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Noisy yeast cells. ENG Biomedical Engineering Professor Jim Collins, codirector of the Center for BioDynamics, and his colleagues in the center’s Applied BioDynamics Lab are noise experts. They have used the small, random fluctuations around a primary signal -- the noise associated with a signal -- for such diverse purposes as controlling the signal-to-noise ratio in networks of neurons, and producing innersoles to enhance balance. Now William Blake (ENG’03), who recently completed his Ph.D. under Collins’ direction, has taken an important step toward understanding the role noise plays in the process by which yeast genes generate proteins.

Protein production is essentially a two-step process. In the first, the transcription phase, DNA produces mRNA (messenger RNA); in the second, the translational phase, mRNA produces protein. Working with batches of 30,000 cells, Blake engineered yeast cells to produce a green fluorescent protein. To do this he created two switches, one to control the efficiency of the transcription phase, the other to control the translation phase. He found that the level of transcription efficiency was related to the amount of noise in the final protein product -- with peak variation in the amount of protein produced occurring at intermediate levels of efficiency. Changing the efficiency of the translation phase did not result in a large variation in the amount of fluorescence produced unless it was coupled to a noisy transciptional state. Blake’s findings were in direct contrast with a similar experiment done previously in bacteria. This led him to hypothesize that the difference is related to reinitiation -- a process that occurs during transcription in eukaryotic cells (cells such as yeast that have a nucleus) but not in prokaryotic cells (cells such as bacteria that have no nucleus).

In a follow-up experiment, Blake examined the effects of noise in the regulatory input. He found that a high level of noise resulted in two distinct groups of cells, some with high and some with low levels of fluorescence. A low level of noise produced a more even distribution of fluorescence in the resulting cells.

Although these experiments were done on one-celled organisms, the mechanisms may one day help us understand how cells are differentiated in more complex organisms. “We tend to think that development needs to be very closely controlled,” says Blake, “but in fact it may be that noise is important to the development of healthy organisms.”

This work was reported in the April 10 issue of the journal Nature. Coauthors, in addition to Blake and Collins, are Mads Kaern, a research associate at the Center for BioDynamics, and Charles R. Cantor, an ENG biomedical engineering professor and director of the Center for Advanced Biotechnology.


Finish safe. Running the Boston Marathon can be an exhilarating experience, but runners -- experienced and novice -- can put themselves at risk for long- or short-term injury or health problems if they are not properly prepared for the rigors of the course of just over 26 miles, according to James Onate, an assistant professor of athletic training at Sargent College.

“Experienced runners and elite athletes sometimes think more is better -- they need to feel pain or discomfort to have a really tough and rewarding workout,” says Onate. He points out that training sessions that are too long or too frequent may lead to stress fractures or strained muscles. Hip or knee pain may develop from the constant pounding of feet on pavement, creating forces that run up through the bones and joints.

A highly motivated athlete may ignore minor injuries until something more serious occurs, such as a stress fracture. Minor injuries left untreated may also contribute to articular cartilage degeneration and possible early onset of osteoarthritis.

Proper hydration is essential for athletes at all levels. “Dehydration can happen to even the most well-trained and conditioned athlete,” says Roberta Durschlag, an assistant professor of nutrition at Sargent. She recommends that athletes stay hydrated during the days and hours leading up to the race, as well as during and after the race. Drinking a sports beverage during the race is best -- ideally two to five cups every hour of a drink containing 10 to 20 grams of carbohydrates and 120 to 170 milligrams of sodium per eight-ounce cup. Thirst, headache, weakness, muscle cramps, and decreased performance are danger signs, indicating that dehydration is already occurring, says Durschlag.

Finally, according to Onate, it’s important for athletes to acclimate, if possible, for running in warmer climates such as Arizona or Florida -- or a sudden blistering hot day in New England.

So for all the athletes running this year, the staff at Sargent College wishes you cool breezes (from behind), blue skies, and light feet.

"Research Briefs" is written by Joan Schwartz in the Office of the Provost. To read more about BU research, visit http://www.bu.edu/research.

       

15 May 2003
Boston University
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