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Biomedical subjects

W Chang

Publications and source records attributed to W Chang.

At least 19 recordsLinked to original sources
PubMed2006

Fibroblast growth factor-10 prevents H2O2-induced cell cycle arrest by regulation of G1 cyclins and cyclin dependent kinases.

We studied the effects of fibroblast growth factor (FGF-10) on H2O2-induced alveolar epithelial cell (AEC) G1 arrest and the role of G1 cyclins. FGF-10 prevented H2O2-induced AEC G1 arrest. FGF-10 induced 2-4-fold increase in cyclin E, cyclin A and CDKs (2,4) alone and in AEC treated with H2O2. H2O2 downregulated cyclin D1; FGF-10 blocked these effects. FGF-10 prevented H2O2-induced upregulation of CDK inhibitor, p21. SiRNAp21 blocked H2O2-induced downregulation of cyclins, CDKs and AEC G1 arrest. Accordingly, we provide first evidence that FGF-10 regulates G1 cyclins and CDKs, and prevents H2O2-induced AEC G1 arrest.

Cell Cycle↗
PubMed2005

Time to treatment and the impact of a physician on prehospital management of acute ST elevation myocardial infarction: insights from the ASSENT-3 PLUS trial.

OBJECTIVES: To assess the impact of variation in prehospital care across distinct health care environments in ASSENT (assessment of the safety and efficacy of a new thrombolytic) -3 PLUS, a large (n = 1639) contemporary multicentred international trial of prehospital fibrinolysis. Specifically, the objectives were to assess predictors of time to treatment, whether components of time to treatment vary across countries, and the impact of physician presence before hospitalisation on time to treatment, adherence to protocol, and clinical events. METHODS: Patient characteristics associated with early treatment (< or = 2 hours), comparison of international variation in time to treatment, and components of delay were assessed. Trial specific patient data were linked with site specific survey responses. RESULTS: Younger age, slower heart rate, lower systolic blood pressure, and prior percutaneous coronary intervention were associated with early treatment. Country of origin accounted for the largest proportion of variation in time. Intercountry heterogeneity was shown in components of elapsed time to treatment. Physicians in the prehospital setting enrolled 63.8% of patients. The presence of a physician was associated with greater adherence to protocol mandated treatments and procedures but with delay in time to treatment (120 v 108 minutes, p < 0.001). CONCLUSION: Country of enrollment accounted for the largest proportion of variation in time to treatment and intercountry heterogeneity modulated components of delay. The effectiveness and safety of prehospital fibrinolysis was not influenced by the presence of a physician. These data, acquired in diverse health care environments, provide new understanding into the components of prehospital treatment delay and the opportunities to further reduce time to fibrinolysis for patients with ST elevation myocardial infarction.

Age Factors↗
PubMed2004

Room-temperature ferroelectricity in strained SrTiO3.

Systems with a ferroelectric to paraelectric transition in the vicinity of room temperature are useful for devices. Adjusting the ferroelectric transition temperature (T(c)) is traditionally accomplished by chemical substitution-as in Ba(x)Sr(1-x)TiO(3), the material widely investigated for microwave devices in which the dielectric constant (epsilon(r)) at GHz frequencies is tuned by applying a quasi-static electric field. Heterogeneity associated with chemical substitution in such films, however, can broaden this phase transition by hundreds of degrees, which is detrimental to tunability and microwave device performance. An alternative way to adjust T(c) in ferroelectric films is strain. Here we show that epitaxial strain from a newly developed substrate can be harnessed to increase T(c) by hundreds of degrees and produce room-temperature ferroelectricity in strontium titanate, a material that is not normally ferroelectric at any temperature. This strain-induced enhancement in T(c) is the largest ever reported. Spatially resolved images of the local polarization state reveal a uniformity that far exceeds films tailored by chemical substitution. The high epsilon(r) at room temperature in these films (nearly 7,000 at 10 GHz) and its sharp dependence on electric field are promising for device applications.

Journal Article↗
PubMed2003

Early neutrophilic expression of vascular endothelial growth factor after traumatic brain injury.

The formation of edema after traumatic brain injury (TBI) is in part associated with the disruption of the blood-brain barrier. However, the molecular and cellular mechanisms underlying these phenomena have not been fully understood. One possible factor involved in edema formation is vascular endothelial growth factor (VEGF). This growth factor has previously been demonstrated to increase the blood-brain barrier permeability to the low molecular weight markers and macromolecules. In this study, we analyzed the temporal changes in VEGF expression after TBI in rats. In the intact brain, VEGF was expressed at relatively low levels and was found in the cells located close to the cerebrospinal fluid space. These were the astrocytes located under the ependyma and the pia-glial lining, as well as the epithelial cells of the choroid plexus. In addition, several groups of neurons, including those located in the frontoparietal cortex and in all hippocampal regions, were VEGF-positive. The pattern of VEGF-immunopositive staining of neurons and choroidal epithelium suggested that in these cells, VEGF binds to the cell membrane-associated heparan sulfate proteoglycans. Following TBI, there was an early (within 4 h post-injury) increase in VEGF expression in the traumatized parenchyma associated with neutrophilic invasion. The ipsilateral choroid plexus appeared to play a role in facilitating the migration of neutrophils from blood into the cerebrospinal fluid space, from where many of these cells infiltrated the brain parenchyma. VEGF-immunopositive staining of neutrophils resembled haloes and was found ipsilaterally within the frontoparietal cortex and around the velum interpositum, a part of the subarachnoid space. These haloes likely represent the deposition of neutrophil-derived VEGF within the extracellular matrix, from where this growth factor may be gradually released during an early post-traumatic period. The maximum number of VEGF-secreting neutrophils was observed between 8 h and 1 day after TBI. In addition, from 4 h post-TBI, there was a progressive increase in the number of VEGF-immunoreactive astrocytes in the ipsilateral frontoparietal cortex. The maximum number of astrocytes expressing VEGF was observed 4 days after TBI, and then the levels of astroglial VEGF expression declined gradually. Early invasion of brain parenchyma by VEGF-secreting neutrophils together with a delayed increase in astrocytic synthesis of this growth factor correlate with the biphasic opening of the blood-brain barrier and formation of edema previously observed after TBI. Therefore, these findings suggest that VEGF plays an important role in promoting the formation of post-traumatic brain edema.

Animals↗
PubMed2003

Circulating interleukin 17 is increased in the acute stage of Kawasaki disease.

OBJECTIVES: During the acute phase, patients with Kawasaki disease (KD), an acute systemic vasculitis, demonstrate a drastic increase in serum interleukin-6 (IL-6), which parallels the duration of the fever. Recently, IL-17 has been reported to induce IL-6 production. The aim of this study was to elucidate the involvement of IL-17 in the pathogenesis of KD. METHODS: Serum samples were obtained from patients with KD (n=30) and normal controls (n=20), and the concentrations of IL-17 and IL-6 measured using enzyme-linked immunosorbent assay (ELISA). RESULTS: Compared with the normal controls (2.08 +/- 2.14 pg/mL), serum IL-17 was markedly elevated in patients with acute KD (25.47 +/- 5.05 pg/mL): levels gradually decreased in the subacute phase (5.94 +/- 2.83 pg/mL). In the acute phase, levels of IL-6 were 83.52 +/- 19.12 pg/L, which correlated well with the serum levels of IL-17. CONCLUSION: These results suggest that IL-17 may be involved in the development of, or the effects of inflammation in KD.

Acute Disease↗
PubMed2003

Polycystic ovary syndrome and ovulation induction.

Polycystic ovary syndrome (PCOS) is likely the most common cause of anovulatory infertility. Although many options are available for ovulation induction in these patients, there is currently no evidence-based algorithm to guide the initial and subsequent choices of ovulation induction methods. In obese women with PCOS, mild to moderate weight loss results in improvement of ovulatory dysfunction, and should be advocated at the onset of the evaluation. Clomiphene citrate is currently the 1st line medical therapy for ovulation induction. Glucocorticoids do not result in consistent ovulation and have significant side effects. Exogenous pulsatile GnRH treatment has low ovulation and pregnancy rates with a high risk of miscarriage. The most commonly used medical agents for ovulation induction in clomiphene-resistant women with PCOS are parenteral gonadotropins. Various gonadotropin preparations and different protocols are available; however the risk of multiple pregnancy and ovarian hyperstimulation is high with gonadotropin therapy. The frequent association between PCOS and insulin resistance has prompted recent studies on the effect of insulin-sensitizing agents on spontaneous and as an adjuvant to conventional ovulation induction therapies. Overall, the improvement in ovulation with insulin sensitizing drugs is modest, and unresolved issues such as variability in ovarian response remain to be addressed in future studies. Nevertheless, these agents may be beneficial in a subset of PCOS patients. Surgical ovulation induction methods such as ovarian diathermy have been reported to be moderately effective. However, due to the inherent associated risks and unknown effect on long-term reproductive potential, this modality should be reserved for patients who are clomiphene-resistant and unable or unwilling to proceed to gonadotropin therapy.

Female↗
PubMed2002

Use of natural zeolite to enhance nitrification in biofilter.

To enhance nitrification, natural zeolite and activated carbon were tested as a media in a biofilter to treat wastewater containing relatively high concentrations of TKN. Using those media, the adsorption isotherms for ammonium ion were compared; the K values for natural zeolite and activated carbon were found to be 0.5117 and 0.0006, respectively. In comparison of the performance of the two media, two identical, lab-scale biofilters were then operated for 4 months. The effect of NH3-N loading rates on the performance was investigated. The results showed that higher NH3-N removal efficiency and faster nitrification were achieved in the biofilter with natural zeolite throughout the experimental period. Nitrosomonas and Nitrobacter, two principal nitrifiers, in biofilm grown on two different media were counted and compared. Nitrobacter which is the more fragile of the two principal nitrifiers was outgrown in the biofilm on natural zeolite media. The reason for this may be due to the ammonium ion exchanging capacity of natural zeolite which provided the favorable environment for Nitrobacter.

Biodegradation, Environmental↗
PubMed2001

Amino acids in the cytoplasmic C terminus of the parathyroid Ca2+-sensing receptor mediate efficient cell-surface expression and phospholipase C activation.

The C-terminal tail of the calcium receptor (CaR) regulates the affinity of the receptor for ligand, desensitization, and membrane localization. To determine the role of specific amino acids in the bovine parathyroid CaR in mediating signal transduction and cell-surface expression, we transfected truncated and mutated CaR cDNAs into HEK-293 cells. The ability of high extracellular [Ca(2+)] ([Ca(2+)](o)) to increase total inositol phosphate (InsP) production, an index of phospholipase C (PLC) activation, was determined. Receptor expression was assessed by immunoblotting and immunocytochemistry. In cells transiently or stably expressing receptors with the C-terminal tail truncated after residue 895 (CaR-(1-895)) or 929 (CaR-(1-929)), raising [Ca(2+)](o) increased InsPs to levels comparable with those of cells expressing wild-type CaRs. There were no PLC responses to high [Ca(2+)](o) (up to 30 mm) in cells expressing CaRs with C-terminal tails of only 3 residues (CaR-(1-866)), even though these receptors were expressed in the membrane. We scanned the residues between Ser(866) and Val(895) using tandem-Ala and single-site mutagenesis. Two point mutants (His(880) --> Ala and Phe(882) --> Ala CaR) showed 50-70% reductions in high [Ca(2+)](o)-induced InsP production. The levels of expression and glycosylation of these mutants were comparable with wild-type CaRs, but both receptors were profoundly retained in intracellular organelles and co-localized with the endoplasmic reticulum marker BiP. This suggested that the signaling defects of these receptors were likely because of defective trafficking of receptors to the cell surface. Modeling of the C-terminal domain of the CaR indicated that His(880) and Phe(882) are situated in a putative alpha-helical structure of 15 amino acids between residues 877 and 891 in the C-terminal tail. Our studies support the idea that specific amino acids, and possibly a unique secondary structure in the C-terminal tail, are required for the efficient targeting of the CaR to the cell surface required for PLC activation.

Amino Acid Sequence↗
PubMed2001

The extracellular calcium-sensing receptor is required for calcium-induced differentiation in human keratinocytes.

In cultured keratinocytes, the acute increase of the extracellular calcium concentration above 0.03 mM leads to a rapid increase in intracellular calcium concentration ([Ca(2+)]i) and inositol trisphosphate production and, subsequently, to the expression of differentiation-related genes. Previous studies demonstrated that human keratinocytes express the full-length extracellular calcium-sensing receptor (CaR) and an alternatively spliced variant lacking exon 5 and suggested their involvement in calcium regulation of keratinocyte differentiation. To understand the role of the CaR, we transfected keratinocytes with an antisense human CaR cDNA construct and examined its impact on calcium signaling and calcium-induced differentiation. The antisense CaR cDNA significantly reduced the protein level of endogenous CaRs. These cells displayed a marked reduction in the rise in [Ca(2+)]i in response to extracellular calcium or to NPS R-467, a CaR activator, whereas the ATP-evoked rise in [Ca(2+)]i was not affected. Calcium-induced inhibition of cell proliferation and calcium-stimulated expression of the differentiation markers involucrin and transglutaminase were also blocked by the antisense CaR cDNA. When cotransfected with luciferase reporter vectors containing either the involucrin or transglutaminase promoter, the antisense CaR cDNA suppressed the calcium-stimulated promoter activities. These results indicate that CaR is required for mediating calcium signaling and calcium-induced differentiation in keratinocytes.

Amino Acid Sequence↗
PubMed2001

An aspartic protease analogue: intermolecular catalysis of peptide hydrolysis by carboxyl groups.

Two aspartic carboxyl groups act as key catalytic groups in the active site of an aspartic protease. We synthesized an aspartic protease analogue by positioning three salicylate residues in close proximity on a cross-linked polystyrene. The immobile artificial protease effectively hydrolyzed albumin into many small fragments by the catalytic action of carboxyl groups contained in the active site. The artificial protease manifested optimum activity at pH 3 just as aspartic proteases.

Albumins↗
PubMed2001

Crystal structure of destripeptide (B28-B30) insulin: implications for insulin dissociation.

Destripeptide (B28-B30) insulin (DTRI) is an insulin analogue that has much weaker association ability than native insulin but keeps most of its biological activity. It can be crystallized from a solution containing zinc ions at near-neutral pH. Its crystal structure has been determined by molecular replacement and refined at 1.9 A resolution. DTRI in the crystal exists as a loose hexamer compared with 2Zn insulin. The hexamer only contains one zinc ion that coordinates to the B10 His residues of three monomers. Although residues B28-B30 are located in the monomer-monomer interface within a dimer, the removal of them can simultaneously weaken both the interactions between monomers within the dimer and the interactions between dimers. Because the B-chain C-terminus of insulin is very flexible, we take the DTRI hexamer as a transition state in the native insulin dissociation process and suggest a possible dissociation process of the insulin hexamer based on the DTRI structure.

Crystallization↗
PubMed2001

Protein phosphatase 2A: identification in Oryza sativa of the gene encoding the regulatory A subunit.

A 2225 bp cDNA, designated RPA1, was isolated from an Oryza sativa cDNA library. Analysis revealed a 1761 bp coding sequence with 15 non-identical repeat units. The ORF encoded the A regulatory subunit of protein phosphatase 2A (PP2A-A) as ascertained by complementation of the yeast tpd3 mutant defective in this gene. The corresponding genomic DNA from a rice genome BAC library revealed that the gene contains eleven introns. The rice genome contains only a single copy of this gene as judged by Southern blot analysis. The PP2A protein is highly conserved in nature; the rice protein shows 88% amino acid identity with its counterparts in Arabidopsis or Nicotiana tabacum.

Amino Acid Sequence↗
PubMed2001

Induction of cardiac FABP gene expression by long chain fatty acids in cultured rat muscle cells.

The induction of cardiac FABP expression by long-chain fatty acids was measured in cultured rat myoblasts, myotubes and adult cardiomyocytes. With quantitative RT-PCR techniques, the primary transcription product of the FABP gene and the mature mRNA were measured. Incubations of 30 min resulted in a larger than 2-fold increase of the primary transcript in all cells, and FABP mRNA more than doubled in myoblasts and cardiomyocytes after 10 h of fatty acid exposure. The results demonstrate that long chain fatty acids induce the expression of the cardiac FABP gene in muscle cells and their undifferentiated precursors at the level of transcription initiation, suggesting that all factors involved in fatty acid dependent gene induction are already present in myoblasts. Thus, myoblast cell lines should be useful for the characterization of fatty acid response elements that control the expression of the FABP gene.

Animals↗
PubMed2001

Effect of lipid-lowering dietary recommendations on the nutritional intake and lipid profiles of chronic peritoneal dialysis and hemodialysis patients.

Patients with end-stage renal failure are a high-risk group for atherosclerotic cardiovascular disease and commonly have dyslipidemia as a major factor. Dietary manipulation is the recommended first line of therapy for reducing lipid levels in people with normal renal function; however, complex dietary requirements of dialysis-treated patients with end-stage renal failure impose significant constraints. In this study, we evaluated the effect of trying to comply with established lipid-lowering recommendations superimposed on our normally prescribed dialysis diet over 14 weeks in stable subjects treated with either hemodialysis (HD) or chronic peritoneal dialysis (PD). Of 306 dialysis patients screened, 75 subjects were enrolled; 8 subjects did not complete the study. In the remainder, HD subjects (n = 41) decreased saturated fat intakes by 18% overall and cholesterol intakes by 16%. This was associated with a decrease in total cholesterol levels from 232 +/- 8 to 209 +/- 4 mg/dL (mean +/- SEM; P = 0.007) and low-density lipoprotein cholesterol levels from 147 +/- 4 to 131 +/- 4 mg/dL (P = 0.009). However, energy intakes decreased by almost 10%. There were no statistically significant changes in PD patients (n = 26). Only 24.4% of HD (10 of 41 patients) and 15.4% of PD patients (4 of 26 patients) normalized their lipid levels. Considerable problems were encountered in maintaining compliance with the modified dialysis diets. This study shows that if adhered to, properly constructed dialysis diets are close to optimal lipid-lowering recommendations. Further dietary manipulation is difficult, leads to little benefit in the majority, and is accompanied by added problems of adherence. We conclude that the vast majority of dyslipidemic patients with end-stage renal failure require pharmacological therapy.

Body Mass Index↗