The environmental risk as a culture in the Sinos Valley, Brazil.

The proposal of analysis of the social-environmental perception will be developed from the discourse as a constitutive element of reality. The discourse practices and their concretion will be the source of meaning and social-cultural value. Thus, the chosen research method was the qualitative and quantitative case study. In the first part of the text we will recapture a theoretical input by Mary Douglas on risk and culture, as well as on the acceptance of the risks in society. In the second part, we cover a few data of the case of the risks resulting from the tanning industry and on how the society of the "Vale do Rio dos Sinos" relates to these risks. In this article we conclude that risk perception of the population is directly related with past experiences, thus, assigning a meaning to all new events. This meaning is the result of a sociocultural construction. It is worth noting that behind this history, there are basic issues related to population survival, i.e., both the industrialists and workers establish partnerships when the society creates a movement against the leather industry.

Dynamics of cytochrome P450 inducers in polluted sites of São Paulo city reservoirs.

The first analysis of water pollutants using biomarkers at the Guarapiranga Reservoir, which supplies water for one-third of the population of the São Paulo megalopolis (Brazil), is reported. Studies were performed before and after the start of water pumping to the Guarapiranga from the highly polluted Billings reservoir. Billings's water was purified by passing through the natural wetland located near Guarapiranga. Liver enzymes of Oreochromis niloticus (tilopias) obtained from both reservoirs served as biomarkers of pollution in a comparison with animals obtained from a reference site. Enhanced levels of total cytochromes P450 (3.4 times) and b5 (2.7 times) and activity of cytochrome c (P450) reductase (2.2 times) were observed in specimens collected near the water influx from the Billings before the pumping started. However, these parameters were significantly decreased 3 months later. This effect is probably due to dilution of pollutants because of the increased level of water in the Guarapiranga.

Comparison of liver mixed-function oxygenase and antioxidant enzymes in vertebrates.

We performed a comparative analysis of cytochrome P450, cytochrome b5, MFO associated enzymes and cytosolic antioxidant enzymes in hepatic microsomes and cytosolic fractions prepared from five animal species representing three vertebrate classes living in tropical conditions (Brazil). The data obtained show that rats have higher hepato-somatic index, specific cytochrome b5 concentration, and NADPH-dependent cytochrome c (P450) activity compared to ectothermic species, SOD activity similar to those in amphibians, and specific concentration of cytochrome P450 and catalase activity lower than in a toad, but higher than in fishes and a frog. Our data indicate that tropical fishes may have reduced xenobiotic-metabolizing ability compared to the rat and amphibians. In contrast to fish and rat, amphibians have a low ratio (< 0.5) of cytochrome b5 concentration to that of P450. Most species showed cytochrome b5 sensitivity to oxygen. Thus, the use of sodium dithionate as a reducer, rather than NADPH, may be preferential in b5 determinations.

Reservoirs as complex systems

Reservoirs are man-made ecosystems with a wide spectra of interactions with the watershed. These interactions are of a ecological, economical and social nature. A reservoir as a complex system consists of many interacting components which vary both in space and time. To understand all4 the processes and components of such systems an integrated approach for observation, experimentation and measurement is necessary. Networks and relationships, direct and indirect effects have to be understood both in qualitative and quantitative terms. Reservoirs as complex Systems present hierarchy of functions, regulatory mechanisms and feedback Systems. The importance of developing models for reservoir studies and management is discussed. The use of ecotechnology for reservoir management is presented.

Synchronous growth of a freshwater diatom Melosira italica under natural environment.

A filamentous diatom Melosira italica was collected at the beginning of rainy season from a shallow lake in the tropical savanna region in Brazil. Even the sample taken from surface water contained empty cells in high percentages. The number of cells per filament of M. italica showed a peculiar pulse-like frequency distribution with peak values at 4, 8, 12 and 16. Evidences of the synchronous cell division in this planktonic diatom under natural environment are discussed.