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Z Yu

Publications and source records attributed to Z Yu.

At least 271 records · Page 15Linked to original sources
PubMed1996

Multi-well ELISA based on independent peptide antigens for antibody capture. Application to Lyme disease serodiagnosis.

Novel procedures for the use of peptides as antibody-capture reagents in the ELISA format have been investigated. Epitope sequences from known immunodominant antigens of Borrelia burgdorferi were selected by screening peptide libraries with sera from patients with Lyme disease. Several epitope peptides were synthesized and immobilized, separately, on the ELISA plate as haptens on bovine serum albumin. Based on a comparative analysis of serum samples, it appears that peptide antigens can be used as effectively as a whole cell lysate to discriminate between Lyme disease and non-Lyme disease sera, thus avoiding dependence on bacterial sonicates which vary from passage to passage. Further improvements in epitope design for enhancement of accuracy in serodiagnosis are discussed.

Amino Acid Sequence↗
PubMed1996

Ion-pair chromatography of methotrexate in a column-switching system using an alkyl-diol silica precolumn for direct injection of plasma.

The retention behaviour of methotrexate as an ion-pair with tetrabutylammonium in a column-switching system, based on an alkyl-diol silica C8 precolumn, combined with an analytical column, LiChrospher RP 18, was studied. Methotrexate is mainly present as a divalent anion at pH 7.4, however, the retention data was consistent with the formation of a 1 + 1 ion pair with the counter ion. The concentration of the tetrabutylammonium and the acetonitrile in the mobile phase could be used to regulate the retention in the system. Relevant chromatographic parameters to estimate the enrichment effect in the column-switching system are also identified and discussed. The column-switching system was applied to direct injection of plasma (100 microliters) giving a limit of detection of 10 ng/ml for methotrexate using UV detection at 307 nm.

Acetonitriles↗
PubMed1996

A novel hydrophobic omega-conotoxin blocks molluscan dihydropyridine-sensitive calcium channels.

A novel calcium channel blocking peptide designated omega-conotoxin-Tx VII has been characterized from the venom of the molluscivorous snail Conus textile. The amino acid sequence (CKQADEPCDVFSLDCCTGICLGVCMW) reveals the characteristic cysteine framework of omega-conotoxins, but it is extremely hydrophobic for this pharmacological class of peptides and further unusual in its net negative charge (-3). It is further striking that the sequence of TxVII, a calcium current blocker, is 58% identical to that of delta-conotoxin-TxVIA, which targets sodium channels. TxVII effects were examined in the caudodorsal cell (CDC) neurons from the mollusc Lymnaea stagnalis. The toxin has no significant effect on sodium or potassium currents in these cells, but it clearly blocks the calcium currents. TxVII most prominently blocks the slowly inactivating, dihydropyridine- (DHP-) sensitive current in CDCs, while blockade of the rapidly inactivating current is less efficient. This novel omega-conotoxin is apparently targeted to DHP-sensitive calcium channels and thereby provides a lead for future design of selective conopeptide probes for L-type channels.

Amino Acid Sequence↗
PubMed1996

Exposure of human CD34+ cells to human immunodeficiency virus type 1 does not influence their expansion and proliferation of hematopoietic progenitors in vitro.

The susceptibility of highly purified human CD34+ cells to monocytotropic (Ba-L) and lymphotropic (A018-post) strains of human immunodeficiency virus-1 (HIV-1) was examined. Liquid cultures initiated with fresh immunomagnetically purified CD34+ cells using the K6.1 CD34 monoclonal antibody (MoAb) (K6.1/CD34+) were positive for HIV expression 2 weeks after exposure to HIV-1 Ba-L. These cells were initially greater than 90% CD34+ and had undetectable monocyte contamination by flow-cytometric staining and side-scatter analyses, respectively, and undetectable T-cell contamination by CD3 polymerase chain reaction (PCR) analysis. However, secondary CD34+ liquid cultures reselected from the primary liquid cultures 24 hours after HIV exposure by panning with the ICH3 CD34 MoAb (ICH3/CD34+) and maintained for an additional 14 days were negative for HIV expression. The ICH3-unbound cells were positive for both spliced and unspliced HIV RNA when exposed to HIV-1 Ba-L, and were DNA PCR positive when exposed to either monocytotropic or lymphotropic HIV-1. To further test that CD34+ cells were not infectible by HIV-1, we exposed K6.1/CD34+ cells continuously to HIV-1 in a culture system capable of maintaining and expanding primitive CD34+ cells. HIV-exposed K6.1/CD34+ cells proliferated and expanded as efficiently as uninfected cultures. However, when reselected magnetically using the K6.1 CD34 MoAb after expansion for 7 days, bound K6.1/CD34+ cells were again negative for HIV-1 expression, whereas unbound cells were positive for HIV-1 expression. These findings suggest that a sequential CD34+ cell-selection process, in which the two selections are separated by a brief culture period, can yield a population of CD34+ cells that are not infected with HIV-1. This process may be useful in the design of stem or progenitor cell-based transplantation therapies for HIV infection.

Antigens, CD34↗
PubMed1996

Direct injection of large volumes of plasma in a column-switching system for the analysis of local anaesthetics. II. Determination of bupivacaine in human plasma with an alkyldiol silica precolumn.

A column-switching high-performance liquid chromatographic system was applied for the determination of bupivacaine in plasma. A 500-microliter plasma sample was directly introduced onto a C18-alkyl-diol silica (ADS) precolumn separating analytes from proteins and polar endogenous compounds. The fraction containing bupivacaine and ropivacaine (internal standard) was back-flushed and transferred to a conventional reversed-phase column (Kromasil C18) for final separation. A single ADS precolumn could withstand more than 50 ml of plasma injections without changing analytical performance. Quantitative studies showed a broad range of linearity (0.033-3.31 micrograms/ml) and high recovery (95-99.9%) with coefficients of variation less than 3.1%. The advantages of the ADS material are its high capability of sample clean-up, due to rapid elution of plasma proteins and endogenous compounds to waste, and its ability to elicit a stable baseline. As a result, UV detection could be performed at 210 nm and clean chromatograms with baseline separation for desired peaks were obtained within 15 min. The detection limit of this system was 10 ng/ml defined by a signal-to-noise ratio of 3:1. The concentration of bupivacaine in patients determined by this method agreed well with the values obtained from an alternative method, making the technique applicable for pharmacokinetic studies in humans.

Amides↗
PubMed1996

Direct injection of large volumes of plasma in a column-switching system for the analysis of local anaesthetics. I. Optimization of semi-permeable surface precolumns in the system and characterization of some interference peaks.

Possibilities for accomplishing direct injection of large volumes (500 microliters) of plasma samples into a column-switching HPLC system were investigated. A new format of precolumn containing a semi-permeable surface (SPS) support (1 cm x 1 cm) was used for the sample clean-up and trace enrichment and was combined with a Kromasil C18 column for the final separation. A stable chromatographic system with respect to the separation selectivity and separation time was constructed and evaluated. The main parameters were the hydrophobicity of the SPS column, pH of the eluents, concentration of the organic modifier in the eluents and the detection wavelength. Two main interference peaks that were eluted in front of the ropivacaine peak were systematically characterized by varying the loading conditions for the SPS precolumn. The SPS column could tolerate large volumes (< or = 500 microliters) of plasma injections with a total volume of more than 50 ml. The developed system is stable, which permits the detection of 30 ng/ml ropivacaine in human plasma.

Amides↗
PubMed1996

Effect of prostatic growth factor, basic fibroblast growth factor, epidermal growth factor, and steroids on the proliferation of human fetal prostatic fibroblasts.

To study the relationship between androgen metabolism and the pathogenesis of benign prostatic hypertrophy, we purified a growth factor from benign hyperplastic tissue of human prostates and assayed the proliferative responses of human fetal prostatic fibroblasts to the purified growth factor (hPGF), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), dihydrotestosterone (DHT), and estradiol (E2). Prostatic tissue extracts were fractionated using heparin-Sepharose chromatography. The fraction that eluted with 1.3-1.7 M NaCl contained the majority of mitogenic activity. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS/PAGE) of the lyophilyzed active fraction showed a band at 17,000 daltons. Human prostatic fibroblasts were isolated from fetal prostate and tested for their proliferative responses to hPGF, bFGF, EGF, DHT, and E2. hPGF, as well as bFGF and EGF, did increase tritiated thymidine incorporation into the cultured fibroblasts. DHT(10(-7) M) had a significant stimulatory effect on cell growth in serum-free media after 6 days of culture. E2(10-7 M) had no effect on cell proliferation. The combination of DHT and E2 showed no synergistic effect. We conclude that our purified hPGF, bFGF, and EGF promote cell growth directly, DHT indirectly, while E2 does not. The effect of DHT appears to be mediated via the increased production and/or secretion of growth factor(s). Possibly, the bFGF-like hPGF purified from human benign hyperplastic prostatic tissue is such a mediator.

Analysis of Variance↗
PubMed1996

Theophylline controlled-release formulations: in vivo-in vitro correlations.

Four experimental controlled-release oral solid dosage formulations were developed and the in vitro dissolution characteristics of theophylline from these formulations were studied in USP apparatus I. Pharmacokinetic evaluation of these formulations was carried out in eight beagle dogs under fasting conditions. Theophylline in a 5% dextrose injection USP, oral solution, and Slo-Phyllin were used as controls to estimate the in vivo dissolution of these four formulations in the GI tract. The percentage cumulative amounts of drug absorbed and the percentage cumulative amounts of drug released into the GI tract from these four controlled-release formulations were obtained by numerical deconvolution methods. The in vivo and in vitro dissolution data demonstrated good correlation indicating that in vitro dissolution tests can be used to optimize the further design of controlled drug release oral solid dosage formulations for theophylline.

Animals↗
PubMed1996

Five modified numerical deconvolution methods for biopharmaceutics and pharmacokinetics studies.

Four improved finite-difference numerical deconvolution methods and one nonlinear regression numerical deconvolution method are proposed and implemented using IMSL/IDLTM. These five numerical deconvolution methods are evaluated using simulated data generated with and without added noise under six different dosing cases. Comparisons between these methods are made in terms of the superimposability of the calculated cumulative amount of drug released or absorbed-time profiles with the theoretical data. The results indicate that the proposed fixed step number equal step length numerical deconvolution method is simple and accurate and therefore is appropriate for pharmacokinetic and biopharmaceutic studies. When an analytic function is legitimate to represent the drug input rate, the nonlinear regression numerical deconvolution method will yield enhanced numerical accuracy and stability.

Absorption↗
PubMed1996

Phenotyping of esterase D and acid phosphatase by rapid isoelectric focusing on PhastSystem.

A rapid isoelectric focusing method on PhastSystem was applied to investigate the distribution of esterase D (ESD) and acid phosphatase (ACP) phenotypes in 152 and 112 unrelated healthy donors, respectively, from the Han population in Beijing. Laboratory-made gels with a pH range of 5.0-7.0 and 5.0-8.0 were used for analysis of ESD and ACP, respectively, with 1 microliter sample loading. The running time was 30-40 min. Gene frequencies for ESD were 0.6809 for ESD*1 and 0.3191 for ESD*2, (sigma chi 2 = 0.8586 and P > or = 0.50); gene frequencies of ACP were 0.2009 for ACP*A, 0.7991 for ACP*B, (sigma chi 2 = 1.7892 and P > 0.20), with good agreement between the observed and the expected values.

Acid Phosphatase↗
PubMed1996

Role of interferon-gamma in immunity to herpes simplex virus.

Removal of herpes simplex virus (HSV)-infected cells from peripheral sites such as the skin is mainly an activity of T cells, particularly the CD4+ T subset. Such cells orchestrate an inflammatory response with interferon-gamma (IFN-gamma) appearing to play the essential role in viral clearance. In accordance with this hypothesis, we show that infection of BALB/c background mice expressing the knockout phenotype for IFN-gamma (GKO mice) are significantly more susceptible to the development of cutaneous zosteriform lesions than are wild-type. However, following HSV immunization, GKO mice become solidly immune to the development of zosteriform lesions. In addition, the transfer of T cells from immune GKO mice to nude mice recipients renders them resistant to zosteriform lesions. Our results are discussed in terms of the major and compensatory mechanisms available to the body to effect immunity to viral infections.

Adoptive Transfer↗
PubMed1996

Mass spectrometric-based revision of the structure of a cysteine-rich peptide toxin with gamma-carboxyglutamic acid, TxVIIA, from the sea snail, Conus textile.

A mollusk-specific toxin, TxVIIA, having potent paralytic activity was isolated from the venom of sea snail Conus textile (Fainzilber M et al., 1991, Eur J Biochem 202:589-595). The structure reported above was based upon amino acid analysis and the Edman degradation. We have recently reinvestigated this toxin employing some of the most novel techniques in mass spectrometry. We now report a revised structure based primarily on high-energy collision-induced dissociation analysis of the two Asp17-N peptides of the reduced, pyridinylethyl derivative representing the entire sequence using matrix-assisted laser desorption ionization (MALDI) as CGGYSTYC gamma VDS gamma CCSDNCVRSYCTLF-NH2 (gamma, gamma-carboxyglutamic acid or Gla). The N-terminus of the previous sequence was incorrect, apparently due to a side reaction of reduction and alkylation, which led to the erroneous assignment of Trp for the N-terminal residue. In addition, the last two C-terminal amino acids and the C-terminal amidation had not been detected. Also, a combination of electrospray ionization mass spectrometry and positive and negative ion MALDI mass spectrometry provided information on the molecular weights of the native and derivatized toxin and presence of two Gla residues. Thus, TxVIIA does not have an "unusual" sequence as previously reported, but in fact belongs to the conserved Cys framework for omega- and delta-conotoxins. However, the four net negative charges with the cysteine-rich structure of this revised sequence is highly unusual for conopeptides.

1-Carboxyglutamic Acid↗
PubMed1996

Evaluation of Bacillus thuringiensis and Bacillus sphaericus Strains from Chinese Soils Toxic to Mosquito Larvae

During our research to isolate and screen microbial agents, eight Bacillus thuringiensis isolates and five Bacillus sphaericus isolates were shown to have high toxicity to mosquito larvae. Comparing the LC50 values, four B. sphaericus isolates with LC50 values ranging from 0.50 to 1.47 ng/ml were about two to six times more toxic than strain 1593 (LC50 3.00 ng/ml) against larvae of Culex quinquefasciatus. Four B. thuringiensis isolates (LC50 values ranging from 3.80 to 7.54 ng/ml) and four B. sphaericus isolates with LC50 of 17.0 to 43.7 ng/ml were more toxic to Aedes aegypti than strain 1897 (LC50 8.46 ng/ml) and strain 1593 (LC50 67.3 ng/ml). As to Anopheles hyrcanus, the LC50 values of three B. sphaericus isolates ranging from 3.63 to 5.73 ng/ml were three to five times smaller than that of strain 1593 (LC50 16.1 ng/ml). Two B. sphaericus isolates showed high toxicity against mosquito larvae in the three genera Culex, Aedes, and Anopheles.

Journal Article↗
PubMed1996

Conditional transgene expression in the heart.

Conditional transgene expression is a potentially useful approach to investigate complex biological systems in vivo. We recently demonstrated that tetracycline-responsive promoters could be employed to achieve regulated, cardiac-specific expression of target genes in transgenic mice. To more fully define the quantitative and spatial parameters associated with tetracycline-regulated gene expression in the heart, we crossed transgenic mice harboring either a firefly luciferase or a nuclear-localized bacterial lacZ target gene with strains expressing a tetracycline-controlled transactivator (tTA) under the regulatory control of 2.9 kb of 5' flanking sequence from the rat alpha-myosin heavy chain gene. Luciferase activity was induced nearly 300-fold in the hearts of binary-transgenic mice compared with mice carrying only the luciferase reporter gene. No significant transactivation was observed in any other tissues examined. Binary transgenics harboring the lacZ reporter gene showed substantial beta-galactosidase activity throughout the heart, but the response of individual cardiac myocytes was heterogeneous. For both reporter genes, tetracycline treatment fully repressed tTA-dependent transactivation. These data provide important insights into the nature of studies that can be successfully addressed using the tetracycline-regulated gene expression system in the heart.

Animals↗
PubMed1996

[Effects of simulated weightlessness on ultrastructures and oxygen supply and consumption of myocardium in rats].

Weightlessness causes atrophy of myocardium in rats, however, properties of ultra-structural changes and oxygen supply and consumption in myocardium are still unclear. Changes in ultrastructures of left ventricular myocardium in rats tail-suspended for 8W were observed. Qualitative analysis showed that the lysosomes, lipofuscins and degenerate mitochondria increased in myocytes of left ventricle in tail-suspended rats (SUS). The sarcoplasmic reticula were reduced in quantity and shrunken in appearance. The number of extended endothelial projections into the lumen of capillaries increased. Quantitative analysis showed that volume densities of mitochondria and sarcoplasmic reticulum in SUS were reduced by 14.5% and 22.2%, respectively. The number density of mitochondria also had a 12.5% decrease in SUS. The morphometric data-estimated oxygen demand of the myocardium in SUS showed a 16.7% decrease. These results suggested that the feature of the changes be chronic degeneration without the evidence of acute hypoxia in myocardium. The decrease of oxygen consumption of myocardium in SUS didn't cause a reflex reduction in the oxygen supply.

Animals↗
PubMed1996

[A pilot study on trihalomethane formation in water treated by chlorine dioxide].

Trihalomethane (THM) formation was determined by gas chromatography in water disinfected with chlorine dioxide (ClO2) only or ClO2 combined with chlorine (Cl2), to lay a basis for water disinfected with ClO2. Results showed no THM was produced in water disinfected with ClO2 only if without existence of bromine (Br) ion in it; certain amount of bromoform could be formed with existence of bromine ion, and THM formation could be inhibited by ClO2 and Cl2, with a ratio of greater than 1 between them. Light irradiation could decrease the amount of THM produced whether in disinfection with ClO2 or combination with ClO2 and Cl2. No significant effect of pH value of water on THM formation was observed, but pH should be controlled under neutral or slightly acidic to ensure the concentration of ClO2 in water.

Carcinogens↗
PubMed1996

Construction of a stable expression vector carrying sop genes [ZJ1].

Mini-F, the fifth fragment of F plasmid from EcoRI digestion, is known to carry an efficient partitioning function. Two pBR322 plasmid derivatives, pDMC32 and pDMC311, have been constructed from this fragment. The plasmid pDMC32 carries all the relative genes for plasmid stability, ccd, repD, and sop genes (sopA, sopB, and sopC), along with oriS and oriV, while pDMC311 carries only sop genes (sopA, sopB, and sopC). The plasmid maintenance proportions for pDMC32 and pDMC311 in E. coli were 93% and 100%, respectively, after 100 generations continuous cultivation of cells harboring the derivatives, MI32 (pDMC32) and MI311 (pDMC311), in a phosphate-limited basal medium. As a control, the maintenance proportion of plasmid pBR322 dropped down to a low of 10% at generation 55 of continuous cultivation of E. coli MIR322 (pBR322) in the same medium. In order to make a stable expression vector that carries only sop genes, plasmid pDMC40 was constructed by adding a trp promoter from pDR720 to pBR322. The stable expression vector pDMC48 was then derived from pDMC40 by inserting sop genes into it from pDMC311. The maintenance proportion of plasmid pDMC48 in E. coli was still 100% after 100 generations of continuous cultivation of cells harboring the plasmid in phosphate-limited basal medium.

Ampicillin↗