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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The biochemical toxicology of serum carboxylesterase in pigeons (Columba livia)

Jackson, John B. January 1994 (has links)
No description available.
2

Studies on the preparation of pentacyclic triterpenoids

Perkins, Gemma January 1995 (has links)
No description available.
3

Biodegradation of algal lipids and significance for sediment studies

Teece, Mark A. January 1994 (has links)
No description available.
4

Lipids in recent sediments of the eastern North Atlantic

Madureira, Luiz Augusto dos Santos January 1994 (has links)
No description available.
5

An investigation of potential immunological and metabolic indices of environmental water quality in the shore crab, Carcinus maenas

Hauton, Christopher January 1995 (has links)
No description available.
6

Biomarkers of exposure to complex environmental mixtures

Naufal, Ziad Sami 15 May 2009 (has links)
Maternal exposure to genotoxic chemicals may produce a variety of adverse birth outcomes. Depending on the dose and duration of exposure, adverse birth outcomes can range from premature or low-birth weight, to congenital abnormalities including neural tube defects (NTDs). The research described in this dissertation focused on several rural counties in Shanxi province, China. Shanxi has one of the highest rates of NTDs in the world. In 2005, the incidence of NTDs in the study counties ranged from 8 to 24 cases per 1,000 births. While some of these birth defects are likely to be related to nutrition, it is also suggested that environmental factors play a significant role. One such factor includes polycyclic aromatic hydrocarbon (PAH) exposure as a result of combustion of coal for indoor heating and cooking. Human populations in Shanxi depend heavily on coal as their main source of energy. This study determined the concentrations of PAHs in house dust, venous blood and placenta of study participants. Dust was collected from homes in the study site. Carcinogenic PAH levels in dust collected from kitchen floors ranged from 12 to 2,000 µg/m2. The genotoxic potential of dust was confirmed by shortterm bioassays. Median concentrations of total PAHs in placenta from children born with NTDs were elevated compared to matched controls and appeared to be associated with the risk of having a child with a NTD. Tobacco smoking was not associated with elevated levels of PAH biomarkers in this study population. Levels of bulky DNA adducts in placenta have also been quantified using 32P-postlabeling. Adduct levels do not appear to be significantly different between cases and controls and were not associated with deletions in enzymes GSTM1 or GSTT1. These data suggest that children born with NTDs may be at increased risk due to exposure to genotoxic PAHs. Studies with a larger number of subjects are needed to further elucidate the relationship between PAH exposure and adverse birth outcomes.
7

A bioinformatics meta-analysis of differentially expressed genes in colorectal cancer

Chan, Simon Kit 05 1900 (has links)
BACKGROUND: Elucidation of candidate colorectal cancer biomarkers often begins by comparing the expression profiles of cancerous and normal tissue by performing high throughput gene expression profiling. While many such studies have been performed, the resulting lists of differentially expressed genes tend to be inconsistent with each other, suggesting that there are some false positives and negatives. One logical solution to this problem is to determine the intersection of the lists of differentially expressed genes from independent studies. It is expected that genes that are biologically relevant to cancer tumorigenesis will be reported most often, while sporadically reported genes are due to the inherent biases and limitations of each of the profiling platforms used. However, the statistical significance of the observed intersection among many independent studies is usually not considered. PURPOSE: To address these issues, we developed a computational meta-analysis method that ranked differentially expressed genes based on the following criteria, which are presented in order of importance: the amount of intersection among studies, total tissue sample sizes, and average fold change in expression. We applied this meta-analysis method to 25 independent colorectal cancer profiling studies that compared cancer versus normal, adenoma versus normal, and cancer versus adenoma tissues. RESULTS: We observed that some genes were consistently reported as differentially expressed with a statistically significant frequency (P <.0001) in the cancer versus normal and adenoma versus normal comparisons, but not in the cancer versus adenoma comparison. We performed a review of some of the high ranking candidates and determined that some have previously been shown to have diagnostic and/or prognostic utility in colorectal cancer. More interestingly, the meta-analysis method also identified genes that had yet to be tested and validated as biomarkers. Thus, these candidates are currently being validated at the protein level on colorectal tissue microarrays. CONCLUSION: Our meta-analysis method identified genes that were consistently reported as differentially expressed. Besides identifying new biomarker candidates, our meta-analysis method also provides another filter to remove false positive genes from further consideration. In conclusion, the genes presented here will aid in the identification of highly sensitive and specific biomarkers in colorectal cancer.
8

A bioinformatics meta-analysis of differentially expressed genes in colorectal cancer

Chan, Simon Kit 05 1900 (has links)
BACKGROUND: Elucidation of candidate colorectal cancer biomarkers often begins by comparing the expression profiles of cancerous and normal tissue by performing high throughput gene expression profiling. While many such studies have been performed, the resulting lists of differentially expressed genes tend to be inconsistent with each other, suggesting that there are some false positives and negatives. One logical solution to this problem is to determine the intersection of the lists of differentially expressed genes from independent studies. It is expected that genes that are biologically relevant to cancer tumorigenesis will be reported most often, while sporadically reported genes are due to the inherent biases and limitations of each of the profiling platforms used. However, the statistical significance of the observed intersection among many independent studies is usually not considered. PURPOSE: To address these issues, we developed a computational meta-analysis method that ranked differentially expressed genes based on the following criteria, which are presented in order of importance: the amount of intersection among studies, total tissue sample sizes, and average fold change in expression. We applied this meta-analysis method to 25 independent colorectal cancer profiling studies that compared cancer versus normal, adenoma versus normal, and cancer versus adenoma tissues. RESULTS: We observed that some genes were consistently reported as differentially expressed with a statistically significant frequency (P <.0001) in the cancer versus normal and adenoma versus normal comparisons, but not in the cancer versus adenoma comparison. We performed a review of some of the high ranking candidates and determined that some have previously been shown to have diagnostic and/or prognostic utility in colorectal cancer. More interestingly, the meta-analysis method also identified genes that had yet to be tested and validated as biomarkers. Thus, these candidates are currently being validated at the protein level on colorectal tissue microarrays. CONCLUSION: Our meta-analysis method identified genes that were consistently reported as differentially expressed. Besides identifying new biomarker candidates, our meta-analysis method also provides another filter to remove false positive genes from further consideration. In conclusion, the genes presented here will aid in the identification of highly sensitive and specific biomarkers in colorectal cancer.
9

Development of an improved diagnostic test for sheep scab based on biomarkers

Wells, Elizabeth Anne January 2013 (has links)
Sheep scab is a highly contagious ectoparasitic disease caused by the mite, Psoroptes ovis, which causes intensely pruritic lesions with severe dermatitis and is a major welfare and production issue in the UK national flock. In an attempt to improve disease control, sheep scab was recently made notifiable in Scotland indicating that early diagnostic tests will be crucial to the success of this legislation. A sensitive and specific antibody based assay has been developed which can diagnose early infestation, but which does not indicate current disease status post-treatment due to residual circulating antibody levels. However, studies into host biology and response to disease have illustrated the potential use of biomarkers (BMs) in diagnostics as indicators of disease progression and the effectiveness of treatment regimes, including a recent microarray analysis which identified over 600 host genes differentially expressed in circulating leukocytes following P. ovis infestation. As many of these genes encoded proteins known to be involved in inflammatory responses, this data was used in the search for potential BMs. Initially the genes were filtered and ranked, using bioinformatic analysis, to identify the most promising BM candidates and then evaluated using Western blot analysis against a range of sera from P. ovis infested and naïve sheep. Promising results were obtained for a complement binding protein, C4BPB, showing it was rapidly up-regulated following infestation and correlated with disease progression as determined by lesion size development. The ovine C4BPB gene was successfully sequenced for the first time and a recombinant form of this protein expressed in E. coli. Antibodies, raised in rabbits against ovine rC4BPB, were used to develop a sandwich ELISA, results from which suggested the potential of C4BPB as a BM for sheep scab as it indicated current disease status postinfestation and post-treatment. The major ruminant acute phase proteins (APPs) serum amyloid A (SAA) and haptoglobin (Hp) were then investigated using commercially available assays, as previous studies indicated they were effective markers of inflammatory disease in ruminants. Results from these analyses indicated that both APPs responded positively to infestation with P. ovis but this was not statistically significant until 4 weeks post-infestation. After treatment, the APPs declined rapidly, as described by their short half life of less than 3 days following successful treatment, compared with 56 days for the estimated half life of the host antibody against the mite antigen Pso o 2. Further statistical analysis of the APP response suggested that SAA was the more discriminatory marker, with lower pre-infestation levels and higher sensitivity at the estimated optimum cut-off values. The possibility of using a signature of BMs, as an alternative to a single BM, was discussed as a method of increasing the sensitivity and specificity of the improved test, along with the potential of combining the BM diagnostic with the existing antibody assay. It was concluded that this would provide a highly sensitive and specific test for sheep scab which would diagnose early infestation as well as indicating current disease status post-treatment, providing a highly beneficial tool to the sheep industry to aid the control of this disease.
10

The sulphur geochemistry of Jurassic source rocks

Hill, Alan Frederick Mark January 1995 (has links)
In immature Jurassic shales of differing depositional environment from Great Britain (Ro<0.5) the C<sub>32</sub> hopane and C<sub>29</sub> sterane isomerisation provide an accurate indication of relative maturities. For mature Viking Graben samples (Ro>0.7) a reliable indication of relative maturity is gained if Tmax, Ts(Ts+Tm), C<sub>29</sub>ββ/(ββ+αα) steranes and the Triaromatic Index are considered together. The most reliable parameters for the determination of depositional redox are pristane/phytane and the C<sub>35</sub>/C<sub>34</sub> homohopane ratio, together with the concentrations of V, Cu, Ni and Mo. In the brackish lagoon of the Brora Coal Formation (BCF) low sulphate availability does not appear to have limited the pyritisation of iron relative to the open marine facies of the Brora Argillaceous Formation (BAF). Despite this δ<sup>34</sup>Spyrite for BCF samples indicates that sulphate reduction took place in a closed system due to the rapid depletion of available sulphate. Only low concentrations of excess H<sub>2</sub>S were available for incorporation within the organic matter, organic sulphur abundances in the BCF being much lower than for the BAF. In open-marine sequences an increase in TOC is associated with an increase in anoxia, the preservation of hydrogen-rich organic matter and the abundance of organic sulphur. A generally correlated increase in pyrite sulphur suggests both these modes of sulphur are associated with increasing concentrations of diagenetic sulphides (H<sub>2</sub>S and its partial oxidation products) generated through bacterial sulphate reduction. The greatest abundances of organic sulphur are formed when sulphide concentrations are high whilst sub-oxic surficial sediments are maintained so that polysulphides are generated within the sediment (by partial oxidation of H<sub>2</sub>S) for rapid sulphur incorporation. Improved preservation of labile organic matter leads to a increase in the abundance of organic compounds (e.g. sterenes and phytol derivatives) in which suitable functionalities exist for sulphur incorporation.

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