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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.
61

Three-dimensional Virtual Histology of Early Vertebrate Scales Revealed by Synchrotron X-ray Phase-contrast Microtomography

Qu, Qingming January 2015 (has links)
Vertebrate hard tissues first appeared in the dermal skeletons of early jawless vertebrates (ostracoderms) and were further modified in the earliest jawed vertebrates. Fortunately, histological information is usually preserved in these early vertebrate fossils and has thus been studied for more than a century, done so by examining thin sections, which provide general information about the specific features of vertebrate hard tissues in their earliest forms. Recent progress in synchrotron X-ray microtomography technology has caused a revolution in imaging methods used to study the dermal skeletons of early vertebrates. Virtual thin sections obtained in this manner can be used to reconstruct the internal structures of dermal skeletons in three-dimensions (3D), such as vasculature, buried odontodes (tooth-like unites) and osteocytes. Several body scales of early vertebrates have been examined using this imaging method and in situ 3D models of internal structures are created. Andreolepis (an early osteichthyan) scale shows linear growth pattern of odontodes in early developmental stage, which is not observable in traditional thin sections. The scale of another early osteichthyan Psarolepis was studied in the same way. Comparison between Andreolepis and Psarolepis shows that cosmine, a tissue complex in dermal skeleton of early sarcopterygians, originated by a developmental change of odontode shape. Two scales of osteostracans, a group of extinct jawless vertebrates, were studied in 3D and more details have been revealed in comparison to previous results based solely on 2D thin sections. 3D data enables us to compare the vasculature and canal system in different taxa in great detail, which forms the basis of formulating primary homology hypothesis and phylogenetic characters. The new data resulting from this study suggests that vertebrate fossils have preserved much more histological information than we currently appreciate, and provide a new data source of microanatomical structures inside the fossils that can contribute new characters for phylogenetic analysis of early jawed vertebrates.
62

Assemblage structure and shallow-water habitat use by small-bodied fishes at lower Missouri River sandbars

Ridenour, Clayton. January 2007 (has links)
Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 8, 2008) Includes bibliographical references.
63

The ontogeny of dual-interstimulus interval eyeblink classical conditioning in a rat model of fetal alcohol spectrum disorders

Brown, Kevin L. January 2008 (has links)
Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: Mark E. Stanton, Dept. of Psychology. Includes bibliographical references.
64

Contemplating the evolution of attachment and cognition in a collaborative learning environment

Marcello, Angelica. January 2006 (has links)
Thesis (Ph. D.)--University of California, San Diego, 2006. / Title from first page of PDF file (viewed June 26, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 192-213).
65

An integrated evaluation of costs and benefits of corticosterone secretion through development

Wada, Haruka, January 1900 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.
66

Biotic and abiotic influences on aggressive interactions within larval <i> Ambystoma</i> assemblages

Mott, Cy Larue 01 May 2010 (has links)
Coexistence among ecologically similar species is often facilitated through temporal or spatial partitioning mechanisms that reduce or eliminate direct interaction. However, in many communities exhibiting guild structure, wherein potential competitors may also prey on one another, sympatric relationships persist despite species' similar life history strategies, spatial and temporal restrictions imposed by ephemeral habitats, and resource limitations that promote competition and predation. To identify the ecological roles of species-specific behavioral patterns within aquatic guilds, I quantified larval intraspecific agonistic behavior among two species of intraguild (IG) predators, Ambystoma opacum and A. tigrinum, and their shared intraguild prey, A. maculatum. All species exhibited similar ontogenetic patterns of aggression, characterized by peaks of aggression early in development and subsequent gradual decreases through metamorphosis. However, the intensity of aggression varied considerably among guild species through development, as did behavioral responses to varying levels of ambient water temperature, invertebrate prey density, and presence of predatory odonate naiads. The observed patterns suggest that guild species, despite morphological and physiological similarities, exhibit unique behavioral responses through ontogeny and in response to habitat variables, suggesting that temporally staggered breeding phenologies have contributed to behavioral divergence among these sympatric congeners. However, in situ observations of larval behavior, although largely in agreement with laboratory results on timing of increased aggression, indicated that IG predators exhibited pond-level species partitioning and do not necessarily co-occur despite being regarded as sympatric. These results, taken together with observed species-specific impacts of IG predators on IG prey, suggest that ecologically similar IG predators exert widely differing predatory pressure on shared prey, and that similarities among guild species may ultimately result in habitat partitioning across local scales.
67

The Development of Adult Sex-typed Social Behavior in Lemur catta

January 2012 (has links)
abstract: Unanswered questions about the evolution of human gender abound and are salient across the anthropological disciplines and beyond. Did adult sex-typed behavioral tendencies actually evolve? If so, when? For what purpose? The best way to gain insight into the evolution of human gender is to understand the evolution and development of sex-typed behavior in comparative primate taxa. Captive research indicates that there are many proximate factors likely to shape the development of sex-typed behavior in non-human primates&mdash;prenatal and postnatal endocrinological experience, social experience, ecological factors, and their interactions. However, it is largely unknown how sex-typed behavior proceeds and is shaped by those factors in evolutionarily salient environments. This study investigated one&mdash;whether extrinsic sexually differentiated social interactions are likely influential in the development of adult sex-typed behavior in wild-living Lemur catta. Little is known about sex-typed development in this species or in strepsirrhines in general. This research therefore addresses an important phylogenetic gap in our understanding of primate sex-typed development. Behavioral observations were carried out on mixed cross-sectional sample of adult females (n=10), adult males (n=8), yearling females (n=4), yearling males (n=4), and newborn females (n=16) and males (n=14) at Beza Mahafaly Special Reserve in southwest Madagascar from September 2008 to August 2009. Twenty-three sex-typed behaviors were identified in adults using linear mixed effects models and models of group response profiles through time. Of those, only eight had a pre-pubertal developmental component. Infants did not exhibit any sex differences in behavior, but juveniles (prepubertal, weaned individuals) resembled adults in their (relatively few) patterns of expression of sex-typed behavior. Most adult sex-typed behaviors in this species apparently develop at or after puberty and may be under gonadal hormone control. Those that develop before puberty do not likely depend on extrinsic sexually differentiation social interactions for their development, because there is no clear evidence that infants and juvenile male and females are not treated differently by others according to sex. If sexually differentiated social interactions are important for sex-typed behavioral development in subadult ,italic>Lemur catta, they are likely intrinsically (rather than extrinsically) driven. / Dissertation/Thesis / Ph.D. Anthropology 2012
68

Ontogeny and characterization of mesenchymal antigens in the sea urchin Strongylocentrotus purpuratus

Tamboline, Colin Richard 19 June 2018 (has links)
The monoclonal antibody Sp12 recognizes an epitope shared by a diverse group of developmentally regulated cell surface and extracellular matrix antigens which are expressed during Strongylocentrotus purpuratus development. Immunofluorescent localization reveals antigen in the cortical granules of eggs and in the hyaline layer from fertilization through to gastrula. Primary (skeletogenic) mesenchyme and two secondary mesenchyme derivatives (blastocoelar cells and pigment cells) express antigen after their release into the blastocoel and maintain it throughout the remainder of larval development. The antibody allows detailed descriptions of blastocoelar cells, a prominent yet poorly described fibroblast-like mesenchyme lineage. In adults antigen is localized to the organic matrix which invests the calcified stereom of the test and spines. Immunogold electron microscopy shows antigen in the cortical granules of eggs, and on cell surfaces, within membrane bound vesicles, and within the Golgi apparatus of mesenchyme cells. On western blots a confluent smear of antigen (Mr primarily >$180K) is present in eggs, but is resolved into seven antigen bands (Mr from 35K to >$200K) after fertilization. A prominent antigen at 140K is newly expressed coincident with mesenchyme immunoreactivity. Antigens at 140K and 120K fade as prisms develop into plutei, while an antigen at 105K appears in older larvae. In adult test six antigens are shared with larvae, and there are two novel antigens at 75K and 110K. Immunoreactivity is eliminated by digestion of samples with endoglycosidase F, is reduced by periodate oxidation, but is unaffected by boiling. Calcium-magnesium-free-seawater or 1M glycine extract a subset of antigens from dissociating embryos, leaving a complementary subset of antigens associated with cell membranes. Membrane antigens are not extracted, at 4 C, with high or low ionic strength, organic solvents, or non-ionic detergents but are solubilized by ionic detergents. Whole antibody has no effect on development of embryos cultured in it from fertilization on, nor is there a specific effect from injection of antibody into the blastocoel of developing embryos. The shape of dissociated cells cultured in Sp12 whole antibody is markedly constrained compared to that of controls, however, this difference is not seen in cells incubated in Sp12 Fab fragments. Sp12 appears to recognize a carbohydrate moiety shared by ten glycoproteins of widely variable Mr and cell membrane affinity which are differentially expressed on mesenchyme throughout S. purpuratus development. The antibody does not disrupt development in vivo, but does affect cell shape in vitro, probably by crosslinking cell surface antigens. / Graduate
69

Morfologia, anatomia e histoquímica de Noteroclada confluens Taylor ex Hook.Wilson (Pelliaceae, Marchantiophyta) / Morphology, anatomy and histochemistry of Noteroclada confluens Taylor ex Hook. & Wilson (Pelliaceae, Marchantiophyta)

Carvalho, Aline Tonin January 2010 (has links)
Noteroclada confluens Taylor ex Hook. & Wilson é uma hepática de aparência folhosa, pertencente à família Pelliaceae (Marchantiophyta). Ocorre predominantemente em regiões montanhosas, declives e locais próximos à córregos, em solos argilosos. O presente estudo teve por objetivo descrever a morfologia, anatomia e histoquímica das estruturas do gametófito e esporófito de N. confluens, coletados no estado do Rio Grande do Sul, Brasil, sob microscopia óptica, eletrônica de varredura e confocal de varredura a laser fornecendo, especialmente, dados sobre as estruturas relacionadas com a reprodução sexuada e assexuada, contribuindo para uma melhor caracterização do gênero e da família. O gametófito de N. confluens apresenta-se na forma de um talo profundamente lobado, com lobos predominantemente com uma única camada de células. Os lobos são conectados a região mediana, mais espessada, rica em grãos de amido. Na região mediana ventral do gametófito, conectam-se inúmeros rizoides unicelulares. Todo o talo é constituído por um parênquima formado por células de paredes delgadas, de constituição pectocelulósica, sem espessamentos angulares. Cada célula apresenta um único e grande vacúolo e diversos oleocorpos. Os oleocorpos formam grupos de corpos esféricos ou ovalados, constituídos por sesquiterpenoides. Pigmentos flavonóides foram encontrados constituindo as paredes de algumas células do talo. A partir da face ventral, podem emergir tubers de formato arredondados, com um parênquima contendo grãos de amido, funcionando como um órgão armazenador de substâncias de reserva. Nas coletas realizadas no Rio Grande do Sul, foram identificados dois morfotipos: morfotipo 1, com poucos oleocorpos por célula e sem tubers; morfotipo 2, com muitos olecorpos por célula e presença de tubers. Os gametângios estão distribuídos em fileiras na região mediana, na face dorsal, sendo normalmente duas fileiras, de anterídios, e uma, de arquegônios. Os arquegônios apresentam um material polissacarídico na região do canal do ventre, o que pode facilitar a entrada dos anterozoides. Os anterídios são pedunculados e ovais, apresentam uma única camada de células estéreis protetora e estão inclusos, individualmente, em uma câmara anteridial, com poro apical. Após a fecundação da oosfera, forma-se um esporófito que permanece circundado pela caliptra e pelo celocaule, até a maturação dos esporos. O esporófito é formado pela cápsula, seta e pé. A parede da cápsula é biestratificada e apresenta espessamentos angulares na epiderme e anelares ou helicoidais, no estrato interno ou subepidérmico. Na base da cápsula, ocorre formação de um denso elateróforo. A cápsula se abre através de quatro fendas longitudinais de deiscência, os estômios, as quais resultam na formação de quatro valvas. A seta é cilíndrica, hialina e levemente estriada, apresentando grãos de amido nas células parenquimáticas da região cortical e epiderme. A elevação ocorre por expansão celular. O pé tem formato de “taça” e apresenta diversos grãos de amido. Na junção gametófitoesporófito (placenta) ocorre um espaço placental. Não foram encontradas células de tranferência na zona da placenta, tanto no gametófito como no esporófito. O tecido esporogênico apresenta células com paredes pectocelulósicas delgadas, a partir do qual se diferenciam dois tipos celulares: os esporócitos, arredondados e com uma parede espessada hialina, e os elaterócitos, mais alongados e com parede espessada de natureza péctica. As células- mãe de esporos são tetralobadas e se individualizam. Nesse estádio apresentam uma parede espessada mais delgada e de natureza hemicelulósica. A meiose leva à formação de quatro esporos unicelulares. Ao redor de cada esporo, deposita-se uma delgada primexina. O desenvolvimento dos esporos é endospórico, e os protonemas jovens, envolvidos ainda pela esporoderme, são esferoidais ou subesferoidais, com células de paredes pectocelulósicas delgadas, muitas vezes repletas de grãos de amido. A esporoderme está estratificada em uma intina, de composição pectocelulósica, e uma exina, impregnada constituída por esporopolenina. A exina forma uma escultura do tipo rugulada. Os elatérios morrem na maturidade e apresentam de duas a três bandas de espessamentos helicoidais, de pigmentação amarronzada e natureza fenólica e polissacarídica. Na exina, a esporoderme apresenta uma região de escultura reduzida. / Noteroclada confluens Taylor ex Hook. & Wilson is a liverwort with a leafy appearance which belongs to the Pelliaceae (Marchantiophyta) family. This species occurs mostly in mountainous regions, descending slopes and places near streams. In this study, the morphology, anatomy and histochemistry of the structures of the gametophyte and sporophyte of N. confluens are described. This species was collected in Rio Grande do Sul state, Brazil. The study in light microscopy, scanning electron microscopy and confocal laser scanning provides, especially, data about structures related to sexual and asexual reproduction, contributing to a better understanding of the genus and family. The gametophyte of N. confluens presents a form of a deeply lobed stem, the lobes predominantly with a single layer of cells. The lobes are connected to a central region, denser, rich in starch grains. Numerous unicellular rhizoids are connected in the ventral surface of the central region. The entire stem is composed by a parenchyma formed by thin-walled pectin and cellulose cells, with no angular thickening. Each cell has a single large vacuole and several oil bodies. The oil bodies form groups of spherical or oval bodies and present sesquiterpenes in its constitution. Flavonoid pigments were found forming the walls of some cells of the stem. In this ventral surface, round shaped tubers may emerge with a parenchyma containing starch grains, acting as a storage organ for substances. Two morphotypes were identified in a collection in Rio Grande do Sul: morphotype 1, with few oil bodies per cell and without tubers; and morphotype 2, with many oil bodies per cell and the presence of tubers. The gametangia are distributed in rows in the central region on the dorsal surface. Usually there are two rows of antheridia and one of archegonia. The archegonia have a polysaccharide material in the channel region of the venter, which may facilitate the entry of antherozoid. The antheridia are stalked and oval. They have a single protective layer of sterile cells and are included individually in a single antheridial chamber, with apical ostiole. After the fertilization of the egg cell, there is the formation of a sporophyte that remains surrounded by calyptra and the caulocalyx until the maturation of the spores. The sporophyte is formed by the capsule, seta and foot. The capsule wall has two layers of cells and presents angular thickening in the epidermis and annular or helical thickening in the internal layer. At the base of the capsule there is a formation of a dense elaterophore. The capsule opens in four longitudinal dehiscence cracks, the stomion, which result in the formation of four valves. The seta is cylindrical, hyaline, slightly striated, showing starch grains in parenchyma cells of the cortical region and epidermis. The increase happens by cell expansion. The foot is cup-shaped and it presents several starch grains. In the gametophyte-sporophyte junction (placenta) there is a placental space. Both gametophyte and sporophyte.do no present transfer cells in the placenta. The sporogenic tissue has cells with pectin and cellulose walls, which are differentiated in two types: the sporocytes, rounded with a thick hyaline wall, and the elaterocytes, more elongated and presenting a wall of pectin. The spore mother cells are tetralobed and become individualized. On this stage, they have a thinner thickened wall cell and it is made of hemicelluloses. After meiosis, four unicellulars spores are formed. Around each spore a thin primexina is deposited. The spore development is endosporic and the young protonemas are spheroidal and still involved by sporoderm. The cells of young protonema have thin cell walls with pectin and cellulose, often presenting many starch grains. The sporoderm presents an intine with pectin and cellulose composition, and an exine, consisting of impregnated esporopolenina. The exine sculpture is rugulate. The elaters die at maturity and have two or three bands of spiral thickening, which have brown pigmentation and a phenolic and polysaccharide composition. the exine, the sporoderm presents a region of small sculpture.
70

Ontogenia do óvulo e da Antera de Cybistax antisyphilitica (Mart.) Mart. (Bignoniaceae)

Pereira Junior, Eduardo João [UNESP] 15 August 2011 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:26:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-15Bitstream added on 2014-06-13T20:54:01Z : No. of bitstreams: 1 pereirajunior_ej_me_sjrp.pdf: 1176824 bytes, checksum: ea26888e0c90e98ae7bc9367c03e1901 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Caracteres embriológicos possuem valor sistemático e sua utilidade foi demonstrada por diversos autores para elucidar o posicionamento filogenético de certas famílias de angiospermas. Este estudo visa analisar a ontogenia das estruturas reprodutivas de Cybistax antisyphilitica, com o propósito de acrescentar dados embriológicos relevantes ao delineamento filogenético da família, ou de categorias taxonômicas infrafamiliares. As características embriológicas observadas demonstraram similaridade com espécies pertencentes à ―Tabebuia alliance‖ cuja embriologia já foi investigada. Observou-se durante a ontogenia do óvulo de C. antisyphilitica que apenas o ginósporo calazal se desenvolve e, durante sua diferenciação em célula-mãe do saco embrionário, a face micropilar de sua parede celular assume uma conformação côncava, na qual há grande deposição de calose. No estádio octonuclear, há acúmulo de uma substância fibrogranular entre o endotélio e a parede do ginófito fazendo com que o saco embrionário apresente um característico afunilamento mediano. Em relação a ontogenia da antera da espécie estudada, verificou-se que as camadas tapetais são dimórficas, embora ao final do estádio pré-meiótico se tornem similares; embora, após a meiose, o dimorfismo se acentua novamente nas camadas tapetais. Os amiloplastos das células-mãe dos andrósporos são herdados pelos andrósporos e grãos de pólen deles resultantes. Os amiloplastos dos grãos de pólen gradualmente aumentam em número e tamanho em um único ciclo de amilogênese/amilólise. Com base nos dados obtidos conclui-se que a configuração da parede distal do ginósporo calazal e o acúmulo de secreção na porção mediana do saco embrionário são características não relatadas para outras espécies da família e podem... / Embryological characters have systematic value and its usefulness has been demonstrated by several authors to elucidate the phylogenetic position of certain angiosperms families. This study aims to analyze the ontogeny of reproductive structures of Cybistax antisyphilitica, with the purpose of adding relevant embryological data to the phylogenetic design of the family or, infra-familiar taxonomic categories. The embryological features observed was similar to species belonging to ―Tabebuia alliance‖ whose embryology has been investigated. During the ontogey of C. antisyphilitica ovule, only the chalazal megaspore develops, and in the course of its differentiation in the embryo sac mother cell, the micropylar side of its cell wall assumes a concave conformation in which there is an expressive deposition of callose. In the octonuclear stage, there is an accumulation of a fibrogranular substance between the endothelium and megagametophyte wall causing a bottleneck in the middle portion of embryo sac. For anther ontogeny of the species studied, the tapetal layers are dimorphic, although becoming similar at the late pre-meiotic stage. After meiosis, the dimorphism is accentuated between the two tapetal layers. The microspore mother cell amyloplasts are inherited by the microspores and the resulting pollen grains. The pollen grain amyloplasts gradually increasing in number and size in a single amylogenesis/amylolyse cycle. Based on the obtained data we concluded that the configuration of the distal wall of the chalazal megaspore and the accumulation of secretion in the median portion of embryo sac are characters not reported for other species of the family, and may possibly be autapomorphic characters. Regarding the ontogeny of the anther, Cybistax antisyphilitic showed a multistratified fibrous endothecium... (Complete abstract click electronic access below)

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