Evaluation of air oxidized PAPC: A multi laboratory study by LC-MS/MS

Oxidized LDL (oxLDL) has been shown to play a crucial role in the onset and development of cardiovascular disorders. The study of oxLDL, as an initiator of inflammatory cascades, led to the discovery of a variety of oxidized phospholipids (oxPLs) responsible for pro-inflammatory actions. Oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PAPC) is frequently used by the scientific community as a representative oxPL mixture to study the biological effects of oxidized lipids, due to the high abundance of PAPC in human tissues and the biological activities of oxidized arachidonic acids derivatives. Most studies focusing on oxPAPC effects rely on in-house prepared mixtures of oxidized species obtained by exposing PAPC to air oxidation. Here, we described a multi-laboratory evaluation of the compounds in oxPAPC by LC-MS/MS, focusing on the identification and relative quantification of the lipid peroxidation products (LPPs) formed. PAPC was air-oxidized in four laboratories using the same protocol for 0, 48, and 72 h. It was possible to identify 55 different LPPs with unique elemental composition and characterize different structural isomeric species within these. The study showed good intra-sample reproducibility and similar qualitative patterns of oxidation, as the most abundant LPPs were essentially the same between the four laboratories. However, there were substantial differences in the extent of oxidation, i.e. the amount of LPPs relative to unmodified PAPC, at specific time points. This shows the importance of characterizing air-oxidized PAPC preparations before using them for testing biological effects of oxidized lipids, and may explain some variability of effects reported in the literature

Air Temperature and Humidity at the Bottom of Desert Wolf Spider Burrows Are Not Affected by Surface Conditions

Burrows are animal-built structures that can buffer their occupants against the vagaries of the weather and provide protection from predators. We investigated whether the trapdoors of wolf spider (Lycosa sp.; temporary working name "L. hyraculus") burrows in the Negev Desert serve to maintain favorable environmental conditions within the burrow by removing trapdoors and monitoring the ensuing temperature and relative humidity regime within them. We also monitored the behavioral responses of “L. hyraculus” to trapdoor removal at different times of the day and in different seasons. “L. hyraculus” often spun silk mesh in their burrow entrances in response to trapdoor removal during the day, possibly to deter diurnal predators. The frequency of web-spinning peaked on summer mornings, but spiders began spinning webs sooner after trapdoor removal later in the day. In addition, we monitored temperature and relative humidity in artificial burrows in the summer during the morning and at midday. At noon, air temperature (Ta) at the bottom of open burrows increased by <1 °C more than in covered burrows, but water vapor pressure in burrows did not change. The relatively small increase in Ta in uncovered burrows at midday can probably be ascribed to the penetration of direct solar radiation. Thus, air temperature and humidity at the bottom of the burrow are apparently decoupled from airflow at the surface

The effect of brackish water irrigation on the above- and below-ground development of pollarded Acacia saligna shrubs in an arid environment

The regrowth capacity after pollarding of a short-rotation plantation of Acacia saligna (Labill.) H. Wendl. was investigated in a field trial. This shrub has been proposed as a provider of biomass (fuelwood and fodder) in an arid environment, using local marginal water resources such as surface runoff and brackish groundwater. The specific objective of this study was to examine the effects of water quality, irrigation frequency and annual runoff flooding on the above- and belowground development of the pollarded shrubs. Treatments consisted of drip-irrigation with freshwater or brackish water, at low (twice a month) or high (weekly) frequency, with or without annual freshwater flooding, and on a well-watered basis (twice a week) without flooding. Each 15x5 m(2) plot contained four rows of four shrubs. After 5 years of growth, the shrubs were pollarded to a height of 1.5 m and during the subsequent year of regrowth, root development was monitored non-destructively using the minirhizotron, shoot growth was estimated from trunk cross-sectional area and allometric equations (obtained at the end of the measuring period by measurements and destructive sampling), and plant water status was monitored by measuring pre-dawn leaf water potential. Dry fodder (leaves and thin branches) production was between 3.50 and 9.75 t ha(-1) and dry wood was between 3.50 and 15.50 t ha(-1). The highest biomass production was obtained in the well-watered freshwater treatment, which also had the highest number of roots and highest predawn leaf water potential throughout the year. Shrubs irrigated with brackish water at low frequency without supplemental flooding produced the lowest yields. Water quality significantly affected shoot development only in the well-watered treatments although root development was reduced wherever brackish water was applied. Flooding the plots with freshwater once a year led to an increase in the number of roots outside the drip-irrigation zone, especially in brackish water treatments. A continued root growth with time was observed in all treatments even though the shoots were pollarded. In fact total root increments and aboveground biomass production were positively linearly related. Moreover the linear response of shoot and root increments to increasing water availability and not to water quality suggests that irrigation frequency was the main factor determining the regrowth capacity and amount of above- and belowground biomass production. Based on the above, runoff water and brackish groundwater could be used in a complementary manner for the sustainable production of fuelwood and fodder in a short-rotation plantation of this shrub

Pruning of Acacia salicina trees irrigated with runoff water in arid zones

In arid and semi arid lands, forest and agricultural productions are declining due to water scarcity and drought. The objective of this study was to determine the effects of shoot pruning at different heights of acacia salicina lindl, grown in the Israeli Negev Desert and irrigated with runoff water. The specific objectives of this study were to examine the most appropriate pruning height, growth rate and biomass production, water use efficiency of A. salicina shrubs irrigated with floodwater and the water uptake rate and soil water content change at the different pruning height treatments. The trees were planted in 1993 in a 0.5 ha plot at a design of 1m between trees within the rows and 4 m between rows (1,250 trees ha-1). The trees were pruned at a height of 0.5m, 1.0m and 2.0m above soil surface and were compared to non-pruned trees (NP treatment, served as control treatment). Measurements of trunk diameter at a height of 0,3 m above soil surface, re-growth of new branches and soil water uptake by trees, using a neutron moisture gauge that has been previously calibrated in the field), were take every two weeks. Three pruning were carried out during the two years of the experiment. The first pruning was at the beginning of the experiment in March 2003, the second one in December 2003 and the third one in October 2004. Biomass measurements were taken after the second and the third pruning. A non-destructive biomass evaluation was carried out to the NP treatment by using a linear regression of cross Sectional Area (CSA) of trunk versus biomass yield developed from an adjacent plot of A. salicina of the same age. The results of the experiment indicate that more biomass was obtained from the 2,0 m pruning treatment followed by the 1,0 m. Water Use Efficiency had the same pattern. Under the condition of this experiment, the most appropriate pruning height for A salicina trees irrigated with floodwater is 2, 0 m

Above and below ground development of Acacia saligna shrubs grown under different irrigation frequencies in an arid environment

Many arid and semiarid areas of the world remain barren due to the lack of water even though the use of ephemeral local water sources, such as runoff water, could change the biomass production patterns. The objective of the present study was to determine the effects of levels of water application and modes of application on the biomass below and above ground development of mature Acacia saligna (Labill.) H.L. Wendl. shrubs. The application treatments were: flooded once a year, low and high frequency irrigation with and without an additional annual flooding, and well-watered. An analysis of the standing biomass data after 5 years of growth indicated that the yearly runoff floods contributed significantly to increase the total above ground biomass. The data collected during the 1999 season, indicated however that during this season flooding had no significant effect on any of the measured growth parameters, while application frequency had a significant effect on the growth rates, water use efficiency and leaf and stem production of shrubs. Below ground, two periods of root growth were observed for the higher irrigation frequency treatments: an initial moderate increase followed by a rapid reduction. The period of rapid reduction in root biomass matched well with the period of rapid increments in above ground biomass production. Furthermore, increased irrigation frequencies resulted in bigger root systems but for lower irrigation frequencies rooting depth increased

Validation and scale dependencies of the triangle method for the evaporative fraction estimation over heterogeneous areas

Remote sensing has proved to be a consistent tool for monitoring water fluxes at regional scales. The triangle method, in particular, estimates the evaporative fraction (EF), defined as the ratio of latent heat flux (LE) to available energy, based on the relationship between satellite observations of land surface temperature and a vegetation index. Among other methodologies, this approach has been commonly used as an approximation to estimate LE, mainly over large semi-arid areas with uniform landscape features. In this study, an interpretation of the triangular space has been applied over a heterogeneous area in central Spain, using Landsat5-TM, Envisat-AATSR/MERIS and MSG-SEVIRI images. Some aspects affecting the model performance such as spatial resolution, terrain conditions, vegetation index applied and method for deriving the triangle edges have been assessed. The derived EF estimations have been validated against ground measurements obtained with scintillometer on a winter crop field during 2010–2011. When working with large spatial windows, removing areas with different topographic characteristics (altitude and slope) improved the performance of the methods. In addition, replacing the typically used NDVI with Leaf Area Index enhances the performance of the triangle method allowing a better characterization of the wet edge. Finally, results showed a relatively good performance for the EF estimates, with an RMSE of 0.11, 0.15 and 0.23 and R2 of 0.77, 0.41, and 0.24 for Landsat, Envisat and MSG satellites respectively, showing a scale dependency on the accuracy.This research was initialized during a visiting stay at the Department of Geosciences and Natural Resource Management of the University of Copenhagen, Denmark, thanks to a grant within the BACH project funded by IMDEA Water Institute. This study is likewise part of the INTEGRATOR Project (CTM2011-27657) funded by the Spanish Ministry of Science and Innovation.Peer reviewe