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Biomedical subjects

Q Han

Publications and source records attributed to Q Han.

At least 37 records · Page 2Linked to original sources
PubMed2000

Matrix survival signaling: from fibronectin via focal adhesion kinase to c-Jun NH(2)-terminal kinase.

Most transformed cells have lost anchorage and serum dependence for growth and survival. Previously, we established that when serum is absent, fibronectin survival signals transduced by focal adhesion kinase (FAK), suppress p53-regulated apoptosis in primary fibroblasts and endothelial cells (Ilić et al. 1998. J. Cell Biol. 143:547-560). The present goals are to identify survival sequences in FAK and signaling molecules downstream of FAK required for anchorage-dependent survival of primary fibroblasts. We report that binding of the SH3 domain of p130Cas to proline-rich region 1 of FAK is required to support survival of fibroblasts on fibronectin when serum is withdrawn. The FAK-p130Cas complex activates c-Jun NH2-terminal kinase (JNK) via a Ras/Rac1/Pak1/MAPK kinase 4 (MKK4) pathway. Activated (phospho-) JNK colocalizes with FAK in focal adhesions of fibroblasts cultured on fibronectin, which supports their survival, but not in fibroblasts cultured on collagen, which does not. Cells often survive in the absence of extracellular matrix if serum factors are provided. In that case, we confirm work of others that survival signals are transduced by FAK, phosphatidylinositol 3'-kinase (PI3-kinase), and Akt/protein kinase B (PKB). However, when serum is absent, PI3-kinase and Akt/PKB are not involved in the fibronectin-FAK-JNK survival pathway documented herein. Thus, survival signals from extracellular matrix and serum are transduced by FAK via two distinct pathways.

Animals↗
PubMed2000

Dehydroepiandrosterone and dihydrotestosterone recognition by human estrogenic 17beta-hydroxysteroid dehydrogenase. C-18/c-19 steroid discrimination and enzyme-induced strain.

Steroid hormones share a very similar structure, but they behave distinctly. We present structures of human estrogenic 17beta-hydroxysteroid dehydrogenase (17beta-HSD1) complexes with dehydroepiandrosterone (DHEA) and dihydrotestosterone (DHT), providing the first pictures to date of DHEA and DHT bound to a protein. Comparisons of these structures with that of the enzyme complexed with the most potent estrogen, estradiol, revealed the structural basis and general model for sex hormone recognition and discrimination. Although the binding cavity is almost entirely composed of hydrophobic residues that can make only nonspecific interactions, the arrangement of residues is highly complementary to that of the estrogenic substrate. Relatively small changes in the shape of the steroid hormone can significantly affect the binding affinity and specificity. The K(m) of estrone is more than 1000-fold lower than that of DHEA and the K(m) of estradiol is about 10 times lower than that of DHT. The structures suggest that Leu-149 is the primary contributor to the discrimination of C-19 steroids and estrogens by 17beta-HSD1. The critical role of Leu-149 has been well confirmed by site-directed mutagenesis experiments, as the Leu-149 --> Val variant showed a significantly decreased K(m) for C-19 steroids while losing discrimination between estrogens and C-19 steroids. The electron density of DHEA also revealed a distortion of its 17-ketone toward a beta-oriented form, which approaches the transition-state conformation for DHEA reduction.

17-Hydroxysteroid Dehydrogenases↗
PubMed2000

Streptozotocin-induced changes in cardiac gene expression in the absence of severe contractile dysfunction.

UNLABELLED: Diabetes mellitus alters energy substrate metabolism and gene expression in the heart. It is not known whether the changes in gene expression are an adaptive or maladaptive process. To answer this question, we determined both the time-course and the extent of the alteration of gene expression induced by insulin-deficient diabetes. Transcript analysis with real-time quantitative polymerase chain reaction (PCR) was performed in rat hearts 1 week (acute group) or 6 months (chronic group) after administration of streptozotocin (55 mg/kg). In the acute group, insulin-dependent diabetes induced a 55-70% decrease of both glucose transporter 1 (GLUT1) and GLUT4 transcripts, a slight decrease of liver-specific carnitine palmitoyltransferase I (CPT I), and no change in muscle-specific CPT I. The uncoupling protein UCP-3 increased three-fold, with no change in UCP-2. These metabolic alterations were accompanied by an isoform switching from the normally expressed alpha myosin heavy chain (MHC) to the fetal isoform betaMHC mRNA, by a 50% decrease of cardiac alpha-actin mRNA, a 30% decrease of the sarcoplasmic Ca++-ATPase mRNA, and a 50% decrease of muscle creatine kinase (P<0.01 v controls). All genomic changes were also present in the chronic group. Genomic markers of ventricular dysfunction [tumor necrosis factor alpha (TNF-alpha), inducible nitric oxide synthase, cyclo-oxygenase-2] were not affected by chronic diabetes. In both groups, there were no changes in resting left ventricular function by echocardiography. CONCLUSION: The heart adapts to insulin-deficient diabetes by a rapid and simultaneous response of multiple genes involved in cardiac metabolism and function. This genomic adaptation resembles the adaptation of cardiac hypertrophy, remains stable over time, and does not lead to major contractile dysfunction.

Animals↗
PubMed2000

Effects of bile on the in vitro hatching, exsheathment, and migration of Ascaris suum larvae.

This study reports on the in vitro egg hatching, exsheathment, migratory activity, and sensitivity to anthelmintics of Ascaris suum larvae in cultures with or without bovine bile. Three methods for egg hatching and/or incubation were used: an object-glass method, a glass-bead method, and an incubation method. An agar migration assay (AMA) was developed to test the migratory activity of Ascaris larvae following hatching. Bile appeared to be an important stimulatory factor for both egg hatching and larval mobility in the incubation method. Incubation in low concentrations of bile (2%, 5%, or 10%) stimulated both egg hatching and larval migration, whereas concentrations of at least 20% impaired egg hatching and larval migration. Furthermore, 5% bile seemed to promote exsheathment of A. suum larvae.

Animals↗
PubMed2000

Crystallization and preliminary X-ray analysis of human grancalcin, a novel cytosolic Ca2+-binding protein present in leukocytes.

Recombinant human grancalcin, a calcium-binding protein from leukocytes, has been crystallized in the presence or absence of Ca(2+) by the vapor-diffusion method. Two crystal forms of apo grancalcin were obtained: space group P2(1), with unit-cell parameters a = 48.4, b = 81.1, c = 46.6 A, beta = 111.3 degrees, diffracting to 1.9 A, and space group C2, with unit-cell parameters a = 97.0, b = 51.9, c = 75.9 A, beta = 108.5 degrees, diffracting to 2.4 A. Crystals were also grown in the presence of 5 mM Ca(2+). They also belong to space group C2, with unit-cell parameters a = 97.4, b = 50.3, c = 77.6 A, beta = 108.2 degrees, which are very similar to the second apo grancalcin form. These crystals diffract to 2.5 A.

Apoproteins↗
PubMed2000

Crystallization and preliminary crystallographic characterization of recombinant L-methionine-alpha-deamino-gamma-mercaptomethane lyase (methioninase).

L-Methionine-alpha-deamino-gamma-mercaptomethane lyase (rMETase) is involved in the alpha,gamma-elimination of methionine to alpha-ketobutyrate, methanethiol and ammonia. The reaction catalyzed by rMETase reduces the methionine concentration of methionine-dependent tumor cells, arresting their growth. Towards the goal of developing rMETase into an effective antitumor therapeutic and also to understand the catalytic mechanism of this enzyme, rMETase from Pseudomonas putida has been expressed, purified and crystallized. The crystals belong to space group P2(1)2(1)2 and diffract X-rays to at least 2.68 A resolution at 100 K using synchrotron radiation. The unit cell has parameters a = 152.8, b = 154.6, c = 80.8 A and contains four molecules in the asymmetric unit.

Carbon-Sulfur Lyases↗
PubMed2000

[Fiberoptic ductoscopy for patients with intraductal papillary lesions].

OBJECTIVE: To investigate the clinical significance of fiberoptic ductoscopy in patients with intraductal papillary lesions. METHODS: Fiberoptic ductoscopy was applied to patients with nipple discharge. The characteristics of those with intraductal papillary lesion were analysed. RESULTS: 92 patients were found to have intraductal papillary lesions. 68 patients were revealed to have single papillomas and 21 multiple papilloma. Three patients were diagnosed with papillomatosis. A total of 114 lesions were observed. 29.8% of these lesions were located in the segmental duct. 43.9% lesions were located in the first branch of the segmental duct and 17.5% in the second branch. Only 7.9% and 0.9% lesions were located in the third and the fourth branch. The average distance from lacteous pore to papillary lesion was 2.7 cm. Fiberoptic ductoscopy did not find lesions in 5 patients. CONCLUSIONS: Fiberoptic ductoscopy can be used to diagnose and locate intraductal papillary lesions. It is an effective diagnostic method for nipple discharge.

Adult↗
PubMed1999

Design and synthesis of potent and selective 5,6-fused heterocyclic thrombin inhibitors.

Thrombin, a serine protease, plays a central role in the initiation of thrombotic events. We report the design, synthesis, and antithrombotic efficacy of XU817 (7), a nonpeptide 5-(amidino) indole thrombin inhibitor. Utilizing the co-crystal structure of XU817 bound in the active site of thrombin we were able to synthesize analogs with enhanced thrombin affinity.

Amidines↗
PubMed1999

Efficacy of recombinant methioninase in combination with cisplatin on human colon tumors in nude mice.

The present treatment of colon cancer is based on 5-fluorouracil (5-FU). Despite promising results of combining leucovorin or levamisole with 5-FU, the 5-year survival rate of patients with advanced colon cancer has not increased significantly. Colon tumors in vitro have been shown previously to have an elevated requirement for methionine, suggesting a new therapeutic target. In this study, targeting the methionine dependence of colon tumors is effected by recombinant methioninase (rMETase), alone and in combination with cisplatin (CDDP). In vitro results demonstrated that CDDP and rMETase act synergistically on the human colon cancer cell line SW 620, with a combination index (CI) of 0.45, as well as on the human colon cancer cell line Colo 205 with a CI of 0.7. Human colon cancer lines HCT 15, HT 29, Colo 205, and SW 620 growing in nude mice were treated with rMETase to determine an effective dose for depletion of tumor methionine. rMETase at 15 units/g/day for 5 days depleted tumor methionine in all four tumor types to approximately 30% of untreated control. rMETase alone arrested growth of HCT 15 and HT29 in nude mice for 1 week after treatment termination. Colo 205 and SW 620 were partially arrested by rMETase. However, CDDP in combination with rMETase resulted in tumor regression of Colo 205 and growth arrest of SW 620 in nude mice. The ratio of the treated:control group (T:C) tumor weights for Colo 205 was 8% when CDDP was given on day-5, followed by treatment on days 5-9 with rMETase. This treatment schedule resulted in two of the six animals having no detectable tumor when the experiment was terminated on day 16. SW620 was resistant to CDDP alone and only partially sensitive to rMETase alone. However, when SW 620 was treated with rMETase from days-5 to -9 and CDDP on day-5, tumor growth was arrested. The results demonstrate that rMETase used simultaneously in combination with CDDP had significant antitumor efficacy in colon cancer in vitro and in vivo. The data suggest a novel and promising therapeutic approach by targeting the elevated methionine dependence of colon cancer.

Animals↗
PubMed1999

An animal and clinical study on the change of neuropeptide Y release evoked by electrical stimulation and myocardial ischemia.

OBJECTIVE: To investigate the change characteristics of neuropeptide Y (NPY) release during acute myocardial ischemia period. METHODS: The animal test was carried out in in situ perfused guinea pig hearts with intact sympathetic innervation. Electrical stimulation-evoked exocytotic release of NPY during ischemia and reperfusion was tested by radioimmunoassay (RIA). The plasma NPY concentrations were measured in patients with acute myocardial infarction (AMI) and angina pectoris (AP) in different times. RESULTS: Electric stimulation of the left ganglion in guinea pig heart evoked an exocytic release of neuropeptide Y. Stimulation after 20 minutes of global ischemia (S2), compared with control period stimulation (S1) produced the inhibition of NPY to a certain extent (S2/S1: 0.72, P < 0.05), whereas the inhibition of NPY release disappeared after 5 minutes reperfusion (with S2/S1 of 1.01, P > 0.05). Ischemia alone, without the electric stimulation, did not apparently induce NPY release. The clinical test found that the plasma NPY level was increased significantly during the acute ischemia attack period of coronary heart disease (CHD). The plasma NPY level reached peak (136.3 +/- 66.5 pg/ml) in patients during the first day after AMI. It began to decrease from the third day and came to normal level in the end of the first week. The plasma NPY level was 159.3 +/- 98.5 pg/ml in AP patients during angina attack. After two weeks treatment, the plasma NPY level was decreased to 118.9 +/- 54.3 pg/ml (P < 0.05). CONCLUSIONS: The NPY release of global ischemia have some relation with sympathetic nerve activity. At the early stage of ischemia, NPY release is inhibited to some degree and the inhibition factors will fade away on reperfusion. NPY interferes with the pathogenesis and the pathophysiolgy.

Aged↗
PubMed1999

[A preliminary study of two Chinese herbs protective tablets on some Chinese traditional medicines].

The protective action of 2 tablets of Chinese herb to 5 Chinese traditional medicines against harm of insects and mildews was tested. It was found that 2 tablets have a obvious effects of insect-repellency and mouthproof in the test with Homalomena occulta and Prunus armeniaca, the bore in the medicinal materials was decreased 94.95% and 95.55% respectively than that of check. The tablets have some effects of mildewproof in the test with Tussilago farfara.

Alisma↗
PubMed1998

Cyclic HIV protease inhibitors: design and synthesis of orally bioavailable, pyrazole P2/P2' cyclic ureas with improved potency.

Highly potent HIV-1 protease (HIVPR) inhibitors have been designed and synthesized by introducing bidentate hydrogen-bonding oxime and pyrazole groups at the meta-position of the phenyl ring on the P2/P2' substituents of cyclic ureas. Nonsymmetrical cyclic ureas incorporating 3(1H)-pyrazolylbenzyl as P2 and hydrophilic functionalities as P2' show potent protease inhibition and antiviral activities against HIV and have good oral bioavailabilities. The X-ray structure of HIVPR.10A complex confirms that the two pyrazole rings of 10A form bidentate hydrogen bonds with the side-chain oxygen (C=O) and backbone nitrogen (N-H) of Asp30/30' of HIVPR.

Administration, Oral↗
PubMed1998

Cell death mediated by Fas-FasL interaction between glial cells and MBP-reactive T cells.

Apoptosis in T cells that have penetrated into the central nervous system (CNS) may be important for the physiological control of T cells with potentially dangerous reactivities to CNS antigens; such control may be dysfunctional in animals suffering from experimental autoimmune encephalomyelitis (EAE). In this study we examined the expression of Fas and FasL genes both in myelin basic protein (MBP)-reactive T cells and in glial cells and the susceptibility of these cells to death induced by Fas/FasL interaction. Both Fas and FasL gene expression is detectable in glial cells and MBP-reactive T cells. Cell death is not unidirectional: when T cells interact with glial cells death can be induced in the former or in the latter population. The ability to induce death of Fas-expressing cells varies greatly among different lines of MBP-reactive T cells, as does resistance to death induction by cells expressing FasL. Moreover, the ability of T cells both to deliver and to resist death signals is a function of their activation status: T cells freshly activated transmit a stronger apoptotic signal to Fas-positive target cells and are also more resistant to FasL-induced suicide. Soluble form of FasL provides a convenient titratable means of delivering death signals via Fas. However, comparison of the susceptibility of different targets to soluble FasL and to FasL expressed on the surface of a transfected glial line revealed differences, suggesting that signals arising from Fas/FasL interaction may be modulated by additional cell-surface molecules.

Animals↗
PubMed1998

Polyethylene glycol conjugation of recombinant methioninase for cancer therapy.

Recombinant methioninase (rMETase) is a homotetrameric pyridoxal 5'-phosphate enzyme of 172-kda molecular mass derived from Pseudomonas putida and cloned in Escherichia coli. rMETase has been found previously to be an effective, anti-tumor agent in vitro and in vivo. The enzyme targets the elevated minimal methionine requirement seen in all tumor types. In order to prevent immunological reactions which might be produced by multiple dosing of rMETase and to prolong the serum half-life of rMETase, the N-hydroxysuccinimidyl ester of methoxypolyethylene glycol propionic acid (M-SPA-PEG 5000) has been coupled to rMETase. Molar ratios of M-SPA-PEG-5000 (PEG) to rMETase from 10 to 40 were used for PEGylation of rMETase. PEGylation reactions were run at 20 degrees C for 30 to 60 min in reaction buffer (20 mM sodium phosphate buffer, pH 8.3). The PEGylated molecules (PEG-rMETase) were purified from unreacted PEG with Amicon 30 K centriprep concentrators or by Sephacryl S-300 HR gel-filtration chromatography. Unreacted rMETase was removed by DEAE Sepharose FF anion-exchange chromatography. The resulting PEG-rMETase subunit, from a PEG/rMETase ratio of 30/1 in the synthetic reaction, had a molecular mass of approximately 53 kda determined by matrix-assisted laser desorption/ionization mass spectrometry, indicating the conjugation of two PEG molecules per subunit of rMETase and eight per tetramer. PEG-rMETase molecules obtained from reacting ratios of PEG /rMETase of 30/1 had enzyme activities of 70% of unmodified rMETase. PEGylation of rMETase increased the serum half-life of the enzyme in rats to approximately 160 min compared to 80 min for unmodified rMETase. PEG-rMETase could deplete serum methionine levels to less than 0.1 microM for approximately 8 h compared to 2 h for rMETase in rats. Efficacy studies of PEG-rMETase on human lung cancer and kidney cancer cells in vitro demonstrated a 50% inhibitory concentration (IC50) of 0.04 and 0.06 units/ml, respectively. These IC50 values were almost identical to unmodified rMETase, thus indicating maintenance of antitumor efficacy in the PEGylated enzyme. PEG-rMETase had an IC50 for normal lung and kidney cells of 0.8 and 1.5 units/ml, respectively, similar to rMETase. The efficacy data indicated that PEG-rMETase maintained the high level tumor selectivity of rMETase. PEG-rMETase injected intravenously in mice demonstrated a tumor/blood retention ratio of approximately 1/6 compared to 1/10 of unmodified enzyme, indicating that PEG-rMETase distributes to the tumor at least as effectively as rMETase.

Animals↗
PubMed1998

High expression, purification, and properties of recombinant homocysteine alpha, gamma-lyase.

Homocysteine alpha,gamma-lyase from the anaerobic protozoan parasite Trichomonas vaginalis has been cloned from genomic DNA using PCR methods and expressed in Escherichia coli with a vector containing the T7 promoter. The recombinant homocysteine alpha,gamma-lyase (rHCYase) is expressed as the major protein in the host E. coli cells. The enzyme was purified to approximately 90% purity using heat treatment at 50 degreesC, precipitation steps with polyethyleneimine, polyethylene glycol 8000, and high sodium chloride, DEAE-Sepharose FF chromatography, and phenyl-Sepharose 6 FF chromatography. The final yield was greater than 50%, which encompassed an approximate 18-fold purification. The enzyme is a homotetramer with a monomer molecular weight of 43K and contains pyridoxal phosphate. The Trichomonas rHCYase is selective for homocysteine with respect to very low cysteinase activity in contrast to the alpha,gamma-lyase from Pseudomonas putida, which has very high cysteinase activity with respect to homocysteine. The T. vaginalis and P. putida alpha,gamma-lyases readily separate on a phenyl-Sepharose 6 FF column with the T. vaginalis enzyme eluting first. rHCYase is stable up to 50 degreesC and active over a pH range of 6-8. These properties of high recombinant expression in E. coli, a simple and effective high-yield purification procedure and high relative specificity for homocysteine with respect to cysteine, make rHCYase a promising candidate to use for the diagnosis of hyperhomocystenemia, which has been demonstrated to be a major risk factor for the onset and mortality of cardiovascular disease of all types.

Animals↗