Search PubMed⌕ Search

Biomedical subjects

Yu Liu

Publications and source records attributed to Yu Liu.

At least 145 records · Page 8Linked to original sources
PubMed2005

Pharmacodynamics and pharmacokinetics of recombinant hirudin via four non-parenteral routes.

One of recombinant hirudin variants, rHV2, a polypeptide used as an anticoagulant agent in clinic, was administered to anesthetized rats via intratracheal, buccal, nasal and rectal routes. Prolongation in clotting time and thrombin time was measured to calculate pharmacological bioavailability. Plasma concentration of rHV2 was determined using a chromogenic thrombin substrate assay and pharmacokinetic parameters were obtained on the basis of a non-compartmental model. Intravenous administration was also performed as the gold standard by which the other routes were compared. Difference in pharmacological bioavailability (P.A.), bioavailability (F) and absorption rate of rHV2 was found for the four non-parenteral routes. The rank order for both P.A. and F was intratracheal>nasal>buccal>rectal. Absorption was more rapid after both intratracheal and rectal administration (tmax approximately 20-40 min), compared with that after nasal and rectal administration. It is evident that the pulmonary route is preferable to other three routes for successful systemic delivery of rHV2.

Absorption↗
PubMed2005

Denitrification on poly-beta-hydroxybutyrate in microbial granular sludge sequencing batch reactor.

Microbial granules were successfully cultivated in an alternating aerobic-anaerobic sequencing batch reactor (SBR) for removing organic carbon and nitrogen. It was found that almost all input ammonium was converted to nitrite and nitrate in the aerobic phase, while the efficiency of denitrification was highly related to the availability of external carbon source in the anaerobic phase. Complete denitrification was achieved with sufficient supply of external carbon, while only partial denitrification was observed with no addition of external carbon. Results showed that in the absence of external carbon source, pre-accumulated poly-beta-hydroxybutyric acid (PHB) in microbial granules could be utilized for cell maintenance and denitrification. With supply of external carbon but no addition of nitrate, PHB accumulation accounted for the main mechanism of the organic removal. Under balanced growth conditions (with organic carbon and nitrogen supply), external organic carbon was consumed simultaneously for denitrification, PHB storage as well as for cell functions. It was revealed that the potential role of PHB for denitrification by microbial granules was very limited, i.e. less than 28 mg nitrate-nitrogen l(-1) was found to be denitrified with internally accumulated PHB. This study for the first time shows the limiting capacity of PHB as reducing power for denitrification by microbial granules.

Bacteria, Aerobic↗
PubMed2005

Cx31 is assembled and trafficked to cell surface by ER-Golgi pathway and degraded by proteasomal or lysosomal pathways.

Gap junctions, consisting of connexins, allow the exchange of small molecules (less than 1 KD) between adjacent cells, thus providing a mechanism for synchronizing the responses of groups of cells to environmental stimuli. Connexin 31 is a member of the connexin family. Mutations on connexin 31 are associated with erythrokeratodermia variabilis, hearing impairment and peripheral neuropathy. However, the pathological mechanism for connexin 31 mutants in these diseases are still unknown. In this study, we analyzed the assembly, trafficking and metabolism of connexin 31 in HeLa cells stably expressing connexin 31. Calcein transfer assay showed that calcein transfer was inhibited when cells were treated with Brefeldin A or cytochalasin D, but not when treated with nocodazole or a-glycyrrhetinic acid, suggesting that Golgi apparatus and actin filaments, but not microtubules, are crucial to the trafficking and assembly of connexin 31, as well as the formation of gap junction intercellular communication by connexin 31. Additionally, a-glycyrrhetinic acid did not effectively inhibit gap junctional intercellular communication formed by connexin 31. Pulse-chase assay revealed that connexin 31 had a half-life of about 6 h. Moreover, Western blotting and fluorescent staining demonstrated that in HeLa cells stably expressing connexin 31, the amount of connexin 31 was significantly increased after these cells were treated with proteasomal or lysosomal inhibitors. These findings indicate that connexin 31 was rapidly renewed, and possibly degraded by both proteasomal and lysosomal pathways.

Brefeldin A↗
PubMed2005

Hexachlorocyclohexane and dichlorodiphenyltrichloroethane residues in the dustfall of Tianjin, China.

Heating and nonheating season dustfall samples were collected from 23 sites in Tianjin, China during 2002-2003 to determine residues of hexachlorocyclohexane isomers (a-HCH, beta-HCH, gamma-HCH, and beta-HCH) and dichlorodiphenyltrichloroethane and metabolites (p,p'-DDE, p,p'-DDD, and p,p'-DDT). Concentrations of sumHCH (sum of alpha-, beta-, gamma-, and delta-HCH) and sumDDT (sum of p,p'-DDE, p,p'-DDD, and p,p'-DDT) varied in ranges of 10.9-3.16 x 10(3) and 37.9-1.53 x 10(3) ng g(-1) dry weight in heating season and in ranges of 6.9-1.12 x 10(3) and 18.6-626 ng g(-1) dry weight in nonheating season, respectively. It was found that HCHs and DDTs concentrations of the most heating season samples were higher than those of nonheating season samples collected from the same sites. Among studied compounds of the HCH family, beta-HCH prevailed in most samples, suggesting a possible volatilization or resuspension from contaminated topsoil. As for DDTs, p,p'-DDT and p,p'-DDE prevailed in most samples, indicating a possible "fresh" input. Correlations between HCHs/DDTs and total organic carbon and particle size are discussed. Atmospheric deposition fluxes were calculated for the heating and nonheating seasons, and the results showed that the annual input of particulate sumHCH and sumDDT from air to surface in the studied area of 1.19 x 10(4) km2 were 89 t and 80 t, respectively.

Air↗
PubMed2005

Sensitization of the reinforcing effects of self-administered cocaine in rats: effects of dose and intravenous injection speed.

Speed of drug onset is assumed to be an important determinant of the abuse liability of a drug. Studies in human and non-human primates suggest that the subjective and reinforcing effects of cocaine can be influenced by route of administration and/or speed of intravenous injection. Sensitization to the reinforcing effects of cocaine was studied in rats and the effects of various injection durations (i.e. speed of injection) on the development of sensitization was examined using a progressive ratio schedule. In addition, the effects of cocaine dose on sensitization and the effects of injection duration on the acute reinforcing effects of cocaine were examined. The initial study demonstrated that the development of sensitization (i.e. progressive increases in breakpoints) was dose-dependent. A robust sensitization of the reinforcing effects of cocaine was replicated in animals receiving cocaine at the highest rate (i.e. shortest duration; 5 s), but not in animals receiving the same dose over 25 or 50 s. Subsequent testing revealed that injection duration did not have profound effects on the acute reinforcing effects of cocaine (assessed by breakpoints or rate of responding on a fixed ratio schedule). These findings are similar to recent studies demonstrating that the development of sensitization, but not the acute responsivity, to cocaine's locomotor-activating effects are influenced by rate of intravenous injection. Taking these findings together, we hypothesize that the process of drug addiction involves both the acute reinforcing effects and the development of sensitization.

Animals↗
PubMed2005

Intracellular distribution, assembly and effect of disease-associated connexin 31 mutants in HeLa cells.

Mutations in connexin 31 (Cx31) are associated with erythrokeratodermia variabilis (EKV), hearing impairment and peripheral neuropathy; however, the pathological mechanism of Cx31 mutants remains unknown. This study analyzed 11 disease-associated Cx31 variants and one non-disease-associated Cx31 variant and compared their intracellular distribution and assembly in HeLa cells and their effect on these cells. The fluorescent localization assay showed no gap junction plaque formation in the cells expressing the recessive EKV-associated mutant (L34P) and four hearing impairment-associated mutants (66delD, 141delI, R180X and E183K), significantly reduced plaque formation in the cells with five EKV-associated dominant mutants (G12R, G12D, R42P, C86S and F137L) and no obvious change in the cells with two other mutants (I141V and 652del12). Immunoblotting analysis showed that 12 mutated Cx31s, like WT-Cx31, are able to form the Triton X-100 insoluble complex; however, the quantity of Triton X-100 insoluble complex in the transfected HeLa cells varied among different Cx31 mutants. Additionally, the expression of five EKV-associated dominant mutants (G12R, G12D, R42P, C86S and F137L) caused cell death in HeLa cells. However, the five hearing impairment-associated mutants did not induce cell death. The above results suggest that disease-associated mutants gain deleterious functions differentially. In summary, disease-associated Cx31 mutants impair the formation of normal gap junctions at different levels, and the diseases associated with Cx31 mutations may result from the abnormal assembly, trafficking and metabolism of the Cx31 mutants.

Apoptosis↗
PubMed2005

DNA vaccine against Taenia solium cysticercosis expressed as a modified hepatitis B virus core particle containing three epitopes shared by Taenia crassiceps and Taenia solium.

Many studies have provided evidence that the hepatitis B core antigen particle is useful as a vaccine carrier for foreign epitopes. Epitopes KETc1, KETc12, and GK-1 are three promising candidates for designing a vaccine against Taenia solium cysticercosis. In the present study, epitopes KETc1 and KETc12 were inserted into the immunodominant loop of the truncated HBc149, and epitope GK-1 was fused to its C-terminus. The fused protein deltaC-3n was expressed and purified successfully. The polymeric character was tested by SDS-PAGE. After inoculation of BALB/c mice with deltaC-3n, antibody titers were assayed by ELISA, and the antibody specification was analyzed by Western blot. Dot ELISA was performed to verify the protection of the three epitopes. Results showed that the purified polymeric protein was formed, high antibody titers were induced in immunized mice and three antibodies different in molecular weight were induced, serum specific antibody recognized the native peptide localized mainly in cyst wall cells, and there was no specific antibody toward the three epitopes in sera of infected pig and humans. All these revealed that the protein deltaC-3n was a potential candidate for vaccine against cysticercosis. So the deltaC-3n sequence and the signal peptide sequence of IL-2 were cloned to a vector pVAX3.0 to construct pVAX-S-deltaC-3n. Pigs were immunized with pVAX-S-deltaC-3n. Two weeks after the immunization booster, pigs were introduced to infectious T. solium eggs. The relative protective rate induced in pigs immunized with the DNA vaccine pVAX-S-deltaC-3n was 83%.

Amino Acid Sequence↗
PubMed2005

Terbium sensitized determination of tosufloxacin using electrochemiluminescence method.

A novel method for determination of trace amounts of tosufloxacin (TFLX) based on electrochemiluminescence (ECL) has been developed. The calibration graphs for TFLX were linear in the range of 5.0 x 10(-11)-3.5 x 10(-7) mol/L, with the detection limit of 1.3 x 10(-11) mol/L. Key factors affecting the determination of TFLX were investigated. TFLX amounts in capsule and serum samples were successfully detected by this method. A possible mechanism of energy transfer, and thus the explanation of ECL in the Tb3+-TFLX-Na2S2O4 system are discussed.

Anti-Bacterial Agents↗
PubMed2005

[Association between serum lipoprotein-cholesterol levels and HDL subpopulations].

OBJECTIVE: To investigate the influence of serum HDL-C or LDL-C levels on the components of serum HDL subpopulations. METHODS: Apolipoprotein (apo) A-I contents of serum HDL subpopulations in 292 subjects were determined by two-dimensional gel electrophoresis in conjunction with immunodection. RESULTS: With the decrease of serum HDL-C levels, the apoA-I contents of pre beta1-HDL and HDL3b increased and were significantly higher (P<0.01; P<0.05) in the low HDL-C group than in the high HDL-C group. But on the contrary, with the decrease of serum HDL-C levels, the apoA-I contents of HDL2b and HDL2a decreased and were significantly lower (P<0.01) in the middle and low HDL-C groups than in the high HDL-C group. With the increase of serum LDL-C levels, the apoA-I contents of pre beta1-HDL, HDL3C and HDL3b increased; the apoA-I contents of pre beta1-HDL and HDL3b were significantly higher in the high LDL-C group (P<0.05) and very high LDL-C group (P<0.01), and those of HDL3C were also significantly higher in the very high LDL-C group (P<0.01). But on the contrary, with the increase of LDL-C levels, the apoA-I contents of HDL2b decreased and were significantly lower in the high LDL-C group (P<0.05) and very high LDL-C group (P<0.01) when compared with the apoA-I contents of the desirable LDL-C group. CONCLUSION: With the decrease of serum HDL-C levels or increase of serum LDL-C levels, the small-sized HDL increased and the large-sized HDL decreased; furthermore, the HDL-C levels were more closely related to the components of the large-sized HDL (HDL2a, HDL2b).

Cholesterol, HDL↗
PubMed2005

[Clinical analysis of aspergillosis in orthotopic liver transplant recipients].

OBJECTIVE: To assess the clinical features of aspergillosis and its diagnosis, prophylaxis and treatment in patients after orthotopic liver transplantation (OLT), and to improve the prognosis of the recipients. METHODS: Medical records of consecutive patients who underwent OLT in our liver transplant center from May 2002 to May 2004 were analyzed retrospectively. Those with aspergillus infection complications were studied in detail regarding their infected organs, related factors, treatments and prognoses. RESULTS: 17 out of 207 recipients of OLT were detected with aspergillosis. The incidence was 8.21 percent. 5 patients infected with superficial aspergillus survived. Of the 12 cases with deep aspergillus infection, 3 with infection limited to the sites of their incisions survived, 2 of the 3 patients with infection in their lungs, and 1 of the 2 patients with it in their livers died, and 4 recipients with multi-organ aspergillus infection died. Among the 7 cases that died, 5 had severe hepatitis, 1 had post-hepatitis liver cirrhosis and 1 had primary liver carcinoma. CONCLUSIONS: Long-term (> or = 3 weeks) broad-spectrum antibiotics and immunosupression were involved in aspergillus infection in our OLT patients. Patients with chronic severe hepatitis had a higher risk of having aspergillus infection. Amphotericin B is still the best choice for treating aspergillosis. Prophylactic administration of anti-fungal medicine, surveillance of fungal infections as a routine, and treatment of the infection in time may help to improve the prognosis of OLT recipients with aspergillosis.

Adult↗
PubMed2005

[Ultrastructural changes of rat ischemic myocardium after bone marrow mesenchymal stem cell transplantation].

OBJECTIVE: To observe the ultrastructural changes of ischemic myocardium of rats after bone marrow mesenchymal stem cells (MSCs) transplantation. METHODS: Rat models of myocardial ischemia were established by ligating the descending anterior branch of the left coronary artery. The isolated and in vitro cultured MSCs labeled with 4' 6-diamidine-2-phenylindole (DAPI) were injected into the rats via the tail vein and the hearts of the rats were taken 1 week and 8 weeks after transplantation, respectively, for observation under fluorescence microscopy. The ultrastructural changes of the ischemic myocardium of the recipient rats were observed by transmission electron microscope. RESULTS: The third passage of cultured MSCs growing in colonies possessed good homogeneity. One week and 8 weeks after transplantation, DAPI-labeled cells were observed in the heart of the recipient rats, but not in the hearts of control rats. One week after transplantation, ultrastructural observation identified a small number of cells in the peripherals of the infarct area of the recipient rats with similar morphology to that of MSCs cultured in vitro. At 8 weeks,a large number of capillaries were seen in the ischemic myocardium on the peripheral of the infarct area. Ultrastructural observation also revealed some immature myocytes surviving in the ischemic region. CONCLUSION: MSCs is capable in vivo of homing to the ischemic myocardium via the blood circulation, and promote regeneration of the myocardium and blood vessels.

Animals↗
PubMed2005

[Isolation and identification of a photosynthetic bacteria producing coenzyme Q10].

13 isolates producing Coenzyme Q10 (CoQ10) of purple non sulfur photosynthetic bacteria were enriched out of pond sludge, one isolate named 2c was selected based on its high CoQ10 content and identified systematically. The gram-negative and short-rod shaped strain 2c is 0.6microm - 0.9microm x 1.2microm - 2.0 microm, has one long flagellum on one end of the cell and contains lamellar intracytoplasmic membrane(ICM) system parallel to cytoplasmic membrane. Cultures produce red pigments in the light. Live cells under phototrophic conditions contain bacteriochlorophyll a and carotenoids. 2c grows anaerobically in the light and aerobically in the dark. Optimal growth occurs at 30degreesC - 35degreesC and at pH7.0 -pH8.0. Various organic compounds are used as photosynthetic electron donors and carbon sources. Peptone and (NH4 )2SO4 are its better nitride source,yeast extracts stimulates its growth. A phylogenetic analysis based on 16S rDNA gene sequences reveales that strain 2c gathers a cluster with 3 strains of Rhodopseudomonas palustris whose accession number in GenBank are AY751758, DQ001155, DQ001158, respectively. 2c subcultures 15 generations stably at least. The results presented here demonstrated strain 2c is Rhodopseudomonas palustris.

Base Sequence↗
PubMed2005

[Effect of exogenous expression of heparanase gene on invasive ability of colorectal cancer cell line HT29].

BACKGROUND & OBJECTIVE: Heparanase (Hpa) is an endoglycosidase that degrades heparin sulfate--the main polysaccharide constituent of extracellular matrix (ECM) and basement. It can enhance the invasive and metastatic potential of malignant tumors and cell lines by destroying ECM and basement. This study was to explore the effects of heparanase gene on the invasive ability of colorectal cancer cell line HT29. METHODS: Heparanase gene was transfected into HT29 cells. Cell growth kinetics was assessed by MTT assay, and in vitro invasive ability was assessed with Boyden chamber. Xenograft and orthotopic implantation of histologically intact tumor in nude mice were constructed to observe the effect of exogenous expression of heparanase gene on invasive ability of HT29 cells. RESULTS: After transfection, the growth rate of heparanase-transfected HT29 (HT29-Hpa) cells was obviously higher than those of untransfected HT29 cells and empty vector-transfected HT29 (HT29-KZ) cells; the invasive cell number was significantly larger in HT29-Hpa cells than in untransfected HT29 cells and HT29-KZ cells (45.5+/-0.5 vs. 29.3+/-0.1 and 30.1+/-0.2, P<0.01). The entity neoplasm formed by HT29-Hpa cells (12 mm x 9 mm x 10 mm) was bigger than that formed by untransfected HT29 cells (6 mm x 8 mm x 6 mm). The prevalence of liver metastasis caused by orthotopic implantation of xenograft was significantly higher in HT29-Hpa group than in control group (71.43% vs. 14.29%, P<0.01). CONCLUSION: Exogenous heparanase gene can facilitate the growth, invasion, and metastasis of HT29 cells.

Animals↗
PubMed2005

[Determination of fleroxacin by photochemical fluorescence of zinc-fleroxacin complex].

Based on the complex formed by Zn2+ which can strengthen the relative fluorescence intensity of fleroxacin evidently, a novel photochemical fluorescence method was developed. The effects of the acidity, the concentration ratio of Zn2+ to fleroxacin, and the time for illumination were studied. Under the optimum experiment conditions, the linear range of the determination was 5.00 x 10(-8) - 5.00 x 10(-6) mol x L(-1). The detection limit was 4.2 x 10(-8) mol x L(-1). The relative standard deviation of the determination of fleroxacin (5.0 x 10(-7) mol x L(-1)) was 1.7% (n = 20). The method was successfully applied to the determination of fleroxacin in specimens, and the recoveries were in the range of 95.0%-105%. The mechanism of this system is proposed.

Fleroxacin↗
PubMed2005

[Expression of cyclooxygenase-2, hMLH1 and hMSH2 proteins, and their relationship with microsatellite instability in gastric carcinoma].

OBJECTIVE: To investigate the expression of cyclooxygenase-2 (COX-2), human mut-l homologue 1 (hMLH1) and human mut-s homologue 2 (hMSH2) proteins in human paired gastric carcinoma (GC) and adjacent normal mucosa, and analyze their relationship with microsatellite instability (MSI). METHODS: The protein expressions were examined by western blotting. Five MSI loci were assessed by PCR. RESULTS: In 30 surgically excised GC tissues, the overexpression rate of COX-2, the low expression rate of hMLH1 and hMSH2 were 66.7%, 40% and 33.3%, respectively. Significant differences were found when compared with those of adjacent normal mucosa (P < 0.05). MSI was detected in 13 GC. The number of MSI-H (MSI-High, > or = 2 loci), MSI-L (MSI-Low, only one locus), and MSS (microsatellite stable) were 9, 4 and 17, respectively. The number of low expression rates of COX-2, hMLH1 and hMSH2 in MSI-H were 6, 8 and 5, respectively. There were significant differences compared to that of MSS (P < 0.05). CONCLUSION: The results suggest that microsatellite instability pathway is probably involved in the carcinogenesis of gastric carcinoma, which is frequently accompanied by low expression of hMLH1 and hMSH2, and may be also by low expression of COX-2.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Selection pressure-driven aerobic granulation in a sequencing batch reactor.

In recent years, the research on aerobic granulation has been intensive. So far, almost all aerobic granules can form only in sequencing batch reactors (SBR), while the reason is not yet understood. This paper attempts to review the factors involved in aerobic granulation in SBR, including substrate composition, organic loading rate, hydrodynamic shear force, feast-famine regime, feeding strategy, dissolved oxygen, reactor configuration, solids retention time, cycle time, settling time and exchange ratio. The major selection pressures responsible for aerobic granulation are identified as the settling time and exchange ratio. A concept of the minimal settling velocity of bioparticles is proposed; and it is quantitatively demonstrated that the effects of settling time and exchange ratio on aerobic granulation in SBR can be interpreted and unified on the basis of this concept very well. It appears that the formation and characteristics of aerobic granules can be manipulated through properly adjusting either the settling time or the exchange ratio in SBR. Consequently, theoretical and experimental evidence point to the fact that aerobic granulation is a selection pressure-driven cell-to-cell immobilization process.

Bacteria, Aerobic↗