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

Univ., Diss.--Halle-Wittenberg, 1997.

Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 68-84).

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.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A guanilina e a uroguanilina foram recentemente descobertas, respectivamente, no intestino e na urina, (Currie et al., 1992; Hamra et al., 1993). Fazem parte da famÃlia de peptÃdeos que ativam a guanilato ciclase de membrana (GC-C), aumentando os nÃveis intracelulares de cGMP (Schulz et al., 1990). EstÃo presentes em diversos tecidos, como respiratÃrio, linfonodos, testÃculos, cÃrebro e medula adrenal (Field et a.l., 1978; Forte et al., 1988, 1989; Hamra et al., 1993; Schulz et al., 1992). Foi comprovado que adicionando uma lisina na porÃÃo N-terminal, obtÃm-se um anÃlogo mais estÃvel e potente que a guanilina. O objetivo desse estudo à pesquisar os efeitos renais de um novo anÃlogo, ser-thr-lys-guanilina em sistema de perfusÃo. Os rins foram perfundidos com a soluÃÃo de Krebs-Henseleit modificada com 6g% de albumina bovina. Os dados foram comparados atravÃs de teste t de Student e ANOVA, com significÃncia p<0,05. Na dose de 0,1 Âg/mL, esse peptÃdeo apresentou efeitos similares aos da uroguanilina, na dose de 0,5 Âg/mL, em todos os parÃmetros testados. Ambas causaram aumento na pressÃo de perfusÃo (PP: de 101,5Â3,7 para 111Â2,9mmHg; de 101,2Â2,6 para 113,4Â2,5mmHg), no fluxo urinÃrio (FU: de 0,158Â0,016 para 0,223Â0,01 mL.g-1.min-1; de 0,16Â0,016 para 0,226Â0,2mL.g-1.min-1) e diminuiÃÃo no transporte tubular total e proximal de sÃdio (%TNa+: de 0,774Â0,06 para 0,724Â0,035; de 0,735Â0,065 para 0,773Â0,084), potÃssio (%TK+: de 66,89Â2,77 para 47,29Â3,34; de 63,54Â3,82 para 42,54Â8,14) e cloreto (%TCl-: de 85,69Â1,19 para 73,59Â2,63). Esses resultados foram similares aos previamente descritos apÃs a administraÃÃo da toxina termo-estÃvel da Escherichia coli (STa), guanilina, uroguanilina e lys-guanilina no mesmo sistema (Lima et al., 1992; Fonteles et al., 1996 e 1998). A dose maior (1 Âg/mL) causou aÃÃo antidiurÃtica (FU: de 0,165Â0,004 para 0,111Â0,009mL.g-1.min-1) e nenhum efeito sobre o transporte de sÃdio, embora a diminuiÃÃo na reabsorÃÃo tubular de potÃssio (%TK+: de 72,29Â1,2 para 49,73Â6,75) e cloreto (%TCl-: de 85,96Â0,79 para 81,9Â1,47) continuassem presentes. Nesta dose, nÃo apenas bloqueou o efeito diurÃtico da uroguanilina, como continuou causando um efeito antidiurÃtico significativo (FU: de 0,168Â0,004 para 0,116Â0,006). No entanto, nÃo foi capaz de bloquear os efeitos natriurÃticos da uroguanilina (%TNa+: de 85,35Â2,55 para 79,92Â1,05). O mecanismo de aÃÃo renal preciso dos peptÃdeos da famÃlia das guanilinas ainda nÃo foi completamente esclarecido. Sabe-se que esses peptÃdeos se ligam aos receptores GC-C (Schulz et al., 1990), porÃm hà indÃcios de que existam outras vias de aÃÃo renal, independentes desse receptor. Hà ainda a possibilidade de que haja duas entidades agindo de modo antagÃnico no sistema. Talvez haja a necessidade de isolÃ-los. A descoberta dos peptÃdeos da famÃlia das guanilinas promoveu avanÃos significativos na compreensÃo da regulaÃÃo endÃgena dos transportes de Ãgua e eletrÃlitos. O completo esclarecimento do seu mecanismo de aÃÃo renal oferece perspectivas reais para o tratamento de doenÃas como a hipertensÃo arterial. / Guanylin and uroguanylin are members of a family of peptides that stimulates cGMP production in several organic tissues, as intestine, kidney, airway, linfonodes, testis, brain and adrenal medulla (Field et a.l., 1978; Forte et al., 1988, 1989; Hamra et al., 1993; Schulz et al., 1992). Their 15 amino acid structures have been identified from rat intestine and opossum urine, respectively (Currie et al., 1992; Hamra et al., 1993), and they seem to be the link between intestine and kidney functions in controling blood pressure, as the âintestinal natriuretic hormoneâ suggested by some authors (Carey, 1978; Lennane et al., 1975). It was demonstrated that a Lysine-1 analog of guanylin is a more potent natriuretic and kaliuretic peptide. The aim of this study was to evaluate the renal effects of a novel analog of guanylin: ser-thr-lys-guanylin. Its effects were examined using isolated perfused kidneys from Wistar rats. All experiments were preceded by a 30 minutes internal control period and an external control group (C), in which the kidneys were perfused only with Krebs-Henseleit solution containing 6g% of a previously dialysed bovine albumine serum. The data was analyzed by Student t-test and ANOVA. The level of significance was set at p<0,05. Ser-thr-lys-guanylin, at the lowest dose (0.1 Âg/mL) and uroguanylin (0.5Âg/mL) caused similar effects. Both groups were able to increase perfusion presure (PP: 101.5Â3.7 to 111Â2.9mmHg; 101.2Â2.6 to 113.4Â2.5 mmHg), urinary flow (UF: 0.158Â0.016 to 0.223Â0.019 mL.g-1.min-1; 0.16Â0.016 to 0.226Â0.2mL.g-1.min-1) and to decrease sodium (%TNa+: 0.774Â0.06 to 0.724Â0.035; 0.735Â0.065 to 0.773Â0.084), potassium (%TK+: 66.89Â2.77 to 47.29Â3.34; 63.54Â3.82 to 42.54Â8.14) and cloride (%TCl-: 85.69Â1.19 to 73.59Â2.63) tubular reabsorption. Similar effects were also found in response to the Escherichia coli heat-stable enterotoxin (STa), guanylin, uroguanylin and lys-guanylin in the same system (Lima et al., 1992; Fonteles et al., 1996 e 1998). However, a greater dose (1Âg/mL), not only caused signifcantly decrease in the urinary flow (UF: 0.165Â0.004 to 0.111Â0.009 mL.g-1.min-1), but was also able to block the diuretic effects of uroguanylin (UF: 0.168Â0.004 to 0.116Â0.006 mL.g-1.min-1), although it still decreased potassium (%TK+: 72.29Â1.2 to 49.73Â6.75) and cloride(%TCl-: 85.96Â0.79 to 81.9Â1.47) tubular reabsorption. The precise renal mecanism of action of this family of peptides has not yet been fully elucidated. Deletion of GC-C genes in transgenic mice reveals that intestinal fluid secretion responses to STa are completely lost (Schulz et al., 1997 & Mann et al., 1997), but the natriuretic responses to STa and uroguanylin are retained (Carrithers et al., 1999), suggesting that other receptors are envolved. There is a possibility that there are to peptides causing antagonic effects. Further isolation may be necessary. Further studies are required to elucidate the specific renal mechanism of action of this new peptide. The discovery of guanylin and its family has promoted significant advances in the understanding of endogenous control of salt, water and eletrolites. The study of its analogs in perfused rat kidneys could help in elucidating their specific renal mecanism of action and bring great perspectives in the control of blood pressure.

Adenylyl Cyclases (ACs) catalyze the formation of the key universal second messenger adenosine 3’, 5’-cyclic monophosphate (cAMP) from adenosine 5’- triphosphate. Cyclic AMP participates in several signal transduction pathways and is present in bacteria and higher and lower eukaryotes including higher plants. Previous studies in plants have shown a role for cAMP in signal transduction during e.g. the cell cycle, elongation of the pollen tube and stimulation of protein kinase activity. More recently cAMP has been shown to play a role in stress responses. Interestingly, cAMP has also been shown to regulate ion transport in plant cells. Here we used a similar strategy that led to the discovery of the first guanylyl cyclase in plants that was based on the alignment of conserved and functionally assigned amino acids in the catalytic centre of annotated nucleotide cyclases from lower and higher eukaryotes, to identify a novel candidate ACs in Arabidopsis (Arabidopsis thaliana K+ Uptake 5 and 7). ATKUP5 and 7 are homologous to K+ uptake permeases (KUPs) from bacteria and high-affinity K+ transporters (HAKs) from fungi. The AC activity was investigated by recombinantly expressing the ATKUP5 and 7 AC domain in vitro and by complementation of an E. coli AC mutant (cyaA). Furthermore, ATKUP5 was tested for its ability to functionally complement a yeast mutant deficient in Trk1 and Trk2 high affinity potassium uptake transporters. Site-mutagenesis in the AC domain was used to test the effect of both functions in each other. Furthermore, ATKUP5 was characterized electrophysiologically in HEK-293 cells to characterize the nature of this transporter. The localization of the ATKUP5 in Arabidopsis was examined using a Green Fluorescent Protein (GFP) fusion with the ATKUP5 to determine whether ATKUP5 is expressed at the plasma or tonoplast membrane. Arabiodpsis thaliana of the wild type, overexpressing ATKUP5 and atkup5 mutant lines were used to examine phenotypic differences.

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.