Browsing by Author "Braathen, M"

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Heavy metals and organochlorine residues in water, sediments, and fish in aquatic ecosystems in urban and peri-urban areas in Tanzania
(Springer, 2009-02-09) Mdegela, R; Braathen, M; Pereka, A; Mosha, R; Sandvik, M; Skaare, J
Heavy metals and organochlorine residues were determined in water, sediment, fish muscle, and freshwater shrimps from aquatic environments in urban and peri-urban areas in Morogoro, Tanzania. Most of the water samples had heavy metal concentrations below WHO acceptable water quality guidelines. All sediment samples had comparable heavy metal concen- trations that suggest natural rather than anthropogenic origin. Hexachlorobenzene, α-hexachlocychlohexane, cis-chlordane, trans-nonachlordane, cis-nonachlor- dane, pp′-DDE, op′-DDD, pp′-DDD, op′-DDT, and pp′-DDT in hairy river prawn (Macrobrachium rude), African sharptooth catfish (Clarias gariepinus), and Wami tilapia (Oreochromis urolepis) were detected at significant concentrations above the methods’ detec- tion limits. The ratio of pp′-DDT to ∑DDTs was 0.4 in O. urolepis and 0.3 in C. gariepinus, which indicated previous rather than current use of DDT. In M. rude, only pp′-DDE was detected and inO. urolepis and C. gariepinus there were higher levels of pp′-DDE than pp′-DDT, which demonstrate uptake of pp′-DDE, rather than pp′-DDT, from the environment. Bioaccumulation of organochlorines and mercury was the highest in C. gariepinus, cadmium in M. rude, and lead in both M. rude and O. urolepis. Maximum detected levels of organochlo- rine pesticides and heavy metals in M. rude, O. urolepis, and C. gariepinus were below the maximum permissible concentrations recommended by FAO/ WHO. It is concluded that, at present, the contribution of anthropogenic sources in pollution of aquatic environments in Morogoro urban and peri-urban areas are low and that the concentrations of heavy metals and organochlorine pesticides in water and fish do not indicate a risk to the consumers.
Vitellogenin in African Sharptooth Catfish (Clarias gariepinus): Purification, Characterization, and Elisa Development
(2009-01-30) Braathen, M; Mdegela, R. H.; Correia, D; Rundberget, T; Myburgh, J; Botha, C; Skaare, J.U; Sandvik, M
Vitellogenin (Vtg) induction in African sharptooth catfish (Clarias gariepinus) was assessed in order to develop a method for monitoring estrogenic pollution in African freshwater systems. Clarias gariepinus Vtg (Cg-Vtg) was purified from serum obtained from 17a-ethynylestradiol (EE2)-exposed fish and polyclonal antibodies against Cg-Vtg were raised. An enzyme-linked immunosorbent assay (ELISA) was developed and the induction and kinetics of Vtg were assessed in male fish in three different exposure trials using both natural estrogen (17a-estradiol [E2]) and synthetic EE2. Concentrations of EE2 in water and levels of EE2 conjugates in bile were quantified by liquid chromatography– mass spectrometry (LC-MS). In addition, co-administration of E2 and benzo[a]pyrene (BaP) were studied. Vtg was induced in all exposure trials and the maximum induction was observed 1 wk after exposure. Exposure of male C. gariepinus to 1.4, 2.7, and 13.9 mg/ml EE2 induced Vtg synthesis at all concentrations. BaP did not influence the Vtg kinetics. However, an increased rate of biliary excretion of EE2 was observed when BaP was additionally administered. In conclusion, Vtg is induced in male C. gariepinus after exposure to both E2 and EE2, rendering it a suitable biomarker for endocrine-disrupting chemicals in African freshwater systems.