scholarly journals THE SARCOPLASMIC RETICULUM AND TRANSVERSE TUBULES OF THE FROG'S SARTORIUS

1965 ◽  
Vol 25 (3) ◽  
pp. 209-231 ◽  
Author(s):  
Lee D. Peachey
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Surface Area ◽  
Osmium Tetroxide ◽  
Fiber Surface ◽  
Sartorius Muscle ◽  
Fiber Volume ◽  
Transverse Tubules ◽  
Contraction Coupling ◽  
Terminal Cisternae

The sarcoplasmic reticulum of the frog's sartorius muscle was examined by electron microscopy following sequential fixation in glutaraldehyde and osmium tetroxide and embedding in Epon. The earlier results of Porter and Palade on Ambystoma muscle were confirmed in the sartorius. In addition, the transverse tubules were observed to be continuous across the width of the fiber, a set of flat intermediate cisternae was seen to connect the terminal cisternae to the longitudinal tubules in the A band, and the continuous reticulum collar at the center of the A band was found to be perforated by circular and elongated pores (the fenestrated collar). The transverse tubules have a volume about 0.3 per cent of the fiber volume, and a surface area about 7 times the outer cylindrical surface area for a fiber 100 µ in diameter. The terminal cisternae, the intermediate cisternae, and the longitudinal tubules together with the fenestrated collar each have a volume of 4 to 5 per cent of the fiber volume and a surface area 40 to 50 times the outer surface area of a fiber 100 µ in diameter. Some evidence for continuity of the transverse tubules with the fiber surface is presented, but this is thought to be not so convincing as evidence presented by others. The results are discussed in terms of a possible mechanism for a role of the transverse tubules and sarcoplasmic reticulum in excitation-contraction coupling, as suggested by their morphology and a variety of physiological studies. In this scheme, the transverse tubules are thought to be electrically coupled to the terminal cisternae, so that depolarization of the fiber surface spreads inward along the transverse tubules and to the terminal cisternae, initiating the release of a contraction-activating substance.

scholarly journals Sizes of components in frog skeletal muscle measured by methods of stereology.

1975 ◽  
Vol 66 (1) ◽  
pp. 31-45 ◽  
Author(s):  
B A Mobley ◽  
B R Eisenberg
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Surface Area ◽  
Volume Ratio ◽  
Sartorius Muscle ◽  
Morphological Parameters ◽  
Frog Skeletal Muscle ◽  
Fiber Volume ◽  
Transverse Tubules ◽  
Terminal Cisternae

Stereological techniques of point and intersection counting were used to measure morphological parameters from light and electron micrographs of frog skeletal muscle. Results for sartorius muscle are as follows: myofibrils comprise 83% of fiber volume; their surface to volume ratio is 3.8 mum-1. Mitochondria comprise 1.6% of fiber volume. Transverse tubules comprise 0.32% of fiber volume, and their surface area per volume of fiber is 0.22 mum-1. Terminal cisternae of the sarcoplasmic reticulum comprise 4.1% of fiber volume; their surface area per volume of fiber is 0.54 mum-1. Longitudinal sarcoplasmic reticullum comprises 5.0% of fiber volume, and its surface area per volume of fiber is 1.48 mum-1. Longitudinal bridges between terminal cisternae on either side of a Z disk were observed infrequently; they make up only 0.035% of fiber volume and their surface area per volume of fiber is 0.009 mum-1. T-SR junction occurs over 67% of the surface of transverse tubules and over 27% of the surface of terminal cisternae. The surface to volume ratio of the caveolae is 48 mum-1; caveolae may increase the sarcolemmal surface area by 47%. Essentially the same results were obtained from semitendinosus fibers.

scholarly journals CHANGES IN THE SARCOPLASMIC RETICULUM AND TRANSVERSE TUBULAR SYSTEM OF FAST AND SLOW SKELETAL MUSCLES OF THE MOUSE DURING POSTNATAL DEVELOPMENT

1971 ◽  
Vol 51 (2) ◽  
pp. 369-383 ◽  
Author(s):  
A. R. Luff ◽  
H. L. Atwood
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Postnatal Development ◽  
Surface Area ◽  
Fiber Surface ◽  
Fiber Volume ◽  
Transverse Tubular System ◽  
Tubular System ◽  
Slow Twitch Muscle ◽  
T Tubules ◽  
Relative Change

The sarcoplasmic reticulum (SR) and transverse tubular system (TTS) of a fast-twitch muscle (extensor digitorum longus-EDL) and a slow-twitch muscle (soleus-SOL) of the mouse were examined during postnatal development. Muscles of animals newborn to 60 days old were fixed in glutaraldehyde and osmium tetroxide and examined with an electron microscope. At birth the few T tubules were often oriented longitudinally, but at the age of 10 days most of them had a transverse orientation. In the EDL, the estimated volume of the TTS increased from 0.08% at birth to 0.4% in the adult; corresponding values for the SOL were 0.04% at birth and 0.22% in the adult. A similar relative change was observed in surface area of the TTS during development. Calculated on the basis of a 30 µm diameter fiber, the surface area of the TTS in the EDL increased from 0.60 cm2 TTS/cm2 fiber surface in the newborn to 3.1 cm2/cm2 in the adult, compared with 0.15 cm2/cm2 at birth to 1.80 cm2/cm2 in the adult for the SOL. The SR in the newborn muscles occurred as a loose network of tubules that developed rapidly within the subsequent 20 days, especially at the I band level. The volume of the SR increased in the EDL from 1.1% of fiber volume at birth to 5.5% in the adult. In the SOL the change was from 1.7% to 2.9%. The SOL approached the adult values more rapidly than the EDL, although the EDL had more SR and T tubules. Fibers of both EDL and SOL muscles showed variation in Z line thickness, mitochondrial content, and diameter, but over-all differences between the two muscles in amount of SR and TTS were significant. It is considered that the differing amounts of SR and TTS are closely related to the differing speeds of contraction that have been demonstrated for these two muscles.

Possible role of the transverse tubules in accumulating calcium released from the terminal cisternae by stimulation and drugs

1982 ◽  
Vol 60 (4) ◽  
pp. 503-507 ◽  
Author(s):  
C. P. Bianchi ◽  
S. Narayan
Keyword(s):  
Kinetic Analysis ◽  
Time Constant ◽  
Transverse Tubules ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Mechanical Threshold ◽  
A New Technique ◽  
Frog Sartorius ◽  
Terminal Cisternae

The sizes of the rapidly exchanging and slowly exchanging Ca2+ pools were estimated in frog sartorius muscles. A new technique using Sr2+ to extract the rapidly exchanging pool was used. The method avoids problems of kinetic analysis. The results showed that stimulation causes Ca2+ to be translocated from a compartment which exchanges with a time constant of 800 min to a compartment that can be washed out in 15 min. This is likely a transfer from the terminal cisternae to the transverse tubule. Calculations show that this would represent 0.9% of the Ca2+ released in each twitch. After 300 twitches produced by a 1-Hz stimulation, this accumulation could have increased the Ca concentration in the transverse tubules to 70 mM. A marked increase of Ca2+ concentration of this magnitude in the transverse tubules would raise the mechanical threshold for excitation–contraction coupling and would decrease the efficiency of coupling between contraction and excitation. This could be the explanation of the fatigue observed during this kind of stimulation.

scholarly journals Localization of Ca2+ + Mg2+-ATPase of the sarcoplasmic reticulum in adult rat papillary muscle.

1982 ◽  
Vol 93 (3) ◽  
pp. 883-892 ◽  
Author(s):  
A O Jorgensen ◽  
A C Shen ◽  
P Daly ◽  
D H MacLennan
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Cardiac Muscle ◽  
Papillary Muscle ◽  
Functional Role ◽  
Transverse Tubules ◽  
Contraction Coupling ◽  
Adult Rat ◽  
Sarcoplasmic Reticulum Membrane ◽  
Rat Papillary Muscle ◽  
Junctional Sarcoplasmic Reticulum

Localization of the Ca2+ + Mg2+-ATPase of the sarcoplasmic reticulum in rat papillary muscle was determined by indirect immunofluorescence and immunoferritin labeling of cryostat and ultracryotomy sections, respectively. The Ca2+ + Mg2+-ATPase was found to be rather uniformly distributed in the free sarcoplasmic reticulum membrane but to be absent from both peripheral and interior junctional sarcoplasmic reticulum membrane, transverse tubules, sarcolemma, and mitochondria. This suggests that the Ca2+ + Mg2+-ATPase of the sarcoplasmic reticulum is antigenically unrelated to the Ca2+ + Mg2+-ATPase of the sarcolemma. These results are in agreement with the idea that the sites of interior and peripheral coupling between sarcoplasmic reticulum membrane and transverse tubules and between sarcoplasmic reticulum and sarcolemmal membranes play the same functional role in the excitation-contraction coupling in cardiac muscle.

scholarly journals STEREOLOGICAL ANALYSIS OF MAMMALIAN SKELETAL MUSCLE

1974 ◽  
Vol 60 (3) ◽  
pp. 732-754 ◽  
Author(s):  
Brenda R. Eisenberg ◽  
Aileen M. Kuda ◽  
James B. Peter
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Surface Area ◽  
Muscle Fibers ◽  
Mammalian Skeletal Muscle ◽  
Fiber Volume ◽  
Spatial Gradients ◽  
Surface Areas ◽  
Orientation Anisotropy ◽  
Mitochondrial Volume ◽  
T System

A quantitative analysis of the volumes, surface areas, and dimensions of the ultrastructural components in the soleus muscle fibers of the guinea pig was made by using point counting methods of stereology. Muscle fibers have structural orientation (anisotropy) and have spatial gradients of the structures within the fiber; therefore the standard stereological methods were modified where necessary. The entire analysis was repeated at two section orientations to test the modifications and identical results obtained from both. The volume of lipid droplets was 0.20 ± 0.06% (mean ± standard error, n = 5 animals) and the nuclei volume was 0.86 ± 0.20% of the fiber volume. The total mitochondrial volume was 4.85 ± 0.66% of the fiber volume with about one-third being found in an annulus within 1 µm of the sarcolemma. The mitochondrial volume in the remaining core of the fiber was 3.6 ± 0.4%. The T system has a volume of 0.14 ± 0.01% and a surface area of 0.064 ± 0.005 µm2/µm3 of the fiber volume. The surface area of the sarcolemma is 0.116 ± 0.013 µm2/µm3 which is twice the T system surface area. The volume of the entire sarcoplasmic reticulum is 3.52 ± 0.33% and the surface area is 0.97 ± 0.09 µm2/µm3. The sarcoplasmic reticulum is composed of the terminal cisternae whose volume is 1.04 ± 0.19% and surface area is 0.24 ± 0.05 µm2/µm3. The tubules of the sarcoplasmic reticulum in the I band and A band have volumes of 1.97 ± 0.24% and 0.51 ± 0.08%, and the surface areas of the I and A band reticulum are 0.56 ± 0.07 µm2/µm3 and 0.16 ± 0.04 µm2/µm3, respectively. The Z line width, myofibril and fiber diameters were measured.

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