Z Disc Ultrastructure in Scutal Depressor Fibers of the Barnacle
Robert A. Leyton 1 and
William C. Ullrick 2
1 Cardiovascular Unit, Department of Medicine, Peter Bent Briglham Hospital and Harvard Medical School, Boston, Massachlusetts 02115
2 Department of Physiology, Boston University School of Medicine, Boston, Massachusetts 02118
The ultrastrlucture of Z discs in nonglycerinated, striated muscle fibers of the barnacle Balanus nubilus Darwin was examined in contracted, resting, and stretched preparations. At all sarcomnere lengths, the Z discs are perforated sheets comprised of "Z rimns" and "Z perforations," extending continuously across the myofibril; the dimensions of the rims and perforations change with changes in sarcomere length. Accordingly, with shortening of the sarcomere, there was an accompanying decrease in the transverse width of the Z rims and an increase in the diameter of the Z perforations.
