Find furthers cancer, stem cell therapies research

STEM CELLS Find advances therapy research

UCSF scientists have discovered that a gene long associated with the health of stem cells plays a critical role in promoting the regeneration of those cells and guiding them into becoming specialized tissues throughout the body.

The new information also implicates the gene, called Bmi1, in cancer. The gene typically is turned off in fully formed cells, but it becomes reactivated in cancer cells, and it may partly explain their ability to proliferate out of control. If the gene could be turned off or controlled, it could slow or even stop tumor growth, the scientists believe.

The discovery was made in mice. The UCSF team looked at stem cells in the incisors of adult mice, which grow teeth throughout their lives and thus need a constant source of new cells. When the Bmi1 gene was removed from mice incisors, the scientists found fewer stem cells in the teeth and defective enamel production.

In addition to possible cancer therapies, the gene may prove useful in developing stem cell therapies to repair or replace cells damaged by injury, illness or aging, scientists said.

The research was published online in June in the journal Nature Cell Biology.

- Erin Allday

EVOLUTION Mammals may be able to 'select' offspring's sex

Mammalian parents may be able to "choose" the sex of their offspring in a gamble to strengthen their genetic line and produce the most grandchildren, according to a Stanford study of more than 2,300 zoo animals.

Biologists have for decades believed that mammals have some physiological ability to manipulate reproduction and unconsciously choose whether they will have male or female offspring. That ability is still a mystery to evolutionary biologists, but it is widely accepted.

The Stanford researchers were able to provide evidence for the first time that this ability to choose the sex of offspring results in more grandchildren. The researchers followed three generations of several species of animals at the San Diego Zoo.

The idea is that female offspring are the "safe" bet, whereas male offspring are a "high risk, high reward" bet. For example, among lions, almost all female lions will produce several offspring, whereas most male lions will never have children - only the leader of the pack gets to reproduce, and he reproduces a lot.

So if a female lion senses she can produce strong male offspring that will someday be leaders, she may take that risk, believing it will result in many more grandchildren. But if she senses her male offspring would be weak, she may go for the safe bet and have female offspring instead.

The scientists were able to back up this premise with data from their study. They found that when females produced more sons than daughters - suggesting that they were likely to have strong sons - those sons had 2.7 times more children each than did the sons of mothers who had an equal number of male and female offspring.

The study results were published July in the journal Plos One.

- Erin Allday

OBESITY Scientists uncover fat-control switch

Researchers at Stanford have uncovered the cellular switch that determines whether fat cells end up becoming the type that stores energy or burns it up.

The study could have implications in developing new methods of controlling obesity.

This fat-controlling toggle is called the vitamin D receptor, a protein that binds with vitamin D hormone. Scientists currently believe that the primary task of the protein is the regulation of calcium and phosphate levels in the bloodstream.

Scientists at Stanford found that the vitamin D receptor also plays a crucial role in determining whether fat cells become the brown sort, which are energy-burning, or white, which store energy. The level of vitamin D in the body does not appear to be a factor in those determinations.

Researchers studied connective tissue cells taken from people with vitamin D-resistant rickets, a condition in which the vitamin D receptor is either nonexistent or underactive. These cells were induced to become fat cells in a laboratory. Compared to cells from people without the condition, the cells from rickets patients were more likely to become energy-burning brown cells.

In other words, the vitamin D receptor has a hand in blocking the production of all that enviable, energy-guzzling brown fat. Previous studies on mice had shown that when the vitamin D receptor was deleted from the genome, the mice had a larger amount of brown fat.

The study was published online Aug. 1 in the journal Molecular Endocrinology.

- Kristen V. Brown

SEXUALLY TRANSMITTED DISEASES Homeless female youth are more prone to risky behavior

Homeless young women are more likely than men to engage in risky behavior - putting themselves at a greater risk for sexually transmitted diseases - because of the structure of their social groups, according to a new study from researchers at UCSF.

The study highlighted the role of social networks in the physical health of young homeless men and women. Researchers examined the social networks of 258 homeless youth between ages 15 and 24 in San Francisco, as well as the rates of sexually transmitted infections.

The women in the study were less likely than the men to use a condom, more likely to have sex with intravenous drug users and had higher rates of sexually transmitted infections. Young women also were less likely to have contacts with friends in stable housing and to have same-sex friendships.

Women with female friends were more likely to use condoms than those without same-sex friends. The presence of family in the lives of young women also reduced the likelihood of risky sexual behavior.

Researchers said the study underscored the importance of reconnecting homeless youth with mainstream society. The study was published online July 17 in the Journal of Adolescent Health.

- Kristen V. Brown

AGRICULTURE

Fruit flies here for good in spite of state's efforts

Despite California's efforts to wipe out tropical fruit flies, as many as nine species are here for good and growing in number, a new UC Davis study shows.

The first fruit fly was discovered in California in 1954. Their presence is a concern for the state's $43.5 billion agricultural industry because both adult and larval flies can damage fruits and vegetables.

For decades, the state has tried to keep out fruit flies by restricting commodity imports from regions with fruit fly outbreaks, for example, or by running large-scale monitoring programs and releasing sterile fruit flies to slow or prevent reproduction of other flies.

But the new study finds that in addition to the olive fly, which is already established, the Mediterranean, Mexican, oriental, melon, peach and guava fruit flies are also here to stay.

The researchers said that their findings showed a need for long-term strategies that reflect the reality that the pests aren't going anywhere soon. Their study appeared in Proceedings of the Royal Society B on Tuesday.

- Stephanie M. Lee