Receptor protein tyrosine phosphatases (RPTPs) are regulators of axon outgrowth and guidance in a variety of different vertebrate and invertebrate systems. Three RPTPs, CRYP-alpha, PTP-delta, and LAR, are expressed in...
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Receptor protein tyrosine phosphatases (RPTPs) are regulators of axon outgrowth and guidance in a variety of different vertebrate and invertebrate systems. Three RPTPs, CRYP-alpha, PTP-delta, and LAR, are expressed in overlapping but distinct patterns in the developing Xenopus retina, including expression in retinal ganglion cells (RGCs) as they send axons to the tectum (Johnson KG, Holt CE. 2000. Expression of CRYP-alpha, LAR, PTP-delta, and PTP-rho in the developing Xenopus visual system. Mech Dev 92:291-294). In order to examine the role of these RPTPs in visual system development, putative dominant negative RPTP mutants (CS-CRYP-alpha, CS-PTP-delta, and CS-LAR) were expressed either singly or in combination in retinal No effect was found on either retinal cell fate determination or on gross RGC axon guidance to the tectum. However, expression of these CS-RPTP constructs differentially affected the rate of RGC axon outgrowth. In vivo, expression of all three CS-RPTPs or CS-PTP-delta alone inhibited RGC axon outgrowth, while CS-LAR and CS-CRYP-alpha had no significant effect. In vitro, expression of CS-CRYP-alpha enhanced neurite outgrowth, while CS-PTP-delta inhibited neurite outgrowth in a substrate-dependent manner. This study provides the first in vivo evidence that RPTPs regulate retinal axon outgrowth. (C) 2001 John Wiley & Sons, Inc.
The present Study employed the gaze-contingent window paradigm to investigate parafoveal and peripheral cueing and masking effects on saccadic selectivity in a triple-conjunction visual search task. In the cueing cond...
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The present Study employed the gaze-contingent window paradigm to investigate parafoveal and peripheral cueing and masking effects on saccadic selectivity in a triple-conjunction visual search task. In the cueing conditions, the information shown outside the gaze-contingent window was restricted to the feature or feature pair shared between the target and a particular distractor type. In the masking conditions, no stimulus features were shown outside the window. Significant cueing and masking effects on saccadic selectivity were observed for saccades directed at items within the window, where all features were visible across experimental conditions. Cueing a particular feature or feature pair biased saccadic selectivity towards this feature or feature pair, while masking generally reduced saccadic selectivity. These findings support the concept of visual guidance being a preattentive process that operates in parallel across the display. (C) 2001 Published by Elsevier Science Ltd.
On their way toward their synaptic targets, motor growth cones encounter multiple choice points, where they are confronted with trajectory choices. We have previously shown that the zebrafish unplugged gene acts as a ...
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On their way toward their synaptic targets, motor growth cones encounter multiple choice points, where they are confronted with trajectory choices. We have previously shown that the zebrafish unplugged gene acts as a somite-derived cue controlling pathway choice of primary motor axons. Here, we demonstrate that this trajectory choice is not exclusively controlled by a single unplugged-dependent process, but depends on the coordinated function of additional cues. We also show that secondary motor neurons, most similar to those in birds and mammals, depend on the unplugged gene to navigate a choice point, suggesting that primary and secondary motor neurons share common mechanisms controlling axonal path selection. Moreover, we show that the unplugged gene plays an additional role guiding secondary motor axons through a single segmental nerve. Finally, we report that unplugged larvae display a striking pharyngeal arch defect, consistent with a dual function of the unplugged gene in axonal guidance and cell Motility. (C) 2001 Elsevier Science.
In this paper I investigate statistical properties of some guidance given by the FDA and by the CPMP on the planning, conduct and analysis of clinical trials with new anti-bacterial substances using an active control ...
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In this paper I investigate statistical properties of some guidance given by the FDA and by the CPMP on the planning, conduct and analysis of clinical trials with new anti-bacterial substances using an active control design. It is demonstrated that the non-inferiority margin proposed by the FDA has some undesirable features, and that the CPMP guidance may need further interpretation with respect to a statement that the non-inferiority margin may be smaller than 10 per cent for response rates > 90 per cent. A new margin is proposed that combines the desirable properties from both the FDA and the CPMP guidance. It is also shown that the approximate unconditional tests that are in use in such trials are quite unreliable with respect to preserving the nominal type I error. Unconditional exact tests are presented as a remedy for this issue. Copyright (C) 2001 John Wiley & Sons, Ltd.
Animals control contact with surfaces when locomoting, catching prey, etc. This requires sensorily guiding the rate of closure of gaps between effecters such as the hands, feet or jaws and destinations such as a ball,...
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Animals control contact with surfaces when locomoting, catching prey, etc. This requires sensorily guiding the rate of closure of gaps between effecters such as the hands, feet or jaws and destinations such as a ball, the ground and a prey. Control is generally rapid, reliable and robust, even with small nervous systems: the sensorimotor processes are therefore probably rather simple. We tested a hypothesis, based on general tau theory, that closing two gaps simultaneously, as required in many actions, might be achieved simply by keeping the taus of the gaps coupled in constant ratio. tau of a changing gap is defined as the time-to-closure of the gap at the current closure-rate. General tau theory shows that tau of a gap could, in principle, be directly sensed without needing to sense either the gap size or its rate of closure. In our experiment, subjects moved an effector (computer cursor) to a destination zone indicated on the computer monitor, to stop in the zone just as a moving target cursor reached it. The results indicated the subjects achieved the task by keeping tau of the gap between effector and target coupled to tau of the gap between the effector and the destination zone. Evidence of tau -coupling has also been found, for example, in bats guiding landing using echolocation. Thus, it appears that a sensorimotor process used by different species for coordinating the closure of two or more gaps between effecters and destinations entails constantly sensing the taus of the gaps and moving so as to keep the taus coupled in constant ratio.
The Relativistic Heavy Ion Collider (RHIC) is a high energy hadron accelerator built to study basic nuclear physics. It consists of two counter-rotating beams of fully stripped gold ions that are accelerated in two ri...
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The Relativistic Heavy Ion Collider (RHIC) is a high energy hadron accelerator built to study basic nuclear physics. It consists of two counter-rotating beams of fully stripped gold ions that are accelerated in two rings to an energy of 100 GeV/nucleon or protons at 250 GeV/c. The beams can be stored for a period of five to ten hours and brought into collision for experiments during that time. The first major physics objective is to recreate a state of matter, the quark-gluon plasma. that has been predicted to have existed at a short time after the creation of the universe. Because there are only a few other high energy particle accelerators like RHIC in the world, the rules promulgated in the US Code of Federal Regulations under the Atomic Energy Act, State regulations, or international guidance documents do not cover prompt radiation from accelerators to govern directly the design and operation of a superconducting collider. Special design criteria for prompt radiation were developed to provide guidance for the design of radiation shielding. Environmental Management at RHIC is accomplished through the ISO 14001 Environmental Management System. The applicability, benefits, and implementation of ISO 14001 within the framework of a large research accelerator complex are discussed in the paper.
To cross or not to cross the midline? This is the question that pathfinding axons in the developing CNS must answer. In the past few years the molecular mechanisms involved in this decision process have been determine...
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To cross or not to cross the midline? This is the question that pathfinding axons in the developing CNS must answer. In the past few years the molecular mechanisms involved in this decision process have been determined for neurones. A recent paper now shows that glia are also affected by these same mechanisms and that the presence of glia can tip the balance in favour of repulsion or attraction of neurones to the midline.
Prudent antimicrobial prescribing in the community may help to prevent the relentless increase in resistance, highlighted worldwide by numerous parliamentary documents. Antibiotic guidance, developed by primary care p...
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Prudent antimicrobial prescribing in the community may help to prevent the relentless increase in resistance, highlighted worldwide by numerous parliamentary documents. Antibiotic guidance, developed by primary care professionals and disseminated locally with outreach workshops, helps to reduce the use of broad-spectrum antimicrobials. Computerised guidance, audit of antibiotic use and restricted laboratory sensitivity reporting moves the prescriber towards the selection of recommended drugs. Educational campaigns and patient leaflets given at the consultation help to modify patients' expectations. Primary care physicians need to consider how much pharmaceutical representatives and free samples influence their prescribing. This multi-faceted approach needs to be backed up with a research programme developing the evidence base for management guidance of antimicrobial use in primary care, (C) 2001 Elsevier Science BN. and International Society of Chemotherapy. All rights reserved.
Background. Lumbar puncture (LP) may be unsuccessful clinically, prompting image-guided LP by radiologists. Objective. To investigate the utility of ultrasound (US) in diagnosing the cause of failed LP and in guiding ...
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Background. Lumbar puncture (LP) may be unsuccessful clinically, prompting image-guided LP by radiologists. Objective. To investigate the utility of ultrasound (US) in diagnosing the cause of failed LP and in guiding LP. Materials and methods. Neonates and infants referred for image-guided LP underwent spine US of the thecal sac. When indicated, image-guided LP was performed. Results. Forty-seven evaluations and interventions were performed in 32 patients. All patients were initially evaluated after failed blind LP attempts. Twenty-three of the initial US studies showed intrathecal and/or epidural echogenic hematoma, which obliterated the CSF space;5 showed minimal fluid, and 4 had normal examinations. LP was deferred or cancelled in 14 cases based upon initial US findings. Image-guided LP was performed 32 times in 19 patients. US guidance was used in 26, fluoroscopy in 3, and fluoroscopy with US assistance in 3. Using US, LP was performed in 9 patients with no visible CSF: 2 samples were sufficient for culture only. Six patients had minimal CSF US: 4 provided usable CSF samples. Clear CSF space was seen in 11: all had successful LP. Conclusions. US can disclose the cause of failed LP, can help determine whether or not to intervene further, and can provide guidance for LP.
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