In this cross-sectional, retrospective study, the bone mineral content (BMC) and density (BMD) of the whole skeleton, upper limbs, lower limbs, femoral neck, and lumbar vertebrae were measured using dual photon absorptiometry and the results compared in healthy young males involved in: weight-lifting, running, cross-training, or recreational exercises. When adjusted for body weight, the upper limb BMD was highest in those engaged solely in weight-lifting, (mean 1.021, SE 0.019, and 95% CI 0.981-1.061) and lowest in runners (mean 0.908, SE 0.019 and 95% CI 0.869-0.946). These differences were significant (P = 0.0004). There were no significant differences in upper limb BMD between weight-lifters and cross-trained athletes and between runners and those engaged in recreational exercises. Significant differences in BMD were observed between weight-lifters and recreational athletes (P = 0.001) and between cross-trained athletes and runners (P = 0.03). No other significant differences were observed. These data suggest that healthy, young, adult males reporting a history of intensive weight-lifting had significantly greater bone mass of the upper limb bones than those reporting a history of non-weight-lifting exercises. These results imply a specific versus generalized effect of mechanical load on bones of the skeleton.

Moderate livestock grazing is often identified as a useful management tool for sustaining biodiverse grassland communities and has long been practiced in Scandinavian mountains. Despite of a growing number of studies focusing on grazing effects along elevational gradients worldwide, there is still limited knowledge of how grazing intensity varies over time and how it affects plant communities on species and functional group level. Moreover, the majority of existing studies are conducted in enclosures with controlled stocking rate, while free-range grazing with a highly varied livestock number is the common practise in Scandinavia. Therefore, the aim of this study was to quantify free-range grazing intensity over the growing season along an elevational gradient and to evaluate how grazing affects plant communities on species, functional group and community level. In order to quantify grazing intensity, we conducted a grazer exclusion experiment along an elevational gradient in Norway in the growing season of 2019. We quantified grazing intensity as the difference in dry above-ground biomass between grazed and caged plots and analyzed plant composition on community and functional group level as well as recorded species-specific grazing damage and potentially influential abiotic factors. To capture the effects of temporal variation in grazing we also relocated caged and grazed plots in four-week intervals during the growing season. We demonstrated that grazing intensity gradually decreased with elevation and elevation explained 77% of the variation in grazing among sites. Lower grazing intensity at high elevation is likely related to decreasing plant productivity and differences in plant community composition along the gradient. Grazers reduced the biomass of graminoids and forbs in the intensively grazed lower sites. Grazing damage varied among sites for five of the eight most commonly grazed plant species, which was mainly driven by a higher grazing damage in the intermediate site (900m a.s.l.). Selective grazing was observed in three sheep-dominated study sites. Grazing intensity did not significantly vary during the growing season at any site, possibly due to weak temporal effects of an overall short growing season. In accordance with other studies, we demonstrated that grazing homogenized plant community composition in actively grazed sites that were relatively species rich. To conclude, livestock grazing can help maintain biodiverse semi-natural grasslands, yet when grazing is applied as a management tool in the mountainous landscapes, we suggest considering that grazing intensity, and therefore its effects, will vary with elevation.

Made available in DSpace on 2016-04-29T13:18:17Z (GMT). No. of bitstreams: 1 Dumas Pereira Ferreira Gomes.pdf: 525538 bytes, checksum: 5b068a1406d7f0e510275aa96a78ebaa (MD5) Previous issue date: 2010-05-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The first experiment of this study was conducted with 8 subjects and aimed to test if a simple discrimination procedure using contingency-specific responses was sufficient for the formation of equivalence classes. After a discrimination training with 3 distinct responses emitted to 3 sets of 3 stimuli, tests for equivalence classes were conducted. Results were positive for 7 of the 8 participants and showed the emergence of 2 stimulus classes: 1) Class 1 (with stimuli A1, B1 ,C1 and response topography 1; 2) and Class 2 with stimuli A2, B2, C2 and R2, the response topography 2. These 7 participants were the subjects of Experiment 2 . Two successive tasks were presented on each trial. On Task 1 the participant formed a compound stimuli by choosing 2 equal or different stimuli. Correct choices were paired with B1 and B2 respectively (stimuli in the equivalence classes formed in experiment 1). In Task 2 subjects were supposed to choose either B1 pr B2 depending upon the kind of stimuli produced on Task 1. The purpose of Experiment 2 was to test if the responses of compounding stimuli made of equal or different parts would be included in the same equivalence classes of B1 and B2, and if the other members of the stimuli classes, including the responses (R1 and R2), would acquire the same function. After training tests were conducted to answer the following questions: 1) The other stimuli of the stimulus classes 1 and 2 acquired the functions of B1 and B2? 2) Stimuli A1, C1 and A2, C2 could control responses in Task 1 (stimuli compounding)? 3) Compounding equal or different stimuli could be evocative of the responses R1 and R2? 4) The task of stimulus composition would be evocative of the same stimulus choice with new stimuli, or else, the equal or different dimension of the stimulus composition could be a controlling variable in Task 2? Compounding equal or different stimuli formed by the new stimuli introduced in Task 1 would control the responses R1 and R2 respectively? Results showed that 6 subjects reached criterion on tests. Results showed that 2equivalence classes were formed: Class 1 consisting of A1, B1, C1, R1 and the response of compounding equal stimuli, and Class 2 consisting of A2, B2, C2, R2 and the response of compounding different stimuli. It was also found that the acquisition of a function by one member of a class transferred to other class members, indicating that the equivalence classes are also functional classes / O primeiro experimento desse estudo teve 8 participantes e o objetivo foi testar se um procedimento de formação de classes de estímulos via seleção de classes operantes com respostas de diferentes topografias seria suficiente para formar classes de equivalência. Depois de um treino de discriminação simples em que respostas de distintas topografias foram pareadas como estímulos arbitrários a formação de classes de estímulos envolvendo os estímulos e as respostas do treino discriminativo foi testada. Os resultados documentaram a formação de classes para 7 participantes. O experimento 2 foi conduzido com estes participantes e teve por objetivo colocar respostas de escolha em uma tarefa de MTS (Tarefa 2), sob controle de outra tarefa (Tarefa 1), de construção de estímulos compostos (iguais ou diferentes) que eram pareadas a dois estímulos (B1 e B2) pertencentes às classes de equivalência formadas no Experimento 1, e testar se as respostas de construção de estímulos compostos se tornariam membros das mesmas classes de equivalência que B1 e B2 e se a função discriminativa adquirida por essas respostas seria também exercida por outros membros da classe de estímulos envolvidas na tarefa de MTS, inclusive pelas respostas diferenciais membros das classes de equivalência formadas no Experimento 1 (R1 e R2). Os participantes do estudo 2 foram divididos em dois grupos para testar o efeito da apresentação ou não do produto da resposta na Tarefa 1. A fase de teste , consistiu em cinco etapas que tinham por objetivo, respectivamente, testar se: 1) outros estímulos, das mesmas classes que B1 e B2, (A1,C1 e A2, C2), passariam a exercer a mesma função de B1 e B2; 2) Ao inverter a ordem das tarefas, os novos estímulos (A1,C1 e A2, C2) passariam a exercer controle sobre as respostas de construir estímulos iguais ou diferentes; 3) as respostas de construir estímulos compostos iguais ou diferentes controlariam a emissão das respostas diferenciais R1 e R2; e 4) diante da introdução de novos estímulos na tarefa de construção de estímulos compostos, na Tarefa 2 os participantes ficariam sob controle da emissão das respostas de construir estímulos compostos iguais ou diferentes, independente dos estímulos utilizados; e 5) A as respostas de construção de estímulos compostos iguais ou diferentes com estímulos novos controlariam a emissão das respostas diferenciais R1 e R2. Os resultados indicaram que 6 dos 7 participantes atingiram critério nos testes, indicando que foram formadas duas grandes classes de equivalência. A Classe 1 composta por A1; B1; C1; R1 e a resposta de construir estímulos compostos de partes iguais e a Classe 2 composta por A2; B2; C2; R2 e a resposta de construção de estímulos compostos de partes diferentes. Foi verificado também que a atribuição de uma função a um dos membros da classe passou a ser exercida também pelos outros membros da classe, demonstrando assim atenderem também aos requisitos de classes funcionais

Malgré les améliorations significatives apportées par la thérapie antirétrovirale à la durée et à la qualité de vie des personnes vivant avec le VIH, elle ne permet pas de complètement éliminer le virus de l’organisme. La persistance du virus est due à l’existence de réservoirs viraux, des cellules infectées de manière latente par le VIH. Ces réservoirs nécessitent un traitement antirétroviral à vie, car le virus réapparait en cas d’interruption du traitement, signifiant que l’immunité des cellules T spécifiques du VIH n’est pas restaurée. Bien que cela soit théoriquement possible, seule une fraction de personne vivant avec le VIH, appelée Contrôleurs Élites, parvient à contrôler le virus en absence de traitement. Pour la majorité des individus, l’infection par le VIH entraîne une évasion virologique ainsi qu’un épuisement et une altération des réponses cellulaires spécifiques au VIH. À ce jour, les stratégies thérapeutiques visant à éliminer les réservoirs viraux ont échoué, en partie en raison de la présence de provirus principalement défectifs dans ces réservoirs. Dans cette thèse, nous avons identifié et caractérisé les provirus défectifs latents du VIH pouvant être transcrits et/ou traduits, ainsi que la relation entre ces réservoirs et les réponses immunitaires spécifique du virus. Dans un premier temps, nous avons montré que bien que défectifs et potentiellement incapable de donner lieu à la réplication virale, ces provirus peuvent être transcrits et traduits soit par réactivation à l’aide d’agents de réversion de la latence, soit de manière spontanée. Ces réservoirs donnent lieu à plusieurs populations de réservoirs, en fonction de la présence ou de l’absence certains gènes viraux. Nous avons déterminé que ces différentes populations sont régies par le profil génomique des cellules infectées. Les provirus identifiés étaient très rarement intacts, mais l’intégrité du génome était associée à la processivité de la transcription et de la traduction. Dans un second objectif, nous avons caractérisé les réponses T CD4+ et CD8+ spécifiques du VIH avant et après le début du traitement antirétroviral. Nous avons observé que les réponses T CD4+ spécifiques étaient comparables pendant l’infection chronique et après le traitement. En revanche, les réponses T CD8+ diminuaient considérablement après l’initiation de la thérapie antirétrovirale. Nous avons également constaté que la taille du réservoir traductionnellement actif pendant le traitement antirétroviral était négativement associée aux réponses T CD8+ spécifiques avant le début de la thérapie, tandis que le réservoir incapable de traduire les protéines du VIH subsistait. Ces observations mettent en évidence le rôle des cellules T CD8+ dans le contrôle de l’infection par le VIH, comme nous l’avons observé chez les Contrôleurs Élites. Nos travaux contribuent à une meilleure compréhension des réservoirs viraux du VIH, qui pourraient potentiellement être impliqués dans l’inflammation chronique et la dysfonction immunitaire associé à la pathogénèse du VIH. / Despite the significant improvement brought by antiretroviral therapy in the duration and quality of life for people living with HIV, it does not completely eliminate the virus from the body. The persistence of the virus is due to the existence of viral reservoirs, which are cells latently infected with HIV. These reservoirs require lifelong antiretroviral treatment because of the viral rebound reoccurring in case of treatment interruption. This suggests that HIV-specific T cell immunity is not restored. Although theoretically possible, only a fraction of people living with HIV, known as Elite Controllers, are able to control the virus in the absence of treatment. For the majority of individuals, HIV infection leads to virologic escape, as well as exhaustion and altered cellular responses to HIV. To date, therapeutic strategies aimed at eliminating viral reservoirs have failed, partly due to the presence of predominantly defective proviruses in these reservoirs. In this thesis, we have identified and characterized latent defective proviruses of HIV that can be transcribed and/or translated. We also have characterized the relationship between these reservoirs and the specific immune responses to the virus. Firstly, we have shown that although defective and potentially replication-incompetent, these proviruses can be transcribed and translated either through reactivation using latency reversal agents or spontaneously. These reservoirs give rise to several populations of reservoirs, depending on the presence or absence of certain viral genes. We have determined that these different populations are governed by the genomic profile of infected cells. The identified proviruses were rarely intact, and genome integrity was associated with the processivity of transcription and translation. Then, we characterized the specific CD4+ and CD8+ T cell responses to HIV before and after the initiation of antiretroviral treatment. We observed that specific CD4+ T cell responses were comparable during chronic infection and after treatment. However, CD8+ T cell responses decreased significantly after the initiation of antiretroviral therapy. We also found that the size of the translationally active reservoir during antiretroviral treatment was negatively associated with the specific CD8+ T cell responses prior to treatment initiation, while the translation-incompetent cells persisted. These observations highlight the role of CD8+ T cells in the control of HIV infection, as observed in Elite Controllers. Our work contributes to a better understanding of HIV viral reservoirs, which could potentially be involved in chronic inflammation and immune dysfunction associated with HIV pathogenesis.