Characterization of a soluble glycolipid galactosyltransferase which occurs in bovine milk.

Bovine milk was found to contain, in soluble form, an enzyme which transfers galactose from UDPgalactose to glucosylceramide. This enzyme was partially purified by the same procedure used to isolate the galactosyltransferase of lactose synthetase. The partially purified enzyme required detergents for activity, had a pH optimum of 7.2--7.3 and required Mn2+. The apparent Km calculated for glucosylceramide was 1.33 . 10(-4) M. With glucosylceramide as acceptor the product of the reaction was identified as lactosylceramide by autoradiography on thin-layer chromatograms. Lactosylceramide was also an effective acceptor for the transferase reaction but neutral glycosphingolipids or gangliosides with terminal galactose of N-acetylgalactosamine residues were ineffective or poorly effective as acceptors. Addition of alpha-lactalbumin inhibited the transferase reaction.

Effect of 5-thio-D-glucose on food and water intakes and on the acquisition and performance of maze tasks in the rat.

A potent inhibitor of D-glucose transport across the membrane, 5-thio-D-glucose (5-TDG) was examined with respect to its effect on runway and maze performance as well as on food and water intakes and body weight. In an initial experiemnt, three groups of Sprague-Dawley rats were matched in terms of their performance to learn a runway taks with Noyes pellets serving as the reinforcement. After extinction, two groups of rats were given 5-TDG in their food for 14 days, in doses of 20 and 100 mg/kg/day, which exerts potent effects on other functions. Retesting in the runway task showed no significant differences in the time required for the controls and for the 5-TDG treated rats to reach the goal box. Nonfed controls and the same two groups were again fed 500 ant 100 mg/kg/day 5-TDG and were tested on the 12 problems of the Hebb-Williams maze. Again, no significant differences were found in the number of erros made on the 12 problems by the 5-TDG treated animals or by the controls. Thus, this sugar analogue, administered in doses that affect spermatogenesis and other processes, has no effect on the ability of the rats to perform these tasks. Similarly, the intakes of food and water were unaffected by the systemic administration of 5-TDG.

Sulfur compounds reduce potato toxins during extrusion cooking.

Free sulfhydryl groups in sulfur compounds have been reported to act directly on natural toxins to reduce toxicity. The objective of this study was to reduce protease inhibitors and glycoalkaloids in simulated snack foods by the addition of sulfur-containing compounds prior to extrusion. Thiamine, methionine, and benzyl disulfide were added to potato flakes at levels of 0.5% or 1.0% prior to twin-screw extrusion. Total and free thiols and protease inhibitors were monitored before and after extrusion by colorimetric assays. Potato glycoalkaloids were analyzed by HPLC and by immunoassay. Extrusion reduced potato flake disulfide bonds; disulfide bonds were higher in samples containing added sulfur compounds. Trypsin inhibitor activity was reduced by as much as 79% by extrusion plus methionine. Extrusion significantly reduced carboxypeptidase inhibitor, but only when benzyl disulfide and 0.5% methionine were not added. One percent methionine and thiamine resulted in 60% reductions in glycoalkaloids.

Composition and synthesis of three higher ganglioside homologs in bovine mammary tissue.

Three higher gangliosides were identified as constituents of bovine mammary gland. The structures of these three gangliosides were shown to be ceramide-glucose-galactose-(sialic acid)-N-acetylgalactosamine-galactose, ceramide-glucose-galactose-(sialic acid)2-N-acetylgalactosamine, and ceramide-glucose-galactose-(sialic acid)2-N-acetylgalactosamine-galactose. These gangliosides accounted for only a small fraction (less than 20%) of the lipid-bound sialic in mammary gland. White fatty acids with even carbon numbers from C14 to C26 were predominant in these gangliosides, they also contained C23 and C25 fatty acids. Mammary gland Golgi apparatus-rich fractions had all glycosyltransferases required for synthesis of these gangliosides starting with ceramide.

Microbial degradation of phosmet on blueberry fruit and in aqueous systems by indigenous bacterial flora on lowbush blueberries (Vaccinium angustifolium).

Phosmet-adapted bacteria isolated from lowbush blueberries (Vaccinium angustifolium) were evaluated for their ability to degrade phosmet on blueberry fruit and in minimal salt solutions. Microbial metabolism of phosmet by isolates of Enterobacter agglomerans and Pseudomonas fluorescens resulted in significant reductions (P < 0.05; 33.8%) in phosmet residues on blueberry fruit. Degradation was accompanied by microbial proliferation of phosmet-adapted bacteria. Preferential utilization of phosmet as a carbon source was investigated in minimal salt solutions inoculated with either E. agglomerans or P. fluorescens and supplemented with phosmet or phosmet and glucose. Microbial degradation concurrent with the proliferation of P. fluorescens was similar in both liquid systems, indicative of preferential utilization of phosmet as an energy substrate. E. agglomerans exhibited the ability to degrade phosmet as a carbon source, yet in the presence of added glucose, phosmet degradation occurred within the 1st 24 h only followed by total population mortality resulting in no appreciable degradation. Characteristic utilization of glucose by this isolate suggests a possible switch in carbon substrate utilization away from phosmet, which resulted in toxicity from the remaining phosmet. Overall, microbial metabolism of phosmet as an energy source resulted in significant degradation of residues on blueberries and in minimal salt solutions. Thus, the role of adapted strains of E. agglomerans and P. fluorescens in degrading phosmet on blueberries represents an extensive plant-microorganism relationship, which is essential to determination of phosmet persistence under pre- and postharvest conditions.

Temporary sterility produced in male mice by 5-thio-D-glucose.

When 5-thio-D-glucose was fed to male mice at daily dose levels greater than 30 mg/kg sperm development was completely inhibited within 3 weeks and remained so without impairment of libido for the experimental period of 7 weeks. Removal of this substance from the diet resulted in a resumption of sperm development and fertility within 5 to 8 weeks. Normal litters were sired by males which had recovered after this treatment.