Abstract
The contraction of isolated smooth-muscle cells has been correlated with evagination of the cell membrane, a marked change in myofilament orientation, and a decrease in cellular volume. Both localized and full contractions have been elicited in the same cell by varying the intensity of electrical stimulation. These results may be explained by a model of the smooth-muscle cell in which the contractile apparatus extends between attachment sites on the cell membrane that are relatively closely spaced.