Biomedical subjects

Z Zhou

Publications and source records attributed to Z Zhou.

At least 199 records · Page 11Linked to original sources

PubMed2000

[In situ time-resolved FTIR studies of HCOOH oxidation on Pt(100)/Sb electrodes].

The electrocatalytic oxidation of formic acid on Pt(100)/Sb electrodes of different coverage of Sb was investigated by using electrochemical techniques and in situ time-resolve FTIRS. The results demonstrated that the dissociative adsorption of formic acid was inhibited by the presence of Sbad on Pt(100) surface, as a consequence HCOOH can be oxidized directly into CO2 via reactive intermediates. The rate of oxidation of formic acid varied with the coverage of Sbad. It was revealed that at a Sbad coverage of 0.24 the Pt(100)/Sb electrode exhibited the highest electrocatalytic activity for HCOOH oxidation.

English Abstract↗

PubMed2000

[In-situ FTIR spectroscopic studies of electro oxidation of ethanol in alkaline media at a nm-Pt/GC electrode].

The electro-oxidation of ethanol on a nm-Pt/GC electrode in alkaline solutions was investigated by using cyclic Voltammetry and in-situ FTIR spectroscopy. The results demonstrated that the main product of ethanol oxidation was CH3COO-, only small quantity of CH3CHO was determined simultaneously. In contrast with the dual path reaction mechanism for the oxidation of ethanol in acid media, the oxidation of ethanol in alkaline media was revealed via the intermediate process of dissociative adsorption.

English Abstract↗

PubMed2000

[In situ FTIR spectrocopic studies of CO and CN- adsorbed on electrode of nanometer thin film of palladium in alkaline solutions].

The adsorption and coadsorption of CO and CN- on electrode of nanometer thin film of palladium (nm-Pd/GC) was studied by using in situ FTIR spectroscopy. The results demonstrated that the nm-Pd/GC electrode exhibited abnormal infrared effects (AIREs) in alkaline solutions as in acid solutions. The characters of AIREs, i.e., the inversion of the direction of IR band, the augmentation of FWHM and the significant enhancement of IR absorption by adsorbed species were observed in all cases of adsorption and coadsorption of CO and CN-. It has been illustrated that strong interaction is existed between adsorbed CO and CN- on nm-Pd/GC surface. The study has contributed towards understanding the surface processes of chemisorption as well as to reveal the origin of nanometer size-effects of thin film materials.

English Abstract↗

PubMed2000

[In situ FTIR spectrocopic investigations of 1,3-butanediol oxidation on Sb and S modified Pt electrodes].

In the present paper, we studied the surface structure effect of Pt electrode modified with antimony and sulfur adatoms towards 1,3-Butanediol oxidation. The results demonstrated that the modification of Sb and S both inhibited the dissociative adsorption of 1,3-Butanediol into CO, which is the main source of self-poisoning in electrocatalysis of small organic molecules. At lower potentials, the principal oxidation pathway of 1,3-Butanediol on Pt/Sbad electrode is towards the production of C=O. However, at higher potentials, the products of CO2 increased. The presence of S(ad) inhibited the oxidation of 1,3-BD at low potentials(< 0.8 V), and yield mainly acid species as products at higher potentials(> 0.8 V).

Antimony↗

PubMed1999

Correction of defective protein trafficking of a mutant HERG potassium channel in human long QT syndrome. Pharmacological and temperature effects.

The chromosome 7-linked form of congenital long QT syndrome (LQT2) is caused by mutations in the human ether-a-go-go-related gene (HERG) that encodes the rapidly activating delayed rectifier potassium channel. One mechanism for the loss of normal channel function in LQT2 is defective protein trafficking, which results in the failure of the channel protein to reach the plasma membrane. Here we show that the N470D LQT2 mutant protein is trafficking-deficient when expressed at 37 degrees C in HEK293 cells, whereas at 27 degrees C its trafficking to the plasma membrane and channel function are markedly improved. We further show that the antiarrhythmic drug E-4031, which selectively blocks HERG channels, also corrects defective protein trafficking of the N470D mutant and can restore the generation of HERG current. Similar findings were obtained with the drugs astemizole and cisapride, as well as with high concentrations of glycerol. The effect of E-4031 on HERG protein trafficking was concentration-dependent and required low drug concentrations (saturation present at 5 microM), developed rapidly with drug exposure, and occurred post-translationally. These findings suggest that protein misfolding leading to defective trafficking of some HERG LQT mutations may be corrected by specific pharmacological strategies.

Anti-Arrhythmia Agents↗

PubMed1999

[Production of HBV surface antigen-specific target cell].

OBJECTIVE: To analyze the hepatitis B virus surface antigen (HBsAg)-specific cytotoxic T-cell (CTL) response during hepatitis development and investigate the effect of some factors on CTL response. METHODS: The recombinant retrovirus plasmid PLXSN-S was tranferred into PA317 by electroporation and the pseudoviruses produced from PA317 were used to infect EL4. Clones which highly expressed HBsAg were selected with limited dilution. RESULTS: A clone expressing-HBsAg the highest (A = 0.85 in supernatant at 48th hour) was obtained which steadly expressed HBsAg in vitro after at least 100 passages. It worked very well when used as target cells in CTL response after C57 mice immunized with PLXSN-S and recombinant adenovirus vector (rAdv-B7-2-S). CONCLUSION: We constructed HBsAg-specific target cell line which steadly expressed HBsAg. It may play an important role in HBsAg CTL response and immunopathogenetic mechanisms of hepatitis B.

Animals↗

PubMed1999

Adenovirus-mediated human topoisomerase IIalpha gene transfer increases the sensitivity of etoposide-resistant human breast cancer cells.

Cellular resistance to chemotherapeutic agents is attributable to several mechanisms, including alteration of topoisomerase IIalpha (topo IIalpha) gene expression. Etoposide-resistant MDA-VP human breast cancer cells express lower amounts of enzymatically active and drug-sensitive topo IIalpha than do MDA parent cells, suggesting that the low level of topo IIalpha is the mechanism of resistance. To determine whether transfer of a normal topo IIalpha gene into MDA-VP cells can increase topo IIalpha gene expression, topo IIalpha protein production, and cell sensitivity to etoposide, a recombinant adenovirus, Ad-hTopoIIalpha, containing the human topo IIalpha gene, was constructed. The shuttle vector pAvCvSv-hTopIIalpha was constructed and co-transfected with the pBHG10 packaging vector into 293 cells. Infectious recombinant adenovirus plaques were isolated and purified. Presence of the topo IIalpha gene was confirmed by PCR and restriction enzyme digestion. After infection with Ad-hTopoIIalpha, topo IIalpha mRNA expression in MDA-VP cells increased 7.4-fold, topo IIalpha protein production increased 5.9-fold, and sensitivity to etoposide was enhanced 4.5-fold compared with control transfected cells. Infection of normal human embryonic lung cells and human fibroblast cells with Ad-hTopoIIalpha did not enhance the expression of topo IIalpha or sensitivity to etoposide. Viral uptake was comparable in the MDA-VP and normal cell lines. These data suggest that topo IIalpha gene transfer using an adenoviral vector can selectively increase etoposide sensitivity in drug-resistant tumor cells and may enhance the therapeutic index of etoposide.

Adenoviridae↗

PubMed1999

Pulmonary epithelial sodium-channel dysfunction and excess airway liquid in pseudohypoaldosteronism.

BACKGROUND: Active sodium absorption is the dominant mechanism of ion transport in airway epithelium, but its role in pulmonary physiology and airway host defense is unknown. To address this question, we studied the function of airway epithelial cells and determined the frequency of pulmonary symptoms in patients with systemic pseudohypoaldosteronism, a salt-losing disorder caused by loss-of-function mutations in the genes for the epithelial sodium channel. METHODS: In nine patients 1.5 to 22 years of age who had systemic pseudohypoaldosteronism, we tested for mutations in the genes for the epithelial sodium channel, estimated the rate of sodium transport in the airway, determined the volume and ion composition of airway surface liquid, reviewed clinical features, collected laboratory data pertinent to pulmonary function, and, in three adults, measured mucociliary clearance. RESULTS: The patients with systemic pseudohypoaldosteronism had loss-of-function mutations in the genes for the epithelial sodium-channel subunits, no sodium absorption from airway surfaces, and a volume of airway surface liquid that was more than twice the normal value. The mean (+/-SE) mucociliary transport rate was higher in the 3 adult patients than in 12 normal subjects (2.0+/-0.7 vs. 0.5+/-0.3 percent per minute, P=0.009). Young patients (those five years of age or less) all had recurrent episodes of chest congestion, coughing, and wheezing, but no airway infections with Staphylococcus aureus or Pseudomonas aeruginosa. Older patients (those more than five years of age) had less frequent respiratory symptoms. CONCLUSIONS: Patients with systemic pseudohypoaldosteronism fail to absorb liquid from airway surfaces; the result is an increased volume of liquid in the airways. These results demonstrate that sodium transport has a role in regulating the volume of liquid on airway surfaces.

Absorption↗

PubMed1999

Lipid A modifications characteristic of Salmonella typhimurium are induced by NH4VO3 in Escherichia coli K12. Detection of 4-amino-4-deoxy-L-arabinose, phosphoethanolamine and palmitate.

Two-thirds of the lipid A in wild-type Escherichia coli K12 is a hexa-acylated disaccharide of glucosamine in which monophosphate groups are attached at positions 1 and 4'. The remaining lipid A contains a monophosphate substituent at position 4' and a pyrophosphate moiety at position 1. The biosynthesis of the 1-pyrophosphate unit is unknown. Its presence is associated with lipid A translocation to the outer membrane (Zhou, Z., White, K. A., Polissi, A., Georgopoulos, C., and Raetz, C. R. H. (1998) J. Biol. Chem. 273, 12466-12475). To determine if a phosphatase regulates the amount of the lipid A 1-pyrophosphate, we grew cells in broth containing nonspecific phosphatase inhibitors. Na2WO4 and sodium fluoride increased the relative amount of the 1-pyrophosphate slightly. Remarkably, NH4VO3-treated cells generated almost no 1-pyrophosphate, but made six major new lipid A derivatives (EV1 to EV6). Matrix-assisted laser desorption ionization/time of flight mass spectrometry of purified EV1 to EV6 indicated that these compounds were lipid A species substituted singly or in combination with palmitoyl, phosphoethanolamine, and/or aminodeoxypentose residues. The aminodeoxypentose residue was released by incubation in chloroform/methanol (4:1, v/v) at 25 degrees C, and was characterized by 1H NMR spectroscopy. The chemical shifts and vicinal coupling constants of the two anomers of the aminodeoxypentose released from EV3 closely resembled those of synthetic 4-amino-4-deoxy-L-arabinose. NH4VO3-induced lipid A modification did not require the PhoP/PhoQ two-component regulatory system, and also occurred in E. coli msbB or htrB mutants. The lipid A variants that accumulate in NH4VO3-treated E. coli K12 are the same as many of those normally found in untreated Salmonella typhimurium and Salmonella minnesota, demonstrating that E. coli K12 has latent enzyme systems for synthesizing these important derivatives.

Amino Sugars↗

PubMed1999

[Relationship between unhealthy dietary behavior and blood lipids and lipid peroxides in coronary heart disease patients].

The effects of unhealthy dietary behavior on blood lipids(TC, TG, HDL-C, LDL-C) and lipid peroxides (LPO) and the occurrence of coronary heart disease(CHD) were measured in 97 CHD patients and 97 controls without any clinical appearance of cardiovascular or cerebrovascular diseases. The results showed that the serum level of TC, TG, HDL-C, LDL-C and LPO were significantly higher in CHD group than control group. More unhealthy dietary behavior was observed in CHD group than in control group. The odds ratio of the population with more than 3 items of unhealthy dietary behavior was 3.88. The results of this study suggested that unhealthy dietary behavior might play an important role in increasing the risk of CHD.

Adult↗

PubMed1999

Recombinant SFD isoforms activate vacuolar proton pumps.

The vacuolar proton pump of clathrin-coated vesicles is composed of two general sectors, a cytosolic, ATP hydrolytic domain (V1) and an intramembranous proton channel, V0. V1 is comprised of 8-9 subunits including polypeptides of 50 and 57 kDa, termed SFD (Sub Fifty-eight-kDa Doublet). Although SFD is essential to the activation of ATPase and proton pumping activities catalyzed by holoenzyme, its constituent polypeptides have not been separated to determine their respective roles in ATPase functions. Recent molecular characterization of these subunits revealed that they are isoforms that arise through an alternative splicing mechanism (Zhou, Z., Peng, S.-B., Crider, B.P., Slaughter, C., Xie, X.S., and Stone, D.K. (1998) J. Biol. Chem. 273, 5878-5884). To determine the functional characteristics of the 57-kDa (SFDalpha)1 and 50-kDa (SFDbeta) isoforms, we expressed these proteins in Escherichia coli. We determined that purified recombinant proteins, rSFDalpha and rSFDbeta, when reassembled with SFD-depleted holoenzyme, are functionally interchangeable in restoration of ATPase and proton pumping activities. In addition, we determined that the V-pump of chromaffin granules has only the SFDalpha isoform in its native state and that rSFDalpha and rSFDbeta are equally effective in restoring ATPase and proton pumping activities to SFD-depleted enzyme. Finally, we found that SFDalpha and SFDbeta structurally interact not only with V1, but also withV0, indicating that these activator subunits may play both structural and functional roles in coupling ATP hydrolysis to proton flow.

Acridine Orange↗

PubMed1999

Mechanism of block and identification of the verapamil binding domain to HERG potassium channels.

Calcium channel antagonists have diverse effects on cardiac electrophysiology. We studied the effects of verapamil, diltiazem, and nifedipine on HERG K+ channels that encode IKr in native heart cells. In our experiments, verapamil caused high-affinity block of HERG current (IC50=143.0 nmol/L), a value close to those reported for verapamil block of L-type Ca2+ channels, whereas diltiazem weakly blocked HERG current (IC50=17.3 micromol/L), and nifedipine did not block HERG current. Verapamil block of HERG channels was use and frequency dependent, and verapamil unbound from HERG channels at voltages near the normal cardiac cell resting potential or with drug washout. Block of HERG current by verapamil was reduced by lowering pHO, which decreases the proportion of drug in the membrane-permeable neutral form. N-methyl-verapamil, a membrane-impermeable, permanently charged verapamil analogue, blocked HERG channels only when applied intracellularly. Verapamil antagonized dofetilide block of HERG channels, which suggests that they may share a common binding site. The C-type inactivation-deficient mutations, Ser620Thr and Ser631Ala, reduced verapamil block, which is consistent with a role for C-type inactivation in high-affinity drug block, although the Ser620Thr mutation decreased verapamil block 20-fold more than the Ser631Ala mutation. Our findings suggest that verapamil enters the cell membrane in the neutral form to act at a site within the pore accessible from the intracellular side of the cell membrane, possibly involving the serine at position 620. Thus, verapamil shares high-affinity HERG channel blocking properties with other class III antiarrhythmic drugs, and this may contribute to its antiarrhythmic mechanism.

Anti-Arrhythmia Agents↗

PubMed1999

Novel mechanism associated with an inherited cardiac arrhythmia: defective protein trafficking by the mutant HERG (G601S) potassium channel.

BACKGROUND: The congenital long-QT syndrome (LQTS) is an inherited disorder characterized by a prolonged cardiac action potential and a QT interval that leads to arrhythmia. Mutations in the human ether-a-go-go-related gene (HERG), which encodes the rapidly activating component of the delayed rectifier current (IKr), cause chromosome 7-linked LQTS (LQT2). Studies of mutant HERG channels in heterologous systems indicate that the mechanisms mediating LQT2 are varied and include mutant subunits that form channels with altered kinetic properties or nonfunctional mutant subunits. We recently reported a novel missense mutation of HERG (G601S) in an LQTS family that we have characterized in the present work. METHODS AND RESULTS: To elucidate the electrophysiological properties of the G601S mutant channels, we expressed these channels in mammalian cells and Xenopus oocytes. The G601S mutant produced less current than wild-type channels but exhibited no change in kinetic properties or dominant-negative suppression when coexpressed with wild-type subunits. To examine the cellular trafficking of mutant HERG channel subunits, enhanced green fluorescent protein tagging and Western blot analyses were performed. These showed deficient protein trafficking of the G601S mutant to the plasma membrane. CONCLUSIONS: Our results from both the Xenopus oocyte and HEK293 cell expression systems and green fluorescent protein tagging and Western blot analyses support the conclusion that the G601S mutant is a hypomorphic mutation, resulting in a reduced current amplitude. Thus, it represents a novel mechanism underlying LQT2.

Animals↗

PubMed1999

Identification and reconstitution of an isoform of the 116-kDa subunit of the vacuolar proton translocating ATPase.

We have identified a cDNA encoding an isoform of the 116-kDa subunit of the bovine vacuolar proton translocating ATPase. The predicted protein sequence of the new isoform, designated a2, consists of 854 amino acids with a calculated molecular mass of 98,010 Da; it has approximately 50% identity to the original isoform (a1) we described (Peng, S.-B., Crider, B. P., Xie, X.-S., and Stone, D.K. (1994) J. Biol. Chem. 269, 17262-17266). Sequence comparison indicates that the a2 isoform is the bovine homologue of a 116-kDa polypeptide identified in mouse as an immune regulatory factor (Lee, C.-K., Ghoshal, K., and Beaman, K.D. (1990) Mol. Immunol. 27, 1137-1144). The bovine a1 and a2 isoforms share strikingly similar structures with hydrophilic amino-terminal halves that are composed of more than 30% charged residues and hydrophobic carboxyl-terminal halves that contain 6-8 transmembrane regions. Northern blot analysis demonstrates that isoform a2 is highly expressed in lung, kidney, and spleen. To determine the possible role of the a2 isoform in vacuolar proton pump function, we purified from bovine lung a vacuolar pump proton channel (VO) containing isoform a2. This VO conducts bafilomycin-sensitive proton flow after reconstitution and acid activation, and supports proton pumping activity after assembly with the catalytic sector (V1) of vacuolar-type proton translocating ATPase (V-ATPase) and sub-58-kDa doublet, a 50-57-kDa polypeptide heterodimer required for V-ATPase function. These data indicate that the a2 isoform of the 116-kDa polypeptide functions as part of the proton channel of V-ATPases.

Amino Acid Sequence↗

PubMed1999

A study of heat shock protein 27 in endometrial carcinoma.

OBJECTIVE: Heat shock protein 27 (HSP27) is a relatively small protein produced in response to pathophysiologic stress. The purpose of this study was to determine prospectively whether HSP27 was associated with known prognostic factors in patients with endometrial carcinoma. METHODS: One hundred fifty-three consecutive patients with endometrial carcinoma were studied. Slides were prepared from fresh tissue. HSP27 was analyzed using a semiquantitative measurement. Patient records were examined for FIGO stage, grade, depth of myometrial invasion, histology, lymphovascular space invasion, time to recurrence, and survival. RESULTS: The mean follow-up was 53 months (median 56 months, range 30-68 months). Endometrioid tumors showed significantly higher HSP27 staining than nonendometrioid tumors (P = 0.005). Patients alive at the conclusion of this study had significantly higher mean HSP27 staining than patients who were deceased (P < 0.001). Logistic regression revealed HSP27 staining (P = 0.02), FIGO stage (P = 0. 014), and lymphovascular space invasion (P = 0.046) to be independently predictive of survival. CONCLUSION: HSP27 staining is significantly higher in endometrioid than nonendometrioid tumors. HSP27 staining is an independent prognostic indicator in patients with endometrial carcinoma, the most common gynecologic malignancy in the United States.

Adult↗

PubMed1999

p53 expression as a prognostic indicator of 5-year survival in endometrial cancer.

BACKGROUND: One of the most common genetic alterations to occur in human cancers is an alteration of the p53 tumor suppressor gene. The purpose of this article was to build upon the authors' previous work with p53 and determine whether p53 was a prognostic indicator of 5-year survival. METHODS: One hundred thirty-seven consecutively surgically treated patients with endometrial cancer had their p53 expression studied by immunoperoxidase staining and quantified by image analysis. All patients were evaluable for 5-year survival. RESULTS: One hundred three patients had endometrioid adenocarcinoma; 6, adenosquamous carcinoma; 14, papillary serous carcinoma; 10, clear cell carcinoma; and 4, undifferentiated carcinoma. p53 expression ranged from 0.0 to 58.2% positive nuclear area with a mean of 11.5% (median 2.6%) for the cohort. For the patients with endometrioid carcinoma, the mean p53 expression was 7.1% while for the nonendometrioid tumors it was 24.6% (P<0.001). Fifty-nine of the 103 endometrioid tumors (57.3%) stained positive for p53 while 32 of the 34 nonendometrioid (94.1%) tumors stained positive (P<0.001). Increasing histologic grade correlated with an increasing p53 expression (P = 0.003). The percentage of tumors expressing p53 was found to be higher in FIGO stage II, III, and IV than in FIGO stage I cancer (P = 0.003). However, mean p53 expression did not differ between early (stage I) and advanced (stage II, III, and IV) cancers (P = 0.088). Utilizing 5-year survival as the endpoint for multivariate analysis, FIGO stage (P = 0.0028) and p53 expression (P<0.001) were the only independent prognostic indicators found. CONCLUSION: p53 expression is more commonly found in nonendometrioid than in endometrioid adenocarcinoma of the endometrium. It, along with FIGO stage, is an independent prognostic indicator of 5-year survival.

Adult↗

PubMed1999

MIB-1 in endometrial carcinoma: prognostic significance with 5-year follow-up.

OBJECTIVE: MIB-1, a monoclonal antibody to the Ki-67 antigen, has presumptively been shown to be predictive of recurrent disease in patients with endometrial cancer. In order to more conclusively establish whether MIB-1 staining can be used as a prognostic indicator of recurrent disease or survival, a larger group of patients with a minimum follow-up of 5 years was analyzed. METHODS: The tumors from 147 consecutive patients receiving primary surgical therapy for endometrial carcinoma were evaluated with the MIB-1 monoclonal antibody. Proliferation index was quantified by image analysis. Patients were followed for a minimum of 60 months. In addition to MIB-1 staining, histologic type, stage, grade, depth of invasion, lymphovascular space invasion, and peritoneal cytology were evaluated as prognostic indicators. RESULTS: Twenty-five of 147 patients died during the study period. MIB-1 staining was not significantly elevated in advanced (stage II, III, and IV) as opposed to early (stage I) carcinomas (P = 0.38). In patients whose tumor MIB-1 staining was less than 33.0%, no deaths occurred. By multivariate analysis, only MIB-1 staining (P < 0.001), FIGO stage (P = 0.005), and LVI (P = 0.005) were shown to be independent prognostic indicators predictive of survival. CONCLUSION: In this series of 147 consecutive patients with endometrial carcinoma, the monoclonal antibody MIB-1 was shown to be an independent prognostic indicator of 5-year survival. This follow-up further validates the previous work regarding the significance and potential usefulness of MIB-1 as a prognostic indicator.

Antibodies, Monoclonal↗

PubMed1999

Regulation of HSD17B1 and SRD5A1 in lymphocytes.

We previously reported lymphocyte expression of genes encoding enzymes required for steroid metabolism; however, only 17beta-HSD and 5alpha-reductase showed significant enzyme activity. We now investigate regulation of lymphocyte expression for genes encoding 17beta-HSD and 5alpha-reductase. Cultured human T and B lymphoid cell lines and peripheral blood mononuclear cells were treated with known regulators of steroidogenic gene expression including forskolin, PMA, ionomycin, various steroids, interleukin (IL)-4, and IL-6. Treatment with 10 or 50 microM forskolin resulted in a 20-60% reduction of expression for HSD17B1 (encoding 17beta-HSD I) in T and B lymphoid cell lines and peripheral blood mononuclear cells, although such a change was not observed in the expression of SRD5A1 (encoding 5alpha-reductase I). No significant changes were found when cells were treated for 24 h with various concentrations of PMA or ionomycin. Incubation with 10(-9) to 10(-7) M androstenedione or estradiol increased expression of HSD17B1, while testosterone decreased the expression of this gene. SRD5A1 expression was increased in the presence of 5alpha-DHT although no consistent changes were observed when the cells were treated with testosterone. Other steroids, including dexamethasone, progesterone, and 6-hydroxypregnanolone, produced no effects on expression of either HSD17B1 or SRD5A1. Treatment with 0.1-10 ng/ml of IL-4 or IL-6 also did not effect significant changes in gene expression. These data implicate the involvement of the cAMP-protein kinase signal transduction pathway in regulating lymphocyte expression of HSD17B1. Furthermore, it appears that lymphocyte HSD17B1 and SRD5A1 are regulated to some extent by specific steroids.

17-Hydroxysteroid Dehydrogenases↗