. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ANAEROBIC METABOLISM OF RADULA MUSCLES 281 100. 80. 0) £ 60 J g I 40 - 2? 20 .. 10 15 mm FIGURE 1. Changes in contractile force for electrically stimulated isotonic contractions of isolated radula protractor muscles from Busycon contrarium versus time. Units are percent change of initial force. Points represent means ± 1 SD, n = 5. min of contractile activity (Fig. 2). Aspartate levels in the muscle declined during contractile activity, with the bulk of the change taking place in the first 5 min (Fig. 2). Succinate and malat
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ANAEROBIC METABOLISM OF RADULA MUSCLES 281 100. 80. 0) £ 60 J g I 40 - 2? 20 .. 10 15 mm FIGURE 1. Changes in contractile force for electrically stimulated isotonic contractions of isolated radula protractor muscles from Busycon contrarium versus time. Units are percent change of initial force. Points represent means ± 1 SD, n = 5. min of contractile activity (Fig. 2). Aspartate levels in the muscle declined during contractile activity, with the bulk of the change taking place in the first 5 min (Fig. 2). Succinate and malate levels in muscles stimulated for 15 min were less than )umoles-g wet wlT1. After min of stimulation, pyruvate levels in the muscle increased dramatically (Fig. 3). Strombine was not a major glycolytic end product, as this compound accu- mulated to levels approaching only 1 /zmole-g wet wt"1 (Fig. 3). In contrast, octopine accumulated linearly during the experiment (Fig. 3, Table II). The sum of octopine, free arginine, and arginine phosphate levels was constant (Table II), indicating no net change in the total arginine pool in the tissue. Alanopine showed the highest accumulation of all the opines, but formation did not begin immediately as this com- pound was not detectable in the first min of stimulation (Fig. 3). D-lactate was the predominant end product formed in the muscle, exhibiting a dramatic increase during the later periods of contraction (Fig. 3). Octopine, alanopine, and strombine were not released into the medium by the muscle preparations. In contrast, a significant amount of D-lactate was found in the TABLE II Total arginine pool (arginine phosphate, arginine. octopine. and total arginine) for neutralized perchloric- acid extracts ofisotonically contracting radula protractor muscles isolated from Busycon contrarium Metabolite Time (min) Free arginine Arginine phosphate Octopine Total 0 ± ± ± .29 ±
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
