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101.
Angata K Long JM Bukalo O Lee W Dityatev A Wynshaw-Boris A Schachner M Fukuda M Marth JD 《The Journal of biological chemistry》2004,279(31):32603-32613
Polysialic acid (PSA) is a post-translational protein modification that is widely expressed among neural cell types during development. Found predominantly on the neural cell adhesion molecule (NCAM), PSA becomes restricted to regions of neurogenesis and neuroplasticity in the adult. In the mammalian genome, two polysialyltransferases termed ST8Sia-II and ST8Sia-IV have been hypothesized to be responsible for the production of PSA in vivo. Approaches to discover PSA function have involved the application of endoneuraminidase-N to remove PSA and genetic manipulations in the mouse to deplete either NCAM or ST8Sia-IV. Here we report the production and characterization of mice deficient in the ST8Sia-II polysialyltransferase. We observed alterations in brain PSA expression unlike those observed in mice lacking ST8Sia-IV. This included a PSA deficit in regions of neurogenesis but without changes in the frequency of mitotic neural progenitor cells. In further contrast with ST8Sia-IV deficiency, loss of ST8Sia-II did not impair hippocampal synaptic plasticity but instead resulted in the misguidance of infrapyramidal mossy fibers and the formation of ectopic synapses in the hippocampus. Consistent with studies of animal models bearing these morphological changes, ST8Sia-II-deficient mice exhibited higher exploratory drive and reduced behavioral responses to Pavlovian fear conditioning. PSA produced by the ST8Sia-II polysialyltransferase modifies memory and behavior processes that are distinct from the neural roles reported for ST8Sia-IV. This genetic partitioning of PSA formation engenders discrete neurological processes and reveals that this post-translational modification forms the predominant basis for the multiple functions attributed to the NCAM glycoprotein. 相似文献
102.
103.
Behavior of Salmonella typhimurium During Manufacture and Curing of Cheddar Cheese 总被引:4,自引:2,他引:2
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Nine vats of stirred-curd granular cheddar cheese were made with whole milk contaminated with Salmonella typhimurium after pasteurization. Enumeration of salmonellae by the most probable number technique during manufacture and curing showed that these organisms multiplied rapidly during manufacture until the curd was salted. Thereafter and throughout the curing period, the salmonellae declined in number at a rate dependent on the temperature of curing. Evidence is presented indicating that the production of volatile fatty acids in the curd during curing may be responsible for this decline. 相似文献
104.
Complex asparagine-linked oligosaccharides are required for morphogenic events during post-implantation development. 总被引:18,自引:3,他引:15
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M Metzler A Gertz M Sarkar H Schachter J W Schrader J D Marth 《The EMBO journal》1994,13(9):2056-2065
Complex asparagine (N)-linked oligosaccharides appear late in phylogeny and are highly regulated in vertebrates. Variations in these structures are found on the majority of cell-surface and secreted proteins. Complex N-linked oligosaccharide biosynthesis is initiated in the Golgi apparatus by the action of Mgat-1-encoded UDP-N-acetylglucosamine:alpha-3-D- mannoside beta-1,2-N-acetylglucosaminyltransferase I (GlcNAc-TI). To determine if these structures govern ontogenic processes in mammals, mouse embryos were generated that lacked a functional Mgat-1 gene. Inactivation of both Mgat-1 alleles produced deficiencies in GlcNAc-TI activity and complex N-linked oligosaccharides. Embryonic lethality occurred by day 10.5, thus establishing that complex N-linked oligosaccharides are required during post-implantation development. Remarkably, embryonic development proceeded into day 9 with the differentiation of multiple cell types. Complex N-linked oligosaccharides are important for morphogenic processes as neural tube formation, vascularization and the determination of left-right body plan asymmetry were impaired in the absence of a functional Mgat-1 gene. 相似文献
105.
Neoplastic transformation induced by an activated lymphocyte-specific protein tyrosine kinase (pp56lck). 总被引:57,自引:23,他引:34
J D Marth J A Cooper C S King S F Ziegler D A Tinker R W Overell E G Krebs R M Perlmutter 《Molecular and cellular biology》1988,8(2):540-550
The lck proto-oncogene encodes a lymphocyte-specific member of the src family of protein tyrosine kinases. Here we demonstrate that pp56lck is phosphorylated in vivo at a carboxy-terminal tyrosine residue (Tyr-505) analogous to Tyr-527 of pp60c-src. Substitution of phenylalanine for tyrosine at this position resulted in increased phosphorylation of a second tyrosine residue (Tyr-394) and was associated with an increase in apparent kinase activity. In addition, this single point mutation unmasked the oncogenic potential of pp56lck in NIH 3T3 cell transformation assays. Viewed in the context of similar results obtained with pp60c-src, it is likely that the enzymatic activity and transforming ability of all src-family protein tyrosine kinases can be regulated by carboxy-terminal tyrosine phosphorylation. We further demonstrate that overexpression of pp56lck in the murine T-cell lymphoma LSTRA as a result of a retroviral insertion event produces a kinase protein that despite wild-type primary structure is nevertheless hypophosphorylated at Tyr-505. Thus, control of normal growth in this lymphoid cell line may have been abrogated through acquisition of a posttranslationally activated version of pp56lck. 相似文献
106.
We describe a new scaffold-free three-dimensional (3D) cell culture model using cholesteryl ester based lyotropic liquid crystal (LC) substrates. Keratinocytes were deposited randomly on the LC surface where they self-assembled into 3D microtissues or keratinospheroids. The cell density required to form spheroids was optimized. We investigated cell viability using dead/live cell assays. The adhesion characteristics of cells within the microtissues were determined using histological sectioning and immunofluorescence staining. Fourier transform infrared spectroscopy (FTIR) was used to characterize the biochemistry of the keratinospheroids. We found that both cells and microtissues could migrate on the LC surface. The viability study indicated approximately 80% viability of cells in the microtissues up to 20 days of culture. Strong intercellular adhesion was observed in the stratification of the multi-layered microspheroids using field emission-scanning electron microscopy (FE-SEM) and histochemical staining. The cytoskeleton and vinculins of the cells in the microtissues were expressed diffusely, but the microtissues were enriched with lipids and nucleic acids, which indicates close resemblance to the conditions in vivo. The basic 3D culture model based on LC may be used for cell and microtissue migration studies in response to cytochemical treatment. 相似文献
107.
108.
VARIOUS BACTERIA, YEASTS, AND MOLDS IMPORTANT TO THE FOOD INDUSTRY WERE INCUBATED IN AEROSOL CANS CONTAINING A C BROTH AND ONE OF THE FOLLOWING THREE GAS HYDRATE FORMERS: propane, dichlorodifluoromethane (f-12), and 1,1-difluoro-1-chloroethane (f-142b). Most hydrate formers were tested at three concentrations: low (vapor state), intermediate (liquid state, low level), and high (liquid state, high level). Samples were continuously agitated for 48 hr at 21 +/- 3 C. Changes in numbers of microorganisms were determined by plate count. With hydrate formers in the vapor state, propane was more toxic to the microorganisms tested than either f-12 or f-142b. The most resistant organisms from these trials were then tested against f-12 or f-142b in the liquid state. Hydrate formers were far more toxic in the liquid state than in the vapor state. With the exception of sporulated cultures of Bacillus cereus, all microorganisms tested were greatly reduced in numbers when agitated for 48 hr at 21 C in the presence of f-12 or f-142b. 相似文献
109.
A sterile glucose-mineral salts broth was inoculated with conidia of Penicillium rubrum P-13 and P-3290. Radiolabeled compounds were added to some cultures, these being incubated quiescently at 28° C for 14 days. Other stationary cultures were grown for 21 days, received labeled compounds, and were then grown for 5 more days. The remaining cultures were inoculated with 72-h-old mycelial pellets, received labeled materials and were incubated with shaking for 60 h. Rubratoxin was resolved by thin-layer chromatography. Labeled [114C]acetate, [1,514C]citrate, [214C]malonate, [114C]glucose, [U14C]glucose or [114C]hexanoate were incorporated into rubratoxins A and B by P. rubrum 3290 and into rubratoxin B by P. rubrum 13. Incorporation of [114C]acetate and [214C]malonate increased when exogenous unlabeled acetate, malonate, pyruvate, or phosphoenol-pyruvate was added. Acetate incorporation was influenced by cultural conditions, attaining maximum amounts in quiescent cultures which received labeled acetate after 21 days of incubation. Acetate incorporation in shake cultures was enhanced by reduced nicotinamide adenine dinucleotide phosphate (NADPH) and by unlabeled exogenous citrate.Abbreviations GMS
glucose-mineral salts
- RCM
replacement culture medium
- TCA
tricarboxylic acid
- PEP
phosphoenolpyruvate
- RIC
relative isotopic content
- PI
percent incorporation 相似文献
110.
Sheran HW Law Rudolf SS Wu Patrick KS Ng Richard MK Yu Richard YC Kong 《BMC molecular biology》2006,7(1):15-13