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Biomedical subjects

Y P Liu

Publications and source records attributed to Y P Liu.

At least 19 recordsLinked to original sources
PubMed2004

Effects of acute and chronic buspirone on impulsive choice and efflux of 5-HT and dopamine in hippocampus, nucleus accumbens and prefrontal cortex.

RATIONALE: Reduced central serotonin (5-HT) activity has been associated with impulsive choice behaviour, but there is no consensus about the precise nature of these effects. Behavioural and neurochemical effects of 5-HT(1A) agonists such as buspirone depend critically on the dose and the duration of treatment. We thus undertook a parametric study of the effects of acute and chronic buspirone on the performance on a test of delayed gratification, as well as on the efflux of serotonin and dopamine (DA) in cortical and subcortical regions in rats. OBJECTIVES: Three experiments examined (i) the effects of acute buspirone on impulsive choice and how such effects were modified by prior chronic exposure to buspirone; (ii) the effects of chronic buspirone on impulsive choice; (iii) the effects on impulsive choice of a selective 5-HT(1A) antagonist, WAY-100635 tested alone and in combination with buspirone; (iv) the effects of chronic and acute buspirone on 5-HT and DA efflux in anaesthetised rats. METHODS: In experiment 1, rats previously trained on the delayed gratification task were tested with acute buspirone (0.5, 1 and 2 mg/kg). The same rats were then treated with chronic buspirone (1 mg/kg/day) over the next 65 days, and the effects of acute buspirone (1 mg/kg) re-determined at 20, 45 and 65 days of chronic treatment. In experiment 2, two groups of rats trained on the delayed gratification task were treated either with saline or buspirone (1 mg/kg/day) continually for 65 days before being tested with acute buspirone (1 mg/kg), WAY-100635 (0.08 mg/kg), or a combination of the two drugs. In experiment 3, rats received the same regimen of buspirone dosing as in experiment 2, before receiving in-vivo microdialysis for 5-HT and DA in the ventral hippocampus, nucleus accumbens and medial prefrontal cortex. RESULTS: Acute buspirone dose dependently increased the choice for the small, immediate reinforcer (impulsive choice) but the effects of 1 mg/kg were reversed on chronic administration of buspirone. This increased choice of the large, delayed reinforcer, which was not accompanied by any changes in baseline (non-drugged) performance, was blocked by the 5-HT(1A) receptor antagonist WAY-100635. The chronic buspirone regimen did not alter buspirone-evoked reductions in 5-HT efflux in hippocampus but did lead to a differential effect of acute buspirone in medial prefrontal cortex, with the chronic buspirone and saline groups exhibiting decreases and increases in efflux, respectively. There were no systematic changes in DA efflux under any condition. CONCLUSIONS: These findings show that the effects of acute buspirone on impulsive choice are reversed following chronic treatment and are mediated by 5-HT(1A) receptors, and suggest, in addition, that the behavioural effects may involve changes in 5-HT functioning in medial prefrontal cortex.

Analysis of Variance↗
PubMed2003

Modelling metal desorption kinetics in estuaries.

The kinetics of desorption of Cd, Cu, Ni and Zn from riverine and estuarine sediments have been determined in deionised water and seawater (salinity=30). The time-dependent release of Cd, Cu and Ni from riverine sediments in both media showed an increase in dissolved metal concentrations within a few minutes, followed by a plateau after several hours of incubation. Desorption of Zn from riverine sediments in seawater was characterised by a maximum dissolved concentration after several minutes, followed by readsorption onto the suspended sediment. The extent of metal desorption from estuarine sediment (relative to a chemical digest of available particulate metal), in both deionised water and seawater, was less than that from the fluvial sediments, even though the available particulate metal concentrations were higher. The desorption kinetics of the metals were modelled using a mechanism consisting of reversible, first-order consecutive reactions. The dissolved metals were assumed to desorb into the bulk solution from exchangeable surface sites and from binding sites located within the particle matrix. A reasonable fit to the observed time-dependent desorption behaviour was simulated by integrating the differential equations resulting from the mechanism, assuming that the exchangeable particulate metal was defined by the chemical digest. The results are discussed within the context of improved understanding of the non-conservative behaviour of dissolved metals in estuaries.

Journal Article↗
PubMed2003

Trace metal behaviour in the Conwy estuary, North Wales.

The distribution of trace metals Zn, Ni, Mn, Fe, Cu, Pb, Cd and Cr between suspended particulate matter (SPM) and water in the Conwy estuary, North Wales, has been studied in three surveys in 1998. Dissolved Cu and Mn showed some monthly variations. Most of the dissolved trace metals displayed a negative association with salinity, indicating rivers as a major source of inputs for them. Particulate Zn, Mn and Fe showed a decreasing concentration seaward, whilst the levels of Ni, Cu, Cr and Pb increased with salinity. SPM concentration was the most important variable significantly related to trace metal concentrations in SPM, with an inverse relationship between the two parameters. This was explained by the relative enrichment of trace metals in fine particles at low SPM concentrations and relative depletion of trace metals in coarse particles at high SPM concentrations. Particulate Zn, Mn and Pb were dominated by the fraction available to acetic acid (non-detrital), whilst particulate Ni, Fe and Cr were dominated by the fraction available to nitric acid (detrital). The partition coefficient of trace metals between SPM and water declined with increasing SPM concentration, consistent with the so-called "particle concentration effect". Such a phenomenon may be explained by the presence of fine particles (including colloids) enriched with trace metals at low SPM concentrations, and the salinity-induced desorption.

Adsorption↗
PubMed2001

Heavy metals in the tissues of common dolphins (Delphinus delphis) stranded on the Portuguese coast.

The concentrations of Hg, Sn, Cr, Zn, Ni, Co, Cd, Mn, Fe and Cu were determined in the liver, kidney and muscle of 24 common dolphins stranded on the Portuguese coast between 1995 and 1998. Nitric acid was used to extract the metals from the tissues for analysis by inductively-coupled plasma/atomic emission spectroscopy (ICP/AES). Those metals with relatively higher concentrations included Fe, Zn and Hg, particularly in liver. Other metals including Cr, Ni and Cd tended to show much lower levels, or were even undetected (e.g. Co). Different metals seemed to show different temporal trends, although due to substantial variations of the mean concentrations for each year obtained, such temporal pattern has to be studied further. Total Hg concentration in the kidney, muscle and particularly liver, were higher in females than in males. Total Hg concentrations in all the organs increased with body length of dolphins, whilst those of Zn and Cu in muscle decreased with dolphin length. A strong correlation was found between essential metals Zn and Cu in muscle, possibly resulting from sequestration of these metals by metallothionein. In addition, significant co-associations existed between the same metal (e.g. Hg, Sn and Zn) in different organs.

Animals↗
PubMed2001

Optimized analytical method for cyclosporin A by high-performance liquid chromatography-electrospray ionization mass spectrometry.

The Micromass Platform LCZ mass detector parameters were optimized for simultaneous recording of the protonated (CsA-H+), sodium adduct (CsA-Na+) and potassium adduct (CsA-K+) of cyclosporin A eluted from a Symmetry Shield RP8 column. The optimized procedure allows a precise analysis of CsA in whole blood or serum without removal of salts prior to analysis. The ratio of the three forms of CsA varied depending on the assay condition and the types of specimens being analyzed. The summation of three ionic forms of CsA detected by LC-ESI-MS is a reliable and simple method to assess CsA concentration in the blood.

Cations, Monovalent↗
PubMed2001

Effects of decreasing the frequency of ventilator circuit changes to every 7 days on the rate of ventilator-associated pneumonia in a Beijing hospital.

INTRODUCTION: We investigated whether decreasing ventilator circuit changes from every 2 days to every 7 days would impact ventilator-associated pneumonia rates at our institution. METHODS: All mechanically ventilated patients at Peking Union Medical College Hospital were studied over a 21 month period. From March 1998 to February 1999, ventilator circuits were changed every 2 days, and from June through December 1999, ventilator circuits were changed every 7 days. Nosocomial pneumonia was identified using the criteria of the Centers for Disease Control. RESULTS: In the 2-day-change group, there were 2,277 ventilator-patient days and 38 patients developed pneumonia, resulting in a pneumonia rate of 16.7 cases per 1,000 ventilator days. The 7-day-change group accumulated 972 ventilator days and 8 patients contracted pneumonia, resulting in a pneumonia rate of 8.2 cases per 1,000 ventilator days. The pneumonia rate was significantly lower in the 7-day-change group (p = 0.007). To standardize for seasonal variability, we compared results from the same seasonal time frames (June to December 1998 for the 2-day-change group, and June to December 1999 for the 7-day-change group), and obtained similar findings: during those periods, pneumonia rates were 24.2 cases per 1,000 ventilator days for the 2-day-change group and 8.9 cases per 1,000 ventilator days for the 7-day-change group (p = 0.001). CONCLUSIONS: A circuit change interval of 7 days had a lower risk of ventilator-associated pneumonia than a 2-day change interval. Therefore, ventilator circuits can be safely changed every 7 days in our setting.

Cross Infection↗
PubMed2001

[Nuclear ribosomal RNA small subunit (18S rRNA) nucleotide sequencing and characterization of sailonggu(whole bone of Myospalax baileyi Thomas)].

OBJECTIVE: Sequencing the nuclear ribosomal RNA small subunit (18S rRNA) gene of Myospalax baileyi (Cricetidae) to develop an ultimate and definitive means for origin identification of genuine Sailonggu. METHODS: The total DNA was prepared from dried tail tissues. The nuclear 18S rRNA gene region was amplified by PCR using a consensus primer set and its nucleotide sequence was determined by PCR direct sequencing. The characteristic analysis of 18S rRNA sequences was generated using software program Genetyx-SV/R Version 10.1. RESULTS: The entire 18S rRNA gene region of M. baileyi spanded 1851 bp in length. Although multiple alignment of sequence indicates that there are only lower homology (72.04%-72.18%) comparing with its two alias Mus musculus (GenBank Accession number X00686) and Rattus norvegicus (M11188) (Muridae), their highly conservative domain is located in 1020-1509 nt. There are many variable sites from upstream of 5'-end, which could provide a novel information for molecular recognition of Sailonggu. CONCLUSION: DNA sequencing could be a useful and reliable tool in the origin identification of genuine Sailonggu.

Animals↗
PubMed2000

Genotypic determination of Mycobacterium tuberculosis antibiotic resistance using a novel mutation detection method, the branch migration inhibition M. tuberculosis antibiotic resistance test.

A novel method for the detection of any alteration within a defined sequence has recently been demonstrated (A. Lishanski, N. Kurn, and E. F. Ullman, Nucleic Acids Res. 28:E42, 2000; A. Lishanski, Clin. Chem. 46:9, 2000). Essential to this method are the generation of partial duplexes that are capable of forming four-stranded structures and the ability to detect inhibition of branch migration in these structures (I. G. Panyutin and P. Hsieh, J. Mol. Biol. 230:413-424, 1993). Inhibition of branch migration indicates the presence of sequence alteration. This mutation detection method, termed branch migration inhibition (BMI), is suitable for the detection of drug resistance in M. tuberculosis, which is frequently associated with multiple mutations within known genes. We describe the genotypic determination of the rifampin (RMP) and pyrazinamide (PZA) susceptibilities of M. tuberculosis isolates, using BMI coupled with the luminescence oxygen channeling immunoassay (LOCI) (E. F. Ullman et al., Proc. Natl. Acad. Sci. USA 91:5426-5430, 1994). RMP and PZA resistances are associated with multiple mutations within the rpoB and pncA genes, respectively. M. tuberculosis genomic DNA samples prepared from 46 clinical isolates were used for genotypic determination of RMP resistance in a "blind study." Similarly, PZA resistance was determined using genomic DNA samples prepared from 37 clinical isolates. Full agreement of the genotypic and phenotypic determinations of drug susceptibility was demonstrated. RMP susceptibility determination directly from cells of 10 clinical isolates grown in culture was also demonstrated. The genotypic result of only 1 out of 10 isolates did not agree with the phenotypic susceptibility testing result. Sequence analysis of the rpoB gene of this clinical isolate revealed a single base substitution, most likely a silent point mutation. The new BMI-LOCI mutation detection method is a rapid and accurate procedure for the genotypic determination of the RMP and PZA susceptibilities of M. tuberculosis clinical isolates. BMI can also be detected by using commercially available automated enzyme-linked immunosorbent assay plate formats (Lishanski et al., Nucleic Acids Res. 28:E42, 2000).

Amidohydrolases↗
PubMed2000

Apoptosis and apoptosis related gene expression in normal conjunctiva and pterygium.

BACKGROUND: Pterygium is a relatively common eye disease in the tropics whose aetiology and pathogenesis remain uncertain. As such, interest has focused on understanding the underlying mechanism of pterygia development. METHODS: 15 specimens of pterygia from 15 eyes were examined, together with normal conjunctival tissue from the same eyes for the pattern of gene expression of genes associated with the induction or repression of apoptosis (p53, bcl-2, and bax). In addition, the samples directly for apoptotic cells were examined by the terminal deoxynucleotide transferase (TdT) mediated nick end labelling (TUNEL) methodology. RESULTS: In pterygia specimens apoptotic cells were found mainly confined to the basal layer of cells of the epithelial layer, situated immediately adjacent to the fibrovascular support layer. These cells were shown to express significant levels of p53 and bax, as well as the apoptosis inhibiting protein bcl-2. In contrast, normal conjunctival specimens displayed no bcl-2 expression and apoptotic cells were seen throughout the entire width of the epithelial layer, coupled with high levels of bax expression. CONCLUSION: These results support a model whereby pterygia development is a result of disruption of the normal process of apoptosis occurring in the conjunctiva.

Apoptosis↗
PubMed2000

Flow cytometry measurements of DNA content in primary and recurrent pterygia.

PURPOSE: To evaluate DNA content and cellular proliferation rates in primary and recurrent pterygia. METHODS: Matched pterygium and superior conjunctiva tissue were obtained in 36 eyes of 36 patients undergoing pterygium excision with conjunctival autografting (24 primary pterygia, 12 recurrent pterygia). Epithelial and fibrovascular layers were separated for analysis. Matched superior conjunctiva obtained at the time of surgery were used as controls. Samples were prepared according to Thompson's method, and flow cytometry was performed with a Becton-Dickinson FACScan. Analysis of histograms and calculations of cell percentages in cell cycle phases were carried out using CellFit software (version 2.0). Mean proliferation indices (MPIs) were compared using the Wilcoxon matched-pair signed-rank test. RESULTS: The MPI of pterygium fibrovascular tissue (13.4) was significantly higher than the MPI of pterygium epithelium (3.1; P = 0.0001). The MPI of pterygium fibrovascular tissue was also significantly higher than that of superior conjunctival fibrovascular tissue (6.0; P = 0.0001). There was no difference in MPI values between pterygium epithelium and superior conjunctival epithelium (3.55; P = 0.12). The MPI of fibrovascular tissue from recurrent pterygium (73.75) was significantly higher than the MPI of fibrovascular tissue from primary pterygium (7.3; P = 0.003). CONCLUSIONS: The finding of high levels of cellular proliferation in the subepithelial fibrovascular layer of pterygium confirms that pterygium is a disorder of excessive cellular proliferation and that the fibrovascular layer is the site of cellular proliferation. Markedly raised levels of cellular proliferation in recurrent pterygium tissue suggest a clinical correlation between fibrovascular tissue upregulation and pterygium recurrence after surgery.

Adult↗
PubMed2000

[Cloning cDNA of extracellular domain of human erythropoietin receptor and its expression in Escherichia coli].

Human erythropoietin receptor (hEpoR) plays an important role in regulating the red blood cell production by promoting the proliferation and differentiation of RBC from erythroid precursors. hEpoR is a transmembrane protein, and its extrocellular domain (sEpoR) is of great importance in Epo signal transduction pathway. We cloned the gene of sEpoR by RT-PCR from the total RNA of human fetal liver and expressed it in E. coli after insertion of the gene in the expression vector pBV220. The cloned gene was confirmed by sequencing analysis and gene product was confirmed by both Western blot and its first 11 amino acid residues sequence of the N-terminal. In vitro bioassay showed that the purified gene product can repress the growth of TF-cells in the presence of Epo.

Cloning, Molecular↗
PubMed2000

[Purification of prothrombin in Nitschmann fraction III by membrane radial column ion-exchange liquid chromatography].

A method is described for the purification of human prothrombin complex concentrate (PCC) from Nitschmann fraction III by membrane radial column ion-exchange chromatography, which allows large sample volumes to be processed at low operation pressure. The Nitschmann fraction III (15 g) was mixed with 1,000 mL 0.06 mol/L Tris-HCl(pH 7.5). The centrifuged supernatant(10,000 r/min, 15 min, 20 degrees C) was applied onto a DEAE ion-exchange liquid chromatographic column(XK-16 DEAE fast flow Sepharose and DEAE membrane radical column chromatography) with almost the same excellent separation efficiency. The parameters of sample flow rate, elution flow rate and sample capacity were optimized.

Blood Coagulation Factors↗
PubMed1999

Sensitivity of thyroid gland growth to thyroid stimulating hormone (TSH) in rats treated with antithyroid drugs.

Antithyroid drugs and phenobarbital (PB) have been shown to promote thyroid tumors in rats. It has been proposed that increased thyroid-stimulating hormone (TSH) mediates the thyroid tumor-promoting effect of antithyroid drugs and PB, and is increased because of decreased thyroxine (T4) concentration. However, PB is much less effective than antithyroid drugs at increasing TSH. It has been proposed that small increases in serum TSH produced by PB treatment is sufficient to promote thyroid tumors. However, the level to which TSH must be increased to stimulate the thyroid gland has not been reported. Therefore, we have examined the effect of increasing serum TSH concentration on thyroid growth by measuring thyroid gland weight and thyroid follicular cell proliferation. Serum TSH concentrations were increased by feeding rats various concentrations of propylthiouracil (PTU) or methimazole (MMI) for 21 days. Serum total T4, free T4, total T3 (triiodothyronine), free T3, and TSH concentrations were measured by radioimmunoassay. Thyroid follicular cell proliferation was measured by autoradiography and expressed as a labeling index (LI). PTU and MMI treatments reduced total and free T4 more than 95% by day 21, whereas total and free T3 were reduced 60%. TSH, thyroid follicular cell proliferation and thyroid weight were increased 560%, 1400%, and 200%, respectively, by day 21. TSH was significantly correlated with thyroid weight and LI. Moderate increases in serum TSH of between 10 and 20 ng/ml increased the number of proliferating thyroid follicular cells, but had no effect on thyroid weight. These results support that small increases in serum TSH can be sufficient to stimulate thyroid follicular cell proliferation. Furthermore, thyroid follicular cell proliferation may be more useful than thyroid weight alone for assessing alterations in thyroid growth in rats treated with chemicals that produce only small to moderate increases in serum TSH.

Animals↗
PubMed1999

Arsenic: health effects, mechanisms of actions, and research issues.

A meeting on the health effects of arsenic (As), its modes of action, and areas in need of future research was held in Hunt Valley, Maryland, on 22-24 September 1997. Exposure to As in drinking water has been associated with the development of skin and internal cancers and noncarcinogenic effects such as diabetes, peripheral neuropathy, and cardiovascular diseases. There is little data on specific mechanism(s) of action for As, but a great deal of information on possible modes of action. Although arsenite [As(III)] can inhibit more than 200 enzymes, events underlying the induction of the noncarcinogenic effects of As are not understood. With respect to carcinogenicity, As can affect DNA repair, methylation of DNA, and increase radical formation and activation of the protooncogene c-myc, but none of these potential pathways have widespread acceptance as the principal etiologic event. In addition, there are no accepted models for the study of As-induced carcinogenesis. At the final meeting session we considered research needs. Among the most important areas cited were a) As metabolism and its interaction with cellular constituents; b) possible bioaccumulation of As; c) interactions with other metals; d) effects of As on genetic material; e) development of animal models and cell systems to study effects of As; and f) a better characterization of human exposures as related to health risks. Some of the barriers to the advancement of As research included an apparent lack of interest in the United States on As research; lack of relevant animal models; difficulty with adoption of uniform methodologies; lack of accepted biomarkers; and the need for a central storage repository for stored specimens.

Arsenic↗