The morphometric study was performed on seven animals in
each of the following four experimental groups: WKY-N (normotensive
nondiabetic), WKY-D (normotensive diabetic), SHR-N (hypertensive
nondiabetic), and SHR-D (hypertensive diabetic). Eyes were enucleated
and fixed by immersion in 2.5% glutaraldehyde in 0.1 M cacodylate
buffer (pH 7.4) containing 0.2% tannic acid. Tissue pieces were washed
overnight in several changes of cacodylate buffer and postfixed with
0.5% osmium tetroxide in the presence of 0.8% potassium ferrocyanide
in 50 mM cacodylate buffer. After block staining in 2% uranyl acetate
in 50% ethanol, the tissue was dehydrated through a graded series of
ethanol and embedded in Epon. Electron micrographs of thin sections
were taken with a video camera at a magnification of ×14,776 and
transferred to a computer (AcerPower Pentium 133; Hewlett Packard,
Geneva, Switzerland). Images were acquired by means of a frame grabber
board (Matrox PCI; Matrox Electronic Systems Ltd, Dorval, Quebec,
Canada).