Fig. 1.

Freeze-fracture and rotary shadowing of BC₃H1 cells. Freeze-fracture replicas of surface membranes from differentiated BC₃H1 and RyR1-expressing 1B5 cells. (A) Patch of membrane containing an array of tetrads in a BC₃H1 cell. Each DHPR particle is coated by platinum on all sides, and thus it appears as a dark ring with a lighter region at its peak. (B and C) Galleries of selected tetrads from control and ryanodine treated cells at higher magnification. Tetrads may be complete (i.e., composed of four particles), or incomplete (i.e., they lack one or more particles), due either to the breaking of particles during fracturing or to a missing DHPR.