The structure of the developing chick retinal pigment epithelium revealed by high resolution scanning electron microscopy

Abstract

The retinal pigment epithelium (RPE) in the developing eye of chick embryos has been studied during the early stages of development by high resolution scanning electron microscopy (HRSEM). Specimen preparation techniques which involve removal of the cytoplasmic matrix permitted visualization of organelles and other subcellular structures within RPE cells in detail and in three dimensional (3-D) stereo HRSEM. Using this technique, we were able to examine changes in melanosome structures during development and demonstrate that pigmentation in the RPE was present by day 4 of development. RPE plasma cell membranes showed extensive folding of the apical portion of the membrane closest to the developing neural retina by day 9. Examination of RPE photoreceptor junction revealed photoreceptor inner segments by day 6 and an outer segment by day 9. Mitochondria in the RPE were found to contain tubular cristae only. The ultra-structure in 3-D of the Golgi apparatus, smooth and rough endoplasmic reticulum, lysosomes and nuclear chromatin of the RPE, and Bruch's layer was revealed by the HRSEM method.

Variations in mitochondrial ultrastructure and dynamics observed by high resolution scanning electron microscopy (HRSEM)

“…Some exceptions have been described, such as the tubular cristae found in adrenal gland cortex mitochondria (Wheatly, 1968). However, since our report of tubular cristae in rat heptocytes (Lea and Hollenberg, 19891, we have systematically used high resolution scanning electron microscopy to observe mitochondria in other tissues, including mouse intestinal cells (Kendall et al, 1991) and embryonic chick retinal pigment epithelium (Weiser et al, 1991), and have to date found that most have tubular cristae. Two exceptions, reported in the results, are found in rat brown fat and striated muscle.…”

Applications of Scanning Electron Microscopy Using Secondary and Backscattered Electron Signals in Neural Structure

“…To expose the subcellular structure on the freeze-cleavage surface of the cell, tissues should be immersed in diluted osmium solution for several days (usually 3–7 days) at 20°C in accordance with the original protocol of the osmium maceration method developed by Tanaka and colleagues (Tanaka and Naguro, 1981 ; Tanaka and Mitsushima, 1984 ). This conventional temperature condition is time-consuming, and the optimal period for adequate extraction of cytosol with diluted OsO 4 is dependent on the cell type (Kendall et al, 1991 ; Weiser et al, 1991 ; Ogata and Yamasaki, 1997 ; Koga and Ushiki, 2006 ; Koga et al, 2020 ). To improve the efficiency of the osmium maceration procedure, we examined the relationship between the reaction temperature and time of the maceration procedure and verified that temperatures higher than the conventional 20°C accelerated this process (Koga et al, 2020 ).…”