34 research outputs found
Relationship Between Alterations in Uterine Blood Flow and the Handling of Glucose by Fetus and Placenta
Placental uptake and transport of the neutral non metabolizable amino acid, aminocyclopentane-1-carboxylic acid (ACP), in an ovine model of FGR
Placental uptake and transport of the neutral non metabolizable amino acid, aminocyclopentane-1-carboxylic acid (ACP), in an ovine model of FGR
Metabolic Alterations in the Fetal Hepatic and Umbilical Circulations during Glucocorticoid-Induced Parturition in Sheep
Validation of transit-time flowmetry for chronic measurements of regional blood flow in resting and exercising rats
The objective of the present study was to validate the transit-time technique for long-term measurements of iliac and renal blood flow in rats. Flow measured with ultrasonic probes was confirmed ex vivo using excised arteries perfused at varying flow rates. An implanted 1-mm probe reproduced with accuracy different patterns of flow relative to pressure in freely moving rats and accurately quantitated the resting iliac flow value (on average 10.43 ± 0.99 ml/min or 2.78 ± 0.3 ml min-1 100 g body weight-1). The measurements were stable over an experimental period of one week but were affected by probe size (resting flows were underestimated by 57% with a 2-mm probe when compared with a 1-mm probe) and by anesthesia (in the same rats, iliac flow was reduced by 50-60% when compared to the conscious state). Instantaneous changes of iliac and renal flow during exercise and recovery were accurately measured by the transit-time technique. Iliac flow increased instantaneously at the beginning of mild exercise (from 12.03 ± 1.06 to 25.55 ± 3.89 ml/min at 15 s) and showed a smaller increase when exercise intensity increased further, reaching a plateau of 38.43 ± 1.92 ml/min at the 4th min of moderate exercise intensity. In contrast, exercise-induced reduction of renal flow was smaller and slower, with 18% and 25% decreases at mild and moderate exercise intensities. Our data indicate that transit-time flowmetry is a reliable method for long-term and continuous measurements of regional blood flow at rest and can be used to quantitate the dynamic flow changes that characterize exercise and recover