Centre for Biomedical Research

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Cell–fibronectin interactions and actomyosin contractility regulate the segmentation clock and spatio-temporal somite cleft formation during chick embryo somitogenesis

Publication . Gomes De Almeida, Patrícia; Rifes, Pedro; Jesus, Ana Patrícia; Pinheiro, Gonçalo; P. Andrade, Raquel; Thorsteinsdóttir, Sólveig

Fibronectin is essential for somite formation in the vertebrate embryo. Fibronectin matrix assembly starts as cells emerge from the primitive streak and ingress in the unsegmented presomitic mesoderm (PSM). PSM cells undergo cyclic waves of segmentation clock gene expression, followed by Notch-dependent upregulation of meso1 in the rostral PSM which induces somite cleft formation. However, the relevance of the fibronectin matrix for these molecular processes remains unknown. Here, we assessed the role of the PSM fibronectin matrix in the spatio-temporal regulation of chick embryo somitogenesis by perturbing (1) extracellular fibronectin matrix assembly, (2) integrin–fibronectin binding, (3) Rho-associated protein kinase (ROCK) activity and (4) non-muscle myosin II (NM II) function. We found that integrin–fibronectin engagement and NM II activity are required for cell polarization in the nascent somite. All treatments resulted in defective somitic clefts and significantly perturbed meso1 and segmentation clock gene expression in the PSM. Importantly, inhibition of actomyosin-mediated contractility increased the period of hairy1/hes4 oscillations from 90 to 120 min. Together, our work strongly suggests that the fibronectin–integrin–ROCK–NM II axis regulates segmentation clock dynamics and dictates the spatio-temporal localization of somitic clefts.

2022-06-22Journal article

Open Access

Superparamagnetic iron oxide nanoparticles and essential oils: a new tool for biological applications

Publication . Miguel, Maria; Lourenço, João P.; Faleiro, Maria Leonor

Essential oils are complex mixtures of volatile compounds with diverse biological properties. Antimicrobial activity has been attributed to the essential oils as well as their capacity to prevent pathogenic microorganisms from forming biofilms. The search of compounds or methodologies with this capacity is of great importance due to the fact that the adherence of these pathogenic microorganisms to surfaces largely contributes to antibiotic resistance. Superparamagnetic iron oxide nanoparticles have been assayed for diverse biomedical applications due to their biocompatibility and low toxicity. Several methods have been developed in order to obtain functionalized magnetite nanoparticles with adequate size, shape, size distribution, surface, and magnetic properties for medical applications. Essential oils have been evaluated as modifiers of the surfacemagnetite nanoparticles for improving their stabilization but particularly to prevent the growth of microorganisms. This review aims to provide an overview on the current knowledge about the use of superparamagnetic iron oxide nanoparticles and essential oils on the prevention of microbial adherence and consequent biofilm formation with the goal of being applied on the surface of medical devices. Some limitations found in the studies are discussed.

2020Journal article

Open Access

Reading and reading-related skills in adults with dyslexia from different orthographic systems: a review and meta-analysis

Publication . Reis, Alexandra; Araujo, Susana; Morais, Inês Salomé; Faisca, Luis

An individual diagnosed with dyslexia in childhood typically remains dyslexic throughout his/her life. However, the cognitive profile of adults with dyslexia has been less explored than that of children. This meta-analytic study is intended to clarify three questions: (1) To what extent, and in what manner, do adults with reading difficulties (dyslexia) differ from typical adult readers in measures of reading and writing competence and related cognitive skills?; (2) To what extent do speed measures pose a greater challenge than accuracy measures in an adult population that has already had years of print exposure?; and (3) To what extent does orthographic transparency modulate the reading profile of adults with dyslexia? A total of 178 studies comparing adults with dyslexia and matched controls were reviewed. The results showed that adults with dyslexia exhibited poor performance on almost all reading and writing tasks expressed by very large effect sizes (range 1.735 <= d <= 2.034), except for reading comprehension (d = 0.729). Deficits in reading- and writing-related variables are also present but with a lower expression (range 0.591 <= d <= 1.295). These difficulties are exacerbated for speed measures, especially for word and pseudoword reading, phonological awareness and orthographic knowledge. Orthographic transparency proved to be a significant moderator of dyslexic deficits in word and pseudoword reading, reading comprehension, spelling and phonological awareness, with the expression of the deficits being weaker on transparent-as opposed to intermediate and opaque-orthographies. Overall, the meta-analysis shows that reading and writing difficulties persist in adulthood and are more pronounced in speed measures. Moreover, symptoms are more severe for reading and writing than they are for measures tapping into the cognitive processes underlying reading skills. Orthographic transparency has a significant effect on the manifestation of dyslexia, with dyslexia symptoms being less marked on transparent orthographies. In addition, phonological awareness seems to be a minor problem in adulthood, especially for transparent orthographies.

2020-10Journal article

Restricted

Extracellular electrical transducers for recording signals of cells in culture

Publication . Inácio, Pedro Miguel Cavaco Carrilho Dos Santos; Félix, Rute Castelo; Gomes, Henrique Leonel

The development of instruments and methods for basic neuroscience and cell biology studies has played a significant role in advancing our understanding about fundamental biological process. Most of this knowledge has been gathered through using invasive methods such as the patch clamp method, to study the electrical response of neuronal cells. Recent advancements in microelectronics have revolutionized these studies by enabling non-invasive extracellular electrode recordings using extracellular electrodes know as Microelectrode array (MEAS) technology. This breakthrough has sparked significant interest in the scientific community, as it opens a wider range of applications, including, fundamental studies in neurosciences, drug screening, environmental monitoring, and toxin detection. Microelectrode array (MEA) technology has evolved into a mature technology, and it is widely considered as the gold standard for electrophysiological studies. Nevertheless, MEAs have been primarily optimized to measure excitable cells. Excitable cell is a term used to refer to cells with biological mechanisms that enable them to generate action potentials (APs). Two examples of excitable cells are neurons and cardiac cells. Somatic cells, such as cancer cells, fibroblasts, secretory cells, and epithelial cells, are considered non-electrogenic cell types. Non-electrogenic cells lack the biological mechanisms to generate a response to an electrical stimulus. However, non-excitable cells have other signaling mechanisms that allow them to generate electrical fluctuations. A well-known example are chemical waves which propagate across the cell tissue. Communication process trough chemical waves requires synchronization among a population of cells. Calcium waves are examples of this signaling mechanism. Chemical waves can be detected and recorded using optical fluorescence techniques. However, the optical detection has a few major handicaps. Optical methods require the incubation using fluorescence molecules with a lifetime limited to a few hours. Furthermore, the require microscopes equipped with lasers as well as fast optical detection systems. Additionally, cells are subjected to light pulse, that may interfere with normal cell behavior. Therefore, there is a strong need for an electrical-based technique that detects voltage oscillations generated by chemical waves in real time. This thesis is positioned in this context and aims to fabricate and test devices to record extracellular signals generated by non-excitable cells. The work builds on the group's previous experience, which was crucial in developing the technique for measuring ultra-weak signals with amplitudes as small as a few micro-volts in the millihertz frequency. It is essential to emphasize that the work developed in this thesis is based on the group's previous experience, whose contribution was fundamental for the development of the technique for measuring ultra-weak signals with amplitudes of just a few micro-volts. The group has already demonstrated electrophysiological based devices with an unrivalled detection limit of 20 nanovolts. However, there are still some challenges to be addressed. A critical objective is to minimize the intrinsic noise of the devices using innovative materials, such as conductive polymers and nano−fibrous bacterial cellulose substrates. This improvement will bring the detection limit of the device to low voltages and allow access to faint signals as well as to increase the signal-to-noise ratio (SNR). Other important goal is to establish a clear relation between the electrode geometry and the properties of the native signals generated by the population of cells.

2023-11-10Doctoral thesis

Open Access