title: AMg2+ -dependent class of thick filaments and correlated nuclear chromatin condensation in catfish photoreceptors.
abstract: Photoreceptor cells of excised catfish retinae show morphological differences when incubated in Ringer's solutions of varying ionic composition. Two striking changes were observed in photoreceptor cells incubated in a high Mg2+ (25 mM) Ringer's: (1) Thick filaments appeared in the cytoplasm of receptor terminals and myoids; (2) A pronounced condensation of nuclear chromatin occurred in certain nuclei in the outer nuclear layer. The filaments occurred in lattices or bundles. The bundles had a diameter of approximately 0.05--0.2 micrometer and had either tapered or frayed ends. They were observed with somewhat higher incidence in tissue incubated in a 25 mM Mg2+ Ringer's with EGTA added to chelate Ca2+. A common basis for the cytoplasmic and nuclear changes may lie in a redistribution of fibrous protiens brought about by the increased Mg2+ concentration.
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002843:Chromatin / Q000187:drug effects*; D005399:Fishes / Q000033:anatomy & histology*; D008274:Magnesium / Q000494:pharmacology*; D008854:Microscopy, Electron; D009218:Myosins / Q000378:metabolism; D009454:Neurofibrils / Q000648:ultrastructure*; D010786:Photoreceptor Cells / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D000199:Actins; D002843:Chromatin; D009218:Myosins; D008274:Magnesium