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Biomedical subjects

C Bohuon

Publications and source records attributed to C Bohuon.

At least 109 records · Page 6Linked to original sources
PubMed1986

A radioimmunoassay for the antimalarial drug chloroquine.

We describe a 3H-based RIA for the antimalarial drug chloroquine (CLQ), the most commonly used antimalarial drug. In the assay a monoclonal antibody is used that is directed against 4-amino-7-chloroquinoline conjugated to keyhole limpet hemocyanin by the glutaraldehyde method. Besides CLQ, this antibody also recognizes with good affinity the 4-aminoquinoline homologs, hydroxychloroquine and amodiaquine. No extraction step or sample preparation is required, and the method can detect as little as 10 micrograms/L, the lower concentration in plasma of humans who are taking CLQ as a preventive measure. The between-assay CV is less than or equal to 10%, the within-assay CV less than or equal to 3%. Results correlate with those by liquid chromatography (r2 = 0.96). The speed and simplicity of the RIA method make it useful in evaluating the CLQ concentrations in acutely toxic patients.

Antibodies, Monoclonal↗
PubMed1985

Ellipticine derivatives interact with muscarinic receptors.

Ellipticine derivatives or analogues, tetracyclic alkaloids used in human cancer treatment, have been evaluated with regard to their interaction with several neurotransmitter receptors, in order to explain or to predict the side effects which occur in man. These drugs were recently found to be reversible non-competitive inhibitors of cholinesterases. In this study, we have shown that ellipticines are also potent muscarinic antagonists, only 100-fold less active than atropine in inhibiting 50% of the specific binding of (3H) quinuclidinyl benzilate on rat brain preparation of muscarinic receptors. That the interaction with muscarinic receptors is quite unique has been demonstrated by the lack of interaction with three other neurotransmitter receptors. Tertiary amines show relatively less blockade of muscarinic receptors, while substituted ammonium ions are better inhibitors of the QNB binding. The possible mechanisms of in vivo action of these alkaloids is discussed.

Alkaloids↗
PubMed1985

Proliferative responses of circulating human NK cells: delineation of a unique pathway involving both direct and helper signals.

The present studies were performed to investigate mechanisms of human natural killer (NK) cell activation. NK-active cells were purified out of heterogeneous large granular lymphocytes (LGL)-enriched suspensions using a "pan NK"-specific monoclonal antibody termed anti-NKH1A. It was found that treatment of NKH1A+-sorted cells by T lymphocyte mitogens such as phytohemagglutinin (PHA) or anti-T11(2) plus anti-T11(3) did not induce proliferative responses. In fact, there was no measurable interleukin 2 (IL2) secretion and no significant increase in IL2 susceptibility following incubation with either PHA or anti-T11(2) plus anti-T11(3). However, as opposed to small resting T lymphocytes, NKH1A+ cells moderately proliferated in the presence of IL2. This IL2-dependent proliferation was dramatically increased after interaction between NK-active lymphocytes and certain hematopoietic cell lines such as K562 or EBV-transformed lymphoblastoid cell lines. These studies indicate that unique activation mechanisms can be identified when NK lymphocytes are purified out of LGL-enriched fractions. The NK activation pathway delineated here appears essentially distinct from those described for T lymphocytes. Indeed the nature of the NK cell/inducing cell interaction is unknown and triggering cannot be related, for example, to a conventional allogeneic effect mediated through membrane exposure of class I or class II major histocompatibility complex gene products. Moreover, these interactions do not lead to the development of autocrine responses. Together the present results support the view that direct signals can preactivate NK cells but are not sufficient to trigger proliferation which must therefore be regulated by helper populations.

Antibodies, Monoclonal↗
PubMed1985

Drug-induced antibodies during 2-N-methyl-9-hydroxyellipticinium acetate (NSC-264137) treatment: schedule dependency and relationship to hemolysis.

Drug-dependent antibodies were investigated in patients treated with elliptinium acetate, a cytostatic drug with activity in advanced breast cancer. Retrospective analysis of 83 patients, receiving weekly intravenous elliptinium, showed a high incidence of anti-elliptinium antibodies (20%). Hemolysis occurred among antibody-positive patients, apparently related to the antibody titer. The predictability of anti-elliptinium antibodies for hemolysis and the schedule dependency of antibody development was examined prospectively. Among 42 patients treated weekly for at least three courses, 40% developed antibodies. Of 30 patients receiving elliptinium daily for three days every three weeks, none developed either antibodies or hemolysis. Only antibody positive patients, with titers greater than or equal to 32 were at risk for hemolysis. The possible mechanisms are discussed.

Alkaloids↗
PubMed1985

A target structure for a series of human cloned natural killer cell lines is recognized by both anti-TNKtar and 4F2 monoclonal antibodies.

It was shown recently that a surface antigen termed TNKtar was likely to serve as a target molecule for three distinct human NK clones expressing the same clonotypic determinant (termed NKTa) present on a 90 KD recognition structure. In the present studies, we investigated whether TNKtar and a previously described antigen termed 4F2 were related. Parallel immunoprecipitations from membrane lysates of the same cells showed that both anti-TNKtar and 4F2 Mab precipitate a heterodimeric structure which resolves as two bands of identical m.w. (40 and 80 KD) in SDS-PAGE analysis under reducing conditions. Sequential immunoprecipitations demonstrated that the two antibodies are directed at the same molecule. However, one antibody did not block subsequent binding of the other, and vice versa, suggesting that anti-TNKtar and 4F2 Mab are directed at two distinct epitopes of the molecule. Functionally, it was found that 4F2 Mab was able, as well as anti-TNKtar, to selectively block cytotoxic function of JT9 cloned cells. Furthermore, as reported previously for anti-TNKtar, 4F2 had no effect when additional NKTa-NK clones were used as effector cells in cytotoxicity assays. Finally, cold target inhibition assays were performed by using cold target cells precoated with either anti-TNKtar or 4F2 Mab. These experiments showed that preincubation of target cells with either antibody blocked their ability to compete with their radiolabeled counterpart. Such results further strengthen the hypothesis that the activation antigen recognized by both anti-TNKtar and 4F2 Mab serves as a specific target structure for NKTa+ NK active clones. We discuss the importance of previous data concerning the 4F2 molecule in light of this functional role, which had not been identified previously.

Antibodies, Monoclonal↗
PubMed1984

Benzodiazepine receptors on human blood platelets.

Binding studies conducted on membrane preparation from human platelets using (3H) Ro5-4864 and (3H) diazepam showed specific and saturable binding. Scatchard analysis revealed a single class of binding sites with KD = 10.8 +/- 0.9 nM and Bmax = 775 +/- 105 fmol/mg protein for (3H) Ro5-4864 and KD = 10.5 +/- 1.1 nM and Bmax = 133 +/- 19 fmol/mg for (3H) diazepam. We were unable to detect any GABA binding site on crude membrane preparation, nor did GABA enhance the binding of (3H) Ro5-4864 or (3H) diazepam. This suggests that benzodiazepine receptors are uncoupled to GABA system on human platelets. Ro15-1788, a specific antagonist for "central type" benzodiazepine (BDZ) binding sites was inactive in displacing (3H) Ro5-4864 from membrane receptors, while PK 11195 (a specific ligand for the "peripheral type" receptor) was the most potent of the drugs tested in inhibiting (3H) Ro5-4864 binding. These results indicate that human blood platelets bear "peripheral-type" BDZ receptor. Moreover, we could not detect any (3H) propyl beta carboline specific binding on platelet membranes. Results on benzodiazepine receptors on human circulating lymphocytes are also reported and similarity in pharmacological properties with platelet benzodiazepine receptors is suggested.

Benzodiazepines↗
PubMed1984

In vivo modulation of muscarine receptors in rat brain by acute lead intoxication.

In our experiments on acutely lead exposed rats we observed a marked increase (a 2-fold or 3-fold increase with 30 mg/kg or 60 mg/kg lead acetate, respectively) in [3H]quinuclidinyl benzilate [( 3H]QNB) specific binding to muscarine receptors from striatum and cortex, without any change in receptor affinity. Muscarine receptor level was maximal 2 h after intoxication, but the effect of lead on [3H]QNB binding was completely reversible in 24 h, without any lead redistribution to other brain areas being observed during this time period. Modulation of muscarine receptors in rat brain during in vivo acute intoxication might be involved in some of the observed neurotoxic effects of lead, resulting of an action on cholinergic neurotransmission. The various possible mechanisms of the lead effect on [3H]QNB binding are discussed.

Acute Disease↗
PubMed1984

Immunological and enzymatic studies of erythrocytic delta-aminolevulinate dehydratase. Comparison of results obtained in normal and lead-exposed subjects.

The delta-aminolevulinate dehydratase (ALA.D) quantitative assay on a centrifugal fast analyser showed that subjects whose blood-lead level varies between 30 and 75 micrograms/100 ml (1.5 to 3.75 microM/l) react to blood intoxication by synthesizing de novo an amount of enzyme correlating to blood-lead levels. At higher concentrations, the reactional synthesis occurs very rarely. These results suggest that enzyme is constitutive, but also inductible as soon as its substrate accumulates; this last ability may disappear at high blood-lead levels: a hypothesis is proposed thereafter.

Adult↗
PubMed1984

Serum alpha-fetoprotein levels in human disease: perspective from a highly specific monoclonal radioimmunoassay.

A rapid multisite radioimmunoassay for measurement of human alpha-fetoprotein (AFP) that uses two high-affinity monoclonal antibodies directed against distinct and separate determinants on the protein was developed and designated M-RIA. The sensitivity of the "simultaneous-sandwich" M-RIA is approximately equal to 0.5 ng/ml of serum after a 1-hr incubation period. Serum AFP levels have been measured in 1747 individuals with hepatocellular carcinoma (HCC), acute and chronic hepatitis B virus infection, chronic hepatitis B surface antigen (HBsAg)-carrier states, cirrhosis, other malignant tumors, and normal and disease controls to determine the specificity of the assay. Eighty percent (68/85) of patients with HBsAg-positive HCC had AFP levels of greater than 200 ng/ml (range, 260 to greater than 200,000 ng/ml). In contrast, all 450 normal subjects and 477 chronic HBsAg-positive carriers had levels of less than 20 ng/ml. More importantly, in acute and chronic hepatitis B, cirrhosis, and other malignant tumors and in the remaining disease controls, AFP levels were less than 20 ng/ml in 99.3% of the subjects, the great majority (greater than 96%) being less than 5 ng/ml. Indeed only two of 1635 individuals, one with acute hepatitis and the other with carcinoma of the esophagus had AFP levels of greater than 100 ng/ml. These observations are at variance with previous studies with conventional polyvalent RIAs of AFP levels of greater than 20 ng/ml in approximately equal to 40% of acute and chronic hepatitis and in 30% of cirrhosis. This striking specificity of the M-RIA is probably due in part to recognition of epitopes unique to AFP and suggest that such an assay may be used in the detection, early identification, and monitoring of AFP-producing tumors in high-risk populations.

Antibodies, Monoclonal↗
PubMed1984

Two-dimensional electrophoretic analysis of cytosols from human breast tumors: optimal migration conditions.

In an examination of cytosols from human breast tumors, we performed two-dimensional electrophoretic analysis. Several migration conditions were tried in a search for a homogeneous repartition of cytosolic proteins. The most workable gels were obtained with a 4.40 to 8.05 pH gradient in the first dimension and a homogeneous 125 g/L acrylamide/sodium dodecyl sulfate gel, 1 mm in thickness, in the second dimension. The practicability of this method is discussed.

Breast Neoplasms↗
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

Characterization of a peripheral-type benzodiazepine binding site on human circulating lymphocytes.

Binding studies conducted with [3H]Ro 5-4864, a specific ligand for peripheral-type benzodiazepine receptors, on circulating lymphocytes from 5 normal volunteers provided evidence for a single, saturable (Bmax 12.2 +/- 3.6 fmol/10(6) cells), and high affinity (KD 7.1 +/- 2.0 nM) specific binding site. We were unable to detect any GABA receptor, suggesting that human lymphocytes bear a peripheral-type benzodiazepine binding site not coupled with the GABA system. Results on lymphocytes from chronic lymphocytic leukemics are also reported.

Adult↗
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↗
PubMed1983

Production and in vitro utilization of monoclonal antibodies to human thyroglobulin.

Human thyroglobulin (Tg) was used as an antigen in the development of antibodies by the hybridoma technique. From four antibodies that bound more than 40% labeled Tg, two were characterized (182/E4 and 211/A5). They were both of the immunoglobulin G 2ab subclass, and provided an affinity constants (Ka) of 1.2 X 10(10) and 7.7 X 10(9) mol-1, respectively. The specificity of these antibodies was demonstrated by the absence of cross-reaction by monoiodothyronine, diiodothyronine, T3, T4, and sialic acid. A RIA was developed with 182/E4 or 211/A5, and the least detectable dose, based on the standard curve, was 10 ng/ml. The immunoreactivities of 182/E4 and 211/A5 to four Tg preparations different in iodine content appeared to be identical. Histochemical staining was used on normal and neoplastic tissues with both antibodies. Positive reactions were obtained in both cells and colloid, with heterogeneous staining from one follicle to another. Papillary carcinoma showed numerous positive cells, in contrast with Hürtle cell tumors which displayed very few positive cells. Anaplasic giant and spindle cells were negative. Monoclonal antibodies to human Tg are useful for in vitro detection of Tg.

Animals↗
PubMed1983

Muscarinic cholinergic receptors on circulating human lymphocytes: evidence for a particulate binding site.

Lymphocytes from thirteen normal volunteers were investigated for their muscarinic cholinergic receptors content. A particular binding site was characterized with 3H-quinuclidinyl benzilate; saturation binding occurred at 80 X 10(-9)M and scatchard analysis provided a dissociation constant of 40 X 10(-9)M. These results showed that there were about 4000 muscarinic receptors on human lymphocyte. Although, it is possible to demonstrate the presence of binding site on a particulate preparation, the significance of such low-affinity receptor is yet unclear.

Adult↗