrogen complex.

We report the identification of the nitrogen-vacancy-hydrogen complex in a freestanding nitrogen-doped isotopically engineered single crystal diamond synthesized by chemical vapor deposition. The hydrogen atom is located in the vacancy of a nearest-neighbor nitrogen-vacancy defect and appears to be bonded to the nitrogen atom maintaining the trigonal symmetry of the center. The defect is observed by electron paramagnetic resonance in the negative charge state in samples containing a suitable electron donor (e.g., substitutional nitrogen N(0)(S)).

Journal Article↗
PubMed2002

Casein interactions studied by the surface plasmon resonance technique.

Surface plasmon resonance technique was investigated for the first time to study the apparent hydrophobicity and association properties of the major bovine caseins: alpha(s)-(alpha(s1)- and alpha(s2)-caseins in a 4:1 proportion), beta-, and kappa-caseins. The apparent hydrophobicities of the caseins were evaluated by a new method based on the binding level of casein on a hydrophobic sensor chip, and kinetic and equilibrium affinity constants were determined for the following casein interactions: alpha(s)/alpha(s), alpha(s)/beta, alpha(s)/kappa, beta/beta, and beta/kappa, using a sensor chip modified with covalent immobilized caseins. The study by surface plasmon resonance technology of these casein interactions under different conditions (pH, ionic strength, calcium concentration, chemical modification) demonstrated that, at neutral pH, electrostatic repulsive forces play an important role since an increase in ionic strength of the medium resulted in a stronger interaction. When charge repulsions were reduced by either acidification, increase in ionic strength, or dephosphorylation, casein interactions were reinforced, presumably due to weak attractive forces. Moreover, in this molecular model, we showed that addition of calcium greatly increased the binding response between the most phosphorylated caseins and that the added calcium (2 mM) participated directly in the formation of bridges between the phosphate groups of the casein molecules.

Adsorption↗
PubMed2001

New competition in the realm of renin-angiotensin axis inhibition; the angiotensin II receptor antagonists in congestive heart failure.

OBJECTIVE: To critically review the studies comparing angiotensin II (AgII) receptor antagonists with placebo or angiotensin-converting enzyme (ACE) inhibitors in patients with congestive heart failure (CHF). DATA SOURCES: A MEDLINE search (1988 to January 2000) was used to identify pertinent literature. Additional references were also retrieved from selected articles. STUDY SELECTION: As most published CHF studies were performed with candesartan and losartan, these agents are the main focus of this article. However, all identified comparative clinical studies were reviewed and included, regardless of the agent used. DATA SYNTHESIS: AgII receptor antagonists inhibit the effects of AgII at its sub-type 1 receptor, independently of AgII's synthesis pathway. They present a hemodynamic profile similar to that of ACE inhibitors, without reflex neurohormonal activation. They have been shown to be at least as effective as ACE inhibitors in improving symptoms, exercise capacity, and New York Heart Association functional class in CHF patients. Although the ELITE (Evaluation of Losartan in the Elderly) trial suggested that losartan improved survival compared with captopril, this study was not designed to look at mortality. ELITE-II, an adequately powered study, showed no difference in mortality rates between patients taking captopril and those taking losartan. The combination of AgII receptor antagonists and ACE inhibitors provides additional benefit on blood pressure lowering and prevention of ventricular remodeling. AgII receptor antagonists are well tolerated, with an incidence of adverse effects similar to or lower than that of ACE inhibitors. Their lack of effect on bradykinin degradation might explain their lower incidence of cough. CONCLUSIONS: The data cumulated thus far in patients with CHF highlight that ACE inhibitors must remain the treatment of choice and that AgII receptor antagonists may be considered as an acceptable alternative for patients who are intolerant to ACE inhibitors.

Angiotensin Receptor Antagonists↗
PubMed1999

In vitro folding and thermodynamic stability of an antibody fragment selected in vivo for high expression levels in Escherichia coli cytoplasm.

We recently isolated a mutant of a human anti-beta-galactosidase single chain antibody fragment (scFv) able to fold at high levels in Escherichia coli cytoplasm. When targeted to the periplasm, this mutant and the wild-type scFv are both expressed at comparable levels in a soluble, active and oxidized form. If a reducing agent is added to the growth medium, only the mutant scFv is still able to fold, showing that in vivo aggregation is a direct consequence of the lack of disulphide bond formation and not of the cellular localization. In vitro denaturation/renaturation experiments show that the mutant protein is more stable than the wild-type scFv. Furthermore, refolding kinetics under reducing conditions show that the mutant folds faster than the wild-type protein. Aggregation does not proceed from the native or unfolded conformation of the protein, but from a species only present during the unfolding/refolding transition. In conclusion, the in vivo properties of the mutant scFv can be explained by, first, an increase in the stability of the protein in order to tolerate the removal of the two disulphide bonds and, second, a modification of its folding properties that reduces the kinetic competition between folding and aggregation of a reduced folding intermediate.

Cytoplasm↗
PubMed1998

Expression of an antibody fragment at high levels in the bacterial cytoplasm.

Recombinant antibody fragments expressed in the cytoplasm of cells have considerable practical potential. However in the reducing environment of the cytoplasm, the intradomain disulphide bonds are not formed and the fragments are unstable and expressed in low yields. Here we attempted to overcome these limitations. We first isolated an antibody single chain Fv fragment that binds and activates an inactive mutant beta-galactosidase. We then subjected the gene encoding the scFv fragment to random mutation in vitro by error-prone polymerase chain reaction, and co-expressed the mutant beta-galactosidase and mutant antibody fragments in lac- bacteria. By plating on limiting lactose, we selected for antibody mutants with improved expression, and after four successive rounds of mutation and selection, isolated an antibody fragment that is expressed in the bacterial cytoplasm with yields of 0.5 g/l in a shaker flask (A600 nm of 5.5) and 3.1 g/l (A600 nm=33) in a fermentor. Analysis of the mutant antibody fragments revealed that the disulphide bonds are reduced in the cytoplasm, and that the fragments could be denatured and renatured efficiently under reducing conditions in vitro. This shows that with a suitable method of screening or selection, it is possible to make folded and functional antibody fragments in excellent yield in the cytoplasm.

Amino Acid Sequence↗
PubMed1998

Immunodominance does not result from peptide competition for MHC class II presentation.

Competition for binding to MHC class II molecules between processed peptides derived from a single protein Ag is considered an important parameter leading to the presentation of a limited set of peptides by APCs. We tested the relevance of this competition process in a model Ag, the MalE protein, by deleting T cell epitopes or by introducing a competitor T cell peptide. We identified in DBA/1 (I-Aq) mice six immunodominant T cell determinants in the MalE sequence, 89-95, 116-123, 198-205, 211-219, 274-281, and 335-341. Synthetic peptides carrying these determinants were classified in three groups as weak, intermediate, or strong I-Aq binders in competition experiments with the PreS:T peptide of hepatitis B surface Ag. In vivo, synthetic MalE peptides with weak and intermediate MHC binding capacity were inhibited in their capacity to stimulate proliferative response in the presence of the PreS:T competitor peptide, whereas the strongest MHC binder was not. Strikingly, the insertion of the potent competitor PreS:T peptide into the MalE sequence, as a single copy or as four copies, did not inhibit the proliferative response to the six immunodominant peptides of the recipient protein. Moreover, deletion in the protein sequence disrupting either the weak (198-205) or strong (335-341) MHC binding determinant of MalE did not modify the proliferative response to the remaining T cell determinants as compared with wild-type MalE protein. Altogether, these results show that peptide competition for MHC binding may not represent the most important event in processes leading to immunodominance.

Animals↗
PubMed1998

Low-molecular-weight heparins in the treatment of deep-vein thrombosis.

OBJECTIVE: To compare the characteristics and clinical efficacy of low-molecular-weight heparins (LMWHs) and unfractionated heparin (UFH) in the treatment of deep-vein thrombosis (DVT). Adverse effects, dosing, and cost issues are also discussed. DATA SOURCES: A MEDLINE search (January 1984-October 1997) was used to identify pertinent French and English literature, including clinical trials and reviews on LMWHs and their use in DVT. STUDY SELECTION: Trials comparing dalteparin, enoxaparin, tinzaparin, and nadroparin with UFH were selected. As studies were numerous, only randomized trials including more than 50 patients were reviewed. Moreover, all patients studied had a first episode of symptomatic DVT confirmed by objective tests (i.e., venography, duplex ultrasonography, impedance plethysmography). Clinical efficacy and safety of LMWHs were assessed in these trials. DATA EXTRACTION: Results pertaining to venographic assessment, recurrent thromboembolism, total mortality, and bleeding complications were extracted from the selected studies. DATA SYNTHESIS: Compared with UFH, LMWHs have a longer plasma half-life, better subcutaneous bioavailability, more predictable anticoagulant response, and require less intense laboratory monitoring. Most trials demonstrate comparable effects on thrombus extension and incidence of recurrent thromboembolism. Compared with UFH, LMWHs do not alter total mortality. Although animal trials predict a lower hemorrhagic potential for LMWHs, the incidence of bleeding complications is generally similar to that observed with UFH. Outpatient management of DVT with LMWHs has shown comparable safety and efficacy with inpatient UFH use but a shorter hospital stay. CONCLUSIONS: Because LMWHs are as safe and as effective as UFH, and because of their more convenient method of administration, they can be considered valuable alternatives for the treatment of DVT. Savings generated by less intensive laboratory monitoring and the possibility of early hospital discharge and outpatient therapy may outweight the higher acquisition cost of LMWHs.

Blood Platelets↗
PubMed1997

Control by Ig genes of the responsiveness to a neutralization viral B cell epitope.

In the present study, we analyzed the capacity of seven strains of mice to produce Abs against the neutralization poliovirus C3 B cell epitope, chemically or genetically linked to two different carrier proteins (MalE and keyhole limpet hemocyanin) or to recombinant hepatitis B surface Ag particles. Following immunization with these different immunogens, all strains of mice developed high Ab titers against the carrier proteins. However, only four strains of mice developed a significant Ab response against the poliovirus C3 B cell epitope. Indeed, in contrast to BALB/c, DBA/1, DBA/2, and 129 sv mice, C57BL/6, C3H, and CBA/J mice failed to produce anti-C3 Abs after immunization with the various C3 immunogens. Using various H-2 congenic strains on BALB/c or C57BL/10 background, this study clearly showed that the response to the C3 B cell epitope is not controlled by MHC genes. In contrast, analysis of anti-C3 Ab responses in IgH congenic mouse lines on BALB/c or C57BL/6 background demonstrated that the capacity to respond to this B cell epitope is controlled by genes closely linked to V(H) genes. This study therefore represents the first demonstration that the V(H) polymorphism can limit the Ab response to a viral neutralization epitope, and therefore has important implications for vaccine development.

Animals↗
PubMed1997

NMR studies on the flexibility of the poliovirus C3 linear epitope inserted into different sites of the maltose-binding protein.

A set of permissive positions that tolerate insertions/deletions without major deleterious consequences for the binding activity of the protein was previously identified in the maltose-binding protein. The C3 epitope from poliovirus VP1 protein (93DNPASTTNKDK103) was inserted into eight of these positions and two nonpermissive control sites. NMR studies were performed on the MalE protein, the insertion/deletion mutants, and the C3MalE hybrids to selectively determine the flexible regions in these proteins. Comparison of the C3 epitope mobility in the different hybrid proteins indicates that, whatever its insertion site and independently from the specific sequences of its linkers, the epitope is mostly flexible. The vector protein was shown to unfold partially only in the two C3MalE hybrids that correspond to nonpermissive positions. For one of them (insertion at site 339), both sides of the insert are flexible, and at most one side for all the other hybrids. This result correlates with the antigenicity data on the inserted epitope (Martineau, P., Leclerc, C., and Hofnung, M. (1997) Mol. Immunol, in press.

Amino Acid Sequence↗
PubMed1997

Enzyme immunoassays using bispecific diabodies.

BACKGROUND: Bispecific antibodies with a first binding specificity to a target antigen and a second to an enzyme have great potential in enzyme immunoassays. As bispecific antibodies are difficult to make, the use of recombinant bispecific antibody fragments may provide a breakthrough. OBJECTIVES: To make bispecific antibody fragments directed against an enzyme and to demonstrate their application in enzyme immunoassays. STUDY DESIGN: Bispecific antibody fragments were assembled as diabodies (Holliger P., Prospero T., Winter G. Proc. Natl. Acad. Sci. USA 90, 1993, 6444-6448) directed to an enzyme, E. coli beta-galactosidase, and to each of three target antigens, hen-egg lysozyme (HEL), carcinoembryonic antigen (CEA), and HIV gpl20 (HIV). The diabodies were then evaluated in immunoassays. RESULTS: The HEL diabody was shown to recruit beta-galactosidase in a microtiter plate immunoassay in which diabody and enzyme were co-incubated with antigen, washed and enzyme substrate added. The CEA diabody was shown to detect CEA by immunocytochemical staining of transfected, CEA-expressing HeLa cells and of adenocarcinoma colon tissue sections, and the HIV diabody to detect gpl20 in immunoblots of total cell extracts. CONCLUSION: The results illustrate the diagnostic potential of diabodies in enzyme immunoassays.

Amino Acid Sequence↗
PubMed1997

A closed system for the filtration of Mycobacterium bovis liquid cultures using disposable capsule filters.

A filtration system was designed to sterilize large volumes of Mycobacterium bovis BCG Tokyo culture safely, needed to purify protein antigens for immunodiagnosis of bovine tuberculosis. A closed system consists of culture bottles connected to three disposable filter capsules of decreasing pore size in series: a depth prefilter over a 1.2 microns filter; 0.8 micron prefilter over a 0.45 micron filter; and a 0.2 micron sterile filter. Low air pressure (3 psi) forces liquid from below the bacillary pellicle. The system features a stainless steel clamp to hold rubber stoppers on the culture bottles, pleated filters to exclude bacillary clumps, a quick disconnector to minimize aerosols, and a closed system with plastic disposable filters that can be autoclaved as a unit without dismantling.

Aerosols↗
PubMed1997

Maltodextrin-binding protein hybrids carrying epitopes from the preS2 region of hepatitis B virus: expression, antibody-binding and preliminary crystallographic studies.

Five hybrid constructions of maltodextrin-binding protein (MBP), each containing an inserted epitope(s) from the preS2 region of the envelope proteins of hepatitis B virus (HBV), have been expressed. The anti-preS2 monoclonal antibody S2.3 was shown to cross-react with the MBP hybrid constructions, demonstrating that the epitopes presented by these recombinant proteins mimic the antigenic behaviour of the native viral antigen. In addition, all five hybrid proteins have been crystallized. Preliminary structural solutions obtained by molecular replacement indicate that the native conformation of MBP is preserved in the hybrid constructions despite the significant length of the epitope insertions.

Amino Acid Sequence↗
PubMed1997

Clarithromycin-induced digoxin intoxication.

OBJECTIVE: To report a case of clarithromycin-induced digoxin intoxication. CASE SUMMARY: A 78-year-old white man with ischemic cardiomyopathy and chronic renal insufficiency was admitted 4 days after being prescribed clarithromycin for a suspected episode of bronchitis. He reported weakness, asthenia, and gastrointestinal symptoms; the digoxin serum concentration was measured at 3.89 ng/mL. The patient recovered uneventfully after digoxin and clarithromycin were discontinued. DISCUSSION: Erythromycin frequently interacts with other drugs that are also metabolized by the CYP3A4 isoenzyme. However, erythromycin is hypothesized to interact with digoxin by inhibiting Eubacterium lentum, which is a normal inhabitant of the human gut and is responsible for intestinal metabolism of digoxin in 10% of patients. Since clarithromycin shares a comparable antibacterial spectrum with erythromycin, the possibility of a drug interaction with digoxin remains. Only four cases of clarithromycin interacting with digoxin have been reported to date. Clinically, this interaction may have been more obvious because of our patient's moderate renal dysfunction and serum digoxin concentrations in the upper therapeutic range prior to clarithromycin initiation. Other causes for digoxin intoxication could not be identified. CONCLUSIONS: Clarithromycin may inhibit the growth of E. lentum, which can lead to an increase in digoxin bioavailability and blood concentrations in patients in whom this intestinal metabolic pathway is present. Patients at risk include those with renal dysfunction, with serum concentrations in the upper therapeutic range, or with measured digoxin concentrations that are much lower than predicted by pharmacokinetic calculations. For these patients, appropriate therapy includes the selection of an alternative, noninteracting antibiotic or, if this is not possible, a temporary reduction of digoxin dosage.

Aged↗
PubMed1997

Competitive and indirect enzyme-linked immunosorbent assays for Mycobacterium bovis infections based on MPB70 and lipoarabinomannan antigens.

A competitive enzyme-linked immunosorbent assay (C-ELISA) using M. bovis BCG Tokyo culture filtrate as antigen and anti-MPB70 4C3/17 monoclonal antibody was developed for use in multiple animal species. An analysis of the C-ELISA data for cattle and bison serum panels revealed specificities of 68% to 85% and sensitivities of 85% to 89%. Receiver operator characteristics (ROC) of this data revealed areas of 81% to 92% for C-ELISA and demonstrated that C-ELISA as well as the indirect ELISA protocols, MPB70-ELISA and LAM-ELISA, discriminate M. bovis infected animals from non-infected animals for these particular panels. The kappa statistic values for agreement beyond chance between C-ELISA and MPB70-ELISA were determined after ELISA cutoffs were adjusted to minimize false positives. There were poor to excellent agreements between C-ELISA and MPB70-ELISA in all species tested (Bovidae, Cervidae, and Camelidae) that were consistently higher than the kappa statistic between C-ELISA and LAM-ELISA. The humoral response to one antigen and little or no response to the other in many animals argued for a parallel interpretation of C-ELISA and LAM-ELISA to increase sensitivity.

Animals↗
PubMed1996

Homogeneous processing and presentation of a recombined T cell epitope in inbred mice of different non-MHC genetic background.

CD4+ T cell responses are restricted by MHC class II-encoded glycoproteins which display antigen-derived peptides. Chimeric MalE proteins expressing foreign T cell epitopes represent a potent means to induce immune responses for recombinant vaccine design. Here, we studied the influence of the non-MHC genetic background and of the processing heterogeneity displayed by various APC types on the presentation of these chimeric proteins to T cells. For this purpose, the I-Ed-restricted poliovirus CD4+ T cell epitope was inserted into five different positions on the surface of MalE protein and the immunogenicity of the recombined T cell epitope was determined in different inbred mice. Immunization of several mouse strains expressing I-Ed with these chimeric proteins induced poliovirus-specific T cell response with four out of five constructs. In vitro presentation studies of the recombined epitope to specific T cells indicated that for a given chimeric protein the fine processing is conserved, whatever the non-H-2 genetic background of APC or the type of APC. Our results show that the insertion site in MalE modulates the immunogenicity of the recombined T cell epitope, but this phenomenon is only related to the MHC genetic background.

Amino Acid Sequence↗