Control of circulatory function in altered gravitational fields.
Explore the source record for details and available documents.
Capillaries↗
Biomedical subjects
G A Breit
Publications and source records attributed to G A Breit.
Four window differential capillary velocimetry.
A video red blood cell velocimeter was implemented with four photometric windows in such a fashion that the upstream and downstream signals are the difference between spatially separated window pairs. The performance of this system was compared with that of a conventional dual window photometric video velocimeter. Tests were made with artificial patterns of red blood cells that simulated long trains of contiguous cells, or large plasma gaps. It was found that the four window system produces a correlogram that is better suited for delay to maximum cross-correlation detection. Similarly, when the responses of the two methods were compared in terms of ability to detect changes of velocity, the time constant for a test step velocity change was found to be 1.2 +/- 0.7 sec for the four window system vs 2.3 +/- 0.6 sec for the two window system. It is concluded that this modification of the capillary red blood cell velocimetry methodology is better suited for detecting the spontaneous flow variations due to vasomotion.
Blood Flow Velocity↗
Effects of hemodilution on skin microcirculation.
Red blood cell (RBC) velocity, capillary hematocrit (Hctcap), RBC flux, and arteriolar diameter were studied in the subcutaneous connective tissue of the Syrian hamster skinfold window preparation during successive normovolemic hemodilutions with 6% solutions of Dextran 70. The experiments were carried out in the unanesthetized animal. Heart rate (HR), mean systemic arterial pressure (Psys), and systemic hematocrit (Hctsys) were monitored throughout the procedure to ensure that normovolemia was maintained and hemodilution caused no adverse effects. The changes of RBC flux in the hemodiluted state, up to 50% hemodilution (Hctsys = 25% +/- 4), were not statistically significant when compared with control (t test, P less than 0.5). At this Hctsys, capillary RBC velocity increased by 60% and Hctcap decreased by 30%. Both of these changes were statistically significant relative to control. The arteriolar diameter did not change significantly during the reduction of Hctsys. The animals were studied during subsequent days to determine the chronic effects of hemodilution. Hctsys increased by approximately 12% per day after the experiment, and the systemic parameters returned to the prehemodiluted state in direct proportion to the reestablishment of the Hctsys.
Animals↗