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971.
Krassowska A Gordon-Keylock S Samuel K Gilchrist D Dzierzak E Oostendorp R Forrester LM Ansell JD 《Experimental cell research》2006,312(18):3595-3603
We investigated whether the in vitro differentiation of ES cells into haematopoietic progenitors could be enhanced by exposure to the aorta-gonadal-mesonephros (AGM) microenvironment that is involved in the generation of haematopoietic stem cells (HSC) during embryonic development. We established a co-culture system that combines the requirements for primary organ culture and differentiating ES cells and showed that exposure of differentiating ES cells to the primary AGM region results in a significant increase in the number of ES-derived haematopoietic progenitors. Co-culture of ES cells on the AM20-1B4 stromal cell line derived from the AGM region also increases haematopoietic activity. We conclude that factors promoting the haematopoietic activity of differentiating ES cells present in primary AGM explants are partially retained in the AM20.1B4 stromal cell line and that these factors are likely to be different to those required for adult HSC maintenance. 相似文献
972.
Persson KE Stenflo J Linse S Stenberg Y Preston RJ Lane DA Rezende SM 《Biochemistry》2006,45(35):10682-10689
Protein S is an anticoagulant protein containing a Gla (enclosing gamma-carboxyglutamic acids) module, a TSR (thrombin sensitive region) module, four EGF (epidermal growth factor)-like modules, and a SHBG (sex hormone binding globulin)-like region. Protein S is a cofactor to activated protein C (APC) in the degradation of coagulation factors Va and VIIIa but also has APC-independent activities. The function of the fourth EGF module (EGF4) in protein S has so far not been clear. We have now investigated this module through studies of recombinant wild-type protein S and a naturally occurring mutant (Asn217Ser). The mutant has essentially normal APC anticoagulant activity and a previously reported secretion defect. In the wild-type protein, Asn217 is normally beta-hydroxylated. The binding of calcium to wild-type protein S is characterized by four high-affinity binding sites with K(D) values ranging from 10(-)(7) to 10(-)(9) M. Three of these binding sites are located in EGF modules. Using surface plasmon resonance, competition with a calcium chelator, and antibody-based methods, we found that one high-affinity binding site for calcium was lost in protein S Asn217Ser but that the mutation also affected the calcium-dependent conformation of EGF1. We conclude that binding of calcium to EGF4 of protein S, involving Asn217, is important for the maintenance of the structure of protein S. Also, the abolition of binding of calcium to EGF4, related to Asn217, impairs both the structure and function of EGF1. 相似文献
973.
Eklund EA Sun L Yang SP Pasion RM Thorland EC Freeze HH 《Biochemical and biophysical research communications》2006,339(3):755-760
We describe a new cause of congenital disorder of glycosylation-Ic (CDG-Ic) in a young girl with a rather mild CDG phenotype. Her cells accumulated lipid-linked oligosaccharides lacking three glucose residues, and sequencing of the ALG6 gene showed what initially appeared to be a homozygous novel point mutation (338G > A). However, haplotype analysis showed that the patient does not carry any paternal DNA markers extending 33 kb in the telomeric direction from the ALG6 region, and microsatellite analysis extended the abnormal region to at least 2.5 Mb. We used high-resolution karyotyping to confirm a deletion (10-12 Mb) [del(1)(p31.2p32.3)] and found no structural abnormalities in the father, suggesting a de novo event. Our findings extend the causes of CDG to larger DNA deletions and identify the first Japanese CDG-Ic mutation. 相似文献
974.
975.
Habura A Goldstein ST Parfrey LW Bowser SS 《The Journal of eukaryotic microbiology》2006,53(3):204-210
The classification of the Foraminifera, a widely distributed group of largely marine protists, has traditionally been based on morphological characters. The most important of these are the composition and structure of the shell or "test." Here, we use both phylogenetic analysis of the genes for small subunit rRNA and beta-tubulin and ultrastructural analysis to document a reversion in wall type from more derived calcareous tests to an agglutinated test. These data indicate that the genus Miliammina, and possibly other members of the Rzehakinidae, should be placed in the Order Miliolida as opposed to their current assignment in Order Textulariida. We also address the effects this reversion may have had on the ability of rzehakinacids to effectively colonize marginal marine environments. Finally, the hypothesis that some multilocular agglutinated foraminiferans descended from calcareous lineages has implications for interpretation of the foraminiferal fossil record. 相似文献
976.
Generation of cloned transgenic pigs rich in omega-3 fatty acids 总被引:33,自引:0,他引:33
Lai L Kang JX Li R Wang J Witt WT Yong HY Hao Y Wax DM Murphy CN Rieke A Samuel M Linville ML Korte SW Evans RW Starzl TE Prather RS Dai Y 《Nature biotechnology》2006,24(4):435-436
Meat products are generally low in omega-3 (n-3) fatty acids, which are beneficial to human health. We describe the generation of cloned pigs that express a humanized Caenorhabditis elegans gene, fat-1, encoding an n-3 fatty acid desaturase. The hfat-1 transgenic pigs produce high levels of n-3 fatty acids from n-6 analogs, and their tissues have a significantly reduced ratio of n-6/n-3 fatty acids (P < 0.001). 相似文献
977.
The olfactory bulb receives signals from olfactory sensory neurons and conveys them to higher centers. The mapping of the sensory inputs generates a reproducible spatial pattern in the glomerular layer of the olfactory bulb for each odorant. Then, this restricted activation is transformed into highly distributed patterns by lateral interactions between relay neurons and local interneurons. Thus, odor information processing requires the spatial patterning of both sensory inputs and synaptic interactions. In other words, odor representation is highly dynamic and temporally orchestrated. Here, we describe how the local inhibitory network shapes the global oscillations and the precise synchronization of relay neurons. We discuss how local inhibitory interneurons transpose the spatial dimension into temporal patterning. Remarkably, this transposition is not fixed but highly flexible to continuously optimize olfactory information processing. 相似文献
978.
Knols BG Hood-Nowotny RC Bossin H Franz G Robinson A Mukabana WR Kemboi SK 《Nature biotechnology》2006,24(9):1067-8; discussion 1068
979.
Essential to salmonellae pathogenesis is an export device called the type III secretion system (TTSS), which mediates the transfer of bacterial effector proteins from the bacterial cell into the host cell cytoplasm. Once inside the host cell, these effectors are then capable of altering a variety of host cellular functions in order to promote bacterial survival and colonization. SspH1 is a Salmonella enterica serovar Typhimurium TTSS effector that localizes to the mammalian nucleus and down-modulates production of proinflammatory cytokines by inhibiting nuclear factor (NF)-kappaB-dependent gene expression. To identify mammalian binding partners of SspH1 a yeast two-hybrid screen against a human spleen cDNA library was performed. It yielded a serine/threonine protein kinase called protein kinase N 1 (PKN1). The leucine-rich repeat domain of SspH1 was demonstrated to mediate this interaction and also inhibition of NF-kappaB-dependent gene expression. This suggested that PKN1 may play a role in modulation of the NF-kappaB signalling pathway. Indeed, we found that expression of constitutively active PKN1 in mammalian cells results in a decrease, while depletion of PKN1 by RNA interference causes an increase in NF-kappaB-dependent reporter gene expression. These data indicate that SspH1 may inhibit the host's inflammatory response by interacting with PKN1. 相似文献
980.
Martin Carr Samuel Cotton David W Rogers Andrew Pomiankowski Hazel Smith Kevin Fowler 《BMC developmental biology》2006,6(1):29-10