Cloning and detection of metallothionein mRNA by RT-PCR in mangrove oysters (Crassostrea rhizophorae).

A semi-quantitative RT-PCR protocol was developed to directly evaluate metallothionein (MT) mRNA expression in different tissues of mangrove oysters (Crassostrea rhizophorae), using beta-Actin (ACT) as a normalizing gene. Clones with high degree of identity from partial coding sequences were obtained for both MT and ACT. Although not statistically significant, high relative accumulation of MT mRNA was observed in the digestive gland (DGG), but not in the gills, from samples collected from both control and contaminated sites. Nevertheless, MT expression was not comparable to the high levels of metal in the contaminated oysters. Results indicate that the variation in relative MT mRNA levels from different samples of the same site could be due to multiple gene copies or different MT isoform induction.

Dichlorodiphenyltrichloroethane in soil, river sediment, and fish in the Amazon in Brazil.

Dichlorodiphenyltrichloroethane (DDT), its main metabolites, and other organochlorines were analyzed in soils (n=6), fluvial sediments (n=14), and fish (n=10) that were collected in several areas of the Amazon region in Brazil. The samples were analyzed by capillary column gas chromatography coupled to electron capture detection. DDT residues were present in most of the collected sediments in concentrations of approximately 10 to 100 micro/kg (ppb, dry weight). Some urban top soils were found to have more than 1 mg/kg (ppm). In fish, as much as 0.5 mg/kg of total DDT (wet weight) was found in the edible parts. The presence of p,p'-DDT in most of the samples reflects the use of this insecticide against vectors of malaria between 1946 and 1993, which has led to its ubiquitous presence in the environment of the Brazilian Amazon.

Zinc detoxification by a cyanobacterium from a metal contaminated bay in Brazil

O presente trabalho descreve o acúmulo de zinco em grânulos de polifosfato da cianobactéria Synechocystis aquatilis NPBS-1 como mecanismo de detoxificação de metais pesados. O microrganismo foi isolado de uma baía contaminada com metais, a Baía de Sepetiba, próxima à cidade do Rio de Janeiro. As células foram cultivadas em 25 µM de cloreto de zinco e preparadas para microscopia eletrônica e análise de dispersão de energia de raios-X. Algumas mudanças morfológicas ocorreram após a exposição ao zinco. A principal modificação foi o aumento no número de grânulos de glicogênio, como provável mecanismo fisiológico de adaptação. Os grânulos de polifosfato continham fósforo, enxofre, cálcio, ferro e zinco. O acúmulo de zinco nesses grânulos parece ser um mecanismo efetivo de detoxificação do metal para sobrevivência da cianobactéria na baía. Devido à sua não-especificidade na captação de cátions metálicos, os grânulos podem ser igualmente efetivos em acumular outros eventuais metais em excesso, além do zinco.

Establishment and analytical quality control of laboratories for Hg determination in biological and geological samples in the Amazon, Brazil

During the past 20 years significant amounts of HG have been released in the Amazonian environment due to goldmining activities. Several Brazilian and foreign research groups have been studying the region, always facing difficulties regarding preservation and transfer of the collected samples from the field to the analytical laboratories. Aiming to solve these problems two high quality Hg analytical laboratories were established in the region. One is located at Fundação Esperança (FE, Santarém, PA), a medical assitance foundation and the other at the Universidade Federal de Rondônia (UNIR), Porto Velho, RO. Their main equipament is: Atomic absorption spectrophotometers for Hg analysis (Klow Injection Mercury System-FIAS 400 with automatic samples-AS90-Perkin Elmer) and a microwave oven digestion system (MDS-2000-CEM). Technicians and researchers were trained in several aspects like environmental and human sampling, digestion methods and Hg analysis for biotic and abiotic materials. This training as well as the installation of the mentioned laboratories were the responsibility of the Universidade Federal do Rio de Janeiro (UFRJ). Intercalibration exercices were performed between several laboratories: Environmental Medicine of Odense University (Denmark), Centre de Toxicologie du Québec, Canada and Occupational Health Sciences (Health-Canada). In the last 18 months the FE laboratory joined the Hg urine analysis intercalibration program of the Laboratory of the Centre of Toxicology in Québec, Canada, reaching accurate results. To date both Amazonian laboratories are able to analyze several different materials: Sediment, soil, fish, urine, hair and blood. The FE laboratory is becoming more specialized in human samples such as urine, blood and hair, wile UNIR laboratory deals with environmental samples such as fish, sediment and soil.