The mechanism accounted for the silver staining "fast techniques" development and its histochemical meaning. II. The...

Results obtained on filter paper strips models show that some protein and fatty acids become argentophil as an effect of a previously binding ferric ion although, in this instance, the silver staining can only be accomplished by using a silver diamine solution, since a silver nitrate solution is not effective. However, if the filter paper model is previously treated by a "multidentate ligand" before the silver nitrate solution treatment becomes able in doing the silver staining. This result shows that the binding between Fe3+ and Ag+ can be done if a suitable negatively charged "multidentate ligand" has been connected between them. The following "multidentate ligands" were tested: thiocarbohydrazide, carbohydrazide, and hexamethylenetetramine: ammonia was also tested, as an attempt to disclose if it is able to act as a "multidentate ligand". The semicarbazide effect was analysed and compared with the "ligands". It was found, either on filter paper strip models or on histological sections, that every "multidentate ligand", as well as ammonia, are effective in producing silver staining whereas semicarbazide is devoid of effect. The "ligands" effectiveness depends upon the solution pH, in the same manner that is does occur when the silver diamine "fast technique" is used on tissue sections. Histophotometric measures, taken on tissue sections, show that the silver staining afforded by the silver diamine "fast technique" is similar to that displayed by the "multidentate ligand" plus a silver nitrate solution treatment.(ABSTRACT TRUNCATED AT 250 WORDS)