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Biomedical subjects

J C Venter

Publications and source records attributed to J C Venter.

At least 145 records · Page 8Linked to original sources
PubMed1981

Autonomic abnormalities and autoantibodies to beta-adrenergic receptors.

We identified autoantibodies to beta 2-adrenergic receptors in the plasma of three apparently normal subjects, four patients with allergic asthma, one subject who was "preallergic" (at risk of allergy), and one patient with cystic fibrosis. Although these antibodies appeared to be heterogeneous, they shared the ability to affect binding of [125]protein A to calf-lung membranes, to inhibit beta-adrenergic ligand binding to calf-lung bet-adrenergic receptors, and to precipitate solubilized calf-lung beta-adrenergic receptors in an indirect immunoprecipitation assay. The presence of autoantibodies to beta-adrenergic receptors in these subjects correlates with abnormal autonomic responsiveness characterized by alpha-adrenergic and cholinergic hypersensitivity and beta-adrenergic hyposensitivity. These findings suggest that autoantibodies to beta-adrenergic receptors may play a part in the development of ment of autonomic abnormalities.

Adult↗
PubMed1980

Reconstitution of turkey erythrocyte beta-adrenergic receptors into human erythrocyte acceptor membranes. Demonstration of guanine nucleotide regulation of agonist affinity.

Digitonin-solubilized turkey erythrocyte beta-adrenergic receptors were reconstituted by dialysis into human erythrocyte acceptor membranes which lack beta receptors. Incorporation of turkey beta receptors into acceptor membranes was directly proportional to the quantity of soluble protein added to the reconstitution system. Reconstituted beta receptors demonstrate saturable [125I]iodohydroxybenzylpindolol binding (Bmax = 11.1 +/- 0.8 fmol/mg, K = 77.8 +/- 8.6 pM) and stereospecificity ((-)-propranolol, K = 11.0 nM; (+)-propranolol, K = 2000 nM; (-)-isoproterenol, K = 250 nM; (+)-isoproterenol, K = 82 micro M). Reconstituted beta receptors appear to be incorporated into acceptor membranes as integral proteins. Reconstituted beta receptors cannot be extracted by high salt or pH (3 to 11); detergent is required for resolubilization of reconstituted beta receptors. Adenylate cyclase stimulation was not obtained in reconstituted membranes since acceptor membranes lack a catalytic subunit. However, guanine nucleotide regulation of agonist affinity was observed indicating a functional reconstitution. GTP (100 micro M) produces a 5-fold decrease in the affinity of isoproterenol for reconstituted beta receptors. Experiments with sulfhydryl reagents indicate that the reconstituted beta receptor couples with the guanine nucleotide regulatory protein of the acceptor membranes. These data describe the successful reconstitution of a beta receptor and indicate that the reconstituted beta receptor can interact with the GTP binding protein of human erythrocyte acceptor membranes.

Animals↗
PubMed1980

Autoantibodies to beta 2-adrenergic receptors: a possible cause of adrenergic hyporesponsiveness in allergic rhinitis and asthma.

Autoantibodies to beta 2-adrenergic receptors have been identified in the serum of one patient with allergic rhinitis ("hay fever") and two patients with asthma. The antibodies precipitate solubilized dog lung beta receptors in an indirect immunoprecipitation assay and inhibit the specific binding of iodine-125-labeled iodohydroxybenzylpindolol to membrane-associated receptors from dog lung, calf lung, and human placenta. Ligand binding to canine heart beta 1 receptors is not affected by the antibodies.

Asthma↗
PubMed1980

Monoclonal antibodies to beta-adrenergic receptors: use in purification and molecular characterization of beta receptors.

We have developed four hybridomas that produce monoclonal antibodies to the turkey erythrocyte beta 1-adrenergic receptor and one hybridoma that produces a monoclonal antibody to the calf lung beta 2 receptor. Splenic lymphocytes from BALB/c mice immunized with partially purified turkey erythrocyte beta 1 receptors or calf lung beta 2 receptors were used with the mouse myeloma line SP2/O-Ag14 to yield hybridoma cultures producing beta receptor monoclonal antibodies of the IgG class. The anti-turkey erythrocyte beta receptor antibodies precipitated partially purified beta receptors and inhibited adrenergic ligand binding. In contrast to autoantibodies to beta 2-adrenergic receptors [Venter, J. C., Fraser, C. M. & Harrison, L. C. (1980) Science 207, 1361-1363] which do not crossreact with cardiac beta 1 receptors, monoclonal antibody FV-104 directed against the adrenergic ligand binding site of turkey erythrocyte beta receptors crossreacted equally with calf liver and lung beta 2 receptors as well as calf heart beta 1 receptors. These data suggest that some molecular homology exists between beta-adrenergic receptors of substantially diverse pharmacological classes. We utilized the monoclonal antibodies in the final stage of turkey erythrocyte beta 1 receptor purification. Turkey erythrocyte beta receptors eluted from FV-104 monoclonal antibody affinity columns with Na-DodSO4 appeared as three components of Mr 70,000, 31,000, and 22,000 on NaDodSO4/polyacrylamide gels. Iodination of material eluted from immunoaffinity columns with propranolol demonstrated the existence of only a single component (Mr, 70,000), indicating that the turkey erythrocyte beta 1 receptor can be purified to homogeneity.

Animals↗
PubMed1976

Biological activity of catecholamines covalently linked to synthetic polymers: proof of immobilized drug theory.

l-Isoproterenol was covalently coupled via an azo linkage to soluble copolypeptides of molecular weight 1500 and 10,000 containing an aromatic amine. The polymeric azo-isoproterenol derivatives were purified by gel chromatography which reduced contamination by the parent isoproterenol to undetectable levels (i.e., less than 0.01%) and by 6-aminoisoproterenol to less than 0.4%. Both polymeric isoproterenol derivatives were found to elicit positive chronotropic responses in isolated perfused guinea pig hearts. The mean effective doses (ED50S) for the 1500 and 10,000 molecular weight derivatives were within 1.3 and 2.0 orders of magnitude, respectively, of the ED50 of l-isoproterenol. The responses cannot be attributed to free isoproterenol because this drug could not be detected in our preparations. Neither can the observed biological activity be attributed to 6-aminoisoproterenol, since this compound's dose-response is shifted 3 orders of magnitude to the right of l-isoproterenol and 1-2 orders of magnitude to the right of the polymeric derivatives. Inotropic response decay times in isolated cat papillary muscles following washouts indicate that the polymer-bound drug does not diffuse into the muscle tissues. We feel that our findings demonstrate that under controlled conditions the catecholamines can retain biological activity while covalently bound to a polymeric support.

Animals↗
PubMed1976

Hormone and neurotransmitter receptors in an established vascular endothelial cell line.

A cell line from the intima of the rabbit aorta has been established. This cell line exhibits strict contact inhibition, and morphologically resembles intimal endothelial cells. B-type blood group antigens and the presence of fibrinolytic activity also distinguish these cells from smooth muscle cells and from fibroblasts of the aortic wall. Endothelial cells were assayed for changes in levels of adenosine 3':5'-cyclic monophosphate (cAMP) and guanosine 3':5'-cyclic monophosphate (cGMP) in response to a series of vasoactive drugs. Control levels for cAMP and cGMP are 7.01 +/- 0.82 and 1.50 +/- 0.06, respectively (mean +/- SEM). Norepinephrine, acetylcholine, 5-hydroxytryptamine, and phenylephrine increased the levels of both nucleotides significantly. Propranolol (10-5 M) and phentolamine (10-5M) inhibited, respectively, the cAMP and cGMP response to norepinephrine. Angiotensin II and histamine significantly increased cGMP levels but not cAMP levels of the endothelial cells. The cGMP increases with acetylcholine were inhibited by atropine. These results indicate that the established cell line is endothelial in nature and contains cellular receptors to a variety of vasoactive agents.

ABO Blood-Group System↗
PubMed1976

Affinity isolation of cultured tumor cells by means of drugs and hormones covalently bound to glass and Sepharose beads.

Isoproterenol, corticotropin (ACTH), and triodothyronine immobilized on glass and Sepharose beads by diazotization procedures have been shown to interact with cultured tumor cells of "target tissue" origin. Cells used were rat glioma cells (C6), rat adrenal tumor cells (Y-1), and rat pituitary tumor cells (GH3). The rat glioma cells bound principally to immobilized isoproterenol, whereas the rat adrenal tumor cells bound to immobilized corticotropin, and rat pituitary tumor cells bound to immobilized triiodothyronine. Binding was inhibited by preincubation of the cells in soluble drug or hormone. With C6 cells there was a positive correlation between adenylate cyclase [ATP pyrophosphate-lyase (cyclizing, EC 4.6.1.1] stimulation and the degree of binding to the immobilized isoproterenol. Norepinephrine, bound through the ethanolamine side chain via an amide linkage, did not bind cells, demonstrating specific structural requirements for drug-cell interactions. HeLa cells were shown to bind tightly to diphtheria toxin coupled to Sepharose beads via an amide bond. This binding was inhibited by prior incubation of the Sepharose toxin with purified antitoxin. Toxin bound to Sepharose via an azo bond did not bind cells. These data suggest that the cell affinities are due to cell surface receptors interacting with the immobilized drugs and hormones, and that the observed affinities possibly reflect the relative receptor complement of these cells.

Adrenal Gland Neoplasms↗