Amoeboid Locomotion

Amoeboid Locomotion - Amoeboid Locomotion Including many...

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Amoeboid Locomotion Including many kinds of amoeboid organisms, not just Amoeba proteus (the one used in teaching labs). Including locomotion of white blood cells, and also structural cells of our body. Also including the mechanical forces by which amoebae and body cells crawl. And also including structure-creating functions of these cell forces ("traction") For this topic, you will be asked to use your computers to look at certain time lapse movie clips which I took and which my wife and I have posted on my departmental web site. For most of the clips we have provided two versions, one darker and one lighter overall. Use whichever one allows you to see more detail on your computer. We hope that the formats of these video clips will be compatible with your computers and software. If or when incompatibilities occur, then tell me and we will change the format or solve the problem some way. 1) In Amoeba proteus, cytoplasmic flow is the most dramatic aspect of the cell's locomotion. In fact, much of the research on them has been more about the cytoplasmic flow than anything else. Please look at the first video clip [or the lighter version of same clip ], and notice carefully the details of cytoplasmic flow in Amoeba proteus. Guess why the front end is called "the fountain zone". (forward flow up the center of the pseudopod, then "gelling" of the cytoplasm to form a hollow tube) [Evidence indicates that this "jelling" reflects polymerization of actin fibers] Can you find some examples where forward flow of liquid cytoplasm also occurs around the outside of the hollow cylinder of jelled cytoplasm? 2) In the next clip , notice whether a single amoeba cell can have more than one fountain zone at the same time. [ lighter version of same clip ] What eventually happens in all but one of these fountain zones? Notice that the shape of the rear of each amoebae consists of the shrinking remainders of protrusions that had been produced by several previously active fountain zones, that have now become inactive. When A. proteus "eats" ( = phagocytizes) some food organism, then the tip of its pseudopod changes shape from a convex bulge to a concave, cup-like shape, which surrounds and engulfs the food. next clip [ lighter version ] another engulfment sequence [ lighter version ] 3) INVENT SOME HYPOTHESES, about what forces move Amoebae forward. For example, one theory was that the gelled tube contracts, and that this squeezes the more liquid parts of the cytoplasm forward, with mechanically weak places therefore becoming the front(s). Such concepts were advocated by a Prof. Mast, who also believed that the same set of phenomena cause locomotion of white blood cells. A very different (almost the opposite) kind of theory was proposed by Prof. Bob Allen in the late 1950s. His idea was that interior cytoplasm gets pulled forward by its own contraction at the front end (in the fountain zone, itself). Can you invent some experiments to test these and other ideas? Perhaps by marking one part of a cell?
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This note was uploaded on 11/05/2011 for the course BIOL 446 taught by Professor Staff during the Fall '10 term at UNC.

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Amoeboid Locomotion - Amoeboid Locomotion Including many...

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