Anterograde tracing of retinal axons in the avian embryo with low molecular weight derivatives of biotin |
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| Authors: | W Halfter |
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| Affiliation: | 1. Département de Pharmacologie, Université de Montréal, 2900 Édouard Montpetit, Montreal, QC H3T 1J4, Canada;2. Renal Division, KCVA Medical Center, 4801 Linwood Blvd, Kansas City, MO 64128, USA;1. Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China;2. Tissue Engineering Laboratory, Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong, China;3. School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China;1. Department of Education and Research, Taipei City Hospital, No.145, Zhengzhou Rd., Datong Dist., Taipei, Taiwan;2. Department and Institute of Pharmacology, National Yang-Ming University, No. 155, Sec. 2, Linong Street, Taipei, 112, Taiwan;3. Institute of Traditional Medicine, National Yang-Ming University, No.155, Sec. 2, Linong Street, Taipei 112, Taiwan;4. National Yang-Ming University School of Medicine, No. 155, Sec. 2, Linong Street, Taipei 112, Taiwan;5. Department of Physical Therapy, College of Medicine, National Cheng Kung University,No. 1, University Road, Tainan City 701, Taiwan;6. Department of Ophthalmology, Taipei Veterans General Hospital, No. 201, Sec. 2, Shipai Rd., Beitou District, Taipei 112, Taiwan;1. Department of Ophthalmology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China;2. Tissue Engineering Laboratory, Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong, China |
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| Abstract: | Several reactive biotin esters were injected into the eyes of chick and quail embryos at various stages of development. Four of the biotin esters reacted with molecules of the eye tissue and were detected with light and electron microscopy in fluorescein isothiocyanate and peroxidase-avidin incubated sections and whole mounts. Intra and extracellular components of the lens, the vitreous body, and the retina were labeled to different degrees. Three of the biotin esters (biotin-N-hydroxysuccinimidester, biotin-epsilon-aminocaproic acid-N-hydroxysuccinimidester, and desthiobiotin-N-hydroxysuccinimidester) prominently marked the optic fiber layer in the retina and the biotin labels were transported along the optic pathway. The tracers were detected up to the growth cone of axons 24 to 36 hr after injection. Explants from biotin marked retinas were cultured on collagen or basal laminae. During culturing axons grew out from these explants into the substratum showing that labeled tissue and nerve fibers were viable. The development of the optic pathway at the chiasma of quail embryos was studied using the biotin/avidin tracing. The bulk of fibers emerging from the retina crossed as shown by double labeling of both optic nerves in a complex pattern of segregated and interdigitizing axon bundles at the chiasma toward the contralateral side of the brain. From stage 25 onward a minor ipsilateral projection was found. At the same developmental stage a few fibers traveled into the contralateral optic nerve and grew retrogradely toward the contralateral eye. The percentage of specimens having this retino-retinal projection increased during development from 53% (stage 24 to 27; E3.5-E5.5) to 89% (stage 29 to 35; E6-E8) and declined to 40% at late embryogenesis (stage 37 to 41; E9-E12). The fact that all retinal axons were found within predictable pathways with some of them running in the wrong direction suggests that nerve fiber pathways provide accurate positional information, but at best weak directional information for growing nerve fibers. |
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