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Hong Guo

Publications and source records attributed to Hong Guo.

At least 19 recordsLinked to original sources
PubMed2006

Universal spin-Hall conductance fluctuations in two dimensions.

We report a theoretical investigation on spin-Hall conductance fluctuation of disordered four-terminal devices in the presence of Rashba or/and Dresselhaus spin-orbital interactions in two dimensions. As a function of disorder, the spin-Hall conductance GsH shows ballistic, diffusive, and insulating transport regimes. For given spin-orbit interactions, a universal spin-Hall conductance fluctuation (USCF) is found in the diffusive regime. The value of the USCF depends on the spin-orbit coupling tso but is independent of other system parameters. It is also independent of whether Rashba or Dresselhaus or both spin-orbital interactions are present. When tso is comparable to the hopping energy t, the USCF is a universal number approximately 0.18e/4pi. The distribution of GsH crosses over from a Gaussian distribution in the metallic regime to a non-Gaussian distribution in the insulating regime as the disorder strength is increased.

Journal Article↗
PubMed2006

Catalytic role of proton transfers in the formation of a tetrahedral adduct in a serine carboxyl peptidase.

Quantum mechanical/molecular mechanical molecular dynamics and 2D free energy simulations are performed to study the formation of a tetrahedral adduct by an inhibitor N-acetyl-isoleucyl-prolyl-phenylalaninal (AcIPF) in a serine-carboxyl peptidase (kumamolisin-As) and elucidate the role of proton transfers during the nucleophilic attack by the Ser278 catalytic residue. It is shown that although the serine-carboxyl peptidases have a fold resembling that of subtilisin, the proton transfer processes during the nucleophilic attack by the Ser residue are likely to be more complex for these enzymes compared to the case in classical serine proteases. The computer simulations demonstrate that both general base and acid catalysts are required for the formation and stabilization of the tetrahedral adduct. The 2D free energy maps further demonstrate that the proton transfer from Ser278 to Glu78 (the general base catalyst) is synchronous with the nucleophilic attack, whereas the proton transfer from Asp164 (the general acid catalyst) to the inhibitor is not. The dynamics of the protons at the active site in different stages of the nucleophilic attack as well as the motions of the corresponding functional groups are also studied. It is found that the side chain of Glu78 is generally rather flexible, consistent with its possible multifunctional role during catalysis. The effects of proton shuffling from Asp82 to Glu78 and from Glu32 to Asp82 are examined, and the results indicate that such proton shuffling may not play an important role in the stabilization of the tetrahedral intermediate analogue.

Aspartic Acid↗
PubMed2006

Disruption of EphA2 receptor tyrosine kinase leads to increased susceptibility to carcinogenesis in mouse skin.

EphA2 receptor tyrosine kinase is frequently overexpressed in different human cancers, suggesting that it may promote tumor development and progression. However, evidence also exists that EphA2 may possess antitumorigenic properties, raising a critical question on the role of EphA2 kinase in tumorigenesis in vivo. We report here that deletion of EphA2 in mouse led to markedly enhanced susceptibility to 7,12-dimethylbenz(a)anthracene/12-O-tetradecanoylphorbol-13-acetate (DMBA/TPA) two-stage skin carcinogenesis. EphA2-null mice developed skin tumors with an increased frequency and shortened latency. Moreover, tumors in homozygous knockout mice grew faster and were twice as likely to show invasive malignant progression. Haploinsufficiency of EphA2 caused an intermediate phenotype in tumor development but had little effects on invasive progression. EphA2 and ephrin-A1 exhibited compartmentalized expression pattern in mouse skin that localized EphA2/ephrin-A1 interactions to the basal layer of epidermis, which was disrupted in tumors. Loss of EphA2 increased tumor cell proliferation, whereas apoptosis was not affected. In vitro, treatment of primary keratinocytes from wild-type mice with ephrin-A1 suppressed cell proliferation and inhibited extracellular signal-regulated kinase 1/2 (ERK1/2) activities. Both effects were abolished in EphA2-null keratinocytes, suggesting that loss of ERK inhibition by EphA2 may be one of the contributing mechanisms for increased tumor susceptibility. Interestingly, despite its tumor suppressive function, EphA2 was overexpressed in skin tumors compared with surrounding normal skin in wild-type mice, similar to the observations in human cancers. EphA2 overexpression may represent a compensatory feedback mechanism during tumorigenesis. Together, these results show that EphA2 is a novel tumor suppressor gene in mammalian skin.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2006

Brief cognitive-behavioral audiotape interventions for cancer-related pain: Immediate but not long-term effectiveness.

BACKGROUND: Few studies have evaluated cognitive-behavioral interventions as an adjunct treatment for chronic cancer-related pain. A randomized clinical trial was performed evaluating the efficacy of 3 brief cognitive-behavioral techniques: relaxation, distraction, and positive mood interventions. METHODS: Fifty-seven patients with chronic cancer-related pain taking opioid medications were randomly assigned to either the relaxation, distraction, positive mood, or waiting-list control group. The patients in the 3 intervention groups received audiotapes of the cognitive-behavioral technique and were asked to practice regularly at home. The tapes were supplemented with written instructions and follow-up telephone calls. RESULTS: Patients in the relaxation and distraction groups reported significantly reduced pain intensity immediately after listening to the tapes. The pain reduction was not maintained, however. At the 2-week follow-up assessment, no significant differences in pain intensity or interference were found among the treatment groups. The groups also did not differ with regard to secondary outcome measures assessing quality of life, mood, self-efficacy, and other symptoms. The results of qualitative interviews indicated that patients often had difficulty focusing on the audiotapes and preferred their own methods of pain reduction. CONCLUSIONS: Brief relaxation and distraction audiotape interventions produced immediate pain reductions but not longer-term pain relief. Additional research with a more individualized intervention is needed to evaluate cognitive-behavioral interventions for cancer pain control.

Adult↗
PubMed2006

Nonlinear spin current and magnetoresistance of molecular tunnel junctions.

We report on a theoretical study of spin-polarized quantum transport through a Ni-bezenedithiol(BDT)-Ni molecular magnetic tunnel junction (MTJ). Our study is based on carrying out density functional theory within the Keldysh nonequilibrium Green's function formalism, so that microscopic details of the molecular MTJ are taken into account from first principles. A magnetoresistance ratio of approximately 27% is found for the Ni-BDT-Ni MTJ which declines toward zero as bias voltage is increased. The spin currents are nonlinear functions of bias voltage, even changing sign at certain voltages due to specific features of the coupling between molecular states and magnetic leads.

Journal Article↗
PubMed2006

Apomorphine-induced activation of dopamine receptors modulates FGF-2 expression in astrocytic cultures and promotes survival of dopaminergic neurons.

Apomorphine (APO), a potent D1/D2 dopamine receptor agonist, is currently used as an antiparkinsonian drug. We have shown previously that APO stimulates synthesis and release of multiple trophic factors, such as brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF), in both mesencephalic and striatal neurons, thereby effectively preventing dopaminergic neuron loss in vitro. The present study was designed to investigate the effects of APO on fibroblast growth factor-2 (FGF-2) expression and regulation in astrocytes, and furthermore, to identify signaling mechanisms underlying these effects. Here, we show that FGF-2 expression is robustly induced in cultured astrocytes in response to APO. FGF-2 expression was proportional to APO concentration and time-dependent. Conversely, treatment with S-APO, a derivative of R-APO lacking DA receptor agonist activity, did not alter FGF-2 levels. APO treatment resulted in enhanced cytosol FGF-2 immunoreactivity, export of high MW forms of FGF-2 to the cytoplasm from the nucleus and increased extracellular release of FGF-2. Interestingly, both high and low MW forms of FGF-2 were detectable in conditioned medium of APO-treated cultures. This APO-induced effect was correlated with activation of D1 and D2 receptors, as it could be either mimicked by dopamine receptor agonists (SKF38393, quinpirole) or partially blocked by antagonists (SCH23390, SKF83566, haloperidol). Activation of the D1 receptor preferentially increased PKA activity, whereas activation of the D2 receptor only promoted phosphorylation of MAPK. Importantly, APO-modulated FGF-2 expression was independent of Akt/phosphoinositide 3-kinase signaling. These data suggest that APO can enhance biosynthesis and release of FGF-2 through activation of dopamine receptors in striatal astrocytes. Both cAMP/PKA and MEK/MAPK signaling cascades are major steps mediating this process.

Animals↗
PubMed2006

Genetic restoration of aldose reductase to the collecting tubules restores maturation of the urine concentrating mechanism.

To investigate the underlying causes for aldose reductase deficiency-induced diabetes insipidus, we carried out studies with three genotypic groups of mice. These included wild-type mice, knockout mice, and a newly created bitransgenic line that was homozygous for both the aldose reductase null mutation and an aldose reductase knockin transgene driven by the kidney-specific cadherin promoter to direct transgene expression in the collecting tubule epithelial cells. We found that from early renal developmental stages onward, urine osmolality did not exceed 1,000 mosmol/kgH2O in aldose reductase-deficient mice. The functional defects were correlated with significant renal cellular and structural abnormalities that included cell shrinkage, apoptosis, disorganized tubular and vascular structures, and segmental atrophy. In contrast, the transgenic aldose reductase expression in the bitransgenic mice largely but incompletely rescued urine concentrating capacity and significantly improved renal cell survival, cellular morphology, and renal structures. Together, these results suggest that aldose reductase not only plays important roles in osmoregulation and medullary cell survival but may also be essential for the full maturation of the urine concentrating mechanism.

Aldehyde Reductase↗
PubMed2006

Cerebral autoregulation is preserved during orthostatic stress superimposed with systemic hypotension.

We sought to determine whether cerebral autoregulation (CA) is compromised during orthostatic stress superimposed with systemic hypotension. Transient systemic hypotension was produced by deflation of thigh cuffs previously inflated to suprasystolic pressure, combined with or without lower body negative pressure (LBNP). Cardiac output (CO) decreased from a baseline of 5.0+/-0.5 l/min by -8.3+/-1.7, -19.2+/-2.0, and -30.6+/-3.4% during LBNP of -15, -30, and -50 Torr, respectively. Mean arterial pressure (MAP) was maintained during LBNP, despite decreases in systolic and pulse pressures. Middle cerebral arterial blood flow velocity (VMCA) decreased significantly from a baseline of 64+/-3 to 58+/-4 cm/s (-9.7+/-2.4%) at -50 Torr of LBNP. The reduction in VMCA was associated with a decrease in regional cerebral O2 saturation. However, the percent decrease in VMCA was markedly less than that of CO. This suggests that the magnitude of the change in VMCA (an index of cerebral blood flow) is less than would be predicted, given the decrease in CO. Transient systemic hypotension decreased MAP by -21+/-2, -24+/-2, -28+/-3, and -26+/-3% at rest and during LBNP of -15, -30, and -50 Torr, respectively. Likewise, this acute hypotension resulted in decreases in VMCA of -20+/-2, -21+/-2, -24+/-25, and -19+/-2% and regional cerebral O2 saturation of -5+/-1, -6+/-1, -6+/-1, and -7+/-2% at rest and during LBNP of -15, -30, and -50 Torr, respectively. Complete recovery of VMCA to baseline values following transient hypotension (ranging from 5 to 8 s) occurred significantly earlier compared with MAP (from 10 to 12 s). No subjects experienced syncope during acute hypotension. We conclude that CA is preserved during LBNP, superimposed with transient systemic hypotension, despite the decrease in VMCA associated with sustained central hypovolemia in normal healthy individuals. This preserved CA is vital for the prevention of orthostatic syncope.

Adult↗
PubMed2006

Comment on "partially coherent flat-topped beam and its propagation".

We point out that the expression of the cross-spectral density (CSD) of a partially coherent flat-topped beam (PCFB) given by Ge et al. [Appl. Opt. 43, 4732 (2004)] is incorrect. The results show that the M2 factor derived based on Ge's expression leads to M2 < 1 in some cases, which is physically unacceptable. A new expression of the CSD for a PCFB is given.

Comment↗
PubMed2006

Efficacy of low-release-rate fluocinolone acetonide intravitreal implants to treat experimental uveitis.

OBJECTIVE: To determine the efficacy of 0.5-mg and 0.1-mg sustained-release fluocinolone acetonide intravitreal implants to inhibit ocular inflammation in a rabbit model of severe uveitis. METHODS: The in vitro pharmacokinetic profile of both the 0.5-mg and 0.1-mg sustained-release fluocinolone intravitreal implants was determined during a 10-day period. A sustained-release fluocinolone acetonide intravitreal implant with a release rate of either 0.5 microg/d (n = 16) or 0.1 microg/d (n = 16) was implanted into the vitreous cavity of the right eye in albino rabbits after a subcutaneous injection of tuberculin antigen. Control animals (n = 14) received empty devices. Uveitis was induced with an intravitreal tuberculin antigen injection. A masked observer graded anterior chamber flare, anterior chamber cells, vitreous opacity, and inflammation on histologic sections. RESULTS: In vitro, the drug was released from both devices in a linear manner. In vivo, treated eyes were significantly less inflamed than untreated eyes (P< or =.02). Inflammation was suppressed to a greater degree with the 0.5-microg/d implant compared with the 0.1-microg/d implant. CONCLUSION: Sustained-release fluocinolone intravitreal implants suppress ocular inflammation in a rabbit model of severe uveitis. CLINICAL RELEVANCE: The efficacy demonstrated with the 0.1-microg/d implant provides the rationale for future human studies with lower-release-rate implants than are currently used in noninfectious uveitis clinical trials.

Animals↗
PubMed2006

Status of cancer pain in Hanoi, Vietnam: A hospital-wide survey in a tertiary cancer treatment center.

Little is known about the prevalence of cancer pain in many developing countries. We report a hospital-wide survey of pain in a tertiary cancer center in Hanoi, Vietnam. All inpatients and outpatients age 18 years or older were approached for participation in the study. Data were collected using the Brief Pain Inventory. Results showed a 70% response rate. Prevalence of moderate to severe pain was 50% (89/178), with 23% reporting severe ratings of pain at its "worst" and 33% reporting severe impairment in their ability to work due to pain. Only 1% and 40% reported total and partial pain relief from medications, respectively. This study is among the first to provide a representative view of pain in a tertiary cancer treatment center in Hanoi, Vietnam. The findings provide empirical support for the need for better programmatic efforts to improve relief of cancer pain in developing countries, including Vietnam.

Adult↗
PubMed2006

Filipino version of the M. D. Anderson Symptom Inventory: validation and multisymptom measurement in cancer patients.

Assessing cancer-related symptoms requires a brief, reliable, valid, and culturally adapted symptom screening tool. In the Philippines, cancer patients (n=206) and community-dwelling adults (n=170) participated in a cross-sectional validation study of the Filipino version of the M. D. Anderson Symptom Inventory (MDASI-F). Both exploratory factor analysis and hierarchical cluster analysis revealed two underlying symptom severity constructs--general and gastrointestinal symptoms--consistent with the English, Japanese, and Chinese versions of the MDASI. Cronbach alpha coefficients of 0.79 and 0.77, respectively, demonstrated acceptable internal consistency for the two factors. Known-group validity was confirmed by significant differences on MDASI-F items by performance status (P<0.01 or P<0.001). Fatigue, sadness, distress, and pain were significant predictors of symptom interference. Cancer patients reported significantly greater symptom severity on multiple items than did the community sample. The MDASI-F is reliable and valid for evaluating cancer-related symptoms and their impact on Filipino cancer patients.

Adolescent↗
PubMed2006

Effects of Transcutol P on the corneal permeability of drugs and evaluation of its ocular irritation of rabbit eyes.

Our purpose was to explore the use of Transcutol P (Trans) in an ocular drug delivery system. The effect of Trans on the corneal permeability of drugs was investigated in-vitro, using isolated rabbit corneas. The ocular irritation of Trans was also tested in rabbits in-vivo. In the presence of Trans, at a concentration of 0.005-0.03%, the maximum increase in the apparent permeability coefficient (P(app)) was 1.5, 1.5, 3.0 and 3.3 fold for ribavirin, gatifloxacin, levofloxacin hydrochloride and enoxacin, respectively. However, the P(app) value of oxaprozin was reduced in the presence of Trans. The maximum reduction was found to be 2.8 fold at a concentration of 0.03% Trans. The results of the ocular irritation studies showed that Trans was non-irritant at the concentrations studied (0.005-0.03%), while it produced slight irritation at a concentration of 0.05%. It was also found that Trans did not cause any visible ocular damage or abnormal clinical signs involving the cornea, iris or conjunctivae at all concentrations. We concluded that Trans may have potential clinical benefits in improving the ocular drug delivery of hydrophilic compounds.

1-Octanol↗
PubMed2006

[A preliminary study on anti-liver cancer immunity of the virus-like particulate peptide-nucleic acid vaccine].

OBJECTIVES: To construct a novel virus-like particulate peptide-nucleic acid vaccine (VPNV) of human telomerase reverse transcriptase (hTERT), and to study its anti-liver cancer immunity. METHODS: A cationic antigenic peptide was synthesized and purified, and then human granulocyte macrophage colony stimulating factor (hGM-CSF) and TERT gene were cloned into the eukaryotic expression vector pTCAE. The peptide was combined with the nucleic acid vaccine to make a VPNV, which was transfected into eukaryotic cell COS-7. The immunogenicity of hGM-CSF and hTERT were detected using ELISA and Western blot. The efficacy of VPNV for inducing antigen specific CTL response was determined using the lactate dehydrogenase release method. RESULTS: VPNV was verified capable to trigger specific CTL responses and has shown a specific cytolytic activity to liver cancer cell HepG2. CONCLUSION: A VPNV which can stimulate antigen specific CTL response was successfully constructed. This paves the way for our further investigation of anti-liver cancer immunity in mice.

Animals↗
PubMed2005

Global analysis of protein phosphorylation in yeast.

Protein phosphorylation is estimated to affect 30% of the proteome and is a major regulatory mechanism that controls many basic cellular processes. Until recently, our biochemical understanding of protein phosphorylation on a global scale has been extremely limited; only one half of the yeast kinases have known in vivo substrates and the phosphorylating kinase is known for less than 160 phosphoproteins. Here we describe, with the use of proteome chip technology, the in vitro substrates recognized by most yeast protein kinases: we identified over 4,000 phosphorylation events involving 1,325 different proteins. These substrates represent a broad spectrum of different biochemical functions and cellular roles. Distinct sets of substrates were recognized by each protein kinase, including closely related kinases of the protein kinase A family and four cyclin-dependent kinases that vary only in their cyclin subunits. Although many substrates reside in the same cellular compartment or belong to the same functional category as their phosphorylating kinase, many others do not, indicating possible new roles for several kinases. Furthermore, integration of the phosphorylation results with protein-protein interaction and transcription factor binding data revealed novel regulatory modules. Our phosphorylation results have been assembled into a first-generation phosphorylation map for yeast. Because many yeast proteins and pathways are conserved, these results will provide insights into the mechanisms and roles of protein phosphorylation in many eukaryotes.

Eukaryotic Cells↗
PubMed2005

Conductance of an ensemble of molecular wires: a statistical analysis.

We report on a first principles analysis of quantum transport through molecular wires made of 4,4'bipyridine and 6-alkanedithiol contacted by Au electrodes. We investigate how charge transport is altered due to small structure changes at the molecule-electrode contacts. These changes include distance between the molecule and the contact, extra metal atoms at the Au surface, binding sites, molecular orientation, and bias voltages. By investigating hundreds of wires we extract a statistical picture on transport properties of the two different molecules. We compare quantitatively with the corresponding experimental data.

Journal Article↗