• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 106
  • 50
  • 15
  • 8
  • 7
  • 5
  • 4
  • 3
  • 3
  • 2
  • Tagged with
  • 239
  • 54
  • 48
  • 43
  • 41
  • 31
  • 29
  • 26
  • 23
  • 22
  • 20
  • 20
  • 20
  • 18
  • 18
  • 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.
71

Evolución de anticuerpos contra el lipopolisacárido rugoso y proteínas citosólicas de Brucella abortus Cepa RB51 en perras infectadas con Brucella canis, detectados por Elisa indirecto

Ruz Oñate, Daniela Alejandra January 2011 (has links)
Memoria para optar al Título Profesional de Médico Veterinario / En el presente trabajo se describe la evolución de anticuerpos caninos contra Brucella canis, de dos perras inoculadas experimentalmente, mediante un ensayo inmunoenzimático indirecto (ELISA-I) usando como antígenos el lipopolisacárido rugoso (LPS-R) y proteínas citosólicas de Brucella abortus Cepa RB51. El objetivo fue discriminar el momento en que se hacen detectables los anticuerpos para cada ELISA-I y describir la evolución de éstos en el tiempo. Se utilizaron sueros de dos perras infectadas con B. canis, A y B, con un total de 20 y 16 muestras de sueros seriados, respectivamente. Para ambos ELISA-I se usaron líneas de corte obtenidas por metodología “Receiver-Operator Characteristic” (ROC), que determinaron la positividad o negatividad a la prueba. Ambos ELISA-I fueron capaces de detectar anticuerpos tempranamente y fue posible constatar su permanencia en el tiempo. La detección de anticuerpos mediante ELISA-I, tanto con antígeno de proteínas citosólicas como con antígeno LPS-R de B. abortus Cepa RB51, se mantuvo detectable, al menos, hasta la semana 38 post infección
72

The detection threshold for odor plume tracking in the smooth dogfish, Mustelus canis.

Jennings, Ashley Robina 12 March 2016 (has links)
The survival of Elasmobranch fishes (sharks, skates and rays) depends critically on their ability to sense odor cues. The outstanding question of detection thresholds to food odors in the shark is investigated in this study. The tracking behavior of Mustelus canis (the smooth dogfish) was analyzed using a binary choice flume designed specifically for testing odor preferences of aquatic animals. To determine threshold, odor was serially diluted until no tracking responses were observed. Sharks spent significantly more time in the odor side of the flume, regardless of their individual side bias, until the "squid juice" was diluted several orders of magnitude. For the whole flume the two greatest dilutions (10-4-10-5 at the odor source) did not cause significant choice and for the upstream flume half, all but the greatest dilution (10-5 at the odor source) caused significant odor side preference. To interpret these results fully we need to consider the structure of odor plumes and the function of the sharks' olfactory responses. Nonetheless, assuming that M. canis represent sharks in general, these findings demonstrate that their extraordinary sensitivity to food attractants may indicate aspects still unknown about life history of elasmobranch fishes including the ranges that benthic elasmobranchs are capable of traveling to feed.
73

Estudo citológico da medula óssea de cães portadores de Ehrlichiose Monocítica Canina na fase aguda / Cytological study of bone marrow in dogs infected with canine monocytic ehrlichiosis during the acute phase

Caxito, Marília Salgado [UNESP] 17 February 2017 (has links)
Submitted by Marília Salgado Caxito null (mariliasalgado@ymail.com) on 2017-02-24T00:12:23Z No. of bitstreams: 1 DISSERTAÇÃO (MARÍLIA SALGADO CAXITO) - Defesa em 17-02-2017.pdf: 1916563 bytes, checksum: ad7825421c4deb080f61ac2ac7c94a42 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2017-03-06T13:44:02Z (GMT) No. of bitstreams: 1 caxito_ms_me_bot.pdf: 1916563 bytes, checksum: ad7825421c4deb080f61ac2ac7c94a42 (MD5) / Made available in DSpace on 2017-03-06T13:44:02Z (GMT). No. of bitstreams: 1 caxito_ms_me_bot.pdf: 1916563 bytes, checksum: ad7825421c4deb080f61ac2ac7c94a42 (MD5) Previous issue date: 2017-02-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A Ehrlichiose Monocítica Canina (EMC), causada por Ehrlichia canis, destaca-se dentre as hemoparasitoses de cães. A EMC causa doença multissistêmica e pode ser classificada em fase aguda, subclínica ou crônica. A fase crônica caracteriza-se por hipoplasia/aplasia medular e muitos cães vêm a óbito por falência medular, embora as causas da supressão medular ainda sejam indefinidas. Neste estudo, foi investigado se a fase crônica resulta de alterações medulares iniciadas na fase aguda. Em particular, verificar se, durante a fase aguda, células precursoras podem ser parasitadas por E. canis e se processos imunomediados podem ser responsáveis por alterações hematológicas durante o curso da doença. Dezoito cães com EMC na fase aguda foram submetidos a exames hematológicos (hemograma, bioquímica sérica e mielograma) e sorológicos. A presença de E. canis foi confirmada mediante PCR e cultivo celular. A citologia de medula óssea revelou alterações principalmente na série eritróide que comumente estão associadas a doenças imunomediadas, inclusive em animais não anêmicos. Também confirmou-se a presença de E. canis na medula óssea de 11/18 cães e certa tendência entre a positividade das amostras medulares e a série eritróide, embora sem significância estatística. Os títulos sorológicos de 2560 em 9/18 e 10240 nos demais confirmou a resposta humoral exacerbada descrita pela literatura, contudo também sem relação significativa com a presença de E. canis na medula e algumas variáveis medulares. Este estudo evidenciou a importância do mielograma na EMC, inclusive para predizer alterações hematológicas em cães com hemograma normal. / The Canine Monocytic Ehrlichiosis (CME), caused by Ehrlichia canis, one of the most frequent hemoparasites dogs. CME causes multisystemic disease and includes a acute, subclinical or chronic phase. The chronic phase is characterized by medullary hypoplasia/aplasia and many dogs die from bone marrow failure. However, the causes of medullary suppression remain unknow. In this study, we investigated whether the chronic phase can result from marrow changes initiated during the acute phase. In particular, we evaluated if precursor cells can be parasitized by E. canis during the acute phase and whether immune-mediated processes are responsible for hematological changes during the course of the disease. Eighteen dogs with CME in the acute phase were submitted to hematological (hemogram, serum biochemistry and myelogram) and serological tests. The presence of E. canis was confirmed by PCR and cell culture. Bone marrow cytology analyses mainly revealed changes in the erythroid series that are usually associated with immune-mediated diseases, including in non-anemic animals. This study confirmed the presence of E. canis in the bone marrow of the 11/18 dogs and a potential positive relation between the positivity of the marrow samples and the erythroid series was observed, although whithout statistical significance. The serological titers of 2560 in 9/18 and 10240 in the others confirmed an exacerbated humoral response to CME described in the literature, but they were not associated with the presence of E. canis in the bone marrow and medullary alterations. This study evidenced the importance of the myelogram, as well predicting hematological alterations in dogs with normal hemogram.
74

Binational collaboration in recovery of endangered species: the Mexican wolf as a case study

Bernal Stoopen, Jose Francisco 30 September 2004 (has links)
The goal of this inductive study was to identify factors that facilitate and inhibit binational collaboration in the recovery of endangered species in the northern Mexico borderlands, focusing on the Mexican wolf (Canis lupus baileyi). A conceptual model was developed using qualitative techniques, providing the basis for design of a mail survey. The target population included participants with experience in recovery efforts for over a dozen species at risk in the region. Long interviews were recorded with 44 participants from Mexico and the United States. Thematic hierarchical analysis was used to develop a conceptual model of how interviewees talked about factors influencing binational collaboration. Issues were classified in five thematic clusters: project, organization, people, resources, culture/history. The survey was used to conduct a needs assessment, measuring respondents' attitudes about the relative priority of issues identified in the conceptual model. High priority needs were identified from each thematic cluster: (a) equitable participation in project design and implementation, (b) continuity of personnel, (c) coordination of federal, state and local efforts, (d) increased funding, managed with accountability, and (e) exchange visits to facilitate understanding of diverse perspectives. Responses to almost half the survey items indicated accord among the sample of respondents, providing a basis for shared common ground. The nature of discord was within the range of "manageable", with no clear polarization of attitudes measured. This exploratory data analysis suggested that the structure of the conceptual model developed from the Mexican wolf case study was generally a valid basis for future deductive analysis and reflection by practitioners. For 82% of 22 statements of need, priorities of participants in the Mexican wolf recovery efforts did not differ significantly from other respondents. Nationality (of respondents) significantly affected priority rankings for only 18% of the need statements. Significant effects of five demographic variables indicated that interactive effects should be examined in future multivariate analyses to determine how respondents' attitudes on issues related to priority rankings. Recommendations were provided for a more efficient and effective approach to collaborative problem-solving, engaging reflective practitioners from the private and public sectors in principled negotiation processes to better understand diverse perspectives.
75

Population genetics, foraging ecology, and trophic relationships of grey wolves in central Saskatchewan

Urton, Erin Jaime Moira 20 December 2004
<p>Habitat fragmentation and anthropogenic development influence the level of isolation and security in and around protected habitats affecting wolf movements and the distribution and abundance of their prey. In light of recent concern about the ecology of animals in protected areas, I initiated a research project to investigate the molecular and foraging ecology of grey wolves in and around Prince Albert National Park (PANP), Saskatchewan. <p>Estimates of genetic diversity and population structure can be used as surrogates to detect effects of habitat degradation on wolves. Genetic diversity was high in these populations relative to other North American wolf populations. My results suggest that wolves in central Saskatchewan form a panmictic population, however there is some evidence showing partial isolation of one group of wolves within PANP. I speculate that the level of human activity such as road networks, hunting, and trapping act as dispersal impediments to this isolated group. Further, the genetic homogenization, indicating high population turnover, of wolf groups that use the periphery and adjacent areas of PANP may also contribute to the observed genetic subdivision. The partially isolated NW group, characterized by slightly lower diversity indices, low migration rates, and higher levels of allele fixation, indicated this group was a more stable social unit comprised of more related individuals.</p><p>Knowledge of wolf food habits and how they change over time is a fundamental component to understanding wolf ecology. Using scat analysis I evaluated wolf foraging ecology by calculating indices of occurrence/faeces (OF) and percent prey biomass contribution: white tailed deer contributed 43% and 33% respectively to wolf diet; elk (33%, 50%), moose (7%, 14%), beaver (5%, 2%), and snowshoe hare (2%, <1%). I found no evidence of livestock depredation nor did wolves prey on bison or caribou. There were no differences in OF indices between years. Prey selectivity was apparent in both years with wolves selecting elk and avoiding beaver. A diversity of ungulate prey are readily available to wolves in this system; however, scat analysis and tests for prey selection indicate a preference for elk. I presume this is a choice made to balance risk with profitability of food items in concordance with optimal foraging theory.</p><p>I examined trophic relationships between the grey wolf and 18 mammalian species from the boreal forest of central Saskatchewan, Canada, using ä13C and ä15N stable isotope values measured in hair samples. Variance in isotope values for wolves and other carnivores was investigated as a proxy for dietary variation. IsoSource, an isotopic source partitioning model, quantified the relative proportions of 5 most likely prey items in the diets of wolves.</p><p>I compared these results with investigations of faecal contents using percent biomass contributions of prey items in wolf diet. I found no difference between percent biomass measures and mean percent contributions derived from IsoSource. Despite social foraging, my results indicate highly variable diets among individual wolves and I discuss this in terms of boreal wolf ecology.
76

Population genetics, foraging ecology, and trophic relationships of grey wolves in central Saskatchewan

Urton, Erin Jaime Moira 20 December 2004 (has links)
<p>Habitat fragmentation and anthropogenic development influence the level of isolation and security in and around protected habitats affecting wolf movements and the distribution and abundance of their prey. In light of recent concern about the ecology of animals in protected areas, I initiated a research project to investigate the molecular and foraging ecology of grey wolves in and around Prince Albert National Park (PANP), Saskatchewan. <p>Estimates of genetic diversity and population structure can be used as surrogates to detect effects of habitat degradation on wolves. Genetic diversity was high in these populations relative to other North American wolf populations. My results suggest that wolves in central Saskatchewan form a panmictic population, however there is some evidence showing partial isolation of one group of wolves within PANP. I speculate that the level of human activity such as road networks, hunting, and trapping act as dispersal impediments to this isolated group. Further, the genetic homogenization, indicating high population turnover, of wolf groups that use the periphery and adjacent areas of PANP may also contribute to the observed genetic subdivision. The partially isolated NW group, characterized by slightly lower diversity indices, low migration rates, and higher levels of allele fixation, indicated this group was a more stable social unit comprised of more related individuals.</p><p>Knowledge of wolf food habits and how they change over time is a fundamental component to understanding wolf ecology. Using scat analysis I evaluated wolf foraging ecology by calculating indices of occurrence/faeces (OF) and percent prey biomass contribution: white tailed deer contributed 43% and 33% respectively to wolf diet; elk (33%, 50%), moose (7%, 14%), beaver (5%, 2%), and snowshoe hare (2%, <1%). I found no evidence of livestock depredation nor did wolves prey on bison or caribou. There were no differences in OF indices between years. Prey selectivity was apparent in both years with wolves selecting elk and avoiding beaver. A diversity of ungulate prey are readily available to wolves in this system; however, scat analysis and tests for prey selection indicate a preference for elk. I presume this is a choice made to balance risk with profitability of food items in concordance with optimal foraging theory.</p><p>I examined trophic relationships between the grey wolf and 18 mammalian species from the boreal forest of central Saskatchewan, Canada, using ä13C and ä15N stable isotope values measured in hair samples. Variance in isotope values for wolves and other carnivores was investigated as a proxy for dietary variation. IsoSource, an isotopic source partitioning model, quantified the relative proportions of 5 most likely prey items in the diets of wolves.</p><p>I compared these results with investigations of faecal contents using percent biomass contributions of prey items in wolf diet. I found no difference between percent biomass measures and mean percent contributions derived from IsoSource. Despite social foraging, my results indicate highly variable diets among individual wolves and I discuss this in terms of boreal wolf ecology.
77

Scaling Patterns and Ecological Correlates of Postcranial Skeletal Robusticity in Canis and Ursus: Implications for Human Evolution

Doyle, Sara Kathleen January 2009 (has links)
<p>There has been a trend toward decreasing skeletal robusticity in the genus Homo throughout the Pleistocene, culminating in the gracile postcrania of living modern humans. This change is typically attributed to changing tool technologies and subsistence patterns among human groups. However, other mammalian groups also experience a similar change in their postcranial strength over the same time period. It is proposed in this dissertation that ecological variables are correlated with measures of postcranial strength and may be a better explanation for Holocene skeletal gracilization in humans, as well as in other mammalian genera. This hypothesis is investigated through a close examination of the scaling patterns in two extant genera, Canis and Ursus, and a comparison of scaling patterns and relative strength of different species of Canis, including a fossil species that provides information about temporal change. Measurements of limb length, joint surface area, bone diameter, and strength measurements derived from radiographic images of long bone midshafts of North American specimens of Canis, (including the fossil Canis dirus) and Ursus were collected. Scaling patterns of the cross-sectional variables on limb length and joint surfaces were analyzed for the interspecific and intraspecific samples. </p><p>The first hypothesis tested was that Canis scales with geometric similarity of cross-sectional variables on bone length and body mass, and the Ursus scales with elastic similarity. Larger Canis have relatively stronger postcrania than smaller Canis. The primary way in which this strength is achieved in larger individuals is through a relatively shortening of the bone length. The second hypothesis tested was that postcranial strength is correlated with ecological variables. To investigate this hypothesis, scaling patterns of different species of Canis were compared, including the fossil dire wolf. The results show that the dire wolf is relatively stronger than its living congenerics. There is also a strong relationship between the ratio of prey body mass to predator body mass and relative strength for these species. Carnivores that are hunting animals much larger than themselves must have postcranial skeletons that are strong enough to withstand the loading of the skeleton that occurs during hunting, taking down, and processing large herbivores.</p> / Dissertation
78

Binational collaboration in recovery of endangered species: the Mexican wolf as a case study

Bernal Stoopen, Jose Francisco 30 September 2004 (has links)
The goal of this inductive study was to identify factors that facilitate and inhibit binational collaboration in the recovery of endangered species in the northern Mexico borderlands, focusing on the Mexican wolf (Canis lupus baileyi). A conceptual model was developed using qualitative techniques, providing the basis for design of a mail survey. The target population included participants with experience in recovery efforts for over a dozen species at risk in the region. Long interviews were recorded with 44 participants from Mexico and the United States. Thematic hierarchical analysis was used to develop a conceptual model of how interviewees talked about factors influencing binational collaboration. Issues were classified in five thematic clusters: project, organization, people, resources, culture/history. The survey was used to conduct a needs assessment, measuring respondents' attitudes about the relative priority of issues identified in the conceptual model. High priority needs were identified from each thematic cluster: (a) equitable participation in project design and implementation, (b) continuity of personnel, (c) coordination of federal, state and local efforts, (d) increased funding, managed with accountability, and (e) exchange visits to facilitate understanding of diverse perspectives. Responses to almost half the survey items indicated accord among the sample of respondents, providing a basis for shared common ground. The nature of discord was within the range of "manageable", with no clear polarization of attitudes measured. This exploratory data analysis suggested that the structure of the conceptual model developed from the Mexican wolf case study was generally a valid basis for future deductive analysis and reflection by practitioners. For 82% of 22 statements of need, priorities of participants in the Mexican wolf recovery efforts did not differ significantly from other respondents. Nationality (of respondents) significantly affected priority rankings for only 18% of the need statements. Significant effects of five demographic variables indicated that interactive effects should be examined in future multivariate analyses to determine how respondents' attitudes on issues related to priority rankings. Recommendations were provided for a more efficient and effective approach to collaborative problem-solving, engaging reflective practitioners from the private and public sectors in principled negotiation processes to better understand diverse perspectives.
79

Parámetros inmunopatogénicos en la infección experimental murina con huevos de <i>Toxocara canis</i>

Minvielle, Marta Cecilia January 1997 (has links)
Objetivos del trabajo de tesis: 1- Analizar el ciclo biológico de <i>Toxocara canis</i> mediante infecciones experimentales con huevos del parásito en ratones. 2- Determinar el número de larvas (carga parasitaria) en distintos órganos del ratón luego de su infectación con huevos de <i>Toxocara canis</i> para evaluar la posible relación entre la carga parasitaria y diferentes métodos de inoculación. 3- Desarrollar una técnica serológica para evaluar la respuesta humoral anti-<i>Toxocara canis</i>. 4- Evaluar distintos parámetros inmunológicos celulares y humorales en la infección murina por <i>Toxocara canis</i>.
80

Studies of blood eosinophil and neutrophil granulocytes in healthy and diseased dogs /

Lilliehöök, Inger, January 1900 (has links) (PDF)
Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Page generated in 0.0527 seconds