Alligator Breath (2 of 3) (VIDEO)
Caption
Both gases and liquids are fluids and will obey the same physical principles under most biological conditions. Thus, to visualize unidirectional flow, we excised a lung of an American alligator and filled it with saline containing fluorescent microspheres (Invitrogen, Frederick, Md.). The saline was alternately pushed into and withdrawn from the lung using a syringe. We imaged the movement using a 2X objective, Olympus (Center Valley, Pa.,) IX70 Microscope, Olympus DP70 CCD camera (Center Valley, Pa.) at 60 frames second-1, and TRITC filter (543/22 Ex, 593/40 Em, 570LP Dichroic, Center Valley, Pa.,). In movies S1 and S2 the microspheres can be seen flowing through the cervical ventral bronchus (green bronchus of Fig. 1). In the cervical ventral bronchus most of the microspheres move in a cranial (head) to caudal (tail) direction (from the right side of the image toward the left) as fluid is injected into the lung (Movie S1) and when fluid is withdrawn (Movie S2). A few microspheres are no longer suspended in the fluid and are caught in lung tissue. These move at a slower speed and spread apart as the injection takes place and move closer together as fluid leaves the lung. The black line in the lower left visual field is a piece suture on the outside of the lung. This video relates to an article that appeared in the January 15, 2010, issue of Science, published by AAAS. The study, by Dr. C.G. Farmer at University of Utah in Salt Lake City, Utah, and colleagues, was titled, "Unidirectional Airflow in the Lungs of Alligators."
Credit
Video courtesy of C.G. Farmer
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