16. CHEMICAL ALTERATION OF GROWTH 

 AND DIFFERENTIATION 



PURPOSE: The study of the effect of a specific chemical, Lithium Chloride, on early- 

 amphibian development. 



MATERIALS: 



Biological : Early gastrula stages of Anura (stage #9) and Urodela (stage #10). 



Technical : Various solutions as follows:* 



1. Balanced lithium solution (Hall, 1942): 



Lithium chloride 1 . 1 2 gr. 



Lithium sulphate 1.5 gr. 



Calcium chloride 0. 1 5 gr. 



Potassium biphosphate 0. 04 gr. 



Sodium bicarbonate 0. 5 gr. 



Glass dist. water 1000. cc. 



2. Unbalanced lithium solution (Hall, 1942): 



Lithium chloride 1 . 09 gr. 



Lithium sulphate 1.5 gr. 



Sodium bicarbonate 0. 1 1 gr. 



Glass dist. water 1000. cc. 



3. Unbalanced sodium, solution (Hall, 1942): 



Sodium chloride 1.5 gr. 



Sodium sulphate 1. 97 gr. 



Sodium bicarbonate 0. 25 gr. 



Glass dist. water 1000. cc. 



4. Pure lithium chloride solutions: 



(a) 1. 9 grams LiCl in 1, 000 cc. of glass distilled water. 



(b) 1. 9 grams of LiCl in 250 cc. of glass distilled water. 



5. Control solutions: 



For Anura: Standard (Holtfreter ' s) solution 

 For Urodela: Urodele Growing Solution 



METHOD: 



Precautions : 



1. Glass distilled water should be used, if possible, to make up the experimental 

 solutions to avoid even the minutest traces of metallic or other ions. 



2. In returning the exposed (experimental) gastrulae to the normal medium, it 

 is wise to pass them through several changes to remove all adherent Lithium. 



Control : This consists of similar gastrula, similarly denuded of their membranes, 

 but kept in control media. Conditions of temperature, light, etc. must be iden- 

 tical. 



Procedure : 



1. Prepare 12 finger bowls, each with 50 cc. of solution as follows: Two finger 

 bowls (a and b) each, of solutions I, 2, 3, 4, and the appropriate control 5. 

 Cover them and keep them at a cool temperature. (About 18 C. for Anura or 

 14°C. for Urodela. ) 



* Note: Effects similar to those produced by Lithium Chloride may be produced by unbalanced solutions of NaCl, NaOH, ethyl 

 alcohol, NH. OH, MgCl,, Mg(NO,)2, ether, chloroform, and by x -rays. 



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