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J Robert

Publications and source records attributed to J Robert.

At least 127 records · Page 7Linked to original sources
PubMed1999

[A new method for the intravital assessment of the functional activity of the membrane transporters performing the efflux of antitumor preparations from the cells of solid tumor specimens].

A new method for intravital assessment of the functional activity of anticancer drug efflux transporters in intact solid tumor specimens was developed. The method is based on the well-known approach to the transporter functional evaluation by intracellular accumulation of antitumor drugs and particularly the anthracycline antibiotic doxorubicin (Dox). The main new point of the method providing investigation of intact solid tumor specimens which markedly simplified the procedure is the fact that the intratissue and intracellular accumulation of Dox is determined not by the level of the drug in the tissue but by its fluorescence decrease in the incubation medium. To assess just the intracellular content of Dox and to estimate the transporter functional activity, investigation of the influence of membrane transporter inhibitors such as verapamil (P-gp inhibitor) and sodium azide (inhibitor of all the energy-dependent ABC transporters) on the drug fluorescence decrease in the incubation medium is stipulated. The validity of such an approach was experimentally proved with the specimens of the Ehrlich solid tumor transplants in mice (a sensitive variant of the tumor and the tumor with induced drug resistance). Biopsy specimens of human breast tumors were investigated with the new method and functional activity of various efflux transporters was revealed: (1) only P-gp, (2) both P-gp and other ABC transporters, (3) only transporters different from P-gp, (4) no functional activity of efflux transporters. The main trends of the further investigation of efflux transporter functional activity in human solid tumors possible for the first time with the use of the new method are defined.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

A national survey of human Mycobacterium bovis infection in France. Network of Microbiology Laboratories in France.

OBJECTIVE: To evaluate the role of Mycobacterium bovis in the epidemiology of human tuberculosis in France. DESIGN: A national survey in France in 1995 using a questionnaire mailed to all French microbiological laboratories performing mycobacteria cultures. RESULTS: M. bovis was isolated in 38 out of 7075 cases of bacteriologically confirmed tuberculosis (0.5%) notified to the National Reference Centre (CNR) in 1995, resulting in an incidence of 0.07 per 100,000 population. Incidence rates increased with age, and were the highest among patients of 75 years or more (range 0.02-0.33/100,000). Two cases of tuberculosis due to M. bovis were reported in foreign-born children who had come to France for treatment of their disease. No cases were reported among French-born children. The site of tuberculosis was pulmonary in 17 cases, extra-pulmonary in 14, both pulmonary and extra-pulmonary in one, and unknown in six. Extra-pulmonary sites were more frequent in older patients, and pulmonary sites more frequent in younger patients. Two patients were coinfected with the human immunodeficiency virus. Occupational exposure was identified in 13 cases and ingestion of non pasteurised milk in three. In addition, 11 patients had a possible risk of exposure related to their country of birth, family contact or occupation. CONCLUSION: In France, the 0.5% proportion of human tuberculosis due to M. bovis is similar to that of other developed countries. The higher incidence of the disease among older people is likely to reflect the efficacy of the control measures for tuberculosis in cattle.

Adolescent↗
PubMed1999

Is chronic non-specific low back pain chronic? Definitions of a problem and problems of a definition.

BACKGROUND: Chronic low back pain (LBP) accounts for the majority of the disability and costs for LBP. However, the definition of chronicity is unclear. AIM: To elicit practitioners' definitions of chronic LBP patients, both in general and in the patients they were treating; to assess the most common characteristics of these practitioners' chronic LBP patients; and to assess the stability of chronicity in a sample of the general population. METHOD: Semi-structured interviews were conducted with 33 practitioners working in private practice, 71 LBP patients and their therapists, and 252 employees of a chain store who were assessed yearly in a prospective study. RESULTS: The therapists' definitions of chronic LBP patients generally included psychosocial aspects. Only physical symptoms and signs were stressed in the patients they were treating. These patients displayed common characteristics with reference to pain, functional problems, and contact with health care services. Duration of symptoms was not sufficient to define chronicity. In the employee population, chronicity defined according to pain duration was unstable. However, the same was true when chronicity was measured according to the criteria defined in the patient population. CONCLUSION: There is a discrepancy between theory and practice regarding the definition of chronic LBP. This discrepancy concerns not only the literature but also clinical practice itself. The term 'chronic' LBP as currently used is therefore equivocal.

Adult↗
PubMed1998

Reference method for detection of Pgp mediated multidrug resistance in human hematological malignancies: a method validated by the laboratories of the French Drug Resistance Network.

Multidrug resistance (MDR) associated with overexpression of the MDR1 gene and of its product, P-glycoprotein (Pgp), plays an important role in limiting cancer treatment efficacy. Many studies have investigated Pgp expression in clinical samples of hematological malignancies but failed to give definitive conclusion on its usefulness. One convenient method for fluorescent detection of Pgp in malignant cells is flow cytometry which however gives variable results from a laboratory to another one, partly due to the lack of a reference method rigorously tested. The purpose of this technical note is to describe each step of a reference flow cytometric method. The guidelines for sample handling, staining and analysis have been established both for Pgp detection with monoclonal antibodies directed against extracellular epitopes (MRK16, UIC2 and 4E3), and for Pgp functional activity measurement with Rhodamine 123 as a fluorescent probe. Both methods have been validated on cultured cell lines and clinical samples by 12 laboratories of the French Drug Resistance Network. This cross-validated multicentric study points out crucial steps for the accuracy and reproducibility of the results, like cell viability, data analysis and expression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

RecA binding to a single double-stranded DNA molecule: a possible role of DNA conformational fluctuations.

Most genetic regulatory mechanisms involve protein-DNA interactions. In these processes, the classical Watson-Crick DNA structure sometimes is distorted severely, which in turn enables the precise recognition of the specific sites by the protein. Despite its key importance, very little is known about such deformation processes. To address this general question, we have studied a model system, namely, RecA binding to double-stranded DNA. Results from micromanipulation experiments indicate that RecA binds strongly to stretched DNA; based on this observation, we propose that spontaneous thermal stretching fluctuations may play a role in the binding of RecA to DNA. This has fundamental implications for the protein-DNA binding mechanism, which must therefore rely in part on a combination of flexibility and thermal fluctuations of the DNA structure. We also show that this mechanism is sequence sensitive. Theoretical simulations support this interpretation of our experimental results, and it is argued that this is of broad relevance to DNA-protein interactions.

Bacteriophage lambda↗
PubMed1998

[Primary pulmonary carcinoma and Pancoast syndrome].

INTRODUCTION: Although the treatment of Pancoast tumours usually combines radiotherapy and surgery, poor prognosis has been reported. The influence of clinical signs and extension of surgical resection on long-term survival has not yet been systematically investigated. METHODS: Between 1977 and 1997, among 1129 patients operated consecutively in our institution for a bronchogenic carcinoma, 14 (1.2%) presented a Pancoast tumour. Delay between the onset of symptoms and definite diagnosis ranged from 1 to 14 months (median 7 months). A complete surgical resection was performed in 7 patients, 6 of whom did not have mediastinal lymph node metastasis. Radiotherapy or radiochemotherapy was performed in all patients. RESULTS: Overall 5-year survival rate is 36%. However, 5-year survival rate increases up to 60% if the diagnosis is established within 6 months after the onset of symptoms, and up to 67% if the tumour has been removed without mediastinal lymph node metastasis. In contrast, the 5-year survival rate decreases to 20% or 0% respectively, if symptoms last more than 6 months, or if tumoral resection is incomplete. CONCLUSIONS: The incidence of Pancoast tumours compared to other bronchogenic carcinomas is low. An early diagnosis allows complete resection of the tumour and contributes to improve survival.

Adult↗
PubMed1998

Doxorubicin-induced alterations of c-myc and c-jun gene expression in rat glioblastoma cells: role of c-jun in drug resistance and cell death.

We studied the effect of doxorubicin on the expression of c-myc and c-jun in the rat glioblastoma cell line C6 and its doxorubicin-resistant variant C6 0.5, at equitoxic exposures. For quantitation, the mRNA levels of these oncogenes were related to those of two domestic genes, beta-actin and glyceraldehyde phosphate dehydrogenase. After a transient overexpression of the genes during the first hour of incubation, there was a selective, dose-dependent down-regulation of both genes by doxorubicin in the sensitive cells. In the resistant cell line, c-myc expression was also decreased in response to doxorubicin incubation, but the expression of c-jun remained unchanged over the whole range of concentrations. In contrast, vincristine had no effect on the amounts of c-myc and c-jun mRNAs in either line. The effect of doxorubicin on the mRNA levels of c-jun was also observed on the JUN proteins by immunoblotting, but the MYC protein levels remained unchanged upon doxorubicin treatment. There was a significant correlation between the levels of c-myc and c-jun gene expression and the degree of growth inhibition induced by doxorubicin. In addition, doxorubicin induced a fragmentation of DNA in sensitive cells, but not in resistant cells, thus revealing a resistance to apoptosis in this line. Doxorubicin-induced cell death did not appear to be mediated by p53 in either cell line.

Animals↗
PubMed1998

[Value and limits of conventional mediastinoscopy in preoperative evaluation of primary bronchial cancer].

PURPOSE OF THE STUDY: Retrospective evaluation of conventional mediastinoscopy in the preoperative staging of primary lung cancer. METHODS: Between 1978 and March 1997, 117 consecutive patients underwent conventional mediastinoscopy in the preoperative staging of primary lung cancer, after imaging had shown mediastinal lymph nodes larger than 1.5 cm. RESULTS: In 8 instances no material was found at mediastinoscopy, in 38 the lymph nodes showed no tumorous infiltration, and in 71 the lymph nodes were metastatic. 48 patients underwent thoracotomy in the same stage, with resection achieved in 41. Contraindications for thoracotomy (in 69) were N2 (45) or N3 (11) disease adn/or small cell lung cancer (18). Mediastinal lymphadenectomy was performed in 26 of the 41 patients who underwent lung resection; half of those with negative nodes at mediastinoscopy had in fact N2 disease, with involvement of 2 areas of more in half. There were no deaths due to mediastinoscopy but 4 complications. CONCLUSIONS: A favorable mediastinoscopy is not synonymous with resectable disease, nor does it exclude N2 disease; it does however serve to avoid unnecessary thoracotomies in more than half of cases.

Adult↗
PubMed1998

[Surgical treatment of severe emphysema: lung transplantation or volume reduction?].

In recent years, lung transplantation (LT) and volume reduction surgery (LVRS) have been proposed for selected patients with end-stage pulmonary emphysema. Retrospectively, we analyzed the perioperative time course of 30 patients with emphysema who underwent either LVRS (n = 17) or LT (n = 13). In the LVRS group, patients were significantly older, presented less severe functional disability and all but one could be extubated at the end of surgery. In contrast, patients undergoing LT required postoperative mechanical ventilation (19 +/- 11 hrs) and had a prolonged hospital stay (37 [25-60] days vs 19 [11-42] days in LVRS patients) due to reperfusion lung edema, infection, hemorrhage and acute rejection. Six months postoperatively, forced expiratory volume in 1 second was improved and was significantly larger after LT compared with LVRS (+200% vs +63%). Our preliminary results suggest that, although LT produces greater functional improvement, LVRS is associated with lower surgical risk and is an alternative therapy in selected patients with severe emphysema.

Aged↗
PubMed1998

Metabolism of irinotecan (CPT-11) by human hepatic microsomes: participation of cytochrome P-450 3A and drug interactions.

Irinotecan (CPT-11) is a water-soluble analogue of camptothecin showing activity in colon cancer. Recently, we identified a major metabolite of CPT-11 in patients' plasma, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino] carbonyloxycamptothecin (APC), which is produced by the oxidation of the distal piperidine ring (P. Rivory et al, Cancer Res., 56: 3689-3694, 1996). As with all active camptothecin derivatives, CPT-11 is subject to spontaneous interconversion between a lactone and a carboxylate form in aqueous media. The kinetics of biotransformation of the two forms of CPT-11 into APC was studied using pooled human liver microsomes. The formation of APC was characterized by the following parameters: Km = 18.4 +/- 1.4 and 39.7 +/- 11.6 microM; and Vmax = 26.0 +/- 0.6 and 13.4 +/- 1.7 pmol/min/mg protein for the lactone and carboxylate forms of CPT-11, respectively. This reaction was found to be catalyzed principally by cytochrome P-450 (CYP) 3A because of three key results: (a) the CYP 3A-selective inhibitors ketoconazole (1 microM) and troleandomycin (100 microM) inhibited APC formation by 98 and 100%, respectively, mostly in a competitive way; (b) using microsomes from transfected lymphoblastoid cells expressing specific CYPs, we found that only those from CYP 3A4 cDNA-transfected cells transformed CPT-11 into APC; and (c) using 15 individual preparations of human liver microsomes, we observed highly significant correlations between the activity of CPT-11 metabolism into APC and both immunoreactivity with anti-CYP 3A antibodies and testosterone 6beta hydroxylation, an activity specifically mediated by CYP 3A. The effect on this metabolism of 11 drugs used at 100 microM was studied with CPT-11 lactone at 25 microM. Amikacin, Bactrim, ciprofloxacin, rocephine, 5-fluorouracil, metoclopramide, morphine, and paracetamol had no effect, but ondansetron, loperamide, and racecadotril inhibited this pathway by 25, 50, and 50%, respectively. These concentrations exceed those expected in vivo. APC formation in patients may thus be influenced by coadministered ketoconazole therapy and may decline after administration of CPT-11 because of the lactonolysis of the latter.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Benefits of pharmacological knowledge in the design and monitoring of cancer chemotherapy.

Prescribing chemotherapy is a difficult task, because of drug resistance, which prevents all tumors to respond to a given protocol and because of drug toxicity, which is generally unavoidable but which must be limited to acceptable levels. The therapeutic window of anticancer drugs is very narrow and clinicians have to try to optimize the individual doses and schedules of the drugs to be administered. They can rely upon simple anthropometric features, such as body weight or surface area; they can also take into account the physiological status of the patient: age, liver and kidney function, genetic characteristics of drug metabolism, etc. The best way for dose adaptation lies in the establishment of pharmacokinetic/pharmacodynamic relationships, i.e., between the behavior of a drug in the body and its efficacy and toxicity. When it is established that the optimal effect of a drug is related to a given parameter, such as the area under the curve plotting plasma concentration vs. time (AUC), it becomes possible to administer the drug with the dose allowing to obtain the target parameter value. Individual dose adaptation can be achieved thanks to the study of the pharmacokinetics of a test dose preceding that of the therapeutic dose, or by the measure of drug plasma levels, either at steady state during a protracted infusion, or from cycle to cycle during repetitive protocols. Population analysis now allows the adaptation of anticancer drug dosing from a minimum knowledge of individual pharmacokinetic features, together with other characteristics of the patients such as age, gender or physiological functions.

Antineoplastic Agents↗
PubMed1998

Drug resistance to topoisomerase II inhibitors.

We describe in this review the mechanisms of resistance to topoisomerase II inhibitors that have been identified in cell lines rendered resistant to drugs. They concern especially both quantitative and qualitative alterations of topoisomerase II, leading to drug insensitivity of the cells. Expression and activity of topoisomerase II have also been studied in a number of tumor specimens originating from patients, but the role of topoisomerase II alterations in drug resistance in the clinical setting has not yet been firmly established. It would be worthwhile, however, to develop predictive assays for drug activity in human cancers, based upon the topoisomerase II status of tumor samples.

Animals↗
PubMed1998

The detection of photodegradation products of irinotecan (CPT-11, Campto, Camptosar), in clinical studies, using high-performance liquid chromatography/atmospheric pressure chemical ionisation/mass spectrometry.

A method for the detection of the photodegradation products of irinotecan (CPT-11, Campto, Camptosar) was developed using high-performance liquid chromatography (HPLC) with fluorescence detection and HPLC/atmospheric pressure chemical ionisation/mass spectrometry (HPLC/APCI/MS). Remnants of infusion solution as well as samples of urine and plasma collected at the end of the infusion of CPT-11 to cancer patients were screened for the five principal known photodegradation products (PDPs) of CPT-11. The concurrent use of standards of the PDPs with ion-extract HPLC/APCI/MS chromatograms enabled the identification of trace quantities of two PDPs in most samples analysed. However, similar analyses of fresh clinical drug solutions revealed that the PDPs were not generated significantly by exposure to light during the infusion period, but were already present in the drug ampoules. Furthermore, this appears to be the source of traces of PDPs detectable in urine and plasma of patients rather than metabolism, per se.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Determination of unbound platinum after oxaliplatin administration: comparison of currently available methods and influence of various parameters.

Variations in plasma protein binding may have profound effects on both disposition and activity of drugs, especially for those which are tightly bound to proteins, such as anticancer platinum derivatives. Methods of separation of the non-protein-bound fraction and some technical parameters may influence the results. We have compared ultrafiltration and ultracentrifugation, as well as the effect of potentially interfering factors, upon the determination of the plasma unbound platinum fraction after oxaliplatin administration to cancer patients. Ultrafiltration and ultracentrifugation provided very closely correlated results, so that either technique can be used. The ultrafiltration cut-off (3000-30,000 Da) devices, the type of tube for blood sampling and the type of anticoagulant (none, lithium heparinate or EDTA) did not influence the results markedly. In contrast, results were greatly influenced by freezing: erratic results were obtained on thawed plasmas when compared with those on fresh serum or plasma. Consequences may be important in usual practice, since many pharmacokinetic studies are carried out in multicentric trials with plasma processing centralized in one reference laboratory. The methods for the determination of protein-drug binding should be standardized and guidelines elaborated where optimal conditions for each type of binding assay are given.

Antineoplastic Agents↗
PubMed1998

Transcriptional down-regulation of c-myc expression in an erythroleukemic cell line, K562, and its doxorubicin-resistant variant by two topoisomerase II inhibitors, doxorubicin and amsacrine.

We have evaluated the effect of two topoisomerase II (Topo II) poisons, amsacrine and doxorubicin, on the expression of the c-myc oncogene, both at the mRNA and protein levels, in the leukemia cell line, K562, and its doxorubicin-resistant counterpart, K562 DoxR. We report in this study a concentration-dependent decrease in c-myc mRNA levels upon exposure of both cell lines to amsacrine and doxorubicin, with a more pronounced effect for amsacrine in the resistant line. In either case, c-myc down-regulation closely paralleled the drug-induced growth inhibition. We have also used the technique of PCR stop-assay to detect the occurrence of DNA breaks within the P2 promoter of the c-myc gene. We have shown that Topo II-mediated breaks induced by amsacrine are probably responsible for the down-regulation of c-myc in the resistant line. In addition, amsacrine induced apoptosis only in the resistant line while doxorubicin did not induce apoptosis in any cell line. These results suggest that c-myc is not involved in the resistance of K562 DoxR cells, but can induce the apoptosis pathway in these cells, while no drug-induced apoptosis could be detected in the sensitive line.

Amsacrine↗
PubMed1998

Resistance to anticancer drugs: are we ready to use biologic information for the treatment of patients with cancer?

Multidrug resistance (MDR) to anticancer drugs can be diagnosed in tumors by molecular biology techniques (expression of the MDR1 gene), by immunologic techniques (expression of P-glycoprotein), and by functional approaches (dye exclusion). Numerous studies have tried to correlate the MDR status of tumors to the clinical response to the treatment, but wide discrepancies prevented definitive conclusions. As a consequence, the routine use of these techniques is still not possible, and continuous efforts are needed for their standardization. The development of MDR modulators in the clinical setting is a promising approach that requires rigorous clinical trials, especially with sequential design of phase 2 protocols. Definitive results are still lacking concerning the interest of combining an MDR modulator to standard chemotherapy for resistant cancers.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Evolution of immune surveillance and tumor immunity: studies in Xenopus.

We have developed a novel experimental model of cancer immunity in the frog, Xenopus, which may provide a useful alternative to murine tumor models and a way to assess whether the control of tumor development is a fundamental function of the immune system of vertebrates. In Xenopus, tumor immunity can be studied in two developmentally distinct immune systems. The larval immune system reflects characteristics of an ancestral system that appears to function without classical MHC class I antigen presentation and an efficient effector mechanism. The adult system appears more highly evolved in that it is remarkably similar to that of mammals and is able to generate a potent antitumor response. This amphibian model also provides a unique system with which to investigate a postulated role of heat shock proteins as components of an ancestral system of antigen presentation and/or immune surveillance that predates the antigen presentation pathway that exclusively involves MHC molecules.

Animals↗