sufficiently high concentrations of cationic ( n-alkyl trimethylammonium ) or neutral ( n-alkanols ) amphipathic agents reduced the amplitude of maximum k contractures of frog toe muscles , an effect which was antagonized by reduced temperature , by the presence of perchlorate anions , or ( to a lesser extent ) by an increased concentration of divalent cations .
C0007447
cationic
C0007448
divalent cations