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.

Neuroprotective effect of melatonin in a rat model of streptozotocin-induced diabetic neuropathy: Light and electron microscopic study

Diabetes mellitus [DM] is the most common cause of peripheral neuropathy in most countries. Oxidative stress appears to be the most important pathogenic factor in underlying diabetic complications, including neuropathy. The present study aimed to investigate the possible neuroprotective effects of melatonin [MLT] in a rat model of streptozotocin [STZ]-induced diabetic neuropathy. Thirty-six [15 weeks old] adult male albino rats were divided into three groups. Group I [n=6] served as the control group. In group II [n=15], DM was induced by a single intraperitoneal injection of STZ at a dose of 60 mg/kg body weight and rats were sacrificed after 6 weeks. Rats in group III [n=15] were rendered diabetic by a single intraperitoneal injection of STZ, and immediately after confirmation of DM, that is, 48 h after STZ [random blood sugar > 200 mg/dl], rats received MLT at a dose of 10 mg/kg/day by intraperitoneal injection for 6 weeks. Body weight and random blood sugar were measured for all groups. Sciatic nerves of all the sacrificed animals were subjected to light microscopic, electron microscopic, and morphometric studies. In group II, DM induction was associated with the occurrence of neuropathy manifested by marked thickening of the epineurium and perineurium. Nerve fibers exhibited marked axonal atrophy, axonal shrinkage, axon-myelin separation, and in some sections total axonal destruction. Severe demyelination with evidence of myelin destruction was observed in the form of splitting and decompaction of myelin sheath lamellae, as well as vacuolization of the myelin sheath, forming fermentation chambers. In the MLT-treated group, vacuolization of the myelin sheath decreased remarkably and mild local axon separation from myelin sheaths was detected. Morphometric analysis revealed a significant increase in the number of total and apparently normal fibers and decrease in the number of apparently degenerated fibers in the nerve sections of MLT-treated rats, compared with nontreated diabetic rats. This study showed that MLT, in early stages of DM induction, decreased the destructive progress of DM and provided neuroprotection against damage resulting from STZ-induced hyperglycemia. Thus, it is recommended to start MLT therapy as soon as diagnosis of DM is established and even earlier in individuals at high risk for developing DM

Histologic study on the protective effect of alpha-lipoic acid in sciatic nerve neurotoxicity induced by cypermethrin in albino rats

This work was undertaken to study the possible protective role of ex-lipoic acid [ALA] in the sciatic nerve of rats intoxicated with the pesticide cypermethrin by histological and morphometric methods. Thirty adult male albino rats were randomly divided into five equal groups [six rats each]: group I [control group] received no treatment, group II received daily 1 ml of corn oil orally, group III received 100 mg/kg of oral ALA daily, group IV received oral cypermethrin [75 mg/kg] daily, and group V received both ALA and cypermethrin. After 5 days treatment, both sciatic nerves were dissected out from each animal, and then semithin and ultrathin sections were prepared for light and electron microscopic examinations. Morphometric and statistical analyses were also conducted, After cypermethrine administration, the sciatic nerve showed nerve damage particularly affecting the myelinated nerve fibers. The lesions were manifested as axonal damage and changes in the myelin sheath. Myelinated nerve fibers were swollen showing Wallerian degeneration. Ultrastructurally, myelin sheaths exhibited fragmentation, vacuolations, and hyalinization, Axoplasm displayed shrinkage, vacuolations, fragmentations, myelin figures, and intra-axonal wipe spaces, with swelling of Schwann cells. Unmyelinated fibers were minimally affected. Concomitant administration of ALA with cypermethrine displayed an observable protection against these changes. ALA showed a protective effect against sciatic neurotoxicity induced by cypermethrin in albino rats

Ethidium bromide-induced demyelination in the sciatic nerve of diabetic rats / Desmielinização induzida pelo brometo de etídio no nervo ciático de ratos diabéticos

This study aims to observe the process of myelin loss and repair following the injection of the gliotoxic agent ethidium bromide (EB) in the sciatic nerve of rats previously induced to diabetes mellitus by streptozotocin. Injection of EB was also done in non-diabetic rats. The animals were euthanatized from 3 to 31 days after intraneural injection and nerve sections were collected for ultrastructural study. In non-diabetic rats, Schwann cells (CS) showed signs of intoxication 3 days after, with cytoplasmic vacuolization and rejection of their myelin sheaths. Myelin debris were removed by macrophages in the endoneurium and mast cells were abundant in the lesions. From 14 days following EB injection, supernumerary CS were seen in the expanded endoneurium as well as thin myelin sheaths indicating remyelination. Diabetic rats presented a more extensive myelin vesiculation and segmentar demyelination, with delayed activities from both macrophages and remyelinating SC. No mast cells were noted.

O estudo visa à observação do processo de perda e reparo mielínico pós-injeção do gliotóxico brometo de etídio (BE) no nervo ciático de ratos previamente induzidos a diabetes mellitus pela estreptozotocina. Injeção de BE foi igualmente realizada em ratos não-diabéticos. Os animais foram eutanasiados dos 3 aos 31 dias pós-injeção intraneural, com colheita de amostras neurais para estudo ultra-estrutural. Nos animais não-diabéticos, as células de Schwann (CS) mostraram sinais de intoxicação a partir dos 3 dias pós-gliotóxico, com vacuolização citoplasmática e rejeição de suas bainhas de mielina. Restos mielínicos eram removidos por macrófagos no interior do endoneuro e mastócitos eram abundantes nas lesões. A partir dos 14 dias, CS supranumerárias foram encontradas no endoneuro expandido, além de finas bainhas de mielina indicativas de remielinização. Os ratos diabéticos apresentaram vesiculação mielínica e desmielinização segmentar mais extensas, bem como ausência de mastócitos e atraso na atividade macrofágica e na função remielinizante das CS.

Ultrastructural evaluation of the effects of cinnamon on the nervus ischiadicus in diabetic rats

To investigate the effects of oral cinnamon supplementation on the nervus ischiadicus at the electron microscopical level in rats. This study was performed between 2004-2006 in Dicle University School of Medicine, Diyarbakir, Turkey in 15 adult Sprague-Dawley rats. Rats were divided into 3 groups: control [C] [n=5], diabetic without cinnamon [D] [n=5], and diabetic with cinnamon [D-C] [n=5]. Diabetes was induced with intraperitoneal alloxan administration. All diabetic rats were treated with human insulin. All rats were fed with standard pellet chow. The D-C group rats were fed with standard pellet chow plus Cinnamomum cassia at the dose of 400 mg/kg. All rats were sacrificed after 3 months and we obtained the nervus ischiadicus of all rats. Contrast stained thin sections evaluated by Jeol-TEM-1010 electron microscope, were not statistically different in both groups and photo samples were obtained. Mean blood glucose, hemoglobin A1C, and lipid profile were not statistically different in both groups. Marked detachment of myelin lamellae at Schmidt-Lanterman clefts, lysis in cristae mitochondrialis and degenerative changes, severe dispersion of organelles in neurolemma, mesoaxon region, and remarkable edema at the endoneurium were found in diabetic rats. On the contrary, mesoaxon, nucleus, nucleolus and myelin sheet were almost of normal appearance at the ultra-structural level in the D-C group. Cinnamon extracts may have beneficial effects on the development of diabetic neuropathy in alloxan induced diabetic rats

Naturally supraorganized collagen increases axonal regeneration after tubulization repair

After axotomy, regeneration can be enhanced by bridging the transected nerve with a biocompatible tube, and the effect of trophic substances or molecules from the extracellular matrix can be investigated by filling the prosthesis. In this study, we assessed the importance of the molecular organization and aggregational state of collagen type I in axonal regeneration and guidance. Two types of collagen were used, namely, a collagen gel derived from bovine tendon that displays supraorganization after extrusion, and collagen from rat tail which does not self-organize under such conditions. Adult male Wistar rats were divided into four groups. In the first group (n=3), the polyethylene tube was filled with bovine collagen, while in the second (n=3), the prosthesis was filled with rat-derived collagen. In the third group (n=3), the tube was left empty, and the fourth group (n=3), consisted of unoperated rats. Six weeks after tubulization, the number of axons was significantly higher with bovine collagen than with rat collagen (7,661 ± 1,018 versus 4,110 ± 1,027, p<0.05), as was the degree of implant absorption. These results support the hypothesis that the use of extracellular matrix substances that self-assembly in an organized pattern can enhance nerve regeneration.

Ultrastructural changes in the endothelial cells of the endoneurial blood vessels of the sciatic nerve of albino rats after crush injury

This study included 14 male albino rats. The sciatic nerves of 12 rats were subjected to crush injury, while 2 rats were used as controls. The sciatic nerves were exposed and the parts distal to the crush injury were taken. The specimens were prepared for study by electron microscope. The results of the present work showed that after crush injury, there was an increase in the permeability of the endothelial cells of blood vessels. Also, the intercellular junctions of the endoneurial blood vessels were distended with the absorbed fat globules. The current study showed that transendothelial transmission was increased leading to the appearance of large electron lucent fat globules. After six weeks of crush injury, there was a marked decrease in the permeability of the endoneurial blood vessels. It could be concluded that after the first week of peripheral nerve injury, the absorption through the endothelial cells was increased. Then, the absorption showed a marked decrease till the sixth week

Ethidium bromide-induced demyelination of the sciatic nerve of adult Wistar rats

Peripheral nerve ultrastructure was assessed after single or multiple local injections of the intercalating dye ethidium bromide. Thirty-four adult Wistar rats of both sexes were divided into five groups and maintained in a controlled environment with rat chow and water ad libitum throughout the experiment. The experimental animals were injected with 1 æl of 0.1 percent ethidium bromide in 0.9 percent saline into the central third of the left sciatic nerve 1 (group 1), 2 (group 2), 4 (group 3), 6 (group 4) or 8 (group 5) times. In groups 2 to 5 the injections were made at 28-day intervals. Control animals received the same amount of 0.9 percent saline. The animals were killed at different times after injection: group 1 at 7 days (2 rats) and 15 days (2 rats); for groups 2, 3, 4 and 5, all rats were killed 10 days after the last injection and the lesions were investigated by light and transmission electron microscopy. In the acute lesions, intoxicated Schwann cells showed a vacuolated cytoplasm and separation of the sheaths from the axon. Myelin sheaths underwent progressive vesiculation and subsequent segmental demyelination. Myelin debris were withdrawn by macrophages and remyelination by Schwann cells was prominent. With the increase in the number of injections collagen fibers also increased in number and progressively enveloped smaller numbers of remyelinated axons composing new fascicles. Wallerian degeneration of fibers apparently not affected by ethidium bromide was more intense in the nerves from groups 4 and 5. The peripheral nerve repairs itself after demyelinating challenges with a profusion of collagen fibers and new fasciculations. This experimental model is valid to mimic recurrent demyelinating neuropathies

role of antioxidant against experimentally induced diabetic peripheral neuropathy in adult male albino rats [histological and immunocytochemical study]

Fifteen healthy adult male albino rats were used in this study aiming to demonstrate the structural changes occurring in the peripheral nerves as a result of chronic diabetes and to investigate the role of vitamin E as an antioxidant. The animals were equally divided into three groups [A, B and C] [5 animals each]. Group A served as a control. Group B animals were injected intra-peritoneally with 40 mg streptozocin/kg body weight for successive 5 days. Group C animals were injected with streptozocin as those of group B then they received a daily dose of vitamin E 70 mg/kg body weight orally for successive 6 weeks. At the time of sacrifice the animals of the all groups were anaesthetized with ether inhalation and their sciatic nerves were dissected out carefully and small pieces were taken and processed for light and electron microscope examinations. Light microscope examination of the diabetic group showed the sciatic nerve was formed of numerous axons with poor myelination and with different diameters. The intensity of the reaction of the nerve growth factor [NGF] was more at the periphery than the center. Ultrastructurally, the myelin sheath showed splitting in the lamellae. The endoneurium contained mast cells and infiltrating cells in close relation with the distorted myelin. Schwann cells nuclei appeared with much heterochromatin and their cytoplasm contained few scattered segments of rough endoplasmic reticulum and poorly developed Golgi. The nodes of Ranvier exhibited irregular neurolemmal terminations. Examination of the diabetic group which received vitamin E by light microscope revealed the sciatic nerve was formed of many well myelinated axons and few ones with poor myelination. The intensity of the reaction of [NGF] was intense in the center and weak in the periphery. Ultrastructurally, Schwann cells appeared with much euchromatic nuclei and their cytoplasm contained several segments of rough endoplasmic reticulum. The related axons appeared with closely packed myelin lamellae. Vitamin E as an antioxidant exhibited a protective role against structural changes in diabetic peripheral neuropathy

Caracterização de um modelo experimental de neuropatia em ratos diabéticos induzidos pela aloxana / Characterization of an experimental model of neuropathy in alloxan-induced diabetic rats

Cem ratos norvégicus, machos, com aproximadamente 3 meses de idade foram distribuídos por sorteio em 2 grupos experimentais: Grupo Controle (GC): com 50 ratos sadios, não diabéticos e Grupo Diabético (GD): com 50 ratos diabéticos, induzidos pela aloxana, sem qualquer tratamento. Cada grupo foi dividido em 5 subgrupos com 10 ratos cada e sacrificados com 1, 3, 6, 9 e 12 meses de seguimento, respectivamente. Parâmetros clínicos (peso, ingestão hídrica e alimentar, e diurese) e laboratoriais (glicemia, glicose urinária e insulina) foram documentados em todos os momentos de avaliação. Um segmento do nervo ciático foi obtido de cada animal, em ambos os grupos, para estudo à MO. e ME. Alterações clínicas e laboratoriais significativas (P<0,01), compatíveis com diabetes grave, foram observadas em todos os animais do GD a partir do 4§ dia após a indução. Ratos de ambos os grupos apresentaram alterações no número de fibras mielínicas e nos depósitos intraaxonais de glicogênio que não diferiram, estatisticamente, aos 1, 3 e 6 meses de seguimento. Entretanto, aos 9 e 12 meses, ratos do GD apresentaram diminuição significativa no número de fibras mielínicas, com aumento do número de fibras mielínicas de menor calibre, quando comparados com ratos do GC (P<0,05). Grânulos de glicogênio intraaxonais também foram mais acentuados em ratos do GD no 9§ e 12§ mês de seguimento. Não foram observadas diferenças na densidade de fibras amielínicas ou alterações ultraestruturais significativas entre os dois grupos, em relação aos espaços intraaxonais e endoneurais, bainhas de mielina e células de Schwann durante todo o estudo.