[
Ciba Found Symp,
1993]
The small soil nematode Caenorhabditis elegans has only 302 neurons in its entire nervous system, so it is possible to analyse the functions of individual neurons in the animal's behaviour. We are using behavioural, cellular and genetic analyses of chemotactic responses to find out how olfactory behaviour patterns are generated and regulated. Single chemosensory neurons in C. elegans can recognize several different attractive odorants that are distinguished by the animal. Distinct sets of chemosensory neurons detect high and low concentrations of a single odorant. Odorant responses adapt after prolonged exposure to an odorant; this adaptation is odorant specific and reversible. Mutants with defects in odorant responses have been identified. Some genes appear to be necessary for the development or function of particular kinds of sensory neurons. Other genes have effects that suggest that they participate in odorant reception or signal transduction.
[
Cold Spring Harb Symp Quant Biol,
1996]
An animal generates appropriate behavioral responses to a stimulus based on the intrinsic qualities of the stimulus, the context in which it appears, and the animal's previous experience. Olfactory stimuli elicit responses that are often reproducible across different individuals in a species: Many animals display characteristic behaviors in response to the smell of members of their species, food sources, or dangerous conditions. Other sensory modalities can also evoke innate responses, but in the olfactory system, odorants that elicit distinct behaviors are differentiated at the first step of sensory detection by the olfactory receptor neurons. Therefore, the neuronal circuitry responsible for different behaviors can be traced starting from the initial sensory events. Our studies have focused on olfaction and chemosensation in the nematode Caenorhabditis elegans. Chemosensation is the richest mechanism C. elegans has for interacting with its environment, both in the number of different stimuli that are recognized and in the variety of different responses that can be elicited. Virtually all behaviors in C. elegans are modulated by chemical cues. Individual molecules can be attractants or repellents, or they can regulate egg-laying, feeding, or movement. In addition, pheromone cues control development of the animal and mating behavior between males and hermaphrodites. How are these chemical cues recognized and discriminated from one another? The answer to this question lies partly in the biochemical mechanisms that recognize individual odorants, and partly in the neuronal circuitry that drives particular
[
Mech Ageing Dev,
2001]
The nematode Caenorhabditis elegans has become a model system for the study of the genetic basis of aging. In particular, many mutations that extend life span have been identified in this organism. When loss-of-function mutations in a gene lead to life span extension, it is a necessary conclusion that the gene normally limits life span in the wild type. The effect of a given mutation depends on a number of environmental and genetic conditions. For example, the combination of two mutations can result in additive, synergistic, subtractive, or epistatic effects on life span. Valuable insight into the processes that determine life span can be obtained from such genetic analyses, especially when interpreted with caution, and when molecular information about the interacting genes is available. Thus, genetic and molecular analyses have implicated several genes classes (dnf, clk and eat) in life span determination and ha iie indicated that aging is affected by alteration of several biological processes, namely dormancy, physiological rates, food intake, and reproduction.