On our obligation to select the best children: a reply to Savulescu

The purpose of this paper is to examine critically Julian Savulescu's claim that people should select, of the possible children they could have, the one who is expected to have the best life, or at least as good a life as the others, based on the relevant, available genetic information, including information about non-disease genes. I argue here that in defending this moral obligation, Savulescu has neglected several important issues such as access to selection technologies, disproportionate burdens on women, difficulties in determining what is best, problems with aggregate effects of individual choices, and questions about social justice. Taking these matters into account would call such a moral requirement into serious question.     

Examining variation in the leaf mass per area of dominant species across two contrasting tropical gradients in light of community assembly

Understanding variation in key functional traits across gradients in high diversity systems and the ecology of community changes along gradients in these systems is crucial in light of conservation and climate change. We examined inter‐ and intraspecific variation in leaf mass per area (LMA) of sun and shade leaves along a 3330‐m elevation gradient in Peru, and in sun leaves across a forest–savanna vegetation gradient in Brazil. We also compared LMA variance ratios (T‐statistics metrics) to null models to explore internal (i.e., abiotic) and environmental filtering on community structure along the gradients. Community‐weighted LMA increased with decreasing forest cover in Brazil, likely due to increased light availability and water stress, and increased with elevation in Peru, consistent with the leaf economic spectrum strategy expected in colder, less productive environments. A very high species turnover was observed along both environmental gradients, and consequently, the first source of variation in LMA was species turnover. Variation in LMA at the genus or family levels was greater in Peru than in Brazil. Using dominant trees to examine possible filters on community assembly, we found that in Brazil, internal filtering was strongest in the forest, while environmental filtering was observed in the dry savanna. In Peru, internal filtering was observed along 80% of the gradient, perhaps due to variation in taxa or interspecific competition. Environmental filtering was observed at cloud zone edges and in lowlands, possibly due to water and nutrient availability, respectively. These results related to variation in LMA indicate that biodiversity in species rich tropical assemblages may be structured by differential niche‐based processes. In the future, specific mechanisms generating these patterns of variation in leaf functional traits across tropical environmental gradients should be explored.     

Tetrathiafulvalene‐[2.2]paracyclophanes: Synthesis,crystal structures,and chiroptical properties

Two racemic tetrathiafulvalene‐[2.2]paracyclophane electron donors EDT‐TTF‐[2.2]paracyclophane 1 and (COOMe)₂‐TTF‐[2.2]paracyclophane 2 have been synthesized via the phosphite mediated cross coupling strategy. Chiral HPLC allowed the optical resolution of the (R_P) and (S_P) enantiomers for both compounds. Solid‐state structures of (R_P)‐ 1 and (rac)‐ 2 have been determined by single crystal X‐ray analysis. Intermolecular π‐π and S???S interactions are disclosed in the packing. Single crystal X‐ray analysis of (R_P)‐ 1 combined with experimental and theoretical circular dichroism spectra allowed the assignment of the absolute configuration of the enantiomers of 1 and 2 .     

Resultados preliminares de un programa comunitario de prevención de caídas: estudio Precari (prevención de caídas en La Ribera)

Objective

To evaluate the results of a fall prevention programme designed to be applied to the elderly living in the community.

Material and methods

The sample consisted of 249 participants ≥70 years of age, who were randomly assigned to one of three groups. The monthly intervention group (GIM): instructions on fall prevention and healthy exercises to improve physical function and balance at beginning of the study, and a monthly theoretical and practical refresher session. The quarterly intervention group (GIT), with the same beginning intervention and a refresher session every three months. The control group (GC), the same beginning intervention but no refresher sessions.

Results

The mean age of the sample was 74.47 years (SD 5.33), with 64% women. The incidence of falls was reduced from 0.64 per patient year in the previous year to 0.39 in the post-intervention year in GIM, from 0.49 to 0.47 in GIT, and in the GC it remained at 0.47 before and twelve months after, but with no significant differences in the reduction between groups (P=.062). At the end of the study there was a decrease in Rizzo scale of 0.72 points (95% CI: 0.57-0.88, P<.001).

Conclusion

An interdisciplinary community intervention programme can contribute to reducing the incidence of falls. Further studies are required to continue research into the incidence of falls in the elderly living in the community.     

Serosurvey of Rickettsia typhi and Rickettsia felis in HIV‐infected patients

Consistent with the effects of HIV on cell‐mediated immunity, an increased susceptibility to intracellular microorganisms has been observed. Rickettsiae are obligate intracellular microorganisms. The aim of this study was to examine Rickettsia typhi and Rickettsia felis infections in HIV+ population. Sera of 341 HIV+ patients were evaluated by indirect immunofluorescent assay. Age, sex, residential locality, risk behavior, stage according to criteria of the Center for Disease Control and Prevention, CD4+/CD8+ T cells, Hepatitis B antigen, and Hepatitis C serology were surveyed. Seroprevalences of R. typhi and R. felis infection were 7.6% and 4.4%, respectively. No associations were found between seropositivities and the assessed variables. Findings were similar to those obtained in healthy subjects from the same region.     

Structure of the Type IX Group B Streptococcus Capsular Polysaccharide and Its Evolutionary Relationship with Types V and VII

The Group B Streptococcus capsular polysaccharide type IX was isolated and purified, and the structure of its repeating unit was determined. Type IX capsule →4)[NeupNAc-α-(2→3)-Galp-β-(1→4)-GlcpNAc-β-(1→6)]-β-GlcpNAc-(1→4)-β-Galp-(1→4)-β-Glcp-(1→ appears most similar to types VII and V, although it contains two GlcpNAc residues. Genetic analysis identified differences in cpsM, cpsO, and cpsI gene sequences as responsible for the differentiation between the three capsular polysaccharide types, leading us to hypothesize that type V emerged from a recombination event in a type IX background.     

Effect of fires on soil nutrient availability in an open savanna in Central Brazil

Fire is common in savannas but its effects on soil are poorly understood. We analyzed long-term effects of fire on surface soil of an open Brazilian savanna (campo sujo) in plots submitted to different fire regimes during 18 years. The five fire regimes were: unburned, quadrennial fires in middle dry season, and biennial fires in early, middle or late dry season. Soil was collected during the wet and the middle dry season of 2008, and analyzed for pH, organic matter, total N, potential acidity, exchangeable cations and available P, S, Mn, Cu, Zn and Fe. We applied multivariate analysis to search for patterns related to fire regimes, and to local climate, fuel, and fire behavior. Spearman test was used to establish correlations between soil variables and the multivariate analysis gradient structure. Seasonal differences were tested using t-test. We found evidence of long-term fire effects: the unburned plot was segregated mainly by lower soil pH; the quadrennial plot was also segregated by lower soil pH and higher amount of exchangeable cations; the time of burning during the dry season in biennial plots did not significantly affect soil availability of nutrients. Differences in elements amounts due to the season of soil sampling (wet or dry) were higher than due to the effect of fires. Higher availability of nutrients in the soil during the wet season was probably related to higher nutrient inputs via rainfall and higher microbial activity.     

Thioredoxin m4 Controls Photosynthetic Alternative Electron Pathways in Arabidopsis

In addition to the linear electron flow, a cyclic electron flow (CEF) around photosystem I occurs in chloroplasts. In CEF, electrons flow back from the donor site of photosystem I to the plastoquinone pool via two main routes: one that involves the Proton Gradient Regulation5 (PGR5)/PGRL1 complex (PGR) and one that is dependent of the NADH dehydrogenase-like complex. While the importance of CEF in photosynthesis and photoprotection has been clearly established, little is known about its regulation. We worked on the assumption of a redox regulation and surveyed the putative role of chloroplastic thioredoxins (TRX). Using Arabidopsis (Arabidopsis thaliana) mutants lacking different TRX isoforms, we demonstrated in vivo that TRXm4 specifically plays a role in the down-regulation of the NADH dehydrogenase-like complex-dependent plastoquinone reduction pathway. This result was confirmed in tobacco (Nicotiana tabacum) plants overexpressing the TRXm4 orthologous gene. In vitro assays performed with isolated chloroplasts and purified TRXm4 indicated that TRXm4 negatively controls the PGR pathway as well. The physiological significance of this regulation was investigated under steady-state photosynthesis and in the pgr5 mutant background. Lack of TRXm4 reversed the growth phenotype of the pgr5 mutant, but it did not compensate for the impaired photosynthesis and photoinhibition sensitivity. This suggests that the physiological role of TRXm4 occurs in vivo via a mechanism distinct from direct up-regulation of CEF.In plant thylakoids, photosynthesis involves a linear electron flow (LEF) from water to NADP⁺ via PSII, cytochrome b₆/f, PSI, and soluble carriers. LEF produces NADPH and generates a transthylakoidal electrochemical proton gradient that drives the synthesis of ATP. Besides LEF, cyclic electron flow (CEF) can also occur, involving only PSI (for review, see Johnson, 2011; Kramer and Evans, 2011). These additional reactions include two main distinct pathways involving either the Proton Gradient Regulation5 (PGR5)/PGRL1 complex (Munekage et al., 2002; DalCorso et al., 2008) or the NADH dehydrogenase-like complex (NDH; for review, see Battchikova et al., 2011; Ifuku et al., 2011). The functioning of either CEF pathway, which generates a pH gradient ΔpH without any accumulation of NADPH, is thought to achieve the appropriate ATP/NADPH balance required for the biochemical needs of the plant, especially under certain environmental conditions such as low CO₂ (Golding and Johnson, 2003), heat (Clarke and Johnson, 2001), cold (Clarke and Johnson, 2001), drought (Golding and Johnson, 2003; Kohzuma et al., 2009), high light (Munekage et al., 2004), or dark-to-light transitions (Joliot and Joliot, 2005; Fan et al., 2007). CEF-generated ΔpH is also involved in photoprotection owing to the down-regulation of PSII via nonphotochemical quenching (Munekage et al., 2004; Takahashi et al., 2009). Very recently, the role of the PGR5 protein as a regulator of LEF has been established. It has proved to be essential in the protection of PSI from photodamage (Suorsa et al., 2012).The two cyclic pathways are redundant (Munekage et al., 2004), sharing ferredoxin (Fd) as a common stromal electron donor (Yamamoto et al., 2011) and electron carriers from plastoquinone (PQ) to PSI with LEF. Thus, LEF and either of the CEF pathways may be in competition. The molecular events that allow CEF to challenge LEF remain enigmatic, particularly when considering that the conditions that require CEF are also those under which LEF is in excess. Efforts to understand the appropriate functioning of CEF have led to the proposition of several models segregating cyclic and linear pathways at a structural level (for review, see Eberhard et al., 2008; Cardol et al., 2011; Johnson, 2011; Rochaix, 2011). According to the restricted diffusion model, founded on the uneven distribution of the photosynthetic protein complexes in the thylakoids, there is little competition between CEF and LEF, as CEF occurs in stroma lamellae where PSI is concentrated while LEF takes place in the grana stacks. In line with the supercomplex model, whose relevance was demonstrated in the microalga Chlamydomonas reinhardtii, CEF happens within tightly bound supercomplexes containing PSI, with its own light-harvesting complex (LHCI), the PSII light-harvesting complex (LHCII), cytochrome b₆/f, Fd, Fd NADP reductase (FNR), and the integral membrane protein PGRL1 (Iwai et al., 2010). In higher plants, an association between NDH and PSI subunits suggests the formation of such supercomplexes (Peng et al., 2009). The availability of FNR, found either free in the stroma or bound to the thylakoids (Zhang et al., 2001), has also been proposed to modulate partitioning between LEF and CEF (Joliot and Joliot, 2006; Joliot and Johnson, 2011). In addition, more dynamic models that illustrate competitive processes involved in the distribution of electrons between the cyclic and linear flows have been proposed. The competition between cytochrome b₆/f and FNR for electrons from Fd could regulate the segregation between LEF and CEF (Breyton et al., 2006; Yamamoto et al., 2006; Hald et al., 2008). A few years ago, Joliot and Joliot (2006) suggested that the ATP/ADP ratio was one of the parameters that triggered on the transition between LEF and CEF. It was also established that the redox poise of chloroplast stroma contributed to the regulation of the photosynthetic pathway and played an important role in defining the extent of CEF. Breyton et al. (2006) scrutinized this redox regulation and established that the fraction of PSI complexes engaged in CEF could be modulated by changes in the stromal redox state. Overreduction of the NADPH pool was involved in the repartition between LEF and CEF (Joliot and Joliot, 2006). The NADPH/NADP⁺ ratio was proposed as a regulator of PGR-dependent CEF in vivo (Okegawa et al., 2008).All the published data supporting a role for the redox status in the regulation of CEF urged us to investigate a putative role of thioredoxins (TRX) in the regulation of CEF. TRX are ubiquitous disulfide reductases regulating the redox status of target proteins (for review, see Lemaire et al., 2007; Meyer et al., 2009). In chloroplast, TRX mediate the light regulation of numerous enzymes, among which some belong to the Calvin cycle (for review, see Schürmann and Buchanan, 2008; Montrichard et al., 2009; Lindahl et al., 2011). Global proteomic approaches have revealed that well-known photosynthetic complex subunits may be partners of TRX, such as PsbO in PSII, plastocyanin, Rieske Fe-S protein in cytochrome b₆/f, and PsaK and PsaN in PSI (for review, see Montrichard et al., 2009; Lindahl et al., 2011). Furthermore, regarding the regulation of photosynthesis, TRX have also been involved in state transitions (Rintamäki et al., 2000; Buchanan and Balmer, 2005), and their participation in the control of the redox poise of the electron transport chain has also been suggested (Johnson, 2003).In this work, we have investigated the possible role of TRX in the regulation of CEF. Using Arabidopsis (Arabidopsis thaliana) mutants with altered expression of genes encoding different plastid TRX, we have established in vivo the inhibitor activity of TRXm4 on the NDH-dependent pathway for plastoquinone reduction. This result was confirmed in transplastomic tobacco (Nicotiana tabacum) plants overexpressing the TRXm4 orthologous gene. Moreover, in vitro assays performed with isolated chloroplasts indicated that TRXm4 negatively controls the PGR-dependent electron flow as well.     

Myrmecochory and short-term seed fate in Rhamnus alaternus: Ant species and seed characteristics

Benefits conferred on plants in ant-mediated seed dispersal mutualisms (myrmecochory) depend on the fate of transported seeds. We studied the effects of elaiosome presence, seed size and seed treatment (with and without passage through a bird's digestive tract) on short-term seed fate in Rhamnus alaternus. In our study, we define short-term seed, or initial, seed fate, as the location where ants release the seeds after ant contact with it. The elaiosomes had the most influence on short-term fate, i.e. whether or not seeds were transported to the nest. The workers usually transported big seeds more often than small ones, but small ants did not transport large seeds. Effect of seed size on transport depended on the ant species and on the treatment of the seed (manual extraction simulating a direct fall from the parent plant vs. bird deposition corresponding to preliminary primary dispersal). Probability of removal of elaiosome-bearing seeds to the nest by Aphaenogaster senilis increased with increasing seed weight.