14/02/21 14:22:04.92
>>142
Low-pH treatment was also used in the ‘autoneuralization’ experiment15–
17 by Holtfreter in 1947, in which exposure to acidic medium
caused tissue-autonomous neural conversion of salamander animal
caps in vitro in the absence of Spemann’s organizer signals. Although
the mechanism has remained elusive, Holtfreter hypothesized that the
strong stimulus releases the animal cap cells fromsome intrinsic inhibitory
mechanisms that suppress fate conversion or, in his words, they
pass through ‘sublethal cytolysis’ (meaning stimulus-evoked lysis of
the cell’s inhibitory state)15,37.AlthoughHoltfreter’s study and ours differ
in the direction of fate conversion―orthograde differentiation and nuclear
reprogramming, respectively―these phenomena may share some
commonaspects, particularly with regard to sublethal stimulus-evoked
release from a static (conversion-resisting) state in the cell.