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Biomedical subjects

C Y Chen

Publications and source records attributed to C Y Chen.

At least 163 records · Page 9Linked to original sources
PubMed2000

Phakomatoses. Part I: Neurofibromatosis type 1: common and uncommon neuroimaging findings.

Neurofibromatosis type I (NF-1) belongs to a family of diseases named phakomatoses, which are characterized by congenital malformations of ectodermal structures. Neurofibromatosis type I affects 1 in 3000 people, and has a diverse clinical presentation as well as an array of imaging findings. In this article the authors review the various neuroimaging findings present in NF-1, including abnormalities of the parenchyma, meninges, vessels, and associated neoplasms.

Brain↗
PubMed2000

Etiology of genital ulcer disease in Dakar, Senegal, and comparison of PCR and serologic assays for detection of Haemophilus ducreyi.

We used PCR assays to determine the etiology of genital ulcers in patients presenting to a sexually transmitted disease clinic in Dakar, Senegal, and evaluated the ability of two PCR tests (groEL and recD) and two serological tests (adsorption enzyme immunoassay [EIA] and lipooligosaccharide [LOS] EIA) to detect current Haemophilus ducreyi infection. We found that in this population, H. ducreyi, T. pallidum, and herpes simplex virus HSV DNA were detected in 56, 15, and 13% of 39 genital ulcer specimens, respectively, and H. ducreyi DNA was detected in 60% (3 of 5) of samples from ulcerated bubos. Among 40 consecutive patients with genital ulcer disease and with sufficient sample for both PCR assays, the recD and groEL H. ducreyi PCR assays were 83% concordant, with the recD PCR assay detecting six (15%) additional positive specimens and the groEL assay detecting one (3%) additional positive specimen. Compared to PCR, the adsorption EIA and LOS EIA tests had sensitivities of 71 and 59% and specificities of 57 and 90%, respectively, for the diagnosis of current H. ducreyi infection. While these differences in specificity could be due either to previous infection with H. ducreyi or to the detection of cross-reacting antibodies, only 6% of patients from a nearby family planning clinic gave a positive reaction in both the adsorption EIA and LOS EIA assays, indicating that cross-reacting antibodies are not prevalent among clinic attendees in this city. Our studies indicate that the adsorption EIA detects both current and past infection, while the LOS EIA assay is more specific for current infection with H. ducreyi in this population.

Adult↗
PubMed2000

PCR assay for species-specific identification of Bacteroides thetaiotaomicron.

Bacteroides thetaiotaomicron is the second most frequently encountered species of the anaerobes isolated from clinical specimens. We developed a PCR-based assay for the rapid identification of B. thetaiotaomicron. Specific primers were based on shared amplicons of about 1.2 kb generated from B. thetaiotaomicron by randomly amplified polymorphic DNA. This 1.2-kb fragment was sequenced and then used to design a set of PCR amplification primers. This PCR generated an amplification product of 721 bp, which was unique to all 65 isolates of B. thetaiotaomicron tested. There was no amplification with isolates of other bacterial species. Restriction enzyme digestion of the amplification product and dot blot hybridization further verified the specificity of the assay. These results suggest that this PCR assay targets a nucleotide sequence that is strongly conserved in B. thetaiotaomicron. This simple and rapid PCR assay provides a rapid and accurate method for identification of B. thetaiotaomicron and shows promise for the detection of B. thetaiotaomicron in clinical samples.

Bacteroides↗
PubMed2000

Ethical dilemmas in palliative care: a study in Taiwan.

OBJECTIVES: To investigate the incidence and solution of ethical dilemmas in a palliative care unit. DESIGN: Health care workers recorded daily all dilemmas in caring for each patient. SETTING: Palliative care unit of National Taiwan University Hospital in Taiwan. PATIENTS: Two hundred and forty-six consecutive patients with terminal cancer during 1997-8. MAIN MEASUREMENT: Ethical dilemmas in the questionnaire were categorised as follows: telling the truth; place of care; therapeutic strategy; hydration and nutrition; blood transfusion; alternative treatment; terminal sedation; use of medication, and others. RESULTS: The type and frequency of ethical dilemmas encountered were: place of care (33.3%); truth-telling (32.1%); hydration and nutrition (25.2%); therapeutic strategy (24.8%), and use of medication (19.1%). Ethical problems relating to the place of care and to therapeutic strategy were unlikely to be solved with increased hospital stay and some ethical dilemmas remained unsolved even in the final week in hospital, including place of care (23.2%), truth-telling (17.1%) and therapeutic strategy (11.4%). Problems of truth-telling occurred in nearly half (42.6%) of patients over sixty-five-years-old. Conflicts about blood transfusion were experienced in all patients below 18-years-old, and the dilemmas concerning the place of care occurred most frequently with head and neck cancer patients (43.8%). CONCLUSIONS: The solution of ethical dilemmas required refocusing by medical professionals on the importance of continuing communication. Improved ethical training for professionals would contribute to solving the moral dilemmas of palliative care.

Aged↗
PubMed2000

Frequency limits on aortic baroreceptor input to nucleus tractus solitarii.

The frequency of baroreceptor volleys to the central nervous system can influence the fidelity of baroreceptor signal transmission and thus may affect baroreflex regulation of blood pressure. We examined 1) the extent to which frequency-dependent depression of aortic baroreceptor signals was initiated at the first central synapse between primary baroreceptor fibers and second-order nucleus tractus solitarii (NTS) neurons; 2) whether the pattern of baroreceptor input influenced the depression; and 3) the potential relevance to baroreflex sympathoinhibition. In urethan-anesthetized rats, NTS action potential responses of neurons classified as second or higher order and averaged lumbar sympathetic nerve activity responses were simultaneously measured during 100 aortic depressor nerve stimuli delivered in constant or phasic patterns (0.8-48 Hz). Frequency-dependent depression was initiated at second-order neurons, with NTS responses decreasing to a 72% response rate at 48 Hz; the depression was greater at higher-order neurons; responses decreased to a 30% response rate. The depression was slightly but significantly greater with phasic inputs. Curve fitting suggested that synaptic depression may limit baroreflex sympathoinhibition. Thus frequency limits on baroreceptor inputs at NTS synapses may affect baroreflex function.

Afferent Pathways↗
PubMed2000

Pressor and renal effects of intracerebroventricularly administered angiotensins II and III in rats.

AIMS: Experiments were performed to assess the effects of intracerebroventricular (ICV) angiotensin (ANG) III on blood pressure and renal function in rats with normal and high sodium intake and to compare these effects with those produced by ICV ANG II. METHODS: Male Sprague-Dawley rats on a normal sodium (0.3%) diet and a normal sodium diet plus 1% NaCl as drinking water were administered ANG II and ANG III ICV through a chronically implanted cannula. Blood pressure and renal clearance function responses were measured before and during peptide administrations. The effect of ICV ANG III on the renal efferent nerve activity was also evaluated. RESULTS: ICV injections of ANG II and ANG III at 5 pmol in rats on a normal sodium diet did not significantly alter the blood pressure, but significantly increased renal plasma flow, glomerular filtration rate, urine flow, and absolute and fractional excretions of sodium and potassium. Increased doses of ANG II and III (10, 50 and 100 pmol) significantly increased blood pressure and further enhanced these renal functional indices. Central ANG-III-induced increases in blood pressure and renal functional indices were not significantly different from those produced by ANG II at each corresponding dose. The pressor and renal effects of ANG III were blunted by a specific antagonist, Ile(7)-ANG III. ICV administration of ANG III decreased the renal efferent nerve activity. In rats with dietary NaCl loading, ICV injections of ANG II and III also significantly enhanced renal function. CONCLUSIONS: Centrally administered ANG III is as potent as ANG II in causing pressor and renal effects in rats on normal and high sodium intake. As ANG II, brain ANG III reduced renal efferent nerve activity which may be partly accounted for the augmented renal function.

Angiotensin II↗
PubMed2000

Surface characterization and platelet adhesion studies on fluorocarbons prepared by plasma-induced graft polymerization.

It is believed that the interactions between the biological environment and biomaterial surface are the key factors influencing its biocompatibility. Therefore, plasma processing, which can vary the surface properties without altering the bulk properties, has been considered as one of the important techniques for improving a materials' biocompatibility. In this investigation, plasma-induced grafting polymerization of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE), instead of direct plasma polymerization, was attempted with an aim to improve the substrate blood compatibility. Contact angle measurement indicated both fluorocarbon-grafted Pdyethylenes (PEs) are hydrophobic. Due to the additional fluorine and chlorine atoms on the CTFE chain, the PCTFE-grafted PE exhibited a higher hydrophobicity than the PVDF-grafted one. ESCA analysis has revealed that these two plasma-induced fluorocarbon deposits contain almost no CFx (x > 2) binding on the surface layer, indicating the grafting polymerization mainly follows the free radical mechanism instead of the molecule-highly-fragmented reaction steps commonly seen in the direct plasma polymerization treatment. In addition, ATR-FTIR has shown the surface chemical configuration of these PVDF- and PCTFE-grafted PEs to be very similar to those of the bulk samples of PVDF and PCTFE. The surface roughness decreased after oxygen plasma treatment and was further reduced by VDF and CTFE grafting polymerization. In vitro platelet adhesion testing indicated these two fluorocarbon grafted PEs are less platelet-activating than the nontreated PE control and oxygen plasma activated one.

Biocompatible Materials↗
PubMed2000

Taxane diterpenoids from seeds of Taxus mairei.

A new 2(3-->20) abeotaxane, taxumairone A (1), and a new cis-p-coumaroyl myo-inositol have been isolated from the seeds of Taxus mairei in addition to taxin B (2), taxinine A, taxuspine X, decinnamoyltaxinine E, 5alpha-cinnamoyloxy-9alpha,10beta,13alpha- triacetoxy-taxa-4(20)11-diene and 5alpha-cinnamoyloxy-2alpha,9alpha,10beta,+ ++13alpha-tetraacetoxy-taxa-4(20)11-diene. The structure of 1 was determined by 2D-NMR spectral analysis and chemical correlation with taxin B (2). Compound 1 exhibited potent cytotoxicity against human colon carcinoma cells with an ED50 of 0.1 microg/ml.

Bridged-Ring Compounds↗
PubMed2000

The effects of adsorbed water on tensile strength and Young's modulus of moldings determined by means of a three-point bending method.

Young's moduli (E) of three representative tableting excipients and their mix powders were measured for compressed rectangular beam specimens over a range of porosities using a three-point bending technique. We also examined the effects of the amount of water adsorbed on the tensile strength of these specimens. The maximal tensile strength (sigma(max)) decreased with increasing water vapor adsorption for microcrystalline cellulose (MCC) and mixed powders of lactose and MCC. Sigma(max) increased with increasing compression stress and specimen weight for all samples. Sigma(max) of an alpha-lactose and cornstarch mixture with a ratio of 7:3 showed a large value. Young's modulus (E) and the crushing energy (CE) of MCC were larger than those of the other samples. Young's modulus of specimens decreased as the proportion of alpha-lactose increased. Disintegration time (DT) of tablets comprised of lactose and MCC mixture was much faster than those of tablets comprised of individual powders. This appeared to demonstrate the effect of MCC swelling on the disintegration time of the tablet. The disintegration time of the lactose/cornstarch series increased only when Young's modulus increased sharply.

Adsorption↗
PubMed2000

Semicontinuous production of lipase by Acinetobacter radioresistens in presence of nonwoven fabric.

The effect of a hydrophobic nonwoven fabric on the lipase production by Acinetobacter radioresistens was investigated with semicontinuous culture. The fermentation medium contained n-hexadecane as the carbon source. The nonwoven fabric was made from nylon 6 and coated with an acrylic resin. Equipping the nonwoven fabric around the baffles of a 2.5-L agitated fermentor could provide a fine dispersion of n-hexadecane, thus enhancing lipase production. The improvement on lipase yield by using the nonwoven fabric was found to be comparable to that of using an emulsifier (gum arabic). Compared with the corresponding culture in the absence of nonwoven fabric, the employment of the nonwoven fabric could significantly enhance both lipase yield and volumetric productivity.

Acinetobacter↗
PubMed2000

T2-Weighted fast MR imaging with true FISP versus HASTE: comparative efficacy in the evaluation of normal fetal brain maturation.

OBJECTIVE: This study compares the relative efficacy of two fast T2-weighted MR imaging techniques-fast imaging with steady-state free precession (true FISP) and half-Fourier acquisition single-shot turbo spin-echo (HASTE)-in the evaluation of the normal fetal brain maturation during the second and third trimesters of gestation. SUBJECTS AND METHODS: The brain maturation of 10 normal nonsedated fetuses (5 during the second trimester and 6 during the third trimester of gestation [1 fetus underwent 2 examinations]) was examined by both techniques using a Vision+ 1.5-T MR system. We specifically looked for developing events, including white matter myelination, neuronal migration, and cortical sulcation. Image quality was graded according to the presence or absence of undesirable blurring. RESULTS: The specific absorption rate was lower for true FISP than for HASTE by a factor of 3 at equivalent imaging conditions. HASTE and true FISP provide comparable image quality in the second trimester when myelination of the cerebrum has not begun. Neuronal migration could be recognized as hypodense bands on both sequences during the second trimester. Myelination beginning at the third trimester was better delineated with true FISP than with HASTE because of point spread function-related blurring effects inherent in HASTE that hampered visualization of short-T2 structures. Cortical sulcation was well delineated by both sequences. CONCLUSION: With relatively superior image quality and significantly lower radiofrequency absorption than HASTE, true FISP is a safer and more effective alternative in the prenatal evaluation of normal fetal brain.

Basal Ganglia↗
PubMed2000

Correlation of genetic instability with mismatch repair protein expression and p53 mutations in non-small cell lung cancer.

To examine the etiological association of genetic instability in lung tumorigenesis, we investigated the frequency of microsatellite instability (MI) of eight dinucleotide repeat markers in 68 patients with non-small cell lung cancer. Twenty-eight patients (41.2%) evidenced instability in multiple tested microsatellite markers ranging from 3-7 and were defined as MI-positive patients. MI occurred more frequently in patients suffering from squamous cell lung carcinoma (P = 0.004). We examined the association between MI and expression of hMLH1 mismatch repair protein by immunohistochemical analysis of hMLH1 protein in paraffin-embedded tumors from 64 patients. Twenty MI-positive patients (76.9%) had no expression of hMLH1 protein. The data showed that MI was associated with altered hMLH1 expression (P = 0.03). To examine the role of genetic instability in the previous identified small intragenic deletion of the p53 gene, we explored the association between MI and p53 gene mutations. All patients, except one, containing small intragenic deletion in p53 gene showed MI (P = 0.018). In addition, we found that MI was not associated with the prognosis. Our data suggest that MI plays a significant role in non-small cell lung cancer tumorigenesis in Taiwan and that MI is associated with the altered expression of hMLH1 mismatch repair protein. In addition, MI may be involved in frequent small intragenic deletions of p53 gene.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Cyclosporine-induced encephalopathy in a patient with relapsed acute myeloid leukemia treated with unrelated allogeneic bone marrow transplantation.

Cyclosporine (CSP) is the most frequently used immunosuppressive agent for prevention of graft versus host disease (GVHD) in allogeneic bone marrow transplantation (BMT). Some adverse effects such as hepatic and renal toxicity have been frequently encountered, but central nervous system (CNS) toxicity caused by CSP is rare. We report an adult male patient with acute myeloid leukemia who developed CSP-induced encephalopathy under treatment for allogeneic BMT from an unrelated donor. Methotrexate and CSP were used for GVHD prophylaxis. Leukocyte and platelet engraftment were successfully achieved on days 21 and 24 after BMT, respectively. Abrupt onset of mental confusion and disorientation occurred on day 25, followed by a generalized tonic clonic seizure and consciousness disturbance. The whole blood CSP level was 160.65 ng/mL. Magnetic resonance (MR) imaging revealed high signal intensities in the bilateral occipital lobes with predominant involvement of the cortical areas. The patient recovered from the CNS toxicity, but with slight memory impairment, 6 days after CSP was discontinued. When patients receiving CSP treatment for allogeneic BMT develop mental confusion, consciousness disturbance, or seizure, CSP-induced CNS toxicity should be taken into consideration.

Adult↗
PubMed2000

Cartilage repair by free periosteal grafts in the knees of pigs: a histologic study.

BACKGROUND AND PURPOSE: Periosteal grafts may result in cartilage formation and, therefore, have the potential to repair cartilage defects. We evaluated the histologic results of free periosteal grafts for the repair of full-thickness cartilage defects in pigs. METHODS: A free autogenous periosteal flap from the proximal tibia was grafted to a size-matched, full-thickness articular defect on the lateral femoral condyle of the knees of 12 pigs. The same defect on the medial femoral condyle was used as a control lesion. Biopsies were performed at 4, 8, and 12 weeks after grafting. RESULTS: The control lesions showed dense fibrous tissue with no evidence of cartilage-like tissues. The predominant tissues after grafting were mixtures of fibrous tissue, fibrocartilage, mesenchyme tissue, and occasional bone islands, but no cartilage tissue was identified. The tissue distribution did not change in the same knee from the week 4 to the week 8 biopsy; nonetheless, there were interindividual variations in tissue distribution. CONCLUSIONS: The results of this study do not support the use of free periosteal transplantation for full-thickness cartilage defects of the knee.

Animals↗
PubMed2000

Modified technique for introducer-type percutaneous endoscopic gastrostomy and jejunostomy: assisted by a novel trocar and fasteners.

BACKGROUND AND PURPOSE: Commercially available kits for percutaneous endoscopic gastrostomy (PEG) and jejunostomy comprise a substantial proportion of the cost of patients for this procedure. A modified introducer-type technique and new instrumentation for PEG and jejunostomy that substantially reduces the cost of the kit were tested for efficacy and safety. METHODS: This technique was tested on 10 pigs as a pilot study, and then applied to seven consecutive patients undergoing gastrostomy and three patients undergoing gastrostomy with jejunostomy. The endoscopy and site selection for gastrostomy were the same as in standard PEG. Two novel fasteners for fixing the gastric wall to the abdominal wall and a guide-wire in the selected site were inserted separately into the stomach through 15-gauge needles. A stainless steel trocar with a detachable sheath was introduced into the stomach over the guide-wire. After the inner stylet was removed, a 24-French Foley catheter was inserted as a feeding tube. Gastrostomy was completed after balloon inflation and external fixation. If jejunostomy was indicated, a 12-French nasogastric tube was inserted through the gastrostomy. The procedure time, complications, and costs were compared with those for another 15 consecutive patients who underwent the conventional pull-through method of PEG and jejunostomy using commercially available kits. RESULTS: No significant difference was found in procedure time between patients who underwent the modified or conventional gastrostomy procedures (mean +/- standard deviation, 15.4 +/- 5.6 min). There was a similar incidence of short-term complications in the two treatment groups. The feeding catheters required replacement more quickly than did those in the commercial kits (80 +/- 58 vs 217 +/- 140 d). The cost to patients was much less with the new method than with conventional PEG. CONCLUSIONS: The new gastrostomy method achieves the same medical quality at far less cost for patients.

Adult↗
PubMed2000

Lingual osteoma: case report.

Lingual osteoma, a rare clinical entity, has been found mainly in the posterior region of tongue. It mostly affects women in their third and fourth decades of life and occurs less frequently in men. We report an unusual case of a 42-year-old male patient who developed a lingual osteoma near the foramen cecum. The patient underwent excision of the tumor mass under local anesthesia and had an uneventful postoperative course. Symptoms of the mass effect were noted to resolve after surgical intervention. Histologically, mature lamellar bone with haversian systems was seen. The pathogenesis of this rare tumor is a controversial problem and its nomenclature also remains an issue of debate. Discussion of the controversial pathogenesis of lingual osteoma and a review of the literature on its clinical characteristics are included in this report.

Adult↗
PubMed2000

Failure of the locking mechanism between the acetabular metal shell and the polyethylene liner after primary total hip arthroplasty--a case report.

The short and intermediate-term clinical and radiographic results associated with Harris-Galante II porous-coated acetabular modular cup without cementing have been excellent in most patients. Nevertheless, its modular design introduced the potential for failure of the locking mechanism. There are four pairs of locking ties on the rim of metal shell to fix the polyethylene liner within it. Failure of any locking tine would result in less rigid fixation between the metal shell and the polyethylene liner and potentially produce instability or even disassembling of the liner. Only nine cases have been reported previously about the fractures of the locking tine, but it has never been reported in literature in Taiwan. We report a case with fracture of one tine following minor trauma at five years after primary total hip arthroplasty. During reoperation, scratching injury on the outer surface of the polyethylene liner in contact with the inferior tines of the metal shell was noted. Although no disassembling of the liner was noted, the remaining locking mechanism was found to be less rigid when the liner was taken out of the shell. The locking mechanism of HG II cup may be mechanically weak and may fail without major trauma; therefore, its design ought to be improved in an attempt to prevent postoperative dissociation of the polyethylene liner.

Acetabulum↗