Identifying the external N and Hg inputs to the estuary ecosystem based on the triple isotopic information (δ15NNO3, Δ17ONO3 and δ18ONO3).

The supply and sources of N and Hg in the Geum estuary of the western coast of Korea were evaluated. Triple isotope proxies (δ15NNO3, Δ17ONO3 and δ18ONO3) of NO3- combined with conservative mixing between river and ocean waters were used to improve isotope finger-printing methods. The N pool in the Geum estuary was primarily influenced by the Yellow Sea water, followed by riverine discharge (821 × 106 mol yr-1) and atmospheric deposition (51 × 106 mol yr-1). The influence of the river was found to be greater for Hg than that of the atmosphere. The triple isotope proxies revealed that the riverine and atmospheric inputs of N have been affected by septic wastes and fossil fuel burning, respectively. From the inner estuary towards offshore region, the influence of the river diminishes, thus increasing the relative impact of the atmosphere. Moreover, the isotope proxies showed a significant influence of N assimilation in February and nitrification in May.

Trophic transfer of citrate, PVP coated silver nanomaterials, and silver ions in a paddy microcosm.

We used replicated paddy microcosm systems to estimate the tropic transfer of citrate-coated silver nanoparticles (AgNP citrate), polyvinylpyrrolidone (PVP)-coated AgNP (AgNP PVP), and silver ions (AgNO3) for 14 days under two exposure regimes (a single high-dose exposure; 60 µg L-1 and a sequential low-dose exposure at 1 h, 4 days and 9 days; 20 µg L-1 × 3 = 60 µg L-1). Most Ag ions from AgNO3 had dispersed in the water and precipitated partly on the sediment, whereas the two Ag NPs rapidly coagulated and precipitated on the sediment. The bioconcentration factors (BCFs) of Ag from AgNPs and AgNO3 in Chinese muddy loaches and biofilms were higher than those of river snails in both exposure conditions. These BCFs were more prominent for 14 days exposure (7.30 for Chinese muddy loach; 4.48 for biofilm) in the low-dose group than in the single high-dose group. Their retention of AgNPs and Ag ions differed between the two exposure conditions, and uptake and elimination kinetics of Ag significantly differed between AgNP citrate and AgNP PVP in the sequential low-dose exposure. Stable isotopes analyses indicated that the trophic levels between Chinese muddy loaches and biofilms and between river snails and biofilms were 2.37 and 2.27, respectively. The biomagnification factors (BMFs) of AgNPs and AgNO3 between Chinese muddy loaches and biofilms were significantly higher than those between river snails and biofilms under both exposure settings. The BMFs of AgNP citrate and AgNO3 between Chinese muddy loaches and biofilms were greater than those of AgNP PVP for 14 days in the single high-dose group, whereas the BMFs of AgNP PVP were greater than those of AgNP citrate and AgNO3 in the sequential low-dose group. These microcosm data suggest that AgNPs have the potential to impact on ecological receptors and food chains.

Trophic transfer of nano-TiO2 in a paddy microcosm: A comparison of single-dose versus sequential multi-dose exposures.

In the present study, replicated paddy microcosm systems were used to investigate the environmental fate and trophic transfer of titanium nanoparticles (NPs) over a period of 14 days. Most TiO2 NPs immediately settled down in the sediment, and high accumulations of nano TiO2 in the sandy loam sediment and biofilm were observed. The test organisms (quillworts, water dropworts, duckweeds, biofilms, river snails, and Chinese muddy loaches) and environmental media (freshwater, sandy loam sediment) were exposed to sequential low doses (2 mg/L at 1 h, 4 days, and 9 days) or a single high-dose (6 mg/L) of TiO2 NPs. The bioconcentration factors (BCFs) of nano-TiO2 in biofilms, quillworts, duckweeds, and Chinese muddy loaches were higher in the sequential multi-dose group than in the single-dose group. Chinese muddy loaches showed higher bioaccumulation factors (BAFs) over their prey than river snails. The difference in the carbon isotope ratios between Chinese muddy loaches and river snails was less than 2‰, and an approximately 4‰ difference in the stable nitrogen isotope ratio was observed in the two aquatic predators from their major prey (e.g., biofilms or particulate organic matter). The trophic levels between biofilms and river snails and between biofilms and Chinese muddy loaches were 2.8 and 2.4 levels, respectively. These results indicate that these two predators consumed biofilm and other alternative preys at a higher level than biofilm. Although the trophic transfer rates of TiO2 are generally low, relatively higher biomagnification factors (BMFs) were found in Chinese muddy loaches (0.04-0.05) than in river snails (0.01-0.02). These results suggest that TiO2 NPs show greater movement in the sediment than in the water and that TiO2 NPs can be retained through aquatic food chains more after a sequential low-dose exposure than after a single high-dose exposure.

The incidence of stroke by socioeconomic status, age, sex, and stroke subtype: a nationwide study in Korea.

OBJECTIVES: To date, studies have not comprehensively demonstrated the relationship between stroke incidence and socioeconomic status. This study investigated stroke incidence by household income level in conjunction with age, sex, and stroke subtype in Korea. METHODS: Contributions by the head of household were used as the basis for income levels. Household income levels for 21 766 036 people were classified into 6 groups. The stroke incidences were calculated by household income level, both overall within income categories and further by age group, sex, and stroke subtype. To present the inequalities among the six ranked groups in a single value, the slope index of inequality and relative index of inequality were calculated. RESULTS: In 2005, 57 690 people were first-time stroke patients. The incidences of total stroke for males and females increased as the income level decreased. The incidences of stroke increased as the income level decreased in those 74 years old and under, whereas there was no difference by income levels in those 75 and over. Intracerebral hemorrhage for the males represented the highest inequality among stroke subtypes. Incidences of subarachnoid hemorrhage did not differ by income levels. CONCLUSIONS: The incidence of stroke increases as the income level decreases, but it differs according to sex, age, and stroke subtype. The difference in the relative incidence is large for male intracerebral hemorrhage, whereas the difference in the absolute incidence is large for male ischemic stroke.

Anticonvulsant effect of wogonin isolated from Scutellaria baicalensis.

In previous studies, we identified sedative effects of Scutellaria baicalensis extracts and found that these extracts or their constituents may also have anticonvulsive effects. Wogonin is a natural product isolated from S. baicalensis, which possesses central nervous system effects such as anxiolytic and neuroprotective activities. In this study, we investigated the effects of wogonin on convulsion related behaviors, such as myorelaxation, motor coordination, and anticonvulsant effects of wogonin on chemical induced seizure and electroshock seizure in mice or rats. The effect of wogonin on membrane potential was also observed. Wogonin was intraperitoneally injected into mice or rats 30 min prior to testing. Animals treated with wogonin did not change locomotor activities as well as endurance times on the rota-rod, which indicates that wogonin did not cause a sedative and myorelaxation effect. Wogonin significantly blocked convulsion induced by pentylenetetrazole and electroshock but not convulsion induced by strychnine. Wogonin also significantly reduced the electrogenic response score, but flumazenil treatment reversed this decrease to the level of the control group. The wogonin treatment increased Cl(-)influx into the intracellular area as dose increased. Flumazenil and bicuculline treatment, however, inhibited the Cl(-) influx induced by wogonin. These results indicate that the anticonvulsive effects produced by wogonin were mediated by the GABAergic neuron.

2-Oxo-3,23-isopropylidene-asiatate (AS2006A), a wound-healing asiatate derivative, exerts anti-inflammatory effect by apoptosis of macrophages.

2-Oxo-3,23-isopropylidene-asiatate (AS2006A), a wound-healing asiatate derivative, exerts anti-inflammatory effect. Macrophages produce cytokines that recruit other inflammatory cells and are responsible for the diverse effects of inflammation. In the present study, we comparatively evaluated the cytotoxicity of AS2006A to Raw264.7, H4IIE and L-929 cells as part of the studies on its anti-inflammatory effect. Among the cells examined, AS2006A was selectively cytotoxic to Raw264.7 cells, a macrophage cell line. AS2006A increased the number of cells positively stained with TdT-mediated dUTP nick end labeling (TUNEL), and upregulated the expression of the genes implicated with apoptosis, which included caspase-8, c-myc, iNOS, mdm2, NF-kappaB1, I-kappaBalpha and NF-kappaB p105 genes, as assessed by the membrane DNA array technique. The expression of the genes related with cell cycle control was not changed. Thus, the primary targets of AS2006A in macrophages might include the genes implicated with apoptosis. Immunoblot analysis revealed that AS2006A caused the release of cytochrome c from the mitochondria to the cytoplasm in macrophages. Caspase-3 activity and poly(ADP-ribose) polymerase cleavage were both increased by AS2006A in macrophages, indicating that AS2006A induced apoptosis. Viability of macrophages activated by lipopolysaccharide and their NO production were also decreased by AS2006A in a concentration-dependent manner. These results demonstrated that AS2006A selectively induces apoptosis of macrophages with cytochrome c release, caspase 3 activation and poly(ADP-ribose) polymerase cleavage, and that cytotoxicity of AS2006A to macrophages may contribute to anti-inflammatory and wound-healing effects.