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41.
沿海防护林防海煞危害初探 总被引:2,自引:0,他引:2
通过后牧村海岸防护林带附近空气中主要盐离子飘尘的观测分析表明,林带对大气盐尘的吸附和截留作用,无林带地区平均沉降量为4.3μg.m^-3.100m^-1,通过林带时为18.4μm^-3.100m^-1。林带的吸队量与树种、枝叶形状有关,侧柏对Cl^-和Na^+的吸附量分别为6330和3350mg.kg^-1,而黑松为1570和950mg.kg^-1,空气中盐尘受天气条件特别是风速的影响,阴天,风速 相似文献
42.
本文用免疫细胞化学方法调查了生长抑素(SOM)免疫反应神经元在人胎丘脑网状核内的分布。流产的胚胎3例,胎龄分别为18周,23周,32周。意外死亡足月新生儿1例、在18周胚胎的丘脑网状核内可见少数染色较浅的SOM免疫反应阳性神经元,呈圆形。从18周到32周,SOM免疫反应阳性细胞数明显增多,突起更丰富。在足月新生儿,SOM阳性细胞数较32周有所减少。结果表明,SOM阳性神经元存在于人胎丘脑网状核内,并且有一定的发育过程。出现于人脑发育的早期阶段,可能在中枢神经系统的发育过程中起重要的作用。 相似文献
43.
本文就植物血细胞凝集素(PHA)作用的不同时间对小鼠脾脏淋巴细胞γ-谷氨酰基转肽酶(γ-GT)活性的影响进行了观察。结果表明,脾脏淋巴细胞转化率随给予PHA时间的延长而上升,对照组<24h组<48h组<72h组;淋巴细胞γ-GT活性于24h明显强于对照组(P<0.001),随着PHA作用时间的延长其γ-GT活性逐渐下降,即48h组与对照组已无显著差异,而72h组却低于对照组(P<0.001)。可见PHA在小鼠体内对γ-GT活性有很大影响。 相似文献
44.
45.
Deletion between direct repeats in T7 DNA stimulated by double-strand breaks. 总被引:6,自引:3,他引:3
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An in vitro system based on extracts of Escherichia coli infected with bacteriophage T7 was used to study genetic deletions between directly repeated sequences. The frequency of deletion was highest under conditions in which the DNA was actively replicating. Deletion frequency increased markedly with the length of the direct repeat both in vitro and in vivo. When a T7 gene was interrupted by 93 bp of nonsense sequence flanked by 20-bp direct repeats, the region between the repeats was deleted in about 1 out of every 1,600 genomes during each round of replication. Very similar values were found for deletion frequency in vivo and in vitro. The deletion frequency was essentially unaffected by a recA mutation in the host. When a double-strand break was placed between the repeats, repair of this strand break was often accompanied by the deletion of the DNA between the direct repeats, suggesting that break rejoining could contribute to deletion during in vitro DNA replication. 相似文献
46.
报道了测定CK-MM亚型的聚焦色谱法,此法简单,快速,结果可靠,线性范围宽,最低检测限(8U/L)较正常参考值低,比国外报道的类似方法高6倍以上,分离度亦有改进.测定了20例健康人血清亚型分布,与文献报道结果相近.该法自动化程度高,已在急性心梗的诊断中实际应用. 相似文献
47.
水平回转对水稻幼苗叶细胞的影响 总被引:9,自引:0,他引:9
对在模拟微重力装置上回转14 天的水稻幼苗叶细胞进行了亚显微形态、电子探针和细胞酶化学研究。发现叶细胞质膜上Ca2+ -ATP酶活性消失,膜内钙总量上升、膜外钙总量下降,细胞骨架变得疏松,细胞壁变薄并凹凸不平。叶绿体的基粒和线粒体的内嵴亦有部分变化。其变化机制,首先是细胞质膜上Ca2+ -ATP酶活性消失,膜上钙泵停止工作,跨膜钙浓度差减小,膜内钙浓度上升,微管、微丝聚合受阻,细胞骨架疏松,分泌泡移动失去导向,从而导致细胞壁变薄等状态 相似文献
48.
Rui L. Mendes Helena L. Fernandes José A.P Coelho Joaquim M.S Cabral António M. F. Palavra Júlio M. Novais 《Journal of applied phycology》1994,6(3):289-293
Samples of the microalgaBotryococcus braunii were submitted to supercritical fluid extraction with carbon dioxide at 40 °C and pressures of 12.5, 20.0 and 30.0 MPa. The extraction yield and the fraction of the hydrocarbons in the extracts both increased with pressure and at 30 MPa these compounds were obtained rapidly. This behaviour is associated with the localization of the hydrocarbons outside the cell wall. In the extracts, which are fluid, golden and limpid, chlorophyll and phospholipids were not detected.Author for correspondence 相似文献
49.
Russell B. Lingham Keith C. Silverman Gerald F. Bills Carmen Cascales Manual Sanchez Rosalind G. Jenkins Suzanne E. Gartner Isabel Martin Maria T. Diez Fernando Peláez Sagrario Mochales Yu-Lin Kong Richard W. Burg Maria S. Meinz Leeyuan Huang Mary Nallin-Omstead Scott D. Mosser Michael D. Schaber Charles A. Omer David L. Pompliano Jackson B. Gibbs Sheo B. Singh 《Applied microbiology and biotechnology》1993,40(2-3):370-374
Chaetomellic acids A and B, isolated from Chaetomella acutiseta, are specific inhibitors of farnesyl-protein transferase that do not inhibit geranylgeranyl transferase type 1 or squalene synthase. Chaetomellic acids A and B are reversible inhibitors, resemble farnesyl diphosphate and probably inhibit FPTase by substituting for farnesyl diphosphate. Chaetomellic acid production appears to be widespread within the genus Chaetomella.
Correspondence to: R. B. Lingham 相似文献
50.
Inorganic cofactors (Mn, Ca2+ and Cl-) are essential for oxidation of H2O to O2 by Photosystem II. The Mn reductants NH2OH and its N-methyl derivatives have been employed as probes to further examine the interactions between these species and Mn at the active site of H2O oxidation. Results of these studies show that the size of a hydroxylamine derivative regulates its ability to inactivate O2 evolution activity, and that this size-dependent inhibition behavior arises from the protein structure of Photosystem II. A set of anions (Cl-, F- and SO4
2-) is able to slow NH2OH and CH3NHOH inactivation of intact Photosystem II membranes by exerting a stabilizing influence on the extrinsic 23 and 17 kDa polypeptides. In contrast to this non-specific anion effect, only Cl- is capable of attenuating CH3NHOH and (CH3)2NOH inhibition in salt-washed preparations lacking the 23 and 17 kDa polypeptides. However, Cl- fails to protect against NH2OH inhibition in salt-washed membranes. These results indicate that the attack by NH2OH and its N-methyl derivatives on Mn occurs at different sites in the O2-evolving complex. The small reductant NH2OH acts at a Cl--insensitive site whereas the inhibitions by CH3NHOH and (CH3)2NOH involve a site that is Cl- sensitive. These findings are consistent with earlier studies showing that the size of primary amines controls the Cl- sensitivity of their binding to Mn in the O2-evolving complex.Abbreviation MES
4-morpholinoethanesulfonic acid
- PS II
Photosystem II 相似文献