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Effects of Ultrasound on Nervous System Development in the Nematode Roundworm, C. elegans

Louise Steele, Ph.D., Biological Sciences, ������, Salem Campus

Background—Ultrasound is widely used in medicine for diagnostic imaging and therapeutic procedures. There is no evidence that diagnostic ultrasound causes deleterious effects in humans.  Research in flies, mice, and chicks has, however, shown that various doses of ultrasound can affect mortality, birth weight, and learning in those species.  Our lab has begun using an even simpler organism—C. elegans worms—to study ultrasound’s bioeffects.  Worms are an attractive model for these studies because their nervous system is simple (302 neurons), and the complete “wiring diagram” is known.

Preliminary Data—We have found that therapeutic ultrasound exposure causes dose-dependent reductions in worm mobility, reproduction, and survival.  Interestingly, worms exposed to ultrasound during adulthood exhibited more limited movement in the posterior half of their bodies than they did in the anterior half.  On agar, those worms appeared to be dragging the posterior portion of their bodies behind them as though they were partially paralyzed. 

Objectives—To follow up on those results, we will ask whether ultrasound exposure damages the worms' nervous system, as observed in other organisms.  We will determine the location and extent of axon damage in worms exposed to ultrasound during adulthood.  We will also examine whether ultrasound-induced damage that occurs during early larval development can be repaired.  Mutant worm strains whose entire nervous system is labeled with green fluorescent protein will facilitate this work.  We also plan to test whether worms whose nervous system has undergone structural repair regain normal sensory and motor function. 

Significance—Ultrasound is becoming an important tool in neuroscience research, and this work may lead to additional innovative laboratory techniques.  Clinically, the mechanisms of some therapeutic ultrasound procedures remain incompletely understood, and this work may help to clarify those details.  This project will also provide valuable undergraduate research opportunities for students in ������’s regional campus system.