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Unformatted text preview: © 2002 American College of Veterinary Ophthalmologists Veterinary Ophthalmology (2002) 5 , 3, 193–196 Blackwel Science, Ltd SHORT COMMUNICATION O O4 STAINING DURING EYE DEVELOPMENT IN RATS Examination of the rat eye at the early stage of development with osmium tetroxide staining Satoru Inagaki* and Tadao Kotani† * Department of Safety Assessment, Development Research Laboratories, Banyu Pharmaceutical Co., Ltd. 810 Nishijo, Menuma, Osato, Saitama, 360–0214, Japan, † Department of Veterinary Surgery I, School of Veterinary Medicine, Rakuno Gakuen University 582 Bunkyodai-Midorimachi, Ebetsu, Hokkaido, 069–8501, Japan Abstract This communication describes the benefit of osmium tetroxide (OsO 4 ) staining on the examination of the eye during the early stage of organogenesis of rat embryos. The embryos were obtained by laparotomy on embryonic day 12 (ED 12) and were stained with OsO 4 for examination of the ocular tissues with a binocular stereo-microscope, light microscope and scanning electron microscope. At the binocular stereo-microscopic level, the invaginated lens placode, lens pit and optic cup were clearly distinguished. The osmium-stained lens placode and the optic cup were light brown and dark brown in color, respectively. Light microscopic examination revealed that OsO 4 postfixation could provide superior paraffin-embedded embryonic sections. Scanning electron microscopic examination revealed the lens pit as a round opening between the lateral nasal prominence and maxillary prominence. Thus, a rapid technique by which the ocular tissues of rat embryos can be examined under a binocular stereo-microscope was developed. This OsO 4 staining method will provide a useful tool for research on organogenesis and ocular development. Key Words: lens placode, ocular morphology, optic system, optic vesicle, osmium tetroxide, rat embryo Address communications to: S. Inagaki Tel.: +81 (48) 588–8416 Fax: +81 (48) 588–4695 e-mail: firstname.lastname@example.org INTRODUCTION During formation of the eye, tissue development is synchro- nized in time and space to form an optically functional organ system. 1 Organogenesis of the eye begins with formation of the optic sulcus and later optic vesicle, which precedes formation of the optic cup and lens pit. In rat embryos, the optic cup and lens pit are first discernible on embryonic day 12 (ED 12). 2 The structural details of the early development of the eye have been described in the human, 3 dog, 4 mouse, 5 hamster, 6 chick 7 and rat. 2 Scanning electron microscopy has also been used to study the morphology of the optic fissure in rat embryos. 8 In these reports, serial sections made from paraffin-embedded eyes for microscopic examination do not easily allow us to reconstruct the ocular tissues into the 3-dimensional figures. The unstained surface ectoderm and neural ectoderm of the developing eye are difficult to dis- tinguish by the use of a binocular stereo-microscope. The developing ocular tissues are small and translucent since the...
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