Separate colour-opponent mechanisms underlie the detection and discrimination of moving chromatic targets.

Current opinion holds that human colour vision is mediated primarily via a colour-opponent pathway that carries information about both wavelength and luminance contrast (type I). However, some authors argue that chromatic sensitivity may be limited by a different geniculostriate pathway, which carries information about wavelength alone (type II). We provide psychophysical evidence that both pathways may contribute to the perception of moving, chromatic targets in humans, depending on the nature of the visual discrimination. In experiment 1, we show that adaptation to drifting, red-green stimuli causes reductions in contrast sensitivity for both the detection and direction discrimination of moving chromatic targets. Importantly, the effects of adaptation are not directionally specific. In experiment 2, we show that adaptation to luminance gratings results in reduced sensitivity for the direction discrimination, but not the detection of moving chromatic targets. We suggest that sensitivity for the direction discrimination of chromatic targets is limited by a colour-opponent pathway that also conveys luminance-contrast information, whereas the detection of such targets is limited by a pathway with access to colour information alone. The properties of these pathways are consistent with the known properties of type-I and type-II neurons of the primate parvocellular lateral geniculate nucleus and their cortical projections. These findings may explain the known differences between detection and direction discrimination thresholds for chromatic targets moving at low to moderate velocities.     

Seedling establishment in different microsites on Mount St. Helens,Washington, USA

On the volcanically devastated Pumice Plain of Mount St. Helens, plant species colonized microsites differentially. Peak colonization did not occur in the same microsites as peak establishment and growth. In addition, observed microsite colonization patterns differed between years. Two studies were conducted. The first assessed seedling establishment and growth from seeds sown at different microsites. The second assessed colonization into four microsite types that were constructed on the Pumice Plain. Hypochaeris radicata was the most common species to survive when the same number of seeds of four species were planted; however, Anaphalis margaritacea was the most common colonizer of microsites. Microsites with the largest biomass plants in the first study generally had the highest colonization in the second study. Sites that do not possess features to trap seeds, such as flats and ridges, are not opportune places for a plant to grow since there is little microclimatic or substrate amelioration. Thus, flat microsites had low biomass in the establishment experiment due to the lack of amelioration and contained few plants in the colonization experiment due to a lack of seed trapping mechanisms. These results show that in the primary successional landscape of Mount St. Helens microsites are critical to revegetation dynamics. Changes in the pattern of microsite colonization between years emphasizes the dynamic nature of the landscape and the important influences of climate, substrate amelioration and seed rain to plant establishment.     

Notch Signalling Is Required for the Formation of Structurally Stable Muscle Fibres in Zebrafish

Background

Accurate regulation of Notch signalling is central for developmental processes in a variety of tissues, but its function in pectoral fin development in zebrafish is still unknown.

Methodology/Principal Findings

Here we show that core elements necessary for a functional Notch pathway are expressed in developing pectoral fins in or near prospective muscle territories. Blocking Notch signalling at different levels of the pathway consistently leads to the formation of thin, wavy, fragmented and mechanically weak muscles fibres and loss of stress fibres in endoskeletal disc cells in pectoral fins. Although the structural muscle genes encoding Desmin and Vinculin are normally transcribed in Notch-disrupted pectoral fins, their proteins levels are severely reduced, suggesting that weak mechanical forces produced by the muscle fibres are unable to stabilize/localize these proteins. Moreover, in Notch signalling disrupted pectoral fins there is a decrease in the number of Pax7-positive cells indicative of a defect in myogenesis.

Conclusions/Significance

We propose that by controlling the differentiation of myogenic progenitor cells, Notch signalling might secure the formation of structurally stable muscle fibres in the zebrafish pectoral fin.     

Aplysia temptin - the 'glue' in the water-borne attractin pheromone complex

Temptin, a component of the complex of water-borne protein pheromones that stimulate attraction and mating behavior in the marine mollusk Aplysia, has sequence homology to the epidermal growth factor (EGF)-like domains of higher organisms that mediate protein-cell surface contact during fertilization and blood coagulation. In this work, recombinant temptin for structural and functional studies was produced in Escherichia coli using a cold shock promoter and purified by RP-HPLC. CD spectra confirmed a predominantly beta-sheet structure. Two disulfide bonds were determined via limited proteolysis and MS. One internal disulfide (Cys57-Cys77) was predicted from initial alignments with class I EGF-like domains; the second, between Cys18 and Cys103, could protect temptin against proteolysis in seawater and stabilize its interacting surface. A three-dimensional model of temptin was prepared with our MPACK suite, based on the Ca(2+)-binding, EGF-like domain of the extracellular matrix protein fibrillin. Two temptin residues, Trp52 and Trp79, which align with cysteine residues conserved in fibrillins, lie adjacent to and could stabilize the disulfide bonds and a proposed metal-binding loop. The water-borne pheromone attractin in egg cordon eluates is complexed with other proteins. Docking results with our model and the NMR structure of attractin suggest that one face of temptin interacts with the pheromone, perhaps controlling its access to the cellular receptors. Gel shifts confirmed that temptin complexes with wild-type attractin. These results indicate that temptin, analogous to the role of fibrillin in controlling transforming growth factor-beta concentration, modulates pheromone signaling by direct binding to attractin.     

Global analysis of nitrogen and phosphorus limitation of primary producers in freshwater, marine and terrestrial ecosystems

The cycles of the key nutrient elements nitrogen (N) and phosphorus (P) have been massively altered by anthropogenic activities. Thus, it is essential to understand how photosynthetic production across diverse ecosystems is, or is not, limited by N and P. Via a large-scale meta-analysis of experimental enrichments, we show that P limitation is equally strong across these major habitats and that N and P limitation are equivalent within both terrestrial and freshwater systems. Furthermore, simultaneous N and P enrichment produces strongly positive synergistic responses in all three environments. Thus, contrary to some prevailing paradigms, freshwater, marine and terrestrial ecosystems are surprisingly similar in terms of N and P limitation.     

Cross-talk between macrophages,smooth muscle cells,and endothelial cells in response to cigarette smoke: the effects on MMP2 and 9

The aim of the present study was to analyze the expression of sex-determining region Y-related high mobility group box 4 (SOX4) in non-small cell lung cancer (NSCLC) and its correlation with clinicopathologic characteristics, including the survival of NSCLC patients. To observe initially the expression status of SOX4 in lung squamous cell carcinoma and adenocarcinoma at gene expression omnibus. The expression of SOX4 mRNA and protein was examined in NSCLC tissues and normal lung tissues through real-time PCR and immunohistochemistry. Meanwhile, the relationship of SOX4 expression levels with clinical characteristics of 168 NSCLC patients was analyzed by immunohistochemistry. Univariate and multivariate analyses were performed to determine the association between SOX4 expression and prognosis of NSCLC patients. In our results, SOX4 expression was increased in NSCLC tissues compared with paired normal lung tissues in microarray data (GSE3268). SOX4 mRNA and protein expression were markedly higher in NSCLC tissues than in normal lung tissues (P = 0.001 and P = 0.001, respectively). Using immunohistochemistry, high levels of SOX4 protein were positively correlated with status of differentiated degree (high vs. middle, P = 0.004; high vs. low, P < 0.001), clinical stage (I–II vs. III–IV, P < 0.001), T classification (T1–T2 vs. T3–T4, P = 0.004), N classification (N0–N1 vs. N2–N3, P = 0.002), and M classification (M0 vs. M1, P = 0.011) in NSCLC. Moreover, the higher level of SOX4 expression was markedly correlated with poor overall survival in NSCLC patients (P < 0.001). Multivariate analysis suggested that increased SOX4 expression was a poor independent prognostic predictor for NSCLC patients (P = 0.002). In conclusion, SOX4 plays an important role on NSCLC progression and prognosis and may serve as a convictive prognostic biomarker for NSCLC patients.     

Cell-Type-Specific Gene Expression Profiling in Adult Mouse Brain Reveals Normal and Disease-State Signatures

1. Download high-res image (238KB)
2. Download full-size image