细胞外基质受体α-Dystroglycan影响胸腺细胞分化发育的可能机制

目的研究细胞外基质受体alpha-Dystroglycan(α-DG)对胸腺细胞分化的影响及机制。方法摘取15日胚龄鼠胸腺小叶进行体外器官培养。将α-DG抗体、对照抗体或培养液滴加在胸腺小叶上。FACS(Fluorescence-activated cell sorting)分析胸腺细胞表面分子CD4、CD8、CD95和CD69等的表达。结果α-DG中和抗体能明显抑制胸腺细胞分化，显示胸腺双阴性细胞比例从对照组的26．5％增高到实验组的71．6％，双阳性细胞和CD8单阳性细胞比例则显著下降，分别从39．8％和20．7％下降到7．5％和6．8％，CD4单阳性细胞比例则无明显变化；同时胸腺细胞数目明显减少；CD95、CD69的表达水平随α-DG中和抗体的持续存在呈现显著升高。结论α-DG通过参与胸腺细胞的活化和凋亡活动影响胸腺细胞的发育。     

Preparation of poly(amide-imide)s by means of triphenyl phosphite, 1. Aliphatic-aromatic poly(amide-imide)s based on trimellitimide

Aliphatic-aromatic poly(amide-imide)s with high molecular weight (η_inh up to 2,91 dl/g in DMAc/5% LiCl) were synthesized by direct polycondensation reaction of imide-containing dicarboxylic acids and aromatic diamines using triphenyl phosphite in N-methyl-2-pyrrolidone (NMP)/pyridine solution in the presence of metal salts. The factors affecting the reaction of N-(trimellitoyl)glycine and 4,4′-oxydianiline were investigated. The molecular weight of the polymer varied with the amount of metal salts, showing a maximum at a concentration of about 1 wt.-% CaCl₂ or about 2 wt.-% LiCl in the reaction mixture. A monomer concentration of about 0,2 mol/l gave the most favorable result. Among the solvents tested, NMP was most effective. Similarly, polycondensations of several combinations of three imide-diacids with various aromatic diamines were carried out. Solubility, thermal properties, and tensile properties of the polymers are discussed.     

Preparation of graded porous titanium coatings on titanium implant materials by plasma spraying

Graded porous titanium coatings have been deposited on titanium substrates for dental implants by plasma spraying in an argon atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), surface roughness measurement, and tensile strength tests were performed on graded porous coatings. The results showed that Ti(3)O(5) was formed in the outermost surface of the porous coatings due to oxidation. The graded porous coatings consisted of three layers. The outer layer was full of macropores with a surface roughness of approximately 100 microm. The diameter of many macropores reached and even surpassed 150 microm, which could be beneficial for tissue to grow into the coating. The middle layer consisted of a mixture of micropores and macropores. The inner layer was a very dense and tight interface layer that included mechanical, physical, and metallurgical bonding. In tensile strength tests, testing bars peeled off the coatings, because the adhesive agent fractured, but the coatings remained intact.     

Characterization of acrylic bone cement using dynamic mechanical analysis

Dynamic mechanical analysis (DMA) was used to characterize the properties of acrylic bone cement with the addition of tricalcium phosphate (TCP), hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA). The glass transition temperature of acrylic bone cement is >100 degrees C; the cement has a flat modulus response near human body temperature. The height of the damping peak decreases and becomes broader with increasing TCP content. Thus, TCP is incompatibile with acrylic bone cement. When the frequency is changed from high to low, the damping peak shifts to low temperature. The shift in damping peak with frequency indicates that this relaxation is time-dependent. When acrylic bone cement contains TCP with HEMA and EGDMA, the incompatibility between acrylic bone cement and TCP can be ameliorated.     

Windows环境下步进电机匀加速的实现与计算机程序设计

本文主要介绍了奔腾计算机和步进电机的接口电路,提出了步进电机匀加速的控制算法,探讨了在 Windows 环境下以 Visual C++实现步进电机匀加速的实现途径和多任务环境下匀加速程序的设计方法。     

The effect of transcranial magnetic stimulation on the latencies of vertical saccades

In this study, we investigated the effect of transcranial magnetic stimulation (TMS) over the right posterior parietal cortex (PPC) on the latency of two different types of visually-guided vertical saccades: reflexive saccades triggered by the sudden onset of a target, and saccades towards target locations known in advance. For this reason, we used two oculomotor tasks: a gap and a delay task, respectively. Nine normal subjects performed vertical saccades at ±7.5 and ±15°. TMS was applied at 80 and 100 ms after target onset in the gap task, and after fixation offset in the delay task. Without TMS, we confirmed a latency asymmetry in the gap task favouring upward saccades at the lower eccentricity (7.5°), and a latency symmetry in the delay task. TMS increased the latencies of all saccades in the delay task, when delivered at 100 ms. This effect was mostly pronounced for downward saccades at 7.5°. As a result, saccade latencies showed an asymmetry in this condition, similar to the one observed in the gap task without TMS. The gap task with TMS resulted in a variable latency distribution and no significant overall effect on saccade latency. Our results indicate that the right PPC is involved in the initiation of vertical saccades in the delay task, and that this involvement appears to be enhanced for downward saccades. A conclusion for the involvement of this area in the gap task could not be drawn from this study.     

The dysregulated glomerular cell growth in Denys–Drash syndrome

While diffuse mesangial sclerosis is traditionally described as being the glomerulopathy of Denys–Drash syndrome (DDS), the podocyte proliferative lesions may be overlooked in these DDS cases. In the present study, an evolving process is extrapolated from a selected case of DDS that demonstrated glomerulopathy with conspicuous podocyte proliferation. The observation that podocytes express proliferation markers (Ki67, proliferating-cell nuclear antigen and topoisomerase II) in non-proliferative, mature-looking glomeruli suggests an initial pathogenic act to activate or to keep podocytes from quiescence. The subsequent proliferation of podocytes is in keeping with downregulation of WT1 and cyclin kinase inhibitors of p16 and p21. The emergence of cytokeratin-positive cells in glomeruli that show typical mesangial sclerosis implies elimination of podocytes and replacement with tubular and/or parietal epithelial cells. The final scene of evolving glomerulopathy displays apoptosis and expression of Fas-L and Bax in sclerotic mesangial lesions, which eventually end up with global sclerosis. This novel concept of DDS glomerulopathy implies complex molecular mechanisms involved in glomerular injury.     

BK polyomavirus interstitial nephritis in a renal allograft recipient

Human polyomavirus (PV) interstitial nephritis has recently been recognized as a cause of severe renal allograft dysfunction. It occurs in immunosuppressed patients after reactivation of the latent virus PV type BK (BK virus) in the renal epithelium. BK disease is defined as a morphologically manifest renal infection with cytopathic signs accompanied by varying degrees of interstitial inflammatory cell infiltrates and functional impairment. It is also identified by the presence of cells containing viral inclusion bodies (decoy cells) in the urine. The authors report a case of BK PV interstitial nephritis in a 36-year-old renal allograft recipient. Under light microscopy the chief diagnostic indicator was detection of intranuclear viral inclusions, which were found exclusively in tubular epithelial cells. Cells with viral changes were often enlarged with nuclear atypia and chromatin basophilia. Widespread interstitial plasma cell infiltrates associated with tubulitis were present. Intranuclear paracrystalline arrays of virus particles 35-38 nm in diameter were present as characteristic ultrastructural indicators. Urine samples revealed decoy cells with ground-glass-type intranuclear inclusions positive for BK virus by electron microcopy.     

Protection of hepatocytes from apoptosis by a novel substance from actinomycetes culture medium

A novel substance, #675, found from an Streptomyces sp. SM675 culture medium, dose-dependently stimulates the proliferation of human functional liver cell 4 (FLC4). When FLC4 cells were incubated under conditions without fetal bovine serum (FBS), typical features of apoptotic cell death such as shrinkage and nuclear condensation appeared; high molecular weight (HMW) DNA fragments were found; and caspase-3 and poly (ADP-ribose) polymerase (PARP) proteins were cleaved. When FLC4 cells were incubated with #675 and without FBS, the cells grew healthy, no HMW DNA fragments were found, and caspase-3 and PARP cleavage weakened, suggesting that #675 protects FLC4 cells from apoptosis induced by FBS-deprivation. The quantitative reverse-transcribed polymerase chain reaction did not show differences in PARP or Bcl-2 mRNA expression in FLC4 cells incubated with or without #675, indicating other genes may be involved in this anti-apoptosis effect. These results show that #675 enhances FLC4 proliferation via an apoptosis-inhibition pathway, implying potential pharmacological and clinical applications.