Michael J. Greenberg
(Ph.D. Harvard University, 1958)

Professor Emeritus of Pharmacology and Therapeutics

mjgberg@gmail.com

Malacobranchiology

An investigation of the gills of bivalve molluscs continues in collaboration with Louis F. Gainey, Jr. of the University of Southern Maine. Clam gills  are complex organs with multiple activities, but especially respiration and filter feeding. The flow of water that enables these functions and the movement of filtered particles on the surface of the gill filaments are controlled by several functionally distinct ciliary tracks, by muscles of various types and distribution and by mucocytes. These diverse structures are, in turn, regulated by a neural network and by chemical signals borne in the ambient aqueous medium, as well as the blood. In general, clam gills are, in their structure and functions, analogous to all organs that are sites of trade between an animal and its environment.

The aim of this  project is to determine the roles of the dissolved gases nitric oxide, carbon monoxide, hydrogen sulfide, and oxygen  in controlling   water flow through the gills of the clam Mercenaria mercenaria. We are characterizing the pharmacology of the gases, and using immunocytochemistry to determine the distinct distributions of serotonin, dopamine, and the gas-generating enzymes in the branchial tissue.

Selected Publications

Gainey, L.F. Jr. and Greenberg, M.J. (2003) Nitric oxide mediates seasonal muscle potential in clam gills. J. Exp. Biol. 206: 3507-3520.

Gainey, L.F. Jr., Walton, J.C. and Greenberg, M.J. (2003) Branchial musculature of a venerid clam: pharmacology, distribution and innervation. Bio. Bull. 204: 81-95.

García-Arrarás, J. E. and M. J. Greenberg (2001) Visceral regeneration in holothurians. Microscopy Research and Technique 55:438-451.

Gainey, L.F., Jr., K.J. Vining, K.E. Doble, J.M. Waldo, A. Candelario-Martinez and M.J. Greenberg. (1999) An endogenous SCP-related peptide modulates ciliary beating in the gills of a venerid clam, Mercenaria mercenaria. Biol. Bull. 197: 159-173.

Price, D.A., K.E. Doble, W. Lesser, M.J. Greenberg, K.M. Swiderek, T.D. Lee, E.M. Lutz, J. Sommerville, S. Falconer, and G.A. Cottrell. (1996). The peptide pQFYRFamide is encoded on the FMRFamide precursor of the snail Helix aspersa but does not activate the FMRFamide-gated sodium channel. in press.

Candelario-Martinez, A., D.M. Reed, S.J. Prichard, K.E. Doble, T.D. Lee, W. Lesser, D.A. Price and M.J. Greenberg. (1993). SCP-related peptides from bivalve mollusks: identification tissue distribution and actions. Biol. Bull. 185:428-439.

Gaus, G., K.E. Doble, D.A. Price, M.J. Greenberg, T.D. Lee and B-A. Battelle. (1993). The sequences of five neuropeptides isolated from Limulus using antisera to FMRFamide. Biol. Bull. 184:322-329.

Lesser, W. and M.J. Greenberg. (1993). Cardiac regulation by endogenous small cardioactive peptides (SCPs) and FMRFamide-related peptides in the snail Helix aspersa. J. Exp. Biol. 178:205-230.

Greenberg, M.J. and D.A. Price. (1992). Relationships among the FMRFamide-like peptides. Prog. Brain Res. 92:25-37.