A mechanobiological model to study upstream cell migration guided by tensotaxis

Biomechanics and Modeling in Mechanobiology - Cell migration is a process of crucial importance for the human body. It is responsible for important processes such as wound healing and tumor...     

The Peculiar Facets of Nitric Oxide as a Cellular Messenger: From Disease-Associated Signaling to the Regulation of Brain Bioenergetics and Neurovascular Coupling

In this review, we address the regulatory and toxic role of ^·NO along several pathways, from the gut to the brain. Initially, we address the role on ^·NO in the regulation of mitochondrial respiration with emphasis on the possible contribution to Parkinson’s disease via mechanisms that involve its interaction with a major dopamine metabolite, DOPAC. In parallel with initial discoveries of the inhibition of mitochondrial respiration by ^·NO, it became clear the potential for toxic ^·NO-mediated mechanisms involving the production of more reactive species and the post-translational modification of mitochondrial proteins. Accordingly, we have proposed a novel mechanism potentially leading to dopaminergic cell death, providing evidence that NO synergistically interact with DOPAC in promoting cell death via mechanisms that involve GSH depletion. The modulatory role of NO will be then briefly discussed as a master regulator on brain energy metabolism. The energy metabolism in the brain is central to the understanding of brain function and disease. The core role of ^·NO in the regulation of brain metabolism and vascular responses is further substantiated by discussing its role as a mediator of neurovascular coupling, the increase in local microvessels blood flow in response to spatially restricted increase of neuronal activity. The many facets of NO as intracellular and intercellular messenger, conveying information associated with its spatial and temporal concentration dynamics, involve not only the discussion of its reactions and potential targets on a defined biological environment but also the regulation of its synthesis by the family of nitric oxide synthases. More recently, a novel pathway, out of control of NOS, has been the subject of a great deal of controversy, the nitrate:nitrite:NO pathway, adding new perspectives to ^·NO biology. Thus, finally, this novel pathway will be addressed in connection with nitrate consumption in the diet and the beneficial effects of protein nitration by reactive nitrogen species.

     

Evidences for genetic differentiation within the highly endemic and endangered annual fish Austrolebias nigrofasciatus (Cyprinodontiformes: Rivulidae)

Samples of Austrolebias nigrofasciatus (n = 103), an endangered species of annual fish endemic to a small area of the Patos-Mirim lagoon system encompassing the São Gonçalo Channel lowlands, were collected from eight isolated temporary ponds, four located at the known distribution range of the species and four located along the Piratini River lowlands, where morphologically different individuals were found. In the laboratory, fragments of the mitochondrial cytochrome c oxidase I (coI), cytochrome b (cytb) and nuclear rhodopsin (rho) genes were amplified, purified and sequenced for 100, 99 and 58 of these individuals, respectively. Samples were further analysed using phylogenetic and phylogeographic methods to evaluate the patterns of genetic diversity and differentiation presented within and between populations, while assessing their evolutionary history, in order to guide the application of further conservation strategies. We found that the four new populations from the Piratini River lowlands encompass a different lineage of A. nigrofasciatus that diverged from that encountered in the São Gonçalo Channel at approximately 0.165 M years before present, during a population expansion and did not yet attain reciprocal monophyly. This divergence was associated with a glacial event that was preceded by an interglacial period putatively associated with the dispersal. Moreover, significant levels of genetic differentiation and a high number of exclusive haplotypes could be encountered even in micro-geographical scales, as in the comparisons between populations located within the same major lineage, indicating each of them may encompass independent management units. Conservation actions are certainly urgent, especially in the face of signs of a recent bottleneck.     

Familial breast/ovarian cancer and BRCA1/2 genetic screening: the role of immunohistochemistry as an additional method in the selection of patients.

Only 20-25% of families screened for BRCA1/2 mutations are found positive. Because only a positive result is informative, we studied the role of BRCA1/2 immunohistochemistry as an additional method for patient selection. From 53 high-risk-affected probands, 18 (34%) had available paraffin blocks of their tumors and were selected for this study. Mutation screening was done by conformation-sensitive gel electrophoresis and multiplex ligation-dependent probe amplification. For immunohistochemistry, 21 neoplastic specimens (15 breast carcinomas, 5 ovary neoplasms, and 1 rectal adenocarcinoma) were analyzed with BRCA1 (monoclonal antibody, Ab-1, oncogene) and BRCA2 (polyclonal antibody, Ab-2, oncogene) antibodies. Absence of the BRCA1 protein was confirmed in negative tumors by Western blotting. Seven patients were positive for BRCA1/2 mutations: 5 for BRCA1 and 2 for BRCA2. Four out of five positive patients had tumors negative for BRCA1 immunostaining, and the remaining 13 BRCA1-negative patients had positive BRCA1 immunostaining in all tumor samples. Sensitivity to predict for BRCA1 mutation carriers was 80%, and specificity was 100%, with a positive predictive value of 100% and a negative predictive value of 93%. This correlation was statistically significant (p=0.001). No correlation was observed for BRCA2. If larger studies confirm these results, high-risk patients with BRCA1-negative tumors should be screened first for this gene.     

Multilocus and morphological analysis of south-eastern Iberian Wall lizards (Squamata,Podarcis)

The phylogenetic relationships among the wall lizards of the Podarcis hispanicus complex that inhabit the south-east (SE) of the Iberian Peninsula and other lineages of the complex remain unclear. In this study, four mitochondrial and two nuclear markers were used to study genetic relationships within this complex. The phylogenetic analyses based on mtDNA gene trees constructed with ML and BI, and a species tree using *BEAST support three divergent clades in this region: the Valencia, Galera and Albacete/Murcia lineages. These three lineages were also corroborated in species delimitation analyses based on mtDNA using bPTP, mPTP, GMYC, ABGD and BAPS. Bayesian inference species delimitation method (BPP) based on both nuclear data and a combined data set (mtDNA + nuclear) showed high posterior probabilities for these three SE lineages (≥0.94) and another Bayesian analysis (STACEY) based on combined data set recovered the same three groups in this region. Divergence time dating of the species tree provided an estimated divergence of the Galera lineage from the other SE group (Podarcis vaucheri, (Albacete/Murcia, Valencia)) at 12.48 Ma. During this period, the Betic–Rifian arc was isolated, which could have caused the isolation of the Galera form distributed to the south of the Betic Corridor. Although lizards from the Albacete/Murcia and Galera lineage are morphologically similar, they clearly represent distinct genetic lineages. The noteworthy separation of the Galera lineage enables us to conclude that this lineage must be considered as a new full species.     

Techniques for the detection of pathogenic Cryptococcus species in wood decay substrata and the evaluation of viability in stored samples

In this study, we evaluated several techniques for the detection of the yeast form of Cryptococcus in decaying wood and measured the viability of these fungi in environmental samples stored in the laboratory. Samples were collected from a tree known to be positive for Cryptococcus and were each inoculated on 10 Niger seed agar (NSA) plates. The conventional technique (CT) yielded a greater number of positive samples and indicated a higher fungal density [in colony forming units per gram of wood (CFU.g^-1) ] compared to the humid swab technique (ST). However, the difference in positive and false negative results between the CT-ST was not significant. The threshold of detection for the CT was 0.05.10³ CFU.g^-1, while the threshold for the ST was greater than 0.1.10³ CFU^-1. No colonies were recovered using the dry swab technique. We also determined the viability of Cryptococcus in wood samples stored for 45 days at 25ºC using the CT and ST and found that samples not only continued to yield a positive response, but also exhibited an increase in CFU.g^-1, suggesting that Cryptococcus is able to grow in stored environmental samples. The ST.1, in which samples collected with swabs were immediately plated on NSA medium, was more efficient and less laborious than either the CT or ST and required approximately 10 min to perform; however, additional studies are needed to validate this technique.     

Adipose Tissue-Derived Stem Cells Reduce Acute and Chronic Kidney Damage in Mice

Acute and chronic kidney injuries (AKI and CKI) constitute syndromes responsible for a large part of renal failures, and are today still associated with high mortality rates. Given the lack of more effective therapies, there has been intense focus on the use stem cells for organ protective and regenerative effects. Mesenchymal stem cells (MSCs) have shown great potential in the treatment of various diseases of immune character, although there is still debate on its mechanism of action. Thus, for a greater understanding of the role of MSCs, we evaluated the effect of adipose tissue-derived stem cells (AdSCs) in an experimental model of nephrotoxicity induced by folic acid (FA) in FVB mice. AdSC-treated animals displayed kidney functional improvement 24h after therapy, represented by reduced serum urea after FA. These data correlated with cell cycle regulation and immune response modulation via reduced chemokine expression and reduced neutrophil infiltrate. Long-term analyses, 4 weeks after FA, indicated that AdSC treatment reduced kidney fibrosis and chronic inflammation. These were demonstrated by reduced interstitial collagen deposition and tissue chemokine and cytokine expression. Thus, we concluded that AdSC treatment played a protective role in the framework of nephrotoxic injury via modulation of inflammation and cell cycle regulation, resulting in reduced kidney damage and functional improvement, inhibiting organ fibrosis and providing long-term immune regulation.     

Evidence from algal bioassays of seasonal nutrient limitations in two English lakes

Comparative laboratory bioassays using Asterionella formosa and Rhodomonas lacustris as test organisms were performed from March to November 1987 on filtered water samples from two English lakes, to assess their potential fertility and to identify possible limiting nutrients. The relative growth responses (log₂ increments) per week, were measured after additions of P, Fe, Si, N, and K singly and in combinations in comparison with unenriched (control) samples. Phosphate appeared to be the major limiting element for both species throughout the year, except during the spring diatom maxima when silicon usually becomes limiting. On most occasions chelated iron increased the growth increments, particularly in combination with phosphate. In general, the bioassay results showed correspondence with the nutrient concentrations in the test waters, which showed low (< 1 µg l^–1) levels of soluble reactive phosphate during all or most of the year and depleted silicon levels in late spring. Comparison between relative (incremental) ratio and absolute (cell concentration) response was made.     

Interaction of CD2 with its ligand, LFA-3, in human T cell proliferation

Recently, it has been demonstrated that lymphocyte function-associated Ag (LFA-3) is a natural ligand for CD2 and that this receptor-ligand interaction functions in cell-cell adhesion. In this report, we demonstrate that LFA-3 plays a role in T cell activation. L cells were transfected with human genomic DNA and sorted for expression of LFA-3. We demonstrate that LFA-3+ L cells, together with anti-CD3 mAb or with suboptimal doses of PHA, stimulate proliferation of human peripheral blood T cells. Furthermore, thymocyte proliferation was induced by LFA-3+ L cells and suboptimal doses of PHA. Proliferation was inhibited by mAb directed against either CD2 or LFA-3. Stimulation of thymocytes by the combination of PHA and LFA-3+ L cells resulted in the increased expression of the IL-2R, as well as of the surface Ag 4F2, transferrin receptor, and HLA-DR. These data support the conclusion that LFA-3 plays a role in CD2-dependent T cell activation. LFA-3 is widely distributed and is expressed on all APC and target cells. Thus, the ability of the CD2/LFA-3 interaction to costimulate with an anti-CD3 mAb suggests that the CD2/LFA-3 interaction may be involved not only in an Ag-independent alternate pathway of T cell activation but also in Ag-specific T cell activation.