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Jamie Seymour - One of the best experts on this subject based on the ideXlab platform.

  • Molecular dissection of Box Jellyfish venom cytotoxicity highlights an effective venom antidote
    Nature Communications, 2019
    Co-Authors: Man-tat Lau, Jamie Seymour, John Manion, Jamie B. Littleboy, Lisa Oyston, Thang M. Khuong, Qiao-ping Wang, David T. Nguyen, Daniel Hesselson, Gregory G. Neely
    Abstract:

    The Box Jellyfish Chironex fleckeri is extremely venomous, and envenoming causes tissue necrosis, extreme pain and death within minutes after severe exposure. Despite rapid and potent venom action, basic mechanistic insight is lacking. Here we perform molecular dissection of a Jellyfish venom-induced cell death pathway by screening for host components required for venom exposure-induced cell death using genome-scale lenti-CRISPR mutagenesis. We identify the peripheral membrane protein ATP2B1, a calcium transporting ATPase, as one host factor required for venom cytotoxicity. Targeting ATP2B1 prevents venom action and confers long lasting protection. Informatics analysis of host genes required for venom cytotoxicity reveal pathways not previously implicated in cell death. We also discover a venom antidote that functions up to 15 minutes after exposure and suppresses tissue necrosis and pain in mice. These results highlight the power of whole genome CRISPR screening to investigate venom mechanisms of action and to rapidly identify new medicines. Box Jellyfish venom causes tissue damage, pain, and death through unknown molecular mechanisms. Here, Lau et al. perform a CRISPR screen to identify genes required for venom action and use this information to develop an antidote that blocks venom-induced pain and tissue damage in vivo.

  • Dose and time dependence of Box Jellyfish antivenom
    The journal of venomous animals and toxins including tropical diseases, 2014
    Co-Authors: Athena Andreosso, Michael J. Smout, Jamie Seymour
    Abstract:

    Background: The effectiveness of the currently available Box Jellyfish (Chironex fleckeri) antivenom has been subject of debate for many years. To assess whether the Box Jellyfish antivenom has the ability to attenuate venom-induced damage at cellular level, the present study analyzed the dose and time dependence of the antivenom in a cell-based assay. Methods: Different doses of antivenom were added to venom and subsequently administered to cells and the cell index was measured using xCelligence Technology (ACEA Biosciences). Similarly, antivenom and venom were incubated over different time periods and cell survival measured as stated above. For both experiments, the cell index was plotted as a measure of cell survival against the dose or incubation time and significance was determined with the use of a one-way ANOVA with a LSD post hoc test. Results: Increasing concentrations of antivenom significantly augmented cell survival, with a concentration of approximately five times the currently recommended dose for human envenomation, causing the first significant increase in cell survival compared venom alone. Further, cell survival improved with increasing incubation time of venom and antivenom prior to addition to the cells, indicating that Box Jellyfish antivenom requires approximately 70 minutes to neutralize C. fleckeri venom. Conclusion: The presented results suggest that the currently recommended dose of antivenom requires adjustment, and more importantly, a human trial to test the effects of higher concentrations is also necessary. Further, antivenom has delayed neutralizing effects (i.e. after 70 minutes) which underlines the eminence of immediate and prolonged cardiopulmonary resuscitation in victims suffering from a C. fleckeri venom-induced cardiovascular collapse.

  • Dose and time dependence of Box Jellyfish antivenom
    Journal of Venomous Animals and Toxins Including Tropical Diseases, 2014
    Co-Authors: Athena Andreosso, Michael J. Smout, Jamie Seymour
    Abstract:

    Background The effectiveness of the currently available Box Jellyfish (Chironex fleckeri) antivenom has been subject of debate for many years. To assess whether the Box Jellyfish antivenom has the ability to attenuate venom-induced damage at cellular level, the present study analyzed the dose and time dependence of the antivenom in a cell-based assay.

  • rapid short term and gradual permanent cardiotoxic effects of vertebrate toxins from chironex fleckeri australian Box Jellyfish venom
    Toxicon, 2014
    Co-Authors: Stephanie Chaousis, Jason Mulvenna, Michael J. Smout, Alex Loukas, David Wilson, Jamie Seymour
    Abstract:

    The vertebrate cardiotoxic components of the venom produced by the Australian Box Jellyfish, Chironex fleckeri, have not previously been isolated. We have uncovered for the first time, three distinct cytotoxic crude fractions from within the vertebrate cardiotoxic peak of C. fleckeri venom by monitoring viability of human muscle cells with an impedance based assay (ACEA xCELLigence system) measuring cell detachment as cytotoxicity which was correlated with a reduction in cell metabolism using a cell proliferation (MTS) assay. When the effects of the venom components on human cardiomyocytes and human skeletal muscle cells were compared, two fractions were found to specifically affect cardiomyocytes with distinct temporal profiles (labelled Crude Toxic Fractions (CTF), α and β). A third fraction (CTF-γ) was toxic to both muscle cell types and therefore not cardio specific. The vertebrate, cardio specific CTF-α and CTF-β, presented distinct activities; CTF-α caused rapid but short term cell detachment and reduction in cell metabolism with enhanced activity at lower concentrations than CTF-β. This activity was not permanent, with cell reattachment and subsequent increased metabolism of heart muscle cells observed when exposed to all but the highest concentrations of CTF-α tested. The cytotoxic effect of CTF-β took twice as long to act on the cells compared to CTF-α, however, the activity was permanent. Furthermore, we showed that the two fractions combined have a synergistic effect causing a much stronger and faster cell detachment (death) when combined than the sum of the individual effects of each toxin. These data presented here improves the current understanding of the toxic mechanisms of the Australian Box Jellyfish, C. fleckeri, and provides a basis for in vivo research of these newly isolated toxic fractions.

  • chironex fleckeri Box Jellyfish venom proteins expansion of a cnidarian toxin family that elicits variable cytolytic and cardiovascular effects
    Journal of Biological Chemistry, 2014
    Co-Authors: Diane L. Brinkman, Jason Mulvenna, Jamie Seymour, Nicki Konstantakopoulos, Geoffrey K. Isbister, Bernie V Mcinerney, Wayne C Hodgson
    Abstract:

    Abstract The Box Jellyfish Chironex fleckeri produces extremely potent and rapid-acting venom that is harmful to humans and lethal to prey. Here, we describe the characterisation of two C. fleckeri venom proteins, CfTX-A (≈40 kDa) and CfTX-B (≈42 kDa), which were isolated from C. fleckeri venom using size exclusion chromatography and cation exchange chromatography. Full-length cDNA sequences encoding CfTX-A and -B and a third putative toxin, CfTX-Bt, were subsequently retrieved from a C. fleckeri tentacle cDNA library. Bioinformatic analyses revealed that the new toxins belong to a small family of potent cnidarian pore-forming toxins that includes two other C. fleckeri toxins, CfTX-1 and CfTX-2. Phylogenetic inferences from amino acid sequences of the toxin family grouped CfTX-A, -B and -Bt in a separate clade from CfTX-1 and -2, suggesting that the C. fleckeri toxins have diversified structurally and functionally during evolution. Comparative bioactivity assays revealed that CfTX-1/-2 (25µg kg-1) caused profound effects on the cardiovascular system of anaesthetised rats whereas CfTX-A/-B elicited only minor effects at the same dose. Conversely, the haemolytic activity of CfTX-A/-B (HU50 = 5ng mL-1) was at least 30 times greater than that of CfTX-1/-2. Structural homology between the cubozoan toxins and insecticidal 3d-Cry toxins (δ-endotoxins) suggests that the toxins have a similar pore-forming mechanism of action involving α-helices of the N-terminal domain, while structural diversification among toxin members may modulate target specificity. Expansion of the cnidarian toxin family therefore provides new insights into the evolutionary diversification of Box Jellyfish toxins from a structural and functional perspective.

Jason Mulvenna - One of the best experts on this subject based on the ideXlab platform.

  • Transcriptome and venom proteome of the Box Jellyfish Chironex fleckeri
    BMC genomics, 2015
    Co-Authors: Diane L. Brinkman, Xinying Jia, Jeremy Potriquet, Dhirendra Kumar, Debasis Dash, David Kvaskoff, Jason Mulvenna
    Abstract:

    The Box Jellyfish, Chironex fleckeri, is the largest and most dangerous cubozoan Jellyfish to humans. It produces potent and rapid-acting venom and its sting causes severe localized and systemic effects that are potentially life-threatening. In this study, a combined transcriptomic and proteomic approach was used to identify C. fleckeri proteins that elicit toxic effects in envenoming. More than 40,000,000 Illumina reads were used to de novo assemble ∼ 34,000 contiguous cDNA sequences and ∼ 20,000 proteins were predicted based on homology searches, protein motifs, gene ontology and biological pathway mapping. More than 170 potential toxin proteins were identified from the transcriptome on the basis of homology to known toxins in publicly available sequence databases. MS/MS analysis of C. fleckeri venom identified over 250 proteins, including a subset of the toxins predicted from analysis of the transcriptome. Potential toxins identified using MS/MS included metalloproteinases, an alpha-macroglobulin domain containing protein, two CRISP proteins and a turripeptide-like protease inhibitor. Nine novel examples of a taxonomically restricted family of potent cnidarian pore-forming toxins were also identified. Members of this toxin family are potently haemolytic and cause pain, inflammation, dermonecrosis, cardiovascular collapse and death in experimental animals, suggesting that these toxins are responsible for many of the symptoms of C. fleckeri envenomation. This study provides the first overview of a Box Jellyfish transcriptome which, coupled with venom proteomics data, enhances our current understanding of Box Jellyfish venom composition and the molecular structure and function of cnidarian toxins. The generated data represent a useful resource to guide future comparative studies, novel protein/peptide discovery and the development of more effective treatments for Jellyfish stings in humans. (Length: 300).

  • Transcriptome and venom proteome of the Box Jellyfish Chironex fleckeri
    BMC Genomics, 2015
    Co-Authors: Diane L. Brinkman, Xinying Jia, Jeremy Potriquet, Dhirendra Kumar, Debasis Dash, David Kvaskoff, Jason Mulvenna
    Abstract:

    Background The Box Jellyfish, Chironex fleckeri , is the largest and most dangerous cubozoan Jellyfish to humans. It produces potent and rapid-acting venom and its sting causes severe localized and systemic effects that are potentially life-threatening. In this study, a combined transcriptomic and proteomic approach was used to identify C. fleckeri proteins that elicit toxic effects in envenoming. Results More than 40,000,000 Illumina reads were used to de novo assemble ∼ 34,000 contiguous cDNA sequences and ∼ 20,000 proteins were predicted based on homology searches, protein motifs, gene ontology and biological pathway mapping. More than 170 potential toxin proteins were identified from the transcriptome on the basis of homology to known toxins in publicly available sequence databases. MS/MS analysis of C. fleckeri venom identified over 250 proteins, including a subset of the toxins predicted from analysis of the transcriptome. Potential toxins identified using MS/MS included metalloproteinases, an alpha-macroglobulin domain containing protein, two CRISP proteins and a turripeptide-like protease inhibitor. Nine novel examples of a taxonomically restricted family of potent cnidarian pore-forming toxins were also identified. Members of this toxin family are potently haemolytic and cause pain, inflammation, dermonecrosis, cardiovascular collapse and death in experimental animals, suggesting that these toxins are responsible for many of the symptoms of C. fleckeri envenomation. Conclusions This study provides the first overview of a Box Jellyfish transcriptome which, coupled with venom proteomics data, enhances our current understanding of Box Jellyfish venom composition and the molecular structure and function of cnidarian toxins. The generated data represent a useful resource to guide future comparative studies, novel protein/peptide discovery and the development of more effective treatments for Jellyfish stings in humans. (Length: 300).

  • rapid short term and gradual permanent cardiotoxic effects of vertebrate toxins from chironex fleckeri australian Box Jellyfish venom
    Toxicon, 2014
    Co-Authors: Stephanie Chaousis, Jason Mulvenna, Michael J. Smout, Alex Loukas, David Wilson, Jamie Seymour
    Abstract:

    The vertebrate cardiotoxic components of the venom produced by the Australian Box Jellyfish, Chironex fleckeri, have not previously been isolated. We have uncovered for the first time, three distinct cytotoxic crude fractions from within the vertebrate cardiotoxic peak of C. fleckeri venom by monitoring viability of human muscle cells with an impedance based assay (ACEA xCELLigence system) measuring cell detachment as cytotoxicity which was correlated with a reduction in cell metabolism using a cell proliferation (MTS) assay. When the effects of the venom components on human cardiomyocytes and human skeletal muscle cells were compared, two fractions were found to specifically affect cardiomyocytes with distinct temporal profiles (labelled Crude Toxic Fractions (CTF), α and β). A third fraction (CTF-γ) was toxic to both muscle cell types and therefore not cardio specific. The vertebrate, cardio specific CTF-α and CTF-β, presented distinct activities; CTF-α caused rapid but short term cell detachment and reduction in cell metabolism with enhanced activity at lower concentrations than CTF-β. This activity was not permanent, with cell reattachment and subsequent increased metabolism of heart muscle cells observed when exposed to all but the highest concentrations of CTF-α tested. The cytotoxic effect of CTF-β took twice as long to act on the cells compared to CTF-α, however, the activity was permanent. Furthermore, we showed that the two fractions combined have a synergistic effect causing a much stronger and faster cell detachment (death) when combined than the sum of the individual effects of each toxin. These data presented here improves the current understanding of the toxic mechanisms of the Australian Box Jellyfish, C. fleckeri, and provides a basis for in vivo research of these newly isolated toxic fractions.

  • chironex fleckeri Box Jellyfish venom proteins expansion of a cnidarian toxin family that elicits variable cytolytic and cardiovascular effects
    Journal of Biological Chemistry, 2014
    Co-Authors: Diane L. Brinkman, Jason Mulvenna, Jamie Seymour, Nicki Konstantakopoulos, Geoffrey K. Isbister, Bernie V Mcinerney, Wayne C Hodgson
    Abstract:

    Abstract The Box Jellyfish Chironex fleckeri produces extremely potent and rapid-acting venom that is harmful to humans and lethal to prey. Here, we describe the characterisation of two C. fleckeri venom proteins, CfTX-A (≈40 kDa) and CfTX-B (≈42 kDa), which were isolated from C. fleckeri venom using size exclusion chromatography and cation exchange chromatography. Full-length cDNA sequences encoding CfTX-A and -B and a third putative toxin, CfTX-Bt, were subsequently retrieved from a C. fleckeri tentacle cDNA library. Bioinformatic analyses revealed that the new toxins belong to a small family of potent cnidarian pore-forming toxins that includes two other C. fleckeri toxins, CfTX-1 and CfTX-2. Phylogenetic inferences from amino acid sequences of the toxin family grouped CfTX-A, -B and -Bt in a separate clade from CfTX-1 and -2, suggesting that the C. fleckeri toxins have diversified structurally and functionally during evolution. Comparative bioactivity assays revealed that CfTX-1/-2 (25µg kg-1) caused profound effects on the cardiovascular system of anaesthetised rats whereas CfTX-A/-B elicited only minor effects at the same dose. Conversely, the haemolytic activity of CfTX-A/-B (HU50 = 5ng mL-1) was at least 30 times greater than that of CfTX-1/-2. Structural homology between the cubozoan toxins and insecticidal 3d-Cry toxins (δ-endotoxins) suggests that the toxins have a similar pore-forming mechanism of action involving α-helices of the N-terminal domain, while structural diversification among toxin members may modulate target specificity. Expansion of the cnidarian toxin family therefore provides new insights into the evolutionary diversification of Box Jellyfish toxins from a structural and functional perspective.

  • Chironex fleckeri (Box Jellyfish) Venom Proteins EXPANSION OF A CNIDARIAN TOXIN FAMILY THAT ELICITS VARIABLE CYTOLYTIC AND CARDIOVASCULAR EFFECTS
    The Journal of biological chemistry, 2014
    Co-Authors: Diane L. Brinkman, Jason Mulvenna, Jamie Seymour, Nicki Konstantakopoulos, Geoffrey K. Isbister, Bernie V Mcinerney, Wayne Clarence Hodgson
    Abstract:

    The Box Jellyfish Chironex fleckeri produces extremely potent and rapid-acting venom that is harmful to humans and lethal to prey. Here, we describe the characterization of two C. fleckeri venom proteins, CfTX-A (∼40 kDa) and CfTX-B (∼42 kDa), which were isolated from C. fleckeri venom using size exclusion chromatography and cation exchange chromatography. Full-length cDNA sequences encoding CfTX-A and -B and a third putative toxin, CfTX-Bt, were subsequently retrieved from a C. fleckeri tentacle cDNA library. Bioinformatic analyses revealed that the new toxins belong to a small family of potent cnidarian pore-forming toxins that includes two other C. fleckeri toxins, CfTX-1 and CfTX-2. Phylogenetic inferences from amino acid sequences of the toxin family grouped CfTX-A, -B, and -Bt in a separate clade from CfTX-1 and -2, suggesting that the C. fleckeri toxins have diversified structurally and functionally during evolution. Comparative bioactivity assays revealed that CfTX-1/2 (25 μg kg(-1)) caused profound effects on the cardiovascular system of anesthetized rats, whereas CfTX-A/B elicited only minor effects at the same dose. Conversely, the hemolytic activity of CfTX-A/B (HU50 = 5 ng ml(-1)) was at least 30 times greater than that of CfTX-1/2. Structural homology between the cubozoan toxins and insecticidal three-domain Cry toxins (δ-endotoxins) suggests that the toxins have a similar pore-forming mechanism of action involving α-helices of the N-terminal domain, whereas structural diversification among toxin members may modulate target specificity. Expansion of the cnidarian toxin family therefore provides new insights into the evolutionary diversification of Box Jellyfish toxins from a structural and functional perspective.

Wayne Clarence Hodgson - One of the best experts on this subject based on the ideXlab platform.

  • Chironex fleckeri (Box Jellyfish) Venom Proteins EXPANSION OF A CNIDARIAN TOXIN FAMILY THAT ELICITS VARIABLE CYTOLYTIC AND CARDIOVASCULAR EFFECTS
    The Journal of biological chemistry, 2014
    Co-Authors: Diane L. Brinkman, Jason Mulvenna, Jamie Seymour, Nicki Konstantakopoulos, Geoffrey K. Isbister, Bernie V Mcinerney, Wayne Clarence Hodgson
    Abstract:

    The Box Jellyfish Chironex fleckeri produces extremely potent and rapid-acting venom that is harmful to humans and lethal to prey. Here, we describe the characterization of two C. fleckeri venom proteins, CfTX-A (∼40 kDa) and CfTX-B (∼42 kDa), which were isolated from C. fleckeri venom using size exclusion chromatography and cation exchange chromatography. Full-length cDNA sequences encoding CfTX-A and -B and a third putative toxin, CfTX-Bt, were subsequently retrieved from a C. fleckeri tentacle cDNA library. Bioinformatic analyses revealed that the new toxins belong to a small family of potent cnidarian pore-forming toxins that includes two other C. fleckeri toxins, CfTX-1 and CfTX-2. Phylogenetic inferences from amino acid sequences of the toxin family grouped CfTX-A, -B, and -Bt in a separate clade from CfTX-1 and -2, suggesting that the C. fleckeri toxins have diversified structurally and functionally during evolution. Comparative bioactivity assays revealed that CfTX-1/2 (25 μg kg(-1)) caused profound effects on the cardiovascular system of anesthetized rats, whereas CfTX-A/B elicited only minor effects at the same dose. Conversely, the hemolytic activity of CfTX-A/B (HU50 = 5 ng ml(-1)) was at least 30 times greater than that of CfTX-1/2. Structural homology between the cubozoan toxins and insecticidal three-domain Cry toxins (δ-endotoxins) suggests that the toxins have a similar pore-forming mechanism of action involving α-helices of the N-terminal domain, whereas structural diversification among toxin members may modulate target specificity. Expansion of the cnidarian toxin family therefore provides new insights into the evolutionary diversification of Box Jellyfish toxins from a structural and functional perspective.

  • Molecular diversity of Box Jellyfish toxins
    Toxicon, 2012
    Co-Authors: Diane L. Brinkman, Jason Mulvenna, Jamie Seymour, Nicki Konstantakopoulos, Wayne Clarence Hodgson, Geoffrey K. Isbister, James N. Burnell
    Abstract:

    Box Jellyfish (cubozoans) are renowned for their ability to immobilise and kill prey and inflict painful and debilitating stings to humans by injecting potent venoms from their nematocysts. Chironex fleckeri is the largest species of Box Jellyfish and its venom produces extremely rapid and potentially life-threatening effects. Advances in Box Jellyfish toxinology using bioactivity-guided purification methods, tandem mass spectrometry and molecular cloning techniques have revealed that C. fleckeri venom contains a diverse array of proteins that is dominated by a family of abundant high molecular weight venom proteins that are cytolytic, cytotoxic and cause profound cardiovascular collapse in experimental animals. Related toxins with similar biological activities are present in other Jellyfish species and comparative analysis of available toxin sequences infers that this expanding family of potent cnidarian toxins forms at least two distinct protein clades. Sequence divergence among family members coupled with experimental evidence suggests there are significant structural variations between clades that may alter their function and target specificity. In this context, an overview of this unique family of protein toxins is presented, including a brief history of their discovery and recent progress in their purification and molecular characterisation primarily from a bioinformatic perspective.

  • A cell-based assay for screening of antidotes to, and antivenom against Chironex fleckeri (Box Jellyfish) venom.
    Journal of pharmacological and toxicological methods, 2009
    Co-Authors: Nicki Konstantakopoulos, Jamie Seymour, Geoffrey K. Isbister, Wayne Clarence Hodgson
    Abstract:

    Introduction: Chironex fleckeri is a large Box Jellyfish that has been labelled the ‘most venomous animal’ in the world. We have recently shown that the primary effect of C. fleckeri venom in vivo is cardiovascular collapse. This study utilised a cell-based assay to examine the effects of C. fleckeri venom on the proliferation of a rat aortic smooth muscle cell line. In addition, the ability of CSL Box Jellyfish antivenom and/or various potential treatment strategies to neutralise the effects of the venom was examined. Methods: A7r5 cells were cultured in media containing venom. The effect of CSL Box Jellyfish antivenom (5 U/mL), CSL polyvalent snake antivenom (5 U/mL), lanthanum (5 µM), MgSO4 (50 mM), verapamil (5 µM) or felodipine (5 µM) was examined. Cell viability was determined using a Cell titer 96 AQueous One Solution cell proliferation assay. Results: Incubation of A7r5 cells with serially diluted venom (2–0.004 µg/mL) caused a concentration-dependent inhibition of cell proliferation with an IC50 value of 0.056 µg/mL. This response was not affected by the absence of calcium or the presence of lanthanum in the media. Box Jellyfish antivenom (5 U/mL) prevented the inhibition of cell proliferation caused by the venom. Verapamil (5 µM) had no significant effect on the inhibition. In contrast, felodipine (5 µM) or MgSO4 (50 mM) potentiated the effects of the venom and partially negated the protective effect of the antivenom. Discussion: This study displayed the ability to utilise a cell-based assay to determine the effects of C. fleckeri venom on vascular cell viability. It showed that CSL Box Jellyfish can neutralise the effects of the venom but only if added prior to the venom. In addition, potential adjunct therapies verapamil, felodipine and MgSO4 were found to be ineffective, with felodipine and MgSO4 potentiating the detrimental effects of the venom.

  • An in vivo comparison of the efficacy of CSL Box Jellyfish antivenom with antibodies raised against nematocyst-derived Chironex fleckeri venom
    Toxicology letters, 2009
    Co-Authors: Kelly Lee Winter, Jamie Seymour, Geoffrey K. Isbister, Tamara Jacoby, Wayne Clarence Hodgson
    Abstract:

    Although CSL Box Jellyfish antivenom (AV) remains the primary treatment for Chironex fleckeri envenoming, there has been considerable debate regarding its clinical effectiveness. Animal studies have shown that AV is largely ineffective in preventing C. fleckeri-induced cardiovascular collapse. This study examined the effectiveness of CSL Box Jellyfish AV (ovine IgG), raised against ‘milked’ venom, and polyclonal rabbit IgG antibodies (Ab) raised against nematocyst-derived venom. A venom dose of 30 μg/kg, i.v., which causes an initial presser response (34 ± 5 mmHg; n = 7) followed by cardiovascular collapse, was used in all experiments. A bolus dose of AV (3000 U/kg, i.v.) or Ab (12 mg; i.e. an equivalent protein ‘load’ to 3000 U/kg AV), administered 15 min prior to a bolus dose of venom, did not significantly attenuate the effects of venom. The venom response was also not significantly attenuated when AV (3000 U/kg) was given as a bolus dose 10–60 min prior to venom infusion. However, when the venom was incubated with either AV (3000 U/kg) or Ab (12 mg) for 3 h prior to infusion, the effect of the venom was almost abolished. The results of this study demonstrate that antibodies raised against both ‘milked’ and nematocyst-derived venom are able to neutralise the cardiovascular collapse produced by the venom. However, large amounts of AV are required and must be preincubated with the venom to be protective. This indicates a very rapid action of the toxin(s) and that AV is unlikely to be clinically effective because it cannot be administered early enough.

  • the in vivo cardiovascular effects of Box Jellyfish chironex fleckeri venom in rats efficacy of pre treatment with antivenom verapamil and magnesium sulphate
    Toxicon, 2004
    Co-Authors: Sharmaine Ramasamy, Jamie Seymour, Geoffrey K. Isbister, Wayne Clarence Hodgson
    Abstract:

    Using a new technique to extract venom from the nematocysts, the efficacy of CSL Box Jellyfish antivenom (AV) and adjunct therapies, verapamil and magnesium sulfate (MgSO4), were investigated against the in vivo cardiovascular effects of Chironex fleckeri venom in anaesthetised rats. C. fleckeri venom (30 μg/kg; i.v.) produced a transient hypertensive response followed by hypotension and cardiovascular collapse within 4 min of administration. Prophylactic treatment of anaesthetised rats with CSL Box Jellyfish AV (3000 U/kg; i.v.) did not have any effect on the venom-induced pressor response, but prevented cardiovascular collapse in four out of 10 animals. Administration of verapamil (20 mM@0.25 ml/min; i.v.) either alone or in combination with AV, did not have any effect on the C. fleckeri venom-induced pressor response nor the consequent hypotension or cardiovascular collapse of animals. However, the administration of verapamil negated the partially protective effects of AV. Concurrent artificial respiration of animals with the above treatments did not attenuate the C. fleckeri venom-induced cardiovascular effects. MgSO4 (0.05–0.07 M@0.25 ml/min; i.v.) alone did not have any effect on the venom-induced pressor response nor the consequent cardiovascular collapse of animals. However, although combined AV and MgSO4 administration could not inhibit the transient pressor effect following the administration of C. fleckeri venom, it prevented cardiovascular collapse in all animals. We show for the first time, the cardiovascular effects of a C. fleckeri venom sample free of tentacular contamination and the potential of MgSO4 as an adjunct therapy for the treatment of potentially fatal C. fleckeri envenomings.

Dan-eric Nilsson - One of the best experts on this subject based on the ideXlab platform.

  • Velarium control and visual steering in Box Jellyfish
    Journal of Comparative Physiology A, 2013
    Co-Authors: Ronald Petie, Anders Garm, Dan-eric Nilsson
    Abstract:

    Directional swimming in the Box Jellyfish Tripedalia cystophora (cubozoa, cnidaria) is controlled by the shape of the velarium, which is a thin muscular sheet that forms the opening of the bell. It was unclear how different patterns of visual stimulation control directional swimming and that is the focus of this study. Jellyfish were tethered inside a small experimental tank, where the four vertical walls formed light panels. All four panels were lit at the start of an experiment. The shape of the opening in the velarium was recorded in response to switching off different combinations of panels. We found that under the experimental conditions the opening in the velarium assumed three distinct shapes during a swim contraction. The opening was (1) centred or it was off-centred and pocketed out either towards (2) a rhopalium or (3) a pedalium. The shape of the opening in the velarium followed the direction of the stimulus as long as the stimulus contained directional information. When the stimulus contained no directional information, the percentage of centred pulses increased and the shape of the off-centred pulses had a random orientation. Removing one rhopalium did not change the directional response of the animals, however, the number of centred pulses increased. When three rhopalia were removed, the percentage of centred pulses increased even further and the animals lost their ability to respond to directional information.

  • Contrast and rate of light intensity decrease control directional swimming in the Box Jellyfish Tripedalia cystophora (Cnidaria, Cubomedusae)
    Hydrobiologia, 2013
    Co-Authors: Ronald Petie, Anders Garm, Dan-eric Nilsson
    Abstract:

    Box Jellyfish respond to visual stimuli by changing the dynamics and frequency of bell contractions. In this study, we determined how the contrast and the dimming time of a simple visual stimulus affected bell contraction dynamics in the Box Jellyfish Tripedalia cystophora . Animals were tethered in an experimental chamber where the vertical walls formed the light stimuli. Two neighbouring walls were darkened and the contraction of the bell was monitored by high-speed video. We found that (1) bell contraction frequency increased with increasing contrast and decreasing dimming time. Furthermore, (2) when increasing the contrast and decreasing the dimming time pulses with an off-centred opening had a better defined direction and (3) the number of centred pulses decreased. Only weak effects were found on the relative diameter of the contracted bell and no correlation was found for the duration of bell contraction. Our observations show that visual stimuli modulate swim speed in T. cystophora by changing the swim pulse frequency. Furthermore, the direction of swimming is better defined when the animal perceives a high-contrast, or fast dimming, stimulus.

  • visual control of steering in the Box Jellyfish tripedalia cystophora
    The Journal of Experimental Biology, 2011
    Co-Authors: Ronald Petie, Anders Garm, Dan-eric Nilsson
    Abstract:

    Box Jellyfish carry an elaborate visual system consisting of 24 eyes, which they use for driving a number of behaviours. However, it is not known how visual input controls the swimming behaviour. In this study we exposed the Caribbean Box Jellyfish Tripedalia cystophora to simple visual stimuli and recorded changes in their swimming behaviour. Animals were tethered in a small experimental chamber, where we could control lighting conditions. The behaviour of the animals was quantified by tracking the movements of the bell, using a high-speed camera. We found that the animals respond predictably to the darkening of one quadrant of the equatorial visual world by (1) increasing pulse frequency, (2) creating an asymmetry in the structure that constricts the outflow opening of the bell, the velarium, and (3) delaying contraction at one of the four sides of the bell. This causes the animals to orient their bell in such a way that, if not tethered, they would turn and swim away from the dark area. We conclude that the visual system of T. cystophora has a predictable effect on swimming behaviour.

  • Box Jellyfish Use Terrestrial Visual Cues for Navigation
    Current biology : CB, 2011
    Co-Authors: Anders Garm, Magnus Oskarsson, Dan-eric Nilsson
    Abstract:

    Box Jellyfish have an impressive set of 24 eyes of four different types, including eyes structurally similar to those of vertebrates and cephalopods [1, 2]. However, the known visual responses are restricted to simple phototaxis, shadow responses, and object avoidance responses [3-8], and it has been a puzzle why they need such a complex set of eyes. Here we report that medusae of the Box Jellyfish Tripedalia cystophora are capable of visually guided navigation in mangrove swamps using terrestrial structures seen through the water surface. They detect the mangrove canopy by an eye type that is specialized to peer up through the water surface and that is suspended such that it is constantly looking straight up, irrespective of the orientation of the Jellyfish. The visual information is used to navigate to the preferred habitat at the edge of mangrove lagoons.

  • Visual pigment in the lens eyes of the Box Jellyfish Chiropsella bronzie
    Proceedings. Biological sciences, 2010
    Co-Authors: Megan O'connor, Anders Garm, Justin Marshall, Nathan S. Hart, Peter Ekström, Charlotta Skogh, Dan-eric Nilsson
    Abstract:

    Box Jellyfish (Cubomedusae) possess a unique visual system comprising 24 eyes of four morphological types. Moreover, Box Jellyfish display several visually guided behaviours, including obstacle avoidance and light-shaft attractance. It is largely unknown what kind of visual information Box Jellyfish use for carrying out these behaviours. Brightness contrast is almost certainly involved, but it is also possible that Box Jellyfish extract colour information from their surroundings. The possible presence of colour vision in Box Jellyfish has previously been investigated using behavioural, electrophysiological and immunohistochemical methods. However, the results from these studies are to some degree conflicting and inconclusive. Here, we present results from an investigation into the visual system of the Box Jellyfish Chiropsella bronzie, using microspectrophotometry and immunohistochemistry. Our results strongly indicate that only one type of visual pigment is present in the upper and lower lens eyes with a peak absorbance of approximately 510 nm. Additionally, the visual pigment appears to undergo bleaching, similar to that of vertebrate visual pigments.

Geoffrey K. Isbister - One of the best experts on this subject based on the ideXlab platform.

  • chironex fleckeri Box Jellyfish venom proteins expansion of a cnidarian toxin family that elicits variable cytolytic and cardiovascular effects
    Journal of Biological Chemistry, 2014
    Co-Authors: Diane L. Brinkman, Jason Mulvenna, Jamie Seymour, Nicki Konstantakopoulos, Geoffrey K. Isbister, Bernie V Mcinerney, Wayne C Hodgson
    Abstract:

    Abstract The Box Jellyfish Chironex fleckeri produces extremely potent and rapid-acting venom that is harmful to humans and lethal to prey. Here, we describe the characterisation of two C. fleckeri venom proteins, CfTX-A (≈40 kDa) and CfTX-B (≈42 kDa), which were isolated from C. fleckeri venom using size exclusion chromatography and cation exchange chromatography. Full-length cDNA sequences encoding CfTX-A and -B and a third putative toxin, CfTX-Bt, were subsequently retrieved from a C. fleckeri tentacle cDNA library. Bioinformatic analyses revealed that the new toxins belong to a small family of potent cnidarian pore-forming toxins that includes two other C. fleckeri toxins, CfTX-1 and CfTX-2. Phylogenetic inferences from amino acid sequences of the toxin family grouped CfTX-A, -B and -Bt in a separate clade from CfTX-1 and -2, suggesting that the C. fleckeri toxins have diversified structurally and functionally during evolution. Comparative bioactivity assays revealed that CfTX-1/-2 (25µg kg-1) caused profound effects on the cardiovascular system of anaesthetised rats whereas CfTX-A/-B elicited only minor effects at the same dose. Conversely, the haemolytic activity of CfTX-A/-B (HU50 = 5ng mL-1) was at least 30 times greater than that of CfTX-1/-2. Structural homology between the cubozoan toxins and insecticidal 3d-Cry toxins (δ-endotoxins) suggests that the toxins have a similar pore-forming mechanism of action involving α-helices of the N-terminal domain, while structural diversification among toxin members may modulate target specificity. Expansion of the cnidarian toxin family therefore provides new insights into the evolutionary diversification of Box Jellyfish toxins from a structural and functional perspective.

  • Chironex fleckeri (Box Jellyfish) Venom Proteins EXPANSION OF A CNIDARIAN TOXIN FAMILY THAT ELICITS VARIABLE CYTOLYTIC AND CARDIOVASCULAR EFFECTS
    The Journal of biological chemistry, 2014
    Co-Authors: Diane L. Brinkman, Jason Mulvenna, Jamie Seymour, Nicki Konstantakopoulos, Geoffrey K. Isbister, Bernie V Mcinerney, Wayne Clarence Hodgson
    Abstract:

    The Box Jellyfish Chironex fleckeri produces extremely potent and rapid-acting venom that is harmful to humans and lethal to prey. Here, we describe the characterization of two C. fleckeri venom proteins, CfTX-A (∼40 kDa) and CfTX-B (∼42 kDa), which were isolated from C. fleckeri venom using size exclusion chromatography and cation exchange chromatography. Full-length cDNA sequences encoding CfTX-A and -B and a third putative toxin, CfTX-Bt, were subsequently retrieved from a C. fleckeri tentacle cDNA library. Bioinformatic analyses revealed that the new toxins belong to a small family of potent cnidarian pore-forming toxins that includes two other C. fleckeri toxins, CfTX-1 and CfTX-2. Phylogenetic inferences from amino acid sequences of the toxin family grouped CfTX-A, -B, and -Bt in a separate clade from CfTX-1 and -2, suggesting that the C. fleckeri toxins have diversified structurally and functionally during evolution. Comparative bioactivity assays revealed that CfTX-1/2 (25 μg kg(-1)) caused profound effects on the cardiovascular system of anesthetized rats, whereas CfTX-A/B elicited only minor effects at the same dose. Conversely, the hemolytic activity of CfTX-A/B (HU50 = 5 ng ml(-1)) was at least 30 times greater than that of CfTX-1/2. Structural homology between the cubozoan toxins and insecticidal three-domain Cry toxins (δ-endotoxins) suggests that the toxins have a similar pore-forming mechanism of action involving α-helices of the N-terminal domain, whereas structural diversification among toxin members may modulate target specificity. Expansion of the cnidarian toxin family therefore provides new insights into the evolutionary diversification of Box Jellyfish toxins from a structural and functional perspective.

  • Molecular diversity of Box Jellyfish toxins
    Toxicon, 2012
    Co-Authors: Diane L. Brinkman, Jason Mulvenna, Jamie Seymour, Nicki Konstantakopoulos, Wayne Clarence Hodgson, Geoffrey K. Isbister, James N. Burnell
    Abstract:

    Box Jellyfish (cubozoans) are renowned for their ability to immobilise and kill prey and inflict painful and debilitating stings to humans by injecting potent venoms from their nematocysts. Chironex fleckeri is the largest species of Box Jellyfish and its venom produces extremely rapid and potentially life-threatening effects. Advances in Box Jellyfish toxinology using bioactivity-guided purification methods, tandem mass spectrometry and molecular cloning techniques have revealed that C. fleckeri venom contains a diverse array of proteins that is dominated by a family of abundant high molecular weight venom proteins that are cytolytic, cytotoxic and cause profound cardiovascular collapse in experimental animals. Related toxins with similar biological activities are present in other Jellyfish species and comparative analysis of available toxin sequences infers that this expanding family of potent cnidarian toxins forms at least two distinct protein clades. Sequence divergence among family members coupled with experimental evidence suggests there are significant structural variations between clades that may alter their function and target specificity. In this context, an overview of this unique family of protein toxins is presented, including a brief history of their discovery and recent progress in their purification and molecular characterisation primarily from a bioinformatic perspective.

  • A cell-based assay for screening of antidotes to, and antivenom against Chironex fleckeri (Box Jellyfish) venom.
    Journal of pharmacological and toxicological methods, 2009
    Co-Authors: Nicki Konstantakopoulos, Jamie Seymour, Geoffrey K. Isbister, Wayne Clarence Hodgson
    Abstract:

    Introduction: Chironex fleckeri is a large Box Jellyfish that has been labelled the ‘most venomous animal’ in the world. We have recently shown that the primary effect of C. fleckeri venom in vivo is cardiovascular collapse. This study utilised a cell-based assay to examine the effects of C. fleckeri venom on the proliferation of a rat aortic smooth muscle cell line. In addition, the ability of CSL Box Jellyfish antivenom and/or various potential treatment strategies to neutralise the effects of the venom was examined. Methods: A7r5 cells were cultured in media containing venom. The effect of CSL Box Jellyfish antivenom (5 U/mL), CSL polyvalent snake antivenom (5 U/mL), lanthanum (5 µM), MgSO4 (50 mM), verapamil (5 µM) or felodipine (5 µM) was examined. Cell viability was determined using a Cell titer 96 AQueous One Solution cell proliferation assay. Results: Incubation of A7r5 cells with serially diluted venom (2–0.004 µg/mL) caused a concentration-dependent inhibition of cell proliferation with an IC50 value of 0.056 µg/mL. This response was not affected by the absence of calcium or the presence of lanthanum in the media. Box Jellyfish antivenom (5 U/mL) prevented the inhibition of cell proliferation caused by the venom. Verapamil (5 µM) had no significant effect on the inhibition. In contrast, felodipine (5 µM) or MgSO4 (50 mM) potentiated the effects of the venom and partially negated the protective effect of the antivenom. Discussion: This study displayed the ability to utilise a cell-based assay to determine the effects of C. fleckeri venom on vascular cell viability. It showed that CSL Box Jellyfish can neutralise the effects of the venom but only if added prior to the venom. In addition, potential adjunct therapies verapamil, felodipine and MgSO4 were found to be ineffective, with felodipine and MgSO4 potentiating the detrimental effects of the venom.

  • An in vivo comparison of the efficacy of CSL Box Jellyfish antivenom with antibodies raised against nematocyst-derived Chironex fleckeri venom
    Toxicology letters, 2009
    Co-Authors: Kelly Lee Winter, Jamie Seymour, Geoffrey K. Isbister, Tamara Jacoby, Wayne Clarence Hodgson
    Abstract:

    Although CSL Box Jellyfish antivenom (AV) remains the primary treatment for Chironex fleckeri envenoming, there has been considerable debate regarding its clinical effectiveness. Animal studies have shown that AV is largely ineffective in preventing C. fleckeri-induced cardiovascular collapse. This study examined the effectiveness of CSL Box Jellyfish AV (ovine IgG), raised against ‘milked’ venom, and polyclonal rabbit IgG antibodies (Ab) raised against nematocyst-derived venom. A venom dose of 30 μg/kg, i.v., which causes an initial presser response (34 ± 5 mmHg; n = 7) followed by cardiovascular collapse, was used in all experiments. A bolus dose of AV (3000 U/kg, i.v.) or Ab (12 mg; i.e. an equivalent protein ‘load’ to 3000 U/kg AV), administered 15 min prior to a bolus dose of venom, did not significantly attenuate the effects of venom. The venom response was also not significantly attenuated when AV (3000 U/kg) was given as a bolus dose 10–60 min prior to venom infusion. However, when the venom was incubated with either AV (3000 U/kg) or Ab (12 mg) for 3 h prior to infusion, the effect of the venom was almost abolished. The results of this study demonstrate that antibodies raised against both ‘milked’ and nematocyst-derived venom are able to neutralise the cardiovascular collapse produced by the venom. However, large amounts of AV are required and must be preincubated with the venom to be protective. This indicates a very rapid action of the toxin(s) and that AV is unlikely to be clinically effective because it cannot be administered early enough.