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Ventral Root (ventral + root)
Selected AbstractsRe-utilization of Schwann cells during ingrowth of ventral root afferents in perinatal kittensJOURNAL OF ANATOMY, Issue 2 2008A. Ingela M. Nilsson Remahl Abstract Ventral roots in all mammalian species, including humans, contain significant numbers of unmyelinated axons, many of them afferents transmitting nociceptive signals from receptive fields in skin, viscera, muscles and joints. Observations in cats indicate that these afferents do not enter the spinal cord via the ventral root, but rather turn distally and enter the dorsal root. Some unmyelinated axons are postganglionic autonomic efferents that innervate blood vessels of the root and the pia mater. In the feline L7 segment, a substantial proportion of unmyelinated axons are not detectable until late in perinatal development. The mechanisms inducing this late ingrowth, and the recruitment of Schwann cells (indispensable, at this stage, for axonal survival and sustenance), are unknown. We have counted axons and Schwann cells in both ends of the L7 ventral root in young kittens and made the following observations. (1) The total number of axons detectable in the root increased throughout the range of investigated ages. (2) The number of myelinated axons was similar in the root's proximal and distal ends. The increased number of unmyelinated axons with age is thus due to increased numbers of small unmyelinated axons. (3) The number of separated large probably promyelin axons was about the same in the proximal and distal ends of the root. (4) Schwann cells appeared to undergo redistribution, from myelinated to unmyelinated axons. (5) During redistribution of Schwann cells they first appear as aberrant Schwann cells and then become endoneurial X-cells temporarily free of axonal contact. We hypothesize that unmyelinated axons invade the ventral root from its distal end, that this ingrowth is particularly intense during the first postnatal month and that disengaged Schwann cells, eliminated from myelinated motoneuron axons, provide the ingrowing axons with structural and trophic support. [source] Expression of RhoA by inflammatory macrophages and T cells in rat experimental autoimmune neuritisJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 1 2007Zhiren Zhang Abstract RhoA is one of the best-studied members of Rho GTPases. Experimental autoimmune neuritis (EAN), which is characterized by infiltration of T cells and macrophages into the peripheral nervous system, is an autoantigen-specific T-cell-mediated animal model of human Guillain-Barr, Syndrome. In this study, RhoA expression has been investigated in the dorsal/ventral roots of EAN rats by immunohistochemistry. A significant accumulation of RhoA+ cells was observed on Day 12, with a maximum around Day 15, correlating to the clinical severity of EAN. In dorsal/ventral roots of EAN, RhoA+ cells were seen in perivascular areas but also in the parenchyma. Furthermore, double-labelling experiments showed that the major cellular sources of RhoA were reactive macrophages and T cells. In conclusion, this is the first demonstration of the presence of RhoA in the dorsal/ventral roots of EAN. The time courses and cellular sources of RhoA together with the functions of RhoA indicate that RhoA may function to facilitate macrophage and T-cell infiltration in EAN and therefore could be a potential therapeutic target. [source] Re-utilization of Schwann cells during ingrowth of ventral root afferents in perinatal kittensJOURNAL OF ANATOMY, Issue 2 2008A. Ingela M. Nilsson Remahl Abstract Ventral roots in all mammalian species, including humans, contain significant numbers of unmyelinated axons, many of them afferents transmitting nociceptive signals from receptive fields in skin, viscera, muscles and joints. Observations in cats indicate that these afferents do not enter the spinal cord via the ventral root, but rather turn distally and enter the dorsal root. Some unmyelinated axons are postganglionic autonomic efferents that innervate blood vessels of the root and the pia mater. In the feline L7 segment, a substantial proportion of unmyelinated axons are not detectable until late in perinatal development. The mechanisms inducing this late ingrowth, and the recruitment of Schwann cells (indispensable, at this stage, for axonal survival and sustenance), are unknown. We have counted axons and Schwann cells in both ends of the L7 ventral root in young kittens and made the following observations. (1) The total number of axons detectable in the root increased throughout the range of investigated ages. (2) The number of myelinated axons was similar in the root's proximal and distal ends. The increased number of unmyelinated axons with age is thus due to increased numbers of small unmyelinated axons. (3) The number of separated large probably promyelin axons was about the same in the proximal and distal ends of the root. (4) Schwann cells appeared to undergo redistribution, from myelinated to unmyelinated axons. (5) During redistribution of Schwann cells they first appear as aberrant Schwann cells and then become endoneurial X-cells temporarily free of axonal contact. We hypothesize that unmyelinated axons invade the ventral root from its distal end, that this ingrowth is particularly intense during the first postnatal month and that disengaged Schwann cells, eliminated from myelinated motoneuron axons, provide the ingrowing axons with structural and trophic support. [source] ULTRASTRUCTURE OF THE BASAL BODY COMPLEX AND PUTATIVE VESTIGIAL FEEDING APPARATUS IN PHACUS PLEURONECTES (EUGLENOPHYCEAE)JOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Shin, W.1, Boo, S. M.2, & Triemer, R. E.1 1Department of Life Science, Rutgers University, Piscataway, New Jersey 08854, USA; 2Department of Biology, Chungnam National University, Daejon 305-764, Korea Phacus pleuronectes (O. F. Müller) Dujardin is a phototrophic euglenoid with small discoid chloroplasts, a flat, rigid body, and longitudinally arranged pellicular strips. The flagellar apparatus consisted of two basal bodies and three flagellar roots typical of many phototrophic euglenoids, but also had a large striated fiber that connected the two basal bodies and associated with the ventral root. The three roots, in combination with the dorsal microtubular band, extended anteriorly and formed the major cytoskeletal elements supporting the reservoir membrane and ultimately the pellicle. A cytoplasmic pocket arose in the reservoir/canal transition region. It was supported by the ventral root and a C-shaped band of electron-opaque material that lined the cytoplasmic side of the pocket. A large striated fiber extended from this C-shaped band toward the reservoir membrane. The presence of striated fibers in the basal apparatus and associated with the microtubule reinforced pocket suggested that P. pleuronectes may be at the base of the Phacus lineage and may be more closely related to the phagotrophic euglenoids than to Phacus species which are ovoid in shape and have thicker pellicle strips. [source] Histopathological basis of Horner's syndrome in obstetric brachial plexus palsy differs from that in adult brachial plexus injuryMUSCLE AND NERVE, Issue 5 2008Yi-Gang Huang MD Abstract Although Horner's syndrome is usually taken as an absolute indicator of avulsions of the C8 and T1 ventral roots in adult brachial plexus injury, its pathological basis in obstetric brachial plexus palsy (OBPP) is unclear. We therefore examined the morphological mechanism for the presence of Horner's syndrome in brachial plexus injury in infants and adults. Some axons of sympathetic preganglionic neurons in T1 innervate the superior cervical ganglion via the C7 ventral root in infants but not in adults. Therefore, the presence of Horner's syndrome may relate in part to avulsion of the C7 root in OBPP. These findings suggest that Horner's syndrome in OBPP is not necessarily indicative of avulsions of the C8 and T1 roots, as it can occur with avulsion of the C7 root. Muscle Nerve, 2008 [source] Morphometric analysis of neuromuscular topography in the serratus anterior muscleMUSCLE AND NERVE, Issue 3 2006S. Potluri PhD Abstract Groups of neurons form ordered topographic maps on their targets, and defining the mechanisms that develop such maps, and reconnect them after disruption, has biological as well as clinical importance. The neuromuscular system is an accessible and well-studied model for defining the principles that guide map formation, both during its development and its reformation after motor nerve damage. We present evidence for the expression of this map at the level of nerve terminal morphology and muscle fiber type in the serratus anterior muscle. Morphometric analyses indicate, first, a rostrocaudal difference in nerve terminal size depending on the ventral root of origin of the axons. Second, motor endplates are larger on type IIB than type IIA muscle fibers. Third, whereas IIB muscle fibers are distributed rather evenly along the rostrocaudal axis of the muscle, the more rostral type IIB fibers are preferentially innervated by anteriorly derived (C6) motor neurons, and more caudal IIB fibers are preferentially innervated by posteriorly derived (C7) motor neurons. This inference is supported by analysis of the size of nerve terminals formed in each muscle sector by rostral and caudal roots, and by evidence that the larger terminals are on IIB fibers. These results demonstrate a subcellular expression of neuromuscular topography in the serratus anterior muscle (SA) muscle in the form of differences in nerve terminal size. These results provide deeper insights into the organization of a neuromuscular system. They also offer a rationale for a topographic map, that is, to allow spinal motor centers to activate selectively different compartments within a muscle. Muscle Nerve, 2006 [source] Preservation of segmental hindbrain organization in adult frogsTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 2 2006Hans Straka Abstract To test for possible retention of early segmental patterning throughout development, the cranial nerve efferent nuclei in adult ranid frogs were quantitatively mapped and compared with the segmental organization of these nuclei in larvae. Cranial nerve roots IV,X were labeled in larvae with fluorescent dextran amines. Each cranial nerve efferent nucleus resided in a characteristic segmental position within the clearly visible larval hindbrain rhombomeres (r). Trochlear motoneurons were located in r0, trigeminal motoneurons in r2,r3, facial branchiomotor and vestibuloacoustic efferent neurons in r4, abducens and facial parasympathetic neurons in r5, glossopharyngeal motoneurons in r6, and vagal efferent neurons in r7,r8 and rostral spinal cord. In adult frogs, biocytin labeling of cranial nerve roots IV,XII and spinal ventral root 2 in various combinations on both sides of the brain revealed precisely the same rostrocaudal sequence of efferent nuclei relative to each other as observed in larvae. This indicates that no longitudinal migratory rearrangement of hindbrain efferent neurons occurs. Although rhombomeres are not visible in adults, a segmental map of adult cranial nerve efferent nuclei can be inferred from the strict retention of the larval hindbrain pattern. Precise measurements of the borders of adjacent efferent nuclei within a coordinate system based on external landmarks were used to create a quantitative adult segmental map that mirrors the organization of the larval rhombomeric framework. Plotting morphologically and physiologically identified hindbrain neurons onto this map allows the physiological properties of adult hindbrain neurons to be linked with the underlying genetically specified segmental framework. J. Comp. Neurol. 494:228,245, 2006. © 2005 Wiley-Liss, Inc. [source] 5-HT1B but not 5-HT6 or 5-HT7 receptors mediate depression of spinal nociceptive reflexes in vitroBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2002G Hedo The identity of the serotonin (5-HT) receptors modulating the transmission of segmental C-fibre mediated signals was studied using an in vitro preparation of the hemisected spinal cord from rat pups. Responses to trains of stimuli delivered to a lumbar dorsal root were recorded from the corresponding ventral root. The resulting cumulative depolarization (CD) mediated by unmyelinated fibres was quantified in terms of integrated area. The amplitude of the mono-synaptic reflex was also measured. Serotonergic agents were superfused at known concentrations and their effects on the reflexes evaluated. 5-HT had depressant effects on the CD (EC50 34 ,M). The rank order of potency of agonists for the depression of the CD was 5-carboxamidotryptamine (5-CT)>,-methylserotonin (,-met-5-HT) ,5-HT>42-methylserotonin (2-met-5-HT),8-OH-DPAT. All the agonists including 2-met-5-HT and 8-OH-DPAT had strong depressant effects on the mono-synaptic reflex with the following order of potency: 5-CT>48-OH-DPAT>4,-met-5-HT ,5-HT,2-met-5-HT. The inhibitory effects of 5-HT, ,-met-5-HT and 5-CT were attenuated by the non-specific 5-HT antagonist methiothepin (1 ,M) and by the 5-HT1A/1B antagonist SDZ 21009 (100 nM) but not by the selective 5-HT1A antagonist WAY 100135 (1 ,M). Other antagonists known to block 5-HT2, 5-HT6 and/or 5-HT7 receptors (ketanserin, RO 04-6790, ritanserin and clozapine) did not change the effect of the agonists. The data suggest an important contribution of 5-HT1B receptors to the inhibition of spinal C-fibre mediated nociceptive reflexes but no experimental support was found for the intervention of 5-HT2, 5-HT6 or 5-HT7 receptors in this in vitro model. British Journal of Pharmacology (2002) 135, 935,942; doi:10.1038/sj.bjp.0704526 [source] Changes in the contractile properties of motor units in the rat medial gastrocnemius muscle after one month of treadmill trainingACTA PHYSIOLOGICA, Issue 4 2008M. Pogrzebna Abstract Aim:, The influence of 4 weeks treadmill training on the contractile properties of motor units (MUs) in the rat medial gastrocnemius muscle was investigated. Methods:, A population of 18 Wistar rats was divided into two groups: trained on a treadmill (n = 7, locomotion speed 27 cm s,1, 1 km daily, 5 days a week, for 4 weeks) and control (n = 11). The contractile properties of isolated MUs were studied. Functional isolation of units was achieved by electrical stimulation of filaments of the ventral roots. A total of 299 MUs were investigated (142 in the control group and 157 in the trained group). They were divided into fast fatigable (FF), fast resistant to fatigue (FR) and slow (S). Their proportions and parameters of contractions were analysed. Results:, Following training, the number of FF units decreased and the number of FR units increased. The distribution of the fatigue index changed within these two types of fast units. The twitch and tetanus forces increased considerably in fast MUs, mainly in those of the FF type. The contraction and relaxation times shortened in the FR and S MUs. The steep part of the force,frequency curves shifted towards higher stimulation frequencies in FR and S units, while in FF units the shift was in the opposite direction. Conclusion:, The significant change in the proportions of fast MUs following training indicates FF to FR transformation. The various effects of training seen in the different MU types help explain the rationale behind mixed training. [source] Altered sensorimotor development in a transgenic mouse model of amyotrophic lateral sclerosisEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2004Julien Amendola Abstract Most neurodegenerative diseases become manifest at an adult age but abnormalities or pathological symptoms appear earlier. It is important to identify the initial mechanisms underlying such progressive neurodegenerative disease in both humans and animals. Transgenic mice expressing the familial amyotrophic lateral sclerosis (ALS)-linked mutation (G85R) in the enzyme superoxide dismutase 1 (SOD1) develop motor neuron disease at 8,10 months of age. We address the question of whether the mutation has an early impact on spinal motor networks in postnatal mutant mice. Behavioural tests showed a significant delay in righting and hind-paw grasping responses in mutant SOD1G85R mice during the first postnatal week, suggesting a transient motor deficit compared to wild-type mice. In addition, extracellular recordings from spinal ventral roots in an in vitro brainstem,spinal cord preparation demonstrated different pharmacologically induced motor activities between the two strains. Rhythmic motor activity was difficult to evoke with N -methyl- dl -aspartate and serotonin at the lumbar levels in SOD1G85R mice. In contrast to lumbar segments, rhythmic activity was similar in the sacral roots from the two strains. These results strongly support the fact that the G85R mutation may have altered lumbar spinal motor systems much earlier than previously recognized. [source] Histopathological basis of Horner's syndrome in obstetric brachial plexus palsy differs from that in adult brachial plexus injuryMUSCLE AND NERVE, Issue 5 2008Yi-Gang Huang MD Abstract Although Horner's syndrome is usually taken as an absolute indicator of avulsions of the C8 and T1 ventral roots in adult brachial plexus injury, its pathological basis in obstetric brachial plexus palsy (OBPP) is unclear. We therefore examined the morphological mechanism for the presence of Horner's syndrome in brachial plexus injury in infants and adults. Some axons of sympathetic preganglionic neurons in T1 innervate the superior cervical ganglion via the C7 ventral root in infants but not in adults. Therefore, the presence of Horner's syndrome may relate in part to avulsion of the C7 root in OBPP. These findings suggest that Horner's syndrome in OBPP is not necessarily indicative of avulsions of the C8 and T1 roots, as it can occur with avulsion of the C7 root. Muscle Nerve, 2008 [source] Gentle dorsal root retraction and dissection can cause areflexia: Implications for intraoperative monitoring during "selective" partial dorsal rhizotomyMUSCLE AND NERVE, Issue 10 2001Eric L. Logigian MD Abstract During partial dorsal rhizotomy (PDR), intraoperative dorsal rootlet stimulation often evokes nonreflex, rather than reflex, motor responses that are due to costimulation of adjacent ventral roots. Intraoperative areflexia typically predicts that motor responses evoked by dorsal rootlet stimulation are nonreflexive. The cause of areflexia during PDR is in part due to anesthesia, but other mechanisms are likely to play a role as well. In this study of three consecutive patients undergoing lumbosacral neurosurgery, soleus H-reflexes evoked by tibial nerve stimulation at the popliteal fossa were found to suddenly decline in amplitude following retraction and gentle dissection of the S-1 dorsal root. In one areflexic patient, dorsal rootlet stimulation proximal to the main site of dissection evoked soleus H-reflexes, although they could not be evoked by tibial nerve stimulation. We conclude that the gentle retraction and dissection of dorsal rootlets that occurs during PDR can induce conduction block of reflex afferents. High-intensity dorsal rootlet stimulation distal to the site of conduction block may then evoke not reflex responses, but rather nonreflex motor responses, due to the costimulation of adjacent ventral roots. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1352,1358, 2001 [source] Selective activation of the sacral anterior roots for induction of bladder voidingNEUROUROLOGY AND URODYNAMICS, Issue 2 2006Narendra Bhadra Abstract Aim We investigated the efficacy of selective activation of the smaller diameter axons in the sacral anterior roots for electrically induced bladder voiding. Materials and Methods Acute experiments were conducted in five adult dogs. The anterior sacral roots S2 and S3 were implanted bilaterally with tripolar electrodes. Pressures were recorded from the bladder and from the proximal urethra and the external urethral sphincter. A detector and flow meter monitored fluid flow. A complete sacral dorsal rhizotomy was carried out. The effects of two types of pulse trains at 20 Hz were compared; quasitrapezoidal pulses (500 µsec with 500 µsec exponential decay) and interrupted rectangular (100 µsec, 2 sec on/2 sec off). Before rhizotomy, rectangular pulse trains (100 µsec) to activate all fibers were also applied. The experimental design was block randomized before and after rhizotomy. Results Quasitrapezoidal pulses showed block of sphincter activation with average minimum current for maximum suppression of 1.37 mA. All pulse types evoked average bladder pressures above the basal sphincter closure pressure. The pressure patterns in the proximal urethra closely followed the bladder pressures. Before dorsal rhizotomy, stimulation evoked a superadded increase in sphincter pressures with slow rise time. After rhizotomy, the sphincter pressure patterns followed the bladder pressures during selective activation and voiding occurred during stimulation with quasitrapezoidal trains and in between bursts with interrupted rectangular stimulation. Conclusions Selective activation of sacral ventral roots combined with dorsal rhizotomy may provide a viable means of low-pressure continuous voiding in neurological impairment. Neurourol. Urdynam. © 2005 Wiley-Liss, Inc. [source] Early Embryonic Development of the Camel Lumbar Spinal Cord SegmentANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005M. E. Abd Elmonem The lumbar spinal cord segment of the camel embryo at CVRL 2.4 to 28 cm was examined. Major changes are occurring in the organization of the lumbar spinal cord segments during this early developmental period. At the CVRL 2.4, 2.7 and 3.6 cm the three primary layers, ependymal cells layer, mantle cells layer, marginal cells layer in the developing lumber spinal cord segment were demonstrated. The mantle layer is the first to show striking differentiation, while the marginal layer is represented by thin outer rim. Proliferation and differentiation of the neuroepithelial cells in the developing spinal cord produce the thick lateral walls, thin roof and floor plates. The spinal ganglion and dorsal root of the spinal nerve are differentiated. At 2.7 cm CVRL differential thickening of the lateral walls produces a shallow longitudinal groove called sulcus limitans, which separates the dorsal part (alar plate) from ventral part (basal plate). The ventral root of the spinal nerve, the spinal cord and ganglion are embedded in loose mesenchyme, which tends to differentiate into spinal meninges. At 3.6 cm CVRL the basal plate, which is the future ventral gray horn, seem to be quite voluminous and the dorsal and ventral roots unite to form the beginning of the spinal nerve. At 5.5 cm CVRL the alar plates enlarge forming the dorsal septum. At 8.4 cm to 10.5 cm CVRL the basal plates enlarge, and bulge ventrally on each side of the midline producing the future ventral medium fissure, and the white and gray matters can be recognized. At 28 cm CVRL the lumen of the spinal cord is differentiated into the central canal bounded dorsally and ventrally by dorsal and ventral gray commissures, and therefore the gray matter takes the appearance of a butterfly. The lumber spinal nerve and their roots are well distinguished. [source] | |||||||||||||||||||||||||