Biomedical subjects

X Tan

Publications and source records attributed to X Tan.

At least 37 records · Page 2Linked to original sources

PubMed2001

Phosphorylation of p90rsk during meiotic maturation and parthenogenetic activation of rat oocytes: correlation with MAP kinases.

This paper reports on the activation of p90rsk during meiotic maturation and the inactivation of p90rsk after electrical parthenogenetic activation of rat oocytes. In addition, the correlation between p90rsk and MAP kinases after different treatments was studied. We assessed p90rsk activity by examining its electrophoretic mobility shift on SDS-PAGE and evaluated ERK1+2 activity by both mobility shift and a specific antibody against phospho-MAP kinase. The phosphorylation of p90rsk during rat oocyte maturation was a sequential process that may be divided into two stages: the first stage was partial phosphorylation, which was irrelevant with MAP kinases because p90rsk phosphorylation took place prior to activation of MAP kinases. The second stage inferred full activation occurred at the time when MAP kinases began to be activated (3 h after germinal visicle breakdown). Evidence for the involvement of MAP kinases in the p90rsk phosphorylation was further obtained by the following approaches: (1) okadaic acid (OA) accelerated the phosphorylation of both MAP kinases and p90rsk; (2) OA induced phosphorylation of both MAP kinases and p90rsk in the presence of IBMX; (3) when activation of MAP kinases was inhibited by cycloheximide, p90rsk phosphorylation was also abolished; (4) dephosphorylation of p90rsk began to take place at 3 h post-activation, temporally correlated with the completion of MAP kinase inactivation; (5) phosphorylation of both kinases was maintained in oocytes that failed to form pronuclei after stimulation; (6) OA abolished the dephosphorylation of both kinases after parthenogenetic activation. Our data suggest that MAP kinases are not required for early partial activation of p90rsk but are required for full activation of p90rsk during rat oocyte maturation, and that p90rsk dephosphorylation occurs following MAP kinase inactivation after parthenogenetic activation of rat oocytes.

1-Methyl-3-isobutylxanthine↗

PubMed2001

Three new sesquiterpene glycosides from Dendrobium nobile with immunomodulatory activity.

Dendroside A (1) and dendronobilosides A and B (2 and 3), three new sesquiterpene glycosides, have been isolated from the stems of Dendrobium nobile, a plant used in Chinese traditional medicine. Their structures and stereochemistry were determined as 10beta,12,14-trihydroxyalloaromadendrane 14-O-beta-D-glucopyranoside (1), 10,12-dihydroxypicrotoxane 10,12-di-O-beta-D-glucopyranoside (2), and 6alpha,10,12-trihydroxypicrotoxane 10-O-beta-D-glucopyranoside (3), respectively, on the basis of spectroscopic and chemical methods. Quantum chemistry calculations were used in support of the structural determination of 1. Compounds 1 and 2 were found to stimulate the proliferation of murine T and B lymphocytes in vitro, while compound 3 showed inhibitory activity in this same assay.

Adjuvants, Immunologic↗

PubMed2001

Electronic spectroscopy and excited state dynamics of the Al-H2/D2 complex.

The electronic spectra of the Al-H2 and Al-D2 complexes are investigated in a collaborative experimental and theoretical study. The complexes were prepared in a pulsed supersonic beam and detected with laser fluorescence excitation spectroscopy. Transitions to bound vibrational levels in electronic states correlating with the excited-state Al(3d, 4p, 4d) + H2/D2 asymptotes were observed by monitoring emission from lower excited Al atomic levels, formed in the non-radiative decay of the excited complex. Fluorescence depletion has also been used to verify that the observed Al-H2 bands all involve the same molecular carrier. The bands have been assigned to the more strongly bound Al-oH2 and Al-pD2 nuclear spin modifications. In contrast to our previous observations for Al(5s)-H2 [X. Yang and P. J. Dagdigian, J. Chem. Phys., 1998, 109, 8920], for which only one potential energy surface (PES) emanates from the dissociation asymptote, the Lorentzian widths of the different vibrational bands in the 3d, 4p, 4d<--3p transitions vary widely, in some cases allowing resolution of the rotational structure of the bands. With the help of the calculated Al(3p)-oH2/pD2 dissociation energies, binding energies of the observed excited vibronic levels are reported. The mechanism of predissociation is investigated theoretically through ab initio calculation of C2 nu cuts of the excited PESs. It is concluded that predissociation occurs through coupling with the repulsive Al(4s)-H2 PES. With these calculations, a qualitative interpretation of the observed bands could be made.

Journal Article↗

PubMed2001

Carbon disulfide exposure assessment in a Chinese viscose filament plant.

UNLABELLED: Carbon disulfide is a well-known occupational hazard in the viscose industry, and studies have shown considerable health effects when workers are exposed to high concentrations of this reagent. At exposure levels below the TLV-TWA(31 mg/m3), findings remain contradictory, probably due to deficient exposure data. The present study tries to identify the occupational hazards and thoroughly assess the exposure levels in a Chinese viscose rayon plant. METHODS: An industrial hygienic field survey and a sampling campaign were carried out, including multi-gas monitoring, on-line measurements, and stationary assessment in the spinning hall as well as personal exposure sampling for spinners (by charcoal tube absorbing and GC-FPD analysis). All data was introduced into Foxpro database, and analyzed by Epi info (6.04) and SPSS. RESULTS: On-line measurement showed that the geometric mean (GM) of carbon disulfide exposure amounted to 12.73 mg/m3 in 'exposure' and 0.08 mg/m3 in 'non-exposure' worksites. These concentrations in the air were related to the subject's activities showing the highest levels when they had to open the shield windows of the spinning machines. Stationary exposure measurements of carbon disulfide in the spinning hall amounted to 23.29 mg/m3 GM (range 5.8-97.94 mg/m3). Personal exposure of spinners was about 17.3 mg/m3 GM. Comparing these methods, the personal exposure sampling could exactly express the exposure levels of the worker's contacting situation. The on-line measurement by multi-gas monitor might also be recommended to the factory as it has its own advantages of rapid and independent assessment, but it under-estimates the exposure level.

Air Pollution, Indoor↗

PubMed2001

Transcriptional analysis of Marek's disease virus glycoprotein D, I, and E genes: gD expression is undetectable in cell culture.

The various alphaherpesviruses, including Marek's disease virus (MDV), have both common and unique features of gene content and expression. The entire MDV U(s) region has been sequenced in our laboratory (P. Brunovskis and L. F. Velicar, Virology 206:324-338, 1995). Genes encoding the MDV glycoprotein D (gD), glycoprotein I (gI), and glycoprotein E (gE) homologs have been found in this region, although no gG homolog was found. In this work, transcription of the tandem MDV gD, gI, and gE genes was studied and found to have both unique characteristics and also features in common with other alphaherpesviruses. MDV gD could not be immunoprecipitated from MDV GA-infected duck embryo fibroblast cells by antisera reactive to its TrpE fusion proteins, while gI and gE could be. When the gD gene was subjected to in vitro-coupled transcription-translation, the precursor polypeptide was produced and could be immunoprecipitated by anti-gD. Northern blot, reverse transcriptase PCR, and RNase protection analyses have shown that (i) no mRNA initiating directly from the gD gene could be detected; (ii) a large but low-abundance 7.5-kb transcript spanning five genes, including the one encoding gD, was seen on longer exposure; and (iii) transcription of the gI and gE genes formed an abundant bicistronic 3.5-kb mRNA, as well as an abundant 2.0-kb gE-specific mRNA. Therefore, the MDV gD gene expression is down-regulated at the transcription level in MDV-infected cell culture, which may be related to the cell-associated nature of MDV in fibroblast cells. Compared to the highly gD-dependent herpes simplex virus and the other extreme of the varicella-zoster virus which lacks the gD gene, MDV is an intermediate type of alphaherpesvirus.

Animals↗

PubMed2001

Phosphorylation of hepatic stimulator substance on mitogen-activated protein kinase in BEL-7402 hepatoma cells.

OBJECTIVE: To obtain more insight into information of signal transduction of EGF-receptor-mediated pathway response to the stimulation of hepatic stimulator substance (HSS). METHODS: HSS was extracted from weanling rat liver and partially purified. Bioactivity of HSS was confirmed with its ability to proliferate hepatoma cell in vitro. Meanwhile, a rat recombinant HSS vector was constructed and expressed in BL-21 E. Coli. Mitogen-activated protein kinase (MAPK) activation marked by phosphorylation at Thr202/Tyr204 was determined by Western blot. RESULTS: The molecular weight of the biochemically purified HSS was found identically to that of the recombined HSS as expressed in the prokaryotic cells. After the treatment of HSS, cellular MAPK phosphorylation was initiated obviously at 15 min and maintained to 30 min. In comparison with EGF, MAPK phosphorylation as stimulated by HSS appeared less intensive and later time-kinetics as well. The HSS induction on cellular MAPK phosphorylation was gradually inhibited by PD98059, a specific inhibitor of MAPK kinase (MEK). A complete blockade was seen at 100 micromol/L of PD98059. CONCLUSIONS: The involvement of HSS on MAPK activation implies that this liver-specific growth factor might take part in, either individually or as combined with other growth factors, the regulation of TPK signaling cascade during hepatocyte proliferation.

Animals↗

PubMed2001

[A lumped parameter model of the peripheral extra-corporeal circulation].

A three-element model of lumped parameter in peripheral extra-corporeal circulation of an animal has been proposed and set up according to the fluid network theory. GEAR method, appropriate for the computation of the rigid problems, was used to solve the ordinary differential equations, so that a good convergence of the solution to the equations has been achieved. Physiological data of a 20 kg dog, obtained from our animal experiments were used to calculate the pressure and flow rate of important organs. The results of the mathematical model and animal tests showed that the peripheral extra-corporeal circulation could supply enough blood to the important organs, e.g. heart and brain, when the natural heart beating stopped. The results from both theoretical and experiments are critical to the cardiopulmonary cerebral resuscitation for the animals as well as for human beings.

Animals↗

PubMed2001

[Expression of monocyte chemotacticp protein-1 in the eutopic endometrium of women with endometriosis].

OBJECTIVE: To examine the expression of monocyte chemotactic protein-1 (MCP-1) messenger ribonucleic acid (mRNA) in the endometrium of patients with and without endometriosis. METHODS: A reverse transcription-polymerase chain reaction (RT-PCR) method was utilized to examine and quantitate MCP-1 mRNA expressions and levels in the eutopic endometrium. Thirty patients with endometriosis were included as study group, and 20 patients without endometriosis selected as control group. RESULTS: 26 (87%) of 30 samples of endometrium from patients with endometriosis expressed MCP-1 mRNA, 19 of which were strong expression, while 15 (75%) of 20 samples of endometrium from patients without endometriosis express MCP-1 mRNA (P > 0.05). When endometriosis were grouped by Revised American Fertility Society (RAFS) stages, there was no obvious correlation between stage and MCP-1 mRNA expression level (P > 0.05). Semi-quantitative PCR showed the expression level of MCP-1 in endometrium of patients with endometriosis were higher than those of patients without endometriosis (0.746 +/- 0.345 Vs 0.460 +/- 0.341 respectively, P < 0.05). CONCLUSIONS: The MCP-1 mRNA is over expressed in the eutopic endometrium from patients with endometriosis, which may play some roles on the pathogenesis of endometriosis.

Adult↗

PubMed2001

[A cross-sectional study on the promotion and execution of "the practiced guidelines for the management of common malignant gynecological tumors"].

OBJECTIVE: To evaluate the promotion and execution of "the practice guidelines for the management of common malignant gynecological tumors (draft)" (guidelines). METHODS: Cross sectional study was applied. All obstetricians and gynecologists (Obs/Gyns) who attended the Chinese Medical Association's Senior Workshop for Department Chairmen of Obstetrics and Gynecology were included. RESULTS: Three hundred and fifty Obs/Gyns were inquired, while two hundred and eighty-one questionnaires were available. Ninety percent (253/281) of Obs/Gyns declared that they had read the guidelines, and 96.4% (271/281) of them thought it necessary to establish the guidelines. In those Obs/Gyns who read the guidelines, 87.7% (222/253) of them managed gynecological tumors according to the guidelines. In those who did not read the guidelines, most were obstetricians or worked in special hospitals, while all gynecological oncologists read the guidelines. In addition, there were still many suggestions on the guidelines. CONCLUSION: The guidelines has been playing a role in the management of common malignant gynecological tumors and need to be revised regularly.

Cross-Sectional Studies↗

PubMed2001

[The effects of low birth weight, gestational age on lung function in childhood].

OBJECTIVE: To evaluate the effects of low birth weight, gestational age on lung function in later childhood. METHODS: Height, body weight and lung function were measured in a cohort of 35 children with low birth weight (aged 6 approximately 9 y) and 35 healthy controls matched for sex and age with normal birth weight. At the same time, we inquired their gestational age and passive smoking history. The correlation analysis was used to analyze the relationship between lung function in these children and birth weight and gestational age. RESULTS: FVC, FEV(1), FEV(1)% pred, V(75), V(50), V(50%) Pred, (V(25%) Pred in children with low birth weight were significantly lower than those in children with normal birth weight (P < 0.05). The lung function statistically positively correlated with birth weight (r = 0.245 approximately 0.365, P < 0.05), but not with gestational age (P > 0.05). CONCLUSION: Low birth weight was positively correlated with most lung function parameters in childhood.

Case-Control Studies↗

PubMed2001

[Study on FM100-HUE color vision in male workers exposed to lower concentration of carbon disulfide].

The effect of CS2 on color vision in workers exposed to CS2 was explored. The color discrimination in 191 exposed and 93 non-exposed male workers was studied by a Farnsworth Munsell 100-HUE (FM100-HUE) test. The results showed that the time weighted average (TWA) concentration of CS2, determined by Japan GC-17A gas chromatography, was (14.75 +/- 6.89) mg/m3 in a long rayon workshop and (16.30 +/- 5.42) mg/m3 in a short rayon workshop. Higher FM100-HUE color vision score was often in the exposed group (106.9) than in the controls (78.3). The discrimination to green and blue zone was also significantly impaired (P < 0.05). It is concluded that the color vision was disturbed in workers exposed to CS2. The workers should be followed by health surveillance.

Adult↗

PubMed2001

[Expression of vascular endothelial growth factor and thrombospondin-1 in the ectopic and eutopic endometrium of women with endometriosis].

OBJECTIVE: To detect the expression of vascular endothelial growth factor (VEGF) and thrombospondin (TSP)-1 mRNA in the ectopic and eutopic endometrium of patients with endometriosis. METHODS: Thirty-two specimens of ovarian endometrioma, 12 red peritoneal lesion, 8 uterosacral ligament nodule, and 30 matched eutopic endometrium were biopsied from 38 patients with endometriosis, another 25 specimens of endometrium were biopsied from women without endometriosis. Reverse transcript-polymerase chain reaction (RT-PCR) and Northern Blot analysis were utilized to examine VEGF mRNA and TSP-1 mRNA expression and their relative levels in the above endometrium. RESULTS: Among endometriotic lesions, red peritoneal lesion expressed higher level of VEGF and lower level of TSP-1, whereas ovarian endometrioma expressed lower level VEGF and higher level of TSP-1. Eutopic endometrium of women with endometriosis had higer level of VEGF expression and lower level of TSP-1 expression than women without endometriosis. CONCLUSIONS: The expression of VEGF and TSP-1 in endometriotic lesion appears to be associated with its neovalscualization extent. The imbalance in expression of VEGF and TSP-1 in endometrium might be related to the development of endometriosis and its biological behavior.

Blotting, Northern↗

PubMed2000

High internight reliability of computer-measured NREM delta, sigma, and beta: biological implications.

BACKGROUND: Computer analysis of the sleep electroencephalogram (EEG) waveforms is widely employed, but there have been no systematic studies of its reliability. METHODS: The most commonly used computer methods are power spectral analysis with the fast-Fourier transform (FFT) and period amplitude analysis (PAA) with zero cross or zero first derivative half-wave measurement. We applied all three computer methods to the digitized EEG of 16 normal subjects who underwent 5 consecutive nights of baseline (placebo) recording. We evaluated the internight reliability of three non-rapid eye movement (NREM) frequency bands of special importance to sleep research: delta (0.3-3 Hz), sigma (12-15 Hz), and beta (15-23 Hz). RESULTS: Both FFT and the two methods of PAA gave excellent internight reliability for delta and sigma. Even a single night of recording correlated highly (r >.9) with the 5-night mean. Beta reliability was lower but still highly significant for both the PAA and the FFT measures. CONCLUSIONS: Computer-analyzed sleep EEG data are highly reliable. Period amplitude methods demonstrate that wave incidence and period as well as amplitude are reliable, indicating that the reliability of composite measures (FFT power, PAA integrated amplitude) is not solely based on individual differences in EEG amplitude. The high internight stability of NREM delta indicates that it possesses traitlike characteristics and is relatively independent of day-to-day variations in state.

Adult↗

PubMed2000

Differences of four catechins in cell cycle arrest and induction of apoptosis in LoVo cells.

(-)-Epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin-3-gallate (ECG), and (-)-epicatechin (EC) were found to have different cytotoxicities to human colon carcinoma LoVo cells. EGCG and EGC suppressed the growth of LoVo cells in dose-dependent manner; ECG and EC, however, had no obvious effects. At lower concentrations, EC did seem to promote slight proliferation. Similarly, EGCG and EGC, rather than ECG and EC, were found to induce apoptosis in LoVo cells. Moreover, EGCG, EGC, and ECG arrested G(1) phase in the cell cycle progression, whereas EC resulted in S phase arrest. We suggest that there are differences in the cytotoxicities of the four catechins to LoVo cells. They exert the effects by inducing apoptosis and regulating the cell cycle.

Apoptosis↗

PubMed2000

PLAG1 fusion oncogenes in lipoblastoma.

Lipoblastomas are pediatric neoplasms resulting from transformation of adipocytes. These benign tumors are typically composed of adipose cells in different stages of maturation within a variably myxoid matrix, and they contain clonal rearrangements of chromosome band 8q12. Because lipoblastomas resemble embryonic adipose tissue, characterization of their transforming mechanisms might reveal biological pathways in physiological adipogenesis. Herein, we demonstrate that lipoblastoma chromosome 8q12 rearrangements bring about promoter-swapping events in the PLAG1 oncqgene. We show that the hyaluronic acid synthase 2 (HAS2) or collagen 1 alpha 2 (COL1A2) gene promoter regions are fused to the entire PLAG1 coding sequence in each of four lipoblastomas. PLAG1 is a developmentally regulated zinc finger gene whose tumorigenic function has been shown previously only in epithelial salivary gland cells. Our findings reveal that PLAG1 activation, presumably resulting from transcriptional up-regulation, is a central oncogenic event in lipoblastoma.

Adipose Tissue↗

PubMed2000

Association of smoking and personality with a polymorphism of the dopamine transporter gene: results from a community survey.

In studies that used mixed volunteer samples, Lerman et al. [1999: Health Psychol 18:14-20] and Sabol et al. [1999: Health Psychol 18:7-13] reported on an association of smoking with a polymorphism of the dopamine transporter gene. We attempted to replicate this association in a nonvolunteer community sample of 861 Caucasians. No associations were found with either smoking initiation or smoking cessation. Sabol et al. [1999] also reported on an association of the dopamine transporter polymorphism with the personality trait of novelty seeking. However, we failed to find any associations with a range of personality traits, including a scale of fun seeking that correlates with novelty seeking. These negative findings suggest that either the original associations are not replicable or that any association is very small.

Adult↗

PubMed2000

Simultaneous determination of zidovudine and its monophosphate in mouse plasma and peripheral red blood cells by high-performance liquid chromatography.

Novel prodrugs for the intracellular delivery of zidovudine monophosphate (AZTMP) have recently been designed. To investigate the bioconversion and pharmacokinetic profiles of these compounds, an analytical method for the simultaneous determination of zidovudine (AZT) and AZTMP in mouse plasma and peripheral red blood cells was developed. Mouse whole blood samples were treated with TBAHS, EDTA and NaH2PO4, and separated into plasma and red blood cell portions. Samples were processed by solid-phase extraction using Bond Elut C18 cartridges. Chromatography was performed using an Hypersil ODS column and a mobile phase of 2.9% (v/v) acetonitrile and 97.1% (v/v) phosphate buffer, pH 7.50, with UV detection at 267 nm. The average extraction recoveries of AZTMP and AZT in plasma were approximately 85% and 97% over their linear ranges of 0.05-5 microg/ml and 0.125-25 microg/ml, respectively. Extraction recoveries of AZTMP and AZT from peripheral red blood cells averaged 56 and 69% over their linear ranges of 0.125-5 microg/ml and 0.125-25 microg/ml, respectively. The accuracy of the assay was 90-100%. The intra- and inter-day variations of the assay were less than 14%. The analytical method was found to be applicable, reliable and suitable for pharmacokinetic studies.

Animals↗

PubMed2000

COMT and DRD3 polymorphisms, environmental exposures, and personality traits related to common mental disorders.

In a community sample of 2,327 Caucasians, we tested the hypotheses that polymorphisms in the COMT and DRD3 genes are associated with personality traits conferring vulnerability to anxiety, depression, or alcohol misuse, or with current symptoms of these; and that the association is stronger in persons who also have been exposed to stressor experiences. To conserve resources and to allow replication, the genetic analysis was undertaken in two stages. For the COMT polymorphism, no statistically significant associations were found in the first sample of 862 persons. The remainder of the sample was therefore not analysed for that gene. For the DRD3 polymorphism, those in the first sample with at least one of the Ser(9) alleles had significantly higher scores in neuroticism (p=0.006) and behavioral inhibition (p=0.003). There was a trend, failing to meet the 1% significance criterion, for those with this genotype also to have higher depression and anxiety. The groups did not differ in alcohol use. In persons with the Ser(9) allele who were also exposed to stressors, there was a higher level of depression at the 5% level; and the depression level was higher in homozygotes. But when the remainder of the sample (1,465) was analysed, none of the associations reached statistical significance. We conclude that neither the COMT nor DRD3 polymorphisms are associated with anxiety, depression, or alcohol abuse. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:102-107, 2000

Catechol O-Methyltransferase↗