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Biomedical subjects

J D Green

Publications and source records attributed to J D Green.

At least 91 records · Page 5Linked to original sources
PubMed1980

Assay of succinate dehydrogenase activity by the tetrazolium method: evaluation of an improved technique in skeletal muscle fractions.

An improved spectrophotometric method for measuring succinate dehydrogenase (EC 1.3.99.1) activity with the use of 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride (INT) is described. The procedure has been evaluated in mitochondrial fractions and homogenates of frog skeletal muscle. For mitochondrial suspensions, extraction of formazan with alcohol was found to be superior to extraction with ethyl acetate. For homogenates, complete extraction of formazan required sequential treatment with alcohol and ethyl acetate; the generally employed procedure of extracting once with ethyl acetate alone led to serious underestimation of the amount of formazan in the tissue. Observations of mitochondrial suspension incubated with various concentrations of INT led to the selection of 0.8 mM INT for optimal results. Higher concentrations, although commonly used, can exert undesirable inhibitory effects on succinate dehydrogenase activity, especially at low concentrations of mitochondria and after longer periods of incubation. The problem of instability of succinate dehydrogenase was solved by the addition of buffer at pH 7.5.

Animals↗
PubMed1979

Isolation of plasma membrane vesicles, derived from transverse tubules, by selective homogenization of subcellular fractions of frog skeletal muscle in isotonic media.

A new technique for isolating fragmented plasma membranes from skeletal muscle has been developed that is based on gentle mechanical disruption of selected homogenate fractions. (Na+ + K+)-stimulated, Mg2+-dependent ATPase was used as an enzymatic marker for the plasma membrane, Ca2+-stimulated, Mg2+-dependent ATPase as a marker for sarcoplasmic reticulum, and succinate dehydrogenase for mitochondria. Cell segments in an amber low-speed (800 x g) pellet of a frog muscle homogenate were disrupted by repeated gentle shearing with a Polytron homogenizer. Sarcoplasmic reticulum was released into the low-speed supernatant, whereas most of the plasma membrane marker remained in a white, fluffy layer of the sediment, which contained sarcolemma and myofibrils. Additional gentle shearing of the white low-speed sediment extracted plasma membranes in a form that required centrifugation at 100,000 x g for pelleting. This pellet, the fragmented plasma membrane fraction, had a relatively high specific activity of (Na+ + K+)-stimulated ATPase compared with the other fractions, but it had essentially no Ca2+-stimulated ATPase activity and only a small percentage of the succinate dehydrogenase activity of the homogenate. Experimental evidence suggests that the fragmented plasma membrane fraction is derived from delicate transverse tubules rather than from the thicker, basement membrane-coated sarcolemmal sheath of muscle cells. Electron microscopy showed small vesicles lined bu a single thin membrane. Hydroxyproline, a characteristic constituent of collagen and basememt membrane, could not be detected in this fraction.

Adenosine Triphosphatases↗
PubMed1979

Zollinger-Ellison syndrome with pneumopericardium.

A 55-year-old white male was found to have the Zollinger-Ellison syndrome in 1971. Supposed total gastrectomy was performed at that time. When an esophageal ulcer was found, six years later, esophagoscopic biopsy revealed residual gastric mucosa. The patient was given cimetidine 300 mg qid because it was felt he could not tolerate further surgery. After eight months of cimetidine therapy, the patient was admitted to the hospital because of retrosternal pain. Pneumopericardium was discovered, and at autopsy a large penetrating gastrojejunal ulcer was demonstrated.

Biopsy↗
PubMed1976

Yolk sac carcinoma.

Yolk sac carcinoma is an uncommon neoplasm which has appeared under a variety of names. It has been reported not only in gonadal sites but also in the mediastinum, pineal body, and sacral areas. The typical histologic appearance of this tumor and the variety of locations are demonstrated by four case reports. A 57-year-old patient with an ovarian tumor is thought to be the oldest patient reported to date.

Child, Preschool↗