Susana Galante-Oliveira

The evolutionary history of the stearoyl-CoA desaturase gene family in vertebrates

BackgroundStearoyl-CoA desaturases (SCDs) are key enzymes involved in de novo monounsaturated fatty acid synthesis. They catalyze the desaturation of saturated fatty acyl-CoA substrates at the delta-9 position, generating essential components of phospholipids, triglycerides, cholesterol esters and wax esters. Despite being crucial for interpreting SCDs roles across species, the evolutionary history of the SCD gene family in vertebrates has yet to be elucidated, in particular their isoform diversity, origin and function. This work aims to contribute to this fundamental effort.ResultsWe show here, through comparative genomics and phylogenetics that the SCD gene family underwent an unexpectedly complex history of duplication and loss events. Paralogy analysis hints that SCD1 and SCD5 genes emerged as part of the whole genome duplications (2R) that occurred at the stem of the vertebrate lineage. The SCD1 gene family expanded in rodents with the parallel loss of SCD5 in the Muridae family. The SCD1 gene expansion is also observed in the Lagomorpha although without the SCD5 loss. In the amphibian Xenopus tropicalis we find a single SCD1 gene but not SCD5, though this could be due to genome incompleteness. In the analysed teleost species no SCD5 is found, while the surrounding SCD5-less locus is conserved in comparison to tetrapods. In addition, the teleost SCD1 gene repertoire expanded to two copies as a result of the teleost specific genome duplication (3R). Finally, we describe clear orthologues of SCD1 and SCD5 in the chondrichthian, Scyliorhinus canicula, a representative of the oldest extant jawed vertebrate clade. Expression analysis in S. canicula shows that whilst SCD1 is ubiquitous, SCD5 is mainly expressed in the brain, a pattern which might indicate an evolutionary conserved function.ConclusionWe conclude that the SCD1 and SCD5 genes emerged as part of the 2R genome duplications. We propose that the evolutionary conserved gene expression between distinct lineages underpins the importance of SCD activity in the brain (and probably the pancreas), in a yet to be defined role. We argue that an expression independent of an external stimulus, such as diet induced activity, emerged as a novel function in vertebrate ancestry allocated to the SCD5 isoform in various tissues (e.g. brain and pancreas), and it was selectively maintained throughout vertebrate evolution.

Imposex levels and tributyltin pollution in Ria de Aveiro (NW Portugal) between 1997 and 2007: evaluation of legislation effectiveness

Nucella lapillus imposex levels and organotin (OT) concentrations in water and female tissues were measured in samples collected from the Ria de Aveiro (NW Portugal) between 1997 and 2007. Vas deferens sequence index (VDSI), relative penis size index (RPSI), mean female penis length (FPL) and percentage of imposex affected females (%I) were used to determine imposex levels at each site. A significant temporal decline in imposex intensity was observed during the assessed period. Imposex decrease was evident after 2003 although improvements were most notable from 2005 to 2007, probably due to the implementation of the EU Council Regulation no.782/2003 forbidding further application of tributyltin (TBT) antifouling on vessels carrying EU flags. Despite these improvements, OT analysis in N. lapillus female tissues and water indicate there are still recent TBT inputs into the study area.

Effects of the PPARα agonist WY-14,643 on plasma lipids, enzymatic activities and mRNA expression of lipid metabolism genes in a marine flatfish, Scophthalmus maximus.

Fibrates and other lipid regulator drugs are widespread in the aquatic environment including estuaries and coastal zones, but little is known on their chronic effects on non-target organisms as marine fish. In the present study, turbot juveniles were exposed to the PPARα model agonist WY-14,643 for 21 days by repeated injections at the concentrations of 5mg/kg (lo-WY) and 50mg/kg (hi-WY), and samples taken after 7 and 21 days. Enzyme activity and mRNA expression of palmitoyl-CoA oxidase and catalase in the liver were analyzed as first response, which validated the experiment by demonstrating interactions with the peroxisomal fatty acid oxidation and oxidative stress pathways in the hi-WY treatment. In order to get mechanistic insights, alterations of plasma lipids (free cholesterol, FC; HDL associated cholesterol, C-HDL; triglycerides, TG; non-esterified fatty acids, NEFA) and hepatic mRNA expression of 17 genes involved in fatty acid and lipid metabolism were studied. The exposure to hi-WY reduced the quantity of plasma FC, C-HDL, and NEFA. Microsomal triglyceride transfer protein and apolipoprotein E mRNA expression were higher in hi-WY, and indicated an increased formation of VLDL particles and energy mobilization from liver. It is speculated that energy depletion by PPARα agonists may contribute to a higher susceptibility to environmental stressors.

Triphenyltin induces imposex in Nucella lapillus through an aphallic route

Triphenyltin (TPT) was used until recently as a biocide in antifouling systems and nowadays is still applied as an agriculture pesticide in some countries. This compound is known to cause imposex (the imposition of male characters in females of gastropod molluscs) in a very limited number of species, when compared with tributyltin (TBT), the universally recognized imposex-causing agent. In this study, we tested if TPT could induce imposex in females of the dog-whelk Nucella lapillus. Experimental groups of 40 females were injected with a volume of 2μL/g of soft tissue wet weight (ww) of one of the following treatments, using DMSO as a solvent carrier: DMSO (solvent control); 1μg/g ww of TBT (positive control); 0.2, 1 and 5μg/g ww of TPT and a non-injected group (negative control). Concentrations were confirmed in the organism tissues by means of chemical analyses of a pool of 10 specimens at T0 and then after the imposex analysis at T56days. After 8-week trial, results pointed out statistically significant differences between treatments, with both TPT and TBT positively inducing imposex. However, imposex development in TPT-injected females differed from that of TBT, since females that developed imposex presented an aphallic condition (no penis development) while the TBT-treated females developed standard imposex (with penis formation). These results suggest that TPT and TBT act differently in the sequential process of female masculinization, casting new insights about the hypothetical pathways underlying imposex development.

The Gastropod Statolith Elemental Composition by EMPA

Concentrations of Ca, O, Na, Sr and S varied between 3.7x10 5 -4.2x10 5 , 1.5x10 5 -1.7x10 5 , 2.5x10 3 -6.1x10 3 , 1.3x10 3 -8.9x10 3 and 4.7x10 2 -1.3x10 3 ppm, respectively; Mg, which was not always detected, ranged from 2.0x10 2 -8.6x10 2 ppm. No significant differences in these elements mean concentrations were found between increments, except Na in one statolith between increments 1 and 5 (higher at the edge; Dunn’s test s=2.014, p<0.05). Thus the general elemental composition is nearly constant throughout lifespan (i.e. along statoliths radiuses). Regarding trace elements: Sn was never detected; Al and Hg were at 22.2% of the punctual analyses conducted while Cu was at 66.7% and Ba at 88.9%. Concentrations of Al, Hg, Cu and Ba varied between 55-71, 176-180, 183-302 and 647-969 ppm, respectively. EMPA proved to be a useful technique in sclerochronology, allowing the characterization of the overall composition of gastropods statoliths and the quantification of elements in specific locations with high resolution. References

TBT pollution - Historical evolution and future perspectives

S (Ag) and zinc oxide (ZnO) nanoparticles were simultaneously deposited on a glass substrate using the radio frequency (RF) sputtering technique at different substrate temperatures. Detailed characterization of the co-sputtered Ag/ZnO thin films were performed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS). The synthesized thin films were tested with UV-Vis diffuse reflectance spectroscopy to evaluate their optical properties. The obtained SEM results show a uniform dispersion of Ag nanoparticles within the ZnO matrix. These nanoparticles have average particle size of 20 nm. The optical band gap value had been calculated from UV transmission spectra of Ag/ZnO thin films deposited at various substrate temperatures. This value was observed to be in the visible light range (i.e. 2.7-3.1 eV), which is much smaller than that of pure ZnO (3.37eV). The photocatalytic activity of the produced thin films was evaluated through visible light photo degradation of 2-chlorophenol (2-CP) which, has been used as a pollutant model in water. The synthesized thin films showed enhanced visible light photocatalytic efficiency towards 2-CP degradation at elevated substrate temperature and retained its catalytic efficiency with only 8% loss in efficiency after four reuse cycles. Kinetic parameters involved in the degradation process were investigated by applying pseudo-second-order kinetic model.T study exposes the extent of contaminations and natural disturbance in soil and tobacco (Nicotiana tabacum) crops with potential health and ecological impacts caused by metals contaminated industrial waste water to surrounding environment. By exploring the extent of metals contamination the study find out the role of geochemical, geostatistical and geospatial inter and intra elemental relationship in soil and tobacco crops. By exploring the relation between and soil and Tobacco crops, a total of 51 samples were collected, pass through acid digestion and analyzed for thirteen major and toxic metals through atomic absorption spectroscopy (AAS 700). Geochemical results showed that the concentration of major and toxic elements in target area was exotically higher than the background areas (control area) with possible percentile (%) variations of 65.7, 27.5, 72.8, 7.5, 56.7, 54.26 23.95, 31.56, 39.3, 22.04, 48.92, 34.11 and 42.6 for Chromium, Cadmium, lead, Nickle, Copper, Zinc, Cobalt, Iron, Manganese, Magnesium, Sodium, Calcium and Potassium respectively. Meanwhile transfer ratio from soil to tobacco crops are 1.64, 5.99, 3.39, 7.59, 7.40, 6.01, 9.29, 1.12, 13.72, 16.37, 1.7, 7.72 and 36.56 (%) respectively. By integrating geochemical and geospatial analysis hereby provide a mobility evidence of metals in the environment. Geostatistical techniques provide scientific evidence and magnitude of toxic and major elements in soils and tobacco crops. All the geostatistical techniques are coherent with each other and can +90 % reliable, except enrichment factor, which were not compatible with these methods. However geospatial analysis proved the mobility of metals in environment. Thus geochemical, geostatistical and geospatial analysis show that industrial discharge are responsible for hyper accumulation of major and toxic elements in soils and tobacco crops and their mobility causes severe ecological and health problems. The study recommends the prohibition of tobacco cultivation and processing. It calls for regular supervision of industrial contamination and its instant remediation through national and international agencies thereby reducing soil contaminations through economic feasibility and in a reasonable time frame.V organic compounds (VOCs) have a variety of negative impacts on human health, some (e.g. benzene and formaldehyde) are known to be human carcinogen. There is, therefore, often a pressing requirement to monitor these compounds. However, monitoring them is not straightforward as their concentrations vary with environmental parameters such temperature, barometric pressure, and groundwater movement. Because of this, the sampling frequency that is used at present is ineffective for determining their representative concentration, therefore, a device which can be left in-situ to collect high temporal resolution data has been developed. VOCs are measured by PID; however, PID measures aggregate VOC concentration. Because VOCs have differing toxicities and behaviours, individual identification is required; therefore, a sample must be collected. In order to do this, a sorbent material must be used to transfer the sample to the GC-MS for identification. The sorbent material must be appropriate for the range of VOCs and of sufficient capacity for extended exposure. The objectives of the work are therefore to: (i) select an appropriate sorbent for incorporation into a dual measurement VOC monitoring device, then to use the instrument to (ii) derive an optimum monitoring methodology.