Miguel A. Canela

Phytosterols: physiologic and metabolic aspects related to cholesterol-lowering properties

The aim of this review is to give a general contemporary overview of the physiologic effects of phytosterols and their role in cholesterol uptake in the intestinal tract. The mechanism of phytosterols action is based on its ability to reduce cholesterol absorption. Doses of 0.8 to 4.0 g/d of phytosterols were used to reduce low-density lipoprotein cholesterol concentrations by 10% to 15%, although most of the studies described used 2 g/d of phytosterol to achieve a reduction of 10% in low-density lipoprotein cholesterol concentrations. Although some studies point to the possibility that elevated plasma phytosterol concentrations could contribute to the development of premature coronary artery diseases, extensive safety evaluation studies have been conducted for these compounds, and they have been considered safe.

Genome size in Echinops L. and related genera (Asteraceae, Cardueae): karyological, ecological and phylogenetic implications.

Abstract Genome size was assessed by flow cytometry in 33 species belonging to seven genera of the tribe Cardueae (Asteraceae), which can be grouped in three taxonomic complexes. 2C nuclear DNA content ranged from 1.49 to 16.98 pg, which is more than elevenfold variation. Genome size correlated well with some karyological traits. Nuclear DNA amount variations also have systematic and evolutionary implications and/or are linked to adaptations to ecological conditions.

Recent updates and developments to plant genome size databases

Two plant genome size databases have been recently updated and/or extended: the Plant DNA C-values database (http://data.kew.org/cvalues), and GSAD, the Genome Size in Asteraceae database (http://www.asteraceaegenomesize.com). While the first provides information on nuclear DNA contents across land plants and some algal groups, the second is focused on one of the largest and most economically important angiosperm families, Asteraceae. Genome size data have numerous applications: they can be used in comparative studies on genome evolution, or as a tool to appraise the cost of whole-genome sequencing programs. The growing interest in genome size and increasing rate of data accumulation has necessitated the continued update of these databases. Currently, the Plant DNA C-values database (Release 6.0, Dec. 2012) contains data for 8510 species, while GSAD has 1219 species (Release 2.0, June 2013), representing increases of 17 and 51%, respectively, in the number of species with genome size data, compared with previous releases. Here we provide overviews of the most recent releases of each database, and outline new features of GSAD. The latter include (i) a tool to visually compare genome size data between species, (ii) the option to export data and (iii) a webpage containing information about flow cytometry protocols.

Over the Long-Run? Short-Run Impact and Long-Run Consequences of Stakeholder Management

The stakeholder view of the firm has been justified under instrumental and normative bases. Whereas the instrumental basis argues that “enlightened stakeholder management” is a necessary precondition to seek shareholders’ value maximization, the normative basis relies on the observance of ethical norms by managers and the notion that the stakeholders should be treated as “ends.” Some scholars argue that both views actually converge. However, this article provides empirical evidence of the negative effects of stakeholder management in shareholders’ value in the short run and the positive effects over the long run, using a longitudinal database of 658 U.S. firms. Given the difficulties of anticipating the instrumental long-term financial effects of short-run decisions affecting the different stakeholders, the authors’ findings support the view of the normative basis for stakeholder theory based on ethics, norms, and heuristic criteria as a way to solve conflicts among the claims of different stakeholders.

Comparison between categorical pollen data obtained by Hirst and Cour sampling methods

Two methods of aerobiological collection, the Burkard(Hirst-based) and the Cour, were compared using datafrom pollen collected at Bellaterra (Barcelona, Spain)between 1994 and 1996. Results for three pollen taxaof allergenic relevance (Urticaceae, Poaceae andOlea) are presented. This study confirmed thedifficulty of finding a reliable conversion formulabetween these sampling methods, as has been found byseveral other authors.An alternative statistical analysis was carried outusing categorical data, the pollen concentration databeing first converted into an ordinal scale with fivelevels based on local records. Our analysis shows thatboth methods provide essentially the sameinformation.

Accuracy and precision in the determination of stokes radii and molecular masses of proteins by gel filtration chromatography

The accuracy and precision of the estimates of hydrodynamic parameters of globular proteins obtained by inverse regression from gel filtration chromatographic data are discussed. The usefulness of gel filtration chromatography as the basis for a rapid and reliable method for the determination of the Stokes radius and the molecular mass is considered. The discussion is supported by an analysis of the models already proposed in the literature, and is based on the precision of the estimates.

Genome size variation and evolution in the family Asteraceae

The nuclear DNA content data available in “A genome size database in the Asteraceae” (GSAD: www.asteraceaegenomesize.com) have been analyzed, together with other parameters (i.e. ecological, karyological, cytogenetic), in order to establish hypotheses on the systematic, phylogenetic and evolutionary aspects of genome size in one of the largest angiosperm families. The novelty of this work is a comprehensive analysis of the whole family with the following aims: (1) to update the knowledge of genome size values in the Asteraceae; (2) to infer evolutionary trends of genome size, compared with other plant groups; and (3) to detect gaps in this field in the family and outline further research priorities. The analysis of this dataset shows that most Asteraceae genomes (57.23%) range from very small (1C ⩽ 1.4 pg) to small (1C ⩽ 3.5 pg). Gains and losses of DNA occur throughout the phylogeny of the family but although ancestral values for the basal nodes remain mostly equivocal, often small and very small ancestral genome sizes are reconstructed. Most genome size data (96.74%) are concentrated in five tribes, which broadly reflect their species richness. The relationships between genome size and other cytogenetic and ecological features have been analyzed and discussed, highlighting several general patterns. Further studies are needed to fill the gaps in genome size knowledge in the Asteraceae and more detailed research in some groups could provide information about mechanisms regulating genome expansions and contractions.

Genome size variation from a phylogenetic perspective in the genus Cheirolophus Cass. (Asteraceae): biogeographic implications

Nuclear DNA amount has been assessed in 21 populations of 19 species of the genus Cheirolophus, and phylogenetic analyses have been performed in order to find the relationships between the species of the Mediterranean Basin and those of Macaronesia. A combined analysis of nuclear ribosomal DNA ITS and ETS has been performed based on Bayesian inference, and nuclear DNA amount has been assessed by flow cytometry. The monophyly of the Macaronesian group and its relationship with Ch. sempervirens indicate a unique colonization event of Macaronesia from the continent. This single event has not been proved in the case of the Canarian archipelago. DNA amount is significantly lower in the insular species than in the continental ones, and a connection appears between the evolution of the genus Cheirolophus (colonization of islands) and the loss of DNA, probably due to the selection pressure existing on the oceanic islands.

GSAD: a genome size in the Asteraceae database.

THE Asteraceae are one of the largest families of angiosperms, comprising 24,000 to 30,000 species in over 1,600 to 2,000 genera (1 and references therein). It has a worldwide distribution, with the exception of Antarctica and includes many economically important species which are used, for example, as foods, medicines, and ornamentals. Asteraceae species are the target of many evolutionary studies and more recently they have also become the focus of new genome sequencing programs. New model species for evolutionary-developmental (evo-devo) research have been selected within the Asteraceae such as Gerbera, Helianthus, and Senecio, whereas Tragopogon is the focus of intensive studies on polyploidization mechanisms (2). The first evo-devo studies in the Asteraceae have been very promising despite complications arising from the genetic and epigenetic changes associated with polyploidy which is very frequent in the family. The term ‘‘C-value’’ was coined by Swift (3) to define the gametic nuclear DNA content (genome size) expressed in picograms. Nowadays, genome size research covers a large and diverse range of biological fields and extends across all plant groups. For example, studies have been carried out on genome size nomenclature (4), to improve methodological aspects (5) and to find possible explanations of how and why genome size changes occur in plants (6). Data on nuclear DNA amounts are interesting not only per se but are also of practical use. For instance, the success of techniques such as AFLPs and nuclear microsatellites are influenced by genome size, while the choice of a species for possible genome sequencing or evo-devo project is also determined, in part, by genome size. Interest in genome size has increased over the years and this has led to the development of several related databases (e.g., for plants 7–9). Following on from our own research studies on genome size in the Asteraceae family and given that the family is one of the most intensely studied from many aspects, we have developed a genome size database focused specifically on the Asteraceae (which we have named the ‘‘Genome size in the Asteraceae database’’, GSAD). It is hoped that this will become a significant tool for comparative research and for future genome size studies.

Aerobiological behaviour of Platanus L. pollen in Catalonia (North-East Spain)

The aim of this paper is to characterise theairborne behaviour of an allergenic andabundant pollen type, Platanus, in sevensites of the Aerobiological Network ofCatalonia (Xarxa Aerobiològica deCatalunya, XAC). In Catalonia, the mostextended Platanus species is Platanus × hybrida Brot., widely planted inforestry and as ornamental tree in streets andgardens. Naturalised specimens can also befound along river banks.The pollen records analysed are from differentperiods comprised between 1994 and 2000 inBarcelona, Bellaterra, Cambrils, Girona,Lleida, Manresa and Tarragona. All data wereobtained using seven-day volumetric spore Hirsttraps.Platanus pollination is concentrated in afew weeks, between March and April. Platanus pollen is present in all theatmospheric pollen spectra for the sitesmentioned above. In Barcelona, Platanuspollen attained the highest concentrations,with an extreme annual index (sum of the meandaily concentrations) of 25790 in 1997, and amaximum daily concentration of 2567 P/m3on 15th March 2000. The lowest annual index(647) corresponds to Cambrils, 2000, and thelowest maximum daily concentration (74P/m3) was registered on 7th April1996, in Manresa.The interannual variation of Platanuspollen values can be explained not only bymeteorological parameters and the endogenousfactors of the tree, but also by human activitysuch as elimination, pruning and watering.