Glycidyl methaerylate (GMA) is a recently recognized chemical mutagen. In order to explore the mutagenicity and mutagenic process of GMA, plasmid pBR322 was used for in vitro binding, mutant screening, and restriction...Glycidyl methaerylate (GMA) is a recently recognized chemical mutagen. In order to explore the mutagenicity and mutagenic process of GMA, plasmid pBR322 was used for in vitro binding, mutant screening, and restriction enzyme mapping. The binding between GMA and DNA in vitro has been verified by means of a spectrophotometric method. When pBR322 and GMAbound pBR322 were used to transform Eschenchia coli HB101, the following results were obtained: (1) The transformation efficiency of GMA-bound pBR322 was much lower than that of pBR322 alone. (2) GMA-bound pBR322 induced phenotype changes in competent cells (i.e., tetracycline-resistance inactivation or ampicillin-resistance inactivation). There were two mutants of pBR322, Ap~RTc~S and Ap~STc~R, in the transformants and a deductive mutant Ap~STc~S in the nontranstormants. (3) All of the selected mutants were stable and heritable. (4) When restriction enzyme maps were used to analyze the mutant Ap~RTc~S, four of seven maps were changed. some sites were shifted to other resistant gene regions, for example, sites of Bgll, EcoRl, Ilindlll. Hinclll, etc., and there was a new recognition site for Hindi (252). We did not observe any DNA fragment insertion or deletion on any maps. Our results suggest that when GMA is covalently linked to the plasmid DNA, it gives rise to a premutagenic lesion of DNA that is converted in vivo into a point mutation. (C)1990 Academic Press, Inc.展开更多
Hybrid tilapia weighing 7.71 g were reared in seawater at 24.0-29.0℃ for 8 weeks. The controls were fed to satiation twice a day throughout the experiment, whereas treatment groups were fed at 0.5%, 1.5% or 3.0% body...Hybrid tilapia weighing 7.71 g were reared in seawater at 24.0-29.0℃ for 8 weeks. The controls were fed to satiation twice a day throughout the experiment, whereas treatment groups were fed at 0.5%, 1.5% or 3.0% body weight per day for 4 weeks, and then to satiation for the remainder of the experiment. During the first 4-week period, there was a curvilinear relationship between growth rate and ration size. Fish fed 0.5% and 1.5% rations displayed compensatory growth response of 2 weeks duration during realimentation. The weight-adjusted growth rate of fish fed at 3% ration was not significantly different from that of the controls by the end of the experiment, when none of the treatment groups had caught up in body weight with the controls. Hyperphagia was observed for the first 2 weeks of realimenatation in fish previously fed at 3% ration, but persisted for the whole realimentation period in groups previously fed at 0.5% and 1.5% rations. None of the feed restricted groups showed improved digestibility, feed efficiency, or protein and energy retention efficiency.展开更多
Aiming to deal with the difficult issues of terrain data model simplification and crack disposal,the paper proposed an improved level of detail(LOD)terrain rendering algorithm,in which a variation coefficient of eleva...Aiming to deal with the difficult issues of terrain data model simplification and crack disposal,the paper proposed an improved level of detail(LOD)terrain rendering algorithm,in which a variation coefficient of elevation is introduced to express the undulation of topography.Then the coefficient is used to construct a node evaluation function in the terrain data model simplification step.Furthermore,an edge reduction strategy is combined with the improved restrictive quadtree segmentation to handle the crack problem.The experiment results demonstrated that the proposed method can reduce the amount of rendering triangles and enhance the rendering speed on the premise of ensuring the rendering effect compared with a traditional LOD algorithm.展开更多
目的:探究低负荷功能性训练组合血流限制训练对高水平女子足球运动员体能及下肢非对称性的影响。方法:选取18名高水平女子足球运动员为研究对象,随机分为实验组和对照组,每组各9人。实验组进行低负荷功能性训练结合血流限制训练,对照组...目的:探究低负荷功能性训练组合血流限制训练对高水平女子足球运动员体能及下肢非对称性的影响。方法:选取18名高水平女子足球运动员为研究对象,随机分为实验组和对照组,每组各9人。实验组进行低负荷功能性训练结合血流限制训练,对照组进行高负荷功能性训练,训练共持续12周。在训练前后对受试者的等速肌力、爆发力、灵敏性、速度、下肢围度、皮褶厚度、身体功能性等指标进行测试。结果:1)实验组和对照组膝关节60°/s角速度峰力矩在训练后显著增强(P<0.05),组间未见显著差异(P>0.05)。2)实验组反向跳跃(countermovement jump,CMJ)、静蹲跳(squat jump,SJ)、30 m冲刺跑、T-test灵敏性、单腿前跳(single leg broad jump, SLBJ)、单腿纵跳(single leg counter movement jump,SLCMJ)、长传球成绩在训练后均显著提升(P<0.05),对照组SLBJ、SLCMJ、长传球、30 m冲刺跑、T-test成绩出现明显提升(P<0.05),但CMJ、SJ成绩未产生明显改变(P>0.05)。两组组间未见显著差异(P>0.05)。3)训练后,实验组功能性动作筛查(functional movement screen,FMS)测试中仅深蹲、前后分腿蹲成绩出现显著性提升(P<0.05),其余动作与对照组一致,并未发生明显变化(P>0.05),但从效应量可以看出,深蹲、前后分腿蹲等下肢测量动作以及FMS总分出现中等及较高程度差异变化。训练后实验组与对照组的Y-balance测试成绩均显著提升(P<0.05),但组间未见显著差异(P>0.05)。4)训练后,实验组和对照组下肢大腿围度显著增加、皮褶厚度显著下降(P<0.05),小腿围度和皮褶厚度变化并不显著(P>0.05),组间未见显著差异(P>0.05)。结论:低负荷功能性训练组合血流限制训练能够提升高水平女子足球运动员体能,改善下肢非对称性。较低的外部负荷训练可能降低运动员的损伤概率,因此低负荷功能性训练组合血流限制训练可能作为高负荷功能性训练和传统训练方式的替代或补充方法。展开更多
目的:探讨营养包(Ying Yang Bao,YYB)服用时长和频率与6~24月龄婴幼儿血红蛋白(Hemoglobin,Hb)水平和贫血率之间的阈值效应关系。方法:研究数据来自于早期儿童营养包干预长期营养健康作用评估项目。采用t检验和卡方检验比较连续变量和...目的:探讨营养包(Ying Yang Bao,YYB)服用时长和频率与6~24月龄婴幼儿血红蛋白(Hemoglobin,Hb)水平和贫血率之间的阈值效应关系。方法:研究数据来自于早期儿童营养包干预长期营养健康作用评估项目。采用t检验和卡方检验比较连续变量和分类变量的组间差异。采用限制性立方样条回归检验YYB服用时长和频率与儿童血红蛋白(Hb)水平和贫血率之间的非线性趋势,探索可能存在的阈值效应关系。结果:YYB服用时长与Hb水平和贫血率的非线性趋势检验P值分别为0.665和0.211,服用频率与Hb水平和贫血率的非线性趋势检验P值分别为0.110和0.157。YYB服用时长达到8.68个月时,Hb水平变化的斜率β=0,贫血发生风险的OR=1;YYB服用频率达5.6袋/周时,Hb水平变化的斜率β=0,服用频率达4.6袋/周时,贫血发生风险的OR=1。结论:YYB服用时长和频率与6~24月龄婴幼儿Hb水平和贫血率之间存在线性关联;改善Hb水平和贫血率的最低有效时长约为8.6个月,最低有效频率约为5~6袋/周。展开更多
文摘Glycidyl methaerylate (GMA) is a recently recognized chemical mutagen. In order to explore the mutagenicity and mutagenic process of GMA, plasmid pBR322 was used for in vitro binding, mutant screening, and restriction enzyme mapping. The binding between GMA and DNA in vitro has been verified by means of a spectrophotometric method. When pBR322 and GMAbound pBR322 were used to transform Eschenchia coli HB101, the following results were obtained: (1) The transformation efficiency of GMA-bound pBR322 was much lower than that of pBR322 alone. (2) GMA-bound pBR322 induced phenotype changes in competent cells (i.e., tetracycline-resistance inactivation or ampicillin-resistance inactivation). There were two mutants of pBR322, Ap~RTc~S and Ap~STc~R, in the transformants and a deductive mutant Ap~STc~S in the nontranstormants. (3) All of the selected mutants were stable and heritable. (4) When restriction enzyme maps were used to analyze the mutant Ap~RTc~S, four of seven maps were changed. some sites were shifted to other resistant gene regions, for example, sites of Bgll, EcoRl, Ilindlll. Hinclll, etc., and there was a new recognition site for Hindi (252). We did not observe any DNA fragment insertion or deletion on any maps. Our results suggest that when GMA is covalently linked to the plasmid DNA, it gives rise to a premutagenic lesion of DNA that is converted in vivo into a point mutation. (C)1990 Academic Press, Inc.
基金Supported by the State Key Laboratory of Freshwater Ecology and Biotechnology of China and Shanghai Fisheries University (Grant No. 200015).
文摘Hybrid tilapia weighing 7.71 g were reared in seawater at 24.0-29.0℃ for 8 weeks. The controls were fed to satiation twice a day throughout the experiment, whereas treatment groups were fed at 0.5%, 1.5% or 3.0% body weight per day for 4 weeks, and then to satiation for the remainder of the experiment. During the first 4-week period, there was a curvilinear relationship between growth rate and ration size. Fish fed 0.5% and 1.5% rations displayed compensatory growth response of 2 weeks duration during realimentation. The weight-adjusted growth rate of fish fed at 3% ration was not significantly different from that of the controls by the end of the experiment, when none of the treatment groups had caught up in body weight with the controls. Hyperphagia was observed for the first 2 weeks of realimenatation in fish previously fed at 3% ration, but persisted for the whole realimentation period in groups previously fed at 0.5% and 1.5% rations. None of the feed restricted groups showed improved digestibility, feed efficiency, or protein and energy retention efficiency.
基金Supported by the National Natural Science Foundation of China(61363075)the National High Technology Research and Development Program of China(863 Program)(2012AA12A308)the Yue Qi Young Scholars Program of China University of Mining&Technology,Beijing(800015Z1117)
文摘Aiming to deal with the difficult issues of terrain data model simplification and crack disposal,the paper proposed an improved level of detail(LOD)terrain rendering algorithm,in which a variation coefficient of elevation is introduced to express the undulation of topography.Then the coefficient is used to construct a node evaluation function in the terrain data model simplification step.Furthermore,an edge reduction strategy is combined with the improved restrictive quadtree segmentation to handle the crack problem.The experiment results demonstrated that the proposed method can reduce the amount of rendering triangles and enhance the rendering speed on the premise of ensuring the rendering effect compared with a traditional LOD algorithm.
文摘目的:探究低负荷功能性训练组合血流限制训练对高水平女子足球运动员体能及下肢非对称性的影响。方法:选取18名高水平女子足球运动员为研究对象,随机分为实验组和对照组,每组各9人。实验组进行低负荷功能性训练结合血流限制训练,对照组进行高负荷功能性训练,训练共持续12周。在训练前后对受试者的等速肌力、爆发力、灵敏性、速度、下肢围度、皮褶厚度、身体功能性等指标进行测试。结果:1)实验组和对照组膝关节60°/s角速度峰力矩在训练后显著增强(P<0.05),组间未见显著差异(P>0.05)。2)实验组反向跳跃(countermovement jump,CMJ)、静蹲跳(squat jump,SJ)、30 m冲刺跑、T-test灵敏性、单腿前跳(single leg broad jump, SLBJ)、单腿纵跳(single leg counter movement jump,SLCMJ)、长传球成绩在训练后均显著提升(P<0.05),对照组SLBJ、SLCMJ、长传球、30 m冲刺跑、T-test成绩出现明显提升(P<0.05),但CMJ、SJ成绩未产生明显改变(P>0.05)。两组组间未见显著差异(P>0.05)。3)训练后,实验组功能性动作筛查(functional movement screen,FMS)测试中仅深蹲、前后分腿蹲成绩出现显著性提升(P<0.05),其余动作与对照组一致,并未发生明显变化(P>0.05),但从效应量可以看出,深蹲、前后分腿蹲等下肢测量动作以及FMS总分出现中等及较高程度差异变化。训练后实验组与对照组的Y-balance测试成绩均显著提升(P<0.05),但组间未见显著差异(P>0.05)。4)训练后,实验组和对照组下肢大腿围度显著增加、皮褶厚度显著下降(P<0.05),小腿围度和皮褶厚度变化并不显著(P>0.05),组间未见显著差异(P>0.05)。结论:低负荷功能性训练组合血流限制训练能够提升高水平女子足球运动员体能,改善下肢非对称性。较低的外部负荷训练可能降低运动员的损伤概率,因此低负荷功能性训练组合血流限制训练可能作为高负荷功能性训练和传统训练方式的替代或补充方法。
文摘目的:探讨营养包(Ying Yang Bao,YYB)服用时长和频率与6~24月龄婴幼儿血红蛋白(Hemoglobin,Hb)水平和贫血率之间的阈值效应关系。方法:研究数据来自于早期儿童营养包干预长期营养健康作用评估项目。采用t检验和卡方检验比较连续变量和分类变量的组间差异。采用限制性立方样条回归检验YYB服用时长和频率与儿童血红蛋白(Hb)水平和贫血率之间的非线性趋势,探索可能存在的阈值效应关系。结果:YYB服用时长与Hb水平和贫血率的非线性趋势检验P值分别为0.665和0.211,服用频率与Hb水平和贫血率的非线性趋势检验P值分别为0.110和0.157。YYB服用时长达到8.68个月时,Hb水平变化的斜率β=0,贫血发生风险的OR=1;YYB服用频率达5.6袋/周时,Hb水平变化的斜率β=0,服用频率达4.6袋/周时,贫血发生风险的OR=1。结论:YYB服用时长和频率与6~24月龄婴幼儿Hb水平和贫血率之间存在线性关联;改善Hb水平和贫血率的最低有效时长约为8.6个月,最低有效频率约为5~6袋/周。
