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Byrne EM, McCarthy MA, Xia Z, Curtin WA. Multiwall nanotubes can be stronger than single wall nanotubes and implications for nanocomposite design. PHYSICAL REVIEW LETTERS 2009; 103:045502. [PMID: 19659369 DOI: 10.1103/physrevlett.103.045502] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2008] [Indexed: 05/28/2023]
Abstract
Molecular dynamics modeling shows that multiwall carbon nanotubes (MWCNTs) with sp;{3} interwall bonding have strengths exceeding those of single-wall carbon nanotubes (SWCNTs) containing the same size initial intrawall defect, and are far less sensitive to defect size. Thus, although processing methods used to increase interwall coupling also create intrawall defects, analyses here show that the strengthening effects and enhanced load transfer compensate for the creation of defects and make MWCNTs with interwall bonding preferable to SWCNTs as mechanical reinforcements in composites. These results are consistent with new experimental data and suggest a new design methodology for CNT-based composites.
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Gong K, Du F, Xia Z, Durstock M, Dai L. Nitrogen-Doped Carbon Nanotube Arrays with High Electrocatalytic Activity for Oxygen Reduction. Science 2009; 323:760-4. [DOI: 10.1126/science.1168049] [Citation(s) in RCA: 5907] [Impact Index Per Article: 393.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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79
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Qu L, Dai L, Stone M, Xia Z, Wang ZL. Carbon Nanotube Arrays with Strong Shear Binding-On and Easy Normal Lifting-Off. Science 2008; 322:238-42. [DOI: 10.1126/science.1159503] [Citation(s) in RCA: 616] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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80
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Xia Z, Murray D, Hulley PA, Triffitt JT, Price AJ. The viability and proliferation of human chondrocytes following cryopreservation. THE JOURNAL OF BONE AND JOINT SURGERY. BRITISH VOLUME 2008; 90:1245-8. [PMID: 18757968 PMCID: PMC2814295 DOI: 10.1302/0301-620x.90b9.20652] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Human articular cartilage samples were retrieved from the resected material of patients undergoing total knee replacement. Samples underwent automated controlled freezing at various stages of preparation: as intact articular cartilage discs, as minced articular cartilage, and as chondrocytes immediately after enzymatic isolation from fresh articular cartilage. Cell viability was examined using a LIVE/DEAD assay which provided fluorescent staining. Isolated chondrocytes were then cultured and Alamar blue assay was used for estimation of cell proliferation at days zero, four, seven, 14, 21 and 28 after seeding. The mean percentage viabilities of chondrocytes isolated from group A (fresh, intact articular cartilage disc samples), group B (following cryopreservation and then thawing, after initial isolation from articular cartilage), group C (from minced cryopreserved articular cartilage samples), and group D (from cryopreserved intact articular cartilage disc samples) were 74.7% (95% confidence interval (CI) 73.1 to 76.3), 47.0% (95% CI 43 to 51), 32.0% (95% CI 30.3 to 33.7) and 23.3% (95% CI 22.1 to 24.5), respectively. Isolated chondrocytes from all groups were expanded by the following mean proportions after 28 days of culturing: group A ten times, group B 18 times, group C 106 times, and group D 154 times. This experiment demonstrated that it is possible to isolate viable chondrocytes from cryopreserved intact human articular cartilage which can then be successfully cultured.
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81
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Xia Z, Zhou X, Yin Z, Sun Y, Wong S, Mao Y. Automated recognition of cellular phenotypes by support vector machines with feature reduction. INTERNATIONAL JOURNAL OF KNOWLEDGE-BASED AND INTELLIGENT ENGINEERING SYSTEMS 2007. [DOI: 10.3233/kes-2007-11407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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82
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Xia Z, Meng Q. Effects of different proportions of dietary structural
and nonstructural carbohydrates on ruminal
fermentation and microbial growth efficiency in
sheep. JOURNAL OF ANIMAL AND FEED SCIENCES 2007. [DOI: 10.22358/jafs/74492/2007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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83
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Lu L, Xia Z, Lin M, Wang X, Meng Q. Effects of dietary concentrate level on ruminal
fermentation and microbial growth efficiency in
dual flow continuous culture. JOURNAL OF ANIMAL AND FEED SCIENCES 2007. [DOI: 10.22358/jafs/74489/2007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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84
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Zou C, Liang X, Yang B, Liang K, Liu J, Xia Z, Zhao F, Wei S. Study on energy metabolism of dairy buffalo heifers
in Guangxi, China. JOURNAL OF ANIMAL AND FEED SCIENCES 2007. [DOI: 10.22358/jafs/74418/2007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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85
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Xia Z, Liu G, Gao Y, Fan Z, Fu Y, Zhang LF, Ren X, Gao C. FK506 in the treatment of children with nephrotic syndrome of different pathological types. Clin Nephrol 2007; 66:85-8. [PMID: 16939063 DOI: 10.5414/cnp66085] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVE To evaluate the efficacy of FK506 in the treatment of children with nephrotic syndrome of different underlying pathology. METHODS 12 patients were treated with FK506 with a dosage of 0.1 - 0.15 mg/kg/d while corticosteroid dose was tapered stepwise. This therapeutic course lasted 3 - 6 months during which the plasma concentration ofFK506 was monitored. RESULTS 12 children with different pathological types nephrotic syndrome were treated with FK506, including 4 cases of MCN, 6 cases of MsPGN, and 1 case of MPGN and 1 case of FSGS. After 2-month duration, 8 patients got complete remission including 4 cases of MCN and 4 cases of MsPGN and 3 children including 1 case of MsPGN, 1 case of MPGN, and 1 case of FSGS got partial remission. Only 1 child with MsPGN was considered to be a treatment failure. The overall response rate was 91.67% with the plasma concentration of FK506 maintained at 5 approximately 12 ng/ml, and the response time was 10 - 38 days. After 1-month duration, all patients except one experienced a reduction in proteinuria to normal levels or a partial response (50% reduction in protein excretion), significant increase in serum albumin, decrease in serum cholesterol and triglyceride and disappearance of edema. 2 months later, in 11 patients, blood biochemical values had returned to normal levels. The drug was generally well-tolerated. 3 patients had anorexia, nausea, vomiting. 2 patients experienced transient elevated serum creatinine which was reversible after the adjustment of dosage. 3 patients had minor changes in urine NAG. Only 2 of all patients relapsed. CONCLUSION FK506 is one of the effective immunosuppressants. In this study, FK506 in combination with a small doses of steroid while decreasing FK506 dosage plays a role in consolidating the curative effect and preventing relapse. In conclusion, FK506 may be effective in the treatment of nephrotic syndrome.
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Liu C, Xia Z, Czernuszka J. Design and Development of Three-Dimensional Scaffolds for Tissue Engineering. Chem Eng Res Des 2007. [DOI: 10.1205/cherd06196] [Citation(s) in RCA: 333] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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87
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Cai J, Yi FF, Yang XC, Lin GS, Jiang H, Wang T, Xia Z. Transplantation of embryonic stem cell-derived cardiomyocytes improves cardiac function in infarcted rat hearts. Cytotherapy 2007; 9:283-91. [PMID: 17464760 DOI: 10.1080/14653240701247838] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
BACKGROUND Post-infarct congestive heart failure is one of the leading causes of morbidity and mortality in industrialized countries. The main purpose of this study was to investigate whether transplantation of embryonic stem cell-derived cardiomyocytes (ESCM) directly into the infarcted myocardium could improve cardiac function in rats. METHODS Cell culture medium with or without ESCM was injected into the borders of cardiac scar tissue 1 week after experimental infarction. Cardiac performance was evaluated 4 weeks later by means of echocardiography after ESCM (n=16) or medium (n=12) injection. RESULTS ESCM implantation significantly improved fractional shortening (31.5+/-3. 8%) compared with medium-treated hearts (21.3+/-5.2%; P<0.05) and preserved left ventricular structure. Co-localization of 4',6-diamidino-2-phenylindole-labeled nuclei of transplanted cells with cardiomyocyte markers for cardiac troponin T and connexin-43, as detected by immunofluorescent microscopy, indicated the regeneration of damaged myocardium and the formation of gap junctions between grafted and host cells. However, intra-myocardial teratomas were observed in the hearts of two of the 16 grafted animals, at the fourth week after ESCM transplantation. DISCUSSION Our results suggest that, although ESCM implantation can improve the function of infarcted myocardium, strategies to prevent tumorigenesis should be developed.
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Mildvan A, Xia Z, Azurmendi H, Legler P, Balfour M, Lairson L, Withers S, Gabelli S, Bianchet M, Amzel L. Hydrogen bonding in the mechanism of GDP-mannose mannosyl hydrolase. J Mol Struct 2006. [DOI: 10.1016/j.molstruc.2005.09.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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89
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Park HK, Luhmann NC, Donné AJH, Classen IGJ, Domier CW, Mazzucato E, Munsat T, van de Pol MJ, Xia Z. Observation of high-field-side crash and heat transfer during sawtooth oscillation in magnetically confined plasmas. PHYSICAL REVIEW LETTERS 2006; 96:195003. [PMID: 16803107 DOI: 10.1103/physrevlett.96.195003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2005] [Indexed: 05/10/2023]
Abstract
High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study the crash process and heat transfer in magnetically confined toroidal plasmas. The combination of kink and local pressure driven instabilities leads to a small poloidally localized puncture in the magnetic surface at both the low and the high field sides of the poloidal plane. This observation closely resembles the "fingering event" of the ballooning mode model with the high- mode only predicted at the low field side.
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90
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Park HK, Donné AJH, Luhmann NC, Classen IGJ, Domier CW, Mazzucato E, Munsat T, van de Pol MJ, Xia Z. Comparison study of 2D images of temperature fluctuations during sawtooth oscillation with theoretical models. PHYSICAL REVIEW LETTERS 2006; 96:195004. [PMID: 16803108 DOI: 10.1103/physrevlett.96.195004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Indexed: 05/10/2023]
Abstract
High temporal and spatial resolution two-dimensional (2D) images of electron temperature fluctuations were employed to study the sawtooth oscillation in the Toroidal Experiment for Technically Oriented Research tokamak plasmas. The 2D images are directly compared with the expected 2D patterns of the plasma pressure (or electron temperature) from various theoretical models. The observed experimental 2D images are only partially in agreement with the expected patterns from each model: The image of the initial reconnection process is similar to that of the ballooning mode model. The intermediate and final stages of the reconnection process resemble those of the full reconnection model. The time evolution of the images of the hot spot or island is partially consistent to those from the full reconnection model but is not consistent with those from the quasi-interchange model.
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91
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Wang X, Liu H, Xia Z, Braby LA. Lineal energy as a function of site size for HZE radiation. RADIATION PROTECTION DOSIMETRY 2006; 122:367-8. [PMID: 17251253 DOI: 10.1093/rpd/ncl482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Monte Carlo calculations have been used to estimate the frequency and magnitude of energy deposition events produced by delta rays originating with high atomic number, high-energy, primary particles. The results show that the spectrum of delta rays incident on small targets is relatively insensitive to primary particle velocity or distance to the primary track. They suggest that measurements of energy deposition in different size sites can be used to characterise the velocity of the incident particle.
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Mildvan AS, Xia Z, Azurmendi HF, Saraswat V, Legler PM, Massiah MA, Gabelli SB, Bianchet MA, Kang LW, Amzel LM. Structures and mechanisms of Nudix hydrolases. Arch Biochem Biophys 2005; 433:129-43. [PMID: 15581572 DOI: 10.1016/j.abb.2004.08.017] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2004] [Revised: 08/16/2004] [Indexed: 12/12/2022]
Abstract
Nudix hydrolases catalyze the hydrolysis of nucleoside diphosphates linked to other moieties, X, and contain the sequence motif or Nudix box, GX(5)EX(7)REUXEEXGU. The mechanisms of Nudix hydrolases are highly diverse in the position on the substrate at which nucleophilic substitution occurs, and in the number of required divalent cations. While most proceed by associative nucleophilic substitutions by water at specific internal phosphorus atoms of a diphosphate or polyphosphate chain, members of the GDP-mannose hydrolase sub-family catalyze dissociative nucleophilic substitutions, by water, at carbon. The site of substitution is likely determined by the positions of the general base and the entering water. The rate accelerations or catalytic powers of Nudix hydrolases range from 10(9)- to 10(12)-fold. The reactions are accelerated 10(3)-10(5)-fold by general base catalysis by a glutamate residue within, or beyond the Nudix box, or by a histidine beyond the Nudix box. Lewis acid catalysis, which contributes 10(3)-10(5)-fold to the rate acceleration, is provided by one, two, or three divalent cations. One divalent cation is coordinated by two or three conserved residues of the Nudix box, the initial glycine and one or two glutamate residues, together with a remote glutamate or glutamine ligand from beyond the Nudix box. Some Nudix enzymes require one (MutT) or two additional divalent cations (Ap(4)AP), to neutralize the charge of the polyphosphate chain, to help orient the attacking hydroxide or oxide nucleophile, and/or to facilitate the departure of the anionic leaving group. Additional catalysis (10-10(3)-fold) is provided by the cationic side chains of lysine and arginine residues and by H-bond donation by tyrosine residues, to orient the general base, or to promote the departure of the leaving group. The overall rate accelerations can be explained by both independent and cooperative effects of these catalytic components.
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93
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Lavertu M, Xia Z, Serreqi AN, Berrada M, Rodrigues A, Wang D, Buschmann MD, Gupta A. A validated 1H NMR method for the determination of the degree of deacetylation of chitosan. J Pharm Biomed Anal 2003; 32:1149-58. [PMID: 12907258 DOI: 10.1016/s0731-7085(03)00155-9] [Citation(s) in RCA: 426] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A method for the determination of the degree of deacetylation (DDA) of chitosan by 1H NMR spectroscopy has been formally validated. Chitosans with DDA ranging from 48 to 100% have been used for the validation. The method is found to be simple, rapid and more precise than other known techniques like IR or titration for %DDA measurements. The precision, ruggedness, robustness, specificity, stability and accuracy of the technique are discussed in this paper.
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Triffitt JT, Oreffo RO, Virdi AS, Xia Z. Osteogenic stem-cell characterization and development: potentials for cytotherapy. Cytotherapy 2003; 3:413-6. [PMID: 11953025 DOI: 10.1080/146532401753277760] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
BACKGROUND Primitive progenitors of bone tissue exist postnatally and exhibit stem-cell characteristics, as shown by extensive renewal potential, and capacity to differentiate into all characteristic connective tissue types, including bone, cartilage, fat, fibrous tissue, muscle and hemopoietic stroma. METHODS A wide variety of investigative techniques have been applied to characterize and assess differentiation of the normally non-cycling osteogenic stem cells. These include methods to assess in vitro and in vivo differentiation potentials, the production and use of Abs to identify surface markers, the expression of specific genes and, more recently, incorporation of marker genes (beta-galactosidase, green fluorescent protein) to study cell fate after implantation at tissue sites. RESULTS Some antigenic cell-surface molecules reactive with MAbs generated by a number of laboratories have been identified. For cell-fate studies, retroviral insertion of beta-galactosidase or green fluorescent protein genes into human marrow stromal progenitors has been accomplished with high efficiency. The stromal cell phenotype and cellular functions in vitro are not significantly altered by these genetic modifications. In vivo transplantation in immunodeficient animals demonstrates migration and persistence of marrow stromal cells to skeletal and other tissue sites. DISCUSSION None of the Abs generated against surface markers of early progenitors are absolutely lineage and cell-stage specific, but the respective Ags appear to participate in cell adhesion and cell-signalling mechanisms. These may be important in stem-cell activation and subsequent early osteogenic development. Studies of cell fate indicate feasibility for future uses in therapy of bone deficiency diseases and the potential for development of gene therapy procedures in these and other conditions.
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Xia Z, Hufeisen SJ, Gray JA, Roth BL. The PDZ-binding domain is essential for the dendritic targeting of 5-HT2A serotonin receptors in cortical pyramidal neurons in vitro. Neuroscience 2003; 122:907-20. [PMID: 14643760 DOI: 10.1016/s0306-4522(03)00589-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The 5-HT(2A) serotonin receptor represents an important molecular target for atypical antipsychotic drugs and for most hallucinogens. In the mammalian cerebral cortex, 5-HT(2A) receptors are enriched in pyramidal neurons, within which 5-HT(2A) receptors are preferentially sorted to the apical dendrites. In primary cortical cultures, 5-HT(2A) receptors are sorted to dendrites and not found in the axons of pyramidal neurons. We identified a sorting motif that mediates the preferential targeting of 5-HT(2A) receptors to the dendrites of cortical pyramidal neurons in vitro. We constructed green fluorescent protein-tagged 5-HT(2A) receptors wherein potential sorting motifs were disrupted, and subsequently employed either the Semliki Forest virus or calcium phosphate for the transient expression of recombinant 5-HT(2A) receptors in cultured cortical pyramidal neurons. Using dual-labeling immunofluorescent confocal microscopy, we quantified the axonal and dendritic sorting patterns of endogenous and recombinant 5-HT(2A) receptors. We discovered that disruption of the PDZ-binding domain of the 5-HT(2A) receptor greatly attenuates the dendritic targeting of 5-HT(2A) receptors without inappropriately sorting 5-HT(2A) receptors to axons. The PDZ-binding domain is therefore a necessary signal for the preferential targeting of the 5-HT(2A) receptor to the dendritic compartment of cultured cortical pyramidal neurons, the first such role ascribed to this protein-protein interaction motif of any G protein-coupled receptor.
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Xia Z, Mao X, Luo Y. [Study on antifungal mechanism of alpha-pinene]. HUNAN YI KE DA XUE XUE BAO = HUNAN YIKE DAXUE XUEBAO = BULLETIN OF HUNAN MEDICAL UNIVERSITY 2002; 24:507-9. [PMID: 12080706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
The antifungal mechanism of alpha-pinene was studied using electronic microscopy and incorporation of isotope-labelled precursor. The results demonstrated that alpha-pinene had significant roles in inhibiting and killing Candida albicans. After treatment with alpha-pinene the fungal morphology and ultrastructure showed obvious changes: their cell wall and cytoplasmic membrane ruptured; intracellular components released out and the cell residue fused to form irregular masses. In addition, the synthesis of DNA, RNA, polysaccharide of cell wall and ergosterol of cytoplasmic membrane was inhibited. It is indicated that these changes are related to antifungal mechanism of alpha-pinene.
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Mabuchi T, Kitagawa K, Kuwabara K, Takasawa K, Ohtsuki T, Xia Z, Storm D, Yanagihara T, Hori M, Matsumoto M. Phosphorylation of cAMP response element-binding protein in hippocampal neurons as a protective response after exposure to glutamate in vitro and ischemia in vivo. J Neurosci 2001; 21:9204-13. [PMID: 11717354 PMCID: PMC6763920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023] Open
Abstract
Although accumulating evidence indicates that cAMP response element-binding protein (CREB) phosphorylation mediates not only synaptic plasticity but also survival of certain neurons, it remains uncertain whether CREB phosphorylation induced after metabolic insult leads to CRE-mediated gene transcription and is involved in cell survival or not. In the present study, we clarified that (1) CREB phosphorylation and ischemic tolerance induced after preconditioning ischemia in the hippocampal neurons was abolished by MK801 administration in gerbil global ischemia model, (2) CREB phosphorylation induced after exposure to glutamate in cultured neurons was inhibited by removal of extracellular calcium, by MK801 and by an inhibitor of calcium-calmodulin-dependent protein kinase (CaMK) II and IV, (3) inhibitor of CaMK II-IV or CRE-decoy oligonucleotide suppressed upregulation of BCL-2 expression and accelerated neuronal damage after exposure to glutamate, and (4) CREB phosphorylation induced in the hippocampal neurons after ischemia and in cultured neurons after exposure to glutamate was followed by CRE-mediated gene transcription in transgenic mice with a CRE-LacZ reporter. Our results suggest that CREB phosphorylation in neurons after ischemia and exposure to glutamate is induced by NMDA receptor-gated calcium influx and subsequent activation of CaMK II-IV and that CREB phosphorylation after metabolic stress might show a neuroprotective response through CRE-mediated gene induction.
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Vonderheide RH, Schultze JL, Anderson KS, Maecker B, Butler MO, Xia Z, Kuroda MJ, von Bergwelt-Baildon MS, Bedor MM, Hoar KM, Schnipper DR, Brooks MW, Letvin NL, Stephans KF, Wucherpfennig KW, Hahn WC, Nadler LM. Equivalent induction of telomerase-specific cytotoxic T lymphocytes from tumor-bearing patients and healthy individuals. Cancer Res 2001; 61:8366-70. [PMID: 11731409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Although high frequencies of T lymphocytes specific for certain tumor-associated antigens have been detected in some cancer patients, increasing evidence suggests that these T cells may be functionally defective in vivo and fail to induce meaningful clinical responses. One strategy to overcome this limitation is to target novel antigens that are ignored during the natural antitumor immune response but are nevertheless capable of triggering effector T-cell responses against tumors after optimal presentation by antigen-presenting cells. Here, we show that the telomerase catalytic subunit (hTERT)-a nearly universal tumor antigen identified by epitope deduction rather than from patient immune responses-is immunologically ignored by patients despite progressive tumor burden. Nevertheless, HLA-A2-restricted CTLs against hTERT are equivalently induced ex vivo from patients and healthy individuals and efficiently kill human tumor cell lines and primary tumors. Thus, telomerase-specific T cells from cancer patients are spared functional inactivation because of immunological ignorance. These findings support clinical efforts to target the hTERT as a tumor antigen with broad therapeutic potential.
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Xia Z, Tian J, Tang H, Wang G. [A study on the myocardial contractile function and intracellular free calcium in scalded rats]. ZHONGHUA SHAO SHANG ZA ZHI = ZHONGHUA SHAOSHANG ZAZHI = CHINESE JOURNAL OF BURNS 2001; 17:342-4. [PMID: 11859610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
OBJECTIVE To explore the relationship between postburn myocardial function and intracellular free calcium concentration. METHODS Sprague-Dawley (SD) rats were employed as the model in which 7 were inflicted with 43% TBSA degree scalding (S group) and 7 as sham scalding control group (C group). The hearts of the injured rats were isolated and perfused in vitro by Langendorff method after 24 postburn hours (PBHs). The hearts were connected to a cardiac function monitor, and the dynamic changes in left ventricular develop pressure (LVDP) were continuously monitored. The cardiac 19F and 31P NMR spectroscopy was determined before and after and TF-BAPTA was added to the perfusate. RESULTS When compared with those in C group, the LVDP of scalded rat heart decreased by 40% (P < 0.01), and the myocardial cytoplasmic free calcium concentration was four times above that in C group (P < 0.01). After TF-BAPTA was taken by myocytes, cardiac LVDP only decreased by 15% to 20%, and the PCr/Pi ratio decreased, while there was no change in ATP. CONCLUSION Myocardial contractile function could be inhibited after burn injury, which might be related to the increase of myocardial cytoplasmic free calcium concentration.
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Kwon YT, Xia Z, Davydov IV, Lecker SH, Varshavsky A. Construction and analysis of mouse strains lacking the ubiquitin ligase UBR1 (E3alpha) of the N-end rule pathway. Mol Cell Biol 2001; 21:8007-21. [PMID: 11689692 PMCID: PMC99968 DOI: 10.1128/mcb.21.23.8007-8021.2001] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The N-end rule relates the in vivo half-life of a protein to the identity of its N-terminal residue. In the yeast Saccharomyces cerevisiae, the UBR1-encoded ubiquitin ligase (E3) of the N-end rule pathway mediates the targeting of substrate proteins in part through binding to their destabilizing N-terminal residues. The functions of the yeast N-end rule pathway include fidelity of chromosome segregation and the regulation of peptide import. Our previous work described the cloning of cDNA and a gene encoding the 200-kDa mouse UBR1 (E3alpha). Here we show that mouse UBR1, in the presence of a cognate mouse ubiquitin-conjugating (E2) enzyme, can rescue the N-end rule pathway in ubr1Delta S. cerevisiae. We also constructed UBR1(-/-) mouse strains that lacked the UBR1 protein. UBR1(-/-) mice were viable and fertile but weighed significantly less than congenic +/+ mice. The decreased mass of UBR1(-/-) mice stemmed at least in part from smaller amounts of the skeletal muscle and adipose tissues. The skeletal muscle of UBR1(-/-) mice apparently lacked the N-end rule pathway and exhibited abnormal regulation of fatty acid synthase upon starvation. By contrast, and despite the absence of the UBR1 protein, UBR1(-/-) fibroblasts contained the N-end rule pathway. Thus, UBR1(-/-) mice are mosaics in regard to the activity of this pathway, owing to differential expression of proteins that can substitute for the ubiquitin ligase UBR1 (E3alpha). We consider these UBR1-like proteins and discuss the functions of the mammalian N-end rule pathway.
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