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203 records · Page 12Linked to original sources
PubMed1983

The molluscan neurosecretory peptide FMRFamide: comparative pharmacology and relationship to the enkephalins.

The molluscan neuropeptide FMRFamide (Phe-Met-Arg-Phe-NH2) has diverse actions on excitable tissues of molluscs, including hearts, noncardiac muscles, complex organs, and neurons. The intracellular transducing mechanisms are also diverse and are not readily correlated with particular responses. FMRFamide increases cyclic AMP levels concomitant with both cardioexcitation and inhibition, but not with muscle contraction. In the same tissues, the effects of 5-hydroxytryptamine are dissimilar and are always accompanied by a cyclic AMP increase. FMRFamide and acetylcholine cause similar tonic contractions of the Busycon radula protractor muscle and identical catch contractures of the mytilid anterior byssus retractor muscle, but the ionic basis of excitation and the sources of activator calcium for contraction are not the same for the two agonists. A comparative study of structure-activity relations showed that FMRFamide receptors are heterogeneous. Helix aspersa ganglia contain no FMRFamide, but a close analog occurs and has been tentatively identified. Evidence supporting a proposed homology between FMRFamide-like and opioid peptides is summarized. The effects of the amphiactive heptapeptide Tyr-Gly-Gly-Phe-Met-Arg-Phe-NH2 on the venus clam rectum support this hypothesis.

Acetylcholine↗
PubMed1982

Structure of the thick filaments in molluscan adductor muscle.

Molluscan adductor muscles are in general of two kinds--a slow-acting smooth muscle, which after contraction can go into a catch state, in which tension is maintained for many hours with a small turnover of ATP, and a quicker-acting muscle, usually to some extent striated, which has not the catch property in marked degree, if at all. The thick filaments of both kinds of adductors contain myosin and paramyosin. Those from catch muscles are noteworthy for their high paramyosin content(up to about 90% by weight), which may be correlated with their great length and diameter. The paramyosin forms a core with a surface layer of myosin. Recently, we have shown that the paramyosin core of catch muscles resembles a single crystal in its molecular arrangement, although the degree of regularity varies from one filament to another. The evidence is from electron microscopy both of individual filaments and of pieces of whole muscle embedded and sectioned. Individual negatively stained filaments change greatly in appearance when rotated round their long axes, in a way not compatible with a helical structure. A three-dimensional reconstruction of the filament from micrographs of a rotated filament confirms this. Transverse sections of smooth adductor muscles show no internal features within the thick filaments when viewed accurately along the filament axis. On tilting striations appear on the filaments that may be correlated with the planes of the Bear-Selby net. They are a general feature of the filaments and have been seen in the smooth adductors of P. maximus, O. edulis, Crassostrea gigas, M. mercenaria, of the anterior byssus retractor of M. edulis and in the red (obliquely striated) adductor of M. mercenaria. The arrangement of the myosin on the paramyosin core is not known.

Animals↗
PubMed1994

A myomodulin-CARP-related peptide isolated from a polychaete annelid, Perinereis vancaurica.

Myomodulin-CARP-family peptides have been isolated only from molluscs. In the present study, a heptapeptide, Ala-Met-Gly-Met-Leu-Arg-Met-NH2, termed Pev-myomodulin, was isolated from a polychaete annelid, Perinereis vancaurica using the esophagus of the animal as the bioassay system. The sequence of the annelid peptide is highly homologous with those of the myomodulin-CARP-family peptides found in molluscs. The annelid peptide is regarded as a member of the myomodulin-CARP family, though all the molluscan peptides have a Leu-NH2 at their C-termini. The annelid peptide showed a potnet contractile action on the esophagus of the annelid. The peptide may be an excitatory neuromediator involved in the regulation of the esophagus. Among various myomodulin-CARP-family peptides and their analogues, the annelid peptide showed the most potent contractile action on the esophagus. Replacement of the C-terminal Met-NH2 of the annelid peptide with a Leu-NH2 decreased its contractile potency, while replacement of the C-terminal Leu-NH2 of myomodulin and CARP with a Met-NH2 increased their potency. The C-terminal Met-NH2 of the annelid peptide seems to be important, but not essential, for exhibiting its contractile activity on the esophagus. On the anterior byssus retractor muscle of the bivalve mollusc Mytilus edulis, the annelid peptide showed catch-relaxing and contraction-modulating effects qualitatively similar to those of the authentic peptide CARP, though the annelid peptide was less potent than CARP.

Amino Acid Sequence↗
PubMed1995

Wresting the muscle from mussel beards: research and applications.

Marine and zebra mussels secrete byssal beards to attach themselves opportunistically to hard surfaces in their environment. By doing this, they naturally earn a reputation as fouling pests. The protein precursors of byssus in mussels are being investigated in the hope not only of discovering specific measures against these marine foulers, but also to gain some insights into the technically challenging task of engineering adhesive bonds underwater. Although byssal proteins are all part of the bearded glue that bonds them to a surface, they can be subdivided into three types depending on the function that they serve in byssal threads: (1) fibrous proteins form the load-bearing cables in the core of the threads, (2) cuticular proteins form a protective coat around the cables, and (3) adhesive proteins connect the cables to a foreign surface. A flaw in any one of these will undermine a mussel's ability to attach. The fibrous proteins can be collagenous, silk-like, elastic, or any combination of these. Covering these are the cuticular proteins, which are distinguished by their surface coupling properties, tandemly repeated primary sequence, and their high content of lysine and the exotic amino acid 3,4-dihydroxyphenyl-L-alanine (DOPA). The adhesive proteins are of low molecular weight, contain DOPA, and assemble to form microcellular solids (foams). Several of these proteins are already attracting biotechnological attention as cell and tissue attachment factors, anticorrosives, and metal-sequestering reagents.

Adhesives↗
PubMed1998

Antifouling activity of Indian marine invertebrates against the green mussel Perna viridis L.

Thirty-one species of marine invertebrates collected from the Indian Coast, belonging to six phyla (Porifera, Coelenterata, Annelida, Mollusca, Echinodermata, and Eurochordata) were tested for antifouling activity against the green mussel Perna viridis L. The repulsive action of the foot and production of byssus threads by green mussels were used for assaying the above activity. Subergorgia suberosa, Sinularia numerosa, Sinularia compressa, Cladiella pachyclados (phylum Coelenterata), Haliclona sp. (phylum Porifera), and Planaxis sulcatus (phylum Mollusca) have shown to be potential sources of antifoulants.

Journal Article↗