Zusammenfassung
Im Jahre 1999 feierte ein Pionier der Netzhautforschung seinen 70. Geburtstag: Richard
W. Young, ehemals Prof. der Anatomie am Department of Anatomy and Jules Stein Eye
Institute, University of Southern California, Los Angeles, California, USA. Entgegen
dem herrschenden Dogma zeigte er, dass die Sinneszellen der Netzhaut einer beständigen
Erneuerung ihrer lichtempfindlichen Membranen unterliegen. Ganze Diskusmembranen oder
einzelne Moleküle der Außensegmente werden synthetisiert, im Gleichgewicht dazu werden
die Spitzen der Außensegmente abgestoßen (disk-shedding) und im Pigmentepithel (PE)
phagozytiert. Etwa 100 Doppelmembranen pro Stäbchen werden in 24 Stunden synthetisiert,
eine PE-Zelle muss etwa 30 000 Doppelmembranen, die von den anliegenden Stäbchen abgestoßen
wurden, phagozytieren und verdauen. Kein Wunder, dass das PE bei dieser enormen Stoffwechselleistung
im Laufe des Lebens das Alterspigment Lipofuszin ansammelt, das die unverdaulichen
Reste der Phagozytose enthält. Heute wissen wir, dass Lipofuszin zur Entstehung oder
dem Fortschreiten der altersabhängigen Makuladegeneration (AMD) beitragen kann. Schon
früh hat Young auf die mögliche Bedeutung von Lichtexposition bei der Entstehung der
AMD und einigen Formen der Retinitis Pigmentosa (RP) hingewiesen. Jetzt zeigen uns
verschiedene RP-Tiermodelle, dass in der Tat Lichtexposition den Krankheitsverlauf
beschleunigen kann. Auch die Apoptose der Netzhaut, die heute als eine gemeinsame
Endstrecke vieler Netzhautdegenerationen und Dystrophien angesehen wird, hat er lange
vor der großen „Apoptose-Welle” beschrieben. So hat er durch seine Forschung viele
wissenschaftliche Kinder hervorgebracht, die direkt oder indirekt durch seine Pionier-Arbeiten
angeregt wurden.
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 degradet 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
concludet 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.
Schlüsselwörter
Sinneszellen - Erneuerung - Stäbchen - Zapfen - Zellalterung - Zelltod - Richard W.
Young
Key words
Visual cells - renewal - rods - cones - cell death - cell ageing - Richard W. Young
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1 *Eingereicht am 7. 12. 99 und in der vorliegenden Form angenommen
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Visual cell renewal systems and the problem of retinitis pigmentosa.
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Cell death during differentiation of the retina in the mouse.
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The renewal of protein in retinal rods and cones.
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