Electron microscopic studies of the endocytotic process of cationized ferritin in cultured human retinal pigment epithelial cells |
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Authors: | Kiyoshi Akeo Yasuhiko Tanaka Tatsuji Fujiwara |
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Institution: | (1) Department of Ophthalmology, School of Medicine, Keio University, Shinano-machi 35, Shinjuku-ku, 160 Tokyo, Japan;(2) Electron Microscopy Laboratory, Keio University, Shinano-machi 35, Shinjuku-ku, 160 Tokyo, Japan |
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Abstract: | Summary The endocytotic process in cultured human RPE cells was observed after 1 min, 20 min, and 2 h incubation with cationized ferritin.
Within 1 min the ferritin particles were seen to attach to the cell membrane, especially between microvilli. Uncoated and
coated pits could be recognized on the cell membranes, and uncoated and coated endocytotic vesicles were found in the cytoplasm
after 20 min of incubation. These vesicles were surrounded by abundant microfilaments and had no visible membranes. Loss of
membrane may be an initial step in the process of developing into the irregular clumps of ferritin particles found inside
the plasma membrane. With time, more irregular clumps of ferritin, smaller than the particles introduced during incubation,
appeared just beneath the cell membrane. Lysosomes were adjacent to the clumps of ferritin particles associated with microtobules
and finally degraded these particles. The phagolysosomes containing many particles were surrounded by many microtubules. Small
ferritin particles surrounded but had not entered the rough endoplasmic reticulums, and no particles were seen either around
or in the Golgi apparatus.
Presented at the 7th International Congress of Eye Research, Nagoya, Japan, 27 September 1986. |
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Keywords: | human retinal pigment epithelium cell culture endocytotic process cationized ferritin |
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