The Experts below are selected from a list of 4770 Experts worldwide ranked by ideXlab platform
Heather L. Hunt - One of the best experts on this subject based on the ideXlab platform.
-
Testing for Sediment Acidification Effects on Within-Season Variability in Juvenile Soft-Shell Clam ( Mya arenaria ) Abundance on the Northern Shore of the Bay of Fundy
Estuaries and Coasts, 2017Co-Authors: Jeff C. Clements, Heather L. HuntAbstract:Soft-Shell Clams (Mya arenaria) can serve important ecological roles in intertidal mudflats and are an important economic and recreational resource in the northwestern Atlantic. However, environmental factors affecting newly-settled and juvenile Clam abundances within a given settlement season remain uncertain. We conducted a field study assessing relationships between juvenile Soft-Shell Clam abundance and spatial, temporal, and environmental variables in coastal mudflats of the northern shore of the Bay of Fundy. Sediment pH and low-tide water temperature (tide pools) were monitored in situ on a biweekly–monthly basis over the course of the M. arenaria settlement season in 2012 at four study sites to quantify diel variation in sediment pH and temperature. Core samples were also collected to quantify M. arenaria (
-
settlement and recruitment patterns of the soft shell Clam mya arenaria on the northern shore of the bay of fundy canada
Estuaries and Coasts, 2009Co-Authors: Jenna E Bowen, Heather L. HuntAbstract:To examine the roles of settlement and early postsettlement processes in the recruitment of the Soft-Shell Clam, Mya arenaria, abundance of recent settlers and juveniles was monitored over two field seasons at four locations on the northern shore of the Bay of Fundy in New Brunswick, Canada. Results showed great spatial and temporal variability in patterns of settlement. M. arenaria appeared to become highly vulnerable to postsettlement processes at a shell length of approximately 2 mm. Postsettlement processes drastically altered patterns of settlement less than 1 year after they were established. Results suggest that local factors at specific sites within the Bay of Fundy, such as hydrodynamics, larval behavior, and early postsettlement events, likely control the abundance of juvenile Clams. Additionally, postsettlement events are extremely important in shaping M. arenaria populations in this area. Very few mature adult Clams greater than 50 mm in shell length were found at any sampling sites, and no relationship was found between abundance of setters and density of juveniles and adults.
-
Effects of epibenthic predators in flow: transport and mortality of juveniles of the soft shell Clam Mya arenaria
Marine Ecology Progress Series, 2004Co-Authors: Heather L. HuntAbstract:During the early post-settlement period, dispersal and predation can drastically alter patterns of distribution and abundance of benthic invertebrates. These 2 processes may interact if predators cause disturbance and alter rates of transport of juvenile Clams. In this study, experiments were conducted in an annular flume to examine the effect of 2 epibenthic predators, the seven-spine bay shrimp Crangon septemspinosa and juveniles of the green crab Carcinus maenas, on rates of ero- sion and mortality of juvenile soft shell Clams Mya arenaria. Clams were exposed to 2 flow speeds (u =9 cm s -1 , shear velocity u * = 0.30 cm s -1 and u = 27 cm s -1 , u * = 0.97 cm s -1 ) in the presence and absence of predators. Erosion of sediment and Clams, and formation of ripples occurred at the high- flow velocity only in the presence of shrimp. This also occurred when shrimp disturbed the sediment prior to the experimental run, suggesting that shrimp activity changed bottom topography and the erosion threshold of the sediment. Juvenile green crabs caused less disturbance of the sediment and their activities did not result in transport of sediment or Clams. Gut content analysis indicated that juvenile green crabs preyed on juvenile M. arenaria. Shrimp preyed on Clams in 1 of 2 experiments, probably due to a difference in size of Clams between experiments (shell length = 1.0 vs. 3.0 mm). This study demonstrates that, in addition to causing mortality, predators can indirectly affect their prey by causing transport of sediment and associated small benthic invertebrates.
-
Post-settlement alteration of spatial patterns of soft shell Clam (Mya arenaria) recruits
Estuaries, 2003Co-Authors: Heather L. Hunt, D. Archie Mclean, Lauren S. MullineauxAbstract:To examine the roles of settlement and early post-settlement processes in patterns of recruitment of the soft shell Clam Mya arenaria , abundance of juvenile Mya at three intertidal sites in Barnstable Harbor, Massachusetts, was monitored over two settlement seasons. Two peaks of settlement occurred in 1998 (July and September) and one peak was recorded in June 1999, indicating that a late season settlement event is not a consistent feature at this site. Abundance of recent settlers (i.e., early recruits, < 1 week past settlement) varied significantly among the tidal flats (sites) that were separated by hundreds of meters to kilometers, but not among plots meters apart. Differences in abundance of settlers likely resulted in these differences in early-recruit abundance among sites. Settlement was greatest at the site with the greatest variability in flow speed. Sites also differed to some extent in their sediment characteristics and macrofaunal assemblages, which may influence larval substrate choice. Between-site differences in abundance of Mya decreased after settlement. The rate of decline of abundance varied among cohorts and sites. Comparison of abundance of recent settlers (up to 145,000 m^−2) to that of juveniles > 3-mm shell length at the end of the settlement season (up to 60 m^−2) indicated large losses of individuals during the early post-settlement period. This study demonstrates that spatial patterns in Mya abundance can change substantially during the early post-settlement period, and that high mortality rates can result in cohorts contributing little to the population size even when rates of settlement are high.
-
The roles of predation and postlarval transport in recruitment of the soft shell Clam (Mya arenaria)
Limnology and Oceanography, 2002Co-Authors: Heather L. Hunt, Lauren S. MullineauxAbstract:Rates of mortality and transport of newly settled benthic invertebrates can be very high and potentially have profound effects on patterns of recruitment. We used the soft shell Clam Mya arenaria as a model organism to compare the magnitude of rates of postlarval transport and predation on juveniles. We hypothesized that there is a critical size below which spatial variation in abundance of juvenile Mya is hydrodynamically controlled and above which abundance is mainly influenced by mortality, particularly due to epibenthic predators. To test this hypothesis, we examined transport and predation of early juvenile Mya in Barnstable Harbor, Massachusetts, USA. A caging experiment demonstrated that exclusion of epibenthic predators had a large impact on the density and size distribution of juvenile Mya within a few weeks of settlement and disproportionately affected juveniles of >2-mm shell length. Enclosure of the green crab Carcinus maenas changed the size distribution of Mya but did not significantly affect abundance. We attributed the effect of predator exclusion primarily to juvenile green crabs and fish. Current meter measurements suggested that tidal currents were strong enough to cause bedload transport of sediment and Mya. Measurement of gross and net rates of transport of Mya, using bedload traps and pans of defaunated sediment, confirmed that juveniles up to 5-mm shell length were routinely redistributed by tidal currents, particularly during spring tides. The number of postlarval Mya transported varied among sites and dates and was significantly related to ambient density of Mya and sediment flux. The loss of Mya during the caging experiment was compared to the rate of net flux of Mya due to transport during an intermediate tide. This comparison suggested that the loss due to predation was considerably larger than the flux due to transport for individuals >2 mm, but that rates of the two processes were more similar for individuals
Franck Berthe - One of the best experts on this subject based on the ideXlab platform.
-
lack of detection of a putative retrovirus associated with haemic neoplasia in the soft shell Clam mya arenaria
Journal of Invertebrate Pathology, 2012Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, T Iwamoto, K F Clark, P Mckenna, J W Casey, A CepicaAbstract:Abstract Haemic neoplasia (HN) is a leukemia-like disease that affects at least 20 species of marine bivalves including soft shell Clam, Mya arenaria. Since the disease was discovered in 1969, the etiology remains unknown. A retroviral etiology has been suggested based on the detection of reverse transcriptase activity and electron microscopic observation of retroviral-like particles using negative staining. To date, however no virus isolate and no retroviral sequence from HN has been obtained. Moreover, transmission of the disease by cell-free filtrate from affected Clams has not been reproduced. In the current study, we reinvestigated the association of HN with a putative retrovirus. Sucrose gradient centrifugation followed by assessment of reverse transcriptase activity, electrophoretic analysis of protein and RNA, and electron microscopic examinations of fractions corresponding to retroviral density were employed. Detection of retroviral pol sequences using degenerate RT-PCR approaches was also attempted. Our results showed visible bands at the expected density of retrovirus in HN-positive and HN-negative Clam tissues and both with reverse transcriptase activity. Electron microscopy, RNA analysis, protein analysis, and PCR systems targeting the pol gene of retroviruses did not however provide clear evidence supporting presence of a retrovirus. We point out that the retrovirus etiology of HN of Mya arenaria proposed some 25 years ago should be reconsidered in the absence of a virus isolate or virus sequences.
-
reverse transcriptase activity in tissues of the soft shell Clam mya arenaria affected with haemic neoplasia
Journal of Invertebrate Pathology, 2009Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, J W Casey, Stephanie Synard, Julie Pariseau, Jeffery Davidson, G Johnson, A CepicaAbstract:Abstract Since all retroviruses possess reverse transcriptase (RT) enzyme, reverse transcriptase activity has been the main supportive evidence of retroviral etiology of haemic neoplasia (HN) in soft shell Clams, Mya arenaria . The objective of the present study was to search for a putative retrovirus in various tissues of diseased Clams following quantification of RT activity (biochemical indicator of retroviral infection). The Clams were assessed by flow cytometry (FCM) for diagnosis of HN. RT activity was quantified by TaqMan-product enhanced reverse transcriptase (TM-PERT) assay in four different organs, gonad, gills, digestive gland, and mantle, at various stages of HN. The digestive gland, the organ with the highest RT activity, and haemocytes, the target cell of HN, were assessed by EM for presence of retroviruses. All organs were assessed by histology. The results of this study demonstrated that although all organs of healthy Clams have some background RT activity, the activity observed in most of organs of diseased Clams was significantly increased ( p 0.05). An association was observed between the degree of neoplastic cell infiltration and the level of RT activity. Digestive gland showed the highest and most consistent RT activity in both healthy and diseased Clams. No evidence for the existence of a retrovirus like particle was found by positive staining EM. The presence of RT activity without indications of retroviral particles in digestive gland and haemocytes suggests a probable endogenous source of RT.
-
Differential in vivo response of Soft-Shell Clam hemocytes against two strains of Vibrio splendidus: changes in cell structure, numbers and adherence.
Journal of invertebrate pathology, 2009Co-Authors: Dante R. Mateo, Ahmed Siah, Mebrahtu T. Araya, Franck Berthe, Gerry R. Johnson, Spencer J. GreenwoodAbstract:Host-pathogen interaction models in aquatic species are useful tools for understanding the pathogenicity of diseases in cultured and wild populations. In this study we report the differential in vivo response of Soft-Shell Clam (Mya arenaria) hemocytes against two strains of Vibrio splendidus. Responses were measured 24h after injecting into the posterior adductor muscle either an endemic wild-type strain (7SHRW) or a strain associated with oyster mortalities (LGP32-GFP). Changes in hemocyte structure (percentage of rounded cells) were assessed microscopically. Changes in adherence and hemocyte numbers were analyzed by flow-cytometric cell counting. Increased percentages of rounded cells were found in response to both strains. However, values from the group infected with LGP32-GFP were significantly higher (p
-
reverse transcriptase activity associated with haemic neoplasia in the soft shell Clam mya arenaria
Diseases of Aquatic Organisms, 2009Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, K F Clark, P Mckenna, Julie Pariseau, A CepicaAbstract:Reverse transcriptase (RT) activity has been reported in bivalves affected by haemic neoplasia (HN). Since all retroviruses have RT, detection of RT activity was regarded as evidence for the retroviral etiology of HN. This study investigates the relationship between RT levels and the progress of HN as indicated by percentages of tetraploid cells in Soft-Shell Clams Mya arenaria. The percentages of tetraploid cells were estimated by flow cytometry, and the RT levels were quantified using TaqMan product-enhanced RT (TM-PERT) assay. Results demonstrated that the amount of RT was positively correlated with the percentage of tetraploid cells circulating in Clam haemolymph (R 2 = 0.974, p < 0.001). Compared to HN-negative Clams (<5% tetraploid cells), 2 stages with significantly elevated levels of RT activity were observed: the first stage at ~10 to ~20% tetraploid cells, and the second at ~30 to ~80% tetraploid cells (p < 0.01). These data support the well established fact from mammalian models that transformed cells express high levels of non-telomeric RT. The observed increase in RT levels at ~30% tetraploidy coincides with previously reported p53 gene expression. Taken together, this could indicate that using RT levels as an indicator of HN, ≥30% tetraploidy is the stage at which the disease process undergoes a change, and perhaps becomes irreversible.
-
Reverse transcriptase activity associated with haemic neoplasia in the Soft-Shell Clam Mya arenaria
Diseases of aquatic organisms, 2009Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, K F Clark, Julie Pariseau, Patricia K. Mckenna, A CepicaAbstract:Reverse transcriptase (RT) activity has been reported in bivalves affected by haemic neoplasia (HN). Since all retroviruses have RT, detection of RT activity was regarded as evidence for the retroviral etiology of HN. This study investigates the relationship between RT levels and the progress of HN as indicated by percentages of tetraploid cells in Soft-Shell Clams Mya arenaria. The percentages of tetraploid cells were estimated by flow cytometry, and the RT levels were quantified using TaqMan product-enhanced RT (TM-PERT) assay. Results demonstrated that the amount of RT was positively correlated with the percentage of tetraploid cells circulating in Clam haemolymph (R 2 = 0.974, p < 0.001). Compared to HN-negative Clams (
Ahmed Siah - One of the best experts on this subject based on the ideXlab platform.
-
disseminated neoplasia in the soft shell Clam mya arenaria membrane lipid composition and functional parameters of circulating cells
Lipids, 2014Co-Authors: Fabienne Le Grand, Ahmed Siah, Rejean Tremblay, Philippe Soudant, Yanic Marty, Edouard KraffeAbstract:In a previous study we compared lipid composition and functional parameters of circulating cells from Cerastoderma edule affected or not by disseminated neoplasia (neoplastic cells vs hemocytes) (Le Grand et al. Chem Phys Lipids 167:9–20 2013). Neoplastic cells presented morpho-functional modifications concomitant to striking membrane lipid alterations: the proportion of particular plasmalogen molecular species was drastically decreased. We wanted to test whether this pattern was representative of bivalve neoplastic cells. For the purpose, a similar study was conducted on another bivalve species affected by disseminated neoplasia, the Soft-Shell Clam (Mya arenaria). Although total reactive oxygen species production was unaffected, M. arenaria neoplastic cells presented some functional alterations: phagocytosis activity was reduced by 33 %. However, lipid compositions were not drastically altered. Particularly, sterol and plasmalogen levels did not differ between both cell types (about 43 % of membrane lipids and 35 % of phospholipids, respectively in hemocytes and neoplastic cells). This could be related to the fact that disseminated neoplasia was not related to hemolymph cell proliferation in M. arenaria (0.9 ± 0.2 106cell mL−1, considering both healthy and neoplastic Clams, n = 6). Nevertheless this study highlighted minor but specific alterations of membrane lipid composition in M. arenaria neoplastic cells. The only phospholipid subclass in which the fatty acid profile strongly differed between both cell types was serine plasmalogen (PlsSer), with neoplastic cells presenting lower specific enrichment of 20:1n-11 in PlsSer. Such specific alteration of membrane lipid composition strengthened the assumption of an implication of key plasmalogen molecular species in this leukemia-like disease in bivalves.
-
lack of detection of a putative retrovirus associated with haemic neoplasia in the soft shell Clam mya arenaria
Journal of Invertebrate Pathology, 2012Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, T Iwamoto, K F Clark, P Mckenna, J W Casey, A CepicaAbstract:Abstract Haemic neoplasia (HN) is a leukemia-like disease that affects at least 20 species of marine bivalves including soft shell Clam, Mya arenaria. Since the disease was discovered in 1969, the etiology remains unknown. A retroviral etiology has been suggested based on the detection of reverse transcriptase activity and electron microscopic observation of retroviral-like particles using negative staining. To date, however no virus isolate and no retroviral sequence from HN has been obtained. Moreover, transmission of the disease by cell-free filtrate from affected Clams has not been reproduced. In the current study, we reinvestigated the association of HN with a putative retrovirus. Sucrose gradient centrifugation followed by assessment of reverse transcriptase activity, electrophoretic analysis of protein and RNA, and electron microscopic examinations of fractions corresponding to retroviral density were employed. Detection of retroviral pol sequences using degenerate RT-PCR approaches was also attempted. Our results showed visible bands at the expected density of retrovirus in HN-positive and HN-negative Clam tissues and both with reverse transcriptase activity. Electron microscopy, RNA analysis, protein analysis, and PCR systems targeting the pol gene of retroviruses did not however provide clear evidence supporting presence of a retrovirus. We point out that the retrovirus etiology of HN of Mya arenaria proposed some 25 years ago should be reconsidered in the absence of a virus isolate or virus sequences.
-
reverse transcriptase activity in tissues of the soft shell Clam mya arenaria affected with haemic neoplasia
Journal of Invertebrate Pathology, 2009Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, J W Casey, Stephanie Synard, Julie Pariseau, Jeffery Davidson, G Johnson, A CepicaAbstract:Abstract Since all retroviruses possess reverse transcriptase (RT) enzyme, reverse transcriptase activity has been the main supportive evidence of retroviral etiology of haemic neoplasia (HN) in soft shell Clams, Mya arenaria . The objective of the present study was to search for a putative retrovirus in various tissues of diseased Clams following quantification of RT activity (biochemical indicator of retroviral infection). The Clams were assessed by flow cytometry (FCM) for diagnosis of HN. RT activity was quantified by TaqMan-product enhanced reverse transcriptase (TM-PERT) assay in four different organs, gonad, gills, digestive gland, and mantle, at various stages of HN. The digestive gland, the organ with the highest RT activity, and haemocytes, the target cell of HN, were assessed by EM for presence of retroviruses. All organs were assessed by histology. The results of this study demonstrated that although all organs of healthy Clams have some background RT activity, the activity observed in most of organs of diseased Clams was significantly increased ( p 0.05). An association was observed between the degree of neoplastic cell infiltration and the level of RT activity. Digestive gland showed the highest and most consistent RT activity in both healthy and diseased Clams. No evidence for the existence of a retrovirus like particle was found by positive staining EM. The presence of RT activity without indications of retroviral particles in digestive gland and haemocytes suggests a probable endogenous source of RT.
-
Differential in vivo response of Soft-Shell Clam hemocytes against two strains of Vibrio splendidus: changes in cell structure, numbers and adherence.
Journal of invertebrate pathology, 2009Co-Authors: Dante R. Mateo, Ahmed Siah, Mebrahtu T. Araya, Franck Berthe, Gerry R. Johnson, Spencer J. GreenwoodAbstract:Host-pathogen interaction models in aquatic species are useful tools for understanding the pathogenicity of diseases in cultured and wild populations. In this study we report the differential in vivo response of Soft-Shell Clam (Mya arenaria) hemocytes against two strains of Vibrio splendidus. Responses were measured 24h after injecting into the posterior adductor muscle either an endemic wild-type strain (7SHRW) or a strain associated with oyster mortalities (LGP32-GFP). Changes in hemocyte structure (percentage of rounded cells) were assessed microscopically. Changes in adherence and hemocyte numbers were analyzed by flow-cytometric cell counting. Increased percentages of rounded cells were found in response to both strains. However, values from the group infected with LGP32-GFP were significantly higher (p
-
reverse transcriptase activity associated with haemic neoplasia in the soft shell Clam mya arenaria
Diseases of Aquatic Organisms, 2009Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, K F Clark, P Mckenna, Julie Pariseau, A CepicaAbstract:Reverse transcriptase (RT) activity has been reported in bivalves affected by haemic neoplasia (HN). Since all retroviruses have RT, detection of RT activity was regarded as evidence for the retroviral etiology of HN. This study investigates the relationship between RT levels and the progress of HN as indicated by percentages of tetraploid cells in Soft-Shell Clams Mya arenaria. The percentages of tetraploid cells were estimated by flow cytometry, and the RT levels were quantified using TaqMan product-enhanced RT (TM-PERT) assay. Results demonstrated that the amount of RT was positively correlated with the percentage of tetraploid cells circulating in Clam haemolymph (R 2 = 0.974, p < 0.001). Compared to HN-negative Clams (<5% tetraploid cells), 2 stages with significantly elevated levels of RT activity were observed: the first stage at ~10 to ~20% tetraploid cells, and the second at ~30 to ~80% tetraploid cells (p < 0.01). These data support the well established fact from mammalian models that transformed cells express high levels of non-telomeric RT. The observed increase in RT levels at ~30% tetraploidy coincides with previously reported p53 gene expression. Taken together, this could indicate that using RT levels as an indicator of HN, ≥30% tetraploidy is the stage at which the disease process undergoes a change, and perhaps becomes irreversible.
A Cepica - One of the best experts on this subject based on the ideXlab platform.
-
lack of detection of a putative retrovirus associated with haemic neoplasia in the soft shell Clam mya arenaria
Journal of Invertebrate Pathology, 2012Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, T Iwamoto, K F Clark, P Mckenna, J W Casey, A CepicaAbstract:Abstract Haemic neoplasia (HN) is a leukemia-like disease that affects at least 20 species of marine bivalves including soft shell Clam, Mya arenaria. Since the disease was discovered in 1969, the etiology remains unknown. A retroviral etiology has been suggested based on the detection of reverse transcriptase activity and electron microscopic observation of retroviral-like particles using negative staining. To date, however no virus isolate and no retroviral sequence from HN has been obtained. Moreover, transmission of the disease by cell-free filtrate from affected Clams has not been reproduced. In the current study, we reinvestigated the association of HN with a putative retrovirus. Sucrose gradient centrifugation followed by assessment of reverse transcriptase activity, electrophoretic analysis of protein and RNA, and electron microscopic examinations of fractions corresponding to retroviral density were employed. Detection of retroviral pol sequences using degenerate RT-PCR approaches was also attempted. Our results showed visible bands at the expected density of retrovirus in HN-positive and HN-negative Clam tissues and both with reverse transcriptase activity. Electron microscopy, RNA analysis, protein analysis, and PCR systems targeting the pol gene of retroviruses did not however provide clear evidence supporting presence of a retrovirus. We point out that the retrovirus etiology of HN of Mya arenaria proposed some 25 years ago should be reconsidered in the absence of a virus isolate or virus sequences.
-
reverse transcriptase activity in tissues of the soft shell Clam mya arenaria affected with haemic neoplasia
Journal of Invertebrate Pathology, 2009Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, J W Casey, Stephanie Synard, Julie Pariseau, Jeffery Davidson, G Johnson, A CepicaAbstract:Abstract Since all retroviruses possess reverse transcriptase (RT) enzyme, reverse transcriptase activity has been the main supportive evidence of retroviral etiology of haemic neoplasia (HN) in soft shell Clams, Mya arenaria . The objective of the present study was to search for a putative retrovirus in various tissues of diseased Clams following quantification of RT activity (biochemical indicator of retroviral infection). The Clams were assessed by flow cytometry (FCM) for diagnosis of HN. RT activity was quantified by TaqMan-product enhanced reverse transcriptase (TM-PERT) assay in four different organs, gonad, gills, digestive gland, and mantle, at various stages of HN. The digestive gland, the organ with the highest RT activity, and haemocytes, the target cell of HN, were assessed by EM for presence of retroviruses. All organs were assessed by histology. The results of this study demonstrated that although all organs of healthy Clams have some background RT activity, the activity observed in most of organs of diseased Clams was significantly increased ( p 0.05). An association was observed between the degree of neoplastic cell infiltration and the level of RT activity. Digestive gland showed the highest and most consistent RT activity in both healthy and diseased Clams. No evidence for the existence of a retrovirus like particle was found by positive staining EM. The presence of RT activity without indications of retroviral particles in digestive gland and haemocytes suggests a probable endogenous source of RT.
-
reverse transcriptase activity associated with haemic neoplasia in the soft shell Clam mya arenaria
Diseases of Aquatic Organisms, 2009Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, K F Clark, P Mckenna, Julie Pariseau, A CepicaAbstract:Reverse transcriptase (RT) activity has been reported in bivalves affected by haemic neoplasia (HN). Since all retroviruses have RT, detection of RT activity was regarded as evidence for the retroviral etiology of HN. This study investigates the relationship between RT levels and the progress of HN as indicated by percentages of tetraploid cells in Soft-Shell Clams Mya arenaria. The percentages of tetraploid cells were estimated by flow cytometry, and the RT levels were quantified using TaqMan product-enhanced RT (TM-PERT) assay. Results demonstrated that the amount of RT was positively correlated with the percentage of tetraploid cells circulating in Clam haemolymph (R 2 = 0.974, p < 0.001). Compared to HN-negative Clams (<5% tetraploid cells), 2 stages with significantly elevated levels of RT activity were observed: the first stage at ~10 to ~20% tetraploid cells, and the second at ~30 to ~80% tetraploid cells (p < 0.01). These data support the well established fact from mammalian models that transformed cells express high levels of non-telomeric RT. The observed increase in RT levels at ~30% tetraploidy coincides with previously reported p53 gene expression. Taken together, this could indicate that using RT levels as an indicator of HN, ≥30% tetraploidy is the stage at which the disease process undergoes a change, and perhaps becomes irreversible.
-
Reverse transcriptase activity associated with haemic neoplasia in the Soft-Shell Clam Mya arenaria
Diseases of aquatic organisms, 2009Co-Authors: Mohammed Aboelkhair, Ahmed Siah, Franck Berthe, Spencer J. Greenwood, K F Clark, Julie Pariseau, Patricia K. Mckenna, A CepicaAbstract:Reverse transcriptase (RT) activity has been reported in bivalves affected by haemic neoplasia (HN). Since all retroviruses have RT, detection of RT activity was regarded as evidence for the retroviral etiology of HN. This study investigates the relationship between RT levels and the progress of HN as indicated by percentages of tetraploid cells in Soft-Shell Clams Mya arenaria. The percentages of tetraploid cells were estimated by flow cytometry, and the RT levels were quantified using TaqMan product-enhanced RT (TM-PERT) assay. Results demonstrated that the amount of RT was positively correlated with the percentage of tetraploid cells circulating in Clam haemolymph (R 2 = 0.974, p < 0.001). Compared to HN-negative Clams (
Suzanne Trottier - One of the best experts on this subject based on the ideXlab platform.
-
Molluscan shellfish biomarker study of the Quebec, Canada, Saguenay Fjord with the soft‐shell Clam, Mya arenaria
Environmental Toxicology, 2002Co-Authors: Christian Blaise, François Gagné, Jocelyne Pellerin, P.-d Hansen, Suzanne TrottierAbstract:A spatial and temporal survey of six sites in the Saguenay Fjord and of one adjacent site in the St. Lawrence River estuary (Quebec, Canada) was undertaken to study the possible effects of anthropogenic contaminant input on Soft-Shell Clam (Mya arenaria) populations. Bivalve sampling sites were selected because they reflected a range of areas representative of either no known (or apparent) pollution sources or of areas potentially influenced by different gradients and types of contamination sources. The most upstream site selected in the Saguenay Fjord, nearest to a highly populated and industrialized sector, and the most downstream site, near its mouth with the St. Lawrence River estuary, spanned a distance of some 70 km and encompassed the entire intertidal area suitable for Mya arenaria habitat. To measure effects in collected animals, we used a comprehensive battery of biomarkers composed of metallothionein-like proteins (MT), 7-ethoxyresorufin O-deethylase activity (EROD), DNA damage (DD), lipid peroxidation (LPO), vitellinlike proteins (Vn), phagocytosis (PHAG), nonspecific esterase (NspE) activity, and condition factor (weight-to-length ratio of Clams). Vn, PHAG, DD, and NspE biomarkers were assayed in hemolymph (or hemocytes), whereas others (MT, EROD, LPO) were determined in the digestive gland. Whole-tissue metal content was also quantified in Clams collected in the spatial survey. The spatial survey conducted in June 1997 showed significant effects at all sites, and principal component analysis indicated in addition that the more important responses were linked to the MT, LPO, and NspE biomarkers. Clams collected from sites closest to the upstream reaches of the fjord generally displayed higher levels of tissue metals (cadmium, manganese), as well as greater responses of NspE activity, MT, LPO, and PHAG. Animals collected from sites influenced by municipal wastewaters had higher levels of Vn, suggesting the presence of environmental estrogens. The results of the temporal survey (six monthly samplings of Clams at three sites from May through October, 1997) showed that the bivalve reproductive cycle (vitellogenesis and spawning) can modulate the expression of several biomarkers. Vn levels, for example, were positively correlated with DD and EROD and negatively correlated with MT, suggesting that reproduction can influence the susceptibility of Clams to some contaminants. Discrimination analysis over the 6 months of sampling revealed that the mean value of the discriminant function changed significantly over time, suggesting important changes in the relative contribution of each biomarker. In short, this study has provided evidence that Clam populations in the Saguenay Fjord are impacted by multiple sources of contamination whose effects can be modulated by reproduction.
-
molluscan shellfish biomarker study of the quebec canada saguenay fjord with the soft shell Clam mya arenaria
Environmental Toxicology, 2002Co-Authors: Christian Blaise, François Gagné, Jocelyne Pellerin, P.-d Hansen, Suzanne TrottierAbstract:A spatial and temporal survey of six sites in the Saguenay Fjord and of one adjacent site in the St. Lawrence River estuary (Quebec, Canada) was undertaken to study the possible effects of anthropogenic contaminant input on Soft-Shell Clam (Mya arenaria) populations. Bivalve sampling sites were selected because they reflected a range of areas representative of either no known (or apparent) pollution sources or of areas potentially influenced by different gradients and types of contamination sources. The most upstream site selected in the Saguenay Fjord, nearest to a highly populated and industrialized sector, and the most downstream site, near its mouth with the St. Lawrence River estuary, spanned a distance of some 70 km and encompassed the entire intertidal area suitable for Mya arenaria habitat. To measure effects in collected animals, we used a comprehensive battery of biomarkers composed of metallothionein-like proteins (MT), 7-ethoxyresorufin O-deethylase activity (EROD), DNA damage (DD), lipid peroxidation (LPO), vitellinlike proteins (Vn), phagocytosis (PHAG), nonspecific esterase (NspE) activity, and condition factor (weight-to-length ratio of Clams). Vn, PHAG, DD, and NspE biomarkers were assayed in hemolymph (or hemocytes), whereas others (MT, EROD, LPO) were determined in the digestive gland. Whole-tissue metal content was also quantified in Clams collected in the spatial survey. The spatial survey conducted in June 1997 showed significant effects at all sites, and principal component analysis indicated in addition that the more important responses were linked to the MT, LPO, and NspE biomarkers. Clams collected from sites closest to the upstream reaches of the fjord generally displayed higher levels of tissue metals (cadmium, manganese), as well as greater responses of NspE activity, MT, LPO, and PHAG. Animals collected from sites influenced by municipal wastewaters had higher levels of Vn, suggesting the presence of environmental estrogens. The results of the temporal survey (six monthly samplings of Clams at three sites from May through October, 1997) showed that the bivalve reproductive cycle (vitellogenesis and spawning) can modulate the expression of several biomarkers. Vn levels, for example, were positively correlated with DD and EROD and negatively correlated with MT, suggesting that reproduction can influence the susceptibility of Clams to some contaminants. Discrimination analysis over the 6 months of sampling revealed that the mean value of the discriminant function changed significantly over time, suggesting important changes in the relative contribution of each biomarker. In short, this study has provided evidence that Clam populations in the Saguenay Fjord are impacted by multiple sources of contamination whose effects can be modulated by reproduction.
