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Respiratory Physiology & Neurobiology Mar 2013High frequency spinal cord stimulation (HF-SCS) is a method of inspiratory muscle activation resulting in phrenic motoneuron activation via stimulation of spinal cord...
High frequency spinal cord stimulation (HF-SCS) is a method of inspiratory muscle activation resulting in phrenic motoneuron activation via stimulation of spinal cord pathways. The specific pathways mediating this response, however, are unknown. The aim of this study was to assess the potential role of upper cervical (C1-C4) pre-phrenic interneurons (UCI) and localize the pathways in the thoracic spinal cord mediating activation of phrenic motoneurons during HF-SCS. In 7 anesthetized, spinalized (C1 level) dogs, HF-SCS was applied at the T2 level. Diaphragm EMG, inspired volume and airway pressure generation were monitored before and following sequential spinal cord sections at the C4 and C8 levels. Section at the C4 level and dorsal columns at C8 resulted in no significant changes. However, lateral funiculi section (C8 level) resulted in significant reductions in each parameter. We conclude that during upper thoracic HF-SCS, the phrenic motoneuron pools are activated via spinal pathways located in the lateral funiculus but UCI are not involved.
Topics: Animals; Diaphragm; Dogs; Electric Stimulation; Intercostal Muscles; Interneurons; Phrenic Nerve; Spinal Cord; Thoracic Vertebrae
PubMed: 23261850
DOI: 10.1016/j.resp.2012.12.003 -
Brain Research Jan 2013Propriospinal pathways, consisting of axons from interneurons that project to other spinal segments, have been implicated as likely candidates to mediate interlimb...
Propriospinal pathways, consisting of axons from interneurons that project to other spinal segments, have been implicated as likely candidates to mediate interlimb coordination in developing and adult mammals during quadrupedal locomotion. The superficial thoracic ventrolateral funiculus (VLF) contains both ascending and descending axons, and when stimulated can induce alternating rhythmic locomotor-like activity in the lumbar ventral roots of the isolated neonatal rat spinal cord. The goal of this work was to characterize the synaptic inputs onto cervical neurons from ascending axons in the VLF. Sprague-Dawley rats (P4-P7) were deeply anesthesized with halothane and their spinal cords were isolated, removed, and maintained in vitro. Intracellular recordings were made from 68 cervical (C5-C7) neurons having 71 latency classifications in response to thoracic VLF stimulation. Antidromic (n=35), monosynaptic (n=2), di-or tri-synaptic (n=18) and long-latency polysynaptic (n=16) responses were recorded. Recordings from reduced preparations (mid-sagittal section at C5-C7) suggest that much of the delay in the long-latency polysynaptic responses require a bilaterally intact cervical spinal cord. Fifty-three percent (17/32) of the VLF responsive cervical interneurons tested also exhibited long latency excitatory responses to lumbar dorsal root stimulation suggesting that many of the cervical VLF responsive interneurons receive indirect input from lumbar primary afferents. We hypothesize that the VLF contains a population of ascending axons originating from lumbar propriospinal interneurons that can influence cervical inter- and motoneurons. These ascending VLF axons may participate in interlimb coordination by providing moment-by-moment feedback to the cervical enlargement of lumbar central pattern generator and/or hindlimb proprioceptive activity.
Topics: Afferent Pathways; Animals; Animals, Newborn; Axons; Cervical Vertebrae; Electric Stimulation; Electrophysiological Phenomena; Functional Laterality; Hindlimb; Interneurons; Lysine; Microelectrodes; Neurons; Rats; Rats, Sprague-Dawley; Spinal Nerve Roots; Synapses
PubMed: 23146714
DOI: 10.1016/j.brainres.2012.11.002 -
PloS One 2012Glutamate is the main excitatory neurotransmitter involved in spinal cord circuits in vertebrates, but in most groups the distribution of glutamatergic spinal neurons is...
Glutamate is the main excitatory neurotransmitter involved in spinal cord circuits in vertebrates, but in most groups the distribution of glutamatergic spinal neurons is still unknown. Lampreys have been extensively used as a model to investigate the neuronal circuits underlying locomotion. Glutamatergic circuits have been characterized on the basis of the excitatory responses elicited in postsynaptic neurons. However, the presence of glutamatergic neurochemical markers in spinal neurons has not been investigated. In this study, we report for the first time the expression of a vesicular glutamate transporter (VGLUT) in the spinal cord of the sea lamprey. We also study the distribution of glutamate in perikarya and fibers. The largest glutamatergic neurons found were the dorsal cells and caudal giant cells. Two additional VGLUT-positive gray matter populations, one dorsomedial consisting of small cells and another one lateral consisting of small and large cells were observed. Some cerebrospinal fluid-contacting cells also expressed VGLUT. In the white matter, some edge cells and some cells associated with giant axons (Müller and Mauthner axons) and the dorsolateral funiculus expressed VGLUT. Large lateral cells and the cells associated with reticulospinal axons are in a key position to receive descending inputs involved in the control of locomotion. We also compared the distribution of glutamate immunoreactivity with that of γ-aminobutyric acid (GABA) and glycine. Colocalization of glutamate and GABA or glycine was observed in some small spinal cells. These results confirm the glutamatergic nature of various neuronal populations, and reveal new small-celled glutamatergic populations, predicting that some glutamatergic neurons would exert complex actions on postsynaptic neurons.
Topics: Animals; Glycine; Immunohistochemistry; In Situ Hybridization; Lampreys; Microscopy, Fluorescence; Neurons; Spinal Cord; Vesicular Glutamate Transport Proteins; gamma-Aminobutyric Acid
PubMed: 23110124
DOI: 10.1371/journal.pone.0047898 -
Brain Structure & Function Sep 2013The present study investigated the projection from the paralemniscal nucleus (PL) to the spinal cord in the mouse by injecting the retrograde tracer fluoro-gold to...
The present study investigated the projection from the paralemniscal nucleus (PL) to the spinal cord in the mouse by injecting the retrograde tracer fluoro-gold to different levels of the spinal cord and injecting the anterograde tracer biotinylated dextran amine into PL. We found that PL projects to the entire spinal cord with obvious contralateral predominance--420 neurons projected to the contralateral cervical cord and 270 to the contralateral lumbar cord. Fibers from PL descended in the dorsolateral funiculus on the contralateral side and terminated in laminae 5, 6, 7, and to a lesser extent in the dorsal and ventral horns. A smaller number of fibers also descended in the ventral funiculus on the ipsilateral side and terminated in laminae 7, 8 and, to a lesser extent in lamina 9. The present study is the first demonstration of the PL fiber termination in the spinal cord in mammals. The PL projection to the spinal cord may be involved in vocalization and locomotion.
Topics: Animals; Biotin; Dextrans; Image Processing, Computer-Assisted; Immunohistochemistry; Mice; Mice, Inbred C57BL; Motor Neurons; Neuroanatomical Tract-Tracing Techniques; Pons; Spinal Cord; Stilbamidines
PubMed: 23052549
DOI: 10.1007/s00429-012-0459-5 -
The Journal of Neuroscience : the... Sep 2012Previous studies have shown that injured dorsal column sensory axons extend across a spinal cord lesion site if axons are guided by a gradient of neurotrophin-3 (NT-3)...
Previous studies have shown that injured dorsal column sensory axons extend across a spinal cord lesion site if axons are guided by a gradient of neurotrophin-3 (NT-3) rostral to the lesion. Here we examined whether continuous NT-3 delivery is necessary to sustain regenerated axons in the injured spinal cord. Using tetracycline-regulated (tet-off) lentiviral gene delivery, NT-3 expression was tightly controlled by doxycycline administration. To examine axon growth responses to regulated NT-3 expression, adult rats underwent a C3 dorsal funiculus lesion. The lesion site was filled with bone marrow stromal cells, tet-off-NT-3 virus was injected rostral to the lesion site, and the intrinsic growth capacity of sensory neurons was activated by a conditioning lesion. When NT-3 gene expression was turned on, cholera toxin β-subunit-labeled sensory axons regenerated into and beyond the lesion/graft site. Surprisingly, the number of regenerated axons significantly declined when NT-3 expression was turned off, whereas continued NT-3 expression sustained regenerated axons. Quantification of axon numbers beyond the lesion demonstrated a significant decline of axon growth in animals with transient NT-3 expression, only some axons that had regenerated over longer distance were sustained. Regenerated axons were located in white matter and did not form axodendritic synapses but expressed presynaptic markers when closely associated with NG2-labeled cells. A decline in axon density was also observed within cellular grafts after NT-3 expression was turned off possibly via reduction in L1 and laminin expression in Schwann cells. Thus, multiple mechanisms underlie the inability of transient NT-3 expression to fully sustain regenerated sensory axons.
Topics: Analysis of Variance; Animals; Antigens; Axons; Cell Transplantation; Cells, Cultured; Cholera Toxin; Disease Models, Animal; Doxycycline; Enzyme-Linked Immunosorbent Assay; Female; Gene Expression Regulation; Genetic Therapy; Glial Fibrillary Acidic Protein; Green Fluorescent Proteins; HEK293 Cells; Humans; Laminin; Leukocyte L1 Antigen Complex; Membrane Glycoproteins; Microtubule-Associated Proteins; Myelin-Oligodendrocyte Glycoprotein; Nerve Growth Factors; Nerve Regeneration; Nerve Tissue Proteins; Neurofilament Proteins; Neurotrophin 3; Proteoglycans; Rats; Rats, Inbred F344; S100 Calcium Binding Protein beta Subunit; S100 Proteins; Schwann Cells; Sciatic Nerve; Sensory Receptor Cells; Spinal Cord Injuries; Stem Cell Transplantation; Time Factors; Transfection
PubMed: 22993437
DOI: 10.1523/JNEUROSCI.5041-11.2012 -
Journal of Neuroscience Methods Nov 2012Techniques used to produce partial spinal cord injuries in animal models have the potential for creating variability in lesions. The amount of tissue affected may...
Techniques used to produce partial spinal cord injuries in animal models have the potential for creating variability in lesions. The amount of tissue affected may influence the functional outcomes assessed in the animals. The recording of somatosensory evoked potentials (SSEPs) may be a valuable tool for assessing the extent of lesion applied in animal models of traumatic spinal cord injury (SCI). Intraoperative tibial SSEP recordings were assessed during surgically induced lateral thoracic hemisection SCI in Sprague-Dawley rats. The transmission of SSEPs, or lack thereof, was determined and compared against the integrity of the dorsal funiculi on each side of the spinal cord upon histological sectioning. An association was found between the presence of an SSEP signal and presence of intact dorsal funiculus tissue. The relative risk is 4.50 (95% confidence interval: 1.83-11.08) for having an intact dorsal funiculus when the ipsilateral SSEP was present compared to when it was absent. Additionally, the amount of spared spinal cord tissue correlates with final functional assessments at nine weeks post injury: BBB (linear regression, R²=0.618, p<0.001) and treadmill test (linear regression, R²=0.369, p=0.016). Therefore, we propose intraoperative SSEP monitoring as a valuable tool to assess extent of lesion and reduce variability between animals in experimental studies of SCI.
Topics: Animals; Disease Models, Animal; Evoked Potentials, Somatosensory; Female; Monitoring, Intraoperative; Rats; Rats, Sprague-Dawley; Spinal Cord Injuries
PubMed: 22960163
DOI: 10.1016/j.jneumeth.2012.08.024 -
Acta Neuropathologica Nov 2012In this autopsy-based study, α-synuclein immunohistochemistry and lipofuscin pigment-Nissl architectonics in serial sections of 100 μm thickness were used to...
In this autopsy-based study, α-synuclein immunohistochemistry and lipofuscin pigment-Nissl architectonics in serial sections of 100 μm thickness were used to investigate the spinal cords and brains of 46 individuals: 28 patients with clinically and neuropathologically confirmed Parkinson's disease, 6 cases with incidental Lewy body disease, and 12 age-matched controls. α-Synuclein inclusions (particulate aggregations, Lewy neurites/bodies) in the spinal cord were present between neuropathological stages 2-6 in all cases whose brains were staged for Parkinson's disease-related synucleinopathy. The only individuals who did not have Lewy pathology in the spinal cord were a single stage 1 case (incidental Lewy body disease) and all controls. Because the Parkinson's disease-related lesions were observable in the spinal cord only after Lewy pathology was seen in the brain, it could be concluded that, within the central nervous system, sporadic Parkinson's disease does not begin in the spinal cord. In addition: (1) α-Synuclein-immunoreactive axons clearly predominated over Lewy bodies throughout the spinal cord and were visible in medial and anterior portions of the anterolateral funiculus. Their terminal axons formed dense α-synuclein-immunoreactive networks in the gray matter and were most conspicuous in the lateral portions of layers 1, 7, and in the cellular islands of layer 9. (2) Notably, this axonopathy increased remarkably in density from cervicothoracic segments to lumbosacral segments of the cord. (3) Topographically, it is likely that the spinal cord α-synuclein immunoreactive axonal networks represent descending projections from the supraspinal level setting nuclei (locus coeruleus, lower raphe nuclei, magnocellular portions of the reticular formation). (4) Following the appearance of the spinal cord axonal networks, select types of projection neurons in the spinal cord gray matter displayed α-synuclein-immunoreactive inclusions: chiefly, nociceptive neurons of the dorsal horn in layer 1, sympathetic and parasympathetic preganglionic neurons in layer 7, the cellular pools of α-motoneurons in layer 9, and the smaller motoneurons in Onuf's nucleus in layer 9 (ventral horn). The spinal cord lesions may contribute to clinical symptoms (e.g., pain, constipation, poor balance, lower urinary tract complaints, and sexual dysfunction) that occur during the premotor and motor phases of sporadic Parkinson's disease.
Topics: Aged; Aged, 80 and over; Biopsy; Brain; Case-Control Studies; Female; Humans; Lewy Body Disease; Male; Middle Aged; Neurites; Neurons; Parkinson Disease; Postmortem Changes; Spinal Cord; Spinal Cord Diseases; alpha-Synuclein
PubMed: 22926675
DOI: 10.1007/s00401-012-1028-y -
Neuroscience Letters Sep 2012In a previous study we found that the EphA4 receptor inhibits regeneration following spinal cord injury by blocking regrowth of axons and regulation of astrocyte...
In a previous study we found that the EphA4 receptor inhibits regeneration following spinal cord injury by blocking regrowth of axons and regulation of astrocyte reactivity. In our original studies using EphA4 null mice [Goldshmit et al., J. Neurosci., 2004] we found attenuated astrocyte reactivity following spinal cord injury. Several other studies have now supported the role of EphA4 in regulating neural regeneration but a recent study [Herrmann et al., Exp. Neurol., 2010] did not find an effect of EphA4 on astrocyte reactivity. Re-examination of astrocytic gliosis following injury in our current cohort of EphA4 null mice revealed that they no longer showed attenuation of astrocyte reactivity, however other EphA4 null mouse phenotypes, such as decreased size of the dorsal funiculus were unaltered. We hypothesised that long-term breeding on the C57Bl/6 background may influence the EphA4-mediated astrocyte phenotype and compared astrocytic gliosis at 4 days following spinal cord injury in wildtype and EphA4 null mice on the C57Bl/6 background and backcrossed C57Bl/6×129Sv(F2) mice, as well as wildtype 129Sv mice. 129Sv mice had increased GFAP expression and increased numbers of reactive GFAP astrocytes compared to C57Bl/6 mice. There was no significant effect of EphA4 deletion on GFAP expression in C57Bl/6 mice or the F2 crosses other than a moderately decreased number of EphA4 null astrocytes in C57Bl/6 mice using one of two antibodies. Therefore, there has been an apparent change in EphA4-mediated astroglial phenotype associated with long term breeding of the EphA4 colony but it does not appear to be influenced by background mouse strain.
Topics: Animals; Astrocytes; Breeding; Cell Proliferation; Female; Glial Fibrillary Acidic Protein; Gliosis; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Phenotype; Receptor, EphA4; Species Specificity; Spinal Cord Injuries; Up-Regulation
PubMed: 22824304
DOI: 10.1016/j.neulet.2012.07.023 -
Brain Research Jul 2012Axonal degeneration is a prominent feature of amyotrophic lateral sclerosis (ALS) both in lower motor nerves as well as descending white matter axons in the spinal cord...
Axonal degeneration is a prominent feature of amyotrophic lateral sclerosis (ALS) both in lower motor nerves as well as descending white matter axons in the spinal cord of human patients. Although the pathology of lower motor axonal degeneration has been described in both human ALS and related transgenic animal models, few studies have examined the pathological features of descending axon degeneration, particularly in mouse models of ALS. We have examined the degeneration of white matter tracts in the G93A mutant superoxide dismutase-1 (mSOD1+) mouse spinal cord white matter from 12 weeks of age to end-stage disease. In a G93A mSOD1 mouse model where green fluorescent protein was expressed in neurons (mSOD1+/GFP+), degeneration of white matter tracts was present from the ventral to dorsolateral funiculi. This pattern of axonal pathology occurred from 16 weeks of age. However, the dorsal funiculus, the site of the major corticospinal tract in mice, showed relatively less degeneration. Immunohistochemical analysis demonstrated that the neurofilament light chain (NFL) and neuronal intermediate filament protein alpha-internexin accumulated in axon swellings in the spinal white matter. Increased levels of alpha-internexin protein, in mSOD1+ mouse spinal cord tissue, were demonstrated by Western blotting. In contrast, degenerating axons did not show obvious accumulations of neurofilament medium and heavy chain proteins (NFM and NFH). These data suggest that white matter degeneration in this mouse model of ALS is widespread and involves a specific molecular signature, particularly the accumulation of NFL and alpha-internexin proteins.
Topics: Amyotrophic Lateral Sclerosis; Animals; Axons; Disease Models, Animal; Female; Green Fluorescent Proteins; Humans; Intermediate Filament Proteins; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Motor Neurons; Nerve Degeneration; Neurofilament Proteins; Spinal Cord; Spinal Cord Diseases; Superoxide Dismutase; Superoxide Dismutase-1
PubMed: 22609817
DOI: 10.1016/j.brainres.2012.05.018 -
Ontogenez 20121H magnetic resonance microtomography imaging was applied to study vascular systems in developing bean (Phaseolus limensis L.) seeds. Using the gradient echo method, we...
1H magnetic resonance microtomography imaging was applied to study vascular systems in developing bean (Phaseolus limensis L.) seeds. Using the gradient echo method, we recorded 2D tomographic sections in the sagittal and axial planes of the fruits sampled from a vegetating plant on days 10, 17, 24, and 31 after fertilization. Any vascular connection between the tissues of maternal plant (bean pod and seed coat) and the embryo were undetectable. The embryo has an autonomous branched network of procambial strands in the cotyledons, converging to the embryonic axis. The bean pods are covered with a network of vascular bundles; large vascular strands run along the dorsal and ventral sutures. The seed coat vascular bundles are formed in the process of seed ripening and are represented by a developed vascular system multiply branching in the middle part of the ground parenchyma at the stage of physiological maturity. They are connected with the source of assimilates via the lateral pod veins and a large vascular bundle, entering the seed below the hilum via the placenta. Assimilates enter the external part of the seed coat, which contains no vascular bundles, via the funiculus vascular bundles and hilum tissue.
Topics: Magnetic Resonance Imaging; Phaseolus; Seeds
PubMed: 22567926
DOI: No ID Found