431 research outputs found
Papel da carga viral celular na imunodeficiência HIV/SIDA : contributo do estudo da infecção pelo HIV-2
Tese de doutoramento, Ciências Biomédicas (Imunologia), Universidade de Lisboa, Faculdade de Medicina, 2011The acquired immunodeficiency syndrome (AIDS), first described in 1981, has caused
more than 25 million deaths worldwide with an estimated 2 million deaths related to
disease in 2008, representing one of the most important public health problems
worldwide.
AIDS is caused by infection with human immunodeficiency virus type 1 (HIV-1) and
type 2 (HIV-2). HIV-1 infection is pandemic, with more than 33 million people
estimated to be infected, whilst HIV-2 infection remains relatively contained to a few
West African countries, with Portugal representing the only non-African country with a
significant HIV-2 prevalence (3.2% of infection cases reported in 2009).
HIV-2 infection is characterized by a slower progression to AIDS as compared to HIV-1
infection, with a limited impact on the survival of the majority of infected adults. The
rate of CD4 T cell decline is much slower than in HIV-1 and the levels of circulating
virus (viremia) are significantly lower irrespective of disease stage. The low levels of
viremia in patients infected with HIV-2 suggest a lower replicative activity. However,
despite the lower viremia in HIV-2, our results, as well as studies from other groups,
showed that levels of proviral DNA in peripheral blood mononuclear cells are similar in
both infections, suggesting that a similar number of cells are infected.
The cell tropism of HIV-2 and HIV-1 is determined by the expression of chemokine
receptors on target cells in addition to the expression of the CD4 molecule. CCR5 and
CXCR4 are the major co-receptors that are used for HIV-1 entry, and their levels of
expression were shown to be directly related to the susceptibility to infection and to the
rate of disease progression in HIV-1 infected individuals. Several studies suggest that, although HIV-2 can use a larger number of co-receptors as compared to HIV-1 in vitro,
the major co-receptors used in vivo are also CCR5 and CXCR4. It is possible that
different expression levels of these co-receptors lead to different patterns of infection in
T cells populations determining the reduced production of virus and disease progression
that is observed in individuals infected with HIV-2. We compared the expression of
CCR5 and CXCR4 in patients infected with HIV-2 and HIV-1 that had similar levels of
CD4 T cell depletion and found that patients infected with HIV-2 had an increased
frequency of cells expressing CCR5 in the CD4 memory-effector population as
compared to seronegative subjects. We also found a significant correlation between the
frequency of cells expressing CCR5 in total CD4 T cells and the level of CD4 T cell
depletion in individuals infected with HIV-2, but not in the ones infected with HIV-1.
The expression of CCR5 is induced by cell activation and is usually restricted to the
memory-effector population. We found the existence of a direct correlation between the
frequency of cells expressing CCR5 and the levels of immune activation in individuals
infected with HIV-2. These results demonstrate an association between the expansion of
cells expressing CCR5 and immune activation in HIV-2. The lower frequency of cells
expressing CCR5 in HIV-1 infected individuals, as compared with HIV-2+ individuals
may be related to a continuous depletion of these cells in the presence of the higher
levels of viremia associated with HIV-1 infection. Regarding the frequency of cells that
express CXCR4 within CD4 T cell population, we found that this frequency was similar
in patients infected with HIV-2 or HIV-1 and HIV-negative individuals. We also
investigated the possibility that the similar levels of proviral DNA in the presence of
different levels of viremia could be due to differences in the target cells. The levels of
proviral DNA were quantified in purified naive and memory CD4 T cells from patients infected with HIV-2 and found to be very low in naive CD4 T cells, in marked contrast
to the levels found in memory CD4 T cells. These results are in agreement with what is
observed in individuals infected with HIV-1, suggesting that the memory CD4 T cell
population is the main target for HIV-2, and further supporting the notion that CCR5 is
the main co-receptor used by HIV-2 for infection in vivo. These data suggest that the
lower viremia observed in patients infected with HIV-2 is not related to co-receptor
availability on target cell populations.
The low to undetectable levels of viremia in the presence of significant levels of
proviral DNA may be due to the regulation of HIV-2 at the transcriptional level.
Therefore, we proceeded with the study of viral mRNA expression through the
development of methodologies based on real-time RT-PCR for the quantification of
unspliced (gag) and multiply spliced (tat) mRNA transcripts of HIV-2 and HIV-1. The
optimization of these approaches allowed the development of assays with high
sensitivity, specificity and reproducibility, which were used to investigate the
transcriptional activity in cohorts of HIV-1 and HIV-2 infected patients. We found that
HIV-2 infected patients expressed significantly lower levels of tat mRNA as compared
to patients infected with HIV-1. However, gag mRNA expression was found to be
similar in the two cohorts. Given that tat mRNA seems to be mainly expressed in
recently infected cells, our data suggest that the rate of new infections at the cellular
level is lower in individuals infected with HIV-2 as compared to their HIV-1 infected
counterparts. On the other hand, the observation of similar levels of gag mRNA in the
two infections suggest that there is significant ongoing viral transcription in individuals
infected with HIV-2, despite the low levels of viremia that characterize this infection.
We further investigated the role of viremia, as well as levels of proviral DNA and tat and gag viral transcripts on the chronic immune hyperactivation observed in HIV-2 and
HIV-1 infections. We found significantly higher levels of CD4 and CD8 T cell
activation in HIV-2 infected individuals with detectable viremia as compared with
aviremic HIV-2+ individuals. These results suggest a contribution of the circulating
virus, even at low levels, to the state of immune activation found in these individuals.
Our results further revealed a direct association between the levels of gag mRNA and
the activation of CD4 T cells, supporting the possibility that persistent viral replication
contributes significantly to the elevated immune activation levels observed in patients
infected with HIV-2 despite the reduced viremia. In addition, we found a direct
association between the levels of tat mRNA and CD8 T cell activation, particularly in
individuals infected with HIV-1, suggesting that the levels of tat, or the number of
newly infected cells, may have a role in CD8 T cell activation.
Next, we evaluated the impact of antiretroviral therapy on the levels of viral transcripts
and proviral DNA levels in treated HIV-2 infected individuals. Studies in treated HIV-1
patients showed that antiretroviral therapy led to decreased levels of viral mRNA, as
well as a progressive decrease in the levels of proviral DNA. However, there were no
data regarding the effects of antiretroviral therapy on the levels of viral transcripts and
proviral DNA in treated HIV-2 infected individuals. We found that these individuals
featured significantly higher levels of tat mRNA than their untreated counterparts,
suggesting that the regimens used were not effective in reducing the rate of infection of
new cells. We also documented the presence of mutations in reverse transcriptase and
protease in the majority of treated patients, which indirectly supports the existence of
persistent viral replication despite antiretroviral therapy. We further noted that these
patients showed elevated levels of CD4 and CD8 T cell activation that negatively correlated with the number of CD4 T cells in circulation, possibly contributing to the
reduced CD4 T cell recovery observed in these patients.
In conclusion, we provide evidence of significant levels of viral replication in patients
infected with HIV-2, and of its relationship with the levels of immune activation in spite
of the low levels of circulating virus. Our data reinforce the importance of monitoring
levels of persistent viral replication, even at low levels and emphasize the need to
pursue clinical trials and studies on the efficacy of antiretroviral therapy in HIV-2
infection.POCI 2010 e o FSE.
Bolsa de Doutoramento da Fundação para a
Ciência e a Tecnologia
(referência: SFRH/BD/23863/2005
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Rapid prototyping and tooling in the manufacture of mould elements for large parts
In the last two decades the advances in rapid prototyping and tooling (RPT) technologies made possible the use of materials alternative to steel in some mould components. They also have allowed novel fabrication strategies and new ways of thinking on the production of injection moulds for short series of plas-tics parts. These technologies induced a new generation of toolmaking techniques. In the scope of the devel-opment project Hybridmould 21 the pros and cons of some RPT technologies were studied to fabricate moulding blocks and inserts for hybrid injection moulds for large plastics parts. Essentially, the studies aimed at finding the best solution for quick production and compliance with specific product requirements, such as complex features, complex cooling layout and large size (around 1 m2) in short production series. This paper discusses the main advantages and disadvantages associated to a number of different RPT technologies for the manufacture of moulding element.Program QREN - ‘Concessão de Incentivos Financeiros no âmbito do Sistema de Incentivos à Investigação e Desenvolvimento Tecnológico’ (contract 2010/013307) – Project Hybridmould 2
Análise do impacto do relevo na ocupação do solo urbano em zonas de montanha – Aplicação à cidade da Guarda, Portugal
O relevo é um dos fatores que influenciam o crescimento urbano e a sua morfologia. Este elemento natural, dependendo da sua intensidade, pode condicionar o desenvolvimento urbano sustentável. A existência de barreiras topográficas obriga à fragmentação do tecido urbano e consequente dispersão. Apresenta-se ao longo deste artigo a metodologia desenvolvida com o objetivo de analisar a integração das classes de uso e ocupação do solo urbano na topografia urbana. A análise espacial desenvolveu-se com recurso a Sistemas de Informação Geográfica. Os resultados obtidos permitiram concluir acerca da integração dos vários tipos de uso e ocupação do solo urbano no declive local; avaliar a existência de barreiras topográficas naturais no interior de espaços urbanos construídos, constituindo elementos fraturantes do crescimento urbano; analisar a inclusão de usos e ocupações de solo artificializado em zonas de risco. Esta análise constitui uma ferramenta de apoio ao planeamento urbano, na identificação de zonas de risco
Psychopathy Checklist-Revised (PCL-R) factor structure in male perpetrators of intimate partner violence
Psychopathy Checklist-Revised (PCL-R) is the gold standard for assessing psychopathy. However, its factorial structure has been subject of debate, and different factor models have been proposed. Furthermore, research has not focused on the PCL-R factorial structure among intimate partner violence (IPV) perpetrators. We analyzed and compared the fit of nine alternative models of PCL-R among a sample of 242 IPV perpetrators. Results revealed PCL-R has adequate factor validity. The three-factor model without testlets provided the best fit to the current data. The three-factor model also showed good reliability, and the factors established differential associations to penal and personal variables thus revealing discriminant validity. In the current study, psychopathy was thus best conceptualized as a clinical construct comprising a particular affective functioning (e.g., shallow affect, lack of empathy), and a specific interpersonal (e.g., egocentricity, deception) and behavioral style (e.g., irresponsibility, impulsivity) among IPV perpetrators.Portuguese Foundation for Science and Technology and the Portuguese Ministry of Science, Technology and Higher Education through national funds and co-financed by FEDER through COMPETE2020 under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007653). The study was also supported by Grant SFRH/ BD/66110/200
A study on the convergence of observer-based kinetics estimators in stirred tank bioreactors
This paper is devoted to the tuning problem of the "observer-based kinetics estimator" in stirred tank
bioreactors. This algorithm estimates the reaction kinetics from the on-line knowledge of the state variables
(either from measurement or by means of state observer), when the yield coefficients are known. The relation
between the dynamics of convergence and the tuning procedure is explored. The method proposed imposes a
second-order dynamics to the convergence of the estimator. This approach will be shown to compare
favourably with a pole placement based technique, in an application to a baker's yeast fed-batch fermentation.Junta Nacional de Investigação Científica e Tecnológica (JNICT) - contract numbers BIC/636/92, BD/224/90-IF, BD/1476/91-RM
Urban sprawl assessment model in the context of sustainable development
The disordered urban growth may prove catastrophic for the future of cities if preventive measures are
not taken. The increase of built-up areas, the growing need for implementation of urban infrastructures, the
resulting increase in soil sealing, the excessive consumption of natural resources, the elevated need for car use
on daily travels, the increase in travel distances, etc., are examples of the negative effects caused by urban
sprawl. In order to implement measures to halt or avoid the damage caused by urban sprawl on the
environment, society and economy, it is necessary to know which areas to intervene. In this sense, a
multicriteria analysis model is presented that combines sustainable development indicators, with the main
objective of calculating an index of sustainable urban expansion. This model, developed according to the
Analytical Hierarchy Process, comprises three levels of analysis. At the first level, the indicators of urban
sustainable development are aggregated and associated withsix criteria. The weighted aggregate of composite
indicators, which constitute the second level of analysis, allows evaluating different scenarios and studying the
level of influence of urban sprawl on the diverse dimensions. In the last level of analysis, an index is
calculated,resulting from the aggregation of all indicatorsconsidered along the hierarchical structure. Thus, the
proposed model allows quantifying the level of sustainability of urban sprawl, according to the lines of
sustainable development defined for this work, serving as a tool to support urban planning interventions
Analyses of DNA damage in Saccharomyces cerevisiae mutant strains affected in the cell integrity (PKC) signaling pathway
The PKC signaling pathway is known to be related to genome integrity. Inclusively, it has already been shown that this pathway transmits information to the nucleus in what concerns genotoxic stress. Although this has been demonstrated it has not been shown that in the absence of a functional PKC pathway cells accumulate DNA damage. This research intends to investigate DNA damage caused by genotoxic stresses, as the one caused by the DNA replication inhibitor drug hydroxyurea, UV radiation and a genotoxic propolis extract, on mutants affected in the PKC pathway. The objective is to test the sensitivity of mutants affected in the genes BCK1, MKK1, MKK2 and SLT2, all fundamental MAPKs of this pathway. The biological model chosen for these experiments is Saccharomyces cerevisiae. As expected the results show higher sensitivity of the mutant strains when exposed to the genotoxicants, when compared to the parental strain, suggesting that PKC-defective mutants have decreased ability to repair DNA damage.info:eu-repo/semantics/publishedVersio
An integrated project of entrepreneurship and innovation in engineering education
This paper presents a new line of project based learning in the School of Engineering of University of Minho:
the Innovation and Entrepreneurship Integrated Project (IEIP). Four groups, each one composed of
students from different engineering integrated master courses – Mechanical, Industrial Electronics and
Computers, Polymer, Industrial Management – compete against each other in developing or improving
commercial products manufactured by actual industries. There have been so far five editions of the IEIP,
with five different companies and five diverse products, however, all these products included components
that required knowledge from all the engineering courses involved. Only with the cooperation
between the students of the various courses that compose each multidisciplinary team, the success is
attainable. As each student has to deal with various engineering scopes, students’ technical skills are
greatly enlarged and they acquire a multidisciplinary knowledge that was not possible in another way.
Their soft skills like project management, teamwork, communication ability and personal development,
which are valuable requisites for their future employers, are also improved. The participating industries
also take advantage of the project: the groups competing against each other act as a multiskilled work
force, actually making proposals capable of improving their products, their efficiency, and reducing costs
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