INGREDIENTS OF CULTURE MEDIA 279 



treating red blood cells in blood grouping work by Kuhns and Bailey.^ Papain, 

 Difco is tested by and meets the National Formulary^ specification for papain 

 in that 0.1 gram digests 2.0 g. Bacto-Beef suspended in 50 ml. distilled water in 

 2 hours at 52 °C. Digestion with Papain may be carried out at an acid or alkaline 

 reaction, but is most active at pH 6.0-6.5 at 52°C. 



Asheshov,^ in a description of the preparation of bacteriological culture media 

 using papain, stated that this enzyme was relatively heat stable, being most active 

 at 60-70°C. Temperatures above 70°G. diminished the rate of digestion and 

 activity stopped at 80°C.; best digestion was obtained at pH 7.0 and at a tem- 

 perature of 60-65 °C. 



Papain, Difco is available in 500, 100 or 25 gram quantities. 



1 Am. J. Clin. Path., 20:1067:1950. ^ Can. J. Pub. Health, 32:468:1941. 



2 National Formulary, Eighth Edition:37i :i946. 



RENNIN, DIFCO (B287) 

 Rennin, Difco is a desiccated enzyme obtained from the glandular layer of 

 the stomach of the calf. It is used for the enzymatic coagulation of milk. Rennin, 

 Difco conforms in every respect to the National Formulary standards for this 

 material. 



Rennin, Difco is available in 500, 100 and 25 gram quantities. 



TRYPSIN, DIFCO, 1:250 (B152) 



Trypsin is used in the preparation of culture media to break down proteins 

 into simpler compounds which are more readily available for bacterial nutrition. 

 One part Trypsin, Difco, 1 : 250 will digest 250 parts of casein under the condi- 

 tions of the U.S. P. test for trypsin in pancreatin. Trypsin acts best at pH 7.8. 



Trypsin, Difco, 1 : 250 has been used in the digestion of sputum and other body 

 fluids in the isolation of Mycobacterium tuberculosis and other acid-fast bacilli. 

 Haynes,^ using this method in comparison with the Hanks flocculation method, 

 reported 11 per cent more positive specimens with trypsin concentration. The 

 technique is easily performed and requires a minimum of time. Trypsin, Difco, 

 1 : 250 has proven especially useful for treating red blood cells to increase their 

 specificity in hemagglutinating systems with anti-Rh sera and other blood group 

 antibodies. A method that has been employed successfully for treating the red 

 cells with the enzyme is described by Wheeler, Luhby and Scholl.-'^ Wiener and 

 Katz* also found Trypsin, Difco, 1 : 250 to be well suited for the preparation of 

 red cells for Rh studies. Such trypsin-modified cells are extremely sensitive indi- 

 cators for the detection of anti-Rh and other blood group antibodies. Agglutina- 

 tion reactions with such cells are specific, easily read, immediate and unlikely to 

 show failure of agglutination or prozones. The complete prepared reagent for 

 Rh testing is discussed on page 280 under Bacto-Trypsin 1% for Hemagglutina- 

 tion. Rosenthal, Dameleshak and Brukhardt^ used Trypsin, Difco, 1 : 250 in 

 treating red blood cells in their study of cells in acquired hemolytic anemia. 

 Morris^ used Trypsin, Difco, 1 : 250 in his study of hemagglutination by murine 

 encephalomyelitis virus. He reported that virus which failed to agglutinate human 

 group O erythrocytes at 20 °C. did so in the presence of trypsin. Additional uses 

 of Try'psin in the microbiological laboratory are given under Bacto-Trypsin page 

 280. 



Trypsin, Difco, 1 :250 is available in 500, 100 or 25 gram quantities. 



1 J. Lab. Clin. Med., 27:806:1942. ^ j, Immunol., 65:39:1950. 



2 Paper presented at a Symposium on Serology * j. inununol., 66:51 : 1951. 



of Blood Groups, American Association of Im- ^ Am. J. Clin. Path., 21:635:1951. 

 munologist, 1949. « J. Immunol., 68:97: 1952. 



