. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 1. Left: The toadfish Opsanus tau (Photo by A. Kuzirian). Center: Toadfish swimbladder; the red swimbladder muscle runs circiimferentntlh- around the white swimbladder (Photo by L. Nelson). Right: Molecular processes of muscle activation and relaxation (Drawing: T. Clark). behavior that it can't be used for another. Neither the red nor the white swimming muscle can physically produce high-frequency sounds because it can't relax fast enough. By contrast, at the low frequencies of steady swimming, the swimbladder muscle
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 1. Left: The toadfish Opsanus tau (Photo by A. Kuzirian). Center: Toadfish swimbladder; the red swimbladder muscle runs circiimferentntlh- around the white swimbladder (Photo by L. Nelson). Right: Molecular processes of muscle activation and relaxation (Drawing: T. Clark). behavior that it can't be used for another. Neither the red nor the white swimming muscle can physically produce high-frequency sounds because it can't relax fast enough. By contrast, at the low frequencies of steady swimming, the swimbladder muscle's extremely low mechanical power output and extremely high energetic cost make it unable to power locomotion (2). The challenge of studying the adaptations of the fastest vertebrate muscle is irresistible. My colleagues and 1 (3, 4) had already determined that the immense speed of the swimbladder is principally due to its extremely fast relaxation rate, which in turn is due to three specific adaptations: the swimbladder removes Ca2 + from the cytoplasm 50-fold faster than the red muscle does (Fig. 1, right: Step 4). swimbladder troponin C has a far faster Ca2 + off-rate than red muscle (Step 5), and swimbladder crossbridges have a 50-fold faster detachment rate constant than red muscle (Step 6). In our attempt to further dissect the molecular mechanisms responsible for the swimbladder's rapid clearing of Ca~ + , we ran into a snag in distinguishing the three competing mechanisms. One of these mechanisms is fast Ca2 + pumping by the sarcoplasmic reticulum (SR); but two other mechanisms—binding of Ca2 + to the soluble protein pan/albumin and binding to the SR-Ca2 + pumps themselves—may also make a very large contribution. Consider that when toadfish call with the swimbladder muscle, it is not a single twitch but a series of many contractions that is produced. When the muscle relaxes after a stimulus, the interval before the next stimulus (Vino s) is not long enough for all t
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
