Thesis (Ph.D.) - University of St Andrews, December 2007. / Restricted until 12th December 2008.

Thesis (Ph.D.)--Victoria University of Wellington, 2009. / Includes bibliographical references.

O transcrito regulado pela cocaína e anfetamina (CART) é amplamente expresso em todo o sistema nervoso central. Ele está envolvido na manutenção de diversas funções neurofisiológicas como comportamento alimentar, comportamento sexual, memória e aprendizagem, controle do estresse, processos sensoriais e plasticidade neuronal. Evidências sugerem que o CART deve participar de processos relacionados ao desenvolvimento neural. Diante disso estudamos a expressão do CART em diferentes idades pós-natais com o intuito de identificar as possíveis regiões prosencefálicas nas quais este peptídeo pode estar participando do desenvolvimento neuronal. Por meio da técnica de hibridização in situ, comparamos a expressão do CART no prosencéfalo de animais de 6, de 26 e de 66 dias de vida. Observamos que os animais de 6 dias expressam uma maior quantidade de CART em várias regiões prosencefálicas comparado com animais jovens (26 dias) e adultos (66 dias). Estas áreas são: o córtex somatossensorial, o córtex piriforme, o indusim griseum, o giro denteado, o núcleo accumbens e o núcleo pré-mamilar ventral. Observamos também que o CART é expresso nos núcleos ventro-póstero lateral e ventro-póstero medial do tálamo nos animais de 6 dias, expressão que não é observada no animal adulto. Em outras regiões como o CA1 e o núcleo arqueado não observamos diferença. Utilizando imunohistoquímica, observamos que o peptídeo CART está presente nas regiões descritas. Nossos dados sugerem que o CART participa de processos relacionados ao desenvolvimento em diversas regiões do prosencéfalo. / Cocaine and amphetamine-regulated transcript (CART) is found widespread in the rodent nervous system. It has been involved in many different functions including feeding and sexual behaviors, learning and memory, stress responses, sensory processing and neuronal plasticity. Recent studies suggest that CART may be also implicated in neural development. Therefore, in the present study we investigated CART expression in the forebrain of rats in different stages of development. Using in situ hybridization, we compared CART expression in the forebrain of 6, 26 and 66 days old Sprague-Dawley rats. In general, we found a higher expression of CART in 6 days old animals comparing to other groups. Specifically, we found increased CART expression in the somatosensory and piriforme cortex, induzium griseum, dentate gyrus, nucleus accumbens, and ventral prepamammillary nucleus. Interestingly, we found CART expression in the ventral posteromedial and ventral posterolateral thalamic nuclei only in 6-days old animals. In other regions including the CA1 and the arcuate nucleus, CART expression did not change. By using immunohistochemistry we found that the CART peptide is produced in the areas where we found the mRNA, in 6 days old animals. Our findings suggest that the CART participate in neural development in various forebrain nuclei.

It has recently been established that the activity of crystalline muscle phosphoglucomutase can be greatly stimulated by preincubation of the enzyme with a Mg++-imidazole complex. This observation has aroused interest in the physiological significance of such a system in the possible cellular control of phosphoglucomutase activity. The present study constitutes, in part, an investigation of the properties of phosphoglucomutase from brain tissue. A procedure for the purification of phosphoglucomutase from beef brain is described. The brain enzyme appears to be similar to that from skeletal muscle. Evidence is also presented which indicates that the "activation" produced by Mg++-imidazole is probably of no physiological importance in brain. This observation is consistent with the more recent reports that the phosphoglucomutase reaction is likely not involved in cellular regulatory mechanisms. It is well established that phosphofructokinase is intimately involved in the cellular regulation of glycolysis and the citric acid cycle. Control mechanisms of the phosphofructokinase reaction in mammalian tissues have been postulated on the basis of the complex kinetics of the enzyme. In yeast, however, two enzymatically interconvertible forms of the enzyme have been reported. Preliminary experiments in this study failed to demonstrate a phosphofructokinase system in brain similar to that found in yeast. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

Organophosphates (OPs), including nerve agents, target the cholinergic system via inhibition of acetylcholinesterase (AChE), with subsequent overstimulation resulting in neural damage and potential detrimental long-term effects. The efficacy of novel pyridinium oxime reactivators, created with moieties to increase blood-brain barrier penetration, was tested using highly relevant sarin and VX surrogates. Glial fibrillary acidic protein (GFAP; an indicator of neural damage) and monoamines (dopamine, serotonin, and their metabolites) were measured in select brain regions via immunohistochemistry and HPLC, respectively. Adult male rats were treated ip with high, sub-lethal doses of surrogates for sarin or VX, nitrophenyl isopropyl methylphosphonate (NIMP) or nitrophenyl ethyl methylphosphonate (NEMP), respectively. Surrogate treatment was followed after 1 hr by im administration of novel oxime. Seizure activity was monitored, and kainic acid (KA) served as a positive control. Administration of KA or surrogate (NIMP or NEMP) significantly increased GFAP expression compared to control animals. Two different formulations of one particular oxime (bromide vs. mesylate salt) attenuated seizures and reduced GFAP levels over NIMP or NEMP treatments alone to levels near those of controls in both the piriform cortex and dentate gyrus region of the hippocampus, while 2-PAM did not provide protection. Serotonergic activity was increased in several brain regions, including the piriform cortex, one hr after NIMP treatment. Markers of oxidative stress (isoprostanes) were also tested. Overall, these results indicate the potential therapeutic efficacy of these oximes and suggest this innovative chemistry may protect against neural damage induced by OP.

No description available.

The interplexiform cells(IP cells) are the most recently discovered neurons in the retina and their function is to provide centrifugal feedback in retina. The anatomical structure of the IP cells has been well studied, but the function of these neurons is largely unknown. I systematically studied the excitatory and inhibitory inputs from IP cells in salamander retina. I found that L-EPSCs in IP cells are mediated by AMPA and NMDA receptors; in addition, L-IPSCs are mediated by glycine receptors and GABAC receptors. In response to light, IP cells reaction potentials transiently at the onset and onset of light stimulation. The major neural transmitter of IP cells in salamander retina is glycine. We also studied the distribution and function of glycine transporters. Our result indicates that GlyT1- and GlyT2-like transporters were present in Muller cells and neurons. The glycine feedback at outer plexiform layer (OPL) has effects on both the bipolar cell dendrites and rod photoreceptor terminals. At bipolar cell dendrites, glycine selectively depolarizes rod-dominant On-bipolar cells, and hyperpolarizes Off- bipolar cells. At rod photoreceptor terminals, 10 M glycine activates voltage-gated Ca2+ channels. These effects facilitated glutamate vesicle release in photoreceptors. It increases the sEPSC in OFF bipolar cells. The combined effect of glycine at rod terminals and bipolar cell dendrites leads to enhanced dim light signal transduction in the rod photoreceptor to ganglion cell pathway. This study provides a model that displays the function of centrifugal feedback through IP cells in the retina. / by Zheng Jiang. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Functional brain changes occur rapidly by alterations in synaptic activity, or more slowly, typified by changes in synaptic density and functional neurochemistry. Functional MRI has focused more on the prior than the latter, even though slow brain changes are important for normal brain function and for many brain disorders. With this in mind, I have adapted and optimized MRI-based tools in mice designed to measure ‘slow functional’ changes in the brain - slow changes in linked to synaptic density or slow changes in functional neurochemistry. First, I developed and optimized a series of tools that can map cerebral blood volume (CBV) across the cortical mantle and within cortical layers. I show that this reflects the known functional architecture of the mouse brain and use a whisker-cutting paradigm to show that this approach is sensitive to slow changes in synaptic density. Second, I demonstrate the utility of this approach for mapping slow changes in the brain associated with disease, by pinpointing changes in synaptic density in a novel mouse model of Alzheimer’s disease. Third, I implemented and optimized in mice an MR spectroscopy technique designed to measure changes in two neurotransmitters, GABA, and glutamate. I then demonstrate the translational capabilities of this approach by identifying glutamate abnormalities in the brains of patients in the prodromal stages of schizophrenia.

Thesis (Ph. D.)--Georgia State University, 2007. / Title from file title page. Gabor Patonay, committee chair; A.L. Baumstark, G. Davon Kennedy, Gregg Pratt, committee members. Electronic text (170 p. : ill. (some col.)) : digital, PDF file. Description based on contents viewed Dec. 10, 2007. Includes bibliographical references.

<p>Reactions and interactions of iron and oxygen can be both beneficial and detrimental to cells and tissues. Iron is mainly found in our blood where it functions as a mediator in the transport of oxygen to the cells and is further vital for the cellular respiration reducing the oxygen to water. The flexible redox state of iron makes it ideal to contribute in single electron transfers, but may also catalyze reactions with oxygen resulting in cell damaging reactive oxygen species (ROS). Normally the cells are protected against iron toxicity by controlling iron uptake and storage. When the intracellular demand for iron increases; the iron uptake is promoted by increasing the expression of transferrin receptor (TfR) and by decreasing the expression of the iron storage protein ferritin. Ferritin has a central role in the cellular iron detoxification by keeping it in a non reactive but still bioavailable form. However, in neurodegenerative diseases like in Alzheimer’s and Parkinson’s disease the iron storage capacity is disturbed and iron induced oxidative stress adds to the pathology of the diseases. The role of iron and its possible contribution to the pathology of prion diseases, like Creutzfeldt-Jakob disease, is less explored. In the first three studies of this thesis, the iron metabolism and the mutual relation between iron and oxygen are studied in scrapie-infected mouse neuroblastoma cells (ScN2a) as compared to control cells (N2a). In the fourth study we have analyzed the expression of ferritin and TfR in response to inflammation by treating the cells with the bacterial endotoxin lipopolysaccharide (LPS). LPS promotes the expression of inducible nitric oxide synthase (iNOS), a producer of nitric oxide (NO), a well known regulator of the iron metabolism.</p><p>In the first study, the scrapie infection was found to reduce the iron levels, to reduce the mRNA and protein levels of ferritin and the TfR. In addition, reduced levels and activities of the iron regulatory proteins 1 and 2 were observed as compared to the uninfected N2a cells.</p><p>In the second study, the addition of iron to the cell medium strongly increased the level of ROS and decreased the cell viability of the ScN2a cells, whereas the N2a cells were unaffected. The ferritin expression in N2a cells in response to the iron treatment was strongly increased and the concomitant measurement of the labile iron pool (LIP) revealed the LIP to be normalized within four hours. In the ScN2a cells the induction of ferritin expression was lower resulting in elevations in LIP that lasted up to 16 h, indicating that the increased ROS levels were iron catalyzed.</p><p>In the third study, the cells were challenged with hydrogen peroxide (H₂O₂) to elevate the oxidative stress and to analyze the effects on the LIP and cell viability. The ScN2a cells were sensitive to the increased oxidative stress according to the cell viability test, and responded to the treatment with marked increase in the LIP levels, probably derived from an intra-cellular source. The cell viability could be reset by the co-addition of an iron chelator to the cell media. The N2a cells did not elevate the LIP and resisted higher concentrations of H₂O₂ than the ScN2a cells, according to the cell viability assay.</p><p>In the fourth study, the LPS treatment resulted in increased mRNA levels of the heavy chain of ferritin, increased the protein levels of ferritin light chain and decreased the protein levels of the TfR in N2a cells, but no effects were observed in the ScN2a cells. Co-treatment with LPS and the iNOS inhibitor aminoguanidine did not affect the LPS induced decrease of TfR in N2a cells, whereas the free radical scavenger N-acetyl-L-cysteine reversed the effect of LPS on TfR expression, indicating that the changes were mediated by an oxidative rather than a nitric oxide mechanism in the N2a cells.</p>