Sporadic inclusion body myositis: morphology, regeneration, and cytoskeletal structure of muscle fibres.

OBJECTIVE: To characterise morphological abnormalities in relation to muscle fibre type in sporadic inclusion body myositis (s-IBM). METHODS: 14 muscle biopsies from 11 patients with s-IBM were characterised for morphological abnormalities and fibre type composition as well as muscle fibre regeneration and cytoskeletal structure, using histochemical and immunohistochemical techniques. RESULTS: Morphological abnormalities included inflammatory infiltrates and "rimmed vacuoles," and pronounced variation in fibre size. There were no significant differences in fibre type composition between s-IBM patients and controls based on the myofibrillar ATPase staining. A differential effect on muscle fibre sizes was noted, type II fibres being smaller in the s-IBM patients than in the controls. Conversely, the mean type I muscle fibre diameter in the s-IBM patients was larger than in the controls, though this difference was not significant. An ongoing intense regeneration process was present in s-IBM muscle, as indicated by the expression of neonatal myosin heavy chain, vimentin, and CD56 (Leu-19) in most of the muscle fibres. The cytoskeletal proteins dystrophin and desmin were normally expressed in s-IBM muscle fibres that were not undergoing degeneration or regeneration. CONCLUSIONS: There are extensive morphological and morphometric alterations in s-IBM, affecting different muscle fibre types in different ways. The cytoskeletal structure of type I and II muscle fibres remains unaffected in different stages of the disease.

Inclusion body myositis--sensory dysfunction revealed with quantitative determination of somatosensory thresholds.

In order to evaluate sensory function in inclusion body myositis (IBM), nine patients were subjected to sensibility screening and quantitative determination of somatosensory thresholds. Data were compared with results from electrophysiological examination and muscle biopsy. On sensibility screening all but one of the IBM patients had abnormal findings in hands and/or feet mostly affecting thermal sensibility. Vibratory thresholds were abnormal in five and thermal thresholds in four of the patients. Mean vibratory thresholds were significantly (P < 0.05) higher in the IBM patients when compared with the controls. Significantly increased heat pain thresholds were found in hands and feet when compared with the controls while thermal thresholds were normal. Nerve conduction velocities were decreased in three patients, EMG showed both myopathic and neuropathic abnormalities in six patients. Eight patients had neuropathic abnormalities on muscle biopsy. The sensory dysfunction found suggests an affection of peripheral nerves in IBM mainly affecting large diameter myelinated nerve fibres corroborating earlier findings of a peripheral neuropathy in IBM.

Report of a patient with inclusion body myositis and CD8+ chronic lymphocytic leukaemia--post-mortem analysis of muscle and brain.

We report a 73-year-old woman with sporadic inclusion body myositis (s-IBM) and a T-cell chronic lymphocytic leukaemia (T-CLL). The s-IBM diagnosis was based on clinical symptoms and muscle biopsy showing inflammatory infiltrates and rimmed vacuoles with 15 18 nm diameter tubulofilamentous inclusions on ultrastructural examination. The inflammatory infiltrates consisted of CD8+ T-lymphocytes and macrophages. The diagnosis of a CD8+ T-CLL was based on peripheral blood samples and bone marrow aspiration. The postmortem analysis of skeletal muscle showed fascicular atrophy, which may support a neurogenic component in s-IBM and the analysis of the brain showed only a few diffuse plaques in different cortical regions and occasionally neuritic plaques. A pathophysiological analogy between s-IBM and Alzheimer's has been suggested on the basis of similarities in protein accumulation in muscle of s-IBM patients and brain of Alzheimer's patients. However, we were unable to detect any changes suggestive of Alzheimer's disease in the brain of the s-IBM patient presented here.

Low back pain, smoking and employment during pregnancy and after delivery - a 3-month follow-up study.

Low back pain (LBP.), smoking and employment was studied among 111 consecutive women admitted to a maternity ward over a 6-week period, 40 were primiparas and 71 multiparas. LBP was defined as any pain in the low back, irrespective of the specific cause of the pain. Two specially constructed questionnaires were utilised. The first was a, 14-item questionnaire which all participants answered before leaving the maternity ward. It included questions on employment and smoking and self-rating Visual Analogue Scales used for rating LBP. LBP was rated during the pregnancy and 3 days after delivery. The second questionnaire was used in a 90-day follow-up interview. The mean age of participants was 28 years. The prevalence of LBP during pregnancy was 58.5% among the 111 participants. Of the 111, 75% continued to have LBP postpartum and at the 90-day post-delivery follow-up, 54% of those with LBP during pregnancy were still experiencing LBP. Previous births and birth weight were not found to correlate positively with LBP. LBP during pregnancy did not affect the length of employment during pregnancy. Smokers had LBP more frequently during pregnancy and also after (P <0.002). It is concluded that smoking does seem to contribute to LBP during and after pregnancy. Birth weight does not affect LBP and LBP does not affect the length of employment during pregnancy.

Excitation and contraction in atrial and ventricular myocardium of the guinea-pig.

Several parameters of excitation-contraction coupling were compared in two types of muscle, using thin strips from the left atria and papillary muscles from the right ventricles of guinea-pigs. (1) The duration of the action potential and twitch is much longer in ventricular than in atrial muscle. (2) Mechanical restitution can usually be described by a monoexponential function in ventricular and biexponential function in atrial muscle. (3) Post-extrasystolic potentiation, when related to the steady state force, is greater in ventricular muscle. (4) When priming with paired-pulse stimulation, mechanical restitution can be studied after the short interval and after the long interval. In atrial muscle, mechanical restitution is very similar after the short and long intervals but in ventricular muscle they are different in size. (5) Ryanodine (10(-6) M) can decrease the steady state force to about 10% of control in atrial but only to about 35% in ventricular muscle. Ryanodine (10(-8) M) causes the slow phase of restitution in atrial muscle to disappear but in ventricular muscle only increases the rate of mechanical restitution. (6) Ca-antagonists (Cd2+ 0.2 mM) can decrease the steady state force to zero in atrial and ventricular muscle. Ca-antagonists, in low concentrations (Cd2+ 0.01 mM), mainly affected the fast phase of mechanical restitution. (7) The recirculation fraction of calcium was about 0.64 in atrial and 0.27 in ventricular muscle. The findings are discussed in the light of known ultrastructural differences between atrial and ventricular myocardium.