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991.
Divalent cations such as Ca+2 can act as bridges between lipopolysaccharide subunits causing large vesicles to form. During a two-stage ultrafiltration Ca+2 re-aggregated lipopolysaccharide subunits in protein solutions into large vesicles that could not pass a 300,000 nominal molecular weight cut-off ultrafiltration membrane. Such re-aggregation occurred at concentration ratio of hemoglobin Ao / lipopolysaccharide equal to or less than 17.0, or at concentration ratio of Ca+2 / hemoglobin Ao / lipopolysaccharide equal to or greater than 8.5. 相似文献
992.
本文观察了疼痛患者脊髓脑脊液中强啡肽含量的变化。共收集31例急性疼痛患者和14例慢性疼痛患者的脊髓脑脊液,测定其中的强啡肽含量,与27例无痛患者的结果进行比较,并结合被测者的性别、年龄、体重、血压、脉搏、体温等一般情况进行分析。结果表明,慢性痛患者脑脊液中强啡肽含量显著升高,而急性痛患者则略有降低。判别分析表明,急性痛患者的强啡肽含量及其他临床资料有明显的特点(判别准确率82%);慢性痛患者未见明显特征。作者认为,在更广泛地收集临床资料和检验结果的基础上,进一步研究不同病因的疼痛患者的临床特征,可能有助于对疼痛疾病进行鉴别诊断 相似文献
993.
通过应用数量化理论和多元回归分析理论,解决了小样本多变量自由度小及各地域数据不能通用的问题,建立了河北、北京等八个试验地域的掖单13号夏玉米产量的通用模型,并由此建立各地域的产量模型,研究地域因素对产量的影响,最后又以河北试验区为例进行了施肥方案的优化研究. 相似文献
994.
用硅藻群集指数(DAIpo)和河流污染指数(RPId)评价珠江广州河段的水质状况 总被引:5,自引:0,他引:5
用硅藻计于1990年采集珠江广州河段的9个采样点的附着硅藻群落.共得硅藻24个属,170个分类单位,其中,适腐性种8个,广腐性种84个,仍腐性种78个.群落相似性聚类分析表明,位于前、后航道中部的员村(st3),新造(st8),沙浴村(si10)三点的硅藻群落结构是为相似,向上,下游相似性逐渐减小.用硅藻群集指数(DAIpo)和河流污染指数(RPId)对各采样断面的水质进行分析表明:大盛(st12)和莲花山(st5)两点受污染最轻,属β-寡污带,黄沙点(st2)污染最严重,属α-中污带.对照点鸦岗(St1)也受到一定的污染,属α-寡污带,其它点的污染程度在α-寡污带与β-中污带之间.DAIpo值与BODS存在着显著的负相关(r=0.86).珠江广州河段的前、后航道的污染程度相差不大(RPId=56.42,56.26),均属中度污染. 相似文献
995.
PCR-SSP技术对广东汉族人HLA-DR基因分型 总被引:13,自引:0,他引:13
探索具有高分辨率、高特异性和简捷快速的方法对HLA-DR基因分型,为临床器官移植配型和疾病相关性分析提供实用的方法和基础资料.利用DR1~DRw18序列特异性的19组引物及1对内参照引物进行PCR扩增即PCR-SSP对HLA-DR进行基因分型,扩增产物经琼脂糖凝胶电泳,溴乙锭染色,在紫外光下观察分型结果.每个被检个体的DR型别可由特异引物扩增出现的电泳谱带直接判断.双盲检测22例的结果100%正确.在102例中国广东地区汉族人中,DR9和DR2的基因频率最高,分别为0.2205和0.1912,DR10为最低(0.0098).与用PCR-SSO方法分型获得的结果比较,基因型别分布基本一致,但一些等位基因的频率有差异,表明HLA-DR基因频率的分布在不同地区、不同种族的人群间存在着差异.PCR-SSP法分辨率和特异性虽不及PCR-SSO法但比血清学方法精细,分型的全过程只需2~4h能满足临床器官移植配型的要求.基因频率调查结果为器官移植配型和疾病相关性分析提供了基础资料. 相似文献
996.
Barbara M. Reed Jeanine Denoma Jie Luo Yongjian Chang Leigh Towill 《In vitro cellular & developmental biology. Plant》1998,34(3):256-260
Summary Germplasm collections of vegetatively propagated crops are usually maintained as plants in fields or potted in greenhouses
or screened enclosures. Safety duplication of these collections, as duplicate plants or separate collections, is costly and
requires large amounts of space. Cryopreservation techniques which were recently developed for long-term storage of pear germalasm
may offer an efficient alternative to conventional germplasm collection maintenance. Pear (Pyrus L.) germplasm may now be stored as seeds (species), dormant buds or pollen from field-grown trees, or shoot tips fromin vitro-grown plants (cultivars). Pear germplasm may now be cryopreserved and stored for long periods (> 100 yr) utilizing slow-freezing
or vitrification ofin vitro-grown shoot-tips. Dormant bud freezing, pollen, and seed cryopreservation of other lines are being developed to complete
the base collection forPyrus. This cryopreserved collection provides base (long-term) storage for the field-grown pear germplasm collection at the National
Clonal Germplasm Repository, Corvallis, Oregon.
Based on a presentation at the 1997 Congress on In Vitro Biology held in Washington, D.C., June 14–18, 1997. 相似文献
997.
Yan Shi Wei Luo Wei-Xi Tian Tong Zhang Hai-Meng Zhou 《The international journal of biochemistry & cell biology》1998,30(12):1319-1330
Fatty acid synthase is an important enzyme participating in energy metabolism in vivo. The inactivation and conformational changes of the multifunctional fatty acid synthase from chicken liver in SDS solutions have been studied. The results show that the denaturation of this multifunctional enzyme by SDS occurred in three stages. At low concentrations of SDS (less than 0.15 mM) the enzyme was completely inactivated with regard to the overall reaction. For each component of the enzyme, the loss of activity occurred at higher concentrations of SDS. Significant conformational changes (as indicated by the changes of the intrinsic fluorescence emission and the ultraviolet difference spectra) occurred at higher concentrations of SDS. Increasing the SDS concentration caused only slight changes of the CD spectra, indicating that SDS had no significant effect on the secondary structure of the enzyme. The results suggest that the active sites of the multifunctional fatty acid synthase display more conformational flexibility than the enzyme molecule as a whole. 相似文献
998.
999.
1000.
Exosomes are nanoscale membrane vesicles, which carry biologically active substances of their cell of origin and play an important role in signal transduction and intercellular communication. At present, exosomes have been identified as a promising non-invasive liquid biopsy biomarker in the tissues and circulating blood of nasopharyngeal carcinoma (NPC) and found to participate in regulating pathophysiological process of the tumor. We here review recent insights gained into the molecular mechanisms of exosome-induced cell growth, angiogenesis, metastasis, immunosuppression, radiation resistance and chemotherapy resistance in the development and progression of NPC, as well as the clinical application of exosomes as diagnostic biomarkers and therapeutic agents. We also discuss the limitations and challenges in exosome application. We hope this review may provide some references for the use of exosomes in clinical intervention. 相似文献