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Thursday, 13 July, 2000, 18:06 GMT 19:06 UK
Body clock 'set before birth'
Zebrafish
The research was carried out on Zebrafish
The reason that jet lag hits some travellers hard and barely fazes others may lie in our mothers' genes, say researchers.

French scientists studying zebrafish have uncovered evidence that the body clock is set before birth.

They believe that it is the genetic information handed down by the mother that determines how easily the body can adjust to changes in its normal daily rhythm.

Scientists have generally assumed that the body or circadian clock does not start working until around the time of birth, or possibly later.

But the French team found a key component of the circadian clock starts "ticking" in zebrafish eggs even before they are fertilised.

The gene's activity keeps the same rhythm as the animal develops.

Researcher Dr Vincent Laudet said: "These findings were quite a surprise. The current belief is that circadian rhythms need a developed brain, so they don't get started until later."

Resetting the body clock

Aircraft
Air travel can disrupt the body clock

Researchers are seeking ways to help the body clock reset itself in response to a trans-Atlantic flight, for example, or a night-time workshift.

Disrupted clocks have been associated with sleep disorders and depression.

Understanding how the clock is set in the first place could be an important step toward treating these ailments.

The genes that run the circadian clock are not yet fully understood.

However, it seems that they are controlled by light.

When a clock gene is switched on, it directs the cell to produce proteins, which eventually trigger a signal that switches the gene off.

The process comes full circle when conditions change again, turning the gene back on.

Working together, the clock genes create circadian rhythms in the body, which help control the timing of a variety of biological changes, including hormone production, blood pressure, and the metabolism's slowdown during sleep.

The Period, or "Per," gene is one of the most important clock genes known in fruit flies and mammals.

Dr Laudet and his colleagues identified a version of this gene, Per3, in zebrafish.

They found that the gene's activity rose and fell at a steady pace in both unfertilised and fertilised eggs.

Therefore, they concluded that zebrafish embryos must have inherited the "ticking" Per3 directly from their mothers.

The scientists suspect that this process may happen in mammals too.

The research was published in the journal Science.

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See also:

27 Apr 00 | Health
Jetlag clues uncovered
24 Jun 00 | Health
Ecstasy 'ruins body clock'
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