胰岛素分泌细胞的干细胞来源及其移植后命运

目的:干细胞诱导分化成的胰岛素分泌细胞移植是治疗糖尿病的方法之一,但因其诱导方法尚未完善及植入体内后的存活分化命运不清等问题而未应用于临床。文章就胰岛素分泌细胞的干细胞来源及其植入体内的命运加以综述。资料来源:应用计算机检索PUBMED1998-01/2007-03期间的相关文章,检索词为“insulin producing cell,cell transplantation,survival”,并限定文章语言种类为English。同时计算机检索中国期刊全文数据库1996-01/2006-12期间的相关文章,检索词为“胰岛素分泌细胞,胚胎干细胞,成体干细胞”,并限定文章语言种类为中文。资料选择:对资料进行初审,并查看每篇文献后的引文。纳入标准:文章所述内容应与胰岛素分泌细胞的干细胞来源或其植入体内后的存活分化相关。排除标准:重复研究。资料提炼:共收集到264篇相关文献,30篇文献符合纳入标准,排除的234篇文献为内容陈旧或重复。符合纳入标准的30篇文献中,分别涉及诱导为胰岛素分泌细胞的干细胞来源、胰岛素分泌细胞移植后的有效性、安全性、解决方法等内容。资料综合:糖尿病是由于胰岛素分泌不足及胰岛素抵抗造成糖代谢紊乱影响人类健康的主要疾病。不管是采用胰腺移植还是胰岛移植都因各种原因而限制了其在临床的应用,因此焦点放在了胰岛素分泌细胞上,包括其来源及移植后的命运。胰岛素分泌细胞来源于胚胎干细胞和成体干细胞,干细胞是一种具有自我更新,能够持续分裂而保持未分化状态,从而诱导分化为各种类型的细胞,因此有“种子细胞”之称。随着研究的深入,发现胰岛素分泌细胞的来源并不是问题,而问题的关键在于如何提高分化率及其移植后的命运,包括有效性、安全性以及解决方法。诱导产生的胰岛素分泌细胞表达活性低下、移植后其再生增殖能力差及容易被诱导凋亡等问题成为有效性最大的威胁,移植后的细胞易受免疫攻击和致瘤等问题也不容忽视。目前已开始着手以基因手段,从信号转导水平对其进行研究解决。结论:由胚胎干细胞和成体干细胞诱导分化的胰岛素分泌细胞,植入体内后有可能通过导入基因GLP-1,用表达B7-H4蛋白的质粒转染293T细胞和激活胰岛素/胰岛素样生长因子1等信号转导途径来解决有效性问题,但仍存在着安全性隐患,无法排除免疫抑制和致瘤的可能性。     

透明质酸钠预防兔膝关节固定后关节软骨退行性改变的作用

目的:多项研究成果已证明透明质酸钠在软骨修复及重建过程中具有重要作用。观察关节内注射透明质酸钠对兔膝关节固定后关节软骨退行性改变中的预防作用,并评估其效率。方法:实验于2004-10/2005-05在泰山医学院基础研究所完成。①实验分组:雄性新西兰大白兔24只,体质量2.5～3.0kg,随机分为生理盐水对照组和透明质酸治疗组,每组12只。②实验方法:透明质酸治疗组给予左膝关节内注射0.3mL透明质酸,1次/周,共行5次;生理盐水对照组给予左膝关节注射同等剂量生理盐水,1次/周,共行5次。各组均于初次注射后将左下肢给予石膏管型固定,膝部预留窗口以备下次注射。于末次注射1周后麻醉处死动物,采集左膝关节股骨髁关节软骨制成石蜡切片。同时采集右膝同部位软骨作为正常对照。③实验评估:普通光学显微镜下观察苏木精-伊红染色切片的形态变化;对甲苯胺蓝染色切片利用Image-ProPlus6.0图像分析系统进行平均染色灰度质分析;激光共聚焦显微镜分析免疫荧光标记的Ⅱ型胶原荧光强度。结果:纳入兔24只,均进入结果分析。透明质酸治疗组苏木精-伊红染色显示软骨层无变薄现象,软骨细胞同源细胞簇排列整齐,细胞大小均匀,细胞核染色均匀,潮线较为完整,无血管翳增生;生理盐水对照组苏木精-伊红染色显示软骨层变薄,细胞排列紊乱无规律,细胞大小不等,核染色浓淡不一,潮线不完整,血管翳有侵入软骨基底部的迹象。透明质酸治疗组软骨甲苯胺蓝染色灰度值及Ⅱ型胶原荧光强度均明显高于生理盐水对照组软骨(P<0.01),与正常软骨亦有显著差异(P<0.01)。结论:透明质酸能够有效地预防兔膝关节固定后的软骨退行性改变,但这种预防作用所产生的效果与正常软骨尚有差距。     

Effects of stem cell factor (kit-ligand) and interleukin-3 on the growth and serine proteinase expression of rat bone-marrow-derived or serosal mast cells

The effects of rat stem-cell factor (SCF) and interleukin-3 (IL-3), alone or in combination, on the in vitro growth and serine proteinase expression of rat serosal/connective-tissue mast cells (CTMC) or bone marrow-derived mast cells (BMMC) were examined. Rat SCF stimulated the growth of both CTMC and BMMC. IL-3 stimulated BMMC growth to a lesser extent than did SCF, whereas CTMC numbers did not increase in IL-3. However, SCF and IL-3 had synergistic effects on the growth of both BMMC and CTMC. SCF favoured the maintenance of rat mast cell proteinase- I (RMCP-I) in CTMC, but did not induce detectable production of RMCP-I in BMMC. In contrast, when IL-3 or lymph node-conditioned medium (LNCM) was added to SCF, a subpopulation of CTMC expressed and stored the soluble proteinase RMCP-II. In BMMC, the RMCP-II content of cells maintained in SCF was significantly less than that of cells maintained in IL-3 or LNCM. RMCP-II also appeared in the supernatants of BMMC, especially when BMMC numbers were increasing rapidly in SCF with or without IL-3 or LNCM. Thus, SCF and IL-3 can regulate the growth of rat BMMC and CTMC, as well as influence their production and release of proteinases.     

The effect of EDTA, cations, and various buffers on the morphology of erythrocyte membranes: an electron-microscopic study

Membranes of human erythrocytes were prepared by stepwise osmotic hemolysis in Ca2+-free solutions. Examination with the electron microscope after negative staining showed some short, conelike protuberances on the surface of about 20 percent of the ghosts, while 80 percent were round, intact spheres. After Ca2+ treatment, all membranes were round and intact. After exposure to ethylenediaminetetraacetic acid (EDTA) (1.0 mM, pH 7.4), the entire ghost surface was covered with long, thin extrusions called stromalytic forms (about 460 per cell). Their sizes, shapes, and fine structure are described. Exposure to ionic calcium (1.4 times 10-minus 4M) abolished the EDTA-induced stromalytic forms. A second exposure to EDTA reversed this Ca2+ effect. ATP, like EDTA, produced stromalytic forms. EDTA- induced stromalytic forms were also abolished by Zn2+, La3+, and Nd3+ at concentrations of 1-5 times 10-minus 4 M. Mg2+ at 10-minus 2 M was ineffective. Ghosts were prepared by graded lysis in various buffers. Those prepared in phosphate were the most stable and provided consistent EDTA effects and Ca2+ reversal. Ghosts in Tris-HCl showed breakdown unless salt was added. Moderately satisfactory ghosts were also obtained in Hepes-NaOH buffer and salt.     

The cDNA and derived amino acid sequence of porcine factor VIII

The cDNA corresponding to 137 bp of the 5' untranslated region, the signal peptide, and the A1, A3, C1, and C2 domains of porcine factor VIII (fVIII) have been cloned and sequenced. Along with previously determined sequences of the porcine fVIII B domain and the A2 domain, this completes the sequence determination of the cDNA corresponding to the translated protein. Alignments of the derived amino acid sequence of porcine fVIII with human and murine fVIII indicate that the A1, A2, A3, C1, and C2 domains are more conserved than the B domains or the proteolytic cleavage peptides corresponding to residues 337-372 and 1649-1689. The knowledge of the porcine fVIII cDNA may be useful to understand functional and immunological differences between human and porcine fVIII and may lead to improved fVIII replacement products for hemophilia. A patients through the development of recombinant porcine fVIII or hybrid human/porcine fVIII derivatives.     

Selective treatment of SCID mice bearing methotrexate-transport- resistant human acute lymphoblastic leukemia tumors with trimetrexate and leucovorin protection

Impaired transport of methotrexate (MTX) is a common resistance mechanism of tumor cells to this drug. Trimetrexate (TMTX), a second- generation folate antagonist, is still active against MTX-transport- resistant cells because it enters cells by passive diffusion and does not use the reduced folate transport system for cell entry. Therefore, although leucovorin (LV) protects MTX-sensitive cells from TMTX toxicity, MTX-transport defective cells are poorly rescued by LV. Severe combined immunodeficiency mice bearing MTX-transport-resistant CCRF-CEM acute lymphoblastic leukemia tumors were treated with TMTX alone or with the combination of TMTX and LV, with tumor regressions in both groups (P < .001) and without significant toxicity. These results indicate that TMTX with LV protection may be a useful therapeutic regimen for patients with MTX-transport-defective acute lymphoblastic leukemia. Furthermore, resistance to TMTX plus LV may result in reversion to MTX sensitivity.     

Incidence of activated protein C resistance caused by the ARG 506 GLN mutation in factor V in 113 unrelated symptomatic protein C-deficient patients. The French Network on the behalf of INSERM

Because multiple risk factors in one patient may increase the clinical expression of thrombophilia, we assessed the presence in protein C- deficient patients of the factor V Arg 506 Gln mutation responsible for activated protein C resistance. Using a strategy allowing rapid screening of factor V exon 10, we studied 113 patients with protein C deficiency and 104 healthy volunteers. We detected the Arg 506 Gln mutation in 15 patients (14%) and in one healthy subject (1%). We identified a previously unpublished sequence variation leading to an Arg 485 Lys substitution in three normal subjects and seven protein C- deficient patients. A significant difference in the allelic frequency of the Arg 506 Gln factor V mutation was found between protein C- deficient patients heterozygous for an identified protein C mutation (n = 84; allelic frequency, 4.8%) and protein C-deficient patients with no identified mutation in the protein C gene coding regions (n = 25; allelic frequency, 14%). The results demonstrate that a significant subset of thrombophilic patients has multiple genetic risk factors although additional secondary genetic risk factors remain to be identified for the majority of symptomatic protein C-deficient patients.     

Evidence for a second type of fibril branch point in fibrin polymer networks, the trimolecular junction

Fibrin molecules polymerize to double-stranded fibrils by intermolecular end-to-middle domain pairing of complementary polymerization sites, accompanied by fibril branching to form a clot network. Mass/length measurements on scanning transmission electron microscopic images of fibrils comprising branch points showed two types of junctions. Tetramolecular junctions occur when two fibrils converge, creating a third branch with twice the mass/length of its constituents. Newly recognized trimolecular junctions have three fibril branches of equal mass/length, and occur when an extraneous fibrin molecule initiates branching in a propagating fibril by bridging across two unpaired complementary polymerization sites. When trimolecular junctions predominate, clots exhibit nearly perfect elasticity.