CHICKEN DYSTROPHY - GEOMETRY OF TRANSVERSE TUBULES

Abstract

The pectoral muscle of chickens afflicted with muscular dystrophy, when examined by EM, contains numerous, often quite large vesicles with and without caveolar evaginations, tubules with caveolar evaginations, and tubular networks. All these structures are derivatives of the transverse tubules as revealed by tracer studies and freeze-fracture complementary replicas. The membranes of transverse tubular origin show a small number of intramembranous particles on both P and E faces with no complementary geometry. The membranes of the free sarcoplasmic reticulum (SR) and the junctional SR of normal and dystrophic muscle appear identical in complementary freeze-fracture replicas. Vesicles that carry only a small number of particles on both E and P faces exposed by freeze-fracturing in isolated SR preparations can be taken as presumptive evidence and serve as a morphologic marker for transverse tubular origin of such vesicles when mitochondrial and lysosomal contamination has been excluded.