Célula de Büngner / Büngner cell

Las lesiones del nervio periférico constituyen una condición clínica frecuente; por ello, entender su fisiopatología y los avances en el campo de la regeneración nerviosa es fundamental para brindar el mejor tratamiento a los pacientes. En los últimos años se ha venido dando cada vez mayor importancia a los eventos regenerativos después de la lesión, donde interviene en gran medida una expresión fenotípica única en este proceso, derivada de células ya presentes, fenómeno clave para la recuperación de la función del nervio lesionado. Este artículo revisó la literatura disponible con el objetivo de entender mejor este evento regenerativo y se encontraron procesos celulares y moleculares que suceden en los axones.

Peripheral nerve injuries are a common clinical condición for which the understanding of the pathophysiology and advances in the fteld of nerve regeneration are important to provide the best treatment for patients. In recent years, it has been giving increasing importance to the regenerative events after injury, where it operares largely unique phenotypic expression in this process, derived from cells already present, kev event for the recoven- of nerve function injured. A review of the literature is done with the aim of a better understanding of this regenerative event, fínding a series of cellular and molecular processes that go on axonal level.

Rescuing axons from degeneration does not affect retinal ganglion cell death

After a traumatic injury to the central nervous system, the distal stumps of axons undergo Wallerian degeneration (WD), an event that comprises cytoskeleton and myelin breakdown, astrocytic gliosis, and overexpression of proteins that inhibit axonal regrowth. By contrast, injured neuronal cell bodies show features characteristic of attempts to initiate the regenerative process of elongating their axons. The main molecular event that leads to WD is an increase in the intracellular calcium concentration, which activates calpains, calcium-dependent proteases that degrade cytoskeleton proteins. The aim of our study was to investigate whether preventing axonal degeneration would impact the survival of retinal ganglion cells (RGCs) after crushing the optic nerve. We observed that male Wistar rats (weighing 200-400 g; n=18) treated with an exogenous calpain inhibitor (20 mM) administered via direct application of the inhibitor embedded within the copolymer resin Evlax immediately following optic nerve crush showed a delay in the onset of WD. This delayed onset was characterized by a decrease in the number of degenerated fibers (P<0.05) and an increase in the number of preserved fibers (P<0.05) 4 days after injury. Additionally, most preserved fibers showed a normal G-ratio. These results indicated that calpain inhibition prevented the degeneration of optic nerve fibers, rescuing axons from the process of axonal degeneration. However, analysis of retinal ganglion cell survival demonstrated no difference between the calpain inhibitor- and vehicle-treated groups, suggesting that although the calpain inhibitor prevented axonal degeneration, it had no effect on RGC survival after optic nerve damage.

Estudo da regeneração simpática pós simpaticotomia seletiva experimental (ramocotomia) / Study of sympathetic regeneration post experimental selective sympathicotomy (ramicotomy)

Introdução: A simpatectomia torácica é o único tratamento, definitivo e eficaz, para a hiperidrose primária. A ramicotomia é um procedimento cirúrgico tão eficaz, mais conservador e com menos efeitos adversos que a simpatectomia convencional, contudo foi abandonada pela alta taxa de recidiva, atribuída, até então, à secção incompleta dos ramos comunicantes, ao desenvolvimento de outras vias de condução para o estímulo central e à regeneração neural. A avaliação histológica dos ramos comunicantes simpáticos após a ramicotomia, pode ajudar a entender o processo de recidiva dos sintomas da hiperidrose e, dessa forma contribuir para o desenvolvimento de estratégias para evitá-la. MATERIAL E MÉTODOS: 28 suínos foram submetidos à ramicotomia por videotoracospia e divididos randomicamente em 5 grupos, sacrificados com 15, 45, 90, 135 e 180 dias de pós-operatório (DPO). Os segmentos operados foram removidos cirurgicamente e submetidos à avaliação macroscópica da regeneração assim como análise histológica dos ramos comunicantes brancos e cinzentos para quantificação da reação inflamatória, deposição de fibras de colágeno grossas e finas, fibras reticulares e células de Schwann por imuno-histoquímica. Os dados foram comparados ao grupo controle, composto por segmentos intactos, não operados. RESULTADOS: Não houve regeneração macroscópica no grupo de 15 DPO sendo presente em 41,6% dos casos no grupo 180 DPO (p < 0,05). A reação inflamatória foi determinante no processo de degeneração Walleriana, com presença importante das células de Schwann nos ramos pré-ganglionares (p < 0,05), as células de Schwann apresentaram evolução semelhante nos dois ramos a partir do grupo de 45DPO, mantendo-se em menor número nos ramos cinzentos. As fibras de colágeno foram cruciais na cicatrização e as fibras reticulares importantes na regeneração neural, com correlação negativa entre elas (r = - 0,414; p < 0,01)...

INTRODUCTION: Thoracic sympathectomy is the only definitive and efficient treatment for primary hyperhidrosis. The ramicotomy is a surgical procedure that is as efficient as conventional sympathectomy but more conservative, having less adverse effects then conventional sympathectomy. This procedure was abandoned on account of the high recurrence rate, attributed to the incomplete section of the rami communicantes and to the development of new pathways of conduction to the central stimuli. MATHERIAL AND METHODS: Twenty-eight swine underwent bilateral videothoracoscopic ramicotomy and were randomly divided into 5 groups. The animals were sacrificed at 15, 45, 90, 135 and 180 days post-operative POD. The segments were removed and evaluated for macroscopic regeneration and histological analysis of the white and gray rami communicantes analyzing the inflammatory reaction, deposition of thin and thick collagen fibers, reticular fibers and Schwann cells. The data was compared to intact segments of sympathetic trunk as a positive control. RESULTS: There was neither macroscopic nor microscopic regeneration at the 15 POD group. The remaining groups had an average of 41,6% of regeneration, more significant at the 180 POD group (p<0.05). The inflammatory reaction was crucial in the process of Wallerian degeneration, with an important participation of the Schwann cells in the pre-ganglionic rami (p<0.05). The Schwann cells presented a similar evolution in both rami beginning at the 45 POD group, with a smaller count in the gray rami. The collagen fibers were significant in the cicatrization and the reticular fibers were important in neural regeneration, with a meaningful negative correlation between them (r = - 0,414; p < 0,01)...

Degeneração Walleriana de origem vascular em ressonância magnética de paciente com paralisia supranuclear progressiva provável: fator etiológico ou associação fortuita? / Vascular Wallerian degeneration on magnetic resonance in a patient with probable progressive supranuclear palsy: aetiology or casual link?

Progressive supranuclear palsy (PSP) is one of the most important causes of parkinsonism non responsive to therapy. Vascular parkinsonism is not uncommon. However, the cause-effect relationship between them is uncertain. We report on a 65 year old man with probable PSP who developed the clinical features of the disease after a ischaemic stroke. Magnetic resonance imaging disclosed a corticospinal tract Wallerian degeneration. There is not such an observation in the literature about this possible correlation.

Paralisia supranuclear progressiva (PSP) é uma das principais causas de parkinsonismo-plus não responsivo a terapia. A ocorrência de doença cerebrovascular associada a parkinsonismo não é infreqüente, no entanto é difícil estabelecer a relação causa-efeito entre ambas. Relatamos o caso de um paciente de 65 anos com PSP provável iniciada após infarto cerebral, em que a imagem por ressonância magnética evidenciou sinais de degeneração walleriana do trato córtico-espinhal. Não há relato na literatura pesquisada sobre esta possível correlação.

Axotomía vago-simpático cervical y degeneración nerviosa intrapulmonar en ratas / Vagosympathetic cervical axotomy and nervous intrapulmonary degeneration in rats

La axotomía de un nervio periférico conduce a la interrupción de la continuidad del axón, con degeneración walleriana en el segmento distal de la neurona. El proceso postraumático del nervio lesiona el axón y su vaina de mielina y el material dañado es invadido por fagocitos hematógenos, que remueven con el tiempo la gran mayoría de las fibras de mielina y otras células endoneurales. Este hecho permitió el seguimiento del trayecto nervioso intrapulmonar, después de la sección del tronco vago-simpático cervical en la rata, por la aparición en el proceso degenerativo de productos de desintegración de lípidos de la mielina, teñidos con Sudán III y IV. El objetivo del trabajo fue poner en evidencia y se demostró el trayecto de las fibras autónomas intrapulmonares y su relación con las divisiones más finas de los bronquios respiratorios, por la función que el sistema autónomo tiene en el asma bronquial

Watery and dark axons in Wallerian degeneration of the opossum's optic nerve: different patterns of cytoskeletal breakdown?

In this paper we report a qualitative morphological analysis of Wallerian degeneration in a marsupial. Right optic nerves of opossums Didelphis marsupialis were crushed with a fine forceps and after 24, 48, 72, 96 and 168 hours the animals were anaesthetized and perfused with fixative. The optic nerves were immersed in fixative and processed for routine transmission electron microscopy. Among the early alterations typical of axonal degeneration, we observed nerve fibers with focal degeneration of the axoplasmic cytoskeleton, watery degeneration and dark degeneration, the latter being prevalent at 168 hours after crush. Our results point to a gradual disintegration of the axoplasmic cytoskeleton, opposed to the previous view of an "all-or-nothing'' process (Griffin et al 1995). We also report that, due to an unknown mechanism, fibers show either a dark or watery pattern of axonal degeneration, as observed in axon profiles. We also observed fibers undergoing early myelin breakdown in the absence of axonal alterations

Early myelin breakdown following sural nerve crush: a freeze-fracture study

In this study we describe the early changes of the myelin sheath following surgical nerve crush. We used the freeze-fracture technique to better evaluate myelin alterations during an early stage of Wallerian degeneration. Rat sural nerves were experimentally crushed and animals were sacrificed by transcardiac perfusion 30 h after surgery. Segments of the nerves were processed for routine transmission electron microscopy and freeze-fracture techniques. Our results show that 30 h after the lesion there was asynchrony in the pattern of Wallerian degeneration, with different nerve fibers exhibiting variable degrees of axon disruption. This was observed by both techniques. Careful examination of several replicas revealed early changes in myelin membranes represented by vacuolization and splitting of consecutive lamellae, rearrangement of intramembranous particles and disappearance of paranodal transverse bands associated or not with retraction of paranodal myelin terminal loops from the axolemma. These alterations are compatible with a direct injury to the myelin sheath following nerve crush. The results are discussed in terms of a similar mechanism underlying both axon and myelin breakdown

Reduced sensory neuron regeneration by C57BL/6J mice

The tube repair method was used to study peripheral nerve regeneration in five different inbred mouse strains. The sciatic nerve of male adult mice of the C57BL/6J,DBA/1J, C3H/HeJ, BALB/cJ and A/J strains (N=3) was cut and both proximal and distal nerve stumps were inserted into a polyethylene tube leaving a 4-mm nerve gap. After 6 weeks the tubes containing the regenerated nerve cables were processed for total myelinated axon counts. C57BL/6J mice regenerated significantly fewer myelinated axons (1024 + or - 178, mean + or - SEM) compared to the BALB/cJ (1618+ or - 64), a/j (1788 + OR - 95), dba/1j(2168 + OR - 296) OR c3h/hEj (3468 + OR - 36) strains. Horseradish peroxidase was applied 3 mm distal to be tube 4 and 40 weeks after tube implantation to further characterize the reduced regenerative response of C57BL/6J mice. Labeled sensory and somatic motor neurons were counted in the spinal cord and L4,5,6 dorsal root ganglia (DRG), respectively. Sciatic nerves from four intact C57BL/6J mice were processed in the same fashion and used as normal controls. No significant difference in the number of motor neurons was detected between the experimental (4 weeks = 663 + or - 13) animals. However, there were fewer labeled neurons in the DRG of the operated group (4 weeks = 1163 + or - 167; 40 weeks = 2574 + or - 104) compared to the control group (4211 + or - 96). These results indicated that sensory neurons are responsible for the diminished regenerative response in C57BL/6J mice after peripheral nerve transection. Neurotrophic factors may be implicated in the reduced response, although no systematic study has been done to quantify either trophic factors or their receptor synthesis in different mouse strains during Wallerian degeneration. Diminished peripheral nerve fiber regeneration makes the C57BL/6J mouse strain an ideal experimental model to evaluate the effects of exogenous substances on nerve repair

Peripheral neuroendocrinology of the cervical autonomic nervous system

1. The sympathetic superior cervical ganglia (SCG) provide innervation to the pineal gland and median eminence through the internal carotid nerve and to the thyroid and parathyroid glands through the external carotid nerve. 2. Postsynaptic activation in median eminence nerve endings shortly after superior cervical ganglionectomy (SCGx) was accompanied by a depression of LH and FSH release and by a 3-5 day delay in rat estrous cyclicity. A decrease in TSH and GH release and an increase in ACTH and prolactin release were also found. These effects were accompanied by a) an increase in medial basal hypothalamic (MBH) LHRH, TRH and GHRH, b) a decrease in MBH somatostatin, AVP and CRH, and c) a normal adenohypophyseal response to hypophysiotropic hormones. Neurohypophyseal AVP release decreased during degeneration of sympathetic nerve terminals in the neurohypophyseal lobe after SCGx. The effects were generally mediated by alpha 1-adrenoceptors and were pineal gland. 3. In thyroid and parathyroid tissue the following events were observed during the wallerian degeneration phase after SCGx: a) alpha 1-adrenoceptor inhibition of thyroxine (T4) release, b) alpha 1-adrenoceptor inhibition, together with beta-adrenoceptor stimulation, of calcitonin release, and c) alpha 1-adrenoceptor inhibition of parathyroid hormone release. Thyroid sympathetic nerves also modulate slow phenomena such as compensatory thyroid growth after partial thyroidectomy. 4. In rats subjected to cholinergic decentralization of the thyroid gland, a decrease of plasma T4 and an increase of plasma TSH, as well as an impaired goitrogenic and thyroid compensatory response were detectable. The calcitonin and PTH response to changes in calcium levels increased after regional parasympathetic denervation. 5. The results indicate that cervical autonomic nerves constitute a parallel pathway through which the brain communicates with the endocrine system

Estudo ultra-estrutural da degeneração e regeneração de fibras nervosas de nervo sural de rato: análise morfológica e citoquímica para cálcio / Ultrastructural study of degeneration and regeneration of nerve fibers in rat sural nerve: morphological and cytochemistry for calcium

Nervos surais de rato submetidos ao esmagamento cirúrgico foram observados , ultra-estruturalmente, 30 e 48 horas após a lesão, para estudo do transporte axonal e da degeneração Walleriana precoce e em estágio mais avançado. A regeneração das fibras nervosas foi igualmente estudado...Nas fibras nervosas com alterações degenerativas mais intensas, os domínios específicos para o íon cálcio foram perdidos. Houve uma aparente concentração e aumento da quantidade de precipitados de cálcio no axoplasma, nas células se Schwann e no endoneiuro circundante. Este fato parece decorrer de um influxo maior do íon cálcio para o interior da fibra, devido à lesão.

Posttetanic potentiation in decentralized and nondecentralized superior cervical ganglia of the cat

La presente investigación se realizó para responder a la siguiente pregunta elemental, aunque importante, de lafisiología del ganglio simpático: ¿Retienen las terminaciones preganglionares descentralizadas su plena capacidad para desarrollar la potenciación postetánica (PPT) antes de que la degeneración walleriana se presente? Se siguió un diseño factorial de experimentos en el ganglio simpático in situ del gato. Los factores fueron: tetanización (pulsos supramáximos, 0.2 ms, 25 Hz, 30 s), descentralización aguda y dosis moderada de hexametonio (5mg/Kg). Dos fueron los niveles; a saber, la maniobra indicada se efectuó o no se efectuó

Proper microsurgical nerve suture may impede Wallerian degeneration of completely transected nerves.

Neste trabalho experimental foi utilizado, como o fizemos em l968, o nervo do musculo biventer cervicis do pintainho. Os nervos transeccionados ao nivel do tendao intermedio do musculo e propositadamente nao suturados, ou acidentalmente mal suturados, apresentaram, como esperado, degeneracao Walleriana total do segmento distal e consequente desnervacao do ventre distal do musculo. Os nervos, transeccionados e imediatamente suturados com tecnica microcirurgico fascicular adequada, apresentaram, em nivel de microscopia eletronica, de 7/12 hs. a 2 meses pos-operatorio, numerosas fibras nervosas mielinicas integras, alem naturalmente, de fibras nervosas em diferentes e progressivas fases de degeneracao Walleriana. Os ventres distais dos musculos cujos nervos foram operados com sucesso apresentavam coloracao e aspectos normais, respondiam a estimulos mecanicos e, em cortes histologicos para microscopia optica, exibiram numerosas placas motoras integras. A afirmacao que fizemos em trabalhos anterioes "a degeneracao Walleriana total que normalmente ocorre em segmentos distais de nervos completamente transeccionados pode ser parcialmente evitada atraves de neurorrafias, com tecnica microcirurgica fascicular adequada: - e agora documentada em nivel de microscopia eletronica