Thesis (Ph.D. in Physiology & Biophysics) -- University of Colorado Denver, 2007. / Typescript. Includes bibliographical references (leaves 125-138). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;

Thesis (M.S.)--University of Michigan, 2001. / Includes bibliographical references.

Abstract Type 2 diabetes causes impairment of peripheral nervous system (PNS) function, which can result in symptoms such as pain and numbness. Disturbances in glucose metabolism inflict negative alterations on PNS function even before diabetes occurs. Forty non-diabetic overweight (BMI 25–30) or obese (BMI > 30) working-age adults without polyneuropathy were enrolled in this study. PNS function was measured at baseline and after 3 years by peroneal motor nerve and radial, sural, and medial plantar sensory nerve conduction studies (NCS). At baseline, serum insulin and glucose levels (fasting, 30 min, and 120 min) were measured with a 2-hour oral glucose tolerance test (OGTT), and fasting serum cholesterol and triglyceride levels were measured. Maximal oxygen uptake (VO2max) was measured with an incremental bicycle ergometer test. Physical activity at the age of 15, 30, and current age was defined by a questionnaire. Current physical activity was also measured with a pedometer. At 3-year follow-up, serum insulin and glucose values were measured with a 2-hour OGTT, and serum fasting cholesterol and triglyceride values were measured. At baseline, a serum insulin level at 120 min was positively and statistically significantly associated with peroneus nerve F-wave minimum and maximum latency time, sural nerve latency and nerve conduction velocity (NCV), and medial plantar NCV. VO2max was positively associated with amplitudes of the distal and proximal peroneus nerve and medial plantar nerve. Physical activity at the age of 30 was positively and significantly associated with peroneus NCV, F-wave maximum latency, medial plantar latency, and NCV. At the 3-year follow-up study, all sensory nerve amplitudes decreased significantly, and a 120-min insulin change was positively associated with changes in peroneus NCV, F-wave average latency, sural NCV, and medial plantar NCV. Serum 120-min insulin values were positively associated with NCVs. Physical activity and fitness were positively associated with PNS function. The significant decrease in all sensory nerve amplitudes during follow-up demonstrates that negative alterations may already occur in overweight and obese adults without diabetes. Overweight and obese adults should be encouraged to have an active lifestyle, as even a small increase in physical activity might have a positive effect on PNS function. / Tiivistelmä Tyypin 2 diabetes aiheuttaa ääreishermoston toiminnan heikentymistä, mikä voi oireilla raajoissa kipuna ja tunnottomuutena. Sokeritasapainon häiriintyminen vaikuttaa haitallisesti ääreishermoston toimintaan jo ennen varsinaisen diabeteksen puhkeamista. Tutkimusaineistona olivat 40 ylipainoista (BMI 25-30) tai lihavaa (BMI>30) työikäistä henkilöä, jotka eivät sairastaneet tyypin 2 diabetesta tai polyneuropatiaa. Heille tehtiin seurannan alussa ja lopussa motorisen peroneushermon sekä sensoristen radius-, suralis- ja mediaalisen plantaarihermon hermoratatutkimus. Seurannan alussa heiltä määritettiin seerumin insuliini- ja glukoosiarvot (paasto, 30 min ja 120 min) kahden tunnin sokerirasituskokeella sekä seerumin paastokolesteroli- ja paastotriglyseridiarvot. Maksimaalinen hapenottokyky (VO2max) mitattiin polkupyöräergometrillä. Fyysinen aktiivisuus 15- ja 30-vuotiaana sekä tutkimushetkellä selvitettiin kyselyllä. Nykyinen aktiivisuus mitattiin myös kiihtyvyysanturiin perustuvalla askelmittarilla. Kolmen vuoden seurannassa 29 tutkittavalta määritettiin seerumin insuliini- ja glukoosiarvot kahden tunnin sokerirasituskokeella sekä seerumin paastokolesteroli- ja paastotriglyseridiarvot. Alkutilanteessa 120 minuutin insuliiniarvo oli positiivisesti ja tilastollisesti merkitsevästi yhteydessä peroneushermon F-aallon minimi- ja maksimilatenssiaikaan, suralishermon latenssiaikaan ja johtumisnopeuteen sekä mediaalisen plantaarihermon johtumisnopeuteen. VO2max oli positiivisesti yhteydessä peroneushermon distaalisen ja proksimaalisen vasteen voimakkuuteen (amplitudi) sekä mediaalisen plantaarihermon vasteen voimakkuuteen. Fyysinen aktiivisuus 30 vuoden iässä oli positiivisesti ja merkitsevästi yhteydessä peroneushermon johtumisnopeuteen, F-aallon maksimilatenssiaikaan, mediaalisen plantaarihermon latenssiaikaan sekä johtumisnopeuteen. Seurantatutkimuksessa kaikkien sensoristen hermojen vasteet pienenivät merkitsevästi ja seerumin 120 min insuliiniarvon muutos oli positiivisesti yhteydessä peroneushermon johtumisnopeuden, F-aallon keskiarvolatenssiajan, suralishermon johtumisnopeuden sekä mediaalisen plantaarihermon johtumisnopeuden muutokseen. Seerumin 120 min insuliiniarvot olivat positiivisesti yhteydessä ääreishermojen johtumisnopeuksiin. Fyysinen aktiivisuus ja kunto olivat positiivisesti yhteydessä ääreishermoston toimintaan. Negatiiviset muutokset sensoristen hermojen vasteissa seurantatutkimuksessa osoittavat, että negatiivisia muutoksia ääreishermoston toimintaan voi tapahtua ylipainoisilla henkilöillä jo ilman diabetesta. Ylipainoisia tulee kannustaa liikkumaan, sillä vähäiselläkin liikunnan lisäyksellä voi olla positiivinen vaikutus myös ääreishermoston toimintaan.

Orientadores: Francesco Langone, Leonilda Maria Barbosa dos Santos / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-08T19:17:03Z (GMT). No. of bitstreams: 1 RodriguezdelaHoz_CristianeLucia_D.pdf: 3716352 bytes, checksum: 29e8652cc135a71b48d8a6442b69e187 (MD5) Previous issue date: 2007 / Resumo: A isoforma induzível da sintase do óxido nítrico (iNOS) e o fator de necrose tumoral-alfa (TNF-a) estão envolvidos em processos inflamatórios desmielinizantes como a síndrome de Guillain Barré e seu modelo animal, a neurite experimental auto-imune (EAN). A presença dessas moléculas foi investigada no sistema nervoso periférico de ratos Lewis em diferentes fases da EAN. Raízes nervosas oriundas dos segmentos medulares torácico 12 (T12) a lombar 3 (L3) (raízes adjacentes à intumescência lombar), cauda eqüina e nervos ciáticos foram coletados e processados para dupla imunofluorescência. Paralelamente, esses espécimes foram analisados quanto à desmielinização e degeneração axonal, por meio de histoquímica de Sudan Black e imunofluorescência para neurofilamentos, respectivamente. Todos os animais com EAN apresentaram células inflamatórias com imunorreatividade para iNOS e TNF-a, correspondendo a macrófagos e polimorfonucleares (neutrófilos). Essas células contendo iNOS e TNF-a foram observadas nos ratos Lewis exibindo os primeiros sinais clínicos da EAN. Sua população tornou-se numerosa durante a fase de agravamento do quadro clínico, diminuiu no decorrer da fase de recuperação e não foi observada nos animais clinicamente recuperados. Conforme o estágio da EAN, essas células contendo iNOS e TNF-a foram encontradas nas diferentes regiões nervosas analisadas. No início dos sinais clínicos observou-se algumas células iNOS/TNF-a-imunorreativas em vasos da cauda eqüina e do nervo ciático. Na fase em que os animais apresentaram paraparesia, houve um aumento dessa população celular ao redor de vasos e infiltrados inflamatórios nos gânglios sensitivos, na cauda eqüina e nas raízes nervosas T12-L3. Alterações na bainha de mielina e nos neurofilamentos não foram detectadas. Com a evolução da EAN, os animais desenvolveram paraparesia severa. Nesta fase, numerosas células com imunorreatividade para iNOS e TNF-a distribuíram-se ao redor de infiltrados inflamatórios e no tecido endoneural das raízes espinhais e do nervo ciático. Próximo às regiões de infiltrado, algumas fibras nervosas apresentaram bainha de mielina fragmentada ou mais delgada. Alguns axônios no nervo ciático exibiram imunomarcação dos neurofilamentos menos intensa, fragmentada ou aglomerada. Na fase de recuperação, raras células iNOS/TNF-a-imunorreativas foram encontradas em vasos das raízes nervosas T12-L3 e do nervo ciático. Em algumas raízes da cauda eqüina, essas células foram observadas em maior número. O auge da desmielinização foi verificado no nervo ciático nesse estágio, com a presença de vários fragmentos e ovóides de mielina. Os neurofilamentos imunomarcados, por sua vez, apresentaram-se contínuos, porém mais delgados do que os normais. Na fase de resolução da EAN não foram evidenciadas células duplamente imunorreativas. A bainha de mielina recobrou seu aspecto normal nas raízes nervosas, enquanto que no nervo ciático, bainhas de mielina e neurofilamentos imunomarcados delgados foram observados em meio a bainhas e imunomarcação de neurofilamentos mais grossas. Nossos resultados sugerem uma correlação entre a presença da iNOS e TNF-a nas diferentes regiões nervosas e os sinais clínicos exibidos pelo animal com EAN. Além disso, o acentuado processo desmielinizante que ocorre no nervo ciático é capaz de promover alterações estruturais nos neurofilamentos, provavelmente afetando o funcionamento normal dos axônios / Abstract:Inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-a) are involved in inflammatory processes such as Guillain Barré Syndrome and its animal model, Experimental Autoimmune Neuritis (EAN). In this study, the presence of these molecules was investigated in the peripheral nervous systems of Lewis rats at different stages of EAN. Thoracic 12 (T12) to lumbar 3 (L3) spinal roots adjacent to lumbar intumescence, cauda equina and sciatic nerves were obtained and processed for double immunofluorescence. These specimens were also analyzed for myelin and axonal degeneration using Sudan Black histochemistry and neurofilament immunolabelling, respectively. All the immunized animals showed double iNOS and TNF-a immunoreactivity in inflammatory cells such as macrophages and polymorphonuclears (neutrophils). These cells were observed in Lewis rats exhibiting the first clinical signs of EAN. Their population increased during the worsening of the disease, diminished during the recovery phase and had disappeared completely in clinically recovered rats. Depending on the EAN phase, iNOS and TNF-a bearing cells were found in the different regions of peripheral nervous system analyzed. At the onset of clinical signs, some iNOS and TNF-a immunoreactive cells were observed in vessels of the cauda equina and the sciatic nerve. In mildly paraparetic rats, an increase in the amount of these cells around vessels and inflammatory infiltrates in the dorsal root ganglia, cauda equina and T12-L3 spinal roots was observed. Changes in the myelin sheath and neurofilaments were not detected. As the EAN evolved, the rats developed severe paraparesis. At this stage, numerous iNOS and TNF-a bearing cells were observed around inflammatory infiltrates and in the endoneurium of the spinal roots and the sciatic nerve. Some nerve fibers near to infiltrated regions showed a thinner or even fragmented myelin sheath. Some sciatic nerve axons exhibited a less intense, fragmented or clustered neurofilament immunolabelling. During recovery stage, rare iNOS/TNF-a immunoreactive cells were detected in vessels of T12-L3 spinal roots and the sciatic nerve. An increased number of these cells was observed in some nerve fibers of cauda equina. The peak stage of demyelination was verified in the sciatic nerve by the presence of several myelin ovoids. Neurofilaments showed continuous immunolabelling, but were more slender than the neurofilaments in naïve rats. Double-immunoreactive cells were not evidenced during the recovery stage. In nerve roots, the myelin sheath recovered its normal appearance, while in sciatic nerves, slenderer myelin sheaths and immunolabelled neurofilaments were observed among thicker ones. Our results suggest that there is a close association between the presence of iNOS and TNF-a bearing cells in the various regions of the peripheral nervous system and the clinical signs exhibited by the animals. Furthermore, the acute demyelinating process in sciatic nerves also promotes structural changes, probably affecting the normal functioning of axons / Doutorado / Biologia Celular / Doutor em Biologia Celular e Estrutural

La synthèse de la gaine de myéline périphérique par les cellules de Schwann dans le système nerveux périphérique est sous le contrôle de plusieurs facteurs de transcription incluant Egr2 qui est aussi impliqué dans la maintenance de la myéline périphérique. Nous avons développé une nouvelle méthode pour étudier l'implication de différents gènes dans la maintenance de la myéline périphérique en utilisant des siRNA pour inactiver des gènes cibles in vitro et in vivo. Nous avons utilisé des siRNA modifiés pour inhyber les gènes candidats sans utiliser de réactif de transfection. Ces siRNA sont d'abord utilisés sur des co-cultures organotypiques de ganglions rachidiens postérieurs d'embryons de rat et aussi en les injectant dans le nerf sciatique de rat adulte. Nous avons montré que les siRNA contrôles n'entrainent pas de démyelinisation significative aussi bien sur les co-cultures que in vivo après l'injection directe dans le nerf sciatique. Nous avons alors montré que les siRNA anti Egr2 régulent à la baisse l'expression de ces gènes cibles d'environ 60%. En plus, le traitement avec les siRNA anti Egr2 entrainent une dégradation de la gaine de myéline périphérique dans les co-cultures. L'injection des siRNA anti-Egr2 dans le nerf sciatique de rat adulte induit une demyelinisation rapide et significative marquée par la perte de l'expression de MPZ (myelin protein zero) dans la zone d'injection montrée par les expériences immunohistochimiques (microscopie optique) et par l'observation directe de la démyelinisation à l’épon sur des sections transversales de nerf sciatique ( microscopie optique et électronique). Ces résultats confirment ceux précédents impliquant Egr2 dans la maintenance active de la myéline qui avaient été obtenus par des expériences de « Knockout » conditionnels sur des souris. Des injections des siRNA anti-dicer ont induit de manière similaire la démyelinisation de nerf sciatique, établissant que l’expression de Dicer dans les nerfs périphériques adultes est nécessaire pour la maintenance correcte de la myéline. Nos résultats constituent une preuve de concept de l’utilisation de siRNA pour comprendre les mécanismes moléculaires de la maintenance de la myéline in vivo et les gènes induisant la démyelinisation dans les nerfs périphériques. / The synthesis of the myelin sheath by Schwann cells in the peripheral nervous system is under the control of several transcription factors including Egr2, which was shown to be also involved in the maintenance of peripheral myelin. We set up a new method to study the involvement of various genes in peripheral myelin maintenance, using small interfering RNAs (siRNAs) to silence target genes in vitro and in vivo. We used modified self-delivery siRNAs to silence candidate genes without using transfection reagents. These siRNAs were first used on organotypic co-cultures of dorsal root ganglia from embryonic rat and then injected into the sciatic nerves of adult rats. We showed that control non-targeting siRNAs did not induce significant demyelination either in co-cultures or in vivo, after direct injection in sciatic nerves. We then showed that anti-Egr2 siRNAs down-regulated in vitro their target gene expression by ~60%. In addition, treatment with anti-Egr2 siRNAs resulted in abnormalities of the myelin sheaths in co-cultures. The injection of anti-Egr2 siRNAs in the sciatic nerves of adult rats induced a significant and rapid demyelination, as shown by the loss of Myelin Protein Zero expression in the injected area on immunohistochemistry experiments (optic microscopy) and by direct evidence of demyelination on epon-embedded transversal sections of sciatic nerves (optic and electron microscopy). These results confirm previous data involving Egr2 in active myelin maintenance, which were obtained using conditional knockout experiments in mice. Injections of anti-Dicer siRNAs similarly induced sciatic nerve demyelination, establishing that Dicer expression in adult peripheral nerves is necessary for proper myelin maintenance. Our results constitute a proof of concept for the use of self-delivery siRNAs to investigate the molecular mechanisms of myelin maintenance in vivo and also to induce a gene-driven demyelination “on demand” in peripheral nerves.

No description available.

The peripheral nervous system can be seen as a huge network of neurons that prop-agates signals across the human body. In fact, as seen in [1] , "All the information streaming in the peripheral nervous system (PNS) is transmitted along axons byelectro-chemical signals called action potentials". The ordinary conduction of such nervous signals, or action potentials, can be prevented however due to nerve damage. In this context, the accurate passage of information to an intended destination or partwithin the organism is obstructed. Admittedly, it is understood that physiotherapy can be quite helpful in regaining correct functionality over a damaged part of the peripheral nervous system. Yet, it is still hard to visualize the nervous activity as it is achieved inside the human body. Simulating the nervous system would providea platform to visualize how the system works and how a damaged nerve can affect the PNS. Indeed, the purpose of this study is to simulate a virtual network that im-itates a general topology of the human peripheral nervous system e.g(simulate the nervous structure and behaviour of the human arm) that shows how the signals canbe routed to their correct destination and showcase how can the simulator created simulate biological nerve damage in its system.

<p> The nervous system exists as our interface to the world, both integrating and interpreting sensory information and coordinating voluntary and involuntary movements. Given its importance, it has become a target for neuromodulatory therapies. The research to develop these therapies cannot be done purely on living tissues - animals, manpower, and equipment make that cost prohibitive and, given the cost of life required, it would be unethical to not search for alternatives. Computation modeling, the use of mathematics and modern computational power to simulate phenomena, has sought to provide such an alternative since the work of Hodgkin and Huxley in 1952. These models, though they cannot yet replace in-vivo and in-vitro experiments, can ease the burden on living tissues and provide details difficult or impossible to ascertain from them. This thesis iterates on previous frameworks for performing in-silico experiments for the purposes of mechanistic exploration and threshold prediction. To do so, an existing volume conductor model and validated nerve-fiber model were joined and a series of programs were developed around them to perform a set of in-silico experiments. The experiments are designed to predict changes in thresholds of behaviors elicited by bioelectric neuromodulation to parametric changes in experimental setup and to explore the mechanisms behind bioelectric neuromodulation, particularly surrounding the recently discovered Low Frequency Alternating Current (LFAC) waveform. This framework improved upon its predecessors through efficiency-oriented design and modularity, allowing for rapid simulation on consumer-grade computers. Results show a high degree of convergence with in-vivo experimental results, such as mechanistic alignment with LFAC and being within an order of magnitude of in-vivo pulse-stimulation threshold results for equivalent in-vivo and in-silico experimental designs. </p>

No description available.

No description available.