Heather G. Kuruvilla

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Chemosensory transduction and adaptation are important aspects of signal transduction mechanisms in many cell types, ranging from prokaryotes to differentiated tissues such as neurons. The eukaryotic ciliated protozoan, Tetrahymena thermophila, is capable of responding to both chemoattractants (O'Neill et al., 1985; Leick, 1992; Kohidai, Karsa & Csaba,(More)
Extracellular nucleotides are ubiquitous signaling molecules. ATP signals through two receptor types: the ionotropic P2X receptors, and the metabotropic P2Y receptors. ATP acts as a chemorepellent in Tetrahymena thermophila, where it causes a distinct avoidance response. The intracellular mechanisms by which ATP causes avoidance in this organism, however,(More)
Pituitary adenylate cyclase activating peptide (PACAP-38) is a peptide hormone which functions in many mammalian systems, including the nervous and digestive systems. Using in vivo behavioral studies, we have found that this hormone functions as a chemorepellent in Tetrahymena thermophila with an EC50 of 10 nM. Cells previously adapted to PACAP-38 were(More)
While lysozyme is a depolarizing chemorepellent in Tetrahymena, the entire lysozyme molecule is not necessary to activate the lysozyme receptor. Reduced lysozyme was cut into three fragments by cyanogen bromide cleavage and the fragments (CB1, CB2 and CB3) were separated by HPLC. Behavioral bioassays showed that the carboxy-terminal 24-amino-acid fragment,(More)
Chemorepellents are compounds that cause ciliated protozoans to reorient their swimming direction. A number of chemorepellents have been studied in the ciliated protozoans, Paramecium and Tetrahymena. Chemorepellents, such as polycations, cause the organism to exhibit "avoidance behavior," a swimming behavior characterized by jerky movements and other(More)
Chemorepellents are signaling molecules, which have been shown to be important for mammalian neuronal development, and are presumed to have a role in protozoan defense. Tetrahymena thermophila represent a good model system in which to study repellents because of their ease of use in biochemical, behavioral, electrophysiological, and genetic analyses. In(More)
Pituitary adenylate cyclase-activating peptide and lysozyme are potent chemorepellents which act through the same receptor in Tetrahymena. Using in vivo behavioral studies, we have found that the pituitary adenylate cyclase-activating peptide /lysozyme receptor appears to signal through a G-protein pathway which is mediated through both adenosine(More)
Guanosine 5'-triphosphate (GTP) is a chemorepellent in Tetrahymena thermophila that has been shown to stimulate cell division as well as ciliary reversal. Previous studies have proposed that GTP avoidance is linked to a receptor-mediated, calcium-based depolarization. However, the intracellular mechanisms involved in GTP avoidance have not been previously(More)
Tetrahymena thermophila are free-living, ciliated eukaryotes. Their behavioral response to stimuli is well characterized and easily observable, since cells swim toward chemoattractants and avoid chemorepellents. Chemoattractant responses involve increased swim speed or a decreased change in swim direction, while chemorepellent signaling involves ciliary(More)