1,578 Matching Results

Search Results

Advanced search parameters have been applied.

Syntheses of Antimetabolites

Description: In these studies several different types of antimetabolites were synthesized, and their biological effects were examined in various assay systems. More extensive investigations were done in microbial systems in which many of the compounds proved to be inhibitory to growth, and attempts were made to determine the mode of biochemical action by adding supplements of the appropriate natural metabolite.
Date: January 1970
Creator: Clifton, George Gil
Partner: UNT Libraries

Mechanisms of immunosuppression and cellular mechanisms of secondary disease. Final report, September 1, 1971--August 31, 1973

Description: The development of antibody-producing cells was studied in vivo and in vitro using radiation, anti-tumor drugs, and antibiotics. The mechanism of action of phenothiazines was studied at the cellular level using a cell separation technique. The effects of puromycin and purine antimetabolites on the various development stages of cells were studied. (HLW)
Date: January 1, 1973
Creator: Uyeki, E M
Partner: UNT Libraries Government Documents Department

Report of Flood, Oil Sheen, and fish Kill Incidents on East Fork Poplar Creek at the Oak Ridge Y-12 Plant

Description: Water quality and plant opemtion irriiormation provided by the Y-12 Plant strongly suggest that a dechlorinating agent, applied to the raw water released below the North-South Pipes was responsible for the toxicity resulting in the fish kill of July 24. Dissolved oxygen (DO) measurements in upper EFPC indicai e that low oxygen levels (3-5 ppm) occurred for a period of up to 30 min. This slug of low DO water traveling down EFPC to the lake could easily explain the massive fish kill and the resulting observations. Dissolved oxygen levels of 5.2 ppm or lower are documented as causing problems for warmwater fish species (Heath 1995). The presence of other stressors, including a range of petrochemicals, tends to lower resistance to low oxygen conditions. Given the sequence of events in upper EFPC in the few days prior to July 24, where extremely high flows were followed by inputs of a wide range of low concentrations of oils, the sensitivity to low DO conditions might be heightened. The possible toxic impact of ::he oils and other contaminants reaching EFPC as a result of the heavy rainfidl on July 22 doesn't appear significant enough to be the sole cause of the kill on July 24. Even during the height of the kill, a large school of fish remained immediately downstream of the North-South Pipes. If the toxicity of waters flowing through this outlet were the primary cause of the kill, then it would be expected that this school of fish would not have been present immediately below the pipes. Any impact of waters entering from other sources, such as pumping of basements WOUIC1 have produced a staggered pattern of mortality, with fishing dying in different localities at different times and rates. Further, it would be expected that the morta.lhy observed would have ...
Date: September 1, 1997
Creator: Skaggs, B.E.
Partner: UNT Libraries Government Documents Department

Molecular dosimetry of chemical mutagens: measurement of molecular dose and DNA repair germ cells

Description: Molecular dosimetry in the germ cells of male mice is reviewed with regard to in vivo alkylation of sperm heads, in vivo alkylation of sperm DNA, and possible alkylation of sperm protamine. DNA repair in male germ cells is reviewed with regard to basic design of experiments, DNA repair in various stages of spermatogenesis, effect of protamine on DNA repair following treatment with EMS or x radiation, and induction of DNA repair by methyl methanesulfonate, propyl methanesulfonate, and isopropyl methanesulfonate. (HLW)
Date: January 1, 1975
Creator: Sega, G.A.
Partner: UNT Libraries Government Documents Department

The effect of elevated carbon dioxide on a Sierra-Nevadan dominant species: Pinus ponderosa

Description: The impact of increasing atmospheric C0{sub 2} has not been fully evaluated on western coniferous forest species. Two year old seedlings of Pinusponderosa were grown in environmentally controlled chambers under increased C0{sub 2} conditions for 6 months. These trees exhibit morphological, physiological, and biochemical alterations when compared to our controls. Analysis of whole plant biomass distribution has shown no significant effect to the root to shoot ratios, however needles subjected to elevated C0{sub 2} exhibited an increased overall specific needle mass and a decreased total needle area. Morphological changes at the needle level included decreased mesophyll to vascular tissue 91 ratio and variations in starch storage in chloroplasts. The elevated CO{sub 2} increased internal CO{sub 2} concentrations and assimilation of carbon. Biochemical assays revealed that ribulose-bisphosphate carboxylase specific activities increased on per unit area basis with C0{sub 2} treatment levels. Sucrose phosphate synthase (SPS) activities exhibited an increase of 55% in the 700 uL L{sup {minus}1} treatment. These results indicate that the sink-source relationships of these trees have shifted carbon allocation toward above ground growth, possibly due to transport limitations.
Date: January 1, 1995
Creator: Pushnik, J.C.; Demaree, R.S.; Flory, W.B.; Bauer, S.M.; Houpis, J.L.J. & Anderson, P.D.
Partner: UNT Libraries Government Documents Department

Modeling DNA Replication Intermediates

Description: While there is now available a great deal of information on double stranded DNA from X-ray crystallography, high resolution NMR and computer modeling, very little is known about structures that are representative of the DNA core of replication intermediates. DNA replication occurs at a single strand/double strand junction and bulged out intermediates near the junction can lead to frameshift mutations. The single stranded domains are particularly challenging. Our interest is focused on strategies for modeling the DNA of these types of replication intermediates. Modeling such structures presents special problems in addressing the multiple minimum problem and in treating the electrostatic component of the force field. We are testing a number of search strategies for locating low energy structures of these types and we are also investigating two different distance dependent dielectric functions in the coulombic term of the force field. We are studying both unmodified DNA and DNA damaged by aromatic amines, carcinogens present in the environment in tobacco smoke, barbecued meats and automobile exhaust. The nature of the structure adopted by the carcinogen modified DNA at the replication fork plays a key role in determining whether the carcinogen will cause a mutation during replication that can initiate the carcinogenic process. In the present work results are presented for unmodified DNA.
Date: June 1, 1997
Creator: Broyde, S.; Roy, D. & Shapiro, R.
Partner: UNT Libraries Government Documents Department

Changes in gene expression following EMF exposure

Description: Experiments were designed to examine the effects of electromagnetic field (EMF) exposure on specific gene expression, an effect that can be deleterious, beneficial, or neutral, depending on the long-term consequences; however, the proof of a reproducible, quantitative biological effect (such as change in gene expression) will lead to latter experiments aimed at determining the relative contribution of these changes to cellular consequences. Past work by ourselves and by others has shown that measures of gene expression are extremely sensitive indicators of the cellular and biological effects of ionizing radiation, with transcriptional changes being detected by exposure of cells to doses of {gamma}-rays as low as 0.01 cGy that have no pronounced cellular consequences. On the basis of this work, the authors hypothesized that measures of gene expression will be equally sensitive to EMF effects on cells.
Date: October 1, 1997
Creator: Woloschak, G.E.; Paunesku, T.; Chang-Liu, C.M.; Loberg, L.; Gauger, J. & McCormick, D.
Partner: UNT Libraries Government Documents Department

Physiological ecology of SRS Carolina bay phytoplankton communities: Effects of nutrient changes and CO{sub 2} sources

Description: Impacts of land-use activities on wetland ecosystems are important issues for environmental planners, conservation groups, and government agencies. The progress report of this project at DOE`s Savannah River Site focused on two specific objectives: determination of the effects of nutrient enrichment (fertilizing during wetlands restoration) on phytoplankton communities and comparison of phytoplankton community dynamics during the current extended hydroperiod for Carolina Bays with patterns in previous drier years.
Date: November 1, 1992
Creator: Williams, J.B.
Partner: UNT Libraries Government Documents Department

Small mammal study of Sandia Canyon, 1994 and 1995

Description: A wide range of plant and wildlife species utilize water discharged from facilities at Los Alamos National Laboratory (LANL). The purpose of this study was to gather baseline data of small mammal populations and compare small mammal characteristics within three areas of Sandia Canyon, which receives outfall effluents from multiple sources. Three small mammal trapping webs were placed in the upper portion of Sandia Canyon, the first two were centered in a cattail-dominated marsh with a ponderosa pine overstory and the third web was placed in a much drier transition area with a ponderosa pine overstory. Webs 1 and 2 had the highest species diversity indices with deer mice the most commonly captured species in all webs. However, at Web 1, voles, shrews, and harvest mice, species more commonly found in moist habitats, made up a much greater overall percentage (65.6%) than did deer mice and brush mice (34.5%). The highest densities and biomass of animals were found in Web 1 with a continual decrease in density estimates in each web downstream. There is no statistical difference between the mean body weights of deer mice and brush mice between sites. Mean body length was also determined not to be statistically different between the webs (GLM [deer mouse], F = 0.89, p = 0.4117; GLM [brush mouse], F = 2.49, p = 0.0999). Furthermore, no statistical difference between webs was found for the mean lean body masses of deer and brush mice (GLM [deer mouse], F = 2.54, p = 0.0838; GLM [brush mouse], F = 1.60, p = 0.2229). Additional monitoring studies should be conducted in Sandia Canyon so comparisons over time can be made. In addition, rodent tissues should be sampled for contaminants and then compared to background or control populations elsewhere at the Laboratory or at an off-site ...
Date: November 1, 1996
Creator: Bennett, K. & Biggs, J.
Partner: UNT Libraries Government Documents Department

Evaluating the risk of air pollution to forests in central and Eastern Europe

Description: Foliar damage to trees by air pollution in Central and Eastern Europe has been a major scientific and political issue. Emissions of toxic gases such as sulfur dioxide and nitrogen oxides can have wide-ranging effects on local and regional vegetation that can be compounded by other environmental stresses to plant growth. Since uptake and physiological effects of these gases on tree leaves we largely, mediated by stomata, surrogate methods for estimating pollutant conductances into leaves and forest canopies may lead to risk assessments for major vegetation types that can then be used in regional planning. Management options to ameliorate or mitigate air pollutant damage to forests and losses in productivity are likely to be more difficult to widely implement than on-the-stack emissions abatement. Informed management and policy decisions regarding Central and Eastern European forests are dependent on the development of quantitative tools and models for risk assessment of the effects of atmospheric pollutants on ecosystem health and productivity.
Date: September 1, 1996
Creator: Ellsworth, D.S. & Oleksyn, J.
Partner: UNT Libraries Government Documents Department

Monitoring and evaluation plan for the Nez Perce Tribal Hatchery

Description: The Nez Perce Tribe has proposed to build and operate the Nez Perce Tribal Hatchery (NPTH) in the Clearwater River subbasin of Idaho for the purpose of restoring self-sustaining populations of spring, summer, and fall chinook salmon to their native habitats. The project comprises a combination of incubation and rearing facilities, satellite rearing facilities, juvenile and adult collection sites, and associated production and harvest management activities. As currently conceived, the NPTH program will produce approximately 768,000 spring chinook parr, 800,000 summer chinook fry, and 2,000,000 fall chinook fry on an annual basis. Hatchery fish would be spawned, reared, and released under conditions that promote wild-type characteristics, minimize genetic changes in both hatchery and wild chinook populations, and minimize undesirable ecological interactions. The primary objective is to enable hatchery-produced fish to return to reproduce naturally in the streams in which they are released. These and other characteristics of the project are described in further detail in the Nez Perce Tribal Hatchery Master Plan, the 1995 Supplement to the Master Plan, and the Nez Perce Tribal Hatchery Program Environmental Impact Statement. The report in hand is referred to in project literature as the NPTH Monitoring and Evaluation (M&E) Plan. This report describes monitoring and evaluation activities that will help NPTH managers determine whether they were successful in restoring chinook salmon populations and avoiding adverse ecological impacts.
Date: August 1, 1996
Creator: Steward, C.R.
Partner: UNT Libraries Government Documents Department


Description: A maturing loblolly pine (Pinus taeda L.) forest was exposed to elevated CO{sub 2} in the natural environment in a perturbation study conducted over three seasons using the free-air CO{sub 2} enrichment (FACE) technique. At the time measurements were begun in this study, the pine canopy was comprised entirely of foliage which had developed under elevated CO{sub 2} conditions (atmospheric [CO{sub 2}] {approx} 550 {micro}mol mol{sup {minus}1}). Measurements of leaf photosynthetic responses to CO{sub 2} were taken to examine the effects of elevated CO{sub 2} on photosynthetic N nutrition in a pine canopy under elevated CO{sub 2}. Photosynthetic CO{sub 2} response curves (A-c{sub i} curves) were similar in FACE trees under elevated CO{sub 2} compared with counterpart trees in ambient plots for the first foliage cohort produced in the second season of CO{sub 2} exposure, with changes in curve form detected in the foliage cohorts subsequently produced under elevated CO{sub 2}. Differences in the functional relationship between carboxylation rate and N{sub a} suggest that for a given N{sub a} allocated among successive cohorts of foliage in the upper canopy, V{sub c max} was 17% lower in FACE versus Ambient trees. The authors also found that foliar Rubisco content per unit total protein derived from Western blot analysis was lower in late-season foliage in FACE foliage compared with ambient-grown foliage. The results illustrate a potentially important mode of physiological adjustment to growth conditions that may operate in forest canopies. Their findings suggest that mature loblolly pine trees growing in the field may have the capacity for shifts in intrinsic nitrogen utilization for photosynthesis under elevated CO{sub 2} that are not dependent on changes in leaf N. While carboxylation efficiency per unit N apparently decreased under elevated CO{sub 2}, photosynthetic rates in trees at elevated CO{sub 2} concentrations {approx} 550 pmol mol{sub ...
Date: March 1, 1998
Partner: UNT Libraries Government Documents Department

Ultrasound: Biological Effects and Industrial Hygiene Concerns

Description: This paper discusses biological effects associated with overexposure to ultrasound, exposure standards proposed for airborne and contact ultrasound, industrial hygiene controls that can be employed to minimize exposure, and the instrumentation that is required for evaluating exposures.
Date: December 3, 1984
Creator: Wiernicki, C.
Partner: UNT Libraries Government Documents Department

Algorithmic Strategies in Combinatorial Chemistry

Description: Combinatorial Chemistry is a powerful new technology in drug design and molecular recognition. It is a wet-laboratory methodology aimed at ``massively parallel'' screening of chemical compounds for the discovery of compounds that have a certain biological activity. The power of the method comes from the interaction between experimental design and computational modeling. Principles of ``rational'' drug design are used in the construction of combinatorial libraries to speed up the discovery of lead compounds with the desired biological activity. This paper presents algorithms, software development and computational complexity analysis for problems arising in the design of combinatorial libraries for drug discovery. The authors provide exact polynomial time algorithms and intractability results for several Inverse Problems-formulated as (chemical) graph reconstruction problems-related to the design of combinatorial libraries. These are the first rigorous algorithmic results in the literature. The authors also present results provided by the combinatorial chemistry software package OCOTILLO for combinatorial peptide design using real data libraries. The package provides exact solutions for general inverse problems based on shortest-path topological indices. The results are superior both in accuracy and computing time to the best software reports published in the literature. For 5-peptoid design, the computation is rigorously reduced to an exhaustive search of about 2% of the search space; the exact solutions are found in a few minutes.
Date: August 1, 2000
Partner: UNT Libraries Government Documents Department

Climate change and wetland processes in the Southwest United States: Response of riparian communities to rising CO{sub 2} levels. Final report

Description: The current impact of Salt Cedar on the riparian areas of the southwestern US are recognized as being negative. If atmospheric levels of CO{sub 2} continue to rise--as seems likely--the results of this study indicate that the Salt Cedar--Cottonwood competitive interaction maybe moved further in the direction of favoring Salt Cedar. Further study confirming these results and elucidating the basis for competitive resource use by Salt Cedar and other riparian species would be prudent.
Date: July 1, 1998
Creator: Hoylman, Anne M.; Peterson, Andrew; Constable, John V.H.; Picone, John B. & Ball, J. Timothy
Partner: UNT Libraries Government Documents Department