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[
International C. elegans Meeting,
1981]
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[
Worm Breeder's Gazette,
1977]
Thermal acclimation in Caenorhabditis ied by evaluating temperature effects on both respiration rate and chemotactic behavior. The rate of oxygen consumption was quite dependent on test temperature (Q10's of two to three) but growth temperature had relatively little effect. C. elegans, therefore, does not exhibit partial metabolic adaptation as reported for two other species of free-living nematodes. Growth temperature does influence the chemotactic behavior of C. elegans. At test temperatures 10 C removed from growth temperature attraction to 10 mM NaCl was greatly weakened. The reduction in behavioral response does not appear to be related to temperature effects on basic metabolic rate but rather is influenced by thermal effects on more specific aspects of the nervous system.
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[
Can J Zool,
1982]
Dauerlarvae are reportedly adapted to withstand adverse environmental conditions. Current knowledge of the mechanisms underlying the unique characteristics of dauerlarvae is limited. This study characterizes superoxide dismutase (SODase) activity in several developmental stages of Caenorhabditis elegans (originally described by E. Maupas in 1900). Extracts of dauerlarvae have 17.1 units SODase per milligram protein, as compared with 4.3 and 3.8 units per milligram for obligate larvae and young adults, respectively. Since oxygen consumption in dauerlarvae is lower than that of young adults, the ratio of SODase to oxygen consumption is markedly higher in dauerlarvae than in young adults. The elevated SODase might contribute to an increased resistance to a variety of environmental stresses, including radiation. Furthermore, the elevation of this activity relative to metabolic rate could account for the long life-span of dauerlarvae.
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[
Environ Toxicol Chem,
2004]
Behavior, even in simple metazoans, depends upon integrated processes at the subcellular, cellular, and organismal level, and thus is susceptible to disruption by a broad spectrum of chemicals. Locomotor behavior (movement) of the small free-living nematode Caenorhabditis elegans has proven to be useful in assessing toxicity. Recently reported observations suggest that behavioral change (reduced movement) occurs after 4 h of exposure to heavy metals, and that with abbreviated exposure, the concentration-response relationship for Pb (a known neurotoxic metal) differs from that for Cu. In this Study, movement was evaluated after 4-h exposures for nine compounds from three chemical classes: organic pesticides, organic solvents, and heavy metals. Concentration-dependent reduction of movement was observed for all test compounds with the exception of mebendazole. for which test concentrations were limited by solubility. Within each chemical class, movement was more sensitive to the neurotoxic compounds than to substances not believed to be neurotoxic, Lis evidenced by behavioral effective concentration to reduce average worm movement to 50% of the control movement values (e.g., levamisole and chlorpyrifos < mebendazole. ethanol and acetone < dimethylsulfoxide. and Pb and Al < Cu). These observations are discussed as they relate to the Use Of acute behavioral tests in assessing general chemical toxicity, and the enhanced Value of 4-h
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[
Canadian Journal of Zoology,
1978]
Larval forms of the free-living nematode Caenorhabditis elegans possess the ability to enter a developmental stage which is thought to be specialized for survival in harsh environmental conditions, i.e. the dauerlarval stage. In this study the responses of dauerlarvae to thermal stress and oxygen deprivation are investigated. Oxygen consumption of dauerlarvae is less sensitive to temperature change than that of adults, with Q10 values of 1.7 and 2.6 respectively. The upper thermal tolerance limit of dauerlarvae is also different from that of adults; dauerlarvae survive approximately three times longer than adults when exposed to 37C. In addition to differences in thermal tolerance, dauerlarvae surrvive longer under anaerobic conditions than adults, 7 days and 2 days respectively. On recovery from anaerobic stress dauerlarvae exhibit behavior changes which are suggestive of emergence from the dauerlarval stage. The responses of dauerlarvae to thermal stress and oxygen deprivation appear to be important aspects of the specialization for survival
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[
Environ Toxicol Chem,
2001]
Toxicity tests in invertebrates often use sublethal endpoints, which may exhibit different sensitivity for various toxicants. Our objective was to characterize the sensitivity of movement, feeding, growth, and reproduction as endpoints for heavy metal toxicity testing with Caenorhabditis elegans. Growth and feeding were assessed in the same nematode samples used to assess movement and reproduction. Median effective concentrations (EC50s) for 24-h exposures to Pb, Cu, and Cd were determined for movement, feeding, and growth and a 72-h EC50 was derived for reproduction. The order of toxicity was Cu > Pb > Cd for each endpoint, including lethality and movement. There were no differences in sensitivity among endpoints for any metal. When exposed for 4 h at (sublethal) concentrations that were 14 times the 24-h EC50 value, Pb and Cu reduced feeding to the same extent while movement was reduced significantly more by Pb than by Cu. Thus, a difference in sensitivity of endpoints was apparent at 4 h, which was not evident at 24 h. These observations suggest potentially different mechanisms of toxicity for 24- and 4-h tests.
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[
Food Microbiol,
2006]
A study was done to characterize the shedding of foodborne pathogenic bacteria by Caenorhabditis elegans, evaluate the persistence of worm populations cocultured with foodborne pathogens, and determine if C. elegans disperses ingested pathogens in soil as a result of shedding. Escherichia. coli O157:H7, Salmonella enterica serotype Poona, and Listeria monocytogenes, as well as E. coli OP50, a non-pathogenic strain, were studied. Synchronous populations of C. elegans were fed for 24 h on confluent lawns of nalidixic acid-adapted bacteria. C. elegans shed viable cells of ingested bacteria on tryptic soy agar supplemented with nalidixic acid (50 microg ml(-1)) (TSAN) throughout a 5-h post-feeding period. C. elegans persisted for up to 10 days by feeding on bacteria that had been shed and grew on TSAN. Eggs harvested from C. elegans cultured on shed foodborne pathogens had the same level of viability as those collected from C. elegans grown on shed E. coli OP50. After 6-7 days, 78%, 64%, 64%, and 76% of eggs laid by C. elegans that had fed on E. coli O157:H7, S. Poona, L. monocytogenes, and E. coli OP50, respectively, were viable. Worms fed on E. coli O157:H7 were inoculated into soil and soil amended with turkey manure compost. Populations of C. elegans persisted in compost-amended soil for at least 7 days but declined in unamended soil. E. coli O157:H7 was detected at 4 and 6 days post inoculation in compost-amended and unamended soil, and in unamended soil inoculated with E. coli OP50. Populations of E. coli O157:H7 in soil amended with turkey manure compost were significantly(alpha = 0.05) higher than those in unamended soil. Results indicate that C. elegans can act as a vector to disperse foodborne pathogens in soil, potentially resulting in increased risk of contaminating the surface of pre-harvest fruits and vegetables.
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[
J Food Prot,
2003]
Free-living nematodes may harbor, protect, and disperse bacteria, including those ingested and passed in viable form in feces. These nematodes are potential vectors for human pathogens and may play a role in foodborne diseases associated with fruits and vegetables eaten raw. In this study, we evaluated the associations between a free-living soil nematode, Caenorhabditis elegans, and Escherichia coli, an avirulent strain of Salmonella Typhimurium, Listeria weshimeri, and Bacillus cereus. On agar medium, young adult worms quickly moved toward colonies of all four bacteria; over 90% of 3-day-old adult worms entered colonies within 16 min after inoculation. After 48 h, worms moved in and out of colonies of L. weshimeri and B. cereus but remained associated with E. coli and Salmonella Typhimurium colonies for at least 96 h. Young adult worms fed on cells of the four bacteria suspended in K medium. Worms survived and reproduced with the use of nutrients derived from all test bacteria, as determined for eggs laid by second-generation worms after culturing for 96 h. Development was slightly slower for worms fed gram-positive bacteria than for worms fed gram-negative bacteria. Worms that fed for 24 h on bacterial lawns formed on tryptic soy agar dispersed bacteria over a 3-h period when they were transferred to a bacteria-free agar surface. The results of the study suggest that C. elegans and perhaps other free-living nematodes are potential vectors for both gram-positive and gram-negative bacteria, including foodborne pathogens in soil.
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[
Worm Breeder's Gazette,
1977]
Temperature-induced phase transitions have been reported to occur in several nematode species. Caenorhabditis s been stored in tap water at 10 C for up to 48 hrs., exhibited a phase transition at about 10 C. The temperature of the 'phase' transition in C. elegans might therefore depend upon the thermal history of the organisms. To test this hypothesis worms were grown at 15 C, 20 C, and 25 C and their oxygen consumption measured over a wide temperature range. Arrhenius plots of oxygen uptake vs temperature were made. Similar experiments were carried out on crude homogenates prepared by disruption in a French press followed by low speed centrifugation. An inflection was evident in plots of both intact and fragmented worms. The temperature at which the inflection occurred was a function of the thermal history of the nematodes being within a few degrees of the growth temperature.