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University of Massachusetts Amherst

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Articles 511 - 520 of 520

Full-Text Articles in Life Sciences

Visuospatial Reasoning In Toddlers: A Correlational Study Of Door Task Performance, Iris Louella Price May 2009

Visuospatial Reasoning In Toddlers: A Correlational Study Of Door Task Performance, Iris Louella Price

Open Access Dissertations

Previous research using violation-of-expectation paradigms suggests that very young infants have a good understanding of unobserved physical events. Yet toddlers appear to lack this knowledge when confronted with the door task, a visuospatial reasoning task which parallels ones used in the habituation/looking time studies. Many studies have been conducted in an effort to determine why toddlers perform poorly on the door task yet the answer remains unclear. The current study used a correlational approach to investigate door task performance from both psychological (executive function), and neuroscience (prefrontal cortex) perspectives. Children between the ages of 2 ½ - 3 years were ...


Spatial Ecology, Population Structure, And Conservation Of The Wood Turtle, Glyptemys Insculpta, In Central New England, Michael T. Jones May 2009

Spatial Ecology, Population Structure, And Conservation Of The Wood Turtle, Glyptemys Insculpta, In Central New England, Michael T. Jones

Open Access Dissertations

Abstract (Summary) Wood turtles ( Glyptemys insculpta ) are of conservation interest rangewide. Anecdotal accounts demonstrate that some populations have been decimated since 1850, and recent studies demonstrate that declines are still underway. From 2004-2008 I investigated the ecology of wood turtles in Massachusetts and New Hampshire. I obtained between one and five years of annual home range data for 150 turtles, and evaluated population structure at 31 sites in five major watersheds. Seasonal floods displaced 7% of wood turtles annually in one watershed, and accounted for elevated mortality. Twelve wood turtles were displaced < 16.8 km, and two were displaced over a 65-foot dam. Several turtles overwintered at their displacement site and two returned successfully, indicating that floods are a mechanism of population connectivity. Several homing turtles ended up in new areas. Turtles occupied stream segments with gradient < 1%, lower than generally available. Agricultural machinery accounted for most observed mortality, followed by automobiles and mammals. Female turtles exhibit smaller home ranges in agricultural areas. Older turtles move farther from the river than do young turtles, possibly reflecting their familiarity with a former landscape. Population density ranged from 0-40.4 turtles/river-kilometer. The highest densities occur in central New Hampshire and lower densities occur in the Housatonic watershed. Population density is negatively correlated with agriculture at both riparian and watershed scales, and responds unimodally to forest cover. Wood turtle populations in western Massachusetts are declining by 6.6-11.2% annually. I estimated ages of turtles by assessing shell-wear rates from photographs. Wood turtles regularly achieve ages over 80 years, and like related species, do not exhibit clear signs of senescence. Old wood turtles are reproductively dominant, and their survival rates are twice as high as young turtles. Carapace scutes appear to require 80 years to become worn. Population modeling indicates that wood turtle populations are declining in New England due to anthropogenic and natural factors. Conservation efforts must address the effects of agriculture on adult survival. Climate change may negatively affect northeastern wood turtles through increased flooding. Populations in mountainous areas may be likely candidates for conservation because they don't occupy prime agricultural land, but may be more susceptible to floods.


Modulation Of Macrophage Responses To Borrelia Burgdorferi In Acute Murine Lyme Carditis, Chris Martin Olson May 2009

Modulation Of Macrophage Responses To Borrelia Burgdorferi In Acute Murine Lyme Carditis, Chris Martin Olson

Open Access Dissertations

The Lyme disease spirochete Borrelia burgdorferi is the only known human pathogen that directly activates invariant natural killer T (iNKT) cells. The number and activation kinetics of iNKT cells vary greatly among different strains of mice. Here, we report the role of the iNKT cell response in the pathogenesis of Lyme disease using C57BL/6 (B6) mice, a strain with optimal iNKT cell activation that is resistant to the development of spirochetal-induced inflammation. During experimental infection of B6 mice with B. burgdorferi , iNKT cells localize to the inflamed heart where they are activated by CD1d-expressing macrophages. Activation of iNKT cells ...


The Conformational Gymnastics Of The Escherichia Coli Seca Molecular Machine And Its Interactions With Signal Sequences, Jenny Lynn Maki May 2009

The Conformational Gymnastics Of The Escherichia Coli Seca Molecular Machine And Its Interactions With Signal Sequences, Jenny Lynn Maki

Open Access Dissertations

Protein secretion is a selective and regulated process that is essential in all organisms. In bacteria the preprotein translocase SecA, either free in the cytosol or associated with the SecYEG translocon, recognizes and binds most post-translational secretory proteins containing an N-terminal signal sequence. In Gram-negative bacteria, the molecular chaperone SecB binds many of the preproteins to keep them in a translocation-competent state. Subsequently, SecB delivers the preproteins to the translocon-associated SecA, which binds the signal sequence and also interacts with mature regions of the preprotein. After the preprotein/SecA/SecYEG complex has formed, the energy derived from ATP hydrolysis by ...


Delayed Anesthetic Preconditioning And Metallothioneins I+Ii: Novel Mediators Of Anesthetic-Induced Protection, Scott David Edmands May 2009

Delayed Anesthetic Preconditioning And Metallothioneins I+Ii: Novel Mediators Of Anesthetic-Induced Protection, Scott David Edmands

Open Access Dissertations

Ischemic injury is a common and debilitating outcome of natural illness and as a complication of commonly performed medical procedures. Whereas naturally occurring ischemic insults are often the result of unpredictable events, such as in the case of stroke or heart attack, the risk of operative and perioperative ischemia is somewhat better characterized in the clinical setting. Given the prevalence and severity of outcomes in ischemic injury, there is significant interest in developing better pharmacological and procedural approaches to improve patient outcomes. One approach that has shown significant promise in the laboratory setting, particularly in the context of planned medical ...


Antioxidant Distribution And Effectiveness In A Model Muscle System, Ann T Ballesteros Feb 2009

Antioxidant Distribution And Effectiveness In A Model Muscle System, Ann T Ballesteros

Doctoral Dissertations 1896 - February 2014

Gallic acid esters (GAE) of varying alkyl chain length were used to determine how antioxidant physical location and partitioning influence hemoglobin-catalyzed lipid oxidation. Specific GAE used were propyl gallate (PG), octyl gallate (OG), and lauryl gallate (LG). GAE partitioning experiments were performed with either isolated cod muscle membranes or washed cod muscle, which primarily contain polar membrane lipids and myofibrillar proteins. Canola oil was used in some experiments to determine how neutral lipids impact partitioning behavior. GAE distribution was determined spectrophotometrically in the recovered membranes, aqueous phase, and oil layer after employing differential centrifugation. Oxidation was monitored by measuring thiobarbituric ...


Factors Influencing The Stability Of Carotenoids In Oil-In-Water Emulsions, Caitlin Suzanne Boon Feb 2009

Factors Influencing The Stability Of Carotenoids In Oil-In-Water Emulsions, Caitlin Suzanne Boon

Doctoral Dissertations 1896 - February 2014

Lycopene has recently received interest as an antioxidant in human tissues. These same antioxidant properties present challenges in preventing oxidative degradation within food products. In this research, degradation of lycopene in model emulsion systems was examined to better understand the chemical stability of this potential functional food ingredient.

Lycopene in corn oil or hexadecane was used to make oil-in-water emulsions using small molecule surfactants. Emulsion color loss was used to estimate lycopene loss and was monitored using an integrating sphere. Lipid hydroperoxide and hexanal formation was used to monitor the development of lipid oxidation.

Oxidation and color loss were found ...


Landscape Ecology Of Large Fires In Southwestern Forests, Usa, Sandra L Haire Feb 2009

Landscape Ecology Of Large Fires In Southwestern Forests, Usa, Sandra L Haire

Doctoral Dissertations 1896 - February 2014

The recent increase in large fires in southwestern forests has prompted concern regarding their ecological consequences. Recognizing the importance of spatial patterns in influencing successional processes, I asked: (1) How do large fires change plant communities?; (2) What are the implications of these changes for ponderosa pine forests?; and (3) What is the relationship of fire severity to gradients of climate, fuels, and topography? To address the first two questions, I studied succession in the woody plant community at two sites that burned in high-severity fire: La Mesa fire in northern New Mexico (1977) and Saddle Mountain in northern Arizona ...


Zinc Metabolism In The Streptozotocin (Stz)-Diabetes, Aizhong Fu Feb 1995

Zinc Metabolism In The Streptozotocin (Stz)-Diabetes, Aizhong Fu

Doctoral Dissertations 1896 - February 2014

Hyperzincuria in diabetics has been regarded as the culprit depleting body zinc stores. Studies were designed to assess rates of 65Zn absorption and retention as a possible compensation mechanism; to assess zinc concentrations and distribution among body compartments, and to assess the kinetics of 65Zn metabolism in STZ-diabetic rats. The rates of 65Zn absorption and retention were not significantly different between STZ-diabetic and control rats. However, STZ-diabetic rats had significantly higher rates of 65Zn absorption (16.88%) and retention (34.36%) when they were "Post-fasted" than when they were "Prior-fasted" (9.04% and 18.68% respectively). These differences were also ...


A Study Of The Sulphur Supply Of Soils And Its Relation To Plant Growth, J. Stanley Cobb Jan 1917

A Study Of The Sulphur Supply Of Soils And Its Relation To Plant Growth, J. Stanley Cobb

Doctoral Dissertations 1896 - February 2014

No abstract provided.