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.

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.

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.

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.