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Biomedical subjects

C H Cheng

Publications and source records attributed to C H Cheng.

At least 19 recordsLinked to original sources
PubMed2004

Dissociation energies of molecular hydrogen and the hydrogen molecular ion.

We have obtained improved values for the dissociation energies of molecular hydrogen and its ion by using a high-resolution pulse-amplified laser to probe the second dissociation limit. The onset of the vibrational continuum is observed by state-selective detection of the atomic products of dissociation, and several auxiliary measurements link the results to the ground state. The dissociation energies are accurate to 0.010-0.026 cm(-1), improving previous measurements by a factor of 3-7. Agreement with ab initio calculations is good for H2, D2, and their ions, but not for HD and HD+.

Journal Article↗
PubMed2004

Biodegradation of phthalate esters by two bacteria strains.

In this study two aerobic phthalic acid ester (PAE) degrading bacteria strains, DK4 and O18, were isolated from river sediment and petrochemical sludge, respectively. The two strains were found to rapidly degrade PAE with shorter alkyl-chains such diethyl phthalate (DEP), dipropyl phthalate (DPrP), di-n-butyl phthalate (DBP), benzylbutyl phthalate (BBP) and diphenyl phthalate (DPP) are very easily biodegraded, while PAE with longer alkyl-chains such as dicyclohexyl phthalate (DCP) and dihexyl phthalate (DHP) and di-(2-ethylhexyl) phthalate (DEHP) are poorly degraded. The degradation rates of the eight PAEs were higher for strain DK4 than for strain O18. In the simultaneous presence of strains DK4 and O18, the degradation rates of the eight PAEs examined were enhanced. When the eight PAEs were present simultaneously, degradation rates were also enhanced. We also found that PAE degradation was delayed by the addition of nonylphenol or selected polycyclic aromatic hydrocarbons (PAHs) at a concentration of 1 microg/g in the sediment. The bacteria strains isolated, DK4 and O18, were identified as Sphigomonas sp. and Corynebacterium sp., respectively.

Biodegradation, Environmental↗
PubMed2004

Risk factors for peptic ulcer disease in renal transplant patients--11 years of experience from a single center.

BACKGROUND: Peptic ulcer disease is a common complication among renal transplant recipients and causes significant morbidity and mortality. METHODS: From 1990 through 2000, 465 renal transplant patients were followed-up in our institute. Most patients received corticosteroids and cyclosporine-based immunosuppressive regimen. About one third (n = 156) of them received mycophenolate mofetil. Patients with endoscopy-proved peptic ulcer disease were identified by reviewing medical records. Possible risk factors were analyzed by univariate analysis and multiple logistic regression analysis. RESULTS: Among 465 kidney transplant patients, there were 181 (38.9%) who suffered at least 1 episode of peptic ulcer disease. The most frequent types of peptic ulcer disease were gastritis, gastric ulcer, duodenal ulcer, esophagitis, duodenitis and esophageal ulcer. By multivariate analysis, the use of methylprednisolone pulse therapy (odds ratio = 3.954, 95% confidence interval = 3.154-18.312, p = 0.03) and history of pre-transplant peptic ulcer disease (odds ratio = 7.599, 95% CI = 1.211-12.905, p < 0.0001) were independent risk factors for posttransplant peptic ulcer disease. CONCLUSIONS: Our findings demonstrated that renal transplant patients who undergo methylprednisolone pulse therapy for acute rejection or who have a history of pre-transplant peptic ulcer disease carry a high risk for the development of peptic ulcer disease and deserve intensive antiulcer treatment.

Adolescent↗
PubMed2003

The Effects of CPOE on ICU workflow: an observational study.

Computerized physician order entry (CPOE) has had demonstrated benefits in error reduction and guideline adherence, but its implementation has often been complicated by disruptions in established workflow processes. We conducted an observational study of the healthcare team in an intensive care unit after the implementation of mandatory CPOE. We found that policies designed to increase flexibility and safety led to an increased coordination load on the healthcare team, and created opportunities for new sources of error. We attribute this in part to implicit assumptions in the CPOE system design that execution of physician orders is a linear work process. Observational workflow studies are an important tool to understand how to redesign CPOE systems so as to avoid harm and achieve the full potential of benefit for improved patient safety.

Attitude of Health Personnel↗
PubMed2002

The ultrastructure of the mature spermatozoon of the bivalve Gafrarium tumidum (Bivalvia, Heterodonta, Veneridae, Circinae).

Using transmission and scanning electron microscopy, we have described the mature spermatozoon of the bivalve Gafrarium tumidum (Heterodonta, Veneridae, Circinae) for the first time. The spermatozoon of G. tumidum is the ect-aquasperm type. The head contains a slightly curved nucleus. At its apex is a short cone-shaped acrosome. The structure of the acrosome is typical of heterodont bivalves and two major components of the acrosome vesicle material can be distinguished. The midpiece is an annular band of five mitochondria which surround the centriole complex. Sperm ultrastructure of G. tumidum provides additional information for the existing Veneridae phylogeny.

Animals↗
PubMed2001

Cross [2 + 2] cycloaddition of bicyclic alkenes with alkynes mediated by cobalt complexes: a facile synthesis of cyclobutene derivatives.

Bicyclic alkenes 1a-e and 5 undergo [2 + 2] cycloaddition with a variety of alkynes PhC(triple bond)CPh, (TMS)C(triple bond)CH, HC(triple bond)C(CH(3))(2)OH, (TMS)C(triple bond)CCO(2)Et, PhC(triple bond)CCH(3), C(2)H(5)C(triple bond)CC(2)H(5), CH(3)C(triple bond)CC(3)H(7), and CH(3)C(triple bond)CC(2)H(5) in the presence of Co(PPh(3))(2)I(2), PPh(3), and Zn powder in toluene to afford the corresponding exo-cyclobutene derivatives 3a-m, 6, and 8a-g in fair to excellent yields. The yield of this cycloaddition is highly sensitive to the cobalt catalyst, solvent, ligand, and temperature used. A mechanism involving a metallacyclopentene intermediate is proposed to account for this cobalt-catalyzed cyclization.

Journal Article↗
PubMed2001

Molecular cloning of a teleost growth hormone receptor and its functional interaction with human growth hormone.

This paper reports the first full-length cDNA sequence of a growth hormone receptor (GHR) from a teleost fish and its functional expression in cultured eukaryotic cells. The cDNA sequence, from Carassius auratus (goldfish), encodes a protein of 602 amino acids (aa) akin in architecture to the GHRs of other species. Despite the presence of motifs characteristic of GHR, the overall homology between the goldfish GHR and other GHRs is very low ( approximately 40% aa identity). CHO cells transfected with this receptor cDNA can be stimulated to proliferate by human growth hormone (hGH). In addition, the transfected cells can transactivate a co-expressed mammalian serine protease inhibitor (Spi) 2.1 promoter upon stimulation by hGH, indicating the successful interaction of the fish receptor with the mammalian ligand to evoke the down-stream post-receptor events. Tissue distribution studies indicated that the receptor is mostly expressed in the liver and hypothalamus of goldfish. A single mRNA transcript of a size of about 4 kb was found in the goldfish liver.

Amino Acid Sequence↗
PubMed2001

Simultaneous monitoring of extracellular glucose, pyruvate, lactate and glutamate in gerbil cortex during focal cerebral ischemia by dual probe microdialysis.

The aim of this study was to monitor dynamic changes in energy-related metabolites in the cortex of gerbils subjected to cerebral ischemia by a dual probe microdialysis technique. Focal cerebral ischemia was produced in anesthetized gerbils by occlusion of the right common carotid artery and the right middle cerebral artery for 60 min. Two microdialysis probes were inserted into both sides of the cortex to simultaneously monitor extracellular glucose, lactate, pyruvate and glutamate. Dynamic and comparative changes in these analytes, on the ipsilateral and contralateral sides of the brain, were simultaneously monitored by liquid chromatography and a microdialysis analyzer. The present study demonstrated decreases in glucose and pyruvate, increases in lactate and glutamate on the ipsilateral side whereas all analytes remain constant on the contralateral side of cortex during cerebral ischemia. In vitro recovery of each microdialysis probe was performed to ensure the quality of experiments. The detection limits of pyruvate, glutamate, lactate and glucose were 0.2, 1.0, 2.0 and 20 microM, respectively. The intra- and inter-assay correlations were less than 5% in standard mixtures and pooled brain dialysates.

Animals↗
PubMed2001

Synthesis of biaryls via unusual deoxygenative dimerization of 1,4-epoxy-1,4-dihydroarenes catalyzed by palladium complexes.

Treatment of various 1,4-epoxy-1,4-dihydroarenes with trichlorosilane in toluene in the presence of a palladium complex affords the corresponding biaryls in good to excellent yields. The process appears to occur via a novel palladium-catalyzed hydrosilylative dimerization of 1,4-epoxy-1,4-dihydroarenes and subsequent elimination of HOSiCl(3) and H(2)O.

Journal Article↗
PubMed2001

Inotropic and chronotropic actions of Ilex latifolia inhibition of adenosine-5 '-triphosphatases as a possible mechanism.

Ilex latifolia is widely used as an ingredient to prepare traditional beverage drinks in southern China. In fact, various Ilex species have been used in Chinese folk medicine to treat coronary heart diseases. The mode of action is believed to be mediated by their coronary vasodilative effects. In this study, the water extract of the leaves of Ilex latifolia (IK-TP) was shown to increase the contractility and decrease the frequency of contraction in an isolated rat heart perfusion system. IK-TP was found to inhibit Na+/K+-ATPase activities in rat heart sarcolemma, rat brain microsomes and a purified enzyme from porcine cerebral cortex. IK-TP also inhibited Ca2+-dependent ATPase at a similar dose. Following exposure of the isolated rat heart to IK-TP at a dose that produces pronounced cardiac effects, inhibition of Na+/K+-ATPase activity can be readily detected in the heart. This study suggests the presence of ATPase inhibitory compounds in Ilex latifolia with specificities different from that of ouabain.

Animals↗
PubMed2001

Effect of isoflurane versus nicardipine on blood flow of lumbar paraspinal muscles during controlled hypotension for spinal surgery.

STUDY DESIGN: This study compared the effects of isoflurane and nicardipine on regional blood flow of the lumbar paraspinal muscles. OBJECTIVES: The purpose of this study was to determine whether treatment with hypotensive agents result in ischemia of the lumbar paraspinal muscles, thereby facilitating surgical procedures. SUMMARY OF BACKGROUND DATA: Despite the general acceptance of controlled hypotension as effective in reducing blood loss during spinal surgery, the changes of blood flow that occur at the lumbar paraspinal muscles when this technique is applied remain unclear. The use of laser Doppler flowmetry allows changes of muscle blood flow to be easily detected in real time with minimal invasion, thereby allowing differences among distinct pharmacological approaches for induction and maintenance of controlled hypotension to be evaluated. METHODS: The prehypotensive and hypotensive (reduction of mean arterial pressure by 20 mm Hg) blood flow of the lumbar paraspinal muscles were assessed with a laser Doppler flowmeter in 40 patients undergoing lumbar spinal surgery. The first half of the patients (n = 20) received isoflurane, whereas the second half received nicardipine to achieve arterial hypotension. RESULTS: Compared with the prehypotensive state, during the hypotensive state, patients in the isoflurane group exhibited a 17% to 46% (mean, 33.7%) decrease in lumbar paraspinal muscle blood flow, whereas patients in the nicardipine group exhibited a 24% to 177% (mean, 82.5%) increase in lumbar paraspinal muscle blood flow. Statistical analysis showed a significant difference in the changes of flux after induced hypotension between the isoflurane and nicardipine group (P < 0.001). CONCLUSIONS: Depending on the pharmacological treatment used to achieve arterial hypotension in spine surgery, there will be either a reduction in paraspinal muscle blood flow (ischemia) or an enhancement of this blood flow (hyperemia).

Adult↗
PubMed2001

A regulatory region rearranged BK virus is associated with tubulointerstitial nephritis in a rejected renal allograft.

A renal allograft transplant patient with high serum creatinine presented clinical symptoms of rejection. Sections of renal biopsy tissue showed mononuclear leukocyte infiltration in the tubulointerstitium and nuclear enlargement with inclusions in the tubular epithelium. The morphological characteristics resembled polyomavirus-induced interstitial nephritis. Electron microscopy of the nuclear inclusions showed paracrystalline arrays of naked viral particles with a diameter of 45 nm. Molecular studies revealed that a new variant of BK virus (BKV) with rearrangement at the regulatory region was involved in the nephritis. The BKV regulatory region contained a tandem repeat from the P-block to the Q-block causing duplication of several important transcriptional elements or transcriptional factor binding motifs. This is the first report to show a naturally occurring BKV variant with regulatory region rearrangement associated with tubulointerstitial nephritis.

Adult↗
PubMed2001

Glycosides and xanthine oxidase inhibitors from Conyza bonariensis.

Fractionation of the xanthine oxidase inhibitory methanol extract of Conyza bonariensis afforded three glycosides, in addition to nine known compounds including amyrin, beta-sitostero1 daucosterol, syringic acid 3-hydroxy-5-methoxybenzoic acid, eugenol 4-O-glucopyranoside, and luteolin, apigenin and takakin 8-O-glucuronide. The structures of the glycosides were established by a combination of spectroscopic methods (IR, MS, 1H and 13C NMR, DEPT, COSY, HMQC and HMBC) as 4-hydroxypyridin-3-carboxylic acid 4-O-glucopyranoside, 8-hydroxy-6,7-dihydrolinalool 8-O-glucopyranoside and bonaroside [viz. 1,3,4,12-tetrahydroxy-2-(9-hexadecenoylamino)octadecane 1-O-glucopyranoside]. The in vitro enzyme assay showed that syringic acid and takakin 8-O-glucuronide displayed weak inhibitory activity against xanthine oxidase with IC50 values of 500+/-41 microM and 170+/-12 microM, respectively.

Asteraceae↗