Bitter-tasting and kokumi-enhancing molecules in thermally processed avocado (Persea americana Mill.)     

Degenhardt AG  Hofmann T 《Journal of agricultural and food chemistry》2010,58(24):12906-12915

Sequential application of solvent extraction and RP-HPLC in combination with taste dilution analyses (TDA) and comparative TDA, followed by LC-MS and 1D/2D NMR experiments, led to the discovery of 10 C(17)-C(21) oxylipins with 1,2,4-trihydroxy-, 1-acetoxy-2,4-dihydroxy-, and 1-acetoxy-2-hydroxy-4-oxo motifs, respectively, besides 1-O-stearoyl-glycerol and 1-O-linoleoyl-glycerol as bitter-tasting compounds in thermally processed avocado (Persea americana Mill.). On the basis of quantitative data, dose-over-threshold (DoT) factors, and taste re-engineering experiments, these phytochemicals, among which 1-acetoxy-2-hydroxy-4-oxo-octadeca-12-ene was found with the highest taste impact, were confirmed to be the key contributors to the bitter off-taste developed upon thermal processing of avocado. For the first time, those C(17)-C(21) oxylipins exhibiting a 1-acetoxy-2,4-dihydroxy- and a 1-acetoxy-2-hydroxy-4-oxo motif, respectively, were discovered to induce a mouthfulness (kokumi)-enhancing activity in sub-bitter threshold concentrations.  相似文献   

Negligible contribution from roots to soil-borne phospholipid fatty acid fungal biomarkers 18:2ω6,9 and 18:1ω9   总被引：1，自引：0，他引：1  

Kaiser C  Frank A  Wild B  Koranda M  Richter A 《Soil biology & biochemistry》2010,42(9):1650-1652

The phospholipid fatty acid biomarkers 18:1ω9, 18:2ω6,9 and 18:3ω3,6,9 are commonly used as fungal biomarkers in soils. They have, however, also been found to occur in plant tissues, such as roots. Thus, the use of these PLFAs as fungal biomarkers in sieved soil, which may still contain small remains of roots, has been questioned. We used data from a recent beech tree girdling experiment to calculate the contribution of roots to these biomarkers and were able to demonstrate that not more than 0.61% of 18:1ω9 and 18:2ω6,9 in sieved soil samples originated from roots (but 4% of 18:3ω3,6,9). Additionally, the abundance of the biomarker 18:2ω6,9 in the soil was found to be highly correlated to ectomycorrhizal root colonization, which further corroborates its fungal origin. PLFA biomarkers were substantially reduced in vital roots from girdled trees compared to roots of control trees (by up to 76%), indicating that the major part of PLFAs measured in roots may actually originate from ectomycorrhizal fungi growing inside the roots. We calculated, that even a near to 50% reduction in fine root biomass - as observed in the girdling treatment - accounted for only 0.8% of the measured decrease of 18:2ω6,9. Our results demonstrate that both 18:1ω9 and 18:2ω6,9 are suitable biomarkers for detecting fungal dynamics in soils and that especially 18:2ω6,9 is a reliable biomarker to study mycorrhizal dynamics in beech forests.  相似文献   

Establishment of proliferative cell nuclear antigen gene as an internal reference gene for polymerase chain reaction of a wide range of archival and fresh mammalian tissues.     

Irene Schiller  Zen Huat Lu  Lloyd Vaughan  Roseline Weilenmann  Stephane Koundrioukoff  Andreas Pospischil 《Journal of veterinary diagnostic investigation》2003,15(6):585-588

Polymerase chain reaction (PCR) from paraffin-embedded tissues provides a powerful tool to amplify DNA from a variety of recent and archival material. Because DNA from paraffin-embedded samples is more degraded than from fresh material, the amplification of reference genes is essential to exclude false-negative results. This study describes the use of the proliferative cell nuclear antigen (PCNA) gene as a reference gene in a range of animal species and in humans. The PCNA-PCR to amplify a fragment extending from exon 5 through exon 6 and including the intervening intron 6 gave a reproducible pattern, with a 280-base pair (bp) band from canine, equine, bovine, ovine, and caprine samples showing high sequence homology. Porcine, guinea pig, tiger, and lion samples, however, gave an additional fragment of approximately 197 bp. The whole intron 6 from these fragments is missing, possibly representing a pseudogene. In feline samples only the 197-bp fragment could be detected. This study shows that the PCNA gene is highly conserved across a broad range of animal species and is well suited as an internal control for PCR analysis in veterinary medicine.  相似文献   

Transformation of organoarsenical species by the microflora of freshwater crayfish     

Devesa V  Loos A  Súñer MA  Vélez D  Feria A  Martínez A  Montoro R  Sanz Y 《Journal of agricultural and food chemistry》2005,53(26):10297-10305

A study of the transformation of arsenic species by the microflora of the freshwater crayfish Procambarus clarkii was carried out. The study of the degradation of AB (arsenobetaine) was performed in aerobic conditions in two culture media (tryptic soy broth and saline medium) at two temperatures (30 and 8 degrees C). The microflora transformed AB into TMAO (trimethylarsine oxide), DMA (dimethylarsinate), MA (methylarsonate), and an unidentified compound (U1). The quickest transformations were carried out by microflora from hepatopancreas incubated in saline medium at 30 degrees C. The individualized study of other arsenic species [AC (arsenocholine), TETRA (tetramethylarsonium ion), TMAO, DMA, and MA] was also performed in saline medium. The only transformation observed was of AC into AB. The bacteria possibly responsible for AB degradation were isolated, identified by phenotypic and genotypic methods, and individually assayed for AB transformation. Only isolates allocated to the species Pseudomonas putida were able to metabolize AB.  相似文献   

Fate of heavy metals in a strongly acidic shooting‐range soil: small‐scale metal distribution and its relation to preferential water flow     

Lars A. Knechtenhofer  Irene O. Xifra  Andreas C. Scheinost  Hannes Flühler  Ruben Kretzschmar 《植物养料与土壤学杂志》2003,166(1):84-92

To assess the mobility of Pb and associated metals in a highly contaminated shooting range soil (Losone, Ticino, Switzerland), we investigated the spatial distribution of the metals and their relation to preferential water flow paths. A 2.2 m² plot located 40 m behind the stop butt was irrigated with a solution containing bromide and Brilliant Blue, a slightly sorbing dye. A soil profile 50 cm in width was sampled down to 80 cm with a spatial resolution of 2.5 cm, resulting in 626 samples. Concentrations of elements (12 ≤ Z ≤ 92) were determined by energy‐dispersive Xray fluorescence spectrometry, and Brilliant Blue concentrations were determined with a chromameter. In the acidic (pH 3), organic matter‐rich, well drained Dystric Cambisol, maximum concentrations of 80.9 g kg^‐1 Pb, 4.0 g kg^‐1 Sb, and 0.55 g kg^‐1 Cu were measured in the topsoil. Within 40 cm soil depth, however, Pb, Sb, and Cu approached background concentrations of 23 mg kg^‐1, 0.4 mg kg^‐1, and 9.4 mg kg^‐1, respectively. The even horizontal distribution and the steep gradient along soil depth indicate tight metal binding in the topsoil, and a fairly homogeneous transport front. In contrast, water flow through the profile was highly heterogeneous. In the uppermost 20 cm, preferential flow was initiated by heterogeneous infiltration at the soil surface, but had no influence on metal distribution. Below 20 cm, however, preferential flow originated from larger tree roots, and metal concentrations were significantly elevated along these macropores. Spatial distributions of Pb, Sb, and Cu were similar, suggesting that all three metals are strongly retained in the topsoil and transported along preferential water flow paths in the subsoil.  相似文献   

Influence of acid soil on nodule numbers in relation to polyamine and tannin concentrations in roots of Phaseolus vulgaris     

Andreas B. Wolff  Maria Sidirelli  Constantinos Paradellis  Kiriakos Kotzabasis 《Biology and Fertility of Soils》1995,20(4):249-252

The relationship between soil acidity and polyamine (putrescine, spermidine, spermine) concentrations in roots was evaluated and compared to (1) nodule numbers in common beans and (2) tannin concentrations in roots. Six Phaseolus vulgaris cultivars were grown in pots in a greenhouse in soil at pH 4.5 or 5.5 and inoculated with Rhizobium leguminosarum bv. phaseoli strains. At pH 4.5 nodule numbers were strongly reduced but polyamine concentrations were 50% higher than at pH 5.5. At both pH levels putrescine and spermidine were the dominant polyamines, while the concentration of spermine was less than half of the other two. There was also a cultivar effect on the polyamine concentration, but this was much less pronounced than the pH effect. By 22 days after planting the uninoculated control plants had about 13% lower levels of polyamines than the inoculated plants. The concentrations of putrescine, spermidine, and spermine were negatively correlated with nodule numbers, but positively correlated with the root tannin content. There were no significant correlations with either root or plant dry weight.  相似文献   

Regionalization of critical loads under uncertainty     

Andreas Barkman  Per Warfvinge  Harald Sverdrup 《Water, air, and soil pollution》1995,85(4):2515-2520

The steady-state model PROFILE was used to perform Monte Carlo simulations of critical loads of acidity and exceedances of forest soils for 128 sites in the province of Scania, southern Sweden. Statistical tests showed that 100 sites had normal distributed critical loads and exceedances and that the variance of these parameters was statistically equal for all sites. Pooled estimates of the standard deviation was 0.19 and 0.31 kmol_c ha^?1 yr^?1 for the critical loads and exceedances, respectively. Introduction of uncertainties, expressed as confidence intervals, in the cumulative distribution function for critical loads showed that overlaps between percentiles were substantial. The 5%-ile was systematically equal to the 57%-ile using a 67% confidence interval and equal to the 87%-ile when a 95% confidence level was chosen. The overlaps of percentiles cause a reduction of acidic deposition according to the mean value of the 5%-ile to protect only 68% of the ecosystem area with an 84% probability and not a guaranteed protection of 95% as if uncertainties did not exist. Thus, uncertainties make it possible to advocate reductions to levels of deposition below the 5%-tile of critical loads.  相似文献   

Impacts of drought on mineral macro- and microelements in provenances of beech (Fagus sylvatica L.) seedlings     

Peuke AD  Rennenberg H 《Tree physiology》2011,31(2):196-207

Beech seedlings originating from 11 German provenances with different climatic conditions were grown in pots and cultivated in a greenhouse. The composition of macro- and microelements in roots, axes and leaves was measured after half of the seedlings were subjected to a simulated summer drought. The recently described sensitivity of these provenances to drought was compared with drought-mediated changes in the elemental and ionic composition in organs of the seedlings; in addition, partitioning between roots and shoots was evaluated. A number of element concentrations were decreased in roots due to drought (K 94% of control, Mg 94%, Mn 75% and Zn 85%). However, chloride concentration increased in all organs (115-125%) and was the only element affected in leaves. Some changes in ionome can be related to sensitivity of provenances, but it is difficult to decide whether these changes are a result of, or a reason for, drought tolerance or sensitivity. Observed increases in chloride concentration in all plant parts of drought-treated beech seedlings can be explained by its function in charge balance, in particular since the level of phosphate was reduced. As a result of chloride accumulation, the sum of added charges of anions (and cations) in water extracts of leaf and root material was similar between drought and control plants. Since only the partitioning of Ca and Al (both only in axis) as well as Mn was affected and other elements (together with previously observed effects on C, N, S and P) remained unaffected by drought in all provenances, it can be concluded that direct effects by means of mass flow inhibition in xylem and phloem are unlikely. Secondary effects, for example on the pH of transport sap and the apoplastic space, cannot be excluded from the present study. These effects may affect partitioning between the apoplast and symplast and therefore may be significant for drought sensitivity.  相似文献   

Little effect of forest age on oribatid mites on the bark of trees   总被引：1，自引：0，他引：1  

Georgia Erdmann  Andreas Floren  K.Eduard Linsenmair  Stefan Scheu  Mark Maraun 《Pedobiologia》2006,50(5):433-441

This study investigates the effect of forest age (20-, 50-, 160-year-old, and primeval forest) on oribatid mite communities on the bark of oak trees in the National Park Pusza Białowieża in eastern Poland. We hypothesized that oribatid mite diversity on bark peaks at forests of intermediate age and that the number of parthenogenetic species of oribatid mites is highest in young stands. In contrast to these hypotheses, the diversity, density, number of juveniles, community structure and the mode of reproduction of oribatid mite species were not significantly affected by forest age. None of the oribatid mite species occurred exclusively on trees of a specific age. The results suggest that oribatid mite communities on the bark of trees are minimally affected by tree harvesting regimes. In contrast to oribatid mites in soil, communities on bark appear to be less sensitive to disturbances.  相似文献   

Photosynthetic water‐use efficiency of irrigated winter and summer crops in a typical mountain oasis of northern Oman     

Sabine D. Golombek  Jens Gebauer  Andreas Buerkert 《植物养料与土壤学杂志》2007,170(1):98-105

The millenia‐old existence of traditional, surface‐irrigated Omani mountain oases implies a remarkable sustainability of such systems in a hyperarid environment. This study was conducted in the mountain oasis of Balad Seet, situated in the Al‐Jabal‐al‐Akhdar mountains of northern Oman, to investigate the water‐use efficiency (WUE) of these oases and how farmers regulate it. In 2005, gas exchange of single leaves of 9–16 plants was measured for the most important perennial field crop alfalfa in both February and August, for the typical winter crop oat in February, and the dominating summer crop sorghum in August. The measurements were conducted five times a day in subplots irrigated the evening before and in the surrounding control plots, where plants had been withheld from irrigation for 14–16 d. Water deficit at the end of the irrigation interval reduced the stomatal conductance (g_s) strongly in summer alfalfa, oat, and sorghum, but only slightly in winter alfalfa. In oat, the reduction of net photosynthetic rate (P_N) at the end of the irrigation cycle was caused mainly by stomatal closure, in sorghum by nonstomatal factors and in summer alfalfa by both, whereas P_N in winter alfalfa remained unaffected. The ratio of net photosynthetic rate to stomatal conductance (P_N/g_s), the “intrinsic water‐use efficiency”, increased in all investigated crops in response to drought because of a stronger reduction of g_s than of P_N. This increase was small in winter alfalfa, but much stronger in oat, sorghum, and summer alfalfa. The data indicate that alfalfa maintains a relatively high CO₂ assimilation rate year‐round, contributing to a relatively high annual dry‐matter production. The decrease of the light intensity in the late afternoon caused by the shading effect of the surrounding mountains diminishes the crop evapotranspiration in the oasis.  相似文献