PubMed Health⌕ Search

Biomedical subjects

Y S Tang

Publications and source records attributed to Y S Tang.

At least 19 recordsLinked to original sources
PubMed2004

Ammonia emission and deposition in Scotland and its potential environmental impacts.

The main source of atmospheric ammonia (NH3) in Scotland is livestock agriculture, which accounts for 85% of emissions. The local magnitude of emissions therefore depends on livestock density, type, and management, with major differences occurring in various parts of Scotland. Local differences in agricultural activities therefore result in a wide range of NH3 emissions, ranging from less than 0.2 kg N ha(-1) year(-1) in remote areas of the Scottish Highlands to over 100 kg N ha(-1) year-1 in areas with intensive poultry farming. Scotland can be divided loosely into upland and lowland areas, with NH3 emission being less than and more than 5 kg N ha(-1) year(-1), respectively. Many semi-natural ecosystems in Scotland are vulnerable to nitrogen deposition, including bogs, moorlands, and the woodland ground flora. Because NH3 emissions occur in the rural environment, the local deposition to sensitive ecosystems may be large, making it essential to assess the spatial distribution of NH3 emissions and deposition. A spatial model is applied here to map NH3 emissions and these estimates are applied in atmospheric dispersion and deposition models to estimate atmospheric concentrations of NH3 and NH4+, dry deposition of NH3, and wet deposition of NHx. Although there is a high level of local variability, modelled NH3 concentrations show good agreement with the National Ammonia Monitoring Network, while wet deposition is largest at high altitude sites in the south and west of Scotland. Comparison of the modelled NHx deposition fields with estimated thresholds for environmental effects ("critical loads") shows that thresholds are exceeded across most of lowland Scotland and the Southern Uplands. Only in the cleanest parts of the north and west is nitrogen deposition not a cause for concern. Given that the most intense effects occur within a few kilometres of sources, it is suggested that local spatial abatement policies would be a useful complement to traditional policies that mitigate environmental effects based on emission reduction technologies.

Ammonia↗
PubMed2004

Concentrations of ammonia and nitrogen dioxide at roadside verges, and their contribution to nitrogen deposition.

Bimonthly integrated measurements of NO2 and NH3 have been made over one year at distances up to 10 m away from the edges of roads across Scotland, using a stratified sampling scheme in terms of road traffic density and background N deposition. The rate of decrease in gas concentrations away from the edge of the roads was rapid, with concentrations falling by 90% within the first 10 m for NH3 and the first 15 m for NO2. The longer transport distance for NO2 reflects the production of secondary NO2 from reaction of emitted NO and O3. Concentrations above the background, estimated at the edge of the traffic lane, were linearly proportional to traffic density for NH3 (microg NH3 m(-3) = 1 x 10(-4) x numbers of cars per day), reflecting emissions from three-way catalysts. For NO2, where emissions depend strongly on vehicle type and fuel, traffic density was calculated in terms of 'car equivalents'; NO2 concentrations at the edge of the traffic lane were proportional to the number of car equivalents (microg NO2 m(-3) = 1 x 10(-4) x numbers of car equivalents per day). Although absolute concentrations (microg m(-3)) of NH3 were five times smaller than for NO2, the greater deposition velocity for NH3 to vegetation means that approximately equivalent amounts of dry N deposition to road side vegetation from vehicle emissions comes from NH3 and NO2. Depending on traffic density, the additional N deposition attributable to vehicle exhaust gases is between 1 and 15 kg N ha(-1) y(-1) at the edge of the vehicle lane, falling to 0.2-10 kg N ha(-1) y(-1) at 10 m from the edge of the road.

Air Pollutants↗
PubMed2003

Identification of novel metabolites of pioglitazone in rat and dog.

1. Four new metabolites of pioglitazone were identified by liquid chromatography-mass spectrometry (LC-MS/MS) as being formed by hydroxylation (M-VII and M-VIII), opening of the thiazolidinedione ring (M-X) and by desaturation of the terminal ethyl side chain or tether ethoxy moiety (M-IX), respectively. The structure of one of the hydroxylated metabolites (M-VII) was confirmed by chemical modification using the Jones reaction. 2. Oxidative cleavage of the thiazolidinedione ring is a novel pathway not previously reported for pioglitazone. 3. The hydroxylated M-VII was detected in incubations with rat, dog and human liver and kidney microsomes, and in plasma from rats and dogs dosed orally with [(3)H]pioglitazone. 4. The carboxylic acid derivative of M-VII (M-V) and its taurine conjugate were the major radioactive components in dog bile.

Animals↗
PubMed2001

Potential for ammonia recapture by farm woodlands: design and application of a new experimental facility.

There has been increasing pressure on farmers in Europe to reduce the emissions of ammonia from their land. Due to the current financial climate in which farmers have to operate, it is important to identify ammonia control measures that can be adopted with minimum cost. The planting of trees around farmland and buildings has been identified as a potentially effective and low-cost measure to enhance ammonia recapture at a farm level and reduce long-range atmospheric transport. This work assesses experimentally what fraction of ammonia farm woodlands could potentially remove from the atmosphere. We constructed an experimental facility in southern Scotland to simulate a woodland shelterbelt planted in proximity to a small poultry unit. By measuring horizontal and vertical ammonia concentration profiles within the woodland, and comparing this to the concentration of an inert tracer (SF6) we estimate the depletion of ammonia due to dry deposition to the woodland canopy. Together with measurements of mean ammonia concentrations and throughfall fluxes of nitrogen, this information is used to provide a first estimate of the fraction of emitted ammonia that is recaptured by the woodland canopy. Analysis of these data give a lower limit of recapture of emitted ammonia, at the experimental facility, of 3%. By careful design of shelterbelt woodlands this figure could be significantly higher.

Agriculture↗
PubMed2001

A spatial analysis of atmospheric ammonia and ammonium in the U.K.

As measures are implemented internationally to reduce SO2 and NOx emissions, attention is falling on the contribution of NH3 emissions to acidification, nitrogen eutrophication, and aerosol formation. In the U.K., a monitoring network has been established to measure the spatial distribution and long-term trends in atmospheric gaseous NH3 and aerosol NH4+. At the same time, an atmospheric chemistry and transport model, FRAME, has been developed with a focus on reduced nitrogen (NHx). The monitoring data are important to evaluate the model, while the model is essential for a more detailed spatial assessment. The national network is established with over 80 sampling locations. Measurements of NH3 and NH4+ (at up to 50 sites) have been made using a new low-cost denuder-filterpack system. Additionally, improved passive sampling methods for NH3 have been applied to explore local variability. The measurements confirm the high spatial variability of NH3 (annual means 0.06 to 11 microg NH3 m(-3)), consistent with its nature as a primary pollutant emitted from ground-level sources, while NH4+, being a slowly formed secondary product, shows much less spatial variability (0.14 to 2.4 mg NH4+ m(-3)). These features are reproduced in the FRAME model, which provides estimates at a 5-km level. Analysis of the underlying NH3 emission inventory shows that sheep emissions may have been underestimated and nonagricultural sources overestimated relative to emissions from cattle. The combination of model and measurements is applied to estimate spatial patterns of dry deposition to different vegetation types. The combined approach provides the basis to assess NHx responses across the U.K. to international emission controls.

Air Pollutants↗
PubMed2001

Development and types of passive samplers for monitoring atmospheric NO2 and NH3 concentrations.

Numerous passive samplers based on the "Palmes-tube" have been developed for ambient air monitoring. In each case, the diffusion path length and/or cross-sectional area are modified to achieve the desired sampling rate. "Tube-type" samplers are low sensitivity samplers suitable for long-term monitoring, whereas the "badge-type" samplers have faster sampling rates suited to short-term monitoring. In the U.K., diffusion tubes are widely used for monitoring nitrogen dioxide (NO2) and ammonia (NH3). The open-ended diffusion tubes are prone to positive bias caused by incursion of wind eddies, leading to a shortening of the diffusion path. By using a porous membrane at the inlet, wind incursion is prevented, but an additional diffusion resistance is imposed and it is necessary to calibrate the tubes against a reference method to obtain an effective sampling rate. For NO2 sampling, positive bias also arises from the reaction of NO with O3 within the sampler. The interference from the chemical reaction is severe close to NO sources, with errors up to 30% for curbside locations when using the "tube-type" sampler. In rural areas, where NO concentrations are small relative to NO2, these errors are small. In some implementations, there is also a negative bias over long sampling periods caused by the degradation of trapped NO2. The low sampling rates of diffusion tubes make them too uncertain for use at background NH3 concentrations (<1 microg NH3 m(-3)) where they significantly overestimate concentrations. Badge-type samplers such as the "Willems badge" samplers permit accurate sampling at low ambient NH3 concentrations, but suffer from saturation at high concentrations and sensitivity to wind speed. A passive sampler optimised for monthly measurements of NH3 is reported here, together with its application in the U.K. National Ammonia Monitoring Network.

Air Movements↗
PubMed2001

Isolation and characterization of a folate receptor mRNA-binding trans-factor from human placenta. Evidence favoring identity with heterogeneous nuclear ribonucleoprotein E1.

The interaction of an 18-base cis-element in the 5'-untranslated region of human folate receptor (FR)-alpha mRNA with a cytosolic trans-factor protein is critical for the translation of FR (Sun, X.-L., and Antony, A. C. (1996) J. Biol. Chem. 271, 25539-25547). This trans-factor was isolated to apparent homogeneity as a 43- and 38-kDa doublet from human placenta using poly(U)-Sepharose, followed by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electro-elution as major purification steps. Amino acid microsequencing of two cyanogen bromide-generated peptide fragments of the 43-kDa trans-factor revealed complete identity with 43-kDa heterogeneous nuclear ribonucleoprotein E1 (hnRNP E1). Purified specific rabbit anti-hnRNP E1 peptide antibodies (generated against a synthetic oligopeptide that was not represented in microsequenced peptides of the trans-factor) also recognized the purified trans-factor on Western blots. Conversely, the 18-base FR RNA cis-element also bound hnRNP E1 protein on Northwestern blots. Moreover, a 19-base RNA cis-element in the 3'-untranslated region of 15-lipoxygenase mRNA that is known to bind hnRNP E1 also interacted with placental 43-kDa trans-factor. In addition, several murine tissues containing a hnRNP E1-related protein (also known as alphaCP-1) readily interacted with the 18-base FR RNA cis-element. Finally, anti-hnRNP E1 antibodies specifically inhibited translation of FR in vitro in a dose-dependent manner, and the antibody effect could be reversed in a dose-dependent manner by either purified trans-factor or hnRNP E1. Collectively, the data favor identity of the FR mRNA-binding trans-factor and hnRNP E1, confirm its critical role in the translation of FR, and highlight yet another role of multifunctional hnRNP E1 in eukaryotic mRNA regulation.

Amino Acid Sequence↗
PubMed2001

Comparison of low cost measurement techniques for long-term monitoring of atmospheric ammonia.

An inter-comparison of techniques for long-term sampling of atmospheric ammonia (NH3) was conducted with a view to establishing a national network with > 50 sites. Key requirements were for: a low cost system, simplicity and durability to enable a postal exchange with local site operators, a precision of < +/- 20% for monthly sampling at expected NH3 concentrations of 1-2 micrograms m-3, a detection limit sufficient to resolve the small NH3 concentrations (< 0.2 microgram m-3) expected in remote parts of the UK, and a quantitative means to establish quality control. Five sampling methods were compared: A, a commercially available membrane diffusion tube (exposed in triplicate), with membranes removed immediately after sampling; B, the above method, with the membranes left in place until analysis; C, open-ended diffusion tubes (exposed with 4 replicates); D, a new active sampling diffusion denuder system; and E, an active sampling bubbler system. Method D consisted of two 0.1 m acid coated glass denuders in series with sampling at approximately 0.3 l min-1. These methods were deployed at 6 locations in the UK and the Netherlands and compared against reference estimates. Method D was the most precise and sensitive of the techniques compared, with a detection limit of < 0.1 microgram m-3. The bubbler provided a less precise estimate of NH3 concentration, and also suffered several practical drawbacks. The diffusion tubes were found to correlate with the reference at high concentrations (> 3 micrograms m-3), but were less precise and overestimated NH3 at smaller concentrations. Of the passive methods, A was the most precise and C the least precise. On the basis of the results, method D has been implemented in the national network, together with application of method A to explore spatial variability in regions with expected high NH3 concentrations.

Air Pollutants↗
PubMed2001

Inhibition of phosphodiesterase type III before aortic cross-clamping preserves intramyocardial cyclic adenosine monophosphate during cardiopulmonary bypass.

UNLABELLED: Inotropes are often used to treat myocardial dysfunction shortly after cardiopulmonary bypass (CPB). beta-Adrenergic agonists improve contractility, in part by increasing cyclic adenosine monophosphate (cAMP) production, whereas phosphodiesterase type III inhibitors prevent its breakdown. CPB is associated with abnormalities at the beta-receptor level and diminished adenyl cyclase activity, both of which tend to decrease cAMP. These effects may be increased in the presence of preexisting myocardial dysfunction. We tested the hypothesis that inhibition of phosphodiesterase type III before global myocardial ischemia and pharmacologic arrest results in the preservation of intramyocardial cAMP concentration during CPB. Twenty adult patients undergoing coronary artery bypass grafting with CPB were studied. After CPB was instituted, a myocardial biopsy was obtained from the apex of the left ventricle. Patients were randomized to receive either placebo or milrinone (50 micro/kg) through the bypass pump 10 min before aortic cross-clamping. Another myocardial biopsy was performed adjacent to the left ventricular apex just before weaning from CPB. Myocardial cAMP concentration was determined by radioimmunoassay. Myocyte protein content was determined by the Bradford method by using a commercial kit. There were no significant demographic differences between the groups; however, patients in the Milrinone group had a lower left ventricular ejection fraction than placebo (41% +/- 13% vs 53% +/- 7%; P < 0.05). Patients who received milrinone had larger cAMP concentrations at the end of CPB compared with placebo (21 +/- 12.5 pmol/mg protein versus 12.8 +/- 2.2 pmol/mg protein; P < 0.05). The administration of milrinone before aortic cross-clamping is associated with increased intramyocardial cAMP concentration at the end of CPB. IMPLICATIONS: The administration of a single dose of milrinone before aortic cross-clamping resulted in significantly larger intramyocardial cyclic adenosine monophosphate concentration in myocardial biopsy specimens compared with controls.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2001

[A primary study on the relationship between condyle position and anterior distraction for cross bite caused by cleft lip and palate].

OBJECTIVE: To evaluate the changes of the position of the mandibular condyle in cleft lip and palate patients with secondary bony cross-bite deformity after early orthodontic treatment with extraoral bow and facial mask. METHODS: The TMJ topograph 6 months before and after treatment was investigated in 8 patients. The width of the anterior,superior and posterior space of the TMJ was compared prior to and post treatment. RESULTS: The results showed that there was no significant difference in the width of the three spaces of the TMJ before and after treatment. CONCLUSION: The position of the mandibular condyle had no significant change after maxillary anterior distraction with extraoral bow and facial mask.

English Abstract↗
PubMed2001

[Assessment of velopharyngeal function in normal speech by CT].

OBJECTIVE: To find an objective method to assess velopharyngeal function by CT. METHODS: Three dimensional conformation of the velopharyngeal orifice of 30 subjects with normal speech at rest and /i:/ position were observed and analyzed. The linear distance and area of velopharyngeal orifice were measured and analyzed statistically. RESULTS: The average minimal area of velopharyngeal orifice at/i:/ position was 11.92+/-11.73 mm(2). The physical RVPI was 4.03+/-4.03%. Coronary closure was the most common type of velopharyngeal contraction which accounted for 50%, semi-ring type being 30%, and ring type being 20%. No sagittal closure were seen in this study. There were 70% subjects whose position of velopharyngeal closure was at the level of the first cervical vertebra, 26.7% above the level and 3.3% below it. The arrange of velopharyngeal closure was 9-12 mm in 83.4% subjects, and 3-6mm in 16.6%. CONCLUSION: As a method of assessing velopharyngeal function, CT can not only observe the conformation of velopharyngeal orifice in three dimensions, but also quantitatively analyze the velopharyngeal function.

English Abstract↗
PubMed2001

[Embolization of AVM of jaws].

OBJECTIVE: To report our experience to embolize the AVM of jaws by direct percutaneous puncture. in conjunction with endovascular therapy. METHODS: 3 cases of AVM of mandible and 3 cases of AVM of maxilla comprised this study group. The patients were embolized with fibered coils, PVA and NBCA. The coils were placed directly into the center of the intraosseous lesion. The procedure was under the guidance of DSA machine (PHILIPS V3000). RESULTS: The acute arterial bleeding in 4 patients was controllable. The other two cases with oozing bleeding and a warm soft mass on the left face with a palpable pulse respectively, their symptoms and signs got improved a lot. The pericoronal oozing of blood in all patients disappeared during a 3 to 24 months follow-up and new bone formation was found in the follow-up radiography. CONCLUSION: The embolization of the AVM of jaws by direct percutaneous puncture in conjunction with endovascular therapy is effective and safe, however the longer follow-up is expected.

English Abstract↗
PubMed2000

Nodulisporic acid opens insect glutamate-gated chloride channels: identification of a new high affinity modulator.

Nodulisporic acid (NA) is an indole diterpene fungal product with insecticidal activity. NA activates a glutamate-gated chloride channel (GluCl) in grasshopper neurons and potentiates channel opening by glutamate. The endectocide ivermectin (IVM) induces a similar, but larger current than NA. Using Drosophila melanogaster head membranes, a high affinity binding site for NA was identified. Equilibrium binding studies show that an amide analogue, N-(2-hydroxyethyl-2,2-(3)H)nodulisporamide ([(3)H]NAmide), binds to a single population of sites in head membranes with a K(D) of 12 pM and a B(max) of 1.4 pmol/mg of protein. A similar K(D) is determined from the kinetics of ligand binding and dissociation. Four lines of evidence indicate that the binding site is a GluCl. First, NA potentiates opening of a glutamate-gated chloride current in grasshopper neurons. Second, glutamate inhibits the binding of [(3)H]NAmide by increasing the rate of dissociation 3-fold. Third, IVM potently inhibits the binding of [(3)H]NAmide and IVM binds to GluCls. Finally, the binding of [(3)H]IVM is inhibited by NA. The B(max) of [(3)H]IVM is twice that of [(3)H]NAmide, and about half of the [(3)H]IVM binding sites are inhibited by NA with high affinity (K(I) = 25 pM). In contrast, [(3)H]IVM binding to Caenorhabditis elegans membranes is not inhibited by NA at 100 nM, and there are no high affinity binding sites for NA on these membranes. Thus, half of the Drosophila IVM receptors and all of the NA receptors are associated with GluCl. NA distinguishes between nematode and insect GluCls and identifies subpopulations of IVM binding sites.

Amides↗
PubMed2000

[Correlation between the changes of soft and hard tissue after advanced Lefort I osteotomy in patients with cleft lip and palate].

OBJECTIVE: The purpose is to evaluate the correlation between the changes of soft and hard tissue after advanced Lefort I osteotomy in patients with complete unilateral cleft lip and palate. METHODS: Lateral cephalometric films were taken from before and after operation. The same landmarks in two films were compared horizontally and vertically. The correlation ratio between changes of soft and hard tissue were analysed statistically. RESULTS: After operation, the length of upper lip of the patients with CLP increased. The ratio between the movement of upper incisor and upper lip was 0.77 horizontally and 0.67 vertically, respectively. CONCLUSION: The slope between hard and soft tissue was treated as ratio. It is more significant than the horizontal difference between soft and hard tissue, since correlative factor was contained in the slope.

English Abstract↗
PubMed2000

[Cephalometric analysis on patients with TMJ ankylosis in different ages].

OBJECTIVE: To determine the cephalometric characteristics of the patients with TMJ ankylosis in deferent ages and to find the relationship between the period with TMJ and the cephalometric characteristics. METHODS: By cephalometric analysis of 46 male patients with TMJ ankylosis and several normal people in deferent ages, we detected the relationship among the ages of the patients, the period with TMJ ankylosis and the cephalometric characteristics by means of SPSS for Win 95/98. RESULTS: The cephalometric characteristics of the patients showed their maxilla and mandible retruded in posterior and superior direction, the hyoid bone displaced posteriorly and inferiorly. The middle and inferior pharygeal space decreased, the TSA/OPA increased significantly. There was an obvious positive correlation between the period with TMJ and hyoid bone position(r=0.46, p=0.009; Y=1.58+0.56X), and remarkable positive correlation between the period with TMJ and TSA/OPA(r=0.5, p=0.00 Y=72.76+0.64X). CONCLUSION: In patients with TMJ ankylosis, the mandible and maxilla retruded posteriorly and superiorly,the hyoid bone displaced posteriorly and inferiorly, the middle and inferior pharygeal space decreased, the TSA/OPA increased remarkably. The longer the period with TMJ ankylosis, the more serious the deformities of the patients in craniomaxillofacial region.

English Abstract↗
PubMed1999

Evaluation of the treatment for micromandibular deformity by distraction osteogenesis with submerged intraoral device.

OBJECTIVE: To evaluate the results of distraction osteogenesis for correcting the micromandible with an intraoral device. MATERIALS AND METHODS: Eight cases of micromandible resulting from temporomandibular joint (TMJ) ankylosis and first and second branchial arch syndrome received treatment by distraction osteogenesis. Subjects included 5 females and 3 males, ranging in age from 10 to 43 years (avg 20.25). Five micromandibles were associated with obvious mandibular asymmetry. An osteotomy was performed on bilateral mandibular bodies by intraoral approach. Elongation was started on the 5th or 6th day postoperation at a rate of 0.8 to 1 mm per day. The distractors were removed after a consolidation period from 71 to 139 days. RESULTS: The distractions were fulfilled with a range of 8.5 to 24.4 mm. Pain appeared in osteotomy region when the 1 mm distraction was carried out once a day and disappeared when it was divided into twice a day. Mandibular lengthening was successful. Micromandible and facial asymmetries were corrected satisfactorily. The follow-up period ranged from a minimum of 1 month to a maximum of 10 months. There was no recurrence. One case of soft tissue infection and one case of lower lip numbness were reported. There were no cases of infection or other disturbance of wound healing or pseudarthrosis. CONCLUSIONS: Because of its advantage in little injury, avoiding bone grafting, and few complications, intraoral distraction osteogenesis is a valuable approach to correct mandibular agenesis. However, in the management of mandibular deformities, distraction osteogenesis achieves better results when combined with other orthognathic operations. How to control the direction of distraction is a problem that needs further study.

Adolescent↗