From: J.F. ® 03/07/2002 08:39:27 Subject: re: Metal Poisoning. post id: 85632 These compounds came from the chemical agents used to prepare the brain sections. The most common tissue staining system is "Haematoxylin and Eosin" (H+E). Haematoxylin can be made up using iron salts as a "mordant" (technical thing; it helps the dye stick to intracellular structures) but usually aluminium is used as a "mordant", as aluminium H+E allows lab staff to use acid to do the "differentiation" step (another technical thing; roughly = selective fading of the Haematoxylin, which helps small differences between intracellular structures in stain - retaining power to show up microscopically). Thus, a tissue slice stained with H+E for routine microscopy will contain aluminium. It may not have contained aluminium while alive. Later studies used other stains + AFAIK they found no excess of aluminium in specimens from people who had died of Alzheimer's disease. I agree that transition metals are often toxic, but we need traces of many (not lead, for example). Anyhow, most things are toxic at some level... even water. I think some toxicities of transition metals occur when the "wrong" metal ion binds to an enzyme or other metabolic system, instead of the chemically - similar "right" metal ion. Examples: lead instead of iron, cadmium instead of calcium (I think). This forum is un-moderated. The views and opinions expressed are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages.