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Biomedical subjects

Yan Xiao

Publications and source records attributed to Yan Xiao.

At least 55 records · Page 3Linked to original sources
PubMed2004

Inverse correlation between cyclin A1 hypermethylation and p53 mutation in head and neck cancer identified by reversal of epigenetic silencing.

Aberrant promoter hypermethylation of tumor suppressor genes is proposed to be a common feature of primary cancer cells. We recently developed a pharmacological unmasking microarray approach to screen unknown tumor suppressor gene candidates epigenetically silenced in human cancers. In this study, we applied this method to identify such genes in head and neck squamous cell carcinoma (HNSCC). We identified 12 novel methylated genes in HNSCC cell lines, including PGP9.5, cyclin A1, G0S2, bone-morphogenetic protein 2A, MT1G, and neuromedin U, which showed frequent promoter hypermethylation in primary HNSCC (60%, 45%, 35%, 25%, 25%, and 20%, respectively). Moreover, we discovered that cyclin A1 methylation was inversely related to p53 mutational status in primary tumors (P = 0.015), and forced expression of cyclin A1 resulted in robust induction of wild-type p53 in HNSCC cell lines. Pharmacological unmasking followed by microarray analysis is a powerful tool to identify key methylated tumor suppressor genes and relevant pathways.

Carcinoma, Squamous Cell↗
PubMed2004

Selective disruption of PPARgamma 2 impairs the development of adipose tissue and insulin sensitivity.

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor that plays a pivotal role in obesity and diabetes. PPARgamma has two isoforms, PPARgamma1 and PPARgamma2. We investigated the functional differences between PPARgamma1 and PPARgamma2 by selectively disrupting PPARgamma2 in mice. In contrast to the embryonic lethality of PPARgamma-deficient mice, PPARgamma2(-/-) mice survived. Although normal development was identified in other tissues we examined, PPARgamma2(-/-) mice exhibited an overall reduction in white adipose tissue, less lipid accumulation, and decreased expression of adipogenic genes in adipose tissue. In addition, insulin sensitivity was impaired in male PPARgamma2(-/-) mice, with dramatically decreased expression of insulin receptor substrate 1 and glucose transporter 4 in the skeletal muscle, but thiazolidinediones were able to normalize this insulin resistance. Consistent with in vivo data, PPARgamma2(-/-) mouse embryonic fibroblasts showed a dramatically reduced capacity for adipogenesis in vitro compared with wild-type mouse embryonic fibroblasts. Taken together, our data demonstrate that PPARgamma2 deficiency impairs the development of adipose tissue and insulin sensitivity. PPARgamma2(-/-) mice may provide a tool to study the role of PPARgamma2 in obesity and diabetes.

Adipose Tissue↗
PubMed2004

Semiconductor nanocrystal probes for human metaphase chromosomes.

To improve signal stability and quantitation, an optically stable, novel class of fluorophore for hybridization analysis of human metaphase chromosomes is demonstrated. Detection of hybridization sites in situ was based on fluorescence from streptavidin-linked inorganic crystals of cadmium selenide [(CdSe)ZnS]. Fluorescence of nanocrystal fluorophores was significantly brighter and more photostable than organic fluorophores Texas Red and fluorescein. Thus, semiconductor nanocrystal fluorophores offer a more stable and quantitative mode of fluorescence in situ hybridization (FISH) for research and clinical applications.

Biotinylation↗
PubMed2004

Supramolecular self-assembly of inclusion complexes of a multiarm hyperbranched polyether with cyclodextrins.

A new class of crystalline inclusion complexes of a multiarm hyperbranched polyether combined with various cyclodextrins (CDs) was successfully prepared. Using self-condensing ring-opening polymerization, a kind of multiarm polyether with a hyperbranched poly(3-ethyl-3-oxetanemethanol) core and multiple linear poly(ethylene glycol) (PEG) arms was obtained. It has been found that this kind of hyperbranched polyether can be dissolved in water. Adding alpha-CDs to the multiarm hyperbranched polyether solution, molecular recognition results in the formation of crystalline inclusion complexes based on the noncovalent interactions between the linear PEG arms of the polyether particles and the alpha-CDs. These multiarm polyether inclusion complexes have been well characterized. Interestingly, quite different from inclusion complexes of CDs and linear polymeric guests, the complexes of the multiarm hyperbranched polyether with alpha-CDs show a novel lamellar morphology. The experimental results validate that the resultant lamellar crystals have a juxtaposed structure. In addition, the formation mechanism of these inclusion complexes of a multiarm polyether with alpha-CDs has also been well described. Besides the role of displacement of associated water molecules and the presence of hydrogen bonding between CDs in channel structure CD inclusion complexes, the noncovalent intermolecular forces between CDs and polymers also play an important role in the formation of complex architectures.

Cyclodextrins↗
PubMed2004

Peroxisome proliferator-activated receptor delta activates fatty acid oxidation in cultured neonatal and adult cardiomyocytes.

Peroxisome proliferator-activated receptors (PPARalpha, -gamma and -delta) are nuclear receptors involved in transcriptional regulations of lipid metabolism. The effect of PPARalpha in regulation of cardiac fatty acid oxidation has been well characterized. Whether PPARdelta also independently regulates fatty acid oxidation in the heart remains unclear. In this study, we tested the hypothesis that PPARdelta activates fatty acids oxidation in cardiomyocytes through transcriptional activation that are independent of PPARalpha. Our results first indicate that PPARdelta abundantly expresses in nucleus of cardiomyocytes. Palmitate oxidation rates were significantly increased in both neonatal and adult cardiomyocytes after treatment of a PPARdelta-selective ligand (GW0742). Further increases of fatty acid oxidation were evident when the treatment was applied to cardiomyocytes overexpressing a wild type PPARdelta, but not a mutant PPARdelta that lacks the intact carboxyl ligand-binding domain. Furthermore, genes of fatty acid oxidation enzymes were significantly upregulated in cultured rat neonatal cardiomyocytes when exposed to GW0742. GW0742 can restore partly the expression of certain key genes of fatty acid oxidation in mouse adult cardiomyocytes isolated from PPARalpha knockout mice. Therefore, while active crosstalk between PPARdelta and -alpha may exist, PPARdelta regulates cardiac fatty acid oxidation in the heart at least partly independent of PPARalpha. We conclude that PPARdelta may play a key role in cardiac energy balance and may serve as a "sensor" of fatty acid of other endogenous ligands in controlling fatty acids oxidation levels in the hearts under normal and pathological conditions.

Animals↗
PubMed2004

Astrocyte activation and dysfunction and neuron death by HIV-1 Tat expression in astrocytes.

Human immunodeficiency virus type 1 (HIV-1) Tat protein plays an important role in HIV-associated neuropathogenesis. Astrocytosis and neuron death are two hallmarks of HIV-1 infection of the central nervous system (CNS). However, whether there is a direct link between Tat expression, astrocytosis and subsequent neuron death is not known. In this study, we expressed Tat in astrocytes and examined Tat effects on astrocyte function and subsequent neuronal survival. The results showed that Tat expression resulted in a significant increase in glial fibrillary acidic protein (GFAP) expression, a cellular marker of astrocyte activation or astrocytosis. The GFAP promoter-driven reporter gene assay showed that Tat transactivated GFAP expression at the transcriptional level. Furthermore, Tat expression markedly impaired glutamate uptake by astrocytes. Importantly, cell culture supernatants from Tat-expressing astrocytes induced dramatic neuron death. Taken together, these data provide evidence for the first time to directly link Tat expression in astrocytes to astrocytosis, astrocyte dysfunction, and subsequent neuron death. In addition, these data suggest that astrocyte dysfunction contributes, at least in part, to Tat neurotoxicity and subsequently HIV-associated neuropathogenesis.

Animals↗
PubMed2004

Spectrophotometric determination of dapsone in pharmaceutical products using sodium 1,2-naphthoquinone-4-sulfonic as the chromogenic reagent.

Spectrophotometric determination of dapsone is described. The dapsone reacts with sodium 1,2-naphthoquinone-4-sulfonic in pH 6.98 buffer solution to form a salmon pink compound, and its maximum absorption wavelength is at 525 nm, epsilon525=3.68 x 10(4) l mol(-1) cm(-1). The absorbance of dapsone from 0.40 to 10 microg ml(-1) obeys Beer's law. The linear regression equation of the calibration graph is C=0.2334 A + 0.01288, with a linear regression correlation coefficient of 0.9998, the detection limit is 0.24 microg ml(-1), and recovery is from 99.2 to 102.4%. Effects of pH, surfactant, organic solvents, foreign ions, and standing time on the determination of dapsone have been examined. This method is simple and can be used for the determination of dapsone in injection solution of dapsone. The results obtained by this method agreed with those by the official method (dead-stop titration method [The Chinese Pharmacopoeia, Pharmacopoeia Commission, Ministry of Health, vol. 2, fifth ed., PRC Chemical Industry Press, Beijing, 2000, p.720]).

Antimalarials↗
PubMed2004

Spectrophotometric determination of ampicillin sodium in pharmaceutical products using sodium 1,2-naphthoquinone-4-sulfonic as the chromogentic reagent.

Spectrophotometric determination of ampicillin sodium is described. The ampicillin sodium reacts with sodium 1,2-naphthoquinone-4-sulfonic in pH 9.00 buffer solution to form a salmon pink compound, and its maximum absorption wavelength is at 463 nm, epsilon463 = 1.14 x 10(4). The absorbance of ampicillin sodium from 2.0-80 microg ml(-1) obeys Beer's law. The linear regression equation of the calibration graph is C = 40.24A - 2.603, with a linear regression correlation coefficient is 0.9997, the detection limit is 1.5 microg ml(-1), recovery is from 97.23 to 104.5%. Effects of pH, surfactant, organic solvents, and foreign ions on the determination of ampicillin sodium have been examined. This method is rapid and simple, and can be used for the determination of ampicillin sodium in the injection solution of ampicillin sodium. The results obtained by this method agreed with those by the official method (HPLC).

Absorption↗
PubMed2004

Making management decisions on the day of surgery based on operating room efficiency and patient waiting times.

The authors review the scientific literature on operating room management operational decision making on the day of surgery. (1) Some decisions should rely on the expected (mean) duration of the scheduled case. Other decisions should use upper prediction bounds, lower prediction bounds, and other measures reflecting the uncertainty of case duration estimates. One single number cannot be used for good decision making, because durations are uncertain. (2) Operational decisions can be made on the day of surgery based on four ordered priorities. (3) Decisions to reduce overutilized operating room time rely on mean durations. Limited additional data are needed to make these decisions well, specifically, whether a patient is in each operating room and which cases are about to finish. (4) Decisions involving reducing patient (and surgeon) waiting times rely on quantifying uncertainties in case durations, which are affected highly by small sample sizes. Future studies should focus on using real-time display of data to reduce patient waiting.

Appointments and Schedules↗
PubMed2004

Improving operating room coordination: communication pattern assessment.

OBJECTIVE: To capture communication patterns in operating room (OR) management to characterize the information needs of OR coordination. BACKGROUND: Technological applications can be used to change system processes to improve communication and information access, thereby decreasing errors and adverse events. The successful design of such applications relies on an understanding of communication patterns among healthcare professionals. METHODS: Charge nurse communication was observed and documented at four OR suites at three tertiary hospitals. The data collection tool allowed rapid coding of communication patterns in terms of duration, mode, target person, and the purpose of each communication episode. RESULTS: Most (69.24%) of the 2074 communication episodes observed occurred face to face. Coordinating equipment was the most frequently occurring purpose of communication (38.7%) in all suites. The frequency of other purposes in decreasing order were coordinating patient preparedness (25.7%), staffing (18.8%), room assignment (10.7%), and scheduling and rescheduling surgery (6.2%). CONCLUSION: The results of this study suggest that automating aspects of preparing patients for surgery and surgical equipment management has the potential to reduce information exchange, decreasing interruptions to clinicians and diminishing the possibility of adverse events in the clinical setting.

Appointments and Schedules↗
PubMed2003

Spectrophotometric determination of procaine hydrochloride in pharmaceutical products using 1,2-naphthoquinone-4-sulfonic acid as the chromogenic reagent.

Spectrophotometric determination of procaine hydrochloride is described. The procaine hydrochloride reacts with 1,2-naphthoquinone-4-sulfonic acid in pH 3.60 buffer solution to form a salmon pink compound, and its maximum absorption wavelength is at 484 nm, epsilon(484)=5.22 x 10(3).The absorbance for procaine hydrochloride from 0.30 to 100 microg ml(-1) obeys Beer's law. The linear regression equation of the calibration graph is C=19.23A-0.03, with a linear regression correlative coefficient is 0.9996, the detection limit is 0.28 microg ml(-1); recovery is from 98.0 to 105.2%. Effects of pH, surfactant, organic solvent, foreign ions, and standing time on the determination of procaine hydrochloride have been examined. This method is rapid and simple, and can be used for the determination of procaine hydrochloride in injection solution of procaine hydrochloride. The results obtained by this method agreed with those by the official method (dead-stop titration).

Hydrogen-Ion Concentration↗
PubMed2003

Why don't physicians use their personal digital assistants?

As the Personal Digital Assistant (PDA) user population continues to expand, there is a need to design more useful devices and applications to facilitate the utilization of PDAs. We conducted a structured interview study to examine PDA usage and non-usage patterns among physicians. The purpose of this descriptive study was to identify the barriers that impede physicians in their PDA use. A data collection tool was developed to record: 1) how physicians use their PDAs, 2) functions and applications used, 3) functions and applications not used, 4) reasons and examples of why physicians don't use PDAs for those functions, and 5) the recall of specific incidents of PDA usage using Critical Incident Technique (CIT). Interview data were transcribed and analyzed. Study findings and how those barriers can be addressed are discussed.

Academic Medical Centers↗
PubMed2003

Coordination challenges in operating-room management: an in-depth field study.

Dynamic settings possess complex information needs all requiring attention in order to be managed effectively. The following study describes the multi-faceted information exchanges essential for an operating room suite to be managed within the context of efficient, cost effective, safe practice. Through the combined use of observation, the Critical Incident Technique, and interviews, this study analyzed information issues that impact coordination. Results demonstrate how distributed team planning is inherent to the efficacy of the system, and discuss implications for information tools to support coordination within in a complex setting.

Anesthesiology↗
PubMed2003

[Effectiveness of Eretmocerus sp. and Aschersonia aleyrodis in controlling Bemsia tabaci populations].

The effectiveness of Eretmocerus sp. and Aschersonia aleyrodis in controlling Bemisia tabaci populations on cucumber were determined in separated and combined greenhouse experiments. The results showed that after spraying A. aleyrodis (5 x 10(6) spores per ml, twice per generation) and releasing Eretmocerus sp. (3 female per plant, twice per generation), 95.74% and 57.58% of whitefly populations were controlled, respectively. However, when the two natural enemies were used together with the same rate mentioned above (A. aleyrodis spraying twice followed by releasing Eretmocerus sp. once or twice in one generation), 97.02%-97.91% of whitefly populations were controlled. Moreover, the increasing index of whitefly population (I) subjected to both natural enemies together was below I, indicating the substantial reduction in whitefly population. The combined treatments provided a better control effect of whitefly than separated ones, and there was no contradicted effect between both natural enemies.

Animals↗
PubMed2002

A role for the beta-catenin/T-cell factor signaling cascade in vascular remodeling.

Beta-catenin and T cell factor (Tcf) are distal components of the highly conserved Wnt pathway that govern cell fate and proliferation in lower organisms. Thus, we hypothesized that the regulation of beta-catenin and Tcf played a critical role in vascular remodeling. The first objective was to define beta-catenin expression in vascular smooth muscle cells (VSMCs) after balloon injury. Indeed, beta-catenin mRNA and protein were significantly elevated 7 days after balloon injury in the rat carotid artery. We hypothesized that beta-catenin accumulation in response to vascular injury inhibited VSMC apoptosis. In line with our hypothesis, transfection of a degradation-resistant beta-catenin transgene into rat VSMCs significantly inhibited apoptosis. Accumulation of beta-catenin also resulted in a 10-fold increase in the activation of Tcf. To test if Tcf was necessary to confer beta-catenin-induced survival, loss of function studies were carried out with a dominant negative Tcf-4 transgene lacking the beta-catenin binding domain, Tcf4(N31). Indeed, loss of Tcf-4 activity abolished beta-catenin-induced survival. We further postulated that beta-catenin and Tcf promoted cell cycle progression by activating cyclin D1, a target gene of Tcf-4. Beta-catenin activated cyclin D1, and this activation was partially blocked with loss of Tcf-4. In parallel, blockade of Tcf-4 resulted in inhibition of [3H]thymidine incorporation and partial blockade of the G1-S phase transition. In conclusion, beta-catenin and Tcf-4 play a dual role in vascular remodeling by inhibiting VSMC apoptosis and promoting proliferation.

Amino Acid Substitution↗
PubMed2002

Peroxisome proliferator-activated receptor delta is up-regulated during vascular lesion formation and promotes post-confluent cell proliferation in vascular smooth muscle cells.

Although peroxisome proliferator-activated receptor (PPAR) delta is widely expressed in many tissues, the role of PPARdelta is poorly understood. In this study, we report that PPARdelta was up-regulated in vascular smooth muscle cells (VSMC) during vascular lesion formation. By using Northern blot analysis, we demonstrated that PPARdelta was increased by 3-4-fold in VSMC treated with platelet-derived growth factor (PDGF) (20 ng/ml). In addition, PDGF-induced PPARdelta mRNA expression neither needs de novo protein synthesis nor affects the stability of PPARdelta mRNA in VSMC. Preincubation of VSMC with phosphatidylinositol 3-kinase inhibitor (LY294002, 50 micromol/liter) or infection of VSMC with an adenovirus carrying the gene for a dominant negative form of Akt abrogated PDGF-induced PPARdelta mRNA expression, suggesting that phosphatidylinositol 3-kinase/Akt signaling pathway is involved in the regulation of PDGF-induced PPARdelta mRNA expression in VSMC. To explore the role of PPARdelta in VSMC, we generated rat vascular smooth muscle cells (A7r5) stably overexpressing PPARdelta and the control green fluorescent protein. Overexpression of PPARdelta in VSMC increased post-confluent cell proliferation by increasing the cyclin A and CDK2 as well as decreasing p57(kip2). Taken together, the results suggest that PPARdelta plays an important role in the pathology of diseases associated with VSMC proliferation, such as primary atherosclerosis and restenosis.

Animals↗