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At least 199 records · Page 11Linked to original sources
PubMed1960

Oxidation of 5-hydroxytryptamine and related compounds by Mytilus gill plates.

Homogenates of gill plates of Mytilus edulis L. used oxygen when 5-hydroxytryptamine was added. The oxidation of 5-hydroxytryptamine was not due to the presence of an amine oxidase, but to that of an enzyme that catalysed the oxidation of other 5-hydroxyindoles (5-hydroxytryptophan, bufotenine). The oxidation was cyanide-sensitive, but was not inhibited by iproniazid. In the reaction a yellowish-brown substance was formed. The occurrence of an amine oxidase in the anterior retractor muscle of the byssus and in the digestive gland was confirmed.

5-Hydroxytryptophan↗
PubMed1975

n the mechanism of inhibitory action of vibrations as studied in a molluscan catch muscle and in vertebrate vascular smooth muscle.

In previous studies longitudinal vibrations have been found to reduce active force development in smooth muscle, possibly due to a direct action on the contractile mechanism. In the present experiments the inhibitory effect of vibrations on isometric tension was studied in isolated preparations of the rat portal vein, the rabbit thoracic aorta and the anterior byssus retractor muscle (ABRM) of the Mytilus edulis. The results demonstrate that vibrations of appropriate frequency and amplitude caused prompt inhibition of contractile tension and that complete recovery of active force normally occurred after cessation of vibration in vertebrate smooth muscle as well as during the phasic contraction of ABRM. However, in the "catch" of the ABRM there was no regain in force following the vibration induced inhibition. The contractile proteins are considered to be a locked state during the catch situation. Thus, this contracted state seems to be released by vibrations. It is therefore concluded that vibrations do interfere with the interrelationship between the myofilaments. This conclusion supports the previously forwarded hypothesis that vibrations act by increasing the rate of detachment of actin-myosin crosslinks in vertebrate smooth muscle.

Acetylcholine↗
PubMed1967

Ca-coupling in the anterior byssal retractor muscle of Mytilus edulis L.

1. Experiments designed to elucidate the role of Ca in the excitation-contraction coupling of the anterior byssus retractor muscle (ABRM) were carried out. Ca influences membrane depolarization and provides for coupling of the contraction in response to repetitive electrical stimulation as well as of ACh and KCl contracture. Depriving ABRM of Ca results in two closely correlated events: disappearance of action potential and of the contraction in response to repetitive electrical stimulation.2. A sigmoid increase in tension with the log-Ca concentration in artificial medium was observed whereas, over the same range of concentrations, the tension remnant decreased.3. Induction of relaxation by 5-HT is Ca dependent. Either thiourea inactivation or Ca deprivation results in failure to relax. Low concentrations of 5-HT (10(-7) g/ml.) bring about increase in peak tension of the contraction in response to repetitive electrical stimulation, whereas higher concentrations (10(-5) g/ml.) undermine peak tension.4. Frequencies exceeding 40 cycles evoke a contraction accompanied by tension remnant, which is eliminated with 5-HT.5. Dropwise addition of Ca on a trypsin window in the muscle induces a latency relaxation before onset of Ca-contracture.

Action Potentials↗
PubMed1967

Excitation of Mytilus smooth muscle.

1. Membrane potentials and tension were recorded during nerve stimulation and direct stimulation of smooth muscle cells of the anterior byssus retractor muscle of Mytilus edulis L.2. The resting potential averaged 65 mV (range 55-72 mV).3. Junction potentials reached 25 mV and decayed to one half maximum amplitude in 500 msec. Spatial summation and facilitation of junction potentials were observed.4. Action potentials, 50 msec in duration and up to 50 mV in amplitude were fired at a membrane potential of 35-40 mV. No overshoot was observed.5. Contraction in response to neural stimulation was associated with spike discharge. Measurement of tension and depolarization in muscle bundles at high K(+) indicated that tension is only produced at membrane potentials similar to those achieved by spike discharge.6. Blocking of junction potentials, spike discharge and contraction by methantheline, an acetylcholine antagonist, supports the hypothesis that the muscle is excited by cholinergic nerves. However, evidence of a presynaptic action of methantheline complicates this argument.

Action Potentials↗
PubMed1968

Energy cost of tonic contraction in a lamellibranch catch muscle.

1. The oxygen consumption of isolated anterior byssus retractor muscle (ABRM) of Mytilus edulis was measured during tonic contraction induced by acetylcholine (ACh).2. The respiration was measured with an oxygen electrode during 95 min, divided into one period of 5 min and six successive periods of 15 min.3. Tonic contraction induced a prolonged increase of the basal respiration that slowly diminished with a time course roughly similar to that of the tonic tension.4. For each period of measurement, the excess respiration over the resting level could be analysed into a constant amount and an amount that depended on the maintained tonic tension. The analysis was performed by fitting regression equations of the type Y = Q+bP, where Y is the excess respiration in n-moles O(2)/g.min, and P, the isometric tension (kg/cm(2)); term b of the equation expresses the amount of oxygen consumption directly proportional to the tonic tension.5. During the first 20 min of contraction, terms b of the equations are not significant, and most of the excess respiration (terms Q) is independent of the tension. The oxygen consumed during this time is supposed to reflect the recovery metabolism for the energy cost of the development of the tension.6. From the 20th to the 80th min of contraction, terms Q are reduced and terms b are significant and constant. The excess respiration during this period is equal to 16.9 (+/-0.5) n-moles O(2)/g.min + P x 6.8 (+/-0.5) n-moles O(2)/kg.cm.min (+/-S.E. of the means, n = 24).7. During a tonic contraction suppression of tension by a release reduced the oxygen consumption which increased again when tension was restored by stretching the muscle back to its original length. This confirmed the role of tension in determining the intensity of respiration during the catch.8. The oxygen consumption related to this tension restored by stretching the muscle, varied from 8.0 to 12.3 n-moles O(2)/kg.cm.min. These figures are of the same order of magnitude as the coefficient b obtained in the case of tonic contraction without modification of tension by length changes.9. These results are taken as a demonstration that the maintenance of tonic tension is an ;active' phenomenon with a metabolic counterpart.

Journal Article↗
PubMed1989

Free calcium at rest during "catch" in single smooth muscle cells.

Tension and intracellular free calcium concentration [( Ca2+]i) were measured simultaneously in single smooth muscle cells isolated from the anterior byssus retractor muscle (ABRM) of Mytilus edulis that were loaded with the fluorescent Ca2+ indicator fura-2. Electrical stimulation evoked a transient elevation of [Ca2+]i associated with a "catch" contraction. During the catch state, however, [Ca2+]i was effectively at its resting level and was unaffected by 5-hydroxytryptamine, which induced a rapid relaxation from catch. The results indicate that a maintained high [Ca2+]i is not required for the maintenance of catch tension in intact ABRM and that there was no significant change in [Ca2+]i upon abolition of catch.

Animals↗
PubMed1997

A nonisometric kinetic model for smooth muscle.

We have modeled the nonisometric contractile dynamics of smooth muscle by modifying a four-state model of actin and myosin bonds originally proposed by Hai and Murphy to simulate the isometric contractions of vertebrate smooth muscle. The model includes a latch bridge, which cycles more slowly than regular cross bridges. We generalized this model to represent the calcium-regulated processes of vertebrate and invertebrate smooth muscles. We added length dynamics by assuming length-dependent bonding and unbonding rates for the cross bridges. The calculation of the cross-bridge length distribution was simplified by assuming a Gaussian distribution, as first done by Zahalak for skeletal muscle. To test the performance of this model, we simulated isometric and nonisometric responses of different kinds of smooth muscle, including vascular smooth muscle, airway smooth muscle, molluscan catch muscle (anterior byssus retractor muscle), and Aplysia I(2) muscle. The model captures the economical force maintenance property at the later stages of isometric muscle contraction and responses to imposed lengthening and shortening movements.

Actomyosin↗
PubMed2006

Effect of pH on the rate of myosin head detachment in molluscan catch muscle: are myosin heads involved in the catch state?

Moderate alkalisation is known to terminate the catch state of bivalve mollusc smooth muscles such as the anterior byssus retractor muscle (ABRM) of Mytilus edulis L. In the present study, we investigated the effect of moderate alkalisation (pH 7.2-7.7 vs control pH 6.7) on the myosin head detachment rate in saponin-skinned fibre bundles of ABRM in order to investigate the possible role of myosin heads in the force maintenance during catch. The detachment rate of myosin heads was deduced from two types of experiments. (1) In stretch experiments on maximally Ca2+-activated fibre bundles (pCa 4.5), the rate of force decay after stepwise stretch was assessed. (2) In ATP step experiments, the rate of force decay from high force rigor (pCa>8) was evaluated. The ATP step was induced by photolysis of caged ATP. We found that moderate alkalisation induces relaxation of skinned fibres in catch, thereby reducing both force and stiffness, whereas it does not accelerate the rate of myosin head detachment. This acceleration, however, would be expected if catch would be simply due to myosin heads remaining sustainably attached to actin filaments. Thus, the myosin heads may be less involved in catch than generally assumed. Catch may possibly depend on a different kind of myofilament interconnections, which are abolished by moderate alkalisation.

Adenosine Triphosphate↗
PubMed2000

Immunolocalization of Dpfp1, a byssal protein of the zebra mussel Dreissena polymorpha.

The zebra mussel is one of only a few freshwater bivalves known to produce a byssus. This fibrous, proteinaceous and highly cross-linked structure allows the mussel to attach to a variety of substrata and contributes to its notoriety as a major freshwater biofouling species. We have successfully expressed a full-length version of Dreissena polymorpha foot protein 1 (Dpfp1), a putative byssal thread precursor, and have used the recombinant protein as an antigen for polyclonal antibody production. Antisera obtained from rabbits immunized with recombinant Dpfp1 recognize the protein in western blots of extracts from foot tissue and byssal threads. On the basis of this evidence, we conclude that Dpfp1 is a byssal precursor protein manufactured and stored in the foot of the mussel. Immunohistochemical localization of Dpfp1 suggests that the protein is localized in secretory granules in a large gland surrounding the ventral groove of the foot. Only a subset of these glandular cells stockpiles the protein, implying that the zebra mussel foot is a complex organ capable of several distinct secretory activities involved in byssal thread formation. The uniform distribution of Dpfp1-containing cells suggests that the protein is a significant load-bearing component of zebra mussel byssal threads, although a more rigorous test of this hypothesis awaits ultrastructural localization of the protein in mature byssal threads.

Amino Acid Sequence↗
PubMed1982

Effects of some ergot alkaloids on dopamine receptors of molluscan smooth muscle.

Some ergot alkaloids relaxed catch contraction of an isolated molluscan smooth muscle (anterior byssus retractor muscle of Mytilus edulis). Haloperidol, a competitive dopamine antagonist, shifted the dose response curves of ergot alkaloids, but methysergide did not. Bromocriptine, a potent dopaminergic ergot alkaloid, did not relax catch contraction. These results suggest that relaxation of catch contraction by some ergot alkaloids is mediated through dopamine receptors of this muscle, but dopamine receptors of this muscle seem to be somewhat different from those of mammalian brain.

Animals↗
PubMed2006

Catch force links and the low to high force transition of myosin.

Catch is characterized by maintenance of force with very low energy utilization in some invertebrate muscles. Catch is regulated by phosphorylation of the mini-titin, twitchin, and a catch component of force exists at all [Ca2+] except those resulting in maximum force. The mechanism responsible for catch force was characterized by determining how the effects of agents that inhibit the low to high force transition of the myosin cross-bridge (inorganic phosphate, butanedione monoxime, trifluoperazine, and blebbistatin) are modified by twitchin phosphorylation and [Ca2+]. In permeabilized anterior byssus retractor muscles from Mytilus edulis, catch force was identified as being sensitive to twitchin phosphorylation, whereas noncatch force was insensitive. In all cases, inhibition of the low to high force transition caused an increase in catch force. The same relationship exists between catch force and noncatch force whether force is varied by changes in [Ca2+] and/or agents that inhibit cross-bridge force production. This suggests that myosin in the high force state detaches catch force maintaining structures, whereas myosin in the low force state promotes their formation. It is unlikely that the catch structure is the myosin cross-bridge; rather, it appears that myosin interacts with the structure, most likely twitchin, and regulates its attachment and detachment.

Animals↗
PubMed1991

Effects of calcium and ADP on tension responses to step length increases in glycerinated Mytilus smooth muscle.

To study the mechanical properties of various crossbridge states in the anterior byssus retractor muscle (ABRM) of Mytilus, the tension response of the glycerinated ABRM to a step increase of the length was examined in rigor solutions with saturating Ca2+ (Rca) and without added Ca2+ (R), rigor ones with ADP (AD) and with both ADP and saturating Ca2+ (ADca), and a low ATP, activating one. The application of ADca to a rigor ABRM caused a slow tension development of less than 0.083 kg/cm2 (n = 6) probably because of contaminant ATP in the presence of 0.25 mM p,p-di(adenosine-5')pentaphosphate (Ap5A) and 10 U/ml hexokinase with 2 mM glucose. The instantaneous stiffness in ADca was slightly smaller than that in the low ATP solution and greater than those in R, Rca, and AD, giving evidence that the stretch response reflected the mechanical property of the crossbridges. The rate of the tension decay during the initial 5 ms after the length change was completed was slowest in the ADca among the solutions examined, while during the initial 30-90 ms it was faster in the low ATP solution than R, Rca, AD, and ADca with little difference of the rate in the latter four solutions. The difference in the time course of the tension decay in between the low ATP solution and ADca may be taken to indicate that the high stiffness in ADca was not due to the formation of the tension-generating crossbridges but to the crossbridges with both bound Ca and ADP (AMCaADP) made directly from the rigor crossbridge (AM). Consequently, it was thought that AMCaADP was stiffer than AM and the crossbridges with either bound Ca (AMCa) or ADP (AM.ADP), the latter three kinds of the crossbridges being formed directly from AM, not as a result of ATP hydrolysis.

Adenosine Diphosphate↗
PubMed1994

The adhesive protein cDNA of Mytilus galloprovincialis encodes decapeptide repeats but no hexapeptide motif.

A mussel is attached to hard surfaces by its byssus, which consists of a bundle of threads, each with a fibrous collagenous core coated with adhesive proteins. We constructed a cDNA library from RNA isolated from the foot of the mussel Mytilus galloprovincialis sampled in Japan. The library was probed with a nucleotide sequence corresponding to a part of the decapeptide repeat motif in the major adhesive protein of the closely related species M. edulis, and a clone including the whole coding region of the same adhesive protein of M. galloprovincialis was isolated. The sequences of the signal and nonrepetitive regions of the protein of M. galloprovincialis were homologous to those of M. edulis, despite several substitutions and a deletion of 18 amino acids. The repetitive region included a tetradecapeptide sequence and 62 repeats of the same decapeptide motif as in M. edulis, but hexapeptide sequences present in M. edulis were absent in the protein of M. galloprovincialis. In the decapeptide motif, two tyrosine residues, two lysine residues, and one of the two proline residues were highly conserved, but other residues were frequently substituted. In some residues in the decapeptide motif, specific codon usages were observed, suggesting that the nucleotide sequence itself has a function.

Amino Acid Sequence↗
PubMed2000

[Parasitic metamorphosis development of Lamprotula fibrosa].

The glochidia of Lamprotula fibrosa develop to maturity in the outer gill of female and are expelled to the outside in winter, and then, the mature glochidia are parasitized to the gill of fish host and start the parasitic metamorphosis development. The parasitic period lasts about 4 months. The inner and outer byssuses disappear after parasitizing for 3 days. The foots develop after 35 days. The intestine, adductor muscle, nephridium and gill anlage develop after 90 days. The shells become thick and protrusive. The glochidia become larvae with a size of 253.37 x 273.26 x 179.96 microns in the next spring, then leave the gill of fish host, and start their independent life.

Animals↗
PubMed1977

Serotonin and dopamine as neurotransmitters in mytilus: block of serotonin receptors by an organic mercurial.

The effects of mersalyl, bromo-LSD (BOL) and methysergide (UML) on the relaxation of catch by certain indole and catechol derivatives were studied in the anterior byssus retractor muscle of Mytilus. Mersalyl antagonized relaxation in response to serotonin whereas BOL and UML were less effective. Two other indole derivatives, ergotamine and gramine, were also blocked by mersalyl; BOL and UML antagonized relaxation in response to dopamine more effectively than did mersalyl. Two other catechols, epinephrine and norepinephrine, were also blocked more effectively by BOL and UML than by mersaly. Relaxation in response to neural stimulation was blocked more effectively by mersalyl than by BOL. The blocking action of mersalyl on neural relaxation reversed very poorly after washing the drug, but complete reversal was induced by brief exposure to dithiothreitol. It is concluded that the evidence supports an hypothesis that the transmitter released by relaxing nerves is serotonin. It is suggested that mersalyl blocks serotonin by combining with a sulfhydryl group at or near the site on the receptor to which the indole nitrogen attaches.

Acetylcholine↗
PubMed1991

A variety of Mytilus inhibitory peptides in the ABRM of Mytilus edulis: isolation and characterization.

1. Five species of Mytilus inhibitory peptides, MIP1-5, were isolated from acetone extracts of the anterior byssus retractor muscle (ABRM) of Mytilus edulis. MIP1 and MIP2 were shown to be S2-MIP and A2-MIP, respectively, first isolated from the pedal ganglia of the animal. 2. All the five peptides had a common C-terminal structure of -Pro-Xaa-Phe-Val-NH2, which was shown to be important for their biological activity. 3. The five MIPs showed similar inhibitory effects on contractions of the ABRM but did not affect catch tension and its relaxation. 4. In addition to the MIPs, catch-relaxing peptide (CARP) was also found in the ABRM.

Amino Acid Sequence↗
PubMed1990

Bioadhesives: a biotechnological opportunity.

Marine mussels secrete the byssus in order to attach to solid surfaces and to survive under the turbulent effects of waves. The adhesive responsible for this attachment is the polyphenolic protein secreted by the phenol gland in the foot of the animal. To purify this adhesive protein from the chilean mussel Mylilus chilensis, a modification of previous procedures has been developed. Accordingly, the protein is differentially precipitated with acetone in the presence of 0.25 N HCl. The purified protein is rich in the amino acids lysine, 3,4-dihydroxyphenylalanine, serine, threonine, proline and hydroxyproline. The protein exhibited strong adhesion to glass and other solid supports. Moreover, it has been found that the adhesive protein can mediate the immobilization of beta-galactosidase to glass. About 75% of the enzyme activity was immobilized under the experimental conditions described. This is the first study reporting the use of the polyphenolic protein to immobilize enzymes.

Amino Acids↗
PubMed1988

The relaxation induced by indole and nonindole 5-HT agonists in the molluscan smooth muscle.

1. The abilities of two indole agonists and some nonindole agonists to induce relaxation of catch contraction and the influence of the agonists on cyclic AMP (cAMP) levels in the anterior byssus retractor muscle (ABRM) of Mytilus were investigated. 2. 5-MeOT (5-methoxytryptamine) and 5-MeODMT (5-methoxy-N,N-dimethyltryptamine) dose-dependently relaxed the contraction. 3. TFMPP (m-trifluoromethylphenyl piperazine), PAPP (p-amino-phenyl TFMPP) and mCPP (1-(3-chlorophenyl)piperazine dose-dependently relaxed the contraction, but 2MPP (1-(2-methylphenyl) piperazine and quipazine did not. 4. 5-MeOT (10(-6)M), 5-MeODMT (10(-6)M), TFMPP (10(-4)M), 2MPP (10(-4)M), quipazine (10(-4)M) and 8-OH-DPAT (3 x 10(-5) M) significantly reduced the cAMP levels, but PAPP (3 x 10(-4)M) and mCPP (10(-4)M) did not have any effect on cAMP levels. 5. These findings indicate that the pharmacological properties of 5-HT1-like receptors in the ABRM are similar to those of 5-HT1A receptors in mammalian tissues, and that the changes in cAMP levels induced by the agonists used are unlikely to be directly linked to the relaxation induced by them.

8-Hydroxy-2-(di-n-propylamino)tetralin↗