The current study features collected information from a heterogeneous group of pilots regarding their prior experiences of hypoxia. The study focuses on whether the group of assembled pilots has received hypoxia training and on their perceptions of the trainings relevancy. Also analyzed is whether the installation of a physiological monitoring system would be considered by pilots as being relevant to improving flight safety. A monitoring system for brain oximetry was tested in light aviation pilots during real flight conditions

Neonatal hypoxic-ischemic encephalopathy (HIE), caused by oxygen and blood flow deprivation to the neonatal brain, is a leading cause of mortality and long-term neurological disabilities in children under five. Its complex pathophysiology— comprising excitotoxicity, inflammation, oxidative stress, and delayed cell death—poses significant therapeutic challenges. Moreover, current management with therapeutic hypothermia (TH) shows limited efficacy, particularly in severe cases, and excludes many neonates due to strict enrollment criteria. To overcome these limitations, preclinical research has explored stem cell therapies (SCT), particularly using stem cells from umbilical cord blood (UCB) and tissue (UC). These therapies show promise in reducing brain injury and improving outcomes, but challenges remain in optimizing doses, delivery methods, and scalability. Building on previous work, this thesis evaluated several approaches to optimize SCT for neonatal HIE. First, administration of UCBCs alone and in combination with TH in a rat model of HIE, reduced brain lesion size and improved functional outcomes more effectively than TH alone, while also reducing glial reactivity—an effect not observed with TH alone. These findings establish UCBCs as a potential therapy, particularly when TH is unavailable or insufficient. Nonetheless, the use of these cells can present disadvantages: autologous use, limited culture and expansion, thus not being possible to manipulate with preconditioning strategies. Thus, we focused on the use of UC-derived MSCs that overcome some of the limitations previously mentioned. Also, since preconditioning strategies are being explored as ways to potentiate MSCs therapeutic effects, we hypothesized that hypoxic preconditioning could enhance UC-MSC efficacy and what explored the potential mechanisms behind neurological recovery. Proteomic analysis revealed that HIE rats treated with hypoxiapreconditioned MSCs had an enrichment of pathways related to synapse function, brain connectivity, and energy metabolism. Moreover, administration of UC-MSCs preconditioned with short hypoxia induced a greater functional recovery in HIE rats than administration of UC-MSCs preconditioned mild hypoxia. Stem cell therapy requires high doses of stem cells, which limits its clinical translatability. To optimize SCT and significantly reduce effective doses of MSCs, we evaluated the impact of two delivery methods and the combination of different strategies on the efficacy of UC-MSCs. Intranasal administration of UC-MSCs was more effective in reducing the infarct volume enhancing motor and cognitive recovery than intravenous administration, restoring myelination in the corpus callosum, and mitigating glial reactivity. Intranasal administration of half the dose of hypoxia-preconditioned UCMSCs reduced neurological deficits associated with neonatal HIE. Strikingly, intranasal administration of secretome from hypoxia-preconditioned MSCs demonstrated similar therapeutic efficacy, offering a promising cell-free alternative. Finally, to address the limitations associated with the expansion of UC-MSCs and donor variability on the therapeutic potency of these cells, we aimed to determine if induced pluripotent stem cell-derived MSCs (iMSCs) could hold the same potential in the neonatal HIE model. Intranasal administration of iMSCs or their secretome improved motor and cognitive recovery, reduced brain lesion size, modulated glial reactivity, and enhanced neurogenesis in the hippocampus of HIE rats. The comparable outcomes between iMSCs and their secretome underscore the critical role of secreted factors, presenting a scalable, cell-free option for clinical application. In summary, this thesis advances the field of regenerative medicine for neonatal HIE by identifying innovative strategies to optimize stem cell therapies. The findings demonstrate the potential of intranasal delivery and hypoxic preconditioning to reduce the required cell doses while maintaining efficacy, making these therapies more feasible for clinical use. Furthermore, secretome-based approaches offer a scalable alternative that addresses logistical challenges. Beyond neonatal HIE, these strategies may have broader implications for other neurodevelopmental and neurological disorders, as well as for veterinary medicine. While significant progress has been made, future research should aim to elucidate the mechanisms underlying MSC and secretome efficacy and advance these approaches toward clinical trials, paving the way for innovations in regenerative medicine.

Biliary atresia (BA) is a rare neonatal cholangiopathy characterized by the progressive obstruction of the extrahepatic bile ducts, leading to cholestasis, liver fibrosis, and often the need for liver transplantation. Although affected infants appear clinically healthy at birth, laboratory evidence of cholestasis is already detectable. Despite advances in understanding the underlying pathophysiological mechanisms, the etiology of BA remains unclear, with proposed causes ranging from viral infections and immune dysregulation to genetic predispositions and vascular anomalies. Recent evidence suggests that hypoxia and primary cilia dysfunction in cholangiocytes may play a central role in BA pathogenesis, influencing cholangiopathy progression and clinical outcomes. This thesis investigates the interplay between hypoxia—specifically, the activation of the hypoxia-inducible factor 1-alpha (HIF-1α) pathway in cholangiocyte nuclei (ischemic cholangiopathy)—and the morphological and functional alterations of primary cilia in cholangiocytes of BA patients. The methodological approach included immunohistochemical, immunofluorescence, and molecular analyses of liver samples obtained from patients undergoing portoenterostomy, detailed characterization of ciliary morphology using advanced digital imaging techniques, and correlation of these findings with clinical and laboratory parameters and post-operative outcomes, including native liver survival. The results demonstrated increased nuclear HIF-1α expression in cholangiocytes of BA patients, particularly in areas near the peribiliary vascular plexus and progenitor cell niches. This activation was absent in liver samples from control patients with other neonatal cholestases (non-BA), suggesting a specific role of hypoxia in BA pathogenesis. Furthermore, gene expression analysis revealed the upregulation of molecular pathways related to ductular reaction, oxidative stress, and angiogenesis, reinforcing the hypothesis that hypoxia actively contributes to bile duct injury and tissue remodeling. These findings justify further studies focused on the mechanisms involved in HIF-1α activation and the clinical effects of hypoxia and/or oxidative stress on cholangiocytes. Additionally, the characterization of primary cilia in cholangiocytes revealed significant structural alterations in BA patient samples. A reduction in ciliary length and a possible disruption in the transport of acetylated tubulin 4α—a key marker of ciliary stability— from the cytoplasm to the cilium was observed. These alterations were associated with worse clinical outcomes, including a significant reduction in native liver survival. Regarding the association between hypoxia and ciliopathy, the co-localization of HIF- 1α and TUBA4A in BA samples suggests an inverse relationship between HIF-1α positivity and the presence of primary cilia on the luminal membrane of cholangiocytes, both in the portal tract and other microanatomical regions of the liver. Quantitative analysis of ciliary characteristics showed that biliary cells without hypoxic features maintained primary cilia integrity, suggesting that hypoxia may negatively impact ciliary formation or maintenance. The correlation between HIF-1α activation and ciliary dysfunction implies that hypoxia not only promotes inflammation and fibrosis but also compromises the structural and functional integrity of primary cilia, exacerbating disease progression. These findings offer new insights into the pathophysiological mechanisms underlying BA, suggesting that HIF-1α activation and ciliary dysfunction may serve as relevant biomarkers for prognosis and potential therapeutic targets. Identifying these molecular alterations not only facilitates the prediction of clinical outcomes but also opens avenues for innovative interventions aimed at modulating the hypoxic response and restoring ciliary function to improve liver survival and patient quality of life. Overall, this work advances the understanding of the relationship between hypoxia, ciliary dysfunction, and cholangiopathy in BA, paving the way for new research directions to develop more effective diagnostic and therapeutic strategies that mitigate the effects of hypoxia and preserve liver function in pediatric patients with this condition.

Ischemic stroke (IS) remains one of the leading causes of death and disability worldwide, representing a major clinical and economic challenge. It is caused by the temporary or permanent interruption of a blood vessel, leading to disruption of the central nervous system and consequent neuronal loss. In the acute phase, therapeutic strategies include thrombolysis and thrombectomy to restore blood flow, whereas in the chronic phase, approaches aimed at promoting neural plasticity, such as cell therapy, are employed. However, these techniques face several limitations, as their efficacy is directly influenced by multiple variables, making their response unpredictable. Recent studies have attributed the effects of mesenchymal stem cells (MSCs) mainly to their paracrine action, thus positioning the use of their secretome as a promising alternative. In this work, we evaluated the impact of secretome derived from umbilical cord MSCs (UC-MSCs), obtained under normoxic and hypoxic conditions, on neuronal viability and on the recovery of synaptic structure after oxygen and glucose deprivation (OGD) in vitro. The results suggest that the secretome can modulate cell survival, preserve the length of neuronal arborization processes, and modulate synaptic markers. Although some results are promising, further studies are required to explore alternative approaches in order to better understand the action of MSC-derived secretome in the treatment of ischemic stroke and other neurological disorders associated with hypoxicischemic injury.

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O microambiente tumoral de hipóxia é uma característica comum a tumores sólidos. O fator de transcrição HIF-1α, ativado em hipóxia, coordena a expressão de genes que tornam as células tumorais mais agressivas. Embora haja um acúmulo da proteína HIF-1α em hipóxia, os níveis de mRNA de HIF1A apresentam-se diminuídos. Até então, pouco se sabe sobre os mecanismos envolvidos na regulação dos transcritos de HIF1A. Dentre os mecanismos conhecidos que, normalmente, associam-se a inibição da transcrição, a metilação do DNA poderia elucidar uma nova forma de controle, a nível transcricional, de HIF1A. Diante disso, o presente trabalho objetivou investigar o papel da metilação do DNA no controle transcricional de HIF1A, em hipóxia. Para verificar a possibilidade de HIF1A e, também de VEGFA, gene alvo de HIF-1α, serem regulados por metilação do DNA, foi realizada uma predição in silico de sítios de metilação, identificados por ilhas CpGs, no promotor e no primeiro éxon do gene de HIF1A e VEGFA, com auxílio do software Methprimer. A ação demetilante de 5-aza-dC foi confirmada pela amplificação, por PCR, de PGR, inibido por metilação, na linhagem de câncer de mama, MDA-MB-231, usada como modelo experimental. O ensaio de WST-1 foi usado para avaliar a toxicidade de 5-aza-dC. Foram avaliados os efeitos da 5-aza-dC sobre os níveis de mRNA de HIF1A e VEGFA, por RT-qPCR. Além disso, Alteração no nível proteico de HIF-1α, após 5-aza-dC, foi avaliada por citometria de fluxo. Em todos os ensaios, foi utilizada a dose de 100 μM 5-aza-dC, em normóxia (48h e 72h) e hipóxia. Em hipóxia, as células foram tratadas com 5-aza-dC por 72h, sendo as últimas 24h de incubação na câmara de hipóxia. A predição in silico identificou 6 ilhas CpGs na região avaliada de HIF1A e 3 ilhas CpGs, em VEGFA. A 5-aza-dC induziu a expressão de PGR, confirmando sua ação demetilante e, não reduziu consideravelmente a viabilidade celular. Em normóxia, 5-aza-dC elevou os níveis de mRNA de HIF1A 6,5 vezes (±3,8) (48h) e 2,0 vezes (±0,5) (72h) e, aumentou os níveis de VEGFA em 2,6 (±0,6) (48h) vezes e 2,4 vezes (±0,5) (72h). Em hipóxia, os níveis de mRNA de HIF1A diminuíram 10 (±6,9) vezes, enquanto que os níveis de VEGFA aumentaram 1,7 (±0,4) vezes. A 5-aza-dC reverteu o resultado obtido com a hipóxia, elevando os níveis de mRNA de HIF1A 7,5 (±2,7) vezes, no entanto diminuiu, em 1,6 (±0,09) vezes, os níveis de VEGFA. Além disso, o nível proteico de HIF-1α também aumentou após 5-aza-dC, em normóxia e hipóxia. Os dados sugerem que os promotores de HIF1A e VEGFA podem estar metilados em normóxia, em um percentual ainda desconhecido. Além disso, sugere-se que, em hipóxia, haja aumento do grau de metilação, capaz de inibir a transcrição de HIF1A. No entanto, em hipóxia, a metilação do DNA parece não contribuir diretamente com a regulação de VEGFA. Portanto, esse trabalho indica que a metilação do DNA pode ser uma nova forma de regulação de HIF-1α, a nível transcricional, sobretudo em hipóxia.

Paracoccidioidomycosis (PCM) is the most important endemic deep mycosis in Latin America. Understanding of the complex interactions between the fungus and host must include the identification of gene expression patterns during infection. Carbonic anhydrase (CA) belongs to the family of zinc metalloenzymes that catalyzes the reversible hydratation of carbon dioxide to bicarbonate. Transcriptional studies have shown that carbonic anhydrase of P. brasiliensis is expressed in yeast cells recovered from liver of infected mice. In the present work, we characterized the cDNAs encoding for four carbonic anhydrases of P.brasiliensis (PbCA1, PbCA2, PbCA3, PbCA4). Recombinant PbCA1, 3 and 4 were obtained in heterologous systems with 33 kDa, 28 kDa and 32 kDa respectively. Mass spectrometry analysis confirmed the sequences of the produced proteins. The expression of PbCAs transcripts was evaluated by using real-time RT-PCR in mycelium, yeast cells and mycelium to yeast transition, in yeast cells exposed to CO2 and yeast cells recovery directly from liver and spleen. In the presence of CO2, PbCA1, PbCA2 and PbCA4 gene expression was reduced in the course of time. PbCA1 transcript expression was induced during the mycelium to yeast transition. PbCA2 and PbCA4 gene expression was higher in yeast cells, when compared to mycelium and mycelium to yeast transition. Pbca1 was induced yeast cells recovery directly from liver and spleen while the transcripts for Pbca2 and Pbca4 were repressed in all condictions. The gene expression data suggest differential roles of the CAs in the fungal physiology.

Due in most part to the rapid growth and adaptability of the Eucalyptus in Brazil, the country's forestry sector is one of the most competitive of the world. Drought is one of the main obstacles of the culture, which has been expanding to the country’s interior regions such as the Cerrado biome. The objective of this work was to identify genes and biological processes involved in the responses of the Eucalyptus roots to drought. The experiment was conducted in a completely randomized design with 2 treatments (control and deficit) x 3 root RNA gathering time (3, 6 and 12h after start of treatment) and three biological replicates (commercial clones 1528, I144, VM1). The plants grew in hydroponics for 50 days, before the experiment start by using PEG8000 to induce water deficit (osmotic potential of -0.9 MPa). The root RNA of the seedlings was extracted using the RNeasy Plant Mini® kit (Quiagen). RNA samples were sequenced on the HiSeq 2000 platform (Illumina), yielding approximately 626 million 50 bp sequences in single end mode. After quality control, the sequences were aligned in the reference genome of Eucalyptus grandis. After counting reads aligned on each gene, differential expression analyses were performed with edgeR package of R/Bioconductor. A total of 6169 differentially expressed genes (DEG) (FDR ≤ 5% and Log2 FoldChange > |2|) were identified. Of these, 3350 were up-regulated and 2819 were repressed under osmotic stress, considering all the time-series evaluations. At three hours after treatment the highest number of DEG was obtained, with 3150, followed by six hours (2494 DEG) and 12h (525 DEG). Functional enrichment analysis was performed with the Fisher exact test, by software Blast2GO, with the DEG associated with their respective Gene Ontology (GO) terms. As a total of 90 GO terms, enriched and non-redundant, was verified that our results indicate a rapid initial response of Eucalyptus roots induced by PEG 8000 in hydroponics. The most remarkable characteristics of this response under hydroponic conditions are: increased energy consumption via carbohydrate catabolism, activation of the glycolytic pathway, repression of the respiratory chain in the mitochondria, increase of the fermentation pathway, partial execution of the citric acid cycle and repression of the primary metabolism (DNA replication and RNA biosynthesis, development and growth). These enriched functional terms point to the predominance of hypoxia stress, induced by the high viscosity of PEG in hydroponics, as compared to the osmotic stress.

O oxigênio é importante não só por sua participação no metabolismo energético, mas também por sua conversão em derivados parcialmente reduzidos, as espécies reativas de oxigênio (ERO). ERO participam de funções importantes em diversas vias do metabolismo, entretanto, em concentrações desequilibradamente elevadas deflagram a peroxidação lipídica, processo deletério que forma aldeídos tóxicos, como o 4-hidroxi-2-nonenal (4-HNE). A manutenção de concentrações não deletérias das ERO é realizada por moléculas componentes do sistema antioxidante. Peixes podem ser expostos a grandes variações das concentrações de oxigênio, o que provoca ciclos oxidantes. A maioria dos estudos usa fígado e rim para avaliar estresse oxidante por meio de ensaios das atividades antioxidantes, o que requer o sacrifício dos animais. Contudo, o sangue sofre efeitos das ERO e avaliações no sangue podem permitir o estudo de antioxidantes no mesmo animal, sem a necessidade de sacrifício. Em consequência, foram nossos objetivos estabelecer uma técnica de cateterismo branquial em peixes, a padronização dos ensaios e a avaliação em sangue de componentes do sistema antioxidante de duas espécies de teleósteos em diferentes tensões de oxigênio. Pacus e tilápias foram avaliados em 6,0 mg de O2.L-1 e em hipoxia a 0,5 mg de O2.L-1 por 42 horas . Para os ensaios de hiperoxia os animais foram avaliados em 6,0 mg de O2.L-1, depois de 6 horas em 9,5 mg de O2.L-1 e depois de 30 horas de recuperação a 6,0 mg de O2.L-1. A utilização de materiais para o cateterismo de humanos permitiu a implantação de um acesso branquial. Infelizmente, houve formação de trombo após 24 horas. Mesmo assim, a observação de fluxo sanguíneo no interior da cânula e a sobrevida dos animais testados, confirmam a viabilidade da técnica. Verificamos em sangue uma maior atividade da enzima glutationa S-transferase (GST) sobre o 4-HNE em relação ao 1-cloro-2-dinitrobenzeno (CDNB). Isto reflete a importância de avaliações de atividade de enzimas, como a GST, sobre substratos endógenos. As respostas enzimáticas de tilápias mostraram-se mais sensíveis que as dos pacus quando comparadas em diferentes tensões de oxigênio.

Os peixes são vertebrados que vivem em vários habitats. Adaptações de sua fisiologia e de sua bioquímica são estudadas para entender como conseguem sobreviver aos desafios presentes em cada ambiente. A diminuição da concentração de oxigênio dissolvido na água é um fenômeno natural cíclico em águas do Pantanal e da Amazônia. A crescente poluição antrópica dos rios da Amazônia e do Pantanal pode, somada à hipoxia, oferecer ameaça à permanência de muitas espécies de peixes. Ao estudarmos a carboxilesterase (CarbE), enzima importante para a biotransformação de xenobióticos, observamos que sua atividade diminuía em plasma de pacu, um peixe típico do Pantanal, mantido em hipoxia durante 42 horas. As carboxilesterases participam de inúmeras reações químicas no organismo, incluindo uma transesterificação capaz de produzir ésteres etílicos tóxicos de ácido graxo (FAEE, fatty acid ethyl esters) a partir de etanol e ésteres de ácidos graxos. Já que a diminuição da atividade de CarbE poderia ser uma vantagem, pois que o etanol (um produto da glicólise em peixes sob hipoxia) seria menos esterificado, resolvemos saber mais sobre a bioquímica da CarbE do plasma e do fígado de pacus. Os pacus foram submetidos à hipoxia por diminuição da concentração até 0,5 mg O2/L por meio de borbulhamento de nitrogênio na água. Os animais ficaram nessas condições por 42 horas, quando então coletamos sangue e retiramos seus fígados. A atividade de CarbE ensaiada foi 50% menor no soro e 25% menor nos microssomos de fígado se comparada com a de peixes sob 6 mg O2/L. A CarbE isolada do soro dos pacus em normoxia possui massa molecular relativa de 56.000. A eletroforese em gel desnaturante com a fração purificada rendeu três bandas, mas o gel nativo apresentou só duas bandas com atividades sobre α-naftil acetato. Inferimos que mais do que uma isoforma da enzima está no plasma dos pacus. A CarbE isolada do soro não possui atividade de lipase sobre o Tween® 20, mas os microssomos dos fígados dos animais em normoxia e hipoxia possuem. No entanto, a CarbE possui atividade sobre acil-CoA assim como o microssomo de fígado. A enzima pura apresenta Vmáx três vezes maior e uma KM quatro vezes maior do que a atividade presente nos microssomos. Além disso, os microssomos do fígado dos pacus em normoxia podem hidrolisar acil-CoA com o dobro da velocidade daqueles em hipoxia. A atividade clássica de CarbE do soro foi inibida por 4-HNE a 4 mM. A atividade de acil-CoA dos microssomos de fígado também foi sensível a 4-HNE a 4 mM, enquanto 2 mM de 4-HNE inibiu metade desta atividade do soro.