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Scans pinpoint moment anaesthetic puts brain under
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H. Morrison, MRC hgu, Igmm, Uni. of Edinburgh
EVEN the prettiest faces are built using junk. In mice, the shapes of the face and skull are finely tuned by “junk DNA”, so called because it was thought to lack function. The same junk DNA is found in humans and may do a similar job. Geneticists have found only a few genes that control face shape. So Axel Visel of the Lawrence Berkeley National Laboratory in California focused on “enhancers”: short sequences of DNA – which are still sometimes called “junk” – that do not code for genes but can influence their activity. Visel and his colleagues studied gene expression in a developing mouse embryo, and found 120 enhancers active in cells of the face. To work out what they did, the team chose three and engineered groups of mice to each lack one of them. The enhancers subtly affected face shape. For instance, deleting one gave mice longer faces but skulls that were broader and shorter (Science, doi.org/pjc). The finding could help make sense of congenital conditions, such as cleft palate, that can develop even when the genes that shape the face seem to be working normally, says Visel. Although the effects of single enhancers are subtle, several acting at once might lead to more pronounced changes.
Brain keeps its chat short and sweet as you go under ANAESTHETICS usually knock you out like a light. Slowing the process down, though, has made clear exactly what happens while you are unconscious. Irene Tracey and her colleagues at the University of Oxford slowly injected 16 volunteers with the anaesthetic propofol. It took about 45 minutes for each one to become fully anaesthetised. EEG recordings revealed that before the volunteers became completely unresponsive to external stimuli they progressed through a sleep-like state
characterised by slow-wave oscillations, in which neurons cycle between activity and inactivity. As the dose of anaesthetic built up, more neurons fell into this pattern, until a plateau was reached where no more neurons were recruited. The time it took to reach this plateau varied between individuals and was determined by the amount of grey matter that people possessed – something that decreases as we age. Brain imaging revealed that conversations between the brain’s
central relay hub, the thalamus, and the cortex continued during deep anaesthesia, but did not spread to far-flung regions of the brain. Messages stopped being routed further out at the same time as neuronal recruitment plateaued (Science Translational Medicine, doi.org/ph4). Tracey suggests that rather than rely on indirect measures such as heart rate, anaesthetists could use the plateau as a measure of when to stop giving drugs, to reduce the risk of side effects such as headaches and memory loss. REUTERS/Arnd Wiegmann
Junk DNA sculpts faces of mice
Mighty nano-beads lift loads with light ANT-LIKE beads of haematite could be the giants of nanoscale construction. Tiny particles of the iron mineral have been made to pick up and carry cargo more than 10 times their size. The feat could be used in targeted drug delivery or building artificial muscles. Iron-based nanoparticles are ideal cargo-carriers because they can be steered using magnetic fields or by following a thinly etched track. Previous versions relied on chemical glues to pick up stuff, but getting them to drop it has proved difficult. Jérémie Palacci at New York University and his colleagues suspended haematite nano-beads and a variety of cargo particles in a hydrogen peroxide solution. Shining a light gave the haematite electrical charge, which broke bonds in the neighbouring solution. The resulting halo of water and oxygen was not in chemical balance with its surroundings, a disturbance which drew larger particles to the beads. The bead and its cargo could then be steered together. To make the bead release its load, the team turned off the light (Journal of the American Chemical Society, doi.org/pjq).
Artificially stimulating a love of art OH YES, darling, it’s fabulous! You don’t need classes to boost your art appreciation, just zap your brain. Zaira Cattaneo at the University of Milan Bicocca in Italy and her colleagues showed paintings to 12 people. Each rated the images before and after receiving either mock treatment or transcranial direct current stimulation, which delivers a low current via electrodes on the head, to the left dorsolateral prefrontal cortex (DLPFC) – a brain area involved in processing emotion. Volunteers rated real-world images more highly after stimulation. There
was no difference in rating after the mock treatment or for abstract art, possibly because different brain areas are used to process abstract art (Social Cognitive and Affective Neuroscience, doi.org/pn5). “Stimulating the DLPFC may improve your mood – like looking through rose-coloured glasses,” says Anjan Chatterjee, a neurologist at the University of Pennsylvania. Cattaneo hopes the technique may help people with anhedonia – an inability to experience pleasure that can accompany Alzheimer’s disease and schizophrenia.
2 November 2013 | NewScientist | 19
H. Morrison, MRC hgu, Igmm, Uni. of Edinburgh
EVEN the prettiest faces are built using junk. In mice, the shapes of the face and skull are finely tuned by “junk DNA”, so called because it was thought to lack function. The same junk DNA is found in humans and may do a similar job. Geneticists have found only a few genes that control face shape. So Axel Visel of the Lawrence Berkeley National Laboratory in California focused on “enhancers”: short sequences of DNA – which are still sometimes called “junk” – that do not code for genes but can influence their activity. Visel and his colleagues studied gene expression in a developing mouse embryo, and found 120 enhancers active in cells of the face. To work out what they did, the team chose three and engineered groups of mice to each lack one of them. The enhancers subtly affected face shape. For instance, deleting one gave mice longer faces but skulls that were broader and shorter (Science, doi.org/pjc). The finding could help make sense of congenital conditions, such as cleft palate, that can develop even when the genes that shape the face seem to be working normally, says Visel. Although the effects of single enhancers are subtle, several acting at once might lead to more pronounced changes.
Brain keeps its chat short and sweet as you go under ANAESTHETICS usually knock you out like a light. Slowing the process down, though, has made clear exactly what happens while you are unconscious. Irene Tracey and her colleagues at the University of Oxford slowly injected 16 volunteers with the anaesthetic propofol. It took about 45 minutes for each one to become fully anaesthetised. EEG recordings revealed that before the volunteers became completely unresponsive to external stimuli they progressed through a sleep-like state
characterised by slow-wave oscillations, in which neurons cycle between activity and inactivity. As the dose of anaesthetic built up, more neurons fell into this pattern, until a plateau was reached where no more neurons were recruited. The time it took to reach this plateau varied between individuals and was determined by the amount of grey matter that people possessed – something that decreases as we age. Brain imaging revealed that conversations between the brain’s
central relay hub, the thalamus, and the cortex continued during deep anaesthesia, but did not spread to far-flung regions of the brain. Messages stopped being routed further out at the same time as neuronal recruitment plateaued (Science Translational Medicine, doi.org/ph4). Tracey suggests that rather than rely on indirect measures such as heart rate, anaesthetists could use the plateau as a measure of when to stop giving drugs, to reduce the risk of side effects such as headaches and memory loss. REUTERS/Arnd Wiegmann
Junk DNA sculpts faces of mice
Mighty nano-beads lift loads with light ANT-LIKE beads of haematite could be the giants of nanoscale construction. Tiny particles of the iron mineral have been made to pick up and carry cargo more than 10 times their size. The feat could be used in targeted drug delivery or building artificial muscles. Iron-based nanoparticles are ideal cargo-carriers because they can be steered using magnetic fields or by following a thinly etched track. Previous versions relied on chemical glues to pick up stuff, but getting them to drop it has proved difficult. Jérémie Palacci at New York University and his colleagues suspended haematite nano-beads and a variety of cargo particles in a hydrogen peroxide solution. Shining a light gave the haematite electrical charge, which broke bonds in the neighbouring solution. The resulting halo of water and oxygen was not in chemical balance with its surroundings, a disturbance which drew larger particles to the beads. The bead and its cargo could then be steered together. To make the bead release its load, the team turned off the light (Journal of the American Chemical Society, doi.org/pjq).
Artificially stimulating a love of art OH YES, darling, it’s fabulous! You don’t need classes to boost your art appreciation, just zap your brain. Zaira Cattaneo at the University of Milan Bicocca in Italy and her colleagues showed paintings to 12 people. Each rated the images before and after receiving either mock treatment or transcranial direct current stimulation, which delivers a low current via electrodes on the head, to the left dorsolateral prefrontal cortex (DLPFC) – a brain area involved in processing emotion. Volunteers rated real-world images more highly after stimulation. There
was no difference in rating after the mock treatment or for abstract art, possibly because different brain areas are used to process abstract art (Social Cognitive and Affective Neuroscience, doi.org/pn5). “Stimulating the DLPFC may improve your mood – like looking through rose-coloured glasses,” says Anjan Chatterjee, a neurologist at the University of Pennsylvania. Cattaneo hopes the technique may help people with anhedonia – an inability to experience pleasure that can accompany Alzheimer’s disease and schizophrenia.
2 November 2013 | NewScientist | 19