Findings from the AAAS

一月 29, 1999

Julia Hinde reports from the meeting of the American Association for the Advancement of Science in Anaheim, California

Gum disease linked to premature births

US scientists have provided what may be the first evidence of a causal link between gum disease in pregnant women and the premature birth of their babies.

Steven Offenbacher, professor of periodontology at the University of North Carolina, said women with gum disease were six to seven times more likely to have a pre-term baby when other factors were controlled for.

Until now scientists have been unable to say whether the much increased risk was down to other reasons, such as stress, which made the mother susceptible to both gum disease and premature birth, or whether the association was causal. New evidence, though small-scale, supports the latter.

Scientists at the university's Centre for Oral and Systemic Diseases drew on research into the rubella virus, which causes measles and in pregnant women increases the risk of birth complications. The virus crosses the placenta, and the foetus shows increased antibody resistance.

The North Carolina team took cord blood from the placenta of ten full-term babies and compared it with cord blood from pre-term babies for evidence of antibodies against oral pathogens. In the full-term children, only one slight reaction was found in one of the ten infants. However, in the premature group, two of the ten displayed significant quantities of antibodies against oral pathogens. Professor Offenbacher said: "This provides us with strong evidence that the foetus is being assaulted by these oral organisms - that when a woman gets oral disease, the bacteria pass into the blood stream and this may pass to the baby. This is the first suggestion from humans that the association may be causal."

The team is now expanding the trial, recruiting hundreds of pregnant women. Professor Offenbacher said that one in five pre-term births linked to gum disease was in line with expectations. In the US alone, this could account for 45,000 premature births each year. He said: "I don't think I will be convinced of the link until we have good intervention studies. But in the meantime, I think it prudent for pregnant mums to have their gums checked."

Gene-altered fish to help in pollution alert

An inch-long transgenic fish may provide a quick and cost-effective way of testing the genetic toxicity of chemicals.

Richard Winn, associate research scientist at the University of Georgia, is pinning his hopes on the medaka fish from southeast Asia. He has bred the fish with new genes that could provide a revolutionary method for monitoring genetic mutations caused by chemical exposure. It may enable us to monitor just how clean our environment is.

Dr Winn said there was a debate about the validity of in vitro tests, where bacteria in a dish are exposed to chemicals to see how they mutate. Such bacteria lack many of the metabolic pathways of higher organisms.

And trials on rodents, to see if exposure to chemicals causes genetic mutations, can be restrictively expensive and time-consuming. Dr Winn said it could take many years and cost between $3 million and $5 million to test just one compound on rodents.

"There are 80,000 chemicals in use in the US," explained Dr Winn. "Some 2,000 new ones are added annually. Among these are some that pose significant health risks to humans, including genetic damage.

"We therefore need a system that has the benefits of in vitro tests, is cost-effective, predictable and easy to use, while using the realistic whole organism model of an in vivo exercise."

The fish are exposed to suitable concentrations of chemicals in a liquid solution. Scientists then extract DNA from the fish and look at the effect of the compound on the new marker genes. "The marker allows you to see what mutation has taken place," Dr Winn said. "These fish are no more sensitive than any other. They just have a gene that allows you to ask questions."

The model should also allow scientists to monitor more realistically how clean rivers and lake sediments are. By allowing the fish to swim in these solutions, long-term, low concentration damage can be monitored.

Rabbits and other aliens cost UK $16bn

Alien species cost Britain about $16 billion a year in economic losses, says a Cornell University ecologist. David Pimentel is building a global picture of the costs to economies of non-indigenous species such as non-native weeds and insects.

He is looking at six countries, including the US, Britain, India and Australia, and plans to scale the figures for a worldwide estimate. He told the meeting that a few "bad players" among more than 30,000 non-indigenous species in the US were costing the country $123 billion a year.

Most introduced species of plants, animals and micro-organisms have been widely accepted and may even be beneficial. "But it doesn't take many trouble-makers to cause tremendous damage," he said. Among the biggest problems in the US are rats, cats and zebra mussels. "The US has become the land of a billion rats," said Professor Pimentel. Rats on poultry farms number about one billion, and each one destroys grain and other goods worth $15 a day.

Professor Pimentel said that the picture of a small number of introduced species doing most of the damage also held for the UK. "You have a greater rabbit problem, but your weed problem is not as big as ours," he argued.

Women forced into men's work patterns

Today's workplace offers outdated "all-or-nothing" jobs preventing many women entering the workforce and forcing others into working long hours against their will.

Marin Clarkberg, assistant professor of sociology at Cornell University, found that only 10 per cent of American couples prefer the traditional breadwinner/full-time housewife family, yet 25 per cent of couples end up fitting that mould. Wives cannot find the part-time opportunities they would like, said Professor Clarkberg.

Although about 14 per cent of couples say they prefer both spouses to work full-time, twice that number actually do. "One-third of married women want to work less," said Professor Clarkberg, who analysed the work-hour preference and work-hour behaviour of more than 4,500 married couples. "But many of the 25 per cent of married women who are not employed want to work more. They stay out of the labour force, however, because of the all-or-nothing nature of the workplace.

"Women who do enter the job market are shoe-horned into men's templates of 40-plus-hour jobs, which works against women and cheats family life."

Why Silicon Valley has echoes of mining blight

The mining boom towns that sprang up 150 years ago to serve the infamous California gold rush have much in common with today's Silicon Valley, said Gray Brechin, an architectural historian at the University of California at Berkeley.

"When I look at Silicon Valley I see a typical mining landscape," Dr Brechin said. He points to the lack of planning and civic responsibility. "Like mining towns in the 1800s, Silicon Valley is characterised by a boom/bust economy dependent on energy and technology, populated by transients with no commitment to the place, which has few amenities anyway.

"The result is all sorts of environmental problems, plus a large but hidden level of poverty. This is like Virginia City, Nevada (150 years ago), where there was a great divide between the mine operators who lived on the hill and the workers who lived below."

Al Gore's IT initiative at AAAS meeting, page 21



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