Biomedical subjects

Y X Zhang

Publications and source records attributed to Y X Zhang.

At least 19 recordsLinked to original sources

PubMed2000

Pressurized gradient capillary electrochromatographic separation of eighteen amino acid derivatives.

A pressurized gradient capillary electrochromatography (pCEC) instrument was developed to separate 18 amino acid derivatives. A reversed-phase C18 column (3 microm, 130 mm x 75 microm I.D.) and an acetate buffer (50 mmol/l NaAc, pH 6.4) with an ion-pair reagent (1% N,N-dimethylformamide) were used to separate derivatized amino acids from a standard solution (2 microg/ml), and the wavelength of the UV-Vis detector was 360 nm. The pressure on the capillary column was kept at approx. 70 Pa and 3 kV positive voltage was added on the outlet end of column. The effect of voltage on the eluting order of amino acids and the resolution of separation were studied, and it was found that when the voltage was higher than 3 kV, the adsorption of amino acids in the porous C18 column occurred. The effect of salt concentration, injection volume, and column length on the separation of amino acids was determined. The amino acid sample was separated by pCEC, and RSDs of the migration times of each amino acid were all less than 2.5%.

Amino Acids↗

PubMed2000

Identification and characterization of promoters regulating tuf expression in Chlamydia trachomatis serovar F.

Gene expression in the obligate intracellular bacterium Chlamydia trachomatis ranges from nil in the infectious EB form to high in the dividing RB form. Little is known about the mechanisms of gene regulation in chlamydiae and only a few promoter sequences have been characterized. The purpose of our study was to examine the expression of a cluster of genes that are required for translation in C. trachomatis serovar F: infA (encoding Initiation Factor 1), tRNA(Thr), tuf (encoding Elongation Factor Tu), and tRNA(Trp). Primer extension analysis indicated that tuf is expressed in three different mRNAs. Putative promoter sequences for these transcripts were defined as P1 (upstream of tRNA(Thr)), P2 (within infA) and P3 (upstream of infA). Quantitative RT-PCR analysis revealed that P1 transcripts were most abundant at 16 h postinfection (pi), whereas P2 transcripts predominated at 24 h pi. P3 was active at all times pi; however, transcription terminated upstream of tuf at early times pi and continued through tuf at later times. P1 and P3 were active in Escherichia coli, as assessed by CAT expression in promoter-fusion vectors and a chlamydial in vitro transcription system. Site-specific mutagenesis confirmed the importance of the -35 and -10 hexamers in the P1 and P3 promoters. P2 was weakly active in E. coli and inactive in the in vitro transcription system, indicating either that the P2 transcript is processed from a longer transcript or that P2 expression requires a sigma or transcription factor which is not present in E. coli or the in vitro transcription system. Our data suggest that multiple processes play a role in the regulation of tuf gene expression during the developmental cycle.

Amino Acid Sequence↗

PubMed2000

Conformational changes and inactivation of calf intestinal alkaline phosphatase in trifluoroethanol solutions.

The changes in activity and unfolding of calf intestinal alkaline phosphatase (CIP) during denaturation in different concentrations of trifluoroethanol (TFE) have been investigated by far-ultraviolet circular dichroism and fluorescence emission spectra. Unfolding and activation rate constants were measured and compared, the activation and inactivation courses were much faster than that of unfolding, which suggests that the active site of CIP containing two zinc ions and one magnesium ion is situated in a limited and flexible region of the enzyme molecule that is more fragile to the denaturant than the protein as a whole. However, compared to other metalloenzymes, CIP is inactivated at higher concentrations of TFE as denaturant.

Alkaline Phosphatase↗

PubMed2000

Arrestment response of the predatory mite Amblyseius longispinosus to Schizotetranychus nanjingensis webnests on bamboo leaves (Acari: Phytoseiidae, Tetranychidae).

The response of the predatory mite Amblyseius longispinosus (Acari: Phytoseiidae) to the webnest of the spider mite Schizotetranychus nanjingensis (Acari: Tetranychidae) was examined using two-choice tests in the laboratory. A. longispinosus females were found significantly more often on leaves with webnests than on leaves without webnests and were often observed searching under the webbing. Because spider mites and their eggs were removed from the webnests before experiments, predators responded to stimuli associated with webbing, mite feeding damage and other residues in the webnests.

Animals↗

PubMed2000

Quantitative chromatics analysis for computer imaging of cytologic subtypes of lung cancer stained by Papanicolaou stain.

OBJECTIVE: To determine the role of quantitative chromatics analysis in the classification of subtypes of lung cancer stained by Papanicolaou stain. STUDY DESIGN: By means of computer image analysis, 60 keratinized squamous carcinoma cells (KSCC), 88 nonkeratinized squamous carcinoma cells (NKSCC) and 150 adenocarcinoma cells (ACC) from lung cancer in sputum smears stained by Papanicolaou stain were analyzed and distinguished based on quantitative colorimetry. The features measured were the content of three primary colors, red (R), green (G) and blue (B) and the coefficients of R, G and B (r, g and b, respectively). Hue, saturation, brightness and gray level were also measured. A stepwise discriminant analysis was carried out. RESULTS: The values of R, G and B and r, g and b, hue and saturation in NKSCC and ACC were significantly different from those of KSCC, and the changes in the three primary colors were more sensitive than those in the gray level. Computer assessment based on three primary color coefficients, hue and saturation yielded accuracy of distinguishing KSCC from NKSCC and KSCC from ACC of 95.2% and 95%, respectively. CONCLUSION: Quantitative analyses of R, G and B and r, g, b and hue and saturation are valuable in distinguishing KSCC from NKSCC and ACC.

Adenocarcinoma↗

PubMed2000

[Growth and metabolism of hybridoma cells in semicontinuous perfusion cultures].

The growth and metabolism of WuT3 hybridoma cells were studied in semicontinuous perfusion cultures. The growth of cells, utilization of glucose, production of lactate, ammonia and monoclonal antibody were investigated. As the perfusion rate increased from 1.0/d to 2.0/d, the lactate yield coefficient from glucose Ylac/glu decreased 18%, the ammonia yield coefficient from glutamine Yamm/gln decreased 40%, the alanine yield coefficient from glutamine Yala/gln increased 58%, the glycine yield coefficient remained almost constant. This indicate that cells would regulated their metabolic flux at higher cell density, and glutamate produced in quantity and pyruvate would turn into alanine rather than glycine by transamination. As a result, potentially toxic effects were reduced because less ammonia and lactate were produced.

Amino Acids↗

PubMed2000

[Growth and metabolism of hybridoma cells cultured in flask and spinner bottles].

The growth and metabolism of WuT3 hybridoma cells were very different when cells were cultured in flask and spinner bottles. In the flask bottles, a longer culture duration and the higher cell density were met, whereas in the spinner bottles the more vigorous cell metabolism took place, resulting in that either the specific consumption rates of glucose and amino acids or the specific production rates of lactate, ammonia and alanine were higher.

Amino Acids↗

PubMed2000

Okadaic acid-mediated induction of the c-fos gene in estrogen receptor-negative human breast carcinoma cells utilized, in part, posttranscriptional mechanisms involving adenosine-uridine-rich elements.

Signal transduction via modulation of phosphorylation after selective inhibition of protein phosphatase (PP) 1 and/or PP2A appears to play a role in okadaic acid (OA)-mediated effects. Treatment of several estrogen receptor-negative human breast carcinoma (HBC) cells with 100 nM OA resulted in induction of c-fos, c-myc, and cyclin-dependent kinase inhibitor p21WAF1/CIP1 genes. Transfections of various luciferase reporter constructs in HBC cells revealed involvement of activator protein-1-dependent as well as -independent pathways in induction of the c-fos gene by OA. MDA-MB-468 HBC cells were stably transfected with plasmids expressing luciferase, chimeric luciferase- c-fos 3' untranslated region (3'UTR), or chimeric luciferase-p21WAF1/CIP 3'UTR mRNAs. Expression of chimeric luciferase-c-fos and luciferase-p21WAF1/CIP1 mRNAs was elevated by OA in several independent sublines. Actinomycin D chase experiments revealed an enhanced rate of decay of luciferase-c-fos mRNA, whereas treatment with OA caused approximately 3.5-fold enhanced stability of the chimeric luciferase-c-fos mRNA only. By transfecting different plasmids containing deletions of c-fos 3'UTR, OA-responsive sequences were mapped to an 86-nucleotide, AU-rich region. UV cross-linking experiments using HBC cell cytosolic proteins showed multiple complexes with the AU-rich region subfragments of c-fos, as well as c-myc and p21WAF1/CIP1 mRNAs. OA enhanced binding of a novel Mr approximately 75,000 protein present in the cytosolic extracts of HBC cells to the AU-rich RNA probes of all of the above three genes. Taken together, OA regulation of HBC cell gene expression involves the activator protein-1 pathway, as well as enhanced binding of a novel Mr approximately 75,000 protein to an AU-rich region of the 3'UTRs of the target genes.

Adenosine↗

PubMed2000

[The ex vivo expansion of cord blood hematopoietic cells: 1. Cell growth behavior].

The population growth and metabolism of hematopoietic cells from cord blood were investigated without and with hematopoietic growth factors and the long-term growth kinetics of cells was studied. In static cultivation of hematopoietic cells, the population specific growth rate was 0.34 d-1, and the average double time 2 days. The greater part of glucose was consumed and 40 mmol/L lactate was formed during cell culture. For the long-term culture, the maximum output of CFU-GM appeared between the 2nd and 3rd weeks and that of BFU-E in the first week. With 50% medium exchange, the expansions of total cells, CFU-GM, and BFU-E came up to 14, 13, and 5 times, respectively.

Cell Division↗

PubMed1999

Coronary C-reactive protein distribution: its relation to development of atherosclerosis.

Two hundred and ninety-nine paraffin-embedded human coronary artery sections from 68 autopsies, both male and female and with various causes of death, were examined for distribution of C-reactive protein (CRP) using the indirect immunofluorescence technique and high-resolution confocal microscopy. The results demonstrate, for the first time, the existence of CRP in human coronary arteries, with evidence of CRP deposits being associated with lipids within in the artery walls. Grades of CRP immunoreactivity positively correlate with relative intimal thickness and negatively correlate with relative lumen size. It is suggested, therefore, that CRP may be related to the development of atherosclerosis and that the development of coronary atherosclerosis is associated with a relapsing inflammatory/necrotic process occurring within the coronary intima.

Adult↗

PubMed1999

Interaction of Eu3+ with yeast alcohol dehydrogenase.

The activity of yeast alcohol dehydrogenase is markedly enhanced by Eu3+ ions. At pH 7.0 two binding constants for Eu3+, 1.0x10(-2) and 2.0x10(-3) microM, were obtained using a Scatchard plot. The presence of Zn2+ ions restricts the Eu3+ -induced increase in the activity of yeast alcohol dehydrogenase. Studies on the tryptophan fluorescence of the enzyme in the absence and presence of Eu3+ or Zn2+ ions showed that Eu3+ affects tertiary or quaternary structures, which is consistent with its activation of the enzyme. The presence of Zn2+ reverses the conformational changes caused by Eu3+. Comparison of the effects of Eu3+ with Zn2+ for apo-yeast alcohol dehydrogenase indicates that their binding sites on the protein are different.

Alcohol Dehydrogenase↗

PubMed1998

Effect of amino acid ergot alkaloids on glutamate transport via human glutamate transporter hGluT-1.

Effect of amino acid ergot alkaloids on glutamate transport via the human glutamate transporter (hGluT-1) was investigated using hGluT-HeLaS3 cells, which stably expressed high levels of hGluT-1. Ergotamine enhanced the glutamate uptake of hGluT-HeLaS3 cells in a concentration-dependent manner, increasing the initial velocity of glutamate uptake by 1.45 times at 10 microM. Other amino acid alkaloids, bromocriptine and dihydroergotamine, also augmented glutamate uptake, whereas amine alkaloids, ergonovine or lisuride did not influence glutamate uptake. The accelerating effect required a preincubation longer than 5 min. Kinetic studies on hGluT-1 revealed that ergot alkaloids decreased a Michaelis constant (Km) for glutamate with unchanged maximum velocity. The effect of bromocriptine was not mediated by dopamine D1 or D2 receptors, and was independent of its antioxidant action. Amino acid ergot alkaloids may serve as a prototype for agents that regulate glutamate transporters. These results may be useful in exploring new agents for neurological diseases associated with glutamatergic neurotoxicity.

ATP-Binding Cassette Transporters↗

PubMed1998

Pycnogenol enhances immune and haemopoietic functions in senescence-accelerated mice.

Pycnogenol (procyanidin extracted from Pinus maritima) has been shown to be a potent free radical scavenger and an antioxidant phytochemical. The effects of pycnogenol on immune and haemopoietic dysfunction in senescence-accelerated mice (SAM), as a murine model of accelerated ageing, were determined. SAMP8, a strain of senile-prone mice, exhibit learning and memory deficits, immunodeficiency and dysfunction of the haemopoietic system. Oral feeding with pycnogenol for 2 months significantly improved their T- and B-cell function. Pycnogenol also augmented the proliferative capacity of haemopoietic progenitors of bone marrow in SAMP8. These data suggest that pycnogenol may be useful for either retardation or restoration of parameters associated with ageing.

Aging↗

PubMed1998

Assessment of prematurely born children at follow-up using a tidal breathing parameter.

Prematurely born children frequently have respiratory problems at follow-up. A non-invasive and easily performed lung function test would greatly facilitate their evaluation and appropriate treatment. We have, therefore, assessed whether the shape of the tidal breathing expiratory flow curve would give useful information in such a population. One hundred and twenty traces were randomly selected from plethysmographic measurements of thoracic gas volume and airway resistance made during a follow-up study of a prematurely born population. The children had a median gestational age of 29 (range 23-35, interquartile range 27-31) weeks and postnatal age at the time of measurement of 11 (range 6-24, interquartile range 7-13) months. From the flow and volume signals, the mean time to reach peak tidal expiratory flow as a proportion of the total expiratory time (tPTEF : tE) was determined for each child. The median tPTEF : tE differed significantly between children who, in the neonatal period, had or had not required mechanical ventilation (p < 0.001) and had or had not had an increased inspired oxygen requirement (p < 0.01), and who were or were not symptomatic at follow-up (p < 0.001). Logistic regression analysis demonstrated that a low tPTEF : tE ratio was independently associated with symptom status. These results suggest that assessment of a tidal breathing parameter during follow-up of prematurely born children may be useful. As tPTEF : tE can be measured without sedation, relatively quickly and with simple equipment, potentially large study populations could be investigated, and this technique should now be evaluated in a non-sedated group of young prematurely born children.

Birth Weight↗

PubMed1998

The effect of intra-articular irrigation injection therapy on osteoarthrosis of the temporomandibular joint.

OBJECTIVE: To investigate the effect of intra-articular irrigation-injection therapy in treating osteoarthrosis of the temporomandibular joint. MATERIALS AND METHODS: Thirty-seven patients (the test group) received intra-articular irrigation injection; 26 patients (the control group) received intra-articular injection of steroid. The synovial fluid, aspirated from five subjects of the test group before and after the therapy, was assayed to determine the tumor necrosis factor. RESULTS: Clinical evaluations were performed 3 months after the therapy. Thirteen subjects in the test group fell into the "excellent" category, 19 into the "good" category, and five into the "no effect" category; in the control group, eight subjects fell into the "excellent" category; nine into the "good" category, and nine into the "no effect" category. The category difference in total effectiveness between the test group and the control group is statistically significant (X2 = 3.9340 P < 0.05). TNF in synovial fluid also showed statistically significant differences before and after treatment (T = 2.8825, P < 0.05). CONCLUSIONS: Intra-articular irrigation injection is an effective therapy method for treating osteoarthrosis and is superior to intra-articular injection of steroid.

Adult↗

PubMed1997

Secretion of proinflammatory cytokines by epithelial cells in response to Chlamydia infection suggests a central role for epithelial cells in chlamydial pathogenesis.

Chlamydia species infect epithelial cells at mucosal surfaces, and are major causes of sexually transmitted diseases. Infection is characterized by inflammation which is exacerbated upon reinfection, ultimately leading to tissue damage and scarring. Although central for the development of disease manifestations, little is known about the mechanisms that initiate and sustain the inflammatory response to Chlamydia. Infection of cervical and colonic epithelial cells with Chlamydia trachomatis and Chlamydia psittaci is shown in the present studies to upregulate mRNA expression and secretion of the proinflammatory cytokines IL-8, GRO alpha, GM-CSF, and IL-6. In contrast to the rapid, but transient, cytokine induction following infection with other invasive bacteria, the epithelial cytokine response to Chlamydia was delayed until 20-24 h after infection, persisted throughout the chlamydial growth cycle (2-4 d), and required bacterial protein synthesis. Moreover, epithelial cell lines and primary endocervical epithelial cells released IL-1alpha after Chlamydia infection, and increased secretion of the proinflammatory cytokines could be inhibited by anti-IL-1alpha. This suggests that IL-1alpha, released following lysis of infected epithelial cells, may amplify the inflammatory response by stimulating additional cytokine production by noninfected neighboring cells. These findings suggest a novel pathophysiologic concept wherein the acute host response to Chlamydia at mucosal surfaces is primarily initiated and sustained by epithelial cells, the first and major targets of chlamydial infection.

Actins↗

PubMed1997

The phtE locus in the phaseolotoxin gene cluster has ORFs with homologies to genes encoding amino acid transferases, the AraC family of transcriptional factors, and fatty acid desaturases.

A cluster of genes involved in the production of phaseolotoxin, a phytotoxin produced by Pseudomonas syringae pv. phaseolicola, contains eight (phtA through phtH) complementation groups (Y. X. Zhang, K. B. Rowley, and S. S. Patil, J. Bacteriol., 175:6451-6458, 1993). In this study, sequencing of the region encompassing the phtE locus revealed six putative open reading frames (ORFs), each preceded by a putative ribosomal binding site, and all oriented in the same direction. Reverse transcription-polymerase chain reaction suggested that the phtE locus is transcribed as one large (6.4 kb) transcript, indicating that the ORFs constitute an operon. Primer extension analysis showed that the transcript begins at a T, located 31 bp upstream of the ATG codon of ORF1. Comparison of the sequences of the putative ORFs with the sequences of known genes revealed that ORF3, encoding a protein containing 395 amino acids, has 55% similarity to the acetylornithine aminotransferase gene from Escherichia coli, and the ornithine aminotransferase genes from other organisms. A lysine residue that is a binding site for pyridoxal phosphate and an arginine residue that is a binding site for the alpha-carboxylate group of the substrate are conserved in ORF3. These data suggest that ORF3 encodes a protein involved in the biosynthesis of ornithine, a constituent of phaseolotoxin. ORF5, encoding a peptide of 378 amino acid residues, possesses a helix-turn-helix motif at the C-terminal end that is characteristic of the AraC family of transcriptional factors, and there is a possible leucine zipper at the N-terminal end of this peptide. ORF6, encoding a protein of 327 amino acids, has about 40% similarity with the fatty acid desaturase gene, desA, of Synechocystis Pcc6803 and considerable similarity with fatty acid desaturase genes from other organisms. ORF6 and desA show very similar hydropathy profiles and both contain a copper binding signature. Computer searches did not discover significant homologies in the data base for the other ORFs, but hydropathy analysis showed that all of them contain one to several hydrophobic domains, suggesting that the gene products of these ORFs may be membrane associated.

Amino Acid Sequence↗

PubMed1997

Structural studies of the surface projections of Chlamydia trachomatis by electron microscopy.

Rod-like projections on the surface of Chlamydia trachomatis have been studied by a combination of computer image analysis and electron microscopy. The rods, c. 60-80 A in diameter and c. 500 A in length, were found on the surface of prokaryocells of C. trachomatis inserted in the cytoplasmic membrane through a ring-like structure in the outer membrane. The rod-like structures were found at all stages of the life cycle, even in very small elementary bodies (EBs) of C. trachomatis and in vesicles < 0.2 micron. Computer image analysis of isolated rods indicated that they comprise helically arranged subunits with a periodicity of c. 50 A. From their localisation and distribution, these structures may be related to the proliferation, or to the infectivity, of chlamydiae.

Animals↗