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Biomedical subjects

G Liu

Publications and source records attributed to G Liu.

At least 541 records · Page 30Linked to original sources
PubMed1995

[A study of epidermal growth factor receptor in human colorectal cancer].

Membrane extracts of surgically resected colorectal cancer and nearby non-cancerous tissues were prepared and the expression of epidermal growth factor receptor (EGF-R) was examined by 125I-EGF binding assay. Scatchard analysis indicated that a single class of EGF-R was present in the cancer as well as the non-cancerous tissues. EGF-R was found over-expressed in cancer (38.07 +/- 4.75 fmol/mg protein) as compared to that in the non-cancerous tissue (29.31 +/- 1.64 fmol/mg protein) (P < 0.05). However, the difference in binding affinities of EGF-R in the cancer and non-cancerous tissues was not statistically significant. The results suggest an important role of an autocrine/paracrine loop of growth regulation in colorectal cancer.

Adenocarcinoma↗
PubMed1995

Calcium supplementation during pregnancy for reducing pregnancy induced hypertension.

Pregnancy induced hypertension (PIH) is a common complication in pregnancy and prenatal stage. Because the direct and indirect relationship between low calcium intake and many diseases, such as rachitis, young age myopia and hypertension, calcium supplementation has been a hot topic among nutritionists. Randomized trials of calcium supplementation during pregnancy were conducted in 212 healthy primipara. They were divided into 4 groups and gave 120mg, 240mg, 1g or 2g of calcium daily from 20 to 28 wks of gestation up to delivery respectively. As a result, the incidence of PIH was 8.9%, 7.5%, 8% and 4% respectively in these groups. The control group (106 pregnant women) who did not receive calcium gave an incidence of 18%. Supplementation of 2g of calcium daily showed significant results in lowering the incidence of PIH (P < 0.05) without any adverse effects. In 1992 calcium supplementation was widely used in antenatal-clinic. 200 cases with intake of 2g calcium were compared with corresponding non-calcium supplementation cases, and the incidence of PIH was 7.5% and 16.5% (P < 0.005) respectively. Mediating parathyroid hormone and renin activity are thought to be the effect of calcium on decreasing the incidence of PIH.

Calcium↗
PubMed1995

[Effects of isorhynchophylline on physiological characteristics of isolated guinea pig atrium].

Isorhynchophylline (Iso) inhibits the automaticity and contractile force of isolated guinea pig atrium in a concentration-dependent manner, 30 mumol/L markedly depresses adrenaline-induced automaticity, 10 mumol/L prolongs functional refractory period and decreases excitability. Furthermore, 10 mumol/L of Iso reduces the effect of ouabain on contractile force in left atrium and 0.3 mmol/L markedly inhibits the response to paired stimulation.

Alkaloids↗
PubMed1995

[Determination of psoralen and isopsoralen in tincture of fructus Psoraleae by HPLC].

A reversed-phase HPLC method was described for the determination of psoralen and isopsoralen in tincture of Fructus Psoraleae. After adding the internal standard and diluting the sample to a definite volume, the sample was injected and analysed. The RSDs were within 2% and the minimum working concentrations below 1 microgram/ml; the average recoveries of psoralen and isopsoralen 102.8% and 99.5% respectively and the linear ranges of psoralen and isopsoralen 12-200 micrograms/ml and 13-210 micrograms/ml (r = 0.999) respectively.

Chromatography, High Pressure Liquid↗
PubMed1995

Fluorescence spectroscopic study of the interaction of adenine and nucleotide with trichosanthin.

Trichosanthin (TCS) is an N-glycosidase that can attack the 28s rRNA of the ribosome at a highly conserved adenine residue. The interactions of adenine and its derivative nucleotides with TCS are reported. The fluorescence of Trp 192 of TCS is sensitive to the proximity of adenine, and produces a marked red shift indicative of trytophan in a more hydrophilic environment. By contrast AMP and ATP quench the maximal emission at 328nm. The binding of the adenine and ATP with TCS result in lower tryptophan accessibility to the quencher acrylamide, but higher tryptophan accessibility to the quencher iodide, while AMP caused higher tryptophan accessibility to acrylamide, and lower tryptophan accessibility to iodide. Also, the binding of nucleotides induces tryptophan heterogeneity in the protein. These findings lead us to propose that binding of nucleotides and adenine base cause different microenvironmental changes of the tryptophan residue, and Trp 192 may be involved in the active site of TCS.

Adenine↗
PubMed1995

Kinetic models of batch and fed-batch culture of single-cell protein with double carbon sources.

Unstructured logistic models were applied to simulate the kinetic process of the SCP batch culture with two species of yeast, in which glucose, xylose, or a mixture of the two were used as carbon sources. A modified logistic growth model was used to describe the fed-batch process of using mixed carbon sources. The model parameters were determined by the simulated model with the experimental data. The simulated curves of the models were in agreement with the experimental data.

Candida↗
PubMed1995

[Reversing effect of dimethyl-4,4'-dimethoxy-5,6,5'6'-dimethylenedioxybiphenyl-2,2'- dicarboxylate(DDB) on the phenotypes of human hepatocarcinoma cell line].

When human Bel-7402 hepatocarcinoma cell line grew in a medium containing 10(-4)M DDB, the secretion of alpha-fetoprotein (AFP) and the activity of gamma-glutamyl-transpeptidase (gamma-GT) were significantly lower than the control cells, whereas the albumin (ALB) secretion and the activity of tyrosine-alpha-ketoglutarate transaminase (TAT) were markedly increased. DDB at the concentration of 10(-4)M could significantly increase the content of cAMP in Bel-7402 cells, and also suppressed the expressions of oncogene c-myc and hepatocarcinoma marker AFP gene and enhanced the anti-oncogene p53 expression. The results of this paper suggest that DDB has some reversing effects on the phenotypes of human Bel-7402 hepatocarcinoma cell line.

Carcinoma, Hepatocellular↗
PubMed1995

[Long-term results following 131I treatment of thyrotoxic heart disease: a report of 68 cases].

The long-term results of 68 cases of thyrotoxic heart disease (THD) treated with 131I were analysed. 17 of 68 patients have been followed for 2-4 years, 32 for 5-9 years, 7 for 10-14 years, 8 for 15-19 years and 4 for 20-33 years. The mean period of follow up was 9 years. Of the 68 patients, 47 did not respond to antithyroid drug (ATD) therapy. Before 131I therapy, all the patients suffered from one or more of cardiac abnormalities caused by hyperthyroidism such as paroxysmal or permanent atrial fibrillation, cardiac enlargement, cardiac failure, frequent atrial or ventricular extrasystoles, angina pectoris and so on. All patients were given individualized therapeutic 131I dose of 2.59-4.44 MBq per gram of thyroid weight. The total 131I dose for patients was 85.1 MBq to 462.2 MBq. The long-term results showed that 55 cases were cured and 11 cases achieved complete remission. The total effective rate was 97 percent. There was no relapse of hyperthyroidism. Except that 4 cases of early hypothyroidism and 5 of delayed hypothyroidism were diagnosed, there were no other complications. The incidence of postradioiodine hypothyroidism at 5-9 years was 7.4 percent and at 10-33 years 20 percent. Our results indicate that 131I is a simple, safe, economic and effective treatment for THD. Pre-treatment with ATD for hyperthyroidism with cardiac complications is not necessary. 131I should be considered as the treatment of first choice for hyperthyroidism with cardiac abnormalities.

Adult↗
PubMed1995

[Chemical constituents of Stellera chamaejasme L].

Twelve compounds were isolated from the roots of Stellera chamaejasma. Five of them were elucidated by spectroscopic and chemical methods as 3', 14-dimethyl-4', 11-dimethoxy-5, 7-dihydroxybenzoflavanone (10), daphnetin (1), umbelliferone (2), daucosterol (5) and beta-sitosterol (3). Compound 10 is new. Compounds 1, 2, 5, 10 were isolated for the first time from S. chamaejasme.

Benzoflavones↗
PubMed1995

[Study on the perinatal infection caused by Chlamydia trachomatis].

OBJECTIVE: Study on the frequency and outcome of chlamydia trachomatis (CT) infection of the pregnant women and their babies. METHODS: Two hundred and seventy eight pregnant women and their 79 infants were studied with McCoy cell culture, polymerase chain reaction (PCR) and DNA sequence analysis. Isolation of CT was performed in McCoy cell culture, and iodine-stained glycogen-positive inclusions were considered to be positive. CT DNAs were extracted by modified NaI method. Two sets of primers derived from CT common plasmid and major outer membrane protein genes were used in the PCR. Dideoxy-mediated chain-termination method was used for DNA sequence analysis. RESULTS: 10.8% (30/278) of the cervical cultures were positive for CT, while the positive rate by PCR was 14.0% (39/278). The vertical transmission rate of CT was 55.0% (11/22). The sequences of DNA amplified from a maternal-infant pair were matched perfectly. The incidence of puerperal endometritis in CT positive women was 28.6%, much higher than 8.1% in those CT negative mothers. Neonatal conjunctivitis and pneumonia in group of CT positive mothers were 45.0% and 30.0%, respectively, much higher than 18.3% and 8.3%, respectively, in that of CT negative mothers (P < 0.05). CONCLUSION: Perinatal infection caused by CT is very common in China.

Chlamydia Infections↗
PubMed1995

Biomechanical study on unilateral single-plane external fixer.

Six tibias removed from 30-40 years old males, who died in an accident for in less than 12 hours, were osteotomized at one-third supra-medium segment. They were fixed by an unilateral adjustable external fixer (UAEF), to be used as a model of external fixation of tibial fracture (MEFTF). The compression, tension, torsion, antero-posterior and lateral bending strength, and the strength for vertically extracting the pins from the tibia were determined in the MEFTF. Within a certain range of load, the correlation of strain to stress was basically a linear relationship. These data provide a theoretical basis of biomechanics for the improvement of UAEF and for early exercises of fracture patients, such as extend-bending of the joint, raising the limb and walking with a walking stick.

Adult↗
PubMed1994

Molecular interaction between ryanodine receptor and glycoprotein triadin involves redox cycling of functionally important hyperreactive sulfhydryls.

The fluorogenic maleimide 7-diethylamino-3-(4'-maleimidylphenyl)-4-methylcoumarin (CPM) has been shown to selectively form Michael adducts with hyperreactive sulfhydryls on the skeletal sarcoplasmic reticulum (SR) ryanodine receptor (RyR1) and triadin which are essential for normal Ca2+ channel function (Liu, G., Abramson, J.J., Zable, A.C., and Pessah, I.N. (1994) Mol. Pharmacol. 45, 189-200). The present report demonstrates a functionally important interaction between RyR1 and triadin which involves, in part, redox cycling of hyperreactive sulfhydryls in response to channel activation and inactivation. Nanomolar CPM is shown to selectively label RyR1 and triadin only in the presence of Ca2+ channel inhibitors (Mg2+, neomycin, ruthenium red, or anti-triadin antibody). Treatment of SR with channel activators (micromolar Ca2+, nanomolar ryanodine, or millimolar caffeine), 1) slows CPM labeling kinetics > 10-fold, 2) negates CPM labeling of channel-associated sulfhydryls, and 3) stabilizes a high molecular weight complex (HMWC) which appears on nonreducing SDS-polyacrylamide gel electrophoresis gels. The HMWC is positively identified as RyR1 and triadin by Western blot and immunoprecipitation analyses. High-affinity [3H]ryanodine-binding sites are immunoprecipitated by either anti-RyR1 or anti-triadin antibody dose dependently. 1,4-Naphthoquinone (< or = 40 pmol/micrograms protein) selectively oxidizes hyperreactive sulfhydryls on RyR1 and triadin, induces Ca2+ efflux from SR, and stabilizes the HMWC. The HMWC is reduced by beta-mercaptoethanol or dithiothreitol into its component RyR1 and triadin promoters. The results provide direct evidence for the existence of a functionally important complex between RyR1 and triadin whose stability is determined by the redox state of hyperreactive sulfhydryl moieties which are allosterically regulated by physiological and pharmacological channel ligands. The present results suggest a possible molecular mechanism by which localized transient changes in the redox state within the RyR1-triadin complex can signal information across the SR membrane.

Animals↗
PubMed1994

Analysis of the thermodynamic linkage of DNA binding and ion binding for dimeric and tetrameric forms of the lac repressor.

The salt concentration dependences of the observed association constants (Kobs) for the binding of wild-type lac repressor tetramer and the dimeric lacI-18 mutant repressor to lactose operator DNA were compared. For both proteins, the data are consistent with a class of linkage models in which ion binding by the protein is driven by differences in the ionic concentrations in bulk solution and in the volume near the DNA surface. The models that best agree with the data are those in which ion-binding reactions are cooperative. In spite of close agreement between these models and the data, the determination of ion stoichiometries and apparent ion-binding affinities requires additional mechanistic or structural information. The simplest ion-binding mechanism consistent with the data is compatible with a current structural model of the repressor-operator complex. At salt concentrations in excess of 50 mM, at which cation displacement from the DNA and anion displacement from the protein are expected to dominate, similar ion stoichiometries are found for the DNA binding of dimeric and tetrameric repressors. This supports the notion that the DNA contacts of these proteins are homologous. At lower salt concentrations, in which cation binding by the proteins is expected to be significant, the net ion stoichiometry of wild-type repressor binding is slightly greater than that of the lacI-18 mutant. This difference may reflect the availability of ion-binding sites in the distal subunits of tetramer that are not present in the dimer, or may be a consequence of the involvement of ion binding in the dimer/monomer equilibrium.

Anions↗
PubMed1994

Molecular sequestration stabilizes CAP-DNA complexes during polyacrylamide gel electrophoresis.

The gel electrophoresis mobility shift assay is widely used for qualitative and quantitative characterization of protein complexes with nucleic acids. Often it is found that complexes that are short-lived in free solution (t1/2 of the order of minutes) persist for hours under the conditions of gel electrophoresis. We have investigated the influence of polyacrylamide gels on the pseudo first-order dissociation kinetics of complexes containing the E.coli cyclic AMP receptor protein (CAP) and lactose promoter DNA. Within the gel matrix, kdiss decreased with increasing [polyacrylamide] and the order of the reaction was changed. In free solution, kdiss was proportional to [DNA]2, while in 5% gels, kdiss was proportional to [DNA]0.3. In gels of [polyacrylamide] > or = 10%, kdiss was nearly independent of [DNA] until fragment concentrations exceeded 0.1 microM. Even in the absence of competing DNA, kdiss(gel) < kdiss(solution). These results suggest that the lifetime of CAP-DNA complexes in free solution is limited by their encounter frequency with molecules of DNA or with protein-DNA complexes; some or all of the stabilization observed in gels may be due to a reduction in this frequency.

Cyclic AMP Receptor Protein↗
PubMed1994

Effective tumor vaccine generated by fusion of hepatoma cells with activated B cells.

Fusion of BERH-2 rat hepatocellular carcinoma cells with activated B cells produced hybrid cells that lost their tumorigenicity and became immunogenic. Syngeneic rats injected with BERH-2-B hybrid cells became resistant to challenge with parental BERH-2 cells, and rats with established BERH-2 hepatomas were cured by subsequent injection of BERH-2-B cells. Both CD4+ and CD8+ cells were essential for the induction of protective immunity; however, only CD8+ cells were required for the eradication of BERH-2 tumors. The generation of hybrid tumor cells that elicit antitumor immune responses may be a useful strategy for cancer immunotherapy.

Animals↗