scholarly journals Developmental effects on myonuclear domain size of rat diaphragm fibers

2008 ◽  
Vol 104 (3) ◽  
pp. 787-794 ◽  
Author(s):  
Carlos B. Mantilla ◽  
Rowan V. Sill ◽  
Bharathi Aravamudan ◽  
Wen-Zhi Zhan ◽  
Gary C. Sieck
Keyword(s):  
Postnatal Development ◽  
Domain Size ◽  
Diaphragm Muscle ◽  
Fiber Types ◽  
Rat Diaphragm ◽  
Cross Sectional ◽  
Early Postnatal Development ◽  
Fiber Growth ◽  
Myonuclear Domain ◽  
Isoform Expression

During early postnatal development in rat diaphragm muscle (Diam), significant fiber growth and transitions in myosin heavy chain (MHC) isoform expression occur. Similar to other skeletal muscles, Diam fibers are multinucleated, and each myonucleus regulates the gene products within a finite volume: the myonuclear domain (MND). We hypothesized that postnatal changes in fiber cross-sectional area (CSA) are associated with increased number of myonuclei so that the MND size is maintained. The Diam was removed at postnatal days 14 (P-14) and 28 (P-28). MHC isoform expression was determined by SDS-PAGE. Fiber CSA, myonuclear number, and MND size were measured using confocal microscopy. By P-14, significant coexpression of MHC isoforms was present with no fiber displaying singular expression of MHCNeo. By P-28, singular expression was predominant. MND size was not different across fiber types at P-14. Significant fiber growth was evident by P-28 at all fiber types (fiber CSA increased by 61, 93, and 147% at fibers expressing MHCSlow, MHC2A, and MHC2X, respectively). The number of myonuclei per unit of fiber length was similar across fibers at P-14, but it was greater at fibers expressing MHC2X at P-28. The total number of myonuclei per fiber also increased between P-14 and P-28 at all fiber types. Accordingly, MND size increased significantly by P-28 at all fiber types, and it became larger at fibers expressing MHC2X compared with fibers expressing MHCSlow or MHC2A. These results suggest that MND size is not maintained during the considerable fiber growth associated with postnatal development of the Diam.

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.

scholarly journals Denervation effects on myonuclear domain size of rat diaphragm fibers

2006 ◽  
Vol 100 (5) ◽  
pp. 1617-1622 ◽  
Author(s):  
Bharathi Aravamudan ◽  
Carlos B. Mantilla ◽  
Wen-Zhi Zhan ◽  
Gary C. Sieck
Keyword(s):  
Fiber Type ◽  
Cross Sectional Area ◽  
Diaphragm Muscle ◽  
Type I ◽  
Fiber Types ◽  
Sectional Area ◽  
Rat Diaphragm ◽  
Cross Sectional ◽  
Fiber Size ◽  
Myonuclear Domain

Denervation (DNV) of rat diaphragm muscle (DIAm) leads to selective atrophy of type IIx and IIb fibers, whereas the cross-sectional area of type I and IIa fibers remains unchanged or slightly hypertrophied. DIAm DNV also increases satellite cell mitotic activity and myonuclear apoptosis. Similar to other skeletal muscles, DIAm fibers are multinucleated, and each myonucleus regulates the gene products in a finite fiber volume, i.e., myonuclear domain (MND). MND size varies across DIAm fiber types in rank order, I < IIa < IIx < IIb [fiber type based on myosin heavy chain isoform expression]. We hypothesized that, after DNV, the total number of myonuclei per fiber does not change and, accordingly, that MND changes proportionately to the change in fiber size regardless of fiber type. Adult rats underwent unilateral (right side) DIAm DNV, and after 2 wk single fibers were dissected. Fiber cross-sectional area, myonuclear number, and MND were measured by confocal microscopy, and these values in DNV DIAm were compared with those obtained in controls. After DNV, type I fibers hypertrophied, type IIa fiber size was unchanged, and type IIx and IIb fibers atrophied compared with control. The total number of myonuclei per fiber was not affected by DNV. Accordingly, after DNV, type I fiber MND increased by 25%, whereas it decreased in type IIx and IIb fibers by 50 and 70%, respectively. These results suggest that MND is not maintained after DNV-induced DIAm fiber hypertrophy or atrophy. These results are interpreted with respect to consequent effects of DNV on myonuclear transcriptional activity and protein turnover.

scholarly journals Selected Contribution: Mechanisms underlying increased force generation by rat diaphragm muscle fibers during development

2001 ◽  
Vol 90 (1) ◽  
pp. 380-388 ◽  
Author(s):  
Paige C. Geiger ◽  
Mark J. Cody ◽  
Rebecca L. Macken ◽  
Megan E. Bayrd ◽  
Yun-Hua Fang ◽  
...  
Keyword(s):  
Postnatal Development ◽  
Developmental Change ◽  
Diaphragm Muscle ◽  
Rat Diaphragm ◽  
Cross Sectional ◽  
Early Postnatal Development ◽  
Standard Curve ◽  
Cross Bridge ◽  
Sds Page ◽  
Cross Bridges

It has been found that maximum specific force (Fmax; force per cross-sectional area) of rat diaphragm muscle doubles from birth to 84 days (adult). We hypothesize that this developmental change in Fmax reflects an increase in myosin heavy chain (MHC) content per half-sarcomere (an estimate of the number of cross bridges in parallel) and/or a greater force per cross bridge in fibers expressing fast MHC isoforms compared with slow and neonatal MHC isoforms (MHCslow and MHCneo, respectively). Single Triton 100-X-permeabilized fibers were activated at a pCa of 4.0. MHC isoform expression was determined by SDS-PAGE. MHC content per half-sarcomere was determined by densitometric analysis and comparison to a standard curve of known MHC concentrations. MHC content per half-sarcomere progressively increased during early postnatal development. When normalized for MHC content per half-sarcomere, fibers expressing MHCslow and coexpressing MHCneoproduced less force than fibers expressing fast MHC isoforms. We conclude that lower force per cross bridge in fibers expressing MHCslow and MHCneo contributes to the lower Fmax seen in early postnatal development.

Influence of corticosteroids on myonuclear domain size in the rat diaphragm muscle

2004 ◽  
Vol 97 (5) ◽  
pp. 1715-1722 ◽  
Author(s):  
A. Jeroen Verheul ◽  
Carlos B. Mantilla ◽  
Wen-Zhi Zhan ◽  
Miguel Bernal ◽  
P. N. Richard Dekhuijzen ◽  
...  
Keyword(s):  
Muscle Growth ◽  
Domain Size ◽  
Male Rats ◽  
Diaphragm Muscle ◽  
Gene Products ◽  
Sectional Area ◽  
Rat Diaphragm ◽  
Normal Muscle ◽  
Cross Sectional ◽  
Myonuclear Domain

Skeletal muscle fibers are multinucleated. Each myonucleus regulates gene products and protein expression in only a restricted portion of the muscle fiber, the myonuclear domain (MND). In the rat diaphragm muscle (DIAm), corticosteroid (CoS) treatment causes atrophy of fibers containing myosin heavy chain (MHC): MHC2X and/or MHC2B. We hypothesized that DIAm fiber MND size is maintained during CoS-induced atrophy. Adult male rats received methylprednisolone for 11 days at 1 (CoS-Low, n = 8) or 8 mg·kg−1·day−1 (CoS-High, n = 8). Age-matched (CTL-AgeM, n = 8), sham-operated (SHAM-AgeM, n = 8), and weight-matched (CTL-WtM, n = 8) animals served as controls. In single DIAm fibers, cross-sectional area (CSA), MND size, and MHC expression were determined. Fiber CSA and MND size were similar in CTL-AgeM and SHAM-AgeM groups. Only fibers containing MHCslow or MHC2A displayed smaller CSA in CTL-WtM than in CTL-AgeM and SHAM-AgeM groups, and MND size was reduced in all fibers. Thus fibers containing MHCslow and MHC2A maintain the number of myonuclei, whereas MHC2X or MHC2B fibers show loss of myonuclei during normal muscle growth. Both CoS groups displayed smaller CSA and MND size than CTL-AgeM and SHAM-AgeM groups. However, compared with CTL-WtM DIAm fibers, only fibers containing MHC2X or MHC2B displayed reduced CSA and MND size after CoS treatment. Thus little, if any, loss of myonuclei was associated with CoS-induced atrophy of MHC2X or MHC2B DIAm fibers. In summary, MND size does not appear to be regulated during CoS-induced DIAm atrophy.

Modulation of myonuclear number in functionally overloaded and exercised rat plantaris fibers

1999 ◽  
Vol 87 (2) ◽  
pp. 634-642 ◽  
Author(s):  
Roland R. Roy ◽  
Steven R. Monke ◽  
David L. Allen ◽  
V. Reggie Edgerton
Keyword(s):  
Fiber Type ◽  
Domain Size ◽  
Cross Sectional Area ◽  
Type I ◽  
Fiber Types ◽  
Sectional Area ◽  
Tight Coupling ◽  
Fiber Volume ◽  
Cross Sectional ◽  
Myonuclear Domain

The effects of 10 wk of functional overload (FO), with and without daily treadmill endurance training, on the cross-sectional area, myonuclear number, and myonuclear domain size of mechanically isolated single fiber segments of the adult rat plantaris were determined. The fibers were typed on the basis of high-resolution gel electrophoresis for separation of specific myosin heavy chain (MHC) isoforms and grouped as type I+ (containing some type I MHC with or without any combination of fast MHCs), type IIa+ (containing some type IIa with or without some type IIx and/or IIb but no type I MHC), and type IIx/b (containing only type IIx and/or IIb MHCs). Type I+ fibers had a higher myonuclear number than did both fast types of fibers in the control and FO, but not in the FO and treadmill trained, rats. All fiber types in both FO groups had a significantly larger (36–90%) cross-sectional area and a significantly higher (61–109%) myonuclear number than did control. The average myonuclear domain size of each fiber type was similar among the three groups, except for a smaller domain size in the type IIx/b fibers of the FO compared with control. In general, these data indicate that during hypertrophy the number of myonuclei increase proportionally to the increase in fiber volume. The maintenance of myonuclear domain size near control values suggests that regulatory mechanisms exist that ensure a tight coupling between the quantity of genetic machinery and the protein requirements of a fiber.

SDH and actomyosin ATPase activities of different fiber types in rat diaphragm muscle

1995 ◽  
Vol 79 (5) ◽  
pp. 1629-1639 ◽  
Author(s):  
G. C. Sieck ◽  
W. Z. Zhan ◽  
Y. S. Prakash ◽  
M. J. Daood ◽  
J. F. Watchko
Keyword(s):  
Atpase Activity ◽  
Rank Order ◽  
Cross Sectional Area ◽  
Diaphragm Muscle ◽  
Type I ◽  
Fiber Types ◽  
Sectional Area ◽  
Rat Diaphragm ◽  
Cross Sectional ◽  
Actomyosin Atpase

In the rat diaphragm muscle, the histochemical classification of type I, IIa, IIb, or IIx fibers was correlated with myosin heavy chain (MHC) immunoreactivity. Expression of MHC isoforms in single dissected fibers was also assessed electrophoretically. Most fibers (approximately 86%) expressed a single MHC isoform, and when present, coexpression of MHC-2X and MHC-2B isoforms was most prevalent. Type I and IIa fibers were the smallest, type IIb fibers were the largest, and type IIx fibers were intermediate. Succinate dehydrogenase (SDH) and calcium-activated myosin adenosinetriphosphatase (actomyosin ATPase) activities were measured with quantitative histochemical procedures. Type I and IIa fibers had the highest SDH activities, followed in rank order by type IIx and IIb fibers. Type I fibers had the lowest actomyosin ATPase activity, followed in rank order by type IIa, IIx, and IIb fibers. Across all fibers, there was an inverse relationship between fiber SDH activity and cross-sectional area and a positive correlation between fiber actomyosin ATPase activity and cross-sectional area. The SDH and actomyosin ATPase activities of muscle fibers were also inversely correlated. These phenotypic differences in SDH and ATPase activities may be important in determining the contractile and fatigue properties of different fiber types in the rat diaphragm muscle.

Interstitial space and collagen alterations of the developing rat diaphragm

1993 ◽  
Vol 74 (5) ◽  
pp. 2450-2455 ◽  
Author(s):  
L. E. Gosselin ◽  
D. A. Martinez ◽  
A. C. Vailas ◽  
G. C. Sieck
Keyword(s):  
Postnatal Growth ◽  
Interstitial Space ◽  
Collagen Content ◽  
Diaphragm Muscle ◽  
Adult Males ◽  
Rat Diaphragm ◽  
Collagen Concentration ◽  
Cross Sectional ◽  
Hydroxyproline Concentration ◽  
Total Muscle

The effect of growth on the relative interstitial space [%total cross-sectional area (CSA)] and collagen content of the rat diaphragm muscle was examined at postnatal ages of 0, 7, 14, and 21 days as well as in adult males. The proportion of interstitial space relative to total muscle CSA was determined by computerized image analysis of lectin-stained cross sections of diaphragm muscle. To assess collagen content and extent of collagen maturation (i.e., cross-linking), high-pressure liquid chromatography analysis was used to measure hydroxyproline concentration and the nonreducible collagen cross-link hydroxylysylpyridinoline (HP), respectively. At birth, interstitial space accounted for approximately 47% of total diaphragm muscle CSA. During postnatal growth, the relative contribution of interstitial space decreased such that by adulthood the interstitial space accounted for approximately 18% of total muscle CSA. The change in relative interstitial space occurred without a concomitant change in hydroxyproline concentration. However, the concentration of HP markedly increased with age such that the adult diaphragm contained approximately 17 times more HP than at birth. These results indicate that during development the relative CSA occupied by interstitial space decreases as muscle fiber size increases. However, the reduction in relative interstitial space is not associated with a change in collagen concentration. Thus collagen density in the interstitial space may increase with age. It is possible that the observed changes in relative interstitial space and collagen influence the passive length-force properties of the diaphragm.

Postnatal expression of myosin isoforms in an expiratory muscle--external abdominal oblique

1992 ◽  
Vol 73 (5) ◽  
pp. 1860-1866 ◽  
Author(s):  
J. F. Watchko ◽  
M. J. Daood ◽  
R. L. Vazquez ◽  
B. S. Brozanski ◽  
W. A. LaFramboise ◽  
...  
Keyword(s):  
Postnatal Development ◽  
Heavy Chain ◽  
Temporal Patterns ◽  
Abdominal Muscle ◽  
Myosin Isoforms ◽  
Early Postnatal Development ◽  
Expiratory Muscle ◽  
Fast Myosin ◽  
Isoform Expression

We studied the postnatal expression of heavy-chain (MHC) and native myosin isoforms in an expiratory abdominal muscle of the rat, the external abdominal oblique (EO). Moreover, we contrasted EO myosin expression with that of the costal diaphragm (DIA) to draw inspiratory vs. expiratory muscle comparisons during development. Examination of MHC gels demonstrated a mature phenotype of slow and adult fast myosin isoforms at an earlier age in the EO (day 60) than in the DIA [day > 115 (adult)]. The mature MHC phenotype of the EO was characterized by a preponderance of MHC 2B, whereas the DIA was characterized by approximately equal portions of MHC slow, MHC 2A, and MHC 2X. During early postnatal development, there was a delay in the expression of MHC 2A in the EO compared with the DIA. However, MHC 2B, expressed later in development in both muscles, was noted in the EO before the DIA. We conclude that 1) the EO mature myosin phenotype is characterized by a preponderance of fast myosin isoforms and 2) the EO and DIA muscles are subject to different temporal patterns of isoform expression during postnatal development.

scholarly journals Power fatigue of the rat diaphragm muscle

2000 ◽  
Vol 89 (6) ◽  
pp. 2215-2219 ◽  
Author(s):  
Bill T. Ameredes ◽  
Wen-Zhi Zhan ◽  
Y. S. Prakash ◽  
Rene Vandenboom ◽  
Gary C. Sieck
Keyword(s):  
Diaphragm Muscle ◽  
Fiber Types ◽  
Rat Diaphragm ◽  
Shortening Velocity ◽  
Reduction In Force ◽  
Novel Technique ◽  
Velocity Relationship ◽  
Stimulus Train ◽  
Force Velocity

We hypothesized that decrements in maximum power output (W˙max) of the rat diaphragm (Dia) muscle with repetitive activation are due to a disproportionate reduction in force (force fatigue) compared with a slowing of shortening velocity (velocity fatigue). Segments of midcostal Dia muscle were mounted in vitro (26°C) and stimulated directly at 75 Hz in 400-ms-duration trains repeated each second (duty cycle = 0.4) for 120 s. A novel technique was used to monitor instantaneous reductions in maximum specific force (Po) andW˙max during fatigue. During each stimulus train, activation was isometric for the initial 360 ms during which Po was measured; the muscle was then allowed to shorten at a constant velocity (30% V max) for the final 40 ms, and W˙max was determined. Compared with initial values, after 120 s of repetitive activation, Po andW˙max decreased by 75 and 73%, respectively. Maximum shortening velocity was measured in two ways: by extrapolation of the force-velocity relationship ( V max) and using the slack test [maximum unloaded shortening velocity ( V o)]. After 120 s of repetitive activation, V max slowed by 44%, whereas V o slowed by 22%. Thus the decrease inW˙max with repetitive activation was dominated by force fatigue, with velocity fatigue playing a secondary role. On the basis of a greater slowing of V max vs. V o, we also conclude that force and power fatigue cannot be attributed simply to the total inactivation of the most fatigable fiber types.

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