O ultra-som é uma das formas de tratamento terapêutico, não-invasivo, que pode auxiliar na regeneração nervosa periférica. Dentre todas estas técnicas não-invasivas de regeneração nervosa periférica, pouco se sabe sobre a influência do ultra-som na regeneração desse tecido. Para tanto foi realizado um trabalho experimental com o objetivo de avaliar o efeito da terapia do ultra-som pulsado de baixa intensidade após lesão por esmagamento do nervo ciático de rato. Foram utilizados 26 ratos Wistar machos, com massa corporal média de 289,61g divididos em 3 grupos: normal (N), lesado (L) e lesado+ultra-som (L+US). A aplicação do ultra-som pulsado (1 MHz, 40 mW/\'CM POT.2\', 8 minutos de duração) iniciou-se 1 dia pós-lesão e repetido por 4 semanas em dias alternados. A análise funcional do nervo ciático (análise de marcha em pista) foi avaliada semanalmente durante todo o período experimental. Para verificar a eficácia do ultra-som sobre a regeneração nervosa foram analisados índice funcional do ciático, morfologia do nervo ciático e morfologia e morfometria muscular dos músculos tibial anterior (TA) e sóleo (SOL). Concluiu-se que o tratamento com o ultra-som pulsado de baixa intensidade na regeneração nervosa periférica não obteve resultados significativos quando se comparou os grupos lesado e lesado+ultra-som, apenas foi observada uma manutenção da área de secção transversa do grupo lesado+ultra-som do músculo TA quando comparado ao grupo normal, levando a indícios de que o ultra-som estimulou o nervo para tal manutenção. / The ultrasound is one of the forms therapeutic treatment, no-invasive, that it assists in regeneration peripheral nerve. For in such a way an experimental work was carried through with the objective to verify the effect of the therapy of low intensity pulsed ultrasound after crush of sciatic nerve. Amongst all these no-invasive techniques of regeneration peripheral nerve, little known on the influence of the ultrasound in the regeneration of this tissue. Twenty six male Wistar rats weighing 289,61 g on average were used and divided into three groups: normal (N), injury (L) and injury+ultrasound (L+US). The application of the pulsed ultrasound (1 Mhz, 40 mW/\'CM POT.2\' and 8 minutes duration) was started one day after lesion and repeated for 4 week in alternate day. The functional analysis of the sciatic nerve (analysis of the march in track) was evaluated at weekly during all the experimental period. To verify the effectiveness of the ultrasound on nerve regeneration they had been analyzed sciatic functional index, morphology of the sciatic nerve and muscle morphology and morfometry of the muscles tibial anterior (TA) and sóleo (SOL). It was concluded that the treatment with the device of ultrasound of low intensity in regeneration peripheral nerve did not get resulted significant when compared the groups injured and injury+ultrasound, was only observed a maintenance of the cross-sectional area of the group injury+ultrasound of the muscle TA when compared with the normal group, taking the indications of that the ultrasound stimulated the nerve for such maintenance.

O presente estudo avaliou a ação precoce do laser terapêutico de baixa potência de Arsenieto de Gálio (AsGa) no processo de regeneração de uma lesão experimental por esmagamento de nervo ciático de ratos. Foram utilizados vinte ratos, da linhagem Wistar, divididos em dois grupos: grupo nãoirradiado (controle, n=10) e grupo irradiado (tratado com laser AsGa, n=10). O nervo ciático dos animais de ambos os grupos foi devidamente exposto, e, uma área de 5mm foi submetida a carga estática de 15000g, aplicada por meio de um dispositivo portátil de esmagamento, durante dez minutos. A irradiação transcutânea de laser de AsGa, com dose pontual de 4J/cm2, teve seu início no 1º dia pós-operatório, sendo a aplicação realizada diariamente, por um período de dez dias consecutivos. A recuperação funcional foi avaliada nos períodos préoperatório, 7º, 14º e 21º dias, através de valores fornecidos por um programa de cálculo do Índice Funcional do Ciático (IFC), apresentando uma melhora progressiva em ambos os grupos, porém, com valores mais expressivos para o grupo irradiado com laser a partir do 14º dia. Os animais foram sacrificados no 21º dia pós-operatório para a análise histológica e morfometria dos nervos. Os resultados demonstram um aumento de densidade média de fibras nervosas em grupo de animais irradiados com laser de baixa potência e uma melhora do aspecto morfológico em comparação ao grupo não-irradiado . A conclusão aponta que o laser de arsenieto de gálio (AsGa), na dose utilizada, possui efeito benéfico temporário sobre o nervo ciático de ratos submetido a lesão por esmagamento, contribuindo para a melhora do aspecto morfológico nervoso, evidenciando um processo regenerativo acentuado, em comparação com o grupo não tratado, segundo avaliação funcional e morfológica. / The present study has investigated the earlier influence of low power laser irradiation (GaAs) on nerve regeneration process after experimental crush injury of the sciatic nerve of rats . Twenty Wistar's rats were used and divided into two groups: non irradiated group (control, n=10) and irradiated group (laser treatement, n=10). The sciatic nerves were exposed, for both groups, and an area of 5mm was crushed with 15000g static load for ten minutes, in a portable crushing device. Low power irradiation (4J/cm2) were aplied transcutaneously for ten consecutive days, after the first day post-operative. Functional recovery was checked before crushing procedure, 7º , 14º and 21º days after crush damage and was evaluated by means of the Sciatic Functional Index (SFI) calculated by a specific software. Values showed a progressive improvement in both groups but more marked in that with laser irradiation, begining at 14º day. Animals were killed on the 21º postoperative day for morphometric and histological examination of the nerves. Results showed an increased nerve fiber density in the laser irradiated group, as well as an improvement in the morphological aspects. In conclusion, low power laser irradiation GaAs , with a dose of 4J/cm2, has a temporary beneficial effect on the sciatic nerve of rats submitted a crush injury, improving morphological nerve aspects and showing an increase regenerative process, according to functional and histologic evaluation.

Orientador: Marcus Alexandre Finzi Corat / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-24T17:01:17Z (GMT). No. of bitstreams: 1 Nicolielo_RenatoLuizCursino_D.pdf: 3694566 bytes, checksum: 9d48540bdf4e330a06198c2b7816ad32 (MD5) Previous issue date: 2014 / Resumo: As lesões traumáticas de nervos periféricos têm sido objeto de numerosos estudos que tentam compreender os processos de reparação pós-lesão. Apesar dos avanços nas técnicas cirúrgicas, os resultados funcionais têm sido bastante decepcionantes, ao que se refere ao intervalo de tempo entre lesão e tratamento. Para tratamento rápido e eficaz de lesões nervosas, a terapia celular torna-se uma possibilidade no aumento do sucesso de reparo do nervo. Propõe-se então avaliar a eficácia da terapia celular, sobre os níveis de melhora funcional dos camundongos com o nervo isquiático lesionado e tratado com células progenitoras GFP da medula óssea em comparação com seus controles. No presente trabalho utilizou-se camundongos C57BL/6-HETGFP/J/Unib geneticamente modificados como doadores de células progenitoras GFP ("green fluoresent protein") da medula óssea que foram usadas no tratamento via sistêmica em camundongos C57BL/6/J/Unib não marcados com GFP submetidos a esmagamento do nervo isquiático. Estes animais foram analisados quanto sua performance funcional, migração celular, imunohistoquímica de proteínas p75NTR e neurofilamento e contagem axonal em imagens de microscopia eletrônica. Através dos resultados obtidos verificou-se que houve uma significativa melhora funcional do grupo tratado de 224,9% quando comparado com o grupo controle, principalmente no início do processo de recuperação. Estes valores de melhora funcional coincidiram com a grande quantidade de células GFP, maior quantidade de axônios mielinizados e menor quantidade de axônios degeneradas encontradas no sitio da lesão, além do aumento de imunorreatividade da proteína p75NTR, envolvida no processo de regeneração nervosa. Tudo isto vem a demonstrar a eficiência da terapia celular utilizada com células progenitoras da medula óssea, com uma purificação não especifica, tornando-a viável para uma terapia celular sistêmica rápida, simples e eficaz sendo assim uma possibilidade terapêutica para lesões de nervo / Abstract: Traumatic injuries of peripheral nerves have been the subject of numerous studies that attempt to understand the processes of repair after injury. Despite advances in surgical techniques, the functional results have been very disappointing to depend on the time interval between injury and treatment. For fast and effective treatment of nerve lesions, cell therapy becomes a possibility in increasing the success of nerve repair. So it is proposed to evaluate the efficacy of cell therapy on levels of functional improvement of mice with injured ischiatic nerve and treated with GFP progenitor cells of bone marrow as compared with their controls. In this study we used mices C57BL/6-HETGFP/J/Unib genetically modified as donors of stem cells GFP ("green fluoresent protein") of bone marrow that were used in the treatment via systemic of mice C57BL/6/J/Unib not marked with GFP underwent sciatic nerve crush. These animals were analyzed for their functional performance, cell migration, immunohistochemistry of p75NTR protein and neurofilament and axonal counts in electron microscope images. From the results obtained it was verified that there was a significant functional improvement in the treated group 224.9% when compared with the control group, mainly at the start of the recovery process. These values of functional improvement have coincided with the large amount of GFP cells, largest amount of myelinated axons and smallest amount of degenerate axons found at the site of injury axons, in addition to the increase of immunoreactivity of the protein of p75NTR involved in nerve regeneration process. All this is to demonstrate the efficiency of cell therapy used in bone marrow progenitor cells with a non-specific purification, making it feasible for a quick, simple and effective systemic cell therapy becoming this way a therapeutic possibility for nerve injured / Doutorado / Clinica Medica / Doutor em Clínica Médica

Des cellules souches dérivées des crêtes neurales ont été trouvées dans divers tissus adultes comme le ganglion de la racine dorsale (GRD). Ce projet de thèse vise à identifier et caractériser la cellule souche de ce tissu. Premièrement, nous avons étudié le potentiel souche de l’ensemble des cellules du GRD. In vitro, certaines sont capables de proliférer pour former des sphères multipotentes qui génèrent des neurones, des glies et des myofibroblastes. In vivo, selon le contexte dans lequel les cellules issues des sphères sont transplantées, elles génèreront différent types cellulaires. Dans le funiculus dorsal démyélinisé de la souris Nude, elles se différencient en cellule de Schwann alors que dans un cerveau de souris nouveau-né Shiverer, elles produisent des péricytes qui s’intègrent aux capillaires sanguins. Bien que le GRD possède une population cellulaire au potentiel souche, son identité et son rôle restent à découvrir. Afin d’identifier cette cellule, nous avons combiné plusieurs techniques et souris transgéniques pour éliminer les diverses cellules candidates. Nous avons découvert plusieurs cellules avec une plasticité intéressante. Deux progéniteurs unipotents ayant la morphologie et la signature moléculaire de péricyte et de fibroblaste de l’endonèvre ont été trouvés dans le nerf sciatique et le GRD adulte. Enfin la cellule souche du GRD correspond de par sa morphologie à une cellule satellite (SGC). Elle prolifère et est bi-potente in vitro. Elle génère, in vivo, des SGC mais également des neurones en condition pathologique. Mieux comprendre ses mécanismes de régulations pourrait ouvrir la voie à de nouvelles stratégies thérapeutiques pour les maladies du SNP. / Neural crest-derived stem cells have been identified in various adult tissues including the dorsal root ganglia (DRG). This thesis project aims to identify and characterize the putative adult DRG stem cell. First, we studied the stemness potential of global DRG cell populations. In vitro, within the adult DRG, some cells were able to form multipotent spheres that gave rise to neurons, glia and myofibroblasts. The graft of the DRG cell forming spheres proved their differentiation plasticity in vivo. Depending upon their graft environment; they generate different cell types. In the demyelinating dorsal funiculus of adult Nude mice, they formed myelinating Schwann cells while in the brain of new born Shiverer mice, they produced pericytes integrated within capillaries. Although, the DRG cells seemed to have an interesting stemness potential, their identity and their physiopathological role remain unknown. In order to characterize this stem cell and study its fate within the DRG, we combined several technics with transgenic mouse lines to exclude the diverse DRG candidate cells. We discovered different cells with interesting plasticity. Two types of unipotent progenitors that have the morphology and molecular characteristics of pericyte and endoneurial fibroblast in the adult sciatic nerve and DRG. But most of all, we found that the DRG stem cell has the phenotype of the satellite glial cell (SGC). They proliferate and are bipotente in vitro. In vivo these stem cells generate SGC under normal condition and produce glia more neurons when necessary in pathological condition. Understanding these regulation mechanisms could open the way to new therapeutic strategies for PNS diseases.

The aim of this work is sexual dimorphism quantification of greater sciatic notch profile using 2D geometric morphometrics methods. The curvature was digitized by two different methods - manually with contact digitizer MicroScribe G2 and automatically with software Morphome3cs. Results from each method were comparised and advatages and disadvantages of boths methods were discussed. Target sample of 114 adult specimens of known sex was analyzed. This collection comes from Maxwell Museum of Anthropology, The University of New Mexico, Albuquerque and contains 57 male and 57 female hip bones. For the method verification the test smaple contains 112 adult specimens of known sex was used. This collection comes from Universidad Nacional Autonóma de México (UNAM). This collection contains 56 male and 56 female hip bones. The procrustes analysis, principal components analysis, thin plate spine and discriminant function analysis were used for analysis. We could make a detail description of morphologic differences in greater sciatic notch shape of men and women because of shape visualisation and difference of both group was confirmed by discriminant function analysis. Sex assesment achieves accuracy 92,11% - 98,25% in dependence on used methods and number of semilandmarks.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Although peripheral motoneurons are phenotypically endowed with robust regenerative capacity, functional recovery is often suboptimal following peripheral nerve injury (PNI). Research to date indicates that the greatest success in achieving full functional recovery will require the use of a combinatorial approach that can simultaneously target different aspects of the post-injury response. In general, the concept of a combinatorial approach to neural repair has been established in the scientific literature but has yet to be successfully applied in the clinical situation. Emerging evidence from animal studies supports the use of electrical stimulation (ES) and testosterone as one type of combinatorial treatment after crush injury to the facial nerve (CN VII). With the facial nerve injury model, we have previously demonstrated that ES and testosterone target different stages of the regeneration process and enhance functional recovery after facial nerve crush injury. What is currently unknown, but critical to determine, is the impact of a combinatorial treatment strategy of ES and testosterone on functional recovery after crush injury to the sciatic nerve, a mixed sensory and motor spinal nerve which is one of the most serious PNI clinical problems. The results of the present study indicate that either treatment alone or in combination positively impact motor recovery. With regard to molecular effects,single and combinatorial treatments differentially alter the expression of regeneration-associated genes following sciatic nerve crush injury relative to facial nerve injury. Thus, our data indicate that not all injuries equally respond to treatment. Furthermore, the results support the importance of treatment strategy development in an injury-dependent manner and based upon the functional characteristics of spinal vs. cranial nerves.

Le récepteur B1 des kinines (RB1) joue un rôle important dans l'inflammation et la nociception. Les sites de liaison du RB1 sont augmentés dans la moelle épinière et le ganglion de la racine dorsale (GRD) chez le rat après la ligature partielle du nerf sciatique (LPNS). Dans ce modèle classique de douleur neuropathique, le traitement aigu avec des antagonistes sélectifs du RB1 renverse l'hyperalgésie thermique mais non pas l’allodynie. Cette étude vise à définir dans ce modèle de LPNS: 1- les effets de traitements aigu et chronique avec des antagonistes du RB1 sur l’hyperalgésie thermique et les allodynies tactile et au froid; 2- la contribution du TRPV1 et du stress oxydatif dans la composante de la douleur neuropathique associée au RB1; 3- l’expression du RB1 au niveau de la moelle épinière lombaire, le GRD et le nerf sciatique par RT-PCR quantitatif (Reverse transcriptase-polymerase chain reaction); 4- la localisation cellulaire du RB1 dans la moelle épinière lombaire par microscopie confocale. L’hyperalgésie thermique et les allodynies tactile et au froid ont été mesurées par le réflexe de retrait de la patte arrière après l’application à la surface plantaire d’une source radiante de chaleur (méthode Hargreaves), de filaments de Von Frey et d’une goutte d’acétone qui produit une sensation de froid par évaporation. Nous avons montré, dans un premier temps, que l'hyperalgésie thermique et les allodynies tactile et au froid sont renversées par un traitement chronique avec l’antagoniste du RB1, SSR240612, administré par gavage à raison de 10 mg /kg/jr entre le 15 e et le 20 e jour après la ligature du nerf sciatique et par un traitement antioxydant, la N-acétyl-L-cystéine, administrée par gavage à la dose de 1g/kg/jr, 4jours précédant la ligature et pendant les 2 semaines après la ligature. Un traitement aigu avec le ii SSR240612 (10 mg/kg) ou avec un antagoniste du RB1 qui ne traverse pas la barrière hémato-encéphalique, le R-954 (2mg/kg, s.c.), n’a bloqué que l’hyperalgésie thermique. Dans un second temps, l’antagoniste du TRPV1, le SB366791, administré à raison de 1 mg/kg/jr par voie sous-cutanée du j-1 au j-14 a renversé l’allodynie tactile et l’hyperalgésie thermique. De plus, nous avons noté deux semaines après la LPNS, des augmentations significatives des niveaux d'ARNm du RB1 dans la moelle épinière lombaire, le nerf sciatique et le GRD du côté ipsilatéral à la ligature. Ces augmentations ont été renversées par le traitement avec la N-acétyl-L-cystéine et l’antagoniste du TRPV1. Le RB1 a été localisé au niveau des fibres de type C avec le marquage au CGRP (Calcitonin Gene-Related Peptide) et au niveau de la microglie utilisant le marquage au Iba-1 dans la moelle épinière lombaire des rats ayant subi une LPNS, 2 semaines plus tôt. Au terme de cette étude, nous avons suggéré que la surexpression du RB1 sur les fibres de type C contribuerait à l’hyperalgésie thermique alors que le RB1 sur la microglie dans la moelle épinière contribuerait aux allodynies tactile et au froid dans le modèle LPNS chez le rat. Le stress oxydatif pourrait être impliqué dans l’induction du RB1. Bien que le rôle du TRPV1 semble plutôt limité à la douleur thermique, il pourrait cependant agir via le RB1 sur les fibres de type C. / The kinin B1 receptor (B1R) plays an important role in inflammation and nociception. B1R binding sites are increased in the spinal cord and dorsal root ganglion (DRG) in rats after partial sciatic nerve ligation (PSNL). In this classic model of neuropathic pain, acute treatment with selective B1R antagonists reversed thermal hyperalgesia but not allodynia. This study aims at determining in this model of PSNL: 1- the acute and chronic effects of B1R antagonists on thermal hyperalgesia and tactile and cold allodynia; 2- the contribution of TRPV1 and the oxidative stress in the component of neuropathic pain associated to B1R; 3 - the expression of B1R in the lumbar spinal cord, the DRG and the sciatic nerve by quantitative RT-PCR (Reverse transcriptase-polymerase chain reaction); 4 - the cellular localization of B1R in the lumbar spinal cord by confocal microscopy. Thermal hyperalgesia and tactile and cold allodynia were measured by the reflex withdrawal of the hindpaw after application to the plantar surface of a radiant heat source (Hargreaves method), Von Frey filaments and a drop of acetone that produces a sensation of cold by evaporation. We have shown, firstly, that the thermal hyperalgesia and tactile and cold allodynia are reversed by chronic treatment with the B1R antagonist, SSR240612, administered by gavage at a dose of 10 mg/ kg / day from day 15 to day 20 after sciatic nerve ligation and with antioxidant treatment, N-acetyl-L-cysteine, administered by gavage at a dose of 1g /kg/ day, four days before ligation and for two weeks after ligation. Acute treatment with SSR240612 (10 mg/kg) or with the B1R antagonist R-954 (2 mg/kg, s.c.) which does not pass the blood-brain barrier blocked thermal hyperalgesia only.

Lesões nervosas periféricas com alterações morfofuncionais são de grande importância clínica, porque pode prejudicar a função, comprometendo a sensibilidade e/ou a motricidade do órgão alvo. Quando o nervo é lesado, o indivíduo torna-se impossibilitado de realizar suas atividades, seja profissional ou pessoal, e a partir do acidente esta situação se agrava ainda mais, pois tem início uma trajetória de sofrimento e humilhações decorrentes do tipo de assistência que passa a receber, tendo em vista, ainda, a fragilidade emocional e o abatimento moral de que passa a ser vítima. Na tentativa de reparo de lesões graves de nervos periféricos, várias técnicas têm sido utilizada, mas algumas com prejuízos funcionais para outras área do corpo, como por exemplo, quando se usa outro nervo no enxerto. Considerando que enxertos venosos tem tido bons resultados na capacidade regenerativa das fibras nervosas, e como elas são encontradas em abundância e em locais de fácil acesso cirúrgico, pensou-se em verificar se o tecido adiposo e o laser de baixa potência alterariam os resultados da reinervação, por tubulização, em músculos de contração rápida (EDL). Para isso foi utilizado 84 ratos (Rattus norvegicus) da linhagem wistar, machos, que foram divididos em 12 grupos (oito experimentais e quatro controles). Nos grupos experimentais (GE) foi utilizada tubulização de veia preenchida, ou não de tecido adiposo (GEVV e GEVG, respectivamente), com e sem tratamento de laser (GEVVL e GEVGL, respectivamente). Os grupos controles (GC) receberam os nomes de positivos (GCP) quando os animais não sofreram intervenção cirúrgica, e negativos (GCN) quando os animais foram submetidos à desnervação do nervo ciático. Todos os grupos tiveram os seus animais sacrificados em dois períodos, 45 e 150 dias, após o início do experimento. A certificação da recuperação foi feita por meio da análise dos músculos inervados por ele (EDL), comparando-os com os respectivos grupos controles. Técnicas de microscopia, Imunofluorescência (MyoD e miogenina), apoptose (Tunel), morfométricas e análise funcional do ciático, foram empregadas nesta investigação. Os resultados mostraram que aos 45 dias pós desnervação os dados dos grupos experimentais estavam mais próximos do grupo controle negativo, mas aos 150 dias eles estavam mais próximos aos do grupo controle positivo. Baseado nos dados obtidos pode-se concluir que o uso de tecido adiposo e do laser de baixa potência na técnica de tubulização do nervo ciático interferem na recuperação do músculo EDL desnervado. / The peripheral nerves injuries with morphofunctional alterations, have great clinical importance because could prejudice the function, committing the sensibility and/or the motricity of target organ. When nerve is damage, the individual becomes disabled to realize yours activities, either professional or personal, in the post accident periods, this situation aggravates each more, therefore initiate a trajectory of suffering and distressing despite of the kind of assistance that this person receives, in view of your emotional fragility and your moral discouragement that pass to be victim. In attempt to repair severe peripheral nerves lesions, many techniques had been used, but some present functional prejudices to other area of bodies, for example when other autologous nerve graft it is used. Considering that, vein graft had demonstrated good results in regenerative nerve fibers capacity, and the vein are found in abundance in many locals of chirurgic access, it thought in verify if the adipose tissue and low power laser could alter the reinnervation results, by tubulization technique, in fast twitch muscle (EDL). For this, was used 84 rats (Rattus norvegicus) wistar, male, divided in 12 groups (eight experimental and four controls). In the experimental groups (EG) was used tubulization by vein combined / or not with adipose tissue (EGV and EGVA, receptively), with or without laser treatment (EGVL and EGVAL, respectively). The controls groups (CG) was called of positives (CGP) when the animals did not subject to transaction nerve, and negatives (CGN) when the sciatic nerve was transaction in this animals. All groups had the animals scarified in two periods, 45 and 150 days post experiments beginning. The recuperation was notified by means of muscle innervated analysis (EDL), comparing with the respective controls groups. Microscope techniques, Immunofluorescence for (MyoD and Miogenin), apoptosis by (Tunel assay), morphometrics and sciatic functional analysis, were employed in this investigation. The results showed that in the 45 days post-dennervation, the data of experimental groups was nearest of negative control group (transaction sciatic nerve), but in the 150 days they was nearest to the positive control group. Based on this, could be conclude that the use of adipose tissue and low power laser used in the tubulization technique by vein in the sciatic nerve interfere in the recuperation of EDL muscle dennervated.

Para avaliar a eficácia do método de pré-degeneração em nervos ciáticos de ratos durante diferentes intervalos de tempo, foram realizados estudos histomorfométricos de cortes laminares obtidos ao nível do enxerto e no segmento distal do nervo receptor. Os resultados foram comparados com a técnica convencional de enxertia nervosa. Verificou-se que o tempo de pré-degeneração interfere na regeneração de novos axônios e que o período mais adequado para sua utilização situou-se ao redor de 2 semanas no modelo experimental adotado / In order to evaluate the efficacy of a predegeneration method in rat sciatic nerves during different periods of time, histomorphometric studies were performed at the graft and distal segment sites of the recipient nerves. The results were compared with the conventional nerve grafting technique. It was shown that the period of predegeneration interfered in the regeneration of new axons and the most favorable time for its use is around 2 weeks, in this experimental model