Effect of perinatal food deficiencies on the compound action potential evoked in sensory nerves of developing rats

The aim of this study was to analyze the possible alterations produced by inadequate perinatal food intake, in quantity (undernutrition) or quality (malnutrition), on the generation and propagation of the compound action potential (CAP) evoked in sensory sural nerves, during the postnatal development of the rat. Low intensity stimulation (2-3 times the threshold of the most excitable nerve fibers; xT) of the sural nerve evoked an early potential (CAP-A component) which is due to activation of low-threshold, fast-conducting myelinated group A afferent fibers. Meanwhile, at higher stimulus intensity (20-30T) it produced a second, long-lasting potential (CAP-C component) probably due to activation of high-threshold, slow-conducting group Adelta or C afferent fibers. Compared to control nerves, the CAP-A component, but not the CAP-C component of undernourished and malnourished nerves showed significant changes in amplitude, area, electrical threshold and conduction velocity (except absolute refractory period) at several postnatal ages. Our results may suggest that a relative large number of myelinated group A afferent fibers in the sural nerve of undernourished and malnourished animals suffer severe alterations on their electrophysiological properties of generation and propagation of the action potential during the postnatal development of the rat.     

Effect of Perinatal Food Deficiencies on the Compound Action Potential Evoked in Sensory Nerves of Developing Rats

The aim of this study was to analyze the possible alterations produced by inadequate perinatal food intake, in quantity (undernutrition) or quality (malnutrition), on the generation and propagation of the compound action potential (CAP) evoked in sensory sural nerves, during the postnatal development of the rat. Low intensity stimulation (2–3 times the threshold of the most excitable nerve fibers; X T) of the sural nerve evoked an early potential (CAP-A component) which is due to activation of low-threshold, fast-conducting myelinated group A afferent fibers. Meanwhile, at higher stimulus intensity (20–30T) it produced a second, long-lasting potential (CAP-C component) probably due to activation of high-threshold, slow-conducting group Aδ or C afferent fibers. Compared to control nerves, the CAP-A component, but not the CAP-C component of undernourished and malnourished nerves showed significant changes in amplitude, area, electrical threshold and conduction velocity (except absolute refractory period) at several postnatal ages. Our results may suggest that a relative large number of myelinated group A afferent fibers in the sural nerve of undernourished and malnourished animals suffer severe alterations on their electrophysiological properties of generation and propagation of the action potential during the postnatal development of the rat.     

Morphometric analysis of normal human sural nerves for systematic clinical application]

To obtain normative data on the sural nerve for clinical evaluation of the pathologic process and severity of the various peripheral nerve disorders, a morphometric analysis was made on 30 control sural nerves from normal volunteers, and from patients and cadavers with no evidence of peripheral nerve involvement. The ages of volunteers, patients and cadavers ranged from 13 to 83 years. The data obtained included 1) the mean frequency of abnormal teased myelinated fibers and its upper limit value of 95% confidence interval, and 2) the mean densities of total, large and small myelinated fibers and of unmyelinated fibers and their lower limit value of 95% confidence interval for each decade. The linear correlation between the age and each of the frequencies of abnormal teased myelinated fibers and the densities of total, large and small myelinated fibers and of unmyelinated fibers were statistically significant (P less than 0.01). Therefore, the morphometric data obtained from the disease nerve should be compared with the normative data adjusted for the age of the subject described in this study.     

Quantitative ultrastructural evidence of myelin malformation in optic nerves of rats submitted to a multideficient diet

Pups were subjected to malnutrition by feeding the lactating mothers a multi-deficient (8% protein content) diet, known as regional basic diet (RBD), from birth up to weaning. The weanings were fed the same diet until 60 days of age. Ultrastructure of the optic nerve was analyzed at postnatal (P) day P8, P13, P21, P30 and P60. Electron microscopy revealed that at P8 the process of myelination has not started yet in neither groups. At P 13 different stages of myelination were observed and, in the experimental group, the optic nerve showed non-organized axon bundles and empty spaces. Control optic nerve at P21 exhibited axons with fully developed myelin sheath; whereas malnourished group had many axons being enveloped by myelin with anomalous alteration. These alterations were present in malnourished group at P30 and P60. Quantitative analysis showed statistically significant difference between control and malnourished groups when compared to the percentage of myelinated axons, axons with myelin anomalous alterations (MAA) and non-myelinated axons. Also, the myelin area was significantly smaller in malnourished groups when compared to control group. Finally, a high percentage of large non-myelinated fibers were found in the malnourished group. In conclusion, our results show that early malnutrition by a multideficient diet (RBD) affects permanently the optic nerve organization and myelination, indicating an impairment of nerve transmission and a probable dysfunction in the visual ability.     

From gene to disease; Charcot-Marie-Tooth disease or the hereditary motor and sensory neuropathies

Charcot-Marie-Tooth disease is a clinically and genetically heterogeneous group of inherited neuropathies. The common clinical symptoms include distal muscle weakness, wasting and impaired distal sensation, more in the legs than in the arms, and reduced or absent reflexes. Moreover, foot and hand deformities are often encountered. A distinction between a primarily demyelinating or axonal neuropathy is often possible by means of nerve conduction studies. The major groups of inheritance are the autosomal dominant CMT1 (demyelinating), CMT2 (axonal) and the X-linked type (CMTX), but there are also autosomal recessive demyelinating (CMT4) and axonal (AR-CMT2) forms. The number of genes and loci is steadily increasing, with genes encoding proteins involved in myelin maintenance and axonal function, but also with genes encoding proteins, the function of which in peripheral nerve maintenance is notyet clear. Despite the increase in the number of known genes, especially for CMT2, there are many patients in whom no mutation can yet be found.     

Determination of the exposure concentration of propylene oxide to produce neuropathy in rats

Although propylene oxide, which is similar in chemical structure to ethylene oxide, is expected to produce neuropathy, there is no convincing evidence of the degeneration of the peripheral nervous system. To determine the exposure concentration of propylene oxide necessary to produce neuropathy in male Wistar rats, we subjected them to repeated exposures of propylene oxide at concentrations of 500, 750, 1000, 1500 and 2000 ppm. The test rats were subjected to a single 6 hour exposure of propylene oxide at a concentration of 1500 parts per million 5 times a week for 3 weeks. They developed a significant decrease in body weight, abnormal posture of the hindlegs and axonal degeneration of myelinated fibers in the peroneal and sural nerves, the nerves to the soleus muscle, and in the fasciculus gracilis of the spinal cord. Therefore, it was concluded that propylene oxide induces neuropathy in rats characterized by axonal degeneration, similar to that produced by ethylene oxide, and that the exposure to the higher concentration of propylene oxide is more necessary to produce neuropathy than in the case of ethylene oxide neuropathy in rats.     

腓骨肌萎缩症家系的基因突变与周围神经电生理特点分析

目的对65个腓骨肌萎缩症家系先证者进行基因突变检测,并进行临床电生理特点总结。方法应用实时荧光定量PCR、多聚酶链反应-单链构象多态性分析、DNA测序等方法 ,对65个腓骨肌萎缩症家系进行基因突变分析,对明确基因诊断的家系患者进行周围神经电生理特点分析。结果发现18个CMT1A家系,神经传导速度均明显减低(38m/s);7个CMTX家系,神经传导速度改变不一,可正常或显著减慢,男性患者的神经传导速度下降通常较女性患者为显著;1个CMT4A家系神经传导速度重度减慢;CMT2L家系、CMT2F家系各1个,正中神经运动传导速度减低不明显(38m/s),复合肌肉动作电位波幅明显降低;CMT1B家系1个,未行周围神经电生理检查。结论在65个临床诊断CMT家系中共确定了6种基因型共29个CMT家系的基因诊断,对CMT先证者及家系内患者的周围神经电生理改变特点的分析可为基因诊断提供指导性信息和发现亚临床症状的患者。     

Ultrastructural changes of cutaneous nerves in scleroderma.

Ultrastructural changes in cutaneous nerves of 38 patients with progressive scleroderma and eight patients with circumscribed scleroderma are described in the present study. Changes in the myelinated as well as in the unmyelinated fibers were observed in all cases. Myelinated fibers exhibited progressive disintegration of their myelin sheaths. Edema of the cytoplasm and various lesions of the organelles were observed in the Schwann cells. The basal membranes of both myelinated and unmyelinated fibers were irregularly thickened and flimsy in appearance. The axis cylinders were affected to a lesser extent. Edema of the axoplasm, and, less often, reduction of the number of neurofibrils and microtubules were observed there. Sometimes, the nerve fibers were enwrapped compactly by a considerable amount of collagen fibrils. The observed changes of the peripheral skin nerves are very often secondary. They are the morphologic basis of a limited or generalized neuropathy which sometimes develops.     

Pathologic processes of lumbar primary sensory neurons produced by high doses of pyridoxine in rats--morphometric and electron microscopic studies

The morphologic effects of the toxicity of high doses of pyridoxine hydrochloride (vitamin B6) on the lumbar primary sensory neurons in rats were studied. The test rats were treated with 1,200 mg/kg of pyridoxine hydrochloride by intraperitoneal injection once a day, and were sacrificed by perfusion at periods ranging from one to seven days after the injection, together with the control rats. Initial lesions consisted of eccentricity and crenation of the nucleus and vacuole formation in the cytoplasm of large dorsal root ganglion neurons, 2 days after the injection. These lesions were followed by segregation of the nucleolus, axon reaction-like changes in the cytoplasm and axonal degeneration of both peripheral axons in the sural nerve and central axons in the fasciculus gracilis. The frequency of teased myelinated fibers showing axonal degeneration during tests was significantly greater than in control 3 to 7 days after the injection. No significant difference of such frequency was found between the proximal and distal sural nerve during tests. The number of large myelinated fibers per nerve in the sural nerve, when compared with control, was preferentially decreased during tests. In the fasciculus gracilis, the decrease of the density of myelinated fibers was more pronounced in the third cervical segment than in the fifth thoracic segment. Because both peripheral and central axons were similarly affected and the initial lesions were found in the neuronal cell body, the mode of degeneration of axons in this study was regarded as "neuronopathy". By both light and electron microscopy, accumulation of mitochondria, vesicles, multilamellar and dense bodies were found in the nodal and distal paranodal axons of myelinated fibers in the sixth dorsal root ganglion on the 2nd day after the injection, which preceded the degeneration of both peripheral and central axons. Such accumulation, revealed for the first time in this study, may reflect the presence of a blockade of the axoplasmic transport in the proximal axon and cell body of the lumbar primary sensory neuron and subsequently give rise to the degeneration of both peripheral and central axons of the lumbar primary sensory neuron. The pathologic alterations at the different sites of the lumbar primary sensory neuron revealed in this study should be taken into consideration for the better understanding not only of the pathogenesis of human pyridoxine-induced sensory neuropathy, but also of other human and experimental neuropathies.     

Electroneurographic findings in patients with solvent induced central nervous system dysfunction.

The function of the peripheral nervous system was examined in a group of 32 men aged 30-65 (mean 49) with diagnosed solvent induced chronic toxic encephalopathy. The subjects were examined at the time of diagnosis and 26 were re-examined after a follow up period of 22-72 months (mean 40) and compared with a group of 50 unexposed male workers aged 27-64 (mean 42) with appropriate adjustment for age. All subjects were carefully scrutinised for alcohol abuse and other neurological diseases. The results of motor fibre neurography disclosed no difference between the groups. Nevertheless, a significant decrease in motor conduction velocity was found in the patients at follow up. Sensory fibre neurography showed signs of slight axonal degeneration with significantly decreased sensory nerve action potential amplitudes in the median and sural nerves; these amplitudes increased during follow up. The duration of sensory nerve action potentials was longer in the exposed group for the median and the sural nerves. The percentage of late components was significantly higher in the median nerve. The warm-cold sensitivity in the exposed group also indicated a slight sensory dysfunction with statistically significant wider detection limits.     

Propylene oxide causes central-peripheral distal axonopathy in rats

In Wistar rats subjected daily to a 6-hr exposure of propylene oxide (PO) at a concentration of 1,500 ppm (5 times a wk for 7 wk), ataxia developed in the hindlegs. Myelinated fibers in hindleg nerves and in the fasciculus gracilis showed axonal degeneration, sparing the nerve cell body of the first sacral dorsal root ganglion and myelinated fibers of the first sacral dorsal and ventral roots. These pathologic findings are compatible with central-peripheral distal axonopathy. This is apparently the first animal model of PO neuropathy to be verified histologically.     

Propylene Oxide Causes Central-Peripheral Distal Axonopathy in Rats

In Wistar rats subjected daily to a 6-hr exposure of propylene oxide (PO) at a concentration of 1,500 ppm (5 times a wk for 7 wk), ataxia developed in the hindlegs. Myelinated fibers in hindleg nerves and in the fasciculus gracilis showed axonal degeneration, sparing the nerve cell body of the first sacral dorsal root ganglion and myelinated fibers of the first sacral dorsal and ventral roots. These pathologic findings are compatible with central-peripheral distal axonopathy. This is apparently the first animal model of PO neuropathy to be verified histologically.     

Hypertrophic neuropathy with diabetes mellitus

A 52-year-old male with diabetes mellitus showed sensorimotor disturbance of symmetrical glove and stocking distribution. Electromyography demonstrated signs of denervation, and motor nerve conduction velocities could not be obtained because the muscle action potential was not evoked by the electrical stimulation of the nerves. Quantitative histologic and ultrastructual studies were performed in the sural nerve biopsy. Determination of fiber densities revealed a striking decrease of both myelinated and unmyelinated fibers and remarkable increase of the onion bulb formations. Hypertrophic changes with onion bulb formations have been observed in various clinical conditions, particularly in hereditary disorders, but uncommon in diabetic neuropathy. Our case was non-familial and may form one atypical type of diabetic neuropathy.     

A family of hereditary neuropathy with liability to pressure palsies with a proband who developed right and left foot drop successively following the left radial nerve palsy

A 41-year-old man developed multifocal mononeuropathies manifesting right and left foot drop successively, following the left radial nerve palsy as an initial symptom. Based on the neurological findings and the results of the genetic study of peripheral myelin protein (PMP) 22 gene and the histological study of the sural nerve on biopsy, the diagnosis of hereditary neuropathy with liability to pressure palsies (HNPP) was made. Two asymptomatic carriers were found among his family members based on the genetic study. The diagnosis of HNPP can be definitely established by the genetic study and this disease is relatively rare. In this report it is important to note that there are a few patients who show radial nerve palsy as an initial symptom, that we should carefully study the family members to obtain the prevalence of HNPP because asymptomatic carriers may be present, and that the carriers should be advised to avoid strenuous exercises and works which may produce excessive extension or compression of nerve trunks with the subsequent development of clinical symptoms.     

Neurotoxicity of 1-bromopropane in rats

Neurotoxicity of 1-bromopropane (1-BP) used as an alternative solvent of fluorocarbons was experimentally studied. Eight rats in the experimental group were exposed to 1-BP at 1500 ppm for six hours a day, five days a week for four weeks in an exposure chamber. Another eight rats in the control group were exposed to room air in a similar exposure chamber as those in the experimental group. During the latter half of the fourth week of exposure, all the rats in the experimental group showed a loss of body weight and ataxic gait compared with control rats. At the end of the fourth week, the rats in both groups were perfused through the ascending aorta and fixed. The cerebellum, medulla oblongata, spinal cord and peripheral nerve were processed for histopathological studies. No statistically significant difference in the frequency of axonal degeneration in both peroneal and sural nerves was found between the experimental and control groups. In the cerebellum, the frequency of degeneration of Purkinje cells in both the vermis and hemisphere was higher in the experimental group than in the control group (P < 0.05). There was no significant difference in the frequency of myelin ovoids in the fifth thoracic and in the third cervical posterior columns of the spinal cord between control and experimental groups. There was also no significant difference in the frequency of axonal swelling in the nucleus gracilis of the medulla oblongata between control and experimental groups. Ataxic gait was considered to be induced by degeneration of Purkinje cells in the cerebellum due to 1-BP exposure. However, degenerative findings of nerve fibers in the peripheral nerve, spinal posterior column and nucleus gracilis of the medulla oblongata due to 1-BP exposure were not evident. At the end of the fourth week of exposure, rats in the experimental group showed loss of body weight and markedly decreased motor activities, and it was considered that they would die if we continued the exposure into the fifth week. Therefore, we feel that our experimental schedule should be reconsidered before undertaking any further studies on the peripheral nerve toxicity of 1-BP.     

丙烯酰胺中毒后小鼠周围神经逆行性坏死的实验病理研究

目的 观察丙烯酰胺（ACR）中毒后变异的C57BL／Ola（Ola）鼠与正常的C57BL／6J（6J）鼠轴突逆行性坏死的病理改变及责任中鼠的不同点;探讨轴突与神经元损伤的关系。方法 利用光镜和电镜技术对腓神经、腓肠神经及背根神经节神经元的改变进行定性和定量分析。结果 光镜下6J鼠总纤维面积明显增大,纤维密度明显降低,大径纤维减少;轴突肿胀,髓鞘深染,形状不规划。背根神经节中一些亮细胞（A型细胞）核偏向一侧,胞浆内有一些暗颗粒。电镜下见轴突内神经微丝增多,线粒体堆积。背根神经节细胞胞浆内线粒体呈空泡样或凝聚样变性。Ola鼠未见明显改变。结论 Ola鼠对ACR所致的类化勒氏变性反应是延迟的,而6J鼠中毒后出现轴突肿胀、变性,电镜下神经微丝的聚集、线粒体堆积为特征;ACR先侵犯神经元,继之产生远端轴突变性。     

Histologic peripheral nerve changes in rats induced by deltamethrin

Synthetic pyrethroid insecticides have been used in the last two decades largely because of their high activity as an insecticide and low mammalian toxicity. Some studies have demonstrated that these products, especially compounds with an alpha-cyano group, are toxic to the mammalian central nervous system (CNS) in acute intoxications. However, morphological studies are scarce. In the present work the histopathologic changes of the sciatic and tibial nerves of rats submitted to acute intoxication with the cyanopyrethroid deltamethrin were studied. For 3 consecutive days male Wistar rats received by oral gavage deltamethrin at a dose of 45 mg/kg body wt. On the 4th day fragments of sciatic and tibial nerves were studied by transmission electron microscopy (TEM) and teasing of individual nerve fibers. In addition, another group of rats were allowed to recover until the 10th day. Teasing of nerves of animals sacrificed on the 4th day revealed myelin ovoids, which are indicative of axonal damage. TEM demonstrated rare degenerated axons completely filled with organelles, in particular mitochondria, and with electron-dense lamellar bodies that resemble myelin figures. In addition, great cytoplasmic vacuolization caused by proliferation and dilation of the rough and smooth endoplasmic reticulum and Golgi apparatus was observed in some Schwann cells. No lesion was found 7 days after discontinuation of the treatment (group2). Since these histologic changes are transitory and scarce, the question arises: Are they related to the changes in NA(+), K(+)-ATPase activity or Na(+) channels caused by pyrethroid compounds?     

Electrophysiology and nerve biopsy in men exposed to lead

ABSTRACT Twenty lead-exposed men were selected on the basis of a maximum level of lead in the blood of 70-140 μg/100 ml within the past year. There was no clinical evidence of neuropathy attributable to lead and haemoglobin levels were normal. In individuals, maximum motor and sensory conduction and the amplitude of the evoked potentials were normal or borderline in the median, peroneal and sural nerves, except in the distal portion of the deep peroneal nerve. In this nerve, motor conduction was slowed because of compression by metal-lined safety shoes; changes in this segment are not included in the findings. When the average conduction velocity in lead-exposed men was compared with the average in nerves of controls matched for age, distal motor latency was slightly prolonged in the median nerve. The average latency for proximal muscle supplied by the peroneal nerve was prolonged, and the maximum motor conduction velocity was slowed in the median nerve from elbow to wrist (0·01 > p <0·001). In addition, the average maximum sensory conduction was slightly slowed along the distal and intermediate portion of the superficial peroneal and sural nerves (p <0·001). The average minimum sensory conduction velocities were normal, as were the average amplitudes of the evoked muscle action potentials and the average ratio of amplitude of the muscle action potential evoked by stimuli at a proximal and a distal nerve site. The average amplitude of the sensory potentials recorded in the median and the superficial peroneal nerves tended to be increased. Electromyography of the abductor pollicis brevis and anterior tibial muscles showed that the only abnormality was an increased incidence of polyphasic potentials in the anterior tibial muscle of seven men. Neither the slowing in conduction nor the histological findings in the sural nerves of eight men were related to the level of lead in the blood. The slight slowing in conduction suggests a minor defect in the excitable membrane of the nerve fibre: it was not attributable to histological abnormalities in the sural nerve, in which the number of myelinated and unmyelinated nerve fibres was normal and demyelination was absent. In teased fibres, those with paranodal remyelination were slightly increased, and few fibres had segments with diminished diameter. The mechanism of the defect causing the slight slowing in conduction in lead-exposed men seems to differ from the lesion in patients with clinical evidence of lead neuropathy, which is axonal in type. It is, therefore, doubtful whether the slight slowing in the nerves of the group of lead-exposed men should be classified as a subclinical neuropathy.     

Assessment of the scientific basis for genetic testing of railroad workers with carpal tunnel syndrome

In 2000, approximately 20 railroad track workers who filed injury reports or compensation claims for carpal tunnel syndrome were tested by their employer for two genetic traits to determine the work relatedness of the condition. The testing involved deletions, variants, or mutations in the genetic coding for peripheral myelin protein (PMP22) and transthyretin (TTR). This article is an assessment of whether there is a scientific basis for such testing. A review of the scientific literature indicated that neither the scientific basis nor the population validity of the PMP22 or TTR tests for carpal tunnel syndrome were adequately established before use on railroad track workers in 2000. Although ethical and legal issues may predominate in this case, the absence of a compelling scientific basis undermines the decision to conduct the tests.