400 Special Procedures III (chap. 24) 



Isotonic buffered osmic acid (working solution): 



solution A 10.0 nil. 



solution B 3.4 ml. 



O.IN HCl 11.0 ml. 



distilled water 50.0 ml. 



Adjust to pH 7.4 with O.IN HCl 



Add osmic acid 0.5 gm. 



Store in brown-glass stoppered bottle in refrigerator. 



method: 



1. Cut tissue in small fragments, 5 mm.; fix immediately. In spite of 

 the small size only the outer cells will be well fixed. Fix 30 minutes 

 to 4 hours minimum = maximum interval), 0-5 °C. 



2. Wash with Ringer's solution: 1 hour, changing every 15 minutes. 



3. Dehydrate and embed. 



Permanganate Fixation (luft, 1956) 



solutions: 



Stock solution: 



potassium permanganate 1.2 gm. 



distilled water 100.0 ml. 



Store in refrigerator in ^vell-filled glass-stoppered bottle. 



Working soltuion: 



Equal volumes of potassium permanganate stock and Palade's veronal 

 acetate buffer (above), pH 7.4-7.6, produces a final concentration of 

 0.6% potassium permanganate. 



method: 



1. Cool fixative in cracked ice. Fix 1-2 mm. pieces at 0°C: 15 min- 

 utes to 12 hours. 



2. Rinse several minutes in cold (0-5°C) 25% ethyl alcohol, allow to 

 warm to room temperature in fresh 25% alcohol (15-20 minutes) 



3. Dehydrate and embed. 



Chromium Fixation (low, 1955; low and freeman, 1956) 



Good for reticulum. 



solution: 



chromic acid 3.0 gm. 



formalin 1 0.0 ml. 



sodium chloride 0.85 gm. 



pH about 3.2 



