CAPILLARY DIVER TECHNIQUE 393 



A 



/ = - X 0.11 X 0.204 - 

 R 



where {Lo) is the thickness of the oil film. 



For a T7 of 0.2-0.3 mm. in the diver {A, Fig. 134) , lO'^ ^l./hr. is 

 the maximum respiration intensity which can be determined. 



5. When the diameter of the diver is about 0.02-0.03 mm. greater 

 than the diameter of the cell, the change in equilibrium pressure 

 will usually be large enough even for weakly respiring cells. The 

 smallest glass divers which have been used have a diameter of 0.13 

 mm., and the smallest cells whose respiration can be measured 

 (about 10"^ /xl./hr.) will therefore be around 100 to 50 jx in diameter 

 for weak and strong respirations, respectively. 



(c) Methods Other Than for Respiration 



CHOLINESTERASE 



Linderstr0m-Lang and Glick (1938) developed a Cartesian-diver 

 method for the measurement of cholinesterase based on the principle 

 of the method utilizing the Warburg apparatus (Ammon, 1933). 

 This principle depends on the fact that if the enzymatic scission of 

 a choline ester proceeds in a bicarbonate buffer, the acid liberated 

 will cause an equivalent evolution of carbon dioxide which can be 

 measured gasometrically. Some investigators use a bicarbonate- 

 Ringer medium while others employ only a bicarbonate solution for 

 the estimation of the enzyme. The advantage of the presence of the 

 other salts which are in the Ringer solution is that they activate 

 the enzyme. By substitution of other ester substrates, the present 

 method can be applied to the measurement of lipolytic enzymes, 

 atropinesterase, etc. For a titrimetric method see page 310. 



Linder8tr0m-Lang and Glick Method for Cholinesterase 



SPECIAL REAGENTS 



Buffer Substrate Solution. Prepare 0.5% acetylcholine chloride in 

 bicarbonate-Ringer soln. 



Bicarbonate Ringer Solution (pH 7.4). Add 2 ml. of 1.2% potas- 

 sium chloride, 2 ml. 1.76% calcium chloride (CaCl2.6HoO), and 

 20 ml., 1.26% sodium bicarbonate to 100 ml. 0.9% sodium 



