To examine whether a capacitative Ca²⁺ entry pathway is present in skeletal muscle, thin muscle fibre bundles were isolated from extensor digitorum longus (EDL) muscle of adult mice, and isometric tension and fura‐2 signals were simultaneously measured. The sarcoplasmic reticulum (SR) in the muscle fibres was successfully depleted of Ca²⁺ by repetitive treatments with high‐K⁺ solutions, initially in the absence and then in the presence of a sarcoplasmic/endoplasmic reticulum Ca²⁺‐ATPase (SERCA) inhibitor. Depletion of the SR of Ca²⁺ enabled us for the first time to show convincingly that the vast majority of the voltage‐sensitive Ca²⁺ store overlaps the caffeine‐sensitive Ca²⁺ store in intact fibres from mouse EDL muscle. This conclusion was based on the observation that both high‐K⁺ solution and caffeine failed to cause a contracture in the depleted muscle fibres. The existence of a Ca²⁺ influx pathway active enough to refill the depleted SR within several minutes was shown in skeletal muscle fibres. Ca²⁺ entry was sensitive to Ni²⁺, but resistant to nifedipine and was suppressed by plasma membrane depolarisation. Evidence for store‐operated Ca²⁺ entry was provided by measurements of Mn²⁺ entry. Significant acceleration of Mn²⁺ entry was observed only when the SR was severely depleted of Ca²⁺. The Mn²⁺ influx, which was blocked by Ni²⁺ but not by nifedipine, was inwardly rectifying, as is the case with the Ca²⁺ entry. These results indicate that the store‐operated Ca²⁺ entry is similar to the Ca²⁺ release‐activated Ca²⁺ channel (CRAC) current described in other preparations.

Summary. A data-adaptive 2-D inversion scheme for magnetotelluric data, which simultaneously finds the smoothest model with the smallest misfit whilst solving

Intraplate earthquake zones in the back arc of NE Japan were imaged by wide‐band magnetotelluric (MT) soundings. The 90km long MT profile of 34 stations extends over the two topographic features, the Dewa Hills and the Ou Backbone Range, which were uplifted by thrust faults. MT data show two‐dimensionality and strong TE/TM anisotropic responses at the periods around 100 s. After tensor decompositions with regional strike of N12°E, two‐dimensional inversion was carried out where static shift was also a model parameter. The final model is characterized by conductive blocks in the mid‐crust to account for the anisotropic responses. Correlation of the conductors to the seismic scatterers and to the low velocity anomalies suggests that the conductors represent fluids. High seismicity clustering near the rims of conductors suggests that the intraplate seismicity results either from the migration of the fluids to less permeable crust or from local stress concentration near the structural boundary.