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Tanatar MA, Reid JP, Shakeripour H, Luo XG, Doiron-Leyraud N, Ni N, Bud'ko SL, Canfield PC, Prozorov R, Taillefer L. Doping dependence of heat transport in the iron-arsenide superconductor Ba(Fe(1-x)Co(x))2As2: from isotropic to a strongly k-dependent gap structure. PHYSICAL REVIEW LETTERS 2010; 104:067002. [PMID: 20366850 DOI: 10.1103/physrevlett.104.067002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Revised: 12/18/2009] [Indexed: 05/29/2023]
Abstract
The temperature and magnetic field dependence of the in-plane thermal conductivity kappa of the iron-arsenide superconductor Ba(Fe(1-x)Co(x))2As2 was measured down to T approximately 50 mK and up to H = 15 T as a function of Co concentration x in the range 0.048 < or = x < or = 0.114. At H = 0, a negligible residual linear term in kappa/T as T-->0 at all x shows that the superconducting gap has no nodes in the ab plane anywhere in the phase diagram. However, while the slow H dependence of kappa(H) at T-->0 in the underdoped regime is consistent with a superconducting gap that is large everywhere on the Fermi surface, the rapid increase in kappa(H) observed in the overdoped regime shows that the gap acquires a deep minimum somewhere on the Fermi surface. Outside the antiferromagnetic-orthorhombic phase, the superconducting gap structure has a strongly k-dependent amplitude.
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102
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Nandi S, Kim MG, Kreyssig A, Fernandes RM, Pratt DK, Thaler A, Ni N, Bud'ko SL, Canfield PC, Schmalian J, McQueeney RJ, Goldman AI. Anomalous suppression of the orthorhombic lattice distortion in superconducting Ba(Fe1-xCox)2As2 single crystals. PHYSICAL REVIEW LETTERS 2010; 104:057006. [PMID: 20366790 DOI: 10.1103/physrevlett.104.057006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Indexed: 05/29/2023]
Abstract
High-resolution x-ray diffraction measurements reveal an unusually strong response of the lattice to superconductivity in Ba(Fe1-xCox)2As2. The orthorhombic distortion of the lattice is suppressed and, for Co doping near x=0.063, the orthorhombic structure evolves smoothly back to a tetragonal structure. We propose that the coupling between orthorhombicity and superconductivity is indirect and arises due to the magnetoelastic coupling, in the form of emergent nematic order, and the strong competition between magnetism and superconductivity.
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Yang J, Yuan H, Liu W, Song C, Xu H, Wang G, Song C, Ni N, Yang D, Lin B. Arginine vasopressin in hypothalamic paraventricular nucleus is transferred to the nucleus raphe magnus to participate in pain modulation. Peptides 2009; 30:1679-82. [PMID: 19520128 DOI: 10.1016/j.peptides.2009.05.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 05/29/2009] [Accepted: 05/30/2009] [Indexed: 11/16/2022]
Abstract
Hypothalamic paraventricular nucleus (PVN) is one of the main sources of arginine vasopressin (AVP) synthesis and secretion. AVP is the most important bioactive substance in PVN regulating pain process. Our previous study has pointed that pain stimulation induced AVP increase in the nucleus raphe magnus (NRM), which plays a role in pain modulation. The present study was designed to investigate the source of AVP in the rat NRM during pain process using the methods of nucleus push-pull perfusion and radioimmunoassay. The results showed that pain stimulation increased the AVP concentration in the NRM perfusion liquid, PVN cauterization inhibited the role that pain stimulation induced the increase of AVP concentration in the NRM perfusion liquid, and PVN microinjection of L-glutamate sodium, which excited the PVN neurons, could increase the AVP concentration in the NRM perfusion liquid. The data suggested that AVP in the PVN might be transferred to the NRM to participate in pain modulation.
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104
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Pratt DK, Tian W, Kreyssig A, Zarestky JL, Nandi S, Ni N, Bud'ko SL, Canfield PC, Goldman AI, McQueeney RJ. Coexistence of competing antiferromagnetic and superconducting phases in the underdoped Ba(Fe0.953Co0.047)2As2 compound using x-ray and neutron scattering techniques. PHYSICAL REVIEW LETTERS 2009; 103:087001. [PMID: 19792748 DOI: 10.1103/physrevlett.103.087001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Indexed: 05/28/2023]
Abstract
Neutron and x-ray diffraction studies show that the simultaneous first-order transition to an orthorhombic and antiferromagnetic (AFM) ordered state in BaFe2As2 splits into two transitions with Co doping. For Ba(Fe0.953Co0.047)2As2, a tetragonal-orthorhombic transition occurs at TS=60 K, followed by a second-order transition to AFM order at TN=47 K. Superconductivity occurs in the orthorhombic state below TC=17 K and coexists with AFM. Below TC, the static Fe moment is reduced along with a redistribution of low energy magnetic excitations indicating competition between coexisting superconductivity and AFM order.
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Chen J, Nikolaitchik O, Singh J, Wright A, Bencsics CE, Coffin JM, Ni N, Lockett S, Pathak VK, Hu WS. High efficiency of HIV-1 genomic RNA packaging and heterozygote formation revealed by single virion analysis. Proc Natl Acad Sci U S A 2009; 106:13535-40. [PMID: 19628694 PMCID: PMC2714765 DOI: 10.1073/pnas.0906822106] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Indexed: 11/18/2022] Open
Abstract
A long-standing question in retrovirus biology is how RNA genomes are distributed among virions. In the studies presented in this report, we addressed this issue by directly examining HIV-1 RNAs in virions using a modified HIV-1 genome that contained recognition sites for BglG, an antitermination protein in the Escherichia coli bgl operon, which was coexpressed with a fragment of BglG RNA binding protein fused to a fluorescent protein. Our results demonstrate that the majority of virions (>90%) contain viral RNAs. We also coexpressed HIV-1 genomes containing binding sites for BglG or the bacteriophage MS2 coat protein along with 2 fluorescent protein-tagged RNA binding proteins. This method allows simultaneously labeling and discrimination of 2 different RNAs at single-RNA-detection sensitivity. Using this strategy, we obtained physical evidence that virions contain RNAs derived from different parental viruses (heterozygous virion) at ratios expected from a random distribution, and we found that this ratio can be altered by changing the dimerization sequences. Our studies of heterozygous virions also support a generally accepted but unproven assumption that most particles contain 1 dimer. This study provides answers to long-standing questions in HIV-1 biology and illustrates the power and sensitivity of the 2-RNA labeling method, which can also be adapted to analyze various issues of RNA biogenesis including the detection of different RNAs in live cell imaging.
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106
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Yang J, Yuan HF, Liu WY, Zhang XX, Feng JP, Ni N, Yang DW, Song CY, Xu HT, Wang G, Song C, Lin BC. Norepinephrine regulates arginine vasopressin secretion in hypothalamic paraventricular nucleus relating with pain modulation. Neuropeptides 2009; 43:259-65. [PMID: 19573913 DOI: 10.1016/j.npep.2009.06.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 06/06/2009] [Accepted: 06/08/2009] [Indexed: 11/28/2022]
Abstract
Our previous study has pointed that arginine vasopressin (AVP) and norepinephrine (NA) are two most important bioactive substances that play a role in hypothalamic paraventricular nucleus (PVN) regulating pain process. The communication was designed to investigate the interaction between AVP and NA in the rat PVN during the pain process. We used the potassium iontophoresis inducing tail-flick to test the pain threshold, PVN push-pull perfusion to collect the samples, high performance chromatography (HPLC) to determine the NA concentration and radioimmunoassay (RIA) to measure the AVP concentration. The results showed that (1) pain stimulation increased both NA and AVP concentrations in the PVN perfusion liquid; (2) PVN administration of l-glutamate sodium increased AVP, not NA concentration in the PVN perfusion liquid; (3) AVP or d(CH(2))(5)Tyr(Et)DAVP (AVP-receptor antagonist) neither changed pain threshold, nor influenced NA concentration in the PVN perfusion liquid; (4) Microinjection of NA into PVN could increase pain threshold in a dose-dependent manner, while PVN administration with phentolamine (alpha-receptor antagonist), not propranolol (beta-receptor antagonist) decreased pain threshold; (5) Administration of NA increased AVP concentration, while phentolamine, not propranolol decreased AVP concentration in the PVN perfusion liquid. These data suggested that it is through alpha-receptor rather than beta-receptor, NA induced PVN secretion of AVP that was delivered to the related brain regions to participate in pain modulation.
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Yang J, Hüvonen D, Nagel U, Rõõm T, Ni N, Canfield PC, Bud'ko SL, Carbotte JP, Timusk T. Optical spectroscopy of superconducting Ba0.55K0.45Fe2As2: evidence for strong coupling to low-energy bosons. PHYSICAL REVIEW LETTERS 2009; 102:187003. [PMID: 19518902 DOI: 10.1103/physrevlett.102.187003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Indexed: 05/27/2023]
Abstract
Normal state optical spectroscopy on single crystals of the new iron arsenide superconductor Ba0.55K0.45Fe2As2 shows that the infrared spectrum consists of two major components: a strong metallic Drude band and a well-separated midinfrared absorption centered at 0.7 eV. It is difficult to separate the two components unambiguously but several fits using Lorentzian peaks suggest a model with a Drude peak having a plasma frequency of 1.6 to 2.1 eV and a midinfrared peak with a plasma frequency of 2.5 eV. Detailed analysis of the frequency dependent scattering rate shows that the charge carriers interact with a broad bosonic spectrum extending beyond 100 meV with a very large coupling constant lambda=3.4 at low temperature. As the temperature increases this coupling weakens to lambda=0.78 at ambient temperature. This suggests a bosonic spectrum that is similar to what is seen in the lower Tc cuprates.
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Diallo SO, Antropov VP, Perring TG, Broholm C, Pulikkotil JJ, Ni N, Bud'ko SL, Canfield PC, Kreyssig A, Goldman AI, McQueeney RJ. Itinerant magnetic excitations in antiferromagnetic CaFe2As2. PHYSICAL REVIEW LETTERS 2009; 102:187206. [PMID: 19518910 DOI: 10.1103/physrevlett.102.187206] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Indexed: 05/27/2023]
Abstract
Neutron scattering measurements of the magnetic excitations in single crystals of antiferromagnetic CaFe2As2 reveal steeply dispersive and well-defined spin waves up to an energy of approximately 100 meV. Magnetic excitations above 100 meV and up to the maximum energy of 200 meV are however broader in energy and momentum than the experimental resolution. While the low energy modes can be fit to a Heisenberg model, the total spectrum cannot be described as arising from excitations of a local moment system. Ab initio calculations of the dynamic magnetic susceptibility suggest that the high energy behavior is dominated by the damping of spin waves by particle-hole excitations.
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Ridge KM, Litvan J, Ni N. Mitochondrial reactive oxygen species are required for hypoxia‐induced degradation of keratin intermediate filaments. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.997.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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110
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Gordon RT, Ni N, Martin C, Tanatar MA, Vannette MD, Kim H, Samolyuk GD, Schmalian J, Nandi S, Kreyssig A, Goldman AI, Yan JQ, Bud'ko SL, Canfield PC, Prozorov R. Unconventional London penetration depth in single-crystal Ba(Fe0.93Co0.07)2As2 superconductors. PHYSICAL REVIEW LETTERS 2009; 102:127004. [PMID: 19392314 DOI: 10.1103/physrevlett.102.127004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2008] [Indexed: 05/27/2023]
Abstract
The London penetration depth lambda(T) has been measured in single crystals of Ba(Fe0.93Co0.07)2As2. The observed low-temperature variation of lambda(T) follows a power law, Deltalambda(T) approximately T(n) with n approximately 2.4+/-0.1, indicating the existence of normal quasiparticles down to at least 0.02T(c). This is in contrast with previous penetration depth measurements on single crystals of NdFeAsO1-xFx and SmFeAsO1-xFx, which indicate an anisotropic but nodeless gap. We discuss possible explanations of the observed power law behavior.
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Ni N, Mojibian H, Pollak J, Tal M. Abstract No. 88: Outcomes of Fibrin Sheath Stripping Versus Catheter Exchange of Malfunctioning Tunneled Hemodialysis Catheters. J Vasc Interv Radiol 2009. [DOI: 10.1016/j.jvir.2008.12.078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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112
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McQueeney RJ, Diallo SO, Antropov VP, Samolyuk GD, Broholm C, Ni N, Nandi S, Yethiraj M, Zarestky JL, Pulikkotil JJ, Kreyssig A, Lumsden MD, Harmon BN, Canfield PC, Goldman AI. Anisotropic three-dimensional magnetism in CaFe2As2. PHYSICAL REVIEW LETTERS 2008; 101:227205. [PMID: 19113520 DOI: 10.1103/physrevlett.101.227205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Indexed: 05/27/2023]
Abstract
Inelastic neutron scattering measurements of the magnetic excitations in CaFe2As2 indicate that the spin wave velocity in the Fe layers is exceptionally large and similar in magnitude to the cuprates. However, the spin wave velocity perpendicular to the layers is at least half as large that in the layer, so that the magnetism is more appropriately categorized as anisotropic three-dimensional, in contrast to the two-dimensional cuprates. Exchange constants derived from band structure calculations predict spin wave velocities that are consistent with the experimental data.
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Ni N, Feng XP, Ye W. [Preliminary study of the clinical indices for halitosis]. SHANGHAI KOU QIANG YI XUE = SHANGHAI JOURNAL OF STOMATOLOGY 2007; 16:136-9. [PMID: 17546378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
PURPOSE To explore the possibility of using other clinical indices to detect halitosis in stead of organoleptic test(OST). MEATHODS: 56 medical students were chosen as the subjects. Spearman test and Pearson test were used to analyze the relationship between OST results and other indices. RESULTS It was found that the value of volatile sulfur compounds (VSC) (r(Max)=0.537,P<0.01) rStable=0.572,P<0.01), pH of the saliva(r=0.344,P<0.01), cadaverine (r=0.352,P<0.01), OHI-S (r=0.323,P<0.05), colonies of facultative anaerobe from saliva(r=0.398,P<0.01) and tongue dorsum(r=0.293,P<0.05), colonies of anaerobe from tongue dorsum(r=0.473,P<0.01) correlated positively with OST score, but the coefficients were all low. CONCLUSION It is not practical and feasible to replace OST with any other single index at present.
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Ni N, Xu W, Morrow CD. Importance of A-loop complementarity with tRNAHis anticodon for continued selection of tRNAHis as the HIV reverse transcription primer. Virol J 2007; 4:4. [PMID: 17214904 PMCID: PMC1785369 DOI: 10.1186/1743-422x-4-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2006] [Accepted: 01/10/2007] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Human immunodeficiency virus (HIV-1) preferentially selects tRNALys,3 as the primer for reverse transcription. HIV-1 can be forced to select alternative tRNAs through mutation in the primer-binding site (PBS) and a region upstream of the PBS designated as the A-loop. Alteration of the PBS and A-loop to be complementary to the 3' terminal nucleotides and anticodon of tRNAHis results in HIV-1 that can stably utilize this tRNA for replication. RESULTS In the current study, we have investigated the effect that mutations within the A-loop have on the stability of HIV-1 with a PBS complementary to tRNAHis. For these studies, we have altered the A-loop to be complementary to tRNAMet, tRNAGln, tRNAIle, tRNAThr and tRNASer. All substitutions of the A-loops with the PBS complementary to tRNAHis resulted in a reduction of infectious virus obtained following transfection of proviral genomes in the 293T cells. Virus replication in SupT1 cells was also impaired as a result of the alteration of the A-loop. Viruses with the A-loop complementary to tRNALys,3 and tRNASer reverted to utilize tRNALys,3 following in vitro replication. In contrast, viruses with the A-loop complementary to the other tRNAs remained stable and continued to use tRNAHis. RNA modeling of the stem-loop structure revealed that nucleotides were displayed on the loop region that could potentially interact with the anticodon of tRNAHis. To further explore the effects of the A-loop mutations on virus replication, the A-loops complementary to tRNASer or tRNAHis were cloned into the wild type genome with the PBS complementary to tRNALys,3. Transfection of proviral genomes which contained the wild type PBS and A-loops complementary to tRNASer or tRNAHis into 293 T cells did not impact on the production of viruses as measured by p24 antigen ELISA. However, viruses with the A-loop complementary to tRNAHis had greatly reduced infectivity and replicated poorly in SupT1 compared to the wild type or viruses with the A-loop complementary to tRNASer. CONCLUSION These studies demonstrate that complementarity of A-loop region with the anticodon of tRNAHis has a pronounced effect on the capacity of HIV-1 to utilize tRNAHis as the primer for reverse transcription. Complementarity between A-loop and anticodon of the tRNA then is important for the selection of the tRNA primer used for reverse transcription.
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Ni N, Morrow CD. Forced primer selection modulates HIV-1 replication and stability of the PBS. Retrovirology 2006. [PMCID: PMC1716866 DOI: 10.1186/1742-4690-3-s1-p45] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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116
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Ni N, Morrow CD. Impact of forced selection of tRNAs on HIV-1 replication and genome stability highlight preferences for selection of certain tRNAs. Virus Res 2006; 124:29-37. [PMID: 17070952 PMCID: PMC1847643 DOI: 10.1016/j.virusres.2006.09.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Revised: 09/22/2006] [Accepted: 09/25/2006] [Indexed: 01/19/2023]
Abstract
Human immunodeficiency virus (HIV-1) exclusively selects tRNA(Lys,3) as the primer for initiation of reverse transcription. How and why HIV-1 selects the tRNA is unresolved. To address this issue, we have generated HIV-1 in which the PBS was changed to be complementary to alternative tRNAs. In this study, we report on HIV-1 that have the PBS mutated to be complementary to tRNA(Thr), tRNA(Phe), tRNA(Ser) and tRNA(Tyr). Virus with a PBS complementary to tRNA(Thr) grew slightly slower than the wild type virus and maintained the PBS for an extended culture period before finally reverting back to utilize tRNA(Lys,3). In contrast, viruses with a PBS complementary to tRNA(Phe) or tRNA(Ser) rapidly reverted to utilize tRNA(Lys,3) following limited in vitro replication, while a virus with a PBS complementary to tRNA(Tyr) had severely compromised infectivity and did not productively infect a continuous T cell line (SupT1) or human peripheral blood mononuclear cells (PBMC). Modification of the A-loop region to be complementary to tRNA(Thr) with the mutation in the PBS to be complementary to tRNA(Thr) resulted in a virus that could stably utilize this tRNA while the modification of the A-loop to be complementary to the anticodon of tRNA(Ser) did not allow the virus to stably utilize tRNA(Ser). Modification of the A-loop region to be complementary to the anticodon of tRNA(Phe) severely impacted the replication of this virus. Finally, the modification of the A-loop region to be complementary to tRNA(Tyr) did not rescue the virus with a PBS complementary to tRNA(Tyr). The results of these studies demonstrate the diverse effects that alteration of the PBS to force selection of alternative primers have on HIV-1 replication and provide a framework to understand the dynamics of primer selection.
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Li M, Eipers PG, Ni N, Morrow CD. HIV-1 designed to use different tRNAGln isoacceptors prefers to select tRNAThr for replication. Virol J 2006; 3:80. [PMID: 17002807 PMCID: PMC1592299 DOI: 10.1186/1743-422x-3-80] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2006] [Accepted: 09/26/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Previous studies have shown that infection with human immunodeficiency virus type 1 (HIV-1) causes acceleration of the synthesis of glutamine tRNA (tRNAGln) in infected cells. To investigate whether this might influence HIV-1 to utilize tRNAGln as a primer for initiation of reverse transcription, we have constructed HIV-1 proviral genomes in which the PBS and the A-loop region upstream of the PBS have been made complementary to either the anticodon region of tRNAGln,1 or tRNAGln,3 and 3' terminal 18 nucleotides of each isoacceptor of tRNAGln. RESULTS Viruses in which the PBS was altered to be complementary to tRNAGln,1 or tRNAGln,3 with or without the A-loop all exhibited a lower infectivity than the wild type virus. Viruses with only the PBS complementary to tRNAGln,1 or tRNAGln,3 reverted to wild type following culture in SupT1 cells. Surprisingly, viruses in which the PBS and A-loop were complementary to tRNAGln,1 did not grow in SupT1 cells, while viruses in which the PBS and A-loop were made complementary to tRNAGln,3 grew slowly in SupT1 cells. Analysis of the PBS of this virus revealed that it had reverted to select tRNAThr as the primer, which shares complementarity in 15 of 18 nucleotides with the PBS complementary to tRNAGln,3. CONCLUSION The results of these studies support the concept that the HIV-1 has preferred tRNAs that can be selected as primers for replication.
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Ni N, Kevil CG, Bullard DC, Kucik DF. Avidity modulation activates adhesion under flow and requires cooperativity among adhesion receptors. Biophys J 2004; 85:4122-33. [PMID: 14645099 PMCID: PMC1303711 DOI: 10.1016/s0006-3495(03)74824-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
An early step in activation of leukocyte adhesion is a release of integrins from cytoskeletal constraints on their diffusion, leading to rearrangement and, consequently, increased avidity. Static adhesion assays using purified ligand as a substrate have demonstrated that very low doses of cytochalasin D disconnect beta2-integrins from their cytoskeletal links, allowing rearrangement and activating adhesion. The adhesion process in blood vessels is poorly simulated by these assays, however, for two reasons: leukocyte adhesion to endothelium 1), occurs in the presence of blood flow and 2), involves the simultaneous interactions of multiple sets of adhesion molecules. We investigated the effect of cytochalasin D, at concentrations that increase integrin diffusion but do not alter leukocyte shape and surface features, on adhesion of leukocytes to endothelial cells under flow. Cytochalasin D increased the number of rolling cells, the number of firmly adherent cells, and the duration of both rolling and firm adhesion. These effects required endothelial cell expression of ICAM-1, the ligand for leukocyte beta2-integrins. The beta2-integrin-ICAM-1 interaction alone was not sufficient, however. Experiments using purified substrates demonstrated that avidity effects on activation of adhesion under flow require functional cooperativity between integrins and other adhesion receptors.
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Fan Z, Wang Y, Ni N, Bu H. Melting Behavior and Morphology of Freeze-Dried Ultra-high Molar Mass Polyethylene. J MACROMOL SCI B 2003. [DOI: 10.1081/mb-120015755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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121
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Ni N, Tesconi M, Tabibi SE, Gupta S, Yalkowsky SH. Use of pure t-butanol as a solvent for freeze-drying: a case study. Int J Pharm 2001; 226:39-46. [PMID: 11532568 DOI: 10.1016/s0378-5173(01)00757-8] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
1-(2-Chloroethyl)-3-sarcosinamide-1-nitrosourea, (SarCNU) (NSC-364432) is a new antitumor drug that is of interest to the National Cancer Institute. It is intended for use as an intravenous injection. Although SarCNU is sufficiently soluble in water to obtain the desired dosage, it is highly unstable. Its T(90) in aqueous solution at room temperature is less than 6 h. Neat tertiary butyl alcohol (TBA), a low toxicity, high vapor pressure and low melting solvent, was determined to be an excellent freeze-drying medium. Lyophilization of SarCNU from pure TBA produces a uniform cake composed of needle-shaped crystals. Thermal analysis and gas chromatography indicate that the cake contains less than 0.001% residual solvent. The SarCNU cake can be readily reconstituted with either water or an aqueous solution of 40% propylene glycol and 10% ethanol. The reconstituted solutions are stable for 4 and 13 h, respectively.
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Ni N, El-Sayed MM, Sanghvi T, Yalkowsky SH. Estimation of the effect of NaCl on the solubility of organic compounds in aqueous solutions. J Pharm Sci 2000; 89:1620-5. [PMID: 11042610 DOI: 10.1002/1520-6017(200012)89:12<1620::aid-jps13>3.0.co;2-n] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Setschenow constant, K(salt), of a nonelectrolyte in a NaCl solution is shown to be related to the logarithm of its octanol-water partition coefficient, log K(ow), determined by K(salt) = A log K(ow) + B, where K(ow) is the octanol-water partition coefficient of the solute and the coefficients A and B are constants. The values of A and B were empirically determined from literature data for 62 organic compounds and validated for a test set of 15 compounds including several drugs.
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Zhao L, Ni N, Yalkowsky SH. A Modification of Trouton's Rule by Simple Molecular Parameters for Hydrocarbon Compounds. Ind Eng Chem Res 1998. [DOI: 10.1021/ie9803570] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Ni N, Yager JD. The co-mitogenic effects of various estrogens for TGF-alpha-induced DNA synthesis in cultured female rat hepatocytes. Cancer Lett 1994; 84:133-40. [PMID: 8076369 DOI: 10.1016/0304-3835(94)90367-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The synthetic estrogens ethinyl estradiol (EE) and mestranol (M) are weak complete hepatic carcinogens and potent tumor promoters. In vivo, EE and M cause a rapid but transient increase in liver growth. However, studies in cultured female rat hepatocytes indicate that EE is not a strong complete hepatic mitogen but rather enhances epidermal growth factor (EGF)-induced DNA synthesis and is thus classified as a co-mitogen (Yager, J.D., Zurlo, J. and Ni, N. (1991) Proc. Soc. Exptl. Biol. Med., 198, 667-674). The endogenous estrogen 17 beta-estradiol (E2) also exhibits co-mitogenic activity, enhancing the fraction of hepatocytes undergoing DNA synthesis induced by both EGF and transforming growth factor alpha (TGF-alpha) (Ni, N. and Yager, J.D. (1994) Hepatology, 19, 183-192). The objectives of the study reported here were: (1) to determine whether the co-mitogenic effects of EE and E2 extend to other synthetic estrogens including mestranol and diethylstilbestrol, and to alpha-zearalanol, a natural product with estrogenic activity; (2) to compare the co-mitogenic effects of endogenous estrogens including E2, estrone, estriol and the catechol metabolites 2- and 4-hydroxy-estradiol; and (3) to determine whether the conditioned medium from E2-treated hepatocytes has co-mitogenic activity. Female rat hepatocytes in primary culture were exposed to the various estrogens +/- TGF-alpha and DNA synthesis was determined by measuring [3H]thymidine incorporation into extracted DNA. The results show that the co-mitogenic effects previously observed with EE and E2 also extend to all of these estrogens and to the E2 catechol metabolites. Although the co-mitogenic potency of these estrogens does not correlate with their reported affinities to the estrogen receptor, their estrogenicity appears necessary since the non-estrogenic metabolite 2-methoxy-estradiol lacks co-mitogenic activity. In addition, enhancement of TGF-alpha-induced DNA synthesis by conditioned medium from E2-treated cells supports the notion that a metabolite mediates its co-mitogenic effect.
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