The karyotypes of 94 species of Indian ants were examined. Their chromosome numbers range almost continuously between n=5 and 38, though the frequency distribution is bimodal with a remarkable antimode at n=11 and two modal points at n=10 and 15. Based on this bimodal distribution, Indian ants were classified into two groups: Lower-numbered species (n<_11) and higher-numbered species (n>11), the former being characterized by metacentric-rich karyotypes, and acrocentrics predominate in the latter.The three major subfamilies (Ponerinae, Myrmicinae, and Formicinae) showed a highly divergent distribution in chromosome number, ranging between n= 7-38, 6-35, and 8-27, respectively, suggesting a convergence in karyotype evolution of each subfamily, Another three subfamilies, of which only a few species were examined, had moderate or lower numbers, i.e., n=5-14 in Dolichoderinae, n=14 in Cerapachyinae, and n=12 in Dorylinae. We found four Robertsonian polymorphisms, two pericentric inversion polymorphisms, and four reciprocal translocations, three of which were fixed. Robertsonian polymorphisms were found only in higher-numbered species, while translocations were restricted to lower-numbered species. A possible biological significance for this nonrandom distribution of rearrangements is discussed with reference to karyotype evolution in ants.
The modulatory effect of vitamin C (Vit C) on the mutagenic effect of the antineoplastic drug cyclophosphamide (CP) was assessed in the in vivo micronucleus test in Swiss mice. Simultaneous oral administration of Vit C with i.p. administration of CP was found to decrease the frequency of micronucleated polychromatic erythrocytes elevated by CP. Vit C exhibited a significant antimutagenic effect over a wide dose range (1.56-200 mg/kg). The dose-response relationship was highly significant. These results demonstrated the ability of the in vivo micronucleus test to detect in vivo modulation of CP mutagenicity by Vit C. Our earlier results and those from other laboratories also indicate that this model system is suitable for primary in vivo screening of modulation of mutagenesis.
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