Antioxidants in aqueous extract of Myristica fragrans (Houtt.) suppress mitosis and cyclophosphamide-induced chromosomal aberrations in Allium cepa L. cells

In this study, freeze-dried water extract from the leaves of Myristica fragrans (Houtt.) was tested for mutagenic and antimutagenic potentials using the Allium cepa assay. Freeze-dried water extract alone and its combination with cyclophosphamide (CP) (50 mg/kg) were separately dissolved in tap water at 500, 1000, 2000, and 4000 mg/kg. Onions (A. cepa) were suspended in the solutions and controls for 48 h in the dark. Root tips were prepared for microscopic evaluation. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radicals’ scavenging power of the extract was tested using butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) as standards. Water extract of Myristica fragrans scavenged free radicals better than BHA, but worse than BHT. The extract alone, as well as in combination with CP suppressed cell division, and induced chromosomal aberrations that were insignificantly different from the negative control (P≤0.05). However, cytotoxic and mutagenic actions of CP were considerably suppressed. The observed effects on cell division and chromosomes of A. cepa may be principally connected to the antioxidant properties of the extract. The obtained results suggest mitodepressive and antimutagenic potentials of water extract of the leaves of M. fragrans as desirable properties of a promising anticancer agent.     

A Comprehensive Analysis of High School Genetics Standards: Are States Keeping Pace with Modern Genetics?

Science education in the United States will increasingly be driven by testing and accountability requirements, such as those mandated by the No Child Left Behind Act, which rely heavily on learning outcomes, or "standards," that are currently developed on a state-by-state basis. Those standards, in turn, drive curriculum and instruction. Given the importance of standards to teaching and learning, we investigated the quality of life sciences/biology standards with respect to genetics for all 50 states and the District of Columbia, using core concepts developed by the American Society of Human Genetics as normative benchmarks. Our results indicate that the states' genetics standards, in general, are poor, with more than 85% of the states receiving overall scores of Inadequate. In particular, the standards in virtually every state have failed to keep pace with changes in the discipline as it has become genomic in scope, omitting concepts related to genetic complexity, the importance of environment to phenotypic variation, differential gene expression, and the differences between inherited and somatic genetic disease. Clearer, more comprehensive genetics standards are likely to benefit genetics instruction and learning, help prepare future genetics researchers, and contribute to the genetic literacy of the U.S. citizenry.     

Mentoring interdisciplinary undergraduate students via a team effort

We describe how a team approach that we developed as a mentoring strategy can be used to recruit, advance, and guide students to be more interested in the interdisciplinary field of mathematical biology, and lead to success in undergraduate research in this field. Students are introduced to research in their first semester via lab rotations. Their participation in the research of four faculty members-two from biology and two from mathematics-gives them a first-hand overview of research in quantitative biology and also some initial experience in research itself. However, one of the primary goals of the lab rotation experience is that of developing teams of students and faculty that combine mathematics and statistics with biology and the life sciences, teams that subsequently mentor undergraduate research in genuine interdisciplinary environments. Thus, the team concept serves not only as a means of establishing interdisciplinary research, but also as a means of incorporating new students into existing research efforts that will then track those students into meaningful research of their own. We report how the team concept is used to support undergraduate research in mathematical biology and what types of team-building strategies have worked for us.     

“认输? 没那么简单!”

在日内瓦的普伦·迪尤·帕勒地区,有一家俄国侨民经营的小咖啡馆,政治流亡者们通常在这家咖啡馆举行集会。在咖啡馆或晚会上,我曾不止一次地看到过列宁下象棋。在同志们中间,弗拉基米尔·伊里奇~①被认为是个棋艺最高超的棋手,大家都把赢下他引以为很大的荣誉。每当弗拉基米尔·伊里奇同别人下象棋的时     

海龟是一个安静的奇迹

那是一个夏日的夜晚,我和女儿麦琪在月光下的佛罗里达海岸漫步。大约快10点了,白天那些日光浴的人、冲浪的人都已经离开了,海岸上只有我们母女在安静地走着。突然,我看见不远处有一只海龟正在慢吞吞地爬出海水。它湿漉漉的背有一米多长,在月光下熠(yi)熠闪光。它左右环顾,然后把头埋进沙里,好像是在品尝沙子的味道、感觉沙子的温度。它记得这片海滩吗?科学家们认为母海龟只会选择它出生的海滩来产卵。这只海龟,也是在海中游荡多年之后,     

青少年投掷运动员的训练负荷

众所周知,青少年的体育训练和高水平的专业运动员的训练无论在任务方面还是在教学一一训练过程的组织安排方面都是截然不同的。同时,目前在训练安排上所使用的普遍原则也不完全适合青少年运动员训练的特点。分析文献、资料表明:在运动训练的理论和方法中,关于高水平专业运动员在一年的训练周期内,运动负荷如何分配的问题,有几种观点。第一种观点提出“波浪式”地分配训练负荷,建议在一定的训练周期内,逐步地、平缓地、呈“波浪式”地增高,降低训练负荷。(马特月耶夫,1964年,1977年;M·炼里赫,1964年:H·阿若林,1977年,等等。)据马特月耶夫1964年和B·菲林1970年研究的资料,在比赛期间运动负荷的“波峰值”应比相应的训练期间的“波峰值”降低10-15%。第二种观点认为,在每次训练、每周、每月的训练周期内,运动量和其它负     

布朗运动是怎样阐明分子运动理论的

布朗运动清楚地揭示了无规则分子运动的存在。本世纪初,A·爱因斯坦和M·斯莫洛柯夫斯基对布朗运动都做过定量的描述,取得了很有价值的结果。     

在不同肌纤维中运动引起分解代谢反应的研究

在威斯特鼠的实验中,10小时游泳引起四头肌白肌中3—甲基组氨酸和游离酪酸含量的即时增加。而在红肌中这一增加发生在运动后恢复的6～48小时间。红肌中糖元的减少非常显著,表明运动中最活性的是氧化糖酵解纤维中,总之,运动中最具活性的肌纤维不引起蛋白质的动员,在运动后恢复的后一阶段,分解代谢的变化发生在最具活性的纤维中,构成了部分蛋白转换增加。     

书评艺术

书评的概念所谓书评,指的是对已出版的图书进行评论。按照肯伊(king)的说法,书评有两大作用,一是对图书的内容进行简述,二是发表评论。“首先应给人们指出图书的内容要点,再者就是对图书进行评论,指出它的