Our research at The University of Texas Medical Branch has focused on the regulation of reproductive behavior in the marine mollusk Aplysia, an animal that has been used extensively over the last 25 years to study the cellular, molecular, and biochemical bases of egg-laying activity (see figure below).
Aplysia has many advantages for these kinds of studies:
It has relatively simple behaviors It has a relatively simple nervous system with large neurons that can be individually identified in different animals and their electrophysiology studied either in vivo or in vitro It has many polyploid neurons that produce relatively large quantities of secretory product, making molecular genetic and biochemical analyses of the secretory products feasible. This is particularly true of the bag cells, two homogeneous clusters of neuroendocrine cells in the abdominal ganglion. These cells are part of the final common pathway leading to egg deposition. Our early studies used a variety of biochemical, immunohistochemical and electrophysiological techniques to identify cells in other parts of the nervous system that may regulate bag-cell activity.
B.A., University of California (Santa Barbara), 1975 Ph.D., Florida State University, 1981 Member, Marine Biomedical Institute Assistant Professor, Anatomy & Neurosciences Cell Biology Graduate Program More recently, we have focused on sexual pheromones. Aplysia are solitary animals during most of the year, but move into breeding aggregations during the summer reproductive season. The aggregations contain both mating and egg-laying animals and are associated with masses of recently deposited egg cordons, often laid one on top of another. Water-borne pheromones derived from the egg cordons are attractive to sexually mature Aplysia and reduce their latency to mating; they may also induce egg laying and be responsible for the masses of egg cordons associated with the aggregation.
Using a combination of biochemical and behavioral techniques, we have now obtained a partial sequence of one of these attractants and have reduced the number of possible tissues of origin to two.
Our immediate goals are to:
Clone the attractant Determine its tissue of origin Establish whether the factor normally functions as an attractant. Examine whether it has related acivities within the aggregation, such as inducing egg-laying or reducing the latency to mating.
Painter, S.D., et al. The anatomy and functional morphology of the large hermaphroditic ducts of three species of Aplysia, with special reference to the atrial gland. J. Morphol., 186:167-194, 1985.
Painter, S.D., et al. Peptide B induction of bag cell activity in Aplysia: Localization of sites of action to the cerebral and pleural ganglia. J. Neurobiol., 19:695-706, 1988.
Painter, S.D., et al. Localization of immunoreactive -bag-cell peptide in the central nervous system of Aplysia. J. Comp. Neurol., 287:515-530, 1989.
Painter, S.D., et al. Induction of copulatory behavior in Aplysia: Atrial gland factors mimic the excitatory effects of freshly deposited egg cordons. Behav. Neural Biol., 51:222-236, 1989.
Painter, S.D., et al. Relative contributions of the egg layer and egg cordon to pheromonal attraction and the induction of mating and egg-laying behavior in Aplysia. Biol. Bull., 181:81-94, 1991.
Painter, S.D. Coordination of reproductive activity in Aplysia: Peptide neurohormones, neurotransmitters and pheromones encoded by the egg-laying hormone family of genes. Biol. Bull., 183:165-172, 1992.
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