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排序方式: 共有388条查询结果,搜索用时 31 毫秒
91.
Lewis TA Leach L Morales S Austin PR Hartwell HJ Kaplan B Forker C Meyer JM 《Environmental microbiology》2004,6(2):159-169
92.
To understand the mechanism by which peptide antigens are processed and presented to T cells, we examined the T-cell response to the 13-amino-acid peptide alpha-melanocyte-stimulating hormone (alpha-MSH). To determine the fine specificity of T-cell recognition, T cells specific for alpha-MSH, and genetically restricted by I-Ab/d, were challenged with different alpha-MSH analogs and homologs. It was found that intact alpha-MSH, including the blocked amino and carboxy termini of the native molecule, was required for T-cell responsiveness. Antigen-presenting cells (APC) could be briefly pulsed with alpha-MSH and then present the alpha-MSH antigenic determinant to T cells, indicating that the relevant antigen was retained by the APC. APC stimulatory capacity was dramatically reduced by aldehyde treatment of the APC, or by pulsing the APC with alpha-MSH at low temperature. Efficient alpha-MSH pulsing was also impaired by treatment of the APC with the carboxylic ionophore, monensin, but not by the lysosomotropic agents chloroquine and methylamine. In addition, isolated APC plasma membranes added to the T cells in the presence of soluble alpha-MSH were not stimulatory. However, plasma membranes isolated from APC that had been previously pulsed with alpha-MSH retained stimulatory activity for T-cell responses. The only detectable alpha-MSH contained in these pulsed APC membranes was in an acid-stable complex of higher molecular weight than native peptide. The amount of alpha-MSH detected in the cellular membrane fraction isolated by density gradient sedimentation was also reduced by treatments that reduced the APC stimulatory capacity, such as pulsing at low temperature or in the presence of monensin. Taken together, these results suggest that processing of alpha-MSH is unlike that heretofore described for other peptide antigens and seems to involve APC handling to form the stimulatory moiety presented on the APC surface. 相似文献
93.
Graft-versus-host disease (GVHD) is the limiting barrier to the broad use of bone marrow transplant as a curative therapy for a variety of hematological deficiencies. GVHD is caused by mature alloreactive T cells present in the bone marrow graft that are infused into the recipient and cause damage to host organs. However, in mice, T cells must be added to the bone marrow inoculum to cause GVHD. Although extensive work has been done to characterize T cell responses post transplant, bioluminescent imaging technology is a non-invasive method to monitor T cell trafficking patterns in vivo. Following lethal irradiation, recipient mice are transplanted with bone marrow cells and splenocytes from donor mice. T cell subsets from L2G85.B6 (transgenic mice that constitutively express luciferase) are included in the transplant. By only transplanting certain T cell subsets, one is able to track specific T cell subsets in vivo, and based on their location, develop hypotheses regarding the role of specific T cell subsets in promoting GVHD at various time points. At predetermined intervals post transplant, recipient mice are imaged using a Xenogen IVIS CCD camera. Light intensity can be quantified using Living Image software to generate a pseudo-color image based on photon intensity (red = high intensity, violet = low intensity). Between 4-7 days post transplant, recipient mice begin to show clinical signs of GVHD. Cooke et al.1 developed a scoring system to quantitate disease progression based on the recipient mice fur texture, skin integrity, activity, weight loss, and posture. Mice are scored daily, and euthanized when they become moribund. Recipient mice generally become moribund 20-30 days post transplant. Murine models are valuable tools for studying the immunology of GVHD. Selectively transplanting particular T cell subsets allows for careful identification of the roles each subset plays. Non-invasively tracking T cell responses in vivo adds another layer of value to murine GVHD models. 相似文献
94.
Determination of guanine-plus-cytosine content of bacterial DNA by dual-laser flow cytometry 总被引:3,自引:0,他引:3
C A Sanders D M Yajko W Hyun R G Langlois P S Nassos M J Fulwyler W K Hadley 《Journal of general microbiology》1990,136(2):359-365
A dual-laser flow cytometer was used to analyse different species of bacteria for the molar percentage of guanine-plus-cytosine (% G + C) without the need for DNA extraction or purification. Ethanol-fixed bacterial cells were stained with a combination of DNA-specific fluorochromes, Hoechst 33258 and chromomycin A3, which bind to AT- and GC-rich regions of DNA, respectively. A linear relationship (r = 0.99) was demonstrated between the log of the ratio of chromomycin A3 to Hoechst 33258 fluorescence and the log of the % G + C as determined by thermal denaturation (Tm) or buoyant density centrifugation (Bd) methods. Linearity was maintained for all bacterial species tested over the range of 28-67% G + C. A standard curve was constructed using five strains whose % G + C had been determined by other methods. From the equation describing this line, the % G + C values of nine other strains with known DNA base composition, together with the five strains used to construct the curve, were calculated using the chromomycin A3 to Hoechst 33258 ratio and were in agreement with values obtained by Tm, Bd or HPLC. The reproducibility of flow cytometric analysis (mean error 0.7% G + C) compared well with the reproducibility of other methods. Mixtures containing two species were also analysed. Two cell populations could be discerned in mixtures containing two species which differed in base composition by as little as 4% G + C.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
95.
96.
Zeyuan Song Tao Wu Jinpeng Sun Haoran Wang Feng Hua Yap San Min Nicolas Rupesh KC Kun Chen Zhen Jin Jun Liu Mingshun Zhang 《Journal of cellular and molecular medicine》2021,25(7):3272-3283
Excessive post-epidural fibrosis is a common cause of recurrent back pain after spinal surgery. Though various treatment methods have been conducted, the safe and effective drug for alleviating post-epidural fibrosis remains largely unknown. Metformin, a medicine used in the treatment of type 2 diabetes, has been noted to relieve fibrosis in various organs. In the present study, we aimed to explore the roles and mechanisms of metformin in scar formation in a mouse model of laminectomy. Post-epidural fibrosis developed in a mouse model of laminectomy by spinous process and the T12-L2 vertebral plate with a rongeur. With the administration of metformin, post-epidural fibrosis was reduced, accompanied with decreased collagen and fibronectin in the scar tissues. Mechanistically, metformin decreased fibronectin and collagen deposition in fibroblast cells, and this effect was dependent on the HMGB1/TLR4 and TGF-β1/Smad3 signalling pathways. In addition, metformin influenced the metabolomics of the fibroblast cells. Taken together, our study suggests that metformin may be a potential option to mitigate epidural fibrosis after laminectomy. 相似文献
97.
Penny J Tricker Carlos M Rodríguez López P Hadley C Wagstaff Mike J Wilkinson 《Plant signaling & behavior》2013,8(10)
Epigenetic modification of the genome via cytosine methylation is a dynamic process that responds to changes in the growing environment. This modification can also be heritable. The combination of both properties means that there is the potential for the life experiences of the parental generation to modify the methylation profiles of their offspring and so potentially to “pre-condition” them to better accommodate abiotic conditions encountered by their parents. We recently identified high vapor pressure deficit (vpd)-induced DNA methylation at 2 gene loci in the stomatal development pathway and an associated reduction in leaf stomatal frequency.1 Here, we test whether this epigenetic modification pre-conditioned parents and their offspring to the more severe water stress of periodic drought. We found that 3 generations of high vpd-grown plants were better able to withstand periodic drought stress over 2 generations. This resistance was not directly associated with de novo methylation of the target stomata genes, but was associated with the cmt3 mutant’s inability to maintain asymmetric sequence context methylation. If our finding applies widely, it could have significant implications for evolutionary biology and breeding for stressful environments. 相似文献
98.
Andrew MF Liu Rico KH Lo Emily X Guo Maurice KC Ho Richard D Ye Yung H Wong 《BMC structural biology》2011,11(1):17
Background
G protein-coupled receptors constitute the largest family of cell surface receptors in the mammalian genome. As the core of the G protein signal transduction machinery, the Gα subunits are required to interact with multiple partners. The GTP-bound active state of many Gα subunits can bind a multitude of effectors and regulatory proteins. Yet it remains unclear if the different proteins utilize distinct or common structural motifs on the Gα subunit for binding. Using Gα16 as a model, we asked if its recently discovered adaptor protein tetratricopeptide repeat 1 (TPR1) binds to the same region as its canonical effector, phospholipase Cβ (PLCβ). 相似文献99.
Jae‐Sung Kim Michael B. Ellman Dongyao Yan Howard S. An Ranjan KC Xin Li Di Chen Guozhi Xiao Gabriella Cs‐Szabo David W. Hoskin Doug D. Buechter Andre J. Van Wijnen Hee‐Jeong Im 《Journal of cellular physiology》2013,228(9):1884-1896
The catabolic cytokine interleukin‐1 (IL‐1) and endotoxin lipopolysaccharide (LPS) are well‐known inflammatory mediators involved in degenerative disc disease, and inhibitors of IL‐1 and LPS may potentially be used to slow or prevent disc degeneration in vivo. Here, we elucidate the striking anti‐catabolic and anti‐inflammatory effects of bovine lactoferricin (LfcinB) in the intervertebral disc (IVD) via antagonism of both IL‐1 and LPS‐mediated catabolic activity using in vitro and ex vivo analyses. Specifically, we demonstrate the biological counteraction of LfcinB against IL‐1 and LPS‐mediated proteoglycan (PG) depletion, matrix‐degrading enzyme production, and enzyme activity in long‐term (alginate beads) and short‐term (monolayer) culture models using bovine and human nucleus pulposus (NP) cells. LfcinB significantly attenuates the IL‐1 and LPS‐mediated suppression of PG production and synthesis, and thus restores PG accumulation and pericellular matrix formation. Simultaneously, LfcinB antagonizes catabolic factor mediated induction of multiple cartilage‐degrading enzymes, including MMP‐1, MMP‐3, MMP‐13, ADAMTS‐4, and ADAMTS‐5, in bovine NP cells at both mRNA and protein levels. LfcinB also suppresses the catabolic factor‐induced stimulation of oxidative and inflammatory factors such as iNOS, IL‐6, and toll‐like receptor‐2 (TLR‐2) and TLR‐4. Finally, the ability of LfcinB to antagonize IL‐1 and LPS‐mediated suppression of PG is upheld in an en bloc intradiscal microinjection model followed by ex vivo organ culture using both mouse and rabbit IVD tissue, suggesting a potential therapeutic benefit of LfcinB on degenerative disc disease in the future. J. Cell. Physiol. 228: 1884–1896, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
100.
Aleksandra Nowicka Frank C. Marini Travis N. Solley Paula B. Elizondo Yan Zhang Hadley J. Sharp Russell Broaddus Mikhail Kolonin Samuel C. Mok Melissa S. Thompson Wendy A. Woodward Karen Lu Bahar Salimian Deepak Nagrath Ann H. Klopp 《PloS one》2013,8(12)