The 3-Phosphorylated Phosphoinositide Response of 3T3-L1 Preadipose Cells Exposed to Insulin,Insulin-Like Growth Factor-1, or Platelet-Derived Growth Factor

We compared the pattern of 3-phosphorylated phosphoinositides produced by confluent 3T3-L1 preadipose cells upon exposure to growth factors that either induce differentiation (insulin, insulin-like growth factor-1) or do not (platelet-derived growth factor). Following addition of insulin or insulin-like growth factor-1, PI(3,4,5)P3 rapidly rose, on average, to levels tenfold over basal. PI(3,4)P₂ either did not change (after insulin) or slightly increased (1.5 fold). Time course studies with insulin demonstrated that the rise in PI(3,4,5)P₃ peaked by 1 minute, and levels then remained steady over 30 minutes. Dose-response experiments showed that insulin at a concentration of 1 nM was sufficient for the PI(3,4,5)P₃ response. Insulin failed to increase PI(3,4)P₂ at any of the time points or at any of the doses used. In contrast, after addition of platelet-derived growth factor, both PI(3,4)P₂ and PI(3,4,5)P₃ rose concurrently and to comparable extents. These data suggest that one possible mechanism contributing to insulin/insulin-like growth factor-1-induced 3T3-L1 preadipose cell differentiation is a distinct pattern of 3-phosphorylated phosphoinositide accumulation, defined by a prominent increase in PI(3,4,5)P₃ with no (in the case of insulin), or a minimal (in the case of IGF-1), rise in PI(3,4)P₂.     

第四纪甲虫研究方法及意义

第四纪甲虫的研究在国外已开展多年,形成了一套完整的方法,而在我国几乎为一空白。第四纪甲虫研究方法一般包括如下几个步骤：野外采样,实验室分离,标本保存,标本鉴定,结果分析。第四纪甲虫研究的意义主要表现在如下三个方面：重建古气候、恢复昆虫地理史和第四纪考古。     

盐或低温胁迫对花生幼苗下胚轴ATP酶和质膜中PIP2含量的影响

经６％－１２％Ｄｅｘｔｒａｎ Ｔ７０密度梯度离心,获得了纯度较高的７ｄ龄花生幼苗下胚轴质膜和液泡膜制剂。１５０ｍｍｏｌ／Ｌ ＮａＣｌ或１０℃低温处理花生幼苗２４ｈ,其下胚轴质膜上的Ｍｇ＾２＋激活的ＡＴＰａｓｅ活性分别提高了３７．６％和１７．２％;Ｃａ＾２＋－ＡＴＰａｓｅ活性分别提高４５．８％和３３．６％。上述盐或低温处理也提高了液泡膜上Ｍｇ＾２＋激活的ＡＴＰａｓｅ活性,分别为对照的１４１．２％和１     

Characterization of phospholipase A2 activation by plasmin in cultured bovine endothelial cells

Treatment of cultured bovine carotid artery endothelial cells with 0.1 µM human plasmin has been reported to induce a receptor-mediated short burst of arachidonate release, which is a pertussis toxin-sensitive and extracellular calcium-dependent reaction. Plasmin-induced calcium influx in cells was significantly inhibited by pretreatment with pertussis toxin, indicating that the former was coupled with a pertussis toxin-sensitive guanosine 5-triphosphate (GTP)-binding protein. Plasmin significantly induced the formation of lysophosphatidylcholine but not lysophosphatidylethanolamine. A cellular phospholipase A₂ with an arachidonyl specificity at the sn-2 position of phosphatidylcholine, which required submicromolar calcium, was identified as a cytosolic phospholipase A₂ by immunoblot analysis. By a cell-free enzyme activity assay and immunoblot analysis, plasmin was found to induce a translocation of the cytosolic phospholipase A₂ from the cytosol to the membrane. Taken together, the results suggest that plasmin bound to its putative receptor and activated a GTP-binding protein coupled to calcium influx channel, followed by translocation and activation of cytosolic phospholipase A₂ in endothelial cells.     

Chemical speciation of arsenic in urine of patients with blackfoot disease

Blackfoot disease is a peripheral vascular disease resulting in gangrene of the lower extremities. Although extensive epidemiological study has implicated high arsenic content in artesian well water of the endemic area bears some important connection with the disease, the etiology of the disease is still not clarified. In this study, attention is paid to chemical speciation of arsenic in order to find out whether the concentrations of arsenic species in urine of Blackfoot disease patients are different from those of controls. Experimental results indicate that the total arsenic, inorganic arsenic, monomethylarsonic acid, and other forms of arsenic in the urine of patients are significantly higher than those of the contols. The possible connection of those arsenic species with the etiology of the disease is discussed.     

Virtual electrodes in cardiac tissue: a common mechanism for anodal and cathodal stimulation.

Traditional cable analyses cannot explain complex patterns of excitation in cardiac tissue with unipolar, extracellular anodal, or cathodal stimuli. Epifluorescence imaging of the transmembrane potential during and after stimulation of both refractory and excitable tissue shows distinctive regions of simultaneous depolarization and hyperpolarization during stimulation that act as virtual cathodes and anodes. The results confirm bidomain model predictions that the onset (make) of a stimulus induces propagation from the virtual cathode, whereas stimulus termination (break) induces it from the virtual anode. In make stimulation, the virtual anode can delay activation of the underlying tissue, whereas in break stimulation this occurs under the virtual cathode. Thus make and break stimulations in cardiac tissue have a common mechanism that is the result of differences in the electrical anisotropy of the intracellular and extracellular spaces and provides clear proof of the validity of the bidomain model.     

Molecular Evolution and Phylogeny of Satellite RNA Associated with Bamboo Mosaic Potexvirus

Satellite RNA of bamboo mosaic potexvirus (satBaMV) is a linear RNA molecule which encodes a 20-kDa nonstructural protein. Sequences of seven different satBaMV isolates from bamboo hosts in three genera showed 0.7% to 7.5% base variation which spanned the whole RNA molecule. However, the putative 20-kDa open reading frame was all preserved in these isolates. The phylogenetic relationship based on the nucleotide sequence did not show particular grouping of satBaMV from the host in one genus; neither was the grouping of satBaMV evident by location of sampling. Putative secondary structures of the 3′ untranslated regions showed a basic pattern with conserved hexanucleotides (ACCUAA) and polyadenylation signal (AAUAAA) located in the loop regions. Although the satBaMV-encoded 20-kDa protein is a nonstructural protein, its predicted secondary structure contains eight-stranded β-sheets which may form ``jelly-roll' structure similar to that found in capsid protein encoded by satellite virus of panicum mosaic virus. Received: 26 June 1996 / Accepted: 9 September 1996     

大鼠烫伤后延髓孤束核β－内啡肽含量的变化及其抗血清的作用

大鼠背部２０％体表面积接触沸水２０ｓ,形成Ⅲ度烫伤后,延髓孤束核推挽灌流液中β－内啡肽免疫活性物质的含量显著升高,在烫后１、４ｈ两次达到峰值。烫后立即向弧束核微量注射０．４μｌβ－内啡肽抗血清（滴度１：３００００）,可在一定程度上改善心功能指标,延缓血压和心率的下降,但未能延长动物的存活时间。提示孤束核的β－内啡肽在烫伤休克的病理过程中起作用,其含量的过量升高有抑制心血管功能的作用,从而不利于烫伤休克的恢复。     

Leukotriene B4 binding to human neutrophils

[³H] Leukotriene B₄ (LTB₄) binds concentration dependency to intact human polymorophonuclear leukocytes (PMN's). The binding is saturable, reaches equilibrium in 10 min at 4°C, and is readily reversible. Mathematical modeling analysis reveals biphasic binding of [³H] LTB₄ indicating two discrete populations of binding sites. The high affinity binding sites have a dissociation constant of 0.46 × 10⁻⁹M and B_max of 1.96 × 10⁴ sites per neutrophil; the low affinity binding sites have a dissociation constant of 541 × 10⁻⁹M and a B_max of 45.6 × 10⁴ sites per neutrophil. Competitive binding experiments with structural analogues of LTB₄ demonstrate that the interaction between LTB₄ and the binding site is stereospecific, and correlates with the relative biological activity of the analogs. At 25°C[³H] LTB₄ is rapidly dissociated from the binding site and metabolized to 20-OH and 20-COOH-LTB₄. Purification of neutrophils in the presence of 5-lipoxygenase inhibitors significantly increases specific [³H] LTB₄ binding, suggesting that LTB₄ is biosynthesized during the purification procedure. These data suggest that stereospecific binding and metabolism of LTB₄ in neutrophils are tightly coupled processes.     

Taenia taeniaeformis: characterization of larval metabolic products and growth of host gastric cells in vitro

Development of larvae of the cestode parasite Taenia taeniaeformis in the liver of rats induces gross hyperplasia of the gastric mucosa and excessive mucus production in the stomach without any direct contact with the stomach. Because the taeniid larvae are known to elaborate excretory-secretory (E-S) product in vivo and in vitro, the product was analyzed further, and its effects on cultured rat and dog stomach cells were investigated. In vitro E-S product contained less negatively charged glycosaminoglycan than either heparin or chondroitin sulfate, and proteins of various molecular weights. It stimulated the growth of both rat and dog stomach cells at concentrations of 3-9 micrograms protein/ml culture medium. At a concentration of 30 micrograms protein/ml culture medium, it stimulated hexosamine production in the cells up to 20 times, and multiple intracytoplasmic granules were found in both rat and dog cultured cells by light and electron microscopy. These results suggest that larval E-S product may be involved in the induction of gastric hyperplasia and hypermucus secretion.