Comment on "Nonreciprocal light propagation in a silicon photonic circuit"

We show that the structure demonstrated by Feng et al. (Reports, 5 August 2011, p. 729) cannot enable optical isolation because it possesses a symmetric scattering matrix. Moreover, one cannot construct an optical isolator by incorporating this structure into any system as long as the system is linear and time-independent and is described by materials with a scalar dielectric function.     

ATP release guides neutrophil chemotaxis via P2Y2 and A3 receptors

Cells must amplify external signals to orient and migrate in chemotactic gradient fields. We find that human neutrophils release adenosine triphosphate (ATP) from the leading edge of the cell surface to amplify chemotactic signals and direct cell orientation by feedback through P2Y2 nucleotide receptors. Neutrophils rapidly hydrolyze released ATP to adenosine that then acts via A3-type adenosine receptors, which are recruited to the leading edge, to promote cell migration. Thus, ATP release and autocrine feedback through P2Y2 and A3 receptors provide signal amplification, controlling gradient sensing and migration of neutrophils.     

Compartmentalized control of skin immunity by resident commensals

Intestinal commensal bacteria induce protective and regulatory responses that maintain host-microbial mutualism. However, the contribution of tissue-resident commensals to immunity and inflammation at other barrier sites has not been addressed. We found that in mice, the skin microbiota have an autonomous role in controlling the local inflammatory milieu and tuning resident T lymphocyte function. Protective immunity to a cutaneous pathogen was found to be critically dependent on the skin microbiota but not the gut microbiota. Furthermore, skin commensals tuned the function of local T cells in a manner dependent on signaling downstream of the interleukin-1 receptor. These findings underscore the importance of the microbiota as a distinctive feature of tissue compartmentalization, and provide insight into mechanisms of immune system regulation by resident commensal niches in health and disease.     

Glutamatergic and dopaminergic neurons mediate anxiogenic and anxiolytic effects of CRHR1

The corticotropin-releasing hormone receptor 1 (CRHR1) critically controls behavioral adaptation to stress and is causally linked to emotional disorders. Using neurochemical and genetic tools, we determined that CRHR1 is expressed in forebrain glutamatergic and γ-aminobutyric acid-containing (GABAergic) neurons as well as in midbrain dopaminergic neurons. Via specific CRHR1 deletions in glutamatergic, GABAergic, dopaminergic, and serotonergic cells, we found that the lack of CRHR1 in forebrain glutamatergic circuits reduces anxiety and impairs neurotransmission in the amygdala and hippocampus. Selective deletion of CRHR1 in midbrain dopaminergic neurons increases anxiety-like behavior and reduces dopamine release in the prefrontal cortex. These results define a bidirectional model for the role of CRHR1 in anxiety and suggest that an imbalance between CRHR1-controlled anxiogenic glutamatergic and anxiolytic dopaminergic systems might lead to emotional disorders.     

BKCa-Cav channel complexes mediate rapid and localized Ca2+-activated K+ signaling

Large-conductance calcium- and voltage-activated potassium channels (BKCa) are dually activated by membrane depolarization and elevation of cytosolic calcium ions (Ca2+). Under normal cellular conditions, BKCa channel activation requires Ca2+ concentrations that typically occur in close proximity to Ca2+ sources. We show that BKCa channels affinity-purified from rat brain are assembled into macromolecular complexes with the voltage-gated calcium channels Cav1.2 (L-type), Cav2.1 (P/Q-type), and Cav2.2 (N-type). Heterologously expressed BKCa-Cav complexes reconstitute a functional "Ca2+ nanodomain" where Ca2+ influx through the Cav channel activates BKCa in the physiological voltage range with submillisecond kinetics. Complex formation with distinct Cav channels enables BKCa-mediated membrane hyperpolarization that controls neuronal firing pattern and release of hormones and transmitters in the central nervous system.     

Parallel patterns of evolution in the genomes and transcriptomes of humans and chimpanzees

The determination of the chimpanzee genome sequence provides a means to study both structural and functional aspects of the evolution of the human genome. Here we compare humans and chimpanzees with respect to differences in expression levels and protein-coding sequences for genes active in brain, heart, liver, kidney, and testis. We find that the patterns of differences in gene expression and gene sequences are markedly similar. In particular, there is a gradation of selective constraints among the tissues so that the brain shows the least differences between the species whereas liver shows the most. Furthermore, expression levels as well as amino acid sequences of genes active in more tissues have diverged less between the species than have genes active in fewer tissues. In general, these patterns are consistent with a model of neutral evolution with negative selection. However, for X-chromosomal genes expressed in testis, patterns suggestive of positive selection on sequence changes as well as expression changes are seen. Furthermore, although genes expressed in the brain have changed less than have genes expressed in other tissues, in agreement with previous work we find that genes active in brain have accumulated more changes on the human than on the chimpanzee lineage.     

Local vs. formal breeding and inbred line vs. synthetic cultivar for organic farming: Case of Vicia faba L.

As organic farming refrains from the use of agrochemical inputs, it is characterized by large environmental heterogeneity. Genotype × location interaction is expected to be larger across organic cropping areas than across conventional ones. When breeding for organic farming, it is important to identify an adequate breeding approach and type of cultivar. The objective was to investigate in the case of faba bean (Vicia faba L.) the effectiveness of local breeding (exploiting local adaptation) vs. formal breeding (exploiting broad adaptation) for grain yield in organic farming and to compare the performance of two types of cultivars: inbred lines and synthetics. A set of 18 inbred lines, their polycross progenies and 13 checks was tested in five locations in Germany from 2004 to 2006. Due to the large genotype × location interaction, local breeding generated higher gains from selection than formal breeding. Based on estimates of genotypic performance and variance of inbred lines and polycross progenies, the best synthetic cultivar at generation Syn-1 and the best inbred line cultivar were predicted. Despite the large variance among inbred lines available in local breeding, the highest performing entry in both breeding strategies was a synthetic, due to its partial realization of heterosis.     

A novel purification method of artemisinin from Artemisia annua

Treatment of uncomplicated malaria relies heavily on the sesquiterpene lactone artemisinin (ART), derived from the Chinese herb Artemisia annua. It is currently used as the first line treatment in the form of ART combination therapies in which different ART derivatives are combined with a non ART-like drug, which displays a different mechanism of action. This treatment regime is prescribed by the WHO in order to (1) effectively treat uncomplicated malaria and (2) to reduce the risk that drug resistance will develop. Considering the importance of ART in this treatment regime, various methods have been developed to increase the global production of ART. These methods include: large scale solvent extraction and purification from high yielding A. annua varieties, chemical/semi-chemical synthesis of artemisinin, and genetic engineering of unrelated organisms to produce ART in high quantities. Currently most of the commercial approaches to produce ART are based on solvent extraction and purification from the plant material. Classical extraction solvents include hexane or petroleum ether while ethanol, which is a more polar solvent, has recently been shown to be equally efficient. We developed a purification method from an ethanolic extract by using a diatomite-based purification protocol. Various volumes and ratios of solvents and diatomite were tested which resulted in ≥98% pure ART with a total recovery of around 60%. Our protocol for the isolation of ART may form a commercial scale alternative as it is both economically attractive due to the small amounts of purification materials needed and also environmentally friendlier than the methods previously described.     

Spatial distribution of soil heavy metal concentrations as indicator of pollution sources at Mount Križna (Great Fatra,central Slovakia)

The objective of this study was to test the suitability of a simple approach to identify the direction from where airborne heavy metals reach the study area as indication of their sources. We examined the distribution of heavy metals in soil profiles and along differently exposed transects. Samples were taken from 10 soils derived from the same parent material along N-, S-, and SE-exposed transects at 0—10, 10—20, and 20—40 cm depth and analyzed for total Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn concentrations. The heavy metal concentrations at 0—10 cm were larger than background concentrations in German arable soils except for Cr (Cd: 0.6—1.8 mg kg^—1; Cr: 39—67; Cu: 40—77; Ni: 87—156; Pb: 48—94; Zn: 71—129; Fe: 26—34 g kg^—1; Mn: 1.1—2.4). Decreasing Cd, Cu, Mn, and Pb concentrations with increasing soil depth pointed at atmospheric inputs. Aluminum and Ni concentrations increased with soil depth. Those of Fe, Cr, and Zn did not change with depth indicating that inputs at most equalled leaching losses. The Pb accumulation in the surface layer (i.e. the ratio between the Pb concentrations at 0—10 to those at 20—40 cm depth) was most pronounced at N-exposed sites; Pb obviously reached Mount Križna mainly by long-range transport from N where several industrial agglomerations are located. Substantial Cd, Cu, and Mn accumulations at the S- and SE-exposed sites indicated local sources such as mining near to the study area which probably are also the reason for slight Cr and Zn accumulations in the SE-exposed soils. Based on a principal component analysis of the total concentrations in the topsoils four metal groups may be distinguished: 1. Cr, Ni, Zn; 2. Mn, Cd; 3. Pb (positive loading), Cu (negative loading); 4. Al, Fe, indicating common sources and distribution patterns. The results demonstrate that the spatial distribution of soil heavy metal concentrations can be used as indication of the location of pollution sources.     

Estimating N status of winter wheat using a handheld spectrometer in the North China Plain

Excessive nitrogen (N) fertilizer application is very common in the North China Plain. Diagnosis of in-season N status in crops is critical for precision N management in this area. Remote sensing, as a timely and nondestructive tool, could be an alternative to traditional plant testing for diagnosing crop N status. The objectives of this study were to determine which vegetation indices could be used to estimate N status in winter wheat (Triticum aestivum L.) under high N input conditions, develop models to predict winter wheat N uptake using spectral vegetation indices and validate the models with data from farmers’ fields. An N rate experiment and a variety-N experiment were conducted in Huimin, Shandong Province from 2005/2006 to 2006/2007 to develop the models. Positive linear relationships between simple ratio vegetation indices (red vegetation index, RVI and green vegetation index, GVI) and N uptake were observed independent of growth stages and varieties (R², 0.48–0.74). In contrast, the relationships between normalized difference vegetation indices (NDVI and GNDVI), red and green normalized difference vegetation index (RGNDI), and red and green ratio vegetation index (RGVI) were exponentially related to N uptake (R², 0.43–0.79). Subsequently, 69 farmers’ fields in four different villages were selected as datasets to validate the developed models. The results indicated that the prediction using RVI had the highest coefficient of determination (R², 0.60), the lowest root mean square error (RMSE, 39.7 kg N ha⁻¹) and relative error (RE, 30.5%) across different years, varieties and growth stages. We conclude that RVI can be used to estimate nitrogen status for winter wheat in over-fertilized farmers’ fields before heading.