Browsing by Issue Date, starting with "2008-10"
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- Increased susceptibility to Mycobacterium avium in hemochromatosis protein HFE-deficient micePublication . Gomes Pereira, Sandra Isabel; Rodrigues, Pedro Nuno; Appelberg, Rui; Gomes, Maria SaloméMycobacterium avium is an opportunistic infectious agent in immunocompromised patients, living inside macrophage phagosomes. As for other mycobacterial species, iron availability is a critical factor for M. avium survival and multiplication. Indeed, an association between host secondary iron overload and increased susceptibility to these mycobacteria is generally acknowledged. However, studies on the impact of primary iron overload on M. avium infection have not been performed. In this work, we used animal models of primary iron overload that mimic the human disease hereditary hemochromatosis. This pathology is characterized by increased serum transferrin saturation with iron deposition in parenchymal cells, mainly in the liver, and is most often associated with mutations in the gene encoding the molecule HFE. In this paper, we demonstrate that mice of two genetically determined primary iron overload phenotypes, Hfe(-/-) and beta 2m(-/-), show an increased susceptibility to experimental infection with M. avium and that during infection these animals accumulate iron inside granuloma macrophages. beta 2m(-/-) mice were found to be more susceptible than Hfe(-/-) mice, but depleting Hfe(-/-) mice of CD8(+) cells had no effect on resistance to infection. Overall, our results suggest that serum iron, rather than total liver iron, levels have a considerable impact on susceptibility to M. avium infection.
- Parameters optimization of filtered back projection in Myocardial Perfusion Imaging reconstructionPublication . Metelo, Luís Francisco; Cunha, L.; Vieira, Domingos; Fonseca, A.; Tavares, A.; Soares, S.; Amorim, I.; Castro, R.; Abrantes, A. M.; Botelho, M. F.Nowadays, even if it is noticed an increasingly wider use of Iterative Methods (IM), a significant number of NM Departments is still routinely using Filtered Backprojection (FBP) as the method of choice in what concerns image processing in MPI. Several authors recommend the use of same filter parameters, no matter what the patient physical characteristics are.
- Hormonal, neurochemical, and behavioral response to a forced swim test in adolescent rats throughout cocaine withdrawalPublication . Alves, Cecília Juliana; Magalhães, Ana; Summavielle, Teresa; Melo, Pedro; Sousa, Liliana De; Tavares, Maria Amélia; Monteiro, PedroThe use of cocaine in adults has been linked to depression and/or anxiety. Several studies have shown an association between cocaine-primed craving and depressive symptoms. In animal models, the forced swim test (FST) is frequently used for screening depressive-like behavior. This study aimed to verify the presence of depression-like symptoms in adolescent rats after chronic cocaine exposure by analyzing behavior in a FST. The subsequent alterations in neurotransmitters and hypothalamus-pituitary-adrenal axis activity induced by this test were also analyzed. Both male and female adolescent Wistar rats were submitted to a chronic “binge” pattern of administration of cocaine hydrochloride, and subjects were tested in a forced swim test 2 days after cocaine's last administration. At the end of the behavioral test, trunk blood was collected for quantification of corticosterone plasma levels, and hypothalamus, prefrontal cortex, amygdala, and hippocampus were dissected for neurochemical determinations. No significant differences were found in the behavior on the FST of both males and females after withdrawal from chronic cocaine administration. Nevertheless, plasma levels of corticosterone were increased in cocaine-treated males, although not significantly (P= 0.065). In females cocaine failed to affect corticosterone levels. Of interest, neurochemical analyses showed that dopamine turnover was decreased in amygdala in cocaine-treated males (not significantly, P= 0.055). No significant differences were found on neurotransmitter levels in the other brain regions analyzed. Withdrawal from chronic cocaine administration during adolescence did not have a significant effect on stress-induced behavioral alterations, although the neurochemical response to the stressful situation provided by FTS seemed to be affected.
- Exploratory behavior in rats postnatally exposed to cocaine and housed in an enriched environmentPublication . Magalhães, Ana; Melo, Pedro; Alves, Cecília Juliana; Tavares, Maria Amélia; Sousa, Liliana De; Summavielle, TeresaExposure to cocaine in early periods of postnatal life is usually associated with changes in development of neurotransmitter systems and structure of the central nervous system. Such changes are most likely correlated with behavioral alterations. Environmental enrichment conditions (EC) in early stages is a factor that affects structural and behavioral development. The purpose of this study is to examine the effects of EC on rats postnatally exposed to cocaine on exploratory behavior. Wistar rats were as signed to four groups—Group 1: pups exposed to cocaine hydrochloride (15 mg/kg body weight/day) s.c., in two daily doses, from postnatal day (PND) 1 to 28 and reared in EC; Group 2: pups exposed to cocaine as previously described and reared in a stan dard environmental conditions (SC); Group 3: pups saline-injected and reared in EC; and Group 4: pups saline-injected and reared in SC. On PND 21, 24, and 28, groups of four rats (to reduce anxiety) were placed for 10 minutes into an arena with sev eral objects. The following exploratory behavioral categories were examined: object interaction, exploration, manipulation, approximation, and total time of object contact. Animals from Group 2 showed decreased object interaction and total contact on PND 21. Control offspring reared in EE showed decreases in exploratory behavior at all ages analyzed compared with the control SE group, while cocaine-exposed animals reared in EC showed decreased object interaction, object approximation, and total exploratory behavior. The results in this group suggest that EC improved information acquisition and memory processes in animals postnatally exposed to cocaine.