Diss. (sammanfattning) Stockholm : Karolinska institutet, 2002. / Härtill 5 uppsatser.

Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 77-85).

Thesis (Ph. D.)--Cornell University, January, 2009. / Vita. Includes bibliographical references (leaves 126-137).

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

In an attempt to determine the mechanism by which the tripeptide l-prolyl-l-leucyl-glycine amide (PLG, MIF-I) exerts its antiparkinsonian effect, the action of this substance on various postsynaptic components of striatal dopaminergic nerves was studied. It was shown that injection of rats with MIF-I (1 mg/kg, IP×5, 24 hr intervals) did not alter tyrosine hydroxylase, dopa decarboxylase, choline acetyltransferase and glutamic acid decarboxylase activities in the striatum under the conditions tested. The activities of adenylate cyclase, dopamine-stimulated adenylate cyclase, and guanylate cyclase were not altered in vitro by various concentrations of MIF-I (0.1 to 1000 μM), although VIP and neurotensin had some effect. Also the rate of uptake of 3H-dopamine by rat striatal synaptosomes was unchanged, as was the binding of 3H-dopamine and 3H-spiperone to beef caudate membranes. This series of studies indicates that MIF-I does not act directly on the striatal dopamine postsynaptic receptor under the conditions tested, although it is possible that MIF-I could act indirectly at this or another site in vivo by releasing or activating some other factor.

G-proteins are heterotrimeric complexes composed of α, β, and τ subunits and are involved in coupling receptor and effector functions during signal transduction across plasma membranes. G-proteins Gs and Gi are stimulatory and inhibitory to the catalytic subunit of adenylyl cyclase, respectively. A chimeric G-protein α subunit cDNA was constructed from the complete 5' untranslated region of Gαs52 (the 52 kD α subunit of Gs), the first 356 codons of the rat Gαs52, and the last 36 codons and 428 bp of the 3' untranslated region of the rat Gai2 (the α subunit of Gi2) cDNA. Expression of the chimeric G-protein alpha subunit (Gαs/i(38)) causes a constitutive increase in adenylyl cyclase activity in three different fibroblast cell lines. In turn, the elevated cyclase activity leads to higher levels of basal cyclic AMP and protein kinase A activity. The effect of Gαs/i(38) on cyclase does not seem to be through an inhibiton of Gαi function, but instead appears to be the consequence of direct action on the catalytic subunit, resulting in both a decreased time required for maximal cyclase activation and a greater maximal activation as well. Such alterations are not noted in cells expressing exogenous, wild-type Gαs. This data is based primarily on reconstitution assays using cholate extracts from fibroblast Gαs/i(38) clones and membranes derived from the S49 murine T-cell lymphoma (cyc- variant). Endogenous G-protein steady-state changes were detected by immunoblot analysis, but do not appear to account for the observed phenotypic alterations in Gαs/i(38) expressing clones. Furthermore, the validity of the above findings is unequivocally demonstrated through the use of amethopterin-mediated amplification of the chimeric Gαs/i(38) gene transcript and the consequent activation of adenylyl cyclase.

No description available.

Heart disease is the leading cause of death in the United States. While many factors can contribute to heart disease, stress plays a significant role. To better understand the mechanisms underlying the impact of stress on cardiovascular function, the intent of this thesis is to focus on the adenylate cyclase (AC) family of isoforms as key mediators of stress hormone signaling. AC operates downstream of ß-adrenergic receptor signaling to produce cAMP as a second messenger. There are at least 9 AC isoforms, all of which have different regulatory properties, but it is not clear which of these isoforms are expressed in the developing heart. Thus, there is still much to be discovered. This project seeks to establish a baseline understanding of AC isoform-specific expression patterns in the developing heart to better comprehend the role of these isoforms in development, beginning in the embryonic period and extending into the postnatal and adult ages. To accomplish this, we extracted RNA from flash-frozen hearts at embryonic days 10.5 and 15.5 (e10.5 and e15.5) as well as postnatal days 9 (juvenile), 38 (pre-pubescent) and young adult (2-3 months). Subsequently, quantitative polymerase chain reaction (qPCR) was performed with isoform-specific primers. To verify the amplification, PCR products were run on ethidium bromide gels. Our initial results show that many isoforms are undetected at e10.5, but AC1-3 and AC6-9 were expressed from e15.5 onward. Only AC4 was robustly expressed at all ages, and AC2 and 8 were strongly upregulated during the embryonic period. Our results suggest that AC isoforms 2, 4, and 8 have an important developmental function from early in the embryonic period. Future studies will seek to test the AC isoforms at later postnatal and adult ages and localize AC expression in various areas of the heart.

Thesis (Ph. D.)--University of Missouri--Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 66-80). Also available on the Internet.

The mechanism by which nicotinamide adenine dinucleotide (NAD) stimulates the activity of adenylate cyclase (AC) in canine plasma membrane has been studied. Using [3 2P]-NAD, the activation by NAD was correlated with the radiolabeling of the stimulatory guanosine triphosphate (GTP) binding protein Gsa. Further characterization demonstrated that the modification occurred only in the presence of G-protein activators and that arginine residue(s) were modified by ADP-ribose by the action of a mono-ADP-ribosyltransferase. Inhibitors of the transferase blocked both the modification of Gsa and the activation of AC. Collectively, these studies suggest that ADP-ribosylation of Gsa by an endogenous mono-ADP-ribosyltransferase may regulate cardiac AC.