von Willebrand factor released from Weibel-Palade bodies binds more avidly to extracellular matrix than that secreted constitutively

Large multimers of von Willebrand factor (vWf) are released from the Weibel-Palade bodies of cultured endothelial cells following treatment with a secretagogue (Sporn et al, Cell 46:185, 1986). These multimers were shown by immunofluorescent staining to bind more extensively to the extracellular matrix of human foreskin fibroblasts than constitutively secreted vWf, which is composed predominantly of dimeric molecules. Increased binding of A23187-released vWf was not due to another component present in the releasate, since releasate from which vWf was adsorbed, when added together with constitutively secreted vWf, did not promote binding. When iodinated plasma vWf was overlaid onto the fibroblasts, the large forms bound preferentially to the matrix. These results indicated that the enhanced binding of the vWf released from the Weibel-Palade bodies was likely due to its large multimeric size. It appears that multivalency is an important component of vWf interaction with the extracellular matrix, just as has been shown for vWf interaction with platelets. The pool of vWf contained within the Weibel-Palade bodies, therefore, is not only especially suited for platelet binding, but also for interaction with the extracellular matrix.     

Hematologic and immunomodulatory effects of an interleukin-1 receptor antagonist coinfusion during low-dose endotoxemia in healthy humans

Endotoxin is a component of gram-negative bacteria that causes hematologic and immunologic changes through its induction of cytokines. Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring inhibitor of IL-1 that competes with IL-1 for occupancy of cell-surface receptors but possesses no agonist activity. We investigated the ability of human recombinant IL-1Ra to block the effects of low-dose endotoxin. Fourteen healthy male volunteers between 18 and 30 years old were injected intravenously with 3 ng/kg Escherichia coli endotoxin. Concurrent with the injections, nine volunteers received a 3-hour continuous intravenous infusion of IL-1Ra. The other five subjects were given a 3-hour infusion of saline. Volunteers injected with endotoxin experienced a threefold increase in circulating neutrophils over baseline. This neutrophilia was significantly reduced by 48% in subjects administered endotoxin plus IL-1Ra (P = .0253). Ex vivo mitogen-induced peripheral blood mononuclear cell proliferation decreased by greater than 60% at 3 and 6 hours after endotoxin injection (P = .0053). This endotoxin-induced reduction in mitogen response was reversed in subjects coinjected with IL-1Ra (P = .0253). Endotoxin-induced symptoms, fever, and tachycardia were unaffected by IL-1Ra. IL-1 appears to be an important mediator in endotoxemia because some of its hematologic and immunomodulatory effects can be blocked by IL-1Ra.     

The factor V B-domain provides two functions to facilitate thrombin cleavage and release of the light chain

Blood coagulation factors V and VIII are homologous proteins that have the domain organization A1-A2-B-A3-C1-C2. Upon thrombin activation, the B-domains of both molecules are released. Previous studies on factor VIII showed that the B-domain was not required for thrombin cleavage or activity. In contrast, deletion of the factor V B-domain (residues 709 to 1545) yielded a molecule with sevenfold reduced procoagulant activity that was not cleaved by thrombin. However, this factor V B- domain deletion molecule was activated by factor Xa, although the fold- activation was 85% that of wild-type factor V. Thrombin cleavage of factor V occurs initially after residue 709 and subsequently after residues 1018 and 1545. The requirement for thrombin cleavage within the B-domain at residue 1018 was evaluated by mutagenesis of Arg1018 to Ile. In the resultant R1018I mutant, the rate of thrombin activation and appearance of maximal cofactor activity was delayed and was consistent with delayed cleavage of the light chain at residue 1545. In contrast, the rate of factor Xa activation in the R1018I mutant was not altered. This finding suggests that thrombin cleavage at 1018 facilitates subsequent thrombin cleavage at 1545. Further mutagenesis was used to study the requirement for sequences within the factor V B- domain for thrombin cleavage at residue 1545. Whereas the factor V deletion molecule removing residues 709 to 1545 was not cleaved by thrombin, a smaller B-domain deletion molecule (residues 709 to 1476) containing an acidic amino acid-rich region (residues 1490 to 1520) was effectively cleaved by thrombin. These results show that residues 1476 to 1545, which contain an acidic amino acid-rich region, were required for thrombin cleavage of the light chain. Introduction of an acidic amino acid-rich region from factor VIII (residues 337 to 372) into the factor V 709 to 1545 deletion also restored thrombin cleavage of the light chain. In contrast, similar replacement with the acidic region from the factor VIII light chain (residues 1649 to 1689) was significantly less effective in promoting thrombin cleavage of the light chain. This finding suggests that the different acidic regions in factors V and VIII are not functionally equivalent in their interaction with thrombin.(ABSTRACT TRUNCATED AT 400 WORDS)     

国内六大行政区域六城市中老年人群膝关节骨性关节炎患病危险因素比较

目的：了解中国不同地区间中老年人群膝关节骨性关节炎患病危险因素。方法：调查时间为2005—07／08。①从中国六大行政区（西北，华北，华东。中南，东北，西南）选出六城市（西安，石家庄，上海。广州，哈尔滨市，成都），用分层多阶段整群抽样方法，抽取6218名40岁及以上具有正式户口常住男女人群进行膝关节骨性关节炎的流行病学问卷调查（包括一般情况、现病史、既往史、体格检查、X射线片检查情况和疾病诊断6个方面，共计94个问题141个变量指标），并对其中4808名有症状者进行X射线平片膝正侧位投照。②膝关节骨性关节炎诊断标准为临床症状阳性加X射线Kellgren ＆ Lawrence分级二级及以上者。③计算患病率，并采用Epilnf06．0和SPSS 10．0软件对其中83个变量进行多因素非条件Logistfc回归分析，表示疾病与暴露因素之间联系强度的指标用比值比（OR），若OR〉1，说明疾病发生危险性增加，与暴露因素呈正关联；若OR〈1，说明疾病发生危险性减少，与暴露因素呈负关联。 结果：①六城市膝关节骨性关节炎总患病率为15．6％，其中西安7．7％，石家庄11．2％，上海9．8％。广州30．5％，哈尔滨16．9％，成都17．5％，各城市患病率比较差异显著（P〈0．01）。②Logistic回归分析膝关节骨性关节炎在大部分城市有共同的危险因素如年龄大（OR=1．032—1．181），使用蹲坑排便年限长（OR=1．021-1．077），体质量高（OR=1．048—1．073），和开始饮酒年龄大（OR=1．008～1．028）；而从事专职体育运动（OR=1．651，西安），骨质疏松病史（OR=3．311，石家庄），吸烟（OR=2．654，石家庄），类风湿关节炎病史（OR=4．964，上海），文化程度高（OR=2．593，上海），女性（OR=2．510，广州），姐妹骨关节炎史（OR=13．251，哈尔滨），母亲骨关节炎史（OR=5．683，成都）等危险因素分别在不同地区出现． 结论：年龄大、使用蹲坑排便年限长、体质量高和开始饮酒年龄大是中国六地区膝关节骨性关节炎患病的共同危险因素，同时，不同地区主要危险因素又有一定差异。     

软骨修复组织蛋白多糖代谢与一氧化氮合酶抑制剂的影响

目的:应用一氧化氮合酶抑制剂可改善骨性关节炎和风湿性关节炎软骨的代谢,作者前期的实验也证明一氧化氮合酶抑制剂能提高软骨修复组织的质量。实验进一步观察一氧化氮合酶抑制剂对软骨修复组织蛋白多糖代谢的影响。方法:实验于1999-06/2002-02在南方医科大学完成。①实验分组:取雄性新西兰兔24只,8月龄,体质量(2.5±0.2)kg。随机抽签法分为对照组、骨形态发生蛋白组和S-甲基异硫脲组,每组8只。②实验方法:将大白兔双侧股骨髁间关节面造成全层软骨缺损,对照组:软骨缺损不充填任何物质;骨形态发生蛋白组:缺损用骨形态发生蛋白纤维蛋白凝胶复合物充填;S-甲基异硫脲组:缺损应用胶原复合骨形态发生蛋白充填,术后按5mg/(kg·12h)皮下注射S-甲基异硫脲。术后1年麻醉后处死动物。③实验评估:应用组织切片番红O-快绿染色和图像分析技术,按照染色百分率、平均灰度(平均染色程度)和染色厚度(软骨厚度)指标来检测糖胺聚糖含量;应用Na235SO4掺入法检测软骨修复组织蛋白多糖合成。结果:纳入新西兰兔24只,均进入结果分析。①术后1年,对照组几乎无红色染色区域;骨形态发生蛋白组可见到少量的不均匀红色区域;S-甲基异硫脲组可见到较多均匀一致的红色染色区域。②S-甲基异硫脲组软骨修复组织番红O染色百分率为89.28%,明显高于骨形态发生蛋白组36.54%和对照组13.4%,S-甲基异硫脲组修复组织番红O-快绿染色平均灰度值134.5,分别为骨形态发生蛋白组平均灰度值56.8的2.5倍,为对照组26.4的7倍。软骨平均厚度S-甲基异硫脲组1.75cm分别为骨形态发生蛋白组0.76cm和对照组0.25cm的2倍和6倍。③Na235SO4掺入法结果显示,S-甲基异硫脲组[35S]摄入量明显高于骨形态发生蛋白组和对照组(P<0.01)。结论:诱导型一氧化氮合酶抑制剂S-甲基异硫脲的应用能明显增加软骨修复组织糖胺聚糖含量和蛋白多糖合成,对于软骨修复质量的提高有积极意义。     

A processive versus a distributive mechanism of action correlates with differences in ability of normal and xeroderma pigmentosum group A endonucleases to incise damaged nucleosomal DNA

A DNA endonuclease, isolated from the nuclei of normal human and xeroderma pigmentosum complementation group A (XPA) cells, which recognizes predominately pyrimidine dimers, was examined for the mechanism by which it locates sites of damage on UVC-irradiated DNA. In reaction mixtures with low ionic strengths (i.e. lacking KCl), the normal and XPA endonuclease locate sites of UV damage on both naked and reconstituted nucleosomal DNA by different mechanisms. On both of these substrates, the normal endonuclease acts by a processive mechanism, meaning that it binds non-specifically to DNA and scans the DNA for sites of damage, whereas the XPA endonuclease acts by a distributive one, meaning that it randomly locates sites of damage on DNA. However, while both the normal and XPA endonucleases can incise UVC irradiated naked DNA, they differ in ability to incise damaged nucleosomal DNA. The normal endonuclease showed increased activity on UVC treated nucleosomal DNA compared with naked DNA, whereas the XPA endonuclease showed decreased activity on the damaged nucleosomal substrate. Since a processive mechanism of action is sensitive to the ionic strength of the micro-environment, the KCl concentration of the reaction was increased. At 70 mM KCI, the normal endonuclease switched to a distributive mechanism of action and its ability to incise damaged nucleosomal DNA also decreased. These studies show that there is a correlation between the ability of these endonucleases to act by a processive mechanism and their ability to incise damaged nucleosomal DNA; the normal endonuclease, which acts processively, can incise damaged nucleosomal DNA, whereas the XPA endonuclease, which acts distributively, is defective in ability to incise this substrate.      

A new amino acid mixture permits new approaches to the treatment of phenylketonuria

A new amino acid mixture for incorporation into medical foods for the treatment of hyperphenylalaninemia has been tested in a regular clinic. The mix is designed to be as unobtrusive as possible, consistent with good nutrition. After more than 1 year of trial as a beverage, we have shown that it is safe and well tolerated but that plasma phenylalanine is no better controlled than with some other products. The mix can be incorporated into a large number of different foods without affecting the taste. Occult monitoring of the quantity of medical foods purchased compared with the amounts reported to be consumed in diet histories provides an excellent way to monitor dietary compliance.