Arsenic Resistance and Bioaccumulation of an Indigenous Bacterium Isolated from Aquifer Sediments of Datong Basin,Northern China

To obtain bacteria with arsenic accumulation potential that can be used to remove arsenic from contaminated waters, experiments were made to investigate the tolerance and accumulation to arsenic of an indigenous bacterium XZM002 isolated from aquifer sediments of Datong Basin, northern China. The results showed that strain XZM002 belongs to the genus Bacillus and has evolved defense mechanisms to reduce arsenic injury: the change of cellular shape from initial rod to oval and then to round with increment of arsenic toxicity. The effect of arsenate or arsenite on the bacterial growth was also investigated. Results showed that growth of the strain was inhibited under As(III) and high concentration As(V) (over 1200 μg l^?1) conditions in the first 2 days and promoted under low concentration As(V) (under 400 μg l^?1) condition. Its arsenic bioaccumulation potential was surveyed by monitoring the concentration changes of total arsenic and arsenic speciation in the medium and in the cytoplasm, and those of total arsenic on the membrane. Methylated arsenic species were not detected throughout the experiment. The results indicated that 11.5% of arsenic was removed from liquid medium into the bacterial cells and 9.22% of As(V) in the medium was transformed gradually to As(III) during 4 d of incubation. Approximately 80% of the total accumulated arsenic was adsorbed onto the membrane instead of into cytoplasm; and the arsenic accumulation almost approached saturation after incubation for 72 h.     

Influence of Arsenate on Lipid Peroxidation Levels and Antioxidant Enzyme Activities in Bacillus cereus Strain XZM002 Isolated from High Arsenic Aquifer Sediments

Bacillus cereus strain XZM002 isolated from high arsenic aquifer sediments of Datong Basin was applied to examine the effects of arsenate stress on antioxidant enzyme activities, lipid peroxidation levels and cell growth inhibition rate. After 2 d exposure, the cell growth inhibition rate enhanced with an increase of As(V) concentrations (0, 800, 1600 μg/l). Reactive oxygen species and glutathione contents, lipid peroxidation levels, and antioxidant enzymes (glutathione peroxidase, and other three) activities of the treated cells were significantly higher than those of the controls during 3 d exposure (p < 0.05). Besides, the levels of nine parameters reached maximum after 2 d exposure and increased significantly with increasing arsenate stress (p < 0.05). However, they returned to levels similar to those of the control on the fourth day of exposure. The results suggested that the antioxidant defense system in B. cereus strain XZM002 could protect the cells from oxidative damage induced by arsenate.     

Evidence for Tissue-Specific JAK/STAT Target Genes in Drosophila Optic Lobe Development

The evolutionarily conserved JAK/STAT pathway plays important roles in development and disease processes in humans. Although the signaling process has been well established, we know relatively little about what the relevant target genes are that mediate JAK/STAT activation during development. Here, we have used genome-wide microarrays to identify JAK/STAT targets in the optic lobes of the Drosophila brain and identified 47 genes that are positively regulated by JAK/STAT. About two-thirds of the genes encode proteins that have orthologs in humans. The STAT targets in the optic lobe appear to be different from the targets identified in other tissues, suggesting that JAK/STAT signaling may regulate different target genes in a tissue-specific manner. Functional analysis of Nop56, a cell-autonomous STAT target, revealed an essential role for this gene in the growth and proliferation of neuroepithelial stem cells in the optic lobe and an inhibitory role in lamina neurogenesis.     

The label free picomolar detection of insulin in blood serum

Insulin, a polypeptide hormone secreted by pancreatic cells, is a key regulator in glucose homeostasis. Its deficiency leads to insulin-dependent (type I) diabetes whereas resistance to insulin is common in type II diabetes, obesity and a range of endocrine disorders. Its determination is of considerable value, particularly in the clinical diagnosis of diabetes mellitus and the doping control of athletes. It has, additionally, been noted as a potential breast cancer marker (serum insulin levels being found to be raised in comparison to control patients). Electrochemical assays are potentially very cheap, highly sensitive, and very readily transposed to a point of care. Though there exist numerous examples of label free impedimetric or capacitative assaying of biomolecules, these are rarely demonstrated to be effective in complex biological mixtures or to be applicable to low molecular weight targets (since they operate through the interfacial displacement of water/ions and/or the steric blocking of a redox probe). We report herein an ultrasensitive electrochemical and label-free biosensor for insulin in blood serum with a clinically relevant linear range and detection limit of 1.2pM. The transducing surfaces, based on readily prepared, antibody modified, polyethylene glycol monolayer modified polycrystalline gold surfaces, respond in a highly specific and re-useable manner to the target in up to 50% blood serum.     

Isolation of Triterpenoid Glycosides (Saikosaponins) from Bupleurum polyclonum Y. Li et S. L. Pan and Their Chemical Structures

Sixteen triterpenoid glycosides, named S13 to S25, S37, S38 and S40, were isolated from the root of Bupleurum polyclonum Y. Li et S. L. Pan, and their structures were determined from NMR spectral analyses. Among them, S24, S37 and S38 were found to be new substances, their structures being established as 30-β-d-glucopyranosyl 30-hydroxysaikosaponin-b₂, 2″-O-acetylsaikosaponin-b₂ and 3″-O>-acetylsaikosaponin-b₂, respectively.     

Neural Response Phase Tracks How Listeners Learn New Acoustic Representations

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Influence of Bio-Lubricants on the Tribological Properties of Ti6Al4V Alloy

Titanium alloy is one of the best materials for biomedical applications due to its superior biocompatibility, outstanding corrosion resistance, and low elastic modulus. However, the friction and wear behaviors of titanium alloys were sensitive to the environment including lubrication. In order to clarify the wear mechanism of titanium alloy under different lubrications including deionized water, physiological saline and bovine serum, the friction and wear tests were performed between Ti6Al4V plates and Si₃N₄ ball on a universal multi-functional tester. The friction and the wear rate of titanium alloy were measured under dry friction and three different lubrication conditions. The worn surfaces were examined by scanning electron microscopy. The results revealed that under the dry friction, the wear resistance of titanium alloy was the worst since the wear mechanism was mainly the combination of abrasive wear and oxidation wear. It was also found that Ti6Al4V alloy had low friction coefficient and wear rate under three lubrication conditions, and its wear mechanism was adhesive wear.