目的 对微囊化猪胰岛的体外、体内功能进行研究。方法 采用经胰导管连续灌注胶原酶技术分离和纯化猪胰岛。国产琼脂糖作为制备微包囊的免疫隔离材料，用“相分离”方法包被成年猪胰岛。21只糖尿病大鼠用于实验，对照组6只，移植组15只。其中6只腹腔内植入微囊化胰岛，6只腹腔内植入未包囊胰岛，3只肾包膜下植入未包囊胰岛。数据做组间比较，用t检验。结果 微囊化胰岛在1个月的培养期间可持续分泌胰岛素。囊内细胞生长良好，微囊没有溶解和破碎。培养2天的微囊化胰岛对高糖与茶碱刺激有明显反应，胰岛素释放量分别为低糖的1.83倍和2.28倍（P<0.01）。对6只糖尿病大鼠施行腹腔内植入微囊化胰岛手术，2000～3000个/只。不用任何免疫抑制剂。移植后第4天血糖明显下降，第7天时血糖降至正常范围，维持30天。结论 琼脂糖微囊具有较好的免疫隔离作用。

目的 探讨天津地区早发糖尿病（DM）患者线粒体DNA tRNALeu（UUR）3243A →G突变的发生率及其相关性。方法 随机选取无亲缘关系、发病年龄≤45岁的DM患者348例，对照组207名，收集相应临床资料，提取外周血基因组DNA，以聚合酶链反应、限制性内切酶片段长度多态性及克隆的方法检测线粒体基因tRNALeu（UUR）3243 A →G突变，并进行家系研究。结果 DM组发现2例3243 A→G突变，检出率为0.6%，有家族史的DM患者中发生率为1.2%。对照组未发现此突变。3243 A→G突变先证者呈典型的线粒体DM表现，其家庭成员的临床表型和基因突变异质性不一致。结论 tRNALeu（UUR）3243 A→G突变在天津地区发病年龄≤45岁的DM患者中检出率低，在合并其他线粒体病的患者中发生率较高;该突变异质性比例在有丝分裂组织中可能随年龄增加而减小。

Although the involvement of complement in hyperacute rejection of xenotransplants is well recognized, its role in rejection of devascularized xenografts, such as pancreatic islets, is not completely understood. In this study, we investigated whether complement participates in the immunopathology of xeno-islet transplantation in a concordant rat to mouse model. Rat pancreatic islets were implanted under the kidney capsule of normal and cobra venom factor (CVF) decomplementized diabetic C57BL/6 mice. Graft survival was monitored by blood glucose levels. Deposition of IgM and C3 on grafted islets in vivo or on isolated islets in vitro (after incubation with normal and decomplementized mouse serum), as well as CD4-and CD8-positive leucocyte infiltration of grafts, was checked by immunohistochemistry. In addition, complement-mediated cytotoxicity on rat islet cells was evaluated by a 3-(4, 5-dimethythiazolyl)-2. 5-diphenyl-2Htetrazolium bromide (MTT) assay. A significant C3 deposition was found on grafted islets from the first day after transplantation in vivo, as well as on isolated islets after incubation with mouse serum in vitro. By MTT assay, complement-mediated cytotoxicity for islet cells was found. Decomplementation by CVF decreased C3 deposition on either isolated or grafted islets, delayed CD4-and CD8-positive leucocyte infiltration, led to significant inhibition of complement-mediated cytotoxicity for islet cells, and prolonged graft survival (mean survival time 21•3 versus 8•5 days; P<0•01). Our results indicate that decomplementation can prolong the survival time of devascularized xenografts across concordant species. The deposition of complement on transplanted islets may contribute to xenograft rejection by direct cytotoxicity and by promoting leucocyte infiltration.

There is a microcirculation system within the islets of Langerhans. However, little is known about the phenotypicand functional characterization of islet microvascular endothelial cells (MVEC). In this study, we purified MVEC from human pancreatic islets by using Ulex europaeus(Sigma, St. Louis, MO)agglutinin-1(UEA-1)-coated dynabeads(Dynal A. S., Oslo, Norway). These purified human islet MVEC (HI-MVEC) express von Willebrand factor, take up high levels of acetylated LDL, and upregulate endothelial cell leukocyte adhesion molecule 1 in response to tumor necrosis factor-a. Ultrastructure examination shows the presence of microvilli and fenestrations on the cell surface, Weibel-Palade bodies in the cytoplasm, and tight junctions between cells. Furthermore, we show that vascular endothelial cell growth factor contributes to the formation of surface fenestrations on cultured HI-MVEC. After purification, HI-MVEC exhibit a very low proliferation capacity and are strongly resistant to trypsin, compared with other original MVEC. We also demonstrate that a-1 proteinase inhibitor(Api)is expressed on HI-MVEC and specifically located at the area of cell-cell junctions. By reverse transcription-polymerase chain reaction, a significant messenger RNA band of Api was found only in HI-MVEC, but not in other organ-derived MVEC, indicating that expression of Api is islet MVEC specific. Antibodies to Api significantly reversed the resistance to trypsin and promoted proliferation of HI-MVEC, suggesting that these specific functional characteristics of HI-MVEC are related to the expression of Api. These results indicate that HI-MVEC exhibit some specific morphological and functional characteristics that differ from MVEC derived from other organs. Diabetes 48: 1773-1778, 1999

Xenogeneic islets could provide an unlimited source of tissue for the treatment of diabetes, and could in theory be transplanted repeatedly in a recipient. However, little is known on the consequences of islet re-transplantation in a recipient who has rejected a