Aspects of the macro and microscopic anatomy of the sciatic nerve in Wistar rats / Aspectos de la anatomía macro y microscópica del nervio ciático en ratas Wistar

The present study seeks to systematize morphological and morphometrical parameters and brings new data on the main branch of the lumbosacral plexus ­ i.e., sciatic nerve ­ in Wistar rats aged four and seven weeks. Sixteen female were divided into two groups, namely animals aged four weeks, and animals aged seven weeks. The specimens were studied at proximal and distal segments of the right hind limb sciatic nerves. Semi-thin transverse sections (0.25 µm thickness) were stained with 1 % toluidine blue, and the morphometric analysis was processed through the KS 400 software. Except for the number of fascicles and fascicular diameter, no differences were found between the proximal and distal segments. We observed differences when morphometric values were compared between 4- and 7- week old animals, with some exceptions (number of fascicles and myelinated fibers, and capillary area and number). The macroscopic data disagree with a previous description of the sciatic nerve being composed by two fascicles. Instead, sciatic nerve's only fascicle trifurcates or quadrifurcates at the distal third of the thigh. The total capillary area and density were calculated, and these are the first referential data for the sciatic nerve. Histograms of myelinated fiber and axons considering the animal ages were built. The results presented here are important because experimental studies, mainly studies on nerve regenerations require comparison with normal reliable data.

El objetivo fue sistematizar los parámetros morfológicos y morfométricos y traer nuevos datos sobre el ramo principal del plexo lumbosacro - es decir nervio ciático - en ratas Wistar de 4 a 7 semanas. Dieciséis ratas fueron divididas en dos grupos, con 4 y 7 semanas de edad. Las muestras estudiadas fueron los segmentos proximal y distal del nervio ciático derecho. Secciones delgadas (espesor 0,25 mm) fueron teñidas con azul de toluidina al 1 % y el análisis morfométrico se llevó a cabo utilizando el programa KS 400. Excepto para el número de fascículos y diámetro fascicular, no se encontraron diferencias entre los segmentos proximal y distal. Fueron observadas diferencias cuando se compararon los valores morfométricos entre animales de 4 y 7 semanas, con algunas excepciones (número de fascículos y fibras mielinizadas, área y número de capilares). Los datos macroscópicos no están de acuerdo con la descripción anterior del nervio ciático siendo compuesto por dos fascículos. En cambio, sólo trifurcación o cuadrifurcación fueron encontrados en el tercio distal del muslo. El área total capilar y la densidad fueron calculadas y estos constituyen los primeros datos de referencia para el nervio ciático. Se construyeron histogramas de fibras mielínicas y axones, teniendo en cuenta las edades de los animales. Los resultados presentados aquí son importantes porque los estudios experimentales, en especial aquellos sobre la regeneración nerviosa, requieren comparación con datos confiables normales.

Effects of running exercise on the hippocapal formation and the myelinated nerve fibers in the hippocampal formation of mid-aged rats / 解剖学报

ObjectiveTo investigate the effects of exercise on the hippocampal formation and the myelinated nerve fibers in the hippocampal formation of middle-aged rats. MethodsTen 14-month female SD rats were randomly divided into exercise group and sedentary group.Rats in the exercise group were forced to run on a treadmill for 4 months. After 4 months, spatial learning capacity of two group rats was tested using the Morris water maze.Then, the hippocampal formation and the myelinated nerve fibers in the hippocampal formation were quantitatively estimated using transmission electronic microscopy and stereological techniques. Results Treadmill running enhanced the spatial learning capacity of the rats. The volume of hippocampal formation and the total length of the myelinated nerve fibers in the hippocampal formation were significantly increased after 4 months exercise.However,there was no significant difference in the total volume of the myelinated fibers in the hippocampal formation between the two groups.The absolute distributions of the total length of the myelinated fibers in the hippocampal formation of two groups indicated that the exercise-induced increase of the total length of the myelinated nerve fibers in the hippocampal formation was mainly due to the increase of the myelinated fibers with small diameter. Conclusions Four months running exercise remarkably influence the spatial learning capacity,hippocampal formation and the myelinated fibers in the hippocampal formation of the middle-aged famale SD rats. The present results reveal a potential mechanism for the fact that exercise might improve brain function.

Stereological study of the age-related changes of the myelinated nerve fibers in the hippocampal formation of rat / 解剖学报

Objective To explore the changes of the hippocampal formation and the myelinated nerve fibers in the hippocampal formation of aged female Long-Evans rat. Methods The hippocampal formation and the myelinated nerve fibers in the hippocampal formation of 5 young (6-month old), 5 middle-aged (18-month old) and 6 aged (28-month old) female Long-Evans rats were quantitatively investigated with the stereological techniques and transmission electronic microscope technique. Results There were no significant changes in the volume of hippocampal formation, the volume density, the total volume, the length density and the mean diameter of the myelinated nerve fibers in the hippocampal formation among young, middle-aged and aged rats. When compared to that of young rats, the total length of the myelinated nerve fibers in the hippocampal formation of middle-aged rats was significantly increased by 63.6%. When compared to that of middle-aged rats, the total length of the myelinated nerve fibers in the hippocampal formation of aged rats was significantly decreased by 47.5%. When compared to that of young rats, the total length of the myelinated nerve fibers in the hippocampal formation of aged rats was non-significantly decreased by 13.8%. Conclusion Although the reason why the total length of the myelinated nerve fibers in the hippocampal formation of middle-aged rats was longer than that of young rats needs further investigations, the present results together with our previous findings in white matter and cortex further suggest that there are age-related changes of the myelinated nerve fibers in the normal aged brains.

The Effects of Soybean Diet on the Diabetic Neuropathy in the Rats / 대한해부학회지

Neuropathy is a serious and disabling complication that contributes to increased morbidity and mortality in diabetic patients. There is progressive distal to proximal axonal atrophy that ultimately leads to Wallerian degeneration. This study was performed to identify the effect of soy bean on diabetic neuropathy using morphometry. Male Sprague-Dawley rats were grouped into control, diabetic with red chow diet and diabetic with soy bean diet. The myelinated nerve fibers were counted and fiber size distributions were evaluated in each group at 4 and 8 weeks, respectively. Diabetic neuropathy didn't develop in streptozotocin-induced diabetic rats at four weeks. At 8 weeks, the myelinated nerve fiber in diabetic with soy bean diet was larger in number than that in diabetic to which did not be administered insulin. The number of myelinated nerve fiber was not different between diabetic group with insulin and without insulin. Mean myelinated nerve fiber size was smaller in diabetic with soy bean diet than diabetic with red chow diet and control. Histogram of fiber size distribution was shifted to left in diabetic with red chow and soy bean diet groups compared to control. Light and electron microscopic findings showed marked degeneration of nerve fibers in diabetic with red chow diet but preservation in diabetic with soy bean diet. The level of glucose and HbA1c was lower in diabetic with soy bean diet than red chow diet. Soy bean could be effective in the protection of neuropathy induced by diabetes mellitus.

Ocular Findings Associated with Peripapillary Myelinated Nerve Fibers of 3 Clock Hours or More

PURPOSE: We evaluated the ocular findings associated with peripapillary myelinated nerve fibers of 3 clock hours or more in 15 patients. METHODS: Ophthalmologic examination was performed in 15 patients with peripapillary myelinated nerve fibers of 3 clock hours or more. Twelve younger patients who wanted occlusion therapy were enrolled into a therapeutic trial with spectacle correction and occlusion for amblyopia. RESULTS: Thirteen out of the 15 patients presented with varying degrees of anisomyopia and amblyopia. The final visual acuities of the 12 younger patients with spectacle correction and occlusion for amblyopia were 0.5 or better in 5, between 0.1 and 0.5 in 4, and worse than 0.1 in 3. Two patients showed no ocular abnormalities except negligible refractive errors. Five out of 13 patients with amblyopia showed constant exotropia and one showed intermittent exotropia in the eyes with myelinated nerve fibers. CONCLUSIONS: Most of the patients with peripapillary myelinated nerve fibers of 3 clock hours or more showed anisomyopia and amblyopia. As some patients responded to spectacle correction and occlusion therapy for amblyopia, aggressive amblyopia therapy should be considered even in patients with myelinated nerve fibers.

Electron Microscopic Study of the Corneal Nerve by Flat Serial Section

PURPOSE: This study was performed to describe the ultrastructure of stromal nerve fibers in central, mid-peripheral, and peripheral parts of the human cornea by flat serial corneal section. METHODS: Seven samples from fresh normal cornea, derived from eyes with retinoblastoma and eyes from eye bank, were processed for transmission electron microscopic examinations. Flat serial sections reaching from mid-epithelium to the anterior stroma were observed. RESULTS: The myelinated and unmyelinated nerve fibers are alternately arranged and run parallel to the stromal collagen fibers at the periphery of the cornea. The main difference between the limbal and the central cornea is the presence of myelinated nerve fibers in the anterior peripheral stroma. The diameter of the unmyelinated nerve fiber measures between 0.25 and 0.63 micrometer in size. The corneal nerve fibers contain vesicles, mitochondria, and glycogen particles. The peripheral nerve fibers contain both clear and dense vesicles. The nerve fiber is separated by an interval of 0.3 micrometer from the cytoplasmic wall of keratocyte at the center of the cornea. CONCLUSIONS: The majority of the corneal nerve fibers can be classified as C-fibers due to their size. The presence of both clear and dense vesicles within the cytoplasm of the periphery of the cornea suggest that a small portion in the peripheral corneal nerve may be originated from the sympathetic nervous system. A close vicinity between the nerve fibers and keratocyte supports that nerve fibers might modulate the release of growth factors in the regulation of stromal and epithelial metabolism.

Morphological Changes of Cerebrum in Rabbits Exposed to Microwaves

The author measured the severity of brain damage of 36 rabbits irradiated 2.45 GHz microwave for 10 minutes, 20 minutes and 30 minutes, respectively. Electromicroscopic and light microscopic findings of just after, 1 weeks, 2 weeks and 4 weeks after irradiated brain were compared in each time. Swelling and vacualization of nerve cell and mitochondria were noted. Also these changes tend to increased severity along amount of radiation, but revealed reversible changes with time. Myelinated and unmyelinated nerve fibers were examined as same manner. These nerve fibers also revealed swelling and vascuolization, these findings also tend to increase severity with irradiation power and more prominent at unmyelinated nerve fibers. Reversability of these findings after each time period were more prominent in myelinated nerve fibers than unmyelinated nerve fibers.

The Effect of Nimodipine on Experimental Spinal Cord Injury

Nimodipine the potent, centrally active, clacium channel blocker, is known to increase cerebral and spinal blood flow. In the present study, the authors investigated the effect on Nimodipine on injured spinal cord. The experiment was a randomized blind study in which four groups of five cats received Nimodipine(0.05mg/kg) intravenously, and control groups of five cats received only Diluent. As a step in the investigation of the possible effect of spinal cord trauma on biochemical and ultrastructural changes in the injured cord, activities of lipid peroxidation were measured in the frozened-dried sample of the spinal cord and fine structure of the mylinated nerve fiber in the white matter were observed. An increase of lipid peroxidation level was found as early as 1 hour after the injury and the highest concentration was reached at 5 hours after the injury(P<0.01). Fine structures of the myelinated nerve fibers were changed progressively with the lapse of time after the injury. The effect of Nimodipine on lipid peroxidation and fine ultrastructural changes of myelinated nerve fibers were studied, and the result of this study revealed that Nimodipine groups showed a lower level of lipid peroxidation with statistical significance(P<0.05) and preservation of ultrastructural myelinated nerve fiber was prominent.

The Effect of Thyrotropin Releasing Hormone on the Somatosensory Evoked Potentials and the Ultrastructure of Myelinated Nerve Fibers in Injuried Spinal Cord

The purpose of this study was to determine the effect of treatment with thyrotropin releasing hormone(TRH) on the somatosensory evoked potentials(SSEPs) and ultrastructures of myelinated nerve fibers in injured spinal cords. Spinal cords of cats were injured expermentally at the second lumbar vertebra level with 20gm-20cm(400gm-cm) impact force using modified Allen's weight drop method. The animals were treated with TRH(2mg/Kg, bolus, then 2mg/Kg/hour, IV, for 4 hours) 1 hour after injury. SSEPs were checked serially in both treated and untreated groups for 24 hours. And the fine strucures of myelinated nerve fibers in the white matters were observed in electronmicroscope before and after the injury in both groups. In treated groups, the inital positive waves were re-elicited 3 hours after injury which was eliminated immediately after injury. Fine structure of the myelinated nerve fibers were changed progressively. With time after injury, the myelinated nerve fibers showed enlarged periaxonal spaces, irregulary contoured axons, and disarray of myelin sheaths. By 4 hours after injury, there appeared marked separation and disrray of myelin sheaths, and mitochondria and neurofibrils in axoplasm showed serve degeneration. The result of this study suggested that TRH has a beneficial effect on the re-elicitation of SSEP's and the preservation of myelinated nerve fibers in the acute stage of spinal cord injury.

A Study of the Effect of Naloxone on the Lipid Peroxidation and the Fine Structure of the Myelin Sheath in the Injured Spinal Cord

Spinal Cord contusions in cats were produced experimentally by impact injuries to the surgically exposed cord at the second lumbar vertebral level. As a step in the investigation of the possible effect of spinal cord trauma on biochemical and ultrastructural changes in the injured cord, activities of lipid peroxidation were measured in the frozen-dried sample of the spinal cord and the fine structure of the myelinated nerve fiber in the white matter were observed before and after the cord injury. An increase of lipid peroxidation level was found as early as 30 minutes after the injury and the highest concentration was reached at 4 hours of injury. Fine structures of the myelinated nerve fibers were changed progressively with the lapse of time after the injury. By 1 hour after the contusion the myelinated nerve fibers showed moderately enlarged periaxonal space, attenuation and disarray of the myelin sheaths. By 4 hour after the contusion, there appeared disarray of the myelin sheaths, greatly enlarged periaxonal space and irregulary contoured axons. The effect of naloxone of the lipid peroxidation and fine ultrastructure of the myelinated nerve fibers were studied, and the results of this study suggested that naloxone have a beneficial effect on the change in lipid peroxidation and the preservation of the myelinated nerve fibers after injury.