scholarly journals Immunoelectron microscopic studies of desmin (skeletin) localization and intermediate filament organization in chicken skeletal muscle.

1983 ◽  
Vol 96 (6) ◽  
pp. 1727-1735 ◽  
Author(s):  
K T Tokuyasu ◽  
A H Dutton ◽  
S J Singer
Keyword(s):  
Skeletal Muscle ◽  
Intermediate Filaments ◽  
Sartorius Muscle ◽  
Adult Skeletal Muscle ◽  
Adult Chicken ◽  
Microscopic Studies ◽  
T Tubules ◽  
Ultrathin Frozen Sections ◽  
Chicken Skeletal Muscle ◽  
Type Intermediate

We studied the localization of desmin (skeletin), the major subunit of muscle-type intermediate filaments, by high resolution immunoelectron microscopy in adult chicken skeletal muscle. Immunoferritin labeling of ultrathin frozen sections of intact fixed sartorius muscle showed the presence of desmin between adjacent Z-bands and as strands peripheral to Z-bands, forming apparent connections between the Z-bands with adjacent sarcolemma, mitochondria, and nuclei. We observed no desmin labeling, however, in the vicinity of the T-tubules. In addition, intermediate filaments were morphologically discernible at the level of the Z-bands in plastic sections of glycerol-extracted muscle that had been infused with unlabeled antidesmin antibodies. Our results indicate that the desmin present in adult skeletal muscle, that had previously been detected by immunofluorescence light microscopy, is largely if not entirely in the form of intermediate filaments. The results provide evidence that these filaments serve to interconnect myofibrils at the level of their Z-bands, and to connect Z-bands with other specific structures and organelles in the myotube, but not with the T-tubule system.

scholarly journals Visualization of longitudinally-oriented intermediate filaments in frozen sections of chicken cardiac muscle by a new staining method.

1983 ◽  
Vol 97 (2) ◽  
pp. 562-565 ◽  
Author(s):  
K T Tokuyasu
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Intermediate Filaments ◽  
Ethyl Cellulose ◽  
Staining Method ◽  
Uranyl Acetate ◽  
Frozen Sections ◽  
Cell Biol ◽  
Ultrathin Frozen Sections

When ultrathin frozen sections of chicken cardiac muscle were osmicated, dehydrated in ethanol, embedded in ethyl cellulose, and stained with acidic uranyl acetate, filaments of 10-12 nm width were visualized in wide interfibrillar spaces. Immunostaining of the frozen sections for desmin resulted in exclusive labeling of such filaments. These observations indicated that longitudinally oriented networks of intermediate filaments were present in the interfibrillar spaces, in addition to the transversely oriented networks that surround myofibrils at the level of Z band. As in skeletal muscle (Tokuyasu, K. T., A. H. Dutton, and S. J. Singer, 1983, J. Cell Biol. 97:1727-1735), desmin in chicken cardiac muscle is believed to be largely, if not entirely, in the form of intermediate filaments.

scholarly journals Na,K-ATPase α2 activity in mammalian skeletal muscle T-tubules is acutely stimulated by extracellular K+

2015 ◽  
Vol 146 (4) ◽  
pp. 281-294 ◽  
Author(s):  
Marino DiFranco ◽  
Hesamedin Hakimjavadi ◽  
Jerry B. Lingrel ◽  
Judith A. Heiny
Keyword(s):  
Skeletal Muscle ◽  
Dynamic Range ◽  
Site Occupancy ◽  
Pump Current ◽  
Substrate Affinity ◽  
Mammalian Skeletal Muscle ◽  
Duration Of Action ◽  
Adult Skeletal Muscle ◽  
T Tubules ◽  
K Concentration

The Na,K-ATPase α2 isoform is the predominant Na,K-ATPase in adult skeletal muscle and the sole Na,K-ATPase in the transverse tubules (T-tubules). In quiescent muscles, the α2 isozyme operates substantially below its maximal transport capacity. Unlike the α1 isoform, the α2 isoform is not required for maintaining resting ion gradients or the resting membrane potential, canonical roles of the Na,K-ATPase in most other cells. However, α2 activity is stimulated immediately upon the start of contraction and, in working muscles, its contribution is crucial to maintaining excitation and resisting fatigue. Here, we show that α2 activity is determined in part by the K+ concentration in the T-tubules, through its K+ substrate affinity. Apparent K+ affinity was determined from measurements of the K1/2 for K+ activation of pump current in intact, voltage-clamped mouse flexor digitorum brevis muscle fibers. Pump current generated by the α2 Na,K-ATPase, Ip, was identified as the outward current activated by K+ and inhibited by micromolar ouabain. Ip was outward at all potentials studied (−90 to −30 mV) and increased with depolarization in the subthreshold range, −90 to −50 mV. The Q10 was 2.1 over the range of 22–37°C. The K1/2,K of Ip was 4.3 ± 0.3 mM at −90 mV and was relatively voltage independent. This K+ affinity is lower than that reported for other cell types but closely matches the dynamic range of extracellular K+ concentrations in the T-tubules. During muscle contraction, T-tubule luminal K+ increases in proportion to the frequency and duration of action potential firing. This K1/2,K predicts a low fractional occupancy of K+ substrate sites at the resting extracellular K+ concentration, with occupancy increasing in proportion to the frequency of membrane excitation. The stimulation of preexisting pumps by greater K+ site occupancy thus provides a rapid mechanism for increasing α2 activity in working muscles.

scholarly journals Immunoelectron microscopic studies of desmin (skeletin) localization and intermediate filament organization in chicken cardiac muscle.

1983 ◽  
Vol 96 (6) ◽  
pp. 1736-1742 ◽  
Author(s):  
K T Tokuyasu ◽  
A H Dutton ◽  
S J Singer
Keyword(s):  
Cardiac Muscle ◽  
Intermediate Filaments ◽  
Striated Muscle ◽  
Three Dimensional ◽  
Major Protein ◽  
Protein Subunit ◽  
Double Labeling ◽  
Adult Chicken ◽  
Microscopic Studies ◽  
Intercalated Disk

We studied the localization of desmin (skeletin), the major protein subunit of muscle-type intermediate filaments, in adult chicken cardiac muscle by high resolution immunoelectron microscopic labeling of ultrathin frozen sections of the intact fixed tissues. We carried out single labeling for desmin and double labeling for both desmin and either vinculin or alpha-actinin. In areas removed from the intercalated disk membranes, we observed desmin labeling between adjacent Z-bands in every interfibrillar space. Where these spaces were wide and contained mitochondria, convoluted strands of desmin labeling bridged between the periphery of neighboring Z-bands and the mitochondria. The intermediate filaments appeared to be organized in a more three-dimensional manner within the interfibrillar spaces of cardiac as compared to skeletal muscle. Near the intercalated disks, desmin labeling was intense within the interfibrillar spaces, but was completely segregated from the microfilament attachment sites (fascia adherens) where vinculin and alpha-actinin were localized. Desmin therefore appears to play no role in the attachment of microfilaments to the intercalated disk membrane. We discuss the role of intermediate filaments in the organization of cardiac and skeletal striated muscle in the light of these and other results.

Identification of intermediate filaments in mature mammalian skeletal muscle by TEM

1990 ◽  
Vol 48 (3) ◽  
pp. 454-455
Author(s):  
Masako Yagyu ◽  
Richard M. Robson ◽  
Marvin H. Stromer
Keyword(s):  
Skeletal Muscle ◽  
Intermediate Filaments ◽  
Mammalian Cells ◽  
Striated Muscle ◽  
Muscle Cells ◽  
Mammalian Skeletal Muscle ◽  
Semitendinosus Muscle ◽  
Cardiac Muscle Cells ◽  
Adult Skeletal Muscle ◽  
Transmission Electron

It is generally assumed that desmin in mature striated muscle cells is in the form of intermediate filaments (IFs) and that its primary locus is at or near the myofibrillar Z-lines. Although IFs have been identified by transmission electron microscopy (TEM) in embryonic and adult smooth and cardiac muscle cells and in differentiating or diseased skeletal muscle cells, IFs have rarely been unambiguously visualized in adult skeletal muscle (especially mammalian) cells by TEM. This is due in part to the small amount of IF protein in normal mature skeletal muscle, and in part to the heavily-packed, myofibril-dominated, intracellular cytoskeleton of these cells. In order to help ascertain the possible mechanism(s) of attachment of IFs to myofibrils, our objectives in this study were to identify, by TEM, IFs in adult mammalian skeletal muscle and to study the structural relationship of IFs and the muscle Z-lines.Samples of porcine semitendinosus muscle were removed from mature animals immediately after death, isometrically restrained and fixed in Karnovsky's fixative for 3 hours at 25°C, and processed by conventional methods followed by embedment in Epon-Araldite resin.

Peripheral neuropathy with giant axons and cardiomyopathy associated with desmin type intermediate filaments in skeletal muscle

1992 ◽  
Vol 109 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Mario Sabatelli ◽  
Enrico Bertini ◽  
Enzo Ricci ◽  
Giovanni Salviati ◽  
Stefania Magi ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Peripheral Neuropathy ◽  
Intermediate Filaments ◽  
Giant Axons ◽  
Type Intermediate

Reinitiation of chondroitin sulphate proteoglycan synthesis in regenerating skeletal muscle

Development ◽  
1988 ◽  
Vol 103 (4) ◽  
pp. 641-656
Author(s):  
D.A. Carrino ◽  
U. Oron ◽  
D.G. Pechak ◽  
A.I. Caplan
Keyword(s):  
Skeletal Muscle ◽  
Basement Membrane ◽  
Muscle Regeneration ◽  
Chondroitin Sulphate ◽  
Proteoglycan Synthesis ◽  
Adult Skeletal Muscle ◽  
Adult Chicken ◽  
Sulphate Proteoglycan ◽  
Chondroitin Sulphate Proteoglycan ◽  
Chondroitin Sulphate Proteoglycans

Previous work from this laboratory involved the characterization of a large chondroitin sulphate proteoglycan unique to chick skeletal muscle. This proteoglycan is synthesized by embryonic skeletal muscle both in ovo and in culture but is not synthesized by adult muscle in vivo and myotubes in advanced cultures. Because regenerating skeletal muscle has been found to recapitulate synthesis of embryonic muscle protein isoforms, an analysis was performed to assess whether synthesis of chondroitin sulphate proteoglycans is reinitiated during muscle regeneration. Adult chicken pectoral and leg (gastrocnemius) muscle was injured by excision of a small piece of tissue or by cold injury; in the latter, the basement membrane has been reported to remain intact. At various times after injury, whole animals were exposed to [35S]sulphate and the proteoglycans were isolated by ion-exchange chromatography and analysed. Synthesis of only small proteoglycans, typical of normal adult skeletal muscle, is observed in the contralateral, uninjured muscle. In the regenerating muscle 4 days after injury, there is increased sulphate incorporation and abundant synthesis of chondroitin sulphate proteoglycans. This is observed in both pectoral and leg muscle irrespective of the type of injury, which suggests that the presence of basement membrane does not affect reinitiation of chondroitin sulphate proteoglycan synthesis. By 25 days after injury, synthesis of chondroitin sulphate proteoglycans is still detected but is significantly diminished. These data are consistent with the notion that skeletal muscle regeneration involves a recapitulation of embryonic events and give further credence to the hypothesis that skeletal muscle chondroitin sulphate proteoglycans play a role in some early aspect of myogenesis.

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