Pesticide-contaminated feeds in integrated grass carp aquaculture: toxicology and bioaccumulation.

Effects of dissolved pesticides on fish are widely described, but little is known about effects of pesticide-contaminated feeds taken up orally by fish. In integrated farms, pesticides used on crops may affect grass carp that feed on plants from these fields. In northern Vietnam, grass carp suffer seasonal mass mortalities which may be caused by pesticide-contaminated plants. To test effects of pesticide-contaminated feeds on health and bioaccumulation in grass carp, a net-cage trial was conducted with 5 differently contaminated grasses. Grass was spiked with 2 levels of trichlorfon/fenitrothion and fenobucarb. Unspiked grass was used as a control. Fish were fed at a daily rate of 20% of body mass for 10 d. The concentrations of fenitrothion and fenobucarb in pond water increased over time. Effects on fish mortality were not found. Fenobucarb in feed showed the strongest effects on fish by lowering feed uptake, deforming the liver, increasing blood glucose and reducing cholinesterase activity in blood serum, depending on feed uptake. Fenobucarb showed increased levels in flesh in all treatments, suggesting bio-concentration. Trichlorfon and fenitrothion did not significantly affect feed uptake but showed concentration-dependent reduction of cholinesterase activity and liver changes. Fenitrothion showed bioaccumulation in flesh which was dependant on feed uptake, whereas trichlorfon was only detected in very low concentrations in all treatments. Pesticide levels were all detected below the maximum residue levels in food. The pesticide-contaminated feeds tested did not cause mortality in grass carp but were associated with negative physiological responses and may increase susceptibility to diseases.

Homologous expression and quantitative analysis of T3SS-dependent secretion of TAP-tagged XoAvrBs2 in Xanthomonas oryzae pv. oryzae induced by rice leaf extract.

Xanthomonas oryzae pv. oryzae (Xoo) produces a putative effector, XoAvrBs2. We expressed XoAvrBs2 homologously in Xoo with a TAP-tag at the C-terminus to enable quantitative analysis of protein expression and secretion. Addition of rice leaf extracts from both Xoo-sensitive and Xoo-resistant rice cultivars to the Xoo cells induced expression of the XoAvrBs2 gene at the transcriptional and translational levels, and also stimulated a remarkable amount of XoAvrBs2 secretion into the medium. In a T3SS-defective Xoo mutant strain, secretion of the TAPtagged XoAvrBs2 was blocked. Thus, we elucidated the transcriptional and translational expressions of the XoAvrBs2 gene in Xoo was induced in vitro by the interaction with rice and the induced secretion of XoAvrBs2 was T3SSdependent. It is the first report to measure the homologous expression and secretion of XoAvrBs2 in vitro by rice leaf extract. Our system for the quantitative analysis of effector protein expression and secretion could be generally used for the study of host-pathogen interactions.

Persistent organochlorine residues in estuarine and marine sediments from Ha Long Bay, Hai Phong Bay, and Ba Lat Estuary, Vietnam.

To assess the organochlorine contamination in the northeast coastal environment of Vietnam, a total of 41 surface sediments were collected from Ha Long Bay, Hai Phong Bay, and Ba Lat estuary, and analyzed for their organochlorine content. Organochlorine compounds (OCs) were widely distributed in the Vietnamese coastal environment. Among the OCs measured, DDT compounds predominated with concentrations ranging from 0.31 to 274 ng g(-1). The overall contamination level of DDTs in coastal sediments from northern Vietnam is comparable with those from other Asian countries. However, concentrations exceeding 100 ng g(-1) are comparable with high concentrations reported from India and China, the largest DDT consumers in the world. The overall concentrations of PCBs, HCHs, and chlordanes in surface sediments were in the ranges of 0.04-18.71 ng g(-1), not detected (n.d.) - 1.00 ng g(-1), and n.d. - 0.75 ng g(-1), respectively. Ha Long Bay and Hai Phong Bay were relatively more contaminated with DDTs and PCBs than other regions, respectively. In contrast, the distribution of HCHs was relatively homogeneous. OCs contamination in the coastal environment of Vietnam is closely related to shipping and industrial activities. The levels of DDT compounds in harbors and industrial areas exceeded their sediment quality guideline values suggested by Environment Canada [CCME (Canadian Council of Ministers of the Environment), 2002. Canadian sediment quality guidelines for the protection of aquatic life. In: Canadian Environmental Quality Guidelines. Canadian Council of Ministers of the Environment, Winnipeg, MB] and Australian and New Zealand [ANZECC and ARMCANZ, 2000. National water quality management strategy. Paper No. 4, Australian and New Zealand Guidelines for Fresh and Marine Water Quality, vol. 1, The Guidelines. Australia. Document: http://www.deh.gov.au/water/quality/nwqms/volume1.html], indicating that adverse effects may occur to marine species in that areas.

Contamination by persistent organic pollutants in dumping sites of Asian developing countries: implication of emerging pollution sources.

In Asian developing countries, large amounts of municipal wastes are dumped daily in open dumping sites without proper management. This practice may cause several adverse environmental consequences and increased health risk to local communities. To elucidate contamination by persistent organic pollutants (POPs)--including dichloro-diphenyl-trichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs), chlordanes, hexachlorobenzene (HCB), and polychlorinated biphenyls (PCBs)--in such dumping sites, soil samples were collected from open dumping sites and respective control sites in Cambodia, India, and Vietnam from 1999 through 2001. Our results demonstrated that DDTs, PCBs, and HCHs were dominant contaminants in the dumping sites. However, the contamination pattern was not consistent, showing higher HCHs in India than in Cambodia and Vietnam. Interestingly, in all of the countries, extremely higher levels of POPs were observed in the dumping sites compared with those in the respective control sites, suggesting significant amplification of POP contamination in the dumping sites of Asian developing countries. Mean concentrations of DDTs and PCBs were 350 and 140 ng/g dry weight, respectively, in the dumping sites of Cambodia and 26 and 210 ng/g, respectively, in India. These residue levels were hundreds to thousands times higher than those in general soils, implying possible risk to human health of the local communities, especially to the rag pickers, including children who work in these sites to collect recyclable materials. Composition of DDT compounds suggested their recent use in populated areas, which in turn might have caused increased levels of DDTs in the open dumping sites. In addition, composition of HCH isomers revealed their different use pattern in different countries.

Dioxins and related compounds in human breast milk collected around open dumping sites in Asian developing countries: bovine milk as a potential source.

In this study, concentrations of dioxins and related compounds (DRCs)--such as polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls--were found in human breast milk from women living near dumping sites of municipal waste and reference sites in India, Cambodia, Vietnam, and the Philippines during 1999 to 2000. DRCs were detected in all human breast milk samples analyzed, demonstrating that residents in these Asian developing countries have been exposed to these contaminants. In India, the concentrations of DRCs in human breast milk from women living near the investigated dumping site were notably higher than those from women living near reference sites and from women in other Asian developing countries. Toxic equivalent quantity (TEQ) levels of DRCs were comparable with or higher than those reported in the general populations of developed countries since 1990. In contrast, levels of these contaminants in human breast milk in women from Cambodia and Vietnam were not significantly different between milk from women living near the dumping and reference sites. These results indicate that significant pollution sources for DRCs are present in Indian dumping sites and that residents there have been exposed to relatively higher levels of these contaminants. TEQ levels in human breast milk from the dumping site in India tended to decrease with an increase in the number of previous deliveries by mothers, whereas no significant relationship was observed in Cambodia, Vietnam, or the Philippines. This suggests that mothers who have been exposed to relatively high levels of DRCs transfer greater amounts of these contaminants to the first infant than later ones through breast-feeding, which in turn implies that the first children of these mothers might be at higher risk from DRCs. When the residue levels of DRCs in bovine milk collected from the Indian dumping site and reference sites were examined, TEQ levels in bovine milk from the dumping site were higher than those from reference sites. This result suggests that bovine milk is a potential source of DRCs for residents living near the dumping site in India. To our knowledge, this is the first comprehensive study on exposure to DRCs of residents living in proximity to open dumping sites of municipal waste in Asian developing countries.

A conductive polypyrrole based ammonium ion selective electrode.

In view of the development of miniaturized sensor arrays, a solid-contact ammonium ion selective electrode has been investigated. A conductive polypyrrole film was electrochemically deposited on a glassy carbon surface and used as an internal solid contact layer between the sensing membrane and solid electrode surface. A systematic evaluation of the important parameters affecting the electromotive force (emf) response is presented. The performances of this solid-contact sensor were verified using a batch-mode measurement setup and a wall-jet flow cell system. The designed sensor exhibited excellent selectivity for the primary ion and a linear response over the pNH4+ range 1-5 with a slope of 56.3 mV decade(-1) . The sensor has a fast response and is relatively robustness, and was also used to determine ammonium concentrations in natural waters, with promising results.

Willingness to donate organs and tissues in Vietnam.

CONTEXT: Few studies on public attitudes toward organ and tissue donation have been carried out in Asia. OBJECTIVE: To determine demographic influences on attitudes toward organ and tissue donation in Vietnam. DESIGN: Face-to-face interviews. SETTING: Tan Binh District, Ho Chi Minh City, Vietnam. PARTICIPANTS: Random sample of adults (N = 785). MAIN OUTCOME MEASURES: Awareness of donation and transplantation, acceptance of organ and tissue donation. RESULTS: 75% of respondents stated they had heard of organ or tissue donation, but only 55% were aware of organ and tissue transplantation taking place in Vietnam. Forty-eight percent of Buddhists and 27.5% of Christians had either no knowledge or incorrect knowledge about their religion's official position toward donation and transplantation. Sixty-four percent stated they would give consent for the donation of their decreased relative's tissues and organs, 66% would themselves become posthumous donors, and 21% to 22% would donate multiple organs and tissues. A significant association was found between respondents' acceptance of organ and tissue donation and their educational level, sex, occupation, and awareness of transplantation. Most respondents stated that their willingness to donate depended on whether other family members agreed. Many noted the importance of preventing commerce in organ and tissue transplantation but were in favor of providing healthcare for the donor's family or monetary incentives as a reward for donating. CONCLUSION: Nearly two thirds of urban Vietnamese surveyed were willing to donate organs or tissues after death. Their willingness was related to awareness of transplantation, sex, education level, and occupation.