Undergraduate Program


   

Lab Opportunities


Nelson, Dave

All semesters

Sophomore

No experience necessary

General Biology

Project Work

10-15 hours, or students preference

A one-semester commitment would be required

We study signal transductions in the protozoan Paramecium, using biochemical, genetic, molecular genetic, cell biological, and electrophysical tools. Paramecium propels itself through the surrounding medium by the coordinated beating of the cilia that cover its surface. In response to chemical, mechanical, and thermal stimuli the cell changes direction or speed by changing the orientation or frequency of its ciliary beat. Stimuli initially register as a change in membrane potential, and then Ca2+, cyclic AMP, and cyclic GMP serve as second messengers that regulate the ciliary beat.

One of the extracellular compounds to which Paramecium responds to is GTP, apparently through a plasma membrane receptor that may be related to the purinoceptors found in many animal cells that respond to extracellular ATP. Extracellular GTP elicits slow oscillations in the membrane potential of Paramecium, which correspond to alternating periods of forward and backward swimming. Mutants specifically defective in their behavioral response to GTP also lack this membrane response to GTP. The mechanism by which the extracellular signal (GTP) is transduced into a change in swimming behavior is central interests of the laboratory.

An undergraduate student beginning in my lab might, for example, explore the role of an enzyme (adenylyl cyclase or phospholipase C (PLC) in the signal transduction. He or she would determine whether a compound that inhibits tone of these enzymes changes the cellular response to GTP. If so, then that enzyme is implicated in the signal transduction mechanism. The student would use a simple behavioral assay for the response (observation of the swimming behavior of individual cells in the dissecting microscope) asking whether the drug alters the swimming response to GTP.



 

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