Biomedical subjects

Q Liu

Publications and source records attributed to Q Liu.

At least 181 records · Page 10Linked to original sources

PubMed2000

Locomotor activity and occupancy of brain cannabinoid CB1 receptors by the antagonist/inverse agonist AM281.

The goals of this study were to examine the relationship between intravenous doses of the cannabinoid CB1 receptor antagonist AM281 (N-(morpholin-4-yl)-5-(4-iodophenyl)-1-(2, 4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide) and the degree of occupancy of this receptor, and to relate occupancy to the ability of this compound to antagonize the sedative effects of the cannabinoid receptor agonist WIN 55,212-2. Occupancy was determined by measuring the ability of intravenous doses of AM281 to inhibit in vivo binding of [(131)I]AM281 in brain areas, and locomotor activity was assessed by measuring the rate of beam crossings in a photocell apparatus. As previously documented, WIN 55,212-2 (1 mg/kg, i.v.) significantly reduced locomotor activity at early times after administration. Co-injection of AM281 (0.3 mg/kg i/v) and WIN 55, 212-2 restored the rate of beam crossings to that seen on injection of vehicle. In addition, AM281 (0.3 mg/kg i/v) approximately doubled locomotor activity between 60-120 min when injected alone. The IC(50) value for displacement of [(131)I]AM281 by AM281 was 0.45 mg/kg. These observations confirm earlier indications that AM281 is a CB1 receptor antagonist or inverse agonist and suggest the existence of an endogenous cannabinoid tone that moderates exploratory locomotor activity.

Animals↗

PubMed2000

Definition of the anterior choroidal artery territory in rats using intraluminal occluding technique.

This manuscript delineates the territory of the anterior choroidal artery (AChA) in rats, as defined by the induction of an AChA infarction. By advancing a 0.24-mm surgical suture up the internal carotid artery (ICA) to a point 0.5-2 mm proximal to the middle cerebral artery (MCA) origin, the AChA could be occluded and a reliable AChA distribution infarction was produced in 62% (23/37) of animals. The infarct volume, as defined by TTC staining, was 55+/-7 mm(3). Maps of the infarction, generated by measuring the entire area of overlapping coronal slices, demonstrated that the internal capsule was always damaged. Other areas that might be affected included the hippocampus, thalamus, amygdaloid complex, piriform cortex, dorsal caudatoputamen, and lateral ventricular wall. Positioning the coated suture proximal to the AChA produced a much smaller infarct involving the medial and lateral hypothalamus, preoptic region, optic chiasm, and marginal region of the internal capsule near to the lateral hypothalamus exempt from AChA territory damage. A causative relationship between AChA occlusion and a deep cerebral infarct centered on the internal capsule was further established by: (1) identifying the AChA on the non-ischemic side with colored silicone perfusion, and subsequent similar delineation on the ischemic side, and (2) delineating infarction in the silicone perfused AChA region using hematoxylin and eosin staining and the TUNEL method. The AChA usually originated from the ICA (91% of cases), 1.75+/-0.12 mm proximal to the MCA bifurcation. Approximately 27% of the AChAs had periamygdaloid branch(es) on its initial segment.

Animals↗

PubMed2000

The effect of preoperative transcatheter hepatic arterial chemoembolization on disease-free survival after hepatectomy for hepatocellular carcinoma.

BACKGROUND: Although surgical resection has produced better results than other therapies for local control of hepatocellular carcinoma (HCC), the long term results have not been satisfactory because of a low disease-free survival rate. The effects of preoperative transcatheter arterial chemoembolization (TACE) on improving disease-free survival of HCC after hepatectomy has remained controversial. METHODS: The current study was retrospective survey of 1725 patients who had hepatectomy for HCC between January 1990 and December 1995 and had follow-up data for 1457 cases. The follow-up rate was 84.5%. The significant prognostic factors were analyzed using a Cox proportional hazards survival model, and the disease-free survival was calculated by Kaplan-Meier estimation. Among 1457 cases, 120 patients underwent preoperative TACE and were divided into a one time TACE group, over two times TACE group, an effective group, and ineffective group. RESULTS: Multivariate analyses revealed significant prognostic factors as follows: preoperative TACE number, preoperative TACE effect, preoperative lesion number, intraoperative tumor thrombus, tumor size, tumor gross type, daughter nodules, vascular invasion, and postoperative alpha-fetoprotein value. Kaplan-Meier estimation showed that the 5-year disease-free survival rates of the over two times group, the one time group, and no TACE group were 51.0%, 35.5%, and 21.4%, respectively, and that the mean disease-free survival times of the three groups were 66.4, 22.5 and 12.5 months, respectively. The effective group had a 5-year disease-free survival rate of 56.8%, with a mean time of 90.1 months. CONCLUSIONS: Effective preoperative TACE may be one of the best methods, which can be clinically performed at present, for resectable HCCs including small HCCs for improving disease-free survival after hepatectomy. According to tumor size, range, location, hepatic function, and TACE effect, TACE can be performed 2-4 times preoperatively within 6 months.

Adolescent↗

PubMed2000

Mitochondrial Hsp70 Ssc1: role in protein folding.

Ssc1, the major Hsp70 of the mitochondrial matrix, is involved in the translocation of proteins from the cytosol into the matrix and their subsequent folding. To better understand the physiological mechanism of action of this Hsp70, we have undertaken a biochemical analysis of Ssc1 and two mutant proteins, Ssc1--2 and Ssc1--201. ssc1--2 is a temperature-sensitive mutant defective in both translocation and folding; ssc1--201 contains a second mutation in this ssc1 gene that suppresses the temperature-sensitive growth defect of ssc1--2, correcting the translocation but not the folding defect. We found that although Ssc1 was competent to facilitate the refolding of denatured luciferase in vitro, both Ssc1--2 and Ssc1--201 showed significant defects, consistent with the data obtained with isolated mitochondria. Purified Ssc1--2 had a lowered affinity for a peptide substrate compared with wild-type Ssc1 but only in the ADP-bound state. This peptide binding defect was reversed in the suppressor protein Ssc1--201. However, a defect in the ability of Hsp40 to stimulate the ATPase activity of Ssc1--2 was not corrected in Ssc1--201. Thus, the inability of these two mutant proteins to efficiently facilitate luciferase refolding correlates with their defect in stimulation of ATPase activity by Hsp40s, indicating that this interaction is critical for protein folding in mitochondria.

Adenosine Diphosphate↗

PubMed2000

Synthesis of Monodisperse Al-Substituted Hematite Particles from Highly Condensed Metal Hydroxide Gels.

Monodispersed aluminum-substituted hematite particles were synthesized from concentrated mixed solutions of FeCl(3) and AlCl(3) using the gel/sol process. With increasing aluminum content (Al/(Fe+Al)) in the starting solutions, hematite particles became more and more elongated. The product particles exhibited ellipsoidal, rod- and peanut-like shapes, depending on Al concentration. Higher Al content (>20 mol%) in the system greatly suppressed the formation of hematite. Atomic emission spectrometry analysis and lattice parameter measurement confirmed the substitution of Al in hematite particles. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Agonist-induced phosphorylation of somatostatin receptor subtype 1 (sst1). Relationship to desensitization and internalization.

The sst1 somatostatin (SRIF) receptor subtype is widely expressed in the endocrine, gastrointestinal, and neuronal systems as well as in hormone-sensitive tumors, yet little is known about its regulation. Here we investigated the desensitization, internalization, and phosphorylation of sst1 expressed in CHO-K1 cells. Treatment of cells with 100 nm SRIF for 30 min reduced maximal SRIF inhibition of adenylyl cyclase from 40 to 10%. This desensitization was rapid (t(12) < 2 min) and dependent on agonist concentration (EC(50) = 2 nm). However, internalization of receptor-bound ligand occurred slowly (t(12) > 180 min). Incubation of cells with SRIF also caused a rapid (t(12) < 2 min) increase in sst1 receptor phosphorylation in a dose-dependent manner (EC(50) = 1.3 nm), as determined in a mobility shift phosphorylation assay. Receptor phosphorylation was not affected by pertussis toxin, indicating a requirement for receptor occupancy rather than signaling. The protein kinase C activator, phorbol 12-myristate 13-acetate also stimulated sst1 receptor phosphorylation whereas forskolin did not. Both agonist- and phorbol 12-myristate 13-acetate-stimulated receptor phosphorylation occurred mainly on serine. These studies are the first to demonstrate phosphorylation of the sst1 receptor and suggest that phosphorylation mediated uncoupling, rather than sequestration, leads to its desensitization.

Animals↗

PubMed2000

Context-dependent EKLF responsiveness defines the developmental specificity of the human epsilon-globin gene in erythroid cells of YAC transgenic mice.

We explored the mechanism of definitive-stage epsilon-globin transcriptional inactivity within a human beta-globin YAC expressed in transgenic mice. We focused on the globin CAC and CAAT promoter motifs, as previous laboratory and clinical studies indicated a pivotal role for these elements in globin gene activation. A high-affinity CAC-binding site for the erythroid krüppel-like factor (EKLF) was placed in the epsilon-globin promoter at a position corresponding to that in the adult beta-globin promoter, thereby simultaneously ablating a direct repeat (DR) element. This mutation led to EKLF-independent epsilon-globin transcription during definitive erythropoiesis. A second 4-bp substitution in the epsilon-globin CAAT sequence, which simultaneously disrupts a second DR element, further enhanced ectopic definitive erythroid activation of epsilon-globin transcription, which surprisingly became EKLF dependent. We finally examined factors in nuclear extracts prepared from embryonic or adult erythroid cells that bound these elements in vitro, and we identified a novel DR-binding protein (DRED) whose properties are consistent with those expected for a definitive-stage epsilon-globin repressor. We conclude that the suppression of epsilon-globin transcription during definitive erythropoiesis is mediated by the binding of a repressor that prevents EKLF from activating the epsilon-globin gene.

Age Factors↗

PubMed2000

Synthetic zinc finger transcription factor action at an endogenous chromosomal site. Activation of the human erythropoietin gene.

We have targeted the activation of an endogenous chromosomal locus including the human erythropoietin gene using synthetic transcription factors. These transcription factors are targeted to particular DNA sequences in the 5'-flanking region of the erythropoietin gene through engineering of a zinc finger DNA binding domain. The DNA binding domain is linked to a VP16 transcriptional activation domain. We find that these synthetic transcription factors invariably activate transiently transfected templates in which sequences within the 5' flank of the erythropoietin gene are fused to a luciferase reporter. The efficiency of activation under these circumstances at a defined site is dependent on DNA binding affinity. In contrast, only a subset of these same zinc finger proteins is able to activate the endogenous chromosomal locus. The activity of these proteins is influenced by their capacity to gain access to their recognition elements within the chromatin infrastructure. Zinc finger transcription factors will provide a powerful tool to probe the determinants of chromatin accessibility and remodeling within endogenous chromosomal loci.

Cells, Cultured↗

PubMed2000

Differential expression of COUP-TFI, CHL1, and two novel genes in developing neocortex identified by differential display PCR.

Genes that control the specification and differentiation of the functionally specialized areas of the mammalian neocortex are likely expressed across the developing neocortex in graded or restricted patterns. To search for such genes we have performed a PCR-based differential display screen using RNAs from rostral neocortex, which included the primary motor area, and caudal neocortex, which included the primary visual area, of embryonic day 16 rats. We identified 82 differentially expressed gene fragments. Secondary screening by in situ hybridization confirmed that five fragments, representing four genes, are differentially expressed across developing rat neocortex. Two of the genes, chick ovalbumin upstream transcription factor I (COUP-TFI) and close homolog of L1 (CHL1), have been cloned previously, but their differential expression in cortex has not been reported. Sequences from the other two fragments suggest that they represent novel genes. The expression patterns include graded, restricted, and discontinuous expression with abrupt borders that might correlate with those of areas. The differential expression patterns of all four genes are established before the arrival of thalamocortical afferents, suggesting that they are independent of thalamic influence, and could direct or reflect arealization. In addition, COUP-TFI and CHL1 exhibit dynamic expression patterns that undergo substantial changes after thalamocortical afferents invade the cortical plate, suggesting that thalamic axons may influence their later expression. Postnatally, COUP-TFI is most prominently expressed in layer 4, in both rats and mice, and CHL1 is expressed in layer 5. COUP-TFI expression in cortex, and in ventral telencephalon and dorsal thalamus, suggests several possible causes for the loss of layer 4 neurons and the reduced thalamocortical projection reported in COUP-TFI knock-out mice.

Animals↗

PubMed2000

Characterization of the human cysteinyl leukotriene 2 receptor.

The contractile and inflammatory actions of the cysteinyl leukotrienes (CysLTs), LTC(4), LTD(4), and LTE(4), are thought to be mediated through at least two distinct but related CysLT G protein-coupled receptors. The human CysLT(1) receptor has been recently cloned and characterized. We describe here the cloning and characterization of the second cysteinyl leukotriene receptor, CysLT(2), a 346-amino acid protein with 38% amino acid identity to the CysLT(1) receptor. The recombinant human CysLT(2) receptor was expressed in Xenopus oocytes and HEK293T cells and shown to couple to elevation of intracellular calcium when activated by LTC(4), LTD(4), or LTE(4). Analyses of radiolabeled LTD(4) binding to the recombinant CysLT(2) receptor demonstrated high affinity binding and a rank order of potency for competition of LTC(4) = LTD(4) LTE(4). In contrast to the dual CysLT(1)/CysLT(2) antagonist, BAY u9773, the CysLT(1) receptor-selective antagonists MK-571, montelukast (Singulair(TM)), zafirlukast (Accolate(TM)), and pranlukast (Onon(TM)) exhibited low potency in competition for LTD(4) binding and as antagonists of CysLT(2) receptor signaling. CysLT(2) receptor mRNA was detected in lung macrophages and airway smooth muscle, cardiac Purkinje cells, adrenal medulla cells, peripheral blood leukocytes, and brain, and the receptor gene was mapped to chromosome 13q14, a region linked to atopic asthma.

Adrenal Medulla↗

PubMed2000

The bulk of UCP3 expressed in yeast cells is incompetent for a nucleotide regulated H+ transport.

The impact of uncoupling protein (UCP) 1, UCP3 and UCP3s expressed in yeast on oxidative phosphorylation, membrane potential and H+ transport is determined. Intracellular ATP synthesis is inhibited by UCP3, much more than by UCP1, while similar levels of UCP3 and UCP1 exist in the mitochondrial fractions. Measurements of membrane potential and H+ efflux in isolated mitochondria show that, different from UCP1, with UCP3 and UCP3s there is a priori a preponderant uncoupling not inhibited by GDP. The results are interpreted to show that UCP3 and UCP3s in yeast mitochondria are in a deranged state causing uncontrolled uncoupling, which does not represent their physiological function.

Animals↗

PubMed2000

Identification of receptors for neuromedin U and its role in feeding.

Neuromedin U (NMU) is a neuropeptide with potent activity on smooth muscle which was isolated first from porcine spinal cord and later from other species. It is widely distributed in the gut and central nervous system. Peripheral activities of NMU include stimulation of smooth muscle, increase of blood pressure, alteration of ion transport in the gut, control of local blood flow and regulation of adrenocortical function. An NMU receptor has not been molecularly identified. Here we show that the previously described orphan G-protein-coupled receptor FM-3 (ref. 15) and a newly discovered one (FM-4) are cognate receptors for NMU. FM-3, designated NMU1R, is abundantly expressed in peripheral tissues whereas FM-4, designated NMU2R, is expressed in specific regions of the brain. NMU is expressed in the ventromedial hypothalamus in the rat brain, and its level is significantly reduced following fasting. Intracerebroventricular administration of NMU markedly suppresses food intake in rats. These findings provide a molecular basis for the biochemical activities of NMU and may indicate that NMU is involved in the central control of feeding.

Amino Acid Sequence↗

PubMed2000

DNA prime-canarypox boost with polycistronic hepatitis C virus (HCV) genes generates potent immune responses to HCV structural and nonstructural proteins.

DNA vaccination was employed to study immune responses to hepatitis C virus (HCV) proteins. As an immunizing strategy, we studied immune responses of BALB/c (H-2d) and C57BL/6 mice (H-2b) to HCV genes delivered intramuscularly as a polycistronic construct capsid/E1/E2/NS2/NS3 (pRC/C-NS3) encoding 5 structural and nonstructural proteins. We also evaluated canarypox virus containing the same HCV genes as a means for potentiating immune responses to naked DNA. Our results indicate that mice that received a polycistronic pRC/C-NS3 with canarypox booster had enhanced antibody and cellular responses to HCV proteins. Immunodominant CD8(+) T cell responses to several HCV structural and nonstructural proteins, characterized by cytotoxicity and interferon (IFN)-gamma production or IFN-gamma production without significant cytotoxicity, were observed in both strains of mice. The combination of naked DNA with a nonreplicating canarypox booster encoding HCV polycistronic pRC/C-NS3 genes appears to diversify and enhance T cell responses to HCV proteins.

Animals↗

PubMed2000

Preparative isolation and purification of notopterol and isoimperatorin from Notopterygium forbessi Boiss (Chinese traditional medicinal herb) by high-speed counter-current chromatography.

Preparative high-speed counter-current chromatography was successfully used for isolation and purification of coumarins from Chinese traditional medicinal herb Notopterygium forbessi Boiss (Qianghuo in Chinese) using stepwise elution with a pair of two-phase solvent systems composed of light petroleum-ethyl acetate-methanol-water at volume ratios of 5:5:4.8:5 and 5:5:5:4. Four major components including notopterol and isoimperatorin were isolated, each at over 98% purity.

Chromatography, Liquid↗

PubMed2000

Molecular cloning, expression characterization, and mapping of a novel putative inhibitor of rho GTPase activity, RTKN, to D2S145-D2S286.

The Rho proteins are a class of small molecular GTPases that regulate multiple fundamental cellular processes by mediating the G-protein-coupled receptor signaling pathway. Rhotekin, which is one of the downstream target molecules of Rho with a Rho binding motif class I domain, can inhibit endogenous or RhoGAP-stimulating Rho GTPase activity to regulate the signaling pathway. Here, a novel human cDNA containing an intact open reading frame that encodes 544 amino acids has been identified. As this putative protein shares 84. 6% amino acid identity with mouse Rhotekin, and has a tandem Rho binding domain class 1 and Pleckstrin homology domain, it was regarded as a human homologue of the mouse Rhotekin and assigned a symbol of RTKN. With the human Rhotekin cDNA as a probe, Northern hybridization revealed that a 4.0-kb transcript was expressed at a high level in prostate and at a middle level in 13 of 16 tissues examined, but it cannot be detected in liver and lung tissues. Meanwhile, a 2.4-kb transcript was expressed at a middle level in prostate and another 3.0-kb transcript in kidney. In addition, the RTKN gene was localized to chromosome 2p13 between markers D2S145 at 6.94 cR (LOD > 12) and D2S286 at 8.12 cR (LOD > 9.7) by radiation hybrid panel mapping. Compared with BAC clone AC005041 sequence, there were 12 exons for the RTKN gene and it spanned a 16.5-kb genomic region.

Amino Acid Motifs↗

PubMed2000

Chk1 is an essential kinase that is regulated by Atr and required for the G(2)/M DNA damage checkpoint.

Chk1, an evolutionarily conserved protein kinase, has been implicated in cell cycle checkpoint control in lower eukaryotes. By gene disruption, we show that CHK1 deficiency results in a severe proliferation defect and death in embryonic stem (ES) cells, and peri-implantation embryonic lethality in mice. Through analysis of a conditional CHK1-deficient cell line, we demonstrate that ES cells lacking Chk1 have a defective G(2)/M DNA damage checkpoint in response to gamma-irradiation (IR). CHK1 heterozygosity modestly enhances the tumorigenesis phenotype of WNT-1 transgenic mice. We show that in human cells, Chk1 is phosphorylated on serine 345 (S345) in response to UV, IR, and hydroxyurea (HU). Overexpression of wild-type Atr enhances, whereas overexpression of the kinase-defective mutant Atr inhibits S345 phosphorylation of Chk1 induced by UV treatment. Taken together, these data indicate that Chk1 plays an essential role in the mammalian DNA damage checkpoint, embryonic development, and tumor suppression, and that Atr regulates Chk1.

Alleles↗

PubMed2000

Dexamethasone inhibits tumor necrosis factor-alpha-induced expression of macrophage inflammatory protein-2 and adhesion of neutrophils to endothelial cells.

Macrophage inflammatory protein-2 (MIP-2) belongs to the C-X-C subfamily of chemokines and appears to play an important role in cytokine-induced inflammatory and immune cell-mediated responses. We found that tumor necrosis factor-alpha (TNF-alpha) time- and dose-dependently increased gene and protein expression of MIP-2 in endothelial cells. Moreover, it was observed that dexamethasone treatment inhibited endothelial cell expression of MIP-2 in response to TNF-alpha stimulation and markedly reduced the number of adherent neutrophils. Moreover, we found that a monoclonal antibody against murine MIP-2 abolished neutrophil adhesion to TNF-alpha-activated endothelial cells. These data demonstrate that TNF-alpha induces expression of MIP-2 in endothelial cells and support the hypothesis that the anti-inflammatory action of dexamethasone may, at least in part, be attributable to an inhibition of MIP-2 induction on cytokine-activated endothelial cells.

Animals↗

PubMed2000

Signal transduction and transforming properties of the TEL-TRKC fusions associated with t(12;15)(p13;q25) in congenital fibrosarcoma and acute myelogenous leukemia.

The TEL-TRKC fusion is expressed as a consequence of t(12;15)(p13;q25), and is associated with two human cancers: congenital fibrosarcoma and acute myelogenous leukemia (AML). We report that the T/T(F) and T/T(L) fusion variants associated with congenital fibrosarcoma and AML, respectively, are constitutively tyrosine phosphorylated, and confer factor-independent growth to the murine hematopoietic cell line Ba/F3. Retroviral transduction of T/T(L) causes a rapidly fatal myeloproliferative disease in a murine bone marrow transplant (BMT) model, whereas T/T(F) causes a long-latency, pre-B-cell lymphoblastic lymphoma. TEL-TRKC variants are potent activators of the MAP kinase pathway, but neither variant activates Stat5 or other Stat family members. T/T(L), but not T/T(F), induces tyrosine phosphorylation of phospholipase Cgamma (PLCgamma), phosphoinositol-3 kinase and SHC. However, mutation analysis demonstrates that PLCgamma tyrosine phos phorylation by T/T(L) is dispensable for induction of the myeloproliferative phenotype by T/T(L). Collectively, these data demonstrate that the TEL-TRKC fusion variants are oncoproteins that activate the MAP kinase pathway, and do not require activation of either PLCgamma or Stat5 for efficient induction of a myeloproliferative phenotype in the murine BMT model.

3T3 Cells↗