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At least 127 records · Page 7Linked to original sources
PubMed1999

Reverse engineering of bioadhesion in marine mussels.

Marine mussels (Mytilus) are experts at bonding to a variety of solid surfaces in a wet, saline and turbulent environment. Bonding is rapid, permanent, versatile and protein-based. In mussels, adhesive bonding takes the form of a byssus--a bundle of extracorporeal threads--each connected to living tissues of the animal at one end and secured by an adhesive plaque at the other. We have investigated the composition and formation of byssal plaques and threads with the hope of discovering technologically relevant innovations in chemistry and materials science. All proteins isolated from the byssus to date share the quality of containing the unusual amino acid, 3,4-dihydroxyphenylalanine. This residue appears to have a dual functionality with significant consequences for adsorption and cohesion. On the one hand, it forms a diverse array of weaker molecular interactions such as metal chelates, H-bonds, and pi-cations: these appear to dominate in surface behavior (adsorption). On the other hand, 3,4-dihydroxyphenylalanine and its redox couple, dopaquinone, can mediate formation of covalent cross-links among byssal proteins (cohesion). One of the challenges in making functional biomimetic versions of byssal adhesion is to understand how these two reactivities are balanced.

Adhesives↗
PubMed2005

Behavioural response to the bioavailability of inorganic mercury in the hydrothermal mussel Bathymodiolus azoricus.

The hydrothermal vent bivalve Bathymodiolus azoricus is naturally exposed to putatively elevated levels of mercury (Hg), exposure that dates back to the geological occurrence of vent ecosystems, and thus may have evolved evolutionary detoxification mechanisms. Therefore, it was used as a model organism in the present investigation to study the Hg-animal interaction. Mussels were exposed to inorganic Hg by daily administration of 20 microg l(-1) Hg for 21 days (cumulative added concentration was 420 microg l(-1), i.e. approximately 2 mmol l(-1)) under controlled laboratory conditions, and consequent bioaccumulation and detoxification patterns were investigated, while shell gaping behaviour indicative of filtering activity was monitored. As a result of Hg exposure, significant increase in duration, as well as decline in frequency of shell gaping occurred, which did not recover to pre-exposure levels following 21 days of Hg-free treatment. An increase in the duration of open-shelled status may indicate the absence of an avoidance reaction in the vent mussel coming in contact with Hg, unlike other bivalves that normally close their shells in response to stress compounds. Alternatively, it may suggest that Hg had an inhibitory effect on the adductor muscle function that is responsible for closing the shells. As a result, elevated Hg levels were measured in the soft tissues (270+/-71 microg g(-1) in gills, 245+/-52 microg g(-1) in digestive glands, 93+/-25 microg g(-1) in the mantle and 46+/-9 microg g(-1) in the foot), in byssus threads (peak levels of 442+/-89 microg g(-1)) and in pseudofaeces (reaching levels as high as 1000 microg g(-1)). Overall, gills contributed 75% to the total Hg body burden followed by mantle (13%), digestive gland (7%), byssus (3%) and foot (2%). Tissue Hg levels remained elevated in mussels transferred to Hg-free seawater even after 21 days, despite the high concentrations persistently eliminated with pseudofaeces both, during and after, exposure. This potential for bioaccumulation of inorganic Hg (concentration factors reached the order of magnitude of 10(4)) by the vent mussel, which does not seem to prevent uptake by shell closure, suggests that the main Hg-handling strategy is elimination via mucus.

Animals↗
PubMed2005

Stepwise length changes in single invertebrate thick filaments.

Previous experiments on thick filaments of the anterior byssus retractor muscle of Mytilus and the telson-levator muscle of Limulus polyphemus have shown large, reversible length changes up to 23% and 66% of initial length, respectively, within the physiological tension range. Using nanofabricated cantilevers and newly developed high-resolution detection methods, we investigated the dynamics of isolated Mytilus anterior byssus retractor muscle thick filaments. Single thick filaments were suspended between the tips of two microbeams oriented perpendicular to the filament axis: a deflectable cantilever and a stationary beam. Axial stress was applied by translating the base of the deflectable nanolever away from the stationary beam, which bent the nanolever. Tips of flexible nanolevers and stationary beam were imaged onto a photodiode array to track their positions. Filament shortening and lengthening traces, obtained immediately after the motor had imposed stress on the filament, showed steps and pauses. Step sizes were 2.7 nm and integer multiples thereof. Steps of this same size paradigm have been seen both during contraction of single sarcomeres and during active interaction between single isolated actin and myosin filaments, raising the question whether all of these phenomena might be related.

Actin Cytoskeleton↗
PubMed1996

Expression sites of two byssal protein genes of Mytilus galloprovincialis.

Mussels form byssal threads that can attach tenaciously to wet and irregular surfaces. The byssus consists of a fibrous collagenous core, and at least two types of polyphenolic proteins surround it. One of these proteins, designated Mgfp-1, coats the collagenous core; the other, designated Mgfp-2, is the major component of the terminal adhesive plaque of byssal threads. Both proteins contain 3,4-dihydroxyphenylalanine (DOPA) in their primary sequences. In this study, the sites of expression of the genes encoding the polyphenolic proteins were investigated in Mytilus galloprovincialis. By northern blot analysis, we found that the expression of both genes is foot-specific. Northern blot analysis of RNA isolated from the distal end and the remaining proximal portion of the foot indicated that the Mgfp-2 gene is expressed primarily in the distal part, whereas Mgfp-1 expression occurs in both parts. In situ hybridization indicated that the Mgfp-1 gene transcript is localized in the accessory gland along the ventral groove of the foot, and the Mgfp-2 gene transcript is localized in the phenol gland near the foot apex. Thus, it was shown that tissues expressing Mgfp-1 and Mgfp-2 are located around the ventral groove in an arrangement appropriate for byssus formation.

Amino Acid Sequence↗
PubMed2002

Does status of attachment influence survival time of zebra mussel, Dreissena polymorpha, exposed to chlorination?

Mussels colonize cooling water circuits of power stations by attaching themselves to the pipe or conduit walls using byssus threads. Once manually detached, they quickly try to reattach by producing new byssus threads. In many published reports on antifouling bioassays, the test specimens are exposed to the biocide in an unattached state. These mussels, while trying to reattach, are likely to expose themselves more frequently to the toxic compound when compared to firmly attached mussels. The results of the assay, therefore, could vary, depending on the status of the mussels used. In this paper, we test the hypothesis that the status of attachment could influence the toxicity response of mussels and show that byssally attached zebra mussel, Dreissena polymorpha (Pallas), is more resistant to chlorine than unattached ones. An average increase of 27% in the survival time was observed for attached mussels over unattached ones in the chlorine concentration range of 0.25 to 3 mg/L. It is conclusively shown that the increase in sensitivity of the unattached mussels was related to an increase in the byssal activity, quantified presently as the byssogenesis index. The results indicate that future laboratory toxicity experiments involving mussels should be carried out using byssally attached ones.

Animals↗
PubMed1987

Reversible inhibition of acetylcholine contracture of molluscan smooth muscle by heavy metals: correlation to Ca++ and metal content.

The present study examined the effects of three heavy metals on the acetylcholine (ACh) contracture and Ca++ kinetics of the anterior byssus retractor muscle of Mytilus edulis. An isolated tissue bioassay using anterior byssus retractor muscle was prepared according to standard procedures and the isometric tension produced in response to ACh was measured. Ten millimolar Ni++, Co++ or Cd++ reduced the maximum contracture response to ACh in zero-Ca medium in a time-dependent manner. The inhibition was reversed upon restoration of medium containing 10 mM Ca++. The loss (and re-establishment) of contracture response to ACh corresponded to the influx (and efflux) of the heavy metal ions opposite to the direction of Ca++ flow. These results are consistent with the concept that the loss of the ACh contracture response is attributable to the displacement of tissue Ca++ from release sites by heavy metals.

Acetylcholine↗
PubMed1979

Foot glands in Perna indica and Perna viridis (Pelecypoda: mytilidae) histology and histochemistry.

The foot of Perna viridis is found to contain three main types of glands, the white gland, phenol gland and the enzyme gland. But in Perna indica there are only two glands, the phenol gland and the enzyme gland. Besides these, mucous glands are found in both of the species. The shape and size of the cells of these glands vary from species to species. Glycogen and 1 : 2 glycol groups are found in these gland cells. Proteins rich in disulfides and sulfhydryls are present in the phenol glands of both the species and in the white gland of p. viridis but they vary in the intensity of staining. The presence of phenols is confirmed in the phenol gland cells. Phospholipids and lipoproteins are intense in the white and phenol gland cells. They are absent in the enzyme gland. Alkaline and acid phosphatases activity in the enzyme gland cells could be demonstrated. The secretions of these glands help in the formation of the byssus threads. The mucous gland cells are subepithelial localised they secrete acid and neutral mucopolysaccharides together with glycoproteins. Which participate in the attachment of the byssus disc.

Animals↗
PubMed1983

Ultrastructural and cytochemical study of a mucous gland of the foot of Mytilus galloprovincialis.

The ultrastructural study of the ventral pair mucous gland (VPMG) of the foot of Mytilus galloprovincialis shows the presence of two cell types (type I and II cells) characterized by the cytoarchitecture typical of mucous secreting cells and distinct for the different structure of their secretory granules. The cytochemical tests performed on semithin (1 micron) and ultrathin sections show that type I secretory granules are made up of proteinaceous nucleoids and of a microfilamentous matrix containing both carboxylated and sulphated glycosaminoglycans. Type II secretory granules are mainly formed by glycoproteins. The ultrastructural and cytochemical studies do not support the hypothesis that VPMG secretions directly contribute to the formation of byssus threads. It is more probable that such secretions provide a protective and lubricating blanket during the multistep process of secretion, moulding and extrusion of byssus threads.

Animals↗
PubMed1984

Nickel inhibition of calcium release from subsarcolemmal calcium stores of molluscan smooth muscle.

Replacement of calcium in artificial sea water (ASW) by nickel causes a loss of calcium at a single exponential rate (tau = 23.2 min) and the loss of contracture response to acetylcholine (ACh) in the anterior byssus retractor muscle of Mytilus edulis L. The ACh contracture response is lost at two rates; 93% of the ACh contracture response is lost rapidly (tau = 7.43 min) and the remaining 7% of ACh contracture response is lost slowly (tau = 66.6 min). The rapid phase of loss of ACh contracture corresponds to the rapid exponential uptake of nickel (tau = 6.5 min). The loss of ACh contracture response is attributed to the displacement of calcium from membrane release sites by nickel. In O-Ca-Mg ASW, the ACh contracture responses are well maintained over a 35-min period when stimulated by ACh every 5 min. Stimulation by ACh after 1, 20 and 40 min in O-Ca-Mg ASW results in a reduction of ACh contracture response to 15% of the response in Ca ASW. Similar treatment in O-Ca-Ni ASW reduces the ACh contracture response to 4%. Potassium and caffeine contracture responses at 1, 20 and 40 min in O-Ca-Mg ASW are reduced to 25 and 28%. Similar treatment in O-Ca-Ni ASW produces a block of potassium contracture response and reduces caffeine contracture response to 3%. Our 45Ca uptake data demonstrate that calcium influx is not required for the ACh contracture responses of anterior byssus retractor muscle.

Acetylcholine↗
PubMed1977

Lanthanum block of contraction and of relaxation in response to serotonin and dopamine in molluscan catch muscle.

Contractile and relaxing responses of the anterior byssus retractor muscle of Mytilus edulis L. were observed after exposure to La+++. After 25 minutes in 5 mM La+++, contraction in response to acetylcholine, to KCl and to stimulation of intramuscular nerves is blocked, whereas contraction in response to direct current pulses is partially blocked and caffeine contraction is unaffected. Exposure to 5 mM La+++ for 3 hours does not block relaxation of catch tension in response to serotonin and dopamine but exposure to 5 mM La+++ in the presence of a depolarizing agent (acetylcholine or KCl) for a brief period (4 minutes) abolishes the relaxing response. The authors concluded that activation of contraction in the anterior byssus retractor muscle can be effected by Ca++ influx from the bathing medium and/or by release of Ca++ from interal sites, depending on the nature of the stimulation. The authors also concluded that the relaxing action of serotonin and dopamine depends neither on Ca++ influx nor on passive efflux of Ca++, but rather on Ca++ combining at an internal site or at sites on the cell membrane which are exposed when the muscle is depolarized.

Acetylcholine↗
PubMed2002

Sensitivity of juvenile Macomona liliana (bivalvia) to UV-photoactivated fluoranthene toxicity.

This study assessed the sensitivity of Macomona liliana (bivalvia, tellinacea) to UV-photoactivated fluoranthene toxicity. Juvenile clams (0.5-2.0 mm) were exposed to a range of aqueous fluoranthene concentrations (5-500 microg/L) for 96 h, after which the clams' ability to rebury in control sediment was determined. Survivors of these fluoranthene-only toxicity tests were then exposed in clean seawater to UV radiation from a solar radiation-simulating light source for 1 h. The differences between EC(50) values before and after UV exposure provided a measure of phototoxicity of the bioaccumulated fluoranthene. Fluoranthene tissue burdens corresponding to the EC(50) values were determined by exposing a second batch of clams to (14)C-radiolabeled fluoranthene. A third experiment quantified the kinetics of fluoranthene uptake and elimination in water-only exposures. Fluoranthene phototoxicity was found to depend on the dose of fluoranthene and the duration of UV exposure. Exposure of animals to 1 h of UV radiation resulted fluoranthene toxicity that was 3 times higher (EC(50) = 46 microg/L) than that of those with no UV exposure (EC(50) = 153 microg/L). The corresponding critical body burden (i.e., fluoranthene tissue concentration at which 50% of the clams failed to rebury) was 6 ng/clam (or 700 microg/g dry weight [dw]) and 21 ng/clam (or 2300 microg/g dw) for UV-exposed and UV-unexposed animals, respectively. First-order uptake and elimination coefficients, determined in the kinetics experiment, were 0.825 Lg(-1) h(-1) and 0.059 h(-1), respectively, indicating rapid uptake and a short fluoranthene tissue half-life of approximately 12 h for M. liliana. Compared with other bivalve species of similar size, M. liliana appeared to be more than 1 order of magnitude less sensitive to UV-activated fluoranthene toxicity, although these differences may be a result in part of differences in the UV exposure regime. Nonetheless, the majority of M. liliana exposed to a fluoranthene concentration of 50 microg/L displayed evidence of UV-photoactivated toxicity within 30-60 min of irradiation, and prolonging UV exposure more than 2 h killed all clams. These results demonstrate that even short UV exposures, as perhaps encountered during normal feeding or byssus-drifting behavior, may significantly increase toxicity to juvenile M. liliana possessing elevated fluoranthene tissue concentrations.

Animals↗
PubMedDate not supplied

Paramyosin polarity in the thick filament of molluscan smooth muscles.

Paramyosin is the main structural component of the thick filament of molluscan smooth muscles. These filaments consist of a large paracrystalline core of paramyosin with myosin arranged on its surface. The detailed molecular packing of paramyosin in the core and the array of myosin on the surface of the paramyosin core remain unknown. An unsolved problem is the polarity of the paramyosin molecules within these thick filaments (i.e., it is not known whether the paramyosin molecules assemble with their NH2-terminal ends pointing toward the center or toward the end of the thick filament). Here a method to distinguish between the NH2- and the COOH-terminal ends of the paramyosin molecule by electron microscopy is described and used to determine their polarity in synthetic paracrystalline arrays. This method consists of labeling the cysteine residues of paramyosin molecules with the avidin-biotin system developed by Sutoh et al. (1984). Accordingly, the sulfhydryl groups of paramyosin--isolated from the anterior byssus retractor muscle (ABRM) of Mytilus edulis--were modified with maleimide-biotin, and the biotinylated thiols were visualized in the electron microscope after glycerol spraying/rotary metal shadowing by attaching monomeric avidin to them. Avidin-biotin labeling of the native molecule and its carboxypeptidase fragments revealed that ABRM paramyosin contains one pair of cysteine at its NH2-terminal end and one pair at approximately 30 nm from its COOH-terminal end. Synthetic paracrystalline arrays of paramyosin with known axial arrangement were also labeled with the avidin-biotin system. The location of the bound avidin in these paracrystals indicated the polarity of paramyosin in these arrays. The polarity was also determined by comparison of the transverse band-like staining pattern of paracrystals of alpha-paramyosin (intact protein) and beta-paramyosin (a proteolytically cleaved alpha-paramyosin that has lost a small segment at its COOH-terminal end). Both methods revealed that paramyosin assembles with its NH2-terminal end pointing toward the center of the paracrystals. The implications of this result for the polarity of paramyosin in the native filament core, and for the arrangement of myosin on the surface of molluscan thick filaments, are discussed.

Actin Cytoskeleton↗
PubMed1998

Molluscan neuropeptides.

Achatin-I, fulicin, fulyal, Mytilus-FFRFamide and Helix CCAP-RP-III are D-amino acid-containing neuropeptides from molluscs. Achatin-I, fulicin and fulyal from Achatina showed excitatory and/or modulatory actions on the penis retractor, radula retractor or ventricular muscles and neurons, though their L isomers were devoid of activity. On the other hand, both Mytilus-FFRFamide and its L isomer showed excitatory effects on the anterior byssus retractor muscle. Moreover, in contrast to Achatina neuropeptides, Helix CCAP-RP-III exhibited no remarkable activities on any of the muscles tested; instead, its L isomer possessed various excitatory effects. The molecular structures of these short peptides would be affected by the L-->D conversion and could influence activity. Molecular biological studies on the fulicin precursor suggest that fulicin, fulyal and related peptides are produced in Achatina ganglia and heart by processing of the ribosomally made precursor, and that L-isomeric fulicin and fulyal further undergo epimerization to yield the D-isomers.

Amino Acids↗
PubMed1994

X-ray evidence for the elongation of thin and thick filaments during isometric contraction of a molluscan smooth muscle.

The elongation of thin and thick filaments during isometric contraction of a molluscan smooth muscle was studied by measuring spacing changes of meridional reflections in the medium-angle X-ray diffraction pattern. X-ray patterns from the anterior byssus retractor muscle of Mytilus edulis in the resting, active, and catch states were taken from the same part of a muscle bundle at a fixed specimen-to-detector distance, using imaging plates and 10 s exposure to synchrotron radiation. The third-order reflection (9.2 A) of the axial period of actin, and the fourteenth-order reflection (10.4 A) of the axial subunit-repeat of the thick filament are increased in spacing in the active and catch states. From accurately measured changes in the axial distance of the 9.2 A layer line from the origin, thin filament elongations in the active and catch states are estimated to be 0.48 and 0.32%, respectively, in a muscle that maintains a tension of 12.2 kg cm-2 in the active state and 9.8 kg cm-2 in the catch state. Thick filament elongations in the active and catch states are similarly estimated to be 0.33, and 0.28%, respectively, based on the axial shift of the 10.4 A reflection. The 0.48% elongation of the thin filament in the active state agrees with an elongation that is presumed by White and Thorson (1973) to estimate the lower limit of the thin-filament stiffness. It seems that in the catch state the activated and resting thin filament structures are intermixed. The activated parts of the thin filament are probably more elongated than the apparent value, 0.32%.

Actin Cytoskeleton↗
PubMed1995

The effect of temperature on contractile activation of intact and chemically skinned 'catch' muscle fibre bundles of Mytilus edulis.

The effect of temperature (5-35 degrees C) on maximum force production was examined in intact and chemically skinned muscle fibre bundles (10-25 fibres) from the anterior byssus retractor muscle of Mytilus edulis. In intact fibre bundles, 10 microM acetylcholine induced a tonic contraction which had a magnitude of 65.4 +/- 4.0 N cm-2 (n = 30) at 23 degrees C. Activation by caffeine (20 mM) produced a force response which was 157.1 +/- 7.9% (n = 16) of the acetylcholine response at 23 degrees C and acetylcholine and caffeine together produced force which was not significantly different from the response to caffeine alone. At 5 degrees C the acetylcholine and caffeine responses were decreased by 9.6 +/- 3.4% (n = 6) and 14.6 +/- 2.8% (n = 8) compared with the respective responses at 23 degrees C. However, there was no significant reduction of the response induced by the combined action of acetylcholine and caffeine when the temperature was decreased from 23 degrees C to 5 degrees C. The 20-80% of peak force activation time increased by about one order of magnitude for all acetylcholine, caffeine and combined acetylcholine-caffeine-induced responses when the temperature was decreased from 23-5 degrees C. Repeated exposure of the intact preparation to caffeine caused a marked decrease in the caffeine-induced response (complete abolition of force after the third exposure to caffeine), but the response to caffeine could be fully restored following one acetylcholine-induced activation. The maximum Ca(2+)-activated force after skinning the preparation with saponin was not significantly different from the caffeine or combined acetylcholine-caffeine-induced responses before skinning. In the saponin skinned fibre preparation a drop in temperature from 23 degrees C to 15 degrees C or 5 degrees C decreased the maximum Ca(2+)-activated force by 13.2 +/- 1.4% (n = 8) and 41.4 +/- 3.1% (n = 5) respectively. The activation time between 20-80% of the peak Ca(2+)-activated force increased at 15 degrees C and 5 degrees C by a factor of 1.5 +/- 0.1 (n = 5) and 6.8 +/- 1.1 (n = 5) respectively when compared to corresponding values at 23 degrees C. The relaxation half-time decreased by a factor of 1.7 +/- 0.2 (n = 5) and 3.0 +/- 0.2 (n = 5) at 15 degrees C and 5 degrees C respectively compared with that at 23 degrees C.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1984

Effect of Ca2+-independent myosin light chain kinase on different skinned smooth muscle fibers.

In various skinned smooth muscle fiber preparations, (porcine carotid artery, rat tail artery, chicken gizzard and Taenia coli from guinea pig) a Ca2+-independent myosin light chain kinase (MLCK) initiated a contraction in absence of Ca2+. While the Ca2+ insensitive MLCK was effective on the vertebrate smooth muscles it did not act on the invertebrate skinned skeletal muscle preparation from Limulus and anterior byssus retractor muscle from Mytilus edulis. The results indicate that in vertebrate smooth muscles phosphorylation is sufficient for activation and that there is no obligatory role for an additional mechanism in initiation of contraction.

Adenosine Triphosphate↗
PubMed1981

The structure of the paramyosin core in molluscan thick filaments.

The thick filaments of molluscan muscles have been examined by electron microscopy and X-ray diffraction in order to test whether the structure of the paramyosin core is crystalline and not helicoidal. In accurately cut transverse sections of the white adductor muscle of the oyster the thick filaments are uniformly stained but, when the sections are titled, parallel striations are revealed. Essentially all the filaments can be shown to exhibit striations which can only be explained in terms of a crystalline structure. The crystallinity is, however, not perfect since the striations although often straight are more frequently curved. Two sets of striations of different spacing can be detected in each filament on tilting to either side of the filament axis. Their spacings when compared to the Bear-Selby net a spacing obtained from X-ray diffraction patterns of the embedded muscle indicate that the striations are seen when the filaments are viewed down the 201 and 301 planes of the Bear-Selby net. Striations have been observed in thick filaments from other catch muscles, the white adductor of the clam, the smooth adductor of the scallop and the anterior byssus retractor of the mussel as well as in a non-catch muscle, the red adductor of the clam. In all cases the spacing striations was similar indicating that, contrary to previous reports, when the conditions are the same the a spacing of the Bear-Selby net is approximately constant from one muscle to another and hence that the paramyosin structure in all these muscles is similar.

Animals↗
PubMed1990

Calcium regulated thin filaments from molluscan catch muscles contain a caldesmon-like regulatory protein.

The thin filaments of the anterior byssus retractor muscle of the edible mussel Mytilus and the transluscent and opaque adductors of the oyster Crassostrea have been isolated and their properties investigated. We find that the thin filaments from all three muscles can activate skeletal muscle myosin ATPase in the presence of calcium but that the activity is inhibited in its absence. The filaments contain a protein which interacts with antibodies to vertebrate smooth muscle caldesmon on immunoblots. The antibodies relieve the inhibition of the thin-filament-activated myosin MgATPase. They can also bundle the thin filaments. We conclude that a caldesmon-like protein is present in molluscan muscle. As in the vertebrate smooth muscle, it could act as part of a control mechanism in addition to the myosin regulatory system. Vertebrate smooth muscle caldesmon can crosslink actin and myosin and it has been suggested that it may in this way contribute to the latch state. A similar interaction may be involved in the catch mechanism in molluscan muscle.

Actin Cytoskeleton↗