A model for the formation of ring mitochondria in retinal pigment epithelium.
OBJECTIVE
To investigate the mechanism and sequence of formation of ring-shaped mitochondria in retinal pigment epithelial cells of a chick model of gyrate atrophy.


METHODS
Electron microscopic analysis of the ultrastructure of retinal pigment epithelial (RPE) mitochondria was carried out in chicks injected intravitreally with formoguanamine regularly (every 4 days) over the first 2 weeks or 4 weeks post-hatching. Formoguanamine is a triazine drug which induces hyperornithinemic symptoms in the chick eye similar to those seen in human gyrate atrophy.


RESULTS
A large population of irregularly shaped mitochondria was observed in the RPE of both peripheral and central retina. They showed extensive morphological changes. At 2 wk, the mitochondria appeared enlarged and abnormal in shape with vacuolisation, partial loss of their double membrane and reduced mitochondrial cristae. By 4 wk, the mitochondria had assumed a rounder, almost circular profile, many with central holes, so-called ring mitochondria.


CONCLUSIONS
The appearance of ring-shaped mitochondria has been previously ascribed to the section of cupshaped three-dimensional structures. We present evidence that ring-shaped mitochondrial profiles arise through at least two different mechanisms of membrane breakdown and intraorganelle vacuolisation. The nature of the three dimensional structures of these abnormal mitochondria is re-examined.
Liang
H
H
School of Optometry, University of N.S.W., Kensington, Australia.
Crewther
S G
SG
Crewther
D P
DP
D000818:Animals; D002642:Chick Embryo; D004195:Disease Models, Animal; D015799:Gyrate Atrophy / Q000139:chemically induced / Q000473:pathology*; D008928:Mitochondria / Q000648:ultrastructure*; D010857:Pigment Epithelium of Eye / Q000648:ultrastructure*; D014227:Triazines
D014227:Triazines; C047858:formoguanamine