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At least 55 records · Page 3Linked to original sources
PubMed2006

The catch state of mollusc catch muscle is established during activation: experiments on skinned fibre preparations of the anterior byssus retractor muscle of Mytilus edulis L. using the myosin inhibitors orthovanadate and blebbistatin.

Catch is a holding state of muscle where tension is maintained passively for long time periods in the absence of stimulation. The catch state becomes obvious after termination of activation; however, it is possible that catch linkages are already established during activation. To investigate this, skinned fibre bundles of the anterior byssus retractor muscle of Mytilus edulis were maximally activated with Ca(2+) and subsequently exposed to 10 mmol l(-1) orthovanadate (V(i)) or 5 mumol l(-1) blebbistatin to inhibit the force-generating myosin head cross-bridges. Repetitive stretches of about 0.1% fibre bundle length were applied to measure stiffness. Inhibitor application depressed force substantially but never resulted in a full relaxation. The remaining force was further decreased by moderate alkalization (change of pH from 6.7 to 7.4) or by cAMP. Furthermore, the stiffness/force ratio was higher during exposure to V(i) or blebbistatin than during partial Ca(2+) activation producing the same submaximal force. The increased stiffness/force ratio was abolished by moderate alkalization or cAMP. Finally, the stretch-induced delayed force increase (stretch activation) disappeared, and the force recovery following a quick release of the fibre length, was substantially reduced when the force was depressed by V(i) or blebbistatin. All these findings suggest that catch linkages are already established during maximal Ca(2+) activation. They seem to exhibit ratchet properties because they allow shortening and resist stretches. In isometric experiments a force decrease is needed to stress the catch linkages in the high resistance direction so that they contribute to force.

Animals↗
PubMed1996

Mechanical design of mussel byssus: material yield enhances attachment strength

The competitive dominance of mussels in the wave-swept rocky intertidal zone is in part due to their ability to maintain a secure attachment. Mussels are tethered to the substratum by a byssus composed of numerous extracellular, collagenous threads secreted by the foot. Each byssal thread has three serially arranged parts: a corrugated proximal region, a smooth distal region and an adhesive plaque. This study examines the material and structural properties of the byssal threads of three mussel species: Mytilus californianus, M. trossulus, and M. galloprovincialis. Tensile tests in general reveal similar material properties among species: the proximal region has a lower initial modulus, a lower ultimate stress and a higher ultimate strain than the distal region. The distal region also yields at a stress well below its ultimate value. In whole thread tests, the proximal region and adhesive plaque are common sites of structural failure and are closely matched in strength, while the distal region appears to be excessively strong. We propose that the high strength of the distal region is the byproduct of a material designed to yield and extend before structural failure occurs. Experimental and theoretical evidence is presented suggesting that thread yield and extensibility provide two important mechanisms for increasing the overall attachment strength of the mussel: (1) the reorientation of threads towards the direction of applied load, and (2) the 'recruitment' of more threads into tension and the consequent distribution of applied load over a larger cross-sectional area, thereby reducing the stress on each thread. This distal region yield behavior is most striking for M. californianus and may be a key to its success in extreme wave-swept environments.

Journal Article↗
PubMed1981

Dopamine receptor in anterior byssus retractor muscle of Mytilus edulis.

Effects of dopamine, N-methyl-, ethyl- and propyl-derivatives of dopamine, and alpha- and beta-adrenoceptor stimulants on catch contraction of anterior byssus retractor muscle of Mytilus edulis were tested. The test drugs except the beta-adrenoceptor stimulants relaxed catch contraction. Dopamine was most active and substitution of amino group in dopamine with ethyl and propyl decreased activity considerably. The concentration-curves of dopamine, its derivatives and norepinephrine shifted in parallel with application of haloperidol but were not influenced by the alpha- and beta-adrenoceptor antagonists. These results suggest that relaxation of catch contraction by catecholamines is mediated through a dopamine receptor. This muscle is considered to be suitable for a study of the dopamine receptor.

Animals↗
PubMed1982

Specific 3H-haloperidol binding to dopamine receptors in the anterior byssus retractor muscle of Mytilus edulis.

The anterior byssus retractor muscle (ABRM) of Mytilus edulis has specific dopamine receptors. We carried out a radioligand binding assay for dopamine receptors in ABRM using (3H)-haloperidol as the radioligand. High affinity binding of (3H)-haloperidol has been shown. Scatchard analysis showed a single component of binding with an apparent equilibrium constant (KD) of 1.6 nM and a maximal number of binding sites (Bmax) of 219 fmoles/mg protein. Some dopamine antagonists displaced 3 nM (3H)-haloperidol binding, and the IC50 and Ki-value of these drugs were calculated. Considering these results, this muscle is thought to be suitable for a study of the dopamine receptors.

Animals↗
PubMed1998

A major protein precursor of zebra mussel (Dreissena polymorpha) byssus: deduced sequence and significance.

The zebra mussel is a nonindigenous invader of North American lakes and rivers and one of the few freshwater bivalve molluscs having a byssus--a sclerotized organ used by the mussel for opportunistic attachment to hard surfaces. We have sequenced a foot-specific cDNA whose composite protein sequence was deduced from a series of overlapping but occasionally nonidentical cDNA fragments. The overall deduced sequence matches tryptic peptides from a major byssal precursor protein--Dreissena polymorpha foot protein 1 (Dpfp1). The calculated mass of Dpfp1 is 49 kDa; but this is known to be extensively hydroxylated and O-glycosylated during maturation. Purified native Dpfp1 analyzed using matrix-assisted laser-desorption ionization mass spectrometry with time-of-flight indicates that the protein occurs as at least two size variants with masses of 48.6 and 54.5 kDa. In all probability, the sequence variants reported in this study are related to the larger mass variant. Dpfp1 has a block copolymer-like structure defined by two consensus motifs that are sharply segregated into domains. The N-terminal side of Dpfp1 has 22 tandem repeats of a heptapeptide consensus (P-[V/E]-Y-P-[T/S/delta]-[K/Q]-X); the C-terminal side has 16 repeats of a tridecapeptide motif (K-P-G-P-Y-D-Y-D-G-P-Y-D-K). Both consensus repeats are unique, with some limited homology to other proteins functioning in tension: marine mussel adhesives, plant extensins, titin, and trematode eggshell precursors.

Amino Acid Sequence↗
PubMed2006

Interspecific comparison of the mechanical properties of mussel byssus.

Byssally tethered mussels are found in a variety of habitats, including rocky intertidal, salt marsh, subtidal, and hydrothermal vents. One key to the survival of mussels in these communities is a secure attachment, achieved by the production of byssal threads. Although many studies have detailed the unique biomechanical properties of byssal threads, only a few prevalent species have been examined. This study assesses the variation in the mechanical properties of byssus in a broad range of mussel species from diverse environments, including intertidal and subtidal Mytilus edulis, Modiolus modiolus, Geukensia demissa, Bathymodiolus thermophilus, and Dreissena polymorpha. A tensometer was used to measure quasi-static and dynamic mechanical properties of individual threads, and several aspects of morphology were quantified. The results indicate that thread mechanical properties vary among mussel species, and several novel properties were observed. For example, of the species examined, D. polymorpha threads were the strongest, stiffest, least resilient, and fastest to recover after partial deformation. Threads of M. modiolus were characterized by the presence of two distinct yield regions prior to tensile failure. This comparative study not only provides insight into the ecological limitations and evolution of mussels, but also suggests new models for the design of novel biomimetic polymers.

Adhesiveness↗
PubMed2000

Complete amino acid sequence of Mytilus anterior byssus retractor paramyosin and its putative phosphorylation site.

A cDNA encoding the full-length paramyosin molecule was cloned from the mussel Mytilus galloprovincialis, a species closely related to Mytilus edulis. It contained 3,497 nucleotides (nt), with 79 and 826 nt for the 5' and 3' non-coding regions, respectively. The coding region was composed of 2,592 nt for 864 amino acid residues, a size typical of paramyosin. While genomic DNA digests with either HindIII or PstI exhibited a single band when hybridized with a SacI fragment of paramyosin cDNA, the digests with either EcoRV or EcoRI showed two bands, suggesting that the mussel has at least two genes encoding paramyosin. The mRNAs encoding paramyosin were most abundant in muscle tissues from byssus retractor and adductor muscles. Only traces of paramyosin transcripts were found in the tissue of foot, gill, inner mantle, and outer mantle. The same phosphorylatable peptide previously reported for paramyosin from the bivalve Mercenaria mercenaria, Ser-Arg-Ser-Met-Ser(P)-Val-Ser-Arg (Watabe et al. 1989. Comp Biochem Physiol 94B:813-821) was found in the C-terminal non-helical part of this Mytilus paramyosin. We predict that this particular paramyosin has a coiled-coil structure composed of two alpha-helices that show the heptad repeats (a-b-c-d-e-f-g) with further 28-amino acid repeat zones, where a and d tend to be occupied by nonpolar residues.

Amino Acid Sequence↗
PubMed1991

Neurotransmitters and neuromodulators controlling the anterior byssus retractor muscle of Mytilus edulis.

1. The anterior byssus retractor muscle (ABRM) of Mytilus edulis is innervated by at least two kinds of nerves, excitatory and relaxing nerves. The principal neurotransmitters released from these nerves have been shown to be acetylcholine and serotonin, respectively. 2. Some other monoamines, such as dopamine and octopamine, and various peptides, such as FMRFamide-related peptides, Mytilus inhibitory peptides, SCP-related peptides and a catch-relaxing peptide, may also be involved in the regulation of the muscle as neurotransmitters or neuromodulators. 3. The ABRM seems to be typical of invertebrate muscles controlled by multiple neurotransmitters and neuromodulators.

Amino Acid Sequence↗
PubMed1982

[Arginine, octopine and alanine during the tonic and phasic contraction of the anterior byssus retractor muscle of Mytilus edulis].

In this work, we compare the energetic cost of tonic and phasic contractions of the anterior byssus retractor muscle (ABRM) of Mytilus edulis. The muscle is stimulated by six different stimulation methods and frozen when it reaches its maximal isometric response. Tonic and phasic tension developments are of similar amplitude and cause a hydrolysis of the same amount of phosphoarginine corresponding to 0.64 mumole per g of muscle and per kg/cm2 of tension (Fig. 1). As compared with the results reported in the literature the values are in good agreement with the biochemical and respiratory measurements, but they are 10 times higher than those measured by the heat production. The total arginine, octopine and alanine contents of those muscles frozen at the peak of contraction are not significantly different from those measured on the resting muscle. On the other hand, these metabolites may show seasonal variations.

Alanine↗
PubMed1980

Paramyosin structures in the thick filaments of the anterior byssus retractor muscle of Mytilus edulis.

Freeze-substituted cells of the anterior byssus retractor muscle of Mytilus edulis contain paramyosin filaments which exhibit a characteristic fine structure. Longitudinally sectioned filaments show a variety of band patterns, those occurring most frequently being cross, oblique or double oblique striations. The periodic spacings within one pattern are precise as can be demonstrated by Markham analysis and optical diffractometry. The patterns arise from structures in the interior of the filament since they persist in serially sectioned filaments and a layered structure is visible in cross-sectioned filaments. The different patterns are found to be convertible by rotating the grid around the filament axis. The observations led to the conclusion that the paramyosin core has some kind of helical arrangement. A model is proposed which consists of concentric layers of parallel paramyosin molecules which are displaced along the molecular axis in such a way that the characteristic Bear-Selby net structure results.

Animals↗
PubMed1978

[Innervation of the anterior byssus retractor muscle (ABRM) in Mytilus edulis L. and in Mytilus galloprovincialis Lmk. V. Cytochemical localization of cholinesterase activities (author's transl)].

Specific and non specific cholinesterase activities were demonstrated in the ABRM of Mytilus edulis L. and Mytilus galloprovincialis L. by means of different techniques. The results were found identical for both species: neuromuscular junctions "en grappe"-type scarely distributed within the ABRM, contain AChE. According to the histochemical inhibition tests, (a) the eserine inhibits AChE activity of the ABRM with a level of 5-10(-5) M or higher, (b) the ChE non specific activities are inhibited by iso-OMPA level between 5.10(-5) to 10(-4) M. The histo- and cytochemical observations were completed by showing the existence of neuromuscular junctions containing small clear vesicles: they probably are the morphological support for ACh presence. Moreover, specific and non specific ChE activities were localized in the glio-interstitial cells. AChE precipitates were developed along the ABRM sarcolemma, some muscle mitochondria and in the intercellular spaces remain enigmatic.

Animals↗