Cardiac muscle following quick-freezing: preservation of in vivo ultrastructure and geometry with special emphasis on intercellular clefts in the intact frog heart.
Intact frog, mouse and finch hearts were quick-frozen on a liquid He-cooled copper block. Adjacent frozen samples from the same heart were processed by freeze-substitution (followed by embedding and thin sectioning), freeze-fracture/etch (followed by platinum/carbon replication) and frozen sectioning (followed by freeze-drying), respectively, and examined with the electron microscope for fidelity of reproducing the in vivo state of heart muscle geometry, especially that of the narrow intercellular clefts between frog cardiac muscle cells. It was concluded that quick-freezing followed by the above procedures accomplishes that and that, therefore, narrow intercellular clefts are an invariant feature of the normal anatomy of frog cardiac muscle, which must be considered in physiological experiments. The methodology showed that quick-freezing through the epicardial surface is capable of producing superb cryopreservation for ultrathin cryosections, as well.
Sommer
J R
JR
Department of Pathology and Physiology, Duke University Medical Center, Durham, N.C. 27710.
Johnson
E A
EA
Wallace
N R
NR
Nassar
R
R
D000818:Animals; D001717:Birds; D002462:Cell Membrane / Q000648:ultrastructure; D005615:Freezing; D051379:Mice; D008809:Mice, Inbred C3H; D008854:Microscopy, Electron; D008929:Mitochondria, Heart / Q000648:ultrastructure; D009206:Myocardium / Q000648:ultrastructure*; D011896:Rana temporaria; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure