Research

Overview - Apoptosis (Programmed Cell Death)
The process of apoptosis (programmed cell death), is a topic of interest in a variety of fields ranging from neurology, embryology, medicine, and genetics. Upon its discovery in the mid 20th century, it has been linked to a variety of developmental pathways in tissues and organs and the interest in this field has exploded due to recent suggestions that flaws in this process may contribute to a variety of disorders including AIDS, cancer, and Alzheimers (Duke et al., 1996; Fadeel and Orrenius 2005).

The possibility of exploiting apoptosis has even been suggested as an effective treatment against cancer cells, which have the ability to evade this cell death (Salvensen and Dixit, 1997). In order to begin to understand this process, early research focused on the round worm because it was a simple multicellular organism with relatively few cells and a small genome. It was soon discovered that the genetic control of this process in the roundworm was quite similar to that of other multicellular organisms, including the human. My current research examines this crucial developmental process using the amphibian model system.

A) The role of apoptosis in amphibians has previously been identified in skin development (Schreiber and Brown, 2003) and tail regression (Rowe et al., 2005). Research has also begun to examine this programmed cell death in the remodeling of the digestive tract as the larval tadpoles metamorphose into adult frogs, however, these studies are few in number and incomplete.

In my recent research on the Northern leopard frog, Rana pipiens, we have examined apoptosis in the remodeling of the digestive tract. This recent study, as well as the proposed one, provides the first comprehensive studies of this process in an herbivorous and carnivorous species. This research project is of particular interest because tadpoles of many anurans are herbivorous, but during metamorphic climax they transform into carnivorous frogs and toads. In some species, however, such as the Argentine horned frog, Ceratophrys ornata, both larvae and adults are carnivorous.

The short larval life of this species (approximately two weeks) culminates in metamorphic climax with similar, but not as pronounced, structural changes in the digestive tract as those in herbivorous larvae. C. ornata larvae also continue to eat during climax, in contrast to the herbivorous larvae of R. pipiens, which stop feeding during its 3 month climax period.

During this event, the larval gut shortens and the layer of cells that line the inside of the larval gut (epithelium) is replaced by an adult type (Fox, 1984). This change in diet is also accompanied by a multitude of structural and biochemical events including the activity of specific enzymes and localization of specific carbohydrates (Hourdry et al., 1996).

Therefore, the purpose of this research is to determine if apoptosis plays a role in the shortening and remodeling of the digestive tract of the carnivorous larvae of C. ornata and then compare this process in this species with that of other species.

B) Sponge Immunology. Sponges are the simplest animals to possess the ability to recognize self vs. non-self (Fernandez-Busquets and Burger, 1999; Fernandez-Busquets. Et all 2002). When two different individuals are brought into contact, a barrier zone of contact (ZOC) forms between the two. The purpose of this research is to explore the cellular processes used by the marine sponge, Microciona prolifera, to elicit an immune response at the ZOC, including (apoptosis), cell migration, and protein expression. In addition, we are interested in determining whether sponges exhibit a memory component (i.e., ability to recognize a foreign individual upon a second encounter and thus display a quicker immune response).