Water relations in grassland and desert ecosystems exposed to elevated atmospheric CO2

Atmospheric CO₂ enrichment may stimulate plant growth directly through (1) enhanced photosynthesis or indirectly, through (2) reduced plant water consumption and hence slower soil moisture depletion, or the combination of both. Herein we describe gas exchange, plant biomass and species responses of five native or semi-native temperate and Mediterranean grasslands and three semi-arid systems to CO₂ enrichment, with an emphasis on water relations. Increasing CO₂ led to decreased leaf conductance for water vapor, improved plant water status, altered seasonal evapotranspiration dynamics, and in most cases, periodic increases in soil water content. The extent, timing and duration of these responses varied among ecosystems, species and years. Across the grasslands of the Kansas tallgrass prairie, Colorado shortgrass steppe and Swiss calcareous grassland, increases in aboveground biomass from CO₂ enrichment were relatively greater in dry years. In contrast, CO₂-induced aboveground biomass increases in the Texas C₃/C₄ grassland and the New Zealand pasture seemed little or only marginally influenced by yearly variation in soil water, while plant growth in the Mojave Desert was stimulated by CO₂ in a relatively wet year. Mediterranean grasslands sometimes failed to respond to CO₂-related increased late-season water, whereas semiarid Negev grassland assemblages profited. Vegetative and reproductive responses to CO₂ were highly varied among species and ecosystems, and did not generally follow any predictable pattern in regard to functional groups. Results suggest that the indirect effects of CO₂ on plant and soil water relations may contribute substantially to experimentally induced CO₂-effects, and also reflect local humidity conditions. For landscape scale predictions, this analysis calls for a clear distinction between biomass responses due to direct CO₂ effects on photosynthesis and those indirect CO₂ effects via soil moisture as documented here.     

Effects of anions and/or cell volume on the permeance of an apical water pathway induced by Hg in toad skin epithelium

Hg compounds block membrane transport units behaving as water channels. Here we show that Hg induces an apical water pathway in toad skins pretreated with 10^–3 M CH₃ClHg or HgCl₂, added to the outer bathing medium. Washing with SO₄-Ringer caused a several-fold increase in net water flow (J _w ) and osmotic permeability coefficient (P _f ) that was reversed by re-exposure to Cl- or NO₃-Ringer and mimicked by gluconate-Ringer. These P _f changes could be elicited repeatedly and were present if, and only if, anion replacements took place in the inner bathing solution. Such inner polarity was related to the anion permeability of the epidermal basolateral membrane: impermeant anions (SO₄, gluconate) increased P _f ; permeant anions (Cl, NO₃) did not change basal P _f but reversed the high P _f induced by impermeant anions. Hg induced the appearance of aggregates that persisted despite repeated washings of the skins during 4–5 h, and whether P _f was high (SO₄-Ringer) or low (Cl-Ringer) before skin fixation.The Hg-induced apical water pathway in toad skin appears to be a unique model for studying the interplay between cell volume, cell ionic composition and water permeability.We thank P. Brawand and P. Fruleux for technical assistance. This work has been supported by grants from the Swiss National Science Foundation (Nos. 31-30030.90 to A.G. and R.C.dS., and 32-34090.92 to P.M.)     

Immunohistochemical expression of HGF, c-MET and transcription factor STAT3 in colorectal tumors

By immunohistochemistry, we have investigated the expression of hepatocyte growth factor (HGF), HGF-R or c-met and the transcritor factor STAT3 in a series of 80 colorectal tumours (40 adenomas and 40 adenocarcinomas). The expression of HGF, c-met and STAT3 was revealed in 40/40 (100%) of adenomas and in 26/40 (65%) of adenocarcinomas; the remaining 14/40 (35%) carcinomas expressed c-met but failed to express HGF and STAT3. Positive immunoreaction score was defined through the number of stained cells: low (1-10%), moderate (11-50%) and high (>51%). In adenomas, the HGF immunoreaction was high in 33 (82.5%) and moderate in 7 (17.5%); the c-met staining was high in 3 (7.5%) and moderate in 37 (92.5%); and the STAT3 reactivity was high in 25 (62.5%) and moderate in 15(37.5%). In carcinomas, the HGF immunoreaction was moderate in 21 (80.7%) and low in 5 (19.2%); the c-met staining was high in 14 (35%), moderate in 25 (62.5) and low in 1 (2.5%); and the STAT3 reactivity was moderate in 17 (65.3%) and low in 9 (34.6%). In both type of lesions, HGF and c-met showed a membranous and cytoplasmic location. In adenomas, STAT3 was detected in cytoplasm and nucleus and in carcinomas it was limited to cytoplasm. While the HGF/c-met/STAT3 expression in adenomas was significantly different from carcinomas (c2 = 17, p < 0.0001), no correlation was found among HGF, c-met, or STAT3 immunostaining with histotype or degree of dysplasia in adenomas and the same for histotype, grading or staging in carcinomas. These features, suggesting a role of the HGF/c-met/STAT3 signal in colon tumorigenesis, indicate that a reduced expression of HGF and c-met is associated to progression of adenoma into carcinoma.     

Mesopelagic N2 Fixation Related to Organic Matter Composition in the Solomon and Bismarck Seas (Southwest Pacific)

Dinitrogen (N₂) fixation was investigated together with organic matter composition in the mesopelagic zone of the Bismarck (Transect 1) and Solomon (Transect 2) Seas (Southwest Pacific). Transparent exopolymer particles (TEP) and the presence of compounds sharing molecular formulae with saturated fatty acids and sugars, as well as dissolved organic matter (DOM) compounds containing nitrogen (N) and phosphorus (P) were higher on Transect 1 than on Transect 2, while oxygen concentrations showed an opposite pattern. N₂ fixation rates (up to ~1 nmol N L^-1 d^-1) were higher in Transect 1 than in Transect 2, and correlated positively with TEP, suggesting a dependence of diazotroph activity on organic matter. The scores of the multivariate ordination of DOM molecular formulae and their relative abundance correlated negatively with bacterial abundances and positively with N₂ fixation rates, suggesting an active bacterial exploitation of DOM and its use to sustain diazotrophic activity. Sequences of the nifH gene clustered with Alpha-, Beta-, Gamma- and Deltaproteobacteria, and included representatives from Clusters I, III and IV. A third of the clone library included sequences close to the potentially anaerobic Cluster III, suggesting that N₂ fixation was partially supported by presumably particle-attached diazotrophs. Quantitative polymerase chain reaction (qPCR) primer-probe sets were designed for three phylotypes and showed low abundances, with a phylotype within Cluster III at up to 10³ nifH gene copies L^-1. These results provide new insights into the ecology of non-cyanobacterial diazotrophs and suggest that organic matter sustains their activity in the mesopelagic ocean.     

Identification of carbapenem‐resistant Acinetobacter baumannii clones using infrared spectroscopy

In this work we assessed the discriminatory ability of Fourier‐transform Infrared Spectroscopy (FTIR) in 22 representative isolates from a collection of 318 carbapenem‐hydrolyzing class D β ‐lactamases (CHDL)‐producing Acinetobacter spp. (5 hospitals; 2001–2008) previously characterized by DNA‐based typing methods. FTIR spectra were acquired with a Bruker spectrometer and analyzed with support of several chemometric tools. The results showed that FTIR spectroscopy was able to distinguish the main CHDL‐producing Acinetobacter baumannii lineages causing infection in Portugal, the ST103 carrying bla_OXA‐58, ST98 carrying bla_OXA‐24/40and ST92 carrying bla_OXA‐23. Moreover, this study revealed distinctive phenotypic features of A. baumannii lineages causing infections that might justify different epidemic potential. Spectroscopy may arise as a low cost and easily to perform alternative for typing A. baumannii isolates. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Role of Omega-3 Fatty Acids in the Treatment of Depressive Disorders: A Comprehensive Meta-Analysis of Randomized Clinical Trials

Background

Despite omega-3 polyunsaturated fatty acids (PUFA) supplementation in depressed patients have been suggested to improve depressive symptomatology, previous findings are not univocal.

Objectives

To conduct an updated meta-analysis of randomized controlled trials (RCTs) of omega-3 PUFA treatment of depressive disorders, taking into account the clinical differences among patients included in the studies.

Methods

A search on MEDLINE, EMBASE, PsycInfo, and the Cochrane Database of RCTs using omega-3 PUFA on patients with depressive symptoms published up to August 2013 was performed. Standardized mean difference in clinical measure of depression severity was primary outcome. Type of omega-3 used (particularly eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) and omega-3 as mono- or adjuvant therapy was also examined. Meta-regression analyses assessed the effects of study size, baseline depression severity, trial duration, dose of omega-3, and age of patients.

Results

Meta-analysis of 11 and 8 trials conducted respectively on patients with a DSM-defined diagnosis of major depressive disorder (MDD) and patients with depressive symptomatology but no diagnosis of MDD demonstrated significant clinical benefit of omega-3 PUFA treatment compared to placebo (standardized difference in random-effects model 0.56 SD [95% CI: 0.20, 0.92] and 0.22 SD [95% CI: 0.01, 0.43], respectively; pooled analysis was 0.38 SD [95% CI: 0.18, 0.59]). Use of mainly EPA within the preparation, rather than DHA, influenced final clinical efficacy. Significant clinical efficacy had the use of omega-3 PUFA as adjuvant rather than mono-therapy. No relation between efficacy and study size, baseline depression severity, trial duration, age of patients, and study quality was found. Omega-3 PUFA resulted effective in RCTs on patients with bipolar disorder, whereas no evidence was found for those exploring their efficacy on depressive symptoms in young populations, perinatal depression, primary disease other than depression and healthy subjects.

Conclusions

The use of omega-3 PUFA is effective in patients with diagnosis of MDD and on depressive patients without diagnosis of MDD.     

Effects of the invasive duckweed Lemna minuta on aquatic animals: evidence from an indoor experiment

Abstract

Since effects of alien invasive free-floating plants can be relevant in aquatic ecosystems, we investigated the non-native Lemna minuta impact on four aquatic animal groups: Hydra vulgaris (Coelenterates), Asellus aquaticus (Arthropods), Gambusia affinis (Fish), Bufo bufo tadpoles (Amphibians). An indoor experiment was conducted keeping animals in water held in tanks with L. minuta mats of 0.5 (WI1), 1.5?cm thick (WI2) and without mats (WOU). Water parameters (DO, DO%, pH) and animal responses (survival rate, vitality) were measured every 48?h (0–288?h). Treatments with mats showed significant impacts on animals which were more severe with increasing mat thickness. Strong decreasing of oxygen and pH associated with mat occurrence had a large impact on animals. In WI2 all individuals died within 144?h (H. vulgaris, B. bufo within 96h), while in WI1 there was a higher survival rate and vitality (excluding B. bufo died within 96?h) and in WOU no deaths. This evidence suggests L. minuta thick mats (≥1.5?cm) could have a high impact on animal biodiversity, especially reducing oxygenation level in aquatic ecosystem.