Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Teng Ma, Florida State University, College of Engineering, Dept. of Chemical and Biomedical Engineering. Title and description from dissertation home page (viewed Feb. 13, 2006). Document formatted into pages; contains xiv, 164 pages. Includes bibliographical references.

Thesis (Ph.D.)--Aberdeen University, 2009. / Title from web page (viewed on Sep. 2, 2009). Includes bibliographical references.

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2010. / Härtill 3 uppsatser.

Thesis (doctoral)--Ludwig-Maximilians-Universität München, 1993.

Proefschrift Universiteit Maastricht. / Met lit. opg. - Met samenvatting in het Nederlands en Frans.

Convergent lines of research suggest there exists an excitatory cholinergic input to the substantia nigra from the pedunculopontine tegmental nucleus and possibly the laterodorsal tegmental nucleus. Previous work has suggested that microinjection of cholinergic agonists into substantia nigra elicits behaviours performed with a high frequency but with a low current rate (Winn 1991). Experiments carried out during my PhD have demonstrated that: Microinjection of cholinergic agonists to anterior substantia nigra (SN) elicited increased consumption of palatable food such as spaghetti but not rat maintenance diet in pre-satiated rats. Stimulation of behaviour was achieved using direct agonists for either muscarinic or nicotinic cholinergic receptors (carbachol and nicotine respectively). Stimulation of behaviour was also achieved using the indirect cholinergic agonist neostigmine which blocks the de-activation of endogenous acetylcholine by AChE. Increased feeding elicited by cholinergic stimulation of the anterior SN was abolished by a selective lesion of ascending dopamine (DA) neurones which significantly depleted caudate DA levels but left accumbens DA levels unaltered. A behaviourally potent dose of carbachol caused a significant increase in the response to different doses of nicotine suggesting an additive effect of muscarinic and nicotinic stimulation at the doses used. Administration of cholinergic agonists to the VTA or SN caused indistinguishable effects on responding for conditioned reinforcement. Cholinergic stimulation caused increased responding for a conditioned reinforcer and also reinstated responding at the primary reward source. The functional significance of the cholinergic innervation of the DA- containing neurones of the substantia nigra is discussed with reference to its relationship to the neighbouring ventral tegmental area, and their innervation of the caudate-putamen and the nucleus accumbens. Cholinergic neurones in the PPTg and LDTN appear to exert a tonic control over the activity of midbrain DA-containing neurones. It is suggested that cholinergic control of midbrain DA-containing neurones facilitates the processing of information in the striatum and hence influence the selection of an appropriate behavioural response to a given situation.

A sucrose gradient technique was developed for the preparation of plasma membrane material from SV40 3T3, Py3T3 and HeLa cells. A modification of this method yielded purified nuclei. The plasma membrane material, which was enriched in both 5'-nucleotidase and (Na+K)-ATP ase activities, was used to establish some of the properties of the latter in 3T3 and SV40 3T3 cells. Many of these properties were similar in both cell lines. The effect of conditioning of the growth medium, on the transport of 86Rb into 3T3 and SV40 3T3 cells was investigated. It was shown that conditioning reduced the uptake from growth media and that when the cells were then transferred to Krebs solution, the uptake was apparently increased. The effect of cell population density on several of the properties of 3T3, SV40 3T3, Py3T3 and HeLa cells was examined. When transformed 3T3 cells were grown in medium containing 10% calf serum, the activities of the cell surface enzymes, (Na+K)-ATPase and 5'-nucleotidase, decreased differently with increasing density. The (Na+K)-ATPase activity decreased sharply as the density exceeded 5 x 10⁴ cells/cm2 while the 5'-nucleotidase activity decreased gradually as the density increased. The activity of the latter plateaued so that the overall decrease in the activities of both enzymes was similar. When 3T3 cells were grown under the same conditions, the activities of the cell surface enzymes increased with cell population density. The cell surface enzymes of HeLa cells were shown to decrease with density in a manner similar to those of the transformed 3T3 cells but the decrease in the (Na+K)-ATPase did not exactly follow that of the specific ouabain binding. The effect of culture density on the intracellular enzyme was shown to depend on the cell type as well as the particular enzyme. In all of the 3T3 cell lines, the acid phosphatase activity was observed to increase with increasing density whereas in HeLa cells this enzyme did not alter. In the transformed 3T3 cell lines, the monoamine oxidase activity did not alter with density and the rotenone insensitive NADH-ferricyanide reductase activity increased but in 3T3 cells, the former increased and the latter decreased. In foetal calf serum, the cell surface enzymes were observed to alter differently with respect to cell population density. The cell protein tended to decrease as did the cell volume but these measurements were not directly related. The specific Concanavalin A binding also decreased with cell population density but the decreases were not related to the volume changes. It was concluded that the activity of many of the enzymes of cultured cells is dependent both on the cell population density and the medium in which the cells are grown.

The role of the pedunculopontine tegmental nucleus (PPTg) in the control of behavioural processes was investigated in this thesis. This was achieved through examination of: (1) Conditioned place preference formation: PPTg lesioned rats were not impaired in forming an appropriate place preference, regardless of their deprivation state. (2) Reward-related responding: both food deprived and non-deprived lesioned rats displayed disinhibited intake across a gradient of sucrose rewards, the degree of disinhibition increasing as the reward became stronger. This disinhibited responding was disassociated from simple approach behaviour as shown by similar runway completion times across control and lesioned rats. (3) Radial arm maze performance: PPTg lesioned rats were impaired in their ability to retrospectively plan and forage in a random foraging task. This impairment was seen in both acquisition and retention tasks. PPTg lesioned rats were also impaired in the acquisition of a spatial working memory task in which they had to prospectively plan and execute responses. (4) These behavioural tasks are related to striatal output. To complement them anatomical experiments examining altered striatal outflow on neurotransmitter expression in the PPTg were conducted. Neither dopamine receptor blockade nor 6- hydroxydopamine (6-OHDA) lesions of striatal dopamine produced changes in nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase expression in the PPTg. This work did, however, lay the foundation for future experimentation to address this question. The combination of these findings extends current literature to outline a role for the PPTg in the control of complex behaviours that have been previously associated with sites higher up the neuraxis. This thesis demonstrates that removal of the PPTg results in behaviours that are inappropriate and disinhibited. In conclusion the PPTg is important for both accurate response selection and execution of goal directed behaviours, elements crucial for effective behavioural responding.

No description available.

Remyelination is the restoration of myelin sheaths to denuded axons following demyelinating events, which occurs spontaneously in adult mammals, including humans. The principal cells which participate in remyelination are the Oligodendrocyte Progenitor Cells (OPCs). Similar to other regenerative processes, remyelination efficiency declines with ageing. It is still unknown how much of this decline can be attributed to intrinsic changes in the OPCs themselves rather than environmental changes arising from changes in the cellular niche. Thus, we currently have a fundamental gap in our knowledge regarding the basic biology of adult OPCs, and therefore the changes that occur to them with ageing. In order to address these questions, I have developed a method to reliably isolate all cell types of the oligodendrocyte (OL) lineage from adult rats. This allowed me to identify the specific transcriptome state unique to adult OPCs, which is different to the transcriptome of neonatal OPCs, upon which previous studies have focused. This included genes which support the notion that following the initial phases of developmental myelination, adult OPCs enter a quiescent mode, in a manner similar to other tissue resident stem cells. Moreover, using a recently established isolation method, I was able to isolate aged OPCs, and develop a transcriptional database that can allow researchers to explore the changes in aged OPCs and identify new targets for enhancing their function. Lastly, I present in this thesis novel ideas regarding the influence of microglia cell surface molecules on OPC differentiation. I show that changes in the cell surface of aged microglia are inhibitory for OPC differentiation into OLs, and that these changes in microglia are a result of the increase in TGFb levels with ageing. In summary, this dissertation introduces new tools and methods that will allow x further in-depth study of adult OPCs, and specifically will help to shed light on the role of adult OPCs in the CNS in homeostasis. Furthermore, I explore the changes that occur within OPCs as they age, and show how such changes reduce aged OPCs ability to efficiently facilitate the process of remyelination.