The inhibition of lipid synthesis in vitro in the locust, Schistocerca gregaria, by factors from the corpora cardiaca

ABSTRACT. The rate of lipid synthesis from [¹⁴C]acetate in fat body from Schistocerca americana gregaria has been studied in vitro. Maximum incorporation is found on days 6–10 in adults and day 4 of the fifth stadium. The label appeared in the fatty acid components of triacyl-glycerol, diacylglycerol and phospholipid.
Lipid synthesis in vitro was inhibited by extracts of corpora cardiaca, and such inhibition was most marked (up to 85%) in fat bodies from insects at stages where fatty acid synthesis was greatest. HPLC separation of corpora cardiaca extracts gave several active fractions of which the most active was adipokinetic hormone 1 (AKH-1).     

Local synthesis of the phosphatidylinositol-3,4-bisphosphate lipid drives focal adhesion turnover

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Specificity of Collybistin-Phosphoinositide Interactions: IMPACT OF THE INDIVIDUAL PROTEIN DOMAINS*

The regulatory protein collybistin (CB) recruits the receptor-scaffolding protein gephyrin to mammalian inhibitory glycinergic and GABAergic postsynaptic membranes in nerve cells. CB is tethered to the membrane via phosphoinositides. We developed an in vitro assay based on solid-supported 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine membranes doped with different phosphoinositides on silicon/silicon dioxide substrates to quantify the binding of various CB2 constructs using reflectometric interference spectroscopy. Based on adsorption isotherms, we obtained dissociation constants and binding capacities of the membranes. Our results show that full-length CB2 harboring the N-terminal Src homology 3 (SH3) domain (CB2_SH3+) adopts a closed and autoinhibited conformation that largely prevents membrane binding. This autoinhibition is relieved upon introduction of the W24A/E262A mutation, which conformationally “opens” CB2_SH3+ and allows the pleckstrin homology domain to properly bind lipids depending on the phosphoinositide species with a preference for phosphatidylinositol 3-monophosphate and phosphatidylinositol 4-monophosphate. This type of membrane tethering under the control of the release of the SH3 domain of CB is essential for regulating gephyrin clustering.     

The Alpha and Omega of Galactosylceramides in T Cell Immune Function

Glycosphingolipids are a subgroup of glycolipids that contain an amino alcohol sphingoid base linked to sugars. They are found in the membranes of cells ranging from bacteria to vertebrates. This group of lipids is known to stimulate the immune system through activation of a type of white blood cell known as natural killer T cell (NKT cell). Here we summarize the extensive research that has been done to identify the structures of natural glycolipids that stimulate NKT cells and to determine how these antigens are recognized. We also review studies designed to understand how glycolipid variants, both natural and synthetic, can alter the responses of NKT cells, leading to dramatic changes in the global immune response.     

Biodiesel preparation from microalgae lipid by two-step lipase catalysis

To overcome the high energy-consuming process of microalgae drying, a two-step lipase catalysis technique for the preparation of biodiesel from microalgae lipid of Chlorella spp. was developed. In the first step, free fatty acids (FAAs) and triacylglycerols (TAGs) are released after cell disruption and extracted, while the TAGs were hydrolysed by free lipase in aqueous phase. In the second step, FAAs were esterified with ethanol in the catalysis of free suspended lipase. The maximum rate of hydrolysis and esterification was 93.6% and 91.3%, respectively. The effects of reaction parameters, such as reaction time, enzyme amount, water content and molar ratio of lipid to ethanol on hydrolysis or esterification, were investigated. The results indicated that two-step reaction process (hydrolyse esterify) for biodiesel production were feasible.     

分泌型磷脂酶PLA2G5的生物学功能及其抑制剂研究进展

分泌型磷脂酶PLA2G5属于磷脂酶A2超家族的一员,在免疫细胞和非免疫细胞中均有表达.研究表明,PLA2G5参与生物学事件的发生发展,在特定的病理条件下具有诱导作用.本文简要阐述了PLA2G5的来源、结构特征、生物学功能和在疾病中的作用,以及现有或潜在的PLA2G5抑制剂,以期探索基于PLA2G5的治疗新靶标.     

Effect of Vaccinium ashei reade Leaf Extracts on Lipid Metabolism in Obese OLETF Rats

The effects of a hot water extract and fractional extracts from rabbiteye blueberry (Vaccinium ashei reade) leaves (BBL) on lipid metabolism were studied in obese Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Feeding the hot water extract and fractional extracts from BBL alleviated hepatic triglyceride accumulation in the rats. Additionally, feeding with the flavonol glycoside (FG) and proanthocyanidin (PA) fractions lowered serum cholesterol levels in the obese rats. The results from measurements of the hepatic enzyme activity indicate that the hypolipidemic effects of the hot water extract and the PA fraction might be attributable to enhanced lipolysis in the liver. The reduced serum levels of C-reactive protein, an inflammatory cytokine, by the chlorogenic acid + rutin fraction and FG fraction might be associated with alleviating the metabolic abnormalities in obese rats. These results indicate that the BBL extracts, and especially FG and PA, exerted hypolipidemic effects on obese OLETF rats and suggest that an infusion of BBL can be useful as a dietary hypolipidemic component.     

Spontaneous opening at zero membrane potential of sodium channels from eel electroplax reconstituted into lipid vesicles

Summary The voltage-dependent sodium channel from the eel electroplax was purified and reconstituted into vesicles of varying lipid composition. Isotopic sodium uptake experiments were conducted with vesicles at zero membrane potential, using veratridine to activate channels and tetrodotoxin to block them. Under these conditions, channel-dependent uptake of isotopic sodium by the vesicles was observed, demonstrating that a certain fraction of the reconstituted protein was capable of mediating ion fluxes. In addition, vesicles untreated with veratridine showed significant background uptake of sodium; a considerable proportion of this flux was blocked by tetrodotoxin. Thus these measurements showed that a significant subpopulation of channels was present that could mediate ionic fluxes in the absence of activating toxins. The proportion of channels exhibiting this behavior was dependent on the lipid composition of the vesicles and the temperature at which the uptake was measured; furthermore, the effect of temperature was reversible. However, the phenomenon was not affected by the degree of purification of the protein used for reconstitution, and channels in resealed electroplax membrane fragments or reconstituted, solely into native eel lipids did not show this behavior. The kinetics of vesicular uptake through these spontaneously-opening channels was slow, and we attribute this behavior to a modification of sodium channel inactivation.