Effect of trypsin on the cell surface proteins of hepatoma tissue culture cells. Characterization of a carbohydrate-rich glycopeptide released from a calcium binding membrane glycoprotein.

Concentrations of trypsin that bring about aggregation of hepatoma tissue culture (HTC) cells also release from the cell surface an Mr = 55,000 glycopeptide fragment. This glycopeptide fragment also accumulates in the medium, including serum-free medium, as a normal consequence of membrane protein turnover. The trypsin-released glycopeptide is labeled when cells are grown in the presence of fucose or leucine before treatment of the cells with the protease. Similarly, the glycopeptide fragment can be labeled by reacting cells in situ by lactoperoxidase-catalyzed radioiodination or by tritiated borohydride reduction of cells treated first with neuraminidase and galactose oxidase. The tryptic glycopeptide fragment was purified by concanavalin A-Sepharose chromatography, and hydroxyapatite chromatography in the presence of dodecyl sulfate. The amino acid and carbohydrate composition was determined, as was the sensitivity of the purified glycopeptide to a variety of endo- and exoglycosidases. The purified glycopeptide contains an average of 17 sialic acid residues and hence, shows charge heterogeneity after electrophoresis in isoelectric focusing gels. The charge heterogeneity can be eliminated completely by treatment with neuraminidase. The glycopeptide after this treatment is homogeneous. The trypsin-sensitive membrane glycoprotein which is the source of the Mr = 55,000 glycopeptide was identified by two-dimensional gel electrophoretic analysis of labeled cells, treated or not treated with trypsin. This glycoprotein, which has an apparent molecular weight of 85,000 and forms a homodimer in the presence of calcium ions, was purified and its identity as the parent of the Mr = 55,000 glycopeptide was confirmed by showing that the same Mr = 55,000 fragment was released by trypsin from the purified glycoprotein as was released from the intact cells.     

A rapid method for the purification of supercoiled PM2 DNA by affinity chromatography on H1 histone covalently coupled to agarose.

A simple and rapid method is described for the purification of supercoiled PM2 DNA by affinity chromatography on columns of H1 histone covalently coupled to agarose. The method does not require the use of intercalating agents or ultracentrifugation procedures. Under the conditions most appropriate for purification, elution is carried out in a single step with buffered 0.7 M NaCl after the sample has been loaded onto the column in buffered 0.2 M NaCl. The DNA eluted at the higher salt concentration consists of supercoiled closed circular DNA at greater than 90% purity independently of the ratio of supercoiled to nicked circular DNA in the input mixture.     

m-OCTOPAMINE, p-OCTOPAMINE AND PHENYLETHANOLAMINE IN RAT BRAIN: A SENSITIVE, SPECIFIC ASSAY AND THE EFFECTS OF SOME DRUGS

Abstract— An enzyme radiochemical assay for p -octopamine, m -octopamine (norphenylephrine) and phenylethanolamine based on the N -methylation of these amines by the enzyme phenylethanolamine N -methyl transferase ( S -adenosyl- l -methionine: phenylethanolamine N -methyl transferase (EC 2.1.1.28) has been developed. [³H]Methyl- S -adenosyl- l -methionine was used as methyl donor. The reaction products are converted to their dansyl derivatives and separated by TLC in three different solvent systems prior to liquid scintillation counting. The method exhibits a sensitivity of less than 10 pg for each amine and is suitable for the measurement of endogenous p -octopamine levels in mammalian brain. The highest levels of p -octopamine were found in the hypothalamus (3.4 ng/g) but despite the sensitivity of the assay, neither phenylethanolamine nor m -octopamine could be detected. After MAO inhibition, however, both of these amines were found to be present. p -Octopamine was increased substantially in all brain regions following the administration of an MAO inhibitor, whereas pretreatment with reserpine produced a significant decrease in the hypothalamus.     

Anaerobic Fish Spoilage by Bacteria II. Kinetics of Bacterial Growth and Substrate Conversions in Herring Extracts

The time course of the conversions of chemical components in herring extracts during anaerobic growth of Proteus sp., str. NTHC 153, Aeromonas sp., str. NTHC 154, and Enterobacter sp., str. NTHC 151 (Strøm & Larsen 1979) has been studied. When the Proteus sp. or the Aeromonas sp. were inoculated into the herring extracts and incubated at 15°C under anaerobic conditions, the sugar components (i.e. mainly ribose, free and bound) were the first substrates utilized. These compounds were converted to acetate and CO₂ by the use of trimethylamine oxide (TMAO) as an external hydrogen acceptor. Growth of bacteria ceased when all TMAO was reduced to trimethylamine (TMA). By adding an extra amount of TMAO to the herring extracts an increased growth of the Proteus sp. and the Aeromonas sp. ensued. The increased growth occurred concomitantly with a further conversion of TMAO to TMA and of lactate to acetate and CO₂. The Enterobacter sp., which did not utilize lactate, did not give an increased growth in herring extracts enriched with TMAO.