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251.
Dang Duc Nhu Teruhiko Kido Nguyen Ngoc Hung Le Thi Hong Thom Rie Naganuma Le Ke Son 《毒物与环境化学》2013,95(4):824-838
Human exposure to polychlorinated dibenzodioxins (PCDD) and dibenzofurans (PCDF), especially 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD), was investigated in Vietnam since initial severe adverse health effects were reported in the late 1970s. The purpose of this study was to determine the effects of dioxin exposure on steroid hormones of primiparae in an Agent Orange/dioxin hot-spot and a non-exposed area in Vietnam. Sixteen primiparae (8 at each site), all of whom were aged between 20 and 30 years with infants aged between 4 and 16 weeks, agreed to participate in this study. The mean dioxin levels in breast milk of primiparae from the hot-spot area, in terms of PCDD, PCDF, and PCDD?+?PCDF toxic equivalents (TEQ), were significantly higher than those for the non-exposed area. PCDD TEQ, PCDF TEQ, and PCDD?+?PCDF TEQ levels showed a significant correlation with dehydroepiandrosterone (DHEA), androstenedione (A-dione), and estradiol (E2) in the saliva of primiparae in a combination of hot-spot and non-exposed areas in Vietnam. The dose–response curve between salivary E2 or A-dione levels and dioxin levels was U-shaped in humans. This study provides an overview of studies regarding dioxin hot-spots and effects on human health and steroid hormone levels in particular, with a focus on the toxicity attributed to dioxins and furans. Furthermore, causal evidence regarding the effects of dioxins on endocrine disruption in humans is provided. 相似文献
252.
N‐acetyltransferase (NAT) activity was determined in different ages of New Zealand White rabbit pineal gland using 2‐aminofluorene and p‐aminobenzoic acid as substrates and it was assayed by high pressure liquid chromatography. Rabbits of different ages were either sacrificed during the light phase, exposed to darkness or light for 1 min during the dark phase of the lighting cycle, returned to their cages in darkness for 30 min and then sacrificed. Pineal gland NAT activity in animal nocturnally exposed to 1 min of light was inhibited in animals 1 ‐day‐old of age. Nocturnal light exposure did not inhibit enzyme activity in 1‐day‐old rabbit, even though these animal displayed clear light : dark differences in pineal gland NAT activity. Nocturnal light exposure also did not inhibit night time levels of NAT activity in 1‐day‐old animals who had been bilaterally enucleated. The result suggested that this effect is retinally mediated. Pre‐treatment of 1‐day‐old and 60‐day‐old animals with the isoproterenol (beta‐noradrenoreceptor agonist drug), prevented the nocturnal light‐induced inhibition of NAT activity. The different sensitivity of 60‐day‐old and 1‐day‐old animals to different illuminances or durations of nocturnal light exposure, was that the duration or intensity of light exposure was enable to inhibit nocturnal NAT activity. The NAT activity was at least 3.2‐ to 4.6‐fold greater in 1‐day‐old rabbits compared to 60‐day‐old rabbits. Kinetic constants for arylamine NAT activity in pineal gland from rabbits were determined. Km and Fmax values for 2‐aminofluorene were 2.6‐fold higher for light exposure than for no light exposure rabbits. This is the first demonstration of the retina‐pineal gland pathway appears light‐induced changes in pineal glands of animals in 1‐day‐old of ages or older; but this pathway does not function in 60‐day‐old rabbits like manner in 1‐day‐old rabbits. 相似文献
253.
N‐acetyltransferase (NAT) activity was determined in 100 fish (Oreochromis mossambicus) livers using 2‐aminofluorene and p‐aminobenzoic acid as substrates. Overall, the liver NAT activity of the 50 females was higher than the liver NAT activity of the 50 males. The activities (mean ± SD) of NAT from kidney, blood, intestine, and liver of males was 0.42 ± 0.11, 0.12 ± 0.03, 0.12 ± 0.08, and 1.56 ± 0.54 nmol/min/mg protein for the acetylation of 2‐aminofluorene and 0.36 ± 0.09, 0.09 ± 0.01, 0.11 ± 0.04, and 0.46 ± 0.15 nmol/min/mg protein for the acetylation of p‐aminobenzoic acid. In kidney, blood, intestine, and liver from female fish, the activities obtained were 1.60 ± 0.12, 0.35 ± 0.07, 0.15 ± 0.09, and 1.89 ± 0.50 nmol/min/mg protein for 2‐aminofluorene and 0.95 ± 0.11, 0.27 ± 0.03, 0.13 ± 0.09, and 0.57 ± 0.12nmol/min/mg protein for p‐aminobenzoic acid. Kinetic constants for arylamine N‐acetyltransferase activity in kidney, blood, intestine, and liver from fish with rapid, intermediate, and slow acetylator activity were determined. Apparent K m and V max values for 2‐aminofluorene were 5.5 and 7‐fold higher for liver than for the other tissues. Apparent K m and V max values for p‐aminobenzoic acid were 3.5 and 4.7‐fold higher for liver than for the other tissues. Based on the 2‐aminofluorene NAT activity of liver, there appears to be a polymorphism in NAT activity with 16 rapid, 28 intermediate, and 56 slow acetylators among the 100 fish assayed. This is the first demonstration of acetyl CoA: arylamine N‐acetyltransferase activity in fresh water fish and could lead to the development of a fish model for monitoring the effect of pollution of water environments on native species. 相似文献
254.
Huei L. Chang Lii T. Wu Feng T. Yeh Hsueh F. Lu Chin C. Yeh Chi F. Hung 《毒物与环境化学》2013,95(1-2):211-219
Paeonol was used to determine effects of arylamine N‐acetyltransferase (NAT) activity in human bladder tumor cells. The NAT activity was measured by high performance liquid chromatography assaying for the amounts of N‐acetyl‐2‐aminofluorene (2‐AAF) and N‐acetyl‐p‐amino‐benzoic acid (N‐Ac‐PABA) and remaining 2‐aminofluorene (2‐AF) and p‐aminobenzoic acid (PABA). The NAT activity in human bladder tumor cells was promoted by paeonol in a dose‐dependent manner, i.e. the higher the concentration of paeonol, the higher the promotion of NAT activity. The data also indicated that paeonol increases the apparent values of Km and Kmax from human bladder tumor cells in cytosols and intact cells. This report is the first demonstration to show paeonol did promote human bladder tumor cell NAT activity. 相似文献
255.
T.?N.?K.?D.?Binhvnn.vn" title="pvpialy@hcm vnn.vn" itemprop="email" data-track="click" data-track-action="Email author" data-track-label="">Email author Nico?Vromant Nguyen?Thanh?Hung Luc?Hens E.?K.?Boon 《Environment, Development and Sustainability》2005,7(4):519-536
Since 2000, the shrimp industry expands at a fast rate in the coastal areas of the Mekong Delta, Vietnam. Shrimp farming is
known for its negative impact on the coastal environment. However, other human interventions like agriculture and urbanization
also deteriorate the coastal environment. The land cover changes between 1968 and 2003 were determined and analyzed for the
Cai Nuoc district, Ca Mau Province, Vietnam, using photos from 1968, 1992 (aerial photographs), 1997/98 (Spot) and 2003 (Landsat).
It was clear that the district underwent serious land cover changes: deforestation between 1968 and 1992, with a simultaneous
increase in rice land; a rapid decline in rice acreage from 1997 onwards, and, simultaneously, a blitz-increase in shrimp
farming area. The forest area declined by 75% between 1968 and 2003. About 40% of this loss could be attributed to shrimp
farming, while the remaining 60% was attributed to needs for agricultural land. Still, at present, shrimp farming is the major
source of mangrove loss in the district. In 1999 shrimp farms covered 6.374 ha, in 2000 they covered 61.049 ha of the Cai
Nuoc area. The swap from rice cultivation to shrimp farming was most-probably driven by households’ hopes for a higher income.
It must be feared that the shrimp industry will have a negative impact on the environment (e.g. salinization) and on the livelihood
of the district’s households. In 1968 saline water covered 219.9 km2, in 1992, 1997/98 and 2003 the saline surface water area covered 92.4, 135.2 and 835.0 km2, respectively.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
256.
Trace metals in different species of mollusca, water and sediments from Taiwan coastal area 总被引:2,自引:0,他引:2
Since October 1994, a long-term program of Asia/Pacific Mussel Watch: Taiwan Regional Studies has been carried out. The results indicate that trace metal contents in mollusca varied among 30 different species and the environments (water and sediments) along the Taiwan coast. The orders of bioaccumulation of trace metals in mollusca were: Cu (over 200 microg/g), Thais clavigera > Isognomon legumen > Clibanarius rivescens > Crassostrea gigas; Zn (over 700 microg/g), Moruta granulata > C. gigas > Asiatica cypraea arabica > T. clavigera; Cd (over 5 microg/g), Trochus hanleyanus > Acanthopleura japonica > Nerita albicilla > Patella flexuosa; Pb (over 2 microg/g), P. flexuosa > C. gigas > T. hanleyanus > T. clavigera > C. gigas > Capiyulum mitella; Ni (over 10 microg/g), Meretrix lusoria > Philine sp. > Littoraria scabra > Tridacna squamosa > T. hanleyanus; Cr (over 30 microg/g), Littoraria undulata > T. hanleyanus > N. albicilla > Nerita chamaelor > M. granulata; As (over 20 microg/g), Perna viridis > L. scabra; and Sn (over 5 microg/g), P. viridis > L. undulata> C. mitella> C. gigas. Their seasonal and regional variations as well as their correlation are evaluated and discussed. 相似文献
257.
This paper studies the design of a mining concession contract as a multi-period adverse selection problem where production is the depletion of a non renewable resource. Compared with symmetric information, we show that overproduction is optimal in the terminal phase of the resource extraction program. Moreover, asymmetric information lengthens the contract duration but reduces the scarcity rent. 相似文献
258.
Hung Tao Shen Roger W. Ruggles 《Journal of the American Water Resources Association》1982,18(2):251-256
ABSTRACT: Winter heat budget and frazil ice production in the St. Lawrence River between the Ogdensburg-Prescott Boom and the Moses-Saunders Power Dam are analyzed. Contributions of each heat exchange component, and spatial distributions of heat exchange rates are calculated for three typical winters. Based on the calculated heat budget, the amount and distribution of frazil ice generated in the study reach is analyzed. The result of this study indicates that the thermal energy contained in the river water flowing into the study reach is a dominate factor in the heat budget analysis. The heat flux from the channel bottom accounts for an important portion of the total heat budget during the ice covered period. 相似文献
259.
Fok TF Lam HS Ng PC Yip AS Sin NC Chan IH Gu GJ So HK Wong EM Lam CW 《Environment international》2007,33(1):84-92
This study was designed to examine newborn infants in Hong Kong prenatally exposed to levels of methylmercury considered to increase risk of neurotoxic effects and to examine subject characteristics that modify the degree of prenatal mercury exposure. Mercury concentrations in 1057 sets of maternal and cord blood samples and 96 randomly selected maternal hair samples were measured. Subject characteristics were measured or collected by questionnaire. Of the 1057 cord blood samples collected only 21.6% had mercury concentrations less than 29 nmol/L (5.8 micro g/L). Median maternal hair mercury concentration was 1.7 ppm. The geometric mean cord to maternal blood mercury ratio was 1.79 to 1. Increasing maternal fish consumption and maternal age were found to be associated with increased cord blood mercury concentrations. Marine fish consumption increased cord blood mercury concentrations more than freshwater fish (5.09%/kg vs 2.86%/kg). Female babies, maternal alcohol consumption and increasing maternal height were associated with decreased cord blood mercury concentrations. Pregnant women in Hong Kong consume large amounts of fish and as a result, most of their offspring have been prenatally exposed to moderately high levels of mercury. In this population, pregnant women should choose freshwater over marine fish and limit fish consumption. 相似文献
260.
Family‐owned micro enterprises operating within the informal sector of most developing countries provide millions of citizens with a livelihood and are the economic backbone of many communities. Yet, the turbulence that emanates up or down respective supply chains following a disaster can cause these entities to fail. This study develops a model that recognises the relative weakness of micro enterprises to such disaster‐related shocks. The model proposes that micro enterprises can moderate the effect of such shocks by creating resilience through cognitive preparation, continuous learning, and the generation of various forms of social capital (cognitive, relational, and structural). The propositions for the model are established through an extensive literature review, coupled with examples drawn from the documents of humanitarian agencies performing disaster relief work in India. This model also serves as a preliminary basis with which to derive metrics to set benchmarks or to assess the viability of a micro enterprise's ability to survive disaster‐related shocks. 相似文献