Biomedical subjects

C Y Chen

Publications and source records attributed to C Y Chen.

At least 55 records · Page 3Linked to original sources

PubMed2001

Evidence for a replication function of FFA-1, the Xenopus orthologue of Werner syndrome protein.

DNA replication in higher eukaryotic cells occurs at a large number of discrete sites called replication foci. We have previously purified a protein, focus-forming activity 1 (FFA-1), which is involved in the assembly of putative prereplication foci in Xenopus egg extracts. FFA-1 is the orthologue of the Werner syndrome gene product (WRN), a member of the RecQ helicase family. In this paper we show that FFA-1 colocalizes with sites of DNA synthesis and the single-stranded DNA binding protein, replication protein A (RPA), in nuclei reconstituted in the egg extract. In addition, we show that two glutathione S-transferase FFA-1 fusion proteins can inhibit DNA replication in a dominant negative manner. The dominant negative effect correlates with the incorporation of the fusion proteins into replication foci to form "hybrid foci," which are unable to engage in DNA replication. At the biochemical level, RPA can interact with FFA-1 and specifically stimulates its DNA helicase activity. However, in the presence of the dominant negative mutant proteins, the stimulation is prevented. These results provide the first direct biochemical evidence of an important role for FFA-1 in DNA replication.

Adenosine Triphosphatases↗

PubMed2001

Crystal structure and site-directed mutagenesis studies of N-carbamoyl-D-amino-acid amidohydrolase from Agrobacterium radiobacter reveals a homotetramer and insight into a catalytic cleft.

The N-carbamoyl-D-amino-acid amidohydrolase (D-NCAase) is used on an industrial scale for the production of D-amino acids. The crystal structure of D-NCAase was solved by multiple isomorphous replacement with anomalous scattering using xenon and gold derivatives, and refined to 1.95 A resolution, to an R-factor of 18.6 %. The crystal structure shows a four-layer alpha/beta fold with two six-stranded beta sheets packed on either side by two alpha helices. One exterior layer faces the solvent, whereas the other one is buried and involved in the tight intersubunit contacts. A long C-terminal fragment extends from a monomer to a site near a dyad axis, and associates with another monomer to form a small and hydrophobic cavity, where a xenon atom can bind. Site-directed mutagenesis of His129, His144 and His215 revealed strict geometric requirements of these conserved residues to maintain a stable conformation of a putative catalytic cleft. A region located within this cleft involving Cys172, Glu47, and Lys127 is proposed for D-NCAase catalysis and is similar to the Cys-Asp-Lys site of N-carbamoylsarcosine amidohydrolase. The homologous active-site framework of these enzymes with distinct structures suggests convergent evolution of a common catalytic mechanism.

Amidohydrolases↗

PubMed2001

A novel clathrin homolog that co-distributes with cytoskeletal components functions in the trans-Golgi network.

A clathrin homolog encoded on human chromosome 22 (CHC22) displays distinct biochemistry, distribution and function compared with conventional clathrin heavy chain (CHC17), encoded on chromosome 17. CHC22 protein is upregulated during myoblast differentiation into myotubes and is expressed at high levels in muscle and at low levels in non-muscle cells, relative to CHC17. The trimeric CHC22 protein does not interact with clathrin heavy chain subunits nor bind significantly to clathrin light chains. CHC22 associates with the AP1 and AP3 adaptor complexes but not with AP2. In non-muscle cells, CHC22 localizes to perinuclear vesicular structures, the majority of which are not clathrin coated. Treatments that disrupt the actin-myosin cytoskeleton or affect sorting in the trans-Golgi network (TGN) cause CHC22 redistribution. Overexpression of a subdomain of CHC22 induces altered distribution of TGN markers. Together these results implicate CHC22 in TGN membrane traffic involving the cytoskeleton.

Cells, Cultured↗

PubMed2001

Experiences in thoracoscopic sympathectomy for axillary hyperhidrosis and osmidrosis: focusing on the extent of sympathectomy.

HYPOTHESIS: A more selective sympathectomy can improve the outcome of axillary hyperhidrosis and osmidrosis and minimize the potential sequelae. DESIGN: Retrospective cohort. SETTING: Tertiary care center. PATIENTS: Between July 1, 1996, and May 30, 2000, 171 patients with axillary hyperhidrosis and osmidrosis were studied. INTERVENTIONS: T3-4 sympathectomies were performed in 40 patients (group 1), T4 sympathectomies were performed in 56 patients (group 2), and T4-5 sympathectomies were performed in 75 patients (group 3). MAIN OUTCOME MEASURES: The surgical outcomes were evaluated by direct patient interview in the outpatient clinic or by telephone or mail questionnaires. The results were categorized as excellent (significant or complete disappearance of symptoms), good (>/=50% improvement), or poor (<50% improvement). RESULTS: There were no surgical mortalities in this study. Twenty-eight group 1 patients (70%), 16 group 2 patients (29%), and 22 group 3 patients (29%) developed compensatory perspiration (P<.001). Six group 1 patients (15%), 1 group 2 patient (2%), and 1 group 3 patient (1%) developed dry hands (P =.02). In the group 1 patients, the surgical outcomes were excellent in 21 (52%), good in 6 (15%), and poor in 13 (32%). In the group 2 patients, the surgical outcomes were excellent in 29 (52%), good in 10 (18%), and poor in 17 (30%). In the group 3 patients, the surgical outcomes were excellent in 53 (71%), good in 11 (15%), and poor in 11(15%) (P =.04). (Percentages may not sum to 100 because of rounding.) CONCLUSION: T4-5 sympathectomies provide higher patient satisfaction rates in treating axillary hyperhidrosis and osmidrosis, with fewer sequelae.

Adolescent↗

PubMed2001

Gender difference in DNA adduct levels among nonsmoking lung cancer patients.

Lung cancer is the leading cause of cancer mortality in Taiwanese women. Cigarette smoking cannot explain the high lung cancer mortality in this population because less than 10% of women in Taiwan are smokers. Therefore, environmental factors other than smoking may play an important role in lung cancer development in female nonsmokers. The purpose of this study was to elucidate the role of environmental carcinogen exposure in lung cancer development in Taiwanese female nonsmokers, based on DNA adduct formation. We collected nontumorous lung tissues resected from 62 nonsmoking lung cancer patients and 20 noncancer controls to investigate whether differences in susceptibility to DNA adduct formation exist between men and women. (32)P-postlabeling and ELISA (enzyme-linked immunosorbent assay) with polyclonal antibody against BPDE (7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene)-DNA adduct were used to evaluate DNA adduct levels in lung tissues of study subjects. Our data showed that the DNA adduct levels of lung cancer patients determined by both assays were significantly higher than those of noncancer controls (P = 0.0001 for (32)P-postlabeling; P = 0.01 for ELISA). Moreover, DNA adduct levels in females were markedly greater than those in males (P = 0.014 for (32)P-postlabeling; P = 0.001 for ELISA). The difference in DNA adduct levels could not be explained by genetic polymorphisms of cytochrome P-4501A1 (CYP1A1) or glutathione S-transferase (GSTM1), as determined by polymerase chain reaction and restriction fragment length polymorphism. These results demonstrate that lung cancer patients have a higher susceptibility to DNA damage than that of noncancer controls. In addition, differences in susceptibility to DNA damage derived from environmental carcinogen exposure were observed between male and female nonsmokers. In conclusion, high susceptibility to DNA damage in females may partially explain the high mortality rate of lung cancer in nonsmoking Taiwanese women.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed2001

High-resolution cranial ultrasound in the shaken-baby syndrome.

With limited near-field resolution and accessible acoustic windows, sonography has not been advocated for assessing central nervous system injuries in the shaken-baby syndrome. Our purpose was to correlate high-resolution ultrasonographic characteristics of central nervous system injuries in whiplash injuries and the shaken-baby-syndrome with MRI and CT. Ultrasonographic images of 13 infants, aged 2-12 months, with whiplash or shaking cranial trauma were reviewed and compared with MRI in 10 and CT in 10. Five patients had serial ultrasonography and MRI or CT follow-up from 1 to 4 months after the initial injury. With ultrasonography we identified 20 subdural haematomas. MRI and CT in 15 of these showed that four were hyperechoic in the acute stage, three were mildly echogenic in the subacute stage, and that one subacute and seven chronic lesions were echo-free. Five patients had acute focal or diffuse echogenic cortical oedema which evolved into subacute subcortical hyperechoic haemorrhage in four, and well-defined chronic sonolucent cystic or noncystic encephalomalacia was seen at follow-up in two. Using ultrasonography we were unable to detect two posterior cranial fossa subdural haematomas or subarachnoid haemorrhage in the basal cisterns in three cases, but did show blood in the interhemispheric cistern and convexity sulci in two. U1-trasonography has limitations in demonstrating abnormalities remote from the high cerebral convexities but may be a useful adjunct to CT and MRI in monitoring the progression of central nervous system injuries in infants receiving intensive care.

Battered Child Syndrome↗

PubMed2001

The influence of growth-induced stress from the surrounding medium on the development of multicell spheroids.

A mathematical model is adapted to the description of the growth of an avascular tumour spheroid embedded in a deformable medium (gel). Attention is focused on the influence that the mechanical properties of the gel have on the tumour's growth dynamics. Following the work of Landman and Please (2000), the tumour is treated as a two phase material, whereby the tumour cells and the extracellular fluid form distinct phases. Its growth is modelled by combining mass conservation and force balances for each phase with the usual concepts of diffusion limited growth in response to an externally supplied nutrient. The mechanical properties of the gel are characterised by a strain energy function. The stress induced in the gel by the tumour's expansion is incorporated into the force balance equations, thereby linking it to the tumour's growth. Numerical simulations of the model equations show that as the stiffness of the gel increases, the tumour's growth rate and equilibrium size decrease and the time at which necrosis is initiated is delayed (if it occurs at all). Similar results are obtained when the initial size of the tumour is reduced whilst the mechanical properties of the surrounding gel are held fixed. Such results, which are in good qualitative agreement with available experimental data, suggest that mechanical interactions between a tumour and the tissue or medium in which it is located can significantly influence its growth dynamics.

Animals↗

PubMed2001

An efficient method for the culture of Helicobacter pylori from gastric biopsies with two-section petri dishes.

PURPOSE: Helicobacter pylori is the principal cause of chronic gastritis and is strongly associated with peptic ulcer disease and gastric cancer, as well as with gastric lymphoma (mucosa-associated lymphoid tissue [MALT] type). H. pylori could be recovered by many kinds of media, however, it could not be detected efficiently. This study was trying to ameliorate the isolation and detection rate with selective and non-selective media. METHODS: First, type strain (ATCC 43504) was cultured with twelve different kinds of sheep blood agar based on brain heart infusion medium for five days. Then five better non-selective media and five selective media were chosen for the biopsy, which were incubated at 37 degrees C in a microaerophilic incubator for five days. Endoscopic biopsies were collected from 623 patients at Kaohsiung Medical University Hospital. RESULTS: It was found that non-selective media, which contain 5% modified chocolate agar (the ratio of fresh and heated sheep blood is 2) with 1% Isovitalex, had the best detection rate (91.1 +/- 0.6)%. Furthermore, 5% modified chocolate agar with 1% Isovitalex and 1% antibiotics would increase the detection rate to (97.1 +/- 0.3)%. CONCLUSIONS: According to Ansorg's method, the best detection rate (98.4 +/- 0.7)% could be obtained with two-section petri dishes which had 5% modified chocolate agar with antibiotics and the other without antibiotics.

Animals↗

PubMed2001

Real-time display of the stomach slow wave and its parameters in a newly designed electrogastrographic system.

We designed a new three-channel electrogastrographic (EGG) system, which was easily operated on the Windows 95 platform and could automatically provide slow wave parameters. The purpose of the present study was to test its reliability and accuracy in clinical recording. The system included a signal acquisition device assembled on a printed circuit board. Recorded myoelectrical signals were filtered, amplified, digitized, and transmitted via this device into a notebook personal computer (PC). Based on the short-term Fourier transform the software could transfer the time domain of the signal into the frequency domain. Real-time displayed slow wave parameters, including dominant frequency/power, percent of normal frequency (2-4 cpm), instability coefficient in frequency/power, and power ratio, were automatically renewed every 64s. Twenty healthy subjects (M/F, 12/8; age, 23-51 years) were enrolled to measure both fast and postprandial myoelectrical activities for each 30-min recording. Our results indicated that meal ingestion significantly increased dominant frequency (3.15+/-0.20 vs 3.23+/-0.23 cpm; P < 0.05) and power (26.1+/-3.8 vs 28.4+/-3.9 dB; P < 0.05). The power ratio of the meal effect was 2.02+/-2.07. Other parameters, including instability coefficient and percent of normal frequency, remained similar despite food ingestion. This newly designed EGG system is acceptable for clinically measuring gastric myoelectrical activity; the real-time display of many EGG parameters is an advantage with this new system.

Adult↗

PubMed2001

Beam hardening correction for computed tomography images using a postreconstruction method and equivalent tissue concept.

A postreconstruction method for correcting the beam-hardening artifacts in computed tomography (CT) images is proposed. This method does not require x-ray spectrum measurement. The authors assumed that a pixel in a CT image can be decomposed into equivalent tissue percentages, depending on its CT number. A scout view of the step wedges made of these equivalent tissues was performed to obtain a beam-hardening correction curve for each tissue. Projecting through the CT image from various angles generated simulated projection data and the total thickness of each tissue along the ray. The correction term was estimated using the tissue thickness traveled by the ray, and this term was then added to its corresponding projection data. A second reconstruction using the corrected projection data yielded a beam-hardening corrected image. The preliminary results show that this method reduces beam hardening artifacts by 14% for aluminum and increased the object contrast by 18% near the aluminum-water boundary. The variation in CT numbers at different locations were reduced, and the aluminum CT number also was restored.

Artifacts↗

PubMed2001

Four alkaloids from Annona cherimola.

Four alkaloids, annocherine A, annocherine B, cherianoine, and romucosine H, along with one known alkaloid, artabonatine B, were isolated from the MeOH extract of the stems of Annona cherimola. Their structures were identified on the basis of both analysis of their spectral data and from chemical evidence.

Alkaloids↗

PubMed2001

Antiplatelet activity of N-methoxycarbonyl aporphines from Rollinia mucosa.

Bioassay-directed fractionation of the stems of Rollinia mucosa led to the isolation of new N-methoxycarbonyl aporphine alkaloids, romucosine A (1), romucosine B (2), romucosine C (3), and romucosine D (4), along with the known alkaloid, N-methoxylcarbonyl-nornuciferine (5). Alkaloids 1 and 4 exhibited significant inhibition of collagen, arachidonic acid, and platelet activating factor-induced platelet aggregation, and alkaloid 3 also showed an inhibitory effect on arachidonic acid induced platelet aggregation.

Alkaloids↗

PubMed2001

Accumulation and depuration of paralytic shellfish poisoning toxins by purple clam Hiatula rostrata Lighttoot.

Purple clams (Hiatula rostrata Lighttoot) accumulated paralytic shellfish poisoning (PSP) toxins produced by a toxic strain of the dinoflagellate Alexandrium minutum Halim for subsequent study of toxin distribution during depuration (detoxification by a nontoxic microalgal diet or starvation). The results confirm the data in the literature concerning the high toxicity of the digestive gland, and the depuration efficiency between feed with nontoxic microalgae and starvation is similar. The toxin profile of the purple clams was similar with that of Alexandrium minutum at the end of the exposure period; GTX4 and GTX1 were dominant. However, at the end of the depuration period, GTX3 and GTX2 were dominant. The non-visceral tissues were toxic after feeding with toxic algae. The toxicity was low and the profile were also similar with that of the toxic algae. No PSP toxins other than GTX-1, 2, 3 and 4 were detected in the experimental period.

Animals↗

PubMed2001

Removal of metal ions and humic acid from water by iron-coated filter media.

Iron oxide is an excellent, regenerable adsorbent, and often controls free metals through adsorption reaction. The utilization of heating process for coating iron oxide on sand surface allowed the media to be used in a packed column. Iron-coated sand was investigated for adsorbing metal ions and natural organic matter from water by batch and column experiments. Chemical analysis (energy dispersive analysis of X-ray, EDAX) was used for characterizing the copper and lead adsorption sites on iron-coated sand. From the batch experiment results, the copper and lead ions could be removed simultaneously by the iron-coated sand in the competition adsorption system. The interaction between copper, lead ions and iron oxide on sand surface was primarily the chemical bonds. The maximum adsorption capacities of iron-coated sand for copper and lead were 0.259 mg Cu/g-sand and 1.211 mg Pb/g-sand, respectively. The presence of humic acid led to increase the adsorption of copper and lead. Results from column experiments indicated that the copper ions, lead ions and humic acid could be removed completely before the breakpoint. Consequently, the iron-coated sand may be applied for the adsorption/filtration of metal ions and natural organic matters from water.

Adsorption↗

PubMed2001

Sedation for refractory symptoms of terminal cancer patients in Taiwan.

This study assessed sedation in terminal cancer patients in terms of three characteristics: frequency; relationship to intractable symptoms; and the extent to which medical staff, family, and patients found sedation to be ethically acceptable and efficacious. Two hundred seventy-six consecutive patients, who were admitted to the palliative care unit of National Taiwan University Hospital in Taiwan between August 1998 and the end of May 1999, were enrolled. A recording form was completed every day. This included demographic data, pain and common symptom scores, and the use of sedation in the terminal phase. Seventy (27.9%) of 251 patients who died received sedation. Sedation was administered to relieve agitated delirium in 40 (57.1%), dyspnea in 16 (22.8%), severe pain in 7 (10%) and insomnia in 5 (7.2%). The drugs used for sedation were haloperidol in 35 (50%), midazolam in 17 (24.3%), and rapidly increasing dosage of morphine in 9 (12.9%). In fewer than half (42.9%) of the patients, sedation was with the consent of both patient and family, and half (50%) had the consent of family alone. The overwhelming majority of medical staff and family felt the decision to use terminal sedation was ethically acceptable. There was no significant difference in survival time between sedated and non-sedated patients (28.49 vs. 24.71 days, t = -0.791, P = 0.430). Positive ethical acceptability and higher satisfaction with symptom control with terminal sedation were found in both medical staff and family in this study. Further work is needed to find the most appropriate time of intervention and to improve management of refractory symptoms in dying patients.

Adolescent↗

PubMed2001

Prediction of prognosis by the extent of lymph node involvement in squamous cell carcinoma of the thoracic esophagus.

OBJECTIVES: Current criteria of the N-category in the TNM staging system for carcinoma of the esophagus needs further subgrouping due to its simplicity in mixing together patients with different prognosis. METHOD: A retrospective cohort study of 186 patients (176 men and ten women; mean age, 59.9 years) with squamous cell carcinoma (SCC) of the thoracic esophagus who underwent esophagectomy followed by two-field lymphadenectomy and cervical lymph node sampling between 1992 and 1999 was conducted. A proposed N-category which involved dividing the nodal status into N0 (no nodal involvement), N1 (< or =4 nodes or < or =20% nodal involvement), and N2 (>4 nodes, or >20%, or non-regional nodal involvement) subgroups was used for survival analysis. RESULTS: The overall 5-year cumulative survival rate was 27%. Lymph node metastases were identified in 101 (54.3%) patients. Cumulative survival rates were 46% at 4 years in the N0 group and 21% at 4 years in the N1 group, whereas no patients in N2 group survived longer than 3 years (P<0.01). A multivariable analysis revealed that independent prognostic factors included the depth of tumor invasion (P<0.01), nodal involvement (P<0.01), and organ metastasis (P<0.01). CONCLUSION: In addition to the location of nodes, the extent of nodal involvement in SCC of the thoracic esophagus also plays an important role in prognosis prediction.

Adult↗

PubMed2001

Review of telemedicine projects in Taiwan.

Taiwan is a heavily populated country, with a small land area and many mountains and isolated islands. Because medical resources are unequally distributed, high quality accessible medical care is a major problem in rural areas. Medical personnel are unwilling to practice in rural areas because of fear of isolation from peers and lack of continuing medical education (CME) in those areas. Telemedicine provides a timeless and spaceless measure for teleconsultation and education. The development of telemedicine in Taiwan began under the National Information Infrastructure (NII) Project. Distance education and teleconsultation were the first experimental projects during the initiation research stage. The cost and effectiveness of the hardware and network bandwidth were evaluated. In the promotion research stage, applications in different medical disciplines were tested to promote multipoint videoconference, electronic journals and VOD. Investigation of user satisfaction put on more emphasis on improving application functions. In 1998, a new Cyber Medical Center (CMC) international collaboration project was begun, integrating technologies of multimedia, networking, database management, and the World Wide Web. The aim of the CMC is to create a multimedia network system for the management of electronic patient records, teleconsultation, online continuing medical education, and information services on the web. A Taiwan mirror site of Virtual Hospital and two international telemedicine trials through Next Generation Internet (NGI) were done at the end of 1998. In the future, telemedicine systems in Taiwan are expected to combine the Internet and broadband CATV, ADSL, and DBS networking to connect clinics, hospitals, insurance organizations, and public health administrations; and, finally, to extend to every household.

Databases, Factual↗

PubMed2001

Implementation and evaluation of a multifunctional telemedicine system in NTUH.

In this article, we proposed a multifunctional telemedicine system supporting both telediagnosis and teleconsultation services. We attempted not only to insure that the implementation of this system satisfied most requirements, but also to evaluate the impact of the system. With regard to system architecture, we designed a unified multimedia database to store all types of data and used two kinds of network (ATM and ISDN) for different possible applications. As for data transmission, the REFRESH and PREFETCH mechanisms were implemented to enhance data transfer efficiency. A total of 1107 consultations employing the telemedicine system were performed during the past 3 years. This technology was used most frequently for radiology consultation (32.7%, n = 362) and ultrasonic examination (19.5%, n = 216). An evaluation of the impact on diagnosis (507 valid cases) indicated that the diagnosis in 80 cases (15.78%) were altered on the basis of second opinions from a medical center; and the number of patients transferred to the medical center was reduced from 24 (4.7%) to eight cases. Most of the rural-site physicians (97%) thought that they did benefit from specialists' experience and knowledge via the telemedicine system. Based on 431 valid questionnaires, the number of the patients with confidence in the telemedicine system at their local healthcare center increased from 72.6% to 87.5%. Overall, more than 90% of patients and physicians believed that the system was valuable and provided satisfactory services.

Adolescent↗