Browsing by Issue Date, starting with "2007-06"
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- Modelling kinetics of watercress (Nasturtium officinale) colour changes due to heat and thermosonication treatmentsPublication . Cruz, R. M. S.; Vieira, M. M. C.; Silva, C. L. M.Watercress (Nasturtium officinale) colour changes due to blanching by heat and a combined treatment of heat/ultrasound (thermosonication) were studied in thetemperature range of 82.5 to 92.5 °C. The application of thermosonication was intended to enable less severe blanching treatments and, therefore, improve the quality of the blanched product. The thermosonication blanching processes promoted changes of the green colour (an parameter) at a higher rate (P < 0.05), when compared with the heat blanching processes. No significant differences (P > 0.05) were detected between heat and thermosonication blanching processes in terms of the colour parameters Ln, bn and TCD changes.In both treatments, a fractional first order model fitted well the experimental data for Ln, an and bn (RH2 = 0.99; RTs2 = 0.99) and TCD (RH2 = 0.92; RTs2 = 0.96) colour parameters. The chlorophylls content showed no significant differences (P > 0.05) between thermally treated and thermosonicated watercress samples. The present findings will help to evaluate the effectiveness of thermosonication as a novel process to replace the classical heat treatment.
- The role of pfmdr1 in Plasmodium falciparum tolerance to artemether-lumefantrine in AfricaPublication . Sisowath, Christin; Ferreira, Pedro E.; Bustamante, Leyla Y.; Dahlstrom, Sabina; Martensson, Andreas; Bjorkman, Anders; Krishna, Sanjeev; Gil, José PedroObjective Artemether-lumefantrine (AL), presently the most favoured combination therapy against uncomplicated Plasmodium falciparum malaria in Africa, has recently shown to select for the pfmdr1 86N allele. The objective of this study was to search for the selection of other mutations potentially involved in artemether-lumefantrine tolerance and/or resistance, i.e. pfmdr1 gene amplification, pfmdr1 Y184F, S1034C, N1042D, D1246Y, pfcrt S163R and PfATP6 S769N. Methods The above mentioned SNPs were analysed by PCR-restriction fragment length polymorphism and pfmdr1 gene amplification by real-time PCR based protocols in parasites from 200 children treated with AL for uncomplicated P. falciparum malaria in Zanzibar. Results A statistically significant selection of pfmdr1 184F mostly in combination with 86N was seen in reinfections after treatment. No pfmdr1 gene amplification was found. Conclusion The results suggest that different pfmdr1 alleles are involved in the development of tolerance/resistance to lumefantrine.
- IB-DFE receivers with space diversity for CP-assisted DS-CDMA and MC-CDMA systemsPublication . Dinis, Rui; Silva, Paulo; Gusmão, AntónioMulti-Carrier Code Division Multiple Access (MC-CDMA), currently regarded as a promising multiple access scheme for broadband communications, is known to combine the advantages of an Orthogonal Frequency Division Multiplexing (OFDM)-based, Cyclic Prefix (CP)-assisted block transmission with those of CDMA systems. Recently, it was recognised that DS-CDMA (Direct Sequence) implementations can also take advantage of the benefits of the CP-assisted block transmission approach, therefore enabling an efficient use of Fast Fourier Transform (FFT)-based, chip level Frequency-Domain Equalisation (FDE) techniques. When employing a linear FDE with both MC-CDMA and DS-CDMA, the FDE coefficients can be optimised under the Minimum Mean Squared Error (MMSE) criterion, so as to avoid significant noise enhancement. The residual interference levels can be very high, especially for fully loaded scenarios, since the FDE/MMSE does not perform a perfect channel inversion. This paper deals with CP-assisted DS-CDMA systems and MC-CDMA systems with frequency-domain spreading. We consider the use of Iterative Block Decision Feedback Equalisation (IB-DFE) FDE techniques as an alternative to conventional, linear FDE techniques, and derive the appropriate IB-DFE parameters in a receiver diversity context. Our performance results show that IB-DFE techniques with moderate complexity allow significant performance gains in both systems, with bit error rate (BER) that can be close to the single-code matched filter bound (MFB) (especially for the CP-assisted DS-CDMA alternative), even with full code usage. Copyright © 2007 John Wiley & Sons. Ltd.
- Vicariance patterns in the Mediterranean Sea: East-west cleavage and low dispersal in the endemic seagrass Posidonia oceanicaPublication . ARNAUD-HAOND, Sophie; Migliaccio, M.; Diaz-Almela, E.; Teixeira, Sara; Van De Vliet, M. S.; Alberto, F.; Procaccini, G.; Duarte, C. M.; Serrão, EsterAim The seagrass, Posidonia oceanica is a clonal angiosperm endemic to the Mediterranean Sea. Previous studies have suggested that clonal growth is far greater than sexual recruitment and thus leads to low clonal diversity within meadows. However, recently developed microsatellite markers indicate that there are many different genotypes, and therefore many distinct clones present. The low resolution of markers used in the past limited our ability to estimate clonality and assess the individual level. New high-resolution dinucleotide microsatellites now allow genetically distinct individuals to be identified, enabling more reliable estimation of population genetic parameters across the Mediterranean Basin. We investigated the biogeography and dispersal of P. oceanica at various spatial scales in order to assess the influence of different evolutionary factors shaping the distribution of genetic diversity in this species. Location The Mediterranean. Methods We used seven hypervariable microsatellite markers, in addition to the five previously existing markers, to describe the spatial distribution of genetic variability in 34 meadows spread throughout the Mediterranean, on the basis of an average of 35.6 (± 6.3) ramets sampled. Results At the scale of the Mediterranean Sea as a whole, a strong east–west cleavage was detected (amova). These results are in line with those obtained using previous markers. The new results showed the presence of a putative secondary contact zone at the Siculo-Tunisian Strait, which exhibited high allelic richness and shared alleles absent from the eastern and western basins. F statistics (pairwise θ ranges between 0.09 and 0.71) revealed high genetic structure between meadows, both at a small scale (about 2 to 200 km) and at a medium scale within the eastern and western basins, independent of geographical distance. At the intrameadow scale, significant spatial autocorrelation in six out of 15 locations revealed that dispersal can be restricted to the scale of a few metres. Main conclusions A stochastic pattern of effective migration due to low population size, turnover and seed survival is the most likely explanation for this pattern of highly restricted gene flow, despite the importance of an a priori seed dispersal potential. The east–west cleavage probably represents the outline of vicariance caused by the last Pleistocene ice age and maintained to this day by low gene flow. These results emphasize the diversity of evolutionary processes shaping the genetic structure at different spatial scales.
- Decapod crustaceans associated with the snakelock anemone Anemonia sulcata. Living there or just passing by?Publication . Calado, Ricardo; Dionisio, Gisela; Dinis, Maria TeresaThe present work identifies the decapod crustaceans that associate with Anemonia sulcata on the southwestern Atlantic coast of Portugal and characterises their host use pattern. It determines whether the anemone is monopolised by any species, resulting in the exclusion of conspecifics or other decapods and, under laboratory conditions, it evaluates the degree of association between each species and A. sulcata. From all sampled anemones, 79% harboured at least I decapod crustacean, with the majority displaying either one or two specimens (32 and 24%, respectively). The most abundant species were the shrimp Periclimenes sagittifer and the crab Inochus pholangium (representing 36 and 3 1 % of collected specimens, respectively), which displayed lasting associations and were commonly recorded among the tentacles of the host. The species Eualus occultus, E. complex cranchii, Clibanarius erythropus, Maja brachydactyla, Pilummus hirtellus and Polybius (Necora) puber displayed short-term associations, were mainly present on the substratum near the base, and avoided the tentacles of A. sulcata. Periclimenes sagittifr and I. phalangium were only recorded alone or in heterosexual pairs, appearing to efficiently defend their host against conspecifics. The majority of recorded species only seem to temporarily associate with A. sulcata, in order to seek protection from predators when other shelters are unavailable.
- Functional analysis of novel genes differentially expressed genes in heart/hemangioblast precursor cells (H/HPC)Publication . Belo, José A.; Bento, Margaret C.; Tavares, Ana T.
- Cerberus is a feedback inhibitor of Nodal asymmetric signaling in the chick embryoPublication . Tavares, Ana Teresa; Andrade, Sofia; Silva, Ana Cristina; Belo, José A.The TGF-beta-related molecule Nodal plays an essential and conserved role in left-right patterning of the vertebrate embryo. Previous reports have shown that the zebrafish and mouse Cerberus-related proteins Charon and Cerberus-like-2 (Cerl-2), respectively, act in the node region to prevent the Nodal signal from crossing to the right side, whereas chick Cerberus (cCer) has an unclear function in the left-side mesoderm. In this study, we investigate the transcriptional regulation and function of cCer in left-right development. By analyzing the enhancer activity of cCer 5' genomic sequences in electroporated chick embryos, we identified a cCer left-side enhancer that contains two FoxH1 and one SMAD binding site. We show that these Nodal-responsive elements are necessary and sufficient for the activation of transcription in the left-side mesoderm. In transgenic mouse embryos, cCer regulatory sequences behave as in chick embryos, suggesting that the cis-regulatory sequences of Cerberus-related genes have diverged during vertebrate evolution. Moreover, our findings from cCer overexpression and knockdown experiments indicate that cCer is a negative-feedback regulator of Nodal asymmetric signaling. We propose that cCer and mouse Cerl-2 have evolved distinct regulatory mechanisms but retained a conserved function in left-right development, which is to restrict Nodal activity to the left side of the embryo.
- Study of Xenopus orthologs of novel genes expressed in the mouse AVEPublication . Becker, Jorg D.; Steinbeisser, Herbert; Belo, A.; Silva, Ana C.; Vitorino, Marta; Filipa, Mário; Marques, Sara
- Phylogenetic relationships of cone snails endemic to Cabo Verde based on mitochondrial genomesPublication . Abalde, Samuel; Tenorio, Manuel J.; Afonso, Carlos; Uribe, Juan E.; Echeverry, Ana M.; Zardoya, RafaelBackground: Due to their great species and ecological diversity as well as their capacity to produce hundreds of different toxins, cone snails are of interest to evolutionary biologists, pharmacologists and amateur naturalists alike. Taxonomic identification of cone snails still relies mostly on the shape, color, and banding patterns of the shell. However, these phenotypic traits are prone to homoplasy. Therefore, the consistent use of genetic data for species delimitation and phylogenetic inference in this apparently hyperdiverse group is largely wanting. Here, we reconstruct the phylogeny of the cones endemic to Cabo Verde archipelago, a well-known radiation of the group, using mitochondrial (mt) genomes. Results: The reconstructed phylogeny grouped the analyzed species into two main clades, one including Kalloconus from West Africa sister to Trovaoconus from Cabo Verde and the other with a paraphyletic Lautoconus due to the sister group relationship of Africonus from Cabo Verde and Lautoconus ventricosus from Mediterranean Sea and neighboring Atlantic Ocean to the exclusion of Lautoconus endemic to Senegal (plus Lautoconus guanche from Mauritania, Morocco, and Canary Islands). Within Trovaoconus, up to three main lineages could be distinguished. The clade of Africonus included four main lineages (named I to IV), each further subdivided into two monophyletic groups. The reconstructed phylogeny allowed inferring the evolution of the radula in the studied lineages as well as biogeographic patterns. The number of cone species endemic to Cabo Verde was revised under the light of sequence divergence data and the inferred phylogenetic relationships. Conclusions: The sequence divergence between continental members of the genus Kalloconus and island endemics ascribed to the genus Trovaoconus is low, prompting for synonymization of the latter. The genus Lautoconus is paraphyletic. Lautoconus ventricosus is the closest living sister group of genus Africonus. Diversification of Africonus was in allopatry due to the direct development nature of their larvae and mainly triggered by eustatic sea level changes during the Miocene-Pliocene. Our study confirms the diversity of cone endemic to Cabo Verde but significantly reduces the number of valid species. Applying a sequence divergence threshold, the number of valid species within the sampled Africonus is reduced to half.
- Comparative thyroid endocrinologyPublication . Richardson, S. J.; Power, Deborah; Klaren, PeterIt has been some time since comparative thyroidologists could meet in a dedicated symposium at a Conference of European Comparative Endocrinologists. Compared to peptide and steroid hormones, the biological activity of iodothyronines is determined by an increasing number of components and processes. Distributor proteins, transporters, deiodinases, conjugation and deconjugation pathways, receptors, and promoters all determine cellular and tissue specific responses to thyroid hormones. The two State-of-the-Art lectures which opened the symposium were ‘‘Novel developmental and cellular targets of thyroid hormone’’ (Barbara Demeneix) and ‘‘Thyroid hormone transporters’’ (Theo Visser). These had common themes reviewing new developments in the complexities of thyroid hormone signaling pathways.