. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. YFAFPRQamide 10-7 M 1 mm Figure 11. Responses of isolated clam rectums to YFAFPRQamide in the presence of 5-hydroxytryptamine (5-HT). The preparations were first stimulated with 5-HT (arrow). When the effect was established (con- tracture with or without rhythmical activity), the peptide was added (arrowhead). *Recording off-scale; baseline adjusted. YFAFPRQamide was again more potent: it inhibited rhythmicity transiently at 10~9 M, and relaxed the tissue at 10 s M. These effects were also produced by AMS- FYFPRMamide. but a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. YFAFPRQamide 10-7 M 1 mm Figure 11. Responses of isolated clam rectums to YFAFPRQamide in the presence of 5-hydroxytryptamine (5-HT). The preparations were first stimulated with 5-HT (arrow). When the effect was established (con- tracture with or without rhythmical activity), the peptide was added (arrowhead). *Recording off-scale; baseline adjusted. YFAFPRQamide was again more potent: it inhibited rhythmicity transiently at 10~9 M, and relaxed the tissue at 10 s M. These effects were also produced by AMS- FYFPRMamide. but at doses about 3- to 10-fold higher (Fig. 13). Heart. The effects of the SCP-related peptides were tested on 42 isolated hearts. More than half of the prep- arations were either not affected (10 7-10 4 A/), or an effect appeared that could not be repeated. The rest of the hearts responded reliably to the SCPs. The threshold ac- tion was an inhibition of beat amplitude (threshold. 10 10~6 M). At higher doses, beat and tone increased tran- siently, and the heart was finally arrested, usually in dias- tole. Acceptable dose-response relationships were seen in only five or six experiments. Discussion We have isolated and sequenced three SCP-related pep- tides in the venerid clam Mercenaria mcrccnaria: 1AMS- FYFPRMamide, AMSFYFPRMamide. and YFAFPRQ- amide. The latter two peptides were also identified in the cockle Dinucanliwu mlniMi/ni But two quite different SCP-like sequences were found in the eastern oyster Crassostrea virginiai (Table II). The features of these bi- valve peptides are best evaluated with reference to an SCP- like sequence found in a mussel, Mylilns edulis (Fujisawa I 3x1 Cr9 M I 3x1 O'8 M I 3x10'9 M 3x1 0'7 M I 3x10'6 M AMSFYFPRMamide. 3x1 rr6 M YFAFPRQamide Figure 12. Dose-dependent effects of two clam SCPs on the isolated typhlosole of the clam intestine. Doses were delivered at the arrows or arrowheads. ct LI/.. 1993), as well as six sequences identified in vari
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
