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Biomedical subjects

J W Liu

Publications and source records attributed to J W Liu.

At least 37 records · Page 2Linked to original sources
PubMed2001

Inhibitory effect of conjugated linoleic acid on linoleic acid elongation in transformed yeast with human elongase.

Conjugated linoleic acid (CLA; 18:2) refers to a group of positional and geometric isomers derived from linoleic acid (LA; delta9,12-18:2). Using a growing baker's yeast (Saccharomyces cerevisiae) transformed with human elongase gene, we examined the inhibitory effect of CLA at various concentrations (10, 25, 50, and 100 microM) on elongation of LA (25 microM) to eicosadienoic acid (EDA; delta11,14-20:2). Among four available individual CLA isomers, only c9,t11- and t10,c12-isomers inhibited elongation of LA to EDA. The extent of inhibition (ranging from 20 to 60%) was related to the concentration of CLA added to the medium. In the meantime, only these two isomers, when added at 50 microM to the media, were elongated to conjugated FDA (c11,t13- and t12,c14-20:2) by the same recombinant elongase at the rate of 28 and 24%, respectively. The inhibitory effect of CLA on LA elongation is possibly due to competition between CLA isomers and LA for the recombinant elongase. Thus, results from this study and a previous study suggest that the biological effect of CLA is exerted through its inhibitory effect on delta6-desaturation as well as elongation of LA which results in a decrease in long-chain n-6 fatty acids and consequently the eicosanoid synthesis.

Acetyltransferases↗
PubMed2001

Effect of occlusal trauma on healing of periapical pathoses: report of two cases.

AIM: To present two clinical cases and demonstrate that occlusal trauma may affect healing of periapical pathoses. SUMMARY: Two teeth with periradicular disease did not respond successfully to conventional root canal treatment or endodontic surgery. Occlusal adjustment was finally performed on both cases. After occlusal adjustment, uncomplicated healing and periapical repair occurred in both cases. The findings in these two cases suggest that occlusal trauma may play a role in the healing of periapical pathoses. KEY LEARNING POINTS: Occlusal trauma is positively correlated with changes in periodontal tissues. Although experiments in animals have shown that application of forces to teeth will not induce further periodontal destruction, we believe that some failures of root canal treatment may be due to the presence of occlusal trauma modulating the responses of inflamed periapical tissues or apical pathoses with persistent infection.

Adult↗
PubMed2001

Comparative studies on utilizing nitrogen capacity between two macroalgae Gracilaria tenuistipitata var. liui (rhodophyta) and Ulva pertusa (chlorophyta). I. Nitrogen storage under nitrogen enrichment and starvation.

This paper deals with the N storage of Gracilaria tenuistipitata var. liui and Ulva pertusa under ammonium enrichment and starvation. After 10 days of ammonium enrichment, ammonium NH4+, free amino acid (FAA), protein (pro), chlorophyll (Chl), phycoerythrin (PE) and total dissolved nitrogen (TDN) of the two macroalgae increased significantly. Total nitrogen (TN) increased significantly from 3.65% to 5.78% dry weight of G. tenuistipitata var. liui and 2.82% to 5.07% dw of U. pertusa, respectively. Protein and FAA were the most important N storage pools in the macroalgae. During N-starvation period, individual N pools of the two species were depleted at exponential rates. Each N pool in U. pertusa decreased more rapidly than in G. tenuistipitata, var. liui and the latter was able to sustain fast growth for more time (> 20 days) than U. pertusa. N demands for supporting growth were different between the two species, U. pertusa grew more rapidly and had higher N demands than G. tenuistipitata var. liui did.

Amino Acids↗
PubMed2001

Comparative studies on utilizing nitrogen capacity between two macroalgae Gracilaria tenuistipitata var. liui (rhodophyta) and Ulva pertusa (chlorophyta). II. Feedback controls of intracellular nitrogen pools on nitrogen uptake.

The potential feedback by intracellular nitrogen pools on maximum N uptake (NH4+) rate were determined for Gracilaria tenuistipitata var. liui and Ulva pertusa. The results of correlation matrix analyzing showed that the surge uptake of ammonium seemed related to rapid changes in small intracellular pools of inorganic nitrogen or small peptide and amino acids rather than to changes in TN content of the macroalgae. The assimilation rates of nitrogen of U. pertusa and G. tenuistipitata increased slowly during N starvation and were mainly regulated by amino acids and some incorporation of amino acids into macromolecules. From ecological point of view, the fast-growing and uptaking nutrient U. pertusa is more suitable to improve water quality in integrated shrimp culture ponds in which external nutrient supplies are usually high and constant during the culture period, while G. tenuistipitata var. liui is more suitable to be polycultured in a waters with intermittence supply of nutrients.

Amino Acids↗
PubMed2001

[Research progresses on degradation mechanism in vivo and medical applications of polylactic acid].

Polylactic acid (PLA), a kind of aliphatic polyester, is a biodegradable polymer with outstanding biocompatibility. The degradation of PLA is a complex process involving four main phenomena, namely water absorption, ester cleavage, diffusion of soluble oligomers, and solubilization of fragments. This paper emphasizes on the following aspects: 1) present understanding of the hydrolytic degradation and enzymatic degradation of PLA and autocatalystic degradation mechanism in the bulk PLA; 2) main factors influencing PLA degradation; 3) biological results; 4) the development in application of PLA.

Aerospace Medicine↗
PubMed2000

Purification, characterization, and cDNA sequence of halysetin, a disintegrin-like/cysteine-rich protein from the venom of Agkistrodon halys Pallas.

By means of DEAE-Sepharose CL-6B column chromatography, gel filtration on Sephadex G-75 and Superose 12 FPLC, halysetin, an antiplatelet protein, was purified from the venom of Agkistrodon halys Pallas with molecular mass of 29 kDa on SDS-PAGE and 23,168 Da by mass spectrometry. The p1 was about 5.0. Halysetin was devoid of phospholipase A2, fibrino-(geno)lytic, esterase, hemorrhagenic activities. Halysetin dose-dependently inhibited the aggregation of human platelet, which was stimulated by collagen with IC50 of 420 nM, but not that stimulated by ADP. The N-and C-terminal sequences of halysetin were characterized. Its full-length cDNA was cloned by RT-PCR from the total RNA extracted from the snake venom gland. It encoded a protein of 212-amino-acid residues with disintegrin-like/cysteine-rich domains and was highly homologous with SYMPs (snake venom metalloprotease).

Adenosine Diphosphate↗
PubMed2000

Depletion of a fatty acid-binding protein impairs neurite outgrowth in PC12 cells.

Epithelial fatty acid-binding protein (E-FABP) is up-regulated in rat dorsal root ganglia after sciatic nerve crush and in differentiating neurons during development. The present study investigates the role of E-FABP during nerve growth factor (NGF)-mediated neurite outgrowth in PC12 cells. Undifferentiated PC12 cells express low levels of E-FABP, while NGF triggers a 6- and 8-fold induction of E-FABP mRNA and protein, respectively. Up-regulation of E-FABP mRNA occurs as early as 24 h after NGF treatment and remains highly expressed over the course of several days, corresponding to NGF-mediated neurite outgrowth. Withdrawal of NGF leads to down-regulation of E-FABP mRNA and retraction of neurites. Immunofluorescence microscopy reveals E-FABP immunoreactivity in the perinuclear cytoplasm, neurites and growth cones of NGF-differentiated cells. To examine the role of E-FABP during neurite outgrowth, PC12 cells were transfected with a constitutive antisense E-FABP vector to create the E-FABP-deficient line PC12-AS. By morphometric analysis, PC12-AS cells treated for 2, 4, and 7 days with NGF exhibited significantly decreased neurite expression relative to control (mock-transfected) cells. Taken together, these data indicate that E-FABP is important in normal NGF-mediated neurite outgrowth in PC12 cells, a finding that is consistent with a potential role in axonal development and regeneration.

Animals↗
PubMed2000

Comparison of growth and fatty acid metabolism in rats fed diets containing equal levels of gamma-linolenic acid from high gamma-linolenic acid canola oil or borage oil.

We have utilized transgenic technology to develop a new source of gamma-linolenic acid (GLA) using the canola plant as a host. The aim of the present study was to compare the growth and fatty acid metabolism in rats fed equal amounts of GLA obtained from the transgenic canola plant relative to GLA from the borage plant. Young male Sprague-Dawley rats (n = 10/group) were randomized and fed a purified AIN93G diet (10% lipid by weight) containing either a mixture of high GLA canola oil (HGCO) and corn oil or a control diet containing borage oil (BO) for 6 wk. GLA accounted for 23%, of the triglyceride fatty acids in both diets. Growth and diet consumption were monitored every 2-3 d throughout the study. At study termination, the fatty acid composition of the liver and plasma phospholipids was analyzed by gas chromatography. The growth and diet consumption of the HGCO group were similar to the BO group. There were no adverse effects of either diet on the general health or appearance of the rats, or on the morphology of the major organs. There was no significant difference between the diet groups for total percentage of n-6 polyunsaturated fatty acids present in either the total or individual phospholipid fractions of liver or plasma. The relative percentage of GLA and its main metabolite, arachidonic acid, in each phospholipid fraction of liver or plasma were also similar between groups. The percentage of 18:2n-6 in liver phosphatidylethanolamine and phosphatidylinositol/serine was higher (P < 0.05) and 22:5n-6 was lower in the HGCO group than the BO group. This finding could be attributed to the higher 18:3n-3 content in the HGCO diet than the BO diet. Results from this long-term feeding study of rats show for the first time that a diet containing transgenically modified canola oil was well-tolerated, and had similar biological effects, i.e., growth characteristics and hepatic metabolism of n-6 fatty acids, as a diet containing borage oil.

Adipose Tissue↗
PubMed2000

Reconciling conflicting findings regarding postcessation weight concerns and success in smoking cessation.

Correlates of concern about weight gain following smoking cessation and self-efficacy about controlling weight gain were examined in 940 men and 1,166 women who were surveyed on 2 occasions as part of a randomized trial of work-site interventions for smoking cessation. Weight concerns were positively associated with female sex, body weight, dieting for weight control, nicotine addiction, and social encouragement to quit. Bivariate analyses replicated prior findings that elevated weight concerns are associated with a reduced likelihood of quitting smoking, at least in women. Analyses controlling for demographics, nicotine dependence, and social factors replicated prior findings that weight concerns are not negatively related to smoking cessation and that some measures of concern are positively related to cessation. These analyses suggest that conflicting findings found in this literature are due primarily to how weight concerns are defined and whether covariates like nicotine addiction are used in data analyses.

Adolescent↗
PubMed2000

Expression, purification and preliminary crystallographic studies of a hyperthermophilic esterase from Archaeoglobus fulgidus.

An esterase from the hyperthermophilic archeon Archaeoglobus fulgidus has been expressed, purified and crystallized in a form suitable for structure analysis. The enzyme has a molecular mass of 35 467 Da and shows sequence similarity to other esterases known to possess the alpha/beta hydrolase fold. The crystals diffract to 2.8 A and belong to space group I222 or I2(1)2(1)2(1), with unit-cell parameters a = 155.6, b = 155.0, c = 162.4 A.

Archaeoglobus fulgidus↗
PubMed2000

Modulation of cholesterol concentration in Caco-2 cells by incubation with different n-6 fatty acids.

Incorporation of exogenous cholesterol was compared in human adenocarcinoma colon cells (Caco-2) after incubation with 100 microM of either linoleic acid (LA, 18:2n-6), gamma-linolenic acid (GLA, 18:3n-6), arachidonic acid (AA, 20:4n-6) or adrenic acid (or n-6 docosatetraenoic acid, DTA, 22:4n-6). In both cells 7 days after seeding and 14 days after confluency, incubation with LA significantly raised the proportion of 18:2n-6 but not its long-chain metabolites in cellular phospholipid. Incubation with GLA increased the levels of 18:3n-6, 20:3n-6, and 20:4n-6. Incubation with AA increased the levels of 20:4n-6 and 22:4n-6, and incubation with DTA increased the levels of 22:4n-6 as well as its retro-conversion metabolite, 20:4n-6. A subsequent addition of cholesterol (180 microM) to the medium significantly raised the cellular cholesterol level but less so in the cells 7 days after seeding incubated with GLA. The increase in cellular cholesterol level was generally greater in the cells of 7 days after seeding, particularly those incubated with long-chain highly unsaturated n-6 fatty acids, than in those of 14 days after confluency. These findings suggest that the cell growth and the extent of unsaturation in cell membrane phospholipid fatty acids modulate the incorporation of the exogenous cholesterol into the Caco-2 cells.

Caco-2 Cells↗
PubMed2000

Cholesterol supplementation attenuates the hypocholesterolemic effect of rice bran oil in rats.

Rice bran oil (RBO), when blended with safflower oil (SFO) at the ratio of 7 to 3, has been shown to lower serum cholesterol in humans consuming cholesterol. The mechanism as to how this oil blend exerts its effect is not yet clear. This study examined the effect of cholesterol supplementation on the cholesterol-lowering ability of different RBO/SFO blends. Male Sprague Dawley rats (4 wk old) were fed purified diets containing 10% fat with or without the addition of 0.5% cholesterol for 3 wk. The fat was either SFO or RBO alone, or the mixture of these two oils at the ratio of 7: 3 (7S/3R), 5:5 (5S/5R), or 3:7 (3S/7R). Without cholesterol supplementation, there were no significant differences in the serum and liver total cholesterol levels among different dietary fats. However, the HDL cholesterol level of rats fed the RBO-containing diets (especially in rats fed the 3S/7R diet) was higher than that of rats fed the diet containing SFO alone. This resulted in an increase in the ratio of HDL/total cholesterol-a desirable outcome. Supplementation of the diets with 0.5% cholesterol significantly increased the cholesterol level in both the serum and the liver. Increasing the proportion of RBO in the diet further raised the total cholesterol level in the serum whereas it reduced liver cholesterol. Then, the specific effect of the 3S/7R mixture on the ratio of HDL/total cholesterol disappeared. These findings suggest that cholesterol supplemented at the level of 0.5% in this study masked the cholesterol-lowering effect of RBO. Smaller percentages of polyunsaturated fatty acid (i.e., 18:2n-6) in the RBO-containing diets than in the SFO diet might have reduced their ability to dispose the circulating serum cholesterol into the liver.

Animals↗
PubMed2000

[Isolation and verification of Triticum aestivum-Eremopyrum orientale addition lines and substitution lines by GISH].

Eremopyrum is a potential genus in wheat improvement. To breed T. aestivum-Er. orientale additional and substitutional lines, chromosome number of 96 BC2F3 individuals were accounted. Fifteen plants with 2n = 43 and eight plants with 2n = 44 were checked out. GISH results of the individuals with 43 chromosomes showed that they blonged to three different monosomic additions. Two disomic additions, one double-monosomic addition, one trible-monosomic addition and one monosomic addition were found in the 2n = 44 individuals. One double-monosomic substitution and one monosomic substitution were obtained. We also proved that it is relatively easier to obtain addition lines in the selfing population than to obtain double-monosomic additions.

In Situ Hybridization↗
PubMed2000

[MDM2 gene expression in nasopharyngeal carcinoma and its relationship with p53 protein expression and EB virus latent infection].

OBJECTIVE: To define the expression levels of MDM2 gene in nasopharyngeal carcinoma (NPC) and its relationship with p53 protein expression and EB virus latent infection. METHOD: MDM2 gene expression at mRNA and protein levels, p53 protein and EB virus DNA were detected by nonradioactive in situ hybridization (ISH), immunohistochemistry(IHC) and polymerase chain reaction (PCR) separately in 46 cases of NPC tissues and 12 cases of chronic inflammation of nasopharyngeal epithelium (CINE). RESULT: Fourteen cases of NPC showed MDM2 mRNA and protein overexpression, 38 cases were p53 protein positive, and 43 cases were EBV-DNA positive. Neither MDM2 nor p53 protein was expressed in any case of CINE. MDM2 expression was significantly related to p53 protein expression (P < 0.05), but not to EB virus latent infection in NPC. CONCLUSION: MDM2 gene may play an important role in the pathogenesis of NPC through interacting with p53 protein.

DNA, Viral↗
PubMed1999

A yeast-based bioassay for the determination of functional and non-functional estrogen receptors.

The response to endocrine therapy of breast cancer is not entirely predictable from hormone receptor status alone since some point mutated or splicing variants of the estrogen receptor (ER) show altered biological activities. In order to characterize the activities of all forms of ER in a heterogeneous breast tumor, a functional assay in Saccharomyces cerevisiae was developed. Total RNA isolated from breast cancer cells and one breast cancer specimen was reverse transcribed and the ER cDNA was amplified by PCR. The products were then cloned into an expression vector by in vivo homologous recombination in yeast. The yeast strain carries a reporter gene ( ADE2 ) coupled to an estrogen response element. Activation of the reporter by ER yielded white colonies whereas lack of ER activity produced red colonies. This permitted the testing for functionality of individual ER molecules and subsequent analysis by rescuing of the ER expression plasmids and complete DNA sequencing. This simple visual test allows discrimination between wild-type ER, constitutively active ER and inactive ER.

Biological Assay↗
PubMed1999

Immunocytochemical studies of aquaporin 4 in the skeletal muscle of mdx mouse.

Immunostainability of anti aquaporin 4 antiserum was investigated in the muscles of dystrophin deficient mdx mice. Western blot analysis showed that the rabbit antiserum against aquaporin 4 reacted with a 28 kDa protein in extracts of normal mouse quadriceps femoris muscles but did not react with the protein in extracts of quadriceps femoris muscles of mdx mice. Immunoperoxidase staining of the muscles from normal and mdx mice revealed the positive immunoreaction at the myofiber surface of normal mice and the negative, or the faint and discontinuous immunostaining at the surface of mdx myofibers. Immunogold electron microscopy disclosed the localization of aquaporin 4 molecules at the myofiber plasma membranes of normal mice and the localization was consistent with that of orthogonal array particles in the protoplasmic face of normal muscle plasma membrane seen in freeze fracture replicas. This study demonstrated that the density of aquaporin 4 molecules was decreased in the muscle plasma membranes of mdx mice, resulting in the faulty function of mdx myofibers.

Animals↗
PubMed1999

Monitoring catalytic reaction of bilirubin oxidase and determination of bilirubin and bilirubin oxidase activity by capillary electrophoresis.

Micellar electrokinetic chromatography (MEKC) has been exploited as an analytical method for the separation as well as for the determination of serum bilirubin fractions (alpha-, beta-, gamma- and delta-fraction), the activity of bilirubin oxidase (BOD), and for monitoring the catalytic reaction of BOD. The samples were followed by detection at 450 nm. The average limit of detection was in the 5.0 microM concentration range. The relative standard deviation (RSD) of migration times and peak area of bilirubin was less than 0.25% and 3.0%, respectively. This allowed us complete separation of the four bilirubin fractions (alpha-, beta-, gamma- and delta-fraction) and monitoring of the oxidation progress and the assay of the activity of bilirubin oxidase. The MEKC method is a convenient technique for studying the catalytic reaction of bilirubin oxidase at different pH and assaying the relationship between the four bilirubin fractions and diseases.

Bilirubin↗