The tyrosine-based YXXØ targeting motif of murine leukemia virus envelope glycoprotein affects pathogenesis

Retroviruses, such as human and simian immunodeficiency viruses (HIV and SIV), and murine leukemia viruses (MuLV), harbor a tyrosine-based motif in the intracytoplasmic domain of their envelope glycoprotein. This motif can act as an endocytosis signal or as a targeting signal, restricting viral budding at specific cell surface membrane domains. In the present study, proviral DNA of the ecotropic Cas-Br-E strain of MuLV was modified by substitution or deletion of the critical tyrosine residue. Mutant viruses lost basolateral targeting in polarized MDCK epithelial cells while expression level of the glycoprotein at the cell surface was not affected. This suggests that the tyrosine-based motif in MuLV does not act as an endocytosis signal. Only a small delay in the appearance of disease was observed in inoculated mice. In contrast, a striking change in the pathology was observed with enlarged thymus and lymph nodes in animals inoculated with mutant viruses.     

Polarized ion transport during migration of transformed Madin-Darby canine kidney cells

Epithelial cells lose their usual polarization during carcinogenesis. Although most malignant tumours are of epithelial origin little is known about ion channels in carcinoma cells. Previously, we observed that migration of transformed Madin-Darby canine kidney (MDCK-F) cells depended on oscillating K⁺ channel activity. In the present study we examined whether periodic K⁺ channel activity may cause changes of cell volume, and whether K⁺ channel activity is distributed in a uniform way in MDCK-F cells. After determining the average volume of MDCK-F cells (2013±270 m³; n=8) by means of atomic force microscopy we deduced volume changes by calculating the K⁺ efflux during bursts of K⁺ channel activity. Therefore, we measured the membrane conductance of MDCK-F cells which periodically rose by 22.3±2.5 nS from a resting level of 6.5±1.4 nS (n=12), and we measured the membrane potential which hyperpolarized in parallel from –35.4±1.2 mV to –71.6±1.8 mV (n=11). The distribution of K⁺ channel activity was assessed by locally superfusing the front or rear end of migrating MDCK-F cells with the K⁺ channel blocker charybdotoxin (CTX). Only exposure of the rear end to CTX inhibited migration providing evidence for horizontal polarization of K⁺ channel activity in transformed MDCK-F cells. This is in contrast to the vertical polarization in parent MDCK cells. We propose that the asymmetrical distribution of K⁺ channel activity is a prerequisite for migration of MDCK-F cells.     

血脂与体外血栓形成的关系

应用国产ＤＪＨ－Ｉ型调速单型血栓形成仪，对４７４名４５岁以上成人体外血栓形成进行了检测，同时检查血脂水平。另外对部分隐性体外血栓阳性者及正常人的红细胞膜荧光偏振度（Ｐ）和微粘度（η）进行比较。结果表明：隐性体外血栓阳性者中血脂增高者为５７／１０９（５４．１２％），其中一级血栓３２／７５（４２．６％），二级血栓１１／１６（６８．７％），三级血栓１４／１８（７７．７％）。红细胞膜Ｐ和η在隐性体外血栓阳性者与正常人之间有显著差异（Ｐ＜０．０５）。提示：隐性体外血栓检测对临床心脑血管的血栓性疾病的早期预防、治疗有较大的参考价值     

HPLC法和FPIA法检测卡马西平血药体积百分比的比较研究

目的高效液相色谱法(HPLC)和荧光偏振免疫法(FPIA)测定血清中卡马西平体积百分比的比较研究。方法收集广州市精神病医院服用CBZ的21例癫痫患者血样。用本实验室已经建立的HPLC法和FPIA法分别检测卡马西平对照品的甲醇溶液、卡马西平对照品标准血清、患者血清中卡马西平体积百分比,采用配对t检验考察两种方法分别测定卡马西平对照品的甲醇溶液、卡马西平对照品标准血清、患者血清中卡马西平体积百分比有无显著性差异。结果HPLC法与FPIA法检测卡马西平对照品甲醇溶液、卡马西平对照品标准血清中卡马西平体积百分比无显著性差异(t值分别为-1.009、0.767,P值分别为0.325、0.452);检测患者血清中卡马西平血药体积百分比有显著性差异(t=4.919,P<0.05),FPIA法检测患者血清中卡马西平血药体积百分比较HPLC法偏高。结论FPIA法检测患者血清中卡马西平血药体积百分比过程中,CBZ的活性代谢产物环氧化卡马西平(carbamazepine-10,11-epoxide,CBZ-E)可能对FPIA法测定CBZ有干扰,导致结果偏高。     

Electrochemistry of calcium precipitating bacteria in orthodontic wire

BackgroundCalculus composed of inorganic and organic components with bacteria formed on teeth gets deposited on orthodontic wires. The reason for calculus formation and impact of calcium precipitating bacteria (CPB) on orthodontic wire were studied. A pilot study on electrochemical characterization of CPB on orthodontic wires was done.MethodsCPB were isolated from orthodontic patients and identified by molecular techniques. The electrochemical behavior of two isolates (CPB-1 and CPB-3) on orthodontic wires was studied by employing polarization and impedance techniques. The CPB morphology by scanning electron microscopy and chemical characterization of CPB and tooth pulp stone were studied by Fourier transform infrared (FTIR) and X-ray diffraction (XRD).ResultsThe two isolates Bacillus megaterium (CPB-1) and Paenibacillus sp. (CPB-3) identified with 16S rRNA sequencing method increased pH of B4 medium from 5.32 to 8.3. The carboxylic acid and phosphate groups identified in FTIR analysis acted as nucleation sites for calcium deposition. The biogenic crystal phases identified in teeth pulp stone by XRD were similar to bacterial isolates cultured in the laboratory. The electrochemical studies with two CPB species revealed that biogenic calcium phosphate species act as cathodic inhibitors on orthodontic wire.ConclusionThe present study concluded that teeth pulp stone formation is due to CPB and high pH determines the mineralization process. Diffusion process and dispersive capacitive behavior indicate that the chloride ions may penetrate through calcium deposits and initiate pitting corrosion on orthodontic wire which may enhance the leaching of toxic elements in saliva.     

Polarization second harmonic generation by image correlation spectroscopy on collagen type I hydrogels

Successful engineering of biomimetic tissue relies on an accurate quantification of the mechanical properties of the selected scaffold. To improve this quantification, typical bulk rheological measurements are often complemented with microscopic techniques, including label-free second harmonic generation (SHG) imaging. Image correlation spectroscopy (ICS) has been applied to obtain quantitative information from SHG images of fibrous scaffolds. However, the typical polarization SHG (P-SHG) effect, which partly defines the shape of the autocorrelation function (ACF), has never been taken into account. Here we propose a new and flexible model to reliably apply ICS to P-SHG images of fibrous structures. By starting from a limited number of straightforward assumptions and by taking into account the P-SHG effect, we were able to cope with the typically observed ACF particularities. Using simulated datasets, the resulting model was thoroughly evaluated and compared with models previously described in the literature. We showed that our new model has no restrictions concerning the fibre length for the density retrieval. For certain length ranges, the model can additionally be used to obtain the average fibre length and the P-SHG related non-zero susceptibility tensor element ratios. From experimental data on collagen type I hydrogels, values of SHG tensor element ratios and fibre thickness were determined which match values reported in the literature, thereby underpinning the validity and applicability of our new model.     

Measurement Of Angiotensinogen In Human Serum By Fluorescence Polarization Immunoassay

Fluorescence polarization immunoassay (F.P.I.A.) has rarely been used to measure components of the renin system. Using an Abbott TDX polarimeter and fluorescein - labelled angiotensin I as a tracer we measured angiotensin I by F.P.I.A. Combining this procedure with a renin incubation step enabled measurement of angiotensinogen in human serum. Using sera from male patients and from pregnant females, a good correlation between radioimmunoassay (R.I.A.). and F.P.I.A. was found. Two procedures were developed; one involving taking samples from the renin incubation mixture, the other involving measurement of generated angiotensin I at intervals without interrupting the renin incubation procedure. F.P.I.A. is less expensive and somewhat simpler than R.I.A. but, with the instrument used, it     

具有自动夺获功能起搏器刺激除极波振幅的影响因素及远期随访

观察刺激除极波 (evokeresponse,ER)振幅及极化电位在远期随访中的稳定性及不同体位对其的影响 ,分析ER振幅与起搏器一般工作参数的关系。对 1996年 12月～ 1998年 12月之间收治的 2 4例埋置了RegencySC +2 40 2L永久起搏器的患者进行 2 .43± 0 .6 2 (2～ 3.5 )年的随访观察。结果 :ER振幅及极化电位在随访期间是稳定的 ,平卧位时ER振幅最低为 8.5 0± 3.0 2mV ,立位时最高达 9.32± 2 .95mV ,两者有统计学差异 ,P <0 .0 5。其他体位之间无差异。极化电位与体位变化无关。 2 / 2 4例分别因极化电位升高、ER振幅降低同时伴极化电位升高 ,而至自动夺获功能不能工作。ER振幅与起搏器一般工作参数无相关性。结论 :ER及极化电位在随访期间是稳定的 ,体位对ER振幅有一定影响 ,个别病例出现ER及 /或极化电位的变化 ,随访时应注意检测     

Role of gingival mesenchymal stem cell exosomes in macrophage polarization under inflammatory conditions

ObjectiveExosomes have been shown to play a strong role in intercellular communication. While GMSCs have been extensively studied, less research exists on exosomes derived from GMSCs, especially on how exosomes affect macrophages. This study aimed to investigate the impact of GMSC-derived exosomes on macrophage polarization and phenotype under inflammatory conditions.MethodsExosomes were isolated from GMSCs-conditioned media by ultracentrifugation (UC) and characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blot (WB). In vitro, GMSC-derived exosomes were co-incubated with macrophages for 24 h in the absence or presence of M1 polarizing conditions in the six-well plate. The protein and mRNA expression levels of M1 and M2 macrophage markers were detected and the supernatants were collected for an enzyme-linked immunosorbent assay (ELISA).ResultsExosomes were successfully isolated from GMSCs. Macrophages co-cultured with exosomes showed significantly decreased levels of the M1 markers Tumor Necrosis Factor-α (TNF-α), Interleukin-12 (IL-12), CD86 and Interleukin-1β (IL-1β). By contrast, M2 marker Interleukin-10 (IL-10) levels moderately increased. Meanwhile, similar results were acquired in the cell culture supernatants.ConclusionGMSC-derived exosomes may promote M1 macrophage transformation into M2 macrophages, reducing the pro-inflammatory factors produced by M1 macrophages.