Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. William M. Landing, Florida State University, College of Arts and Sciences, Dept. of Oceanography. Title and description from dissertation home page (viewed June 15, 2004). Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 39-43).

Thesis (doctoral)--University of Tartu, 2006. / This dissertation is based on 4 papers. Includes bibliographical references.

Trilostane and epostane are synthetic steroids which inhibit the 3beta-hydroxysteroid dehydrogenase enzyme. This enzyme is part of a system which catalyses an essential step in the synthesis of biologically active steroids. In animals and man trilostane preferentially inhibits adrenal steroid synthesis whilst epostane inhibits placental/ovarian steroid synthesis. The synthesis of radiolabelled trilostane and epostane are described. Stability investigations showed these radiolabelled compounds to be susceptible to degradation, although trilostane less so than epostane. Careful handling procedures were essential for metabolism studies. Animal studies showed no difference in the overall excretion and distribution of radioactivity for [[14]Cl-trilostane and [[14]C]-epostane. However the site specific localisation of active components within adrenals and ovaries reflected the in vivo organ selectivity observed for these compounds. In man a major plasma metabolite of trilostane was shown to be 17-ketotrilostane which is intrinsically twice as active as parent compound with regard to 3beta-hydroxysteroid dehydrogenase inhibition. A specific, sensitive and accurate HPLC assay was developed which enabled the measurement of trilostane and 17-ketotrilostane in plasma. Plasma concentrations of 17-ketotrilostane in male volunteers were approximately three-fold higher than trilostane, and consequently this metabolite may be an important contributor to the clinical efficacy of this drug. Micronisation of both trilostane and epostane was shown to be appropriate in order to maximise the oral systemic availability of these compounds. However even with micronised formulations considerable inter-and intra-subject variability was noted. For trilostane, variability in absorption, coupled with individual differences in the metabolism to the more active 17-ketotrilostane, may in part account for the variable efficacy encountered in clinical trials.

This thesis applies spatial and spatio-temporal modelling to two broad areas of environmental statistics: wildlife abundance estimation and vegetation dynamics. The first methodology considered is spatial modelling for estimating global characteristics through predicting the value of a response variable at new locations. The approach is based on generalized additive models and illustrated using spatio-temporal fisheries survey data. The method incorporates historical data to overcome shortcomings in the survey design. The GAM-based method substantially improves the precision of estimates over a traditional estimation method and is also useful in explaining complex space-time trends using environmental variables. The second methodology addressed is spatial modelling for the description of the underlying process. Its objectives lie in exploring local properties, such as autocorrelation. Auto-models (Markov Random Fields) are used for modelling discrete data. Autocorrelation is estimated directly from the response, as a fixed effect, through the specification of a conditional probability of each observation, given its neighbouring values. The auto-Poisson model for counts has traditionally been restricted to the modelling of negative autocorrelation. This restriction is overcome by right truncating the Poisson distribution. Further modifications of this model are also investigated. Parameter estimation methods for this truncated auto-Poisson model are then compared via a simulation study. The method with accompanying model selection and validation techniques is illustrated for the auto-Poisson and auto-negative binomial model using seed and mite counts. An example of modelling the presence and absence of deer illustrating the auto-logistic model for binary data is also presented. Finally, methodology for spatio-temporal modelling of the underlying process is considered. The use of transition models for modelling change of semi-natural vegetation in Scotland is investigated. The transition model is extended to incorporate spatial effects and it is shown that estimates of transition probabilities for Markov models can be improved.

Genetic toxicity tests used for regulatory screening must be rigorously validated to ensure accuracy, reliability and relevance. Hence, prior to establishment of an internationally-accepted test guideline, a new assay must undergo multi-stage validation. An in vitro transgene mutagenicity assay based on an immortalized cell line derived from MutaMouse lung (i.e., FE1 cells) is currently undergoing formal validation. FE1 cells retain a lacZ transgene in a λgt10 shuttle vector that can be retrieved for scoring of chemically-induced mutations. This work contributes to validation of the in vitro transgene (lacZ) mutagenicity assay in MutaMouse FE1 cells. More specifically, the work includes an intra-laboratory variability study, and a follow-up study to assess the endogenous metabolic capacity of FE1 cells. The former is essential to determine assay reliability, the latter to define the range of chemicals that can be reliably screened without an exogenous metabolic activation mixture (i.e., rat liver S9). The intra-laboratory variability assessment revealed minimal variability; thus, assay reproducibility can be deemed acceptable. Assessment of metabolic capacity involved exposure of FE1 cells to 5 known mutagens, and subsequent assessment of changes in the expression of genes involved in xenobiotic metabolism; induced transgene mutant frequency (±S9) was assessed in parallel. The results revealed that the FE1 cell line is capable of mobilising several Phase I and Phase II gene products known to be involved in the bioactivation of mutagens. Collectively, the results presented support the contention that the FE1 cell mutagenicity assay can be deemed reliable and reproducible. Consequently, the assay is an excellent candidate for continued validation, and eventual establishment of an OECD (Organization for Economic Cooperation and Development) Test Guideline.

The detection of bacterial contamination of water, pharmaceutical products etc. is of great importance, and is most conveniently performed by the detection of bacterial ATP (Adenosine TriPhosphate) using the luciferin-luciferase bioluminescence system. This system uses unstable and expensive reagents, and emits transient light signals. In this study an FIA (Flow Injection Analysis) system was set up to monitor the light signal produced by the reaction. Using a luminometric detector (a liquid scintillation counter) with the FIA system, the reaction length, sample volume, flow rates, pH etc. were investigated.

A ¹⁴C primary productivity bioassay was developed to detect selenium limitation in marine phytoplankton. Addition of Na₂Se0₃ to Se-deplete cultures of Thalassiosira pseudonana stimulated carbon uptake rates by up to 40%, when uptake was expressed on a per cell volume or relative basis. Recovery from Se-starvation was verified by changes in the growth rate and morphology of T. pseudonana. Carbon uptake rates of Katodinium rotundatum, grown in nutrient enriched artificial seawater supplemented with 10⁻¹⁰ M or 10⁻⁶ M Se, were unaffected by Na₂SeO₃ additions. Since Katodinium rotundatum did not exhibit growth responses to Se additions, it was concluded that 10⁻¹⁰ M Se was sufficient for the growth of this alga, which has not displayed an obligate Se requirement. Natural phytoplankton assemblages in the Strait of Georgia were examined for Se limitation with this ¹⁴C bioassay. Relative carbon uptake rates did not change following Na₂SeO₃ addition, indicating that these assemblages were not Se-limited at the time of the study. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No / Human biomonitoring studies aim to identify potential exposures to environmental, occupational, or lifestyle toxicants in human populations and are commonly used by public health decision makers to predict disease risk. The Comet assay measures changes in genomic stability and is one of the most reliable biomarkers to indicate early biological effects, and therefore accepted by various governmental regulatory agencies. The appeal of the Comet assay lies in its relative simplicity, rapidity, sensitivity, and economic efficiency. Furthermore, the assay is known for its broad versatility, as it can be applied to virtually any human cell and easily adapted in order to detect particular biomarkers of interest, such as DNA repair capacity or single- and double-strand breaks. In a standard experiment, isolated single cells are first embedded in agarose, and then lysed in high-salt solutions in order to remove all cellular contents except the DNA attached to a nuclear scaffold. Subsequent electrophoresis results in accumulation of undamaged DNA sequences at the proximity of the nuclear scaffold, while damaged sequences migrate towards the anode. When visualized with fluorochromes, these migrated DNA fragments resemble a comet tail and can be quantified for their intensity and shape according to internationally drafted guidelines.

No description available.