Biomedical subjects

C Chen

Publications and source records attributed to C Chen.

At least 19 recordsLinked to original sources

PubMed2026

[Genomic evolution and epidemiological patterns of respiratory syncytial virus and their implications for surveillance and early warning].

Respiratory syncytial virus (RSV) is an important respiratory pathogen in infants, young children and older adults. Based on global RSV genomic surveillance data, this review systematically summarizes the geographic distribution, seasonal epidemic patterns, and long-term evolutionary trends of RSV, with particular emphasis on the sustained circulation and evolutionary mechanisms of dominant genotypes such as ON1 in RSV-A and BA9 in RSV-B. Current evidence indicates that RSV transmission dynamics are tightly coupled with viral evolution. The G gene evolves relatively rapidly and contains multiple positively selected sites, suggesting an important role in immune escape and population adaptation. In recent years, changes in social behavior patterns and population immunity have further disrupted the seasonal rhythm of RSV and may have influenced the spread of dominant genotypes. Under routine respiratory infectious disease surveillance, strengthened genomic monitoring and integration of multi-source data are needed to improve early warning of abnormal RSV epidemics and variant-associated risks, thereby providing prospective evidence for protecting high-risk populations and informing public health decision-making.

Humans↗

PubMed2002

Search for new physics in photon-lepton events in pp collisions at sqrt[s] = 1.8 TeV.

We present the results of a search in pp collisions at sqrt[s] = 1.8 TeV for anomalous production of events containing a photon and a lepton (e or mu), both with large transverse energy, using 86 pb(-1) of data collected with the Collider Detector at Fermilab during the 1994-1995 collider run at the Fermilab Tevatron. The presence of large missing transverse energy (E(T)), additional photons, or additional leptons in these events is also analyzed. The results are consistent with standard model expectations, with the possible exception of photon-lepton events with large E(T), for which the observed total is 16 events and the expected mean total is 7.6+/-0.7 events.

Journal Article↗

PubMed2002

Coupled lactic acid fermentation and adsorption.

Polyvinylpyridine (PVP) and activated carbon were evaluated for coupled lactic acid fermentation and adsorption, to prevent the product concentration from reaching inhibitory levels. The lactic acid production doubled as a result of periodical circulation of the fermentation broth through a PVP adsorption column. The adsorbent was then regenerated and the adsorbed lactate harvested, by passing 0.1 N NaOH through the column. However, each adsorption-regeneration cycle caused about 14% loss of the adsorption capacity, thus limiting the practical use of this rather expensive adsorbent. Activated carbon was found much more effective than PVP in lactic acid and lactate adsorption. The cells of Lactobacillus delbrueckii subsp. delbrueckii (LDD) also had strong tendency to adsorb on the carbon. A study was therefore conducted using an activated carbon column for simultaneous cell immobilization and lactate adsorption, in a semi-batch process with periodical medium replacement. The process produced lactate steadily at about 1.3 g l(-1)h(-1) when the replacement medium contained at least 2 g l(-1) of yeast extract. The production, however, stopped after switching to a medium without yeast extract. Active lactic acid production by LDD appeared to require yeast extract above a certain critical level (<2 g l(-1)).

Adsorption↗

PubMed2002

Upsilon production and polarization in p p macro collisions at square root of s = 1.8 TeV.

We report on measurements of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) differential cross sections (d(2)sigma/dp(T)dy)(/y/<0.4), as well as on the Upsilon(1S) polarization in p p macro collisions at square root of s = 1.8 TeV using a sample of 77+/-3 pb(-1) collected by the collider detector at Fermilab. The three resonances were reconstructed through the decay Upsilon-->mu(+)mu(-). The measured angular distribution of the muons in the Upsilon(1S) rest frame is consistent with unpolarized meson production.

Journal Article↗

PubMed2002

Diffractive dijet production at sqrt[s] = 630 and 1800 GeV at the Fermilab Tevatron.

We report a measurement of the diffractive structure function F(D)(jj) of the antiproton obtained from a study of dijet events produced in association with a leading antiproton in pp collisions at sqrt[s] = 630 GeV at the Fermilab Tevatron. The ratio of F(D)(jj) at sqrt[s] = 630 GeV to F(D)(jj) obtained from a similar measurement at sqrt[s] = 1800 GeV is compared with expectations from QCD factorization and other theoretical predictions. We also report a measurement of the xi ( x-Pomeron) and beta ( x of parton in Pomeron) dependence of F(D)(jj) at sqrt[s] = 1800 GeV. In the region 0.035<xi<0.095, /t/<1 GeV2, and beta<0.5, F(D)(jj)(beta,xi) is found to be of the form beta(-1.0+/-0.1)xi(-0.9+/-0.1), which obeys beta-xi factorization.

Journal Article↗

PubMed2002

Search for new heavy particles in the WZ0 final state in pp collisions at square root[s] = 1.8 TeV.

We present the first general search for new heavy particles, X, which decay via X --> WZ0 --> e(nu)+jj as a function of M(X) and Gamma(X) in pp collisions at square root[s] = 1.8 TeV. No evidence is found for production of X in 110 pb(-1) of data collected by the Collider Detector at Fermilab. General cross section limits are set at the 95% C.L. as a function of mass and width of the new particle. The results are further interpreted as mass limits on the production of new heavy charged vector bosons which decay via W' --> WZ0 in an extended gauge model as a function of the width, Gamma(W'), and mixing factor between the W' and the standard model W bosons.

Journal Article↗

PubMed2002

Study of B0 --> J/psiK(*)0pi(+)pi(-) decays with the collider detector at Fermilab.

We report a study of the decays B0 --> J/psiK(*)0pi(+)pi(-), which involve the creation of a uu or dd quark pair in addition to a b -->c(cs) decay. The data sample consists of 110 pb(-1) of pp collisions at square root[s] = 1.8 TeV collected by the CDF detector at the Fermilab Tevatron collider during 1992-1995. We measure the branching fractions to be B(B0 --> J/psiK(*0)pi(+)pi(-)) = (6.6 +/- 1.9 +/- 1.1)x10(-4) and B(B0 --> J/psiK0pi(+)pi(-)) = (10.3 +/- 3.3 +/- 1.5)x10(-4). Evidence is seen for contributions from psi(2S)K(*)0, J/psiK0rho(0), J/psiK(*+)pi(-), and J/psiK1(1270).

Journal Article↗

PubMed2002

Measurement of the strong coupling constant from inclusive jet production at the Tevatron pp collider.

We report a measurement of the strong coupling constant, alpha(s)(MZ), extracted from inclusive jet production in pp collisions at square root[s] = 1800 GeV. The QCD prediction for the evolution of alpha(s) with jet transverse energy ET is tested over the range 40<ET<450 GeV using ET for the renormalization scale. The data show good agreement with QCD in the region below 250 GeV. The value of alpha(s) at the mass of the Z0 boson averaged over the range 40<ET<250 GeV is found to be alpha(s)(MZ) = 0.1178+/-0.0001(stat)+0.0081(-0.0095)(expt. syst). The associated theoretical uncertainties are mainly due to the choice of renormalization scale ((+6%)(-4%)) and input parton distribution functions (5%).

Journal Article↗

PubMed2002

Search for gluinos and scalar quarks in pp collisions at square root[s] = 1.8 TeV using the missing energy plus multijets signature.

We have performed a search for gluinos (g) and scalar quarks (q) in a data sample of 84 pb(-1) of pp collisions at square root[s] = 1.8 TeV, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and three or more jets, a characteristic signature in R-parity-conserving supersymmetric models. The analysis has been performed "blind," in that the inspection of the signal region is made only after the predictions from standard model backgrounds have been calculated. Comparing the data with predictions of constrained supersymmetric models, we exclude gluino masses below 195 GeV/c2 (95% C.L.), independent of the squark mass. For the case m(q) approximately m(g), gluino masses below 300 GeV/c2 are excluded.

Journal Article↗

PubMed2002

Gastric bypass model in the obese rat to study metabolic mechanisms of weight loss.

A rat model replicating gastric bypass with Roux-en-Y (GB) as used in morbidly obese patients, evolved in our laboratory in stages, using the Zucker rat as an obese model (GB) is presented. In the final model, a 20% gastric fundic pouch to limit the gastric reservoir was created using two staple lines (Ethicon). A 4- to 5-mm end-to-side gastrojejunostomy and a 6- to 8-mm jejunojejunostomy, at 10 cm length of the Roux-en-Y limb, placed 16 cm below the ligament of Treitz, was hand sewn to create a limited area of nutrient digestion and absorption. Controls underwent sham operation. Rats were divided into: (i) sham-op ad lib-fed (Control); (ii) GB; and (iii) sham-op pair fed (PF) in two experiments. In Experiment 1, 24 Zuckers (control n = 8; GB n = 8; PF n = 8) were studied to assess the effectiveness of the model for weight loss. In Experiment 2, 24 Zuckers (8/group) were studied to confirm the effects of the operation on weight loss and on metabolic parameters. Boost was given for 4 days starting 24 h postop and then ground chow was given. Daily food intake (FI), meal size (MZ), meal number (MN), and body weight (BW) were measured. Rats were sacrificed on Day 20 in Experiment 1 and on Day 10 in Experiment 2. Serum metabolites and body fat weight were measured. Data were evaluated using Student's t test. Controls steadily gained BW (5.2-6.1 g/day), reaching approximately 500 g. In GB: FI, MZ, MN, BW, glucose, free fatty acids, insulin, and body fat decreased (P < 0.05). In PF: BW, insulin, triglycerides, and body fat decreased. A dependable, reproducible gastric bypass with Roux-en-Y obesity model was developed. This permits the study of biochemical and eventually molecular mechanism(s) of weight loss resulting from the operation.

Adipose Tissue↗

PubMed2002

Development and evaluation of a novel decellularized vascular xenograft.

Although autogenous saphenous vein remains the standard for coronary and infrapopliteal bypass, many patients do not have a suitable vein. Attempts at developing a small-caliber vascular graft have failed largely due to occlusion, neointimal hyperplasia, or aneurismal degradation. We have designed and characterized a novel small-caliber vascular xenograft that may overcome these failure modes. To reduce immune reactions, porcine common carotid arteries were decellularized by enzymatic and detergent treatments. Histology and electron microscopic examination showed complete removal of cellular components while the extracellular matrix structure remained intact. To reduce thrombogeneity, decellularized vascular grafts were covalently linked with heparin. The efficiency of heparin linkage was demonstrated with toluidine blue staining and the antithrombogeneity of the heparin-treated grafts was demonstrated with a clot time test. Mechanical testing of the graft was performed. Decellularized-heparin-treated grafts were similar in compliance to fresh vessels and burst testing showed grafts to withstand pressures exceeding 10 times physiologic blood pressure. There was no difference in suture retention strength between fresh vessels and decellularized-heparin-treated grafts. Decellularized, heparinized grafts were implanted in dogs as carotid artery bypass grafts and showed smooth muscle cells densely populating the wall, and endothelial cells lining the lumen by two months. This study provides a new strategy to develop a small-caliber vascular graft with excellent mechanical properties, antithrombogeneity, and tissue compatibility.

Animals↗

PubMed2002

Novel peptide inhibitors for Grb2 SH2 domain and their detection by surface plasmon resonance.

One of the critical intracellular signal transduction pathways involves the binding of the Grb2 SH2 domain to the phosphotyrosine (pTyr) motifs on growth factor receptors, such as epidermal growth factor receptor (EGFR) and erbB2, leading to downstream activation of the oncogenic Ras signaling pathway. Therefore, the Grb2 SH2 domain has been chosen as our target for the development of potential anticancer agents. As a continuation of our earlier work, herein we report the design and synthesis of new peptide analogs, and their inhibitory effect on the Grb2 SH2 domain using surface plasmon resonance (SPR) technology. These novel agents do not contain phosphotyrosine or phosphotyrosine mimics. Binding interactions between these peptides and the Grb2 SH2 domain were measured and analyzed using a BIAcore X instrument, which provides detailed information on the real-time detection of the binding interaction. The results of this study should provide important information for the further development of peptides or peptidomimetics with high affinity for the Grb2 SH2 domain.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Application of actinomycetes to soil to ameliorate water repellency.

AIMS: The aim of this study was to develop a novel isolation technique using a mixture of Bacillus and Streptomyces phages to selectively isolate wax-utilizing non-streptomycete actinomycetes effective in ameliorating water repellency in a problem soil. METHODS AND RESULTS: Phages added to a soil suspension reduced the dominance of Bacillus and Streptomyces isolates and significantly increased the number of non-streptomycete actinomycetes on isolation plates. Promising isolates, grown on a medium containing beeswax as sole carbon source, were selected for application to water repellent soil. Their addition significantly reduced water repellency. CONCLUSIONS: Phage application significantly increased the isolation of non-streptomycete actinomycetes. Wax-utilizing isolates were found to significantly reduce water repellency in a problem soil. SIGNIFICANCE AND IMPACT OF THE STUDY: The phage technique can be used for the routine isolation of non-streptomycete actinomycetes. Beeswax medium can be used to selectively isolate wax-utilizing micro-organisms with the potential to ameliorate water repellency in soil.

Actinobacteria↗

PubMed2002

Reliability of serial urine HCG as a biomarker to detect early pregnancy loss.

BACKGROUND: To examine the reliability of HCG as a biomarker for early pregnancy loss, five experienced researchers independently assessed data from 153 menstrual cycles, determining whether each cycle represented 'no conception,' a 'continuing conception' or a 'conception lost.' METHODS: Urine samples were analysed by immunoradiometric assay using a combination of capture antibodies for the intact heterodimer (B109) and for an epitope common to the beta subunit and the beta core fragment (B204). For each cycle, HCG data were presented as graphs of daily assay results. Summary statistics for HCG assays from 46 women who had undergone bilateral tubal ligation represented baseline values. RESULTS: Pairwise agreement among the assessors for any of the three options ranged from 78-89%. At least three experts agreed for 147 cycles (96%), accounting for 28 conception losses and 19 continuing conceptions. The multi-rater kappa was 0.62 for the conception lost category and 0.68 for continuing conceptions, indicating substantial agreement. CONCLUSION: The main sources of disagreement involved deciding whether there was sufficient information for assessment, interpreting cycle parameters such as cycle length or bleeding event, and interpreting a distinct HCG rise pattern that does not exceed the baseline value obtained from the sterilized women.

Abortion, Spontaneous↗

PubMed2002

Pain as a factor complicating recovery and discharge after ambulatory surgery.

UNLABELLED: Pain complicates the recovery process after ambulatory surgery. We surveyed 175 ambulatory surgery patients to determine pain severity, analgesic use, relationship of pain to duration of recovery, and the relative importance of various factors to predicting these outcomes. Multivariate regression analysis was used to determine unique contributions of predictor variables to outcome. Surgical procedures included knee arthroscopy (n = 50), hernia surgery (n = 25), pelvic laparoscopy (n = 25), transvaginal uterine surgery (n = 25), surgery for breast disease (n = 25), and plastic surgery (n = 25). Maximum pain (on a scale of 0-10) varied from 2.3 +/- 0.5 to 5.1 +/- 0.5 (mean +/- SE), depending on surgical procedure; 24% of patients had pain scores of > or =7, and 24% were delayed in Phase 1 recovery by pain. Pain scores were lower if local anesthetic or ketorolac was administered intraoperatively (22% and 26% respectively). Fentanyl dose during recovery correlated with maximum pain scores; fentanyl dose was 42% less if ketorolac was administered intraoperatively. In females, the recovery fentanyl dose increased in proportion to the intraoperative fentanyl dose. The maximum pain score was predictive of total recovery time (135, 172, and 212 min of recovery for maximum pain scores of 0-3, 4-6, and 7-10, respectively; P < 0.001). We conclude that improvements in pain therapy are warranted to improve patient comfort and to expedite recovery. IMPLICATIONS: Moderate to severe pain is common after ambulatory surgery and is a frequent cause of delayed discharge. Postoperative pain, opioid-related side effects, and time to discharge were less when nonsteroidal antiinflammatory drugs or local anesthetics were used intraoperatively to prevent pain before patient awakening.

Adult↗

PubMed2002

Diffusion weighted MR imaging in acute stroke: the SGH experience.

Cerebrovascular accident (CVA) is a leading cause of death and disability in many countries. Diffusion-weighted (DW) magnetic resonance (MR) imaging has been reported to be useful in the detection of acute strokes and as an investigative tool evaluating the therapeutic effects of neuroprotective and thrombolytic agents. The objectives of this study are to share our experience using the commercially available isotropic DW scan in imaging of acute stroke, assess its usefulness over conventional T2-weighted (T2W) scans in a busy clinical radiology unit and highlight it pitfalls. We found the rapid sub-minute DW technique well suited for ill and restless stroke patients and superior to T2W scans in many ways. It was highly sensitive to acute ischaemic lesions, made lesions easily identifiable and readily differentiated the acute lesion from a background of multiple chronic infarcts. However, there are potential pitfalls in the evaluation of small hyperacute posterior fossa strokes and venous infarcts. The major strength of this MR technique lies in its ability to diagnose hyperacute strokes and thence the potential for therapeutic thrombolysis, but unfortunately patients qualifying for the "therapeutic window" were a minority. More efforts need to be focused on public education in order for this powerful imaging modality to find its true value and contribute to viability of an effective thrombolytic programme.

Adult↗

PubMed2002

Cerebral infarct mimicking glioma in Sjogren's syndrome.

A 50-year-old Chinese woman with a chronic 20-year history of ataxic gait associated with dry eyes and mouth, was admitted to hospital after a single episode of syncope. Magnetic resonance imaging scans showed a large left frontal hypodense lesion suggestive of a glioma. Craniotomy was performed and the lesion excised, with histology showing only infarcted tissue and no malignant cells. Further diagnostic evaluation revealed that the patient had primary Sjogren's syndrome, with demyelinating polyneuropathy. In the absence of risk factors for stroke, it was considered likely that the cerebral infarct was secondary to autoimmune-related vasculitis. Functional neuroimaging, such as magnetic resonance spectroscopy, should be considered in evaluating doubtful or unusual brain lesions in patients with autoimmune disease.

Brain↗

PubMed2002

Over-expression of beta-1,4-galactosyltransferase V increases the growth of astrocytoma cell line.

Our previous study showed that the gene expression of beta-1,4-galactosyltransferase V (beta-1,4-GalT V), preferentially galactosylating GlcNAc1-->6Man of oligosaccharides, increased in the process of astrocytoma progress, with the highest level in grade IV astrocytoma. To investigate the function of this beta-1,4-GalT in cell proliferation, the sense and antisense cDNA of beta-1,4-GalT V was constructed as pcDNA3-HA-GalT V and pcDNA3-anti-GalT V respectively and transfected into SHG cell, a kind of human astrocytoma cell line. The transfection was confirmed with Northern and Western blot assay. It was found that the growth of SHG/HA-GalT V in serum-containing medium was faster than that of mock-transfectant with the vector pcDNA3, whereas the growth of SHG/GalTV-AS was slower than that of mock-transfectant. GalTV-HA/SHG showed a stronger capability for colony formation than that of GalTV-AS/SHG as evaluated by anchorage-independent growth in soft agar assay. This result was consistent with that of the growth curve. By RCA-1 lectin assay, the galactosylation on the surface of GalTV-HA/SHG and SHG/GalTV-AS was stained stronger (P<0.001) and weaker (P<0.05) respectively compared with the mock transfectant. This indicates that beta-1,4-GalT V was involved in the malignant phenotype of astrocytoma cells, possibly causing the high galactosylation on the cell surface.

Astrocytoma↗