Human Dietary Exposure to Uranium in Catalonia, Spain

The purpose of this study was to determine the daily dietary intake of uranium (U) by the general population of Catalonia, Spain. Uranium concentrations were measured in foods widely consumed by the population living in that autonomous community. Food samples were randomly acquired in 12 representative cities of Catalonia. The dietary intake of U was estimated for various age–gender groups: children, adolescents, adults, and seniors. Fish and seafood was the food group showing the highest U concentrations (0.090 μg/g of fresh weight (fw)), followed by dairy products (0.044 μg/g fw). In contrast, the lowest U levels were found in oils and fats (0.003 μg/g fw), while in tubers and milk, U was not detected in any sample. The estimated dietary intake of U for a standard male adult of 70 kg body weight living in Catalonia was 15.48 μg/day. According to the age/gender of the population, the highest dietary intake of U corresponded to children (20.32 μg/day), while senior females was the subgroup with the lowest U intake (10.04 μg/day). Based on the tolerable daily intake established for U, the current dietary intake of this metal by the general population of Catalonia should not mean health risks for any of the different age/gender groups of consumers.     

Regime shifts of Mediterranean forest carbon uptake and reduced resilience driven by multidecadal ocean surface temperatures

The mechanisms translating global circulation changes into rapid abrupt shifts in forest carbon capture in semi‐arid biomes remain poorly understood. Here, we report unprecedented multidecadal shifts in forest carbon uptake in semi‐arid Mediterranean pine forests in Spain over 1950–2012. The averaged carbon sink reduction varies between 31% and 37%, and reaches values in the range of 50% in the most affected forest stands. Regime shifts in forest carbon uptake are associated with climatic early warning signals, decreased forest regional synchrony and reduced long‐term carbon sink resilience. We identify the mechanisms linked to ocean multidecadal variability that shape regime shifts in carbon capture. First, we show that low‐frequency variations of the surface temperature of the Atlantic Ocean induce shifts in the non‐stationary effects of El Niño Southern Oscillation (ENSO) on regional forest carbon capture. Modelling evidence supports that the non‐stationary effects of ENSO can be propagated from tropical areas to semi‐arid Mediterranean biomes through atmospheric wave trains. Second, decadal changes in the Atlantic Multidecadal Oscillation (AMO) significantly alter sea–air heat exchanges, modifying in turn ocean vapour transport over land and land surface temperatures, and promoting sustained drought conditions in spring and summer that reduce forest carbon uptake. Third, we show that lagged effects of AMO on the winter North Atlantic Oscillation also contribute to the maintenance of long‐term droughts. Finally, we show that the reported strong, negative effects of ocean surface temperature (AMO) on forest carbon uptake in the last decades are unprecedented over the last 150 years. Our results provide new, unreported explanations for carbon uptake shifts in these drought‐prone forests and review the expected impacts of global warming on the profiled mechanisms.     

Native-like cyclic peptide models of a viral antigenic site: finding a balance between rigidity and flexibility

Antigenic site A of foot-and-mouth disease virus (serotype C) has been reproduced by means of cyclic versions of peptide A15, YTASARGDLAHLTTT, corresponding to residues 136-150 of envelope protein VP1. A structural basis for the design of the cyclic peptides is provided by crystallographic data from complexes between the Fab fragments of anti-site A monoclonal antibodies and A15, in which the bound peptide is folded into a quasi-cyclic pattern. Head-to-tail cyclizations of A15 do not provide peptides of superior antigenicity. Internal disulfide cyclization, however, leads to analogs which are recognized as one to two orders of magnitude better than linear A15 in both ELISA and biosensor experiments. CD and NMR studies show that the best antigen, CTASARGDLAHLTT-Ahx-C (disulfide), is very insensitive to environment-induced conformational change, suggesting that cyclization helps to stabilize a bioactive-like structure.     

Ring‐opening of azetidiniums by nucleophiles. Synthesis of polysubstituted linear amines

This microreview focuses on the nucleophilic ring‐opening of azetidiniums presenting various substitution patterns at C2, C3, and C4. In most cases, the nucleophilic ring‐opening occurred in a stereoselective and regioselective fashion producing functionalized linear amines. Experimental selectivities associated with Density Functional Theory (DFT) calculations have allowed a better understanding of the parameters governing the regioselectivities.     

Size of genetic bottlenecks leading to virus fitness loss is determined by mean initial population fitness.

Genetic bottlenecks are important events in the genetic diversification of organisms and colonization of new ecological niches. Repeated bottlenecking of RNA viruses often leads to fitness losses due to the operation of Muller's ratchet. Herein we use vesicular stomatitis virus to determine the transmission population size which leads to fitness decreases of virus populations. Remarkably, the effective size of a genetic bottleneck associated with fitness loss is greater when the fitness of the parental population increases. For example, for starting virus populations with low fitness, population transfers of five-clone-to-five-clone passages resulted in a fitness increase. However, when a parental population with high fitness was transferred, 30-clone-to-30-clone passages were required simply to maintain fitness values.     

Thermodynamic concepts in the study of microbial populations: age structure in Plasmodium falciparum infected red blood cells

Variability is a hallmark of microbial systems. On the one hand, microbes are subject to environmental heterogeneity and undergo changeable conditions in their immediate surroundings. On the other hand, microbial populations exhibit high cellular diversity. The relation between microbial diversity and variability of population dynamics is difficult to assess. This connection can be quantitatively studied from a perspective that combines in silico models and thermodynamic methods and interpretations. The infection process of Plasmodium falciparum parasitizing human red blood cells under laboratory cultivation conditions is used to illustrate the potential of Individual-based models in the context of predictive microbiology and parasitology. Experimental data from several in vitro cultures are compared to the outcome of an individual-based model and analysed from a thermodynamic perspective. This approach allows distinguishing between intrinsic and external constraints that give rise to the diversity in the infection forms, and it provides a criterion to quantitatively define transient and stationary regimes in the culture. Increasing the ability of models to discriminate between different states of microbial populations enhances their predictive capability which finally leads to a better the control over culture systems. The strategy here presented is of general application and it can substantially improve modelling of other types of microbial communities.     

Use of the MIDI-FAME technique to characterize groundwater communities

Fatty acid methyl ester (FAME) profiles were identified directly from groundwater microbial communities concentrated on and extracted with polycarbonate filters. The sensitivity of this direct extraction method was determined using pure cultures of Acinetobacter junii, Pseudomonas putida and Stenotrophomonas maltophilia. A minimum concentration of 107 cells filter-1 was required to identify the predominant fatty acids from each culture. However, at least 3.7 x 109 cells filter-1 were required to obtain fatty acid profiles that matched the signature profiles for pure cultures in a commercial database. While several saturated fatty acids (i.e. 14 : 0, 16 : 0, 18 : 0) were extracted from the polycarbonate filters, they were readily subtracted from microbial fatty acid profiles and did not interfere with the characterization of pure cultures or environmental samples. For the environmental samples, 3 l of groundwater from the Savannah River Site, Aiken, SC, (USA) contained sufficient biomass for direct extraction. A comparative analysis of FAME groundwater profiles demonstrated a qualitative difference among communities sampled from spatially discrete locations, while a groundwater well that was sampled at two time points showed strong similarities over time. Concentration of microbial biomass on polycarbonate filters coupled with the MIDI-FAME extraction of both biomass and filter was a useful technique to characterize microbial communities from groundwater.     

Laying date and clutch size of Great Tits(Parus major) in the Mediterranean region: a comparison of four habitat types

Summary Laying data and clutch size of Great Tits were studied in four different habitats in eastern Spain: two holm oak(Quercus ilex) forests, at 500 and 900–950 m a.s.l., a zeen oak(Quercus faginea) forest, at 900–1100 m a.s.l., a pine(Pinus sylvestris) forest, at 1000–1050 m a.s.l., and orange(Citrus aurantium) plantations, at 30 m a.s.l. All sites were placed at about the same latitude (39–41°N), and all were studied during the same years (1992–95). Our results show that (1) laying date did not differ between the natural habitats at the same altitude (range of the means of yearly means 4–8 May); (2) within the same habitat type (holm oak forest) laying date was earlier at low altitude (30 Aprilvs. 8 May); (3) laying date was earlier in the orange plantations (21 April) than in natural habitats; (4) among natural habitats at the same altitude, clutch size decreased from zeen oak (mean of yearly means 7.3 eggs) to holm oak (7.0 eggs) to pine forests (6.4 eggs), though only the difference between zeen oak and pine forests was significant; (5) within the same habitat type (holm oak forest), the clutch size tended to be larger at high altitude (7.0vs. 5.9 eggs); and (6) clutch size in orange plantations (7.7 eggs) did not differ significantly from that of the zeen oak forest, but was larger than in the holm oak and pine forests. We discuss the effect of the habitat type on laying date and clutch size of Great Tits.

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Legedatum und Gelegegröße der Kohlmeise(Parus major) in mediterranen Gebieten: Ein Vergleich zwischen vier verschiedenen Biotopen

Zusammenfassung Legedatum und Gelegegröße der Kohlmeise wurden in vier unterschiedlichen Biotopen in Ostspanien untersucht: zwei Steineichenwälder(Quercus ilex) in 500 m und 900–950 mNN, ein Bergeichenwald(Quercus faginea) in 900–1100 mNN, ein Kiefernwald(Pinus sylvestris) in 1000–1050 mNN und eine Orangenpflanzung(Citrus aurantium) in 30 mNN. Alle fünf Gebiete lagen auf etwa demselben Breitengrad (39–41°N) und wurden 1992–1995 parallel untersucht.(1) Auf gleicher Meereshöhe unterscheidet sich der Legebeginn nicht zwischen den verschiedenen Waldbiotopen (im Mittel 4.–8. Mai). (2) Innerhalb desselben Biotoptyps (Steineichenwald) war der Legebeginn auf niedrigerer Meereshöhe früher als in höheren Lagen (30. April vs. 8. Mai). (3) Im Orangenhain wurde früher mit der Eiablage begonnen (21. April) als in den Waldbiotopen. (4) Auf gleicher Meereshöhe nahm die Gelegegröße vom Bergeichenwald (Mittelwert 7.3 Eier) über die Steineichenwälder (7,0 Eier) zum Kiefernwald hin ab (6.4 Eier), jedoch ist nur der Unterschied zwischen Bergeichenwald und Kiefernwald signifikant. (5) Innerhalb der Steineichenwälder besteht die Tendenz zu größerer Gelegegröße in den höheren Lagen (7.0 vs. 5.9 Eier). (6) Im Orangenhain war die Gelegegröße mit durchschnittlich 7.7 Eier ähnlich der im Bergeichenwald, aber größer als in den Steineichen- und Kiefernwälder.

     

In vitro induction of a trisomic of Agave tequilana Weber var. Azul (Agavaceae) by para-fluorophenylalanine treatment

The effect of para-fluorophenylalanine (PFP) on the production of trisomic plants of Agave tequilana Weber var. Azul produced through somatic embryogenesis was investigated. Normal diploid plants with 2n = 2x = 60 were obtained in the control treatment and with 4 mg L⁻¹ PFP exposure, while use of 8 and 12 mg L⁻¹ PFP led to production of trisomics with 2n = 2x = 61. Normal diploid plants showed a bimodal karyotype with five pairs of large chromosomes and 25 pairs of small chromosomes. Trisomic plants also had a bimodal karyotype with a group of three chromosomes in position five of the chromosome set. More than 13 homologous chromosome pairs exhibited structural changes. Differences in chromosome arm ratio (long arm/short arm) were also found in eight chromosome pairs; all these aberrations in the chromosome complement of trisomic plants were probably caused by inversions, deletions, and/or duplications produced by high concentrations of PFP. The gross chromosome structural changes and the presence of a single extra chromosome could have been induced by the effect of PFP on the mitotic spindle by inducing nondisjunction of sister chromatids, resulting in hyperploids (2n + x) and hypoploids (2n − x). Flow cytometric analysis of nuclear DNA content was performed using nuclei isolated from young leaves of normal and trisomic plants. The 2C DNA content of 8.635 pg (1Cx = 4,223 Mbp of trisomic plants was different (p < 0.001) than that of normal plants (2C DNA = 8.389 pg (1Cx = 4,102 Mbp). The difference in genome size was correlated with the large structural changes in the trisomic plant genomes.     

Relationship between ultrasonic properties and structural changes in the mesophyll during leaf dehydration

The broad-band ultrasonic spectroscopy technique allows the determination of changes in the relative water content (RWC) of leaves with contrasting structural features. Specifically, the standardized frequency associated with the maximum transmittance (f/f(o)) is strongly related to the RWC. This relationship is characterized by the existence of two phases separated by an inflexion point (associated with the turgor loss point). To obtain a better understanding of the strong relationship found between RWC and f/f(o), this work has studied the structural changes experienced by Quercus muehlenbergii leaves during dehydration in terms of ultrasounds measurements, cell wall elasticity, leaf thickness, leaf density, and leaf structure. The results suggest that the decrease found in f/f(o) before the turgor loss point can be attributed to the occurrence of changes in the estimation of the macroscopic effective elastic constant of the leaf (c(33)), mainly associated with changes in the bulk modulus of elasticity of the cell wall (ε). These changes are overriding or compensating for the thickness decreases recorded during this phase. On the other hand, the high degree of cell shrinkage and stretching found in the mesophyll cells during the second phase seem to explain the changes in the acoustic properties of the leaf beyond the turgor loss point. The formation of large intercellular spaces, which increased the irregularity in the acoustic pathway, may explain the increase of the attenuation coefficient of ultrasounds once the turgor loss point threshold is exceeded. The direct measurement of c(33) from ultrasonic measurements would allow a better knowledge of the overall biomechanical properties of the leaf further than those derived from the P-V analysis.