Lab notes: Bi-weekly news from the world of science
Sunday 15 November 1998
Children seem to be far more susceptible to bronchitis, chronic coughing and asthma than adults - and researchers from the University of North Carolina think they have discovered why. In a recent study, William Bennett and his colleagues had children inhale harmless carnauba wax particles. They then measured the density of the wax particles deposited on the children's lungs using a laser device. They found that children's lungs retain 35 per cent more airborne particles on their surface than those of adolescents or adults. And the bad news is that particles of a similar size are extremely prevalent in urban air pollution.
Better prenatal tests for Down's syndrome, a form of retardation caused by an extra copy of chromosome 21, are on the horizon. These hold the promise of detecting the syndrome earlier in the pregnancy, and with a lower risk of the complications that the current tests can create.
Today, blood tests can determine whether a foetus has Down's, but only between 16 and 18 weeks of gestation. If parents opt for an abortion on the basis of these tests, it is particularly traumatic and involved because it is so late. But now Laird Jackson and his team at Jefferson Medical College in Philadelphia are evaluating whether a range of tests - one of them new - could be combined with a novel ultrasound technique to detect Down's reliably as early as 10 weeks after conception.
The new blood test measures pregnancy-associated plasma protein A, which scientists have only recently learned is lower in women carrying Down's foetuses. The researchers then use sonography to measure membranes in the back of developing foetuses' necks : these membranes are slightly thicker in Down's foetuses. In preliminary studies, Jackson's group found that the combination of blood tests and ultrasound detected 90 per cent of Down's as early as 10 weeks into pregnancy. A larger study should yield results by the end of 2000.
Sticking to the point
Think of its as tofu glue. A researcher at Kansas State University, Xiuzhi Susan Sun, has created a non-toxic, water-resistant, formaldehyde-free adhesive from soy protein. Sun found a group of non-toxic chemicals that unfold the soy protein molecule, increasing its contact area and thus the molecule's adhesive strength. So far, the substance has done well in standard testing: it stayed strong after eight weeks in a chamber at 90 per cent relative humidity, proving its sticking power. And as for its ability to withstand the weather, the glue held plywood together after three cycles of being soaked in water for two days and then dried.
Stuart Levy of Tufts University has warned that the proliferation in recent years of antibacterial household products that kill or inhibit bacteria may be creating a generation of supergerms that are immune to lifesaving drugs. Stoking fears further, he and his colleagues have now published a study chronicling how overexposure and a single gene mutation in a laboratory strain of intestinal bacteria can induce resistance to a common antibacterial product, triclosan.
Triclosan is routinely used in consumer goods ranging from toothpaste to children's toys. Antibacterials generally disable a microbe in various ways, which makes the development of resistance more difficult. But the new work at Tufts shows that triclosan may attack microbes in just one way, making them more likely to develop resistance. Although Levy's results came from a laboratory, its implications are wide: if such resistance did develop, it would render ineffective the antiseptic soaps used in hospitals and in the homes of patients with weak immune systems.
As you'd expected, the findings provoked immediate objections from industry groups, which note that after 30 years of widespread triclosan use, no evidence of resistance has emerged. Still, for healthy individuals, antibacterial chemicals are generally no more useful than ordinary household cleaners. "People are trying to sterilise their environments," Levy says, "but that's only possible in a laboratory. Using one antibacterial agent only removes some bacteria and replaces them with others that are insensitive to the product."
! All items are adapted from 'Scientific American'. Visit the website at www.sciam.com. Copyright 1998, Scientific American Inc. All rights reserved.
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