In its first versions, the CDR file format was a completely proprietary file format primarily used for vector graphic drawings, recognizable by the first two bytes of the file being \"WL\". Starting with CorelDraw 3, the file format changed to a Resource Interchange File Format (RIFF) envelope, recognizable by the first four bytes of the file being \"RIFF\", and a \"CDR*vrsn\" in bytes 9 to 15, with the asterisk \"*\" being just a blank in early versions. Beginning with CorelDraw 4 it included the version number of the writing program in hexadecimal (\"4\" meaning version 4, \"D\" meaning version 13). The actual data chunk of the RIFF remains a Corel proprietary format.
To estimate the viability of cells, an average number of pyknotic nuclei we counted relative to the total number of nuclei in the RPE layer on 100 - 150 cross-sections of the periphery and central region of each eye cup sample. The frequency of the phenotype transformation of the RPE cells was determined in the same cross-sections by counting the withdrawn cells in proximity of the RPE layer, which also lost epithelial morphology; rare mitotic cells were also counted. In addition images obtained were registered by digital camera and computer (software Lite) and studied using visual evaluation and computer programs. Eye cup samples obtained on 14 day of in vitro culturing we used for estimation of a relative extension of destroyed regions of RPE layer. For that we made digital photos of the serial slices of cultivated eye posterior cups and then taken images were treated by means of Corel Draw, Adobe Photoshop, Excel and Plot Calc. Statistic analysis of the data was carried out using Microsoft Excel 2010. That made possible to evaluate the dimensions of RPE layer and those of regions of RPE destruction and bring the data in correlation with each other.
However, the morphology of the transformed RPE cells differed from that of macrophages and served for RPE cell identification. RPE cells leaving the layer contained one, or more often two, large diffusely-stained oval nuclei localized in the center of a cell. Whereas macrophages had one larger tightly-stained crescent nucleus shifted to the cell periphery (not shown). Transformation of RPE cells to the macrophagal phenotype was more pronounced in the centre of the eye cup than in its periphery. Direct counting of the number of transformed RPE cells on the serial cross-sections gave the values of 20.0 5.8 and 9.0 2.3 per section for central part of RPE and its periphery, respectively (Figure 3). 153554b96e