SUBJECTING unborn babies to radiation during medical X-rays or
intercontinental flights may increase their risk of developing mental illness
later in life, German researchers told the New Orleans conference.
Christoph Schmitz at the University of Aachen and his colleagues have shown
for the first time that mice exposed to low doses of radiation in the womb
undergo changes in a part of the brain called the hippocampus. The effects of
these changes only show up in early adulthood.
The researchers think their findings may provide important clues to the
development of mental illnesses such as schizophrenia that appear in adulthood.
They note recent reports that children who were born within nine months of the
Chernobyl disaster have abnormal hippocampuses. They are also more likely to
have behavioural problems and are considered to be at high risk of
schizophrenia.
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Schmitz鈥檚 team wanted to know if events in the womb could help to account for
unexplained mental illness in adults. They exposed pregnant mice to the
equivalent of about 10 medical X-rays when they were about a third of the way
through pregnancy.
They examined the fetuses of these mothers the day after they were
irradiated, and looked at their pups when they were one month and six months
old. The researchers looked for damage such as single-strand breaks in DNA, and
also measured the total number of neurons in different parts of the brain.
The day after irradiation, there was no evidence of damage. 鈥淭he damaged
cells were either lost or repaired,鈥� speculates Schmitz. At one month old there
was some evidence of single-strand breaks.
The big surprise came at six months, the equivalent of about 20 years old in
humans. The researchers found a significant loss of cells in the hippocampus.
鈥淵ou don鈥檛 see it at one month,鈥� says Schmitz. 鈥淚t鈥檚 an extremely delayed
迟丑颈苍驳.鈥�
The researchers suggest that the problem stems from damage to mitochondria,
which generate energy for cells. They think the mitochondria are increasingly
unable to provide energy to repair the DNA damage.
Over the past decade, the importance of antenatal health has come to the
fore. For instance, malnutrition in the womb can predispose an adult to heart
disease.
Schmitz now wants to start analysing placentas of newborns, because they form
at the same time as the brain. He thinks the placenta might be used to predict
the risk that damage to the hippocampus will show up later in life.
