EFFECT OF CENTR I F UGAT 1 ON ON DEVELOPMENT 



195 



B. RESISTANCE OF EMBRYONIC STAGES TO CENTR IFUGATION DAMAGE 



There are two aspects of this study: (A) The ability of various stages to survive 

 centrifugation damage and (B) The variety of ahnormallties produced hy standard centrifu- 

 gation at different stages of development. 



The stages that are to he used are: Uterine eggs, recently fertilized ("but uncleaved) 

 eggs; hlastulae; and gaatrulae. With the large International Centrifuge the approximate 

 speed to he used should range from about 1500 to 3000 R.P.M., but the data should be 

 recorded in terms of the value times gravity (see formula on preceding page). The dura- 

 tion should be from 1 to 10 minutes, the shorter interval at the higher speeds. (For ex- 

 ample, a speed of 180 times gravity for 10 minutes to 1800 times gravity for 1 minute 

 might be the extremes tested. ) If but one speed and time are used, the lower force for 

 the longer interval is recommended for all stages. 



It has been suggested (Brachet) that if the eggs are centrifuged immediately after 

 fertilization, the eggs that do not develop fail because all of the ribonucleic acid is 

 carried to one pole, opposite that of the yolk. Centrifugation at later stages (e.g., 

 blastula) may produce trlploid embryos because of the excessive concentration of ribo- 

 nucleic acid in specific areas. 



The effect of fertilization can be tested very simply by stripping several hundred 

 eggs from an ovulating female Into a concentrated sperm suspension. The female is then 

 to be opened and the uteri tied off above and below, eind removed as a double sack full of 

 eggs. The two uterine sacks may then be separated and placed directly into a centrifuge 

 tube, previously coated (internally) with Nujol (paraffin oil). In a balancing tube, 

 place the fertilized eggs, and centrifuge simultaneously. All eggs will be from the same 

 female and the only difference will be that one group are fertilized. The unfertilized 

 eggs should be fertilized Immediately upon removal from the centrifuge, by cutting open 

 the uteri and stripping the eggs into a concentrated sperm suspension. 



The later stages of development, such as the blastula and gastrula, are to be cen- 

 trifuged within their Jelly membranes and in the Standard Solution. 



Eecord the data in the following tables: 



TABLE I: CENTRIFUGATION. 



_X GRAVITY 



