Methyl parathion (MP) is a commonly used organophosphorus insecticide, commercially available as Folidol 600. This chemical substance was tested to determine micronucleus (MN) frequencies in peripheral erythrocytes of the fish Cypnnus c e i o treated in vivo. The concentrations tested were 1.25,2.50,5.00 and 7.50 ppm. Fish were killed after 24 or 48 h of treatment. There was a significant increase in the frequency of micronuclei in the animals treated with 2.50 and 5.00 ppm after 24 h. At higher dosages this effect disap peared probably due to the increased cell lethality. The frequency of MN induction was lower at 48 than at 24 h after treatment. There was a dosedependent increase in MN frequency which, however, was significant only at the highest concentration (7.50 ppm) compared to control. RESUMENEl metil paratión (MP) es un insecticida organofosforado disponible comercialmente como Folidol 600. Esta substancia fue probada para determinar la frecuencia de micronúcleos (MN) en eritrocitos periféricos de peces Cyprinus ca+o tratados in vivo. Las concentraciones utilizadas fueron 1.25,2.50, 5.00 y 7.50 ppm. Los peces fueron sacrificados 24 y 48 h después del tratamiento. Se notó un aumento significativo en la frecuencia de micronúcleos en los animales tratados con 2.50 y 5.00 ppm y sacrificados después de 24 h. A concentraciones mayores este efecto desapareció probablemente debido al incremento de la letalidad celular. La frecuencia de inducción de MN fue menor después de 48 h que a 24 h del tratamiento. En la primera hubo una elevación en la frecuencia de MN dependiente de la concentración que, sin embargo, fue significativa cuando se comparó con el testigo solamente en la mayor (7.50 ppm).

Genetic toxicology testing has initially concentrated on induction of gene mutations and chromosome aberrations because these genetic changes are considered of great importance for it induces heritable diseases as well as the initiation of cancer. The classical studies on the genetic events underlying the development of tumors proved the importance of phenomenon termed "loss of heterozygosity". Gene conversion and, mitotic recombination are potent mechanisms leading to loss of heterozigosity. The most important is that the step of induced loss of heterozygosity may be an early or a late step in carcinogenesis. During early embryonic development, groups of cells (imaginal discs) are set apart. They proliferate mitotically during the larval development until they differentiate during metamorphosis into structures of the body of the adult fly (eyes, wings). If a genetic alteration occurs in one of these imaginal disc cells, this alteration will be present in all the descendant cells and will form a clone of mutant cells. The wts (warts) gene was identified based on its ability to act as a tumor suppressor in Drosophila. Deletion, recombination of this gene leads to the formation of cells clones that are rounded and greatly overgrown, and literally generate "warts" (tumors) on their body. This system test will be a useful additional genetic endpoint in toxicological studies in general, as well as in studies to evaluate carcinogenic agents.

ABSTRACT. The search for new and effective antitumor agents with fewer cytotoxic side effects on normal tissue has increasingly become important. Lapachol, a natural organic compound isolated from the lapacho tree (Tabebuia avellandedae), is chemically identified as belonging to the naphthoquinone group and is known for its antiinflammatory, analgesic and antibiotic properties, although there are questions about its effectiveness for treating neoplasic cells. We evaluated the antitumoral effects of lapachol by testing for clones of epithelial tumors in Drosophila melanogaster. Seventy-two-hour old larvae bred from wts/TM3, Sb 1 females and mwh/mwh males, were treated with different concentrations of lapachol (20, 40 and 60 µg/mL). Lapachol alone did not significantly increase the number of epithelial tumors. However, lapachol did significantly reduce the number of tumors provoked by doxorubicin.

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In this study the mutagenic, recombinagenic, carcinogenic and anticarcinogenic potential of orlistat was assessed using the somatic mutation and recombination test (SMART) and the epithelial tumor detection test (wts). The experiments were conducted on Drosophila melanogaster. In the assessment using SMART, larvae, descendants from the standard (ST) cross and the high bioactivation (HB) cross, were treated chronically with three orlistat concentrations. The results revealed a recombinagenic effect, associated with orlistat, in the descendants of the HB cross, at all three levels of concentration. Homologous recombination can function as a determinant at different stages of carcinogenesis. For verification, larvae from the wts test, descendants of the wts/TM3 virgin female and mwh/mwh male cross, were treated with the same three orlistat concentrations separately and in association with mitomicin C (0.1mM). The results did not, however, provide evidence that orlistat has carcinogenic potential nor was it associated with the reduction of tumors induced by mitomicin C in D. melanogaster.

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