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INTRODUÇÃO: A técnica de eletromiografia de fibra única (EMGFU), mediante análise do jitter, é o método neurofisiológico mais sensível para a confirmação do distúrbio da junção neuromuscular na miastenia gravis (MG). Os registros são tradicionalmente obtidos com agulha de fibra única, de alto custo e reutilizável. Por causa da necessidade atual do uso de material descartável, a agulha concêntrica vem sendo utilizada em substituição à agulha de fibra única. A técnica utilizada é semelhante, porém os potencias de ação para a análise do jitter são obtidos com eletrodo de agulha concêntrica (Eletromiografia de fibra única - jitter com agulha concêntrica, EMGFU-JAC). Contudo, os estudos são escassos e as metodologias utilizadas são heterogêneas com a utilização dessa agulha. OBJETIVOS: Este estudo tem por objetivo mensurar os valores de jitter obtidos com agulha concêntrica, no músculo Orbicularis Oculi, em sujeitos saudáveis e em pacientes com MG autoimune adquirida e avaliar a validade do método nas formas generalizada e ocular da doença. MÉTODOS: Foram estudados 20 sujeitos saudáveis, 20 pacientes com miastenia gravis forma generalizada (grupo MGG) e 13 com a forma ocular da doença (grupo MGO). A EMGFU-JAC foi realizada em todos os participantes, idealmente com 20 medidas de jitter em cada estudo. O jitter foi expresso como a média das diferenças consecutivas (MCD). Em todos os pacientes do estudo foram realizados o teste de estimulação repetitiva e dosagem sérica de anticorpo antirreceptor de acetilcolina (ac-AChR) no momento da análise do jitter. Nos pacientes soronegativos para ac-AChR, foi pesquisado o anticorpo antimúsculo específico tirosina-quinase (ac-MuSK). Foram definidos o limite superior da normalidade (LSN) para a média do MCD de cada estudo e para valores individuais de MCD. Os critérios de anormalidade foram: (1) média do MCD acima do LSN; ou (2) mais de 10% dos valores individuais de MCD acima do LSN. A definição do LSN para valores individuais de MCD baseou-se no conceito de que dois entre 20 valores de MCD acima do LSN são aceitáveis em um músculo saudável, para a técnica de contração voluntária. Portanto, estimou-se o LSN para o 18o valor mais alto de MCD (18o par). Para análise da acurácia do método, foram construídas duas curvas ROC (Receiver Operating Characteristic) para as variáveis média do MCD e 18o par, no grupo de pacientes (MGG e MGO) versus controle. RESULTADOS: No grupo controle a média das médias do MCD foi (19,0 ± 2,4)us e a média do 18o valor mais alto de cada estudo foi (24,5 ± 3,6)us. Esses valores obtidos apresentaram distribuição Gaussiana e o LSN foi definido como a média desses valores + 2 DP. O LSN para a média do MCD foi 24us, e 32?s para valores individuais de MCD. No grupo MGG, a análise do jitter foi anormal em todos os 20 pacientes por ambos os critérios de anormalidade, exceto em um paciente que apresentou anormalidade por apenas um dos critérios. No grupo MGO, apenas um dos 13 pacientes não preencheu os critérios de anormalidade. No grupo de pacientes, a positividade da EMGFU-JAC foi maior do que o teste de estimulação repetitiva e dosagens de anticorpos. Nas curvas ROC para as variáveis médias do MCD e 18o par, o valor de melhor sensibilidade (93,9%), sem resultados falsos positivos, foi 24,7us e 33,1us, respectivamente. CONCLUSÕES: A EMGFU-JAC apresenta alta sensibilidade e especificidade na identificação de distúrbio da transmissão neuromuscular em pacientes com MG. A utilização da agulha concêntrica é válida para a análise do jitter, como alternativa à agulha de fibra única / INTRODUCTION: Single fiber electromyography (SFEMG) technique, through jitter analysis, is the most sensitive neurophysiological method for confirmation of neuromuscular junction disorder in myasthenia gravis (MG). Records are traditionally obtained with single fiber needle, which is reusable and has a high-cost. Due to the current need of using disposable material, concentric needle has been used to replace single fiber needle. The technique is similar, but the action potential for jitter analysis is obtained with concentric needle electrode (SFEMG - concentric needle jitter, SFEMG-CNJ). However, studies are scarce and methodologies used are heterogeneous with the use of this needle. OBJECTIVES: This study aims to measure jitter values obtained with concentric needle in the Orbicularis Occuli muscle in healthy subjects and in patients with autoimmune acquired MG and to assess the validity of the method in generalized and ocular forms of the disease. METHODS: 20 healthy subjects, 20 patients with generalized myasthenia gravis (GMG group) and 13 with the ocular form of the disease (OMG group) were studied. SFEMG-CNJ was performed on all participants, ideally with 20 jitter values in each study. Jitter was expressed as the mean consecutive difference (MCD). Repetitive nerve stimulation and serum acetylcholine receptor antibody (AChR-ab) were performed in all patients in the study, by the time of jitter analysis. Tyrosine kinase specific antibody muscle antibodies (MuSK-ab) were performed in AChR-ab negative patients. The upper limit of normality (ULN) for the mean MCD and for individual jitter values were defined. The abnormality criteria were: (1) mean MCD above ULN; or (2) more than 10% of individual jitter values above ULN. The definition of ULN for individual jitter values was based on the concept that two out of 20 jitter values above ULN are acceptable in a healthy muscle for voluntary contraction technique. Therefore, the ULN for the 18th highest jitter value (18 pair) was estimated. To analyze the method\'s accuracy, two ROC curves (Receiver Operating Characteristic) for the mean MCD and 18th pair in the group of patients (MGG and MGO) versus control were constructed. RESULTS: In the control group the mean of MCD means was (19.0 ± 2.4)us and the mean of the 18 highest value of each study was (24.5 ± 3.6)us. These values showed Gaussian distribution and the ULN was set as the mean of these values + 2 SD. The ULN for the mean MCD was 24us, and 32us for individual values of MCD. In GMG group, jitter analyses were abnormal in all 20 patients based on both abnormality criteria, except in one patient, who had abnormalities in only one of the criteria. In OMG group, only one patient from 13 met neither of the abnormality criteria. In patients, the positivity of SFEMG-CNJ was higher than repetitive nerve stimulation test and antibody detection. The ROC curve threshold showing the best sensitivity (93.9%) with no false positive results was 24.7Us for the mean MCD and 33.1us for individual pairs, respectively. CONCLUSIONS: SFEMG-CNJ has high sensitivity and specificity in identifying neuromuscular transmission disorder in patients with MG. The use of concentric needle is valid for jitter analysis as an alternative to single fiber needle

Tam Wing-yip. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 91-113). / Abstracts in English and Chinese. / Abstract --- p.i / Chinese Abstract --- p.iv / Acknowledgements --- p.vi / Table of Contents --- p.vii / Chapter Chapter 1 --- General Introduction --- p.1 / Chapter 1.1 --- Hirschsprung's disease --- p.1 / Chapter 1.2 --- Neural crest cells and enteric nervous system --- p.3 / Chapter 1.3 --- Genetics of Hirschsprun´gةs disease --- p.10 / Chapter 1.3.1 --- RET/GDNF/NTN signaling pathway --- p.10 / Chapter 1.3.2 --- EDNRB/EDN3/ECE-1 signaling pathway --- p.13 / Chapter 1.3.3 --- Dominant megacolon and Sox10 --- p.15 / Chapter 1.3.4 --- Other genes involved in intestinal aganglionosis --- p.16 / Chapter 1.4 --- Objectives of the present study --- p.19 / Chapter Chapter 2 --- Enteric Neural Crest Cells Migration in Dominant Megacolon Mouse Embryos --- p.21 / Chapter 2.1 --- Introduction --- p.21 / Chapter 2.2 --- Materials and Methods --- p.26 / Chapter 2.2.1 --- Animal --- p.26 / Chapter 2.2.2 --- Preparation of rat serum --- p.26 / Chapter 2.2.3 --- Isolation of embryos from pregnant mice --- p.27 / Chapter 2.2.4 --- Preparation of wheat germ agglutinin-gold (WGA-Au) --- p.28 / Chapter 2.2.5 --- Microinjection of WGA-Au conjugate --- p.28 / Chapter 2.2.6 --- Whole embryo culture --- p.29 / Chapter 2.2.7 --- Examination of cultured embryos --- p.30 / Chapter 2.2.8 --- Histological preparation of WGA-Au injected embryos --- p.30 / Chapter 2.2.9 --- Silver enhancement staining and histological examination of the sections --- p.31 / Chapter 2.2.10 --- Genotyping by polymerase chain reaction --- p.32 / Chapter 2.2.11 --- TUNEL assays --- p.33 / Chapter 2.3 --- Results --- p.35 / Chapter 2.3.1 --- In vivo development of Dominant megacolon mouse embryos of different genotypes --- p.35 / Chapter 2.3.2 --- In vitro development of embryos in control and experimental groups --- p.35 / Chapter 2.3.3 --- Migration of vagal neural crest cells in Dom embryos --- p.36 / Chapter 2.3.4 --- Apoptotic cells detection at the vagal region by TUNEL assay --- p.37 / Chapter 2.3.5 --- Migration of sacral neural crest cells in Dom embryos --- p.37 / Chapter 2.3.6 --- Apoptotic cells detection at the sacral region by TUNEL assay --- p.38 / Figures and Tables / Chapter 2.4 --- Discussion --- p.40 / Chapter 2.4.1 --- In vitro culture system supporting the normal development of mouse embryos --- p.40 / Chapter 2.4.2 --- WGA-Au as a cell marker for tracing the NCCs migration --- p.41 / Chapter 2.4.3 --- Vagal neural crest cells migration in Dom mouse embryos --- p.42 / Chapter 2.4.4 --- Apoptotic cell death does not contribute to the total aganglionosis in Dom homozygous embryos --- p.43 / Chapter 2.4.5 --- Sacral neural crest cells migration in Dom mouse embryos --- p.45 / Chapter 2.4.6 --- NCCs migration in zebrafish colourless mutant --- p.47 / Chapter 2.4.7 --- Limitation of the method used in this study --- p.49 / Chapter 2.4.8 --- Conclusions --- p.49 / Appendices / Chapter Chapter 3 --- Migration of Enteric Neural Crest-derived Cells in the Developing Gut of Dominant Megacolon Mouse Embryos --- p.51 / Chapter 3.1 --- Introduction --- p.51 / Chapter 3.2 --- Materials and Methods --- p.55 / Chapter 3.2.1 --- Isolation of the gut from Dom mouse embryos --- p.55 / Chapter 3.2.2 --- Whole mount immunohistochemistry --- p.55 / Chapter 3.3 --- Results --- p.57 / Chapter 3.3.1 --- PGP9.5 immunoreactivity in the 12.5 d.p.c. Dom embryos --- p.57 / Chapter 3.3.2 --- TH immunoreactivity in the 12.5 d.p.c. Dom embryos --- p.58 / Chapter 3.3.3 --- PGP9.5 immunoreactivity in the 14.5 d.p.c. Dom embryos --- p.59 / Figures and Tables / Chapter 3.4 --- Discussion --- p.61 / Chapter 3.4.1 --- The use of PGP9.5 and TH antibodies as markers for studying the migration of enteric neural crest-derived cells --- p.61 / Chapter 3.4.2 --- Incomplete migration of neural crest-derived cells within the gut of Dom heterozygous embryos --- p.62 / Chapter 3.4.3 --- Failure of sacral NCCs to invade the hindgut of Dom heterozygous embryos --- p.63 / Chapter 3.4.4 --- PGP9.5 and TH positive signals in the gut of Dom homozygous embryos --- p.64 / Chapter 3.4.5 --- Early differentiation of neural crest-derived cells into neurons due to haploinsufficiency of Sox10 --- p.65 / Chapter 3.4.6 --- Conclusions --- p.66 / Chapter Chapter 4 --- Localization of Interstitial Cells of Cajal in the Gut of Dominant Megacolon Mice --- p.67 / Chapter 4.1 --- Introduction --- p.67 / Chapter 4.2. --- Materials and Methods --- p.72 / Chapter 4.2.1 --- Isolation of the gut from mouse embryos and adult mice --- p.72 / Chapter 4.2.2 --- Cryosection and immunohistochemistry --- p.73 / Chapter 4.2.3 --- Whole-mount immunohistochemistry --- p.73 / Chapter 4.2.4 --- Total RNA extraction --- p.74 / Chapter 4.2.5 --- Reverse transcription for the first strand cDNA synthesis --- p.75 / Chapter 4.2.4 --- Reverse transcription-Polymerase chain reaction (RT-PCR) --- p.76 / Chapter 4.3 --- Results --- p.77 / Chapter 4.3.1 --- PGP9.5 and c-kit immunoreactivity in the Dom wild type colon --- p.77 / Chapter 4.3.2 --- c-kit immunoreactivity in the Dom heterozygous adult colon --- p.78 / Chapter 4.3.3 --- c-kit and SCF expression during gut development --- p.78 / Figures and Tables / Chapter 4.4 --- Discussion --- p.80 / Chapter 4.4.1 --- The importance in studying the development of ICCs in aganglionic gut --- p.80 / Chapter 4.4.2 --- ICCs development in Dominant megacolon mice --- p.81 / Chapter 4.4.3 --- The relationship between enteric neurons and ICCs development --- p.83 / Chapter 4.4.4 --- Advantages of using confocal microscopy and whole- mount preparations to study the ICCs development --- p.85 / Chapter 4.4.5 --- Conclusions --- p.86 / Chapter Chapter 5 --- General Discussion and Conclusions --- p.87 / References --- p.91

The auditory brainstem is comprised of a number of synapses specialized for the transmission of high-fidelity synaptic signals. Within the first three postnatal weeks, these pathways acquire the ability to process high-frequency signals without compromising timing information. However, little is known regarding developmental adaptations which confer this ability. Situated in the sound localization pathway, the calyx of Held-medial nucleus of the trapezoid body synapse provides an ideal model for investigating such adaptations as both the pre- and postsynaptic neurons are accessible to electrophysiological experimentation. Using this synapse, we have shown herein that the spatial coupling between voltage-gated calcium channels (VGCCs) and synaptic vesicles (SVs) tightens during development. Immature synapses use a loosely-coupled arrangement of many N- and P/Q-type VGCCs (“microdomain” modality) while mature synapses use a tightly-coupled arrangement of fewer P/Q-type VGCCs, to release SVs (“nanodomain” modality). As a consequence of this tightening, synaptic delay (SD) shortens. By fluorescence- and electron microscopy of SVs near active zones, we further identified the filamentous protein septin 5 as a molecular substrate, differentiating the two release modalities, which may act as a spatial barrier separating VGCCs and SVs in immature synapses. Finally, we have demonstrated that changes in release modality affect the nature of short-term plasticity observed at this synapse. Using trains of action potentials as presynaptic voltage-commands, we showed that, downstream of calcium influx, the microdomain modality promotes short-term facilitation in excitatory postsynaptic currents (IEPSC), and calcium-dependent decreases in SD, with these being absent in synapses employing the nanodomain modality. In contrast, we found that as a result of depletion of SVs, short-term depression of IEPSC dominates in synapses using the nanodomain modality, and correlates with calcium-dependent increases in SD. These findings imply that the type of release modality has a significant impact on the strength and timing of synaptic responses. The microdomain modality imparts greater dynamic range in timing and strength, but does so at the cost of efficiency and fidelity, while the nanodomain modality is a key accomplishment consolidating the high-fidelity abilities of this synapse.

The auditory brainstem is comprised of a number of synapses specialized for the transmission of high-fidelity synaptic signals. Within the first three postnatal weeks, these pathways acquire the ability to process high-frequency signals without compromising timing information. However, little is known regarding developmental adaptations which confer this ability. Situated in the sound localization pathway, the calyx of Held-medial nucleus of the trapezoid body synapse provides an ideal model for investigating such adaptations as both the pre- and postsynaptic neurons are accessible to electrophysiological experimentation. Using this synapse, we have shown herein that the spatial coupling between voltage-gated calcium channels (VGCCs) and synaptic vesicles (SVs) tightens during development. Immature synapses use a loosely-coupled arrangement of many N- and P/Q-type VGCCs (“microdomain” modality) while mature synapses use a tightly-coupled arrangement of fewer P/Q-type VGCCs, to release SVs (“nanodomain” modality). As a consequence of this tightening, synaptic delay (SD) shortens. By fluorescence- and electron microscopy of SVs near active zones, we further identified the filamentous protein septin 5 as a molecular substrate, differentiating the two release modalities, which may act as a spatial barrier separating VGCCs and SVs in immature synapses. Finally, we have demonstrated that changes in release modality affect the nature of short-term plasticity observed at this synapse. Using trains of action potentials as presynaptic voltage-commands, we showed that, downstream of calcium influx, the microdomain modality promotes short-term facilitation in excitatory postsynaptic currents (IEPSC), and calcium-dependent decreases in SD, with these being absent in synapses employing the nanodomain modality. In contrast, we found that as a result of depletion of SVs, short-term depression of IEPSC dominates in synapses using the nanodomain modality, and correlates with calcium-dependent increases in SD. These findings imply that the type of release modality has a significant impact on the strength and timing of synaptic responses. The microdomain modality imparts greater dynamic range in timing and strength, but does so at the cost of efficiency and fidelity, while the nanodomain modality is a key accomplishment consolidating the high-fidelity abilities of this synapse.

The purpose of this thesis work is to model the gate control theory, which explains the modulation of pain signals, with a motivation of finding new possible targets for pain treatment and to find novel control algorithms that can be used in engineering practice. The difference of the current study from the previous modeling trials is that morphologies of neurons that constitute gate control system are also included in the model by which structure-function relationship can be observed. Model of an excitable neuron is constructed and the response of the model for different perturbations are investigated. The simulation results of the excitable cell model is obtained and when compared with the experimental findings obtained by using crayfish, it is found that they are in good agreement. Model encodes stimulation intensity information as firing frequency and also it can add sub-threshold inputs and fire action potentials as real neurons. Moreover, model is able to predict depolarization block. Absolute refractory period of the single cell model is found as 3.7 ms. The developed model, produces no action potentials when the sodium channels are blocked by tetrodotoxin. Also, frequency and amplitudes of generated action potentials increase when the reversal potential of Na is increased. In addition, propagation of signals along myelinated and unmyelinated fibers is simulated and input current intensity-frequency relationships for both type of fibers are constructed. Myelinated fiber starts to conduct when current input is about 400 pA whereas this minimum threshold value for unmyelinated fiber is around 1100 pA. Propagation velocity in the 1 cm long unmyelinated fiber is found as 0.43 m/s whereas velocity along myelinated fiber with the same length is found to be 64.35 m/s. Developed synapse model exhibits the summation and tetanization properties of real synapses while simulating the time dependency of neurotransmitter concentration in the synaptic cleft. Morphometric analysis of neurons that constitute gate control system are done in order to find electrophysiological properties according to dimensions of the neurons. All of the individual parts of the gate control system are connected and the whole system is simulated. For different connection configurations, results of the simulations predict the observed phenomena for the suppression of pain. If the myelinated fiber is dissected, the projection neuron generates action potentials that would convey to brain and elicit pain. However, if the unmyelinated fiber is dissected, projection neuron remains silent. In this study all of the simulations are preformed using Simulink.

Thesis (Ph.D. in Pharmacology) -- University of Colorado Denver, 2007. / Typescript. Includes bibliographical references (leaves 132-151). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;

Diss. (sammanfattning) Umeå : Umeå universitet, 2009. / Härtill 4 uppsatser. Även tryckt utgåva.

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Synapses vary widely in the probability of transmitter release. For instance, in response to an action potential the phasic synapses of the crayfish have a 100-1000-fold higher release probability than tonic synapses. The difference in release probability is attributed to differences in the exocytotic machinery such as the degree of “zippering” of the trans-SNARE (Soluble N-ethylmaleimide-sensitive factor Attachment protein REceptor) complex. I used physiological and molecular approaches to determine if the zippered state of SNAREs associated with synaptic vesicles and the interaction between the SNARE complex and Complexin influence the probability of release at the synapse. I used three Botulinum neurotoxins which bind and cleave at different sites on VAMP to determine whether these sites were occluded by SNARE interaction (zippering) or open to proteolytic attack. Under low stimulation conditions, the light-chain fragment of botulinum B (BoNT/B-LC) but not BoNT/D-LC or tetanus neurotoxin (TeNT-LC) cleaved VAMP and inhibited evoked release at both phasic and tonic synapses. In addition, a peptide based on the C-terminal half of crayfish VAMP’s SNARE motif (Vc peptide) designed to interfere with SNARE complex zippering at the C-terminal end inhibited release at both synapses. The susceptibility of VAMP to only BoNT/B-LC and interference by the Vc peptide indicated that SNARE complexes at both phasic and tonic synapses were partially zippered only at the N-terminal end with the C-terminal end exposed under resting conditions. I used a peptide containing part of the crayfish Complexin central α-helix domain to interfere with the interaction between Complexin and the SNARE complex. The peptide enhanced phasic evoked release and inhibited tonic evoked release under low stimulation but attenuated release at both synapses under intense stimulation. Therefore, Complexin appeared to exhibit a dual function under low synaptic activity but only promoted release under high synaptic activity. The results showed that the zippered state of the SNARE complex does not determine initial release probability as a similar zippered SNARE complex structure under resting conditions is common to both phasic and tonic synapses. However, Complexin may have a role in influencing the initial release probability of a synapse. Therefore, the interaction between the SNARE complex and Complexin is important for release but other factors contribute more significantly to synaptic strength.