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The extent and frequency of harmful cyanobacterial blooms are increasing, owing to the climate change caused by global warming, and some harmful filamentous cyanobacteria that were first reported in the tropics are spreading to temperate regions, such as North America, Europe, and Northeast Asia. Although these exotic invasive cyanobacteria have a high toxigenic potential, they are not targeted in management plans in many countries. This study analyzed the occurrence of and potential toxin and off-flavor secondary metabolite production by invasive nostocalean cyanobacteria in the Nakdong River in Korea, which is a temperate region. The occurrence of four species belonging to three genera of cyanobacteria was confirmed in the Nakdong River. The quantities of cyanobacteria in the Nakdong River were mostly low, fewer than 1,000 cells mL-1. Twenty-four strains belonging to four species in three genera of cyanobacteria were isolated from the Nakdong River. Analysis revealed no off-flavor secondary metabolite production by any of the isolates, and those belonging to Cylindrospermopsis raciborskii, Sphaerospermopsis aphanizomenoides, and S. reniformis were identified as nontoxic strains. However, anatoxin-a production was observed in two of the eleven isolates of Cuspidothrix issatschenkoi. Given the sites and the timing of its occurrence, C. issatschenkoi had the highest potential for toxin production among the invasive nostocalean cyanobacteria appearing in the Nakdong River.

Flow regulation is one of the most common anthropogenic factors affecting rivers worldwide. In Korea, 16 weirs were constructed along four major rivers from 2009 to 2012. This study aimed to elucidate initial changes in physical, chemical, and biological variables after the construction of consecutive weirs on the Nakdong River, a major large river system. Water quality variables and phytoplankton cell densities were investigated at eight representative sites and compared with the data recorded before the weir construction. There were spatial and temporal changes in the hydraulic retention time (HRT), total phosphorus (TP), and chlorophyll a concentrations among the eight weir sections. HRT increased after the weir construction, while TP and chlorophyll a tended to decrease from the middle to lower section of the Nakdong River. Furthermore, differences were observed in the phytoplankton community composition between 2006&ndash, 2007 and 2013. There was a marginal decrease in the duration of centric diatom (Stephanodiscus hantzschii) blooms after weir construction. However, Microcystis aeruginosa proliferated more extensively during summer and autumn than it did before the weir construction. Our results suggest that changes in hydrological factors, in response to consecutive weir construction, may contribute to greater physical, chemical, and ecological variability.

Elemental cellular stoichiometry of natural phytoplankton communities was examined in six large dam reservoirs in the Han River system. Carbon (C) and nitrogen (N) contents of the phytoplankton-dominated seston from Lake Soyang was higher than that from other lakes. Phosphorus (P) content showed slight variations among six lakes in the range of 0.04~0.18 μmol P mg DW -1 . The phosphorus concentrations of lake water showed obvious positive relationship with P and C contents of the phytoplankton-dominated seston. In all six lakes, N:P ratios and C:P ratios in the phytoplankton-dominated seston were more than 23 and 133 respectively, indicating the phytoplankton communities in six lakes have been exposed in phosphorus limited condition. The relative abundance of diatoms showed significant negative correlation with C, N, P contents of the phytoplankton-dominated seston and that of cyanobacteria showed significant positive correlation. Elemental stoichiometry of diatoms-dominated seston showed distinctive less content than that of cyanobacteria-dominated seston. The cellular N:P ratios of diatoms- and cyanobacteria-dominated seston indicate that both main classes of phytoplankton in six lakes are in phosphorus deficiency. Elemental stoichiometry of the phytoplankton-dominated seston in this study could be used for the further ecological stoichiometric studies in six lakes.

The purpose of this research was to characterize physicochemical properties and sensory evaluation of schizandra wines fermented by the yeasts, Sacchromyces cerevisiae SH8094 (S. cerevisiae SH8094) and Sacchromyces cerevisiae SH2855 (S. cerevisiae SH2855) isolated from schizandra fruits and stems and compare these results with the results from commercial activated yeast (Lalvin 1118) and a commercial schizandra wine. Three different schizandra wines fermented by S. cerevisiae SH8094, S. cerevisiae SH2855, and Lalvin 1118 showed similar results in pH and titratable acidity. On the other hand, the schizandra wines fermented by S. cerevisiae SH8094 and S. cerevisiae SH2855 showed high brix (brix), low alcohol content (9%), and low yeasts count (4.1 log CFU/mL), compared with the schizandra wine fermented by Lalvin 1118. Both schizandra wines made with S. cerevisiae SH8094 and S. cerevisiae SH2855 showed higher scores in swallowing and overall acceptability than the schizandra wine made with Lalvin 1118. When compared with a commercial schizandra wine, the schizandra wine fermented with S. cerevisiae SH8094 showed better qualities in aroma (), color (), and overall acceptability (). In conclusion, S. cerevisiae SH8094 which was isolated from schizandra fruits and stems has a high potential in schizandra wine fermentation.

Aphanizomenon spp. have formed harmful cyanobacterial blooms in the Nakdong River during spring, autumn, and now in winter, and the expansion of blooming period and area, associated with the global warming is predicted. The genus Aphanizomenon has been described to produce harmful secondary metabolites such as off-flavors and cyanotoxins. Therefore, the production of harmful secondary metabolites from the Aphanizomenon blooms in the Nakdong River needs to be monitored to minimize the risk to both water quality and public health. Here, we sampled the cyanobacterial blooms in the Nakdong River and isolated ten Aphanizomenon strains, morphologically classified as Aphanizomenon flos-aquae Ralfs ex Bornet et Flahault 1888. Phylogenetic analysis using 16S rRNA and internal transcribed spacer (ITS) region nucleotide sequences confirmed this classification. We further verified the harmful secondary metabolites-producing potential of A. flos-aquae isolates and water samples containing cyanobacterial blooms using PCR with specific primer sets for genes involved in biosynthesis of off-flavor metabolites (geosmin) and toxins (microcystins, saxitoxins and cylindrospermopsins). It was confirmed that these metabolite biosynthesis genes were not identified in all isolates and water samples containing only Aphanizomenon spp. Thus, it is likely that there is a low potential for the production of off-flavor metabolites and cyanotoxins in Aphanizomenon blooms in the Nakdong River.

Part of the neurodegenerative cascade in AIDS dementia may involve overexpression of matrix metalloproteinases (MMPs). Here, we examined the possible effect of HIV-1 gp41, which has been shown as a key determinant associated with pathogenesis of AIDS dementia, on the activity of MMPs using human neuronal and glial cell lines. Zymographic analysis revealed that treatment with the gp41 peptide (aa 583-599) for 24 h markedly elevated the activity of MMP with Mr 66 kDa in the cultured media of glioblastoma cell line T98G in a concentration-dependent manner as well as of neuroblastoma cell line SK-N-SH despite of lower magnitude of the activity. In contrast, the immediately adjacent gp41 peptide (aa 598-613) as well as the reverse peptide (aa 598-583) had a little effect. Recombinant gp41 protein containing extracellular domain also elicited a similar effect, although with a lesser extent. This 66 kDa MMP was confirmed as gelatinase A (MMP-2) based on the results of its activity dependent on Ca2+ and inhibited in the presence of 1,10-phenanthroline or EDTA, as well as its specific immunoreactivity on the Western blot. N-acetyl cysteine (NAC) downregulated this gp41 peptide-induced MMP-2 activity in T98G. The soluble form of amyloid precursor protein (sAPP), which is synthesized in the Escherichia coli system, also inhibited the MMP-2 activity in vitro. Taken together, these results implicate that high production of HIV-1 gp41 or its metabolites containing aa 583-599 within central nervous system (CNS) could result in the increased activity of MMP-2 and that the extracellular deficiency of reducing agent or decreased level of sAPP within CNS could exacerbate this gp41-induced MMP-2 activity.

The production and release of microcystins during the batch culture of Microcystis aeruginosa LERL 031 which was isolated from Korean freshwater were investigated. Total amounts of two major toxins (microcystin-RR and -LR) did not decrease at the death phase of the culture while chlorophyll-a concentration decreased. The ratio of two major intracellular microcystin amounts of the cyanobacteria was changed depending on the growth phase.The grazing effects on Microcystis biomass and microcystins by micrometazoa and protozoan which were isolated from biofilm oxidation reactor were examined. Among three microanimals Monas guttula was turned out to be the most effective grazer of M. aeruginosa LERL-031. In the condition of coexistence of Aeolosoma hemprichi, Philodina erythrophthalma, Monas guttula in the cyano-bacterial as grazer, chlorophyll-a concentration decreased by 73% of initial concentration after 31 days. In the condition of no addition of microanimals, intracellular microcystins were released to surrounding water during the lysis of cells but not degraded.

Human immunodeficiency virus-1 (HIV-1) associated dementia (HAD) has been attributed to an encephalitis resulting from intense infiltration of monocytes. Evidence suggests that the viral protein Tat, which is released actively from HIV-1 infected cells, can contribute significantly to this process. Therefore, the principal objective of this study was to evaluate the potential molecular basis for the role of extracellular HIV-1 Tat in the induction of monocyte chemotactic protein-1 (MCP-1/CCL2) in the hippocampus, which is primarily linked to cognitive function and most commonly damaged in HAD. We also attempted to identify the mechanism by which resveratrol (trans-3,5,4'-trihydroxystilbene) modulates MCP-1 release in hippocampal tissues exposed to Tat. An ex vivo study using rat hippocampal slices demonstrated a time- and dose-dependent increase in MCP-1 production from Tat-treated hippocampal tissues. This increase was accompanied by the activation of the MEK/ERK pathway and TNF-α production. Tat-induced MCP-1 release was abrogated by inhibitors of tyrosine kinases (TK), herbimycin A or genistein, a finding that supports the MAPK signaling mechanism. The inhibition of the ERK1/2 pathway with SL327 induced a near-complete abolition of the observed Tat-induced effects. Furthermore, anti-TNF-α antibodies suppressed Tat-induced MCP-1 release. Resveratrol, to a level similar to that of SL327, downregulated Tat-induced proinflammatory responses via the inactivation of ERK1/2. These results indicate that the activation of the ERK1/2 pathway and TK are critical factors in the production of TNF-α and MCP-1 in the Tat-exposed hippocampus. Additionally, the inhibition of Tat-induced production of MCP-1 and TNF-α via the inactivation of the ERK1/2 pathway may represent the anti-inflammatory mechanism of resveratrol in the hippocampus.

[1] We investigated the sources, fluxes, and spatial and temporal distribution of organic carbon in two large reservoirs in Korea having different trophic and hydrologic features. In Lake Paldang (river-type reservoir) most of the organic carbon comes from allochthonous sources (88%), while in Lake Chungju (lake-type reservoir) the allochthonous load contributed 52% (48% autochthonous). Strong correlations were found between the amount and contribution of allochthonous and autochthonous organic carbon and hydrologic parameters in Lake Paldang but not in Lake Chungju. The spatiotemporal fluctuation patterns of C/N ratios of particulate organic matter, chlorophyll a/particulate organic carbon values, and specific ultraviolet absorption of dissolved organic carbon were different, indicating differences in state and source of organic carbon in the two reservoirs. Our results indicate that meteorologic and hydrologic controls directly determine the state of lacustrine organic carbon in Lake Paldang, whereas autochthonous production and in situ transformation may play important roles in determining the state of lacustrine organic carbon in Lake Chungju.

To elucidate the pathogenic mechanisms involved in neurodegeneration in AIDS patients with cognitive deficits, we have examined the toxic effect of the lentivirus lytic peptide 1 (LLP-1) corresponding to the carboxyl terminus of HIV-1 transmembrane glycoprotein gp41 on human neuronal and glial cell lines. LLP-1 induced a significant lactate dehydrogenase (LDH, a marker of cell death) release from these cells in a concentration- and time-dependent manner, while the noncytolytic LLP-1 analog 2 had little effect. Application of LLP-1 to SH-SY5Y, a well-characterized human neuronal cell line, caused the decline of intracellular glutathione (GSH) content that appeared to occur before a significant LDH release. Furthermore, LLP-1 elicited a significant loss of mitochondrial function as measured by mitochondrial transmembrane potential (MTP). Among the reducing agents and antioxidants tested, GSH and a GSH prodrug N-acetylcysteine (NAC) provided protection against LLP-1-induced neuronal cell death, evidently by restoring the intracellular GSH levels and blocking the disruption of mitochondrial integrity. Thus, gp41-derived LLP-1 may be a potential neurotoxic agent capable of causing the intracellular GSH depletion and disturbing the mitochondrial function, possibly contributing to the neurodegenerative cascade as seen in HIV-1-associated dementia. Our data indicate that restoring both GSH concentration and mitochondrial function may hold promise as possible therapeutic strategies for slowing disease progression of dementia in AIDS patients.

Salmonella penetrates the basement membrane of intestinal epithelial cells into deeper tissues, in which process extracellular matrix proteases should be required. Hypothesizing that the proteases might be provided by host cells, we investigated the changes of expression of urokinase type plasminogen activator(u-PA), plasminogen activator inhibitor-1(PAI-1), and collagenases in epithelial cells(Caco-2) infected with Salmonella typhimurium. The change of mRNA levels, amount of the enzyme secretion and functional activity were analyzed by Northern blot, ELISA, and Zymography. The mRNA level of u-PA was elevated by Salmonella infection itself without any exogenous transcription regulators. u-PA was actively secreted into the medium and was enzymatically active. The synthesis and secretion of PAI-1 was increased over time from 2 hrs post infection(pi) to 8 hrs pi. Zymographic assay revealed that the secretion of collagenases (type IV, type V and interstitial collagenase) were also increased. Taken together, S. typhimurium infection might induce accumulation of pericellular proteolytic activity and consequently degrade the extracellular matrix surrounding the infected cells. These in turn might enable Salmonella to invade into deeper tissues.