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Biomedical subjects

Hong Guo

Publications and source records attributed to Hong Guo.

At least 73 records · Page 4Linked to original sources
PubMed2003

A spin cell for spin current.

We propose and investigate a spin-cell device which provides the necessary spin-motive force to drive a spin current for future spintronic circuits. Our spin cell has four basic characteristics: (i) it has two poles so that a spin current flows in from one pole and out from the other pole, and in this way a complete spin circuit can be established; (ii) it has a source of energy to drive the spin current; (iii) it maintains spin coherence so that a sizable spin current can be delivered; (iv) it drives a spin current without a charge current. The proposed spin cell for spin current should be realizable using technologies presently available.

Journal Article↗
PubMed2003

Gapped DNA is anisotropically bent.

Ionizing radiation damages DNA in several ways, including through formation of a single-nucleoside gap in one DNA strand. We have developed a two-dimensional gel electrophoresis method to investigate the effect of a strand gap on DNA structure. We generate a library of gapped DNA molecules by treating a DNA restriction fragment with the hydroxyl radical, generated by the reaction of Fe(II) EDTA with hydrogen peroxide. The DNA molecule studied contains a fixed bend produced by a set of phased adenine tracts. The A-tract bend serves as a reference bend for investigating the conformational nature of a strand gap. In the first electrophoretic dimension, a bent DNA molecule that has been treated with the hydroxyl radical is electrophoresed on a native gel. Smearing of the band on the native gel indicates that the library of gapped DNA molecules contains a variety of DNA conformations. In the second electrophoretic dimension, gapped DNA molecules having different native gel mobilities are electrophoresed on separate lanes of a denaturing gel to reveal how each strand gap affects the native gel mobility (and thus shape) of the DNA. Our results demonstrate that a single-nucleoside gap in a DNA duplex leads to an anisotropic, directional bend in the DNA helix axis. The implications of our findings for recognition of this lesion by DNA repair proteins are discussed.

Anisotropy↗
PubMed2003

Hemangioblastic characteristics of fetal bone marrow-derived Flk1(+)CD31(-)CD34(-) cells.

OBJECTIVE: To investigate whether Flk1(+)CD31(-)CD34(-) cells isolated from fetal bone marrow (BM) have characteristics of hemangioblasts, i.e., progenitors of endothelial and hematopoietic cells. MATERIALS AND METHODS: Mononuclear cells from fetal BM were negatively sorted by CD45, GlyA, and CD34 micromagnetic beads, then cultured to form cell colonies. A single colony was harvested. Culture-expanded cells were seeded on ECM gel or semisolid media supplemented with endothelial and hematopoietic growth factors, respectively. Immunochemistry staining and RT-PCR were performed for cell characterization. RESULTS: 99% of cells from the single colony maintained Flk1(+) and CD31/CD34(-) during passaging. On ECM gel, Flk1(+)CD31(-)CD34(-) cells could grow into vascular structure that was positive for CD31 and vWF. There were round CD34(+) cells around the vascular structure. When angiogenesis inhibitor suramin was added before tube formation, formation of vascular structure was blocked. Additionally, Flk1(+)CD31(-)CD34(-) cells cultured on hematopoietic condition could differentiate into hematopoietic cells which expressed GATA-1, 2, and gamma, beta globin gene. After being replated in methylcellulose medium, they formed typical erythroid colonies. CONCLUSIONS: Flk1(+)CD31(-)CD34(-) cells derived from fetal BM could differentiate into endothelial and hematopoietic cells. The results suggested that these Flk1(+)CD31(-)CD34(-) cells after embryo stage bear characteristics of hemangioblast and may have potential application for the hematopoietic and vascular diseases.

Antigens, CD34↗
PubMed2003

Pediatric cancer pain management practices and attitudes in China.

Children with cancer often receive less adequate pain management than adults. This survey was designed to examine current practices, knowledge, and attitudes pertaining to pediatric pain management in China. Based on the choice of opioid use and self-identification as having a conservative or liberal approach to pain management, we identified two clusters. Members of cluster 1 (60%) had more conservative attitudes and did not perceive that young children experienced pain. Members of cluster 2 (40%) had more liberal attitudes. Four factors predicted conservative membership: never having prescribed opioids for cancer pain (OR=2.67, CI=1.11-6.45), use of placebos for pain management (OR=2.32, CI=1.05-5.08), belief that the adequacy of pain management was fair or good (OR=2.10, CI=1.31-3.37), and belief that children are less sensitive to pain (OR=1.96, CI=1.02-3.76). The top barriers to optimal pediatric pain management were identified as fear of opioid addiction and inadequate knowledge of pain management.

Adult↗
PubMed2003

Methyl-beta-cyclodextrin but not retinoic acid reduces EAAT3-mediated glutamate uptake and increases GTRAP3-18 expression.

The Na+-dependent glutamate transporter EAAT3 facilitates glutamate uptake into neurons as well as many other cell types. GTRAP3-18 (JWA, Arl6ip5) is a novel protein that interacts with EAAT3 and negatively modulates EAAT3-mediated glutamate uptake. Previous studies suggest that retinoic acid (RA) decreases Na+-dependent glutamate uptake and increases GTRAP3-18 protein expression. However, the RA used in those studies was complexed with methyl-beta-cyclodextrin (MebetaCD). In the present study we found that MebetaCD, but not RA, significantly reduced Na+-dependent EAAT3-mediated [3H]glutamate uptake in human embryonic kidney 293 (HEK293) cells. MebetaCD also significantly increased GTRAP3-18 protein expression in HEK293 cells as well as in rat hypothalamic neuron cultures. Intracerebroventricular administration of MebetaCD to the mouse brain resulted in a significant increase in GTRAP3-18 immunoreactivity in the hippocampus and cerebral cortex. In conclusion, we have shown that MebetaCD reduces EAAT3-mediated glutamate uptake and induces the expression of GTRAP3-18 protein.

Amino Acid Transport System X-AG↗
PubMed2003

[An analysis of measurement error in Orbscan topography system].

OBJECTIVE: To discuss the measurement error and the influence factor of Orbscan Topography to provide more accurate data for clinical application. METHODS: Orbscan Topography System and A-scan ultrasonography were used to measure the corneal thickness and anterior chamber depths pre-operatively and post-operatively, including 200 cases (400 eyes) undergoing laser in situ keratomileusis (Lasik) and 50 cases (100 eyes) undergoing photorefractive keratectomy (PRK). The curvature of posterior corneal surface was measured by Orbscan topography before and after the operations, and the result of measurement was compared. RESULTS: Pre-operatively, the value of corneal thickness was (18.83 - 24.29) microm lower measured by Orbscan topography than that by A-ultrasonography, and post-operatively the value was (56.32 - 139.52) micro m lower than that by A-ultrasonography. The postoperative value was obviously higher than the pre-operative one. The value of central anterior chamber depth was (0.16 - 0.25) mm lower measured by Orbscan system than that by A-ultrasonography pre-operatively and post-operatively. There was no clinical significance. The difference in the comparison of posterior corneal surface curvature before and after Lasik was -0.60 D measured by Orbscan System. The difference in the comparison of posterior corneal surface curvature before and after PRK was -0.51 D in the lower diopter group and -1.12 D in medium diopter group. CONCLUSIONS: It is necessary to improve the accuracy of Orbscan Topography System. The Haze and the change of anterior corneal surface curvature after Lasik and PRK are the main causes of measurement error in Orbscan Topography System. Clinically, it is an un-negligible important problem in the measurement of Orbscan system.

Adolescent↗
PubMed2003

[The characteristics of enhanced gadolinium DTPA brain magnetic resonance images in 298 multiple sclerosis patients].

OBJECTIVE: To investigate the characteristics of enhanced brain magnetic resonance imaging (MRI) with gadolinium-DTPA (GD) in patients with multiple sclerosis (MS). METHODS: Brain enhanced MRI were studied in 186 patients with clinically definite multiple sclerosis. 298 MRI enhanced lesions were followed every 4 weeks and the study lasted 3 months to 2 years. RESULTS: Of the 298 enhanced MRI lesions 207 (69.5%) lasted less than 4 weeks, 251 (84.2%) 8 weeks, and 272 (91.3%) 12 weeks. There were 3 lesions lasting more than 2 years. Round, oval, ring form, arcuate, spotty, or irregular MRI GD enhanced lesions were found in our MS data. CONCLUSIONS: Most of the MRI GD enhanced lesions disappear in 4 weeks. Very few can last more than 2 years. So it is necessary to perform the GD enhanced MRI in 4 weeks for studying MS intracranial GD enhanced lesions. The DA enhanced MRI lesions in MS may be round, oval, ring form, arcuate, spotty or irregular.

Adolescent↗
PubMed2003

[310 cases of thymectomy for myasthenia gravis].

OBJECTIVE: To evaluate the clinical characteristics and long-term outcome of 310 cases of thymectomy for myasthenia Gravis. METHODS: The data of 310 patients with thymectomy were analyzed retrospectively to study the patient selection, operative techniques, perioperative management and results for myasthenia Gravis. Absolute and relative scores for clinical evaluation were used as the criteria to determine the therapeutic effects of thymectomy. RESULTS: There were no operative death and postoperative complication rates were 8.7% (27/310). The extra anatomic thymic tissue was found in up to 38.7% (120/310) patients and thymus hyperplasia occurred in 92.9% (288/310) cases. 92.6% (287/310) postoperative patients were followed up for 3 or more months; the percentage of patients being remitted, essentially remitted, significantly effective, effective and non-effective were 7.1% (22/310), 11.3% (35/310) 40.0% (124/310), 27.1% (84/310), 7.1% (22/310) respectively. The total long-term effective rate was 85.5% (265/310). The effective rate for type I, IIa, IIb, III, IV was 90.9% (20/22), 97.6% (40/41), 95.3% (162/170), 80.6% (29/36), 77.8% (14/18) respectively. CONCLUSIONS: Generalized typed and properly selected recurrent ocular-typed patients with Myasthenia Gravis undergoing extensive thymectomy would have good long-term outcomes.

Adult↗
PubMed2003

Induction of immune responses in mice by vaccination with Liposome-entrapped DNA complexes encoding Toxoplasma gondii SAG1 and ROP1 genes.

OBJECTIVE: To evaluate the immune responses induced by experimental DNA construct encoding Toxoplasma gondii (T. gondii) surface antigen1 (SAG1) and rhoptry protein 1 (ROP1) in mice as a hybrid gene. METHODS: Truncated SAG1 and ROP1 DNA fragments were amplified using polymerase chain reaction (PCR) and inserted into pEGFP-N3 vector to construct recombinant plasmid pSAG1-ROP1. NIH3T3 mammalian cells were transiently transfected with the DNA construct. Female BALB/c mice were given three intramuscular injections of 10 micro g plasmid DNA entrapped in liposome. Four weeks after the final booster injection, blood samples were collected and subjected to enzyme-linked immuno sorbent assay (ELISA) to investigate humoral and cell-mediated immune responses. Reversal transcript-polymerase chain reaction (RT-PCR) was used to evaluate the transcription of inoculated DNA-liposome complex in the injected site. Dot-blot hybridization was employed in order to detect whether or not the injected DNA was incorporated into the genomic DNA of the immunized mice. RESULTS: Green fluorescence was observed in pSAG1-ROP1-transfected cells. Western blot analysis showed antibody recognition of the expressed SAG1-ROP1 was between 58 kDa and 75 kDa. No expression was observed in blank control plasmid-transfected cells. The sera of immunized mice exhibited antibodies to T. gondii tachyzoites and primarily interferon-gamma and interlukin-2. RT-PCR showed that the duration of transcribed inoculated liposome entrapped DNA in the injected muscular tissue was at least ten days post the first injection. Dot-blot hybridization revealed that the presence of foreign DNA in the splenocytes and peripheral blood leukocytes was transient and that no foreign DNA had inserted into the genomic DNA of mice immunized with pSAG1-ROP1. CONCLUSIONS: Immunization with a liposome-encapsulated DNA construct encoding the T. gondii SAG1 and ROP1 can induce humoral and cell-mediated immune responses.

Animals↗
PubMed2003

[The prevalence of orthodontic treatment need in Urumqi Han's adolescent].

OBJECTIVE: To assess the severity of malocclusion and the need for orthodontic treatment in Urumqi Hans' adolescent. METHODS: 562 children aged from 11-19 years old were chosen randomly and were investigated. The severity of malocclusion and the need for orthodontic treatment were assessed using the Malocclusion Severity Index (MSI, Hill PA 1992). RESULTS: The MSI scores for this population were 21.91 +/- 17.09 in male and 22.28 +/- 17.26 in female, respectively, there were no significant differences between sexes (P > 0.05). According to the classifications of MSI scores, the rates of the need for orthodontic treatment were 54.55% in male and 55.40% in female. CONCLUSIONS: (1) The rates of orthodontic treatment need in Urumqi Hans' adolescent were highly frequent. (2) The MSI is a simple precise valid index for assessing the orthodontic Treatment Need. It is suggested to be used widely.

Adolescent↗
PubMed2002

(-)-Stepholidine promotes proliferation and neuronal differentiation of rat embryonic striatal precursor cells in vitro.

The present study investigated the influence of (-)-stepholidine, an effective dopamine D1 receptor agonist and D2 receptor antagonist, on the development of neural precursor cells. Incubation of striatal neural precursor cells with stepholidine resulted in significant increase in the number of proliferating precursor cell spheres when in the presence of fibroblast growth factor-2. This action can be blocked by application of haloperidol. Treatment with stepholidine also increased the number of microtubule-associated protein-2-immunoreactive cells in the cultures and promoted marked increases in tyrosine hydroxylase expression. These findings suggest that stepholidine is involved in the regulation of proliferation of precursor cells. The effect appears to be mediated by dopamine receptors. Stepholidine also promotes the differentiation of precursor cells, however, this action may be independent of its effect on dopaminergic receptors.

Animals↗
PubMed2002

Four-terminal thermal conductance of mesoscopic dielectric systems.

A four-terminal thermal conductance formula for a mesoscopic dielectric system with arbitrary central scattering region is derived. Similar to four-terminal electric conductance, the four-terminal thermal conductance also has a set of Onsager relations. In the temperature T-->0 limit, in contrast to the two-terminal thermal conductance which is a monotonic function of T and tends to zero, the four-terminal thermal conductance is nonmonotonic and tends to infinity. We also find that temperatures of the two terminals without thermal flux become very close to each other at low temperatures. Rather different behaviors are found for systems satisfying fractional exclusion statistics.

Journal Article↗
PubMed2002

Synthesis of ketone analogues of prolyl and pipecolyl ester FKBP12 ligands.

The recently discovered small-molecule ligands for the peptidyl and prolyl isomerases (PPIase) of FKBP12 have been shown to possess powerful neuroprotective and neuroregenerative effects. Ketone analogues of the prolyl and pipecolyl esters, which mimic only the FKBP binding domain portion of FK506, are proposed and an efficient synthetic strategy is presented in this report, along with the preliminary results of in vitro and in vivo biological studies.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2002

Laser-plasma electron-density measurement using x-ray interferometry.

In this paper, the propagation of x-rays in laser-produced plasma is studied both analytically and numerically. The coupling relation between phase and amplitude of x-rays is derived, the solutions with higher-order corrections are given where the higher-order electron-density gradients have been taken into account. An important parameter eta was introduced, which is related to the errors of the electron-density measurement using x-ray interferometry. It is justified that so long as eta<1, the x-ray interferometry can be used for the measurement of electron density and for greater value of eta, higher-order modifications are needed.

Journal Article↗
PubMed2002

Spatial nonparaxial correction of the ultrashort pulsed beam propagation in free space.

In this paper, a family of integral solutions representing ultrashort pulsed beam propagation in free space is studied by using the comoving frame coordinates and the Fourier transformation for time variable in terms of well-known paraxial approximation. The pulsed Gaussian-like beam solution is obtained as a special case of the integral solution, where the pulsed Gaussian beam solution is included. Further, starting from the nonparaxial pulsed beam propagation equation in the temporal-frequency domain and making use of the spatial Fourier transform, the nonparaxial pulsed beam solution is derived based on the paraxial pulsed beam solution, where the nonparaxiality is evaluated by a series of expansions.

Journal Article↗