Ultrastructure and calcium transport in crustacean muscle microsomes.

Fragmented sarcoplasmic reticulum (FSR) from crustacean muscle was examined following preparation by a variety of electron microscopic techniques. The 30-40 A particles which appeared on the outer surface of FSR vesicles following negative staining were not observed following preparation by freeze-drying, freeze-etching, thin sectioning, or critical-point drying. Crustacean FSR exhibited high values of calcium uptake and extensive nodular formation in the presence of oxalate. 80-90 A diameter membrane particles were seen in freeze-etch preparations of both intact lobster muscle and FSR vesicles. Thin sections of FSR vesicles revealed a membrane thickness of 60-70 A. The membrane appeared to be triple layered, each layer having a thickness of 20-25 A.