scholarly journals THE STRUCTURE OF INTERSEGMENTAL MUSCLE FIBERS IN AN INSECT, PERIPLANETA AMERICANA L

1966 ◽  
Vol 29 (3) ◽  
pp. 449-459 ◽  
Author(s):  
David S. Smith
Keyword(s):  
Periplaneta Americana ◽  
Flight Muscle ◽  
Muscle Fibers ◽  
Structural Features ◽  
Mitochondrial Content ◽  
Thin Filaments ◽  
Transverse Tubular System ◽  
Thick Filaments ◽  
Tubular System ◽  
Contraction And Relaxation

The organization of intersegmental muscle fibers associated with the dorsal abdominal sclerites of the cockroach is described. These fibers correspond closely, in the disposition and derivation of the membranes of the transverse tubular system and sarcoplasmic reticulum cisternae, with insect synchronous flight muscle fibers, but differ markedly from these in their fibrillar architecture and mitochondrial content. The mitochondria are small and generally aligned alongside the prominent I bands of the sarcomere, and, in the best-oriented profiles of the A bands, thick filaments are associated with orbitals of twelve thin filaments, a configuration that has also been observed in striated fibers of insect visceral muscle. These structural features of insect muscles are compared and discussed in terms of possible variations in the control of contraction and relaxation, and in the nature of their mechanical role.

scholarly journals Polarization of Tryptophan Fluorescence from Single Striated Muscle Fibers

1972 ◽  
Vol 59 (1) ◽  
pp. 103-120 ◽  
Author(s):  
C. G. dos Remedios ◽  
R. G. C. Millikan ◽  
M. F. Morales
Keyword(s):  
Sarcomere Length ◽  
Striated Muscle ◽  
Muscle Fibers ◽  
Tryptophan Fluorescence ◽  
Thin Filaments ◽  
A Value ◽  
Striated Muscle Fibers ◽  
Types Of Muscle Fibers ◽  
Cross Bridges ◽  
Contraction And Relaxation

Instrumentation has been developed to detect rapidly the polarization of tryptophan fluorescence from single muscle fibers in rigor, relaxation, and contraction. The polarization parameter (P⊥) obtained by exiciting the muscle tryptophans with light polarized perpendicular to the long axis of the muscle fiber had a magnitude P⊥ (relaxation) > P⊥ (contraction) > P⊥ (rigor) for the three types of muscle fibers examined (glycerinated rabbit psoas, glycerinated dorsal longitudinal flight muscle of Lethocerus americanus, and live semitendinosus of Rana pipiens). P⊥ from single psoas fibers in rigor was found to increase as the sarcomere length increased but in relaxed fibers P⊥ was independent of sarcomere length. After rigor, pyrophosphate produced little or no change in P⊥, but following an adenosine triphosphate (ATP)-containing solution, pyrophosphate produced a value of P⊥ that fell between the contraction and relaxation values. Sinusoidal or square wave oscillations of the muscle of amplitude 0.5–2.0% of the sarcomere length and frequency 1, 2, or 5 Hz were applied in rigor when the myosin cross-bridges are considered to be firmly attached to the thin filaments. No significant changes in P⊥ were observed in either rigor or relaxation. The preceding results together with our present knowledge of tryptophan distribution in the contractile proteins has led us to the conclusion that the parameter P⊥ is a probe of the contractile state of myosin which is probably sensitive to the orientation of the myosin S1 subfragment.

scholarly journals Chloride currents from the transverse tubular system in adult mammalian skeletal muscle fibers

2010 ◽  
Vol 137 (1) ◽  
pp. 21-41 ◽  
Author(s):  
Marino DiFranco ◽  
Alvaro Herrera ◽  
Julio L. Vergara
Keyword(s):  
Skeletal Muscle ◽  
Time Course ◽  
Muscle Fibers ◽  
Optical Data ◽  
Mammalian Skeletal Muscle ◽  
Chloride Currents ◽  
Actual Distribution ◽  
Transverse Tubular System ◽  
Skeletal Muscle Fibers ◽  
Tubular System

Chloride fluxes are the main contributors to the resting conductance of mammalian skeletal muscle fibers. ClC-1, the most abundant chloride channel isoform in this preparation, is believed to be responsible for this conductance. However, the actual distribution of ClC-1 channels between the surface and transverse tubular system (TTS) membranes has not been assessed in intact muscle fibers. To investigate this issue, we voltageclamped enzymatically dissociated short fibers using a two-microelectrode configuration and simultaneously recorded chloride currents (ICl) and di-8-ANEPPS fluorescence signals to assess membrane potential changes in the TTS. Experiments were conducted in conditions that blocked all but the chloride conductance. Fibers were equilibrated with 40 or 70 mM intracellular chloride to enhance the magnitude of inward ICl, and the specific ClC-1 blocker 9-ACA was used to eliminate these currents whenever necessary. Voltage-dependent di-8-ANEPPS signals and ICl acquired before (control) and after the addition of 9-ACA were comparatively assessed. Early after the onset of stimulus pulses, di-8-ANEPPS signals under control conditions were smaller than those recorded in the presence of 9-ACA. We defined as attenuation the normalized time-dependent difference between these signals. Attenuation was discovered to be ICl dependent since its magnitude varied in close correlation with the amplitude and time course of ICl. While the properties of ICl, and those of the attenuation seen in optical records, could be simultaneously predicted by model simulations when the chloride permeability (PCl) at the surface and TTS membranes were approximately equal, the model failed to explain the optical data if PCl was precluded from the TTS membranes. Since the ratio between the areas of TTS membranes and the sarcolemma is large in mammalian muscle fibers, our results demonstrate that a significant fraction of the experimentally recorded ICl arises from TTS contributions.

scholarly journals A filamentous cytoskeleton in vertebrate smooth muscle fibers.

1976 ◽  
Vol 68 (3) ◽  
pp. 539-556 ◽  
Author(s):  
P Cooke
Keyword(s):  
Molecular Weight ◽  
Smooth Muscle ◽  
Muscle Protein ◽  
Muscle Fibers ◽  
Thin Filaments ◽  
The Third ◽  
Dense Bodies ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Cell Fractions

There are three classes of myofilaments in vertebrate smooth muscle fibers. The thin filaments correspond to actin and the thick filaments are identified with myosin. The third class of myofilaments (100 A diam) is distinguished from both the actin and the myosin on the basis of fine structure, solubility, and pattern of localization in the muscle fibers. Direct structural evidence is presented to show that the 100A filament constitute an integrated filamentous network with the dense bodies in the sarcoplasm, and that they are not connected to either the actin or myosin filaments. Examination of (a) isolated dense bodies, (b) series of consecutive sections through the dense bodies, and (c) redistributed dense bodies in stretched muscle fibers supports this conclusion. It follows that the 100-A filaments complexes constitute a structrally distinct filamentous network. Analysis of polyacrylamide gels after electrophoresis of cell fractions that are enriched with respect to the 100-A filaments shows the presence of a new muscle protein with a molecular weight of 55,000. This protein can form filamentous segments that closely resemble in structure the native, isolated 100-A filaments. The results indicate that the filamentous network has a structure and composition that distinguish it from the actin and myosin in vertebrate smooth muscle.

scholarly journals An improved vaseline gap voltage clamp for skeletal muscle fibers.

1976 ◽  
Vol 67 (3) ◽  
pp. 265-293 ◽  
Author(s):  
B Hille ◽  
D T Campbell
Keyword(s):  
Skeletal Muscle ◽  
Voltage Clamp ◽  
Sodium Current ◽  
Muscle Fibers ◽  
Complex Impedance ◽  
Sodium Currents ◽  
Disk Model ◽  
Transverse Tubular System ◽  
Skeletal Muscle Fibers ◽  
Tubular System

A Vaseline gap potentiometric recording and voltage clamp method is developed for frog skeletal muscle fibers. The method is based on the Frankenhaeuser-Dodge voltage clamp for myelinated nerve with modifications to improve the frequency response, to compensate for external series resistance, and to compensate for the complex impedance of the current-passing pathway. Fragments of single muscle fibers are plucked from the semitendinosus muscle and mounted while depolarized by a solution like CsF. After Vaseline seals are formed between fluid pools, the fiber ends are cut once again, the central region is rinsed with Ringer solution, and the feedback amplifiers are turned on. Errors in the potential and current records are assessed by direct measurements with microelectrodes. The passive properties of the preparation are simulated by the "disk" equivalent circuit for the transverse tubular system and the derived parameters are similar to previous measurements with microelectrodes. Action potentials at 5 degrees C are long because of the absence of delayed rectification. Their shape is approximately simulated by solving the disk model with sodium permeability in the surface and tubular membranes. Voltage clamp currents consist primarily of capacity currents and sodium currents. The peak inward sodium current density at 5 degrees C is 3.7 mA/cm2. At 5 degrees C the sodium currents are smoothly graded with increasing depolarization and free of notches suggesting good control of the surface membrane. At higher temperatures a small, late extra inward current appears for small depolarizations that has the properties expected for excitation in the transverse tubular system. Comparison of recorded currents with simulations shows that while the transverse tubular system has regenerative sodium currents, they are too small to make important errors in the total current recorded at the surface under voltage clamp at low temperature. The tubules are definitely not under voltage clamp control.

scholarly journals Voltage Clamp Experiments on Single Muscle Fibers of Rana pipiens

1972 ◽  
Vol 60 (1) ◽  
pp. 1-19 ◽  
Author(s):  
L. E. Moore
Keyword(s):  
Voltage Clamp ◽  
Rana Pipiens ◽  
Muscle Fibers ◽  
Petroleum Jelly ◽  
Single Muscle ◽  
Transverse Tubular System ◽  
Anomalous Rectification ◽  
Outward Currents ◽  
Delayed Rectification ◽  
Tubular System

A voltage clamp for single muscle fibers has been developed. Stability of the system was achieved when an artificial node was created by enclosing a single muscle fiber in a petroleum jelly seal which served as an analogue of the myelin sheath. Typical voltage clamp records were obtained with large inward transient currents followed by a delayed rectification of the outward currents. These currents looked qualitatively similar when the transverse tubular system was destroyed. Errors in current measurement, especially those due to anomalous rectification, are discussed.

scholarly journals The Mode of Transverse Spread of Contraction Initiated by Local Activation in Single Frog Muscle Fibers

1967 ◽  
Vol 50 (9) ◽  
pp. 2167-2176 ◽  
Author(s):  
Haruo Sugi ◽  
Rikuo Ochi
Keyword(s):  
Muscle Fibers ◽  
Fiber Surface ◽  
Ringer Solution ◽  
Frog Muscle ◽  
Transverse Tubular System ◽  
Local Activation ◽  
Current Pulses ◽  
Negative Current ◽  
Tubular System

Isolated single frog muscle fibers were locally activated by applying negative current pulses to a pipette whose tip was in contact with the fiber surface. In contrast to the graded inward spread of contraction initiated by a moderate depolarization, the contraction in response to a strong negative current was observed to spread transversely around the whole perimeter but not through the center of the fiber. This response was elicited only with pipettes of more than 6 µ diameter. The response was still present if the sodium of the Ringer solution was replaced by choline, or the chloride was replaced by nitrate or propionate. The duration of the response appeared to be independent of the duration of stimulating current in fresh fibers, while the contraction lasted as long as the current went on in deteriorated fibers. The contraction was first initiated at the area of fiber surface covered by the pipette, and spread around the perimeter of the fiber with a velocity of 0.8–6 cm/sec. Possible mechanisms of the response are discussed in connection with the properties of the transverse tubular system, the possibility of some self-propagating process along the walls of the tubules being suggested.

The Fibrillar Flight Muscles of Giant Water-Bugs: An Electron-Microscope Study

1967 ◽  
Vol 2 (3) ◽  
pp. 435-444
Author(s):  
DOREEN E. ASHHURST
Keyword(s):  
Electron Microscope ◽  
Sarcoplasmic Reticulum ◽  
Flight Muscle ◽  
Muscle Fibres ◽  
Transverse Tubular System ◽  
Tropical Water ◽  
Tubular System ◽  
Flight Muscles ◽  
And Function ◽  
Water Bugs

The fibrillar flight muscles of several species of tropical water-bugs of the family Belostomatidae have been examined in the electron microscope. The myofibrils are very similar to those of the other fibrillar flight muscles which have been studied. The membrane systems, however, display features which appear to be peculiar to this family. The sarcoplasmic reticulum can be divided into three parts: a series of interconnecting vesicles surrounding the Z-lines, randomly scattered small vesicles around the myofibrils, and flattened cisternae which lie along the transverse tubular system, and form the dyads. These three components of the sarcoplasmic reticulum do not appear to be interconnected. The cisternae of the dyads contain an electrondense substance. The narrow tubules of the transverse tubular system or T-system penetrate deep into the fibre from the cell membrane. They follow a course roughly perpendicular to the myofibrils at the level of the M-lines. The dyads are scattered along their length, and may not be near a myofibril. Another system of very large vesicles is found in the muscle fibres, interspersed among the mitochondria. These vesicles usually appear to be empty; their nature and function are not at present known. Numerous mitochondria are present among the myofibrils. The peculiarities of the water-bug fibrillar flight muscle are discussed in relation to the flight muscles of other insects and the physiological properties of fibrillar flight muscle.

scholarly journals Effects of Caffeine on Crayfish Muscle Fibers

1970 ◽  
Vol 55 (5) ◽  
pp. 640-664 ◽  
Author(s):  
Dante J. Chiarandini ◽  
John P. Reuben ◽  
Philip W. Brandt ◽  
Harry Grundfest
Keyword(s):  
Time Course ◽  
Muscle Fibers ◽  
Resting Potential ◽  
Induced Responses ◽  
Single Muscle ◽  
Transverse Tubular System ◽  
Crayfish Muscle ◽  
Number Of Factors ◽  
Tubular System

Contractions are evoked in single muscle fibers of crayfish by intracellular as well as extracellular applications of caffeine. Responses to external applications in concentrations above 2 mM could be induced indefinitely. With concentrations above 5 mM the caffeine-induced responses were highly repeatable. Tensions were transient even when the caffeine remained in the bath. There was no change in resting potential, but during the contraction the effective resistance decreased about 10%. A number of factors (change in pH, Ca, K, and Cl) modified the responses. The time course of the tension was greatly prolonged when the transverse tubular system (TTS) was s swollen and was again shortened when the TTS was caused to shrink. An increased permeability to Ca induced by caffeine was evidenced by the transformation of the normally graded electrical responses to Ca spikes, which are insensitive to tetrodotoxin. The overshoot is a function of both external Ca and caffeine. A 10-fold change in Ca changed the overshoot by 19 mv in the presence of 10 mM caffeine and by 29 mv in 80 mM caffeine. The role of the increased permeability to Ca for caffeine-induced contractions will be analyzed in the accompanying paper.

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