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6 July 2013 | NewScientist | 15 Lasers pinpoint sickly blood cells BLOOD disorders could be rapidly diagnosed using lasers that detect oddly shaped red blood cells. Human red blood cells are usually disc-shaped with a central dimple but conditions such as sickle-cell anaemia alter their shape. Blood cells stored for transfusion also change shape as they age. Eric Strohm at Ryerson University in Toronto, Canada, used laser light to heat the protein haemoglobin within red blood cells without affecting the surroundings. This resulted in an ultrasonic pressure wave that can be detected as sound to give information about the cell’s size and shape. The team compared a sample of fresh red blood cells with cells that looked spiky because their energy stores had been depleted. Just 21 cells, and measurements that take a few seconds, were all that was needed for the team to distinguish normal from spiky cells (Biophysical Journal, DOI: 10.1016/j.bpj.2013.05.037). Strohm says that Canadian Blood Services is interested in seeing if this technology can be used as a quality-control measure to test the blood it stores. How to tell if DNA will be useful as evidence WEAK, noisy and incomplete: it’s easy to see why the genetic profiles constructed from tiny traces of crime scene DNA can fail to meet the high standards needed for criminal courts. But these low-template DNA (LTDNA) profiles could prove useful, thanks to new software. Forensic scientists can now construct a partial DNA profile from just a few cells, says David Balding at University College London. However, natural contamination from DNA in the environment, together with the fact that it is impossible to build a complete genetic profile from so few cells, means that interpreting LTDNA evidence is challenging. Consequently, court cases where it plays a central role – such as the trial of Amanda Knox for the murder of Meredith Kercher – often become controversial. That largely reflects a lack of proper statistical techniques to handle the data, Balding says. His software is a step towards improving that. It compares a full DNA profile of a suspect with an incomplete THE best of times can follow the worst of times. An analysis of raccoon dog DNA shows that the canid species has thrived after surviving hardship during the last ice age. Raccoon dogs (Nyctereutes procyonoides) are found across large parts of Eurasia – largely because fur lovers in the former Soviet Union introduced them to countries near its western borders in the 20th century. Some 20,000 years ago, it was a different story: Earth was in the grip of the last ice age, and raccoon dogs were stuck in a small area of east Asia. To work out how the raccoon dogs made it through the ice age, Mi-Sook Min of Seoul National University in South Korea and colleagues examined their genes. They found that animals from Korea, Russia, China and Vietnam were all genetically similar but distinct from Japanese raccoon dogs. That suggests the animals were holed up in two ice-age refugia: one in Japan and one probably on the Korean peninsula. Since then, the Japanese raccoon dogs have largely stayed where they are, but the Korean animals have spread widely, with a little help from their Soviet friends (Journal of Zoology, doi.org/m3m). Invasion of the raccoon dog cuties ARTUR TABOR/NATUREPL.COM DNA profile found at a crime scene. By incorporating factors such as the natural decay of a DNA sample, or the presence of DNA from another person entirely, the software can provide a probability score that a suspect was at the crime scene. Using the software on data from Knox’s trial suggests that it was very unlikely that her DNA was at the crime scene (PNAS, DOI: 10.1073/pnas.1219739110). The next step is to present those results in an intuitive manner that courts can understand, says Balding. Bomb fallout to snare ivory sellers NUCLEAR bomb tests 50 years ago have given us a conservation weapon. Determining the levels of radioactive isotope in ivory should allow us to find out whether it is being illegally traded. The amount of carbon-14 in the atmosphere peaked in 1962 just before the introduction of an international ban on surface testing of nuclear weapons. The rapid rise and subsequent decline of this isotope is known as the bomb curve. Animal cells take up carbon-14 when they are formed, and because the decay rate of carbon-14 is known, the time of death can be deduced from the amount of isotope left. Linking the amount of carbon-14 found in organic material with the bomb curve has been used to date human tooth enamel and even brain cell regeneration. Kevin Uno at Columbia University in Palisades, New York, and colleagues have now used the technique to test 29 samples, including elephant tusks and rhino horn collected in East Africa. They dated them to within about 1.4 years of the known collection date (PNAS, DOI: 10.1073/ pnas.1302226110). The technique could be used to age confiscated animal parts – to determine, say, whether African elephant ivory was harvested before or after the 1989 trade ban. XINHUA NEWS AGENCY/EYEVINE For new stories every day, visit newscientist.com/news
