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Browsing by Subject "Caenorhabditis elegans"

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  • Tukiainen, Kristiina (2019)
    Anisakiasis is a parasitic disease caused by larval nematodes of the genus Anisakis. Humans become infected by consuming contaminated raw or undercooked seafood products. Most human infections are caused by Anisakis simplex (A. simplex) complex. Currently there is no effective drug for this global emerging disease. Novel active compounds against the nematode are needed for drug development purposes. The research with A. simplex requires the isolation of the larvae from fish, which is time-consuming, unecological and uneconomical. Thus, the utilization of the model nematode Caenorhabditis elegans (C. elegans) in the research of A. simplex is considered in this study. Activities of Tea tree, Java citronella and Ho wood essential oils against C. elegans were studied. Aim of the assays was to examine whether C. elegans could be used as a model for A. simplex. Observed effects on C. elegans were compared to the previously reported effects on A. simplex. Activity of Tea tree and Java citronella essential oils against A. simplex was also examined to confirm previously reported activity. In addition, activity of six coumarins against A. simplex was investigated. The aim of the assays was to discover novel active compounds against the pathogenic nematode. Four coumarins were tested against C. elegans to examine possible comparable effects. Toxicity studies were performed in aquatic medium in a 6 well plate format (A. simplex) and in a 96 well plate format or in 1.5 mL Eppendorf tubes (C. elegans). Tea tree essential oil showed dose dependent activity against C. elegans, producing 100% mortality with the concentration 20 μL/mL after 24 hours exposure. Compared to A. simplex, two to three times higher doses were required to produce same degree of mortality in C. elegans. By contrast, Java citronella and Ho wood essential oils showed no significant activity against C. elegans. The activity of Tea tree and Java citronella essential oils against A. simplex was confirmed. The tested coumarins displayed no significant activity against the nematodes. Due to the contradictory results, further investigation about the suitability of C. elegans as a model for A. simplex is needed. Differences between the effective concentrations are probably caused by the differences in the biology of the nematodes, which result from the phylogenetic distance. Based on current results, the tested coumarins were excluded as potential antinematodal compounds against A. simplex, due to the lack of any significant activity on this model.
  • Seppälä, Katariina (2024)
    General anaesthetics are pharmaceutical agents used to induce general anaesthesia, a reversible state of unconsciousness. Caenorhabditis elegans, a nematode species, has been successfully used as a model organism in the study of gaseous anaesthetics due to its amenability to genetic modification, fully mapped nervous system connectome and high evolutionary conservation. However, C. elegans is less well characterised as a model organism in the study of non-gaseous anaesthetics. The primary aim of the study was to study the potential of ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, and urethane, a nonselective modulator of various neurotransmitter-gated ion channels, to immobilise C. elegans without activating antioxidant response signalling by transcription factor SKN-1, the nematode orthologue of the mammalian Nrf/CNC proteins. The transparent body of C. elegans enables microscopic imaging of cellular processes, but high-quality imaging requires the immobilisation of the worm. A commonly used chemical immobilising agent, sodium azide, causes SKN-1 activation in C. elegans, which may limit the use of sodium azide in studies on SKN-1 promoters. A secondary aim of this study was to study the impact of ketamine, an activator of mTOR (mechanistic target of rapamycin) signalling, on the lifespan of C. elegans. The lifespan of C. elegans has been found to increase with inhibition of the mTOR homologue pathway in previous studies. Ketamine and urethane were administered to wild-type C. elegans in aqueous media in 96-well plates. Behavioural endpoints of immobility and uncoordination were assessed manually via microscopic observation and video recordings. SKN-1 activation was studied by measuring drug-induced fluorescence in mutant strain CL2166, which carries a green fluorescent protein reporter of SKN-1 downstream target GST-4 (glutathione-S-transferase). A lifespan assay was performed with sterile C. elegans strain SS104 by incorporating ketamine in the worm maintenance agar. In this study, urethane did not appear to be a potent immobilisation agent. Ketamine was found to cause reversible weak immobilisation at a similar concentration at which sodium azide fully paralyses wild-type C. elegans. At lower doses ketamine caused uncoordinated locomotion. Short-term exposure to an immobility-inducing dose of ketamine was not found to significantly activate SKN-1. In the lifespan assay, ketamine unexpectedly appeared to significantly increase the nematode lifespan compared to control treatment.