Attempt to induce, in the rat, a hepatitis of cirrhotic origin, using amino steroids: holaphyllaminol or amino 3-beta hydroxy-20-beta pregnene-5]

Holaphyllaminol, or Amino-3 beta-Hydroxy-20-beta Pregnene-5, was administered by gastric tube to male Wistar rats at dose of 50, 100 and 200 mg/kg/24 hr respectively, during 10, 20, 40 and 80 days. This substance provokes hepatic lesions beginning at the periportal region, the characteristics of which are a cholestasis, a canalar proliferation and a fibrosis. The interest of these alterations lies in the fact that they present the same features as certain human chronic hepatitis; their progression, a function of the dose of the toxin and the duration of treatment, may make possible to realisation of a model of experimental chronic hepatitis.     

A relevant in vitro rat model for the evaluation of blood-brain barrier translocation of nanoparticles

Poly(MePEG₂₀₀₀cyanoacrylate-co-hexadecylcyanoacrylate) (PEG-PHDCA) nanoparticles have demonstrated their capacity to reach the rat central nervous system after intravenous injection. For insight into the transport of colloidal systems across the blood-brain barrier (BBB), we developed a relevant in vitro rat BBB model consisting of a coculture of rat brain endothelial cells (RBECs) and rat astrocytes. The RBECs used in our model displayed and retained structural characteristics of brain endothelial cells, such as expression of P-glycoprotein, occludin and ZO-1, and immunofluorescence studies showed the specific localization of occludin and ZO1. The high values of transendothelial electrical resistance and low permeability coefficients of marker molecules demonstrated the functionality of this model. The comparative passage of polyhexadecylcyanoacrylate and PEG-PHDCA nanoparticles through this model was investigated, showing a higher passage of PEGylated nanoparticles, presumably by endocytosis. This result was confirmed by confocal microscopy. Thanks to a good in vitro/in vivo correlation, this rat BBB model will help in understanding the mechanisms of nanoparticle translocation and in designing new types of colloidal carriers as brain delivery systems.Received 4 March 2005; accepted 14 April 2005     

近断层长周期地震动前向性效应对峰值影响研究

筛选了断层距不大于15km的具有前向性效应的长周期近断层地震记录,分类汇总建立了统计分析数据样本库,对长周期地震动的竖向分量和水平向分量峰值比进行了分析,研究了震级、脉冲周期、不同分量对峰值加速度比的影响。在此基础上,采用前期建立的回归分析模型,对长周期地震动竖向分量和水平向两分量的峰值加速度进行了回归分析,拟合给出了峰值参数与震级和断层距的衰减关系式,通过拟合曲线与数据样本的峰值实测值对比,说明拟合关系式在一定的范围内可以用于近断层长周期地震峰值的预测。     

GTP-dependent twisting of dynamin implicates constriction and tension in membrane fission

Dynamin, a crucial factor in endocytosis, is a member of a family of GTPases that participates in membrane fission. It was initially proposed to act as a machine that constricts and cuts the neck of nascent vesicles in a GTP-hydrolysis-dependent reaction, but subsequent studies suggested alternative models. Here we monitored the effect of nucleotides on dynamin-coated lipid tubules in real time. Addition of GTP, but not of GDP or GTP-gammaS, resulted in twisting of the tubules and supercoiling, suggesting a rotatory movement of the helix turns relative to each other during GTP hydrolysis. Rotation was confirmed by the movement of beads attached to the tubules. Twisting activity produced a longitudinal tension that was released by tubule breakage when both ends of the tubule were anchored. Fission also occurred when dynamin and GTP were added to lipid tubules that had been generated from liposomes by the motor activity of kinesin on microtubules. No fission events were observed in the absence of longitudinal tension. These findings demonstrate a mechanoenzyme activity of dynamin in endocytosis, but also imply that constriction is not sufficient for fission. At the short necks of endocytic vesicles, other factors leading to tension may cooperate with the constricting activity of dynamin to induce fission.     

用超临界CO_2浓缩α生育酚的试验研究

对利用超临界ＣＯ２ 从豆油脱臭馏出物中萃取、浓缩生育酚的工业化生产的可行性进行了试验研究,提出了初步的工艺框架,研究了压力、ＣＯ２ 流量及温度场分布对精馏柱萃取效果的影响－ 研究结果表明,为了保证α生育酚的浓缩效果,适宜的萃取压力为１３－５ ＭＰａ 、ＣＯ２流量为３ ～５ Ｌ／ｍｉｎ ,精馏柱温度分布为６０／５０／４０／３５ ℃（ 顶／ 上中／ 下中／ 底）－ 文中对试验提出了进一步完善的措施     

振动评价标准的变化及数字式振级计

通过对比ＩＳＯ 振动评价标准新旧版本的变化,介绍了适应新标准的一种数字式振级计的设计－ 它采用虚拟仪器的方案、高速串行通讯和Ｗｉｎｄｏｗｓ ９Ｘ 下的多线程设计－ 试验结果表明仪器可满足新标准的要求－ 还对振动响应的数据处理作了讨论－     

改进声矢量阵相干信号源方位估计算法

为提高声矢量阵相干信号方位估计能力,针对二维紧凑结构的声矢量均匀线阵情况,给出一种改进算法。该算法首先利用解析振速与声压信息,重构接收数据,求出协方差矩阵,并提取信号子空间第一列的3个分矢量进行孔径扩展。然后,利用类单块拍条件下的矩阵重构得到3个新矩阵并合并。最后,套用奇异值分解的多重信号分类算法得到目标波达方位估计。分析表明,所提算法利用数据的组织形式使信号矩阵对角化,最终恢复了矩阵的秩,而且具有一定的孔径扩展能力。同时,所提算法矢量阵阵列流形所具备的方向因子可以在模糊角度处形成抑制,保留了矢量阵的单边指向性。仿真结果证明,此算法无论在角度估计精度还是分辨率方面都要优于矢量阵空间平滑与矢量平滑算法。