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51.
Parag R. Chitnis Daryl T. Morishige Rachel Nechushtai J. Philip Thornber 《Plant molecular biology》1988,11(2):95-107
A barley gene encoding the major light-harvesting chlorophyll a/b-binding protein (LHCP) has been sequenced and then expressed in vitro to produce a labelled LHCP precursor (pLHCP). When barley etiochloroplasts are incubated with this pLHCP, both labelled pLHCP and LHCP are found as integral thylakoid membrane proteins, incorporated into the major pigment-protein complex of the thylakoids. The presence of pLHCP in thylakoids and its proportion with respect to labelled LHCP depends on the developmental stage of the plastids used to study the import of pLHCP. The reduced amounts of chlorophyll in a chlorophyll b-less mutant of barley does not affect the proportion of pLHCP to LHCP found in the thylakoids when import of pLHCP into plastids isolated from the mutant plants is examined. Therefore, insufficient chlorophyll during early stages of plastid development does not seem to be responsible for their relative inefficiency in assembling pLHCP. A chase of labelled pLHCP that has been incorporated into the thylakoids of intact plastids, by further incubation of the plastids with unlabelled pLHCP, reveals that the pLHCP incorporated into the thylakoids can be processed to its mature size. Our observations strongly support the hypothesis that after import into plastids, pLHCP is inserted into thylakoids and then processed to its mature size under in vivo conditions. 相似文献
52.
53.
Hubert Felle 《Planta》1988,176(2):248-255
In cells of Zea mays (root hairs, coleoptiles) and Riccia fluitans (rhizoids, thalli) intracellular Ca2+ and pH have been measured with double-barrelled microelectrodes. Free Ca2+ activities of 109–187 nM (Riccia rhizoids), 94–160 nM (Riccia thalli), 145–231 nM (Zea root hairs), 84–143 nM (Zea coleoptiles) were found, and therefore identified as cytoplasmic. In a few cases (Riccia rhizoids), free Ca2+ was in the lower millimolar range (2.3±0.8 mM). A change in external Ca2+ from 0.1 to 10 mM caused an initial and short transient increase in cytoplasmic free Ca2+ which finally levelled off at about 0.2 pCa unit below the control, whereas in the presence of cyanide the Ca2+ activity returned to the control level. It is suggested that this behaviour is indicative of active cellular Ca2+ regulation, and since it is energy-dependent, may involve a Ca2+-ATPase. Acidification of the cytoplasmic pH and alkalinization of the vacuolar pH lead to a simultaneous increase in cytoplasmic free Ca2+, while alkalinization of pHc decreased the Ca2+ activity. Since this is true for such remote organisms as Riccia and Zea, it may be concluded that regulation of cytoplasmic pH and free Ca2+ are interrelated. It is further concluded that double-barrelled microelectrodes are useful tools for investigations of intracellular ion activities in plant cells.Symbols and abbreviations m, m
membrane potential difference, changes thereof
- PVC
polyvinylchloride 相似文献
54.
Summary To assay the functional significance of the multiple but closely related - and -tubulin polypeptides (termed isotypes) that are expressed in mammalian cells, we have generated a number of sera that uniquely discriminate among these isotypes. These sera have been used to demonstrate that there is no subcellular sorting of either - or -tubulin isotypes among microtubules of diverse function, either in cells growing in culture or in tissues consisting of cell types that contain specialized kinds of microtubule. In spite of this failure to segregate between functionally distinct kinds of microtubule, the fact that isotype-specific amino acid sequences have been strictly conserved over extensive periods of evolutionary time argues persuasively for a functional role for the different tubulin gene products. One possibility is that they are required for specific interactions with microtubule associated proteins (MAPs), and that tubulin isotypes have coevolved with different cell type-specific MAPs with which they must interact. We have tested this hypothesis by examining the distribution of -tubulin isotypes in mammalian cerebellum in relationship to the known patterns of expression of a number of MAPs, and find that these patterns correlate in the case of M 2 and MAP 3, and M 6 and MAP 1 a. These data, plus emerging data based on a structural analysis of tau, MAP 1 b and MAP 2 obtained via sequence determination of cloned cDNAs, are discussed in terms of the possible functional significance of tubulin isotype/MAP interactionsin vivo. 相似文献
55.
56.
1985年4~10月与1986年6~8月,在贵州省沿河县的纸坊村和崔家坨村先后发生了病因不明的传染病。纸坊村约有1/5的村民发病,病死率为12%,崔家坨村有1/10的村民发病,病死率高达30%。发病波及各年龄组,以青壮年为多,有家庭集聚现象。 本病起病急,轻症者只有头晕、乏力、肌痛、多汗、心悸伴以低热,有的初期有短暂的腹泻。重症者有高热(40℃以上)、大汗、心悸、游走性肌肉痉挛伴有明显疼痛和触痛,以腰骶部及四肢肌肉为好发部位。病人烦燥不安,2~5天内死亡。经实验室检查,排除了食物中毒、农药中毒、钩端螺旋体病和弓形体感染。从病人和接触者的粪便中分离到9株病毒,性状一致,为RNA型25nm的球形颗粒,耐酸,耐乙醚,能凝集人“O”型血球。经血清学鉴定为ECHO3型病毒。16份病人双份血清的检测结果表明,恢复期血清对该病毒中和抗体有4倍以上升高者共8例(纸坊村和崔家坨各4例)。病人单份血清也都有较高的抗体。有理由认为两年中先后在两个村庄发生的传染病与ECHO3型病毒有密切关系。查阅文献,尚未见有关ECHO3型病毒引起以肌痛、游走性肌痉挛为特征的疾病的报道。 相似文献
57.
P Mentré F Escaig 《Biology of the cell / under the auspices of the European Cell Biology Organization》1992,74(1):119-126
Flotation on hot water (about 60 degrees C) which is frequently employed to stretch semithin sections on substrates for SIMS (secondary ion mass spectrometry) microscopy, is the cause of numerous artefacts. In the case of epoxy resin-embedded tissue, one observes loss of potassium and sodium and accumulation of calcium. The relative contrast of cell nuclei in the ionic images, is rapidly affected by these ion migrations. After prolonged contact with hot water, tissue becomes uniformly emissive. In the case of hydrosoluble resin-embedded tissue, potassium and sodium do not appear to be affected by the action of water, which suggests that they are covalently bound with chelating sites buried beneath the layer of water bound to the surface of the macromolecules. Calcium accumulates, probably on widely exposed anionic sites. Moreover, the domains observed in hydrosoluble resin-embedded tissue shrink differently according to the proportion of water removed by melamine; this can provide interesting information on the initial equilibrium between water, ion sand macromolecules. Our results seem to support the assumption that bound water should play an important role in the preservation of both macromolecular architecture and ion distributions. 相似文献
58.
本文记述了云南省(虫齿)目二新种,Tapinella bannana sp.n.和Peripsocus plurimaculatus sp.n.及一新种记录种Ophiodopelma semicets Lee and Thornton,其雄虫为首次记载。 相似文献
59.
Chika Kawashima Koji Terayama Masayuki II Shogo Oka Toshisuke Kawasaki 《Glycoconjugate journal》1992,9(6):307-314
The properties of a rat brain glucuronyltransferase, which is presumed to be associated with the biosynthesis of the HNK-1 epitope on sulfoglucuronyl glycolipids, are described. The enzyme required divalent cations for reaction, with maximal activity at 10mm Mn2+, and exhibited a dual optimum at pH 4–5 and pH 6 depending upon the buffer used, with the highest activity at pH 4.5 in MES buffer. This enzyme strictly recognized the Gal1-4GlcNAc terminal structure, and was highly specific for neolacto (type 2) glycolipids as acceptor. The enzyme was localized specifically in the brain, and was barely detected in other issues, including the thymus, spleen, liver, kidney, lung, and sciatic nerve fibres. Phosphatidylinositol and phosphatidylserine increased the enzymatic reaction 4.4- and 2.3-fold, respectively, whereas phosphatidylcholine slightly decreased the rate.Abbreviations GlcA
glucuronic acid
- Lc-PA14
lactotetraose-phenyl-C14H29
- nLc-PA14
neolactotetraose-phenyl-C14H29
- nLcOse4-Cer
neolactotetraosylceramide
- NP-40
Nonidet P-40
- PC
phosphatidylcholine
- PE
phosphatidylethanolamine
- PI
phosphatidylinositol
- PS
phosphatidylserine
- SGGL
sulfoglucuronyl glycolipid 相似文献
60.
In this paper, we study the effect of introducing a delay in a model of cell proliferation considered originally by O. Arino and M. Kimmel (J. Math. Biol. 27, 341–354 (1989)). We prove that slow oscillations take place and periodic oscillations appear for appropriate values of a parameter. 相似文献