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NAT 665-6 Mxnew news Head start Dust storm Hot house Not guilty Fetal transplants Is pollution from Tension in the Weapons scientist offer relief for Asia reaching the Philippines hampers walks free from Parkinson’s sufferers shores of the US? zoologists South African court p666 p668 p669 p670 Frogs put in the gender blender by America’s favourite herbicide Rex Dalton,Berkeley Low levels of the most widely used herbi- cide in the United States have been found to disrupt the sexual development of frogs. The finding will heighten concerns about the persistence of endocrine-disrupting J. MACDONALD/CORBIS chemicals in the environment — and throws the spotlight on another potential factor involved in the global decline of amphibian populations. In the United States, about 27,000 tonnes of atrazine are applied each year to fields used to grow crops such as maize, sorghum and sugar cane. It is also used in 80 other nations, making it one of the world’s most important herbicides. But concerns about atrazine’s Do environmental levels of atrazine cause sexual defects in leopard frogs in the US midwest? potential ability to disrupt sex hormones,and the presence of residues in drinking water, observed effects at concentrations that reflect “This is not a worst-case scenario where have led it to be banned in Germany, France, those found in the environment. “Hayes’s animals are exposed to mega-doses,” says Italy,Sweden,Norway and Switzerland. work is some of the best to show how a con- Louis Guillette,a zoologist at the University of Tyrone Hayes and his colleagues at the taminant affects amphibian reproduction,” Florida in Gainesville. “These are concentra- University of California, Berkeley, exposed says Andrew Blaustein, who studies amphib- tions we know wild amphibians are exposed tadpoles of the African clawed frog (Xenopus ians at Oregon State University in Corvallis. to.” Indeed, atrazine is routinely found at L laevis) to water containing different levels of atrazine throughout their larval develop- ment. Levels as low as 0.1 parts per billion (p.p.b.) caused males to develop ovaries in addition to testes. And at concentrations Scripps to trawl sea-microbe data above 1 p.p.b.,male frogs’larynges — used to call for mates — failed to develop normally, Jonathan Knight,San Francisco the new facility’s emphasis will be on teasing Hayes reports in a paper published on 16 The genomic secrets of the ocean’s microbes information about ocean life from the April (T. B. Hayes et al. Proc. Natl Acad. Sci. are set to be revealed by the world’s first sequence databases. USA 99, 5476–5480;2002). centre devoted to marine bioinformatics. For example, Brian Palenik’s laboratory In addition, when the researchers put The Scripps Institution of Oceanography in at Scripps has already started to apply adult males in water containing 25 p.p.b. of La Jolla, California, plans to establish the bioinformatics techniques to learn how atrazine, their testosterone levels plum- facility within the next few months. microbes relate to their ocean environment. meted. And in preliminary, unpublished The centre’s main focus will be microbial Traditionally, biologists have probed this research, Hayes has found similar reproduc- genomics, says Ron Burton, director of question by studying microorganisms in tive anomalies in wild leopard frogs (Rana marine biology at Scripps. Most of the laboratory flasks. But genomics can help to pipiens) at six locations in the midwestern marine genomes sequenced so far have been reveal the factors that contribute to a United States with high levels of atrazine. microorganisms — yet their biochemistry microbe’s survival. Palenik has discovered “It is obviously affecting frogs,” says and ecology remains poorly understood, several overlooked metabolic pathways in Hayes, who suspects that atrazine boosts despite their crucial role in the global cyanobacteria, photosynthetic microbes that production of the enzyme aromatase, which cycling of carbon and nitrogen (see Nature are responsible for 80% of the carbon fixed catalyses the conversion of testosterone into 415, 572–574; 2002). from the atmosphere in the open ocean. oestrogen.“We need to ask:what are the envi- The Scripps centre will not itself The new division will eventually consist ronmental costs of using atrazine?”he says. sequence marine genomes, Burton says. of about 10 faculty members, and will cost Although previous studies have suggested That work will continue at places such as the upwards of $20 million to establish. A that atrazine is an endocrine disrupter, these Joint Genome Institute in Walnut Creek, director has yet to be appointed, but the have mostly used much higher doses. Hayes’s California, where a number of marine leading candidate is said to be a well-known study is causing alarm because he has microbes have so far been sequenced. Rather, figure in the bioinformatics field. I NATURE | VOL 416 | 18 APRIL 2002 | www.nature.com © 2002 Macmillan Magazines Ltd 665 news L 50 p.p.b. in water throughout the United States, experts say, and can rise to several parts per million in agricultural run-off. Parkinson’s patients show Amphibians are highly sensitive to pol- lutants and are regarded as ‘sentinel’species positive response to implants that can provide the first indications of damage to an ecosystem. Hayes’s results Erika Check,Washington come as the US Environmental Protection Fetal cells transplanted into the brains of Agency (EPA) is re-evaluating the risks patients with Parkinson’s disease can survive posed by atrazine — following a 1999 ruling and mature for up to eight years after the on a lawsuit from the Natural Resources surgery, helping to alleviate the debilitating Defense Council and other environmental tremors seen in the disease. These positive groups, requiring the agency to accelerate results, from a trial that last year attracted its efforts to reassess the environmental and controversy because of the side-effects expe- health risks posed by a range of potential rienced by a small number of patients,should endocrine disrupters. help to lift the cloud that has since hung over The EPA currently cellular therapies for the condition. allows levels of atrazine to Parkinson’s is caused by the death of cells reach 3 p.p.b.in US drink- that secrete the neurotransmitter dopamine. ing water. An EPA panel When Curt Freed of the University of will hold a public meeting Colorado and his colleagues reported on the this week in Arlington, trial last year, their results confirmed that Virginia, on suggested transplanted cells from the brains of aborted residue levels of atrazine fetuses can help to relieve the symptoms of in food products. the disease (see Nature 410, 401; 2001). Hayes has provided But five of the 20 patients treated experi- Tyrone Hayes has the EPA with a report on enced jerky, uncontrolled movements called fears for frogs. his unpublished field- dyskinesias. work on frogs from This week, at a meeting of the American Colorado to Wisconsin, but EPA officials Academy of Neurology in Denver,Colorado, declined to comment on this, or on Hayes’s Freed reported that these patients have newly published paper. The agency aims to since responded to treatment aimed at issue final reports on the risks posed by addressing this unwanted side-effect — atrazine by August. either by giving them drugs to remove excess Atrazine is manufactured by Syngenta dopamine or by implanting a device called a Fetal cells transplanted into the brains of patients SPL of Basel, Switzerland. Alan Hosmer, Syn- ‘deep-brain stimulator’, which delivers with Parkinson’s can ease the disease’s symptoms. genta’s manager of ecological sciences in timed electric shocks to the brain region that Greensboro, North Carolina, says that the causes the dyskinesias. Indeed, one of the Harvard Medical School.“Maturation is the firm is aware of some of Hayes’s results. dyskinetic patients was working in the key,”he says.“These grafts need to grow and But the company failed to provide a World Trade Center at the time of the 11 mature to become effective.” detailed statement before Nature went to September attacks last year, and was able to But Isacson and other researchers say that press. For three years, Hayes worked on make his escape by walking down 33 flights cellular therapies will need further refine- contract research at Berkeley for Syngenta. of stairs. ment if they are to deliver better results than But he severed relations with the firm last The new results are from a total of 32 conventional drug therapy. They note that year, independently pursuing the studies patients. The trial was expanded by relaxing Freed’s team transplanted cells into a brain that led to this week’s paper. its double-blind design and allowing some structure called the putamen, which con- Aside from their implications for the patients who had initially been in the control tains the cells that respond to dopamine. But use of atrazine in the United States and group to have the transplants. The degree of Ivar Mendez, a neurosurgeon at Dalhousie elsewhere, Hayes’s results add another improvement varied between patients, but University in Halifax,Nova Scotia,has begun element to the debate over why amphibian seemed to be independent of age — the a pilot study in which five patients have populations are declining across the team’s earlier data had suggested that received fetal-cell transplants into both the world. Many factors are thought to be only those younger than 60 benefited. putamen and the substantia nigra — the involved, including pathogens, pollution, Patients who did best were those who had structure that contains the dopamine- competition with invading alien species, previously responded most strongly to the secreting cells lost in Parkinson’s.
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