In vitro activation of the human Harvey-ras proto-oncogene by aflatoxin B1

Activation of ras proto-oncogenes occurs frequently in vivo in chemically induced rodent tumours, including rat hepatomas induced by aflatoxin B1. This study examines the in vitro activation of a human ras gene by this mycotoxin. A plasmid containing the human Ha-ras proto- oncogene, together with a neomycin resistance gene (pECneo), was incubated in vitro with a microsomal system generating aflatoxin B1 8,9- epoxide. Subsequent transfection of the plasmid into mouse NIH 3T3 fibroblasts, followed by G418 selection and s.c. injection of surviving cells into immunodeficient mice demonstrated that the proto-oncogene had acquired transforming capacity. Although a single tumour resulted from similar treatment of incubated unconjugated plasmid, no tumours were produced by a secondary round of transfections using DNA from this tumour. Selective PCR amplification of the human Ha-ras gene in extracted tumour DNA followed by sequencing demonstrated the presence of G-->T transversions either at the first or middle base of codon 12 in tumours resulting from transfection with the aflatoxin-B1-modified pECneo plasmid, but this was not detected in the single tumour resulting from transfection with the unmodified plasmid. Thus, although a mutation in the Ha-ras gene has not been reported for human primary hepatomas occurring in aflatoxin-exposed populations, metabolically activated aflatoxin B1 is capable of mutating this proto-oncogene to its oncogenic form in vitro. No mutations were observed in codon 61. It appears that, in contrast to the frequently reported G-->T transversions in codon 249 of the p53 gene in primary hepatomas in aflatoxin-exposed humans, the failure to detect Ha-ras mutations in these tumours is not due to an inability of aflatoxin B1 to activate this proto-oncogene. The G-->T transversions observed in this study contrast with the most frequent aflatoxin B1 in vivo induced mutations, G-->A transitions in the rat Ki-ras gene. Possible mechanisms for these differences are discussed.      

Epstein-Barr virus-associated hemophagocytic syndrome: virological and immunopathological studies

The virus-associated hemophagocytic syndrome (VAHS) is a disorder characterized by a benign, generalized histiocytic proliferation, with marked hemophagocytosis associated with systemic viral infections. We have studied the virological and immunopathological events occurring in two children experiencing Epstein-Barr VAHS. Neither of the patients had an underlying immunodeficiency and both recovered from their disease and are completely well one year after follow-up. In each patient, evidence for primary Epstein-Barr virus (EBV) infection was documented with a typical humoral immune response, including IgM antibody directed against virus capsid antigen. EBV was demonstrated in lymphoreticular tissues by electron microscopy and molecular hybridization studies. Permissive EBV infection was suggested by the finding of mature virus particles and linear viral DNA in lymphoreticular tissues. Immunopathological studies demonstrated complete effacement of lymph node architecture by a marked proliferation of immunoblasts in patient 1 and infiltration and effacement of the lymph node architecture with benign-appearing histiocytes in patient 2. Atypical lymphocytes characteristic of acute EBV infection were notably absent in the peripheral blood of both patients and cytotoxic T cells, which normally lyse EBV-infected B cells, were also absent from the peripheral circulation. Our observations suggest that EBV-induced VAHS may be the result of an increased virus burden in the face of immunoregulatory cell imbalances.     

Wilms tumor occurring as a botryoid renal pelvicalyceal mass

Wilms tumor usually occurs as an abdominal mass arising from the renal parenchyma. A case was encountered in which the neoplasm filled the pelvicalyceal system of an 8-year-old boy as a botryoid mass, with minimal parenchymal involvement. The radiologic manifestations, pathologic features, and surgical implications are discussed.     

Bone marrow transplantation for refractory acute leukemia in 34 patients with identical twins

Thirty-four patients aged 4-67 yr (median 17) with acute lymphocytic leukemia (ALL) (18 patients) or acute nonlymphocytic leukemia (ANL) (16 patients) who failed to enter complete remission (CR) or relapsed on conventional chemotherapy were treated with cyclophosphamide (CY), 60 mg/kg/day for 2 days, 1000 rad total body irradiation, and a marrow transplant from a genotypically identical normal twin. Sixteen of the patients received additional chemotherapy within the week before CY. After the transplant, 23 patients received immunotherapy consisting of killed autologous leukemic cells and/or normal twin peripheral blood lymphocytes, 16 as part of a prospectively randomized study. One moribund patient died before engraftment. Nine patients (6 ALL, 3 ANL) continued to have detectable leukemic cells. Twenty-four patients (70%) achieved CR. One of them died of viral hepatitis at 1 mo and another of viral interstitial pneumonitis at 4 mo in CR. Fourteen patients (7 ALL, 7 ANL) relapsed 2-16 mo (median 4) after transplantation. However, 8 patients (24%) (3 ALL, 5 ANL) remain in CR without any maintenance chemotherapy at 29-103 mo (median 80) after the transplant. The end results were not signficantly influenced by the type of leukemia, the immediated pre-CY chemotherapy, or the immunotherapy. The results show that this approach, even when applied to endstage patients with acute leukemia in relapse, causes tolerable morbidity, rare nonleukemic deaths, and frequent remissions, some of which represent cures.     

酶标仪性能评价与鉴定的基本方法及其初步应用

酶标仪性能评价与鉴定的基本方法及其初步应用成军孙关忠郑怀竞李早荣倪方荣表１滤光片波长精度检查滤光片波长（ｎｍ）标定值４０５．０４５０．０４９０．０５４０．０５５０．０５８５．０６２０．０６５５．０实测值４０４．８４４８．２４８９．１５４０．３５４９．...     

广东东莞地区中老年非暴力性骨折107例及无骨折求诊者392例超声骨密度测定

目的:应用超声骨密度/骨质量测量仪对东莞地区中老年非暴力性骨折患者进行检测,探讨各参数的变化规律及临床意义,并确立骨折的骨密度阈值。方法:①实验对象:选择2003-09/2006-08在东莞石龙人民医院进行超声骨密度测定的非暴力性骨折东莞地区中老年患者107例,男30例,女77例;同期同龄进行超声骨密度测定的无骨折求诊者392例,作为对照组,男83例,女309例。②实验分组:根据年龄分为3个时期:46～60岁为老年前期、61～75岁为老年期、76岁以上为高龄期,以及相应男女组及骨折与非骨折组。③实验方法:采用法国DMS公司UBIS5000型超声骨密度/骨质量测量仪对中老年非暴力性骨折者、无骨折就诊者进行超声骨密度测量。④实验评估:比较两组男女及不同年龄段超声振幅衰减平均值、超声传播速度、骨硬度指数、T值(代表患者测量值如超声振幅衰减平均值和20岁正常人的测量值之间的差异)、Z值(代表患者测量值如超声振幅衰减平均值和同龄正常人的测量值之间的差异)。结果:两组499例患者全部进入结果分析。①总体比较:男、女性骨折组与非骨折组比较,除超声传播速度差别无统计学意义外(P>0.05),其余指标(超声振幅衰减、骨硬度指数、T值、Z值)非骨折组高于骨折组(P<0.01)。②分年龄组比较:老年前期组与总体一致,老年组、高龄组主要指标无统计学意义。应用方差分析对女性骨折组各年龄组之间进行比较,除骨硬度指数外(P<0.05),其余指标差异无显著性;男性骨折组各年龄组之间比较得出与女性一样结果。③男性与女性骨折组比较:除T值男性组高于女性组外(P<0.01),其余指标(超声振幅衰减、超声传播速度、骨硬度指数、Z值)差异均无统计学意义。结论:①中老年人群骨质下降至一定程度(相应测量参数为骨折阈值)时容易发生脆性骨折。②致脆性骨折的骨质量条件与性别、年龄因素无明显相关性。③东莞地区步入老年期后不论男女骨质疏松现象相当普遍,是否会出现骨折关键在于有否外力作用,对其预防性诊断很有价值。     

Spine2000脊柱三维运动分析系统评估腰椎椎弓崩裂后4种植人体内固定的生物力学

目的：目前对TSRH内固定系统重新组合成钩钉系统还缺少相关的生物力学方面的比较及研究。实验对腰椎椎弓崩裂直接修复的4种内固定方法进行生物力学比较。方法：实验于2003-9/10在南方医科大学（原解放军第一军医大学）生物力学实验室完成。①实验材料：选用雄性健康小牛8具（上海市南汇区光明乳业特种屠宰场提供）,实验符合动物伦理学要求,常规方法处死后截取L2～6脊柱标本。②实验分组及过程：正常标本作为对照组,然后制成L4双侧椎弓崩裂模型,分别以改良Scott法（内固定由通用公司提供）、钩螺钉法（为枢法模公司提供TSRH的重新匹配）、钉杆法（由枢法模公司提供）和Buck螺钉法（德国确卓公司提供）固定。③实验评估：通过计算机扫描观察L3～4及L4～5的活动范围。结果：4种内固定固定后脊柱稳定性均能得到有效恢复（P〉0.05）,但钩螺钉法、钉杆法和Buck钉固定法在提高屈曲稳定性方面优于改良Scott法（P〈0.05）;在旋转或侧弯状态,4种固定方法间差异都无显著性（P〉0.05）。但是,从均值比较来看,钩螺钉法、钉杆法在抗旋转不稳方面要优于改良Scott法和Buck钉法。结论：改良Scott法、钩螺钉法、钉杆法和Buck螺钉法内固定方式均能有效恢复失稳脊柱的稳定性,但钩螺钉法、钩钉法在维持脊柱稳定性方面更具优势,且操作简单、易行、安全有效,是较理想的直接修复内固定器。