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161.
Zhao M Harris SE Horn D Geng Z Nishimura R Mundy GR Chen D 《The Journal of cell biology》2002,157(6):1049-1060
Functions of bone morphogenetic proteins (BMPs) are initiated by signaling through specific type I and type II serine/threonine kinase receptors. In previous studies, we have demonstrated that the type IB BMP receptor (BMPR-IB) plays an essential and specific role in osteoblast commitment and differentiation. To determine the role of BMP receptor signaling in bone formation in vivo, we generated transgenic mice, which express a truncated dominant-negative BMPR-IB targeted to osteoblasts using the type I collagen promoter. The mice are viable and fertile. Tissue-specific expression of the truncated BMPR-IB was demonstrated. Characterization of the phenotype of these transgenic mice showed impairment of postnatal bone formation in 1-mo-old homozygous transgenic mice. Bone mineral density, bone volume, and bone formation rates were severely reduced, but osteoblast and osteoclast numbers were not significantly changed in the transgenic mice. To determine whether osteoblast differentiation is impaired, we used primary osteoblasts isolated from the transgenic mice and showed that BMP signaling is blocked and BMP2-induced mineralized bone matrix formation was inhibited. These studies show the effects of alterations in BMP receptor function targeted to the osteoblast lineage and demonstrate a necessary role of BMP receptor signaling in postnatal bone growth and bone formation in vivo. 相似文献
162.
Four expression vectors based on formate dehydrogenase promoter (FMDp) and methanol oxidase promoter (MOXp) from Hansenula polymorpha were developed to express heterologous genes in Hansenula polymorpha. A secretion signal sequence of the mating factor-alpha from Saccharomyces cerevisiae was inserted in the secretory expression plasmids for efficient secretion. A modified green fluorescent protein (mGFP5) was used as the marker of expression for the first time in H. polymorpha NCYC495 (leu 1.1) to determine the expression ability of these plasmids. The mGFP5 thus expressed retained its biochemical and physiological properties, such as accumulation inside cells and efficient secretion into the culture media. These results indicated that the four integrative vectors are useful expression systems which could be directly applied for production of heterologous proteins of interests in H. polymorpha. 相似文献
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165.
While interferons (IFNs) (alpha, beta and gamma), a family of cytokines, have the ability to exert the growth-inhibitory effect on target cells, the molecular mechanism(s) by which IFNs inhibit cell growth remains to be identified. Because IFN-inducible 'effector' proteins mediate the biological activities of IFNs, characterization of IFN-inducible proteins is critical to identify their functional role in IFN action. One family (the 200-family) of IFN-inducible proteins is encoded by structurally related murine (Ifi202a, Ifi202b, Ifi203, Ifi204 and D3) and human (IFI16, MNDA and AIM2) genes. The proteins encoded by genes in the family share a unique repeat of 200-amino acids and are primarily nuclear. The AIM2 gene is a newly identified gene that is not expressed in a human melanoma cell line. Here we report that AIM2 is estimated to be a 39 kDa protein and, unlike other proteins in the family, is localized primarily in the cytoplasm. Interestingly, overexpression of AIM2 in transfected cells retards proliferation and, under reduced serum conditions, increases the susceptibility to cell death. Moreover, AIM2 can heterodimerize with p202 in vitro. Together, these observations provide support to the idea that AIM2 may be an important mediator of IFN action. 相似文献
166.
Synechocystis: sp. PCC 6803 is a unicellular motile cyanobacterium, which shows positive or negative phototaxis on agar plates under lateral illumination. By gene disruption in a substrain showing of positive phototaxis, it was demonstrated that mutants defective in sll0038, sll0039, sll0041, sll0042 or sll0043 lost positive phototaxis but showed negative phototaxis away from the light source. Mutants of sll0040, which is located within the cluster of these genes, retained the capacity of positive phototaxis but to a lesser extent than the parent cells. These genes are homologous to che genes, which are involved in flagellar switching for bacterial chemotaxis. Interestingly, sll0041 (designated pisJ1) is predicted to have a chromophore-binding motif of phytochrome-like proteins and a signaling motif of chemoreceptors for bacterial chemotaxis. It is strongly suggested that the positive phototactic response was mediated by a phytochrome-like photoreceptor and CheA/CheY-type signal transduction system. 相似文献
167.
Propagation of potato tubers in a nutrient mist bioreactor 总被引:1,自引:0,他引:1
Zhenlong Hao Fan Ouyang Yuxuan Geng Xiangdong Deng Zanmin Hu Zhenghua Chen 《Biotechnology Techniques》1998,12(8):641-644
The newly designed nutrient mist bioreactor provided an environment supporting multiple-layer culture. In vitro tubers of potato (Solanum tuberosum L.) were induced and cultured in this bioreactor by using two culture methods. The percentage of the inocula eventually forming tubers in a two-step method was 98% with only 54% being formed in a one-step method. The two-step method improved the efficiency of tuber induction, expedited and synchronized the tuberization. © Rapid Science Ltd. 1998 相似文献
168.
为了改进精制白喉毒素脱毒工艺中存在的时间长和损失大等问题,我们考虑进行脱毒过程中加入L-赖氨酸协同脱毒的试验,并以原工艺进行比较,结果使原工艺存在的问题均得到较好的解决。 相似文献
169.
枳壳外植体离体再生及农杆菌介导的遗传转化 总被引:5,自引:0,他引:5
以枳壳实生苗的上胚轴及茎段为材料,在附加有BA和MT培养基上进行培养,上胚轴出芽率普遍高于茎段,BA为1mg/L时,出芽率最高,BA浓度升高,出芽率随之下降。外植体在培养基上的接种方式,对出芽有一定影响,上胚轴切段 形态学下端垂直插入,出芽率高。 相似文献
170.
Hai-Yun Xiao Aaron Balog Ricardo M. Attar David Fairfax Linda B. Fleming Christian L. Holst Gregory S. Martin Lana M. Rossiter Jing Chen Mary-Ellen Cvjic Janet Dell-John Jieping Geng Marco M. Gottardis Wen-Ching Han Andrew Nation Mary Obermeier Cheryl A. Rizzo Liang Schweizer Thomas Spires Weifang Shan Gregory Vite 《Bioorganic & medicinal chemistry letters》2010,20(15):4491-4495
A novel series of 4-[3,5-dioxo-11-oxa-4,9-diazatricyclo[5.3.1.02,6]undec-4-yl]-2-trifluoromethyl-benzonitriles has been synthesized. The ability of these compounds to act as antagonists of the androgen receptor was investigated and several were found to have potent activity in vitro and in vivo. 相似文献