Search PubMed⌕ Search

Biomedical subjects

C Bohuon

Publications and source records attributed to C Bohuon.

At least 19 recordsLinked to original sources
PubMed1992

Immune modification due to chemical interference with transmembrane signalling: application to polycyclic aromatic hydrocarbons.

Triggering of the T-cell antigen receptor complex and some other surface molecules is coupled to the phosphodiesterase (phospholipase C)-mediated hydrolysis of membrane phosphoinositides, in particular, phosphatidylinositol-4,5-biphosphate (PiP2). PiP2 hydrolysis generates two products, inositol 1,4,5-triphosphate and diacylglycerol, which act in concert as second messengers to increase the free intracellular calcium concentration and activate protein kinase C, respectively, thereby stimulating subsequent events leading to cellular activation and proliferation. Transmembrane signalling in T-lymphocytes represents a potential target for designated drugs as well as immunotoxicants. Immunotoxic effects of polycyclic aromatic hydrocarbons are discussed in the view of interaction with transmembrane signalling in the T-lymphocyte.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1992

Brain and adrenal monoamines and neuropeptide Y in codeine tolerant rats.

1. Monoamine turnover and neuropeptide Y (NPY) levels were investigated in the central and peripheral nervous systems in adult male rats chronically treated with codeine. 2. An increase in the dopaminergic turnover was observed in the striatum and cortex. The norepinephrine levels and the serotoninergic turnover were unchanged in all the brain areas. 3. Epinephrine levels were decreased in the adrenal glands. 4. In addition, we observed a significant decrease of NPY levels in the hypothalamus, the striatum and the adrenal glands. These observed changes were not found when assessing NPY level in plasma fluid. 5. The implication of these modifications in the induction of codeine dependence are discussed in view of previous results obtained with morphine.

Adrenal Glands↗
PubMed1992

Production and characterization of four anti-neuropeptide Y monoclonal antibodies.

Human neuropeptide Y (hNPY) is a potent vasoconstrictor peptide of 36 aminoacid residues. We isolated hybridomas secreting four monoclonal antibodies directed against various epitopes of neuropeptide Y and studied their cross-reactivity with peptide YY (PYY) and the pancreatic polypeptide (PP), two peptides sharing sequence homologies with hNPY (respectively 70% and 50%). The antibody NPY02 is an IgG1 with a Ka of 5.5 x 10(10) liters/mol. It binds to the 11-24 region of NPY (IC50 = 2 x 10(-7)M), does not recognize PP but cross-reacts weakly with PYY. Antibodies NPY03 and NPY05 are IgG2 with respective Ka's of 6.7 x 10(9) and 2.5 x 10(10) liters/mol. They interact with a C-terminal epitope on NPY (NPY 27-34, IC50 = 2 x 10(-9) M for NPY03 and NPY 32-36, IC50 = 1 x 10(-9) M for NPY05). These two antibodies cross-react with PYY whereas only NPY05 binds PP. NPY05 is unable to bind the free acid form of neuropeptide Y. The 32-36 COOH free subpeptide is recognized 50,000 less efficiently by NPY05 than its amidated form. Antibody NPY04 is an IgG3 with a Ka of 3.8 x 10(8) liters/mol. It recognizes a N-terminal epitope between aminoacids 1 and 12 (IC50 = 2.5 x 10(-6) M). NPY04 interacts weakly with PYY but not detectably with PP. These results obtained with 4 different monoclonal antibodies demonstrate the presence of at least four epitopes on hNPY, two of them being continuous. These antibodies will be used to study the interaction of NPY with its receptor and to develop sensitive and specific assays for determination of NPY concentrations in biological fluids.

Amino Acid Sequence↗
PubMed1992

Relationship among neuropeptide Y, catecholamines and haemodynamics in congestive heart failure.

The relationship among neuropeptide Y (NPY), catecholamines and haemodynamics was assessed both at baseline and during inotropic intervention in patients with congestive heart failure. Eighteen patients with idiopathic dilated cardiomyopathy (left ventricular ejection fraction (LVEF) = 26 +/- 10%) underwent both right and left catheterization. Haemodynamic parameters were recorded at baseline and during dobutamine infusion. To measure norepinephrine (NE), epinephrine (E) (nmol.l-1: radioenzymatic assay) and NPY (pmol.l-1: immunoradiometric assay) plasma concentrations, blood samples were drawn from the femoral artery and from the coronary sinus, both at baseline and during dobutamine infusion. At baseline, NPY concentration were 2.15 +/- 0.97 pmol.l-1 in the femoral artery and 1.97 +/- 0.63 pmol.l-1 in the coronary sinus. Peripheral concentrations of NPY were, however, no different from those of patients without congestive heart failure: 2.4 +/- 2.7 pmol.l-1. Peripheral NE concentration was correlated to haemodynamic parameters: LVEF (r = -0.65; P less than 0.01), cardiac index (r = -0.54; P less than 0.05), LV end-diastolic pressure (r = +0.59; P less than 0.05), while peripheral NPY and E concentrations were not. Dobutamine improved haemodynamics, since cardiac index increased by 30% and LV end-diastolic pressure decreased by 40% (P less than 0.01). Peripheral NE concentration decreased from 6.48 +/- 4.5 to 4.82 +/- 2.69 nmol.l-1 (P less than 0.05) but there was no change in E (0.99 +/- 0.61 vs 1.04 +/- 0.74 nmol.l-1) or NPY concentrations (2.41 +/- 0.99 pmol.l-1). In the coronary sinus, neither NE nor NPY concentrations changed during dobutamine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Activity and specificity of a mouse monoclonal antibody to ferric aerobactin.

We isolated a monoclonal antibody directed against the ferric complex of aerobactin purified from Escherichia coli KH576. This antibody, which we designated MAb AERO1, was identified as an immunoglobulin G, subtype 2. A competitive enzyme-linked immunosorbent assay with MAb AERO1 had a limit of 10 nM for the detection of purified ferric aerobactin and allowed detection of the crude aerobactin produced by various members of the family Enterobacteriaceae isolated from cancer patients with bacteremia. The only two other structurally related siderophores recognized by MAb AERO1 were ferric arthrobactin and ferrioxamine B. These results suggest that the epitope recognized by MAb AERO1 was the lysyl moiety of ferric aerobactin. We also showed that MAb AERO1 reduced the growth of an aerobactin-producing strain of E. coli in newborn calf serum, which indicates that it might be effective in reducing the severity of infections caused by bacteria for which the production of aerobactin is an important virulence factor.

Animals↗
PubMed1992

[Stomach adenocarcinomas: comparison between CA 19-9 and carcinoembryonic antigen for the diagnosis of recurrences after surgical treatment].

The aim of this study was to compare carcinoembryonic antigen (CEA) and CA19-9 for the detection of local recurrences and distant metastases after complete resection of gastric carcinoma. At least one postoperative measurement of CEA and CA19-9 was performed in 54 patients. Among these, 32 had recurrence (59%) with a median follow-up of 618 days. Significantly higher sensitivity was observed for CA19-9 in comparison with CEA (68.8% vs 38.2% respectively), but specificity was slightly lower (81.8% vs 95.6% respectively). Increased CEA plasma level never preceded the diagnosis of recurrence while increasing CA19-9 preceded diagnosis in 13 patients (40.6%) from 1 to 22 months (median = 4.5 months). Increasing the normal range of CA19-9 to 80 UI/mL (2.5 x N) raises the specificity to 100% with acceptable sensitivity (53.1%). This study shows that CA19-9, compare with CEA, allows diagnosis of recurrence more often and earlier in the follow-up of resected gastric cancer.

Adenocarcinoma↗
PubMed1992

Effects of chloral, chloralose and pentobarbitone on monoamine and (neuropeptide Y) NPY levels in various tissues in the rat.

Sampling of blood or tissues in experimental animals need frequently a general anesthesia. Some anesthetic agents are known to modify plasma levels of catecholamines; moreover NPY is co-released with noradrenaline or adrenaline under certain conditions. Thus, we investigated the effect of three general anesthetic agents, chloral, chloralose and pentobarbital (pentobarbitone) on the levels of monoamines and NPY in rat hypothalamus, medulla, atria and adrenals. Monoamines were analysed by high pressure liquid chromatography using an electrochemical detection and NPY was measured by radioimmunoassay (immunoradiometric assay, IRMA). Chloralose or pentobarbitone did not affect monoamine tissue levels. In contrast, chloral increased 5-hydroxyindolacetic acid and to a lesser extent serotonin levels in the hypothalamus. NPY tissue levels did not change whatever the anesthetic used. These results must be taken into account in pharmacological or toxicological studies which need the use of a general anesthesia.

Adrenal Glands↗
PubMed1991

Characterization of two monoclonal antibodies against the COOH-terminal part of the human epidermal growth factor receptor and potential clinical use.

Two monoclonal antibodies of the IgG2 subclass, designated A 01 and B 11, were prepared against two synthetic peptides corresponding to the COOH-terminal sequence of the human epidermal growth factor receptor (EGF-R), in order to detect EGF-R in a radioimmunometric assay and by immunohistochemistry. Characterization of these Mabs showed that they recognized two different eptiopes on the original peptides with Kd of 1.7 x 10(-8) M and 1.3 x 10(-7) M, respectively, without crossreaction. The A 431 antigen recognized by A 01 and B 11 had an apparent molecular weight of approximately 170,000 and was able to specifically link to EGF. Thus, A 01 and B 11 are directed against an antigenic site on the human EGF-R. With Western blot analysis and immunostaining, A 01 was shown to be EGF-R specific. In addition to the EGF-R, B 11 recognized two unidentified soluble proteins present in the cytoplasm of the SKBR-3 cell line but different from the c-erb B-2 oncoprotein expressed by these cells. Mabs A 01 and B 11 were used in an IRMA for the determination of EGF-R using the A 431 cell line as a source of EGF-R. Mab A 01 was also shown to be a useful tool for immunohistochemical detection of EGF-R.

Amino Acid Sequence↗
PubMed1991

Antigenic properties associated with Vinca alkaloid resistance in ovarian cancer cells: identification of a 92,000 Da protein.

In order to characterize the membrane changes related to Vinca alkaloid resistance, we raised monoclonal antibodies (mAbs) against a Vincristine resistant subline (OV1/VCR) derived from a human ovarian adenocarcinoma cell line (OV1/p). Among three monoclonal antibodies selected for a higher binding to OV1/VCR than to OV1/p cells, one designated OVR09, recognized a Mr 92,000 protein. This protein appears to be gradually overexpressed along the drug resistance establishment in vitro, and to decrease slowly in absence of drug. Further, mAb OVR09 showed a much higher binding to the vinblastine resistant epidermoid tumor cell line KbV1 than to its parental counterpart. The Mr 92,000 protein was also detected in various tumor cell lines and in an ovarian carcinoma surgical sample.

Animals↗
PubMed1991

Immunochemical mapping of antigenic regions on the human thyrotropin beta-subunit by antipeptide antibodies.

To study antigenic sites present in the beta-subunit of human thyrotropin (hTSH), we produced site-specific antibodies directed against synthetic peptides analogous to the 1-18, 44-59, and 85-112 regions of the thyrotropin beta-subunit. The hTSH beta(1-18) peptide-carrier conjugate elicited antisera capable of binding to both radiolabeled hTSH and its beta-subunit whereas antibodies elicited against the hTSH beta(44-59) peptide-carrier conjugate bound only to the peptide. Thus, the NH2-terminal region of hTSH beta appears to be accessible at the surface of the hormone whereas the hTSH beta(44-59) region may be poorly accessible. Two monoclonal antipeptide antibodies that bound to 125I-hTSH beta, designated as TS01 and TS02, were selected after immunization with the hTSH beta(85-112) peptide-carrier conjugate. The antigenic site recognized by TS01 was located on the eight COOH-terminal(105-112) amino acid residues. TS02 antibody bound to an antigenic region included within Cys95 and Cys105. Both antigenic sites appeared to be more accessible on the free hTSH beta than on the hormone. Immunoblots performed on various preparations containing TSH revealed that TS02 antibody detected the beta-subunit from both the human and bovine species but not the rat TSH beta. Under reducing conditions, a low molecular weight material was identified in hTSH beta, likely caused by intrachain nicking.

Amino Acid Sequence↗
PubMed1991

The effects of chronic administration of morphine on the levels of brain and adrenal catecholamines and neuropeptide Y in rats.

1. Monoamine turnover and neuropeptide Y (NPY) levels were investigated in the central and peripheral nervous systems in adult male rats chronically treated with morphine. 2. The well-recognized biochemical alterations (serotoninergic turnover increased in the hypothalamus, hippocampus and striatum; dopaminergic turnover increased in the striatum and cortex; adrenaline levels decreased in the adrenal glands) were observed. 3. In addition, we observed a significant decrease of the NPY levels in the hypothalamus, the striatum and the adrenal glands. The observed changes were not reflected in plasma. 4. Our results contribute to the evidence that brain and adrenal monoamines and NPY could be involved in the mechanism of morphine tolerance and/or dependence.

Adrenal Glands↗
PubMed1990

Neuropeptide Y and neuron-specific enolase levels in benign and malignant pheochromocytomas.

Neuron-specific enolase (NSE) is the isoform of enolase, a glycolytic enzyme found in the neuroendocrine system. Neuropeptide Y (NPY) is a peptide recently discovered in the peripheral and central nervous systems. Serum NSE and plasma NPY levels have been reported to be increased in some patients with pheochromocytoma. The authors evaluated whether the measurement of these molecules could help to discriminate between benign and malignant forms of pheochromocytoma. The NSE levels were normal in all patients with benign pheochromocytoma (n = 13) and elevated in one half of those with malignant pheochromocytoma (n = 13). Plasma NPY levels were on the average significantly higher in the malignant (177.1 +/- 38.9 pmol/l, n = 16) than in the benign forms of the disease (15.7 +/- 389 pmol/l, n = 24). However, there was no difference in the percentage of patients with elevated NPY levels. These results show that determination of serum NSE may be useful for distinguishing between malignant and benign pheochromocytoma; the measurement of plasma NPY is not useful for differentiating the two kinds of tumors.

Adrenal Gland Neoplasms↗
PubMed1990

Changes in hypothalamic neuropeptide Y concentrations induced by cholecystokinin analogues.

Neuropeptide Y (NPY) and cholecystokinin (CCK) are two peptides involved in opposite ways in the control of food intake. A possible interaction between NPY and CCK has not yet been well defined. Two CCK derivatives with agonistic and antagonistic properties were studied with regard to their effects on brain and plasma NPY levels. The CCK agonist decreased NPY levels in plasma and in the hypothalamus but not in the other brain areas assayed. The CCK antagonist reversed the agonist-induced decrease in both plasma and hypothalamus. These results suggest a negative relation between NPY and CCK peptides, which is not surprising given their opposite role in feeding regulation. The hypothalamus, a preferential site of this regulation, appears to be the brain area most involved in the NPY-CCK interaction. The plasma NPY level variations closely reflect the hypothalamic profile, suggesting a direct release of NPY by a mechanism that remains to be investigated.

Animals↗
PubMed1990

Peptide immunogen mimicry of a protein-specific structural epitope on human choriogonadotropin.

It is a challenge to construct synthetic immunogens that elicit antibodies (Abs) both directed to conformational epitopes and specific for a complex protein like human choriogonadotropin (hCG). A monoclonal antibody specific for hCG bound to regions around Lys45 of the alpha subunit (hCG alpha) and Asp112 of the beta subunit (hCG beta). A peptide comprising residues 46 to 55 of hCG alpha and residues 106 to 116 of hCG beta elicited Abs in rabbits that were directed to a discontinuous epitope and were specific for hCG. These Abs inhibited the binding of hCG to its receptor. Thus, a synthetic immunogen can mimic a conformational-specific epitope and can be useful for vaccine development.

Amino Acid Sequence↗
PubMed1990

Changes in brain neuropeptide Y induced by cholecystokinin peptides.

Cholecystokinin (CCK) and neuropeptide Y (NPY) are two peptides with opposite effects on the regulation of feeding behaviour. The possible interaction between these two systems has always been controversial. In this study, rat brain NPY levels were assayed after treatment with CCK 8 S and with a potent CCK agonist (Boc-(Nle 28-Nle 31)-CCK 26-33). CCK 8 S and its agonist analogue (50 micrograms/kg i.p.) both decreased hypothalamic and hippocampal NPY levels. This result suggests a negative relationship between NPY and CCK-peptides which is not surprising given their opposite role in the control of feeding. The hypothalamus and secondarily the hippocampus appear to be the site of this interaction; no change in NPY levels was observed in other brain areas (striatum and cortex). The same pattern of variation was found in the plasma, suggesting a direct release from the brain via a mechanism which remains to be investigated. The effect appeared later with the CCK analogue than with CCK 8 S itself; this is not surprising with regard to other behavioural and biochemical effects of the analogue and provides further characterization of its action.

Animals↗
PubMed1990

Structural probing of human lutropin using antibodies raised against synthetic peptides constructed by classical and multiple antigen peptide system approaches.

Antibodies were elicited against a synthetic peptide which encompassed two different regions of the human lutropin beta-subunit (hLH-beta). These antibodies were raised against either the peptide which was assembled using a conventional approach and conjugated to the tetanus toxoid, or with the peptide assembled using the multiple antigen peptide system approach. Automated simultaneous synthesis of the two forms of the immunizing peptide was successfully achieved. Animal injected with the peptide conjugated to tetanus toxoid produced high titers of antibodies to the synthetic peptide, but did not bind to the native hLH-beta subunit. In contrast, antisera induced by the peptide in its MAP form displayed reactivity with both the peptide and the native hLH-beta subunit; these latter antisera appeared to preferentially recognize the beta 47-55 portion of the molecule and were able to bind to the beta-subunit of human choriogonadotropin. Present results demonstrate that the beta 47-55 region is accessible to antibody binding and appears to be located at the surface of both hLH-beta and hLH. Moreover, this study confirms that the MAP approach provides a chemically unambiguous method for obtaining antibodies of predetermined specificity, capable of recognizing cognate sequences of various native proteins.

Amino Acid Sequence↗