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关键词： des-gamma-carboxy prothrombin   hepatocellular carcinoma   vitamin K   clathrin-mediated endocytosis   epithelial to fibroblastoid conversion  

摘要： Des-gamma-carboxy prothrombin (DCP) has been well established as a hepatocellular carcinoma (HCC) tumor marker. However, the precise mechanism by which HCC cells produce DCP remains unknown. Importantly, DCP is not specific for HCC. For example, vitamin K-deficiency or ingestion of a vitamin K antagonist (warfarin) also leads to DCP production. In addition, supplementary administration of vitamin K2 analogues to HCC patients has led to reduce serum DCP levels. From these observations, we hypothesize that DCP might be produced from HCC cells with functional impairment of vitamin K uptake. Because, as previously reported. the down-regulation of E-cadherin or high serum DCP in HCC patients is associated with a high risk of vascular invasion. intra-hepatic metastasis and tumor recurrence, we examined if HCC cells might produce DCP by epithelial to fibroblastoid conversion (EFC) in vitro. HepG2 cells were induced EFC by tumor promoter, 12-O-tetracanoylphorbol-13-acetate (TPA). DCP production was observed in HepG2 cells that had lost E-cadherin expression in a TPA-dose-dependent manner. The DCP production was inhibited by introducing additional vitamin K2 into the treated cells. In addition, LDL uptake as a surrogate of vitamin K uptake was significantly impaired in TPA-treated HepG2 cells. The cells with impairment of LDL uptake produced DCP. Fat soluble vitamins are taken up into cells through clathrin-mediated endocytosis, in which the dynamic polymerization of F-actin plays a crucial role. We found that HepG2 cells with F-actin rearrangement produced DCP. In addition, latrunculin A, an actin depolymerizer, induced naive HepG2 cells to produce DCP, confirming that impairment of F-actin polymerization is a key mechanism of DCP production. We showed ill vitro that cytoskeletal filament change by EFC is Crucial for DCP production in HepG2 cells.

关键词： MUC1   EGFR   Endocytosis   Clathrin   Dynamin   Rab5  

摘要： MUC1, a transmembrane glycoprotein, is abnormally over-expressed in most human adenocarcinomas. MUC1 association with cytoplasmic cell signal regulators and nuclear accumulation are important for its tumor related activities. Little is known about how MUC1 translocates from the cell membrane to the cytoplasm. In this study, live cell imaging was used to study MUC1 intracellular trafficking. The interaction between EGFR and MUC1 was mapped by FRET analysis and EGF stimulated MUC1 endocytosis was observed directly through live cell imaging. MUC1-CT endocytosis was clathrin and dynamin dependent. Rab5 over-expression resulted in decreased cell membrane localization of MUC1, with accumulation of MUC1 endocytic vesicles in the peri-nuclear region. Conversely, over-expression of a Rab5 dominant negative mutant (S34N) resulted in redistribution of MUC1 from the peri-nuclear region to the cytoplasm. Collectively, these results indicated that MUC1 intra-cellular trafficking occurs through a regulated process that was stimulated by direct EGFR and MUC1 interaction, mediated by clathrin coated pits that were dynamin dependent and regulated by Rab5. (C) 2008 Elsevier Inc. All rights reserved.

关键词： 自适应   脉冲耦合神经网络   学习准则   时间序列  

摘要： 尽管Johnson提出的PCNN模型具有强大的图像处理功能,以时间序列进行特征提取时具有旋转、尺度、平移、扭曲不变性,可实践中发现依然存在着不足,特别对图像亮度、对比度比较敏感。添加了误差反向传播(Error Back Propagation,EBP)学习准则的自适应脉冲耦合神经网络模型能自适应设定模型参数,是脉冲耦合神经网络模型研究的主要内容。特别地,应用这种自适应模型进行特征提取时,能弥补原来PCNN模型对亮度、对比度敏感的缺陷,而且具有一定的泛化能力,有效克服了亮度、对比度对图像识别精度的影响。

关键词： 脉冲耦合神经网络   动态行为   图像处理   神经元  

摘要： 为了进一步拓展脉冲耦合神经网络(Pulse coupled neural network,PCNN)在图像处理领域的应用深度,本文对改进型PCNN在图像处理中的动态行为结合网络参数进行了具体的理论分析和公式推导,明确了PCNN的动态行为特性受网络参数变化的影响,并给出了保证其所有神经元只点火一次的网络参数确定准则,最后将改进型PCNN应用于实际图像分割中.实验结果证明了其动态行为特性与参数确定准则之间关系的正确性和算法的有效性.

关键词： 噪声抑制   脉冲耦合神经网络   数学形态学   声纳图像  

摘要： 为解决声纳图像中存在的高斯与脉冲噪声的同时去除问题,在简化的脉冲耦合神经网络(Pulse Coupled Neural Network,PCNN)模型的基础上,提出了一种结合了数学形态学与中值滤波的噪声抑制算法。首先利用PCNN输出二值图像确定噪声在图像中的位置,用数学形态学方法保持目标的完整性,然后利用中值滤波方法去除图像的脉冲噪声并对PCNN逐次迭代的输出结果进行调整去除高斯噪声。实验结果证明,方法在保持图像边缘信息的前提下,与其他方法相比获得了更好的去噪效果。

关键词： 图像分割   脉冲耦合神经网络   点火图  

摘要： 提出了一种基于脉冲耦合神经网络的图像分割方法。在每次迭代时将脉冲耦合神经网络点火的神经元对应的像素作为目标,未点火的神经元对应的像素作为背景。实验结果表明该方法能在图像分割获得很好视觉效果的同时提高图像分割的速度。

关键词： 细胞神经网络(CNNs)   Lyapunov函数   系统稳定性   时滞   脉冲稳定性  

摘要： 脉冲对神经网络动态行为的影响是多方面的,它可能使不稳定系统稳定化,也可能使得稳定的网络产生震荡甚至出现混沌。讨论脉冲对时滞细胞神经网络指数稳定性的镇定影响。运用Lyapunov函数,建立确保脉冲系统的全局指数稳定的充分条件。发现即使初始系统(不带脉冲)发散,脉冲系统仍能因为有适当的脉冲而保持全局指数稳定。数值例子说明了理论分析的正确性。

关键词： Hopfield神经网络   脉冲   全局指数稳定性   变时滞  

摘要： 研究了一类新的具有脉冲的时滞Hopfield神经网络系统模型,引入了新的脉冲条件,在不假设激励函数的可微性、单调性的条件下,得到了系统平衡点的存在性、唯一性及全局指数稳定性的充分条件和指数收敛速率,且所得结果改进了一些已知文献的结论.

关键词： PCNN   蓝藻   水华   分析  

摘要： 蓝藻的大面积爆发会对生态产生灾难性的影响。针对蓝藻爆发区域水面颜色的不同,本文采用脉冲耦合神经网络(PCNN)对获取的蓝藻水域图像进行分析,从而获知蓝藻的爆发程度。采用PCNN网络对蓝藻水域图像建立模型。实验证明,这种方法能够对蓝藻爆发程度进行准确的分析从而为蓝藻的治理提供理论上的指导。

关键词： 细胞神经网络   脉冲   全局指数稳定性   时滞  

摘要： 讨论了一类具有时滞的脉冲细胞神经网络的全局指数稳定性。利用Lyapunov函数和不等式技巧得到了该系统全局指数稳定的一个充分条件,同时给出示例说明结果的有效性。