T cell Maturation and Regulatory T Cell Differentiation:From the Thymus to the Periphery

Immunological tolerance, that is, the failure to mount an immune response to an otherwise immunogenic molecule, is one of the fundamental questions in immunology. The fact that lymphocytes express antigen receptors that are generated randomly and have the potential to recognize any conceivable antigen, adds another puzzle to the physiology of immunological tolerance. The other side of the coin, the general absence of immune responses to self antigens, is ensured by a tight regulation and several selection steps during T and B cell differentiation. One of these processes is the differentiation of regulatory T cells (Treg). While developing in the thymus, T cell clones bearing receptors with high affinity/avidity to antigens present at the time of differentiation may be eliminated by apoptosis or, alternatively, express Foxp3 and become Treg. Treg are key players in the regulation of immunological tolerance since humans and mice with complete loss of function variants of this gene develop fatal autoimmune conditions early in life.(...)

Enterococcus and biocides: mechanisms of tolerance and selection for vancomycin resistance

Dissertation presented to obtain a Doctoral degree in Biology, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa.

Interculturality in the Primary EFL Classroom: Increasing Tolerance through (Inter) Cultural Awareness

Dissertação apresentada para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Didáctica do Inglês,

Proteomic and Transcriptomic Approaches to Abiotic Stress Tolerance in Rice (Oryza sativaL.)

Dissertação para a obtenção de grau de doutor em Biologia pelo Instituto de Tecnologia Química e Biológica da Universidade Nova de Lisboa

Evaluation of drought tolerance in several genotypes of spelt (Triticum aestivum Var. Spelta)

Domestication of plants and plant breeding have dramatically eroded the allelic variations of crop species which led to an increasing susceptibility of crop plants to environmental stresses, diseases and pests. Drought is a major environmental stress factor that affects the growth and development of plants so the selection of tolerant genotypes becomes increasingly important with respect to the predicted effects of global warming. In this study, several genotypes of Spelt (Triticum aestivum var. spelta) were tested under low water supply in soil with the aim of to find Spelt genotypes more resistant than wheat to these conditions, and select them so that in future may be used to improve wheat crops. Morphological analyses were performed and mineral and enzymatic analyses and also dry matter production were calculated. Our results suggests that the genotypes Sp53, Sp96, Sp912, Sp757 and Sp804 are a potential ones to use in breeding programs to improve wheat production. Under drought, these genotypes had growth efficiency of 38%, 45%, 64%, 37%, and 31% respectively and also showed higher biomass than modern wheat and were also mineralogical richer. The genotypes Sp96 and Sp912 showed highest activity of all antioxidants enzymes tested. This work proves that Spelt is a good wheat to continue to study in order to improve wheat crops in dry areas and consequently increase the quality of life and health of the populations living in those areas.

Study of salt stress tolerance in spelt

World population is increasing at an alarming rate while food productivity is decreasing due to the effect of various abiotic stresses. Soil salinity is one of the most important abiotic stress and a limiting factor for worldwide plant production. In addition to its important effects on yield, salt stress affects numerous cellular activities, including cell wall composition, photosynthesis, protein synthesis, ions and organic solutes. Up to 20% of the irrigated arable land in arid and semiarid regions is already salt affected and is still expanding. Improving salt tolerant varieties is of major importance, and efforts should be focused on finding adaptive mechanisms which are involved in salinity tolerance. In this study, several spelt wheat (Triticum aestivum var. Spelta) genotypes and one cultivar of modern bread wheat were used to screen them for salt tolerance. Spelt is an old-European cereal crop currently attracting renewed interest as a food grain because it is said to be harder than wheat and requires less fertilizer. Spelt wheat is also becoming very attractive genetic source by plant breeders due to its wide adaptation ability to various stressful conditions such as soil salinity. In this study morphological parameters (e.g., leaf appearance; shoot elongation), dry matter production, mineral nutrients (especially Na and K), and activity of antioxidative enzymes were measured to select superior genotypes of spelt for salt tolerance. The results showed that Spelt genotype Sp41 is a salt sensitive genotype and genotypes Sp69, Sp96 and Sp912 are good candidates for salt tolerant genotypes.