Biomedical subjects
A F Hayward
Publications and source records attributed to A F Hayward.
Ultrastructural changes in contents of membrane-coating granules after extrusion from epithelial cells of hamster cheek pouch.
Membrane-coating granules of the epithelium of the hamster cheek pouch displayed a lamellated internal structure consisting of alternating thick and thin electron dense bands separated by translucent bands of equal width. The repeat distance of the contents was 8.5 nm +/- sd. 0.7 nm and the thickness of the major electron dense band was 3 nm +/- sd 0.4 nm. After exocytosis from the cells the lamellated material became organised into extensive sheets and the dimensions changed so that the repeat distance was 10.9 nm +/- sd 0.6 nm but the major electron dense band was virtually unchanged at 3.33 nm +/- sd 1.1 nm. The narrower or intermediate dense band became progressively less easy to see and was virtually invisible at the surface of the epithelium. It is suggested that the changes observed may be due to an increase in hydration of a phospholipid/protein complex in the granules by permeaton of water along the intermediate dense band.
Ingestion of colloid in a keratinized epithelium and its localization in membrane-coating granules.
An electron-dense tracer (Thorotrast) was injected into the lamina propria of the keratinized epithelium of the buccal mucosa of rats. Electron microscopy showed that it crossed the basal lamina and penetrated the intercellular spaces of the epithelium up to the proximal layers of the stratum granulosum. Thorotrast was ingested by the epithelial cells in the stratum basale and stratum spinosum and localized in large vesicles and eventually in the membrane-coating granules. The latter, already known to contain lysosomal enzymes, are therefore to be regarded as secondary lysosomes formed in part as a sequel of endocytosis in deeper cell layers. The postulated origin of MCGs directly from the Golgi apparatus is rendered less likely by this observation. Thorotrast remaining in the cells when keratinization is completed is either dispersed into the cytoplasm or else incorporated into keratohyalin granules.