Leaving a Trace

Your brain is hungry, constantly demanding a supply of nutrients and oxygen that are brought in by a dense network of blood vessels. But your brain is also precious and needs to be protected from harmful chemicals that might have got into the bloodstream. This is the job of the blood-brain barrier – a protective layer that acts as a filter between the brain and the bloodstream. To find out more about how this barrier forms during development, researchers are studying tiny transparent zebrafish. These pictures show the networks of blood vessels (pink) forming inside the brains of living fish embryos ranging from three days (left) to ten days old (right), which have had different coloured and sized fluorescent tracer molecules injected into their blood. The tracers leak out from the blood vessels in the younger embryos but not the older ones, helping to pinpoint the time when the barrier forms.

Written by Kat Arney

Kat Arney

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Dr Kat Arney is an award-winning science writer, broadcaster and public speaker, and is the founder and Creative Director of First Create The Media.

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• Image from work by Natasha M O'Brown, Sean G Megason and Chenghua Gu
• Harvard Medical School, Boston, MA, USA
• Image originally published under a Creative Commons Licence (BY 4.0)
• Published in eLife, August 2019