Coalignment of the muscle cell and nucleus, cell geometry and Vv in the tunica media of monkey cerebral arteries, by electron microscopy.

We undertook to ascertain how well aligned is the rod-shaped nucleus within the spindle-shaped cell of vascular muscle in order that we might use the darkly staining nucleus in histological sections to indicate precisely the directional alignment of the cell. We fixed cerebral arteries from five monkeys under physiological pressure and embedded portions of the tissue so that mid-plane longitudinal sections of the arteries were obtained; the circumferentially arranged muscle cells were cut in cross-section. From the electron micrographs we obtained the cross-sectional profile of the cell and its nucleus, determining that the centre of the nucleus was on average 9.5 +/- 5.8% (SD) away from the centre of the cell (expressed as a ratio of the cellular diameter). We calculated the alignment between the cell and nucleus to be from 0 to 3 degrees, and obtained a volume fraction of 59% for muscle tissue in the tunica media of these arteries.