Mycorrhizal‐mediated nitrogen acquisition in switchgrass under elevated temperatures and N enrichment

Arbuscular mycorrhizal fungi (AMF) can perform key roles in ecosystem functioning through improving host nutrient acquisition. Nitrogen (N) is an essential nutrient for plant growth, however, anthropogenic N loading (e.g. crop fertilization and deposition from combustion sources) is increasing so that N now threatens ecosystem sustainability around the world by causing terrestrial and aquatic eutrophication and acidification. It is important to better understand the capacity of AMF to directly uptake N from soils and transfer it to host plants because this process may increase N recycling and retention within ecosystems. In addition to understanding the role of AMF in the N cycle in the present day it is important to understand how AMF function may change as global change proceeds. Currently the net effects of N enrichment and elevated temperature predicted with global change on AMF are unknown. In this study, we examined the effects of N enrichment by simulated N‐deposition loading, elevated temperatures expected by future global changes and their interactions on growth and AMF‐mediated N acquisition of switchgrass (Panicum virgatum var. Alamo), an important species for biofuel production. Switchgrass plants were grown in microcosm units that divided mycorrhizal roots from AMF hyphae and organic residues enriched with ¹⁵N by compartments separated by an air gap to reduce N diffusion. While AMF did not enhance switchgrass biomass, mycorrhizas significantly increased ¹⁵N in shoots and total shoot N. Neither N enrichment nor elevated temperatures influenced this mycorrhizal‐mediated N uptake and transfer. Results from this study can aid in developing sustainable bioethanol and switchgrass production practices that are less reliant on synthetic fertilizers and more dependent on internal N recycling from AMF.     

A strategy for modelling dynamic responses in metabolic samples characterized by GC/MS

A multivariate strategy for studying the metabolic response over time in urinary GC/MS data is presented and exemplified by a study of drug-induced liver toxicity in the rat. The strategy includes the generation of representative data through hierarchical multivariate curve resolution (H-MCR), highlighting the importance of obtaining resolved metabolite profiles for quantification and identification of exogenous (drug related) and endogenous compounds (potential biomarkers) and for allowing reliable comparisons of multiple samples through multivariate projections. Batch modelling was used to monitor and characterize the normal (control) metabolic variation over time as well as to map the dynamic response of the drug treated animals in relation to the control. In this way treatment related metabolic responses over time could be detected and classified as being drug related or being potential biomarkers. In summary the proposed strategy uses the relatively high sensitivity and reproducibility of GC/MS in combination with efficient multivariate curve resolution and data analysis to discover individual markers of drug metabolism and drug toxicity. The presented results imply that the strategy can be of great value in drug toxicity studies for classifying metabolic markers in relation to their dynamic responses as well as for biomarker identification.     

Sequence diversity of the peptaibol antibiotic suzukacillin-A from the mold Trichoderma viride.

From the culture broth of the mold Trichoderma viride, strain 63 C-I, the polypeptide antibiotic suzukacillin (SZ) was isolated. A peptide mixture named SZ-A was obtained by crystallization from crude SZ. Individual peptides from SZ-A were isolated by semipreparative HPLC and sequences were determined by HPLC-ESI-MS. The data confirm a general sequence of SZ-A published previously and in addition establish the individual sequences of 15 acetylated eicosa peptides with C-terminal alcohols. The major peptide SZ-A4 (21% of all peptides) shows the sequence:Ac-Aib-Ala-Aib-Ala-Aib-Ala(6)-Gln-Aib-Lx(9)-Aib-Gly-Aib(12)-Aib-Pro-Vx(15)-Aib-Vx(17)-Gln-Gln-Fol. Amino acid exchanges of the peptaibol are located in position 6 (Ala/Aib), 9 (Vx/Lx), 12 (Aib/Lx), 17 (Aib/Vx) and possibly at position15 (Val/Iva) (uncommon abbreviations: Aib (alpha-aminoisobutyric acid); Iva (D-isovaline); Lx (L-leucine or L-isoleucine); Vx (L-valine or D-isovaline); Fol (L-phenylalaninol)).     

Effect of Somatostatin Analog on Postprandial Satiation in Obesity

Objective: Altered satiation may impact postprandial symptoms and potentially change food intake in obesity. Our aim was to compare effects of octreotide and placebo on postprandial symptoms, satiation, and gastric volumes in obesity. Research Methods and Procedures: In a randomized, parallel‐group, double‐blind, placebo‐controlled study, 26 obese but otherwise healthy participants received 100 μg of octreotide or placebo subcutaneously 30 minutes before each study. Studies were performed on 2 separate days and included validated non‐invasive techniques: ^99mTc‐single photon emission computed tomography imaging to measure fasting stomach volume and gastric volume changes after 90 mL of water and 240 mL of Ensure and a standardized nutrient drink test to measure the maximum tolerated volume and postprandial symptoms. Results: Relative to placebo, octreotide increased gastric volume after 90 mL of water; however, fasting and gastric volume change post‐Ensure and maximum tolerated volume of Ensure were not different. Octreotide decreased sensations of fullness (p = 0.035) and bloating (p = 0.05) and tended to reduce aggregate symptoms (p = 0.07) after the fully satiating meal. Discussion: In obese individuals, somatostatin analog significantly reduced postprandial sensations after a satiating meal without altering maximum tolerated meal volume or postnutrient gastric volume, suggesting an effect on upper gut sensation. The role of somatostatin as a permissive factor in the development of obesity by reducing postprandial sensations deserves further study.     

Intracellular compartmentation of cardiac fibres from rainbow trout and Atlantic cod--a general design of heart cells

In mammalian cardiomyocytes, mitochondria and adjacent ATPases with participation of creatine kinase (CK) constitute functional compartments with an exchange of ADP and ATP delimited from cytosolic bulk solution. The question arises if this extends to ectothermic vertebrates: their low body temperature and thinner cardiomyocytes with a lower density of membrane structures may reduce the need and structural basis for compartmentation. In saponin-skinned cardiac fibres from rainbow trout and Atlantic cod, we investigated mitochondrial respiration induced by endogenous ADP generated by ATPases and its competition for this ADP with pyruvate kinase (PK) in excess. At low Ca(2+) activity (pCa = 7.0), PK lowered ATP-induced respiration by 40% in trout and 26% in cod. At high Ca(2+) activity (pCa = 5.41), PK had no effect. Additionally, ADP release from the fibres was almost zero but increased drastically upon inhibition of respiration with 1 mM Na-azide. This suggests that fibres are compartmented. PK abolished creatine-stimulated respiration in trout suggesting a less tight coupling of CK to respiration than in mammals. In conclusion, intracellular compartmentation seems to be a general feature of vertebrate cardiomyocytes, whereas the role of CK is unclear, but it seems to be less important for energy transport in species with lower metabolism.     

Quartz crystal microbalance-with dissipation monitoring (QCM-D) for real time measurements of blood coagulation density and immune complement activation on artificial surfaces

A recently developed variant of quartz crystal microbalance (QCM) called QCM-with dissipation monitoring (QCM-D) allows simultaneous and simple measurements of changes in adsorbed mass as well as the viscoelastic property (D-factor) of deposited protein layers on the sensor surface. We have taken the QCM-D technology a step further and demonstrated its advantages in the study of protein assembly as a consequence of surface induced immune complement activation, or contact activated blood coagulation. In the present study we have continued our QCM-D investigations of surface assembly of fibrin clot formation and complement activation and incubated differently modified quartz sensor surfaces in blood plasma and sera. Polymer surfaces used were spin-coated polyethylene, poly(ethylene terephtalate), poly(methylmetacrylate) and poly(dimethylsiloxane). Also used were sputtered titanium and heparin grafted surfaces. In this investigation we found that we could describe the surface induced coagulation with four independent parameters: (1) Time of onset of coagulation, (2) fibrin deposition rate, (3) total frequency shift at stable plateau, and (4) fibrin clot density. The most important finding was that the blood plasma clot density can be assessed with the use of D determinations and that the clot density varied significantly with the chemical composition of the surface. However, the D-factor did not give any new analytical information about the possible complement activation mechanisms. Nevertheless, the QCM-D was found to be a reliable tool for the analysis of surface induced complement activation. We also compared the QCM-D technique with traditional enzyme immuno assay (EIA) measurements of soluble products from the surface activation of the complement and coagulation systems. We found that the results from EIA and QCM-D measurements corresponded well for the complement activation but not for the coagulation, probably due to the biological complexity of the coagulation system.     

Regulation of cyp26a1 on Th17 cells in mouse peri‐implantation

Cytochrome P450 26A1 (cyp26a1) is expressed in the mouse uterus during peri‐implantation. The repression of this protein is closely associated with a reduction in implantation sites, suggesting a specific role for cyp26a1 in pregnancy and prompting questions concerning how a metabolic enzyme can generate this distinct outcome. To explore the effective downstream targets of cyp26a1 and confirm if its role in peri‐implantation depends on its metabolic substrate RA (retinoic acid), we characterized the changes in the peripheral blood, spleen and uterine implantation sites using the cyp26a1 gene vaccine constructed before. Flow cytometry results showed a significant increase in CD4⁺RORγt⁺ Th17 cells in both the peripheral blood and spleen in the experimental group. The expression of RORγt and IL‐17 presented the Th17 cells reduction in uterus followed by the suppression of cyp26a1 expression. For greater certainty, cyp26a1 antibody blocking model and RNA interference model were constructed to determine the precise target immune cell group. High performance liquid chromatography results showed a significant increase in uterine at‐RA followed by the immunization of cyp26a1 gene vaccine. Both the ascertain by measuring RARα protein levels in peri‐implantation uterus after gene vaccine immunization and researches using the specific agonist and antagonist against RARα suggested that RARα may be the main RA receptor for signal transduction. These results provided more evidence for the signal messenger role of RA in cyp26a1 regulation from the other side. Here, we showed that the cyp26a1‐regulated Th17 cells are dependent on at‐RA signalling, which is delivered through RARα in mouse peri‐implantation.     

Knockdown of phosphotyrosyl phosphatase activator induces apoptosis via mitochondrial pathway and the attenuation by simultaneous tau hyperphosphorylation

Phosphotyrosyl phosphatase activator (PTPA) is decreased in the brains of Alzheimer's disease (AD) and the AD transgenic mouse models. Here, we investigated whether down‐regulation of PTPA affects cell viability and the underlying mechanisms. We found that PTPA was located in the integral membrane of mitochondria, and knockdown of PTPA induced cell apoptosis in HEK293 and N2a cell lines. PTPA knockdown decreased mitochondrial membrane potential and induced Bax translocation into the mitochondria with a simultaneous release of Cyt C, activation of caspase‐3, cleavage of poly (DNA ribose) polymerase (PARP), and decrease in Bcl‐xl and Bcl‐2 protein levels. Over‐expression of Protein phosphatase 2A (PP2A) catalytic subunit (PP2A_C) did not rescue the apoptosis induced by PTPA knockdown, and PTPA knockdown did not affect the level of and their phosphorylation of mitogen‐activated protein kinases (MAPKs), indicating that PP2A and MAPKs were not involved in the apoptosis induced by PTPA knockdown. In the cells with over‐expression of tau, PTPA knockdown induced PP2A inhibition and tau hyperphosphorylation but did not cause significant cell death. These data suggest that PTPA deficit causes apoptotic cell death through mitochondrial pathway and simultaneous tau hyperphosphorylation attenuates the PTPA‐induced cell death.