scholarly journals Longitudinal impedance of single frog muscle fibers.

1975 ◽  
Vol 65 (1) ◽  
pp. 97-113 ◽  
Author(s):  
B A Mobley ◽  
J Leung ◽  
R S Eisenberg
Keyword(s):  
Skeletal Muscle ◽  
Phase Shift ◽  
Muscle Fibers ◽  
Mean Value ◽  
Sartorius Muscle ◽  
Semitendinosus Muscle ◽  
Skeletal Muscle Fibers ◽  
Longitudinal Impedance ◽  
Small Phase ◽  
The Mean

The longitudinal impedance of single skeletal muscle fibers has been measured from1 to 10,000 Hz in an oil gap apparatus which forces current to flow longitudinally down the fiber. The impedance observed is purely resistive in some fibers from the semitendinosus muscle and in two fibers from the sartorius muscle. In other fibers from the semitendinosus muscle a small phase shift is observed. The mean value of the maximum phase shift observed from all fibers is 1.07 degrees. The artifacts associated with the apparatus and method are examined theoretically and it is shown that one of the likely artifacts could account for the small phase observed. It is concluded that the longitudinal impedance of skeletal muscle fibers is essentially resistive and that little, if any, longitudinal current crosses the membranes of the sarcoplasmic reticulum.

scholarly journals Effects of Tetracaine on Voltage-activated Calcium Sparks in Frog Intact Skeletal Muscle Fibers

2006 ◽  
Vol 127 (3) ◽  
pp. 291-307 ◽  
Author(s):  
Stephen Hollingworth ◽  
W. Knox Chandler ◽  
Stephen M. Baylor
Keyword(s):  
Skeletal Muscle ◽  
Single Channel ◽  
Ryanodine Receptors ◽  
Muscle Fibers ◽  
Mean Value ◽  
Half Maximum ◽  
Mean Values ◽  
Skeletal Muscle Fibers ◽  
The Mean ◽  
Ca2 Channels

The properties of Ca2+ sparks in frog intact skeletal muscle fibers depolarized with 13 mM [K+] Ringer's are well described by a computational model with a Ca2+ source flux of amplitude 2.5 pA (units of current) and duration 4.6 ms (18 °C; Model 2 of Baylor et al., 2002). This result, in combination with the values of single-channel Ca2+ current reported for ryanodine receptors (RyRs) in bilayers under physiological ion conditions, 0.5 pA (Kettlun et al., 2003) to 2 pA (Tinker et al., 1993), suggests that 1–5 RyR Ca2+ release channels open during a voltage-activated Ca2+ spark in an intact fiber. To distinguish between one and greater than one channel per spark, sparks were measured in 8 mM [K+] Ringer's in the absence and presence of tetracaine, an inhibitor of RyR channel openings in bilayers. The most prominent effect of 75–100 μM tetracaine was an approximately sixfold reduction in spark frequency. The remaining sparks showed significant reductions in the mean values of peak amplitude, decay time constant, full duration at half maximum (FDHM), full width at half maximum (FWHM), and mass, but not in the mean value of rise time. Spark properties in tetracaine were simulated with an updated spark model that differed in minor ways from our previous model. The simulations show that (a) the properties of sparks in tetracaine are those expected if tetracaine reduces the number of active RyR Ca2+ channels per spark, and (b) the single-channel Ca2+ current of an RyR channel is ≤1.2 pA under physiological conditions. The results support the conclusion that some normal voltage-activated sparks (i.e., in the absence of tetracaine) are produced by two or more active RyR Ca2+ channels. The question of how the activation of multiple RyRs is coordinated is discussed.

scholarly journals Characterization of the effects of Mg2+ on Ca2+- and Sr2+-activated tension generation of skinned skeletal muscle fibers.

1975 ◽  
Vol 66 (4) ◽  
pp. 427-444 ◽  
Author(s):  
S K Donaldson ◽  
W G Kerrick
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Competitive Inhibitor ◽  
Semitendinosus Muscle ◽  
Maximum Tension ◽  
Skeletal Muscle Fibers ◽  
Contractile System ◽  
Constant Ph ◽  
Inverse Effect ◽  
Tension Generation

Changes in [Mg2+] in a millimolar range have a significant inverse effect on the Ca2+- (or Sr2+)activated tension generation of skeletal muscle fibers. Single frog (Rana pipiens) semitendinosus muscle fibers were "skinned" (sarcolemma removed) and contracted isometrically in bathing solutions of varying [Ca2+] or [Sr2+] and [Mg2+] but a constant pH, [MgATP2-], [K+], [CP2-], [CPK], and ionic strength. Ca2+- (or Sr2+-)activated steady-state tensions were recorded for three [Mg2+]'s: 5 X 10(-5)M, 1 X 10(-3) M, and 2 X 10(-3) M; and these tensions were expressed as the percentages of maximum tension generation of the fibers for the same [Mg2+]. Maximum tension was not affected by [Mg2+] within Ca2+-activating or Sr2+-activating sets of solutions; however, the submaximum Ca2+-(or Sr2+)activated tension is strongly affected in an inverse fashion by increasing [Mg2+]. Mg2+ behaves as a competitive inhibitor of Ca2+ and also affects the degree of cooperativity in the system. At [Mg2+] = 5 X 10(-5)M the shape of tension versus [Ca2+] (or [Sr2+]) curve showed evidence of cooperativity of Ca2+ (or Sr2+) binding or activation of the contractile system. As [Mg2+] increased, the apparent affinity for Ca2+ or Sr2+ and cooperativity of the contractile system declined. The effect on cooperativity suggests that as [Mg2+] decreases a threshold for Ca2+ activation appears.

The “KIMWIPE” Effect in Ultra-Thin Cryosections

1985 ◽  
Vol 43 ◽  
pp. 458-459
Author(s):  
I. Taylor ◽  
P. Ingram ◽  
J.R. Sommer
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Muscle Fibers ◽  
Ice Crystals ◽  
Crystal Formation ◽  
Ice Crystal ◽  
Thin Sections ◽  
Skeletal Muscle Fibers ◽  
Freeze Dried ◽  
Ice Crystal Formation

In studying quick-frozen single intact skeletal muscle fibers for structural and microchemical alterations that occur milliseconds, and fractions thereof, after electrical stimulation, we have developed a method to compare, directly, ice crystal formation in freeze-substituted thin sections adjacent to all, and beneath the last, freeze-dried cryosections. We have observed images in the cryosections that to our knowledge have not been published heretofore (Figs.1-4). The main features are that isolated, sometimes large regions of the sections appear hazy and have much less contrast than adjacent regions. Sometimes within the hazy regions there are smaller areas that appear crinkled and have much more contrast. We have also observed that while the hazy areas remain still, the regions of higher contrast visibly contract in the beam, often causing tears in the sections that are clearly not caused by ice crystals (Fig.3, arrows).

Effect of External Calcium and other Divalent Cations on K+ Contractures in Denervated Slow Skeletal Muscle Fibers of the Frog

2019 ◽  
Author(s):  
Leonardo Hernández
Keyword(s):  
Skeletal Muscle ◽  
Binding Capacity ◽  
Divalent Cations ◽  
Muscle Fibers ◽  
Free Calcium ◽  
Slow Skeletal Muscle ◽  
Skeletal Muscle Fibers ◽  
Free Calcium Concentration ◽  
Chronic Denervation ◽  
Denervated Muscles

The influence of Ca2+ and other divalent cations on contractile responses of slow skeletal muscle fibers of the frog (Rana pipiens) under conditions of chronic denervation was investigated.Isometric tension was recorded from slow bundles of normal and denervated cruralis muscle in normal solution and in solutions with free calcium concentration solution or in solutions where other divalent cations (Sr2+, Ni2+, Co2+ or Mn2+) substituted for calcium. In the second week after nerve section, in Ca2+-free solutions, we observed that contractures (evoked from 40 to 80 mM-K+) of non-denervated muscles showed significantly higher tensions (p<0.05), than those from denervated bundles. Likewise, in solutions where calcium was substituted by all divalent cations tested, with exception of Mn2+, the denervated bundles displayed lower tension than non-denervated, also in the second week of denervation. In this case, the Ca2+ substitution by Sr2+ caused the higher decrease in tension, followed by Co2+ and Ni2+, which were different to non-denervated bundles, as the lowest tension was developed by Mn2+, followed by Co2+, and then Ni2+ and Sr2+. After the third week, we observed a recovery in tension. These results suggest that denervation altering the binding capacity to divalent cations of the voltage sensor.

scholarly journals Development of a human neuromuscular tissue-on-a-chip model on a 24-well-plate-format compartmentalized microfluidic device

Lab on a Chip ◽  
2021 ◽  
Author(s):  
Kazuki Yamamoto ◽  
Nao Yamaoka ◽  
Yu Imaizumi ◽  
Takunori Nagashima ◽  
Taiki Furutani ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Microfluidic Device ◽  
Motor Neurons ◽  
Muscle Fibers ◽  
Three Dimensional ◽  
Tissue Model ◽  
Skeletal Muscle Fibers

A three-dimensional human neuromuscular tissue model that mimics the physically separated structures of motor neurons and skeletal muscle fibers is presented.

scholarly journals Glycogenin is Dispensable for Glycogen Synthesis in Human Muscle, and Glycogenin Deficiency Causes Polyglucosan Storage

2019 ◽  
Vol 105 (2) ◽  
pp. 557-566 ◽  
Author(s):  
Kittichate Visuttijai ◽  
Carola Hedberg-Oldfors ◽  
Christer Thomsen ◽  
Emma Glamuzina ◽  
Cornelia Kornblum ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Skeletal Muscle ◽  
Western Blot ◽  
Cardiac Muscle ◽  
Glycogen Synthesis ◽  
Muscle Fibers ◽  
Human Muscle ◽  
Missense Mutations ◽  
Skeletal Muscle Fibers ◽  
Glycogen Biosynthesis

Abstract Context Glycogenin is considered to be an essential primer for glycogen biosynthesis. Nevertheless, patients with glycogenin-1 deficiency due to biallelic GYG1 (NM_004130.3) mutations can store glycogen in muscle. Glycogenin-2 has been suggested as an alternative primer for glycogen synthesis in patients with glycogenin-1 deficiency. Objective The objective of this article is to investigate the importance of glycogenin-1 and glycogenin-2 for glycogen synthesis in skeletal and cardiac muscle. Design, Setting, and Patients Glycogenin-1 and glycogenin-2 expression was analyzed by Western blot, mass spectrometry, and immunohistochemistry in liver, heart, and skeletal muscle from controls and in skeletal and cardiac muscle from patients with glycogenin-1 deficiency. Results Glycogenin-1 and glycogenin-2 both were found to be expressed in the liver, but only glycogenin-1 was identified in heart and skeletal muscle from controls. In patients with truncating GYG1 mutations, neither glycogenin-1 nor glycogenin-2 was expressed in skeletal muscle. However, nonfunctional glycogenin-1 but not glycogenin-2 was identified in cardiac muscle from patients with cardiomyopathy due to GYG1 missense mutations. By immunohistochemistry, the mutated glycogenin-1 colocalized with the storage of glycogen and polyglucosan in cardiomyocytes. Conclusions Glycogen can be synthesized in the absence of glycogenin, and glycogenin-1 deficiency is not compensated for by upregulation of functional glycogenin-2. Absence of glycogenin-1 leads to the focal accumulation of glycogen and polyglucosan in skeletal muscle fibers. Expression of mutated glycogenin-1 in the heart is deleterious, and it leads to storage of abnormal glycogen and cardiomyopathy.

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