Todd M. Hennessey

Membrane Biochemistry and Cell Physiology

Professor

PhD 1981 University of Wisconsin-Madison
Postdoctoral work 1981 University of Wisconsin-Madison
Assistant Professor 1985;
Associate Professor 1991 University at Buffalo

 


Address Information

Todd M. Hennessey
Department of Biological Sciences
610 Hochstetter Hall
State University of New York at Buffalo
Buffalo, NY 14260

(716) 645-4973

To send e-mail: thennes@buffalo.edu


RESEARCH SUMMARY

Paramecium is an excellent model system for studying the biochemical and electrophysiological mechanisms involved in chemosensory transductions. Swimming behavior is used in convenient bioassays to estimate the responsiveness of these free swimming sensory cells. These unicellular eukaryotic cells can be grown to high densities in clonal, axenic cultures so that large amounts of homogeneous cells can be obtained as starting material for biochemical analyses. Their large size also permits intracellular voltage clamp analysis and microinjection experiments. "Genetic dissection" of a sensory transduction pathway can be approached by selecting for behavioral mutants that have altered responses to chemoeffectors. Similar studies are also being pursued in the related ciliate, Tetrahymena. Tetrahymena have the advantage of higher density growth in a simpler medium but their small size makes electrophysiological analysis difficult. Since genomic and cDNA libraries are available for these ciliates, modern Molecular Biological approaches will be used to study the regulation and functional expression of the gene products involved in chemosensory transductions.


SELECTED PROJECTS

  • Purification, cloning and regulated expression of and ectonucleotidases in Tetrahymena
    T. Smith, T. Santangelo, T. Hennessey
    Tetrahymena hydrolyze external nucleotide triphosphates (like ATP and GTP) by an ecto-nTPase and external nucleotide monophosphates (like AMP and GMP) by a different ecto-nMPase. The ecto-nTPase may be involved in inactivating external GTP as a signaling molecule because GTP is a chemorepellent (Clark et al., 1993). This may be analogous to a system such as acetylcholine/acetylcholinesterase. The ecto-nTPase may also act as either a cell adhesion molecule in the mating response or in extracellular metabolism of nucleotide phosphates to provide for their guanine auxotrophy. The ecto-nMPase may also be involved in this extracellular scavenge pathway for nucleotides. These two enzymes (ecto-nTPase and ecto-nMPase) will be characterized in vivo and in vitro, purified, sequenced, and cloned to provide the molecular tools necessary to study their functions and possible regulation of functional surface expression. Monoclonal antibodies are also being generated to aid in these efforts.

    PUBLICATIONS



  • Surface membrane preparation (pellicle) from Paramecium.


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