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31.
32.
Donald J. Brasch Hi Mui Chang Chaw T. Chuah Laurence D. Melton 《Carbohydrate research》1981,97(1):113-125
A galactan sulfate has been isolated from the seaweed Porphyra columbina, and its structure established by a combination of methylation, methanolysis, treatment with alkali followed by methylation, and 13C-n.m.r. spectroscopy. The polysaccharide belongs to the porphyran class, and consists of 3-linked β-d-galactosyl residues and 4-linked α-l-galactosyl residues. 3,6-Anhydro-l-galactose and l-galactose 6-sulfate residues total approximately half of the sugar units, the other half being made up of d-galactose and 6-O-methyl-d-galactose residues. Some evidence is presented that suggests that the galactan sulfate does not have a completely alternating structure. 相似文献
33.
In vivo studies were done on mongrel dogs to determine the effect of angiotensin II on renal electrolyte excretion. Angiotensin II was infused directly into the left renal artery at a rate of 1 ng/kg/min. Angiotensin produced consistent reductions in the excretion of Na+, K+, and Cl- in the left kidney. These reductions could not be attributed to decreases in GFR or RPF. Electrolyte excretion by the right kidney was constant. These data are consistent with the hypothesis that angiotensin II may function as an intrarenal, antinatriuretic hormone. 相似文献
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Plasmid pIJ699, a multi-copy positive-selection vector for Streptomyces 总被引:22,自引:0,他引:22
36.
Pancreatic lineage analysis using a retroviral vector in embryonic mice demonstrates a common progenitor for endocrine and exocrine cells 总被引:3,自引:0,他引:3
The origin of pancreatic endocrine cells is unknown. Some studies have suggested that there is a common pancreatic progenitor which gives rise to both endocrine and exocrine cells, while others have suggested separate endocrine and exocrine lineages. Previous conclusions have been based on indirect data, such as the co-expression of molecular markers. We directly assessed the relationship between endocrine and exocrine cells during development using a lineage tracer. A replication-incompetent retrovirus was used to introduce the reporter gene alkaline phosphatase into single cells in explants of mouse embryonic pancreas. After a week in culture, the subsequent fate of the infected cells could then be determined. The results show that a common pancreatic progenitor cell exists, which gives rise to both endocrine and exocrine cells. 相似文献
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Robert Chan Madaline Gilbert Kristin M. Thompson H. Nicholas Marsh David M. Epstein P. Shannon Pendergrast 《Nucleic acids research》2006,34(5):e36
The specific down-regulation of gene expression in cells is a powerful method for elucidating a gene's function. A common method for suppressing gene expression is the elimination of mRNA by RNAi or antisense. Alternatively, oligonucleotide-derived aptamers have been used as protein-directed agents for the specific knock-down of both intracellular and extracellular protein activity. Protein-directed methods offer the advantage of more closely mimicking small molecule therapeutics' mechanism of activity. Furthermore, protein-directed methods may synergize with RNA-directed methods since the two methods attack gene expression at different levels. Here we have knocked down a well-characterized intracellular protein's activity, NFκB, by expressing either aptamers or small interfering RNAs (siRNAs). Both methods can diminish NFκB's activity to similar levels (from 29 to 64%). Interestingly, expression of both aptamers and siRNAs simultaneously, suppressed NFκB activity better than either method alone (up to 90%). These results demonstrate that the expression of intracellular aptamers is a viable alternative to siRNA knock-down. Furthermore, for the first time, we show that the use of aptamers and siRNA together can be the most effective way to achieve maximal knock-down of protein activity. 相似文献
39.
Global change‐driven effects on dissolved organic matter composition: Implications for food webs of northern lakes
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Irena F. Creed Ann‐Kristin Bergström Charles G. Trick Nancy B. Grimm Dag O. Hessen Jan Karlsson Karen A. Kidd Emma Kritzberg Diane M. McKnight Erika C. Freeman Oscar E. Senar Agneta Andersson Jenny Ask Martin Berggren Mehdi Cherif Reiner Giesler Erin R. Hotchkiss Pirkko Kortelainen Monica M. Palta Tobias Vrede Gesa A. Weyhenmeyer 《Global Change Biology》2018,24(8):3692-3714
Northern ecosystems are experiencing some of the most dramatic impacts of global change on Earth. Rising temperatures, hydrological intensification, changes in atmospheric acid deposition and associated acidification recovery, and changes in vegetative cover are resulting in fundamental changes in terrestrial–aquatic biogeochemical linkages. The effects of global change are readily observed in alterations in the supply of dissolved organic matter (DOM)—the messenger between terrestrial and lake ecosystems—with potentially profound effects on the structure and function of lakes. Northern terrestrial ecosystems contain substantial stores of organic matter and filter or funnel DOM, affecting the timing and magnitude of DOM delivery to surface waters. This terrestrial DOM is processed in streams, rivers, and lakes, ultimately shifting its composition, stoichiometry, and bioavailability. Here, we explore the potential consequences of these global change‐driven effects for lake food webs at northern latitudes. Notably, we provide evidence that increased allochthonous DOM supply to lakes is overwhelming increased autochthonous DOM supply that potentially results from earlier ice‐out and a longer growing season. Furthermore, we assess the potential implications of this shift for the nutritional quality of autotrophs in terms of their stoichiometry, fatty acid composition, toxin production, and methylmercury concentration, and therefore, contaminant transfer through the food web. We conclude that global change in northern regions leads not only to reduced primary productivity but also to nutritionally poorer lake food webs, with discernible consequences for the trophic web to fish and humans. 相似文献
40.
Finger JN Lich JD Dare LC Cook MN Brown KK Duraiswami C Bertin J Bertin JJ Gough PJ 《The Journal of biological chemistry》2012,287(30):25030-25037
Nucleotide-binding domain leucine-rich repeat proteins (NLRs) play a key role in immunity and disease through their ability to modulate inflammation in response to pathogen-derived and endogenous danger signals. Here, we identify the requirements for activation of NLRP1, an NLR protein associated with a number of human pathologies, including vitiligo, rheumatoid arthritis, and Crohn disease. We demonstrate that NLRP1 activity is dependent upon ASC, which associates with the C-terminal CARD domain of NLRP1. In addition, we show that NLRP1 activity is dependent upon autolytic cleavage at Ser(1213) within the FIIND. Importantly, this post translational event is dependent upon the highly conserved distal residue His(1186). A disease-associated single nucleotide polymorphism near His(1186) and a naturally occurring mRNA splice variant lacking exon 14 differentially affect this autolytic processing and subsequent NLRP1 activity. These results describe key molecular pathways that regulate NLRP1 activity and offer insight on how small sequence variations in NLR genes may influence human disease pathogenesis. 相似文献