Metabolic transformation of dinophysistoxin-3 into dinophysistoxin-1 causes human intoxication by consumption of O-acyl-derivatives dinophysistoxins contaminated shellfish.
This paper describes for the first time a massive intoxication episode due to consumption of shellfish contaminated with 7-O-acyl-derivative dinophysistoxin-1, named Dinophysistoxin-3 (DTX-3). 7-O-acyl-derivative dinophysistoxin-1, a compound recently described in the literature, was found in shellfish samples collected in the Chilean Patagonia fjords. This compound does not inhibit Protein Phosphatases and also does not elicit the symptoms described for Diarrheic Shellfish Poisoning (DSP). The data showed here, give evidence of metabolic transformation of 7-O-acyl-derivative dinophysistoxin-1 (DTX-3) into Dinophysistoxin-1 (DTX-1, Methyl-Okadaic acid) in intoxicated patients. This metabolic transformation is responsible for the diarrheic symptoms and the intoxication syndrome showed by patients that consumed contaminated shellfish, which showed only the presence of 7-O-acyl-derivative dinophysistoxin-1. Patients fecal bacterial analysis for the presence of enteropathogens was negative and the mouse bioassay for DSP, performed as described for regulatory testing, was also negative. The HPLC-FLD and HPLC-MS analysis showed only the presence of DTX-3 as the only compound associated to DSP toxins in the contaminated shellfish samples. No other DSP toxins were found in the shellfish sample extracts. However, the patient fecal samples showed DTX-1 as the only DSP toxins detected in fecal. Moreover, the patient fecal samples did not show DTX-3. Since 7-O-acyl-derivative dinophysistoxin-1 (DTX-3) was the only compound associated to DSP toxins detected in the shellfish samples, an explanation for the diarrheic symptoms in the intoxicated patients would be the metabolic transformation of DTX-3 into DTX-1. This transformation should occur in the stomach of the poisoned patients after consuming 7-O-acyl-derivatives dinophysistoxin-1 (DTX-3) contaminated bivalves. (+info)
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. (+info)
Seasonal influence of wave action on thread production in Mytilus edulis.
The blue mussel Mytilus edulis maintains a strong attachment to the substrate in high energy environments by producing byssal threads. On the shores of Rhode Island, USA, mussel attachment strength increases twofold in spring compared to that in the fall. While many factors could influence attachment strength (temperature, food supply, predator cues, etc.), it has been proposed that the variation observed is primarily due to increased thread production during winter and spring in response to increased wave action. This study evaluates the influence of three aspects of wave action on the thread production of M. edulis. Mussels were exposed to flow, acceleration and byssal loading stimuli and the subsequent number of byssal threads produced in the laboratory was monitored. Increased flow elicited the strongest response, significantly decreasing thread production in mussels. This result was confirmed in flume experiments exposing mussels to a range of flows, with reduced thread production above 15 cm s-1. The influence of both acceleration and byssal loading was sporadic and inconsistent across seasons. Surprisingly, overall thread production in the laboratory was lowest in winter, a time when mussels typically peak in attachment. A similar seasonal pattern was observed in field assays, with high thread production during periods of elevated temperature, reduced wave action, and high reproductive condition. These results suggest that seasonal variation in attachment strength does not reflect increased thread production in response to wave action, and that other possible factors, such as seasonal variability in both the material properties of byssal threads and thread decay rates, warrant further investigation. (+info)
Occurrence of Vibrio parahaemolyticus, V. cholerae, and V. vulnificus in Norwegian Blue Mussels (Mytilus edulis).
Vibrio parahaemolyticus, V. cholerae, and V. vulnificus were isolated from 10.3%, 1.0%, and 0.1% of 885 blue mussel samples, respectively. Four of the samples contained trh(+) V. parahaemolyticus, while no tdh-positive isolates were detected. The V. cholerae isolates were non-O:1/non-O:139 serotypes and were ctxA negative. (+info)
Identification of proteomic signatures of exposure to marine pollutants in mussels (Mytilus edulis).
Bivalves and especially mussels are very good indicators of marine and estuarine pollution, and so they have been widely used in biomonitoring programs all around the world. However, traditional single parameter biomarkers face the problem of high sensitivity to biotic and abiotic factors. In our study, digestive gland peroxisome-enriched fractions of Mytilus edulis (L., 1758) were analyzed by DIGE and MS. We identified several proteomic signatures associated with the exposure to several marine pollutants (diallyl phthalate, PBDE-47, and bisphenol-A). Animals collected from North Atlantic Sea were exposed to the contaminants independently under controlled laboratory conditions. One hundred and eleven spots showed a significant increase or decrease in protein abundance in the two-dimensional electrophoresis maps from the groups exposed to pollutants. We obtained a unique protein expression signature of exposure to each of those chemical compounds. Moreover a set of proteins composed a proteomic signature in common to the three independent exposures. It is remarkable that the principal component analysis of these spots showed a discernible separation between groups, and so did the hierarchical clustering into four classes. The 14 proteins identified by MS participate in alpha- and beta-oxidation pathways, xenobiotic and amino acid metabolism, cell signaling, oxyradical metabolism, peroxisomal assembly, respiration, and the cytoskeleton. Our results suggest that proteomic signatures could become a valuable tool to monitor the presence of pollutants in field experiments where a mixture of pollutants is often present. Further studies on the identified proteins could provide crucial information to understand possible mechanisms of toxicity of single xenobiotics or mixtures of them in marine ecosystems. (+info)
Seasonal variation in mussel byssal thread mechanics.
The blue mussel, Mytilus edulis, attaches itself to the substrate by producing a radially arranged complex of collagenous byssal threads. The strength of byssal attachment, or tenacity, has been shown to vary seasonally on Rhode Island shores, increasing twofold in spring in comparison with fall. It was previously assumed that this seasonality was due to increased thread production following periods of increased wave action; however, recent findings do not support this view. As an alternate hypothesis, this study evaluates the contribution of seasonal changes in the material properties of byssal threads to an annual cycle in mussel attachment strength. Tensile mechanical tests were performed seasonally, on both newly produced threads and on threads outplanted in the field for up to nine weeks. Threads produced in spring were over 60% stronger and 83% more extensible than threads produced in all other seasons. The mechanical integrity of byssal threads also deteriorated over time in spring and summer. These results suggest that reduced attachment strength in fall reflects the production of inferior quality threads following a period of increased decay. Here, we propose a new scheme where variation in byssal thread material properties, rather than quantity, explains the seasonal pattern in attachment strength observed on Rhode Island shores. (+info)
Fitness landscapes support the dominance theory of post-zygotic isolation in the mussels Mytilus edulis and M. galloprovincialis.
We studied the genetic basis of post-zygotic isolation in the marine mussels Mytilus edulis and Mytilus galloprovincialis. Evidence was obtained for a high number of recessive Dobzhansky-Muller substitutions in the genome of these two mussel taxa. We analysed the segregation of unlinked diagnostic markers in the progeny of two backcrosses and an F2 cross, 36 h and 200 days after fertilization. Directional selection favouring M. galloprovincialis genotypes was observed in both kinds of cross. In the F2, epistatic interactions between each pair of chromosome fragments mapped by the markers were identified in addition. Our results imply that homozygous-homozygous interactions are required for breakdown of coadaptation, in accordance with the dominance theory of post-zygotic isolation. Endogenous post-zygotic selection distributed over many loci throughout the genome provides the missing factor explaining the astonishing persistence and strength of barriers to neutral introgression in such a dispersive taxon as Mytilus. (+info)
Mussel (Mytilus edulis) byssus deposition in response to variations in surface wettability.
Mussels (Mytilus edulis) are economically important in their role as an aquaculture species and also with regard to marine biofouling. They attach tenaciously to a wide variety of submerged surfaces by virtue of collagenous attachment threads termed 'byssi'. The aim of this study was to characterize the spreading of the byssal attachment plaque, which mediates attachment to the surface, on a range of surfaces in response to changes in wettability. To achieve this, well characterized self-assembled monolayers of omega-terminated alkanethiolates on gold were used, allowing correlation of byssal plaque spreading with a single surface characteristic--wettability. The present results were inconsistent with those from previous studies, in that there was a positive correlation between plaque size and surface wettability; a trend which is not explained by conventional wetting theory for a three-phase system. A recent extension to wetting theory with regard to hydrophilic proteins is discussed and the results of settlement assays are used to attempt reconciliation of these results with those of similar previous studies and, also, with recent data presented for the spreading of Ulva linza spore adhesive. (+info)