In the present study, the influence of astrocyte alignment on the direction and length of regenerating neurites was examined in vitro. Astrocytes were experimentally manipulated by different approaches to create longi...
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In the present study, the influence of astrocyte alignment on the direction and length of regenerating neurites was examined in vitro. Astrocytes were experimentally manipulated by different approaches to create longitudinally aligned monolayers. When cultured on the aligned monolayers, dorsal root ganglion neurites grew parallel to the long axis of the aligned astrocytes and were significantly longer than controls. Engineered monolayers expressed linear arrays of fibronectin, laminin, neural cell adhesion molecule, and chondroitin sulfate proteoglycan that were organized parallel to one another, suggesting that a particular spatial arrangement of these molecules on the astrocyte surface may be necessary to direct nerve regeneration in vivo. In contrast, no bias in directional outgrowth was observed for neurites growing on unorganized monolayers. The results suggest that altering the organization of astrocytes and their scar-associated matrix at the lesion site may be used to influence the direction and the length of adjacent regenerating axons in the damaged brain and spinal cord. (C) 2003 Elsevier Science (USA). All rights reserved.
This paper is in response to a previous article;in a Special Issue of Toxicology Letters. That article criticised the current regulatory framework in the European, Union for the environmental risk assessment of veteri...
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This paper is in response to a previous article;in a Special Issue of Toxicology Letters. That article criticised the current regulatory framework in the European, Union for the environmental risk assessment of veterinary medicinal products (VMPs) and feed additives (FAs), in particular the ongoing process of international harmonisation of guidance. This response addresses the concerns raised in relation to veterinary medicinal products and demonstrates that the VICH process has been brought within the scope of current EU regulatory processes for veterinary medicines and therefore is not separate to them. Consultation with stakeholders takes place throughout the VICH process, with an additional period of open public consultation before guidance is adopted and implemented. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.
Neuroembryogenesis critically depends on signaling molecules that modulate cell proliferation, differentiation, and the formation of neural networks. In an attempt to identify potential morphogenetic active components...
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Neuroembryogenesis critically depends on signaling molecules that modulate cell proliferation, differentiation, and the formation of neural networks. In an attempt to identify potential morphogenetic active components that are distributed in a graded fashion in the developing nervous system, we generated substraction libraries of the embryonic nasal and temporal chick retina. Selected clones were analyzed by sequencing, Northern and Western blotting, in situ hybridization, and immunocytochemistry. Retinal fatty acid-binding protein (R-FABP) mRNA displayed the most pronounced topographic gradient. R-FABP was most strongly expressed in nasal retina, though topographic differences were not evident on the protein level. R-FABP expression was subject to a pronounced spatio-temporal regulation. Peak expression was at the period of cell generation/migration and differentiation. To identify the cell types involved in R-FAPB synthesis, ganglion cells as the only retinal projection neurons were enriched by enzymatic delayering. Cell somata, axons, and growth cones were R-FABP immunoreactive. Most interestingly, R-FABP immunoreactivity was critically dependent on the growth substratum. It was abrogated when axons grew on isolated glial endfeet. Radial glia purified by complement-mediated cytolysis also expressed R-FABP at moderate levels. The expression level was significantly increased during mitosis and dropped down again in postmitotic cells. Further on, transient loss of cell-cell and substratum contact induced a subcellular redistribution of R-FABP. In conjunction with the morphogen-binding activity of other FABP family members and their impact on cell migration and tissue differentiation, R-FABP characteristics suggest a regulatory function during retinal histogenesis but not during topographic map formation. (C) 2003 Elsevier Science (USA). All rights reserved.
Caenorhabditis elegans has two genes, unc-59 and unc-61, encoding septin-family GTPases. Mutations in the septin genes cause defects in locomotory behavior that have been previously attributed to cytokinesis failures ...
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Caenorhabditis elegans has two genes, unc-59 and unc-61, encoding septin-family GTPases. Mutations in the septin genes cause defects in locomotory behavior that have been previously attributed to cytokinesis failures in postembryonic neuroblasts. We find that mutations in either septin gene frequently cause uncoordination in newly hatched larvae in the absence of cytokinesis failures. The septins exhibit developmentally regulated expression, including expression in various neurons at times when processes are extending and synapses are forming. Motor neurons in the mutant larvae display defects in multiple aspects of axonal migration and guidance that are likely to be responsible for the locomotory behavior defects. The septins are also expressed in migrating distal. tip cells, which are leaders for gonad arm extension. Septin mutants affect morphology of the distal tip cells, as well as their migration and guidance during gonadogenesis, These results suggest that septins may be generally required for developmental migrations and pathfinding. (C) 2003 Elsevier Inc. All rights reserved.
AIM: To determine factors influencing diagnostic yield in computed tomography (CT)-guided biopsy of lung lesions. MATERIALS AND METHODS: One hundred and ninety-five consecutive CT-guided lung biopsies were performed i...
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AIM: To determine factors influencing diagnostic yield in computed tomography (CT)-guided biopsy of lung lesions. MATERIALS AND METHODS: One hundred and ninety-five consecutive CT-guided lung biopsies were performed in 182 patients between August 1995 and September 2000 and either fine-needle aspirate samples for cytology or core biopsy samples for histology were collected. Procedures were divided into a diagnostic group (true-positive and true-negative results) and a non-diagnostic group (false-positive and false-negative results) and the factors affecting diagnostic accuracy assessed. RESULTS: One hundred and fifty-six lesions (86%) were malignant, and 26 (14%) were benign. More than one biopsy was performed for 12 lesions. One hundred and thirty-two biopsies were true-positive, 27 true-negative and 36 false-negative. No false-positive results occurred in the study. Overall diagnostic accuracy was 81.5%. Significantly more core biopsies than fine-needle aspirates were diagnostic: 93 versus 78% (p < 0.005). No difference was found in frequency of pneumothorax between these two groups. There was a difference in the average depth from the pleural surface of lesions in the diagnostic and non-diagnostic groups, but this did not attain statistical significance: 9.8 versus 17.2 mm (p = 0.054). CONCLUSION: In this study CT-guided lung biopsy core biopsy was a more accurate method of tissue sampling than fine-needle aspiration, and was not associated with an excess of complications. (C) 2003 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Coordinated motor behaviors rely on a maze-like network of axonal connections between motoneurons and the body musculature. Since the time of the Renaissance, scientists have been fascinated by the question of how suc...
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Coordinated motor behaviors rely on a maze-like network of axonal connections between motoneurons and the body musculature. Since the time of the Renaissance, scientists have been fascinated by the question of how such complex, yet stereotypic, connectivity arises during embryogenesis. Here. we review the long journey of motor axons, which traverse diverse territories along predetermined routes riddled with a wealth of divergent pathway options. We conclude that motor axon migration occurs in a stepwise manner, with each step being controlled by local guidance cues, that motor axons rely on some of the same cues that also control axon migration within the CNS, and that, due to species-specific anatomical variations, the cell types providing such local cues may vary. Although studies of motor axon migration have not yet resulted in a complete understanding of the cellular and molecular mechanisms regulating this process, we have come a long way since the days of da Vinci. (C) 2003 Elsevier Inc. All rights reserved.
The World Health Organization's International Programme on Chemical Safety (IPCS), the Organization for Economic Cooperation and Development (OECD), and the U.S. Environmental Protection Agency have developed a co...
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The World Health Organization's International Programme on Chemical Safety (IPCS), the Organization for Economic Cooperation and Development (OECD), and the U.S. Environmental Protection Agency have developed a collaborative partnership to foster integration of assessment approaches for human health and ecological risks. This paper presents the framework developed by that group. Integration provides coherent expressions of assessment results, incorporates the interdependence of humans and the environment, uses sentinel organisms, and improves the efficiency and quality of assessments relative to independent human health and ecological risk assessments. The paper describes how integration can occur within each component of risk assessment, and communicates the benefits of integration at each point. The goal of this effort is to promote the use of this internationally accepted guidance as a basis for harmonization of risk assessment.
作者：
Thies, EDavenport, RWUniv Maryland
Dept Biol Program Neurosci & Cognit Sci College Pk MD 20742 USA DESY
Max Planck Unit Struct Mol Biol D-2000 Hamburg Germany
Many external signals influence growth cone motility, pathfinding, and the formation of synapses that lead to the final map formation of the retinotectal system. Chick temporal retinal ganglion cell axons (RGCs) colla...
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Many external signals influence growth cone motility, pathfinding, and the formation of synapses that lead to the final map formation of the retinotectal system. Chick temporal retinal ganglion cell axons (RGCs) collapse and retract after encountering posterior tectal cells in vitro. During this process lateral extensions appear along the RGC axonal shaft. Lateral extensions appear as nascent interstitial axonal branches and also as defasciculating growth cones that are trailing along the pioneer axon. RGC branching controlled by repellent tectal cues has recently been shown to be the critical event in retinotectal map development. The intracellular mechanism underlying this phenomenon, however, is not understood. Inhibiting RhoA with either C3 toxin or inhibiting p160Rock kinase, an effector of RhoA, with Y27632 inhibited collapse, retraction, and the number of axons that showed lateral extensions. Lateral extension length increased significantly. Inhibiting Rac1A and cdc42 with cell permeable peptide inhibitors did not inhibit collapse of growth cones, but did inhibit axon retraction. In addition, the number of axons that showed lateral extensions and lateral extension length were significantly reduced. A dynamic cytoskeleton is necessary to react to incoming guidance information. This study addresses the problems of how growth cone motility and branching or defasciculation are affected by Rho-GTPases as extracellular signals are transmitted to the cytoskeleton. (C) 2002 Wiley Periodicals, Inc.
This study uses National Educational Longitudinal Study data to show that information about higher education, guidance, and essential preparatory actions taken by secondary students influence whether they will attend ...
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This study uses National Educational Longitudinal Study data to show that information about higher education, guidance, and essential preparatory actions taken by secondary students influence whether they will attend post-secondary educational institutions (PEIs) within 2 years of high school graduation, and, if so, what types of institutions. The conceptual framework is embedded in research on college choice and talent loss. Talent loss is described as the occurrence of promising students not reaching their full educational potential. Choice theory attempts to explain the myriad factors contributing to individuals' postsecondary destinations. We find that increased levels of information, guidance, and critical actions taken are positively and significantly associated with initial enrollment in a 4-year PET, as opposed to enrollment in a 2-year PEI (full or part time) or no enrollment. These factors explain a large part of the effect of socioeconomic status on postsecondary destination, controlling for high school achievement.
Decisional guidance is defined as how a decision support system (DSS) influences its users as they structure and execute the decision-making process. It is assumed that decisional guidance has profound effects on deci...
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Decisional guidance is defined as how a decision support system (DSS) influences its users as they structure and execute the decision-making process. It is assumed that decisional guidance has profound effects on decision making, but these effects are understudied and empirically unproven. This paper describes an empirical, laboratory-experinient-based evaluation of the effectiveness of deliberate decisional guidance and its four types. We developed and used a comprehensive model consisting of four evaluation criteria: decision quality, user satisfaction, user learning, and decision-making efficiency. On these criteria, we compared decisional guidance versus no guidance, informative versus suggestive decisional guidance, and predefined versus dynamic decisional guidance. We found that deliberate decisional guidance was more effective on all four criteria;suggestive guidance was more effective in improving decision quality and user satisfaction, and informative guidance was more effective in user learning about the problem domain, whereas dynamic guidance was more effective than predefined guidance in improving decision quality and user learning;and both suggestive guidance and dynamic guidance reduced the decision time.
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