[Photoreceptor renewal and the pigment epithelium of the retina--congratulations to a pioneer in retinal research: Richard W. Young].
In 1999, a pioneer in retinal cell biology celebrates his seventieth birthday: Richard W. Young, Professor of Anatomy at the Dept. of Anatomy and Jules Stein Eye Institute, University of Southern California, Los Angeles, California, USA. Against the current dogma of visual cells as static structures he demonstrated that they undergo continual renewal of their light-sensitive outer segments. Entire membranes and/or single molecules are being replaced, and the tips of outer segments are shed (disk-shedding), and phagocytized and degrade by pigment epithelial (PE) cells. About 100 disks are made per rod within 24 hours, and about 30,000 disk membranes from overlying rods are degraded by one PE cell thus rendering the PE one of the most active phagocytic systems of the body. It is not surprising, therefore, that the age pigment lipofuscin accumulates within PE cells, which is mainly composed of undigestible outer segment material. It is generally concluded that lipofuscin can contribute to the pathogenesis of age related macular degeneration (AMD). Early on Young has postulated that light exposure may accelerate AMD and some forms of retinitis pigmentosa (RP). Today we know that indeed in several animal models of RP light exposure can significantly enhance the disease progression. With a similar insight and intuition he described apoptosis of the retina thus preceding the "apoptotic wave" in eye research. Apoptosis now is considered the final common death pathway of many retinal diseases including degenerations and dystrophies. With his work young has created may scientific children, who directly or indirectly were inspired by his pioneering work.
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Laboratorium für Zellbiologie der Netzhaut, Universitäts-Augenklinik, Zürich, Schweiz. chreme@opth.unizh.ch
D049673:History, 20th Century; D006801:Humans; D009416:Nerve Regeneration / Q000502:physiology*; D009885:Ophthalmology / Q000266:history; D010786:Photoreceptor Cells / Q000502:physiology*; D010857:Pigment Epithelium of Eye / Q000502:physiology*; D014481:United States