Nitric oxide (NO) is a neurotransmitter involved in memory processes. Currently, the only recognized physiological signalling pathway controlled by NO is the activation of guanylyl cyclase. In this thesis, we propose an alternative NO-signalling pathway that involves the Heme-regulated eukaryotic initiation factor-2a kinase (HRI) and eIF2a phosphorylation. We have found that the enzyme BACE1, a key protein in Alzheimer’s disease (AD), is controlled by this novel pathway. This pathway would be involved in the physiology of memory formation and learning processes. We have also studied how an external stress factor, the Herpes Simplex Virus 1, can disrupt this cascade leading to a pathological increase in BACE1 and amyloid ß-peptide (Aß) production. Aß aggregates forming fibrils that generate free radicals. These react with NO producing peroxynitrite, which contribute to AD progression. Since NO turns toxic when produced in a pro-oxidant environment we have also studied the effect of peroxynitrite in Stroke. / L’òxid nítric (NO) és un neurotransmissor involucrat en processos de memòria. Actualment, l’única cascada de senyalització fisiològica controlada per NO consisteix en l’activació de la guanilat ciclasa. En aquesta tesi, en proposem una d’alternativa que inclou la fosforilació de eIF2a per la Heme-regulated eukaryotic initiation factor-2a kinase (HRI). Hem mostrat com l’enzim BACE1, una proteïna clau en la malaltia d’Alzheimer (AD), és controlat per aquesta nova cascada de senyalització, que podria estar involucrada en la fisiologia de l’aprenentatge i la memòria. També hem estudiat com un factor d’estrès extern, l’ Herpes Simplex Virus 1, pot pertorbar aquesta cascada donant lloc a increments patològics en BACE1 i pèptid ß-amiloide (Aß). L’Aß agrega formant fibril·les que generen radicals lliures. Aquests reaccionen químicament amb NO produint peroxinitrit, que contribueix a la progressió de l’AD. Pel fet que l’NO esdevé tòxic quan és produït en un entorn pro-oxidant, hem estudiat també l’impacte que el peroxinitrit té en l’ictus.

This work is concerned with the characterization of mesenchymal stem cells (MSC) specifically from bone marrow samples derived from patients with osteoarthritis (OA). The multilineage potential of mesenchymal stem cells as well as their ease of exvivo expansion makes these cells an attractive therapeutic tool for applications such as autologous transplantation and tissue engineering. Bone marrow is considered a source of MSC. However, there is a general assumption that the occurrence of MSCs and their activity in bone marrow diminishes with age and disease. This prompted us to isolate and identify multipotential and self-renewing cells from patients with the degenerative disease osteoarthritis, with the view of using these cells for autologous cell therapies. It is therefore of great potential benefit to investigate the isolation and characterization of stem cell/progenitors from bone marrow samples of patients with osteoarthritis in greater detail. We employed a single cell clone culture method in order to develop clonal cell populations from three bone marrow samples and characterized them based on their proliferation and differentiation capabilities. The clonal populations were grouped into fast-growing and slow-growing clones based on their proliferation rates. The fastgrowing clones displayed 20-30% greater proliferation rate than the slow-growing clones. The study also revealed that the proliferation rates were directly proportional to their differentiation capacities. Most of the fast-growing clones were found to be tripotential for osteogenic, chondrogenic and adipogenic lineages, whereas the slow growing clones were either uni or bipotential. Flow cytometry analysis for the phenotype determination using putative MSC surface markers did not reveal any difference between the two clonal populations indicating a need for further molecular studies. Two approaches were employed to further investigate the molecular processes involved in the existence of such varying populations. In the first method gene expression studies were performed between the fast-growing (n=3) and slow-growing (n=3) clonal populations to identify potential genetic markers associated with cell 'sternness' using the Stem Cell RT2 ProfilerTM PCR Array comprising a series of 84 genes related to stem cell pathways. Ten genes were identified to be commonly and significantly over represented in the fast-growing stem cell clones when compared to slow-growing clones. This included expression of transcripts beyond MSC lineage specification such as SOX2, NOTCH1 and FOXA2 which signified that stem cell maintenance requires a coordinated regulation by multiple signalling pathways. The second study involved an extensive protein expression profiling of the fast growing (n=2) and slow growing (n=2) clonal populations using off-line Two Dimensional Liquid Chromatography (2D-LC)/Matrix-Assisted Laser Desorption/Ionization (MALDI) Mass Spectrometry (MS). A total of 67 proteins were identified, of which 11 were expressed at significantly different levels between the subpopulations. Protein ontology revealed these proteins to be associated with cellular organization, cytokinesis, signal transduction, energy pathways and cell stress response. Of particular interest was the differential presentation of the proteins calmodulin, tropomyosin and caldesmon between fast- and slow-growing clones. Based on their reported roles in the regulation of cell proliferation and maintenance of cell integrity, we draw an association between their expression and the altered status in which the subpopulations exist. Based on our observations, these proteins may be prospective molecular markers to distinguish between the fast-growing and slow-growing subpopulations. In summary, this study demonstrated the existence of potential stem cells of therapeutic importance in spite of a supposedly smaller stem cell compartment in patients with osteoarthritis. Furthermore, the differentially expressed genes between the sub-populations highlight the 'sternness' of the potential clones, an observation supported by the expression of proteins which act as effective modulators in the maintenance of cell integrity and cell cycle regulation. This study provides a basis for more detailed investigations in search of selective cell surface markers

O câncer pediátrico é raro em números absolutos, porém quando comparado às incidências em adultos vem apresentando aumento nas taxas de incidência, exigindo um preparo do sistema de saúde para acompanhamento. Este acompanhamento não pode ser igual ao do adulto, visto que crianças possuem diferenças fisiológicas nas diferentes faixas etárias pediátricas. Sendo assim, estudos de utilização de medicamentos são importantes nesta população, a fim de promover o uso racional dos mesmos, bem como, garantir seu uso seguro e uma terapêutica eficaz. O presente estudo tem por objetivo avaliar as prescrições de antineoplásicos, na unidade de oncologia pediátrica de um hospital universitário de Porto Alegre, identificando os protocolos mais utilizados, e posteriormente contextualizando-os com o preconizado no referencial teórico. Foi realizado um estudo transversal prospectivo envolvendo internações realizadas na unidade de oncologia pediátrica do Hospital de Clínicas de Porto Alegre (HCPA). Foram analisadas 274 internações, das quais 40 eram primeira internação e 234 reinternações. A maioria dos pacientes tinha idade de 0 a 10 anos, uma discreta prevalência do sexo masculino, de raça/cor branca, residentes na mesorregião metropolitana. A principal forma de financiamento das internações foi o público, e a principal causa de internação foi o tratamento, sendo o mais frequente o quimioterápico. Foram analisados os protocolos utilizados durante as internações de pacientes com diagnóstico de Leucemia Linfocítica Aguda, Retinoblastoma e Sarcoma de Ewing. Os protocolos são conjunto de regras criadas a partir de grupos cooperativos ou da indústria farmacêutica, permitindo um maior conhecimento sobre os medicamentos utilizados na pediatria. A oncologia pediátrica com sua particularidade de ser uma doença culturalmente ligada ao óbito possui maior facilidade de estudos deste porte. Porém, ainda são necessários mais estudos de utilização destes medicamentos, a fim de agregar conhecimento aos protocolos de tratamento. / Pediatric cancer is rare in absolute numbers, but when compared to the incidence in adults has shown an increase in incidence rates, requiring a prepared system health for following. Pediatrics treatment can’t be the same as that of adults, because children have different physiological differences in pediatric age groups. Studies of medication use in this population are very important in order to promote the rational use of drugs, as well as to guarantee their safe use and effective therapy. The present study aims to evaluate the anticancer prescriptions in pediatric oncology unit of a university hospital in Porto Alegre, identifying the most used protocols, and contextualizing them later with the recommendations in the theoretical framework. A prospective cross-sectional study involving hospital admissions in the pediatric oncology unit of the Hospital de Clínicas de Porto Alegre (HCPA) was performed. We analyzed 274 admissions, which 40 were first admission and 234 were readmissions. These admissions most patients were aged 0 to 10 years, white race, a slight male prevalence, residing in Metropolitan Mesoregion. The financing the hospital admissions was public, and the maining cause of hospitalization was treatment, the most frequent being the chemotherapy. We analyzed the protocols used during the admissions of patients diagnosed with Acute Lymphocytic Leukemia, Retinoblastoma and Ewing's Sarcoma. Protocols are studies that allow a greater knowledge about medicines for pediatric use. The pediatric oncology with its characteristic of being a disease has culturally linked with death ease of studies of this size. However, more studies of medication use are still needed to use these drugs in order to knowledge to the treatment protocols.

O câncer pediátrico é raro em números absolutos, porém quando comparado às incidências em adultos vem apresentando aumento nas taxas de incidência, exigindo um preparo do sistema de saúde para acompanhamento. Este acompanhamento não pode ser igual ao do adulto, visto que crianças possuem diferenças fisiológicas nas diferentes faixas etárias pediátricas. Sendo assim, estudos de utilização de medicamentos são importantes nesta população, a fim de promover o uso racional dos mesmos, bem como, garantir seu uso seguro e uma terapêutica eficaz. O presente estudo tem por objetivo avaliar as prescrições de antineoplásicos, na unidade de oncologia pediátrica de um hospital universitário de Porto Alegre, identificando os protocolos mais utilizados, e posteriormente contextualizando-os com o preconizado no referencial teórico. Foi realizado um estudo transversal prospectivo envolvendo internações realizadas na unidade de oncologia pediátrica do Hospital de Clínicas de Porto Alegre (HCPA). Foram analisadas 274 internações, das quais 40 eram primeira internação e 234 reinternações. A maioria dos pacientes tinha idade de 0 a 10 anos, uma discreta prevalência do sexo masculino, de raça/cor branca, residentes na mesorregião metropolitana. A principal forma de financiamento das internações foi o público, e a principal causa de internação foi o tratamento, sendo o mais frequente o quimioterápico. Foram analisados os protocolos utilizados durante as internações de pacientes com diagnóstico de Leucemia Linfocítica Aguda, Retinoblastoma e Sarcoma de Ewing. Os protocolos são conjunto de regras criadas a partir de grupos cooperativos ou da indústria farmacêutica, permitindo um maior conhecimento sobre os medicamentos utilizados na pediatria. A oncologia pediátrica com sua particularidade de ser uma doença culturalmente ligada ao óbito possui maior facilidade de estudos deste porte. Porém, ainda são necessários mais estudos de utilização destes medicamentos, a fim de agregar conhecimento aos protocolos de tratamento. / Pediatric cancer is rare in absolute numbers, but when compared to the incidence in adults has shown an increase in incidence rates, requiring a prepared system health for following. Pediatrics treatment can’t be the same as that of adults, because children have different physiological differences in pediatric age groups. Studies of medication use in this population are very important in order to promote the rational use of drugs, as well as to guarantee their safe use and effective therapy. The present study aims to evaluate the anticancer prescriptions in pediatric oncology unit of a university hospital in Porto Alegre, identifying the most used protocols, and contextualizing them later with the recommendations in the theoretical framework. A prospective cross-sectional study involving hospital admissions in the pediatric oncology unit of the Hospital de Clínicas de Porto Alegre (HCPA) was performed. We analyzed 274 admissions, which 40 were first admission and 234 were readmissions. These admissions most patients were aged 0 to 10 years, white race, a slight male prevalence, residing in Metropolitan Mesoregion. The financing the hospital admissions was public, and the maining cause of hospitalization was treatment, the most frequent being the chemotherapy. We analyzed the protocols used during the admissions of patients diagnosed with Acute Lymphocytic Leukemia, Retinoblastoma and Ewing's Sarcoma. Protocols are studies that allow a greater knowledge about medicines for pediatric use. The pediatric oncology with its characteristic of being a disease has culturally linked with death ease of studies of this size. However, more studies of medication use are still needed to use these drugs in order to knowledge to the treatment protocols.

This thesis reports a passive method for Fermi level regulation in quantum dot assemblies through ground state transfer between QDs. Here, ZnTe/CdS, and PbSe/CdSe core/shell QDs were used as valence band electron donors, while Cu containing CdS or ZnSe acts as electron acceptor QDs. Prior to study of ground state charge transfer process, this report discusses the synthesis of ZnTe/CdS, and PbSe/CdSe core shell QDs, which are later used to study charge transfer. Since ZnTe QDs are unstable and prone to oxidation, a CdS coated ZnTe QDs were used. Growing a CdS shell on ZnTe core is difficult because high reduction potential of Te. To overcome this problem, partially reduced sulphur is used for the synthesis of ZnTe/CdS. The peculiar optical properties exhibited by ZnTe/CdS also have been discussed. Even though the synthesis of Lead chalcogenide nanoparticles has been investigated previously, certain inconsistencies between the behavior expected from known mechanisms and empirical observations. An anion exchange mechanism is proposed and demonstrated to be involved in PbSe formation. Both ZnTe and PbSe based QDs are extensively used to study hole injection and copper containing QDs were used as acceptors. The charge transfer has been studied using optical spectroscopy. The structure and composition of the assemblies was identified using powder crystallography, electron-microscopy and composition analysis. The unique physical and chemical properties of these materials are exciting both fundamentally as well as from the point of view of applications.

Esse trabalho de tese descreve a síntese e a caracterização de materiais amorfos e cristalinos na forma de pó e de filmes finos pertencentes ao sistema Er2O3-Y2O3-Al2O3-B2O3. O principal objetivo do trabalho foi o de obter filmes finos amorfos contendo íons Er3+ próximo à composição YAI3(BO3)4 (YAB), visando sua aplicação como amplificador em dispositivos ópticos integrados. Na síntese das amostras foi empregado o método dos precursores poliméricos e o método sol-gel. Uma vez estabelecida às condições de síntese das resinas e de sóis estáveis, diferentes parâmetros foram otimizados visando à deposição de filmes relativamente espessos e amorfos. As propriedades térmicas, estruturais e ópticas de amostras cristalinas ou amorfas, na forma de pó e na forma de filmes finos, foram caracterizadas através das técnicas de análise termogravimétrica, calorimetria exploratória diferencial, difração de raios X, espectroscopia vibracional na região do infravermelho com transformada de Fourier, espectroscopia Raman e microscopia eletrônica de varredura de alta resolução, microscopia de força atômica, espectroscopia \"m-line\", medidas de espectros de luminescência. Baseado na análise térmica e estrutural das amostras na forma de pó, foi possível realizar a síntese de amostras na forma de filmes finos de composição Y1-xErxAl3(BO3)4 que apresentaram características estruturais, microestruturais e ópticas adequadas à aplicação desejada. Através do estudo das propriedades térmicas e estruturais, foi observado que as amostras preparadas através do método dos precursores poliméricos e do método sol-gel apresentam respectivamente uma temperatura de transição vítrea (Tg) à 723 &#176C e à 746 &#176C e uma temperatura de cristalização (Tc) à 814 &#176C e à 830&#176C. O tratamento térmico à aproximadamente 1150 &#176C da amostra amorfa na forma de pó de composição Y0,9Er0,1Al3(BO3)4 contendo boro em excesso levou a obtenção de uma solução sólida cristalina de composição Y0,9Er0,1Al3(BO3)4. No que se refere às propriedades dos filmes finos, as melhores condições de densificação, homogeneidade, eficiência de guiamento, emissão luminescente e tempo de vida foram observadas quando os filmes de composição Y0,9Er0,1Al3(BO3)4 foram tratados entre as temperaturas de Tg e Tc. Os filmes amorfos de composição Y0,9Er0,1Al3(BO3)4 se comportam como guias monomodos, apresentando alta emissão luminescente e um tempo de vida comparável a outros sistemas amorfos a base de boro. Esse comportamento mostra a viabilidade de aplicação desses filmes amorfos como amplificadores ópticos planares. / This work specifies the synthesis and the characterization of amorphous and crystalline powder and thin films materials belonging to the Er2O3-Y2O3-Al2O3-B2O3 system. The main objective of this work was to develop amorphous thin film samples near the YAI3(BO3)4 composition with yttrium partially substituted by erbium Y1-xErxAl3(BO3)4 with the aim of applying these thin films as waveguide amplifiers in integrated optical systems. The polymeric precursor and the sol-gel methods were applied in order to produce such thin films. After the first step where the conditions to obtain very stable resins and sols was established, different parameters were adjusted aiming the deposition of thick and stable thin films. To well define the best conditions to obtain amorphous and dense thin films, the powder samples of the same compositions were first characterized by thermal analysis techniques, X-ray diffraction, IR and Raman spectroscopies, high resolution electron microscopy and atomic force microscopy. From thermal analysis and structural results, it was observed that the samples prepared from the polymeric precursor and sol-gel methods exhibit glass transition temperatures, Tg, at 723 and 746 &#176C and cristallisation temperatures, Tc, at 814 and 830 &#176C, respectively. The heat treatment at around 1150 &#176C of Y0,9Er0,1Al3(BO3)44 powder sample containing a smaller amount of boron in excess produced by both methods lead to the formation of a crystalline solid solution of the same composition without the presence of secondary phases. These results show that dense, free of cracks, thick and homogeneous thin films could be obtained when they were submitted at a heat treatment in temperatures between Tg and Tc. From the \"m-line\" spectroscopy technique and luminescence measurements we observed that the Y0,9Er0,1Al3(BO3)4 amorphous thin films can be considered as monomode waveguides showing a high luminescence intensities and a lifetime similar to other amorphous borate systems. These results show the potentiality to apply such amorphous thin films as optical planar amplifiers.

O câncer pediátrico é raro em números absolutos, porém quando comparado às incidências em adultos vem apresentando aumento nas taxas de incidência, exigindo um preparo do sistema de saúde para acompanhamento. Este acompanhamento não pode ser igual ao do adulto, visto que crianças possuem diferenças fisiológicas nas diferentes faixas etárias pediátricas. Sendo assim, estudos de utilização de medicamentos são importantes nesta população, a fim de promover o uso racional dos mesmos, bem como, garantir seu uso seguro e uma terapêutica eficaz. O presente estudo tem por objetivo avaliar as prescrições de antineoplásicos, na unidade de oncologia pediátrica de um hospital universitário de Porto Alegre, identificando os protocolos mais utilizados, e posteriormente contextualizando-os com o preconizado no referencial teórico. Foi realizado um estudo transversal prospectivo envolvendo internações realizadas na unidade de oncologia pediátrica do Hospital de Clínicas de Porto Alegre (HCPA). Foram analisadas 274 internações, das quais 40 eram primeira internação e 234 reinternações. A maioria dos pacientes tinha idade de 0 a 10 anos, uma discreta prevalência do sexo masculino, de raça/cor branca, residentes na mesorregião metropolitana. A principal forma de financiamento das internações foi o público, e a principal causa de internação foi o tratamento, sendo o mais frequente o quimioterápico. Foram analisados os protocolos utilizados durante as internações de pacientes com diagnóstico de Leucemia Linfocítica Aguda, Retinoblastoma e Sarcoma de Ewing. Os protocolos são conjunto de regras criadas a partir de grupos cooperativos ou da indústria farmacêutica, permitindo um maior conhecimento sobre os medicamentos utilizados na pediatria. A oncologia pediátrica com sua particularidade de ser uma doença culturalmente ligada ao óbito possui maior facilidade de estudos deste porte. Porém, ainda são necessários mais estudos de utilização destes medicamentos, a fim de agregar conhecimento aos protocolos de tratamento. / Pediatric cancer is rare in absolute numbers, but when compared to the incidence in adults has shown an increase in incidence rates, requiring a prepared system health for following. Pediatrics treatment can’t be the same as that of adults, because children have different physiological differences in pediatric age groups. Studies of medication use in this population are very important in order to promote the rational use of drugs, as well as to guarantee their safe use and effective therapy. The present study aims to evaluate the anticancer prescriptions in pediatric oncology unit of a university hospital in Porto Alegre, identifying the most used protocols, and contextualizing them later with the recommendations in the theoretical framework. A prospective cross-sectional study involving hospital admissions in the pediatric oncology unit of the Hospital de Clínicas de Porto Alegre (HCPA) was performed. We analyzed 274 admissions, which 40 were first admission and 234 were readmissions. These admissions most patients were aged 0 to 10 years, white race, a slight male prevalence, residing in Metropolitan Mesoregion. The financing the hospital admissions was public, and the maining cause of hospitalization was treatment, the most frequent being the chemotherapy. We analyzed the protocols used during the admissions of patients diagnosed with Acute Lymphocytic Leukemia, Retinoblastoma and Ewing's Sarcoma. Protocols are studies that allow a greater knowledge about medicines for pediatric use. The pediatric oncology with its characteristic of being a disease has culturally linked with death ease of studies of this size. However, more studies of medication use are still needed to use these drugs in order to knowledge to the treatment protocols.

Hereditary spastic paraplegia type 54 is a rare autosomal recessive neurological gait disorder characterized by paraplegia, muscle spasticity, and intellectual disability. This length-dependent distal axonopathy is caused by mutations in the DDHD2 gene, which encodes the intracellular phospholipase A1 DDHD2. Little is known about the molecular function of the DDHD2 protein, especially in the context of HSP54. Thus, there is a need to further investigate its molecular functions and investigate the impact of DDHD2 deficiency in disease-relevant cells. Here, lipidomic profiling of dermal fibroblasts derived from three unrelated patients has revealed 19 glycerophosphoethanolamine species at differential levels in patients relative to unaffected controls. However, patient cells appear to have an unaffected Golgi apparatus morphology and lipid droplet formation, despite DDHD2’s proposed roles in these processes. To study the gene function in neuronal cells, I transdifferentiated the fibroblasts into induced neuronal precursor cells and found all the patient cells arrested in the G0/G1 phase of upon conversion. Given that these cell lines are unsustainable, I generated a stable knockdown cell line in the highly proliferative HEK293A to study the molecular biology of DDHD2. The knockdown cells had a reduced growth, were delayed in the G2/M phase of the cell cycle, and became multinucleated. I then treated the cells with antineoplastic compounds paclitaxel and nocodazole and found more knockdown cells in G0/G1 than controls, suggesting the possible occurrence of mitotic slippage. Lastly, I report a novel subcellular localization for DDHD2 at the microtubule organization center.

Adult neural precursor cells (NPCs) are a heterogeneous population of mitotically active, self-renewing multipotent cells of both adult and developing CNS. They can be expanded in vitro in the presence of mitogens. The B05 transgenic SCA1 mice, expressing human ataxin-1 with an expanded polyglutamine tract in cerebellar Purkinje cells (PCs), recapitulate many pathological and behavioral characteristics of the neurodegenerative disease spinocerebellar ataxia type 1 (SCA1), including progressive ataxia and PC loss. We transplanted neural precursor cells (NPCs) derived from the subventricular zone of GFP-expressing adult mice into the cerebellar white matter of SCA1 mice when they showed absent (5 weeks), initial (13 weeks) and significant PC loss (24 weeks). A stereological count demonstrates that mice with significant cell loss exhibit highest survival of grafted NPCs and migration to the vicinity of PCs as compared to wt and younger grafted animals. These animals showed improved motor skills as compared to sham animals. Confocal analysis and profiling shows that many of implanted cells present in the cerebellar cortex have formed gap junctions with host PCs and express connexin43. Grafted cells did not adopt characteristics of PCs, but stereological and morphometric analysis of the cerebellar cortex revealed that grafted animals had more surviving PCs and a better preserved morphology of these cells than the control groups. Perforated patch clamp recordings revealed a normalization of the PC basal membrane potential, which was abnormally depolarized in sham-treated animals. No significant increase in levels of several neurotrophic factors was observed, suggesting, along with morphological observation, that the neuroprotective effect of grafted NPCs was mediated by direct contact with the host PCs. In this study, evidence for a neuroprotective effect came, in addition to motor behavior improvement, from stereological and electrophysiological analyses and suggest that timing of stem cell delivery is important to determine its therapeutic effect.<p>In a brain stem cell niche, NSCs reside in a complex cellular and extracellular microenvironment comprising their own progeny, ependymal cells, numerous blood vessels and various extracellular matrix molecules. Recently, it was reported that blood vessel ECs-NSCs crosstalk plays an important role in tissue homeostasis. Bloodstream offers a natural delivery vehicle especially in case of diffuse neurodegenerative diseases which require widespread distribution of exogenous cells. As NSCs are confronted with blood-brain barrier endothelial cells (BBB-ECs) before they can enter into brain parenchyma, we investigated their interaction using primary cultures in an in vitro BBB model. We isolated human fetal neural precursor cells (hfNPCs) from aborted fetal brain tissues and expanded in vitro. We showed that in an in vitro model, human BBB endothelium induces the rapid differentiation of hfNPCs and allows them to cross the endothelial monolayer, with the differentiated progeny remaining in close contact with endothelial cells. These results are not reproduced when using a non-BBB endothelium and are partly dependent on the cytokine MCP1. Our data suggest that, in the presence of attractive signals released by a damaged brain, intravascularly administered NPCs can move across an intact BBB endothelium and differentiate in its vicinity. Overall, our findings have implications for the development of cellular therapies for cerebellar degenerative diseases and understanding of the brain stem cell niche. / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished

Polybrominated dibenzo-p-dioxins (PBDD) and dibenzofurans (PBDF) are a group of compounds of emerging interest as potential environmental stressors. Their structures as well as toxic responses are similar to the highly characterized toxicants polychlorinated dibenzo-p-dioxins. High levels of PBDDs have been found in algae, shellfish, and fish, also from remote areas in theBaltic Sea. This thesis presents studies on PBDD behavior in fish and offspring, and natural formation of PBDDs from naturally abundant phenolic precursors. The uptake, elimination, and maternal transfer of mono- to tetraBDD/Fs were investigated in an exposure study reported in Paper I. The effects of PBDDs in fish were examined in a dose-response study (Paper II). It was shown that fish can assimilate PBDD/Fs from their feed, although non-laterally substituted congeners were rapidly eliminated. Laterally substituted congeners were retained as was congeners without vicinal hydrogens to some extent. PBDD/Fs were transferred to eggs, and congeners that were rapidly eliminated in fish showed a higher transfer ratio to eggs. Exposure to the laterally substituted 2,3,7,8-TeBDD had significant effects on the health, gene expression and several reproduction end-points of zebrafish, even at the lowest dose applied. The geographical and temporal variations of PBDD in biota samples from the Baltic Seasuggest biogenic rather than anthropogenic origin. In Paper III, bromoperoxidase-mediated coupling of 2,4,6-tribromophenol yielded several PBDD congeners, some formed after rearrangement. The overall yield was low, but significantly higher at low temperature, and the product profile obtained was similar to congener profiles found in biota from the Swedish West Coast. In Paper IV, photo­chemi­cally induced cyclization of hydroxylated polybrominated diphenyl ethers under natural conditions produced PBDDs at percentage yield. Rearranged products were not detected, and some abundant congeners do not seem to be formed this way. However, the product profile obtained was similar to congener profiles found in biota from the Baltic Proper. Since the PBDD congeners found in biota have a high turn-over in fish, the exposure must be high and continuous to yield the PBDD levels measured in wild fish. Thus, PBDDs must presumably be formed by common precursors in general processes, such as via enzymatic oxidations, UV-initiated reactions or a combination of both. The presented pathways for formation of PBDDs are both likely sensitive to changes in climatic conditions.