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Biomedical subjects

Y Liao

Publications and source records attributed to Y Liao.

At least 91 records · Page 5Linked to original sources
PubMed1999

[Investigation of aluminum oxide matrix of the machinable infiltrated ceramic(MIC)].

OBJECTIVE: To explore the effects of different powder/liquid ratio during the procedure of aluminum oxide slip preparation on the properties and microstructure of the machinable infiltrated ceramic(MIC) aluminum matrice. METHODS: PI alpha-Al2O3 powder was employed in this study. Aluminum slip with different powder/liquid ratios of 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, 9.5 and 10.5 was prepared separately. Specimens were slip-casted and pre-fired, and whose physical properties were determined and morphology of specimens was examined under scanning electromicroscope. RESULTS: The packing density increased while the linear shrinkage decreased, when the powder/liquid ratio increased. Elevated pre-firing temperature resulted in higher flexural strength of the matrice. The matrice demonstrated porous morphology under electromicroscope, and neck-fusion between Al2O3 particles was observed and increased with elevated prefiring temperature. CONCLUSION: MIC is a kind of easy-manipulated material with high packing density, optimum porosity and lower linear shrinkage, so it may be an ideal aluminum matrix for infiltrated ceramic.

Aluminum Oxide↗
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↗
PubMed1999

[A comparative study of finger plethysmography and aortic pressure for monitoring the effect of external counterpulsation].

Invasive pressure detecting and monitoring of aortic root was conducted in 20 volunteers so as to study the effect of Enhanced External Counterpulsation (EECP) on aortic pressure and finger plethysmography. The results demonstrated that the changes of aortic diastolic pressure linearly related to the counterpusation's bladder pressure, and the aortic augmentation increased to the top of 168.56 mmHg with a D/S ratio of 2.75(amplitude ratio of diastolic waveform and systolic waveform, D/S ratio) following the bladder pressure of 0.45 Kg/cm2. With the increase of bladder pressure, the dp/dt of aortic augmentation elevated gradually, but a down-regulating trend was seen in systolic waveform. During EECP, the starting time of plethysmographic augmentation had a mean delay of 108.20 +/- 25.70 ms comparing with that of aortic augmentation. The duration between the starting time of aortic systolic waveform and that of finger plethysmogram was arround 96.69 +/- 38.70 ms. When the bladder pressure changed, no significant difference was observed among them. The D/S ratio of finger plethysmographic waveform changed in concord with that of aortic pressure with the promotion of bladder pressure. Therefore, a relationship between aortic D/S ratio (Y) and plethysmographic D/S ratio (x) was constructed by the linear regression analysis: Y = 0.376 + 0.457X. It can be concluded that EECP has significant effects on aortic D/S ratio, aortic peak augmentation and its dp/dt value. Finger plethysmography, to date, still plays important roles in monitoring and controlling EECP work safely and effectively.

Adolescent↗
PubMed1999

[Pharmacognostic identification of Ampelopsis grossedentata].

Pharmacognostic identification of Ampelopsis grossedentata was carried out by studying its microscopic characteristics, UV spectra and TLC. The results may provide a scientific basis for the comprehensive development and utilization of the drug.

Ampelopsis↗
PubMed1998

Identification of Ce-AF-6, a novel Caenorhabditis elegans protein, as a putative Ras effector.

Mammalian Ras proteins associate with multiple effectors, including Raf, Ral guanine nucleotide dissociation stimulator, phosphoinositide 3-kinase and AF-6. In the nematode Caenorhabditis elegans, LIN-45/Raf has been identified genetically as an effector of LET-60/Ras. To search for other effectors in C. elegans, we carried out a yeast two-hybrid screening for LET-60-associating proteins. The screening identified a novel protein, designated Ce-AF-6, which exhibited a strong structural homology with human AF-6, rat Afadin and Drosophila melanogaster Canoe and possessed both the Ras-associating (RA) domain and the PSD-95/DlgA/ZO-1 (PDZ) domain. Ce-AF-6 associated with human Ha-Ras in a GTP-dependent manner, with an efficiency comparable to that of human Raf-1 Ras-binding domain. When the effects of mutations of the Ras effector region residues were examined for associations with various effectors, Ce-AF-6 was found to possess a distinct and the most rigorous requirement for the effector region residues. These results strongly suggest that Ce-AF-6 is a putative effector of Ras that possesses a distinct recognition mechanism for association with Ras.

Amino Acid Sequence↗
PubMed1998

New antipsychotic agents with serotonin and dopamine antagonist properties based on a pyrrolo[2,1-b][1,3]benzothiazepine structure.

The development of a synthetic approach to the novel pyrrolo[2, 1-b][1,3]benzothiazepine and its derivatives and their biological evaluation as potential antipsychotic drugs are described. In binding studies these compounds proved to be potent 5-HT2, D2, and D3 receptor ligands. The more potent benzothiazepine (+/-)-3b was resolved into its enantiomers by using HPLC techniques. In vitro testing confirmed that (-)-3b is a more potent D2 receptor ligand, maintaining high affinity for 5-HT2 receptors. In contrast, the (+)-3b enantiomer presents a 35 times higher affinity for 5-HT2 than for dopamine D2 receptors with a similar dopamine D1 receptor affinity to that of (-)-3b. Overall, (+)-3b shows an "atypical" neuroleptic binding profile, while (-)-3b has a more "classical" profile. Furthermore pharmacological and biochemical testing displayed that the novel benzothiazepine (+/-)-3b is able to increase the extracellular levels of dopamine in the rat striatum and causes a dose-related suppression of apomorphine-induced locomotor activity. At low doses (+/-)-3b does not induce catalepsy, showing atypical antipsychotic properties similar to those of olanzapine. These heterocyclic compouds represent new leads for the development of novel antipsychotic drugs with atypical properties.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1998

Direct enantiomeric separation of mianserin and 6-azamianserin derivatives using chiral stationary phases.

The direct enantiomeric separation of mianserin and 6-azamianserin and some of their derivatives, respectively, by means of HPLC using two different chiral selectors was investigated. For the cellulose-based Chiralcel OD column, a strong dependence of the lipophilicity of the compounds tested on the retention behaviour was observed. To some extent, this was also found for the enantiomeric separation on the amylose-based Chiralpak AD column. In some cases a complementary behaviour of these two phases was observed: racemic mixtures that could not be separated by one column could be resolved by the other one.

Adrenergic alpha-Antagonists↗
PubMed1998

Mortality and optimal body mass index in a sample of the US population.

In this paper, the authors model the nonmonotonic relation between body mass index (BMI) (weight (kg)/height2 (m2)) and mortality in 13,242 black and white participants in the NHANES I Epidemiologic Follow-up Study in order to estimate the BMI at which minimum mortality occurs. The BMI of minimum mortality was 27.1 for black men (95% confidence interval (CI) 24.8-29.4), 26.8 for black women (95% CI 24.7-28.9), 24.8 for white men (95% CI 23.8-25.9), and 24.3 for white women (95% CI 23.3-25.4). Each confidence interval included the group average. Analyses conducted by smoking status and after exclusion of persons with baseline illness and persons who died during the first 4 years of follow-up led to virtually identical estimates. The authors determined the range of values over which risk of all-cause mortality would increase no more than 20% in comparison with the minimum. This interval was nine BMI units wide, and it included 70% of the population. These results were confirmed by parallel analyses using quantiles. The model used allowed the estimation of parameters in the BMI-mortality relation. The resulting empirical findings from each of four race/sex groups, which are representative of the US population, demonstrate a wide range of BMIs consistent with minimum mortality and do not suggest that the optimal BMI is at the lower end of the distribution for any subgroup.

Adult↗
PubMed1998

Identification of PLC210, a Caenorhabditis elegans phospholipase C, as a putative effector of Ras.

Mammalian Ras proteins regulate multiple effectors including Raf, Ral guanine nucleotide dissociation stimulator (RalGDS), and phosphoinositide 3-kinase. In the nematode Caenorhabditis elegans, LIN-45 Raf has been identified by genetic analyses as an effector of LET-60 Ras. To search for other effectors in C. elegans, we performed a yeast two-hybrid screening for LET-60-binding proteins. The screening identified two cDNA clones encoding a phosphoinositide-specific phospholipase C (PI-PLC) with a predicted molecular mass of 210 kDa, designated PLC210. PLC210 possesses two additional functional domains unseen in any known PI-PLCs. One is the C-terminal Ras-associating domain bearing a structural homology with those of RalGDS and AF-6. This domain, which could be narrowed down to 100 amino acid residues, associated in vitro with human Ha-Ras in a GTP-dependent manner and competed with yeast adenylyl cyclase for binding Ha-Ras. The binding was abolished by specific mutations within the effector region of Ha-Ras. The other functional domain is the N-terminal CDC25-like domain, which possesses a structural homology to guanine nucleotide exchange proteins for Ras. These results strongly suggest that PLC210 belongs to a novel class of PI-PLC, which is a putative effector of Ras.

Amino Acid Sequence↗
PubMed1998

Influence of left ventricular geometric patterns on prognosis in patients with or without coronary artery disease.

OBJECTIVES: We sought to examine patterns of left ventricular (LV) geometry as determined by echocardiography and their association with mortality in patients with or without coronary artery disease (CAD). BACKGROUND: The independent prognostic role of LV geometry remains uncertain. METHODS: We performed a cohort study based on 988 consecutive patients who underwent both coronary arteriography for presumed CAD and echocardiography and were followed up for a mean of 9 years (range 5 to 13). Patients were classified into four LV geometry patterns: normal, concentric remodeling, eccentric LV hypertrophy (LVH) and concentric LVH. RESULTS: Patients with concentric LVH consistently showed the largest increase in LV posterior wall and septal thickness and LV mass index, as well as relative wall thickness (RWT), regardless of status of the coronary arteries. This pattern conferred the highest risk of both all-cause and cardiac mortality. Eccentric LVH moderately increased the risk of death compared with normal geometry; no substantial increase in mortality was noted in patients with concentric remodeling. When LV index and RWT were analyzed as continuous measures and considered in the same Cox proportional hazards model, increases in LV mass were independently associated with risk, but this outcome was less clear for RWT. CONCLUSIONS: In this series of patients referred to coronary angiography for suspected CAD, LVH conferred most of the predictive information from echocardiography. Patients with both LVH and abnormal RWT--concentric LVH--represent a group with the greatest mortality risk. Concentric remodeling may not be associated with increased risk of death because the predictive value of RWT is not as strong as for LV mass.

Black People↗
PubMed1998

The impact of obesity and body fat distribution on ambulatory blood pressure in children and adolescents.

To assess the relationship between obesity, body fat distribution, and blood pressure in children and adolescents, various measures of obesity and the waist-to-hip circumference ratio were related to casual and ambulatory blood pressure as measured using a SpaceLabs 90207 monitor during a regular school day. Seventy obese and 70 nonobese children aged 6 to 16 years were included in the study. Regardless of the time period analyzed (24 h, daytime, or nighttime), ambulatory blood pressure and casual blood pressure were significantly higher among the obese children. The differences in systolic blood pressure observed between the groups were attributable to the presence of obesity as estimated by the ponderal index and by skinfold thickness. Similarly, systolic and diastolic loads, as an assessment of high blood pressure values over 24 h, were significantly higher in the obese children when compared to the loads for the nonobese children. Waist-to-hip circumference ratio was independently associated, (in multiple regression analysis) with systolic blood pressure, whether during 24 h, daytime, or nighttime periods, after controlling for age, sex, current height, ponderal index, and tricipital skinfold thickness. This study demonstrates that obesity is a determinant of ambulatory and casual blood pressure. Since obese children with a predominantly abdominal fat mass show higher blood pressure values, evaluation of body fat distribution in children may help to identify subjects more susceptible to developing hypertension later in life.

Adipose Tissue↗
PubMed1998

Mortality patterns among adult Hispanics: findings from the NHIS, 1986 to 1990.

OBJECTIVES: The purpose of this study was to assess the mortality pattern of the adult Hispanic population in the United States. METHODS: This was a cohort study using data from the National Health Interview Survey from 1986 through 1990. Deaths were ascertained by matching the National Death Index through 1991. RESULTS: This representative national sample included 297,640 non-Hispanic Whites, 53,552 Blacks, and 27,239 Hispanics, all aged 18 years or older at baseline. Different matching criteria resulted in modest differential estimates of the number of deaths by ethnic groups; these differences were quantitatively more important for Hispanics. Overall age-standardized mortality was lower among Hispanics. A prominent age by race interaction was apparent. The Hispanic: White mortality ratio was 1.33, 0.92, and 0.76 among men aged 18 through 44, 45 through 64, and 65 and older, respectively. Among women in the same age groups the Hispanic: White mortality ratio was 1.22, 0.75, and 0.70, respectively. CONCLUSIONS: Longitudinal cohorts provide an important source of health status information on Hispanics. These results suggest that overall mortality is lower among Hispanics than among non-Hispanic Whites, especially in the oldest age group. Among younger and middle-aged persons, the mortality of Hispanics is similar to or even higher than that of Whites.

Adult↗
PubMed1998

[The application of a Salmonella typhimurium biotyping method to the epidemiological surveys and surveillance].

In order to explore a new and effective means to the investigation and surveillance on Salmonella typhimurium infection, the authors applied a biotyping method of S. typhimurium invented by Duguid to the surveillance of nosocomial infection and tracing of infected case as well as cause of food-poisoning. Results showed that the major biotypes of strains isolated from children of acquired nosocomial infection with biotypes of strains from hospital environment and medical staff were quite similar. The biotype of cultures from the urine in a paralytic patient was the same as from the environment of the household and the wife's hands. The biotypes of strains identified from food-poison cases and leftovers was the same as isolated from ducks. It is believed that nosocomicial infection among children was caused by contamination of bacteria in hospital environment and carriers of medical staff. The urinary infection of a paralytic patient was due to environment pollution of the household, but not to nosocomial infection. The food-poisoning case was caused by the consumption of ducks infected with the bacteria.

Bacterial Typing Techniques↗
PubMed1998

Alterations of oncogenes, tumor suppressor genes and growth factors in hepatocellular carcinoma: with relation to tumor size and invasiveness.

OBJECTIVE: To make a better understanding of the molecular mechanisms involved in recurrence and metastasis of the hepatocellular carcinoma (HCC), some invasion related oncogenes, and growth factors have been investigated. METHODS: The studies were separately carried out, the results of which were summarized in this article with relation to tumor size and invasiveness of HCC. RESULTS: The aberration rates of p53 and CDKN2 in HCC were 45.9% and 36.4% respectively, which were higher in invasive HCC compared with non-invasive HCC. H-ras expression was positive in 29.3% of HCC, which was associated with recurrence and extrahepatic metastasis of HCC. Intralesional injection of H-ras antisense gene markedly inhibited the tumor growth and metastasis of HCC in nude mice. The positive rates of transforming growth factor (TGF)-alpha, epidermal growth factor receptor (EGFR) and c-erbB-2 were 45.7%, 47.1% and 92.3% respectively. The expression of EGFR was closely related to TGF-alpha, which was related to HCC recurrence. But no obvious difference of TGF-alpha or c-erbB-2 expression was found between HCC with and without recurrence, or with and without extrahepatic metastasis. Expression of nm23/tissue inhibitor of metalloproteinase (TIMP)-2 was positively associated with the prognosis of HCC patients (Log-rank, P < 0.001). The alterative rates of above-mentioned genes and growth factors in small HCC were slightly lower than that in large ones, but no significant difference was shown except the p53 mutation. CONCLUSIONS: The p53/CDKN2 mutation, over-expression of H-ras/EGFR, were associated with the invasiveness and recurrence of HCC. H-ras antisense gene might be of potential implication in the control of HCC recurrence and metastasis. Expression of nm23/TIMP-2 was closely related to the prognosis of HCC patients. Biological characteristics remained critical points to the prognosis even in small HCC.

Animals↗
PubMed1998

[Effect of crystalling temperatures on microstructure of dental glass-ceramic].

To know well the effect of crystalling temperature on the microstructure of dental glass-ceramic, the parameters of microstructure such as the type of crystal, crystal percentage, crystal size and crystal form were investigated by altering crystalling temperatures and using scanning electronic microscope, energy dispersive X-ray analysis and X-ray diffraction techniques. The results showed that the crystalline phase was identified to be tetrasilicic fluromica, and the promotion of crystalling temperature contributed to the increased crystal percentage, crystal size and the transformation of crystal form from 830 degrees C to 950 degrees C.

Crystallization↗