16 results on '"Class-A"'
Search Results
2. Investigation and Modeling of the Behavior of Temperature Characteristics of 0.3–1.1 GHz Complementary Metal Oxide Semiconductor Class-A Broadband Power Amplifiers
- Author
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Ruiliang Li, Shaohua Zhou, Cheng Yang, and Jian Wang
- Subjects
PA ,temperature ,SVM ,model ,CMOS ,class-A ,Mechanical engineering and machinery ,TJ1-1570 - Abstract
A power amplifier (PA) stands as a central module within the electronic information system (EIS), and any variation in a PA’s specifications has a direct impact on the EIS’s performance, especially in the face of temperature fluctuations. In examining the influence of PA specification changes on the EIS, we employed support vector machine (SVM) to model the behavior of the temperature characteristics of 0.3–1.1 GHz complementary metal oxide semiconductor (CMOS) class-A broadband PAs. The results show that the parameters of S11, S12, S21, and S22 can be effectively modeled. SVM outperforms Elman and GRNN in terms of combined modeling time and modeling accuracy. This research can be extended to modeling the behavior of other types of power amplifiers or devices and circuits.
- Published
- 2024
- Full Text
- View/download PDF
3. Experimental Investigation of Relationship between Humidity Conditions and Degradation of Key Specifications of 0.1–1.2 GHz PA in 0.18 μm CMOS.
- Author
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Zhou, Shaohua, Yang, Cheng, and Wang, Jian
- Subjects
POWER amplifiers ,HUMIDITY ,THRESHOLD voltage - Abstract
The specification of power amplifiers (PA) is closely related to humidity variation, and few reports on the humidity properties of PA are available in the literature. Therefore, an experimental study of PA specifications was conducted under different humidity conditions to elucidate the relationship between the degradation of PA specifications and humidity conditions. This paper studies and provides results of the degradation of a PA subjected to different humidity levels. The experimental results show that the S
21 and output power decrease with the increase in humidity. The main cause of this degradation is the decrease in oxide capacitance and increase in threshold voltage with increasing humidity, resulting in a reduction of transconductance and an increase in on-resistance. The results of this study can guide designers in designing compensation circuits to achieve some degree of compensation for the degradation of PA specifications. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
4. A new very high output resistance FVF based class-A super-cascode CCII.
- Author
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Aggarwal, Bhawna, Yogi, Naveen, Ahmad, Imran, and Verma, Lakshay
- Subjects
- *
CURRENT conveyors , *LOW voltage systems , *VOLTAGE - Abstract
Second generation current conveyor (CCII) is a versatile fundamental building block that is used nowadays for designing of almost all kinds of current mode devises. A wide variety of CCII configuration offering diverse characteristics have been proposed in literature. However, not much effort has been put to improve the output resistance of this block. High output resistance is a very essential parameter that makes CCII a versatile block to be used in integrated circuits, without affecting its performance parameters. In this paper, an extensive survey has been carried out to explore high performance CCII topologies. Among these configurations flipped voltage follower (FVF) based class-A CCII architecture has been chosen because of its compact design, low voltage and current/voltage matching characteristics. Output resistance of this configuration has been increased by using super-cascode (SC) configuration and replacing the biasing circuitry by low voltage cascode current mirror. Small signal analysis of the proposed circuit has been carried out to mathematically validate the improvement achieved by this circuit. The proposed FVF based class-A SC-CCII offers very high output resistance while maintaining all the characteristics of FVF based class-A CCII. However, a small sacrifice has to be made in the required in supply voltage of the proposed design. The proposed CCII is simulated in LtSpice using 0.18 µm CMOS technology and is compared with various CCII configurations available in literature. The simulated results validate the high performance operation of the proposed SC-CCII and show that this block offers around 70 times increase in output resistance. The characteristic of this proposed SC-CCII makes it a versatile block to be used in wide applications with diverse characteristics. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
5. Experimental Investigation of Relationship between Humidity Conditions and Degradation of Key Specifications of 0.1–1.2 GHz PA in 0.18 μm CMOS
- Author
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Shaohua Zhou, Cheng Yang, and Jian Wang
- Subjects
class-A ,CMOS ,humidity ,performance degradation ,power amplifier (PA) ,Mechanical engineering and machinery ,TJ1-1570 - Abstract
The specification of power amplifiers (PA) is closely related to humidity variation, and few reports on the humidity properties of PA are available in the literature. Therefore, an experimental study of PA specifications was conducted under different humidity conditions to elucidate the relationship between the degradation of PA specifications and humidity conditions. This paper studies and provides results of the degradation of a PA subjected to different humidity levels. The experimental results show that the S21 and output power decrease with the increase in humidity. The main cause of this degradation is the decrease in oxide capacitance and increase in threshold voltage with increasing humidity, resulting in a reduction of transconductance and an increase in on-resistance. The results of this study can guide designers in designing compensation circuits to achieve some degree of compensation for the degradation of PA specifications.
- Published
- 2022
- Full Text
- View/download PDF
6. High Linearity Transmit Power Mixers Using Baseband Current Feedback.
- Author
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Praveen, M. V. and Krishnapura, Nagendra
- Subjects
BASEBAND ,CIRCUIT feedback ,POWER amplifiers ,PROTOTYPES ,LEAKAGE ,ELECTRIC power - Abstract
Transmit mixers frequently use Gilbert cells driven by common-source baseband amplifiers. Class-AB biasing is used in the latter for high efficiency, but this causes poor linearity. In this article, linearity is enhanced by using negative feedback to directly sense and linearize the baseband current flowing into the switching pair of the mixer. By suppressing both gate- and drain-induced nonlinearities, it achieves higher linearity and permits a higher power output compared to using replica devices of the common-source amplifiers in negative feedback. The technique is demonstrated using two prototypes: a 130 nm prototype designed for 1.9 GHz long term evolution (LTE) signals and a 65 nm LP prototype designed for Bluetooth basic data rate (BDR) and enhanced data rate (EDR) modes. The 130 nm prototype has an adjacent channel leakage ratio (ACLR) of −41.3/−40.4/−37.6 dBc for LTE5/10/20 at 11.7 dBm output, −148.6 dBc/Hz noise at 80 MHz offset for 10 dBm output, and −53.8 dBc CIM3 for 9 dBm output power. It consumes 335 mW from 3 V and 1.3 V supplies, including 79 mW in the LO buffers. The 4.4% efficiency represents 70% improvement over the state-of-the-art. The 65 nm prototype provides 4 dBm output power (EDR) while consuming 50.5 mW from 1.8 V. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
7. The impulsive noise reduction using it's replica signal under Class-A impulsive channel.
- Author
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Kitamura, Takuya, Ando, Hiroshi, Ohno, Kohei, and Itami, Makoto
- Abstract
In Power Line Communication (PLC), Orthogonal Frequency Division Multiplexing (OFDM) scheme is used mainly. In OFDM transmission, performance is degraded by the existence of time domain impulsive noise because the influence of impulsive noise is spread by Discrete Fourier Transform (DFT), if impulsive noise adds to the OFDM time signals. This noise has very wide bandwidth and it affects all the carriers in the OFDM symbol. Moreover, transmission characteristic is extremely degraded under multi-path channel. In this paper, the impulsive noise reduction scheme using the estimated replica signal is proposed. The proposed scheme can reduce the influence of additive impulsive noise in OFDM transmission under the Middleton Class A noise for PLC system. By computer simulation, the proposed scheme is compared with the conventional schemes of clipping and nulling on the bit error performance. From the simulation results, the proposed scheme is more effective to reduce the influence of impulsive noise than the conventional schemes. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
8. Bishop’s property (β) and weighted conditional type operators in k-quasi class A*n
- Author
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Azimi, Mohammad Reza, Akbarbaglu, İbrahim, and Abedi, Fahimeh
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Conditional expectation ,Pre-frame ,Tensor-products ,Spectrum ,Class-A ,Asterisk-class ,Measurable function ,Isolated points ,Weighted translation - Abstract
An operator T is said to be k-quasi class A*n operator if T*ᵏ (|Tⁿ⁺¹|²/ⁿ⁺¹− |T*|² ) Tᵏ ≥ 0, for some positive integers n and k. In this paper, we prove that the k-quasi class A*n operators have Bishop, s property (β). Then, we give a necessary and sufficient condition for T ⊗S to be a k-quasi class A*n operator, whenever T and S are both non-zero operators. Moreover, it is shown that the Riesz idempotent for a non-zero isolated point λ0 of a k-quasi class A*n operator T say Rᵢ, is self-adjoint and ran(Rᵢ) = ker(T −λ₀) = ker(T −λ₀)*. Finally, as an application in the last section, a necessary and sufficient condition is given in such a way that the weighted conditional type operators on L² (Σ), defined by Tw,u(f) := wE(uf), belong to k-quasi- A*n class. Publisher's Version
- Published
- 2020
9. Crescimento do meloeiro Cantaloupe sob manejo de irrigação por gotejamento em Janaúba, Minas Gerais.
- Author
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Carvalho Lemos, Lorena Moreira, Rodrigues dos Santos, Silvânio, and Lemos, João Paulo
- Subjects
MELONS ,ARID regions ,WATER quality management ,WATER in agriculture ,IRRIGATION management - Abstract
Copyright of Revista Ceres is the property of Revista Ceres and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2012
- Full Text
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10. A 60 GHz 19.6 dBm Power Amplifier With 18.3% PAE in 40 nm CMOS.
- Author
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Tseng, Chien-Wei and Wang, Yu-Jiu
- Abstract
This letter reports a fully integrated 60 GHz power amplifier (PA) implemented in TSMC 40 nm CMOS technology. This PA is based on a three-stage two-way differential topology with an output transformer-based power combining network. This topology improves layout symmetry and mitigates parasitic effects between different signal paths to increase overall efficiency. The use of parasitic coupling capacitors inside a vertically-coupled transformer can increase impedance transformation ratio. This PA achieves 20.3 dB power gain, 19.6 dBm output power with 18.3% peak PAE, and 12 GHz bandwidth. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
11. Class-A operation of an optically-pumped 1.6 µm-emitting quantum dash-based vertical-external-cavity surface-emitting laser on InP
- Author
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Salvatore, Pes, Cyril, Paranthoën, Christophe, Levallois, Nicolas, Chevalier, Cyril, Hamel, Kevin, Audo, Goulc'hen, Loas, Steve, Bouhier, Carmen, Gomez, Jean-Christophe, Harmand, Sophie, Bouchoule, Hervé, Folliot, Mehdi, Alouini, Institut des Fonctions Optiques pour les Technologies de l'informatiON (Institut FOTON), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Centre de Nanosciences et de Nanotechnologies [Marcoussis] (C2N), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), ANR, DGA, Région Bretagne, ANR-14-ASTR-0007,HYPOCAMP,Lasers à cavités verticales accordables hybrides , contrôlées en polarisation et entièrement monolithiques pour la conception systèmes optiques et micro-ondes embarqués et compacts.(2014), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Quantum dash lasers ,Semiconductor lasers ,[PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics] ,Vertical External Cavity Surface-Emitting Lasers ,Phase noise ,Class-A ,VECSEL ,Single-frequency ,Linewidth ,[SPI.MAT]Engineering Sciences [physics]/Materials ,RIN noise ,Semiconductor disk laser ,III V semiconductors ,[SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,[SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics - Abstract
International audience; A continuous-wave 1.6 µm-emitting InAs Quantum Dash-based Optically-Pumped Vertical-External-Cavity Surface-Emitting Laser on InP is demonstrated. The laser emits in the L-band with a stable linear polarization. Up to 163 mW output power has been obtained in multi-transverse mode regime. Single-frequency regime is achieved in the 1609-1622 nm range, with an estimated linewidth of 22 kHz in a 49 mm cavity, and a maximum emitted power of 7.9 mW at 1611 nm. In such conditions, the laser exhibits a Class-A behavior, with a cut-off frequency of 800 kHz and a shot-noise floor of −158 dB/Hz for 2 mA of detected photocurrent.
- Published
- 2017
- Full Text
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12. DESIGN AND SIMULATION OF A GENERAL PURPOSE, CLASS-A AMPLIFIER FOR HIGH TEMPERATURE APPLICATIONS
- Author
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Grgurich, Aaron James
- Subjects
- Electrical Engineering, Class-A, High-Temperature, Temperature, Amplifier
- Abstract
The advancements of high temperature sensors has created the need for high performance interface electronics, where in many applications, these sensors are deployed where wireless connectivity is the only practical option. In such cases, small sensor signals require on-board amplification. This thesis involves the development of a power amplifier designed to operate at 300℃. The Cree CRF24010D SiC MESFET was chosen as the active device due to its proven high temperature performance and mature Keysight, Advanced Design System (ADS) simulation model. The proposed amplifier utilizes capacitors and inductors designed and simulated using Sonnet and based on previously developed devices that exhibit stable operation at 300℃. Simulation results indicate that the amplifier exhibits a center frequency of 400 MHz, a 3dB passband of ~250 MHz, and a peak gain of 12 dB. These results compare favorably with the desired performance specifications, providing the technical justification for the future fabrication and high temperature testing of the amplifier.
- Published
- 2020
13. High throughput analysis of integron gene cassettes in wastewater environments
- Author
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Damiano Cacace, Christophe Merlin, Carsten Ulrich Schwermer, Joao Gatica, Despo Fatta-Kassinos, Edouard Jurkevitch, Stefan J. Green, Luigi Rizzo, Hemda Garelick, Thomas U. Berendonk, Thomas Schwartz, Eddie Cytryn, Norbert Kreuzinger, Vijay Tripathi, Célia M. Manaia, Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization - the Volcani Center, The Hebrew University of Jerusalem (HUJ), University of Illinois [Chicago] (UIC), University of Illinois System, Centro de Biotecnologia e Química Fina, Escola Superior de Biotecnologia, Universidade Católica Portuguesa [Porto], Institute for Hydrobiology, Technische Universität Dresden = Dresden University of Technology (TU Dresden), Institut für Hydrobiologie, Laboratoire de Chimie Physique et Microbiologie pour les Matériaux et l'Environnement (LCPME), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Vienna University of Technology, Karlsruhe Institute of Technology (KIT), University of Cyprus [Nicosia], Università degli Studi di Salerno (UNISA), Norwegian Institute for Water Research (NIVA), Middlesex University [London], and Veritati - Repositório Institucional da Universidade Católica Portuguesa
- Subjects
0301 basic medicine ,Sequence analysis ,Molecular Sequence Data ,030106 microbiology ,DIVERSITY ,Microbial Sensitivity Tests ,Wastewater ,010501 environmental sciences ,Biology ,Integron ,01 natural sciences ,complex mixtures ,beta-Lactam Resistance ,beta-Lactamases ,Integrons ,03 medical and health sciences ,ENTEROBACTERIACEAE ,Environmental Chemistry ,TREATMENT-PLANT ,Gene ,CLASS-A ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,Genetics ,[SDV.EE]Life Sciences [q-bio]/Ecology, environment ,METAL RESISTANCE ,ANTIBIOTIC-RESISTANCE GENES ,Sequence Analysis, DNA ,General Chemistry ,biochemical phenomena, metabolism, and nutrition ,[SDV.MP.BAC]Life Sciences [q-bio]/Microbiology and Parasitology/Bacteriology ,6. Clean water ,Anti-Bacterial Agents ,High throughput analysis ,SPECTRUM BETA-LACTAMASES ,CLASS-1 INTEGRON ,BACTERIAL COMMUNITIES ,MUNICIPAL ,Gene cassette ,biology.protein ,Amplicon sequencing ,Antibiotic resistance genes - Abstract
Integrons are extensively targeted as a proxy for anthropogenic impact in the environment. We developed a novel high-throughput amplicon sequencing pipeline that enables characterization of thousands of integron gene cassette-associated reads, and applied it to acquire a comprehensive overview of gene cassette composition in effluents from wastewater treatment facilities across Europe. Between 38 100 and 172 995 reads per-sample were generated and functionally characterized by screening against nr, SEED, ARDB and β-lactamase databases. Over 75% of the reads were characterized as hypothetical, but thousands were associated with toxin-antitoxin systems, DNA repair, cell membrane function, detoxification and aminoglycoside and β-lactam resistance. Among the reads characterized as β-lactamases, the carbapenemase blaOXA was dominant in most of the effluents, except for Cyprus and Israel where blaGES was also abundant. Quantitative PCR assessment of blaOXA and blaGES genes in the European effluents revealed similar trends to those displayed in the integron amplicon sequencing pipeline described above, corroborating the robustness of this method and suggesting that these integron-associated genes may be excellent targets for source tracking of effluents in downstream environments. Further application of the above analyses revealed several order-of-magnitude reductions in effluent-associated β-lactamase genes in effluent-saturated soils, suggesting marginal persistence in the soil microbiome.
- Published
- 2016
- Full Text
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14. Crescimento do meloeiro Cantaloupe sob manejo de irrigação por gotejamento em Janaúba, Minas Gerais
- Author
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Lemos, Lorena Moreira Carvalho, Santos, Silvânio Rodrigues dos, and Lemos, João Paulo
- Subjects
semiarid ,tanque Classe-A ,semiárido ,Class-A ,"Coronado F1" - Abstract
O manejo de água para a cultura do meloeiro é, sem dúvida, um dos aspectos que exige mais cuidados, isto porque as necessidades hídricas são bastante variáveis. Este trabalho teve por objetivo analisar o desenvolvimento vegetativo da variedade de meloeiro Cantaloupe "Coronado F1", sob manejo de irrigação simplificado, nas condições edafoclimáticas do semiárido mineiro (Janaúba-MG). O experimento foi realizado no Campus da UNIMONTES, em Janaúba-MG; o delineamento utilizado foi o de blocos casualizados, com cinco tratamentos e quatro repetições e os tratamentos foram: T1(testemunha): manejo recomendado por literatura; T2: 50% ECA (evaporação do tanque Classe-A); T3: 75% ECA; T4: 100% ECA; T5: 125% ECA. Avaliaram-se o comprimento e a largura da planta, o número de frutos/planta, o comprimento do maior ramo, a área sombreada. Para o teor de sólidos solúveis (°Brix), a classificação dos frutos na colheita, o peso do fruto, a relação de formato e a produtividade comercial, utilizaram-se 20 frutos/parcela. Os resultados indicaram que é possível utilizar como manejo da irrigação o método simplificado, baseado em frações do tanque Classe-A, em comparação com o método recomendado pela literatura para o plantio do meloeiro Cantaloupe "Coronado F1" e que as diferentes frações não influenciaram as características de pós-colheita do meloeiro. Water management for the melon crop is undoubtedly one aspect that requires more care, since the hydric needs are very variable. This study aimed to analyze the vegetative development of the cantaloupe "Coronado F1" melon under simplified irrigation management, in the soil and climatic conditions of the semi-arid region of Minas Gerais (Janaúba MG). The experiment was conducted in the campus of UNIMONTES in Janaúba-MG, arranged in randomized blocks with five treatments and four replicates. The treatments consisted of: T1 (control): management recommended by the literature, T2: 50% ECA (evaporation of the Class-A tank), T3: 75% ECA, T4: 100% ECA, T5: 125% ECA. The evaluated carachteristics included: the length and width of the plant, number of fruits/plant, length of the longest branch, the shaded area for the soluble solids content (° Brix), sorting of fruits at the time of harvest, fruit weight, shape and business productivity relationship. Twenty fruits were analyzed plot. The results indicated that it is possible to use as irrigation management, the simplified methodology based on fractions of the Class-A tank compared with the methodology recommended by the literature for the planting of Cantaloupe "Coronado F1" melon and that the different fractions did not influence the characteristics of postharvest of the crop.
- Published
- 2012
15. Lipid accumulation and dendritic cell dysfunction in cancer
- Author
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Vladimir A. Tyurin, Dmitry I. Gabrilovich, Donna L. Herber, Esteban Celis, Brianna Lennox, Yulia Nefedova, Hyun Ii Cho, Robert L. Ferris, Valerian E. Kagan, Srinivas Nagaraj, Stella C. Knight, Sergey V. Novitskiy, Alex Corzo, Scott J. Antonia, Wei Cao, Tapan A. Padhya, Mayer Fishman, Thomas V. McCaffrey, Judith C. McCaffrey, and Medical Research Council (MRC)
- Subjects
Research & Experimental Medicine ,CELL BIOLOGY ,ACTIVATION ,Mice ,0302 clinical medicine ,Neoplasms ,Tumor Cells, Cultured ,CLASS-A ,POLYUNSATURATED FATTY-ACIDS ,Mice, Knockout ,0303 health sciences ,Mice, Inbred BALB C ,biology ,Fatty Acids ,Scavenger Receptors, Class A ,hemic and immune systems ,MACROPHAGE SCAVENGER RECEPTOR ,General Medicine ,11 Medical And Health Sciences ,3. Good health ,Medicine, Research & Experimental ,lipids (amino acids, peptides, and proteins) ,Life Sciences & Biomedicine ,EXPRESSION ,Boron Compounds ,Biochemistry & Molecular Biology ,Spectrometry, Mass, Electrospray Ionization ,Antigen presentation ,Immunology ,INHIBITION ,chemical and pharmacologic phenomena ,IMMUNITY ,Major histocompatibility complex ,General Biochemistry, Genetics and Molecular Biology ,Article ,MATURATION ,03 medical and health sciences ,Immune system ,Antigen ,Downregulation and upregulation ,ANTIGEN PRESENTATION ,Animals ,Humans ,Scavenger receptor ,030304 developmental biology ,Fluorescent Dyes ,Science & Technology ,Lipid metabolism ,Dendritic cell ,Dendritic Cells ,Lipid Metabolism ,Mice, Inbred C57BL ,ATHEROSCLEROSIS ,biology.protein ,Neoplasm Transplantation ,030215 immunology - Abstract
Dendritic cells (DCs), a type of professional antigen-presenting cells, are responsible for initiation and maintenance of immune responses. Here we report that a substantial proportion of DCs in tumor-bearing mice and people with cancer have high amounts of triglycerides as compared with DCs from tumor-free mice and healthy individuals. In our studies, lipid accumulation in DCs was caused by increased uptake of extracellular lipids due to upregulation of scavenger receptor A. DCs with high lipid content were not able to effectively stimulate allogeneic T cells or present tumor-associated antigens. DCs with high and normal lipid levels did not differ in expression of major histocompatibility complex and co-stimulatory molecules. However, lipid-laden DCs had a reduced capacity to process antigens. Pharmacological normalization of lipid abundance in DCs with an inhibitor of acetyl-CoA carboxylase restored the functional activity of DCs and substantially enhanced the effects of cancer vaccines. These findings suggest that immune responses in cancer can be improved by manipulating the lipid levels in DCs.
- Published
- 2010
16. Role of macrophage scavenger receptors in atherosclerosis
- Author
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Kzhyshkowska, Julia, Neyen, Claudine, and Gordon, Siamon
- Subjects
Inflammation ,Monocyte-Derived Macrophages ,Macrophage ,Class-A ,Protein-Tyrosine Kinases ,Scavenger receptor ,Endocytosis ,Low-Density-Lipoprotein ,Surface-Connected Compartments ,Foam Cell-Formation ,Adhesion ,Sr-Bi ,Modified lipoproteins ,Cholesterol efflux ,Alternatively Activated Macrophages ,Microvascular Endothelial-Cells ,Smooth-Muscle-Cells ,Foam cell ,Migration - Abstract
Accumulating evidence indicates that atherosclerosis is a chronic inflammatory disease. The key innate immune cells that are involved in the pathogenesis of atherosclerosis are circulating monocytes and plaque macrophages. Complex interplay between immune and metabolic processes results in pathological activity of these cells. The best understood pathological process mediated by macrophages is their inability to process modified lipoproteins properly resulting in the formation of foamy cells, which are a dangerous component of atherosclerotic plaques. Key molecules involved in the recognition and processing of modified lipoproteins are scavenger receptors (SR). This is a large family of surface expressed structurally heterogeneous receptors with a broad spectrum of endogenous and exogenous ligands. The common functional feature of SR is internalisation of extracellular components and targeting them for lysosomal degradation. However, these relatively simple functions can have complex consequences, since they are linked to diverse specific signalling pathways and to other membrane transport pathways. Moreover, scavenger receptors can co-operate with other types of receptors increasing the variability of the macrophage response to multiple extracellular ligands. At least some SRs respond to modified lipoproteins by amplification of inflammation and accumulation of macrophages in the plaque, while some SRs may support tolerogenic reactions. Outcome of different SR activities will be the decision of monocytes and macrophage to guard homeostatic balance, support atherosclerosis progression and plaque instability by inflammatory reactions, or support rapid fibrotic processes in the plaque that stabilise it. Despite the accumulating knowledge about the molecular mechanisms of scavenger receptor action, their role in the progression of atherosclerosis remains controversial. The activities of scavenger receptors that can contribute to each of these processes are a subject of current review. (C) 2012 Elsevier GmbH. All rights reserved.
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