Percorrer por autor "Pereira, T."
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- Circadian and Biological Rhythms in Shift Workers—A Firefighter’s StudyPublication . Duarte, I.F.; Pereira, J.; Lima, JPM.; Simões, H.; Pereira, T.; Conde, J.Shift Work contribute to dysregulation of the typical sleep and awake periods that cause circadian distortions, increasing the risk of cardiovascular mortality and morbidity and developing metabolic diseases. Firefighting is a career that demands much of individuals and has a great impact on their health, making it a high-risk job. Objectives: This study aims to characterize shift workers’ blood pressure profiles in an attempt to understand the repercussions of shift work on the circadian blood pressure rhythm in a sample of professional firefighters. Materials and methods: Participants were classified based on their dipping status: dipper drop of 10–20%; non-dipper 0–10%; invert-dipper when there is a rise in BP; extreme-dipper superior to 20%. Results: Abnormal dipping was found in 55.6% of the participants, and there was a marked difference in gender in percentage where dipping is concerned, with 66.7% of women having abnormal dipping against 50% of the men. It was proved that men had a slower heart rate than women (p-value = 0.029) and that dippers had a higher 24 h DBP compared with those of abnormal dipping (p-value = 0.049). Conclusions: Shift work is a high-risk module of labor, and its consequences require a more thorough examination. Abnormal dip- ping prevailed in firefighters, and the differences between genders need to be better characterized in future studies. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
- Effects of Human Mesenchymal Stem Cells Isolated from Wharton’s Jelly of the Umbilical Cord and Conditioned Media on Skeletal Muscle Regeneration Using a Myectomy ModelPublication . Pereira, T.; Armada-da Silva, P.A.S.; Amorim, I.; Rêma, A.; Caseiro, A.R.; Gärtner, A.; Rodrigues, M.; Lopes, M. A.; Bartolo, P.J.; Santos, J.D.; Luís, A.L.; Maurício, A.C.keletal muscle has good regenerative capacity, but the extent of muscle injury and the developed fibrosis might prevent complete regeneration. Thein vivoapplication of human mesenchymal stem cells (HMSCs) of the umbilical cord and the conditioned media (CM) where the HMSCs were cultured and expanded, associated with different vehicles to induce muscle regeneration, was evaluated in a rat myectomy model. Two commercially available vehicles and a spherical hydrogel developed by our research group were used. The treated groups obtained interesting results in terms of muscle regeneration, both in the histological and in the functional assessments. A less evident scar tissue, demonstrated by collagen type I quantification, was present in the muscles treated with HMSCs or their CM. In terms of the histological evaluation performed by ISO 10993-6 scoring, it was observed that HMSCs apparently have a long-term negative effect, since the groups treated with CM presented better scores. CM could be considered an alternative to thein vivotransplantation of these cells, as it can benefit from the local tissue response to secreted molecules with similar results in terms of muscular regeneration. Searching for an optimal vehicle might be the key point in the future of skeletal muscle tissue engineering.
- Heatsinks to Cool Batteries for Unmanned Aerial VehiclesPublication . Galvão, J.; Faria, P.; Mateus, A.; Pereira, T.; Fernandes, S.This study aims to develop several different models of heatsinks, designed to cool a vertical take-off and landing unmanned aerial vehicle (UAV) battery, through topology optimization, aimed at being manufactured through selective laser melting (SLM) technology. A battery’s temperature must be properly managed for a safe and efficient operation. The methodology developed was with the support of software to carry out several simulations which, starting from several scenarios and restrictions imposed by the small space available to accommodate these small batteries in this type of aircraft. The conception resulted in several battery thermal management systems (BTMS) models, with different applications and efficiency degrees. A relevant aspect is the topology optimization being coupled to computational thermal analysis to reduce the mass of the heatsink whilst ensuring a maximum battery temperature threshold. Together with the use of topology optimization, the SLM process was selected to manufacture the heat sinks, under conditions of geometric freedom, using several high thermal conductivity metal alloys, such as, aluminium and copper to obtain the designed models.
- Mesenchymal Stem Cells and Biomaterials Systems – Perspectives for Skeletal Muscle Tissue Repair and RegenerationPublication . Caseiro, A.R.; Pereira, T.; Bártolo, P. J.; Santos, J.D.; Luís, A.L.; Maurício, A.C.Skeletal muscle is essential in voluntary movement and other major vital functions. Muscle injuries are important in clinical practice and, despite skeletal muscle's good regenerative ability, severe tissue loss impairs complete myofibre regeneration, limiting structural and functional recovery of the affected muscle, eventually leading to the development of non-contractile fibrous scar. The intrinsic healing mechanisms rely in great extent on the residing progenitor population but significant drawbacks to their practical application in regenerative strategies boosted the search for alternative cell sources, such as extra-fetal mesenchymal stem cells (MSCs). MSCs have demonstrated to positively influence the regeneration of different disease models. When severe volumetric muscle tissue loss occurs, the body is seldom capable of replacing the lost portions with fully functional tissue. A rational strategy to aid the healing of such situations is the application of biomaterial implants that provide a structural matrix for the ingrowth of regenerating muscle fibres. Both synthetic and natural biomaterials have been hypothesized for this purpose and some have reached as far clinical cases applications. Obvious improvements are observed in most cases, but reaction to some biomaterials and functional recovery are still a challenge. The addition of MSCs to the biomaterials seems to improve the systems' performance in the overall regenerative milieu. This strategies promote scaffold's vascularization and integration, as well as accelerated tissue ingrowth and reduces scar formation, resulting in improved recovery rates at both structural and functional levels.
- Promoting Nerve Regeneration in a Neurotmesis Rat Model Using Poly(DL-lactide-ε-caprolactone) Membranes and Mesenchymal Stem Cells from the Wharton’s Jelly: In Vitro and In Vivo AnalysisPublication . Pereira, T.; Gärtner, A.; Amorim, I.; Almeida, A.; Caseiro, A.R.; Armada-da-Silva, Paulo A. S.; Amado, Sandra; Fregnan, Federica; Varejão, A. S. P.; Santos, J. D.; Bártolo, P. J.; Geuna, S.; Luís, A. L.; Maurício, A. C.In peripheral nerves MSCs can modulate Wallerian degeneration and the overall regenerative response by acting through paracrine mechanisms directly on regenerating axons or upon the nerve-supporting Schwann cells. In the present study, the effect of human MSCs from Wharton’s jelly (HMSCs), differentiated into neuroglial-like cells associated to poly (DL-lactide-ε-caprolactone) membrane, on nerve regeneration, was evaluated in the neurotmesis injury rat sciatic nerve model. Resultsin vitroshowed successful differentiation of HMSCs into neuroglial-like cells, characterized by expression of specific neuroglial markers confirmed by immunocytochemistry and by RT-PCR and qPCR targeting specific genes expressed.In vivotesting evaluated during the healing period of 20 weeks, showed no evident positive effect of HMSCs or neuroglial-like cell enrichment at the sciatic nerve repair site on most of the functional and nerve morphometric predictors of nerve regeneration although the nociception function was almost normal. EPT on the other hand, recovered significantly better after HMSCs enriched membrane employment, to values of residual functional impairment compared to other treated groups. When the neurotmesis injury can be surgically reconstructed with an end-to-end suture or by grafting, the addition of a PLC membrane associated with HMSCs seems to bring significant advantage, especially concerning the motor function recovery.