scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Inferior mechanical properties of spastic muscle bundles due to hypertrophic but compromised extracellular matrix material.

TL;DR: The passive mechanical properties of small muscle fiber bundles obtained from surgical patients with spasticity and patients without neuromuscular disorders were measured to determine the relative influence of intracellular and extracellular components.
Abstract: The passive mechanical properties of small muscle fiber bundles obtained from surgical patients with spasticity (n = 9) and patients without neuromuscular disorders (n = 21) were measured in order to determine the relative influence of intracellular and extracellular components. For both types of patient, tangent modulus was significantly greater in bundles compared to identical tests performed on isolated single cells (P < 0.05). However, the relative difference between bundles and single cells was much greater in normal tissue than spastic tissue. The tangent modulus of normal bundles (462.5 +/- 99.6 MPa) was 16 times greater than normal single cells (28.2 +/- 3.3 MPa), whereas the tangent modulus of spastic bundles (111.2 +/- 35.5 MPa) was only twice that of spastic muscle cells (55.0 +/- 6.6 MPa). This relatively small influence of the extracellular matrix (ECM) in spastic muscle was even more surprising because spastic muscle cells occupied a significantly smaller fraction of the total specimen area (38.5 +/- 13.6%) compared to normal muscle (95.0 +/- 8.8%). Based on these data, normal muscle ECM is calculated to have a modulus of 8.7 GPa, and the ECM from spastic muscle of only 0.20 GPa. These data indicate that spastic muscle, although composed of cells that are stiffer compared to normal muscle, contains an ECM of inferior mechanical strength. The present findings illustrate some of the profound changes that occur in skeletal muscle secondary to spasticity. The surgical implications of these results are discussed.
Citations
More filters
Journal ArticleDOI
TL;DR: The structure, composition, and mechanical properties of skeletal muscle ECM are reviewed; the cells that contribute to the maintenance of the ECMAreas for future study are proposed; and overview changes that occur with pathology are described.
Abstract: The skeletal muscle extracellular matrix (ECM) plays an important role in muscle fiber force transmission, maintenance, and repair. In both injured and diseased states, ECM adapts dramatically, a property thathas clinical manifestations and alters muscle function. Here, we review the structure, composition, and mechanical properties of skeletal muscle ECM, describe the cells that contribute to the maintenance of the ECM and, finally, overview changes that occur with pathology. New scanning electron micrographs of ECM structure are also presented with hypotheses about ECM structure-function relationships. Detailed structure-function relationships of the ECM have yet to be defined and, as a result, we propose areas for future studies.

737 citations


Cites background from "Inferior mechanical properties of s..."

  • ...modulus of spastic muscle bundles is significantly lower than in normal bundles.(78) It is tempting to speculate that the reduced spastic bundle modulus...

    [...]

  • ...bral palsy is characterized by increased extracellular material(119) and stiffer fibers.(78,120) Interestingly, the modulus of spastic muscle fibers is about two-...

    [...]

Journal ArticleDOI
TL;DR: A 66-year-old man was suddenly unable to speak, follow directions, or move his right arm and leg within 90 minutes and his speech was limited to effortful answers of yes or no.
Abstract: A 66-year-old man was suddenly unable to speak, follow directions, or move his right arm and leg. He received tissue plasminogen activator within 90 minutes. Four days later, his speech was limited to effortful answers of yes or no. He could not walk or use his right arm, and self-care tasks required maximal assistance. What advice would you offer him and his family regarding rehabilitation for his disabilities?

731 citations

Journal ArticleDOI
TL;DR: Clinicians should encourage patients to build greater strength, speed, endurance, and precision of multijoint movements on tasks that increase independence and enrich daily activity to augment rehabilitation in the next decade.
Abstract: Summary Rehabilitation after hemiplegic stroke has typically relied on the training of patients in compensatory strategies. The translation of neuroscientific research into care has led to new approaches and renewed promise for better outcomes. Improved motor control can progress with task-specific training incorporating increased use of proximal and distal movements during intensive practice of real-world activities. Functional gains are incorrectly said to plateau by 3–6 months. Many patients retain latent sensorimotor function that can be realised any time after stroke with a pulse of goal-directed therapy. The amount of practice probably best determines gains for a given level of residual movement ability. Clinicians should encourage patients to build greater strength, speed, endurance, and precision of multijoint movements on tasks that increase independence and enrich daily activity. Imaging tools may help clinicians determine the capacity of residual networks to respond to a therapeutic approach and help establish optimal doseresponse curves for training. Promising adjunct approaches include practice with robotic devices or in a virtual environment, electrical stimulation to increase cortical excitability during training, and drugs to optimise molecular mechanisms for learning. Biological strategies for neural repair may augment rehabilitation in the next decade.

642 citations

Journal ArticleDOI
TL;DR: A three-dimensional finite-element model of the biceps brachii was created and it was revealed that the variation in fascicle lengths within the muscle and the curvature of the fascicles were the primary factors contributing to nonuniform strains.

405 citations

Journal ArticleDOI
TL;DR: The literature supports the notion that, although spasticity is multifactorial and neural in origin, significant structural alterations in muscle also occur and an understanding of the specific changes that occur in the muscle and extracellular matrix may facilitate the development of new conservative or surgical therapies for this problem.
Abstract: This review summarizes current information regarding the changes in structure or function that occur in skeletal muscle secondary to spasticity. Most published studies have reported an increase in fiber size variability in spastic muscle. There is no general agreement regarding any shift in fiber type distribution secondary to spasticity. Mechanical studies in whole limbs as well as in isolated single cells support the notion of an intrinsic change in the passive mechanical properties of muscle after spasticity in addition to the more widely reported neural changes that occur. Evidence is presented for changes within both the muscle cell and extracellular matrix that contribute to the overall changes in the tissue. Taken together, the literature supports the notion that, although spasticity is multifactorial and neural in origin, significant structural alterations in muscle also occur. An understanding of the specific changes that occur in the muscle and extracellular matrix may facilitate the development of new conservative or surgical therapies for this problem.

357 citations

References
More filters
Book
01 Jul 1981
TL;DR: This chapter discusses the mechanics of Erythrocytes, Leukocytes, and Other Cells, and their role in Bone and Cartilage, and the properties of Bioviscoelastic Fluids, which are a by-product of these cells.
Abstract: Prefaces. 1. Introduction: A sketch of the History and Scope of the Field. 2. The Meaning of the Constitutive Equation. 3. The Flow Properties of Blood. 4. Mechanics of Erythrocytes, Leukocytes, and Other Cells. 5. Interaction of Red Blood Cells with Vessel Wall, and Wall Shear with Endothelium. 6 Bioviscoelastic Fluids. Bioviscoelastic Solids. 8. Mechanical Properties and Active Remodeling of Blood Vessels. 9. Skeletal Muscle. 10. Heart Muscle. 11. Smooth Muscles. 12. Bone and Cartilage. Indices

6,027 citations

Journal ArticleDOI
13 Oct 1995-Science
TL;DR: The architecture of sequences in the A band region of titin suggests why thick filament structure is conserved among vertebrates and compares two elements that correlate with tissue stiffness that suggest that titin may act as two springs in series.
Abstract: In addition to thick and thin filaments, vertebrate striated muscle contains a third filament system formed by the giant protein titin. Single titin molecules extend from Z discs to M lines and are longer than 1 micrometer. The titin filament contributes to muscle assembly and resting tension, but more details are not known because of the large size of the protein. The complete complementary DNA sequence of human cardiac titin was determined. The 82-kilobase complementary DNA predicts a 3-megadalton protein composed of 244 copies of immunoglobulin and fibronectin type III (FN3) domains. The architecture of sequences in the A band region of titin suggests why thick filament structure is conserved among vertebrates. In the I band region, comparison of titin sequences from muscles of different passive tension identifies two elements that correlate with tissue stiffness. This suggests that titin may act as two springs in series. The differential expression of the springs provides a molecular explanation for the diversity of sarcomere length and resting tension in vertebrate striated muscles.

1,154 citations

Journal ArticleDOI
TL;DR: The maximum stresses to which a wide range of mammalian limb tendons could be subjected in life were estimated by considering the relative cross‐sectional areas of each tendon and of the fibres of its muscle, and a new theory explains the thickness of the majority of tendons.
Abstract: The maximum stresses to which a wide range of mammalian limb tendons could be subjected in life were estimated by considering the relative cross‐sectional areas of each tendon and of the fibres of its muscle. These cross‐sectional areas were derived from mass and length measurements on tendons and muscles assuming published values for the respective densities. The majority of the stresses are low. The distribution has a broad peak with maximum frequency at a stress of about 13 MPa, whereas the fracture stress for tendon in tension is about 100 MPa. Thus, the majority of tendons are far thicker than is necessary for adequate strength. Much higher stresses are found among those tendons which act as springs to store energy during locomotion. The acceptability of low safety factors in these tendons has been explained previously (Alexander, 1981). A new theory explains the thickness of the majority of tendons. The muscle with its tendon is considered as a combined system which delivers mechanical energy: the thickness of the tendon is optimized by minimizing the combined mass. A thinner tendon would stretch more. To take up this stretch, the muscle would require longer muscle fibres, which would increase the combined mass. The predicted maximum stress in a tendon of optimum thickness is about 10 MPa, which is within the main peak of the observed stress distribution. Individual variations from this value are to be expected and can be understood in terms of the functions of the various muscles.

364 citations

Journal ArticleDOI
TL;DR: The fact that muscle cells from patients with spasticity have a shorter resting sarcomere length and increased modulus compared with normal muscle cells suggests dramatic remodeling of intracellular or extracellular muscle structural components such as titin and collagen.
Abstract: The mechanical properties of isolated single muscle fiber segments were measured in muscle cells obtained from patients undergoing surgery for correction of flexion contractures secondary to static perinatal encephalopathy (cerebral palsy). “Normal” muscle cells from patients with intact neuromuscular function were also mechanically tested. Fiber segments taken from subjects with spasticity developed passive tension at significantly shorter sarcomere lengths (1.84 ± 0.05 μm, n = 15) than fibers taken from normal subjects (2.20 ± 0.04 μm, n = 35). Elastic modulus of the stress–strain relationship in fibers from patients with spasticity (55.00 ± 6.61 kPa) was almost double that measured in normal fibers (28.25 ± 3.31 kPa). The fact that these muscle cells from patients with spasticity have a shorter resting sarcomere length and increased modulus compared with normal muscle cells suggests dramatic remodeling of intracellular or extracellular muscle structural components such as titin and collagen. Such changes in muscles of patients with spasticity may have implications for therapy. Muscle Nerve, 27: 157–164 ,2003

338 citations

Journal ArticleDOI
TL;DR: The expectations and variances of coefficients of variation under the assumption of normality are reviewed and the effects of appreciable departures from this assumption are examined.
Abstract: Sokal, R. R., and C. A. Braumann (Department of Ecology and Evolution, State University of New York at Stony Brook, Stony Brook, New York 11794) 1980. Significance tests for coefficients of variation and variability profiles. Syst. Zool. 29:50-66.-The distribution of sample estimates of the coefficient of variation is studied analytically and by Monte Carlo simulation. Derivations are given for the expected value of a coefficient of variation and for its standard error. Various proposed standard errors for coefficients of variation are evaluated. Standard errors are derived for differences between coefficients of variation for samples of independent and correlated characters. Methods are proposed for testing the homogeneity of sets of independent and correlated coefficients of variation. Tests of homogeneity of variability profiles as well as for parallelism of such profiles are furnished. [Coefficients of variation, variability profiles.] The employment of coefficients of variation in systematic research is of long standing. Various evolutionary hypotheses require for their examination the establishment of differences in the amounts by which characters vary in populations. Such differences can be examined for the same character across several populations of the same species or of different species, or the comparison may be within the same population but among different characters. Such comparisons of the amounts of variation are generally adjusted for differences in magnitude of the character means, hence the employment of the coefficient of variation, V. A recent renewal of interest in the coefficient of variation is due to two developments. Various studies, collectively called population phenetics, have probed the effects of evolutionary processes on variability patterns in animal and plant populations and have tried to establish the converse-the drawing of inferences about evolutionary processes from observed variability patterns. Studies such as those of Soule (1967), Soule and Stewart (1970), Rothstein (1973), Lande (1977), or Sokal (1976) come to mind readily. A second reason for an increased interest in coefficients of variation is the stimulating book by Yablokov (1974) introducing the study of variability profiles in mammalian populations. Variability profiles are graphs in which the amount of variation expressed as a variance or coefficient of variation is plotted against a horizontal axis representing the suite of characters under study. Examination of variability profiles within and among populations leads to inferences about the amount of developmental (and ultimately evolutionary) control of variability for different characters in the same population and among populations. There is a need for appropriate methods to examine the types of comparisons being considered. In this paper we shall briefly review the expectations and variances of coefficients of variation under the assumption of normality and examine the effects of appreciable departures from this assumption. We shall then turn to the comparison of two or more coefficients of variation for the same character from different populations. This account will be followed by a discussion of tests applicable to a single variability profile, which in turn will lead to the comparison of several profiles. These can be considered for the same hierarchic level, as in local population samples of the same species, or the comparison may be between different hierarchic levels representing natural sampling units, such as variability within local populations versus variability across populations. Analytical work on the expectations

315 citations