单选题梅毒树胶样肿病灶中极少见到

单选题原核生物的双向复制是指

单选题明适应的产生机制是

单选题淋巴细胞显著减少的霍奇金淋巴瘤的组织学类型是

单选题类风湿因子实质上是

单选题在下列坏死中，有特征性钙皂形成的是

单选题下列不符合良性畸胎瘤的描述是

单选题下列符合霍奇金淋巴瘤预后好坏的排列顺序为

单选题下列不符合萎缩的描述是

单选题心室肌细胞动作电位的2期复极(平台期)的离子基础是

单选题远曲小管和集合管所分泌的NH 3 主要来自

单选题激素作用的一般特性不包括

单选题A．FEV 1 减小，FVC基本不变，FEV 1 ／FVC减小 B．FEV 1 基本不变，FVC减小，FEV 1 ／FVC增大 C．FEV 1 和FVC均减小，FEV 1 ／FVC基本不变 D．FEV 1 和FVC均增大，FEV 1 ／FVC基本不变

单选题下列不符合三尖瓣狭窄的是

单选题慢性硬化性肾小球肾炎导致肾衰竭的主要厉因是

单选题真核基因组结构特点不包括

单选题British cancer' researchers have found that childhood leukaemia is caused by an infection and clusters of cases around industrial sites are the result of population mixing that increases exposure. The research published in the British Journal of Cancer backs up a 1988 theory that some as yet unidentified infection caused leukaemia--not the environmental factors widely blamed for the disease. "Childhood leukaemia appears to be an unusual result of a common infection," said Sir Richard Doll, an internationally-known cancer expert who first linked tobacco with lung cancer in 1950. "A virus is the most likely explanation. You would get an increased risk of it if you Suddenly put a lot of people from large towns in a rural area, where you might have people who had not been exposed to the infection. " Doll was commenting on the new findings by researchers at Newcastle University, which focused on a cluster of leukaemia cases around the Sellafield nuclear reprocessing plant in Cumbria in northern England. Scientists have been trying to establish why there was more leukaemia in children around the Sellafield area, but have failed to establish a link with radiation or pollution. The Newcastle University research by Heather Dickinson and Louise Parker showed the cluster of cases could have been predicted because of the amount of population mixing going on in the area, as large numbers of construction workers and nuclear staff moved into a rural setting. "Our study shows that population mixing can account for the (Sellafield) leukaemia cluster and that all children, whether their parents are incomers or locals, are at a higher risk if they are born in an area of high population mixing," Dickinson said in a statement issued by the Cancer Research Campaign, which publishes the British Journal of Cancer. Their paper adds crucial weight to the 1988 theory put forward by Leo Kinlen, a cancer epidemiologist at Oxford University, who said that exposure to a common unidentified infection through population mixing resulted in the disease.

单选题分泌活动日节律最为明显，清晨后可达分泌高峰的激素是

单选题下列结构中不属前庭器官的是

单选题关于局部神经元回路，不正确的论述是