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Biomedical subjects

H Winkler

Publications and source records attributed to H Winkler.

At least 361 records · Page 20Linked to original sources
PubMed1968

Lysosomal phospholipases A1 and A2 of bovine adrenal medulla.

1. [(32)P]Lecithin and [(32)P]phosphatidylethanolamine were prepared by incubating rat liver mince with [(32)P]phosphate. With these (32)P-labelled phospholipids conditions for the quantitative assay of phospholipase A activity were established. 2. The distribution of phospholipase A activity between subcellular fractions of the bovine adrenal medulla was determined. Phospholipases A(1) and A(2), with pH optima at 4.2 and 6.5 respectively, were found in the large-granule fraction. By means of sucrose-density-gradient centrifugation it was shown that both these phospholipases were localized in lysosomes. 3. Lysosomal phospholipase A(1) catalysed the hydrolysis of [(32)P]lecithin and [(32)P]phosphatidylethanolamine at the same rate. The enzymic activity was inhibited by 70% in the presence of 10mm-calcium chloride. 4. Lysosomal phospholipase A(2) catalysed the hydrolysis of [(32)P]phosphatidylethanolamine more rapidly than it hydrolysed [(32)P]lecithin. The hydrolysis of [(32)P]phosphatidylethanolamine, but not that of [(32)P]lecithin, by phospholipase A(2) was activated by 0.8mm-calcium chloride. However, the hydrolysis of both substrates was inhibited by 8mm-calcium chloride. 5. The significance of the presence of phospholipase activity in lysosomes is discussed in relation to the functions of lysosomes in general and in the adrenal medulla.

Adrenal Medulla↗
PubMed1967

A simple method for the isolation of adrenal chromaffin granules on a large scale.

Highly purified chromaffin granules can be obtained from homogenates of either ox, pig, horse or rat adrenal medullae by ultracentrifugation of the large-granule fraction layered on 1.6m-sucrose solution, by using angle-head rotors. The chromaffin granules are obtained as a pink sediment that is only slightly contaminated by mitochondria and lysosomes.

Adenosine Triphosphate↗
PubMed1967

Purification and properties of an acidic protein from chromaffin granules of bovine adrenal medulla.

1. A soluble protein has been purified from an aqueous extract of bovine adrenal chromaffin granules by chromatography on Sephadex G-200. This protein comprises 25% of the total protein of the granules and gave a single band on gel electrophoresis. 2. The protein is unusually rich in acidic amino acids, notably glutamic acid (26.0%, w/w); it is also relatively rich in proline (8.6%, w/w) but poor in cystine (0.35%, w/w). 3. A molecular weight of 77000 was obtained from sedimentation and diffusion measurements on the protein, and approach-to-equilibrium measurements gave apparent molecular weights of the same order. 4. A molecular weight 7 times that given above was estimated from the results of chromatography on a column of Sephadex G-200 that had been calibrated with globular proteins. However, good agreement between the ultracentrifuge and Sephadex experiments was obtained on the assumption that Sephadex chromatography depends on the effective hydrodynamic radii of proteins and not on their molecular weights. 5. The hydrodynamic properties of the protein differed from those of a typical globular protein. Thus the protein had a high intrinsic viscosity, a high frictional ratio and a large effective hydrodynamic volume. 6. The hydrodynamic properties of the protein, but not its molecular weight, were dependent on the ionic strength of the solvent. Increasing the ionic strength caused an increase in the sedimentation and diffusion coefficients, but a decrease in the intrinsic viscosity and in the frictional ratio of the protein. 7. Optical-rotatory-dispersion measurements indicated that only a small part of the polypeptide chain was in an alpha-helical conformation. 8. These results are compatible with the protein's having a conformation approaching that of a random-coil polypeptide, the volume occupied by the molecule being determined by electrostatic repulsion between the excess of negative charges.

Adrenal Medulla↗
PubMed1967

Lipids of the adrenal medulla. Lysolecithin, a characteristic constituent of chromaffin granules.

1. The lipid composition of microsomes, mitochondria and chromaffin granules, obtained from homogenates of bovine adrenal medulla, has been investigated. 2. The three types of particle showed characteristic differences of phospholipid and cholesterol content. The lipid composition of microsomes and mitochondria resembled that of corresponding particles from other tissues. The chromaffin granules contained 19% of the cholesterol and 14% of the phospholipids of the low-speed supernatant. 3. Thin-layer chromatography indicated the presence of these phospholipids in extracts from each particle: lecithin, lysolecithin, phosphatidylethanolamine (partly plasmalogen), phosphatidylserine, phosphatidylinositol and sphingomyelin. 4. On quantitative analysis of the phospholipids, chromaffin granules were found to contain a high concentration of lysolecithin (17% of the lipid phosphorus). Mitochondria and microsomes, on the other hand, contained very little lysolecithin (less than 2% of the lipid phosphorus).

Adrenal Medulla↗