Production of consistent crush lesions in murine quadriceps muscle--a biomechanical, histomorphological and immunohistochemical study.

Poor healing of high-energy fractures is often associated with severe muscle damage. This may be partly due to the production, by the injured muscle, of inflammatory cytokines that somehow misdirect bone healing. In order to investigate this question, an animal model was established which embodies a controlled degree of muscle injury with a dose response to the energy absorbed, that can be characterised histologically. Using a custom crush jig, 60 CFLP mice had either 100 or 200 g masses dropped from a fixed height onto the quadriceps muscle, with mechanical measurement of the impact. Energy of impact was reliably and significantly different between the small and large impact conditions, though there was more variability when the large mass was used. Animals were sacrificed at day 2, 4, 8, 16, and 24 post-injury. Muscle histomorphometry at all time points and immunohistochemistry for IL-1beta, IL-6, and TNF-alpha up to day 8 were used as measures of muscle damage, inflammation and repair. Histological sections were analysed into areas of normal muscle fibres, damaged/regenerating muscle fibres and fibrous/inflammatory infiltrate. Early histological response was similar between the two groups; the large crush group displayed significantly greater areas of inflammatory infiltrate and damaged muscle at the later time points after day 8. In the large crush group, IL-1beta and IL-6 expression were significantly higher at day 2 and TNF-alpha was higher at day 8 when compared to the small crush group. The experiment demonstrated that more severe injury to muscle was reliably followed by increased inflammatory cytokine production and a greater degree of inflammation and fibrosis. Increased production of inflammatory cytokines such as TNF-alpha and IL-1beta in the damaged muscles may activate macrophages and recruit fibroblasts, promote scar formation and lead to delayed union or non-union of the adjacent fracture(s).     

Bone architecture and disc degeneration in the lumbar spine of mice lacking GDF-8 (myostatin).

GDF-8, also known as myostatin, is a member of the transforming growth factor-beta superfamily of secreted growth and differentiation factors that is expressed in vertebrate skeletal muscle. Myostatin functions as a negative regulator of skeletal muscle growth and myostatin null mice show a doubling of muscle mass compared to normal mice. We describe here morphology of the lumbar spine in myostatin knockout (Mstn(-/-)) mice using histological and densitometric techniques. The Mstn(-/-) mice examined in this study weigh approximately 10% more than controls (p<0.001) but the iliopsoas muscle is over 50% larger in the knockout mice than in wild-type mice (p<0.001). Peripheral quantitative computed tomography (pQCT) data from the fifth lumbar vertebra show that mice lacking myostatin have approximately 50% greater trabecular bone mineral density (p=0.001) and significantly greater cortical bone mineral content than normal mice. Toluidine blue staining of the intervertebral disc between L4-L5 reveals loss of proteoglycan staining in the hyaline end plates and inner annulus fibrosus of the knockout mice. Loss of cartilage staining in the caudal end plate of L4 is due to ossification of the end plate in the myostatin-deficient animals. Results from this study suggest that increased muscle mass in mice lacking myostatin is associated with increased bone mass as well as degenerative changes in the intervertebral disc.     

芳香族氨基酸脱羧酶转基因骨骼肌细胞脑内移植后对纹状体区多巴胺含量的影响

目的探讨帕金森病(PD)大鼠模型脑内移植人类神经元性芳香族氨基酸脱羧酶(AADC)基因对PD的治疗作用及其在左旋多巴(L-dopa)治疗过程中的地位,并检测脑内多巴胺含量的变化.方法将pCDNA3-AADC转染的原代培养的骨骼肌细胞,移植于SD大鼠PD模型毁损侧纹状体,并在此基础上予以外源性 L-dopa 10 mg·kg-1·d-1腹腔内注射,分别观察基因治疗前后以及结合给予外源性L-dopa前后各组动物病理性旋转行为的改善,并行高效液相电化学法检测脑内多巴胺(DA)含量.结果 AADC转基因骨骼肌细胞脑内移植后,实验组PD模型大鼠旋转行为较前明显改善,并可持续15周以上,尤以第11周时最为明显,约为64.6%(P<0.05),结合外源性L-dopa治疗后动物模型的旋转行为有更进一步的改善,达到86.5%;脑内DA含量测定证实,PD模型鼠脑内AADC水平较健康鼠明显降低,仅(2 119.0±47.2) ng/mg,约为健康鼠的31.0%;在补充了AADC后,脑内纹状体区DA含量则显著提高,达到(3 907.5±56.3) ng/mg;结合补充外源性L-dopa后,脑内DA的水平得到进一步提高达(5 443.0±78.7) ng/mg.结论脑内植入AADC转基因骨骼肌细胞,增加了脑内AADC基因的表达,可有效改善帕金森病大鼠的旋转行为,并可通过增加对L-dopa的脱羧作用而提高其治疗效果,有助于在低剂量上长期维持L-dopa的疗效,减轻L-dopa治疗中的不良反应.     

用纤颤电位波幅衡量失神经肌肉萎缩程度的临床研究

目的研究失神经支配肱二头肌纤颤电位波幅的变化规律，并探索其与肌肉萎缩程度的关系。方法１９９５年８月～１９９６年１２月，检测１７３块因臂丛神经损伤致完全失神经支配的肱二头肌纤颤电位并计算其波幅；６３例在检测同一部位取肌组织送病理检查。被检肌肉行ＡＴＰ酶染色，测定Ｉ、Ｉ型肌纤维面积。结果纤颤电位的波幅和肌纤维的横断面积与失神经时间呈负相关；失神经后第５、６个月及１年以后为纤颤电位波幅的显著下降期；失神经后第４个月为肌纤维的显著萎缩期。纤颤电位的波幅与肌纤维的横截面积呈正相关；男性纤颤电位的波幅及ＩＩ型肌纤维面积均较女性为高（Ｐ＜０．０５）。结论纤颤电位波幅与肌纤维萎缩状态相一致，可作为评估肌肉萎缩程度的定量指标     

Effects of systemic and regional taurine on skeletal muscle function following ischaemia-reperfusion injury.

INTRODUCTION: Tissues subjected to prolonged ischaemia are paradoxically further damaged when their perfusion is restored. The mechanisms underlying this ischaemia-reperfusion injury are complex, but oxidative attack is a central feature. Among the therapeutic agents used to attenuate ischaemia-reperfusion injury, endogenous agents such as taurine which form part of the native defence mechanism against oxidative damage are of particular interest. METHODS: Using a model of hindlimb ischaemia-reperfusion injury in the rat, taurine solution was administered either into the operated hindlimb, into the systemic circulation, or both. Contraction strengths of gastrocnemius biopsies from the operated and contralateral (control) hindlimbs of each animal were measured. RESULTS: Fast twitch strength was impaired significantly by ischaemia-reperfusion injury, and taurine injected into the operated limb conferred partial protection. A similar trend was observed for tetany, but protection by taurine was not statistically significant for tetanic contraction strength. CONCLUSION: Preservation of fast twitch strength following ischaemia-reperfusion injury by administration of taurine before ischaemia has clinical potential. However, delivery to the affected tissues during ischaemia presents technical difficulties.     

Age-related quadriceps-dominant muscle atrophy and incident radiographic knee osteoarthritis

Muscle atrophy is common in the elderly. However, the etiologic role of muscle atrophy associated with osteoarthritis of the knee has not been studied in detail. We assessed the association between age-related muscle atrophy around the knee joint and incident radiographic osteoarthritis of the knee. Twenty-one women in their thirties and 17 women in their sixties participated. They had no history, symptoms, or objective findings of any knee problems, and none of the participants was limited in performing daily activities. Radiographs of the knee joint were graded for the presence of osteoarthritis, and the cross-sectional imaging around the knee joint was carried out using computed tomography. Incident radiographic osteoarthritis was observed in 6 of the 17 women in their sixties. Quadriceps-dominant muscle atrophy was marked in the elderly women with radiographic osteoarthritis. In a multivariate analysis, the risk of incident radiographic osteoarthritis of the knee was significantly increased among women with a higher hamstrings/quadriceps cross-sectional area ratio. The results suggest the possibility that age-related quadriceps-dominant muscle atrophy may play a role in the pathogenesis of osteoarthritis of the knee.     

Early-onset facioscapulohumeral muscular dystrophy: two case reports

This report concerns two patients with facioscapulohumeral muscular dystrophy (FSHD) whose facial weakness began in infancy. In both patients, biopsied muscle histology showed mild myogenic changes accompanied by some regenerating and some small angular fibers, while endomysial inflammatory cellular infiltration was observed in Patient 1. The finding that our very young patients had muscle histopathological findings compatible with classical FSHD supports the previously expressed view that muscle histopathology is not related to either age or duration of the disease. Although Patient 2 was a sporadic case, both patients had the abnormal EcoRI DNA fragment detected by Southern blot analysis with probes p13E-11 and pFR-1, a finding compatible with FSHD. This indicates that gene analysis of sporadic cases must be as significant as that of familial cases. This report on patients with very early-onset and with common muscle histopathological and molecular genetic findings should contribute to widening the clinical spectrum of FSHD.     

Alcohol Protects the Diaphragm during Dietary Restriction

We recently reported that alcoholic rat diaphragm develops greater contractile force than diaphragm of pair-fed control animals. The present experiment examines whether alcohol or dietary restriction is the more likely cause of this surprising finding. We conditioned 10 rats using a liquid diet containing ethanol as 36% of calories. Ten pair-fed control animals received an equal amount of isocaloric, ethanol-free liquid diet. Ten ad libitum control animals had unrestricted access to lab chow and water. Rats were killed after 30 weeks. Left costal diaphragm strips were studied in vitro at optimal length using direct stimulation at supramaximal voltage. Isometric force was measured and divided by muscle cross-section to compute stress. Maximal tetanic stresses developed by muscle from pair-fed controls were systematically less than alcoholic and ad libitum control values (p less than 0.0001); this did not depend on temperature (25 degrees vs. 37 degrees; p greater than 0.50). Pair-feeding increased twitch half-relaxation times (p less than 0.03) and shifted the tetanic stress-stimulation frequency relationship leftward by 10 Hz (p less than 0.01). Diaphragm of pair-fed rats continued to generate lower stresses during the fatigue caused by repeated contractions (p less than 0.01). We conclude that dietary restriction associated with pair-feeding compromises diaphragm performance in rats. Chronic alcohol consumption prevents or reverses these changes, since diaphragm function of alcoholic and ad libitum control animals was not different.     

Applied muscle modelling: Implementation of muscle-specific models

Recent work in musculoskeletal modelling has seen the use of models which represent individual muscles in the human system. This paper presents a model of forearm supination in which models generate specific muscular forces to produce external supinator torque. The model output is compared to measured external torque for isometric and dynamic loading conditions. These data are used to construct isometric torque-angle and torque-angular velocity graphs for both model and experimental output. The discussion focuses on specific topics regarding implementation of muscle models in applied situations. These topics are demonstrated by observing the effect of parameter alteration on model output.