检索结果-内蒙古大学图书馆

Visualizing tmRNA entry into a stalled ribosome

SCIENCE 2003年第5616期300卷 127-130页

作者： Valle, M Gillet, R Kaur, S Henne, A Ramakrishnan, V Frank, J MRC Mol Biol Lab Cambridge CB2 2QH England Hlth Res Inc Wadsworth Ctr Howard Hughes Med Inst Albany NY 12201 USA Inst Microbiol & Genet Gottingen Genom Lab D-37077 Gottingen Germany SUNY Albany Dept Biomed Sci Albany NY 12201 USA

Bacterial ribosomes stalled on defective messenger RNAs (mRNAs) are rescued by tmRNA, an similar to300-nucleotide-long molecule that functions as both transfer RNA (tRNA) and mRNA. Translation then switches from the defective message to a short open reading frame on tmRNA that tags the defective nascent peptide chain for degradation. However, the mechanism by which tmRNA can enter and move through the ribosome is unknown. We present a cryo-electron microscopy study at similar to13 to 15 angstroms of the entry of tmRNA into the ribosome. The structure reveals how tmRNA could move through the ribosome despite its complicated topology and also suggests roles for proteins S1 and SmpB in the function of tmRNA.

关键词： Alanine Anticodon Bacterial Proteins/metabolism Codon Codon, Terminator Cryoelectron Microscopy Guanosine Triphosphate/metabolism image processing, computer-assisted Models, Molecular Nucleic Acid Conformation Open Reading Frames Peptide Elongation Factor Tu/metabolism Protein Biosynthesis Pyridones/pharmacology Ribosomal Proteins/chemistry Ribosomal Proteins/metabolism Ribosomes/metabolism RNA, Bacterial/chemistry RNA, Bacterial/metabolism RNA, Messenger/chemistry RNA, Messenger/metabolism RNA, Transfer/chemistry RNA, Transfer/metabolism RNA-Binding Proteins/chemistry RNA-Binding Proteins/metabolism Thermus thermophilus/chemistry Thermus thermophilus/genetics Thermus thermophilus/metabolism

来源：评论

学校读者我要写书评

暂无评论

Integration of local features into global shapes: Monkey and human fMRI studies

引用

NEURON 2003年第2期37卷 333-346页

作者： Kourtzi, Z Tolias, AS Altmann, CF Augath, M Logothetis, NK Max Planck Inst Biol Cybernet D-72076 Tubingen Germany

The integration of local image features into global shapes was investigated in monkeys and humans using fMRI. An adaptation paradigm was used, in which stimulus selectivity was deduced by changes in the course of adaptation of a pattern of randomly oriented elements. Accordingly, we observed stronger activity when orientation changes in the adapting stimulus resulted in a collinear contour than a different random pattern. This selectivity to collinear contours was observed not only in higher visual areas that are implicated in shape processing, but also in early visual areas where selectivity depended on the receptive field size. These findings suggest that unified shape perception in both monkeys and humans involves multiple visual areas that may integrate local elements to global shapes at different spatial scales.

关键词： Adaptation, Physiological Adult Animals Form Perception/physiology Humans image processing, computer-assisted Macaca mulatta Magnetic Resonance Imaging Photic Stimulation Retina/physiology Visual Cortex/physiology

来源：评论

学校读者我要写书评

暂无评论

Salmonella SipA polymerizes actin by stapling filaments with nonglobular protein arms

引用

SCIENCE 2003年第5641期301卷 1918-1921页

作者： Lilic, M Galkin, VE Orlova, A VanLoock, MS Egelman, EH Stebbins, CE Rockefeller Univ Lab Struct Microbiol New York NY 10021 USA Univ Virginia Hlth Sci Ctr Dept Biochem & Mol Genet Charlottesville VA 22908 USA

Like many bacterial pathogens, Salmonella spp. use a type III secretion system to inject virulence proteins into host cells. The Salmonella invasion protein A ( SipA) binds host actin, enhances its polymerization near adherent extracellular bacteria, and contributes to cytoskeletal rearrangements that internalize the pathogen. By combining x-ray crystallography of SipA with electron microscopy and image analysis of SipA-actin. laments, we show that SipA functions as a "molecular staple," in which a globular domain and two nonglobular "arms" mechanically stabilize the. lament by tethering actin subunits in opposing strands. Deletion analysis of the tethering arms provides strong support for this model.

关键词： Actin Cytoskeleton/metabolism Actins/metabolism Bacterial Proteins/chemistry Bacterial Proteins/genetics Bacterial Proteins/metabolism Binding Sites Crystallography, X-Ray image processing, computer-assisted Microfilament Proteins/chemistry Microfilament Proteins/genetics Microfilament Proteins/metabolism Microfilaments/metabolism Microscopy, Electron Models, Molecular Protein Binding Protein Conformation Protein Folding Protein Structure, Secondary Protein Structure, Tertiary Recombinant Proteins/chemistry Recombinant Proteins/metabolism Salmonella typhimurium/chemistry Salmonella typhimurium/metabolism Sequence Deletion Subtilisin/metabolism

来源：评论

学校读者我要写书评

暂无评论

Control of localized structures in an optical feedback interferometer

引用

CHAOS 2003年第1期13卷 335-341页

作者： Ramazza, PL Boccaletti, S Bortolozzo, U Arecchi, FT Ist Nazl Ott Applicata I-50125 Florence Italy Univ Navarra Dept Appl Math & Phys E-31080 Pamplona Spain Univ Florence Dept Phys Florence Italy

We report a detailed experimental investigation of the dependence of localized structures, observed in a nonlinear optical device, on several control parameters. A first step of the study consists in the determination of the region of existence of localized states as a function of the system variables. Subsequently, we show how different control parameters can be used to the aim of tuning several localized structures properties;among these, of particular relevance are the contrast and the amplitude and frequency of the oscillations appearing on the tails of the structures. A discussion of the relation between the localized states here studied and the one predicted by general model for pattern forming systems is also given. (C) 2003 American Institute of Physics.

关键词： Biophysical Phenomena Biophysics image processing, computer-assisted Interferometry/methods Models, Statistical Statistics as Topic Thermodynamics

来源：评论

学校读者我要写书评

暂无评论

Early detection of radiation-induced structural changes in rat trabecular bone

引用

DENTOMAXILLOFACIAL RADIOLOGY 2003年第1期32卷 30-38页

作者： Kiyohara, S Sakurai, T Kashima, I Kanagawa Dent Coll Dept Oral & Maxillofacial Radiol Yokosuka Kanagawa 2388580 Japan

Objective: Early detection of bone changes following radiotherapy is very important. The aim of this study is to establish a radiographic image analysis method for early detection of radiation-induced trabecular bone changes. Methods: Thirty-five Wistar rats were used for the experimental model of trabecular bone changes, which were induced by X-ray irradiation with 30 Gy to develop simulated osteomyelitis. Standardized 2.2 x direct magnification radiography was performed immediately prior to X-ray irradiation and once a week for 4 weeks following irradiation. The latent X-ray images were scanned using a computed radiography (CR) system. Mathematical morphological processing was then applied to the CR image data, which allowed the bone trabecular pattern features to be extracted as skeletal binary images. The sensitivity and specificity for detecting early trabecular bone changes in CR images and in skeletal binary images were evaluated. Quantitative analyses with quantum level value (QL value), skeletal pixel percentage (SKP) and star volume analysis (skeletal volume (Vsk), skeletal space volume (Vsp)) were performed. Histopathological examination was also conducted for confirmation of physical changes in the bone. Results: Visual observation of the skeletal binary images provided a higher sensitivity than the CR images. In the quantitative analysis, SKP, Vsk and Vsp values provided higher sensitivity than QL values. Conclusion: The results of the present study suggest that a combined radiographic image analysis method using CR, mathematical morphological processing, SKP, Vsk and Vsp can be useful for the early detection of radiation-induced trabecular bone changes.

关键词： image processing, computer-assisted trabecular meshwork radiation effects rats, Wistar

来源：评论

学校读者我要写书评

暂无评论

Neural mechanisms of transient and sustained cognitive control during task switching

引用

NEURON 2003年第4期39卷 713-726页

作者： Braver, TS Reynolds, JR Donaldson, DI Washington Univ Dept Psychol St Louis MO 63130 USA Univ Stirling Dept Psychol Stirling FK9 4LA Scotland

A hybrid blocked and event-related functional magnetic resonance imaging (fMRI) study decomposed brain activity during task switching into sustained and transient components. Contrasting task-switching blocks against single-task blocks revealed sustained activation in right anterior prefrontal cortex (PFC). Contrasting task-switch trials against task-repeat and single-task trials revealed activation in left lateral PFC and left superior parietal cortex. In both sets of regions, activation dynamics were strongly modulated by trial-by-trial fluctuations in response speed. In addition, right anterior PFC;activity selectively covaried with the magnitude of mixing cost (i.e., task-repeat versus single-task trial performance), and left superior parietal activity selectively covaried with the magnitude of the switching cost (i.e., task-switch versus task-repeat trial performance). These results indicate a functional double dissociation in brain regions supporting different components of cognitive control during task switching and suggest that both sustained and transient control processes mediate the behavioral performance costs of task switching.

关键词： Adult Behavior/physiology Brain/physiology Brain Mapping Brain Mapping Cognition/physiology Evoked Potentials/physiology Female Functional Laterality Humans image processing, computer-assisted Magnetic Resonance Imaging Male Psychomotor Performance/physiology

来源：评论

学校读者我要写书评

暂无评论

Perceptibility curve test for digital radiographs before and after correction for attenuation and correction for attenuation and visual response

引用

DENTOMAXILLOFACIAL RADIOLOGY 2003年第6期32卷 372-378页

作者： Li, G Welander, U Yoshiura, K Shi, XQ McDavid, WD Karolinska Inst Dept Oral Radiol S-14104 Huddinge Sweden Kyushu Univ Fac Dent Sci Dept Oral & Maxillofacial Radiol Fukuoka 812 Japan Univ Texas Hlth Sci Ctr Dept Dent Diagnost Sci San Antonio TX USA

Objective: Two digital image processing methods, correction for X-ray attenuation and correction for attenuation and visual response, have been developed. The aim of the present study was to compare digital radiographs before and after correction for attenuation and correction for attenuation and visual response by means of a perceptibility curve test. Material and methods: Radiographs were exposed of an aluminium test object containing holes ranging from 0.03 mm to 0.30 mm with increments of 0.03 mm. Fourteen radiographs were exposed with the Dixi system (Planmeca Oy, Helsinki, Finland) and twelve radiographs were exposed with the F1 iOX system (Fimet Oy, Monninkyla, Finland) from low to high exposures covering the full exposure ranges of the systems. Radiographs obtained from the Dixi and F1 iOX systems were 12 bit and 8 bit images, respectively. Original radiographs were then processed for correction for attenuation and correction for attenuation and visual response. Thus, two series of radiographs were created. Ten viewers evaluated all the radiographs in the same random order under the same viewing conditions. The object detail having the lowest perceptible contrast was recorded for each observer. Perceptibility curves were plotted according to the mean of observer data. Results: The perceptibility curves for processed radiographs obtained with the F1 iOX system are higher than those for originals in the exposure range up to the peak, where the curves are basically the same. For radiographs exposed with the Dixi system, perceptibility curves for processed radiographs are higher than those for originals for all exposures. Perceptibility curves show that for 8 bit radiographs obtained from the F1 iOX system, the contrast threshold was increased in processed radiographs up to the peak, while for 12 bit radiographs obtained with the Dixi system, the contrast threshold was increased in processed radiographs for all exposures. When comparisons were made between radio

关键词： radiography dental radiography dental, digital perception image processing, computer-assisted

来源：评论

学校读者我要写书评

暂无评论

Quantification of posterior capsule opacification with round and sharp edge intraocular lenses

引用

OPHTHALMOLOGY 2003年第4期110卷 772-780页

作者： Auffarth, GU Golescu, A Becker, KA Völcker, HE Univ Heidelberg Dept Ophthalmol D-69120 Heidelberg Germany

Purpose: To quantitatively evaluate and compare intraocular lenses (IOLs) with a round or sharp optic edge design for posterior capsule opacification (PCO). Study Design: Prospective comparative observational case series. Participants/Materials: Photographs from 174 eyes were analyzed for PCO at the Department of Ophthalmology, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany. Main Outcome Measures: Part 1: 121 eyes of 121 patients were analyzed for quantification of PCO. IOLs evaluated were Corneal ACR6 (n = 21), Alcon Acrysof (n = 20), Allergan AR40 (n = 27), Pharmacia 811 one-piece polymethyl methacrylate (PM MA) IOL (n = 24), and Pharmacia 911 A silicone IOL (n = 29). Mean follow-up was 14.01 +/- 2.81 months;mean patient age was 73.2 +/- 7.3 years. The morphologic PCO formation was evaluated for the entire optic and in the central 3-mm zone. Part 11: In 53 eyes of 46 patients aged 73.4 +/- 10.8 years with an Alcon Acrysof IOL, PCO formation and capsulorrhexis/optic overlapping were analyzed 34.2 +/- 4 months after cataract surgery using EPCO Software. Results: Part 1: The PCO values of the entire optic were for Corneal ACR6, 1.93 +/- 0.62;PMMA, 0.64 +/- 0.63;AR40, 0.55 +/- 0.28;Alcon Acrysof, 0.145 +/- 0.27;and 0.161 +/- 0.181 for the Pharmacia 911A IOL (P < 0.01). The PCO values of the central 3-mm zone were for Corneal ACR6, 1.64 +/- 0.96;PMMA, 0.49 +/- 0.39;AR40, 0.22 +/- 0.32;Alcon Acrysof, 0.08 +/- 0.21;and 0.06 +/- 0.11 for the Pharmacia 911A IOL (P < 0.01). Part II: Average overlapping of capsulorrhexis and Acrysof IOL optic was 40.5% +/- 12.4%. There was a significant correlation between PCO values and overlapping (r = -0.69, P < 0.001). Conclusions: The sharp-edge IOL types (Alcon Acrysof and Pharmacia 911 A silicone IOL) resulted in statistically significantly lower PCO values for analysis of the entire optic area and central 3-mm zone. There was no statistically significant difference in PCO values between the two sharp-edge optic IOLs. An

关键词： Acrylic Resins Aged Capsulorhexis Cataract/etiology Cataract/prevention & control Humans image processing, computer-assisted Lens Capsule, Crystalline/pathology Lens Implantation, Intraocular Lenses, Intraocular Polymethyl Methacrylate Postoperative Complications/prevention & control Prospective Studies Prosthesis Design Silicone Elastomers

来源：评论

学校读者我要写书评

暂无评论

Determination of percent area density of epithelial and stromal components in development of prostatic hyperplasia in spontaneously hypertensive rats

引用

UROLOGY 2003年第2期61卷 484-489页

作者： Yamashita, M Zhang, XH Shiraishi, T Uetsuki, H Kakehi, Y Kagawa Med Univ Dept Urol Miki Kagawa 7610793 Japan Mie Univ Sch Med Dept Pathol 2 Tsu Mie Japan

Objectives. To determine the percent area density of epithelial and stromal components in the development of prostatic hyperplasia in spontaneously hypertensive (SH) rats. Methods. The ventral lobes of prostates obtained from male SH rats and their normotensive counterparts, Wistar Kyoto (WKY) rats, were examined histopathologically at 15, 29, 40, and 54 weeks of age (5 SH and WKY rats each at each age group). The degree of prostatic hyperplasia was evaluated with a score-chart protocol, histoscore. The percent area density of epithelium and stroma of the ventral prostate were determined using a computerized image analysis system. Results. Definite lesions of hyperplastic changes were demonstrated in the ventral prostate of SH rats from 15 to 54 weeks. In comparison with WKY rats, SH rats showed a significantly increased degree of prostatic hyperplasia as reflected by the histoscore values. Furthermore, the histoscore of the ventral prostate of SH rats increased with age (from 21.7 +/- 0.7 at 15 weeks to 26.1 +/- 0.4 at 54 weeks). The percent area density of epithelium and stroma were significantly increased in SH rats, and the ratio of stroma to epithelium ranged from 1:2.94 to 1:3.50 in SH rats but was maintained at 1:1.15 to 1:1.19 in WKY rats during the observation period. Conclusions. The hyperplastic changes of the ventral prostate may develop with advancing age in SH rats. The development of prostatic hyperplasia may result from both epithelial and stromal proliferation and may be predominantly expressed as a glandular type in SH rats.

关键词： Age Factors Animals Apoptosis/genetics Apoptosis/physiology Cell Count Cell Count Cell Division/genetics Cell Division/physiology Disease Models, Animal Epithelial Cells/pathology Epithelium/growth & development Epithelium/pathology Humans image processing, computer-assisted Male Prostate/growth & development Prostate/pathology Prostatic Hyperplasia/pathology Rats Rats, Inbred SHR/growth & development Rats, Inbred WKY

来源：评论

学校读者我要写书评

暂无评论

The impact of individual differences on the neural circuitry underlying sadness

引用

NEUROimage 2003年第2期19卷 354-364页

作者： Eugène, F Lévesque, J Mensour, B Leroux, JM Beaudoin, G Bourgouin, P Beauregard, M Univ Montreal Inst Geriatr Ctr Rech Montreal PQ H3W 1W5 Canada Univ Montreal Dept Psychol Montreal PQ H3C 3J7 Canada Ctr Hosp Univ Montreal Hop Notre Dame Dept Radiol Montreal PQ Canada Univ Montreal Fac Med Dept Radiol Montreal PQ H3C 3J7 Canada Univ Montreal Fac Med Ctr Rech Sci Neurol Montreal PQ H3C 3J7 Canada

Several functional neuroimaging studies have been carried out in healthy subjects to investigate the neural correlates of sadness. Importantly, there is little consistency among the results of these studies. Hypothesizing that individual differences may account for the discrepancies among these investigations, we conducted two functional magnetic resonance imaging (fMRI) studies to identify the neural circuitry underlying this basic emotion. In these two methodologically identical studies, two different groups (n = 10 for each study) of the first of these studies, sadness was correlated with significant loci of activation in the anterior temporal pole and insula (P < 0.05, corrected). In the second study, however, sadness was correlated with significant activation in the orbitofrontal and medial prefrontal cortices (P < 0.05, corrected). In addition, individual statistical parametric maps revealed a marked degree of interindividual variability in both Study 1 and Study 2. These results strongly support the view that individual differences may be responsible for the inconsistencies found in the literature regarding the neural substrates of sadness and of other basic emotions. These findings also suggest that individual data should be reported in addition to group data, because they provide useful information about the variability present in the subjects investigated and, thus, about the typicality and generalizability of the results. (C) 2003 Elsevier Science (USA). All rights reserved.

关键词： Adult Brain Mapping Brain Mapping Cerebral Cortex/physiology Dominance, Cerebral/physiology Echo-Planar Imaging Emotions/physiology Female Humans image Enhancement image processing, computer-assisted Individuality Magnetic Resonance Imaging Mathematical Computing Nerve Net/physiopathology Oxygen Consumption/physiology Temporal Lobe/physiology

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：