Fast green should be used as a counterstain when using PAS staining procedures to demonstrate the presence of fungal organisms in tissue sections.
For a fast green counterstain, continue any of the PAS staining protocols with the following step:
- Fast green (0.02% solution) for 30 seconds
Expected result: The PAS-negative background elements will stain green.
Post staining procedure:
- After counterstain, tissue sections should be rinsed quickly in distilled water, as fast green is easily rinsed out of tissue sections.
- Following the quick water rinse, sections should be dehydrated with 95% alcohol, followed by 100% alcohols, cleared with xylene (or xylene substitute), and cover-slipped.