Volume 52 (12): 1619-1625, 2004 Copyright ©The Histochemical Society, Inc. Immersion Autometallography : Histochemical In Situ Capturing of Zinc Ions in Catalytic ZincSulfur Nanocrystals
Department of Neurobiology, Institute of Anatomy, University of Aarhus, Aarhus, Denmark Correspondence to: Prof. Gorm Danscher, Dept. of Neurobiology, Inst. of Anatomy, University of Aarhus, DK-8000 Aarhus C, Denmark. E-mail: gd{at}neuro.au.dk In the mid-1980s, two versions of Timm's original immersion sulfide silver method were published. The authors used immersion of tissue in a sulfide solution as opposed to Timm, who used immersion of tissue blocks in hydrogen sulfide-bubbled alcohol. The autometallography staining resulting from the "sulfide only immersion" was not particularly impressive, but the significance of this return to an old approach became obvious when Wenzel and co-workers presented their approach in connection with introduction by the Palmiter group of zinc transporter 3 (ZnT3). The Wenzel/Palmiter pictures are the first high-resolution, high-quality pictures taken from tissues in which free and loosely bound zinc ions have been captured in zincsulfur nanocrystals by immersion. The trick was to place formalin-fixed blocks of mouse brains in a solution containing 3% glutaraldehyde and 0.1% sodium sulfide, ingredients used for transcardial perfusion in the zinc-specific NeoTimm method. That the NeoTimm technique results in silver enhancement of zincsulfur nanocrystals has been proved by proton-induced X-ray multielement analyses (PIXE) and in vivo chelation with diethyldithiocarbamate (DEDTC). The aims of the present study were (a) to make the immersion-based capturing of zinc ions in zincsulfur nanocrystals work directly on sections and slices of fixed brain tissue, (b) to work out protocols that ensure zinc specificity and optimal quality of the staining, (c) to apply "immersion autometallography" (iZnSAMG) to other tissues that contain zinc-enriched (ZEN) cells, and (d) to make the immersion approach work on unfixed fresh tissue. (J Histochem Cytochem 52:16191625, 2004)
Key Words: immersion autometallography (iZnSAMG) zinc ions brain zinc-enriched (ZEN) ZEN terminals NeoTimm
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