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Biomedical subjects

S Y Tang

Publications and source records attributed to S Y Tang.

At least 19 recordsLinked to original sources
PubMed2002

Parallelisation and application of a multi-layer atmospheric transport model to quantify dispersion and deposition of ammonia over the British Isles.

An atmospheric transport model, FRAME (Fine Resolution AMmonia Exchange), has been used to model the spatial pattern of ammonia concentrations and deposition over the British Isles for the first time. The model uses a multi-layer approach with diffusion through 33 layers to describe vertical concentration profiles in the atmosphere explicitly. Together with the necessary description of atmospheric reactions with sulphur and oxidised nitrogen, this imposes a major computational requirement, with the model having a run-time of 8.5 days on a mid-range workstation. Improvement in the model run-time was sought by developing a parallel implementation coded in a data-parallel approach using High Performance Fortran. Running the code on a Cray T3E with 128 processors provided a speedup by a factor of 69. The code's portability, its validation with measurements and new maps of its application to the British Isles, are presented. Good agreement is found with measured NH3 concentrations, while wet de-position is underestimated. In addition to model uncertainties, this may be due to an underestimation of the NH3 emissions input data.

Air Movements↗
PubMed2001

[Applying photocclusion method to study occlusion mechanics on wedge shaped teeth defect with computer assisting].

OBJECTIVE: Study the occlusal force of wedge shaped teeth defect and its relation with the clinical condition. METHODS: Use the method of clinical examination and plaster model measurement to decide the parameters of axial gradient degree of the teeth, abrasion index, missing teeth number and so on; Adopt the computer image processing technology and program to analyse the photocclusion sheet, take the date and image information of occlusion force, areas, and occlusal stress of wedge shaped teeth defect. RESULTS: The occlusion contact data and graph of wedge-shaped teeth defect had the features of trauma occlusion. 42.97% of them has the larger axial gradient degree, 96.09% of them has abration in different classes, 46.29% missing the front teeth and 57.03% missing the buccal teeth. Occlusal contact force increase took up 78.91% in the wedge shaped teeth defect. CONCLUSION: It can be concluded that the not uniformly distributed occlusal force produced from the larger axial gradient degree, the defect of dentition, and the abrasion of teeth, may be the important factors which cause wedge shaped teeth defect.

English Abstract↗
PubMed1999

Application of evaporative light scattering detection to the characterization of combinatorial and parallel synthesis libraries for pharmaceutical drug discovery.

The advent of combinatorial and parallel synthesis methodologies in drug discovery have necessitated the development of analytical techniques which permit high throughput quantitative analysis of mixtures of small organic molecules. High pressure liquid chromatography with evaporative light scattering detection has become the major tool for this task. In this article we briefly review the theory of evaporative light scattering detection and the design of commercial instruments, as well as discuss the operational constraints imposed by the exigency of analyzing en masse the product libraries generated by these new drug discovery methods. The application of evaporative light scattering detection to library analysis is illustrated using examples from our library synthesis program. Complemented by ultraviolet absorbance detection for purity assessment and mass spectrometry for product identification, evaporative light scattering detection is the only technique affording sufficient accuracy and sensitivity for high throughput library analysis.

Chemistry, Pharmaceutical↗
PubMed1999

Human agency and the process of healing: lessons learned from women living with a chronic illness--'re-writing the expert'.

In this paper we examine the notion of human agency in the context of women experiencing a chronic illness. Based on two qualitative studies conducted with Canadian women of Chinese- and Anglo-descent living with diabetes, we unmask the complex power relations inherent in patient-practitioner interactions, and problematize the privileging of healthcare providers as knowers and experts on the patient's body. Specifically, we analyse the meanings that women ascribe to their illness experience. We discuss how women experience the loss of agency in healthcare encounters, how they resist patienthood by reclaiming agency, and how healthcare providers foster agency in their interactions with women. Rather than suggesting that biomedical experts should be 'written out', we propose to rewrite healthcare providers as 'reflexive practitioners' through the construction of transformative knowledge. We argue that praxis-oriented practice, which is based on transformative knowledge, will provide the space for women and healthcare providers to enter into a new dialogue and a relation in which women can sustain a sense of self, and begin the journey of healing.

Adaptation, Psychological↗
PubMed1999

Interpreter services in healthcare. Policy recommendations for healthcare agencies.

The author discusses the need for interpreter services for delivering effective healthcare in a country such as Canada, which is made up of people from diverse ethnocultural and linguistic backgrounds. As well as examining the complexity of allocation decisions and policy implementation, the author proposes policy recommendations for healthcare agencies to set up an integrated system of interpreter services based on cost-effective and equitable use of finite resources and partnership between agencies.

Canada↗
PubMed1998

Synthesis and diversity analysis of lead discovery piperazine-2-carboxamide libraries.

A Lead Discovery Library of piperazine-2-carboxamide derivatives was produced for general screening. This paper discloses two novel solid phase synthetic routes used to produce 15,000 single compounds via the Irori directed sorting technique. Computational methods such as reagent clustering and library profiling were used to maximize reagent diversity and optimize pharmacokinetic parameters. The results of a four center pharmacophore analysis revealed the added diversity gained by using two independent synthetic routes.

Combinatorial Chemistry Techniques↗
PubMed1997

Degradation pathways of salmon calcitonin in aqueous solution.

Salmon calcitonin (sCT), a 32-amino-acid peptide, is the active component in many pharmaceuticals used for the management of bone diseases. The degradation pathways of sCT were determined, and the structures of the major degradation products were identified. Aqueous solutions of sCT at pH values of 3, 4, 5, and 6 were degraded, and the major degradation products were detected using reversed phase and size-exclusion high-performance liquid chromatography (HPLC). The degradation rate and pathways of sCT are strongly dependent on pH in the pH range between 3 and 6. The major degradation products were isolated by semipreparative HPLC and identified using a variety of spectroscopic and bioanalytical techniques. The results show that sCT can undergo hydrolyses resulting in cleavage of the 1-2 amide bond and deamidation of the Gln14 and Gln20 residues, sulfide exchange that leads to an unusual trisulfide derivative, and dimerization to reducible and nonreducible dimers. The mechanisms for the pathways can be rationalized from known degradation pathways of peptide and proteins.

Amino Acid Sequence↗
PubMed1997

[Clinical application of inspiring psychological nursing in vaginal delivery].

A new nursing method named Inspiring Psychological Nursing was initiated and applied to 176 primigravida undergoing vaginal delivery from Jan. to Jun. 1994. 202 primigravida who received general medical care during vaginal delivery from Jan. to Jun. 1993 was served as control group. No significant differences were found between the two groups regarding to age, gestational weeks, times of pregnancy, fetal position and newborn's weight. However significant differences were found regarding the duration of the second stage of labor and incidence of newborn asphyxia. Primigravida in the control group usually delivered after 60 min. and carried a higher incidence of newborn asphyxia, being 6.7%. It's concluded that Inspiring Psychological Nursing could significantly improve pregnancy outcome.

Asphyxia Neonatorum↗
PubMed1995

Enzyme inhibition during the conversion of squalene to cholesterol.

Two separate enzymatic assays were developed in order to test the selectivity of inhibitors in cholesterol biosynthesis. One assay detects inhibition of delta 5.7-sterol delta 7-reductase, the enzyme involved in the conversion of 7-dehydrocholesterol to cholesterol. Delta 5.7-Sterol delta 7-reductase was inhibited by both RPR 101821, a protonated cyclohexylamine, and BM 15.766, a piperazine derivative, with IC50 values of 1 microM. The second assay detects accumulation of any of five intermediates (squalene oxide, squalene dioxide, lanosterol, desmosterol, and 7-dehydrocholesterol) upon inhibition of enzymes catalyzing reactions in the conversion of squalene to cholesterol. In this assay, inhibition data were most accurate when control assays exhibited a conversion of squalene to cholesterol in the order of 50%. The time required to attain 50% conversion of squalene to cholesterol was 6 h. Given a high inhibitor to substrate concentration ratio and the possible values of Ki, kon, and koff for the reaction between enzymes and inhibitor to form enzyme-inhibitor complexes, it was predicted that in the presence of inhibitors, intermediate accumulation could still be observed after 6 h incubation. The experimental results were in agreement with this prediction.

Animals↗
PubMed1994

Primary structure control of recombinant proteins using high-performance liquid chromatography, mass spectrometry and microsequencing.

The conformity of two recombinant proteins (a von Willbrand factor fragment and human serum albumin, consisting of respectively 289 and 585 amino acids) has been examined by HPLC combined with mass spectrometry and microsequencing, on both intact material and fragment peptides obtained by proteolytic cleavage. These studies confirmed that the primary structure of the recombinant proteins corresponds to that predicted from their gene, particularly the integrity of their N and C termini, and, in the case of albumin, the agreement between the observed disulfide bond pattern and the published model. Furthermore, the structure of an albumin-related compound could be elucidated. Application of LC-MS for batch-to-batch quality control is also under discussion.

Amino Acid Sequence↗
PubMed1991

Thiamin requirement of juvenile shrimp (Penaeus monodon).

In a 9-wk feeding trial, juvenile shrimp (Penaeus monodon) were fed semipurified diets containing seven levels (0, 20, 40, 60, 80, 160 and 320 mg/kg diet) of supplemental thiamin hydrochloride. The dietary thiamin level required for optimal growth in P. monodon was found to be approximately 14 mg/kg diet based on hemolymph (blood) thiamin analysis. The minimum dietary thiamin level that produced substantial shrimp growth was approximately 13 mg/kg diet. Shrimp fed unsupplemented diets (thiamin content of 0.12 mg/kg diet) did not demonstrate specific deficiency signs, except those universal signs such as retarded growth, poor food conversion and low survival rates.

Animals↗
PubMed1991

Analysis of duodenal bile acids by high performance liquid chromatography in infants with cholestasis.

Non-sulfated bile acid levels including cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), lithocholic acid (LCA), ursodeoxycholic acid (UDCA), five taurine conjugates, and five glycine conjugates in duodenal juice were measured in 50 Chinese infants with cholestasis to test their diagnostic value. All 17 with biliary atresia (BA) cases, 11 out of 26 neonatal hepatitis (NH) cases and one case with paucity of the interlobular bile duct were without detectable bile acids. In those NH patients with detectable bile acids, the major components were conjugated forms of CA and CDCA, which was similar to all 6 cases of the comparison group with other diseases. The minor bile acid components identified in them were glycine conjugated UDCA, free CDCA, free CA, and free and conjugated DCA. Only one patient with NH had taurine conjugated LCA. The mean total duodenal bile acid level in 15 patients with NH was significantly lower than that in the 6 patients of the comparison group. Most patients with NH had a CDCA/CA ratio of less than one, indicating that cholic acid is the predominant form in their bile. Glycine conjugated bile acids were the predominant bile acids present in 11 out of 15 patients with NH and 4 out of 6 of the comparison group patients. The results suggest that the detection of duodenal bile acids by a sensitive HPLC method is of limited value in making a differential diagnosis between BA and NH.(ABSTRACT TRUNCATED AT 250 WORDS)

Bile Acids and Salts↗
PubMed1987

Phthalate esters and semen quality parameters.

Analysis of reports in the world's literature suggests that average sperm densities for groups of unselected males were relatively constant at about 108 million cells per ml prior to 1950. Subsequent to that time mean sperm densities appear to have declined. Regression analysis indicates the existence of significant negative correlations between mean sperm densities and production of synthetic organic chemicals among other parameters. Phthalate esters are one class of large volume organic chemicals that are known to disturb testicular function in laboratory animals. These compounds are also the most abundant man-made chemicals in the environment. Plots of the concentration of dibutylphthalate in the cellular fraction of ejaculates against either the sperm density or the total number of sperm for the same ejaculates gave two clusters of points. These clusters suggest the existence of two or more populations vis à vis phthalate metabolism; both of which show a negative correlation between phthalate concentration and sperm production.

Dibutyl Phthalate↗
PubMed1985

Polychlorinated biphenyl poisoning: correlation of sensory and motor nerve conduction, neurologic symptoms, and blood levels of polychlorinated biphenyls, quaterphenyls, and dibenzofurans.

In 1979 in Taiwan, more than 2000 people were poisoned with rice cooking oil contaminated with polychlorinated biphenyls (PCB). One hundred ten patients were studied within one year of the exposure. The blood PCB levels were 39.3 +/- 16.6 ppb. The blood levels of the PCB derivatives, polychlorinated quaterphenyls (PCQ) and polychlorinated dibenzofurans (PCDF), were 8.6 +/- 4.8 and 0.076 +/- 0.038 ppb, respectively. Both the sensory and motor nerve conduction velocities (NCV) of the patients were significantly lower than the control. Abnormal slowing of sensory NCV was found in 43.6% and abnormal slowing of motor NCV was seen in 21.8%. Patients who had higher PCQ blood levels had significantly slower median nerve sensory NCV than those with lower PCQ levels. Patients with higher PCB blood levels had significantly slower peroneal nerve motor NCV than those with lower PCB levels.

Adolescent↗