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71.
在海拔2300m选择健康成年男性5人,急进抵海拔4660m,用多导监测仪分别在两地连续7h监测夜间睡眠、呼吸状态和血氧饱和度变化,进行自身对比。结果发现:(1)急进高海拔后,总睡眠时间、有效睡眠指数、Ⅲ~Ⅳ期深睡眠均较中度高原减少(p<0.01);总觉醒时间、Ⅰ~Ⅱ期浅睡眠高海拔较中度高原增多(p<0.05):(2)急进高海拔后,有3名健康人出现周期性呼吸,其中1名健康者出现周期性呼吸119次,伴有中枢性睡眠呼吸暂停,最低Sao_2为78%;(3)同海拔高度夜间睡眠时与清醒时Sao_2相比较,中度高原下降4.2%,高海拔下降11.2%(p<0.01);高海拔与中度高原夜间清醒时Sao_2相比较下降7.4%,睡眠时下降14.4%(p<0.001)。结果提示:(1)睡眠加重了高原人原有的低氧血症;(2)低氧血症导致睡眠结构的紊乱和睡眠质量的降低;(3)睡眠中出现的周期性呼吸,应视为机体的一种自我保护机制;(4)频发的周期性呼吸或睡眠呼吸暂停将影响大脑机能。 相似文献
72.
我们分子鉴别了一个缺失型中国(A_γδβ)°-地贫家系。先证者为这一缺失的纯合子,具有中度贫血症状。家系的另五个成员均为这一缺失的杂合子,其胎儿血红蛋白(HbF)为16—21%,接近或达到HPFH杂合子的HbF水平,并且几乎不表现贫血症状。限制性内切酶图谱分析证明了β-珠蛋白基因簇内的DNA顺序缺失,缺失的5′端点位于Aγ基因IVSⅡ内,3′端点在β-珠蛋白基因下游区远端,距HPFH-2的3′缺失端点上游区约11kb。缺失的总长度约为80kb。本文讨论了这一缺失导致胎儿血红蛋白在成人中持续活跃表达的可能机制。 相似文献
73.
D Manor G Z Weng H Deng S Cosloy C X Chen V Balogh-Nair K Delaria F Jurnak R Callender 《Biochemistry》1991,30(45):10914-10920
We have measured the Raman spectrum of GDP bound to the elongation factor protein, EF-Tu, and the c-Harvey-ras protein, p21, two proteins of the guanine nucleotide binding family. In order to separate the Raman spectrum of the nucleotide from the much more intense protein spectrum, we investigate the feasibility of "tagging" the normal modes of the nucleotide by isotopic substitution, here by incoporating deuterium-labeled guanine at the C8 position into the active site. A difference spectrum between the labeled and unlabeled protein-nucleotide complex shows the changes in the Raman spectrum of the bound nucleotide that arise from the isotopic exchange. We find that surprisingly good Raman spectra of bound ligands can be obtained with this method and that the method can be easily generalized to other systems. The data show that the guanine amino group of the nucleotide interacts differently with both EF-Tu and p21 than it does with water, showing a change in hydrogen-bonding properties upon binding. On the other hand, no change in hydrogen bonding is observed at guanine's N7. The data strongly suggest that the conformation of the nucleotide when bound to EF-Tu and that p21 is the C2' endo pucker of the ribose ring and anti about the glycosidic bond. These results are compared to previous structural and chemical studies. 相似文献
74.
Structure-function studies of human cholesteryl ester transfer protein by linker insertion scanning mutagenesis 总被引:5,自引:0,他引:5
Human plasma cholesteryl ester transfer protein (CETP) enhances transfer and exchange of cholesteryl ester (CE) and triglyceride (TG) between high-density lipoprotein and other lipoproteins. To define regions responsible for the neutral lipid transfer activities at the molecular level, a total of 27 linker insertion mutants at 18 different sites along the CETP molecule were prepared and transiently expressed in a mammalian cell line (COS). The inserted linkers were small (usually 6 bp) and did not interrupt the translational reading frame of the CETP cDNA. Although secretion of each mutant protein was less than that of wild-type CETP, the majority of the mutants had normal cholesteryl ester transfer activity (transfer activity per nanogram of CETP in media). However, insertional alterations in three regions severely impaired CE transfer activity: (1) in the region of amino acids 48-53; (2) at amino acid 165; and (3) in the region of amino acids 373-379. Although the impaired activities could also be a result of globally incorrect folding of these CETP mutants, hydrophobicity analysis and secondary structure predictions tended to exclude this possibility for most of the insertion sites at which insertions resulted in inactivation. The insertion at amino acid 379 occurs immediately after a triplet of lysine residues, suggesting that this region might be involved in an essential step in the mechanism of CE and TG transfer, such as the binding of CETP to phosphatidylcholine molecules in the lipoprotein surface. Effects on TG transfer activity were generally similar to those on CE transfer activity, suggesting a similar structural requirement for both neutral lipid transfer activities. 相似文献
75.
A patient with cervical carcinoma was found to have selective IgA deficiency. The intact cell-mediated immunity, normal levels of IgG and IgM, and the absence of serum and salivary IgA established the diagnosis. Contrary to those of normal persons, salivary IgM was elevated and salivary IgA was not detectable in this patient. The patient had no signs attributable to IgA deficiency, but she always had dryness of the mouth. The association between cervical carcinoma and selective IgA deficiency was discussed. 相似文献
76.
Uridine kinase (ATP: uridine 5'-phosphotransferase, EC 2.7.1.48) has been partially purified from ungerminated hybrid corn seed. It is associated with a soluble high molecular weight fraction from which it apparently cannot be dissociated without loss of activity. The stability of the enzyme is enhanced by the addition of dithiothreitol, glycerol and nucleotide substrate. The nucleoside specificity of the enzyme is limited to nucleosides containing pyrimidine and ribose moieties, such as uridine and cytidine. High concentrations of nucleosides cause substrate inhibition, however. The Km values for uridine and cytidine are 53 muM and 125 muM, respectively, and under subsaturating conditions uridine is phosphorylated about five times faster than cytidine. The reaction follows an ordered Bi Bi kinetic pattern, with ATP and ADP in competition for the free form of the enzyme. Purine, but not pyrimidine, nucleoside triphosphates serve as phosphate donors without regard to the sugar moiety. However, all of these triphosphates appear to compete for the same site on the enzyme. (Km ATP equals 590 muM, Km (app) GTP equals 61 muM, and CTP and UTP are linear competitive inhibitors against ATP, with Ki values of 60 muM and 240 muM, respectively.) Therefore, end product control of uridine kinase apparently does not involve allosteric sites, but instead is envisioned as simple competition between relatively effective or ineffective phosphate donors for a position on the enzyme. 相似文献
77.
78.
Zhihui Deng Jianxin Zhen Genelle F Harrison Guobin Zhang Rui Chen Ge Sun Qiong Yu Neda Nemat-Gorgani Lisbeth A Guethlein Liumei He Mingzhong Tang Xiaojiang Gao Siqi Cai William H Palmer Jonathan A Shortt Christopher R Gignoux Mary Carrington Hongyan Zou Peter Parham Wenxu Hong Paul J Norman 《Molecular biology and evolution》2021,38(6):2582
Human natural killer (NK) cells are essential for controlling infection, cancer, and fetal development. NK cell functions are modulated by interactions between polymorphic inhibitory killer cell immunoglobulin-like receptors (KIR) and polymorphic HLA-A, -B, and -C ligands expressed on tissue cells. All HLA-C alleles encode a KIR ligand and contribute to reproduction and immunity. In contrast, only some HLA-A and -B alleles encode KIR ligands and they focus on immunity. By high-resolution analysis of KIR and HLA-A, -B, and -C genes, we show that the Chinese Southern Han (CHS) are significantly enriched for interactions between inhibitory KIR and HLA-A and -B. This enrichment has had substantial input through population admixture with neighboring populations, who contributed HLA class I haplotypes expressing the KIR ligands B*46:01 and B*58:01, which subsequently rose to high frequency by natural selection. Consequently, over 80% of Southern Han HLA haplotypes encode more than one KIR ligand. Complementing the high number of KIR ligands, the CHS KIR locus combines a high frequency of genes expressing potent inhibitory KIR, with a low frequency of those expressing activating KIR. The Southern Han centromeric KIR region encodes strong, conserved, inhibitory HLA-C-specific receptors, and the telomeric region provides a high number and diversity of inhibitory HLA-A and -B-specific receptors. In all these characteristics, the CHS represent other East Asians, whose NK cell repertoires are thus enhanced in quantity, diversity, and effector strength, likely augmenting resistance to endemic viral infections. 相似文献
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