Insights into molecular and cellular events involved in normal and pathological vertebral development and fusion using zebrafish as model organism

The vertebral column and its units, the vertebrae, are fundamental features, characteristic of all vertebrates. Developmental segregation of the vertebral bodies as articulated units is an intrinsic requirement to guarantee the proper function of the spine. Whenever these units become fused either during development or postsegmentation, movement is affected in a more or less severe manner, depending on the number of vertebrae affected. Nevertheless, fusion may occur as part of regular development and as a physiological requirement, like in the tetrapod sacrum or in fish posterior vertebrae forming the urostyle. In order to meet the main objective of this PhD project, which aimed to better understand the molecular and cellular events underlying vertebral fusion under physiological and pathological conditions, a detailed characterization of the vertebral fusion occurring in zebrafish caudal fin region was conducted. This showed that fusion in the caudal fin region comprised 5 vertebral bodies, from which, only fusion between [PU1++U1] and ural2 [U2+] was still traceable during development. This involved bone deposition around the notochord sheath while fusion within the remaining vertebral bodies occur at the level of the notochord sheath, as during the early establishment of the vertebral bodies. A comparison approach between the caudal fin vertebrae and the remaining vertebral column showed conserved features such as the presence of mineralization related proteins as Osteocalcin were identified throughout the vertebral column, independently on the mineralization patterns. This unexpected presence of Osteocalcin in notochord sheath, here identified as Oc1, suggested that this gene, opposing to Oc2, generally associated with bone formation and mature osteoblast activity, is potentially associated with early mineralization events including chordacentrum formation. Nevertheless, major differences between caudal fin region and anterior vertebral bodies considering arch histology and mineralization patterns, led us to use RA as an inductive factor for vertebral fusion, allowing a direct comparison of equivalent structures under normal and fusion events. This fusion phenotype was associated with notochord sheath ectopic mineralization instead of ectopic perichordal bone formation related with increased osteoblast activity, as suggested in previous reports. Additionally, alterations in ECM content, cell adhesion and blood coagulation were discussed as potentially related with the fusion phenotype. Finally, Matrix gla protein, upregulated upon RA treatment and shown to be associated with chordacentrum mineralization sites in regular development, was further described considering its potential function in vertebral formation and pathological fusion. Therefore with this work we propose zebrafish caudal fin vertebral fusion as a potential model to study both congenital and postsegmentation fusion and we present candidate factors and genes that may be further explored in order to clarify whether we can prevent vertebral fusion.

Dissection of the early steps in the assembly of the 20S proteasome in Saccharomyces cerevisiae

Tese de dout., Bioquímica (Biologia Celular e Molecular), Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2010

Age and growth of the bigeye thresher shark, Alopias superciliosus, from the pelagic longline fisheries in the tropical northeastern Atlantic Ocean, determined by vertebral band counts

The bigeye thresher, Alopias supercilious, is commonly caught as bycatch in pelagic longline fisheries targeting swordfish. Little information is yet available on the biology of this species, however. As part of an ongoing study, observers sent aboard fishing vessels have been collecting set of information that includes samples of vertebrae, with the aim of investigating age and growth of A. supercilious. A total of 117 specimens were sampled between September 2008 and October 2009 in the tropical northeastern Atlantic, with specimens ranging from 101 to 242 cm fork length (FL) (176 to 407 cm total length). The A. supercilious vertebrae were generally difficult to read, mainly because they were poorly calcified, which is typical of Lamniformes sharks. Preliminary trials were carried out to determine the most efficient band enhancement technique for this species, in which crystal violet section staining was found to be the best methodology. Estimated ages in this sample ranged from 2 to 22 years for females and 1 to 17 years for males. A version of the von Bertalanffy growth model (VBGF) re-parameterised to estimate L(0), and a modified VBGF using a fixed L(0) were fitted to the data. The Akaike information criterion (AIC) was used to compare these models. The VBGF produced the best results, with the following parameters: L(inf) = 293 cm FL, k = 0.06 y(-1) and L(0) = 111 cm FL for females; L(inf) = 206 cm FL, k = 0.18 y(-1) and L(0) = 93 cm FL for males. The estimated growth coefficients confirm that A. supercilious is a slow-growing species, highlighting its vulnerability to fishing pressure. It is therefore urgent to carry out more biological research to inform fishery managers more adequately and address conservation issues.

Age and growth of the smooth hammerhead shark, Sphyrna zygaena, in the Eastern Equatorial Atlantic Ocean, using vertebral sections

The smooth hammerhead shark Sphyrna zygaena (Sphyrnidae) is regularly caught as bycatch in pelagic longline fisheries, but is one of the least studied of all pelagic sharks. Recently, ICCAT (International Commission for the Conservation of Atlantic Tunas) issued recommendations underlining the need for more studies on the life history parameters of this and other pelagic shark species. To this end, the age and growth of S. zygaena were studied in the Eastern Equatorial Atlantic Ocean, in an area where growth parameters were not yet available for this species. Data from 139 specimens, caught between June and September 2009, ranging in size from 136 to 233 cm fork length (FL), were analysed. Preliminary trials were carried out to assess the most efficient growth band enhancement technique. These indicated that sectioning the vertebrae into 500 μm sections followed by staining with crystal violet produced the best results. Growth models were fitted using the traditional von Bertalanffy growth equation and a modification of this equation using a known size at birth. Growth models were compared using the Akaike information criterion (AIC). The von Bertalanffy growth equation seemed to be the most adequate model to describe growth in this species, with resulting growth parameters of L inf = 272 cm FL, k = 0.06 year for males and L inf = 285 cm FL, k = 0.07 year for females. In the first four years of life, S. zygaena grows 25 cm per year on average, but its growth slows down in later life. Future stock assessment models should incorporate these age and growth parameters for species management and conservation.

Avaliação da resposta sísmica de edifícios sitos em solos brandos estratificados

O Eurocódigo 8 exige um estudo mais aprofundado da resposta dinâmica de solos brandos classificados como tipo S1, tendo em vista o dimensionamento de edifícios. Neste trabalho apresenta-se uma metodologia visando a avaliação da segurança, ou o dimensionamento, de edifícios construídos sobre solos brandos estratificados. A metodologia proposta baseia-se nas velocidades das ondas de corte VS, obtidas de estudos geofísicos/geotécnicos, realizados in situ, tal como é proposto na parte 5 do EC8. A amplificação dinâmica das vibrações, em resultado dos contrastes das impedâncias dos diversos estratos, é obtida admitindo a propagação unidimensional das ondas sísmicas VS, na vertical, a partir do substrato rochoso. A resposta superficial é quantificada com base na análise não linear da coluna de solo sobre o substrato rochoso. A acção sísmica é caracterizada com base em vários acelerogramas “strong motion”, registados noutros países, em afloramentos rochosos, multiplicados por um factor de escala. Os factores de escala são obtidos de modo a que o espectro de resposta médio se ajuste ao espectro objectivo do EC8 (solo tipo A). A análise sísmica da estrutura do edifício é realizada com o espectro de resposta médio, que é obtido tendo em conta as funções de transferência determinadas para o terreno em estudo. Aplica-se a metodologia proposta a um caso de estudo no Algarve.

Influência de marés na distribuição vertical de larvas de peixes de recifes costeiros e escolha de substratos de assentamento no Parque Marinho Luíz Saldanha

Dissertação mest., Biologia Marinha, Universidade do Algarve, 2009

Amino acid requirements of white seabream (Diplodus sargus) larvae: effects on growth and performance

Tese dout., Aquacultura, Universidade do Algarve, 2008

Efeito de um concentrado de microalgas liofilizadas na larvicultura de dourada, Sparus aurata

Dissesrtação de Mestrado, Biologia Marinha, Especialização em Pescas e Aquacultura, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2009

Organic-walled dinoflagellate cysts in recent sediments from the Guadiana river estuary, South-East Portugal

Dissertação de Mestrado, Biologia Marinha, Faculdade de Ciências do Mar e do Ambiente, Universidade do Algarve, 2007

Estudo da variabilidade genética de marcadores moleculares ligados ao gene da MGP e sua aplicação para paternidades em Sparus aurata

Dissertação de Mestrado, Biologia Marinha, Especialização em Biotecnologia Marinha, Faculdade de Ciências do Mar e do Ambiente, Universidade do Algarve, 2008

Filogeografia de Brachidontes puniceus (Gmelin, 1791) no arquipélago de Cabo Verde

Dissertação mest., Biologia Marinha, Universidade do Algarve, 2009

Padrões temporais de fornecimento de Megalopas de Carcinus Maenas na Ria de Aveiro: influência dos ventos e das marés

Dissertação mest., Biologia marinha - Ecologia e conservação marinha, Universidade do Algarve, 2007

Does variability in temperature and chlorophyll concentration influence Wahoo and Yellowfin tuna landings in Bermuda (1990-2006)?

Dissertação de mest., Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2009

Padrões de distribuição da abundância larvar de crustáceos decápodes na baía de Cascais

Dissertação mest., Biologia marinha, Universidade do Algarve, 2009

Dinâmica da matéria particulada em suspensão na plataforma continental minhota e sua relação com a cobertura sedimentar

Tese de dout., Ciências do Mar, Faculdade de Ciências do Mar e do Ambiente, Univ. do Algarve, 2001