37 results on '"J. B. Cheng"'
Search Results
2. Unusual magnetization process and magnetocaloric effect in α-CoV
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C B, Liu, J B, Cheng, J B, He, R, Chen, X Y, Yue, Y S, Luo, G, Yang, D W, Zhou, J S, Huang, R M, Yu, and Y M, Leng
- Abstract
In low-dimensional Ising spin systems, an interesting observation is the presence of step magnetization at low temperatures. Here we combine both DC and pulsed magnetic fields to study the 1/3 magnetization plateau and multiple steps in the Ising spin-chain material α-CoV
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- 2021
3. Performance Evaluation for Lab-Scale Inductive Fault Current Limiter with Different Iron Core Structures
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Z. Hong, Derong Qiu, Wenrong Li, Jie Sheng, Haosheng Ye, Z. H. Wang, J. B. Cheng, and Z. Y. Li
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Materials science ,Magnetic core ,Electromagnetic coil ,Nuclear engineering ,0103 physical sciences ,Fault current limiter ,Lab scale ,Superconducting fault current limiters ,Limiter ,Current (fluid) ,010306 general physics ,01 natural sciences ,Electrical impedance - Abstract
Inductive superconducting fault current limiter (ISFCL) has shown great potential in limiting large short-circuit current. This paper focuses on the effect of iron core structures of ISFCL. Lab-scaled ISFCLs with different iron core structures are designed and fabricated. Short-circuit properties especially impedance properties are investigated by traditional short-circuit tests. The performance of current limiters with different iron core structures are analyzed and compared.
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- 2020
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4. Unusual magnetization process and magnetocaloric effect in α-CoV2O6 driven by pulsed magnetic fields
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Y S Luo, C B Liu, J B He, J S Huang, G Yang, D W Zhou, J B Cheng, R M Yu, R Chen, Y M Leng, and X Y Yue
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Hysteresis ,Magnetization ,Materials science ,Ferromagnetism ,Condensed matter physics ,Field (physics) ,Ferrimagnetism ,Magnetic refrigeration ,General Materials Science ,Ising model ,Condensed Matter Physics ,Magnetic field - Abstract
In low-dimensional Ising spin systems, an interesting observation is the presence of step magnetization at low temperatures. Here we combine both DC and pulsed magnetic fields to study the 1/3 magnetization plateau and multiple steps in the Ising spin-chain material α-CoV2O6. Magnetization in pulsed fields is quite different from that in DC fields, showing multiple steps in an intermediate range of 4.2-6 K, inverted hysteresis below 4.2 K and asymmetric magnetization in negative fields below 11 K. We demonstrate that these unusual behaviors in magnetization are caused by the spin dynamics and the anomalous magnetocaloric effect (MCE) in α-CoV2O6, i.e., abrupt changes of sample temperature in adiabatic conditions. We successfully separate the influence between the intrinsic slow spin dynamics and the quasi-extrinsic temperature change. From the MCE, we find that some irreversible behavior is originated from the slow spin dynamics. Two different slow dynamics associated with the metastable steps are observed: one is sensitive to the slow field sweep rate at the order of ∼mT s-1and weakly depends on temperature, while the other responds to the rapid field sweep rate of ∼kT s-1and dominates at lowest temperature. We also distinguish that the metastable transition atH4is the first order and crucial for the ferrimagnetic to ferromagnetic transition. This study is useful to the understanding of multistep magnetization in α-CoV2O6and sheds light on recent experimental findings of related compounds.
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- 2021
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5. A New SCR-LDMOSFET Embedded P-Region for Electrostatic Discharge Protection
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L. Tian, J. B. Cheng, and S. S. Chen
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010302 applied physics ,Materials science ,Electrostatic discharge ,business.industry ,020208 electrical & electronic engineering ,Transistor ,02 engineering and technology ,01 natural sciences ,Avalanche breakdown ,law.invention ,Electrostatic discharge protection ,law ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Optoelectronics ,Field-effect transistor ,business ,Technology CAD ,Voltage ,Leakage (electronics) - Abstract
In this paper, a new Silicon Controlled Rectifier and Lateral Double-diffused Metal-Oxide-Semiconductor Field Effect Transistor with shallow P-region (SPSCR- LDMOSFET) is proposed for electrostatic discharge (ESD) protection. The shallow P-region junction causes P-region/N- epi junction being apt to avalanche breakdown. So, trigger voltage is reduced. Furthermore, a new parasitic PNP transistor including the P-region as collector provides another leakage channel for ESD current and then the conductivity modulation in the SCR is weakened. As a result, holding voltage is increased. The physics mechanism of the above high performance is investigated via Technology Computer Aided Design (TCAD) simulation under ESD condition. We also present a detailed analysis of the current paths at trigger point, holding point and second breakdown point.
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- 2018
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6. Electrochemical behaviours of (NiCoFeCrCu)95B5high entropy alloy coatings
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H. Ling, D. Liu, and J. B. Cheng
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Cladding (metalworking) ,Materials science ,Mechanical Engineering ,High entropy alloys ,Alloy ,Metallurgy ,Intermetallic ,engineering.material ,Condensed Matter Physics ,Microstructure ,Corrosion ,Coating ,Mechanics of Materials ,engineering ,General Materials Science ,Solid solution - Abstract
Plasma transferred arc cladding process was used to fabricate (NiCoFeCrCu)95B5 multielement alloy coating. The microstructure and electrochemical behaviours of the coating were investigated. Results show that the precipitation of intermetallic compounds in the coating is effectively inhibited by the rapid solidification process. The coating has simple ordered body centred cubic and face centred cubic solid solution phases. The as prepared coating has excellent corrosion resistance in hydrochloric acid solution. The corresponding corrosion current and corrosion rates are effectively reduced, and the electrochemical impedance is significantly improved referenced to those of the 304 stainless steel.
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- 2014
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7. Application of magnetic field control technology in plasma arc surfacing
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Z. J. Liu, J. B. Cheng, Y. H. Su, H. Chen, D. Liu, and C. Liu
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Diffraction ,Materials science ,Mineralogy ,Surfaces and Interfaces ,Plasma ,Condensed Matter Physics ,Microstructure ,Surfaces, Coatings and Films ,Magnetic field ,Wear resistance ,Plasma arc welding ,Iron based ,Materials Chemistry ,Composite material ,Solid solution - Abstract
In order to control the shape and distribution of hard phases in a surfacing deposit, a longitudinal DC magnetic field was applied during plasma arc surfacing of low carbonsted with two iron based alloys (Fe 5 and Fe 3). Hardness and wear testing as well as microstructural X-ray diffraction analyses and microstructure of two surfacing deposits were investigated. The results show that the surfacing deposit subjected to a magnetic field exhibits higher hardness and better wear resistance than that produced without the application of magnetic field. When the magnetic field current is 3 A, properties of the surfacing deposit are optimal. Under this processing condition, both α and γ solid solutions are sufficiently refined and such hard phases as Cr7C3 and CrB can be obtained.
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- 2006
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8. New Coupled Equations of P- and SV-wave for Reverse-time Migration in TI Media
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J. B. Cheng and W. Kang
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Independent equation ,Mathematical analysis ,Seismic migration ,Wavenumber ,Anisotropy ,Acoustic approximation ,Residual ,Petrology ,Impulse response ,Domain (mathematical analysis) ,Geology - Abstract
We present new P- and SV-wave equations involving no acoustic approximation in TI media. They are derived by projecting the wavefield of elastic equations onto phase vector and its normal in the wavenumber domain, respectively. Both the P- and SV-wave equations have clear physical meaning and can be used for modeling and migration (e.g. RTM). Although strong anisotropy results in residual SV- or P-wave noise, we discuss a straightforward approach of replacing the source to suppress it. Impulse response and numerical examples on a 2D overthrust model validate the wave equations.
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- 2011
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9. Object-oriented database management systems: evolution and performance issues
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S.H. Pakzad, Ali R. Hurson, and J.-B. Cheng
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General Computer Science ,Database ,Computer science ,InformationSystems_DATABASEMANAGEMENT ,Object oriented database management system ,Object (computer science) ,computer.software_genre ,Database design ,Object oriented databases ,Database theory ,Object-relational mapping ,Representation (mathematics) ,Cluster analysis ,computer - Abstract
Several research prototypes and commercial object-oriented database management systems (DBMSs) that emphasize the representation and manipulation of complex objects are reviewed. It is argued that clustering and buffering schemes tailored to typical complex object operations offer the best near-term means of improving the performance of databases and that research in clustering and buffering should address recent advances in disk technology: optical and parallel disks. The object-oriented DBMSs reviewed are Orion, Iris, GemStone, Encore, Ontos, Versant, and ObjectStore. >
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- 1993
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10. ChemInform Abstract: Structure-Activity Relationship of Quinazolinedione Inhibitors of Calcium-Independent Phosphodiesterase
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P. F. Moore, D. Helweg, B. K. Koe, Douglas S. Chapin, J. Johnson, J. A. Russo, J. A. Nielsen, J. B. Cheng, John A. Lowe, J. T. Shirley, R. L. Archer, and Lorraine A. Lebel
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Stereochemistry ,Chemistry ,Calcium independent ,Structure–activity relationship ,Phosphodiesterase ,General Medicine - Published
- 2010
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11. ChemInform Abstract: Synthesis and Pharmacological Profile of Two Novel Heterocyclic Chromanols, CP-80,798 and CP-85,958, as Potent LTD4 Receptor Antagonists
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E. G. ANDREWS, G. W. ANTOGNOLI, R. BRESLOW, M. P. CARTA, T. J. CARTY, R. J. CHAMBERS, J. B. CHENG, V. L. COHAN, J. L. COLLINS, D. B. DAMON, J. DELEHUNT, J. F. EGGLER, J. D. ESKRA, K. W. FREIERT, W. A. HADA, A. MARFAT, H. MASAMUNE, L. S. MELVIN, C. J. MULARSKI, B. A. NACLERIO, and et al. et al.
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LTD4 receptor ,Stereochemistry ,Chemistry ,General Medicine - Published
- 2010
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12. The effect of implanting an antigen release device on lactoferrin concentration in serum and milk
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G. L. Liu, J. B. Cheng, S. P. A. Iaschi, J. Z. Wang, C. G. Zhang, J. Q. Wang, D. P. Bu, H. Y. Wei, K. G. Tay, and L. Y. Zhou
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medicine.medical_specialty ,Biology ,Antibodies ,fluids and secretions ,Immune system ,Blood serum ,Antigen ,Immunity ,Pregnancy ,Lactation ,Internal medicine ,medicine ,Animals ,Antigens ,Drug Implants ,General Veterinary ,Antigen release ,Lactoferrin ,food and beverages ,Housing, Animal ,Lipoprotein Lipase ,Parity ,Endocrinology ,medicine.anatomical_structure ,Milk ,biology.protein ,Cattle ,Female ,Early phase - Abstract
The objective of this study was to evaluate the effect of implanting an Antigen Release Devices (ARD) into dairy cows during the lactation cycle to induce an immune response. Subsequently, the concentrations of lactoferrin in serum and milk were measured. Forty healthy adult Chinese Holstein cows were divided into two equal groups: a test group and a control group. Animals in the test group received ARD implants, whereas the control group animals were not treated. An even spread across the two groups was maintained with animal selection based on parity, the lactation days and milk yields. The concentrations of lactoferrin in the serum and milk of all forty animals were measured using an Enzyme-Linked Immunosorbent Assay (ELISA). The results show that the implantation of an ARD did not significantly increase the concentration of lactoferrin in the serum and milk throughout the whole experiment period except on two occasions. The levels of lactoferrin in the milk and serum significantly increased on day 7 and on day 11 after implantation (p
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- 2008
13. Multifunctional roles of bile acid biosynthetic enzymes and the isolation of a new vitamin D 25-hydroxylase
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D. W. Russell and J. B. Cheng
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- 2007
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14. Differential in vivo and in vitro bronchorelaxant activities of CP-80,633, a selective phosphodiesterase 4 inhibitor
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K F, Wright, C R, Turner, R, Jayasinghe-Beck, V L, Cohen, J B, Cheng, and J W, Watson
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Male ,Dose-Response Relationship, Drug ,Phosphodiesterase Inhibitors ,Muscle Relaxation ,Adrenergic beta-Antagonists ,Guinea Pigs ,Muscle, Smooth ,Pyrimidinones ,Propranolol ,Pyrrolidinones ,Bronchodilator Agents ,Cyclic Nucleotide Phosphodiesterases, Type 4 ,Pyridazines ,Trachea ,Catecholamines ,3',5'-Cyclic-AMP Phosphodiesterases ,Animals ,Rolipram - Abstract
CP-80,633, a selective phosphodiesterase (PDE) 4 inhibitor, potently reverses histamine bronchoconstriction in anesthetized guinea pigs (ED50 10 micrograms/kg) but only weakly relaxes histamine-constricted guinea pig trachea (EC50 137 microM). Using CP-80,633 as a prototype PDE4 inhibitor, we evaluated the hypothesis that bronchodilation induced by PDE4 inhibitors is not mediated by direct relaxation of airway smooth muscle. In anesthetized guinea pigs, a bronchodilatory dose of CP-80,633 did not increase plasma catecholamines, nor did propranolol pretreatment significantly alter the ability of CP-80,633 to reverse histamine bronchoconstriction. In an isolated organ system, the activity of bronchorelaxants may be attenuated by the lack of endogenous activators of adenylyl cyclase or by decreased levels of intracellular cyclic nucleotides. Pretreatment with the beta-adrenoceptor agonist, salbutamol, or the PDE3 inhibitor imazodan did not potentiate the bronchorelaxant ability of CP-80,633. Milrinone pretreatment increased the potency of CP-80,633 to relax carbachol-constricted tracheal rings, but only at concentrations where nonspecific effects have been reported. By comparing the bronchorelaxant abilities of PDE inhibitors in tracheal rings with or without epithelium, we determined that the epithelium did not serve as a barrier to drug penetration. In conclusion, CP-80,633 is a potent bronchodilator in vivo, whose activity is neither mediated by direct airway smooth muscle relaxation nor dependent upon endogenous catecholamines.
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- 1997
15. The phosphodiesterase type 4 (PDE4) inhibitor CP-80,633 elevates plasma cyclic AMP levels and decreases tumor necrosis factor-alpha (TNFalpha) production in mice: effect of adrenalectomy
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J B, Cheng, J W, Watson, C J, Pazoles, J D, Eskra, R J, Griffiths, V L, Cohan, C R, Turner, H J, Showell, and E R, Pettipher
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Lipopolysaccharides ,Male ,Mice, Inbred BALB C ,Time Factors ,Epinephrine ,Purinones ,Phosphodiesterase Inhibitors ,Phosphoric Diester Hydrolases ,Tumor Necrosis Factor-alpha ,Adrenalectomy ,Dipyridamole ,Pyrimidinones ,Propranolol ,Monocytes ,Cyclic Nucleotide Phosphodiesterases, Type 4 ,Thromboxane B2 ,Kinetics ,Mice ,Piroxicam ,3',5'-Cyclic-AMP Phosphodiesterases ,Cyclic AMP ,Animals ,Humans ,Cyclic GMP ,Vinca Alkaloids - Abstract
Rolipram was previously reported to elevate plasma cyclic adenosine 3',5'-monophosphate (cAMP) and inhibit serum tumor necrosis factor-alpha (TNF-alpha) production in mice. CP-80,633, a new cyclic nucleotide phosphodiesterase (PDE4) inhibitor, has been shown to augment intracellular cAMP levels and to inhibit TNFalpha release from human monocytes in vitro. This study was undertaken to determine the effect of p.o. CP-80,633 on plasma cAMP levels and lipopolysaccharide-induced TNFalpha production in mice with and without adrenal glands. CP-80,633 dose-dependently (3-32 mg/kg p.o.) elevated plasma cAMP levels and decreased systemic TNFalpha production in response to i.p. injection of lipopolysaccharide. Elevated plasma cAMP levels can be detected for up to 4 hr. CP-80,633 (10 mg/kg p.o.) caused a 6-fold increase in the plasma cAMP level, a 2-fold increase in the plasma epinephrine level and a greater than 95% reduction in TNFalpha production. Unlike CP-80,633, neither vinpocetine, dipyridamole, SKB-94,120 nor zaprinast, at 100 mg/kg p.o., modified the cAMP response, which suggests that this response is mediated by inhibition of PDE4. Adrenalectomy reduced the cAMP response and completely blocked the epinephrine response; however, the levels of plasma cAMP in the CP-80,633-treated mice (10 mg/kg p.o.) remained elevated (vehicle: 47.3 +/- 6.8 vs. CP-80,633: 98.4 +/- 10.3 pmol/ml, n = 7, P.05). This effect is mimicked by treatment of control mice with propranolol, which demonstrates that beta adrenoreceptors contribute to the cAMP response. Removal of adrenal glands significantly increased the LPS-induced elevation of serum TNFalpha. The ability of CP-80,633 to block the TNFalpha response was only slightly affected by adrenalectomy (ED50 = 1.2 mg/kg in controls vs. 3.9 mg/kg in adrenalectomized mice). Taken together, these results show that CP-80,633, when given p.o. to mice, is capable of elevating plasma cAMP and inhibiting TNFalpha production and that adrenal catecholamines contribute significantly to the effect of CP-80,633 on the cAMP response but only slightly to its effect on the systemic TNFalpha response.
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- 1997
16. The in vivo pharmacology of CP-80, 633, a selective inhibitor of phosphodiesterase 4
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C R, Turner, V L, Cohan, J B, Cheng, H J, Showell, C J, Pazoles, and J W, Watson
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Male ,Cross-Over Studies ,Eosinophil Peroxidase ,Interleukin-6 ,Ovalbumin ,Phosphodiesterase Inhibitors ,Phosphoric Diester Hydrolases ,Anti-Inflammatory Agents, Non-Steroidal ,Guinea Pigs ,Interleukin-8 ,Pyrimidinones ,Bronchodilator Agents ,Cyclic Nucleotide Phosphodiesterases, Type 4 ,Peroxidases ,3',5'-Cyclic-AMP Phosphodiesterases ,Animals ,Bronchoalveolar Lavage Fluid ,Histamine ,Interleukin-1 - Abstract
The following studies were conducted to characterize the bron-chodilatory and antiinflammatory activity of the novel, selective phosphodiesterase-IV inhibitor, CP-80,633 (2'S)5-[3-(2'-exobicyclo[2.2.1]heptyloxy-4-methoxy-phenyl]te trahydro- 2(1H)-pyrimidone, a compound in clinical development for atopic disease. In IgG1 passively sensitized guinea pigs, aerosolized ovalbumin challenge increases both pulmonary eosinophil peroxidase levels and airway obstruction. CP-80,633, administered before ovalbumin challenge, significantly attenuated both the increase in tissue eosinophil peroxidase levels (ED50 = 1.4 mg/kg, p.o.) and airway obstruction (ED50 = 0.93 +/- 0.14 mg/kg,p.o.) 10 to 30 times more potently than theophyl-line. Intraarterially administered CP-80,633 also reversed an established bronchoconstriction initiated by continuous infusion of histamine to guinea pigs (ED50 of 8.2 micrograms/kg vs. 5.6 mg/kg for theophylline). The antiinflammatory effect of CP-80,633 was also examined in atopic monkeys challenged with Ascaris suum (Ag) aerosol. CP-80,633 (1 mg/kg, qid, s.c., 1 hr before antigen challenge) significantly reduced antigen-induced increases in bronchoalveolar lavage neutrophils (72.8 +/- 15.8% inhibition) and eosinophils (61.1 +/- 5.7% inhibition) 4 hr postchallenge, but did not reduce leukocytes 24 hr postchallenge. CP-80,633 did not inhibit antigen-induced increases in BAL levels of interleukin-1 beta, -6 or -8 as measured by enzyme-linked immunosorbant assay. These results indicate that CP-80,633 possesses bronchodilatory activity in guinea pigs and some antiinflammatory effects in both guinea pigs and monkeys.
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- 1996
17. In vitro pharmacology of the novel phosphodiesterase type 4 inhibitor, CP-80633
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V L, Cohan, H J, Showell, D A, Fisher, C J, Pazoles, J W, Watson, C R, Turner, and J B, Cheng
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Phosphodiesterase Inhibitors ,Phosphoric Diester Hydrolases ,Anti-Inflammatory Agents, Non-Steroidal ,Guinea Pigs ,Receptors, Purinergic P1 ,Pyrimidinones ,Cyclic Nucleotide Phosphodiesterases, Type 1 ,Binding, Competitive ,Monocytes ,Pyrrolidinones ,Bronchodilator Agents ,Cyclic Nucleotide Phosphodiesterases, Type 4 ,Rats ,Substrate Specificity ,Eosinophils ,Isoenzymes ,Kinetics ,Theophylline ,3',5'-Cyclic-AMP Phosphodiesterases ,Superoxides ,Cyclic AMP ,Animals ,Humans ,Cloning, Molecular ,Rolipram - Abstract
We present the in vitro pharmacology of a novel adenosine 3'-5' -cyclic monophosphate-specific phosphodiesterase (PDE) type 4 inhibitor, CP-80633 ((2'S)5-[3-(2' -exobicyclo[2.2.1]-heptyloxy)4-methoxyphenyl] tetrahydro-2(1H)-primidone), which has shown efficacy in phase II clinical trials for atopic dermatitis. CP-80633 inhibits PDE4 isozymes (human lung IC50 = 1.27 microM) in the absence of effects on PDE1, PDE2, PDE3 and PDE5 isozymes (IC50100 microM). It exhibits no significant selectivity for any single cloned PDE4A, B, C or D isoform. CP-80633 inhibits adenosine 3'-5'-cyclic monophosphate hydrolysis in partially purified human peripheral blood monocyte cytosol (IC50 = 3.52 microM), eosinophil membrane (IC50 = 1.10 microM) and T cell membrane (IC50 = 2.28 microM) preparations. Inhibition of eosinophil PDE4 adenosine 3'-5'-cyclic mono-phosphate hydrolysis by CP-80,633 occurs in a noncompetitive manner. Unlike theophylline, CP-80,633 is inactive against ratrain adenosine (A1,A2) receptors. Consistent with its action as a PDE4 inhibitor in whole cells, CP-80633 potentiates PGE1 dependent increases in adenosine 3'-5'-cyclic monophosphate levels in human U937 cells, and in human eosinophils, monocytes and T cells (EC200 approximately 1.0 microM). Consequently, CP-80633 inhibits many inflammatory cell functions including 1) human eosinophil superoxide anion production (IC500.6 microM), 2 C5a-(IC50 = 0.40 microM) and LTB4-(IC50 = 0.20 microM) mediated guinea pig peritoneal eosinophil chemotaxis and 3) lipopolysac-charide-induced tumor necrosis factor-alpha release from human monocytes (IC50 = 0.219 microM). These data clearly demonstrate that CP-80633 is a selective inhibitor of PDE4 isozymes, and support its potential use as a therapeutic agent for a number of inflammatory and immune disorders.
- Published
- 1996
18. The in vitro and in vivo pharmacologic activity of the potent and selective leukotriene B4 receptor antagonist CP-105696
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H J, Showell, E R, Pettipher, J B, Cheng, R, Breslow, M J, Conklyn, C A, Farrell, G P, Hingorani, E D, Salter, B C, Hackman, and D J, Wimberly
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Male ,Neutrophils ,Guinea Pigs ,Carboxylic Acids ,Macrophage-1 Antigen ,In Vitro Techniques ,Leukotriene B4 ,Monocytes ,Eosinophils ,Chemotaxis, Leukocyte ,Hydroxyeicosatetraenoic Acids ,Animals ,Humans ,Leukotriene Antagonists ,Benzopyrans ,Calcium ,12-Hydroxy-5,8,10,14-eicosatetraenoic Acid - Abstract
CP-105696, (+)-1-(3S,4R)-[3-(4-phenyl-benzyl)-4-hydroxy-chroman-7-yl] cyclopentane carboxylic acid, is a structurally novel, selective and potent leukotriene B4 (LTB4) receptor antagonist. In vitro, CP-105696 inhibited [3H]LTB4 (0.3 nM) binding to high-affinity LTB4 receptors on human neutrophils with an IC50 value of 8.42 +/- 0.26 nM. Scatchard analyses of [3H]LTB4 binding to these high-affinity receptors indicated that CP-105696 acted as a noncompetitive antagonist. CP-105696 inhibited human neutrophil chemotaxis mediated by LTB4 (5 nM) in a noncompetitive manner with an IC50 value of 5.0 +/- 2.0 nM. Scatchard analyses of [3H]LTB4 binding to low-affinity receptors on neutrophils indicated that CP-105696 acted as a competitive antagonist at this receptor, and inhibition of LTB4-mediated CD11b upregulation on human neutrophils was competitively inhibited by CP-105696 (pA2 = 8.03 +/- 0.19). CP-105696 at 10 microM did not inhibit either human neutrophil chemotaxis or CD11b upregulation mediated through alternate (i.e., C5a, IL-8, PAF) G-protein coupled chemotactic factor receptors. In isolated human monocytes, LTB4 (5 nM)-mediated Ca++ mobilization was inhibited by CP-105696 with an IC50 value of 940 +/- 70 nM. In vivo, after oral administration, CP-105696 blocked neutrophil and eosinophil infiltration in cavine dermis mediated by either LTB4 or arachidonic acid with ED50 values of 0.3 +/- 0.1 mg/kg. 12(R)-Hydroxyeicosatetraenoic acid-mediated neutrophil infiltration was blocked by 76.4 +/- 14.8% at 3 mg/kg.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1995
19. Vortex flow filtration of mammalian and insect cells
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S. E. Lee, S. J. Hawrylik, J. B. Cheng, D. J. Wasilko, and J. S. Pillar
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Lysis ,Cell Survival ,Clinical Biochemistry ,Biomedical Engineering ,Bioengineering ,Biology ,Spodoptera ,law.invention ,Cell Line ,law ,Culture Techniques ,Bioreactor ,medicine ,Tumor Cells, Cultured ,Animals ,Humans ,Viability assay ,Cell damage ,Filtration ,Mammals ,Chromatography ,Membrane Proteins ,Cell Biology ,medicine.disease ,Vortex ,Receptors, Interleukin-4 ,Membrane ,Cell culture ,Culture Media, Conditioned ,Receptors, Mitogen ,Electrophoresis, Polyacrylamide Gel ,Lymphoma, Large B-Cell, Diffuse ,Biotechnology - Abstract
The use of vortex flow filtration for harvesting cells or conditioned medium from large scale bioreactors has proven to be an efficient, low shear method of cell concentration and conditioned medium clarification. Several 8-10 L batches of the human histiocytic lymphoma U-937 cell line (ATCC CRL 1593) were concentrated to less than 1 L by vortex flow filtration through a 3.0 microns membrane. An aggressive filtration regimen caused a 17% loss of cell viability and a 32% loss of IL-4 receptor binding capacity when compared to a batch centrifuged control. A reduction of the rotor speed from 1500 to 500 RPM and reduction of system back pressure from 10 to 0 PSIG resulted in cell viability and IL-4 binding capacity comparable to the control. Several 10 L batches of baculovirus infected Sf-9 cells were also concentrated to less than 1 L by vortex flow filtration through a 3.0 microns membrane. SDS-PAGE analysis of filtrate samples showed that aggressive filtration caused cell damage which led to contamination of the process stream by cellular lysate. When rotor speed was reduced to 500 RPM and system back pressure was reduced to 0 PSIG, the amount of contaminating lysate proteins in filtrate samples was comparable to a batch centrifuged control.
- Published
- 1994
20. Low substrate-current and high breakdown voltage JI-LIGBT
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Bo Zhang, Li Zhixuan, B. X. Duan, and J. B. Cheng
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Materials science ,Heterostructure-emitter bipolar transistor ,business.industry ,Transistor ,Bipolar junction transistor ,Insulated-gate bipolar transistor ,law.invention ,Current injection technique ,law ,Optoelectronics ,Breakdown voltage ,Field-effect transistor ,Electrical and Electronic Engineering ,business ,Static induction transistor - Abstract
A novel bulk junction isolated lateral insulated gate bipolar transistor (JI-LIGBT) with a heavily doped buried-layer in substrate is presented. Due to electric field modulation and current-gain reduction of the vertical parasitic transistor from the buried-layer, in comparison with the conventional LIGBT without a buried-layer, the novel structure offers not only high breakdown voltage but also short turn-off time and significantly low substrate leakage current.
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- 2011
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21. Antigen-mediated pulmonary eosinophilia in immunoglobulin G1-sensitized guinea pigs: eosinophil peroxidase as a simple specific marker for detecting eosinophils in bronchoalveolar lavage fluid
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J B, Cheng, J S, Pillar, J T, Shirley, H J, Showell, J W, Watson, and V L, Cohan
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Eosinophil Peroxidase ,Ovalbumin ,Guinea Pigs ,Eosinophils ,Peroxidases ,Immunoglobulin G ,Leukocytes ,Animals ,Female ,Antigens ,Platelet Activating Factor ,Pulmonary Eosinophilia ,Bronchoalveolar Lavage Fluid ,Biomarkers - Abstract
Eosinophil peroxidase (EPO) has been used previously to detect the number of eosinophils in the peritoneal exudate and bone marrow of mice. The present study was undertaken to determine 1) whether EPO activity may provide a measure of a change in eosinophils in bronchoalveolar lavage fluid (BALF) of guinea pigs, 2) whether immunoglobulin (Ig)G1 could play a role in pulmonary eosinophilia and 3) effects of pharmacological agents on the EPO response in an IgG1 passively sensitized animal model. The activity of EPO was assessed by the ability of cell lysates (0.1% Triton-100 treatment) to oxidize 1 mM o-phenylenediamine in the presence of 1 mM H2O2 for 5 min at 22 degrees C. The enzyme activity was found to be eosinophil dependent, inhibited by the EPO inhibitor 3-amino-1,2,4-triazole (IC50 = approximately 0.1 mM) and relatively resistant to heat treatment (no loss of activity after 2-hr preincubation at 56 degrees C). To determine antigen-dependent eosinophil and EPO responses, guinea pigs were passively sensitized i.p. with 0.5 mg/kg of an affinity-purified antiovalbumin (OA) IgG1. Two to 3 days later, the sensitized animals were injected with pyrilamine (5 mg/kg, i.p.) before OA aerosol challenge. Aerosolized OA (0.1%) caused a significant increase in both eosinophil number and EPO activity in BALF of sensitized guinea pigs at 18 to 24 hr post-challenge. At a given concentration of aerosolized OA, the enzyme activity increased as a function of the antibody dose and time post-OA challenge.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1993
22. Competition of leukotrienes and ICI-198,615 for [3H]LTD4 binding sites in guinea pig lung membranes suggests the involvement of two LTD4 receptor subtypes
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J T, Shirley and J B, Cheng
- Subjects
Receptors, Leukotriene ,Leukotrienes ,Indazoles ,Guinea Pigs ,Animals ,Magnesium ,SRS-A ,Isoxazoles ,In Vitro Techniques ,Receptors, Immunologic ,Binding, Competitive ,Lung - Abstract
Pharmacological analysis of the effects of leukotriene D4 (LTD4) antagonists on contraction of guinea pig airway smooth muscle to leukotrienes reveals the presence of two subtypes of the LTD4 receptor. This finding is, however, inconsistent with [3H]LTD4 equilibrium binding results, which show no evidence of a heterogeneity of pulmonary [3H]LTD4 binding sites. It is possible that LTD4 binds to the two receptor subsets with equal affinity, and the pharmacological difference between them lies in the relative ability of leukotriene (LT) agonists and antagonists to interact at the receptor sites. This study was, therefore, undertaken to determine the rank order of potency of LTs and ICI-198,615 in competing with [3H]LTD4 for their respective binding sites in guinea pig lung membranes. To determine precisely the inhibitory constant (Ki) of LTC4, we used the irreversible gamma-glutamyl transpeptidase inhibitor, acivicin (AT-125), to prevent LTC4 metabolism. Incubation of lung membranes with 5 mM AT-125 for 120 min at 25 degrees C resulted in greater than 98% recovery of LTC4. Unlike L-serine-borate complex, AT-125 failed to inhibit pulmonary [3H]LTD4 binding. These results suggest that AT-125 can be used in this study. Nonlinear least squares analysis of the results of LTD4/[3H]LTD4 or ICI-198,615/[3H]LTD4 competitive binding reveals that either LTD4 (Ki = 0.49 nM) or ICI-198,615 (Ki = 6.89 nM) interacts at a single homogenous population of [3H]LTD4 binding sites. However, the data of competitive binding results of LTC4 (in the presence of AT-125) or LTE4 are best fitted for its interaction with high- and low-affinity [3H]LTD4 binding sites, designated as LTD4 alpha and LTD4 beta sites, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1991
23. Formation of extremely high current density LaB6 field emission arrays via e-beam deposition
- Author
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J. B. Cheng, Xiao Wei Sun, Z. L. Lin, G. C. Cao, K. C. Qi, and W. B. Chen
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Analytical chemistry ,Oxide ,Electron beam physical vapor deposition ,Evaporation (deposition) ,Field electron emission ,chemistry.chemical_compound ,Vacuum deposition ,chemistry ,Electron beam processing ,Physics::Accelerator Physics ,Optoelectronics ,Deposition (phase transition) ,business ,Common emitter - Abstract
In this paper, we report a Spindt-type field emission array (FEA) with LaB6 as the emitting material. The LaB6 emitters were deposited by e-beam evaporation with low oxide content. As LaB6 in its vapor form is active and absorbs large quantity of residual gases, which oxidizes the LaB6 films, a special e-beam configuration was designed to ensure high evaporation rate which is essential for depositing pure phase LaB6. FEAs with LaB6 emitter tips exhibited an average emission current as high as about 0.23 μA/tip suggesting that LaB6 emitters are promising candidates for high current density vacuum electronic devices.
- Published
- 2008
- Full Text
- View/download PDF
24. Evidence that peptidoleukotriene is a prerequisite for antigen-dependent thromboxane synthesis in IgG1-passively sensitized guinea pig lungs
- Author
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J B, Cheng, J S, Pillar, M J, Conklyn, R, Breslow, J T, Shirley, and H J, Showell
- Subjects
Male ,Thromboxane B2 ,Indazoles ,Immunoglobulin G ,Guinea Pigs ,Animals ,SRS-A ,Isoxazoles ,Antigens ,Platelet Activating Factor ,Lung - Abstract
Lungs from guinea pigs passively sensitized with an affinity-purified IgG1 antibody produce both leukotriene (LT)D4 and thromboxane (Tx)B2 upon ex vivo antigen challenge. This study was undertaken to determine the possibility of endogenously generated peptido-LTs being a prerequisite for Tx synthesis. In immunoglobulin G1-sensitized lungs, exogenous LTD4 induced TxB2 production with a median effective dose of 4.1 nM, whereas the response to LTE4, LTB4 or platelet-activating factor was relatively weak. Although LTC4 was as potent as LTD4 in stimulating TxB2 generation, LTC4's dose-response curve was shifted significantly to the right by AT-125, an irreversible gamma-glutamyl transpeptidase inhibitor, suggesting that at least a part of LTC4 sensitized lungs with antigen (0.01-30 micrograms/ml ovalbumin) for 20 min precipitated a significant amount of LTD4 production. The levels of LTD4 range from 8 to 26 nM (without taking LTD4 recovery into consideration). This level is 2- to 7-fold greater than the median effective dose value observed with exogenous LTD4. Moreover, pretreatment of sensitized lungs with ICI-198,615 a specific LTD4 antagonist, blocked equally both antigen (IC50 = 0.01 microM)- and LTD4 (IC50 = 0.017 microM)-induced TxB2 production. When sensitized lung fragments were treated with 5 mM AT-125, ICI-198,615 was effective in preventing not only antigen-but also LTC4-dependent production of TxB2 (IC50 = 0.018 and 0.021 microM, respectively). In contrast, neither WEB-2086, a platelet-activating factor antagonist, nor pyrilamine, a histamine antagonist, inhibited antigen and LTD4 responses (IC50 greater than 30 microM). Unlike its effect on antigen response, ICI-198,615 was unable to block Ca2+ ionophore-induced TxB2 production.2
- Published
- 1990
25. PMNs and airway inflammation/hyperreactivity
- Author
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A. N. Payne and J. B. Cheng
- Subjects
Pharmacology ,medicine.medical_specialty ,Allergy ,Neurology ,business.industry ,Neutrophils ,Immunology ,Pharmacology toxicology ,Airway inflammation ,Bronchi ,Toxicology ,medicine.disease ,Rheumatology ,Asthma ,Internal medicine ,Medicine ,Animals ,Humans ,Pharmacology (medical) ,business ,Bronchitis - Published
- 1990
26. Identification of calcium antagonist receptor binding sites using (3H)nitrendipine in bovine tracheal smooth muscle membranes
- Author
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A. Bewtra, R. G. Townley, and J. B. Cheng
- Subjects
medicine.medical_specialty ,Nifedipine ,Nisoldipine ,chemistry.chemical_element ,Receptors, Nicotinic ,Calcium ,Cellular and Molecular Neuroscience ,Nitrendipine ,Internal medicine ,Cromolyn Sodium ,medicine ,Animals ,Binding site ,Molecular Biology ,Pharmacology ,Antagonist ,Muscle, Smooth ,Cell Biology ,Calcium Channel Blockers ,Trachea ,Kinetics ,Endocrinology ,Membrane ,Verapamil ,chemistry ,Molecular Medicine ,Cattle ,Calcium Channels ,medicine.drug - Abstract
(3H)Nitrendipine binding to the bovine tracheal muscle membrane at 25 degrees C was rapid, saturable (Bmax = 14.8 +/- 3.9 fmol/mg protein) and of high affinity (Kd = 0.15 +/- 0.04 nM). The rank order of Ca2+ antagonists competing for airway (3H)nitrendipine binding was nitrendipine not equal to nisoldipine not equal to nifedipine much greater than verapamil. Cromolyn, however, neither inhibited nor increased the binding.
- Published
- 1984
- Full Text
- View/download PDF
27. Tissue distribution and functional correlation of [3H]leukotriene C4 and [3H]leukotriene D4 binding sites in guinea-pig uterus and lung preparations
- Author
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J B, Cheng, D, Lang, A, Bewtra, and R G, Townley
- Subjects
Leukotriene E4 ,Arachidonic Acid ,Binding Sites ,Guinea Pigs ,Uterus ,Brain ,Arachidonic Acids ,Leukotriene B4 ,Rats ,Uterine Contraction ,Dogs ,Chromones ,Animals ,Humans ,Cattle ,Female ,SRS-A ,Tissue Distribution ,Rabbits ,Lung - Abstract
To determine the distribution of leukotriene (LT) C4 and LTD4 receptors and functional significance of each receptor, we used [3H]LTC4 and [3H]LTD4 to measure the binding activity in various tissue homogenates and to correlate the relative ability of the LT agonists to inhibit binding with their contractile responses in guinea-pig uterine or lung parenchymal preparations. Guinea-pig brain contained the highest binding activity of 1 to 2 nM [3H] LTC4 followed by small intestine, heart, lung, kidney, uterus, etc., whereas guinea-pig lung had at least 2.7-fold greater [3H] LTD4 binding activity than any other tissues tested. In the brain and uterine homogenates, the rank order of potency for the compounds in competing with [3H]LTC4 for binding sites was LTC4 much greater than LTD4 greater than LTE4 greater than FPL-55712 = arachidonic acid. The in vitro functional study showed that the ability of the LT agonists to produce uterine contraction was in the order of LTC4 greater than LTD4 greater than LTE4, which is compatible with their relative effect for inhibition of uterine or brain [3H]LTC4 binding. In the lung homogenate, either LTC4, LTD4 or LTE4 inhibited effectively [3H]LTD4 binding and the potency order for the [3H]LTD4 competition study was LTD4 greater than LTE4 greater than LTC4 much greater than FPL-55712 greater than arachidonic acid. These LT agonists also produced lung contraction effectively and the difference among their contractile ability was not significant. We conclude that 1) there are distinct functional LTC4 and LTD4 receptors, 2) activation of the LTC4 receptor could account for the uterine contraction due to the LT agonists and 3) the lung contraction induced by LTC4, LTD4 and LTE4 is at least mediated partly by the LTD4 receptor.
- Published
- 1985
28. Comparison of the effects of verapamil and nifedipine on airway muscarinic reactivity and receptors
- Author
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J B, Cheng, A J, Bewtra, and R G, Townley
- Subjects
Nifedipine ,Airway Resistance ,Respiratory System ,Rats, Inbred Strains ,In Vitro Techniques ,Receptors, Muscarinic ,Potassium Chloride ,Rats ,Trachea ,Verapamil ,Animals ,Methacholine Compounds ,Cattle ,Methacholine Chloride - Abstract
Previous studies have shown inconsistent results of the effect of verapamil and nifedipine on airway reactivity. This study was undertaken to determine and compare their effects on the activity of airway muscarinic receptors by contraction experiments and by radioligand receptor binding assays. We found that verapamil (10(-5)-10(-4) M) reduced contraction at rat tracheal muscle to methacholine, a finding consistent with its inhibition on binding of (3H)QNB to bovine tracheal muscle membranes. Unlike verapamil, nifedipine (10(-5)-3 X 10(-5) M) inhibited neither methacholine response nor (3H)QNB binding. Verapamil but not nifedipine decreased the affinity of binding sites. Neither of them affected the concentration of (3H)QNB binding sites. We conclude that the effect of verapamil on airway muscarinic receptor binding sites differs qualitatively from that of nifedipine, and suggests that its effect on the binding sites could account for the inhibitory action of verapamil on airway muscarinic response.
- Published
- 1985
29. Pharmacological characterization of effects of nifedipine on isolated guinea-pig and rat tracheal smooth muscle
- Author
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J B, Cheng and R G, Townley
- Subjects
Male ,Serotonin ,Nifedipine ,Pyridines ,Airway Resistance ,Muscle Relaxation ,Guinea Pigs ,Muscle, Smooth ,Rats, Inbred Strains ,In Vitro Techniques ,Calcium Channel Blockers ,Rats ,Trachea ,Calcium Chloride ,Animals ,Methacholine Compounds ,Drug Interactions ,Female ,Methacholine Chloride ,Histamine ,Muscle Contraction - Abstract
Nifedipine, a relatively new Ca2+-channel blocking agent, has recently been shown to be effective in the treatment of exercise-induced asthma; however, the pharmacological mechanism by which it blocks bronchospasm is little understood. We have investigated and characterized its effects on the reactivity of isolated guinea-pig and rat tracheal smooth muscle. Although it (10(-8)--10(-7)M) blocked the contraction of the rat tracheal muscle to KCl and CaCl2, nifedipine (10(-7)--10(-6)M) did not significantly inhibit histamine, methacholine or serotonin-induced muscle contractions in guinea-pigs and the methacholine contraction in rats. Nifedipine produced a potent relaxation on contracted tracheal muscle. The concentration required to produce 50% relaxation on 10(-5)M histamine-precontracted guinea-pig tracheal muscle was 8.31 +/- 3.12 X 10(-9)M, and the extent of the nifedipine-induced relaxation could be modified by the baseline and active contracted tension. Nifedipine was more potent in producing the relaxation in guinea-pig tracheal muscle than isoproterenol, theophylline or verapamil. However, the time required for 50% relaxation by 3 X 10(-5)M isoproterenol was significantly less than the time for the nifedipine (3 X 10(-5)M) or verapamil (10(-4)M) effect. In addition, the Hill number of the nifedipine-induced relaxation was different from the value of the isoproterenol or verapamil effect. Our results indicate that nifedipine exerts a potent dilatory effect directly on airway muscle, and suggest that such effect could be one of its pharmacological actions on relieving bronchospasm.
- Published
- 1983
30. Fetal pulmonary beta-adrenergic receptors: characterization in the human and in vitro modulation by glucocorticoids in the rabbit
- Author
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J M, Roberts, M M, Jacobs, J B, Cheng, P J, Barnes, A T, O'Brien, and P J, Ballard
- Subjects
Isoproterenol ,Gestational Age ,Pulmonary Surfactants ,In Vitro Techniques ,Dexamethasone ,Radioligand Assay ,Body Water ,Receptors, Adrenergic, beta ,Cyclic AMP ,Dihydroalprenolol ,Animals ,Humans ,Lung ,Adenylyl Cyclases - Abstract
At least two developmental responses necessary to prepare the fetal lung to serve as a gas-exchange organ, the release of surface-active material and the reabsorption of alveolar water, can be stimulated by beta-adrenergic agonists. The sensitivity of these responses increases dramatically in late gestation. beta-Adrenergic receptors can be identified by radioligand binding and are present in human fetal lung as early as 16 weeks of gestation. The temporal relationship of the increases in both pulmonary beta-receptors and plasma-free cortisol in the fetal rabbit during gestation suggests that endogenous glucocorticoids may cause increased concentration of pulmonary beta-receptors. Treatment of pregnant rabbits at 24 or 25 days of gestation results in precocious increases in both fetal lung beta-receptors and agonist-specific, high-affinity binding. The increase in receptor concentration with glucocorticoid is not dependent on other endocrine response inasmuch as 0.1 microM dexamethasone increases beta-receptor concentrations at 24 and 48 hours of incubation in cultures of fetal rabbit lung organ. This effect of glucocorticoid to increase beta-receptor concentration and high-affinity binding may explain the increased fetal pulmonary beta-adrenergic response at term and may be responsible in part for the reduction in neonatal respiratory syndrome seen after antenatal glucocorticoid therapy.
- Published
- 1985
31. Comparison of antigen and Ca++-ionophore-induced peptidoleukotriene release from guinea pig lung preparations using high-performance liquid chromatography
- Author
-
J B, Cheng, J D, Eskra, and J, Pillar
- Subjects
Kinetics ,Time Factors ,Ovalbumin ,Guinea Pigs ,Animals ,Calcium ,SRS-A ,Lipoxygenase Inhibitors ,Lung ,Calcimycin ,Chromatography, High Pressure Liquid - Abstract
This study was undertaken to investigate antigen-induced peptidoleukotriene release from lungs of sensitized guinea pigs using a recently developed solid-phase extraction and high-performance liquid chromatography assay system. This release was compared to the response due to Ca++-ionophore (A23187) challenge. Incubation of lung fragments (0.6 g) from actively sensitized guinea pigs with ovalbumin (3 micrograms/ml) for 20 min at 37 degrees C resulted in the release of 40 to 60 ng of leukotriene (LT)D4 detected in the extracted filtrate (40-50% recovery of LTD4). The amount of LTD4 determined using the high-performance liquid chromatography assay correlated well with the quantity determined by a LTC4 radioimmunoassay. LTD4 release was saturable and was optimal at a tissue concentration of 0.6 g/2.5 ml of buffer. Kinetic analysis of LT generation showed that after antigen challenge, LTC4 levels peaked at 3 min and declined rapidly with time; LTD4 levels then increased significantly, reaching a maximum at 15 min and decreased slightly at 60 min. LTE4 was not detected until 30 min after antigen challenge after which it increased slowly. The kinetic results permit an estimation of the rate of LTD4 and LTE4 formation to be 5 and 0.17 ng/min/g of lung, respectively. In contrast to antigen challenge, LTD4 release from Ca++-ionophore-stimulated lung fragments was not saturable and was biphasic with increasing amounts of tissues. Moreover, LTD4 produced by Ca++-ionophore stimulation could not be detected during the first 10 min but thereafter increased linearly with incubation time.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1987
32. [3H]leukotriene B4 binding to the guinea-pig spleen membrane preparation: a rich tissue source for a high-affinity leukotriene B4 receptor site
- Author
-
J B, Cheng, E I, Cheng, F, Kohi, and R G, Townley
- Subjects
Binding Sites ,Cell Membrane ,Guinea Pigs ,Magnesium Chloride ,Receptors, Leukotriene B4 ,In Vitro Techniques ,Sodium Chloride ,Tritium ,Leukotriene B4 ,Calcium Chloride ,Kinetics ,Chromones ,Animals ,Humans ,Female ,Magnesium ,Receptors, Immunologic ,Spleen ,Granulocytes - Abstract
Intact human granulocytes contain a leukotriene (LT) B4 receptor binding site, but the limited supply of these cells could adversely affect further progress of the study of this receptor. To select a tissue homogenate rich for this site, we have characterized the binding of highly specific [3H]LTB4 to guinea-pig spleen membranes and we have determined the ability of LTB4 to compete with [3H]LTB4 for binding sites in the membranes of 10 nonspleen tissues. In the spleen membrane, MgCl2 and CaCl2 enhanced [3H]LTB4 binding, but NaCl and KCl decreased it. Spleen [3H] LTB4 binding was a function of protein concentration and was rapid, reversible, stereoselective and saturable. Kinetic analyses showed that the rate constant for association and dissociation at 25 degrees C was 0.47 nM-1 min-1 and 0.099 min-1, respectively. A Scatchard plot of the data of the equilibrium experiment resulted a straight line with a dissociation constant of 1.8 nM and a density of 274 fmol/mg of protein. Moreover, the LTB4/[3H]LTB4 competition study performed at 4 or 25 degrees C revealed the inhibitory constant (Ki) of LTB4 to be in the nanomolar range. The rank order of agents competing for spleen [3H]LTB4 binding was: LTB4 (Ki = 2.8 nM) greater than 20-hydroxy-LTB4 (23 nM) greater than LTA4 (48 nM) greater than LTA4 methyl ester (0.13 microM) greater than 20-carboxy-LTB4 (greater than 6.6 microM) greater than or equal to arachidonic acid (0.15mM) = FPL-55,712 and FPL-57,231 (0.1-0.2 mM). Competition studies further indicated that felodipine, a 1,4-dihyropyridine Ca++ channel blocker, exhibited micromolar inhibition of spleen [3H]LTB4 binding.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1986
33. Effects of chronic histamine and ovalbumin aerosols on pulmonary beta adrenergic receptors in sensitized guinea pigs
- Author
-
J B, Cheng and R G, Townley
- Subjects
Aerosols ,Male ,Ovalbumin ,Guinea Pigs ,Receptors, Adrenergic, beta ,Animals ,Lung ,Asthma ,Histamine ,Receptors, Adrenergic - Abstract
Using (3H) dihydroalprenolol, we demonstrated that the concentration of pulmonary beta adrenergic receptor binding sites was lower in guinea pigs showing a marked bronchoconstrictive response to histamine and in ovalbumin-treated guinea pigs. This result suggests that the changed concentration of the pulmonary beta receptors in an animal model of asthma could be resulted from bronchoconstriction stress.
- Published
- 1982
34. A simple and sensitive radioreceptor assay for leukotrienes
- Author
-
Devendra K. Agrawal, F. Kohi, J. B. Cheng, Againdra K. Bewtra, and Robert G. Townley
- Subjects
Leukotriene E4 ,Leukotriene ,Chromatography ,Leukotriene D4 ,Chemistry ,Leukotriene B4 ,Guinea Pigs ,Ionophore ,Radioimmunoassay ,respiratory system ,Biochemistry ,High-performance liquid chromatography ,Radioligand Assay ,chemistry.chemical_compound ,Endocrinology ,Animals ,Humans ,lipids (amino acids, peptides, and proteins) ,Female ,SRS-A ,Lung ,Granulocytes - Abstract
A simple and sensitive radioreceptor assay (RRA) for leukotrienes (LTs) was developed using a highly specific [3H]leukotriene D4 (LTD4) binding to guinea pig lung membrane homogenates. The assay can detect down to 0.15 pmol of LTD4. The values for fifty percent inhibition of bound [3H]LTD4 was 1.5 nM for LTD4, 45 nM for LTC4 and 24 nM for LTE4. LTB4 at 3.0 X 10(-5)M had no effect on [3H]LTD4 binding. The RRA for LTs in the absence of serine-borate complex was bi-specific for both LTC4 and LTD4. However, in the presence of 20 mM serine-borate this method was highly specific for LTD4. Recovery rate averaged 87.2% after ethanol extraction and evaporation of known amounts of LTD4. When the radioreceptor assay and radioimmunoassay data for leukotriene levels in the samples were compared to each other, an excellent correlation was observed with a correlation coefficient 'r' of 0.992. The assay was also validated by quantitation of Lts released from human granulocytes stimulated with calcium ionophore, A23187. The method is simpler, less expensive, and more specific for LTD4 than the other methods such as high pressure liquid chromatography and radioimmunoassay and is suitable for routine measurement of either LTD4 specifically or LTC4 plus LTD4 simultaneously in one cell system.
- Published
- 1987
35. Involvement of peptidoleukotrienes in antigen-dependent thromboxane (TX) synthesis in IgG1-sensitized guinea pig lungs
- Author
-
J B, Cheng, J, Pillar, M, Conklyn, R, Breslow, J, Shirley, and H J, Showell
- Subjects
Receptors, Leukotriene ,Kinetics ,Leukotrienes ,Immunoglobulin G ,Guinea Pigs ,Immunization, Passive ,Animals ,Thromboxanes ,SRS-A ,Receptors, Immunologic ,Lung ,Histamine - Abstract
Lungs from IgG1-sensitized guinea pigs synthesize both leukotrienes (LTs) and thromboxane (Tx) upon ex vivo antigen challenge. This study was undertaken to investigate whether antigen-dependent Tx synthesis could result from prior formation of LTD4. In IgG1-sensitized lungs, LTD4 effectively induced Tx formation (ED50 = 2-4 nM). In these lungs, the levels of antigen-dependent formation of LTD4 (8-26 nM formed by 0.01-10 micrograms/ml antigen challenge) were 2-7 X greater than the ED50 value of LTD4-stimulated Tx synthesis. In addition, incubation of the sensitized lungs with ICI-198,615, a LTD4 antagonist, prior to antigen-challenge prevented Tx formation (IC50 = 0.01 microM). Our results indicate that LTD4 generated from IgG1-sensitized lungs could play a prominent role in stimulating Tx synthesis. LTC4 may also be involved because of rapid formation of LTC4 upon antigen-stimulation and its capacity to induce Tx synthesis.
- Published
- 1989
36. Differences in effect of 6-hydroxydopamine on the right and left atria from guinea-pig
- Author
-
J A, Bentley, S, Shibata, and J B, Cheng
- Subjects
Male ,Hydroxydopamines ,Nicotine ,Norepinephrine ,Catecholamines ,Guinea Pigs ,Animals ,Tyramine ,Female ,Heart Atria ,Piperazines - Abstract
The effect of chemical sympathectomy by 6-hydroxydopamine (6-OHDA) treatment was studied on guinea-pig atria. 6-OHDA treatment significantly reduced the positive inotropic effect of nicotine and tyramine on the left atrium, while similar treatment on the intact atria and the right atrium showed a decreased response to tyramine but not to nicotine. After 6-OHDA treatment the left atrium but not the right atrium showed supersensitivity to noradrenaline. The 6-OHDA induced reduction of catecholamine content and noradrenaline uptake was less effective on the right atrium in comparison to the left atrium and ventricles. After 6-OHDA treatment, tissue catecholamine fluorescence disappeared from all tissue layers of the left atrium but the number of specific fluorescent nerve terminals of the right atrium was only slightly decreased. These results indicate that adrenergic mechanisms of the right atrium exhibit higher resistance to sympathectomy by 6-OHDA than the left atrium.
- Published
- 1976
37. Pressor response to 5-hydroxytryptamine, norepinephrine and KCi in the perfused hindquarter preparation from the spontaneously hypertensive rat
- Author
-
J B, Cheng and S, Shibata
- Subjects
Male ,Perfusion ,Norepinephrine ,Serotonin ,Methysergide ,Hypertension ,Animals ,Blood Pressure ,Aorta, Abdominal ,Phentolamine ,Hindlimb ,Potassium Chloride ,Rats - Abstract
The pressor response to 5-hydroxytryptamine (5-HT), norepinephrine (NE), and KCI was studied in the blood- and Ringer's- perfused hindquarters of the spontaneously hypertensive rat (SHR) and the Kyoto normotensive Wistar rat in two age groups: 8 to 10 weeks and 6 to 8 months. In both preparations, the response to 5-HT, NE and KCI was greater in the young and old SHRs than in the age-matched normotensive Wistar rats. The enhanced responsiveness to 5-HT in old SHRs was of greater magnitude than that to NE or KCI, whereas in young SHRs the enhanced responsiveness to the three pressor agents was of similar magnitude. This appears to be due in part to a greater reduction in responsiveness to NE and KCI than to 5-HT as the animal becomes older. Enhanced responsiveness to 5-HT also occurs in the renal hypertensive rat. However, there was no difference in responsiveness to low doses of NE or KCI in the renal hypertensive rat. The response to 5-HT in the old SHR was blocked by methysergide but was not affected by phentolamine, isoproterenol or nitroglycerin. In the old SHR made hypotensive by occlusion of the abdominal aorta for a duration of 3 to 5 weeks, the responsiveness to all three pressor agents was reduced but was most marked for 5-HT. These latter results suggest that blood pressure per se contributes to the enhanced responsiveness to NE, KCI and, to a greater extent, 5-HT.
- Published
- 1980
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