Study suggests mice produce egg cells after birth
Shanghai scientists say they have detected germ-line cells that produce unfertilized eggs, or oocytes, in both young and old mice.
The scientists worked only with mice, but because all mammals are physiologically similar, any proof that the rodents could produce eggs after birth would encourage research to see if humans could, too.
This challenges the conventional view that women are born with all the egg cells they will produce for their entire lifetime and never generate new ones. If the Chinese team’s findings are correct, this could create a major change in fertility treatment.
Although similar theories have been made before, none have been sustainable. Earlier this month, however, the same idea relating to heart muscle cells – that they never get replaced throughout a person’s lifetime – was found incorrect by Swedish scientist Jonas Frisen.
The team, led by Kang Zou and Ji Wu of Shanghai Jiao Tong University, scanned the mice’s ovaries for cells that produce the vasa homolog protein, found only in germ-line cells. During the embryo’s formation, the cells make all the oocytes for the females‘ lifetime.
The scientists detected vasa-producing cells in the mouse ovaries, removed them and put them in laboratory glassware. Then, they were injected with a green fluorescent protein – a way to mark cells.
The researchers later injected the cells into the ovaries of another group of mice whose own eggs have been killed. When the mice mated, some of their offspring were green, suggesting that they were from the eggs produced by the injected germ-line cells.
However, other experts say that the findings are still difficult to interpret and more research must be done before the study is clinically relevant, as there are significant differences between mice and people.
Study suggests astronauts‘ muscles age in space
A new study has found that astronauts lose a significant amount of muscle mass in space.
The study, paid for by NASA and published in the April issue of The Journal of Applied Physiology, looked at nine American and Russian astronauts who spent at least six months in space and had access to various aerobic and resistance exercise machines.
The researchers measured leg and muscle volume with MRI scans, muscle performance with dynamometers, and constructed calf-muscle biopsies before and after the astronauts went to space.
After observing the astronauts‘ exercise routines using logs and videos, the researchers estimated that they averaged the equivalent of about 50 minutes of aerobic activity and 30 minutes of resistance training a day.
Despite this exercise, it was found that the astronauts lost an average of 13 percent of muscle mass and 20 to 29 percent in muscle performance.
Scott Trappe, lead author of the study, said that astronauts need to develop new modes of exercise that will provide for higher intensity, as they do not get the everyday exercise available to people on earth.
ANNA OPALKA compiled SCIENCE SCENE and can be reached at email@example.com.