Search results for "kinetics"
showing 10 items of 2224 documents
Investigations of the dual contractile/relaxant properties showed by antioquine in rat aorta.
1993
1. In the present study we assessed the activity of antioquine, a bisbenzyltetrahydroisoquinoline alkaloid isolated from Pseudoxandra sclerocarpa, by examining its effects on the contractile activity of rat isolated aorta, specific binding of [3H]-(+)-cis-diltiazem, [3H]-nitrendipine and [3H]-prazosin to cerebral cortical membranes and the different molecular forms of cyclic nucleotide phosphodiesterases (PDE) isolated from bovine aorta. 2. Contractions in rat aorta induced by high concentrations of KCl (80 mM) and noradrenaline (1 microM) were inhibited by antioquine in a concentration-dependent manner (0.1 microM- 300 microM). The alkaloid appeared more potent against KCl-induced contract…
Pregnane X receptor and yin yang 1 contribute to the differential tissue expression and induction of CYP3A5 and CYP3A4.
2012
The hepato-intestinal induction of the detoxifying enzymes CYP3A4 and CYP3A5 by the xenosensing pregnane X receptor (PXR) constitutes a key adaptive response to oral drugs and dietary xenobiotics. In contrast to CYP3A4, CYP3A5 is additionally expressed in several, mostly steroidogenic organs, which creates potential for induction-driven disturbances of the steroid homeostasis. Using cell lines and mice transgenic for a CYP3A5 promoter we demonstrate that the CYP3A5 expression in these organs is non-inducible and independent from PXR. Instead, it is enabled by the loss of a suppressing yin yang 1 (YY1)-binding site from the CYP3A5 promoter which occurred in haplorrhine primates. This YY1 sit…
C1-Esterase-Inhibitor Treatment at Early Reperfusion of Hemorrhagic Shock Reduces Mesentery Leukocyte Adhesion and Rolling
2001
Objective: Complement activation probably plays a pathogenic role in multiple organ failure in shock. This study evaluates the effects of C1-esterase-inhibitor treatment on leukocyte-endothelial interaction in the mesenteric microcirculation in hemorrhagic shock. Methods: Rats underwent median laparotomy and exteriorization of an ileal loop for intravital microscopy of the mesenteric microcirculation. Volume controlled hemorrhagic shock was provoked by arterial blood withdrawal (2.5 mL/ 100 g body wt. for 60 minutes) followed by a 4-hour reperfusion period. C1-INH (100 IU/kg body wt. i.v.) or 0.9% NaCl i.v. were administered as a bolus at the beginning of reperfusion. Reperfusion time mimic…
Bioavailability and pharmacokinetic model for ritonavir in the rat.
2007
The aim of this study is to investigate in vivo the oral bioavailability of ritonavir and to evaluate the pharmacokinetic model that best describes the plasma concentration behavior after oral and intravenous administration. Male Wistar rats were intravenously administered at 3 mg dose of pure ritonavir and oral administered at 4.6 +/- 2.5 mg of diluted Norvir. Blood samples were taken by means of the jugular vein for a 24 h period of time. An analytical high-performance liquid chromatography (HPLC) technique was developed in order to quantify ritonavir plasma concentrations. A nonlinear modeling approach was used to estimate the pharmacokinetic parameters of interest. Results showed that a…
Early kinetics of integration of collagen-glycosaminoglycan regenerative scaffolds in a diabetic mouse model.
2013
Collagen-glycosaminoglycan scaffolds, originally designed to treat severe burns, are now commonly used in patients with complex wounds associated with diabetes mellitus. In this study, the authors investigated how the thickness of the scaffold would affect cellular integration with the diabetic host and whether this can be accelerated using subatmospheric pressure wound therapy devices.Collagen-glycosaminoglycan scaffolds, 500 to 2000-μm thick, were applied to dorsal wounds in genetically diabetic mice. In addition, 1000-μm collagen-glycosaminoglycan scaffolds with and without silicone were treated with a subatmospheric pressure device (-125 mmHg). On days 5 and 10, cellular and vascular in…
L-type calcium channel activity in human atrial myocytes as influenced by 5-HT.
1993
5-Hydroxytryptamine (10 mumol/l; 5-HT) exerted a positive inotropic effect associated with an increase in the Ca2+ current (ICa) in the human right atrium. For detailed analysis, L-type Ca2+ channel currents were recorded from cell-attached patches using 100 mmol/l Ba2+ as charge carrier. Ca2+ channel activity was identified, first, by burst-like inwardly directed currents and, second, by the appearance of long channel openings promoted by Bay K 8644 (1 mumol/l) upon repetitive depolarizations from -80 to 0 mV. The unitary conductance of the Ca2+ channel amounted to 25.8 pS. During superfusion with 5-HT, ensemble averaged (mean) current was enhanced by about 60%. The increase in mean curren…
Evidence that neuronally released vasoactive intestinal polypeptide inhibits the release of serotonin from enterochromaffin cells of the guinea pig s…
1991
Abstract. Isolated small intestinal segments of the guinea pig were arterially perfused and the release of serotonin (5-hydroxytryptamine) and 5-hydroxyindoleacetic acid into the portal venous effluent was determined by HPLC with electrochemical detection. Test substances were intra-arterially applied. The muscarine receptor agonist oxotremorine (1 μmol/l inhibited the release of 5-hydroxytryptamine by about 50%. In the presence of the neurotoxin tetrodotoxin, oxotremorine enhanced the release of 5-hydroxytryptamine by 145%, indicating that the inhibitory effect of oxotremorine was mediated by the release of a neurotransmitter. Exogenous vasoactive intestinal polypeptide ( 1-100 pmol/l inhi…
Effects of the flavonol quercetin on the bioavailability of simvastatin in pigs
2009
The influence of the dietary flavonol quercetin on the pharmacokinetics of the HMG-CoA reductase inhibitor simvastatin was investigated in pigs. Simvastatin (0.25mg/kg body weight) was orally administered to six pigs either without or with quercetin (10mg/kg). In addition, simvastatin was administered to three pigs that had received a diet supplemented with the flavonol over a period of 1 week. Daily quercetin intake was 10mg/kg in these animals. Co-ingestion of quercetin with the statin did not alter area under the concentration time curve (AUC(0-->infinity)), time to achieve maximum plasma concentration (t(max)) or half-life (t(1/2)) of simvastatin. However, there was a trend towards a re…
Kinematics and subpopulations' structure definition of blue fox (Alopex lagopus) sperm motility using the ISAS® V1 CASA system.
2013
Contents Over recent years, technological advances have brought innovation in assisted reproduction to the agriculture. Fox species are of great economical interest in some countries, but their semen characteristics have not been studied enough. To advance the knowledge of function of fox spermatozoa, five samples were obtained by masturbation, in the breeding season. Kinetic analysis was performed using ISAS® v1 system. Usual kinematic parameters (VCL, VSL, VAP, LIN, STR, WOB, ALH and BCF) were considered. To establish the standardization for the analysis of samples, the minimum number of cells to analyse and the minimum number of fields to capture were defined. In the second step, the pre…
Thymidylate synthases from Hymenolepis diminuta and regenerating rat liver: purification, properties, and inhibition by substrate and cofactor analog…
1995
Comparative studies of thymidylate synthases, isolated from the tapeworm, Hymenolepis diminuta, and regenerating liver of its host, rat, aimed at a possibility of specific inhibition of the helminthic enzyme, are presented. While similar in structure (dimers with monomer molecular masses of 33.7 kDa and 34.9 kDa, respectively) and parameters describing interactions with substrates and products, the tapeworm and rat enzymes differed in the dependences of reaction velocity on temperature (Arrhenius plots biphasic and linear, respectively). The tapeworm, compared with the host, enzyme was less sensitive to the competitive slow-binding inhibition by 5-fluoro-dUMP and its 2-thio congener, but eq…