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F.M. Ferreira, S.M. Petersen-Jones; Detailed Characterization of Electroretinographic Abnormalities in the Retinopathy, Globe Enlarged (rge) Chick . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4534.
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Purpose: We have previously reported that rge chicks become functionally blind by about 7 weeks post hatch and have an abnormal ERG waveform. The purpose of this study was to further characterize the ERG in this retinopathy model. Methods: Dark-adapted and and light-adapted electroretinograms were recorded using a UTAS-E 3000 (LKC) from normal (-/-), carrier (rge/-) and affected (rge/rge) chicks at 1, 7 , 14, 28 and 150 days post-hatch. Naka-Rushton function fit was applied to the b-wave data using SigmaPlot 2001, version 7.101 (SPSS, Inc), which employs a Marquardt-Levenberg algorithm to perform least-squares fits. Results: The ERGs from rge/+ and +/+ were not significantly different. Amplitude vs intensity function for both a- and b-waves shows a fairly mature form in the day-old chicks, reflecting the relative maturity of the retina at hatch in this species. There is no discernable difference between the control and rge/rge b-wave Vmax functions. A-wave sensitivity is decreased in the rge/rge birds. A-wave Vmax approximately doubles in the control group as the chick matures but does not increase in the rge/rge birds. The steepness of the slope of the a-wave is much reducued in rge/rge chicks at all ages. Conclusions: The rge/rge birds show reduced sensitivity and lack of developmental change in a-wave Vmax compared to the control groups. The similarity of effect on the sensitivity parameter in a- and b-waves suggests that the main effect of the rge mutation is on the photoreceptors themselves with effects propagated through to the bipolar cells underlying the b-wave response. This is supported by the lack of increase in a-wave Vmax with age in the rge/rge group. The reduction in sensitivity is present at the earliest age tested (at hatch), suggesting that photoreceptor dysfunction is present from hatch.
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