Search PubMed⌕ Search

Biomedical subjects

D Bellet

Publications and source records attributed to D Bellet.

At least 109 records · Page 6Linked to original sources
PubMed1987

Radiolabelled monoclonal antibodies against alpha-fetoprotein for in vivo localization of human hepatocellular carcinoma by immunotomoscintigraphy.

Two high affinity monoclonal antibodies, designated AF01 and AF04, directed against distinct epitopes of human alpha-fetoprotein (AFP) and the Fab fragments of one of them, were labelled with 131I and injected into 18 patients with AFP producing hepatocellular carcinoma (HCC) in order to carry out imaging studies by tomoscintigraphy. Twelve patients were injected with whole antibody, only three of seven patients injected with AF01 and two of five patients injected with AF04 had a positive scan. In contrast, five out of six patients injected with labelled Fab fragments of AF04 had positive imaging. These results confirm that tumour imaging of HCC using 131I labelled monoclonal antibody against AFP is feasible. Moreover, utilization of tomoscintigraphy in place of linear scintigraphy and Fab fragments instead of whole immunoglobulin may improve the sensitivity of radioimmunolocalization. This technique provides useful information on the in vivo distribution of monoclonal antibodies directed against AFP and on the practicability of the eventual therapeutic use of anti-AFP antibodies in HCC.

Adult↗
PubMed1987

Utilization of synthetic peptides for the study of calcitonin and biosynthetic precursors for calcitonin.

By using synthetic peptides and a library of monoclonal anti-peptide antibodies, we have developed a panel of techniques that allow the dissection of circulating immunoreactive calcitonin in the serum. C Cells of the thyroid were found to release both mature calcitonin and biosynthetic intermediates in the circulation. Finally, these products were found to circulate as heterogenous molecular species. A methodology for the standardization of the measurement of calcitonin is proposed in the form of a two-site immunoradiometric assay specific for mature calcitonin.

Antibodies, Monoclonal↗
PubMed1987

Physiological studies of human chorionic gonadotropin (hCG), alpha hCG, and beta hCG as measured by specific monoclonal immunoradiometric assays.

Several libraries of monoclonal antibodies have been produced against epitopes that reside on hCG, alpha hCG, and beta hCG. Having characterized them physically, we explored their use in the construction of highly specific and sensitive immunoradiometric assays. There were several important immunochemical considerations with respect to developing assays that accurately detect low levels of free subunits in serum in the presence of high concentrations of the native hormone. These include physical properties and specificities of the monoclonal antibodies, choice of capture antibody on the solid phase support, assay design, and purity of hormone standards. Using such assays, we found early pregnancy (in vitro fertilization) to be characterized by the sequential appearance of hCG, followed by beta hCG and then alpha hCG. Molar ratios of beta hCG to alpha hCG and beta hCG to hCG were highest in early gestation. However, there was a reversal of the beta hCG to alpha hCG ratio at 12-13 weeks gestation, and an excess of free alpha hCG was observed thereafter. Except for values obtained in very early pregnancy, the beta hCG to hCG ratio remained remarkably constant at approximately 0.5% throughout gestation. In contrast, choriocarcinoma was distinguished by absolute serum beta hCG concentrations 3-100 times greater than the maximum values observed during pregnancy and, more importantly, by exceedingly high beta hCG to hCG ratios. For comparison, we studied hCG, alpha hCG, and beta hCG levels in an additional 178 patients with nontrophoblastic tumors. Ectopic production of alpha hCG and beta hCG was rare (3%), and thus far, we have been unable to demonstrate the presence of hCG in such patients. Therefore, hCG and the free subunits appear not to be useful as serological markers for nontrophoblastic tumors.

Adolescent↗
PubMed1987

Ectopic beta-human chorionic gonadotropin production by a human hepatoma cell line (FOCUS): isolation and immunochemical characterization.

We have established a human hepatocellular carcinoma cell line designed FOCUS that produces and secretes the beta-subunit of hCG. In the study of beta hCG production by FOCUS cells, we have developed and employed a series of monoclonal immunoradiometric assays (IRMAs) that detect epitopes unique to beta hCG, alpha hCG, hCG, and sequence-specific regions of the carboxyl-terminal peptide of beta hCG. The cells secrete approximately 15 ng beta hCG/10(6) cells and per 24 h; however, we were unable to detect either hCG or the alpha-subunit. The ectopic beta hCG was subsequently affinity purified from the culture medium and partially characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The mol wt of ectopic beta hCG was approximately 35,000 daltons. Immunochemical analysis of ectopic beta hCG by sequence-specific monoclonal antibodies revealed that epitopes corresponding to amino acid sequences 109-115, 121-145, 134-140, and 139-145 of the carboxyl-terminal peptide were present. FOCUS cells also demonstrate an intracytoplasmic localization of beta hCG by immunoperoxidase-staining techniques. Taken together, these findings suggest that FOCUS cells produce and secrete only beta hCG and that thus far, its physical properties appear indistinguishable from those of the native subunit. This unique cell line will be useful to study beta hCG gene(s) regulation as well as the mechanisms of ectopic beta hCG production and secretion.

Antibodies, Monoclonal↗
PubMed1987

Two-phase pulsatile flows through porous conical tubes of small diameters. Modelisation of the blood microcirculation.

A theoretical study concerning two-component fluid pulsating flow through porous conical ducts is presented. The model corresponds to blood flows through small diameter porous conical vessels. This approach is based on a finite difference method. The physical hypothesis used were based on findings from simultaneous visualization methods. The influence of geometrical, hydrodynamical and structural parameters is systematically examined and related to velocity profiles, hydrostatic pressure.

Blood Flow Velocity↗
PubMed1986

Evaluation of protocols for purification of mouse monoclonal antibodies. Yield and purity in two-dimensional gel electrophoresis.

Protocols for purification of mouse monoclonal antibodies (MAbs) from nude mice ascites were investigated in order to assess the yield and to compare the purified products in two-dimensional gel electrophoresis (2DGE). Three MAbs (one IgG2 and two IgG1), selected for their differing behaviours towards protein A, were purified by ammonium sulphate precipitation and/or gel filtration, anion exchange (DEAE), hydroxylapatite and affinity (protein A) chromatography, or by a combination of these methods. Protein A constantly provided the highest purity whatever the IgG subclass. The best results in terms of yields and purity were a function of the optimization of the protein A protocol. In our study, they were obtained in a 3 h protocol (IgG2), a 16 h protocol with discontinuous pH gradient method (IgG1 with sufficiently high affinity for protein A) or a multi-step protocol involving DEAE and protein A (IgG1 with low affinity for protein A). DEAE chromatography alone provided a slightly better yield, but only moderate purity. Hydroxylapatite chromatography appeared to be less potent in terms of yield, purity and day-to-day reproducibility. Salt precipitation and gel filtration enabled only relative enrichment of the MAb solution. Some degradation products of both heavy and light chains clearly appeared in the 2DGE patterns of antibodies purified by different protocols, and seem to be partly related to the elution pH and to the duration of the purification procedure. Finally, this work highlights considerable heterogeneity not only between two different MAbs of the IgG1 subclass but also within a monoclonal population of immunoglobulins.

Ammonium Sulfate↗
PubMed1986

Radioiodination of human calcitonin using the Iodogen reagent.

A method is described for the radioiodination of human calcitonin using the Iodogen reagent. The tracer was purified by 2 successive gel filtrations. The first, using Sephadex G-10, resulted in the complete removal of free 125iodide as assessed by ascending paper chromatography. The second, involving Sephadex G-75, permitted the separation of the tracer from high molecular weight aggregates. Analytical RP-HPLC showed a slight proportion (13%) of a contaminating product, probably (sulfoxyl-methionine9)calcitonin. The final yield, after radioiodination, was found to be 42.7 +/- 5.5% and the tracer displayed a specific activity of 850 +/- 110 Ci/mmol. The effects of long-term storage of the frozen tracer were studied.

Calcitonin↗
PubMed1986

Blood flow through a stenosis in microcirculation.

A theoretical and experimental study concerning two-component fluid pulsating flow through cylindrical ducts having a slight constriction is presented. The model corresponds to blood flows through small diameter vessels (smaller than 400 micron) affected by a singular stenosis. The theoretical approach is based on a asymptotical expansion of the stream function. The physical hypotheses used were based on findings from simultaneous visualization methods. The influence of geometrical, hydrodynamical and structural parameters is systematically examined and related to velocity profiles, hydrostatic pressure, surface stresses.

Blood Flow Velocity↗
PubMed1984

A monoclonal antibody against a synthetic peptide is specific for the free native human chorionic gonadotropin beta-subunit.

A totally synthetic molecule (109-145 peptide) analogous to the beta-subunit carboxyl terminus was used as an antigen in the development of antibodies by the hybridoma technique. A monoclonal antibody (702 D7) specifically recognized the free native beta-human CG (beta hCG). 702 D7 was of the immunoglobulin G1 subclass and was directed against an antigenic site localized in a 10-amino acid sequence (109-118) or less. The recognition of an epitope located in the 109-118 region could explain the specific recognition of beta hCG observed with 702 D7, in contrast to monoclonal antibodies directed against a 118-145 region with a recognition of both beta hCG and whole hCG, as observed with a second monoclonal antibody (1032) to synthetic peptide. Immunohistochemical results and preliminary data obtained from the immunoradiometric assay show that 702 D7 provides a clinical tool for the detection of free beta-subunit secretion even at low concentrations, and could allow the study of this subunit or its metabolites produced by normal and tumoral cells.

Animals↗
PubMed1984

In vitro blood flows through small tubes.

This text recalls the main sequences of a videofilm in which we have looked at the blood flow through small diameter tubes, varying from 200 to 500 micron diameter, using a video equipment where the camera is fixed to a phase contrast microscope. Flows of two fluid model through converging-diverging small tubes have been studied both theoretically and experimentally, where we have considered the influence of tube diameter, stenosis, flow rate, haematocrit upon the red blood cells repartitions and the thickness of peripheral plasma layer.

Blood Flow Velocity↗
PubMed1984

[Monoclonal antibodies directed against the beta hCG subunit and against a synthetic peptide analog of the carboxyl-terminal end. Clinical use in vivo and in vitro].

In order to detect specifically the beta-hCG, we have produced monoclonal antibodies (Mabs), using as immunogens hCG, beta hCG or a totally synthetic molecule (109-145 peptide) analogous to the beta-subunit carboxyl terminus. 34 fusion experiments were performed and led to 8 Mabs which presented a high reactivity to 125I beta hCG in the screening test. Mab D1E8 was directed to the 1-115 region of beta hCG and was cross reactive with hLH (greater than 60%). Mabs 702, 1032, and 1211 were directed against three different epitopes located in the 109-145 region and were specific for the beta hCG. The in vivo localization of tumors containing beta hCG ty tomoscintigraphy (SPECT) was evaluated in 5 patients by injecting 131I-Mab D1E8, selected for imaging because of its high affinity to beta hCG (Ka = 1.9 X 10(9)). SPECT was performed 48 h and 96 h after injection: 2 patients with proven tumor sites had positive "immunoscintigraphy" results. One patient, simultaneously injected with 125I non-specific IgG, had a tumor resection: the count ratio between normal and tumoral tissues revealed a low specific uptake. Two and three-site immunoradiometric assays (IRMA) were performed with monoclonal antibodies purified from nude mice ascitic fluids. IRMA were based upon two or three Mabs, with D1E8 on a solid phase and 125I Mab 702 or a mixing of 125I-702 and 125I-1032 as tracer. The specificity of IRMA was demonstrated by the absence of binding with increasing amount of hLH, hFSH and hTSH up to 5000 ng/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1984

Immunoscintigraphy in human squamous lung cancer using monoclonal antibodies.

We describe immunoscintigraphy using a radiolabelled anti-tumor monoclonal antibody 181-23 in 6 patients with squamous lung cancer. Double-label method using simultaneous injections of 131I MAB and 125I control immunoglobulin was performed to evaluate the specificity of MAB localization in the tumor. Immunohistological localization of MAB in resected specimen was obtained by immunoperoxidase technique. All our data are negative but correlated.

Aged↗
PubMed1983

Catechol-O-methyltransferase activity and aminergic binding sites distribution in human peripheral blood lymphocyte subpopulations.

We have studied the binding of [3H]dihydroalprenolol, a beta-adrenergic ligand, and [3H]spiroperidol, a dopaminergic ligand, to human peripheral blood lymphocyte subpopulations. The catechol-O-methyltransferase activity on these different cells was also determined. On intact living cells, an unequal distribution of both beta-adrenergic and dopaminergic binding sites was found between B- and T-lymphocyte subpopulations. In each binding, T cells exhibited a lower number of binding sites than B cells. On particulate preparation, catechol-O-methyltransferase activity showed a similar distribution, but binding data with such material were quite different. Although it was not possible to detect dopaminergic binding sites on particulate preparation, T and B lymphocytes contained equivalent numbers of beta-adrenergic binding sites. Different explanations for these results are proposed.

B-Lymphocytes↗