TY - JOUR
T1 - A pathologic study of photoreceptor cell death in retinal photic injury
AU - Shahinfar, Shahin
AU - Edward, Deepak P.
AU - Tso, Mark O.M.
N1 - Funding Information:
ACKNOWLEDGEMENTS Supported by NIH Grants EY01903 and EY06761 and the Lions of Illinois Eye Foundation. Presented at the annual meeting of the Association for Research in Vision and Ophthalmology, Sarasota, Florida, April 29-May 4, 1990.
PY - 1991
Y1 - 1991
N2 - In the studies of retinal photic injury in the rat model, about 14-47% of the photoreceptor cell loss occurs in the first 24 hours. To understand the mechanism of this massive cell death and subsequent dissolution, we studied the early morphologic changes and examined the effect of cycloheximide, a protein synthesis inhibitor, on photic injury in rats. Groups of 2 dark-adapted albino Lewis rats were sacrificed immediately after 8, 16 or 24 hr of continuous exposure to green fluorescent light (intensity, 160-180 foot-candles; wavelength, 490-560 nm). An additional 2 rats were sacrificed 8 hr after a 24 hr light exposure, and 2 animals served as unexposed controls. The morphologic findings of the degenerating photoreceptor cells were assessed by light and electron microscopy. The integrity of the nuclear chromatin was investigated using a monoclonal anti-DNA antibody. Most of the photoreceptor cell loss was observed between 16 and 24 hr of exposure. No inflammatory or macrophagic cells were seen. Different stages of nuclear condensation and chromatin margination could be defined. The chromatin showed a progressive decrease in DNA labelling density. Scattered photoreceptor cells showed early cytoplasmic densification. To study the effect of cycloheximide, 4 rats were treated with 5 mg/kg subcutaneously at the start of a 24 hr exposure period and were sacrificed 6 hr after the exposure. Four untreated animals served as exposed controls for morphometric comparison of the outer nuclear layer (ONL). The control rats showed a 24% decrease in the thickness of the ONL when compared to cycloheximide-treated rats (p<0.001). The observations of mitochondrial changes and early DNA digestion were consistent with necrosis as the mechanism of cell death. However, in scattered photoreceptor cells, cytoplasmic densification, margination of nuclear chromatin, the lack of associated inflammation and the protective effect of cycloheximide were suggestive of apoptosis as another mechanism of cell death.
AB - In the studies of retinal photic injury in the rat model, about 14-47% of the photoreceptor cell loss occurs in the first 24 hours. To understand the mechanism of this massive cell death and subsequent dissolution, we studied the early morphologic changes and examined the effect of cycloheximide, a protein synthesis inhibitor, on photic injury in rats. Groups of 2 dark-adapted albino Lewis rats were sacrificed immediately after 8, 16 or 24 hr of continuous exposure to green fluorescent light (intensity, 160-180 foot-candles; wavelength, 490-560 nm). An additional 2 rats were sacrificed 8 hr after a 24 hr light exposure, and 2 animals served as unexposed controls. The morphologic findings of the degenerating photoreceptor cells were assessed by light and electron microscopy. The integrity of the nuclear chromatin was investigated using a monoclonal anti-DNA antibody. Most of the photoreceptor cell loss was observed between 16 and 24 hr of exposure. No inflammatory or macrophagic cells were seen. Different stages of nuclear condensation and chromatin margination could be defined. The chromatin showed a progressive decrease in DNA labelling density. Scattered photoreceptor cells showed early cytoplasmic densification. To study the effect of cycloheximide, 4 rats were treated with 5 mg/kg subcutaneously at the start of a 24 hr exposure period and were sacrificed 6 hr after the exposure. Four untreated animals served as exposed controls for morphometric comparison of the outer nuclear layer (ONL). The control rats showed a 24% decrease in the thickness of the ONL when compared to cycloheximide-treated rats (p<0.001). The observations of mitochondrial changes and early DNA digestion were consistent with necrosis as the mechanism of cell death. However, in scattered photoreceptor cells, cytoplasmic densification, margination of nuclear chromatin, the lack of associated inflammation and the protective effect of cycloheximide were suggestive of apoptosis as another mechanism of cell death.
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U2 - 10.3109/02713689109007610
DO - 10.3109/02713689109007610
M3 - Article
C2 - 2029848
AN - SCOPUS:0026026358
VL - 10
SP - 47
EP - 59
JO - Current Eye Research
JF - Current Eye Research
SN - 0271-3683
IS - 1
ER -