Inanga (Galaxias maculatus) is an amphidromous fish species that is able to successfully inhabit a variety of salinities. Using an integrated approach this thesis has characterised for the first time the physiological characteristics that facilitate acclimation in inanga. Structural studies using scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) revealed freshwater-acclimated inanga have a high density of apical pits and freshwater-type mitochondria-rich cells (MRCs) that can facilitate ion absorption from the hypo-osmotic environment. In seawater, inanga remodel their gills by increased proliferation of seawater-type MRCs to facilitate ion secretion in the hyper-osmotic environment. Concentration-dependent sodium (Na+) kinetic analysis revealed that at a whole body level, inanga regulate Na+ using a saturable, high affinity, low capacity uptake system which makes them extremely adept at extracting Na+ from very dilute freshwater environments. In fact inanga displayed an uptake affinity (Km) of 52 ± 29 µM, which is one of the lowest ever recorded in freshwater fish. The sodium/potassium ATPase transporter (NKA) is central to Na+ regulation within the gill. In high salinties inanga displayed increased NKA activity (6.42 ± 0.51 µmol ADP mg protein-1 h-1) in an effort to excrete the excess Na+, diffusively gained from the hyper-osmotic environment. This increase in NKA was most likely a reflection of the proliferation of NKA-containing MRCs. The NKA activities seen in freshwater- and 50% seawater-acclimated inanga were similar (2.54 ± 0.19 and 2.07 ± 0.22 µmol ADP mg protein-1 h-1 respectively) to each other suggesting the inanga gill is capable of supporting ion regulation in brackish waters without a significant increase in NKA activities, and the energetically-expensive changes in gill structure and function that accompany such a change. Molecular investigation of NKA isoform expression using quantitative PCR (qPCR) showed that inanga displayed salinity-induced changes in the expression of the three α NKA isoform variants investigated. Isoform α1a exhibited a pattern consistent with an important role in freshwater, confirming results from other fish species. While it is generally accepted that α1b isoform is the predominant NKA isoform in seawater, inanga did not display this pattern with a freshwater dominance seen. None of the salinity-induced changes could quantitatively explain the increased NKA activity in seawater suggesting that different isoforms may convey different activities, that there is also regulation of NKA at a post-transcriptional level, and/or other isoforms or subunits may have a significant role. The importance of the osmoregulatory hormone cortisol and prolactin is widely accepted and inanga were treated with cortisol, prolactin and a combination of the two in an effort to further elucidate their role. NKA activity and NKA isoform expression were assessed but no specific patterns were deduced, except for a decrease in both NKA activity and isoform expression in 100% seawater-acclimated inanga treated with cortisol and prolactin. The reasons for this decrease were not evident, although the impact of stress induced by the injection protocol was likely to be a confounding factor. The development of a new confocal-based technique in this study was able to describe, for the first time, intracellular sodium levels ([Na+]i) as a function of salinity in an intact euryhaline fish gill cell. Using the fluorescent Na+ indicator dye CoroNa Green this study demonstrated the ability of inanga gill cells to maintain [Na+]i in the face of environmental change. Freshwater-acclimated inanga displayed basal [Na+]i of 5.2 ± 1.8 mM, with 12 ± 2.3 mM and 16.2 ± 3.0 mM recorded in 50% seawater- and 100% seawater-acclimated cells, respectively. Low [Na+]i is advantageous in hypo-osmotic environments as it provides a gradient between the cell and the blood which is essential for generating electrochemical gradients cell volume regulation and other cellular homeostatic mechanisms. A slightly elevated [Na+]i seen at the higher sanities would help minimise the diffusive gradient for passive influx from the environment which would be of benefit in hyper-osmotic environments. Upon salinity challenge 50% seawater cells were equally adept at maintaining a constant [Na+]i at any salinity, suggesting these cells are have the necessary constituents to regulate Na+ in both lower and higher salinities. This novel LSCM approach is advantageous relative to existing transport models as it will allow the observation of cellular ion transport in real time, within a native filament structure displaying functional interaction of different cell types. The extreme ion uptake characteristics of the inanga and their amenability to in situ confocal-based studies demonstrated in this study, confirm inanga as a valuable model species for future research.

The FGLa/ASTs are one family of allatostatin peptides and share an amidated C-terminal sequence (FGL-amide). The inhibitory effect of FGLa/ASTs on juvenile hormone (JH) biosynthesis in Diploptera punctata led to their discovery, but there is a lack of allatostatic function across most insect species that suggests this function may not be their primary role. Rather, the FGLa/ASTs are implicated as brain/gut peptides, modulating gut physiology. This thesis demonstrates the pleiotropic nature of FGLa/ASTs in Locusta migratoria and emphasizes the role of FGLa/ASTs as brain/gut peptides involved in homeostatic processes. FGLa/AST-like immunoreactivity (FLI) is associated with the corpus cardiacum (CC) and corpus allatum (CA). FGLa/ASTs increase adipokinetic hormone release from the CC and alter JH biosynthesis from the CA, suggesting roles in energy utilization and in growth and metamorphosis. Each region of the gut exhibits FLI. The gut is dually innervated: neurons in the abdominal ganglia of the central nervous system (CNS) innervate the posterior gut and some contain FLI, while neurons within the stomatogastric nervous system (STNS) that innervate the anterior gut do not seem to contain FLI, indicating that source of FLI on the gut are cells within the CNS, which may release FGLa/ASTs at the gut to alter aspects of gut physiology. FGLa/ASTs are involved in peristalsis, neural control of foregut contractions, and ileal K+ transport. In particular, FGLa/ASTs inhibit contractions of each gut region and also modulate the rhythmic motor output of a central pattern generator within the ventricular ganglion of the STNS. FGLa/ASTs also inhibit ileal K+ efflux, suggesting a diuretic action and implicating FGLa/ASTs in fluid and ion homeostasis. This work provides a comprehensive picture of how FGLa/ASTs play an integral role in nutrient processing, energy mobilization, and growth and metamorphosis to contribute to the overall maintenance of homeostasis. This reinforces the role of FGLa/ASTs as brain/gut peptides and emphasizes their involvement in the flexibility of nervous communication and integration of the endocrine system with the CNS to achieve homeostasis.

The FGLa/ASTs are one family of allatostatin peptides and share an amidated C-terminal sequence (FGL-amide). The inhibitory effect of FGLa/ASTs on juvenile hormone (JH) biosynthesis in Diploptera punctata led to their discovery, but there is a lack of allatostatic function across most insect species that suggests this function may not be their primary role. Rather, the FGLa/ASTs are implicated as brain/gut peptides, modulating gut physiology. This thesis demonstrates the pleiotropic nature of FGLa/ASTs in Locusta migratoria and emphasizes the role of FGLa/ASTs as brain/gut peptides involved in homeostatic processes. FGLa/AST-like immunoreactivity (FLI) is associated with the corpus cardiacum (CC) and corpus allatum (CA). FGLa/ASTs increase adipokinetic hormone release from the CC and alter JH biosynthesis from the CA, suggesting roles in energy utilization and in growth and metamorphosis. Each region of the gut exhibits FLI. The gut is dually innervated: neurons in the abdominal ganglia of the central nervous system (CNS) innervate the posterior gut and some contain FLI, while neurons within the stomatogastric nervous system (STNS) that innervate the anterior gut do not seem to contain FLI, indicating that source of FLI on the gut are cells within the CNS, which may release FGLa/ASTs at the gut to alter aspects of gut physiology. FGLa/ASTs are involved in peristalsis, neural control of foregut contractions, and ileal K+ transport. In particular, FGLa/ASTs inhibit contractions of each gut region and also modulate the rhythmic motor output of a central pattern generator within the ventricular ganglion of the STNS. FGLa/ASTs also inhibit ileal K+ efflux, suggesting a diuretic action and implicating FGLa/ASTs in fluid and ion homeostasis. This work provides a comprehensive picture of how FGLa/ASTs play an integral role in nutrient processing, energy mobilization, and growth and metamorphosis to contribute to the overall maintenance of homeostasis. This reinforces the role of FGLa/ASTs as brain/gut peptides and emphasizes their involvement in the flexibility of nervous communication and integration of the endocrine system with the CNS to achieve homeostasis.

Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Missouri--Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves: 152-155). Also available on the Internet.

Thesis (Ph. D.)--Case Western Reserve University, 2005. / [School of Medicine] Department of Physiology and Biophysics. Includes bibliographical references. Available online via OhioLINK's ETD Center.

Diss. med. dent. Zürich. / Literaturverz.

Enhanced mass transport in carbon-based nanoscale conduits (e.g. carbon nanotubes, graphene nanochannels/capillaries, graphene/graphene oxide membranes) has attracted tremendous interest over the last decade due to its significant implications for water desalination/purification, nanofiltration, electronic cooling, battery/fuel cells, and lab-on-a-chip. Further development of carbon-based nanoscale conduits for practical applications relies on understanding fundamental mechanisms of transport through individual conduits, which have not been well studied due to challenges in fabrication and measurement. In this thesis, the construction of two-dimensional planar graphene nanochannel devices and the studies of enhanced water and ion transport inside the graphene nanochannels are reported for the first time. The graphene nanochannels are fabricated by conformally covering high-quality graphene on the surfaces of silica nanochannels. A new fabrication scheme consisting of graphene wet transfer, graphene patterning and vacuum anodic bonding is developed to create such graphene nanochannels with heights ranging from 24 to 124 nm. Using these nanochannels and a new hybrid nanochannel based capillary flow measurement technique, we successfully measured the hydraulic resistance (water permeability) of single graphene nanochannels. Our results demonstrate that the frictionless surface of graphene induces a boundary slip and enhances water flow inside the graphene nanochannel. The measured slip length of graphene in the graphene nanochannels poses a median value around 16 nm, albeit with a large variation from 0 to 200 nm regardless of the channel height. The small-yet-widely-varying values of the graphene slip length are attributed to the surface charge of graphene and the interaction between graphene and underneath silica substrate, which are in good agreement with the prediction of our molecular dynamics (MD) simulation. In addition, we also investigated enhanced ion transport inside the graphene nanochannels. Higher electroosmotic conductance at low electrolyte concentrations (10-6 M~10-2 M) is observed in graphene nanochannels when compared with silica nanochannels with the same geometry. Our results suggest that the enhanced electroosmotic flow is also due to the boundary slip at the graphene/electrolyte interface. Besides, our analysis shows that the surface charge on the graphene, originating from the dissociation of oxygen-containing functional groups, is crucial to the enhanced electroosmotic flow inside nanochannels.

Made available in DSpace on 2014-06-11T19:31:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-03Bitstream added on 2014-06-13T20:02:12Z : No. of bitstreams: 1 palo_rm_dr_arafo.pdf: 467649 bytes, checksum: 183d6a08f321f5dff7b6917fb6e2cee1 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste trabalho foi avaliar a quantidade de peróxido que passa da câmara pulpar para a superfície dentária externa durante o clareamento interno no esmalte, cemento e dentina. Foram utilizados 50 incisivos bovinos extraídos que receberam aberturas coronárias, as raízes foram cortadas a 5 mm da junção amelo-cementária e foi realizado um tampão de 2mm de ionômero de vidro selando a entrada do canal. A extremidade apical dos espécimes foi isolada externamente com resina composta fotoativada. Os dentes foram então impermeabilizados completamente, deixando exposto somente as áreas a serem estudadas. As câmaras coronárias foram preenchidas com peróxido de hidrogênio a 35%. Os dentes foram divididos em três grupos experimentais e dois grupos controles, com 10 espécimes cada. GE – esmalte exposto a ser avaliado; GC – cemento exposto a ser avaliado; GD – dentina exposta a ser avaliada; e dois grupos Controle: GC1 – sem a presença de clareador internamente e sem impermeabilização e GC2 – câmara pulpar preenchida com clareador e impermeabilização total. Cada amostra foi colocado no interior de reservatórios individuais com 1000μl de solução tampão de acetato 2M (pH 4,5). Após 7 dias a 37±1ºC a solução foi transferida para um tubo de ensaio onde foram adicionados 100μl do corante violeta leucocristal e 50 μl de peroxidase, resultando em uma solução de coloração azul. A mensuração da absorbância foi feita em um espectrofotômetro e convertida em μg/ml de peróxido. Para avaliar se houve diferença entre os grupos experimentais e controle, realizou-se os testes de Kruskall-Walis e Dunn-Bunferroni e os resultados mostraram os íon passaram mais pela dentina exposta, seguida da dentina recoberta pelo esmalte e dentina recoberta pelo cemento, sem diferenças estatísticas. Todos os grupos experimentais foram diferentes dos controles... / The aim of this study was evaluated the pulp chamber penetration of peroxide bleaching agent to the root surface during the internal bleach technique in the enamel, dentin and cement. Bovine teeth were sectioned 5mm apical of the cemento-enamel junction and was performed a 2mm cervical seal with glass ionomer cement. The external apical part of samples was filled with composite resin. The teeth were divided into three experimental groups and two control groups: GE – exposition of enamel; GC – exposition of cement; GD – exposition of dentin and control groups: GC1 – no presence of internal agent bleaching e no waterproof and GC2 – pulp chamber filled with bleaching agent and total waterproof. Each sample was placed inside of individual flasks with 1000μl of acetate buffer solution 2M (pH 4.5). After 7 days, the buffer solution was transferred to a glass tube where leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined by spectrophotometer and converted into microgram equivalents of hydrogen peroxide. Data were submitted to Kruskal-Wallis, and Dunn-Bunferroni tests. The results showed that the ions penetration was higher in dentin followed by enamel and cement. All experimental groups presented statistical differences to the control groups.

De nombreux dispositifs pour l’électronique organique et la bioélectronique reposent sur le transport mixte (électronique et ionique).Le transport électronique dans les matériaux organique est relativement bien compris, mais une compréhension fondamentale du transport des ions est manquante. J'ai développé un modèle analytique qui décrit le transport d'ions dans une jonction planaire entre un électrolyte et un film de polymère conducteur.Le modèle permet des prédictions de l'évolution temporelle du courant et du drift length des ions.Ces prédictions sont validées par des simulations numériques et en utilisant des paramètres réalistes, je montre que le modèle analytique peut être utilisé pour obtenir la mobilité des ions dans le film. De plus, j'ai développé une méthode expérimentale qui permet l'application du modèle analytique et conduit à une estimation de la mobilité des ions dans les polymères conducteurs. Le PEDOT:PSS offre un transport efficace pour les ions, qui peut être mis en relation avec le gonflement important du film dans l'eau. Je montre que la réticulation du film diminue son gonflement ainsi que la mobilité des ions. Comprendre la forte corrélation entre l'hydratation et la conductivité ionique nous permet de développer des matériaux à mobilité ionique définie et importante. A titre d'exemple, le réglage de la mobilité ionique du PEDOT:TOS est présenté en ajustant le rapport relatif de la phase hygroscopique. Pour finir, j'ai effectué des mesures de spectroscopie d'impédance électrochimique au cours d'une expérience de moving front, afin de proposer une interprétation physique des spectres d'impédance mesurés à une jonction polymère conducteur/électrolyte / Many organic electronic and bioelectronics devices rely on mixed (electronic and ionic) transport within a single organic layer. Although electronic transport in these materials is relatively well understood, a fundamental understanding of ion transport is missing. I developed a simple analytical model that describes ion transport in a planar junction between an electrolyte and a conducting polymer film. The model leads to predictions of the temporal evolution of drift length of ions and current. These predictions are validated by numerical simulations and by using realistic parameters, I show that the analytical model can be used to obtain the ion mobility in the film. Furthermore, I developed an experimental method which allows the application of the analytical model and leads to a straightforward estimation of the ion drift mobilities in conducting polymers. PEDOT:PSS was found to support efficient transport of common ions, consistent with extensive swelling of the film in water. Crosslinking the film decreased its swelling and the ion mobility. Understanding the high correlation of hydration and ionic conductivity enables us to engineer materials with high and defined ion mobilities. As an example tuning of ion mobility by adjusting the relative ratio of the hydroscopic phase to PEDOT:TOS is presented. Finally I performed electrochemical impedance spectroscopy during a moving front experiment, in order to give a physical interpretation of the impedance spectra at a conducting polymer/electrolyte junction.