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.

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 Action of Iontophoretically Applied Glutamate on Insect Muscle Fibres

1968 ◽  
Vol 49 (1) ◽  
pp. 83-93
Author(s):  
R. BERÁNEK ◽  
P. L. MILLER
Keyword(s):  
Equilibrium Point ◽  
Neuromuscular Junctions ◽  
Schistocerca Gregaria ◽  
Locusta Migratoria ◽  
Extracellular Recording ◽  
Fibre Surface ◽  
Adductor Muscle ◽  
Muscle Fibres ◽  
Glass Capillary ◽  
Insect Muscle

1. Electrophoretic application of L-glutamate from glass capillary micro-pipettes was used to investigate the ‘spot sensitivity’ of the membrane of coxal adductor muscle fibres from adult specimens of Schistocerca gregaria Forskål and Locusta migratoria (L.). 2. Circumscribed spots could be detected on the fibre surface where brief applications of L-glutamate produced transient depolarizations (glutamate potentials). 3. Extracellular recording of excitatory junction potentials revealed that focal points of glutamate sensitivity are closely related to, and probably identical with, neuromuscular junctions. 4. Large doses readily de-sensitized the membrane to L-glutamate for periods greatly exceeding the duration of the glutamate potentials. 5. In chronically denervated muscles peaks of sensitivity could still be detected. 6. Spots sensitive to L-glutamate were not depolarized by D-glutamate. 7. The equilibrium point for glutamate potentials coincides with the equilibrium point of miniature excitatory potentials and lies between -10 and -25 mV.

Nitrendipine blocks high potassium contractures but not twitches in rat skeletal muscle

1988 ◽  
Vol 66 (9) ◽  
pp. 1210-1213 ◽  
Author(s):  
G. B. Frank ◽  
L. Konya ◽  
T. Subrahmanyam Sudha
Keyword(s):  
Skeletal Muscle ◽  
Calcium Ions ◽  
Calcium Uptake ◽  
Channel Blocker ◽  
Mechanical Response ◽  
Extracellular Calcium ◽  
The Other ◽  
Rat Skeletal Muscle ◽  
Potassium Depolarization ◽  
High Potassium

The effects of the organic calcium channel blocker nitrendipine was tested on electrically evoked twitches and on potassium depolarization-induced contractures of rat lumbricalis muscles. Nitrendipine (10−7 to 5 × 10−5 M) blocked only the potassium contractures. It was concluded that blocking calcium uptake through the slow voltage-senstitive calcium channels during potassium depolarization blocks the mechanical response of the muscle. Thus extracellular calcium ions are required for the excitation–contraction (E–C) coupling during depolarization contractures. On the other hand, electrically evoked twitches were not affected by nitrendipine; therefore, extracellular calcium ions entering via the slow voltage-sensitive channels are not required for E–C coupling during the twitch.

Studies on Water in Barnacle Muscle Fibres II. Role of ions and Organic Solutes in Swelling of Chemically-skinned Fibres

1981 ◽  
Vol 90 (1) ◽  
pp. 43-63
Author(s):  
M. E. CLARK ◽  
J. A. M. HINKE ◽  
M. E. TODD
Keyword(s):  
Water Content ◽  
Fibre Volume ◽  
Tween 20 ◽  
Muscle Fibres ◽  
Skinned Fibres ◽  
Organic Solutes ◽  
Net Charge ◽  
Trimethylamine Oxide ◽  
Organic Solute

Single muscle fibres from the giant barnacle, Balanus nubilis, were chemically skinned (2% Tween 20), then equilibrated for 40 h in salt solutions ranging in ionic strength from 0·025 to 0·6M at pH 7·0. The water content of the fibres and the net charge on the myofilaments increased with increasing salt concentration. Cation accumulation in the fibres was about equal to anion exclusion at all salt concentrations. When an organic solute (trimethylamine oxide, glycine, alanine, serine, proline, or glycerol) in the concentration range from 0·1 to 0·6 M was added to the salt solution, cation accumulation increased and water content decreased. Myofilament architecture was disrupted when the fibres were equilibrated in high salt (> 0·4 M) solutions and preserved when 0·5 M-triethylamine oxide was also added. The results are consistent with the view that organic solutes enhance the association between the fixed charge sites and their counterions. This hypothesis is examined quantitatively using the Oosawa relationship between the volume and the counterion association for cylindrical polyelectrolytes. The results illustrate that organic solutes can influence fibre volume in a way other than through osmo-regulation.

scholarly journals THE CAPILLARY PATTERN IN HUMAN MASSETER MUSCLE DURING AGEING

2013 ◽  
Vol 32 (3) ◽  
pp. 135 ◽  
Author(s):  
Erika Cvetko ◽  
Jiří Janáček ◽  
Lucie Kubínová ◽  
Ida Eržen
Keyword(s):  
Muscle Fibre ◽  
Masseter Muscle ◽  
3D Visualization ◽  
Fibre Length ◽  
Fibre Surface ◽  
Fibre Volume ◽  
Immunohistochemical Method ◽  
Muscle Fibres ◽  
Age Related ◽  
Novel Approach

The effect of ageing on the capillary network in skeletal muscles has produced conflicting results in both, human and animals studies. Some of the inconsistencies are due to non-comparable and biased methods that were applied on thin transversal sections, especially in muscles with complicated morphological structures, such as in human masseter muscle. We present a new immunohistochemical method for staining capillaries and muscle fibres in 100 µm thick sections as well as novel approach to 3D visualization of capillaries and muscle fibres. Applying confocal microscopy and virtual 3D stereological grids, or tracing capillaries in virtual reality, length of capillaries within a muscle volume or length of capillaries adjacent to muscle fibre per fibre length, fibre surface or fibre volume were evaluated in masseter muscle of young and old subjects by an unbiased approach. Our findings show that anatomic capillarity is well maintained in masseter muscle in old subjects; however, vascular remodelling occurs with age, which could be a response to changed muscle function and age-related muscle fibre type transformations.

Functional significance of compensatory overloaded rat fast muscle

1982 ◽  
Vol 52 (2) ◽  
pp. 473-478 ◽  
Author(s):  
R. R. Roy ◽  
I. D. Meadows ◽  
K. M. Baldwin ◽  
V. R. Edgerton
Keyword(s):  
Biochemical Properties ◽  
Slow Muscle ◽  
Repetitive Stimulation ◽  
Contractile Properties ◽  
Sectional Area ◽  
Shortening Velocity ◽  
Cross Sectional ◽  
Time To Peak ◽  
Isometric Twitch

Chronic overload of a skeletal muscle by removing its synergists produces hypertrophy and marked changes in its metabolic and biochemical properties. In this study alterations in the contractile properties of the plantaris 12–14 wk after bilateral removal of the soleus and gastrocnemius were investigated. In situ isometric and isotonic contractile properties of overloaded plantaris (OP), normal plantaris (NP), and normal soleus (NS) were tested at 33 +/- 1 degree C. Op were 97% heavier than NP and produced 43 and 46% higher twitch (Pt) and tetanic (Po) tensions. However, NP produced more tension per cross-sectional area than OP (mean 26.2 vs. 21.6 N/cm2; P less than 0.001). Isometric twitch time to peak tension (TPT) and half-relaxation time (1/2RT) were significantly longer in OP (mean 36.4 vs. 32.5 ms and 23.9 vs. 18.4 ms). Mean maximum shortening velocity (Vmax, mm/s per 1,000 sarcomeres) were 34.1 for NP and 18.1 for OP (P less than 0.001). The degree of conversion toward the Vmax of NS was 74% compared with only 19 and 14% for TPT and 1/2RT. OP produced a higher proportion of Po at a given stimulation frequency than NP and showed less fatigue than NP after repetitive stimulation. Chronic overload of the fast plantaris modified to varying degrees the contractile properties studied toward that resembling a slow muscle. Although the maximum tension of OP was markedly enhanced it was not in proportion to the increase in muscle mass.

Average but not continuous speed match between motoneurons and muscle units of rat tibialis anterior

1993 ◽  
Vol 70 (4) ◽  
pp. 1300-1306 ◽  
Author(s):  
R. Bakels ◽  
D. Kernell
Keyword(s):  
Tibialis Anterior ◽  
Time Course ◽  
Muscle Fibers ◽  
Total Duration ◽  
Medial Gastrocnemius ◽  
Tetanic Force ◽  
Time To Peak ◽  
Time Courses ◽  
Isometric Twitch ◽  
Fatigue Sensitivity

1. Properties of single motoneuron/muscle-unit combinations were determined for tibialis anterior (TA) in rats anesthetized with pentobarbital. The TA observations were systematically compared with those obtained earlier by the use of the same techniques from rat medial gastrocnemius (MG). 2. TA motoneurons were investigated with regard to afterhyperpolarization (AHP; total duration 32-74 ms, amplitude 0.39-4.96 mV) and axonal conduction velocity (41-79 m/s). TA muscle-unit measurements included the time course of the isometric twitch (time-to-peak force 10.8-18.0 ms; total duration 42-92 ms), the maximum tetanic force (22-217 mN), and a measure of fatigue sensitivity (fatigue index 5-100%). The range of twitch and AHP durations ("speed range") was markedly smaller in the present TA material than for MG. 3. The mean duration of the TA motoneuronal AHP (49 +/- 8 ms, mean +/- SD) was close to that of its muscle-unit twitch (56 +/- 12 ms). Thus an "average" speed match existed between TA motoneurons and their muscle fibers. 4. For TA there was no correlation between the time courses of AHP and twitch. Thus there was for TA no "continuous" speed match between the motoneurons and their muscle fibers. 5. For TA twitches or AHPs studied separately, there was a significant correlation between different time course measures. Furthermore, compared with TA units having relatively fast twitches, those with slower twitches tended to show 1) a smaller maximum tetanic force and 2) a greater AHP amplitude. Fatigue-resistant units tended to have slower twitches than fatigue-sensitive ones.(ABSTRACT TRUNCATED AT 250 WORDS)

Nano-additive reinforcement of mixture epoxy syntactic foams

2019 ◽  
Vol 33 (12) ◽  
pp. 1674-1691 ◽  
Author(s):  
Kerrick R Dando ◽  
David R Salem
Keyword(s):  
Impact Analysis ◽  
Mechanical Response ◽  
Analysis Data ◽  
Halloysite Nanotubes ◽  
Peak Force ◽  
Syntactic Foams ◽  
Response Properties ◽  
Weight Percentage ◽  
Time To Peak ◽  
The Matrix

Carbon nanofibers (CNFs) and halloysite nanotubes (HNTs) were incorporated in syntactic foams containing a 90% by volume homogeneous mixture of (20/80 wt%) glass/thermoplastic microballoons to enhance the mechanical and impact response properties. Tensile, compressive, and impact tests were employed to comparatively characterize the effect of nano-additive reinforcement on mechanical response properties. Compressive strength and modulus enhancements as large as 39% and 18%, respectively, were achieved with a 0.125 wt% addition of CNF and increases of 61% and 7%, respectively, were achieved with a 0.125 wt% addition of HNT. Tensile strength and modulus enhancements as large as 107% and 68%, respectively, were achieved with a 0.125 wt% addition of CNF and increases of 104% and 70%, respectively, were achieved with a 0.125 wt% addition of HNT. Impact analysis data were used to show that measured peak force increased and build-up time to peak force decreased with increasing CNF or HNT weight percentage due to stiffening of the matrix. The smallest increase observed in peak force was 20% for a 0.125 wt% addition of CNF and 17% for a 0.125 wt% addition of HNT.

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