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Biomedical subjects

R B Scott

Publications and source records attributed to R B Scott.

At least 217 records · Page 12Linked to original sources
PubMed1968

Glycogen in human peripheral blood leukocytes. I. Characteristics of the synthesis and turnover of glycogen in vitro.

In the present paper a model system is described utilizing suspensions of peripheral blood leukocytes in which glycogen synthesis and degradation can be studied. Leukocyte suspensions containing 72-94% granulocytes were prepared essentially free of platelets and erythrocytes and consisted almost entirely of neutrophile granulocytes. Initial glycogen content averaged 7.36 +/- 2.05 mg/10(9) neutrophiles. In a glucose-free medium glycogenolysis took place with glycogen losses averaging 38% in 2 hr. When adequate glucose was added to the medium, glycogen was resynthesized to the original level. Glycogen resynthesis was studied with varying glucose "loads" to determine (a) the glucose level which was adequate for cell maintenance without utilization of glycogen stores, and (b) the glucose level which provided maximal glycogen resynthesis. With cell densities of 20-50 x 10(6)/ml the minimum glucose load which allowed maintenance of glycogen stores was 2 mg and 5.3 mg/10(9) neutrophiles for 30 and 60 min, respectively. During resynthesis with glucose-(14)C, as much as 88.9% of the intracellular radioactivity could be found in glycogen. Leukocyte glycogen was made radioactive by a "pulse" of glucose-(14)C followed by a "chase" with nonradioactive glucose. Specific activity changes in glycogen isolated during the "chase" showed that glycogen was in constant turnover. When glycogen was made radioactive by a "pulse" of glucose-(14)C and the cells placed in glucose-free medium, the specific activity of isolated glycogen fell rapidly. Thus, the most recently added glucose units of the molecule were also the first to be removed when conditions favoring synthesis were changed to conditions favoring degradation.Even though glycogen is constantly turning over, the enzymatic "machinery" for its synthesis is relatively stable and not dependent on continuous protein or RNA synthesis, as shown by experiments with puromycin and actinomycin.

Amino Acids↗
PubMed1968

Glycogen in human peripheral blood leukocytes. II. The macromolecular state of leukocyte glycogen.

Glycogen of normal human blood leukocytes was studied in cell suspensions containing chiefly neutrophiles. In electron micrographs of neutrophiles stained with lead the glycogen particles appear to be relatively uniform with a diameter of 20 mmu. At high magnification the 20 mmu particle appears to be composed of at least eight subunits. Leukocyte glycogen released by lysis or homogenization sediments as a single peak of high molecular weight material. The great majority of the cell glycogen can be accounted for in the large molecular weight material. The large molecular weight material is degraded to small fragments by alpha-amylase and partially degraded by beta-amylase. Purification of cell glycogen by alkali extraction and ethanol precipitation produces a relatively uniform particle smaller than the original native macromolecule. Native glycogen was prepared in pure form by a sucrose density gradient technique and its purity demonstrated by its susceptibility to purified alpha-amylase and by analytical ultracentrifugation.

Adult↗