Biomedical subjects

X Liang

Publications and source records attributed to X Liang.

At least 199 records · Page 11Linked to original sources

PubMed1997

[The determination of enantiomeric purity for ibuprofen by high performance liquid chromatography].

Ibuprofen is an excellent anti inflammatory and analgesic drug. It possesses a chiral carbon atom in its molecule. For the two enantiomers, only the S(+)-isomer is highly active, whereas the R(-)-isomer has very low activity. S-isomer can be isolated by resolution from its racemoid and the R-isomer can be racemized under basic condition. Consequently it is highly important to determine its enantiomeric purity. In this paper, an efficient HPLC method for determination of enantiomeric purity for ibuprofen (1) through the formation of a couple of diastereomers, N-(S)-(alpha-methylbenzyl)-alpha-methyl-4-(alpha-methylpropyl)benzeneacetic amide [R,S-(2)], and (S)-(alpha-methylbenzyl)-alpha-methyl-4-(2-methyl-propyl)benzeneacetic amide [S,S-(2)], was developed using Micropak Si-5 column, petroleum ether and ethyl ether (1:1 volume) as eluate and UV detector (lambda = 300 nm). The method is convenient, rapid and accurate. The accuracy was between 99.71%-100.25%, and the average deviation was 0.064%.

Analgesics, Non-Narcotic↗

PubMed1997

Clozapine and haloperidol modulate N-methyl-D-aspartate- and non-N-methyl-D-aspartate receptor-mediated neurotransmission in rat prefrontal cortical neurons in vitro.

The effects of the antipsychotic drugs haloperidol and clozapine on N-methyl-D-aspartate (NMDA) and non-NMDA receptor-mediated neurotransmission were examined and compared in pyramidal cells of the medial prefrontal cortex in rat brain slices by using the techniques of intracellular recording and single-electrode voltage-clamp. The bath administration of either haloperidol or clozapine produced a marked facilitation (300-400%) of NMDA-evoked responses in a concentration-dependent manner. The EC50 values of haloperidol and clozapine were 38 and 14 nM, respectively. At concentrations of > or =100 nM, clozapine, but not haloperidol, produced bursts of excitatory postsynaptic potentials (EPSPs), which were blocked by glutamate receptor antagonists, suggesting that these EPSPs were the result of increasing release of excitatory amino acids. Haloperidol, but not clozapine, produced a concentration-dependent inhibition of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-induced current with an EC50 value of 37 nM. Haloperidol significantly decreased the amplitude of EPSPs evoked by the electrical stimulation of the forceps minor, whereas clozapine increased the amplitude of these EPSPs. The study of current-voltage relationship indicates that clozapine preferentially potentiates NMDA receptor-mediated transmission, whereas haloperidol depresses the non-NMDA receptor-mediated response, which probably obscures its potentiating effect on NMDA receptor-mediated EPSPs.

Action Potentials↗

PubMed1997

Clinical significance of the immunohistochemical detection of p53 protein in endoscopic biopsy specimens.

OBJECTIVE: To evaluate the utility of immunohistochemical staining of p53 expression in endoscopic biopsy specimens in clinical practice. METHODS: Using a streptavidin-peroxidase (S-P) conjugate method with monoclonal p53 antibody Do-7, the expression of p53 was investigated immunohistochemically in 150 endoscopic biopsies and paired brushings from patients with benign and malignant gastric diseases. Among them, 22 cases with gastric carcinoma underwent the gastrectomy and the immunohistochemistry was repeated in the resected cancerous tissues of the same patient. RESULTS: p53 expression in endoscopic specimens was detectable in 35.7% cases of gastric carcinoma (n = 70), 5.9% of gastric polyps (n = 17), 16.7% of gastric mucosal dysplasia (n = 18) and 4.0% of chronic atrophic gastritis (n = 25), but no protein expression was observed in cases of chronic active gastritis (n = 20). In 22 patients with tumor resection, 8 (36.4%) were identified with p53 expression in endoscopic specimens before surgery, while 10 (45.5%) were identified with the same expression in surgical specimens, the real positive rate was 80.0%, no false positives were observed in endoscopic specimens. Furthermore, p53 expression in gastric carcinoma was closely correlated with clinical stage and lymph nodes involvement, but did not correlate with histologic type. CONCLUSIONS: Assay of p53 by immunohistochemistry in endoscopic biopsy specimens and brushings is an easy and reliable technique to assess p53 status in gastric carcinoma, and thus could serve as a marker to foresee the prognosis in these patients and assist in the diagnosis of malignancy before surgery. It may also be a valuable marker in screening patients with high risk of gastric carcinoma.

Adenocarcinoma↗

PubMed1997

[The effects of hyperinsulinmia and insulin-like growth factor-1 on hyperandrogenism in polycystic ovarian syndrome].

OBJECTIVE: To investigate the effects of insulin (INS) and insulin-like growth factor-1 (IGF-1) on ovarian androgen production in women with polycystic ovarian syndrome (PCOS). METHOD: 48 patients with PCOS were divided into two groups based on body mass index (BMI) (24 were obese BMI > 25 and 24 nonobese) (BMI < 25). 10 women with normal weight and menstruation were recruited as controls. The serum LH, FSH and testosterone (T) levels were determined. 40 cases were measured INS, IGF-1, androstenodine (A) and sex hormone binding globulin (SHBG) after a 3-hour oral glucose tolerance test (OGTT). Ovarian stroma obtained from 10 patients with PCOS and 5 healthy women were cultured in the medium with high INS concentration (30 ng/ml and 60 ng/ml). The IGF-1 and A levels were determined. RESULTS: Two groups of patients with PCOS demonstrated significant hyperinsulinmia (HI) and hyperandrogenism. Significantly higher IGF-1 level was observed in nonobese patients (P < 0.01). Insulin markedly stimulated release of IGF-1 (4 times, P < 0.01) and A (6 times, P < 0.05) in incubation of ovarian stroma obtained from PCOS patients. A positive correlation between IGF-1 and A was present in the culture medium (r = 0.679, P < 0.05). The serum levels of SHBG were significantly lower in PCOS patients. CONCLUSION: The findings suggest that the women with PCOS have HI, since INS may play an important role in hyperandrogenism by upregulating IGF-1 system in ovary.

Adult↗

PubMed1997

[The secretion and receptor gene of insulin-like growth factor-I quantitative expression in ovarian stroma in polycystic ovarian syndrome patients].

OBJECTIVE: To explore varying different degrees of the action of insulin-like growth factor-I (IGF-I) and its receptor gene quantitative expression in the ovarian stroma of women with obese and nonobese polycystic ovarian syndrome (PCOS). METHOD: The expression of IGF-I receptor gene in the ovarian stroma from 35 cases of PCOS (obese: 15 cases; nonobese: 20 cases) and 20 cases of control were quantitatively determined by reverse transcript polymerase chain reaction (RT-PCR) combined with beta(2) micro globlin (beta(2) MG) gene as inner-control to amplificate sychronously. The grey value ratio of them were determined. The PCR-amplified cDNA fragments were put in restriction analysis (DdeI). RESULTS: The expression of IGF-I receptor in PCOS ovary stroma was significantly greater than in the control group (P < 0.001). The nonobese group presents more enhancement than obese group in IGF-I receptor gene expression. The restrictive fragments were same between the PCOS and the control group. CONCLUSIONS: The expression of IGF-I receptor in PCOS ovarian stroma is abnormally excessive and the nonobese PCOS have more potential action of IGF-I system in ovary stroma.

Adult↗

PubMed1997

[Expression level of MDR1, and MRP in patients with malignant blood disease and its clinical significance].

RT-PCR method was used to detect the expression level of multi-drug resistance gene (MDR1) and multi-drug resistance associated protein (MRP) in patients with malignant blood disease, including 19 cases of acute leukemia and 6 cases of multiple myeloma. The results showed: expression level of MDR1 in patients with known clinical drug resistance elevated obviously and was significantly associated with clinical drug resistance (r = 0.612, P < 0.01), which indicated that expression of MDR1 was the main mechanism of clinical drug resistance. There is no obvious relationship between expression level of MDR1 and MRP (r = 0.035, P > 0.05).

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

[Studies on purging leukemic cells by photosensitizer PSD-007 laser photoradiation in vitro].

The sensitivity to photosensitization mediated by the hematoporphyrin photosensitizer PSD-007 of acute promyelocytic leukemic cell line (HL-60) was compared with normal human hemopoietic progenitor cells. The results showed that the leukemic cells were more sensitive. After being treated with 10 micrograms.ml-1 PSD-007 followed by 2J.cm-2 copper vapor laser light irradiation, the clonogenic leukemic (HL-60) cells were reduced 98%, but the survival rate of human granulocyte-macrophage colony-forming units (CFU-GM) was 40 +/- 8%. Mixing of normal human marrow cells with leukemic (HL-60) cells (ratio 100:1) did not interfere with elimination of tumor cells. The ultrastructure changes of HL-60 cells treated by laser photoradiation was observed under the trans-electronic microscope. The mitochondria, endoplasmic reticulum and cell membrane were involved. This means that the cell biomembrane is the main target to be attacked. It is considered that PSD-007-laser photoradiation therapy is efficient for killing leukemic cells.

Adult↗

PubMed1996

A novel cationic lipid greatly enhances plasmid DNA delivery and expression in mouse lung.

Effective gene therapy for lung tissue requires the use of efficient vehicles to deliver the gene of interest into lung cells. When plasmid DNA encoding chloramphenicol acetyltransferase (CAT) was administered intranasally to BALB/c mice without carrier lipids, CAT activity was detected in mouse lung extracts. Plasmid DNA delivered with optimally formulated commercially available transfection reagents expressed up to 10-fold more CAT activity in lung than observed with naked DNA alone. Liposome formulations consisting of (+/-)-N-(3-aminopropyl)-N,N-dimethyl-2,3-bis (dodecyloxy)-1-propanaminium bromide (GAP-DLRIE) plus the neutral colipid dioleoylphosphatidylethanolamine (DOPE) enhanced CAT expression by more than 100-fold relative to plasmid DNA alone. A single administration of GAP-DLRIE liposome-CAT DNA complexes to mouse lung elicited peak expression at days 1-4 posttransfection, followed by a gradual return to baseline by day 21 postadministration. Readministration of GAP-DLRIE liposome CAT complexes at day 21 led to another transient peak of reporter gene expression. Histological examination of lungs treated with GAP-DLRIE complexed beta-galactosidase DNA revealed that alveolar epithelial cells were the primary locus of expression and that up to 1% of all alveoli contained epithelial cells expressing the transgene.

Administration, Intranasal↗

PubMed1996

The cytoplasmic domain of bovine herpesvirus 1 glycoprotein B is important for maintaining conformation and the high-affinity binding site of gB.

Bovine herpesvirus 1 (BHV-1) glycoprotein B (gB) has been shown to interact with two types of receptor on Madin Darby bovine kidney cells. The first receptor is heparan sulfate proteoglycan, whereas the second high-affinity receptor remains unknown. In order to study the structural requirement for gB's high-affinity binding activity, different forms of the gB ectodomain were expressed and compared with authentic gB. By using chemical cross-linking and sucrose gradient centrifugation, we found that BHV-1 gB was able to form dimers. A region between the cleavage site and the transmembrane anchor region, residues 506 to 763, was found to be required for gB oligomerization. Although the purified gBt and gBtM, two truncated forms of gB, formed oligomers, they did not block the high-affinity cellular receptor, suggesting that oligomerization was not the reason for the loss of the high-affinity binding site on gB. However, an N-terminal juxtamembrane region-located epitope recognized by a monoclonal antibody, designated epitope I, was lost from gBt and gBtM, indicating that both truncated gBs are conformationally changed. Therefore, the structure around this particular region may be required for the existence of the gB high-affinity binding site.

Animals↗

PubMed1996

The Cytoplasmic Domain of Bovine Herpesvirus 1 Glycoprotein B Is Important for Maintaining Conformation and the High-Affinity Binding Site of gB

Journal Article↗

PubMed1996

Expression of bovine interleukin-1 beta in a bovine herpesvirus-1 vector: in vitro analysis.

In order to evaluate whether bovine herpesvirus-1 (BHV-1) could be used as a live viral vector for the expression of cytokines, we constructed a recombinant BHV-1 expressing bovine interleukin-1 beta (boIL-1 beta). The boIL-1 beta coding sequence, corresponding to the cleaved mature product, was fused with the BHV-1 glycoprotein C (gC) signal peptide sequence; the resultant gC-boIL-1 beta fusion gene was recombined into the gC locus of the BHV-1 genome. Southern blot analysis confirmed the proper genomic configuration of the recombinant virus. Results from transcript analysis showed that boIL-1 beta was expressed in infected cells with kinetics similar to that of gC. Indirect immunofluorescence and immunoprecipitation assays showed that the recombinant protein was produced in both cell-associated and secreted forms. Western blot analysis detected a 19.3-kDa protein. Further analysis, using an IL-1 beta bioassay demonstrated that both the cellular and secreted forms of recombinant boIL-1 beta possessed biological activity. The expression of the boIL-1 beta protein did not affect the in vitro growth efficiency of the virus, which exhibited similar growth kinetics to that of a simple gC deletion mutant. The results from this study demonstrate that BHV-1 can be used to express a functional cytokine, thereby establishing the basis to further study recombinant BHV-1 expressing cytokines as an alternative means to attenuate the virus and also as a potential in situ cytokine delivery system to modulate immune responses against BHV-1 and other cattle pathogens.

Amino Acid Sequence↗

PubMed1996

Characterization of SDS--PAGE-separated proteins by matrix-assisted laser desorption/ionization mass spectrometry.

A new strategy to characterize SDS--PAGE-separated proteins with MALDI MS is described. The proteins, electroblotted onto nitrocellulose after SDS--PAGE separation and stained with reversible Ponceau S dye, are readily recovered by dissolving the membrane in matrix solutions prepared with acetone. The resulting mixtures are amenable to direct MALDI MS analysis, which provides a rapid and accurate means of measuring the molecular weights of SDS--PAGE-separated proteins and of peptides that result from CNBr digestion of proteins on the nitrocellulose membrane. Compared with the traditional elution method, this procedure provides more efficient detection of proteins and peptides, especially the higher molecular weight proteins from the membrane. As little as 3.5 pmol of lysozyme and 15 pmol of bovine albumin loaded onto a gel can be detected using this method. The detection sensitivity is higher than or comparable to that of the traditional Coomassie Brilliant Blue staining procedure.

Electrophoresis, Polyacrylamide Gel↗

PubMed1996

Agrobacterium tumefaciens-mediated transformation of yeast.

Agrobacterium tumefaciens transfers a piece of its Ti plasmid DNA (transferred DNA or T-DNA) into plant cells during crown gall tumorigenesis. A. tumefaciens can transfer its T-DNA to a wide variety of hosts, including both dicotyledonous and monocotyledonous plants. We show that the host range of A. tumefaciens can be extended to include Saccharomyces cerevisiae. Additionally, we demonstrate that while T-DNA transfer into S. cerevisiae is very similar to T-DNA transfer into plants, the requirements are not entirely conserved. The Ti plasmid-encoded vir genes of A. tumefaciens that are required for T-DNA transfer into plants are also required for T-DNA transfer into S. cerevisiae, as is vir gene induction. However, mutations in the chromosomal virulence genes of A. tumefaciens involved in attachment to plant cells have no effect on the efficiency of T-DNA transfer into S. cerevisiae. We also demonstrate that transformation efficiency is improved 500-fold by the addition of yeast telomeric sequences within the T-DNA sequence.

Agrobacterium tumefaciens↗

PubMed1996

Characterization of two new matrices for matrix-assisted laser desorption/ionization mass spectrometry.

Three structurally related compounds, 4-hydroxy-33-methoxyphenylpyruvic acid (HMPPA), indole-3 pyruvic acid (IPA), and indole-3-glyoxylic acid have been evaluated as matrix-assisted laser desorption/ionization (MALDI) matrices. HMPPA and IPA were found to be effective matrices for MALDI-MS analysis of proteins and peptides and have been characterized in this work. HMPPA was found to be a particularly good matrix for the analysis of proteins and peptides because of its tolerance towards impurities and the resulting sensitivity in MALDI-MS experiments. Analysis of model proteins and peptides, including those in biological fluid, are demonstrated.

Glyoxylates↗

PubMed1996

Determination of bacterial protein profiles by matrix-assisted laser desorption/ionization mass spectrometry with high-performance liquid chromatography.

A rapid method for profiling bacterial and cellular proteins has been developed using a combination of capillary high-performance liquid chromatography separation followed by (MALDI-MS) matrix-assisted laser desorption/ionization mass spectrometric analysis. In this method, bacteria are sonicated, the cell walls broken, and the water-soluble proteins precipitated for analysis. The proteins are separated by capillary liquid chromatography and detected on-line by a UV absorption detector. The eluents are then collected for off-line analysis by MALDI-MS. Using this method, it is demonstrated that bacteria can be discriminated based upon their protein profiles to the species level with only pmol level detection of proteins. It has also proved to be a fast and accurate means for monitoring the expression of Hsp27 in an insect cell system.

Animals↗

PubMed1996

Production and characterization of bovine herpesvirus 1 glycoprotein B ectodomain derivatives in an hsp70A gene promoter-based expression system.

Different derivatives of bovine herpesvirus 1 (BHV-1) glycoprotein B (gB) ectodomain were expressed in a novel heat-shock expression system. The putative ectodomain, gBt, and the N-terminal subunit, gBb, were of the expected molecular weight and were secreted. Their production were heat-inducible and the purified proteins were able to elicit antibody responses in mice of a comparable level as induced by authentic gB. The truncated C-terminal subunit, gBct, was retained in the endoplasmic reticulum. Our studies suggest that the gBb subunit may play a major role in constituting the overall configuration of gB and is required for the intracellular transport of gB.

Animals↗

PubMed1996

Novel viral vaccines for livestock.

Recent advances in our understanding of virulence factors of viruses and the proteins or glycoproteins involved in inducing neutralizing antibodies or cell mediated immunity are forming the foundation for the development of a new generation of viral vaccines. Using bovine herpesvirus as an example, we have identified glycoproteins gB, gC, and gD as important targets for inducing neutralizing antibody responses, with gD being able to induce the highest neutralizing and cellular responses. For subunit vaccine development, the glycoproteins were produced in both prokaryotic and eukaryotic expression systems. Glycoproteins produced in eukaryotic systems were very effective in stimulating a broad range of immune responses in cattle. These glycoproteins were then formulated into effective vaccines that prevented both virus shedding and clinical disease. Herpesviruses also served as an excellent model for the identification and deletion of specific genes which lead to attenuation. In herpesviruses, two major classes of genes can be deleted. Class I includes glycoprotein genes that are nonessential for virus replication in vitro, and Class II includes genes involved in nucleic acid metabolism. these gene deleted regions can then be replaced with genes coding for protective antigens of other pathogens to develop multivalent vaccines in a single vector. Similar approaches are being used for other viruses including vaccinia virus and adenovirus. Finally, we introduced plasmids coding for protective antigens, gB, gC, and gD, into animals and developed immunity to these antigens. This approach has the potential to revolutionize vaccination regimes of the future.

Animals↗

PubMed1996

Li(+)-regulated 1-aminocyclopropane-1-carboxylate synthase gene expression in Arabidopsis thaliana.

In Arabidopsis thaliana, 1-aminocyclopropane-1-carboxylate synthase (ACS) is encoded by a multigene family consisting of at least five members whose expression is induced by hormones, developmental signals, and protein synthesis inhibition. Li+, known to interfere with the phosphoinositide (PI) second messenger system by inhibiting the activity of inositol-phosphate phosphatases, is one of the strongest inducers of ACC synthase activity in plants. Treatment of etiolated Arabidopsis seedlings with LiCl results in a rapid induction of the ACS5 gene. Also, LiCl represses the cycloheximide (CHX)-induced accumulation of the ACS2 mRNA. The effects of Li+ on the expression of ACS5 and ACS2 are specific, dose-dependent, and can be reversed by Ca2+ and mimicked by the protein kinase inhibitor K-252a. The results suggest that the regulation of some ACS genes by various inducers may involve protein kinase activity, which in turn may be controlled through an inositol 1,4,5-triphosphate (IP3)-mediated Ca2+ mobilization. Since plants contain no Li+, the cation appears to unmask pre-existing biochemical capacity that may be utilized by various unknown transducers during plant growth and development.

Amino Acid Sequence↗