A gel film technique was adopted for kinetic enzyme activity determination in single cells using cryostat sections by means of a microscope photometer. The main principle of the method is a comparative activity determination, based on bipositional recording of initial reaction kinetics in two preselected measuring fields in
Abstract. 1. Activities of phosphoglucomutase, hexokinase, glucose‐6‐phosphate dehydrogenase, triosephosphate dehydrogenase, mitochondrial glycerophosphate dehydrogenase, hexosediphosphatase and phosphoenolpyruvate‐carboxykinase, of enzymes involved in the citric acid cycle and connected pathways, of hydroxyacyl‐CoA dehydrogenase and carnitine acetyltransferase were determined in biopsy specimens of liver and of tibialis anterior muscle from thyrotoxic and hypothyroid patients and from controls. The results are compared with data obtained from liver and red and white muscle of thyrotoxic rats and guinea pigs. 2. Concomitant with diminished glucose tolerance, the glucokinase activity is decreased in thyrotoxic human liver. The decrease of rat liver glucokinase activity as a response to administered thyroid hormones is found to be dose‐dependent. A relationship between the diminished glucose tolerance in thyrotoxicosis and the decrease of glucokinase activity is discussed. The increase of hexokinase activity (isozyme II) is the most interesting finding in thyrotoxic human muscle because of its possible significance with respect to the elevated metabolic rate. The activity of triosephosphate dehydrogenase, (NADP) malate dehydrogenase, phosphoenolpyruvate carboxykinase and carnitine acetyltransferase is markedly enhanced in human thyrotoxic liver, whereas that of phosphoglucomutase is diminished. 3. Mitochondrial glycerophosphate dehydrogenase, which is known to be markedly increased in the liver and red muscle of thyrotoxic rats, is not increased in the liver and tibialis anterior muscle of thyrotoxic patients, nor in the liver and white muscle of thyrotoxic guinea pigs. The enzyme responses to thyrotoxicosis in human liver and muscle are more similar to those of the guinea pig than of the rat.
Complete extraction of aldolase from minced rabbit psoas muscle was achieved by successive extraction steps in 0.1 M phosphate buffer. Aldolase was then readsorbed quantitatively to the depleted myofibrils. Extraction, readsorption and a final redsorption of the enzyme were followed quantitatively by enzyme activity determinations and qualitatively by histochemical staining of aldolase. The intracellular location of the readsorbed enzyme was found to be identical with that of aldolase In native muscle. In both cases, aldolase was localized within the isotropic bands. These results as well as the previously demonstrated binding of the enzyme to F-actin suggest that aldolase is located within the interfilamentary sarcoplasm of the isotropic bands and is probably also bound in vivo to the actin filaments. DESORPTION AND READSORPTION OF ALDOLASE IN MUSCLE
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