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Biomedical subjects

D G WALKER

Publications and source records attributed to D G WALKER.

At least 19 recordsLinked to original sources
PubMed1965

FACTORS AFFECTING HEPATIC GLYCOLYSIS AND SOME CHANGES THAT OCCUR DURING DEVELOPMENT.

1. Glycolysis by the supernatant fraction of homogenates of liver from guinea pigs and rats at various stages of development (foetal, newborn and adult) has been examined in a suitably fortified medium by measurement of inorganic phosphate uptake and production of lactate and glycerol 1-phosphate. 2. Starting with glucose as substrate, two rate-determining steps in glycolysis occur at the stages of glucose phosphorylation and the phosphofructokinase reaction in liver tissue from animals of all ages. Effects of the post-natal development of glucokinase are recorded. 3. The appearance of microsomal glucose 6-phosphatase activity around birth has an effect on glycolysis owing to competition for glucose 6-phosphate. 4. A stimulating effect of the nuclear fraction, especially from foetal liver, on glycolysis by the supernatant fraction is interpreted as being due to stimulation by adenosine-triphosphatase activity at the 3-phosphoglycerate-kinase stage.

Adenine Nucleotides↗
PubMed1963

The use of formalin fixation in the cytochemical demonstration of succinic and DPN- and TPN-dependent dehydrogenases in mitochondria.

Brief formalin fixation in the cold prior to histochemical assay of rat liver and pancreas for various dehydrogenases has been used successfully to circumvent the structural damage and enzymatic loss to which mitochondria of frozen sections would otherwise be subject. To obtain an optimal result a single set of conditions has been devised, including fixation prior to freezing of minute (finely diced) organ blocks in graded concentrations (0.7 to 2.0 per cent) of formaldehyde in chilled (1-4 degrees C) Hanks' balanced salt solution, freezing at not higher than -70 degrees C, and use of nitro-BT or, preferably, tetranitro-BT. The present histochemical study of hepatic and acinar cells indicates that not only are succinic and D-beta-hydroxybutyric dehydrogenases located exclusively in the mitochondria but so are lactic, malic, and the isocitric dehydrogenases.

Animals↗
PubMed1963

A survey of dehydrogenases in various epithelial cells in the rat.

Several different epithelial elements that have intense active transport or protein secretory functions were histochemically assayed in several dehydrogenase media by a recently perfected method. The mitochondria represented the only site of activity, not only when tested in the succinate and D-beta-hydroxybutyrate media, but also when tested in the lactate, malate, and isocitrate media. The reaction for D-beta-hydroxybutyric dehydrogenase in the mouse kidney was curiously limited to the mitochondria of the distal segment of the proximal convoluted tubule, a finding that most convincingly shows that dehydrogenase activity may be differentiated in certain instances from diaphorase activity by the ditetrazole methods and that D-beta-hydroxybutyric dehydrogenase is not present in all mitochondria. Tetranitro-BT is favored over nitro-BT in studies conducted on most organs prepared without fixation and on formalin-fixed tissues that consist of lipid-containing or active transport cells.

Animals↗