28 research outputs found
Phenobarbital Specifically Increases the Hepatocellular Uptake of Sulfobromophthalein-Glutathione
No full textDynamics of a metabolic system: what single-action agents reveal about acid secretion
No full text A simple single-state nonlinear mathematical model of an open metabolic system is shown to be an adequate representation of acid secretion in frog gastric mucosa. The parameters of the elemental model were estimated from data, and subsystems of augmented models were established for histamine, a nonconservative stimulus acting via binding to receptors, and for two inhibitors of acid secretion. The latter included metiamide, a nonconservative histamine antagonist, which affects the formation of acid by competitive binding to the histamine receptors, and nitrite, a conservative inhibitor, which affects the rate of acid translocation. For parameter estimation, two data sets were analyzed by a nonlinear least-squares procedure: a dynamic (time dependent) set consisting of individual acid secretion rate curves and an integral (time independent) set consisting of the curves of acid secreted and suppressed above or below baseline, respectively, as functions of agent exposure. Because the model is instrumental in the estimation of parameters of subsystems that are not accessible through direct observation, it can serve as a research tool in the investigation of the mechanism of gastric acid secretion under a variety of experimental conditions. </jats:p
Conservative and nonconservative inhibitors of gastric acid secretion
No full text Inhibitors of the initial step (H2-antagonist) and of the final step (thiocyanate, SCN-; and nitrite, NO2-) were used to study the dynamics of acid secretion in isolated frog gastric mucosa. Tissues were mounted in flow-through chambers, and the acid secretion rate (SR) was recorded on a pH-stat microprocessor. Continuous presence of H2-antagonist decreases the SR to a lower steady state, and on removal the SR returns to basal SR, causing a net loss of acid, the nonconservative effect. The amount of lost acid is a unique function of exposure, thus, independent of the patterns (pulses or steps) of inhibition. In contrast, continuous presence of SCN- or NO2- (below 3 mM) results in an undershoot in SR with a return to basal SR, whereas at higher concentrations there is no return. Removal of these inhibitors causes an overshoot in SR with return to basal SR. The rebound acid is equal to acid suppressed by NO2- and low concentration of SCN-, resulting in no net loss of acid, the conservative effect, whereas at high concentrations of SCN- there is an apparent loss of acid. In maximally secreting tissue the overshoot of SR is not observed. However, the acid is not lost, merely delayed. In resting tissue NO2- also merely delays the exit of the acid produced in response to forskolin. The rebound acid is proposed to reside in a sequestered "acid" pool that is stable for at least 120 min. Results with NO2- and SCN- suggest an effect on a saturable exit enzyme, possibly the K+-H+-ATPase. </jats:p
Invariant relation between total acid secretion and secretagogue exposure: secretory dynamics in bullfrog
No full text Using a continuous recording of acid secretion in frog gastric mucosa by pH-stat interfaced with a microcomputer, the pattern of secretion rate was studied under variable concentrations and durations of stimulation by histamine and forskolin. This tissue can respond with only a limited range of secretory rates. Larger concentrations and/or longer durations of stimulation may result in a secretion rate pattern prolonged far beyond the duration of stimulation. Although for the concentration-response curve the steady-state or peak acid secretion varies with the duration of stimulation, total acid secreted as a function of exposure to stimulator (time integral of the stimulatory pattern) is independent of the stimulatory pattern. </jats:p
A model eliciting transient responses
No full text A simple parametrically controlled chemical transformation scheme is used to exemplify a model with transient response to sustained stimulation. More complicated schemes are also discussed. Analyses of three experimental examples are given: short-circuit current changes in toad bladder exposed to adenosine 3',5'-cyclic monophosphate (cAMP) stimulation; histamine secretion in acetylcholine-stimulated frog gastric mucosa; and cAMP dynamics, expressed in terms of adenylate cyclase dynamics, in histamine-stimulated frog gastric mucosa. The model responds primarily to the changes of the stimulator level, although it is not a model with derivative control. </jats:p
Fast Adaptive Controllers.
No full textAvailable from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi
The Hepatocellular Transport of Sulfobromophthalein-Glutathione by Clofibrate Treated, Perfused Rat-Liver
No full textThe hypolipidemic drug clofibrate is known to affect the hepatic transport of various organic anions including bilirubin, fatty acids and sulfobromophthalein. Changes in the rate of metabolism and/or intracellular transport have been claimed responsible for the effect. To evaluate these possibilities, the transport of sulfobromophthalein-glutathione, a model compound that does not require metabolism for biliary excretion, was studied in perfused livers isolated from clofibrate-treated and control rats. Cytosolic fatty acid binding protein and glutathione S-transferase activity were also measured. Clofibrate treatment significantly increased liver weight; as a result glutathione S-transferase activity (toward 1-chloro-2,4-dinitrobenzene) fell if expressed per gram of liver (4560±420 (SE) vs 7010±260 nmoles/min for clofibrate treated and controls respectively, p0.5). Irrespective of how it was expressed fatty acid binding protein was significantly increased by the drug treatment. Steady state sulfobromophthalein-glutathione removal velocity was saturble with increasing concentrations of sulfobromophthalein-glutathione in both control and clofibrate-treated livers. Steady state extraction ratio, as well as Vmax and Km for removal, did not differ between the two groups. In keeping with other observations, these data collectively indicate that the hepatic steady state removal of nonmetabolized compounds is not affected by clofibrate. Because the concomitant decrease in glutathione S-transferase activity only reflects an opposite change in liver weight, it remains to be determined whether clofibrate alters the hepatic transport of sulfobromophthalein and other compounds that are conjugated with glutathione solely by changing their rate of metabolis
A Study of the scenology of Bahia from Núcleo Afro-brasileiro de Teatro de Alagoinhas - NATA
No full textThe dissertative Padê, presented in the now, seeks to investigate the black candomblé theater of the Núcleo Afro-brasileiro de Teatro de Alagoinhas – NATA (1998-2019), through the analysis of its last four shows - Siré Obá - A Festa do Rei; Ogum - Deus e Homem; Exu - A Boca do Universo and Oxum. It references the Teatro Experimental do Negro – TEN (1944- 1961), Bando de Teatro Olodum – 1990, Companhia dos Comuns (2001) and Grupo de Teatro Abdias Nascimento – CAN (2002), which are references for black theaters in Brazil and for the poetic work of NATA. Having Oral History os its center methodology, this qualitative and historical research, with an exploratory-descriptive approach, considers an analysis from the inside out. In order to contextualize the reader, the 20th century is pointed out as a turning point in the perspective of an engaged/political black theater, and of movements that contribute to promote resistance outside the scene, such as the Frente Negra Brasileira – FNB (1931-1937) and the Fórum Nacional de Performance Negra – FPN (2005). Having this as a principle, it is aimed to point out the negrocenic presence in the counter flow of the arts in the western canon, considering the historical construction and the African and/or Afro-Brazilian ancestry in the poetic and aesthetic scene of the theatrical making, understanding the black bodies, the relation between art and politics, the socio-historical confrontations, and the fight for visibility and space, reflecting on the ethno-racial identities in the subversion of the logic in the spaces of power.O Padê dissertativo procura investigar o teatro negro de candomblé do Núcleo Afro-brasileiro de Teatro de Alagoinhas — NATA (1998 – 2019), através da análise de seus quatro últimos espetáculos: Siré Obá — A Festa do Rei; Ogum — Deus e Homem; Exu — A Boca do Universo e Oxum. Reverenciando o Teatro Experimental do Negro — TEN (1944 – 1961), Bando de Teatro Olodum – 1990, Companhia dos Comuns (2001) e Grupo de Teatro Abdias Nascimento
— CAN (2002), referências para os teatros negros no Brasil e para o fazer poético do NATA. Tendo como metodologia central a História Oral, a pesquisa de natureza qualitativa, cunho histórico e percurso exploratório-descritivo, pondera uma análise de dentro para fora. Visando contextualizar o leitor, aponta-se o século XX como chave de virada na perspectiva de um teatro negro engajado/político e de movimentos que contribuem para fomentar resistência fora de cena, como a Frente Negra Brasileira — FNB (1931 – 1937) e, na atualidade, o Fórum Nacional de Performance Negra — FPN (2005). Tendo isso por princípio, objetiva-se apontar a presença negrocênica no contra fluxo das artes no cânone ocidental. Considerando a construção histórica e a ancestralidade africana e/ou afro-brasileira na cena poética do fazer teatral. Compreendendo os corpos negros, a relação entre arte e política, os enfrentamentos, sócio históricos, e a luta por visibilidade e espaço. Refletindo sobre as identidades étnico-raciais na subversão da lógica nos espaços de poder
