Filaments in the Microvillous Border of Intestinal Cells

Adult Sprague-Dawley rats were perfused through the left ventricle first with balanced salt (10) to remove the blood. They were then fixed by perfusion with a mixture of 6.5 per cent glutaraldehyde and 2 per cent acrolein in a phosphate buffer (pH 7.5) (11). After 15 minutes, the duodenum was removed, fixed for an additional hour in the same aldehyde mixture, and rinsed in Veronal-acetate buffer for 15 minutes. It was then postfixed in Veronal-acetate-buffered 2 per cent osmium tetroxide (8) and embedded in Epon (6). Sections were stained with lead according to Karnovsky's method A (3) and/or uranyl acetate (17), and examined in a Siemens Elmiskop I.