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Peter Gouras, Maerta Lena Ingeborg Ivert, Martha Neuringer, Takayuki Nagasaki; Lipofuscin bodies decrease and melanosomes increase in number progressively with retinal eccentricity in elderly rhesus monkey RPE. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2383.
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To determine how the cytoplasmic organelles, lipofuscin bodies and melanosomes, change in number and size with retinal eccentricity and age.
Transmission electron microscopy was used to identify and measure the number and length of lipofuscin bodies and melanosomes in the retinal pigment epithelium (RPE) along the temporal horizontal meridian at the macula, peri-macula, equator, periphery, and ora serrata in young and old monkeys.
In elderly monkeys, lipofuscin bodies are maximum in number and total area at the macula and decrease progressively with eccentricity. There are more than 10 times as many lipofuscin bodies in the macula than in the peripheral RPE. No lipofuscin bodies are in the ora. Aside from a foveal dip, the results resemble the fluorescent measurements of human eyes by Wing et al. (IOVS 17:601, 1978). In elderly monkeys, melanosomes are minimal in number and total area in the macula RPE and increase progressively with eccentricity. There are more than 5 times as many melanosomes in the peripheral than the macula RPE. In young monkeys there are no lipofuscin bodies and more melanosomes and less of an increase in number with eccentricity than in elderly RPE.
Lipofuscin bodies are mainly undigested lysosomal degradation products resulting from the phagocytic turnover of photoreceptor outer segments. If this turnover rate is the same across the retina, the macular RPE of elderly monkeys must have a unique defect in being less able to digest outer segment material, or has a greater phagocytic load (Dory et al., IOVS 30:169, 1989). The higher concentration of lipofuscin could be responsible for the lower amounts of melanosomes in the macula.
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