scholarly journals Anomalous ipsilateral optic fibre projection in Xenopus induced by larval tectal ablation

Development ◽  
1979 ◽  
Vol 50 (1) ◽  
pp. 111-122
Author(s):  
Charles Straznicky ◽  
John Glastonbury
Keyword(s):  
Contact Guidance ◽  
Retinal Projection ◽  
Guidance Cues ◽  
Optic Fibre ◽  
The Right

Unilateral left tectal ablation was carried out in Xenopus between stage 48 and 1 month after metamorphosis. Six to 12 weeks after metamorphosis the retinal projection from the right eye was examined with the use of [3H]proline autoradiography. The autoradiographs indicated that optic fibres whose tectal target was destroyed recrossed to the ipsilateral tectum and basal optic nucleus via the posterior and pretectal commissures. No anomalous recrossing occurred if the tectal ablation was carried out at stage 58 or later. The aberrant optic fibres were restricted to the rostrolateral and central parts of the ipsilateral tectum and they terminated in a discontinuous manner. It is concluded that available surfaces serving as contact guidance cues are needed to direct aberrant optic fibres to the ipsilateral tectum.

scholarly journals Transfer of assembled collagen fibrils to flexible substrates for mechanically tunable contact guidance cues

2018 ◽  
Vol 10 (11) ◽  
pp. 705-718 ◽  
Author(s):  
Juan Wang ◽  
Joseph Koelbl ◽  
Anuraag Boddupalli ◽  
Zhiqi Yao ◽  
Kaitlin M. Bratlie ◽  
...  
Keyword(s):  
Wound Healing ◽  
Cancer Invasion ◽  
Collagen Fibrils ◽  
Contact Guidance ◽  
Flexible Substrates ◽  
Guidance Cues ◽  
Aligned Fibers

Contact guidance or bidirectional migration along aligned fibers modulates many physiological and pathological processes such as wound healing and cancer invasion.

scholarly journals Ultra-fast broadband in New Zealand: Progress Accelerating

2015 ◽  
Vol 3 (4) ◽  
pp. 12
Author(s):  
Rohan MacMahon ◽  
Murray Milner
Keyword(s):  
New Zealand ◽  
Service Delivery ◽  
Service Providers ◽  
Public Lands ◽  
Population Coverage ◽  
Broadband Service ◽  
Retail Service ◽  
Additional Funding ◽  
Optic Fibre ◽  
The Right

The New Zealand Government’s Ultrafast Broadband (UFB) initiative is now more than halfway completed. Pleasingly, deployment of Fibre To The Premises (FTTP) has tracked ahead of schedule over the last two years. As at September 2015, deployment was 56% complete, with over 800,000 households and businesses able to connect, equating to around 44% of the NZ population able to connect to an optic fibre broadband service. Communal deployment has been completed in 11 of the 35 eligible towns and cities, meaning fibre has been laid on public lands, enabling every household to order a UFB connection. A further eight towns/ cities are expected to be completed by June 2016. Uptake of UFB services is accelerating as Retail Service Providers (RSPs) increasingly see UFB as the right choice for themselves and their customers. Presently around 10,000 households and businesses connect every month. With over 130,000 connections in place as at September 2015, uptake is around one in 6, indicating that there is still a long way to go for New Zealanders to connect to improved broadband. Importantly, deployment to “priority” premises (businesses, schools and health facilities) is close to completion, and many of these customers report that UFB usage has helped them improve business productivity or service delivery. The goal for the UFB initiative is recognised as being delivered well by the New Zealand Government, to the point that at the 2014 election it committed to provide additional funding to increase the FTTP rollout from 75% population coverage to 80%.

Electric fields, contact guidance and the direction of nerve growth

Development ◽  
1986 ◽  
Vol 94 (1) ◽  
pp. 245-255
Author(s):  
Colin D. McCaig
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Free Choice ◽  
Contact Guidance ◽  
Orthogonal Direction ◽  
Nerve Growth ◽  
Guidance Cues

Nerve orientation in response to electrical guidance cues in one direction and contact guidance cues in an orthogonal direction has been studied. Where neurites had a free choice between following contact guidance cues or electrical cues, the direction of nerve growth was determined predominantly by the vector of the applied electric field.

Regeneration of an abnormal ipsilateral visuotectal projection in Xenopus is delayed by the presence of optic fibres from the other eye

Development ◽  
1980 ◽  
Vol 57 (1) ◽  
pp. 129-141
Author(s):  
Charles Straznicky ◽  
David Tay ◽  
John Glastonbury
Keyword(s):  
Optic Nerve ◽  
The Other ◽  
Nerve Section ◽  
Eye Enucleation ◽  
Contralateral Projection ◽  
Electrophysiological Findings ◽  
Optic Fibre ◽  
Tectal Neurons ◽  
The Right ◽  
Early Regeneration

Optic fibre regeneration was studied by [3H]proline autoradiography and by mapping electrophysiologically the direct visuotectal projections to thecontralateral and ipsilateral tecta 12–16 weeks after sectioning the right optic nerve in Xenopus two to four weeks after metamorphosis. The experiments were carried out in three groups: (A) optic nerve section in newly metamorphosed animals withembryonic left-eye enucleation; (B) optic nerve section with simultaneous left-eye enucleation; and (C) optic nerve section with delayed left-eye enucleation 5–31 days prior to sacrifice. In all but three animals regenerated optic fibres were demonstrated morphologically both in the contralateral and ipsilateral tecta. The contralateral visuotectal projectionwas fully restored within the 12–16 weeks in all animals. In animals with embryonic enucleation or in those where the enucleation was carried out simultaneously with optic nerve section, a direct ipsilateral visuotectal projection was established at the same time as the restoration of the contralateral projection. In contrast, no direct ipsilateral visuotectal projection was detectable in the presence of optic fibres from the other eye in the doubly innervated tecta. However, 14–31 days after the removal of the incumbent optic fibres by left-eye enucleation a direct visuotectal projection from the right eye to the ipsilateral tectum was established, and its polarity corresponded to the normal contralateral retinotectal projection. The apparent disparity between morphological and electrophysiological findings in the doubly innervated tectum suggests that superimposed optic fibres are unable to form normal synaptic relations with tectal neurons during early regeneration, delaying the establishment of the induced direct ipsilateral visuotectal projection.

scholarly journals Requirement of Pax6 for the integration of guidance cues in cell migration

2017 ◽  
Vol 4 (10) ◽  
pp. 170625 ◽  
Author(s):  
Miguel Arocena ◽  
Ann M. Rajnicek ◽  
Jon Martin Collinson
Keyword(s):  
Cell Migration ◽  
Electric Fields ◽  
Neural Development ◽  
Mouse Embryos ◽  
Contact Guidance ◽  
Wild Type ◽  
General Direction ◽  
Vast Array ◽  
Guidance Cues ◽  
Flat Substrate

The intricate patterns of cell migration that are found throughout development are generated through a vast array of guidance cues. Responding integratively to distinct, often conflicting, migratory signals is probably crucial for cells to reach their correct destination. Pax6 is a master transcription factor with key roles in neural development that include the control of cell migration. In this study, we have investigated the ability of cells derived from cortical neurospheres from wild-type (WT) and Pax6 −/− mouse embryos to integrate diverging guidance cues. We used two different cues, either separately or in combination: substratum nanogrooves to induce contact guidance, and electric fields (EFs) to induce electrotaxis. In the absence of an EF, both WT and Pax6 −/− cells aligned and migrated parallel to grooves, and on a flat substrate both showed marked electrotaxis towards the cathode. When an EF was applied in a perpendicular orientation to grooves, WT cells responded significantly to both cues, migrating in highly oblique trajectories in the general direction of the cathode. However, Pax6 −/− cells had an impaired response to both cues simultaneously. Our results demonstrate that these neurosphere derived cells have the capacity to integrate diverging guidance cues, which requires Pax6 function.

scholarly journals Polarization of hippocampal neurons with competitive surface stimuli: contact guidance cues are preferred over chemical ligands

2006 ◽  
Vol 4 (13) ◽  
pp. 223-233 ◽  
Author(s):  
Natalia Gomez ◽  
Shaochen Chen ◽  
Christine E Schmidt
Keyword(s):  
Hippocampal Neurons ◽  
Artificial Substrates ◽  
Contact Guidance ◽  
Neural Engineering ◽  
Environmental Signals ◽  
Guidance Cues ◽  
Unique System ◽  
Extracellular Stimuli ◽  
Regeneration Processes ◽  
Microfabrication Techniques

Neuronal behaviour is profoundly influenced by extracellular stimuli in many developmental and regeneration processes. Understanding neuron responses and integration of environmental signals could impact the design of successful therapies for neurodegenerative diseases and nerve injuries. Here, we have investigated the influence of localized extracellular cues on polarization (i.e. axon formation) of hippocampal neurons. Electron-beam lithography, microfabrication techniques and protein immobilization were used to create a unique system that provided simultaneous and independent chemical and physical cues to individual neurons. In particular, we analysed competitive responses between simultaneous stimulation with chemical ligands, including immobilized nerve growth factor and laminin, and contact guidance cues mediated by surface topography (i.e. microchannels). Contact guidance cues were preferred 70% of the time over chemical ligands by neurons extending axons, which suggests a stronger stimulation mechanism triggered by topography. This investigation contributes to the understanding of neuronal behaviour on artificial substrates, which is applicable to the creation of artificial environments for neural engineering applications.

Survival of ganglion cells which form the retino-retinal projection during optic nerve regeneration in the frog

1993 ◽  
Vol 10 (4) ◽  
pp. 681-686 ◽  
Author(s):  
M. Tennant ◽  
S. R. Bruce ◽  
L. D. Beazley
Keyword(s):  
Optic Nerve ◽  
Horseradish Peroxidase ◽  
Nerve Regeneration ◽  
Ganglion Cells ◽  
Retinal Projection ◽  
Optic Nerve Regeneration ◽  
Diamidino Yellow ◽  
The Right ◽  
The Brain

AbstractDuring optic nerve regeneration in the frog, axons transiently grow along the opposite optic nerve forming a retino-retinal projection. In the present study, we crushed the left optic nerve in the frog Litoria (Hyla) moorei and later applied horseradish peroxidase (HRP) or diamidino yellow (DY) to the right optic nerve. In one series, retinae were examined 3 days after application of the tracer. The retino-retinal projection was found to be maximal at 5 weeks, fell significantly by 7 weeks, and returned to close-to-normal levels by 24 weeks. In a second series, we applied DY at 5 weeks as before but did not sacrifice the frogs until 7 weeks. Numbers of labeled ganglion cells were not significantly different from those frogs in the first series labeled and examined at 5 weeks. We conclude that ganglion cells giving rise to the retino-retinal projection had not died in appreciable numbers, presumably being sustained by collateral axons in the brain.

scholarly journals Ultra-fast broadband in New Zealand: Progress Accelerating

2015 ◽  
Vol 3 (4) ◽  
pp. 12-25
Author(s):  
Rohan MacMahon ◽  
Murray Milner
Keyword(s):  
New Zealand ◽  
Service Delivery ◽  
Service Providers ◽  
Public Lands ◽  
Population Coverage ◽  
Broadband Service ◽  
Retail Service ◽  
Additional Funding ◽  
Optic Fibre ◽  
The Right

The New Zealand Government’s Ultrafast Broadband (UFB) initiative is now more than halfway completed. Pleasingly, deployment of Fibre To The Premises (FTTP) has tracked ahead of schedule over the last two years. As at September 2015, deployment was 56% complete, with over 800,000 households and businesses able to connect, equating to around 44% of the NZ population able to connect to an optic fibre broadband service. Communal deployment has been completed in 11 of the 35 eligible towns and cities, meaning fibre has been laid on public lands, enabling every household to order a UFB connection. A further eight towns/ cities are expected to be completed by June 2016. Uptake of UFB services is accelerating as Retail Service Providers (RSPs) increasingly see UFB as the right choice for themselves and their customers. Presently around 10,000 households and businesses connect every month. With over 130,000 connections in place as at September 2015, uptake is around one in 6, indicating that there is still a long way to go for New Zealanders to connect to improved broadband. Importantly, deployment to “priority” premises (businesses, schools and health facilities) is close to completion, and many of these customers report that UFB usage has helped them improve business productivity or service delivery. The goal for the UFB initiative is recognised as being delivered well by the New Zealand Government, to the point that at the 2014 election it committed to provide additional funding to increase the FTTP rollout from 75% population coverage to 80%.

Investor-State Dispute Settlement under NAFTA Chapter 11: The Shape of Things to Come?

1998 ◽  
Vol 35 ◽  
pp. 263-290
Author(s):  
J. Anthony VanDuzer
Keyword(s):  
Free Trade Agreement ◽  
Dispute Settlement ◽  
Trade Agreement ◽  
Minimum Standards ◽  
The North ◽  
State Behaviour ◽  
Nafta Chapter 11 ◽  
To Come ◽  
The Right

SummaryRecently, there has been a proliferation of international agreements imposing minimum standards on states in respect of their treatment of foreign investors and allowing investors to initiate dispute settlement proceedings where a state violates these standards. Of greatest significance to Canada is Chapter 11 of the North American Free Trade Agreement, which provides both standards for state behaviour and the right to initiate binding arbitration. Since 1996, four cases have been brought under Chapter 11. This note describes the Chapter 11 process and suggests some of the issues that may arise as it is increasingly resorted to by investors.

What face familiarity feelings say about the lateralization of specific entities within the core system

2019 ◽  
Vol 42 ◽  
Author(s):  
Guido Gainotti
Keyword(s):  
Temporal Lobe ◽  
Memory System ◽  
Core System ◽  
The Core ◽  
Memory Traces ◽  
Specific Memory ◽  
Target Article ◽  
Temporal Structures ◽  
The Right

Abstract The target article carefully describes the memory system, centered on the temporal lobe that builds specific memory traces. It does not, however, mention the laterality effects that exist within this system. This commentary briefly surveys evidence showing that clear asymmetries exist within the temporal lobe structures subserving the core system and that the right temporal structures mainly underpin face familiarity feelings.

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