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Methods Cell Biol,
2012]
Laser killing of cell nuclei has long been a powerful means of examining the roles of individual cells in C. elegans. Advances in genetics, laser technology, and imaging have further expanded the capabilities and usefulness of laser surgery. Here, we review the implementation and application of currently used methods for target edoptical disruption in C. elegans.
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Neuronal Development, Synaptic Function and Behavior, Madison, WI,
2010]
C. elegans moves forward by propagating sinusoidal dorso-ventral bending waves from head to tail. While the basic elements of the locomotory circuit were identified by laser ablation experiments (Chalfie et al), relatively little is known about how the circuit generates and propagates undulatory waves. We have used quantitative behavioral assays of worms in structured environments and during ChR2/Halo-mediated perturbations to explore basic principles of locomotory circuit function. To test the hypothesis that the propagation of the bending wave is mediated by bending itself (sometimes called the stretch receptor hypothesis) we analyzed the behavior of worms before and after transient Halorhodopsin-mediated paralysis of body wall muscles. We found that (1) after cessation of paralysis the undulatory wave recovers nearly uniformly over the entire length of the animal, and (2) the phase shift between pre-paralysis and post-paralysis undulations increases linearly with the duration of optical paralysis, with slope approximately equal to the undulatory frequency. These results suggest that the generation and propagation of locomotory undulations do not strictly require bending feedback. We also describe results using an optical system capable of arbitrary spatiotemporal perturbation of neural circuits in freely behaving worms.
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Proc Natl Acad Sci U S A,
2010]
To navigate different environments, an animal must be able to adapt its locomotory gait to its physical surroundings. The nematode Caenorhabditis elegans, between swimming in water and crawling on surfaces, adapts its locomotory gait to surroundings that impose approximately 10,000-fold differences in mechanical resistance. Here we investigate this feat by studying the undulatory movements of C. elegans in Newtonian fluids spanning nearly five orders of magnitude in viscosity. In these fluids, the worm undulatory gait varies continuously with changes in external load: As load increases, both wavelength and frequency of undulation decrease. We also quantify the internal viscoelastic properties of the worm's body and their role in locomotory dynamics. We incorporate muscle activity, internal load, and external load into a biomechanical model of locomotion and show that (i) muscle power is nearly constant across changes in locomotory gait, and (ii) the onset of gait adaptation occurs as external load becomes comparable to internal load. During the swimming gait, which is evoked by small external loads, muscle power is primarily devoted to bending the worm's elastic body. During the crawling gait, evoked by large external loads, comparable muscle power is used to drive the external load and the elastic body. Our results suggest that C. elegans locomotory gait continuously adapts to external mechanical load in order to maintain propulsive thrust.
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Philos Trans R Soc Lond B Biol Sci,
2015]
The development of optogenetics, a family of methods for using light to control neural activity via light-sensitive proteins, has provided a powerful new set of tools for neurobiology. These techniques have been particularly fruitful for dissecting neural circuits and behaviour in the compact and transparent roundworm Caenorhabditis elegans. Researchers have used optogenetic reagents to manipulate numerous excitable cell types in the worm, from sensory neurons, to interneurons, to motor neurons and muscles. Here, we show how optogenetics applied to this transparent roundworm has contributed to our understanding of neural circuits.
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Proc Natl Acad Sci U S A,
2009]
Caenorhabditis elegans is a filter feeder: it draws bacteria suspended in liquid into its pharynx, traps the bacteria, and ejects the liquid. How pharyngeal pumping simultaneously transports and filters food particles has been poorly understood. Here, we use high-speed video microscopy to define the detailed workings of pharyngeal mechanics. The buccal cavity and metastomal flaps regulate the flow of dense bacterial suspensions and exclude excessively large particles from entering the pharynx. A complex sequence of contractions and relaxations transports food particles in two successive trap stages before passage into the terminal bulb and intestine. Filtering occurs at each trap as bacteria are concentrated in the central lumen while fluids are expelled radially through three apical channels. Experiments with microspheres show that the C. elegans pharynx, in combination with the buccal cavity, is tuned to specifically catch and transport particles of a size range corresponding to most soil bacteria.
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Methods Mol Biol,
2022]
Many experiments in C. elegans neurobiology rely on imaging its behavior. Here we describe procedures for building a flexible and inexpensive imaging system using standard optical and mechanical components.
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Methods Mol Biol,
2015]
Many experiments in C. elegans neurobiology and development benefit from automated imaging of worm behavior. Here we describe procedures for building a flexible and inexpensive imaging system using standard optical and mechanical components.
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Worm Breeder's Gazette
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Methods Mol Biol,
2015]
Optogenetic approaches have proven powerful for examining the role of neural circuits in generating behaviors, especially in systems where electrophysiological manipulation is not possible. Here we describe a method for optogenetically manipulating single pharyngeal neurons in intact C. elegans while monitoring pharyngeal behavior. This approach provides bidirectional and dynamic control of pharyngeal neural activity simultaneously with a behavioral readout and has allowed us to test hypotheses about the roles of individual pharyngeal neurons in regulating feeding behavior.
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Methods Mol Biol,
2022]
Optogenetic approaches have proven to be powerful for examining the roles of specific neurons in generating behaviors, especially in systems where electrophysiological manipulation is not possible. Here we describe a method for optogenetically manipulating single pharyngeal neurons in intact C. elegans while monitoring pharyngeal behavior. This approach provides bidirectional and dynamic control of pharyngeal neural activity while quantitatively assessing behavior and has allowed us to test hypotheses about the roles of individual pharyngeal neurons in feeding behavior.