Sickness and Healing: An Anthropological Perspective

Sickness and Healing: An Anthropological Perspective. Robert A. Hahn. New Haven, CT: Yale University Press, 1995 (cloth and paper), viii. 327 pp.     

Enhanced ability of skeletal muscle containing cyclocreatine phosphate to sustain ATP levels during ischemia following beta-adrenergic stimulation

Breast muscle of young chicks fed chow diets containing the creatine analog 1-carboxymethyl-2-iminoimidazolidine (cyclocreatine) accumulated up to 40 mumol/g wet weight of the synthetic phosphagen 1-carboxymethyl-2-imino-3-phosphonoimidazolidine (cyclocreatine-P2-). ATP levels were sustained at high values substantially longer in breast muscle of cyclocreatine-fed chicks, compared to control-fed chicks, during total ischemia initiated 2 h after injection of both groups with the beta-adrenergic agonist isoproterenol (5 mg/kg subcutaneous). For example, in chicks fed 0.5% cyclocreatine for 10-19 days ATP levels in isoproterenol-stimulated breast muscles after 1 h of ischemia at 37 degrees C were 6.1 mumol/g, compared to 1.9 mumol/g for the control-fed group, and after 2 h of ischemia were 3.5 mumol/g compared to 0.6 mumol/g for controls. Creatine-P reserves in isoproterenol-stimulated breast muscles of all dietary groups were essentially exhausted within the first hour of ischemia. In contrast, breast muscle of chicks fed either 1 or 0.5% cyclocreatine still contained 28 and 19 mumol/g of cyclocreatine-P, respectively, after 1 h of ischemia; after 2 h of ischemia, the respective cyclocreatine-P values were 20 and 13 mumol/g. Isoproterenol-stimulated chick breast muscle provides the first skeletal muscle model system for studying the molecular mechanisms by which dietary cyclocreatine helps sustain ATP levels during ischemia. Although adaptive factors are also involved, it is suggested that a significant portion of the ATP-sustaining activity of dietary cyclocreatine in ischemic breast muscle can be attributed to the unique thermodynamic properties of the accumulated cyclocreatine-P. These properties enable cyclocreatine-P to continue to thermodynamically buffer the adenylate system and transport high energy phosphate throughout the long muscle fibers at cytosolic pH values and phosphorylation potentials well below the range where the creatine-P system can function effectively. Synergism between glycolysis and this long-acting synthetic phosphagen might well help delay depletion of ATP levels in skeletal muscles during ischemia. Cyclocreatine feeding provides a unique experimental tool for quantitative evaluation of the proposed protective role of ATP against irreversible cellular damage in skeletal and cardiac muscles during ischemic episodes.     

Rapid separation of the chloroplast and cytoplasmic fractions from intact leaf protoplasts

Intact protoplasts are ruptured by rapid centrifugation through a narrow-aperture nylon mesh and the intact chloroplasts are then separated from the cytoplasm by sedimentation through a layer of silicone oil below the mesh. Within 6 to 8 s of starting the centrifuge, 90% of the chloroplasts are separated into the pellet fraction which contains only 10 to 15% contamination by mitochondria and peroxisomes and less than 5% contamination by soluble cytoplasm as judged by the distribution of marker enzymes. This technique should allow determination of the distribution of metabolites between the chloroplast and cytoplasmic compartments of intact protoplasts.     

The Escherichia coli dnaW mutation is an allele of the adk gene

Summary A dnaW mutant, isolated on the basis of inability to effect conjugal DNA transfer at high temperature, has been shown by complementation and enzyme assay to be defective in the adk (adenylate kinase; EC 2.7.4.3) locus. The adk mutant, known to have reduced ATP concentration at the nonpermissive temperature (Cousin and Belaich 1966), was used to demonstrate a donor energy requirement for stable aggregate formation and for chromosome transfer in conjugation.