Detection of the genotoxicity of air pollutants in and around the city of São Paulo (Brazil) with the Tradescantia-micronucleus (Trad-MCN) assay

Tradescantia pallida cv. purpurea, a popular garden plant in Brazil, was used for the Tradescantia micronucleus (Trad-MCN) assay. In situ monitoring of the genotoxicity of air pollutants was carried out by sentinel approach, using the plant grown in the field or using the plants in pots which were carried to the monitoring sites. Two highly polluted sites, in São Paulo city (Cerqueira Cesar and Congonhas) and two rural sites (the cities of Pirassununga, 200 km and Caucaia do Alto, 50 km from São Paulo, respectively) were chosen for this study, in order to determine the gradient difference of the air pollution levels. Sentinel plants in Congonhas site presented the highest frequency of micronuclei (4.4%), in comparison with 2.2 and 2.3% found in plants from Pirassununga and Cerqueira Cesar sites, respectively (Kruskal-Wallis; P<0.020). Significant increases (F test; P<0.0001) in the frequency of micronuclei were observed in plants exposed in the polluted urban sites (Cerqueira Cesar: 5.7%; Congonhas: 7.1% and Caucaia do Alto: 2.3%). The increase in the frequency of micronuclei observed indicates the potential risk of mutagenicity in presence of high concentrations of pollutants.

Correlation of thyrotropin secretion with morphometric data of secretory granules from individual thyrotropes. An ultrastructural study on rat cells identified by reverse hemolytic plaque assay

We investigated the existence of functional subpopulations of thyrotropes in pituitary glands of male rats, also seeking to establish any correlation of thyrotropin secretion with morphometric data of secretory granules. Pituitary cells secreting thyrotropin were detected using a reverse hemolytic plaque assay. Population analysis of the plaque sizes (TSH secreted) of individual thyrotropes in control cultures from male rats revealed a unimodal frequency distribution. TRH added to the medium resulted in a shift to a bimodal distribution of sizes, consisting of small and large modes, but did not alter the fraction of plaque-forming thyrotropes. The plaque size of control cultures was the same as that of the fraction of TRH-stimulated thyrotropes forming small plaques. Because the extent of hemolysis is related to the amount of thyrotropin secreted by each individual thyrotrope, these results suggest that: a) all thyrotropes secrete thyrotropin even in the absence of a stimulatory dose of TRH; b) the thyrotrope subpopulation secreting small amounts of thyrotropin when incubated with TRH may be unresponsive to this stimulatory factor. After performing reverse hemolytic plaque assay, plaque-forming cells were subsequently processed for electron microscopy. Morphometric analysis of the secretory granules correlated well with plaque size (TSH secreted). It is thus concluded that the functional subtypes of thyrotropes can be recognized on the basis of their ultrastructural images.

Distribution of elastic system fibres in the rat tail tendon and its associated sheaths

The distribution of elastic, elaunin and oxytalan fibres in tendons and tendon sheaths was studied by means of light and electron microscopy. The different fibres were characterised by comparing their typical ultrastructural pictures with a combination of selective staining techniques for light microscopy with the appropriate enzymatic digestions. Since it was observed that the rat tail tendon and its associated sheaths are not homogeneous structures from the point of view of the distribution of the elastic system fibres, a systematic description of the differential distribution of the oxytalan, elaunin and elastic fibres in the tendon and in the endo-, peri-, epi- and paratendineum is presented. Mature elastic fibres are present in the tendon and in the para-, epi- and endotendineum, whereas these fibres could not be detected in the peritendineum. Very many elaunin fibres are characteristically recognised in the endotendineum; these fibres are present in the peritendineum and in the tendon fascicles too, while the epi- and paratendineum are devoid of elaunin fibres. The peri- and endotendineum contain numerous oxytalan fibres, whereas these fibres are absent from the tendon fascicles and the epi- and paratendineum. The functional implications of the foregoing findings are discussed.