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Biomedical subjects

Y M Liu

Publications and source records attributed to Y M Liu.

At least 19 recordsLinked to original sources
PubMed2006

Field study of a thermal environment and adaptive model in Shanghai.

A long-term field investigation was carried out in naturally ventilated residential buildings in Shanghai from April 2003 to November 2004. A total of 1,768 returned questionnaires were collected in the study. This study deals with the thermal sensation of occupants in naturally ventilated buildings and the change in thermal neutral temperature with season. The range of accepted temperature in naturally ventilated buildings is between 14.7 degrees C T(op) and 29.8 degrees C T(op). The results also report the findings of the adaptive comfort model in Shanghai that determines the adaptive relationship of neutral temperature with outdoor air temperature. A long-term field study was carried out in residential buildings in Shanghai to find the relationship between thermal sensation, indoor neutral temperature and outdoor temperature. This paper presents findings of thermal comfort and discusses the more sustainable standard for the indoor climate of residential buildings in Shanghai.

Air Movements↗
PubMed2005

17beta-estradiol suppresses proliferation of fibroblasts derived from cardinal ligaments in patients with or without pelvic organ prolapse.

BACKGROUND: Estrogen replacement therapy (ERT) has been used in the treatment of pelvic organ prolapse (POP) but clinical results are inconclusive. The purpose of this study was to investigate the effect of 17beta-estradiol (E(2)) on the proliferation of fibroblasts derived from cardinal ligaments in women with or without POP. METHODS: Fibroblasts were derived from seven patients with POP and seven age-matched controls. The growth rate of POP fibroblasts was compared with that of control by 3-(4,5,-dimethyl thiazolyl-2)-2,5-diphenyl tetrazolium bromide (MTT) assay. Four cell strains from each patient and control group were treated with different concentrations of E2 (10(-4), 10(-8), 10(-9) and 10(-10) mol/l). The effect of E2 on cell proliferation was then measured by MTT assay. RESULTS: The overall growth rate of POP fibroblasts was significantly slower than that of controls under normal culture conditions. Addition of E2 suppressed cell proliferation of all the fibroblasts, especially in POP fibroblasts. POP fibroblasts showed a significantly lower proliferative rate than that of controls at all E2 concentrations, with the most prominent inhibitory effect at physiological concentration (10.83 34.41% versus 81.56 48.10% at 10(-8) mol/l). CONCLUSIONS: Our results suggest that decreased fibroblast turnover may contribute to the development of POP; and ERT may not be an effective POP treatment.

Cell Proliferation↗
PubMed2004

Epidemiology of hepatitis A and hepatitis E infection and their determinants in adult Chinese community in Hong Kong.

Current epidemiology of hepatitis A virus (HAV) and hepatitis E virus (HEV) in Hong Kong was evaluated in 936 adult Chinese subjects recruited through a telephone interview in 2001. Some 15% of the subjects had IgG antibodies to both HAV and HEV while 665 (71.0%) and 176 (18.8%) had anti-HAV and anti-HEV, respectively. Age was the most significant independent factor. Six hundred thirty-eight (79.8%) and 165 (20.7%) subjects aged > or =30 had anti-HAV and anti-HEV, respectively, as compared with 27 (19.7%) and 11 (8.0%) in people aged <30. The corresponding adjusted Odds ratio (OR) was 14.94 (95% CI: 9.13-24.44; P<0.001) for anti-HAV positivity and 2.99 (95% CI: 1.58-5.67; P=0.001) for anti-HEV positivity. Subjects born outside Hong Kong were more likely to have anti-HAV (adjusted OR: 3.41; 95% CI: 2.21-5.26; P<0.001) but not anti-HEV. Non-labour work people were less likely to have anti-HAV-adjusted OR, 0.40 (95% CI: 0.26-0.62; P<0.001). Age-specific HAV prevalence right shifted in the last 20 years. Anti-HAV positivity was less frequent, across all age groups, in subjects >21-years-old in the present study than another study done in 1987-89 (P<0.001). HAV prevalence only increased slightly in every 10-year age groups of people aged 21-50 when compared with their corresponding 10-year-younger age groups (P=0.11), suggesting an ageing cohort effect with no major infections in the last decade. For HEV, both the overall and age-specific prevalence decreased over the last decade (P<0.001). The increasing proportion of susceptible population to enterically transmitted viral hepatitis has implications to future prevention and control programmes, including vaccination strategies.

Adolescent↗
PubMed2003

Near-threshold production of the multistrange Xi- hyperon.

The yield for the multistrange Xi(-) hyperon has been measured in 6A GeV Au+Au collisions via reconstruction of its decay products pi(-) and Lambda, the latter also being reconstructed from its daughter tracks of pi(-) and p. The measurement is rather close to the threshold for Xi(-) production and therefore provides an important test of model predictions. The measured yield for Xi(-) and Lambda are compared for several centralities. In central collisions the Xi(-) yield is found to be in excellent agreement with statistical and transport model predictions, suggesting that multistrange hadron production approaches chemical equilibrium in high baryon density nuclear matter.

Journal Article↗
PubMed2003

Comparison of source images for protons, pi-'s, and lambda's in 6A GeV Au+Au collisions.

Source images are extracted from two-particle correlations constructed from strange and nonstrange hadrons produced in 6A GeV Au+Au collisions. Very different source images result from pp vs p Lambda vs pi(-)pi(-) correlations. Scaling by transverse mass can describe the apparent source size ratio for p/pi(-) but not for Lambda/pi(-) or Lambda/p. These observations suggest important differences in the space-time emission histories for protons, pions, and neutral strange baryons produced in the same events.

Journal Article↗
PubMed2002

Longitudinal flow of protons from (2-8)A GeV central Au+Au collisions.

Rapidity distributions of protons from central 197Au+197Au collisions measured by the E895 Collaboration in the energy range from (2-8)A GeV at the Brookhaven AGS are presented. Longitudinal flow parameters derived using a thermal model including collective longitudinal expansion are extracted from these distributions. The results show an approximately linear increase in the longitudinal flow velocity, (L), as a function of the logarithm of beam energy.

Journal Article↗
PubMed2001

Ultrasensitive chemiluminescence detection of sub-fM level Co(II) in capillary electrophoresis.

A method of on-line ultrasensitive chemiluminescence detection with capillary electrophoresis for Co(II) is reported. Using our newly developed capillary electrophoresis with chemiluminescence detection system and novel mixing mode of the reagents, the effects of field-amplified injection on detection limits of metal ions were studied in detail. The sub-fM level (1.3 x 10(-16) M, 1.6 x 10(-24) mol, 1 molecule) detection of cobalt ions in ultradilute solution was performed. The catalytic behavior of the chemiluminescence reaction of luminol and hydrogen peroxide by cobalt ions and the reaction conditions, such as the concentration of luminol, H2O2, and pH of chemiluminescence reagent were investigated. The separation of fM level Co(II) and trace amounts of Ni(II) was performed successfully.

Cobalt↗
PubMed2001

Determination of free aspartic acid enantiomers in rat brain by capillary electrophoresis with laser-induced fluorescence detection.

Quantification of aspartic acid enantiomers in rat brain by using a chiral capillary electrophoresis procedure is described. Amino acids were pre-column derivatized with naphthalene-2,3-dialdehyde. Enantiomeric separation was achieved by micellar electrokinetic chromatography in the presence of methanol and beta-cyclodextrin as chiral selector. The chiral separation was coupled with laser-induced fluorescence detection. Contents of D- and L-aspartic acids in rats at different stages of growth (from 1 day before birth to 90 days after birth) were determined. D-Aspartic acid was detected in all the brain tissue samples tested, but at different levels. In the cerebrum of rats 1 day before birth, D-aspartic acid was found to be at the highest concentration of 81 nmol/g wet tissue. The level of D-aspartic acid in rat brain falls rapidly after birth, while the L-aspartic acid level increases with age.

Aging↗
PubMed2001

Model-independent source imaging using two-pion correlations in (2 to 8)a GeV Au+Au collisions.

We report a particle source imaging analysis based on two-pion correlations in high multiplicity Au+Au collisions at beam energies between 2A and 8A GeV. We apply the imaging technique introduced by Brown and Danielewicz, which allows a model-independent extraction of source functions with useful accuracy out to relative pion separations of about 20 fm. The extracted source functions have Gaussian shapes. Values of source functions at zero separation are almost constant across the energy range under study. Imaging results are found to be consistent with conventional source parameters obtained from a multidimensional Hanburg-Brown-Twiss analysis.

Journal Article↗
PubMed2001

Directed flow of lambda hyperons in (2-6 )A GeV Au+Au collisions.

Directed flow measurements for Lambda hyperons are presented and compared to those for protons produced in the same Au+Au collisions (2A, 4A, and 6A GeV; b<5-6 fm). The measurements indicate that Lambda hyperons flow consistently in the same direction but with smaller magnitudes. A strong positive flow [for Lambdas] has been predicted in calculations which include the influence of the Lambda-nucleon potential. The experimental flow ratio Lambda/p is in qualitative agreement with expectations (approximately 2/3) from the quark counting rule at 2A GeV but is found to decrease with increasing beam energy.

Journal Article↗
PubMed2001

Electrophoretic separation of tryptophan enantiomers in biological samples.

A method for the determination of D- and L-tryptophan (Trp) in biological samples is described. The amino acid enantiomers were precolumn-derivatized with a fluorescence tagging reagent, naphthalene-2,3-dialdehyde (NDA). In the presence of hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) as the chiral selector, NDA-tagged Trp enantiomers were well resolved by micellar electrokinetic chromatography (MEKC). Using laser induced fluorescence (LIF) detection, a detection limit of 3.3 x 10(-8) M Trp was obtained. The method was applied to the determination of Trp enantiomers in biological samples including human urine and cerebrospinal fluid (CSF), rat brain tissue, and Aplysia ganglia. No interference from other amino acids or the endogenous compounds in the sample matrices was observed. D-Trp was found at the sub-microM level in human urine samples collected from several healthy subjects. Further, the determination of DL-Trp residues in small quantities (10 microg) of peptides after acid hydrolysis is demonstrated.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2001

Quantification of D/L-aspartic acids in Aplysia californica central nervous system by beta-cyclodextrin modified micellar electrokinetic chromatography.

In presence of an organic modifier (e.g. methanol), separation of amino acid enantiomers tagged with naphthalene-2,3-dicarboxaldehyde by beta-cyclodextrin modified micellar electrokinetic chromatography was dramatically improved. Coupled with laser-induced fluorescence detection, the method was well suited for analysis of D/L-amino acid enantiomers present in mass/volume-limited biological samples such as cell clusters. The five major ganglia dissected from the central nervous system of Aplysia californica, a widely used neuronal model, were analyzed to determine D- and L-aspartic acid enantiomers both free and bound in proteins/tissue matrix. The analyses revealed high levels of free D-aspartic acid ranging from 0.13 to 0.82 micromol/g wet tissue (or 6.0-21.2% of the total free aspartic acid) in all of the five ganglia. However, no D-aspartic acid was detected bound in protein/tissue matrix. The content of free D-aspartic acid in the liver tissue was also found below the detection limit of the method, which was 1 x 10(-8) M.

Animals↗
PubMed2001

Determination of enterostatin in human cerebrospinal fluid by capillary electrophoresis with laser induced fluorescence detection.

A capillary electrophoresis (CE) method with laser induced fluorescence (LIF) detection is described for quantification of enterostatin (Val-Pro-Asp-Pro-Arg), a pentapeptide involved in appetite regulation and insulin secretion. Enterostatin and two other pentapeptides belonging to the enterostatin family (i.e. Ala-Pro-Gly-Pro-Arg and Val-Pro-Gly-Pro-Arg) were well separated from each other. The peptides were fluorescently tagged with naphthalene-2,3- dicarboxaldehyde (NDA) and separated by micellar electrokinetic chromatography (MEKC) in the presence of methanol as an organic modifier. Coupled with LIF detection, the method had a detection limit of 4.8 x 10(-6) M for enterostatin. The relative standard deviation was to be 4.0% from five determinations of enterostatin at 37.2 microM in a human cerebrospinal fluid (CSF) sample. Twenty-three human CSF samples were analyzed. The level of enterostatin ranged from 24 microM to 51 microM with a mean (+/- SEM) value of 41.7 +/- 2.0 microM.

Amino Acid Sequence↗
PubMed2001

Circular F-actin bundles and a G-actin gradient in pollen and pollen tubes of Lilium davidii.

The distribution of and relationship between F-actin and G-actin were investigated in pollen grains and pollen tubes of Lilium davidii Duch. using a confocal laser scanning microscope after fluorescence and immunofluorescence labeling. Circular F-actin bundles were found to be the main form of microfilament cytoskeleton in pollen grains and pollen tubes. Consistent with cytoplasmic streaming in pollen tubes, there were no obvious F-actin bundles in the 10- to 20-microm tip region of long pollen tubes, only a few short F-actin fragments. Labeling with fluorescein isothiocyanate (FITC)-DNase I at first established the presence of a tip-focused gradient of intracellular G-actin concentration at the extreme apex of the tube, the concentration of G-actin being about twice as high in the 10- to 20-microm region of the tip as in other regions of the pollen tube. We also found that the distribution of G-actin was related negatively to that of the F-actin in pollen tubes of L. davidii. Caffeine treatment caused the G-actin tip-focused gradient to disappear, and F-actin to extend into the pollen tube tip. Based on these results, we speculate that the circular F-actin bundles may be the track for bidirectional cytoplasmic streaming in pollen tubes, and that in the pollen tube tip most of the F-actin is depolymerized into G-actin, leading to the absence of F-actin bundles in this region.

Actins↗
PubMed2001

[Effect of ATXII on opening modes of myocyte sodium channel, action potential and QT intervals of ECG].

Single sodium channel currents were recorded by patch clamp technique in isolated guinea-pig ventricular myocytes, and action potentials of papillary muscle and ECG were conventionally measured. Sea anemone toxin (ATXII), a high affinity toxin to sodium channel, was used to change the sodium channel dynamics. Changes in the duration of action potentials and the QT interval of ECG depending on the channel modes were studied in order to provide hints to an understanding of pathogenesis of the long QT syndrome (a genetic disease). With the binding of ATXII to the sodium channel, the occurrence frequency and the open time constant of the "long opening" mode of single Na channels increased significantly, whereas the action potential durations, APD50 and APD90, were prolonged by 23% and 27% respectively. Following application of ATXII, on the other hand, the QT interval and the QTc, a rectified QT interval, increased by 18.6% and 18.9% respectively. The results suggest that the dynamics or modes of Na channel play an important role in determining the action potential duration and the QT interval of ECG. The dynamical changes in Na channels induced by genetic mutation may be partially responsible for the long QT syndrome.

Action Potentials↗
PubMed2001

Effects of endothelin receptor A antagonist FR139317 on rats with congestive heart failure.

AIM: To study the effects of a selective endothelin receptor A (ETA) antagonist FR139317 on rats with congestive heart failure. METHODS: A congestive heart failure model was established via left coronary artery ligation in adult male Wistar rats. The rats with congestive heart failure were treated with FR139317 at two doses (1 and 5 mg . kg-1 . d-1 respectively for 6 weeks) or with vehicle. Hemodynamics, plasma level of endothelin-1 (ET-1), and mortality rate of rats were measured. RESULTS: Both groups treated with FR139317 (high and low dose) have lower mortality rate (25.0 % and 28.6 % vs 50.0 %) and lower plasma level of ET-1 than that of vehicle [(3.6 +/- 1.2) ng/L and (4.9 +/- 1.5) ng/L vs (5.8 +/- 1.3) ng/L]. Comparing to vehicle group, left ventricular end-diastolic pressures of the FR139317-treated groups were improved significantly [(12 +/- 6) mmHg and (14 +/- 7) mmHg vs (22 +/- 9) mmHg]. FR139317 at a higher dose reduced the mean arterial pressure of the rats with congestive heart failure and decreased the plasma concentration of endothelin to a closer level of rats with normal heart function than lower dose. CONCLUSION: Selective ETA antagonist FR139317 improved the hemodynamics and reduced the plasma ET-1 level and the mortality of rats with congestive heart failure

Animals↗