Abstract
Purpose :
To determine how the sub-cellular organelles, multi laminar and lipofuscin bodies, change with age in monkey retinal epithelium.
Methods :
Retinal epithelium is examined in young and old rhesus monkeys using transmission electron microscopy. Changes in osmium tetroxide fixation was used to distinguish melanosomes from poly-unsaturated fatty acids.
Results :
Multi lamellar bodies (MLBs) resemble myeloid bodies found in retinal epithelium usually during the light phase of the circadian cycle. We find them to be common in the aging but not in young monkey retinal epithelium. They can be very large, formed by 50 or more circumferential lamellae. They are normally found in lung epithelium and when seen elsewhere are often a sign of pathology, usually in fatty acid and cholesterol metabolism. In monkey MLBs stratify in the basal third of the retinal epithelium where large lipofuscin bodies are found. Three types off lipofuscin bodies can be distinguished. The most common is a relatively small circular structure with an irregular perimeter and dark particulate electron densities. They stratify in the middle third of the cell. A second type lipofuscin body is larger, has a linear perimeter and contains a lighter electron density, homogenous and centrally placed in the organelle; it stratifies in the basal third of the cell. The third lipofuscin body is rare, has an elliptical or circular shape with a strong electron density; the organelle is located centrally or basally in the cell. If osmium tetroxide was not used, the first two types of lipofuscin bodies lose their electron densities indicating that they contain poly unsaturated fatty acids. The third type of lipofuscin body keeps its electron density indicating that it contains melanin.
Conclusions :
Aging promotes the formation of MLBs and lipofuscin bodies both of which are involved in lipid metabolism and both locate in the basal third of the cell where drusen form from budding plasma membrane.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.