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[
1997]
Caenorhabditis elegans aquatic toxicity assays were standardized with five common reference toxicants: CdCl2, NaCl, KCl, sodium lauryl sulfate (SLS), and sodium pentachlorophenate (PCP). Aquatic toxicity testing was conducted in 3 media: a standard C. elegans medium; EPA moderately hard reconstituted water; and EPA moderately hard mineral water. Test duration in each medium was 24h without a food source, and 24h and 48h with Escherichia coli strain OP50 as a food source. Each test was replicated three times with each replicate having 6 wells per concentration, 10 worms per well. LC50 values were calculated using probit analysis. The average LC50s for each set of replicants were compared to assess sensitivity and reproducibility of the data, identifying expected variation between replicate tests. These reference toxicants increase the database for C. elegans and provide a benchmark for further application.
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[
WormBook,
2007]
Because of their free-living life cycle alternatives, Strongyloides and related nematode parasites may represent the best models for translating C. elegans science to the study of nematode parasitism. S. stercoralis, a significant pathogen of humans, can be maintained in laboratory dogs and gerbils. Biosafety precautions necessary for work with S. stercoralis, though unfamiliar to many C. elegans researchers, are straightforward and easily accomplished. Although specialized methods are necessary for large-scale culture of the free-living stages of S. stercoralis, small-scale cultures for experimental purposes may be undertaken using minor modifications of standard C. elegans methods. Similarly, the morphological similarities between C. elegans and the free-living stages of S. stercoralis allow investigational methods such as laser cell ablation and DNA transformation by gonadal microinjection to be easily adapted from C. elegans to S. stercoralis. Comparative studies employing these methods have yielded new insights into the neuronal control of the infective process in parasites and its similarity to regulation of dauer development in C. elegans. Furthermore, we have developed a practical method for transient transformation of S. stercoralis with vector constructs having various tissue- and cell-specific expression patterns and have assembled these into a modular vector kit for distribution to the community.
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[
1981]
A neuron can be characterized by its morphology, transmitter (s?), receptor(s) and the nature of its synaptic contacts (chemical or electrical; excitatory or inhibitory; number and distribution of synapses; identity of the cells to which it is presynaptic or postsynaptic). It is clear that according to such criteria nervous sytems consist of neurons of many distinct types. The origin of neuronal diversity is unknown. Both how such diversity is generated during development and how the relevant developmental programme is encoded in the genome remain to
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[
1983]
Nematodes are a very large group of animals. The estimated 500,000 species represent an independent phylum, and a very successful one, since they are found, with the exception of the pelagic and aerial habitats, in every type of environment. The great majority of nematodes are free-living and inhabit in large numbers the top few centimeters of the ocean's bed, fresh water muds, and a variety of soils. In the soil, where it has been measured, their biomass is comparable to that of insects. A few hundred species are extremely important in human health and agriculture because of their parasitic relationship to plants and animals. In humans, parasitic nematodes can cause very severe diseases, such as filariasis and river blindness (Oncocercus)...
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[
1987]
Current knowledge of sterol biochemistry and physiology in nematodes is reviewed. Nematodes possess a nutritional requirement for sterol because they lack the capacity for de novo sterol biosynthesis. The free-living nematode Caenorhabditis elegans has recently been used as a model organism for investigation of nematode sterol metabolism. C. elegans is capable of removal of the C-24 alkyl substituent of plant sterols such as sitosterol and also possesses the remarkable ability to attach a methyl group at C-4 on the sterol nucleus. An azasteroid and several long-chain alkyl amines disrupt the phytosterol dealkylation pathway in C. elegans by inhibiting its *24-sterol reductase. These compounds inhibit growth and reproduction in certain parasitic nematodes and provide model compounds for development of novel nematode control
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[
WormBook,
2005]
Nematodes are the most abundant type of animal on earth, and live in hot springs, polar ice, soil, fresh and salt water, and as parasites of plants, vertebrates, insects, and other nematodes. This extraordinary ability to adapt, which hints at an underlying genetic plasticity, has long fascinated biologists. The fully sequenced genomes of Caenorhabditis elegans and Caenorhabditis briggsae, and ongoing sequencing projects for eight other nematodes, provide an exciting opportunity to investigate the genomic changes that have enabled nematodes to invade many different habitats. Analyses of the C. elegans and C. briggsae genomes suggest that these include major changes in gene content; as well as in chromosome number, structure and size. Here I discuss how the data set of ten genomes will be ideal for tackling questions about nematode evolution, as well as questions relevant to all eukaryotes.
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[
1989]
Classical embryological studies of nematodes, primarily by Van Beneden and Boveri near the turn of the century, have made lasting contributions to our understanding of embryonic development (1). However, during most of this century, nematodes have been eclipsed as a model system for embryology by organisms with more tractable embryos such as sea urchins, insects, amphibians, birds, and mice. Two features of the free-living soil nematode Caenorhabditis elegans have returned nematodes to a prominent place in embryological investigations: its suitability for genetic analysis and its invariant and completely described cell lineage. These two features, combined with technological advances in microscopy and molecular biology, are providing the opportunity to combine experimental embryology with genetic and molecular analyses of embryonic development at the level of individual cells in a single organism. This chapter focuses on efforts to understand the molecular and cellular events of early development in C. elegans with particular emphasis on events relating to the determination of embryonic cell fates. Extensive coverage of the various contributions that the study of Caenorhabditis has made to our knowledge of developmental biology can be found in ref. 2.
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[
Methods Mol Biol,
2013]
The nematode Caenorhabditis elegans secretes a family of water-soluble small molecules, known as the ascarosides, into its environment and uses these ascarosides in chemical communication. The ascarosides are derivatives of the 3,6-dideoxysugar ascarylose, modified with different fatty acid-derived side chains. C. elegans uses specific ascarosides, which are together known as the dauer pheromone, to trigger entry into the stress-resistant dauer larval stage. In addition, C. elegans uses specific ascarosides to control certain behaviors, including mating attraction, aggregation, and avoidance. Although in general the concentration of the ascarosides in the environment increases with population density, C. elegans can vary the types and amounts of ascarosides that it secretes depending on the culture conditions under which it has been grown and its developmental history. Here, we describe how to grow high-density worm cultures and the bacterial food for those cultures, as well as how to extract the culture medium to generate a crude pheromone extract. Then, we discuss how to analyze the types and amounts of ascarosides in that extract using mass spectrometry and NMR spectroscopy.
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[
1990]
The free-living nematode Caenorhabditis elegans is a small and unpretentious organism. It may thrive unnoticed in the cabbage patch in your backyard or the flower pot on your balcony. In their natural habitat soil nematodes live in a thin film of water. In the laboratory C. elegans dwells on Petri dishes in the liquid film on the top of an agar layer, but can also be grown in liquid culture. As in other nematodes the liquid-filled body cavity (pseudocoelom) functions as a hydroskeleton. When the worm dries out, the hydroskeleton collapses and the animal inevitably dies. In a loose sense C. elegans may therefore be considered as a kind of aquatic animal. Because of this and because C. elegans is particularly well suited to the study of certain aspects of development, the following chapter is included in this book on Experimental Embryology of Aquatic Organisms. The intention of this contribution is to serve as an introduction and as a reference source rather than as a complete summary of present knowledge in the field. As indicated by the title, the review will focus on embryonic cell lineages, pattern formation in the embryo and the analysis of mutants affecting early
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[
1999]
Caenorhabditis elegans is a free-living soil nematode that is commonly used as a biological model. Recently, much work has been done using the nematode as a toxicological model as well. Much of the work involving C. elegans has been performed in aquatic media, since it lives in the interstitial water of soil. However, testing in soil would be expected to more accurately reproduce the organism's normal environment and may take into consideration other factors not available in an aquatic test, i.e., toxicant availability effects due to sorption, various chemical interactions, etc. This study used a modification of a previous experimental protocol to determine 24h LC50 values for Cu in a Cecil series soil mixture, and examined the use of CuCl2 as a reference toxicant for soil toxicity testing with C. elegans. Three different methods of determining percent lethality were used, each dependent on how the number of worms missing after the recovery process was used in the lethality calculations. Only tests having >/= 80% worm recovery and >/= 90% control survival were used in determining the LC50S, by Probit analysis. The replicate LC50 values generated a control chart for each method of calculating percent lethality. The coefficient of variation (CV) for each of the three methods was </= 14%. The control charts and the protocol outlined in this study are intended to be used to assess test organism health and to monitor precision of future soil toxicity tests with C.