Immunoglobulin G from patients with heparin-induced thrombocytopenia binds to a complex of heparin and platelet factor 4

Heparin-induced thrombocytopenia (HIT) is an important complication of heparin therapy. Although there is general agreement that platelet activation in vitro by the HIT IgG is mediated by the platelet Fc receptor, the interaction among the antibody, heparin, and platelet membrane components is uncertain and debated. In this report, we describe studies designed to address these interactions. We found, as others have noted, that a variety of other sulfated polysaccharides could substitute for heparin in the reaction. Using polysaccharides selected for both size and charge, we found that reactivity depended on two independent factors: a certain minimum degree of sulfation per saccharide unit and a certain minimum size. Hence, highly sulfated but small (< 1,000 daltons) polysaccharides were not reactive nor were large but poorly sulfated polysaccharides. The ability of HIT IgG to recognize heparin by itself was tested by Ouchterlony gel diffusion, ammonium sulfate and polyethylene glycol precipitation, and equilibrium dialysis. No technique demonstrated reactivity. However, when platelet releasate was added to heparin and HIT IgG, a 50-fold increase in binding of radio-labeled heparin to HIT IgG was observed. The releasate was then depleted of proteins capable of binding to heparin by immunoaffinity chromatography. Only platelet factor 4-immunodepleted releasate lost its reactivity with HIT IgG and heparin. Finally, to determine whether the reaction occurred on the surface of platelets or in the fluid phase, washed platelets were incubated with HIT IgG or heparin and after a wash step, heparin or HIT IgG was added, respectively. Reactivity was only noted when platelets were preincubated with heparin. Consistent with these observations was the demonstration of the presence of PF4 on platelets using flow cytometry. These studies indicate that heparin and other large, highly sulfated polysaccharides bind to PF4 to form a reactive antigen on the platelet surface. HIT IgG then binds to this complex with activation of platelets through the platelet Fc receptors.     

Inhibition of thromboxane formation in vivo and ex vivo: implications for therapy with platelet inhibitory drugs

The capacity of platelets to generate thromboxane A2, reflected by measurement of serum thromboxane B2 (TxB2), greatly exceeds the systemic production of thromboxane in vivo. Thus, it is possible that substantial but incomplete inhibition of thromboxane formation ex vivo would still allow marked augmentation of thromboxane production in vivo. To address this hypothesis, we administered aspirin 120 mg, a selective inhibitor of thromboxane synthase (TxSl), 3-(1H-imidazol-1-yl- methyl)-2-methyl-1H-indole-1-propanoic acid (UK-38, 485) 200 mg, and a combination of both drugs to 12 healthy volunteers and measured the effects on serum TxB2 and urinary 2,3-dinor-thromboxane B2 (Tx-M), an index of endogenous thromboxane biosynthesis. Although serum TxB2 was maximally inhibited by 94 +/- 1% after aspirin and 96 +/- 2% after the TxSl, maximal depression of Tx-M was only 28 +/- 8% and 37 +/- 9%, respectively. Combination of aspirin with the TxSl resulted in a small but significant increase in inhibition of thromboxane generation ex vivo (98 +/- 1% v 94 +/- 1%; P less than 0.05), but a disproportionately greater fall in thromboxane synthesis in vivo (58 +/- 7%; P less than 0.01). Consistent with further inhibition of platelet thromboxane synthesis, addition of the TxSl abolished the transient decline in prostacyclin formation after aspirin alone. Administration of a lower dose of aspirin (20 mg) to 6 healthy subjects caused a small reduction in Tx-M (12 +/- 4%; P less than 0.05) and inhibited serum TxB2 by 48 +/- 2%. The relationship between inhibition of platelet capacity to form thromboxane ex vivo (serum TxB2) and synthesis in vivo (Tx-M) departed markedly from the line of identity. When total blockade of the capacity of platelets to generate thromboxane is approached, minor decrements in capacity result in a disproportionate depression of actual thromboxane biosynthesis. These results imply that pharmacologic inhibition of serum TxB2 must be virtually complete before thromboxane- dependent platelet activation is influenced in vivo.     

江苏省太仓市胆囊结石危险因素病例对照研究

胆石症是江苏省太仓市的常见病,１９９７年江苏省太仓市人民医院外科手术病例的１／４是胆石症。本文概括胆囊结石的主要危险因素,为当地胆石症的预防和干预提供科学依据。材料与方法本研究采用了基本人群的成组病例对照研究设计。在太仓市选取５个自然村,作为研究现场。病例通过Ｂ超检查获取,共检查３５～７９岁居民２４５８例,以受检人群中胆囊结石病人为研究对象。对照为随机人群,共６１１例。直接面访被调查者,对研究对象实施同一问卷的询问调查。调查内容包括一般情况、饮食、行为、胆石症家族史、既往史、女性生理与生育因素等…     

Ectopic expression of rhombotin-2 causes selective expansion of CD4-CD8- lymphocytes in the thymus and T-cell tumors in transgenic mice

Although the proto-oncogene rhombotin-2 (RBTN-2) is widely expressed in most tissues, it is not expressed in T cells. We investigated the potential for overexpression of RBTN-2 to cause tumors in T cells and other tissues by constructing transgenic mice that expressed RBTN-2 under control of the metallothionein-1 promoter. Despite overexpression of RBTN-2 in all tissues, transgenic mice developed T-cell tumors only, thus indicating that tumorigenesis caused by RBTN-2 is T-cell-specific. Thymic tumors were found between 37 and 71 weeks and were invariably associated with metastasis to nonlymphoid organs. Thymuses from apparently healthy transgenic mice were also examined. In some mice there was an 10-fold increase in the CD4-CD8- thymocyte subset, yet the total number of thymocytes was the same as that in wild-type mice. Thymic homeostasis was maintained by a compensatory reduction in the CD4+CD8+ subset. The expansion of CD4-CD8- thymocytes was associated with increased expression of RBTN-2 and with increased cell proliferation. No differences were found in the proportion of thymocytes undergoing apoptosis in transgenic mice. Furthermore, RBTN-2- induced expansion of CD4-CD8- cells did not block differentiation of these cells. Thymuses with 30% CD4-CD8- cells were essentially monoclonal, indicating that all thymic immunophenotypes were derived from a single clone. Overall, our data are consistent with the following scenario: (1) RBTN-2 expression in T cells causes selective and polyclonal proliferation of CD4-CD8- thymocytes accompanied by a compensatory decrease in other thymocyte subsets; (2) a clone with growth advantage and differentiation potential is selected and populates the thymus; and (3) this clone eventually breaches homeostasis of the thymus, accompanied or followed by metastasis to other organs.     

Enhanced leukocyte binding by intestinal microvascular endothelial cells in inflammatory bowel disease

BACKGROUND & AIMS: Microvascular endothelial cells mediate leukocyte homing, angiogenesis, and inflammation and healing and show tissue- specific adhesion molecules and functions. The activation of human intestinal mucosal microvascular endothelial cells (HIMECs) was studied in vitro to uncover possible abnormalities associated with inflammatory bowel disease. METHODS: HIMECs were isolated from normal and inflammatory bowel disease mucosa and assessed for phenotypic and morphological features, proliferative response, leukocyte binding capacity, and adhesion molecule expression. RESULTS: Basal proliferation by HIMECs was less than that of human umbilical vein endothelial cells (HUVECs) but increased proportionally more in response to vascular endothelial growth factor. Proinflammatory stimuli induced an activated, spindle-shaped morphology in HIMEC monolayers. Compared with HUVECs, unstimulated HIMECs showed less adhesiveness for U937 and MOLT4 cells and neutrophils, but cytokines and lipopolysaccharide substantially increased the binding capacity of HIMECs. HIMECs derived from inflammatory bowel disease mucosa showed a markedly greater leukocyte-binding capacity than normal mucosal HIMECs. Patterns of intercellular adhesion molecule 1, vascular cell adhesion molecule 1 and E-selectin messenger RNA expression were distinct in HIMECs, HUVECs, and mucosal mesenchymal cells. CONCLUSIONS: HIMECs represent differentiated endothelial cells with unique functional properties. Their dramatically enhanced capacity to bind leukocytes in inflammatory bowel disease suggests that HIMECs play an important role in initiating or maintaining inflammation. (Gastroenterology 1997 Jun;112(6):1895-907)     

酶联免疫吸附试验中HBsAg室内质控参考品的制备和应用

目的建立室内质控参考品以鉴别诊断试剂的质量和控制操作误差,提高乙型肝炎病毒表面抗原的检测准确度。方法以国家标准品为标准制备灵敏度系列参考品、特异性参考品及精密性参考品。检测其稳定性,并进行同厂家、不同批号试剂的比较及不同厂家、三批试剂的比较。结果制备的室内质控参考品在-20℃与4℃保存3～4周检测结果无统计学差异。采用同一厂家、不同批号的HBsAg诊断试剂检测室内质控参考品,结果无统计学差异。采用不同厂家、同一批号的HBsAg诊断试剂检测结果有统计学差异。结论我们建立的室内质控参考品适宜作HBsAg室内质控,提醒我们在更换试剂厂家时应特别注意室内质控参考品的变化。     

急性有机磷杀虫药中毒中间综合征的临床分析

目的探讨急性有机磷杀虫药中毒中间综合征（intermediate syndrome,IMS）的诊断治疗。方法回顾性分析10例IMS患者临床表现和治疗方法。结果有机磷中毒中间综合征的10例患者均出现不同程度呼吸肌麻痹症,及时建立人工气道及机械通气和乙酰胆碱酯酶（AchE）复能剂应用,治愈8例,死亡2例。结论 IMS应早期识别,建立人工气道与机械通气是抢救成功的重要方法。