Browsing by Author "Afonso, Nuno"
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- Arte Teoria nº7 (2005)Publication . Barata, Ana Martins; Marques, Ana Luísa; Guerreiro, Ana Santos; Dias, Fernando; Murteira, Helena; Souto, Maria Helena; Ferrão, Hugo; Simão, Inês Cunha; Duarte, João Miguel Couto; Martins, João Paulo; Mesquita, Marieta Dá; Baptista-Bastos, Miguel; Afonso, Nuno; Rodrigues, Paulo Simões; Janeiro, Pedro; Craveiro, Pedro; Figueiredo, Rute; Silva, Vitor
- Arte Teoria, nº2 (2001)Publication . Pereira, José Fernandes; Duarte, Eduardo; Antunes, Sandra; Capucho, Teresa d'Orey; Albuquerque, Isabel; Sardo, Delfim; Nunes, Paulo Simões; Queirós, António dos Santos; Afonso, Nuno; Pereira, Teresa; Rodrigues, Sofia Leal; Ferrão, Hugo; Costa, Carlos Couto Sequeira; Azevedo Tavares, Cristina; Calado, Margarida
- Denervation impairs regeneration of amputated Zebrafish finsPublication . Simões, Mariana G; Bensimon-Brito, Anabela; Fonseca, Mariana; Farinho, Ana; Valério, Fábio; Sousa, Sara; Afonso, Nuno; Kumar, Anoop; Jacinto, AntonioBackground: Zebrafish are able to regenerate many of its tissues and organs after damage. In amphibians this process is regulated by nerve fibres present at the site of injury, which have been proposed to release factors into the amputated limbs/fins, promoting and sustaining the proliferation of blastemal cells. Although some candidate factors have been proposed to mediate the nerve dependency of regeneration, the molecular mechanisms involved in this process remain unclear. Results: We have used zebrafish as a model system to address the role of nerve fibres in fin regeneration. We have developed a protocol for pectoral fin denervation followed by amputation and analysed the regenerative process under this experimental conditions. Upon denervation fins were able to close the wound and form a wound epidermis, but could not establish a functional apical epithelial cap, with a posterior failure of blastema formation and outgrowth, and the accumulation of several defects. The expression patterns of genes known to be key players during fin regeneration were altered upon denervation, suggesting that nerves can contribute to the regulation of the Fgf, Wnt and Shh pathways during zebrafish fin regeneration. Conclusions: Our results demonstrate that proper innervation of the zebrafish pectoral fin is essential for a successful regenerative process, and establish this organism as a useful model to understand the molecular and cellular mechanisms of nerve dependence, during vertebrate regeneration.
- Determination of baseline groundwater levels for tree conservation in urban historical botanical gardens using applied geophysicsPublication . Paz, Maria Catarina; Falcão, Ana Paula; Garcia, César Augusto; Esteves, Miguel; Afonso, Nuno; Mendes, Maria PaulaHistorical botanical gardens hold a significant place in cultural heritage. They serve as interpretive repositories of past botanical knowledge and practices, showcase plant collections cultivated over centuries, provide space for the emergence of new ecologies, offer numerous human well-being benefits, and supply vital regulating ecosystem services, which are especially important in urban areas. Nowadays, however, plants within urban historical botanical gardens can be at risk due to urban development. Therefore, it is crucial to achieve a comprehensive understanding of these spaces to help implement protective measures and support proper urban planning of the surrounding areas. This study investigates the subsurface of the Botanical Garden of Lisbon (JBL), which is subject to nearby construction works that may alter groundwater flow and depth. We employed a methodology designed for minimal on-site disturbance and high adaptability to the spatial constraints typical of these spaces. Two non-invasive applied geophysical techniques were used: ground-penetrating radar (GPR) and electrical resistivity tomography (ERT). Our main objectives were: (1) to assess groundwater levels in the construction area and establish the piezometric surface, and (2) to determine if the tree-root zones reach the saturated zone, establish a groundwater baseline, and suggest protective measures. The establishment of the piezometric surface and the delimitation of the tree-root zone, extending up to 3.0 m in depth, revealed that tree-root zones can reach groundwater levels. This finding underscores the critical need for vigilant monitoring and management of groundwater levels during excavation activities, as decreased lateral groundwater contributions from the potential excavation site can adversely affect groundwater levels in the plant beds. These findings and methodology can be applied to urban botanical gardens worldwide, as many of these gardens face similar challenges due to urbanization and environmental changes.
- Differentiated skeletal cells contribute to blastema formation during zebrafish fin regenerationPublication . Sousa, Sara; Afonso, Nuno; Bensimon-Brito, Anabela; Fonseca, Mariana; Simões, Mariana; Leon, Joaquín; Roehl, Henry; Cancela, Maria Leonor; Jacinto, AntonioThe origin of cells that generate the blastema following appendage amputation has been a long-standing question in epimorphic regeneration studies. The blastema is thought to originate from either stem (or progenitor) cells or differentiated cells of various tissues that undergo dedifferentiation. Here, we investigate the origin of cells that contribute to the regeneration of zebrafish caudal fin skeletal elements. We provide evidence that the process of lepidotrichia (bony rays) regeneration is initiated as early as 24 hours post-amputation and that differentiated scleroblasts acquire a proliferative state, detach from the lepidotrichia surface, migrate distally, integrate into the blastema and dedifferentiate. These findings provide novel insights into the origin of cells in epimorphic appendage regeneration in zebrafish and suggest conservation of regeneration mechanisms between fish and amphibians.
- Francisco de Holanda e Sophia PerennisPublication . Afonso, Nuno
- Motorways, urban growth, and suburbanisation : evidence from three decades of motorway construction in PortugalPublication . Rocha, Bruno T.; Melo, Patrícia C.; Afonso, Nuno; Silva, João de Abreu ePortugal moved from having less than 200 km of motorways before joining the European Union in 1986 to having the fifth highest motorway density relative to population in the Union in 2017. This paper studies the relationship between the expansion of the Portuguese motorway network between 1981 and 2011 and the growth of population and employment in the 275 mainland municipalities of the country. We address the endogeneity of the geography of motorways using instrumental variables based on historical transport networks from 1800 and 1945. Our findings suggest that, on average, new motorways caused large increases in both population and employment. In line with existing evidence for other countries, we find that motorways contributed to suburbanisation, as the impact of motorways on population growth (but not on employment growth) is particularly strong in suburban municipalities. In addition, motorways also appear to have influenced urban agglomeration dynamics, as their effect on population growth depends positively on the municipality’s population size in 1970.
- The heterogeneous effects of motorways on urban sprawl: causal evidence from PortugalPublication . Rocha, Bruno T.; Melo, Patrícia C.; Colaço, Rui; Silva, João de Abreu e; Afonso, NunoAs urban land increased in mainland Portugal by 55.9% between 1990 and 2012 and the country developed an extensive motorway network between the 1980s and the early 2010s, we set out to investigate the effect of motorways on urban sprawl across mainland municipalities. We document the evolution of urban sprawl for these 275 municipalities across several dimensions, including the population density of urban land, its degree of fragmentation and shape irregularity (which we combine in a summary “total interface” indicator), and the differences between the central urban unit and the remaining “peripheral” urban land. Given that the spatial distribution of motorways is likely to be endogenous, we use road itineraries from the 18th century as an instrumental variable. Our results suggest that motorways contributed to the fragmentation of urban land into numerous urban patches. Also, we identify important within-municipality heterogenous effects, in that motorways did not cause the contiguous growth of the central urban unit (typically the largest urban unit in each municipality) but, conversely, appeared to contribute in a significant manner to the development of peripheral urban land. There is also some evidence that motorways contributed to an increase in the shape irregularity of urban areas. Finally, we show that motorways caused a decrease in urban population density, but only in the relatively small group of more urbanised municipalities.
- What drives the allocation of motorways? Evidence from Portugal’s fast-expanding networkPublication . Rocha, Bruno T.; Afonso, Nuno; Melo, Patrícia C.; Silva, João de Abreu eThis study investigates the factors that influenced the allocation of motorways across municipalities in mainland Portugal over the period from 1981 to 2011. Our analysis, based on Poisson Pseudo-maximum Likelihood models, suggests that population size and market potential in 1981 are important determinants of motorway density in 2011. Likewise, physical and geographical variables also help explain the spatial distribution of motorway investment, as terrain ruggedness, distance to the coast, and distance to the border with Spain are negatively associated with motorway density. In addition, we consider the influence of the proximity to historical and pre-existing transport networks on the allocation of motorways; we find that municipalities that are closer to the 1800’s itineraries, the main roads of the 1945’s National Road Plan, and 1981’s train stations appear to have higher motorway densities in 2011, but this effect is concentrated in the vast and sparsely populated area of the country that excludes what we term the highdensity Portuguese “blue banana”. Interestingly, it is also only in this low-density region that partisan alignment between the municipal and the national levels of government appears to affect the allocation of transport investment, which suggests that motorways are more of a political asset in more remote or less urbanised areas.