86 Specialized Embedding Technics (chap. 8) 



References: Manufacturing Chemists' Association (1957) and Simonds 

 et al. (1949). 



Kuhn and Lutz (1958) Method 



Advantages of the method. Polyester embedding supports hard struc- 

 tures adjacent to soft ones, is faster than the nitrocellulose method and 

 can be sectioned on a rotary microtome. Size of blocks should be 5-16 

 mm. in diameter and can be sectioned at 5 to 50 microns. The method 

 uses a nonrigid plasticized resin prepared by Natcol Laboratories [Route 

 2, Box 515 , Redlands, California), known as C.M.E. Tissue Support 

 Resin (soft, medium and firm), plus a catalyst (#1) and a promoter 

 (#2) also supplied by the company. 



PROCEDURE 



1. Dehydrate tissue in ethyl or isopropyl alcohol. 



2. Remove alcohol in anhydrous ether: 2-4 hours. 



3. (a) Transfer soft specimens directly to resin with one drop of catalyst 

 (#1) added for each 30 ml. of resin. Keep specimen submerged. 

 Exhaust the ether from the specimen in a vacuum chamber using 

 reduced atmospheric pressure (10-15 in. Hg); 1-4 hours. 



(b) For hard or dense tissues prepare 10-20 ml. of a mixture of the 

 resin and styrene monomer (1:1), add one drop of the catalyst (#1). 

 Submerge tissue. Place in vacuum chamber with reduced pressure: 

 1-4 hours. In stubborn cases, alternate the reduced pressure with 

 positive pressure (20 Ib/sq. in.) at 15 to 20 miniue intervals. Follow 

 this treatment with undiluted resin as in Sa: 1 hour, preferably in 

 vacuum. 



4. For embedding, use gelatine capsules :;^000 and veterinary capsules 

 4^10 for larger specimens. 



5. Remove tissue from resin and allow excess to drain off. 



6. Warm 30 ml. of resin in a beaker set in a water bath at 65 °C. Have 

 a stirring rod warming in the resin. Add three drops of catalyst (#1) 

 and four drops of promoter (#2) for a reasonably fast curing solu- 

 tion. If a thinned preparation (as in step 3^) was used, add four 

 drops of catalyst, as well as of promoter, to the embedding resin. Stir 

 rapidly until all mixing lines have disappeared. 



7. When resin is thoroughly mixed, fill capsules about half full. Place 

 tissue in position and complete filling. If the tissue floats push it back 

 into place imtil the resin cures enough to prevent floating. If this 

 takes longer than 5 minutes, warm capsules with a lamp, but only 

 until the resin has reached curing stage (obviously begins to thicken). 



