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Biomedical subjects

Jun Liu

Publications and source records attributed to Jun Liu.

At least 361 records · Page 20Linked to original sources
PubMed2002

'Streptomyces nanchangensis', a producer of the insecticidal polyether antibiotic nanchangmycin and the antiparasitic macrolide meilingmycin, contains multiple polyketide gene clusters.

Several independent gene clusters containing varying lengths of type I polyketide synthase genes were isolated from 'Streptomyces nanchangensis' NS3226, a producer of nanchangmycin and meilingmycin. The former is a polyether compound similar to dianemycin and the latter is a macrolide compound similar to milbemycin, which shares the same macrolide ring as avermectin but has different side groups. Clusters A-H spanned about 133, 132, 104, 174, 122, 54, 37 and 59 kb, respectively. Two systems were developed for functional analysis of the gene clusters by gene disruption or replacement. (1) Streptomyces phage phiC31 and its derived vectors can infect and lysogenize this strain. (2) pSET152, an Escherichia coli plasmid with phiC31 attP site, and pHZ1358, a Streptomyces-Escherichia coli shuttle cosmid vector, both carrying oriT from RP4, can be mobilized from E. coli into NS3226 by conjugation. pHZ1358 was shown to be generally useful for generating mutant strains by gene disruption and replacement in NS3226 as well as in several other Streptomyces strains. A region in cluster A (approximately 133 kb) seemed to be involved in nanchangmycin production because replacement of several DNA fragments in this region by an apramycin resistance gene [aac3(IV)] gave rise to nanchangmycin non-producing mutants.

Anti-Bacterial Agents↗
PubMed2002

APS facilitates c-Cbl tyrosine phosphorylation and GLUT4 translocation in response to insulin in 3T3-L1 adipocytes.

APS is a Cbl-binding protein that is tyrosine phosphorylated by the insulin receptor kinase. Insulin-stimulated phosphorylation of tyrosine 618 in APS is necessary for its association with c-Cbl and the subsequent tyrosine phosphorylation of Cbl by the insulin receptor in both 3T3-L1 adipocytes and CHO-IR cells. When overexpressed in these cells, wild-type APS but not an APS/Y(618)F mutant facilitated the tyrosine phosphorylation of coexpressed Cbl and its association with Crk upon insulin stimulation. APS-facilitated phosphorylation occurred on tyrosines 371, 700, and 774 in the Cbl protein. APS also interacted directly with the c-Cbl-associated protein (CAP) and colocalized with the protein in cells. The association was dependent on the SH3 domains of CAP and was independent of insulin treatment. Overexpression of the APS/Y(618)F mutant in 3T3-L1 adipocytes blocked the insulin-stimulated tyrosine phosphorylation of endogenous Cbl and binding to Crk. Moreover, the translocation of GLUT4 from intracellular vesicles to the plasma membrane was also inhibited by overexpression of the APS/Y(618)F mutant. These data suggest that APS serves as an adapter protein linking the CAP/Cbl pathway to the insulin receptor and, further, that APS-facilitated Cbl tyrosine phosphorylation catalyzed by the insulin receptor is a crucial event in the stimulation of glucose transport by insulin.

3T3 Cells↗
PubMed2002

Mechanical spectral signatures of malignant disease? A small-sample, comparative study of continuum vs. nano-biomechanical data analyses.

Thin sections from human breast biopsies were employed to perform a differential analysis of the ultrasound spectral responses from invasive ductal carcinoma and normal tissue. A non-destructive testing methodology was employed, yielding the reflection coefficients as function of frequency in the clinical ultrasound range. The spectral responses were simulated both in the context of continuum and nano-biomechanics, with the objective of quantifying the physical properties that determine the differences in the spectral signature of normal vs. malignant tissue. The properties that were employed for the theoretical reconstruction of the spectra were: the density, the continuum and the nanomechanical elastic constants, and the nanomechanical theory internodal distance. The latter is a measure of the depth-of-penetration of mechanical actions between contiguous tissue elements. Together with vectorial descriptors of the tissue spatial arrangement, the internodal distance variable affords the quantitative incorporation of tissue architectural data in the theoretical model. In this paper, the validity of the nanomechanical approach to tissue characterization is discussed, and its potential extensions to biomolecular marker-based cancer diagnostics and therapeutics are considered.

Breast Neoplasms↗
PubMed2002

HEN1 functions pleiotropically in Arabidopsis development and acts in C function in the flower.

Four classes of floral homeotic MADS domain proteins specify the identities of the four organ types in an Arabidopsis flower. While the activities of the MADS domain proteins are essentially confined to the flower or to the inflorescence, several genes, such as APETALA2, HUA1 and HUA2, also act outside the flower in addition to their organ identity functions inside the flower. We identified a new gene, HUA ENHANCER 1 (HEN1) from a sensitized genetic screen in the hua1-1 hua2-1 background that is compromised in floral homeotic C function. We showed that HEN1, like the C function gene AGAMOUS, acts to specify reproductive organ identities and to repress A function. HEN1 also shares AG's non-homeotic function in controlling floral determinacy. HEN1 may achieve these functions by regulating the expression of AG. hen1 single mutants exhibit pleiotropic phenotypes such as reduced organ size, altered rosette leaf shape and increased number of coflorescences, during most stages of development. Therefore, HEN1, like the A function gene AP2, plays multiple roles in plant development as well as acting in organ identity specification in the flower. HEN1 codes for a novel protein and is expressed throughout the plant.

Amino Acid Sequence↗
PubMed2002

HUA ENHANCER2, a putative DExH-box RNA helicase, maintains homeotic B and C gene expression in Arabidopsis.

Reproductive organ identity in Arabidopsis is controlled by the B, C and SEPALLATA classes of floral homeotic genes. We have identified a recessive mutation in a novel gene, HUA ENHANCER2, which, when combined with mutations in two weak class C genes, HUA1 and HUA2, leads to the production of third whorl sepal-petal-stamens and fourth whorl sepal-carpels. Quadruple mutant analysis and in situ localization of A, B, C and SEPALLATA floral homeotic RNAs suggest that HUA ENHANCER2 is required for the maintenance of B and C gene expression in the reproductive whorls. In addition to its role in floral homeotic gene expression, HUA ENHANCER2 is required for normal spacing and number of perianth organ primordia. We show that HUA ENHANCER2 encodes a putative DExH-box RNA helicase that is expressed in specific patterns in the inflorescence meristem and developing flowers. As a possible ortholog of the yeast exosome-associated protein, Dob1p (Mtr4p), HUA ENHANCER2 may affect floral organ spacing and identity through the regulation of protein synthesis or mRNA degradation. Therefore, our studies on HUA ENHANCER2 not only demonstrate that B and C gene expression is established and maintained separately, but also implicate the existence of post-transcriptional mechanisms in the maintenance of B and C gene expression.

Amino Acid Sequence↗
PubMed2002

A mineralizing rat dental pulp cell subline expressing collagen type I and dentin sialoprotein-phosphophoryn transcripts.

A mineralizing rat dental pulp cell subclone, termed M2H4, was selected from single-cell cloning of the rat dental pulp cell line RPC-C2A by screening confluent single-cell cultures for their ability to undergo mineralization. To induce mineralization, confluent single-cell cultures were treated for 8 d with ascorbic acid followed by the addition of inorganic phosphate to a final concentration of 4 mM for an additional 3 d. Confluent M2H4 subclones were shown by immunofluorescence and electron microscopy to form collagen type I fibrils. Furthermore, using reverse transcriptase-polymerase chain reaction, this subclone was found to be capable of expressing dentin sialoprotein-phosphophoryn (DSP-PP) transcripts, an odontoblast-specific marker. Thus, this newly identified mineralizing rat M2H4 subclone possesses odontoblast-like characteristics and can serve as an in vitro model for examining the role of DSP and PP in the formation of mineralized dentin.

Animals↗
PubMed2002

The interaction of DNA with dopamine by spectroscopic and electrochemical methods.

It has recently been reported that dopamine may show some biological activities in antitumor and cell apoptosis. We have thoroughly investigated the interaction between dopamine and DNA by CD, UV, fluorescence and electrochemical methods. The results of spectroscopic measurements have indicated that a binding event occurs in a dopamine-DNA system. Besides the electronstatic interaction between a negatively charged DNA molecule and a positively charged dopamine molecule, other binding modes, such as hydrogen-bond and intercalation may also exist in this system. The interaction parameters, including the equilibrium constant and binding numbers, were estimated by an electrochemical method based on the redox current and formal potentials. Both of the two calculation methods showed that the 1:1 type of complex was formed in the dopamine-DNA system and that its equilibrium constant was about 5.85 x 10(6) M(-1). Based on the results of UV, fluorescence and electrochemical experiments in the present study, dopamine may be employed as an effective probe for a DNA assay.

Animals↗
PubMed2002

[Super-selective pump-insertion into the target artery and regional intraarterial infusion chemotherapeutant and immunizator in treatment of the latter gastrointestinal cancer].

OBJECTIVE: To evaluate the effect of operative selective pump-insertion into the tumorous target artery, postoperative regional infusion chemotherapeutant and immunizator for treatment the latter gastrointestinal cancer. METHODS: The effect of operative super-selective pump-insertion into the tumorous nutritious artery, postoperative regional infusion chemotherapeutant and immunizator for treatment 88 cases patients suffering from irremovable gastrointestinal cancer was observed. Of them, 45 cases were gastric cancer, 31 cases were rectal cancer, 11cases were colic cancer. RESULTS: Complete response 2 case; Part response 77 cases, 11 cases patients had received secondary resection after intraarterial chemotherapy. Non chang 9 cases; effective rates reach to 89.8%. One, two and three years survival rates were 86.4%, 30.7% and 10.2%. Average survival period were 21.5 mouths. CONCLUSION: Super-selective pump-insertion into the artery and regional intraarterial chemotherapy is an efficient way in treatment of the latter gastrointestinal cancer, which can delay the survival period of patients with tumor, and increase the resectable rate.

Adolescent↗
PubMed2002

[Expression and hypoxic regulation of vascular endothelial growth factor and matrix metalloproteinase-9 in esophageal carcinoma].

OBJECTIVE: To investigate the the expression and hypoxic regulation of vascular endothelial growth factor(VEGF) and matrix metalloproteinase-9. METHODS: VEGF mRNA and MMP-9 mRNA were examined by reverse transcription-polymerase chain reaction (RT-PCR) in 43 esophageal carcinoma specimens including 18 para-tumorous esophageal tissues. The expression of VEGF protein and mean microvessel density (MVD) in 56 specimens were examined by immunohistochemical stain. The effect of hypoxia on VEGF and MMP-9 expression in esophageal cancer cell lines was quantitatively determined by enzyme linked immunosorbent assay (ELISA). RESULTS: The VEGF expression in the tumorous tissue, being significantly correlated with MVD in the tumor, was remarkably higher than that in the para-tumorous tissue. VEGF and MVD expression in the tumor was significantly associated with stage and metastasis of esophageal carcinoma. The MMP-9 expression in the tumorous tissue, being uncorrelated with vessel count and clinicopathologic features in esophageal carcinoma, was significantly higher than that in the para-tumorous tissue. Hypoxia significantly increased the VEGF expression in esophageal cancer cell lines but did not affect the MMP-9 expression. CONCLUSIONS: The expression of VEGF plays an important role in the angiogenesis and metastasis of esophageal cancer, which is regulated by hypoxia. VEGF may serve as a predictor of progression in esophageal carcinoma and a potential target for antiangiogenic therapy of esophageal carcinoma.

Endothelial Growth Factors↗
PubMed2002

[The distribution of serum homocysteine and its associated factors in a population of 1 168 subjects in Beijing area].

OBJECTIVE: To describe serum homocysteine distribution and its associated factors in population of urban and rural areas in Beijing. METHODS: The study population was represented by a randomly selected sample with 1 168 subjects, including both males and females aged 35 - 64. The levels of serum homocycteine were compared and the correlation with other risk factors were analyzed statistically. RESULTS: (1) Geometric mean of serum homocycteine was 15.4 micromol/L in males and 12.2 micromol/L in females (P < 0.001). (2) There was a significant difference in homocysteine levels between urban population and rural population. Men from rural area had 1.5 times higher homocyteine than from urban (18.0 micromol/L vs 12.0 micromol/L, P < 0.001), while the rural women had 1.3 times higher homocysteine level than urban women did. (3) The prevalence rate of hyperhomocysteinemia was 15.3% in population aged 35 - 64 in Beijing area. (4) Gender, residential location (urban or rural), smoking and education had independent effects on level of serum homocysteine by multivariate analysis. CONCLUSION: Population in Beijing had higher serum level and prevalence rate of homocysteine than some western countries. Gender, geographic distribution, smoking and education had some influence on homocysteine level.

Adult↗
PubMed2002

[Enhancement by hypoxia of antisense VEGF(165) gene expression in esophageal cancer cells].

To demonstrate effects of antisense VEGF(165) to suppress esophageal cancer cells and to improve efficacy of the gene therapy of tumor by using hypoxic environment, hypoxia response element (HRE) was cloned from promoter of VEGF by PCR and employed to construct an eukaryotic expression vector containing luciferase and antisense VEGF(165) by using recombinant DNA techniques. The recombinant vectors were transfered into esophageal cancer cells by lipofectin methods, and hypoxia inducible reporter gene expression was determined by luminometer and the expression of antisense VEGF was evaluated indirectly by ELISA that detected of VEGF. The esophageal cells tansfected by antisense VEGF(165) gene were transplanted into nude mice, in order to evaluate the suppressive effect of antisense VEGF(165). Our results showed that, in vitro, hypoxia increased expression of reporter gene to 3 780 % and enhanced greatly expression of antisense VEGF. In vivo, the growth of esophageal cancer cells transfected by antisense VEGF in the vector containing HRE was suppressed more significantly, with suppression rate being 71.1%, than that by the vector without HRE, whose inhibiting rate 56.1%. It was concluded that antisense VEGF(165) suppressed significantly growth of esophageal cancer, and by using a gene expression vector containing HRE, the expression of target genes could be regulated autonomously by hypoxic environment of tumor and the efficiency of gene therapy could be greatly improved.

Animals↗
PubMed2002

[Experimental study of monoclonal antibody to intercellular adhesion molecule-1 for incipient acute tubular necrosis].

OBJECTIVE: To explore the role of leukocyte adhesion in the pathophysiology of glycerol-induced acute renal tubular necrosis (ATN). METHODS: Rat models of ATN were established by intramuscular injection of glycerol in 24 Wistar rats, which were divided randomly into 3 groups of equal number according to the agents coinjected with glycerol for the prevention of ATN, with another 8 rats serving as normal control. One of the 3 groups received a monoclonal antibody (mAb) against intercellualr adhesion molecule-1 (anti-ICAM-1) and another received CD3 mAb, leaving one group untreated. Both functional impairment and histological changes in the rats were observed. RESULTS: Plasma creatinine measured 24 h after the injection of glycerol was 412.31+/-94.42 micromol/L in rats treated with anti-ICAM-1, significantly lower than that in CD3 mAb-treated rats (990.21 +/-171.25 micromol/L, P<0.05). Moderate to severe necrosis in the outer renal medulla with frequent mitoses was present in rats with ATN receiving CD3 mAB or nothing, but only mild necrosis with few mitoses occurred in merely 2 of those rats with anti-ICAM-1 treatment. CONCLUSION: Leukocytes and adhesion molecules play critical roles in the pathophysiology of glycerol-induced ATN, and anti-ICAM-1 which blocks the adhesion of the leukocytes may alleviate the pathological changes in the kidney.

Animals↗
PubMed2002

[Study on temporal patterns of stroke onset from community-based cohort in Beijing].

OBJECTIVE: To Study the temporal patterns of stroke onset, and to provide insights into the triggers which might cause the acute onset of stroke and to develop preventive strategies. METHODS: Using a 10-year period of the SINO-MONICA-Beijing study cohort a total number of 700 000 people, aged 25 to 74 years was recruited. The diagnostic criteria exactly followed the WHO MONICA project. Date of the week, season and month occurrence of stroke were ascertained. Percentage of stroke onset on date in the week, season and month were calculated. chi(2) test was used to identify the deviation from expected frequencies. Multiple stepwise regression was carried out for multivariate analysis. RESULTS: Most stroke occurred and recurred (chi(2) = 7.02, P = 0.008 in male and chi(2) = 12.32, P = 0.000 4 in female) in winter. The most frequent occurrence on the dates of stroke events were Monday in the urbans and Saturday in the rurals. The finding were confirmed (the stroke occurrence and recurrence positively correlated with season, correlation coefficient 0.032, P = 0.01) by correlation and multiple stepwise regression. CONCLUSION: It was important to find out the circadian variation and the external triggering factors together with unhealthy behaviour of life that would contribute to the prevention and reduction of stroke onset.

Adult↗
PubMed2002

[Establishment and characterization of human extrahepatic growing hepatocellular carcinoma cell line EGHC-9901].

OBJECTIVE: To establish a new extrahepatic growing hepatocellular carcinoma cell line. METHODS: A specimen from extrahepatic growing hepatocellular carcinoma was cultured in vitro. Cancer cells were studied morphologically and subjected to karyotype analysis, DNA analysis, and tumor formation evaluation. RESULTS: Morphological observation and functional analysis showed that their features were similar to those of HCC. Chromosomes with a variation of 76 approximately 104 were able to secret AFP in vitro and to form bile canaliculi with microvilli. CONCLUSION: EGHC-9901 cell line has characteristics of the extrahepatic growing hepatocellular carcinoma.

Adult↗
PubMed2002

[High expression of human angiogenesis inhibitor HIAF-1 in insect cells and biological activity].

BACKGROUND & OBJECTIVE: Human inhibiting angiogenesis factor-1(HIAF-1) expressed in E coli. shown the activity of inhibiting the angiogenesis of tumors. This study was designed to investigate the expression of HIAF-1 in insect cells and to elucidate its biological activity. METHODS: Recombinant baculovirus expression vector pAcuW51-HIAF-1 was constructed by recombinant DNA technique and cotransfected with linearized baculovirus DNA into sf9 cells to produce recombinant virus. The expression of recombinant HIAF-1 in insect cells infected by recombinant virus was detected by SDS-PAGE and Western blot. The recombinant protein was purified by affinity chromatography. In vitro endothelial proliferation inhibiting activity of recombinant HIAF-1 was examined by MTT method, its antitumor activity in vivo was studied in human esophageal cancer transplanted in nude mice. RESULTS: HIAF-1 was effectively expressed in insect cells as 26 KD fusing protein and its expression level was about 5-10% of insect cellular total soluble proteins. Recombinant HIAF-1 protein could inhibit endothelial cell proliferation in vitro with IC50 value of 3.1 micrograms/ml and inhibited remarkably growth of human esophageal cancer transplanted in nude mice. CONCLUSIONS: The recombinant HIAF-1 with better activity was successfully expressed in insect cells and establish a base for clinical application.

Angiogenesis Inhibitors↗
PubMed2002

[Trend analyses in the incidence of acute intracerebral hemorrhage events and acute cerebral infarction events in urban areas in Beijing].

OBJECTIVE: To study the trends of incidence on acute intracerebral hemorrhage events and acute cerebral infarction events in the population aged 25 - 74 in urban areas of Beijing from 1984 to 1999. METHODS: In monitoring the trends and determinants in the cardiovascular disease (MONICA) project and subsequent study, acute intracerebral hemorrhage events and acute cerebral infarction events were registered in a standardized way in men and women aged 25 to 74 years from 1984 - 1999. RESULTS: Both intracerebral hemorrhage attack rates decreased but cerebral infarction attack rates increased significantly; The proportion of intracerebral hemorrhage events in stroke events decreased from 42.0% to 16.0% while the proportion of cerebral infarction events in stroke events increased from 55.8% to 81.6%, the changes in incidences of acute intracerebral hemorrhage events and acute cerebral infarction events in various age groups were different. CONCLUSION: Cerebral infarction was the most important risk causing stroke, so prevention of cerebral infarction should be strengthened in the area.

Acute Disease↗
PubMed2002

[Preliminary experience of video-mediastinoscopy in clinical application].

OBJECTIVE: To determine the value of video-mediastinoscopy in clinical application. METHODS: The clinical data of 54 patients receiving video-mediastinoscopy were reviewed retrospectively. This operation consisted of cervical mediastinoscopy in 44 patients, parasternal mediastinoscopy in 6, and combined procedures in 4. Of these patients, 18 underwent video-mediastinoscopy for the evaluation of undifferentiated mediastinal disease. Thirty-six patients with suspected lung cancer showed enlarged mediastinal lymph nodes radiographically in the chest and underwent video-mediastinoscopy. RESULTS: Seventeen of 18 patients with undetermined mediastinal diseases had a definitive pathologic diagnosis, with an accuracy of 94.4% (17/18). In the 36 patients with suspected lung cancer, 22 were positive, and 14 negative. In the negative patients who underwent thoracotomy with resection, mediastinal lymph nodes revealed no evidence of metastasis. There were no postoperative complication and deaths. CONCLUSION: Video-mediastinoscopy as a highly effective and safe procedure could be used in the diagnosis and staging of thoracic diseases.

Adolescent↗