Browsing by Issue Date, starting with "2023-01-16"
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- From pluripotency to early events leading to cardiogenesisPublication . Silva, Leonardo Mendes e; Bragança, José; Martinho, Rui GonçaloHeart diseases are the leading cause of death worldwide, which includes acquired cardiovascular diseases and congenital heart diseases. The Cited2 gene is important for proper heart development and cardiac cell differentiation from pluripotent stem cells. Previous studies suggested that the role of Cited2 in cardiac differentiation could begin during the early events that occur in pluripotent cells that undergo differentiation. In mouse embryonic stem cells, Cited2 is important for self-renewal maintenance, as cells die or differentiate under Cited2-depleted conditions. In differentiation, embryonic stem cells depleted of Cited2 at the onset of differentiation show an impairment of cardiac cell differentiation. However, the mechanisms behind these observed phenotypes of Cited2-depletion are not well established. In this work, differentially expressed genes were identified in undifferentiated mouse embryonic stem cells and differentiated cells on day-4 of differentiation. Thus, using mouse embryonic stem cells that can be conditionally depleted of Cited2, after 16 hours of incubation it was observed that Cited2-depleted cells under undifferentiation conditions tend to show increased levels of the DNA damage marker γH2AX, concomitant with decreased expression of DNA repair genes (Rad51c, Rad9b, and Mdc1) and increased expression of pro-apoptotic genes (p21, Ptges, Plk2). In differentiation conditions using the hanging drop method, on day-4 of differentiation, epigenetic mark H3K27ac showed a decrease in the promoter region of cardiopoietic genes concordant with their downregulation (Brachyury, Cdx2, Dkk1, Isl1, Kdr, Mesp1, Wnt5a). However, the results of the H3K27me3 marks, showed higher variability and did not match the reciprocal marks of H3K27ac. Moreover, the increase in H3K27ac mark in undifferentiated Cited2-depleted cells corresponded, as expected, to an upregulation of the same genes. Lastly, histone acetyltransferase activity assay using the whole cell extract showed a tendency to increase acetylation in Cited2-depleted cells. In conclusion, the role of Cited2 in DNA repair and the cause of increased cell death remains to be established, while delayed expression of mesoderm/cardiac genes could be associated with misregulation of epigenetic H3K27(me3/ac) marks at the promoters of cardiopoietic genes.
- Duration, but not bottle volume, affects Phytoplankton Community Structure and growth rates in microcosm experimentsPublication . B. Domingues, Rita; Mosley, Benjamin A.; Nogueira, Patricia; Maia, Inês Beatriz; B. Barbosa, AnaIt is generally assumed that the larger the bottle volume, the longer the duration of phytoplankton microcosm experiments. We hypothesize that volume and duration are independent, as volume does not regulate the extension of the exponential growth phase. We conducted two microcosm experiments using 1, 2, and 8 L bottles, inoculated with phytoplankton collected in the Ria Formosa lagoon (SE Portugal) and incubated for 1, 2, 4, and 8 days. Phytoplankton net growth rates were estimated using chlorophyll a concentration and cell abundance, determined with epifluorescence and inverted microscopy. Results show that the experimental duration significantly affected net growth rates, independently of volume, with decreasing net growth rates with time. Regarding volume, we found significant, but weak, differences in net growth rates, and significant two-way interactions only for the larger-sized cells. No significant differences in net growth rates across the different volumes were detected for the smaller, most abundant taxa and for the whole assemblage. We conclude that duration, not volume, is the main factor to consider in microcosm experiments, and it should allow the measurement of responses during the exponential growth phase, which can be detected through daily sampling throughout the duration of the experiment.
- Mecanismos multiplicadores dos comportamentos de verificação: um estudo prospetivo em contexto natural, numa amostra da comunidadePublication . Micaelo, Ana Laura Aleixo; Jiménez-Ros, Antonia MaríaAs compulsões de verificação consistem na necessidade excessiva de verificar repetidamente se um comportamento foi realizado corretamente. Já os comportamentos de verificação são considerados comportamentos adaptativos, uma vez que surgem para prevenir problemas futuros e não causam ansiedade excessiva nem uma necessidade incontrolável de verificar. O presente estudo pretende analisar as variáveis implícitas aos comportamentos de verificação, bem como as variáveis que podem conduzir à sua finalização em indivíduos pertencentes a uma população não-clínica, dando um especial foco à responsabilidade percebida. Participaram nesta investigação 118 indivíduos da população não-clínica, maioritariamente mulheres. Num primeiro momento e após o preenchimento do consentimento informado, os participantes responderam a um questionário sociodemográfico, e a três instrumentos para avaliar as obsessões e compulsões, as crenças obsessivas, o evitamento do dano e os sentimentos de incompletude. Num segundo momento, os participantes responderam a um instrumento para avaliar os comportamentos de verificação, o qual foi preenchido sempre que os participantes se envolveram em episódios de verificação durante a semana seguinte.