<p>  </p> <p>Understanding the mechanical properties of peripheral nerves is essential for chronically implanted device design. The work in this thesis aimed to understand the relationship between local deformation responses to global strain changes in peripheral nerves. A custom-built mechanical testing rig and sample holder enabled an improved cyclical uniaxial tensile testing environment on rabbit sciatic nerves (N=5). A speckle was placed on the surface of the nerve and recorded with a microscope camera to track local deformations. The development of a semi-automated digital image processing algorithm systematically measured local speckle dimension and nerve diameter changes. Combined with the measured force response, local and global strain values constructed a stress-strain relationship and corresponding elastic modulus. Preliminary exploration of models such as Fung and 2-Term Mooney-Rivlin confirmed the hyperelastic nature of the nerve. The results of strain analysis show that, on average, local strain levels were approximately five times smaller than globally measured strains; however, the relationship was dependent on global strain magnitude. Elastic modulus values corresponding to ~9% global strains were 2.070 ± 1.020 MPa globally and 10.15 ± 4 MPa locally. Elastic modulus values corresponding to ~6% global strains were 0.173 ± 0.091 MPa globally and 1.030 ± 0.532 MPa locally.   </p>

En relation avec sa position anatomique, la détection portale de nutriments se situe au coeur de l’impact de la composition nutritionnelle d’un repas sur la prise alimentaire et le métabolisme énergétique. Ainsi, la détection portale de glucose, produit par exemple en réponse aux protéines alimentaires, induit un signal nerveux à l’origine d’une induction de la satiété et d’une amélioration de l’homéostasie glucidique. Grâce à des travaux physiologiques et anatomiques chez le rat, nous proposons un modèle pour cette détection dans lequel deux modes interviennent, soit un transport et un catabolisme intracellulaire, soit une détection purement extracellulaire du glucose. La glycémie portale est détectée par l’un ou l’autre de ces mécanismes en fonction de sa différence avec la glycémie artérielle, reflet du statut nutritionnel et métabolique des individus. Un signal nerveux est ensuite initié dans les neurones périportaux, dont les axones aboutissent à proximité de la lumière veineuse. Les études immunohistochimiques réalisées ont permis de montrer que ce signal induit une activation cérébrale étendue en relation avec les effets multiples du glucose portal, dans le tronc cérébral, les systèmes sensoriels et cortico-limbiques, et l’hypothalamus. Dans ce dernier, la nature cellulaire de l’activation conforte notamment l’hypothèse de l’implication du signal glucose portal dans l’effet de satiété induit par les régimes riches en protéines. / Nutrient sensing in the portal vein occurs in a strategic location to relay the effects of the diet on food intake and energy metabolism. The portal sensing of glucose produced for instance in response to dietary proteins initiates a nervous signal that ultimately induces satiety and a better control of glucose metabolism. Our physiological and anatomical approaches enable us to propose a sensing model in which two different mechanisms can occur, involving either the intracellular transport and catabolism of glucose or a direct extracellular detection. Portal glycaemia is detected by one pathway or the other depending on its difference with arterial blood glucose, which reflects the nutritional and metabolic state of the subject. A nervous signal is then initiated in periportal neurons, whose axons terminate close to the venous lumen. Our immunohistochemical studies have shown that this signal induces a widespread activation in the brain that relates to the multiple effects of portal glucose appearance, in the brainstem, the sensory and cortico-limbic systems and the hypothalamus. In this latter area, the cellular nature of the activation supports the hypothesized central role of portal glucose appearance in the satiety effect of high-protein diets.

Vinte e seis pacientes com paralisia facial unilateral de longa duração foram submetidos à reanimação facial em único estágio com transplante do músculo grácil inervado pelo ramo massetérico do nervo trigêmeo. Foram divididos em 2 grupos não-randomizados de acordo com a técnica de fixação: Grupo I (19 pacientes), fixação do músculo com uso do tendão palmar longo inserido no músculo orbicular nos lábios superior e inferior do lado não paralisado (além da linha média); Grupo II (7 pacientes), fixação do retalho apenas com pontos separados no músculo orbicular dos lábios superior e inferior no lado paralisado. A avaliação qualitativa demonstrou melhores resultados no Grupo I (94,1% vs 66,6%). Na comparação do posicionamento do arco de cúpido em repouso, no pré e pós-operatório, observamos melhora estatisticamente significante (p<0,05) em ambos os grupos. Durante o sorriso, entretanto, houve melhora significativamente maior na centralização do arco de cúpido nos pacientes submetidos à fixação com tendão palmar longo (Grupo I) / Twenty-six patients with unilateral long-stading facial palsy underwent 1-stage reanimation with free gracilis muscle transplant innervated by the masseteric branch of the trigeminal nerve. They were divided into 2 nonrandomized groups according to insertion technique: group I (19 patients), palmaris longus tendon graft placed between the gracilis free flap and the orbicularis oris of the upper and lower lip on the nonparalyzed side; group II (7 patients), interrupted suture between the free flap and the orbicularis oris of the upper and lower lip on the paralyzed side. Qualitative evaluation of the smile demonstrated better results in patients from group I (94,1% vs 66,6%). Comparing the position of the Cupid`s bow at rest, pre- and postoperatively in each patient, we observed significant improvement of facial symmetry in both groups. During smile, however, there was significantly higher rate of centralization of the Cupid`s bow in patients submitted to reanimation with the use of the palmaris longus tendon (group I)

Dor neuropática e neuropatia causadas pelo quimioterápico oxaliplatina são comuns e causam restrições às atividades funcionais e qualidade de vida. Muitos estudos têm quantificado e qualificado esses sintomas, porém raramente utilizando amostra expressiva e instrumentos validados e específicos para este fim. Neste estudo é proposta uma análise ampla, por instrumentos que quantificam e qualificam a dor e neuropatia relacionadas à oxaliplatina e suas características associadas. Objetivos: Identificar a prevalência de dor neuropática e neuropatia periférica em doentes com câncer colorretal recebendo tratamento com oxaliplatina durante os seis meses de tratamento quimioterápico e após seguimento (de 3 a 6 meses); avaliar, comparar e descrever as características da dor e neuropatia nesta população e avaliar seu impacto nas atividades de vida diária e qualidade de vida. Métodos: Foram incluídos 110 doentes (média 55,6 anos) com câncer colorretal durante o tratamento quimioterápico com oxaliplatina e seguidos por 3 a 6 meses após quimioterapia. Os doentes responderam ao questionário sócio-demográfico e a questionários específicos para dor e neuropatia antes da quimioterapia e bimestralmente por até seis meses durante a quimioterapia e em avaliação de seguimento realizada de 3 a 6 meses após o término da quimioterapia. Os instrumentos utilizados foram: Questionário de Qualidade de Vida da Organização Européia para Pesquisa e Tratamento do Câncer - C30 (EORTC QLQ-C30); Questionário de Dor McGill reduzido (QDMR), Inventário de Sintomas de Dor Neuropática (ISDN), Inventário Breve de Dor (BPI-Brief Pain Inventory) Questionário de Dor Neuropática 4 (DN4), Escala Hospitalar de Ansiedade e Depressão (HADS), Escore Total de Neuropatia (TNS - Total Neuropathy Score). Resultados: Em geral, a dor e neuropatia aumentaram durante o período de quimioterapia e diminuíram após fim do tratamento, permanecendo em níveis significativamente mais elevados após o fim do tratamento quimioterápico. A média de intensidade de dor (dor mais intensa) segundo o IBD foi 2,54 na V3 (após 4 meses de tratamento com oxaliplatina). A dor foi do tipo neuropática em 21,67% dos doentes ao fim da quimioterapia e em 10,00% após fim do seguimento. As médias segundo o ISDN foram 0,67 no basal, 18,67 na V2, 17,77 na V3, 17,44 após quimioterapia e 11,03 após seguimento. A característica da dor mais frequente foi em choque elétrico, enjoada e incômoda segundo o QDMR e segundo o ISDN foram choque elétrico, frio doloroso e dormência. A qualidade de vida sofreu impacto negativo. Conclusões: Dor neuropática foi prevalente após a quimioterapia e após seguimento e se associou com interferência negativa sobre as atividades diárias. Estes dados poderão auxiliar o desenvolvimento de tratamentos individualizados da neuropatia relacionada à oxaliplatina / Neuropathic pain and neuropathy caused by oxaliplatin chemotherapy are common and cause restrictions in activities of daily living and quality of life. Many studies have quantified and qualified these symptoms but only rarely used a comprehensive sample of patients and employed validated and specific instruments for pain assessment. In this study we proposed a comprehensive analysis by instruments that quantify and qualify the pain and neuropathy and its characteristics. Aim of Investigation: To identify the prevalence of neuropathic pain and peripheral neuropathy in patients with colorectal cancer receiving treatment with oxaliplatin during the six months of chemotherapeutic treatment and after follow-up (3 to 6 months); to evaluate, compare and describe pain and peripheral neuropathy characteristics in this population and evaluate their impact on activities of daily living. Methods:110 patients (mean 55.6 years) with colorectal cancer were included during the six months of chemotherapy with oxaliplatin and follow-up (3 to 6 months) after chemotherapeutic treatment. Patients answered socio-demographic questionnaires and specific assessment tools for pain and neuropathy evaluation at the baseline visit and every 2 months during chemotherapy and after follow-up (3-6 months). The instruments used were: The European Organization for Research and Treatment of Cancer QLQ-C30 (EORTC QLQ-C30); Reduced McGill Pain Questionnaire (MPQ), Neuropathic Pain Symptom Inventory (NPSI), Brief Pain Inventory (BPI) Neuropathic Pain Diagnostic Questionnaire (DN4), Hospital Anxiety and Depression Scale (HADS), Total Neuropathy Score (TNS), Results: In general, pain and neuropathy intensity increased during chemotherapy and decreased after the end of treatment (follow-up). The most severe pain according to the BPI was 2.54 in V3 (after 4 months treatment with oxaliplatin). Pain was neuropathic in 21.67% right after chemotherapy and in 10.00% after follow-up according to the DN4. The average sum of neuropathic pain symptoms according to the NPSI were 0.67 in V1, 18.67 in V2, 17.77 in V3, 17.44 after chemotherapy and 11.03 after follow-up. The most common characteristics of the pain was electric shocks, nauseating and fearful, according to MPQ and according to NPSI were electric shock, evoked by cold stimuli and tingling. Conclusions: Patients treated with oxaliplatin had significant pain and neuropathy that negatively interfeared with daily activities. These data may help tailor individualized treatment of chemotherapy related neuropathic pain

A hanseníase causada pelo Mycobacterium leprae é a infecção que mais gera danos ao sistema nervoso periférico. Este microrganismo tem como alvo a célula de Schwann, o qual se liga à laminina, um dos constituintes da lâmina basal. Através desta ligação o Mycobacterium leprae penetra nas células de Schwann onde se multiplica, infectando o sistema nervoso periférico e desse modo comprometendo sua estrutura e funções. Provavelmente tal como ocorre em outras neuropatias degenerativas, inflamatórias ou neoplásicas, no processo de agressão nervosa na hanseníase, participam outras moléculas como a integrina beta1 e a proteína S-100. O presente trabalho estudou 44 doentes de hanseníase, classificados de acordo com Ridley e Jopling, distribuídos em: 12 doentes indeterminados, 7 doentes tuberculóides, 17 doentes dimorfo-tuberculóides, 2 doentes dimorfo-dimorfos, 2 doentes dimorfo virchowianos e 4 doentes virchowianos. Os propósitos foram estudar o dano nervoso nas terminações nervosas da pele por meio da expressão da integrina beta1 e da proteína S100; e ainda a análise da relação entre as manifestações dermatológica, neurológica, reação de Mitsuda, bacterioscopia e os achados imunohistoquímicos. A alteração da expressão da integrina beta1 nas terminações nervosas da pele foi variável, precoce e constante em 100% dos doentes. A alteração da proteína S-100 nas terminações nervosas da pele nos doentes foi de 88,6%. Apesar da significativa correlação entre elas, a sensibilidade da integrina beta1 foi maior. Encontrou-se correlação entre a clínica dermatológica e neurológica, bem como com a bacteriscopia e a reação intradérmica de Mitsuda. Não houve correlação das reações imunohistoquímicas com os dados clínicos, provavelmente em decorrência das alterações moleculares ocorrerem antes das manifestações clínicas / Leprosy caused by Mycobacterium Leprae is the infection that most causes damage to the peripheral nervous system. This microorganism has its principal target in the Schwann cells, which bind themselves to laminin, one of the constituints of the basic lamina. The Mycobacterium Leprae, by way of this link, penetrates the Schwann cells, where they multiply, infecting the peripheral nervous system and thus compromising its structure and functions. Probably, as happens in other degenerative neuropathies, inflammatory or neoplastic, other molecules participate in the process of nervous aggression of leprosy, such as beta1 integrin and S-100 protein. This paper studied 44 patients with leprosy, classified according to Ridley and Jopling, distributed as: 12 indetermined patients, 7 tuberculoid patients, 17 borderline-tuberculoid patients, 2 mid-borderline patients, 2 borderline-lepromatous patients and 4 lepromatous patients. The aims were to study the damage to the skin nerve endings by way of the levels of beta1-integrin and S-100 protein; and also the analysis of relation between dermatological, neurological clinical manifestations, the Mitsuda reactions, bacterioscopical and the immunohistochemical findings. The alterations in the amounts of beta1 integrin in the skin nerve endings were variable, premature and constant in 100 % of the patients. The alteration in the S-100 level in the skin nerve endings in the patients was 88,6 %. In spite of the correlation between them, the sensibility of the beta1 integrin was greater. There was found to be correlation between dermatological and neurological clinical manifestations as well as with the bacterioscopy and the Mitsuda intradermal reactions. There was no correlation between immunohistochemical reactions with the clinical data, probably because of the molecular alterations that occur before the clinical manifestations

A resposta do sistema nervoso para diversas lesões acarreta a ativação das células gliais entéricas. Este trabalho tem como objetivo analisar o efeito da isquemia e reperfusão intestinal (I/R-i) sobre as células gliais entéricas, neurônios e receptores P2X2 e P2X7. Foram analisados o íleo de ratos Controle, Sham e I/R-i com 0 hora, 24 horas e 14 dias de reperfusão. Foram realizadas dupla marcação dos receptores P2X2 e P2X7 com Hu e S100, densidade, área do perfil e marcação de proliferação celular. Os resultados mostraram dupla marcação de células gliais entéricas e neurônios com os receptores P2X2 e P2X7; a densidade apresentou um aumento de células gliais e diminuição de neurônios imunorreativos ao Hu. A área do perfil de células gliais entericas S100-IR apresentaram diminuição nos grupos I/R-i e foi detectada proliferação de células gliais entéricas nos grupos I/R-i 0 hora e 24 horas. Conclui-se que a isquemia levou a alterações diferenciadas nos receptores P2X2 e P2X7, células gliais entéricas e neurônios, que podem causar disfunções gastrointestinais. / The nervous system response to various injuries involves the activation of enteric glial cells. The aim of the work was to analyze the effect of ischemia and reperfusion (I/R-i) on enteric glial cells, neurons and receptors P2X2 and P2X7. We analyzed the ileum of Control, Sham and I/R-i with 0 hour, 24 hours and 14 days of reperfusion. Double staining were performed P2X2 and P2X7 receptors with Hu and S100, density, area profile and marking of cellular proliferation. The results show double staining of neurons and enteric glial cell with the P2X2 and P2X7; density increased by glial cells and decrease of neurons immunoreactive to Hu. The area profile of enteric glial cell S100-IR showed decreased in Groups I/R-I and enteric glial cell proliferation was observed in groups I/R-i 0 hours and 24 hours. It is concluded that ischemia has led to changes in differential P2X2 and P2X7 receptors, neurons and enteric glial cells, which can cause gastrointestinal dysfunction.

A avaliação sensitiva de pacientes tratados com oxaliplatina tem se tornado objeto de estudo, pelo fato deste medicamento causar como efeito colateral, uma neuropatia periférica com características sensitivas, imediatamente após início da infusão. Sintomas que causam restrições nas atividades de vida diárias e na qualidade de vida do paciente durante o tratamento. Para uma melhor compreensão do mecanismo das alterações sensitivas, atualmente tem se utilizado o teste quantitativo da sensibilidade (TQS), que através da mensuração quantitativa dos limiares de detecção aos estímulos quente, frio e de vibração, nos concede um perfil para melhor relacionar com as possibilidades de manejo ou tratamento. Neste estudo propomos uma análise da através do TQS e de instrumentos que quantificam e qualificam a neuropatia, a dor neuropática e suas características. Objetivos: Descrever de forma prospectiva as alterações de sensibilidade exteroceptiva somática causadas pelo uso da oxaliplatina em doentes com câncer colorretal. Métodos: Foram incluídos 110 doentes (média 55 anos) com câncer colorretal que realizaram tratamento antineoplásico com oxaliplatina por seis meses, e foram avaliados por mais seis após a quimioterapia. Os pacientes realizaram avaliação sensitiva com TQS e responderam questionário sócio demográfico e questionários específicos para dor e neuropatia na visita basal (VB), ao término da quimioterapia (VT) e novamente após 6 meses de seguimento (VS). Resultados: Os questionários de dor e neuropatia mostraram seu início e as suas características, na qual foi evidente a dor com características neuropáticas na visita término do tratamento em 21,7% dos participantes manifestada pela dormência, choque elétrico, alfinetadas e agulhadas e a sensibilidade ao frio. As principais alterações demonstradas pelo TQS foram: nos limiares de detecção mecânica; aumento dos limiares dolorosos térmicos; diminuição da hiperalgesia mecânica; diminuição do limiar de detecção vibratória na mão e aumento no pé. O TQS indicou alterações entre os participantes do estudo e o grupo de voluntários saudáveis em algum momento das avaliações. Conclusão: Os pacientes com câncer colorretal submetidos ao tratamento com oxaliplatina cursam com dor com características neuropáticas que interferem em suas atividades diárias. O TQS caracterizou as principais alterações relacionadas ao início do tratamento, término do tratamento e durante o seguimento. As comparações com voluntários saudáveis sugerem que a presença da neoplasia e outras comorbidades são capazes de causarem alterações no TQS / Sensory evaluation of patients treated with oxaliplatin has become an object of study, because this medication cause as a side effect, peripheral neuropathy with sensory characteristics, immediately after start of infusion. Symptoms that cause restrictions in daily activities and in the patient\'s quality of life during treatment. For a better understanding of the mechanism of sensory changes, currently it has used quantitative sensitivity testing (QST). That by the quantitative measurement of thresholds to warm stimuli, cold and vibration, gives us a profile to better relate to the possibilities of management or treatment. In this study we propose an analysis by QST and tools to quantify and qualify neuropathy, neuropathic pain and its features. Objectives: To describe prospectively the somatic exteroceptive sensitivity changes caused by the use of oxaliplatin in patients with colorectal cancer. Methods: We included 110 patients (mean 55 years) with colorectal cancer who underwent anticancer treatment with oxaliplatin for six months and were evaluated for six after chemotherapy. Patients underwent sensory evaluation with QST and answered sociodemographic questionnaire and specific questionnaires for pain and neuropathy at baseline, at the end of chemotherapy (visit six months) and again after 6 months of follow-up (visit twelve months). The instruments used were reduced McGill Pain Questionnaire (MPQ), Inventory symptoms of neuropathic pain (ISDN), Brief Pain Inventory (BPI-Brief Pain Inventory) Questionnaire neuropathic pain 4 (DN4), hospital scale of anxiety and depression (HADS). Results: The pain questionnaires and neuropathy showed its beginning and its characteristics, which was evident pain with neuropathic characteristics in the end visit of treatment in 21.7% of participants manifested by numbness, electric shock, pins and needles and sensitivity to cold. The main changes demonstrated by QST were in mechanical thresholds; painful increase in thermal thresholds; reduction in mechanical hyperalgesia; reduction of vibration detection limit for the hand and foot increases. The QST indicated changes between the study participants and the group of healthy volunteers at some point of the evaluations. Conclusion: Patients with colorectal cancer undergoing treatment with oxaliplatin occur with pain with neuropathic characteristics that interfere with their daily activities. QST characterized the major changes related to the start of treatment, end of treatment and during follow-up. Comparisons with healthy volunteers suggest that the presence of neoplasia and other comorbid conditions are capable of causing changes in the QST

INTRODUÇÃO: A formação do hematoma intraneural com comprometimento dos nervos periféricos pode ocorrer após traumas ou em associação com distúrbios de coagulação. A opção por conduta conservadora (expectante) ou descompressão cirúrgica ainda é controversa. Essas duas condutas foram analisadas comparativamente por meio de modelo experimental em ratos submetidos a hematoma intraneural associado à compressão extrínseca. MATERIAL E MÉTODOS: Cinqüenta ratos Wistar foram divididos em 5 grupos. Em 4 grupos (A, B, C e D) o nervo ciático direito foi envolvido por tubo de silicone de diâmetro interno maior que o do nervo, simulando o trajeto do nervo periférico através de regiões inextensíveis (exemplo: túnel do carpo). No grupo B, foi realizada injeção intraneural no segmento envolvido pelo tubo de 0,2 ml de sangue autógeno. No grupo C, após produção do hematoma, foi feita a imediata remoção do tubo de silicone simulando-se a descompressão túnel do carpo, e epineurotomia longitudinal complementar. No grupo D, após produção do hematoma, foi realizada apenas a remoção do tubo de silicone. No grupo E (CONTROLE) o nervo foi apenas exposto sem a presença de hematoma ou compressão extrínseca. A avaliação funcional foi feita periodicamente durante 61 dias através do Índice de Função Ciática (IFC) de Bain-Mackinnon-Hunter, e a análise histomorfométrica realizada ao término deste período. RESULTADOS: O grupo A (compressão extrínseca) apresentou IFC inicial de -26,29±2,89 com retorno aos valores pré-operatórios no 5º dia de pós-operatório. O grupo B (hematoma e compressão extrínseca) foi aquele com pior função ciática inicial (IFC -85,23±3,51) com recuperação da função no 23º dia. O grupo C apresentou IFC inicial de -32,78±7,45 com normalização no 5º dia. O grupo D apresentou IFC inicial de -45,13±6,84 com normalização da função ciática no 5º pós-operatório. A análise estatística do IFC identificou diferença significativa (p<0,0001) entre a conduta expectante (grupo B) e o tratamento cirúrgico descompressivo (grupos C e D) até o 19° dia. O número e a densidade de fibras mielínicas em degeneração foi significativamente maior no grupo B quando comparado aos outros grupos. CONCLUSÃO: Neste estudo experimental, descompressão cirúrgica e epineurotomia reduziram a perda de fibras mielínicas e determinaram recuperação funcional mais rápida. / INTRODUCTION: Intraneural hematoma can result in the median nerve in the carpal tunnel after trauma or coagulation disorders. The decision for expectant management or descompressive surgical techniques is still controversial. MATERIAL AND METHODS: Fifty male Wistar rats were divided into 5 groups. The sciatic nerve was wrapped around with a silastic device in 4 groups. Group A the sciatic nerve was just wrapped by the silastic tube. In group B an intraneural injection of autologous blood was added. In group C, after the hematoma creation the silastic device was removed and a longitudinal epineurotomy was performed. In group D, we removed the silastic device after the hematoma but the nerve was not opened. In the group E (sham-operated) sciatic nerve was exposed without hematoma or compression. Nerve function recovery was assessed periodically over 61 days using the Bain-Mackinnon-Hunter Sciatic Function Index (SFI). RESULTS: Group A (extrinsic compression) presented initial SFI of -26.29±2.89, with return to baseline values on the 5th postoperative day. Group B (hematoma and extrinsic compression) exhibited the poorest function (SFI - 85.23±3,51) after surgery and recovery in 23 days. Group C (liberation of silastic and hematoma drainage through epineurotomy) and Group D (only removal of the silastic tube) presented similar initial SFI values of - 32.78±7.45 and - 45.13±6.84, respectively. In both groups SFI values returned to baseline level on 5th postoperative day. The statistical analysis of SFI identified a significant difference (p<0.0001) between the expectant management (group B) and the descompressive surgery approach (groups C & D) by 1st to 19th postoperative day. The number of degenerative fibers and density of degenerative fibers were statistically significant bigger in the group B when compared to the other groups. There was no statistical difference between the other groups when these parameters were analysed. CONCLUSION: Thus, immediate descompressive procedures of the intraneural hematoma provide a faster functional recovery and reduce the damage to the axon fibers.

This body of work details the exploitation of an incredibly powerful neural culture system, which enables the in vitrostudy of events involved in peripheral nervous system (PNS) development. Using a myelinating dorsal root ganglion (DRG) explant culture system, node of Ranvier formation and maintenance and the associated generation and maturation of myelin segments was examined. In addition, Schwann cell (SC) development, dynamics, and migration were extensively studied. First, in characterizing these cultures, the discrete axonal localization of specific ankyrin isoforms was revealed. Ankyrins are peripheral membrane proteins that immobilize classes of integral membrane proteins to the spectrin based-membrane skeleton. Ankyrins interact with proteins such as the voltage-dependent/gated sodium channel (vgsc) and members of the L1 family of cell adhesion molecules. These interactions are physiologically relevant to the formation of membrane specializations involved in axon guidance and the initiation and propagation of action potentials. We examined ankyrinB and ankyrinG expression in cultured DRG explants, which allowed visualization of individual axons. AnkyrinB and ankyrinG exhibited differential localizations to specific axonal populations. This was evident as early as one day in vitro and persisted over time. In mature pre-myelinated cultures, axons having an apparent diameter of less than 1 µm predominantly expressed ankyrinB, whereas axons having a diameter greater than or equal to 1 µm predominantly expressed ankyrinG (based on immunocytochemical reactivity). When myelination was induced, ankyrinGwas appropriately localized to sites of nodal development flanked by myelinating glial processes in the large caliber axons. These observations suggest that axons destined for myelination may express a distinct complement of peripheral, and perhaps integral, membrane proteins as compared to those observed in non-myelinated axons. These distinguishing features may play a role in the selection of axons for myelination. This work was followed with defining the role axo-glial interactions play in organizing domains along the axon being myelinated. Nodes of Ranvier are specialized, highly polarized axonal domains crucial to the propagation of saltatory action potentials. In the PNS, axon-glial cell contacts have been implicated in SC differentiation and the formation of nodes of Ranvier. SC microvilli establish axonal contact at mature nodes, and their components have been observed to localize early to sites of developing nodes. However, a role for these contacts in node formation remains controversial. Using the myelinating explant culture system, we observed that SCs reorganize and polarize microvillar components, such as the ezrin-binding phosphoprotein 50kDa (EBP50)/regulatory co-factor of the sodium-hydrogen exchanger isoform 3 (NHERF-1), actin, and the activated ezrin, radixin, and moesin (ERM) family of proteins, concomitant with myelination in response to inductive signals. These components were targeted to the SC distal tips where live cell imaging revealed novel, dynamic growth cone-like behavior. Further, localized activation of the Rho signaling pathway at SC tips gave rise to these microvillar component-enriched “caps” and influenced the efficiency of node formation. Extending these findings, a more profound examination of SC dynamics was undertaken. This was a particularly important experimental transition, as SC motility is crucial in the development and regeneration of the PNS. The seemingly equivalent bipolarity of mature SCs represents a conundrum in terms of directed motility. Fluorescence time-lapse microscopy of transfected SCs within the myelinating DRG explants revealed a novel cycling of these cells between static, bipolar and motile, unipolar morphologies via asymmetric process retraction and extension. Concentrations of PIP2 (phosphatidylinositol (4,5)-bisphosphate), activated ERMs, and EBP50 delineated the transitory asymmetry associated with the generation and neuron-like migration of the unipolar cell. EBP50 over-expression enhanced unipolar SC migration, suggesting a new role for this adaptor protein in cell motility. Further, the ERMs themselves were found to be essential to both motility and process dynamics with ERM disruption yielding a dysfunctional, multipolar SC phenotype. We propose this novel form of motility may be associated with the correct alignment and spacing of SCs along axons prior to elaboration of the myelin sheath. These compiled studies present significant advances in understanding and examining axo-glial interactions in the PNS. This work establishes the foundation for further, novel exploration of normal PNS development and the regeneration and repair mechanisms involved in PNS injury and disease states.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2010. / Härtill 4 uppsatser.