Spastic long-lasting reflexes in the awake rat after sacral spinal cord injury.
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Following chronic sacral spinal cord transection in rats the affected tail muscles exhibit marked spasticity, with characteristic long-lasting tail spasms evoked by mild stimulation. The purpose of the present paper was to characterize the long-lasting reflex seen in tail muscles in response to electrical stimulation of the tail nerves in the awake spastic rat, including its development with time and relation to spasticity. Before and after sacral spinal transection, surface electrodes were placed on the tail for electrical stimulation of the caudal nerve trunk (mixed nerve) and for recording EMG from segmental tail muscles. In normal and acute spinal rats caudal nerve trunk stimulation evoked little or no EMG reflex. By 2 wk after injury, the same stimulation evoked long-lasting reflexes that were 1) very low threshold, 2) evoked from rest without prior EMG activity, 3) of polysynaptic latency with >6 ms central delay, 4) about 2 s long, and 5) enhanced by repeated stimulation (windup). These reflexes produced powerful whole tail contractions (spasms) and developed gradually over the weeks after the injury (< or =52 wk tested), in close parallel to the development of spasticity. Pure low-threshold cutaneous stimulation, from electrical stimulation of the tip of the tail, also evoked long-lasting spastic reflexes, not seen in acute spinal or normal rats. In acute spinal rats a strong C-fiber stimulation of the tip of the tail (20 x T) could evoke a weak EMG response lasting about 1 s. Interestingly, when this C-fiber stimulation was used as a conditioning stimulation to depolarize the motoneuron pool in acute spinal rats, a subsequent low-threshold stimulation of the caudal nerve trunk evoked a 300-500 ms long reflex, similar to the onset of the long-lasting reflex in chronic spinal rats. A similar conditioned reflex was not seen in normal rats. Thus there is an unusually long low-threshold polysynaptic input to the motoneurons (pEPSP) that is normally inhibited by descending control. This pEPSP is released from inhibition immediately after injury but does not produce a long-lasting reflex because of a lack of motoneuron excitability. With chronic injury the motoneuron excitability is increased markedly, and the pEPSP then triggers sustained motoneuron discharges associated with long-lasting reflexes and muscle spasms. (+info)
Alpha-1 adrenoceptor agonists generate a "fast" NMDA receptor-independent motor rhythm in the neonatal rat spinal cord.
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Noradrenaline, a potent activator of rhythmogenic networks in adult mammals has not been reported to produce functional rhythmic patterns in isolated spinal cords of newborn rats. We now show that a "fast" (cycle time: 1-4 s) transient rhythm was induced in sacrococcygeal (SC) and rostral-lumbar spinal segments of the neonatal rat by bath-applied noradrenaline. The fast rhythm was blocked by 1 microM of the alpha1-adrenoceptor antagonist prazosin but not by 1-20 microM of the alpha2-adrenoceptor blocker yohimbine, it could be initiated and maintained by alpha1-adrenoceptor agonists, and it was accompanied by a slow nonlocomotor rhythm. Transection at the lumbosacral junction abolished the fast-thoracolumbar (TL) rhythm while the fast-SC and slow-TL rhythms were unaffected. The N-methyl-d-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonopentanoic acid (AP5) abolished the slow- and did not interrupt the fast rhythm. Thus alpha1-adrenoceptor agonists induce an NMDA receptor-independent rhythm in the SC cord and modulate NMDA receptor-dependent rhythmicity in TL segments. Injection of current steps into S(2) and flexor-dominated L(2) motoneurons during the fast rhythm revealed a 20-30% decrease in input-resistance (R(N)), coinciding with contralateral bursting. The R(N) of extensor-dominated L(5) motoneurons did not vary with the fast rhythm. The rhythmic fluctuations of R(N) in L(2) motoneurons were abolished, but the alternating left-right pattern of the fast rhythm was unchanged in midsagittally split TL cords. We suggest that the locomotor generators were not activated during the fast rhythm, that crossed-inhibitory pathways activated by SC projections controlled the rhythmic decrease in R(N) in L(2) motoneurons, and that the alternating pattern of the split TL cord was maintained by excitatory SC projections. (+info)
First-trimester diagnosis of sacrococcygeal teratoma: the role of three-dimensional ultrasound.
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A fetus was suspected of having a sacrococcygeal teratoma (SCT) on routine nuchal translucency evaluation by sonography at 12+3 weeks. The patient was referred for three-dimensional (3D) sonography to further delineate the extent of the mass. In this case, real-time scanning of the mass in 3D mode assisted the diagnosis of the mass and patient counseling. We present what we believe to be the first case of SCT imaged in the first trimester using 3D ultrasound. (+info)
MAdCAM-1 expressing sacral lymph node in the lymphotoxin beta-deficient mouse provides a site for immune generation following vaginal herpes simplex virus-2 infection.
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The members of the lymphotoxin (LT) family of molecules play a critical role in lymphoid organogenesis. Whereas LT alpha-deficient mice lack all lymph nodes and Peyer's patches, mice deficient in LT beta retain mesenteric lymph nodes and cervical lymph nodes, suggesting that an LT beta-independent pathway exists for the generation of mucosal lymph nodes. In this study, we describe the presence of a lymph node in LT beta-deficient mice responsible for draining the genital mucosa. In the majority of LT beta-deficient mice, a lymph node was found near the iliac artery, slightly misplaced from the site of the sacral lymph node in wild-type mice. The sacral lymph node of the LT beta-deficient mice, as well as that of the wild-type mice, expressed the mucosal addressin cell adhesion molecule-1 similar to the mesenteric lymph node. Following intravaginal infection with HSV type 2, activated dendritic cells capable of stimulating a Th1 response were found in this sacral lymph node. Furthermore, normal HSV-2-specific IgG responses were generated in the LT beta-deficient mice following intravaginal HSV-2 infection even in the absence of the spleen. Therefore, an LT beta-independent pathway exists for the development of a lymph node associated with the genital mucosa, and such a lymph node serves to generate potent immune responses against viral challenge. (+info)
Distinct profiles of refilling of inhibitory neurotransmitters into presynaptic terminals projecting to spinal neurones in immature rats.
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Corelease of glycine and GABA from the single synaptic terminal (synaptic bouton) is well accepted in immature rat spinal cord and brainstem. However, it raises the question of how glycine and GABA are accumulated in the same synaptic vesicles and coreleased. To address this issue, spontaneous miniature inhibitory postsynaptic currents (mIPSCs) and focally evoked IPSCs (eIPSCs) mediated via a single synapse were recorded from synaptic bouton preparations of the rat immature sacral dorsal commissural nucleus (SDCN) neurones by whole-cell patch recording. Focal stimulation of a single synaptic bouton revealed that three different quantal releases occur from a single synaptic bouton: i.e. pure glycine, pure GABA, and mixed. Prolonged treatment with bafilomycin A1, a vacuolar-type H+/ATPase inhibitor, to the SDCN neurone greatly suppressed frequency and amplitude of the mIPSCs. During washing out of bafilomycin A1, complete recovery in the amplitude of glycinergic mIPSCs was observed, while that of GABAergic and mixed mIPSCs was incomplete. These observations indicate that three types of vesicles coexist in single synaptic terminals, and that refilling of glycine into the synaptic vesicle predominantes over GABA after pretreatment with bafilomycin A1 in immature rats. This could be explained by the decrease in the cytosolic concentration of GABA, or by the presence of subtypes of vesicular inhibitory amino acid transporter in the synaptic vesicle membrane. (+info)
Suspected metastatic coccygeal chordoma in a ferret (Mustela putorius furo).
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A chordoma was removed from the tail base of a 6.5-year-old ferret (Mustela putorius furo). A nodule was observed in the area of tumor development when the ferret was purchased at 3 months of age. Although the nodule did not enlarge for 2 years, slow, steady growth of the tumor was observed for 4 years before surgical removal. Eight months after removal of the chordoma, the ferret developed 2 cutaneous masses. One was adjacent to the vulva, close to where the chordoma had been removed from, whereas the other was in the nasofacial region. After 4 months of slow growth, both masses were removed and both were histologically and immunohistochemically consistent with chordoma. Over the next 8 weeks, additional masses developed in the facial, maxillary gingival, and scapular regions. Enlargement of the gingival mass caused dysphagia, and the ferret was euthanized. Although a necropsy was not performed, these additional masses had a clinical appearance and texture that was similar to the 2 previously removed cutaneous chordomas. To the authors' knowledge, this is the first report of a ferret coccygeal chordoma that developed close to the base of the tail. Ferret chordomas have been reported previously to metastasize to the subcutis overlying the tumor. However, this is the first report of a ferret chordoma that metastasized to a location distant to the primary site of neoplasm development. Cell proliferation indices did not predict this metastatic behavior. It is hypothesized that the long clinical period before removal may have predisposed this neoplasm to metastasis. Observations from this case suggest that chordomas in ferrets may have metastatic potential and so should be removed promptly. (+info)
Biomechanics of back pain.
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This paper offers a mechanistic account of back pain which attempts to incorporate all of the most important recent advances in spinal research. Anatomical and pain-provocation studies show that severe and chronic back pain most often originates in the lumbar intervertebral discs, the apophyseal joints, and the sacroiliac joints. Psychosocial factors influence many aspects of back pain behaviour but they are not important determinants of who will experience back pain in the first place. Back pain is closely (but not invariably) associated with structural pathology such as intervertebral disc prolapse and endplate fractures, although age-related biochemical changes such as those revealed by a 'dark disc' on MRI have little clinical relevance. All features of structural pathology (including disc prolapse) can be re-created in cadaveric specimens by severe or repetitive mechanical loading, with a combination of bending and compression being particularly harmful to the spine. Structural disruption alters the mechanical environment of disc cells in a manner that leads to cell-mediated degenerative changes, and animal experiments confirm that surgical disruption of a disc is followed by widespread disc degeneration. Some people are more vulnerable to spinal degeneration than others, largely because of their genetic inheritance. Age-related biochemical changes and loading history can also affect tissue vulnerability. Finally the concept of 'functional pathology' is introduced, according to which, back pain can arise because postural habits generate painful stress concentrations within innervated tissues, even though the stresses are not high enough to cause physical disruption. (+info)
Coccygectomy for intractable coccygodynia.
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BACKGROUND: Coccygectomy is an uncommon procedure that many surgeons are reluctant to perform due to its proximity to the anus and the risk of rectal perforation and infection. OBJECTIVES: To evaluate the diagnostic accuracy and outcome of coccygectomy. METHODS: We retrospectively reviewed the operative results in nine patients (seven females and two males) who underwent coccygectomy for coccygodynia in the last 5 years following failure of conservative treatment. RESULTS: The outcome of the procedure was excellent in five patients, good in one patient and poor in two patients. CONCLUSIONS: It is mandatory to perform bone scanning in every patient with coccygodynia and before coccygectomy in order to rule out the presence of malignancy. Coccygectomy is recommended for patients with isolated coccygodynia. (+info)