Biomedical subjects
Publications and source records attributed to A Sobel.
Explore the source record for details and available documents.
Hereditary angioedema (HANE) is a rare, life-threatening disease due to the deficiency of C1 inhibitor (C1 Inh). Androgen therapy has been recently shown to be effective for prophylaxis of Hane attacks. Since life-long androgen therapy may be hazardous, this study was designed to define the minimal doses required for effectiveness. Ten patients from six different families were treated during cumulative 73 months by danazol and/for methandrostenolone. One tablet/day of either drug was the minimal requirement to prevent any attack in all patients. When 3 tablets/day were given, complement abnormalities were simultaneously rapidly reversed. When 1 tablet/day was given the biological effect was barely detectable, except for C2. Serum C2 levels may, therefore, represent the best criteria of androgen therapy effectiveness. Thus, an excellent clinical result can be obtained with much lower doses of androgens than previously stated. This result seemed important with respect to the serious dose-dependent risk of androgens.
Highly purified subsynaptic membrane fragments prepared from Torpedo marmorata electric organ (specific activity, greater than 4 mumol of Naja nigricollis alpha-[3H]toxin per mg of protein) exhibit, on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, two major protein bands of apparent molecular weight 40,000 and 43,000, respectively. Dissolution of these membranes by the nondenaturing detergents Triton X-100 and Berol 043 followed by standard fractionation yielded (i) the 9S acetylcholine-receptor protein which still binds the alpha-[3H]toxin and after further purification yielded, in the presence of sodium dodecyl sulfate, the 40,000-dalton component, covalently labeled by the affinity reagent 4-(N-maleimido)phenyl[3H]trimethylammonium; only serine was found as the NH2-terminal amino acid of this protein; and (ii) a high molecular weight aggregate named 43,000 protein which was resolved in denaturing gels almost exclusively as the 43,000-dalton band, In the absence of detergents, the 43,000 protein binds compounds known to interact with the acetylcholine ionophore: a fluorescent local anesthetic quinacrine and histrionicotoxin (apparent dissociation constant, 7 +/- 1 X 10(-7) M). The regulation of quinacrine fluorescennce by carbamylcholine, observed in the intact membrane, no longer occurs with the isolated 43,000 component.
Membrane fragments rich in cholinergic (nicotinic) receptor protein were purified from the electric organ of Torpedo marmorata. Their lipid composition is essentially characterized by the prominence of cholesterol, phosphatidylethanolamine and phosphatidylcholine, long-chain fatty acyl constituents, and the absence of sphingomyelin. Solubilised receptor was purified from these fragments and the concentration of sodium cholate lowered by dialysis to 0.01% (w/v). When this preparation was injected under a lipid monolayer, an increase of surface pressure developed, which was not observed with the detergent alone nor in the absence of lipid film. When covalently radiolabelled receptor preparations were injected at a constant surface pressure the radioactivity recovered with the film was proportional to the increase in area. It is concluded that the pressure or area increases are due to the penetration of the cholinergic receptor protein into the lipid film. Incorporation experiments into films formed from various pure lipids showed that the protein interacts more readily with cholesterol than with ergosterol, phosphatidylcholine, or other phospholipids. Its affinity is also higher for long-chain phosphatidylcholines than for short-chain ones. The degree of unsaturation and fluidity of the 3-sn-phosphatidylcholine (lecithin) films are of secondary importance. Parallel experiments with covalently and non-covalently labelled receptor preparations showed that part of the protein recovered with the film lost its alpha-toxin binding ability during the penetration. Similar data were obtained with the receptor purified from Electrophorus electricus electric organ.
Explore the source record for details and available documents.
A protein is purified by differential centrifugation from membrane fragments rich in acetylcholine receptor prepared from Torpedo marmorata electric organ after dissolution by a mixture of non denaturing detergents. After polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate and Coomassie blue staining the purified protein yields a single band of apparent molecular weight 43,000. Spectroscopic experiments carried out in the absence of Ca++ and detergents reveal that the 43 K protein interacts with the fluorescent local anesthetic quinacrine and with the frog toxin histrionicotoxin (apparent KD : 7 X 10(-7) M) but not with carbamylcholine and the alpha toxin from N. nigricollis.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The interaction of the cholinergic (nicotinic) receptor protein purified from Torpedo marmorata electric organ with lipidic monomolecular films is studied at constant film area or constant superficial pressure. In both experimental situations, it is incorporated more efficiently into cholesterol than into egg lecithin films without showing any selectivity for a particular phospholipid class.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The C1q deviation test measures the interference of circulating immune complexes in the fixation of radioactive C1q on target cells. The test was carried out in a large sample of cases of glomerular nephropathies, on the serum of patients with hypertension and on control sera. Positive results were frequently obtained with the sera of patients suffering from acute glomerulonephritis and membranous glomerulonephritis. Positive results were rarer in cases of minimal change discase and of membranoproliferative glomerulonephritis. These results suggest that the deviation of C1q in the serum of patients with various types of glomerulone phropathy may be due to circulating complexes but also to other substances. They indicate that efforts should be continued to isolate and biochemically identify the C1q binding substances in pathological sera.
The injection of acetylcholine receptors, from the Electrophorus electricus induces in Guinea Pigs and Rats an experimental disease, which is characterized by the appearance of antibodies to sarcolemma and by massive histological alterations of the degenerative type, similar to those observed in clinical polymyositis.