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41.
Rui M Costa Nikolai B Federov Jeff H Kogan Geoffrey G Murphy Joel Stern Masuo Ohno Raju Kucherlapati Tyler Jacks Alcino J Silva 《Nature》2002,415(6871):526-530
Neurofibromatosis type I (NF1) is one of the most common single-gene disorders that causes learning deficits in humans. Mice carrying a heterozygous null mutation of the Nfl gene (Nfl(+/-) show important features of the learning deficits associated with NF1 (ref. 2). Although neurofibromin has several known properties and functions, including Ras GTPase-activating protein activity, adenylyl cyclase modulation and microtubule binding, it is unclear which of these are essential for learning in mice and humans. Here we show that the learning deficits of Nf1(+/-) mice can be rescued by genetic and pharmacological manipulations that decrease Ras function. We also show that the Nf1(+/-) mice have increased GABA (gamma-amino butyric acid)-mediated inhibition and specific deficits in long-term potentiation, both of which can be reversed by decreasing Ras function. Our results indicate that the learning deficits associated with NF1 may be caused by excessive Ras activity, which leads to impairments in long-term potentiation caused by increased GABA-mediated inhibition. Our findings have implications for the development of treatments for learning deficits associated with NF1. 相似文献
42.
N. Ait-Langomazino R. Sellier G. Jouquet M. Trescinski 《Cellular and molecular life sciences : CMLS》1991,47(6):533-539
Summary A blown bitumen Mexphalte R 90/40 with a high content of saturated hydrocarbons was degraded by several microorganisms to the same extent. In batch cultures ofSaccharomycopsis lipolytica, maximal biodegradation was estimated to be about 9% w/w, 3.2·10–3 g/cm2 and 3.1·10–3 cm of degraded bitumen. The Mexphalte R 90/40 degradation rate was closely coupled to biofilm formation. The microbial activity concerned predominantly the oxidation of saturated hydrocarbons. A direct distillation bitumen 80/100 with a low content of saturated hydrocarbons and a high content of aromatic hydrocarbons and resins was more resistant to biodegradation. 相似文献
43.
Abnormal pattern detected in fragile-X patients by pulsed-field gel electrophoresis. 总被引:26,自引:0,他引:26
The fragile-X syndrome is the most frequent inherited form of mental retardation, with an incidence of 1 in 1,500 males. It is characterized by the presence of a fragile site at Xq27.3 induced in vitro by folate deprivation or by inhibitors of deoxynucleotide synthesis. Its mode of inheritance is unusual for an X-linked trait, with incomplete penetrance in both males and females. Some phenotypically normal males transmit the mutation to all their daughters who rarely express any symptoms, but penetrance is high in sons and daughters of these carrier women. Genetic and physical mapping of the Xq27-q28 region has confirmed that the disease locus is located at or very near the fragile site. Hypotheses proposed to account for the abnormalities in the inheritance of the disease include sequence rearrangements by meiotic recombination or a mutation that affects reactivation of an inactive X chromosome during differentiation of female germ cells. To detect such rearrangements, or methylation changes that may reflect a locally inactive X chromosome, we used pulsed-field gel analysis of DNA from fragile-X patients with probes close to the fragile-X locus. The probe Do33 (DXS465) detected abnormal patterns in fragile-X patients, but not in normal controls or in non-expressing male transmitters. 相似文献
44.
复合材料薄平板经热压制成后,都需要进行质量检测。本文探索用测量模态阻尼和振型的方法,对复合材料薄平板的制作质量进行无损检测,作为对其它昂贵的无损检测方法的补充。略述用振动方法进行无损检测的原理,测量薄平板阻尼的方法以及提高测量精度的措施。还讨论在测量薄平板阻尼时可能遇到的一些特殊问题(如非线性刚度、拍、模态密集等问题);以云母基复合材料薄平板作为例子,从测量其阻尼和振型的结果,对这种板的制作质量进行讨论。 相似文献
45.
Chromosomal effects of adeno-associated virus vector integration. 总被引:17,自引:0,他引:17
Adeno-associated virus (AAV) vectors are currently being used in several clinical gene-therapy trials (see the NIH OBA Human Gene Transfer Clinical Trials Database); however, little is known about the chromosomal effects of vector integration. Here we report that integrated vector proviruses are associated with chromosomal deletions and other rearrangements and are frequently located on chromosome 19 (although not at the wildtype AAV integration site). 相似文献
46.
We discuss a generalization of the standard notion of probability space and show that the emerging framework, to be called operational probability theory, can be considered as underlying quantal theories. The proposed framework makes special reference to the convex structure of states and to a family of observables which is wider than the familiar set of random variables: it appears as an alternative to the known algebraic approach to quantum probability. 相似文献
47.
D Ashall B Parkinson 《厦门大学学报(自然科学版)》2002,(Z1)
Background: During the last fifteen years there ha s been an increased drive for organisations to reduce costs. From a production po int, this has often centred on lean manufacturing and JIT waste elimination proc esses. However, in 1991, the Iaccocca Institute Bethlehem P.A commissioned a re port specifically to analyse the changing nature of the marketplace. As a result , in the following year, the Agile Manufacturing Forum was initiated and the ter m ‘agile or responsive manufacturing‘ was first intr... 相似文献
48.
当 Kjell Ekhorn 还在学校学习图形设计,Jon Forss 已在这个行业里工作了不少年头。1989年 Jon Forss 于1LeicesterPolytechnic 毕业后就在 Bath 为一家广告代理商工作,四年之后他移居伦敦为 namara 设计公司设计图书封面。五年以后,他遇到从伦敦 Centrl St.Martins 学校毕业不过两年,正以自由职业者身份从事图书封面设计、图片制作和摄影工作的 Kjell Ekhorn。两人惊讶于互相对图书封面设计的看法,一时相见恨晚,然后自然而然的开始了两人合作的NON-FORMAT 时代。 相似文献
49.
50.
就近几年图书馆界关于新世纪馆员意识转换及社会角色转换等方面的研究进行了综述,指出新时期的馆员要实现自我社会角色的转换,首先是要明确转换的必要性,然后采取有效的策略逐步地、系统地推进转换,才能取得较好的效果。 相似文献