There are at least five lipoxygenases (TomloxA, TomloxB, TomloxC, TomloxD, and TomloxE) present in tomato (Lycopersicon esculentum Mill.) fruit, but their role in generation of fruit flavor volatiles has been unclear. To assess the physiological role of TomloxC in the generation of volatile C6 aldehyde and alcohol flavor compounds, we produced transgenic tomato plants with greatly reduced TomloxC using sense and antisense constructs under control of the cauliflower mosaic virus 35S promoter. The expression level of the TomloxC mRNA in some transgenic plants was selectively reduced by gene silencing or antisense inhibition to between 1% and 5% of the wild-type controls, but the expression levels of mRNAs for the four other isoforms were unaffected. The specific depletion of TomloxC in transgenic tomatoes led to a marked reduction in the levels of known flavor volatiles, including hexanal, hexenal, and hexenol, to as little as 1.5% of those of wild-type controls following maceration of ripening fruit. Addition of linoleic or linolenic acid to fruit homogenates significantly increased the levels of flavor volatiles, but the increase with the TomloxC-depleted transgenic fruit extracts was much lower than with the wild-type control. Confocal imaging of tobacco (Nicotiana tabacum) leaf cells expressing a TomloxC-GFP fusion confirmed a chloroplast localization of the protein. Together, these results suggest that TomloxC is a chloroplast-targeted lipoxygenase isoform that can use both linoleic and linolenic acids as substrates to generate volatile C6 flavor compounds. The roles of the other lipoxygenase isoforms are discussed.Lipoxygenases (LOX; EC1.13.11.12) are nonheme iron-containing dioxygenases that catalyze the incorporation of molecular oxygen into polyunsaturated fatty acids containing a cis, cis-1.4-pentadiene moiety, such as linoleic and linolenic acids, converting them into fatty acid hydroperoxides (HPOs). Multiple isoforms of LOX have been detected in a wide range of plants, animals, and microorganisms (Zimmerman and Vick, 1973;Eskin et al., 1977;Shechter and Grossman, 1983;Hamberg, 1986;Samuelsson et al., 1987;Vick and Zimmerman, 1987). The LOX isoforms are distinguished by differences in reaction pH optimum, pI, substrate and product specificity, tissue-specific or subcellular localization, and synthesis at particular developmental stages (Axelrod, 1974;Bild et al., 1977;Axelrod et al., 1981;Ferrie et al., 1994;Royo et al., 1996;Heitz et al., 1997).In animals, it is well established that HPOs are the primary metabolites of the pathways that lead to the formation of important regulatory molecules in inflammatory responses such as leukotrienes and lipoxins (Yamamoto, 1991). In higher plants, on the other hand, the physiological role of HPOs generated by individual LOX isoforms is still uncertain. It has been postulated that plant lipoxygenases may be involved in plant growth and development; biosynthesis of regulatory molecules, such as jasmonic acid (JA) and traumatin; biosynthesis of volatile compounds, s...

The interaction between the volume and composition of fluids ingested was investigated in terms of rehydration effectiveness. Twelve male volunteers, dehydrated by 2.06 +/- 0.02% (mean +/- SE) of body mass by intermittent cycle exercise, consumed a different drink volume on four separate weeks; six subjects received drink L (23 mmol.l-1 Na+) in each trial and six were given drink H (61 mmol.l-1 Na+). Volumes consumed were equivalent to 50%, 100%, 150%, and 200% of body mass loss (trials A, B, C, and D, respectively). Blood and urine samples were obtained before exercise and for 7.5 h after exercise. Less urine was excreted following rehydration in trial A than in all other trials. Cumulative urine output (median ml) was less in trial B (493, range 181-731) than D (1361, range 1014-1984), which was not different from trial C (867, range 263-1191) in group L. In group H, the volume excreted in trial B (260, range 137-376) was less than trials C (602, range 350-994) and D (1001, range 714-1425), and the volume in trial C was less than in trial D. These results suggest that both sodium concentration and fluid volume consumed interact to affect the rehydration process. A drink volume greater than sweat loss during exercise must be ingested to restore fluid balance, but unless the sodium content of the beverage is sufficiently high this will merely result in an increased urinary output.

Graphical abstract

Biologic scaffolds are derived from mammalian tissues, which must be decellularized to remove cellular antigens that would otherwise incite an adverse immune response. Although widely used clinically, the optimum balance between cell removal and the disruption of matrix architecture and surface ligand landscape remains a considerable challenge. Here we describe the use of time of flight secondary ion mass spectroscopy (ToF-SIMS) to provide sensitive, molecular specific, localized analysis of detergent decellularized biologic scaffolds. We detected residual detergent fragments, specifically from Triton X-100, sodium deoxycholate and sodium dodecyl sulphate (SDS) in decellularized scaffolds; increased SDS concentrations from 0.1% to 1.0% increased both the intensity of SDS fragments and adverse cell outcomes. We also identified cellular remnants, by detecting phosphate and phosphocholine ions in PAA and CHAPS decellularized scaffolds. The present study demonstrates ToF-SIMS is not only a powerful tool for characterization of biologic scaffold surface molecular functionality, but also enables sensitive assessment of decellularization efficacy.

In this study we have explored several aspects of regional analyte suppression in mass spectrometry imaging (MSI) of a heterogeneous sample, transverse cryosections of mouse brain. Olanzapine was homogeneously coated across the section prior to desorption electrospray ionization (DESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging. We employed the concept of a tissue extinction coefficient (TEC) to assess suppression of an analyte on tissue relative to its intensity in an off tissue region. We expanded the use of TEC, by first segmenting anatomical regions using graph-cuts clustering and calculating a TEC for each cluster. The single ion image of the olanzapine [M + H] ion was seen to vary considerably across the image, with anatomical features such as the white matter and hippocampus visible. While trends in regional ion suppression were conserved across MSI modalities, significant changes in the magnitude of relative regional suppression effects between techniques were seen. Notably the intensity of olanzapine was less suppressed in DESI than for MALDI. In MALDI MSI, significant differences in the concentration dependence of regional TECs were seen, with the TEC of white matter clusters exhibiting a notably stronger correlation with concentration than for clusters associated with gray matter regions. We further employed cluster-specific TECs as regional normalization factors. In comparison to published pixel-by-pixel normalization methods, regional TEC normalization exhibited superior reduction ion suppression artifacts. We also considered the usefulness of a segmentation-based approach to compare spectral information obtained from complementary modalities.

Strawberries cv. Elsanta were grown in peat bags in a glasshouse and subjected to three shading levels (0%, 25%, 47%) for 2 weeks, commencing 1 week prior to first fruit ripening. Fruit was harvested at five intervals and analysed using Atmospheric Pressure Chemical Ionization (APCI) and direct liquid-mass spectrometry techniques. Thirteen volatiles implicated in strawberry flavour and three non-volatiles, sucrose, glucose and citric acid, were measured. Highly significant differences in volatile and non-volatile concentrations existed between harvest dates. Shading had a significant effect on hexanal, hexenal, ethyl methyl butyrate, and methyl butyrate concentrations at some harvests. In general, at each harvest the higher the level of shading the lower the level of the volatile in the fruit. Sucrose concentration showed a decrease throughout the harvest period, whereas glucose and citric acid showed less clear trends. Shading had a significant effect on glucose and sucrose concentrations. Some possible reasons for the variability in strawberry flavour are discussed.

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The persistence of volatile compounds in the breath was monitored after their consumption in aqueous solutions. Factors studied were variation in volatile release patterns between panelists, effect of adding hydroxy propyl methyl cellulose (HPMC), and differences among compounds. For any given compound, the extent of volatile persistence was broadly similar for all panelists. Adding HPMC at concentrations in excess of c did not substantially affect persistence. The largest differences in persistence were observed when compounds were compared (>20-fold). The differences were modeled using a quantitative structure property relationship approach, based on the persistence data from 41 compounds. Major components of the model were terms that described the hydrophobicity and vapor pressure of a molecule. The model was validated with a test set, which showed that there was a significant correlation between persistence predicted by the model and the actual values observed.