Identification of cysteine pairs within the amino-terminal 5% of apolipoprotein B essential for hepatic lipoprotein assembly and secretion

There is growing evidence that the amino-terminal globular domain of apolipoprotein B (apoB) is essential for lipoprotein particle formation in the hepatic endoplasmic reticulum. To identify the structural requirements for its function in lipoprotein assembly, cysteine (Cys) pairs required to form the seven disulfide bonds within the amino-terminal 21% of apoB were replaced in groups or individually by serine. Substitution of Cys pairs required for formation of disulfide bonds 1-3 or 4-7 (numbered from amino to carboxyl terminus) completely blocked the secretion of apoB28 in transfected HepG2 cells. To identify the specific disulfide bonds required for secretion, Cys pairs were mutated individually. Substitution of Cys pairs required for disulfide bonds 1, 3, 5, 6, or 7 had little or no impact on apoB28 secretion or buoyant density. In contrast, individual substitution of Cys pair 2 (amino acid residues 51 and 70) or 4 (218 and 234) severely inhibited apoB28 secretion and its capacity to undergo intracellular assembly with lipid. The same assembly and secretion defects were observed when these mutations were expressed as part of apoB50. These studies provide direct evidence that the ability of the internal lipophilic regions of apoB to engage in the recruitment and sequestration of lipid during translation is critically dependent upon a structural configuration contained within or affected by the amino-terminal 5% of the protein.     

Binding of tissue plasminogen activator to endothelial cells. The effect on functional properties. Localization of a ligand in the B-chain of tPA

The binding of 125I-labelled tissue plasminogen activator (tPA), the tPA A- or B-chain to endothelial cells (EC) were studied in suspensions of cultured human umbilical vein EC (HUVEC) or immortalized microvascular EC (HMEC). By determinations of the concentration-dependent binding it was shown that both the A-chain and the B-chain, which were isolated after partial reduction of two-chain tPA, contain ligands for binding to EC. The affinity for the B-chain was much higher than for the A-chain according to Scatchard analysis (Kd 24 and 515 nM, respectively), whereas the number of binding sites was higher for the A-chain than for the B-chain (Bmax 8 x 10(5) and 1.2 x 10(5), respectively). There were no cross interactions between the A- and B-chains and their binding sites. The binding of tPA to EC induced an almost 100-fold increase of the activation rate when compared to the same amount of enzyme in free solution, which in contrast to the fibrin-induced stimulation was not inhibited by antibodies against fibrin. The enzymatic activity of the B-chain was much less affected by the association to the cells. Both tPA and the tPA B-chain were largely protected against inhibition by an excess plasminogen activator type-1 (PAI-1) when bound to EC, whereas the same amount of free tPA was totally inactivated. The competition studies strongly indicated that an N-terminal segment in the B-chain, AKHRRSPGER, may be the ligand part of the B-chain. It is interesting to note that this polypeptide segment also participates in a binding site for PAI-1, necessary for effective inhibition. This implies a possible competition between PAI-1 and a tPA-receptor for binding of tPA. High molecular weight urokinase had no quenching effect on the binding of the B-chain to EC.     

激光角膜矫正术中所用激光波长的选择

用分光光度计测定了12例兔角膜和1例人角膜的吸收光谱,结果表明波长小于300nm的准分子激光和波长在1.88μm～2.64μm,2.36μm～40μm的激光,均可对角膜进行切割并可望用于激光角膜矫正术。     

Molecular mechanisms of transforming growth factor-beta signaling

The present experiments examined the effects of posttraining intrahippocampal injections of the degradative enzyme-resistant methylcarbamyl analog of the bioactive phospholipid platelet-activating factor (mc-PAF) and the platelet-activating factor (PAF) receptor antagonists BN52021 and BN 50730 on memory in male Long-Evans rats trained in a hidden platform version of the Morris water maze. Following an eight-trial training session, rats received a unilateral intrahippocampal injection of mc-PAF (0.5, 1.0, or 2.0 microgram/0.5 microliter), lyso-PAF (1.0 microgram/0.5 microliter), the cell surface PAF receptor antagonist BN 52021 (0.25, 0.5, or 1.0 micrigram/0.5 microliter/, the intracellular PAF receptor antagonist BN 50730 (2.0, 5.0, or 10.0 microgram/0.5 microliter), or vehicle (50% DMSO in 0.9% saline; 0.5 microliter). On a retention test conducted 24 h after training, the escape latencies of rats administered mc-PAF (1.0 or 2.0 microgram) were significantly lower than those of the vehicle-injected controls, demonstrating a memory-enhancing effect of mc-PAF. Injections of lyso-PAF, a structurally similar metabolite of PAF, had no influence on memory, indicating that the memory-enhancing effect of mc-PAF is not caused by membrane perturbation by the phospholipid. The retention test escape latencies of rats administered BN 52021 (0.5 microgram) and BN 50730 (5.0 or 10 microgram) were significantly higher than those of the controls, indicating a memory impairing effect of both PAF antagonists. When mc-PAF, BN 52021, or BN 50730 was administered 2 h posttraining, no effect on retention was observed, indicating a time-dependent effect of the neuroactive substances on memory storage. The findings suggest a role for endogenous PAF in hippocampal-dependent memory processes.     

Correlation between lymphocyte-induced donor-specific tolerance and donor cell recirculation. Role of class I and class II major histocompatibility complex

Intravenous infusion of mice with viable allogeneic lymphocytes can produce donor-specific enhancement of skin graft survival, but only if the injected lymphocytes can persist in the host's recirculating lymphocyte pool for at least 3 days. We have investigated the relative roles of class I and class II MHC for C57BL/6 mice infused with lymphoid cells from co-isogenic strains mutated at class I MHC (bm1) or class II MHC (bm12), and for A.TH lymphoid cells infused into C3H (class I different, class II identical) or A.TH (class II different, class I identical). Injected cells differing from the host at class I MHC, but not at class II MHC, can be rapidly removed by host natural immune mechanisms (probably NK cells). Persistence is favored if the injected cells also carry host class I MHC, i.e., tolerance is more readily induced by injecting F1 (A x B) into A rather than B into A, consistent with the "missing self" hypothesis of NK recognition, with class I MHC being the relevant self-marker. Injected cells differing from the host at class II MHC but not at class I MHC always persist for at least 3 days, even when class I-different cells are being actively removed.     

腋静脉留置针在早产儿中的应用

目的探讨早产儿腋静脉穿刺置人留置针的保留时间及不良反应。方法从2008年2月至2009年8月,68例留置针在早产儿输液对象中的33例采用腋静脉输液,35例采用外周静脉输液,对2组一次穿刺成功率、导管脱出、保留时间进行分析。结果腋静脉穿刺置管留置时间明显长于外周静脉,也无明显不良反应。结论腋静脉置管大大减少了患儿的痛苦和护士的工作量,是一种既安全又经济的给药途径,可以在新生儿病房和NICU广泛使用。     

持续热灌注腹腔化疗在胃肠肿瘤治疗中的作用研究

目的比较持续热灌注腹腔化疗 静脉化疗(HIPC IVC)、常规腹腔化疗 静脉化疗(IPC IVC)和单纯静脉化疗(SIVC)对于进展期胃肠肿瘤患者的疗效。方法将2003年1月～2007年2月间住院转移性胃癌患者53例随机分成3组。14位患者接受HIPC IVC,18位患者接受IPC IVC,21位患者接受SIVC,化疗毒副反应对症处理。2个周期以上评价疗效及毒副反应。结果HIPC IVC与IPC IVC或SIVC相比,缓解率、总体疗效有明显差异,HIPC在治疗转移性腹水方面有明显的优势。引起全身副作用比SIVC组小,而且多属于I～II级。结论HIPC IVC治疗方法对机体的免疫打击小,患者生活质量改善明显,临床受益率高。     

人细小病毒B19感染与早期自然流产关系的探讨

目的探讨人细小病毒B19(HPVB19)感染与早期自然流产的关系。方法用酶联免疫吸附试验(ELISA)法检测52例早期自然流产患者(研究组)和45例无异常人工流产孕妇(对照组)血清中HPVB19-IgM和IgG。结果研究组血中B19V-IgM阳性率为23.08%,而对照组阳性率为6.67%,2组间具有显著性差异(P<0.05);研究组近期HPVB19感染的概率是对照组的4.20倍(95%CI 1.10～15.99)。研究组B19V-IgG阳性率为32.69%,对照组为28.89%,2组差异无统计学意义(P>0.05)。结论 HPVB19感染可能是导致早期自然流产的原因之一。     

阴式子宫肌瘤剔除术与经腹子宫肌瘤剔除术的疗效比较

目的观察比较阴式肌瘤剔除术与经腹肌瘤剔除术治疗子宫肌瘤的疗效。方法入选对象为我院2009年1月至2010年1月80例子宫肌瘤患者,根据手术方法不同按照入院先后顺序随机分为观察组(阴式子宫肌瘤剔除术)和对照组(经腹子宫肌瘤剔除术)各40例,比较2组的手术疗效。结果观察组应用经阴道肌瘤剔除术的有效率高于对照组,且与对照组比较,观察组手术时间短、术中出血少,术后肛门排气快,住院时间明显缩短(P<0.05),随访4～6个月,观察组复发率明显低于对照组(P<0.05)。结论与经腹肌瘤剔除术相比,阴式肌瘤剔除术治疗子宫肌瘤手术效果确切,手术时间短、术中出血少、住院时间短、复发率低。     

脑出血后肺组织炎症损伤情况的研究

目的研究脑出血后肺组织炎症损伤的发病机制。方法用病理学常规HE染色法观察脑出血组和对照组肺标本的出血、渗出和炎症细胞浸润改变情况,在光镜下对白细胞、巨噬细胞进行记数。结果与对照组比较,脑出血组肺组织存在明显渗出、出血及大量白细胞、巨噬细胞浸润,炎症细胞记数有显著意义P<0.05。结论脑出血可以通过引发炎症反应导致急性肺损伤;炎症反应在3~5d时最明显。