人纤溶酶原Kringle 1 结构域在大肠杆菌中的克隆、表达和纯化

Ｐｌａｓｍｉｎ(ｏｇｅｎ)ｗａｓｋｎｏｗｎｆｏｒｉｔｓｆｉｂｒｉｎｏｌｙｔｉｃａｃｔｉｖｉｔｙａｓｗｅｌｌａｓｉｔｓω ａｍｉｎｏｃａｒｂｏｘｙｌｉｃａｃｉｄ ｂｉｎｄｉｎｇａｂｉｌｉｔｙ.Ｏｎｅｈｉｇｈａｎｄ 4ｌｏｗ ａｆｆｉｎｉｔｙｂｉｎｄｉｎｇｓｉｔｅｓｗｅｒｅｄｅｔｅｃｔｅｄｉｎｐｌａｓｍｉｎｏｇｅｎｈｅａｖｙｃｈａｉｎ .Ｃｏｎｃｕｒ ｒｅｎｔｌｙ 5ｈｉｇｈｌｙｈｏｍｏｌｏｇｏｕｓｔｒｉｐｌｅｌｏｏｐｓｔｒｕｃｔｕｒｅｓｎａｍｅｄａｓｋｒｉｎｇｌｅｄｏｍａｉｎｓｗｅｒｅｆｏｕｎｄｆｏｒｍｉｎｇ…     

Nonlinear dynamics of controlled mechanical systems

Unavoidable time delays in the feedback path of a controlled mechanical system may render the sys- tem unstable, and block the development and the application of dynamic control. This paper summarizes the recent work of the authors on the dynamics of controlled mechanical system with time delays. It starts with the dimensional reduction of delayed nonlinear systems composed of stiff and soft substructures and then presents the experimental modeling of lin¬ear and nonlinear mechanical systems with the time delays in state feedback taken into account. In the frame of linear controlled systems, this paper outlines the analysis of delay-independent stability and stability switches with the increase of time delay, the stability analysis in the case of short time delay, and the robust stability analysis of the system pos¬sessing uncertain parameters. Afterwards, the paper briefly discusses the primary resonance and subharmonic resonance, as well as the corresponding stability analysis, of a kind of harmonically forced Duffing oscillators with time delay, and the stabilization of periodic motion of nonlinear delayed systems. Finally, the applications of the stability analysis ap¬proaches to structure controls and active chassis of ground vehicles are outlined.     

MDR1, cholesterol certification and cell growth: a comparative study in normal and multidrug-resistant KB cell lines

The product of the MDR1 gene (P-gp) has been implicated in the transport of cholesterol from plasma membrane to endoplasmic reticulum for esterification. In previous studies on leukemia cell lines, we suggested that cholesterol esterification may regulate the rate of cell growth and that the MDR1 gene might be involved in this process by modulating intracellular cholesterol esters levels. To further investigate this matter, the rate of cell growth, cholesterol metabolism, expression of the MDR1 gene, and P-gp activity were compared in KB cell lines displaying differences in expression and function of P-gp (drug-sensitive phenotype versus MDR phenotype). The rate of cell growth correlated with cholesterol esterification in all KB cell lines, whereas the over-expression of MDR1 observed in the MDR cell lines was not always associated with an increased capacity of cells to esterify cholesterol. Two known inhibitors of P-gp activity, progesterone and verapamil, strongly inhibited both cholesterol esterification and cell proliferation in all KB cell lines, but they affected intracellular accumulation of labeled vinblastine only in MDR cell lines. These results further support a role for cholesterol esters in the regulation of cell growth and suggest that the P-gp expressed in MDR KB cells is not involved in the general process leading to cholesterol esterification. Received 14 February 2000; received after revision 10 April 2000; accepted 8 May 2000     

Construction of High Level Expression Cell Lines of Erythropoietin *

Ｅｒｙｔｈｒｏｐｏｉｅｔｉｎ（ＥＰＯ）ｉｓｏｎｅｏｆｔｈｅｍｏｓｔｉｍｐｏｒｔａｎｔｒｅｇｕｌａｔｏｒｙｆａｃｔｏｒｓｄｕｒｉｎｇｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｍａｍｍａｌｉａｎｅｒｙｔｈｒｏｃｙｔｅ,ａｃｔｉｎｇｍａｉｎｌｙｏｎｔｈｅｅｒｙｔｈｒ...     

Endothelial Cell Culture on Different Phospholipid Surfaces *

ＩｎｔｒｏｄｕｃｔｉｏｎＢｉｏｍａｔｅｒｉａｌｓａｒｅａｌｗａｙｓｕｓｅｄｉｎａｎｅｎｖｉｒｏｎｍｅｎｔａｄｊａｃｅｎｔｔｏｌｉｖｉｎｇｔｉｓｓｕｅｓａｎｄｂｌｏｏｄ．Ｃｅｌｕｌａｒｉｎｔｅｒａｃｔｉｏｎｓｗｉｔｈｉｍｐｌａｎｔｓａｒｅｏｆｐｒｉｍａ...     

非线性MDDEs系统的隐式Euler法的稳定性

给出了一类非线性多滞量时滞微分方程系统的理论解为稳定的一个充分条件,特别指出隐式Ｅｕｌｅｒ法求解该类问题时是数值稳定的。     

灵芝抗纤毛虫细胞衰老机理的初探

本文检测了用灵芝处理棘尾虫和草履虫衰老细胞后的效果,发现灵芝的制剂和浸液可衰老棘尾虫在核ＤＮＡ含量消减速度减慢核仁膨胀程度降低;还发现灵芝浸液能增强衰老棘尾虫和草履虫消除自由基的能力。     

Dexamethasone enhances CTLA-4 expression during T cell activation

T cell activation is enhanced by the costimulatory interaction of B7 on antigen-presenting cells and CD28 on T cells, resulting in long-term T cell proliferation, differentiation and production of large amounts of cytokines, such as interleukin (IL)-2. CTLA-4 is a co-stimulation receptor that shares 31% homology with CD28 and binds B7 family members with higher affinity. CTLA-4 is transiently expressed intracellularly and on the cell surface following activation of T cells. We have studied the kinetics of CTLA-4 expression and the effects of dexamethasone on CTLA-4 expression during T cell activation in cultures of mouse spleen cells stimulated by a mixture of immobilized anti-CD3 and anti-CD28 monoclonal antibodies (anti-CD3/CD28 mAb) or concanavalin A (ConA). CTLA-4 expression peaked on day 2 and returned to background levels after 7 days. Dexamethasone was found to potentiate CTLA-4 expression in a dose-dependent manner with an EC₅₀ effective concentration 50%) of about 10⁻⁸ M. In contrast, other immunosuppressive agents, such as rapamycin or cyclosporin A had no or an inhibitory effect on CTLA-4 expression, respectively. Dexamethasone also stimulated CD28 expression, but inhibited IL-2R expression during anti-CD3/CD28 mAb-induced mouse splenic T cell activation. Western blot analyses of lysates of activated mouse T cells showed that dexamethasone increased CTLA-4 protein levels twofold during anti-CD3/CD28 mAb-induced activation. Dexamethasone also enhanced CTLA-4 messenger RNA twofold as quantified by ribonuclease protection assay. The effects of dexamethasone on CTLA-4 expression were glucocorticoid-specific and completely inhibited by the glucocorticoid receptor antagonist mifepristone (RU486), indicating that the effect of dexamethasone on CTLA-4 expression is mediated through the glucocorticoid receptor. In conclusion, the immunosuppressive agent dexamethasone actually stimulates CTLA-4 expression, which is involved in downregulation of T cell activation. Received 19 May 1999; received after revision 13 July 1999; accepted 13 July 1999     

The involvement of the renin-angiotensin system in the regulation of cell proliferation in the rat endometrium

Oestrogens are known to enhance angiotensin biosynthesis by increasing the elaboration of its precursor, angiotensinogen. On the other hand, we found that inhibition of angiotensin-converting enzyme (ACE) suppressed the proliferative response of the rat anterior pituitary gland to oestrogens. To answer the question whether the angiotensin system is involved in the control of the cell proliferation of the uterine epithelium, the effects of an ACE inhibitor, enalapril maleate, and of angiotensins II and IV, alone or together with losartan, an antagonist of angiotensin receptor type 1 (AT1), on endometrial epithelial cell proliferation have been studied. The experiments were performed on ovariectomized female Wistar rats. In the first experiment the animals were injected with a single dose of oestradiol benzoate or received an injection of solvent only. Half of the oestrogen-treated rats were injected additionally with enalapril maleate (EN, twice daily). The incorporation of bromodeoxyuridine (BrDU) into endometrial cell nuclei was used as an index of cell proliferation. It was found that oestradiol alone dramatically increased the BrDU labelling index (LI) of endometrial cell nuclei, and this effect was partially blocked by the simultaneous treatment with EN. In the second experiment, the animals were injected intraperitoneally with angiotensin II (AII), angiotensin IV (AIV) or saline, alone or together with losartan. It was found that AIV induced an increase in the LI in uterine epithelium, and this effect was not blocked by the simultaneous treatment with losartan. The increase in LI in uterine epithelium was also observed in the rats treated with AII and with losartan. These findings suggest an involvement of angiotensin IV in the control of uterine epithelium cell proliferation. Received 12 October 1998; received after revision 6 January 1999; accepted 2 February 1999