alexa Toxicity of the cyanobacterial cyclic heptapeptide toxins microcystin-LR and -RR in early life-stages of the African clawed frog (Xenopus laevis).
Environmental Sciences

Environmental Sciences

Journal of Ecosystem & Ecography

Author(s): Fischer WJ, Dietrich DR

Abstract Share this page

Abstract Numerous cyanobacterial species are capable of producing potent toxins, which have been known to cause intoxications and fatalities in wildlife, livestock and humans. Microcystis is amongst the most ubiquitously distributed blue-green algal genus and almost invariably produces cyclic heptapeptide toxins called microcystins (MC). These toxins are highly persistent in water (several weeks). Highest concentrations are found in shallow littoral areas, the primary environment for aquatic early life-stage development. Therefore, the present study focussed on the potential embryotoxic effects of MC (MC-LR and -RR) in early life-stages of the amphibian Xenopus laevis. The endpoints chosen were mortality, malformation and growth inhibition. To achieve an improved dose-response relationship the uptake of MC was quantified simultaneously, using a radiolabeled derivative of MC-LR. As one of the best described molecular mechanisms of MC toxicity involves the specific inhibition of serine/threonine protein phosphatases-1 and -2A (PP), essential enzymes involved in the mechanisms of cell cycle regulation and maintenance of cellular morphology, the inhibition of PP in X. laevis exposed to MC was monitored. For this the presence of both PP-1 and PP-2A was confirmed by means of SDS-PAGE and immunoblotting. Second, the capacity of MC to inhibit X. laevis embryo-larval PP was corroborated by in vitro incubation of embryo-larval homogenates with MC-LR and -RR and subsequent determination of PP-inhibition. No increased mortality, malformation, or growth inhibition was observed even at the highest MC concentrations employed. MC had neither a demonstrable inhibitory effect on X. laevis PP-activity in vivo in the first 96 h of exposure. However, as of 96 and 120 h exposure a significant inhibition of PP activity was observed at the highest dose (2000 µg/l) in MC-LR and MC-RR exposed embryo-larvae, respectively. By the same token, no notable amounts of radiolabeled [3H]-MC-LR were taken up during the first 96 h, whereas a drastic increase in [3H]-MC-LR was observed after feeding of the larvae had commenced. The [3H]-MC-LR concentration was consistently found to be highest in the viscerothoracal sections of the larvae (2112+/-429 µg MC/kg dry weight after 120 h). The present findings indicate that transchorional/transdermal absorption of MC in X. laevis is minimal or absent and that oral uptake of MC with ambient water is necessary for the development of MC related toxicity. Furthermore, the comparison of the MC doses used in this study with the concentrations reported in surface waters indicate that early life-stages of amphibians (up to 5 days of development) are unlikely to be affected by cyanobacterial blooms producing MC-LR and -RR.
This article was published in Aquat Toxicol and referenced in Journal of Ecosystem & Ecography

Relevant Expert PPTs

Relevant Speaker PPTs

  • Maik Auricht
    PPT Version | PDF Version
  • K Mulkijanyan
    Plant biopolymers from Boraginaceae family species and their synthetic derivatives: Prospective pharmacological agents
    PPT Version | PDF Version
  • Yosef Yarden
    Classically, the 3’untranslated region (3’UTR) is that region in eukaryotic protein-coding genes from the translation termination codon to the polyA signal. It is transcribed as an integral part of the mRNA encoded by the gene. However, there exists another kind of RNA, which consists of the 3’UTR alone, without all other elements in mRNA such as 5’UTR and coding region. The importance of independent 3’UTR RNA (referred as I3’UTR) was prompted by results of artificially introducing such RNA species into malignant mammalian cells. Since 1991, we found that the middle part of the 3’UTR of the human nuclear factor for interleukin-6 (NF-IL6) or C/EBP gene exerted tumor suppression effect in vivo. Our subsequent studies showed that transfection of C/EBP 3’UTR led to down-regulation of several genes favorable for malignancy and to up-regulation of some genes favorable for phenotypic reversion. Also, it was shown that the sequences near the termini of the C/EBP 3’UTR were important for its tumor suppression activity. Then, the C/EBP 3’UTR was found to directly inhibit the phosphorylation activity of protein kinase CPKC in SMMC-7721, a hepatocarcinoma cell line. Recently, an AU-rich region in the C/EBP 3’UTR was found also to be responsible for its tumor suppression. Recently we have also found evidence that the independent C/EBP 3’UTR RNA is actually exists in human tissues, such as fetal liver and heart, pregnant uterus, senescent fibroblasts etc. Through 1990’s to 2000’s, world scientists found several 3’UTR RNAs that functioned as artificial independent RNAs in cancer cells and resulted in tumor suppression. Interestingly, majority of genes for these RNAs have promoter-like structures in their 3’UTR regions, although the existence of their transcribed products as independent 3’UTR RNAs is still to be confirmed. Our studies indicate that the independent 3’UTR RNA is a novel non-coding RNA species whose function should be the regulation not of the expression of their original mRNA, but of some essential life activities of the cell as a whole.
    PPT Version | PDF Version
  • Chioma Nwakanma
    PPT Version | PDF Version
  • Paul W Sammarco
    Geomorphological relief on mesophotic banks of the northern Gulf of Mexico, including geographic patterns and relationship to benthic species diversity
    PPT Version | PDF Version
  • Ballagere Puttaraju Harini
    Distribution and divergence of few common termites species: A study at Jnanabharathi
    PPT Version | PDF Version
  • Anna Lange-Consiglio
    PPT Version | PDF Version
  • Iqbal Parwez
    Genetic diversity and molecular declining population of four Channid species from North India and possible strategies
    PPT Version | PDF Version
  • V.Barbakadze
    Novel biologically active caffeic acid-derived biopolymer from different species of Boraginaceae family with potential therapeutic effect
    PPT Version | PDF Version
  • Maria Teresa Mascellino
    Candida bloodstream infections: species distribution and antifungal resistance in General Medicine wards and in Intensive Care Units (ICUs)
    PPT Version | PDF Version

Recommended Conferences

Relevant Topics

Peer Reviewed Journals
Make the best use of Scientific Research and information from our 700 + peer reviewed, Open Access Journals
International Conferences 2017-18
Meet Inspiring Speakers and Experts at our 3000+ Global Annual Meetings

Contact Us

© 2008-2017 OMICS International - Open Access Publisher. Best viewed in Mozilla Firefox | Google Chrome | Above IE 7.0 version