Section 21
Chapter 20,689

Carcinogens on regeneration. Effects of N-methyl-N'-nitro-N-nitrosoguanidine and 4-nitroquinoline-1-oxide on limb regeneration in adult newts

Tsonis, P.A.; Eguchi, G.

Differentiation; Research in Biological Diversity 20(1): 52-60


ISSN/ISBN: 0301-4681
PMID: 6796448
Accession: 020688254

A microcrystal (ca circa 5 .mu.g) of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or 4-nitroquinoline-1-oxide (4NQO) was directly administered to the regeneration blastema on day 7 after amputation of a forelimb in the newt to analyze the effect of such potent carcinogenic substances on regeneration cells. Although neither MNNG nor 4NQO arrested regeneration completely, they caused great retardation of the regeneration cone formation followed by various abnormalities in the bony structures. Abnormal regenerants could be classified into the following 4 categories: complete absence of both ulna and radius, subregeneration or superregeneration of carpals and digits, multiple disorganization of skeletal elements and arrest of regeneration at the stage of regeneration cone. The polarity of regenerants developed after application of MNNG or 4NQO was very often shifted, during which the regeneration cone was always formed from the site where a microcrystal of the carcinogens was administered. The secondary regeneration initiated by reamputation of the regenerating limb, which had received the carcinogens at the early blastema stage, proceeded in the same way as observed in the case of a simple amputation. This suggested local and temporal effects of the carcinogens applied. Nevertheless, tumor formation has not been induced in the newt limb so far. MNNG and 4NQO apparently only alter behavior of the newt regeneration cells without excerting their carcinogenic effects on them, and newt cells appear highly resistant and stable against the above-mentioned carcinogens.

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