scholarly journals ULTRASTRUCTURE OF THE RESTING AND CONTRACTED STRIATED MUSCLE FIBER AT DIFFERENT DEGREES OF STRETCH

1961 ◽  
Vol 11 (1) ◽  
pp. 95-117 ◽  
Author(s):  
F. Carlsen ◽  
G. G. Knappeis ◽  
F. Buchthal
Keyword(s):  
Isometric Contraction ◽  
Sarcomere Length ◽  
Striated Muscle ◽  
Fiber Diameter ◽  
Filament Length ◽  
Filament Diameter ◽  
Cent Increase ◽  
Passive Stretch ◽  
Tetanic Tension ◽  
Striated Muscle Fiber

Passive stretch, isometric contraction, and shortening were studied in electron micrographs of striated, non-glycerinated frog muscle fibers. The artifacts due to the different steps of preparation were evaluated by comparing sarcomere length and fiber diameter before, during, and after fixation and after sectioning. Tension and length were recorded in the resting and contracted fiber before and during fixation. The I filaments could be traced to enter the A band between the A filaments on both sides of the I band, creating a zone of overlap which decreased linearly with stretch and increased with shortening. This is consistent with a sliding filament model. The decrease in the length of the A and I filaments during isometric contraction and the finding that fibers stretched to a sarcomere length of 3.7 µ still developed 30 per cent of the maximum tetanic tension could not be explained in terms of the sliding filament model. Shortening of the sarcomeres near the myotendinous junctions which still have overlap could account for only one-sixth of this tension, indicating that even those sarcomeres stretched to such a degree that there is a gap between A and I filaments are activated during isometric contraction (increase in stiffness). Shortening, too, was associated with changes in filament length. The diameter of A filaments remained unaltered with stretch and with isometric contraction. Shortening of 50 per cent was associated with a 13 per cent increase in A filament diameter. The area occupied by the fibrils and by the interfibrillar space increased with shortening, indicating a 20 per cent reduction in the volume of the fibrils when shortening amounted to 40 per cent.

scholarly journals POLARIZED LIGHT OBSERVATIONS ON STRIATED MUSCLE CONTRACTION IN A MITE

1967 ◽  
Vol 32 (1) ◽  
pp. 169-179 ◽  
Author(s):  
John F. Aronson
Keyword(s):  
Light Microscopy ◽  
Sarcomere Length ◽  
Striated Muscle ◽  
Polarized Light ◽  
Rate Of Change ◽  
Filament Length ◽  
Relative Movement ◽  
Significant Difference ◽  
Average Slope ◽  
Region Length

Contraction of individual sarcomeres within the living mite Tarsonemus sp. was observed by polarized light microscopy. In unflattened animals the usual range of contraction was such that the minimum sarcomere length approximated the length of the A region, and the maximum sarcomere length was about twice the length of the A region. The central sarcomeres of the dorsal metapodosomal muscles were observed in detail. The A band length increased slightly with increasing sarcomere length since the regression of I region length on sarcomere length had an average slope of 0.91. When the A band length in a sarcomere which was shortening was compared with the length when the same sarcomere lengthened, no significant difference was seen. The A band of each sarcomere seemed to act as a not too rigid limit to further shortening; this agreed with the reversible shortening of a muscle in which the A band had been experimentally shortened. An H region was visible at long sarcomere lengths and was not visible at short sarcomere lengths, even when the muscle was actively shortening. The rate of change of H region length with sarcomere length suggested that I filament length may increase as sarcomere length increases. Despite this effect and the small increase in A length with sarcomere length, the results are considered to be consistent with a model in which shortening occurs by the relative movement of A and I filaments, with little or no change in length of either set of filaments. Sarcomere shortening was clearly associated with an increase in the retardation of the A region.

Sarcomere length control in striated muscle

1982 ◽  
Vol 242 (3) ◽  
pp. H411-H420 ◽  
Author(s):  
R. van Heuningen ◽  
W. H. Rijnsburger ◽  
H. E. ter Keurs
Keyword(s):  
Sarcomere Length ◽  
Striated Muscle ◽  
Feedforward Control ◽  
Muscle Length ◽  
Transient Behavior ◽  
Loop Filter ◽  
Internal Position ◽  
Optimal Damping ◽  
Internal Velocity ◽  
Muscle Responses

A system that makes control of muscle length (ML), sarcomere length (SL), and force (F) possible in striated muscle preparations is described. SL was measured by light diffraction techniques and two diffractometers. Control was performed by influencing ML with a penmotor system with a frequency response of 190 Hz. SL or F could be controlled by interrupting the internal position (i.e., ML) feedback of the motor and by closing the respective loop. Velocity feedback of the motor through an internal velocity coil was maintained in all cases for optimal damping. Steady-state error of the system was minimized by an integrating loop filter. The feedback path was selected by means of potentiometers or analog switches. Electronic stops in the circuit protected the muscle against excessive stretch and load. A microprocessor-based average-response computer could be used for feedforward control to eliminate noise or to analyze longitudinal uniformity of the muscle. Responses of rat cardiac trabeculae during SL and F control are shown. Transient behavior of SL and F during control and measures to eliminate the transients are discussed.

scholarly journals In Vivo Sarcomere Length Measurement in Whole Muscles during Passive Stretch and Twitch Contractions

2017 ◽  
Vol 112 (4) ◽  
pp. 805-812 ◽  
Author(s):  
Kevin W. Young ◽  
Bill P.-P. Kuo ◽  
Shawn M. O’Connor ◽  
Stojan Radic ◽  
Richard L. Lieber
Keyword(s):  
Sarcomere Length ◽  
Length Measurement ◽  
Passive Stretch

Sarcomere strain and heterogeneity correlate with injury to frog skeletal muscle fiber bundles

2004 ◽  
Vol 97 (5) ◽  
pp. 1803-1813 ◽  
Author(s):  
Tina J. Patel ◽  
Ronnie Das ◽  
Jan Fridén ◽  
Gordon J. Lutz ◽  
Richard L. Lieber
Keyword(s):  
Line Width ◽  
Muscle Fiber ◽  
Muscle Activation ◽  
Sarcomere Length ◽  
Eccentric Contraction ◽  
Fiber Bundles ◽  
Lower Yield ◽  
Bathing Medium ◽  
Average Maximum ◽  
Tetanic Tension

Sarcomere length and first-order diffraction line width were measured by laser diffraction during elongation of activated frog tibialis anterior muscle fiber bundles (i.e., eccentric contraction) at nominal fiber strains of 10, 25, or 35% ( n = 18) for 10 successive contractions. Tetanic tension, measured just before each eccentric contraction, differed significantly among strain groups and changed dramatically during the 10-contraction treatment ( P < 0.01). Average maximum tetanic tension for the three groups measured before any treatment was 203.7 ± 6.8 kN/m2, but after the 10-eccentric contraction sequence decreased to 180.3 ± 3.8, 125.1 ± 7.8, and 78.3 ± 5.1 kN/m2 for the 10, 25, and 35% strain groups, respectively ( P < 0.0001). Addition of 10 mM caffeine to the bathing medium decreased the loss of tetanic tension in the 10% strain group but had only a minimal effect on either the 25 or 35% strain groups. Diffraction pattern line width, a measure of sarcomere length heterogeneity, increased significantly with muscle activation and then continued to increase with successive stretches of the activated muscle. Line width increase after each stretch was significantly correlated with the lower yield tension of the successive contractile record. These data demonstrate a direct association and, perhaps, a causal relationship between sarcomere strain and fiber bundle injury. They also demonstrate that muscle injury is accompanied by a progressive increase in sarcomere length heterogeneity, yielding lower yield tension as injury progresses.

scholarly journals What makes skeletal muscle striated? Discoveries in the endosarcomeric and exosarcomeric cytoskeleton

2018 ◽  
Vol 42 (4) ◽  
pp. 672-684 ◽  
Author(s):  
Jack A. Rall
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fiber ◽  
Intermediate Filament ◽  
Sarcomere Length ◽  
Thick Filament ◽  
Skeletal Muscle Fiber ◽  
Elastic Behavior ◽  
Filament Length ◽  
Iconic Images ◽  
Elastic Protein

One of the most iconic images in biology is the cross-striated appearance of a skeletal muscle fiber. The repeating band pattern shows that all of the sarcomeres are the same length. All of the A bands are the same length and are located in the middle of the sarcomeres. Furthermore, all of the myofibrils are transversely aligned across the muscle fiber. It has been known for 300 yr that skeletal muscle is striated, but only in the last 40 yr has a molecular understanding of the striations emerged. In the 1950s it was discovered that the extraction of myosin from myofibrils abolished the A bands, and the myofibrils were no longer striated. With the further extraction of actin, only the Z disks remained. Strangely, the sarcomere length did not change, and these “ghost” myofibrils still exhibited elastic behavior. The breakthrough came in the 1970s with the discovery of the gigantic protein titin. Titin, an elastic protein ~1 µm in length, runs from the Z disk to the middle of the A band and ensures that each sarcomere is the same length. Titin anchors the A band in the middle of the sarcomere and may determine thick-filament length and thus A-band length. In the 1970s it was proposed that the intermediate filament desmin, which surrounds the Z disks, connects adjacent myofibrils, resulting in the striated appearance of a skeletal muscle fiber.

scholarly journals Changes in thick filament length in Limulus striated muscle.

1977 ◽  
Vol 75 (2) ◽  
pp. 366-380 ◽  
Author(s):  
M M Dewey ◽  
B Walcott ◽  
D E Colflesh ◽  
H Terry ◽  
R J Levine
Keyword(s):  
Horseshoe Crab ◽  
Striated Muscle ◽  
Thick Filament ◽  
Filament Length ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Wide Range ◽  
The Difference

Here we describe the change in thick filament length in striated muscle of Limulus, the horseshoe crab. Long thick filaments (4.0 microns) are isolated from living, unstimulated Limulus striated muscle while those isolated from either electrically or K+-stimulated fibers are significantly shorter (3.1 microns) (P less than 0.001). Filaments isolated from muscle glycerinated at long sarcomere lengths are long (4.4 microns) while those isolated from muscle glycerinated at short sarcomere lengths are short (2.9 microns) and the difference is significant (P less than 0.001). Thin filaments are 2.4 microns in length. The shortening of thick filaments is related to the wide range of sarcomere lengths exhibited by Limulus telson striated muscle.

scholarly journals FILAMENT LENGTHS IN STRIATED MUSCLE

1963 ◽  
Vol 19 (2) ◽  
pp. 369-390 ◽  
Author(s):  
Sally G. Page ◽  
H. E. Huxley
Keyword(s):  
Electron Microscope ◽  
Striated Muscle ◽  
Filament Length

Filament lengths in resting and excited frog muscles have been measured in the electron microscope, and investigations made of the changes in length that are found under different conditions, to distinguish between those changes which arise during preparation and the actual differences in the living muscles. It is concluded that all the measured differences in filament length are caused by the preparative procedures in ways that can be simply accounted for, and that the filament lengths are the same in both resting and excited muscles at all sarcomere lengths greater than 2.1 µ, viz., A filaments, 1.6 µ; I filaments, 2.05 µ. The fine periodicity visible along the I filaments also has been measured in frog, toad, and rabbit muscles and found to be 406 A.

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