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School of Molecular & Biomedical Science |
Grocott's Methenamine Silver (GMS) stain.For the detection of fungal elements in tissue sections. This is an essential stain and should be used whenever a fungal etiology is suspected. Mechanism: Chromic acid treated fungi possess aldehydes which will reduce the hexamine-silver mixture to produce a black deposit, i.e. an argentaffin reaction. Fungi stain black. Solutions.1. 5% aqueous chromic acid 2. 1% aqueous sodium bisulphite 3. 5% aqueous borax 4. 0.1% aqueous gold chloride 5. 2% aqueous sodium thiosulphate 6. Stock Methenamine Silver solution. Add 5 ml of 5% silver nitrate to 100 ml of 3% hexamine. A white precipitate will form which, on shaking, will dissolve. This solution will keep from 1-2 months at 4oC. 7. Working silver solution (filter before use). Stock methenamine silver solution 25 ml Distilled water 25 ml 5% Borax 1-2 ml Method:1. Take sections to water. 2. Oxidize in 5% chromic acid for 1 hour. 3. Wash in running tap water for 10 minutes. 4. Treat with sodium bisulphite for 1 minute to remove any residual chromic acid. 5. Wash in tap water then distilled water. 6. Place section in the working silver solution at 60oC in a water bath. 7. Rinse in distilled water. 8. Tone in 0.1% gold chloride for 5 minutes. 9. Rinse in distilled water. 10. Remove unreduced silver by treating with 2% sodium thiosulphate for 1-2 minutes. 11. Wash thoroughly. 12. Counterstain with Light green. 13. Dehydrate clear and mount in D.P.X. Safety Precautions: silver nitrate is toxic and skin contact should be avoided; methenamine is a flammable solid and an irritant; chromic acid is also toxic. Therefore, when preparing any of the above solutions protective clothing should be worn, including gloves, aprons and protective glasses. Any spill should be mopped up immediately with water.
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