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Methods Mol Biol,
1999]
The nematode Caenorhabditis elegans has gained widespread popularity for use in addressing many biological problems, particularly those relating to development (for brief topical reviews, see 1-5; for comprehensive treatises, see 6-10). This can be attributed to both inherent properties of the organism as well as the collegiality extant within the "worm community". With respect to the former, C. elegans is extremely east to grow in the laboratory (animals are typically propagated on agar-filled Petri dishes seeded with the bacterium Escherichia coli) and possesses a short generation time (3 d at 20C). The system is genetically robust, with the availability of thousands of mutants as well as the existence of a physical map whose sequencing (over 82 Mb finished at present) is scheduled for completion in 1999. Developmental studies have been advantaged by the animal's transparent nature, facilitating complete elucidation of C. elegans' largely invariant cell
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Vitam Horm,
2011]
Germline proliferation in Caenorhabditis elegans is emerging as a compelling model system for understanding the molecular basis for the developmental and physiological control of cell proliferation. This review covers the discovery and implications of the role of the insulin/IGF-like signaling pathway in germline proliferation during germline development. This pathway plays a host of important roles in C. elegans biology. Its role in germline proliferation is important to generate the proper adult stem/progenitor population and to ensure optimal fecundity. Moreover, in this role, it is restricted to reproductive (as opposed to dauer) larval stages and impinges on the G2 of the cell cycle. Two putative insulin ligands are especially important for the germline role but do not mediate signaling in other tissues. A picture is emerging of a complex web of developmentally and temporally restricted, ligand- and tissue-specific responses to insulin signaling. Avenues for future studies include the regulation of specific insulin-like ligands and the mechanisms for tissue-specific responses to them.
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Ann N Y Acad Sci,
1959]
A detailed summary of methods for axenic cultivation of Caenorhabditis briggsae is given. Results of axenic culture on chemically defined basal media (GM and GS) and on these media supplemented with undefined preparations of horse liver and chick embryos are reported in detail, with a review of the formulation of the GM and GS designs and of the chronology of changes made therein. The best growth so far realized with C. briggsae in axenic culture is suboptimal as compared with growth in the presence of bacteria, and maturation takes longer (4 to 5 days instead of about 3 days at 20C). Suitable media of the GM design give good axenic growth with relatively low levels of complex supplements-Liver Protein Fraction C (LPF-C) and chick embryo extract (CEE), both of which presumably include a protein-linked requirement, Factor Rb. With GM-16 plus CEE or certain GSs plus CEE, requirements have been variously demonstrated for 6 B-vitamins: folic acid, niacinamide, pantothenic acid, pyridoxine, riboflavin, and thiamine; one of these-folic acid-had already been shown to be required. Only niacinamide is also demonstrated as a requirement in the presence of low levels of LPF-C. In the presence of CEE we have tested the essentiality of the other 5 vitamins only by omitting them singly from vitamin mixes added at increased (5 to 50 times GS) levels to media of GM or GS type. Preliminary evidence is given that the ten "rat-essential" amino acids are required. Improvement of nutritional balance with respect to amino acid levels and to relative levels of amino acids in relation to vitamins or salts is discussed as an explanation of differential growth on different media. Possibly the variations of DM-GS so far tested contain unnecessarily high amino acid levels. The definition of nutritional requirements for C. briggsae still presents many