Solid tumours are a hostile tissue environment in which the cells are exposed to many stresses including hypoxia. One consequence of hypoxic conditions is an increase in extracellular levels of the purine nucleoside adenosine, which enhances tumour cell migration. This is achieved in part through an increase in the levels of the chemokine receptor CXCR4, which along with its ligand CXCL12, is a key player in breast cancer metastasis. The cellular response to stress is mediated by a family of proteins known as heat-shock proteins (HSPs). The small heat shock protein 27 (HSP27) has been implicated in changes in cancer cell migration. I have therefore studied the regulation of HSP27 in human breast cancer cells by conditions that normally exist in the stressful tumor environment. My project specifically aimed to establish whether changes in HSP27 are linked to hypoxia, adenosine levels and alterations in the CXCL12-CXCR4 migratory pathway.

Osteoarthritis is the end result of damage to articular cartilage, which lacks the ability to self-repair. Tissue engineering of cartilage is a promising field of study that aims to promote healing of cartilage in vivo by manipulation of the chondrocytes that maintain the tissue, or through in vitro production of new cartilage for implantation into cartilage defects. Tissue-engineered cartilage constructs require mechanical stimulation to produce matrix components in quantities and proportions similar to native cartilage tissue, and adenosine triphosphate (ATP) is thought to be an autocrine/paracrine biochemical mediator of these mechanical forces on the cell, after its release from chondrocytes under mechanical stress. This study determined culture conditions for chondrocytes in 3D agarose scaffolds from mature donors undergoing total joint arthroplasty for the treatment of osteoarthritis, then supplemented these cells in vitro with exogenous ATP in concentrations varying from 50 nM to 1 mM in the presence of the radioisotopes [35S] and [3H]-proline, with radioisotope incorporation acting as markers of proteoglycan and collagen synthesis respectively. The basal concentrations of ATP in the chondrocyte cultures as well as the ATP half-life in the cultures were determined by lucifer/luciferase assay and luminometry. The P2Y receptor expression on the populations of chondrocytes from 8 donors was determined by flow cytometry, with largely varied individual expression and heterogeneity of P2Y1 and P2Y2 receptors. Exogenous ATP was found to increase synthesis of matrix components by 200% of the control cultures at doses of 100 nM to 1 µM. Patients with worse arthritis patterns, who were on chronic narcotic medications and who smoked were more likely to have a negative response to the exogenous ATP supplementation. The basal concentration of ATP in the cultures was less than 1 nM, and the ATP half-life varied from 1-2 hours, depending on the expression of P2Y1 receptors expressed by the donor’s chondrocyte population (R2 = 0.99). Supplementation of exogenous ATP to tissue-engineered cartilage in vitro appears to be a promising technique for improving the matrix synthesis of these constructs. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2011-01-28 10:49:47.118

Adenosine is an important neuromodulator. In the present study, we used mice with expression of human ENT1 (hENT1) and deficiency of CD73, respectively, to address the relative importance of intracellular and extracellular pathways in adenosine regulation. [3H]Nitrobenzylthioinosine binding assays were performed and found increased expression of hENT1 with increased gene dose. We performed a series of behavioural experiments with caffeine and ethanol and compared hENT1 heterozygous and homozygous transgenic mice to their wild type littermates. We found that the expression of hENT1 leads to a change in behavioural responses relative to wild type mice, but no sign of a gene dose dependent increase was observed. With CD73 knockout mice, we performed a series of behavioural experiments with caffeine and ethanol that showed a change in adenosine related behaviours. We also performed experiments that tested anxiety-like behaviours and found reduced anxiety-like behaviours with CD73 knockout mice relative to wild type mice. These studies show that mice with enhanced expression of ENT1 or knockout of CD73 have altered extracellular level of adenosine.

V-ATPases are enzymes found in all eukaryotic cells. They are organized into a peripheral membrane complex (V1) and an integral membrane complex (V0). VI is responsible for ATP hydrolysis and generates the energy used by Vo to pump protons from the cytosol into the vacuole. Subunit d is a component of Vo possibly located at the interface between V 1 and V. in the V-ATPase complex. We hypothesize that subunit d could be involved in the structural and functional coupling of VI and Vo. This was tested by generating point mutations along the open reading frame of subunit d from yeast. The mutations F94A, H128A, D173A, D217A, D261A, E317A, W325A, E328A and C329A, all in conserved regions of the protein sequence, were characterized by examining their growth phenotype and by assessing their ATPase specific activity, proton transport and V1Vo assembly in purified vacuolar membranes. The mutations E317A, W325A, E328A and C329A had reduced ATPase and proton transport activities. In addition, V1Vo assembly was compromised by the mutation W325A. Our results suggest that residues at the carboxyl-end of subunit d are important for ATPase activity, proton pumping and V1Vo assembly at the membrane. / Department of Chemistry

Previous studies of serum adenosine deaminase have neglected consideration of the two molecular forms of this enzyme that exist in human tissues. The purpose of this study was to survey the distribution of these forms in normal and pathological human sera. Both molecular forms were present in normal serum, though the small form predominated. This form also predominates in lymphocytes, erythrocytes, and in tissues with high specific activity of this enzyme. The ratio of the two forms is different for plasma and serum and can change with sample storage. The activity of the small form varied over a wider range than the activity of the large form in normal serum. Many pathological samples showed an altered distribution of the two forms. This study demonstrates the potential usefulness of serum forms of adenosine deaminase for distinguishing some pathological conditions.

Adenosine is an important neuromodulator. In the present study, we used mice with expression of human ENT1 (hENT1) and deficiency of CD73, respectively, to address the relative importance of intracellular and extracellular pathways in adenosine regulation. [3H]Nitrobenzylthioinosine binding assays were performed and found increased expression of hENT1 with increased gene dose. We performed a series of behavioural experiments with caffeine and ethanol and compared hENT1 heterozygous and homozygous transgenic mice to their wild type littermates. We found that the expression of hENT1 leads to a change in behavioural responses relative to wild type mice, but no sign of a gene dose dependent increase was observed. With CD73 knockout mice, we performed a series of behavioural experiments with caffeine and ethanol that showed a change in adenosine related behaviours. We also performed experiments that tested anxiety-like behaviours and found reduced anxiety-like behaviours with CD73 knockout mice relative to wild type mice. These studies show that mice with enhanced expression of ENT1 or knockout of CD73 have altered extracellular level of adenosine.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1989. / Includes bibliographical references. / Microfiche. / xvii, 206 leaves, bound ill. 29 cm

The difficulty with movement initiation, or akinesia, is a cardinal symptom of Parkinson�s disease (PD) and the loss of dopaminergic cells, affecting the function of the basal ganglia, the thalamus and the motor cortex, has long been documented. From a broader perspective, it has been proposed that akinesia is caused by impaired function in different brain areas, inside and outside the basal ganglia, operating as a �behavioural arrest control system� (Klemm, 2001). Several neurotransmitters seem to modulate the activity of this system and, contrasting the well-known effects of dopamine, the involvement of adenosine has only recently emerged, particularly via A2A receptors. Adenosine plays an opposite role to dopamine in the brain: adenosine stimulation at A2A receptors inhibits movement (Ferre et al., 1991a; Hauber and Munkle, 1995; Rimondini et al., 1997), whereas A2A antagonists seem to promote movement (Kanda et al., 2000; Bara-Jimenez et al., 2003; Pinna et al., 2005). Although specific adenosine A2A and dopamine D2 receptors are known to antagonistically interact (Ferre et al., 1997; Fuxe et al., 1998; Ferre et al., 2001), little is known of the involvement of A2A receptors in regulating neural activity in the basal ganglia, a crucial point for the future use of A2A antagonists as adjuvant therapy in Parkinson�s disease. In fact, although it is generally accepted that akinesia results from altered function in the cortico-basal ganglia-cortical loop, as confirmed in several studies reporting changes in basal ganglia activity following dopamine depletion (Blandini et al., 2000; Bevan et al., 2002; Boraud et al., 2002), no study to date has systematically investigated electrophysiological changes in the basal ganglia during akinesia induced by adenosine receptor stimulation. Starting from a common behavioural effect, this study tries to bridge this gap by investigating and comparing, in two basal ganglia structures, the neural substrate of akinesia after acute dopamine D2 receptor blockade and adenosine A2A receptor stimulation. The external segment of the globus pallidus (GP, or simply globus pallidus in the rat) and the substantia nigra pars reticulata (SNr) were chosen as the recording sites because both nuclei are included into the �behavioural arrest control system� and seem to express somewhat complementary functions, as a respective key integrative station and main output of the basal ganglia. Dopamine function was manipulated by acute decrease in availability of dopamine binding sites in the brain, through specific dopamine D2 receptor blockade with systemic injections (1.0 and 1.5 mg/kg) of raclopride(3,5-dichloro-N-[(1-ethylpyrrolidin-2-y)methyl]-2-hydroxy-6-methoxy-benzamide), resulting in akinesia. Conversely, movement was inhibited by specific adenosine A2A receptor stimulation with systemic injections (2.5 and 5.0 mg/kg) of the drug CGS21680 (sodium-2-p-carboxyethylphenylamino-5-N-carboxamidoadenosine). In both situations, behaviour was assessed through specific akinesia tests. Single neuron activity before injection and changes in the firing frequency and firing pattern occurring after injection have been analysed and compared for each cell recorded from GP and SNr, during periods of behavioural rest. Synchronised firing between cell pairs has also been assessed. However, the small number of cell pairs showing correlated firing in each structure after systemic injection of drugs was not statistically relevant for further analysis and interpretation of synchronised firing during drug induced akinesia. In our experiments, both drugs inhibited movement, albeit somewhat differently, with lack of rigidity and �flat� body position after adenosine stimulation. Dopamine blockade decreased mean firing rate and dramatically altered the firing pattern in both investigated structures, generally increasing burst activity (increased percentage of spikes in bursts, mean number of bursts, mean number of spikes per burst, mean intra-burst firing frequency) and decreasing regularity of firing (increased coefficient of variation of the inter-spike intervals). Increased burst activity in the rat basal ganglia in an acute model of parkinsonian akinesia, following systemic raclopride injections, confirmed the importance of changes in the firing pattern in PD. The only electrophysiological effect of systemic A2A stimulation was decreased mean firing rate in the GP, a weak effect that could not propagate towards output stations of the basal ganglia. The lack of changes in the firing pattern, at both input and output levels of the basal ganglia, suggests a correlation with the lack of rigidity in adenosine-stimulation-induced akinesia.

Proefschrift Maastricht. / Lit. opg. - Met samenvatting in het Nederlands.

Proefschrift Universiteit van Amsterdam. / Met lit. opg. - Met samenvatting in het Nederlands.