The chemistry of the retina: Function, renewal, rhythms, and the nucleus

Investigation of the chemical activities of retinal cells began with functional chemistry, an origin which can be traced to the pioneering studies of Kühne and Wald. Next to develop was renewal chemistry, which is concerned with the continued replacement of retinal cell structure. A third field of retinal chemistry, more recently evolved, is the analysis of chemical change associated with daily rhythms. In the living cell, all such groups of chemical reactions are merged into a single, integrated metabolism which ultimately is regulated by molecular systems sequestered within the nucleus. Although nuclear chemistry has so far been neglected in vision research, a theory of nuclear metabolism has been maturing in other fields of biological chemistry. One salient aspect of the theory is the temporal stability of the fundamental constituents of the chromosomes: DNA and histone. Alone among all cellular molecules, they may persist indefinitely. Nuclear theory has proved to have important predictive value in preliminary applications to analysis of the mammalian retina. Evidence is presented in the following report which indicates that retinal cells can repair DNA lesions provoked by UV radiation. Other experiments suggest that in retinal nuclei there is a reversible acetylation of histones and non-histone chromosomal proteins-a process which is implicated in gene regulation.