| 61. |
- Lieber, R. L., et al.
(författare)
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Inferior mechanical properties of spastic muscle bundles due to hypertrophic but compromised extracellular matrix material
- 2003
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Ingår i: Muscle Nerve. - 0148-639X. ; 28:4, s. 464-71
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Tidskriftsartikel (refereegranskat)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.
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| 62. |
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| 63. |
- Löscher, Wolfgang N, et al.
(författare)
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Central fatigue and motor cortical excitability during repeated shortening and lengthening actions.
- 2002
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 25:6, s. 864-72
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Tidskriftsartikel (refereegranskat)abstract
- A decline in voluntary muscle activation and adaptations in motor cortical excitability contribute to the progressive decline in voluntary force during sustained isometric contractions. However, the neuronal control of muscle activation differs between isometric and dynamic contractions. This study was designed to investigate voluntary activation, motor cortex excitability, and intracortical inhibition during fatiguing concentric and eccentric actions. Eight subjects performed 143 torque motor-controlled, repeated shortening and lengthening actions of the elbow flexor muscles. Transcranial magnetic stimulation (TMS) was applied three times every 20 cycles. Magnetic evoked motor potentials (MEP), duration of the silent period (SP), and the torque increase due to TMS were analyzed. TMS resulted in a small torque increase in unfatigued actions. With repeated actions, voluntary torque dropped rapidly and the amplitude of the TMS-induced twitches increased, especially during repeated lengthening actions. MEP area of biceps brachii and brachioradialis muscles increased during repeated actions to a similar extent during lengthening and shortening fatigue. The duration of biceps and brachioradialis SP did not change with fatigue. Thus, voluntary activation became suboptimal during fatiguing dynamic actions and motor cortex excitability increased without any changes in intracortical inhibition. The apparent dissociation of voluntary activation and motor cortex excitability suggests that the central fatigue observed, especially during lengthening actions, did not result from changes in motor cortex excitability.
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| 64. |
- Mackey, A. L., et al.
(författare)
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Assessment of satellite cell number and activity status in human skeletal muscle biopsies
- 2009
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Ingår i: Muscle and Nerve. - : John Wiley & Sons. - 0148-639X .- 1097-4598. ; 40:3, s. 455-465
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Tidskriftsartikel (refereegranskat)abstract
- The primary aim of our study was to validate the assessment of myonuclear and satellite cell number in biopsies from human skeletal muscle. We found that 25 type I and 25 type II fibers are sufficient to estimate the mean number of myonuclei per fiber. In contrast, the assessment of satellite cells improved when more fibers were included. Second, we report that small differences in counting satellite cells using CD56 and Pax7 antibodies can be attributed to the different staining profiles. Third, we provide support for the use of Ki67 in evaluating the proportion of active satellite cells. We observed very few (up to 1.3%) active satellite cells in healthy adult skeletal muscle at rest, but they increased significantly (up to 7-fold) following muscle activity. This study provides valuable tools to assess the behavior of satellite cells, both in pathological conditions and in response to physiological stimuli.
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| 65. |
- Marrero, Humberto Gonzalez, et al.
(författare)
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Optimizing testing methods and collection of reference data for differentiating critical illness polyneuropathy from critical illness myopathy.
- 2016
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 53:4, s. 555-563
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: In severe acute quadriplegic myopathy in intensive care unit (ICU) patients, muscle fibers are electrically inexcitable; in critical illness polyneuropathy the excitability remains normal. Conventional electrodiagnostic methods do not provide the means to adequately differentiate between them.OBJECTIVE: To further optimize methodology for the study of critically ill ICU patients and to create a reference database in healthy controls.METHODS: Different electrophysiologic protocols were tested to find sufficiently robust and reproducible techniques for clinical diagnostic applications.RESULTS: Many parameters show large test-retest variability within the same healthy subject. Reference values have been collected and described as a basis for studies of weakness in critical illness.DISCUSSION: Using the ratio of neCMAP/dmCMAP (response from nerve and direct muscle stimulation), refractory period, and stimulus-response curves may optimize the electrodiagnostic differentiation of patients with critical illness myopathy from those with critical illness polyneuropathy.
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| 66. |
- Martinez-Aparicio, Carmen, et al.
(författare)
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Nerve conduction study of the three supraclavicular nerve branches
- 2018
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 58:2, s. 300-303
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: We describe a new nerve conduction study technique with reference values for the 3 branches of the supraclavicular nerve (SCN) in young healthy subjects and application of it in 2 patients.Methods: The recording electrode was placed on the posterior border of the sternocleidomastoid muscle, 6–7 cm from the sternoclavicular joint. SCN branches were stimulated below the clavicle, 2.5, 7, and 10.5 cm lateral to the sternoclavicular joint.Results: Twenty healthy volunteers (10 men), 19–38 years, mean 25.9 years (SD 6.3), and 2 patients with SCN lesions were studied. The mean conduction velocities of the SCN branches were 70–78 m/s (SD 8–10 m/s), and amplitudes 3–4 µV (SD 0.9–2.0 µV). There were no side‐to‐side or gender differences.Discussion: The 3 SCN branches could be studied in all subjects. We provide reference values for young subjects. This new method was useful in verifying SCN lesions in 2 patients.
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| 67. |
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| 68. |
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| 69. |
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| 70. |
- Melberg, Atle, et al.
(författare)
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Anticipation of autosomal dominant progressive external ophthalmoplegia with hypogonadism
- 1996
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Ingår i: Muscle and Nerve. - 0148-639X .- 1097-4598. ; 19:12, s. 1561-9
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Tidskriftsartikel (refereegranskat)abstract
- A large Swedish family with members affected by progressive external ophthalmoplegia with hypogonadism were followed-up and reviewed. Hypogonadism included delayed sexual maturation, primary amenorrhea, early menopause, and testicular atrophy. Cataracts, cerebellar ataxia, neuropathy, hypoacusia, pes cavus, tremor, parkinsonism, depression, and mental retardation were other features observed in this family. Muscle biopsy samples of advanced cases showed ragged-red fibers, focal cytochrome c oxidase deficiency, and multiple mtDNA deletions by Southern blot analysis. An autosomal dominant mode of inheritance was evident with anticipation in successive generations. Linkage analysis excluded the chromosome 10q23.3-q24.3 region reported as being linked to the disease in a Finnish family with autosomal dominant progressive external ophthalmoplegia. We report for the first time clinical evidence for anticipation in a family with autosomal dominant progressive external ophthalmoplegia. We hypothesize that the nuclear gene causing this enigmatic disorder may be directly influenced by an expansion of an unstable DNA sequence and that the resulting phenotype is caused by a concerted action with multiple deletions of mtDNA.
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