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Biomedical subjects

C K Chen

Publications and source records attributed to C K Chen.

At least 19 recordsLinked to original sources
PubMed2006

Dissociation dynamics of positive-ion and negative-ion fragments of gaseous and condensed Si(CH(3))(2)Cl(2) via Si 2p, Cl 2p, and Cl 1s core-level excitations.

The state-selective positive-ion and negative-ion dissociation pathways of gaseous and condensed Si(CH(3))(2)Cl(2) following Cl 2p, Cl 1s, and Si 2p core-level excitations have been characterized. The excitations to a specific antibonding state (15a(1) (*) state) of gaseous Si(CH(3))(2)Cl(2) at the Cl 2p, Cl 1s, and Si 2p edges produce significant enhancement of fragment ions. This ion enhancement at specific core-excited states correlates closely with the ion kinetic energy distribution. The results deduced from ion kinetic energy distribution are consistent with results of quantum-chemical calculations on Si(CH(3))(2)Cl(2) using the ADF package. The Cl(-) desorption yields for Si(CH(3))(2)Cl(2)Si(100) at approximately 90 K are notably enhanced at the 15a(1) (*) resonance at both Cl 2p and Si 2p edges. The resonant enhancement of Cl(-) yield occurs through the formation of highly excited states of the adsorbed molecules. These results provide insight into the state-selective ionic fragmentation of molecules via core-level excitation.

Chlorine↗
PubMed2006

The lead content of currently available new residential paint in several Asian countries.

Worldwide prohibitions on lead gasoline additives were a major international public health accomplishment, the results of which are still being documented in parts of the world. Although the need to remove lead from paints has been recognized for over a century, evidence reported in this article indicates that lead-based paints for household use, some containing more than 10% lead, are readily available for purchase in some of the largest countries in the world. Sixty-six percent of new paint samples from China, India, and Malaysia were found to contain 5000 ppm (0.5%) or more of lead, the US definition of lead-based paint in existing housing, and 78% contained 600 ppm (0.06%) or more, the limit for new paints. In contrast, the comparable levels in a nearby developed country, Singapore, were 0% and 9%. In examining lead levels in paints of the same brands purchased in different countries, it was found that some brands had lead-based paints in one of the countries and paints meeting US limits in another; another had lead-free paint available in all countries where samples were obtained. Lead-based paints have already poisoned millions of children and likely will cause similar damage in the future as paint use increases as countries in Asia and elsewhere continue their rapid development. The ready availability of lead-based paints documented in this article provides stark evidence of the urgent need for efforts to accomplish an effective worldwide ban on the use of lead in paint.

China↗
PubMed2005

The vertebrate phototransduction cascade: amplification and termination mechanisms.

The biochemical cascade which transduces light into a neuronal signal in retinal photoreceptors is a heterotrimeric GTP-binding protein (G protein) signaling pathway called phototransduction. Works from psychophysicists, electrophysiologists, biochemists, and geneticists over several decades have come together to shape our understanding of how photon absorption leads to photoreceptor membrane hyperpolarization. The insights of phototransduction provide the foundation for a mechanistic account of signaling from many other G protein-coupled receptors (GPCR) found throughout nature. The application of reverse genetic techniques has strengthened many historic findings and helped to describe this pathway at greater molecular details. However, many important questions remain to be answered.

Animals↗
PubMed2005

Raising and controlling study of dissolved oxygen concentration in closed-type aeration tank.

This study investigated the promotion and control of dissolved oxygen (DO) concentration of the closed-type aeration tank via practical experiments in the wastewater treatment system of a 5-star hotel in Taipei. As with limited and treasured space in Taiwan, before the completion of the sewer system construction in cities, to utilize the mat foundation under large buildings as the space of sewage treatment plant still has been one of the alternatives of those sewage treatments. However, aeration tanks constructed in the mat foundation of buildings have smaller effective water depth, which will cause a lower total transfer amount of DO. Controlling the total exhaust gas flow rate can increase the pressure on such closed-type aeration tanks. The DO concentration thus may increase according to Henry's Law. Furthermore, it may enable operators to adjust the DO concentration of the aeration tank more precisely and thus sustain optimal operating conditions in these treatment facilities. Practical experiments indicated that the DO concentration of aeration tank maintains an average of 3.8 mg l(-1), obtaining the optimum operating conditions. The efficiency of the biological treatment facilities in the mat foundation could be markedly improved.

Bioreactors↗
PubMed2005

Implications of the changing pattern of bacterial infections following total joint replacements.

PURPOSE: To retrospectively review the causative organisms isolated from infected hip and knee replacements requiring revision. METHODS: We reviewed a consecutive series of 36 patients who underwent revision hip or knee arthroplasties due to bacterial infection at Pamela Youde Nethersole Eastern Hospital in Hong Kong between 1995 and 2003. The male to female ratio was 1:2, and the mean age of patients was 70 years (range, 54-82 years). The mean duration of follow-up was 3.8 years (range, 1.1-8.3 years). No patient was lost to follow-up. All 14 revision knee patients had previously undergone cemented and patella-resurfacing total knee arthroplasties. Of the 22 revision hip patients, 9 had cementless, 6 had cemented, and 7 had hybrid total hip arthroplasties previously. RESULTS: None of the bacteria isolated from 1995 to 1996 were multiple-drug resistant. Subsequently, however, most of the isolates were multiple-drug resistant, with methicillin-resistant Staphylococcus aureus (MRSA) being the most common. Half of the isolates of Staphylococcus epidermidis and Escherichia coli demonstrated multiple-drug resistance. The incidence of positive culture in revision hip patients was 59%, 46% of which were MRSA. All 13 revision hips with positive cultures showed chronic sepsis: 4 occurred within one year and 10 occurred 2 or more years after the index arthroplasty. The incidence of positive culture in revision knee patients was 57%, 46% of which were MRSA. All 8 revision knees with positive cultures showed chronic sepsis: 3 occurred within one year, 5 occurred 2 or more years after the index arthroplasty. Only one patient, who was infected with gram-negative bacilli, required a second revision for residual sepsis. Harris hip scores for the revision hip patients improved from a mean of 65 (range, 55-75) to 85 (range, 75-90). Knee Society knee scores of the revision knee patients improved from a mean of 68 (range, 55-75) to 80 (range, 70-85). There were no radiological signs suggestive of loosening in the 2 groups at the latest follow-up. CONCLUSION: This study found a definite increase in multiple-drug-resistant bacteria isolated from periprosthetic infections around total hip and knee prostheses.

Age Distribution↗
PubMed2003

Pre-morbid characteristics and co-morbidity of methamphetamine users with and without psychosis.

BACKGROUND: The long-term use of methamphetamine (MAMP) can result in psychosis but it is not clear why some individuals develop psychotic symptoms, while others use MAMP regularly over long periods and remain unscathed. We set out to characterize MAMP users and to examine the relationship of pre-morbid personality, pre-morbid social function and other psychiatric disorders to MAMP psychosis. METHOD: Four hundred and forty-five amphetamine users were recruited from a psychiatric hospital and a detention centre in Taipei, and were assessed with the Diagnostic Interview for Genetic Studies (DIGS). Their parents were interviewed with the Premorbid Schizoid and Schizotypal Traits (PSST) and the Premorbid Social Adjustment (PSA) schedules. Pre-morbid characteristics and psychiatric co-morbidity were compared between the MAMP users with a lifetime diagnosis of MAMP psychosis and those without. RESULTS: The MAMP users with psychosis presented a clinical picture which mimicked the positive symptoms of schizophrenia: 85% had auditory hallucinations; 71% persecutory delusions; 63% delusions of reference. Compared with their non-psychotic counterparts, these MAMP users were younger at first MAMP use, used larger amounts of MAMP, had a significantly higher mean PSST score, and higher rates of major depressive disorder, alcohol dependence and antisocial personality disorder. CONCLUSIONS: Earlier and larger use of MAMP was associated with increased risk of psychosis. Our data are also compatible with the view that pre-morbid schizoid/schizotypal personality predisposes MAMP users to develop psychosis, and that the greater the personality vulnerability, the longer the psychosis will persist.

Adolescent↗
PubMed2003

Treatment of slaughterhouse wastewater using an activated sludge/contact aeration process.

This study combines a two-phase biological treatment system of activated sludge/contact aeration process by adding biological contact filters into the rear sector of the activated sludge aeration tank of the slaughterhouse wastewater treatment plant. This system keeps the advantages of complete mixing of substrates and microorganisms and flexible operation of the activated sludge process, and increased biological phase, less sludge, process stability and good settleability of sludge of the contact aeration process. This system could avoid the defects of sludge bulking, increased sludge production and difficult operation of the activated sludge process, and system clogging and rigid operation of the contact aeration process. Because suspended microorganisms are flowing into the contact aeration system, which then degrade or suspend within the biological contact filters after being adsorbed by the fixed biological film, on which partial bio-solids will act as seeding microorganisms. Suspended microorganisms and the dropped biological film will settled in the secondary settling tank, then reflux into the activated sludge aeration tank. The partial dropped biological film will decompose in the activated sludge aeration tank to achieve the function of decreasing sludge. Large specific gravity and good settling ability of biofilm sludge will provide better effluent quality. It has been proven through a practical experiment at a slaughterhouse wastewater treatment plant in Taiwan, that the activated sludge process effluent COD value of 150-200 mg/L and SS value of 80-100 mg/L were decreased to around 40 mg/L and 22 mg/L, respectively, after changing its system to the two-phase biological treatment system of activated sludge/contact aeration process.

Abattoirs↗
PubMed2001

Characterization of human GRK7 as a potential cone opsin kinase.

PURPOSE: Homozygous inactivation of the mouse gene for GRK1 (G protein-coupled receptor kinase 1, or rhodopsin kinase) causes severe defects in the recovery of cone phototransduction. However, electroretinographic (ERG) analyses of human oguchi patients with defective GRK1 alleles showed normal or slightly abnormal photopic responses. It remains unclear why the loss of GRK1 yields such different phenotypes in the recovery of mouse and human cones. We examined the localization and enzyme activity of GRK7, the human ortholog of the seventh member of the GRK family, in an attempt to understand its potential role in photopic vision. METHODS: Bioinformatic approaches were used to identify the human GRK7 gene. Human and bovine GRK7 cDNAs were isolated by RT-PCR. Recombinant GRK7, expressed in insect cells, was used to phosphorylate activated rhodopsin. Antibodies raised against GRK7 peptides were used to examine the retina specific expression of GRK7 by immunoblotting and its subcellular localization by immunocytochemistry. RESULTS: The human GRK7 gene is located on chromosome 3q21, spans at least 10 Kb and consists of 4 exons. In human, GRK7 is expressed exclusively in the retina and is found in all retinal neurons, and specifically, in cone outer segments. Recombinant human GRK7 catalyzes rhodopsin phosphorylation in a light dependent manner. We provide evidence that GRK1 and GRK7 are co-expressed in human cones. In contrast, mouse GRK7 is expressed in many tissues including retina where photoreceptors apparently do not express GRK7. CONCLUSIONS: The presence of GRK7 in human, but not in mouse, cone outer segments suggests that GRK7 may function to provide the normal photopic vision reported by oguchi patients with a defective GRK1 gene. The absence of GRK7 expression in cone outer segments of mice is consistent with the notion that mouse cones rely solely on GRK1 to shutoff cone visual pigments.

Amino Acid Sequence↗
PubMed2001

Gene expression profiles of light-induced apoptosis in arrestin/rhodopsin kinase-deficient mouse retinas.

To examine the molecular processes that lead to light-induced retinal degeneration, mutant mice deficient in arrestin and rhodopsin kinase were raised in the dark and then subjected to relatively low doses of white light. The kinetics of the subsequent induction of apoptosis, change in mRNA transcript level, and photoreceptor cell death were monitored. Analysis of transcript profiles identified clusters of genes that responded differently to illumination, including a cluster of photoreceptor-specific genes that showed marked decreases in levels long before morphological damage could be readily ascertained. The behaviors of other gene clusters demonstrate the coordinate induction of stress gene responses early in the course of irradiation. There was little, if any, change in transcript levels corresponding to genes associated with the initiation of apoptosis or antiapoptotic effects. Transcript analysis provides insight into the patterns of gene expression that are associated with the different stages of retinal degeneration in this model system.

Animals↗
PubMed2001

Long-lived immune response to early secretory antigenic target 6 in individuals who had recovered from tuberculosis.

We sought to understand the persistence and relevance of the long-lived immune response to early secretory antigenic target (ESAT-6) of Mycobacterium tuberculosis in humans. ESAT-6 is recognized by memory cells involved in protection of animals against tuberculosis (TB). Recent reports also showed that ESAT-6 response can be recovered in patients with TB and in those soon after anti-TB therapy. We chose 18 individuals who had recovered from pulmonary TB (some in remission for >5 years), and 14 bacille Calmette-Guérin-vaccinated healthy individuals for this study. The results showed that peripheral blood mononuclear cells of 10 (55.6%) of 18 patients with TB remission responded to ESAT-6 with stimulation indices >3.0, whereas none of the healthy controls responded. Functional analysis showed that 13 (72.2%) of 18 patients with TB remission produced significant amounts of IFN-gamma in response to ESAT-6, whereas only 1 (7.1%) of the 14 healthy control subjects did so. It appears that responses to ESAT-6 can persist in individuals who had recovered from pulmonary TB.

Adult↗
PubMed2001

Chemical constituents from Drypetes littoralis.

Chemical investigation of Drypetes littoralis yielded three new tricyclic diterpenes, drypetenones A, B, and C (1--3), and one new xanthone (4). Spectral analyses and chemical correlations established the structures as 10S-12-hydroxy-11-methoxy-13-methylpodocarpa-1,5,8,11,13-pentaene-3,7-dione, (1), 10S-12-hydroxy-11-methoxy-13-methylpodocarpa-5,8,11,13-tetraene-3,7-dione (2), 10S-12-hydroxy-6,11-dimethoxy-13-methylpodocarpa-1,5,8,11,13-pentaene-3,7-dione (3), and 1-hydroxy-7-hydroxymethyl-6-methoxyxanthone (4). Complete (13)C NMR assignment of boehmenan D (5) is also made.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Vastus medialis obliquus and vastus lateralis activity in open and closed kinetic chain exercises in patients with patellofemoral pain syndrome: an electromyographic study.

OBJECTIVES: To evaluate the electromyographic activities of vastus medialis obliquus (VMO) and vastus lateralis (VL) muscles in open and closed kinetic chain exercises in subjects with patellofemoral pain syndrome (PFPS). DESIGN: Case-controlled study. SETTING: Rehabilitation science center in a tertiary medical center. PARTICIPANTS: Ten patients with bilateral knee pain diagnosed with PFPS and 10 healthy volunteers. INTERVENTIONS: Subjects performed open kinetic chain exercise on an isokinetic dynamometer and closed kinetic chain exercise by squat-to-stand and stand-to-squat tasks. Surface electromyography was done for the VMO and VL muscles. MAIN OUTCOME MEASURES: VMO/VL ratios were calculated after normalization of muscle activities. RESULTS: The VMO/VL ratios of PFPS subjects were significantly lower than were those of unimpaired subjects during knee isokinetic closed kinetic chain exercises (p = .047). However, there was no statistical difference in VMO/VL ratio between subjects with and without PFPS during closed kinetic chain exercises (p = .623). Maximum VMO/VL ratio was obtained at 60 degrees knee flexion in closed kinetic chain exercise. CONCLUSION: In closed kinetic chain exercises, more selective VMO activation can be obtained at 60 degrees knee flexion. Maximal VMO/VL ratio was observed at this knee flexion angle, and muscle contraction intensity was also greatest.

Adult↗
PubMed2001

Anti-HBc IgG subclasses in different populations by comparing a variety of ELISA plates.

The number of IgG subclasses for hepatitis B virus (HBV) core antigen (anti-HBc), demonstrated for HBV-infected individuals, was measured by enzyme-linked immunosorbent assay (ELISA). Four commercially available hepatitis B core antigen (HBcAg) plates and one prepared plate were tested for ELISA sensitivity by the detection of 14 serum samples drawn from HBV chronic carriers, cured patients, vaccinees, and non-infected individuals. Differences in optical density (OD) values were obtained by comparing data gathered from the five plate types, suggesting that different plates may have different binding capabilities for each anti-HBc IgG subclass and, thus, contribute to the different ELISA sensitivities. Of these plates, the GB plate showed the most obvious absorbance changes for anti-HBc subclasses in different populations. These data also indicated different patterns for IgG-specific subclasses for various populations. For HBsAg+ carriers, the OD for IgG1 was greater than for IgG3. By contrast, the OD for IgG3 was higher than that for IgG1 in those subjects who were negative for HBsAg.

Adult↗
PubMed2001

Lipoma arborescens of the knee: a case report.

Lipoma arborescens is a rare intraarticular lesion of unknown etiology. We describe the radiographic, computerized tomographic, and magnetic resonance (MR) imaging characteristics of lipoma arborescens in a 17-year-old boy presenting with chronic painful swollen knee. Histologic examination after surgical synovectomy confirmed the diagnosis of lipoma arborescens. The fatty nature and frond-like appearance of this lesion can be demonstrated on imaging studies, especially MR imaging. Open synovectomy is curative in most cases. Although lipoma arborescens is rare, it is important to recognize and differentiate it from other synovial lesions by MR imaging.

Adolescent↗
PubMed2000

Modules in the photoreceptor RGS9-1.Gbeta 5L GTPase-accelerating protein complex control effector coupling, GTPase acceleration, protein folding, and stability.

RGS (regulators of G protein signaling) proteins regulate G protein signaling by accelerating GTP hydrolysis, but little is known about regulation of GTPase-accelerating protein (GAP) activities or roles of domains and subunits outside the catalytic cores. RGS9-1 is the GAP required for rapid recovery of light responses in vertebrate photoreceptors and the only mammalian RGS protein with a defined physiological function. It belongs to an RGS subfamily whose members have multiple domains, including G(gamma)-like domains that bind G(beta)(5) proteins. Members of this subfamily play important roles in neuronal signaling. Within the GAP complex organized around the RGS domain of RGS9-1, we have identified a functional role for the G(gamma)-like-G(beta)(5L) complex in regulation of GAP activity by an effector subunit, cGMP phosphodiesterase gamma and in protein folding and stability of RGS9-1. The C-terminal domain of RGS9-1 also plays a major role in conferring effector stimulation. The sequence of the RGS domain determines whether the sign of the effector effect will be positive or negative. These roles were observed in vitro using full-length proteins or fragments for RGS9-1, RGS7, G(beta)(5S), and G(beta)(5L). The dependence of RGS9-1 on G(beta)(5) co-expression for folding, stability, and function has been confirmed in vivo using transgenic Xenopus laevis. These results reveal how multiple domains and regulatory polypeptides work together to fine tune G(talpha) inactivation.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2000

Determination of bisbenzylisoquinoline alkaloids by high-performance liquid chromatography (II).

After the earlier analysis of nine bisbenzylisoquinoline alkaloids with ion pair chromatography, seven other bisbenzylisoquinoline alkaloids were analyzed using gradient elution with an acetonitrile-phosphate buffer (pH 8.0) mixture, and UV detection. Four alkaloids were detected in the stem woods of a Lauraceous plant, Dehaasia triandra Merr. and their contents determined. LC-MS suggested that a major unknown compound in the plant was also a bisbenzylisoquinoline alkaloid.

Alkaloids↗
PubMed2000

Co-expression of Gbeta5 enhances the function of two Ggamma subunit-like domain-containing regulators of G protein signaling proteins.

Regulators of G protein signaling (RGS) stimulate the GTPase activity of G protein Galpha subunits and probably play additional roles. Some RGS proteins contain a Ggamma subunit-like (GGL) domain, which mediates a specific interaction with Gbeta5. The role of such interactions in RGS function is unclear. RGS proteins can accelerate the kinetics of coupling of G protein-coupled receptors to G-protein-gated inwardly rectifying K(+) (GIRK) channels. Therefore, we coupled m2-muscarinic acetylcholine receptors to GIRK channels in Xenopus oocytes to evaluate the effect of Gbeta5 on RGS function. Co-expression of either RGS7 or RGS9 modestly accelerated GIRK channel kinetics. When Gbeta5 was co-expressed with either RGS7 or RGS9, the acceleration of GIRK channel kinetics was strongly increased over that produced by RGS7 or RGS9 alone. RGS function was not enhanced by co-expression of Gbeta1, and co-expression of Gbeta5 alone had no effect on GIRK channel kinetics. Gbeta5 did not modulate the function either of RGS4, an RGS protein that lacks a GGL domain, or of a functional RGS7 construct in which the GGL domain was omitted. Enhancement of RGS7 function by Gbeta5 was not a consequence of an increase in the amount of plasma membrane or cytosolic RGS7 protein.

Animals↗