Expression of Sirt1 and Sirt2 in the Injured Optic Retina of Calorie-Restricted Rats

Purpose:To investigate retinal ganglion cell (RGC) survival after optic nerve injury in calorie-restricted (CR) rats,and analyze the potential role of Sirtuins.Methods:Ten-month old male Sprague-Dawley rats (n=14) were divided into calorie restricted (CR) and ad libitum (AL) groups.In the CR group (n=7),the rats were denied access to food every other day.Animals in the AL group (n=7) had had free access to food.PN-ON grafting was carried out on the right eye of all subjects after 5 months of feeding.Three weeks postoperatively,retina samples were collected,half of which were fixed in 4% paraformaldehyde (PFA) and subjected to standard immunofluorescence staining for TUJ-1.The remaining samples were subjected to total RNA analysis and RT-PCR for Sirt1 and 2 expression.Results:Comparing the amount of TUJ-1 staining between the groups,the mean density and the total number of RGCs showed no significant difference.RT-PCR results indicated that mRNA expression of Sirtuin2 in the CR group was significantly lower than that in the AL group,whereas no statistically significant difference was observed between the two groups regarding the mRNA expression of Sirt1.Conclusion:Calorie restriction had no impact on the survival of injured RGCs.The down-regulated mRNA expression of Sirt2 in the CR group may indicate an improved capacity for regeneration among these animals,but more work is needed to explore this possibility.

Comparison on Photopic Electroretinogram Negative Response between Young and Old Lewis Rats

Purpose:To investigate and compare the latency and amplitude of the electroretinogram(ERG) photopic negative response(PhNR) between young and old Lewis rats.Methods:Thirteen Lewis rats were divided into two groups according to ages,young group(3-month old,n=5) and old group(24 month old,n=8).The ERGs of the left eyes were measured and the latency and amplitude of a-wave,b-wave and PhNRs were recorded and compared according to ages.The mean values between two groups were statistically analysed by t-test.Results:The latency of PhNRs was evidently prolonged in old group and showed significant difference(P<0.05).There was no statistically significant difference between two groups regarding the amplitude and latency,and no significant difference was noted in the amplitude of PhNRs.Conclusion:The prolonged latency of PhNR in aged rats possibly associate with the influence of aging upon retinal ganglion cell layer(RGCL).