Biomedical subjects

S Zhang

Publications and source records attributed to S Zhang.

At least 739 records · Page 41Linked to original sources

PubMed1998

[Study on the determination of trace mercury in foods by circulating enrichment-cold vapour atomic absorption spectrometry].

The determination of trace mercury using the self-developed circulating enrichment apparatus with cold vapour atomic absorption spectrometry was investigated. Various experimental conditions were discussed and optimized. The effect of interferences was examined. The developed method is sensitive, accurate, simple and available and has already been used in the analysis of various kinds of food samples and national standard reference materials, and the results obtained were satisfactory.

Cold Temperature↗

PubMed1998

[Simultaneous determination of metronidazolum and vitamin B6 by the derivative spectrophotometry].

A new method for simultaneous determination of metronidazolum and vitamin B6 was established by the third derivative spectrophotometry in 0.1 mol/L HCl solution. The detection limits were 0.81 microg/mL for metronidazolum and 0.16 microg/mL for vitamin B6. The linear range of determination was 1.6-22.4 microg/mL for both metronidazolum and vitamin B6. This method has been applied to the determination of metronidazolum and vitamin B6 in tabellae metronidazoli compositae with satisfactory results. The coefficients of variation are below 2.26 and 2.65% and the recoveries are 93-102% and 99-101% for metronidazolum and vitamin 6, respectively.

Limit of Detection↗

PubMed1998

Expression of potential target antigens for immunotherapy on primary and metastatic prostate cancers.

Defining the expression of tumor-associated antigens on primary and metastatic prostate cancer is the crucial first step in selecting appropriate targets for immune attack. In this study, the distribution of the tumor-associated antigens GM2, Tn, sTn, Thompson-Friedenreich antigen (TF), Globo H, Le(y), MUC1, MUC2, MUC3, MUC4, MUC5AC, MUC5B, MUC7, carcinoembryonic antigen, beta chain of human chorionic gonadotropin (hCG beta), HER2/neu, PSMA, and KSA on primary and metastatic prostate cancer and 16 types of normal tissues was compared by immunohistochemistry, using a panel of well-characterized monoclonal antibodies. Our results show that GM2, KSA, and MUC2 were strongly expressed on 8 or 9 of 9 metastatic prostate cancer biopsy specimens and, with PSMA, hCG beta, TF, Tn, and sTn, on 8 or more of 11 primary prostate cancer specimens. Tn, MUC1, and PSMA were expressed on 4-6 of 9 metastatic specimens. The remaining antigens were expressed on no more than three of nine metastatic specimens. Normal tissues were also tested with all antibodies. With regard to the eight antigens most widely expressed on prostate cancers, PSMA was not expressed significantly on any of the normal tissues except prostate epithelium. Tn, sTn, hCG beta, and MUC2 were detected on up to 3 of 10 types of normal epithelia. GM2, TF, MUC1, and KSA were more broadly distributed on normal epithelia, all primarily at the secretory borders. STn, KSA, and hCG beta were also detected in the testis, and GM2 was expressed on gray matter of brain. From the 30 antigens that we have screened, this study provides the basis for selecting GM2, TF, Tn, sTn, hCG beta, MUC1, MUC2, KSA, and PSMA as target antigens for specific immunotherapy of prostate cancer.

Amino Acid Sequence↗

PubMed1998

Expression of a 50 kDa putative receptor for bovine viral diarrhea virus in bovine fetal tissues.

The expression of a 50 kDa bovine viral diarrhea virus putative receptor in different bovine fetal tissues from 3-month old fetuses was studied. The receptor expression was examined by immunocytochemical staining and by immunoblotting using antiidiotypic probe (anti-D89). Intense specific staining in enterocytes of the small and large intestines, cortical tubular epithelial cells of kidneys, respiratory epithelial cells of the trachea and esophageal mucosal epithelial cells was observed, demonstrating the strong expression of bovine viral diarrhea virus receptor in the tissues. Weak staining was found in cerebellum, thymus, spleen, liver, cerebrum, and lung tissues; however, heart tissues were negative. Immunoblotting results correlated with the immunoperoxidase staining assays. Thus, the expression levels of the receptor are variable in different tissues. This pattern of expression may provide clues to the pathogenic potential of bovine viral diarrhea virus in the bovine fetus.

Animals↗

PubMed1998

Dynorphin A as a potential endogenous ligand for four members of the opioid receptor gene family.

Dynorphin A is an endogenous opioid peptide that activates the kappa opioid receptor (KOR) with high potency. Some studies also showed that the distribution and functional activity of dynorphin A are not completely correlated with those of KOR, suggesting that dynorphin A may interact with other receptors. To investigate the possibility that dynorphin A may serve as an agonist for other opioid receptors, we took the advantage of the cloning of the three major types of opioid receptors, mu (MOR), delta (DOR) and KOR, and examined their affinity for and their activation by dynorphin A. We used mammalian cells transfected with each of the cDNA clones for the human receptors hMOR, hDOR, hKOR and showed that dynorphin A displaced [3H]-diprenorphine binding with Ki values in the nanomolar range at all three receptors. We also showed that, when hMOR, hDOR or hKOR was coexpressed with a G protein-activated potassium channel in Xenopus oocytes, dynorphin A induced a potassium current with EC50 values in the nanomolar range for all three receptors. Furthermore, we showed that the human hORLI, an opioid receptor-like receptor that has been identified as a novel member of the opioid receptor gene family, displayed dynorphin A binding and functional activation. These results indicate that dynorphin A is capable of binding to and functional activation of all members of the opioid receptor family, suggesting that, as a potential endogenous agonist, its activity in humans may involve interaction with other members of the opioid receptor family in addition to kappa receptors.

Animals↗

PubMed1998

Carbon dioxide-induced retinopathy in the neonatal rat.

PURPOSE: Hypercarbia has been suggested as a risk factor for retinopathy of prematurity (ROP). We investigated the effect of hypercarbia on the retinal vasculature of the neonatal rat to determine whether hypercarbia alone could induce preretinal neovascularization analogous to ROP. METHODS: In a preliminary blood gas study, 8-11-day-old rats were exposed to specific levels of inspired O2 and either 0.2% CO2 or 10% CO2. Arterial blood gases were obtained, and a level of inspired O2 was determined that, when combined with inspired 10% CO2, would produce a PaO2 equivalent to room air (pure hypercarbia). In the formal retinopathy study, 300 newborn rats raised in 12 expanded litters (n = 25 each) were exposed for 7 days to either room air, 10% CO2 in 21% O2 and nitrogen (high-inspired CO2 group) or 10% CO2 in 12.5% O2 and nitrogen (pure-hypercarbia group). Each type of exposure was followed by recovery in room air for 5 days. Animals were sacrificed on day 13 and retinae were analyzed, using fluorescein perfusion and ADPase staining techniques. RESULTS: Neovascularization occurred in 19% of rats in the high-inspired CO2 group, and 14% of rats in the pure-hypercarbia group, compared to 0% of rats exposed to room air alone (p = 0.001, Chi square). CONCLUSIONS: In the neonatal rat model, exposure to hypercarbia alone, followed by room air recovery, results in preretinal neovascularization similar to that seen in oxygen-induced retinopathy. Our results support the suggestion that hypercarbia may be a risk factor for retinopathy of prematurity.

Animals↗

PubMed1998

[Chinese Human Genome Project--opportunity and challenge].

The Chinese Human Genome Project(HGP) started in 1993 and has since made substantial progress in 3 major aspects: the genome resource conservation and genetic polymorphism studies of multiple Chinese nationalities; the development of an advanced technological system for genome research; the cloning of some desease-related genes and a large number of expressed sequence tags(ESTs). At the same time a qualified research team has been formed and some centers for genome studies have been founded in the country. The major tasks in the next phase of the project are: (1) Further expanding the genetic material conservation scope including collection of more DNA samples and establishment of more immortalized cell lines; (2) Developing morbid genomics which includes epidemiological survey and registration, collection, maintenance and banking of the data and genetic material resource; making significant progress in mapping, cloning, mutation screening, and large-scale sequencing of the genes related to tumors, inheritable diseases and particularly multigenic diseases in the hope that a number of genes for important diseases will be obtained; (3) Initiation of the functional genomics which includes studies on bioinformatics, expression spectrum of transcription and translation of the genome in physiological and pathological processes; (4) Enhancing the studies on the ethical, legal and social issues related to human genome sciences.

China↗

PubMed1998

[The influence of several factors on automated DNA sequencing].

OBJECTIVE: To investigate the influence of several factors on isothermal automated DNA sequencing. METHODS: The effects of DNA purity and DNA concentration, as well as the quality of water used during sequencing on automated DNA sequencing results were retrospectively analyzed. RESULTS: When the DNA was not pure enough, the nucleotide curve showed lower ratio of signal to noise, or compression would occur, leading to difficulty in correctly judging the nucleotides; the readable length of nucleotides was shorter when low concentration of DNA was used; when the quality of water used in sequencing reaction and polyacrylamide gel solution was not high enough, the peaks of nucleotides became wider and flatter, or double peaks would occur, resulting in unreadable sequences. CONCLUSION: DNA purity and concentration as well as quality of water used in sequencing reaction and polyacrylamide gel solution had apparent influence on isothermal automated DNA sequencing. This suggests that high purity of DNA and high quality of water should be used in isothermal automated DNA sequencing; if longer DNA sequence needs to be obtained, DNA concentration should not be too low.

DNA↗

PubMed1998

[Analysis of diabetic optic neuropathy with a topographic laser scanning system].

Optic disc topography was done with a 3-dimensional scanning laser ophthalmoscope in 53 eyes of 53 diabetic patients and compared with that of 34 control eyes. In diabetic eyes, the parameters for contour variation of the optic nerve head was significantly greater than in control eyes. The cup of the disc, on the other hand, did not increase or decrease in diabetic eyes. The area of the neuroretinal rim area, and the tissue volume of the neuroretinal rim area was increased in eyes with pre-proliferative retinopathy, and proliferative retinopathy, respectively. The cup of the disc was not enlarged in diabetic eyes in spite of discrete signs of retinal nerve fiber layer defects. Topographic features of eyes with diabetic optic neuropathy were very different from those with glaucomatous optic neuropathy in spite of the similar appearance of retinal nerve fiber layer defects.

Diabetic Neuropathies↗

PubMed1998

Role of potassium channels in halothane-epinephrine arrhythmias.

It has been reported that antiarrhythmic drugs possessing the property of potassium channel blockade were most effective in preventing halothane-epinephrine induced arrhythmias. Recent attention has focused on ATP-sensitive potassium (K(ATP)) channels because of their contribution to the cardiovascular actions of volatile anesthetics. The present study was designed to evaluate whether K(ATP) channels or transient outward potassium channels (Ito) were involved in the mechanism of halothane-epinephrine arrhythmias in rat. Rats were anesthetized with halothane (1.5%), and the lungs were mechanically ventilated. The arrhythmogenic thresholds of epinephrine during halothane anesthesia were determined in 74 rats receiving saline or one of tested agents. The arrhythmogenic dose of epinephrine (ADE) was significantly increased by a K(ATP) channel opener, JTV506 (P < 0.01), and had a tendency to be increased by other K(ATP) channel openers, cromakalim, nicorandil, KRN2391 and Y 26763, but were not affected by a K(ATP) channel blocker, glibenclamide. The Ito blocker, 4-aminopyridine, also significantly increased the ADE. Epinephrine produced second-degree or complete atrioventricular block in 4 out of 7 rats receiving glibenclamide. These results suggest that Ito but not K(ATP) channels might be involved in the mechanism in producing halothane-epinephrine arrhythmias.

Adenosine Triphosphate↗

PubMed1998

Analysis of random recombination between human MDR1 and mouse mdr1a cDNA in a pHaMDR-dihydrofolate reductase bicistronic expression system.

Human P-glycoprotein (Pgp) confers multidrug resistance (MDR) to otherwise sensitive cells. The homologous mouse Pgps, which are encoded by mouse mdr1a (also known as mdr3) and mdr1b (also known as mdr1), confer different degrees of resistance to the same MDR drugs and inhibitors. To create recombinants for the study of sequences responsible for these differences in drug-resistance, chimeric cDNA libraries can be constructed by homologous recombination of pools of related sequences. This mutagenesis approach is called DNA shuffling. To select for chimeric Pgp with an altered resistance profile, DNA shuffling between the homologous but not identical drug interacting transmembrane domains 5 and 6 of human MDR1 and mouse mdr1a was used. The chimeric proteins were expressed in human KB-3-1 cells. One recombinant Pgp (clone 3-4) with a novel phenotype was analyzed in detail. Inhibitors of Pgp, including verapamil and cyclosporin A, were less effective in reversing resistance of the chimeric Pgp compared with wild-type Pgp, for certain drugs. However, [125I]iodoarylazidoprazosin photoaffinity labeling of the chimeric Pgp and its binding competition with cyclosporin A, showed that cyclosporin A competed for the photoaffinity labeling. The chimeric Pgp cells stained less well with human-specific anti-Pgp mAb MRK16 than wild-type Pgp, despite having the described epitopes for MRK16. Staining with human-specific mAb UIC2 was increased when the chimeric protein was compared with wild-type Pgp. These results suggest an alteration in exposure of human Pgp specific epitopes in this chimeric Pgp, as well as a change in the interaction of reversing agents with the chimeric protein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1998

Plasma endothelin 1 concentrations in children with congenital heart defects.

BACKGROUND: To investigate the changes in plasma endothelin-1 (ET-1) concentrations in patients with congenital heart defects. METHODS: Plasma ET-1 concentrations were measured by using radio-immunoassay in 50 patients in a prospective study. In 35 patients with ventricular septal defect, 20 cases had pulmonary hypertension (group 1) and 15 cases had normal pulmonary artery pressure (group 2). The other 15 patients with atrial septal defect had normal pulmonary artery pressure (group 3). Blood samples were obtained from pulmonary artery, aorta and radial artery. RESULTS: Plasma ET-1 concentration in group 1 was significantly higher than those in group 2 and group 3 at all sampling sites and all different times (p < 0.01), and plasma ET-1 concentration was slightly higher in group 3 than in group 2 (p > 0.05). Plasma ET-1 concentration at aorta were also significantly higher than that at pulmonary artery in group 1 (p < 0.01). In patients with ventricular septal detect, pulmonary blood flow had a linear positive correlation with plasma ET-1 concentration (r = 0.75, p < 0.01) and there was also a significant positive correlation between plasma ET-1 concentration and pulmonary artery pressure (r = 0.68, p < 0.05). After surgical repair of the defects, plasma ET-1 concentration decreased except for 6 cases with the pulmonary resistance more than 800 dyne.sec.cm-5. CONCLUSIONS: Plasma ET-1 concentrations are elevated in patients with congenital heart defect associated with left-to-right shunt and may have an important role in the pathogenesis of pulmonary hypertension.

Child↗

PubMed1998

Selection of tumor antigens as targets for immune attack using immunohistochemistry: protein antigens.

The relative expression of mucin antigens MUC1, MUC2, MUC3, MUC4, MUC5AC, MUC5B, and MUC7 and glycoprotein antigens KSA, carcinoembryonic antigen, prostate-specific membrane antigen (PSMA), HER-2/neu, and human chorionic gonadotropin-beta on different cancers and normal tissues is difficult to determine from available reports. We have compared the distribution of these antigens by immunohistology on a broad range of malignant and normal tissues. MUC1 expression was most intense in cancers of breast, lung, ovarian, and endometrial origin; MUC2 was most intense in cancers of colon and prostate origin; and MUC5AC was most intense in cancers of breast and gastric origin. MUC4 was intensely expressed in 50% of cancers of colon and pancreas origin, and MUC3, MUC5B, and MUC7 were expressed in a variety of epithelial cancers, but not so intensely. KSA was intensely and uniformly expressed on all epithelial cancers; carcinoembryonic antigen was expressed in most cancers of breast, lung, colon, pancreas, and gastric origin; and PSMA was expressed only in cancers of prostate origin. Human chorionic gonadotropin-beta was expressed on the majority of sarcomas and cancers of breast, lung, and pancreas origin, although intense staining was not seen. Staining on normal tissues was restricted to one or many normal epithelial tissues ranging from MUC3, MUC4, and PSMA, which were expressed only on epithelia of pancreas, stomach, and prostate origin, respectively, to MUC1 and KSA, which were expressed on most normal epithelia. Expression was restricted to the secretory borders of these epithelia while stroma and other normal tissues were completely negative. These results plus the results of the two previous papers (S. Zhang et al, Int. J. Cancer, 73: 42-49, 1997; S. Zhang et al., Int. J. Cancer, 73: 50-56, 1997) in this series provide the basis for selection of multiple cell surface antigens as targets for antibody-mediated attack against these cancers.

Antibodies, Monoclonal↗

PubMed1997

Maturation and degradation of beta-galactosidase in the post-Golgi compartment are regulated by cathepsin B and a non-cysteine protease.

Lysosomal beta-galactosidase precursor is processed to a mature form and associated with protective protein in lysosomes. In this study we used two cysteine protease proinhibitors, E64-d for cathepsins B, S, H, and L, and CA074Me for cathepsin B. They are converted intracellularly to active forms, E-64c and CA074, respectively. Both active compounds inhibited maturation of the exogenous beta-galactosidase precursor, but E-64c did not inhibit further degradation to an inactive 50-kDa product. We concluded that cathepsin B participated exclusively in maturation of beta-galactosidase, and a non-cysteine protease was involved in further degradation and inactivation of the enzyme molecule.

Cathepsin B↗

PubMed1997

Differential dependence on GluR2 expression of three characteristic features of AMPA receptors.

The GluR2 subunit controls three key features of ion flux through the AMPA subtype of glutamate receptors-calcium permeability, inward rectification, and channel block by external polyamines, but whether each of these features is equally sensitive to GluR2 abundance is unknown. The relations among these properties were compared in native AMPA receptors expressed by acutely isolated hippocampal interneurons and in recombinant receptors expressed by Xenopus oocytes. The shape of current-voltage (I-V) relations between -100 and +50 mV for either recombinant or native AMPA receptors was well described by a Woodhull block model in which the affinity for internal polyamine varied over a 1000-fold range in different cells. In oocytes injected with mixtures of GluR2:non-GluR2 mRNA, the relative abundance of GluR2 required to reduce the log of internal blocker affinity by 50% was two- to fourfold higher than that needed to half-maximally reduce divalent permeability or channel block by external polyamines. Likewise, in interneurons the affinity of externally applied argiotoxin for its blocking site was a steep function of internal blocker affinity. These results indicate that the number of GluR2 subunits in AMPA receptors is variable in both oocytes and interneurons. More GluR2 subunits in an AMPA receptor are required to maximally reduce internal blocker affinity than to abolish calcium permeability or external polyamine channel block. Accordingly, single-cell RT-PCR showed that approximately one-half of the physiologically characterized interneurons exhibiting inwardly rectifying AMPA receptors expressed detectable levels of edited GluR2. The physiological effects of a moderate change in GluR2 relative abundance, such as occurs after ischemia or seizures or after chronic exposure to morphine, thus will be dependent on the ambient GluR2 level in a cell-specific manner.

Animals↗

PubMed1997

Effects of Ca++ mobilization on expression of androgen-regulated genes: interference with androgen receptor-mediated transactivation by AP-I proteins.

BACKGROUND: The adult prostate is maintained through an equilibrium between cell growth and death rates. Androgen deprivation induces an increase in intracellular Ca++, AP-1 gene expression of androgen-inducible genes. METHODS: Northern blot analysis, band-shift assays, and transient cotransfection assays were used to study the effects of Ca++ mobilizer A23187 on gene expression in human prostate cancer cells. RESULTS: A23187 repressed androgen-upregulated mRNAs for prostate-specific antigen (PSA) and hKLK2, and rapidly induced mRNA levels for c-fos and c-jun. AP-1 protein-DNA binding activities were elevated after A23187 treatments. Androgen receptor (AR)-mediated induction of chloramphenicol acetyltransferase (CAT) reporter was repressed by AP-1 proteins. CONCLUSIONS: The repression of AR-mediated induction of PSA and hKLK2 genes by Ca++ mobilizers is due to the interference of AR transactivation activity by AP-1 proteins.

Androgens↗

PubMed1997

Rapid determination of 1,4-dioxane in water by solid-phase extraction and gas chromatography-mass spectrometry.

A highly sensitive and accurate gas chromatography-mass spectrometry method for rapidly quantitative analysis of dioxane in water samples is described. Dioxane in water sample was extracted by hexane-methylene chloride (80:20, v/v) then transferred to a C18 solid-phase extraction (SPE) cartridge and eluted by acetonitrile. An aliquot of this solution was analyzed by gas chromatography-mass spectrometry with electron impact ionization and selected ion monitoring (dioxane m/z 88) mode. The quantitative limit was set to be 0.05 microgram/ml with an injection volume of 2 microliters and a sample volume of 1 ml. The isotopically labelled [2H8]dioxane (m/z 96) was used as internal standard. Analysis time is approximately 6 min. The results for various kinds of SPE cartridges in this method are also discussed.

Carcinogens, Environmental↗

PubMed1997

The efficiency of a cis-cleaving ribozyme in an mRNA coding region is influenced by the translating ribosome in vivo.

A cis -cleaving hammerhead ribozyme (Rz) expression system (3A'-Rz) in Escherichia coli has been constructed that can be used to study the involvement of factors that affect ribozyme cleavage in vivo . The ribozyme sequence is placed in the coding region of 3A' mRNA, which is expressed from a semi-synthetic translation assay gene. The size and the 5'-end sequences of the 3' cleavage fragments were determined and the efficiencies of different Rz variants were measured by quantitative primer extension. It is shown that one of the semi-active constructs (3A'-RzIII) can be used as an indicator for ribosomes that read through or terminate at a stop codon upstream of the Rz hammerhead sequence in the mRNA. Readthrough of the stop codon in an uncleaved mRNA gives a full length 3A' protein. Termination at the stop codon upstream of the ribozyme sequence gives a shortened termination product. However, the mRNA fragment that should arise as a result of the auto-cleavage does not give rise to any detectable corresponding truncated protein. Besides studies on translating ribosomes, the 3A'-Rz system can be used to isolate mutant strains that are changed in ribozyme activity either from internal base alterations, or changed interacting host factors.

Base Sequence↗