The structure and function of headwater streams was evaluated in response to livestock exclusion implemented through Virginia's Conservation Reserve Enhancement Program (CREP). We measured riparian plant characteristics along with stream organic matter dynamics, benthic macroinvertebrates, algal biomass, and leaf breakdown in non-fenced, fenced, and forested streams. Increased growth of non-woody vegetation and the pre-existence of woody plants had a significant influence on stream organic matter dynamics. Tree basal area in a 20 m wide riparian corridor was predictive of stream coarse benthic organic matter standing stocks. Higher benthic organic matter standing stocks and differences in algal biomass in fenced and forested sites indicate different food resources may be structuring macroinvertebrate communities in these systems. We found a significant relationship between coarse benthic organic matter and percent shredder density, and scraper density generally followed patterns of algal biomass among treatments. Leaf breakdown rates among treatments were not indicative of differences in shredder density with two of the three fenced sites having the fastest overall breakdown rates observed. We attributed faster breakdown rates in these streams to available food resources and shredder community structure existing prior to the implementation of livestock exclusion. Our results suggest that a certain amount of ecological recovery may be possible through livestock exclusion. Macroinvertebrate structure in our study streams was primarily influenced by the presence or absence of riparian trees. Maturation and successional changes in woody riparian vegetation after livestock exclusion may allow certain characteristics of pastoral streams to return to those found in forested reaches. / Master of Science

No description available.

ER stress occurs in response to the accumulation of unfolded or misfolded proteins in the ER lumen, subsequently activating three signal transduction pathways collectively called the unfolded protein response (UPR). Although the goal of the UPR is to restore ER homeostasis, it can result in apoptosis when ER stress is too severe or prolonged. CHOP, which is induced by all three branches of the UPR, is central to inducing ER stress-induced apoptosis by regulating the expression of numerous pro-apoptotic genes. One of the downstream targets of CHOP is GADD34, which contributes to PP1-mediated dephosphorylation of eIF2α together with its homolog CReP to restore the attenuated global translation. A previous study reveals that morpholino knockdown of GADD34 rescued chronic ER stress-induced apoptosis in zebrafish caudal fin epidermal cells in vivo. However, due to the limitations of morpholino, any morpholino data about novel phenotypes should be verified with comparative mutant data. Therefore, we sought to investigate how GADD34 and CReP are involved in acute and chronic ER stress-induced apoptosis using GADD34 or CReP mutant zebrafish embryos. GADD34 heterozygous or CReP heterozygous zebrafish are crossed to produce the embryos of the following genotypes: wildtype, GADD34 heterozygous mutant, GADD34 homozygous mutant, CReP heterozygous mutant, and CReP homozygous mutant embryos. At 24hpf, embryos were treated with ER stress inducer Thapsigargin for either 4 hours or 24 hours to induce acute or chronic ER stress. After stained with acridine orange for an apoptosis assay, each embryo was imaged under a confocal microscope and subsequently genotyped. GADD34 or CReP mutation alone did not affect levels of apoptosis induced by acute ER stress. Similarly, CReP mutation alone did not affect levels of apoptosis induced by chronic ER stress. However, GADD34 mutation rescued chronic ER stress-induced apoptosis, and the differences between the apoptosis level in GADD34 homozygous mutants and those in wildtype and GADD34 heterozygous mutants were statistically significant. Our results indicate no obvious role of GADD34 and CReP in acute ER stress-induced apoptosis, which is consistent with the previous morpholino data. However, as GADD34 mutation rescued chronic ER stress-induced apoptosis, the CHOP- GADD34 downstream pathway is likely to be involved in chronic ER stress-induced apoptosis. In the future, GADD34 and CReP double mutant embryos should be used to analyze for the redundancy of GADD34 and CReP.

No description available.

Measurements in paired stream reaches with and without livestock access in southwestern Virginia suggest that livestock exclusion practices installed on short, isolated stream reaches result in improved geomorphic and riparian vegetation condition, but do not significantly improve the benthic macroinvertebrate assemblage. Detailed longitudinal and cross-sectional surveys, pebble counts, and rapid geomorphic assessments were conducted on contiguous, paired stream reaches (5 pairs) with and without active livestock access across a range of time since livestock exclusion was implemented. In addition, bank characteristics were quantified by measuring groundcover biomass, shrub crown volume, tree density and diameter, soil bulk density, and particle-size analysis. Benthic macroinvertebrates were collected with a D-frame dip net and quantified using the Virginia Stream Condition Index (SCI), and other benthic macroinvertebrate metrics. We determined that: 1) small lengths of livestock exclusion can significantly increase channel depth and decrease the width to depth ratio, and increase groundcover vegetation growth, but do not significantly alter benthic macroinvertebrate assemblages; and, 2) qualitative geomorphic assessment results showed trends over time since exclusion (0 to greater than 50 years), but not in any of the other parameters evaluated. These observations suggest that a more targeted and holistic approach that addresses watershed-wide impacts must be implemented to restore aquatic habitat. (Key Words: CREP, stream channel morphology, livestock exclusion, agriculture, benthic macroinvertebrates, riparian buffers.) / Master of Science

The failure to balance protein synthesis, folding, and degradation in the endoplasmic reticulum (ER) leads to the accumulation of unfolded proteins, leading to ER stress. Cells respond to this stress by activating a response signaling pathway known as the Unfolded Protein Response (UPR). One of the branches of the UPR induces the phosphorylation of eIF2α (Eukaryotic Initiation Factor 2) to attenuate global protein synthesis, allowing for a chance to clear misfolded and unfolded proteins. This phosphorylation of eIF2α is opposed by a phosphatase, containing a catalytic subunit, Protein Phosphatase 1, and a scaffolding protein, either GADD34 or CReP. Inhibition of eIF2α phosphatases has shown to promote survival in cell types by prolonging the effects of the UPR. This research focuses on understanding the gene expression patterns and localization of UPR specific genes with the presence of constant ER stress. Zebrafish are an ideal model for this research because they are a good mimic of what happens in humans and provide the ability to study gene expression and localization patterns at different stages during ER stress and its recovery. The eIF2α phosphatases were shown to have a protective effect on apoptosis when overexpressed in acute ER stress but were shown to have a protective effect on apoptosis when knocked out in chronic ER stress. We sought to determine the flow of gene expression of these phosphatases as well as other UPR specific genes, such as BiP and CHOP, to determine the contradictory effects of acute versus chronic ER-stress induced apoptosis. We studied the changes in gene expression for these genes in zebrafish embryos by isolating RNA and performing RT-qPCR after the induction of ER stress with pharmacological drugs across multiple time points. There was increased gene upregulation and mRNA localization to the fin epidermis and eye of GADD34, CReP, and BiP in acute ER stress from 2 hours to 6 hours, and these genes steadily declined in chronic ER stress from 24 hours to 48 hours. CHOP is a late-phase pro-apoptotic protein whose gene expression was upregulated in chronic ER stress from 12 hours to 48 hours. This data was also supported by mRNA localization studies performed by conducting whole mount in-situ hybridization on zebrafish embryos treated with ER stress inducers for 4 hours and 24 hours. Our results indicate that all UPR genes examined are affected by ER stress and their expression patterns are dependent on the time length of ER stress induction, allowing us to get a more in-depth working model of this branch of the UPR signaling pathway in zebrafish.

No description available.

<p>Proces pečenja u proizvodnji keramičkog crepa u većini slučajeva se izvodi u<br />oksidavionoj atmosferi. Dobijena mikrostruktura koja obezbeđuje najvažnije osobine<br />primene zavisi od mineralo&scaron;kog sastava polaznog materijala i temperature termičkog<br />tretmana.<br />Sa stanovi&scaron;ta proizvodnje glinenog crepa, sirovina sa značajnim sadržajem karbonata kao &scaron;to je kop gline u Kanjiži, predstavlja problem te se ne može koristiti u njenom prirodnom sastavu. U oksidacionom termičkom tretmanu, staklasta faza koja se formira razgradnjom lakotopivih glinenih minerala ne kvasi u dovoljnoj meri zemnoalkalne okside nastale razgradnjom karbonata. Očekivane nove kristalne faze, kao &scaron;to su gelenit i anortit, koje predstavljaju osnovu dobrih tehničkih osobina crepa, ne mogu nastati u potrebnoj količini. Jedno od re&scaron;enja ovog problema je pobolj&scaron;anje interakcije između silikata i CaO/MgO promenom kvaliteta atmosfere pečenja.<br />Cilj je bio da se dobije odgovor na pitanje, da li se mogu promenom tehnolo&scaron;kih<br />parametara pečenja pobolj&scaron;ati karakteristike finalnog proizvoda dobijenog od sirovinske sme&scaron;e sa visokim masenim udelom karbonata.<br />Dati su rezultati pečenja u oksidacionoj i redukcionoj atmosferi u pogledu fizičkomehaničkih karakteristika i nastanka novih kristalnih faza. U radu su primenjene metode 57Fe M&ouml;ssbauer spektroskopije, difrakcija X zraka i dilatometrijska analiza za<br />identifikaciju promena faza tokom pečenja u oksidacionoj i redukcionoj atmosferi<br />(CO/N2 atmosfera) na temperaturama od 700-1060&deg;C. Ove promene reflektuju<br />dehidroksilaciju glinenih minerala, dekompoziciju karbonata, denzifikaciju i formiranje<br />novih kristalnih faza (plagioklasi). U cilju analize industrijskih uzoraka, pored 57Fe<br />M&ouml;ssbauer spektroskopije, primenjene su i sledeće metode: skenirajuća elektronska<br />mikroskopija (SEM) sa EDS analizom, živina porozimetrija, fotoelektronska spektroskopija (XPS) i karakterizacija apsorbcije vode, otpornosti na mraz i nosivosti.<br />Primena redukujuće atmosfere pokazala se kao opravdana, dobijen je glineni crep<br />pobolj&scaron;anih karakteristika u odnosu na standardni proizvod pečen u oksidacionoj<br />atmosferi.</p> / <p>The firing process in clay roofing tile production is normally carried out in oxidizing<br />firing atmosphere. The obtained microstructure which provides the most important<br />properties of the application depends on the mineralogical composition of the starting raw material and the firing temperature.<br />Concerning the production of roofing tiles, clay raw materials with a high content of<br />carbonates such as the Kanjiza clay material, possess an inappropriate composition. The melt phase is formed after the decomposition of clay minerals during the common firing process. This liquid phase, due to its extent wetting characteristics, is not able to wet properly the earth alkali oxides obtained after the decomposition of the carbonates. The expected new crystalline phases, like gehlenite and anorthite, which are needed for the favorable technical properties of the roofing tiles, can not be formed in the required quality and quantity. One solution to this problem is the limebonding improvement by changing the conditions of the firing atmosphere.<br />The main aim of this work is to examine the effects of firing conditions on the<br />properties of clay roofing tiles with high carbonate content. The obtained physical and<br />mechanical properties and the obtained new crystalline phases are described in detail.<br />The experiment used dilatometry, X-ray diffractometry, 57Fe M&ouml;ssbauer<br />spectroscopy to identify the changes during the firing process in oxidizing and<br />reducing atmosphere (CO/N2 atmosphere) at temperatures between 700 and 1060&deg;C.<br />Furthermore, for industrial sample analysis, scanning electronmicroscopy with EDS,<br />XPS, Hg porosimetry, water absorption procedure, frost resistance and bending<br />measurements were applied.<br />The application of reducing atmosphere was proved to be valid. The obtained<br />roofing tiles had improved properties compared to the standard production which uses<br />oxidizing firing atmosphere.</p>