Increased levels of serum-creatine-phosphokinase after transient limb ischaemia in patients with muscular dystrophy

Sarcolemmal damage in dystrophin deficiency is modulated by synergistic interactions between mechanical and oxidative/nitrosative stresses

Dystrophin deficiency is the cause of Duchenne muscular dystrophy, but the precise physiological basis for muscle necrosis remains unclear. To determine whether dystrophin-deficient muscles are abnormally susceptible to oxidative and nitric oxide (NO)-driven tissue stress, a hindlimb ischemia/reperfusion (I/R) model was used. Dystrophic mdx mice exhibited abnormally high levels of lipid peroxidation and protein nitration, which were preceded by exaggerated NO production during ischemia. Visualization of NO with the fluorescent probe 4,5-diaminofluorescein diacetate suggested that excess NO production during ischemia occurred within a subset of mdx fibers. In mdx muscles only, prior exposure to I/R dramatically increased the level of sarcolemmal damage resulting from stretch-mediated mechanical stress, indicating greatly exacerbated hyperfragility of the dystrophic fiber membrane. Treatment with NO synthase inhibitors (l-N(G)-nitroarginine methyl ester hydrochloride or 7-nitroindazol) effectively blocked the synergistic interaction between I/R and mechanical stress-mediated sarcolemmal damage under these conditions. Taken together, our findings provide direct ex-perimental evidence that several prevailing hy-potheses regarding the cause of muscle fiber damage in dystrophin-deficient muscle can be integrated into a common pathophysiological framework involving interactions between oxidative stress, ab-normal NO regulation, and hyperfragility of the sarcolemma.

The cardiomyopathy associated with methylsalicylate

Dogs challenged with toxic doses of methylsalicylate developed acute myocardiopathy. Metabolic manifestations of uncoupling of oxidative phosphorylation by methylsalicylate (MS) were observed. Oxygen consumption increased two-fold. The haemodynamic abnormalities produced by intervention were minimal. The measured metabolic parameters indicated profound derangement. A net efflux of orthophosphate, lactate and potassium was observed from the myocardium. Marked hyperkalaemia occurred terminally. Morphological changes were observed on electron microscopy.

Serum creatine kinase studies in the detection of carriers of Duchenne dystrophy

A number of methods which might improve the detection of carriers of Duchenne muscular dystrophy, based on the estimation of serum creatine kinase (CK), have been tried in an attempt to improve the 70% detection rate obtained with random samples. One series of experiments involved controlled exercise on a bicycle ergometer, the second series was based on sampling of muscle venous blood after controlled ischaemic exercise, and a third series of experiments was carried out to see whether the rate of enzyme inactivation was different in carriers of Duchenne dystrophy compared with controls. These methods were not found to improve the carrier detection rate based upon serum CK estimation.