This Thesis attempts to develop an amphibian model system for exploring the role of the thymus, particularly its stromal cells, in the acquisition of allotolerance. Inbred, clonal and cytogenetically-marked Xenopus are used in this work. The initial experiments (Chapter 2) describe in vitro attempts to deplete the larval and post-metamorphic thymus of its lymphocyte component, while leaving its stromal elements intact. The histologic effects of deoxyguanosine-treatment and 6 -irradiation on the organ-cultured thymus are examined in wax sections. In vivo whole-body irradiation (3000R) and subsequent in situ residence for ~ 10 days proves the most successful technique for depleting thymic lymphocyte numbers from the froglet thymus (Chapter 3). This technique provides a lymphocyte-depleted thymus with a fairly normal 3-d stromal network. Furthermore, these thymuses show no sign of lymphocyte regeneration when organ-cultured for ~ 2 weeks. In Chapter 3, 1 um sections and electron microscopy of plastic-embedded sections provides a detailed picture of the froglet thymus following irradiation. Chapters 4 and 5 employ ploidy labelling and the X. borealis (quinacrine-fluorescence) cell marker system, to show that larval and adult (normal or in vivo irradiated) thymuses, implanted to early- thymectomized Xenopus (MHC-compatible. or -incompatible), become infiltrated by host lymphoid cells, the thymic epithelium remaining donor-derived. A time-course study shows that for normal thymus implants, host cells begin to immigrate in good number only after metamorphosis is complete; with these thymus implants, donor-derived lymphocytes can still be found in the blood and spleen of thymectomized hosts several months post-implantation. Irradiated thymus implants attracted host cells more rapidly, their lymphoid complement becoming almost exclusively host-type within 2 weeks post-implantation when animals were at a late larval stage of development. Despite rapid colonization of irradiated implants by host lymphoid cells, these thymuses degenerate soon after metamorphosis, presumably due to irradiation damage of stromal elements. The experiments in Chapter 6 compare the proliferative responses of thymocytes from normal and organ-cultured thymuses. The technical conditions (e.g. cell numbers per well) for obtaining good stimulation indices with T cell mitogens, and in mixed leucocyte culture (MLC), are examined. Thymocytes organ-cultured for 12 days generally display elevated 3HTdR uptake compared with cells tested straight from the animal. Both control and experimental (mitogen- or alloantigen-treated) cultures of organ-cultured thymocytes show these elevated DPM. Surprisingly, in vivo-irradiated, organ-cultured thymocytes, are still stimulated by phytohaemagglutinin (PHA)-treatment. Chapter 7 investigates in vitro T-cell proliferative responses of splenocytes and thymocytes in allothymus-implanted, early- thymectomized Xenopus. Splenocyte reactivity to PHA and to third- party alloantigens (in MLC) is restored when normal allogeneic thymus is implanted ("adoptively-transferred"). However, MLC reactivity of thymocytes and splenocytes to thymus-donor strain cells is generally lacking; allothymus-implanted animals are also tolerant to thymus-donor strain skin grafts. Unfortunately, thymectomized animals implanted with in vivo irradiated, allothymuses died prior to in vitro assaying. Preliminary attempts to generate supernatants (by treating cultured splenocytes with PHA and/or phorbol myristate acetate) that would routinely enhance T cell proliferative responses of thymocytes, are outlined in Chapter 8. General conclusions to be drawn from this Thesis and suggestions for future work with this amphibian model are to be found in Chapter 9.

Thesis (Ph.D.) - James Cook University, 2006. / Typescript (photocopy) Bibliography: leaves 90-102.

Thesis (M.S.)--University of Tennessee, Knoxville, 2010. / Title from title page screen (viewed on July 20, 2010). Thesis advisor: Benjamin M. Fitzpatrick. Vita. Includes bibliographical references.

Batrachochytrium dendrobatidis (Bd) is a fungal pathogen causing amphibian population declines. Bd has a narrow thermal tolerance and requires moisture to survive. Differences in frog biology, pathogen biology or temperature and moisture conditions may determine population response to disease. Population responses to Bd vary among sites, habitats, species and populations. In the tropics, stream-dwelling species decline to a greater degree than forest species, yet not all stream species decline to extirpation and not all forest species survive. I hypothesized that variation in operative temperature (Te) or body temperature (Tb) might explain differences in host population change documented among sites, seasons, habitats, and species. I sampled three moist-forest Panamanian sites (elevation 375 - 1300 m) during 2.5 months of the 2008 wet season and four different moist-forest sites (elevation 400 - 1300 m) during 3 weeks of the 2008 dry season. I measured Te and Tb of anurans along stream and forest transects. Additional environmental variables such as height, substrate, canopy cover and sunfleck presence were measured concomitantly. I used analysis of covariance to determine whether these factors influenced Te and Tb. I compared frequency distributions of Tb and Te to a Bd thermal growth curve to determine: 1) whether temperatures above Bd's critical thermal maximum were available to frogs, and 2) whether populations of species that have declined occupied habitats more frequently in Bd's optimal thermal range than species that have not. Te and Tb differed among sites, with cooler temperatures at higher elevation. Te was cooler during the dry season yet the presence of sunflecks and open canopy had greater effect on Te during the dry season. Within a site, Te and Tb were not different between habitats. Within a site, Tb did not vary among species. Average Te and Tb for all sites fell within Bd's thermal tolerance range, but the low elevation sites had Tb ranges extending above Bd's critical thermal maximum. Although temperature may explain greater losses at higher elevations, I found no significant difference in operative temperatures between stream and forest habitats at any site which indicates that temperature alone does not explain greater losses of stream anurans. Species that have declined to extirpation elsewhere did not consistently have cooler body temperatures compared to surviving species. Within the Neotropics, moisture, instead of temperature, may explain patterns of Bd prevalence among seasons, habitats, and species.

Made available in DSpace on 2014-06-11T19:30:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-20Bitstream added on 2014-06-13T20:39:51Z : No. of bitstreams: 1 rolim_dc_me_botib.pdf: 1412629 bytes, checksum: 46a91961ad1d650a606738f802971bba (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os objetivos deste trabalho foram analisar o status de conservação de Odontophrynus moratoi na região de Botucatu, mapear as áreas de ocorrência, incluindo os registros históricos, realizar um estudo ecológico das populações remanescentes e identificar as possíveis ameaças a estas populações. Odontophrynus moratoi tinha registro de ocorrência restrito ao Distrito de Rubião Jr., Botucatu, onde era registrada somente em duas localidades, desde sua descoberta em 1976, até 2003. Recentemente foi encontrada na região de Itirapina e de Brotas. Durante o estudo a espécie foi registrada em duas novas localidades, uma na região de Brotas e uma em Bauru. A espécie demonstrou ser altamente especialista na ocupação do habitat, por ter sido registrada somente em dois ambientes dentre os 129 amostrados, os quais compõem as 26 localidades estudadas e considerando que os mesmos são áreas de nascente de cerrado próximas de mata. A espécie não foi registrada em sua localidade-tipo, nem em sua segunda área de ocorrência na região de Botucatu e nem em outras nove localidades amostradas no município de Botucatu durante o estudo, demonstrando um possível desaparecimento da espécie da área onde foi primeiramente descoberta. As possíveis causas deste desaparecimento são alterações antrópicas que ocorreram em suas áreas de ocorrência, modificando os microambientes reprodutivos e de desenvolvimento larval da espécie. É de suma importância a preservação das localidades de ocorrência de O. moratoi e da área de entorno das mesmas / The objectives of this work were to analyse the conservation status of Odontophrynus moratoi in Botucatu region, map the occurrence areas, including the historical registers, to carry out an ecological study of the leftover populations and to identify the possible threats to these populations. Odontophrynus moratoi had limited occurrence to Rubião Jr. District, Botucatu, where it was registered only in two localities, from his discovery in 1976 up to 2003. Recently it was found in Itirapina and Brotas region. During the study the species was registered in two new localities, one in Brotas region and one in Bauru. The species demonstrated to be highly an occupation specialist of this habitat, because the species was being registered only in two environments among the 129 sampled, which compose 26 studied localities and considering that same are areas of source of Cerrado near forest. The species was not registered in his locality-type, not even in his second area of occurrence in Botucatu region and not even in another nine localities sampled in Botucatu local municipality during the study, demonstrating a possible disappearance of the species of the area where it was firstly uncovered. The possible causes of this disappearance are anthropics alterations that occurred in his place areas, modifying the reproductive microenvironments and larval development of the species. It is of abridgement importance the preservation of the occurrence localities of O. moratoi and the area that involve the same

Gyrinicola Yamaguti, 1938 are oxyurid mutualists found within the intestinal tract of numerous larval anuran species in Europe, Asia, South America and North America, with 6 species being currently recognized. The systematic placement and hierarchical treatment of the genus has shifted since its discovery, originally considered as its own family (Gyrinicolidae), then treated as a subfamily (Gyrinicolinae) within Cosmocercidae, then considered a member of the Pharyngodonidae, followed by a transference to the Cosmocercidae, and finally a recent proposal to resurrect Gyrinicolidae. The morphology of the uterine tract is a characteristic often used to diagnose members the genus; yet, species show variability in the morphology of these tracts. Until recently very few DNA sequences were available to aid in the phylogenetic placement of this unique group of worms. Within North America, only Gyrinicola batrachiensis is recognized. This species, however, also has a controversial taxonomic history. Historically, two nematodes infecting larval anurans were once recognized in North America: Pharyngodon batrachiensis and Pharyngodon armatus though these were synonymized due to morphological similarity. To evaluate the potential distribution, taxonomic relation, and possible species diversity of Gyrinicola I used an integrative approach utilizing locality, morphology and genetic information of specimens from a wide range within the United States. Phylogenies of the nuclear ribosomal genes 28S, 18S, ITS1-5.8S-ITS2, and newly sequenced partial mitochondrial genomes suggest at least four species groups exist among the nematodes from North America and that these groups, alongside G. japonica, form a well-supported group within Oxyuroidea. This study represents the first genetic evaluation of the diversity of the genus in North America, and the first comparison of these nematodes collected from such distant localities, and clearly indicates that further investigation of these worms is required to characterize their true diversity. It also suggests further representation of Pharyngodonidae from other vertebrate classes may help clarify the relations of this historical grouping to other members of the Oxyuroidea.

No description available.

No description available.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.