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Find video protocols related to scientific articles indexed in Pubmed.
Biochemistry of high stearic sunflower, a new source of saturated fats.
Prog. Lipid Res.
PUBLISHED: 02-07-2014
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Fats based on stearic acid could be a healthier alternative to existing oils especially hydrogenated fractions of oils or palm, but only a few non-tropical species produce oils with these characteristics. In this regard, newly developed high stearic oil seed crops could be a future source of fats and hard stocks rich in stearic and oleic fatty acids. These oil crops have been obtained either by breeding and mutagenesis or by suppression of desaturases using RNA interference. The present review depicts the molecular and biochemical bases for the accumulation of stearic acid in sunflower. Moreover, aspects limiting the accumulation of stearate in the seeds of this species are reviewed. This included data obtained from the characterization of genes and enzymes related to fatty acid biosynthesis and triacylglycerol assembly. Future improvements and uses of these oils are also discussed.
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Studies on the regulation of lipid biosynthesis in plants: application of control analysis to soybean.
Biochim. Biophys. Acta
PUBLISHED: 02-03-2014
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Although there is much knowledge of the enzymology (and genes coding the proteins) of lipid biosynthesis in higher plants, relatively little attention has been paid to regulation. We have demonstrated the important role for cholinephosphate cytidylyltransferase in the biosynthesis of the major extra-plastidic membrane lipid, phosphatidylcholine. We followed this work by applying control analysis to light-induced fatty acid synthesis. This was the first such application to lipid synthesis in any organism. The data showed that acetyl-CoA carboxylase was very important, exerting about half of the total control. We then applied metabolic control analysis to lipid accumulation in important oil crops - oilpalm, olive, and rapeseed. Recent data with soybean show that the block of fatty acid biosynthesis reactions exerts somewhat more control (63%) than lipid assembly although both are clearly very important. These results suggest that gene stacks, targeting both parts of the overall lipid synthesis pathway will be needed to increase significantly oil yields in soybean. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.
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Protective role for properdin in progression of experimental murine atherosclerosis.
PLoS ONE
PUBLISHED: 01-01-2014
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Genetic, dietary and immune factors contribute to the pathogenesis of atherosclerosis in humans and mice. Complement activation is an integral part of the innate immune defence but also shapes cellular responses and influences directly triglyceride synthesis. Deficiency of Factor B of the alternative pathway (AP) of complement is beneficial in LDLR(-/-) mice fed a high fat diet. The serum glycoprotein properdin is a key positive regulator of the AP but has not been studied in experimental atherosclerosis. Atherosclerosis was assessed after feeding low fat (LFD) or high fat (HFD) Western type diets to newly generated LDLR(-/-) Properdin(KO) (LDLR(-/-)P(KO)) and LDLR-/-PWT mice. Lipids, lymphocytes and monocytes were similar among genotypes, genders and diets. Complement C3, but not C3adesarg, levels were enhanced in LDLR(-/-)P(KO) mice regardless of diet type or gender. Non-esterified fatty acids (NEFA) were decreased in male LDLR(-/-)P(KO) fed a HFD compared with controls. All mice showed significant atherosclerotic burden in aortae and at aortic roots but male LDLR(-/-) mice fed a LFD were affected to the greatest extent by the absence of properdin. The protective effect of properdin expression was overwhelmed in both genders of LDLR(-/-)mice when fed a HFD. We conclude that properdin plays an unexpectedly beneficial role in the development and progression of early atherosclerotic lesions.
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A risk function for behavioral disruption of Blainville's beaked whales (Mesoplodon densirostris) from mid-frequency active sonar.
PLoS ONE
PUBLISHED: 01-01-2014
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There is increasing concern about the potential effects of noise pollution on marine life in the world's oceans. For marine mammals, anthropogenic sounds may cause behavioral disruption, and this can be quantified using a risk function that relates sound exposure to a measured behavioral response. Beaked whales are a taxon of deep diving whales that may be particularly susceptible to naval sonar as the species has been associated with sonar-related mass stranding events. Here we derive the first empirical risk function for Blainville's beaked whales (Mesoplodon densirostris) by combining in situ data from passive acoustic monitoring of animal vocalizations and navy sonar operations with precise ship tracks and sound field modeling. The hydrophone array at the Atlantic Undersea Test and Evaluation Center, Bahamas, was used to locate vocalizing groups of Blainville's beaked whales and identify sonar transmissions before, during, and after Mid-Frequency Active (MFA) sonar operations. Sonar transmission times and source levels were combined with ship tracks using a sound propagation model to estimate the received level (RL) at each hydrophone. A generalized additive model was fitted to data to model the presence or absence of the start of foraging dives in 30-minute periods as a function of the corresponding sonar RL at the hydrophone closest to the center of each group. This model was then used to construct a risk function that can be used to estimate the probability of a behavioral change (cessation of foraging) the individual members of a Blainville's beaked whale population might experience as a function of sonar RL. The function predicts a 0.5 probability of disturbance at a RL of 150 dBrms re µPa (CI: 144 to 155) This is 15dB lower than the level used historically by the US Navy in their risk assessments but 10 dB higher than the current 140 dB step-function.
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Applying distance sampling to fin whale calls recorded by single seismic instruments in the northeast Atlantic.
J. Acoust. Soc. Am.
PUBLISHED: 11-05-2013
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Automated methods were developed to detect fin whale calls recorded by an array of ocean bottom seismometers (OBSs) deployed off the Portuguese coast between 2007 and 2008. Using recordings collected on a single day in January 2008, a standard seismological method for estimating earthquake location from single instruments, the three-component analysis, was used to estimate the relative azimuth, incidence angle, and horizontal range between each OBS and detected calls. A validation study using airgun shots, performed prior to the call analysis, indicated that the accuracy of the three-component analysis was satisfactory for this preliminary study. Point transect sampling using cue counts, a form of distance sampling, was then used to estimate the average probability of detecting a call via the array during the chosen day. This is a key step to estimating density or abundance of animals using passive acoustic data. The average probability of detection was estimated to be 0.313 (standard error: 0.033). However, fin whale density could not be estimated due to a lack of an appropriate estimate of cue (i.e., vocalization) rate. This study demonstrates the potential for using a sparse array of widely spaced, independently operating acoustic sensors, such as OBSs, for estimating cetacean density.
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Plasma membranes as heat stress sensors: From lipid-controlled molecular switches to therapeutic applications.
Biochim. Biophys. Acta
PUBLISHED: 10-30-2013
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The classic heat shock (stress) response (HSR) was originally attributed to protein denaturation. However, heat shock protein (Hsp) induction occurs in many circumstances where no protein denaturation is observed. Recently considerable evidence has been accumulated to the favour of the "Membrane Sensor Hypothesis" which predicts that the level of Hsps can be changed as a result of alterations to the plasma membrane. This is especially pertinent to mild heat shock, such as occurs in fever. In this condition the sensitivity of many transient receptor potential (TRP) channels is particularly notable. Small temperature stresses can modulate TRP gating significantly and this is influenced by lipids. In addition, stress hormones often modify plasma membrane structure and function and thus initiate a cascade of events, which may affect HSR. The major transactivator heat shock factor-1 integrates the signals originating from the plasma membrane and orchestrates the expression of individual heat shock genes. We describe how these observations can be tested at the molecular level, for example, with the use of membrane perturbers and through computational calculations. An important fact which now starts to be addressed is that membranes are not homogeneous nor do all cells react identically. Lipidomics and cell profiling are beginning to address the above two points. Finally, we observe that a deregulated HSR is found in a large number of important diseases where more detailed knowledge of the molecular mechanisms involved may offer timely opportunities for clinical interventions and new, innovative drug treatments. This article is part of a Special Issue entitled: Membrane structure and function: Relevance in the cells physiology, pathology and therapy. This article is part of a Special Issue entitled: Membrane structure and function: Relevance in the cells physiology, pathology and therapy.
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Estimating resource acquisition and at-sea body condition of a marine predator.
J Anim Ecol
PUBLISHED: 05-13-2013
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Body condition plays a fundamental role in many ecological and evolutionary processes at a variety of scales and across a broad range of animal taxa. An understanding of how body condition changes at fine spatial and temporal scales as a result of interaction with the environment provides necessary information about how animals acquire resources. However, comparatively little is known about intra- and interindividual variation of condition in marine systems. Where condition has been studied, changes typically are recorded at relatively coarse time-scales. By quantifying how fine-scale interaction with the environment influences condition, we can broaden our understanding of how animals acquire resources and allocate them to body stores. Here we used a hierarchical Bayesian state-space model to estimate the body condition as measured by the size of an animals lipid store in two closely related species of marine predator that occupy different hemispheres: northern elephant seals (Mirounga angustirostris) and southern elephant seals (Mirounga leonina). The observation model linked drift dives to lipid stores. The process model quantified daily changes in lipid stores as a function of the physiological condition of the seal (lipid:lean tissue ratio, departure lipid and departure mass), its foraging location, two measures of behaviour and environmental covariates. We found that physiological condition significantly impacted lipid gain at two time-scales - daily and at departure from the colony - that foraging location was significantly associated with lipid gain in both species of elephant seals and that long-term behavioural phase was associated with positive lipid gain in northern and southern elephant seals. In northern elephant seals, the occurrence of short-term behavioural states assumed to represent foraging were correlated with lipid gain. Lipid gain was a function of covariates in both species. Southern elephant seals performed fewer drift dives than northern elephant seals and gained lipids at a lower rate. We have demonstrated a new way to obtain time series of body condition estimates for a marine predator at fine spatial and temporal scales. This modelling approach accounts for uncertainty at many levels and has the potential to integrate physiological and movement ecology of top predators. The observation model we used was specific to elephant seals, but the process model can readily be applied to other species, providing an opportunity to understand how animals respond to their environment at a fine spatial scale.
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Key role of lipids in heat stress management.
FEBS Lett.
PUBLISHED: 04-30-2013
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Heat stress is a common and, therefore, an important environmental impact on cells and organisms. While much attention has been paid to severe heat stress, moderate temperature elevations are also important. Here we discuss temperature sensing and how responses to heat stress are not necessarily dependent on denatured proteins. Indeed, it is clear that membrane lipids have a pivotal function. Details of membrane lipid changes and the associated production of signalling metabolites are described and suggestions made as to how the interconnected signalling network could be modified for helpful intervention in disease.
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Regulation of lipid synthesis in oil crops.
FEBS Lett.
PUBLISHED: 04-26-2013
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Oil crops are in increasing demand both for food and as renewable sources of chemicals. It is therefore vital to understand how oil accumulation is regulated. Different ways of obtaining such information are discussed with an emphasis on metabolic control analysis. The usefulness of the latter has been well-illustrated by its application to help raise yields in oilseed rape.
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Molecular markers for identifying municipal, domestic and agricultural sources of organic matter in natural waters.
Chemosphere
PUBLISHED: 04-05-2013
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Molecular markers can be used to determine the sources of organic pollution in water. This review summarizes progress made during the last two decades in identifying reliable molecular markers to distinguish pollution from sewage, animal production, and other sources. Two artificial sweeteners, sucralose and acesulfame-K, are sufficiently stable to be molecular markers and easily associated with domestic wastewater. Waste from different animal species may be distinguished by profiling fecal sterols and bile acids. Other markers which have been evaluated, including caffeine, detergent components, and compounds commonly leached from landfills are discussed.
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Conserved valproic-acid-induced lipid droplet formation in Dictyostelium and human hepatocytes identifies structurally active compounds.
Dis Model Mech
PUBLISHED: 10-14-2011
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Lipid droplet formation and subsequent steatosis (the abnormal retention of lipids within a cell) has been reported to contribute to hepatotoxicity and is an adverse effect of many pharmacological agents including the antiepileptic drug valproic acid (VPA). In this study, we have developed a simple model system (Dictyostelium discoideum) to investigate the effects of VPA and related compounds in lipid droplet formation. In mammalian hepatocytes, VPA increases lipid droplet accumulation over a 24-hour period, giving rise to liver cell damage, and we show a similar effect in Dictyostelium following 30 minutes of VPA treatment. Using (3)H-labelled polyunsaturated (arachidonic) or saturated (palmitic) fatty acids, we shown that VPA treatment of Dictyostelium gives rise to an increased accumulation of both types of fatty acids in phosphatidylcholine, phosphatidylethanolamine and non-polar lipids in this time period, with a similar trend observed in human hepatocytes (Huh7 cells) labelled with [(3)H]arachidonic acid. In addition, pharmacological inhibition of ?-oxidation in Dictyostelium phenocopies fatty acid accumulation, in agreement with data reported in mammalian systems. Using Dictyostelium, we then screened a range of VPA-related compounds to identify those with high and low lipid-accumulation potential, and validated these activities for effects on lipid droplet formation by using human hepatocytes. Structure-activity relationships for these VPA-related compounds suggest that lipid accumulation is independent of VPA-catalysed teratogenicity and inositol depletion. These results suggest that Dictyostelium could provide both a novel model system for the analysis of lipid droplet formation in human hepatocytes and a rapid method for identifying VPA-related compounds that show liver toxicology.
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A raison dêtre for two distinct pathways in the early steps of plant isoprenoid biosynthesis?
Prog. Lipid Res.
PUBLISHED: 10-06-2011
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When compared to other organisms, plants are atypical with respect to isoprenoid biosynthesis: they utilize two distinct and separately compartmentalized pathways to build up isoprene units. The co-existence of these pathways in the cytosol and in plastids might permit the synthesis of many vital compounds, being essential for a sessile organism. While substrate exchange across membranes has been shown for a variety of plant species, lack of complementation of strong phenotypes, resulting from inactivation of either the cytosolic pathway (growth and development defects) or the plastidial pathway (pigment bleaching), seems to be surprising at first sight. Hundreds of isoprenoids have been analyzed to determine their biosynthetic origins. It can be concluded that in angiosperms, under standard growth conditions, C??-phytyl moieties, C??-triterpenes and C??-carotenoids are made nearly exclusively within compartmentalized pathways, while mixed origins are widespread for other types of isoprenoid-derived molecules. It seems likely that this coexistence is essential for the interaction of plants with their environment. A major purpose of this review is to summarize such observations, especially within an ecological and functional context and with some emphasis on regulation. This latter aspect still requires more work and present conclusions are preliminary, although some general features seem to exist.
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Induction of expression of a 14-3-3 gene in response to copper exposure in the marine alga, Fucus vesiculosus.
Ecotoxicology
PUBLISHED: 08-13-2011
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The macro-alga Fucus vesiculosus has a broad global and estuarine distribution and exhibits exceptional resistance to toxic metals, the molecular basis of which is poorly understood. To address this issue a cDNA library was constructed from an environmental isolate of F. vesiculosus growing in an area with chronic copper pollution. Characterisation of this library led to the identification of a cDNA encoding a protein known to be synthesised in response to toxicity, a full length 14-3-3 exhibiting a 71% identity to human/mouse epsilon isoform, 70-71% identity to yeast BMH1/2 and 95 and 71% identity to the Ectocarpus siliculosus 14-3-3 isoforms 1 and 2 respectively. Preliminary characterisation of the expression profile of the 14-3-3 indicated concentration- and time-dependent inductions on acute exposure of F. vesiculosus of copper (3-30 ?g/l). Higher concentrations of copper (?150 ?g/l) did not elicit significant induction of the 14-3-3 gene compared with the control even though levels of both intracellular copper and the expression of a cytosolic metal chaperone, metallothionein, continued to rise. Analysis of gene expression within environmental isolates demonstrated up-regulation of the 14-3-3 gene associated with the known copper pollution gradient. Here we report for the first time, identification of a gene encoding a putative 14-3-3 protein in a multicellular alga and provide preliminary evidence to link the induction of this 14-3-3 gene to copper exposure in this alga. Interestingly, the threshold exposure profile may be associated with a decrease in the organisms ability to control copper influx so that it perceives copper as a toxic response.
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Heat stress causes spatially-distinct membrane re-modelling in K562 leukemia cells.
PLoS ONE
PUBLISHED: 05-01-2011
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Cellular membranes respond rapidly to various environmental perturbations. Previously we showed that modulations in membrane fluidity achieved by heat stress (HS) resulted in pronounced membrane organization alterations which could be intimately linked to the expression and cellular distribution of heat shock proteins. Here we examine heat-induced membrane changes using several visualisation methods. With Laurdan two-photon microscopy we demonstrate that, in contrast to the enhanced formation of ordered domains in surface membranes, the molecular disorder is significantly elevated within the internal membranes of cells preexposed to mild HS. These results were compared with those obtained by anisotropy, fluorescence lifetime and electron paramagnetic resonance measurements. All probes detected membrane changes upon HS. However, the structurally different probes revealed substantially distinct alterations in membrane heterogeneity. These data call attention to the careful interpretation of results obtained with only a single label. Subtle changes in membrane microstructure in the decision-making of thermal cell killing could have potential application in cancer therapy.
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NMR quantitation: influence of RF inhomogeneity.
Magn Reson Chem
PUBLISHED: 04-03-2011
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The NMR peak integral is ideally linearly dependent on the sine of excitation angle (?), which has provided unsurpassed flexibility in quantitative NMR by allowing the use of a signal of any concentration as the internal concentration reference. Controlling the excitation angle is particularly critical for solvent proton concentration referencing to minimize the negative impact of radiation damping, and to reduce the risk of receiver gain compression. In practice, due to the influence of RF inhomogeneity for any given probe, the observed peak integral is not exactly proportional to sin ?. To evaluate the impact quantitatively, we introduce a RF inhomogeneity factor I(?) as a function of the nominal pulse excitation angle and propose a simple calibration procedure. Alternatively, I(?) can be calculated from the probes RF profile, which can be readily obtained as a gradient image of an aqueous sample. Our results show that without consideration of I(?), even for a probe with good RF homogeneity, up to 5% error can be introduced due to different excitation pulse angles used for the analyte and the reference. Hence, a simple calibration of I(?) can eliminate such errors and allow an accurate description of the observed NMR signals dependence on the excitation angle in quantitative analysis.
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A survey on the utility of the USEPA CADDIS stressor identification procedure.
Environ Monit Assess
PUBLISHED: 03-03-2011
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The Environmental Protection Agency (EPA) has made available on the worldwide web a systematic stream stressor identification procedure, the "Causal Analysis/Diagnosis Decision Information System" or CADDIS. We report here the results of a survey of regulators and scientists in 11 states who use CADDIS or another stressor identification procedure in their work. The 13 survey questions address guidelines as to what impairment scenarios to approach with stressor identification, what information is needed to perform stressor identification, and what the stakeholder role is in performing stressor identification. At the time of this survey (the summer of 2009), the EPA CADDIS website was less commonly used among the state regulators surveyed than the published EPA stressor identification document on which it is based. The respondents generally find the EPA stressor identification procedure useful and capable of being adapted to their individual needs. Survey respondents all use stressor identification in their Total Maximum Daily Load work, but also in a wide variety of other applications. All the "types of evidence" included in the CADDIS stressor identification procedure are used by the practitioners surveyed with the exception of the results of ecological simulation models. While the CADDIS documentation encourages the involvement of stakeholders in stressor identification, most respondents do not assemble stakeholder teams of local officials and citizens to participate in stressor analyses.
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Eicosapentaenoic acid and docosahexaenoic acid regulate modified LDL uptake and macropinocytosis in human macrophages.
Lipids
PUBLISHED: 01-21-2011
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There is evidence that long chain n-3 PUFA (such as from fish oils) provide atheroprotection through, in part, changes in macrophage function although it has not been fully determined whether these n-3 PUFA target cellular mechanisms that control macrophage foam cell formation. Therefore, we investigated whether the n-3 PUFA, EPA and DHA, modulate modified low-density lipoprotein (LDL) uptake by human macrophages. The uptake of fluorophore labeled acetylated LDL (AcLDL) and/or oxidized LDL (OxLDL) by THP-1 macrophages and primary human monocyte-derived macrophages were measured by flow cytometry following co-incubation with EPA or DHA in vitro. DHA inhibited both AcLDL and OxLDL uptake in human macrophages whilst EPA reduced AcLDL and increased OxLDL uptake. These effects were only partly explained by changes in the mRNA and protein expression of key scavenger receptors, such as CD36 and scavenger receptor-A, in these cells suggesting the involvement of a scavenger receptor-independent mechanism. EPA and DHA inhibited macropinocytosis, as measured by Lucifer Yellow uptake, in human macrophages and attenuated the expression of Syndecan-4, which has been implicated in the uptake of other modified forms of LDL. EPA and DHA reduced modified LDL uptake by human macrophages through a mechanism that is in part scavenger receptor-independent and may involve inhibition of macropinocytosis and Syndecan-4 expression. This suggests that both EPA and DHA are capable of regulating macrophage foam cell formation and adds to the evidence describing an atheroprotective role for n-3 PUFA, implicating them as potential therapeutic agents for the treatment of clinical atherosclerosis.
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A quick diagnostic test for NMR receiver gain compression.
Magn Reson Chem
PUBLISHED: 09-03-2010
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Modern NMR spectrometers require receivers to work within their linear ranges to maintain high fidelity line shape and peak integration. For better sensitivity, the receiver gain has to be optimized to detect dilute analytes; however, gain compression needs to be avoided. Here, we explore if and how linear receiver performance can be achieved for a couple of representative gain settings on a spectrometer. In the case of slight receiver gain compression, not only will the peak integral be attenuated but a very small line-shape change can also be observed. Hence, we can resort to resonance integration and line-shape analysis for gain compression diagnosis. As such, NMR signals, regardless of their observed amplitude difference in frequency domain, can be accurately compared in quantitative analysis.
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The action of herbicides on fatty acid biosynthesis and elongation in barley and cucumber.
Pest Manag. Sci.
PUBLISHED: 06-10-2010
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Herbicides that affect lipid metabolism have been used commercially for many years. Here, napropamide, diphenamid, dimethachlor and cafenstrole are compared; these have all been classified by the Herbicide Resistance Action Committee (HRAC) as K(3) herbicides and inhibitors of cell division and/or synthesis of very-long-chain fatty acids (VLCFAs). In addition, spiro-decanedione A and pinoxaden dione are compared as inhibitors of lipid synthesis through inhibition of acetyl-CoA carboxylase (ACCase).
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Lipid classes and fatty acid patterns are altered in the brain of ?-synuclein null mutant mice.
Lipids
PUBLISHED: 05-07-2010
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The well-documented link between ?-synuclein and the pathology of common human neurodegenerative diseases has increased attention to the synuclein protein family. The involvement of ?-synuclein in lipid metabolism in both normal and diseased nervous system has been shown by many research groups. However, the possible involvement of ?-synuclein, a closely-related member of the synuclein family, in these processes has hardly been addressed. In this study, the effect of ?-synuclein deficiency on the lipid composition and fatty acid patterns of individual lipids from two brain regions has been studied using a mouse model. The level of phosphatidylserine (PtdSer) was increased in the midbrain whereas no changes in the relative proportions of membrane polar lipids were observed in the cortex of ?-synuclein-deficient compared to wild-type (WT) mice. In addition, higher levels of docosahexaenoic acid were found in PtdSer and phosphatidylethanolamine (PtdEtn) from the cerebral cortex of ?-synuclein null mutant mice. These findings show that ?-synuclein deficiency leads to alterations in the lipid profile in brain tissues and suggest that this protein, like ?-synuclein, might affect neuronal function via modulation of lipid metabolism.
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Lipidomics reveals membrane lipid remodelling and release of potential lipid mediators during early stress responses in a murine melanoma cell line.
Biochim. Biophys. Acta
PUBLISHED: 04-15-2010
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Membranes are known to respond rapidly to various environmental perturbations by changing their composition and microdomain organization. In previous work we showed that a membrane fluidizer benzyl alcohol (BA) could mimic the effects of heat stress and enhance heat shock protein synthesis in different mammalian cells. Here we explore heat- and BA-induced stress further by characterizing stress-induced membrane lipid changes in mouse melanoma B16 cells. Lipidomic fingerprints revealed that membrane stress achieved either by heat or BA resulted in pronounced and highly specific alterations in lipid metabolism. The loss in polyenes with the concomitant increase in saturated lipid species was shown to be a consequence of the activation of phopholipases (mainly phopholipase A(2) and C). A phospholipase C-diacylglycerol lipase-monoacylglycerol lipase pathway was identified in B16 cells and contributed significantly to the production of several lipid mediators upon stress including the potent heat shock modulator, arachidonic acid. The accumulation of cholesterol, ceramide and saturated phosphoglyceride species with raft-forming properties observed upon both heat and BA treatments of B16 cells may explain the condensation of ordered plasma membrane domains previously detected by fluorescence microscopy and may serve as a signalling platform in stress responses or as a primary defence mechanism against the noxious effects of stresses.
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Comparison of the 1988 and 2002 phocine distemper epizootics in British harbour seal Phoca vitulina populations.
Dis. Aquat. Org.
PUBLISHED: 04-10-2010
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In 1988 and 2002 dramatic and well-documented phocine distemper epizootics occurred in Europe. While their progression and impact were remarkably similar and consistent over much of Europe, mortality in the UK varied greatly between and within the 2 epizootics. We use antibody levels in blood samples to show that 51% (Bayesian 95% CI: 41 to 61%) of the individuals alive in 5 UK harbour seal populations at the end of the 1988 epizootic had been exposed to the virus, and that the equivalent figure after the 2002 outbreak was 22% (95% CI: 16 to 30%). Antibody prevalence was significantly higher in females than males after the 2002 epizootic. Combining these estimates with information on reductions in the numbers of animals observed hauled out during surveys of the Wash, Moray Firth, and Orkney populations and a simple epidemiological model, suggests that the differences between the 2 epizootics were primarily due to a 27% (95% CI: 8 to 43%) fall in R0, the basic reproductive rate of the virus. The large geographic variation in population effects observed within the UK during each epizootic appears to have been mainly due to differences in case mortality, with R0 being remarkably similar in all the populations investigated.
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The functional response of a generalist predator.
PLoS ONE
PUBLISHED: 01-12-2010
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Predators can have profound impacts on the dynamics of their prey that depend on how predator consumption is affected by prey density (the predators functional response). Consumption by a generalist predator is expected to depend on the densities of all its major prey species (its multispecies functional response, or MSFR), but most studies of generalists have focussed on their functional response to only one prey species.
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Receiver gain function: the actual NMR receiver gain.
Magn Reson Chem
PUBLISHED: 01-12-2010
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The observed NMR signal size depends on the receiver gain parameter. We propose a receiver gain function to characterize how much the raw FID is amplified by the receiver as a function of the receiver gain setting. Although the receiver is linear for a fixed gain setting, the actual gain of the receiver may differ from what the gain setting suggests. Nevertheless, for a given receiver, we demonstrate that the receiver gain function can be calibrated. Such a calibration enables accurate comparison of separately acquired NMR signals in quantitative analysis, which frequently requires different receiver gain settings to avoid receiver saturation or achieve optimum sensitivity. The application of receiver gain function, along with the definition of receiving efficiency, allows easy concentration determination by a single internal or external concentration reference.
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The versatility of algae and their lipid metabolism.
Biochimie
PUBLISHED: 09-26-2009
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Eukaryotic algae are a very diverse group of organisms that are key components of ecosystems ranging from deserts to the Antarctic. They account for over half of the primary production at the base of food chains. The lipids of different classes are varied and contain unusual compounds not found in other phyla. In this short review, we introduce the major cellular lipids and their fatty acids and then describe how the latter (particularly the polyunsaturated fatty acids, PUFAs) are synthesised. The discovery of different elongases and desaturases important for PUFA production is detailed and their application for biotechnology described. Finally, the potential for algae in commercial applications is discussed, particularly in relation to the production of very long chain PUFAs and biofuel.
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Effect of irrigation on quality attributes of olive oil.
J. Agric. Food Chem.
PUBLISHED: 09-03-2009
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Two irrigation treatments were applied to olive trees of the major commercial Cretan variety cv. Koroneiki, (a) irrigation with 0.4 evaporation class "A" pan and (b) rain-feed only, in two successive crop years to assess the effect of irrigation on olive oil quality. Olive fruits were harvested at their semiblack maturity stage. Data obtained indicated that irrigation increased fruit weight and oil content, but the standard quality indices (free fatty acids, peroxide value, K(232), and K(270)) of the oil were not affected significantly. However, irrigation affected some aspects of olive oil composition. There were changes in the proportions of polyunsaturated fatty acids (PUFAs), triacylglycerol molecular species, sterols, and aliphatic alcohols. Furthermore, the concentrations of the dialdehydic form of elenolic acid linked to 3,4-DHPEA (3,4-DHPEA-EDA) and the isomer of oleuropeine aglycon (3,4-DHPEA-EA) were higher in oils from non-irrigated trees. Tocopherol and total volatiles were higher in the oil produced from the non-irrigated trees. Such oil was graded more pungent when compared to oils produced from fruits of irrigated trees, although both oils were graded satisfactory by consumers.
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Use of metabolic control analysis to give quantitative information on control of lipid biosynthesis in the important oil crop, Elaeis guineensis (oilpalm).
New Phytol.
PUBLISHED: 07-27-2009
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* Oil crops are a very important commodity. Although many genes and enzymes involved in lipid accumulation have been identified, much less is known of regulation of the overall process. To address the latter we have applied metabolic control analysis to lipid synthesis in the important crop, oilpalm (Elaeis guineensis). * Top-down metabolic control analysis (TDCA) was applied to callus cultures capable of accumulating appreciable triacylglycerol. The biosynthetic pathway was divided into two blocks, connected by the intermediate acyl-CoAs. Block A comprised enzymes for fatty acid synthesis and Block B comprised enzymes of lipid assembly. * Double manipulation TDCA used diflufenican and bromooctanoate to inhibit Block A and Block B, respectively, giving Block flux control coefficients of 0.61 and 0.39. Monte Carlo simulations provided extra information from previously-reported single manipulation TDCA data, giving Block flux control coefficients of 0.65 and 0.35 for A and B. * These experiments are the first time that double manipulation TDCA has been applied to lipid biosynthesis in any organism. The data show that approaching two-thirds of the total control of carbon flux to lipids in oilpalm cultures lies with the fatty acid synthesis block of reactions. This quantitative information will assist future, informed, genetic manipulation of oilpalm.
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Characterization and partial purification of acyl-CoA:glycerol 3-phosphate acyltransferase from sunflower (Helianthus annuus L.) developing seeds.
Plant Physiol. Biochem.
PUBLISHED: 06-25-2009
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The glycerol 3-phosphate acyltransferase (GPAT, EC 2.3.1.15) from sunflower (Helianthus annuus L.) microsomes has been characterised and partially purified. The in vitro determination of activity was optimized, and the maximum value for GPAT activity identified between 15 and 20 days after flowering. The apparent Michaelis-Menten K(m) for the glycerol 3-phosphate was 354 muM. The preferred substrates were palmitoyl-CoA = linoleoyl-CoA > oleoyl-CoA with the lowest activity using stearoyl-CoA. High solubilisation was achieved using 0.75% Tween80 and the solubilised GPAT was partially purified by ion-exchange chromatography using a Hi-Trap DEAE FF column, followed by gel filtration chromatography using a Superose 12 HR column. The fraction containing the GPAT activity was analysed by SDS-PAGE and contained a major band of 60.1 kDa. Finally, evidence is provided which shows the role of GPAT in the asymmetrical distribution, between positions sn-1 and sn-3, of saturated fatty acids in highly saturated sunflower triacylglycerols. This work provides background information on the sunflower endoplasmic reticulum GPAT which may prove valuable for future modification of oil deposition in this important crop.
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Contrasting effects of n-3 and n-6 fatty acids on cyclooxygenase-2 in model systems for arthritis.
Lipids
PUBLISHED: 06-08-2009
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Cyclooxygenase-2 (COX-2) is intimately involved in symptoms of arthritis while dietary n-3 polyunsaturated fatty acids (PUFA) are thought to be beneficial. In these experiments, using both bovine and human in vitro systems that mimic features of arthritis, we show that the n-3 PUFA eicosapentaenoic acid (EPA) is able to reduce mRNA and protein levels of COX-2. Activity, as assessed through prostaglandin E(2) formation, was also reduced in a dose-dependent manner. These effects of EPA contrasted noticeably with the n-6 PUFA, arachidonic acid. The data provide direct evidence for a molecular mechanism by which dietary n-3 PUFA, such as EPA, can reduce inflammation and, hence, associated symptoms in arthritis.
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The microaerophilic flagellate, Trichomonas vaginalis, contains unusual acyl lipids but no detectable cardiolipin.
J. Eukaryot. Microbiol.
PUBLISHED: 04-02-2009
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Previous lipid analysis of trichomonads has led to controversy as to whether these hydrogenosome-containing organisms contain cardiolipin (CL), which is a characteristic component of mitochondria. Here we report a careful lipid analysis of the sexually transmitted protist Trichomonas vaginalis. Major lipids were phosphatidylethanolamine (42%) and phosphatidylcholine (20%) with lesser amounts of phosphatidylglycerol (PG) (12%) and non-polar components. Two unusual lipids, acyl-PG (8%) and ceramide phosphorylethanolamine (2%), were also significant components. The structures of these lipids were confirmed by tandem mass spectrometry following reverse-phase high-performance liquid chromatography. This is the first time ceramide phosphorylethanolamine has been reported in a trichomonad. In contrast, CL (diphosphatidylglycerol) could not be detected either by two-dimensional thin-layer chromatography or by mass spectrometry. These data are discussed in relation to the organisms phylogenetic origin as a parasite showing secondary adaptation to microaerobic conditions.
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R: A quantitative measure of NMR signal receiving efficiency.
J. Magn. Reson.
PUBLISHED: 03-03-2009
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Recognizing that the sensitivity of NMR is influenced by factors such as conductance and dielectric constant of the sample, we propose the receiving efficiency R to characterize how efficiently the NMR signal can be observed from a unit transverse magnetization in a sample under optimal probe tuning and matching conditions. Conveniently, the relative receiving efficiency can be defined as the ratio of the NMR signal induced by a unit transverse magnetization in a sample of interest and a reference solution. Based on the reciprocal relationship between excitation and observation in NMR, the relative receiving efficiency can be correlated with the 90 degrees pulse length (tau(90)). In the special case of perfect probe tuning (impedance matched to 50 Omega), R is inversely proportional to tau(90). Application of the NMR receiving efficiency in quantitative analysis potentially enables a single external concentration reference for almost any sample, eliminating the need to know its exact chemical composition or detailed electromagnetic properties.
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Increasing the flow of carbon into seed oil.
Biotechnol. Adv.
PUBLISHED: 02-02-2009
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The demand for vegetable oils for food, fuel (bio-diesel) and bio-product applications is increasing rapidly. In Canada alone, it is estimated that a 50 to 75% increase in canola oil production will be required to meet the demand for seed oil in the next 7-10years. Plant breeding and genetics have demonstrated that seed oil content is a quantitative trait based on a number of contributing factors including embryo genetic effects, cytoplasmic effects, maternal genetic effects, and genotype-environment interactions. Despite the involvement of numerous quantitative trait loci in determining seed oil content, genetic engineering to over-express/repress specific genes encoding enzymes and other proteins involved in the flow of carbon into seed oil has led to the development of transgenic lines with significant increases in seed oil content. Proteins encoded by these genes include enzymes catalyzing the production of building blocks for oil assembly, enzymes involved in oil assembly, enzymes regulating metabolic carbon partitioning between oil, carbohydrate and secondary metabolite fractions, and transcription factors which orchestrate metabolism at a more general level.
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Olive oil qualitative parameters after orchard irrigation with saline water.
J. Agric. Food Chem.
PUBLISHED: 01-29-2009
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The effect of irrigation with saline water on oil quality was studied in the two olive ( Olea europaea L.) cultivars Koroneiki and Mastoidis, which are the main varieties grown extensively on the island of Crete. Plants (5 years old) were grown outdoors in containers, filled with freely drained light soil. Four treatments were applied, differing in the NaCl added to the irrigation water as follows: 0 (control) 50, 100, and 150 mM NaCl. Drip irrigation was applied regularly, during the dry season (from April to October). Plants in all treatments were irrigated when the soil-water potential reached -40 kPa at a depth of 30 cm. Data showed that increased NaCl levels in irrigation water resulted in a decrease in oil content in the fruits and an increase in total phenols and their secoiridoid derivatives in olive oils from harvested fruits. Furthermore, changes also took place in the composition of fatty acids and triacylglycerol molecular species. The extent of alterations was different for the two varieties and greater in cv. Koroneiki. This fitted with agronomic evidence that cv. Koroneiki is less saline-tolerant than cv. Mastoidis.
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Modification of palm oil for anti-inflammatory nutraceutical properties.
Lipids
PUBLISHED: 01-09-2009
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Palm oil is one of the most important edible oils in the world. Its composition (rich in palmitate and oleate) make it suitable for general food uses but its utility could be increased if its fatty acid quality could be varied. In this study, we have modified a palm olein fraction by transesterification with the n-3 polyunsaturated fatty acids, alpha-linolenate or eicosapentaenoic acid (EPA). Evaluation of the potential nutritional efficacy of the oils was made using chondrocyte culture systems which can be used to mimic many of the degenerative and inflammatory pathways involved in arthritis. On stimulation of such cultures with interleukin-1alpha, they showed increased expression of cyclooxygenase-2, the inflammatory cytokines tumour necrosis factor-alpha (TNF-alpha), IL-1alpha and IL-1beta and the proteinase ADAMTS-4. This increased expression was not affected by challenge of the cultures with palm olein alone but showed concentration-dependent reduction by the modified oil in a manner similar to EPA. These results show clearly that it is possible to modify palm oil conveniently to produce a nutraceutical with effective anti-inflammatory properties.
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Metabolic control analysis of developing oilseed rape (Brassica napus cv Westar) embryos shows that lipid assembly exerts significant control over oil accumulation.
New Phytol.
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Metabolic control analysis allows the study of metabolic regulation. We applied both single- and double-manipulation top-down control analysis to examine the control of lipid accumulation in developing oilseed rape (Brassica napus) embryos. The biosynthetic pathway was conceptually divided into two blocks of reactions (fatty acid biosynthesis (Block A), lipid assembly (Block B)) connected by a single system intermediate, the acyl-coenzyme A (acyl-CoA) pool. Single manipulation used exogenous oleate. Triclosan was used to inhibit specifically Block A, whereas diazepam selectively manipulated flux through Block B. Exogenous oleate inhibited the radiolabelling of fatty acids from [1-(14)C]acetate, but stimulated that from [U-14C]glycerol into acyl lipids. The calculation of group flux control coefficients showed that c. 70% of the metabolic control was in the lipid assembly block of reactions. Monte Carlo simulations gave an estimation of the error of the resulting group flux control coefficients as 0.27±0.06 for Block A and 0.73±0.06 for Block B. The two methods of control analysis gave very similar results and showed that Block B reactions were more important under our conditions. This contrasts notably with data from oil palm or olive fruit cultures and is important for efforts to increase oilseed rape lipid yields.
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Nutritional lipid supply can control the heat shock response of B16 melanoma cells in culture.
Mol. Membr. Biol.
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The in vitro culture of cells offers an extremely valuable method for probing biochemical questions and many commonly-used protocols are available. For mammalian cells a source of lipid is usually provided in the serum component. In this study we examined the question as to whether the nature of the lipid could become limiting at high cell densities and, therefore, prospectively influence the metabolism and physiology of the cells themselves. When B16 mouse melanoma cells were cultured, we noted a marked decrease in the proportions of n-3 and n-6 polyunsaturated fatty acids (PUFAs) with increasing cell density. This was despite considerable quantities of these PUFAs still remaining in the culture medium and seemed to reflect the preferential uptake of unesterified PUFA rather than other lipid classes from the media. The reduction in B16 total PUFA was reflected in changes in about 70% of the molecular species of membrane phosphoglycerides which were analysed by mass spectrometry. The importance of this finding lies in the need for n-3 and n-6 PUFA in mammalian cells (which cannot synthesize their own). Although the cholesterol content of cells was unchanged the amount of cholesterol enrichment in membrane rafts (as assessed by fluorescence) was severely decreased, simultaneous with a reduced heat shock response following exposure to 42°C. These data emphasize the pivotal role of nutrient supply (in this case for PUFAs) in modifying responses to stress and highlight the need for the careful control of culture conditions when assessing cellular responses in vitro.
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Heat shock response in photosynthetic organisms: membrane and lipid connections.
Prog. Lipid Res.
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The ability of photosynthetic organisms to adapt to increases in environmental temperatures is becoming more important with climate change. Heat stress is known to induce heat-shock proteins (HSPs) many of which act as chaperones. Traditionally, it has been thought that protein denaturation acts as a trigger for HSP induction. However, increasing evidence has shown that many stress events cause HSP induction without commensurate protein denaturation. This has led to the membrane sensor hypothesis where the membranes physical and structural properties play an initiating role in the heat shock response. In this review, we discuss heat-induced modulation of the membranes physical state and changes to these properties which can be brought about by interaction with HSPs. Heat stress also leads to changes in lipid-based signaling cascades and alterations in calcium transport and availability. Such observations emphasize the importance of membranes and their lipids in the heat shock response and provide a new perspective for guiding further studies into the mechanisms that mediate cellular and organismal responses to heat stress.
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