Biomedical subjects

Y Chao

Publications and source records attributed to Y Chao.

At least 145 records · Page 8Linked to original sources

PubMed1999

[A study of load stress on an implant and a tooth supported fixed bridge for the first mandibular molar].

OBJECTIVE AND METHODS: A study of load stress on an implant and a tooth supported fixed bridge for the first mandibular molar was performed by means of 3-D FEA in order to reveal the displacement and stress distribution. RESULTS: The results show that the maximum displacement of the second premolar is greater than that of the terminal implant, but there is no difference between the mean (mean) under dispersed load statistically, due to the framework function of the bridge. The stress concentration appears around the neck of the abutments, on the contrary, a little stress is found around the apical portion of the second premolar. When the load concentrates on-to the abutments, the displacement and stress value increase obviously. CONCLUSION: The attention should be paid to the load and occlusion of the terminal implant. This kind of bridge design may be used in clinical practice.

Dental Implantation↗

PubMed1999

[Study on relationship of different thickness and opaquing capacity of various opaques].

OBJECTIVE: To evaluate the relation between different opaque thickness and color difference. METHODS: Model made of the thin plastic paper was used to control the ceramic thickness. The data of chromaticity was measured by TC-PIIG auto color difference meter and its results were processed by computer. RESULTS: There are two thickness values which can be considered as ideal range of opaque thickness for color opaquing: one is the values of ceramic thickness which is based on the color difference values of the infinite chromaticity thickness (ICT) and the other is the values of ceramic thickness which is depended on the color difference values which is 1.5 compared with ICT. The ideal range for VITA is (0.207-0.152) mm, SHOFO is (0.190-0.160) mm, CARAT is (0.140-0.074) mm and EXCELCO is (0.169-0.144) mm. CONCLUSION: There is a relationship of non linear direct ratio between opaque thickness and its shadow capacity. However, no more increase of color difference values in respect to the thickness was found when the ceramic thickness reach a certain value. Different ceramic porcelain needs different ideal range of thickness.

Ceramics↗

PubMed1999

[Mutation and expression of p16 in human ovarian neoplasms].

OBJECTIVES: To detect mutation and expression of p16 in human ovarian neoplasms and to understand the relations between p16 and development of ovarian neoplasms. METHODS: Polymerase chain reaction-single strand polymorphism analysis and immunohistochemistry were respectively used to detect mutations in exon 1 and 2 and protein expression in 14 patients with ovarian neoplasms. Metastasis tissue of 5 mentioned patients were screened at the same time. RESULTS: No expression of p16 was found in 7 ovarian neoplasm tissues. No mutation in exon 1 of p16 was found in any patient tissues, but mutations in exon 2 were found in 4 patients tissues and expression of p16 was not found in 2 of them. There was correspondence between primary focus and metastasis in either gene mutation or protein expression. CONCLUSIONS: Inactivation of p16 may be involved in the development of ovarian neoplasms. Gene mutation is a kind of inactivation. Alterations of p16 probably occur before metastasis.

Cyclin-Dependent Kinase Inhibitor p16↗

PubMed1999

[Comparative study of the effect on stress distribution of porcelain laminate complex with different elastic moduli].

Porcelain laminate has been a kind of popular treatment modality for its aesthetics and less tooth reduction. The models of 3-D FEA of left upper permanent central incisor were designed by microtomy. Comparative studies of stress distribution were carried out to reveal the stress of three designs of tooth preparation with two kinds of occlusions. The results showed that under loads imitating of central occlusion, the stress level increased a little with the rising of elastic modulus of the porcelain material, while the stress values of type II veneer seemed the highest under loads imitating of protruding occlusion. For the designing of laminate, it implies that porcelain material with low elastic modulus should be used in case of type II veneers.

Dental Porcelain↗

PubMed1999

[Effects of alumina particle-size on mechanical properties of alumina-glass composite].

OBJECTIVE: To study the effects of alumina particle-size on mechanical properties of alumina-glass composite. METHODS: Alumina compacts were prepared by isostatic press method and sintered at 1400 degrees C for 2 hours with two various particle-size alumina. Alumina-glass composite was made by infiltrating partially sintered porous alumina with glass at 1200 degrees C for 4 hours. RESULTS: The strength and fracture toughness of nanometre alumina-glass composite were 358.2 MPa, 2.38 MPam1/2 respectively. The strength and fracture toughness of micrometer alumina-glass composite were 432.2 MPa, 5.12 MPam1/2 respectively. Image analysis of SEM micrograph showed that porous rate was about 11.5% in the nanometer alumina-glass composite, 1.2% in the micrometer alumina-glass composite, and there was more glass composition in the nanometer alumina-glass composite than that in the micrometer alumina-glass composite. CONCLUSION: The alumina volume percentage and porous rate play an important role in the strength and fracture toughness of alumina-glass composite.

Aluminum Oxide↗

PubMed1999

[Determination of major expansion properties of refractory die material compatible with slip casting core of sintered titanium powder].

OBJECTIVE: To determinate major expansion properties of refractory die material. METHODS: The setting expansion ratio of refractory die material for slip casting core of sintered titanium powder at room temperature was performed, as well as thermal expansion ratio from room temperature to 800 degrees C. RESULTS: The maximum setting expansion ratio in 2 hours reached 0.3407%; The final setting expansion ratio in 24 hours was 0.3117%; The mean thermal expansion coefficient was mainly in range of 8 x 10(-6)-11 x 10(-6)/degree C; The expansion property seemed very stable after sintering repeatedly and the small shrinkage after sintering could be compensated with the die spacer and setting expansion. CONCLUSION: The expansion properties of the refractory die material that we synthesized can fulfil the application requirements of slip casting core of sintered titanium powder.

Crowns↗

PubMed1999

[A comparative study of mechanical properties of microwave-cured and conventional water bath-cured denture base resins].

OBJECTIVE: To study the mechanical properties of microwave-cured polymethyl methacrylate (PMMA) denture base resins. METHODS: Using experiment research, the mechanical properties of microwave-cured and water bath-cured PMMA materials were compared. RESULTS: The microwave-cured acrylic strips had equal or better mechanical properties than conventionally processed strips. CONCLUSION: The microwave-cured denture materials satisfies the requirements of the prosthetic clinic.

Biomechanical Phenomena↗

PubMed1999

[Determination of normal temperature properties of refractory die material compatible with slip casting core of sintered titanium powder].

OBJECTIVE: The refractory die is the precondition for developing slip casting core of sintered powder. This study is to determine the normal temperature properties of the refractory die material compatible with slip casting core. METHODS: to mix the die material at five different ratios (8/1, 7.5/1, 7/1, 6.5/1, and 6/1) and measure their solidification time with self-manufactured Vicker's needle; to prepare five cylindrical specimens (phi 10 x 15 mm) in different drying time for determining their compressive strength, and then to let another five specimens fire at 1000 degrees C four times for measuring the residual compressive strength at room temperature. RESULTS: The setting time was 16.25 minutes (7.5/1), and the lower the powder-liquid ratio, the longer the setting time. The normal compressive strength was 25.32 MPa (drying 24 hours), while the longer the drying time, the higher the compressive strength achieved (P < 0.01). The residual compressive strength was 24 MPa. CONCLUSION: The normal temperature properties of the refractory die material meet the demand of slip casting core of sintered powder.

Compressive Strength↗

PubMed1999

[Determination of high temperature compressive strength and refractory degree of die material compatible with slip casting core of sintered titanium powder].

OBJECTIVE: The refractory die is the precondition for developing slip casting core of sintered powder. This study is to determine the high temperature properties of the refractory die material compatible with slip casting core. METHODS: To prepare three cylindrical specimens (phi 10 x 15 mm) and determine their compressive strength at 1000 degrees C: to make four specimens in flat-topped cone for determining the practical refractory degree by decreasing the pressing temperatures in a sequence of 1420, 1400, 1350 and 1100 degrees C. RESULTS: The compressive strength of this material was 17.8 MPa at 1000 degrees C. Its practical refractory degree was higher than 1100 degrees C. CONCLUSION: The high temperature properties of the refractory die material that we developed meet the demand of slip casting core of sintered powder.

Compressive Strength↗

PubMed1998

Detection and modeling of NonTidal oceanic effects on Earth's rotation rate

Subdecadal changes in Earth's rotation rate, and hence in the length of day (LOD), are largely controlled by variations in atmospheric angular momentum. Results from two oceanic general circulation models (OGCMs), forced by observed wind stress and heat flux for the years 1992 through 1994, show that ocean current and mass distribution changes also induce detectable LOD variations. The close similarity of axial oceanic angular momentum (OAM) results from two independent OGCMs, and their coherence with LOD, demonstrate that global ocean models can successfully capture the large-scale circulation changes that drive OAM variability on seasonal and shorter time scales.

Journal Article↗

PubMed1998

Diagnostic and prognostic values of plasma levels of fibrinolytic markers in gastric cancer.

In the present study, we determined the plasma and tissue concentrations of tissue-type plasminogen activator, urokinase-type plasminogen activator, plasminogen activator inhibitor-1, plasminogen activator inhibitor-2 and urokinase-type plasminogen activator receptor in 32 patients with pathology-proved gastric cancer. The plasma levels of the same markers were compared in 37 patients with benign gastric ulcer in order to find out if these plasma levels could be used to evaluate the prognostic value in patients with gastric cancer. Plasma plasminogen activator inhibitor-1 was significantly higher in gastric cancer than in benign gastric disease (p < 0.0005), whereas plasma urokinase-type plasminogen activator was significantly lower in patients with gastric cancer than in those with benign ulcer (p = 0.003). There was no significant correlation between tissue and plasma concentrations of the same parameters. The plasma and tissue levels of fibrinolytic parameters were not affected by tumor size or distant metastasis, whereas tumor tissue concentration of urokinase-type plasminogen activator receptor and plasminogen activator inhibitor-2 were significantly higher in N0 than in N1 and N2, and tissue plasminogen activator inhibitor-1 was significantly higher in N0 than in N1. Plasma levels of the five fibrinolytic parameters could not take the place of the corresponding tissue concentrations on the diagnosis and prediction of prognosis in patients with gastric cancer. Tissue concentrations of urokinase-type plasminogen activator receptor and plasminogen activator inhibitor-2, especially the latter, can be used to predict lymph node involvement in patients with gastric cancer.

Aged↗

PubMed1998

S- and G2-phase cell cycle arrests and apoptosis induced by ganciclovir in murine melanoma cells transduced with herpes simplex virus thymidine kinase.

Mechanism of cell killing by transfer of Herpes simplex virus type-1 thymidine kinase (HSVtk) and subsequent ganciclovir (GCV) treatment was examined in B16F10 murine melanoma model. While parental B16F10 melanoma cells were resistant to GCV at 100 microM or higher, HSVtk-transduced B16F10 melanoma cell clones became susceptible to GCV with IC50 of 0.1 to 0.3 microM. By means of various parameters including characteristic morphological changes, in situ DNA end-labeling, DNA ladder pattern, flow cytometric detection of sub-G1 DNA content, and annexin V binding of inverted cell surface phosphatidylserine, apoptosis was shown to be associated with the cell killing of ganciclovir on HSVtk-transduced melanoma B16F10 cells. Kinetic analysis showed that the signs of apoptosis were observed not until 60 h of continued GCV treatment and preceded first by a rise in p53 protein level in 12 h and then by S-phase/G2-phase cell cycle arrest associated with corresponding increases in the level of cyclin B1 protein but no apparent change in protein level of Bax or Cdc2. These results suggest that apoptosis occurred as a result of ganciclovir-induced cell cycle arrests rather than direct chemical effect on HSVtk-transduced B16F10 melanoma cells.

Animals↗

PubMed1998

Overexpression of cyclin A but not Skp 2 correlates with the tumor relapse of human hepatocellular carcinoma.

Cyclin A is an S- and G2-M-phase regulatory protein, and its abnormal expression has been implicated in cellular transformation. This work was undertaken to investigate the frequency of cyclin A overexpression and the correlated clinical outcome in human hepatocellular carcinoma (HCC). Herein, 12 of 31 (39%) patients exhibited cyclin A overexpression in their tumorous tissues, resulting from gene amplification in 6 of 12 patients, (post)transcription in 4 of 12 patients, and (post)translation in 2 of 12 patients. Patients who overexpressed cyclin A had significantly more tumor cells in the S and G2-M phases compared with those expressing a normal cyclin A level (P = 0.007 and 0.039, respectively). Increased levels of Skp 2, a cyclin A-interacting protein, were also found in 17 of 31 (55%) of HCC patients who showed a trend to have more S-phase tumor cells (P = 0.07). By an unpaired Student's t test and a Fisher's exact or chi2 analysis, overexpression of cyclin A had a strong correlation with elevated Skp 2 expression and increased alpha-fetoprotein levels (P = 0.001 and 0.009, respectively), but it was not associated with patients' age, tumor size, cirrhosis, or the positive detection of hepatitis B virus surface antigen. In the disease-free survival analysis, patients whose tumors overexpressed cyclin A had a median disease-free survival of 6 months, whereas patients who lacked cyclin A overexpression exhibited a longer median period of 29 months (P = 0.046). The overall survival analysis revealed the same trend, i.e., cyclin A-overexpressing patients had shorter overall survival periods (median, 12 versus 50 months; P = 0.09). By multivariate analysis, the correlation of cyclin A overexpression with shorter disease-free periods remained significant after adjustment for Skp 2 overexpression and alpha-fetoprotein induction (P = 0.019). These data suggest that overexpression of cyclin A can be an independent prognostic factor for the tumor relapse of human HCC.

Adult↗

PubMed1998

Weekly etoposide, epirubicin, cisplatin, 5-fluorouracil and leucovorin: an effective chemotherapy in advanced gastric cancer.

In order to optimize the therapeutic index of combining etoposide, epirubicin, cisplatin, 5-fluorouracil (5-FU), leucovorin (EEPFL) chemotherapy in the treatment of advanced gastric cancer, a trial of a novel schedule of weekly administration was conducted. Weekly EEPFL treatment consisted of a concomitant boost of etoposide 40 mg m(-2) i.v. over 30 min, epirubicin 10 mg m(-2) i.v. over 5 min to a backbone regimen, weekly PFL chemotherapy with cisplatin 25 mg m(-2), 5-FU 2200 mg m(-2), leucovorin 120 mg m(-2) given simultaneously by 24-h i.v. infusion. Response, survival and toxicity were evaluated. Forty-two patients were studied. Median age was 69 (range 31-84) years. Twenty-six per cent of patients showed complete response and 45% partial response. The overall response rate was 71% (95% confidence interval 58-84%). For a total of 507 weekly EEPFL cycles delivered, the incidence of grade 4 leucopenia was 1% of cycles. One patient died of neutropenia septicaemia. There was no other grade 4 toxicity. Grade 3 and 2 leucopenia occurred in 7% and 14% of cycles. The incidence of grade 3 and 2 mucositis was 1% and 3% of cycles. Grade 3 and 2 diarrhoea occurred in 0.4% and 1.6% of cycles. Overall median survival was 10 months (range 3-41+ months). Weekly EEPFL chemotherapy is an effective regimen with tolerable toxicities in the treatment of advanced gastric cancer. A randomized controlled clinical trial to formally assess the efficacy and benefit of EEPFL chemotherapy is under way.

Adult↗

PubMed1998

Phase II and pharmacokinetic study of paclitaxel therapy for unresectable hepatocellular carcinoma patients.

Hepatocellular carcinoma (HCC) is a common lethal disease in Asia and there is no effective chemotherapy. Identification of new effective drugs in the treatment of inoperable HCC is urgently need. This is a phase II clinical study to investigate the efficacy, toxicity and pharmacokinetics of paclitaxel in HCC patients. Twenty patients with measurable, unresectable HCC, normal serum bilirubin, normal bone marrow and renal functions were studied. Paclitaxel 175 mg m(-2) was given intravenously over 3 h every 3 weeks. No complete or partial responses were observed. Five patients had stable disease. Major treatment toxicities (grade 3-4) were neutropenia (25%), thrombocytopenia (15%), infection (10%) and allergy (10%). Treatment-related deaths occurred in two patients. The median survival was 12 weeks (range 1-36). Paclitaxel is metabolized by the liver and the pharmacokinetics of paclitaxel in cancer patients with liver involvement or impairment may be important clinically. Pharmacokinetic study was completed in 13 HCC patients. The paclitaxel area under the curve was significantly increased (P < 0.02), clearance decreased (P < 0.02) and treatment-related deaths increased (P = 0.03) in patients with hepatic impairment. In conclusion, paclitaxel in this dose and schedule has no significant anti-cancer effect in HCC patients. Paclitaxel should be used with caution in cancer patients with liver impairment.

Adult↗

PubMed1998

Age is one of the risk factors in developing gallstone disease in Taiwan.

OBJECTIVES: To assess the prevalence and risk factors of gallstone disease (GSD) in Taiwan. DESIGN: Descriptive and cross-sectional. METHODS: A prospective ultrasonographic study of GSD was conducted in 3647 Chinese subjects who received a paid hospital physical check-up. Their demographic characteristics and biochemical parameters were recorded and compared. Ultrasonographic diagnosis revealed 2946 (M/F: 1838/1108) with normal gallbladder, 286 (M/F: 196/90) with gallbladder stones, 100 (M/F: 56/44) with previous cholecystectomy for gallstones, 243 (M/F: 174/69) with gallbladder polyps, 17 (M/F: 10/7) with mixed gallbladder stones/polyps and 35 as 'miscellaneous'. We enrolled subjects showing either gallbladder stones or cholecystectomy for gallstones in the GSD group. RESULTS: Excluding those subjects with mixed gallbladder stones/polyps, the overall prevalence of GSD in the studied group was 10.7%. The studied factors manifesting an increase in risk for the development of GSD were age (P<0.05), high body mass index (P< 0.05), diabetes mellitus (adjusted odds ratio: 1.998; P< 0.05) and glucose intolerance (adjusted odds ratio: 2.056; P<0.05) by multivariate analysis. Other demographic characteristics and biochemical parameters, such as body height, ABO blood type, cigarette smoking, alcohol consumption, blood pressure, lipid profiles, hepatitis B virus infection, liver function and multiparity did not show any correlation to GSD. CONCLUSIONS: Age, high body mass index, diabetes mellitus and glucose intolerance are the risk factors for developing GSD in Taiwan.

Adult↗

PubMed1998

Continuous infusion cisplatin and etoposide chemotherapy for cancer of unknown primary site (CUPS) in Taiwan, a region with a high prevalence of endemic viral infections.

BACKGROUND: To evaluate the efficacy and toxicity of cisplatin/etoposide continuous infusion chemotherapy for cancer of unknown primary site in Taiwan, a region with a high prevalence of endemic viral infections. METHOD: Between April 1994 and February 1996, 20 patients with a diagnosis of CUPS were treated, including 15 males and five females, of average age 63.3 years (range 41-83 years). Continuous intravenous infusion of etoposide 80 mg/m2 and cisplatin 25 mg/m2 was given for 3 days every 3 weeks. Pretreatment tumor marker and viral serology studies were performed for baseline evaluation. Nearly two-thirds of the patients had poorly differentiated carcinoma. The average number of metastatic sites was 2.65 (range 1-4), with liver and lymph node involvement predominating. RESULTS: The overall response rate was 25% (95% CI 17.7-32.3%); 30.7% for poorly differentiated cancers and 25% for well differentiated cancers. Median survival was 4 months (range 1-12 months), 4.8 months for patients attaining partial response. Toxicity was moderate, grade 3 and 4 neutropenia occurred in 55% and grade 3 and 4 thrombocytopenia in 40%; other toxicities were mild. CA125 and CA199 were elevated in more than 50% of patients. Viral serology studies were not significantly different from those of the indigenous population. CONCLUSION: Etoposide and cisplatin combination chemotherapy has modest activity in patients with extensive CUPS and, at the schedule and dosage given, it is associated with moderate toxicity.

Adult↗

PubMed1998

Radiotherapy in the treatment of duodenal bleeding due to hepatocellular carcinoma invasion.

Haemorrhage from an hepatocellular carcinoma (HCC) directly invading the gastrointestinal (GI) tract is uncommon. A 58-year-old man was admitted with upper gastrointestinal (UGI) bleeding and panendoscopy on examination revealed a large duodenal ulcerative bleeding mass. The mass was eventually diagnosed as HCC by pathological examination. The bleeding failed to respond to conventional management of haemostasis, but resolved with an external beam of radiotherapy with a total dose of 6000 cGy over a 5 week period. This unusual presentation of UGI bleeding, due to HCC invading the duodenum and treated by radiotherapy, has not been previously reported.

Carcinoma, Hepatocellular↗