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Gilbert SL Zhang L Forster ML Anderson JR Iwase T Soliven B Donahue LR Sweet HO Bronson RT Davisson MT Wollmann RL Lahn BT 《Nature genetics》2006,38(2):245-250
Hypertonia, which results from motor pathway defects in the central nervous system (CNS), is observed in numerous neurological conditions, including cerebral palsy, stroke, spinal cord injury, stiff-person syndrome, spastic paraplegia, dystonia and Parkinson disease. Mice with mutation in the hypertonic (hyrt) gene exhibit severe hypertonia as their primary symptom. Here we show that hyrt mutant mice have much lower levels of gamma-aminobutyric acid type A (GABA(A)) receptors in their CNS, particularly the lower motor neurons, than do wild-type mice, indicating that the hypertonicity of the mutants is likely to be caused by deficits in GABA-mediated motor neuron inhibition. We cloned the responsible gene, trafficking protein, kinesin binding 1 (Trak1), and showed that its protein product interacts with GABA(A) receptors. Our data implicate Trak1 as a crucial regulator of GABA(A) receptor homeostasis and underscore the importance of hyrt mice as a model for studying the molecular etiology of hypertonia associated with human neurological diseases. 相似文献
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Small molecules such as NO, O2, CO or H2 are important biological ligands that bind to metalloproteins to function crucially in processes such as signal transduction, respiration and catalysis. A key issue for understanding the regulation of reaction mechanisms in these systems is whether ligands gain access to the binding sites through specific channels and docking sites, or by random diffusion through the protein matrix. A model system for studying this issue is myoglobin, a simple haem protein. Myoglobin has been studied extensively by spectroscopy, crystallography, computation and theory. It serves as an aid to oxygen diffusion but also binds carbon monoxide, a byproduct of endogenous haem catabolism. Molecular dynamics simulations, random mutagenesis and flash photolysis studies indicate that ligand migration occurs through a limited number of pathways involving docking sites. Here we report the 1.4 A resolution crystal structure of a ligand-binding intermediate in carbonmonoxy myoglobin that may have far-reaching implications for understanding the dynamics of ligand binding and catalysis. 相似文献
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Arnold L. Sweet 《Journal of forecasting》1985,4(2):235-243
This paper presents expressions for the variance of the forecast error for arbitrary lead times for both the additive and multiplicative Holt-Winters seasonal forecasting models. It is shown that even when the smoothing constants are chosen to have values between zero and one, when the period is greater than four, the variance may not be finite for some values of the smoothing constants. In addition, the regions where the variance becomes infinite are almost the same for both models. These results are of importance for practitioners, who may choose values for the smoothing constants arbitrarily, or by searching on the unit cube for values which minimize the sum of the squared errors when fitting the model to a data set. It is also shown that the variance of the forecast error for the multiplicative model is nonstationary and periodic. 相似文献
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记述中国〖XC5XCC.TIF〗目2新种, 井冈山无齿股〖XC5XCC.TIF〗Parasipyloideajinggangshanensis Ho, sp nov.及七州瘦〖XC5XCC.TIF〗Macellina qizhouense Ho, sp nov。新种模式标本存放于广州中山大学生物博物馆。 相似文献
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在网络安全系统中,基于软件的包分类系统受处理器性能与软件串行执行等因素影响,包分类速度有限.为了提高包分类和规则预处理的速度并快速适应规则的更新,本文用硬件电路与通过预规则处理生成的二叉树结构,设计并实现了基于FPGA的包分类系统.实验结果显示:50 000个规则的预处理时间不超过0.051 s;系统的包分类平均速度大于10 Gbit/s,Snort入侵检测系统的规则头的分类平均速度大于20 Gbit/s. 相似文献
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王丽凤女士邀请我替伍连德(Wu Lien-Teh,1879-1960年)博士<鼠疫斗士--伍连德博士自述>(Plague Fighter;the Autobiography of a Modern Chinese Physician,Cambridge;W.Heffer & Sons,1959;以下简称<自述>)的中文版作序.回想60多年前我大学生时代,伍连德博士就曾鼓励我多多写作,假如我没有受到他的影响,大概不会有这篇拙作向读者们献丑了.伍玉玲博士在<回忆鼠疫斗士伍连德博士>(Memories of the Plague Fighter Dr.Wu Li-en-Teh,Singapore,New Jersey;World Scientific,1995;以下简称<回忆>)一书的序文中,已经提及我是在1941年由伍博士的一位胞弟伍德安先生介绍而认识他.我进大学前,曾在一所英文中学做临时教员.伍博士的两位公子--长生和长员--先后在我所教的班念书,他的长女玉玲、次女玉珍也先后和我一起考进同一所大学,当时他的三千金玉珠还年幼.伍博士是我申请升学的推荐人. 相似文献
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A new class of angiotensin-converting enzyme inhibitors 总被引:22,自引:0,他引:22
A A Patchett E Harris E W Tristram M J Wyvratt M T Wu D Taub E R Peterson T J Ikeler J ten Broeke L G Payne D L Ondeyka E D Thorsett W J Greenlee N S Lohr R D Hoffsommer H Joshua W V Ruyle J W Rothrock S D Aster A L Maycock F M Robinson R Hirschmann C S Sweet E H Ulm D M Gross T C Vassil C A Stone 《Nature》1980,288(5788):280-283
Much current attention focuses on the renin-angiotensin system in relation to mechanisms controlling blood pressure and renal function. Recent demonstrations (ref. 1, ref. 2 and refs therein) that angiotensin-converting enzyme inhibitors show promising clinical antihypertensive properties have been of particular interest. We now report on the design of a novel series of substituted N-carboxymethyl-dipeptides which are active in inhibiting angiotensin-converting enzyme at nanomolar levels. We suggest that these compounds are transition-state inhibitors and that extensions of this design to other metalloendopeptidases merit further study. 相似文献