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[
2008]
In this chapter, selected aspects of the early embryogenesis of five representatives from different branches of the phylogenetic tree are compared with C. elegans and the impact of the observed differences for evolutionary considerations are discussed. Following a brief reference to phylogeny, basic features of early embryogenesis of C. elegans will be summarised to aid in appreciating the data from other nematodes reported subsequently.
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[
Molecular Biology of Aging,
1999]
"Gerontogenes" (genes that affect the rate of aging) can be defined operationally to refer to genes that can be altered such that a longer than normal maximum lifespan is the result. The last two decades of research in aging have demonstrated overwhelmingly that gerontogenes exist and modulate the rate of aging. The first direct demonstration that genes play a role in the aging process was carried out in the nematode Caenorhabditis elegans. Despite original prejudices that the aging process is "ineluctable" or that genes controlling longevity cannot be selected for, these results and others have shown that the process of aging, just as other biological processes, is specified by the gene. This is not to say that aging is programmed. Statements by noted developmental biologists that aging must be programmed to prevent competition with offspring are untenable for the nematode C. elegans, which has billions of descendents by the time its hypothetical "death program" kicks in to kill it. In the text below I will provide an overview, first of work primarily from my laboratory having to do with the detection and study of gerontogene variants using multigenic approaches. Subsequent work on mutants, initially from my lab but more recently from a variety of other labs as well, showing the molecular nature of these gerontogenes will be subsequently reviewed. Finally, we will close with a discussion of the role of resistance to stress in determining life-extension: a hypothesis that is gaining increasing support from a wide variety of observations in both invertebrate and vertebrate
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[
Resistance of Parasites to Antiparasitic Drugs,
1990]
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[
Methods Mol Biol,
2013]
Metabolomic analyses can provide valuable information about the internal metabolism of an organism; however, these studies can become quickly complicated by the large number of metabolites that are often detected. Overcoming this limitation requires high-resolution analytical separation techniques, coupled with high-power deconvolution software. Additionally, much care must be taken in metabolomic sample preparation to quench active enzymes and avoid artifactual changes in the metabolome. Here we present a relatively simple and straightforward technique, exometabolome mapping, which bypasses each of these concerns, is noninvasive, and provides a concise summary of the key metabolic processes operative in an organism. We illustrate our method using the nematode C. elegans, an organism which has been widely exploited in aging studies; however, with only minimal modification, our technique is extendible to other sample types, and indeed we have successfully used it both to perform yeast footprinting and to study the excreted metabolic end products of human kidney cancer cell lines.
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[
1990]
The biological processes collectively called aging are being dissected in our laboratory using classic genetic analyses akin to those used in the dissection of other fundamental biological processes, e.g., development or metabolism. Many pitfalls are inherent in the genetic analysis of components of fitness; many result from effects of inbreeding. These inbreeding effects have been avoided by the use of the small free-living nematode Caenorhabditis elegans. The hermaphroditic life-style of this animal facilitates the analysis of life span and senescence by permitting the direct isolation and genetic analysis of long-lived mutants and recombinant inbred (RI) lines without complications resulting from inbreeding problems. Both approaches to obtaining long-lived genotypes have been used effectively in the analysis of the aging processes of C. elegans and the reader will find a brief summary of
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Normal development and homeostasis result from a tenuous balance between cell proliferation and cell death. Disruption of this balance, in favor of cell death in particular, could easily lead to pathological states in postmitotic organs such as the adult brain. For example, many neurodegenerative disorders are characterized by the premature death of specific subsets of neurons, which gives rise to their full clinical spectra. Although a complete understanding of the selective cell degeneration in these conditions is still lacking, recent observations suggest that it may occur through apoptosis, a gene-directed type of cell death. In many cases, cell death by apoptosis requires an active role by the dying cells, because apoptosis is most often significantly blocked or delayed by inhibitors of RNA or protein synthesis. This genetic regulation of apoptosis offers a potential for therapeutic intervention and further assessment of apoptotic mechanisms in manifestations of neuropathology is warranted. However, employing conventional molecular and biochemical approaches, attempts to determine the genetic machinery responsible for specifying which cells live and which cells die have not always been successful in vertebrate systems. One organism in which programmed cell death (PCD), a physiological counterpart of apoptosis, has been extensively examined is the nematode Caenorhabditis elegans....
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Programmed cell death is a common cell fate in most if not all multicellular organisms. Apoptosis, which will be used as a synonym for programmed cell death throughout this chapter, occurs extensively during development as well as during later life. The development of the nematode worm Caenorhabditis elegans provides a good example of the extensive use of programmed cell death.
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[
1960]
For the purpose of the present chapter the noun 'cultivation' is to be taken as the maintenance, in the laboratory, of a population of organisms belonging to a desired species through successive generations and subcultures over a prolonged period of time (weeks, months, or years). This is a deliberate restriction of the term. The noun 'culture' is most aptly used for a population within a circumscribed vessel or container (test-tube, Petri dish, U.S. Bureau of Plant Industry watch glass, etc.); it is also used in a looser, more general way (as "in culture") to cover conditions of substantial growth whether or not leading to cultivation in the strict sense
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[
Methods Mol Biol,
2013]
The principle of commonly used methods to create mutations in the nematode Caenorhabditis elegans (C. elegans) is straightforward. In general, worms are exposed to a dose of mutagen resulting in DNA damages and mutations. Screening the progeny of the mutagenized animals for a certain phenotype is the regular forward genetic approach in C. elegans. A mutant selected from such a population is stabilized to recover a pure homozygous strain. In this chapter, we categorize the protocol into mutagenesis, phenotype screen, and outcross and provide time-tested procedures for their implementation to create long-lived worm mutants.
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[
2000]
Computer tracking of Caenorhabditis elegans, a free-living soil nematode, is a promising tool to assess behavioral changes upon exposure to contaminants. A short life cycle, a known genetic make-up, thoroughly studied behavior, and a completely mapped nervous system make C. elegans an attractive soil test organism with many advantages over the commonly used earthworm. Although many toxicity tests have been performed with C. elegans, the majority focused on mortality, a much less sensitive endpoint than behavior. A computer tracking system has been developed to monitor behavioral changes using C. elegans. Because conditions unrelated to specific toxicant exposures, such as changes in temperature, developmental stage, and presence of adequate food sources, can affect behavior, there is a need to standardize tracking procedures. To this end, we have developed reference charts for control movement comparing the movement of four and five day-old adult nematodes. The use of K-medium versus deionized (DI) H2O for pre-tracking rinses was also investigated. A final reference chart compared the behavioral responses of nematodes at various food densities (i.e. bacterial concentrations).