The Cytological Distribution in Pigeon Skeletal Muscle of Enzymes Acting on Phosphorylated Nucleotides

Abstract

The elaboration of high energy phosphate bonds has assumed a crucial role (1) in the energy conversions associated with the maintenance of biological systems. The transfer of this bound energy is mediated principally through the turnover of adenosinetriphosphate 1 which is derived either from aerobic respiration or by glycolysis in animal tissues when integrated enzyme systems catalyze the esterification of adenine nucleotide acceptors with inorganic phosphate. The bulk of the evidence for this concept is derived from studies on tissue dispersions or "cell-free homogenates" which are essentially suspensions of cellular particles obtained by mashing or grinding tissues until few intact cells remain. Several workers have shown that the metabolic activity of mashed tissue is brief but can be slightly prolonged by procedures which generate and conserve the high energy phosphorylated intermediates. It is not oxidation alone but the extent of accompanying oxidative phosphorylation and the utilization of phosphorylation energy which determine the structural and metabolic perpetuation of the constituents of tissue dispersions (2). Under such severe treatment as maceration it is not very remarkable, as Barron, Ardao, and He~ron (3) so aptly demonstrate in their studies, that the metabolic patterns and pathways of disrupted and whole cells are very different.It is pertinent, therefore, to inquire into the circumstances which contribute to alterations in metabolism when cells are ruptured. The injurious effect of breaking cells has been attributed to the dissolution of organization and the consequent release of autolytic enzymes normally segregated in the cell among the different discrete cellular particles. A rapid depletion of ,-~P reserves en-

Interaction of creatine kinase and adenylate kinase systems in muscle cells

“…The cytosolic AK (AK1) is polymorphic in man (AKI*I and AKI*2) and AKI*I accounts for 95 % of the AK1 isoenzyme [16]. Part of the cytosolic AK is bound to myofibrils and is called myofibrillar AK [17][18][19]. The mitochondrial AK is located between the mitochondrial membranes with fatty acid-CoA ligase [14,19].…”

Phase and Electron Microscope Studies of the Interrelationship of Cytochondria and Myofibrils in Pigeon Breast Muscle

“…The ultrastructure of the sarcosomes is still uncertain. There is little doubt that the dense spheres shown with the electron microscope are really sarcosomes (12,13), since their positions correlate so well with phase microscope observations. However, even when sectioned at 0.025 /~, the dense portion still appears homogeneous, although one electron micrograph did give a vague impression of a finely laminated structure.…”

“…Because of their specific occurrence in muscle these small particles are more correctly designated sarcosomes (muscle bodies). In accord with previously published work (12,13) all sarcoplasmic inclusions, excluding nuclei and myofibrils, are grouped together and considered under the inclusive term cytochondria.…”

“…Kitiyakara and Harman (12) report that sarcosomes are more osmiophilic and refringent than mitochondria, do not undergo osmotic swelling, and are highly soluble in organic solvents. Harman and Osborne (13) have demonstrated negligible oxidative enzyme activity for sarcosomes as compared to mitochondria.…”

The Decrease in Volume of the Sarcosomes during Myocardial Contraction and its Biochemical Significance

“…the dephospho -For further information as to I lie structure and function of the sacrosonies see the publications cited in the bibliography (1,2,11,26,27,29,31,34,35) o rylation of adenosine triphosphate which liberates the energy required to elicit I he systole and the rigidity of t lie heart in vivo and post mortem re spectively.…”