title: Identification of sulfur groups in the outer plexiform layer of the newt retina.
abstract: The staining of newt photoreceptor synaptic vesicles with the zinc iodide-osmium (ZIO) method can be abolished by prior incubation in amphibian Ringer's containing 0.1 M-N-ethyl maleimide which specifically blocks -SH groups. The existence of high concentrations of sulfur groups in the outer plexiform layer of the newt retina has been further demonstrated with mercury orange and a newly synthesized fluorescent thiol probe, DACM. The reason why such high concentrations of -SH groups are present within photoreceptor synaptic vesicles is unclear, however, it is possible that ZIO stains the photoreceptor neurotransmitter itself.
mesh_terms: D000818:Animals; D008301:Maleimides; D008854:Microscopy, Electron; D009673:Notophthalmus viridescens; D009992:Osmium; D009993:Osmium Tetroxide; D010663:Phenylmercury Compounds; D010786:Photoreceptor Cells / Q000032:analysis / Q000648:ultrastructure; D012160:Retina / Q000032:analysis* / Q000648:ultrastructure; D013194:Staining and Labeling; D013438:Sulfhydryl Compounds / Q000032:analysis*; D013439:Sulfhydryl Reagents; D013572:Synaptic Vesicles / Q000032:analysis / Q000648:ultrastructure; D015032:Zinc; D017967:Zinc Compounds
chemical_list: D008301:Maleimides; D010663:Phenylmercury Compounds; D013438:Sulfhydryl Compounds; D013439:Sulfhydryl Reagents; D017967:Zinc Compounds; D009992:Osmium; C035252:osmium zinc iodide; C019347:N-(7-dimethylamino-4-methylcoumarinyl)maleimide; D015032:Zinc; D009993:Osmium Tetroxide; C031504:mercury orange