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Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
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ABSTRACT |
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Top
Abstract
Introduction
Methods
Results
Discussion
References
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Sarcomere
lesions were previously observed with reloading of rat adductor longus
muscles after spaceflight and hindlimb unloading (HU).
Spaceflown rats displayed more lesioned fibers in the
"slow-fiber" region, suggesting a damage-susceptible fiber type.
Unloading induces fast myosin expression in some slow fibers,
generating hybrid fibers. We examined whether lesion damage differed
among slow-, hybrid-, and fast-fiber types in HU-reloaded adductor
longus muscles. Temporal HU for 5, 8, 11, 14, and 17 days revealed that hybrid fiber percent, detected by antimyosin immunostaining, peaked at
29 ± 12% by 14 days. A 14-day HU followed by 12-14 h of
voluntary reloading was performed to induce lesions.
2 analysis showed that slow
fibers were preferentially damaged, accounting for 92 ± 5% of
lesioned fibers; hybrid and fast fibers accounted for 7 ± 4 and
<0.5%, respectively. Atrophy did not explain differential lesion
damage across fiber types, as slow and hybrid fibers atrophied to a
similar extent. Because active myofiber contractions are requisite for
lesion formation, selective recruitment of slow fibers most likely
explains their damage susceptibility.
hindlimb unloading; voluntary reloading; eccentric contraction; hybrid fibers; recruitment
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INTRODUCTION |
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Top
Abstract
Introduction
Methods
Results
Discussion
References
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UNLOADING ATROPHY has been previously induced in rat hindlimb antigravity muscles by spaceflight and simulated microgravity by using the hindlimb unloading (HU) model. Subsequent reloading (return to weight bearing), in which rats walked voluntarily, resulted in the production of sarcomere lesions in 3-46% of the fibers in antigravity rat adductor longus (AL) muscles (4, 17, 26, 27, 29). The lesions were morphologically similar to those observed in eccentrically contracted muscles (2, 8, 10, 12, 23, 30). Eccentric contractions are known to generate high forces and have repeatedly been shown to be more damaging to skeletal muscles than are concentric or isometric contractions (12, 21). Although the activity of walking during reload is not an eccentrically biased exercise, it does have an eccentric component (18). Hargens et al. (14) have hypothesized that unloading removed the eccentric component in antigravity muscles, which rendered them more sensitive to the eccentric component during reload. Evidence from a study conducted by Warren et al. (31) supports this hypothesis: for normal muscles of mice, damage assessed by decreased optimal tension (Po) and increased efflux of lactate dehydrogenase was more severe for fast-twitch extensor digitorum longus (EDL) than for slow-twitch antigravity soleus muscles subjected to eccentric load. The degree of damage in EDL muscles from 14-day HU mice was similar to that of normal EDL muscles (31). Soleus muscles from 14-day HU mice, however, showed greater damage than those of normal mice, similar to the degree of damage in EDL muscles (31). The susceptibility of the antigravity soleus muscle to eccentric contraction damage was increased by HU, whereas the susceptibility of the nonantigravity EDL was unchanged (31). This makes sense, as HU induces lowered contractile activity and weight bearing, resulting in atrophy of the soleus (5, 15, 28). Plantar flexion of the rat hind feet during HU causes postural shortening of the soleus similar to muscle shortening after tenotomy, resulting in the formation of central core lesions, which are evidenced by areas of extensive myofilament breakdown in fibers (28). The EDL, however, is lengthened during plantar flexion, and lengthening has been shown to induce muscle growth (26).
Sarcomere lesion damage in reloaded AL muscles appeared as disturbances in the regular banding pattern of fibers. At the light microscopic level, lesions appeared as pale foci of widened cross-striations, indicating A-band disruption and abnormal widening of sarcomeres (17, 26, 27, 29, 30). When examined ultrastructurally, broken thick filaments were observed in A-band regions, and the Z lines had a streaming appearance (4, 17, 26, 27, 29). Myofibers showing sarcomere lesion damage were more frequent in the caudal "slow-fiber" region of reloaded AL muscles from spaceflown rats, suggesting a damage-susceptible slow-fiber type (26, 27, 29). This finding is in contrast to findings in eccentrically contracted normal muscles, which report damage occurring mainly in fast fibers (9, 10, 19, 20). Our spaceflight results suggest that chronic unloading selectively increases the damage susceptibility of slow fibers. Evidence from the findings of Warren et al. (31) support this hypothesis, whereby the damage susceptibility of the slow-twitch soleus was increased by unloading, whereas that of the predominantly fast-twitch EDL was unchanged. The situation, however, is not so simple, because the slow fibers in soleus and AL muscles are not homogenous in their response to decreased load: unloading induces fast myosin expression in some slow fibers, generating hybrid fibers (1, 3, 16, 25-27). The question becomes, Is there a difference in damage susceptibility between the slow fibers that remain slow vs. those that become hybrid during unloading? Perhaps the increased damage susceptibility of unloaded slow fibers is explained by the population of slow fibers expressing fast myosin, i.e., hybrid fibers. Because myosin thick filaments are the main force-generating components of sarcomeres, heterogeneous myosin isoform expression in fibers could produce inhomogeneities in the distribution of force between adjacent sarcomeres and disrupt structure.
The rat AL muscle is a good model in which to investigate unloading-induced fiber-type damage susceptibility. The AL is an antigravity muscle with fiber-type proportions similar to the soleus, serving in adduction and extension of the femur. During standing, the hindlimbs are adducted by AL activity. The reloading behavior of spaceflown rats showed quadrupedal rats adopting a lowered stance with the hindlimbs splayed out (abducted) and flexed, indicating failure of the weakened AL, and other atrophic weight-bearing muscles to maintain normal posture in terrestrial gravity (27). The posture suggests excessive loading of the atrophic AL, as evidenced by the increased body weight-to-muscle weight ratio and operation of the AL at a longer length on the length-tension curve (27). Unlike the soleus, central core lesions are not found in AL muscle fibers of HU rats, suggesting that HU does not induce chronic shortening of AL muscles. The absence of central core lesions in AL makes it preferable over the soleus for studying reloading-induced damage in myofibers, because the presence of myofibrillar disruptions induced by an excessively shortened working range would be difficult to distinguish from structural damage caused by reloading.
The present study examined whether the incidence of sarcomere lesion damage in reloaded rat AL muscles was similar across slow, fast, and hybrid fibers or was fiber-type selective. To make a valid comparison of damage across fiber types, all fiber types need to be present in sufficient numbers for adequate sampling. Because hybrid fibers are rare in normal rat AL muscles and are mainly generated during unloading, a temporal HU experiment was conducted first to define the duration of HU that generated the maximum proportion of hybrid fibers. HU for this duration, followed by voluntary reloading, was subsequently performed to elicit sarcomere lesions in rat AL muscles and evaluate damage across fiber types.
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METHODS |
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Top
Abstract
Introduction
Methods
Results
Discussion
References
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Hindlimb Unloading and Reloading
Adult male Sprague-Dawley rats were obtained from Harlan Sprague Dawley. Rats to be suspended were acclimated for 1 wk in a designated suspension room with a 12:12-h light-dark cycle, while control rats were housed under similar conditions in the Animal Resource Center at the Medical College of Wisconsin. At the time of suspension, rats weighed 275-300 g and were tail suspended by the method of Riley et al. (28). Food and water were provided ad libitum. For the temporal HU experiment, a total of 10 rats was suspended (2 rats at each of five time points: 5, 8, 11, 14, and 17 days). AL muscles were removed at the end of each suspension period with no reloading permitted. Six control rats were processed on the same day as the 11-day suspended rats. For the HU-reloading experiment, eight rats were suspended for 14 days and let down at the end of suspension to allow voluntary reloading of their hindlimbs for 12-14 h in plastic vivarium cages. After reloading, the AL muscles were removed from the suspended rats and six control rats. All procedures were in compliance with guidelines approved by the Animal Care and Use Committee of the Medical College of Wisconsin.Muscle Biopsy and Processing
Rats were anesthetized by an intraperitoneal injection of 8% chloral hydrate (300 mg/kg), and the AL muscles were excised. The anesthetized animals were euthanized by cardiac extirpation. Right AL muscles were weighed and quick-frozen in Freon-22 before storage under liquid nitrogen. Left AL muscles were pinned out straight on a mild stretch to prevent shortening when they were immersion fixed in 0.1 M sodium cacodylate buffered fixative (pH 7.2), with 1% paraformaldehyde and 0.05% glutaraldehyde, for 2 h on a rotator at room temperature. Muscles were rinsed briefly for 5 s in 0.1 M sodium cacodylate buffer followed by a 30-min rinse in 0.1 M sodium cacodylate buffer containing 50 mM NH4Cl to inhibit further fixation. After a second, brief 5-s rinse in 0.1 M cacodylate buffer, muscles were stored in fresh buffer overnight at 4°C. The muscles were dehydrated in graded ethanols, gradually infiltrated with hard grade LR White resin (Ted Pella), and cut into ~2 × 4-mm pieces. The pieces were placed in aluminum pans containing LR White resin. Polymerization required sealing of the resin surface from air by pressing a second pan within the first pan before placement in a 60°C oven overnight.Histochemistry and Immunohistochemistry
Frozen AL muscles. Muscles were mounted in Tissue Tek (S/P Baxter), and 8-µm cryostat cross sections were cut and picked up on clean slides. Serial sections were reacted for myofibrillar ATPase activity and immunostained with primary antibodies to slow and fast myosin isoforms. The myofibrillar ATPase staining method of Guth and Samaha (13), modified by Riley et al. (28), was used; sections were preincubated at the alkaline and acid pH for fiber-type verification. ATPase sections were mounted in Canada Balsam (Carolina Biological) and coverslipped. Sections to be immunostained were incubated for 20 min in PBS containing 1% BSA and 2% normal goat serum to minimize nonspecific protein binding. After removal of the blocking solution, primary antibodies to slow myosin (monoclonal antibody 16F45, 1:50, provided by K. M. Baldwin) and fast myosin (MY32 M7246, 1:400, Sigma Chemical) were applied. After a 1-h incubation at room temperature, sections were rinsed twice for 10 min each in PBS with 1% BSA followed by two 10-min rinses in PBS without BSA. Fluorescein-conjugated goat anti-rat IgG (41-162, 1:50, Antibodies Inc.) and goat anti-mouse IgG (55514, 1:50, ICN) secondary antibodies were applied to slow and fast myosin antibody-treated sections, respectively. After a 45-min incubation at room temperature, sections were rinsed in PBS containing BSA and then in PBS without BSA as previously described. Immunocontrol sections included untreated "blank" controls to which no antibodies were applied and secondary controls to which only the secondary antibodies were applied. The sections were mounted in Gelmount (Fisher).
Embedded AL muscles.
Rectangular LR White blocks, containing AL muscle pieces, were sawed
out, trimmed, and mounted in chucks. Semithin 0.5-µm sections were
cut with glass knives on an Ultracut E microtome. The sections were cut
obliquely so that a large number of fibers could be examined while
still maintaining the cross-striated banding pattern requisite for
sarcomere lesion detection. Sections were floated on water and
transferred to slides that were placed on an 80°C hot plate for 1 min to allow sections to dry and adhere flat. Adjacent sections were
stained with toluidine blue and with antibodies to total sarcomeric
myosin and fast myosin. For toluidine blue staining, a drop of 0.5%
toluidine blue dye was pipetted onto each section, and the slide was
placed on an 80°C hot plate for 20 s. Excess dye was flushed off
with distilled water. The slide was dried on the hot plate for 20 s.
The sections were then mounted in Permount (Fisher) and coverslipped.
Sections to be immunostained were incubated with blocking solution
containing PBS with 2% normal goat serum for 20 min. BSA was excluded
to facilitate antibody penetration into fixed LR White sections. Primary antibodies to total 
-sarcomeric myosin (IgG M7523, 1:20, Sigma Chemical) and fast myosin (IgG MY32 M7246, 1:300, Sigma Chemical)
were applied to sections. After overnight incubation at 4°C, the
sections were rinsed four times for 10 min each in PBS.
Fluorescein-conjugated goat anti-rabbit IgG (55646, 1:50, ICN) and goat
anti-mouse IgG (55514, 1:50, ICN) secondary antibodies were applied to
total and fast myosin-immunostained sections, respectively. After a
45-min incubation at room temperature, sections were rinsed in PBS as
previously described and mounted in Gelmount. Blank and secondary
controls were processed as described for cryostat cross sections.
Fiber-Type Quantification
Serial AL cross sections immunostained for myosin isoforms were examined under a microscope equipped with epifluorescence. Fiber types were identified on photographic montages of myosin-immunostained sections by comparing slow and fast myosin staining patterns and were verified by comparison to ATPase-stained sections. Fiber-type percents were calculated as the proportions of the total number of fibers in the section. Mean fiber-type percent values representing two rats at each HU time point and six control rats were obtained. All values are reported as the mean ± SD. Serial myosin-immunostained semithin sections from caudal and rostral regions were examined under epifluorescence. Fiber types were identified on photographic montages of immunostained sections by comparing total and fast myosin fiber staining patterns. The proportion of fiber types was calculated as a percentage of the total number of fibers in the section. Mean fiber-type percents were calculated.Analysis of Damage
Acid-preincubated, ATPase-stained cross sections of AL muscles from rats in the temporal HU experiment were screened for central core lesions to ascertain whether these lesions appeared at the time points at which they were present in the soleus (28). Central core lesions appeared in soleus slow fibers as pale patches lacking ATPase activity, indicating extensive myofibrillar breakdown (28). Reloading-induced sarcomere lesions were identified by light microscope in toluidine blue-stained AL semithin sections from 14-day HU-reloaded rats as hyperstretched pale regions in fibers where A bands showed disruption of the thick filament arrangement (17, 26, 27, 29, 30). Sections from both the caudal slow-fiber and rostral "mixed" regions of AL muscles were screened. The proportion of lesioned fibers in both regions was assessed and statistically compared by using Student's t-test and the Mann-Whitney U-test. The fiber type of a lesioned or nonlesioned fiber was determined by comparing toluidine blue-stained sections to photographic montages of serial sections immunostained for total and fast myosin antibodies. Contingency tables with numbers of lesioned vs. nonlesioned fibers for each of the three fiber types were constructed.2 analysis,
testing the independence of lesion frequency and fiber type, was
performed by using a BIOM statistical software package. Mean values of
damaged fibers for each fiber type from HU-reloaded rats displaying
considerable sarcomere lesion injury were calculated.
Determination of Fiber Atrophy
Fiber types in AL were identified in alkaline-preincubated myofibrillar ATPase-stained cross sections from 14-day HU-reloaded and control rats and were verified by comparison to photographs of slow and fast myosin-immunostained serial cross sections. ATPase-stained sections were examined by bright field light microscopy, and video images of sections were obtained by using the frame capture feature of the Bioquant IV digitizing system. For each rat, cross-sectional areas (CSAs) of 30-60 fibers of each type were measured. The mean CSA for each fiber type was calculated and normalized to the body weight. Mean fiber-type CSAs for the six control rats were combined to generate a grand control mean CSA ± SD for each fiber type. The mean fiber-type CSA from each of the 14-day HU-reloaded rats was subtracted from its respective grand control mean fiber-type CSA to obtain the percent decrease in fiber-type CSA. The mean percent decrease in fiber-type CSA for eight HU-reloaded rats was calculated.| |
RESULTS |
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Top
Abstract
Introduction
Methods
Results
Discussion
References
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Serial AL cross sections (Fig. 1) from 11-day HU rats stained with antibodies to slow (Fig. 1A) and fast (Fig. 1B) myosin revealed hybrid fibers. Slow and fast fibers immunostained exclusively for slow and fast myosin, respectively, whereas hybrid fibers showed intense staining for slow myosin and weak staining for fast myosin. Control sections stained with the fluorescence-labeled IgG 2% goat anti-mouse showed only interstitial immunoglobulin staining (Fig. 1C) and no intracellular staining. Similar staining was observed in AL sections treated with the fluorescence-labeled 2% goat anti-rat antibody alone (not shown). This validated the specificity of the primary myosin antibodies for muscle fibers. The percentage of hybrid fibers increased with the duration of HU, reaching a peak of 29 ± 12% after 14 days of HU (Fig. 2). The percentage of hybrid fibers in control AL muscles did not exceed 11%. The percentage of slow fibers decreased from 84 ± 5 in control to 58 ± 8% in 14-day and 17-day HU rats. If some slow fibers had shifted completely to the fast phenotype in terms of myosin expression, an increase in the percentage of fast fibers would be expected in HU rats. Such a change could not be discerned from this study because of the interanimal variability in the percentage of fast fibers occurring in both the control and HU groups.
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No central core lesions were detected in acid-preincubated ATPase sections of control ALs or at any of the HU time points examined, although some HU fibers had a slightly mottled appearance compared with control (not shown). In 14-day HU-reloaded rats, sarcomere lesions appeared as pale patches in toluidine blue-stained AL semithin sections (Fig. 3), indicating A-band disruptions (17, 26, 27, 29, 30). Fiber types of lesioned and nonlesioned fibers were identified in low magnification serial sections immunostained for total and fast myosin (Fig. 4). Slow fibers showed intense cross-striated staining for total myosin (Fig. 4A) and diffuse weak staining for fast myosin (Fig. 4B). Fast fibers showed intense, cross-striated staining for fast myosin (Fig. 4B) and diffuse staining for total myosin (Fig. 4A). Hybrid fibers showed intense staining for total myosin (Fig. 4A) and light staining for fast myosin (Fig. 4B). Semithin sections treated with IgG fluorescent labeled secondary antibodies exhibited very faint, nonspecific background staining of all fibers (not shown), thereby validating the specificity of the primary myosin antibodies. Semithin sections from rostral and caudal regions of AL muscles from four of the eight HU-reloaded rats contained sarcomere lesions. The incidence of sarcomere lesions was similar across both AL regions, with 43 ± 6 and 57 ± 6% occurring in rostral and caudal regions, respectively. The percentage of fibers exhibiting lesion damage did not differ significantly between caudal (20 ± 6%) and rostral (22 ± 11%) regions (P < 0.01). No sarcomere lesion damage was detected in control muscles.
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Table 1 shows the average percentage of
damaged fibers for each fiber type from caudal and rostral AL regions
from the four rats. The percent occurrence of fiber types indicates the
fiber-type composition within a region.
2 statistical analysis showed
lesion frequency and fiber type not to be independent parameters, with
slow fibers being selectively damaged in both regions
(P < 0.05). The proportion
of lesioned fibers that was slow was similar in caudal (94 ± 7%)
and rostral (90 ± 3%) regions. Overall, slow fibers accounted for
92 ± 5% of lesioned fibers, hybrid fibers accounted for 7 ± 4%, and fast fibers accounted for <0.5%.
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Myofiber CSA was compared in cross sections from control (Fig. 5A) and 14-day HU (Fig. 5B) AL muscles stained for myofibrillar ATPase activity with alkaline preincubation to determine the degree of HU-induced atrophy of fiber types. Slow and hybrid fibers in 14-day HU AL muscles showed similar decreases in CSA (13 ± 6 and 15 ± 5%, respectively), compared with controls. Fast fibers atrophied much less (2 ± 3%).
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DISCUSSION |
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Top
Abstract
Introduction
Methods
Results
Discussion
References
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This investigation assessed fiber-type susceptibility to reloading damage in unloaded AL muscles by examining whether the incidence of sarcomere lesion damage differed across fiber types. The first step was to ensure that sufficient numbers of all fiber types were present in unloaded AL muscles so that a valid comparison could be made. Because hybrid fibers are generated during unloading, a temporal HU experiment was performed to maximize hybrid fiber proportion in AL muscles. The percentage of hybrid fibers peaked at 29 ± 12% after 14 days of HU. The increase in hybrid fibers with HU was accompanied by a concomitant decrease in the percentage of slow fibers, indicating that hybrid fibers originated from the slow-fiber population. This finding agrees with the fiber-type changes reported for soleus muscles of rats flown aboard the 14-day COSMOS 2044 mission (24). It was difficult to discern a change in the fast-fiber proportion because of the wide variability of fast-fiber number in AL muscles among animals within a group. Central core lesions induced by chronic shortening and/or unloading were extensive in soleus slow fibers after 1 wk of HU but were not found in AL muscles from HU rats at any of the suspension time points (28). The occurrence of myofibrillar damage in myofibers induced by excessive shortening would complicate the interpretation of structural damage induced by reloading because both types of lesions are studied at the light microscopic level.
A 14-day HU treatment followed by voluntary reloading was performed to induce sarcomere lesion damage in the AL muscles. Rats were reloaded for 12-14 h, at which time sarcomere lesion damage in AL muscles reaches its peak (17). One-half of the HU-reloaded rats in the present study showed no sarcomere lesion damage, whereas the other one-half exhibited severe damage. Interanimal differences in voluntary movement and motor unit recruitment might account for this disparity. Video recording of rat movement and electromyographic analysis of AL activity are necessary to assess the contribution of motor behavior to the degree of sarcomere lesion damage. Of the rats that exhibited sarcomere lesions, the incidence of lesions did not differ significantly between caudal (57 ± 6%) and rostral (43 ± 6%) AL regions. Also, the proportion of lesioned fibers did not vary significantly between caudal (20 ± 6%) and rostral (22 ± 11%) regions. This contrasts with our previous findings from spaceflown rats, which displayed more lesioned fibers in the caudal region (27). Differences in movement and motor recruitment between spaceflown and HU-reloaded rats might account for this disparity.
The present investigation determined that sarcomere lesion damage in HU-reloaded rat AL muscles was fiber-type related, with slow fibers being preferentially damaged. Within the population of lesioned fibers, slow fibers comprised 92 ± 5% of the affected fibers, hybrid fibers accounted for 7 ± 4%, and fast fibers accounted for <0.5%. The percentage of slow fibers exhibiting sarcomere lesion damage was similar in caudal (94 ± 7%) and rostral (90 ± 3%) regions, indicating that the uneven distribution of fiber types across the regions did not bias sarcomere lesion occurrence. Slow and hybrid fibers atrophied by 13 ± 6 and 15 ± 5%, respectively, whereas fast fibers atrophied by only 2 ± 3%. This differential atrophy is congruous with previous findings from our laboratory (26). Similar findings were reported in soleus muscles from rats flown aboard the STS-58 14-day spaceflight mission (1). Slow fibers were the most atrophied in vastus medialis muscles of both 14-day HU rats and rats flown aboard the 14-day COSMOS 2044 mission (22). Our results indicate that the degree of atrophy and the incidence of sarcomere lesions are independent, because slow and hybrid fibers atrophied to a similar extent yet manifested vast differences in lesion occurrence. Atrophy, therefore, did not account for the differential fiber-type occurrence of sarcomere lesion damage in unloaded muscle. However, this does not rule out atrophic changes as contributing factors to myofiber susceptibility to reloading injury. Our study determined that damage in HU-reloaded AL muscles was slow fiber specific, indicating that unloading selectively increased the damage susceptibility of slow fibers. The next step is to investigate why this is the case.
Recent electrophoretic studies have revealed that slow fibers can be
heterogeneous in myosin isoform expression (7, 11). Slow myosin exists
in two different heavy chain (HC) isoforms: one is designated type Ia
HC and the other represents a co-migrating, lower mobility type I
HC
(7, 11). Slow fibers in rabbit plantaris muscles are composed of fibers
expressing only type I HC and those expressing both type I and Ia
HC (11). Fauteck and Kandarian (7) showed that type I HC content
decreased by 20%, whereas type Ia remained constant in soleus slow
fibers from 28-day HU rats (7). The impact of slow HC isoforms on the
damage susceptibility of slow fibers is not known and requires investigation. If there is an impact, is it equal across all slow fibers or does it vary in degree between fibers expressing only type
I HC and those expressing both I and Ia? It must be noted that
changes in content or isoform expression of other thick
filament-associated proteins in slow fibers during unloading, such as
titin, may also influence their damage susceptibility and should be
considered.
Irrespective of any unloading-induced changes in sarcomere-associated proteins, for damage to occur in muscle fibers, active contraction is required (27, 29). Thus the simplest explanation for preferential damage of slow fibers is that of selective recruitment of slow motor units (27, 29). Slow fibers would be active and vulnerable to damage because of their low threshold for recruitment (6, 29), whereas high-threshold fast motor units likely remained quiescent. Unloading appears to structurally and functionally compromise slow fibers in AL muscles, which, when coupled with active recruitment, may account for their increased susceptibility to sarcomere lesion damage during reloading. Experiments are underway to determine whether fiber-type damage susceptibility in unloaded rat AL muscles is recruitment related.
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ACKNOWLEDGEMENTS |
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The authors wish to acknowledge the assistance of Glenn Slocum with the photography. The authors are grateful to Dr. K. M. Baldwin for providing monoclonal antibody 16F45, the antibody to slow myosin. The immunomyosin staining technique for semithin sections was developed by Dr. J. L. Thompson and was supported in part by Biomedical Research Support Grant 92-F001.
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FOOTNOTES |
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Research was funded by National Aeronautics and Space Administration Grant NAG2-956 and National Institutes of Health Grant U01NS-33472 (D. A. Riley).
Address for reprint requests: D. A. Riley, Dept. of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226.
Received 27 October 1997; accepted in final form 12 May 1998.
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REFERENCES |
|---|
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Top
Abstract
Introduction
Methods
Results
Discussion
References
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1.
Allen, D. L.,
W. Yasui,
T. Tanaka,
Y. Ohira,
S. Nagaoka,
C. Sekiguchi,
W. E. Hinds,
R. R. Roy,
and
V. R. Edgerton.
Myonuclear number and myosin heavy chain expression in rat soleus single muscle fibers after spaceflight.
J. Appl. Physiol.
81:
145-151,
1996
2.
Armstrong, R. B.,
R. W. Ogilvie,
and
J. A. Schwane.
Eccentric exercise-induced injury to rat skeletal muscle.
J. Appl. Physiol.
54:
80-93,
1983
3.
Caiozzo, V. J.,
F. Haddad,
M. J. Baker,
R. E. Herrick,
N. Prietto,
and
K. M. Baldwin.
Microgravity-induced transformations of myosin isoforms and contractile properties of skeletal muscle.
J. Appl. Physiol.
81:
123-132,
1996
4.
D'Amelio, F.,
and
N. G. Daunton.
Effects of spaceflight in the adductor longus muscle of rats flown in the Soviet biosatellite COSMOS 2044. A study employing neural cell adhesion molecule (N-CAM) immunocytochemistry and conventional morphological techniques (light and electron microscopy).
J. Neuropathol. Exp. Neurol.
51:
415-431,
1992[Medline].
5.
Diffee, G. M.,
V. J. Caiozzo,
R. E. Herrick,
and
K. M. Baldwin.
Contractile and biochemical properties of rat soleus and plantaris after hindlimb suspension.
Am. J. Physiol.
260 (Cell Physiol. 29):
C528-C534,
1991
6.
Edgerton, V. R.,
and
R. R. Roy.
Neuromuscular adaptation to actual and simulated weightlessness.
Adv. Space Biol. Med.
4:
33-67,
1994[Medline].
7.
Fauteck, S. P.,
and
S. C. Kandarian.
Sensitive detection of myosin heavy chain composition in skeletal muscle under different loading conditions.
Am. J. Physiol.
268 (Cell Physiol. 37):
C419-C424,
1995
8.
Fridèn, J.,
and
R. L. Lieber.
Structural basis of muscle cellular damage.
BAM
4:
35-42,
1994.
9.
Fridèn, J.,
J. Seger,
M. Sjöström,
and
B. Ekblom.
Adaptive response in human skeletal muscle subjected to prolonged eccentric training.
Int. J. Sports Med.
4:
177-183,
1983[Medline].
10.
Fridèn, J.,
M. Sjöström,
and
B. Ekblom.
Myofibrillar damage following intense eccentric exercise in man.
Int. J. Sports Med.
4:
170-176,
1983[Medline].
11.
Galler, S.,
K. Hilber,
B. Gohlsch,
and
D. Pette.
Two functionally distinct myosin heavy chain isoforms in slow skeletal muscle fibers.
FEBS Lett.
410:
150-152,
1997[Medline].
12.
Gibbala, M. J.,
J. D. MacDougall,
M. A. Tarnopolsky,
W. T. Stauber,
and
A. Ellorriaga.
Changes in human skeletal muscle ultrastructure and force production after acute resistance exercise.
J. Appl. Physiol.
78:
702-708,
1995
13.
Guth, L.,
and
F. J. Samaha.
Procedure for the histochemical demonstration of actomyosin ATPase.
Exp. Neurol.
28:
365-367,
1970[Medline].
14.
Hargens, A. R.,
S. Parazynski,
M. Aratow,
and
J. Fridèn.
Muscle changes with eccentric exercise: implications on Earth and in space.
In: Advances in Myochemistry (2nd ed.), edited by G. Benzi. Nice, France: J. Libbey Eurotext, 1989, p. 299-312.
15.
Jaspers, S. R.,
J. M. Fagan,
S. Satarug,
P. H. Cook,
and
M. E. Tischler.
Effects of immobilization on rat hindlimb muscles under non-weightbearing conditions.
Muscle Nerve
11:
458-466,
1988[Medline].
16.
Krippendorf, B. B.,
and
D. A. Riley.
Distinguishing unloading- versus reloading-induced changes in rat soleus muscle.
Muscle Nerve
16:
99-108,
1993[Medline].
17.
Krippendorf, B. B.,
and
D. A. Riley.
Temporal changes in sarcomere lesions of rat adductor longus muscles during hindlimb unloading.
Anat. Rec.
238:
304-310,
1994[Medline].
18.
Lieber, R. L.
Skeletal Muscle Structure and Function. Baltimore, MD: Williams & Wilkins, 1995, chapt. 3, p. 145-149.
19.
Lieber, R. L.,
and
J. Fridèn.
Selective damage of fast glycolytic muscle fibers with eccentric contraction of the rabbit tibialis anterior.
Acta Physiol. Scand.
133:
587-588,
1988[Medline].
20.
Macpherson, P. C. D.,
M. A. Schork,
and
J. A. Faulkner.
Contraction-induced injury to single fiber segments from fast and slow muscles of rats by single stretches.
Am. J. Physiol.
271 (Cell Physiol. 40):
C1438-C1446,
1996
21.
McCully, K. K.,
and
J. A. Faulkner.
Characteristics of lengthening contractions associated with injury to skeletal muscle fibers.
J. Appl. Physiol.
61:
293-299,
1986
22.
Musacchia, X. J., J. M. Steffen, R. D. Fell, M. J. Dombrowski, V. W. Oganov, and E. Ilyina-Kakueva. Skeletal muscle atrophy in response to 14 days of
weightlessness: vastus medialis. J. Appl.
Physiol. 73, Suppl.:
44S-50S, 1992.
23.
Ogilvie, R. W.,
R. B. Armstrong,
K. E. Baird,
and
C. L. Bottoms.
Lesions in rat soleus muscle following eccentrically biased exercise.
Am. J. Anat.
182:
335-346,
1988[Medline].
24.
Ohira, Y., B. Jiang, R. Roy, V. Oganov, E. Ilyina-Kakueva,
J. F. Marini, and V. R. Edgerton. Rat soleus
muscle fiber responses to 14 days of spaceflight and hindlimb
suspension. J. Appl. Physiol. 73, Suppl.: 51S-57S, 1992.
25.
Oishi, Y.,
H. Yamamoto,
and
E. Miyamoto.
Changes in fibre-type composition and myosin heavy-chain IId isoform in rat soleus muscle during recovery period after hindlimb suspension.
Eur. J. Appl. Physiol.
68:
102-106,
1994.
26.
Riley, D. A., S. Ellis, C. S. Giometti,
J. F. Y. Hoh, E. I. Ilyina-Kakueva, V. S. Oganov, G. R. Slocum, J. L. W. Bain, and F. R. Sedlak. Muscle sarcomeric lesions and thrombosis after
spaceflight and suspension unloading. J. Appl.
Physiol. 73, Suppl.:
33S-43S, 1992.
27.
Riley, D. A.,
S. Ellis,
G. R. Slocum,
F. R. Sedlak,
J. L. W. Bain,
B. B. Krippendorf,
C. T. Lehman,
M. Y. Macias,
J. L. Thompson,
K. Vijayan,
and
J. A. Debruin.
Inflight and postflight changes in skeletal muscles of SLS-1 and SLS-2 spaceflown rats.
J. Appl. Physiol.
81:
133-144,
1996
28.
Riley, D. A.,
G. R. Slocum,
J. L. W. Bain,
F. R. Sedlak,
T. E. Sowa,
and
J. W. Mellender.
Rat hindlimb unloading: soleus histochemistry, ultrastructure, and electromyography.
J. Appl. Physiol.
69:
58-66,
1990
29.
Riley, D. A.,
J. L. Thompson,
B. B. Krippendorf,
and
G. R. Slocum.
Review of spaceflight and hindlimb suspension unloading induced sarcomere damage and repair.
BAM
5:
139-145,
1995.
30.
Thompson, J. L., E. Balog, R. H. Fitts, and
D. A. Riley. Five myofibrillar lesion types in
eccentrically challenged unloaded rat adductor longus muscle.
Anat. Rec. In press.
31.
Warren, G. L.,
D. A. Hayes,
D. A. Lowe,
J. H. Williams,
and
R. B. Armstrong.
Eccentric contraction-induced injury in normal and hindlimb-suspended mouse soleus and EDL muscles.
J. Appl. Physiol.
77:
1421-1430,
1994
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