Search PubMed⌕ Search

Biomedical subjects

Y S Liu

Publications and source records attributed to Y S Liu.

At least 37 records · Page 2Linked to original sources
PubMed2000

Upregulation of tyrosine kinase TKT by the Epstein-Barr virus transactivator Zta.

The Zta protein is a key transactivator involved in initiating the Epstein-Barr virus (EBV) lytic cascade. In addition to transactivating many viral genes, Zta has the capacity to influence host cellular signals by binding to promoter regions or by interacting with several important cellular factors. Based on the observation that tyrosine kinases play central roles in determining the fate of cells, a kinase display assay was used to investigate whether cells expressing Zta have an altered pattern of kinase expression. The assay revealed that TRK-related tyrosine kinase (TKT) is expressed at significant levels in Zta transfectants but not in control cells. Additional evidence was obtained from Northern and Western blotting. Importantly, the upregulation of phosphorylated TKT and TKT downstream effector matrix metalloproteinase 1 in Zta transfectants hinted that TKT might initiate a signaling cascade in Zta-expressing cells. In addition, deletion analysis of the Zta protein revealed that the transactivation and dimerization domains were both essential for the upregulation of TKT transcription. Moreover, correlation of expression levels of Zta and TKT transcripts in nasopharyngeal carcinoma biopsy specimens was clearly demonstrated by quantitative PCR (Q-PCR), which provides the first evidence for an effect of Zta on cellular gene expression in vivo. These findings offer insight into the virus-cell interactions and may help us elucidate the role of EBV in tumorigenesis.

Cell Line, Transformed↗
PubMed2000

[Effects of noise and music on EEG power spectrum].

Objective. To observe the effect of noise and music on EEG power spectrum. Method. 12 healthy male pilots aged 30 +/- 0.58 years served as the subjects. Dynamic EEG from 16 regions was recorded during quiet, under noise or when listening to music using Oxford MR95 Holter recorder. Changes of EEG power spectrum of delta, theta, alpha1, alpha2, beta1 and beta2, frequency components in 16 regions were analyzed. Result. The total alpha1 power was significantly decreased, while the total theta power was significantly increased when listening to music; It implies that the interhemispheric transmission of information in the frontotemporal areas might be involved. Conclusion. The changes of the EEG power spectrum were closely related to man's emotions; relaxation was associated with music; Individual difference exists in the influence of sound on EEG.

Adult↗
PubMed1999

Examination of ionic liquids and their interaction with molecules, when used as stationary phases in gas chromatography.

Stable room-temperature ionic liquids (RTILs) have been used as novel reaction solvents. They can solubilize complex polar molecules such as cyclodextrins and glycopeptides. Their wetting ability and viscosity allow them to be coated onto fused silica capillaries. Thus, 1-butyl-3-methylimidazolium hexafluorophosphate and the analogous chloride salt can be used as stationary phases for gas chromatography (GC). Using inverse GC, one can examine the nature of these ionic liquids via their interactions with a variety of compounds. The Rohrschneider-McReynolds constants were determined for both ionic liquids and a popular commercial polysiloxane stationary phase. Ionic liquid stationary phases seem to have a dual nature. They appear to act as a low-polarity stationary phase to nonpolar compounds. However, molecules with strong proton donor groups, in particular, are tenaciously retained. The nature of the anion can have a significant effect on both the solubilizing ability and the selectivity of ionic liquid stationary phases. It appears that the unusual properties of ionic liquids could make them beneficial in many areas of separation science.

Chromatography, Gas↗
PubMed1999

Comparison of pure nicotine- and smokeless tobacco extract-induced toxicities and oxidative stress.

The toxicities and oxidative stress-inducing actions of (-)-nicotine and smokeless tobacco extract (STE), containing equivalent amounts of nicotine, were studied. Toxicities were determined by colony formation assays using Chinese hamster ovary (CHO) cells. Results indicated that nicotine is less toxic than smokeless tobacco extract that contained the same amount of nicotine. The generation of reactive oxygen species, following treatment with smokeless tobacco extract and nicotine, was assessed by measurement of changes in glutathione (GSH) and malondialdehyde (MDA) levels. CHO cells (5 x 10(5) cells/5 ml media) were incubated with 4, 0.8, and 0.08 mg of nicotine and STE containing the same amounts of nicotine. All preparations of smokeless tobacco extract significantly decreased GSH levels and increased MDA generation. However, 0.08 mg of nicotine treatment did not result in a significant change in GSH level, and only 4 mg of nicotine were sufficient to increase MDA generation. Addition of free radical scavenging enzymes, superoxide dismutase (SOD) and catalase (CAT), and an intracellular GSH precursor, N-acetyl-L-cysteine (NAC), replenished the GSH levels in nicotine-treated cells. GSH levels in cells exposed to smokeless tobacco extract containing 4 and 0.8 mg nicotine remained significantly lower than the control with the addition of SOD and CAT. However, co-addition of NAC with smokeless tobacco extract preparations returned the GSH levels to the control level. Lactate dehydrogenase (LDH) activities were measured in the media to establish the membrane damage following exposure to smokeless tobacco extract and nicotine. Treatment of cells with 4 mg nicotine caused a significant increase in LDH activity, which was returned to control level in the presence of the antioxidant enzymes and NAC. Smokeless tobacco extract did not change the LDH activity. http://link.springer-ny. com/link/service/journals/00244/bibs/37n4p434.html</++ +HEA

3,4-Methylenedioxyamphetamine↗
PubMed1999

Use of infrared emission detection thermometer in Chinese neonates.

OBJECTIVE: To evaluate the reproducibility of Thermoscan, an infrared emission detection ear thermometer, and to establish the normal reference range of ear temperature in Chinese neonates. METHODS: Neonates were recruited from the inpatients population with exclusion of those suffering from infections. RESULTS: Forty-nine neonates were recruited with 1,115 temperature taking sessions. Mean left ear temperature was 36.64 degrees C +/- 0.35 degree C. Mean right ear temperature was 36.64 degrees C +/- 0.37 degree C. Clinical repeatability for left and right ear was 0.17 degree C and 0.17 degree C, respectively. CONCLUSION: Thermoscan produced reproducible results in Chinese neonates. The normal range of ear temperature for Chinese neonates is 35 degrees C to 37 degrees C. Ear temperature > 37.8 degrees C should be regarded as fever.

Asian People↗
PubMed1998

Bilateral idiopathic infantile pyoceles: a case report.

A 15-day-old infant was admitted to the 803 Military Hospital with swelling, bilateral erythematous changes, a tender firm mass in the scrotum and fever of six hours' duration. Scrotal sonography showed accumulated fluid with internal echoes in both hydrocele sacs. Aspirated fluid was found to contain Escherichia coli and bilateral scrotal pyoceles was diagnosed. The most common etiologic factor for this is meconium peritonitis, with surgical drainage being the necessary treatment. The case is reported, with a review of the literature.

Escherichia coli Infections↗
PubMed1997

Transcriptional analysis of the threonine dehydrogenase gene of Xanthomonas campestris.

The nucleotide sequence has previously been determined for the Xanthomonas campestris pv. campestris gene coding for threonine dehydrogenase (tdh). Flanking this gene are the upstream region possessing promoter activity and the downstream perfect inverted repeat having potential to form a stem-loop structure which resembles a transcription terminator. In addition, Northern blot analysis suggested the transcript of this gene to be monocistronic. In the present study, the essential region for promoter activity was narrowed down to a stretch of 57 bp which still retained 84% of the promoter activity. The first nucleotide to be transcribed is the guanosine at 30 nt upstream from the proposed tdh start codon. The putative terminator exhibited transcriptional termination activity bidirectionally in both Escherichia coli and X. campestris. These observations indicate that the transcriptional structure of X. campestris tdh is different from that of E. coli where tdh and kbl are organized into the tdh operon. Furthermore, the expression of tdh in X. campestris is repressed by leucine, a situation different from that in E. coli where leucine induces the expression of tdh operon.

Alcohol Oxidoreductases↗
PubMed1997

Molecular characterization of the gene coding for threonine dehydrogenase in Xanthomonas campestris.

The Xanthomonas campestris pv. campestris 17 gene tdh, which codes for the threonine dehydrogenase (TDH), was cloned and sequenced. The deduced gene product, a polypeptide consisting of 340 amino acids (Mr = 37,048), has 63.5% identity to the E. coli TDH in amino acid sequence and shares residue conservation with the alcohol/polyol dehydrogenases from different organisms. TDH activity was not detectable in the tdh mutant constructed by gene replacement; however, the enzyme activity in the mutant complemented in trans by a plasmid containing the complete tdh sequence was increased by 15 folds over Xc17. Northern blot analysis detected an mRNA with a size similar to that of the Xc17 tdh coding region, suggesting that the tdh gene-containing transcript may be monocistronic.

Alcohol Oxidoreductases↗
PubMed1997

Phosphotyrosine phosphatase activity in the macrophage is enhanced by lipopolysaccharide, tumor necrosis factor alpha, and granulocyte/macrophage-colony stimulating factor: correlation with priming of the respiratory burst.

Tyrosine phosphorylation is now recognised as a key event in the activation of the macrophage respiratory burst. Since vanadate, a phosphotyrosine phosphatase (PTP) inhibitor is able to enhance the respiratory burst, we proposed that agents which prime the macrophage for enhance respiratory burst activity may do so by suppressing cellular PTP activity. The level of PTP activity in murine bone marrow-derived macrophages (BMM) was assessed by the ability of cell lysates to dephosphorylate 32P-labelled RR-src peptide. In contrast to our hypothesis, pretreatment of BMM with bacterial lipopolysaccharide (LPS), tumor necrosis factor alpha (TNF alpha) or granulocyte/macrophage-colony stimulating factor (GMCSF), agents which prime for enhanced respiratory burst activity, was found to dramatically increase the level of cellular PTP activity. The time-course for this increase correlated well with the time course of priming by these agents. In addition, colony stimulating factor-1, a cytokine which does not prime the macrophage respiratory burst, did not enhance PTP levels. The physiological relevance of the increased PTP activity was further supported by confirming it was active against endogenous tyrosine phosphorylated substrates. Interestingly, phorbol myristate acetate and zymosan, agents which trigger the macrophage respiratory burst, were found to inhibit the PTP activity of BMM. Our results demonstrate the regulation of cellular PTP activity by priming agents and further highlight the importance of tyrosine phosphorylation and dephosphorylation events in the regulation of macrophage function.

Animals↗
PubMed1997

Heparin and heparan sulfate bind to snake cardiotoxin. Sulfated oligosaccharides as a potential target for cardiotoxin action.

Cardiotoxins (CTXs) from cobra venom show cytotoxicity toward several cell types. They cause systolic heart arrest and severe tissue necrosis. Their interaction with phospholipids is established but by itself fails to explain the specificity of these toxins; other component(s) of membrane must, therefore, intervene to direct them toward their target. We herein show, for the first time, that sulfated glycosaminoglycans, heparin, heparan sulfate (HS), chondroitin sulfate (CS), and dermatan sulfate (DS), interact with CTX A3, a major component of Taiwan cobra venom, by use of affinity chromatography, circular dichroism, absorbance, and fluorescence intensity and anisotropy measurements. The relative strength of binding, determined by the NaCl concentration required to dissociate the CTX-glycosaminoglycan complex, varied as follows: heparin > DS > CS > HS. In physiological buffer (8 mM Na2HPO4, 2.7 mM KCl, 1.8 mM KH2PO4, 138 mM NaCl, pH 7.4), however, only heparin and HS bound to CTX, with respective dissociation constants of 1.4 and 16 microM, while CS and DS failed to exhibit well defined binding behavior, as indicated by fluorescence measurements. We estimate that CTX makes 3-4 ionic contacts with heparin based on a salt-dependent binding study and that approximately 40% of binding free energy is derived from purely electrostatic interactions under physiological conditions. Sulfated pentasaccharide may be sufficient to bind to CTX. We also found that heparin accentuates the penetration of CTX into phospholipid membranes as analyzed by Langmuir monolayer measurement. In view of these results we propose that heparin-like moieties of the cell surface may modulate the action of CTX.

Binding Sites↗
PubMed1997

Frequency and clinico-pathological associations of ras mutations in colorectal cancer in the Victorian population.

BACKGROUND: Mutations in the oncogene ras occur in 20-50% of colorectal cancers. The presence of these mutations allows screening tests to be developed based on the identification of mutant DNA in cells derived from cancers. A study of the prevalence and clinicopathological associations of ras mutations was undertaken. METHODS: The frequency of mutations in codons 12 and 13 of the K-ras gene was investigated in 103 colorectal carcinomas using restriction fragment length polymorphism. RESULTS: Mutations were detected in 32% (33/103) of the tumours, predominantly in codon 12 (25/33). No mutations were detected in normal-appearing mucosa from the same patients. CONCLUSIONS: Analysis of the frequency of ras mutations compared with various independent clinical variables revealed a sex-linked relationship between the presence of a ras mutation and nodal status but no correlation with any other clinical parameter was found. The findings suggest that screening tests based on ras mutation detection may lack sensitivity because of the presence of mutations in only 32% of tumours.

Aged↗
PubMed1997

Combinations of three immunological assays for detecting anti-Toxoplasma IgG in the sera of patients infected with Toxoplasma gondii.

Enzyme-linked immunosorbent assay (ELISA), Dot-ELISA and Dot-immunogold silver staining (Dot-IGSS) were simultaneously used to detect the specific IgG against Toxoplasma gondii in 65 patients infected with the protozoa. The positive rates were 86.51%, 92.51% and 98.64%, respectively. When ELISA and Dot-ELISA results were put together, the positive rate increased to 95.38%. When Dot-IGSS results were combined with those of ELISA or Dot-ELISA, the positive rate was raised to 100%. The difference in positive rate between ELISA and Dot-IGSS was significant (x2 = 6.93, p < 0.01), but no statistically significant differences were found between ELISA and Dot-ELISA or between Dot-ELISA and Dot-IGSS. Paired comparison of the reacting intensities of the sera in the 3 assays showed the correlations were highly significant (p < 0.001), with r = 0.608 between Dot-IGSS and Dot-ELISA, r = 0.8194 between Dot-IGSS and ELISA and r = 0.517 between Dot-ELISA and ELISA. Hence combination of different serological assays may increase their sensitivity and specificity for detecting the anti-Toxoplasma antibodies.

Animals↗
PubMed1996

Dot-immunogold-silver staining in the diagnosis of cysticercosis.

Dot-immunogold-silver staining (Dot-IGSS) and Dot-ELISA were used, with Taenia solium cyst fluid antigen, to detect specific antibodies in the sera of patients with cysticercosis. All 40 confirmed cases of cysticercosis were found to be positive when tested by 2 methods. The average titer of the sera detected by Dot-IGSS was 1:27,470, which was significantly higher than that detected by Dot-ELISA. The false positive rates were 2% and 4% in 50 healthy controls for Dot-IGSS and Dot-ELISA, respectively, with a low titer of 1:20.

Antibodies, Helminth↗
PubMed1995

Application of dot-immunogold-silver staining in the diagnosis of clonorchiasis.

All 35 confirmed clonorchiasis cases showed a positive reaction in dot-immunogold-silver staining (Dot-IGSS) with a mean serum titre of 1:1656, while none of the sera from 35 normal individuals reacted. A seroepidemiological survey of middle-school students revealed a positive rate of 17.0% (142/836), and 76.1% (105/138) of the serologically positive students were egg positive in stool examination. The egg positive rates in those with antibody at levels of 1+ to 4+ were 57.1% (28/49), 75.7% (28/37), 94.7% (36/38) and 92.9% (13/14) respectively. It is believed that Dot-IGSS can be used for the clinical diagnosis and epidemiological survey of clonorchiasis.

China↗
PubMed1994

Comparative study of Dot-immunogold silver staining and Dot-ELISA for the detection of serum antibodies against Wuchereria bancrofti.

Dot-immunogold silver staining (Dot-IGSS) and Dot-ELISA, using the soluble antigen of Brugia malayi, were employed to detect anti-Wuchereria bancrofti antibodies in 50 cases of Wuchereria bancrofti microfilaremia. The positive rates were 100% and 90% in Dot-IGSS and Dot-ELISA respectively. The average titer in the 45 positive cases was 1:184 (1:10-1:2560) for Dot-IGSS and 1:150 (1:10-1:2560) for Dot-ELISA, with 30 cases showing the same titer in both tests, 13 cases showing higher titer in Dot-IGSS than in Dot-ELISA and 2 cases in the former showing lower titers than in the latter. There was a linear relationship between the titers of antibodies detected by Dot-IGSS and by Dot-ELISA (r = 0.8443). Dot-IGSS, similar to Dot-ELISA, is easy to carry out and the result is easy to read. It is seen that Dot-IGSS is highly sensitive and specific and is practicable for immunodiagnosis and surveillance of filariasis.

Animals↗