Potential oxidative stress due to Pb exposure

Digitized from print original stored in HDR. Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references: leaves 15-18.Program year: 1997/1998The hazards of Pb exposure has been a topic of concern for many years. This research was developed to investigate the possibility of Pb induced oxidative stress. The research objectives were to observe Pb induced lipid peroxidation and Pb induced increases in oxidation of glutathione in K562 myelogenous leukemia cells at low Pb levels. The approach consisted of incubating K562 cells in solutions of 0, 300, and 700 ppb Pb dissolved in RPMI cell medium for a total of 96 hours. After this period of incubation, aliquots of cells were taken, placed in clean medium, and incubated for 96 hours. Samples were taken at 24 and 96 hours of Pb exposure, and at 96 hours after cessation of Pb exposure, then subsequently assayed for lipid peroxidation and glutathione levels. Lipid peroxidation was determined by the detection of malondialdehyde (MDA) spectrophotometrically at 535nm by the Thiobarbituric acid (TBA) assay, while oxidized and reduced glutathione levels were determined spectrophotometrically at 412 nm. Results showed no change in MDA levels in treated cells as compared to the control. The GSH: GSSG ratios were significantly greater for treated cells at 96 hours of exposure as compared to the controls, indicating a possible compensatory response

Potential oxidative stress due to Pb exposure

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references: leaves 15-18.The hazards of Pb exposure has been a topic of concern for many years. This research was developed to investigate the possibility of Pb induced oxidative stress. The research objectives were to observe Pb induced lipid peroxidation and Pb induced increases in oxidation of glutathione in K562 myelogenous leukemia cells at low Pb levels. The approach consisted of incubating K562 cells in solutions of 0, 300, and 700 ppb Pb dissolved in RPMI cell medium for a total of 96 hours. After this period of incubation aliquots of cells were taken, placed in clean medium, and incubated for 96 hours. Samples were taken at 24 and 96 hours of Pb exposure, and at 96 hours after cessation of Pb exposure, then subsequently assayed for lipid peroxidation and glutathione levels. Lipid peroxidation was determined by the detection of malondialdehyde (MDA) spectrophotometrically at 535nm by the Thiobarbituric acid (TBA) assay, while oxidized and reduced glutathione levels were determined spectrophotometrically at 412 nm. Results showed no change in MDA levels in treated cells as compared to the control. The GSH:GSSG ratios were significantly greater for treated cells at 96 hours of exposure as compared to the controls, indicating a possible compensatory response

Microfabricated Genomic Analysis System

Genetic sequencing and many genetic tests and assays require electrophoretic separation of DNA. In this technique, DNA fragments are separated by size as they migrate through a sieving gel under the influence of an applied electric field. In order to conduct these analyses on-orbit, it is essential to acquire the capability to efficiently perform electrophoresis in a microgravity environment. Conventional bench top electrophoresis equipment is large and cumbersome and does not lead itself to on-orbit utilization. Much of the previous research regarding on-orbit electrophoresis involved altering conventional electrophoresis equipment for bioprocessing, purification, and/or separation technology applications. A new and more efficient approach to on-orbit electrophoresis is the use of a microfabricated electrophoresis platform. These platforms are much smaller, less expensive to produce and operate, use less power, require smaller sample sizes (nanoliters), and achieve separation in a much shorter distance (a few centimeters instead of 10 s or 100 s of centimeters.) In contrast to previous applications, this platform would be utilized as an analytical tool for life science/medical research, environmental monitoring, and medical diagnoses. Identification of infectious agents as well as radiation related damage are significant to NASA s efforts to maintain, study, and monitor crew health during and in support of near-Earth and interplanetary missions. The capability to perform genetic assays on-orbit is imperative to conduct relevant and insightful biological and medical research, as well as continuing NASA s search for life elsewhere. This technology would provide an essential analytical tool for research conducted in a microgravity environment (Shuttle, ISS, long duration/interplanetary missions.) In addition, this technology could serve as a critical and invaluable component of a biosentinel system to monitor space environment genotoxic insults to include radiation

A Process Integration Approach to the Strategic Design and Scheduling of Biorefineries

This work focused upon design and operation of biodiesel production facilities in support of the broader goal of developing a strategic approach to the development of biorefineries. Biodiesel production provided an appropriate starting point for these efforts. The work was segregated into two stages. Various feedstocks may be utilized to produce biodiesel, to include virgin vegetable oils and waste cooking oil. With changing prices, supply, and demand of feedstocks, a need exists to consider various feedstock options. The objective of the first stage was to develop a systematic procedure for scheduling and operation of flexible biodiesel plants accommodating a variety of feedstocks. This work employed a holistic approach and combination of process simulation, synthesis, and integration techniques to provide: process simulation of a biodiesel plant for various feedstocks, integration of energy and mass resources, optimization of process design and scheduling, and techno-economic assessment and sensitivity analysis of proposed schemes. An optimization formulation was developed to determine scheduling and operation for various feedstocks and a case study solved to illustrate the merits of the devised procedure. With increasing attention to the environmental impact of discharging greenhouse gases (GHGs), there has been growing public pressure to reduce the carbon footprint associated with fossil fuel use. In this context, one key strategy is substitution of fossil fuels with biofuels such as biodiesel. Design of biodiesel plants has traditionally been conducted based on technical and economic criteria. GHG policies have the potential to significantly alter design of these facilities, selection of feedstocks, and scheduling of multiple feedstocks. The objective of the second stage was to develop a systematic approach to design and scheduling of biodiesel production processes while accounting for the effect of GHG policies. An optimization formulation was developed to maximize profit of the process subject to flowsheet synthesis and performance modeling equations. The carbon footprint is accounted for through a life cycle analysis (LCA). The objective function includes a term reflecting the impact of the LCA of a feedstock and its processing to biodiesel. A multiperiod approach was used and a case study solved with several scenarios of feedstocks and GHG policies

Chemical and gravity dependent factors affecting Escherichia coli lag phase termination

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 88-91).Issued also on microfiche from Lange Micrographics.The objectives of this study were to identify and quantify chemical compounds suspected to induce and affect bacterial lag phase termination and to characterize the role of gravity in lag phase termination by correlating effects on chemical concentration gradients. The organism used for this study was Escherichia coli ATCC 4157. Acetic acid was not found in the extracellular environment of E. coli at the end of lag phase. Lactic acid was found in the extracellular environment of E. coli at the end of lag phase in small amounts. Evidence was not found to support the hypothesis that either lactic acid or CO₂ are critical by-products for lag phase termination. At a significance level of α = 0.05, lactic acid (20 and 30 mg/L) supplementation increased E. coli lag phase length. At a significance level of α = 0.10, CO₂ supplementation via bubbling through 5% CO₂ in air from a pressurized canister and equilibration of media with CO₂ in a flask increased lag phase length by 1.39 and 2.12 hours, respectively. Based on mathematical analysis, gravity does not affect the mass transfer of lactic acid and CO₂ away from a single E. coli cell, but does affect the mass transfer of proteins having diffusivities on the order of 1 to10 []m²/s. Mass transfer for such proteins is greater when gravity is present. Evidence was not found to support the hypotheses that lactic acid and CO₂ are critical components for lag phase termination. This conclusion was supported by the outcome of the supplementation experiments, and the relative movement and by-product concentration gradient analyses. The latter two analyses indicate by-products the size of lactic acid (D = 2200 []m²/s) and CO₂ (D = 2800 []m²/s) readily diffuse away from a single E. coli cell while by-products with diffusivities closer to 1 to 10 []m²/s will remain at higher concentrations closer to the cell. Therefore, working with the supposition that critical by-products are necessary for lag phase termination it is suggested that by-products having diffusivities on the order of 1 to 10 []m²/s are likely candidates to be critical by-products for lag phase termination

Potential Oxidative Stress due to Pb Exposure

Program year: 1997/1998Digitized from print original stored in HDRThe hazards of Pb exposure has been a topic of concern for many years. This research was developed to investigate the possibility of Pb induced oxidative stress. The research objectives were to observe Pb induced lipid peroxidation and Pb induced increases in oxidation of glutathione in K562 myelogenous leukemia cells at low Pb levels. The approach consisted of incubating K562 cells in solutions of 0, 300, and 700 ppb Pb dissolved in RPMI cell medium for a total of 96 hours. After this period of incubation, aliquots of cells were taken, placed in clean medium, and incubated for 96 hours. Samples were taken at 24 and 96 hours of Pb exposure, and at 96 hours after cessation of Pb exposure, then subsequently assayed for lipid peroxidation and glutathione levels. Lipid peroxidation was determined by the detection of malondialdehyde (MDA) spectrophotometrically at 535nm by the Thiobarbituric acid (TBA) assay, while oxidized and reduced glutathione levels were determined spectrophotometrically at 412 nm. Results showed no change in MDA levels in treated cells as compared to the control. The GSH: GSSG ratios were significantly greater for treated cells at 96 hours of exposure as compared to the controls, indicating a possible compensatory response

GNU Radio

GNU Radio is a free & open-source software development toolkit that provides signal processing blocks to implement software radios. It can be used with readily-available, low-cost external RF hardware to create software-defined radios, or without hardware in a simulation-like environment. It is widely used in hobbyist, academic, and commercial environments to support both wireless communications research and real-world radio systems