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金沙网站登录:New clue in BSE fiasco

发布时间:2019-03-05 06:12:15来源:未知点击:

By Andy Coghlan A flawed UK study to investigate whether sheep catch BSE may have been ruined through contamination from earlier experiments on cow brains. The four-year study collapsed in ruins last week when it emerged that liquefied sheep brain used for the experiment was in fact liquefied cow brain. Investigations by New Scientist suggest that the brain tissue might have got muddled following separate experiments in the mid-1990s. In these earlier experiments, David Taylor and his colleagues at the Institute for Animal Health’s Neuropathogenesis Unit in Edinburgh investigated rendering – the process by which animal remains were ground up into “meat and bonemeal” animal feed. Taylor wanted to know whether rendering could destroy prions, the malformed proteins which cause BSE in cattle, scrapie in sheep and variant Creutzfeldt-Jakob disease (vCJD) in people. Between 1990 and 1992, Taylor and his colleagues collected and liquefied 2867 brains of sheep that had died of scrapie. The liquefied remains filled six sterilised buckets and weighed 450 kilograms. Taylor decanted some into polythene bags for the rendering experiments, and saved some 10-gramme samples for injection into mice, to see if the mice developed scrapie. All his rendering experiments took place at a pilot plant specifically built for the project by the feed processing company, Prosper de Mulder of Doncaster, Yorkshire. Taylor and his colleagues published their results in the Veterinary Record in 1997 (vol 141, p643). But the scrapie experiments were a re-run of a study by the same team in the same place two years earlier to see if BSE from 861 cow brains collected in 1990 could survive rendering. Exactly the same procedure was used, yielding six bucketloads of BSE-infected cow brain from which 10-gramme extracts were taken for injection into mice. “The whole objective was to make the two experiments as similar as possible so the results could be compared,” says Steve Woodgate, a member of Taylor’s team at Prosper de Mulder. Results of the BSE rending experiment appeared in the Veterinary Record in 1995 (vol 137, p605). Afterwards, says Woodgate, any remaining sheep and cow material was sent to the IAH’s Neuropathogenesis Unit. It was from this stored “pool” that researchers took scrapie-infected “sheep” brain for the now-flawed experiment. Woodgate doubts whether the cow and sheep brains got mixed up during the experiments at Doncaster. “There was a two-year hiatus during which we completely dismantled and disposed of the pilot plant for the BSE experiment,” he says. Woodgate says that only when vets had collected sufficient scrapie-infected sheep brain two years later was the plant rebuilt from scratch for the scrapie rendering experiment. There is a possibility that the cow and sheep brains got muddled when sent to Edinburgh for storage,