ArticlesWe analyzed cytogenetic end points in three populations of two species of wild rodents-Akodon montensis and Oryzomys nigripes-living in an industrial, an agricultural, and a preservation area at the Itajaí Valley, state of Santa Catarina, Brazil. Our purpose was to evaluate the performance of the following end points in the establishment of a genotoxic profile of each area: the polychromatic/normochromatic cell ratio; the mitotic index; the frequency of micronucleated cells both in the bone marrow and peripheral blood; and the frequency of cells with chromosome aberrations in the bone marrow. Preparations were obtained using conventional cytogenetic techniques. The results showed a) the role of the end points used as biomarkers in the early detection of genotoxic agents and in the identification of species and populations at higher risk; b) the difference in sensitivity of the species selected as bioindicators in relation to the cytogenetic end points analyzed; c) the need to use at least two sympatric species to detect the presence of genotoxins in each locality; and d) the need to use several end points when trying to establish a genotoxic profile of an area.

The induction of cytogenetic effects by inhalation of ethylene oxide was tested in bone marrow cells and primary spermatocytes at diakinesis-metaphase I cells from mouse after a single treatment (6 h/1 day) at 0, 200, 400 and 600 ppm, and multiple treatment (6 h/5 days/2 weeks) at 0, 200 and 400 ppm. Ethylene oxide induced chromosomal aberrations in both somatic as well as in germ cells of mice. In the single treatment the response observed for germ cells was not equivalent to that observed for somatic cells. In the latter there was a greater sensibility for bone marrow cells. With multiple treatment the effects on the chromosomes were equivalent in somatic and in germ cells.

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SUMMARYThis paper is the natural sequel to Madruga ef al. (Environmetrics, 547-56 (1994)) where data from literature were analysed. Here, three sets of experimental data were obtained at IPEN (Energetic and Nuclear Research Institute) from blood cultures from three patients with basal cellular carcinoma (1 male, age 68, and 2 females, ages 47 and 66), four healthy young subjects (2 males, ages 24 and 27, and 2 females, ages 20 and 27) and two older healthy subjects (1 male, age 50, and 1 female, age 46). These cultures were exposed in vitro to ' %o radiati0.n ranging from 0 to 500cGy. The frequencies of cells with one or two nuclei, with or without micronuclei (MN), are the responses. Models for mono-and binucleated cells were obtained. As suggested in Madruga et al., models for mononucleated are simpler than for binucleated cells. The novelty is that, based on the observed frequencies of micronucleated cells, we can generate credible intervals for unknown doses to which an individual was exposed. The purpose of this paper is to obtain calibration models that will be helpful in establishing credible intervals for unknown exposure doses of a given agent once we have the observed responses. The agent in our case is radiation and the responses are frequencies of mono-and binucleated cells with none, one and two or more micronuclei.The underline probability distribution of the vector of these frequencies, yi = ( y a , yil, yi2), for each dose i, and for each type of cell (mono-and binucleated), is the trinomial distribution with parameter vector xi = ( R~, nil, 7ri2), where 7rio + 7ril + 7ri2 = 1. Recall that yi0 is the frequency of cells with no MN, yil with one, and yi2 with two or more MN.The Bayesian approach is used taking the conjugate Dirichlet distribution as the prior. The CCC 1 180-4009/96/030325-07

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