Publications by Colleges and Departments (MSU - Bozeman)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/3
Browse
869 results
Search Results
Item Cytoprotective Nrf2 pathway is induced in chronically txnrd 1-deficient hepatocytes(2009-07) Suvorova, Elena S.; Lucas, Olivier; Weisend, Carla M.; Rollins, MaryClare F.; Merrill, Gary F.; Capecchi, Mario R.; Schmidt, Edward E."Background Metabolically active cells require robust mechanisms to combat oxidative stress. The cytoplasmic thioredoxin reductase/thioredoxin (Txnrd1/Txn1) system maintains reduced protein dithiols and provides electrons to some cellular reductases, including peroxiredoxins. Principal Findings Here we generated mice in which the txnrd1 gene, encoding Txnrd1, was specifically disrupted in all parenchymal hepatocytes. Txnrd1-deficient livers exhibited a transcriptome response in which 56 mRNAs were induced and 12 were repressed. Based on the global hybridization profile, this represented only 0.3% of the liver transcriptome. Since most liver mRNAs were unaffected, compensatory responses were evidently effective. Nuclear pre-mRNA levels indicated the response was transcriptional. Twenty-one of the induced genes contained known antioxidant response elements (AREs), which are binding sites for the oxidative and chemical stress-induced transcription factor Nrf2. Txnrd1-deficient livers showed increased accumulation of nuclear Nrf2 protein and chromatin immunoprecipitation on the endogenous nqo1 and aox1 promoters in fibroblasts indicated that Txnrd1 ablation triggered in vivo assembly of Nrf2 on each. Conclusions Chronic deletion of Txnrd1 results in induction of the Nrf2 pathway, which contributes to an effective compensatory response."Item Measurement of local effective diffusivity in heterogeneous biofilms(1998-11) Beyenal, Haluk; Tanyolac, A.; Lewandowski, ZbigniewWe have developed a novel technique to measure local effective diffusivity distribution in heterogeneous biofilms. Mobile microelectrodes (tip diameter 10 μm) and the limiting current technique were employed to measure the effective diffusivity of electroactive species introduced to natural and artificial biofilms. We calibrated the microelectrodes in artificial biofilms of known effective diffusivity and known density. In mixed population biofilms, local effective diffusivity varied from one location to another and decreased toward the bottom of the biofilm. We related local effective diffusivity to local biofilm density using an empirical equation. Surface-averaged biomass density depended on liquid flow velocity at which the biofilms were grown. The higher the flow velocity, the denser were the biofilms. Our technique permits fast evaluation of local effective diffusivity and biofilm density in heterogeneous biofilms.Item Evaluation of regulations for monitoring the microbial quality of drinking water(1998) Camper, Anne K.; Hamilton, Martin A.Item Spatial relations between bacteria and metal surfaces(1997) Little, Brenda J.; Wagner, Patricia A.; Lewandowski, ZbigniewItem Strategies for prophylaxis against prosthetic valve endocarditis: a review article(1998-05) Hyde, J. A.; Darouiche, R. O.; Costerton, J. WilliamItem Development and structure of drinking water biofilms and techniques for their study(1999-12) Camper, Anne K.; Burr, Mark D.; Ellis, B. D.; Butterfield, Phillip W.; Abernathy, Calvin G.Item Quantifying biofilm structure(1999) Lewandowski, Zbigniew; Webb, D.; Hamilton, Martin A.; Harkin, GaryThis article defines some quantitative parameters for describing the structure of a biofilm. The parameters can be calculated from a two-dimensional cross-sectional image on a plane parallel to the substratum within an in situ biofilm. Such images can be acquired using a confocal scanning laser microscope (CSLM). The parameters will eventually be used for eliciting relationships between the biofilm's structure and its biochemical function, and for computer model evaluation. The results shown here indicate that the structural parameters appear to be reaching steady-state conditions as the biofilm grows to a steady state.Item The role of (bio)surfactant sorption in promoting the bioavailability of nutrients localized at the solid-water interface(1999) Jordan, Ryan N.; Nichols, E. P.; Cunningham, Alfred B.Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailability of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.Item Influence of hydrodynamics and nutrients on biofilm structure(1999-12) Stoodley, Paul; Dodds, I.; Boyle, John D.; Lappin-Scott, H. M.Hydrodynamic conditions control two interlinked parameters; mass transfer and drag, and will, therefore, significantly influence many of the processes involved in biofilm development. The goal of this research was to determine the effect of flow velocity and nutrients on biofilm structure. Biofilms were grown in square glass capillary flow cells under laminar and turbulent flows. Biofilms were observed microscopically under flow conditions using image analysis. Mixed species bacterial biofilms were grown with glucose (40 mg/l) as the limiting nutrient. Biofilms grown under laminar conditions were patchy and consisted of roughly circular cell clusters separated by interstitial voids. Biofilms in the turbulent flow cell were also patchy but these biofilms consisted of patches of ripples and elongated ‘streamers' which oscillated in the flow. To assess the influence of changing nutrient conditions on biofilm structure the glucose concentration was increased from 40 to 400 mg/l on an established 21 day old biofilm growing in turbulent flow. The cell clusters grew rapidly and the thickness of the biofilm increased from 30 μ to 130 μ within 17 h. The ripples disappeared after 10 hours. After 5 d the glucose concentration was reduced back to 40 mg/l. There was a loss of biomass and patches of ripples were re-established within a further 2 d.Item Bacterial biofilms: A common cause of persistent infections(1999-05) Costerton, J. William; Stewart, Philip S.; Greenberg, E. P.Bacteria that attach to surfaces aggregate in a hydrated polymeric matrix of their own synthesis to form biofilms. Formation of these sessile communities and their inherent resistance to antimicrobial agents are at the root of many persistent and chronic bacterial infections. Studies of biofilms have revealed differentiated, structured groups of cells with community properties. Recent advances in our understanding of the genetic and molecular basis of bacterial community behavior point to therapeutic targets that may provide a means for the control of biofilm infections.