Aging Related Changes of Retina and Optic Nerve of Uromastyx aegyptia and Falco tinnunculus

摘要

Aging is a biological phenomenon that involves gradual degradation of the structure and function of the retina and optic nerve. To our knowledge, little is known about the aging-related ocular cell loss in avian (Falco tinnunculus) and reptilian species (Uromastyx aegyptia). A selected 90 animals of pup, middle, and old age U. aegyptia (reptilian) and F. tinnunculus (avian) were used. The retinae and optic nerves were investigated by light and transmission electron microscopy (TEM) and assessments of neurotransmitters, antioxidant enzymes (catalase, superoxide dismustase and glutathione s transferase), caspase-3 and -7, malonadialdhyde, and DNA fragmentation. Light and TEM observations of the senile specimens revealed apparent deterioration of retinal cell layers, especially the pigmented epithelium and photoreceptor outer segments. Their inclusions of melanin were replaced by lipofuscins. Also, vacuolar degeneration and demyelination of the optic nerve axons were detected. Concomitantly, there was a marked increase of oxidative stress involved reduction of neurotransmittersand antioxidant enzymes and an increase of lipid peroxidation, caspase-3and -7, subG0/G1 apoptosis, and P53. We conclude that aging showedan inverse relationship with the neurotransmitters and antioxidantenzymes and a linear relationship of caspases, malondialdhyde, DNAapoptosis, and P53 markers of cell death. These markers reflectedthe retinal cytological alterations and lipofuscin accumulation withininner segments.