point to a cell that expresses PKC but does not express Islet-1: this is likely a DB4 cell. bipolar cells (from 9% to 15%). The proportion of Mller cells near the fovea (17%) is lower than in the peripheral retina (27%). Conclusions Despite large changes in G15 the absolute density of INL cell populations across the retina, their proportions G15 remain relatively constant. These data may have relevance for interpreting diagnostic signals such as G15 the electroretinogram and optical coherence tomogram. = is usually cell density (cells/mm2), 1,?2,?and?3 are exponential coefficients, is eccentricity (mm). Unfavorable fit values in the fovea were set to zero. As in our previous study,5 cumulative density across the horizontal meridian was calculated by circular integration of spatial densities within annuli of defined eccentricity ranges, radiating from the foveal center in a bullseye pattern. The following formula was applied to calculate the number (represents the radius of the outer border and represents the radius of the inner border of the eccentricity range FLB7527 in question. Integrated cell numbers were calculated by taking into account the spatial offset caused by Henle’s fibers (postreceptoral displacement), as well as the larger volume of INL made up of each population’s cell bodies with respect to the foveal cone outer segments10,16 (for detailed methodology see5). Table 3. Best Fit Parameters for Pooled Data in BCD (in some cases smaller than the marker symbols) show standard deviations for pooled data. We quantified the spatial density of H1 and H2 cells across the temporal retina for six preparations.?Figure 3A shows the densities of parvalbumin immunoreactive (H1 and H2) horizontal cells. The pooled data are shown in?Physique 3B. Horizontal cell density peaks at an average of 16,200 cells/mm2 at roughly 0.75 mm temporal to the foveal center. Horizontal cell density declines steeply within the central-most 6 mm then plateaus and remains in excess of 2500 cells/mm2 at 10 mm eccentricity. The spatial distribution of H1 and H2 cells was calculated by pooling data from preparations which were double labeled with parvalbumin and calbindin (13587, 14064, 15415). The density of H1 cells (Fig. 3C) is usually higher than that of H2 cells (Fig. 3D) at all eccentricities. The density of H1 cells peaks at an average of 15,000 cells/mm2 at 0.6 mm and drops to roughly 2500 cells/mm2 by 12 mm eccentricity. The density of H2 cells declines steadily from a peak density of 2000 cells/mm2 at 2.5 mm to below 300 cells/mm2 at 12 mm. The peak density of H2 cells was in the range of 2000 to 4000 cells/mm2 within 1 and 2.5 mm eccentricity. At about 0.6?mm the ratio of H1 to H2 cells is 15:1, at 2.5 mm the ratio is 4.4:1, and beyond 4 mm the ratio is about 3:1. We also found some cells in the horizontal cell layer which only expressed calbindin (Figs. 2F,?2G arrowhead). Comparable cells were found in all preparations, but they were very rare (n = 35 cells out of a total of 2447 horizontal cells counted). Thus we assume that they do not represent a separate population of horizontal cells. It is possible that these cells are DB3a bipolar cells where the axon is not labeled.5,21 Bipolar Cells Antibodies against recoverin were used to identify OFF midget bipolar cells,5,22 antibodies against calbindin and CD15 were used to identify the OFF diffuse bipolar (DB) types DB3a and DB3b, respectively,5,21,22 and antibodies against the transcription factor Islet-1 were used to label ON cone bipolar and rod bipolar G15 cells.21,23 We first compared the expression of Islet-1 with that of recoverin (Fig. 4). Islet-1 was localized to cell bodies in the middle of the inner nuclear layer (Figs. 4B,?4E), and, as expected, we found no overlap between the two markers (Figs. 4C,?4F). Open in a separate window Physique 4. Fluorescence micrographs of bipolar cells. A-F: Confocal micrographs from preparation #15649 (aged 36 years) stained with antibodies against recoverin (green, A,D) to label OFF-midget bipolar cells and antibodies against islet-1 (magenta, B,E) to label ON bipolar cell nuclei, Nomarski optics images are superimposed. Regions of interest are shown at 1.2 mm (ACC) and 2.5 mm eccentricity (DCF). Merged images C and F show that there is no colocalization between recoverin and Islet-1. Abbreviations as in?Figure.