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Biomedical subjects

G M Gray

Publications and source records attributed to G M Gray.

At least 109 records · Page 6Linked to original sources
PubMed1970

Factors affecting the glycosphingolipid composition of murine tissues.

The effects of genetic strain, sex, age, and pathological state on the distribution and concentration of glycosphingolipids in mouse kidneys and livers were studied. The concentrations of glycosphingolipids and phospholipids in the kidneys and livers of different strains were compared. The major glycosphingolipid in the kidneys of male and female BALB/c, C3H/He, C57/BL, A, and C57xA (F(1) hybrid) mice was a sulfatide, monoglycosyl-(3-sulfate) ceramide; monoglycosyl ceramide was the major component in livers. The kidneys of males of all strains contained significant amounts of diglycosyl ceramide, but those of females contained, at most, only traces. Glycosphingolipid concentration in the male kidneys of C57/BL and C57xA (F(1) hybrid) was much higher than in the female and was also much higher than in the male kidneys of C3H/He, BALB/c, and A strains. The kidneys of "old" (36 wk) male and female C3H/He mice contained much higher proportions of monoglycosyl ceramide than 10-12-wk-old adults. The distributions of glycosphingolipids in kidneys of female C3H/He mice with BP8 ascites tumors and male C57xA (F(1) hybrid) mice with EL4 ascites tumors differed from those in the normal mice. An unknown lipid, present in all glycosphingolipid extracts from kidney and liver, was tentatively identified as cholesterol sulfate.

Age Factors↗
PubMed1970

Fluorimetric determination of sphingosine and its application to natural mixtures of glycosphingolipids.

A sensitive estimation of sphingosine, by measurement of the fluorescence of a complex formed with 1-naphthylamino-4-sulfonic acid, is described. The practical range is 5-35 nmoles sphingosine. The method is used to estimate, in terms of sphingosine, amounts of ceramide and glycosphingolipids. The isolation of microamounts (5-30 micro g) of individual glycosphingolipids from a mixture, and their quantitative estimation is described. The percentage composition of a glycosphingolipid mixture from the kidneys of adult C57/BL male mice is given.

Amino Alcohols↗
PubMed1969

Intestinal beta-galactosidases. I. Separation and characterization of three enzymes in normal human intestine.

Previous studies based on work in the rat and preliminary experiments with human intestine have suggested that two beta-galactosidases are present in small intestine, and it is believed that only one of these enzymes is a lactase important for the digestion of dietary lactose. The high prevalence of intestinal lactase deficiency in man prompted more complete study of these enzymes. Human intestinal beta-galactosidases were studied by gel filtration on Sephadex G-200 and Biogel P-300 as well as by density gradient ultracentrifugation. Gel filtration produced partial separation into three peaks of enzyme activity, but much activity against synthetic substrates was lost. Only the trailing peak with specificity for synthetic beta-galactosides was completely separated from the other enzymes. Thus gel filtration was not a suitable preparative procedure for biochemical characterization. Density gradients separated the enzymes more completely, and they were designated according to their sedimentation rates and further characterized. Enzyme I has a molecular weight of 280,000, pH optimum of 6.0, and specificity for lactose of at least five times that for cellobiose or synthetic substrates. A second lactase, enzyme II, possesses slightly greater activity against lactose than for some synthetic substrates and is incapable of splitting cellobiose. Further, it has a lower pH optimum (4.5) and is present in two molecular species (molecular weights 156,000 and 660,000). Enzyme III shows specificity only for synthetic beta-galactosides but has a pH activity curve identical with enzyme I and a molecular weight of 80,000. Whereas human liver and kidney contain a beta-galactosidase with the same biochemical characteristics as intestinal enzyme II, enzymes I and III appear to be peculiar to intestine, and enzyme I most probably represents the lactase of importance in the mucosal digestion of dietary lactose. The following paper considers this further in terms of the biochemical change in intestinal lactase deficiency.

Chromatography↗
PubMed1969

Intestinal beta-galactosidases. II. Biochemical alteration in human lactase deficiency.

Despite the high prevalence of intestinal lactase deficiency in some racial groups and in patients with intestinal disease, the biochemical defect has not been characterized. In the preceding paper normal intestine was found to have two lactases with distinctly different pH optima. Therefore, pH activity curves of homogenates from lactase-deficient intestine were studied, and the pH optimum was found to be shifted from the normal of 5.8 to 4.8. Density gradient ultracentrifugation of intestinal material from five lactase-deficient patients demonstrated absence of a lactase with pH optimum 6.0 and molecular weight 280,000. A second lactase with pH optimum 4.5 and molecular weights of 156,000 and 660,000 remained at normal levels accounting for the shift in the pH optimum in whole intestinal homogenates. In addition, three of the five patients had absence of a smaller beta-galactosidase (molecular weight 80,000) that had specificity only for synthetic substrates. Although not a lactase, this enzyme had a pH optimum identical with the missing lactase, and its activity was inhibited by lactose in a partially competitive manner suggesting that it is capable of binding lactose. It is possible that this enzyme is a precursor or fragment of the missing lactase.The residual lactase activity provided by the lactase with low pH optimum represents 20-70% of the activity of the missing enzyme, and yet these patients are not able to digest dietary lactose. Thus it appears that the residual enzyme plays no significant role in the hydrolysis of ingested lactose.

Adult↗