The effects of heating,rhizosphere, and depth on root litter decomposition are mediated by soil moisture

The breakdown and decomposition of plant inputs are critical for nutrient cycling, soil development, and climate-ecosystem feedbacks, but uncertainties persist in how the rates and products of litter decomposition are affected by soil temperature, rhizosphere, and depth of input. We investigated the effects of soil warming (+ 4 °C), rhizosphere, and depth of litter placement on the decomposition of Avena fatua (wild oat grass) root litter in a Mediterranean grassland ecosystem. Field lysimeters were subjected to three environmental treatments (heating, control, and plant removal) and three ¹³C-labeled root litter addition treatments (to A horizon, to B horizon, and no-addition disturbance control) for each of two harvest time points. We buried root litter in February 2014 and measured loss of ¹³C in CO₂ from the soil surface and in leachate as dissolved organic carbon (DOC) over two growing seasons. At the end of each growing season we recovered the ¹³C remaining in the soil. Loss of root litter C occurred almost entirely via heterotrophic respiration, with an estimated < 2% lost as DOC during the initial decay period. The added roots were broken down and incorporated into bulk soil material very quickly; only ~ 30% of added root was visible after 6 months. In the first growing season, decomposition occurred faster in the B than in the A horizon, the latter having greater moisture limitation. Subsequently, there was almost no further decomposition in the B horizon. After two growing seasons, less than 20% of the added root litter C remained in the A or B horizons of all environmental treatments. Heating did not stimulate decomposition, likely because it exacerbated the moisture limitation. However, while plots without plants dried down more slowly than plots with plants, their decomposition rate was not significantly greater, possibly due to the lack of rhizosphere processes such as priming. We conclude that in this Mediterranean grassland ecosystem, soil moisture, which is affected by season, depth, heating, and rhizosphere, plays a dominant role in mediating the effect of those factors on root litter decomposition, which after two seasons did not differ by depth or by treatment.     

Multiple models and experiments underscore large uncertainty in soil carbon dynamics

Soils contain more carbon than plants or the atmosphere, and sensitivities of soil organic carbon (SOC) stocks to changing climate and plant productivity are a major uncertainty in global carbon cycle projections. Despite a consensus that microbial degradation and mineral stabilization processes control SOC cycling, no systematic synthesis of long-term warming and litter addition experiments has been used to test process-based microbe-mineral SOC models. We explored SOC responses to warming and increased carbon inputs using a synthesis of 147 field manipulation experiments and five SOC models with different representations of microbial and mineral processes. Model projections diverged but encompassed a similar range of variability as the experimental results. Experimental measurements were insufficient to eliminate or validate individual model outcomes. While all models projected that CO₂ efflux would increase and SOC stocks would decline under warming, nearly one-third of experiments observed decreases in CO₂ flux and nearly half of experiments observed increases in SOC stocks under warming. Long-term measurements of C inputs to soil and their changes under warming are needed to reconcile modeled and observed patterns. Measurements separating the responses of mineral-protected and unprotected SOC fractions in manipulation experiments are needed to address key uncertainties in microbial degradation and mineral stabilization mechanisms. Integrating models with experimental design will allow targeting of these uncertainties and help to reconcile divergence among models to produce more confident projections of SOC responses to global changes.     

Ischemia–Reperfusion Injury of Sciatic Nerve in Rats: Protective Role of Combination of Vitamin C with E and Tissue Plasminogen Activator

An ischemia/reperfusion injury of rat’s sciatic nerve was experimentally developed. In this model, we measured the in vivo production of superoxide radical, as a marker of oxidative stress and the occludin expression as an indicator of blood-nerve barrier function and we examined potential protective innervations against these abnormalities. Right sciatic nerves of the animals underwent 3 h of ischemia followed by 7 days of reperfusion and were divided into three groups: ischemic, pretreated with vitamin C in conjunction with vitamin E and treated with tissue plasminogen activator. Compared to measurements from left sciatic nerves used as sham, the ischemic group showed significantly increased superoxide radical and reduced expression of occludin in western blot and immunohistochemistry. No such differences were detected between sham and nerves in the vitamin or tissue plasminogen activator groups. It is suggested that the experimental ischemia/reperfusion model was suitable for studying the relationship between oxidative state and blood-nerve barrier. The reversion of abnormalities by the applied neuroprotective agents might prove to be a clinically important finding in view of the implication of vascular supply derangement in various neuropathies in humans.     

Laser Porosificated Silicon Anodes for Lithium Ion Batteries

This study presents the first laser porosificated silicon anode for lithium‐ion batteries. The pulsed laser induced pore creation improves the cycling stability of the d = 210 nm thick sputtered thin film anodes compared to plain Si. Galvanostatic cycling with a charge capacity limited to C = 932 mAh g^?1 and a 2C current rate shows a stable cycling for more than N = 600 cycles. After N = 3000 cycles the laser porosificated and crystallized Si has a remaining capacity of C₃₀₀₀ > 120 mAh g^?1. Postmortem scanning electron microscopy images after N = 3000 cycles prove that the laser porosification reduces cracks in the active layer.     

Application of methyl jasmonate to grey willow (<Emphasis Type="Italic">Salix cinerea</Emphasis>) attracts insectivorous birds in nature

It has been suggested that insectivorous birds may be guided by herbivore-induced plant volatiles (HIPVs) to herbivore-rich trees with herbivorous damage. The HIPV production in plants is partly mediated by jasmonic acid signalling pathway. Methyl jasmonate (MeJA) was proved to be a suitable agent for induction of HIPVs similar to those induced by herbivorous insects in many plant species. We studied the effects of methyl jasmonate on volatile emission and natural enemy attraction using mature grey willow (Salix cinerea) under natural conditions in Czech Republic. We treated 12 experimental shrubs with 30 mM MeJA and completed the experiment with 12 control shrubs. We monitored attacks by natural predators with artificial plasticine caterpillars which were checked daily. Birds most often pecked the caterpillars exposed on MeJA-treated shrubs and this attractiveness differed significantly from control. Attractiveness of MeJA-treated shrubs did not differ significantly from control shrubs for arthropod predators. Spraying MeJA on grey willows resulted in significantly higher production of α-pinene, β-pinene, 3-carene, limonene and β-ocimene. There was a marginally significant positive correlation between the predation rate by birds and relative change in α-pinene emissions.     

The RhoA pathway mediates MMP‐2 and MMP‐9‐independent invasive behavior in a triple‐negative breast cancer cell line

Breast cancer is a heterogeneous disease that varies in its biology and response to therapy. A foremost threat to patients is tumor invasion and metastasis, with the greatest risk among patients diagnosed with triple‐negative and/or basal‐like breast cancers. A greater understanding of the molecular mechanisms underlying cancer cell spreading is needed as 90% of cancer‐associated deaths result from metastasis. We previously demonstrated that the Tamoxifen‐selected, MCF‐7 derivative, TMX2‐28, lacks expression of estrogen receptor α (ERα) and is highly invasive, yet maintains an epithelial morphology. The present study was designed to further characterize TMX2‐28 cells and elucidate their invasion mechanism. We found that TMX2‐28 cells do not express human epidermal growth factor receptor 2 (HER2) and progesterone receptor (PR), in addition to lacking ERα, making the cells triple‐negative. We then determined that TMX2‐28 cells lack expression of active matrix metalloproteinases (MMPs)‐1, MMP‐2, MMP‐9, and other genes involved in epithelial–mesenchymal transition (EMT) suggesting that TMX2‐28 may not utilize mesenchymal invasion. In contrast, TMX2‐28 cells have high expression of Ras Homolog Gene Family Member, A (RhoA), a protein known to play a critical role in amoeboid invasion. Blocking RhoA activity with the RhoA pathway specific inhibitor H‐1152, or a RhoA specific siRNA, resulted in inhibition of invasive behavior. Collectively, these results suggest that TMX2‐28 breast cancer cells exploit a RhoA‐dependent, proteolytic‐independent invasion mechanism. Targeting the RhoA pathway in triple‐negative, basal‐like breast cancers that have a proteolytic‐independent invasion mechanism may provide therapeutic strategies for the treatment of patients with increased risk of metastasis. J. Cell. Biochem. 114: 1385–1394, 2013. © 2013 Wiley Periodicals, Inc.     

A Novel Method for the Culture and Polarized Stimulation of Human Intestinal Mucosa Explants

Few models currently exist to realistically simulate the complex human intestine''s micro-environment, where a variety of interactions take place. Proper homeostasis directly depends on these interactions, as they shape an entire immunological response inducing tolerance against food antigens while at the same time mounting effective immune responses against pathogenic microbes accidentally ingested with food.Intestinal homeostasis is preserved also through various complex interactions between the microbiota (including food-associated beneficial bacterial strains) and the host, that regulate the attachment/degradation of mucus, the production of antimicrobial peptides by the epithelial barrier, and the "education" of epithelial cells'' that controls the tolerogenic or immunogenic phenotype of unique, gut-resident lymphoid cells'' populations. These interactions have been so far very difficult to reproduce with in vitro assays using either cultured cell lines or peripheral blood mononuclear cells. In addition, mouse models differ substantially in components of the intestinal mucosa (mucus layer organization, commensal bacteria community) with respect to the human gut. Thus, studies of a variety of treatments to be brought in the clinics for important stress-related or pathological conditions such as irritable bowel syndrome, inflammatory bowel disease or colorectal cancer have been difficult to carry out.To address these issues, we developed a novel system that enables us to stimulate explants of human intestinal mucosa that retain their in situ conditioning by the host microbiota and immune response, in a polarized fashion. Polarized apical stimulation is of great importance for the outcome of the elicited immune response. It has been repeatedly shown that the same stimuli can produce completely different responses when they bypass the apical face of the intestinal epithelium, stimulating epithelial cells basolaterally or coming into direct contact with lamina propria components, switching the phenotype from tolerogenic to immunogenic and causing unnecessary and excessive inflammation in the area.We achieved polarized stimulation by gluing a cave cylinder which delimited the area of stimulation on the apical face of the mucosa as will be described in the protocol. We used this model to examine, among others, differential effects of three different Lactobacilli strains. We show that this model system is very powerful to assess the immunomodulatory properties of probiotics in healthy and disease conditions.     

Mechanisms of direct radiation damage in DNA, based on a study of the yields of base damage, deoxyribose damage, and trapped radicals in d(GCACGCGTGC)(2)

Dose-response curves were measured for the formation of direct-type DNA products in X-irradiated d(GCACGCGTGC)(2)prepared as dry films and as crystalline powders. Damage to deoxyribose (dRib) was assessed by HPLC measurements of strand break products containing 3' or 5' terminal phosphate and free base release. Base damage was measured using GC/ MS after acid hydrolysis and trimethylsilylation. The yield of trappable radicals was measured at 4 K by EPR of films X-irradiated at 4 K. With exception of those used for EPR, all samples were X-irradiated at room temperature. There was no measurable difference between working under oxygen or under nitrogen. The chemical yields (in units of nmol/J) for trapped radicals, free base release, 8-oxoGua, 8-oxoAde, diHUra and diHThy were G(total)(fr) = 618 +/- 60, G(fbr) = 93 +/- 8, G(8-oxoGua) = 111 +/- 62, G(8-oxoAde) = 4 +/- 3, G(diHUra) = 127 +/- 160, and G(diHThy) = 39 +/- 60, respectively. The yields were determined and the dose-response curves explained by a mechanistic model consisting of three reaction pathways: (1) trappable-radical single-track, (2) trappable-radical multiple-track, and (3) molecular. If the base content is projected from the decamer's GC:AT ratio of 4:1 to a ratio of 1:1, the percentage of the total measured damage (349 nmol/J) would partition as follows: 20 +/- 16% 8-oxoGua, 3 +/- 3% 8-oxoAde, 28 +/- 46% diHThy, 23 +/- 32% diHUra, and 27 +/- 17% dRib damage. With a cautionary note regarding large standard deviations, the projected yield of total damage is higher in CG-rich DNA because C combined with G is more prone to damage than A combined with T, the ratio of base damage to deoxyribose damage is approximately 3:1, the yield of diHUra is comparable to the yield of diHThy, and the yield of 8-oxoAde is not negligible. While the quantity and quality of the data fall short of proving the hypothesized model, the model provides an explanation for the dose-response curves of the more prevalent end products and provides a means of measuring their chemical yields, i.e., their rate of formation at zero dose. Therefore, we believe that this comprehensive analytical approach, combined with the mechanistic model, will prove important in predicting risk due to exposure to low doses and low dose rates of ionizing radiation.     

Heat- and light-induced reorganizations in the phycobilisome antenna of Synechocystis sp. PCC 6803. Thermo-optic effect

By using absorption and fluorescence spectroscopy, we compared the effects of heat and light treatments on the phycobilisome (PBS) antenna of Synechocystis sp. PCC 6803 cells. Fluorescence emission spectra obtained upon exciting predominantly PBS, recorded at 25 °C and 77 K, revealed characteristic changes upon heat treatment of the cells. A 5-min incubation at 50 °C, which completely inactivated the activity of photosystem II, led to a small but statistically significant decrease in the F₆₈₀/F₆₅₅ fluorescence intensity ratio. In contrast, heat treatment at 60 °C resulted in a much larger decrease in the same ratio and was accompanied by a blue-shift of the main PBS emission band at around 655 nm (F₆₅₅), indicating an energetic decoupling of PBS from chlorophylls and reorganizations in its internal structure. (Upon exciting PBS, F₆₈₀ originates from photosystem II and from the terminal emitter of PBS.). Very similar changes were obtained upon exposing the cells to high light (600-7500 μmol photons m⁻² s⁻¹) for different time periods (10 min to 3 h). In cells with heat-inactivated photosystem II, the variations caused by light treatment could clearly be assigned to a similar energetic decoupling of the PBS from the membrane and internal reorganizations as induced at around 60 °C. These data can be explained within the frameworks of thermo-optic mechanism [Cseh et al. 2000, Biochemistry 39, 15250]: in high light the heat packages originating from dissipation might lead to elementary structural changes in the close vicinity of dissipation in heat-sensitive structural elements, e.g. around the site where PBS is anchored to the membrane. This, in turn, brings about a diminishment in the energy supply from PBS to the photosystems and reorganization in the molecular architecture of PBS.