Effects of Denervation on the Ultrastructure of Insect Muscle

1972 ◽  
Vol 10 (3) ◽  
pp. 667-682 ◽  
Author(s):  
D. REES ◽  
P. N. R. USHERWOOD
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Motor Neurons ◽  
Muscle Hypertrophy ◽  
Schistocerca Gregaria ◽  
Muscle Volume ◽  
Muscle Fibres ◽  
Denervated Muscle ◽  
Transverse Tubular System ◽  
Insect Muscle ◽  
Tubular System

The structure of normal and denervated muscle fibres in the metathoracic retractor unguis muscle of the locust (Schistocerca gregaria) has been examined. Section of the 2 motor neurons which innervate this muscle results initially in muscle hypertrophy but this is followed about 4 days post neurotomy by progressive atrophy. Atrophy of the retractor unguis muscle is characterized by a decrease in muscle volume and degeneration of muscle organelles, e.g. mitochondria, sarcoplasmic reticulum, transverse tubular system, protein filaments, etc. During its later stages the degeneration of the denervated muscle is possibly assisted by the phagocytic action of haemocytes which invade the muscle.

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.

Ultrastructural localization of dystropin in human muscle by using gold immunolabelling

1990 ◽  
Vol 240 (1297) ◽  
pp. 197-210 ◽  
Keyword(s):  
Plasma Membrane ◽  
Ultrastructural Localization ◽  
Ultrastructural Level ◽  
Human Muscle ◽  
Muscle Fibres ◽  
Mouse Muscle ◽  
Transverse Tubular System ◽  
Cytoplasmic Face ◽  
Tubular System ◽  
Gold Probe

Immunolabelling with a 5 nm gold probe was used to localize dystrophin at the ultrastructural level in human muscle. The primary antibody was monoclonal, raised against a segment (amino acids 1181-1388) from the rod domain of dystrophin. The antibody (Dy4/6D3) is specific for dystrophin and shows no immunoreactivity with any protein from mdx mouse muscle or from patients with a gene deletion spanning part of the molecule recognized by the antibody (Nicholson et al . 1989 a ; England et al . 1990). Using this antibody, labelling was almost entirely confined to a narrow 75 nm rim at the periphery of the muscle fibres. Histograms of the distance from the gold probe to the cytoplasmic face of the plasma membrane and of the distance between gold probes (nearest neighbour in a plane parallel with the plasma membrane) displayed modes at approximately 15 nm and 120 nm, respectively. The distribution of the probe was the same in longitudinal and transverse sections of the muscle. These observations suggest that the rod portion of the dystrophin mole­cule is normally arranged close to the cytoplasmic face of the plasma membrane and that the molecules form an interconnecting network. Labelling was not associated with the transverse tubular system.

The Ultrastructure of the White Striated Myotomal Muscle of the Cod, Gadus morhua

1967 ◽  
Vol 24 (12) ◽  
pp. 2549-2553 ◽  
Author(s):  
C. M. Bishop ◽  
P. H. Odense
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Cross Section ◽  
Actin Filaments ◽  
Gadus Morhua ◽  
Striated Muscle ◽  
Fish Muscle ◽  
Transverse Tubular System ◽  
Tubular System ◽  
Myotomal Muscle

The structure of the white skeletal muscle of the cod (Gadus morhua) is described. The peripheral fibrils are ribbon-like and rectangular in cross section with the long axis normal to the sarcolemma. The inner fibrils are mainly polygonal in cross section. Most of the mitochondria and nuclei are peripheral to the fibrils and next to the sarcolemma. The arrangement of the contractile proteins is typical for striated muscle, and the sarcoplasmic reticulum and transverse tubular system are similar to those in other white skeletal fish muscle. A distinct N-band is apparent with indications of branching and reorientation of the actin filaments. Mitochondria are often closely associated with the Z line.

Physiology and Ultrastructure of Phasic and Tonic Skeletal Muscle Fibres in the Locust, Schistocerca Gregaria

1972 ◽  
Vol 10 (2) ◽  
pp. 419-441
Author(s):  
D. G. COCHRANE ◽  
H. Y. ELDER ◽  
P. N. R. USHERWOOD
Keyword(s):  
Mechanical Response ◽  
Schistocerca Gregaria ◽  
Fibre Volume ◽  
Muscle Fibres ◽  
Potassium Depolarization ◽  
Insect Muscle ◽  
Time To Peak ◽  
Decay Times ◽  
T Tubules ◽  
Isometric Twitch

Insect muscle fibres can be classed as either phasic or tonic according to their response to potassium depolarization. The phasic fibres contract only transiently during prolonged potassium depolarization, whereas the tonic fibres give a sustained contracture. The extensor tibiae muscle in the metathoracic leg of the locust contains both tonic (T/et) and phasic (P/et) fibres; the electrical, mechanical and ultrastructural properties of these fibres have been compared with those of phasic fibres from the retractor unguis muscle (P/ru) in the same leg. A broad correlation has been established between the mechanical response and the amount of sarcoplasmic reticulum (SR) in the fibres. At maximal body length the rise time to peak twitch tension for the T/et fibres was found to be 790±60 ms, for the P/et fibres 59±2.5 ms and for the P/ru fibres, 30±1.1 ms. The half-decay times for the isometric twitch contractions were 2950±88 ms for the T/et fibres, 119±4.2 ms for the P/et, and 35±2.3 ms for the P/ru. The P/et and P/ru gave brief isometric contractures during potassium depolarization; under the same treatment the T/et fibres remained contracted throughout the treatment period. The major structural differences between the 3 types lies in the SR. Expressed as percentages of total fibre volume, the SR represents in the T/et 1.1%, in the P/et 6.8%, and in the P/ru 19%. The surface area of the SR, in terms of µm2/µm3 of fibre volume is 1.0±0.1 in the T/et, 2.9±0.2 in the P/et and 11.9±1.0 in the P/ru. Microtubules, often associated with elements of the SR, are sparsely distributed amongst the contractile elements in the T/et fibres. All 3 muscle types have a well developed T-system which forms dyadic associations with the SR. Larger-diameter Z-invaginations which conduct tracheoles into the muscles also give rise to ‘longitudinal T-tubules’, particularly in the T/et fibres. Dyads arise by association of cisternae of the SR: (i) with T-tubules sensu strictu, (ii) with Z-invaginations and T-tubule-like extensions from them, and (iii) directly with the plasma membrane at the surface of the fibre.

Calycophoran siphonophore muscle fibres without any sarcoplasmic reticulum but with tubular invaginations morphologically analogous to a T-system

1999 ◽  
Vol 79 (6) ◽  
pp. 1111-1116
Author(s):  
Q. Bone ◽  
C. Carré ◽  
I. Tsutsui ◽  
I. Inoue
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Action Potentials ◽  
Marine Invertebrates ◽  
Exchange Mechanism ◽  
Muscle Fibres ◽  
Previous Suggestion ◽  
Tubular System ◽  
Intracellular Ca ◽  
Morphological Equivalent ◽  
T System

Different marine invertebrates have different tubular or vesicular systems within their locomotor muscle fibres. The siphonophores Chelophyes, Abylopsis and Muggeia have invaginated tubules which are the morphological equivalent of the vertebrate invaginated tubular system, but lack a sarcoplasmic reticulum. In Chelophyes the previous suggestion that Ca2+ channels in the extensive invaginated tubule system allow ingress of Ca2+ is shown to be incorrect. Contraction of the swimming muscles in Chelophyes is not blocked by 20 μM ryanodine, nor is it induced by 10 mM caffeine, hence intracellular Ca2+ stores appear absent. Contraction is, however, maintained by replacement of the greater part of the usual external Na+ by Li+ or by or N-methyl-D-glucamine, although action potentials can still be evoked. Hence we conclude that following contraction, internal Ca2+ is reduced by a Na/Ca2+ exchange mechanism.

Changes in Striated Muscle Fibres During Contraction and Growth with Particular Reference to Myofibril Splitting

1971 ◽  
Vol 9 (1) ◽  
pp. 123-137
Author(s):  
G. GOLDSPINK
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Actin Filaments ◽  
Sarcomere Length ◽  
Biceps Brachii ◽  
Hexagonal Lattice ◽  
Muscle Fibres ◽  
Cross Sectional ◽  
Tension Development ◽  
Transverse Tubular System ◽  
Myosin Filaments

Ultrastructural measurements were carried out on the mouse biceps brachii and soleus muscles fixed at different states of contraction and stretch. At a sarcomere length of 2.7-2.9 µm the more peripheral actin filaments ran slightly obliquely from the Z-disk to the A-band. This is due to a mismatch between the rhombic actin lattice at the Z-disk and the hexagonal lattice at the M-line. For a perfect transformation of a rhombic lattice into a hexagonal lattice the ratio of the lattice spacings has to be 1:1.51. However, at this sarcomere length the ratio is about 1:2.0 (Z:M). During contraction the angle of the peripheral actin filaments remains approximately the same because the expansion of the M lattice is compensated for, partly by an increase in the Z-lattice spacing and partly by the bowing of the peripheral myosin filaments. When the sarcomeres are stretched beyond 3.0 µm the myosin filaments straighten out and the Z:M ratio decreases. The ratio of 1:1.51 is almost attained when there is no overlap of the actin and myosin filaments. Ultrastructural measurements were also carried out on biceps brachii muscles of different ages. The lattice spacings for a standard sarcomere length did not change during the post-natal growth period. The amount of myofibrillar material and sarcoplasmic reticulum plus transverse tubular system were estimated using linear analysis for muscles at 3 different stages of growth. It was found that the myofibrillar cross-sectional area in an individual muscle fibre may increase 40-fold during growth and that the transverse tubular and sarcoplasmic reticulum systems increase at about the same rate. In both the biceps brachii and the soleus muscles the myosin and actin filaments are not built into a continuous mass but they are divided into numerous discrete myofibrils. Subdivision of the myofibril mass occurs because the myofibrils split once they attain a certain size. The evidence presented in this paper supports the suggestion that the longitudinal splitting of the myofibrils occurs by the ripping of the Z-disks. When tension is rapidly developed by 2 adjacent sarcomeres a stress is produced at the centre of the Z-disk resulting from the oblique pull of the actin filaments. This causes some of the Z-disk filaments to rip and the rip then extends across the disk with the direction of the weave of the lattice. Evidence for the mechanism includes electron-micrographs showing Z-disks that are apparently just commencing to split; in these cases a hole can be seen in the centre of the disk. A model experiment is described which demonstrates the importance of the rate of tension development in causing myofibril splitting. Rapid tension development produces a snatch effect which causes the Z-disk filaments to break more readily. This may explain why the myofibrils in fast muscles tend to be small and discrete whilst those in slow muscles are larger and more irregular in shape.

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