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Biomedical subjects

M Silverberg

Publications and source records attributed to M Silverberg.

At least 91 records · Page 5Linked to original sources
PubMed1976

The effect of carboxymethylating a single methionine residue on the subunit interactions of glycophorin A.

Human red cell glycophorin A shows an equilibrium between dimeric and monomeric forms which have been disignated PAS-1 and PAS-2, respectively. This equilibrium, which is dependent upon protein concentration is achieved by incubation in sodium dodecyl sulfate solutions at elevated temperatures and is assayed by sodium dodecyl sulfate gel electrophoresis. Carboxymethylation of glycophorin A in guanidine hydrochloride or urea alters the interactions between polypeptide chains so that the lower molecular weight form (PAS-2) is obtained much more readily. If the carboxymethylation is performed at pH 3.0 the reaction is limited to the two methionine residues of glycophorin A which are located at positions 8 and 81 in the sequence. In the presence of sodium dodecyl sulfate, only one of the two methionine residues is carboxymethylated, and glycoprotein modified under these conditions does not exhibit the change in electrophoretic mobility. Experiments with [1-14C]iodoacetic acid demonstrated that Met-81, located in the hydrophobic domain of the protein, is the residue protected by sodium dodecyl sulfate. Modification of Met-81 destabilizes the dimeric form relative to the monomer by weakening the interactions between polypeptide chains. The experiments described in this paper confirm that the hydrophobic domain of glycophorin A is involved in subunit interactions and that Met-81 plays a critical role in those interactions.

Amino Acids↗
PubMedDate not supplied

Arteriohepatic dysplasia. I. Pitfalls in diagnosis and management.

Differentiating intrahepatic cholestasis from extrahepatic biliary tract obstruction may be difficult. Four patients with intraoperative cholangiographic evidence of extrahepatic ductal atresia who underwent hepatoportoenterostomy are described. All were ultimately shown to have arteriohepatic dysplasia with hypoplastic but patent extrahepatic ductal systems. The difficulty in establishing an accurate diagnosis, hazards associated with hepatoportoenterostomy, and suggestions for evaluation and management are discussed.

Bile Ducts↗
PubMedDate not supplied

Arteriohepatic dysplasia. II. Hepatobiliary morphology.

Five children were noted to have arteriohepatic dysplasia (Alagille's syndrome) between 3 and 7 months of age. Prior to diagnosis, four underwent Kasai procedures after intraoperative cholangiograms failed to demonstrate patency of the extrahepatic bile ducts. In three patients, a focal proximal hypoplasia of the common hepatic duct was demonstrated with fibrosis and increased vascularity. Hypoplasia of the gallbladder occurred in two patients. Changes were observed in the porta hepatis. Eighty of 208 micrometers bile ducts were associated with peripherally located gland-like structures. These changes are indistinguishable from those in fibrous remnants of extrahepatic biliary atresia. Hepatic features of sequential liver biopsies obtained in the five patients were divided into early and late changes. From birth to 3 months of age, the pathology consisted of cholestasis and bile duct destruction. After 3 months of age, there was persistent cholestasis, paucity of interlobular bile ducts, and portal fibrosis. Ductular proliferation was not an intrinsic change. When present, it was related to a recent episode of cholangitis.

Bile Ducts↗