PROTEIN UPTAKE IN AMOEBAE 6x1 



CHANGES WITHIN VESICLES AFTER UPTAKE OF FERRITIN OR METHYL 



FERRITIN 



The second question asked at the beginnnig of this work was: what 

 happens to the pinocytosis vesicle, and to its contents, after it is taken into 

 the cell ? Amoebae bearing bound ferritin or methyl ferritin were warmed 

 to room temperature in the wash medium at pH 4. The cells began to 

 change shape, to move, and the orange-stained coat substance was seen 

 to collect in smaller regions of the surface, most commonly in the tail 

 region. Pinocvtosis occurred rapidly. The cells were kept at neutral pH, 



'% ■ 



■^ 

 J4 



Fig. 6. 



and individual specimens were fixed at intervals from i hr. to 48 hr. after 

 uptake. When sections were examined by electron microscopy, a complex 

 sequence of morphological changes was found to have occurred. Five 

 features of the process may be described in summary form : 



I, Within an hour after a pinocytosis vesicle is formed, ferritin is 

 released from the carrier substance, and collects in irregular masses, 

 usually in the centre of the vesicle. Methyl ferritin, by contrast, remains 

 bound to the carrier substance for the entire 48 hr. period of observation. 

 This difference, because it parallels the effects already described in washing 

 experiments at different pH values, is thought to indicate a rise in pH 

 within the \esicle. 



