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Dorsal Columns (dorsal + column)

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	50%

Selected Abstracts

Technical Performance of Percutaneous and Laminectomy Leads Analyzed by Modeling

NEUROMODULATION, Issue 4 2004
Ljubomir Manola Dipl.
Abstract The objective of this study was to compare the technical performance of laminectomy and percutaneous spinal cord stimulation leads with similar contact spacing by computer modeling. Monopolar and tripolar (guarded cathode) stimulation with both lead types in a low-thoracic spine model was simulated using UT-SCS software. Dorsal column and dorsal root fiber thresholds were calculated as well as the area of recruited fibers in the dorsal columns, the rostrocaudal span of recruited dorsal root fibers and the energy consumption at discomfort threshold. Tripolar stimulation is superior to monopolar stimulation in the recruitment of the dorsal columns, a percutaneous lead recruits a ,12% larger dorsal column area than a laminectomy lead does. This difference is reduced when the contact spacing of the lead models is the same. A percutaneous lead with significant wire impedance (140 Ohms) consumes ,115,240% more energy, whereas the same lead with negligible wire impedance consumes ,40,85% more energy. A deterioration of all performance parameters is predicted when a percutaneous lead is placed more dorsally in the epidural tissue. When positioned next to the dura mater, a percutaneous lead has a similar performance (fiber recruitment in the dorsal columns and the dorsal roots) as a laminectomy lead with similar contact spacing, but substantially higher energy consumption. The superior clinical performance of the laminectomy lead is most probably due to the difference in volume and insertion technique of the two lead types. [source]

Convergence of multisensory inputs in Xenopus tadpole tectum

DEVELOPMENTAL NEUROBIOLOGY, Issue 14 2009
Masaki Hiramoto
Abstract The integration of multisensory information takes place in the optic tectum where visual and auditory/mechanosensory inputs converge and regulate motor outputs. The circuits that integrate multisensory information are poorly understood. In an effort to identify the basic components of a multisensory integrative circuit, we determined the projections of the mechanosensory input from the periphery to the optic tectum and compared their distribution to the retinotectal inputs in Xenopus laevis tadpoles using dye-labeling methods. The peripheral ganglia of the lateral line system project to the ipsilateral hindbrain and the axons representing mechanosensory inputs along the anterior/posterior body axis are mapped along the ventrodorsal axis in the axon tract in the dorsal column of the hindbrain. Hindbrain neurons project axons to the contralateral optic tectum. The neurons from anterior and posterior hindbrain regions project axons to the dorsal and ventral tectum, respectively. While the retinotectal axons project to a superficial lamina in the tectal neuropil, the hindbrain axons project to a deep neuropil layer. Calcium imaging showed that multimodal inputs converge on tectal neurons. The layer-specific projections of the hindbrain and retinal axons suggest a functional segregation of sensory inputs to proximal and distal tectal cell dendrites, respectively. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source]

Measurement of T1 and T2 in the cervical spinal cord at 3 tesla

MAGNETIC RESONANCE IN MEDICINE, Issue 1 2008
Seth A. Smith
Abstract T1 and T2 were measured for white matter (WM) and gray matter (GM) in the human cervical spinal cord at 3T. T1 values were calculated using an inversion-recovery (IR) and B1 -corrected double flip angle gradient echo (GRE) and show significant differences (p = 0.002) between WM (IR = 876 ± 27 ms, GRE = 838 ± 54 ms) and GM (IR = 973 ± 33 ms, GRE = 994 ± 54 ms). IR showed significant difference between lateral and dorsal column WM (863 ± 23 ms and 899 ± 18 ms, respectively, p = 0.01) but GRE did not (p = 0.40). There was no significant difference (p = 0.31) in T2 between WM (73 ± 6 ms) and GM (76 ± 3 ms) or between lateral and dorsal columns (lateral: 73 ± 6 ms, dorsal: 72 ± 7 ms, p = 0.59). WM relaxation times were similar to brain structures with very dense fiber packing (e.g., corpus callosum), while GM values resembled deep GM in brain. Optimized sequence parameters for maximal contrast between WM and GM, and between WM and cerebrospinal fluid (CSF) were derived. Since the spinal cord has rostral-caudal symmetry, we expect these findings to be applicable to the whole cord. Magn Reson Med 60:213,219, 2008. © 2008 Wiley-Liss, Inc. [source]

Select spinal lesions reveal multiple ascending pathways in the rat conveying input from the male genitalia

THE JOURNAL OF PHYSIOLOGY, Issue 7 2010
C. H. Hubscher
The specific white matter location of all the spinal pathways conveying penile input to the rostral medulla is not known. Our previous studies using rats demonstrated the loss of low but not high threshold penile inputs to medullary reticular formation (MRF) neurons after acute and chronic dorsal column (DC) lesions of the T8 spinal cord and loss of all penile inputs after lesioning the dorsal three-fifths of the cord. In the present study, select T8 lesions were made and terminal electrophysiological recordings were performed 45,60 days later in a limited portion of the nucleus reticularis gigantocellularis (Gi) and Gi pars alpha. Lesions included subtotal dorsal hemisections that spared only the lateral half of the dorsal portion of the lateral funiculus on one side, dorsal and over-dorsal hemisections, and subtotal transections that spared predominantly just the ventromedial white matter. Electrophysiological data for 448 single unit recordings obtained from 32 urethane-anaesthetized rats, when analysed in groups based upon histological lesion reconstructions, revealed (1) ascending bilateral projections in the dorsal, dorsolateral and ventrolateral white matter of the spinal cord conveying information from the male external genitalia to MRF, and (2) ascending bilateral projections in the ventrolateral white matter conveying information from the pelvic visceral organs (bladder, descending colon, urethra) to MRF. Multiple spinal pathways from the penis to the MRF may correspond to different functions, including those processing affective/pleasure/motivational, nociception, and mating-specific (such as for erection and ejaculation) inputs. [source]

Maintenance of the relative proportion of oligodendrocytes to axons even in the absence of BAX and BAK

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2009
Kumi Kawai
Abstract Highly purified oligodendroglial lineage cells from mice lacking functional bax and bak genes were resistant to apoptosis after in-vitro differentiation, indicating an essential role of the intrinsic apoptotic pathway in apoptosis of oligodendrocytes in the absence of neurons (axons) and other glial cells. These mice therefore provide a valuable tool with which to evaluate the significance of the intrinsic apoptotic pathway in regulating the population sizes of oligodendrocytes and oligodendroglial progenitor cells. Quantitative analysis of the optic nerves and the dorsal columns of the spinal cord revealed that the absolute numbers of mature oligodendrocytes immunolabeled for aspartoacylase and adult glial progenitor cells expressing NG2 chondroitin sulfate proteoglycan were increased in both white matter tracts of adult bax/bak -deficient mice and, to a lesser extent, bax -deficient mice, except that there was no increase in NG2-positive progenitor cells in the dorsal columns of these strains of mutant mice. These increases in mature oligodendrocytes and progenitor cells in bax/bak -deficient mice were unexpectedly proportional to increases in numbers of axons in these white matter tracts, thus retaining the oligodendroglial lineage to axon ratios of at most 1.3-fold of the physiological numbers. This is in contrast to the prominent expansion in numbers of neural precursor cells in the subventricular zones of these adult mutant mice. Our study indicates that homeostatic control of cell number is different for progenitors of the oligodendroglial and neuronal lineages. Furthermore, regulatory mechanism(s) operating in addition to apoptotic elimination through the intrinsic pathway, appear to prevent the overproduction of highly mitotic oligodendroglial progenitor cells. [source]

Brain-derived neurotrophic factor applied to the motor cortex promotes sprouting of corticospinal fibers but not regeneration into a peripheral nerve transplant

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2002
G.W. Hiebert
Abstract Previous experiments from our laboratory have shown that application of brain-derived neurotrophic factor (BDNF) to the red nucleus or the motor cortex stimulates an increase in the expression of regeneration-associated genes in rubrospinal and corticospinal neurons. Furthermore, we have previously shown that BDNF application stimulates regeneration of rubrospinal axons into a peripheral graft after a thoracic injury. The current study investigates whether application of BDNF to the motor cortex will facilitate regeneration of corticospinal neurons into a peripheral nerve graft placed into the thoracic spinal cord. In adult Sprague Dawley rats, the dorsal columns and the corticospinal tract between T9 and T10 were ablated by suction, and a 5-mm-long segment of predegenerated tibial nerve was autograft implanted into the lesion. With an osmotic pump, BDNF was infused directly into the parenchyma of the motor cortex for 14 days. Growth of the corticospinal tract into the nerve graft was then evaluated by transport of an anterograde tracer. Anterogradely labeled corticospinal fibers were not observed in the peripheral nerve graft in animals treated with saline or BDNF. Serotinergic and noradrenergic fibers, as well as peripheral sensory afferents, were observed to penetrate the graft, indicating the viability of the peripheral nerve graft as a permissive growth substrate for these specific fiber types. Although treatment of the corticospinal fibers with BDNF failed to produce regeneration into the graft, there was a distinct increase in the number of axonal sprouts rostral to the injury site. This indicates that treatment of corticospinal neurons with neurotrophins, e.g., BDNF, can be used to enhance sprouting of corticospinal axons within the spinal cord. Whether such sprouting leads to functional recovery after spinal cord injury is currently under investigation. © 2002 Wiley-Liss, Inc. [source]

Measurement of T1 and T2 in the cervical spinal cord at 3 tesla

Technical Performance of Percutaneous and Laminectomy Leads Analyzed by Modeling

Micturitional disturbance in a patient with a spinal cavernous angioma

NEUROUROLOGY AND URODYNAMICS, Issue 6 2003
Ryuji Sakakibara
Abstract A 58-year-old woman had a 3-year history of numbness in the right leg, which developed into thoracic transverse myelopathy and urinary retention. After referral to our department, MRI scans revealed a lesion with a target appearance at the T10,11 spinal cord with multiple silent cerebral lesions, which confirmed the diagnosis of cavernous angioma. Gamma-knife surgery was not indicated, considering the risk of adverse effects. The patient gradually became able to urinate, but had urge urinary incontinence. The first urodynamic studies (conducted 3 months after full clinical manifestations of transverse myelopathy) showed detrusor hyperreflexia (DH), decreased bladder sensation during bladder filling, detrusor-sphincter dyssynergia (DSD), and weak detrusor on voiding. However, urinary retention appeared again without change of neurologic signs. The second urodynamic studies (conducted 2 months later) showed less marked DH during bladder filling, and equivocal DSD but marked weak detrusor on voiding. The patient started taking oral prazosin hydrochloride (6 mg/day), which gradually ameliorated her voiding difficulty. Lesions in the lateral and dorsal columns of the spinal cord seem to be responsible for the micturitional disturbance in our patient with spinal cavernous angioma. Neurourol. Urodynam. 22:606,610, 2003. © 2003 Wiley-Liss, Inc. [source]

Complex interplay between glutamate receptors and intracellular Ca2+ stores during ischaemia in rat spinal cord white matter

THE JOURNAL OF PHYSIOLOGY, Issue 1 2006
Mohamed Ouardouz
Electrophysiological recordings of propagated compound action potentials (CAPs) and axonal Ca2+ measurements using confocal microscopy were used to study the interplay between AMPA receptors and intracellullar Ca2+ stores in rat spinal dorsal columns subjected to in vitro combined oxygen and glucose deprivation (OGD). Removal of Ca2+ or Na+ from the perfusate was protective after 30 but not 60 min of OGD. TTX was ineffective with either exposure, consistent with its modest effect on ischaemic depolarization. In contrast, AMPA antagonists were very protective, even after 60 min of OGD where 0Ca2++ EGTA perfusate was ineffective. Similarly, blocking ryanodine receptor-mediated Ca2+ mobilization from internal stores (0Ca2++ nimodipine or 0Ca2++ ryanodine), or inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ release (block of group 1 metabotropic glutamate receptors with 1-aminoindan-1,5-dicarboxylic acid, inhibition of phospholipase C with U73122 or IP3 receptor block with 2APB; each in 0Ca2+) were each very protective, with the combination resulting in virtually complete functional recovery after 1 h OGD (97 ± 32% CAP recovery versus 4 ± 6% in artificial cerebrospinal fluid). AMPA induced a rise in Ca2+ concentration in normoxic axons, which was greatly reduced by blocking ryanodine receptors. Our data therefore suggest a novel and surprisingly complex interplay between AMPA receptors and Ca2+ mobilization from intracellular Ca2+ stores. We propose that AMPA receptors may not only allow Ca2+ influx from the extracellular space, but may also significantly influence Ca2+ release from intra-axonal Ca2+ stores. In dorsal column axons, AMPA receptor-dependent mechanisms appear to exert a greater influence than voltage-gated Na+ channels on functional outcome following OGD. [source]