Exchange of energy,nitrogen and phosphorus between water,bottom and ice in a near-shore ecosystem of the Sea of Japan

The processes taking place at the partioning boundaries of a marine ecosystem are still rather obscure. At a permanent research station, water (in winter, ice) samples were taken throughout the year from 6 different depths, and 16 variables related to productivity and hydrochemistry were determined. Transparent and black-walled bell jars were installed on the sea bottom at depths ranging from 0 to 10 m in order to record rates of photosynthesis, respiration and chemical metabolism. In the region studied, two peaks of phytoplankton development occurred: one in winter and one in summer. The winter one coincided with a rise in orthophosphate and nitrate concentrations; the summer peak, with a rise in water temperature and increase of bottom regeneration. Photosynthesis of bottom diatoms was evidenced for all depths investigated. Ammonia and orthophosphate excretion were recorded in all experiments conducted on soft substrata. The measured rates of regeneration corresponded with the values expected in accordance with seasonal changes in nitrogen and phosphorus concentrations. Turnover rates of nitrogen and phosphorus between water and sediment were about 2 to 4 months. Higher production of coastal sea regions may be partly explained by the proximity of the photic layer to sediments and by the increased regeneration rates of biogenous elements.     

Potent inhibition of microRNA in vivo without degradation

Chemically modified antisense oligonucleotides (ASOs) are widely used as a tool to functionalize microRNAs (miRNAs). Reduction of miRNA level after ASO inhibition is commonly reported to show efficacy. Whether this is the most relevant endpoint for measuring miRNA inhibition has not been adequately addressed in the field although it has important implications for evaluating miRNA targeting studies. Using a novel approach to quantitate miRNA levels in the presence of excess ASO, we have discovered that the outcome of miRNA inhibition can vary depending on the chemical modification of the ASO. Although some miRNA inhibitors cause a decrease in mature miRNA levels, we have identified a novel 2′-fluoro/2′-methoxyethyl modified ASO motif with dramatically improved in vivo potency which does not. These studies show there are multiple mechanisms of miRNA inhibition by ASOs and that evaluation of secondary endpoints is crucial for interpreting miRNA inhibition studies.     

Advective Mixing of Pore Waters and Ecology of Sandy Sediments of the Ocean Shelf

Sand sediments are widely distributed in the shelf zone of the World Ocean. The main physical and ecological peculiarity of marine sands is the mobility of pore waters and their mixing with the near-bottom waters of the sea. The mixing is closely related to turbulent processes in the water column; the most important of these processes is wave mixing. This causes filtration of seawater through the sand, ensuring therefore, perhaps, the most large-scale filtration process on the Earth. Advective mixing redistributes dissolved oxygen and nutrients between the pore waters of the sand and the bulk of the seawater column and determines redox conditions in the sediment column, which usually are either oxidative or suboxic; the metals with variable valence, mostly iron, serve as a redox buffer. The regeneration of nutrients and nitrification of ammonia also take place in the sand column. The instability of advective mixing is considered as the major difficulty for qualitative assessment of energetic metabolism and regeneration of nutrients in sands as well as for revealing the ecological role of marine sands in coastal ecosystems.     

The denitrification potential and density of denitrifying bacteria in the bottom sediments of Matupi Harbor (Papua New Guinea)

The denitrification potential and density of denitrifying bacteria were determined in suboxidized sediments of Matupi Harbor (Papua New Guinea). The sediments were characterized by low denitrification potentials, not exceeding 0.8 nM/(g h). The maximum density of denitrifying bacteria was recorded in the upper sediment horizons and was 10⁴ cells/g of wet ground.     

The distribution of major biochemical components in the waters of the Kuril Islands

In this paper, data are presented on the distribution of dissolved and particulate carbohydrates, proteins, lipids, and nucleic acids (NAs) in the waters of the Kuril Islands on both the Sea of Okhotsk and Pacific Ocean sides. By analyzing discrepancies in the absolute and relative concentrations of these substances, it is revealed that the waters of the Sea of Okhotsk have a strong bioproductivity. Changes in the absolute and relative conventrations of the major biochemical components of dissolved organic matter (DOM) and particulate organic matter (POM) are shown to result from the biological activity of auto- and heterotrophs of shelf and deep-sea ecosystems. Carbohydrates and proteins prove to be the major biochemical components of DOM and POM, respectively. Given high primary productivity, the carbohydrate content in POM is comparable to that of protein. In the southern Kuril area, the high concentration of dissolved and particulate NAs (which exceeds that of dissolved protein) and the high content of dissolved lipids are both strongly associated with local fish and zooplankton distribution. In the shelf and pelagic waters, biological factors dominate the horizontal and vertical distribution patterns of the major biochemical components of DOM and POM. The hydrological regime only affects these patterns in the straits of the Kuril Islands. For the first time, the biochemical composition of DOM and POM in the sea surface microlayer (SML) is characterized. In this microlayer, the concentrations of major biochemical components of DOM and POM are, to a great extent, higher than in the underlying layer.     

Competition for RISC binding predicts in vitro potency of siRNA

Short interfering RNAs (siRNA) guide degradation of target RNA by the RNA-induced silencing complex (RISC). The use of siRNA in animals is limited partially due to the short half-life of siRNAs in tissues. Chemically modified siRNAs are necessary that maintain mRNA degradation activity, but are more stable to nucleases. In this study, we utilized alternating 2′-O-methyl and 2′-deoxy-2′-fluoro (OMe/F) chemically modified siRNA targeting PTEN and Eg5. OMe/F-modified siRNA consistently reduced mRNA and protein levels with equal or greater potency and efficacy than unmodified siRNA. We showed that modified siRNAs use the RISC mechanism and lead to cleavage of target mRNA at the same position as unmodified siRNA. We further demonstrated that siRNAs can compete with each other, where highly potent siRNAs can compete with less potent siRNAs, thus limiting the ability of siRNAs with lower potency to mediate mRNA degradation. In contrast, a siRNA with low potency cannot compete with a highly efficient siRNA. We established a correlation between siRNA potency and ability to compete with other siRNAs. Thus, siRNAs that are more potent inhibitors for mRNA destruction have the potential to out-compete less potent siRNAs indicating that the amount of a cellular component, perhaps RISC, limits siRNA activity.     

In vitro metabolism of 19-nor-1alpha, 25-(OH)2D2 in cultured cell lines: inducible synthesis of lipid- and water-soluble metabolites

The active vitamin D analog, 19-nor-1alpha,25-dihydroxyvitamin D2 (19-nor-1alpha,25-(OH)2D2), has a similar structure to the natural vitamin D hormone, 1a,25-dihydroxyvitamin D3 (1alpha,25-(OH)2D3), but lacks the C10-19 methylene group and possesses an ergosterol/ vitamin D2 rather than a cholesterol/vitamin D3 side chain. We have used this analog to investigate whether any of these structural features has any effect upon the type and rate of in vitro metabolism observed. Using a vitamin D-target cell, the human keratinocyte, HPK1A-ras, we observed formation of a number of metabolites, three of which were purified by extensive HPLC and conclusively identified by a combination of GC-MS and chemical derivatization as 19-nor-1alpha,24,25-(OH) 3D2, 19-nor-1alpha,24,25,26-(OH) 4D2, and 19-nor-1alpha,24,25,28-(OH)4,D2. The first metabolite is probably a product of the vitamin D-inducible cytochrome P450, P450cc24 (CYP24), while the latter two metabolites are likely to be further metabolic products of 19-nor-1alpha,24,25-(OH)3D2. These hydroxylated metabolites resemble those identified by other workers as products of the metabolism of 1alpha,25-(OH)2D2 in the perfused rat kidney. It therefore appears from the similar metabolic fate of 19-nor-1alpha,25-(OH)2D2 and 1alpha,25-(OH)2D2 that the lack of the C10-19 methylene group has little effect upon the nature of the lipid-soluble metabolic products and the rate of formation of these products seems to be comparable to that of products of 1alpha,25-(OH)2D3 in vitamin D-target cells. We also found extensive metabolism of 19-nor-1alpha,25(OH)2D2 to water-soluble metabolites in HPK1A-ras, metabolites which remain unidentified at this time. When we incubated 19-nor-1alpha,25-(OH)2D2 with the liver cell line HepG2, we obtained only 19-nor-1alpha,24,25-(OH)3D2. We conclude that 19-nor-1alpha,25-(OH)2D2 is efficiently metabolized by both vitamin D-target cells and liver cells.     

An autumn bloom of diatoms of the genus Pseudo-nitzschia H. Peragallo, 1900 in Amursky Bay, the Sea of Japan

A bloom of potentially toxic diatoms of the genus Pseudo-nitzschia was observed in October?CNovember 2005 in the northeastern part of Amursky Bay in the vicinity of Vladivostok (northeastern Sea of Japan) at a salinity of 31?C33.5?? and a water temperature of 6?C12°C. The most intense peak of Pseudo-nitzschia spp. cell density (with a mean value of 1428.9 thousand cells/liter), which was recorded in the second half of October after heavy rains, was mainly caused by the massive development of P. multistriata (67% of the total density) and P. calliantha (9%). A negative correlation was found between Pseudo-nitzschia spp. cell density and water salinity and NH4 concentration; a positive correlation was observed between diatom population density and water temperature.     

miR-122 regulation of lipid metabolism revealed by in vivo antisense targeting

Current understanding of microRNA (miRNA) biology is limited, and antisense oligonucleotide (ASO) inhibition of miRNAs is a powerful technique for their functionalization. To uncover the role of the liver-specific miR-122 in the adult liver, we inhibited it in mice with a 2'-O-methoxyethyl phosphorothioate ASO. miR-122 inhibition in normal mice resulted in reduced plasma cholesterol levels, increased hepatic fatty-acid oxidation, and a decrease in hepatic fatty-acid and cholesterol synthesis rates. Activation of the central metabolic sensor AMPK was also increased. miR-122 inhibition in a diet-induced obesity mouse model resulted in decreased plasma cholesterol levels and a significant improvement in liver steatosis, accompanied by reductions in several lipogenic genes. These results implicate miR-122 as a key regulator of cholesterol and fatty-acid metabolism in the adult liver and suggest that miR-122 may be an attractive therapeutic target for metabolic disease.