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A 46-year-old womanpresented with rippling muscle phenomenon. She complained of uncomfortable muscular stiffness of extremities and abdominal wall. Muscle contraction was easily elicited by percussion, which was visible from the surface and propagated in a rolling manner. The mounding(or myoedema)phenomenonwas also remarkable. Three years later, malignant lymphoma (histologically, lymphoplasmacytoid lymphoma) was found in the sacrum. The lymphomasubsided with treatment by vincristine, cyclophosphamide, doxorubicin and prednisolone.SerumIgG as well as creatine kinase values were normalized. The rippling phenomenonalso responded to the treatment. The present rippling muscle syndrome might be of a paraneoplastic or autoimmuneorigin related to lymphoma, although the evidence seemed indirect. Wediscussed the role of the internal membranesystem of the skeletal muscle in the pathogenesis of rippling muscle. (Internal Medicine 41: 147-150, 2002)

Immunohistochemical studies were performed on muscle biopsy specimens of polymyalgia rheumatica (PMR)to evaluate the extent of muscle and peripheral nerve involvement. The routine histochemistry revealed a mild variation of fiber size, type 2 fiber atrophy and type 2A or 2B fiber deficiency. In 63% of the PMR cases small angular fibers, pyknotic nuclear clumps or target-targetoid fibers were observed, suggesting neurogenic changes, although abnormalities were mild in degree. In immunocytochemicalstudies, neither major histocompatibility complex (MHC)class 1 nor class 2 products were expressed on the muscle surface membraneof PMR.But regarding intramuscular vessels, MHCclass 2 products were distinctly visualized. On serial sections, combined deposits of IgG and Clq in perimysial arteries were seen in 38%of PMR. These results suggest that arteries of small caliber might be involved in immunopathological processes, causing muscle and peripheral nerve damage.

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When intramuscular pH was raised from 7.0 to 7.2, the contractile system became more sensitive to Ca, resulting in a larger tension. The process of Ca-induced Ca release in the sarcoplasmic reticulum was also facilitated. With a slight increase in the intracellular pH, sustained muscle contracture could easily be introduced.The ischemic exercise elicits muscle contracture in patients with metabolic myopathies such as McArdle's disease or Tarui's disease. Pathophysiology of this phenomenon is still obscure (16). The ischemic exercise induces intracellular alkalinization in these diseases, contrary to acidification in the healthy muscle (3, 14). It is assumed that the intracellular alkalinization facilitates contracture, since the function of the contractile system or the sarcoplasmic reticulum (SR) is very sensitive to changes in pH (13). In the present study, influence of intracellular alkalinization was studied with the rat skeletal muscle. A preliminary study was also performed with the human biopsied muscle.The function of the contractile system and SR was studied at 22°C with the singleskinned muscle fiber prepared from the rat leg or human biopsied muscle (19). Activation of the contractile system by Ca ions was analyzed in solutions at pH 6.80, 7.00 and 7.20. Ca uptake and Ca release by SR was also measured in various pH solutions. Effect of pH upon the Ca-induced Ca release (CICR) was studied according to Endo er al. (5). Briefly, after SR in the skinned fiber was loaded with Ca ions under standard conditions, the fiber was exposed to ATP-free solutions of different pCa. Then, the amount of Ca ions that remained in SR was estimated based on the magnitude of caffeine contracture. One arbitrary unit of Ca release per minute was about 0.5 micromol/min/g muscle. The apparent binding constant for Ca-EGTA at different pH was calculated according to Harafuji and Ogawa (8).In the type 2 fiber of rat extensor digitorum longus (EDL) muscle, sensitivity of the contracile system to Ca ions increased as the pH of solution increased, resulting in a shift of the pCa-tension curve to the left (Fig. 1). The threshold of contraction was lower at pH 7.20 than at pH 7.00. The maximum tension was 110% at both pH 7.0 and pH 7.2, taking the tension at pH 6.8 as 100%. The relative tension at pCa 6.5 or pCa 6.0 was significantly larger at pH 7.2 than at pH 7.0. Similar results were obtained in the type 1 fiber of rat soleus muscle. In human type 2 fibers, the effect of pH was more marked (Fig. 2). In all the range of pCa examined, the relative tension was 10% higher at pH 7.2 than at pH 7.0.Ca uptake by SR was estimated with skinned fiber on the basis of the magnitude of caffeine contracture. The time course and maximum values of Ca uptake were the same among three different solutions of pH 6.80, 7.00 or 7.20. However, CICR was markedly increased at pH 7.20 (Fig. 3). At pCa 5, CICR was 1.6 times larger at pH 7.20 than at pH 7.00.Rowland er al. analyzed the effect of ischemic exercise on the muscle content of ATP, creatine...

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