Reimagining pheromone signalling in the model nematode Caenorhabditis elegans

Caenorhabditis elegans is an important, widely used developmental and genetic model. A pheromone has long been known to cause juvenile developmental arrest in C. elegans, a phenomenon that is common among nematodes more widely. Many novel effects of this pheromone are now being discovered—most recently, that exogenous supply of this pheromone controls adult worms reproduction. Here, we suggest that to properly understand and interpret these phenomena, C. elegans natural ecology must be considered, about which rather little is known. With this perspective, we suggest that C. elegans pheromone signalling evolves very locally, such that there are different dialects of pheromone signalling among ecological communities and among kin groups, and we also argue that pheromone signals may also evolve to be manipulative and dishonest. New approaches must be undertaken to study these phenomena in C. elegans. While model systems have been tremendously important tools in modern biological research, taking account of their natural history is necessary, and key, to properly understand and interpret laboratory-based discoveries.understand and interpret laboratory-based discoveries

Macro-level Modeling of the Response of C. elegans Reproduction to Chronic Heat Stress

A major goal of systems biology is to understand how organism-level behavior arises from a myriad of molecular interactions. Often this involves complex sets of rules describing interactions among a large number of components. As an alternative, we have developed a simple, macro-level model to describe how chronic temperature stress affects reproduction in C. elegans. Our approach uses fundamental engineering principles, together with a limited set of experimentally derived facts, and provides quantitatively accurate predictions of performance under a range of physiologically relevant conditions. We generated detailed time-resolved experimental data to evaluate the ability of our model to describe the dynamics of C. elegans reproduction. We find considerable heterogeneity in responses of individual animals to heat stress, which can be understood as modulation of a few processes and may represent a strategy for coping with the ever-changing environment. Our experimental results and model provide quantitative insight into the breakdown of a robust biological system under stress and suggest, surprisingly, that the behavior of complex biological systems may be determined by a small number of key components

Pargyline-induced increases in sensitivity to the effects of drugs on operant behavior in pigeons

Pigeons responded under a multiple fixedinterval 5-min, 30-response fixed-ratio schedule of food reinforcement. Acute pargyline doses between 10.0 and 50.0 mg/kg (i.m.), given immediately prior to the session, decreased responding. Daily administration of 50 mg/kg pargyline (24 mg/kg, every 12 h) initially decreased responding. Tolerance developed so that after 4 days of daily pargyline, responding had returned to control values. Chronic pargyline resulted in an enhanced sensitivity to the effects of d -amphetamine, ephedrine, tyramine, and morphine on schedule-controlled responding. Both d -amphetamine and pentobarbital increased fixed-interval responding at relatively low doses, while higher doses decreased responding. Daily pargyline resulted in an increased sensitivity to both the increases and decreases in response rates produced by d -amphetamine. In contrast, sensitivity to pentobarbital was not changed after daily pargyline. Ephedrine, tyramine, and morphine only decreased fixed-interval responding. Chronic pargyline resulted in an increased sensitivity to the response-rate decreasing effects of ephedrine, tyramine, and morphine. In addition to the increased sensitivity of fixed-interval responding to the effects of tyramine, the dose-effect curve for fixed-ratio responding was also a shifted to the left. Daily pargyline did not result in changes in sensitivity of fixedratio responding to the effects of the other drugs tested.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46399/1/213_2004_Article_BF00426607.pd