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Biomedical subjects

B Charpentier

Publications and source records attributed to B Charpentier.

At least 289 records · Page 16Linked to original sources
PubMed1976

In vitro monitoring of cadaver kidney donor pretreatment by lymphocyte culture.

Fourteen cadaver kidney donors were pretreated with a rapid infusion of 5 g of cyclophosphamide and 5 g of methylprednisolone in an attempt to reduce graft immunogenicity by altering immunogenic "passenger" leucocytes. The effects of this drug infusion on peripheral lymphocytes were monitored by measuring the ability of donor lymphocytes to respond and to stimulate recipient cells in mixed lymphocyte culture and by measuring their ability to respond to phytohaemagglutinin stimulation before and after infusion of the drugs. Pretreatment severely decreased the ability of donor cells to function in these tests, but the maximum effect was not seen until several hours after completion of the infusion. The results of this study suggest that donor nephrectomy should be delayed for at least 4 hr after pretreatment to obtain maximum lymphocyte effect using this regimen. This type of in vitro testing may provide means of monitoring donor pretreatment and comparing different pretreatment protocols in human cadaveric allotransplantation.

Antibody Formation↗
PubMedDate not supplied

Synthesis of 7 alpha- and 7 beta-carboxymethyl-9(11)-ene derivatives of estrone and estradiol.

As part of a search for derivatives designed to conjugate to amino groups, either of a protein carrier for antibody production or of an immobilized side-chain on a polymer for affinity chromatography, functionalized estrone and estradiol analogues were prepared. These modified steroids were obtained via the introduction of a carboxymethyl side-chain at the C-7 alpha and C-7 beta position on an adrenosterone derivative and were then aromatized on the A ring. These new compounds are unsaturated at the C-9 (11) position, which could be useful for a second modification.

Androstenes↗
PubMedDate not supplied

Multiple cleavage sites of cholecystokinin heptapeptide by "enkephalinase".

Degradation of Boc CCK7 (Boc Tyr1 (SO3H)-Met2-Gly3-Trp4-Met5-Asp6-Phe7-NH2), a fully active analog of CCK8, by purified rabbit kidney neutral metalloendopeptidase (enkephalinase) was studied as a basis for the rational design of potent peptidases-resistant analogs of cholecystokinin. Characterization of the metabolites was performed by HPLC using several elution procedures. Three cleavage sites were evidenced: one major at the Asp6-Phe7 bond and two minor at Gly3-Trp4 and Trp4-Met5 bonds. All cleavages were fully inhibited by thiorphan, a potent inhibitor of enkephalinase. The relative importance of the different cleavages was established using several cholecystokinin analogs. At 25 degrees C the half-disappearance time was 18 min for Boc CCK7, Boc[diNle2,5]CCK7 and 70 min for Boc[diNle2,5 D.Asp6]CCK7. Although, half-life of Boc CCK7 and Boc[diNle2,5]CCK7 were identical, the replacement of Met by Nle, a more hydrophobic aminoacid, greatly favoured the cleavage at the Trp4-Nle5 bond which became the major breakdown. This feature was exemplified by the substitution of L.Asp by D.Asp, preventing the Trp4-Nle5 cleavage, which gave rise to the most enkephalinase-resistant analog in this series.

Amino Acid Sequence↗
PubMedDate not supplied

Enzyme-resistant CCK analogs with high affinities for central receptors.

Based on the results of the in vitro metabolism of CCK8 by various peptidases, we have synthesized three CCK analogs: Boc-Tyr(SO3H)-Nle-Gly-Trp-(N- Me)Nle-Asp-Phe-NH2 (compound I), Boc-Tyr(SO3H)-gNle-mGly-Trp-Nle-Asp-Phe-Nh2 (compound II), Boc-Tyr(SO3H)-gNle-mGly-Trp-(N-Me)Nle-Asp-Phe-NH2 (compound III). In in vitro enzymatic degradation studies, these compounds showed a high stability toward either enkephalinase or the enzymes present in crude rat brain membranes preparations. Moreover, in binding studies on guinea pig tissues, these CCK-related peptides were characterized by high apparent affinities for brain CCK receptors and by a broader range of affinities for pancreatic CCK receptors. This broad range of affinities was reflected by their pharmacological potencies in the guinea pig pancreatic amylase release and ileum contraction assays. These enzyme-resistant CCK analogs provide therefore valuable tools to investigate the pharmacology of CCK.

Animals↗
PubMedDate not supplied

Electrophysiological studies with new CCK analogs: correlation with binding affinity on B-type receptors.

The electrophysiological effects of Boc-D-Asp-Tyr(SO3H)-Nle-D-Lys-Trp-Nle-Asp-Phe-NH2 (compound I) and Boc-gamma-D-Glu-Tyr(SO3H)-Nle-D-Lys-Trp-Nle-Asp-Phe-NH2 (compound II), two cyclic cholecystokinin analogs with high selectivity for CCK-B receptors, as well as the effects of the linear enzyme-resistant analog Boc-[Nle28,Nle31]-CCK7 (BDNL), were compared with those of CCK8 using extracellular recordings in rat hippocampal slices in vitro. Bath applications of the three synthetic compounds resulted in concentration-dependent and reversible increases in single-unit activity. Comparison of equieffective concentrations yielded the following potency rank order: BDNL greater than CCK8 greater than compound II greater than compound I. There was a close correlation (r = .96, slope = 0.98) between the excitatory activities of the analogs and their potencies in displacing radiolabelled CCK8 from CCK-B receptors on rat brain membranes.

Animals↗
PubMedDate not supplied

Antibody-mediated endocytosis of G250 tumor-associated antigen allows targeted gene transfer to human renal cell carcinoma in vitro.

Specific gene transfer into targeted tumor cells remains a critical issue for the development of systemic gene therapy protocols. With this end in view, we have tested the possibility of selectively directing genes to tumor cells through the recognition of tumor-associated antigens (TAA). This was approached in vitro on four human renal cell carcinoma (RCC) lines by means of the highly specific mouse G250 monoclonal antibody (mAb) chemically conjugated to a plasmid DNA conveying a reporter activity. This mAb directed to a TAA that is present on 95% of primary RCCs and on 60% of metastatic human RCCs was extensively characterized, including during clinical trials. Epifluorescence microscopy analysis indicated that upon specific binding to G250 TAA, G250 mAb alone or conjugated to plasmid DNA was internalized by an active endocytic process and colocalized with the transferrin concentrated in the late recycling perinuclear compartment. We also observed that both unconjugated G250 mAb or G250 mAb conjugated to plasmid DNA remained in the perinuclear region of the cells for > or = 20 hours and were not rapidly translocated to lysosomes or recycled to the plasma membrane. In contrast, unconjugated plasmid DNA was not internalized. After transfection of G250 TAA-positive RCC lines with G250 mAb conjugated to a plasmid cDNA encoding mouse interleukin-2, a significant and sustained production of mouse interleukin-2 protein was detected from days 5-15 and was abrogated by inhibiting the internalization process. Altogether, our data showed that endocytosis of G250 TAA should be the basis of gene transfer to RCC, suggesting that targeting of TAA capable of internalization may be the basis of new approaches for designing alternative cancer gene therapy procedures.

Animals↗
PubMedDate not supplied

Low levels of lymphocyte MDR1 gene expression during early renal transplantation in patients treated with tacrolimus.

P-glycoprotein (P-gp) is a membrane efflux pump increasing the transport of drugs such as tacrolimus out of the cells. The aim of the study was to determine the kinetics of lymphocyte P-gp expression in patients treated with tacrolimus during the first 3 months following renal transplantation. Lymphocyte MDR1 gene expression was measured by semi-quantitative RT-PCR a few hours before transplantation, 3 weeks and 3 months after the graft. Lymphocyte MDR1 gene expression was low in all the 10 patients compared to 10 healthy volunteers: 0.30 +/- 0.07 arbitrary units (patients) vs. 1.74 +/- 0. 55 (healthy volunteers) (P = 0.0002). MDR1 gene expression decreased among the patients during the study: 0.28 +/- 0.12 (3 weeks later) and 0.12 +/- 0.09 (3 months later) (P = 0.006). We can conclude that lymphocyte MDR1 gene expression among patients before renal transplantation is low and remains low during the first 3 months following the graft.

ATP Binding Cassette Transporter, Subfamily B, Mem↗