Localization of vinculin and talin at perineurial cells of human sural nerve
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Stiff-man syndrome (SMS) is a rare disorder characterized by fluctuating stiffness of axial and proximal limb muscles. The diagnosis is made on clinical signs and symptoms, and there is no diagnostic test specific for SMS. We here report a SMS patient who showed characteristic abnormal late responses upon transcranial magnetic stimulation (TMS).A 29-year-old woman complained of attacks of painful muscle stiffness mostly provoked by emotional stress or unexpected events. Thoracic and lumbar paraspinal, abdominal, and proximal left leg muscles were involved. During the attacks, which lasted for up to 2 min, the patient was unable to walk. Between attacks, there was fluctuating rigidity of the involved muscles. An insulin-dependent diabetes mellitus had been diagnosed 15 years before. On neurological examination, she fulfilled the criteria' for the diagnosis of SMS. Magnetic resonance imaging of the skull was normal. Cerebrospinal fluid was normal, but in 1991 there had been oligoclonal banding. Immunological studies showed high titers of autoantibodies against pancreatic islet cells. Anti-glutamic acid decarboxylase (GAD) antibodies were positive. Motor and sensory nerve conduction, needle electromyography of limb muscles, visual evoked potentials, and blink reflex were normal.Spasmodic reflex myoclonus, as recently described in 8 other cases of SMS,' was found only in lumbar and thoracic, and habituating excessive acoustic startle reflex' only in the lumbar paraspinal muscles.Upon TMS central motor conduction time (CMCT) was normal t o the hypothenar and anterior tibial muscles. Additionally, in the anterior tibial muscles there were late responses (LRs) upon cortical (latency 69-70 ms) and lumbar (latency 82-85 ms) stimulation (Fig. l a ) . The amplitude of the LR in the affected left leg was higher compared to the unaffected right leg. The LRs were independent of an attack of stiffness and did not habituate. The LRs were seen by different examiners on different days. Treatment b) right M Tib ant left M Tib ant v -T--7 %Mant right M Tib ant 20 ms/Div FIGURE 1. Results of magnetic stimulation (a) before and (b) after treatment with diazepam. Each trace shows the superposition of five responses, the upper two traces after contralateral cortical stimulation, the lowertwotracesafter ipsilateral lumbar stimulation (recordings from the anterior tibial muscles). Note the abnormal late response to the cortical stimulus in the affected left leg (arrow).with diazepam abolished the LRs (Fig. l b ) , but did not completely remove the symptoms of' the patient.In normal subjects the compound rnuscle actiori potential elicited by TMS is followed by a silent period that terminates at least 80 ms after the stimulus.' Hence, the LRs upon cortical stimulation were clearly abnormal. The amplitude of the LRs corresponded with the symptoms: the response was much higher in the clinically affected left leg compared to the right leg, and the LRs disappeared under treatment with diazepam. From this we conclude that the LRs are symptomatic...
Stiff-man syndrome (SMS) is a rare disorder characterized by fluctuating stiffness of axial and proximal limb muscles. The diagnosis is made on clinical signs and symptoms, and there is no diagnostic test specific for SMS. We here report a SMS patient who showed characteristic abnormal late responses upon transcranial magnetic stimulation (TMS).A 29-year-old woman complained of attacks of painful muscle stiffness mostly provoked by emotional stress or unexpected events. Thoracic and lumbar paraspinal, abdominal, and proximal left leg muscles were involved. During the attacks, which lasted for up to 2 min, the patient was unable to walk. Between attacks, there was fluctuating rigidity of the involved muscles. An insulin-dependent diabetes mellitus had been diagnosed 15 years before. On neurological examination, she fulfilled the criteria' for the diagnosis of SMS. Magnetic resonance imaging of the skull was normal. Cerebrospinal fluid was normal, but in 1991 there had been oligoclonal banding. Immunological studies showed high titers of autoantibodies against pancreatic islet cells. Anti-glutamic acid decarboxylase (GAD) antibodies were positive. Motor and sensory nerve conduction, needle electromyography of limb muscles, visual evoked potentials, and blink reflex were normal.Spasmodic reflex myoclonus, as recently described in 8 other cases of SMS,' was found only in lumbar and thoracic, and habituating excessive acoustic startle reflex' only in the lumbar paraspinal muscles.Upon TMS central motor conduction time (CMCT) was normal t o the hypothenar and anterior tibial muscles. Additionally, in the anterior tibial muscles there were late responses (LRs) upon cortical (latency 69-70 ms) and lumbar (latency 82-85 ms) stimulation (Fig. l a ) . The amplitude of the LR in the affected left leg was higher compared to the unaffected right leg. The LRs were independent of an attack of stiffness and did not habituate. The LRs were seen by different examiners on different days. Treatment b) right M Tib ant left M Tib ant v -T--7 %Mant right M Tib ant 20 ms/Div FIGURE 1. Results of magnetic stimulation (a) before and (b) after treatment with diazepam. Each trace shows the superposition of five responses, the upper two traces after contralateral cortical stimulation, the lowertwotracesafter ipsilateral lumbar stimulation (recordings from the anterior tibial muscles). Note the abnormal late response to the cortical stimulus in the affected left leg (arrow).with diazepam abolished the LRs (Fig. l b ) , but did not completely remove the symptoms of' the patient.In normal subjects the compound rnuscle actiori potential elicited by TMS is followed by a silent period that terminates at least 80 ms after the stimulus.' Hence, the LRs upon cortical stimulation were clearly abnormal. The amplitude of the LRs corresponded with the symptoms: the response was much higher in the clinically affected left leg compared to the right leg, and the LRs disappeared under treatment with diazepam. From this we conclude that the LRs are symptomatic...
The overall distribution of the actin cytoskeleton in perineurial cells of rat spinal nerves was examined by confocal laser and thin-section electron microscopy. Confocal laser microscopy of whole-mount nerves stained with fluorescent-labelled phalloidin revealed two types of actin bundles in perineurial cells; stress fiber-type actin bundles and circumferential actin bundles. The degree of development of the actin cytoskeleton varied in different segments of different nerves. Stress fiber-type actin bundles were also immunostained for myosin and vinculin and were well-developed in the perineurial cells of large-sized nerves and dorsal root ganglia, whereas they were poor in spinal nerve root sheaths within the subarachnoid space. In peripheral nerves, stress fiber-type actin bundles tended to be arranged transverse to the nerve axis. Circumferential actin bundles were localized along intercellular junctions, which were immunostained with several junctional proteins such as alpha-catenin, occludin and ZO-1. Thin-section electron microscopy confirmed the distribution pattern of actin bundles observed by confocal laser microscopy. These findings suggest that actin bundles may play some roles in structurally stabilizing the perineurium by providing mechanical support for the cell layers as well as cell junctions to maintain perineurial integrity and form diffusion barriers in peripheral nerves.
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