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J Robert

Publications and source records attributed to J Robert.

At least 55 records · Page 3Linked to original sources
PubMed2001

Phylogenetic conservation of the molecular and immunological properties of the chaperones gp96 and hsp70.

The heat shock proteins (HSP) gp96 and hsp70 have been shown to have a critical role in eliciting adaptive immune responses to cancers and viruses. This role derives from (i) their ability to chaperone antigenic peptides generated in the cells from which the HSP are isolated, and (ii) their capacity to interact with antigen presenting cells (APC) which re-present the HSP-chaperoned peptides in context of MHC I molecules. We have asked whether the immunological properties of HSP extend beyond the mammals to other phyla. We report here the serological, biochemical, genetic, and immunological characterization of the Xenopus gp96. Like mammalian gp96, Xenopus gp96 forms non-covalent complexes with peptides. Immunization with gp96 and hsp70 purified from Xenopus tumors, elicits potent and specific anti-tumor immunity, which is dependent on their ability to chaperone peptides in vivo. An immunogenic peptide chaperoned by the Xenopus gp96 can be processed and presented by mouse APC, to antigen-specific CD8+ T cells of mice. The remarkable conservation of these essential immunological properties of gp96 and hsp70 between amphibians and mammals suggests the importance of HSP in the evolution of the vertebrate immune system.

Amino Acid Sequence↗
PubMed2001

Hepatic extraction, metabolism, and biliary excretion of irinotecan in the isolated perfused rat liver.

Irinotecan (CPT-11) is a semisynthetic derivative of camptothecine that has proved activity in the treatment of colorectal carcinoma. The metabolites identified in humans include SN-38, SN-38 glucuronide, and several CYP3A-derived metabolites. We have studied the hepatic extraction, metabolism, and biliary excretion of irinotecan in the isolated perfused rat liver. After injection of a bolus dose of 5 micromol in the reservoir, irinotecan lactone disappeared from the perfusate following a two-exponential decay with half-lives of 3.5 and 120 min and a total clearance of 1.54 +/- 0.07 mL/min per gram of liver. The area under the curve (AUC) ratio lactone/total drug was 0.212 +/- 0.098 and the half-life of interconversion was 5.02 +/- 0.10 min. Bolus administrations of 2.5, 5, and 25 micromol of irinotecan gave AUCs proportional to the doses administered, indicating that no saturation occurred during dose increase. However, the relative formation of SN-38 and SN-38 glucuronide decreased at the high dose. This result was not the case for the CYP3A metabolites, which had identical metabolic ratios at all three doses. Infusions of 30 and 90 min of a dose of 5 micromol led to the same AUCs and metabolic ratios as a bolus of the same dose. Biliary elimination of irinotecan and metabolites represented 18-22% of the dose administered at 2.5 and 5 micromol but only 7-9% at 25 micromol, suggesting a saturation of this process. These data indicate that the hepatic disposition of irinotecan may vary at high dose, both at the level of biliary excretion and of activation to SN-38.

Animals↗
PubMed2001

Pharmacokinetics of liposomal daunorubicin (DaunoXome) during a phase I-II study in children with relapsed acute lymphoblastic leukaemia.

PURPOSE: The pharmacokinetics of DaunoXome were studied during a multicentric phase I-II study performed in children suffering from relapsed acute lymphoblastic leukaemia and treated on a weekly schedule. PATIENTS AND METHODS: A group of 18 patients were studied during the first course of treatment at dose levels between 40 and 120 mg/m2. Blood samples were obtained up to 72 h after infusion. The liposomal and free forms of daunorubicin, as well as daunorubicinol, were separated and quantified by HPLC using fluorometric detection, and data were analysed using a model-independent approach. RESULTS: Unchanged liposomal daunorubicin disappeared from plasma following a monoexponential decay. Its AUC represented 95.8% of the total fluorescent species found in plasma and increased linearly with the dose administered. The elimination half-life was 5.23 h, total plasma clearance 0.344 1/h per m2, and volume of distribution at steady state 2.08 l/m2. Free daunorubicin and daunorubicinol were detected in plasma at all time-points studied. Their AUCs represented, respectively, 2.53% and 1.70% of total fluorescent species and their elimination half-lives were, respectively, 16.6 h and 22.3 h. The daunorubicinol/daunorubicin AUC ratio was 0.82%. CONCLUSIONS: This study is the first to demonstrate that free daunorubicin is present in plasma after DaunoXome administration and that it originates from in vivo release from the liposomes. The pharmacokinetics of free daunorubicin appeared to be comparable to those observed after conventional administration. However, the concentration of daunorubicinol appeared to be lower than that found after conventional administration of daunorubicin.

Adolescent↗
PubMed2001

[Thyroid cancers: the Geneva experience].

AIM OF THE STUDY: To study the survival of patients with thyroid cancer operated in the same centre from 1978 to 1999. PATIENTS AND METHOD: This retrospective study included 218 patients operated on for thyroid carcinoma from january 1978 to december 1999. Modified neck dissection was performed only in the presence of one or more suspected lymph nodes. The stage of the cancer was defined according to the last TNM classification (1997). Survival data were taken from the Geneva Tumour Registry (168 patients = 77% of the series, 109 papillary carcinomas, 37 follicular, 14 undifferentiated and 8 medullary carcinomas). RESULTS: The overall 5, 10 and 15-year survival rates were respectively 88%, 84% and 80%. Papillary carcinoma was associated with the best survival at 5, 10 and 15 years (99%, 97% and 93%), despite a recurrence rate of 20% treated mainly by surgery often associated with radioiodine therapy. Follicular carcinoma had a survival rate of 83% at 5 years and 75% at 10 years. Undifferentiated carcinoma had a median survival rate of 56 days. None of the 8 patients with medullary carcinoma had died from that cancer in this series. CONCLUSION: Thyroid carcinoma carries such a good prognosis (except for undifferentiated carcinoma) that invasive surgery at first operation, like radical neck dissection, is not justified, despite a high rate of recurrence.

Adenocarcinoma, Follicular↗
PubMed2001

In vitro thymocyte differentiation in MHC class I-negative Xenopus larvae.

CTX is a surface antigen whose expression in larval and adult Xenopus is primarily restricted to MHC class I-negative immature cortical thymocytes. In adult Xenopus, surface expression of CTX marks a population of MHC class I(-) CD8(+) immature thymocytes that appears to be the equivalent of the mammalian CD4CD8 double positive subset. The present study reveals that transient in vitro exposure of immature CTX(+) thymocytes from MHC class I-negative tadpoles to suboptimal mitogenic concentrations of phorbol ester (PMA) plus ionomycin, induces larval cells to differentiate into more mature T-lymphoblasts that express high level of surface CD5 and CD45. These T-lymphoblasts have downregulated CTX, Rag 1 and TdT genes, whereas TCR-beta genes remain actively transcribed. Signaling induced by PMA/ionomycin modulates both class I and class II expression of MHC class I/II-negative larval thymocytes. This study also reveals that larval T-lymphoblasts are composed of two distinct subsets: CD5(high)CD8(-) and CD5 (high)CD8 (high).

Animals↗
PubMed2001

Resistance to cytotoxic agents.

Conflicting results have been published concerning the role of apoptosis impairment in cytotoxic drug resistance. This has shed important doubts on the currently accepted dogma, which presents apoptosis as a universal determinant of drug activity. These differing results are likely to be related to the cell-type specificity of apoptotic pathways. New genetic tools have recently been made available for the study of anticancer drug resistance. Differential or subtractive analyses of gene expression, especially using cDNA microarrays, allow the identification of multiple genes and complex pathways involved in drug activity, and the use of genetic suppressor elements represents a functional approach for the identification of resistance genes.

Antineoplastic Agents↗
PubMed2001

Short- and long-term results of total vs subtotal thyroidectomies in the surgical treatment of Graves' disease.

OBJECTIVE: Approximately one out of five patients with Graves' disease (GD) undergoes a thyroidectomy after a mean period of 18 months of medical treatment. This retrospective and non-randomized study from a teaching hospital compares short- and long-term results of total (TT) and subtotal thyroidectomies (ST) for this disease. METHODS: From 1987 to 1997, 94 patients were operated for GD. Thirty-three patients underwent a TT (mostly since 1993) and 61 a ST (keeping 4 to 8 grams of thyroid tissue--mean 6 g). All patients had received propylthiouracil and/or neo-mercazole and were in a euthyroid state at the time of surgery; they also took potassium iodide (lugol) for ten days before surgery. RESULTS: There were no deaths. Transient hypocalcemia (< 3 months) occurred in 32 patients (15 TT and 17 ST) and persistent hypocalcemia in 8 having had TT. Two patients developed transient recurrent laryngeal nerve palsy after ST (< 3 months). After a median follow-up period of seven years (1-15) with five patients lost to follow-up, 41 patients having had a ST are in a hypothyroid state (73%), thirteen are euthyroid (23%), and two suffered recurrent hyperthyroidism, requiring completion of thyroidectomy. All 33 patients having had TT--with follow-ups averaging two years (0.5-8)--are receiving thyroxin substitution. CONCLUSIONS: There were no instances of persistent recurrent laryngeal nerve palsy in either group, but persistent hypoparathyroidism occurred more frequently after TT. Long after ST, hypothyroidism developed in nearly three of four cases, whereas euthyroidy was maintained in only one-fourth; recurrent hyperthyroidy was rare.

Adolescent↗
PubMed2001

Role of daunorubicinol in daunorubicin-induced cardiotoxicity as evaluated with the model of isolated perfused rat heart.

Cardiotoxicity is the major side-effect and limits the clinical use of the anthracyclines, doxorubicin and daunorubicin. A special problem is raised by the metabolites of these drugs, the amount of which may vary according to drug combinations and formulations. Doxorubicinol, the 13-dihydroderivative of doxorubicin, has been shown to be more cardiotoxic than unchanged doxorubicin. Daunorubicinol has been assumed also to be more cardiotoxic than unchanged daunorubicin but its direct effect on cardiac function has never been evaluated in preclinical models. We have compared the cardiac effects (developed pressure, contractility and relaxation of the left ventricle) induced by daunorubicinol to those induced by daunorubicin, using the model of the isolated perfused rat heart. After treatment of rats with 6 doses of 3 mg/kg intraperitoneally, daunorubicin strongly decreased the cardiac functional parameters, while daunorubicinol did not induce cardiotoxicity. Both treatments induced a similar accumulation of daunorubicinol in the myocardium, while daunorubicin was only found in the hearts of rats treated with this drug. Direct perfusion of the hearts of untreated rats with both drugs at 10 microM induced a depression in heart function, but daunorubicin induced a progressive increase in diastolic pressure, reflecting the difficulties encountered by the heart to maintain its activity in the presence of this drug, while daunorubicinol did not. We conclude that daunorubicinol is not responsible for the important cardiac toxicity of daunorubicin.

Animals↗
PubMed2001

Trends in quinolone susceptibility of Enterobacteriaceae among inpatients of a large university hospital: 1992-98.

OBJECTIVES: To assess trends in quinolone susceptibility of Enterobacteriaceae isolated in a large university hospital. METHODS: Between 1992 and 1998, bacterial isolates were collected each year during a 3-month period to evaluate annual changes in susceptibility. In addition, the activities of fluoroquinolones (pefloxacin, norfloxacin, ofloxacin, ciprofloxacin) against nalidixic acid-resistant strains were determined by disk diffusion and MIC methodologies during the first and last year of the study. RESULTS: The susceptibility of Enterobacteriaceae to nalidixic acid was unchanged between 1992 and 1998 (86% versus 85%). However, at the species level, the susceptibility rates to nalidixic acid decreased for Escherichia coli from 92% to 89%, and for Enterobacter cloacae from 87% to 82%. In contrast, there was a 10% increase in the nalidixic acid susceptibility rates for Klebsiella pneumoniae (74% versus 83%), which was thought to be due to the control of the spread of epidemic extended-spectrum beta-lactamase (ESBL)-producing strains. The overall susceptibility of the Enterobacteriaceae to the fluoroquinolones remained high during the study period, greater than 90% in the case of ciprofloxacin. However, nalidixic acid-resistant Escherichia coli showed decreased susceptibility to ciprofloxacin between 1992 and 1998, as reflected by a decrease in median zone diameter (26 mm to 19 mm), an increase in MIC(50) (0.25 mg/L to 1 mg/L) and a shift in MIC distribution (unimodal in 1992 to bimodal in 1998). This has resulted in the reduced susceptibility of Escherichia coli to fluoroquinolones between 1992 and 1998 (pefloxacin, 95-90%; ciprofloxacin, 99-95%). CONCLUSIONS: The susceptibility of Escherichia coli to quinolones has decreased, and the level of susceptibility of the resistant strains has increased over the 7-year study period.

Anti-Infective Agents↗
PubMed2001

Metabolism of methoxymorpholino-doxorubicin in rat, dog and monkey liver microsomes: comparison with human microsomes.

The morpholino anthracycline, methoxymorpholino-doxorubicin (MMDx) is a novel anticancer agent. The metabolism of this highly lipophilic doxorubicin analogue is not fully elucidated. MMDx is metabolically activated in vivo, resulting in an 80-fold increase in potency over the parent drug. In this study, MMDx in vitro metabolism was compared in rat, dog, monkey and human liver microsomes. When microsomal fractions were incubated with MMDx, 6-8 metabolites were formed depending on the species and on the substrate concentrations. Among these eight metabolites, three comigrated with authentic standards, namely MMDx-ol, PNU156686 and PNU159682, and the five others are in the process of being characterized. Quantitatively, monkey and human metabolize MMDx with a higher rate than rat and dog. Qualitatively, MMDx metabolic profile in dog microsomes was different from the three other species. MMDx-ol was predominant in dog and only minor in other species. In conclusion, MMDx metabolism was species-different. Rat and monkey liver microsomes may be used as models to study MMDx metabolism in humans. Dog liver microsomes may be a good model for studying the formation of MMDx-ol.

Animals↗
PubMed2001

Verapamil prevents stretch-induced shortening of atrial effective refractory period in langendorff-perfused rabbit heart.

INTRODUCTION: Atrial dilation and rapid pacing reduce atrial effective refractory periods (AERPs), thereby increasing the susceptibility to sustained atrial fibrillation (AF) in Langendorff-perfused rabbit hearts. It is unclear whether similar pathophysiologic mechanisms are operative in short-term electrophysiologic changes caused by dilation and rapid pacing. Therefore, we analyzed whether both forms of short-term electrophysiologic changes are similarly affected by pharmacologic interventions acting on different potential mechanisms underlying these changes. METHODS AND RESULTS: Thirty Langendorff-perfused rabbit hearts underwent a protocol with stepwise increase of intra-atrial pressure from 0 to 12 cm H2O followed by 10 minutes of rapid pacing at 4 cm H2O. The protocol was repeated after addition of glibenclamide (10 micromol/L, n = 7), cariporide (1 micromol/L, n = 7), or verapamil (1 micromol/L, n = 9). In the basal state, increase of intra-atrial pressure from 0 to 12 cm H2O decreased AERPs from 85 +/- 11 to 55 +/- 9 msec (P < 0.01), rapid pacing at low intra-atrial pressure (4 cmH2O) decreased AERP to a similar extent, from 81 +/- 11 to 60 +/- 10 (P < 0.01). At higher intra-atrial pressure, decrease of AERP was more pronounced (10 cm H2O: 37 +/- 2 msec) (n = 7). Addition of verapamil decreased basal AERP from 86 +/- 10 msec to 68 +/- 11 msec (P < 0.05). Short-term electrophysiologic changes due to atrial dilation were abolished; changes due to rapid pacing were reduced but still present. Glibenclamide and cariporide had no significant effect. CONCLUSION: Langendorff-perfused rabbit heart is a suitable model for studying short-term electrophysiologic changes due to both rapid pacing and atrial dilation. AERPs are shortened to a similar extent by both mechanisms, whereas a combination of the two leads to more pronounced AERP reduction. Calcium overload plays a crucial role in short-term electrophysiologic changes caused by atrial dilation, whereas atrial ischemia or acidosis has no significant impact.

Animals↗
PubMed2001

Sequential gene expression of P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP) and lung resistance protein: functional activity of P-gp and MRP present in the doxorubicin-resistant human K562 cell lines.

Previous studies have reported that P-glycoprotein (P-gp), a transmembrane efflux pump involved in multidrug resistance (MDR), was overexpressed in the doxorubicin (Dox)-resistant human erythroleukemia cell line K562. Nevertheless, several results suggested that P-gp was not the only mechanism involved in these resistant cells. Sequential co-expression of other MDR-associated proteins was sometimes reported, as MDR-associated protein (MRP) and lung resistance protein (LRP), in different MDR cell lines. Thus, mRNA expression and stability of P-gp, MRP and LRP were analyzed, while their corresponding protein levels were quantified in correlation with functional assay, in the K562 cell line and two Dox-resistant variants (K562/R). Their P-gp content was in accordance with their degree of resistance, but not as much in the level of mRNA expression, suggesting a post-transcriptional regulation. On the other hand, MRP could play a minor role in MDR because of an unchanged expression in K562/R sublines. A surprising progressive disappearance of LRP in both resistant cells suggested that the original mechanism of drug redistribution may be operative, involving a negative role for LRP.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Activities of new macrolides and fluoroquinolones against Mycobacterium ulcerans infection in mice.

Mice infected in the left hind footpad with 5 log(10) acid-fast bacilli of Mycobacterium ulcerans were divided into an untreated control group and 17 treatment groups that received one of the following regimens for 4 weeks (all doses in milligrams per kilogram): 100 mg of azithromycin (AZM), 100 mg of clarithromycin (CLR), or 50 mg of AZM for a duration of 5 days a week (daily), three times a week, or once weekly. In addition, the following regimens were administered daily: 100 mg of telithromycin (TLM), sparfloxacin (SPX), or moxifloxacin (MOX); 200 mg of levofloxacin (LVX); 100 mg of streptomycin (STR) or amikacin (AMK); 10 mg of rifampin (RIF); and the combination of 10 mg of RIF and 100 mg of AMK (RIF+AMK). After completion of treatment, mice were observed for 30 weeks. The effectiveness of treatment regimens was assessed in terms of the delay in median time to footpad swelling in treated mice compared with that in the untreated controls. Clear-cut bactericidal activity, i.e., an observed delay in footpad swelling that exceeded the period of treatment, was observed in the STR-, AMK-, and RIF+AMK-treated mice. However, all mice treated with either AMK or STR alone had swollen footpads before the end of the 30-week observation period, suggesting regrowth of M. ulcerans. In contrast, 50% of the mice treated with the RIF+AMK combination exhibited no lesion even after 30 weeks, suggesting cure. The remaining regimens could be assigned to one of three groups: (i) no activity (50 mg of AZM, 100 mg of AZM thrice weekly, TLM, and LVX); (ii) bacteriostatic activity, i.e., a delay in footpad swelling shorter than the 4-week treatment duration (100 mg of AZM daily or once weekly, CLR thrice or once weekly, and MOX); or (iii) weak bactericidal activity (CLR daily and SPX). The RIF+AMK combination and possibly RIF+STR warrant further study for the treatment of M. ulcerans infection in humans.

Animals↗