Word: miceli
(lookup in dictionary)
(lookup stats)
Dates: during 2000-2009
Sort By: most recent first
(reverse)
...first described by Japanese biologist Shinya Yamanaka, who, in 2007, showed that the introduction of four genes into an adult human skin cell could reprogram it back to an embryonic state (Yamanaka had reported the same achievement in mice the previous year). Like embryonic stem cells, these reprogrammed adult cells could be coaxed into becoming any other type of cell - from skin to nerve to muscle. But researchers questioned whether the new stem cells would behave as predictably or as safely as embryonic stem cells, or whether iPS would consistently yield usable cells. "Our work shows that the original method...
...activity, so many people still choose not to exercise. A lecture at Johns Hopkins University about genetics and lung disease served as Lightfoot's eureka moment, and he became interested in studying genes as our prime mover. For the new study, Lightfoot and his team bred two strains of mice - active and inactive. Researchers then crossbred two generations of the active and inactive mice, ending up with a study group of 310 genetically mixed offspring. At about 9 weeks old, each mouse was housed in an individual cage and given an exercise wheel. Researchers measured how far, how long...
Exercise-prone mice put in a good 5 to 8 miles per day (the equivalent of an average man running 40 to 50 miles a day) vs. 0.3 miles per day for inactive mice. While the exercise wheels of the activity-prone mice would turn all night, some of the sedentary mice devised ingenious ways to avoid activity. One stuffed wood shavings around the wheel and turned it into a bed; one used it as an, ahem, toilet; and one climbed on top of her wheel only to get a better look at the overhead sensors tracking her movements...
Although the animals' activity levels could not be entirely attributed to genes, researchers calculated that heredity accounted for about 50% of the differences in activity. They also found that activity-promoting genes were dominant traits in 75% of the exercise-loving mice. (Researchers don't know yet how often the activity-inclined genotype would naturally occur; Lightfoot says he found a fairly continuous range of activity levels, from extremely active to very low-active, in about 30 mice strains he tested.) "When we used to talk about activity, it was whether or not people decided to be active," says Lightfoot...
...theories, Lightfoot says: Genes may affect either the way muscles work - perhaps causing them to use energy more efficiently and preventing fatigue - or some higher-order biochemical circuit in the brain, such as levels of the neurotransmitters dopamine or serotonin. Researchers have examined the muscle tissue of the mice in the study, however, and early data, which has not yet been published, suggests that there's no difference in their function. So the researchers' best guess is that the drive to exercise is at least partly influenced by brain chemicals - a reasonable hypothesis, given that dopamine or serotonin plays...