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11.
Sphingolipids are degraded by sphingomyelinase and ceramidase in the gut to ceramide and sphingosine, which may inhibit cell proliferation and induce apoptosis, and thus have anti-tumour effects in the gut. Although previous rodent studies including experiments on knockout mice indicate a role of neutral ceramidase in ceramide digestion, the human enzyme has never been purified and characterized in its purified form. We here report the purification and characterization of neutral ceramidase from human ileostomy content, using octanoyl-[(14)C]sphingosine as substrate. After four chromatographic steps, a homogeneous protein band with 116kDa was obtained. MALDI mass spectrometry identified 16 peptide masses similar to human ceramidase previously cloned by El Bawab et al. [Molecular cloning and characterization of a human mitochondrial ceramidase, J. Biol. Chem. 275 (2000) 21508-21513] and Hwang et al. [Subcellular localization of human neutral ceramidase expressed in HEK293 cells, Biochem. Biophys. Res. Commun. 331 (2005) 37-42]. By RT-PCR and 5'-RACE methods, a predicted partial nucleotide sequence of neutral ceramidase was obtained from a human duodenum biopsy sample, which was homologous to that of known neutral/alkaline ceramidases. The enzyme has neutral pH optimum and catalyses both hydrolysis and formation of ceramide without distinct bile salt dependence. It is inhibited by Cu(2+) and Zn(2+) ions and by low concentrations of cholesterol. The enzyme is a glycoprotein but deglycosylation does not affect its activity. Our study indicates that neutral ceramidase is expressed in human intestine, released in the intestinal lumen and plays a major role in ceramide metabolism in the human gut. 相似文献
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13.
Abundant and well-preserved remains of noncalcareous algae and soft-bodied metazoans were collected from Middle Cambrian Kaili biota in Taijiang county, Guizhou Province, China. These remains provide further evidence for the wide geographic distribution of many Burgess Shale taxa. Among the algae, 5 genera (including two new genera) and 5 species are described. They are Marpolia spissa Walcott, Acinocricus stichus Conway Morris and Robison, Udotealga erecta Yang, Eosargassum sawata Yang, and Rhizophyton zhaoyuanlongii Yang. Contrasting the macroalgal fossil assemblage in the Kaili biota with one in the Burgess Shale biota, it is clear that similarity of the Kaili biota and the Burgess Shale biota is reflected by the same content of not only the soft-bodied metazoans, but also the noncalcareous algae. 相似文献
14.
贵州台江早-中寒武世凯里组保存大量的生物化石,它构成了寒武纪重要的生物群之一--凯里生物群.在凯里生物群中保存有丰富的碳质薄膜藻类化石,新发现类似苔藓植物化石(Parafunaria sinensis Yang(gen.et sp.nov)),它具有藓类植物所拥有的典型的叶状体轮生现象、孢朔、孢朔柄和复杂的根系特征.推测它是藓类植物祖先,它为进一步研究藓类植物和陆生高等植物的起源和演化提供了新的线索. 相似文献
15.
Cellular boron allocation and pectin composition in two citrus rootstock seedlings differing in boron-deficiency response 总被引:3,自引:0,他引:3
Gui-Dong Liu Rui-Dong Wang Lei-Chao Liu Li-Shu Wu Cun-Cang Jiang 《Plant and Soil》2013,370(1-2):555-565
Aims
Variation in boron (B) efficiency in citrus in different rootstock genotypes is expressed as large differences in the occurrence of leaf symptoms and dry mass production under low B conditions, but the mechanisms responsible for such differences are unknown. This paper aims to determine whether differences in B uptake, cellular B allocation, and pectin content can explain genotype differences in B efficiency between B-efficient citrange (Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.) and B-inefficient trifoliate orange (Poncirus trifoliata (L.) Raf.) citrus rootstock.Methods
Plants were grown hydroponically in a nutrient solution supplemented with 5 μM B for 14 days and then transferred to a B-free medium (0 μM B) or control medium (5 μM B) for 35 days. Boron uptake and allocation and cell wall pectin contents were examined.Results
After 35 days under B deprivation, shoot dry mass in trifoliate orange decreased by 28 %, but shoot dry mass of citrange was not significantly affected. Root growth of both types of rootstock seedlings was inhibited, but the trifoliate orange was affected more than the citrange. In comparison with B concentrations in plants prior to the commencement of B treatments, B deprivation for 35 days decreased B concentration in various parts of citrange plants, and the reduction was much greater in trifoliate orange plants. Trifoliate orange seedlings contained higher B concentration and total B in cell wall on a dry leaf basis than citrange subject to 5 μM B treatment. However, the proportion of leaf B allocated in cell wall was higher in citrange than trifoliate orange when B supply was deficient in the nutrient. The changes in pectin composition in cell wall due to B deprivation differed between citrange and trifoliate orange. The decreased uronic acid (UA) content in the Na2CO3-soluble pectin was observed in both rootstock, but the increased UA content in CDTA-soluble pectin was observed only in citrange.Conclusions
These results demonstrated that a combination of greater B uptake ability, greater B accumulation in cell walls, as well as the increased CDTA-soluble pectin, under limited external B supply, contribute to the integrity of cell walls in citrange and therefore increased tolerance to B deficiency. 相似文献16.
引进天敌椰甲截脉姬小蜂防治椰心叶甲的可行性探讨 总被引:17,自引:2,他引:17
从2 0 0 2年海南省首次在海口市发现新入侵害虫椰心叶甲Brontispalongissima(Gestro)以来,现该虫已蔓延到海南省的1 1个市县。从地理纬度、气候条件、寄主分布范围等自然条件来看,椰心叶甲也完全有可能向高纬度的临近省份扩散。直接影响到种植业及旅游业的健康发展,因此防治该虫迫在眉睫。通过海南省的生态条件,椰心叶甲的寄主和天敌特点综合分析,认为引进天敌椰甲截脉姬小蜂Asecodeshispinarum防治该害虫是经济有效的方法。 相似文献
17.
Duan RD Cheng Y Hansen G Hertervig E Liu JJ Syk I Sjostrom H Nilsson A 《Journal of lipid research》2003,44(6):1241-1250
Sphingomyelin (SM) metabolism in the gut may have an impact on colon cancer development. In this study, we purified alkaline sphingomyelinase (alk-SMase) from human intestinal content, and studied its location in the mucosa, expression in colon cancer, and function on colon cancer cells. The enzyme was purified by a series of chromatographies. The molecular mass of the enzyme is 60 kDa, optimal pH is 8.5, and isoelectric point is 6.6. Under optimal conditions, 1 mg of the enzyme hydrolyzed 11 mM SM per hour. The properties of the enzyme are similar to those of rat intestinal alk-SMase but not to those of bacterial neutral SMase. Immunogold electronmicroscopy identified the enzyme on the microvillar membrane in endosome-like structures and in the Golgi complexes of human enterocytes. The expression and the activity of the enzyme were decreased in parallel in human colon cancer tissues compared with the adjacent normal tissue. The enzyme inhibited DNA biosynthesis and cell proliferation dose dependently and caused a reduction of SM in HT29 cells. Intestinal alk-SMase is localized in the enterocytes, down-regulated in human colon cancer, and may have antiproliferative effects on colon cancer cells. 相似文献
18.
The plant cytoskeleton is a highly dynamic component of plant cells and mainly based on microtubules (MTs) and actin filaments (AFs). The important functions of dynamic cytoskeletal networks have been indicated for almost every intracellular activity, from cell division to cell movement, cell morphogenesis and cell signal transduction. Recent studies have also indicated a close relationship between the plant cytoskeleton and plant salt stress tolerance. Salt stress is a significant factor that adversely affects crop productivity and quality of agricultural fields worldwide. The complicated regulatory mechanisms of plant salt tolerance have been the subject of intense research for decades. It is well accepted that cellular changes are very important in plant responses to salt stress. Because the organization and dynamics of cytoskeleton may play an important role in enhancing plant tolerance through various cell activities, study on salt stress-induced cytoskeletal network has been a vital topic in the subject of plant salt stress tolerance mechanisms. In this article, we introduce our recent work and review some current information on the dynamic changes and functions of cytoskeletal organization in response to salt stress. The accumulated data point to the existence of highly dynamic cytoskeletal arrays and the activation of complex cytoskeletal regulatory networks in response to salt stresses. The important role played by cytoskeleton in mediating the plant cell''s response to salt stresses is particularly emphasized.Key words: cytoskeleton, microtubules (MTs), microfilaments (MFs), salt stress, response mechanisms, plant tolerance 相似文献
19.
Cárdenas M Schillén K Alfredsson V Duan RD Nyberg L Arnebrant T 《Chemistry and physics of lipids》2008,151(1):10-17
The interactions of the bile salt sodium taurocholate (TC) in 50 mM Trizma-HCl buffer and 150 mM NaCl (pH 9) at 37 degrees C with membranes composed of sphingomyelin (SM) were studied by dynamic light scattering, cryogenic transmission electron microscopy (cryo-TEM) and turbidity measurements. Small unilamellar SM vesicles were prepared by extrusion. Below the CMC of TC, taurocholate addition leads to vesicle growth due to incorporation of the taurocholate molecules into the vesicle bilayer. At around half the CMC of the bile salt, the SM vesicles are transformed into SM/TC mixed worm-like micelles, which are visualized by cryo-TEM for the first time. Further increase in the taurocholate concentration leads to the rupture of these structures into small spherical micelles. Interestingly, large non-spherical micelles were also identified for pure taurocholate solutions. Similar threadlike structures have been reported earlier for the bile salt sodium taurodeoxycholate [Rich, A., Blow, D., 1958. Nature 182, 1777; Blow, D.M., Rich, A., 1960. J. Am. Chem. Soc. 82, 3566-3571; Galantini, L., Giglio, E., La Mesa, C., Viorel-Pavel, N., Punzo, F., 2002. Langmuir 18, 2812] and for mixtures of taurocholate and phosphatidylcholate [Ulmius, J., Lindblom, G., Wennerstr?m, H., Johansson, L.B.-A., Fontel, K., S?derman, O., Ardvisson, G., 1982. Biochemistry 21, 1553; Hjelm, R.P., Thiyagarajan, P., Alkan-Onyuksel, H., 1992. J. Phys. Chem. 96, 8653] as determined by various scattering methods. 相似文献
20.
Boron distribution and mobility in navel orange grafted on citrange and trifoliate orange 总被引:2,自引:0,他引:2
Gui-Dong Liu Rui-Dong Wang Li-Shu Wu Shu-Ang Peng Yun-Hua Wang Cun-Cang Jiang 《Plant and Soil》2012,360(1-2):123-133