A cerâmica encontrada no sítio arqueológico Cerâmica Preta, localizado entre Camanducaia e Itapeva, Sul do Estado de Minas Gerais, Brasil, apresenta marcas negras de redução que levaram o autor a formular a hipótese sobre uma técnica específica de queima utilizada por aquele povo que habitou o local preteritamente. O conjunto de fragmentos e as marcas neles encontradas representam os remanescentes de uma técnica morta de cerâmica preta, praticada com maestria e regularidade intencionalmente pelo povo que o produziu. A queima da cerâmica, assim como seu uso ao fogo, deixam marcas de diferentes cores e características nas peças submetidas a estes processos. Relata-se aqui a pesquisa de correlatos entre estas marcas, os processos e comportamentos em que esta coleção de fragmentos cerâmicos arqueológicos participou durante sua produção e uso, sua história de vida. Os parâmetros da arqueologia experimental, com base na teoria comportamental, orientam o desenvolvimento dos experimentos sobre as técnicas da queima redutora em fogueiras. Apresento uma análise do material encontrado no sítio Cerâmica Preta em coletas sistemática e assistemáticas, tendo como foco a marcas de queima, buscou-se reproduzir a morfologia e colorimetria para se entender as condições de sua formação através de experimentações em laboratório e em campo. Obtivemos resultados nas experimentações que foram compatíveis com a amostragem arqueológica tendo sucesso em reproduzir condições de queima, investigando o papel das diversas técnicas possíveis para a situação. Conclui-se, pelos correlatos levantados que as ceramistas que viveram no local do sítio praticavam uma determinada tradição técnica de queima de cerâmica que envolvia o uso de recipientes para conter atmosferas redutoras no sentido de produzir uma cerâmica extremamente reduzida de tamanho pequeno a médio e tendo como produto paralelo uma cerâmica reduzida internamente de maiores proporções que serviu de ferramenta na produção da cerâmica preta. O material arqueológico também indica a utilização de uma segunda técnica de queima que difere da primeira principalmente na forma de colocação das peças na fogueira para a queima. Outras marcas encontradas no material arqueológico sugerem que um tipo de queima seria utilizado especificamente para os vasilhames utilizados como panelas e outro para vasilhas e potes de armazenamento. A ligação encontrada entre as marcas de queima e a utilização posterior dos potes leva a proposição de uma ligação estreita entre a técnica de queima e a cosmologia destes povos. O simbolismo das cores resultantes e das superfícies coloridas remetem ao universo feminino, ao útero que gera a vida, ao pote negro e à inserção desta cultura na ordem do mundo em uma camada entre o telúrico e o celeste. / The ceramic artifacts found in Cerâmica Preta archaeological site, situated at Camanducaia and Itapeva county, at southern Minas Gerais State, Brazil, show reduction marks that led the author to formulate an hypothesis about a specific technique of reducing firing of ceramics, used by the people who lived in this site preteritally. The black marks on the ceramic fabric and the black sherds, are remains of a forgotten technique of black pottery practiced intentionally and skillfully by the people who lived in this site preteritally. Firing of the ceramic and its use on the bonfire as pans, leaves different color and characteristic marks on the tissue of the pieces submitted to these processes. The search for correlates between these marks, processes and behaviors lead to the inference of activities in which the artifacts took part during its production and use. The Experimental Archaeology parameters, based on the Behavioral Theory, guided the development of the experiments on techniques of reduction firing in bonfires. The analisys of the material found in the ceramic site, by systematic and unsystematic search, focusing on the burning marks of which, through laboratory and field experiments, aim to reproduce the morphology and colorimetry, in the way to understand the conditions of its formation. The results of the experiments were compatible with the archaeological sampling and successfully reproduced burning conditions with similar results. The research investigated the role of various possible conditions for the production of black pottery. The correlates found by the research, lead to the conclusion that the ceramists, who lived in the site preteritally, practiced a certain technical tradition of ceramic firing, wich involved the use of containers to retain reducing atmospheres, in the sense of producing an extremely thin black ceramic of small to medium size. This firing has as parallel product, an internally reduced ceramic of greater proportions that served as a tool in the production of black pottery, a sagar. Archaeological material also indicates the use of a second firing technique which differs from the first one mainly in the way the parts are placed in the bonfire, but also in its production and use. Other marks found in archaeological material suggest that the people who practiced this tradition used the pots of one kind of firing as pans and diferent ones for consuming and for storage pots too. The connection found between the firing marks and other, dued to the later use of the pots over the fire, leads to the proposition of a close connection between the burning technique and the cosmology of these peoples. The symbolism of the resulting colors and colored surfaces refers to the female universe, the life-giving uterus, the black pot, and the insertion of this culture into the order of the world in a layer between the tellurian and the celestial.

Cette recherche porte sur les techniques de production des matériaux de construction en terre cuiteà l’époque romaine dans les provinces de Gaule et de Germanie. Ces techniques ne nous sontaccessibles directement que par l’archéologie, à la fois par les vestiges mobiliers : les matériauxfabriqués eux-mêmes, et par les vestiges immobiliers : les tuileries qui sont régulièrement mises aujour. Seules les structures de production sont examinées, mais il est souvent fait référence auxmatériaux. L’étude est menée selon deux lignes directrices, l’une horizontale : la chaîne opératoire, l’autreverticale : le temps, du présent vers le passé. Les structures de production sont traitées selon l’ordrede la chaîne opératoire : l’extraction, la préparation de la terre, le façonnage, le séchage et lacuisson. À l’intérieur de chacune de ces cinq phases sont étudiées successivement des structuresd’époque contemporaine (ateliers artisanaux), moderne, médiévale et enfin gallo-romaine. Cettedémarche régressive permet de mettre en évidence les continuités et les ruptures dans lestechniques mises en oeuvre et ainsi de mieux caractériser et comprendre la plus ancienne d’entreelles, celle des tuiliers gallo-romains. Le fonctionnement des structures de production les plusrécentes éclaire celui des structures romaines. Des comparaisons ponctuelles ne sont utilisées quepour tenter d’expliquer certaines caractéristiques originales des structures gallo-romaines. Lesrésultats les plus novateurs ont été obtenus dans l’étude des structures employées dans les phasesde façonnage, de séchage et de cuisson. / This research concerns the techniques of tile and brick-making in Roman time in the provinces ofGaul and Germania. We have only access to these techniques through archaeology. First, there arethe movable vestiges: the objects (tiles and bricks), then there are the real estate vestiges: the tilemakingsites which are regularly uncovered. Only the structures of production are examined here,but it is often made reference to materials. The study is led according to two guidelines. One is horizontal: the “chaîne opératoire”, the other is vertical: Time, from present to past. The structures of production are treated according to the orderof the making process: quarrying, preparing clay, shaping, drying, and firing. Inside each of thesefive phases are successively studied structures of contemporary time (craft production), modern,medieval and finally Gallo-Roman. This regressive approach allows us to bring to light thecontinuities and the breaks in the techniques used and thus, to better characterize and understandthe most ancient of them, the Gallo-Roman tile-makers one. The functioning of the most recentstructures of production sheds light on that of the Roman ones. Punctual comparisons are only usedto try and explain some original characteristics of the Gallo-Roman structures. The most innovativeresults were obtained in the study of the structures used in the phases of shaping, drying and firing.

In vielen Kommunikationssytemen wird Information durch die zeitliche Struktur von Signalen kodiert. Ein neuronales System, welches rhythmische Signale verarbeitet, sollte davon profitieren, seine inhärenten Filtereigenschaften den Frequenzcharakteristika dieser Signale anzupassen. Die Grille Gryllus bimaculatus stellt ein einfaches biologisches System dar, für welches nur wenige, spezifische Modulationsfrequenzen verhaltensrelevant sind. Ich habe einzelne Neuronen im peripheren und höheren auditorischen System der Grille hinsichtlich einer möglichen Anpassung auf diese Frequenzen untersucht. Hierfür habe ich extrazelluläre Elektrophysiologie mit verschiedenen Stimulationsparadigmen kombiniert, welche auf amplitudenmodulierten Tönen basierten. Die Analyse der experimentellen Daten ergab, dass bereits in der auditorischen Peripherie einige der untersuchten Neurone Bandpasseigenschaften aufwiesen, da sie verhaltensrelevante Modulationsfrequenzen mit den höchsten Feuerraten beantworteten. Anhand einfacher mathematischer Modelle demonstriere ich, wie weitverbreitete, zellintrinsische und netzwerkbasierte Mechanismen die beobachteten Feuerratenresonanzen erklären könnten. Diese Mechanismen umfassen unterschwellige Resonanz von Membranströmen, aktivitätsabhängige Adaptation, sowie das Zusammenwirken von Exzitation und Inhibition. Ich zeige, wie eine serielle Kombination solcher elementarer Filter die deutliche Selektivität im Verhalten der Grille erklären könnte, ohne dabei auf ein dediziertes Filterelement zurückzugreifen. Allgegenwärtige neuronale Mechanismen könnten demnach eine dezentralisierte Filterkaskade in einem hochspezialisierten und größenbeschränkten neuronalen System begründen. / In many communication systems, information is encoded in the temporal pattern of signals. For rhythmic signals that carry information in specific frequency bands, a neuronal system may profit from tuning its inherent filtering properties towards a peak sensitivity in the respective frequency range. The cricket Gryllus bimaculatus is a simple biological system for which only a narrow range of modulation frequencies is behaviorally relevant. I examined individual neurons in the peripheral and higher auditory system for tuning towards specific temporal parameters and modulation frequencies. To this end, I combined extracellular electrophysiology with different stimulation paradigms involving amplitude-modulated sounds. Analysis of the experimental data revealed that—even in the auditory periphery—some of the examined neurons acted as tuned band-pass filters, yielding highest firing-rates for behaviorally relevant modulation frequencies. Using simple computational models, I demonstrate how common, cell-intrinsic or network-based mechanisms could account for the experimentally observed firing-rate resonances. These mechanisms include subthreshold resonances, spike-triggered adaptation, as well as the interplay of excitation and inhibition. I present how a serial combination of such elementary filters could explain the strong selectivity evident in the cricket’s behavior—without the need for a dedicated filter element. Pervasive neuronal mechanisms could therefore constitute an efficient, distributed frequency filter in a highly specialized, size-constrained neuronal system.

Electromyographic (EMG) signal decomposition is the process of resolving an EMG signal into its component motor unit potential trains (MUPTs). The extracted MUPTs can aid in the diagnosis of neuromuscular disorders and the study of the neural control of movement, but only if they are valid trains. Before using decomposition results and the motor unit potential (MUP) shape and motor unit (MU) firing pattern information related to each active MU for either clinical or research purposes the fact that the extracted MUPTs are valid needs to be confirmed. The existing MUPT validation methods are either time consuming or related to operator experience and skill. More importantly, they cannot be executed during automatic decomposition of EMG signals to assist with improving decomposition results. To overcome these issues, in this thesis the possibility of developing automatic MUPT validation algorithms has been explored. Several methods based on a combination of feature extraction techniques, cluster validation methods, supervised classification algorithms, and multiple classifier fusion techniques were developed. The developed methods, in general, use either the MU firing pattern or MUP-shape consistency of a MUPT, or both, to estimate its overall validity. The performance of the developed systems was evaluated using a variety of MUPTs obtained from the decomposition of several simulated and real intramuscular EMG signals. Based on the results achieved, the methods that use only shape or only firing pattern information had higher generalization error than the systems that use both types of information. For the classifiers that use MU firing pattern information of a MUPT to determine its validity, the accuracy for invalid trains decreases as the number of missed-classification errors in trains increases. Likewise, for the methods that use MUP-shape information of a MUPT to determine its validity, the classification accuracy for invalid trains decreases as the within-train similarity of the invalid trains increase. Of the systems that use both shape and firing pattern information, those that separately estimate MU firing pattern validity and MUP-shape validity and then estimate the overall validity of a train by fusing these two indices using trainable fusion methods performed better than the single classifier scheme that estimates MUPT validity using a single classifier, especially for the real data used. Overall, the multi-classifier constructed using trainable logistic regression to aggregate base classifier outputs had the best performance with overall accuracy of 99.4% and 98.8% for simulated and real data, respectively. The possibility of formulating an algorithm for automated editing MUPTs contaminated with a high number of false-classification errors (FCEs) during decomposition was also investigated. Ultimately, a robust method was developed for this purpose. Using a supervised classifier and MU firing pattern information provided by each MUPT, the developed algorithm first determines whether a given train is contaminated by a high number of FCEs and needs to be edited. For contaminated MUPTs, the method uses both MU firing pattern and MUP shape information to detect MUPs that were erroneously assigned to the train. Evaluation based on simulated and real MU firing patterns, shows that contaminated MUPTs could be detected with 84% and 81% accuracy for simulated and real data, respectively. For a given contaminated MUPT, the algorithm on average correctly classified around 92.1% of the MUPs of the MUPT. The effectiveness of using the developed MUPT validation systems and the MUPT editing methods during EMG signal decomposition was investigated by integrating these algorithms into a certainty-based EMG signal decomposition algorithm. Overall, the decomposition accuracy for 32 simulated and 30 real EMG signals was improved by 7.5% (from 86.7% to 94.2%) and 3.4% (from 95.7% to 99.1%), respectively. A significant improvement was also achieved in correctly estimating the number of MUPTs represented in a set of detected MUPs. The simulated and real EMG signals used were comprised of 3–11 and 3–15 MUPTs, respectively.

Optogenetics is a set of technologies that enable optically triggered gain or loss of function in genetically specified populations of cells. Optogenetic methods have revolutionized experimental neuroscience by allowing precise excitation or inhibition of firing in specified neuronal populations embedded within complex, heterogeneous tissue. Although optogenetic tools have greatly improved our ability manipulate neural activity, they do not offer control of neural firing in the face of ongoing changes in network activity, plasticity, or sensory input. In this thesis, I develop a feedback control technology that automatically adjusts optical stimulation in real-time to precisely control network activity levels. I describe hardware and software tools, modes of optogenetic stimulation, and control algorithms required to achieve robust neural control over timescales ranging from seconds to days. I then demonstrate the scientific utility of these technologies in several experimental contexts. First, I investigate the role of connectivity in shaping the network encoding process using continuously-varying optical stimulation. I show that synaptic connectivity linearizes the neuronal response, verifying previous theoretical predictions. Next, I use long-term optogenetic feedback control to show that reductions in excitatory neurotransmission directly trigger homeostatic increases in synaptic strength. This result opposes a large body of literature on the subject and has significant implications for memory formation and maintenance. The technology presented in this thesis greatly enhances the precision with which optical stimulation can control neural activity, and allows causally related variables within neural circuits to be studied independently.

Electromyographic (EMG) signal decomposition is the process of resolving an EMG signal into its component motor unit potential trains (MUPTs). The extracted MUPTs can aid in the diagnosis of neuromuscular disorders and the study of the neural control of movement, but only if they are valid trains. Before using decomposition results and the motor unit potential (MUP) shape and motor unit (MU) firing pattern information related to each active MU for either clinical or research purposes the fact that the extracted MUPTs are valid needs to be confirmed. The existing MUPT validation methods are either time consuming or related to operator experience and skill. More importantly, they cannot be executed during automatic decomposition of EMG signals to assist with improving decomposition results. To overcome these issues, in this thesis the possibility of developing automatic MUPT validation algorithms has been explored. Several methods based on a combination of feature extraction techniques, cluster validation methods, supervised classification algorithms, and multiple classifier fusion techniques were developed. The developed methods, in general, use either the MU firing pattern or MUP-shape consistency of a MUPT, or both, to estimate its overall validity. The performance of the developed systems was evaluated using a variety of MUPTs obtained from the decomposition of several simulated and real intramuscular EMG signals. Based on the results achieved, the methods that use only shape or only firing pattern information had higher generalization error than the systems that use both types of information. For the classifiers that use MU firing pattern information of a MUPT to determine its validity, the accuracy for invalid trains decreases as the number of missed-classification errors in trains increases. Likewise, for the methods that use MUP-shape information of a MUPT to determine its validity, the classification accuracy for invalid trains decreases as the within-train similarity of the invalid trains increase. Of the systems that use both shape and firing pattern information, those that separately estimate MU firing pattern validity and MUP-shape validity and then estimate the overall validity of a train by fusing these two indices using trainable fusion methods performed better than the single classifier scheme that estimates MUPT validity using a single classifier, especially for the real data used. Overall, the multi-classifier constructed using trainable logistic regression to aggregate base classifier outputs had the best performance with overall accuracy of 99.4% and 98.8% for simulated and real data, respectively. The possibility of formulating an algorithm for automated editing MUPTs contaminated with a high number of false-classification errors (FCEs) during decomposition was also investigated. Ultimately, a robust method was developed for this purpose. Using a supervised classifier and MU firing pattern information provided by each MUPT, the developed algorithm first determines whether a given train is contaminated by a high number of FCEs and needs to be edited. For contaminated MUPTs, the method uses both MU firing pattern and MUP shape information to detect MUPs that were erroneously assigned to the train. Evaluation based on simulated and real MU firing patterns, shows that contaminated MUPTs could be detected with 84% and 81% accuracy for simulated and real data, respectively. For a given contaminated MUPT, the algorithm on average correctly classified around 92.1% of the MUPs of the MUPT. The effectiveness of using the developed MUPT validation systems and the MUPT editing methods during EMG signal decomposition was investigated by integrating these algorithms into a certainty-based EMG signal decomposition algorithm. Overall, the decomposition accuracy for 32 simulated and 30 real EMG signals was improved by 7.5% (from 86.7% to 94.2%) and 3.4% (from 95.7% to 99.1%), respectively. A significant improvement was also achieved in correctly estimating the number of MUPTs represented in a set of detected MUPs. The simulated and real EMG signals used were comprised of 3–11 and 3–15 MUPTs, respectively.

An AC system’s voltage unbalance by a fundamental frequency negative sequence system is usually the main cause for the emission of non-characteristic harmonics by current source converters as used in conventional HVDC systems. This emission takes place on both sides of each 12-pulse converter. On the DC side mainly a 2nd harmonic voltage appears driving a 2nd harmonic current. The magnitude of this harmonic current can exceed the magnitudes of the characteristic harmonics even if no low order resonance exists. Further non-characteristic harmonics generated by the converter under such unbalanced supply voltage conditions have frequencies with a frequency distance to the characteristic harmonics of 2 times the fundamental frequency. The main technical drawbacks are the unintended coupling between both AC systems and the risk of thyristor over-stresses by DC current discontinuities at low power transfer levels. On both AC sides the largest 2 non-characteristic current harmonics generated by a 12-pulse HVDC converter under unbalanced supply voltage conditions are a negative sequence system of the fundamental harmonic and a positive sequence system of the 3rd harmonic. Also on the AC sides further harmonics are emitted by the converter with a order number distance of 2 to the orders of the characteristic harmonics. However, in practical AC system operation special attention has to be paid to the 3rd harmonic distortion level, in particular when low order resonance appears between the system impedance and the impedance of the converter station AC filters. In order to avoid the above mentioned problems, large smoothing reactors and sometimes large blocking filters are installed on the DC side and the voltage distortion on the AC sides is reduced by AC filters. However, these filters require an expensive high component rating if they are tuned to the 2nd or 3rd harmonic respectively. The work shows that a modification of the valve firing can reduce the levels of the 2nd and 3rd harmonic without investment into additional primary equipment. Furthermore, this offers the chance to reduce the minimum power transfer level since also the risk of an intermittent DC current can be reduced. A corresponding algorithm and a control strategy are proposed. However, the calculation of an appropriate firing pattern requires a detailed modelling of the processes within the converters, especially the formation of the harmonics and the harmonic transfer between AC and DC sides. The work proposes a component vector model for the calculation of the harmonics. This model assumes that each harmonic consists of a first component representing the ideal conversion process, a 2nd component representing the impact of different commutation angles and in the case of the modified firing a 3rd component considering the impact of the intended non-equidistant firing. The work shows, that the harmonic component vectors resulting from voltage unbalance and from firing modulation can be treated separately and superimposed linearly. The calculation of the harmonic component vectors is performed applying the method of switching functions. For the consideration of the commutation and firing angle differences the modelling of switching functions based on differential impulses is proposed. However, especially an accurate representation of the above mentioned 2nd component vector requires a correct calculation of the commutation angles and their valve-specific differences. The investigations of this work have revealed that the conventional method of calculating the commutation angles – assuming an ideal smoothed DC current - may not produce results of sufficient accuracy. This is especially true in the case of a high ripple of the DC current, e.g. smoothed with a small smoothing reactor. A small smoothing reactor is typical for HVDC back-to-back applications. Therefore a new analytical method for the calculation of the commutation angles has been developed which in particular considers the typical pulse form of the DC current and additionally the impacts of the voltage unbalance and of the proposed modification of the firing on the ripple shape of the DC current. Moreover, as this analytical method requires the instantaneous values of the DC current at the instants of valve firing, a further analytical method for the calculation of these discrete current values has been developed. The equations are valid under the same conditions as the new ones for calculation of the commutation angles, i.e. resistive-inductive AC system fundamental frequency impedances, any degree of DC current smoothing between ideal smoothing and a ripple at the limit for current discontinuities. Symmetrical conditions, supply voltage unbalances and non-equidistant firing as proposed are applied. It is shown that, using this method, also the discrete values of the DC current at the end of the commutation intervals can be determined. In practice one of these discrete current values indicates the minimum value during one period of the fundamental frequency. This offers the chance for a more exact analytical determination of the limit for the appearance of DC current discontinuities. For typical parameters of a back-to-back installation the new methods and the new analytical equations have been compared with simulation results showing excellent correlation for typical voltage unbalances of not more than 1...2% and firing angle differences of not more than 2.5°. This verification is performed for the harmonics, the commutation angles and the discrete values of the DC current at the firing instants as well.

Heterozygous and recently identified homozygous mutations in the SPTBN2 gene, encoding b-III spectrin, are implicated in spinocerebellar ataxia type 5 (SCA5) and spectrin-associated autosomal recessive cerebellar ataxia type 1 (SPARCA1), respectively. Our mouse model, lacking b-III spectrin (KO), mimics the progressive human phenotype displaying motor deficiencies as well as reduced Purkinje cell firing frequency followed by dendritic tree degeneration and cell death. The aims of this study were to evaluate progression of Purkinje cell degeneration following loss of b-III spectrin function and determine whether the reintroduction of C-terminus (C-trm) of b-III spectrin to the cerebellum is enough to halt, alleviate or reverse the disease phenotype. Additionally, this study investigated whether the abnormal electrophysiological and morphological phenotypes of Purkinje cells from KO mice are re-capitulated in a primary cerebellar culture and if so, whether they could be rescued by modulating calcium signaling. Morphological and histological analyses revealed that Purkinje cell degeneration is not uniform throughout the cerebellum of KO mice with Purkinje cells from posterior cerebellar regions possessing significantly smaller dendritic trees when compared to anterior cerebellum (p=0.0003, N=4-6, n=11-29). Similarly, significant reduction in Purkinje cell density was observed in posterior, not anterior regions of KO mice when compared to WT animals (p=0.014, N=3) and reduced tonic firing is most significant in Purkinje cells from the posterior cerebellum compared to WT mice (p=0.0328, N=3-6, n=11-29), with posterior KO PCs appearing to have elevated input resistance. Two-week expression of C-trm b-III spectrin in 3-month old KO animals significantly reduced Purkinje cell input resistance when compared to non-transduced cells (p=0.0139, N=4-5, n=15), but no effect was seen 9 months after viral injection. In contrast, a difference in cell surface area was no longer detected between WT and KO animals at 12 months of age following 9-months of viral expression. Nevertheless, using the elevated beam test motor deterioration was still observed 5 months after surgery (p=0.0023, N=4). In contrast, earlier stereotaxic injections at 6-weeks of age had a positive effect on mice motor performance with no deterioration in performance detected 5 months after the surgery. Latency to stay on the rotarod at 3 rpm was also significantly extended 6 months after stereotaxic injections at 6-weeks of age with slower motor deterioration (p=0.0348, N=6). In primary cerebellar cultures, Purkinje cells from KO animals exhibit an abnormal morphology with significantly more dendritic branches (p < 0.0001, N=4-7, n=35-69) and a larger total dendritic length (p=0.0079). Chronic application of 2 μM mibefradil, a T-type calcium channel blocker, was observed to reduce total dendritic length and branching in KO animal cultures bringing these morphological measurements closer to WT Purkinje cell levels. Finally although after 14 days in vitro 40% of Purkinje cells were found to be spontaneously firing, no significant difference in firing frequency (p=0.9434) or input resistance (p=0.8434, N=4, n=6-10) was detectable between WT and KO cultures. In summary, Purkinje cells in posterior cerebellar regions of KO mice were found to be more susceptible to dendritic degeneration and cellular death than cells in the anterior cerebellum. Expression of C-trm b-III spectrin at 3 months of age had an immediate effect on cell input resistance and a modest effect on Purkinje cell morphology but no effect on motor decline. Viral injections at 6-weeks of age, however, significantly slowed motor decline. Although an abnormal KO cell morphology could be successfully recapitulated in primary cell culture, it was not possible to discern any differences in electrophysiological properties. Nevertheless, the abnormal cell morphology was successfully modified in vitro by manipulating calcium signaling via T-type calcium channels.

Dopamine (DA) neurons of the substantia nigra pars compacta (SNc) have a key role in regulation of voluntary movement control. Their death is a hallmark of Parkinson’s disease, characterised by inhibited motor control, including muscle rigidity and tremor. Excitatory input to SNc-DA neurons is primarily from the subthalamic nucleus, and in PD these afferents display a higher frequency firing, as well as increased burst firing, which could cause increased excitatory activity in SNc-DA neurons. NMDA receptors (NMDARs) bind the excitatory neurotransmitter glutamate, and are essential for learning and memory. In SNc-DA neurons, NMDARs have a putative triheteromeric subunit arrangement of GluN1 plus GluN2B and/or GluN2D. Wild type (WT) mice, and those lacking the gene for GluN2D (Grin2D-null), were used to explore its role in various aspects of DA neuronal function and dysfunction using patch-clamp electrophysiology, viability assaying, and immunofluorescence. Pharmacological intervention using subunit-specific inhibitors ifenprodil and DQP-1105 on elicited NMDAR-EPSCs suggested a developmental shift from primarily GluN2B to GluN2B/D. Activity dependent regulation was assessed by high frequency burst stimulation of glutamatergic afferents: in comparison to controls, significant downregulation of NMDARs was observed in SNc-DA neurons, though no differences were observed based on genotype. This regulatory function may be a neuroprotective or homeostatic response. Ambient extracellular glutamate elicits tonic NMDAR activity in SNc-DA neurons, which may be important for maintaining basal levels of excitability: the role of GluN2D was assessed by recording the deflection in baseline current caused by application of competitive NMDAR antagonist D-AP5. There was a significantly larger NMDAR-mediated current in WT vs Grin2D-null mice, indicating that GluN2D has a role in binding ambient glutamate. Dysfunction of glutamate uptake could be a secondary pathophysiological occurrence in the SNc, leading to increased ambient glutamate: the effect of this was explored by application of the competitive glutamate transporter blocker TBOA. Here, the NMDAR-mediated portion of this current was significantly higher in WT mice in comparison to Grin2D-null. Interestingly, dose-response data obtained from bath application of NMDA showed significantly larger currents in Grin2D-null animals vs WT, but only at the top of the response curve (~1-10 mM), which may indicate a capability for larger conductance in Grin2D-null animals at high NMDAR saturation due to replacement of GluN2D with GluN2B. GluN2D may therefore be neuroprotective, by attenuating peak current flow in response to very high agonist concentrations. Lastly, GluN2D has been found to decrease NMDAR open probability under hypoxic conditions, potentially conferring resistance to hypoxia / ischemia related excitotoxicity. Therefore, low (15% O2 / 80% N2 / 5% CO2) vs high (95% O2 / 5% CO2) oxygen conditions were used along with immunofluorescent propidium iodide cell death assaying and immunofluorescent labeling for DA neurons in order to compare levels of DA neuronal death in the SNc based on oxygen status and genotype. Whilst there was a significant submaximal effect based on O2 status, genotype did not confer a practical resistance under these conditions. In summary, NMDARs have diverse roles in SNc-DA neurons which may both serve to maintain normal function and protect the cell against potentially pathological conditions.

Made available in DSpace on 2014-12-17T14:57:46Z (GMT). No. of bitstreams: 1 JoseCCSJ.pdf: 1343903 bytes, checksum: aa2a5fbffd13b95d16ec1f429e355eb5 (MD5) Previous issue date: 2008-08-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The industries of structural ceramics are among the most important production chains in the state of Rio Grande do Norte. The industry and other interest groups to target the replacement of firewood by natural gas. Studies accordingly concluded that simple change does not guarantee products of superior quality, and that the increase in spending on fuel can economically cripple the use of gas for burning the majority of products manufactured by that action. However some proposals of innovations in terms of process and product are being studied in an attempt to justify the use of natural gas in industry, structural ceramics. One of the aspects investigated is the development of ceramic products differentiated, with new designs and greater value added. Inserted in that context, this paper aims to investigate the potential use of clay-firing clear fabrication of the "bricks of apparent joins drought", a new ceramic product with an innovative way. The development of the work was done in three stages. In the initial stage was held the characterization of raw materials, sought information on physical, chemical, mineralogical and mechanical samples. In the second stage five bodies were made using two of the nine ceramic clay characterized the first step. The masses were analyzed and compared with respect to the size distribution, plasticity and technological properties. In the last part of this work was carried out tests on massive bricks manufactured on an industrial scale. The results show that the nine clays can be used in the manufacture of new ceramic products, is the only constituent of mass ceramic or by mixing with other(s) clay(s / As ind?strias de cer?mica estrutural figuram entre as cadeias produtivas mais importantes do estado do Rio Grande do Norte. O setor e outros grupos de interesse almejam a substitui??o da lenha pelo g?s natural. Estudos realizados nesse sentido conclu?ram que a simples mudan?a n?o garante produtos de qualidade superior, e que o aumento no gasto com combust?vel pode inviabilizar economicamente o uso do g?s para queima da maioria dos produtos fabricados por esse seguimento. Entretanto algumas propostas de inova??es em termos de processo e produto v?m sendo estudadas na tentativa de justificar o uso do g?s natural na ind?stria de cer?mica estrutural. Uma das vertentes pesquisadas ? o desenvolvimento de produtos cer?micos diferenciados, com novos designs e maior valor agregado. Inserido nesse contexto, o presente trabalho tem como objetivo investigar a potencialidade do uso de argilas de queima clara para fabrica??o dos tijolos de junta seca , um novo produto cer?mico com forma inovadora. O desenvolvimento do trabalho foi efetuado em tr?s etapas. Na etapa inicial foi realizada a caracteriza??o das mat?rias-primas, buscando obter informa??es em rela??o ?s propriedades f?sicas, qu?micas, mineral?gicas e mec?nicas das amostras. Na segunda etapa foram formuladas cinco massas cer?micas utilizando duas das nove argilas caracterizadas na primeira etapa. As massas foram analisadas e comparadas em rela??o ? distribui??o granulometria, plasticidade e propriedades tecnol?gicas. Na ?ltima parte desse trabalho foi realizado testes em tijolos maci?os fabricados em escala industrial. Os resultados mostram que as nove argilas podem ser utilizadas na fabrica??o dos novos produtos cer?micos, seja como ?nica constituinte da massa cer?mica ou pela mistura com outra(s) argila(s)