血人参石油醚部位化学成分研究

为深入探究血人参中的活性物质成分，该文采用硅胶柱色谱、Sephadex LH-20柱色谱、半制备高效液相色谱以及重结晶等方法对血人参石油醚部位进行了系统分离纯化，并利用现代波谱技术对分离得到的单体化合物进行结构鉴定。结果表明：从血人参石油醚部位共分离得到22个单体化合物，分别鉴定为β-谷甾酮(1)、豆甾烷3,6-二酮(2)、6β-羟基-豆甾-4-烯-3-酮(3)、(22E)-5α,8α-epidioxyergosta-6, 22-dien-3β-ol(4)、美迪紫檀素(5)、sativan(6)、2′,4′-二羟基查尔酮(7)、6,7-dimethoxy-4-hydroxy-1-naphthoic acid(8)、对羟基苯甲酸乙酯(9)、2,4-二羟基苯甲酸乙酯(10)、(9E,11E)-13-oxo-9,11-ocatadecadienoic acid(11)、(9E,11E)-13-oxo-9,11-octadecadienoic acid methyl ester(12)、9-oxo-10E,12E-octadecadienoic acid methyl ester(13)、9-...     

Jumping Transmission of Action Potential between Separately Placed Internodal Cells of Chora corallina

We report here a new type of cell-to-cell communication. Wenoticed that a characean cell can transmit its action potentialsto one or more cells which lie parallel to it separately inartificial pond water without any special connection betweenthe cells. Two experimental facts proved this transmission notchemical but electrical. No transmission was observed firstwhen an Ag-AgCl wire was placed between two cells, and secondwhen the whole length of the first cell was stimulated so thatnon-propagated action potential was induced. The results showthat the traveling electrical field strength might be the fundamentalfactor in the jumping transmission. (Received November 10, 1989; Accepted December 22, 1989)     

Some dicopper complexes of benzimidazole-containing ligands.

Dicopper complexes of the following benzimidazole-containing ligands have been studied as possible models for the active site of hemocyanin: EDTB (N,N,N',N'-tetrakis-(2-benzimidazolylmethyl)-1,2-ethanediamine), EGTB (1,1,10,10-tetrakis-(2-benzimidazolylmethyl)-1,10-diaza-4,7- dioxadecane), and MEGTB (1,1,10,10-tetrakis-(1-methylbenzimidazol-2-y lmethyl)-1,10-diaza-4,7-dioxadecane). The initial oxygenation product of Cu2(EDTB)(ClO4)2 in Me2SO gives optical absorption maxima at 315 nm (epsilon = 3750 M-1 cm-1) and 690 nm (epsilon = 100 M-1 cm-1). The fluorescence emission intensities of Cu2(EDTB)(ClO4)2 at 400 and 700 nm (excitation at 350 nm) decreases rapidly on exposure to air. This suggests oxidation of Cu2(I) to Cu2(II). The x-ray absorption edge spectra suggest that both coppers in the oxygenation product, analyzed as Cu2(EDTB)(ClO4)2(O).3H2O, are Cu(II). From spectrophotometric titration of Cu2(MEGTB)Cl4 with azide, formation constant of the Cu2(MEGTB)N3Cl3 complex has been obtained. Data from cyclic voltammetry experiments suggest that in the presence of azide, Cu(II)(N3)Cu(II) species is present.     

p27 phosphorylation by Src regulates inhibition of cyclin E-Cdk2

The kinase inhibitor p27Kip1 regulates the G1 cell cycle phase. Here, we present data indicating that the oncogenic kinase Src regulates p27 stability through phosphorylation of p27 at tyrosine 74 and tyrosine 88. Src inhibitors increase cellular p27 stability, and Src overexpression accelerates p27 proteolysis. Src-phosphorylated p27 is shown to inhibit cyclin E-Cdk2 poorly in vitro, and Src transfection reduces p27-cyclin E-Cdk2 complexes. Our data indicate that phosphorylation by Src impairs the Cdk2 inhibitory action of p27 and reduces its steady-state binding to cyclin E-Cdk2 to facilitate cyclin E-Cdk2-dependent p27 proteolysis. Furthermore, we find that Src-activated breast cancer lines show reduced p27 and observe a correlation between Src activation and reduced nuclear p27 in 482 primary human breast cancers. Importantly, we report that in tamoxifen-resistant breast cancer cell lines, Src inhibition can increase p27 levels and restore tamoxifen sensitivity. These data provide a new rationale for Src inhibitors in cancer therapy.     

IKK beta suppression of TSC1 links inflammation and tumor angiogenesis via the mTOR pathway

TNFalpha has recently emerged as a regulator linking inflammation to cancer pathogenesis, but the detailed cellular and molecular mechanisms underlying this link remain to be elucidated. The tuberous sclerosis 1 (TSC1)/TSC2 tumor suppressor complex serves as a repressor of the mTOR pathway, and disruption of TSC1/TSC2 complex function may contribute to tumorigenesis. Here we show that IKKbeta, a major downstream kinase in the TNFalpha signaling pathway, physically interacts with and phosphorylates TSC1 at Ser487 and Ser511, resulting in suppression of TSC1. The IKKbeta-mediated TSC1 suppression activates the mTOR pathway, enhances angiogenesis, and results in tumor development. We further find that expression of activated IKKbeta is associated with TSC1 Ser511 phosphorylation and VEGF production in multiple tumor types and correlates with poor clinical outcome of breast cancer patients. Our findings identify a pathway that is critical for inflammation-mediated tumor angiogenesis and may provide a target for clinical intervention in human cancer.     

Mechanism of resistance to Bacillus thuringiensis toxin Cry1Ac in a greenhouse population of the cabbage looper, Trichoplusia ni

The cabbage looper, Trichoplusia ni, is one of only two insect species that have evolved resistance to Bacillus thuringiensis in agricultural situations. The trait of resistance to B. thuringiensis toxin Cry1Ac from a greenhouse-evolved resistant population of T. ni was introgressed into a highly inbred susceptible laboratory strain. The resulting introgression strain, GLEN-Cry1Ac-BCS, and its nearly isogenic susceptible strain were subjected to comparative genetic and biochemical studies to determine the mechanism of resistance. Results showed that midgut proteases, hemolymph melanization activity, and midgut esterase were not altered in the GLEN-Cry1Ac-BCS strain. The pattern of cross-resistance of the GLEN-Cry1Ac-BCS strain to 11 B. thuringiensis Cry toxins showed a correlation of the resistance with the Cry1Ab/Cry1Ac binding site in T. ni. This cross-resistance pattern is different from that found in a previously reported laboratory-selected Cry1Ab-resistant T. ni strain, evidently indicating that the greenhouse-evolved resistance involves a mechanism different from the laboratory-selected resistance. Determination of specific binding of B. thuringiensis toxins Cry1Ab and Cry1Ac to the midgut brush border membranes confirmed the loss of midgut binding to Cry1Ab and Cry1Ac in the resistant larvae. The loss of midgut binding to Cry1Ab/Cry1Ac is inherited as a recessive trait, which is consistent with the recessive inheritance of Cry1Ab/Cry1Ac resistance in this greenhouse-derived T. ni population. Therefore, it is concluded that the mechanism for the greenhouse-evolved Cry1Ac resistance in T. ni is an alteration affecting the binding of Cry1Ab and Cry1Ac to the Cry1Ab/Cry1Ac binding site in the midgut.     

New criteria on global exponential stability of bam neural networks with distributed delays and reaction-diffusion terms

This paper presents new theoretical results on global exponential stability of bi-directional associative memory neural networks with distributed delays and reaction-diffusion terms based on the inequality technique, Lyapunov functional, and analysis technique. The results remove the usual assumption that the activation functions are of monotonous or differential character. Exponential converging velocity index is estimated, which depends on the delay kernel functions and system parameters. Finally, two numerical examples are given to show the validity and feasibility of our results.     

Preparation and properties of modified chitosan as potential matrix materials for drug sustained-release beads

Modified chitosan such as chitosan alpha-ketoglutaric acid (KCTS) and hydroxamated chitosan alpha-ketoglutaric acid (HKCTS) were successfully prepared. The modified chitosan were employed in the formation of drug-loaded, iron(III)-crosslinked polymeric beads. The produced polymers were characterized by IR, NMR, WXRD and DSC measurements. The resulting beads were evaluated in vitro as drug prolonging and potentially orally administered delivery system. Theophylline was used as the loaded model drug. The generated beads proved to be successful in prolonging drug release. The release kinetics was evaluated by fitting the experimental data to standard release equations (zero-, first- and Higuchi equation). The best fit was found with Higuchi model for the polymeric beads.