Biomedical subjects

Ying Liu

Publications and source records attributed to Ying Liu.

At least 199 records · Page 11Linked to original sources

PubMed2005

Asymmetric division of spindle microtubules and microfilaments during bovine meiosis from metaphase I to metaphase III.

The kinetics of spindle and chromosomes during bovine oocyte meiosis from meiosis I to meiosis III is described. The results of this study showed that (1) oocytes began to extrude the first polar body (Pb1) at the early anaphase I stage and the Pb1 totally separated from the mother cell only when oocytes reach the MII stage; (2) the morphology of the spindle changed from barrel-shaped at the metaphase stage to cylinder-shaped at early anaphase, and then to a thin, long triangle-shaped cone at late anaphase and telophase stages; (3) chromosome morphology went from an individual visible stage at metaphase to a less defined chromatin state during anaphase and telophase stages, and then back to visible individual chromosomes at the next metaphase; (4) chromatin that connected with the floor of the cone became the polar bodies and expelled, and almost all of the microtubules (MTs) and microfilaments (MFs) composing the spindles moved towards and contributed to the polar bodies; and (5) the size of the metaphase I (MI) spindle was larger than the metaphase II (MII) and metaphase III (MIII) spindles. The MII spindle, however, is more barrel-shaped than the MI spindle. This study suggests that spindle MTs and MFs during bovine oocyte meiosis are asymmetrically divided into the polar bodies.

Actin Cytoskeleton↗

PubMed2005

Asymmetric reduction of ethyl 4-chloro-3-oxobutanoate to ethyl (R)-4-chloro-3-hydroxybutanoate with two co-existing, recombinant Escherichia coli strains.

Two recombinant strains, E. coli M15 (pQE30-alr0307) and E. coli M15 (pQE30-gdh0310), which were constructed to express, respectively, an NADPH-dependent aldehyde reductase gene and a glucose dehydrogenase gene, were mixed in an appropriate ratio and used for the asymmetric reduction of ethyl 4-chloro-3-oxobutanoate to ethyl (R)-4-chloro-3-hydroxybutanoate. The former strain acted as catalyst and the latter functioned in NADPH regeneration. The biotransformation was completed effectively without any addition of glucose dehydrogenase or NADP+/NADPH. An optical purity of 99% (ee) was obtained and the product yield reached 90.5% from 28.5 mM: substrate.

Acetoacetates↗

PubMed2005

Simvastatin regulates myocardial cytokine expression and improves ventricular remodeling in rats after acute myocardial infarction.

PURPOSE: Studies have showed that inflammatory cytokines were involved in the process of left ventricular (LV) remodeling after acute myocardial infarction (AMI), anti-inflammation treatment ameliorated LV remodeling and improved cardiac performance. Hydroxymethylglutary coenzyme A reductase inhibition (statins) could affect the expression of inflammatory cytokines. We hypothesized that statins have beneficial effects on early LV remodeling and cardiac performance in rats with AMI by modulating the production of inflammatory cytokines. METHODS: Rats with AMI were treated with placebo or simvastatin (gastric gavage) for 4 weeks. The pro-inflammatory cytokines: tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and the anti-inflammatory cytokine: IL-10 excreted by cardiac myocytes was examined. Echocardiography, hemodynamics and collagen type I production were measured to evaluate LV remodeling and cardiac function. RESULTS: The mRNA expression and protein production of TNF-alpha, IL-1beta, IL-6 and IL-10 in AMI group were significantly elevated compared with sham rats. Simvastatin markedly attenuated the production of TNF-alpha, IL-1beta, IL-6 and increased IL-10 levels in the noninfarcted and infarcted regions, reduced collagen deposition in the noninfarcted myocardium and improved left ventricular function. However simvastatin did not alter plasma lipids. CONCLUSIONS: Simvastatin ameliorates early LV remodeling and improve cardiac function after AMI. Simultaneously, it decreased pro-inflammatory and increased anti-inflammatory cytokines, which suggests, but does not prove, a causal relationship independent of plasma lipid-lowering effects.

Animals↗

PubMed2005

Activation and coreceptor expression of T lymphocytes in HIV/AIDS patients of China.

The objective of this paper was to investigate the activation and coreceptor CCR5, CXCR4 expression of T lymphocytes in HIV/AIDS patients of China, and to study their association with disease progression. Seventy-seven HIV/AIDS patients and thirteen normal controls were enrolled and three-color flow-cytometry was used to detect the activation marker HLA-DR, CD38 and the coreceptor CCR5, CXCR4 expression on T lymphocytes in whole blood samples taken from the patients and the controls. The HLA-DR, CD38 and CCR5 expression on CD4, CD8+ T cells in AIDS patients was higher than in asymptomatic HIV-1 infected patients and normal controls (p < 0.05); The activation and CCR5 expression on T lymphocytes significantly correlated with CD4+ T lymphocyte number and viral load. The activation on T lymphocytes and the expression of CCR5 on T lymphocytes in HIV/AIDS patients of China are significantly correlated with disease progression.

ADP-ribosyl Cyclase↗

PubMed2005

TH1/TH2 functional imbalance after acute myocardial infarction: coronary arterial inflammation or myocardial inflammation.

OBJECTIVES: The study clarified whether the T-helper (Th)1/Th2 imbalance existed only in coronary arterial inflammation or in both coronary arterial inflammation and myocardial inflammation and explored the significance of the imbalance of Th1/Th2 function after acute myocardial infarction (AMI). BACKGROUND: There are two different inflammatory processes in patients with AMI: the coronary arterial inflammation that leads to the pathogenesis of AMI and the myocardial inflammation after AMI that leads to ventricular remodeling, which are positively and negatively regulated by Th1 and Th2 lymphocytes, respectively. METHODS: Peripheral blood mononuclear cells from 33 AMI patients, 22 unstable angina (UA) patients and splenocytes from 35 AMI Wistar rats were collected. Cytokine-producing Th cells were ambulatorily monitored by 3-color flow cytometry. Interferon (IFN)-gamma and interleukin (IL)-4 mRNA in the rat myocardium and chemokine receptors CCR3,CCR5 and CXCR3 mRNA on the surface of rat T-lymphocytes after AMI were measured by RT-PCR. RESULTS: IFN-gamma-producing T-cells significantly increased in patients with AMI and UA within 24 hours after the onset of symptom. The high ratio of IFN-gamma-producing T-cells recovered 1 week after the onset in UA patients, while it could be examined 1 week and even 1 month after the onset in AMI patients. The up-regulation of Th1 cell function is consistent with bad heart function. There was no significant difference on the frequencies of IL-4-producing T-cells between each group. 1 week, 2 weeks and 1 month after AMI, IFN-gamma mRNA increased in the myocardium of rats, but there was no significant change on global Th cell functions. CONCLUSIONS: Th1/Th2 functional imbalance exists in both coronary arterial inflammation and myocardial inflammation processes. The up-regulation of Th1 cell-functions may participate in the immune-mediated ventricular remodeling after AMI.

Aged↗

PubMed2005

Effect of metallothionein on cell viability and its interactions with cadmium and zinc in HEK293 cells.

Metallothioneins (MTs) are thought to participate in a wide variety of physiological roles, but the mechanisms involved are still unclear. The study was designed to examine the possible factors related to these mechanisms. Methods, including transfection, MTT assay and flow cytometry, were used to investigate the effect of MTs on cell viability and their interactions with cadmium and zinc in HEK293 cells. The results showed that transient overexpression of human MT1A, MT2 and MT3 genes dynamically affected cell viability, and the effect was influenced by zinc and cadmium ions. Overexpressed MTs with added zinc showed a greater inhibitory effect on cell viability. Overexpressed MTs protected cells against low concentrations of cadmium ions (10 microM), but increased cell death in response to high concentrations (20-50 microM). Out of the three MTs, MT1A was more efficient than MT2 and MT3 in its resistance to cadmium (10 microM), and MT3 together with zinc showed more cell growth inhibition than MT1 and MT2. These results indicate that both of the divalent metal ions that could bind MTs, as well as the individual MT isoforms, affect the role of MTs on cell viability, which may explain in part why the comprehensive effect of MTs on the cells was elusive.

Blotting, Western↗

PubMed2005

Effects of Atorvastatin on Th polarization in patients with acute myocardial infarction.

BACKGROUND: The development of heart failure after acute myocardial infarction (AMI) has been shown to be associated with inflammation, which is positively and negatively regulated by T helper (Th) 1 and Th2 lymphocytes, respectively. Several studies have indicated that statins can improve heart function after AMI. AIMS: To study the effects of atorvastatin on Th polarization in patients with AMI. METHODS: Peripheral blood mononuclear cells were collected from 20 patients with AMI treated with oral atorvastatin (10 mg/d, group AMI-A) and 18 patients with AMI (group AMI-C) who did not receive treatment with statins. Cytokine-producing Th lymphocytes were quantified by 3-color flow cytometry. After in vitro culturing in the presence or absence of atorvastatin (0, 0.3, 1 and 3 micromol/L) for 6 days, cytokine-producing Th lymphocytes were quantified again in AMI-C group. RESULTS: The ratio of IFN-gamma-producing T cells was significantly higher in AMI-C group (17.8% +/- 6.4%) than in the AMI patients treated with oral atorvastatin (AMI-A, 13.1% +/- 4.6%). In vitro culturing with atorvastatin significantly reduced Th1 development in the AMI-C group. There was no significant difference on the frequencies of interleukin (IL)-4-producing T cells between each group. CONCLUSIONS: Atorvastatin can reduce Th1 development but has no effect on Th2 cell-functions in AMI patients. Our findings suggest that atorvastatin can regulate the polarization of Th1/Th2, this may be one of the mechanisms through which atorvastatin improves heart function after AMI.

Atorvastatin↗

PubMed2005

Endogenous Nkx2.2+/Olig2+ oligodendrocyte precursor cells fail to remyelinate the demyelinated adult rat spinal cord in the absence of astrocytes.

Chronic demyelination is a pathophysiologic component of compressive spinal cord injury (SCI) and a characteristic finding in demyelinating diseases including multiple sclerosis (MS). A better characterization of endogenous cells responsible for successful remyelination is essential for designing therapeutic strategies aimed at restoring functional myelin. The present study examined the spatiotemporal response of endogenous oligodendrocyte precursor cells (OPCs) following ethidium bromide (EB)-induced demyelination of the adult rat spinal cord. Beginning at 2 days post-EB injection (dpi), a robust mobilization of highly proliferative NG2(+) cells within the lesion was observed, none of which expressed the oligodendrocyte lineage-associated transcription factor Nkx2.2. At 7 dpi, a significant up-regulation of Nkx2.2 by OPCs within the lesion was observed, 90% of which coexpressed NG2 and virtually all of which coexpressed the bHLH transcription factor Olig2. Despite successful recruitment of Nkx2.2(+)/Olig2(+) OPCs within the lesion, demyelinated axons were not remyelinated by these OPCs in regions lacking astrocytes. Rather, Schwann cell remyelination predominated throughout the central core of the lesion, particularly around blood vessels. Oligodendrocyte remyelination was observed in the astrogliotic perimeter, suggesting a necessary role for astrocytes in oligodendrocyte maturation. In addition, reexpression of the radial glial antigen, RC-1, by reactive astrocytes and ependymal cells was observed following injury. However, these cells did not express the neural stem cell (NSC)-associated transcription factors Sox1 or Sox2, suggesting that the endogenous response is primarily mediated by glial progenitors. In vivo electrophysiology demonstrated a limited and unsustained functional recovery concurrent with endogenous remyelination following EB-induced lesions.

Animals↗

PubMed2005

Cyclooxygenases and prostaglandin E synthases in preimplantation mouse embryos.

Prostaglandin E2 (PGE2) is shown to be essential for female reproduction. Cyclooxygenase (COX) is a rate-limiting enzyme in prostaglandin synthesis from arachidonic acid and exists in two isoforms: COX-1 and COX-2. Prostaglandin E synthase (PGES) is a terminal prostanoid synthase and can catalyse the isomerization of the COX product PGH2 to PGE2, including microsomal PGES-1 (mPGES-1), cytosolic PGES (cPGES) and mPGES-2. This study examined the protein expression of COX-1, COX-2, mPGES-1, cPGES and mPGES-2 in preimplantation mouse embryos by immunohistochemistry. Embryos at different stages collected from oviducts or uteri were transferred into a flushed oviduct of non-pregnant mice. The oviducts containing embryos were paraffin-embedded and processed for immunostaining. COX-1 immunostaining was at a basal level in zygotes and a low level at the 2-cell stage, reaching a high level from the 4-cell to blastocyst stage. COX-2 immunostaining was at a low level at the zygote stage and was maintained at a high level from the 2-cell to blastocyst stages. A low level of mPGES-1 immunostaining was observed from the zygote to 8-cell stages. The signal for mPGES-1 immunostaining became stronger at the morula stage and was strongly seen at the blastocyst stage. cPGES immunostaining was strongly observed in zygotes, 2-cell and 8-cell embryos. There was a slight decrease in cPGES immunostaining at the 4-cell, morula and blastocyst stages. mPGES-2 immunostaining was at a low level from the zygote to morula stages and at a high level at the blastocyst stage. We found that the COX-1, COX-2, mPGES-1, cPGES and mPGES-2 protein signals were all at a high level at the blastocyst stage. PGE2 produced during the preimplantation development may play roles during embryo transport and implantation.

Age Factors↗

PubMed2005

The lexical constituency model: some implications of research on Chinese for general theories of reading.

The authors examine the implications of research on Chinese for theories of reading and propose the lexical constituency model as a general framework for word reading across writing systems. Word identities are defined by 3 interlinked constituents (orthographic, phonological, and semantic). The implemented model simulates the time course of graphic, phonological, and semantic priming effects, including immediate graphic facilitation followed by graphic inhibition with simultaneous phonological facilitation, a pattern unique to the Chinese writing system. Pseudocharacter primes produced only facilitation, supporting the model's assumption that lexical thresholds determine phonological and semantic, but not graphic, effects. More generally, both universal reading processes and writing system constraints exist. Although phonology is universal, its activation process depends on how the writing system structures graphic units.

Humans↗

PubMed2005

Distributions and source apportionment of ambient volatile organic compounds in Beijing city, China.

Ambient measurements of 108 volatile organic compounds (VOCs), including alkanes, alkenes, aromatics, and halogenated hydrocarbons, were conducted from 2002 to 2003 at six sites in Beijing city. The mean mass concentration of total VOCs was 132.6 +/- 52.2 microg/m3, with alkanes, aromatics, and alkenes accounting for 35%, 22%, and 17%, respectively. The concentrations of most VOC species showed a seasonal pattern, with higher values in November, mildly lower in March, and much lower in July. In winter and spring, apparent diurnal variations of reactive compounds such as 1,3-butadiene and isoprene were observed, whereas those were not distinct in summer. The propylene equivalent concentration was used to evaluate the contribution of individual VOCs in ozone formation. Reactive olefins from anthropogenic emissions dominated the reactions with OH at each season. In summer, isoprene became the largest contributor, followed by 1-butene and propene. The source profiles in Beijing, including vehicle exhaust, gasoline vapor, painting operations, and asphalt pavement, were investigated. Based on the measurement of source profiles and ambient concentrations of VOCs in Beijing, chemical mass balance receptor model was applied to estimate contributions of several potential VOCs sources in Beijing. The results indicated that vehicle exhaust contributed on average 57.7%, followed by painting operations, gasoline vapor, and liquefied petroleum gas (LPG) at 12.4%, 11.3%, and 5.8%, respectively.

Air Pollutants↗

PubMed2005

Efficient production of recombinant aldehyde reductase and its application for asymmetric reduction of ethyl 4-chloro-3-oxobutanoate to ethyl (R)-4-chloro-3-hydroxybutanoate.

An NADPH-dependent aldehyde reductase (ALR, EC1.1.1.2) gene is cloned from Sporobolomyces salmonicolor ZJUB 105, and inserted into plasmid pQE30 to construct the expression plasmid (pQE30-ALR). A variety of E. coli strains were employed as hosts to obtain transformants with pQE30-ALR, respectively. Among these different types of transformants, the highest enzyme activity of ALR can be produced with E. coli M15 (pQE30-ALR). The bioactivity of ALR could be further improved significantly by the optimization of induction conditions. The results showed that the enzyme activity of ALR reached 6.48 U/mg protein, which is fifteen times higher than that of S. salmonicolor ZJUB 105. This recombinant strain was applied to the asymmetric reduction of ethyl 4-chloro-3-oxobutanoate (COBE) to ethyl (R)-4-chloro-3- hydroxybutanoate (CHBE). The results showed that the yield and optical purity of (R)-CHBE reached 98.5% and 99% e.e. (enantiomeric excess), respectively.

Acetoacetates↗

PubMed2005

Maternal methylenetetrahydrofolate reductase deficiency and low dietary folate lead to adverse reproductive outcomes and congenital heart defects in mice.

BACKGROUND: Genetic or nutritional disturbances in folate metabolism may affect embryonic development because of the critical role of folate in nucleotide synthesis and methylation reactions. The possible role of a mild deficiency in methylenetetrahydrofolate reductase (MTHFR) and low dietary folate in pregnancy outcomes and heart morphogenesis requires further investigation. OBJECTIVE: We investigated the effect of mild MTHFR deficiency, low dietary folate, or both on resorption rates, on length and weight, and on the incidence of heart malformations in murine embryos. DESIGN: Female Mthfr +/+ and +/- mice were fed a control diet (CD) or a folic acid-deficient diet (FADD) before mating with male Mthfr +/- mice. On gestational day 14.5, implantation and resorption sites were recorded and viable embryos were examined for gross malformations, growth delay, and congenital heart defects. RESULTS: Plasma homocysteine in Mthfr +/- dams and in FADD-treated dams was significantly higher than that in Mthfr +/+ dams and CD-treated dams, respectively. A significantly higher rate of resorption and greater developmental delay were observed in hyperhomocysteinemic mice than in CD-treated +/+ dams. Heart defects were identified in 4 of 11, 5 of 10, and 4 of 10 litters from CD-treated +/-, FADD-treated +/+, and FADD-treated +/- dams, respectively, but not in any of those from CD-treated +/+ dams (0/11 litters). CONCLUSION: Our findings suggest that mild MTHFR deficiency, low dietary folate, or both in the dams increase the incidence of fetal loss, intrauterine growth retardation, and heart defects. These data support the benefit of folic acid supplementation in pregnant women, particularly in those with MTHFR deficiency.

Animals↗

PubMed2005

Investigation into biomedical literature classification using support vector machines.

Specific topic search in the PubMed Database, one of the most important information resources for scientific community, presents a big challenge to the users. The researcher typically formulates boolean queries followed by scanning the retrieved records for relevance, which is very time consuming and error prone. We applied Support Vector Machines (SVM) for automatic retrieval of PubMed articles related to Human genome epidemiological research at CDC (Center for disease Control and Prevention). In this paper, we discuss various investigations into biomedical literature classification and analyze the effect of various issues related to the choice of keywords, training sets, kernel functions and parameters for the SVM technique. We report on the various factors above to show that SVM is a viable technique for automatic classification of biomedical literature into topics of interest such as epidemiology, cancer, birth defects etc. In all our experiments, we achieved high values of PPV, sensitivity and specificity.

Abstracting and Indexing↗

PubMed2005

Vaccine efficacy of recombinant GAPDH of Edwardsiella tarda against Edwardsiellosis.

Thirty-seven kilodalton glyceraldehyde-3-phosphate dehydrogenase (GAPDH) of Edwardsiella tarda was suggested to be an effective vaccine candidate against E. tarda infection in previous research. For developing a vaccine, obtaining GAPDH in large quantities is necessary. In this study, we determined the complete nucleotide sequence of the gene that encodes GAPDH of E. tarda, and overexpressed the GAPDH of E. tarda by using the Escherichia coli expression system. We immunized Japanese flounder with recombinant GAPDH (rGAPDH) and evaluated its vaccine efficacy. Our results showed that rGAPDH effectively protected Japanese flounder from experimental E. tarda infection, and will contribute to the development of a vaccine against E. tarda.

Animals↗

PubMed2005

Dorsoventral patterning of the Xenopus eye: a collaboration of Retinoid, Hedgehog and FGF receptor signaling.

In the developing spinal cord and telencephalon, ventral patterning involves the interplay of Hedgehog (Hh), Retinoic Acid (RA) and Fibroblast Growth Factor (FGF) signaling. In the eye, ventral specification involves Hh signaling, but the roles of RA and FGF signaling are less clear. By overexpression assays in Xenopus embryos, we found that both RA and FGF receptor (FGFR) signaling ventralize the eye, by expanding optic stalk and ventral retina, and repressing dorsal retina character. Co-overexpression experiments show that RA and FGFR can collaborate with Hh signaling and reinforce its ventralizing activity. In loss-of-function experiments, a strong eye dorsalization was observed after triple inhibition of Hh, RA and FGFR signaling, while weaker effects were obtained by inhibiting only one or two of these pathways. These results suggest that the ventral regionalization of the eye is specified by interactions of Hh, RA and FGFR signaling. We argue that similar mechanisms might control ventral neural patterning throughout the central nervous system.

Animals↗

PubMed2005

Three new podocarpane-type diterpenoids from callus of Securinega suffruticosa.

Three new podocarpane-type diterpenoids, 3beta,12-dihydroxy-13-methyl-6,8,11,13-podocarpatetraen (1), 3beta,12-dihydroxy-13-methyl-5,8,11,13-podocarpatetraen-7-one (2), and 1-(7-hydroxy-2,6-dimethyl-1-naphthyl)-4-methyl-3-pentanone (3) (20(10-->5)-abeo-4,5-seco-5(10),6,8,11,13-podocarpapentaen-3-one) were isolated from callus of Securinega suffruticosa. The structures were elucidated by spectroscopic methods. Compounds 1, 2, and 3 showed cytotoxic activity against five human cancer cell lines (A549, BEL 7402, BGC-823, HCT-8, A2780).

Antineoplastic Agents, Phytogenic↗

PubMed2005

Behavioral response of tilapia (Oreochromis niloticus) to acute ammonia stress monitored by computer vision.

The behavioral responses of a tilapia (Oreochromis niloticus) school to low (0.13 mg/L), moderate (0.79 mg/L) and high (2.65 mg/L) levels of unionized ammonia (UIA) concentration were monitored using a computer vision system. The swimming activity and geometrical parameters such as location of the gravity center and distribution of the fish school were calculated continuously. These behavioral parameters of tilapia school responded sensitively to moderate and high UIA concentration. Under high UIA concentration the fish activity showed a significant increase (P<0.05), exhibiting an avoidance reaction to high ammonia condition, and then decreased gradually. Under moderate and high UIA concentration the school's vertical location had significantly large fluctuation (P<0.05) with the school moving up to the water surface then down to the bottom of the aquarium alternately and tending to crowd together. After several hours' exposure to high UIA level, the school finally stayed at the aquarium bottom. These observations indicate that alterations in fish behavior under acute stress can provide important information useful in predicting the stress.

Ammonia↗