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Perfusion Model (perfusion + model)
Selected AbstractsTransport of Benzo[,]pyrene in the Dually Perfused Human Placenta Perfusion Model: Effect of Albumin in the Perfusion MediumBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 3 2009Line Mathiesen Foetal exposure to this substance is highly relevant but is difficult to estimate. The human placenta is unique compared to other species; since it is available without major ethical obstacles, we have used the human placenta perfusion model to study transport from mother to foetus. Placentas were donated after births at Rigshospitalet in Copenhagen from pregnant mothers who signed an informed consent. BaP is lipophilic and studies using cell culture medium in 6-hr placenta perfusions showed minimal transport through the placenta. To increase the solubility of BaP in perfusion medium and to increase physiological relevance, perfusions were also performed with albumin added to the perfusion medium [2 and 30 mg/ml bovine serum albumin (BSA) and 30 mg/ml human serum albumin (HSA)]. The addition of albumin resulted in increased transfer of BaP from maternal to foetal reservoirs. The transfer was even higher in the presence of an HSA formulation containing acetyltryptophanate and caprylate, resulting in a foetal,maternal concentration (FM) ratio of 0.71 ± 0.10 after 3 hr and 0.78 ± 0.11 after 6 hr, whereas the FM ratio in perfusions without albumin was only 0.05 ± 0.03 after 6 hr of perfusion. Less BaP accumulated in placental tissue in perfusions with added albumin. This shows that transplacental transport of the pro-carcinogenic substance BaP occurs, and emphasizes the importance of adding physiological concentrations of albumin when studying the transport of lipophilic substances. [source] Perfusion MR imaging with pulsed arterial spin-labeling: Basic principles and applications in functional brain imagingCONCEPTS IN MAGNETIC RESONANCE, Issue 5 2002Yihong Yang Abstract Basic principles of the arterial spin-labeling perfusion MRI are described, with focus on a brain perfusion model with pulsed labeling. A multislice perfusion imaging sequence with adiabatic inversion and spiral scanning is illustrated as an example. The mechanism of the perfusion measurement, the quantification of cerebral blood flow, and the suppression of potential artifacts are discussed. Applications of the perfusion imaging in brain activation studies, including simultaneous detection of blood flow and blood oxygenation, are demonstrated. Important issues associated with the applications such as sensitivity, quantification, and temporal resolution are discussed. © 2002 Wiley Periodicals, Inc. Concepts Magn Reson 14: 347,357, 2002 [source] Quantification of myoglobin deoxygenation and intracellular partial pressure of O2 during muscle contraction during haemoglobin-free medium perfusionEXPERIMENTAL PHYSIOLOGY, Issue 5 2010Hisashi Takakura Although the O2 gradient regulates O2 flux from the capillary into the myocyte to meet the energy demands of contracting muscle, intracellular O2 dynamics during muscle contraction remain unclear. Our hindlimb perfusion model allows the determination of intracellular myoglobin (Mb) saturation () and intracellular oxygen tension of myoglobin () in contracting muscle using near infrared spectroscopy (NIRS). The hindlimb of male Wistar rats was perfused from the abdominal aorta with a well-oxygenated haemoglobin-free Krebs,Henseleit buffer. The deoxygenated Mb (,[deoxy-Mb]) signal was monitored by NIRS. Based on the value of ,[deoxy-Mb],,,and,,were calculated, and the time course was evaluated by an exponential function model. Both,,and,,started to decrease immediately after the onset of contraction. The steady-state values of,,and,,progressively decreased with relative work intensity or muscle oxygen consumption. At the maximal twitch rate,,,and,,were 49% and 2.4 mmHg, respectively. Moreover, the rate of release of O2 from Mb at the onset of contraction increased with muscle oxygen consumption. These results suggest that at the onset of muscle contraction, Mb supplies O2 during the steep decline in,, which expands the O2 gradient to increase the O2 flux to meet the increased energy demands. [source] Simvastatin effects on portal-systemic collaterals of portal hypertensive ratsJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 8 2010Hui-Chun Huang Abstract Background and Aim:, Portal-systemic collateral vascular resistance and vasoconstrictor responsiveness are crucial in portal hypertension and variceal bleeding control. Statins enhance vasodilators production, but their influence on collaterals is unknown. This study aimed to survey the effect of simvastatin on collaterals. Methods:, Partially portal vein-ligated rats received oral simvastatin (20 mg/kg/day) or distilled water from ,2 to +7 day of ligation. After hemodynamic measurements on the eighth postoperative day, baseline perfusion pressure (i.e. an index of collateral vascular resistance) and arginine vasopressin (AVP, 0.1 nM,0.1 µM) responsiveness were evaluated with an in situ perfusion model for collateral vascular beds. RT-PCR of endothelial NO synthase (eNOS), inducible NOS (iNOS), cyclooxygenase-1 (COX-1), COX-2, thromboxane A2 synthase (TXA2 -S) and prostacyclin synthase genes was performed in parallel groups for splenorenal shunt (SRS), the most prominent intra-abdominal collateral vessel. To determine the acute effects of simvastatin, collateral AVP response was assessed with vehicle or simvastatin. SRS RT-PCR of eNOS, iNOS, COX-1, COX-2 and TXA2 -S, and measurements of perfusate nitrite/nitrate, 6-keto-PGF1, and TXB2 levels were performed in parallel groups without AVP. Results:, Acute simvastatin administration enhanced SRS eNOS expression and elevated perfusate nitrite/nitrate and 6-keto-PGF1, concentrations. Chronic simvastatin treatment reduced baseline collateral vascular resistance and portal pressure and enhanced SRS eNOS, COX-2 and TXA2 -S mRNA expression. Neither acute nor chronic simvastatin administration influenced collateral AVP responsiveness. Conclusion:, Simvastatin reduces portal-systemic collateral vascular resistance and portal pressure in portal hypertensive rats. This may be related to the enhanced portal-systemic collateral vascular NO and prostacyclin activities. [source] Transport of Benzo[,]pyrene in the Dually Perfused Human Placenta Perfusion Model: Effect of Albumin in the Perfusion MediumBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 3 2009Line Mathiesen Foetal exposure to this substance is highly relevant but is difficult to estimate. The human placenta is unique compared to other species; since it is available without major ethical obstacles, we have used the human placenta perfusion model to study transport from mother to foetus. Placentas were donated after births at Rigshospitalet in Copenhagen from pregnant mothers who signed an informed consent. BaP is lipophilic and studies using cell culture medium in 6-hr placenta perfusions showed minimal transport through the placenta. To increase the solubility of BaP in perfusion medium and to increase physiological relevance, perfusions were also performed with albumin added to the perfusion medium [2 and 30 mg/ml bovine serum albumin (BSA) and 30 mg/ml human serum albumin (HSA)]. The addition of albumin resulted in increased transfer of BaP from maternal to foetal reservoirs. The transfer was even higher in the presence of an HSA formulation containing acetyltryptophanate and caprylate, resulting in a foetal,maternal concentration (FM) ratio of 0.71 ± 0.10 after 3 hr and 0.78 ± 0.11 after 6 hr, whereas the FM ratio in perfusions without albumin was only 0.05 ± 0.03 after 6 hr of perfusion. Less BaP accumulated in placental tissue in perfusions with added albumin. This shows that transplacental transport of the pro-carcinogenic substance BaP occurs, and emphasizes the importance of adding physiological concentrations of albumin when studying the transport of lipophilic substances. [source] | ||||||||||