Further Investigations on the Mutagenic Activity of Acridines (XXXIII–LI)

Abstract

Continuing his work on acridines (cf. D'AMATO 1950 b. c; 1951 a), the author has studied the cytological effect of other 19 compounds on the onion root meristems, following similar methods to those of his previous investigations (room temperature; ordinary conditions of diurnal laboratory illumination; colorless glass jars and tap-water solutions). In figs. I and II the structural formulae of the 19 compounds, grouped in the two categories of « mutagenic » and « non-mutagenic », have been reported. The general picture of the chromosome changes found in the present investigation is quite similar to that induced by the acridines studied previously by the author (D'AMATO 1950 b, c; 1951 a). Apart from the various types of chromosome stickiness and of chromosome breakage and reunion, other cases of the following cytological phenomena were observed: metaphasas with strongly « eroded » chromosomes and « pulverized » anaphases; persistence of chromosome stickiness in some « recovery » experiments; i. e. during the « structural effect » following the mitosis-free period; occurrence of « pseudochiasmata » in a complete absence of stickiness. This condition makes our first suggestion still more likely that the « pseudochiasma » be a true aberration due to breakage and reunion, probably resulting from the fusion in one point of 4 broken chromatid ends (D'AMATO 1950 b, c; and later). As to the effect of acridines on mitosis, all of them appear as typical « prephophase inhibitors of mitosis », the characteristic effect of which on dividing cells is « prophase poisoning » (cf. D'AMATO 1950 a). A general Discussion follows concerning both the « primary » and « secondary » effect, as well as the connexion between chemical constitution and mutagenic activity. Comparing our results with the actually available data on antibacterial acridines (cf. ALBERT 1951) a parallel seems to exist between antibacterial and mutagenic activity for many, but not all, of the acridines found mutagenic in Allium. The reasons for preferring the term « mutagenic » to others in defining chromosome-breaking agents are presented. The actually available data on the mutagenic and anti-mitotic activity of acridines in other organisms are also briefly considered.