Shifting Pacific storm tracks as stressors to ecosystems of western North America

Much of the precipitation delivered to western North America arrives during the cool season via midlatitude Pacific storm tracks, which may experience future shifts in response to climate change. Here, we assess the sensitivity of the hydroclimate and ecosystems of western North America to the latitudinal position of cool‐season Pacific storm tracks. We calculated correlations between storm track variability and three hydroclimatic variables: gridded cool‐season standardized precipitation‐evapotranspiration index, April snow water equivalent, and water year streamflow from a network of USGS stream gauges. To assess how historical storm track variability affected ecosystem processes, we derived forest growth estimates from a large network of tree‐ring widths and land surface phenology and wildfire estimates from remote sensing. From 1980 to 2014, cool‐season storm tracks entered western North America between approximately 41°N and 53°N. Cool‐season moisture supply and snowpack responded strongly to storm track position, with positive correlations to storm track latitude in eastern Alaska and northwestern Canada but negative correlations in the northwestern U.S. Ecosystems of the western United States were greener and more productive following winters with south‐shifted storm tracks, while Canadian ecosystems were greener in years when the cool‐season storm track was shifted to the north. On average, larger areas of the northwestern United States were burned by moderate to high severity wildfires when storm tracks were displaced north, and the average burn area per fire also tended to be higher in years with north‐shifted storm tracks. These results suggest that projected shifts of Pacific storm tracks over the 21st century would likely alter hydroclimatic and ecological regimes in western North America, particularly in the northwestern United States, where moisture supply and ecosystem processes are highly sensitive to the position of cool‐season storm tracks.     

Temporal and spatial variation characteristics of China shrubland net primary production and its response to climate change from 2001 to 2013

Aims Net primary production (NPP) is the input to terrestrial ecosystem carbon pool. Climate and land use change affect NPP significantly. Shrublands occupy more than 20% of the terrestrial area of China, and their NPP is comparable to those of the forests. Our objective was to estimate China shrubland NPP from 2001 to 2013, and to analyze its variation and response to climate change.Methods We used a Carnegie-Ames-Stanford Approach (CASA) model to estimate the NPP of six shrubland types in China from 2001 to 2013. Furthermore, we used Theil-Sen slope combined with Mann-kendall test to analyze its spatial variation and a linear regression of one-variable model to analyze its inter- and intra-annual variation. Finally, a multi-factor linear regression model was used to analyze its response to climate change.Important findings We found the annual mean NPP of China shrubland was 281.82 g•m^-2•a^-1. The subtropical evergreen shrubland has the maximum NPP of 420.47 g•m^-2•a^-1, while the high cold desert shrubland has the minimum NPP of 52.65 g•m^-2•a^-1. The countrywide shrublands NPP increased at the rate of 1.23 g•m^-2•a^-1, the relative change rate was 5.99%. The temperate deciduous shrubland NPP increased the fastest with a speed of 3.05 g•m^-2•a^-1 and subalpine evergreen shrubland had a decreasing trend with a speed of -0.73 g•m^-2•a^-1. Moreover, the other four shrublands NPP had a growing trend, only subalpine deciduous shrubland NPP did not change significantly. The response of NPP to climate change of different seasons varies to different shrubland types. In general, the NPP variation was mainly affected by precipitation, and the spring warming also contributed to it. The increase of countrywide shrubland NPP may promote its contribution to the regional ecosystem function.     

Metabolic compensation constrains the temperature dependence of gross primary production

Gross primary production (GPP) is the largest flux in the carbon cycle, yet its response to global warming is highly uncertain. The temperature dependence of GPP is directly linked to photosynthetic physiology, but the response of GPP to warming over longer timescales could also be shaped by ecological and evolutionary processes that drive variation in community structure and functional trait distributions. Here, we show that selection on photosynthetic traits within and across taxa dampens the effects of temperature on GPP across a catchment of geothermally heated streams. Autotrophs from cold streams had higher photosynthetic rates and after accounting for differences in biomass among sites, biomass‐specific GPP was independent of temperature in spite of a 20 °C thermal gradient. Our results suggest that temperature compensation of photosynthetic rates constrains the long‐term temperature dependence of GPP, and highlights the importance of considering physiological, ecological and evolutionary mechanisms when predicting how ecosystem‐level processes respond to warming.     

Temperature and rainfall interact to control carbon cycling in tropical forests

Tropical forests dominate global terrestrial carbon (C) exchange, and recent droughts in the Amazon Basin have contributed to short‐term declines in terrestrial carbon dioxide uptake and storage. However, the effects of longer‐term climate variability on tropical forest carbon dynamics are still not well understood. We synthesised field data from more than 150 tropical forest sites to explore how climate regulates tropical forest aboveground net primary productivity (ANPP) and organic matter decomposition, and combined those data with two existing databases to explore climate – C relationships globally. While previous analyses have focused on the effects of either temperature or rainfall on ANPP, our results highlight the importance of interactions between temperature and rainfall on the C cycle. In cool forests (< 20 °C), high rainfall slowed rates of C cycling, but in warm tropical forests (> 20 °C) it consistently enhanced both ANPP and decomposition. At the global scale, our analysis showed an increase in ANPP with rainfall in relatively warm sites, inconsistent with declines in ANPP with rainfall reported previously. Overall, our results alter our understanding of climate – C cycle relationships, with high precipitation accelerating rates of C exchange with the atmosphere in the most productive biome on earth.     

Tumor-specific frequencies and ocular melanoma

Specific kilohertz frequencies in the environment from variable frequency drives on electric motors at a liquid natural gas compressor and storage station on a natural gas pipeline seem to be associated with the development of a very rare cancer, ocular melanoma, at a high school and in individuals living or working in a neighborhood near the plant. Primary neutral-to-earth oscilloscope voltage waveforms and spectra measured near the high school were nearly identical to the ground voltage 2.3 miles away at the gas pipeline. Peak frequencies of 7440 and 19,980 Hz were found at both places. The electric utility practice of using the earth as a conduit for return currents facilitated this exposure.     

Augmenter of liver regeneration (ALR) protects human hepatocytes against apoptosis

Augmenter of liver regeneration (ALR) is known to support liver regeneration and to stimulate proliferation of hepatocytes. However, it is not known if ALR exerts anti-apoptotic effects in human hepatocytes and whether this protective effect is cell type specific. This is relevant, because compounds that protect the liver against apoptosis without undesired effects, such as protection of metastatic tumour cells, would be appreciated in several clinical settings. Primary human hepatocytes (phH) and organotypic cancer cell lines were exposed to different concentrations of apoptosis inducers (ethanol, TRAIL, anti-Apo, TGF-β, actinomycin D) and cultured with or without recombinant human ALR (rhALR). Apoptosis was evaluated by the release of cytochrome c from mitochondria and by FACS with propidium iodide (PI) staining.ALR significantly decreased apoptosis induced by ethanol, TRAIL, anti-Apo, TGF-β and actinomycin D. Further, the anti-apoptotic effect of ALR was observed in primary human hepatocytes and in HepG2 cells but not in bronchial (BC1), colonic (SW480), gastric (GC1) and pancreatic (L3.6PL) cell lines.Therefore, the hepatotrophic growth factor ALR acts in a liver specific manner with regards to both its mitogenic and its anti-apoptotic effect. Unlike the growth factors HGF and EGF, rhALR acts in a liver specific manner. Therefore, ALR is a promising candidate for further evaluation as a possible hepatoprotective factor in clinical settings.     

Endothelial cell responses towards low-fouling surfaces bearing RGD in a three-dimensional environment

This study reveals that it is possible to obtain a specific cell response towards low-fouling carboxymethyl dextran (CMD) surfaces bearing the RGD adhesive peptide in fibrin. To avoid cell sedimentation on surfaces observed in traditional cell culture systems, CMD surfaces bearing RGD were vertically embedded in fibrin containing human umbilical vein endothelial cells (HUVEC) and their effect over cells was investigated. Compared to the CMD surfaces and to CMD layers bearing the negative control RGE, RGD coatings promoted cell adhesion, induced focal contact formation indicated by co-localization of vinculin and actin fibers, and presented a significant effect over HUVEC net growth during the first 24 h of the culture, as revealed by Ki67 staining and cell counting. The intracellular localization of caveolin-1 combined with the expression of beta 1 integrins was investigated and the orientation of HUVEC towards and on the RGD surfaces was studied. When compared to the negative controls, HUVEC responded to the RGD surface in fibrin resulting in acceleration of morphological changes. RGD surfaces supported fibrin degradation by HUVEC as revealed by fluorescent fibrin experiments as well as multi-cellular structure formation, vacuolation and lumen formation.     

Primary productivity and anthropogenic disturbance as determinants of Upland Goose Chloephaga picta distribution in southern Patagonia

A species distribution may be determined by its responses to patterns of human disturbance as well as by its habitat preferences. Here we investigate the distribution of the Upland Goose Chloephaga picta, which has been historically persecuted by farmers and ranchers in Patagonia because it feeds on crops and pastures and is assumed to compete with sheep for forage. We assess whether its current breeding distribution is shaped by persecution by ranchers or whether it can be better explained by differences in habitat primary productivity and preference for wetlands, or by other anthropogenic disturbances not associated with ranching. We built species distribution models to examine the relative effect of environmental and anthropogenic predictors on the regional distribution of Upland Goose. We performed vehicle surveys in the province of Santa Cruz, Argentina, in two years, surveying 8000 km of roads and recording 6492 Geese. Generalized additive models were used to model the presence/absence of Geese in 1‐km cells. The models suggested that Upland Goose distribution is not currently affected by rancher control, as the species is more abundant in areas with high sheep stocking levels, but it is positively influenced by primary productivity and negatively influenced by urban areas. Anthropogenic disturbance caused by urban areas and oil extraction camps had a greater impact in limiting the species distribution than sheep ranching.     

Ambient UV-B radiation reduces PSII performance and net photosynthesis in high Arctic Salix arctica

Ambient ultraviolet-B (UV-B) radiation potentially impacts the photosynthetic performance of high Arctic plants. We conducted an UV-B exclusion experiment in a dwarf shrub heath in NE Greenland (74°N), with open control, filter control, UV-B filtering and UV-AB filtering, all in combination with leaf angle control. Two sites with natural leaf positions had ground angles of 0° (‘level site’) and 45° (‘sloping site’), while at a third site the leaves were fixed in an angle of 45° to homogenize the irradiance dose (‘fixed leaf angle site’). The photosynthetic performance of the leaves was characterized by simultaneous gas exchange and chlorophyll fluorescence measurements and the PSII performance through the growing season was investigated with fluorescence measurements. Leaf harvest towards the end of the growing season was done to determine the specific leaf area and the content of carbon, nitrogen and UV-B absorbing compounds. Compared to a 60% reduced UV-B irradiance, the ambient solar UV-B reduced net photosynthesis in Salix arctica leaves fixed in the 45° position which exposed leaves to maximum natural irradiance. Also a reduced Calvin Cycle capacity was found, i.e. the maximum rate of electron transport (J_max) and the maximum carboxylation rate of Rubisco (V_cmax), and the PSII performance showed a decreased quantum yield and increased energy dissipation. A parallel response pattern and reduced PSII performance at all three sites indicate that these responses take place in all leaves across position in the vegetation. These findings add to the evidence that the ambient solar UV-B currently is a significant stress factor for plants in high Arctic Greenland.     

Spectrofluorimetric analysis of the interaction of amyloid peptides with neuronal nitric oxide synthase: Implications in Alzheimer's disease

Background

The deposition of aggregated β-amyloid peptide senile plaques and the accumulation of arginine within the astrocytes in the brain of an Alzheimer's patient are classic observations in the neuropathology of the disease. It would be logical, in the aetiology and pathogenesis, to investigate arginine-metabolising enzymes and their intimate association with amyloid peptides.

Methods

Neuronal nitric oxide synthase (nNOS) was isolated, purified and shown, through fluorescence quenching spectroscopy and fluorescence resonance energy transfer (FRET), to interact with structural fragments of Aβ_1–40 and be catalytic towards amyloid fibril formation.

Results

Only one binding site on the enzyme was available for binding. Two amyloid peptide fragments of Aβ_1–40 (Aβ_17–28 and Aβ_25–35) had Stern–Volmer values (K_SV) of 0.111 μM⁻¹ and 0.135 μM⁻¹ indicating tight binding affinity to nNOS and easier accessibility to fluor molecules during binding. The polarity of this active site precludes binding of the predominantly hydrophobic amyloid peptide fragments contained within Aβ_17–28 and within two glycine zipper motifs [G-X-X-X-G-X-X-X-G] [Aβ_29–37] and bind to the enzyme at a site remote to the active region.

Conclusions

The interaction and binding of Aβ_17–28 and Aβ_25–35 to nNOS causes the movement of two critical tryptophan residues of 0.77 nm and 0.57 nm respectively towards the surface of the enzyme.

General significance

The binding of Aβ-peptide fragments with nNOS has been studied by spectrofluorimetry. The information and data presented should contribute towards understanding the mechanism for deposition of aggregated Aβ-peptides and fibrillogenesis in senile plaques in an AD brain.