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Cell structure - Cytoskeleton - Actin - The Actin-Myosin-System in the Slime Mold Physarum polycephalum
The Actin-Myosin-System in the Slime Mold Physarum polycephalum
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| Description |
This huge mass of moving protoplasm is a single multinucleated cell, or plasmodium as it is called, of the slime mold Physarum. It is shown moving at many times the real speed using time lapse cinematography. Actin and myosin are involved in cytoplasmic streaming and locomotion of this giant amoeba.
Suspended plasmodia of Physarum show rhythmic contractions and clearly show that this non-muscle cell can produce mechanical force. The physiology and biochemistry of actin and myosin have been extensively studied in Physarum.
Here purified Physarum actin is mixed with myosin. The product of the reaction, acto-myosin, makes the mixture go turbid. Shortly after the addition of ATP the acto-myosin contracts down to a single mass which continues to shrink further. This phenomenon was first demonstrated using acto-myosin isolated from rabbit skeletal muscle and has been extensively studied as an in vitro model of muscle contraction. Can we expect the energy released by Physarum actin in this in vitro model system to be equivalent to that released in muscle contraction? To check this viscous actomyosin was pulled out into a solution of low salt concentration to obtain a gelled strand. On addition of ATP the strand contracts, and can even be used to lift a weight.
Duration: 01:57 min
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Sources
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Where there is Life, there is Motion - Function of Microtubules. OKADA, Kazuo. Col., com. engl., 270 m, 24 1/2 min.
IWF, Göttingen: W 1975
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For further films please search the IWF media catalogue for "cell biology".
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