A heterogeneous beta-D-glucosidase activator from monkey parotid gland and its use as an affinity ligand in the purification of human salivary beta-D-glucosidase

We have isolated a heat-stable, low molecular weight activator peptide(s) from monkey parotid gland that specifically activated human salivary beta-D-glucosidase. This activator appeared to be heterogeneous on Sephadex G-25 gel filtration and polyacrylamide gel electrophoresis under non-denaturing conditions. About 45% of the human salivary beta-glucosidase could bind to the activator immobilised on Sepharose and be eluted by Cutscum. The purified enzyme was nearly homogeneous, with a subunit Mr of 46,000 as revealed by SDS-gel electrophoresis and silver staining.     

Albumin bound nonesterified fatty acids inhibit in vitro lipid peroxidation

Individual nonesterified fatty acids were bound to albumin in vitro and these fatty acid albumin complexes were used to study their effect on lipid peroxidation in liver microsomes. Peroxidation was induced by various methods and malondialdehyde (MDA) was measured as an index of peroxidation. Among the fatty acids tested, albumin-bound monounsaturated fatty acids showed more inhibition of peroxidation as compared to other fatty acids. Increasing the concentration of iron in the peroxidizing system, partially reversed the inhibition by fatty acids. Moreover, albumin-bound fatty acid did not inhibit iron independent peroxidation. This suggests that, like nonesterified fatty acids, albumin-bound fatty acids inhibit peroxidation by chelating the iron. Albumin fatty acid complex, similar to the fatty acid composition present in the circulating albumin, also showed inhibition of peroxidation. These data indicate that nonesterified fatty acids even when bound to albumin are capable of inhibiting peroxidation and circulating albumin, which contains various fatty acids bound to it, may impart some antioxidant effect in addition to other plasma antioxidants.     

In vivo absorption of 14C-glucose and 14C-glycine by the rat intestine during ochratoxin A toxicosis.

Ochratoxin A was administered orally at a dose level of 6 mg/kg/day for eight weeks to rats. Studies on the intestinal cellular macromolecules, activities of membrane bound enzymes and in vivo absorption of 14C-glucose and 14C-glycine exhibited significant alterations. The observed reduction in the absorption of these nutrients during ochratoxin A toxicosis is corroborated by the changes observed in the levels of cellular macromolecules and the activity of membrane bound enzymes which are involved in the transport system.     

Electro-osmosis at the surface of phospholipid bilayer membranes

The electro-osmotic velocity is the velocity of a fluid near an interface produced by an electric field parallel to a surface. The velocity adjacent to fixed phospholipid bilayer membranes was measured by observing the velocity of small vesicles suspended in the fluid. The charge densities of the bilayers ranged from 0 to 1 electronic charge per lipid and experiments were performed at temperatures above and below the transition temperature of the phospholipid bilayer in 1, 10 and 100 mM NaCl solutions. The Helmholtz-Smoluchowski equation correctly predicted the electro-osmotic velocity from the known value of zeta potential of the phospholipid bilayer.     

Phosphorylation of the lysosomal enzyme binding receptor protein from monkey brain and evidence for a tyrosine kinase activity associated with it

The lysosomal enzyme binding receptor protein prepared from monkey brain by phosphomannan-Sepharose affinity chromatography could undergo phosphorylation in the presence of [gamma-32P] ATP. The phosphorylated receptor protein appeared as a single radioactive band on polyacrylamide gel electrophoresis under nondenaturing conditions. Upon SDS-gel electrophoresis two radioactive bands, one corresponding to a high molecular weight (Mr greater than 116,000) component and another corresponding to Mr 45,000 were seen. Phosphoamino acid analysis showed that the receptor protein was phosphorylated on serine and tyrosine residues. The receptor protein could also phosphorylate histone on tyrosine residues exclusively. The phosphorylated receptor protein bound lysosomal enzymes to a lesser extent as compared to the non-phosphorylated receptor protein.     

Studies on the influence of foliar nutrient sprays on the root exudation pattern in four crop plants

Summary Studies conducted to examine the exudation pattern of amino acids and sugars in four crop plants,viz sorghum, sunnhemp, ragi, and tomato indicated that in all, 17 known amino acids and 4 sugars were exuded and that the number and nature of the exuded amino acids and sugars differed with the plant species and with the age of plant. Glutamic and aspartic acids were found to be present in the exudates of all the plant species at all stages of plant growth examined. The quantities of amino acids and sugars differed with plant species and the maximum quantity of the chemicals was exuded during the early stages of plant growth. Glutamic acid among amino acids, and glucose among sugars, were always present in higher concentrations than the others, in the exudates in all the four crop plants.Foliar application of nitrogen in the form of NaNO₃ and phosphorus as Na₂HPO₄, was found to alter the exudation pattern of amino acids and sugars and such influence differed in different plant species. There was a general increase in the total concentration of amino acids and a decrease in sugar content in the exudates after treatment of the foliage with N, while a decrease in the amino acid content and increase in total sugars with P-treatment was observed.