scholarly journals Autoradiographic Studies of Intracellular Calcium in Frog Skeletal Muscle

1965 ◽  
Vol 48 (3) ◽  
pp. 455-479 ◽  
Author(s):  
Saul Winegrad
Keyword(s):  
Skeletal Muscle ◽  
Theoretical Analysis ◽  
Intracellular Calcium ◽  
Tissue Section ◽  
Room Temperature ◽  
Freeze Substitution ◽  
Frog Skeletal Muscle ◽  
Thin Filaments ◽  
Emulsion Film

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 Ca45. The muscles had been fixed with an oxalate-containing osmium solution at rest at room temperature, at rest at 4°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 µ 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 µ) 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.

scholarly journals The Intracellular Site of Calcium Activation of Contraction in Frog Skeletal Muscle

1970 ◽  
Vol 55 (1) ◽  
pp. 77-88 ◽  
Author(s):  
Saul Winegrad
Keyword(s):  
Skeletal Muscle ◽  
Room Temperature ◽  
Half Time ◽  
Frog Skeletal Muscle ◽  
Calcium Efflux ◽  
Transverse Tubules ◽  
Calcium Activation ◽  
Thin Filaments ◽  
Almost All ◽  
Terminal Cisternae

Radioautography has been used to localize 45Ca in isotopically labeled frog skeletal muscle fibers which had been quickly frozen during a maintained tetanus, a declining tetanus, or during the period immediately following a tetanus or a contracture. During a tetanus almost all of the myofibrillar 45Ca is localized in the region of the sarcomere occupied by the thin filaments. The amount varies with the tension being developed by the muscle. The movement of calcium within the reticulum from the tubular portion to the terminal cisternae during the posttetanic period has a half-time of about 9 sec at room temperature and a Q10 of about 1.7. Repolarization is not necessary for this movement. Evidence is given to support the notion that most calcium efflux from the cell occurs from the terminal cisternae into the transverse tubules.

Ultra-Rapid Freezing of Isolated Skeletal Muscle Fibers

1977 ◽  
Vol 35 ◽  
pp. 576-577
Author(s):  
Joachim R. Sommer ◽  
Nancy R. Wallace
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Granular Material ◽  
Nuclear Envelope ◽  
Intracellular Calcium ◽  
Ruthenium Red ◽  
Threshold Concentration ◽  
Rapid Freezing ◽  
Frog Skeletal Muscle ◽  
Electrical Isolation

After Howell (1) had shown that ruthenium red treatment of fixed frog skeletal muscle caused collapse of the intermediate cisternae of the sarcoplasmic reticulum (SR), forming a pentalaminate structure by obi iterating the SR lumen, we demonstrated that the phenomenon involves the entire SR including the nuclear envelope and that it also occurs after treatment with other cations, including calcium (2,3,4).From these observations we have formulated a hypothesis which states that intracellular calcium taken up by the SR at the end of contraction causes the M rete to collapse at a certain threshold concentration as the first step in a subsequent centrifugal zippering of the free SR toward the junctional SR (JSR). This would cause a) bulk transport of SR contents, such as calcium and granular material (4) into the JSR and, b) electrical isolation of the free SR from the JSR.

Determinants of relaxation rate in skinned frog skeletal muscle fibers

1998 ◽  
Vol 274 (6) ◽  
pp. C1608-C1615 ◽  
Author(s):  
Philip A. Wahr ◽  
J. David Johnson ◽  
Jack. A. Rall
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Slow Phase ◽  
Frog Skeletal Muscle ◽  
Force Of Contraction ◽  
Thin Filaments ◽  
Fast Phase ◽  
Skeletal Muscle Fibers ◽  
Kinetics Of ◽  
Overall Kinetics

The influences of sarcomere uniformity and Ca2+ concentration on the kinetics of relaxation were examined in skinned frog skeletal muscle fibers induced to relax by rapid sequestration of Ca2+ by the photolysis of the Ca2+ chelator, diazo-2, at 10°C. Compared with an intact fiber, diazo-2-induced relaxation exhibited a faster and shorter initial slow phase and a fast phase with a longer tail. Stabilization of the sarcomeres by repeated releases and restretches during force development increased the duration of the slow phase and slowed its kinetics. When force of contraction was decreased by lowering the Ca2+concentration, the overall kinetics of relaxation was accelerated, with the slow phase being the most sensitive to Ca2+ concentration. Twitchlike contractions were induced by photorelease of Ca2+ from a caged Ca2+ (DM-Nitrophen), with subsequent Ca2+ sequestration by intact sarcoplasmic reticulum or Ca2+ rebinding to caged Ca2+. These twitchlike responses exhibited relaxation kinetics that were about twofold slower than those observed in intact fibers. Results suggest that the slow phase of relaxation is influenced by the degree of sarcomere homogeneity and rate of Ca2+ dissociation from thin filaments. The fast phase of relaxation is in part determined by the level of Ca2+ activation.

scholarly journals Intracellular Calcium Movements of Frog Skeletal Muscle during Recovery from Tetanus

1968 ◽  
Vol 51 (1) ◽  
pp. 65-83 ◽  
Author(s):  
Saul Winegrad
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Skeletal Muscles ◽  
Room Temperature ◽  
Complete Recovery ◽  
Mechanical Activity ◽  
Tetanic Stimulation ◽  
Frog Skeletal Muscle ◽  
Fixation Techniques ◽  
Terminal Cisternae

Radioautographs of 45Ca-labeled frog skeletal muscles have been prepared using freeze-dry and vapor fixation techniques to avoid displacement of the isotope during the preparation of the radioautographs. 45Ca has been localized in resting muscles exposed to 45Ca Ringer's for 5 min or 5 hr and in isotopically labeled muscles recovering from tetanic stimulation at room temperature or at 4°C. In muscles soaked at rest for 5 min 45Ca was present almost exclusively in the terminal cisternae. In all other muscles there were three sites at which the isotope was concentrated: (a) the terminal cisternae, (b) the intermediate cisternae and the longitudinal tubules, and (c) the A band portion of the myofibrils. The terminal cisternae were labeled more rapidly than the myofibrils, but both exchanges were accelerated by electrical stimulation. The amount of 45Ca in the longitudinal tubules and the intermediate cisternae decreased with time after a tetanus as the amount in the terminal cisternae increased. It is proposed that electrical stimulation releases calcium from the terminal cisternae and that relaxation occurs from the binding of the released calcium by the longitudinal tubules and the intermediate cisternae. Complete recovery from mechanical activity involves the transport of this bound calcium into the reticulum and its subsequent binding by the terminal cisternae. Resting exchange of calcium occurs primarily between the terminal cisternae and the transverse tubules.

Side bridge geometry after quick-freezing of stimulated and unstimulated frog skeletal muscle fibers

1983 ◽  
Vol 41 ◽  
pp. 464-465
Author(s):  
J.R. Sommer ◽  
R. Nassar ◽  
S. Walker
Keyword(s):  
Skeletal Muscle ◽  
Time Course ◽  
Muscle Fibers ◽  
Freeze Fracture ◽  
Freeze Substitution ◽  
Frog Skeletal Muscle ◽  
Specimen Holder ◽  
Skeletal Muscle Fibers ◽  
Quick Freezing ◽  
The Impact

Quick-freezing allows the structural analysis of timed perturbations of morphology. We are presenting preliminary results concerning the feasibility of studying directly the side bridge geometry of actin-myosin interactions within the time course of a twitch in single intact frog skeletal muscle fibers, both by freeze-substitution and freeze-fracture after quick-freezing, and following various time intervals between stimulation and impact of the fibers on a liquid He-cooled copper block.Materials and Methods. The quick-freezing device was a "Slammer"(Polaron) for which the electronics had been redesigned; they are capable, in combination with a Grass S48 stimulator, of any stimulation interval between 0 and 1 sec prior to freezing, including tetanus. The actual elapsed time between stimulation and freezing is recorded with a digital clock. Single intact tendonto- tendon frog skeletal muscle fibers (semitendinosus of r. temporaria) or toe muscle bundles (r.pipiens) were isolated by sharp dissection and placed between coextensive Pt stimulation wires on blackened 2% agarose, the height of which on the specimen holder was adjusted appropriately with respect to a spacer ring both, to calibrate the impact time and to prevent smashing of the fibers.

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