Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also in a digital version from UMI/Dissertation Abstracts International.

Thesis (Ph. D.)--University of Washington, 1987. / Vita. Bibliography: leaves [144]-166.

Many fishes are planktivorous during early life and switch to piscivory or consume larger food items as ontogeny progresses. In contrast, paddlefish begin life as active feeders selecting for larger organisms and then switch to planktivory as they grow. Few studies have quantified these changes in early life foraging. I identified distinct early life foraging behaviors and prey preferences of age-0 paddlefish and how these change with habitat and paddlefish size. Gut contents of 189 age-0 wild paddlefish were used to determine which prey are most preferred and whether habitat variables and paddlefish size influence diet composition. I also performed an experiment to identify differences in foraging behavior and prey preference between age-0 and age-1 paddlefish. Dominant prey, based on percent by number and percent occurrence, of wild age-0 paddlefish ranging from 10 to 116 mm TL was trichoptera larvae (28.5%N, 67.7%O) and hemiptera (18.3%N, 51.3%O). Prey size increased with size of age-0 paddlefish. However, the highest ratio of zooplankton to invertebrates in the gut occurred in a 60 mm paddlefish. The size range of fish in this study was likely too narrow to confirm presence of an ontogenetic diet shift. Habitat had no effect on diet. My experimental study revealed that if provided a mixture of organisms, age-0 paddlefish will primarily consume macroinvertebrates while age-1 paddlefish will mainly filter zooplankton, but occasionally consume larger organisms. Features of river channels (e.g., woody snags, gravel beds in the photic zone) that contribute to the diverse diet paddlefish require in early life may ultimately increase survival and recruitment.

Note:

No description available.

The extinct diprotodontoids were large bodied, browsing herbivorous marsupials most closely related to, among living marsupials, wombats. Referred to two families, Diprotodontidae and Palorchestidae, diprotodontoids are geographically and temporally widespread vombatimorphian taxa in Australian and New Guinean Cenozoic deposits. The most diverse diprotodontoid fauna recorded from any single region in Australia comes from Oligo-Miocene limestone deposits of the Riversleigh World Heritage Area, northwestern Queensland. In this thesis a new diprotodontoid genus and five new species are described from Riversleigh, as well as additional material from Riversleigh for the palorchestids Propalorchestes novaculacephalus and Pr. ponticulus and diprotodontids Nimbadon lavarackorum, Neohelos tirarensis, Neohelos stirtoni and Ngapakaldia bonythoni. A new vombatomorphian family, Maradidae, known from a single species at Riversleigh, is recognised as the sister-group of a vombatid-diprotodontoid clade. New abundant, exceptionally well-preserved cranial material of the zygomaturine Nimbadon lavarackorum enables characterisation of intraspecific variation and ontogenetic development. The results of these analyses have been used to discriminate species boundaries throughout this work. Consequently: Nimbadon whitelawi is now considered a junior synonym of Ni. lavarackorum; Nimbadon scottorrorum is a junior synonym of Neohelos tirarensis; and Bematherium angulum is a synonym of Ngapakaldia bonythoni. The new Riversleigh diprotodontoids clarify phylogenetic relationships within and between diprotodontoid families. The monophyly of both Palorchestidae and Diprotodontidae is strongly supported as is their union in the superfamily Diprotodontoidea. Monophyly of the Zygomaturinae and Diprotodontinae is not supported, primarily due to the unstable position of Alkwertatherium webbi as well as the high degree of homoplasy in cranial morphology of the more derived members of each subfamily. Overall phylogenetic and distribution patterns for diprotodontoids is generally consistent with current interpretations of Riversleigh's stratigraphy. Five diprotodontoid species allow direct biocorrelation with other Australian Tertiary mammal faunas. Riversleigh's basal System A deposits correlate with late Oligocene deposits of the Etadunna Formation of South Australia. Riversleigh's low-mid System C deposits correlate with the middle Miocene Bullock Creek Local Fauna of the Northern Territory. Riversleigh's high System C Jaw Junction and Encore Local Faunas contain diprotodontoid taxa antecedent to diprotodontoids of the late Miocene Alcoota Local Fauna of the Northern Territory.

Infantile exposure to xenobiotics, e.g. from breastfeeding, poses a serious toxicity risk. Since the toxicokinetic mechanisms that principally determine exposure outcomes undergo a significant developmental maturation, infants may respond to exposures in a different way than adults. Hence, suitable model systems are required to provide risk relevant information in pediatric populations. This dissertations primary goal was to provide a critical evaluation of two such model systems; first, a pharmacokinetic model that may predict an infants capacity to eliminate toxicants by cytochrome P-450 (CYP) mechanisms and second, the developing rat as a model of human CYP2E1 and CYP1A2 ontogeny.<p>The first objective was to evaluate underlying assumptions of a pharmacokinetic model that describes the ontogeny of hepatic CYP activity using the rat. The study recognized some discrepancies with the stated assumptions. The impact of these discrepancies on the potential applicability of the model is discussed. As proof-of-concept, the observed data were fit to a model describing rat CYP2E1 and CYP1A2 ontogeny. A reasonable correlation (r = 0.75) was observed between observed and predicted oral clearance values of a CYP2E1 substrate indicating the potential applicability of such a model in risk assessment. <p>The second objective was to conduct an extensive characterization of rat hepatic CYP2E1 and CYP1A2 ontogeny at mRNA, protein, activity and intrahepatic expression levels. The results were compared to available human data to determine the appropriateness of the rat for assessment of toxicokinetic mechanisms underlying age-dependent differences in susceptibility to toxicity. Similarities in age-dependent changes in mRNA, activity and zonal hepatic expression patterns were noted between the rat and human prior to weaning. Unlike human data, rats show good correlation between changes in CYP2E1 and CYP1A2 activity and transcript levels, but not with the immunoquantifiable protein. Recognizing such similarities and differences between rats and human regarding onset, rate and pattern of CYP ontogeny will improve the accuracy of rat-to-human extrapolation of developmental toxicokinetic data. <p>Overall, the dissertation research provides mounting and supportive evidence for the use of such model systems in providing risk-relevant information in pediatric populations and to identify toxicokinetic mechanisms underlying age-dependent differences in susceptibility to toxicity.

Infantile exposure to xenobiotics, e.g. from breastfeeding, poses a serious toxicity risk. Since the toxicokinetic mechanisms that principally determine exposure outcomes undergo a significant developmental maturation, infants may respond to exposures in a different way than adults. Hence, suitable model systems are required to provide risk relevant information in pediatric populations. This dissertations primary goal was to provide a critical evaluation of two such model systems; first, a pharmacokinetic model that may predict an infants capacity to eliminate toxicants by cytochrome P-450 (CYP) mechanisms and second, the developing rat as a model of human CYP2E1 and CYP1A2 ontogeny.<p>The first objective was to evaluate underlying assumptions of a pharmacokinetic model that describes the ontogeny of hepatic CYP activity using the rat. The study recognized some discrepancies with the stated assumptions. The impact of these discrepancies on the potential applicability of the model is discussed. As proof-of-concept, the observed data were fit to a model describing rat CYP2E1 and CYP1A2 ontogeny. A reasonable correlation (r = 0.75) was observed between observed and predicted oral clearance values of a CYP2E1 substrate indicating the potential applicability of such a model in risk assessment. <p>The second objective was to conduct an extensive characterization of rat hepatic CYP2E1 and CYP1A2 ontogeny at mRNA, protein, activity and intrahepatic expression levels. The results were compared to available human data to determine the appropriateness of the rat for assessment of toxicokinetic mechanisms underlying age-dependent differences in susceptibility to toxicity. Similarities in age-dependent changes in mRNA, activity and zonal hepatic expression patterns were noted between the rat and human prior to weaning. Unlike human data, rats show good correlation between changes in CYP2E1 and CYP1A2 activity and transcript levels, but not with the immunoquantifiable protein. Recognizing such similarities and differences between rats and human regarding onset, rate and pattern of CYP ontogeny will improve the accuracy of rat-to-human extrapolation of developmental toxicokinetic data. <p>Overall, the dissertation research provides mounting and supportive evidence for the use of such model systems in providing risk-relevant information in pediatric populations and to identify toxicokinetic mechanisms underlying age-dependent differences in susceptibility to toxicity.

The extinct diprotodontoids were large bodied, browsing herbivorous marsupials most closely related to, among living marsupials, wombats. Referred to two families, Diprotodontidae and Palorchestidae, diprotodontoids are geographically and temporally widespread vombatimorphian taxa in Australian and New Guinean Cenozoic deposits. The most diverse diprotodontoid fauna recorded from any single region in Australia comes from Oligo-Miocene limestone deposits of the Riversleigh World Heritage Area, northwestern Queensland. In this thesis a new diprotodontoid genus and five new species are described from Riversleigh, as well as additional material from Riversleigh for the palorchestids Propalorchestes novaculacephalus and Pr. ponticulus and diprotodontids Nimbadon lavarackorum, Neohelos tirarensis, Neohelos stirtoni and Ngapakaldia bonythoni. A new vombatomorphian family, Maradidae, known from a single species at Riversleigh, is recognised as the sister-group of a vombatid-diprotodontoid clade. New abundant, exceptionally well-preserved cranial material of the zygomaturine Nimbadon lavarackorum enables characterisation of intraspecific variation and ontogenetic development. The results of these analyses have been used to discriminate species boundaries throughout this work. Consequently: Nimbadon whitelawi is now considered a junior synonym of Ni. lavarackorum; Nimbadon scottorrorum is a junior synonym of Neohelos tirarensis; and Bematherium angulum is a synonym of Ngapakaldia bonythoni. The new Riversleigh diprotodontoids clarify phylogenetic relationships within and between diprotodontoid families. The monophyly of both Palorchestidae and Diprotodontidae is strongly supported as is their union in the superfamily Diprotodontoidea. Monophyly of the Zygomaturinae and Diprotodontinae is not supported, primarily due to the unstable position of Alkwertatherium webbi as well as the high degree of homoplasy in cranial morphology of the more derived members of each subfamily. Overall phylogenetic and distribution patterns for diprotodontoids is generally consistent with current interpretations of Riversleigh's stratigraphy. Five diprotodontoid species allow direct biocorrelation with other Australian Tertiary mammal faunas. Riversleigh's basal System A deposits correlate with late Oligocene deposits of the Etadunna Formation of South Australia. Riversleigh's low-mid System C deposits correlate with the middle Miocene Bullock Creek Local Fauna of the Northern Territory. Riversleigh's high System C Jaw Junction and Encore Local Faunas contain diprotodontoid taxa antecedent to diprotodontoids of the late Miocene Alcoota Local Fauna of the Northern Territory.

Thesis (Ph. D.)--Columbia University, 1914. / Vita. Published also as Contributions to education, Teachers college, Columbia university, no. 65. "Books and articles cited": p. 102-105.