Mobile Phones Cause Human Cell Changes: Study Wed Jun 19, 5:29 PM ET HELSINKI (Reuters) - A study by scientists in Finland has found that mobile phone radiation can cause changes in human cells that might affect the brain, the leader of the research team said Wednesday. But Darius Leszczynski, who headed the 2-year study and will present findings next week at a conference in Quebec, said more research was needed to determine the seriousness of the changes and their impact on the brain or the body. The study at Finland's Radiation and Nuclear Safety Authority found that exposure to radiation from mobile phones can cause increased activity in hundreds of proteins in human cells grown in a laboratory, he said. "We know that there is some biological response. We can detect it with our very sensitive approaches, but we do not know whether it can have any physiological effects on the human brain or human body," Leszczynski said. Nonetheless the study, the initial findings of which were published last month in the scientific journal Differentiation, raises new questions about whether mobile phone radiation can weaken the brain's protective shield against harmful substances. The study focused on changes in cells that line blood vessels and on whether such changes could weaken the functioning of the blood-brain barrier, which prevents potentially harmful substances from entering the brain from the bloodstream, Leszczynski said. The study found that a protein called hsp27 linked to the functioning of the blood-brain barrier showed increased activity due to irradiation and pointed to a possibility that such activity could make the shield more permeable, he said. "(Increased protein activity) might cause cells to shrink--not the blood vessels but the cells themselves--and then tiny gaps could appear between those cells through which some molecules could pass," he said. Leszczynski declined to speculate on what kind of health risks that could pose, but said a French study indicated that headache, fatigue and sleep disorders could result. "These are not life-threatening problems but can cause a lot of discomfort," he said, adding that a Swedish group had also suggested a possible link with Alzheimer's disease ( news - web sites). "Where the truth is I do not know," he said. Leszczynski said that he, his wife and children use mobile phones, and he said that he did not think his study suggested any need for new restrictions on mobile phone use.