AUTORADIOGRAPHIC STUDIES OF INTRACELLULAR CALCIUM IN FROG SKELETAL MUSCLE.
Autoradiographs consisting of a 1000 A thick tissue section and a 1400 A thick emulsion film have been prepared from frog toe muscles labeled with Ca(45). The muscles had been fixed with an oxalate-containing osmium solution at rest at room temperature, at rest at 4 degrees C, during relaxation following K(+) depolarization or after prolonged depolarization. From 6 to 39 per cent of K(+) contracture tension was produced during fixation. The grains in the autoradiographs were always concentrated in the center 0.2 to 0.3 micro of the I band and the region of the overlapping of the thick and thin filaments. The greater the tension produced during fixation, the greater was the concentration in the A band and the smaller the concentration in the I band. Autoradiographs of two muscles fixed by freeze-substitution resembled those of muscles which produced little tension during osmium fixation. Muscles which shortened during fixation produced fewer grains. In the narrow (<2.0 micro) sarcomeres of the shortened muscles, grain density decreased with decreasing sarcomere width. A theoretical analysis of the significance of these grain distributions is proposed and discussed.
D000818:Animals; D001001:Anura; D001345:Autoradiography; D002118:Calcium; D002127:Calcium Isotopes; D003593:Cytoplasm; D004583:Electrons; D006652:Histological Techniques; D008853:Microscopy; D008854:Microscopy, Electron; D009119:Muscle Contraction; D018482:Muscle, Skeletal; D009132:Muscles; D012106:Research; D012518:Sarcomeres
D002127:Calcium Isotopes; D002118:Calcium
CALCIUM; CALCIUM ISOTOPES; EXPERIMENTAL LAB STUDY; FROGS; HISTOLOGICAL TECHNICS; MICROSCOPY, ELECTRON; MUSCLE CONTRACTION; MUSCLES; RADIOAUTOGRAPHY