Biomedical subjects

Steven N Liss

Publications and source records attributed to Steven N Liss.

8 recordsLinked to original sources

PubMed2006

The effects of methanol on the biofiltration of dimethyl sulfide in inorganic biofilters.

Air emissions from the pulp and paper industry frequently contain reduced sulfur compounds (RSC), such as dimethyl sulfide (DMS) mixed with volatile organic compounds (VOC) (e.g., methanol, MeOH) and it is desirable to treat either one or both of these groups of compounds. The objective of this study was to assess the effects of VOC (MeOH) on the biofiltration of DMS. Results obtained from continuous experiments using three bench-scale biofilters packed with inorganic material clearly show that MeOH has a positive effect (11-fold increase) on the biofiltration of DMS. Further experiments indicate that MeOH addition enhances biomass concentration and viability (threefold) in the biofilters. However, a suspension of MeOH addition causes a rapid significant increase (twofold) in the removal rate of DMS, suggesting that the presence of MeOH also has a competitive effect on DMS biodegradation. This negative effect was also confirmed in batch experiments. The decrease of biofilter performance with time for a long-term suspension of MeOH addition indicates that MeOH addition is necessary to sustain a high removal rate of DMS in inorganic biofilters. Results on metabolic products of DMS biodegradation demonstrate that DMS is almost completely converted to sulfate in the absence of MeOH, while it is partially oxidized to elemental sulfur in the presence of MeOH. This study suggests that there exists an optimum mix of DMS and MeOH for the treatment of DMS emissions in inorganic biofilters.

Air Pollutants↗

PubMed2005

Assessing the impact of land-applied biosolids from a thermomechanical (TMP) pulp mill to a suite of terrestrial and aquatic bioassay organisms under laboratory conditions.

The potential impact on a variety of bioassay organisms when pulp-mill biosolids from a thermomechanical pulp mill (western Canada) were applied to a reference soil has been investigated in a laboratory setup. The current research assessed acute, chronic, and reproductive impacts using a battery of terrestrial and aquatic organisms. Terrestrial organisms were exposed to soil amended with different concentrations of biosolids, while aquatic organisms were used to assess the impact of biosolids' runoff into receiving waters. The former bioassays showed that an application rate of 20 tonneshectare(-1) (tha(-1)) "bone-dry" biosolids applied to reference soil produced no observable adverse impact on the terrestrial organisms. In the latter assays, undiluted (100%) and 50% diluted biosolids' runoff into receiving water had a detrimental impact on the aquatic organisms. However, concentrations not exceeding 25% (environmentally relevant concentrations) had neither an acute nor chronic impact compared to reference populations. The organisms' abilities to reproduce were also unaltered. While this study only examined the biosolids from one mill, there is the potential that land-application of characteristically well-defined pulp mill biosolids may constitute an acceptable way of disposing of pulp and paper mill biosolid residues. However, the biosolids coming from different mills, with differing processes, must be dealt with on a case-by-case situation. Each series of biosolids must be rigorously tested for toxicological impact in the laboratory under tightly controlled conditions. Subsequently, field experimentation must be conducted before definitive conclusions can be made.

Animals↗

PubMed2004

Gene expression profiles for detecting and distinguishing potential endocrine-disrupting compounds in environmental samples.

Industrial and municipal processes may produce and release endocrine-disrupting compounds (EDCs) into the environment, but the exact nature of their effects is difficult to investigate. EDCs typically exert their effect by affecting gene expression aberrantly. To determine if gene expression profiles could be used to detect and distinguish estrogenic EDCs, an estrogen receptor positive human breast cancer cell line (MCF-7) was exposed to known estrogenic compounds, suspected EDCs, and extracts from three effluent samples. A set of specifically estrogen-regulated genes was identified by microarray analysis. Nine estrogen up-regulated genes (IGFBP4, HSPA8, B4GALT1, XBP1, KRT8, GTPBP4, HNRPAB, SLC2A1, and CALM1) and two estrogen down-regulated genes (ID2 and ZNF217) were consistently detectable in response to estrogen and other estrogenic compounds. Gene expression patterns in cells that were exposed to effluent sample extracts were compared to gene expression patterns in cells that were exposed to known endocrines. Using this technique, two of the effluent samples were shown to have estrogenic activity. This approach could easily be extended to screen for other types of receptor-mediated endocrine disruption. For example, cells expressing androgen or aryl hydrocarbon receptors could be used in gene expression profiling assays to detect androgenic effects or for the presence of bioactive aromatic hydrocarbons. Gene expression profiling is emerging as a sensitive and specific method to screen complex samples for endocrine disrupting activity.

Androgens↗

PubMed2003

Identification of estrogen-responsive genes by complementary deoxyribonucleic acid microarray and characterization of a novel early estrogen-induced gene: EEIG1.

Estrogen receptors (ERs) are nuclear transcription factors that regulate gene expression in response to estrogen and estrogen-like compounds. Identification of estrogen-regulated genes in target cells is an essential step toward understanding the molecular mechanisms of estrogen action. Using cDNA microarray examinations, 19 genes were identified as induced by 17 beta-estradiol in MCF-7 cells, 10 of which have been reported previously to be estrogen responsive or to be linked with ER status. Five known estrogen-regulated genes, E2IG4, IGFBP4, SLC2A1, XBP1 and B4GALT1, and AFG3L1, responded quickly to estrogen treatment. A novel estrogen-responsive gene was identified and named EEIG1for early estrogen-induced gene 1. EEIG1 was clearly induced by 17 beta-estradiol within 2 h of treatment, and was widely responsive to a group of estrogenic compounds including natural and synthetic estrogens and estrogenic environmental compounds. EEIG1 was expressed in ER-positive but not in ER-negative breast cancer cell lines. EEIG1 expression was repressed by antiestrogens 4-OH-tamoxifen and ICI 182,780 but not by protein synthesis inhibitors cycloheximide and puromycin. These results provide evidence that some estrogenic compounds differentially enhance the transcription of estrogen-regulated genes and suggest a role for EEIG1 in estrogen action.

Breast Neoplasms↗

PubMed2003

DNA microarrays for detecting endocrine-disrupting compounds.

It has recently been discovered that a number of synthetic chemicals and naturally occurring compounds released into the environment can influence endocrine activity. These endocrine-disrupting compounds (EDCs) are highly varied in structure, provenance, and mode of action (MOA). Many EDCs are anthropogenic, products of the chemical industry. Others are natural compounds. Although natural hormones exist at low levels in the environment, industrial sites such as pulp and paper mills and municipal sewage treatment plants can gather large amounts of natural EDCs and release them into the environment as part of their daily operations, thus increasing background environmental concentrations. The potential consequences of endocrine disruption are serious; however, comparatively little is known about the phenomenon. There is considerable debate over the true concentrations, sources, identity, and effects of potential EDCs. Investigation of the problem is hampered by the diversity of potential EDCs, which may have synergistic as well as individual effects, and the complexity of the endocrine system itself. Effective and standardized tests to accurately detect the presence of such chemicals in the environment are not available. While many tests have been proposed, they are unsatisfactory because they have only one limited endpoint (e.g., they can detect only one of many potential hormonal responses) and do not provide any mechanistic information. In addition, results from rapid screening tests are difficult to correlate with whole organism response, while larger whole organism bioassays are very costly and time consuming to perform. There is tremendous potential in the application of DNA microarray technology to screen for EDCs. DNA microarrays provide a "snapshot" of transcriptional activity in tissue samples showing which genes were actively expressed within the cells at one point in time. By combining this technology with human cell lines grown in vitro, it should be possible to conduct relatively rapid and straightforward assays to identify EDCs by observing the changes in gene expression patterns in response to exposure.

Animals↗

PubMed2003

Monitoring gene expression in mixed microbial communities by using DNA microarrays.

A DNA microarray to monitor the expression of bacterial metabolic genes within mixed microbial communities was designed and tested. Total RNA was extracted from pure and mixed cultures containing the 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading bacterium Ralstonia eutropha JMP134, and the inducing agent 2,4-D. Induction of the 2,4-D catabolic genes present in this organism was readily detected 4, 7, and 24 h after the addition of 2,4-D. This strain was diluted into a constructed mixed microbial community derived from a laboratory scale sequencing batch reactor. Induction of two of five 2,4-D catabolic genes (tfdA and tfdC) from populations of JMP134 as low as 10(5) cells/ml was clearly detected against a background of 10(8) cells/ml. Induction of two others (tfdB and tfdE) was detected from populations of 10(6) cells/ml in the same background; however, the last gene, tfdF, showed no significant induction due to high variability. In another experiment, the induction of resin acid degradative genes was statistically detectable in sludge-fed pulp mill effluent exposed to dehydroabietic acid in batch experiments. We conclude that microarrays will be useful tools for the detection of bacterial gene expression in wastewaters and other complex systems.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2003

Phylogenetic analysis of bacterial populations in an anaerobic microbial consortium capable of degrading saturation concentrations of tetrachloroethylene.

An anaerobic microbial consortium able to biodegrade saturation levels of perchloroethylene (PCE) in a column containing a source zone of PCE was examined phylogenetically to determine microbial community structure and spatial variation in relation to the PCE source. The consortium was comprised of at least 34 members with 7 organisms sharing affiliations with known respiratory or cometabolic dechlorinators. Seven other organisms had their closest phylogenetic relative detected in other environments containing chlorinated compounds. Based on denaturing gradient gel electrophoresis, significant Bacteria were Dehalococcoides ethenogenes, Shewanella putrefaciens, and an Acetobacterium species. Spatial variations in community structure of the consortium relative to the PCE source zone were observed. A Pseudomonas species was predominant in a zone 30 cm from the PCE source. A Methanothrix species was predominant at points over 85 cm from the source zone. A Trichlorobacter species was detected where PCE concentrations were highest, up to 85 cm from the PCE source, whereas D. ethenogenes was ubiquitous to over 128 cm from the PCE source.

Anaerobiosis↗

PubMedDate not supplied

Compartmentalization of metals within the diverse colloidal matrices comprising activated sludge microbial flocs.

Activated sludge floc from a wastewater treatment system was characterized, with regard to principal structural, chemical, and microbiological components and properties, in relation to contaminant-colloid associations and settling. Multiscale analytical microscopies, in conjunction with multimethod sample preparations, were used correlatively to characterize diverse colloidal matrices within microbial floc. Transmission electron microscopy, in conjunction with energy dispersive spectroscopy (EDS), revealed specific associations of contaminant heavy metals with individual bacterial cells and with extracellular polymeric substances (EPS). Floc structure was mapped from the level of gross morphology down to the nano-scale, and flocs were described with respect to settling properties, size, shape, density, porosity, bound water content, and EPS chemical composition; gross surface properties were also measured for correlation with principal floc features. Compartmentalization results based on 171 EDS analyses and representative high-resolution images showed that nano-scale agglomerations of (i) silver (100%) and (ii) zinc (91%) were confined almost entirely to EPS matrices while (iii) Pb (100%) was confined to intracellular granules and (iv) aluminum was partitioned between EPS matrices (41%) and intracellular matrices (59%). The results suggest that engineered changes in microbial physiology and/or in macromolecular EPS composition may influence metal removal efficiencies.

Flocculation↗