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21.
Melanocortin receptors: their functions and regulation by physiological agonists and antagonists 总被引:14,自引:0,他引:14
Abdel-Malek ZA 《Cellular and molecular life sciences : CMLS》2001,58(3):434-441
The melanocortins are a family of bioactive peptides derived from proopiomelanocortin, and share significant structural similarity.
Those peptides are best known for their stimulatory effects on pigmentation and steroidogenesis. Melanocortins are synthesized
in various sites in the central nervous system and in peripheral tissues, and participate in regulating multiple physiological
functions. Research during the past decade has provided evidence that melanocortins elicit their diverse biological effects
by binding to a distinct family of G protein-coupled receptors with seven transmembrane domains. To date, five melanocortin
receptor genes have been cloned and characterized. Those receptors differ in their tissue distribution and in their ability
to recognize the various melanocortins and the physiological antagonists, agouti signaling protein and agouti-related protein.
These advances have opened new horizons for exploring the significance of melanocortins, their antagonists, and their receptors
in a variety of important physiological functions.
Received 5 October 2000; accepted 10 November 2000 相似文献
22.
Advances in methods of structure determination have led to the accumulation of large amounts of protein structural data. Some 500 distinct protein folds have now been characterized, representing one-third of all globular folds that exist. The range of known structural types and the relatively large fraction of the protein universe that has already been sampled have greatly facilitated the discovery of some unifying principles governing protein structure and evolutionary relationships. These include a highly skewed distribution of topological arrangements of secondary-structure elements that favors a few very common connectivities and a highly skewed distribution in the capacity of folds to accommodate unrelated sequences. These and other observations suggest that the number of folds is far fewer than the number of genes, and that the fold universe is dominated by a small number of giant attractors that accommodate large numbers of unrelated sequences. Thus all basic protein folds will likely be determined in the near future, laying the foundation for a comprehensive understanding of the biochemical and cellular functions of whole organisms. 相似文献
23.
FANGJianwu HUANGSiluo LIUHuisheng M.Crepin XUTao LIUJianfeng 《科学通报(英文版)》2003,48(15):1539-1547
Fibroblast growth factor-2 (FGF-2) is a member of a large family of proteins that bind heparin and heparan sulfate and modulate the function of a wide range of cell types. It has been proved that FGF-2 stimulates the growth and development of new blood vessels (angiogenesis) that contribute to the pathogenesis of several diseases (i.e. cancer, atherosclerosis). However, many of the biological activities of FGF-2 have been found to depend on its receptor抯 intrinsic tyrosine kinase activity and second messengers such as the mitogen activated protein kinases. This review will focus on the mechanism of FGF-2/FGFR induced signaling pathway in tumor and human breast cancer. 相似文献
24.
黄桂金 《华中科技大学学报(自然科学版)》1997,(2)
在电信领域,尤其在7号信令系统应用中,定时器有决定性的重要影响.以TUP为对象,剖析7号信令系统定时特点,分析定时服务器的服务对象和设计需求.基于UNIX和VMEexec实时操作系统平台,扩展了标准的UNIX定时服务,提供了一个实时、高分辨率定时处理机制,并从设计方案、实现算法及性能等方面进行了讨论 相似文献
25.
Regulation of insulin receptor function 总被引:1,自引:0,他引:1
Youngren JF 《Cellular and molecular life sciences : CMLS》2007,64(7-8):873-891
Resistance to the biological actions of insulin contributes to the development of type 2 diabetes and risk of cardiovascular
disease. A reduced biological response to insulin by tissues results from an impairment in the cascade of phosphorylation
events within cells that regulate the activity of enzymes comprising the insulin signaling pathway. In most models of insulin
resistance, there is evidence that this decrement in insulin signaling begins with either the activation or substrate kinase
activity of the insulin receptor (IR), which is the only component of the pathway that is unique to insulin action. Activation
of the IR can be impaired by post-translational modifications of the protein involving serine phosphorylation, or by binding
to inhibiting proteins such as PC-1 or members of the SOCS or Grb protein families. The impact of these processes on the conformational
changes and phosphorylation events required for full signaling activity, as well as the role of these mechanisms in human
disease, is reviewed in this article.
Received 3 August 2006; received after revision 1 December 2006; accepted 8 January 2007 相似文献
26.
戴海鸿 《南京邮电大学学报(自然科学版)》1995,(2)
介绍了目前应用于我国长途电话交换局的两种主要的线路信令方式及其转换原理.分析了可能出现的“闭塞”现象,提出了解决方法,给出了实现方案和实际应用结果. 相似文献
27.
A model of calcium signaling and degranulation dynamics induced by laser irradiation in mast cells 总被引:3,自引:0,他引:3
Recent experiments show that calcium signaling and degranulation dynamics induced by low power laser irradiation in mast cells must rely on extracellular Ca^2+ influx. An analytical expression of Ca^2+ flux through TRPV4 cation channel in response to interaction of laser photon energy and extracellular Ca^2+ is deduced, and a model characterizing dynamics of calcium signaling and degranulation activated by laser irradiation in mast cells is established. The model indicates that the characteristics of calcium signaling and degranulation dynamics are determined by interaction between laser photon energy and Ca^2+ influx. Extracellular Ca^2+ concentration is so high that even small photon energy can activate mast cells, thus avoiding the possible injury caused by laser irradiation with shorter wavelengths. The model predicts that there exists a narrow parameter domain of photon energy and extracellular Ca^2+ concentration of which results in cytosolic Ca^2+ limit cycle oscillations, and shows that PKC activity is in direct proportion to the frequency of Ca^2+ oscillations. With the model it is found that sustained and stable maximum plateau of cytosolic Ca^2+ concentration can get optimal degranulation rate. Furthermore, the idea of introducing the realistic physical energy into model is applicable to modeling other physical signal transduction systems. 相似文献
28.
剖析了 STORNO信令集群移动通信系统的信令格式及通信规程 ,给出了自行研制的移动台硬件及软件 .所研制的手持移动台体积小巧、通话距离远且话音质量良好 . 相似文献
29.
张铎 《甘肃联合大学学报(自然科学版)》2007,21(3):36-38
以具体例题浅析怎样解决非惯性系的动力学问题,分别应用牛顿第二定律、拉格朗日方程、哈密顿正则方程等方法求解:牛顿第二定律解决问题,需要对质点进行受力分析,比较复杂;用拉格朗日方程解决,思路清晰,是一个二阶常微分方程组;而哈密顿正则方程则是一个一阶常微分方程组,形式简单,使用方便. 相似文献
30.
樊彦香 《科技情报开发与经济》2008,18(17):164-165
详细介绍了在配置数据时要连接的双方必须进行协商,取得一致的几项参数,并列举了这些参数设置错误产生的后果。 相似文献