Lynette Feeney-Burns

Lipofuscin of human retinal pigment epithelium.

Analysis of the fluorescent spectra of chloroform-methanol extracts of human retinal pigment epithelium confirmed the presence of lipofuscin pigments in the pigment epithelium of older individuals. Similar fractions in the pigment epithelium of young individuals were present in insufficient quantities for spectral analysis. Electron microscopy of the pigment epithelium of these eyes showed few or no lipofuscin granules in young eyes but large numbers in older eyes.

Age-related Macular Changes in Humans Over 90 Years Old

The macula lutea of 23 donors aged 90 to 101 years were examined by light and electron microscopy and compared to maculas from a 49- to 68-year-old age group. The number of foveal photoreceptors and retinal pigment epithelial cells, the presence of macular pigment, and lipofuscin fluorescence were assessed. Pathologic characteristics typical of age-related macular degeneration occurred in nine of the 90- to 101-year-old group with changes ranging from early neovascularization to fully developed disciform scars, geographic atrophy, and macular holes. Several retinas had pigment epithelial and photoreceptor cell numbers equal to those of the younger group, but most showed cell loss. Thickened, debris-filled Bruchs membrane and choriocapillary atrophy, although common, were not an invariable accompaniment to old age. Clinicians should advise elderly patients that their chances of maintaining macular structure, and hopefully function, are better than 50%.

Development of amelanotic retinal pigment epithelium in eyes with a tapetum lucidum: Melanosome autophagy and termination of melanogenesis

Abstract Bovine eyes of embryos and fetuses were examined to determine the developmental processes involved in establishment of the amelanotic retinal pigment epithelium (RPE) which overlies the tapetum lucidum. Melanogenesis was detectable at the optic vesicle stage (Day 28); premelanosomes were visible by electron microscopy in neuroepithelium temporal to the lens placode. Pigmentation of the eye was visible by light microscopy at the optic cup stage (about Day 30) and spread from the lip of the optic cup throughout the entire fundus by the 40th day. Thereafter, pigmentation of the superior temporal fundus diminished and by the 65th day the adult pattern of amelanotic and melanotic RPE was established. Calculations showed that after the 40th day, growth of the eyeball brought about a 16-fold dilution of those melanosomes which had been synthesized by RPE cells of the presumptive amelanotic zone during the initial wave of pigmentation. Enzyme cytochemical studies showed that the remaining melanosomes became sequestered in autophagic vacuoles. Also, individual premelanosomes of these RPE cells became positive for acid phosphatase and aryl sulfatase. The contents of these autophagosomes were later consolidated into a single macromelanosome which was present in adult eyes and was generally positive for acid hydrolases. In contrast, melanosomes of melanotic areas of RPE were negative for acid hydrolases. Thus, the RPE overlying the tapetum lucidum becomes amelanotic by at least three processes: (1) premature termination of melanogenesis, (2) dilution of preexisting melanosomes, and (3) autophagic digestion (melanolysis) and centralization of the residua of preexisting premelanosomes and melanosomes into a macromelanosome.

[16] Methods for isolating and fractionating pigment epithelial cells

Publisher Summary This chapter discusses the methods for isolating and fractionating pigment epithelial cells. The retinal pigment epithelium (RPE) is a single layer of hexagonally shaped cells underlying the neurosensory retina. The apical processes of the RPE interdigitate with the photoreceptor outer segments, but there are no structural attachments between them. The isolation of pure populations of cells is therefore an important goal and is best achieved by microscopic monitoring of the preparations during each step of the purification. The basic method could, however, be adapted to isolate RPE from other species, provided the eyes are large enough to allow efficient brushing out of the cells. The crude RPE cell suspension is passed through a double layer of cheesecloth to remove any pieces of retina that may have broken off during the peeling procedure. Isolated washed RPE suspensions consisting of both single cells and sheets of cells are resistant to disruption in shear-type hemogenizers unless they are very tight-fitting.

Vitamin E in human neural retina and retinal pigment epithelium: Effect of age

Vitamin E levels were measured in retina and retinal pigment epithelium from human eye bank donors of from 12-82 years of age. In comparison to an age group of 12-45 years, humans 59-82 years of age had a higher concentration of vitamin E in both retina and retinal pigment epithelium. Depending on age, the concentration of vitamin E in retinal pigment epithelium was from 4-7 times higher than in retina. Vitamin E accumulated in the human retinal pigment epithelium in an age dependent fashion, so that by 80 years it was from 3-4 times higher than in those 20 years old. The level of vitamin E in young human retinal epithelium, however, was higher than in comparable bovine tissue. The age-related increase in human tissue vitamin E levels does not appear to be affected by postmortem time.