scholarly journals Intracellular Po2 kinetics at different contraction frequencies in Xenopus single skeletal muscle fibers

2007 ◽  
Vol 102 (4) ◽  
pp. 1456-1461 ◽  
Author(s):  
Richard A. Howlett ◽  
Casey A. Kindig ◽  
Michael C. Hogan
Keyword(s):  
Skeletal Muscle ◽  
Metabolic Response ◽  
Muscle Fibers ◽  
Metabolic Stress ◽  
Metabolic Demand ◽  
Phosphorescence Quenching ◽  
Contraction Frequency ◽  
Single Fibers ◽  
Mean Response Time ◽  
Skeletal Muscle Fibers

Increasing contraction frequency in single skeletal muscle fibers has been shown to increase the magnitude of the fall in intracellular Po2 (PiO2), reflecting a greater metabolic rate. To test whether PiO2 kinetics are altered by contraction frequency through this increase in metabolic stress, PiO2 was measured in Xenopus single fibers ( n = 11) during and after contraction bouts at three different frequencies. PiO2 was measured via phosphorescence quenching at 0.16-, 0.25-, and 0.5-Hz tetanic stimulation. The kinetics of the change in PiO2 from resting baseline to end-contraction values and end contraction to rest were described as a mean response time (MRT) representing the time to 63% of the change in PiO2. As predicted, the fall in PiO2 from baseline following contractions was progressively greater at 0.5 and 0.25 Hz than at 0.16 Hz (32.8 ± 2.1 and 29.3 ± 2.0 Torr vs. 23.6 ± 2.2 Torr, respectively) since metabolic demand was greater. The MRT for the decrease in PiO2 was progressively faster at the higher frequencies (0.5 Hz: 45.3 ± 4.5 s; 0.25 Hz: 63.3 ± 4.1 s; 0.16 Hz: 78.0 ± 4.1 s), suggesting faster accumulation of stimulators of oxidative phosphorylation. The MRT for PiO2 off-kinetics (0.5 Hz: 84.0 ± 11.7 s; 0.25 Hz: 79.1 ± 8.4 s; 0.16 Hz: 81.1 ± 8.3 s) was not different between trials. These data demonstrate in single fibers that the rate of the fall in PiO2 is dependent on contraction frequency, whereas the rate of recovery following contractions is independent of either the magnitude of the fall in PiO2 from baseline or the contraction frequency. This suggests that stimulation frequency plays an integral role in setting the initial metabolic response to work in isolated muscle fibers, possibly due to temporal recovery between contractions, but it does not determine recovery kinetics.

Effect of extracellular Po 2 on the fall in intracellular Po 2 in contracting single myocytes

2003 ◽  
Vol 94 (5) ◽  
pp. 1964-1970 ◽  
Author(s):  
Casey A. Kindig ◽  
Richard A. Howlett ◽  
Michael C. Hogan
Keyword(s):  
Skeletal Muscle ◽  
Time Delay ◽  
Time Constant ◽  
Initial Rate ◽  
Metabolic Response ◽  
Rate Of Change ◽  
Phosphorescence Quenching ◽  
Mean Response Time ◽  
The Mean ◽  
Lumbrical Muscles

The purpose of this investigation was to study the effects of altered extracellular Po 2 (Pe O2 ) on the intracellular Po 2(Pi O2 ) response to contractions in single skeletal muscle cells. Single myocytes ( n = 12) were dissected from lumbrical muscles of adult female Xenopus laevis and injected with 0.5 mM Pd- meso-tetra(4-carboxyphenyl)porphine for assessment of Pi O2 via phosphorescence quenching. At a Pe O2 of ∼20 (low), ∼40 (moderate), and ∼60 (high) Torr, tetanic contractions were induced at a frequency of 0.67 Hz for ∼2 min with a 5-min recovery between bouts (blocked order design). The Pi O2 response to contractions was characterized by a time delay followed by a monoexponential decline to steady-state (SS) values. The fall in Pi O2 to SS values was significantly greater at each progressively greater Pe O2 (all P < 0.05). The mean response time (time delay + time constant) was significantly faster in the low (35.2 ± 5.1 s; P < 0.05 vs. high) and moderate (43.3 ± 6.4 s; P < 0.05 vs. high) compared with high Pe O2 (61.8 ± 9.4 s) and was correlated positively ( r = 0.965) with the net fall in Pi O2 . However, the initial rate of change of Pi O2 (calculated as net fall in Pi O2 /time constant) was not different ( P > 0.05) among Pe O2 trials. These latter data suggest that, over the range of 20–60 Torr, Pe O2 does not play a deterministic role in setting the initial metabolic response to contractions in isolated frog myocytes. Additionally, these results suggest that oxidative phosphorylation in these myoglobin-free myocytes may be compromised by Pe O2 at values nearing 60 Torr.

Phosphorescence quenching method for measurement of intracellular P O 2 in isolated skeletal muscle fibers

1999 ◽  
Vol 86 (2) ◽  
pp. 720-724 ◽  
Author(s):  
Michael C. Hogan
Keyword(s):  
Skeletal Muscle ◽  
Single Cells ◽  
Muscle Fibers ◽  
Ringer Solution ◽  
Phosphorescence Lifetime ◽  
Phosphorescence Quenching ◽  
Skeletal Muscle Fibers ◽  
Lumbrical Muscle ◽  
Novel Method ◽  
Quenching Method

Values of skeletal muscle intracellular[Formula: see text] during conditions ranging from rest to maximal metabolic rates have been difficult to quantify. A method for measurement of intracellular[Formula: see text] in isolated single skeletal muscle fibers by using O2-dependent quenching of a phosphorescent-O2probe is described. Intact single skeletal muscle fibers from Xenopus laevis were dissected from the lumbrical muscle and mounted in a glass chamber containing Ringer solution at 20°C. The chamber was placed on the stage of an inverted microscope configured for epi-illumination. A solution containing palladium- meso-tetra (4-carboxyphenyl) porphine bound to bovine serum albumin was injected into single fibers by micropipette pressure injection. Phosphorescence-decay curves (average of 10 rapid flashes) were recorded every 7 s from single cells ( n = 24) in which respiration had been eliminated with NaCN, while the [Formula: see text]of the Ringer solution surrounding the cell was varied from 0 to 159 Torr. For each measurement, the phosphorescence lifetime was calculated at the varied extracellular [Formula: see text] by obtaining a best-fit estimate by using a monoexponential function. The phosphorescence lifetime varied from 40 to 70 μs at an extracellular[Formula: see text] of 159 Torr to 650–700 μs at 0 Torr. The phosphorescent lifetimes for the varied[Formula: see text] were used to calculate, by using the Stern-Volmer relationship, the phosphorescence-quenching constant (100 Torr−1 ⋅ s−1), and the phosphorescence lifetime in a zero-O2 environment (690 μs) for the phosphor within the intracellular environment. This technique demonstrates a novel method for determining intracellular[Formula: see text] in isolated single skeletal muscle fibers.

scholarly journals Coupled expression of troponin T and troponin I isoforms in single skeletal muscle fibers correlates with contractility

2006 ◽  
Vol 290 (2) ◽  
pp. C567-C576 ◽  
Author(s):  
Marco A. Brotto ◽  
Brandon J. Biesiadecki ◽  
Leticia S. Brotto ◽  
Thomas M. Nosek ◽  
Jian-Ping Jin
Keyword(s):  
Skeletal Muscle ◽  
Troponin I ◽  
Troponin T ◽  
Muscle Fibers ◽  
Contractile Properties ◽  
Type I ◽  
Myosin Isoforms ◽  
Mammalian Skeletal Muscle ◽  
Single Fibers ◽  
Skeletal Muscle Fibers

Striated muscle contraction is powered by actin-activated myosin ATPase. This process is regulated by Ca2+ via the troponin complex. Slow- and fast-twitch fibers of vertebrate skeletal muscle express type I and type II myosin, respectively, and these myosin isoenzymes confer different ATPase activities, contractile velocities, and force. Skeletal muscle troponin has also diverged into fast and slow isoforms, but their functional significance is not fully understood. To investigate the expression of troponin isoforms in mammalian skeletal muscle and their functional relationship to that of the myosin isoforms, we concomitantly studied myosin, troponin T (TnT), and troponin I (TnI) isoform contents and isometric contractile properties in single fibers of rat skeletal muscle. We characterized a large number of Triton X-100-skinned single fibers from soleus, diaphragm, gastrocnemius, and extensor digitorum longus muscles and selected fibers with combinations of a single myosin isoform and a single class (slow or fast) of the TnT and TnI isoforms to investigate their role in determining contractility. Types IIa, IIx, and IIb myosin fibers produced higher isometric force than that of type I fibers. Despite the polyploidy of adult skeletal muscle fibers, the expression of fast or slow isoforms of TnT and TnI is tightly coupled. Fibers containing slow troponin had higher Ca2+ sensitivity than that of the fast troponin fibers, whereas fibers containing fast troponin showed a higher cooperativity of Ca2+ activation than that of the slow troponin fibers. These results demonstrate distinct but coordinated regulation of troponin and myosin isoform expression in skeletal muscle and their contribution to the contractile properties of muscle.

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.

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