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51.
Jason D. Whiteley 《Water, air, and soil pollution》2005,160(1-4):77-93
The emission of Platinum–group elements (PGE) from automobile catalytic converters has led to rapid increases in Pt, Pd and Rh concentrations in roadside media. This paper examines the temporal variability of PGE levels in road dusts and roadside soils on a seasonal basis over a 12 month period. Road dust and roadside soil samples were analysed by ICP–MS following microwave digestion and cation exchange. Concentrations of PGE in all road dust and roadside soil samples are elevated above local background concentrations with maximum levels of Pt?440 ng g?1, Rh?91 ng g?1 and Pd?440 ng g?1. Systematic seasonal variations in PGE levels are observed in both sample types and the temporal distribution of PGE levels is affected by a number of factors including surface morphology and rainfall. PGE ratios in road dusts and soils are consistent with known catalytic converter composition throughout the sampling period indicating the PGE remain associated during mobilisation and transport. 相似文献
52.
Jason?M.?ConderEmail author Roman?P.?LannoEmail author 《Journal of Soils and Sediments》2003,3(1):13-20
Background. Earthworm heavy metal concentrations (critical body residues, CBRs) may be the most relevant measures of heavy
metal bioavailability in soils and may be linkable to toxic effects in order to better assess soil ecotoxicity. However, as
earthworms possess physiological mechanisms to secrete and/or sequester absorbed metals as toxicologically inactive forms,
total earthworm metal concentrations may not relate well with toxicity.
Objective The objectives of this research were to: i) develop LD50s (total earthworm metal concentration associated with 50% mortality) for Cd, Pb, and Zn; ii) evaluate the LD50 for Zn in a lethal Zn-smelter soil; iii) evaluate the lethal mixture toxicity of Cd, Pb, and Zn using earthworm metal concentrations
and the toxic unit (TU) approach; and iv) evaluate total and fractionated earthworm concentrations as indicators of sublethal
exposure.
Methods Earthworms (Eisenia fetida (Savigny)) were exposed to artificial soils spiked with Cd, Pb, Zn, and a Cd-Pb-Zn equitoxic mixture to estimate lethal CBRs
and mixture toxicity. To evaluate the CBR developed for Zn, earthworms were also exposed to Zn-contaminated field soils receiving
three different remediation treatments. Earthworm metal concentrations were measured using a procedure devised to isolate
toxicologically active metal burdens via separation into cytosolic and pellet fractions.
Results and Discussion Lethal CBRs inducing 50% mortality (LD50, 95% CI) were calculated to be 5.72 (3.54-7.31), 3.33 (2.97-3.69), and 8.19 (4.78-11.6) mmol/kg for Cd, Pb, and Zn, respectively.
Zn concentrations of dead earthworms exposed to a lethal remediated Zn-smelter soil were 3-fold above the LD50 for Zn and comparable to earthworm concentrations in lethal Zn-spiked artificial soils, despite a 14-fold difference in total
soil Zn concentration between lethal field and artificial soils. An evaluation of the acute mixture toxicity of Cd, Pb, and
Zn in artificial soils using the Toxic Unit (TU) approach revealed an LD50 (95% CI) of 0.99 (0.57-1.41) TU, indicating additive toxicity.
Conclusions Total Cd, Pb, and Zn concentrations in earthworms were good indicators of lethal metal exposure, and enabled the calculation
at LD50s for lethality. The Zn-LD50 developed in artificial soil was applicable to earthworms exposed to remediated Zn-smelter soil, despite a 14-fold difference
in total soil Zn concentrations. Mixture toxicity evaluated using LD50s from each single metal test indicated additive mixture toxicity among Cd, Pb, and Zn. Fractionation of earth worm tissues
into cytosolic and pellet digests yielded mixed results for detecting differences in exposure at the sublethal level
Recommendation and Outlook CBRs are useful in describing acute Cd, Pb, and Zn toxicity in earthworms, but linking sublethal exposure to total and/or
fractionated residues may be more difficult. More research on detoxification, regulation, and tissue and subcellular partitioning
of heavy metals in earthworms and other invertebrates is needed to establish the link between body residue and sublethal exposure
and toxicity. Keywords: Bioavailability; Cd; critical body residues; earthworms; metals; Pb; soil; Zn
An erratum to this article is available at . 相似文献
53.
Gram-positive bacteria face unique challenges in generating biologically active conformations for their exported proteins because they lack a dedicated compartment for folding secreted polypeptides. We have discovered that protein secretion by way of the general secretory (Sec) pathway in the important human pathogen Streptococcus pyogenes proceeds through a single microdomain. Unlike other mechanisms for asymmetry involving the Sec pathway, proteins destined for secretion are targeted to a single locus distal to either cell pole that has specialized to contain the Sec translocons. This subcellular organization may represent a paradigm for secretion common to other Gram-positive pathogens with profound implications for pathogenesis. 相似文献
54.
Wang Z Shen D Parsons DW Bardelli A Sager J Szabo S Ptak J Silliman N Peters BA van der Heijden MS Parmigiani G Yan H Wang TL Riggins G Powell SM Willson JK Markowitz S Kinzler KW Vogelstein B Velculescu VE 《Science (New York, N.Y.)》2004,304(5674):1164-1166
Tyrosine phosphorylation, regulated by protein tyrosine phosphatases (PTPs) and kinases (PTKs), is important in signaling pathways underlying tumorigenesis. A mutational analysis of the tyrosine phosphatase gene superfamily in human cancers identified 83 somatic mutations in six PTPs (PTPRF, PTPRG, PTPRT, PTPN3, PTPN13, PTPN14), affecting 26% of colorectal cancers and a smaller fraction of lung, breast, and gastric cancers. Fifteen mutations were nonsense, frameshift, or splice-site alterations predicted to result in truncated proteins lacking phosphatase activity. Five missense mutations in the most commonly altered PTP (PTPRT) were biochemically examined and found to reduce phosphatase activity. Expression of wild-type but not a mutant PTPRT in human cancer cells inhibited cell growth. These observations suggest that the mutated tyrosine phosphatases are tumor suppressor genes, regulating cellular pathways that may be amenable to therapeutic intervention. 相似文献
55.
Computational improvements reveal great bacterial diversity and high metal toxicity in soil 总被引:4,自引:0,他引:4
The complexity of soil bacterial communities has thus far confounded effective measurement. However, with improved analytical methods, we show that the abundance distribution and total diversity can be deciphered. Reanalysis of reassociation kinetics for bacterial community DNA from pristine and metal-polluted soils showed that a power law best described the abundance distributions. More than one million distinct genomes occurred in the pristine soil, exceeding previous estimates by two orders of magnitude. Metal pollution reduced diversity more than 99.9%, revealing the highly toxic effect of metal contamination, especially for rare taxa. 相似文献
56.
Prevention of vaginal SHIV transmission in rhesus macaques through inhibition of CCR5 总被引:1,自引:0,他引:1
Lederman MM Veazey RS Offord R Mosier DE Dufour J Mefford M Piatak M Lifson JD Salkowitz JR Rodriguez B Blauvelt A Hartley O 《Science (New York, N.Y.)》2004,306(5695):485-487
Topical agents, such as microbicides, that can protect against human immunodeficiency virus (HIV) transmission are urgently needed. Using a chimeric simian/human immunodeficiency virus (SHIV SF162), which is tropic for the chemokine receptor CCR5, we report that topical application of high doses of PSC-RANTES, an amino terminus-modified analog of the chemokine RANTES, provided potent protection against vaginal challenge in rhesus macaques. These experimental findings have potentially important implications for understanding vaginal transmission of HIV and the design of strategies for its prevention. 相似文献
57.
58.
Protein aggregation is involved in the pathogenesis of neurodegenerative diseases and hence is considered an attractive target for therapeutic intervention. However, protein-protein interactions are exceedingly difficult to inhibit. Small molecules lack sufficient steric bulk to prevent interactions between large peptide surfaces. To yield potent inhibitors of beta-amyloid (Abeta) aggregation, we synthesized small molecules that increase their steric bulk by binding to chaperones but also have a moiety available for interaction with Abeta. This strategy yields potent inhibitors of Abeta aggregation and could lead to therapeutics for Alzheimer's disease and other forms of neurodegeneration. 相似文献
59.
Biological imaging is now a quantitative technique for probing cellular structure and dynamics and is increasingly used for cell-based screens. However, the bioinformatics tools required for hypothesis-driven analysis of digital images are still immature. We are developing the Open Microscopy Environment (OME) as an informatics solution for the storage and analysis of optical microscope image data. OME aims to automate image analysis, modeling, and mining of large sets of images and specifies a flexible data model, a relational database, and an XML-encoded file standard that is usable by potentially any software tool. With this design, OME provides a first step toward biological image informatics. 相似文献
60.