排序方式: 共有16条查询结果,搜索用时 15 毫秒
1.
Regulation of oocyte growth in the mouse ovary 总被引:3,自引:0,他引:3
2.
Long-term potentiation of chemical synapses is closely related to memory and learning. Studies of this process have concentrated on chemically mediated excitatory synapses. By contrast, activity-dependent modification of gap junctions, which also widely exist in higher structures such as hippocampus and neocortex, has not been described. Here we report that at mixed synapses between sensory afferents and an identified reticulospinal neuron, the electrotonic coupling potential can be potentiated, as well as the chemically mediated excitatory postsynaptic potential, for a prolonged time period using a stimulation paradigm like that which produces long-term potentiation in hippocampus. The effect on coupling is due to an increase in gap-junctional conductance. Our data indicate that the potentiation of both synaptic components requires an increase in intracellular calcium, involves activation of NMDA (N-methyl-D-aspartate) receptors, and is specific to the tetanized pathway. 相似文献
3.
Carpten JD Faber AL Horn C Donoho GP Briggs SL Robbins CM Hostetter G Boguslawski S Moses TY Savage S Uhlik M Lin A Du J Qian YW Zeckner DJ Tucker-Kellogg G Touchman J Patel K Mousses S Bittner M Schevitz R Lai MH Blanchard KL Thomas JE 《Nature》2007,448(7152):439-444
Although AKT1 (v-akt murine thymoma viral oncogene homologue 1) kinase is a central member of possibly the most frequently activated proliferation and survival pathway in cancer, mutation of AKT1 has not been widely reported. Here we report the identification of a somatic mutation in human breast, colorectal and ovarian cancers that results in a glutamic acid to lysine substitution at amino acid 17 (E17K) in the lipid-binding pocket of AKT1. Lys 17 alters the electrostatic interactions of the pocket and forms new hydrogen bonds with a phosphoinositide ligand. This mutation activates AKT1 by means of pathological localization to the plasma membrane, stimulates downstream signalling, transforms cells and induces leukaemia in mice. This mechanism indicates a direct role of AKT1 in human cancer, and adds to the known genetic alterations that promote oncogenesis through the phosphatidylinositol-3-OH kinase/AKT pathway. Furthermore, the E17K substitution decreases the sensitivity to an allosteric kinase inhibitor, so this mutation may have important clinical utility for AKT drug development. 相似文献
4.
A mutant T4 lysozyme displays five different crystal conformations 总被引:14,自引:0,他引:14
Phage T4 lysozyme consists of two domains between which is formed the active-site cleft of the enzyme. The crystallographically determined thermal displacement parameters for the protein suggested that the amino terminal of the two domains undergoes 'hinge-bending' motion about an axis passing through the waist of the molecule. Such conformational mobility may be important in allowing access of substrates to the active site of the enzyme. We report here a crystallographic study of a mutant T4 lysozyme which demonstrates further the conformational flexibility of the protein. A mutant form of the enzyme with a methionine residue (Met 6) replaced by isoleucine crystallizes with four independent molecules in the crystal lattice. These four molecules have distinctly different conformations. The mutant protein can also crystallize in standard form with a structure very similar to the wild-type protein. Thus the mutant protein can adopt five different crystal conformations. The isoleucine for methionine substitution at the intersection of the two domains of T4 lysozyme apparently enhances the hinge-bending motion presumed to occur in the wild-type protein, without significantly affecting the catalytic activity or thermal stability of the protein. 相似文献
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本文调查了上海市百岁老人的性别、职业和谱系,并绘制了57个完整的寿命谱系图,其中男性10名(占总数的17.5%),女性47名(占82.5%).男性中脑力劳动者4名(占男性总数的40%),体力劳动者6名(占60%);女性中脑力劳动者1人(占女性总数的2.1%),体力劳动者3人(占6.4%),操持家务者43人(占91.5%).有长寿家族史者40人(占寿命家族史清楚者的70.2%),无长寿家族史者17人(占29.8%).百岁老人配偶寿长≥70岁者,其已故子女的平均寿命高于配偶<70岁的.作者认为长寿是遗传的,并着重从遗传和环境两方面分析了女寿星数明显多于男寿星数的原因. 相似文献
7.
艾摩尔 《华东师范大学学报(自然科学版)》2004,2004(1):40-44
在二次损失函数下,作者研究了多元线性模型协方差矩阵的MINQUE估计和简单估计的比较问题,其中多元线性模型的设计矩阵和离散矩阵可以不满秩,得到了一个充分和必要条件。 相似文献
8.
Monocytes and their pathophysiological role in Crohn’s disease 总被引:1,自引:1,他引:0
Zhou L Braat H Faber KN Dijkstra G Peppelenbosch MP 《Cellular and molecular life sciences : CMLS》2009,66(2):192-202
Our immune system shows a stringent dichotomy, on the one hand displaying tolerance towards commensal bacteria, but on the
other hand vigorously combating pathogens. Under normal conditions the balance between flora tolerance and active immunity
is maintained via a plethora of dynamic feedback mechanisms. If, however, the balancing act goes faulty, an inappropriate
immune reaction towards an otherwise harmless intestinal flora causes disease, Crohn’s disease for example. Recent developments
in the immunology and genetics of mucosal diseases suggest that monocytes and their derivative cells play an important role
in the pathophysiology of Crohn’s disease. In our review, we summarize the recent studies to discuss the dual function of
monocytes - on the one hand the impaired monocyte function initiating Crohn’s disease, and on the other hand the overactivation
of monocytes and adaptive immunity maintaining the disease. With a view to developing new therapies, both aspects of monocyte
functions need to be taken into account.
Received 1 June 2008; received after revision 24 July 2008; accepted 13 August 2008 相似文献
9.
心肌宁冲剂按1.75g/kg,0.875g/kg剂量,每天早晚分两次灌胃给药,连续7天,均能明显对抗垂体后叶素所诱发的大鼠急性心肌缺血的心电图改变。 相似文献
10.
该文通过34只罗猴头颈实验研究,从中决定罗猴的颅脑损伤容限.当颅脑受到冲击时,颅壳发生局部变形瞬间,大脑亦发生变形,致使颅内压升高.利用这些结果来确定它的损伤机制,以模拟宇航员在冲击载荷下的创伤分析模型,将有助于进行临床创伤治疗和宇航弹射时的防护. 相似文献