ULTRASTRUCTURAL-STUDY OF AXONAL CYTOSKELETONS IN THE OPTIC-NERVE DAMAGED BY ACUTELY ELEVATED INTRAOCULAR-PRESSURE USING THE QUICK-FREEZING AND DEEP-ETCHING TECHNIQUE

The aim of this study was to examine the ultrastructure of axonal cyto skeletons in guinea pig optic nerve damage induced by acutely elevated intraocular pressure (IOP) employing the quick-freezing and deep-etch ing method. An IOP of 60 mm Hg was maintained for 4 h. The unmyelinate d axoplasm of the optic nerve at the normal IOP was filled with longit udinally oriented neurofilaments and bundled microtubules, which were cross-linked by numerous cross-bridges. Membranous organelles, such as mitochondria and vesicles, were scattered in the axoplasm. These orga nelles were similarly interconnected with microtubules or neurofilamen ts by the cross-bridges. The unmyelinated axoplasm of the optic nerve following acutely elevated IOP was shown to include intraaxonal collec tions of various membranous organelles and reduction of microtubules a nd neurofilaments. The crossbridges linking microtubules, neurofilamen ts and membranous organelles in such axoplasm appeared to be dramatica lly reduced in number. Thus, it is suggested that the ultrastructural changes of axonal cytoskeletons in some optic nerves following elevate d IOP might include the reduction of microtubules, neurofilaments and their associated cross-bridges.