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Entry Zone (entry + zone)

Distribution by Scientific Domains

Life Sciences	50%

Kinds of Entry Zone

root entry zone

Selected Abstracts

Axon behaviour at Schwann cell , astrocyte boundaries: manipulation of axon signalling pathways and the neural adhesion molecule L1 can enable axons to cross

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2004
Kathryn H. Adcock
Abstract Axon regeneration in vivo is blocked at boundaries between Schwann cells and astrocytes, such as occur at the dorsal root entry zone and around peripheral nerve or Schwann cell grafts. We have created a tissue culture model of these boundaries in Schwann cell , astrocyte monolayer co-cultures. Axon behaviour resembles that in vivo, with axons showing a strong preference for Schwann cells over astrocytes. At boundaries between the two cell types, axons growing on astrocytes cross readily onto Schwann cells, but only 15% of axons growing on Schwann cells are able to cross onto astrocytes. Treatment with chondroitinase or chlorate to reduce inhibition by proteoglycans did not change this behaviour. The neural adhesion molecule L1 is present on Schwann cells and not astrocytes, and manipulation of L1 by application of an antibody, L1-Fc in solution, or adenoviral transduction of L1 into astrocytes increased the proportion of axons able to cross onto astrocytes to 40,50%. Elevating cAMP levels increased crossing from Schwann cells onto astrocytes in live and fixed cultures, and had a co-operative effect with NT-3 but not with NGF. Inactivation of Rho with a cell-permeant form of C3 exoenzyme also increased crossing from Schwann cells to astrocytes. Our experiments indicate that the preference of axons for Schwann cells is largely mediated by the presence of L1 on Schwann cells but not astrocytes, and that manipulation of growth cone signalling pathways can allow axons to disregard boundaries between the two cell types. [source]

A Case With Prepontine (Clival) Arachnoid Cyst Manifested as Trigeminal Neuralgia

HEADACHE, Issue 10 2008
Emine Genc MD
Most cases of "idiopathic" trigeminal neuralgia are thought to originate from vascular compression of the trigeminal root entry zone. In this case, we describe a young man presenting with the symptoms of trigeminal neuralgia associated with a prepontine (clival) arachnoid cyst. [source]

Repeat Trigeminal Nerve Radiosurgery for Refractory Cluster Headache Fails to Provide Long-Term Pain Relief

HEADACHE, Issue 2 2007
Shearwood McClelland III MD
Objective/Background.,Medically refractory cluster headache (MRCH) is a debilitating condition that has proven resistant to many modalities. Previous reports have indicated that radiosurgery for MRCH provides little long-term pain relief, with moderate/significant morbidity. However, there have been no reports of repeated radiosurgery in this patient population. We present our findings from the first reports of repeat radiosurgery for MRCH. Methods.,Two patients with MRCH underwent repeat gamma knife radiosurgery at our institution. Each fulfilled clinical criteria for treatment, including complete resistance to pharmacotherapy, pain primarily localized to the ophthalmic division of the trigeminal nerve, and psychological stability. Both patients previously received gamma knife radiosurgery (75 Gy) for MRCH with no morbidity, but no long-term improvement of pain relief (Patient 1 = 5 months, Patient 2 = 10 months) after treatment. For repeat radiosurgery, each patient received 75 Gy to the 100% isodose line delivered to the root entry zone of the trigeminal nerve, and was evaluated postretreatment. Pain relief was defined as: excellent (free of MRCH with minimal/no medications), good (50% reduction of MRCH severity/frequency with medications), fair (25% reduction), or poor (less than 25% reduction). Results.,Following repeat radiosurgery, long-term pain relief was poor in both patients. Neither patient sustained any immediate morbidity following radiosurgery. Patient 2 experienced right facial numbness 4 months postretreatment, while Patient 1 experienced no morbidity. Conclusion.,Repeat radiosurgery of the trigeminal nerve fails to provide long-term pain relief for MRCH. Given the reported failures of initial and repeat radiosurgery for MRCH, trigeminal nerve radiosurgery should not be offered for MRCH. [source]

Modélisation de l'efficacité de filtration d'un échangeur cyclone

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2003
Richard Caetano
Abstract This work is a modelling of the Aireco® filtration system. This heat exchanger, with particle catching capabilities, is made of a cyclonic body which contains refrigerated coils. The water vapour contained in the gas to be treated condensed on the coils surface. Our modelling considers two main capture surfaces: the entry zone in which particles are collected by inertial impaction and the cyclonic body in which particles diffused by centrifugal force is the main phenomena. We found that these considerations explain our experimental results with an accuracy more than 90%, when the Aireco® is on a normal point of working. Ce travail consiste à modéliser l'efficacité de filtration du système d'épuration Aireco®. Cet échangeur épurateur se compose d'un corps cyclonique et de nappes de serpentins réfrigérés provoquant la condensation de la vapeur d'eau contenue dans le gaz pollué traité. Dans ce modèle nous modélisons l'échangeur en considérant les zones de piégeage prépondérantes que sont l'entrée et le corps cyclonique. Notre modèle prend en compte les effets d'impaction inertielle en entrée et la centrifugation dans le corps du système. Cette démarche théorique corrobore à plus de 95 % les valeurs obtenues expérimentalement lorsque l'Aireco® fonctionne dans ses conditions nominales. [source]

Caspr reveals an aggregation of nodes and flanking node free zones at the rat trigeminal sensory root and dorsal root entry zones

GLIA, Issue 3 2005
Michael A. Henry
Abstract The sensory root entry zone demarcates the transition from the peripheral nervous system (PNS) to the central nervous system (CNS). In this study, we describe the organization of nodes of Ranvier at the trigeminal sensory and dorsal root entry zones of the rat. Caspr immunoreactivity (IR) was used to identify the paranodal region of nodes of Ranvier, while L-MAG-IR was used to identify CNS oligodendrocytes. Immunofluorescence confocal microscopy revealed a dense aggregation of nodes precisely at the PNS to CNS transition with prominent node-depleted zones on either side, while L-MAG-IR was confined to ensheathing fibers on the central side of nodes located in this dense band and identified these as transitional nodes. Morphometric analysis of the PNS and CNS sides of the trigeminal and the PNS side of the dorsal root entry zones confirmed the presence of virtually node-free domains flanking the transitional zone. Further, the reappearance of nodes on the far side of the node-free zones strongly correlated with nodal diameter, with small nodes reappearing first. These findings suggest that the PNS/CNS transition may represent the initial site of myelination of the primary afferent axon within this area. © 2004 Wiley-Liss, Inc. [source]