Biomedical subjects

Y Qin

Publications and source records attributed to Y Qin.

At least 19 recordsLinked to original sources

PubMed2006

Origin of nonlinear transport across the magnetically induced superconductor-metal-insulator transition in two dimensions.

We have studied the effect of perpendicular magnetic fields and temperatures on nonlinear electronic transport in amorphous Ta superconducting thin films. The films exhibit a magnetic field-induced metallic behavior intervening the superconductor-insulator transition in the zero temperature limit. We show that the phase-identifying nonlinear transport in the superconducting and metallic phases arises from an intrinsic origin, not from an electron heating effect. The nonlinear transport is found to accompany an extraordinarily long voltage response time.

Journal Article↗

PubMed2006

Lipoprotein lipase gene S447X polymorphism modulates the relation between central obesity and serum lipids, a twin study.

OBJECTIVE: To investigate the impact of lipoprotein lipase (LPL) gene S447X polymorphism on the relation between central obesity and lipid levels. DESIGN: A total of 961 adult twin pairs were included from the program of Chinese Twin Registry, between 2001 and 2002. Central obesity was defined as waist circumference > or =90 cm for male and > or =80 cm for female. Two statistical methods were performed to test the modification effect of S447X polymorphism of LPL gene on the relation between central obesity and lipid levels: one was Generalized Estimating Equation (GEE) models for all twin pairs and the other was co-twin matched case-control analysis in 82 central obesity discordant monozygotic twin pairs. RESULTS: In GEE models for all twins, central obesity was significantly associated with serum lipids except for high-density lipoprotein (HDL), while X447 allele had favorable effects on the levels of triglyceride (TG), HDL and TG to HDL ratio (TG/HDL). The interactions of S447X polymorphism and central obesity were statistically significant for TG/HDL and HDL. In central obesity discordant monozygotic twin pairs, central obesity was significantly related with 26.2% increase of TG and 27.2% increase of TG/HDL in S/S447 genotype, while in 447X allele carrier, central obesity was significantly related with 13.7% increase of HDL. CONCLUSION: These results suggest that LPL gene S447X polymorphism modifies the relation between central obesity and serum lipids, which also stresses the importance of reducing waist circumference to improve serum lipids for people with central obesity, especially those with S/S447 genotype.

Adult↗

PubMed2006

Cytotoxicity induced by grape seed proanthocyanidins: role of nitric oxide.

Grape seed proanthocyanidin extract (GPSE) at high doses has been shown to exhibit cytotoxicity that is associated with increased apoptotic cell death. Nitric oxide (NO), being a regulator of apoptosis, can be increased in production by the administration of GSPE. In a chick cardiomyocyte study, we demonstrated that high-dose (500 microg/ml) GSPE produces a significantly high level of NO that contributes to increased apoptotic cell death detected by propidium iodide and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. It is also associated with the depletion of intracellular glutathione (GSH), probably due to increased consumption by NO with the formation of S-nitrosoglutathione. Co-treatment with L-NAME, a NO synthase inhibitor, results in reduction of NO and apoptotic cell death. The decline in reduced GSH/oxidized GSH (GSSG) ratio is also reversed. N-Acetylcysteine, a thiol compound that reacts directly with NO, can reduce the increased NO generation and reverse the decreased GSH/GSSG ratio, thereby attenuating the cytotoxicity induced by high-dose GSPE. Taken together, these results suggest that endogenous NO synthase (NOS) activation and excessive NO production play a key role in the pathogenesis of high-dose GSPE-induced cytotoxicity.

Acetylcysteine↗

PubMed2006

Ultraviolet spectrophotometry as an index parameter for estimating the biochemical oxygen demand of domestic wastewater.

The relationship between ultraviolet absorbance at 280 nm (UV280) and the 5-day Biochemical Oxygen Demand (BOD5) test was evaluated using wastewater samples collected during March - December 1998 from the Fort Meade wastewater treatment plant (Maryland, U.S.A.). Three types of samples were collected: raw influent wastewater, primary effluent, and the effluent from the nitrification settling basin. A regression of BOD5 on UV280 was obtained using half of the data, with the other half of the data used to test application of the equation. The presence of NO3 and NO2, did not interfere with the BOD5/UV relationship. However, the relative fraction of organic compounds that absorb at UV280 and are biodegradable did appear to decrease across the treatment plant, thereby reducing the strength of the association between BOD5 and UV280 further along the treatment train. Interestingly, the exclusion of solids > 1 microm from the BOD5 test did not strengthen the association between BOD5 and UV280. These results suggest that simple UV absorbance measurements may be a useful analytical tool for wastewater treatment personnel, allowing them to quickly monitor for changes in the BOD5 during the treatment process and to quickly estimate the BOD5 when determining what dilutions to use in the standard BOD5 test. However, such relationships are likely to be wastewater and treatment plant specific and variable with time and treatment.

Bioreactors↗

PubMed2006

Centrosome changes during meiosis in horse oocytes and first embryonic cell cycle organization following parthenogenesis, fertilization and nuclear transfer.

Various types of cell cycle organization occur in mammals. In this study, centrosome changes during meiosis in horse oocytes, and first cell cycle organization following fertilization, parthenogenesis and nuclear transfer, were monitored. Cumulus oocyte complexes harvested from horse ovaries obtained from slaughtered mares were cultured in vitro. Meiotic oocytes of germinal vesicle (GV), germinal vesicle breakdown (GVBD), metaphase I and II (MI and MII) stages were selected at various set times during in vitro maturation. Embryos at the first cell cycle stage were generated by subjecting MII stage oocytes to fertilization by intracytoplasmic sperm injection (ICSI), parthenogenetic treatment or nuclear transfer. Centrosome changes during meiosis and the first cell cycle organization were detected by indirect immunofluorescent staining, using a mouse anti-alpha-tubulin antibody for microtubules and a rabbit anti-gamma-tubulin antibody for centrosomes. These examinations showed that the centrosomes of the horse oocyte reorganize themselves from the beginning of GV stage to leave only PCM of gamma-tubulin surrounding both poles of the MI and MII stage spindles. These MII oocytes can organize the separation of metaphase chromosomes during the first embryonic cell cycle by parthenogenetic treatment. When the MII oocytes were subjected to ICSI or nuclear transfer, one or two red-stained centrosomes of gamma-tubulin were introduced by the fertilising spermatozoon or the donor cell which associated with the sperm chromatin in the fertilized embryos and with the donor cell chromatin and microtubules in the cloned embryos. This finding suggests that centrosomes are not an essential component in the formation of the metaphase spindle during meiotic maturation of horse oocytes, but they can be introduced from the spermatozoon or donor cell and are necessary for the organization of normal embryonic development.

Animals↗

PubMed2006

Transfection of nm23-H1 increased expression of beta-Catenin, E-Cadherin and TIMP-1 and decreased the expression of MMP-2, CD44v6 and VEGF and inhibited the metastatic potential of human non-small cell lung cancer cell line L9981.

Nm23 is a metastasis suppressor gene. In this report, we transfected nm23-H1 cDNA into L9981, a human large cell lung cancer cell line with nm23 negative expression, and made a stable transfectant. L9981-nm23-H1 cells exhibited lower cells proliferation rate, more G0/G1 phase growth and an increase in apoptosis with a dramatic decreased in the tumor cells ability to metastasize. L9981-nm23-H1 cells also demonstrated a significantly reduced lymph node and pulmonary metastatic capacity in vivo when injected into the nude mice. Furthermore, we used DNA microarray analysis to explore the change in expression of the metastasis-related genes in L9981-nm23-H1 cells. We found that the expression of beta-Catenin, E-Cadherin and TIMP-1 were significantly increased while expression MMP-2, CD44v6, and VEGF was dramatically decreased in L9981-nm23-H1, as confirmed by RT-PCR and western blot. These results demonstrated that nm23-H1 can suppress the mobility and metastatic capacity of cancer cells and the molecular mechanism by which nm23-H1 suppresses tumor metastasis may be via increasing the expression of metastasis-related genes such as beta-Catenin, E-Cadherin and TIMP-1 and decreasing the expression of MMP-2, CD44V6 and VEGF.

Adenocarcinoma↗

PubMed2005

Dendritic cells pulsed with gp96-peptide complexes derived from human hepatocellular carcinoma (HCC) induce specific cytotoxic T lymphocytes.

Dendritic cells (DCs) are one of the most potent antigen-presenting cells (APCs) capable of activating immune responses. Different forms of tumor antigens have been used to load DCs to initiate tumor-specific immune responses. Heat shock proteins (HSPs) are considered natural adjuvants which have the ability to chaperone peptides associated with them presented efficiently by interaction with professional APCs through specific receptors. In the present study, we used HSP, gp96-peptide complexes, derived from human hepatocellular carcinoma (HCC) cells as antigens for pulsing DCs. We found that gp96-peptide complexes derived from HCC cells induced the maturation of DCs by enhancing expression of human leukocyte antigen class II, CD80, CD86, CD40, and CD83. The matured DCs stimulated a high level of autologous T cell proliferation and induced HCC specific cytotoxic T lymphocytes, which specifically killed HCC cells by a major histocompatability complex (MHC) class I restricted mechanism. These findings demonstrate that DCs pulsed with gp96-peptide complexes derived from HCC cells are effective in activating specific T cell responses against HCC cells.

Antigen Presentation↗

PubMed2005

Calcium changes and the response to methyl jasmonate in rice lodicules during anthesis.

Potassium pyroantimonate precipitation was used to locate loosely bound calcium in rice (Oryza sativa L.) lodicules before and after anthesis, and flowering of panicles was accelerated by treatment with methyl jasmonate. From 1 day to 4 h before anthesis, the number of calcium precipitates in the cell walls and vacuole membranes decreased gradually, whereas they increased remarkably in the cytoplasm and nucleolus. At the beginning of anthesis, the number of calcium granules in lodicules reduced sharply, but there was a large accumulation of flocculent precipitates in the vacuoles. After anthesis, the flocculent precipitates decreased in number until they disappeared, whereas the granular precipitates started to accumulate once again. The rice florets treated with 2 mM methyl jasmonate were induced to open within 10-30 min and they then closed 0.5-1 h later. The nucleolus, cytoplasm, and vacuole membrane of the lodicule cells contained many calcium granules during flowering, although the cell walls lacked calcium. At 1 h after treatment, the number of calcium granules had decreased, while flocculent precipitates were regularly observed in the nondegenerated cells. At 6 h after treatment, calcium grains started to reappear in the cell walls. These changes in calcium precipitates before and after anthesis indicate that the opening and closing of florets correlates with the calcium level in lodicule cells. In addition, excised panicles, with florets judged to be nearing anthesis, were soaked in 2-200 mM EGTA solution for 2 min after treatment with 2 mM methyl jasmonate. The results indicate that EGTA had an antagonistic effect on the methyl jasmonate-induced floret opening in rice.

Acetates↗

PubMed2005

Human papillomavirus type 16 E7 peptide(38-61) linked with an immunoglobulin G fragment provides protective immunity in mice.

OBJECTIVE: To explore whether the recombinant protein (Human papillomavirus (HPV) type16 E7 peptide(38-61) linked with an immunoglobulin G fragment) will generate protective immunity in mouse model. METHODS: In our study, we combined the HPV16 E7 peptide(38-61) with a murine IgG heavy chain constant region to construct a chimeric protein compound, which was highly expressed as inclusion bodies in a bacterial expression system with Escherichia coli. The purified chimeric protein was injected into C57BL/6 mice and the efficiency of the chimeric vaccine candidate was evaluated by antibody response assay, T cell proliferation assay, CTL assay, tumor challenge assay and therapeutic experiment. RESULTS: The chimeric vaccine candidate was able to induce anti-HPV antibodies as well as to elicit HPV16 E7-specific CTLs and T cell proliferation in a pre-clinical mouse model. It was also able to effectively protect mice against the challenge of HPV16-positive tumor cells, and to eradicate HPV16-expressing tumors in mice. CONCLUSIONS: The chimeric protein vaccine can induce E7-specific immune responses and protect mice against challenge of HPV16-positive tumor, even eradicate developed tumor. The results indicated a possibility to use the chimeric protein vaccine to protect human against HPV infection.

Animals↗

PubMed2004

The role of Zn in the interplay among Langmuir-Blodgett multilayer and myelin basic protein: a quantitative analysis of XANES spectra.

We have performed a quantitative analysis of the X-ray absorption near-edge structure (XANES) spectra at the Zinc K-edge of systems formed by phospholipid Langmuir-Blodgett multilayers (LBMLs) in the presence and in the absence of myelin basic protein (MBP) and in two hydration conditions. These spectra have been analysed by a new procedure called Minuit XANes (MXAN) which is able to perform a quantitative fit of XANES data in terms of structural parameters. By this method, we have been able to correlate the relevant differences between the spectra observed in the XANES range with the coordination changes due to reduction of the space around the Zinc when the level of hydration is lowered and/or the myelin basic protein is added. These spectral differences are peculiar of the XANES energy range, and are not present in the extended X-ray absorption fine structure (EXAFS) energy range where the analysis was previously performed. With this investigation, we give an unambiguous answer to the question of the role of zinc in such complexes by showing that the metal interacts with both the phospholipid heads of the substrate and the myelin basic protein.

Absorption↗

PubMed2003

Application of high-performance liquid chromatography-mass spectrometry to detection of diuretics in human urine.

A rapid, sensitive and reliable high-performance liquid chromatographic-mass spectrometric method for the detection of 25 diuretics in human urine has been developed. Atmosphere pressure chemical ionization (APCI) and electrospray ionization (ESI) modes were evaluated. A 2-ml volume of urine was extracted under basic conditions and separated on an Agilent Zorbax SB-C(18) column (150 x 2.1 mm, 5 microm). The mobile phase consisted of formic ammonium-formic acid buffer (pH 3.5) and acetonitrile. The effects of capillary temperature, sheath gas pressure and compositions of mobile phase on the sensitivity were studied. The recoveries of most of the diuretics were 75-95%. In the full scan mode, the limits of detection of the 25 diuretics were 0.25-25 ng/ml for APCI and 0.6-250 ng/ml for ESI. Under the optimal conditions, 14 diuretics from authentic urine samples were detected successfully by LC-APCI-MS. To obtain more fragmentation information on the chemical structure for positive confirmation, tandem mass analysis was also investigated.

Chromatography, High Pressure Liquid↗

PubMed2003

B-cell immunity in MS.

T-cell-mediated immunity has dominated studies of multiple sclerosis (MS) pathogenesis, mainly due to detection of activated T-cells in MS lesions, and analogies with the animal model experimental allergic encephalomyelitis. The prevailing aetiological hypothesis is that MS is a multifactorial disorder, affecting individuals predisposed by a combination of susceptibility genes and environmental factors. Plaque formation is attributed to immune mechanisms, triggered by an autoimmune attack directed against antigens in the myelin membrane. This article reviews the roles of components of the immune response in MS including B-cells, the complement cascade, antibodies and genes. Evidence suggests that B-cell clonal expansion in cerebrospinal fluid and plaques of MS patients indicate an ongoing, antigen-driven response in the central nervous system. That MS is an autoimmune disease remains inconclusive, but the assumption is that humoral immunity plays a role in lesion formation and perpetuation, or is involved in tissue-repair mechanisms. The paradigm of MS as a T-cell disease must be revisited, as B-cells are involved during the initial and later disease stages, and evidence is mounting for a 'degenerative process', in addition to (and possibly even preceding) inflammation.

Antibody Formation↗

PubMed2002

Second-trimester ultrasonographic assessment of the umbilical coiling index.

OBJECTIVE: To determine the relationship between gestational age and the ultrasonic measurement of umbilical coiling index (UCI), and to assess the ability of second-trimester ultrasonic measurements of UCI to predict the true UCI, determined at birth. SUBJECTS/METHODS: Five hundred and thirty-one consecutive women with uncomplicated pregnancies, booking for delivery with a singleton pregnancy, were recruited during a routine second-trimester fetal morphology scan. Multiple ultrasonographic measurements of the intercoil distance were performed between two to three coils of the umbilical cord, along its entire visible length. Three hundred and seventy-four patients (70%) were followed until delivery when the true UCI was measured. RESULTS: An adequate portion of umbilical cord for assessment of coiling was visualized in 99% of cases. Adequate ultrasonographic visibility rates for the fetal, middle and placental regions of the cord were different. All three regions of the umbilical cord could only be visualized adequately in 10% of cases, and two regions were visible in 75%. The UCI progressively decreased along the cord from the fetal insertion to the placental insertion. The mean decrease in UCI with increasing gestational age was similar in all parts of the cord before the 23rd week (160 days) of pregnancy, and plateaued off after this point, except in measurements performed near the fetal insertion. The sensitivity of second-trimester ultrasound examination for predicting hypercoiling at birth was 17.3% and for predicting hypocoiling was 9.1%. DISCUSSION: Whilst UCI can be measured easily and reliably in the second trimester these estimates do not accurately reflect the UCI at term. Our original assumption that umbilical coiling does not alter after the initial formation of coils in the first trimester is incorrect; mixed patterns occurred in about 25% of cases. These patterns develop during the second and third trimesters, presumably due to snarls in the cord, and influence the final coiling number and therefore the relationship between the two measurements of UCI.

Female↗

PubMed2001

Genetic analysis of bipartite geminivirus tissue tropism.

The bipartite geminiviruses bean golden mosaic virus (BGMV), cabbage leaf curl virus (CabLCV), and tomato golden mosaic virus (TGMV) exhibit differential tissue tropism in Nicotiana benthamiana. In systemically infected leaves, BGMV remains largely confined to vascular-associated cells (phloem-limited), whereas CabLCV and TGMV can escape into the surrounding mesophyll. Previous work established that TGMV BRi, the noncoding region upstream from the BR1 open reading frame (ORF), is required for mesophyll invasion, but the virus must also contain the TGMV AL23 or BL1/BR1 ORFs. Here we show that, in a BGMV-based hybrid virus, CabLCV AL23 also directed efficient mesophyll invasion in conjunction with TGMV BRi, which suggests that host-adaptation of AL23 is important for the phenotype. Cis-acting elements required for mesophyll invasion were delineated by analyzing BGMV-based hybrid viruses in which various parts of BRi were exchanged with those of TGMV. Interestingly, mesophyll invasion efficiency of hybrid viruses was not correlated with the extent of viral DNA accumulation. In conjunction with TGMV AL23, a 52-bp region of TGMV BRi with sequence homology to DNA A was sufficient for mesophyll invasion. This 52-bp sequence also directed mesophyll invasion in combination with the TGMV BL1/BR1 ORFs. Overall, these results are consistent with a model for mesophyll invasion in which AL2 protein, in association with host factors, acts through the 52-bp region in TGMV BRi to affect expression of the BR1 gene.

Adaptation, Physiological↗

PubMed2001

CED-12/ELMO, a novel member of the CrkII/Dock180/Rac pathway, is required for phagocytosis and cell migration.

The C. elegans genes ced-2, ced-5, and ced-10, and their mammalian homologs crkII, dock180, and rac1, mediate cytoskeletal rearrangements during phagocytosis of apoptotic cells and cell motility. Here, we describe an additional member of this signaling pathway, ced-12, and its mammalian homologs, elmo1 and elmo2. In C. elegans, CED-12 is required for engulfment of dying cells and for cell migrations. In mammalian cells, ELMO1 functionally cooperates with CrkII and Dock180 to promote phagocytosis and cell shape changes. CED-12/ELMO-1 binds directly to CED-5/Dock180; this evolutionarily conserved complex stimulates a Rac-GEF, leading to Rac1 activation and cytoskeletal rearrangements. These studies identify CED-12/ELMO as an upstream regulator of Rac1 that affects engulfment and cell migration from C. elegans to mammals.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Polymorphisms of 5,10-methylenetetrahydrofolate reductase and risk of gastric cancer in a Chinese population: a case-control study.

Low dietary folate intake has been associated with increased risk of gastric cancer. The 5,10-methylenetetrahydrofolate reductase (MTHFR) involved in folate metabolism has 2 variants, C677T and A1298C, that result in decreased MTHFR activity and lower plasma folate levels. Therefore, we hypothesized that these 2 variants play a role in gastric carcinogenesis. We tested this hypothesis in a Chinese population-based case-control study of 187 histopathologically confirmed gastric cancer cases and 166 healthy controls frequency-matched by age (+/-5 years), gender and residential area. The 677TT genotype was associated with increased risk for gastric cancer [adjusted odds ratio (OR) = 1.87, 95% confidence interval (CI) = 1.00-3.48] compared to the 677CC genotype. This association was more pronounced for gastric cardia cancer (adjusted OR = 2.47, 95% CI = 1.14-5.32). However, no evidence was found for risk associated with the MTHFR A1298C polymorphism. Our findings support the hypothesis that MTHFR C677T variants contribute to gastric carcinogenesis, particularly in gastric cardia. Larger studies incorporating dietary folate intake and serum levels are needed to confirm our findings.

Adenocarcinoma↗

PubMed2001

Quantification of the concentration of ionic impurities in polymeric sensing membranes with the segmented sandwich technique.

Ionic impurities in solvent polymeric membranes have been the main reason early ion-selective electrodes (ISEs) without added ion exchanger exhibited a functional potentiometric response. Today, knowledge of such impurities and their elimination becomes important in view of designing ISEs with low detection limits and voltammetric ion-selective electrodes, to increase operational lifetime, and to optimize sensing selectivity. Here, a potentiometric segmented sandwich membrane technique is used to study the amount and properties of impurities in situ directly in the membrane phase. This technique can be used with a number of ionophores and with different membrane matrixes and does not require specialized equipment. The concentration of anionic impurities in PVC-DOS (bis(2-ethylhexyl) sebacate) and PVC-NPOE (o-nitrophenyloctyl ether) was found to be on the order of 100 micromol/kg with membranes containing weakly binding potassium ionophores. The concentration of cation-exchanger sites of carboxylated PVC-NPOE was found to be higher (1.62 mmol/kg). Addition of the neutral lipophilic salt ETH 500 to both membrane segments had only a marginal effect on the results for PVC-NPOE membranes but had a large impact on the observed membrane potential for PVC-DOS membranes. Theory explains that the addition of such salt to membranes where ion pairing is predominant is essential for the accurate assessment of ionic impurities with this technique.

Algorithms↗

PubMed2001

The syntheses of 16a'-homo-leurosidine and 16a'-homo-vinblastine. Generation of atropisomers.

The synthesis of 16a'-homo-leurosidine was achieved through enantioselective generation of a ring D'-seco-precursor 33 (without requirement of a chiral auxiliary). Its cyclization provided the N(b')-quaternary salt 35 with a configuration corresponding to the atropisomeric form 8a rather than 8b of the target product. On debenzylation, the amine 8a was obtained and found not to isomerize thermally to the anticipated atropisomer 8b (in contrast to its lower homologue, with its formation of natural leurosidine). However, on protonation, a 1:1 mixture of atropisomers of 16a'-homo-leurosidine was obtained. A synthesis of 16a'-homo-vinblastine provided two atropisomers 5a and 5b for the free base at equilibrium (1:2.3 at room temperature in CDCl(3)), with a shift to the major conformer 5b with increasing solvent acidity or decreasing temperature. The synthesis was achieved through a stereoselective inversion of the tertiary hydroxyl function in the enantioselectively generated C-20' progenitor 39.

Alkaloids↗