Characterization of damage modes in dental ceramic bilayer structures

Results of contact tests using spherical indenters on flat ceramic coating layers bonded to compliant substrates are reported for selected dental ceramics. Critical loads to produce various damage modes, cone cracking, and quasiplasticity at the top surfaces and radial cracking at the lower (inner) surfaces are measured as a function of ceramic-layer thickness. It is proposed that these damage modes, especially radial cracking, are directly relevant to the failure of all-ceramic dental crowns. The critical load data are analyzed with the use of explicit fracture-mechanics relations, expressible in terms of routinely measurable material parameters (elastic modulus, strength, toughness, hardness) and essential geometrical variables (layer thickness, contact radius). The utility of such analyses in the design of ceramic/substrate bilayer systems for optimal resistance to lifetime-threatening damage is discussed.     

人肿瘤细胞与正常细胞内微管的PAP免疫酶细胞化学观察

我们利用兔抗微管蛋白抗体和兔抗辣根过氧化物酶(HRP)抗血清制备的HRP—抗HRP(PAP)复合物,建立了微管的PAP免疫酶细胞化学方法。应用此法观察到人食管癌ECa 109、胃癌SGC 7901,乳腺癌MCF 7和成骨肉瘤OS 732细胞间期胞质微管减少或消失,只有大量弥散分布的微管蛋白棕色反应产物,在微管组织中心(MTOC)附近十分密集,而正常成纤维细胞和胎儿胃粘膜上皮细胞间期,都有发达的胞质微管结构(CMTC)。在分裂期,这些肿瘤细胞都显示纺锤体微管,与正常细胞比较无明显差异。本研究应用PAP方法进一步证明,以前用免疫荧光细胞化学方法观察到的人肿瘤细胞间期胞质微管缺陷的特征。除去低温(4℃)或秋水仙酰胺处理后,解聚的CMTC又可恢复,表明本方法与免疫荧光染色法,同样具有很高的特异性。本工作在细胞固定及免疫反应的某些步骤上有所改进。     

The ability of heat-killed Mycobacterium vaccae to stimulate a cytotoxic T-cell response to an unrelated protein is associated with a 65 kilodalton heat-shock protein

Exogenous antigens are generally presented by Class II major histocompatibility (MHC) molecules. When administered with an adjuvant, however, they are capable of inducing a CD8+ T-cell response where antigen recognition is associated with Class I MHC. Accordingly, immunization with soluble ovalbumin (OVA) alone does not activate CD8+ cytotoxic T cells (CTL) but when given in complete Freund's adjuvant (CFA), or in formulations of a number of novel adjuvants, an OVA-specific CD8+ CTL response can be detected. We show in this report that immunization with soluble OVA mixed with heat-killed Mycobacterium vaccae, but not with other common pathogenic and saprophytic mycobacteria, can activate OVA-specific CD8+ CTL. An OVA-specific CTL response is detected when mice are immunized by either the intraperitoneal or intranasal route and their spleen cells are re-stimulated in vitro. Adjuvant activity of heat-killed M. vaccae is present in M. vaccae culture filtrate, in soluble protein components of whole M. vaccae and in the 65 kDa heat-shock protein (hsp) of M. vaccae. Mycobacterium vaccae has previously been shown to have no adverse side-effects in humans. The current results suggest that M. vaccae may be useful as an adjuvant for vaccines and other immunotherapies where CD8+ CTL responses to exogenous proteins are crucial.     

Nucleolar localization of non-structural protein 3b, a protein specifically encoded by the severe acute respiratory syndrome coronavirus

The open reading frame 3 (ORF3) of the severe acute respiratory syndrome coronavirus (SARS-CoV) genome encodes a predicted 154-amino acid protein, which lacks similarities to any known protein, and is named 3b. In this study, it was shown that 3b protein was predominately localized to nucleus with EGFP tag at its N- or C-terminus. The localization patterns were similar in different transfected cells. Immuno-fluorescence assay revealed that 3b protein was co-localized well with C23 in nucleolus. C23, B23 and fibrillarin all are important nucleolar proteins, which localize in the region of the nucleolus. Co-transfection of p3b-EGFP with pC23-DsRed, pB23-DsRed and pfibrillarin-DsRed further confirmed 3b's nucleolus localization. With construction of serial truncated mutants of 3b, a region (residues 134-154 aa) responsible for nucleolar localization was determinated in 3b protein. These results provide a new insight for further functional studies of SARS-CoV 3b protein.     

硝苯啶、硫氮(艹卓)酮对兔实验性动脉粥样硬化症的影响

硝苯啶和硫氮(艹桌)酮不明显影响血清脂蛋白组分水平,但均显著抑制家兔主动脉动脉粥样硬化形成,降低血浆过氧化脂质、血栓烷和主动脉内中膜胆固醇、磷脂及钙含量,升高血浆6-酮-PGF_(1α),使,TXB_2/6-酮-PGF_(1α)趋于平衡。说明钙在血栓烷-前列环素代谢中起重要作用。     

多发性骨髓瘤患者血清IL-6活性与急性相蛋白浓度的相关性研究

运用敏感的B_9细胞增殖试验检测了81例多发性骨髓瘤(MM)患者血清IL-6活性,同时分析了标本的几种急性相蛋白含量,结果表明,68％MM患者血清中IL-6活性大于5μ/ml(正常对照为5μ/ml以下),几种急性相蛋白中C-反应性蛋白(CRP)在MM时升高(P<0.01),平均达正常对照组的17倍以上,MM患者补体C_4与正常对照组无差异(p>0.05),C_3、白蛋白及转铁蛋白在MM时分别比正常下降24.42％、38.83％和32.80％,且与疾病分期有关,在血清IL-6大于5μ/ml的55例中,IL-6活性与CRP、C_3、白蛋白的相关系数分别为0.46,-0.34和-0.29,IL-6与转铁蛋白浓度相关不明显。本文结果提示:CRP、C_3及白蛋白等含量的变化可作为反映MM病情的简易而敏感的指标。     

The modulation of excitatory synaptic transmission by adenosine in area CA1 of the rat hippocampus is temperature dependent

We tested the possibility that extracellular adenosine concentration varies with tissue temperature by measuring the tonic adenosinergic inhibition of excitatory synaptic transmission at different temperatures in the in vitro rat hippocampus. Application of the A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) enhanced population excitatory postsynaptic potentials (EPSPs) by antagonizing tonic adenosinergic inhibition; this effect was greatest at 25 degrees C, and was progressively reduced at 35 and 37.5 degrees C. These results demonstrate that tonic adenosinergic inhibition is inversely related to temperature. In a second experiment, an exogenous A1 agonist, N6-cyclohexyladenosine (CHA), was applied to slices to inhibit evoked EPSPs. CHA inhibition of EPSPs was greater at 35 than at 25 degrees C, demonstrating that the reduced adenosinergic inhibition at higher temperatures is not a result of reduced A1 receptor function.     

Mouse embryonic diastema region is an ideal site for the development of ectopically transplanted tooth germ.

The anterior eye chamber and the kidney capsule of the mouse have been traditionally used for long-term culture of tooth germ grafts. However, although these sites provide an excellent growth environment, they do not represent real in situ sites for the development of a grafted tooth germ. Here, we describe a protocol to transplant a tooth germ into the mandibular diastema region of mouse embryos using exo utero surgery. Our results demonstrate that the mouse embryonic diastema region represents a normal physiological environment for the development of transplanted tooth germs. Transplanted tooth germs developed synchronically with and became indistinguishable from the endogenous ones. These ectopic teeth were vascularized and surrounded with nerve fibers, and were able to erupt normally. Thus, the exo utero transplantation approach will provide a new avenue to study tooth development and regeneration.     

Activation of the parapyramidal region in the ventral medulla stimulates gastric acid secretion through vagal pathways in rats

Neurons synthesizing thyrotropin-releasing hormone, substance P and serotonin in the medullary caudal raphe nuclei project to the dorsal vagal complex and play a role in the central vagal regulation of gastric function. Neurons in the parapyramidal region in the ventral medulla share similar biochemical coding and projections as those in the caudal raphe nuclei. The role of the parapyramidal region in the autonomic regulation of gastric acid secretion was investigated in urethane-anesthetized rats. Unilateral microinjection of kainate into the parapyramidal region at 10, 15 and 20 ng induced a dose-related stimulation of gastric acid secretion (net increases: 22.2+/-11.2, 40.5+/-8.5 and 89.8+/-19.4 micromol/60 min, respectively), while injection of vehicle had no effect (net change: -0.1+/-1.4 micromol/60 min). Time-course studies showed a nine-fold peak increase over basal at 30 min after parapyramidal injection of kainate (20 ng) and acid secretion returned to basal level at 70 min. Microinjections of kainate (15-20 ng) outside the parapyramidal region or into the parapyramidal region in vagotomized rats had no effect. Exposure to cold (4 degrees C) for 2 h, which is known to induce vagally mediated gastric secretory and motor responses through medullary thyrotropin-releasing hormone pathways, increased the number of Fos-positive cells in the caudal, middle and rostral parts of the parapyramidal region to 4.3+/-0.4, 9.4+/-0.9 and 18.4+/-1.6/section, respectively, compared with 0.1+/-0. 1, 0.1+/-0.0 and 0.7+/-0.6/section, respectively, in rats maintained at room temperature. Most of the Fos-labeled cells co-expressed pro-thyrotropin-releasing hormone messenger RNA signal and/or were serotonin immunoreactive. These data show that chemical activation of neurons in the parapyramidal region results in a vagal-dependent stimulation of gastric acid secretion and that acute cold exposure activates parapyramidal neurons containing pro-thyrotropin-releasing hormone and/or serotonin, suggesting a potential role of the parapyramidal region, in addition to the caudal raphe nuclei, as medullary sites involved in the vagal regulation of gastric function.     

HIV－1Protease在大肠杆菌中的高表达

艾滋病的致病因子为人免疫缺陷病毒。该病毒的蛋白酶在病毒复制和成熟中具有决定性的意义。由于目前国内外尚未获得艾滋病病毒蛋白酶高效表达的重组子及简便的活性检测系统，限制了它的研究与应用。本文将用ＰＣＲ技术修饰的ＨＩＶＰｒ基因克隆入原核高效表达载体ｐＴＴＱ１８的ＥｃｏＲⅠ和ＨｉｎｄⅢ酶切位点之间，并用豆芽核酸酶将ＥｃｏＲⅠ的粘端削平，构建了读框正确的表达载体，ＩＰＴＧ诱导表明，该重组子在大肠杆菌中获得了高表达，激光扫描结果表明：重组的ＨＩＶＰｒ占细菌总蛋白８．９％以上。