Urban airborne pollen in a semiarid environment

The present investigation was conducted to determine the pollen types and their quantities in the atmosphere of Obregón City (a semiarid region) and establish the relationship with meteorological parameters in 2008 and 2011. A bimodal pattern with peaks in dry warm (spring) and late rainy (autumn) seasons was observed. The highest monthly pollen indexes were observed in October 2008 and September 2011. Precipitation in 2008 was 2.6 times higher than in 2011, beginning in June in both years, and ending in November (2008) and September (2011). Main pollen types were Poaceae, Chenopodiaceae/Amaranthaceae, Asteraceae and Parkinsonia (the latter was dominant in the dry warm season). Statistical correlations (Spearman’s rank-order correlation p < 0.05) with meteorological parameters were performed. In both sampling years, relative humidity caused adverse effects on the atmospheric pollen content, while temperature, solar radiation and wind speed in the dry season were associated with increased pollen indexes. Compared to other studies of semiarid areas, the pollen index at Obregón is low, which is attributed to a relatively high humidity and to the large area of grain crops surrounding the city.     

A theory that predicts behaviors of disordered cytoskeletal networks

Morphogenesis in animal tissues is largely driven by actomyosin networks, through tensions generated by an active contractile process. Although the network components and their properties are known, and networks can be reconstituted in vitro, the requirements for contractility are still poorly understood. Here, we describe a theory that predicts whether an isotropic network will contract, expand, or conserve its dimensions. This analytical theory correctly predicts the behavior of simulated networks, consisting of filaments with varying combinations of connectors, and reveals conditions under which networks of rigid filaments are either contractile or expansile. Our results suggest that pulsatility is an intrinsic behavior of contractile networks if the filaments are not stable but turn over. The theory offers a unifying framework to think about mechanisms of contractions or expansion. It provides the foundation for studying a broad range of processes involving cytoskeletal networks and a basis for designing synthetic networks.     

Interfaces in Perovskite Solar Cells

Rapid improvement in photoconversion efficiency (PCE) of solution processable organometallic hybrid halide based perovskite solar cells (PSCs) have taken the photovoltaic (PV) community with a surprise and has extended their application in other electronic devices such as light emitting diodes, photo detectors and batteries. Together with efforts to push the PCE of PSCs to record values >22% – now at par with that of crystalline silicon solar cells – origin of their PV action and underlying physical processes are also deeply investigated worldwide in diverse device configurations. A typical PSC consists of a perovskite film sandwiched between an electron and a hole selective contact thereby creating ESC/perovskite and perovskite/HSC interfaces, respectively. The selective contacts and their interfaces determine properties of perovskite layer and also control the performance, origin of PV action, open circuit voltage, device stability, and hysteresis in PSCs. Herein, we define ideal charge selective contacts, and provide an overview on how the choice of interfacing materials impacts charge accumulation, transport, transfer/recombination, band‐alignment, and electrical stability in PSCs. We then discuss device related considerations such as morphology of the selective contacts (planar or mesoporous), energetics and electrical properties (insulating and conducting), and its chemical properties (organic vs inorganic). Finally, the outlook highlights key challenges and future directions for a commercially viable perovskite based PV technology.     

Modeling xeroderma pigmentosum associated neurological pathologies with patients-derived iPSCs

Xeroderma pigmentosum (XP) is a group of genetic disorders caused by mutations of XP-associated genes, resulting in impairment of DNA repair. XP patients frequently exhibit neurological degeneration, but the underlying mechanism is unknown, in part due to lack of proper disease models. Here, we generated patientspecific induced pluripotent stem cells (iPSCs) harboring mutations in five different XP genes including XPA, XPB, XPC, XPG, and XPV. These iPSCs were further differentiated to neural cells, and their susceptibility to DNA damage stress was investigated. Mutation of XPA in either neural stem cells (NSCs) or neurons resulted in severe DNA damage repair defects, and these neural cells with mutant XPA were hyper-sensitive to DNA damage-induced apoptosis. Thus, XP-mutant neural cells represent valuable tools to clarify the molecular mechanisms of neurological abnormalities in the XP patients.     

Germination and reproductive biology in salty conditions of Asplenium marinum (Aspleniaceae), a European coastal fern

Although there are several species of ferns that are important components of many coastal ecosystems, the adaptations that allow these species to live in salty conditions have been studied only in two Acrostichum species. We have studied the effects of salt on germination, development of the gametophyte and sexual expression of the fern Asplenium marinum, which lives on coastal cliffs of Europe. Cultures at four different levels of salt concentration, 0%, 0.98%, 1.96% and 3.26%, were established for this purpose. Salt caused a significant delay in spore germination, and prevented it completely at high concentrations (3.26%). However, spores were able to recover germination ability after a period of seawater incubation once salinity concentrations decreased. Variable salinity conditions are a typical feature of sea cliffs where halophytes can grow. A salty culture medium also affects the development of the prothalli. Higher salinity of the substrate produced a significant decrease in gametophyte sizes, and affected the development of gametangia as well. Only males were found in a 0.98%-salt medium, and no gametangia were observed in cultures at 1.96%-salt medium. Recovered spores after one and a half month in high salinity concentration, 3.26%, were able, when transplanted to 0%-salt medium, to develop normal sexual prothalli, and this occurred in a shorter time than spores without any prior treatment. A. marinum can be considered as a halophyte fern that is able to germinate and grow in salty conditions. But it takes advantage of rainy periods that cause decrease of salt concentration, which seems to be important in particular for gametangia development and fertilization.     

BMP-2/6 Heterodimer Is More Effective than BMP-2 or BMP-6 Homodimers as Inductor of Differentiation of Human Embryonic Stem Cells

Background

Bone Morphogenetic Protein (BMP) signaling pathways are involved in differentiation of stem cells into diverse cell types, and thus BMPs can be used as main guidance molecules for in vitro differentiation of human stem cells.

Methodology/Principal Findings

We have analyzed the ability for inducing differentiation of the heterodimer BMP-2/BMP-6 (BMP-2/6) compared to the homodimers BMP-2 or BMP-6, using human embryonic stem (hES) cells H9 as model system. When incubated in a medium with high concentration of basic fibroblastic growth factor (FGF2), 100 ng/ml of human recombinant BMPs induced morphological changes and differentiation of hES cells in 24 to 48 hours. After 5 days, expression of differentiation markers was induced and quantified by quantitative PCR (qPCR) and flow cytometry. BMP-2/6 exhibited stronger activity for the induction of the expression of trophectodermal (CDX2) and endodermal (SOX17, GATA4, AFP) markers than BMP-2 or BMP-6 homodimers. BMP-2/6 also induced the expression of BMPR2 gene more effectively than BMP-2 or BMP-6 when used at the same concentration and time. Moreover, the percentage of cells expressing the surface endodermal marker CXCR4 was also increased for the heterodimer when compared to both homodimers. BMP-2/6 was a more potent activator of Smad-dependent (SMAD1/5) and Smad-independent signaling (mitogen-activated protein kinases ERK and p38) than BMP-2 and BMP-6, and the activation of these pathways might play a role in its increased potency for inducing hES cell differentiation.

Conclusions/Significance

Therefore, we conclude that BMP-2/6 is more potent than BMP-2 or BMP-6 for inducing differentiation of hES cells, and it can be used as a more powerful substitute of these BMPs in in vitro differentiation guidance.     

Selective Alterations Within Executive Functions in Adolescents With Excess Weight

Increasing evidence underscores overlapping neurobiological pathways to addiction and obesity. In both conditions, reward processing of preferred stimuli is enhanced, whereas the executive control system that would normally regulate reward‐driven responses is altered. This abnormal interaction can be greater in adolescence, a period characterized by relative immaturity of executive control systems coupled with the relative maturity of reward processing systems. The aim of this study is to explore neuropsychological performance of adolescents with excess weight (n = 27, BMI range 24–51 kg/m²) vs. normal‐weight adolescents (n = 34, BMI range 17–24 kg/m²) on a comprehensive battery of executive functioning tests, including measures of working memory (letter‐number sequencing), reasoning (similarities), planning (zoo map), response inhibition (five‐digit test (FDT)–interference and Stroop), flexibility (FDT–switching and trail‐making test (TMT)), self‐regulation (revised‐strategy application test (R‐SAT)), and decision‐making (Iowa gambling task (IGT)). We also aimed to explore personality traits of impulsivity and sensitivity to reward. Independent sample t‐ and Z Kolmogorov–Smirnov tests showed significant differences between groups on indexes of inhibition, flexibility, and decision‐making (excess‐weight participants performed poorer than controls), but not on tests of working memory, planning, and reasoning, nor on personality measures. Moreover, regression models showed a significant association between BMI and flexibility performance. These results are indicative of selective alterations of particular components of executive functions in overweight adolescents.