This experimental animal model of chemical mammary induced carcinogenesis is feasible and can be used in further experiments on the role of tumorigenic biomodulator substances.

Karyotypes and nuclear DNA content were studied in 11 species of the genus Corydoras from rivers in South America: C. sp. from Caripi river 2n = 60, C. cf. simulatus 2n = 62, C. simulatus 2n = 62, C. reticulafus 2n = 74, C. sp. from Galheiro river 2n = 84, C. aff. punctatus from Negro river 2n = 102, C.Javeolus 2n = 58, C. arcuatus 2n = 46, C . trilineatus 2n =46, C. schwartzi 2n = 46, and C. metae 2n=92. Extensive chromosome diversity and differences in DNA content were detected among species. The high variability in chromosome counts was not exclusively related to chromosomal structural rearrangements, but also to large changes in DNA content. Species could be grouped using their shared cytogenetic characteristics, suggesting that within the genus Corydoras different groups of species followed distinct evolutionary trends. Chromosomal rearrangements in Corydoras are, apparently, more frequent that morphological modifications, so cytogenetic data may be very useful for species delimitation and for the understanding of interrelationships among species.

SUMMARY -Cytogenetic studies involving conventional Giemsa stammg, Cbanding analysis and silver staining of NORs were performed on nine species belonging to six genera of the family Callichthyidae. The diploid number ranged from 2n = 44 to 2n = 100, the number of chromosomal pairs with NORs ranged from 1 to 4 and constitutive heterochromatin was mainly distributed in the centromeric and/or pericentromeric position of the chromosomes. The DNA content of erythrocytes from six species studied ranged from 1.18±0.07 to 2.77±0.22 pg/nucleus. The extensive variability in karyotypes and in nuclear DNA content detected are in accordance with the initial hypothesis that chromosome rearrangements and polyploidy have played a significant role in the evolutionary history of Callichthyidae.

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ROLL and SLN biopsy are emerging procedures that can be used simultaneously. They permit exact breast lesion excision, immediate local breast surgery, and intraoperative SLN biopsy in a single procedure. The combination of radioguided nonpalpable lesion localization and SLN biopsy is a suitable alternative to working up subclinical imaging-detected breast carcinomas.