Trophic structures of artificial reef communities off the southern coast of the Korean peninsula as determined using stable isotope analyses.

The deployment of artificial reefs (ARs) has become a popular technique for creating new hard-bottom habitats, and for enhancing biodiversity and resource abundance for fisheries. We compared colonizing faunal assemblages and reef-associated food-web structures between ARs and nearby natural reefs (NRs) off the Korean coast using stable isotope techniques. Reef communities showed high compositional disparities in colonizing assemblages. Distinct δ13C and δ15N ranges of functional groups could be used to distinguish pelagic from benthic trophic pathways in the reef food web. The isotopic niches of entire faunal assemblages, as well as individual functional groups, overlapped between NRs and ARs, resulting in equivalency for the isotopic functional indices. Mixing model estimates for carnivorous invertebrates and fish suggested strong trophic links to reef-associated faunal prey at both reef types. Finally, these results highlight a convergence in trophic structure between ARs and NRs in accordance with functional diversity in the colonized faunal assemblages.

Identifying patterns in the multitrophic community and food-web structure of a low-turbidity temperate estuarine bay.

Food web dynamics outline the ecosystem processes that regulate community structure. Challenges in the approaches used to capture topological descriptions of food webs arise due to the difficulties in collecting extensive empirical data with temporal and spatial variations in community structure and predator-prey interactions. Here, we use a Kohonen self-organizing map algorithm (as a measure of community pattern) and stable isotope-mixing models (as a measure of trophic interaction) to identify food web patterns across a low-turbidity water channel of a temperate estuarine-coastal continuum. We find a spatial difference in the patterns of community compositions between the estuarine and deep-bay channels and a seasonal difference in the plankton pattern but less in the macrobenthos and nekton communities. Dietary mixing models of co-occurring dominant taxa reveal site-specific but unchanging food web topologies and the prominent role of phytoplankton in the trophic base of pelagic and prevalent-detrital benthic pathways. Our approach provides realistic frameworks for linking key nodes from producers to predators in trophic networks.

Combined Effects of Temperature and Seston Concentration on the Physiological Energetics of the Manila Clam Ruditapes philippinarum.

The suspension-feeding Manila clam Ruditapes philippinarum is a native species of the western Pacific that is now widely distributed around the globe because of its commercial importance. To determine the adaptive physiological responses to changing thermal and nutritional conditions, clearance, filtration, feces production, ammonium excretion, respiration rates, and scope for growth (SFG) were measured in adult clams. The clams were exposed to 24 treatments involving the combination of four water temperatures (8, 13, 18, and 23°C) and six concentrations of suspended particulate matter (SPM: 9.5 to 350.5 mg L(-1)). Physiological rates were standardized by using the mean (480 mg) of tissue dry weights of experimental clams using allometric equations between physiological variables and tissue dry weight. Higher clearance rates were recorded at higher temperatures and lower SPM concentrations, and these rates decreased with increasing SPM concentration at individual temperatures. Consumed energy increased with increasing temperature and SPM concentration, peaking at around 100-200 mg L(-1) at 18-23°C. Whereas fecal energy was largely determined by SPM concentration, ammonia excretion was mainly governed by temperature. Respiration rate studies revealed a predominant quadratic effect of temperature on the metabolism, indicating a lack of acclimatory adjustment of metabolic rate to rising temperature. SFG values were positive under almost all the treatment conditions and were much higher at higher SPM concentrations (> 45 mg L(-1)), with the highest level being recorded at 18°C and 100-200 mg L(-1) SPM. Increased filtration rate offset the increased metabolic cost at warm temperatures. Our holistic findings suggest that a high degree of physiological plasticity allows R. philippinarum to tolerate the wide range of temperatures and SPM concentrations that are found in tidal flats, accounting in part for the successful distribution of this species over a wide variety of geographical areas.

Potential chemoprevention of LPS-stimulated nitric oxide and prostaglandin E2 production by α-L-rhamnopyranosyl-(1→6)-ß-D-glucopyranosyl-3-indolecarbonate in BV2 microglial cells through suppression of the ROS/PI3K/Akt/NF-κB pathway.

α-l-Rhamnopyranosyl-(1→6)-ß-d-glucopyranosyl-3-indolecarbonate (RG3I) is a chemical constituent isolated from the commonly used Asian traditional medicinal plant, Clematis mandshurica; however, no studies have been reported on its anti-inflammatory properties. In the present study, we found that RG3I attenuates the lipopolysaccharide (LPS)-induced DNA-binding activity of nuclear factor-κB (NF-κB) via the dephosphorylation of PI3K/Akt in BV2 microglial cells, leading to a suppression of nitric oxide (NO) and prostaglandin E2 (PGE2) production, along with that of their regulatory genes, inducible NO synthase (iNOS) and cyclooxygenase-2 (Cox-2). Further, the PI3K/Akt inhibitor, LY294002 diminished the expression of LPS-stimulated iNOS and COX-2 genes by suppressing NF-κB activity. Moreover, RG3I significantly inhibited LPS-induced reactive oxygen species (ROS) generation similar to the ROS inhibitors, N-acetylcysteine (NAC) and glutathione (GSH). Notably, NAC and GSH abolished the LPS-induced expression of iNOS and Cox-2 in BV2 microglial cells by inhibiting NF-κB activity. Taken together, our data indicate that RG3I suppresses the production of proinflammatory mediators such as NO and PGE2 as well as their regulatory genes in LPS-stimulated BV2 microglial cells by inhibiting the PI3K/Akt- and ROS-dependent NF-κB signaling pathway, suggesting that RG3I may be a good candidate to regulate LPS-induced inflammatory response.

Xestospongin C induces monocytic differentiation of HL60 cells through activation of the ERK pathway.

Xestospongin C (XC), which is a group of macrocyclic bis-1-oxaquinolizidines, is a potent inhibitor of sarcoendoplasmic reticulum calcium transport ATPase and IP3 receptor. Nevertheless, very less information is available regarding whether XC induces AML differentiation. We investigated the potential role of XC in the differentiation of human leukemia HL60 cells and mechanisms underlying XC actin. XC treatment inhibited proliferation by inducing G1-phase cell cycle arrest in the HL60 cells. In addition, XC induced differentiation of HL60 cells into the CD14(+) monocytic lineage, which was indicated by morphological changes, nitroblue tetrazolium reduction assay, and expressions of CD11b and CD14 surface antigens. Our results also showed that XC promotes phagocytic activity and granularity in HL60 cells, suggesting that the cells are functionally activated. Furthermore, XC enhanced tumor necrosis factor (TNF)-α-mediated cytotoxic effect by increasing the numbers of TNF receptors. Moreover, we showed that XC activates extracellular signal-regulated kinase (ERK) pathway in the differentiation stages. Inhibition of ERK activation using PD98059 significantly decreased NBT+HL60 cells induced by XC treatment. Taken together, the results show that XC promotes monocytic differentiation of HL60 cells via ERK pathway activation, suggesting that XC could be a candidate for use as a differentiation-inducing agent for AML treatment.

Verrucarin A enhances TRAIL-induced apoptosis via NF-κB-mediated Fas overexpression.

We investigated whether verrucarin A (VA) sensitizes HepG2 hepatoma cells to tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-mediated apoptosis. We found that VA alone induces little apoptosis, but when combined with TRAIL (VA/TRAIL), it triggered significant apoptosis, causing little or no toxicity in normal mouse splenocytes. VA/TRAIL-induced cell death is involved in the loss of mitochondrial transmembrane potential and the consequent activation of caspases. Because nuclear factor (NF)-κB inhibition has been known as a critical target in TRAIL-mediated apoptosis, we also investigated the role of NF-κB in VA/TRAIL treatment. We found that VA upregulated the DNA binding activity of NF-κB, but that the antioxidants glutathione and N-acetyl-l-cysteine, as well as NF-κB inhibitor MG132, and mutant-IκB (m-IκB) transfection, significantly downregulated VA/TRAIL-induced cell death by inhibiting caspase-3 and NF-κB activities. Transfection of mutant-eIF2α also resulted in a decrease in VA/TRAIL-induced cell death by inhibiting of caspase-3, but not NF-κB activity. Although VA/TRAIL treatment led to an increase of DR5 expression, transfection of m-IκB had no influence on the DR5 expressional level. Finally, we showed that NF-κB-mediated Fas expression is critical to VA/TRAIL-induced apoptosis. Taken together, these results indicate that VA/TRAIL sensitizes HepG2 cells to apoptosis via NF-κB-mediated overexpression of Fas.

Molecular characterization of gonadotropin subunits and gonadotropin receptors in black porgy, Acanthopagrus schlegeli: effects of estradiol-17beta on mRNA expression profiles.

The cDNAs of three gonadotropin (GTH) subunits (GTHalpha, FSHbeta, and LHbeta) and two GTH receptors (FSHR and LHR) from pituitary and gonads of black porgy were cloned. The nucleotide sequences of the GTHalpha, FSHbeta, and LHbeta cDNA were 354, 363, and 414 base pairs (bps) in length with open reading frames (ORF) encoding peptides of 117, 120, and 137 amino acids, respectively. The FSHR and LHR cDNA was 2118 and 2076 bps in length with ORFs encoding peptides of 705 and 691 amino acids, respectively. To study the mechanism of the estradiol-17beta (E(2)) action, we examined the expression pattern of GTH subunit mRNAs in pituitary and GTH-receptor mRNAs in gonads, and the changes of plasma E(2) level when E(2) treatment was applied to immature black porgy. E(2) treatment increased mRNA expression levels of the genes and plasma E(2) levels, indicating that E(2) stimulated the increases in GTH subunit and GTH-receptor mRNAs. These data indicate that E(2) plays an important regulatory role in the brain-pituitary-gonad axis of immature black porgy. We provide the molecular characterization and expression of the GTH subunits and GTH receptors during sex change in the protandrous black porgy.

Effects of sediment disturbance caused by bridge construction on macrobenthic communities in Asan Bay, Korea.

Changes in soft-bottom macrobenthic communities and the effects of anthropogenic disturbances were studied. We compared biological and environmental samples during and after bridge construction (DBC and ABC). Significant differences were detected in sediment composition at three stations, although hydrographic conditions were similar for DBC and ABC samples. From DBC to ABC, the number of species and density of macrobenthic fauna tended to decrease, whereas biomass increased. Non-metric multidimensional scaling (MDS) analysis identified two sampling period groups from eight temporal samples, plus three station groups and one station from 12 spatial samples, which corresponded to macrobenthic faunal assemblages and theircharacteristic species. In addition, contributions of variables to similarity showed that the DBC and ABC samples differed significantly in the distribution of characteristic species and proportion of polychaete trophic groups, suggesting that the macrobenthic community structure was a factor affecting sediment disturbance caused by bridge construction.

Radiocesium reaction with illite and organic matter in marine sediment.

The mineralogical effect on the (137)Cs reaction with marine sediment has not been systematically studied yet, even though illite has been known to adsorb Cs preferentially on its frayed edge sites in a low Cs concentration. Ninety-three marine sediment samples were collected near Yangnam, Korea for quantitative X-ray-diffraction (XRD), gamma-ray, and total organic carbon (TOC) analysis. Illite content was in the range of 0-23 wt.% and those of (137)Cs and TOC were minimum detectable activity (MDA) approximately 7.19 Bq/kg-dry and approximately 3.32%, respectively. The illite content in the marine sediment showed a good relationship with the (137)Cs content (R(2)=0.69), but with an increase in the illite content, the relationship became less linear. This trend can be clearly shown in two groups of samples with different size fractions (< and >5Mdvarphi). For the samples of larger particle sizes (low contents of illite), the relationship is linear, but for the samples of the smaller particle sizes (high illite content) it is less linear with a decreased slope, indicating that increase in illite content does not significantly contribute to the fixation of (137)Cs in marine sediment. Rather, the TOC has a more linear relationship with (137)Cs content with no slope change in all particle size ranges. This may indicate that humic materials in marine sediment block the access of (137)Cs to the frayed edge site and reduces the adsorption of (137)Cs on illite and that the organic materials in marine sediment play more important roles in adsorbing Cs than illite.