Polar transport of the plant hormone auxin – the role of PIN-FORMED (PIN) proteins

The PIN-FORMED (PIN) protein family is a group of plant transmembrane proteins with a predicted function as secondary transporters. PINs have been shown to play a rate-limiting role in the catalysis of efflux of the plant growth regulator auxin from cells, and their asymmetrical cellular localization determines the direction of cell-to-cell auxin flow. There is a functional redundancy of PINs and their biochemical activity is regulated at many levels. PINs constitute a flexible network underlying the directional auxin flux (polar auxin transport) which provides cells in any part of the plant body with particular positional and temporal information. Thus, the PIN network, together with downstream auxin signalling system(s), coordinates plant development. This review summarizes recent progress in the elucidation of the role of PIN proteins in polar auxin transport at the cellular level, with emphasis on their structure and evolution and regulation of their function. Received 28 December 2006; received after revision 16 February 2007; accepted 26 March 2007     

What can we learn from the fifties?

Economists have increasingly elicited probabilistic expectations from survey respondents. Subjective probabilistic expectations show great promise to improve the estimation of structural models of decision making under uncertainty. However, a robust finding in these surveys is an inappropriate heap of responses at “50%,” suggesting that some of these responses are uninformative. The way these 50s are treated in the subsequent analysis is of major importance. Taking the 50s at face value will bias any aggregate statistics. Conversely, deleting them is not appropriate if some of these answers do convey some information. Furthermore, the attention of researchers is so focused on this heap of 50s that they do not consider the possibility that other answers may be uninformative as well. This paper proposes to take a fresh look at these questions using a new method based on weak assumptions to identify the informativeness of an answer. Applying the method to probabilistic expectations of equity returns in three waves of the Survey of Economic Expectations in 1999–2001, I find that: (i) at least 65% of the 50s convey no information at all; (ii) it is the answer most often provided among the answers identified as uninformative; (iii) but even if the 50s are a major contributor to noise, they represent at best 70% of the identified uninformative answers. These findings have various implications for survey design.     

基于小波阀值降噪和BP神经网络的超短期风电功率预测

针对超短期风电功率预测问题，考虑了风电场复杂的噪声背景和风电功率的波动性，提出了一种基于小波阀值降噪-BP神经网络的超短期风电功率预测方法。该方法采用近似对称光滑的紧支撑双正交小波db4（Daubechies函数）作为小波基，通过多分辨分析的Mallat算法对历史时序风电功率数据进行3尺度分解。根据Donoho阀值法对各层小波系数进行软阀值降噪处理，再通过小波逆变换重构历史时序风电功率，由BP神经网络对其进行训练，预测目的风电功率序列。仿真算例将该方法与普通BP神经网络方法进行了对比，比较结果证明其预测精度优于后者，具有很好鲁棒性和降噪性能，适用噪声复杂的风电场超短期风电功率在赣预测．     

Botulinum toxin as a carrier for oral vaccines

Botulinum toxin is an unusually potent substance that acts on the nervous system to produce the clinical outcome of flaccid paralysis. To produce this effect, the toxin ordinarily proceeds through two separate but essential sequences of events. During the first, the toxin is ingested, it traverses a portion of the gastrointestinal system and then it is transcytosed from the lumen of the gut to the general circulation. During the second, circulating toxin binds to peripheral cholinergic nerve endings, it is endocytosed and then it acts as a metalloendoprotease to cleave polypeptides that are essential for exocytosis. Although botulinum toxin is antigenic, it ordinarily does not evoke an immune response during or after cases of oral poisoning. This is due to the fact that the dose of toxin that produces flaccid paralysis—and potentially death—is less than the dose needed to evoke an antibody response. In the recent past, the techniques of molecular biology have been used to generate an expression product of botulinum toxin that retains the ability to escape the gut and reach the general circulation, retains the ability to evoke an immune response, but has lost the ability to produce neurotoxicity. This modified toxin may have two clinical applications. The expression product itself may have utility as an oral vaccine against botulism. Beyond this, the modified toxin, or a truncation mutant of the toxin, may have utility as a carrier in the construction of other oral vaccines. Both potential applications could lead to the expression of oral vaccines in common foods. Received 29 December 1998; received after revision 22 March 1999; accepted 24 March 1999     

Spatial control of mitosis by the GTPase Ran

Mitosis is the most potentially dangerous event in the life of a cell, during which the cell genetic identity is transmitted to daughters; errors at this stage may yield aneuploid cells that can initiate a genetically unstable clone. The small GTPase Ran is the central element of a conserved signaling network that has a prominent role in mitotic regulation. Pioneering studies with amphibian oocytes indicated that Ran, in the GTP-bound form, activates factors that regulate spindle assembly and dynamics. An increasing body of data indicate higher specificity and complexity in mitotic control operated by Ran in somatic cells. Newly identified target factors of Ran operate with different specificity, and it is emerging that mitotic progression requires the precise positioning of Ran network components and effectors at specific sites of the mitotic apparatus according to a highly regulated schedule in space and time. In this review we summarize our current understanding of Ran control of mitosis and highlight the specificity of mechanisms operating in mammalian somatic cells. M. Ciciarello, R. Mangiacasale: These authors contributed equally to this work. Received 29 December 2006; received after revision 13 March 2007; accepted 29 March 2007     

Predicting nominal variable relationships with multiple response

For forecasting purposes, it is useful to predict the most likely response of an individual to a nominally-scaled variable using the response to a predictor variable which is also nominally scaled. Traditional statistical approaches are not suitable when respondents provide multiple responses. For practical applications it is desirable to provide a simple measure of prediction that is easy to calculate and understand. Two situations are described where predictions of multiple response are implemented and two indices of predictive association are developed for the situations. These indices provide predictive explanations where none were possible using traditional methods of predictive association. The need to complement these indices with conditional probabilities and log-linear models is suggested. The evaluation and implications of these indices are discussed.     

Foreign exchange market prediction with multiple classifiers

Foreign exchange market prediction is attractive and challenging. According to the efficient market and random walk hypotheses, market prices should follow a random walk pattern and thus should not be predictable with more than about 50% accuracy. In this article, we investigate the predictability of foreign exchange spot rates of the US dollar against the British pound to show that not all periods are equally random. We used the Hurst exponent to select a period with great predictability. Parameters for generating training patterns were determined heuristically by auto‐mutual information and false nearest‐neighbor methods. Some inductive machine‐learning classifiers—artificial neural network, decision tree, k‐nearest neighbor, and naïve Bayesian classifier—were then trained with these generated patterns. Through appropriate collaboration of these models, we achieved a prediction accuracy of up to 67%. Copyright © 2009 John Wiley & Sons, Ltd.     

Predicting multistage financial distress: Reflections on sampling,feature and model selection criteria

This research proposes a prediction model of multistage financial distress (MSFD) after considering contextual and methodological issues regarding sampling, feature and model selection criteria. Financial distress is defined as a three‐stage process showing different nature and intensity of financial problems. It is argued that applied definition of distress is independent of legal framework and its predictability would provide more practical solutions. The final sample is selected after industry adjustments and oversampling the data. A wrapper subset data mining approach is applied to extract the most relevant features from financial statement and stock market indicators. An ensemble approach using a combination of DTNB (decision table and naïve base hybrid model), LMT (logistic model tree) and A2DE (alternative N dependence estimator) Bayesian models is used to develop the final prediction model. The performance of all the models is evaluated using a 10‐fold cross‐validation method. Results showed that the proposed model predicted MSFD with 84.06% accuracy. This accuracy increased to 89.57% when a 33.33% cut‐off value was considered. Hence the proposed model is accurate and reliable to identify the true nature and intensity of financial problems regardless of the contextual legal framework.     

Differential signaling in presynaptic neurotransmitter release

Neuronal communication is tightly regulated by presynaptic signaling, thereby temporarily and locally secreting one or more transmitters in order to exert propagation or modulation of network activity. In the last 2 decades our insight into the molecular regulation of presynaptic transmitter vesicle traffic and fusion has exponentionally grown due to the identification of specific functional interactions between presynaptic proteins involved in these processes. In addition, a plethora of extracellular and intracellular messengers regulate neurotransmitter release, occasionally leading to short- or long-term adaptations of the synapse to altered environmental signals. Important in this respect is the ability of various nerve terminals to diverge their output by differentiation in secretion of co-localized transmitters. This divergence in presynaptic signaling may converge in the postsynaptic target neuron or spread to neighbouring cells. In this review differential presynaptic signaling mechanisms will be related to their potential divergent roles in transmitter release.Received 25 November 2004; received after revision 23 December 2004; accepted 28 December 2004 Available online 09 March 2005     

Molecular insights into the novel aspects of diatom biology

Diatoms are unicellular photosynthetic eukaryotes that are thought to contribute as much as 25% of global primary productivity. In spite of their ecological importance in the worlds oceans, very little information is available at the molecular level about the novel aspects of their biology. Recent advances, such as the development of gene transfer protocols, are now allowing the genetic dissection of diatom biology. Notable examples are advances in understanding the genetic basis for the silica-based bioinorganic pattern formation of their cell walls and for elucidating key aspects of diatom ecophysiology. The potentiation of current research will allow an evaluation of the use of diatoms to construct submicrometre-scale silicon structures for the nanotechnology industry and will reveal the molecular secrets underlying their ecological success. Received 29 March 2001; received after revision 31 May 2001; accepted 31 May 2001     

Tetraspanins

The first tetraspanins were discovered on surface of human leucocytes, but it was rapidly demonstrated that they had a wider tissue expression. Twenty-six molecules display sufficient homology to belong to the same superfamily. Their function is not precisely known, but data coming from biochemical studies or knockout mice suggest that they play a major role in membrane biology. One of their outstanding properties is their ability to form a network of multimolecular complexes, the 'tetraspanin web', in which integrins are included. The structure of these complexes is under investigation, but some of the rules that govern their organization have already been unraveled. The challenge is to determine how the organization of the 'tetraspanin web' modifies the function of its constitutive molecules and consequently influences cellular behaviour. The implications may be considerable for the understanding of basic cellular processes such as migration and also of diseases related to loss or mutation of a single tetraspanin. Received 29 December 2000; received after revision 26 February 2001; accepted 19 March 2001     

Preparation of lymphocytes from small volumes of peripheral mouse blood.

A method was developed which allowed for the isolation of lymphocytes (95% of leukocytes in the final suspensions) from small volumes of peripheral mouse blood (38% recovery). The method proved of value for studies of murine lymphocytes which required biochemical analysis of samples from individual animals on a serial basis.     

Multiple roles of the DSCR1 (Adapt78 or RCAN1) gene and its protein product Calcipressin 1 (or RCAN1) in disease

The DSCR1 (Adapt78) gene¹ is transiently induced by stresses to temporarily protect cells against further potentially lethal challenges. However, chronic expression of the DSCR1 (Adapt78) gene has now been implicated in several pathological conditions including Alzheimer’s disease, Down syndrome and cardiac hypertrophy. Calcipressin 1 has been shown to function through direct binding and inhibition of the serine threonine protein phosphatase Calcineurin. Pharmacological inhibition of calcineurin, by the immunosuppressive drugs cyclosporin A and FK506, affects a wide variety of diseases. It is, therefore, likely that this endogenous calcineurin inhibitor, calcipressin 1, may also play a role in a variety of human diseases. ¹Please note that the mammalian DSCR1 gene is also called Adapt78 or RCAN1, and its protein products have been named Calcipressin1, MCIP1 and RCAN1. A proposal to adopt a single gene name of RCAN1 and a protein name RCAN1 (for Regulator of Calcineurin) has been endorsed by the HUGO Gene Nomenclature Committee, but final approval must await agreement from a majority of researchers in the field. Received 2 March 2005; received after revision 27 May 2005; accepted 19 July 2005     

Lamellipodia mediate the heterogeneity of central olfactory ensheathing cell interactions

The growth and guidance of primary olfactory axons are partly attributed to the presence of olfactory ensheathing cells (OECs). However, little is understood about the differences between the subpopulations of OECs and what regulates their interactions. We used OEC-axon assays and determined that axons respond differently to peripheral and central OECs. We then further purified OECs from anatomically distinct regions of the olfactory bulb. Cell behaviour assays revealed that OECs from the olfactory bulb were a functionally heterogeneous population with distinct differences which is consistent with their proposed roles in vivo. We found that the heterogeneity was regulated by motile lamellipodial waves along the shaft of the OECs and that inhibition of lamellipodial wave activity via Mek1 abolished the ability of the cells to distinguish between each other. These results demonstrate that OECs from the olfactory bulb are a heterogeneous population that use lamellipodial waves to regulate cell–cell recognition.     

The cellular functions of clathrin

Membranes and proteins are moved around the cell in small vesicles. A protein coat aids the budding of such vesicles from donor membranes. The major type of coat used by the cell is composed of clathrin, a three-legged protein that can form lattice-like coats on membranes destined for trafficking. In this review, I outline what we know about clathrin and discuss some recent advances in understanding the basic biology of this fascinating molecule, which include building a molecular model of a clathrin lattice and discovery of a new function for clathrin that occurs during mitosis. Received 12 December 2005; received after revision 21 March 2006; accepted 29 March 2006     

Acetylcholinesterase decrease in the optic lobe after unilateral eye deprivation

Unilateral eye enucleation in a teleost and a turtle results in progressive AChE decrease in the optic lobe controlateral to the extirpated eye. The final difference reaches 15% in teleost and more than 20% in turtle. No drastic differences in localization, but a rearrangement of histochemical pattern, due to the degeneration of retinal fibres, is noticed.     

Acetylcholinesterase decrease in the optic lobe after unilateral eye deprivation

Summary Unilateral eye enucleation in a teleost and a turtle results in progressive AChE decrease in the optic lobe controlateral to the extirpated eye. The final difference reaches 15% in teleost and more than 20% in turtle. No drastic differences in localization, but a rearrangement of histochemical pattern, due to the degeneration of retinal fibres, is noticed.     

Preparation of lymphocytes from small volumes of peripheral mouse blood

Summary A method was developed which allowed for the isolation of lymphocytes (95% of leukocytes in the final suspensions) from small volumes of peripheral mouse blood (38% recovery). The method proved of value for studies of murine lymphocytes which required biochemical analysis of samples from individual animals on a serial basis.This work was supported in part by a University College Faculty Research Grant.     

面向三峡库区水环境监测的分区多跳LEACH算法

针对无线传感器网络节点能量受限的问题，结合三峡库区水环境的具体应用环境，提出一种基于LEACH算法的改进型无线传感器网络节能路由算法——LEACH—PM。该算法将整个网络划分为若干个区域，各个分区内按轮进行建立分簇和传输数据。在簇建立阶段，考虑了节点的剩余能量；在数据传输阶段，采用单跳与多跳相结合的方式以降低网络的能耗。应用MATLAB对LEACH-PM算法与已有的LEACH算法进行仿真比较。实验结果显示，LEACH—M算法能更好平衡网络节点能耗，降低簇头节点能耗，延长整个网络的生存期。     

Primary culture of dispersed skin epidermal cells of rainbow trout Oncorhynchus mykiss Walbaum

This is the first report on a primary culture of dispersed skin epidermal cells of rainbow trout Oncorhynchus mykiss Walbaum. These primary cells revealed a low seeding efficiency after 3 days (11.6 ± 4.6%), whereas subcultured cells had a higher seeding efficiency at the same time point (75.5 ± 34.0%) and increased in cell number (150 – 200% of seeded cells after 20 to 30 days). The cells were characterized applying histological, immunocytochemical and ultrastructural methods. The culture consisted of undifferentiated keratinocytes. Mucous cells as well as differentiated epithelial cells were absent. To date the cells were cultured for maximally 9 passages and 402 days and therefore provide the possibility for long-term studies. Received 31 March 1998; received after revision 14 July 1998; accepted 14 July 1998