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排序方式: 共有231条查询结果,搜索用时 46 毫秒
71.
Alexandra R. Keegan Stella Fanok Paul T. Monis Christopher P. Saint 《Applied microbiology》2003,69(5):2505-2511
Cryptosporidium parvum represents a challenge to the water industry and a threat to public health. In this study, we developed a cell culture-quantitative PCR assay to evaluate the inactivation of C. parvum with disinfectants. The assay was validated by using a range of disinfectants in common use in the water industry, including low-pressure UV light (LP-UV), ozone, mixed oxidants (MIOX), and chlorine. The assay was demonstrated to be reliable and sensitive, with a lower detection limit of a single infectious oocyst. Effective oocyst inactivation was achieved (>2 log10 units) with LP-UV (20 mJ/cm2) or 2 mg of ozone/liter (for 10 min). MIOX and chlorine treatments of oocysts resulted in minimal effective disinfection, with <0.1 log10 unit being inactivated. These results demonstrate the inability of MIOX to inactivate Cryptosporidium. The assay is a valuable tool for the evaluation of disinfection systems for drinking water and recycled water. 相似文献
72.
IL-4 activates a distinct signal transduction cascade from IL-3 in factor-dependent myeloid cells. 总被引:13,自引:0,他引:13 下载免费PDF全文
L M Wang A D Keegan W E Paul M A Heidaran J S Gutkind J H Pierce 《The EMBO journal》1992,11(13):4899-4908
Interleukin-4 (IL-4) was shown to induce a potent mitogenic response in the IL-3-dependent myeloid progenitor cell line, FDCP-2. Although IL-4 could not sustain long-term growth of FDCP-2 cells, it enhanced their growth in serum-free medium containing IL-3. IL-4 triggered prominent tyrosine phosphorylation of a substrate(s) migrating at 170 kDa and less striking phosphorylation of several other proteins, including the IL-4 receptor. By contrast, IL-3 induced distinct tyrosine phosphorylation of proteins migrating at 145, 97, 70, 55 and 52 kDa in the same cell line. IL-4 treatment of FDCP-2 cells caused a dramatically strong association of phosphatidylinositol 3-kinase (PI 3-kinase) both with the 170 kDa tyrosine phosphorylated substrate and with the IL-4 receptor itself. By contrast, IL-3 triggered only weak association of PI 3-kinase activity with the 97 kDa substrate. While IL-4 did not affect cellular raf, IL-3 stimulation did induce a shift in its mobility presumably due to serine/threonine phosphorylation. Taken together, our results indicate that IL-4 and IL-3 activate distinct phosphorylation cascades in the same cell background; this may reflect a difference in the biological function of these two cytokines. 相似文献
73.
Summary 1. On the west coast of Ireland, a number of echinoderm species have been found to exhibit extreme aggregation. Population densities for some of these animals are amongst the highest on record.2. Detailed studies have been carried out on aggregations of the holothurianPseudocucumis mixta
Östergren. These provided information on habitat preference, mode of burrowing, method of feeding and the animal's sensitivity.3. In situ observation established the existence of a diurnal feeding rhythm which may be primarily controlled by light.4. The manner of defecation and the nature of the faeces would appear to rule out self-fouling by the aggregation.
In-situ-Verhaltensstudien an Aggregationen von Echinodermen. Teil I.Pseudocucumis mixta
Kurzfassung An der Westküste Irlands wurden extrem dichte Aggregationen einiger Echinodermen-Arten beobachtet. Die für die Populationsdichten einiger dieser Stachelhäuter ermittelten Werte gehören zu den höchsten, die bisher bekannt geworden sind. Die Untersuchungen konzentrieren sich auf die Lebensweise der HolothuriePseudocucumis mixta Östergren unter besonderer Berücksichtigung der Habitatpräferenz, der Art des Einbohrens in den Untergrund, der Nahrungsweise, der Defäkation und des Sinneslebens. In-situ-Studien zeigten, daß ein offensichtlich vom Tag-Nacht-Wechsel gesteuerter Freßrhythmus vorliegt.相似文献
74.
Desterro JM Keegan LP Jaffray E Hay RT O'Connell MA Carmo-Fonseca M 《Molecular biology of the cell》2005,16(11):5115-5126
We identify ADAR1, an RNA-editing enzyme with transient nucleolar localization, as a novel substrate for sumoylation. We show that ADAR1 colocalizes with SUMO-1 in a subnucleolar region that is distinct from the fibrillar center, the dense fibrillar component, and the granular component. Our results further show that human ADAR1 is modified by SUMO-1 on lysine residue 418. An arginine substitution of K418 abolishes SUMO-1 conjugation and although it does not interfere with ADAR1 proper localization, it stimulates the ability of the enzyme to edit RNA both in vivo and in vitro. Moreover, modification of wild-type recombinant ADAR1 by SUMO-1 reduces the editing activity of the enzyme in vitro. Taken together these data suggest a novel role for sumoylation in regulating RNA-editing activity. 相似文献
75.
Atwell S Adams JM Badger J Buchanan MD Feil IK Froning KJ Gao X Hendle J Keegan K Leon BC Müller-Dieckmann HJ Nienaber VL Noland BW Post K Rajashankar KR Ramos A Russell M Burley SK Buchanan SG 《The Journal of biological chemistry》2004,279(53):55827-55832
Spleen tyrosine kinase (Syk) is a non-receptor tyrosine kinase required for signaling from immunoreceptors in various hematopoietic cells. Phosphorylation of two tyrosine residues in the activation loop of the Syk kinase catalytic domain is necessary for signaling, a phenomenon typical of tyrosine kinase family members. Syk in vitro enzyme activity, however, does not depend on phosphorylation (activation loop tyrosine --> phenylalanine mutants retain catalytic activity). We have determined the x-ray structure of the unphosphorylated form of the kinase catalytic domain of Syk. The enzyme adopts a conformation of the activation loop typically seen only in activated, phosphorylated tyrosine kinases, explaining why Syk does not require phosphorylation for activation. We also demonstrate that Gleevec (STI-571, Imatinib) inhibits the isolated kinase domains of both unphosphorylated Syk and phosphorylated Abl with comparable potency. Gleevec binds Syk in a novel, compact cis-conformation that differs dramatically from the binding mode observed with unphosphorylated Abl, the more Gleevec-sensitive form of Abl. This finding suggests the existence of two distinct Gleevec binding modes: an extended, trans-conformation characteristic of tight binding to the inactive conformation of a protein kinase and a second compact, cis-conformation characteristic of weaker binding to the active conformation. Finally, the Syk-bound cis-conformation of Gleevec bears a striking resemblance to the rigid structure of the nonspecific, natural product kinase inhibitor staurosporine. 相似文献
76.
Chronic morphine treatment promotes specific Th2 cytokine production by murine T cells in vitro via a Fas/Fas ligand-dependent mechanism 总被引:2,自引:0,他引:2
Greeneltch KM Kelly-Welch AE Shi Y Keegan AD 《Journal of immunology (Baltimore, Md. : 1950)》2005,175(8):4999-5005
Improper homeostasis of Th1 and Th2 cell differentiation can promote pathological immune responses such as autoimmunity and asthma. A number of factors govern the development of these cells including TCR ligation, costimulation, death effector expression, and activation-induced cell death (AICD). Although chronic morphine administration has been shown to selectively promote Th2 development in unpurified T cell populations, the direct effects of chronic morphine on Th cell skewing and cytokine production by CD4(+) T cells have not been elucidated. We previously showed that morphine enhances Fas death receptor expression in a T cell hybridoma and human PBL. In addition, we have demonstrated a role for Fas, Fas ligand (FasL), and TRAIL in promoting Th2 development via killing of Th1 cells. Therefore, we analyzed whether the ability of morphine to affect Th2 cytokine production was mediated by regulation of Fas, FasL, and TRAIL expression and AICD directly in purified Th cells. We found that morphine significantly promoted IL-4 and IL-13 production but did not alter IL-5 or IFN-gamma. Furthermore, morphine enhanced the mRNA expression of Fas, FasL and TRAIL and promoted Fas-mediated AICD of CD4(+) T cells. Additionally, blockade of Fas/FasL interaction by anti-FasL inhibited the morphine-induced production of IL-4 and IL-13 and AICD of CD4(+) T cells. These results suggest that morphine preferentially enhances Th2 cell differentiation via killing of Th1 cells in a Fas/FasL-dependent manner. 相似文献
77.
78.
Sergi López-Torres Keegan R. Selig Kristen A. Prufrock Derrick Lin Mary T. Silcox 《Historical Biology》2018,30(1-2):76-88
AbstractPlesiadapiforms, appearing near the Cretaceous-Paleogene boundary, represent the first primate radiation and show a diverse array of tooth morphologies. Dental topographic metrics provide quantitative data on occlusal surface shape. We used three metrics, Dirichlet Normal Energy, Relief Index, and 3D Orientation Patch Count Rotated, to assess changes in the morphology of lower fourth premolars and lower second molars in a taxonomically broad sample of one family of plesiadapiforms, Paromomyidae, stretching more than 15 million years. Our results indicate that paromomyids occupied a more diverse range of dietary categories than suspected. Whereas all paromomyids were likely omnivores, some species show higher levels of insectivory, while other taxa are inferred to have been mixed-feeding omnivores with high levels of fruit intake. The results also show that the more primitive members of the different paromomyid lineages were more insectivorous than the derived and more recent members of those lineages. Relief Index values also show taxonomic signals that are consistent with ancestor-descendant relationships hypothesised for species of Phenacolemur. These results suggest that dental topographic metrics are informative to the study of paromomyids for both dietary categorisation and for the distinction of species at a fine taxonomic level. 相似文献
79.
Oxidation of glucose, ribose, alanine, and glutamate by Leishmania braziliensis panamensis 总被引:3,自引:0,他引:3
The metabolism of [1-14C]- and [6-14C]glucose, [1-14C]ribose, [1-14C]- and [U-14C]alanine, and [1-14C]- and [5-14C]glutamate by the promastigotes of Leishmania braziliensis panamensis was investigated in cells resuspended in Hanks' balanced salt solution supplemented with ribose, alanine, or glutamate. The ratio of 14CO2 produced from [1-14C]glucose to that from [6-14C]glucose ranged from about two to six, indicating appreciable carbon flow through the pentose phosphate pathway. A functional pentose phosphate pathway was further demonstrated by the production of 14CO2 from [1-14C]ribose although the rate of ribose oxidation was much lower than the rate of glucose oxidation. The rate of 14CO2 production from [1-14C]glucose was almost linear with time of incubation, whereas that of [6-14C]glucose accelerated, consistent with an increasing rate of flux through the Embden-Meyerhof pathway during incubation. Increasing the assay temperature from 26 degrees C to 34 degrees C had no appreciable effect on the rates or time courses of oxidation of either [1-14C]- or [6-14C]glucose or of [1-14C]ribose. Both alanine and glutamate were oxidized by L. b. panamensis, and at rates comparable to or appreciably greater than the rate of oxidation of glucose. The ratios of 14CO2 produced from [1-14C]- to [U-14C]alanine and from [1-14C]- to [5-14C]glutamate indicated that these compounds were metabolized via a functioning tricarboxylic acid cycle and that most of the label that entered the tricarboxylic acid cycle was oxidized to carbon dioxide.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
80.
The Optimal Foraging Analysis of Horticultural Production 总被引:3,自引:0,他引:3
This paper extends the application of optimal foraging theory to horticultural economies. The Machiguenga, a native Amazonian population of southeastern Peru, are used as a test case. The results demonstrate the theory's utility in structuring questions and predicting the outcome of horticultural production. By extending the range of foraging theory the evolution of subsistence strategies from hunting-gathering to agriculture can be examined in quantitative terms. The evolutionary sequence is illustrated with a hypothetical population. Additional insights are gained when the theory is used to structure specific production decisions. Disagreements concerning the scarcity of protein in Amazonian economies are shown to be a consequence of the measurement units employed. 相似文献