Asymmetry of focal macular photopic negative responses (PhNRs) in monkeys.

The photopic negative response (PhNR) is a slow, negative-going wave of the photopic electroretinogram (ERG) that appears after the b-wave. Recent studies have shown that the PhNR originates from the spiking activities of inner retinal neurons including the ganglion cells and their axons. The aim of this study was to determine whether there is any asymmetry in the amplitude of the PhNR elicited from the upper and lower macular areas, and between the nasal and temporal macular areas in rhesus monkeys. To accomplish this, we recorded focal macular PhNRs that were elicited by red hemi-circular stimuli presented on a blue background. We show that the PhNR from the upper macular area was significantly larger than that of the lower macular area, and the PhNR of the nasal macula was significantly larger than that of the temporal macula. These asymmetries were present in the focal PhNR elicited by both brief and long duration stimuli, and the asymmetries were completely eliminated by an intravitreal injection of tetrodotoxin (TTX). These results suggest that the upper-lower and nasal-temporal asymmetries of PhNR in the primate retina are mainly caused by TTX-sensitive spiking activities of inner retinal neurons.

Generation of a transgenic rabbit model of retinal degeneration.

PURPOSE: To generate a transgenic (Tg) rabbit model of retinal degeneration and to characterize the pattern of degeneration by using histology and electrophysiology. METHODS: Rhodopsin Pro347Leu Tg rabbits were generated by BAC transgenesis. Tg rabbits were identified by Southern blot analysis, and the expression levels were measured by quantitative RT-PCR. Retinal histology was examined by light and electron microscopy and immunohistochemistry. Retinal function was assessed by full-field electroretinograms (ERGs). RESULTS: Six lines of Tg rabbits were generated, and two lines with higher levels of expression showed rod-dominant progressive retinal degeneration. Retinal histology indicated a marked regional variation in the loss of photoreceptors with the central retina more severely affected than the peripheral retina. The characteristics of the ERGs of transgenic rabbits indicated that the rod components of the ERGs were reduced to only 5% by 48 weeks, whereas the cone components remained at 35% in the wild-type at the same time point. The retinal ultrastructure of Tg rabbits showed a large number of small vesicles that accumulated in the extracellular space of the photoreceptors. CONCLUSIONS: To the best of the authors' knowledge, this is the first rabbit model of progressive retinal degeneration. Because rabbits have large eyes and are easy to handle and breed, they will provide a useful animal model for the study of the pathophysiology of and new treatments for retinal degeneration.

Recording focal macular photopic negative response (PhNR) from monkeys.

PURPOSE: To record the photopic negative response (PhNR) of the focal electroretinograms (ERGs) from the macula of monkeys and to study the properties of the focal macular PhNRs. METHODS: Focal macular ERGs were recorded from five rhesus monkeys using a modified infrared fundus camera, in which a red stimulus spot on a blue illuminated background were incorporated. The effects of different stimulus intensities and durations presented on a steady blue background of 100 scot cd/m(2) on the focal macular PhNRs were investigated. Focal macular PhNRs were also recorded before and after an intravitreous injection of tetrodotoxin (TTX). RESULTS: Focal ERG responses from a photocoagulated retinal site were recordable when the luminance of the red stimulus spot was

Phylogenetic relationship of the populations within and around Japan using 105 short tandem repeat polymorphic loci.

We have analyzed 105 autosomal polymorphic short tandem repeat (STR) loci for nine East and South-eastern Asian populations (two Japanese, five Han Chinese, Thai, and Burmese populations) and a Caucasian population using a multiplex PCR typing system. All the STR loci are genomewide tetranucleotide repeat markers of which the total number of observed alleles and the observed heterozygosity were 756 and 0.743, respectively, for Japanese populations. Phylogenetic analysis for these allele frequency data suggested that the Japanese populations are more closely related with southern Chinese populations than central and/or northern ones. STRUCTURE program analysis revealed the almost clearly divided and accountable population structure at K=2-6, that the two Japanese populations always formed one group separated from the other populations and never belong to different groups at K> or =3. Furthermore, our new allele frequency data for 91 loci were analyzed with those for 52 worldwide populations published by previous studies. Phylogenetic and multidimensional scaling (MDS) analyses indicated that Asian populations with large population size (six Han Chinese, three Japanese, two Southeast Asia) formed one distinct cluster and are closer to each other than other ethnic minorities in east and Southeast Asia. This pattern may be the caviar of comparing populations with greatly differing population sizes when STR loci were analyzed.