No description available.

α-Synuclein (α-syn), is a self-aggregating protein that has been identified as a pathologically important component in a number of diseases, such as Parkinson’s disease (PD). PD, a progressive neurological disorder affecting 1 in 500 people, results in motor dysfunction following the loss of dopaminergic neurones of the nigrastriatal pathway. A pathological hallmark of PD is the presence of α-syn containing Lewy bodies and Lewy neurites. Although α-syn has been linked to PD by both histology and genetic studies on familial PD, neither the physiological function nor the pathophysiological role of α-syn in PD has been fully elucidated. This thesis examines the cellular responses to exogenously applied recombinant α-syn under normal and disease-like conditions. Within this thesis large-scale expression and purification of α-syn was successfully established, reproducibly producing large quantities of pure recombinant α-syn that was utilised within in vitro experiments. In SHSY-5Y neuroblastoma cells, α-syn (10 and 30 μM) significantly decreased NAD(P)H levels after 48 h incubation, indicative of either cell death or disruption to energy metabolism of the cells. However, α-syn (0.1 - 30 μM) did not induce cell death, as determined by the LDH assay, even when the cells were exposed for 48 h. Therefore our studies show that under normal, physiological conditions, α-syn is not inherently toxic, but does result in a decrease of total cellular energy levels. The mitochondrial toxin, 1-methyl-4-phenylpyridinium ion (MPP+), induced cell death in SHSY-5Y cells that was both concentration- and time-dependent. α-Syn (30 μM) significantly exacerbated MPP+-induced cell death in this model of PD. This suggests that while α-syn is normally non-toxic, under PD-like conditions it can exacerbate the cell death process. We identified that α-syn (30 μM) significantly increased cytosolic Ca2+ levels in a time-dependent manner as well as increasing the levels of the apoptotic mediator, cytochrome c (cyt c). The release of cyt c from the mitochondria into the cytosol is indicative of mitochondrial dysfunction and pore formation within mitochondrial membranes. However, α-syn-induced increase in cytosolic Ca2+ was not blocked by the mitochondrial pore inhibitor, cyclosporine A. This suggests that α-syn effects were not mediated through the mitochondrial pore usually associated with dysfunction and cyt c release. α-Syn therefore releases cyt c and Ca2+ by a separate mechanism, such as the formation of α-syn protofibril pores. This was further compounded by data that showed that α-syn (30 μM) significantly decreased mitochondrial membrane potential after 48 h incubation. The loss of the mitochondrial membrane potential coincided with a decrease in NAD(P)H. These data would therefore suggest that physiologically α-syn induces a low, non-toxic effect on the mitochondrial membrane. Under pathological conditions similar to PD however, this mitochondrial stress mediated by α-syn acts to exacerbate cell death.

A community-based, prospective study of the incidence of parkinsonism using multiple, overlapping recruitment methods was undertaken. From a base population of 311,770, followed over 3 years, 628 people were assessed. 293 were diagnosed with parkinsonism, of whom 53.2% had a baseline diagnosis of Parkinson’s disease (PD). 190 age and sex matched controls were also recruited. This cohort was combined with one recruited during a pilot study (83 patients) for calculation of incidence figures and follow-up, which will continue long-term. Using this combined cohort, age and sex specific incidence rates were calculated for parkinsonism (29/100,000/year) and PD (17.5/100,000/year). Incidence of both of these increased with age. PD was more common in men. Incidence did not vary by socioeconomic group. The results of the incidence study were compared with those found in an updated systematic review of incidence studies in PD. Mortality was compared between the control and patient groups at a median of 24 months follow-up. The adjusted hazard ratio for death compared with controls for patients with a clinical diagnosis of PD was 2.00 (95% CI 1.19-3.36) and for patients with causes of other parkinsonism was 3.36 (95% CI 1.93-5.84). Clinical diagnosis of the cause of parkinsonism changed over time, with most changes occurring within the first year. A validation study for the English language version of the PD-specific cognitive screening tool (the mini-mental Parkinson) used in this cohort was undertaken. A systematic review of the occurrence of psychotic features in PD, found 45 studies reporting median prevalence of hallucinations of 29.2%. The prevalence of hallucinations in this cohort was 5.5% at baseline and 16.7% at 3 years. Comparison of the results from this cohort with those of similar ongoing studies will give a greater understanding of the course of PD and allow more effective targeting of health-care resources.

No description available.

University of Macau / Institute of Chinese Medical Sciences

Parkinson's disease (PD) is a progressive neurodegenerative disorder with evolving layers of complexity. In the present thesis we replicated the PD neurodegenerative pattern using a mouse model characterized by systemic injections of the neurotoxin 1-methyl-4-phenyl1,2,3,6-tethrahydropyridine (MPTP). Firstly, we investigated the role of a pro-inflammatory mediator called high mobility group box 1 (HMGB1), in-vivo and in post-mortem human tissue of PD patients. Our study shows increased protein levels of HMGB1 in substantia nigra of PD patients and MPTP treated mice. Inhibition of HMGB1, using the antagonist glycyrrhizin, and a HMGB1 neutralising antibody, has shown neuroprotection against MPTP neurotoxicity as well as prevented nuclear translocation of the protein in dopaminergic neurons. Secondly, we profiled the expression of two HMGB1 cognate receptors: TLR2 and TLR4. Levels of the receptors were upregulated in mouse ventral midbrain following the acute and sub-acute MPTP regimen. However, TLR4 knock out mice were not protected against MPTP-induced dopaminergic toxicity. Thirdly, we developed a novel method of brain tissue dissociation and isolation of immune cells viable for downstream flow cytometric analyses. The technique allowed us to investigate the effects of low grade chronic systemic inflammation within the CNS of mice. The method has proven to be sensitive enough for the qualitative and quantitative measurement of immune cells isolated from brain parenchyma. Lastly, an extensive behavioural characterization on the three different MPTP mouse models was performed in order to identify translational behavioural paradigms in relation to the nigrostriatal lesion induced by the neurotoxin MPTP. Major gait and balance impairments were identified in acute and chronic MPTP mouse models. The findings on HMGB1, TLR2 and TLR4 proteins are the overarching element between the identification of the behavioural endpoints in the MPTP models and the newly developed method for the isolation of immune cells from the mouse brain parenchyma.

Parkinson's disease (PD) is the 14th leading cause of the death in the United States. There is a strong relationship between cognitive decline, subsequent dementia, and mortality in PD. Cognitive reserve contributes to the maintenance of cognitive functioning in old age. However, the importance of cognitive reserve in the clinical course of PD is largely unknown. The current study examined cognitive and psychosocial parameters and their effect on survival in PD. It was proposed that cognitive factors (most specifically, higher semantic fluency) and psychosocial factors (i.e., higher educational/occupational attainment, absence of threshold level depressive symptomatology, absence of a personal/familial psychiatric history, and having a spouse/life partner) will predict increased post-onset survival in PD. After obtaining informed consent, 192 PD participants underwent a 3-hour comprehensive neuropsychological evaluation, neurological examination, and interview. Results from a multivariate Cox proportional hazards model indicated that semantic fluency is predictive of post-onset survival in PD, independent of age of onset, disease duration at examination, gender, years of education, and disease stage. The present study did not find a relationship between psychosocial factors and post-onset survival in PD. These findings indicate that a brief assessment of semantic fluency, able to be obtained in a clinic in less than five minutes, may be a useful prognostic indicator of post-onset survival in PD.

Undergraduate honors paper--Mount Holyoke College, 2006. Program in Neuroscience and Behavior. / Includes bibliographical references (leaves 69-77).

This thesis provides new insight into how learned skilled movements are affected in a disease with basal ganglia damage, within what task demands these deficits can be detected, and how this detection can occur within the constraints of primary motor symptoms. Hence the purpose of this thesis was threefold. Firstly, the aim was to take a model-based approach to apraxia in PD, in order to determine the nature of the errors in reference to other populations that experience apraxia. Apraxia by definition cannot be the product of primary motor deficits, weakness, sensory loss, or lack of comprehension, therefore the second objective of the study was to detect apraxia while remaining true to these prerequisites. The third objective was to extend the examination of apraxia beyond the upper limbs, and investigate the relationship between upper limb and lower limb apraxia, as well as the relationship between freezing (which shares similarities with gait apraxia) and upper limb and lower apraxia. Overall, the most common pattern of apraxia identified in this PD group was impairment at both pantomime and imitation, suggesting issues with executive function. However, there are other results that suggest an issue with visuomotor transformation may be superimposed on this executive function deficit, including a higher frequency of participants impaired at imitation and a very pronounced impairment at meaningless gestures. To ensure that these deficits are not the product of primary motor symptoms, correlation analyses were conducted between gestural impairment and total motor impairment, cardinal symptom impairment, and degree of asymmetry of these symptoms. While there was a significant correlation of total motor severity and gestural impairment, there were no significant correlations between cardinal motor symptoms and total gestural impairment, or limb specific gestural impairment and the degree of motor asymmetry. These results indicate that the outward manifestation of primary motor symptoms does not necessarily correspond with gestural impairment, however the overall relationship (total UPDRS) hints to an indirect influence of the basal ganglia on healthy praxis. With regards to the third objective, the lower limb assessment turned out to be very consistent with the results yielded in the upper limb assessment. While there were similar frequencies of impairment in both pantomime and imitation, the upper limb and lower limbs assessments were found to correlate very strongly. This is a promising result, because the lower limb battery is easy to administer, there are typically less motor symptoms to deal with, and preliminary analyses show a high inter-rater reliability established. Furthermore, there was a higher proportion of freezers with apraxia compared to non-freezers, and this is the first study to reveal this. All these results taken together are evidence of similar underlying mechanisms for these impairments (upper limb apraxia, lower limb apraxia, and freezing). The model-based approach to studying apraxia in both the upper and lower limbs of PD, enables us to determine the frequencies, patterns and severities of apraxia, and better equips us to predict which systems are more susceptible to deterioration. This thesis project has hopefully created a framework for determining coping strategies and future interventions for apraxia, specifically in basal ganglia disordered populations.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 127-153).