An Improved Staining Method for Electron Microscopy

A n a q u e o u s so lu t ion of u r a n y l ace t a t e was first e m p l o y e d as a n e l ec t ron s ta in by W a t s o n (1958). W e h a v e f o u n d t h a t this s ta in , a l t h o u g h f r e q u e n t l y effective, is capr ic ious . T h e s ta in m a y no t inc rease con t r a s t of a g iven spec imen , a n d m a y , in o the r ins tances , l eave u n d e s i r a b l e c o n t a m i n a t i o n on a s t a ined grid. W h i l e a n e x p e r i m e n t on d e h y d r a t i n g a g e n t s for e l ec t ron m i c r o s c o p y was in progress , u r a n y l ace t a t e was d issolved in m e t h a n o l in a n effort to a c c o m pl ish en bloc s ta in ing . I t was no t ed t h a t the u r a n y l a ce t a t e was ve ry soluble in m e t h a n o l in con t r a s t to its l im i t ed solubi l i ty in w a t e r a n d e thano l . A t the t ime of this obse rva t ion , it was felt t h a t a n inc reased c o n c e n t r a t i o n of u r a n y l ace t a t e m i g h t a id in s t a i n i ng some t issue c o m p o n e n t s or m i g h t s ta in t issue m o r e cons i s t en t ly t h a n the less c o n c e n t r a t e d a q u e o u s s tain.