Thesis (Ph. D.)--University of Missouri--Columbia, 1998. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri--Columbia, 1998. / Includes bibliographical references.

Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.

Thesis (Ph. D.)--University of Virginia, 2008. / In title: [A] is subscript upper case A; [B] is subscript upper case B. Includes bibliographical references. Also available online through Digital Dissertations.

In the present study, we investigated the mechanism of adenosine-induced apoptosis in Drosophila imaginal disc cell line using the overexpression and silencing of several candidate genes. Our results indicate that the cell death is associated with the activity of c-Jun N-terminal kinase (JNK).

Adenosine is a ubiquitous metabolite with multiple physiological functions in organisms. In this thesis, I studied the effect of extracellular adenosine on Huntington´s disease (HD) model Drosophila melanogaster. I show that extracellular Adenosine signaling mitigates HD pathology by observing three main types of symptoms of the disease in Drosophila. The results suggest that the mechanism involves Drosophila melanogaster adenosine receptor signaling.

Using a mechanism-based approach to drug discovery, efforts have been directed towards developing novel ATP mimics that can act as GS inhibitors. The purine-based systems, adenosine, adenine and allopurinol, were identified as possible scaffolds for potential ATP mimics, while various meta-disubstituted benzenoid compounds, 3-aminobenzonitrile, 3-aminophenol, resorcinol, 3-aminobenzyl alcohol, 3-hydroxybenzoic acid and 3-aminobenzoic acid have been explored as adenine analogues. These compounds were treated with different alkylating and acylating agents. Allylation of all the substrates was achieved using allyl bromide and N-9 alkylation of protected allopurinol was effected using a number of specially prepared Baylis-Hillman adducts. Acylation of the benzenoid precursors with chloroacetyl chloride, acetoxyacetyl chloride, acryloyl chloride and specially prepared 2,3,4,5,6-pentaacetylgluconoyl chloride afforded the corresponding mono- and /or diacylated products in varying yields (4-96%). Elaboration of the alkylated and acylated products has involved the reaction of hydroxy systems with diethyl chloro phosphate and chloro derivatives with triethyl phosphite in Arbuzov-type reactions to afford phosphorylated products. In all cases, products were fully characterized using 1- and 2-D NMR analysis and, where appropriate, high-resolution mass spectrometry. The application of Modgraph and ChemWindow NMR prediction programmes has been explored and the resulting data have been compared with experimental chemical shift assignments to confirm chemical structures and, in some cases, to establish the position of allylation or acylation. Experimental assignments were found to be generally comparable with the Modgraph data, but not always with the ChemWindow values. The docking of selected products in the 'active-site' of GS and their structural homology with ATP, both in their free and bound conformations have been studied using the ACCELERYS Cerius² platform. All the selected ATP mimics exhibit some form of interaction with the 'active-site' residues, and a number of them appear to be promising GS ligands.

Modification of proteins by ADP-ribose has been shown to be a versatile modification with respect to the amino acid side chain. The results described here will allow the study of the biological importance of ADP-ribose glycation and also allow differentiation on crude extracts between enzymatic modifications from protein ADP-ribose glycation that can occur due to the presence of NAD glycohydrolases.

Extracellular adenosine has the potential to influence many aspects of target cell metabolism. The present study has determined the endogenous levels of adenosine in the pregnant mouse uterus and developing embryodecidual unit with respect to the expression of two key enzymes of adenosine metabolism, 5′‐nucleotidase (5′‐NT; EC 3.1.3.5) and adenosine deaminase (ADA; EC 3.5.4.4). To measure adenosine levels, nucleoside extracts were etheno‐derivatized and quantitated by high‐performance liquid chromatography‐fluorescence detection (0.03 pmol/mg protein sensitivity). Adenosine levels were determined to be 0.18 nmol/mg protein in the nonpregnant uterus; however, two statistically significant changes were identified in the pregnant uterus: (1) a periimplantation surge between day 3 (0.24 nmol/mg protein) and day 5 (0.59 nmol/mg protein) of gestation (plug day 0; implantation day 4); and (2) an early postimplantation decline between day 6 (0.54 nmol/mg protein) and day 7 (0.10 nmol/mg protein). The periimplantation adenosine surge coincided with uterine expression of 5′‐NT, an enzyme which catalyzes the irreversible dephos‐phorylation of 5′‐AMP to adenosine. 5′‐NT expression was shown by Northern blot analysis to peak in the embryo‐decidual unit on day 5 of gestation and then to decline through day 9; transcripts remained elevated in the placenta between day 9 and day 13 (the latest day examined in this study). By use of specific enzyme histochemistry, most 5′‐NT activity was localized to the primary decidual zone on day 5. This expression subsequently declined during regression of the primary decidua; however, 5′‐NT appeared on giant trophoblast (days 7–13) and the metrial gland (days 11–13). Other purine catabolic enzymes degrading AMP (adenylate deaminase) or generating adenosine (S‐adenosylhomocysteine hydrolase) were not detected in the embryo‐decidual unit suggesting that the net flux of utero‐placental AMP catabolism proceeds with adenosine as an intermediate, this being the major pathway of adenosine formation. The sharp drop in adenosine levels between day 6 and day 7 coincided with a rise in the activity and mRNA expression of ADA, an enzyme which catalyzes the irreversible deamination of adenosine to inosine. ADA was previously localized to the secondary decidual zone (days 6–11), secondary giant cells (days 7–13), and spongiotrophoblasts (days 8–13) in the mouse (Knudsen et al., 1991). Results of developmental Northern blot analysis demonstrated a direct correlation of relative 5′‐NT/ADA mRNA band intensity to adenosine content between day 4 and day 9 of gestation, suggesting that the local availability of adenosine in the antimesometrium is dependent upon the distribution of these enzymatic activities. Purine nucleoside phosphorylase and xanthine oxidase, which are two catabolic enzymes acting subsequent to 5′‐NT and ADA in the sequential degradation of AMP to xanthine, remained low and constant in the tissues examined suggesting that the catabolic pathway is geared toward regulation of adenosine levels. These results suggest the establishment of an adenosine gradient across the developing antimesometrium. It is proposed that the source of adenosine is AMP released during uterine cell death, and that adenosine, in turn, serves as a regulatory signal to coordinate early postimplantation morphogenetic events with the progression of cell death at the uterine‐embryo interface.

Objective: The aim was to determine if in vitro ischaemic preincubation can precondition cardiomyocytes and if the responses to adenosine receptor antagonists are similar to those previously determined during 'metabolic' preconditioning with glucose deprivation or adenosine agonists. Methods: Isolated rabbit cardiomyocytes were preconditioned with 10 min of ischaemic preincubation, followed by a 30 min postincubation before the final sustained ischaemic period. The protein kinase C inhibitor calphostin C or the adenosine receptor antagonists 8-sulphophenyltheophylline (SPT), BW 1433U, and 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) were added either during the preincubation or into the final ischaemic pellet. Adenosine deaminase (10 U·ml-1) was added during ischaemic preincubation. Rates of contracture and extent of injury were determined by sequential sampling and assessment of trypan blue permeability following 85 mOsM swelling. Results: Myocytes were preconditioned by a 10 min in vitro ischaemic preincubation. Preincubation with 100 μM SPT or with adenosine deaminase, or addition of 200 nM calphostin C into the final ischaemic pellet did not alter rates of rigor contracture but nearly abolished protection. A significant degree of protection was maintained following ischaemic preincubation with the highly selective adenosine A1 receptor blocker DPCPX (10 μM), while the A1/A3 antagonist BW 1433U (1 μM) severely limited protection. SPT and BW 1433U added only into the final ischaemic pellet of preconditioned cells significantly blocked protection, while protection was maintained in the presence of DPCPX. Conclusions: Ischaemic preconditioning of cardiomyocytes is blocked by adenosine receptor antagonists known to bind to A3 receptors but not by DPCPX which has high affinity for A1 receptors, but little affinity for A3 receptors. Maintenance of protection during the final ischaemic phase has a similar receptor specificity. Blockade of protein kinase C activity abolishes protection. Ischaemic and metabolic preconditioning in vitro appear to occur through similar pathways.