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Cognitive impairment in premature babies not permanent
THIS WEEK
Preterm babies not short of grey matter PREMATURE birth need not lead to learning difficulties. That’s the exciting conclusion of two independent but complementary studies. Together, the studies suggest that the relatively small cerebral cortex seen in many preterm babies contains a normal number of neurons that can be nurtured back to health with the right care. A small cerebral cortex was widely assumed to reflect a lack of neurons, perhaps because some of the cells die following the ischemia – reduced blood flow to brain tissue – often experienced by premature babies. To study the effects of ischemia in more detail, Stephen Back at the Oregon Health & Science University in Portland and colleagues turned to fetal sheep brains, a good animal model of the brain of human fetuses. Back’s team compared neuron numbers in sheep brains that had experienced ischemic injury and those that had not: the numbers matched. “We counted the money and it was all there,” says Back. “But the cells were all squished
Get cirrus in the fight against climate change FEATHERY cirrus clouds are beautiful, but when it comes to climate change, they are the enemy. Found at highaltitude and made of small ice crystals, they trap heat – so more cirrus means a warmer world. Now it seems that, by destroying cirrus, we could reverse all the warming Earth has experienced so far. In 2009, David Mitchell of the 14 | NewScientist | 26 January 2013
together.” The cells from the injured brain did differ in shape, though, lacking the branches – dendrites – that radiate from healthy neurons. “Instead of oak trees, we saw saplings,” says Back. The team used an MRI technique that measures how water diffuses through brain tissue, called diffusion tensor
cortex that is influenced, not the whole brain,” says Miller. MRI scans of the premature babies when they were 32 and 40 weeks old showed the same pattern of underdeveloped – but not dead – neurons that Back’s team found in the animal tissue (Science Translational Medicine, doi.org/j8t). “There’s a remarkable agreement between the two studies,” says Back. “The data is spot on.” Miller agrees: “We think we’re seeing the same thing.” The findings could change the way we think about brain damage. “The injury is not as bleak as we used to think,” says Back. “It’s a disorder of maturation, not loss.” Miller’s study suggests that better nutrition or cognitive stimulation might promote brain growth. “You could jump-start the cells and get them developing again,” says Back. Zoltán Molnár at the University of Oxford describes the work as groundbreaking, although he thinks Back’s team could have studied other brain regions too for a more complete picture. The findings are genuinely illuminating, says David Edwards at University College London, but he adds that we shouldn’t be too quick to settle on underdeveloped neurons as the only explanation for reduced cortical volume. “They have room to grow, but –Nurture the neurons– by how much?” he says. n Luis Davilla/Cover/Getty Images
Douglas Heaven
imaging, to explore the effect this has. In tissue with fully branching neurons, water diffuses randomly in all directions. In the damaged neurons, however, water diffused towards the surface of the brain – an indication of neuron immaturity (Science Translational Medicine, doi.org/j8s). In a sister study, Steven Miller at the Hospital for Sick Children in Toronto, Canada, and colleagues studied the links between neonatal care and brain development in 95 preterm babies. “The surprising detail was that it was mostly the cerebral
Desert Research Institute in Reno, Nevada, proposed a radical way to stop climate change: get rid of some cirrus. Now Trude Storelvmo of Yale University and colleagues have used a climate model to test the idea. Storelvmo added powdered bismuth triiodide into the model’s troposphere, the layer of the atmosphere in which these clouds form. Ice crystals grew around these particles and expanded, eventually falling out of the sky, reducing cirrus coverage. Without the particles, the ice crystals remained small and stayed up high for longer.
The technique, done on a global scale, created a powerful cooling effect, enough to counteract the 0.8 °C of warming caused by all the greenhouse gases released by humans (Geophysical Research Letters, DOI: 10.1002/grl.50122). But too much bismuth triiodide made the ice crystals shrink, so cirrus clouds lasted longer. “If you get the concentrations wrong, you could get
“A powerful cooling effect was created – enough to counteract all the humaninduced global warming”
the opposite of what you want,” says Storelvmo. And, like other schemes for geoengineering, side effects are likely – changes in the jet stream, say. Different model assumptions give different “safe” amounts of bismuth triiodide, says Tim Lenton of the University of Exeter, UK. “Do we really know the system well enough to be confident of being in the safe zone?” he asks. “You wouldn’t want to touch this until you knew.” Mitchell says seeding would take 140 tonnes of bismuth triiodide every year, which by itself would cost $19 million. Michael Marshall n
Preterm babies not short of grey matter PREMATURE birth need not lead to learning difficulties. That’s the exciting conclusion of two independent but complementary studies. Together, the studies suggest that the relatively small cerebral cortex seen in many preterm babies contains a normal number of neurons that can be nurtured back to health with the right care. A small cerebral cortex was widely assumed to reflect a lack of neurons, perhaps because some of the cells die following the ischemia – reduced blood flow to brain tissue – often experienced by premature babies. To study the effects of ischemia in more detail, Stephen Back at the Oregon Health & Science University in Portland and colleagues turned to fetal sheep brains, a good animal model of the brain of human fetuses. Back’s team compared neuron numbers in sheep brains that had experienced ischemic injury and those that had not: the numbers matched. “We counted the money and it was all there,” says Back. “But the cells were all squished
Get cirrus in the fight against climate change FEATHERY cirrus clouds are beautiful, but when it comes to climate change, they are the enemy. Found at highaltitude and made of small ice crystals, they trap heat – so more cirrus means a warmer world. Now it seems that, by destroying cirrus, we could reverse all the warming Earth has experienced so far. In 2009, David Mitchell of the 14 | NewScientist | 26 January 2013
together.” The cells from the injured brain did differ in shape, though, lacking the branches – dendrites – that radiate from healthy neurons. “Instead of oak trees, we saw saplings,” says Back. The team used an MRI technique that measures how water diffuses through brain tissue, called diffusion tensor
cortex that is influenced, not the whole brain,” says Miller. MRI scans of the premature babies when they were 32 and 40 weeks old showed the same pattern of underdeveloped – but not dead – neurons that Back’s team found in the animal tissue (Science Translational Medicine, doi.org/j8t). “There’s a remarkable agreement between the two studies,” says Back. “The data is spot on.” Miller agrees: “We think we’re seeing the same thing.” The findings could change the way we think about brain damage. “The injury is not as bleak as we used to think,” says Back. “It’s a disorder of maturation, not loss.” Miller’s study suggests that better nutrition or cognitive stimulation might promote brain growth. “You could jump-start the cells and get them developing again,” says Back. Zoltán Molnár at the University of Oxford describes the work as groundbreaking, although he thinks Back’s team could have studied other brain regions too for a more complete picture. The findings are genuinely illuminating, says David Edwards at University College London, but he adds that we shouldn’t be too quick to settle on underdeveloped neurons as the only explanation for reduced cortical volume. “They have room to grow, but –Nurture the neurons– by how much?” he says. n Luis Davilla/Cover/Getty Images
Douglas Heaven
imaging, to explore the effect this has. In tissue with fully branching neurons, water diffuses randomly in all directions. In the damaged neurons, however, water diffused towards the surface of the brain – an indication of neuron immaturity (Science Translational Medicine, doi.org/j8s). In a sister study, Steven Miller at the Hospital for Sick Children in Toronto, Canada, and colleagues studied the links between neonatal care and brain development in 95 preterm babies. “The surprising detail was that it was mostly the cerebral
Desert Research Institute in Reno, Nevada, proposed a radical way to stop climate change: get rid of some cirrus. Now Trude Storelvmo of Yale University and colleagues have used a climate model to test the idea. Storelvmo added powdered bismuth triiodide into the model’s troposphere, the layer of the atmosphere in which these clouds form. Ice crystals grew around these particles and expanded, eventually falling out of the sky, reducing cirrus coverage. Without the particles, the ice crystals remained small and stayed up high for longer.
The technique, done on a global scale, created a powerful cooling effect, enough to counteract the 0.8 °C of warming caused by all the greenhouse gases released by humans (Geophysical Research Letters, DOI: 10.1002/grl.50122). But too much bismuth triiodide made the ice crystals shrink, so cirrus clouds lasted longer. “If you get the concentrations wrong, you could get
“A powerful cooling effect was created – enough to counteract all the humaninduced global warming”
the opposite of what you want,” says Storelvmo. And, like other schemes for geoengineering, side effects are likely – changes in the jet stream, say. Different model assumptions give different “safe” amounts of bismuth triiodide, says Tim Lenton of the University of Exeter, UK. “Do we really know the system well enough to be confident of being in the safe zone?” he asks. “You wouldn’t want to touch this until you knew.” Mitchell says seeding would take 140 tonnes of bismuth triiodide every year, which by itself would cost $19 million. Michael Marshall n