Browsing by Issue Date, starting with "2016-02"
Now showing 1 - 10 of 76
Results Per Page
Sort Options
- Equation of state of a laser-cooled gasPublication . Rodrigues, J. D.; Rodrigues, J. A.; Moreira, O. L.; Tercas, H.; Mendonca, J. T.We experimentally determine the equation of state of a laser-cooled gas. By employing the Lane-Emden formalism, widely used in astrophysics, we derive the equilibrium atomic profiles in large magneto-optical traps where the thermodynamic effects are cast in a polytropic equation of state. The effects of multiple scattering of light are included, which results in a generalized Lane-Emden equation for the atomic profiles. A detailed experimental investigation reveals an excellent agreement with the model, with a twofold significance. On one hand, we can infer the details of the equation of state of the system, from an ideal gas to a correlated phase due to an effective electrical charge for the atoms, which is accurately described by a microscopical description of the effective electrostatic interaction. On the other hand, we are able map the effects of multiple scattering onto directly controllable experimental variables, which paves the way to subsequent experimental investigations of this collective interaction.
- Pre-sedation and transport of Rhamdia quelen in water containing essential oil of Lippia alba: metabolic and physiological responsesPublication . Becker, Alexssandro G.; Parodi, Thaylise V.; Zeppenfeld, Carla C.; Salbego, Joseania; Cunha, Mauro A.; Heldwein, Clarissa G.; Loro, Vania L.; Heinzmann, Berta M.; Baldisserotto, BernardoThe effects of transporting silver catfish (Rhamdia quelen) for 6 h in plastic bags containing 0 (control), 30 or 40 A mu L/L of essential oil (EO) from Lippia alba leaves were investigated. Prior to transport, the fish in the two experimental groups were sedated with 200 A mu L/L of EO for 3 min. After transport, dissolved oxygen, carbon dioxide, alkalinity, water hardness, pH, temperature and un-ionized ammonia levels in the transport water did not differ significantly among the groups. However, total ammonia nitrogen levels and net Na+, Cl- and K+ effluxes were significantly lower in the groups transported with EO of L. alba than those in the control group. PvO(2), PvCO(2) and HCO3 (-) were higher after transporting fish in 40 A mu L/L of EO of L. alba, but there were no significant differences between groups regarding blood pH or hematocrit. Cortisol levels were significantly higher in fish transported in 30 A mu L/L of EO of L. alba compared to those of the control group. The metabolic parameters (glycogen, lactate, total amino acid, total ammonia and total protein) showed different responses after adding EO to the transport water. In conclusion, while the EO of L. alba is recommended for fish transport in the conditions tested in the present study because it was effective in reducing waterborne total ammonia levels and net ion loss, the higher hepatic oxidative stress in this species with the same EO concentrations reported by a previous study led us to conclude that the 10-20 A mu L/L concentration range of EO and lack of pre-sedation before transport are more effective.
- The transcriptional landscape of the photosynthetic model cyanobacterium synechocystis sp PCC6803Publication . Hernandez-Prieto, Miguel A.; Semeniuk, Trudi Ann; Joaquín, Giner-Lamia; Futschik, Matthias E.Cyanobacteria exhibit a great capacity to adapt to different environmental conditions through changes in gene expression. Although this plasticity has been extensively studied in the model cyanobacterium Synechocystis sp. PCC 6803, a detailed analysis of the coordinated transcriptional adaption across varying conditions is lacking. Here, we report a meta-analysis of 756 individual microarray measurements conducted in 37 independent studies-the most comprehensive study of the Synechocystis transcriptome to date. Using stringent statistical evaluation, we characterized the coordinated adaptation of Synechocystis' gene expression on systems level. Evaluation of the data revealed that the photosynthetic apparatus is subjected to greater changes in expression than other cellular components. Nevertheless, network analyses indicated a significant degree of transcriptional coordination of photosynthesis and various metabolic processes, and revealed the tight co-regulation of components of photosystems I, II and phycobilisomes. Detailed inspection of the integrated data led to the discovery a variety of regulatory patterns and novel putative photosynthetic genes. Intriguingly, global clustering analyses suggested contrasting transcriptional response of metabolic and regulatory genes stress to conditions. The integrated Synechocystis transcriptome can be accessed and interactively analyzed via the CyanoEXpress website (http://cyanoexpress.sysbiolab.eu).
- Comparison of small remotely operated vehicles and diver-operated video of circalittoral benthosPublication . Boavida, Joana; Assis, J.; Reed, John; Serrão, Ester; Gonçalves, Jorge Manuel SantosUnderwater video transect methods using small remotely operated vehicles (ROVs) and diver-operated video (DOV) are commonly used in benthic biodiversity assessments. Constraints posed by deeper waters have made surveys of the circalittoral zone (> 30 m depth), a particularly challenging problem. Here we compare benthic diversity metrics and cluster analyses obtained with ROV and DOV between 45 and 65 m depth off southwest Iberia, across local (tens to hundreds of meters) and regional scales (tens of kilometers). Results showed no difference between methods in terms of the benthic species richness, taxonomic distinctness, and beta diversity, but only minor differences in the spatial structure depicted at the regional level. At the local scale, DOV performed better at discriminating patterns likely because of the divers visual acuity. We found that small ROV and DOV are reliable and comparable methods for the study of circalittoral benthic assemblages and can be used in a complimentary way to detect the greatest amount of variation in benthic ecosystems. Our study facilitates the understanding of capabilities and limitations of two underwater video methods and provides important insight into choice of the most appropriate technique.
- MEF2C orthologues from zebrafish: evolution, expression and promoter regulationPublication . Adrião, Andreia Lúcia Gonçalves; Conceição, Natércia; Cancela, LeonorMEF2C is a crucial transcription factor for cranial neural crest cells development. An abnormal expression of this protein leads to severe abnormalities in craniofacial features. Recently, a human disease (MRD20) was described as a consequence of MEF2C haploinsufficiency. These patients show severe developmental delay, intellectual disability and dysmorphic features. Zebrafish presents two MEF2C orthologues, mef2ca and mef2cb. In this study we demonstrate a highly conserved pattern of chromosome localization for MEF2C between human and zebrafish, a similar protein sequence and tissue expression profile. We have focused our functional analysis on the zebrafish orthologue mef2cb. We identified three new exons through 5' RACE and described two new transcriptional start sites (TSS). These alternative TSS reflect the occurrence of two alternative promoters differentially regulated by nuclear factors related to craniofacial or neuronal development such as Sox9b, Sox10 and Runx2. We also predict that mef2cb gene may be post transcriptionally regulated by analysing the structure of its 5' UTR region, conserved throughout evolution. Our study provides new insights in MEF2C conservation and provides the first evidence of mef2cb regulation by both transcriptional and post transcriptional mechanisms, thus contributing to validate zebrafish as a good model for future studies concerning MEF2C dependent pathologies. (c) 2015 Elsevier Inc. All rights reserved.
- 24-hour rhythmicity of seizures in refractory focal epilepsyPublication . Nzwalo, Hipólito; Cordeiro, Inês Menezes; Santos, Ana Catarina; Peralta, Rita; Paiva, Teresa; Bentes, CarlaThe occurrence of seizures in specific types of epilepsies can follow a 24-hour nonuniform or nonrandom pattern. We described the 24-hour pattern of clinical seizures in patients with focal refractory epilepsy who underwent video-electroencephalography monitoring. Only patients who were candidates for epilepsy surgery with an unequivocal seizure focus were included in the study. A total of 544 seizures from 123 consecutive patients were analyzed. Specific time of seizures were distributed along 3- or 4-hour time blocks or bins throughout the 24-hour period. The mean age of the subjects was 37.7 years, with standard deviation of 11.5 years, median of 37. The majority were females (70/56%). The majority of patients had a seizure focus located in the mesial temporal lobe (102/83%) and in the neocortical temporal lobe (13/11%). The remaining patients had a seizure focus located in the extratemporal lobe (8/6%). The most common etiology was mesial temporal sclerosis (86/69.9%). Nonuniform seizure distribution was observed in seizures arising from the temporal lobe (mesial temporal lobe and neocortical temporal lobe), with two peaks found in both 3- and 4-hour bins: 10:00-13:00/16:00-19:00 and 08:00-12:00/16:00-20:00 respectively (p = 0.004). No specific 24-hour pattern was identified in seizures from extratemporal location. The 24-hour rhythmicity of seizure distribution is recognized in certain types of epilepsy, but studies on the topic are scarce. Their replication and validation is therefore needed. Our study confirms the bimodal pattern of temporal lobe epilepsy independently of the nature of the lesion. However, peak times differ between different studies, suggesting that the ambient, rhythmic exogenous factors or environmental/social zeitgebers, may modulate the 24-hour rhythmicity of seizures. Characterization of these 24-hour patterns of seizure occurrence can influence diagnosis and treatment in selected types of epilepsy, such as the case of temporal lobe epilepsy, the most common drug-resistant epilepsy. (C) 2015 Elsevier Inc. All rights reserved.
- The effect of mixotrophy in the ex situ culture of the soft coral Sarcophyton cf. glaucumPublication . Costa, Ana P. L.; Calado, Ricardo; Marques, Bruna; Lillebo, Ana I.; Serôdio, João; Soares, Amadeu M. V. M.; Serrão, Ester; Rocha, Rui J. M.In toto aquaculture is a promising approach towards the bioprospecting and production of bioactive compounds from the coral holobiont. Coral aquaculture ex situ allows a better control of culture conditions to maximize coral growth and reduce production costs. Light (either the Photosynthetically Active Radiation-PAR, or the emitted spectrum) is one of the most important factors affecting the growth of symbiotic corals, due to their association with photosynthetic dinoflagellates. Additionally, the balance between autotrophy and heterotrophy is also known to play a key role in the successful growth of mixotrophic corals. The present study aimed to evaluate the effect of: 1) light spectrum (white and blue light), 2) PAR intensity (50 and 120 mu mol quanta m(-2) s(-1)), and 3) heterotrophic feeding (rotifers-Brachionus plicatilis), in the physiology, photobiology and growth of coral fragments obtained from three mother colonies of the mixotrophic soft coral Sarcophyton cf. glaucum, cultured ex situ in recirculated systems during 80 days. The supply of rotifers did not affect coral growth and promoted the increase of dissolved inorganic nitrogen and phosphorous concentrations (DIN and DIP, respectively) in the water column. Coral fragments originating from the different mother colonies presented distinct responses to the tested light PAR intensities and spectra, as well as to the interaction of these factors with the supply of rotifers. We concluded that the variability displayed between different mother colonies of the same species can affect the growth response of corals under contrasting scenarios of mixotrophy. Statement of relevance: Improvement of in toto aquaculture of Sarcophyton cf. glaucum. (C) 2015 Elsevier B.V. All rights reserved.
- Taurine depresses cardiac contractility and enhances systemic heart glucose utilization in the cuttlefish, Sepia officinalisPublication . MacCormack, Tyson J.; Callaghan, N. I.; Sykes, António V.; Driedzic, W. R.Taurine is the most abundant amino acid in the blood of the cuttlefish, Sepia officinalis, where levels can exceed 200 mmol L-1. In mammals, intracellular taurine modulates cardiac Ca2+ handling and carbohydrate metabolism at much lower concentrations but it is not clear if it exerts similar actions in cephalopods. Blood Ca2+ levels are high in cephalopods and we hypothesized that taurine would depress cardiac Ca2+ flux and modulate contractility in systemic and branchial hearts of cuttlefish. Heart performance was assessed with an in situ perfused systemic heart preparation and contractility was evaluated using isometrically contracting systemic and branchial heart muscle rings. Stroke volume, cardiac output, and Ca2+ sensitivity were significantly lower in systemic hearts perfused with supplemental taurine (100 mmol L-1) than in controls. In muscle ring preparations, taurine impaired relaxation at high contraction frequencies, an effect abolished by supra-physiological Ca2+ levels. Taurine did not affect oxygen consumption in non-contracting systemic heart muscle, but extracellular glucose utilization was twice that of control preparations. Collectively, our results suggest that extracellular taurine depresses cardiac Ca2+ flux and potentiates glucose utilization in cuttlefish. Variations in taurine levels may represent an important mechanism for regulating cardiovascular function and metabolism in cephalopods.
- Production of carotenoids by microalgae: achievements and challengesPublication . Varela, J.; Pereira, Hugo; Vila, Marta; León, RosaCarotenoids are a wide group of lipophylic isoprenoids synthesized by all photosynthetic organisms and also by some non-photosynthetic bacteria and fungi. Animals, which cannot synthesize carotenoids de novo, must include them in their diet to fulfil essential provitamin, antioxidant, or colouring requirements. Carotenoids are indispensable in light harvesting and energy transfer during photosynthesis and in the protection of the photosynthetic apparatus against photooxidative damage. In this review, we outline the factors inducing carotenoid accumulation in microalgae, the knowledge acquired on the metabolic pathways responsible for their biosynthesis, and the recent achievements in the genetic engineering of this pathway. Despite the considerable progress achieved in understanding and engineering algal carotenogenesis, many aspects remain to be elucidated. The increasing number of sequenced microalgal genomes and the data generated by high-throughput technologies will enable a better understanding of carotenoid biosynthesis in microalgae. Moreover, the growing number of industrial microalgal species genetically modified will allow the production of novel strains with enhanced carotenoid contents.
- Transient up- and down-regulation of expression of myosin light chain 2 and myostatin mRNA mark the changes from stratified hyperplasia to muscle fiber hypertrophy in larvae of gilthead sea bream (Sparus aurata L.)Publication . Georgiou, Stella; Alami-Durante, Helene; Power, Deborah M.; Sarropoulou, Elena; Mamuris, Zissis; Moutou, Katerina A.Hyperplasia and hypertrophy are the two mechanisms by which muscle develops and grows. We study these two mechanisms, during the early development of white muscle in Sparus aurata, by means of histology and the expression of structural and regulatory genes. A clear stage of stratified hyperplasia was identified early in the development of gilthead sea bream but ceased by 35 dph when hypertrophy took over. Mosaic recruitment of new white fibers began as soon as 60 dph. The genes mlc2a and mlc2b were expressed at various levels during the main phases of hyperplasia and hypertrophy. The genes myog and mlc2a were significantly up-regulated during the intensive stratified formation of new fibers and their expression was significantly correlated. Expression of mstn1 and igf1 increased at 35 dph, appeared to regulate the hyperplasia-to-hypertrophy transition, and may have stimulated the expression of mlc2a, mlc2b and col1a1 at the onset of mosaic hyperplasia. The up-regulation of mstn1 at transitional phases in muscle development indicates a dual regulatory role of myostatin in fish larval muscle growth.