Alternate partial root-zone irrigation induced dry/wet cycles of soils stimulate N mineralization and improve N nutrition in tomatoes

Given the same amount of irrigation volume, applying alternate partial root-zone irrigation (PRI) has improved crop N nutrition as compared to deficit irrigation (DI), yet the mechanisms underlying this effect remain unknown. Therefore, the objective of this study was to investigate whether PRI induced soil dry/wet cycles facilitate soil organic N mineralization hereby contributing to the improvement of N nutrition in tomatoes. The plants were grown in split-root pots in a climate-controlled glasshouse and were subjected to PRI and DI treatments during early fruiting stage. ¹⁵N-labeled maize residues were incorporated into the soils. Results showed that PRI resulted in 25% higher net ¹⁵N mineralization than did DI, indicating that the enhanced mineralization of soil organic N alone could account for the 16% increase of N accumulation in the PRI than in the DI plants. The higher net N mineralization under PRI was coincided with an intensified soil microbial activity. In addition, even though soil chloroform fumigation labile carbon (CFL-C, as an index of microbial biomass) was similar for the two irrigation treatments, a significant increase of chloroform fumigation labile nitrogen (CFL-N) was found in the PRI wetting soil. Consequently, the C:N ratio of the chloroform fumigation labile pool was remarkably modified by the PRI treatment, which might indicate physiological changes of soil microbes or changes in labiality of soil organic C and N due to the dry/wet cycles of soils, altering conditions for net N mineralization. Moreover, in both soil compartments PRI caused significantly less extractable organic carbon (EOC) as compared with DI; whilst in the PRI wetting soil significantly higher extractable organic nitrogen (EON) was observed. A low EOC:EON ratio in the PRI wetting soil may indicate an increasing net mineralization of the organic N as a result of microbial metabolism. Conclusively, PRI induced greater microbial activity and higher microbial substrates availability are seemingly responsible for the enhanced net N mineralization and improved N nutrition in tomato plants.     

Overall charge and local charge density of pectin determines the enthalpic and entropic contributions to complexation with β-lactoglobulin

The complex formation between β-lactoglobulin and pectins of varying overall charge and local charge density were investigated. Isothermal titration calorimetry experiments were carried out to determine the enthalpic contribution to the complex formation at pH 4.25 and various ionic strengths. Complex formation was found to be an exothermic process for all conditions. Combination with previously published binding constants by Sperber et al. (Sperber, B. L. H. M.; Cohen Stuart, M. A.; Schols, H. A.; Voragen, A. G. J.; Norde, W. Biomacromolecules 2009, 10, 3246-3252) allows for the determination of the changes in the Gibbs energy and the change in entropy of the system upon complex formation between β-lactoglobulin and pectin. The local charge density of pectin is found to determine the balance between enthalpic and entropic contributions. For a high local charge density pectin, the main contribution to the Gibbs energy is of an enthalpic nature, supported by a favorable entropy effect due to the release of small counterions. A pectin with a low local charge density has a more even distribution of the enthalpic and entropic part to the change of the Gibbs energy. The enthalpic part is reduced due to the lower charge density, while the relative increase of the entropic contribution is thought to be caused by a change in the location of the binding place for pectin on the β-lactoglobulin molecule. The association of the hydrophobic methyl esters on pectin with an exposed hydrophobic region on β-lg results in the release of water molecules from the hydrophobic region and surrounding the methyl esters of the pectin molecule. An increase in the ionic strength decreases the enthalpic contribution due to the shielding of electrostatic attraction in favor of the entropic contribution, supporting the idea that the release of water molecules from hydrophobic areas plays a part in the complex formation.     

Rare extra-pair fertilizations in the semi-colonially breeding linnet Carduelis cannabina

Microsatellite analysis was used to analyse the level of extra-pair paternity (EPP) in the semi-colonially breeding linnet Carduelis cannabina in Denmark. During the breeding seasons of 1998 and 1999 EPP accounted for only 3.8% of young (4/106, 95% CL=1–13%). These extra-pair young were found in 9.1% of the broods (2/22, 95% CL=1–29%). We hypothesize that this low level of EPP is due to an efficient use of both mate guarding and frequent copulations as paternity guards. However, experimental tests with temporary detainment of males would be needed to establish whether there is a causal relationship between the low EPP level and the double paternity guard.     

Metabolomic profiling of rapid cold hardening and cold shock in Drosophila melanogaster

A short exposure to a mild cold stress is sufficient to increase cold tolerance in many insects. This phenomenon, termed rapid cold hardening (RCH) expands the thermal interval that can be exploited by the insect. To investigate the possible role of altered metabolite levels during RCH, the present study used untargeted (1)H NMR metabolomic profiling to examine the metabolomic response in Drosophila melanogaster during the 72 h following RCH and cold shock treatment. These findings are discussed in relation to the costs and benefits of RCH that are measured in terms of survival and reproductive output. Cold shock caused a persistent disturbance of the metabolite profile that correlated well with a delayed onset of cold shock mortality. The disruption of metabolite homeostasis was smaller following RCH, where control levels were fully recovered after 72 h. RCH improved both survival and reproductive output after a subsequent cold shock but the RCH treatment alone was associated with costs in terms of reduced survival and reproductive output. The most pronounced changes following the RCH treatment were elevated levels of glucose and trehalose. Although, it is difficult to discern if a change in a specific metabolite is linked to physiological processes of adaptive, neutral or detrimental nature we observed that the onset and magnitude of the increased sugar levels correlated tightly with the improved chill tolerance following RCH. These findings suggest a putative role of cryoprotectants during RCH which are discussed in the light of the existing literature on the mechanistic background of RCH.     

Manual pressure distension of the human saphenous vein changes its biomechanical properties-implication for coronary artery bypass grafting

Patency rates of saphenous vein grafts following coronary artery bypass grafting (CABG) depend on multiple factors. Information regarding the impact of biomechanical properties of vein grafts on patency rates is not available. The objective of the present study was to evaluate whether uncontrolled manual pressure distension during routine preparation of the saphenous vein in CABG-induced changes in the biomechanical properties of the vein. The morphometric and stress-strain properties were studied in isolated segments of the saphenous vein from 12 patients undergoing elective CABG. Six segments were manually distended without pressure control and six were not distended. The mechanical test was performed as a ramp inflation using syringe pump. The vein dimensions were obtained from digitised images at different pressures as well as at the no-load and zero-stress states. The circumferences, the wall and lumen area, the wall thickness, and the outer diameter as function of the applied pressure were largest in the segments with uncontrolled manual distension compared to those without distension (P<0.05). The opening angle and the absolute value of the residual strains were lower (P<0.01) and the circumferential stress-strain curve shifted to the left, indicating the wall became stiffer with uncontrolled manual distension compared to those without distension (P<0.05). In conclusion, manual pressure distension changed the morphometric and biomechanical properties of the saphenous vein. The perspective is that studies on biomechanical properties on the saphenous vein may guide surgeons how to handle graft material without causing major changes of the biomechanical properties during harvesting and preparation.     

Small molecule ago-allosteric modulators of the human glucagon-like peptide-1 (hGLP-1) receptor

Following our previous publication describing the biological profiles, we herein describe the structure-activity relationships of a core set of quinoxalines as the hGLP-1 receptor agonists. The most potent and efficacious compounds are 6,7-dichloroquinoxalines bearing an alkyl sulfonyl group at the C-2 position and a secondary alkyl amino group at the C-3 position. These findings serve as a valuable starting point for the discovery of more drug-like small molecule agonists for the hGLP-1 receptor.     

Endothelium-dependent vascular responses induced by leukotriene B4

Leukotriene B(4) (LTB(4)) is an inflammatory mediator derived from the 5-lipoxygenase pathway of arachidonic acid metabolism and has recently implicated in the pathogenesis of atherosclerosis. There are two membrane bound receptors for LTB(4): BLT(1) and BLT(2), which represent the high and low affinity receptors, respectively. BLT receptors are expressed on leukocytes, and LTB(4) is a potent chemoattractant for neutrophils, eosinophils, and T lymphocytes. Recent studies have in addition shown that LTB(4) is an indirectly acting vasoconstrictor of isolated vascular preparations. In the guinea pig aorta, the LTB(4)-induced contractions were inhibited by endothelium-denudation. In addition, pre-treatment with the NO synthase inhibitor, L-NOARG, significantly enhanced the contractions induced by LTB(4). The contractile response induced by LTB(4) in the guinea pig aorta was abolished by the selective BLT(1) receptor antagonist U75302 and the expression of BLT(1) receptor mRNA in the guinea pig aorta was established by RT-PCR. Taken together, these results suggest that LTB(4) activates BLT(1) receptors on the endothelium of the guinea pig aorta, associated with the release of both contractile factors and NO.