Electron Microscopy 401 



method: 



1. Short fixation best: 0.25-0.5 hour. 



2. W^ash: 0.5 hour, in distilled water. 



3. Dehydrate and embed. 



Chromium-Osmium Fixation (dalton, 1955) 



solution: 



chromic acid, 4% 10.0 ml. 



sodium chloride, 3.4% 10.0 ml. 



Add osmic acid, 2% 20.0 ml. 



Can be used for longer period than some of others (18-24 hotirs) and 

 is good for tissue of high lipid content, but produces lower contrast 

 and increased diffictdty in obtaining thin sections. 



Lehmann and Mancuso's Fixative (1957) 



solutions: 

 Sol lU ion I: 



20% formalin 80.0 ml. 



acetone 16.0 ml. 



glacial acetic acid 0.5 ml. 



Solution II: 



2.5% osmic acid, aqueous 



method: 



1. Mix equal parts of solutions I and II. Fix for 30 minutes. This is 

 recommended for preservation of fibrous cytoplasmic structures; 

 penetrates rapidly and partially dehydrates. 



2. A subsequent treatment with chromic acid improves preservation 

 of some lipid and fibrous structures. After 20 minutes in original 

 fixative, add 10% chromic acid (2 ml. for every 5 ml. of above). 

 Leave for additional 20 minutes. 



3. Rinse in tap Avater: 15 minutes, dehydrate and embed. 



Embedding 



Only plastic embedding permits sections of 0.01 to 0.05 microns to be 

 cut. Glauert and Glauert {1958) recommend the epoxy resin Araldite, 

 saying that there is greater stability of resin, less shrinkage of tissue, 

 greater degree of variation possible in viscosity of mixture, less tend- 

 ency to form bubbles and greater hardness and imiformity of block 



