Yeung, Pollen
Permanent URI for this collectionhttps://hdl.handle.net/10222/15683
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Item Open Access Exercise hemodynamic and neurohormone responses as sensitive biomarkers for diltiazem in rats(2006-05) Yeung, Pollen K. F.; Feng, Joe D.; Fice, DebbraPurpose. To investigate the potential of exercise hemodyanamic and neurohormone variables as sensitive biomarkers for pre-clinical evaluation of diltiazem (DTZ). Methods. Sprague Dawley (SD) rats were randomly divided into 3 groups (n = 6-8 each), and each group received DTZ 10 mg/kg twice daily for 5 doses or saline followed by a treadmill exercise protocol for 7 min with speed set at 7 m/min at 3% grade. The 3rd group received saline but no exercise. Results. Exercise increased SBP from 108 +/- 2 to 131 +/- 3 mmHg, and HR from 437 +/- 6 to 503 +/- 6 bpm, and plasma epinephrine concentrations from 2.0 +/- 0.6 to 5.8 +/- 1.7 ng/mL in control rats (p 0.05). Conclusion. Exercise hemodynamic and neurohormone responses are sensitive biomarkers which could be used for safety and efficacy evaluation of DTZ and perhaps also other calcium antagonists in pre-clinical animal models.Item Open Access Scale disparity and spectral transfer in anisotropic numerical turbulence(1996-01) Zhou, Y.; Yeung, P. K.; Brasseur, J. G.No abstract available.Item Open Access Development and validation of a sensitive and specific HPLC assay of cladribine for pharmacokinetics studies in rats(2007) Yeung, P. K.; Ferguson, C.; Jarrar, A.; King, B.; Li, M. L.PURPOSE: To develop and validate a sensitive and specific HPLC assay for cladribine (CdA) in plasma for pharmacokinetic studies in rats. METHODS: CdA and the internal standard AZT were purchased from Sigma-Aldrich Chem. The HPLC system consisted of a Shimadzu LC-9A pump, a 3 im, 250 x 2.0 mm I.D. high speed C18 column (Jupitertrade mark), preceded by a 5 im 4 4 mm I.D. C18 guard column (Licrocarttrade mark), an Agilent Model 1050 UV-VIS detector and a 3395 Integrator. The mobile phase was made up of 0.01M KH2PO4 (pH 5): methanol: acetonitrile 90:5:5). The system was operated at ambient temperature with a flow rate of 0.3 mL/min, and UV wavelength at 265 nm, and an operating pressure of ca. 1.56 kpsi. Extraction of cladribine and AZT from plasma was achieved by solid phase extraction using 100 mg/mL C18 SPE columns Extra-septrade mark). The assay was validated for sensitivity, precision, specificity and application for pharmacokinetic study in rats. RESULTS: Under these conditions, the average retention times of CdA and AZT were 13.5 and 21 min, respectively, and recoveries were between 80 - 95%. Standard curve constructed from plasma standards was linear from 0.1 ug/mL to 1 ug/mL with regression coefficient (r2) 0.99 or greater. Sensitivity assessed by on column injection was < 1 ng. Using a 50-uL plasma sample size, the mean intra assay variations 0.1 ug/mL were 7%, and inter assay variations over a period of 3 months for 5 separate batches were less than 20%. The assay was used to study a single dose pharmacokinetic study of CdA in rats after a 2 mg/kg subcutaneous injection. CONCLUSION: The described HPLC assay has adequate sensitivity and specificity to study pharmacokinetics of CdA in rats, and could be adapted also to clinical pharmacokinetic studies.Item Open Access Incidence of Deep Vein Thrombosis in Hospitalized Chinese Medical Patients and the Impact of DVT Prophylaxis(2011) Cheng, G.; Chan, C.; Liu, Y. T.; Choy, Y. F.; Wong, M. M.; Yeung, P. K.; Ng, K. L.; Tsang, L. S.; Wong, R. S.Objective. To evaluate the incidence of deep vein thrombosis in hospitalized Chinese medical patients and the impact of DVT prophylaxis. Methods. All cases of confirmed proximal DVT from 1 January 2005 to 31 December 2008 were reviewed retrospectively to determine the presence of risk factors and whether DVT developed: during hospitalization in medical wards or in case of readmission with a diagnosis of DVT within 14 days of discharge from a recent admission to medical wards. The impact of prophylaxis will be estimated by comparing the annual incidence of proximal DVT among medical patients hospitalized from 2005 to 2007 with that of 2008 (DVT prophylaxis commonly used). Results. From 1 January 2005 to 31 December 2008, 3938 Doppler ultrasound studies were performed for suspected DVT. Proximal DVT was diagnosed in 687 patients. The calculated incidence of proximal DVT among medical patients hospitalized for at least two days was 1.8%, 2%, and 1.7% for the year 2005, 2006, and 2007, respectively. The incidence was 1.1% for 2008 (P < .001). Conclusion. Proximal DVT was substantial in Chinese medical patients, and DVT prophylaxis might reduce such risk.Item Open Access Universal intermittent properties of particle trajectories in highly turbulent flows(2008-06) Arneodo, A.; Benzi, R.; Berg, J.; Biferale, L.; Bodenschatz, E.; Busse, A.; Calzavarini, E.; Castaing, B.; Cencini, M.; Chevillard, L.; Fisher, R. T.; Grauer, R.; Homann, H.; Lamb, D.; Lanotte, A. S.; Leveque, E.; Luthi, B.; Mann, J.; Mordant, N.; Muller, W. C.; Ott, S.; Ouellette, N. T.; Pinton, J. F.; Pope, S. B.; Roux, S. G.; Toschi, F.; Xu, H.; Yeung, P. K.; International Collaboration for Turbulence ResearchWe present a collection of eight data sets from state-of-the-art experiments and numerical simulations on turbulent velocity statistics along particle trajectories obtained in different flows with Reynolds numbers in the range R{lambda}in[120:740]. Lagrangian structure functions from all data sets are found to collapse onto each other on a wide range of time lags, pointing towards the existence of a universal behavior, within present statistical convergence, and calling for a unified theoretical description. Parisi-Frisch multifractal theory, suitably extended to the dissipative scales and to the Lagrangian domain, is found to capture the intermittency of velocity statistics over the whole three decades of temporal scales investigated here.Item Open Access Development and validation of the Chinese version of the Reintegration to Normal Living Index for use with stroke patients(2011-02) Pang, M. Y.; Lau, R. W.; Yeung, P. K.; Liao, L. R.; Chung, R. C.OBJECTIVE: To develop and validate a Chinese version of the Reintegration to Normal Living Index. DESIGN: Descriptive case-series. SUBJECTS: Seventy-five individuals with chronic stroke and 55 age-matched healthy subjects. METHODS: The English version of the Reintegration to Normal Living Index was translated into Chinese using standardized procedures, and then administered to both the stroke and control groups. The same instrument was administered again to the stroke subjects 1-2 weeks later. RESULTS: The Chinese version of the Reintegration to Normal Living Index had good internal consistency (Cronbach's alpha = 0.92) and test-retest reliability (intraclass coefficient = 0.87). The minimal detectable difference of the Index score was 14.8 (out of 100). Convergent validity of the Index was demonstrated by its significant association with Frenchay Activities Index (r = 0.439, p < 0.001) and Personal Wellbeing Index (r = 0.250, p = 0.033) scores among stroke subjects. The Reintegration to Normal Living Index score was significantly lower in the stroke group than in controls (p < 0.001), thus demonstrating discriminant validity. Factor analysis confirmed the two-factor structure of the Index, namely, daily functioning and perception of self. CONCLUSION: The Reintegration to Normal Living Index is a reliable and valid tool for assessing satisfaction with community reintegration among Chinese people with chronic stroke.Item Open Access Embryonic lethality in mice lacking the nuclear factor of activated T cells 5 protein due to impaired cardiac development and function(2011) Mak, M. C.; Lam, K. M.; Chan, P. K.; Lau, Y. B.; Tang, W. H.; Yeung, P. K.; Ko, B. C.; Chung, S. M.; Chung, S. K.Nuclear factor of activated T cells 5 protein (NFAT5) is thought to be important for cellular adaptation to osmotic stress by regulating the transcription of genes responsible for the synthesis or transport of organic osmolytes. It is also thought to play a role in immune function, myogenesis and cancer invasion. To better understand the function of NFAT5, we developed NFAT5 gene knockout mice. Homozygous NFAT5 null (NFAT5(-/-)) mouse embryos failed to develop normally and died after 14.5 days of embryonic development (E14.5). The embryos showed peripheral edema, and abnormal heart development as indicated by thinner ventricular wall and reduced cell density at the compact and trabecular areas of myocardium. This is associated with reduced level of proliferating cell nuclear antigen and increased caspase-3 in these tissues. Cardiomyocytes from E14.5 NFAT5(-/-) embryos showed a significant reduction of beating rate and abnormal Ca(2+) signaling profile as a consequence of reduced sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) and ryanodine receptor (RyR) expressions. Expression of NFAT5 target genes, such as HSP 70 and SMIT were reduced in NFAT5(-/-) cardiomyocytes. Our findings demonstrated an essential role of NFAT5 in cardiac development and Ca(2+) signaling. Cardiac failure is most likely responsible for the peripheral edema and death of NFAT5(-/-) embryos at E14.5 days.