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31.
Ruhl M Bonis NR Reichart GJ Sinninghe Damsté JS Kürschner WM 《Science (New York, N.Y.)》2011,333(6041):430-434
The end-Triassic mass extinction (~201.4 million years ago), marked by terrestrial ecosystem turnover and up to ~50% loss in marine biodiversity, has been attributed to intensified volcanic activity during the break-up of Pangaea. Here, we present compound-specific carbon-isotope data of long-chain n-alkanes derived from waxes of land plants, showing a ~8.5 per mil negative excursion, coincident with the extinction interval. These data indicate strong carbon-13 depletion of the end-Triassic atmosphere, within only 10,000 to 20,000 years. The magnitude and rate of this carbon-cycle disruption can be explained by the injection of at least ~12 × 10(3) gigatons of isotopically depleted carbon as methane into the atmosphere. Concurrent vegetation changes reflect strong warming and an enhanced hydrological cycle. Hence, end-Triassic events are robustly linked to methane-derived massive carbon release and associated climate change. 相似文献
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In order to quantify the importance of ectomycorrhizal fungi on nutrient uptake from the coarse-soil fraction of a haplic Cambisol (alumic), a microcosm study that allowed for nutrient budgets was designed. Ectomycorrhizal- and fungicide-treated spruce seedlings were grown on isolated and cleaned gneiss fragments (6.3 mm > Ø > 2 mm) from 90 cm soil depth. The substrate was the only source of Ca, K and Mg. Ectomycorrhizal seedlings showed no signs of nutrient deficiencies and biomass increased significantly compared to initial seedling biomass. Ectomycorrhizal seedlings seemed well adapted to survive on the coarse-soil substrate and acquired Ca, K and Mg from the coarse-soil substrate. Gneiss fragments of the ectomycorrhizal treatment were covered by fine roots and ectomycorrhizal hyphae, as observed microscopically. Fungicide-treated seedlings?? root development was retarded, and shoot biomass only increased from stored nutrient reserves of the seedlings. The suppression of EcM colonization by the fungicide Topas® apparently caused a root growth inhibiting effect. Furthermore, the extinction of mycorrhiza initiated an increased nitrification and acidification and a consequent nutrient cation release triggered by nitrate in the drainage. 相似文献
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Although morel mushrooms are widely used as tasty ingredients in savory dishes, knowledge of the key compounds evoking their attractive taste is still very fragmentary. In the present study, taste activity-guided fractionation of an aqueous morel extract by means of the recently developed taste dilution analysis (TDA) enabled the localization of several umami-like-tasting fractions as well as a fraction imparting an intense mouth-drying sensation to the oral cavity. Hydrophilic interaction liquid chromatography (HILIC), LC-MS, and amino acid analysis led to the successful identification of gamma-aminobutyric acid as the chemical inducer of the mouth-drying and mouth-coating oral sensations imparted by the morel extract. Besides the well-known umami-like taste contributors L-glutamic acid, L-aspartic acid, and succinic acid, an additional HILIC fraction was isolated and evaluated as tasting umami-like. LC-MS and NMR studies revealed that this fraction consisted of a mixture of (S)-malic acid 1-O-alpha-D-glucopyranoside and (S)-malic acid 1-O-beta-D-glucopyranoside, the structure of which could be successfully confirmed by independent synthesis. To the best of our knowledge, this morel-derived glycoside, which we named (S)-morelid, has previously not been reported in any food products. Sensory analysis of aqueous solutions of the compounds identified revealed threshold concentrations of 0.02 mmol/L for the mouth-drying effect of gamma-aminobutyric acid and 6.0 mmol/L for the umami-like, slightly sour taste of (S)-morelid. 相似文献
34.
Nielsen NS Petersen A Meyer AS Timm-Heinrich M Jacobsen C 《Journal of agricultural and food chemistry》2004,52(25):7690-7699
The influence of the addition of metal chelators on oxidative stability was studied in a milk drink and in a mayonnaise system containing highly polyunsaturated lipids. Milk drinks containing 5% (w/w) of specific structured lipid were supplemented with lactoferrin (6-24 muM) and stored at 2 degrees C for up to 9 weeks. Mayonnaise samples with 16% fish oil and 64% rapeseed oil (w/w) were supplemented with either lactoferrin (8-32 muM), phytic acid (16-124 muM), or EDTA (16-64 muM) and were stored at 20 degrees C for up to 4 weeks. The effect of the metal chelators was evaluated by determination of peroxide values, secondary volatile oxidation products, and sensory analysis. Lactoferrin reduced the oxidation when added in concentrations of 12 muM in the milk drink and 8 muM in the mayonnaise, whereas it was a prooxidant at higher concentrations in both systems. In mayonnaise, EDTA was an effective metal chelator even at 16 muM, whereas phytic acid did not exert a distinct protective effect against oxidation. The differences in the equimolar effects of the metal chelators are proposed to be due to differences in their binding constants to iron and their different stabilities toward heat and low pH. 相似文献
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Actinobacillus (A.) pleuropneumoniae is the causative agent of a porcine pleuropneumonia occurring worldwide. In order to identify novel non-cytoplasmic putative virulence-associated proteins, we prepared fractions enriched in surface-associated proteins for differential proteome analysis by two-dimensional (2D) gel electrophoresis and quadrupole time-of-flight mass spectrometry (Q-Tof MS). Bacteria grown under standard culture conditions were compared to an ex vivo model based on the addition of bronchoalveolar lavage fluid (BALF) to the culture media. Twelve proteins were found to be upregulated upon induction with BALF, among them a superoxide dismutase, a parvulin-like peptidy-prolyl isomerase, a polynucleotide phosphorylase and the highly immunogenic lipoprotein OmlA. Four of the proteins upregulated by BALF were additionally constitutively expressed by an isogenic A. pleuropneumoniae fur deletion mutant and could be identified by Q-Tof MS as the heat shock protein GroES, a putative dipeptide transporter, a putative metal ion transporter and a conserved protein of unknown function. In silico analysis of the putative promoter regions of the encoding genes revealed putative Fur boxes upstream of two genes, one of which encodes part of a putative metal ion transporter. An isogenic mutant with a deletion in this protein was constructed and designated as A. pleuropneumoniae Deltafui. Analysis of the mutant in an aerosol infection model revealed symptoms indistinguishable from those seen upon infection with wild type A. pleuropneumoniae. This result implies that not all proteins upregulated by BALF are directly involved in A. pleuropneumoniae virulence. 相似文献
37.
OBJECTIVE: To characterize the use of antiemetic agents in dogs with canine parvovirus (CPV)-associated enteritis in a veterinary teaching hospital. DESIGN: Retrospective case series. ANIMALS: 77 dogs with CPV-associated enteritis. PROCEDURE: Medical records of 560 dogs with confirmed CPV-associated enteritis that were admitted to a veterinary teaching hospital were reviewed. Exclusion criteria included vaccination against CPV infection within the preceding 2 weeks, hospitalization for < 24 hours or removal from the hospital against advice, or an incomplete record. Signalment, duration of hospitalization, and daily antiemetic administrations were assessed; WBC counts and clinical findings were used to classify dogs as having systemic inflammatory response syndrome (SIRS). RESULTS: 77 dogs were included in the study; 55 (71%) received antiemetics (53 received metoclopramide at least once). Seventy-one dogs survived, and 6 dogs died (all 6 received antiemetics). Compared with dogs that did not receive antiemetics, duration of hospitalization was significantly longer for antiemetic-treated dogs. Daily values of rectal temperature and heart and respiratory rates did not predict administration of antiemetics or duration of hospitalization; however, compared with survivors, SIRS developed more frequently among nonsurvivors. Assessment of emetic events recorded hourly for 17 dogs indicated that antiemetic treatment did not control emesis. CONCLUSIONS AND CLINICAL RELEVANCE: Many dogs with CPV-associated enteritis had persistent vomiting despite antiemetic administration. The apparent difference in duration of hospitalization between antiemetic-treated dogs and other dogs may reflect a difference in disease severity between groups, although antiemetic-associated adverse events (e.g., signs of depression, hypotension, and immune modulation) may prolong hospitalization. 相似文献
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