scholarly journals Congenital myopathy associated with the triadin knockout syndrome

Neurology ◽  
2017 ◽  
Vol 88 (12) ◽  
pp. 1153-1156 ◽  
Author(s):  
Andrew G. Engel ◽  
Keeley R. Redhage ◽  
David J. Tester ◽  
Michael J. Ackerman ◽  
Duygu Selcen
Keyword(s):  
Electron Microscopy ◽  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Light And Electron Microscopy ◽  
Deltoid Muscle ◽  
Congenital Myopathy ◽  
Compound Heterozygous

Objective:Triadin is a component of the calcium release complex of cardiac and skeletal muscle. Our objective was to analyze the skeletal muscle phenotype of the triadin knockout syndrome.Methods:We performed clinical evaluation, analyzed morphologic features by light and electron microscopy, and immunolocalized triadin in skeletal muscle.Results:A 6-year-old boy with lifelong muscle weakness had a triadin knockout syndrome caused by compound heterozygous null mutations in triadin. Light microscopy of a deltoid muscle specimen shows multiple small abnormal spaces in all muscle fibers. Triadin immunoreactivity is absent from type 1 fibers and barely detectable in type 2 fibers. Electron microscopy reveals focally distributed dilation and degeneration of the lateral cisterns of the sarcoplasmic reticulum and loss of the triadin anchors from the preserved lateral cisterns.Conclusions:Absence of triadin in humans can result in a congenital myopathy associated with profound pathologic alterations in components of the sarcoplasmic reticulum. Why only some triadin-deficient patients develop a skeletal muscle phenotype remains an unsolved question.

scholarly journals Slowed Relaxation in Fatigued Skeletal Muscle Fibers of Xenopus and Mouse

1997 ◽  
Vol 109 (3) ◽  
pp. 385-399 ◽  
Author(s):  
Håkan Westerblad ◽  
Jan Lännergren ◽  
David G. Allen
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Skeletal Muscle Fatigue ◽  
Cross Bridge ◽  
Relative Contribution ◽  
Force Curves ◽  
Reduced Rate

Slowing of relaxation is an important characteristic of skeletal muscle fatigue. The aim of the present study was to quantify the relative contribution of altered Ca2+ handling (calcium component) and factors down-stream to Ca2+ (cross-bridge component) to the slowing of relaxation in fatigued fibers of Xenopus and mouse. Two types of Xenopus fibers were used: easily fatigued, type 1 fibers and fatigue resistant, type 2 fibers. In these Xenopus fibers the free myoplasmic [Ca2+] ([Ca2+]i) was measured with indo-1, and the relaxation of Ca2+-derived force, constructed from tetanic [Ca2+]i records and in vivo [Ca2+]i-force curves, was analyzed. An alternative method was used in both Xenopus and mouse fibers: fibers were rapidly shortened during the initial phase of relaxation, and the time to the peak of force redevelopment was measured. These two methods gave similar results and showed proportional slowing of the calcium and cross-bridge components of relaxation in both fatigued type 1 and type 2 Xenopus fibers, whereas only the cross-bridge component was slowed in fatigued mouse fibers. Ca2+ removal from the myoplasm during relaxation was markedly less effective in Xenopus fibers as compared to mouse fibers. Fatigued Xenopus fibers displayed a reduced rate of sarcoplasmic reticulum Ca2+ uptake and increased sarcoplasmic reticulum Ca2+ leak. Some fibers were stretched at various times during relaxation. The resistance to these stretches was increased during fatigue, especially in Xenopus fibers, which indicates that longitudinal movements during relaxation had become less pronounced and this might contribute to the increased cross-bridge component of relaxation in fatigue. In conclusion, slowing of relaxation in fatigued Xenopus fibers is caused by impaired Ca2+ handling and altered cross-bridge kinetics, whereas the slowing in mouse fibers is only due to altered cross-bridge kinetics.

scholarly journals CARDIAC MUSCLE

1968 ◽  
Vol 36 (3) ◽  
pp. 497-526 ◽  
Author(s):  
Joachim R. Sommer ◽  
Edward A. Johnson
Keyword(s):  
Electron Microscopy ◽  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Cardiac Muscle ◽  
Extracellular Space ◽  
Light And Electron Microscopy ◽  
Rabbit Heart ◽  
Contraction Coupling ◽  
The Difference

With light and electron microscopy a comparison has been made of the morphology of ventricular (V) and Purkinje (P) fibers of the hearts of guinea pig, rabbit, cat, dog, goat, and sheep. The criteria, previously established for the rabbit heart, that V fibers are distinguished from P fibers by the respective presence and absence of transverse tubules is shown to be true for all animals studied. No evidence was found of a permanent connection between the sarcoplasmic reticulum and the extracellular space. The sarcoplasmic reticulum (SR) of V fibers formed couplings with the sarcolemma of a transverse tubule (interior coupling) and with the peripheral sarcolemma (peripheral coupling), whereas in P fibers the SR formed only peripheral couplings. The forms of the couplings were identical. The significance, with respect to excitation-contraction coupling, of the difference in the form of the couplings in cardiac versus skeletal muscle is discussed together with the electrophysiological implications of the differing geometries of bundles of P fibers from different animals.

Neuromuscular junction alterations in extraocular muscles of myotonic rats

1983 ◽  
Vol 41 ◽  
pp. 654-655
Author(s):  
Bruce R. Pachter ◽  
Arthur Eberstein
Keyword(s):  
Electron Microscopy ◽  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Neuromuscular Junction ◽  
High Frequency ◽  
Light And Electron Microscopy ◽  
Extraocular Muscles ◽  
Dense Bodies ◽  
Myofibrillar Degeneration ◽  
Cell Vacuolization

Rats treated with 20,25-diazacholesterol manifest clinical as well as physiological signs characteristic of human myotonic dystrophy. The extraocular muscles (EOMs) of such myotonic rats were shewn in a prior study to exhibit by electromyography, prolonged insertion activity, high frequency bizzare discharges, and myotonic responses, which are comparable to that observed in skeletal muscle. Light and electron microscopy of the EOMs revealed numerous fiber alterations, i.e., dense bodies, atrophic and angulated fibers, cell vacuolization, dilation and proliferation of the sarcoplasmic reticulum, mu11ilamllar membranous bodies, atypical mitochondrial clusters and disruptions, mitochondrial inclusions, excessive lipid accumulations, and myofibrillar degeneration. Many of these changes have been reported in human myotonic peripheral musculature. The most susceptible fiber populations in the EOMs were found to be the pale, intermediate, and red singly-innervated fibers of the global region; the pale fibers were the most affected.

Caffeine treatment inhibits drug-induced calcium release from sarcoplasmic reticulum and caffeine contracture but not tetanus in frog skeletal muscle

1989 ◽  
Vol 67 (8) ◽  
pp. 890-895 ◽  
Author(s):  
Makoto Koshita ◽  
Toshiharu Oba
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Electrical Stimulus ◽  
Final Concentration ◽  
Heavy Fraction ◽  
Frog Skeletal Muscle ◽  
Drug Induced ◽  
Physiological Signal ◽  
Caffeine Contracture

Effects of pretreatment with caffeine on Ca2+ release induced by caffeine, thymol, quercetin, or p-chloromercuriphenylsulfonic acid (pCMPS) from the heavy fraction of sarcoplasmic reticulum (SR) were studied and compared with those effects on caffeine contracture and tetanus tension in single fibers of frog skeletal muscle. Caffeine (1–5 mM) did induce transient Ca2+ release from SR vesicles, but subsequent further addition of caffeine (10 mM, final concentration) induced little Ca2+ release. Ca2+ release induced by thymol, quercetin, or pCMPS was also inhibited by pretreatment with caffeine. In single muscle fibers, pretreatment with caffeine (1–5 mM) partially reduced the contracture induced by 10 mM caffeine. However, tetanus tension was almost maximally induced by electrical stimulus in caffeine-treated fibers. These results indicate that SR, which becomes less sensitive to caffeine, thymol, quercetin, or pCMPS by pretreatment with caffeine, can still respond to a physiological signal transmitted from transverse tubules.Key words: Ca2+ release, sarcoplasmic reticulum, caffeine, tetanus, skeletal muscle.

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