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Biomedical subjects

N Liu

Publications and source records attributed to N Liu.

At least 73 records · Page 4Linked to original sources
PubMed2001

[Mammaglobin mRNA measurement in the detection of micrometastasis in peripheral blood of breast cancer patients].

OBJECTIVE: To investigate mammanglobin (hMAM) mRNA as a marker for the detection of carcinoma cells by reverse transcriptase chain reaction (RT-PCR) in the peripheral blood of breast cancer patients. METHODS: Blood samples from 63 breast cancer patients obtained at various stages of their disease, blood samples from 8 breast hyperplasia, 5 breast adenofibroma, 25 other cancers (stomach, colon, esophagus, lung, ovary) and 31 healthy volunteers were screened for hMAM mRNA by a nested RT-PCR combined with fluorescence quantitative PCR (FQ-PCR) assay. RESULTS: Among 63 breast carcinoma patients, 19(30.2%) were RT-PCR positive for hMAM mRNA which was elevated with the tumor stage. None of the other cancer patients or those suffering from benign breast diseases were positive but only 1 of the 31 healthy volunteers gave detectable hMAM mRNA findings. hMAM mRNA was not detectable in the peripheral blood after operation in 6(32%) of 19 patients whose pre-operative test had been positive even though the hMAM mRNA expression increased with tumor stage. These results did not correlate with patients' stage, estrogen or pregnant receptor status. CONCLUSION: hMAM transcripts are detectable in the peripheral blood of some breast cancer patients. hMAM may be a novel candidate and a clinically useful breast tumor marker, especially in detecting micrometastasis.

Breast Neoplasms↗
PubMed2001

[Effects of psychosocial factors on recurrent aphthous ulcer].

OBJECTIVE: The aim of this study is to investigate the effects of patients' psychosocial background on the recurrence of aphthous ulcer (RAU). METHODS: A total of 105 patients with RAU and 100 normal subjects of the control group were evaluated for psychosocial background. All subjects were required to complete the EPQ questionnaire, the SCL 90 questionnaire, and the enquired data were analyzed by using chi-square test. RESULTS: Special personality and social factors in RAU patients might be reasons leading to the occurrence of this disease (P < 0.01). CONCLUSION: Psychosocial disorder caused by stresses of social life events on the people with special personality could impact the occurrence of RAU.

Adolescent↗
PubMed2001

Role of calcineurin in angiotensin II-induced cardiac myocyte hypertrophy of rats.

OBJECTIVE: The present study investigated the role of calcineurin in angiotensin II(AngII) -induced cardiac myocyte hypertrophy of rats. METHOD: The primary cardiac myocytes were cultured under the standard conditions. The calcineurin activity in AngII-treated cardiomyocytes was tested by using PNPP; protein synethsis rate was assessed by 3H-leucine incorporation; atrial natriuretic factor(ANF) mRNA level was determined by Northern blot analysis. Cell viability was estimated by lactate dehydrogenase (LDH) levels in cultured medium and by dyed cell numbers. RESULT: After stimulation of 10, 100 and 1 000 nmol/L of AngIi, calcineurin activities in the cardiomyocytes were increased by 13%, 57% (P < 0.05) and 228% (P < 0.01) respectively, compared with control group. Cyclosporin A(CsA), a specific inhibitor of calcineurin, markedly inhibited the calcineurin activity and decreased the 3H-leucine incorporation in AngII-treated cardiomyocytes in a dose-dependent manner. It was also found that CsA slightly reduced the mRNA level of ANF gene in AngII-stimulated cardiomyocytes. CONCLUSION: During AngII-induced cardiac myocyte hypertrophy, calcineurin signal pathway is activated, and inhibition of the pathway can attenuate AngII-induced cardiac myocyte hypertrophy, which suggests that the calcineurin signal pathway may play an important role in AngII-induced myocardial hypertrophy of rats.

Angiotensin II↗
PubMed2001

Externalization and internalization of cardiac endothelin receptors during different phases of sepsis in rat.

OBJECTIVE: To study the redistribution of endothelin-1 (ET-1) receptors in two subcellular organelles, the sarcolemmal membrane and the light vesicle, of rat heart during the progression of sepsis. METHODS: Sepsis was induced by cecal ligation and puncture (CLP). ET1 receptor was assayed by using [125I]-ET1 binding. Marker enzyme activities, protein yield, and dry-to-wet weight ratio of cardiac membranes were measured. RESULTS: Septic rat heart exhibited two distinct phases: an initial hyperdynamic phase( 9h after CLP; early stage of sepsis) followed by a hypodynamic (18h after CLP, late stage of sepsis) phase. [125I]-ET1 binding study showed that during early stage of sepsis, the B(max) of ET1 receptors was increased by 30% in sarcolemma but decreased by 19% in light vesicles, while during late stage of sepsis, the B(max) was decreased by 24% in sarcolemma but increased by 38% in light vesicles. The total binding of sarcolemma and light vesicles was increased by 25% during early stage of sepsis but decreased by 17% during late stage of sepsis. CONCLUSIONS: These data indicated that ET1 receptors in the rat heart were externalized from light vesicles to sarcolemmal membranes during early hyperdynamic phase while internalized from surface membranes to intracellular compartment during late hypodynamic phase of sepsis.

Animals↗
PubMed2000

MRG1 expression in fibroblasts is regulated by Sp1/Sp3 and an Ets transcription factor.

MRG1 (melanocyte-specific gene 1 (MSG1)-related gene), a ubiquitously expressed transcription factor that interacts with p300/CBP, TATA-binding protein and Lhx2, is the founding member of a new family of transcription factors. Initial characterization of this newly discovered transcription factor has underscored its potential involvement in many important cellular processes through transcriptional modulation. We previously demonstrated that MRG1 can be induced by various biological stimuli (Sun, H. B., Zhu, Y. X., Yin, T., Sledge, G., and Yang, Y. C. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 13555-13560). As a first step in understanding its role in different biological processes, we investigated mechanisms that regulate transcription of the mouse MRG1 gene in fibroblasts. Transient transfection of Rat1 fibroblast cells with sequential 5'-deletions of mouse MRG1 promoter-luciferase fusion constructs indicated that the -104 to +121 region contains the full promoter activity. Deletion and site-directed mutations within this region revealed that the Ets-1 site at -97 to -94 and the Sp1 site at -51 to -46 are critical for MRG1 expression in fibroblasts. Gel mobility shift and supershift assays performed with Rat1 nuclear extracts identified nucleoprotein complexes binding to the Ets-1 site and the Sp1 site. In Drosophila SL2 cells, which lack the Sp and Ets family of transcription factors, expression of Sp1, Sp3, and Ets-1 or Elf-1 functionally stimulated MRG1 promoter activity in a synergistic manner. These results suggest that multiple transcription factors acting in synergy are responsible for MRG1 expression and the responsiveness of cells to different biological stimuli.

Animals↗
PubMed2000

The retro-GCN4 leucine zipper sequence forms a stable three-dimensional structure.

The question of whether a protein whose natural sequence is inverted adopts a stable fold is still under debate. We have determined the 2. 1-A crystal structure of the retro-GCN4 leucine zipper. In contrast to the two-stranded helical coiled-coil GCN4 leucine zipper, the retro-leucine zipper formed a very stable, parallel four-helix bundle, which now lends itself to further structural and functional studies.

Amino Acid Sequence↗
PubMed2000

Evidence that gingko biloba extract does not inhibit MAO A and B in living human brain.

Extracts of Ginkgo biloba have been reported to reversibly inhibit both monoamine oxidase (MAO) A and B in rat brain in vitro leading to speculation that MAO inhibition may contribute to some of its central nervous system effects. Here we have used positron emission tomography (PET) to measure the effects of Ginkgo biloba on human brain MAO A and B in 10 subjects treated for 1 month with 120 mg/day of the Ginkgo biloba extract EGb 761, using [11C]clorgyline and [11C]L-deprenyl-D2 to measure MAO A and B respectively. A three-compartment model was used to calculate the plasma to brain transfer constant K1 which is related to blood flow, and lambdak3, a model term which is a function of the concentration of catalytically active MAO molecules. Ginkgo biloba administration did not produce significant changes in brain MAO A or MAO B suggesting that mechanisms other than MAO inhibition need to be considered as mediating some of its CNS effects.

Adult↗
PubMed2000

Nonuniform composition profile in In0.5Ga0.5As alloy quantum dots

We use cross-sectional scanning tunneling microscopy to examine the shape and composition distribution of In0.5Ga0.5As quantum dots (QDs) formed by capping heteroepitaxial islands. The QDs have a truncated pyramid shape. The composition appears highly nonuniform, with an In-rich core having an inverted-triangle shape. Thus the electronic properties will be drastically altered, relative to the uniform composition generally assumed in device modeling. Theoretical analysis of the QD growth suggests a simple explanation for the unexpected shape of the In-rich core.

Journal Article↗
PubMed2000

Developmentally regulated expression of two transcripts for heme oxygenase-2 with a first exon unique to rat testis: control by corticosterone of the oxygenase protein expression.

Heme oxygenase (HO)-2, the constitutive cognate of oxidative stress inducible HO-1 (HSP32), degrades heme to biliverdin, carbon monoxide, and iron. The highest levels of HO-2 are found in the testis. Previously we identified multiple HO-2 homologous transcripts that differ in size and use three different 5' UTRs that form the untranslated first exon of the gene (referred to as rHO-2, rHO-2-1 and rHO-2-2) and two poly(A) signals. Also, we have characterized a functional glucocorticoid response element (GRE) in the promoter region of rHO-2. In this study, we have examined the structural basis for size heterogeneity of HO-2 transcripts and whether expression of HO-2 at mRNA and protein levels is subject to regulation by corticosterone. Age and tissue-dependence of transcript expression were examined as well. Our data indicate that the remarkable increase in HO-2 mRNA in adult rat testis is due primarily to generation of two HO-2 homologous transcripts of approx. 2.1kb and approx. 1.45kb size that use rHO-2 and are unique to this tissue, and that rHO-2 is not used within other organs. These transcripts are not present in the brain, kidney, thymus, heart, spleen, liver, or in prepubertal 14day old rat testis. The testis-specific transcripts contain all of the coding region exons present in the approx. 1.3kb and approx. 1.9kb transcripts that are common to all organs, including the adult and prepubertal rat testis. Differential use of the poly(A) signals accounts for the difference in size of these two transcripts. Treatment of newborn rats with corticosterone for 5days, starting on day 2 after birth, induced HO-2 protein expression in the testis as detected by Western blotting. In adult rat testis, corticosterone treatment, however, was not an effective regulator of HO-2 transcript populations or levels. The findings suggest that HO-2 levels in the testis are controlled by glucocorticoids; and that developmental and tissue-specific factor(s) determine generation of transcripts unique to the organ. The apparent exclusive use of rHO-2 by the mature testis is consistent with the possibility that HO-2 may play a role in male reproduction.

3' Untranslated Regions↗
PubMed2000

Influence of different chelators (HYNIC, MAG3 and DTPA) on tumor cell accumulation and mouse biodistribution of technetium-99m labeled to antisense DNA.

We have shown recently that cell accumulation in culture of antisense DNA is strongly influenced by the presence of a 99mTc-MAG3 group for radiolabeling. We have now compared the in vitro and mouse in vivo behavior of 99mTc when radiolabeled to one antisense phosphorothioate DNA by three different methods. The 18-mer antisense DNA against the RIalpha subunit of PKA was conjugated via a primary amine on the 5'-end with the NHS esters of HYNIC and MAG3 and by the cyclic anhydride of DTPA. Surface plasmon resonance measurements revealed that the association rate constant for hybridization was unchanged for all three chelators as compared with that of the native DNA. Size exclusion HPLC showed rapid and quantitative protein binding for all three chelators upon incubation of labeled DNAs in 37 degrees C serum and cell culture medium. However, in each case, radiolabeled and intact oligonucleotide was still detectable after 24 h. Cellular uptake was tested in an RIalpha mRNA-positive cancer cell line. The order of cellular accumulation of 99mTc was DTPA>HYNIC(tricine) >MAG3, with the differences increasing with time between 4 and 24 h. The rate of 99mTc egress from cells was found to be MAG3>HYNIC>DTPA, which may explain the order of cellular accumulation. The biodistribution in normal mice was heavily influenced by the labeling method and followed a pattern similar to that seen previously by us for peptides labeled with the same chelators. In conclusion, although these studies concerned only one antisense DNA in one cell line, the results suggest that the success of antisense imaging may depend, in part, on the method of radiolabeling.

Animals↗
PubMed2000

Immortal human pancreatic duct epithelial cell lines with near normal genotype and phenotype.

Immortal epithelial cell lines were previously established after transduction of the HPV16-E6E7 genes into primary cultures of normal pancreatic duct epithelial cells. Single clones were isolated that demonstrated near normal genotype and phenotype. The proliferation of HPDE6-E6E7c7 and c11 cells is anchorage-dependent, and they were nontumorigenic in SCID mice. The cell lines demonstrated many phenotypes of normal pancreatic duct epithelium, including mRNA expression of carbonic anhydrase II, MUC-1, and cytokeratins 7, 8, 18, and 19. These cells have normal Ki-ras, p53, c-myc, and p16(INK4A) genotypes. Cytogenetic studies demonstrated losses of 3p, 10p12, and 13q14, the latter included the Rb1 gene. The wild-type p53 protein was detectable at very low levels consistent with the presence of E6 gene product, and the lack of functional p53 pathway was confirmed by the inability for gamma-irradiation to up-regulate p53 and p21waf1/cip1 protein. The p110/Rb protein level was also not detectable consistent with the expression of E7 protein and haploid loss of Rb1 gene. Despite this, the proliferation of both c7 and c11 cells were markedly inhibited by transforming growth factor-beta1. This was associated with up-regulation of p21cip1/waf1 but not p27kip1. Further studies showed that p130/Rb2 and cyclin D3 were expressed, suggesting that p130/Rb2 may have partially assumed the maintenance of G(1) cell cycle checkpoint regulation. These results indicate that except for the loss of p53 functional pathway, the two clones of HPDE6-E6E7 cells demonstrated a near normal genotype and phenotype of pancreatic duct epithelial cells. These cell lines will be useful for future studies on the molecular basis of pancreatic duct cell carcinogenesis and islet cell differentiation.

Animals↗
PubMed2000

Constitutive and inducible nitric oxide synthases after dynorphin-induced spinal cord injury.

It has recently been demonstrated that selective inhibition of both neuronal constitutive and inducible nitric oxide synthases (ncNOS and iNOS) is neuroprotective in a model of dynorphin (Dyn) A(1-17)-induced spinal cord injury. In the present study, various methods including the conversion of 3H-L-arginine to 3H-citrulline, immunohistochemistry and in situ hybridization are employed to determine the temporal profiles of the enzymatic activities, immunoreactivities, and mRNA expression for both ncNOS and iNOS after intrathecal injection of a neurotoxic dose (20 nmol) of Dyn A(1-17). The expression of ncNOS immunoreactivity and mRNA increased as early as 30 min after injection and persisted for 1-4 h. At 24-48 h, the number of ncNOS positive cells remained elevated while most neurons died. The cNOS enzymatic activity in the ventral spinal cord also significantly increased at 30 min 48 h, but no significant changes in the dorsal spinal cord were observed. However, iNOS mRNA expression increased later at 2 h, iNOS immunoreactivity and enzymatic activity increased later at 4 h and persisted for 24-48 h after injection of 20 nmol Dyn A(1-17). These results indicate that both ncNOS and iNOS are associated with Dyn-induced spinal cord injury, with ncNOS predominantly involved at an early stage and iNOS at a later stage.

Animals↗
PubMed2000

Synthesis and evaluation of 6-[(18)F]fluoro-3-(2(S)-azetidinylmethoxy)pyridine as a PET tracer for nicotinic acetylcholine receptors.

Both ABT-594 ((R)-2-chloro-5-(2-azetidinylmethoxy)pyridine) and A-85380 (3-[2(S)-2-azetidinylmethoxy]pyridine), novel nicotinic agonists that possess potent non-opioid analgesic properties, have high affinity for neuronal nicotinic acetylcholine receptors (nAChR) but do not elicit the pronounced toxicity of epibatidine. 6-[(18)F]Fluoro-3-(2(S)-azetidinylmethoxy)pyridine (6-[(18)F]fluoro-A-85380), a F-18 labeled analogue of these two compounds, is therefore a promising radioligand for positron emission tomography (PET) studies in humans. The use of trimethylammonium as a leaving group in nucleophilic aromatic substitution reactions has proven to be a versatile and efficient strategy, and offers several advantages over other leaving groups. Here, we report the synthetic strategy for the preparation of a precursor, as a trimethylammonium iodide salt, and its use in the radiosynthesis to 6-[(18)F]fluoro-A-85380. Preliminary compartative PET studies of 6-[(18)F]fluoro-A-85380 and 2-[(18)F]fluoro-A-85380 were carried out in baboon to examine their suitability as tracers for studying nAChR system.

Animals↗
PubMed2000

Assessment of systematic use of intraoperative transesophageal echocardiography during cardiac surgery in adults: a prospective study of 203 patients.

OBJECTIVE: To determine the usefulness of systematic intraoperative transesophageal echocardiography in a cardiac surgical unit. DESIGN: Open prospective observational survey. SETTING: University Hospital. PARTICIPANTS: Consecutive adult patients (n = 203) undergoing elective or urgent cardiac operations. MEASUREMENTS AND MAIN RESULTS: Pre-cardiopulmonary bypass imaging yielded unsuspected findings in 26 patients (12.8%) and changed the planned surgery in 22 patients (10.8%). Transesophageal echocardiography modified the diagnosis in eight patients (17%) operated on for mitral valvulopathy, in seven patients (15.5%) with aortic valvular disease, in four patients (4.6%) with coronary artery disease, in five patients operated on for thoracic aorta diseases regardless of their localization (18.5%), and in two miscellaneous cases. On the basis of the data obtained from the transesophageal echocardiography carried out at the end of cardiopulmonary bypass, an immediate reintervention was required in five cases (2.5%). CONCLUSIONS: It is concluded that systematic intraoperative transesophageal echocardiography significantly affected decision making in this cardiac surgical unit. Its routine use in all cardiac surgical patients is recommended.

Adult↗
PubMed2000

Role of the peripheral myelin protein 22 N-linked glycan in oligomer stability.

Peripheral myelin protein 22 (PMP22) is a 22-kDa glycoprotein containing a single N-linked carbohydrate moiety. This posttranslational modification is conserved in PMP22 across species and within members of the PMP22 gene family; however, the function of the oligosaccharide is not known. To study the role of the PMP22 carbohydrate, site-directed mutagenesis was used to alter the glycosylation consensus sequence and produce a glycosylation-deficient mutant protein. This modified PMP22 was expressed in primary Schwann cells (SCs), and the effect of the N-glycan on the turnover rate, oligomerization, and intracellular trafficking of PMP22 was determined. Our data show a slight decrease in turnover rate from a half-life of approximately 70 min for the wild-type (wt) protein to 100 min for the glycosylation mutant. Although the presence of glycosylation-deficient PMP22 oligomers could be detected in SCs, we observed a decrease in oligomer stability compared with the wt oligomers. Both wt and mutant proteins showed similar localization in the endoplasmic reticulum and Golgi compartments and were transported to the SC surface. These results suggest that the N-glycan of PMP22 facilitates, in part, the stability of the PMP22 oligomer; however, the implications of PMP22 oligomerization remain unknown.

Amino Acid Substitution↗
PubMed2000

Mesangial factor V expression colocalized with fibrin deposition in IgA nephropathy.

BACKGROUND: Factor V in its active form (Va) plays a key role at the termination of the intrinsic coagulation pathway, serving as a membrane-bound cofactor for the conversion of prothrombin to thrombin by factor Xa. Cross-linked fibrin (XFb) is often observed in mesangial areas in active types of human glomerulonephritis. In this study, to clarify contribution of factor V in intramesangial coagulation, mesangial factor V expression and its relationship to mesangial proliferation and fibrin deposition in IgA nephropathy (IgAN) were investigated. METHODS: Twenty-two patients with IgAN were studied. XFb was detected in renal biopsy specimens using anti-d-dimer antibody combined with plasmin exposure, and factor V was detected with rabbit antibody against human factor V. Double-labeling immunohistochemistry was used to investigate the relationship of the glomerular distribution of factor V to XFb. The relationship of factor V staining to the activity index or XFb deposition was evaluated. The expression of factor V mRNA was assessed by in situ hybridization in relationship to the antigen staining of alpha-smooth muscle actin (alpha-SMA). The ultrastructural distribution of factor V in glomeruli was studied by immunoelectron microscopy. RESULTS: XFb and factor V were observed in the mesangium and along capillary loops in seven and nine specimens, respectively. Factor V had intense, frequent expression in the proliferating and necrotizing areas, showing a significant relationship to XFb (P < 0.05). Furthermore, XFb deposition and factor V expression were markedly correlated with disease activity (P = 0.005 and P = 0.008, respectively). By double-labeling experiments, XFb and factor V were often seen colocalized in mesangial areas of the glomeruli, which showed necrotizing lesions and/or intense cellular proliferation. By in situ hybridization, factor V mRNA was detected mainly in the mesangial cells, which were positive for alpha-SMA, and partly in the endothelial cells. By immunoelectron microscopy, factor V presence was confirmed in the mesangium and endothelium. CONCLUSION: The present findings suggest that factor V is strongly expressed in mesangial cells in active IgAN accompanied with mesangial proliferation and may exert procoagulant activity, leading to intramesangial coagulation.

Actins↗