Turkey's Prime Minister Recep Tayyip Erdogan has undergone follow-up surgery after a November operation on his intestine, his office said Saturday.

"The second and final part of the operation on his intestinal system started on November 26 has been carried out successfully," said the statement, adding that it had taken 30 minutes. It did not way when the operation took place.

Top Russian psychiatrists on Friday called for urgent measures to battle the soaring teenage suicide rate, one of the world's highest.

The number of 15 to 19-year-olds taking their own lives is almost three times higher than the world average at 19 to 20 per 100,000, the health ministry's chief psychiatrist Zurab Kekelidze told a round table in Moscow.

Four years after U.S. drug-maker Baxter International's blood thinner heparin was contaminated in China, causing dozens of deaths, U.S. regulators on Friday issued draft guidelines for safe production.

Heparin, a blood thinner used by millions of patients during kidney dialysis and heart surgery to prevent blood clots, is normally produced from pig intestines.

Women who are given chemotherapy during pregnancy do not run a risk of harming their baby, doctors reported in The Lancet Oncology on Friday.

European cancer specialists looked at 68 pregnancies, producing 70 children, during which 236 cycles of cancer drugs were administered.

Driving under the influence of cannabis almost doubles the risk of a serious accident, according to a paper published on Friday in the British Medical Journal (BMJ).

The risk of collision is substantially higher if the driver is aged under 35, it said.

Early research on mice with cancer shows that fasting may weaken tumors and help chemotherapy work better, scientists said on Wednesday.

While it remains unknown if the same approach could work in humans, or if it would even be safe, researchers said the findings suggest a promising new route of study for improving response to cancer treatment.

U.S. scientists on Wednesday reported a new advance in using gene therapy to restore eyesight in people with a rare, inherited form of blindness.

The therapy, which had been previously tried in just one eye of 12 people, worked well when injected into the other eye of three of the patients, offering a sign that the treatment is safe, effective and will not be rejected by the body.

Mediator, a drug licensed for use by diabetics that became widely prescribed in France as a slimming aid, "probably" caused at least 1,300 deaths before it was withdrawn, a study published on Thursday said.

Mahmoud Zureik of the National Institute of Health and Medical Research (Inserm), who co-led the probe, told Agence France Presse that around 3,100 people had required hospitalization during the 33 years during which the drug was sold.

People with Parkinson's disease who practiced the Chinese martial art tai chi for six months showed better balance than counterparts who did other forms of exercise, said a U.S. study Wednesday.

A total of 195 people took part in the randomized study in four different cities in the western state of Oregon, according to the results published in the New England Journal of Medicine.

California scientists said Wednesday they may have found a way to stimulate a part of the brain so that it forms memories more easily.

Someday, the process might be used to make a neuroprosthetic device, or thinking cap, that people could turn on when they need to remember new information, or it may even help people with dementia restore their memories.