The Pearson Silver-Gelatin Method for Light Microscopy of 0.5-2 μ Plastic Sections

Sections 0.5-2 μ thick of liver, kidney, lung, cartilage and brown fat embedded in Maraglas, Araldrite, Epon and Spurr's medium were deplasticized in alcoholic NaOH for 15 min. Following several alcohol rinses, the tissues were exposed to 2% AgNO3 at 50 C for 1-2 hr, and then developed in a solution containing 3% gelatin, 40 ml; 2% AgNO3, 10 ml; and 1% hydroquinone, 4 ml. Sections were then toned in 1% gold chloride (several dips), washed in water for 5 min and dipped in 2% oxalic acid. After a brief rinse in water the sections were placed in 5% Na2S2O3 for 5 min, washed in water for 5 min, dehydrated in alcohol, cleared and covered. Compared to similar sections retained in plastic and deplasticized sections stained in the routine manner with 1% toluidine blue, silver impregnated sections of all tissue free of plastic, displayed greater clarity of cellular detail. Especially clear were mitochondria of liver and brown fat cells. Type II cells of the lungs were exceptionally prominent as were podocyte foot processes of the kidney.