648 research outputs found

    Sugar receptor specificity in the fleshfly, Sarcophaga bullata

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    Various carbohydrates were tested for stimulating activity of the sweet receptor of Sarcophaga bullata. Efficacy appears to be highest in -pyranosides having equatorial substituents at C-2, C-3, C-4 and C-5, with the exception of the C-1 position where equatorial substituents detract. Similarly, myo-inositol, having 5 equatorial and 1 axial hydroxyl, is the most stimulatory of the cyclitols tested. The anomalous action of several compounds remains unexplained. -Glucose is stimulatory, while its [alpha]- and [beta]-pyranosides are not. Similarly, free fructose, an extremely potent sugar, is completely inactive as its [alpha]- or [beta]-furanoside or its [alpha]- or [beta]-pyranoside. This finding is discussed in relation to the stimulatory action of sucrose.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33504/1/0000001.pd

    Use of [1 or 3-3H, U-14c]glucose to estimate the synthesis of glycerolipids via acyl dihydroxyacetone phosphate

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    SummaryBHK-21-cl3 fibroblasts were incubated with [1-3H, U-14c]glucose or [3-3H, U-14c]glucose to produce intracellular [3H]NADPH via the phosphogluconate pathway. 3H and 14C were then determined at the three positions of glycerol in glycerol phosphate, saponifiable glycerolipids, alkyl ether glycerolipids and plasmalogens. The 3H/14C ratio at C-2 in glycerol of saponifiable glycerolipids is 2-10 fold greater than in glycerol phosphate and approaches the ratio found in ether-containing glycerolipids. This suggests that a significant fraction of the glycerolipids in BHK-21-cl3 fibroblasts is synthesized via acyl dihydroxyacetone phosphate.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22025/1/0000441.pd

    Measurement of Receptor-Activated Phosphoinositide Turnover in Rat Brain: Nonequivalence of Inositol Phosphate and CDP-Diacylglycerol Formation

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    Two methods for the measurement of receptor-activated phosphoinositide turnover were evaluated for their degree of correspondence in slices of rat brain; they involved the Li + -dependent accumulations of either [ 3 H]-inositol-labeled inositol phosphates or [ 3 H]cytidine-labeled CDP-diacylglycerol. In contrast to the expectation that the ratio of these two responses would remain approximately constant, varying degrees of correspondence were obtained. The two extremes are exemplified by carbachol, which elicited large increases in both inositol phosphate and CDP-diacylglycerol labeling, and endothelin, which gave a robust inositol phosphate response with little or no accumulation of 3 H-CDP-diacylglycerol. No instance of the presence of the latter response in the absence of 3 H-inositol phosphate accumulation was observed. Measurement of 3 H-CDP-diacylglycerol accumulation thus may add additional insight into the regulation of phosphoinositide turnover and the complex actions of Li + .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66135/1/j.1471-4159.1993.tb03258.x.pd

    DISTRIBUTION AND PROPERTIES OF CDP-DIGLYCERIDE:INOSITOL TRANSFERASE FROM BRAIN 1

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    CDP-diglyceride is converted to phosphatidyl inositol by several particulate subcellular fractions of guinea pig brain, with highest specific activity in the microsomal fraction. Optimal conditions with respect to pH, metal ion concentration, and substrate concentrations have been determined. The reaction was stimulated by the addition of bovine serum albumin and by Tween 80. Of several dl-CDP-diglycerides synthesized and used as substrates in a spectrophoto-metric assay for the enzyme, dl-CDP-didecanoin was the most active. The enzyme showed a high selectivity for myo-inositol. Of a number of compounds tested, only scyllo -inosose and epi -inosose served as substrates. Three inositol isomers and three myo -inositol monophosphates inhibited the reaction slightly. The most potent inhibitor found was galactinol, a myo -inositol galactoside.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66197/1/j.1471-4159.1969.tb06850.x.pd

    Uridine Metabolism in the Goldfish Retina During Optic Nerve Regeneration: Cell-Free Preparations

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    The activities of uridine kinase (EC 2.7.1.48), uridine monophosphate (UMP) kinase (EC 2.7.1.3.14), and uridine diphosphate (UDP) kinase (EC 2.7.4.6) were measured in retinal high-speed supernatant fractions following unilateral optic nerve crush in the goldfish. The enzyme activities followed a similar time course, with initial increases 2-3 days following nerve crush, peak activity at 4 days, and a gradual return to basal levels by day 21. The magnitude of the stimulation on day 4 was about 35% in each case. Activities of two enzymes of intermediary metabolism, pyruvate kinase (EC 2.7.1.40) and lactic dehydrogenase (EC 1.1.1.27), were not altered, indicating that the coordinate increases in nucleoside and nucleotide kinase activities were specific responses to the nerve injury. The increased labeling could not be explained by altered phosphohydrolytic activities. The nature of the enhancement was further studied in UDP kinase, the most active of the kinases examined. Neither low-molecular-weight components nor substrate availability could account for the observed increase in UDP kinase in the 4 day post-crush retinas. The K m , for UDP was unaltered, and a mixing experiment did not support the possibility that stimulatory or inhibitory factors played a role. The enhancement of UDP kinase activity was blocked by injection of actinomycin D following nerve crush. The results suggest that the observed increases in enzymes of uridine metabolism result from their increased formation following nerve crush.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65504/1/j.1471-4159.1981.tb01714.x.pd

    Receptor Activation and Inositol Lipid Hydrolysis in Neural Tissues

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66228/1/j.1471-4159.1987.tb05618.x.pd
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