Bidirectional transmembrane signaling by cytoplasmic domain separation in integrins

Although critical for development, immunity, wound healing, and metastasis, integrins represent one of the few classes of plasma membrane receptors for which the basic signaling mechanism remains a mystery. We investigated cytoplasmic conformational changes in the integrin LFA-1 (alphaLbeta2) in living cells by measuring fluorescence resonance energy transfer between cyan fluorescent protein-fused and yellow fluorescent protein-fused alphaL and beta2 cytoplasmic domains. In the resting state these domains were close to each other, but underwent significant spatial separation upon either intracellular activation of integrin adhesiveness (inside-out signaling) or ligand binding (outside-in signaling). Thus, bidirectional integrin signaling is accomplished by coupling extracellular conformational changes to an unclasping and separation of the alpha and beta cytoplasmic domains, a distinctive mechanism for transmitting information across the plasma membrane.     

Protein kinase translocation as an early event in the hormonal control of uterine contraction

beta-Adrenergic stimulation with isoproterenol inhibits contractility, increases cyclic adenosine monophosphate (AMP) concentration, decreases the concentration of unsaturated cyclic AMP receptor sites, and increases cyclic AMP-independent kinase in the uterus of ovariectomized rats. The total soluble kinase activity is reduced. The protein kinase activity lost from the cytosol was translocated to the microsomal fraction mostly in a cyclic AMP-independent form, suggesting a particulate substrate for the activated enzyme.     

New early Jurassic tetrapod assemblages constrain Triassic-Jurassic tetrapod extinction event

The discovery of the first definitively correlated earliest Jurassic (200 million years before present) tetrapod assemblage (Fundy basin, Newark Supergroup, Nova Scotia) allows reevaluation of the duration of the Triassic-Jurassic tetrapod extinction event. Present are tritheledont and mammal-like reptiles, prosauropod, theropod, and ornithischian dinosaurs, protosuchian and sphenosuchian crocodylomorphs, sphenodontids, and hybodont, semionotid, and palaeonisciform fishes. All of the families are known from Late Triassic and Jurassic strata from elsewhere; however, pollen and spore, radiometric, and geochemical correlation indicate an early Hettangian age for these assemblages. Because all "typical Triassic" forms are absent from these assemblages, most Triassic-Jurassic tetrapod extinctions occurred before this time and without the introduction of new families. As was previously suggested by studies of marine invertebrates, this pattern is consistent with a global extinction event at the Triassic-Jurassic boundary. The Manicouagan impact structure of Quebec provides dates broadly compatible with the Triassic-Jurassic boundary and, following the impact theory of mass extinctions, may be implicated in the cause.     

TCR-induced transmembrane signaling by peptide/MHC class II via associated Ig-alpha/beta dimers

Previous findings suggest that during cognate T cell-B cell interactions, major histocompatability complex (MHC) class II molecules transduce signals, leading to Src-family kinase activation, Ca2+ mobilization, and proliferation. Here, we show that antigen stimulation of resting B cells induces MHC class II molecules to associate with Immunoglobulin (Ig)-alpha/Ig-beta (CD79a/CD79b) heterodimers, which function as signal transducers upon MHC class II aggregation by the T cell receptor (TCR). The B cell receptor (BCR) and MHC class II/Ig-alpha/Ig-beta are distinct complexes, yet class II-associated Ig-alpha/beta appears to be derived from BCR. Hence, Ig-alpha/beta are used in a sequential fashion for transduction of antigen and cognate T cell help signals.     

江汉平原一次初夏暴雨的诊断分析

利用常规气象资料和客观物理量场、卫星云图和多普勒雷达回波产品资料,对2009年6月8日发生在湖北省江汉平原的一次暴雨过程进行诊断分析。结果表明,高空低槽东移是影响此次强降水过程的主要大尺度环流背景;低涡切变和低空急流是暴雨的直接影响系统;有利的热力水汽条件和动力条件是强降水产生和维持的机制;卫星云图上"人"字型云系可作为判断强降水落区落点的依据。     

An early center of bovine husbandry in southeast Asia

Non Nok Tha is a prehistoric site in northeast Thailand. The radiocarbon dates suggest that it was first occupied by at least 3500 B.C., and possibly as early as 5000 B.C. The deepest levels contain unexpectedly early evidence for rice cultivation and bronze casting. Multivariate and cultural analyses of the bovine bones suggest that the first inhabitants raised domesticated cattle. This is among the earliest evidence for bovine domestication known.     

哈尔滨沙尘天气成因及其对城市大气污染的影响

文章从空气动力学和天气学角度出发探讨了大风、对流层低层的强烈垂直不稳定及高、低空急流对哈尔滨沙尘天气做出的贡献,分析了沙尘天气时城市大气中几种主要污染物变化情况。研究表明,哈尔滨的沙尘天气主要来源是内蒙古中部的沙地,但近年也常出现本地沙源引起的沙尘天气;沙尘天气期间,城市大气中的可吸入颗粒物浓度出现异常,其浓度变化和沙尘天气具有同步性特征;沙尘天气期间,SO2含量呈明显减弱趋势;NO2污染物的浓度变化则表现较平稳。     

三位一体的高校廉政风险预警防控机制研究

近年来,高校腐败案件的高发与频发引起社会广泛关注。只有坚持预防在先,防患于未然,才能减少和控制诱发腐败的风险。腐败动机和腐败机会的共同作用导致了腐败行为的发生。腐败机会是外在的,是外因,因为缺乏对权力的有效制约和监督得以实现;动机是内在的,是内因,因为思想道德防线瓦解和崩溃而成实践。因此,在对权力运行的风险预警中,要靠制度建设、科技监督来减少腐败的机会,同时,也要靠文化的浸润来加筑个体内心的道德防线。加强制度建设与科技监督、提高廉政意识是有效预防高校廉政风险发生的三个关键要素。如何将三者有机结合,使制度的约束力、教育的说服力、监督的制衡力共同作用于风险发生的抑制与化解上,构筑“制度+文化+科技”三位一体的廉政风险预警防控系统,为我们提供了较为满意的选择。只有三管齐下,权力运行的廉政风险预警防控机制建设才能实现源头防腐的目的。     

Control of the interferon-induced 68-kilodalton protein kinase by the HIV-1 tat gene product

The tat-responsive region (TAR) of the human immunodeficiency virus-1 (HIV-1) exhibits a trans-inhibitory effect on translation in vitro by activating the interferon-induced 68-kilodalton protein kinase (p68 kinase). Productive infection by HIV-1 was shown to result in a significant decrease in the amount of cellular p68 kinase. The steady-state amount of p68 kinase was also reduced in interferon-treated HeLa cell lines stably expressing tat, as compared to the amount of the kinase in interferon-treated control HeLa cells. Thus, the potential translational inhibitory effects of the TAR RNA region mediated by activation of p68 kinase may be downregulated by tat during productive HIV-1 infection.     

Fiber-optical analog of the event horizon

The physics at the event horizon resembles the behavior of waves in moving media. Horizons are formed where the local speed of the medium exceeds the wave velocity. We used ultrashort pulses in microstructured optical fibers to demonstrate the formation of an artificial event horizon in optics. We observed a classical optical effect: the blue-shifting of light at a white-hole horizon. We also showed by theoretical calculations that such a system is capable of probing the quantum effects of horizons, in particular Hawking radiation.     

An ultrasensitive bacterial motor revealed by monitoring signaling proteins in single cells

Understanding biology at the single-cell level requires simultaneous measurements of biochemical parameters and behavioral characteristics in individual cells. Here, the output of individual flagellar motors in Escherichia coli was measured as a function of the intracellular concentration of the chemotactic signaling protein. The concentration of this molecule, fused to green fluorescent protein, was monitored with fluorescence correlation spectroscopy. Motors from different bacteria exhibited an identical steep input-output relation, suggesting that they actively contribute to signal amplification in chemotaxis. This experimental approach can be extended to quantitative in vivo studies of other biochemical networks.     

谈行为事件访谈法在胜任素质模型构建中的应用

行为事件访谈法作为构建胜任力模型的重要工具之一,是目前得到公认的最有效的信息采集方法。与其他胜任素质模型研究方法相比,行为事件访谈法具有客观性、真实性、有效性等优势,但在其实际操作中存在耗时长、具有主观偏差、需受访者配合等问题。