Effect of denervation on ATP consumption rate of diaphragm muscle fibers

2007 ◽  
Vol 103 (3) ◽  
pp. 858-866 ◽  
Author(s):  
Gary C. Sieck ◽  
Wen-Zhi Zhan ◽  
Young-Soo Han ◽  
Y. S. Prakash
Keyword(s):  
Consumption Rate ◽  
Atp Hydrolysis ◽  
Maximum Velocity ◽  
Diaphragm Muscle ◽  
Single Type ◽  
Shortening Velocity ◽  
Cycling Rate ◽  
Cross Bridge ◽  
Atpase Reaction ◽  
The Difference

Denervation (DNV) of rat diaphragm muscle (DIAm) decreases myosin heavy chain (MHC) content in fibers expressing MHC2X isoform but not in fibers expressing MHCslow and MHC2A. Since MHC is the site of ATP hydrolysis during muscle contraction, we hypothesized that ATP consumption rate during maximum isometric activation (ATPiso) is reduced following unilateral DIAm DNV and that this effect is most pronounced in fibers expressing MHC2X. In single-type-identified, permeabilized DIAm fibers, ATPiso was measured using NADH-linked fluorometry. The maximum velocity of the actomyosin ATPase reaction ( Vmax ATPase) was determined using quantitative histochemistry. The effect of DNV on maximum unloaded shortening velocity ( Vo) and cross-bridge cycling rate [estimated from the rate constant for force redevelopment ( kTR) following quick release and restretch] was also examined. Two weeks after DNV, ATPiso was significantly reduced in fibers expressing MHC2X, but unaffected in fibers expressing MHCslow and MHC2A. This effect of DNV on fibers expressing MHC2X persisted even after normalization for DNV-induced reduction in MHC content. With DNV, Vo and kTR were slowed in fibers expressing MHC2X, consistent with the effect on ATPiso. The difference between Vmax ATPase and ATPiso reflects reserve capacity for ATP consumption, which was reduced across all fibers following DNV; however, this effect was most pronounced in fibers expressing MHC2X. DNV-induced reductions in ATPiso and Vmax ATPase of fibers expressing MHC2X reflect the underlying decrease in MHC content, while reduction in ATPiso also reflects a slowing of cross-bridge cycling rate.

scholarly journals Changes in actomyosin ATP consumption rate in rat diaphragm muscle fibers during postnatal development

2003 ◽  
Vol 94 (5) ◽  
pp. 1896-1902 ◽  
Author(s):  
Gary C. Sieck ◽  
Y. S. Prakash ◽  
Young-Soo Han ◽  
Yun-Hua Fang ◽  
Paige C. Geiger ◽  
...  
Keyword(s):  
Postnatal Development ◽  
Consumption Rate ◽  
Rank Order ◽  
Maximum Velocity ◽  
Diaphragm Muscle ◽  
Reserve Capacity ◽  
Rat Diaphragm ◽  
Early Postnatal Development ◽  
Atpase Reaction ◽  
Isoform Expression

Early postnatal development of rat diaphragm muscle (Diam) is marked by dramatic transitions in myosin heavy chain (MHC) isoform expression. We hypothesized that the transition from the neonatal isoform of MHC (MHCNeo) to adult fast MHC isoform expression in Diam fibers is accompanied by an increase in both the maximum velocity of the actomyosin ATPase reaction ( V max ATPase) and the ATP consumption rate during maximum isometric activation (ATPiso). Rat Diam fibers were evaluated at postnatal days 0, 14, and 28 and in adults ( day 84). Across all ages, V max ATPase of fibers was significantly higher than ATPiso. The reserve capacity for ATP consumption [1 − (ratio of ATPiso to V max ATPase)] was remarkably constant (∼55–60%) across age groups, although at day 28 and in adults the reserve capacity for ATP consumption was slightly higher for fibers expressing MHCSlow compared with fast MHC isoforms. At day 28 and in adults, both V max ATPase and ATPiso were lower in fibers expressing MHCSlow followed in rank order by fibers expressing MHC2A, MHC2X, and MHC2B. For fibers expressing MHCNeo, V maxATPase, and ATPiso were comparable to values for adult fibers expressing MHCSlow but significantly lower than values for fibers expressing fast MHC isoforms. We conclude that postnatal transitions from MHCNeo to adult fast MHC isoform expression in Diam fibers are associated with corresponding but disproportionate changes in V max ATPase and ATPiso.

Oxytocin-mediated recruitment of slowly cycling cross bridges and isometric force in rat myometrium

1996 ◽  
Vol 270 (2) ◽  
pp. E203-E208
Author(s):  
A. L. Ruzycky ◽  
B. T. Ameredes
Keyword(s):  
Isometric Force ◽  
Additional Stress ◽  
Shortening Velocity ◽  
Cycling Rate ◽  
Quick Release ◽  
Cross Bridge ◽  
Cross Bridges ◽  
Unit Stress ◽  
Release Method ◽  
The Relationship

The relationship between cross-bridge cycling rate and isometric stress was investigated in rat myometrium. Stress production by myometrial strips was measured under resting, K+ depolarization, and oxytocin-stimulated conditions. Cross-bridge cycling rates were determined from measurements of maximal unloaded shortening velocity, using the quick-release method. Force redevelopment after the quick release was used as an index of cross-bridge attachment. With maximal K+ stimulation, stress increased with increased cross-bridge cycling (+76%; P < 0.05) and attached cross bridges (+112%; P < 0.05). Addition of oxytocin during K+ stimulation further increased stress (+30%; P < 0.05). With this force component, the cross-bridge cycling rate decreased (-60%; P < 0.05) similar to that under resting conditions. Attached cross-bridges did not increase with this additional stress. The results suggest two distinct mechanisms mediating myometrial contractions. One requires elevated intracellular calcium and rapidly cycling cross bridges. The other mechanism may be independent of calcium and appears to be mediated by slowly cycling cross bridges, supporting greater unit stress.

Contractile properties of the developing diaphragm correlate with myosin heavy chain phenotype

1994 ◽  
Vol 77 (1) ◽  
pp. 481-487 ◽  
Author(s):  
B. D. Johnson ◽  
L. E. Wilson ◽  
W. Z. Zhan ◽  
J. F. Watchko ◽  
M. J. Daood ◽  
...  
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Diaphragm Muscle ◽  
Shortening Velocity ◽  
Cross Bridge ◽  
Isoform Expression ◽  
The Relationship ◽  
Laser Densitometry

The objective of this study was to determine the relationship between developmental transitions in myosin heavy chain (MHC) composition and changes in maximum unloaded shortening velocity (Vo) and maximum specific force (Po) of the rat diaphragm muscle. The diaphragm was excised at postnatal days 0, 3, 7, 14, 21, and 28 and in adults. MHC isoform expression was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and laser densitometry. In muscle fiber bundles, Vo was determined at 15 degrees C by use of the “slack” test. Isometric Po was determined at 15 and 26 degrees C. Simple and stepwise regressions were used to evaluate the correlations between Vo, Po, and MHC phenotype transitions and the various developmental ages. The progressive increases in Vo and Po with age were found to be inversely correlated to MHC-neonatal isoform expression (r2 = -0.84 and -0.63, respectively) and positively correlated to MHC-2X (r2 = 0.78 and 0.57) and MHC-2B (r2 = 0.51 and 0.40) isoform expression (P < 0.001). Changes in MHC-neonatal isoform expression contributed to most of the developmental variance in Vo and Po, with changes in MHC-2X and MHC-2B expression also contributing significant increments to total variance. The postnatal increase in Vo most likely relates to differences in the actomyosin adenosinetriphosphatase activity between neonatal and adult fast MHC phenotypes. The increase in Po may reflect inherent differences in myofibrillar density, cross-bridge cycling kinetics, and/or the force produced per cross bridge among fibers composed of the different MHC isoforms.

Force Maintenance with Reduced Ability to Shorten Actively in Barnacle Striated Muscle

1990 ◽  
Vol 148 (1) ◽  
pp. 281-291
Author(s):  
H. IWAMOTO ◽  
A. MURAOKA ◽  
A. GOTO ◽  
H. SUGI
Keyword(s):  
Electrical Stimulation ◽  
Mechanical Response ◽  
Striated Muscle ◽  
Isometric Force ◽  
Shortening Velocity ◽  
Cycling Rate ◽  
Quick Release ◽  
Mechanical Responses ◽  
Cross Bridge ◽  
Force Maintenance

1. Fibres from adductor scutorum muscle of a barnacle Tetraclita squamosa were made to contract isometrically by electrical stimulation, and the change in the ability to shorten actively during the mechanical responses was examined by suddenly allowing the fibres to shorten under a very small load (&lt;3 % of the force immediately before shortening) at various times after the onset of stimulation. 2. The shortening velocity (Vsl) was nearly constant during stimulation. After the cessation of stimulation, shortening velocity decreased steeply while isometric force decayed slowly, indicating that isometric force was maintained with reduced ability to shorten actively. 3. Similar results were obtained when the maximum rate of force redevelopment following a quick release was measured at various times during the mechanical response to electrical stimulation. 4. In these fibres, but not in fibres from frog skeletal muscle, a quick restretch following a quick release could restore the force to a level similar to that observed without a quick release. These results, together with those above, indicated a reduced cross-bridge cycling rate during the relaxation phase of mechanical responses of barnacle fibres to electrical stimulation. 5. During electrical stimulation, Vsl showed less dependence on [Ca2+]o than was shown by isometric force. 6. These results are discussed in connection with the mechanism of force maintenance with reduced cross-bridge cycling rate.

Relaxation of smooth muscle

1994 ◽  
Vol 72 (11) ◽  
pp. 1345-1350 ◽  
Author(s):  
N. L. Stephens ◽  
H. Jiang
Keyword(s):  
Smooth Muscle ◽  
Muscle Relaxation ◽  
Late Phase ◽  
Contractile Element ◽  
Smooth Muscle Relaxation ◽  
Shortening Velocity ◽  
Cycling Rate ◽  
Cross Bridge ◽  
Cross Bridges ◽  
And Control

We have demonstrated that in dogs antigen sensitization results in alterations of contractile properties. These changes could account for the hyperresponsiveness reported in asthma. The failure of the muscle to relax could be another important factor responsible for maintaining high airway resistance. We therefore developed an index of isotonic relaxation, t1/2,CE (half time for relaxation that is independent of muscle load and initial contractile element length), for evaluation of the relaxation process. Because the maximum shortening velocity at 2 s but not at 10 s was greater in sensitized bronchial smooth muscle than that in controls, studies of relaxation were also undertaken at these two times. The mean half-relaxation time indicated by t1/2,CE showed no difference between sensitized and control muscles after 10 s of stimulation (8.38 ± 0.92 vs. 7.78 ± 0.93 s, means ± SE); however, it was prolonged significantly in the sensitized muscle only stimulated for 1 s (12.74 ± 2.5 s, mean ± SE) compared with the control (6.98 ± 1.01 s). During the late phase of isotonic relaxation, both groups showed an unexpected spontaneous increase in zero-load shortening velocity, which is an index of cross-bridge cycling rate. We conclude that (i) both contraction and relaxation properties of early normally cycling cross bridges are altered after sensitization and these changes may account for the hyperresponsiveness observed in asthmatics and (ii) the cross-bridge cycling rate increases spontaneously during isotonic relaxation, probably as a result of reactivation of the contractile mechanism.Key words: smooth muscle relaxation, isotonic relaxation, spontaneous activation in late relaxation, mechanisms for airway hyperresponsiveness, new index of muscle relaxation.

ATP consumption rate per cross bridge depends on myosin heavy chain isoform

2003 ◽  
Vol 94 (6) ◽  
pp. 2188-2196 ◽  
Author(s):  
Young-Soo Han ◽  
Paige C. Geiger ◽  
Mark J. Cody ◽  
Rebecca L. Macken ◽  
Gary C. Sieck
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Consumption Rate ◽  
Diaphragm Muscle ◽  
Rat Diaphragm ◽  
Myosin Heavy Chain Isoform ◽  
Standard Curve ◽  
Cross Bridge ◽  
Sds Page ◽  
Triton X

In the present study, we tested the hypothesis that intrinsic differences in ATP consumption rate per cross bridge exist across rat diaphragm muscle (Diam) fibers expressing different myosin heavy chain (MHC) isoforms. During maximum Ca2+ activation (pCa 4.0) of single, Triton X-permeabilized Diam fibers, isometric ATP consumption rate was determined by using an NADH-linked fluorometric technique. The MHC concentration in single Diam fibers was determined by densitometric analysis of SDS-PAGE gels and comparison to a standard curve of known MHC concentrations. Isometric ATP consumption rate varied across Diam fibers expressing different MHC isoforms, being highest in fibers expressing MHC2X (1.14 ± 0.08 nmol · mm−3 · s−1) and/or MHC2B (1.33 ± 0.08 nmol · mm−3 · s−1), followed by fibers expressing MHC2A (0.77 ± 0.11 nmol · mm−3 · s−1) and MHCSlow (0.46 ± 0.03 nmol · mm−3 · s−1). These differences in ATP consumption rate also persisted when it was normalized for MHC concentration in single Diam fibers. Normalized ATP consumption rate for MHC concentration varied across Diam fibers expressing different MHC isoforms, being highest in fibers expressing MHC2X (2.02 ± 0.19 s−1) and/or MHC2B (2.64 ± 0.15 s−1), followed by fibers expressing MHC2A(1.57 ± 0.16 s−1) and MHCSlow (0.77 ± 0.05 s−1). On the basis of these results, we conclude that there are intrinsic differences in ATP consumption rate per cross bridge in Diam fibers expressing MHC isoforms.

Mechanical alterations in sensitized canine saphenous vein

1990 ◽  
Vol 69 (1) ◽  
pp. 171-178 ◽  
Author(s):  
Z. Wang ◽  
C. Y. Seow ◽  
W. Kepron ◽  
N. L. Stephens
Keyword(s):  
Smooth Muscle ◽  
Saphenous Vein ◽  
Specific Antigen ◽  
Isometric Tension ◽  
Antigen Challenge ◽  
Pollen Extract ◽  
Shortening Velocity ◽  
Tension Development ◽  
Cycling Rate ◽  
Cross Bridge

Because it is likely that antigen sensitization is not restricted to airway smooth muscle but probably involves all tissues in the animal, we decided to test the hypothesis that saphenous vein from pollen extract-sensitized dogs is sensitized and is, in addition, mechanically altered. To this end, we studied responses to specific antigen challenge and length-tension and force-velocity relationships in sensitized (SSV) and control saphenous veins (CSV). The antigen challenge revealed that the venous smooth muscle was strongly sensitized and developed a Schultz-Dale response, the two main mediators of which were histamine and norepinephrine. Length-tension relationship studies showed that whereas there is no difference in maximum isometric tension development between SSV and CSV [93.95 +/- 7.34 and 87.86 +/- 4.00 (SE) mN/mm2, respectively], SSV exhibited a significantly greater maximum isotonic shortening capacity of 0.613 +/- 0.009 optional length (lo) vs. 0.578 +/- 0.012 lo for CSV. Unloaded shortening velocity (Vo), which reflects the cross-bridge cycling rate, was determined at different times after the onset of electrical stimulation. Maximum Vo was attained early (5 s) in the contraction; a 15% decline in Vo was observed at the plateau of the contraction (15 s). At 5 s, Vo of SSV (0.316 +/- 0.019 lo/s) was significantly higher than that of CSV (0.269 +/- 0.018 lo/s), although Vos were same at 15 (0.249 +/- 0.021 lo/s for SSV and 0.237 +/- 0.019 lo/s for CSV). The increase in shortening likely results from th e increase in the early cross-bridge cycling rate because our studies show that the bulk of shortening occurs in the first 5 s.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Acute Respiratory and Metabolic Acidosis on Diaphragm Muscle Obtained from Rats

2015 ◽  
Vol 122 (4) ◽  
pp. 876-883 ◽  
Author(s):  
Pierre Michelet ◽  
Serge Carreira ◽  
Alexandre Demoule ◽  
Julien Amour ◽  
Olivier Langeron ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Isometric Force ◽  
Respiratory Acidosis ◽  
Diaphragm Muscle ◽  
Peak Power Output ◽  
Control Group ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Cross Bridge

Abstract Background: Acute respiratory acidosis is associated with alterations in diaphragm performance. The authors compared the effects of respiratory acidosis and metabolic acidosis in the rat diaphragm in vitro. Methods: Diaphragmatic strips were stimulated in vitro, and mechanical and energetic variables were measured, cross-bridge kinetics calculated, and the effects of fatigue evaluated. An extracellular pH of 7.00 was obtained by increasing carbon dioxide tension (from 25 to 104 mmHg) in the respiratory acidosis group (n = 12) or lowering bicarbonate concentration (from 24.5 to 5.5 mM) in the metabolic acidosis group (n = 12) and the results compared with a control group (n = 12, pH = 7.40) after 20-min exposure. Results: Respiratory acidosis induced a significant decrease in maximum shortening velocity (−33%, P &lt; 0.001), active isometric force (−36%, P &lt; 0.001), and peak power output (−59%, P &lt; 0.001), slowed relaxation, and decreased the number of cross-bridges (−35%, P &lt; 0.001) but not the force per cross-bridge, and impaired recovery from fatigue. Respiratory acidosis impaired more relaxation than contraction, as shown by impairment in contraction–relaxation coupling under isotonic (−26%, P &lt; 0.001) or isometric (−44%, P &lt; 0.001) conditions. In contrast, no significant differences in diaphragmatic contraction, relaxation, or contraction–relaxation coupling were observed in the metabolic acidosis group. Conclusions: In rat diaphragm, acute (20 min) respiratory acidosis induced a marked decrease in the diaphragm contractility, which was not observed in metabolic acidosis.

Heat production of rat anococcygeus muscle during isometric contraction

1988 ◽  
Vol 255 (4) ◽  
pp. C536-C542 ◽  
Author(s):  
J. S. Walker ◽  
I. R. Wendt ◽  
C. L. Gibbs
Keyword(s):  
Energy Expenditure ◽  
Heat Production ◽  
Progressive Increase ◽  
Isometric Contractions ◽  
Shortening Velocity ◽  
Anococcygeus Muscle ◽  
Cross Bridge ◽  
Time Integral ◽  
Rat Anococcygeus Muscle ◽  
Cross Bridges

Heat production, unloaded shortening velocity (Vus), and load-bearing capacity (LBC) were studied in the isolated rat anococcygeus muscle during isometric contractions at 27 degrees C. The relation between the total suprabasal heat produced and the stress-time integral for isometric contractions of various durations was curvilinear, demonstrating a decreasing slope as contractile duration increased. The rate of heat production at 600 s was approximately 68% of the peak value of 6.55 mW/g that occurred at 10 s. At the same time, force rose from a mean of 92 mN/mm2 at 10 s to a value of 140 mN/mm2 at 600 s. This produced a nearly threefold increase in the economy of force maintenance. The decline in the rate of heat production was accompanied by a decline in Vus from 0.56 Lo/s at 10 s to 0.28 Lo/s at 600 s, where Lo is the length for optimal force development. This suggests the fall in the rate of heat production was caused, at least in part, by a slowing of cross-bridge kinetics. The ratio of LBC to developed tension at 10 s was not significantly different from the ratio at 600 s, suggesting that the increase in tension was due to an increased number of attached cross bridges. The decline in heat production, therefore, appears contradictory, since an increased number of attached cross bridges would predict an increased rate of energy expenditure. The observations can be reconciled if either 1) the increase in force is caused by a progressive increase in the attachment time of a constant number of cross bridges that cycle at a lower frequency or 2) the decline in energy expenditure caused by the slowing of cross-bridge cycling is sufficient to mask the increase caused by the recruitment of additional cross bridges.

scholarly journals Corticosteroid effects on isotonic contractile properties of rat diaphragm muscle

1997 ◽  
Vol 83 (4) ◽  
pp. 1062-1067 ◽  
Author(s):  
Roland H. H. Van Balkom ◽  
Wen-Zhi Zhan ◽  
Y. S. Prakash ◽  
P. N. Richard Dekhuijzen ◽  
Gary C. Sieck
Keyword(s):  
Isometric Force ◽  
Contractile Properties ◽  
Diaphragm Muscle ◽  
Peak Power Output ◽  
Rat Diaphragm ◽  
Fiber Morphology ◽  
Shortening Velocity ◽  
Maximum Isometric Force ◽  
Induced Changes ◽  
Isotonic Contractions

Van Balkom, Roland H. H., Wen-Zhi Zhan, Y. S. Prakash, P. N. Richard Dekhuijzen, and Gary C. Sieck. Corticosteroid effects on isotonic contractile properties of rat diaphragm muscle. J. Appl. Physiol. 83(4): 1062–1067, 1997.—The effects of corticosteroids (CS) on diaphragm muscle (Diam) fiber morphology and contractile properties were evaluated in three groups of rats: controls (Ctl), surgical sham and weight-matched controls (Sham), and CS-treated (6 mg ⋅ kg−1 ⋅ day−1prednisolone at 2.5 ml/h for 3 wk). In the CS-treated Diam, there was a selective atrophy of type IIx and IIb fibers, compared with a generalized atrophy of all fibers in the Sham group. Maximum isometric force was reduced by 20% in the CS group compared with both Ctl and Sham. Maximum shortening velocity in the CS Diamwas slowed by ∼20% compared with Ctl and Sham. Peak power output of the CS Diam was only 60% of Ctl and 70% of Sham. Endurance to repeated isotonic contractions improved in the CS-treated Diam compared with Ctl. We conclude that the atrophy of type IIx and IIb fibers in the Diam can only partially account for the CS-induced changes in isotonic contractile properties. Other factors such as reduced myofibrillar density or altered cross-bridge cycling kinetics are also likely to contribute to the effects of CS treatment.

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