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Yu Liu

Publications and source records attributed to Yu Liu.

At least 217 records · Page 12Linked to original sources
PubMed2003

The role of cell hydrophobicity in the formation of aerobic granules.

Cell hydrophobicity is an important affinity force in cell self-immobilization and attachment processes. The role of cell hydrophobicity in the formation of aerobic granules has not been clear. Therefore, two series of experiments were conducted to investigate the role of cell hydrophobicity in the formation of aerobic heterotrophic and nitrifying granules in sequencing batch reactors, while the effects of shear strength, hydraulic selection pressure, and organic loading rate on the cell hydrophobicity were also studied. Results showed that the formations of heterotrophic and nitrifying granules were associated very closely with the cell hydrophobicity. The hydrophobicity of granular sludge was nearly twofold higher than that of conventional bioflocs. A high shear force or hydraulic selection pressure imposed on microorganisms resulted in a significant increase in the cell hydrophobicity, while the cell hydrophobicity seemed not to be sensitive to the changes in the organic loading rates in the range studied. In conclusion, the cell hydrophobicity could induce and further strengthen cell-cell interaction, and might be a main triggering force to initiate the granulation of heterotrophic and nitrifying bacteria.

Aerobiosis↗
PubMed2003

A thermodynamic interpretation of the Monod equation.

The Monod equation for microbial growth is purely empirical, and the theoretical basis of this model stays unclear. Similar to any chemical reactions, overall microbial growth process is dependent upon the changes in free energy. This study showed that the Monod equation could be interpreted in a thermodynamic sense very well. It was probably for the first time demonstrated that the Monod constant ( K(s)) was inversely related to the equilibrium constant of the overall microbial growth process.

Bacteria↗
PubMed2003

Mechanisms and models for anaerobic granulation in upflow anaerobic sludge blanket reactor.

Upflow anaerobic sludge blanket (UASB) reactor has been employed in industrial and municipal wastewater treatment for decades. However, the long start-up period required for the development of anaerobic granules seriously limits the application of this technology. In order to develop the strategy for rapid UASB start-up, the mechanisms for anaerobic granulation should be understood. This paper attempts to provide a up-to-date review on the existing mechanisms and models for anaerobic granulation in the UASB reactor, which include inert nuclei model, selection pressure model, multi-valence positive ion-bonding model, synthetic and natural polymer-bonding model, Capetown's model, spaghetti theory, syntrophic microcolony model, multi-layer model, secondary minimum adhesion model, local dehydration and hydrophobic interaction model, surface tension model, proton translocation-dehydration theory, cellular automaton model and cell-to-cell communication model. Based on those previous works, a general model for anaerobic granulation is also proposed. It is expected that this paper would be helpful for researchers to further develop a unified theory for anaerobic granulation and technology for expediting the formation of the UASB granules.

Bacteria, Anaerobic↗
PubMed2003

Selective binding of chiral molecules of cinchona alkaloid by beta- and gamma-cyclodextrins and organoselenium-bridged bis(beta-cyclodextrin)s.

The inclusion complexation behavior of chiral members of cinchona alkaloid with beta- and gamma-cyclodextrins (1 and 2) and 6,6(')-trimethylenediseleno-bridged bis(beta-cyclodextrin) (3) was assessed by means of fluorescence and 2D-NMR spectroscopy. The spectrofluorometric titrations have been performed in aqueous buffer solution (pH 7.20) at 25.0 degrees C to determine the stability constants of the inclusion complexation of 1-3 with guest molecules (i.e., cinchonine, cinchonidine, quinine, and quinidine) in order to quantitatively investigate the molecular selective binding ability. The stability constants of the resulting complexes of 2 with guest molecules are larger than that of 1. As a result of cooperative binding, the stability constants of inclusion complexation of dimeric beta-cyclodextrin 3 with cinchonidine and cinchonine are higher than that of parent 1 by factor of 4.5 and 2.4, respectively. These results are discussed from the viewpoint of the size-fit and geometric complementary relationship between the host and guest.

Binding Sites↗
PubMed2003

Chemically reduced excess sludge production in the activated sludge process.

Excess sludge production from wastewater biological treatment process is highly, and the disposal of excess sludge will be forbidden in a near future, thus increased attention has been turned to look into potential technology for sludge reduction. Recently, some novel sludge reduction techniques have been developed based on chemical oxidation and metabolic uncoupling. This paper attempts to review those chemical-assisted sludge reduction processes, including sludge alkaline-thermal treatment, activated sludge-ozonation process, chlorination-combined activated sludge process, sludge reduction by metabolic uncouplers and high dissolved oxygen activated sludge process. In these combined activated sludge processes, excess sludge production can be reduced up to 100% without significant effect on process efficiency and stability. This paper would be useful when one is looking for appropriate environmentally and economically acceptable solutions for reducing or minimizing excess sludge production from wastewater biological treatment process.

Alkalies↗
PubMed2003

Investigation of nanocomposites based on semi-interpenetrating network of [L-poly (epsilon-caprolactone)]/[net-poly (epsilon-caprolactone)] and hydroxyapatite nanocrystals.

In this paper the semi-interpenetrating network (semi-IPN) technique was used for the first time to prepare bone implant composites containing hydroxyapatite (HAP) nanocrystals. The prepared nanocomposites are expected to combine several property advantages including good mechanical strength, modified degradation rate and excellent osteoconductivity. The semi-IPN matrix based on the linear poly (epsilon-caprolactone) (L-PCL) and the network poly (epsilon-caprolactone) (net-PCL) structures are revealed to be phase separation structures. The morphology of net-PCL is featured by intracrosslinked microdomains (1-10 microm) that further interconnect with each other to form the network over the whole sample. The net-PCL component is totally amorphous at room temperature for the nanocomposites containing HAP up to 12.3 wt%. Further, the crystallinity of L-PCL is greatly decreased due to the presence of net-PCL as compared with that for pure L-PCL. The incorporation of L-PCL into the net-PCL network could significantly improve the mechanical properties of pure net-PCL. A great improvement in mechanical properties is observed for the nanocomposites if the HAP content is increased to 15.8 wt%. This transition is in agreement with that the net-PCL component changes from amorphous state to crystalline state at this composition.

Biocompatible Materials↗
PubMed2003

The association of E-cadherin expression and the methylation status of the E-cadherin gene in nasopharyngeal carcinoma cells.

Loss of E-cadherin (E-cad) has been associated with progression and poor survival in nasopharyngeal carcinoma (NPC). In this study, we investigated the role of methylation on E-cad inactivation in NPC cell lines, as well as in NPC tissue samples. Using 6 NPC cell lines, we found that methylation of the E-cad 5' CpG island promoter region was correlated with the loss of both mRNA and E-cad protein expression in these cell lines. In addition, using 29 NPC and 10 non-malignant nasopharyngeal samples, we also observed 5' CpG methylation of the E-cad gene in 52% (15 out of 29) NPC samples, but in only 10% (1 out of 10) of the non-malignant nasopharyngeal tissues. Our findings indicate that 5' CpG island methylation of the E-cad gene may play an important part in the inactivation of E-cad in NPC. Our results also suggest that reducing the methylation of the E-cad gene may be a potential therapeutic strategy for NPC.

Blotting, Western↗
PubMed2003

Inhibitive effect of zinc ion on fatty acid synthase from chicken liver.

Fatty acid synthase (FAS; acyl-CoA:malonyl-CoA C-acyltransferase [decarboxylating, oxoacyl- and enoyl-reducing and thioester-hydrolyzing], EC 2.3.1.85) is an important enzyme participating in energy metabolism in vivo which is related to adiposis and cancer [Cancer Lett. 167 (1) (2001) 99; Nat. Med. 8 (4) (2002) 335]. Tests of fast- and slow-binding inhibitions showed that fatty acid synthase of chicken liver is rapidly and irreversibly inactivated by low Zn(2+) concentrations. Electrophoresis and FPLC results showed that FAS cross-links occurred in the presence of high Zn(2+) concentrations (>4 microM) which may be another reason that FAS lost its activity. The modification velocity of FAS by DTNB decreased with increasing Zn(2+) concentration, which confirmed that Zn(2+) interacted with SH groups. Substrate protective experiments and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that all three substrates tested had some protective effects on FAS in the presence of Zn(2+), and malonyl-CoA was the most effective of the three substrates. In the presence of malonyl-CoA, the activity loss of FAS decreased sharply and almost no cross-link was observed in SDS-PAGE. This suggests that the phosphopantetheine SH group is the critical group in the cross-link and inhibition of FAS in the presence of Zn(2+).

Animals↗
PubMed2003

Ca2+ augmentation for enhancement of aerobically grown microbial granules in sludge blanket reactors.

Two sequential aerobic sludge blanket reactors were concurrently operated to examine the effect of Ca2+ augmentation on aerobic granulation. Augmentation with 100 mg Ca2+ l(-1) significantly decreased the time to cultivate aerobically grown microbial granules from 32 d to 16 d. Ca2+-fed granules were denser and more compact, showed better settling and strength characteristics, and had higher polysaccharide contents.

Aerobiosis↗
PubMed2003

Kinetic responses of activated sludge microorganisms to individual and joint copper and zinc.

The individual and joint effects of copper and zinc on the growth kinetics of activated sludge microorganisms were studied in batch reactors fed with glucose as sole carbon source. The observed specific growth rate, substrate utilization rate and removal efficiency were determined at different concentrations of individual and joint Cu and Zn. Activated sludge microorganisms showed different kinetic responses to Cu and Zn, and the Haldane model seemed applicable for the inhibitory effect of Zn, while a first-order kinetics for Cu. Compared to Zn, Cu exhibited high toxicity to activated sludge microorganisms even at a very low concentration of 1.0 mg/dm3. However, Zn concentrations less than 40 mg/dm3 would stimulate the growth of activated sludge microorganism, and Zn acted as inhibitory chemical only at concentrations above this value. The combined effect of Cu and Zn could be regarded as neither synergistic nor antagonistic action.

Bacteria↗
PubMed2003

Alterations of biologic properties and gene expression in nasopharyngeal epithelial cells by the Epstein-Barr virus-encoded latent membrane protein 1.

Undifferentiated nasopharyngeal carcinoma (NPC) is closely associated with EBV infection, and the EBV-encoded latent membrane protein 1 (LMP1) is frequently detected in NPC. However, little is known about the pathologic roles of LMP1 in this disease. Recently, we reported the morphologic transformation and increased expression of the LAMC2 and ITGalpha6 genes in LMP1-expressing NPC cell lines. In this study, we further examine the effects of LMP1 in an immortalized nasopharyngeal epithelial cell line called NP69. This cell line was established from primary nonmalignant nasopharyngeal epithelial cells and may represent a model of premalignant nasopharyngeal epithelial cells. LMP1 induced many phenotypic changes in NP69 cells. These include morphologic transformation, increased cell proliferation, anchorage-independent growth, resistance to serum free-induced cell death, and enhanced cell migration and invasion. In addition, expression array analysis identified 28 genes that demonstrated a more than 2-fold difference in expression of NP69 cells expressing LMP1 when compared with a vector control. Two of the up-regulated genes (VEGF and vimentin) identified have been previously reported as LMP1 targets. The majority of the identified genes are associated with cell growth, differentiation, cell shape, and invasion. The present findings support the proposed roles of LMP1 in promoting cell transformation, migration, and invasion in premalignant nasopharyngeal epithelial cells. The present study also indicates the activation of the Ras/MAPK pathway in LMP1-expressing cells, which may be involved in mediating some of the transforming effects of LMP1 observed in nasopharyngeal epithelial cells.

Blotting, Western↗
PubMed2003

Translocation of annexin I from cellular membrane to the nuclear membrane in human esophageal squamous cell carcinoma.

AIM: To investigate the alteration of the annexin I subcellular localization in esophageal squamous cell carcinoma (ESCC) and the correlation between the translocation and the tumorigenesis of ESCC. METHODS: The protein localization of annexin I was detected in both human ESCC tissues and cell line via the indirect immunofluorescence strategy. RESULTS: In the normal esophageal epithelia the annexin I was mainly located on the plasma membrane and formed a consecutive typical trammels net. Annexin I protein also expressed dispersively in cytoplasm and the nuclei without specific localization on the nuclear membrane. In esophageal cancer annexin I decreased very sharply with scattered disappearance on the cellular membrane, however it translocated and highly expressed on the nuclear membrane, which was never found in normal esophageal epithelia. In cultured esophageal cancer cell line annexin I protein was also focused on the nuclear membrane, which was consistent with the result from esophageal cancer tissues. CONCLUSION: This observation suggests that the translocation of annexin I protein in ESCC may correlate with the tumorigenesis of the esophageal cancer.

Annexin A1↗
PubMed2003

Loss of clusterin both in serum and tissue correlates with the tumorigenesis of esophageal squamous cell carcinoma via proteomics approaches.

AIM: To identify the differentially secreted proteins or polypeptides associated with tumorigenesis of esophageal squamous cell carcinoma (ESCC) from serum and to find potential tumor secreted biomarkers. METHODS: Proteins from human ESCC tissue and its matched adjacent normal tissue; pre-surgery and post-surgery serum; and pre-surgery and normal control serum were separated by two-dimensional electrophoresis (2-DE) to identify differentially expressed proteins. The silver-stained 2-DE were scanned with digital ImageScanner and analyzed with ImageMaster 2D Elite 3.10 software. A cluster of protein spots differentially expressed were selected and identified with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). One of the differentially expressed proteins, clusterin, was down-regulated in cancer tissue and pre-surgery serum, but it was reversed in post-surgery serum. The results were confirmed by semi-quantitative reverse-transcription (RT)-PCR and western blot. RESULTS: Comparisons of the protein spots identified on the 2-DE maps from human matched sera showed that some proteins were differentially expressed, with most of them showing no differences in composition, shape or density. Being analyzed by MALDI-TOF-MS and database searching, clusterin was differentially expressed and down-regulated in both cancer tissue and pre-surgery serum compared with their counterparts. The results were also validated by RT-PCR and western blot. CONCLUSION: The differentially expressed clusterin may play a key role during tumorigenesis of ESCC. The 2DE-MS based proteomic approach is one of the powerful tools for discovery of secreted markers from peripheral.

Aged↗
PubMed2003

The effect of lumbrokinase on P-selectin and E-selectin in cerebral ischemia model of rat.

PURPOSE: To find the effect of lumbrokinase (LK) on P-selectin and E-selectin in ischemic rats. METHODS: Male healthy Spragur-Dawley rats weighing 180-220 g (n = 90) were divided into 4 groups: (1) normal control group (n = 5), (2) sham-operated group (n = 35), (3) ischemic group (n = 35), (4) LK group (n = 15). LK 10 mg/kg (2000 UK activity of LK) was given by intraperitoneal injection in the LK group 30 minutes before experiment. Same volume of normal saline was given in the sham-operated group and ischemic group. The ischemic model was made by modified Haruo Nagasawa's method. Immunohistochemistry was used to observe the P-selectin and E-selectin positive cells in the ischemic region. RESULTS: P-selectin and E-selectin positive cells in ischemic regions were observed in the ischemic group, and the peak of expression was at 6 hours and 12 hours, respectively. The similar changes were not observed in normal control group. There were only a few positive cells in the sham-operated group. In LK group, the P-selectin and E-selectin positive cells were significantly less than those in the ischemic group (P < 0.05 at 3 hours after the onset, P < 0.01 at 6 hours and P < 0.01 at 12 hours, respectively). CONCLUSIONS: LK might significantly decrease the immunoreactions of P-selectin and E-selectin in ischemic lesion.

Animals↗
PubMed2003

[Plasma haemostatic and fibrinolytic activities and their relationship to levels of serum lipids and apolipoproteins in endogenous hypertriglyceridemic patients].

OBJECTIVE: To investigate the changes of plasma haemostatic and fibrinolytic activities and their relationship to serum lipids and apolipoproteins levels in endogenous hypertriglyceridemic patients. METHODS: We determined the plasma prothrombin time(PT), activated partial thromplastin time(APTT), activity of tissue-type plasminogen activator(t-PA), activity of plasminogen activator inhibitor-1 (PAI-1) and fibrinogen(Fg) level of 24 endogenous hyper-triglyceridemic patients and 34 healthy controls, and observed their relationship to serum lipids and apolipoproteins. RESULTS: The PT and APTT of patients with hypertriglyceridemia were obviously shorter than those of control subjects (P < 0.01, P < 0.05); PAI-1 of patients was significant higher than that of control group (P < 0.01); there was no statistically significant difference in t-PAI-1: a between the control subjects and the hypertriglyceridemic patients; the levels of Fg in patients was 27% higher than that in healthy control (P < 0.01). The correlation analysis indicated that PT was significantly associated with the levels of plasma HDL-C (r = 0.445, P < 0.01), and inversely associated with the levels of plasma TG, apoC III, BG and BMI (r = -0.294, -0.320, -0.282, -0.272, P < 0.05); APTT was negatively correlated with serum TG and apoC III levels (r = -0.345, -0.320, P < 0.05); t-PA was negatively correlated with BG levels (r = -0.336, P < 0.01). PAI-1 and Fg levels were strongly correlated with serum TG, apoC II, C III and E levels (r = 0.400, 0.408, 0.497, 0.454, P < 0.01 and r = 0.642, 0.581, 0.673, 0.304, P < 0.01, respectively), and negatively correlated with HDL-C (r = -0.366, -0.524, P < 0.01). CONCLUSION: Increasing of coagulating activity and decreasing of fibrinolytic activity in hypertriglyceridemic patients were significantly associated with serum lipids and apolipoproteins levels.

Apolipoproteins↗
PubMed2003

[Polymorphism of insulin receptor substrate-1 gene in patients with coronary heart diseases].

OBJECTIVE: To explore the relationship between the polymorphism of insulin receptor substrate-1 (IRS-1) gene and coronary heart diseases in Chinese population. METHODS: A total of 113 patients with coronary heart diseases and 194 healthy Chengdu residents with less than 82 mmol/L of TG and 6.2 mmol/L of TC in fasting serum testing were selected and compared. The genotype and allele frequency of IRS-1 gene polymorphism was assayed by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). The serum lipids were measured by enzymatic kits. RESULTS: The GG genotype dominated in the IRS-1 gene with frequency of 0.960 and 0.985 for patients and healthy controls respectively. Difference appeared in R allele frequency (0.015 for healthy controls and 0.040 for patients, P = 0.05). Patients with genotype G/R had significantly higher level of serum TC and lower level of plasma glucose than patients with genotype G/G (P < 0.05). CONCLUSION: IRS-1 gene polymorphism is associated with coronary heart disease in Chinese population. The G/R and G/G genotype of IRS-1 gene contributes to the increasing of serum cholesterol and plasma glucose respectively.

Aged↗
PubMed2003

[Effect of androgen on erythropoietin in patients with hypogonadism].

OBJECTIVES: To observe the change of erythropoietin (EPO) in patients of hypogonadism who received androgen replacement treatment and explore the mechanism of androgen-induced increase of red blood cells and haemoglobin. METHODS: Eight patients with Klinefelter's syndrome, divided into two groups, received TU intramuscular injections of 500 mg or 1000 mg dose, respectively. After three months, seven patients received the second injection of crossover dose. Testosterone levels in serum were measured with RIA before and after the injections treatment. RBC count, impacted volume of blood cells and haemoglobin concentration were measured before treatment and 4, 8 weeks after treatment. At the same interval, EPO levels were measured with ELISA method. RESULTS: Development of the secondary sex characters was improved in all patients after the TU injection. Serum testosterone levels raised significantly and reached the peak one week after the injections. Effective level of testosterone lasted for over 6 weeks. RBC count, impacted volume of blood cells and haemoglobin increased at different degrees after TU injections, but these changes were not significant in statistic(P < 0.05). The increased levels remained for 8 weeks. EPO levels were elevated significantly (P < 0.01 or 0.05) after the TU injection(Pbat > 0.05). The second injection could still make the EPO level go up. CONCLUSIONS: Androgen replacement treatment can increase the EPO levels in patients of hypogonadism, which is one of the mechanism of RBC production increase.

Adolescent↗