Propionate is not an important regulator of plasma leptin concentration in dairy cattle

Propionate was recently shown to increase leptin synthesis in rodents. To determine if a similar effect occurs in ruminants, propionate was administered to lactating dairy cows. In experiment 1, 31 cows were given an intrajugular Na propionate bolus (1,040 micromol/kg body weight), increasing plasma propionate from 160 to 5,680 microM and plasma insulin from 6.8 to 77.8 microIU/mL. Plasma leptin concentration decreased from 2.11 ng/mL before bolus to 1.99 ng/mL after dosing (P<0.05) with no differences in leptin concentrations at 20, 50, and 100 min post-bolus (P>0.10). In experiment 2, 12 cows were used in a duplicated 6 x 6 Latin square experiment to assess the dose-response effect of ruminal propionate infusion on plasma leptin concentration. Sodium propionate was infused at rates of 0, 260, 520, 780, 1040, or 1,300 mmol/h, while total short-chain fatty acid infusion rate was held constant at 1,300 mmol/h by addition of Na acetate to the infusate. Coccygeal blood was sampled following 18 h of infusion. Increasing the rate of propionate infusion linearly increased plasma propionate concentration from 180 to 330 microM (P<0.001) and plasma insulin concentration from 6.7 to 9.1 microIU/mL (P<0.05). There was a quadratic response in plasma leptin concentration (P=0.04) with a maximum at 780 mmol/h propionate, but leptin concentrations increased by no more than 8% relative to the 0 mmol/h propionate infusion. Leptin concentrations were correlated with insulin concentrations but not with propionate concentrations in plasma. Propionate is not a physiological regulator of leptin secretion in lactating dairy cows.     

Ectomycorrhizal fungi affect the physiological responses of Picea glauca and Pinus banksiana seedlings exposed to an NaCl gradient

We tested the effects of ectomycorrhizal (ECM) inoculation on greenhouse-grown white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana L.) seedlings to be used for revegetation of salt-affected tailing sands resulting from the exploitation of oil sand in northeastern Alberta, Canada. White spruce and jack pine seedlings were inoculated with three ECM fungi selected for their in vitro tolerance to excess Na+ and Cl-: Hebeloma crustuliniforme (Bull) Quel. UAMH 5247, Laccaria bicolor Maire (Orton) UAMH 8232 and a Suillus tomentosus (Kauff.) Sing., Snell and Dick isolate from a salt-affected site. The physiological responses of the seedlings to a gradient of NaCl concentration (0, 50, 100 and 200 mM) were assessed over four weeks by: (1) Na+ accumulation and allocation; (2) chlorophyll a fluorescence; (3) growth, (4) water content; and (5) organic osmolyte accumulation. Jack pine seedlings were more sensitive than white spruce seedlings to increasing Na+ and Cl- concentrations. Both species showed decreasing biomass accumulation, and increasing concentrations of organic osmotica and Na with increasing NaCl concentration. White spruce seedlings inoculated with the S. tomentosus isolate had the best growth response at all NaCl concentrations tested. Although jack pine seedlings inoculated with the L. bicolor or S. tomentosus isolate exhibited the highest growth in the 50 and 100 mM NaCl treatments, both fungi increased the photochemical stress and dehydration of their hosts in the 200 mM NaCl treatment. At the latter concentration, jack pine seedlings inoculated with H. crustuliniforme showed the greatest tolerance to salt stress. Although the different fungi altered the physiological response of the host in different ways, inoculation with salt-stress-tolerant ECM fungi increased growth and reduced the negative effects of excess NaCl. Use of controlled mycorrhization may increase survival of coniferous seedlings used for revegetation of salt-affected sites.     

Large‐scale,seasonal habitat use and movements of yellow American eels in the St. Lawrence River revealed by acoustic telemetry

Large‐scale habitat use and movements of yellow American eels (Anguilla rostrata) from the St. Lawrence River were examined using acoustic telemetry from early summer to late fall in 2010 and 2011. Sixty‐seven eels were tagged, and their passage or presence was recorded using fixed acoustic arrays covering a 400 km distance along the St. Lawrence River and Estuary. Sixty‐four per cent of the 67 tagged eels were detected. Most eels were detected at only one array; the closest to their release location and at several occasions during the tracking period, suggesting a high proportion of freshwater residency in the upstream part of the St. Lawrence River. Downstream movements towards the brackish estuary (63–418 km distance) were demonstrated for 16.4% of the eels, particularly for those caught at the most downstream site that is close to the brackish estuary. Our results strongly suggest a lower activity of freshwater resident yellow eels during summer, a behaviour that may be related to day length, which defines time available for their nocturnal foraging. Indeed, yellow eels were detected primarily at night; no effect of moon phase was revealed. Movements in the vicinity of arrays (up to 116 km in the fluvial estuary) were suggested and smaller‐scale movements within Lac St. Louis were demonstrated, highlighting a yellow‐eel home range far more extensive than previously reported in smaller systems. Evidence for within‐season homing and site fidelity is also reported.     

Variation in cell wall composition among forage maize (Zea mays L.) inbred lines and its impact on digestibility: analysis of neutral detergent fiber composition by pyrolysis-gas chromatography-mass spectrometry

Cell wall digestibility is an important determinant of forage quality, but the relationship between cell wall composition and digestibility is poorly understood. We analyzed the neutral detergent fiber (NDF) fraction of nine maize inbred lines and one brown midrib3 mutant with pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). Among 29 pyrolysis fragments that were quantified, two carbohydrate-derived and six lignin-derived fragments showed statistically significant genetic variation. The pyrolysis products 4-vinyl phenol and 2,6-dimethoxy-4-vinyl phenol were negatively correlated with digestibility, whereas furfural and 3-(4-hydroxyphenyl)-3-oxopropanal showed a positive correlation with digestibility. Linear discriminant analysis of the pyrolysis data resulted in the resolution of groups of inbred lines with different digestibility properties based on their chemical composition. These analyses reveal that digestibility is governed by complex interactions between different cell wall compounds, but that several pyrolysis fragments can be used as markers to distinguish between maize lines with different digestibility.     

A simple dose-effect model of lake acidity in Québec (Canada)

A simple dose-effect model expressing the relationships between lake acidity, weighted mean annual sulfate concentration in wet deposition, Ca, Mg and true color (as an index of organic anion concentration) is presented. The agreement between observed and estimated pH for more than a 1000 lakes is high according to the Pearson coefficients of correlation (0.81 to 0.90) and the standard error of estimation (0.22 to 0.27 pH unit). Results obtained with this model show that an airborne sulfate target loading of 20 kg ha^?1 yr^?1 would be too high to adequately protect sensitive lake ecosystems. A target loading of 15 kg ha^?1 yr^?1 in wet deposition would be best suited for the protection of the greater portion of sensitive lakes. However, a target loading of 10 kg ha^?1 yr^?1 would be required to protect the most sensitive lake ecosystems.     

Radiolysis of quercetin in methanol solution: observation of depside formation

Radiolysis of the flavonol quercetin, a natural antioxidant, was performed in methanol. The degradation process was followed by HPLC analyses. The major product was identified as a depside (Q1) by NMR and LC-MS. The G(Q1) radiolytic factor was plotted versus the initial concentration of quercetin. This radiolytic process was attributed to the CH3O* radicals presented in the irradiated medium. The proposed mechanism invoked a stereospecific oxidation of the 3-hydroxyl group of quercetin which led to C-ring opening and to the formation of the depside Q1. In presence of water, Q1 was transformed into another depside, Q2, by an inverse esterification reaction. A chemical equilibrium was observed between Q1 and Q2. The comprehension of the radiolytic process of quercetin in methanol solution is of importance. Indeed, the same type of oxidative reactions could occur on flavonoids during preservation of food by ionizing radiation.     

Fractionation of beta-lactoglobulin tryptic peptides by ampholyte-free isoelectric focusing.

Solutions of tryptic hydrolysate of bovine beta-lactoglobulin were fractionated by liquid-phase IEF in a preparative Rotofor cell at constant power for 2 h without ampholytes in order to identify interactions between peptides. The 20 peptide fractions collected were analyzed by capillary electrophoresis and SDS-PAGE under native, denaturing, and reducing conditions. The hydrolysate was shown to be composed mainly of acidic peptides (pI 2-5, 62%) of molecular mass below 6 kDa, and numerous disulfide bonds were detected. Purified peptides (beta-LG 15-20, 71-75, 76-82, and 84-91) were also focused individually and in mixtures and matched to components of the IEF fractions obtained from the tryptic hydrolysate of beta-LG. The separation of acidic (beta-LG 84-91) and basic (beta-LG 76-82) peptides was achieved by IEF, whereas uncharged peptides (beta-LG 15-20 and 71-75) were poorly separated due to their low electrophoretic mobility. Because no peptide-peptide interaction could be identified by IEF fractionation, it is suggested that electrical fields may decrease electrostatic interactions between charged peptides.     

Co-inoculation of Acacia mangium with Glomus intraradices and Bradyrhizobium sp. in aeroponic culture

Acacia mangium grown in aeroponic culture was co-inoculated with selected strains of Bradyrhizobium sp. and Glomus intraradices. A single-step technique using alginate as an embedding and sticking agent for an inoculum composed of arbuscular mycorrhiza (AM)-infected sheared roots was used to infect plants. This method resulted in the successful establishment of AM in 100% of the inoculated plants after 7 weeks. The results indicated that dual microbial inoculation with Glomus intraradices strain S-043 and Bradyrhizobium strain AUST 13C stimulated the growth of A. mangium in aeroponic culture. The effects of single and dual microbial inoculations were also evaluated at two levels of P in the nutrient medium. A concentration of 5 mg P kg^–1 stimulated the development of AM without affecting plant development or establishment of Bradyrhizobium symbiosis. In contrast, saplings supplemented with a higher concentration of P (25 mg kg^–1) alone or co-inoculated with Bradyrhizobium had lower AM frequencies.     

Gallic esters of sucrose as efficient radical scavengers in lipid peroxidation

Three tests of increasing complexity were used to assess the antioxidant activity of five synthetic gallic esters of sucrose bearing 3, 6, 7, or 8 galloyl units. In addition, two of these compounds had 1 or 2 hydrocarbon (C10-C12) acyl chains. Reaction with the DPPH radical led to the evaluation of the number of radicals trapped per galloyl unit n (3-4), as well as the apparent second-order rate constant for H atom donation k (1200-1500/M/s). These results indicated similar contribution and reactivity of all the galloyl units. Inhibition of the AAPH-initiated peroxidation of linoleic acid in a micellar medium confirmed the additive contribution of the galloyl units, whereas the presence of the hydrocarbon acyl chains had no influence. These results suggest an inhibition of initiation at high antioxidant levels and an underlying prooxidant effect of the galloyl radicals at low concentrations. Finally, LDL peroxidation was inhibited in proportion to the number of galloyl units, in agreement with the preceding tests.     

Effects of tillage and fallow period management on soil physical behaviour and maize development

Effects of two tillage treatments and two fallow period managements under continuous maize cropping on soil temperature, soil water dynamics and maize development were evaluated over a 4-year period (2005–2008). Tillage treatments were conventional tillage with mouldboard ploughing and conservation tillage with disk harrowing. The fallow period managements were bare soil or soil sown with a cover crop after maize harvest. For each year, topsoil temperature (0–20 cm-depth) was lower under conservation tillage systems at sowing, from 0.8 to 2.8 °C. This difference persisted several weeks after sowing, and disappeared afterwards. Under conservation tillage, higher soil water content was generally measured at sowing and during the growing season strong fluctuations were observed at 40 cm-depth. Under conventional tillage, soil water content varied mainly in the tilled layer (20 cm-depth). Tillage and fallow period management affected water flow rate at 40 cm-depth. During the maize growing season, the lowest drainage volumes were measured in 2006 and 2008 under conservation tillage in cover cropped plots. No effect of fallow period management on maize development and yield was observed but significantly higher yields were measured under conservation tillage in 2005 and 2007. From this 4-year experiment under continuous maize cropping, using cover crop and reducing tillage intensity enhanced water use efficiency while maintaining or increasing maize yields.