PSU Magazine Spring 2005

Lheir dormant phase, for example, or we can expose them Lo lighL. We also look al other ways in which they won't break dormancy," he says. 0 ne characteristic of all embryos is that they grow rapidly from a single cell. The cell divides, Lhen divides again, doubling continuously until it reaches a certain point. Then the rapid development phase stops. The cells are programmed to stop dividing so that other phases of development– such as building of the skeleton, ner– vous system and organs--can take the forefront. Cancer cells are immune to Lhe negative regulators that halt cell growth. They divide uncontrollably. "These killifish embryos have the ability to globally shut down or regu– late cell proliferation and metabolism. If we can figure that out, we can address cell proliferation in cancers,'' Poclrabsky says. Each type of Lissue in the human body has its own unique types of cells, each wiLh its own set of cues telling it to grow or not grow. So studying a liver cell won't tell you much about colon cancer, for example. "But in Lhesc embryos," Podrabsky explains, "everything is shmting down. We are looking for Lhis master con– troller Lhat could act in any cell at any one time Podrabsky says Lhat if he can find the genes responsible for cell prolifera– tion, he will pursue National Institutes of Heallh funding for cancer research. While he is working on that problem, the American Heart Association has given him funding to study another: the effects of oxygen deprivation. hile adult killifish have to have oxygen, early embryos and embryos that are in their dor– mant phase can go 90 days without it. If we can understand the differences at the cellular level between the heart of an embryo and that of an adult, Podrabsky says, we will gain a better understanding of how to survi.ve heart attacks and strokes. When a person has a heart attack, for example, Lhe heart is deprived of oxygen. Some heart cells will die as a result, but other cells will survive the low-O\.')'gen event only to die when oxygenated blood f1ows back into the area, Poclrabsky explains. "So it's not a given thaL a heart attack victim will survive after they've been stabilized. Much of the damage happens when blood is reintroduced," he says. The killifish embryos Podrabsky 1s studying don't have Lhat problem. They can go for extended periods of time \vi.Lhout oxygen and suffer no ill Biology professor Jason Podrabsky has more than 80 fish aquariums in a new campus laboratory. effects when oxygen is reintroduced. Is iL their genes or the environment? One theory holds that the heart cells that die when they are reexposed to oxygen do so because they are pro– grammed to self destrucl. This phe– nomenon of programmed cell death, called "apoptosis," is inherent in all healthy cells. Under normal condi– tions, cells die off to make room for new cells or LO make way for a new phase in Lhe organism's development. "Every cell in your body is ready LO commit suicide if given the right signals," Podrabsky says. For example, humans are born with fingers insLead of paddle-like fins because the cells that form the web– bing beLween the fingers kill them– selves off during embryonic development. One reason cancer is such a lethal disease is that cancer cells ha\·e lost this ability to self destrucl. o why would a heart cell choose Lo do away with itself instead of taking advantage of a new chance at life in the form of oxy– gen-rich blood? Poclrabsky is hoping that the killifish, whose embryonic hearts make that choice LO live, will provide an answer. "These fish are a gold mine," he says. □ SPRING 2005 PSU \1AGAZINE 15