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John L. Harwood

Bio: John L. Harwood is an academic researcher from Cardiff University. The author has contributed to research in topics: Lipid metabolism & Fatty acid. The author has an hindex of 60, co-authored 420 publications receiving 16081 citations. Previous affiliations of John L. Harwood include John L. Scott & Spanish National Research Council.


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TL;DR: There is an increasing interest in the inflammatory characteristics of lipid signalling molecules which have important consequences for many common skin complaints and can be regulated through dietary intervention or by topical therapies.
Abstract: Lipids are important for normal skin function. They are generated from two main sources – the epithelial cells and the sebum which is secreted onto the surface. Important functions of the lipids are to contribute to an effective barrier towards water loss, to protect from radiation and to prevent entry of harmful chemicals and microbes. There is also an increasing interest in the inflammatory characteristics of lipid signalling molecules which have important consequences for many common skin complaints. In many cases, these bioactive lipids can be regulated through dietary intervention or by topical and other therapies.

7 citations

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TL;DR: Under conditions of increased carbon flux through the pathway to TAG, there was a significant build-up of material in the PA and DAG pools, suggesting that PAP and D AGAT could be limiting for fat accumulation during light treatment.
Abstract: Oilseed rape is an important agricultural crop with the seed oil having many industrial as well as nutritional uses [l]. Considerable work has been carried out on the enzymes leading to the formation of storage TAGS by the Kennedy pathway [2]. We have examined this pathway for possible points which might show significant flux control and previous data have indicated that DAGAT (the final enzyme) may do so when TAG accumulation is high [3]. We have found that TAG synthesis was higher in the light compared with dark periods and have used these conditions to manipulate carbon flux. A low-erucate spring variety of oilseed rape (Brmsica napus L. cv Shiralee) was grown [4] and seeds harvested at 30 DAP, either towards the end of the dark period or 4 hr into the light period. For lipid analysis the seeds were steam-killed and the embryos rapidly dissected into [so-propanol, heated for 30 min at 70°C and analyzed as previously [4]. For n.m.r. studies and enzyme preparations the seeds were stored at -70°C until needed. Embryos were dissected out a few at a time and again stored at -70°C prior to use. In the P-n.m.r. analyses for G3P, neutralized perchloric acid extracts were prepared !?om 4 g frozen embryos [5]. For G3PAT, LPAAT and DAGAT assays radiolabelled substrates were used and the lipid products extracted, separated and analyzed [4]. PAP activity was determined by measuring the production of Pi, by the method of Chen et al. [6] as modified by Ichihara et al. [7]. The rate of lipid synthesis in the light was higher than in the dark as deduced from radiolabelling experiments involving ["Clacetate and ['Hlglycerol precursors [S]. When we compared pool sizes of intermediates in the Kennedy pathway, there were significant changes in their amounts on light treatment (Table 1). Thus, under conditions of increased carbon flux through the pathway to TAG, there was a significant build-up of material in the PA and DAG pools. There was also an apparent increase in the level of G3P, although because of the amount of material needed for n.m.r. we were only able to make a single determination. The increased levels of endogenous PA and DAG suggested that PAP and DAGAT could be limiting for fat accumulation during light treatment. Microsomal fractions from embryos are capable of incorporating radioactivity from precursors into TAG [S]. In addition, subcellular fractionation studies have shown that activity of Kennedy pathway enzymes are found in such membranes. Therefore, we measured the 'four enzymes in microsomes from embryos derived from rape plants subjected to light or dark treatment. In terms of either total or specific activity (Table 2), there were no significant changes for any of the enzymes assayed. Therefore, the increases in pool sizes induced by light treatment (Table 1) cannot be explained by decreases in particular enzyme activities. Three enzymes of the Kennedy pathway had relatively low activities (Table 2) and the substrate pool sizes for each rose when carbon flux was increased through the pathway (Table 1). 31

7 citations

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7 citations

Journal ArticleDOI
TL;DR: Intact olive callus cultures were used to investigate any possible effects which dimethoate, a commonly used organophosphorus insecticide in olive agriculture, may have on lipid synthesis and changed patterns of both lipid class and fatty acid labelling.

6 citations


Cited by
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Yusuf Chisti1
TL;DR: As demonstrated here, microalgae appear to be the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels.

9,030 citations

Journal ArticleDOI
TL;DR: In this article, the transesterification reaction is aected by molar ratio of glycerides to alcohol, catalysts, reaction temperature, reaction time and free fatty acids and water content of oils or fats.

4,902 citations

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TL;DR: The current understanding of IFN‐γ ligand, receptor, ignal transduction, and cellular effects with a focus on macrophage responses and to a lesser extent, responses from other cell types that influence macrophages function during infection are reviewed.
Abstract: Interferon-gamma (IFN-gamma) coordinates a diverse array of cellular programs through transcriptional regulation of immunologically relevant genes. This article reviews the current understanding of IFN-gamma ligand, receptor, signal transduction, and cellular effects with a focus on macrophage responses and to a lesser extent, responses from other cell types that influence macrophage function during infection. The current model for IFN-gamma signal transduction is discussed, as well as signal regulation and factors conferring signal specificity. Cellular effects of IFN-gamma are described, including up-regulation of pathogen recognition, antigen processing and presentation, the antiviral state, inhibition of cellular proliferation and effects on apoptosis, activation of microbicidal effector functions, immunomodulation, and leukocyte trafficking. In addition, integration of signaling and response with other cytokines and pathogen-associated molecular patterns, such as tumor necrosis factor-alpha, interleukin-4, type I IFNs, and lipopolysaccharide are discussed.

3,589 citations

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TL;DR: A brief summary of the current knowledge on oleaginous algae and their fatty acid and TAG biosynthesis, algal model systems and genomic approaches to a better understanding of TAG production, and a historical perspective and path forward for microalgae-based biofuel research and commercialization are provided.
Abstract: Microalgae represent an exceptionally diverse but highly specialized group of micro-organisms adapted to various ecological habitats. Many microalgae have the ability to produce substantial amounts (e.g. 20-50% dry cell weight) of triacylglycerols (TAG) as a storage lipid under photo-oxidative stress or other adverse environmental conditions. Fatty acids, the building blocks for TAGs and all other cellular lipids, are synthesized in the chloroplast using a single set of enzymes, of which acetyl CoA carboxylase (ACCase) is key in regulating fatty acid synthesis rates. However, the expression of genes involved in fatty acid synthesis is poorly understood in microalgae. Synthesis and sequestration of TAG into cytosolic lipid bodies appear to be a protective mechanism by which algal cells cope with stress conditions, but little is known about regulation of TAG formation at the molecular and cellular level. While the concept of using microalgae as an alternative and renewable source of lipid-rich biomass feedstock for biofuels has been explored over the past few decades, a scalable, commercially viable system has yet to emerge. Today, the production of algal oil is primarily confined to high-value specialty oils with nutritional value, rather than commodity oils for biofuel. This review provides a brief summary of the current knowledge on oleaginous algae and their fatty acid and TAG biosynthesis, algal model systems and genomic approaches to a better understanding of TAG production, and a historical perspective and path forward for microalgae-based biofuel research and commercialization.

3,479 citations