Child DNA in his mother's brain

The phrase "you are always in my mind" can find a literal meaning in relation to their children, at least, if they - boys. How do I find American scientists, male DNA may be present in the brain cells of women, which means that they do not belong to them, and their sons, with whom they exchanged during pregnancy. Built on this phenomenon microchimerism. We know that he has a place in the mouse, but it turned out now, and humans.
Normally, the barrier to entering the brain from the blood of different foreign substances, bacteria, etc. is the blood-brain barrier. However, during pregnancy, it seems to be waning, which allows cells to get in there baby.
This came from an immunologist William Chan and his colleagues Cancer Research Center Fred Hutchinson in Seattle.
They investigated the brain 59 women who died at the age of 32 to 101 years. They were interested in men's DNA, which could only be there thanks to the birth of boys. DNA daughters scientists have not considered, because it would have been difficult to separate from the mother's genes.
Men's Y-chromosomes were found in nearly two-thirds of cases (37) in different parts of the brain. The oldest woman who they survived, was 94 years old. Remarkably, those who suffered from Alzheimer's disease, and there were 33, filial genes were present in smaller amounts. Perhaps this suggests a certain relationship between microchimerism and dementia, yet to be set. In any case, is already established that the disease is more common in women who have children than ever becomes a mother.