Two independent growth factor-generated signals regulate c-fos and c-myc mRNA levels in Swiss 3T3 cells

Polypeptide growth factors that stimulate cell proliferation bind to cell surface receptors and activate intracellular signal transduction pathways. One major signalling pathway, initiated by phosphatidylinositol (PI) turnover, involves activation of protein kinase C. Some polypeptide growth factors, including mitogens that activate protein kinase C, induce a rapid increase in expression of the proto-oncogenes, c-myc and c-fos. In order to characterize the signal transduction pathways responsible for proto-oncogene activation, we treated Swiss 3T3 cells with the tumor promoter phorbol dibutyrate to generate cells deficient in protein kinase C. These cells were then stimulated with platelet extract, bombesin, or epidermal growth factor (EGF) and the levels of c-myc and c-fos mRNA were determined. Platelet extract or bombesin, which stimulate PI turnover, were substantially weaker inducers of c-myc and c-fos mRNA levels in the protein kinase C-depleted cells, although some variability with platelet extract was noted. EGF, which does not stimulate PI turnover in several cell systems, was by contrast a potent inducer of both proto-oncogenes whether or not the cells were deficient in protein kinase C. Pretreatment of cells with phorbol dibutyrate caused little or no change in the basal levels of c-myc or c-fos mRNA, but led to a small but significant increase in basal levels of ornithine decarboxylase mRNA. These results demonstrate that EGF and growth factors that activate PI turnover induce expression of the c-myc and c-fos proto-oncogenes through different pathways.     

Viscous macromolecules inhibit erythrocyte hemolysis induced by snake venom phospholipase A2

The effect of medium viscosity on lysis of red blood cells (RBC) induced by snake venom phospholipase A2 (PLA2) was examined. The medium viscosity was modified by the addition of various macromolecules which differ in their chemical nature and in their capacity to increase fluid viscosity. PLA2 and Ca++ were applied to cells suspended in viscous medium to induce hemolysis. It was found that the hemolysis is inhibited in direct proportion to increasing viscosity of the extracellular fluid. This phenomenon was observed with aggregated as well as disaggregated RBC. To examine whether the viscosity interferes with the accessibility of the enzyme to the cell, the medium viscosity was modified after binding of the enzyme to the cells; PLA2 was added to a RBC suspension in the presence of Ba++ which binds the enzyme to the cell membrane but does not activate it. The cell-enzyme complex was separated by gel filtration and suspended in viscous medium in the presence of Ca++ which activates the reaction. Also in this case RBC lysis was inhibited as the medium viscosity was increased. It is proposed that the action of PLA2 on RBC membrane is regulated by the viscosity of the cell surface aqueous environment.     

Salt-induced cooperativity in ATPase activity of plasma membrane-enriched fractions from cultured Citrus cells: kinetic evidence

ATPase activity was studied in plasma membrane-enriched fractions prepared from cultured Citrus sinensis L. cv. Osbeck cells. In general, properties of the plasma membrane ATPase from cultured cells, such as optimal pH and temperature. V_max and K_m were similar to those already observed in higher plants. The effects of high salt concentrations on ATPase activity were studied in membrane fractions derived from salt-sensitive and salt-tolerant cells grown in the presence or absence of salt. NaCl did not have an in vivo effect on V_max and the apparent K_m value for ATP. However, high concentrations of NaCl, or KCl, added in vitro, induced cooperativity in the enzyme and reduced the affinity of the enzyme for its substrate. Isoosmolar concentrations of sucrose or choline chloride failed to do so. Our results suggest that the plasma membrane ATPase of Citrus cells has more than one substrate-binding site on the native form of the enzyme which interact in the presence of salt and act independently in its absence.     

肝胆显像螯合物—氮基三乙酸单酰苯胺及其类似物的合成

本课题合成四个氮基三乙酸单酰苯胺(IDA)类及其类似物肝胆显像螯合物。(1)用家兔做了肝胆显像扫描实验,其显像效果较好。(2)～(3)为未见报道的化合物。     

Research Progress on Anti-Inflammatory Mechanisms of Black Ginseng

In recent years, black ginseng, a new type of processed ginseng product, has attracted the attention of scholars globally. Ginsenoside and ginseng polysaccharide, the main active substances of black ginseng, have been shown to carry curative effects for many diseases. This article focuses on the mechanism of their action in anti-inflammatory response, which is mainly divided into three aspects: activation of immune cells to exert immune regulatory response; participation in inflammatory response-related pathways and regulation of the expression level of inflammatory factors; effect on the metabolic activity of intestinal flora. This study identifies active anti-inflammatory components and an action mechanism of black ginseng showing multi-component, multi-target, and multi-channel characteristics, providing ideas and a basis for a follow-up in-depth study of its specific mechanism.     

盐生荒漠地表水热与二氧化碳通量的季节变化及驱动因素

以古尔班通古特沙漠南缘原始盐生荒漠为对象,利用涡度相关法,对原始盐生荒漠地表水热、二氧化碳通量进行了连续观测,对通量的季节变化、浅层土壤水分条件改变对盐生荒漠植物群落水汽、二氧化碳通量以及水分利用效率的影响进行了系统的分析.结果表明:净辐射通量、潜热通量和二氧化碳通量都具有明显的季节变化趋势,而显热通量的季节变化不明显.在有效能量的分配上,显热通量是有效能量的主要输出项.在降水影响期和非影响期,二氧化碳通量没有明显的变化;而在非降水影响期潜热通量明显降低,表明土壤水分处于亏缺状态,但二氧化碳通量并没有降低的趋势,而与前期保持高度的一致性.以此可以推断,该荒漠盐生植物群落并不以降水为主要水分来源,降水后水汽通量和二氧化碳通量变化的不一致性是该原始盐生荒漠独特植物特征决定的.降水影响期原始盐生荒漠植物群落的水分利用效率低于非影响期,是由于降水后土壤蒸发迅速增加,而植物蒸腾与光合并未随之增加造成的.     

基于小波神经网络的麦蚜发生程度预测模型

【目的】建立基于小波神经网络病虫害预测预报模型,对提前采取防病防虫措施、减少农作物病虫害损失、提高农作物产量与质量具有重要意义。【方法】本研究以山西省运城市芮城县1980-2014年麦蚜发生程度和气象因子数据为基础,采用主成分分析法从40个基础气象因子中整合形成9个新的自变量输入模型,采用试凑法筛选隐含层节点数,用1980-2009年的数据进行网络训练,对2010-2014年麦蚜发生程度进行回测,建立了以Morlet小波函数为传递函数的小波神经网络模型,并与以Sigmoid函数为传递函数的BP神经网络模型进行了比较。【结果】小波和BP神经网络两种模型对训练样本的平均拟合精度均有10年以上超过80%,两者MAPE 值分别为 89.83% 和83.07%,MSE 值分别为0.0578和0.6192。【结论】两个模型都能较好地描述麦蚜发生程度;从预测精度和模型的稳定性来看,小波神经网络好于BP神经网络。