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Biomedical subjects

I Schenkein

Publications and source records attributed to I Schenkein.

28 records · Page 2Linked to original sources
PubMed1970

Immunoglobulin synthesis and secretion, IV. Sites of incorporation of sugars as determined by subcellular fractionation.

P(3)K cells were uniformly labeled with [(14)C]leucine and also for 1 hr with [(3)H]leucine, [(3)]galactose, or [(3)H]glucosamine. Subcellular fractionation of labeled cells was performed and the amounts of radioactive immunoglobulin G in each fraction were determined. The results indicate that amino acids are incorporated in the rough endoplasmic reticulum, galactose primarily in the smooth endoplasmic reticulum, and glucosamine at both sites. A small portion of radioactivity was found in the microsomal supernatant regardless of the radioisotope employed.

Animals↗
PubMed1970

Immunoglobulin synthesis and secretion. I. Biosynthetic studies of the addition of the carbohydrate moieties.

This study was designed to determine the time in the intracellular life of immunoglobulin when the carbohydrate moieties are added. Plasma cells from a mouse myeloma tumor were exposed to glucosamine-(3)H (a "bridge" sugar), galactose-(3)H, or leucine-(3)H. With each of the above isotopes, the percentage of total radioactive immunoglobulin that has been secreted after different periods of labeling and the extent to which puromycin prevented incorporation into immunoglobulin were determined. The results indicate that both galactose and glucosamine (in its N-acetyl form) become covalently incorporated into immunoglobulin G late in its intracellular life and suggest that glucosamine is also added onto nascent polypeptide chains (i.e., on polyribosomes).

Animals↗
PubMed1969

Regulatory effects of substrates on a phosphotransferase from Aerobacter aerogenes and modification of its activity by partial proteolysis.

An enzyme isolated from Aerobacter aerogenes acts both as phosphomonoesterase and phosphotransferase with glucose, glucosides, glucosamine, and N-acetyl glucosamine as acceptors. When glucose-6-phosphate is the phosphate donor, these acceptors appear to act as activators of the enzyme, while with p-nitrophenyl phosphate, alpha-glycerophosphate, fructose-1,6-diphosphate, and several other phosphate esters as donors, the same acceptors act as noncompetitive inhibitors. With p-nitrophenyl phosphate as the phosphate donor, no inhibition is observed when glucose is replaced as acceptor by 2-deoxy glucose. The inhibition by glucose and other acceptors is eliminated at low pH or by increasing the temperature of reaction. Partial proteolysis of the enzyme by chymotrypsin produces a modified enzyme (gl-phosphotransferase-Ch) that shows altered relative velocities for the hydrolysis of several substrates as well as altered regulatory effects by acceptors.

Chymotrypsin↗
PubMed1968

Nerve growth factor of very high yield and specific activity.

Nerve growth factor has been isolated from submaxillary glands of mnature male mice at specific activities about a million times, and in yields of biological activity ten million times, greater than best previous results. The major improvement in the isolation is related to the separation of a highly active tosylarginine methyl esterase present in cruder preparations. The new nerve growth factor may be an entity different from the older one, although no gross differences in the qualitative aspects of their actions are apparent on superficial examination of chick ganglia influenced by them. The neurites which develop from a ganglion in the presence of nerve growth factor are of nearly equal length. The amount of nerve growth factor determines the number of neurites but not the extent of individual development. The amount of the new nerve growth factor which evokes the appearance of a hundred neurites from a single ganglion appears to be about ten molecules. Since each neurite seems to arise from a different neuron each molecule of nerve growth factor must affect several cells. This result can be rationalized by a catalytic mechanism or by indirect action of nerve growth factor through a hypothetical cell which produces a neurite evocator on contact with the molecule of nerve growth factor.

Animals↗