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1.
Among all the metabolites present in the plasma, lipids, mainly triacylglycerol and diacylglycerol, show extensive circadian rhythms. These lipids are transported in the plasma as part of lipoproteins. Lipoproteins are synthesized primarily in the liver and intestine and their production exhibits circadian rhythmicity. Studies have shown that various proteins involved in lipid absorption and lipoprotein biosynthesis show circadian expression. Further, intestinal epithelial cells express circadian clock genes and these genes might control circadian expression of different proteins involved in intestinal lipid absorption. Intestinal circadian clock genes are synchronized by signals emanating from the suprachiasmatic nuclei that constitute a master clock and from signals coming from other environmental factors, such as food availability. Disruptions in central clock, as happens due to disruptions in the sleep/wake cycle, affect intestinal function. Similarly, irregularities in temporal food intake affect intestinal function. These changes predispose individuals to various metabolic disorders, such as metabolic syndrome, obesity, diabetes, and atherosclerosis. Here, we summarize how circadian rhythms regulate microsomal triglyceride transfer protein, apoAIV, and nocturnin to affect diurnal regulation of lipid absorption.  相似文献   
2.
We recently published two papers detailing the structures of fluid phase phosphatidylglycerol (PG) lipid bilayers (Ku?erka et al., 2012 J. Phys. Chem. B 116: 232–239; Pan et al., 2012 Biochim. Biophys. Acta Biomembr. 1818: 2135–2148), which were determined using the scattering density profile model. This hybrid experimental/computational technique utilizes molecular dynamics simulations to parse a lipid bilayer into components whose volume probabilities follow simple analytical functional forms. Given the appropriate scattering densities, these volume probabilities are then translated into neutron scattering length density (NSLD) and electron density (ED) profiles, which are used to jointly refine experimentally obtained small angle neutron and X-ray scattering data. However, accurate NSLD and ED profiles can only be obtained if the bilayer's chemical composition is known. Specifically, in the case of neutron scattering, the lipid's exchangeable hydrogens with aqueous D2O must be accounted for, as they can have a measureable effect on the resultant lipid bilayer structures. This was not done in our above-mentioned papers. Here we report on the molecular structures of PG lipid bilayers by appropriately taking into account the exchangeable hydrogens. Analysis indicates that the temperature-averaged PG lipid areas decrease by 1.5 to 3.8 Å2, depending on the lipid's acyl chain length and unsaturation, compared to PG areas when hydrogen exchange was not taken into account.  相似文献   
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厌氧条件下微量琼脂糖弥散法抑菌试验的建立及应用   总被引:1,自引:0,他引:1  
作者建立了在厌氧条件下两种微量而敏感的抑菌试验,可用于鉴定蛋白质或多肽类抑菌物质。(1)琼脂糖弥散法:可检测抗菌蛋白抑菌活性,(2)电泳凝胶弥散法:可直接确定存在于PAGE凝胶中抗菌蛋白条带。应用这两种方法,作者首次鉴定出血链球菌培养上清液中存在抑制牙周可疑致病菌的抗菌蛋白。  相似文献   
5.
探讨了利用蚕茧近红外反射光谱识别雌雄茧、死笼茧的方法及可行性。采用6250型近红外光谱分析仪,从波长680nm到1235nm对205颗鲜茧做了非破坏性扫描测试,用逐步判别方法从一、二阶导数光谱数据中抽取特征向量,以此特征向量建立Bayes判别函数,对375个检验样本进行识别,其符合率达95.7%,该方法明显优于以茧的重量和大小判别雌雄的方法。实验结果还表明,雌雄茧近红外反射光谱的差别,主要是由于蚕蛹性质不同所致,而与茧层的关系不大。  相似文献   
6.
The intestinal epithelium metabolism of glutamine plays a critical role in inter-organ nitrogen flow. Although it is known that glutamine is the primary oxidative energy source and nucleotide precursor in intestinal cells, the luminal uptake of glutamine by the apical surface of enterocytes is poorly understood. In this study we have uncovered the sodium-dependent transporter system responsible for L-glutamine uptake by the apical membrane of a human intestinal epithelial cell line. The sodium-dependent Michaelis constant (Km) = 247 +/- 45 microM glutamine, and Jmax = 4.44 +/- 0.65 x 10(-9) mole min-1(mg protein)-1 (37 degrees C). Glutamine shares the transporter with alanine, as demonstrated by unlabeled glutamine inhibition of [3H]alanine uptake kinetics with a purely competitive-type inhibition pattern, and glutamine inhibition Ki = 205 +/- 18 microM by Dixon analysis. The inhibition pattern for a series of amino acid analogs indicated that this intestinal apical membrane sodium-dependent transporter for glutamine is distinct from any other transport system found in membranes of non-intestinal cells.  相似文献   
7.
Many eucaryotic cell surface proteins are anchored to the plasma membrane via a glycosylphosphatidylinositol (GPI), of which the core region is highly conserved from protozoa to mammalian cells. Previous studies (Lisanti, M. P., Field, M. C., Caras, I. W., Menon, A. K., and Rodiguez-Boulan, E. (1991) EMBO J. 10, 1969-1977) showed that mannosamine blocked the expression of a recombinant GPI-anchored protein in Madin-Darby canine kidney cells and converted this protein to an unpolarized secretory product. In the present study, we examined the effect of mannosamine on the formation of the glycan portion of the GPI anchor precursors. This amino sugar inhibited the incorporation of mannose into the glycan portion, and the inhibition was dose-dependent. Mannosamine was shown to be incorporated into the glycan as mannosamine, probably mostly in the second mannose position and thereby to block the further addition of mannose and other anchor components. The products formed in the presence of this drug were characterized by gel filtration and high resolution TLC both before and after deamination with nitrous acid and dephosphorylation by HF. Galactosamine and trehalosamine were inactive in this system, whereas glucosamine also inhibited mannose incorporation into GPI intermediates.  相似文献   
8.
To investigate the effect and mechanism of microRNA-186-5p (miR-186-5p) on the apoptosis in high glucose (HG)–treated cardiomyocytes. Diabetic cardiomyopathy model was established in cardiomyocytes by stimulating with HG. The expressions of miR-186-5p and toll-like receptor 3 (TLR3) were detected by quantitative polymerase chain reaction or Western blot analysis, respectively. Apoptosis was detected in HG-treated cardiomyocytes by flow cytometry and Western blot analysis. The interaction between miR-186-5p and TLR3 was explored by bioinformatics analysis and luciferase activity assay. Results showed that miR-186-5p expression was downregulated in HG-treated cardiomyocytes and its overexpression reversed HG-induced apoptosis and cleaved caspase-3 protein expression. Moreover, TLR3 was indicated as a target of miR-186-5p and regulated by miR-186-5p. Knockdown of TLR3 suppressed HG-induced apoptosis and cleaved caspase-3 protein expression. Besides, restoration of TLR3 ablated the effect of miR-186-5p on cell apoptosis. Collectively, miR-186-5p attenuated HG-induced apoptosis by regulating TLR3 in cardiomyocytes, providing novel biomarker for treatment of diabetic cardiomyopathy.  相似文献   
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A recursive least squares based on Multi-model is proposed for non-uniformly sampled-data nonlinear (NUSDN) systems. The corresponding state space model of an NUSDN system is derived using lifting technique. Taking advantage of the Fuzzy c-Mean Clustering algorithm, NUSDN is divided into several local models. The basic idea is that the NUSDN system is viewed as a model switching system under a given rule. Once the local models are identified, the global model is determined. A pH neutralization process validate the performance of the proposed algorithm.  相似文献   
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