WorldWideScience

Sample records for cdr1 efflux pump

  1. Mitochondria influence CDR1 efflux pump activity, Hog1-mediated oxidative stress pathway, iron homeostasis, and ergosterol levels in Candida albicans.

    Science.gov (United States)

    Thomas, Edwina; Roman, Elvira; Claypool, Steven; Manzoor, Nikhat; Pla, Jesús; Panwar, Sneh Lata

    2013-11-01

    Mitochondrial dysfunction in Candida albicans is known to be associated with drug susceptibility, cell wall integrity, phospholipid homeostasis, and virulence. In this study, we deleted CaFZO1, a key component required during biogenesis of functional mitochondria. Cells with FZO1 deleted displayed fragmented mitochondria, mitochondrial genome loss, and reduced mitochondrial membrane potential and were rendered sensitive to azoles and peroxide. In order to understand the cellular response to dysfunctional mitochondria, genome-wide expression profiling of fzo1Δ/Δ cells was performed. Our results show that the increased susceptibility to azoles was likely due to reduced efflux activity of CDR efflux pumps, caused by the missorting of Cdr1p into the vacuole. In addition, fzo1Δ/Δ cells showed upregulation of genes involved in iron assimilation, in iron-sufficient conditions, characteristic of iron-starved cells. One of the consequent effects was downregulation of genes of the ergosterol biosynthesis pathway with a commensurate decrease in cellular ergosterol levels. We therefore connect deregulated iron metabolism to ergosterol biosynthesis pathway in response to dysfunctional mitochondria. Impaired activation of the Hog1 pathway in the mutant was the basis for increased susceptibility to peroxide and increase in reactive oxygen species, indicating the importance of functional mitochondria in controlling Hog1-mediated oxidative stress response. Mitochondrial phospholipid levels were also altered as indicated by an increase in phosphatidylserine and phosphatidylethanolamine and decrease in phosphatidylcholine in fzo1Δ/Δ cells. Collectively, these findings reinforce the connection between functional mitochondria and azole tolerance, oxidant-mediated stress, and iron homeostasis in C. albicans.

  2. Overcoming the heterologous bias: An in vivo functional analysis of multidrug efflux transporter, CgCdr1p in matched pair clinical isolates of Candida glabrata

    Energy Technology Data Exchange (ETDEWEB)

    Puri, Nidhi; Manoharlal, Raman; Sharma, Monika [Membrane Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067 (India); Sanglard, Dominique [Institut de Microbiologie, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne (Switzerland); Prasad, Rajendra, E-mail: rp47jnu@gmail.com [Membrane Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067 (India)

    2011-01-07

    Research highlights: {yields} First report to demonstrate an in vivo expression system of an ABC multidrug transporter CgCdr1p of C. glabrata. {yields} First report on the structure and functional characterization of CgCdr1p. {yields} Functional conservation of divergent but typical residues of CgCdr1p. {yields} CgCdr1p elicits promiscuity towards substrates and has a large drug binding pocket with overlapping specificities. -- Abstract: We have taken advantage of the natural milieu of matched pair of azole sensitive (AS) and azole resistant (AR) clinical isolates of Candida glabrata for expressing its major ABC multidrug transporter, CgCdr1p for structure and functional analysis. This was accomplished by tagging a green fluorescent protein (GFP) downstream of ORF of CgCDR1 and integrating the resultant fusion protein at its native chromosomal locus in AS and AR backgrounds. The characterization confirmed that in comparison to AS isolate, CgCdr1p-GFP was over-expressed in AR isolates due to its hyperactive native promoter and the GFP tag did not affect its functionality in either construct. We observed that in addition to Rhodamine 6 G (R6G) and Fluconazole (FLC), a recently identified fluorescent substrate of multidrug transporters Nile Red (NR) could also be expelled by CgCdr1p. Competition assays with these substrates revealed the presence of overlapping multiple drug binding sites in CgCdr1p. Point mutations employing site directed mutagenesis confirmed that the role played by unique amino acid residues critical to ATP catalysis and localization of ABC drug transporter proteins are well conserved in C. glabrata as in other yeasts. This study demonstrates a first in vivo novel system where over-expression of GFP tagged MDR transporter protein can be driven by its own hyperactive promoter of AR isolates. Taken together, this in vivo system can be exploited for the structure and functional analysis of CgCdr1p and similar proteins wherein the arte-factual concerns

  3. Multidrug Efflux Pumps in the Genus Erwinia: Physiology and Regulation of Efflux Pump Gene Expression.

    Science.gov (United States)

    Thekkiniath, J; Ravirala, R; San Francisco, M

    2016-01-01

    Plant pathogens belonging to the genus Erwinia cause diseases in several economically important plants. Plants respond to bacterial infection with a powerful chemical arsenal and signaling molecules to rid themselves of the microbes. Although our understanding of how Erwinia initiate infections in plants has become clear, a comprehensive understanding of how these bacteria rid themselves of noxious antimicrobial agents during the infection is important. Multidrug efflux pumps are key factors in bacterial resistance toward antibiotics by reducing the level of antimicrobial compounds in the bacterial cell. Erwinia induce the expression of efflux pump genes in response to plant-derived antimicrobials. The capability of Erwinia to co-opt plant defense signaling molecules such as salicylic acid to trigger multidrug efflux pumps might have developed to ensure bacterial survival in susceptible host plants. In this review, we discuss the developments in Erwinia efflux pumps, focusing in particular on efflux pump function and the regulation of efflux pump gene expression. PMID:27571694

  4. Vulvovaginal candidiasis: species distribution, fluconazole resistance and drug efflux pump gene overexpression.

    Science.gov (United States)

    Zhang, Jie-Yu; Liu, Jin-Hui; Liu, Fa-Di; Xia, Yan-Hua; Wang, Jing; Liu, Xi; Zhang, Zhi-Qin; Zhu, Na; Yan-Yan; Ying, Ying; Huang, Xiao-Tian

    2014-10-01

    The increasing incidence of vulvovaginal candidiasis (VVC) and the emergence of fluconazole resistance are an indisputable fact. However, little information is available regarding the correlation between fluconazole resistance in vaginal Candida albicans and the expression of drug efflux pump genes. In this study, we investigated the species distribution, fluconazole susceptibility profiles and the mechanisms of fluconazole resistance in Candida strains. In total, 785 clinical Candida isolates were collected from patients with VVC. C. albicans was the most frequently isolated species(n = 529) followed by C. glabrata (n = 164) and C. krusei (n = 57). Of all Candida isolates, 4.7% were resistant to fluconazole. We randomly selected 18 fluconazole resistant isolates of C. albicans to evaluate the expression of CDR1, CDR2, MDR1 and FLU1 genes. Compared with fluconazole-susceptible C. albicans isolates, CDR1 gene expression displayed 3.16-fold relative increase, which was statistically significant. CDR2, MDR1 and FLU1 overexpression was observed in several fluconazole-resistant C. albicans isolates, but statistical significance was not achieved. These results demonstrate a high frequency of non-albicans species (32.6%); however, C. albicans is the most common Candida species implicated in vaginitis, and this strain displays considerable fluconazole resistance. Meanwhile, our study further indicates that fluconazole resistance in C. albicans may correlate with CDR1 gene overexpression.

  5. Biochemistry of Bacterial Multidrug Efflux Pumps

    Directory of Open Access Journals (Sweden)

    Sanath Kumar

    2012-04-01

    Full Text Available Bacterial pathogens that are multi-drug resistant compromise the effectiveness of treatment when they are the causative agents of infectious disease. These multi-drug resistance mechanisms allow bacteria to survive in the presence of clinically useful antimicrobial agents, thus reducing the efficacy of chemotherapy towards infectious disease. Importantly, active multi-drug efflux is a major mechanism for bacterial pathogen drug resistance. Therefore, because of their overwhelming presence in bacterial pathogens, these active multi-drug efflux mechanisms remain a major area of intense study, so that ultimately measures may be discovered to inhibit these active multi-drug efflux pumps.

  6. Modified host cells with efflux pumps

    Energy Technology Data Exchange (ETDEWEB)

    Dunlop, Mary J.; Keasling, Jay D.; Mukhopadhyay, Aindrila

    2016-08-30

    The present invention provides for a modified host cell comprising a heterologous expression of an efflux pump capable of transporting an organic molecule out of the host cell wherein the organic molecule at a sufficiently high concentration reduces the growth rate of or is lethal to the host cell.

  7. Efflux Pump-Mediated Resistance in Chemotherapy

    OpenAIRE

    Ughachukwu, PO; Unekwe, PC

    2012-01-01

    Efflux pump mechanisms perform important physiological functions such as prevention of toxin absorption from the gastrointestinal tract, elimination of bile from the hepatocytes, effective functioning of the blood–brain barrier and placental barrier, and renal excretion of drugs. They exist in all living cells, but those in the bacterial and mammalian cells are more important to the clinician and pharmacologist, as they constitute an important cause of antimicrobial drug resistance, which con...

  8. Targeting efflux pumps to overcome antifungal drug resistance.

    Science.gov (United States)

    Holmes, Ann R; Cardno, Tony S; Strouse, J Jacob; Ivnitski-Steele, Irena; Keniya, Mikhail V; Lackovic, Kurt; Monk, Brian C; Sklar, Larry A; Cannon, Richard D

    2016-08-01

    Resistance to antifungal drugs is an increasingly significant clinical problem. The most common antifungal resistance encountered is efflux pump-mediated resistance of Candida species to azole drugs. One approach to overcome this resistance is to inhibit the pumps and chemosensitize resistant strains to azole drugs. Drug discovery targeting fungal efflux pumps could thus result in the development of azole-enhancing combination therapy. Heterologous expression of fungal efflux pumps in Saccharomyces cerevisiae provides a versatile system for screening for pump inhibitors. Fungal efflux pumps transport a range of xenobiotics including fluorescent compounds. This enables the use of fluorescence-based detection, as well as growth inhibition assays, in screens to discover compounds targeting efflux-mediated antifungal drug resistance. A variety of medium- and high-throughput screens have been used to identify a number of chemical entities that inhibit fungal efflux pumps. PMID:27463566

  9. Bacterial Multidrug Efflux Pumps: Much More Than Antibiotic Resistance Determinants

    OpenAIRE

    Paula Blanco; Sara Hernando-Amado; Jose Antonio Reales-Calderon; Fernando Corona; Felipe Lira; Manuel Alcalde-Rico; Alejandra Bernardini; Maria Blanca Sanchez; Jose Luis Martinez

    2016-01-01

    Bacterial multidrug efflux pumps are antibiotic resistance determinants present in all microorganisms. With few exceptions, they are chromosomally encoded and present a conserved organization both at the genetic and at the protein levels. In addition, most, if not all, strains of a given bacterial species present the same chromosomally-encoded efflux pumps. Altogether this indicates that multidrug efflux pumps are ancient elements encoded in bacterial genomes long before the recent use of ant...

  10. How to Measure Export via Bacterial Multidrug Resistance Efflux Pumps

    Science.gov (United States)

    Blair, Jessica M. A.

    2016-01-01

    ABSTRACT Bacterial multidrug resistance (MDR) efflux pumps are an important mechanism of antibiotic resistance and are required for many pathogens to cause infection. They are also being harnessed to improve microbial biotechnological processes, including biofuel production. Therefore, scientists of many specialties must be able to accurately measure efflux activity. However, myriad methodologies have been described and the most appropriate method is not always clear. Within the scientific literature, many methods are misused or data arising are misinterpreted. The methods for measuring efflux activity can be split into two groups, (i) those that directly measure efflux and (ii) those that measure the intracellular accumulation of a substrate, which is then used to infer efflux activity. Here, we review the methods for measuring efflux and explore the most recent advances in this field, including single-cell or cell-free technologies and mass spectrometry, that are being used to provide more detailed information about efflux pump activity. PMID:27381291

  11. How to Measure Export via Bacterial Multidrug Resistance Efflux Pumps.

    Science.gov (United States)

    Blair, Jessica M A; Piddock, Laura J V

    2016-01-01

    Bacterial multidrug resistance (MDR) efflux pumps are an important mechanism of antibiotic resistance and are required for many pathogens to cause infection. They are also being harnessed to improve microbial biotechnological processes, including biofuel production. Therefore, scientists of many specialties must be able to accurately measure efflux activity. However, myriad methodologies have been described and the most appropriate method is not always clear. Within the scientific literature, many methods are misused or data arising are misinterpreted. The methods for measuring efflux activity can be split into two groups, (i) those that directly measure efflux and (ii) those that measure the intracellular accumulation of a substrate, which is then used to infer efflux activity. Here, we review the methods for measuring efflux and explore the most recent advances in this field, including single-cell or cell-free technologies and mass spectrometry, that are being used to provide more detailed information about efflux pump activity. PMID:27381291

  12. Efflux pump inhibitors: targeting mycobacterial efflux systems to enhance TB therapy.

    Science.gov (United States)

    Pule, Caroline M; Sampson, Samantha L; Warren, Robin M; Black, Philippa A; van Helden, Paul D; Victor, Tommie C; Louw, Gail E

    2016-01-01

    The emergence of drug resistance continues to plague TB control, with a global increase in the prevalence of MDR-TB. This acts as a gateway to XDR-TB and thus emphasizes the urgency for drug development and optimal treatment options. Bedaquiline is the first new anti-TB drug approved by the FDA in 40 years and has been shown to be an effective treatment option for MDR Mycobacterium tuberculosis infection. Bedaquiline has also recently been included in clinical trials for new regimens with the aim of improving and shortening treatment periods. Alarmingly, efflux-mediated bedaquiline resistance, as well as efflux-mediated cross-resistance to clofazimine, has been identified in treatment failures. This mechanism of resistance results in efflux of a variety of anti-TB drugs from the bacterial cell, thereby decreasing the intracellular drug concentration. In doing so, the bacillus is able to render the antibiotic treatment ineffective. Recent studies have explored strategies to reverse the resistance phenotype conferred by efflux pump activation. It was observed that the addition of efflux pump inhibitors partially restored drug susceptibility in vitro and in vivo. This has significant clinical implications, especially in MDR-TB management where treatment options are extremely limited. This review aims to highlight the current efflux pump inhibitors effective against M. tuberculosis, the effect of efflux pump inhibitors on mycobacterial growth and the clinical promise of treatment with efflux pump inhibitors and standard anti-TB therapy. PMID:26472768

  13. Bacterial Multidrug Efflux Pumps: Much More Than Antibiotic Resistance Determinants

    Directory of Open Access Journals (Sweden)

    Paula Blanco

    2016-02-01

    Full Text Available Bacterial multidrug efflux pumps are antibiotic resistance determinants present in all microorganisms. With few exceptions, they are chromosomally encoded and present a conserved organization both at the genetic and at the protein levels. In addition, most, if not all, strains of a given bacterial species present the same chromosomally-encoded efflux pumps. Altogether this indicates that multidrug efflux pumps are ancient elements encoded in bacterial genomes long before the recent use of antibiotics for human and animal therapy. In this regard, it is worth mentioning that efflux pumps can extrude a wide range of substrates that include, besides antibiotics, heavy metals, organic pollutants, plant-produced compounds, quorum sensing signals or bacterial metabolites, among others. In the current review, we present information on the different functions that multidrug efflux pumps may have for the bacterial behaviour in different habitats as well as on their regulation by specific signals. Since, in addition to their function in non-clinical ecosystems, multidrug efflux pumps contribute to intrinsic, acquired, and phenotypic resistance of bacterial pathogens, the review also presents information on the search for inhibitors of multidrug efflux pumps, which are currently under development, in the aim of increasing the susceptibility of bacterial pathogens to antibiotics.

  14. A D-octapeptide drug efflux pump inhibitor acts synergistically with azoles in a murine oral candidiasis infection model.

    Science.gov (United States)

    Hayama, Kazumi; Ishibashi, Hiroko; Ishijima, Sanae A; Niimi, Kyoko; Tansho, Shigeru; Ono, Yasuo; Monk, Brian C; Holmes, Ann R; Harding, David R K; Cannon, Richard D; Abe, Shigeru

    2012-03-01

    Clinical management of patients undergoing treatment of oropharyngeal candidiasis with azole antifungals can be impaired by azole resistance. High-level azole resistance is often caused by the overexpression of Candida albicans efflux pump Cdr1p. Inhibition of this pump therefore represents a target for combination therapies that reverse azole resistance. We assessed the therapeutic potential of the D-octapeptide derivative RC21v3, a Cdr1p inhibitor, in the treatment of murine oral candidiasis caused by either the azole-resistant C. albicans clinical isolate MML611 or its azole-susceptible parental strain MML610. RC21v3, fluconazole (FLC), or a combination of both drugs were administered orally to immunosuppressed ICR mice at 3, 24, and 27 h after oral inoculation with C. albicans. FLC protected the mice inoculated with MML610 from oral candidiasis, but was only partially effective in MML611-infected mice. The co-application of RC21v3 (0.02 μmol per dose) potentiated the therapeutic performance of FLC for mice infected with either strain. It caused a statistically significant decrease in C. albicans cfu isolated from the oral cavity of the infected mice and reduced oral lesions. RC21v3 also enhanced the therapeutic activity of itraconazole against MML611 infection. These results indicate that RC21v3 in combination with azoles has potential as a therapy against azole-resistant oral candidiasis.

  15. Inactivation of Efflux Pumps Abolishes Bacterial Biofilm Formation

    DEFF Research Database (Denmark)

    Kvist, Malin; Hancock, Viktoria; Klemm, Per

    2008-01-01

    to get rid of toxic substances. We discovered that efflux pumps are highly active in bacterial biofilms, thus making efflux pumps attractive targets for antibiofilm measures. A number of efflux pump inhibitors (EPIs) are known. EPIs were shown to reduce biofilm formation, and in combination they could...... abolish biofilm formation completely. Also, EPIs were able to block the antibiotic tolerance of biofilms. The results of this feasibility study might pave the way for new treatments for biofilm-related infections and may be exploited for prevention of biofilms in general.......Bacterial biofilms cause numerous problems in health care and industry; notably, biofilms are associated with a large number of infections. Biofilm-dwelling bacteria are particularly resistant to antibiotics, making it hard to eradicate biofilm-associated infections. Bacteria rely on efflux pumps...

  16. New methods for the identification of efflux mediated MDR bacteria, genetic assessment of regulators and efflux pump constituents, characterization of efflux systems and screening for inhibitors of efflux pumps

    DEFF Research Database (Denmark)

    Viveiros, M; Martins, M; Couto, I;

    2008-01-01

    We have developed a number of methods that identify efflux pump mediated multi-drug resistant bacteria, characterize efflux systems and screen for inhibitors of efflux pumps. These approaches were complemented by the quantification of the expression of genes that regulate and code for constituents...

  17. Efflux Pump Control Alters Synthetic Gene Circuit Function.

    Science.gov (United States)

    Diao, Junchen; Charlebois, Daniel A; Nevozhay, Dmitry; Bódi, Zoltán; Pál, Csaba; Balázsi, Gábor

    2016-07-15

    Synthetic biology aims to design new biological systems for predefined purposes, such as the controlled secretion of biofuels, pharmaceuticals, or other chemicals. Synthetic gene circuits regulating an efflux pump from the ATP-binding cassette (ABC) protein family could achieve this. However, ABC efflux pumps can also drive out intracellular inducer molecules that control the gene circuits. This will introduce an implicit feedback that could alter gene circuit function in ways that are poorly understood. Here, we used two synthetic gene circuits inducible by tetracycline family molecules to regulate the expression of a yeast ABC pump (Pdr5p) that pumps out the inducer. Pdr5p altered the dose-responses of the original gene circuits substantially in Saccharomyces cerevisiae. While one aspect of the change could be attributed to the efflux pumping function of Pdr5p, another aspect remained unexplained. Quantitative modeling indicated that reduced regulator gene expression in addition to efflux pump function could fully explain the altered dose-responses. These predictions were validated experimentally. Overall, we highlight how efflux pumps can alter gene circuit dynamics and demonstrate the utility of mathematical modeling in understanding synthetic gene circuit function in new circumstances. PMID:27111147

  18. Current Advances in Developing Inhibitors of Bacterial Multidrug Efflux Pumps.

    Science.gov (United States)

    Mahmood, Hannah Y; Jamshidi, Shirin; Sutton, J Mark; Rahman, Khondaker M

    2016-01-01

    Antimicrobial resistance represents a significant challenge to future healthcare provision. An acronym ESKAPEE has been derived from the names of the organisms recognised as the major threats although there are a number of other organisms, notably Neisseria gonorrhoeae, that have become equally challenging to treat in the clinic. These pathogens are characterised by the ability to rapidly develop and/or acquire resistance mechanisms in response to exposure to different antimicrobial agents. A key part of the armoury of these pathogens is a series of efflux pumps, which effectively exclude or reduce the intracellular concentration of a large number of antibiotics, making the pathogens significantly more resistant. These efflux pumps are the topic of considerable interest, both from the perspective of basic understanding of efflux pump function, and its role in drug resistance but also as targets for the development of novel adjunct therapies. The necessity to overcome antimicrobial resistance has encouraged investigations into the characterisation of resistance-modifying efflux pump inhibitors to block the mechanisms of drug extrusion, thereby restoring antibacterial susceptibility and returning existing antibiotics into the clinic. A greater understanding of drug recognition and transport by multidrug efflux pumps is needed to develop clinically useful inhibitors, given the breadth of molecules that can be effluxed by these systems. This review discusses different bacterial EPIs originating from both natural source and chemical synthesis and examines the challenges to designing successful EPIs that can be useful against multidrug resistant bacteria. PMID:26947776

  19. Efflux Pump-mediated Drug Resistance in Burkholderia

    Directory of Open Access Journals (Sweden)

    Nicole L Podnecky

    2015-04-01

    Full Text Available Several members of the genus Burkholderia are prominent pathogens. Infections caused by these bacteria are difficult to treat because of significant antibiotic resistance. Virtually all Burkholderia species are also resistant to polymyxin, prohibiting use of drugs like colistin that are available for treatment of infections caused by most other drug resistant Gram-negative bacteria. Despite clinical significance and antibiotic resistance of Burkholderia species, characterization of efflux pumps lags behind other non-enteric Gram-negative pathogens such as Acinetobacter baumannii and Pseudomonas aeruginosa. Although efflux pumps have been described in several Burkholderia species, they have been best studied in B. cenocepacia and B. pseudomallei. As in other non-enteric Gram-negatives, efflux pumps of the resistance nodulation cell division (RND family are the clinically most significant efflux systems in these two species. Several efflux pumps were described in B. cenocepacia, which when expressed confer resistance to clinically significant antibiotics, including aminoglycosides, chloramphenicol, fluoroquinolones, and tetracyclines. Three RND pumps have been characterized in B. pseudomallei, two of which confer either intrinsic or acquired resistance to aminoglycosides, macrolides, chloramphenicol, fluoroquinolones, tetracyclines, trimethoprim, and in some instances trimethoprim+sulfamethoxazole. Several strains of the host-adapted B. mallei, a clone of B. pseudomallei, lack AmrAB-OprA and are therefore aminoglycoside and macrolide susceptible. B. thailandensis is closely related to B. pseudomallei, but non-pathogenic to humans. Its pump repertoire and ensuing drug resistance profile parallels that of B. pseudomallei. An efflux pump in B. vietnamiensis plays a significant role in acquired aminoglycoside resistance. Summarily, efflux pumps are significant players in Burkholderia drug resistance.

  20. Functionally Relevant Residues of Cdr1p: A Multidrug ABC Transporter of Human Pathogenic Candida albicans

    Directory of Open Access Journals (Sweden)

    Rajendra Prasad

    2011-01-01

    Full Text Available Reduced intracellular accumulation of drugs (due to rapid efflux mediated by the efflux pump proteins belonging to ABC (ATP Binding Cassette and MFS (Major Facilitators superfamily is one of the most common strategies adopted by multidrug resistance (MDR pathogenic yeasts. To combat MDR, it is essential to understand the structure and function of these transporters so that inhibitors/modulators to these can be developed. The sequence alignments of the ABC transporters reveal selective divergence within much conserved domains of Nucleotide-Binding Domains (NBDs which is unique to all fungal transporters. Recently, the role of conserved but divergent residues of Candida Drug Resistance 1 (CDR1, an ABC drug transporter of human pathogenic Candida albicans, has been examined with regard to ATP binding and hydrolysis. In this paper, we focus on some of the recent advances on the relevance of divergent and conserved amino acids of CaCdr1p and also discuss as to how drug interacts with Trans Membrane Domains (TMDs residues for its extrusion from MDR cells.

  1. Biochemistry of Bacterial Multidrug Efflux Pumps

    OpenAIRE

    Sanath Kumar; Varela, Manuel F.

    2012-01-01

    Bacterial pathogens that are multi-drug resistant compromise the effectiveness of treatment when they are the causative agents of infectious disease. These multi-drug resistance mechanisms allow bacteria to survive in the presence of clinically useful antimicrobial agents, thus reducing the efficacy of chemotherapy towards infectious disease. Importantly, active multi-drug efflux is a major mechanism for bacterial pathogen drug resistance. Therefore, because of their overwhelming presence in ...

  2. Tripartite assembly of RND multidrug efflux pumps

    Science.gov (United States)

    Daury, Laetitia; Orange, François; Taveau, Jean-Christophe; Verchère, Alice; Monlezun, Laura; Gounou, Céline; Marreddy, Ravi K. R.; Picard, Martin; Broutin, Isabelle; Pos, Klaas M.; Lambert, Olivier

    2016-02-01

    Tripartite multidrug efflux systems of Gram-negative bacteria are composed of an inner membrane transporter, an outer membrane channel and a periplasmic adaptor protein. They are assumed to form ducts inside the periplasm facilitating drug exit across the outer membrane. Here we present the reconstitution of native Pseudomonas aeruginosa MexAB-OprM and Escherichia coli AcrAB-TolC tripartite Resistance Nodulation and cell Division (RND) efflux systems in a lipid nanodisc system. Single-particle analysis by electron microscopy reveals the inner and outer membrane protein components linked together via the periplasmic adaptor protein. This intrinsic ability of the native components to self-assemble also leads to the formation of a stable interspecies AcrA-MexB-TolC complex suggesting a common mechanism of tripartite assembly. Projection structures of all three complexes emphasize the role of the periplasmic adaptor protein as part of the exit duct with no physical interaction between the inner and outer membrane components.

  3. Engineering microbial biofuel tolerance and export using efflux pumps.

    Science.gov (United States)

    Dunlop, Mary J; Dossani, Zain Y; Szmidt, Heather L; Chu, Hou Cheng; Lee, Taek Soon; Keasling, Jay D; Hadi, Masood Z; Mukhopadhyay, Aindrila

    2011-05-10

    Many compounds being considered as candidates for advanced biofuels are toxic to microorganisms. This introduces an undesirable trade-off when engineering metabolic pathways for biofuel production because the engineered microbes must balance production against survival. Cellular export systems, such as efflux pumps, provide a direct mechanism for reducing biofuel toxicity. To identify novel biofuel pumps, we used bioinformatics to generate a list of all efflux pumps from sequenced bacterial genomes and prioritized a subset of targets for cloning. The resulting library of 43 pumps was heterologously expressed in Escherichia coli, where we tested it against seven representative biofuels. By using a competitive growth assay, we efficiently distinguished pumps that improved survival. For two of the fuels (n-butanol and isopentanol), none of the pumps improved tolerance. For all other fuels, we identified pumps that restored growth in the presence of biofuel. We then tested a beneficial pump directly in a production strain and demonstrated that it improved biofuel yields. Our findings introduce new tools for engineering production strains and utilize the increasingly large database of sequenced genomes.

  4. Farnesol, a Potential Efflux Pump Inhibitor in Mycobacterium smegmatis

    Directory of Open Access Journals (Sweden)

    Jing Jin

    2010-10-01

    Full Text Available The active multidrug efflux pump (EP has been described as one of the mechanisms involved in the natural drug resistance of bacteria, such as mycobacteria. As a result, the development of efflux pumps inhibitors (EPIs is an important topic. In this study, a checkerboard synergy assay indicated that farnesol both decreased the minimum inhibitory concentration (MIC of ethidium bromide (EtBr 8-fold against Mycobacterium smegmatis (M. smegmatis mc2155 ATCC 700084 when incorporated at a concentration of 32 μg/mL (FICI = 0.625 and decreased MIC 4-fold at 16 μg/mL (FICI = 0.375. Farnesol also showed synergism when combined with rifampicin. A real-time 96-well plate fluorometric method was used to assess the ability of farnesol to inhibit EPs in comparison withfour positive EPIs: chlorpromazine, reserpine, verapamil, and carbonyl cyanide m-chlorophenylhydrazone (CCCP. Farnesol significantly enhanced the accumulation of EtBr and decreased the efflux of EtBr in M. smegmatis; these results suggest that farnesol acts as an inhibitor of mycobacterial efflux pumps.

  5. Multidrug efflux pumps of Gram-positive bacteria.

    Science.gov (United States)

    Schindler, Bryan D; Kaatz, Glenn W

    2016-07-01

    Gram-positive organisms are responsible for some of the most serious of human infections. Resistance to front-line antimicrobial agents can complicate otherwise curative therapy. These organisms possess multiple drug resistance mechanisms, with drug efflux being a significant contributing factor. Efflux proteins belonging to all five transporter families are involved, and frequently can transport multiple structurally unrelated compounds resulting in a multidrug resistance (MDR) phenotype. In addition to clinically relevant antimicrobial agents, MDR efflux proteins can transport environmental biocides and disinfectants which may allow persistence in the healthcare environment and subsequent acquisition by patients or staff. Intensive research on MDR efflux proteins and the regulation of expression of their genes is ongoing, providing some insight into the mechanisms of multidrug recognition and transport. Inhibitors of many of these proteins have been identified, including drugs currently being used for other indications. Structural modifications guided by structure-activity studies have resulted in the identification of potent compounds. However, lack of broad-spectrum pump inhibition combined with potential toxicity has hampered progress. Further work is required to gain a detailed understanding of the multidrug recognition process, followed by application of this knowledge in the design of safer and more highly potent inhibitors. PMID:27449594

  6. Modulation of Bacterial Multidrug Resistance Efflux Pumps of the Major Facilitator Superfamily

    Directory of Open Access Journals (Sweden)

    Sanath Kumar

    2013-01-01

    Full Text Available Bacterial infections pose a serious public health concern, especially when an infectious disease has a multidrug resistant causative agent. Such multidrug resistant bacteria can compromise the clinical utility of major chemotherapeutic antimicrobial agents. Drug and multidrug resistant bacteria harbor several distinct molecular mechanisms for resistance. Bacterial antimicrobial agent efflux pumps represent a major mechanism of clinical resistance. The major facilitator superfamily (MFS is one of the largest groups of solute transporters to date and includes a significant number of bacterial drug and multidrug efflux pumps. We review recent work on the modulation of multidrug efflux pumps, paying special attention to those transporters belonging primarily to the MFS.

  7. Method for Regulated Expression of Single-Copy Efflux Pump Genes in a Surrogate Pseudomonas aeruginosa Strain: Identification of the BpeEF-OprC Chloramphenicol and Trimethoprim Efflux Pump of Burkholderia pseudomallei 1026b

    OpenAIRE

    Kumar, Ayush; Chua, Kim-Lee; Schweizer, Herbert P.

    2006-01-01

    Construction and integration of recombinant mini-Tn7 expression vectors into the chromosome of a surrogate, efflux-sensitized, and biosafe Pseudomonas aeruginosa host was validated as a generally applicable method for studies of uncharacterized bacterial efflux pumps. Using this method, the Burkholderia pseudomallei bpeEF-oprC operon was shown to encode a chloramphenicol and trimethoprim efflux pump.

  8. Resistance to Antimicrobials Mediated by Efflux Pumps in Staphylococcus aureus

    OpenAIRE

    Isabel Couto; Leonard Amaral; José Melo-Cristino; Miguel Viveiros; Cláudia Palma; Elisabete Junqueira; Costa, Sofia S.

    2013-01-01

    Resistance mediated by efflux has been recognized in Staphylococcus aureus in the last few decades, although its clinical relevance has only been recognized recently. The existence of only a few studies on the individual and overall contribution of efflux to resistance phenotypes associated with the need of well-established methods to assess efflux activity in clinical isolates contributes greatly to the lack of solid knowledge of this mechanism in S. aureus. This study aims to provide inform...

  9. A Microfluidic Device for Simple and Rapid Evaluation of Multidrug Efflux Pump Inhibitors

    OpenAIRE

    Iino, Ryota; Nishino, Kunihiko; Noji, Hiroyuki; Yamaguchi, Akihito; Matsumoto, Yoshimi

    2012-01-01

    Recently, multidrug-resistant pathogens have disseminated widely owing essentially to their increased multidrug efflux pump activity. Presently, there is a scarcity of new antibacterial agents, and hence, inhibitors of multidrug efflux pumps belonging to the resistance–nodulation–cell division (RND) family appear useful in the treatment of infections by multidrug-resistant pathogens. Moreover, recent progress in microfabrication technologies has expanded the application of nano/micro-devices ...

  10. A microfluidic device for simple and rapid evaluation of multidrug efflux pump inhibitors

    OpenAIRE

    Ryota eIino; Kunihiko eNishino; Hiroyuki eNoji; Akihito eYamaguchi; Yoshimi eMatsumoto

    2012-01-01

    Recently, multidrug resistant pathogens have disseminated widely owing essentially to their increased multidrug efflux pump activity. Presently, there is a scarcity of new antibacterial agents, and hence, inhibitors of multidrug efflux pumps belonging to the resistance-nodulation-cell division (RND) family appear useful in the treatment of infections by multidrug-resistant pathogens. Moreover, recent progress in microfabrication technologies has expanded the application of nano/micro-devices ...

  11. The Efflux Pump Inhibitor Timcodar Improves the Potency of Antimycobacterial Agents

    OpenAIRE

    Grossman, Trudy H.; Shoen, Carolyn M.; Jones, Steven M.; Peter L Jones; Cynamon, Michael H.; Locher, Christopher P.

    2014-01-01

    Previous studies indicated that inhibition of efflux pumps augments tuberculosis therapy. In this study, we used timcodar (formerly VX-853) to determine if this efflux pump inhibitor could increase the potency of antituberculosis (anti-TB) drugs against Mycobacterium tuberculosis in in vitro and in vivo combination studies. When used alone, timcodar weakly inhibited M. tuberculosis growth in broth culture (MIC, 19 μg/ml); however, it demonstrated synergism in drug combination studies with rif...

  12. Crystal structure of the Neisseria gonorrhoeae MtrD inner membrane multidrug efflux pump.

    Directory of Open Access Journals (Sweden)

    Jani Reddy Bolla

    Full Text Available Neisseria gonorrhoeae is an obligate human pathogen and the causative agent of the sexually-transmitted disease gonorrhea. The control of this disease has been compromised by the increasing proportion of infections due to antibiotic-resistant strains, which are growing at an alarming rate. The MtrCDE tripartite multidrug efflux pump, belonging to the hydrophobic and amphiphilic efflux resistance-nodulation-cell division (HAE-RND family, spans both the inner and outer membranes of N. gonorrhoeae and confers resistance to a variety of antibiotics and toxic compounds. We here report the crystal structure of the inner membrane MtrD multidrug efflux pump, which reveals a novel structural feature that is not found in other RND efflux pumps.

  13. Overexpression of MexAB-OprM efflux pump in carbapenem-resistant Pseudomonas aeruginosa.

    Science.gov (United States)

    Pan, Ya-Ping; Xu, Yuan-Hong; Wang, Zhong-Xin; Fang, Ya-Ping; Shen, Ji-Lu

    2016-08-01

    Efflux pump systems are one of the most important mechanisms conferring multidrug resistance in Pseudomonas aeruginosa. MexAB-OprM efflux pump is one of the largest multi-drug resistant efflux pumps with high-level expression, which is controlled by regulatory genes mexR, nalC, and nalD. This study investigated the role of efflux pump MexAB-OprM in 75 strains of carbapenem-resistant P. aeruginosa and evaluated the influence of point mutation of the regulatory genes. The minimum inhibitory concentrations of imipenem and meropenem, with or without MC207110, an efflux pump inhibitor, were determined by agar dilution method to select the positive strains for an overexpressed active efflux pump. Carba NP test and EDTA-disk synergy test were used for the detection of carbapenemase and metallo-β-lactamases, respectively. The gene mexA, responsible for the fusion protein structure, and the reference gene rpoD of the MexAB-OprM pump were amplified by real-time PCR. The quantity of relative mRNA expression was determined simultaneously. By PCR method, the efflux regulatory genes mexR, nalC, and nalD and outer membrane protein OprD2 were amplified for the strains showing overexpression of MexAB-OprM and subsequently analyzed by BLAST. Among the 75 P. aeruginosa strains, the prevalence of efflux pump-positive phenotype was 17.3 % (13/75). Carba NP test and EDTA-disk synergy test were all negative in the 13 strains. PCR assay results showed that ten strains overexpressed the MexAB-OprM efflux pump and were all positive for the regulatory genes mexR, nalC, and nalD. Sequence analysis indicated that of the ten isolates, nine had a mutation (Gly → Glu) at 71st amino acid position in NalC, and eight also had a mutation (Ser → Arg) at 209th position in NalC. Only one strain had a mutation (Thr → Ile) at the 158th amino acid position in NalD, whereas eight isolates had mutations in MexR. In conclusion, overexpression of efflux pump MexAB-OprM plays an important role in

  14. Resistance to Antimicrobials Mediated by Efflux Pumps in Staphylococcus aureus

    Directory of Open Access Journals (Sweden)

    Isabel Couto

    2013-03-01

    Full Text Available Resistance mediated by efflux has been recognized in Staphylococcus aureus in the last few decades, although its clinical relevance has only been recognized recently. The existence of only a few studies on the individual and overall contribution of efflux to resistance phenotypes associated with the need of well-established methods to assess efflux activity in clinical isolates contributes greatly to the lack of solid knowledge of this mechanism in S. aureus. This study aims to provide information on approaches useful to the assessment and characterization of efflux activity, as well as contributing to our understanding of the role of efflux to phenotypes of antibiotic resistance and biocide tolerance in S. aureus clinical isolates. The results described show that efflux is an important contributor to fluoroquinolone resistance in S. aureus and suggest it as a major mechanism in the early stages of resistance development. We also show that efflux plays an important role on the reduced susceptibility to biocides in S. aureus, strengthening the importance of this long neglected resistance mechanism to the persistence and proliferation of antibiotic/biocide-resistant S. aureus in the hospital environment.

  15. Efflux pump genes of the resistance-nodulation-division family in Burkholderia cenocepacia genome

    Directory of Open Access Journals (Sweden)

    Manina Giulia

    2006-07-01

    Full Text Available Abstract Background Burkholderia cenocepacia is recognized as opportunistic pathogen that can cause lung infections in cystic fibrosis patients. A hallmark of B. cenocepacia infections is the inability to eradicate the organism because of multiple intrinsic antibiotic resistance. As Resistance-Nodulation-Division (RND efflux systems are responsible for much of the intrinsic multidrug resistance in Gram-negative bacteria, this study aims to identify RND genes in the B. cenocepacia genome and start to investigate their involvement into antimicrobial resistance. Results Genome analysis and homology searches revealed 14 open reading frames encoding putative drug efflux pumps belonging to RND family in B. cenocepacia J2315 strain. By reverse transcription (RT-PCR analysis, it was found that orf3, orf9, orf11, and orf13 were expressed at detectable levels, while orf10 appeared to be weakly expressed in B. cenocepacia. Futhermore, orf3 was strongly induced by chloramphenicol. The orf2 conferred resistance to fluoroquinolones, tetraphenylphosphonium, streptomycin, and ethidium bromide when cloned and expressed in Escherichia coli KAM3, a strain lacking the multidrug efflux pump AcrAB. The orf2-overexpressing E. coli also accumulate low concentrations of ethidium bromide, which was restored to wild type level in the presence of CCCP, an energy uncoupler altering the energy of the drug efflux pump. Conclusion The 14 RND pumps gene we have identified in the genome of B. cenocepacia suggest that active efflux could be a major mechanism underlying antimicrobial resistance in this microorganism. We have characterized the ORF2 pump, one of these 14 potential RND efflux systems. Its overexpression in E. coli conferred resistance to several antibiotics and to ethidium bromide but it remains to be determined if this pump play a significant role in the antimicrobial intrinsic resistance of B. cenocepacia. The characterization of antibiotic efflux pumps in B

  16. Action of cholecalciferol and alpha-tocopherol on Staphylococcus aureus efflux pumps.

    Science.gov (United States)

    Tintino, Saulo R; Morais-Tintino, Cícera D; Campina, Fábia F; Pereira, Raimundo L; Costa, Maria do S; Braga, Maria Flaviana B M; Limaverde, Paulo W; Andrade, Jacqueline C; Siqueira-Junior, José P; Coutinho, Henrique Douglas Melo; Balbino, Valdir Q; Leal-Balbino, Tereza C; Ribeiro-Filho, Jaime; Quintans-Júnior, Lucindo J

    2016-01-01

    Alpha-tocopherol is one the most abundant and biologically active isoforms of vitamin E. This compound is a potent antioxidant and one of most studied isoforms of vitamin E. Vitamin D3 (cholecalciferol) is an important nutrient for calcium homeostasis and bone health, that has also been recognized as a potent modulator of the immune response. Methicillin-resistant Staphylococcus aureus (MRSA) is the most important causative agent of both nosocomial and community-acquired infections. The aim of this study was to evaluate the inhibitory effect of alpha-tocopherol and cholecalciferol on both S. aureus and multidrug resistant S. aureus efflux pumps. The RN4220 strain has the plasmid pUL5054 that is the carrier of gene that encodes the macrolide resistance protein (an efflux pump) MsrA; the IS-58 strain possesses the TetK tetracycline efflux protein in its genome and the 1199B strain resists to hydrophilic fluoroquinolones via a NorA-mediated mechanism. The antibacterial activity was evaluated by determining the Minimal Inhibitory Concentration (MIC) and a possible inhibition of efflux pumps was associated to a reduction of the MIC. In this work we observed that in the presence of the treatments there was a decrease in the MIC for the RN4220 and IS-58 strains, suggesting that the substances presented an inhibitory effect on the efflux pumps of these strains. Significant efforts have been done to identify efflux pump inhibitors (EPIs) from natural sources and, therefore, the antibacterial properties of cholecalciferol and alpha-tocopherol might be attributed to a direct effect on the bacterial cell depending on their amphipathic structure. PMID:27298617

  17. Outer Membrane Protein Changes and Efflux Pump Expression Together May Confer Resistance to Ertapenem in Enterobacter cloacae

    OpenAIRE

    Szabó, Dóra; Silveira, Fernanda; Hujer, Andrea M.; Robert A Bonomo; Hujer, Kristine M.; Jane W Marsh; Bethel, Christopher R.; Doi, Yohei; Deeley, Kathleen; Paterson, David L.

    2006-01-01

    We investigated ertapenem-susceptible and -resistant extended-spectrum β-lactamase-producing Enterobacter cloacae isolates obtained from the same patient. Gene transcription of OmpD and OmpF was diminished in the ertapenem-resistant isolate. An efflux pump inhibitor decreased the MICs of ertapenem in the resistant strain, suggesting a potential role of efflux pumps in ertapenem resistance.

  18. Use and engineering of efflux pumps for the export of olefins in microbes

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, Aindrila [Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States)

    2016-07-14

    The scope of the project is to investigate efflux pump systems in engineered host microorganisms, such as E. coli, and develop a pump engineered to export a target compound. To initiate the project in coordination with other TOTAL driven projects, the first target compound to be studied was 1-hexene. However, we were investigating other chemicals as Styrene. The main goal of the project was to generate a set of optimized efflux pump systems for microorganisms (E. coli and Streptomyces or other host) engineered to contain biosynthetic pathways to export large titers of target compounds that are toxic (or accumulate and push back biosynthesis) to the host cell. An optimized microbial host will utilize specific and efficient cell wall located pumps to extrude harmful target compounds and enable greater production of these compounds.

  19. Expression of Multidrug Efflux Pump SmeDEF by Clinical Isolates of Stenotrophomonas maltophilia

    OpenAIRE

    Alonso, Ana; Jose L Martinez

    2001-01-01

    The presence of the multidrug efflux pump SmeDEF was assessed in a collection of clinical isolates of Stenotrophomonas maltophilia. All isolates encoded this pump, as demonstrated by PCR. Forty-seven percent of the strains overproduced a protein of the same size that was immunoreactive against an anti-SmeF antibody, and 33% overexpressed the gene semD when they were tested by reverse transcription-PCR. A correlation between smeDEF overexpression and antibiotic resistance was observed.

  20. Multidrug resistance in oncology and beyond : from imaging of drug efflux pumps to cellular drug targets

    NARCIS (Netherlands)

    Nagengast, Wouter B; Oude Munnink, Thijs H; Dijkers, Eli; Hospers, Geesiena; Brouwers, Adrienne H; Schröder, Carolien P; Lub-de Hooge, Marjolijn; de Vries, Elisabeth G E

    2010-01-01

    Resistance of tumor cells to several structurally unrelated classes of natural products, including anthracyclines, taxanes, and epipodophyllotoxines, is often referred as multidrug resistance (MDR). This is associated with ATP-binding cassette transporters, which function as drug efflux pumps such a

  1. The prevalence of OqxAB multidrug efflux pump amongst olaquindox resistant Escherichia coli in pigs

    DEFF Research Database (Denmark)

    Hansen, L. H.; Sørensen, S. J.; Jørgensen, H. S.;

    2005-01-01

    The quinoxaline olaquindox has been used extensively as a growth promoter for pigs. Recently, we isolated a plasmid (pOLA52) conferring resistance to olaquindox from swine manure. On this plasmid, the oqxA and oqxB genes encode an RND-family multidrug efflux pump, OqxAB. It facilitates resistance...

  2. Multidrug Efflux Pumps Attenuate the Effect of MGMT Inhibitors.

    Science.gov (United States)

    Tomaszowski, Karl-Heinz; Schirrmacher, Ralf; Kaina, Bernd

    2015-11-01

    Various mechanisms of drug resistance attenuate the effectiveness of cancer therapeutics, including drug transport and DNA repair. The DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) is a key factor determining the resistance against alkylating anticancer drugs inducing the genotoxic DNA lesions O(6)-methylguanine and O(6)-chloroethylguanine, and MGMT inactivation or depletion renders cells more susceptible to treatment with methylating and chloroethylating agents. Highly specific and efficient inhibitors of the repair protein MGMT were designed, including O(6)-benzylguanine (O(6)BG) and O(6)-(4-bromothenyl)guanine (O(6)BTG) that are nontoxic on their own. Unfortunately, these inhibitors do not select between MGMT in normal and cancer cells, causing nontarget effects in the healthy tissue. Therefore, a targeting strategy for MGMT inhibitors is required. Here, we used O(6)BG and O(6)BTG conjugated to β-d-glucose (O(6)BG-Glu and O(6)BTG-Glu, respectively) in order to selectively inhibit MGMT in tumors, harnessing their high demand for glucose. Both glucose conjugates efficiently inhibited MGMT in several cancer cell lines, but with different extents of sensitization to DNA alkylating agents, with lomustine being more effective than temozolomide. We further show that the glucose conjugates are subject to ATP-binding cassette (ABC) transporter mediated efflux, involving P-glycoprotein, MRP1, and BCRP, which impacts the efficiency of MGMT inhibition. Surprisingly, also O(6)BG and O(6)BTG were subject to an active transport out of the cell. We also show that pharmacological inhibition of efflux transporters increases the induction of cell death following treatment with these MGMT inhibitors and temozolomide. We conclude that strategies of attenuating the efflux by ABC transporters are required for achieving successful MGMT targeting. PMID:26379107

  3. Prevalence of Multidrug Efflux Pump Requiring Ciprofloxacin, Ofloxacin and Pefloxacin as Substrates, Among Clinical Isolates of Pseudomonas aeruginosa

    Directory of Open Access Journals (Sweden)

    Omoregie, R.

    2007-01-01

    Full Text Available Forty two consecutive clinical isolates of Pseudomonas aeruginosa were screened for the presence of reserpine inhibited multidrug (MDR efflux pump, utilizing ciprofloxacin ofloxacin and/or pefloxacin as substrates, by determining the minimum inhibitory concentration in the presence and absence of 100 mg/L reserpine. The result showed that 50% of the Pseudomonas aeruginosa isolates possessed reserpine inhibited MDR efflux pump. MDR efflux pump requiring ofloxacin (40.48% were significantly (p<0.01 more among the isolates when compared with those requiring ciprofloxacin (16.67% or pefloxacin (11.90%. Only one isolate possessed reserpine inhibited MDR efflux pumps that utilize all three fluiroquinolones. Research into suitable combination of antibacterials and appropriate pump mactivators or antibacterials that are less likely to be substrate for MDR pumps is advocated.

  4. A microfluidic device for simple and rapid evaluation of multidrug efflux pump inhibitors

    Directory of Open Access Journals (Sweden)

    Ryota eIino

    2012-02-01

    Full Text Available Recently, multidrug resistant pathogens have disseminated widely owing essentially to their increased multidrug efflux pump activity. Presently, there is a scarcity of new antibacterial agents, and hence, inhibitors of multidrug efflux pumps belonging to the resistance-nodulation-cell division (RND family appear useful in the treatment of infections by multidrug-resistant pathogens. Moreover, recent progress in microfabrication technologies has expanded the application of nano/micro-devices to the field of human healthcare, such as the detection of infections and diagnosis of diseases. We developed a microfluidic channel device for a simple and rapid evaluation of bacterial drug efflux activity. By combining the microfluidic device with a fluorogenic compound, fluorescein-di-β-D-galactopyranoside, which is hydrolyzed to a fluorescent dye in the cytoplasm of Escherichia coli, we successfully evaluated the effects of inhibitors on the RND-type multidrug efflux pumps MexAB-OprM and MexXY-OprM from Pseudomonas aeruginosa in E. coli. Our new method successfully detected the MexB-specific inhibitory effect of D13-9001 and revealed an unexpected membrane-permeabilizing effect of Phe-Arg-β-naphthylamide, which has long been used as an inhibitor.

  5. Structure of the periplasmic adaptor protein from a major facilitator superfamily (MFS) multidrug efflux pump

    OpenAIRE

    Hinchliffe, Philip; Greene, Nicholas P.; Paterson, Neil G.; Crow, Allister; Hughes, Colin; Koronakis, Vassilis

    2014-01-01

    Periplasmic adaptor proteins are key components of bacterial tripartite efflux pumps. The 2.85 Å resolution structure of an MFS (major facilitator superfamily) pump adaptor, Aquifex aeolicus EmrA, shows linearly arranged α-helical coiled-coil, lipoyl, and β-barrel domains, but lacks the fourth membrane-proximal domain shown in other pumps to interact with the inner membrane transporter. The adaptor α-hairpin, which binds outer membrane TolC, is exceptionally long at 127 Å, and the β-barrel co...

  6. The Role of Efflux Pumps in Schistosoma mansoni Praziquantel Resistant Phenotype

    Science.gov (United States)

    Armada, Ana; Belo, Silvana; Carrilho, Emanuel; Viveiros, Miguel; Afonso, Ana

    2015-01-01

    Background Schistosomiasis is a neglected disease caused by a trematode of the genus Schistosoma that is second only to malaria in public health significance in Africa, South America, and Asia. Praziquantel (PZQ) is the drug of choice to treat this disease due to its high cure rates and no significant side effects. However, in the last years increasingly cases of tolerance to PZQ have been reported, which has caused growing concerns regarding the emergency of resistance to this drug. Methodology/Principal Findings Here we describe the selection of a parasitic strain that has a stable resistance phenotype to PZQ. It has been reported that drug resistance in helminths might involve efflux pumps such as members of ATP-binding cassette transport proteins, including P-glycoprotein and multidrug resistance-associated protein families. Here we evaluate the role of efflux pumps in Schistosoma mansoni resistance to PZQ, by comparing the efflux pumps activity in susceptible and resistant strains. The evaluation of the efflux activity was performed by an ethidium bromide accumulation assay in presence and absence of Verapamil. The role of efflux pumps in resistance to PZQ was further investigated comparing the response of susceptible and resistant parasites in the absence and presence of different doses of Verapamil, in an ex vivo assay, and these results were further reinforced through the comparison of the expression levels of SmMDR2 RNA by RT-PCR. Conclusions/Significance This work strongly suggests the involvement of Pgp-like transporters SMDR2 in Praziquantel drug resistance in S. mansoni. Low doses of Verapamil successfully reverted drug resistance. Our results might give an indication that a combination therapy with PZQ and natural or synthetic Pgp modulators can be an effective strategy for the treatment of confirmed cases of resistance to PZQ in S. mansoni. PMID:26445012

  7. The quorum-sensing molecule farnesol is a modulator of drug efflux mediated by ABC multidrug transporters and synergizes with drugs in Candida albicans.

    Science.gov (United States)

    Sharma, Monika; Prasad, Rajendra

    2011-10-01

    Overexpression of the CaCDR1-encoded multidrug efflux pump protein CaCdr1p (Candida drug resistance protein 1), belonging to the ATP binding cassette (ABC) superfamily of transporters, is one of the most prominent contributors of multidrug resistance (MDR) in Candida albicans. Thus, blocking or modulating the function of the drug efflux pumps represents an attractive approach in combating MDR. In the present study, we provide first evidence that the quorum-sensing molecule farnesol (FAR) is a specific modulator of efflux mediated by ABC multidrug transporters, such as CaCdr1p and CaCdr2p of C. albicans and ScPdr5p of Saccharomyces cerevisiae. Interestingly, FAR did not modulate the efflux mediated by the multidrug extrusion pump protein CaMdr1p, belonging to the major facilitator superfamily (MFS). Kinetic data revealed that FAR competitively inhibited rhodamine 6G efflux in CaCdr1p-overexpressing cells, with a simultaneous increase in an apparent K(m) without affecting the V(max) values and the ATPase activity. We also observed that when used in combination, FAR at a nontoxic concentration synergized with the drugs at their respective nonlethal concentrations, as was evident from their resistant clinical isolates of C. albicans. Our biochemical experiments revealed that the synergistic interaction of FAR with the drugs led to reactive oxygen species accumulation, which triggered early apoptosis, and that both could be partly reversed by the addition of an antioxidant. Collectively, FAR modulates drug extrusion mediated exclusively by ABC proteins and is synergistic to fluconazole (FLC), ketoconazole (KTC), miconazole (MCZ), and amphotericin (AMB). PMID:21768514

  8. Efflux pump inhibitors (EPIs as new antimicrobial agents against Pseudomonas aeruginosa

    Directory of Open Access Journals (Sweden)

    Momen Askoura

    2011-05-01

    Full Text Available Pseudomonas aeruginosa is an opportunistic human pathogen and one of the leading causes of nosocomial infections worldwide. The difficulty in treatment of pseudomonas infections arises from being multidrug resistant (MDR and exhibits resistance to most antimicrobial agents due to the expression of different mechanisms overcoming their effects. Of these resistance mechanisms, the active efflux pumps in Pseudomonas aeruginosa that belong to the resistance nodulation division (RND plays a very important role in extruding the antibiotics outside the bacterial cells providing a protective means against their antibacterial activity. Beside its role against the antimicrobial agents, these pumps can extrude biocides, detergents, and other metabolic inhibitors. It is clear that efflux pumps can be targets for new antimicrobial agents. Peptidomimetic compounds such as phenylalanine arginyl β-naphthylamide (PAβN have been introduced as efflux pump inhibitors (EPIs; their mechanism of action is through competitive inhibition with antibiotics on the efflux pump resulting in increased intracellular concentration of antibiotic, hence, restoring its antibacterial activity. The advantage of EPIs is the difficulty to develop bacterial resistance against them, but the disadvantage is their toxic property hindering their clinical application. The structure activity relationship of these compounds showed other derivatives from PAβN that are higher in their activity with higher solubility in biological fluids and decreased toxicity level. This raises further questions on how can we compact Pseudomonas infections. Of particular importance, the recent resurgence in the use of older antibiotics such as polymyxins and probably applying stricter control measures in order to prevent their spread in clinical sittings.

  9. Structure of the periplasmic adaptor protein from a major facilitator superfamily (MFS) multidrug efflux pump.

    Science.gov (United States)

    Hinchliffe, Philip; Greene, Nicholas P; Paterson, Neil G; Crow, Allister; Hughes, Colin; Koronakis, Vassilis

    2014-08-25

    Periplasmic adaptor proteins are key components of bacterial tripartite efflux pumps. The 2.85 Å resolution structure of an MFS (major facilitator superfamily) pump adaptor, Aquifex aeolicus EmrA, shows linearly arranged α-helical coiled-coil, lipoyl, and β-barrel domains, but lacks the fourth membrane-proximal domain shown in other pumps to interact with the inner membrane transporter. The adaptor α-hairpin, which binds outer membrane TolC, is exceptionally long at 127 Å, and the β-barrel contains a conserved disordered loop. The structure extends the view of adaptors as flexible, modular components that mediate diverse pump assembly, and suggests that in MFS tripartite pumps a hexamer of adaptors could provide a periplasmic seal. PMID:24996185

  10. AcrAB efflux pump plays a role in decreased susceptibility to tigecycline in Morganella morganii.

    Science.gov (United States)

    Ruzin, Alexey; Keeney, David; Bradford, Patricia A

    2005-02-01

    Transposon mutagenesis of a clinical isolate of Morganella morganii, G1492 (tigecycline MIC of 4 microg/ml), yielded two insertion knockout mutants for which tigecycline MICs were 0.03 microg/ml. Transposon insertions mapped to acrA, which is constitutively overexpressed in G1492, suggesting a role of the AcrAB efflux pump in decreased susceptibility to tigecycline in M. morganii.

  11. Prevalence and role of efflux pump activity in ciprofloxacin resistance in clinical isolates of Klebsiella pneumoniae

    OpenAIRE

    Aathithan, S.; French, G L

    2011-01-01

    Abstract We investigated the prevalence and role of efflux pump activity and possible drug influx resistance in ciprofloxacin susceptibility amongst 26 distinct clinical isolates of Klebsiella pneumoniae of varying ciprofloxacin susceptibilities and known quinolone resistance-determining region (QRDR) genotypes. Cellular [14C]ciprofloxacin accumulation patterns and the amount of cell-associated [14C]ciprofloxacin of mid-logarithmic phase cells were determined before and after chall...

  12. Cloning of a Cation Efflux Pump Gene Associated with Chlorhexidine Resistance in Klebsiella pneumoniae

    OpenAIRE

    Fang, Chi-Tai; Chen, Haur-Chuan; Chuang, Yi-Ping; Chang, Shan-Chwen; Wang, Jin-Town

    2002-01-01

    Expression libraries of a chlorhexidine-resistant Klebsiella pneumoniae strain were constructed and transformed into Escherichia coli XLOLR. Twenty chlorhexidine-resistant transformants were obtained after selection. All clones contained a novel 903-nucleotide locus. Its sequences were compatible with a cation efflux pump, and the locus was thus designated as cepA. Retransformation using cepA-containing plasmids conferred chlorhexidine resistance to both XLOLR and a chlorhexidine-sensitive K....

  13. Broad Specificity Efflux pumps and Their Role in Multidrug Resistance of Gram Negative Bacteria

    OpenAIRE

    Nikaido, Hiroshi; Pagès, Jean-Marie

    2011-01-01

    Antibiotic resistance mechanisms reported in Gram-negative bacteria are producing a worldwide health problem. The continuous dissemination of «multi-drug resistant» (MDR) bacteria drastically reduces the efficacy of our antibiotic “arsenal” and consequently increases the frequency of therapeutic failure. In MDR bacteria, the over-expression of efflux pumps that expel structurally-unrelated drugs contributes to the reduced susceptibility by decreasing the intracellular concentration of antibio...

  14. Influence of efflux pump inhibitors on the multidrug resistance of Helicobacter pylori

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    AIM:To evaluate the effect of efflux pump inhibitors (EPIs) on multidrug resistance of Helicobacter pylori (H. pylori).METHODS: H. pylori strains were isolated and cultured on Brucella agar plates with 10% sheep's blood. The multidrug resistant (MDR) H. pylori were obtained with the inducer chloramphenicol by repeated doubling of the concentration until no colony was seen, then the susceptibilities of the MDR strains and their parents to 9 antibiotics were assessed with agar dilution tests. The present stud...

  15. EFFECTS OF PSYCHOTROPIC DRUGS AS BACTERIAL EFFLUX PUMP INHIBITORS ON QUORUM SENSING REGULATED BEHAVIORS

    OpenAIRE

    Aynur Aybey; Alev Usta; Elif Demirkan

    2014-01-01

    Psychotropic drugs are known to have antimicrobial activity against several groups of microorganisms. The antidepressant agents such as duloxetine, paroxetine, hydroxyzine and venlafaxine are shown to act as efflux pump inhibitors in bacterial cells. In order to the investigation of the effects of psychotropic drugs were determined for clinically significant pathogens by using standart broth microdillusion method. The anti-quorum sensing (anti-QS) activity of psychotropic drugs was tested aga...

  16. Multidrug Efflux Pumps from Enterobacteriaceae, Vibrio cholerae and Staphylococcus aureus Bacterial Food Pathogens

    Directory of Open Access Journals (Sweden)

    Jody L. Andersen

    2015-01-01

    Full Text Available Foodborne illnesses caused by bacterial microorganisms are common worldwide and constitute a serious public health concern. In particular, microorganisms belonging to the Enterobacteriaceae and Vibrionaceae families of Gram-negative bacteria, and to the Staphylococcus genus of Gram-positive bacteria are important causative agents of food poisoning and infection in the gastrointestinal tract of humans. Recently, variants of these bacteria have developed resistance to medically important chemotherapeutic agents. Multidrug resistant Escherichia coli, Salmonella enterica, Vibrio cholerae, Enterobacter spp., and Staphylococcus aureus are becoming increasingly recalcitrant to clinical treatment in human patients. Of the various bacterial resistance mechanisms against antimicrobial agents, multidrug efflux pumps comprise a major cause of multiple drug resistance. These multidrug efflux pump systems reside in the biological membrane of the bacteria and actively extrude antimicrobial agents from bacterial cells. This review article summarizes the evolution of these bacterial drug efflux pump systems from a molecular biological standpoint and provides a framework for future work aimed at reducing the conditions that foster dissemination of these multidrug resistant causative agents through human populations.

  17. Palytoxin induces K+ efflux from yeast cells expressing the mammalian sodium pump.

    Science.gov (United States)

    Scheiner-Bobis, G; Meyer zu Heringdorf, D; Christ, M; Habermann, E

    1994-06-01

    Palytoxin causes potassium efflux and sodium influx in all investigated animals cells. Much evidence points to the sodium pump (Na+/K(+)-ATPase) as the target of the toxin. A heterologous expression system for mammalian Na+/K(+)-ATPase in the brewers yeast Saccharomyces cerevisiae has been used to test this hypothesis. Yeast cells do not contain endogenous sodium pumps but can be transformed with vectors coding for the alpha and beta subunits of the mammalian sodium pump. We now show that transformed yeast cells expressing both alpha and beta subunits of Na+/K(+)-ATPase are highly sensitive to the toxin, as measured by the loss of intracellular potassium. Palytoxin-induced potassium efflux is completely inhibited by 500 microM ouabain. In contrast, nontransformed yeast cells or cells expressing either the alpha or beta subunits are insensitive to palytoxin. Thus, the alpha/beta heterodimer of the sodium pump is required for the release of potassium induced by palytoxin. The results suggest that palytoxin converts the sodium pump into an open channel, allowing the passage of alkali ions.

  18. Structure of the AcrAB-TolC multidrug efflux pump.

    Science.gov (United States)

    Du, Dijun; Wang, Zhao; James, Nathan R; Voss, Jarrod E; Klimont, Ewa; Ohene-Agyei, Thelma; Venter, Henrietta; Chiu, Wah; Luisi, Ben F

    2014-05-22

    The capacity of numerous bacterial species to tolerate antibiotics and other toxic compounds arises in part from the activity of energy-dependent transporters. In Gram-negative bacteria, many of these transporters form multicomponent 'pumps' that span both inner and outer membranes and are driven energetically by a primary or secondary transporter component. A model system for such a pump is the acridine resistance complex of Escherichia coli. This pump assembly comprises the outer-membrane channel TolC, the secondary transporter AcrB located in the inner membrane, and the periplasmic AcrA, which bridges these two integral membrane proteins. The AcrAB-TolC efflux pump is able to transport vectorially a diverse array of compounds with little chemical similarity, thus conferring resistance to a broad spectrum of antibiotics. Homologous complexes are found in many Gram-negative species, including in animal and plant pathogens. Crystal structures are available for the individual components of the pump and have provided insights into substrate recognition, energy coupling and the transduction of conformational changes associated with the transport process. However, how the subunits are organized in the pump, their stoichiometry and the details of their interactions are not known. Here we present the pseudo-atomic structure of a complete multidrug efflux pump in complex with a modulatory protein partner from E. coli. The model defines the quaternary organization of the pump, identifies key domain interactions, and suggests a cooperative process for channel assembly and opening. These findings illuminate the basis for drug resistance in numerous pathogenic bacterial species. PMID:24747401

  19. The pseudo-atomic structure of an RND-type tripartite multidrug efflux pump.

    Science.gov (United States)

    Du, Dijun; Voss, Jarrod; Wang, Zhao; Chiu, Wah; Luisi, Ben F

    2015-09-01

    Microorganisms encode several classes of transmembrane molecular pumps that can expel a wide range of chemically distinct toxic substances. These machines contribute to the capacity of the organisms to withstand harsh environments, and they help to confer resistance against clinical antimicrobial agents. In Gram-negative bacteria, some of the pumps comprise tripartite assemblies that actively transport drugs and other harmful compounds across the cell envelope. We describe recent structural and functional data that have provided insights into the architecture and transport mechanism of the AcrA-AcrB-TolC pump of Escherichia coli. This multidrug efflux pump is powered by proton electrochemical gradients through the activity of AcrB, a member of the resistance/nodulation/cell division (RND) transporter family. Crystallographic data reveal how the small protein AcrZ binds to AcrB in a concave surface of the transmembrane domain, and we discuss how this interaction may affect the efflux activities of the transporter. PMID:25803077

  20. Role of novel multidrug efflux pump involved in drug resistance in Klebsiella pneumoniae.

    Directory of Open Access Journals (Sweden)

    Vijaya Bharathi Srinivasan

    Full Text Available BACKGROUND: Multidrug resistant Klebsiella pneumoniae have caused major therapeutic problems worldwide due to the emergence of the extended-spectrum β-lactamase producing strains. Although there are >10 major facilitator super family (MFS efflux pumps annotated in the genome sequence of the K. pneumoniae bacillus, apparently less is known about their physiological relevance. PRINCIPAL FINDINGS: Insertional inactivation of kpnGH resulting in increased susceptibility to antibiotics such as azithromycin, ceftazidime, ciprofloxacin, ertapenem, erythromycin, gentamicin, imipenem, ticarcillin, norfloxacin, polymyxin-B, piperacillin, spectinomycin, tobramycin and streptomycin, including dyes and detergents such as ethidium bromide, acriflavine, deoxycholate, sodium dodecyl sulphate, and disinfectants benzalkonium chloride, chlorhexidine and triclosan signifies the wide substrate specificity of the transporter in K. pneumoniae. Growth inactivation and direct fluorimetric efflux assays provide evidence that kpnGH mediates antimicrobial resistance by active extrusion in K. pneumoniae. The kpnGH isogenic mutant displayed decreased tolerance to cell envelope stressors emphasizing its added role in K. pneumoniae physiology. CONCLUSIONS AND SIGNIFICANCE: The MFS efflux pump KpnGH involves in crucial physiological functions besides being an intrinsic resistance determinant in K. pneumoniae.

  1. Evaluation of the tannic acid inhibitory effect against the NorA efflux pump of Staphylococcus aureus.

    Science.gov (United States)

    Tintino, Saulo R; Oliveira-Tintino, Cícera D M; Campina, Fábia F; Silva, Raimundo L P; Costa, Maria do S; Menezes, Irwin R A; Calixto-Júnior, João T; Siqueira-Junior, José P; Coutinho, Henrique D M; Leal-Balbino, Tereza C; Balbino, Valdir Q

    2016-08-01

    During the early periods of antibiotic usage, bacterial infections were considered tamed. However, widespread antibiotic use has promoted the emergence of antibiotic-resistant pathogens, including multidrug resistant strains. Active efflux is a mechanism for bacterial resistance to inhibitory substances, known simply as drug efflux pumps. The bacterium Staphylococcus aureus is an important pathogenic bacterium responsible for an array of infections. The NorA efflux pump has been shown to be responsible for moderate fluoroquinolone resistance of S. aureus. The inhibition of the efflux pump was assayed using a sub-inhibitory concentration of standard efflux pump inhibitors and tannic acid (MIC/8), where its capacity to decrease the MIC of Ethidium bromide (EtBr) and antibiotics due to the possible inhibitory effect of these substances was observed. The MICs of EtBr and antibiotics were significantly reduced in the presence of tannic acid, indicating the inhibitory effect of this agent against the efflux pumps of both strains causing a three-fold reduction of the MIC when compared with the control. These results indicate the possible usage of tannic acid as an adjuvant in antibiotic therapy against multidrug resistant bacteria (MDR). PMID:27057677

  2. Identification and evolution of drug efflux pump in clinical Enterobacter aerogenes strains isolated in 1995 and 2003.

    Directory of Open Access Journals (Sweden)

    Jacqueline Chevalier

    Full Text Available BACKGROUND: The high mortality impact of infectious diseases will increase due to accelerated evolution of antibiotic resistance in important human pathogens. Development of antibiotic resistance is a evolutionary process inducing the erosion of the effectiveness of our arsenal of antibiotics. Resistance is not necessarily limited to a single class of antibacterial agents but may affect many unrelated compounds; this is termed 'multidrug resistance' (MDR. The major mechanism of MDR is the active expulsion of drugs by bacterial pumps; the treatment of gram negative bacterial infections is compromised due to resistance mechanisms including the expression of efflux pumps that actively expel various usual antibiotics (beta-lactams, quinolones, .... METHODOLOGY/PRINCIPAL FINDINGS: Enterobacter aerogenes has emerged among Enterobacteriaceae associated hospital infections during the last twenty years due to its faculty of adaptation to antibiotic stresses. Clinical isolates of E. aerogenes belonging to two strain collections isolated in 1995 and 2003 respectively, were screened to assess the involvement of efflux pumps in antibiotic resistance. Drug susceptibility assays were performed on all bacterial isolates and an efflux pump inhibitor (PAbetaN previously characterized allowed to decipher the role of efflux in the resistance. Accumulation of labelled chloramphenicol was monitored in the presence of an energy poison to determine the involvement of active efflux on the antibiotic intracellular concentrations. The presence of the PAbetaN-susceptible efflux system was also identified in resistant E. aerogenes strains. CONCLUSIONS/SIGNIFICANCE: For the first time a noticeable increase in clinical isolates containing an efflux mechanism susceptible to pump inhibitor is report within an 8 year period. After the emergence of extended spectrum beta-lactamases in E. aerogenes and the recent characterisation of porin mutations in clinical isolates, this study

  3. A novel nanoparticle formulation overcomes multiple types of membrane efflux pumps in human breast cancer cells.

    Science.gov (United States)

    Prasad, Preethy; Cheng, Ji; Shuhendler, Adam; Rauth, Andrew M; Wu, Xiao Yu

    2012-04-01

    Multidrug resistance (MDR) in cancer cells can involve overexpression of different types of membrane drug efflux pumps and other drug resistance mechanisms. Hence, inhibition of one resistance mechanism may not be therapeutically effective. Previously we demonstrated a new polymer lipid hybrid nanoparticle (PLN) system was able to circumvent drug resistance of P-glycoprotein (P-gp) overexpressing breast cancer cells. The objectives of the present study were 2-fold: (1) to evaluate the ability of the PLN system to overcome two other membrane efflux pumps-multidrug resistance protein 1 (MRP1+) and breast cancer resistance protein (BCRP+) overexpressed on human breast cancer cell lines MCF7 VP (MRP1+) and MCF7 MX (BCRP+); and (2) to evaluate possible synergistic effects of doxorubicin (Dox)-mitomycin C (MMC) in these cell lines. These objectives were accomplished by measuring in vitro cellular uptake, intracellular trafficking, and cytotoxicity (using a clonogenic assay and median effect analysis), of Dox, MMC, or Dox-MMC co-loaded PLN. Treatment of MDR cells with PLN encapsulating single anticancer agents significantly enhanced cell kill compared to free Dox or MMC solutions. Dox-MMC co-loaded PLN were 20-30-folds more effective in killing MDR cells than free drugs. Co-encapsulated Dox-MMC was more effective in killing MDR cells than single agent-encapsulated PLN. Microscopic images showed perinuclear localization of fluorescently labelled PLN in all cell lines. These results are consistent with our previous results for P-gp overexpressing breast cancer cells suggesting the PLN system can overcome multiple types of membrane efflux pumps increasing the cytotoxicity of Dox-MMC at significantly lower doses than free drugs. PMID:25786718

  4. Disulphide cross linked pullulan based cationic polymer for improved gene delivery and efflux pump inhibition.

    Science.gov (United States)

    S, Priya S; R, Rekha M

    2016-10-01

    Multidrug resistance is a hurdle to successful cancer chemotherapy. Over expression of P-glycoprotein (P-gp) is a prime contributing factor for drug resistance. In this study, a disulphide cross-linked pullulan-based cationic polymer (PPSS) was synthesized to act simultaneously as gene delivery vehicle and efflux pump inhibitor. The PPSS nanoplexes were of size p53/PPSS/DOX nanoplexes was attributed to the synergistic effect of P-gp inhibition and p53 transfection efficiency. Therefore, this multifunctional polymeric system may have significant promise for therapeutic application against cancer drug resistance. PMID:27459414

  5. Multidrug resistant Acinetobacter baumannii--the role of AdeABC (RND family efflux pump in resistance to antibiotics.

    Directory of Open Access Journals (Sweden)

    Marcin Zórawski

    2008-12-01

    Full Text Available Acinetobacter baumannii is an opportunistic pathogen which play the more and more greater role in the pathogenicity of the human. It is often attached with the hospital environment, in which is able easily to survive for many days even in adverse conditions. Acinetobacter baumannii is the species responsible for a serious nosocomial infections, especially in the intensive care units. Option of surviving in natural niches, and in the hospital environment could also be associated with the efflux pump mechanisms. Mechanisms of efflux universally appear in all cells (eukaryotic and prokaryotic and play the physiological important role. In prokaryote, the main functions are evasion of such naturally produced molecules, removal of metabolic products and toxins. These pumps could also be involved in an early stage of infection, such as adhesion to host cells and the colonization. Importantly, they remove commonly used antibiotics from the cell in therapy of infections caused by these bacteria. Efflux pumps exemplify a unique phenomenon in drug resistance: a single mechanism causing resistance against several different classes of antibiotics. In Acinetobacter baumannii, the AdeABC efflux pump, a member of the resistance-nodulation-cell division family (RND, has been well characterized. Aminoglicosides, tetracyclines, erythromycin, chloramphenicol, trimethoprim, fluoroquinolones, some beta-lactams, and also recently tigecycline, were found to be substrates for this pump. Drugs, as substrates for the AdeABC pump, can increase the expression of the AdeABC genes, leading to multidrug resistance (MDR. From this reason, treatment failure and death caused by Acinetobacter baumannii infections or underlying diseases are common. Because the AdeABC pump is widespread in Acinetobacter baumannii, similarly to other pumps in Gram-negative and Gram-positive bacteria, exists a need of searching a new therapeutic solutions. Specific efflux inhibitors of pumps (EPIs

  6. Evaluation of efflux pump gene expression among drug susceptible and drug resistant strains of Mycobacterium tuberculosis from Iran.

    Science.gov (United States)

    Kardan Yamchi, Jalil; Haeili, Mehri; Gizaw Feyisa, Seifu; Kazemian, Hossein; Hashemi Shahraki, Abdolrazagh; Zahednamazi, Fatemeh; Imani Fooladi, Abbas Ali; Feizabadi, Mohammad Mehdi

    2015-12-01

    Absence of mutations within the genes encoding drug targets in some phenotypically drug resistant strains of Mycobacterium tuberculosis suggests possible involvement of alternative mechanisms such as over-expression of efflux pumps. We investigated the expression level of Rv1410c, Rv2459, Rv1218c and Rv1273c efflux pumps gene by real-time quantitative reverse transcription PCR (qRT-PCR) in 31 clinical isolates of M. tuberculosis. Susceptibility to first-line drugs was performed using the proportion method. Twenty one isolates were characterized with drug resistance (DR), and among them 12 showed a significantly elevated level of expression (>4 fold) for at least one of the studied genes encoding for efflux pumps. Point mutations in the katG (codons 315 or 335) and rpoB (codons 456 and 441) genes were found in 42.85% and 66.6% of drug resistant isolates, respectively. Only one isolate showed mutation at position -15 of the inhA promoter region. Among the 7 isolates (33.33%) which had no mutation in the studied regions of drug target genes, 5 isolates showed over-expression for efflux pumps. Our results demonstrated that over-expression of efflux pumps can contribute to drug resistance in M. tuberculosis.

  7. EFFECTS OF PSYCHOTROPIC DRUGS AS BACTERIAL EFFLUX PUMP INHIBITORS ON QUORUM SENSING REGULATED BEHAVIORS

    Directory of Open Access Journals (Sweden)

    Aynur Aybey

    2014-10-01

    Full Text Available Psychotropic drugs are known to have antimicrobial activity against several groups of microorganisms. The antidepressant agents such as duloxetine, paroxetine, hydroxyzine and venlafaxine are shown to act as efflux pump inhibitors in bacterial cells. In order to the investigation of the effects of psychotropic drugs were determined for clinically significant pathogens by using standart broth microdillusion method. The anti-quorum sensing (anti-QS activity of psychotropic drugs was tested against four test pathogens using the agar well diffusion method. All drugs showed strong inhibitory effect on the growth of S. typhimurium. Additionally, quorum sensing-regulated behaviors of Pseudomonas aeruginosa, including swarming, swimming and twitching motility and alkaline protease production were investigated. Most effective drugs on swarming, swimming and twitching motility and alkaline protease production, respectively, were paroxetine and duloxetine; duloxetine; hydroxyzine and venlafaxine; paroxetine and venlafaxine; venlafaxine. Accordingly, psychotropic drugs were shown strongly anti-QS activity by acting as bacterial efflux pump inhibitors and effection on motility and alkaline protease production of P. aeruginosa.

  8. Virtual screening for novel Staphylococcus Aureus NorA efflux pump inhibitors from natural products.

    Science.gov (United States)

    Thai, Khac-Minh; Ngo, Trieu-Du; Phan, Thien-Vy; Tran, Thanh-Dao; Nguyen, Ngoc-Vinh; Nguyen, Thien-Hai; Le, Minh-Tri

    2015-01-01

    NorA is a member of the Major Facilitator Superfamily (MFS) drug efflux pumps that have been shown to mediate antibiotic resistance in Staphylococcus aureus (SA). In this study, QSAR analysis, virtual screening and molecular docking were implemented in an effort to discover novel SA NorA efflux pump inhibitors. Originally, a set of 47 structurally diverse compounds compiled from the literature was used to develop linear QSAR models and another set of 15 different compounds were chosen for extra validation. The final model which was estimated by statistical values for the full data set (n = 45, Q(2) = 0.80, RMSE = 0.20) and for the external test set (n = 15, R(2) = 0.60, |res|max = 0.75, |res|min = 0.02) was applied on the collection of 182 flavonoides and the traditional Chinese medicine (TCM) database to screen for novel NorA inhibitors. Finally, 33 lead compounds that met the Lipinski's rules of five/three and had good predicted pIC50 values from in silico screening process were employed to analyze the binding ability by docking studies on NorA homology model in place of its unavailable crystal structures at two active sites, the central channel and the Walker B. PMID:25181985

  9. The ABCs of Candida albicans Multidrug Transporter Cdr1.

    Science.gov (United States)

    Prasad, Rajendra; Banerjee, Atanu; Khandelwal, Nitesh Kumar; Dhamgaye, Sanjiveeni

    2015-12-01

    In the light of multidrug resistance (MDR) among pathogenic microbes and cancer cells, membrane transporters have gained profound clinical significance. Chemotherapeutic failure, by far, has been attributed mainly to the robust and diverse array of these proteins, which are omnipresent in every stratum of the living world. Candida albicans, one of the major fungal pathogens affecting immunocompromised patients, also develops MDR during the course of chemotherapy. The pivotal membrane transporters that C. albicans has exploited as one of the strategies to develop MDR belongs to either the ATP binding cassette (ABC) or the major facilitator superfamily (MFS) class of proteins. The ABC transporter Candida drug resistance 1 protein (Cdr1p) is a major player among these transporters that enables the pathogen to outplay the battery of antifungals encountered by it. The promiscuous Cdr1 protein fulfills the quintessential need of a model to study molecular mechanisms of multidrug transporter regulation and structure-function analyses of asymmetric ABC transporters. In this review, we cover the highlights of two decades of research on Cdr1p that has provided a platform to study its structure-function relationships and regulatory circuitry for a better understanding of MDR not only in yeast but also in other organisms. PMID:26407965

  10. Efflux Pump Blockers in Gram-Negative Bacteria: The New Generation of Hydantoin Based-Modulators to Improve Antibiotic Activity.

    Science.gov (United States)

    Otręebska-Machaj, Ewa; Chevalier, Jacqueline; Handzlik, Jadwiga; Szymańska, Ewa; Schabikowski, Jakub; Boyer, Gérard; Bolla, Jean-Michel; Kieć-Kononowicz, Katarzyna; Pagès, Jean-Marie; Alibert, Sandrine

    2016-01-01

    Multidrug resistant (MDR) bacteria are an increasing health problem with the shortage of new active antibiotic agents. Among effective mechanisms that contribute to the spread of MDR Gram-negative bacteria are drug efflux pumps that expel clinically important antibiotic classes out of the cell. Drug pumps are attractive targets to restore the susceptibility toward the expelled antibiotics by impairing their efflux activity. Arylhydantoin derivatives were investigated for their potentiation of activities of selected antibiotics described as efflux substrates in Enterobacter aerogenes expressing or not AcrAB pump. Several compounds increased the bacterial susceptibility toward nalidixic acid, chloramphenicol and sparfloxacin and were further pharmacomodulated to obtain a better activity against the AcrAB producing bacteria. PMID:27199950

  11. Evaluation of multidrug efflux pump inhibitors by a new method using microfluidic channels.

    Directory of Open Access Journals (Sweden)

    Yoshimi Matsumoto

    Full Text Available Fluorescein-di-β-D-galactopyranoside (FDG, a fluorogenic compound, is hydrolyzed by β-galactosidase in the cytoplasm of Escherichia coli to produce a fluorescent dye, fluorescein. We found that both FDG and fluorescein were substrates of efflux pumps, and have developed a new method to evaluate efflux-inhibitory activities in E. coli using FDG and a microfluidic channel device. We used E. coli MG1655 wild-type, ΔacrB (ΔB, ΔtolC (ΔC and ΔacrBΔtolC (ΔBC harboring plasmids carrying the mexAB-oprM (pABM or mexXY-oprM (pXYM genes of Pseudomonas aeruginosa. Two inhibitors, MexB-specific pyridopyrimidine (D13-9001 and non-specific Phe-Arg-β-naphthylamide (PAβN were evaluated. The effects of inhibitors on pumps were observed using the microfluidic channel device under a fluorescence microscope. AcrAB-TolC and analogous pumps effectively prevented FDG influx in wild-type cells, resulting in no fluorescence. In contrast, ΔB or ΔC easily imported and hydrolyzed FDG to fluorescein, which was exported by residual pumps in ΔB. Consequently, fluorescent medium in ΔB and fluorescent cells of ΔC and ΔBC were observed in the microfluidic channels. D13-9001 substantially increased fluorescent cell number in ΔBC/pABM but not in ΔBC/pXYM. PAβN increased medium fluorescence in all strains, especially in the pump deletion mutants, and caused fluorescein accumulation to disappear in ΔC. The checkerboard method revealed that D13-9001 acts synergistically with aztreonam, ciprofloxacin, and erythromycin only against the MexAB-OprM producer (ΔBC/pABM, and PAβN acts synergistically, especially with erythromycin, in all strains including the pump deletion mutants. The results obtained from PAβN were similar to the results from membrane permeabilizer, polymyxin B or polymyxin B nonapeptide by concentration. The new method clarified that D13-9001 specifically inhibited MexAB-OprM in contrast to PAβN, which appeared to be a substrate of the pumps and

  12. Synergistic Activities of an Efflux Pump Inhibitor and Iron Chelators against Pseudomonas aeruginosa Growth and Biofilm Formation

    DEFF Research Database (Denmark)

    Liu, Yang; Yang, Liang; Molin, Søren

    2010-01-01

    The efflux pump inhibitor phenyl-arginine-beta-naphthylamide (PA beta N) was paired with iron chelators 2,2'-dipyridyl, acetohydroxamic acid, and EDTA to assess synergistic activities against Pseudomonas aeruginosa growth and biofilm formation. All of the tested iron chelators synergistically...

  13. The prevalence of the OqxAB amongst olaquindox-resistant multidrug efflux pump Escherichia coli in pigs

    DEFF Research Database (Denmark)

    Hansen, L.H.; Sørensen, S.J.; Jørgensen, H.S.;

    2005-01-01

    The quinoxaline olaquindox has been used extensively as a growth promoter for pigs. Recently, we isolated a plasmid (pOLA52) conferring resistance to olaquindox from swine manure. On this plasmid, the oqxA and oqxB genes encode an RND-family multidrug efflux pump, OqxAB. It facilitates resistance...

  14. The efflux pump inhibitor timcodar improves the potency of antimycobacterial agents.

    Science.gov (United States)

    Grossman, Trudy H; Shoen, Carolyn M; Jones, Steven M; Jones, Peter L; Cynamon, Michael H; Locher, Christopher P

    2015-03-01

    Previous studies indicated that inhibition of efflux pumps augments tuberculosis therapy. In this study, we used timcodar (formerly VX-853) to determine if this efflux pump inhibitor could increase the potency of antituberculosis (anti-TB) drugs against Mycobacterium tuberculosis in in vitro and in vivo combination studies. When used alone, timcodar weakly inhibited M. tuberculosis growth in broth culture (MIC, 19 μg/ml); however, it demonstrated synergism in drug combination studies with rifampin, bedaquiline, and clofazimine but not with other anti-TB agents. When M. tuberculosis was cultured in host macrophage cells, timcodar had about a 10-fold increase (50% inhibitory concentration, 1.9 μg/ml) in the growth inhibition of M. tuberculosis and demonstrated synergy with rifampin, moxifloxacin, and bedaquiline. In a mouse model of tuberculosis lung infection, timcodar potentiated the efficacies of rifampin and isoniazid, conferring 1.0 and 0.4 log10 reductions in bacterial burden in lung, respectively, compared to the efficacy of each drug alone. Furthermore, timcodar reduced the likelihood of a relapse infection when evaluated in a mouse model of long-term, chronic infection with treatment with a combination of rifampin, isoniazid, and timcodar. Although timcodar had no effect on the pharmacokinetics of rifampin in plasma and lung, it did increase the plasma exposure of bedaquiline. These data suggest that the antimycobacterial drug-potentiating activity of timcodar is complex and drug dependent and involves both bacterial and host-targeted mechanisms. Further study of the improvement of the potency of antimycobacterial drugs and drug candidates when used in combination with timcodar is warranted. PMID:25534740

  15. Hyper Accumulation of Arsenic in Mutants of Ochrobactrum tritici Silenced for Arsenite Efflux Pumps.

    Directory of Open Access Journals (Sweden)

    Tânia Sousa

    Full Text Available Ochrobactrum tritici SCII24T is a highly As-resistant bacterium, with two previously described arsenic resistance operons, ars1 and ars2. Among a large number of genes, these operons contain the arsB and Acr3 genes that encode the arsenite efflux pumps responsible for arsenic resistance. Exploring the genome of O. tritici SCII24T, an additional putative operon (ars3 was identified and revealed the presence of the Acr3_2 gene that encodes for an arsenite efflux protein but which came to prove to not be required for full As resistance. The genes encoding for arsenite efflux pumps, identified in this strain, were inactivated to develop microbial accumulators of arsenic as new tools for bioremediation. Six different mutants were produced, studied and three were more useful as biotools. O. tritici wild type and the Acr3-mutants showed the highest resistance to As(III, being able to grow up to 50 mM of arsenite. On the other hand, arsB-mutants were not able to grow at concentrations higher than 1 mM As(III, and were the most As(III sensitive mutants. In the presence of 1 mM As(III, the strain with arsB and Acr3_1 mutated showed the highest intracellular arsenic concentration (up to 17 ng(As/mg protein, while in assays with 5 mM As(III, the single arsB-mutant was able to accumulate the highest concentration of arsenic (up to 10 ng(As/mg protein. Therefore, arsB is the main gene responsible for arsenite resistance in O. tritici. However, both genes arsB and Acr3_1 play a crucial role in the resistance mechanism, depending on the arsenite concentration in the medium. In conclusion, at moderate arsenite concentrations, the double arsB- and Acr3_1-mutant exhibited a great ability to accumulate arsenite and can be seen as a promising bioremediation tool for environmental arsenic detoxification.

  16. P-glycoprotein in adriamycin-resistant cells functions as an efflux pump for benzopyrene, a chemical carcinogen

    Energy Technology Data Exchange (ETDEWEB)

    Chao Yeh, G.; Poore, C.M.; Lopaczynska, J.; Phang, J.M. (NCI-FCRDC, Frederick, MD (United States))

    1991-03-15

    The physiological function of multidrug resistant gene (MDR 1) coded P-glycoprotein 170 (P-gp) in normal tissues remains unknown. The authors propose that P-gp functions as an efflux pump in normal tissues for benzopyrene and other xenobiotic substances. To examine their hypothesis the authors used a series of MDR human breast cancer MCF-7 cells with increasing degrees of drug resistance, expression of MDR and levels of P-gp. First, they found the IC{sub 50} for benzopyrene is linearly correlated with the levels of P-gp at different stages of adriamycin resistant MCF-7 cells. Using P-gp ({sup 3}H)azidopine labeling as a measurement of P-gp they found benzopyrene competes for labeling of P-gp. Finally, they directly measured cellular efflux of benzopyrene with adherent cell laser cytometry and found that resistant cells expressing high levels of P-gp showed rapid efflux of benzopyrene. By contrast, drug sensitive wild type cells with undetectable P-gp showed negligible efflux. They conclude that P-gp can function as an efflux pump for benzopyrene and suggest that P-gp may be a cellular mechanism for resistance to carcinogens.

  17. Contribution of efflux pumps in fluroquinolone resistance in multi-drug resistant nosocomial isolates of Pseudomanas aeruginosa from a tertiary referral hospital in north east India

    Directory of Open Access Journals (Sweden)

    D Choudhury

    2015-01-01

    Full Text Available Background: Pseudomonas aeruginosa is one of the leading opportunistic pathogen and its ability to acquire resistance against series of antimicrobial agents confine treatment option for nosocomial infections. Increasing resistance to fluroquinolone (FQ agents has further worsened the scenario. The major mechanism of resistance to FQs includes mutation in FQs target genes in bacteria (DNA gyrase and/or topoisomerases and overexpression of antibiotic efflux pumps. Objective: We have investigated the role of efflux pump mediated FQ resistance in nosocomial isolates of P. aeruginosa from a tertiary referral hospital in north eastern part of India. Materials and Methods: A total of 234 non-duplicate, consecutive clinical isolates of P. aeruginosa were obtained from a tertiary referral hospital of north-east India. An efflux pump inhibitor (EPI, carbonyl cyanide m-chlorophenylhydrazone (CCCP based method was used for determination of efflux pump activity and multiplex polymerase chain reaction (PCR was performed for molecular characterisation of efflux pump. Minimum inhibitory concentration (MIC reduction assay was also performed for all the isolates. Results and Conclusion: A total number of 56 (23% have shown efflux mediated FQ resistance. MexAB-OprM efflux system was predominant type. This is the first report of efflux pump mediated FQ resistance from this part of the world and the continued emergence of these mutants with such high MIC range from this part of the world demands serious awareness, diagnostic intervention, and proper therapeutic option.

  18. Contribution of AcrAB efflux pump to ciprofloxacin resistance in Klebsiella pneumoniae isolated from burn patients

    Directory of Open Access Journals (Sweden)

    Pakzad, Iraj

    2013-11-01

    Full Text Available [english] Resistance to fluoroquinolones has been recently increased among bacterial strains isolated from outpatients. Multidrug-resistant is one of the major organisms isolated from burn patients and the AcrAB efflux pump is the principal pump contributing to the intrinsic resistance in against multiple antimicrobial agents including ciprofloxacin and other fluoroquinolones. Fifty-two isolated from burn patients in Shahid Motahari hospital and confirmed by conventional biochemical tests. Antimicrobial susceptibility testing was done according to CLSI 2011 guidelines, to determine the antimicrobial resistance pattern of isolates. A gene was detected among ciprofloxacin-resistant isolates by PCR assay. MICs to ciprofloxacin were measured with and without carbonyl cyanide . Forty out of the 52 isolated from burn patients in Shahid Motahari hospital were resistant to ciprofloxacin according to breakpoint of CLSI guideline. PCR assay for A gene demonstrated that all ciprofloxacin-resistant isolates harbored A gene coding the membrane fusion protein AcrA and is a part of AcrAB efflux system. Among these isolates, 19 strains (47.5% showed 2 to 32 fold reduction in MICs after using CCCP as an efflux pump inhibitor. The other 21 strains (52.5% showed no disparity in MICs before and after using CCCP. In conclusion, the AcrAB efflux system is one of the principal mechanisms contribute in ciprofloxacin resistance among isolates but there are some other mechanisms interfere with ciprofloxacin resistance such as mutation in target proteins of DNA gyrase of topoisomerase IV enzymes.

  19. An alternative physiological role for the EmhABC efflux pump in Pseudomonas fluorescens cLP6a

    Directory of Open Access Journals (Sweden)

    Adebusuyi Abigail A

    2011-11-01

    Full Text Available Abstract Background Efflux pumps belonging to the resistance-nodulation-division (RND superfamily in bacteria are involved in antibiotic resistance and solvent tolerance but have an unknown physiological role. EmhABC, a RND-type efflux pump in Pseudomonas fluorescens strain cLP6a, extrudes hydrophobic antibiotics, dyes and polycyclic aromatic hydrocarbons including phenanthrene. The effects of physico-chemical factors such as temperature or antibiotics on the activity and expression of EmhABC were determined in order to deduce its physiological role(s in strain cLP6a in comparison to the emhB disruptant strain, cLP6a-1. Results Efflux assays conducted with 14C-phenanthrene showed that EmhABC activity is affected by incubation temperature. Increased phenanthrene efflux was measured in cLP6a cells grown at 10°C and decreased efflux was observed at 35°C compared with cells grown at the optimum temperature of 28°C. Membrane fatty acids in cLP6a cells were substantially altered by changes in growth temperature and in the presence of tetracycline. Changed membrane fatty acids and increased membrane permeability were associated with ~30-fold increased expression of emhABC in cLP6a cells grown at 35°C, and with increased extracellular free fatty acids. Growth of P. fluorescens cLP6a at supra-optimal temperature was enhanced by the presence of EmhABC compared to strain cLP6a-1. Conclusions Combined, these observations suggest that the EmhABC efflux pump may be involved in the management of membrane stress effects such as those due to unfavourable incubation temperatures. Efflux of fatty acids replaced as a result of membrane damage or phospholipid turnover may be the primary physiological role of the EmhABC efflux pump in P. fluorescens cLP6a.

  20. Development of a novel antimicrobial screening system targeting the pyoverdine-mediated iron acquisition system and xenobiotic efflux pumps.

    Science.gov (United States)

    Sato, Kazuki; Ushioda, Kenichi; Akiba, Keiji; Matsumoto, Yoshimi; Maseda, Hideaki; Ando, Tasuke; Isogai, Emiko; Nakae, Taiji; Yoneyama, Hiroshi

    2015-01-01

    The iron acquisition systems in Pseudomonas aeruginosa are inducible in response to low-iron conditions and important for growth of this organism under iron limitation. OprM is the essential outer membrane subunit of the MexAB-OprM xenobiotic efflux pump. We designed and constructed a new model antimicrobial screening system targeting both the iron-uptake system and xenobiotic efflux pumps. The oprM gene was placed immediately downstream of the ferri-pyoverdine receptor gene, fpvA, in the host lacking chromosomal oprM and the expression of oprM was monitored by an antibiotic susceptibility test under iron depleted and replete conditions. The recombinant cells showed wild-type susceptibility to pump substrate antibiotics, e.g., aztreonam, under iron limitation and became supersusceptible to them under iron repletion, suggesting that expression of oprM is under control of the iron acquisition system. Upon screening of a chemical library comprising 2952 compounds using this strain, a compound-ethyl 2-(1-acetylpiperidine-4-carboxamido)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate-was found to enhance the efficacy of aztreonam under iron limitation, suggesting that the compound inhibits either the iron acquisition system or the MexAB-OprM efflux pump. This compound was subsequently found to inhibit the growth of wild-type cells in the presence of sublethal amounts of aztreonam, regardless of the presence or absence of dipyridyl, an iron-chelator. The compound was eventually identified to block the function of the MexAB-OprM efflux pump, showing the validity of this new method. PMID:25939068

  1. Development of a Novel Antimicrobial Screening System Targeting the Pyoverdine-Mediated Iron Acquisition System and Xenobiotic Efflux Pumps

    Directory of Open Access Journals (Sweden)

    Kazuki Sato

    2015-04-01

    Full Text Available The iron acquisition systems in Pseudomonas aeruginosa are inducible in response to low-iron conditions and important for growth of this organism under iron limitation. OprM is the essential outer membrane subunit of the MexAB-OprM xenobiotic efflux pump. We designed and constructed a new model antimicrobial screening system targeting both the iron-uptake system and xenobiotic efflux pumps. The oprM gene was placed immediately downstream of the ferri-pyoverdine receptor gene, fpvA, in the host lacking chromosomal oprM and the expression of oprM was monitored by an antibiotic susceptibility test under iron depleted and replete conditions. The recombinant cells showed wild-type susceptibility to pump substrate antibiotics, e.g., aztreonam, under iron limitation and became supersusceptible to them under iron repletion, suggesting that expression of oprM is under control of the iron acquisition system. Upon screening of a chemical library comprising 2952 compounds using this strain, a compound—ethyl 2-(1-acetylpiperidine-4-carboxamido-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate—was found to enhance the efficacy of aztreonam under iron limitation, suggesting that the compound inhibits either the iron acquisition system or the MexAB-OprM efflux pump. This compound was subsequently found to inhibit the growth of wild-type cells in the presence of sublethal amounts of aztreonam, regardless of the presence or absence of dipyridyl, an iron-chelator. The compound was eventually identified to block the function of the MexAB-OprM efflux pump, showing the validity of this new method.

  2. Contribution of efflux pumps, porins, and β-lactamases to multidrug resistance in clinical isolates of Acinetobacter baumannii.

    Science.gov (United States)

    Rumbo, C; Gato, E; López, M; Ruiz de Alegría, C; Fernández-Cuenca, F; Martínez-Martínez, L; Vila, J; Pachón, J; Cisneros, J M; Rodríguez-Baño, J; Pascual, A; Bou, G; Tomás, M

    2013-11-01

    We investigated the mechanisms of resistance to carbapenems, aminoglycosides, glycylcyclines, tetracyclines, and quinolones in 90 multiresistant clinical strains of Acinetobacter baumannii isolated from two genetically unrelated A. baumannii clones: clone PFGE-ROC-1 (53 strains producing the OXA-58 β-lactamase enzyme and 18 strains with the OXA-24 β-lactamase) and clone PFGE-HUI-1 (19 strains susceptible to carbapenems). We used real-time reverse transcriptase PCR to correlate antimicrobial resistance (MICs) with expression of genes encoding chromosomal β-lactamases (AmpC and OXA-51), porins (OmpA, CarO, Omp33, Dcap-like, OprB, Omp25, OprC, OprD, and OmpW), and proteins integral to six efflux systems (AdeABC, AdeIJK, AdeFGH, CraA, AbeM, and AmvA). Overexpression of the AdeABC system (level of expression relative to that by A. baumannii ATCC 17978, 30- to 45-fold) was significantly associated with resistance to tigecycline, minocycline, and gentamicin and other biological functions. However, hyperexpression of the AdeIJK efflux pump (level of expression relative to that by A. baumannii ATCC 17978, 8- to 10-fold) was significantly associated only with resistance to tigecycline and minocycline (to which the TetB efflux system also contributed). TetB and TetA(39) efflux pumps were detected in clinical strains and were associated with resistance to tetracyclines and doxycycline. The absence of the AdeABC system and the lack of expression of other mechanisms suggest that tigecycline-resistant strains of the PFGE-HUI-1 clone may be associated with a novel resistance-nodulation-cell efflux pump (decreased MICs in the presence of the inhibitor Phe-Arg β-naphthylamide dihydrochloride) and the TetA(39) system. PMID:23939894

  3. Influence of induced ciprofloxacin resistance on efflux pump activity of Klebsiella pneumoniae

    Institute of Scientific and Technical Information of China (English)

    Hai-qin ZHONG; Shun ZHANG; Hong PAN; Ting CAI

    2013-01-01

    The efflux pump (EP) is one of the major mechanisms of antibiotic resistance in Klebsiella pneumoniae.However,there are few reports on the effect of the abuse of antibiotic use on the activity of EPs.To determine whether the use of low efficacy antibiotics has any effect on the activity of EPs and induces drug resistance in K.pneumoniae,we investigated the effect of ciprofloxacin on the activity of EPs in K.pneumoniae strains.Methods:Sixteen susceptible K.pneumoniae strains were isolated from patients and their minimum inhibitory concentrations (MICs) of ciprofloxacin were measured in the absence and presence of the pump inhibitor carbonyl cyanide m-chlorophenyl hydrazone (CCCP).The strains were then induced with a gradient of ciprofloxacin until the MICs of the strains showed no further increase,to obtain induced resistant strains.The EP activities of the strains before and after induction were compared using EP inhibition and ethidium bromide (EtBr) accumulation assays.Results:The MIC values of the strains were 16-256 times higher after induction than before induction.In the presence of CCCP,the MIC values of 50% of the induced strains were 2-4-fold lower than that in the absence of this inhibitor.The EtBr accumulation assay showed that the fluorescence of EtBr in the induced cells was lower than that in the cells before induction.Conclusions:EPs are widespread in susceptible and drug-resistant K.pneumoniae strains.Induction with ciprofloxacin may increase the activity of EPs in K.pneumoniae.The EtBr accumulation assay is more sensitive than the EP inhibition assay in evaluating the activity of EPs in K.pneumoniae.

  4. Structure and Function of Neisseria gonorrhoeae MtrF Illuminates a Class of Antimetabolite Efflux Pumps

    Directory of Open Access Journals (Sweden)

    Chih-Chia Su

    2015-04-01

    Full Text Available Neisseria gonorrhoeae is an obligate human pathogen and the causative agent of the sexually transmitted disease gonorrhea. The control of this disease has been compromised by the increasing proportion of infections due to antibiotic-resistant strains, which are growing at an alarming rate. N. gonorrhoeae MtrF is an integral membrane protein that belongs to the AbgT family of transporters for which no structural information is available. Here, we describe the crystal structure of MtrF, revealing a dimeric molecule with architecture distinct from all other families of transporters. MtrF is a bowl-shaped dimer with a solvent-filled basin extending from the cytoplasm to halfway across the membrane bilayer. Each subunit of the transporter contains nine transmembrane helices and two hairpins, posing a plausible pathway for substrate transport. A combination of the crystal structure and biochemical functional assays suggests that MtrF is an antibiotic efflux pump mediating bacterial resistance to sulfonamide antimetabolite drugs.

  5. Efflux pump-deficient mutants as a platform to search for microbes that produce antibiotics

    Science.gov (United States)

    Molina-Santiago, Carlos; Udaondo, Zulema; Daddaoua, Abdelali; Roca, Amalia; Martín, Jesús; Pérez-Victoria, Ignacio; Reyes, Fernando; Ramos, Juan-Luis

    2015-01-01

    Pseudomonas putida DOT-T1E-18 is a strain deficient in the major antibiotic efflux pump (TtgABC) that exhibits an overall increased susceptibility to a wide range of drugs when compared with the wild-type strain. We used this strain as a platform to search for microbes able to produce antibiotics that inhibit growth. A collection of 2400 isolates from soil, sediments and water was generated and a drop assay developed to identify, via growth inhibition halos, strains that prevent the growth of DOT-T1E-18 on solid Luria–Bertani plates. In this study, 35 different isolates that produced known and unknown antibiotics were identified. The most potent inhibitor of DOT-T1E-18 growth was an isolate named 250J that, through multi-locus sequence analysis, was identified as a Pseudomonas sp. strain. Culture supernatants of 250J contain four different xantholysins that prevent growth of Gram-positive bacteria, Gram-negative and fungi. Two of the xantholysins were produced in higher concentrations and purified. Xantholysin A was effective against Bacillus, Lysinibacillus and Rhodococcus strains, and the effect against these microbes was enhanced when used in combination with other antibiotics such as ampicillin, gentamicin and kanamycin. Xantholysin C was also efficient against Gram-positive bacteria and showed an interesting antimicrobial effect against Pseudomonas strains, and a synergistic inhibitory effect with ampicillin, chloramphenicol and gentamicin. PMID:26059350

  6. Plasmid-encoded tetracycline efflux pump protein alters bacterial stress responses and ecological fitness of Acinetobacter oleivorans.

    Directory of Open Access Journals (Sweden)

    Hyerim Hong

    Full Text Available Acquisition of the extracellular tetracycline (TC resistance plasmid pAST2 affected host gene expression and phenotype in the oil-degrading soil bacterium, Acinetobacter oleivorans DR1. Whole-transcriptome profiling of DR1 cells harboring pAST2 revealed that all the plasmid genes were highly expressed under TC conditions, and the expression levels of many host chromosomal genes were modulated by the presence of pAST2. The host energy burden imposed by replication of pAST2 led to (i lowered ATP concentrations, (ii downregulated expression of many genes involved in cellular growth, and (iii reduced growth rate. Interestingly, some phenotypes were restored by deleting the plasmid-encoded efflux pump gene tetH, suggesting that the membrane integrity changes resulting from the incorporation of efflux pump proteins also resulted in altered host response under the tested conditions. Alteration of membrane integrity by tetH deletion was shown by measuring permeability of fluorescent probe and membrane hydrophobicity. The presence of the plasmid conferred peroxide and superoxide resistance to cells, but only peroxide resistance was diminished by tetH gene deletion, suggesting that the plasmid-encoded membrane-bound efflux pump protein provided peroxide resistance. The downregulation of fimbriae-related genes presumably led to reduced swimming motility, but this phenotype was recovered by tetH gene deletion. Our data suggest that not only the plasmid replication burden, but also its encoded efflux pump protein altered host chromosomal gene expression and phenotype, which also alters the ecological fitness of the host in the environment.

  7. Homology modeling, molecular dynamics, and virtual screening of NorA efflux pump inhibitors of Staphylococcus aureus

    Science.gov (United States)

    Bhaskar, Baki Vijaya; Babu, Tirumalasetty Muni Chandra; Reddy, Netala Vasudeva; Rajendra, Wudayagiri

    2016-01-01

    Emerging drug resistance in clinical isolates of Staphylococcus aureus might be implicated to the overexpression of NorA efflux pump which is capable of extruding numerous structurally diverse compounds. However, NorA efflux pump is considered as a potential drug target for the development of efflux pump inhibitors. In the present study, NorA model was constructed based on the crystal structure of glycerol-3-phosphate transporter (PDBID: 1PW4). Molecular dynamics (MD) simulation was performed using NAMD2.7 for NorA which is embedded in the hydrated lipid bilayer. Structural design of NorA unveils amino (N)- and carboxyl (C)-terminal domains which are connected by long cytoplasmic loop. N and C domains are composed of six transmembrane α-helices (TM) which exhibits pseudo-twofold symmetry and possess voluminous substrate binding cavity between TM helices. Molecular docking of reserpine, totarol, ferruginol, salvin, thioxanthene, phenothiazine, omeprazole, verapamil, nalidixic acid, ciprofloxacin, levofloxacin, and acridine to NorA found that all the molecules were bound at the large hydrophobic cleft and indicated significant interactions with the key residues. In addition, structure-based virtual screening was employed which indicates that 14 potent novel lead molecules such as CID58685302, CID58685367, CID5799283, CID5578487, CID60028372, ZINC12196383, ZINC72140751, ZINC72137843, ZINC39227983, ZINC43742707, ZINC12196375, ZINC66166948, ZINC39228014, and ZINC14616160 have highest binding affinity for NorA. These lead molecules displayed considerable pharmacological properties as evidenced by Lipinski rule of five and prophecy of toxicity risk assessment. Thus, the present study will be helpful in designing and synthesis of a novel class of NorA efflux pump inhibitors that restore the susceptibilities of drug compounds. PMID:27757014

  8. Inducible and Constitutive Activation of Two Polymorphic Promoter Alleles of the Candida albicans Multidrug Efflux Pump MDR1

    OpenAIRE

    Sasse, Christoph; Schillig, Rebecca; Reimund, Alexandra; Merk, Julia; Morschhäuser, Joachim

    2012-01-01

    Overexpression of the multidrug efflux pump MDR1 confers resistance to the antifungal drug fluconazole on Candida albicans. It has been reported that two types of MDR1 promoters exist in C. albicans and that homozygosity for the allele with higher activity may promote fluconazole resistance. We found that the two MDR1 promoter alleles in strain SC5314 were equally well activated by inducing chemicals or hyperactive forms of the transcription factors Mrr1 and Cap1, which control MDR1 expressio...

  9. Resistance-nodulation-division efflux pump acrAB is modulated by florfenicol and contributes to drug resistance in the fish pathogen Piscirickettsia salmonis.

    Science.gov (United States)

    Sandoval, Rodrigo; Oliver, Cristian; Valdivia, Sharin; Valenzuela, Karla; Haro, Ronie E; Sánchez, Patricio; Olavarría, Víctor H; Valenzuela, Paulina; Avendaño-Herrera, Rubén; Romero, Alex; Cárcamo, Juan G; Figueroa, Jaime E; Yáñez, Alejandro J

    2016-06-01

    Piscirickettsia salmonis is a fastidious intracellular pathogen responsible for high mortality rates in farmed salmonids, with serious economic consequences for the Chilean aquaculture industry. Oxytetracycline and florfenicol are the most frequently used antibiotics against P. salmonis, but routine use could contribute to drug resistance. This study identified differentiated florfenicol susceptibilities in two P. salmonis strains, LF-89 and AUSTRAL-005. The less susceptible isolate, AUSTRAL-005, also showed a high ethidium bromide efflux rate, indicating a higher activity of general efflux pump genes than LF-89. The P. salmonis genome presented resistance nodulation division (RND) family members, a family containing typical multidrug resistance-related efflux pumps in Gram-negative bacteria. Additionally, efflux pump acrAB genes were overexpressed in AUSTRAL-005 following exposure to the tolerated maximal concentration of florfenicol, in contrast to LF-89. These results indicate that tolerated maximum concentrations of florfenicol can modulate RND gene expression and increase efflux pump activity. We propose that the acrAB efflux pump is essential for P. salmonis survival at critical florfenicol concentrations and for the generation of antibiotic-resistant bacterial strains. PMID:27190287

  10. Impact of anatase and rutile titanium dioxide nanoparticles on uptake carriers and efflux pumps in Caco-2 gut epithelial cells

    Science.gov (United States)

    Dorier, M.; Brun, E.; Veronesi, G.; Barreau, F.; Pernet-Gallay, K.; Desvergne, C.; Rabilloud, T.; Carapito, C.; Herlin-Boime, N.; Carrière, M.

    2015-04-01

    TiO2 microparticles are widely used in food products, where they are added as a white food colouring agent. This food additive contains a significant amount of nanoscale particles; still the impact of TiO2 nanoparticles (TiO2-NPs) on gut cells is poorly documented. Our study aimed at evaluating the impact of rutile and anatase TiO2-NPs on the main functions of enterocytes, i.e. nutrient absorption driven by solute-liquid carriers (SLC transporters) and protection against other xenobiotics driven by efflux pumps from the ATP-binding cassette (ABC) family. We show that acute exposure of Caco-2 cells to both anatase (12 nm) and rutile (20 nm) TiO2-NPs induce early upregulation of a battery of efflux pumps and nutrient transporters. In addition they cause overproduction of reactive oxygen species and misbalance redox repair systems, without inducing cell mortality or DNA damage. Taken together, these data suggest that TiO2-NPs may increase the functionality of gut epithelial cells, particularly their property to form a protective barrier against exogenous toxicants and to absorb nutrients.TiO2 microparticles are widely used in food products, where they are added as a white food colouring agent. This food additive contains a significant amount of nanoscale particles; still the impact of TiO2 nanoparticles (TiO2-NPs) on gut cells is poorly documented. Our study aimed at evaluating the impact of rutile and anatase TiO2-NPs on the main functions of enterocytes, i.e. nutrient absorption driven by solute-liquid carriers (SLC transporters) and protection against other xenobiotics driven by efflux pumps from the ATP-binding cassette (ABC) family. We show that acute exposure of Caco-2 cells to both anatase (12 nm) and rutile (20 nm) TiO2-NPs induce early upregulation of a battery of efflux pumps and nutrient transporters. In addition they cause overproduction of reactive oxygen species and misbalance redox repair systems, without inducing cell mortality or DNA damage. Taken

  11. Disulfiram is a potent modulator of multidrug transporter Cdr1p of Candida albicans

    International Nuclear Information System (INIS)

    To find novel drugs for effective antifungal therapy in candidiasis, we examined disulfiram, a drug used for the treatment of alcoholism, for its role as a potential modulator of Candida multidrug transporter Cdr1p. We show that disulfiram inhibits the oligomycin-sensitive ATPase activity of Cdr1p and 2.5 mM dithiothreitol reverses this inhibition. Disulfiram inhibited the binding of photoaffinity analogs of both ATP ([α-32P]8-azidoATP; IC50 = 0.76 μM) and drug-substrates ([3H]azidopine and [125I]iodoarylazidoprazosin; IC50 ∼ 12 μM) to Cdr1p in a concentration-dependent manner, suggesting that it can interact with both ATP and substrate-binding site(s) of Cdr1p. Furthermore, a non-toxic concentration of disulfiram (1 μM) increased the sensitivity of Cdr1p expressing Saccharomyces cerevisiae cells to antifungal agents (fluconazole, miconazole, nystatin, and cycloheximide). Collectively these results demonstrate that disulfiram reverses Cdr1p-mediated drug resistance by interaction with both ATP and substrate-binding sites of the transporter and may be useful for antifungal therapy

  12. Multidrug efflux pumps: the structures of prokaryotic ATP-binding cassette transporter efflux pumps and implications for our understanding of eukaryotic P-glycoproteins and homologues.

    Science.gov (United States)

    Kerr, Ian D; Jones, Peter M; George, Anthony M

    2010-02-01

    One of the Holy Grails of ATP-binding cassette transporter research is a structural understanding of drug binding and transport in a eukaryotic multidrug resistance pump. These transporters are front-line mediators of drug resistance in cancers and represent an important therapeutic target in future chemotherapy. Although there has been intensive biochemical research into the human multidrug pumps, their 3D structure at atomic resolution remains unknown. The recent determination of the structure of a mouse P-glycoprotein at subatomic resolution is complemented by structures for a number of prokaryotic homologues. These structures have provided advances into our knowledge of the ATP-binding cassette exporter structure and mechanism, and have provided the template data for a number of homology modelling studies designed to reconcile biochemical data on these clinically important proteins. PMID:19961540

  13. Multidrug efflux pumps: the structures of prokaryotic ATP-binding cassette transporter efflux pumps and implications for our understanding of eukaryotic P-glycoproteins and homologues.

    Science.gov (United States)

    Kerr, Ian D; Jones, Peter M; George, Anthony M

    2010-02-01

    One of the Holy Grails of ATP-binding cassette transporter research is a structural understanding of drug binding and transport in a eukaryotic multidrug resistance pump. These transporters are front-line mediators of drug resistance in cancers and represent an important therapeutic target in future chemotherapy. Although there has been intensive biochemical research into the human multidrug pumps, their 3D structure at atomic resolution remains unknown. The recent determination of the structure of a mouse P-glycoprotein at subatomic resolution is complemented by structures for a number of prokaryotic homologues. These structures have provided advances into our knowledge of the ATP-binding cassette exporter structure and mechanism, and have provided the template data for a number of homology modelling studies designed to reconcile biochemical data on these clinically important proteins.

  14. Efflux pump blockers in Gram-negative bacteria:The new generation of hydantoin based-modulators to improve antibiotic activity

    Directory of Open Access Journals (Sweden)

    Ewa eOtrębska-Machaj

    2016-05-01

    Full Text Available Multidrug resistant (MDR bacteria are an increasing health problem with the shortage of new active antibiotic agents. Among effective mechanisms that contribute to the spread of MDR Gram-negative bacteria are drug efflux pumps that expel clinically important antibiotic classes out of the cell. Drug pumps are attractive targets to restore the susceptibility towards the expelled antibiotics by impairing their efflux activity. Arylhydantoin derivatives were investigated for their potentiation of activities of selected antibiotics described as efflux substrates in Enterobacter aerogenes expressing or not AcrAB pump. Several compounds increased the bacterial susceptibility towards nalidixic acid, chloramphenicol and sparfloxacin and were further pharmacomodulated to obtain a better activity against the AcrAB producing bacteria.

  15. Adaptive and Mutational Resistance: Role of Porins and Efflux Pumps in Drug Resistance

    OpenAIRE

    Fernández, Lucía; Robert E W Hancock

    2012-01-01

    Summary: The substantial use of antibiotics in the clinic, combined with a dearth of new antibiotic classes, has led to a gradual increase in the resistance of bacterial pathogens to these compounds. Among the various mechanisms by which bacteria endure the action of antibiotics, those affecting influx and efflux are of particular importance, as they limit the interaction of the drug with its intracellular targets and, consequently, its deleterious effects on the cell. This review evaluates t...

  16. 细菌的多药耐药外排泵%Mutidrug-Restistance Efflux Pumps of Bacteria

    Institute of Scientific and Technical Information of China (English)

    刘茜醇; 王丹; 何亚峰; 陈未中; 陈浩

    2013-01-01

    During the past decades,the drug resistant pathogenic microorganism has been an increasingly serious problem with the abuse of antibiotics which have threatened the effective treatment of bacteria infections. Consequently, it also has caused people's high attention and continued to be a global concern. It is shown that the microorganism has many ways to resist the antibiotics and the mutidrug-restistance efflux pump is one of the most important paths. Recently,the study is focusing on how to inhibit the activity of mutidrug-restistance efflux pumps. It's quite helpful to develop new bacterial sensitive drugs using the efflux pumps as target through the structure and molecular mechanism study. The research will do a great help to slow down the drug resistance of bacterial in clinical therapy. In this paper,the main distribution, classification,structure features,mechanism of action and regulation of expression are summarized. The research significance and value as well as the research prospects are also clarified.%由于抗生素药物的不合理使用等原因,病原微生物耐药性问题日益突出,严重影响了细菌性感染疾病的治疗效果,也逐渐成为目前人类着重关注的健康问题.微生物可通过多种方式来抵御抗生素引起的毒性,其中利用耐药泵将药物直接外排的方式是细菌主要的耐药性机制之一.通过对耐药泵结构和机制的研究,有利于开发以多药耐药泵为作用靶点的细菌敏感型药物,对于降低细菌耐药性和进行临床治疗有重要指导意义.文章概述了当前细菌的多药耐药外排泵的主要分类和分布、结构特征、作用机制及表达调控等方面,阐明了多药耐药外排泵抑制剂的研究意义和价值,并对其研究前景进行展望.

  17. Amino acid amides of piperic acid (PA) and 4-ethylpiperic acid (EPA) as NorA efflux pump inhibitors of Staphylococcus aureus.

    Science.gov (United States)

    Wani, Naiem Ahmad; Singh, Samsher; Farooq, Saleem; Shankar, Sudha; Koul, Surrinder; Khan, Inshad Ali; Rai, Rajkishor

    2016-09-01

    A total of eighteen piperic acid (PA) and 4-ethylpiperic acid (EPA) amides (C1-C18) with α-, β- and γ-amino acids were synthesized, characterized and evaluated for their efflux pump inhibitory activity against ciprofloxacin resistant Staphylococcus aureus. The amides were screened against NorA overexpressing S. aureus SA-1199B and wild type S. aureus SA-1199 using ethidium bromide as NorA efflux pump substrate. EPI C6 was found to be most potent and reduced the MIC of ciprofloxacin by 16 fold followed by C18 which showed 4 fold reduction of MIC. Ethidium bromide efflux inhibition and accumulation assay proved these compounds as NorA inhibitors. PMID:27503686

  18. Structures of Gate Loop Variants of the AcrB Drug Efflux Pump Bound by Erythromycin Substrate

    Science.gov (United States)

    Ababou, Abdessamad; Koronakis, Vassilis

    2016-01-01

    Gram-negative bacteria such as E. coli use tripartite efflux pumps such as AcrAB-TolC to expel antibiotics and noxious compounds. A key feature of the inner membrane transporter component, AcrB, is a short stretch of residues known as the gate/switch loop that divides the proximal and distal substrate binding pockets. Amino acid substitutions of the gate loop are known to decrease antibiotic resistance conferred by AcrB. Here we present two new AcrB gate loop variants, the first stripped of its bulky side chains, and a second in which the gate loop is removed entirely. By determining the crystal structures of the variant AcrB proteins in the presence and absence of erythromycin and assessing their ability to confer erythromycin tolerance, we demonstrate that the gate loop is important for AcrB export activity but is not required for erythromycin binding. PMID:27403665

  19. From phenothiazine to 3-phenyl-1,4-benzothiazine derivatives as inhibitors of the Staphylococcus aureus NorA multidrug efflux pump.

    Science.gov (United States)

    Sabatini, Stefano; Kaatz, Glenn W; Rossolini, Gian Maria; Brandini, David; Fravolini, Arnaldo

    2008-07-24

    Overexpression of efflux pumps is an important mechanism by which bacteria evade effects of substrate antimicrobial agents and inhibition of such pumps is a promising strategy to circumvent this resistance mechanism. NorA is a Staphylococcus aureus multidrug efflux pump, the activity of which confers decreased susceptibility to many structurally unrelated agents, including fluoroquinolones, resulting in a multidrug resistant (MDR) phenotype. In this work, a series of 1,4-benzothiazine derivatives were designed and synthesized as a minimized structural template of phenothiazine MDR efflux pump inhibitors (EPIs) in an effort to identify more potent S. aureus NorA EPIs. Almost all derivatives evaluated showed good activity in combination with ciprofloxacin against S. aureus ATCC 25923; some were capable of completely restoring ciprofloxacin activity in a norA-overexpressing strain (SA-K2378). Compounds 6k and 7j displayed good activity against SA-1199B, a strain that also overexpresses norA, in an ethidium bromide (EtBr) efflux inhibition assay. PMID:18578473

  20. Effects of chlorophyll-derived efflux pump inhibitor pheophorbide a and pyropheophorbide a on erythromycin resistance of Staphylococcus aureus, Enterococcus faecalis, Salmonella Typhimurium and Escherichia coli

    Science.gov (United States)

    The purpose of this study was to validate the hypothesis that pheophorbide a and pyropheophorbide a reduce erythromycin resistance of reference strains of facultative anaerobic bacteria with multidrug or macrolide efflux pumps, as indicative of their effect on bacteria indigenous to anaerobic swine ...

  1. The Prevalence of the OqxAB Multidrug Efflux Pump amongst Olaquindox-Resistant Escherichia coli in Pigs

    DEFF Research Database (Denmark)

    Hansen, Lars Hestbjerg; Sørensen, Søren Johannes; Jørgensen, Helle S.;

    2005-01-01

    The quinoxaline olaquindox has been used extensively as a growth promoter for pigs. Recently, we isolated a plasmid (pOLA52) conferring resistance to olaquindox from swine manure. On this plasmid, the oqxA and oqxB genes encode an RND-family multidrug efflux pump, OqxAB. It facilitates resistance...

  2. Mutational Analysis of Intracellular Loops Identify Cross Talk with Nucleotide Binding Domains of Yeast ABC Transporter Cdr1p

    OpenAIRE

    Shah, Abdul Haseeb; Rawal, Manpreet Kaur; Dhamgaye, Sanjiveeni; Komath, Sneha Sudha; Saxena, Ajay Kumar; Prasad, Rajendra

    2015-01-01

    The ABC transporter Cdr1 protein (Cdr1p) of Candida albicans, which plays a major role in antifungal resistance, has two transmembrane domains (TMDs) and two nucleotide binding domains (NBDs) that are interconnected by extracellular (ECLs) and intracellular (ICLs) loops. To examine the communication interface between the NBDs and ICLs of Cdr1p, we subjected all four ICLs to alanine scanning mutagenesis, replacing each of the 85 residues with an alanine. The resulting ICL mutant library was an...

  3. The MerR-like regulator BrlR confers biofilm tolerance by activating multidrug efflux pumps in Pseudomonas aeruginosa biofilms.

    Science.gov (United States)

    Liao, Julie; Schurr, Michael J; Sauer, Karin

    2013-08-01

    A defining characteristic of biofilms is antibiotic tolerance that can be up to 1,000-fold greater than that of planktonic cells. In Pseudomonas aeruginosa, biofilm tolerance to antimicrobial agents requires the biofilm-specific MerR-type transcriptional regulator BrlR. However, the mechanism by which BrlR mediates biofilm tolerance has not been elucidated. Genome-wide transcriptional profiling indicated that brlR was required for maximal expression of genes associated with antibiotic resistance, in particular those encoding the multidrug efflux pumps MexAB-OprM and MexEF-OprN. Chromatin immunoprecipitation (ChIP) analysis revealed a direct regulation of these genes by BrlR, with DNA binding assays confirming BrlR binding to the promoter regions of the mexAB-oprM and mexEF-oprN operons. Quantitative reverse transcriptase PCR (qRT-PCR) analysis further indicated BrlR to be an activator of mexAB-oprM and mexEF-oprN gene expression. Moreover, immunoblot analysis confirmed increased MexA abundance in cells overexpressing brlR. Inactivation of both efflux pumps rendered biofilms significantly more susceptible to five different classes of antibiotics by affecting MIC but not the recalcitrance of biofilms to killing by bactericidal agents. Overexpression of either efflux pump in a ΔbrlR strain partly restored tolerance of ΔbrlR biofilms to antibiotics. Expression of brlR in mutant biofilms lacking both efflux pumps partly restored antimicrobial tolerance of biofilms to wild-type levels. Our results indicate that BrlR acts as an activator of multidrug efflux pumps to confer tolerance to P. aeruginosa biofilms and to resist the action of antimicrobial agents.

  4. The Biocide Triclosan Selects Stenotrophomonas maltophilia Mutants That Overproduce the SmeDEF Multidrug Efflux Pump

    OpenAIRE

    Sanchez, Patricia; Moreno, Eduardo; Jose L Martinez

    2005-01-01

    The possibility that triclosan selects Stenotrophomonas maltophilia mutants overexpressing the multidrug resistance pump SmeDEF is analyzed. Five out of 12 triclosan-selected mutants were less susceptible to antibiotics than the wild-type strain and overproduced SmeDEF. Results are discussed in relation to current debates on the potential selection of antibiotic-resistant bacteria by household biocides.

  5. Genetic Exchange of Multidrug Efflux Pumps among Two Enterobacterial Species with Distinctive Ecological Niches

    Directory of Open Access Journals (Sweden)

    Matthias S. Ullrich

    2009-02-01

    Full Text Available AcrAB-TolC is the major multidrug efflux system in Enterobacteriaceae recognizing structurally unrelated molecules including antibiotics, dyes, and detergents. Additionally, in Escherichia coli it mediates resistance to bile salts. In the plant pathogen Erwinia amylovora AcrAB-TolC is required for virulence and phytoalexin resistance. Exchange analysis of AcrAB-TolC was conducted by complementing mutants of both species defective in acrB or tolC with alleles from either species. The acrB and tolC mutants exhibited increased susceptibility profiles for 24 different antibiotics. All mutants were complemented with acrAB or tolC, respectively, regardless of the taxonomic origin of the alleles. Importantly, complementation of E. amylovora mutants with respective E. coli genes restored virulence on apple plants. It was concluded that AcrAB and TolC of both species could interact and that these interactions did not yield in altered functions despite the divergent ecological niches, to which E. coli and E. amylovora have adopted.

  6. Selecting surfactants for the maximum inhibition of the activity of the multidrug resistance efflux pump transporter, P-glycoprotein: conceptual development.

    Directory of Open Access Journals (Sweden)

    Apte Shireesh Prakash

    2010-12-01

    Full Text Available Amphiphilic excipients, such as surfactants, have been shown to be inhibitors of the multidrug resistance (MDR efflux pump transporter protein, P-glycoprotein (Pgp. In vitro studies using manysurfactants have demonstrated that those with an optimum hydrophilic-lipophilic balance (HLB exhibit greater efflux pump inhibition than those that are either very hydrophobic, or very hydrophilic, although the correlation of HLB to Pgp inhibition activity remains weak. Using the data from multiple in vitro studies, a model has been conceptualized that underscores the attributes of both the HLB and the critical micellar concentration (CMC, occurring in tandem, and unable of being varied independently, as key determinants toward prediction of surfactant Pgp inhibition activity. The algorithm that formalizes this concept provides a ‘semi-rational’ method of choosingsurfactants for a specific type of cancer for maximum inhibition of MDR.

  7. Structure-function analysis of the ATP-driven glycolipid efflux pump DevBCA reveals complex organization with TolC/HgdD.

    Science.gov (United States)

    Staron, Peter; Forchhammer, Karl; Maldener, Iris

    2014-01-31

    In Gram-negative bacteria, trans-envelope efflux pumps have periplasmic membrane fusion proteins (MFPs) as essential components. MFPs act as mediators between outer membrane factors (OMFs) and inner membrane factors (IMFs). In this study, structure-function relations of the ATP-driven glycolipid efflux pump DevBCA-TolC/HgdD from the cyanobacterium Anabaena sp. PCC 7120 were analyzed. The binding of the MFP DevB to the OMF TolC absolutely required the respective tip-regions. The interaction of DevB with the IMF DevAC mainly involved the β-barrel and the lipoyl domain. Efficient binding to DevAC and TolC, substrate recognition and export activity by DevAC were dependent on stable DevB hexamers. PMID:24361095

  8. Verapamil, and Its Metabolite Norverapamil, Inhibit Macrophage-induced, Bacterial Efflux Pump-mediated Tolerance to Multiple Anti-tubercular Drugs

    OpenAIRE

    Adams, Kristin N.; Szumowski, John D.; Ramakrishnan, Lalita

    2014-01-01

    Drug tolerance likely represents an important barrier to tuberculosis treatment shortening. We previously implicated the Mycobacterium tuberculosis efflux pump Rv1258c as mediating macrophage-induced tolerance to rifampicin and intracellular growth. In this study, we infected the human macrophage-like cell line THP-1 with drug-sensitive and drug-resistant M. tuberculosis strains and found that tolerance developed to most antituberculosis drugs, including the newer agents moxifloxacin, PA-824,...

  9. The Transcription Factor Mrr1p Controls Expression of the MDR1 Efflux Pump and Mediates Multidrug Resistance in Candida albicans

    OpenAIRE

    Joachim Morschhäuser; Katherine S. Barker; Liu, Teresa T.; Julia BlaB-Warmuth; Ramin Homayouni; P David Rogers

    2007-01-01

    Constitutive overexpression of the MDR1 (multidrug resistance) gene, which encodes a multidrug efflux pump of the major facilitator superfamily, is a frequent cause of resistance to fluconazole and other toxic compounds in clinical Candida albicans strains, but the mechanism of MDR1 upregulation has not been resolved. By genome-wide gene expression analysis we have identified a zinc cluster transcription factor, designated as MRR1 (multidrug resistance regulator), that was coordinately upregu...

  10. Differential Requirement of the Transcription Factor Mcm1 for Activation of the Candida albicans Multidrug Efflux Pump MDR1 by Its Regulators Mrr1 and Cap1▿

    OpenAIRE

    Mogavero, Selene; Tavanti, Arianna; Senesi, Sonia; Rogers, P. David; Morschhäuser, Joachim

    2011-01-01

    Overexpression of the multidrug efflux pump Mdr1 causes increased fluconazole resistance in the pathogenic yeast Candida albicans. The transcription factors Mrr1 and Cap1 mediate MDR1 upregulation in response to inducing stimuli, and gain-of-function mutations in Mrr1 or Cap1, which render the transcription factors hyperactive, result in constitutive MDR1 overexpression. The essential MADS box transcription factor Mcm1 also binds to the MDR1 promoter, but its role in inducible or constitutive...

  11. Azole resistance in Candida spp. isolated from Catú Lake, Ceará, Brazil: an efflux-pump-mediated mechanism

    Directory of Open Access Journals (Sweden)

    Raimunda S.N. Brilhante

    2016-03-01

    Full Text Available Abstract Since, there is no study reporting the mechanism of azole resistance among yeasts isolated from aquatic environments; the present study aims to investigate the occurrence of antifungal resistance among yeasts isolated from an aquatic environment, and assess the efflux-pump activity of the azole-resistant strains to better understand the mechanism of resistance for this group of drugs. For this purpose, monthly water and sediment samples were collected from Catú Lake, Ceará, Brazil, from March 2011 to February 2012. The obtained yeasts were identified based on morphological and biochemical characteristics. Of the 46 isolates, 37 were Candida spp., 4 were Trichosporon asahii, 3 were Cryptococcus laurentii, 1 Rhodotorula mucilaginosa, and 1 was Kodamaea ohmeri. These isolates were subjected to broth microdilution assay with amphotericin B, itraconazole, and fluconazole, according to the methodology standardized by the Clinical and Laboratory Standards Institute (CLSI. The minimum inhibitory concentrations (MICs of amphotericin B, itraconazole, and fluconazole were 0.03125–2 µg/mL, 0.0625 to ≥16 µg/mL, and 0.5 to ≥64 µg/mL, respectively, and 13 resistant azole-resistant Candida isolates were detected. A reduction in the azole MICs leading to the phenotypical reversal of the azole resistance was observed upon addition of efflux-pump inhibitors. These findings suggest that the azole resistance among environmental Candida spp. is most likely associated with the overexpression of efflux-pumps.

  12. Genome Sequence of a Clinical Strain of Acinetobacter baumannii Belonging to the ST79/PFGE-HUI-1 Clone Lacking the AdeABC (Resistance-Nodulation-Cell Division-Type) Efflux Pump.

    Science.gov (United States)

    López, M; Álvarez-Fraga, L; Gato, E; Blasco, L; Poza, M; Fernández-García, L; Bou, G; Tomás, M

    2016-01-01

    Increased expression of chromosomal genes for resistance-nodulation-cell division-type efflux systems plays a major role in the multidrug resistance of Acinetobacter baumannii Little is known about the genetic characteristics of clinical strains of Acinetobacter baumannii lacking the AdeABC pump. In this study, we sequenced the genome of clinical strain Ab421 GEIH-2010 (belonging to clone ST79/PFGE-HUI-1 from the GEIH-REIPI Ab. 2010 project) which lacks this efflux pump. PMID:27609928

  13. Overexpression of the novel MATE fluoroquinolone efflux pump FepA in Listeria monocytogenes is driven by inactivation of its local repressor FepR.

    Directory of Open Access Journals (Sweden)

    François Guérin

    Full Text Available Whereas fluoroquinolone resistance mainly results from target modifications in gram-positive bacteria, it is primarily due to active efflux in Listeria monocytogenes. The aim of this study was to dissect a novel molecular mechanism of fluoroquinolone resistance in this important human pathogen. Isogenic L. monocytogenes clinical isolates BM4715 and BM4716, respectively susceptible and resistant to fluoroquinolones, were studied. MICs of norfloxacin and ciprofloxacin were determined in the presence or in the absence of reserpine (10 mg/L. Strain BM4715 was susceptible to norfloxacin (MIC, 4 mg/L and ciprofloxacin (MIC, 0.5 mg/L whereas BM4716 was highly resistant to both drugs (MICs 128 and 32 mg/L, respectively. Reserpine was responsible for a 16-fold decrease in both norfloxacin and ciprofloxacin MICs against BM4716 suggesting efflux associated resistance. Whole-genome sequencing of the strains followed by comparative genomic analysis revealed a single point mutation in the gene for a transcriptional regulator, designated fepR (for fluoroquinolone efflux protein regulator belonging to the TetR family. The frame-shift mutation was responsible for the introduction of a premature stop codon resulting in an inactive truncated protein. Just downstream from fepR, the structural gene for an efflux pump of the MATE family (named FepA was identified. Gene expression was quantified by qRT-PCR and demonstrated that fepA expression was more than 64-fold higher in BM4716 than in BM4715. The clean deletion of the fepR gene from BM4715 was responsible for an overexpression of fepA with resistance to norfloxacin and ciprofloxacin, confirming the role of FepR as a local repressor of fepA. In conclusion, we demonstrated that overexpression of the new MATE efflux pump FepA is responsible for fluoroquinolone resistance in L. monocytogenes and secondary to inactivation of the FepR repressor.

  14. Detection of AdeABC efflux pump genes in tetracycline-resistant Acinetobacter baumannii isolates from burn and ventilator-associated pneumonia patients

    Directory of Open Access Journals (Sweden)

    Maryam Beheshti

    2014-01-01

    Full Text Available Purpose: Acinetobacter baumannii is the most prevalent nosocomial pathogen which have been emerged in the past three decades worldwide. The aim of this study was to assess the distribution of the AdeABC efflux pump genes, associated with tetracycline resistance in Acinetobacter baumannii isolates collected from burn infection and Ventilator Associated Pneumonia (VAP. Materials and Methods: Ninety-eight A. baumannii isolates were collected from two different hospitals in Tehran, Iran. Tetracycline susceptibility testing was performed by disk diffusion and agar dilution methods according to the CLSI guidelines. The presence of adeSR, adeB, drug efflux system genes in resistant isolates was assessed by polymerase chain reaction (PCR. Carbonyl cyanide 3-chlorophenylhydrazone (CCCP was used as a chemical inhibitor agent to assess the contribution of AdeABC efflux pump in tetracycline resistance isolates. Results: Approximately 48% (47 out of 98 of isolates showed resistance to tetracycline which 14 (14.2% isolates were corresponded to burn infection and the remaining 33 (33.8% strains were isolated from VAP. All tetracycline resistant isolates have AdeABC in PCR assay. The reduction of tetracycline MICs by using 50 μg/ml CCCP were as follows: in 18 isolates 2-4 fold reduction in MICs, 26 isolates showed 8 fold reduction,1 isolate showed 16 fold, 1 isolate showed 32 fold and the remaining 1 isolate showed 128 fold reduction in MICs. Conclusion: The results showed significant correlation between tetracycline resistance and AdeABC efflux pump genes in resistant A. baumannii isolates.

  15. 樱桃新砧木——马哈利‘CDR-1’的选育%A new cherry dwarf rootstock variety——Mahaleb ‘ CDR-1'

    Institute of Scientific and Technical Information of China (English)

    蔡宇良; 冯瑛; 张雪; 宛甜; 高平; 王玉

    2013-01-01

    樱桃新砧木马哈利‘CDR-1’属于马哈利樱桃种(Prunus mahaleb),为自然杂交种.‘CDR-1’萌芽力和成枝力强;抗根癌病能力优于中国樱桃和考特砧木;‘CDR-1’砧甜樱桃比酸樱桃及中国樱桃砧甜樱桃早果1~2 a;‘CDR-1’砧甜樱桃矮化效果达到中国樱桃砧甜樱桃的70%;有较强的耐盐碱性.适宜在陕西渭北、关中、陕南等同类地区栽植.%Mahaleh 'CDR-1' is a new Cherry rootstock of Prunus mahaleb , a natural hybrid with strong sprout capacity and branching ability. The resistance ability of 'CDR-1' rootstock to crown gall disease is superior to Chinese cherry (P. pseudo- cerasus) and Colt; Sweet cherry grafted on 'CDR-1' is one or two years earlier bearing than that on sour cherry(prunus cera- sus) and Chinese cherry (P. pseudocerasus); Dwarfing effect of 'CDR-1' compared with Chinese cherry (P. pseudocerasus L) is 70 percent and it has strong salt and alkaline tolerance ability. It is suitable for cultivation in Weibei Plateau , middle and south parts of Shaanxi or the similar area.

  16. Thiomers: Influence of molecular mass and thiol group content of poly(acrylic acid) on efflux pump inhibition.

    Science.gov (United States)

    Grabovac, Vjera; Laffleur, Flavia; Bernkop-Schnürch, Andreas

    2015-09-30

    The aim of the present study was to investigate the influence of molecular mass and thiol group content of poly(acrylic acid)-cysteine conjugates on the permeation of sulforhodamine 101 and penicillin G. acting as substrates for multidrug resistance-associated protein 2 efflux pump. Poly(acrylic acids) of 2 kDa, 100 kDa, 250 kDa, 450 kDa and 3000 kDa were conjugated with cysteine. The thiol group content of all these polymers was in the range from 343.3 ± 48.4 μmol/g to 450.3 ± 76.1 μmol/g. Transport studies were performed on rat small intestine mounted in Ussing-type chambers. Since 250 kDa poly(acrylic acid) showed the highest permeation enhancing effect, additionally thiolated 250 kDa polyacrylates displaying 157.2 μmol/g, 223.0 ± 18.1 and 355.9 μmol/g thiol groups were synthesized in order to investigate the influence of thiol group content on the permeation enhancement. The permeation of sulforhodamine was 3.93- and 3.85-fold improved using 250 kDa poly(acrylic acid)-cysteine conjugate exhibiting 355.9 ± 39.5 μmol/g and 223.0 ± 18.1 μmol/g thiol groups. Using the same conjugates the permeation of penicillin G was 1.70- and 1.59-fold improved, respectively. The study demonstrates that thiolated poly(acrylic acid) inhibits Mrp2 mediated transport and that the extent of inhibition depends on the molecular mass and degree of thiolation of the polymer. PMID:26238816

  17. Regulation of the AcrAB multidrug efflux pump in Salmonella enterica serovar Typhimurium in response to indole and paraquat.

    Science.gov (United States)

    Nikaido, Eiji; Shirosaka, Ikue; Yamaguchi, Akihito; Nishino, Kunihiko

    2011-03-01

    Salmonella enterica serovar Typhimurium has at least nine multidrug efflux pumps. Among these, AcrAB is constitutively expressed and is the most efficient, playing a role in both drug resistance and virulence. The acrAB locus is induced by indole, Escherichia coli-conditioned medium, and bile salts. This induction is dependent on RamA through the binding sequence in the upstream region of acrA that binds RamA. In the present study, we made a detailed investigation of the ramA and acrAB induction mechanisms in Salmonella in response to indole, a biological oxidant for bacteria. We found that acrAB and ramA induction in response to indole is dependent on RamR. However, the cysteine residues of RamR do not play a role in the induction of ramA in response to indole, and the oxidative effect of indole is therefore not related to ramA induction via RamR. Furthermore, we showed that paraquat, a superoxide generator, induces acrAB but not ramA. We further discovered that the mechanism of acrAB induction in response to paraquat is dependent on SoxS. The data indicate that there are at least two independent induction pathways for acrAB in response to extracellular signals such as indole and paraquat. We propose that Salmonella utilizes these regulators for acrAB induction in response to extracellular signals in order to adapt itself to environmental conditions. PMID:21148208

  18. Relation between bacterial efflux pump and antibiotic resistance%细菌外排泵与抗生素耐药的相关性

    Institute of Scientific and Technical Information of China (English)

    孙渊; 查伟斌; 周芳; 吴晓兰; 张经纬; 王广基

    2012-01-01

    抗生素耐药与临床用药紧密相关,一直以来都受到广泛关注.除了药物失活、靶点改变这些已经熟知的耐药机制以外,细菌外排泵的作用也是抗生素耐药的重要原因.外排泵在细菌中普遍存在并且底物十分广泛,其表达对多种细菌的先天耐药和后天耐药都有贡献.对于金黄色葡萄球菌、大肠杆菌、绿脓杆菌等细菌,外排泵导致的耐药是其耐药的主要原因,因此在临床用药过程中,外排泵产生的耐药成了不可忽略的因素.这也给新药研发提供了新的思路,已经有研究以外排泵为靶点开发新药,而开发能够规避外排泵作用的新型抗生素也是克服外排泵耐药的一个途径.本文从分类,结构,调控以及抑制剂等方面对近年来细菌外排转运体方面的研究进行综述,为进一步的探索提供参考.%Drug resistance in bacteria has attracted much attention in clinical antibacterial therapy for years. In addition to the well known mechanisms, such as inactivation of drugs and alteration of targets, drug extruding pumps also play a major role in resistance to antibacterials. Efflux pumps are widespread in bacteria and have broad variety of substrates. Their presence contributes both intrinsic and acquired bacterial resistance. Efflux-mediated drug-resistance has been recognized as the major mechanism of resistance to antibacterial agents in Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The impact of antibiotic efflux pumps on therapy must be taken fully into ac- count for the selection of antimicrobials. The design of specific, potent inhibitors appears to be an important goal for the improved control of infectious diseases in the near future. An alternative approach is to develop antibacterials that would bypass the action of efflux pumps. This paper will review recent progress on the role of bacterial efflux transporters in antibiotic resistance from the aspects of classification

  19. Insertion sequence disruption of adeR and ciprofloxacin resistance caused by efflux pumps and gyrA and parC mutations in Acinetobacter baumannii.

    Science.gov (United States)

    Lopes, B S; Amyes, S G B

    2013-02-01

    Acinetobacter baumannii is a pathogenic bacterium responsible for a wide range of infections in immunocompromised patients. This study examined the role of insertional inactivation of the adeR gene and its effect on adeABC gene expression along with characterisation of the gyrA and parC mutations involved in ciprofloxacin resistance in three A. baumannii clinical isolates and their derivatives. Primers designed for the detection of adeSRABC detected the presence of ISAba16, which disrupted the adeR gene in strain Ab12M, and ISAba1, which disrupted the same gene in strains Ab18 and Ab209. A second copy of ISAba1 was detected upstream of the adeA gene in Ab209 leading to AdeABC pump expression. AdeIJK pump expression was seen in all of the isolates but was not as significant as AdeABC expression. Minimum inhibitory concentrations of ciprofloxacin were ≥256 mg/L for all of the isolates and a decrease of ≥8-fold was seen following addition of the efflux pump inhibitor 1-(1-naphthylmethyl)-piperazine. Fluorometric analysis also demonstrated active efflux, with upregulation of adeIJK and some genes of the adeABC operon in some strains. Sequencing of the quinolone resistance-determining region of the gyrA and parC genes revealed a Ser83→Leu change in the gyrA gene and a novel change of Ser80→Trp in the parC gene of Ab12, Ab12M and Ab209; in Ab18 there was a Ser80→Leu change in parC. This study shows the multifactorial contribution of different mechanisms in A. baumannii leading to ciprofloxacin resistance. PMID:23217848

  20. Efflux pump gene hefA of Helicobacter pylori plays an important role in multidrug resistanceZhi-Qiang Liu,Peng-Yuan Zheng,Ping-Chang Yang

    Institute of Scientific and Technical Information of China (English)

    Zhi-Qiang Liu; Peng-Yuan Zheng; Ping-Chang Yang

    2008-01-01

    AIM:To determine whether efflux systems contribute to multidrug resistance of H pylori.METHODS:A chloramphenicol-induced multidrug resistance model of six susceptible H pylori strains(5 isolates and H pylori NCTC11637)was developed.Multidrug-resistant(MDR)strains were selected and the minimal inhibitory concentration(MIC)of erythromycin,metronidazole,penicillin G,tetracycline,and ciprofloxacin in multidrug resistant strains and their parent strains was determined by agar dilution tests.The level of mRNA expression of hefA was assessed by fluorescence real-time quantitative PCR.A H pylori LZ1026 knockout mutant(△H pylori LZ1026)for(putative)efflux protein was constructed by inserting the kanamycin resistance cassette from pEGFP-N2 into hefA,and its susceptibility profiles to 10 antibiotics were evaluated.RESULTS:The MIC of six multidrug-resistant strains(including 5 clinical isolates and H pylori NaCTC11637)increased significantly(≥4-fold)compared with their parent strains.The expression level of herA gene was significantly higher in the MDR strains than in their parent strains(P=0.033).A H pylori LZ1026 mutant was successfully constructed and the △H pylori LZ1026 was more susceptible to four of the 10 antibiotics.All the 20 strains displayed transcripts for hefA that con-firmed the in vitro expression of these genes.CONCLUSION:The efflux pump gene hefA plays an important role in multidrug resistance of H pylori.(C)2008 The WJG Press.All rights reserved.

  1. Reduced aeration affects the expression of the NorB efflux pump of Staphylococcus aureus by posttranslational modification of MgrA.

    Science.gov (United States)

    Truong-Bolduc, Que Chi; Hsing, Liao Chun; Villet, Regis; Bolduc, Gilles R; Estabrooks, Zoe; Taguezem, G Florent; Hooper, David C

    2012-04-01

    We previously showed that at acid pH, the transcription of norB, encoding the NorB efflux pump, increases due to a reduction in the phosphorylation level of MgrA, which in turn leads to a reduction in bacterial killing by moxifloxacin, a substrate of the NorB efflux pump. In this study, we demonstrated that reduced oxygen levels did not affect the transcript levels of mgrA but modified the dimerization of the MgrA protein, which remained mostly in its monomeric form. Under reduced aeration, we also observed a 21.7-fold increase in the norB transcript levels after 60 min of growth that contributed to a 4-fold increase in the MICs of moxifloxacin and sparfloxacin for Staphylococcus aureus RN6390. The relative proportions of MgrA in monomeric and dimeric forms were altered by treatment with H(2)O(2), but incubation of purified MgrA with extracts of cells grown under reduced but not normal aeration prevented MgrA from being converted to its dimeric DNA-binding form. This modification was associated with cleavage of a fragment of the dimerization domain of MgrA without change in MgrA phosphorylation and an increase in transcript levels of genes encoding serine proteases in cells incubated at reduced aeration. Taken together, these data suggest that modification of MgrA by proteases underlies the reversal of its repression of norB and increased resistance to NorB substrates in response to reduced-aeration conditions, illustrating a third mechanism of posttranslational modification, in addition to oxidation and phosphorylation, that modulates the regulatory activities of MgrA. PMID:22287526

  2. The impact of ColRS two-component system and TtgABC efflux pump on phenol tolerance of Pseudomonas putida becomes evident only in growing bacteria

    Directory of Open Access Journals (Sweden)

    Kivisaar Maia

    2010-04-01

    Full Text Available Abstract Background We have recently found that Pseudomonas putida deficient in ColRS two-component system is sensitive to phenol and displays a serious defect on solid glucose medium where subpopulation of bacteria lyses. The latter phenotype is significantly enhanced by the presence of phenol in growth medium. Here, we focused on identification of factors affecting phenol tolerance of the colR-deficient P. putida. Results By using transposon mutagenesis approach we identified a set of phenol-tolerant derivatives of colR-deficient strain. Surprisingly, half of independent phenol tolerant clones possessed miniTn5 insertion in the ttgABC operon. However, though inactivation of TtgABC efflux pump significantly enhanced phenol tolerance, it did not affect phenol-enhanced autolysis of the colR mutant on glucose medium indicating that phenol- and glucose-caused stresses experienced by the colR-deficient P. putida are not coupled. Inactivation of TtgABC pump significantly increased the phenol tolerance of the wild-type P. putida as well. Comparison of phenol tolerance of growing versus starving bacteria revealed that both ColRS and TtgABC systems affect phenol tolerance only under growth conditions and not under starvation. Flow cytometry analysis showed that phenol strongly inhibited cell division and to some extent also caused cell membrane permeabilization to propidium iodide. Single cell analysis of populations of the ttgC- and colRttgC-deficient strains revealed that their membrane permeabilization by phenol resembles that of the wild-type and the colR mutant, respectively. However, cell division of P. putida with inactivated TtgABC pump seemed to be less sensitive to phenol than that of the parental strain. At the same time, cell division appeared to be more inhibited in the colR-mutant strain than in the wild-type P. putida. Conclusions ColRS signal system and TtgABC efflux pump are involved in the phenol tolerance of P. putida. However, as

  3. Progress on reversal of activity of efflux pump in gram-negative resistance bacteria%逆转革兰阴性耐药菌外排泵活性的研究进展

    Institute of Scientific and Technical Information of China (English)

    徐艳玲; 王彤

    2013-01-01

    外排泵的过度表达是多重耐药菌的耐药机制之一,要对抗这种耐药机制,必须从基因、结构和功能多方面破译这个转运系统.通过了解外排泵如何工作,我们有可能发现一群新的抗菌分子,并可以统一叫做外排泵逆转剂,如膜通透性增高剂、外排泵抑制剂和外排泵竞争剂、特异性外排泵阻断剂、外排泵能量毒性剂等.目前已经发现一些化合物显示出有效阻断一些多重耐药革兰阴性菌的外排泵的作用,这一类家族代表了一个新的特异作用于细菌主动转运的抗菌素种类.%Over-expression of efflux pumps is one of the mechanisms causing multidrug resistant bacteria.It is necessary to clearly decipher this transport system from the genetic,structural,and functional aspects in order to combat this poly-selective mechanism.By understanding how efflux pumps work,we may be able to find a new group of antibacterial agents,termed efflux reversals,including membrane permeabilisers,efflux pump inhibitors and flux-competitive agents,specific blockers,energy poisons,etc.Several chemical families of efflux pump inhibitors have been described and characterized.This new family of molecules represents the first antibacterial class of compound specifically targeting active transport in the bacterial cell.

  4. Enhanced resistance to fluoroquinolones in laboratory-grown mutants & clinical isolates of Shigella due to synergism between efflux pump expression & mutations in quinolone resistance determining region

    Directory of Open Access Journals (Sweden)

    Neelam Taneja

    2015-01-01

    Full Text Available Background & objectives: There is a worldwide emergence of fluoroquinolone resistance in Shigella species. To understand the molecular mechanisms associated with fluoroquinolone resistance, naturally occurring fluoroquinolone-resistant strains and laboratory-induced spontaneous mutants of Shigella spp. were used and the relative contributions of acrAB-tolC efflux pumps, gyrase and topoisomerase target gene mutations towards fluoroquinolone resistance were determined. Methods: Eight Shigella flexneri and six S. dysenteriae clinical isolates were studied. Three consecutive mutants resistant to ciprofloxacin for S. flexneri SFM1 (≥0.25 µg/ml, SFM2 (≥4 µg/ml and SFM3 (≥32 µg/ml were selected in 15 steps from susceptible isolates by serial exposure to increasing concentrations of nalidixic acid and ciprofloxacin. Similarly, two mutants for S. dysenteriae SDM1 (≥0.25 µg/ml and SDM2 (≥4 µg/ml were selected in eight steps. After PCR amplification sequence analyses of gyrase and topoisomerase target genes were performed. Expression of efflux genes acrA, acrB, acrR and tolC was measured using real-time PCR. Results: Mutations were observed in gyrA Ser [83]→Leu, Asp [87]→Asn/Gly, Val [196]→Ala and in parC Phe [93]→Val, Ser [80]→Ile, Asp [101]→Glu and Asp [110]→Glu. Overall, acrA and acrB overexpression was associated with fluoroquinolone resistance ( p0 <0.05; while tolC and acrR expression levels did not. Interpretation & conclusions: Fluoroquinolone resistance in Shigella spp. is the end product of either a single or a combination of mutations in QRDRs and/ or efflux activity. Novel polymorphisms were observed at Val [196]→Ala in gyrA in clinical isolates and Phe [93]→Val, Asp [101]→Glu, Asp [110]→Glu and in parC in majority of laboratory-grown mutants.

  5. Tolerance of Listeria monocytogenes to Quaternary Ammonium Sanitizers Is Mediated by a Novel Efflux Pump Encoded by emrE.

    Science.gov (United States)

    Kovacevic, Jovana; Ziegler, Jennifer; Wałecka-Zacharska, Ewa; Reimer, Aleisha; Kitts, David D; Gilmour, Matthew W

    2016-02-01

    A novel genomic island (LGI1) was discovered in Listeria monocytogenes isolates responsible for the deadliest listeriosis outbreak in Canada, in 2008. To investigate the functional role of LGI1, the outbreak strain 08-5578 was exposed to food chain-relevant stresses, and the expression of 16 LGI1 genes was measured. LGI1 genes with putative efflux (L. monocytogenes emrE [emrELm]), regulatory (lmo1851), and adhesion (sel1) functions were deleted, and the mutants were exposed to acid (HCl), cold (4°C), salt (10 to 20% NaCl), and quaternary ammonium-based sanitizers (QACs). Deletion of lmo1851 had no effect on the L. monocytogenes stress response, and deletion of sel1 did not influence Caco-2 and HeLa cell adherence/invasion, whereas deletion of emrE resulted in increased susceptibility to QACs (P monocytogenes to QACs via emrELm. Since QACs are commonly used in the food industry, there is a concern that L. monocytogenes strains possessing emrE will have an increased ability to survive this stress and thus to persist in food processing environments. PMID:26590290

  6. Effects of Astragalus polysaccharides on P-glycoprotein efflux pump function and protein expression in H22 hepatoma cells in vitro

    Directory of Open Access Journals (Sweden)

    Tian Qing E

    2012-07-01

    Full Text Available Abstract Background Astragalus polysaccharides (APS are active constituents of Astragalus membranaceus. They have been widely studied, especially with respect to their immunopotentiating properties, their ability to counteract the side effects of chemotherapeutic drugs, and their anticancer properties. However, the mechanism by which APS inhibit cancer and the issue of whether that mechanism involves the reversal of multidrug resistance (MDR is not completely clear. The present paper describes an investigation of the effects of APS on P-glycoprotein function and expression in H22 hepatoma cell lines resistant to Adriamycin (H22/ADM. Methods H22/ADM cell lines were treated with different concentrations of APS and/or the most common chemotherapy drugs, such as Cyclophosphamid, Adriamycin, 5-Fluorouracil, Cisplatin, Etoposide, and Vincristine. Chemotherapeutic drug sensitivity, P-glycoprotein function and expression, and MDR1 mRNA expression were detected using MTT assay, flow cytometry, Western blotting, and quantitative RT-PCR. Results When used alone, APS had no anti-tumor activity in H22/ADM cells in vitro. However, it can increase the cytotoxicity of certain chemotherapy drugs, such as Cyclophosphamid, Adriamycin, 5-Fluorouracil, Cisplatin, Etoposide, and Vincristine, in H22/ADM cells. It acts in a dose-dependent manner. Compared to a blank control group, APS increased intracellular Rhodamine-123 retention and decreased P-glycoprotein efflux function in a dose-dependent manner. These factors were assessed 24 h, 48 h, and 72 h after administration. APS down regulated P-glycoprotein and MDR1 mRNA expression in a concentration-dependent manner within a final range of 0.8–500 mg/L and in a time-dependent manner from 24–72 h. Conclusion APS can enhance the chemosensitivity of H22/ADM cells. This may involve the downregulation of MDR1 mRNA expression, inhibition of P-GP efflux pump function, or both, which would decrease the expression

  7. RND type efflux pump system MexAB-OprM of pseudomonas aeruginosa selects bacterial languages, 3-oxo-acyl-homoserine lactones, for cell-to-cell communication

    Directory of Open Access Journals (Sweden)

    Minagawa Shu

    2012-05-01

    Full Text Available Abstract Background Bacteria release a wide variety of small molecules including cell-to-cell signaling compounds. Gram-negative bacteria use a variety of self-produced autoinducers such as acylated homoserine lactones (acyl-HSLs as signal compounds for quorum sensing (QS within and between bacterial species. QS plays a significant role in the pathogenesis of infectious diseases and in beneficial symbiosis by responding to acyl-HSLs in Pseudomonas aeruginosa. It is considered that the selection of bacterial languages is necessary to regulate gene expression and thus it leads to the regulation of virulence and provides a growth advantage in several environments. In this study, we hypothesized that RND-type efflux pump system MexAB-OprM of P. aeruginosa might function in the selection of acyl-HSLs, and we provide evidence to support this hypothesis. Results Loss of MexAB-OprM due to deletion of mexB caused increases in QS responses, as shown by the expression of gfp located downstream of the lasB promoter and LasB elastase activity, which is regulated by a LasR-3-oxo-C12-HSL complex. Either complementation with a plasmid containing wild-type mexB or the addition of a LasR-specific inhibitor, patulin, repressed these high responses to 3-oxo-acyl-HSLs. Furthermore, it was shown that the acyl-HSLs-dependent response of P. aeruginosa was affected by the inhibition of MexB transport activity and the mexB mutant. The P. aeruginosa MexAB-OprM deletion mutant showed a strong QS response to 3-oxo-C10-HSL produced by Vibrio anguillarum in a bacterial cross-talk experiment. Conclusion This work demonstrated that MexAB-OprM does not control the binding of LasR to 3-oxo-Cn-HSLs but rather accessibility of non-cognate acyl-HSLs to LasR in P. aeruginosa. MexAB-OprM not only influences multidrug resistance, but also selects acyl-HSLs and regulates QS in P. aeruginosa. The results demonstrate a new QS regulation mechanism via the efflux system MexAB-OprM in P

  8. Prevalence of Genes of OXA-23 Carbapenemase and AdeABC Efflux Pump Associated with Multidrug Resistance of Acinetobacter baumannii Isolates in the ICU of a Comprehensive Hospital of Northwestern China

    Directory of Open Access Journals (Sweden)

    Wei Jia

    2015-08-01

    Full Text Available The objective of this study was to explore the molecular epidemiology and the genetic support of clinical multidrug resistant (MDR Acinetobacter baumannii (A. baumannii isolates in an ICU ward of a comprehensive hospital. A total of 102 non-duplicate drug-resistant A. baumannii isolates were identified and 93 (91.1% of them were MDR strains. Molecular analysis demonstrated that carbapenemase genes blaOXA-23 and blaOXA-51 were presented in all 93 MDR isolates (100%, but other carbapenemase genes, including blaOXA-24, blaOXA-58, blaIMP-1, blaIMP-4, blaSIM, and blaVIM genes were completely absent in all isolates. In addition, genes of AdeABC efflux system were detected in 88.2% (90/102 isolates. Interestingly, an addition to efflux pump inhibitor, reserpine could significantly enhance the susceptibility of MDR isolates to moxifloxacin, cefotaxime, and imipenem (p < 0.01. Clonal relationship analysis further grouped these clinical drug-resistant isolates into nine clusters, and the MDR strains were mainly in clusters A, B, C, and D, which include 16, 13, 25, and 15 isolates, respectively. This study demonstrated that clinical isolates carrying carbapenemase-encoding genes blaOXA-23 and AdeABC efflux pump genes are the main prevalent MDR A. baumannii, and the co-expression of oxacillinase and efflux pump proteins are thus considered to be the important reason for the prevalence of this organism in the ICU of this hospital.

  9. A MATE-family efflux pump rescues the Escherichia coli 8-oxoguanine-repair-deficient mutator phenotype and protects against H(2O(2 killing.

    Directory of Open Access Journals (Sweden)

    Javier R Guelfo

    2010-05-01

    Full Text Available Hypermutation may accelerate bacterial evolution in the short-term. In the long-term, however, hypermutators (cells with an increased rate of mutation can be expected to be at a disadvantage due to the accumulation of deleterious mutations. Therefore, in theory, hypermutators are doomed to extinction unless they compensate the elevated mutational burden (deleterious load. Different mechanisms capable of restoring a low mutation rate to hypermutators have been proposed. By choosing an 8-oxoguanine-repair-deficient (GO-deficient Escherichia coli strain as a hypermutator model, we investigated the existence of genes able to rescue the hypermutable phenotype by multicopy suppression. Using an in vivo-generated mini-MudII4042 genomic library and a mutator screen, we obtained chromosomal fragments that decrease the rate of mutation in a mutT-deficient strain. Analysis of a selected clone showed that the expression of NorM is responsible for the decreased mutation rate in 8-oxoguanine-repair-deficient (mutT, mutY, and mutM mutY strains. NorM is a member of the multidrug and toxin extrusion (MATE family of efflux pumps whose role in E. coli cell physiology remains unknown. Our results indicate that NorM may act as a GO-system backup decreasing AT to CG and GC to TA transversions. In addition, the ability of NorM to reduce the level of intracellular reactive oxygen species (ROS in a GO-deficient strain and protect the cell from oxidative stress, including protein carbonylation, suggests that it can extrude specific molecules-byproducts of bacterial metabolism-that oxidize the guanine present in both DNA and nucleotide pools. Altogether, our results indicate that NorM protects the cell from specific ROS when the GO system cannot cope with the damage.

  10. 泵抑制剂提高肺炎克雷伯菌对环丙沙星的敏感性%Efflux pump Inhibitors improve the sensitivity of ciprofloxacin in drug-resistance Klebsiella pneumoniae

    Institute of Scientific and Technical Information of China (English)

    王若伦; 叶晓光

    2007-01-01

    目的 研究泵抑制剂利血平和羰基氰氯苯腙(CCCP)能否提高肺炎克雷伯菌对环丙沙星的敏感性.方法 收集临床分离对环丙沙星敏感的肺炎克雷伯菌20株,随机抽取10株,应用不同浓度梯度环丙沙星逐级诱导为高耐药株.用琼脂稀释法测定应用泵抑制剂前后,分离的临床敏感株和诱导耐药株的最小抑菌浓度(MIC).结果 应用泵抑制剂利血平和CCCP后,分别有6株(60%)和8株(80%)诱导耐药株的MIC值有所下降,泵阳性株分别有4株和7株.结论 起始低浓度后梯度环丙沙星可以人工诱导出肺炎克雷伯菌高度耐药株.泵抑制剂利血平和CCCP能提高耐药肺炎克雷伯菌对环丙沙星的敏感性.%Objective To explore whether efflux pump inhibitors can improve the sensitivity of ciprofloxacin in drug-resislance Klebsilla pneumoniae. Methods Twenty sensitive strains of Klebsiella pneumoniae were isolated from patients. Ten strains were induced by concentration gradient ciprofloxacin and changed into ciprofloxacin-high resistant Klebsiella pneumoniae. The MICs of ciprofloxacin in the absence or presence of reserpine or carbonyl cyanide m-chlorophenyl hydrazone(CCCP) were detected by agar dilution method. Results After treated with efflux pump inhibitor, the MICs of most induced-resistant bacteria to ciprofloxacin were decreased:6 strains (60%) and 8 strains (80%) in the presence of reserpine and CCCP respectively. The positive efflux pump Klebsiella prveumoniae strains in the presence of reserpine and CCCP were 4(40%) and 6(60%) respectively. Conclusions The high drug-resistance Klebsiella pneumoniae can be artificialy induced with concentration gradient of ciprofloxaein. The efflux pump inhibitors can obviously improve the antibacterial activities of ciprofloxacin in drug-resistance Klebsiella pneumoaiae.

  11. The Circular RNA Cdr1as Promotes Myocardial Infarction by Mediating the Regulation of miR-7a on Its Target Genes Expression.

    Directory of Open Access Journals (Sweden)

    Hai-Hua Geng

    Full Text Available Recent studies have demonstrated the role of Cdr1as (or CiRS-7, one of the well-identified circular RNAs (circRNAs, as a miR-7a/b sponge or inhibitor in brain tissues or islet cells. This study aimed to investigate the presence of Cdr1as/miR-7a pathway in cardiomyocytes, and explore the mechanism underlying the function of miR-7a in protecting against myocardial infarction (MI-induced apoptosis.Mouse MI injury model was established and evaluated by infarct size determination. Real-time PCR was performed to quantify the expression of Cdr1as and miR-7a in cardiomyocytes. Cell apoptosis was determined by caspase-3 activity analysis and flow cytometry assays with Annexin V/PI staining. Transfection of Cdr1as overexpressing plasmid and miR-7a mimic were conducted for gain-of-function studies. Luciferase reporter assay and western blot analysis were performed to verity potential miR-7a targets.Cdr1as and miR-7a were both upregulated in MI mice with increased cardiac infarct size, or cardiomyocytes under hypoxia treatment. Cdr1as overexpression in MCM cells promoted cell apoptosis, but was then reversed by miR-7a overexpression. The SP1 was identified as a new miR-7a target, in line with previously identified PARP, while miR-7a-induced decrease of cell apoptosis under hypoxia treatment was proven to be inhibited by PARP-SP1 overexpression. Moreover, Cdr1as overexpression in vivo increased cardiac infarct size with upregulated expression of PARP and SP1, while miR-7a overexpression reversed these changes.Cdr1as also functioned as a powerful miR-7a sponge in myocardial cells, and showed regulation on the protective role of miR-7a in MI injury, involving the function of miR-7a targets, PARP and SP1.

  12. The purine efflux pump PbuE in Bacillus subtilis modulates expression of the PurR and G-box (XptR) regulons by adjusting the purine base pool size

    DEFF Research Database (Denmark)

    Nygaard, P.; Saxild, Hans Henrik

    2005-01-01

    R protein and PRPP. The expression of the genes belonging to the G-box (XptR) regulon, including the pbuE gene, is negatively regulated by a ribo switch-control led transcription termination mechanism. The G-box regulon effector molecules are hypoxanthine and guanine. pbuE encodes a purine base efflux pump...... express a functional PbuE pump. In a mutant defective in the metabolism of adenine, the ade apt mutant, we found a high intracellular level of adenine and constitutive high levels of PbuE. A growth test using a purine auxotroph provided further evidence for the role of PbuE in lowering the intracellular...... evidence for important functions of the PbuE protein, such as acting as a pump that lowers the purine base pool and affects the expression of the G-box and PurR regulons, including pbuE itself, and as a pump involved in protection against toxic purine base analogs....

  13. 3-(Benzo[d][1,3]dioxol-5-ylamino)-N-(4-fluorophenyl)thiophene-2-carboxamide overcomes cancer chemoresistance via inhibition of angiogenesis and P-glycoprotein efflux pump activity.

    Science.gov (United States)

    Mudududdla, Ramesh; Guru, Santosh K; Wani, Abubakar; Sharma, Sadhana; Joshi, Prashant; Vishwakarma, Ram A; Kumar, Ajay; Bhushan, Shashi; Bharate, Sandip B

    2015-04-14

    3-((Quinolin-4-yl)methylamino)-N-(4-(trifluoromethoxy)phenyl)thiophene-2-carboxamide (OSI-930, 1) is a potent inhibitor of c-kit and VEGFR2, currently under phase I clinical trials in patients with advanced solid tumors. In order to understand the structure-activity relationship, a series of 3-arylamino N-aryl thiophene 2-carboxamides were synthesized by modifications at both quinoline and amide domains of the OSI-930 scaffold. All the synthesized compounds were screened for in vitro cytotoxicity in a panel of cancer cell lines and for VEGFR1 and VEGFR2 inhibition. Thiophene 2-carboxamides substituted with benzo[d][1,3]dioxol-5-yl and 2,3-dihydrobenzo[b][1,4]dioxin-6-yl groups 1l and 1m displayed inhibition of VEGFR1 with IC50 values of 2.5 and 1.9 μM, respectively. Compounds 1l and 1m also inhibited the VEGF-induced HUVEC cell migration, indicating its anti-angiogenic activity. OSI-930 along with compounds 1l and 1m showed inhibition of P-gp efflux pumps (MDR1, ABCB1) with EC50 values in the range of 35-74 μM. The combination of these compounds with doxorubicin led to significant enhancement of the anticancer activity of doxorubicin in human colorectal carcinoma LS180 cells, which was evident from the improved IC50 of doxorubicin, the increased activity of caspase-3 and the significant reduction in colony formation ability of LS180 cells after treatment with doxorubicin. Compound 1l showed a 13.8-fold improvement in the IC50 of doxorubicin in LS180 cells. The ability of these compounds to display dual inhibition of VEGFR and P-gp efflux pumps demonstrates the promise of this scaffold for its development as multi-drug resistance-reversal agents.

  14. Membrane fusion proteins of type I secretion system and tripartite efflux pumps share a binding motif for TolC in gram-negative bacteria.

    Directory of Open Access Journals (Sweden)

    Minho Lee

    Full Text Available The Hly translocator complex of Escherichia coli catalyzes type I secretion of the toxin hemolysin A (HlyA. In this complex, HlyB is an inner membrane ABC (ATP Binding Cassette-type transporter, TolC is an outer membrane channel protein, and HlyD is a periplasmic adaptor anchored in the inner membrane that bridges HlyB to TolC. This tripartite organization is reminiscent of that of drug efflux systems such as AcrA-AcrB-TolC and MacA-MacB-TolC of E. coli. We have previously shown the crucial role of conserved residues located at the hairpin tip region of AcrA and MacA adaptors during assembly of their cognate systems. In this study, we investigated the role of the putative tip region of HlyD using HlyD mutants with single amino acid substitutions at the conserved positions. In vivo and in vitro data show that all mutations abolished HlyD binding to TolC and resulted in the absence of HlyA secretion. Together, our results suggest that, similarly to AcrA and MacA, HlyD interacts with TolC in a tip-to-tip manner. A general model in which these conserved interactions induce opening of TolC during drug efflux and type I secretion is discussed.

  15. Assembly & Transport Mechanism of Tripartite Drug Efflux Systems

    OpenAIRE

    Misra, Rajeev; Bavro, Vassiliy N

    2009-01-01

    Multidrug efflux (MDR) pumps remove a variety of compounds from the cell into the external environment. There are five different classes of MDR pumps in bacteria, and quite often a single bacterial species expresses multiple classes of pumps. Although under normal circumstances MDR pumps confer low-level intrinsic resistance to drugs, the presence of drugs and mutations in regulatory genes lead to high level expression of MDR pumps that can pose problems with therapeutic treatments. This revi...

  16. The Transcriptional Repressor, MtrR, of the mtrCDE Efflux Pump Operon of Neisseria gonorrhoeae Can Also Serve as an Activator of “off Target” Gene (glnE Expression

    Directory of Open Access Journals (Sweden)

    Paul J. T. Johnson

    2015-06-01

    Full Text Available MtrR is a well-characterized repressor of the Neisseria gonorrhoeae mtrCDE efflux pump operon. However, results from a previous transcriptional profiling study suggested that MtrR also represses or activates expression of at least sixty genes outside of the mtr locus. Evidence that MtrR can directly repress so-called “off target” genes has previously been reported; in particular, MtrR was shown to directly repress glnA, which encodes glutamine synthetase. In contrast, evidence for the ability of MtrR to directly activate expression of gonococcal genes has been lacking; herein, we provide such evidence. We now report that MtrR has the ability to directly activate expression of glnE, which encodes the dual functional adenyltransferase/deadenylase enzyme GlnE that modifies GlnA resulting in regulation of its role in glutamine biosynthesis. With its capacity to repress expression of glnA, the results presented herein emphasize the diverse and often opposing regulatory properties of MtrR that likely contributes to the overall physiology and metabolism of N. gonorrhoeae.

  17. In vitro activity of levofloxacin against planktonic and biofilm Stenotrophomonas maltophilia lifestyles under conditions relevant to pulmonary infection in cystic fibrosis, and relationship with SmeDEF multidrug efflux pump expression.

    Science.gov (United States)

    Pompilio, Arianna; Crocetta, Valentina; Verginelli, Fabio; Bonaventura, Giovanni Di

    2016-07-01

    The activity of levofloxacin against planktonic and biofilm Stenotrophomonas maltophilia cells and the role played by the multidrug efflux pump SmeDEF were evaluated under conditions relevant to the cystic fibrosis (CF) lung. MIC, MBC and MBEC of levofloxacin were assessed, against five CF strains, under 'standard' (CLSI-recommended) and 'CF-like' (pH 6.8, 5% CO2, in a synthetic CF sputum) conditions. Levofloxacin was tested against biofilms at concentrations (10, 50 and 100 μg mL(-1)) corresponding to achievable serum levels and sputum levels by aerosolisation. smeD expression was evaluated, under both conditions, in planktonic and biofilm cells by RT-PCR. The bactericidal effect of levofloxacin was decreased, in three out of five strains tested, under 'CF-like' conditions (MBC: 2-4 vs 8-16 μg mL(-1), under 'standard' and 'CF-like' conditions, respectively). Biofilm was intrinsically resistant to levofloxacin, regardless of conditions tested (MBECs ≥ 100 μg mL(-1) for all strains). Only under 'CF-like' conditions, smeD expression increased during planktonic-to-biofilm transition, and in biofilm cells compared to stationary planktonic cells. Our findings confirmed that S. maltophilia biofilm is intrinsically resistant to therapeutic concentrations of levofloxacin. Under conditions relevant to CF, smeD overexpression could contribute to levofloxacin resistance. Further studies are warranted to define the clinical relevance of our findings. PMID:27242375

  18. The Transcriptional Repressor, MtrR, of the mtrCDE Efflux Pump Operon of Neisseria gonorrhoeae Can Also Serve as an Activator of "off Target" Gene (glnE) Expression.

    Science.gov (United States)

    Johnson, Paul J T; Shafer, William M

    2015-06-01

    MtrR is a well-characterized repressor of the Neisseria gonorrhoeae mtrCDE efflux pump operon. However, results from a previous transcriptional profiling study suggested that MtrR also represses or activates expression of at least sixty genes outside of the mtr locus. Evidence that MtrR can directly repress so-called "off target" genes has previously been reported; in particular, MtrR was shown to directly repress glnA, which encodes glutamine synthetase. In contrast, evidence for the ability of MtrR to directly activate expression of gonococcal genes has been lacking; herein, we provide such evidence. We now report that MtrR has the ability to directly activate expression of glnE, which encodes the dual functional adenyltransferase/deadenylase enzyme GlnE that modifies GlnA resulting in regulation of its role in glutamine biosynthesis. With its capacity to repress expression of glnA, the results presented herein emphasize the diverse and often opposing regulatory properties of MtrR that likely contributes to the overall physiology and metabolism of N. gonorrhoeae. PMID:26078871

  19. An attenuated mutant of the Rv1747 ATP-binding cassette transporter of Mycobacterium tuberculosis and a mutant of its cognate kinase, PknF, show increased expression of the efflux pump-related iniBAC operon

    Science.gov (United States)

    Spivey, Vicky L; Whalan, Rachael H; Hirst, Elizabeth M A; Smerdon, Stephen J; Buxton, Roger S

    2013-01-01

    The ATP-binding cassette transporter Rv1747 is required for the growth of Mycobacterium tuberculosis in mice and in macrophages. Its structure suggests it is an exporter. Rv1747 forms a two-gene operon with pknF coding for the serine/threonine protein kinase PknF, which positively modulates the function of the transporter. We show that deletion of Rv1747 or pknF results in a number of transcriptional changes which could be complemented by the wild type allele, most significantly up-regulation of the iniBAC genes. This operon is inducible by isoniazid and ethambutol and by a broad range of inhibitors of cell wall biosynthesis and is required for efflux pump functioning. However, neither the Rv1747 or pknF mutant showed increased susceptibility to a range of drugs and cell wall stress reagents including isoniazid and ethambutol, cell wall structure and cell division appear normal by electron microscopy, and no differences in lipoarabinomannan were found. Transcription from the pknF promoter was not induced by a range of stress reagents. We conclude that the loss of Rv1747 affects cell wall biosynthesis leading to the production of intermediates that cause induction of iniBAC transcription and implicates it in exporting a component of the cell wall, which is necessary for virulence. PMID:23915284

  20. The inhibition of autoreactive T cell functions by a peptide based on the CDR1 of an anti-DNA autoantibody is via TGF-beta-mediated suppression of LFA-1 and CD44 expression and function.

    Science.gov (United States)

    Sela, Uri; Mauermann, Nora; Hershkoviz, Rami; Zinger, Heidy; Dayan, Molly; Cahalon, Liora; Liu, Jian Ping; Mozes, Edna; Lider, Ofer

    2005-12-01

    Systemic lupus erythematosus (SLE), which is characterized by the increased production of autoantibodies and defective T cell responses, can be induced in mice by immunization with a human anti-DNA mAb that expresses a major Id, designated 16/6Id. A peptide based on the sequence of the CDR1 of the 16/6Id (human CDR1 (hCDR1)) ameliorated the clinical manifestations of SLE and down-regulated, ex vivo, the 16/6Id-induced T cell proliferation. In this study, we examined the mechanism responsible for the hCDR1-induced modulation of T cell functions related to the pathogenesis of SLE. We found that injection of hCDR1 into BALB/c mice concomitant with their immunization with 16/6Id resulted in a marked elevation of TGF-beta secretion 10 days later. Addition of TGF-beta suppressed the 16/6Id-stimulated T cell proliferation similarly to hCDR1. In addition, we provide evidence that one possible mechanism underlying the hCDR1- and TGFbeta-induced inhibition of T cell proliferation is by down-regulating the expression, and therefore the functions, of a pair of key cell adhesion receptors, LFA-1 (alphaLbeta2) and CD44, which operate as accessory molecules in mediating APC-T cell interactions. Indeed, T cells of mice treated with hCDR1 showed a TGF-beta-induced suppression of adhesion to the LFA-1 and CD44 ligands, hyaluronic acid and ICAM-1, respectively, induced by stromal cell-derived factor-1alpha and PMA. The latter suppression is through the inhibition of ERK phosphorylation. Thus, the down-regulation of SLE-associated responses by hCDR1 treatment may be due to the effect of the up-regulated TGF-beta on the expression and function of T cell adhesion receptors and, consequently, on T cell stimulation, adhesion, and proliferation. PMID:16301630

  1. Pseudoatomic Structure of the Tripartite Multidrug Efflux Pump AcrAB-TolC Reveals the Intermeshing Cogwheel-like Interaction between AcrA and TolC.

    Science.gov (United States)

    Jeong, Hyeongseop; Kim, Jin-Sik; Song, Saemee; Shigematsu, Hideki; Yokoyama, Takeshi; Hyun, Jaekyung; Ha, Nam-Chul

    2016-02-01

    The resistance-nodulation-division type tripartite pump AcrAB-TolC and its homologs are responsible for multidrug resistance in Gram-negative bacteria by expelling a wide variety of toxic substrates. The three essential components, AcrA, AcrB, and TolC, must function in concert with each respective binding partner within the complex. In this study, we report an 8.2-Å resolution cryo-electron microscopy (cryo-EM) 3D reconstruction of the complex that consists of an AcrAB fusion protein and a chimeric TolC protein. The pseudoatomic structure derived from the cryo-EM reconstruction clearly demonstrates a model only compatible with the adaptor bridging mechanism, wherein the funnel-like AcrA hexamer forms an intermeshing cogwheel-like interaction with the α-barrel tip region of TolC. These observations provide a structural milestone for understanding multidrug resistance in pathogenic Gram-negative bacteria, and may also lead to the design of new antibacterial drugs.

  2. Study of the Effective of Efflux Pump-Inhibitors in Photodynamic Therapy's Anticaries Effect%细菌外排泵抑制剂对光动力疗法防龋效果的影响

    Institute of Scientific and Technical Information of China (English)

    陶亚东; 邹朝晖; 孙盼盼; 阴慧娟

    2013-01-01

    Objective: To Study the effective of efflux pump-inhibitors---Verapamil in photodynamic therapy using toluidine blue O as photosensitizer on the cariogenic bacteria in dental plaque biofilms. Methods: According to the order of the verapamil and photosensitizer in the PDT process, Streptococcus mutans. Streptococcus sanguis, eosinophilic Lactobacillus and Actinomyces viscosus to establish the dental plaque biofilm model. The experiment is divided into five groups. Group A: saline-treated group, Group Bronly PDT group, Group C: Cells were incubated with the photosensitizer and verapamil group, Group D: Cells were incubated with verapamil before incubated the photosensitizer group, Group E: Cells were incubated with the photosensitizer before incubated verapamil group, the influence of the dental plaque biofilms was observed according to plate counting of bacteria method. The changes in the structure of biofilms after PDT were analysed by means of confocal laser scanning microscopy. Results: Compared to saline-treated group, in artificial caries model of only PDT group, the number of living cariogenic bacteria (CFU/mL) in plaque biofilms reduced more significantly (P<0. 05), the bactericidal rate upward to 81.02%, comperesd to group B, Cells were incubated with group D, there are a significant Declineing trend in the number of cariogenic bacteria (P<0.05), the sterilization rate was 93.60%. And the structure of dental plaque biofilms changed evidently. Conclusion: PDT is an effective method in eliminate cariogenic bacteria of dental plaque biofilms. And bacterial efflux pump inhibitors can improve PDT inhibition cariogenic bacteria in dental plaque biofilm.%目的:探讨细菌外排泵抑制剂(microbial efflux pump Inhibitor,EPI)——维拉帕米对以甲苯胺蓝O(toluidine blue O,TBO)为光敏剂的光动力疗法(photodynamic therapy,PDT)抑制牙菌斑生物膜内主要致龋菌作用的影响.方法:以变形链球菌、血链球菌、嗜酸性乳杆菌和粘

  3. 病原真菌外排转运蛋白与真菌耐药的研究进展%The progress of research on efflux pumps in pathogenic fungi and drug resistant

    Institute of Scientific and Technical Information of China (English)

    廖勇; 敖俊红; 杨蓉娅

    2011-01-01

    Only after overcoming both the host defenses system and antifungal treatment, maybe the pathogenic fungi can successfullymaintain its colonization and eventually lead to the infection of the host Efflux pumps in fungi play an important role in this process, mainlyincluding the ATP-binding cassette (ABC) pumps and the major facilitator superfamily (MFS) transporters. Through coupling transportwith ATP hydrolysis or a proton gradient respectively, they can transport and remove the intracellular toxic chemicals. Compared withother organisms, fungi have more coding genes of transporter families. These transporters of pathogenic fungi can export the compoundsproduced in the process of pathogenesis and antimicrobial components secreted by the host cell, meanwhile they also play an important rolein resistance of the pathogenic fungi against clinical antifungals. In this review, we discussed the role of these two superfamily transporters inresistance of main pathogenic fungi.%病原真菌通过对抗机体防御系统和抗真菌药物的攻击,从而成功定植于宿主体内并最终导致机体感染,真菌外排转运蛋白在上述过程中起着重要作用,主要包括ATP结合盒转运蛋白(ATP-binding cassette transporters,ABC)与主要易化子超家族(the major facilitator superfamily,MFS),分别通过与ATP水解酶或质子梯度耦台来运输并清除真菌胞内的毒性物质.与其它生物相比,真菌基因组中具有更多转运蛋白家族编码基因,这些转运蛋白不仅对真菌致病过程中所产生的代谢产物和宿主细胞分泌的抗菌成分起外排作用;同时,在病原真菌对抗临床抗真菌药物中也发挥着重要作用.本文就这两个超家族的转运蛋白在主要病原真菌耐药性中所发挥的作用进行综述.

  4. An ace up their sleeve: a transcriptomic approach exposes the AceI efflux protein of Acinetobacter baumannii and reveals the drug efflux potential hidden in many microbial pathogens

    Directory of Open Access Journals (Sweden)

    Karl A Hassan

    2015-04-01

    Full Text Available The era of antibiotics as a cure-all for bacterial infections appears to be coming to an end. The emergence of multidrug resistance in many hospital-associated pathogens has resulted in superbugs that are effectively untreatable. Multidrug efflux pumps are well known mediators of bacterial drug resistance. Genome sequencing efforts have highlighted an abundance of putative efflux pump genes in bacteria. However, it is not clear how many of these pumps play a role in antimicrobial resistance. Several studies have demonstrated that efflux pump genes that participate in drug resistance are typically under tight regulatory control and expressed only in response to their substrates. Consequently, changes in gene expression following antimicrobial shock treatments may be used to identify efflux pumps that mediate antimicrobial resistance, informing targeted functional analyses of these proteins. Using this approach we have characterised novel efflux pumps in both Gram-negative and Gram-positive bacteria. Notably, we recently applied this strategy to characterise the AceI efflux pump from Acinetobacter. AceI is a prototype for a new family of multidrug efflux proteins that is conserved across many proteobacterial lineages. Different efflux pumps in this family have been shown to confer resistance to biocides including chlorhexidine, dequalinium, benzalkonium, proflavine and/or acriflavine. The discovery of this novel family of multidrug efflux proteins raises the possibility that additional undiscovered intrinsic resistance proteins may be encoded in the core genomes of pathogenic bacteria.

  5. Relationship of AcrAB-TolC efflux pump and its regulatory gene mutation with fluoroquinolones resistance by Shigella.spp%志贺菌属外排泵AcrAB-TolC及其调控基因突变与氟喹诺酮耐药性的关系

    Institute of Scientific and Technical Information of China (English)

    杨贤; 董利娟; 祁伟; 程玉谦; 吕星; 梁帆

    2015-01-01

    Objective To investigate the role of AcrAB-TolC efflux pump in fluoroquinolones resistance by Shigella. spp and to explore the significance of AcrAB-TolC efflux pump on mutation of acrR, soxS and marOR as well as on drug re⁃sistence. Methods Drug resistant bacteria were selected by Kirby-Bauer disk diffusion test. After addition of efflux pump inhibitor carbonylcyanide-m-chlorophenylhydrazone (CCCP), change of minimal inhibitory concentration (MIC)s of nilidixic acid, Levofloxacin, ofloxacin, ciprofloxacin and Norfloxacin were examined. The DNA binding region of acrA, acrB, soxS, acrR and marOR gene in these mutants were amplified by PCR and sequenced. Results Among the 159 clinical isolates of Shigella,11 strains are resistant to fluoroquinolone. After the addition of CCCP, MICs of 2 fluoroquinolone resistant strains decreased; the MICs of 7 fluoroquinolone resistant strains did not change; MICs of 2 fluoroquinolone resistant strains in⁃creased. The corresponding nucleotides C, A, T, T on the 36th to 39th of marOR gene were missing, showing by sequencing, in fluoroquinolone resistent strains which might be regulated by the efflux pump gene AcrAB-TolC. Conclusion Efflux pump inhibitor could restrain the activity of efflux partially. The mutations of marOR might play an important role in fluoroquino⁃lone resistent by shigella.%目的:探讨临床分离耐氟喹诺酮志贺菌外排泵AcrAB-TolC基因及其调控基因marOR、acrR、soxS突变与耐药性的关系。方法使用K-B纸片扩散法筛选临床耐药菌,测定加入泵抑制剂羰基氢氯苯腙(CCCP)后萘啶酸、左氧氟沙星、氧氟沙星、环丙沙星、诺氟沙星的最低抑菌浓度(MIC)的变化,PCR扩增外排泵基因acrA、acrB及其调控基因marOR、acrR、soxS并测序。结果159株志贺菌中共筛选出11株氟喹诺酮耐药菌株;加入质子泵抑制剂后2株耐药菌株对氟喹诺酮类抗菌药的MIC下降;7株耐药菌对氟喹

  6. Efflux in fungi: la piece de resistance.

    Directory of Open Access Journals (Sweden)

    Jeffrey J Coleman

    2009-06-01

    Full Text Available Pathogens must be able to overcome both host defenses and antimicrobial treatment in order to successfully infect and maintain colonization of the host. One way fungi accomplish this feat and overcome intercellular toxin accumulation is efflux pumps, in particular ATP-binding cassette transporters and transporters of the major facilitator superfamily. Members of these two superfamilies remove many toxic compounds by coupling transport with ATP hydrolysis or a proton gradient, respectively. Fungal genomes encode a plethora of members of these families of transporters compared to other organisms. In this review we discuss the role these two fungal superfamilies of transporters play in virulence and resistance to antifungal agents. These efflux transporters are responsible not only for export of compounds involved in pathogenesis such as secondary metabolites, but also export of host-derived antimicrobial compounds. In addition, we examine the current knowledge of these transporters in resistance of pathogens to clinically relevant antifungal agents.

  7. 药物外排泵基因表达与结核分枝杆菌耐药关系的探讨%Association of drug efflux pump gene expression with Mycobacterium tuberculosis drug resistance

    Institute of Scientific and Technical Information of China (English)

    李桂莲; 王撷秀; 谢彤; 巨韩芳; 赵慧; 穆成; 赵德福

    2011-01-01

    目的 探讨MTB药物外排泵基因的表达与耐药表型、耐药相关基因突变型的关系.方法 从2007年天津市结核病控制中心参比室库存菌株中选择对异烟肼、利福平、链霉素和乙胺丁醇联合或单一耐药的全部耐药MTB菌株45株及对以上4种药物全敏感的MTB菌株26株(全敏组).采用直接测序法检测异烟肼耐药相关基因katG、inhA、oxyR-ahpC、ndh,利福平耐药相关基因rpoB,链霉素耐药相关基因rpsL、rrs和乙胺丁醇耐药相关基因embB、embC、embA的突变情况.提取菌株RNA后逆转录并采用real-time PCR方法检测药物外排泵基因Rv1410c、Rv2136c、Rv0783c和Rv1819c的表达量,并用方差分析和t检验的方法分析药物外排泵基因表达量在不同菌株耐药表型、耐药相关基因突变型菌株中的差异.结果 Rv1410c表达量在耐链霉素组[(8.48±6.33)×10-5],耐异烟肼组[(8.43±6.38)×10-5],耐利福平组[(9.59±7.27)×10-5],耐多药组[(10.37±7.86)×10-5],耐异烟肼+链霉素组[(9.39±6.81)×10-5],均高于全敏组表达量[(5.67±3.29)×10-5],差异有统计学意义(t′值分别为2.18、2.20、2.29、2.34、2.43,P均<0.05).Rv2136c表达量在耐异烟肼组[(3.51±2.43)×10-5],耐多药组[(4.21±2.94)×10-5],耐异烟肼+链霉素组[(3.81±2.46)×10-5]均高于全敏组表达量[(2.50±1.44)×10-5],差异有统计学意义(t′值分别为2.03、2.22、2.28,P均<0.05).rpoB 531突变型菌株Rv0783c的表达量[(5.41±3.03)×10-6]高于野生型耐利福平菌株[(2.29±1.62)×10-6],差异有统计学意义(t′=2.81,P<0.05).结论 Rv1410c和Rv2136c表达量高低与MTB对多种药物耐药有关,Rv0783c的高表达与利福平耐药株rpoB 531位密码子突变可能相关.%Objectives To explore the associations between drug efflux pump gene expression and phenotypic drug resistance as well as gene mutation patterns related to drug resistance of Mycobacterium tuberculosis.Methods Forty-five Mycobacterium tuberculosis

  8. Enhancement of antibiotic activity by efflux inhibitors against multidrug resistant Mycobacterium tuberculosis clinical isolates from Brazil

    Directory of Open Access Journals (Sweden)

    Tatiane eCoelho

    2015-04-01

    Full Text Available Drug resistant tuberculosis continues to increase and new approaches for its treatment are necessary. The identification of M. tuberculosis clinical isolates presenting efflux as part of their resistant phenotype has a major impact in tuberculosis treatment. In this work, we used a checkerboard procedure combined with the tetrazolium microplate-based assay (TEMA to study single combinations between antituberculosis drugs and efflux inhibitors (EIs against multidrug resistant M. tuberculosis clinical isolates using the fully susceptible strain H37Rv as reference. Efflux activity was studied on a real-time basis by a fluorometric method that uses ethidium bromide as efflux substrate. Quantification of efflux pump genes mRNA transcriptional levels were performed by RT-qPCR. The fractional inhibitory concentrations (FIC indicated synergistic activity for the interactions between isoniazid, rifampicin, amikacin, ofloxacin, and ethidium bromide plus the EIs verapamil, thioridazine and chlorpromazine. The FICs ranged from 0.25, indicating a four-fold reduction on the MICs, to 0.015, 64-fold reduction. The detection of active efflux by real-time fluorometry showed that all strains presented intrinsic efflux activity that contributes to the overall resistance which can be inhibited in the presence of the EIs. The quantification of the mRNA levels of the most important efflux pump genes on these strains shows that they are intrinsically predisposed to expel toxic compounds as the exposure to subinhibitory concentrations of antibiotics were not necessary to increase the pump mRNA levels when compared with the non-exposed counterpart. The results obtained in this study confirm that the intrinsic efflux activity contributes to the overall resistance in multidrug resistant clinical isolates of M. tuberculosis and that the inhibition of efflux pumps by the EIs can enhance the clinical effect of antibiotics that are their substrates.

  9. Association of AcrAB-tolC efflux pump and marA-soxS-rob regulon with ciprofloxacin-resistance in Shigella flexneri isolates%AcrAB-tolC外排泵及marA-soxS-rob调控系统对福氏志贺菌环丙沙星耐药性的影响

    Institute of Scientific and Technical Information of China (English)

    程玉谦; 杨贤; 祁伟

    2015-01-01

    Objective To investigate the association of AcrAB-tolC efflux pump and marA-soxS-rob regulon with ciprofloxacin-resistance in Shigella flexneri isolates.Methods Forty five strains of Shigella flexneri were isolated in stool samples collected from outpatient diarrhea clinics in Tianjin from 2009 to 2013.The antimicrobial susceptibility of bacteria was analyzed by Kirby-Bauer disk diffusion method.Ten ciprofloxacin-resistant Shigella flexneri isolates and 10 ciprofloxacin-sensitive isolates were randomly selected.The gyrA and parC genes,plasmid mediated quinolone resistant (PMQR) determinants,efflux pump genes (acrA,acrB) and regulation genes (marA,soxS,rob) were screened and sequenced.Minimum inhibition concentrations (MICs) of the strains were determined before and after efflux pump inhibitor carbonyl cyanide m-chlorophenylhydrazone (CCCP) was added.The expression of acrA,acrB,marA,soxS and rob genes in ciprofloxacin-resistant and ciprofloxacin-sensitive strains was detected by realtime fluorescence quantitative RCR (RT-PCR),and the differences of expression were evaluated using t test.Results Both gyrA and parC mutations were detected in all ciprofloxacin-resistant strains; qnrS1 was positive in ciprofloxacin-resistant strain CR2 and aac(6')-Ib-cr was positive in ciprofloxacin-resistant strain CR5.Efflux pump genes and regulation genes were not detected in ciprofloxacin-sensitive strains,while soxRS mutation was detected in all ciprofloxacin-resistant strains except CR10.MICs of quinolones in ciprofloxacin-resistant strains decreased to one-fourth or one-eighth when CCCP added,while not changed or only decreased to one-half in ciprofloxacin-sensitive strains.Expressions of acrA,acrB,marA and soxS were significantly higher in ciprofloxacin-resistant strains than those in ciprofloxacin-sensitive strains (P < 0.05 or P < 0.01).Conclusion Efflux pump may involve in the high-level ciprofloxacin resistance in Shigella flexneri through activating transcription of

  10. Exploring the contribution of efflux on the resistance to fluoroquinolones in clinical isolates of Staphylococcus aureus

    LENUS (Irish Health Repository)

    Costa, Sofia SANTOS

    2011-10-27

    Abstract Background Antimicrobial resistance mediated by efflux systems is still poorly characterized in Staphylococcus aureus, despite the description of several efflux pumps (EPs) for this bacterium. In this work we used several methodologies to characterize the efflux activity of 52 S. aureus isolates resistant to ciprofloxacin collected in a hospital in Lisbon, Portugal, in order to understand the role played by these systems in the resistance to fluoroquinolones. Results Augmented efflux activity was detected in 12 out of 52 isolates and correlated with increased resistance to fluoroquinolones. Addition of efflux inhibitors did not result in the full reversion of the fluoroquinolone resistance phenotype, yet it implied a significant decrease in the resistance levels, regardless of the type(s) of mutation(s) found in the quinolone-resistance determining region of grlA and gyrA genes, which accounted for the remaining resistance that was not efflux-mediated. Expression analysis of the genes coding for the main efflux pumps revealed increased expression only in the presence of inducing agents. Moreover, it showed that not only different substrates can trigger expression of different EP genes, but also that the same substrate can promote a variable response, according to its concentration. We also found isolates belonging to the same clonal type that showed different responses towards drug exposure, thus evidencing that highly related clinical isolates may diverge in the efflux-mediated response to noxious agents. The data gathered by real-time fluorometric and RT-qPCR assays suggest that S. aureus clinical isolates may be primed to efflux antimicrobial compounds. Conclusions The results obtained in this work do not exclude the importance of mutations in resistance to fluoroquinolones in S. aureus, yet they underline the contribution of efflux systems for the emergence of high-level resistance. All together, the results presented in this study show the potential

  11. Sodium content and sodium efflux of mononuclear leucocytes from young subjects at increased risk of developing essential hypertension

    DEFF Research Database (Denmark)

    Pedersen, K E; Nielsen, J R; Klitgaard, N A;

    1990-01-01

    Mononuclear leucocytes were used as a cellular model for the in vitro measurements of volume, sodium and potassium content, sodium efflux rate constants and absolute sodium efflux in order to assess any cellular changes in young men at increased risk of developing essential hypertension, and to a...... the sodium-potassium pump seems activated....

  12. Calcium efflux systems in stress signalling and adaptation in plants

    Directory of Open Access Journals (Sweden)

    Jayakumar eBose

    2011-12-01

    Full Text Available Transient cytosolic calcium ([Ca2+]cyt elevation is an ubiquitous denominator of the signalling network when plants are exposed to literally every known abiotic and biotic stress. These stress-induced [Ca2+]cyt elevations vary in magnitude, frequency and shape, depending on the severity of the stress as well the type of stress experienced. This creates a unique stress-specific calcium signature that is then decoded by signal transduction networks. While most published papers have been focused predominantly on the role of Ca2+ influx mechanisms in shaping [Ca2+]cyt signatures, restoration of the basal [Ca2+]cyt levels is impossible without both cytosolic Ca2+ buffering and efficient Ca2+ efflux mechanisms removing excess Ca2+ from cytosol, to reload Ca2+ stores and to terminate Ca2+ signalling. This is the topic of the current review. The molecular identity of two major types of Ca2+ efflux systems, Ca2+-ATPase pumps and Ca2+/H+ exchangers, is described, and their regulatory modes are analysed in detail. The spatial and temporal organisation of calcium signalling networks is described, and the importance of existence of intracellular calcium microdomains is discussed. Experimental evidence for the role of Ca2+ efflux systems in plant responses to a range of abiotic and biotic factors is summarised. Contribution of Ca2+-ATPase pumps and Ca2+/H+ exchangers in shaping [Ca2+]cyt signatures is then modelled by using a four-component model (plasma- and endo- membrane-based Ca2+-permeable channels and efflux systems taking into account the cytosolic Ca2+ buffering. It is concluded that physiologically relevant variations in the activity of Ca2+-ATPase pumps and Ca2+/H+ exchangers are sufficient to fully describe all the reported experimental evidence and determine the shape of [Ca2+]cyt signatures in response to environmental stimuli, emphasising the crucial role these active efflux systems play in plant adaptive responses to environment.

  13. Deciphering the role of RND efflux transporters in Burkholderia cenocepacia.

    Directory of Open Access Journals (Sweden)

    Silvia Bazzini

    Full Text Available Burkholderia cenocepacia J2315 is representative of a highly problematic group of cystic fibrosis (CF pathogens. Eradication of B. cenocepacia is very difficult with the antimicrobial therapy being ineffective due to its high resistance to clinically relevant antimicrobial agents and disinfectants. RND (Resistance-Nodulation-Cell Division efflux pumps are known to be among the mediators of multidrug resistance in gram-negative bacteria. Since the significance of the 16 RND efflux systems present in B. cenocepacia (named RND-1 to -16 has been only partially determined, the aim of this work was to analyze mutants of B. cenocepacia strain J2315 impaired in RND-4 and RND-9 efflux systems, and assess their role in the efflux of toxic compounds. The transcriptomes of mutants deleted individually in RND-4 and RND-9 (named D4 and D9, and a double-mutant in both efflux pumps (named D4-D9, were compared to that of the wild-type B. cenocepacia using microarray analysis. Microarray data were confirmed by qRT-PCR, phenotypic experiments, and by Phenotype MicroArray analysis. The data revealed that RND-4 made a significant contribution to the antibiotic resistance of B. cenocepacia, whereas RND-9 was only marginally involved in this process. Moreover, the double mutant D4-D9 showed a phenotype and an expression profile similar to D4. The microarray data showed that motility and chemotaxis-related genes appeared to be up-regulated in both D4 and D4-D9 strains. In contrast, these gene sets were down-regulated or expressed at levels similar to J2315 in the D9 mutant. Biofilm production was enhanced in all mutants. Overall, these results indicate that in B. cenocepacia RND pumps play a wider role than just in drug resistance, influencing additional phenotypic traits important for pathogenesis.

  14. The Study of Antibiotic-Induced Expression of SmeDEF Efflux Pump in Stenotrophomonas Maltophilia%抗生素诱导嗜麦芽窄食单胞菌临床株外排泵 SmeDEF 表达的研究

    Institute of Scientific and Technical Information of China (English)

    岳玮; 谭薇; 李晓明

    2013-01-01

    Objective To investigate the changes of antibiotic resistance in two clinical isolates of Smaltophilia and the repres -sion level of efflux pump SmeDEF induced by antibiotics .Methods The resistance of clinical strains was compared and the resistance chan -ges were investigated of clinical strains incubation in the LB broth ,containing different sub-inhibitory concentration(1 /2,1 /4 MIC) levofloxa-cin.The mRNA level of smeD was investigated by RTP -PCR.Results The two antibiotic-sensitive strains performed positive or negative to pump inhibits.The levofloxacin MICof of two strains after induced by the levofloxacin were higher by 1 ~3 dilution than before,but the tuime-thoprim-sulfamethoxazole MIChad showed no significant change .After using the efflux pump inhibitor CCCP ,MIC of two induced strains sig-nificantly reduced,but one could not be restored to the level that before induced .The level of mRNA of smeD of both antibiotic -induced strains rose.Conclusion The antibiotic resistance of Stenotrophomonas maltophilia clinical isolates induced by levofloxacin had increased , which was related to the expression of efflux pump Sme DEF .%  目的了解嗜麦芽窄食单胞菌2株临床分离株在抗生素诱导下耐药性和外排泵 SmeDEF 表达的变化。方法比较左氧氟沙星诱导前后嗜麦芽窄食单胞菌的 MIC 值,在不同亚抑菌浓度(1/2,1/4MIC)左氧氟沙星中培育后的菌株 MIC 变化。监测左氧氟沙星诱导前后菌株外排泵 SmeD 基因 RT-PCR 扩增后的表达水平。结果对抗生素敏感的两株菌泵抑制呈阳性或者阴性表现。两株菌经左氧氟沙星诱导后对左氧氟沙星的MIC 值比诱导前高1~3个稀释度,复方新诺明的 MIC 无明显变化。加用泵抑制 CCCP 后,2株诱导后的菌株MIC 值有较明显的降低,但其中1株不能恢复到诱导前水平。泵抑制剂阳性菌株抗生素过夜组和对数生长期添加组均明显高于无抗生素组的 SmeD 的表达。结论

  15. [Efflux systems in Serratia marcescens].

    Science.gov (United States)

    Mardanova, A M; Bogomol'naia, L M; Romanova, Iu D; Sharipova, M R

    2014-01-01

    A widespread bacterium Serratia marcescens (family Enterobacteriaceae) is an opportunistic and exhibits multiple drug resistance. Active removal of antibiotics and other antimicrobials from pathogen and exhibits multiple drug resistance. Active removal of antibiotics and other antimicrobials from the cells by efflux systems is one of the mechanisms responsible for microbial resistance to these compounds. Among enterobacteria, efflux systems of Escherichia coli and Salmonella enterica var. Typhimurium have been studied most extensively. Few efflux systems that belong to different families have been reported for S. marcescens. In this review, we analyzed available literature about S. marcescens efflux systems and carried out the comparative analysis of the genes encoding the RND type systems in different Serratia species and in other enterobacteria. Bioinformatical analysis of the S. marcescens genome allowed us to identify the previously unknown efflux systems based on their homology with the relevant E. coli genes. Identification of additional efflux systems in S. marcescens genome will promote our understanding of physiology of these bacteria, will detect new molecular mechanisms of resistance and will reveal their resistance potential.

  16. The Heterodimeric ABC Transporter EfrCD Mediates Multidrug Efflux in Enterococcus faecalis.

    Science.gov (United States)

    Hürlimann, Lea M; Corradi, Valentina; Hohl, Michael; Bloemberg, Guido V; Tieleman, D Peter; Seeger, Markus A

    2016-09-01

    Nosocomial infections with Enterococcus faecalis are an emerging health problem. However, drug efflux pumps contributing to intrinsic drug resistance are poorly studied in this Gram-positive pathogen. In this study, we functionally investigated seven heterodimeric ABC transporters of E. faecalis that are annotated as drug efflux pumps. Deletion of ef0789-ef0790 on the chromosome of E. faecalis resulted in increased susceptibility to daunorubicin, doxorubicin, ethidium, and Hoechst 33342, and the corresponding transporter was named EfrCD. Unexpectedly, the previously described heterodimeric multidrug ABC transporter EfrAB contributes marginally to drug efflux in the endogenous context of E. faecalis In contrast, heterologous expression in Lactococcus lactis revealed that EfrAB, EfrCD, and the product of ef2226-ef2227 (EfrEF) mediate the efflux of fluorescent substrates and confer resistance to multiple dyes and drugs, including fluoroquinolones. Four of seven transporters failed to exhibit drug efflux activity for the set of drugs and dyes tested, even upon overexpression in L. lactis Since all seven transporters were purified as heterodimers after overexpression in L. lactis, a lack of drug efflux activity is not attributed to poor expression or protein aggregation. Reconstitution of the purified multidrug transporters EfrAB, EfrCD, and EfrEF in proteoliposomes revealed functional coupling between ATP hydrolysis and drug binding. Our analysis creates an experimental basis for the accurate prediction of drug efflux transporters and indicates that many annotated multidrug efflux pumps might be incapable of drug transport and thus might fulfill other physiological functions in the cell. PMID:27381387

  17. Efflux transporter engineering markedly improves amorphadiene production in Escherichia coli.

    Science.gov (United States)

    Zhang, Congqiang; Chen, Xixian; Stephanopoulos, Gregory; Too, Heng-Phon

    2016-08-01

    Metabolic engineering aims at altering cellular metabolism to produce valuable products at high yields and titers. Achieving high titers and productivity can be challenging if final products are largely accumulated intracellularly. A potential solution to this problem is to facilitate the export of these substances from cells by membrane transporters. Amorphadiene, the precursor of antimalarial drug artemisinin, is known to be secreted from Escherichia coli overexpressing the biosynthetic pathway. In order to assess the involvement of various endogenous efflux pumps in amorphadiene transport, the effects of single gene deletion of 16 known multidrug-resistant membrane efflux transporters were examined. The outer membrane protein TolC was found to be intimately involved in amorphadiene efflux. The overexpression of tolC together with ABC family transporters (macAB) or MFS family transporters (emrAB or emrKY) enhanced amorphadiene titer by more than threefold. In addition, the overexpression of transporters in the lipopolysaccharide transport system (msbA, lptD, lptCABFG) was found to improve amorphadiene production. As efflux transporters often have a wide range of substrate specificity, the multiple families of transporters were co-expressed and synergistic benefits were observed in amorphadiene production. This strategy of screening and then rationally engineering transporters can be used to improve the production of other valuable compounds in E. coli. Biotechnol. Bioeng. 2016;113: 1755-1763. © 2016 Wiley Periodicals, Inc. PMID:26804325

  18. IP3 stimulates CA++ efflux from fusogenic carrot protoplasts

    International Nuclear Information System (INIS)

    Polyphosphoinositide breakdown plays an important role in signal transduction in animal cells (Berridge and Irvine, 1984, Nature, 312:315). Upon stimulation, phospholipase C hydrolyzes phosphatidylinositol 4,5-bisphosphate to inositol 1,4,5-trisphosphate (IP3) and diacylglycerol both of which act as cellular second messengers. IP3 mobilizes Ca++ from internal stores, hence the cytosolic free Ca++ concentration increases and those physiological activities regulated by Ca++ are stimulated. To test if plant cells also responded to IP3, Ca++ efflux studies were done with fusogenic carrot protoplasts released in EGTA. The protoplasts were preloaded with 45Ca++ placed in a Ca++-free medium, and efflux determined as 45Ca++ loss from the protoplasts. IP3 (10-20μM) caused enhanced 45Ca++ efflux and the response was sustained for at least 15 min. In plants, as in animals, the observed IP3-enhanced 45Ca++ efflux suggested that IP3 released Ca++ from internal stores, and the increased free cytosolic Ca++ activated Ca++ pumping mechanisms which restored the Ca++ concentration in the cytosol to the normal level

  19. Computational Study of Correlated Domain Motions in the AcrB Efflux Transporter

    OpenAIRE

    Schulz, Robert; Attilio V. Vargiu; Ruggerone, Paolo; Kleinekathöfer, Ulrich

    2015-01-01

    As active part of the major efflux system in E. coli bacteria, AcrB is responsible for the uptake and pumping of toxic substrates from the periplasm toward the extracellular space. In combination with the channel protein TolC and membrane fusion protein AcrA, this efflux pump is able to help the bacterium to survive different kinds of noxious compounds. With the present study we intend to enhance the understanding of the interactions between the domains and monomers, for example, the transduc...

  20. The role of active efflux in antibiotic - resistance of clinical isolates of Helicobacter pylori

    Directory of Open Access Journals (Sweden)

    Falsafi T

    2009-01-01

    Full Text Available Purpose: In gram-negative bacteria, active efflux pumps that excrete drugs can confer resistance to antibiotics however, in Helicobacter pylori this role is not well established. The purpose of this study is to evaluate the role of active efflux in resistance of H. pylori isolates to antibiotics. Materials and Methods: Twelve multiple antibiotic resistant (MAR isolates resistant to at least four antibiotics, including β-lactams, metronidazole, tetracycline, erythromycin, and ciprofloxacin; three resistant to only β-lactams, and two hyper-susceptible isolates, were obtained from screening of 96 clinical isolates of H. pylori . Their minimal inhibitory concentrations (MICs for antibiotics and ethidium-bromide (EtBr were compared in the presence- and absence of a proton-conductor, carbonyl cyanide-m chlorophenyl-hydrazone (CCCP using agar-dilution and disc diffusion. Drug accumulation studies for EtBr and antibiotics were assessed in the presence and absence of CCCP using spectrofluorometry. Results: MIC of EtBr for eight MAR-isolates was decreased two- to four-folds in the presence of CCCP, of which five showed reduced MICs for β-lactam, metronidazole, tetracycline, and ciprofloxacin with CCCP. Accumulation of EtBr by the MAR-isolates was rapid and not dependant on the pattern of multiple resistance. Antibiotic accumulation assay confirmed the presence of energy-dependant efflux of β-lactam, metronidazole, tetracycline, and ciprofloxacin, but no erythromycin in five MAR isolates. Energy-dependant efflux of EtBr or antibiotics was not observed for four MAR-isolates, and three isolates were resistant only to β-lactams. Conclusion: Energy-dependant efflux plays a role in the resistance of H. pylori clinical isolates to structurally unrelated antibiotics in a broadly specific multidrug efflux manner. Difference in the efflux potential of MAR isolates may be related to the presence or absence of functional efflux-pumps in diverse H. pylori

  1. Aminoglycoside Efflux in Pseudomonas aeruginosa: Involvement of Novel Outer Membrane Proteins

    OpenAIRE

    Jo, James T. H.; Brinkman, Fiona S.L.; Hancock, Robert E W

    2003-01-01

    The expression of tripartite multidrug efflux pumps such as MexA-MexB-OprM in Pseudomonas aeruginosa contributes to intrinsic resistance to a wide variety of antimicrobials, including β-lactams, chloramphenicol, macrolides, quinolones, and tetracycline. The MexX-MexY linker-pump combination has been shown to be involved in intrinsic resistance to aminoglycosides, but the identity of the cognate outer membrane channel component remains under debate. Fourteen uncharacterized OprM homologs ident...

  2. Peptide mediators of cholesterol efflux

    Energy Technology Data Exchange (ETDEWEB)

    Bielicki, John K.; Johansson, Jan

    2013-04-09

    The present invention provides a family of non-naturally occurring polypeptides having cholesterol efflux activity that parallels that of full-length apolipoproteins (e.g., Apo AI and Apo E), and having high selectivity for ABAC1 that parallels that of full-length apolipoproteins. The invention also provides compositions comprising such polypeptides, methods of identifying, screening and synthesizing such polypeptides, and methods of treating, preventing or diagnosing diseases and disorders associated with dyslipidemia, hypercholesterolemia and inflammation.

  3. Can celecoxib affect P-glycoprotein-mediated drug efflux? A microPET study

    NARCIS (Netherlands)

    De Vries, Erik F. J.; Doorduin, Janine; Vellinga, Namkje A. R.; Van Waarde, Aren; Dierckx, Rudi A.; Klein, Hans C.

    2008-01-01

    Introduction: P-glycoprotein (Pgp) is an efflux pump that protects vital organs like the brain from toxic substances, but which is also associated with therapy resistance. The anti-inflammatory drug celecoxib potentiates the efficacy of several cytostatic and neurotropic drugs that are known Pgp sub

  4. 细菌外排泵抑制剂对光动力疗法抑制牙菌斑生物膜内主要致龋菌作用的影响%Impact of Efflux Pump-Inhibitors on Inhibition of Cariogenic Bacteria in Dental Plaque Biofilms with Photodynamic Therapy

    Institute of Scientific and Technical Information of China (English)

    陶亚东; 邹朝晖; 孙盼盼; 郭鹏; 阴慧娟

    2012-01-01

    To Study the impact of the efflux pump-inhibitor, verapamil, on the cariogenic bacteria in dental plaque biofilms in the photodynamic therapy using hematoporphyrin monomethylether as photosensitizer.The dental plaque biofilm models were established with streptococcus mutans, streptococcus sanguis, eosinophilic lactoba- cillus and actinomyces viscosus. By the order to add verapamil and photosensitizer in the PDT process, five groups were created; Group A, in which cells were incubated with photosensitizer and verapamil simultaneously; Group B, in which cells were incubated with verapamil before photosensitizer, Group C, in which cells were incubated with photosensitizer before verapamil; Group D, in which cells were given only PDT; and Group E, the saline-treated group. After the laser irradiation, plate count of bacteria was obtained to evaluate the vitality of the dental plaque bacteria after the PDT. Results The reduction of living cariogenic bacteria (CFU/mL) in plaque biofilms was much more distinctive (P <0.05 ) in the sole PDT group than in the saline-treatment group, showing a bactericidal rate up to 94.92% . The comparison between Group B and Group D indicated a significant upward trend in the number of living cariogenic bacteria (P < 0. 05), and the sterilizationrate of the latter was 80.92%. Conclusions HMME-PDT inhibits effectively the growth of cariogenic bacteria and bacterial efflux pump plays an extremely important role in the process.%目的 探讨细菌外排泵抑制剂(microbial efflux pump Inhibitor,EPI)——维拉帕米对以血卟啉单甲醚(hematoporphyrin monomethylether,HMME)为光敏剂的光动力疗法(photodynamic therapy,PDT)抵抗牙菌斑生物膜内主要致龋菌作用的影响.方法 以变形链球菌、血链球菌、嗜酸性乳杆菌和粘性放线菌为实验菌株,建立牙菌斑生物膜模型.以维拉帕米作为细菌外排泵抑制剂,根据在PDT过程中加入维拉帕米和光敏剂的先后顺序,实验分为5

  5. Accumulation and efflux of polychlorinated biphenyls in Escherichia coli.

    Science.gov (United States)

    Geng, Shen; Fang, Jun; Turner, Kendrick B; Daunert, Sylvia; Wei, Yinan

    2012-06-01

    Polychlorinated biphenyls (PCBs) are environmental pollutants that have been associated with numerous adverse health effects in human and animals. Hydroxylated PCBs (HPCBs) are the product of the oxidative metabolism of PCBs. The presence of hydroxyl groups in HPCBs makes these compounds more hydrophilic than the parent PCBs. One of the best approaches to break down and remove these contaminants is bioremediation; an environmentally friendly process that uses microorganisms to degrade hazardous chemicals into non-toxic ones. In this study, we investigated the cellular accumulation and toxicity of selected PCBs and HPCBs in Gram-negative bacteria, using Escherichia coli as a model organism. We found that none of the five PCBs tested were toxic to E. coli, presumably due to their limited bioavailability. Nevertheless, different HPCBs tested showed different levels of toxicity. Furthermore, we demonstrated that the primary multidrug efflux system in E. coli, AcrAB-TolC, facilitated the efflux of HPCBs out of the cell. Since AcrAB-TolC is constitutively expressed in E. coli and is conserved in all sequenced Gram-negative bacterial genomes, our results suggest that the efflux activities of multidrug resistant pumps may affect the accumulation and degradation of PCBs in Gram-negative bacteria.

  6. CO2 Efflux from Cleared Mangrove Peat

    OpenAIRE

    Lovelock, Catherine E.; Roger W Ruess; Feller, Ilka C.

    2011-01-01

    BACKGROUND: CO(2) emissions from cleared mangrove areas may be substantial, increasing the costs of continued losses of these ecosystems, particularly in mangroves that have highly organic soils. METHODOLOGY/PRINCIPAL FINDINGS: We measured CO(2) efflux from mangrove soils that had been cleared for up to 20 years on the islands of Twin Cays, Belize. We also disturbed these cleared peat soils to assess what disturbance of soils after clearing may have on CO(2) efflux. CO(2) efflux from soils de...

  7. Structure and operation of bacterial tripartite pumps.

    Science.gov (United States)

    Hinchliffe, Philip; Symmons, Martyn F; Hughes, Colin; Koronakis, Vassilis

    2013-01-01

    In bacteria such as Pseudomonas aeruginosa and Escherichia coli, tripartite membrane machineries, or pumps, determine the efflux of small noxious molecules, such as detergents, heavy metals, and antibiotics, and the export of large proteins including toxins. They are therefore influential in bacterial survival, particularly during infections caused by multidrug-resistant pathogens. In these tripartite pumps an inner membrane transporter, typically an ATPase or proton antiporter, binds and translocates export or efflux substrates. In cooperation with a periplasmic adaptor protein it recruits and opens a TolC family cell exit duct, which is anchored in the outer membrane and projects across the periplasmic space between inner and outer membranes. Assembled tripartite pumps thus span the entire bacterial cell envelope. We review the atomic structures of each of the three pump components and discuss how these have allowed high-resolution views of tripartite pump assembly, operation, and possible inhibition. PMID:23808339

  8. Antiproliferation of Berberine in Combination with Fluconazole from the Perspectives of Reactive Oxygen Species, Ergosterol and Drug Efflux in a Fluconazole-Resistant Candida tropicalis Isolate

    Science.gov (United States)

    Shao, Jing; Shi, GaoXiang; Wang, TianMing; Wu, DaQiang; Wang, ChangZhong

    2016-01-01

    Candida tropicalis has emerged as an important pathogenic fungus in nosocomial infections due to its recalcitrant resistance to conventional antifungal agents, especially to fluconazole (FLC). Berberine (BBR) is a bioactive herbal-originated alkaloids and has been reported to possess antifungal functions against C. albicans. In this paper, we tried to figure out the antifungal mechanisms of BBR and/or FLC in a clinical C. tropicalis isolate 2006. In the microdilution test, the minimum inhibitory concentration (MIC) of BBR was found 16 μg/mL with fractional inhibitory concentration index (FICI) 0.13 in C. tropicalis 2006. The synergism of BBR and FLC was also confirmed microscopically. After the treatments of BBR and/or FLC, the studies revealed that (i) FLC facilitated BBR to increase reactive oxygen species (ROS), (ii) FLC enhanced the intranuclear accumulation of BBR, (iii) BBR decreased the extracellular rhodamine 123 (Rh123) via inhibiting efflux transporters, (iv) FLC assisted BBR to reduce ergosterol content, and (v) BBR in combined with FLC largely downregulated the expressions of Candida drug resistance 1 (CDR1) and CDR2 but impact slightly multidrug resistance 1 (MDR1), and upregulate the expression of ergosterol 11 (ERG11). These results suggested that BBR could become a potent antifungal drug to strengthen FLC efficacy in FLC-resistant C. tropicalis via ROS increase, intracellular BBR accumulation, ergosterol decrease and efflux inhibition. PMID:27721812

  9. Study of the effective of efflux pump inhibitors in photodynamic therapy inhibition the cariogenic bacteria in dental plaque biofilms%激光共聚焦显微镜观察维拉帕米对HMME-PDT抑制混合菌菌斑生物膜作用的影响

    Institute of Scientific and Technical Information of China (English)

    邹朝晖; 陶亚东; 孙盼盼; 阴慧娟; 李迎新

    2013-01-01

    Objective To Study the effect of efflux pump-inhibitors(EPI)-Verapamil in photodynamic therapy (PDT) using hematoporphyrin monomethylether (HMME) as photosensitizer on the cariogenic bacteria in dental plaque biofilms.Methods According to the administrator order of the verapamil and photosensitizer in PDT,streptococcus mutans,streptococcus sanguis,eosinophilic lactobacillus and actinomyces viscosus were used to establish the dental plaque biofilm model.The experiment was divided into five groups,group A was incubated with the photosensitizer and verapamil group,group B using verapamil before incubated the photosensitize,group C suing photosensitizer before incubated verapamil,group D with PDT only,group E was control group.After laser treatment,the influence of the dental plaque biofilms was observed by confocal laser scanning microscope.Results As saline-treated group is a group of normal the dental plaque biofilms.In PDT only group,compared with the saline group,red fluorescence increased significantly,the bacteria lose accumulation capacity,and were isolated and scattered in dispersed state.In PDT plus verapamil group,compared with only PDT group,green staining increased,bacterial activity increased.In group B,cells were incubated with verapamil before incubated the photosensitizer group,green staining increased significantly,red fluorescence reduced,indicating live bacteria increased,and bacteria activity was significantly increased.Conclusion PDT is an effective method in eliminating cariogenic bacteria of dental plaque biofilms.Bacterial efflux pump inhibitors can lower HMME-PDT inhibition cariogenic bacteria in dental plaque biofilm,and pre-verapamil administration could significantly inhibit the effect of PDT treatment of dental caries.%目的 探讨细菌外排泵抑制剂(EPI)——维拉帕米对以血卟啉单甲醚(HMME)为光敏剂的光动力疗法(PDT)抵抗牙菌斑生物膜内主要致龋菌作用的影响.方法 以变形链球菌、血链球菌

  10. Genomic potential for arsenic efflux and methylation varies among global Prochlorococcus populations.

    Science.gov (United States)

    Saunders, Jaclyn K; Rocap, Gabrielle

    2016-01-01

    The globally significant picocyanobacterium Prochlorococcus is the main primary producer in oligotrophic subtropical gyres. When phosphate concentrations are very low in the marine environment, the mol:mol availability of phosphate relative to the chemically similar arsenate molecule is reduced, potentially resulting in increased cellular arsenic exposure. To mediate accidental arsenate uptake, some Prochlorococcus isolates contain genes encoding a full or partial efflux detoxification pathway, consisting of an arsenate reductase (arsC), an arsenite-specific efflux pump (acr3) and an arsenic-related repressive regulator (arsR). This efflux pathway was the only previously known arsenic detox pathway in Prochlorococcus. We have identified an additional putative arsenic mediation strategy in Prochlorococcus driven by the enzyme arsenite S-adenosylmethionine methyltransferase (ArsM) which can convert inorganic arsenic into more innocuous organic forms and appears to be a more widespread mode of detoxification. We used a phylogenetically informed approach to identify Prochlorococcus linked arsenic genes from both pathways in the Global Ocean Sampling survey. The putative arsenic methylation pathway is nearly ubiquitously present in global Prochlorococcus populations. In contrast, the complete efflux pathway is only maintained in populations which experience extremely low PO4:AsO4, such as regions in the tropical and subtropical Atlantic. Thus, environmental exposure to arsenic appears to select for maintenance of the efflux detoxification pathway in Prochlorococcus. The differential distribution of these two pathways has implications for global arsenic cycling, as their associated end products, arsenite or organoarsenicals, have differing biochemical activities and residence times.

  11. Recent advances in the brain-to-blood efflux transport across the blood-brain barrier.

    Science.gov (United States)

    Hosoya, Ken-ichi; Ohtsuki, Sumio; Terasaki, Tetsuya

    2002-11-01

    Elucidating the details of the blood-brain barrier (BBB) transport mechanism is a very important step towards successful drug targeting to the brain and understanding what happens in the brain. Although several brain uptake methods have been developed to characterize transport at the BBB, these are mainly useful for investigating influx transport across the BBB. In 1992, P-glycoprotein was found to act as an efflux pump for anti-cancer drugs at the BBB using primary cultured bovine brain endothelial cells. In order to determine the direct efflux transport from the brain to the circulating blood of exogenous compounds in vivo, the Brain Efflux Index method was developed to characterize several BBB efflux transport systems. Recently, we have established conditionally immortalized rat (TR-BBB) and mouse (TM-BBB) brain capillary endothelial cell lines from transgenic rats and mice harboring temperature-sensitive simian virus 40 large T-antigen gene to characterize the transport mechanisms at the BBB in vitro. TR-BBB and TM-BBB cells possess certain in vivo transport functions and express mRNAs for the BBB. Using a combination of newly developed in vivo and in vitro methods, we have elucidated the efflux transport mechanism at the BBB for neurosteroids, excitatory neurotransmitters, suppressive neurotransmitters, amino acids, and other organic anions to understand the physiological role played by the BBB as a detoxifying organ for the brain. PMID:12429456

  12. Efflux as a Glutaraldehyde Resistance Mechanism in Pseudomonas fluorescens and Pseudomonas aeruginosa Biofilms

    OpenAIRE

    Vikram, Amit; Jennifer M Bomberger; Kyle J Bibby

    2015-01-01

    A major challenge in microbial biofilm control is biocide resistance. Phenotypic adaptations and physical protective effects have been historically thought to be the primary mechanisms for glutaraldehyde resistance in bacterial biofilms. Recent studies indicate the presence of genetic mechanisms for glutaraldehyde resistance, but very little is known about the contributory genetic factors. Here, we demonstrate that efflux pumps contribute to glutaraldehyde resistance in Pseudomonas fluorescen...

  13. Effect of efflux pump inhibitor CCCP on antibiotic resistance of multidrug resistant Escherichia coli%外排泵抑制剂羰酰氰间氯苯腙对多重耐药大肠埃希菌的耐药性影响

    Institute of Scientific and Technical Information of China (English)

    邹永胜; 王旭; 黄永茂; 游春芳; 陈枫; 钟利; 向成玉; 陈庄

    2013-01-01

    Objective To investigate the effect of carbonyl cyanide m-chlorophenylhydrazone (CCCP) on drug resistance of multidrug resistant Escherichia coli. Methods Disk diffusion (Kirby-Bauer test method) was used to detect the susceptibility of 71 strains of E. coli to 6 kinds of antibiotics, PCR assay to detect the acrA and acrB genes in E. coli strains, and constant broth dilution method to determine minimum inhibitory concentrations (MICs) of 2 fluoroquinolones to E. coli. MICs detected before and after CCCP was added were compared. Results Totally 71 strains were found resistant to 6 kinds of antibiotics (3 categories). The resistant rate of E. coli to ciprofloxacin was the highest (73.24%), and that of E. coli to aztreonam was the lowest (30.99%). Multidrug resistance (52.11%) was the main resistance pattern. AcrA/acrB positive rates were high (91.89% and 81.03%, respectively) in multidrug resistant strains. Variations of MICs detected before and after CCCP was added in multidrug resistant and sensitive strains were significantly different. Conclusion Efflux pump inhibitor CCCP can reduce the MICs of fluoroquinolone antibiotics to multidrug resistant E. coli.%目的 探讨外排泵抑制剂羰酰氰间氯苯腙(carbonyl cyanide m-chlorophenylhydrazone,CCCP)对多重耐药大肠埃希菌的耐药性影响.方法 采用纸片扩散法(K-B法)进行71株大肠埃希菌对6种抗菌药物的药物敏感性检测,用PCR技术检测受试菌株携带的acrA和acrB基因,用常量肉汤稀释法测定2种氟喹诺酮类抗菌药物对大肠埃希菌的最低抑菌浓度(minimum inhibitory concentrations,MICs),并对比加入CCCP前后的MICs值.结果 71株大肠埃希菌对3类6种抗菌药物耐药,其中对环丙沙星耐药率最高(73.24%),对氨曲南耐药率最低(30.99%),耐药模式以多重耐药为主(52.11%);外排泵基因acrA和acrB在多重耐药菌株中阳性率高达91.89%和81.03%;加入CCCP前后多重耐药菌株和敏感菌株的MICs值

  14. Pumped limiter results on TFR Tokamak plasma

    International Nuclear Information System (INIS)

    Pump limiter experiments are carried out in the TFR Tokamak. The pump limiter is located in the outer part of the torus, its double- throat head is made of graphite tiles and it is pumped by a 2000 ls-1 titanium sublimation pump. The first attempts showed that the exhaust efficiency of this pump limiter was low (ε = 1.5% of the total plasma particle efflux). To improve these results, a new limiter head with a single longer throat has been built; particles were better trapped and the pumping provided an important decrease of the recycling coefficient. Geometric features mainly explain the increase by a factor 3.5 of the exhaust efficiency (ε = 5.5%). Ion temperature of the order of a few eV has been deduced from Doppler broadening measurements at the neutralizer plate of the pump limiter

  15. Basal efflux of bile acids contributes to drug-induced bile acid-dependent hepatocyte toxicity in rat sandwich-cultured hepatocytes.

    Science.gov (United States)

    Susukida, Takeshi; Sekine, Shuichi; Ogimura, Eiichiro; Aoki, Shigeki; Oizumi, Kumiko; Horie, Toshiharu; Ito, Kousei

    2015-10-01

    The bile salt export pump (BSEP or Bsep) functions as an apical transporter to eliminate bile acids (BAs) from hepatocytes into the bile. BSEP or Bsep inhibitors engender BA retention, suggested as an underlying mechanism of cholestatic drug-induced liver injury. We previously reported a method to evaluate BSEP-mediated BA-dependent hepatocyte toxicity by using sandwich-cultured hepatocytes (SCHs). However, basal efflux transporters, including multidrug resistance-associated proteins (MRP or Mrp) 3 and 4, also participate in BA efflux. This study examined the contribution of basal efflux transporters to BA-dependent hepatocyte toxicity in rat SCHs. The apical efflux of [(3)H]taurocholic acid (TC) was potently inhibited by 10 μM cyclosporine A (CsA), with later inhibition of basal [(3)H]TC efflux, while MK571 simultaneously inhibited both apical and basal [(3)H]TC efflux. CsA-induced BA-dependent hepatocyte toxicity was 30% at most at 10 μM CsA and ∼60% at 50 μM, while MK571 exacerbated hepatocyte toxicity at concentrations of ≥50 μM. Quinidine inhibited only basal [(3)H]TC efflux and showed BA-dependent hepatocyte toxicity in rat SCHs. Hence, inhibition of basal efflux transporters as well as Bsep may precipitate BA-dependent hepatocyte toxicity in rat SCHs. PMID:26055650

  16. Lack of efflux mediated quinolone resistance in Salmonella enterica serovars Typhi and Paratyphi A

    Directory of Open Access Journals (Sweden)

    Sylvie eBaucheron

    2014-01-01

    Full Text Available Salmonella enterica serovars Typhi and Paratyphi A isolates from human patients in France displaying different levels of resistance to quinolones or fluoroquinolones were studied for resistance mechanisms to these antimicrobial agents. All resistant isolates carried either single or multiple target gene mutations (i.e. in gyrA, gyrB, or parC correlating with the resistance levels observed. Active efflux, through upregulation of multipartite efflux systems, has also been previously reported as contributing mechanism for other serovars. Therefore, we investigated also the occurrence of non-target gene mutations in regulatory regions affecting efflux pump expression. However, no mutation was detected in these regions in both Typhi and Paratyphi isolates of this study. Besides, no overexpression of the major efflux systems was observed for these isolates. Nevertheless, a large deletion of 2334 bp was identified in the acrS-acrE region of all S. Typhi strains but which did not affect the resistance phenotype. As being specific to S. Typhi, this deletion could be used for specific molecular detection purposes. In conclusion, the different levels of quinolone or FQ resistance in both S. Typhi and S. Paratyphi A seem to rely only on target modifications.

  17. Assessment of three Resistance-Nodulation-Cell Division drug efflux transporters of Burkholderia cenocepacia in intrinsic antibiotic resistance

    Directory of Open Access Journals (Sweden)

    Venturi Vittorio

    2009-09-01

    Full Text Available Abstract Background Burkholderia cenocepacia are opportunistic Gram-negative bacteria that can cause chronic pulmonary infections in patients with cystic fibrosis. These bacteria demonstrate a high-level of intrinsic antibiotic resistance to most clinically useful antibiotics complicating treatment. We previously identified 14 genes encoding putative Resistance-Nodulation-Cell Division (RND efflux pumps in the genome of B. cenocepacia J2315, but the contribution of these pumps to the intrinsic drug resistance of this bacterium remains unclear. Results To investigate the contribution of efflux pumps to intrinsic drug resistance of B. cenocepacia J2315, we deleted 3 operons encoding the putative RND transporters RND-1, RND-3, and RND-4 containing the genes BCAS0591-BCAS0593, BCAL1674-BCAL1676, and BCAL2822-BCAL2820. Each deletion included the genes encoding the RND transporter itself and those encoding predicted periplasmic proteins and outer membrane pores. In addition, the deletion of rnd-3 also included BCAL1672, encoding a putative TetR regulator. The B. cenocepacia rnd-3 and rnd-4 mutants demonstrated increased sensitivity to inhibitory compounds, suggesting an involvement of these proteins in drug resistance. Moreover, the rnd-3 and rnd-4 mutants demonstrated reduced accumulation of N-acyl homoserine lactones in the growth medium. In contrast, deletion of the rnd-1 operon had no detectable phenotypes under the conditions assayed. Conclusion Two of the three inactivated RND efflux pumps in B. cenocepacia J2315 contribute to the high level of intrinsic resistance of this strain to some antibiotics and other inhibitory compounds. Furthermore, these efflux systems also mediate accumulation in the growth medium of quorum sensing molecules that have been shown to contribute to infection. A systematic study of RND efflux systems in B. cenocepacia is required to provide a full picture of intrinsic antibiotic resistance in this opportunistic

  18. Computational Study of Correlated Domain Motions in the AcrB Efflux Transporter

    Directory of Open Access Journals (Sweden)

    Robert Schulz

    2015-01-01

    Full Text Available As active part of the major efflux system in E. coli bacteria, AcrB is responsible for the uptake and pumping of toxic substrates from the periplasm toward the extracellular space. In combination with the channel protein TolC and membrane fusion protein AcrA, this efflux pump is able to help the bacterium to survive different kinds of noxious compounds. With the present study we intend to enhance the understanding of the interactions between the domains and monomers, for example, the transduction of mechanical energy from the transmembrane domain into the porter domain, correlated motions of different subdomains within monomers, and cooperative effects between monomers. To this end, targeted molecular dynamics simulations have been employed either steering the whole protein complex or specific parts thereof. By forcing only parts of the complex towards specific conformational states, the risk for transient artificial conformations during the simulations is reduced. Distinct cooperative effects between the monomers in AcrB have been observed. Possible allosteric couplings have been identified providing microscopic insights that might be exploited to design more efficient inhibitors of efflux systems.

  19. Efflux Inhibition with Verapamil Potentiates Bedaquiline in Mycobacterium tuberculosis

    OpenAIRE

    Gupta, Shashank; Cohen, Keira A.; Winglee, Kathryn; Maiga, Mamoudou; Diarra, Bassirou; Bishai, William R.

    2014-01-01

    Drug efflux is an important resistance mechanism in Mycobacterium tuberculosis. We found that verapamil, an efflux inhibitor, profoundly decreases the MIC of bedaquiline and clofazimine to M. tuberculosis by 8- to 16-fold. This exquisite susceptibility was noted among drug-susceptible and drug-resistant clinical isolates. Thus, efflux inhibition is an important sensitizer of bedaquiline and clofazimine, and efflux may emerge as a resistance mechanism to these drugs.

  20. Drug efflux proteins in multidrug resistant bacteria

    NARCIS (Netherlands)

    vanVeen, HW; Konings, WN

    1997-01-01

    Bacteria contain an array of transport proteins in their cytoplasmic membrane. Many of these proteins play an important role in conferring resistance to toxic compounds. The multidrug efflux systems encountered in prokaryotic cells are very similar to those observed in eukaryotic cells. Therefore, a

  1. CO2 efflux from cleared mangrove peat.

    Directory of Open Access Journals (Sweden)

    Catherine E Lovelock

    Full Text Available BACKGROUND: CO(2 emissions from cleared mangrove areas may be substantial, increasing the costs of continued losses of these ecosystems, particularly in mangroves that have highly organic soils. METHODOLOGY/PRINCIPAL FINDINGS: We measured CO(2 efflux from mangrove soils that had been cleared for up to 20 years on the islands of Twin Cays, Belize. We also disturbed these cleared peat soils to assess what disturbance of soils after clearing may have on CO(2 efflux. CO(2 efflux from soils declines from time of clearing from ∼10,600 tonnes km(-2 year(-1 in the first year to 3000 tonnes km(2 year(-1 after 20 years since clearing. Disturbing peat leads to short term increases in CO(2 efflux (27 umol m(-2 s(-1, but this had returned to baseline levels within 2 days. CONCLUSIONS/SIGNIFICANCE: Deforesting mangroves that grow on peat soils results in CO(2 emissions that are comparable to rates estimated for peat collapse in other tropical ecosystems. Preventing deforestation presents an opportunity for countries to benefit from carbon payments for preservation of threatened carbon stocks.

  2. MpeR regulates the mtr efflux locus in Neisseria gonorrhoeae and modulates antimicrobial resistance by an iron-responsive mechanism.

    Science.gov (United States)

    Mercante, Alexandra Dubon; Jackson, Lydgia; Johnson, Paul J T; Stringer, Virginia A; Dyer, David W; Shafer, William M

    2012-03-01

    Previous studies have shown that the MpeR transcriptional regulator produced by Neisseria gonorrhoeae represses the expression of mtrF, which encodes a putative inner membrane protein (MtrF). MtrF works as an accessory protein with the Mtr efflux pump, helping gonococci to resist high levels of diverse hydrophobic antimicrobials. Regulation of mpeR has been reported to occur by an iron-dependent mechanism involving Fur (ferric uptake regulator). Collectively, these observations suggest the presence of an interconnected regulatory system in gonococci that modulates the expression of efflux pump protein-encoding genes in an iron-responsive manner. Herein, we describe this connection and report that levels of gonococcal resistance to a substrate of the mtrCDE-encoded efflux pump can be modulated by MpeR and the availability of free iron. Using microarray analysis, we found that the mtrR gene, which encodes a direct repressor (MtrR) of mtrCDE, is an MpeR-repressed determinant in the late logarithmic phase of growth when free iron levels would be reduced due to bacterial consumption. This repression was enhanced under conditions of iron limitation and resulted in increased expression of the mtrCDE efflux pump operon. Furthermore, as judged by DNA-binding analysis, MpeR-mediated repression of mtrR was direct. Collectively, our results indicate that both genetic and physiologic parameters (e.g., iron availability) can influence the expression of the mtr efflux system and modulate levels of gonococcal susceptibility to efflux pump substrates. PMID:22214775

  3. Overcoming drug efflux-based multidrug resistance in cancer with nanotechnology

    Institute of Scientific and Technical Information of China (English)

    Xue Xue; Xing-Jie Liang

    2012-01-01

    Multidrug resistance (MDR),which significantly decreases the efficacy of anticancer drugs and causes tumor recurrence,has been a major challenge in clinical cancer treatment with chemotherapeutic drugs for decades.Several mechanisms of overcoming drug resistance have been postulated.Well known Pglycoprotein (P-gp) and other drug efflux transporters are considered to be critical in pumping anticancer drugs out of cells and causing chemotherapy failure.Innovative theranostic (therapeutic and diagnostic)strategies with nanoparticles are rapidly evolving and are anticipated to offer opportunities to overcome these limits.In this review,we discuss the mechanisms of drug efflux-mediated resistance and the application of multiple nanoparticle-based platforms to overcome chemoresistance and improve therapeutic outcome.

  4. Efflux protein expression in human stem cell-derived retinal pigment epithelial cells.

    Directory of Open Access Journals (Sweden)

    Kati Juuti-Uusitalo

    Full Text Available Retinal pigment epithelial (RPE cells in the back of the eye nourish photoreceptor cells and form a selective barrier that influences drug transport from the blood to the photoreceptor cells. At the molecular level, ATP-dependent efflux transporters have a major role in drug delivery in human RPE. In this study, we assessed the relative expression of several ATP-dependent efflux transporter genes (MRP1, -2, -3, -4, -5, -6, p-gp, and BCRP, the protein expression and localization of MRP1, MRP4, and MRP5, and the functionality of MRP1 efflux pumps at different maturation stages of undifferentiated human embryonic stem cells (hESC and RPE derived from the hESC (hESC-RPE. Our findings revealed that the gene expression of ATP-dependent efflux transporters MRP1, -3, -4, -5, and p-gp fluctuated during hESC-RPE maturation from undifferentiated hESC to fusiform, epithelioid, and finally to cobblestone hESC-RPE. Epithelioid hESC-RPE had the highest expression of MRP1, -3, -4, and P-gp, whereas the most mature cobblestone hESC-RPE had the highest expression of MRP5 and MRP6. These findings indicate that a similar efflux protein profile is shared between hESC-RPE and the human RPE cell line, ARPE-19, and suggest that hESC-RPE cells are suitable in vitro RPE models for drug transport studies. Embryonic stem cell model might provide a novel tool to study retinal cell differentiation, mechanisms of RPE-derived diseases, drug testing and targeted drug therapy.

  5. Importance of Non-Diffusive Transport for Soil CO2 Efflux in a Temperate Mountain Grassland

    Science.gov (United States)

    Roland, Marilyn; Vicca, Sara; Bahn, Michael; Ladreiter-Knauss, Thomas; Schmitt, Michael; Janssens, Ivan A.

    2015-04-01

    A key focus in climate change is on the dynamics and predictions of the soil CO2 efflux (SCE) from terrestrial ecosystems. Limited knowledge of CO2 transport through the soil restricts our understanding of the various biotic and abiotic processes underlying these emissions. Diffusion is often thought to be the main transport mechanism for trace gases in soils, an assumption that is reflected in the increasing popularity of the flux-gradient approach (FGA). Based on Fick's law, the FGA calculates soil CO2 efflux from CO2 concentration profiles, given good estimates of the diffusion coefficient. The latter can be calculated via different commonly used models, and solid-state sensors allow continuous high-frequency measurements of soil CO2 concentrations with minimal disturbance to the soil conditions in a cost-effective way. Fast growing evidence of pressure pumping and advection, makes it impossible to disregard non-diffusive gas transport when evaluating diel and day-to-day dynamics of soil CO2 emissions. We have analyzed combined measurements from solid-state sensors and soil chambers to gain insight in the CO2 transport mechanisms in a grassland site in the Austrian Alps. The FGA-derived efflux underestimated the chamber efflux by 10 to 87% at our site, depending on which model was used for calculation of the diffusion coefficient. We found that the actual transport rates correlated well with irradiation and wind speed, even more when the soil moisture content was below 33%. These findings suggest that bulk soil air transport was enhanced by pressure changes induced by wind shear at the surface and by local heating of the soil surface. Considering the importance of non-diffusive transport processes is a prerequisite when using solid-state CO2 concentration measurements to estimate soil CO2 efflux at any given site.

  6. Can celecoxib affect P-glycoprotein-mediated drug efflux? A microPET study

    International Nuclear Information System (INIS)

    Introduction: P-glycoprotein (Pgp) is an efflux pump that protects vital organs like the brain from toxic substances, but which is also associated with therapy resistance. The anti-inflammatory drug celecoxib potentiates the efficacy of several cytostatic and neurotropic drugs that are known Pgp substrates. To clarify whether Pgp is involved in the sensitizing effect of celecoxib, we investigated in vivo whether celecoxib is a substrate of Pgp and whether it can affect the efflux activity of the pump. Methods: In control rats and in rats treated with the Pgp modulator cyclosporin A (CsA), cerebral accumulation of radiolabeled [11C]celecoxib was investigated by ex vivo biodistribution and micro-positron emission tomography imaging. In addition, the effect of unlabeled celecoxib and CsA (positive control) on the cerebral uptake of the Pgp substrate [11C]verapamil was studied. Results: [11C]Celecoxib uptake in rat brain was relatively high and homogeneously distributed. Treatment of rats with CsA only marginally increased cerebral tracer uptake, which is most likely due to reduced tracer clearance from plasma. [11C]Verapamil brain uptake was more than 10-fold higher after treatment with CsA. In contrast, a high dose of celecoxib increased cerebral [11C]verapamil uptake only twofold, which was accompanied by a similar increase in tracer concentration in plasma. Conclusions: This study shows that celecoxib is not a substrate of Pgp and does not substantially affect the Pgp-mediated efflux of [11C]verapamil. Therefore, celecoxib-induced augmentation of the efficacy of chemotherapeutic and neurotropic drugs must be due to another mechanism than modulation of Pgp-mediated drug efflux

  7. Can celecoxib affect P-glycoprotein-mediated drug efflux? A microPET study

    Energy Technology Data Exchange (ETDEWEB)

    Vries, Erik F.J. de [Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB Groningen (Netherlands)], E-mail: e.f.j.de.vries@ngmb.umcg.nl; Doorduin, Janine; Vellinga, Namkje A.R.; Waarde, Aren van; Dierckx, Rudi A. [Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB Groningen (Netherlands); Klein, Hans C. [Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB Groningen (Netherlands); Department of Psychiatry, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB Groningen (Netherlands)

    2008-05-15

    Introduction: P-glycoprotein (Pgp) is an efflux pump that protects vital organs like the brain from toxic substances, but which is also associated with therapy resistance. The anti-inflammatory drug celecoxib potentiates the efficacy of several cytostatic and neurotropic drugs that are known Pgp substrates. To clarify whether Pgp is involved in the sensitizing effect of celecoxib, we investigated in vivo whether celecoxib is a substrate of Pgp and whether it can affect the efflux activity of the pump. Methods: In control rats and in rats treated with the Pgp modulator cyclosporin A (CsA), cerebral accumulation of radiolabeled [{sup 11}C]celecoxib was investigated by ex vivo biodistribution and micro-positron emission tomography imaging. In addition, the effect of unlabeled celecoxib and CsA (positive control) on the cerebral uptake of the Pgp substrate [{sup 11}C]verapamil was studied. Results: [{sup 11}C]Celecoxib uptake in rat brain was relatively high and homogeneously distributed. Treatment of rats with CsA only marginally increased cerebral tracer uptake, which is most likely due to reduced tracer clearance from plasma. [{sup 11}C]Verapamil brain uptake was more than 10-fold higher after treatment with CsA. In contrast, a high dose of celecoxib increased cerebral [{sup 11}C]verapamil uptake only twofold, which was accompanied by a similar increase in tracer concentration in plasma. Conclusions: This study shows that celecoxib is not a substrate of Pgp and does not substantially affect the Pgp-mediated efflux of [{sup 11}C]verapamil. Therefore, celecoxib-induced augmentation of the efficacy of chemotherapeutic and neurotropic drugs must be due to another mechanism than modulation of Pgp-mediated drug efflux.

  8. Centrifugal pumps

    CERN Document Server

    Anderson, HH

    1981-01-01

    Centrifugal Pumps describes the whole range of the centrifugal pump (mixed flow and axial flow pumps are dealt with more briefly), with emphasis on the development of the boiler feed pump. Organized into 46 chapters, this book discusses the general hydrodynamic principles, performance, dimensions, type number, flow, and efficiency of centrifugal pumps. This text also explains the pumps performance; entry conditions and cavitation; speed and dimensions for a given duty; and losses. Some chapters further describe centrifugal pump mechanical design, installation, monitoring, and maintenance. The

  9. ROLE OF A NOVEL TERPENOID AS EFFLUX INHIBITOR IN TARGETING THE EFFLUX PROTEIN (MexA OF MULTI-DRUG RESISTANT PSEUDOMONAS AERUGINOSA

    Directory of Open Access Journals (Sweden)

    R. Jasmine*, B.N. Selvakumar and S. Aishwarya

    2012-06-01

    Full Text Available Pseudomonas aeruginosa, is one among the few drug resistant organisms causing Urinary Tract Infection. Most strains of Pseudomonas aeruginosa are significantly more resistant, even in the absence of R plasmids, to many antimicrobial agents, including β-lactams, tetracycline, chloramphenicol, and fluoroquinolones, than most other gram-negative rods. This broad-range resistance has so far been assumed to be mainly due to the low permeability of the P. aeruginosa outer membrane. Mex-proteins are the multidrug exporter proteins that are significant in drug ejection, which is the main reason for drug resistance. This limits the therapeutic options. Inhibition of multi drug resistant efflux pumps can restore the activities of antimicrobial agents that are substrates for these proteins. Hence efforts are now taken to screen few medicinal plants, which are both economic and less toxic. Among the several plants screened, we have chosen the acetone extract of Elephantopus scaber from which we purified a new terpenoid for our study. Its structure was generated using CHEMSKETCH software. The novel terpenoid was evaluated as potent efflux inhibitor. In this present study the Mex A protein and terpenoid were docked using Auto dock software and the docking score with minimum binding energy value of -6.82kcal/mol was calculated. It infers that the terpenoid can inhibit the activity of Mex A by forming a strong atomic interaction with the active site residues. Hence the terpenoid can act as a drug for bacterial infections. This study on inhibition of efflux pump using terpenoid would be an alternate but effective solution to combat drug resistant Pseudomonas infections without side effects.

  10. Efflux transporters of the human placenta.

    Science.gov (United States)

    Young, Amber M; Allen, Courtni E; Audus, Kenneth L

    2003-01-21

    The use of pharmaceuticals during pregnancy is often a necessity for the health of the mother. Until recently, the placenta was viewed as a passive organ through which molecules are passed indiscriminately between mother and fetus. In reality, the placenta contains a plethora of transporters, some of which appear to be specifically dedicated to removal of xenobiotics and toxic endogenous compounds. Drug efflux transporters such as P-glycoprotein (P-gp), several multidrug resistant associated proteins (MRPs) and breast cancer resistant protein (BCRP) may provide mechanisms that protect the developing fetus. Bile acid transporters may also play a role in exporting compounds back into the maternal compartment. Steroid hormones directly influence the level of expression and function in some of these transporters. Investigating the link between the hormones of pregnancy and these drug efflux transporters is one possible key in developing strategies to deliver drugs to the mother with minimal fetal risk. PMID:12535577

  11. Potent and selective mediators of cholesterol efflux

    Energy Technology Data Exchange (ETDEWEB)

    Bielicki, John K; Johansson, Jan

    2015-03-24

    The present invention provides a family of non-naturally occurring polypeptides having cholesterol efflux activity that parallels that of full-length apolipoproteins (e.g., Apo AI and Apo E), and having high selectivity for ABAC1 that parallels that of full-length apolipoproteins. The invention also provides compositions comprising such polypeptides, methods of identifying, screening and synthesizing such polypeptides, and methods of treating, preventing or diagnosing diseases and disorders associated with dyslipidemia, hypercholesterolemia and inflammation.

  12. CO₂ efflux from shrimp ponds in Indonesia.

    Directory of Open Access Journals (Sweden)

    Frida Sidik

    Full Text Available The conversion of mangrove forest to aquaculture ponds has been increasing in recent decades. One of major concerns of this habitat loss is the release of stored 'blue' carbon from mangrove soils to the atmosphere. In this study, we assessed carbon dioxide (CO₂ efflux from soil in intensive shrimp ponds in Bali, Indonesia. We measured CO₂ efflux from the floors and walls of shrimp ponds. Rates of CO₂ efflux within shrimp ponds were 4.37 kg CO₂ m⁻² y⁻¹ from the walls and 1.60 kg CO₂ m⁻² y⁻¹ from the floors. Combining our findings with published data of aquaculture land use in Indonesia, we estimated that shrimp ponds in this region result in CO₂ emissions to the atmosphere between 5.76 and 13.95 Tg y⁻¹. The results indicate that conversion of mangrove forests to aquaculture ponds contributes to greenhouse gas emissions that are comparable to peat forest conversion to other land uses in Indonesia. Higher magnitudes of CO₂ emission may be released to atmosphere where ponds are constructed in newly cleared mangrove forests. This study indicates the need for incentives that can meet the target of aquaculture industry without expanding the converted mangrove areas, which will lead to increased CO₂ released to atmosphere.

  13. Heat pumps

    CERN Document Server

    Macmichael, DBA

    1988-01-01

    A fully revised and extended account of the design, manufacture and use of heat pumps in both industrial and domestic applications. Topics covered include a detailed description of the various heat pump cycles, the components of a heat pump system - drive, compressor, heat exchangers etc., and the more practical considerations to be taken into account in their selection.

  14. Heat pumps

    CERN Document Server

    Brodowicz, Kazimierz; Wyszynski, M L; Wyszynski

    2013-01-01

    Heat pumps and related technology are in widespread use in industrial processes and installations. This book presents a unified, comprehensive and systematic treatment of the design and operation of both compression and sorption heat pumps. Heat pump thermodynamics, the choice of working fluid and the characteristics of low temperature heat sources and their application to heat pumps are covered in detail.Economic aspects are discussed and the extensive use of the exergy concept in evaluating performance of heat pumps is a unique feature of the book. The thermodynamic and chemical properties o

  15. Multi-drug resistance in Salmonella enterica: efflux mechanisms and their relationships with the development of chromosomal resistance gene clusters.

    Science.gov (United States)

    Quinn, Teresa; O'Mahony, Rebecca; Baird, Alan W; Drudy, Denise; Whyte, Paul; Fanning, Séamus

    2006-07-01

    Bacterial drug resistance represents one of the most crucial problems in present day antibacterial chemotherapy. Of particular concern to public health is the continuing worldwide epidemic spread of Salmonella enterica serovar Typhimurium phage type DT104 harbouring a genomic island called Salmonella genomic island I (SGI-1). This island contains an antibiotic gene cluster conferring resistance to ampicillin, chloramphenicol, florfenicol, streptomycin, sulfonamides and tetracyclines. These resistance genes are assembled in a mosaic pattern, indicative of several independent recombinational events. The mobility of SGI-1 coupled with the ability of various antibiotic resistance genes to be integrated and lost from the chromosomal resistance locus allows for the transfer of stable antibiotic resistance to most of the commonly used antibiotics and adaptation to new antibiotic challenges. This, coupled with the incidence of increasing fluoroquinolone resistance in these strains increases the risk of therapeutic failure in cases of life-threatening salmonellosis. Fluoroquinolone resistance has largely been attributed to mutations occurring in the genes coding for intracellular targets of these drugs. However, efflux by the AcrAB-TolC multi-drug efflux pump has recently been shown to directly contribute to fluoroquinolone resistance. Furthermore, the resistance to chloramphenicol-florfenicol and tetracyclines in DT104 isolates, is due to interaction between specific transporters for these antibiotics encoded by genes mapping to the SGI-1 and the AcrAB-TolC tripartite efflux pump. The potential for the use of efflux pump inhibitors to restore therapeutic efficacy to fluoroquinolones and other antibiotics offers an exciting developmental area for drug discovery. PMID:16842216

  16. Continuous monitoring of soil gas efflux with Forced Diffusion (FD) chamber technique in a tundra ecosystem, Alaska

    Science.gov (United States)

    Kim, Y.; Park, S. J.; Lee, B. Y.

    2015-12-01

    Continuous measurements of soil carbon dioxide (CO2) efflux provide essential information about the soil carbon budget in response to an abruptly changing climate at Arctic and Subarctic scales. The Forced Diffusion (FD) chamber technique has a gas permeable membrane, which passively regulates the mixing of atmosphere and soil air in the chamber, in place of the active pumping system inside a regular dynamics efflux chamber system (Risk et al., 2011). Here the system has been modified the sampling routine to eliminate the problem of sensor drift. After that, we deployed the FD chamber system in a tundra ecosystem over the discontinuous permafrost regime of Council, Alaska. The representative understory plants are tussock (17 %), lichen (32 %), and moss (51 %), within a 40 נ40 m plot at an interval of five meters (81 points total) for efflux-measurement by dynamic chamber. The FD chamber monitored soil CO2 efflux from moss, lichen, and tussock regimes at an interval of 30 min during the growing season of 2015. As the results, mean soil CO2 effluxes in sphagnum moss, lichen, and tussock were 1.98 ± 1.10 (coefficient of variance: 55.8 %), 3.34 ± 0.84 (CV: 25.0 %), and 5.32 ± 1.48 (CV: 27.8 %) gCO2/m2/d, respectively. The difference between the 30-min efflux interval and the average efflux of three 10-min intervals is not significant for sphagnum (n = 196), lichen (n = 918), and tussock (n = 918) under a 95 % confidence level. The deploying interval was then set to 30 min and synchronized with eddy covariance tower data. During the deployment period of 2015, soil CO2 efflux over moss, lichen, and tussock using the FD chamber system were 44 ± 24, 73 ± 18, and 117 ± 33 gCO2/m2/period, respectively. Using the dynamic chamber, mean ecosystem respiration (Re) ranges for moss, lichen, and tussock were 2.2-2.6, 1.8-2.0, and 3.3-3.6 gCO2/m2/d, respectively, during June and July of 2015. These techniques provide the representativeness of spatiotemporal variation of soil

  17. Sodium efflux in plant roots: what do we really know?

    Science.gov (United States)

    Britto, D T; Kronzucker, H J

    2015-08-15

    The efflux of sodium (Na(+)) ions across the plasma membrane of plant root cells into the external medium is surprisingly poorly understood. Nevertheless, Na(+) efflux is widely regarded as a major mechanism by which plants restrain the rise of Na(+) concentrations in the cytosolic compartments of root cells and, thus, achieve a degree of tolerance to saline environments. In this review, several key ideas and bodies of evidence concerning root Na(+) efflux are summarized with a critical eye. Findings from decades past are brought to bear on current thinking, and pivotal studies are discussed, both "purely physiological", and also with regard to the SOS1 protein, the only major Na(+) efflux transporter that has, to date, been genetically characterized. We find that the current model of rapid transmembrane sodium cycling (RTSC), across the plasma membrane of root cells, is not adequately supported by evidence from the majority of efflux studies. An alternative hypothesis cannot be ruled out, that most Na(+) tracer efflux from the root in the salinity range does not proceed across the plasma membrane, but through the apoplast. Support for this idea comes from studies showing that Na(+) efflux, when measured with tracers, is rarely affected by the presence of inhibitors or the ionic composition in saline rooting media. We conclude that the actual efflux of Na(+) across the plasma membrane of root cells may be much more modest than what is often reported in studies using tracers, and may predominantly occur in the root tips, where SOS1 expression has been localized.

  18. Centrifugal pumps

    CERN Document Server

    Gülich, Johann Friedrich

    2014-01-01

    This book gives an unparalleled, up-to-date, in-depth treatment of all kinds of flow phenomena encountered in centrifugal pumps including the complex interactions of fluid flow with vibrations and wear of materials. The scope includes all aspects of hydraulic design, 3D-flow phenomena and partload operation, cavitation, numerical flow calculations, hydraulic forces, pressure pulsations, noise, pump vibrations (notably bearing housing vibration diagnostics and remedies), pipe vibrations, pump characteristics and pump operation, design of intake structures, the effects of highly viscous flows, pumping of gas-liquid mixtures, hydraulic transport of solids, fatigue damage to impellers or diffusers, material selection under the aspects of fatigue, corrosion, erosion-corrosion or hydro-abrasive wear, pump selection, and hydraulic quality criteria. As a novelty, the 3rd ed. brings a fully analytical design method for radial impellers, which eliminates the arbitrary choices inherent to former design procedures. The d...

  19. Pumping life

    DEFF Research Database (Denmark)

    Sitsel, Oleg; Dach, Ingrid; Hoffmann, Robert Daniel

    2012-01-01

    The name PUMPKIN may suggest a research centre focused on American Halloween traditions or the investigation of the growth of vegetables – however this would be misleading. Researchers at PUMPKIN, short for Centre for Membrane Pumps in Cells and Disease, are in fact interested in a large family o......’. Here we illustrate that the pumping of ions means nothing less than the pumping of life....

  20. Cholesterol efflux capacity: An introduction for clinicians.

    Science.gov (United States)

    Anastasius, Malcolm; Kockx, Maaike; Jessup, Wendy; Sullivan, David; Rye, Kerry-Anne; Kritharides, Leonard

    2016-10-01

    Epidemiologic studies have shown an inverse correlation between high-density lipoprotein (HDL) cholesterol (HDL-C) levels and cardiovascular disease outcomes. However, the hypothesis of a causal relationship between HDL-C and cardiovascular disease has been challenged by genetic and clinical studies. Serum cholesterol efflux capacity (CEC) is an important measure of HDL function in humans. Recent large clinical studies have shown a correlation between in vitro CEC and cardiovascular disease prevalence and incidence, which appears to be independent of HDL-C concentration. The present review summarizes recent large clinical studies and introduces important methodological considerations. Further studies are required to standardize and establish the reproducibility of this measure of HDL function and clarify whether modulating CEC will emerge as a useful therapeutic target. PMID:27659883

  1. Pumping of drugs by P-glycoprotein

    DEFF Research Database (Denmark)

    Litman, Thomas; Skovsgaard, Torben; Stein, Wilfred D

    2003-01-01

    The apparent inhibition constant, Kapp, for the blockade of P-glycoprotein (P-gp) by four drugs, verapamil, cyclosporin A, XR9576 (tariquidar), and vinblastine, was measured by studying their ability to inhibit daunorubicin and calcein-AM efflux from four strains of Ehrlich cells with different...... levels of drug resistance and P-gp content. For daunorubicin as a transport substrate, Kapp was independent of [P-gp] for verapamil but increased strictly linearly with [P-gp] for vinblastine, cyclosporin A, and XR9576. A theoretical analysis of the kinetics of drug pumping and its reversal shows...... but rather, in serial, i.e., a drug that is pumped from the cytoplasmic phase has to pass the preemptive route upon leaving the cell. Our results are consistent with the Sauna-Ambudkar two-step model for pumping by P-gp. We suggest that the vinblastine/cyclosporin A/XR9576-binding site accepts daunorubicin...

  2. Detection of inhibitors of Candida albicans Cdr transporters using a diS-C3(3 fluorescence

    Directory of Open Access Journals (Sweden)

    Joanna eSzczepaniak

    2015-03-01

    Full Text Available Candida albicans is a major cause of opportunistic and life-threatening, systemic fungal infections. Hence new antifungal agents, as well as new methods to treat fungal infections, are still needed. The application of inhibitors of drug-efflux pumps may increase the susceptibility of C. albicans to drugs. We developed a new fluorescence method that allows the in vivo activity evaluation of compounds inhibiting of C. albicans transporters. We show that the potentiometric dye 3,3′-dipropylthiacarbocyanine iodide diS-C3(3 is pumped out by both Cdr1 and Cdr2 transporters. The fluorescence labeling with diS-C3(3 enables a real-time observation of the activity of C. albicans Cdr1 and Cdr2 transporters. We demonstrate that enniatin A and beauvericin show different specificities toward these transporters. Enniatin A inhibits diS-C3(3 efflux by Cdr1 while beauvericin inhibits both Cdr1p and Cdr2p.

  3. Identification of a Cyanobacterial RND-Type Efflux System Involved in Export of Free Fatty Acids.

    Science.gov (United States)

    Kato, Akihiro; Takatani, Nobuyuki; Use, Kazuhide; Uesaka, Kazuma; Ikeda, Kazutaka; Chang, Yajun; Kojima, Kouji; Aichi, Makiko; Ihara, Kunio; Nakahigashi, Kenji; Maeda, Shin-Ichi; Omata, Tatsuo

    2015-12-01

    An RND (resistance-nodulation-division)-type transporter having the capacity to export free fatty acids (FFAs) was identified in the cyanobacterium Synechococcus elongatus strain PCC 7942 during characterization of a mutant strain engineered to produce FFAs. The basic strategy for construction of the FFA-producing mutant was a commonly used one, involving inactivation of the endogenous acyl-acyl carrier protein synthetase gene (aas) and introduction of a foreign thioesterase gene ('tesA), but a nitrate transport mutant NA3 was used as the parental strain to achieve slow, nitrate-limited growth in batch cultures. Also, a nitrogen-regulated promoter PnirA was used to drive 'tesA to maximize thioesterase expression during the nitrate-limited growth. The resulting mutant (dAS2T) was, however, incapable of growth under the conditions of nitrate limitation, presumably due to toxicity associated with FFA overproduction. Incubation of the mutant culture under the non-permissive conditions allowed for isolation of a pseudorevertant (dAS2T-pr1) capable of growth on nitrate. Genome sequence and gene expression analyses of this strain suggested that expression of an RND-type efflux system had rescued growth on nitrate. Targeted inactivation of the RND-type transporter genes in the wild-type strain resulted in loss of tolerance to exogenously added FFAs including capric, lauric, myristic, oleic and linolenic acids. Overexpression of the genes in dAS2T, on the other hand, enhanced FFA excretion and cell growth in nitrate-containing medium, verifying that the genes encode an efflux pump for FFAs. These results demonstrate the importance of the efflux system in efficient FFA production using genetically engineered cyanobacteria. PMID:26468506

  4. The transport mechanism of bacterial Cu+-ATPases: distinct efflux rates adapted to different function.

    Science.gov (United States)

    Raimunda, Daniel; González-Guerrero, Manuel; Leeber, Blaise W; Argüello, José M

    2011-06-01

    Cu(+)-ATPases play a key role in bacterial Cu(+) homeostasis by participating in Cu(+) detoxification and cuproprotein assembly. Characterization of Archaeoglobus fulgidus CopA, a model protein within the subfamily of P(1B-1) type ATPases, has provided structural and mechanistic details on this group of transporters. Atomic resolution structures of cytoplasmic regulatory metal binding domains (MBDs) and catalytic actuator, phosphorylation, and nucleotide binding domains are available. These, in combination with whole protein structures resulting from cryo-electron microscopy analyses, have enabled the initial modeling of these transporters. Invariant residues in helixes 6, 7 and 8 form two transmembrane metal binding sites (TM-MBSs). These bind Cu(+) with high affinity in a trigonal planar geometry. The cytoplasmic Cu(+) chaperone CopZ transfers the metal directly to the TM-MBSs; however, loading both of the TM-MBSs requires binding of nucleotides to the enzyme. In agreement with the classical transport mechanism of P-type ATPases, occupancy of both transmembrane sites by cytoplasmic Cu(+) is a requirement for enzyme phosphorylation and subsequent transport into the periplasmic or extracellular milieus. Recent transport studies have shown that all Cu(+)-ATPases drive cytoplasmic Cu(+) efflux, albeit with quite different transport rates in tune with their various physiological roles. Archetypical Cu(+)-efflux pumps responsible for Cu(+) tolerance, like the Escherichia coli CopA, have turnover rates ten times higher than those involved in cuproprotein assembly (or alternative functions). This explains the incapability of the latter group to significantly contribute to the metal efflux required for survival in high copper environments. PMID:21210186

  5. PI3K signaling supports amphetamine-induced dopamine efflux.

    Science.gov (United States)

    Lute, Brandon J; Khoshbouei, Habibeh; Saunders, Christine; Sen, Namita; Lin, Richard Z; Javitch, Jonathan A; Galli, Aurelio

    2008-08-01

    The dopamine (DA) transporter (DAT) is a major molecular target of the psychostimulant amphetamine (AMPH). AMPH, as a result of its ability to reverse DAT-mediated inward transport of DA, induces DA efflux thereby increasing extracellular DA levels. This increase is thought to underlie the behavioral effects of AMPH. We have demonstrated previously that insulin, through phosphatidylinositol 3-kinase (PI3K) signaling, regulates DA clearance by fine-tuning DAT plasma membrane expression. PI3K signaling may represent a novel mechanism for regulating DA efflux evoked by AMPH, since only active DAT at the plasma membrane can efflux DA. Here, we show in both a heterologous expression system and DA neurons that inhibition of PI3K decreases DAT cell surface expression and, as a consequence, AMPH-induced DA efflux.

  6. Measurement of Ca/sup 2 +/ effluxes from bone

    Energy Technology Data Exchange (ETDEWEB)

    Neuman, W.F.; Brommage, R.; Myers, C.R.

    1977-01-01

    To facilitate the study of membrane function in the control of the flow of ions into and out of bone, it was desirable to develop a system for the direct quantitation of unidirectional effluxes of calcium and phosphate from bones. Based on a mathematical analysis of the problem, a specially designed Ussing chamber was developed which proved successful. Calvaria from 2-day-old rat pups, 3-day chicks and adult mice were evaluated. Calcium influxes which exceeded the corresponding effluxes were observed in the neonatal calvaria but not with those from adult mice. Also, an asymmetry in efflux was observed in rat calvaria, the inner side of the skull showed a higher efflux than did the external side. No such asymmetry was seen with calvaria from chicks or mice. This new technology should permit a further exploration of the role of the bone membrane in electrolyte homeostasis.

  7. Pump impeller

    International Nuclear Information System (INIS)

    A mixed-flow pump impeller, which may be used, for example, as a primary pump for circulating sodium as the primary coolant in a fast nuclear reactor, is described which comprises an impeller with evenly-spaced blades. Some of the blades, which are symmetrically disposed around the axis of rotation of the impeller, extend beyond the ends of the other blades towards the suction side of the pump to form an inducer. The channels defined between the extensions of the extended blades follow helical paths parallel to the axis of rotation. The leading edges of the unextended blades are interposed between the extended blades in the region of divergence of flow from the axis of rotation. The provision of the inducer reduces the risk of cavitation in the pump, which could cause rapid wear of the impeller. A shroud may be provided for the unextended blades. (author)

  8. Cadmium induced potassium efflux from Scenedesmus quadricauda

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, G.N.; Prasad, M.N.V. [Univ. of Hyderabad (India)

    1992-10-01

    Plants, algae and bacteria respond to heavy metal toxicity by inducing different enzymes, ion influx/efflux for ionic balance and synthesize small peptides such as poly({gamma}-glutamyl cysteinyl) glycines called phytochelatins (PCs) mainly consisting of glutamate, cysteine and glycine. These peptides bind metal ions and reduce toxicity. The uptake of metal ions comprises two phases. The first phase consists of a quick and nonspecific binding of the cations to negatively-charged membrane components located at the cell surface. The second phase consists of energy-dependent intracellular uptake of the metal ions. During uptake of Co{sup 2+} by yeast cells, an electroneutral 2:1 exchange with K{sup +} was found. Cd{sup 2+} uptake by yeast also caused loss of cell K{sup +}, however, there was no electroneutral exchange of K{sup +}. The molar ratio of K{sup +} released and Cd{sup 2+} accumulated by yeast in the initial stage of incubation is 22 and seems to be independent of the Cd concentration. Disruption of the cell membrane of part of the cells, according to an all-or-none process, by Cd{sup 2+} may explain the disproportional loss of cell K{sup +} during Cd{sup 2+} uptake. This paper examines the exchange of K{sup +} with Cd{sup 2+} uptake in Scenedesmus quadricauda, and whether it follows an electroneutral 2:1 exchange or an all-or-none process. 11 refs., 2 figs.

  9. Cholesterol efflux analyses using stable isotopes and mass spectrometry

    OpenAIRE

    Robert J Brown; Shao, Fei; Baldán, Ángel; Albert, Carolyn J.; Ford, David A.

    2012-01-01

    Cholesterol efflux from macrophages and the vascular wall is the initial step of the cardiovascular protective reverse cholesterol transport process. This study demonstrates a mass spectrometry based assay to measure the cellular and media content of [d7]-cholesterol and unlabeled cholesterol that can be used to measure cholesterol efflux from cell lines. Using a triple quadrupole ESI-MS instrument in direct infusion mode, product ion scanning for m/z 83, neutral loss (NL) 375.5 scanning and ...

  10. A Selective ATP-binding Cassette Sub-family G Member 2 Efflux Inhibitor Revealed Via High-Throughput Flow Cytometry

    OpenAIRE

    Strouse, J. Jacob; Ivnitski-Steele, Irena; Khawaja, Hadya M.; Perez, Dominique; Ricci, Jerec; Yao, Tuanli; Weiner, Warren S.; Schroeder, Chad E.; Simpson, Denise S.; Maki, Brooks E.; Li, Kelin; Golden, Jennifer E.; Foutz, Terry D.; Waller, Anna; Evangelisti, Annette M.

    2012-01-01

    Chemotherapeutics tumor resistance is a principal reason for treatment failure and clinical and experimental data indicate that multidrug transporters such as ATP-binding Cassette (ABC) B1 and ABCG2 play a leading role by preventing cytotoxic intracellular drug concentrations. Functional efflux inhibition of existing chemotherapeutics by these pumps continues to present a promising approach for treatment. A contributing factor to the failure of existing inhibitors in clinical applications is ...

  11. Nucleotide sequence of pOLA52: a conjugative IncX1 plasmid from Escherichia coli which enables biofilm formation and multidrug efflux

    DEFF Research Database (Denmark)

    Norman, Anders; Hansen, Lars H.; She, Qunxin;

    2008-01-01

    The large conjugative multidrug resistance (MDR) plasmid pOLA52 was sequenced and annotated. The plasmid encodes two phenotypes normally associated with the chromosomes of opportunistic pathogens, namely MDR via a resistance-nodulation-division (RND)-type efflux-pump (oqxAB), and the formation of...... and Tn6011) that seemed to originate from Klebsiella pneumoniae, thus demonstrating the capability of IncX1 plasmids of facilitating lateral transfer of gene cassettes between different Enterobacteriaceae....

  12. Control of Angiogenesis by AIBP-mediated Cholesterol Efflux

    Science.gov (United States)

    Fang, Longhou; Choi, Soo-Ho; Baek, Ji Sun; Liu, Chao; Almazan, Felicidad; Ulrich, Florian; Wiesner, Philipp; Taleb, Adam; Deer, Elena; Pattison, Jennifer; Torres-Vázquez, Jesús; Li, Andrew C.; Miller, Yury I.

    2013-01-01

    Cholesterol is a structural component of the cell, indispensable for normal cellular function, but its excess often leads to abnormal proliferation, migration, inflammatory responses and/or cell death. To prevent cholesterol overload, ATP-binding cassette (ABC) transporters mediate cholesterol efflux from the cells to apolipoprotein A-I (ApoA-I) and to the ApoA-I-containing high-density lipoprotein (HDL)1-3. Maintaining efficient cholesterol efflux is essential for normal cellular function4-6. However, the role of cholesterol efflux in angiogenesis and the identity of its local regulators are poorly understood. Here we show that ApoA-I binding protein (AIBP) accelerates cholesterol efflux from endothelial cells (EC) to HDL and thereby regulates angiogenesis. AIBP/HDL-mediated cholesterol depletion reduces lipid rafts, interferes with VEGFR2 dimerization and signaling, and inhibits VEGF-induced angiogenesis in vitro and mouse aortic neovascularization ex vivo. Remarkably, Aibp regulates the membrane lipid order in embryonic zebrafish vasculature and functions as a non-cell autonomous regulator of zebrafish angiogenesis. Aibp knockdown results in dysregulated sprouting/branching angiogenesis, while forced Aibp expression inhibits angiogenesis. Dysregulated angiogenesis is phenocopied in Abca1/Abcg1-deficient embryos, and cholesterol levels are increased in Aibp-deficient and Abca1/Abcg1-deficient embryos. Our findings demonstrate that secreted AIBP positively regulates cholesterol efflux from EC and that effective cholesterol efflux is critical for proper angiogenesis. PMID:23719382

  13. Cyclic AMP efflux inhibitors as potential therapeutic agents for leukemia

    Science.gov (United States)

    Perez, Dominique R.; Smagley, Yelena; Garcia, Matthew; Carter, Mark B.; Evangelisti, Annette; Matlawska-Wasowska, Ksenia; Winter, Stuart S.; Sklar, Larry A.; Chigaev, Alexandre

    2016-01-01

    Apoptotic evasion is a hallmark of cancer. We propose that some cancers may evade cell death by regulating 3′-5′-cyclic adenosine monophosphate (cAMP), which is associated with pro-apoptotic signaling. We hypothesize that leukemic cells possess mechanisms that efflux cAMP from the cytoplasm, thus protecting them from apoptosis. Accordingly, cAMP efflux inhibition should result in: cAMP accumulation, activation of cAMP-dependent downstream signaling, viability loss, and apoptosis. We developed a novel assay to assess cAMP efflux and performed screens to identify inhibitors. In an acute myeloid leukemia (AML) model, several identified compounds reduced cAMP efflux, appropriately modulated pathways that are responsive to cAMP elevation (cAMP-responsive element-binding protein phosphorylation, and deactivation of Very Late Antigen-4 integrin), and induced mitochondrial depolarization and caspase activation. Blocking adenylyl cyclase activity was sufficient to reduce effects of the most potent compounds. These compounds also decreased cAMP efflux and viability of B-lineage acute lymphoblastic leukemia (B-ALL) cell lines and primary patient samples, but not of normal primary peripheral blood mononuclear cells. Our data suggest that cAMP efflux is a functional feature that could be therapeutically targeted in leukemia. Furthermore, because some of the identified drugs are currently used for treating other illnesses, this work creates an opportunity for repurposing. PMID:27129155

  14. PfeT, a P1B4 -type ATPase, effluxes ferrous iron and protects Bacillus subtilis against iron intoxication.

    Science.gov (United States)

    Guan, Guohua; Pinochet-Barros, Azul; Gaballa, Ahmed; Patel, Sarju J; Argüello, José M; Helmann, John D

    2015-11-01

    Iron is an essential element for nearly all cells and limited iron availability often restricts growth. However, excess iron can also be deleterious, particularly when cells expressing high affinity iron uptake systems transition to iron rich environments. Bacillus subtilis expresses numerous iron importers, but iron efflux has not been reported. Here, we describe the B. subtilis PfeT protein (formerly YkvW/ZosA) as a P1B4 -type ATPase in the PerR regulon that serves as an Fe(II) efflux pump and protects cells against iron intoxication. Iron and manganese homeostasis in B. subtilis are closely intertwined: a pfeT mutant is iron sensitive, and this sensitivity can be suppressed by low levels of Mn(II). Conversely, a pfeT mutant is more resistant to Mn(II) overload. In vitro, the PfeT ATPase is activated by both Fe(II) and Co(II), although only Fe(II) efflux is physiologically relevant in wild-type cells, and null mutants accumulate elevated levels of intracellular iron. Genetic studies indicate that PfeT together with the ferric uptake repressor (Fur) cooperate to prevent iron intoxication, with iron sequestration by the MrgA mini-ferritin playing a secondary role. Protection against iron toxicity may also be a key role for related P1B4 -type ATPases previously implicated in bacterial pathogenesis. PMID:26261021

  15. Modulation of Membrane Influx and Efflux in Escherichia coli Sequence Type 131 Has an Impact on Bacterial Motility, Biofilm Formation, and Virulence in a Caenorhabditis elegans Model.

    Science.gov (United States)

    Pantel, Alix; Dunyach-Remy, Catherine; Ngba Essebe, Christelle; Mesureur, Jennifer; Sotto, Albert; Pagès, Jean-Marie; Nicolas-Chanoine, Marie-Hélène; Lavigne, Jean-Philippe

    2016-05-01

    Energy-dependent efflux overexpression and altered outer membrane permeability (influx) can promote multidrug resistance (MDR). The present study clarifies the regulatory pathways that control membrane permeability in the pandemic clone Escherichia coli sequence type 131 (ST131) and evaluates the impact of efflux and influx modulations on biofilm formation, motility, and virulence in the Caenorhabditis elegans model. Mutants of two uropathogenic E. coli (UPEC) strains, MECB5 (ST131; H30-Rx) and CFT073 (ST73), as well as a fecal strain, S250 (ST131; H22), were in vitro selected using continuous subculture in subinhibitory concentrations of ertapenem (ETP), chloramphenicol (CMP), and cefoxitin (FOX). Mutations in genes known to control permeability were shown for the two UPEC strains: MECB5-FOX (deletion of 127 bp in marR; deletion of 1 bp and insertion of an IS1 element in acrR) and CFT073-CMP (a 1-bp deletion causing a premature stop in marR). We also demonstrated that efflux phenotypes in the mutants selected with CMP and FOX were related to the AcrAB-TolC pump, but also to other efflux systems. Alteration of membrane permeability, caused by underexpression of the two major porins, OmpF and OmpC, was shown in MECB5-ETP and mutants selected with FOX. Lastly, our findings suggest that efflux pump-overproducing isolates (CMP mutants) pose a serious threat in terms of virulence (significant reduction in worm median survival) and host colonization. Lack of porins (ETP and FOX mutants) led to a high level of antibiotic resistance in an H30-Rx subclone. Nevertheless, this adaptation created a physiological disadvantage (decreased motility and ability to form biofilm) associated with a low potential for virulence. PMID:26926643

  16. Modulation of Membrane Influx and Efflux in Escherichia coli Sequence Type 131 Has an Impact on Bacterial Motility, Biofilm Formation, and Virulence in a Caenorhabditis elegans Model

    Science.gov (United States)

    Pantel, Alix; Dunyach-Remy, Catherine; Ngba Essebe, Christelle; Mesureur, Jennifer; Sotto, Albert; Nicolas-Chanoine, Marie-Hélène

    2016-01-01

    Energy-dependent efflux overexpression and altered outer membrane permeability (influx) can promote multidrug resistance (MDR). The present study clarifies the regulatory pathways that control membrane permeability in the pandemic clone Escherichia coli sequence type 131 (ST131) and evaluates the impact of efflux and influx modulations on biofilm formation, motility, and virulence in the Caenorhabditis elegans model. Mutants of two uropathogenic E. coli (UPEC) strains, MECB5 (ST131; H30-Rx) and CFT073 (ST73), as well as a fecal strain, S250 (ST131; H22), were in vitro selected using continuous subculture in subinhibitory concentrations of ertapenem (ETP), chloramphenicol (CMP), and cefoxitin (FOX). Mutations in genes known to control permeability were shown for the two UPEC strains: MECB5-FOX (deletion of 127 bp in marR; deletion of 1 bp and insertion of an IS1 element in acrR) and CFT073-CMP (a 1-bp deletion causing a premature stop in marR). We also demonstrated that efflux phenotypes in the mutants selected with CMP and FOX were related to the AcrAB-TolC pump, but also to other efflux systems. Alteration of membrane permeability, caused by underexpression of the two major porins, OmpF and OmpC, was shown in MECB5-ETP and mutants selected with FOX. Lastly, our findings suggest that efflux pump-overproducing isolates (CMP mutants) pose a serious threat in terms of virulence (significant reduction in worm median survival) and host colonization. Lack of porins (ETP and FOX mutants) led to a high level of antibiotic resistance in an H30-Rx subclone. Nevertheless, this adaptation created a physiological disadvantage (decreased motility and ability to form biofilm) associated with a low potential for virulence. PMID:26926643

  17. Insulin pumps.

    Science.gov (United States)

    Pickup, J

    2011-02-01

    The last year has seen a continued uptake of insulin pump therapy in most countries. The USA is still a leader in pump use, with probably some 40% of type 1 diabetic patients on continuous subcutaneous insulin infusion (CSII), but the large variation in usage within Europe remains, with relatively high use (> 15%) in, for example, Norway, Austria, Germany and Sweden and low use (companies or funding from national health services, the availability of sufficient diabetes nurse educators and dietitians trained in pump procedures, and clear referral pathways for the pump candidate from general practitioner or general hospital to specialist pump centre. There are now several comprehensive national guidelines on CSII use (see ATTD Yearbook 2009) but more work needs to be done in unifying uptake and ensuring all those who can benefit do so. Technology developments recently include increasing use of pumps with continuous glucose monitoring (CGM) connectivity (see elsewhere in this volume) and the emergence of numerous manufacturers developing so-called 'patch pumps', often for the type 2 diabetes market. Interestingly, the evidence base for CSII in this group is not well established, and for this reason the selected papers on CSII in this section include several in this area. The use of CSII in diabetic pregnancy is a long-established practice, in spite of the lack of evidence that it is superior to multiple daily injections (MDI), and few randomised controlled trials have been done in recent years. Several papers in this field this year continue the debate about the usefulness of CSII in diabetic pregnancy and are reviewed here. It is pleasing to see more research on the psychosocial aspects of CSII during the year, both from the point of view of how psychological beliefs influence outcomes on CSII (is there a type of patient who does particularly well or poorly on CSII?) and how CSII affects psychological factors like mood, behaviour and quality of life. Quality of

  18. Fullerene inhibits benzo(a)pyrene Efflux from Cyprinus carpio hepatocytes by affecting cell membrane fluidity and P-glycoprotein expression.

    Science.gov (United States)

    Chen, Qiqing; Hu, Xialin; Wang, Rui; Yuan, Jin; Yin, Daqiang

    2016-05-01

    P-Glycoprotein (P-gp) can protect cells by pumping out toxic compounds, and has been found widely expressed in fish tissues. Here, we illustrate the P-gp efflux ability for benzo(a)pyrene (BaP) in the hepatocytes of common carp (Cyprinus carpio) after exposing to fullerene aqueous suspension (nC60). The results revealed that nC60 increased the membrane fluidity by decreasing the ratio of saturated to unsaturated fatty acids, and increased the cholesterol contents. These findings, combined with 10-38% and 70-75% down-regulation of P-gp mRNA and protein respectively, suggested that nC60 caused inhibition on P-gp efflux transport system. Therefore, we further investigated the cellular efflux ability for BaP. Results showed unequivocally that nC60 is a potent P-gp inhibitor. The retaining BaP amounts after efflux were elevated by 1.7-2.8 fold during the 10 day exposure. Meanwhile, 5mg/L humic acid (one of the important fractions of natural organic matter, which is ubiquitous in aquatic environment) alleviated the nC60 damage to hepatocytes in terms of oxidative damage, cholesterol increment, and P-gp content reduction; and finally attenuated the suppressed P-gp efflux ability. Collectively, this study provides the first evidence of nC60 toxicity to P-gp functionality in fish and illustrates the possible mechanism of the suppressed P-gp efflux ability for BaP.

  19. Arsenic efflux from Microcystis aeruginosa under different phosphate regimes.

    Directory of Open Access Journals (Sweden)

    Changzhou Yan

    Full Text Available Phytoplankton plays an important role in arsenic speciation, distribution, and cycling in freshwater environments. Little information, however, is available on arsenic efflux from the cyanobacteria Microcystis aeruginosa under different phosphate regimes. This study investigated M. aeruginosa arsenic efflux and speciation by pre-exposing it to 10 µM arsenate or arsenite for 24 h during limited (12 h and extended (13 d depuration periods under phosphate enriched (+P and phosphate depleted (-P treatments. Arsenate was the predominant species detected in algal cells throughout the depuration period while arsenite only accounted for no greater than 45% of intracellular arsenic. During the limited depuration period, arsenic efflux occurred rapidly and only arsenate was detected in solutions. During the extended depuration period, however, arsenate and dimethylarsinic acid (DMA were found to be the two predominant arsenic species detected in solutions under -P treatments, but arsenate was the only species detected under +P treatments. Experimental results also suggest that phosphorus has a significant effect in accelerating arsenic efflux and promoting arsenite bio-oxidation in M. aeruginosa. Furthermore, phosphorus depletion can reduce arsenic efflux from algal cells as well as accelerate arsenic reduction and methylation. These findings can contribute to our understanding of arsenic biogeochemistry in aquatic environments and its potential environmental risks under different phosphorus levels.

  20. Berberine Is a Novel Type Efflux Inhibitor Which Attenuates the MexXY-Mediated Aminoglycoside Resistance in Pseudomonas aeruginosa

    Science.gov (United States)

    Morita, Yuji; Nakashima, Ken-ichi; Nishino, Kunihiko; Kotani, Kenta; Tomida, Junko; Inoue, Makoto; Kawamura, Yoshiaki

    2016-01-01

    The emergence and spread of multidrug-resistant P. aeruginosa infections is of great concern, as very few agents are effective against strains of this species. Methanolic extracts from the Coptidis Rhizoma (the rhizomes of Coptis japonica var. major Satake) or Phellodendri Cortex (the bark of Phellodendron chinense Schneider) markedly reduced resistance to anti-pseudomonal aminoglycosides (e.g., amikacin) in multidrug-resistant P. aeruginosa strains. Berberine, the most abundant benzylisoquinoline alkaloid in the two extracts, reduced aminoglycoside resistance of P. aeruginosa via a mechanism that required the MexXY multidrug efflux system; berberine also reduced aminoglycoside MICs in Achromobacter xylosoxidans and Burkholderia cepacia, two species that harbor intrinsic multidrug efflux systems very similar to the MexXY. Furthermore this compound inhibited MexXY-dependent antibiotic resistance of other classes including cephalosporins (cefepime), macrolides (erythromycin), and lincosamides (lincomycin) demonstrated using a pseudomonad lacking the four other major Mex pumps. Although phenylalanine-arginine beta-naphthylamide (PAβN), a well-known efflux inhibitor, antagonized aminoglycoside in a MexXY-dependent manner, a lower concentration of berberine was sufficient to reduce amikacin resistance of P. aeruginosa in the presence of PAβN. Moreover, berberine enhanced the synergistic effects of amikacin and piperacillin (and vice versa) in multidrug-resistant P. aeruginosa strains. Thus, berberine appears to be a novel type inhibitor of the MexXY-dependent aminoglycoside efflux in P. aeruginosa. As aminoglycosides are molecules of choice to treat severe infections the clinical impact is potentially important. PMID:27547203

  1. Berberine Is a Novel Type Efflux Inhibitor Which Attenuates the MexXY-Mediated Aminoglycoside Resistance in Pseudomonas aeruginosa.

    Science.gov (United States)

    Morita, Yuji; Nakashima, Ken-Ichi; Nishino, Kunihiko; Kotani, Kenta; Tomida, Junko; Inoue, Makoto; Kawamura, Yoshiaki

    2016-01-01

    The emergence and spread of multidrug-resistant P. aeruginosa infections is of great concern, as very few agents are effective against strains of this species. Methanolic extracts from the Coptidis Rhizoma (the rhizomes of Coptis japonica var. major Satake) or Phellodendri Cortex (the bark of Phellodendron chinense Schneider) markedly reduced resistance to anti-pseudomonal aminoglycosides (e.g., amikacin) in multidrug-resistant P. aeruginosa strains. Berberine, the most abundant benzylisoquinoline alkaloid in the two extracts, reduced aminoglycoside resistance of P. aeruginosa via a mechanism that required the MexXY multidrug efflux system; berberine also reduced aminoglycoside MICs in Achromobacter xylosoxidans and Burkholderia cepacia, two species that harbor intrinsic multidrug efflux systems very similar to the MexXY. Furthermore this compound inhibited MexXY-dependent antibiotic resistance of other classes including cephalosporins (cefepime), macrolides (erythromycin), and lincosamides (lincomycin) demonstrated using a pseudomonad lacking the four other major Mex pumps. Although phenylalanine-arginine beta-naphthylamide (PAβN), a well-known efflux inhibitor, antagonized aminoglycoside in a MexXY-dependent manner, a lower concentration of berberine was sufficient to reduce amikacin resistance of P. aeruginosa in the presence of PAβN. Moreover, berberine enhanced the synergistic effects of amikacin and piperacillin (and vice versa) in multidrug-resistant P. aeruginosa strains. Thus, berberine appears to be a novel type inhibitor of the MexXY-dependent aminoglycoside efflux in P. aeruginosa. As aminoglycosides are molecules of choice to treat severe infections the clinical impact is potentially important. PMID:27547203

  2. Whole blood pumping with a microthrottle pump

    OpenAIRE

    Davies, M J; Johnston, I. D.; Tan, C. K. L.; Tracey, M. C.

    2010-01-01

    We have previously reported that microthrottle pumps (MTPs) display the capacity to pump solid phase suspensions such as polystyrene beads which prove challenging to most microfluidic pumps. In this paper we report employing a linear microthrottle pump (LMTP) to pump whole, undiluted, anticoagulated, human venous blood at 200 μl min−1 with minimal erythrocyte lysis and no observed pump blockage. LMTPs are particularly well suited to particle suspension transport by virtue of their relatively ...

  3. Rapid efflux of Ca2+ from heart mitochondria in the presence of inorganic pyrophosphate.

    Science.gov (United States)

    Vercesi, A; Lehninger, A L

    1984-01-13

    Inorganic pyrophosphate (PPi) in the intracellular concentration range causes rapid efflux of Ca2+ from rat heart mitochondria oxidizing pyruvate + malate in a low Na+ medium. Half-maximal rates of Ca2+ efflux were given by 20 microM PPi. During and after PPi-stimulated Ca2+ efflux the mitochondria retain their structural integrity and complete respiratory control. Carboxyatractyloside inhibits PPi-stimulated Ca2+ efflux, indicating PPi must enter the matrix in order to promote Ca2+ efflux. Heart mitochondria have a much higher affinity for PPi uptake and PPi-induced Ca2+ efflux than liver mitochondria. PMID:6199026

  4. Using a Breast Pump

    Science.gov (United States)

    ... you can relax and not be disturbed while pumping. If you have an electric pump, find an ... otherwise irritating your nipple or breast tissue. Begin Pumping If your pump is electric or battery-powered, ...

  5. Methane efflux in rice paddy field under different irrigation managements

    Directory of Open Access Journals (Sweden)

    Diovane Freire Moterle

    2013-04-01

    Full Text Available Paddy rice fields may contribute to methane (CH4 emission from soil due to anaerobic conditions after flooding. Alternatives to continuous flooding irrigation in rice have been developed to mitigate CH4 efflux into the atmosphere. This study aims to investigate the effects of irrigation managements in the CH4 efflux during the rice growing season. An experiment was carried out at in Santa Maria, Rio Grande do Sul State, Brazil, during 2007/08 and 2009/10 growing seasons. The treatments were continuous flooding and intermittent irrigation in 2007/08 and continuous flooding, intermittent irrigation and flush irrigation in 2009/10. Intermittent irrigation is effective in mitigating CH4 efflux from rice fields when climatic conditions enable water absence during cultivation, but its efficiency depends on the electrochemical soil conditions during the flooding cycles.

  6. Organic carbon efflux from a deciduous forest catchment in Korea

    Directory of Open Access Journals (Sweden)

    S. J. Kim

    2010-04-01

    Full Text Available Soil infiltration and surface discharge of precipitation are critical processes that affect the efflux of Dissolved Organic Carbon (DOC and Particulate Organic Carbon (POC in forested catchments. Concentrations of DOC and POC can be very high in the soil surface in most forest ecosystems and their efflux may not be negligible particularly under the monsoon climate. In East Asia, however, there are little data available to evaluate the role of such processes in forest carbon budget. In this paper, we address two basic questions: (1 how does stream discharge respond to storm events in a forest catchment? and (2 how much DOC and POC are exported from the catchment particularly during the summer monsoon period? To answer these questions, we collected hydrological data (e.g., precipitation, soil moisture, runoff discharge, groundwater level and conducted hydrochemical analyses (including DOC, POC, and six tracers in a deciduous forest catchment in Gwangneung National Arboretum in west-central Korea. Based on the end-member mixing analysis of the six storm events during the summer monsoon in 2005, the surface discharge was estimated as 30 to 80% of the total runoff discharge. The stream discharge responded to precipitation within 12 h during these storm events. The annual efflux of DOC and POC from the catchment was estimated as 0.04 and 0.05 t C ha−1 yr−1, respectively. Approximately 70% of the annual organic carbon efflux occurred during the summer monsoon period. Overall, the annual efflux of organic carbon was estimated to be about 10% of the Net Ecosystem carbon Exchange (NEE obtained by eddy covariance measurement at the same site. Considering the current trends of increasing intensity and amount of summer rainfall and the large interannual variability in NEE, ignoring the organic carbon efflux from forest catchments would result in an inaccurate estimation of the carbon sink strength of forest ecosystems in the monsoon

  7. The MRP1-mediated effluxes of arsenic and antimony do not require arsenic-glutathione and antimony-glutathione complex formation.

    Science.gov (United States)

    Salerno, Milena; Petroutsa, Maria; Garnier-Suillerot, Arlette

    2002-04-01

    Arsenic trioxide is an effective treatment for acute promyelocytic leukemia, but resistance to metalloid salts is found in humans. Using atomic absorption spectroscopy, we have measured the rate of uptake of arsenic trioxide and of antimony tartrate in GLC4 and GLC4/ADR cells overexpressing MRP1 and the rate of their MRP1-mediated effluxes as a function of the intracellular GSH concentration. In sensitive cells, after 1 h, a pseudosteady state is reached where intra- and extracellular concentrations of metalloid are the same. This precludes the formation, at short term, of complexes between arsenic or antimony with GSH. In resistant cells reduced intracellular accumulation of arsenic (or antimony), reflecting an increased rate of arsenic (or antimony) efflux from the cells, is observed. No efflux of the metalloid is observed in GSH depleted cells. The two metalloids and GSH are pumped out by MRP1 with the same efficiency. Moreover for the three compounds 50% of the efflux is inhibited by 2 microM MK571. This led us to suggest that As- and Sb-containing species could be cotransported with GSH. PMID:12018890

  8. Moderate alcohol consumption increases cholesterol efflux mediated by ABCA1

    NARCIS (Netherlands)

    Beulens, J.W.J.; Sierksma, A.; Tol, van A.; Fournier, C.

    2004-01-01

    Moderate alcohol consumption increases HDL cholesterol, which is involved in reverse cholesterol transport (RCT). The aim of this study was to investigate the effect of moderate alcohol consumption on cholesterol efflux, using J774 mouse macrophages and Fu5AH cells, and on other parameters in the RC

  9. Influence of doxorubicin on fluconazole susceptibility and efflux pump gene expression of Candida dubliniensis.

    LENUS (Irish Health Repository)

    Schulz, Bettina

    2012-05-01

    The effect of doxorubicin (DOX) on the fluconazole (FLU) susceptibility of C. dubliniensis was investigated. Isolates were exposed to DOX and FLU in a chequerboard assay and resistance gene expressions were analysed after DOX exposure. The susceptibility of the yeast to FLU was decreased in the presence of DOX in the chequerboard assay with FIC indices suggesting an antagonistic effect. Gene expression analyses showed an overexpression of CdCDR2. Hence, DOX was found to have an impact on resistance mechanisms in C. dubliniensis isolates.

  10. Contributions of efflux pumps to high level resistance of Pseudomonas aeruginosa to ciprofloxacin

    Institute of Scientific and Technical Information of China (English)

    WANG Dan-dan; SUN Tie-ying; HU Yun-jian

    2007-01-01

    @@ Pseudomonas aeruginosa (P. aeruginosa) is one of the leading pathogens involved in nosocomial pneumonia. In addition, P. aeruginosa infection is associated with significant morbidity and mortality.1 A major problem in P. aeruginosa infection is that this organism exhibits natural and acquired resistance to many structurally and functionally diverse antibiotics.

  11. Mycobacterium smegmatis MSMEG_3705 encodes a selective major facilitator superfamily efflux pump with multiple roles.

    Science.gov (United States)

    Zhang, Zhen; Wang, Rui; Xie, Jianping

    2015-06-01

    Mycobacterium smegmatis mc(2)155 MSMEG_3705 gene was annotated to encode a transporter protein that contains 12 alpha-helical transmembrane domains. We predicted MSMEG_3705 encoding a major facilitator superfamily (MFS) member. To confirm the prediction, the M. smegmatis mc(2)155 MSMEG_3705 gene was deleted. The MSMEG_3705 deletion mutant strain M. smegmatis mc(2)155 ∆MSMEG_3705 was more sensitive to capreomycin. Moreover, M. smegmatis mc(2)155 ∆MSMEG_3705 strain accumulated more ethidium bromide intracellular than wild-type M. smegmatis mc(2)155. Quite unexpectedly, M. smegmatis mc(2)155 ∆MSMEG_3705 grew faster than the wild-type M. smegmatis mc(2)155. The upregulation of the expression of MSMEG_3706, a gene encoding isocitrate lyase downstream MSMEG_3705, in the deletion mutant, might underlie such faster growth in the mutant. The study showed that MSMEG_3705 encodes a genuine MFS member and plays significant role in bacterial growth and antibiotics resistance.

  12. Promising therapy of XDR-TB/MDR-TB with thioridazine an inhibitor of bacterial efflux pumps

    DEFF Research Database (Denmark)

    Amaral, L; Martins, M; Viveiros, M;

    2008-01-01

    Global rates of pulmonary tuberculosis (TB) continue to increase. Moreover, resistance of the causative organism Mycobacterium tuberculosis to the two most effective anti-TB medications continue to rise. Now, multi-drug resistant TB (MDR-TB) has progressed to extensively drug resistant TB (XDR......-TB) - a M. tuberculosis organism that is resistant to the most effective second line drugs available for the treatment of TB. This review provides detailed, significant evidence that supports the use of an old neuroleptic compound, thioridazine (TZ), for the management of MDR-TB and XDR-TB infections and...

  13. Pump characteristics and applications

    CERN Document Server

    Volk, Michael

    2013-01-01

    Providing a wealth of information on pumps and pump systems, Pump Characteristics and Applications, Third Edition details how pump equipment is selected, sized, operated, maintained, and repaired. The book identifies the key components of pumps and pump accessories, introduces the basics of pump and system hydraulics as well as more advanced hydraulic topics, and details various pump types, as well as special materials on seals, motors, variable frequency drives, and other pump-related subjects. It uses example problems throughout the text, reinforcing the practical application of the formulae

  14. Exploring the HME and HAE1 efflux systems in the genus Burkholderia

    Directory of Open Access Journals (Sweden)

    Pasca Maria

    2010-06-01

    Full Text Available Abstract Background The genus Burkholderia includes a variety of species with opportunistic human pathogenic strains, whose increasing global resistance to antibiotics has become a public health problem. In this context a major role could be played by multidrug efflux pumps belonging to Resistance Nodulation Cell-Division (RND family, which allow bacterial cells to extrude a wide range of different substrates, including antibiotics. This study aims to i identify rnd genes in the 21 available completely sequenced Burkholderia genomes, ii analyze their phylogenetic distribution, iii define the putative function(s that RND proteins perform within the Burkholderia genus and iv try tracing the evolutionary history of some of these genes in Burkholderia. Results BLAST analysis of the 21 Burkholderia sequenced genomes, using experimentally characterized ceoB sequence (one of the RND family counterpart in the genus Burkholderia as probe, allowed the assembly of a dataset comprising 254 putative RND proteins. An extensive phylogenetic analysis revealed the occurrence of several independent events of gene loss and duplication across the different lineages of the genus Burkholderia, leading to notable differences in the number of paralogs between different genomes. A putative substrate [antibiotics (HAE1 proteins/heavy-metal (HME proteins] was also assigned to the majority of these proteins. No correlation was found between the ecological niche and the lifestyle of Burkholderia strains and the number/type of efflux pumps they possessed, while a relation can be found with genome size and taxonomy. Remarkably, we observed that only HAE1 proteins are mainly responsible for the different number of proteins observed in strains of the same species. Data concerning both the distribution and the phylogenetic analysis of the HAE1 and HME in the Burkholderia genus allowed depicting a likely evolutionary model accounting for the evolution and spreading of HME and HAE

  15. Glutamate Efflux at the Blood-Brain Barrier

    DEFF Research Database (Denmark)

    Cederberg-Helms, Hans Christian; Uhd-Nielsen, Carsten; Brodin, Birger

    2014-01-01

    L-Glutamate is considered the most important excitatory amino acid in the mammalian brain. Strict control of its concentration in the brain interstitial fluid is important to maintain neurotransmission and avoid excitotoxicity. The role of astrocytes in handling L-glutamate transport and metabolism...... is well known, however endothelial cells may also play an important role through mediating brain-to-blood L-glutamate efflux. Expression of excitatory amino acid transporters has been demonstrated in brain endothelial cells of bovine, human, murine, rat and porcine origin. These can account for high......-glutamate, metabolism of L-glutamate and transport of metabolites or a combination of the two. However, both in vitro and in vivo studies have demonstrated blood-to-brain transport of L-glutamate, at least during pathological events. This review summarizes the current knowledge on the brain-to-blood L-glutamate efflux...

  16. Metabolic Targeting of Lactate Efflux by Malignant Glioma Inhibits Invasiveness and Induces Necrosis: An In Vivo Study

    Directory of Open Access Journals (Sweden)

    Chaim B Colen

    2011-07-01

    Full Text Available Glioblastoma multiforme (GBM are the most malignant among brain tumors. They are frequently refractory to chemotherapy and radiotherapy with mean patient survival of approximately 6 months, despite surgical intervention. The highly glycolytic nature of glioblastomas describes their propensity to metabolize glucose to lactic acid at an elevated rate. To survive, GBMs efflux lactic acid to the tumor microenvironment through transmembrane transporters denoted monocarboxylate transporters (MCTs. We hypothesized that inhibition of MCT function would impair the glycolytic metabolism and affect both glioma invasiveness and survival. We examined the effect on invasiveness with α-cyano-4-hydroxy-cinnamic acid (ACCA, 4CIN, CHCA, a small-molecule inhibitor of lactate transport, through Matrigel-based and organotypic (brain slice culture invasive assays using U87-MG and U251-MG glioma cells. We then conducted studies in immunodeficient rats by stereotaxic intracranial implantation of the glioma cells followed by programmed orthotopic application of ACCA through osmotic pumps. Effect on the implanted tumor was monitored by small-animal magnetic resonance imaging. Our assays indicated that glioma invasion was markedly impaired when lactate efflux was inhibited. Convection-enhanced delivery of inhibitor to the tumor bed caused tumor necrosis, with 50% of the animals surviving beyond the experimental end points (3 months after inhibitor exhaustion. Most importantly, control animals did not display any adverse neurologic effects during orthotopic administration of ACCA to brain through programmed delivery. These results indicate the clinical potential of targeting lactate efflux in glioma through delivery of small-molecule inhibitors of MCTs either to the tumor bed or to the postsurgical resection cavity.

  17. LMFBR with booster pump in pumping loop

    Science.gov (United States)

    Rubinstein, H.J.

    1975-10-14

    A loop coolant circulation system is described for a liquid metal fast breeder reactor (LMFBR) utilizing a low head, high specific speed booster pump in the hot leg of the coolant loop with the main pump located in the cold leg of the loop, thereby providing the advantages of operating the main pump in the hot leg with the reliability of cold leg pump operation.

  18. Old carbon efflux from tropical peat swamp drainage waters

    Science.gov (United States)

    Vihermaa, Leena; Waldron, Susan; Evers, Stephanie; Garnett, Mark; Newton, Jason

    2014-05-01

    Tropical peatlands constitute ~12% of the global peatland carbon pool, and of this 10% is in Malaysia1. Due to rising demand for food and biofuels, large areas of peat swamp forest ecosystems have been converted to plantation in Southeast Asia and are being subjected to degradation, drainage and fire, changing their carbon fluxes eg.2,3. Dissolved organic carbon (DOC) lost from disturbed tropical peat can be derived from deep within the peat column and be aged from centuries to millennia4 contributing to aquatic release and cycling of old carbon. Here we present the results of a field campaign to the Raja Musa Peat Swamp Forest Reserve in N. Selangor Malaysia, which has been selectively logged for 80 years before being granted timber reserve status. We measured CO2 and CH4efflux rates from drainage systems with different treatment history, and radiocarbon dated the evasion CO2 and associated [DOC]. We also collected water chemistry and stable isotope data from the sites. During our sampling in the dry season CO2 efflux rates ranged from 0.8 - 13.6 μmol m-2 s-1. Sediments in the channel bottom contained CH4 that appeared to be primarily lost by ebullition, leading to sporadic CH4 efflux. However, dissolved CH4 was also observed in water samples collected from these systems. The CO2 efflux was aged up to 582±37 years BP (0 BP = AD 1950) with the associated DOC aged 495±35 years BP. Both DOC and evasion CO2 were most 14C-enriched (i.e. younger) at the least disturbed site, and implied a substantial component of recently fixed carbon. In contrast, CO2 and DOC from the other sites had older 14C ages, indicating disturbance as the trigger for the loss of old carbon. 1Page et al., 2010 2Hooijer et al., 2010 3Kimberly et al., 2012 4Moore et al., 2013

  19. Heat pump technology

    CERN Document Server

    Von Cube, Hans Ludwig; Goodall, E G A

    2013-01-01

    Heat Pump Technology discusses the history, underlying concepts, usage, and advancements in the use of heat pumps. The book covers topics such as the applications and types of heat pumps; thermodynamic principles involved in heat pumps such as internal energy, enthalpy, and exergy; and natural heat sources and energy storage. Also discussed are topics such as the importance of the heat pump in the energy industry; heat pump designs and systems; the development of heat pumps over time; and examples of practical everyday uses of heat pumps. The text is recommended for those who would like to kno

  20. Test of the mechanism of UV-induced K+ efflux

    International Nuclear Information System (INIS)

    UV radiation and certain plant pathogens stimulate a net efflux of K+ from cultured plant cells. Many aspects of the efflux are uncertain, including the counterion(s) involved. In the case of UV irradiation of rose cells, Murphy and Wilson suggest a coordinate loss of K+ and HCO3-; in contrast, Atkinson et al. suggest that treatment of tobacco cells with Erwinia pectate lyase introduces a counterflux of K+ and H+. In respiring cells, the cytoplasm and medium are buffered by respiratory CO2, and it is difficult to distinguish between the two mechanisms. Still, the two models predict different influences of external pH on the rate of K+ flux. The authors have found that increasing pH from 4 to 8 by use of MES-TRIS buffer, pH state, or controlled external CO2 concentration does not significantly decrease the rate of UV-induced K+ efflux. This evidence does not support the application of the K+/H+ counterflux model to the case of the UV-irradiated rose cells

  1. Bacillus cereus efflux protein BC3310 - a multidrug transporter of the unknown major facilitator family, UMF-2

    Directory of Open Access Journals (Sweden)

    Jasmin K Kroeger

    2015-10-01

    Full Text Available Phylogenetic classification divides the major facilitator superfamily (MFS into 82 families, including 25 families that are comprised of transporters with no characterized functions. This study describes functional data for BC3310 from Bacillus cereus ATCC 14579, a member of the unknown major facilitator family 2 (UMF 2. BC3310 was shown to be a multidrug efflux pump conferring resistance to ethidium bromide, SDS and silver nitrate when heterologously expressed in E. coli DH5α ΔacrAB. A conserved aspartate residue (D105 in putative transmembrane helix 4 was identified, which was essential for the energy dependent ethidium bromide efflux by BC3310. Transport proteins of the MFS comprise specific sequence motifs. Sequence analysis of UMF 2 proteins revealed that they carry a variant of the MFS motif A, which may be used as a marker to distinguish easily between this family and other MFS proteins. Genes orthologous to bc3310 are highly conserved within the B. cereus group of organisms and thus belong to the core genome, suggesting an important conserved functional role in the normal physiology of these bacteria.

  2. Crystallization and preliminary X-ray diffraction analysis of the multidrug efflux transporter NorM from Neisseria gonorrhoeae

    Energy Technology Data Exchange (ETDEWEB)

    Su, Chih-Chia [Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011 (United States); Long, Feng [Molecular, Cellular and Developmental Biology Interdepartmental Graduate Program, Iowa State University, Ames, IA 50011 (United States); McDermott, Gerry [Department of Anatomy, School of Medicine, University of California, San Francisco, CA 94143 (United States); Shafer, William M. [Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia 30322 (United States); Laboratories of Microbial Pathogenesis, VA Medical Center, Decatur, Georgia 30033 (United States); Yu, Edward W., E-mail: ewyu@iastate.edu [Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011 (United States); Molecular, Cellular and Developmental Biology Interdepartmental Graduate Program, Iowa State University, Ames, IA 50011 (United States); Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)

    2008-04-01

    The multidrug efflux transporter NorM from N. gonorrhoeae has been crystallized and X-ray diffraction data have been collected to a resolution of 6.5 Å. The crystallization and preliminary X-ray data analysis of the NorM multidrug efflux pump produced by Neisseria gonorrhoeae are reported. NorM is a cytoplasmic membrane protein that consists of 459 amino-acid residues. It is a member of the recently classified multidrug and toxic compound extrusion (MATE) family of transporters and recognizes a number of cationic toxic compounds such as ethidium bromide, acriflavin, 2-N-methylellipticinium and ciprofloxacin. Recombinant NorM protein was expressed in Escherichia coli and purified by metal-affinity and gel-filtration chromatography. The protein was crystallized using hanging-drop vapor diffusion. X-ray diffraction data were collected from cryocooled crystals at a synchrotron light source. The best crystal diffracted anisotropically to 3.8 Å and diffraction data were complete to 6.5 Å resolution. The space group was determined to be C2, with unit-cell parameters a = 81.5, b = 164.4, c = 111.5 Å.

  3. Efflux of rhodamine from CD56+ cells as a surrogate marker for reversal of P-glycoprotein-mediated drug efflux by PSC 833

    DEFF Research Database (Denmark)

    Robey, R; Bakke, S; Stein, W;

    1999-01-01

    The expression of high levels of P-glycoprotein (Pgp) in circulating mononuclear cells allowed us to use an ex vivo assay as a surrogate measure of Pgp antagonism. Efflux of rhodamine from CD56(+) cells was measured before the start of PSC 833 and at varying times thereafter. Patients receiving PSC...... 833 had decreased rhodamine efflux from their circulating CD56(+) cells. Time course studies showed that following a single oral dose of PSC 833, decreased rhodamine efflux was found in some patients within 15 minutes of treatment. Maximal inhibition was observed at times ranging from 45 minutes to 60...... minutes. A dose-response relationship was shown between the concentration of PSC 833 in the blood and the inhibition of rhodamine efflux, with an apparent plateau of the inhibition of rhodamine efflux at approximately 1,000 ng/mL. The Ki, defined as the concentration required for half-maximal inhibition...

  4. Reducing Both Pgp Overexpression and Drug Efflux with Anti-Cancer Gold-Paclitaxel Nanoconjugates

    Science.gov (United States)

    Li, Fei; Zhou, Xiaofei; Zhou, Hongyu; Jia, Jianbo; Li, Liwen; Zhai, Shumei; Yan, Bing

    2016-01-01

    Repeated administrations of anti-cancer drugs to patients often induce drug resistance. P-glycoprotein (Pgp) facilitates an efficient drug efflux, preventing cellular accumulation of drugs and causing multi-drug resistance (MDR). In this study, we developed a gold-paclitaxel nanoconjugate system to overcome MDR. Gold nanoparticles (GNPs) were conjugated with β-cyclodextrin enclosing paclitaxel (PTX) molecules and PEG molecules. GNP conjugates were effectively endocytosed by both drug-sensitive human lung cancer H460 cells and Pgp-overexpressed drug-resistant H460PTX cells. Compared with PTX, PGNPs did not induce the Pgp overexpression in drug-sensitive H460 cells after long-term treatment and also avoided being pumped out of cells by overexpressed Pgp molecules in H460PTX with a 17-fold lower EC50 compared to PTX. Fluorescent microscopy and flow cytometry further confirmed that fluorescent labeled PGNPs (f-PGNPs) maintained a high cellular PTX level in both H460 and H460PTX cells. These results demonstrated that nano-drug conjugates were able to avoid the development of drug resistance in sensitive cells and evade Pgp-mediated drug resistance and to maintain a high cytotoxicity in drug-resistant cancer cells. These findings exemplify a powerful nanotechnological approach to the long-lasting issue of chemotherapy-induced drug resistance. PMID:27467397

  5. Reducing Both Pgp Overexpression and Drug Efflux with Anti-Cancer Gold-Paclitaxel Nanoconjugates.

    Science.gov (United States)

    Li, Fei; Zhou, Xiaofei; Zhou, Hongyu; Jia, Jianbo; Li, Liwen; Zhai, Shumei; Yan, Bing

    2016-01-01

    Repeated administrations of anti-cancer drugs to patients often induce drug resistance. P-glycoprotein (Pgp) facilitates an efficient drug efflux, preventing cellular accumulation of drugs and causing multi-drug resistance (MDR). In this study, we developed a gold-paclitaxel nanoconjugate system to overcome MDR. Gold nanoparticles (GNPs) were conjugated with β-cyclodextrin enclosing paclitaxel (PTX) molecules and PEG molecules. GNP conjugates were effectively endocytosed by both drug-sensitive human lung cancer H460 cells and Pgp-overexpressed drug-resistant H460PTX cells. Compared with PTX, PGNPs did not induce the Pgp overexpression in drug-sensitive H460 cells after long-term treatment and also avoided being pumped out of cells by overexpressed Pgp molecules in H460PTX with a 17-fold lower EC50 compared to PTX. Fluorescent microscopy and flow cytometry further confirmed that fluorescent labeled PGNPs (f-PGNPs) maintained a high cellular PTX level in both H460 and H460PTX cells. These results demonstrated that nano-drug conjugates were able to avoid the development of drug resistance in sensitive cells and evade Pgp-mediated drug resistance and to maintain a high cytotoxicity in drug-resistant cancer cells. These findings exemplify a powerful nanotechnological approach to the long-lasting issue of chemotherapy-induced drug resistance. PMID:27467397

  6. Multiple pump housing

    Science.gov (United States)

    Donoho, II, Michael R.; Elliott; Christopher M.

    2010-03-23

    A fluid delivery system includes a first pump having a first drive assembly, a second pump having a second drive assembly, and a pump housing. At least a portion of each of the first and second pumps are located in the housing.

  7. Types of Breast Pumps

    Science.gov (United States)

    ... breast-shield. Some experts discourage the use of bicycle horn pumps because they may be difficult to clean and dry. Battery-Powered and Electric Pumps A powered breast pump uses batteries or a cord plugged into an electrical outlet to power a small motorized pump that ...

  8. Centrifugal pump handbook

    CERN Document Server

    Pumps, Sulzer

    2010-01-01

    This long-awaited new edition is the complete reference for engineers and designers working on pump design and development or using centrifugal pumps in the field. This authoritative guide has been developed with access to the technical expertise of the leading centrifugal pump developer, Sulzer Pumps. In addition to providing the most comprehensive centrifugal pump theory and design reference with detailed material on cavitation, erosion, selection of materials, rotor vibration behavior and forces acting on pumps, the handbook also covers key pumping applications topics and operational

  9. Inhibitory Effect of Flavonoids on the Efflux of -Acetyl 5-Aminosalicylic Acid Intracellularly Formed in Caco-2 Cells

    Directory of Open Access Journals (Sweden)

    Shin Yoshimura

    2009-01-01

    Full Text Available -acetyl 5-aminosalicylic acid (5-AcASA that was intracellularly formed from 5-aminosalicylic acid (5-ASA at 200 M was discharged 5.3, 7.1, and 8.1-fold higher into the apical site than into the basolateral site during 1, 2, and 4-hour incubations, respectively, in Caco-2 cells grown in Transwells. The addition of flavonols (100 M such as fisetin and quercetin with 5-ASA remarkably decreased the apically directed efflux of 5-AcASA. When 5-ASA (200 M was added to Caco-2 cells grown in tissue culture dishes, the formation of 5-AcASA decreased, and, in addition, the formed 5-AcASA was found to be accumulated within the cells in the presence of such flavonols. Thus, the decrease in 5-AcASA efflux by such flavonols was attributed not only to the inhibition of -acetyl-conjugation of 5-ASA but to the predominant cellular accumulation of 5-AcASA. Various flavonoids also had both of the effects with potencies that depend on their specific structures. The essential structure of flavonoids was an absence of a hydroxyl substitution at the C5 position on the A-ring of flavone structure for the inhibitory effect on the -acetyl-conjugation of 5-ASA, and a presence of hydroxyl substitutions at the C3 or C4 position on the B-ring of flavone structure for the promoting effect on the cellular accumulation of 5-AcASA. Both the decrease in 5-AcASA apical efflux and the increase in 5-AcASA cellular accumulation were also caused by MK571 and indomethacin, inhibitors of MRPs, but not by quinidine, cyclosporin A, P-glycoprotein inhibitors, and mitoxantrone, a BCRP substrate. These results suggest that certain flavonoids suppress the apical efflux of 5-AcASA possibly by inhibiting MRPs pumps located on apical membranes in Caco-2 cells.

  10. Development of Classification Models for Identifying “True” P-glycoprotein (P-gp Inhibitors Through Inhibition, ATPase Activation and Monolayer Efflux Assays

    Directory of Open Access Journals (Sweden)

    Anna Maria Bianucci

    2012-06-01

    Full Text Available P-glycoprotein (P-gp is an efflux pump involved in the protection of tissues of several organs by influencing xenobiotic disposition. P-gp plays a key role in multidrug resistance and in the progression of many neurodegenerative diseases. The development of new and more effective therapeutics targeting P-gp thus represents an intriguing challenge in drug discovery. P-gp inhibition may be considered as a valid approach to improve drug bioavailability as well as to overcome drug resistance to many kinds of tumours characterized by the over-expression of this protein. This study aims to develop classification models from a unique dataset of 59 compounds for which there were homogeneous experimental data on P-gp inhibition, ATPase activation and monolayer efflux. For each experiment, the dataset was split into a training and a test set comprising 39 and 20 molecules, respectively. Rational splitting was accomplished using a sphere-exclusion type algorithm. After a two-step (internal/external validation, the best-performing classification models were used in a consensus predicting task for the identification of compounds named as “true” P-gp inhibitors, i.e., molecules able to inhibit P-gp without being effluxed by P-gp itself and simultaneously unable to activate the ATPase function.

  11. Loss of receptor-mediated 86Rb efflux from pig aortic endothelial cells in culture.

    OpenAIRE

    Ager, A.; Martin, W

    1983-01-01

    The responsiveness of freshly-isolated and subcultured pig aortic endothelial cells to adenosine triphosphate (ATP), bradykinin and ionophore A23187 was compared by monitoring agonist-induced 86Rb efflux. ATP, bradykinin and ionophore A23187 stimulated 86Rb efflux from freshly-isolated cells. ATP and bradykinin, which act via specific receptors, were less effective at inducing 86Rb efflux from subcultured cells but ionophore A23187 was as effective on subcultured as on freshly-isolated cells....

  12. Novel Chromosomally Encoded Multidrug Efflux Transporter MdeA in Staphylococcus aureus

    OpenAIRE

    Huang, Jianzhong; O'Toole, Paul W.; Shen, Wei; Amrine-Madsen, Heather; Jiang, Xinhe; Lobo, Neethan; Palmer, Leslie M.; Voelker, LeRoy; Fan, Frank; Gwynn, Michael N.; McDevitt, Damien

    2004-01-01

    Antibiotic efflux is an important mechanism of resistance in pathogenic bacteria. Here we describe the identification and characterization of a novel chromosomally encoded multidrug resistance efflux protein in Staphylococcus aureus, MdeA (multidrug efflux A). MdeA was identified from screening an S. aureus open reading frame expression library for resistance to antibiotic compounds. When overexpressed, MdeA confers resistance on S. aureus to a range of quaternary ammonium compounds and antib...

  13. Different harvest intensity and soil CO2 efflux in sessile oak coppice forests

    OpenAIRE

    Darenova E; Cater M; Pavelka M

    2016-01-01

    Soil CO2 efflux accounts for about 45-80% of total ecosystem respiration and is therefore an important part of the ecosystem carbon cycle. Soil CO2 efflux has been poorly studied in forests managed in the ancient coppicing manner. In our study, soil CO2 efflux, temperature, and moisture were measured in sessile oak stands with different harvesting intensity (control: 0% intensity; V1: 75%; V2: 80 %; V3: 85%; and V4: 100%) during the fifth and sixth years after harvesting. Soil CO2 efflux was ...

  14. Chunnel vision: Export and efflux through bacterial channel-tunnels

    OpenAIRE

    Andersen, Christian; Hughes, Colin; Koronakis, Vassilis

    2000-01-01

    The Escherichia coli TolC protein is central to toxin export and drug efflux across the inner and outer cell membranes and the intervening periplasmic space. The crystal structure has revealed that TolC assembles into a remarkable α-helical trans-periplasmic cylinder (tunnel) embedded in the outer membrane by a contiguous β-barrel (channel), so providing a large duct open to the outside environment. The channel-tunnel structure is conserved in TolC homologues throughout Gram-negative bacteria...

  15. Peptides having reduced toxicity that stimulate cholesterol efflux

    Energy Technology Data Exchange (ETDEWEB)

    Bielicki, John K.; Johansson, Jan; Danho, Waleed

    2016-08-16

    The present invention provides a family of non-naturally occurring polypeptides having cholesterol efflux activity that parallels that of full-length apolipoproteins (e.g., Apo AI and Apo E), and having high selectivity for ABCA1 that parallels that of full-length apolipoproteins. Further, the peptides of the invention have little or no toxicity when administered at therapeutic and higher doses. The invention also provides compositions comprising such polypeptides, methods of identifying, screening and synthesizing such polypeptides, and methods of treating, preventing or diagnosing diseases and disorders associated with dyslipidemia, hypercholesterolemia and inflammation.

  16. Large electromagnetic pumps. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Kilman, G.B.

    1976-01-01

    The development of large electromagnetic pumps for the liquid metal heat transfer systems of fission reactors has progressed for a number of years. Such pumps are now planned for fusion reactors and solar plants as well. The Einstein-Szilard (annular) pump has been selected as the preferred configuration. Some of the reasons that electromagnetic pumps may be preferred over mechanical pumps and why the annular configuration was selected are discussed. A detailed electromagnetic analysis of the annular pump, based on slug flow, is presented. The analysis is then used to explore the implications of large size and power on considerations of electromagnetic skin effect, geometric skin effect and the cylindrical geometry.

  17. Single-step selection of drug resistant Acinetobacter baylyi ADP1 mutants reveals a functional redundancy in the recruitment of multidrug efflux systems.

    Directory of Open Access Journals (Sweden)

    Anthony J Brzoska

    Full Text Available Members of the genus Acinetobacter have been the focus recent attention due to both their clinical significance and application to molecular biology. The soil commensal bacterium Acinetobacter baylyi ADP1 has been proposed as a model system for molecular and genetic studies, whereas in a clinical environment, Acinetobacter spp. are of increasing importance due to their propensity to cause serious and intractable systemic infections. Clinically, a major factor in the success of Acinetobacter spp. as opportunistic pathogens can be attributed to their ability to rapidly evolve resistance to common antimicrobial compounds. Whole genome sequencing of clinical and environmental Acinetobacter spp. isolates has revealed the presence of numerous multidrug transporters within the core and accessory genomes, suggesting that efflux is an important host defense response in this genus. In this work, we used the drug-susceptible organism A. baylyi ADP1 as a model for studies into the evolution of efflux mediated resistance in genus Acinetobacter, due to the high level of conservation of efflux determinants across four diverse Acinetobacter strains, including clinical isolates. A single exposure of therapeutic concentrations of chloramphenicol to populations of A. baylyi ADP1 cells produced five individual colonies displaying multidrug resistance. The major facilitator superfamily pump craA was upregulated in one mutant strain, whereas the resistance nodulation division pump adeJ was upregulated in the remaining four. Within the adeJ upregulated population, two different levels of adeJ mRNA transcription were observed, suggesting at least three separate mutations were selected after single-step exposure to chloramphenicol. In the craA upregulated strain, a T to G substitution 12 nt upstream of the craA translation initiation codon was observed. Subsequent mRNA stability analyses using this strain revealed that the half-life of mutant craA mRNA was significantly

  18. The Role of Bile Salt Export Pump Gene Repression in Drug-Induced Cholestatic Liver Toxicity

    OpenAIRE

    Garzel, Brandy; Yang, Hui; Zhang, Lei; Huang, Shiew-Mei; Polli, James E.; Wang, Hongbing

    2014-01-01

    The bile salt export pump (BSEP, ABCB11) is predominantly responsible for the efflux of bile salts, and disruption of BSEP function is often associated with altered hepatic homeostasis of bile acids and cholestatic liver injury. Accumulating evidence suggests that many drugs can cause cholestasis through interaction with hepatic transporters. To date, a relatively strong association between drug-induced cholestasis and attenuated BSEP activity has been proposed. However, whether repression of...

  19. Ezetimibe Promotes Brush Border Membrane-to-Lumen Cholesterol Efflux in the Small Intestine.

    Science.gov (United States)

    Nakano, Takanari; Inoue, Ikuo; Takenaka, Yasuhiro; Ono, Hiraku; Katayama, Shigehiro; Awata, Takuya; Murakoshi, Takayuki

    2016-01-01

    Ezetimibe inhibits Niemann-Pick C1-like 1 (NPC1L1), an apical membrane cholesterol transporter of enterocytes, thereby reduces intestinal cholesterol absorption. This treatment also increases extrahepatic reverse cholesterol transport via an undefined mechanism. To explore this, we employed a trans-intestinal cholesterol efflux (TICE) assay, which directly detects circulation-to-intestinal lumen 3H-cholesterol transit in a cannulated jejunal segment, and found an increase of TICE by 45%. To examine whether such increase in efflux occurs at the intestinal brush border membrane(BBM)-level, we performed luminal perfusion assays, similar to TICE but the jejunal wall was labelled with orally-given 3H-cholesterol, and determined elevated BBM-to-lumen cholesterol efflux by 3.5-fold with ezetimibe. Such increased efflux probably promotes circulation-to-lumen cholesterol transit eventually; thus increases TICE. Next, we wondered how inhibition of NPC1L1, an influx transporter, resulted in increased efflux. When we traced orally-given 3H-cholesterol in mice, we found that lumen-to-BBM 3H-cholesterol transit was rapid and less sensitive to ezetimibe treatment. Comparison of the efflux and fractional cholesterol absorption revealed an inverse correlation, indicating the efflux as an opposite-regulatory factor for cholesterol absorption efficiency and counteracting to the naturally-occurring rapid cholesterol influx to the BBM. These suggest that the ezetimibe-stimulated increased efflux is crucial in reducing cholesterol absorption. Ezetimibe-induced increase in cholesterol efflux was approximately 2.5-fold greater in mice having endogenous ATP-binding cassette G5/G8 heterodimer, the major sterol efflux transporter of enterocytes, than the knockout counterparts, suggesting that the heterodimer confers additional rapid BBM-to-lumen cholesterol efflux in response to NPC1L1 inhibition. The observed framework for intestinal cholesterol fluxes may provide ways to modulate the flux

  20. Ezetimibe Promotes Brush Border Membrane-to-Lumen Cholesterol Efflux in the Small Intestine.

    Directory of Open Access Journals (Sweden)

    Takanari Nakano

    Full Text Available Ezetimibe inhibits Niemann-Pick C1-like 1 (NPC1L1, an apical membrane cholesterol transporter of enterocytes, thereby reduces intestinal cholesterol absorption. This treatment also increases extrahepatic reverse cholesterol transport via an undefined mechanism. To explore this, we employed a trans-intestinal cholesterol efflux (TICE assay, which directly detects circulation-to-intestinal lumen 3H-cholesterol transit in a cannulated jejunal segment, and found an increase of TICE by 45%. To examine whether such increase in efflux occurs at the intestinal brush border membrane(BBM-level, we performed luminal perfusion assays, similar to TICE but the jejunal wall was labelled with orally-given 3H-cholesterol, and determined elevated BBM-to-lumen cholesterol efflux by 3.5-fold with ezetimibe. Such increased efflux probably promotes circulation-to-lumen cholesterol transit eventually; thus increases TICE. Next, we wondered how inhibition of NPC1L1, an influx transporter, resulted in increased efflux. When we traced orally-given 3H-cholesterol in mice, we found that lumen-to-BBM 3H-cholesterol transit was rapid and less sensitive to ezetimibe treatment. Comparison of the efflux and fractional cholesterol absorption revealed an inverse correlation, indicating the efflux as an opposite-regulatory factor for cholesterol absorption efficiency and counteracting to the naturally-occurring rapid cholesterol influx to the BBM. These suggest that the ezetimibe-stimulated increased efflux is crucial in reducing cholesterol absorption. Ezetimibe-induced increase in cholesterol efflux was approximately 2.5-fold greater in mice having endogenous ATP-binding cassette G5/G8 heterodimer, the major sterol efflux transporter of enterocytes, than the knockout counterparts, suggesting that the heterodimer confers additional rapid BBM-to-lumen cholesterol efflux in response to NPC1L1 inhibition. The observed framework for intestinal cholesterol fluxes may provide ways to

  1. Posttranslational modification and trafficking of PIN auxin efflux carriers.

    Science.gov (United States)

    Löfke, Christian; Luschnig, Christian; Kleine-Vehn, Jürgen

    2013-01-01

    Cell-to-cell communication is absolutely essential for multicellular organisms. Both animals and plants use chemicals called hormones for intercellular signaling. However, multicellularity of plants and animals has evolved independently, which led to establishment of distinct strategies in order to cope with variations in an ever-changing environment. The phytohormone auxin is crucial to plant development and patterning. PIN auxin efflux carrier-driven polar auxin transport regulates plant development as it controls asymmetric auxin distribution (auxin gradients), which in turn modulates a wide range of developmental processes. Internal and external cues trigger a number of posttranslational PIN auxin carrier modifications that were demonstrated to decisively influence variations in adaptive growth responses. In this review, we highlight recent advances in the analysis of posttranslational modification of PIN auxin efflux carriers, such as phosphorylation and ubiquitylation, and discuss their eminent role in directional vesicle trafficking, PIN protein de-/stabilization and auxin transport activity. We conclude with updated models, in which we attempt to integrate the mechanistic relevance of posttranslational modifications of PIN auxin carriers for the dynamic nature of plant development.

  2. Molecular mechanisms associated with Fluconazole resistance in clinical Candida albicans isolates from India.

    Science.gov (United States)

    Mane, Arati; Vidhate, Pallavi; Kusro, Chanchal; Waman, Vaishali; Saxena, Vandana; Kulkarni-Kale, Urmila; Risbud, Arun

    2016-02-01

    Resistance to azole antifungals is a significant problem in Candida albicans. An understanding of resistance at molecular level is essential for the development of strategies to tackle resistance and rationale design of newer antifungals and target-based molecular approaches. This study presents the first evaluation of molecular mechanisms associated with fluconazole resistance in clinical C.albicans isolates from India. Target site (ERG11) alterations were determined by DNA sequencing, whereas real-time PCRs were performed to quantify target and efflux pump genes (CDR1, CDR2, MDR1) in 87 [Fluconazole susceptible (n = 30), susceptible-dose dependent (n = 30) and resistant (n = 27)] C.albicans isolates. Cross-resistance to fluconazole, ketoconazole and itraconazole was observed in 74.1% isolates. Six amino acid substitutions were identified, including 4 (E116D, F145L, E226D, I437V) previously reported ones and 2 (P406L, Q474H) new ones. CDR1 over-expression was seen in 77.7% resistant isolates. CDR2 was exclusively expressed with CDR1 and their concomitant over-expression was associated with azole cross-resistance. MDR1 and ERG11 over-expression did not seem to be associated with resistance. Our results show that drug efflux mediated by Adenosine-5'-triphosphate (ATP)-binding cassette transporters, especially CDR1 is the predominant mechanism of fluconazole resistance and azole cross-resistance in C. albicans and indicate the need for research directed towards developing strategies to tackle efflux mediated resistance to salvage azoles.

  3. Proton pump inhibitors

    Science.gov (United States)

    Proton pump inhibitors (PPIs) are medicines that work by reducing the amount of stomach acid made by ... Proton pump inhibitors are used to: Relieve symptoms of acid reflux, or gastroesophageal reflux disease (GERD). This ...

  4. Development of chitosan-SLN microparticles for chemotherapy: in vitro approach through efflux-transporter modulation.

    Science.gov (United States)

    Dharmala, Kiran; Yoo, Jin Wook; Lee, Chi H

    2008-11-12

    Drug efflux-transporters serve as a major barrier to anticancer drugs at the target site. One strategy to enhance the therapeutic efficacy of drugs against cancer is to increase their available concentrations at the target site by suppressing or modulating efflux-transporters. This manuscript deals with the development and evaluation of the particle type drug delivery system made of stearic acid (Solid Lipid Nanoparticle - SLN) and chitosan for the delivery of Phenethyl Isothiocyanate (PEITC), a tumor-suppressive agent, through the pulmonary route. The rationale behind the particle type drug delivery system involves a prior release of the efflux-transporter inhibitors, such as tamoxifen, verapamil HCl or nifedipine, to suppress or modulate the efflux activity of ABC transporters followed by the release of the efflux-transporter substrate, PEITC. The efficacy of Chitosan-SLN Microparticles (CSM) as a carrier for PEITC was evaluated by investigating the release profiles of PEITC loaded in CSM and its cytotoxicity in the presence or absence of the efflux-transporter inhibitors. An initial burst release of the inhibitors, followed by gradual, sustained release of PEITC and subsequent increase in cytotoxicity was observed. This finding indicated that the efflux transporter inhibitors significantly affected the PEITC uptake rate by Calu-3 cells. Judging from these results, CSM can be an efficient drug delivery system for the substrates susceptible to the efflux-transporters. PMID:18723057

  5. Cholesterol efflux monitoring in macrophage form cells by using fluorescence lifetime imaging

    Science.gov (United States)

    Song, Young Sik; Lee, Sang Hak; Park, Byoung Hee; Kim, Soo Hyeok; Hwang, Won Sang; Kim, Dug Young

    2015-03-01

    Macrophages play a key role in atherosclerotic plaque destabilization and rupture, since they accumulate large amounts of lipid through the uptake of modified lipoproteins which results in foam cell formation. Cholesterol efflux is the process of removing cholesterol from macrophages in the subintima of the vessel wall, and efflux mechanism in a cell is one of the critical issues for the prevention of cardiovascular diseases. High density lipoproteins (HDL) stimulate cholesterol efflux from macrophage foam cells in the arterial wall. Radioisotope-labeled cholesterol analysis method is well known conventional method for observing cholesterol efflux. The major drawback of this method is its long and complicated process. Fluorescence intensity imaging schemes are replacing the radioisotope-labeled method in recent years for cholesterol efflux monitoring. Various spectroscopic methods are also adapted for cholesterol efflux imaging. Here we present a fluorescence lifetime imaging method for more quantitative observation of cholesterol efflux process in macrophages, which enables us to observe cholesterol level changes with various conditions. We used J774 macrophage cell and 25-NBD-cholesterol which is a famous cholesterol specific dye. Our lifetime imaging results clearly show cholesterol efflux rate very effectively. We believe that fluorescence lifetime analysis is new and very powerful for cholesterol imaging or monitoring.

  6. Photovoltaic pump systems

    Science.gov (United States)

    Klockgether, J.; Kiessling, K. P.

    1983-09-01

    Solar pump systems for the irrigation of fields and for water supply in regions with much sunshine are discussed. For surface water and sources with a hoisting depth of 12 m, a system with immersion pumps is used. For deep sources with larger hoisting depths, an underwater motor pump was developed. Both types of pump system meet the requirements of simple installation and manipulation, safe operation, maintenance free, and high efficiency reducing the number of solar cells needed.

  7. Receptor kinase-mediated control of primary active proton pumping at the plasma membrane

    DEFF Research Database (Denmark)

    Fuglsang, AT; Kristensen, A; Cuin, TA;

    2014-01-01

    Acidification of the cell wall space outside the plasma membrane is required for plant growth and is the result of proton extrusion by the plasma membrane-localized H+ -ATPases. Here we show that the major plasma membrane proton pumps in Arabidopsis, AHA1 and AHA2, interact directly in vitro...... heterologous expression system, the introduction of a negative charge at this position caused pump activation. Application of PSY1 to plant seedlings induced rapid in planta phosphorylation at Thr-881, concomitant with an instantaneous increase in proton efflux from roots. The direct interaction between AHA2...

  8. Pump for Saturated Liquids

    Science.gov (United States)

    Elliott, D. G.

    1986-01-01

    Boiling liquids pumped by device based on proven components. Expanding saturated liquid in nozzle and diverting its phases along separate paths in liquid/vapor separator raises pressure of liquid. Liquid cooled in process. Pump makes it unnecessary to pressurize cryogenic liquids in order to pump them. Problems of introducing noncondensable pressurizing gas avoided.

  9. Breast milk - pumping and storing

    Science.gov (United States)

    ... a comfortable chair, sink, and electric pump. If pumping at work is going to be hard, build ... up your milk supply. Wash your hands before pumping. Collect breast milk when pumping. You can use: ...

  10. Nitrogen Fertilization Modifies the Phenology of Ground CO2 Efflux in a Boreal Scots Pine Forest

    Science.gov (United States)

    Marshall, J. D.; Näsholm, T.; Linder, S.; Tarvainen, L.; Peichl, M.; Lundmark, T.

    2015-12-01

    Problems with the extraction of ecosystem respiration rates from eddy covariance data have led to renewed interest in chamber-based estimates of CO2 efflux from near the ground surface. However, chamber measurements frequently have their own issues. Here we describe the results of a study using large (≈2 m radius), transparent chambers over intact ground vegetation to describe the net efflux of CO2 and its environmental controls during the growing season at Rosinedal, a research site in northern Sweden. Measurements were made at thirty-minute intervals over the course of three growing seasons in a heavily fertilized and an unfertilized Scots pine stand. Ammonium nitrate was added at rates of 100 kg N ha-1 for the first five years, after which the rate was halved but the additions continued. The CO2 efflux results were simultaneously fitted to a nonlinear model describing the exponential increase in dark efflux with temperature, the Michaelis-Menten saturation of light-driven CO2 uptake in photosynthesis, the reduction in efflux due to soil drying, and a residual term that we ascribe to weekly shifts in the photosynthate partitioning of canopy trees to belowground processes. We found the expected exponential increase in dark efflux with temperature, however the net efflux in daytime was often negative, reflecting the high GPP of the ground vegetation, especially in dense canopies of bilberry (Vaccinium myrtillus L.). There was a clear reduction in dark efflux under dry conditions. The empirical phenology parameters increased sharply in early July, around the time that leaf expansion and rapid cambial growth were completed. This increase was more pronounced on the control plot than on the fertilized plot, consistent with expectations based on the notion that N fertilization should favor aboveground partitioning. The empirical "partitioning coefficient" shifted net efflux by nearly as much as the seasonal temperature range. Dark efflux of CO2 was nearly halved as a

  11. Efflux time of soap bubbles and liquid spheres.

    Science.gov (United States)

    Grosse, A V

    1967-06-01

    The efflux time, T, of gas from soap bubbles of radius, R, through their blow tube of length, 1, and radius, p, is given by the equation see pdf for equation where eta is the viscosity of the gas and omicron the surface tension of the bubble solution, all in centimeter-gram-second units. Similar relations between time and diameter were established for the flow from one bubble to another or from one bubble within another. The same relations hold for the flow of liquid spheres, suspended in another liquid of equal density, following Plateau's classic method. They have been extended to the flow of spheres to cylinders and catenoids of rotation. In all these cases the driving force is the surface or interfacial tension, creating an excess pressure as defined by Laplace's equation. PMID:17792780

  12. A second mechanism for aluminum resistance in wheat relies on the constitutive efflux of citrate from roots.

    Science.gov (United States)

    Ryan, Peter R; Raman, Harsh; Gupta, Sanjay; Horst, Walter J; Delhaize, Emmanuel

    2009-01-01

    The first confirmed mechanism for aluminum (Al) resistance in plants is encoded by the wheat (Triticum aestivum) gene, TaALMT1, on chromosome 4DL. TaALMT1 controls the Al-activated efflux of malate from roots, and this mechanism is widespread among Al-resistant genotypes of diverse genetic origins. This study describes a second mechanism for Al resistance in wheat that relies on citrate efflux. Citrate efflux occurred constitutively from the roots of Brazilian cultivars Carazinho, Maringa, Toropi, and Trintecinco. Examination of two populations segregating for this trait showed that citrate efflux was controlled by a single locus. Whole-genome linkage mapping using an F(2) population derived from a cross between Carazinho (citrate efflux) and the cultivar EGA-Burke (no citrate efflux) identified a major locus on chromosome 4BL, Xce(c), which accounts for more than 50% of the phenotypic variation in citrate efflux. Mendelizing the quantitative variation in citrate efflux into qualitative data, the Xce(c) locus was mapped within 6.3 cM of the microsatellite marker Xgwm495 locus. This linkage was validated in a second population of F(2:3) families derived from a cross between Carazinho and the cultivar Egret (no citrate efflux). We show that expression of an expressed sequence tag, belonging to the multidrug and toxin efflux (MATE) gene family, correlates with the citrate efflux phenotype. This study provides genetic and physiological evidence that citrate efflux is a second mechanism for Al resistance in wheat.

  13. Calibration and analysis of soil carbon efflux estimates with closed chambers at Forsmark and Laxemar

    Energy Technology Data Exchange (ETDEWEB)

    Tagesson, Torbern (Dept. of Physical Geography and Ecosystem Analysis, Lund Univ., Lund (SE))

    2006-08-15

    The Forsmark and the Laxemar investigation areas are examined by the Swedish Nuclear Fuel and Waste Management Co. for a possible construction of a deep repository for nuclear waste. In the case of a future leakage of waste, the radioactive isotopes could end up in the ecosystems above the repository. The fate of the radionuclides and their possible radiological impacts are then highly determined by ecosystem carbon cycling. An important part of the carbon cycling is the soil carbon effluxes, and in the investigation areas soil carbon effluxes have been examined with the closed chamber technique. This paper is divided into two parts. Firstly, there were problems with the equipment measuring the soil carbon dioxide efflux, and the first part is a description of the problem, how it was corrected and its possible causes. The second part is a manual in how to analyse data and calculate annual estimates of soil carbon efflux. The field measurement by the EGM-4 is just an occasional estimate of the soil carbon efflux at a certain spot and at a certain point in time. To make an interpretation of the measurements, it is essential to analyse the data and to temporally extrapolate them. It is necessary to prepare the raw data for the analysis. The problems with the EGM-4 doing the measurements at the Forsmark and the Laxemar investigation area makes it necessary to correct the data taken up by this EGM-4. The data should also be separated into soil respiration and gross primary production (GPP). Soil carbon dioxide effluxes should be changed to soil carbon effluxes. Soil carbon effluxes are strongly controlled by abiotic factors; temperature is the main factor to influence soil respiration and photosynthetically active radiation (PAR) and air temperature are the main factors to influence GPP. Regression with soil respiration against temperature and with GPP against PAR or temperature can therefore be done. These equations can then be used on datasets with temperature and PAR

  14. Serum albumin acts as a shuttle to enhance cholesterol efflux from cells[S

    Science.gov (United States)

    Sankaranarayanan, Sandhya; de la Llera-Moya, Margarita; Drazul-Schrader, Denise; Phillips, Michael C.; Kellner-Weibel, Ginny; Rothblat, George H.

    2013-01-01

    An important mechanism contributing to cell cholesterol efflux is aqueous transfer in which cholesterol diffuses from cells into the aqueous phase and becomes incorporated into an acceptor particle. Some compounds can enhance diffusion by acting as shuttles transferring cholesterol to cholesterol acceptors, which act as cholesterol sinks. We have examined whether particles in serum can enhance cholesterol efflux by acting as shuttles. This task was accomplished by incubating radiolabeled J774 cells with increasing concentrations of lipoprotein-depleted sera (LPDS) or components present in serum as shuttles and a constant amount of LDL, small unilamellar vesicles, or red blood cells (RBC) as sinks. Synergistic efflux was measured as the difference in fractional efflux in excess of that predicted by the addition of the individual efflux values of sink and shuttle alone. Synergistic efflux was obtained when LPDS was incubated with cells and LDL. When different components of LPDS were used as shuttles, albumin produced synergistic efflux, while apoA-I did not. A synergistic effect was also obtained when RBC was used as the sink and albumin as shuttle. The previously observed negative association of albumin with coronary artery disease might be linked to reduced cholesterol shuttling that would occur when serum albumin levels are low. PMID:23288948

  15. Modulation of drug efflux by aloe materials: An In Vitro investigation across rat intestinal tissue

    Directory of Open Access Journals (Sweden)

    Beneke Carien

    2013-01-01

    Full Text Available Background: Clinically, significant herb-drug interactions have been previously documented and can be pharmacodynamic and/or pharmacokinetic in nature. Pharmacokinetic interactions have been attributed to induction or inhibition of either metabolic enzymes or efflux transporters. Objective: The effect of gel and whole leaf materials from 3 different aloe species namely Aloe ferox, Aloe marlothii, and Aloe vera as well as polysaccharides precipitated from the A. vera materials on the bi-directional transport of cimetidine across rat intestinal tissue was investigated. Materials and Methods: Cimetidine transport studies were performed across excised rat intestinal tissue mounted in Sweetana-Grass diffusion chambers in both the apical-to-basolateral and basolateral-to-apical directions. Results: While A. vera gel and whole leaf materials did not inhibit the efflux of cimetidine, the polysaccharides precipitated from them did show a reduction of cimetidine efflux. On the other hand, both A. ferox and A. marlothii gel and whole leaf materials exhibited an inhibition effect on cimetidine efflux. Conclusions: This study identified a modulation effect of efflux transporters by certain aloe materials. This may cause herb-drug pharmacokinetic interactions when drugs that are substrates for these efflux transporters are taken simultaneously with aloe materials. On the other hand, these aloe materials may be used for drug absorption enhancement for drugs with low bioavailability due to extensive efflux.

  16. Pump application and maintenance

    International Nuclear Information System (INIS)

    Nuclear maintenance programs are typically organized by overall application, function, cost impact, and failure histories. Each maintenance program is uniquely tailored for each plant's specific goals and objectives. Most maintenance programs include pump maintenance within an application and/or a function. NMAC provides guidance on maintenance, troubleshooting, and applications of Deep Draft Vertical Centrifugal Pumps, Main Coolant Pump Seals, Feedwater Pumps, and Charging Pumps. Each maintenance guide includes a technical discussion of the design and operating issues which influence pump and component performance, reliability, and availability. The guides also discuss comprehensive inspection and corresponding repair Advisory groups consisting of utility, manufacturer, and regulatory representatives oversee the development of the NMAC guides, and review by utility personnel further augments the development process

  17. Electrokinetic pumps and actuators

    International Nuclear Information System (INIS)

    Flow and ionic transport in porous media are central to electrokinetic pumping as well as to a host of other microfluidic devices. Electrokinetic pumping provides the ability to create high pressures (to over 10,000 psi) and high flow rates (over 1 mL/min) with a device having no moving parts and all liquid seals. The electrokinetic pump (EKP) is ideally suited for applications ranging from a high pressure integrated pump for chip-scale HPLC to a high flow rate integrated pump for forced liquid convection cooling of high-power electronics. Relations for flow rate and current fluxes in porous media are derived that provide a basis for analysis of complex microfluidic systems as well as for optimization of electrokinetic pumps

  18. Identification of efflux proteins using efficient radial basis function networks with position-specific scoring matrices and biochemical properties.

    Science.gov (United States)

    Ou, Yu-Yen; Chen, Shu-An; Chang, Yun-Min; Velmurugan, Devadasan; Fukui, Kazuhiko; Michael Gromiha, M

    2013-09-01

    Efflux proteins are membrane proteins, which are involved in the transportation of multidrugs. The annotation of efflux proteins in genomic sequences would aid to understand the function. Although the percentage of membrane proteins in genomes is estimated to be 25-30%, there is no information about the content of efflux proteins. For annotating such class of proteins it is necessary to develop a reliable method to identify efflux proteins from amino acid sequence information. In this work, we have developed a method based on radial basis function networks using position specific scoring matrices (PSSM) and amino acid properties. We noticed that the C-terminal domain of efflux proteins contain vital information for discrimination. Our method showed an accuracy of 78 and 92% in discriminating efflux proteins from transporters and membrane proteins, respectively using fivefold cross-validation. We utilized our method for annotating the genomes E. coli and P. aeruginosa and it predicted 8.7 and 9.2% of proteins as efflux proteins in these genomes, respectively. The predicted efflux proteins have been compared with available experimental data and we observed a very good agreement between them. Further, we developed a web server for classifying efflux proteins and it is freely available at http://rbf.bioinfo.tw/∼sachen/EFFLUXpredict/Efflux-RBF.php. We suggest that our method could be an effective tool for annotating efflux proteins in genomic sequences.

  19. The Insulin Pump

    OpenAIRE

    Toews, C. J.

    1985-01-01

    Subcutaneous continuous insulin infusion systems deliver insulin at a basal rate designed to keep blood glucose levels normal in the non-fed state. Additional insulin is delivered at meal time. Pumps can provide near optimal control of blood glucose concentrations in selected, highly motivated patients. The pump provides better diabetic control than once daily insulin injections, although several daily injections can provide comparable control. Optimal control with the pump causes some short-...

  20. Fakir fuel pump

    Science.gov (United States)

    1922-01-01

    In designing the Fakir fuel pump, the fundamental idea was to obtain a simple and reliable method of conveying the fuel from a low tank to the carburetor, with the avoidance of the faults of all former methods and the simultaneous warming of the fuel by means of the heat of compression generated. The principle of the Fakir fuel pump rests on the well-known principle of the diaphragm pump, which must be suitably adapted to the present purpose.

  1. Detection of pump degradation

    Energy Technology Data Exchange (ETDEWEB)

    Greene, R.H.; Casada, D.A.; Ayers, C.W. [and others

    1995-08-01

    This Phase II Nuclear Plant Aging Research study examines the methods of detecting pump degradation that are currently employed in domestic and overseas nuclear facilities. This report evaluates the criteria mandated by required pump testing at U.S. nuclear power plants and compares them to those features characteristic of state-of-the-art diagnostic programs and practices currently implemented by other major industries. Since the working condition of the pump driver is crucial to pump operability, a brief review of new applications of motor diagnostics is provided that highlights recent developments in this technology. The routine collection and analysis of spectral data is superior to all other technologies in its ability to accurately detect numerous types and causes of pump degradation. Existing ASME Code testing criteria do not require the evaluation of pump vibration spectra but instead overall vibration amplitude. The mechanical information discernible from vibration amplitude analysis is limited, and several cases of pump failure were not detected in their early stages by vibration monitoring. Since spectral analysis can provide a wealth of pertinent information concerning the mechanical condition of rotating machinery, its incorporation into ASME testing criteria could merit a relaxation in the monthly-to-quarterly testing schedules that seek to verify and assure pump operability. Pump drivers are not included in the current battery of testing. Operational problems thought to be caused by pump degradation were found to be the result of motor degradation. Recent advances in nonintrusive monitoring techniques have made motor diagnostics a viable technology for assessing motor operability. Motor current/power analysis can detect rotor bar degradation and ascertain ranges of hydraulically unstable operation for a particular pump and motor set. The concept of using motor current or power fluctuations as an indicator of pump hydraulic load stability is presented.

  2. Comparative effects of auxin and abscisic acid on growth, hydrogen ion efflux and gravitropism in primary roots of maize

    Science.gov (United States)

    Evans, M. L.; Mulkey, T. J.

    1984-01-01

    In order to test the idea that auxin action on root growth may be mediated by H(+) movement, the correlation of auxin action on growth and H(+) movement in roots was examined along with changes in H(+) efflux patterns associated with the asymmetric growth which occurs during gravitropism. The effects of indoleacetic acid (IAA) and abscisic acid (AbA) on growth, H(+) secretion, and gravitropism in roots were compared. Results show a close correlation existent between H(+) efflux and growth in maize roots. In intact roots there is strong H(+) efflux from the elongation zone. Growth-promoting concentrations of IAA stimulate H(+) efflux. During gravitropism the H(+) efflux from the elongation zone becomes asymmetric; the evidence indicates that auxin redistribution contributes to the development of acid efflux asymmetry. That AbA stimulates root growth is reflected in its ability to stimulate H(+) efflux from apical root segments.

  3. Champagne Heat Pump

    Science.gov (United States)

    Jones, Jack A.

    2004-01-01

    The term champagne heat pump denotes a developmental heat pump that exploits a cycle of absorption and desorption of carbon dioxide in an alcohol or other organic liquid. Whereas most heat pumps in common use in the United States are energized by mechanical compression, the champagne heat pump is energized by heating. The concept of heat pumps based on other absorption cycles energized by heat has been understood for years, but some of these heat pumps are outlawed in many areas because of the potential hazards posed by leakage of working fluids. For example, in the case of the water/ammonia cycle, there are potential hazards of toxicity and flammability. The organic-liquid/carbon dioxide absorption/desorption cycle of the champagne heat pump is similar to the water/ammonia cycle, but carbon dioxide is nontoxic and environmentally benign, and one can choose an alcohol or other organic liquid that is also relatively nontoxic and environmentally benign. Two candidate nonalcohol organic liquids are isobutyl acetate and amyl acetate. Although alcohols and many other organic liquids are flammable, they present little or no flammability hazard in the champagne heat pump because only the nonflammable carbon dioxide component of the refrigerant mixture is circulated to the evaporator and condenser heat exchangers, which are the only components of the heat pump in direct contact with air in habitable spaces.

  4. Detection of pump degradation

    Energy Technology Data Exchange (ETDEWEB)

    Casada, D. [Oak Ridge National Lab., TN (United States)

    1995-04-01

    There are a variety of stressors that can affect the operation of centrifugal pumps. Although these general stressors are active in essentially all centrifugal pumps, the stressor level and the extent of wear and degradation can vary greatly. Parameters that affect the extent of stressor activity are manifold. In order to assure the long-term operational readiness of a pump, it is important to both understand the nature and magnitude of the specific degradation mechanisms and to monitor the performance of the pump. The most commonly applied method of monitoring the condition of not only pumps, but rotating machinery in general, is vibration analysis. Periodic or continuous special vibration analysis is a cornerstone of most pump monitoring programs. In the nuclear industry, non-spectral vibration monitoring of safety-related pumps is performed in accordance with the ASME code. Pump head and flow rate are also monitored, per code requirements. Although vibration analysis has dominated the condition monitoring field for many years, there are other measures that have been historically used to help understand pump condition; advances in historically applied technologies and developing technologies offer improved monitoring capabilities. The capabilities of several technologies (including vibration analysis, dynamic pressure analysis, and motor power analysis) to detect the presence and magnitude of both stressors and resultant degradation are discussed.

  5. Optically pumped atoms

    CERN Document Server

    Happer, William; Walker, Thad

    2010-01-01

    Covering the most important knowledge on optical pumping of atoms, this ready reference is backed by numerous examples of modelling computation for optical pumped systems. The authors show for the first time that modern scientific computing software makes it practical to analyze the full, multilevel system of optically pumped atoms. To make the discussion less abstract, the authors have illustrated key points with sections of MATLAB codes. To make most effective use of contemporary mathematical software, it is especially useful to analyze optical pumping situations in the Liouville spa

  6. Soil carbon effluxes in ecosystems of Forsmark and Laxemar

    Energy Technology Data Exchange (ETDEWEB)

    Tagesson, Torbern (Dept. of Physical Geography and Ecosystem Analysis, Lund Univ. (Sweden))

    2007-12-15

    Soil carbon effluxes were estimated in a number of ecosystems in Laxemar and Forsmark investigations areas. It was done in a young Scots pine (Pinus sylvestris) stand, a wet deciduous stand, a poor fen and an agricultural field in the Laxemar investigation area in south-eastern Sweden (57 deg 5 min N, 16 deg 7 min E) and in a pasture, two Norway spruce (Picea abies) stands, a deciduous forest, a mire, a wet deciduous forest and a clear-cut in the Forsmark investigation area (60 deg 4 min N, 18 deg 2 min E). It was measured with the closed chamber technique in 2005 and 2006. Soil temperature at 10 cm depth, air temperature and photosynthetically active radiation (PAR) were also measured. Exponential regressions with soil respiration against air and soil temperature were used to estimate annual soil respiration. A hyperbolic curve with Gross Primary Production (GPP) against PAR was used for modelling GPP for the growing season in the poor fen and the agricultural area of Laxemar. The exponential regressions with soil respiration against air and soil temperature explained on average 33.6% and 44.0% of the variation, respectively. GPP of the ground vegetation were reducing soil carbon effluxes, in all stands but one of the spruce stands, the deciduous forest, the mire and the wet deciduous forest of Forsmark. The significant (all but spruce 2 in Forsmark) curves with GPP against PAR explained on average 22.7% of the variation in GPP. The cubic regressions with GPP against air temperature were only significant for the poor fen and the agricultural field in Laxemar and it explained on average 34.8% of the variation in GPP for these ecosystems. The exponential regressions with air and soil temperature against soil respiration could be used to temporally extrapolate the occasional field measurements. The hyperbolic curve with GPP against PAR could also be used for temporal extrapolation of GPP for the ecosystems without a tree layer, i.e. the poor fen and the agricultural

  7. Soil carbon effluxes in ecosystems of Forsmark and Laxemar

    International Nuclear Information System (INIS)

    Soil carbon effluxes were estimated in a number of ecosystems in Laxemar and Forsmark investigations areas. It was done in a young Scots pine (Pinus sylvestris) stand, a wet deciduous stand, a poor fen and an agricultural field in the Laxemar investigation area in south-eastern Sweden (57 deg 5 min N, 16 deg 7 min E) and in a pasture, two Norway spruce (Picea abies) stands, a deciduous forest, a mire, a wet deciduous forest and a clear-cut in the Forsmark investigation area (60 deg 4 min N, 18 deg 2 min E). It was measured with the closed chamber technique in 2005 and 2006. Soil temperature at 10 cm depth, air temperature and photosynthetically active radiation (PAR) were also measured. Exponential regressions with soil respiration against air and soil temperature were used to estimate annual soil respiration. A hyperbolic curve with Gross Primary Production (GPP) against PAR was used for modelling GPP for the growing season in the poor fen and the agricultural area of Laxemar. The exponential regressions with soil respiration against air and soil temperature explained on average 33.6% and 44.0% of the variation, respectively. GPP of the ground vegetation were reducing soil carbon effluxes, in all stands but one of the spruce stands, the deciduous forest, the mire and the wet deciduous forest of Forsmark. The significant (all but spruce 2 in Forsmark) curves with GPP against PAR explained on average 22.7% of the variation in GPP. The cubic regressions with GPP against air temperature were only significant for the poor fen and the agricultural field in Laxemar and it explained on average 34.8% of the variation in GPP for these ecosystems. The exponential regressions with air and soil temperature against soil respiration could be used to temporally extrapolate the occasional field measurements. The hyperbolic curve with GPP against PAR could also be used for temporal extrapolation of GPP for the ecosystems without a tree layer, i.e. the poor fen and the agricultural

  8. Liquid pump for astronaut cooling

    Science.gov (United States)

    Carson, M. A.

    1972-01-01

    The Apollo portable life support system water-recirculation pump used for astronaut cooling is described. The problems associated with an early centrifugal pump and how these problems were overcome by the use of a new diaphragm pump are discussed. Performance comparisons of the two pump designs are given. Developmental problems and flight results with the diaphragm pump are discussed.

  9. Leiurus quinquestriatus venom inhibits BRL 34915-induced 86Rb+ efflux from the rat portal vein

    International Nuclear Information System (INIS)

    The effect of the crude venom of the Israeli scorpion Leiurus quinquestriatus hebraeus on the 86Rb+ efflux stimulated by the K+ channel opener BRL 34915 in the rat portal vein was examined. Applied alone, the venom greatly increased the spontaneous mechanical activity of and the concomitant 86Rb+ efflux from the vessel. When the excitability of the vein was suppressed by the dihydropyridine calcium antagonist, PN 200-110, the 86Rb+ efflux stimulated by BRL 34915 could be shown to be inhibited by the venom. From the concentration dependence of this inhibition an IC50 value of 0.17 +/- 0.01 mg/ml was estimated. This venom is thus the most potent blocker of BRL 34915-evoked 86Rb+ efflux reported so far. 17 references, 2 figures

  10. Amyloid-β efflux from the CNS into the plasma

    Science.gov (United States)

    Roberts, Kaleigh Filisa; Elbert, Donald L.; Kasten, Tom P.; Patterson, Bruce W.; Sigurdson, Wendy C.; Connors, Rose E.; Ovod, Vitaliy; Munsell, Ling Y.; Mawuenyega, Kwasi G.; Miller-Thomas, Michelle M.; Moran, Christopher J.; Cross, Dewitte T.; Derdeyn, Colin P.; Bateman, Randall J.

    2015-01-01

    Objective The aim of this study was to measure the flux of amyloid-β (Aβ) across the human cerebral capillary bed in order to determine if transport into the blood is a significant mechanism of clearance for Aβ produced in the central nervous system (CNS). Methods Time-matched blood samples were simultaneously collected from a cerebral vein (including the sigmoid sinus, inferior petrosal sinus, and the internal jugular vein), femoral vein, and radial artery of patients undergoing Inferior Petrosal Sinus Sampling (IPSS). For each plasma sample, Aβ concentration was assessed by three assays and the venous to arterial Aβ concentration ratios were determined. Results Aβ concentration was increased by ~7.5% in venous blood leaving the CNS capillary bed compared to arterial blood, indicating efflux from the CNS into the peripheral blood (p < 0.0001). There was no difference in peripheral venous Aβ concentration compared to arterial blood concentration. Interpretation Our results are consistent with clearance of CNS-derived Aβ into the venous blood supply with no increase from a peripheral capillary bed. Modeling these results suggests that direct transport of Aβ across the blood-brain barrier accounts for ~25% of Aβ clearance, and reabsorption of cerebrospinal fluid Aβ accounts for ~25% of the total CNS Aβ clearance in humans. PMID:25205593

  11. Pump element for a tube pump

    DEFF Research Database (Denmark)

    2011-01-01

    relative to the rod element so as to allow for a fluid flow in the tube through the first valve member, along the rod element, and through the second valve member. The tube comprises an at least partly flexible tube portion between the valve members such that a repeated deformation of the flexible tube...... pump as mentioned above, thereby acting to generate a fluid flow through the tube upon repeated deformation of the tube between the two valve members. The pump element may comprise a connecting part for coupling to another tube and may comprise a sealing part establishing a fluid tight connection...

  12. The Association between Bile Salt Export Pump Single-Nucleotide Polymorphisms and Primary Biliary Cirrhosis Susceptibility and Ursodeoxycholic Acid Response

    OpenAIRE

    Rui-rui Chen; Yuan-jun Li; Xin-min Zhou; Lu Wang; Juan Xing; Shuang Han; Li-na Cui; Lin-hua Zheng; Kai-chun Wu; Yong-quan Shi; Zhe-yi Han; Ying Han; Dai-ming Fan

    2014-01-01

    Background. Primary biliary cirrhosis (PBC) is a chronic and progressive cholestasis liver disease. Bile salt export pump (BSEP) is the predominant bile salt efflux system of hepatocytes. BSEP gene has been attached great importance in the susceptibility of PBC and the response rate of ursodeoxycholic acid (UDCA) treatment of PBC patients. Methods. In this study, TaqMan assay was used to genotype four variants of BSEP, and the Barcelona criteria were used for evaluating the response rate of U...

  13. Bile Salt Export Pump is Dysregulated with Altered Farnesoid X Receptor Isoform Expression in Patients with Hepatocellular Carcinoma

    OpenAIRE

    Chen, Yuan; Song, Xiulong; Valanejad, Leila; Vasilenko, Alexander; More, Vijay; Qiu, Xi; Chen, Weikang; Lai, Yurong; Slitt, Angela; Stoner, Matthew; Yan, Bingfang; Deng, Ruitang

    2013-01-01

    As a canalicular bile acid effluxer, bile salt export pump (BSEP) plays a vital role in maintaining bile acid homeostasis. BSEP deficiency leads to severe cholestasis and hepatocellular carcinoma (HCC) in young children. Regardless of the etiology, chronic inflammation is the common pathological process for HCC development. Clinical studies showed that bile acid homeostasis is disrupted in HCC patients with elevated serum bile acid level as a proposed marker for HCC. However, the underlying m...

  14. Blood-Brain Barrier Active Efflux Transporters: ATP-Binding Cassette Gene Family

    OpenAIRE

    Löscher, Wolfgang; Potschka, Heidrun

    2005-01-01

    Summary: The blood-brain barrier (BBB) contributes to brain homeostasis by protecting the brain from potentially harmful endogenous and exogenous substances. BBB active drug efflux transporters of the ATP-binding cassette (ABC) gene family are increasingly recognized as important determinants of drug distribution to, and elimination from, the CNS. The ABC efflux transporter P-glycoprotein (Pgp) has been demonstrated as a key element of the BBB that can actively transport a huge variety of lip...

  15. Sensitivity of Chloride Efflux vs. Transepithelial Measurements in Mixed CF and Normal Airway Epithelial Cell Populations

    OpenAIRE

    Illek, Beate; Lei, Dachuan; Fischer, Horst; Gruenert, Dieter C.

    2011-01-01

    Background/Aims: While the Cl- efflux assays are relatively straightforward, their ability to assess the efficacy of phenotypic correction in cystic fibrosis (CF) tissue or cells may be limited. Accurate assessment of therapeutic efficacy, i.e., correlating wild type CF transmembrane conductance regulator (CFTR) levels with phenotypic correction in tissue or individual cells, requires a sensitive assay. Methods: Radioactive chloride (36Cl) efflux was compared to Ussing chamber analysis for me...

  16. A new tetracycline resistance determinant, Tet H, from Pasteurella multocida specifying active efflux of tetracycline.

    OpenAIRE

    Hansen, L M; McMurry, L M; Levy, S. B.; Hirsh, D C

    1993-01-01

    The tetracycline resistance determinant on plasmid pVM111 from an avian strain of Pasteurella multocida mediates tetracycline resistance by a regulated active efflux mechanism. DNA coding for the determinant did not hybridize at high stringency with DNA representing a group of common tetracycline resistance determinants. The DNA sequence, however; revealed a structural gene and a repressor gene which had significant (37 to 64%) sequence similarities with previously described classes of efflux...

  17. Role of outer membrane barrier in efflux-mediated tetracycline resistance of Escherichia coli.

    OpenAIRE

    Thanassi, D. G.; Suh, G S; Nikaido, H

    1995-01-01

    Accumulation of tetracycline in Escherichia coli was studied to determine its permeation pathway and to provide a basis for understanding efflux-mediated resistance. Passage of tetracycline across the outer membrane appeared to occur preferentially via the porin OmpF, with tetracycline in its magnesium-bound form. Rapid efflux of magnesium-chelated tetracycline from the periplasm was observed. In E. coli cells that do not contain exogenous tetracycline resistance genes, the steady-state level...

  18. Serum albumin acts as a shuttle to enhance cholesterol efflux from cells[S

    OpenAIRE

    Sankaranarayanan, Sandhya; de la Llera-Moya, Margarita; Drazul-Schrader, Denise; Phillips, Michael C.; Kellner-Weibel, Ginny; Rothblat, George H.

    2013-01-01

    An important mechanism contributing to cell cholesterol efflux is aqueous transfer in which cholesterol diffuses from cells into the aqueous phase and becomes incorporated into an acceptor particle. Some compounds can enhance diffusion by acting as shuttles transferring cholesterol to cholesterol acceptors, which act as cholesterol sinks. We have examined whether particles in serum can enhance cholesterol efflux by acting as shuttles. This task was accomplished by incubating radiolabeled J774...

  19. Amino acid efflux in response to chemotactic and osmotic signals in Bacillus subtilis.

    OpenAIRE

    Wong, L S; Johnson, M. S.; Sandberg, L. B.; Taylor, B L

    1995-01-01

    We observed a large efflux of nonvolatile radioactivity from Bacillus subtilis in response to the addition of 31 mM butyrate or the withdrawal of 0.1 M aspartate in a flow assay. The major nonvolatile components effluxed were methionine, proline, histidine, and lysine. In studies of the release of volatile radioactivity in chemotaxis by B. subtilis cells that had been labeled with [3H]methionine, the breakdown of methionine to methanethiol can contribute substantially to the volatile radioact...

  20. Environmental And Stand Variables Influencing Soil CO2 Efflux Across The Managed Range Of Loblolly Pine

    OpenAIRE

    Templeton, Benjamin Sean

    2009-01-01

    Managed loblolly pine forests comprise an important pool in the global carbon cycle. Understanding the influences upon inputs and outputs of this pool, including the effects of management activities, will allow landowners to understand how carbon can be sequestered in their stands. Specific to this study, we sought to create multivariate models of the output of carbon from the soil in the form of soil CO2 efflux (Rs) and a component of that total efflux, heterotrophic respiration index (Rh)...

  1. Efflux-mediated multidrug resistance in Bacillus subtilis: similarities and dissimilarities with the mammalian system.

    OpenAIRE

    Neyfakh, A A; Bidnenko, V E; L. B. CHEN

    1991-01-01

    Bacillus subtilis cells selected for their resistance to rhodamine 6G demonstrated a multidrug-resistance (MDR) phenotype resembling that of mammalian MDR cells. Like MDR in mammalian cells, MDR in bacteria was mediated by the efflux of the drugs from the cells. The bacterial multidrug efflux system transported similar drugs and was sensitive to similar inhibitors as the mammalian multidrug transporter, P-glycoprotein. The gene coding for the bacterial multidrug transporter, like the P-glycop...

  2. Magnetic heat pump design

    Science.gov (United States)

    Kirol, L. D.; Dacus, M. W.

    1988-03-01

    Heat pumps utilizing the magnetocaloric effect offer a potentially attractive alternative to conventional heat pumps and refrigerators. Many physical configurations of magnetic heat pumps are possible. Major classes include those requiring electrical energy input and those with mechanical energy input. Mechanical energy is used to move magnets, working material, or magnetic shielding. Each type of mechanical magnetic heat pump can be built in a rotary (recuperative) or reciprocal (regenerative) configuration. Machines with electrical energy input utilize modulation of the magnetic field to cause working material to execute the desired thermodynamic cycle, and can also be recuperative or regenerative. Recuperative rotary heat pumps in which working material is moved past stationary magnets is the preferred configuration. Regenerative devices suffer performance degradation from temperature change of regenerator material and mixing and conduction in the regenerator. Field modulated cycles are not practical due to ac losses in superconducting magnets. Development of methods for recuperator fluid pumping is the major challenge in design of rotary recuperative devices. Several pumping options are presented, and the design of a bench scale heat pump described.

  3. Water Treatment Technology - Pumps.

    Science.gov (United States)

    Ross-Harrington, Melinda; Kincaid, G. David

    One of twelve water treatment technology units, this student manual on pumps provides instructional materials for three competencies. (The twelve units are designed for a continuing education training course for public water supply operators.) The competencies focus on the following areas: types of pumps in plant and distribution systems, pump…

  4. The effect of N-acetylcysteine on chloride efflux from airway epithelial cells.

    Science.gov (United States)

    Varelogianni, Georgia; Oliynyk, Igor; Roomans, Godfried M; Johannesson, Marie

    2010-01-27

    Defective chloride transport in epithelial cells increases mucus viscosity and leads to recurrent infections with high oxidative stress in patients with CF (cystic fibrosis). NAC (N-acetylcysteine) is a well known mucolytic and antioxidant drug, and an indirect precursor of glutathione. Since GSNO (S-nitrosoglutathione) previously has been shown to be able to promote Cl- efflux from CF airway epithelial cells, it was investigated whether NAC also could stimulate Cl- efflux from CF and non-CF epithelial cells and through which mechanisms. CFBE (CF bronchial epithelial cells) and normal bronchial epithelial cells (16HBE) were treated with 1 mM, 5 mM, 10 mM or 15 mM NAC for 4 h at 37 degrees C. The effect of NAC on Cl- transport was measured by Cl- efflux measurements and by X-ray microanalysis. Cl- efflux from CFBE cells was stimulated by NAC in a dose-dependent manner, with 10 mM NAC causing a significant increase in Cl- efflux with nearly 80% in CFBE cells. The intracellular Cl- concentration in CFBE cells was significantly decreased up to 60% after 4 h treatment with 10 mM NAC. Moreover immunocytochemistry and Western blot experiments revealed expression of CFTR channel on CFBE cells after treatment with 10 mM NAC. The stimulation of Cl- efflux by NAC in CF airway epithelial cells may improve hydration of the mucus and thereby be beneficial for CF patients.

  5. The role of the rice aquaporin Lsi1 in arsenite efflux from roots.

    Science.gov (United States)

    Zhao, Fang-Jie; Ago, Yukiko; Mitani, Namiki; Li, Ren-Ying; Su, Yu-Hong; Yamaji, Naoki; McGrath, Steve P; Ma, Jian Feng

    2010-04-01

    *When supplied with arsenate (As(V)), plant roots extrude a substantial amount of arsenite (As(III)) to the external medium through as yet unidentified pathways. The rice (Oryza sativa) silicon transporter Lsi1 (OsNIP2;1, an aquaporin channel) is the major entry route of arsenite into rice roots. Whether Lsi1 also mediates arsenite efflux was investigated. *Expression of Lsi1 in Xenopus laevis oocytes enhanced arsenite efflux, indicating that Lsi1 facilitates arsenite transport bidirectionally. *Arsenite was the predominant arsenic species in arsenate-exposed rice plants. During 24-h exposure to 5 mum arsenate, rice roots extruded arsenite to the external medium rapidly, accounting for 60-90% of the arsenate uptake. A rice mutant defective in Lsi1 (lsi1) extruded significantly less arsenite than the wild-type rice and, as a result, accumulated more arsenite in the roots. By contrast, Lsi2 mutation had little effect on arsenite efflux to the external medium. *We conclude that Lsi1 plays a role in arsenite efflux in rice roots exposed to arsenate. However, this pathway accounts for only 15-20% of the total efflux, suggesting the existence of other efflux transporters.

  6. Uptake, efflux, and mass transfer coefficient of fluorescent PAMAM dendrimers into pancreatic cancer cells.

    Science.gov (United States)

    Opitz, Armin W; Czymmek, Kirk J; Wickstrom, Eric; Wagner, Norman J

    2013-02-01

    Targeted delivery of imaging agents to cells can be optimized with the understanding of uptake and efflux rates. Cellular uptake of macromolecules is studied frequently with fluorescent probes. We hypothesized that the internalization and efflux of fluorescently labeled macromolecules into and out of mammalian cells could be quantified by confocal microscopy to determine the rate of uptake and efflux, from which the mass transfer coefficient is calculated. The cellular influx and efflux of a third generation poly(amido amine) (PAMAM) dendrimer labeled with an Alexa Fluor 555 dye was measured in Capan-1 pancreatic cancer cells using confocal fluorescence microscopy. The Capan-1 cells were also labeled with 5-chloromethylfluorescein diacetate (CMFDA) green cell tracker dye to delineate cellular boundaries. A dilution curve of the fluorescently labeled PAMAM dendrimer enabled quantification of the concentration of dendrimer in the cell. A simple mass transfer model described the uptake and efflux behavior of the PAMAM dendrimer. The effective mass transfer coefficient was found to be 0.054±0.043μm/min, which corresponds to a rate constant of 0.035±0.023min(-1) for uptake of the PAMAM dendrimer into the Capan-1 cells. The effective mass transfer coefficient was shown to predict the efflux behavior of the PAMAM dendrimer from the cell if the fraction of labeled dendrimer undergoing non-specific binding is accounted for. This work introduces a novel method to quantify the mass transfer behavior of fluorescently labeled macromolecules into mammalian cells.

  7. The effect of N-acetylcysteine on chloride efflux from airway epithelial cells.

    Science.gov (United States)

    Varelogianni, Georgia; Oliynyk, Igor; Roomans, Godfried M; Johannesson, Marie

    2010-03-01

    Defective chloride transport in epithelial cells increases mucus viscosity and leads to recurrent infections with high oxidative stress in patients with CF (cystic fibrosis). NAC (N-acetylcysteine) is a well known mucolytic and antioxidant drug, and an indirect precursor of glutathione. Since GSNO (S-nitrosoglutathione) previously has been shown to be able to promote Cl- efflux from CF airway epithelial cells, it was investigated whether NAC also could stimulate Cl- efflux from CF and non-CF epithelial cells and through which mechanisms. CFBE (CF bronchial epithelial cells) and normal bronchial epithelial cells (16HBE) were treated with 1 mM, 5 mM, 10 mM or 15 mM NAC for 4 h at 37 degrees C. The effect of NAC on Cl- transport was measured by Cl- efflux measurements and by X-ray microanalysis. Cl- efflux from CFBE cells was stimulated by NAC in a dose-dependent manner, with 10 mM NAC causing a significant increase in Cl- efflux with nearly 80% in CFBE cells. The intracellular Cl- concentration in CFBE cells was significantly decreased up to 60% after 4 h treatment with 10 mM NAC. Moreover immunocytochemistry and Western blot experiments revealed expression of CFTR channel on CFBE cells after treatment with 10 mM NAC. The stimulation of Cl- efflux by NAC in CF airway epithelial cells may improve hydration of the mucus and thereby be beneficial for CF patients. PMID:19947928

  8. Normetex Pump Alternatives Study

    Energy Technology Data Exchange (ETDEWEB)

    Clark, Elliot A.

    2013-04-25

    A mainstay pump for tritium systems, the Normetex scroll pump, is currently unavailable because the Normetex company went out of business. This pump was an all-metal scroll pump that served tritium processing facilities very well. Current tritium system operators are evaluating replacement pumps for the Normetex pump and for general used in tritium service. An all-metal equivalent alternative to the Normetex pump has not yet been identified. 1. The ideal replacement tritium pump would be hermetically sealed and contain no polymer components or oils. Polymers and oils degrade over time when they contact ionizing radiation. 2. Halogenated polymers (containing fluorine, chlorine, or both) and oils are commonly found in pumps. These materials have many properties that surpass those of hydrocarbon-based polymers and oils, including thermal stability (higher operating temperature) and better chemical resistance. Unfortunately, they are less resistant to degradation from ionizing radiation than hydrocarbon-based materials (in general). 3. Polymers and oils can form gaseous, condensable (HF, TF), liquid, and solid species when exposed to ionizing radiation. For example, halogenated polymers form HF and HCl, which are extremely corrosive upon reaction with water. If a pump containing polymers or oils must be used in a tritium system, the system must be designed to be able to process the unwanted by-products. Design features to mitigate degradation products include filters and chemical or physical traps (eg. cold traps, oil traps). 4. Polymer components can work in tritium systems, but must be replaced regularly. Polymer components performance should be monitored or be regularly tested, and regular replacement of components should be viewed as an expected normal event. A radioactive waste stream must be established to dispose of used polymer components and oil with an approved disposal plan developed based on the facility location and its regulators. Polymers have varying

  9. Polyamines cause plasma membrane depolarization, activate Ca2+-, and modulate H+-ATPase pump activity in pea roots.

    Science.gov (United States)

    Pottosin, Igor; Velarde-Buendía, Ana María; Bose, Jayakumar; Fuglsang, Anja T; Shabala, Sergey

    2014-06-01

    Polyamines regulate a variety of cation and K(+) channels, but their potential effects on cation-transporting ATPases are underexplored. In this work, noninvasive microelectrode ion flux estimation and conventional microelectrode techniques were applied to study the effects of polyamines on Ca(2+) and H(+) transport and membrane potential in pea roots. Externally applied spermine or putrescine (1mM) equally activated eosin yellow (EY)-sensitive Ca(2+) pumping across the root epidermis and caused net H(+) influx or efflux. Proton influx induced by spermine was suppressed by EY, supporting the mechanism in which Ca(2+) pump imports 2 H(+) per each exported Ca(2+). Suppression of the Ca(2+) pump by EY diminished putrescine-induced net H(+) efflux instead of increasing it. Thus, activities of Ca(2+) and H(+) pumps were coupled, likely due to the H(+)-pump inhibition by intracellular Ca(2+). Additionally, spermine but not putrescine caused a direct inhibition of H(+) pumping in isolated plasma membrane vesicles. Spermine, spermidine, and putrescine (1mM) induced membrane depolarization by 70, 50, and 35 mV, respectively. Spermine-induced depolarization was abolished by cation transport blocker Gd(3+), was insensitive to anion channels' blocker niflumate, and was dependent on external Ca(2+). Further analysis showed that uptake of polyamines but not polyamine-induced cationic (K(+)+Ca(2+)+H(+)) fluxes were a main cause of membrane depolarization. Polyamine increase is a common component of plant stress responses. Activation of Ca(2+) efflux by polyamines and contrasting effects of polyamines on net H(+) fluxes and membrane potential can contribute to Ca(2+) signalling and modulate a variety of transport processes across the plasma membrane under stress. PMID:24723394

  10. Spatial variation in spring CO2 efflux along the trans-Alaska pipeline, Alaska: Contribution of spring carbon

    Science.gov (United States)

    Kim, Y.

    2013-12-01

    Spring soil CO2 efflux-measurement was conducted in representative sites along the trans-Alaska pipeline during 2010 to 2012 for the understanding of spatial variation in spring CO2 efflux response to change in snow-melting timing. The sites is 3 tundra sites (coastal tundra, upland tundra, upland tundra, and sub-alpine tundra), 2 white spruce sites in tundra-boreal forest ecotone, and Gold Creek, and 3 black spruce sites in Coldfoot, upper and lower reaches of the Yukon River. Soil CO2 efflux-measurement, which is a portable manual chamber CO2 efflux system, was conducted during snow-covered and snow-melting periods, minimizing artificial effects. CO2 effluxes in snow-covered and exposed soils showed a significantly difference, suggesting that spring CO2 efflux is much higher than that in snow-covered soil. The efflux was measured at 4-direction due to the difference of exposed extent, implying the magnitude of CO2 production. Average diameter in breast height (DBH: 85 × 11 cm) of white spruce is much thicker than black spruce (DBH: 33 × 5 cm), suggesting the difference of heat uptake and emission capacity between both forests. Soil temperature at 5 cm below the surface is one of significant keys in determining soil CO2 efflux. The magnitude of spring CO2 efflux showed white spruce, black spruce, and tundra in turn, suggesting that spring CO2 efflux (> 8 gC/m2/day) of corresponds to summer soil CO2 efflux. Then, spring soil CO2 efflux should be not overlooked the contribution of annual soil carbon efflux in spite of difficulties in snow-disappeared timing and springtime.

  11. Apparatus for Pumping a Fluid

    Science.gov (United States)

    Boeyen, Robert Van; Reeh, Jonathan

    2013-01-01

    A fluid pump has been developed for mechanically pumped fluid loops for spacecraft thermal control. Lynntech's technology utilizes a proprietary electrochemically driven pumping mechanism. Conventional rotodynamic and displacement pumps typically do not meet the stringent power and operational reliability requirements of space applications. Lynntech's developmental pump is a highly efficient solid-state pump with essentially no rotating or moving components (apart from metal bellows).

  12. 细菌多重耐药泵的研究进展%Multidrug Efflux Systems Involved in Resistance to Antibacterial Drugs

    Institute of Scientific and Technical Information of China (English)

    王春梅; 何启盖; 操继跃

    2011-01-01

    细菌主要通过药物代谢酶将药物失活、靶向改造药物作用部位、降低细胞膜通透性和通过耐药泵主动将胞内药物泵出胞外4种方式抵抗抗生素和其他药物的毒性作用,其中细菌通过耐药泵将药物排出胞外是细菌的主要耐药机制之一,尤其是多重耐药泵,可以外排结构迥异的多种药物或对细菌有毒的代谢产物.由于细胞膜结构的不同,革兰氏阴性菌和革兰氏阳性菌所具有的耐药泵种类和结构也有所不同.革兰氏阴性菌中,目前发现的细菌耐药泵种类主要包括ATP结合盒超家族(ATP-binding cassette family,ABC)、耐药节结化细胞分化(resistance nodulation division,RND)家族、主要易化子超家族(major facilitator superfamily,MFS)、小多重耐药(small multidrug resistance,SMR)家族和多药及毒性化合物外排家族(multidrug and toxic-compound extrusion family,MATE).革兰氏阳性菌中,目前发现的细菌耐药泵种类主要包括ABC、MFS、SMR和MATE家族.近年来,诸多学者开展了细菌耐药泵的结构及其耐药机制的研究,并且已有新药研发团队以绿脓杆菌耐药泵MexAB-OprM的结构为作用靶点开发新的抗菌药物做了大量的探索工作,天然化合物和常规药物中也存在能够抑制耐药泵活性的化合物.作者主要针对耐药泵的分类、不同细菌中耐药泵的特征及耐药泵作为新药作用靶点的潜在应用价值进行综述.%Bacteria have developed various ways to resist the toxic effects of antibiotics and other drugs, such as produce enzymes that inactivate antibiotics, target alteration by mutation or enzymatic modification, inhibit drug entry into the cell and active efflux of drugs. Actively exporting an antibiotic from the bacterial cell by the efflux pump is essential to ensure significant levels of drug resistance. The multidrug efflux pumps that affect such efflux typically export several unrelated substances, including antibiotics

  13. Pumping machinery theory and practice

    CERN Document Server

    Badr, Hassan M

    2014-01-01

    Pumping Machinery Theory and Practice comprehensively covers the theoretical foundation and applications of pumping machinery. Key features: Covers characteristics of centrifugal pumps, axial flow pumps and displacement pumpsConsiders pumping machinery performance and operational-type problemsCovers advanced topics in pumping machinery including multiphase flow principles, and two and three-phase flow pumping systemsCovers different methods of flow rate control and relevance to machine efficiency and energy consumptionCovers different methods of flow rate control and relevance to machine effi

  14. Efflux of RNA from resealed nuclear envelope ghosts.

    Science.gov (United States)

    Prochnow, D; Thomson, M; Schröder, H C; Müller, W E; Agutter, P S

    1994-08-01

    mRNA translocation across the nuclear envelope and the appropriate signal-receptor interactions have been studied using resealed rat liver nuclear envelope ghosts (RNEG). We compared export kinetics of nonadenylated (tRNAs, histone-2 poly(A)- mRNA), and adenylated RNAs (poly(A)+ tRNAs, synthetic histone-2 poly(A) +mRNA, albumin mRNA, beta-globin poly(A) +mRNA and a total poly(A) + mRNA extract from rat liver cells). ATP-dependent export of mRNAs and of total poly(A)+ RNA was prevented by inhibitors of a nuclear envelope NTPase. All adenylated RNA species competed with each other for export, but nonadenylated RNAs did not. This indicates the existence of different translocation mechanisms for different RNA species with their appropriate nuclear envelope associated RNA receptors involved in export. The attachment of a poly(A)250 sequence at the 3'-end of tRNA or histone messenger masks the intrinsic RNA export signal of nonadenylated RNAs and results in efflux comparable to that of beta-globin poly(A)+ mRNA. The attachment on oligo(A)5 does not have any comparable effect of nonadenylated RNA translocation. Export of all polyadenylated RNAs from RNEGs is blocked by a monoclonal antibody, which is directed against an intranuclear envelope poly(A) binding protein. The results suggest that the pore complexes do not select RNAs for export to the cytoplasm and are therefore not responsible for nuclear restriction of mRNA precursors.

  15. Crystallization and preliminary X-ray diffraction analysis of the multidrug efflux transporter NorM from Neisseria gonorrhoeae

    Energy Technology Data Exchange (ETDEWEB)

    Su, C.C.; Long, F.; McDermott, G.; Shafer, W.M.; Yu, E.W. (Emory-MED); (UCSF); (Iowa State)

    2008-06-03

    The crystallization and preliminary X-ray data analysis of the NorM multidrug efflux pump produced by Neisseria gonorrhoeae are reported. NorM is a cytoplasmic membrane protein that consists of 459 amino-acid residues. It is a member of the recently classified multidrug and toxic compound extrusion (MATE) family of transporters and recognizes a number of cationic toxic compounds such as ethidium bromide, acriflavin, 2-N-methylellipticinium and ciprofloxacin. Recombinant NorM protein was expressed in Escherichia coli and purified by metal-affinity and gel-filtration chromatography. The protein was crystallized using hanging-drop vapor diffusion. X-ray diffraction data were collected from cryocooled crystals at a synchrotron light source. The best crystal diffracted anisotropically to 3.8 {angstrom} and diffraction data were complete to 6.5 {angstrom} resolution. The space group was determined to be C2, with unit-cell parameters a = 81.5, b = 164.4, c = 111.5 {angstrom}.

  16. The ABC transporter ATR1 is necessary for efflux of the toxin cercosporin in the fungus Cercospora nicotianae.

    Science.gov (United States)

    Amnuaykanjanasin, Alongkorn; Daub, Margaret E

    2009-02-01

    The Cercospora nicotianae mutant deficient for the CRG1 transcription factor has marked reductions in both resistance and biosynthesis of the toxin cercosporin. We cloned and sequenced full-length copies of two genes, ATR1 and CnCFP, previously identified from a subtractive library between the wild type (WT) and a crg1 mutant. ATR1 is an ABC transporter gene and has an open reading frame (ORF) of 4368bp with one intron. CnCFP encodes a MFS transporter with homology to Cercospora kikuchii CFP, previously implicated in cercosporin export, and has an ORF of 1975bp with three introns. Disruption of ATR1 indicated atr1-null mutants had dramatic reductions in cercosporin production (25% and 20% of WT levels) in solid and liquid cultures, respectively. The ATR1 disruptants also showed moderately higher sensitivity to cercosporin. Constitutive expression of ATR1 in the crg1 mutant restored cercosporin biosynthesis and moderately increased resistance. In contrast, CnCFP overexpression in the mutant did not restore toxin production, however, it moderately enhanced toxin resistance. The results together indicate ATR1 acts as a cercosporin efflux pump in this fungus and plays a partial role in resistance.

  17. Vertical profile of branch CO2 efflux in a Norway spruce tree: a case study

    Science.gov (United States)

    Acosta, M.; Pavelka, M.

    2012-04-01

    Despite woody-tissue CO2 effluxes having been recognized as an important component of forest carbon budget due to the fraction of assimilates used and the dramatic increase in woody with stand development, there is limited research to determine the CO2 efflux vertical variability of woody-tissue components. For a better understanding and quantification of branch woody-tissue CO2 efflux in forest ecosystems, it is necessary to identify the environmental factors influencing it and the role of the branch distribution within the canopy. The proper assessment of this forest component will improve the knowledge of the ratio between ecosystem respiration and gross primary production at forest ecosystem. In order to achieve this goal, branch CO2 efflux of Norway spruce tree was measured in ten branches at five different whorls during the growing season 2004 (from June till October) in campaigns of 3-4 times per month at the Beskydy Mts., the Czech Republic, using a portable infrared gas analyzer operating as a closed system. Branch woody tissue temperature was measured continuously in ten minutes intervals for each sample position during the whole experiment period. On the basis of relation between CO2 efflux rate and woody tissue temperature a value of Q10 and normalized CO2 efflux rate (E10 - CO2 efflux rate at 10° C) were calculated for each sampled position. Estimated Q10 values ranged from 2.12 to 2.89 and E10 ranged from 0.41 to 1.19 ?molCO2m-2 s-1. Differences in branch CO2 efflux were found between orientations; East side branches presented higher efflux rate than west side branches. The highest branch CO2 efflux rate values were measured in August and the lowest in October, which were connected with woody tissue temperature and ontogenetic processes during these periods. Branch CO2 efflux was significantly and positively correlated with branch position within canopy and woody tissue temperature. Branches from the upper whorls showed higher respiration activity

  18. Correlations between proton-efflux patterns and growth patterns during geotropism and phototropism in maize and sunflower.

    Science.gov (United States)

    Mulkey, T J; Kuzmanoff, K M; Evans, M L

    1981-07-01

    By placing seedlings of sunflower (Helianthus annuus L.) or maize (Zea mays L.) on agar plates containing a pH indicator dye it is possible to observe surface pH patterns along the growing seedling by observing color changes of the indicator dye. Using this method we find that in geotropically stimulated sunflower hypocotyls or maize coleoptiles there is enhanced proton efflux on the lower surface of the organ prior to the initiation of curvature. As curvature develops the pattern of differential acid efflux becomes more intense. A similar phenomenon is observed when these organs are exposed to unilateral illumination, i.e. enhanced acid efflux occurs on the dark side of the organ prior to the initiation of phototropic curvature and the pattern of differential acid efflux intensifies as phototropic curvature develops. These observations indicate that differential acid efflux occurs in response to tropistic stimuli and that the acid efflux pattern may mediate the development of tropistic curvatures.

  19. Variability in soil CO2 efflux across distinct urban land cover types

    Science.gov (United States)

    Weissert, Lena F.; Salmond, Jennifer A.; Schwendenmann, Luitgard

    2015-04-01

    As a main source of greenhouse gases urban areas play an important role in the global carbon cycle. To assess the potential role of urban vegetation in mitigating carbon emissions we need information on the magnitude of biogenic CO2 emissions and its driving factors. We examined how urban land use types (urban forest, parklands, sportsfields) vary in their soil CO2 efflux. We measured soil CO2 efflux and its isotopic signature, soil temperature and soil moisture over a complete growing season in Auckland, New Zealand. Soil physical and chemical properties and vegetation characteristics were also measured. Mean soil CO2 efflux ranged from 4.15 to 12 μmol m-2 s-1. We did not find significant differences in soil CO2 efflux among land cover types due to high spatial variability in soil CO2 efflux among plots. Soil (soil carbon and nitrogen density, texture, soil carbon:nitrogen ratio) and vegetation characteristics (basal area, litter carbon density, grass biomass) were not significantly correlated with soil CO2 efflux. We found a distinct seasonal pattern with significantly higher soil CO2 efflux in autumn (Apr/May) and spring (Oct). In urban forests and sportsfields over 80% of the temporal variation was explained by soil temperature and soil water content. The δ13C signature of CO2 respired from parklands and sportsfields (-20 permil - -25 permil) were more positive compared to forest plots (-29 permil) indicating that parkland and sportsfields had a considerable proportion of C4 grasses. Despite the large intra-urban variability, our results compare to values reported from other, often climatically different cities, supporting the hypothesis of homogenization across urban areas as a result of human management practices.

  20. Sediment properties and CO2 efflux from intact and cleared temperate mangrove forests

    Science.gov (United States)

    Bulmer, R. H.; Lundquist, C. J.; Schwendenmann, L.

    2015-10-01

    Temperate mangrove forests in New Zealand have increased in area over recent decades. Expansion of temperate mangroves in New Zealand is associated with perceived loss of other estuarine habitats, and decreased recreational and amenity values, resulting in clearing of mangrove forests. In the tropics, changes in sediment characteristics and carbon efflux have been reported following mangrove clearance. This is the first study in temperate mangrove (Avicennia marina) forests investigating the impact of clearing on sediment CO2 efflux and associated biotic and abiotic factors. Sediment CO2 efflux rates from intact (168.5 ± 45.8 mmol m-2 d-1) and cleared (133.9 ± 37.2 mmol m-2 d-1) mangrove forests in New Zealand are comparable to rates measured in tropical mangrove forests. We did not find a significant difference in sediment CO2 efflux rates between intact and cleared temperate mangrove forests. Pre-shading the sediment for more than 30 min prior to dark chamber measurements was found to have no significant effect on sediment CO2 efflux. This suggests that the continuation of photosynthetic CO2 uptake by biofilm communities was not occurring after placement of dark chambers. Rather, above-ground mangrove biomass, sediment temperature and chlorophyll a concentration were the main factors explaining the variability in sediment CO2 efflux in intact mangrove forests. The main factors influencing sediment CO2 efflux in cleared mangrove forest sites were sediment organic carbon concentration, nitrogen concentration and sediment grain size. Our results show that greater consideration should be given regarding the rate of carbon released from mangrove forest following clearance and the relative contribution to global carbon emissions.

  1. Arctigenin promotes cholesterol efflux from THP-1 macrophages through PPAR-γ/LXR-α signaling pathway

    International Nuclear Information System (INIS)

    Highlights: •Arctigenin enhanced cholesterol efflux in oxLDL-loaded THP-1 macrophages. •The expression of ABCA1, ABCG1 and apoE was upregulated in arctigenin-treated cells. •Arctigenin promoted the expression of PPAR-γ and LXR-α. •Inhibition of PPAR-γ or LXR-α reversed arctigenin-mediated biological effects. •Arctigenin promotes cholesterol efflux via activation of PPAR-γ/LXR-α/ABCA1 pathway. -- Abstract: Cholesterol efflux from macrophages is a critical mechanism to prevent the development of atherosclerosis. Here, we sought to investigate the effects of arctigenin, a bioactive component of Arctium lappa, on the cholesterol efflux in oxidized low-density lipoprotein (oxLDL)-loaded THP-1 macrophages. Our data showed that arctigenin significantly accelerated apolipoprotein A-I- and high-density lipoprotein-induced cholesterol efflux in both dose- and time-dependent manners. Moreover, arctigenin treatment enhanced the expression of ATP binding cassette transporter A1 (ABCA1), ABCG1, and apoE, all of which are key molecules in the initial step of cholesterol efflux, at both mRNA and protein levels. Arctigenin also caused a concentration-dependent elevation in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and liver X receptor-alpha (LXR-α). The arctigenin-mediated induction of ABCA1, ABCG1, and apoE was abolished by specific inhibition of PPAR-γ or LXR-α using small interfering RNA technology. Our results collectively indicate that arctigenin promotes cholesterol efflux in oxLDL-loaded THP-1 macrophages through upregulation of ABCA1, ABCG1 and apoE, which is dependent on the enhanced expression of PPAR-γ and LXR-α

  2. Arctigenin promotes cholesterol efflux from THP-1 macrophages through PPAR-γ/LXR-α signaling pathway

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xiaolin [Department of Cardiothoracic Surgery, Huashan Hospital, Fudan University, Shanghai 200032 (China); Li, Qian [Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai (China); Pang, Liewen; Huang, Guoqian; Huang, Jiechun; Shi, Meng; Sun, Xiaotian [Department of Cardiothoracic Surgery, Huashan Hospital, Fudan University, Shanghai 200032 (China); Wang, Yiqing, E-mail: yiqingwangbiopaper@163.com [Department of Cardiothoracic Surgery, Huashan Hospital, Fudan University, Shanghai 200032 (China)

    2013-11-15

    Highlights: •Arctigenin enhanced cholesterol efflux in oxLDL-loaded THP-1 macrophages. •The expression of ABCA1, ABCG1 and apoE was upregulated in arctigenin-treated cells. •Arctigenin promoted the expression of PPAR-γ and LXR-α. •Inhibition of PPAR-γ or LXR-α reversed arctigenin-mediated biological effects. •Arctigenin promotes cholesterol efflux via activation of PPAR-γ/LXR-α/ABCA1 pathway. -- Abstract: Cholesterol efflux from macrophages is a critical mechanism to prevent the development of atherosclerosis. Here, we sought to investigate the effects of arctigenin, a bioactive component of Arctium lappa, on the cholesterol efflux in oxidized low-density lipoprotein (oxLDL)-loaded THP-1 macrophages. Our data showed that arctigenin significantly accelerated apolipoprotein A-I- and high-density lipoprotein-induced cholesterol efflux in both dose- and time-dependent manners. Moreover, arctigenin treatment enhanced the expression of ATP binding cassette transporter A1 (ABCA1), ABCG1, and apoE, all of which are key molecules in the initial step of cholesterol efflux, at both mRNA and protein levels. Arctigenin also caused a concentration-dependent elevation in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and liver X receptor-alpha (LXR-α). The arctigenin-mediated induction of ABCA1, ABCG1, and apoE was abolished by specific inhibition of PPAR-γ or LXR-α using small interfering RNA technology. Our results collectively indicate that arctigenin promotes cholesterol efflux in oxLDL-loaded THP-1 macrophages through upregulation of ABCA1, ABCG1 and apoE, which is dependent on the enhanced expression of PPAR-γ and LXR-α.

  3. 9-cis β-Carotene Increased Cholesterol Efflux to HDL in Macrophages

    Directory of Open Access Journals (Sweden)

    Sapir Bechor

    2016-07-01

    Full Text Available Cholesterol efflux from macrophages is a key process in reverse cholesterol transport and, therefore, might inhibit atherogenesis. 9-cis-β-carotene (9-cis-βc is a precursor for 9-cis-retinoic-acid (9-cis-RA, which regulates macrophage cholesterol efflux. Our objective was to assess whether 9-cis-βc increases macrophage cholesterol efflux and induces the expression of cholesterol transporters. Enrichment of a mouse diet with βc from the alga Dunaliella led to βc accumulation in peritoneal macrophages. 9-cis-βc increased the mRNA levels of CYP26B1, an enzyme that regulates RA cellular levels, indicating the formation of RA from βc in RAW264.7 macrophages. Furthermore, 9-cis-βc, as well as all-trans-βc, significantly increased cholesterol efflux to high-density lipoprotein (HDL by 50% in RAW264.7 macrophages. Likewise, food fortification with 9-cis-βc augmented cholesterol efflux from macrophages ex vivo. 9-cis-βc increased both the mRNA and protein levels of ABCA1 and apolipoprotein E (APOE and the mRNA level of ABCG1. Our study shows, for the first time, that 9-cis-βc from the diet accumulates in peritoneal macrophages and increases cholesterol efflux to HDL. These effects might be ascribed to transcriptional induction of ABCA1, ABCG1, and APOE. These results highlight the beneficial effect of βc in inhibition of atherosclerosis by improving cholesterol efflux from macrophages.

  4. 9-cis β-Carotene Increased Cholesterol Efflux to HDL in Macrophages

    Science.gov (United States)

    Bechor, Sapir; Zolberg Relevy, Noa; Harari, Ayelet; Almog, Tal; Kamari, Yehuda; Ben-Amotz, Ami; Harats, Dror; Shaish, Aviv

    2016-01-01

    Cholesterol efflux from macrophages is a key process in reverse cholesterol transport and, therefore, might inhibit atherogenesis. 9-cis-β-carotene (9-cis-βc) is a precursor for 9-cis-retinoic-acid (9-cis-RA), which regulates macrophage cholesterol efflux. Our objective was to assess whether 9-cis-βc increases macrophage cholesterol efflux and induces the expression of cholesterol transporters. Enrichment of a mouse diet with βc from the alga Dunaliella led to βc accumulation in peritoneal macrophages. 9-cis-βc increased the mRNA levels of CYP26B1, an enzyme that regulates RA cellular levels, indicating the formation of RA from βc in RAW264.7 macrophages. Furthermore, 9-cis-βc, as well as all-trans-βc, significantly increased cholesterol efflux to high-density lipoprotein (HDL) by 50% in RAW264.7 macrophages. Likewise, food fortification with 9-cis-βc augmented cholesterol efflux from macrophages ex vivo. 9-cis-βc increased both the mRNA and protein levels of ABCA1 and apolipoprotein E (APOE) and the mRNA level of ABCG1. Our study shows, for the first time, that 9-cis-βc from the diet accumulates in peritoneal macrophages and increases cholesterol efflux to HDL. These effects might be ascribed to transcriptional induction of ABCA1, ABCG1, and APOE. These results highlight the beneficial effect of βc in inhibition of atherosclerosis by improving cholesterol efflux from macrophages. PMID:27447665

  5. Soil Carbon Dioxide Efflux Across Four Age Classes Of Plantation Loblolly Pine (Pinus taeda L.)On The Virginia Piedmont

    OpenAIRE

    Wiseman, Phillip Eric

    2001-01-01

    Soil carbon dioxide efflux resulting from microbial and root respiration is a major component of the forest carbon cycle. We undertook this investigation to better understand the nature of soil carbon dioxide efflux of plantation loblolly pine, an important ecological and economical resource in the southeastern United States. Specifically, we hoped to learn how soil carbon dioxide efflux differs both spatially and temporally for four age classes of plantation loblolly pine on the Virginia p...

  6. Regenerative Hydride Heat Pump

    Science.gov (United States)

    Jones, Jack A.

    1992-01-01

    Hydride heat pump features regenerative heating and single circulation loop. Counterflow heat exchangers accommodate different temperatures of FeTi and LaNi4.7Al0.3 subloops. Heating scheme increases efficiency.

  7. Advanced heat pump

    Science.gov (United States)

    Ashley, Joseph L.; Matthews, John D.

    1989-09-01

    This patent application discloses a heat pump which includes a first packed bed of liquid desiccant for removing moisture from outside air in the heating mode of operation, and a pump for transferring the moisture laden desiccant to a second packed bed which humidifies condenser heated inside air by adding water vapor to the air. The first packed bed, by removing moisture from the outside air before it passes through the heat pump's evaporator coils, prevents frost from forming on the coils. In the cooling mode of operation the second packed bed of liquid desiccant removes water vapor from the air inside of the building. The moisture laden desiccant is then transferred to the first packed bed by a second pump where condenser heat transfers the moisture from the desiccant to outside air.

  8. High Voltage Charge Pump

    KAUST Repository

    Emira, Ahmed A.

    2014-10-09

    Various embodiments of a high voltage charge pump are described. One embodiment is a charge pump circuit that comprises a plurality of switching stages each including a clock input, a clock input inverse, a clock output, and a clock output inverse. The circuit further comprises a plurality of pumping capacitors, wherein one or more pumping capacitors are coupled to a corresponding switching stage. The circuit also comprises a maximum selection circuit coupled to a last switching stage among the plurality of switching stages, the maximum selection circuit configured to filter noise on the output clock and the output clock inverse of the last switching stage, the maximum selection circuit further configured to generate a DC output voltage based on the output clock and the output clock inverse of the last switching stage.

  9. Nuclear-pumped lasers

    CERN Document Server

    Prelas, Mark

    2016-01-01

    This book focuses on Nuclear-Pumped Laser (NPL) technology and provides the reader with a fundamental understanding of NPLs, a review of research in the field, and exploration of large scale NPL system design and applications. Early chapters look at the fundamental properties of lasers, nuclear-pumping and nuclear reactions that may be used as drivers for nuclear-pumped lasers. The book goes on to explore the efficient transport of energy from the ionizing radiation to the laser medium and then the operational characteristics of existing nuclear-pumped lasers. Models based on Mathematica, explanations and a tutorial all assist the reader’s understanding of this technology. Later chapters consider the integration of the various systems involved in NPLs and the ways in which they can be used, including beyond the military agenda. As readers will discover, there are significant humanitarian applications for high energy/power lasers, such as deflecting asteroids, space propulsion, power transmission and mining....

  10. Keeping Hearts Pumping

    Science.gov (United States)

    2002-01-01

    A collaboration between NASA, Dr. Michael DeBakey, Dr. George Noon, and MicroMed Technology, Inc., resulted in a life-saving heart pump for patients awaiting heart transplants. The MicroMed DeBakey VAD functions as a "bridge to heart transplant" by pumping blood throughout the body to keep critically ill patients alive until a donor heart is available. Weighing less than 4 ounces and measuring 1 inch by 3 inches, the pump is approximately one-tenth the size of other currently marketed pulsatile VADs. This makes it less invasive and ideal for smaller adults and children. Because of the pump's small size, less than 5 percent of the patients implanted developed device-related infections. It can operate up to 8 hours on batteries, giving patients the mobility to do normal, everyday activities.The MicroMed DeBakey VAD is a registered trademark of MicroMed Technology, Inc.

  11. Tokamak pump limiters

    International Nuclear Information System (INIS)

    Recent experiments with a scoop limiter without active internal pumping have been carried out in the PDX tokamak with up to 6MW of auxiliary neutral beam heating. Experiments have also been done with a rotating head pump limiter in the PLT tokamak in conjunction with RF plasma heating. Extensive experiments have been done in the ISX-B tokamak and first experiments have been completed with the ALT-I limiter in TEXTOR. The pump limiter modules in these latter two machines have internal getter pumping. Experiments in ISX-B are with ohmic and auxiliary neutral beam heating. The results in ISX-B and TEXTOR show that active density control and particle removal is achieved with pump limiters. In ISX-B, the boundary layer (or scape-off layer) plasma partially screens the core plasma from gas injection. In both ISX-B and TEXTOR, the pressure internal to the module scales linearly with plasma density but in ISX-B, with neutral beam injection, a nonlinear increase is observed at the highest densities studied. Plasma plugging is the suspected cause. Results from PDX suggest that a region may exist in which core plasma energy confinement improves using a pump limiter during neutral beam injection. Asymmetric radial profiles and an increased edge electron temperature are observed in discharges with improved confinement. The injection of small amounts of neon into ISX-B has more clearly shown an improved electron core energy confinement during neutral beam injection. While carried out with a regular limiter, this Z-mode of operation is ideal for use with pump limiters and should be a way to achieve energy confinement times similar to values for H-mode tokamak plasmas. The implication of all these results for the design of a reactor pump limiter is described

  12. Lunar Base Heat Pump

    Science.gov (United States)

    Walker, D.; Fischbach, D.; Tetreault, R.

    1996-01-01

    The objective of this project was to investigate the feasibility of constructing a heat pump suitable for use as a heat rejection device in applications such as a lunar base. In this situation, direct heat rejection through the use of radiators is not possible at a temperature suitable for lde support systems. Initial analysis of a heat pump of this type called for a temperature lift of approximately 378 deg. K, which is considerably higher than is commonly called for in HVAC and refrigeration applications where heat pumps are most often employed. Also because of the variation of the rejection temperature (from 100 to 381 deg. K), extreme flexibility in the configuration and operation of the heat pump is required. A three-stage compression cycle using a refrigerant such as CFC-11 or HCFC-123 was formulated with operation possible with one, two or three stages of compression. Also, to meet the redundancy requirements, compression was divided up over multiple compressors in each stage. A control scheme was devised that allowed these multiple compressors to be operated as required so that the heat pump could perform with variable heat loads and rejection conditions. A prototype heat pump was designed and constructed to investigate the key elements of the high-lift heat pump concept. Control software was written and implemented in the prototype to allow fully automatic operation. The heat pump was capable of operation over a wide range of rejection temperatures and cooling loads, while maintaining cooling water temperature well within the required specification of 40 deg. C +/- 1.7 deg. C. This performance was verified through testing.

  13. Soil CO2 efflux in an old-growth southern conifer forest (Agathis australis) - magnitude, components and controls

    Science.gov (United States)

    Schwendenmann, Luitgard; Macinnis-Ng, Cate

    2016-08-01

    Total soil CO2 efflux and its component fluxes, autotrophic and heterotrophic respiration, were measured in a native forest in northern Aotearoa-New Zealand. The forest is dominated by Agathis australis (kauri) and is on an acidic, clay rich soil. Soil CO2 efflux, volumetric soil water content and soil temperature were measured bi-weekly to monthly at 72 sampling points over 18 months. Trenching and regression analysis was used to partition total soil CO2 efflux into heterotrophic and autotrophic respiration. The effect of tree structure was investigated by calculating an index of local contribution (Ic, based on tree size and distance to the measurement location) followed by correlation analysis between Ic and total soil CO2 efflux, root biomass, litterfall and soil characteristics. The measured mean total soil CO2 efflux was 3.47 µmol m-2 s-1. Autotrophic respiration accounted for 25 % (trenching) or 28 % (regression analysis) of total soil CO2 efflux. Using uni- and bivariate models showed that soil temperature was a poor predictor of the temporal variation in total soil CO2 efflux (soil CO2 efflux, root biomass and mineral soil CN ratio within 5-6 m of the sampling points. Using multiple regression analysis revealed that 97 % of the spatial variability in total soil CO2 efflux in this kauri-dominated stand was explained by root biomass and soil temperature. Our findings suggest that biotic factors such as tree structure should be investigated in soil carbon related studies.

  14. Studies on alterations of the 86-rubidium efflux from rat pancreatic islets caused by thiol and thiol oxidants

    International Nuclear Information System (INIS)

    The following findings were revealed by this study: 1) Oxidation-reduction (redox) of the intracellular system of glutathione influences the potassium efflux by way of an increase in the 86-rubidium efflux brought about by the oxidation of intracellular thiols. 2) The 86-rubidium efflux is not subject to change by oxidation of extracellular thiols located in the membrane, nor can it in any way be influenced by reduced glutathione of exogenous origin. 3) The potassium efflux from rat pancreatic islets, being generally known to trigger the electric activities of the beta-cell, is controlled by the oxidation-reduction of intracellular thiols rather than by that of extracellular thiols. (TRV)

  15. Complex interplay between the P-glycoprotein multidrug efflux pump and the membrane: its role in modulating protein function

    Directory of Open Access Journals (Sweden)

    Frances Jane Sharom

    2014-03-01

    Full Text Available Multidrug resistance in cancer is linked to expression of the P-glycoprotein multidrug transporter (Pgp, ABCB1, which exports many structurally diverse compounds from cells. Substrates first partition into the bilayer and then interact with a large flexible binding pocket within the transporter’s transmembrane regions. Pgp has been described as a hydrophobic vacuum cleaner or an outwardly-directed drug/lipid flippase. Recent X-ray crystal structures have shed some light on the nature of the drug-binding pocket and suggested routes by which substrates can enter it from the membrane. Detergents have profound effects on Pgp function, and several appear to be substrates. Biochemical and biophysical studies in vitro, some using purified reconstituted protein, have explored the effects of the membrane environment. They have demonstrated that Pgp is involved in a complex relationship with its lipid environment, which modulates the behaviour of its substrates, as well as various functions of the protein, including ATP hydrolysis, drug binding and drug transport. Membrane lipid composition and fluidity, phospholipid headgroup and acyl chain length all influence Pgp function. Recent studies focusing on thermodynamics and kinetics have revealed some important principles governing Pgp-lipid and substrate-lipid interactions, and how these affect drug binding and transport. In some cells, Pgp is associated with cholesterol-rich microdomains which may modulate its functions. The relationship between Pgp and cholesterol remains an open question; however it clearly affects several aspects of its function in addition to substrate-membrane partitioning. The action of Pgp modulators appears to depend on their membrane permeability, and membrane fluidizers and surfactants reverse drug resistance, likely via an indirect mechanism. A detailed understanding of how the membrane affects Pgp substrates and Pgp’s catalytic cycle may lead to new strategies to combat clinical drug resistance.

  16. Complex Interplay between the P-Glycoprotein Multidrug Efflux Pump and the Membrane: Its Role in Modulating Protein Function.

    Science.gov (United States)

    Sharom, Frances Jane

    2014-01-01

    Multidrug resistance in cancer is linked to expression of the P-glycoprotein multidrug transporter (Pgp, ABCB1), which exports many structurally diverse compounds from cells. Substrates first partition into the bilayer and then interact with a large flexible binding pocket within the transporter's transmembrane regions. Pgp has been described as a hydrophobic vacuum cleaner or an outwardly directed drug/lipid flippase. Recent X-ray crystal structures have shed some light on the nature of the drug-binding pocket and suggested routes by which substrates can enter it from the membrane. Detergents have profound effects on Pgp function, and several appear to be substrates. Biochemical and biophysical studies in vitro, some using purified reconstituted protein, have explored the effects of the membrane environment. They have demonstrated that Pgp is involved in a complex relationship with its lipid environment, which modulates the behavior of its substrates, as well as various functions of the protein, including ATP hydrolysis, drug binding, and drug transport. Membrane lipid composition and fluidity, phospholipid headgroup and acyl chain length all influence Pgp function. Recent studies focusing on thermodynamics and kinetics have revealed some important principles governing Pgp-lipid and substrate-lipid interactions, and how these affect drug-binding and transport. In some cells, Pgp is associated with cholesterol-rich microdomains, which may modulate its functions. The relationship between Pgp and cholesterol remains an open question; however, it clearly affects several aspects of its function in addition to substrate-membrane partitioning. The action of Pgp modulators appears to depend on their membrane permeability, and membrane fluidizers and surfactants reverse drug resistance, likely via an indirect mechanism. A detailed understanding of how the membrane affects Pgp substrates and Pgp's catalytic cycle may lead to new strategies to combat clinical drug resistance. PMID:24624364

  17. Antimicrobial and efflux pump inhibitory activity of caffeoylquinic acids from Artemisia absinthium against Gram-positive pathogenic bacteria

    NARCIS (Netherlands)

    Fiamegos, Y.C.; Kastritis, P.; Exarchou, V.; Han, H.; Bonvin, A.M.J.J.; Vervoort, J.; Lewis, K.; Hamblin, M.R.; Tegos, G.P.

    2011-01-01

    Background: Traditional antibiotics are increasingly suffering from the emergence of multidrug resistance amongst pathogenic bacteria leading to a range of novel approaches to control microbial infections being investigated as potential alternative treatments. One plausible antimicrobial alternative

  18. Antimicrobial and efflux pump inhibitory activity of caffeoylquinic acids from Artemisia absinthium against gram-positive pathogenic bacteria.

    NARCIS (Netherlands)

    Fiamegos, Y.C.; Kastritis, P.L.; Exarchou, V.; Han, H.; Bonvin, A.M.; Vervoort, J.J.M.; Lewis, K.; Hamblin, M.R.; Tegos, G.P.

    2011-01-01

    Background Traditional antibiotics are increasingly suffering from the emergence of multidrug resistance amongst pathogenic bacteria leading to a range of novel approaches to control microbial infections being investigated as potential alternative treatments. One plausible antimicrobial alternative

  19. Plasmid-Encoded Tetracycline Efflux Pump Protein Alters Bacterial Stress Responses and Ecological Fitness of Acinetobacter oleivorans

    OpenAIRE

    Hong, Hyerim; Jung, Jaejoon; Park, Woojun

    2014-01-01

    Acquisition of the extracellular tetracycline (TC) resistance plasmid pAST2 affected host gene expression and phenotype in the oil-degrading soil bacterium, Acinetobacter oleivorans DR1. Whole-transcriptome profiling of DR1 cells harboring pAST2 revealed that all the plasmid genes were highly expressed under TC conditions, and the expression levels of many host chromosomal genes were modulated by the presence of pAST2. The host energy burden imposed by replication of pAST2 led to (i) lowered ...

  20. Identification and Evolution of Drug Efflux Pump in Clinical Enterobacter aerogenes Strains Isolated in 1995 and 2003

    OpenAIRE

    Jacqueline Chevalier; Céline Mulfinger; Eric Garnotel; Pierre Nicolas; Anne Davin-Régli; Jean-Marie Pagès

    2008-01-01

    BACKGROUND: The high mortality impact of infectious diseases will increase due to accelerated evolution of antibiotic resistance in important human pathogens. Development of antibiotic resistance is a evolutionary process inducing the erosion of the effectiveness of our arsenal of antibiotics. Resistance is not necessarily limited to a single class of antibacterial agents but may affect many unrelated compounds; this is termed 'multidrug resistance' (MDR). The major mechanism of MDR is the ac...

  1. Rotary blood pump

    Science.gov (United States)

    Benkowski, Robert J. (Inventor); Kiris, Cetin (Inventor); Kwak, Dochan (Inventor); Rosenbaum, Bernard J. (Inventor); Bacak, James W. (Inventor); DeBakey, Michael E. (Inventor)

    1999-01-01

    A blood pump that comprises a pump housing having a blood flow path therethrough, a blood inlet, and a blood outlet; a stator mounted to the pump housing, the stator having a stator field winding for producing a stator magnetic field; a flow straightener located within the pump housing, and comprising a flow straightener hub and at least one flow straightener blade attached to the flow straightener hub; a rotor mounted within the pump housing for rotation in response to the stator magnetic field, the rotor comprising an inducer and an impeller; the inducer being located downstream of the flow straightener, and comprising an inducer hub and at least one inducer blade attached to the inducer hub; the impeller being located downstream of the inducer, and comprising an impeller hub and at least one impeller blade attached to the impeller hub; and preferably also comprising a diffuser downstream of the impeller, the diffuser comprising a diffuser hub and at least one diffuser blade. Blood flow stagnation and clot formation within the pump are minimized by, among other things, providing the inducer hub with a diameter greater than the diameter of the flow straightener hub; by optimizing the axial spacing between the flow straightener hub and the inducer hub, and between the impeller hub and the diffuser hub; by optimizing the inlet angle of the diffuser blades; and by providing fillets or curved transitions between the upstream end of the inducer hub and the shaft mounted therein, and between the impeller hub and the shaft mounted therein.

  2. BIOMATERIALS FOR ROTARY BLOOD PUMPS

    NARCIS (Netherlands)

    VANOEVEREN, W

    1995-01-01

    Rotary blood pumps are used for cardiac assist and cardiopulmonary support since mechanical blood damage is less than with conventional roller pumps. The high shear rate in the rotary pump and the reduced anticoagulation of the patient during prolonged pumping enforces high demands on the biocompati

  3. Arctigenin promotes cholesterol efflux from THP-1 macrophages through PPAR-γ/LXR-α signaling pathway.

    Science.gov (United States)

    Xu, Xiaolin; Li, Qian; Pang, Liewen; Huang, Guoqian; Huang, Jiechun; Shi, Meng; Sun, Xiaotian; Wang, Yiqing

    2013-11-15

    Cholesterol efflux from macrophages is a critical mechanism to prevent the development of atherosclerosis. Here, we sought to investigate the effects of arctigenin, a bioactive component of Arctium lappa, on the cholesterol efflux in oxidized low-density lipoprotein (oxLDL)-loaded THP-1 macrophages. Our data showed that arctigenin significantly accelerated apolipoprotein A-I- and high-density lipoprotein-induced cholesterol efflux in both dose- and time-dependent manners. Moreover, arctigenin treatment enhanced the expression of ATP binding cassette transporter A1 (ABCA1), ABCG1, and apoE, all of which are key molecules in the initial step of cholesterol efflux, at both mRNA and protein levels. Arctigenin also caused a concentration-dependent elevation in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and liver X receptor-alpha (LXR-α). The arctigenin-mediated induction of ABCA1, ABCG1, and apoE was abolished by specific inhibition of PPAR-γ or LXR-α using small interfering RNA technology. Our results collectively indicate that arctigenin promotes cholesterol efflux in oxLDL-loaded THP-1 macrophages through upregulation of ABCA1, ABCG1 and apoE, which is dependent on the enhanced expression of PPAR-γ and LXR-α. PMID:24140409

  4. Effects of ELF fields on calcium-ion efflux from brain tissues in vitro

    International Nuclear Information System (INIS)

    It has been previously demonstrated that carrier waves of 50 and 147 MHz, when sinusoidally amplitude modulated at 16 Hz (ELF), can cause enhanced efflux of radiolabeled calcium ions from chick brain tissue in vitro. This phenomenon occurs only when the samples are exposed to specific intensity ranges of the carrier wave. Unmodulated carrier waves do not affect the ion efflux. Since the ELF signal must be demodulated from the carrier wave to be effective, a study of the efflux ehnancement due to the ELF signal alone may lead to an identification of the site of demodulation, as well as provide clues to the underlying mechanism. We report here that 16-Hz sinusoidal fields in the absence of a carrier wave can alter the efflux rate of calcium ions. The results show a frequency-dependent, field-induced enhancement of calcium-ion efflux within the ranges 5 to 7.5 V/m and 35 to 50 V/m (peak-to-peak incident field in air) with no enhancement within the ranges 1 to 2, 10 to 30, and 60 to 70 V/m

  5. Effects of weak amplitude-modulated microwave fields on calcium efflux from awake cat cerebral cortex

    International Nuclear Information System (INIS)

    Calcium (45Ca2+) efflux was studied from preloaded cortex in cats immobilized under local anesthesia, and exposed to a 3.0-mW/cm2 450-MHz field, sinusoidally amplitude modulated at 16 Hz modulation depth 85%). Tissue dosimetry showed a field of 33 V/m in the interhemispheric fissure (rate of energy deposition 0.29 W/kg). Field exposure lasted 60 min. By comparison with controls, efflux curves from field exposed brains were disrupted by waves of increased 45Ca2+ efflux. These waves were irregular in amplitude and duration, but many exhibited periods of 20-30 min. They continued into the postexposure period. Binomial probability analysis indicates that the field-exposed efflux curves constitute a different population from controls at a confidence level of 0.96. In about 70% of cases, initiation of field exposure was followed by increased end-tidal CO2 excretion for about 5 min. However, hypercapnea induced by hypoventilation did not elicit increased 45Ca2+ efflux. Thus this increase with exposure does not appear to arise as a secondary effect of raised cerebral CO2 levels. Radioactivity measurements in cortical samples after superfusion showed 45Ca2+ penetration at about 1.7 mm/hr, consistent with diffusion of the ion in free solution

  6. Thermally Actuated Hydraulic Pumps

    Science.gov (United States)

    Jones, Jack; Ross, Ronald; Chao, Yi

    2008-01-01

    Thermally actuated hydraulic pumps have been proposed for diverse applications in which direct electrical or mechanical actuation is undesirable and the relative slowness of thermal actuation can be tolerated. The proposed pumps would not contain any sliding (wearing) parts in their compressors and, hence, could have long operational lifetimes. The basic principle of a pump according to the proposal is to utilize the thermal expansion and contraction of a wax or other phase-change material in contact with a hydraulic fluid in a rigid chamber. Heating the chamber and its contents from below to above the melting temperature of the phase-change material would cause the material to expand significantly, thus causing a substantial increase in hydraulic pressure and/or a substantial displacement of hydraulic fluid out of the chamber. Similarly, cooling the chamber and its contents from above to below the melting temperature of the phase-change material would cause the material to contract significantly, thus causing a substantial decrease in hydraulic pressure and/or a substantial displacement of hydraulic fluid into the chamber. The displacement of the hydraulic fluid could be used to drive a piston. The figure illustrates a simple example of a hydraulic jack driven by a thermally actuated hydraulic pump. The pump chamber would be a cylinder containing encapsulated wax pellets and containing radial fins to facilitate transfer of heat to and from the wax. The plastic encapsulation would serve as an oil/wax barrier and the remaining interior space could be filled with hydraulic oil. A filter would retain the encapsulated wax particles in the pump chamber while allowing the hydraulic oil to flow into and out of the chamber. In one important class of potential applications, thermally actuated hydraulic pumps, exploiting vertical ocean temperature gradients for heating and cooling as needed, would be used to vary hydraulic pressures to control buoyancy in undersea research

  7. Non-equivalent roles of two periplasmic subunits in the function and assembly of triclosan pump TriABC from Pseudomonas aeruginosa.

    Science.gov (United States)

    Weeks, Jon W; Nickels, Logan M; Ntreh, Abigail T; Zgurskaya, Helen I

    2015-10-01

    In Gram-negative bacteria, multidrug efflux transporters function in complexes with periplasmic membrane fusion proteins (MFPs) that enable antibiotic efflux across the outer membrane. In this study, we analyzed the function, composition and assembly of the triclosan efflux transporter TriABC-OpmH from Pseudomonas aeruginosa. We report that this transporter possesses a surprising substrate specificity that encompasses not only triclosan but the detergent SDS, which are often used together in antibacterial soaps. These two compounds interact antagonistically in a TriABC-dependent manner and negate antibacterial properties of each other. Unlike other efflux pumps that rely on a single MFP for their activities, two different MFPs, TriA and TriB, are required for triclosan/SDS resistance mediated by TriABC-OpmH. We found that analogous mutations in the α-helical hairpin and membrane proximal domains of TriA and TriB differentially affect triclosan efflux and assembly of the complex. Furthermore, our results show that TriA and TriB function as a dimer, in which TriA is primarily responsible for stabilizing interactions with the outer membrane channel, whereas TriB is important for the stimulation of the transporter. We conclude that MFPs are engaged into complexes as asymmetric dimers, in which each protomer plays a specific role. PMID:26193906

  8. Electronic Unit Pump Test Bench Development and Pump Properties Research

    Institute of Scientific and Technical Information of China (English)

    LIU Bo-lan; HUANG Ying; ZHANG Fu-jun; ZHAO Chang-lu

    2006-01-01

    A unit pump test bench is developed on an in-line pump test platform. The bench is composed of pump adapting assembly, fuel supply subsystem, lubricating subsystem and a control unit. A crank angle domain injection control method is given out and the control accuracy can be 0.1° crank degree. The bench can test bot h mechanical unit pump and electronic unit pump. A test model-PLD12 electronic unit pump is tested. Full pump delivery map and some influence factors test is d one. Experimental results show that the injection quantity is linear with the de livery angle. The quantity change rate is 15% when fuel temperature increases 30℃. The delivery quantity per cycle increases 30mg at 28V drive voltage. T he average delivery difference for two same type pumps is 5%. Test results show that the bench can be used for unit pump verification.

  9. Specificity of drug transport mediated by CaMDR1: a major facilitator of Candida albicans

    Indian Academy of Sciences (India)

    Avmeet Kohli; Vinita Gupta; Shankarling Krishnamurthy; Seyed E Hasnain; Rajendra Prasad

    2001-09-01

    CaMDR1 encodes a major facilitator superfamily (MFS) protein in Candida albicans whose expression has been linked to azole resistance and which is frequently encountered in this human pathogenic yeast. In this report we have overexpressed CaMdr1p in Sf9 insect cells and demonstrated for the first time that it can mediate methotrexate (MTX) and fluconazole (FLC) transport. MTX appeared to be a better substrate for CaMdr1p among these two tested drugs. Due to severe toxicity of these drugs to insect cells, further characterization of CaMdr1p as a drug transporter could not be done with this system. Therefore, as an alternative, CaMdr1p and Cdr1p, which is an ABC protein (ATP binding cassette) also involved in azole resistance in C. albicans, were independently expressed in a common hypersensitive host JG436 of Saccharomyces cerevisiae. This allowed a better comparison between the functionality of the two export pumps. We observed that while both FLC and MTX are effluxed by CaMdr1p, MTX appeared to be a poor substrate for Cdr1p. JG436 cells expressing Cdr1p thus conferred resistance to other antifungal drugs but remained hypersensitive to MTX. Since MTX is preferentially transported by CaMdr1p, it can be used for studying the function of this MFS protein.

  10. LXR/RXR ligand activation enhances basolateral efflux of beta-sitosterol in CaCo-2 cells.

    Science.gov (United States)

    Field, F Jeffrey; Born, Ella; Mathur, Satya N

    2004-05-01

    To examine whether intestinal ABCA1 was responsible for the differences observed between cholesterol and beta-sitosterol absorption, ABCA1-facilitated beta-sitosterol efflux was investigated in CaCo-2 cells following liver X receptor/retinoid X receptor (LXR/RXR) activation. Both the LXR agonist T0901317 and the natural RXR/LXR agonists 22-hydroxycholesterol and 9-cis retinoic acid enhanced the basolateral efflux of beta-sitosterol without altering apical efflux. LXR-mediated enhanced beta-sitosterol efflux occurred between 6 h and 12 h after activation, suggesting that transcription, protein synthesis, and trafficking was likely necessary prior to facilitating efflux. The transcription inhibitor actinomycin D prevented the increase in beta-sitosterol efflux by T0901317. Glybenclamide, an inhibitor of ABCA1 activity, and arachidonic acid, a fatty acid that interferes with LXR activation, also prevented beta-sitosterol efflux in response to the LXR ligand activation. Influx of beta-sitosterol mass did not alter the basolateral or apical efflux of the plant sterol, nor did it alter ABCA1, ABCG1, ABCG5, or ABCG8 gene expression or ABCA1 mass. Similar to results observed with intestinal ABCA1-facilitated cholesterol efflux, LXR/RXR ligand activation enhanced the basolateral efflux of beta-sitosterol without affecting apical efflux. The results suggest that ABCA1 does not differentiate between cholesterol and beta-sitosterol and thus is not responsible for the selectivity of sterol absorption by the intestine. ABCA1, however, may play a role in beta-sitosterol absorption.

  11. An assessment of some methodological criticisms of studies of RNA efflux from isolated nuclei.

    Science.gov (United States)

    Agutter, P S

    1983-09-15

    RNA efflux from isolated nuclei can be studied either as a means of elucidating the general mechanism of nucleo-cytoplasmic RNA transport, or as part of an investigation of the processing and utilization of particular gene transcripts. The present paper describes an assessment of three methodological criticisms of RNA-efflux measurements that are made for the former reason: for such measurements, it is sufficient to show that the post-incubation supernatant RNA is similar overall to homologous cytoplasmic mRNA, rather than to nuclear RNA, that is nevertheless of intranuclear origin, and that alterations to the medium during experiments do not markedly perturb this general nuclear restriction. The results seem to justify the following conclusions. (1) Although degradation of the nuclear RNA occurs during incubation in vitro, this process does not account for the appearance of RNA in the postnuclear supernatant. The degradation can be largely prevented by the addition of serine-proteinase inhibitors without altering the RNA efflux rate. (2) Some adsorption of labelled cytoplasmic RNA to the nuclear surface occurs during both isolation and incubation of the nuclei, and some desorption occurs during incubation. However, these effects introduce errors of less than 10% into the measurements of efflux rates. (3) Exogenous acidic polymers, including polyribonucleotides, disrupt nuclei and increase the apparent RNA efflux rate by causing leakage of nuclear contents. However, this effect can largely be overcome by including the nuclear stabilizers spermidine, Ca2+ and Mn2+ in the medium. In terms of this assessment, it appears that RNA efflux from isolated nuclei in media containing nuclear stabilizers serves as a reasonable model for transport in vivo.

  12. Syntaxin 1A interaction with the dopamine transporter promotes amphetamine-induced dopamine efflux.

    Science.gov (United States)

    Binda, Francesca; Dipace, Concetta; Bowton, Erica; Robertson, Sabrina D; Lute, Brandon J; Fog, Jacob U; Zhang, Minjia; Sen, Namita; Colbran, Roger J; Gnegy, Margaret E; Gether, Ulrik; Javitch, Jonathan A; Erreger, Kevin; Galli, Aurelio

    2008-10-01

    The soluble N-ethylmaleimide-sensitive factor attachment protein receptor protein syntaxin 1A (SYN1A) interacts with and regulates the function of transmembrane proteins, including ion channels and neurotransmitter transporters. Here, we define the first 33 amino acids of the N terminus of the dopamine (DA) transporter (DAT) as the site of direct interaction with SYN1A. Amphetamine (AMPH) increases the association of SYN1A with human DAT (hDAT) in a heterologous expression system (hDAT cells) and with native DAT in murine striatal synaptosomes. Immunoprecipitation of DAT from the biotinylated fraction shows that the AMPH-induced increase in DAT/SYN1A association occurs at the plasma membrane. In a superfusion assay of DA efflux, cells overexpressing SYN1A exhibited significantly greater AMPH-induced DA release with respect to control cells. By combining the patch-clamp technique with amperometry, we measured DA release under voltage clamp. At -60 mV, a physiological resting potential, AMPH did not induce DA efflux in hDAT cells and DA neurons. In contrast, perfusion of exogenous SYN1A (3 microM) into the cell with the whole-cell pipette enabled AMPH-induced DA efflux at -60 mV in both hDAT cells and DA neurons. It has been shown recently that Ca2+/calmodulin-dependent protein kinase II (CaMKII) is activated by AMPH and regulates AMPH-induced DA efflux. Here, we show that AMPH-induced association between DAT and SYN1A requires CaMKII activity and that inhibition of CaMKII blocks the ability of exogenous SYN1A to promote DA efflux. These data suggest that AMPH activation of CaMKII supports DAT/SYN1A association, resulting in a mode of DAT capable of DA efflux.

  13. Association between cholesterol efflux capacity and coronary restenosis after successful stent implantation.

    Science.gov (United States)

    Imaizumi, Satoshi; Miura, Shin-Ichiro; Takata, Kohei; Takamiya, Yosuke; Kuwano, Takashi; Sugihara, Makoto; Ike, Amane; Iwata, Atsushi; Nishikawa, Hiroaki; Saku, Keijiro

    2016-08-01

    The measurement of high-density lipoprotein (HDL) functionality could be useful for identifying patients who have an increased risk of coronary restenosis after stent implantation. In the present study, we elucidates whether HDL functionality can predict restenosis. The participants included 48 consecutive patients who had stable angina and were successfully implanted with a drug-eluting stent (DES) or bare-metal stent. Follow-up coronary angiography was performed after 6-8 months of stenting. Cholesterol efflux and the anti-inflammatory capacity of HDL were measured before stenting (at baseline) and at follow-up. The mean age was 64 ± 11 years and the body mass index was 24 ± 3 kg/m(2). While HDL cholesterol (HDL-C) significantly increased from baseline to follow-up, there was no significant association between HDL-C level at baseline and in-stent late loss. Cholesterol efflux capacity was significantly increased from baseline to follow-up. The efflux capacity at baseline was negatively correlated with in-stent late loss, whereas the anti-oxidative activity of HDL at baseline was not associated with in-stent late loss. We analyzed the predictors of in-stent late loss using independent variables (efflux capacity and anti-oxidative capacity at baseline in addition to age, gender, HDL-C and low-density lipoprotein cholesterol at baseline, hypertension, diabetes mellitus, smoking, lesion length and DES implantation, history of myocardial infarction and prior percutaneous coronary intervention) by a multiple regression analysis. The efflux capacity at baseline was only independently associated with in-stent late loss. In conclusion, cholesterol efflux capacity at baseline could predict coronary restenosis in patients with successful stent implantation. PMID:26337618

  14. Soil CO2 efflux among four coniferous forest types of Kashmir Himalaya, India.

    Science.gov (United States)

    Dar, Javid Ahmad; Ganie, Khursheed Ahmad; Sundarapandian, Somaiah

    2015-11-01

    Soil CO2 efflux was measured in four different coniferous forest types (Cedrus deodara (CD), Pinus wallichiana (PW), mixed coniferous (MC), and Abies pindrow (AP)) for a period of 2 years (April 2012 to December 2013). The monthly soil CO2 efflux ranged from 0.8 to 4.1 μmoles CO2 m(-2) s(-1) in 2012 and 1.01 to 5.48 μmoles CO2 m(-2) s(-1) in 2013. The soil CO2 efflux rate was highest in PW forest type in both the years, while it was lowest in MC and CD forest types during 2012 and 2013, respectively. Soil temperature (TS) at a depth of 10 cm ranged from 3.8 to 19.4 °C in 2012 and 3.5 to 19.1 °C in 2013 in all the four forest types. Soil moisture (MS) ranged from 19.8 to 58.6% in 2012 and 18.5 to 58.6% in 2013. Soil CO2 efflux rate was found to be significantly higher in summer than the other seasons and least during winter. Soil CO2 efflux showed a significant positive relationship with TS (R2=0.52 to 0.74), SOC% (R2=0.67), pH (R2=0.68), and shrub biomass (R2=0.51), whereas, only a weak positive relationship was found with soil moisture (R2=0.16 to 0.41), tree density (R2=0.25), tree basal area (R2=0.01), tree biomass (R2=0.07), herb biomass (R2=0.01), and forest floor litter (R2=0.02). Thus, the study indicates that soil CO2 efflux in high mountainous areas is greatly influenced by seasons, soil temperature, and other environmental factors. PMID:26514798

  15. Sediment CO2 efflux from cleared and intact temperate mangroves and tidal flats

    Science.gov (United States)

    Bulmer, R. H.; Schwendenmann, L.; Lundquist, C. J.

    2015-02-01

    Temperate mangroves in Southern Australia and New Zealand have been increasing in area over the past 50 years, whereas tropical mangroves have declined by 30-50% over a similar time frame. Tropical mangroves are understood to be an important carbon sink and carbon dioxide (CO2) emissions following clearance are estimated to be comparable or greater than CO2 emissions following the clearance of many terrestrial forest systems. Recreational and amenity values or perceived loss of other estuarine habitats due to expanding temperate mangrove forests have resulted in clearing of temperate mangroves. In this study, we investigated the impact of temperate mangrove clearance on CO2 efflux from the sediment to the atmosphere along with a range of other biotic and abiotic factors. Significantly higher CO2 efflux rates were measured in cleared (1.34 ± 0.46 μmol m2 s-1) and intact mangrove sites (2.31 ± 0.72 μmol m2 s-1) than in tidal flats (-0.23 ± 0.27 μmol m2 s-1). Site and sediment characteristics such as sediment carbon and nitrogen concentration, chlorophyll α concentration, grain size, mangrove height, macrofaunal abundance, sediment temperature and moisture were strongly correlated with sediment CO2 efflux. Our results suggest that carbon stored within temperate mangrove sediment is released over a period of years to decades after mangrove clearance. CO2 efflux from intact and cleared temperate mangroves was found to be comparable to rates observed in the tropics. Disturbance of the surface biofilm resulted in elevated CO2 efflux across all habitats, suggesting the important role of surface biofilm communities in mediating CO2 efflux.

  16. Different harvest intensity and soil CO2 efflux in sessile oak coppice forests

    Directory of Open Access Journals (Sweden)

    Darenova E

    2016-08-01

    Full Text Available Soil CO2 efflux accounts for about 45-80% of total ecosystem respiration and is therefore an important part of the ecosystem carbon cycle. Soil CO2 efflux has been poorly studied in forests managed in the ancient coppicing manner. In our study, soil CO2 efflux, temperature, and moisture were measured in sessile oak stands with different harvesting intensity (control: 0% intensity; V1: 75%; V2: 80 %; V3: 85%; and V4: 100% during the fifth and sixth years after harvesting. Soil CO2 efflux was in the range 2-8 µmol CO2 m-2 s-1 and indicated an increasing pattern with increasing harvesting intensity. The slope of that pattern became less steep from the fifth to the sixth year after harvesting, thus indicating gradual recovery of soil carbon dynamics in the coppiced stand toward the equilibrium state existing before harvesting. Temperature sensitivity of soil CO2 efflux ranged between 2.1 and 2.8, with the lowest values measured in the control stand. Soil CO2 efflux in the control stand was more sensitive to changes in soil moisture than was that on harvested plots. By our calculations, 6.2 tC ha-1 was released from the control stand and 6.2-6.8 tC ha-1 from the harvested stands during the sixth year after harvesting. If mean temperature were to rise by 1 °C, the amount of soil carbon released would increase by 7.7% in the control stand and, depending on harvesting intensity, by 9.0-10.8% in the harvested stands.

  17. Soil CO2 efflux among four coniferous forest types of Kashmir Himalaya, India.

    Science.gov (United States)

    Dar, Javid Ahmad; Ganie, Khursheed Ahmad; Sundarapandian, Somaiah

    2015-11-01

    Soil CO2 efflux was measured in four different coniferous forest types (Cedrus deodara (CD), Pinus wallichiana (PW), mixed coniferous (MC), and Abies pindrow (AP)) for a period of 2 years (April 2012 to December 2013). The monthly soil CO2 efflux ranged from 0.8 to 4.1 μmoles CO2 m(-2) s(-1) in 2012 and 1.01 to 5.48 μmoles CO2 m(-2) s(-1) in 2013. The soil CO2 efflux rate was highest in PW forest type in both the years, while it was lowest in MC and CD forest types during 2012 and 2013, respectively. Soil temperature (TS) at a depth of 10 cm ranged from 3.8 to 19.4 °C in 2012 and 3.5 to 19.1 °C in 2013 in all the four forest types. Soil moisture (MS) ranged from 19.8 to 58.6% in 2012 and 18.5 to 58.6% in 2013. Soil CO2 efflux rate was found to be significantly higher in summer than the other seasons and least during winter. Soil CO2 efflux showed a significant positive relationship with TS (R2=0.52 to 0.74), SOC% (R2=0.67), pH (R2=0.68), and shrub biomass (R2=0.51), whereas, only a weak positive relationship was found with soil moisture (R2=0.16 to 0.41), tree density (R2=0.25), tree basal area (R2=0.01), tree biomass (R2=0.07), herb biomass (R2=0.01), and forest floor litter (R2=0.02). Thus, the study indicates that soil CO2 efflux in high mountainous areas is greatly influenced by seasons, soil temperature, and other environmental factors.

  18. Winter soil CO2 efflux in two contrasting forest ecosystems on the eastern Tibetan Plateau, China

    Institute of Scientific and Technical Information of China (English)

    Zhenfeng Xu; Feifei Zhou; Huajun Yin; Qing Liu

    2015-01-01

    Significant CO2 fluxes from snow-covered soils occur in cold biomes. However, little is known about winter soil respiration on the eastern Tibetan Plateau of China. We therefore measured winter soil CO2 fluxes and estimated annual soil respiration in two contrasting coniferous forest ecosystems (a Picea asperata plantation and a natural forest). Mean winter soil CO2 effluxes were 1.08 lmol m-2 s-1 in the plantation and 1.16 lmol m-2 s-1 in the natural forest. These values are higher than most reported winter soil CO2 efflux values for temperate or boreal forest ecosystems. Winter soil respiration rates were similar for our two forest ecosystems but mean soil CO2 efflux over the growing season was higher in the natural forest than in the plantation. The estimated winter and annual soil effluxes for the natural forest were 176.3 and 1070.3 g m-2, respectively, based on the relationship between soil respiration and soil temperature, which were 17.2 and 9.7 % greater than their counterparts in the plantation. The contributions of winter soil respiration to annual soil efflux were 15.4 % for the plantation and 16.5 % for the natural forest and were statistically similar. Our results indicate that winter soil CO2 efflux from frozen soils in the alpine coniferous forest ecosystems of the eastern Tibetan Plateau was considerable and was an important component of annual soil respiration. Moreover, reforestation (natural coniferous forests were deforested and reforested with P. asperata plantation) may reduce soil respiration by reducing soil carbon substrate availability and input.

  19. Underground pumped hydroelectric storage

    Energy Technology Data Exchange (ETDEWEB)

    Allen, R.D.; Doherty, T.J.; Kannberg, L.D.

    1984-07-01

    Underground pumped hydroelectric energy storage was conceived as a modification of surface pumped storage to eliminate dependence upon fortuitous topography, provide higher hydraulic heads, and reduce environmental concerns. A UPHS plant offers substantial savings in investment cost over coal-fired cycling plants and savings in system production costs over gas turbines. Potential location near load centers lowers transmission costs and line losses. Environmental impact is less than that for a coal-fired cycling plant. The inherent benefits include those of all pumped storage (i.e., rapid load response, emergency capacity, improvement in efficiency as pumps improve, and capacity for voltage regulation). A UPHS plant would be powered by either a coal-fired or nuclear baseload plant. The economic capacity of a UPHS plant would be in the range of 1000 to 3000 MW. This storage level is compatible with the load-leveling requirements of a greater metropolitan area with population of 1 million or more. The technical feasibility of UPHS depends upon excavation of a subterranean powerhouse cavern and reservoir caverns within a competent, impervious rock formation, and upon selection of reliable and efficient turbomachinery - pump-turbines and motor-generators - all remotely operable.

  20. Heat driven pulse pump

    Science.gov (United States)

    Benner, Steve M (Inventor); Martins, Mario S. (Inventor)

    2000-01-01

    A heat driven pulse pump includes a chamber having an inlet port, an outlet port, two check valves, a wick, and a heater. The chamber may include a plurality of grooves inside wall of the chamber. When heated within the chamber, a liquid to be pumped vaporizes and creates pressure head that expels the liquid through the outlet port. As liquid separating means, the wick, disposed within the chamber, is to allow, when saturated with the liquid, the passage of only liquid being forced by the pressure head in the chamber, preventing the vapor from exiting from the chamber through the outlet port. A plurality of grooves along the inside surface wall of the chamber can sustain the liquid, which is amount enough to produce vapor for the pressure head in the chamber. With only two simple moving parts, two check valves, the heat driven pulse pump can effectively function over the long lifetimes without maintenance or replacement. For continuous flow of the liquid to be pumped a plurality of pumps may be connected in parallel.

  1. Fluid pumping apparatus

    Science.gov (United States)

    West, Phillip B.

    2006-01-17

    A method and apparatus suitable for coupling seismic or other downhole sensors to a borehole wall in high temperature and pressure environments. In one embodiment, one or more metal bellows mounted to a sensor module are inflated to clamp the sensor module within the borehole and couple an associated seismic sensor to a borehole wall. Once the sensing operation is complete, the bellows are deflated and the sensor module is unclamped by deflation of the metal bellows. In a further embodiment, a magnetic drive pump in a pump module is used to supply fluid pressure for inflating the metal bellows using borehole fluid or fluid from a reservoir. The pump includes a magnetic drive motor configured with a rotor assembly to be exposed to borehole fluid pressure including a rotatable armature for driving an impeller and an associated coil under control of electronics isolated from borehole pressure.

  2. Contribution of vesicular and cytosolic dopamine to the increased striatal dopamine efflux elicited by intrastriatal injection of SKF38393.

    NARCIS (Netherlands)

    Saigusa, T.; Aono, Y.; Sekino, R.; Uchida, T.; Takada, K.; Oi, Y.; Koshikawa, N.; Cools, A.R.

    2009-01-01

    Like dexamphetamine, SKF38393 induces an increase in striatal dopamine efflux which is insensitive for tetrodotoxin, Ca(2+) independent and prevented by a dopamine transporter inhibitor. The dexamphetamine-induced striatal dopamine efflux originates from both the reserpine-sensitive vesicular dopami

  3. Association between increased arterial-wall thickness and impairment in ABCA1-driven cholesterol efflux : an observational study

    NARCIS (Netherlands)

    van Dam, MJ; de Groot, E; Clee, SM; Hovingh, GK; Roelants, R; Brooks-Wilson, A; Zwinderman, AH; Smit, AJ; Smelt, A.H.; Groen, AK; Hayden, MR; Kastelein, JJP

    2002-01-01

    Background Decreased concentrations of HDL cholesterol are associated with increased cardiovascular risk. These concentrations are directly related to cholesterol efflux from cells-the first step and a key process in reverse cholesterol transport. Cholesterol efflux is mediated by the ATP-binding ca

  4. Soil CO2 efflux in an old-growth southern conifer forest (Agathis australis) - magnitude, components and controls

    Science.gov (United States)

    Schwendenmann, Luitgard; Macinnis-Ng, Cate

    2016-08-01

    Total soil CO2 efflux and its component fluxes, autotrophic and heterotrophic respiration, were measured in a native forest in northern Aotearoa-New Zealand. The forest is dominated by Agathis australis (kauri) and is on an acidic, clay rich soil. Soil CO2 efflux, volumetric soil water content and soil temperature were measured bi-weekly to monthly at 72 sampling points over 18 months. Trenching and regression analysis was used to partition total soil CO2 efflux into heterotrophic and autotrophic respiration. The effect of tree structure was investigated by calculating an index of local contribution (Ic, based on tree size and distance to the measurement location) followed by correlation analysis between Ic and total soil CO2 efflux, root biomass, litterfall and soil characteristics. The measured mean total soil CO2 efflux was 3.47 µmol m-2 s-1. Autotrophic respiration accounted for 25 % (trenching) or 28 % (regression analysis) of total soil CO2 efflux. Using uni- and bivariate models showed that soil temperature was a poor predictor of the temporal variation in total soil CO2 efflux (mineral soil CN ratio within 5-6 m of the sampling points. Using multiple regression analysis revealed that 97 % of the spatial variability in total soil CO2 efflux in this kauri-dominated stand was explained by root biomass and soil temperature. Our findings suggest that biotic factors such as tree structure should be investigated in soil carbon related studies.

  5. Air-Operated Sump Pump

    Science.gov (United States)

    Nolt, Gary D.

    1988-01-01

    Pump removes liquid seepage from small, restricted area and against large pressure head. Developed for moving small amounts of water and oil from sump pit 85 ft (25.91 m) deep. Fits in space only 6 1/2 in. (16.5 cm) in diameter and 18 in. (45.7 cm) long. In discharge part of pumping cycle, air forces liquid out of pump chamber through pipe. During filling part of pumping cycle, water enters pump chamber from sump pit. Float in chamber next to pump chamber controls pressurization through timer and solenoid valve.

  6. Noise through Quantum Pumps

    OpenAIRE

    Polianski, M. L.; Vavilov, M. G.; Brouwer, P.W.

    2002-01-01

    We study the current noise through an unbiased quantum electron pump and its mesoscopic fluctuations for arbitrary temperatures and beyond the bilinear response. In the bilinear regime, we find the full distributions of the noise power and the current-to-noise ratio for a chaotic quantum dots with single-channel and many-channel ballistic point contacts. For a dot with many-channel point contacts we also calculate the ensemble-averaged noise at arbitrary temperature and pumping strength. In t...

  7. Reactor coolant pump flywheel

    Science.gov (United States)

    Finegan, John Raymond; Kreke, Francis Joseph; Casamassa, John Joseph

    2013-11-26

    A flywheel for a pump, and in particular a flywheel having a number of high density segments for use in a nuclear reactor coolant pump. The flywheel includes an inner member and an outer member. A number of high density segments are provided between the inner and outer members. The high density segments may be formed from a tungsten based alloy. A preselected gap is provided between each of the number of high density segments. The gap accommodates thermal expansion of each of the number of segments and resists the hoop stress effect/keystoning of the segments.

  8. Heat pump planning handbook

    CERN Document Server

    Bonin, Jürgen

    2015-01-01

    The Heat Pump Planning Handbook contains practical information and guidance on the design, planning and selection of heat pump systems, allowing engineers, designers, architects and construction specialists to compare a number of different systems and options. Including detailed descriptions of components and their functions and reflecting the current state of technology this guide contains sample tasks and solutions as well as new model calculations and planning evaluations. Also economic factors and alternative energy sources are covered, which are essential at a time of rising heat costs. T

  9. Regenerative adsorbent heat pump

    Science.gov (United States)

    Jones, Jack A. (Inventor)

    1991-01-01

    A regenerative adsorbent heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system and at least a portion of the heat of adsorption. A series of at least four compressors containing an adsorbent is provided. A large amount of heat is transferred from compressor to compressor so that heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

  10. Aquaflo pump vs FMS 4 pump for shoulder arthroscopic surgery.

    OpenAIRE

    Ampat, G.; Bruguera, J.; Copeland, S A

    1997-01-01

    A prospective controlled trial was carried out to compare two different fluid delivery systems used for shoulder arthroscopy. One an advanced pump system that controls both pressure and flow of fluid delivered, the other an air-driven diaphragm pump that only controls fluid pressure. Blood loss, presence of bleeding vessels and visual clarity were parameters used to assess the pump systems. There was no difference between the pumps in straightforward shoulder procedures. However, complicated ...

  11. Seasonal dynamics of soil CO2 effluxes with responses to environmental factors in lower subtropical forests of China

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    <正>Seasonal metrics and environmental responses to forestry soil surface CO2 emission effluxes among three types of lower subtropical forests were consistently monitored over two years with static chamber-gas chromatograph techniques among three types of lower subtropical forests. Results showed that annual CO2 effluxes (S+L) reached 3942.20, 3422.36 and 2163.02 CO2 g·m-2·a-1, respectively in the monsoon evergreen broadleaf forest, mixed broadleaf-coniferous forest and coniferous forest. All the three types of forests revealed the same characteristics of seasonal changes with the CO2 effluxes peaking throughout June to August. During this peaking period, the effluxes were 35.9%, 38.1% and 40.2% of the total annual effluxes, respectively. The CO2 emission process responding to the environmental factors displayed significantly different patterns in forestry soils of the three types of forests. The coniferous forest (CF) was more sensitive to temperature than the other two types. The Q10 values were higher, along with greater seasonal variations of the CO2 efflux, indicating that the structurally unique forestry ecosystem has disadvantage against interferences. All the three types of forestry CO2 effluxes showed significant correlation with the soil temperature (Ts), soil water content (Ms) and air pressure (Pa). However, stepwise regression analysis indicated no significant correlation between air pressure and the soil CO2 efflux. With an empirical model to measure soil temperature and water content in 5 cm beneath the soil surface, the CO2 effluxes accounting for 75.7%, 77.8% and 86.5% of the efflux variability respectively in soils of BF, MF and PF were calculated. This model can be better used to evaluate the CO2 emission of soils under water stress and arid or semi-arid conditions.

  12. Radiofrequency radiation-induced calcium ion efflux enhancement from human and other neuroblastoma cells in culture.

    Science.gov (United States)

    Dutta, S K; Ghosh, B; Blackman, C F

    1989-01-01

    To test the generality of radiofrequency radiation-induced changes in 45Ca2+ efflux from avian and feline brain tissues, human neuroblastoma cells were exposed to electromagnetic radiation at 147 MHz, amplitude-modulated (AM) at 16 Hz, at specific absorption rates (SAR) of 0.1, 0.05, 0.01, 0.005, 0.001, and 0.0005 W/kg. Significant 45Ca2+ efflux was obtained at SAR values of 0.05 and 0.005 W/kg. Enhanced efflux at 0.05 W/kg peaked at the 13-16 Hz and at the 57.5-60 Hz modulation ranges. A Chinese hamster-mouse hybrid neuroblastoma was also shown to exhibit enhanced radiation-induced 45Ca2+ efflux at an SAR of 0.05 W/kg, using 147 MHz, AM at 16 Hz. These results confirm that amplitude-modulated radiofrequency radiation can induce responses in cells of nervous tissue origin from widely different animal species, including humans. The results are also consistent with the reports of similar findings in avian and feline brain tissues and indicate the general nature of the phenomenon. PMID:2540756

  13. The ABCG2 efflux transporter from rabbit placenta: Cloning and functional characterization.

    Science.gov (United States)

    Halwachs, Sandra; Kneuer, Carsten; Gohlsch, Katrin; Müller, Marian; Ritz, Vera; Honscha, Walther

    2016-02-01

    In human placenta, the ATP-binding cassette efflux transporter ABCG2 is highly expressed in syncytiotrophoblast cells and mediates cellular excretion of various drugs and toxins. Hence, physiological ABCG2 activity substantially contributes to the fetoprotective placenta barrier function during gestation. Developmental toxicity studies are often performed in rabbit. However, despite its toxicological relevance, there is no data so far on functional ABCG2 expression in this species. Therefore, we cloned ABCG2 from placenta tissues of chinchilla rabbit. Sequencing showed 84-86% amino acid sequence identity to the orthologues from man, rat and mouse. We transduced the rabbit ABCG2 clone (rbABCG2) in MDCKII cells and stable rbABCG2 gene and protein expression was shown by RT-PCR and Western blot analysis. The rbABCG2 efflux activity was demonstrated with the Hoechst H33342 assay using the specific ABCG2 inhibitor Ko143. We further tested the effect of established human ABCG2 (hABCG2) drug substrates including the antibiotic danofloxacin or the histamine H2-receptor antagonist cimetidine on H33342 accumulation in MDCKII-rbABCG2 or -hABCG2 cells. Human therapeutic plasma concentrations of all tested drugs caused a comparable competitive inhibition of H33342 excretion in both ABCG2 clones. Altogether, we first showed functional expression of the ABCG2 efflux transporter in rabbit placenta. Moreover, our data suggest a similar drug substrate spectrum of the rabbit and the human ABCG2 efflux transporter. PMID:26907376

  14. Efflux of hydraulically lifted water from mycorrhizal fungal hyphae during imposed drought

    Science.gov (United States)

    Querejeta, José Ignacio; Allen, Michael F

    2008-01-01

    Apart from improving plant and soil water status during drought, it has been suggested that hydraulic lift (HL) could enhance plant nutrient capture through the flow of mineral nutrients directly from the soil to plant roots, or by maintaining the functioning of mycorrhizal fungi. We evaluated the extent to which the diel cycle of water availability created by HL covaries with the efflux of HL water from the tips of extramatrical (external) mycorrhizal hyphae, and the possible effects on biogeochemical processes. Phenotypic mycorrhizal fungal variables, such as total and live hyphal lengths, were positively correlated with HL efflux from hyphae, soil water potential (dawn), and plant response variables (foliar 15N). The efflux of HL water from hyphae was also correlated with bacterial abundance and soil enzyme activity (P), and the moistening of soil organic matter. Such findings indicate that the efflux of HL water from the external mycorrhizal mycelia may be a complementary explanation for plant nutrient acquisition and survival during drought. PMID:19704776

  15. Mechanism of cAMP-induced H+ -efflux of Dictyostelium cells: a role for fatty acids

    Indian Academy of Sciences (India)

    H Flaadt; R Schaloske; D Malchow

    2000-09-01

    Aggregating Dictyostelium cells release protons when stimulated with cAMP. To find out whether the protons are generated by acidic vesicles or in the cytosol, we permeabilized the cells and found that this did not alter the cAMP-response. Proton efflux in intact cells was inhibited by preincubation with the V-type H+ ATPase inhibitor concanamycin A and with the plasma membrane H+ ATPase blocker miconazole. Surprisingly, miconazole also inhibited efflux in permeabilized cells, indicating that this type of H+ ATPase is present on intracellular vesicles as well. Vesicular acidification was inhibited by miconazole and by concanamycin A, suggesting that the acidic vesicles contain both V-type and P-type H+ ATPases. Moreover, concanamycin A and miconazole acted in concert, both in intact cells and in vesicles. The mechanism of cAMP-induced Ca2+-fluxes involves phospholipase A2 activity. Fatty acids circumvent the plasma membrane and stimulate vesicular Ca2+-efflux. Here we show that arachidonic acid elicited H+-efflux not only from intact cells but also from acidic vesicles. The target of regulation by arachidonic acid seemed to be the vesicular Ca2+-relase channel.

  16. Modeling of Cd Uptake and Efflux Kinetics in Metal-Resistant Bacterium Cupriavidus metallidurans

    NARCIS (Netherlands)

    Hajdu, R.; Pinheiro, J.P.; Galceran, J.; Slaveykova, V.I.

    2010-01-01

    The Model of Uptake with Instantaneous Adsorption and Efflux, MUIAE, describing and predicting the overall Cd uptake by the metal-resistant bacterium Cupriavidus metallidurans CH34, is presented. MUIAE takes into account different processes at the bacteria-medium interface with specific emphasis on

  17. Curcumin promotes cholesterol efflux from adipocytes related to PPARgamma-LXRalpha-ABCA1 passway.

    Science.gov (United States)

    Dong, Shao-zhuang; Zhao, Shui-ping; Wu, Zhi-hong; Yang, Jun; Xie, Xiang-zhu; Yu, Bi-lian; Nie, Sai

    2011-12-01

    Curcumin affects the functions of adipocytes. But it is not known whether curcumin has some effect on the cholesterol efflux process of adipocytes. Rabbit subcutaneous adipocytes were incubated with 5, 10 and 20 μg/ml curcumin for 24 h. The cholesterol efflux onto apoAI was assessed, and the peroxisome proliferators-activated receptor (PPAR) γ, liver X receptor (LXR) α and ATP-binding cassette transporter A1 (ABCA1) mRNA expression in adipocytes were quantified by reverse-transcription polymerase chain reaction (RT-PCR). Curcumin increased the cholesterol efflux from adipocytes in dose-dependent manner. The increased expression of PPARγ, LXRα and ABCA1 caused by curcumin were parallel. When the adipocytes were pre-treated by GW9662, the increased expression of PPARγ induced by curcumin was partially prevented, subsequent to the down-regulation of LXRα and ABCA1. Curcumin can affect the cholesterol efflux from adipocytes by regulating the PPARγ-LXR-ABCA1 passway.

  18. Winter carbon dioxide effluxes from Arctic ecosystems: An overview and comparison of methodologies

    DEFF Research Database (Denmark)

    Björkman, M.P.; Morgner, E.; Cooper, E.J.;

    2010-01-01

    The winter CO2 efflux from subnivean environments is an important component of annual C budgets in Arctic ecosystems and consequently makes prediction and estimations of winter processes as well as incorporations of these processes into existing models important. Several methods have been used fo...

  19. Comparison of surficial CO2 efflux to other measures of subsurface crude oil degradation

    Science.gov (United States)

    Warren, Ean; Sihota, Natasha J.; Hostettler, Frances D.; Bekins, Barbara A.

    2014-08-01

    At a spill site near Bemidji, Minnesota, crude oil at the water table has been undergoing anaerobic biodegradation for over 30 years. Previous work at this site has shown that methane produced from biodegradation of the oil migrates upward and is oxidized in a methanotrophic zone midway between the water table and the surface. To compare microbial activity measurement methods from multiple locations in the oil body, surficial carbon dioxide efflux, methanogen and methanotroph concentrations, and oil degradation state were collected. Carbon dioxide effluxes over the oil body averaged more than four times those at the background site. Methanotrophic bacteria concentrations measured using pmoA were over 105 times higher above the oil-contaminated sediments compared with the background site. Methanogenic archaea measured using mcrA ranged from 105 to over 107 in the oil and were below detection in the background. Methanogens correlated very well with methanotroph concentrations (r = 0.99), n-alkylcyclohexane losses as a proxy for degradation state (r = - 0.96), and somewhat less well with carbon dioxide efflux (r = 0.92). Carbon dioxide efflux similarly correlated to methanotroph concentrations (r = 0.90) and n-alkylcyclohexane losses (r = - 0.91).

  20. Piston for rod pumping

    Energy Technology Data Exchange (ETDEWEB)

    Pastushenko, G.I.

    1965-06-22

    A piston, or plunger, for rod pumping, is made up of a cylindrical housing with labryinthal seals, a nose piece, and a scraper. In order to remove paraffin from the inside surface of the production pipe, the housing is made in telescopic form. The scraper consists of an arrangement of springs installed on the outer surface of the housing.

  1. Pump Flow Analysis

    Science.gov (United States)

    1981-01-01

    Ingersoll-Rand Research, Inc.'s use of COSMIC's computer program MERIDL permits designers to evaluate performance and efficiency characteristics to be expected from the pump's impeller. It also provides information that enables a trained hydraulic engineer to make design improvements. Company was able to avoid the cost of developing new software and to improve some product design features.

  2. Microfluidic "blinking" bubble pump

    NARCIS (Netherlands)

    Yin, Zhizhong; Prosperetti, Andrea

    2005-01-01

    The paper reports data obtained on a simple micropump, suitable for electrolytes, based on the periodic growth and collapse of a single vapor bubble in a microchannel. With a channel diameter of the order of 100 µm, pumping rates of several tens of µl/min and pressure differences of several kPa are

  3. Optimization of compound gear pump

    Institute of Scientific and Technical Information of China (English)

    栾振辉

    2002-01-01

    This paper introduces the performances of compound gear pump. Based on the target of having the smallest mass per unit volume, the paper established a mathematical model of optimization, and obtained the results of optimization of the pump.

  4. Orbital Liquid Oxygen Pump Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposed work will develop a pump, which is based on two novel and unique design features. The first feature is a lobed pumping mechanism which operates with...

  5. Fuel Pumping System And Method

    Science.gov (United States)

    Shafer, Scott F.; Wang, Lifeng

    2005-12-13

    A fuel pumping system that includes a pump drive is provided. A first pumping element is operatively connected to the pump drive and is operable to generate a first flow of pressurized fuel. A second pumping element is operatively connected to the pump drive and is operable to generate a second flow of pressurized fuel. A first solenoid is operatively connected to the first pumping element and is operable to vary at least one of a fuel pressure and a fuel flow rate of the first flow of pressurized fuel. A second solenoid is operatively connected to the second pumping element and is operable to vary at least one of a fuel pressure and a fuel flow rate of the second flow of pressurized fuel.

  6. Oral and inhaled corticosteroids: Differences in P-glycoprotein (ABCB1) mediated efflux

    Energy Technology Data Exchange (ETDEWEB)

    Crowe, Andrew, E-mail: a.p.crowe@curtin.edu.au; Tan, Ai May

    2012-05-01

    There is concern that P-glycoprotein mediated efflux contributes to steroid resistance. Therefore, this study examined bidirectional corticosteroid transport and induction capabilities for P-glycoprotein (P-gp) to understand which of the systemic and inhaled corticosteroids interacted with P-gp to the greatest extent. Hydrocortisone, prednisolone, prednisone, methylprednisolone, and dexamethasone represented systemically active drugs, while fluticasone propionate, beclomethasone dipropionate, ciclesonide and budesonide represented inhaled corticosteroids. Aldosterone and fludrocortisone represented mineralocorticoids. All drugs were detected using individually optimised HPLC protocols. Transport studies were conducted through Caco-2 monolayers. Hydrocortisone and aldosterone had efflux ratios below 1.5, while prednisone showed a P-gp mediated efflux ratio of only 1.8 compared to its active drug, prednisolone, with an efflux ratio of 4.5. Dexamethasone and beclomethasone had efflux ratios of 2.1 and 3.3 respectively, while this increased to 5.1 for methylprednisolone. Fluticasone showed an efflux ratio of 2.3. Protein expression studies suggested that all of the inhaled corticosteroids were able to induce P-gp expression, from 1.6 to 2 times control levels. Most of the systemic corticosteroids had higher passive permeability (> 20 × 10{sup −6} cm/s) compared to the inhaled corticosteroids (> 5 × 10{sup −6} cm/s), except for budesonide, with permeability similar to the systemic corticosteroids. Inhaled corticosteroids are not transported by P-gp to the same extent as systemic corticosteroids. However, they are able to induce P-gp production. Thus, inhaled corticosteroids may have greater interactions with other P-gp substrates, but P-gp itself is less likely to influence resistance to the drugs. -- Highlights: ► Inhaled corticosteroids are only weak substrates for P-gp, including budesonide. ► Inhaled corticosteroid potent P-gp inducers especially

  7. Amino acid efflux in the isolated perfused rat pancreas: trans-stimulation by extracellular amino acids.

    Science.gov (United States)

    Mann, G E; Norman, P S; Smith, I C

    1989-01-01

    1. Epithelial uptake and efflux of the non-metabolized system A analogue 2-methylaminoisobutyric acid (MeAIB) and L-serine were studied in the isolated perfused rat pancreas using a dual tracer loading and wash-out technique. Uptakes of 2-[14C]MeAIB and L-[3H]serine were measured relative to D-[3H or 14C]mannitol (extracellular tracer) during a 20 min cell loading period. Maximal uptake for MeAIB (34 +/- 2%, n = 6) occurred within 2-3 min and decreased to 14 +/- 2% after 20 min tracer loading. Uptake for L-serine reached a maximum (62 +/- 4%, n = 7) within 1 min and decreased to 19 +/- 2% after 20 min tracer loading. 2. When tracer wash-out was monitored during subsequent perfusion of the preloaded pancreas with an isotope-free solution, D-mannitol predominantly cleared from a fast exchanging compartment (0.54 +/- 0.05 ml g-1, n = 9) with a time constant (Tfast) of 0.68 +/- 0.04 min. Although MeAIB and L-serine exhibited similar fast phases of wash-out, a much larger efflux occurred from a slowly exchanging pool with respective time constants (Tslow) of 15.47 +/- 0.45 min (n = 6) and 5.98 +/- 0.46 min (n = 7). 3. A rapid vascular challenge of the pancreas with 100 mM-L-serine transiently accelerated cellular efflux of 2-[14C]MeAIB and L-[3H]serine without affecting wash-out of D-[14C]mannitol. Tracer efflux following cell loading with 2-[14C]MeAIB or L-[3H]serine was not stimulated by a challenge with 100 mM-MeAIB. 4. The time course of amino acid evoked 2-[14C]MeAIB and L-[3H]serine efflux paralleled the extracellular dilution profile of a vascular stimulus, suggesting that the acceleration of efflux was due to trans-stimulation. 5. Trans-stimulation of 2-[14C]MeAIB and L-[3H]serine efflux by a further twenty-two naturally occurring and three synthetic amino acids was then examined. L-Proline, N-methyl-DL-alanine, L-lysine and D-lysine selectively stimulated MeAIB efflux. Efflux of both tracer amino acids was accelerated by aminoisobutyric acid (AIB), L-serine, L

  8. Blood Pump Bearing System

    Science.gov (United States)

    Aber, Gregory S. (Inventor)

    2000-01-01

    An apparatus is provided for a blood pump bearing system within a pump housing to support long-term highspeed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the Ir shaft to support big speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

  9. Absorption heat pumps

    Science.gov (United States)

    Huhtinen, M.; Heikkilae, M.; Andersson, R.

    1987-03-01

    The aim of the study was to analyze the technical and economic feasibility of absorption heat pumps in Finland. The work was done as a case study: the technical and economic analyses have been carried out for six different cases, where in each the suitable size and type of the heat pump plant and the auxiliary components and connections were specified. The study also detailed the costs concerning the procurement, installation and test runs of the machinery, as well as the savings in energy costs incurred by the introduction of the plant. Conclusions were drawn of the economic viability of the applications studied. The following cases were analyzed: heat recovery from flue gases and productin of district heat in plants using peat, natural gas, and municipal wastes as a fuel. Heat recovery in the pulp and paper industry for the upgrading of pressure of secondary steam and for the heating of white liquor and combustion and drying the air. Heat recovery in a peat-fulled heat and power plant from flue gases that have been used for the drying of peat. According to the study, the absorption heat pump suits best to the production of district heat, when the heat source is the primary energy is steam produced by the boiler. Included in the flue as condensing is the purification of flue gases. Accordingly, benefit is gained on two levels in thick applications. In heat and power plants the use of absorption heat pumps is less economical, due to the fact that the steam used by the pump reduces the production of electricity, which is rated clearly higher than heat.

  10. Proof of concept for a novel functional screening system for plant sucrose effluxers

    Directory of Open Access Journals (Sweden)

    Yuchan Zhou

    2014-07-01

    Full Text Available Membrane transporters play pivotal roles in facilitating sucrose transport in plants and their activities have been shown to impact plant growth rates and crop yield.  In contrast to the well-defined mechanism of sucrose influx across plasma membranes, less is known about sucrose efflux mechanisms and the membrane proteins supporting this function.  A major impediment blocking progress in this key area of plant science is the absence of a functional screening system for genes encoding sucrose effluxers.  Here we report a novel yeast system for screening sucrose effluxers based on sucrose release from yeast cells genetically modified to synthesize, but not to metabolize, sucrose.  Inhibiting sucrose metabolism was achieved using yeast strains, SEY 6210 and YSL4-6, carrying mutations in genes encoding invertase and maltase, respectively.  Genes encoding essential components of sucrose biosynthesis, sucrose phosphate synthase (SPS and sucrose phosphate phosphatase (SPP, were used to transform the two yeast hosts to make strains SuPy (from SEY6210 and Ysu (from YSL4-6.  Cultures of SuPy15 cells were found to be capable of synthesizing sucrose when supplied with various compounds as the sole carbon source, including non-fermentable sugars and non-sugar substrates.  A proof of concept of the screening system was demonstrated by transforming SuPy15 with sucrose transporter genes known to encode plasma membrane proteins that mediate sucrose efflux.  The robustness of the yeast SuPy15 system as a novel platform to screen putative plant sucrose effluxers is discussed.

  11. Getting Pumped About Heart Failure

    OpenAIRE

    Mann, Douglas L.

    2014-01-01

    Heart failure is a clinical syndrome caused by dysregulated calcium handling and abnormal cardiac pumping capacity. Whalquist et al. (2014) show that upregulation of micro-RNA25 impairs calcium handling leading to pump dysfunction, and that targeting micro-RNA25 using antisense oligonucleotides reverses pump dysfunction and improves survival in mice with heart failure.

  12. VIRTUAL FUEL-PUMP DESIGN

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Some concepts of virtual product are discussed. The key technologies of virtual fuel-pump development are in detail analysed, which include virtual fuel-pump product modeling, intelligent simulation, distributed design environment, and virtual assembly. The virtual fuel-pump development prototype system considers requirement analysis, concept design, injection preferment analysis, detailed design, and assembly analysis.

  13. Small Scroll Pump for Cryogenic Liquids Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The innovation is a compact, reliable, light weight, electrically driven pump capable of pumping cryogenic liquids, based on scroll pump technology. This pump will...

  14. Improving pumping system efficiency at coal plants

    Energy Technology Data Exchange (ETDEWEB)

    Livoti, W.C.; McCandless, S.; Poltorak, R. [Baldor Electric Co. (United States)

    2009-03-15

    The industry must employ ultramodern technologies when building or upgrading power plant pumping systems thereby using fuels more efficiently. The article discusses the uses and efficiencies of positive displacement pumps, centrifugal pumps and multiple screw pumps. 1 ref., 4 figs.

  15. Pumping characteristics of roots blower pumps for light element gases

    International Nuclear Information System (INIS)

    The pumping speed and compression ratio of the two-stage roots blower pumping system were measured for light element gases (H2, D2 and He) and for N2, in order to assess validity of the ITER torus roughing system as an ITER R and D task (T234). The pumping system of an Edwards EH1200 (nominal pumping speed of 1200 m3/s), two EH250s (ibid. 250 m3/s) and a backing pump (ibid. 100 m3/s) in series connection was tested under PNEUROP standards. The maximum pumping speeds of the two-stage system for D2 and N2 were 1200 and 1300 m3/h, respectively at 60 Hz, which satisfied the nominal pumping speed. These experimental data support the design validity of the ITER torus roughing system. (author)

  16. Effects of Atmospheric CO2 Enrichment on Soil CO2 Efflux in a Young Longleaf Pine System

    Directory of Open Access Journals (Sweden)

    G. Brett Runion

    2012-01-01

    Full Text Available The southeastern landscape is composed of agricultural and forest systems that can store carbon (C in standing biomass and soil. Research is needed to quantify the effects of elevated atmospheric carbon dioxide (CO2 on terrestrial C dynamics including CO2 release back to the atmosphere and soil sequestration. Longleaf pine savannahs are an ecologically and economically important, yet understudied, component of the southeastern landscape. We investigated the effects of ambient and elevated CO2 on soil CO2 efflux in a young longleaf pine system using a continuous monitoring system. A significant increase (26.5% in soil CO2 efflux across 90 days was observed under elevated CO2; this occurred for all weekly and daily averages except for two days when soil temperature was the lowest. Soil CO2 efflux was positively correlated with soil temperature with a trend towards increased efflux response to temperature under elevated CO2. Efflux was negatively correlated with soil moisture and was best represented using a quadratic relationship. Soil CO2 efflux was not correlated with root biomass. Our data indicate that, while elevated CO2 will increase feedback of CO2 to the atmosphere via soil efflux, terrestrial ecosystems will remain potential sinks for atmospheric CO2 due to greater biomass production and increased soil C sequestration.

  17. Can citrate efflux from roots improve phosphorus uptake by plants? Testing the hypothesis with near-isogenic lines of wheat.

    Science.gov (United States)

    Ryan, Peter R; James, Richard A; Weligama, Chandrakumara; Delhaize, Emmanuel; Rattey, Allan; Lewis, David C; Bovill, William D; McDonald, Glenn; Rathjen, Tina M; Wang, Enli; Fettell, Neil A; Richardson, Alan E

    2014-07-01

    Phosphorus (P) deficiency in some plant species triggers the release of organic anions such as citrate and malate from roots. These anions are widely suggested to enhance the availability of phosphate for plant uptake by mobilizing sparingly-soluble forms in the soil. Carazinho is an old wheat (Triticum aestivum) cultivar from Brazil, which secretes citrate constitutively from its root apices, and here we show that it also produces relatively more biomass on soils with low P availability than two recent Australian cultivars that lack citrate efflux. To test whether citrate efflux explains this phenotype, we generated two sets of near-isogenic lines that differ in citrate efflux and compared their biomass production in different soil types and with different P treatments in glasshouse experiments and field trials. Citrate efflux improved relative biomass production in two of six glasshouse trials but only at the lowest P treatments where growth was most severely limited by P availability. Furthermore, citrate efflux provided no consistent advantage for biomass production or yield in multiple field trials. Theoretical modeling indicates that the effectiveness of citrate efflux in mobilizing soil P is greater as the volume of soil into which it diffuses increases. As efflux from these wheat plants is restricted to the root apices, the potential for citrate to mobilize sufficient P to increase shoot biomass may be limited. We conclude that Carazinho has other attributes that contribute to its comparatively good performance in low-P soils.

  18. SHINE Vacuum Pump Test Verification

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, Gregg A; Peters, Brent

    2013-09-30

    Normetex pumps used world-wide for tritium service are no longer available. DOE and other researchers worldwide have spent significant funds characterizing this pump. Identification of alternate pumps is required for performance and compatibility with tritium gas. Many of the pumps that could be used to meet the functional performance requirements (e.g. pressure and flow conditions) of the Normetex pump have features that include the use of polymers or oils and greases that are not directly compatible with tritium service. This study assembles a test system to determine the flow characteristics for candidate alternate pumps. These tests are critical to the movement of tritium through the SHINE Tritium Purification System (TPS). The purpose of the pump testing is two-fold: (1) obtain baseline vacuum pump characteristics for an alternate (i.e. ''Normetex replacement'') pump intended for use in tritium service; and (2) verify that low pressure hydrogen gas can be transported over distances up to 300 feet by the candidate pumps. Flow rates and nominal system pressures have been identified for the SHINE Mo-99 production process Tritium Purification System (TPS). To minimize the line sizes for the transfer of low pressure tritium from the Neutron Driver Accelerator System (NDAS) to the primary processing systems in the TPS, a ''booster'' pump has been located near the accelerator in the design. A series of pump tests were performed at various configurations using hydrogen gas (no tritium) to ensure that this concept is practical and maintains adequate flow rates and required pressures. This report summarizes the results of the tests that have been performed using various pump configurations. The current design of the Tritium Purification System requires the ''booster'' pump to discharge to or to be backed by another vacuum pump. Since Normetex pumps are no longer manufactured, a commercially available Edwards

  19. VIBRATION ANALYSIS IN OVERHUNG PUMP

    OpenAIRE

    Neelendra Pratap Singh*, Prateek Gupta, Siddharth Agnihotri

    2016-01-01

    In the present scenario, Energy demand is increasing day by day. To meet that demand, the production or extraction of crude oil, natural gas and other energy resources is done with the help of various pumps. Pumps are the second largest used machinery in world and plays a vital role. In this paper, we have done analysis on centrifugal pump categorised as overhung pump (OH2). It is commonly known that vibration problems on centrifugal pumps can result from multitude of possible parameters whic...

  20. Advanced heat pump cycle

    Energy Technology Data Exchange (ETDEWEB)

    Groll, E.A.; Radermacher, R.

    1993-07-01

    The desorption and absorption process of a vapor compression heat pump with a solution circuit (VCHSC) proceeds at gliding temperature intervals, which can be adjusted over a wide range. In case that the gliding temperature intervals in the desorber and the absorber overlap, a modification of the VCHSC employing a desorber/absorber heat exchange (DAHX) can be introduced, which results in an extreme reduction of the pressure ratio. Although the DAHX-cycle has features of a two-stage cycle, it still requires only one solution pump, one separator and one compressor. Such a cycle for the working pair ammonia/water is built in the Energy Laboratory of the Center for Environmental Energy Engineering at the University of Maryland. The experimental results obtained with the research plant are discussed and compared to those calculated with a simulation program. The possible temperature lift between heat source and heat sink depending on the achievable COP are presented.

  1. Solar-powered pump

    Science.gov (United States)

    Kirsten, C. C. (Inventor)

    1976-01-01

    A solar powered pump particularly suited for intermittently delivering a stream of water is reported. The pump is characterized by a housing adapted to be seated in a source of water having a water discharge port disposed above the water line of the source, a sump including a valved inlet port through which water is introduced to the sump, disposed beneath the water line, a displacer supported for vertical reciprocation in said housing, an air passageway extended between the vertically spaced faces of the displacer, and a tipple disposed adjacent to the water discharge port adapted to be filled in response to a discharge of water from the housing. Air above a displacer is expanded in response to solar energy impinging on the housing and transferred into pressurizing relation with the sump for forcing water from the sump.

  2. Water displacement mercury pump

    Science.gov (United States)

    Nielsen, Marshall G.

    1985-01-01

    A water displacement mercury pump has a fluid inlet conduit and diffuser, a valve, a pressure cannister, and a fluid outlet conduit. The valve has a valve head which seats in an opening in the cannister. The entire assembly is readily insertable into a process vessel which produces mercury as a product. As the mercury settles, it flows into the opening in the cannister displacing lighter material. When the valve is in a closed position, the pressure cannister is sealed except for the fluid inlet conduit and the fluid outlet conduit. Introduction of a lighter fluid into the cannister will act to displace a heavier fluid from the cannister via the fluid outlet conduit. The entire pump assembly penetrates only a top wall of the process vessel, and not the sides or the bottom wall of the process vessel. This insures a leak-proof environment and is especially suitable for processing of hazardous materials.

  3. Sucker rod pump

    Energy Technology Data Exchange (ETDEWEB)

    Brewer, J.R.

    1992-04-14

    This patent describes a subsurface well pump, it comprises: a working barrel; a plunger which reciprocates along the vertical axis within the working barrel between an upper and lower position; a rod connected to the plunger and extending to a means for providing reciprocating force; a well string extending from the top of the working barrel to the surface; an outlet check valve which permits flow to exit the working barrel into the well string and does not permit flow to exit the well string into the working barrel; and an inlet check valve which permits flow into the working barrel from outside of the subsurface pump, the inlet check valve being above the top position of the plunger, the inlet check valve having a cross sectional flow area about equal to or greater than the horizontal cross sectional area of the working barrel, and the inlet check valve being a hinged flapper valve.

  4. Pocket pumped image analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kotov, I.V., E-mail: kotov@bnl.gov [Brookhaven National Laboratory, Upton, NY 11973 (United States); O' Connor, P. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Murray, N. [Centre for Electronic Imaging, Open University, Milton Keynes, MK7 6AA (United Kingdom)

    2015-07-01

    The pocket pumping technique is used to detect small electron trap sites. These traps, if present, degrade CCD charge transfer efficiency. To reveal traps in the active area, a CCD is illuminated with a flat field and, before image is read out, accumulated charges are moved back and forth number of times in parallel direction. As charges are moved over a trap, an electron is removed from the original pocket and re-emitted in the following pocket. As process repeats one pocket gets depleted and the neighboring pocket gets excess of charges. As a result a “dipole” signal appears on the otherwise flat background level. The amplitude of the dipole signal depends on the trap pumping efficiency. This paper is focused on trap identification technique and particularly on new methods developed for this purpose. The sensor with bad segments was deliberately chosen for algorithms development and to demonstrate sensitivity and power of new methods in uncovering sensor defects.

  5. Nonazeotropic Heat Pump

    Science.gov (United States)

    Ealker, David H.; Deming, Glenn

    1991-01-01

    Heat pump collects heat from water circulating in heat-rejection loop, raises temperature of collected heat, and transfers collected heat to water in separate pipe. Includes sealed motor/compressor with cooling coils, evaporator, and condenser, all mounted in outer housing. Gradients of temperature in evaporator and condenser increase heat-transfer efficiency of vapor-compression cycle. Intended to recover relatively-low-temperature waste heat and use it to make hot water.

  6. Effect of sterol carrier protein-2 gene ablation on HDL-mediated cholesterol efflux from cultured primary mouse hepatocytes

    OpenAIRE

    Storey, Stephen M.; Atshaves, Barbara P.; McIntosh, Avery L.; Kerstin K. Landrock; Martin, Gregory G.; Huang, Huan; Ross Payne, H.; Johnson, Jeffery D.; Macfarlane, Ronald D.; Kier, Ann B.; Schroeder, Friedhelm

    2010-01-01

    Although HDL-mediated cholesterol transport to the liver is well studied, cholesterol efflux from hepatocytes back to HDL is less well understood. Real-time imaging of efflux of 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-amino)-23,24-bisnor-5-cholen-3β-ol (NBD-cholesterol), which is poorly esterified, and [3H]cholesterol, which is extensively esterified, from cultured primary hepatocytes of wild-type and sterol carrier protein-2 (SCP-2) gene-ablated mice showed that 1) NBD-cholesterol efflux w...

  7. Stirling Engine Heat Pump

    Science.gov (United States)

    Kagawa, Noboru

    Recent advances in the feasibility studies related to the Stirling engines and Stirling engine heat pumps which have been considered attractive due to their promising role in helping to solve the global environmental and energy problems,are reviewed. This article begins to describe the brief history of the Stirling engines and theoretical thermodynamic analysis of the Stirling cycle in order to understand several advantages on the Stirling engine. Furthermore,they could throw light on our question why the dream engines had not been promoted to practical applications during two hundred years. The present review shows that the Stirling engines with several unique advantages including 30 to 40% thermal efficiency and preferable exhaust characteristics,had been designed and constructed by recent tackling for the development of the advanced automobile and other applications using them. Based on the current state of art,it is being provided to push the Stirling engines combined with heat pumps based on the reversed Rankine cycle to the market. At present,however, many problems, especially for the durability, cost, and delicate engine parts must be enforced to solve. In addition,there are some possibilities which can increase the attractiveness of the Stirling engines and heat pumps. The review closes with suggestions for further research.

  8. Electrocentrifugal pumping; Bombeo electrocentrifugo

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Perez, Guillermo; Medellin Otero, Hector [Instituto Mexicano del Peroleo (Mexico)

    1996-07-01

    The exploitation of isolated oil deposits, in losing their own energy, enter a phase of secondary recovery. One of the technologies of new development in Mexico is the one of electrocentrifugal pumping , which consists of introducing the motor-pump as an integral part of the production pipe down to the well bottom and pumping directly up to central complexes, from where it is sent inland. In the present paper is intended to explain what this type of secondary recovery consists of. [Spanish] La explotacion de yacimientos aislados de petroleo, al perder su energia propia, entran en una fase de recuperacion secundaria. Una de las tecnologias de nuevo desarrollo en Mexico es la de bombeo electrocentrifugo, la cual consiste en introducir la motobomba como parte integral de la tuberia de produccion hasta el fondo del pozo y bombearlo directamente hasta los complejos centrales, de donde se envia a tierra. En el presente trabajo se pretende explicar en que consiste este tipo de recuperacion secundaria.

  9. Pumping potential wells

    Science.gov (United States)

    Hershkowitz, N.; Forest, C.; Wang, E. Y.; Intrator, T.

    1987-01-01

    Nonmonotonic plasma potential structures are a common feature of many double layers and sheaths. Steady state plasma potential wells separating regions having different plasma potentials are often found in laboratory experiments. In order to exist, such structures all must find a solution to a common problem. Ions created by charge exchange or ionization in the region of the potential well are electrostatically confined and tend to accumulate and fill up the potential well. The increase in positive charge should eliminate the well. Nevertheless, steady state structures are found in which the wells do not fill up. This means that it is important to take into account processes which 'pump' ions from the well. As examples of ion pumping of plasma wells, potential dips in front of a positively biased electro collecting anode in a relatively cold, low density multidipole plasma is considered. Pumping is provided by ion leaks from the edges of the potential dip or by oscillating the applied potential. In the former case the two dimensional character of the problem is shown to be important.

  10. A Magnetically Coupled Cryogenic Pump

    Science.gov (United States)

    Hatfield, Walter; Jumper, Kevin

    2011-01-01

    Historically, cryogenic pumps used for propellant loading at Kennedy Space Center (KSC) and other NASA Centers have a bellows mechanical seal and oil bath ball bearings, both of which can be problematic and require high maintenance. Because of the extremely low temperatures, the mechanical seals are made of special materials and design, have wearing surfaces, are subject to improper installation, and commonly are a potential leak path. The ball bearings are non-precision bearings [ABEC-1 (Annular Bearing Engineering Council)] and are lubricated using LOX compatible oil. This oil is compatible with the propellant to prevent explosions, but does not have good lubricating properties. Due to the poor lubricity, it has been a goal of the KSC cryogenics community for the last 15 years to develop a magnetically coupled pump, which would eliminate these two potential issues. A number of projects have been attempted, but none of the pumps was a success. An off-the-shelf magnetically coupled pump (typically used with corrosive fluids) was procured that has been used for hypergolic service at KSC. The KSC Cryogenics Test Lab (CTL) operated the pump in cryogenic LN2 as received to determine a baseline for modifications required. The pump bushing, bearings, and thrust rings failed, and the pump would not flow liquid (this is a typical failure mode that was experienced in the previous attempts). Using the knowledge gained over the years designing and building cryogenic pumps, the CTL determined alternative materials that would be suitable for use under the pump design conditions. The CTL procured alternative materials for the bearings (bronze, aluminum bronze, and glass filled PTFE) and machined new bearing bushings, sleeves, and thrust rings. The designed clearances among the bushings, sleeves, thrust rings, case, and case cover were altered once again using experience gained from previous cryogenic pump rebuilds and designs. The alternative material parts were assembled into

  11. Soil CO2 efflux of a larch forest in northern Japan

    Directory of Open Access Journals (Sweden)

    Y. Fujinuma

    2010-11-01

    Full Text Available We had continuously measured soil CO2 efflux (Rs in a larch forest in northern Japan at hourly intervals for the snow-free period in 2003 with an automated chamber system and partitioned Rs into heterotrophic respiration (Rh and autotrophic respiration (Rr by using the trench method. In addition, we applied the soil CO2 concentration gradients method to continuously measure soil CO2 profiles under snowpack in the snowy period and to partition Rs into topsoil (Oa and A horizons CO2 efflux (Ft with a depth of 0.13 m and sub-soil (C horizon CO2 efflux (Fc. We found that soil CO2 effluxes were strongly affected by the seasonal variation of soil temperature but weakly correlated with soil moisture, probably because the volumetric soil moisture (30–40% at 95% confidence interval was within a plateau region for root and microbial activities. The soil CO2 effluxes changed seasonally in parallel with soil temperature in topsoil with the peak in late summer. On the other hand, the contribution of Rr to Rs was the largest at about 50% in early summer, when canopy photosynthesis and plant growth were more active. The temperature sensitivity (Q10 of Rr peaked in June. Under snowpack, Rs was stable until mid-March and then gradually increased with snow melting. Rs summed up to 79 gC m−2 during the snowy season for 4 months. The annual Rs was determined at 934 gC m−2 y−1 in 2003, which accounted for 63% of ecosystem respiration. The annual contributions of Rh and Rs to Rs were 57% and 43%, respectively. Based on the gradient approach, Rs was partitioned vertically into litter (Oi and Oe horizons with a depth of 0.01–0.02 m, topsoil and sub-soil respirations with proportions of 6, 72 and 22%, respectively, on an annual basis. The vertical distribution of CO2 efflux was consistent with those of soil carbon and root biomass.

  12. PUMPED LASER SYSTEM USING FEEDBACK TO PUMP MEANS

    DEFF Research Database (Denmark)

    2008-01-01

    A laser system according to the invention comprises pump generating means (xO2, xO3) for generating at least a first and a second, preferably focused, pump beam, and lasing means (xO6, xO7) for emitting radiation by being appropriately pumped. The lasing means (xO6, xO7) is disposed in a first...... resonator so as to receive the first pump beam in order to generate a first beam (x21) having a first frequency, and the lasing means (xO6, xO7) is disposed in a second resonator so as to receive the second pump beam in order to generate a second beam (x22) having a second frequency. At least one Q...... fed back to a regulation system (x14), said regulation system (x14) controlling said pump generating means (xO2, xO3)....

  13. Experimental Study on Series Operation of Sliding Vane Pump and Centrifugal Pump

    OpenAIRE

    Tao Li; Weiming Zhang; Ming Jiang; Zhengyang Li

    2013-01-01

    A platform for sliding vane pump and centrifugal pump tests is installed to study the series operation of them under different characteristics of pipeline. Firstly, the sliding vane pump and the centrifugal pump work independently, and the performance is recorded. Then, the two types of pumps are combined together, with the sliding vane pump acting as the feeding pump. Comparison is made between the performance of the independently working pump and the performance of series operation pump. Re...

  14. Supercritical waste oxidation pump investigation

    International Nuclear Information System (INIS)

    This report investigates the pumping techniques and pumping equipment that would be appropriate for a 5,000 gallon per day supercritical water oxidation waste disposal facility. The pumps must boost water, waste, and additives from atmospheric pressure to approximately 27.6 MPa (4,000 psia). The required flow ranges from 10 gpm to less than 0.1 gpm. For the higher flows, many commercial piston pumps are available. These pumps have packing and check-valves that will require periodic maintenance; probably at 2 to 6 month intervals. Several commercial diaphragm pumps were also discovered that could pump the higher flow rates. Diaphragm pumps have the advantage of not requiring dynamic seals. For the lower flows associated with the waste and additive materials, commercial diaphragm pumps. are available. Difficult to pump materials that are sticky, radioactive, or contain solids, could be injected with an accumulator using an inert gas as the driving mechanism. The information presented in this report serves as a spring board for trade studies and the development of equipment specifications

  15. Supercritical waste oxidation pump investigation

    Energy Technology Data Exchange (ETDEWEB)

    Thurston, G.; Garcia, K.

    1993-02-01

    This report investigates the pumping techniques and pumping equipment that would be appropriate for a 5,000 gallon per day supercritical water oxidation waste disposal facility. The pumps must boost water, waste, and additives from atmospheric pressure to approximately 27.6 MPa (4,000 psia). The required flow ranges from 10 gpm to less than 0.1 gpm. For the higher flows, many commercial piston pumps are available. These pumps have packing and check-valves that will require periodic maintenance; probably at 2 to 6 month intervals. Several commercial diaphragm pumps were also discovered that could pump the higher flow rates. Diaphragm pumps have the advantage of not requiring dynamic seals. For the lower flows associated with the waste and additive materials, commercial diaphragm pumps. are available. Difficult to pump materials that are sticky, radioactive, or contain solids, could be injected with an accumulator using an inert gas as the driving mechanism. The information presented in this report serves as a spring board for trade studies and the development of equipment specifications.

  16. RP-200: Design of PD pump for pumping of molasses

    OpenAIRE

    Skåtun, Kim

    2008-01-01

    Abstract Motivation There is, at the present time, no submerged molasses pump on the market that is designed specifically for cargo tankers. Due to this I, find it interesting to look into the possibilities of installing a molasses pump in cargo tankers to transport molasses instead of transporting molasses in containers as it is done today. It is challenging to come up with a new product, and the motivation of actual be able to release a pump for the international marked is indescribable...

  17. Comparative Molecular Docking Studies with ABCC1 and Aquaporin 9 in the Arsenite Complex Efflux

    Science.gov (United States)

    Poojan, Shiv; Dhasmana, Anupam; Jamal, Qazi Mohammad Sajid; Haneef, Mohd; Lohani, Mohtashim

    2014-01-01

    Arsenic is the most toxic metalloid present in the natural environment in both organic and inorganic arsenic forms. Inorganic arsenic is often more hazardous than the organic form. Arsenite and arsenate compounds are the major inorganic forms which are toxic causing severe human health dysfunction including cancer. Excretion of arsenic from the system is found elusive. Therefore, it is of interest to screen channel proteins with the arsenic complex in the different combination of arsenic, GSH (glutathione) and arsenic, selenium using docking methods. The mode of arsenic removal. The complex structure revealed the mode of arsenic binding efficiency with the receptor aquaporine 9 and ABCC1 channel protein. This provides insights to understand the mechanism of arsenic efflux. These inferences find application in the design, identification and development of novel nutracetucal or any other formulation useful in the balance of arsenic efflux. PMID:25258480

  18. Comparative Molecular Docking Studies with ABCC1 and Aquaporin 9 in the Arsenite Complex Efflux.

    Science.gov (United States)

    Poojan, Shiv; Dhasmana, Anupam; Jamal, Qazi Mohammad Sajid; Haneef, Mohd; Lohani, Mohtashim

    2014-01-01

    Arsenic is the most toxic metalloid present in the natural environment in both organic and inorganic arsenic forms. Inorganic arsenic is often more hazardous than the organic form. Arsenite and arsenate compounds are the major inorganic forms which are toxic causing severe human health dysfunction including cancer. Excretion of arsenic from the system is found elusive. Therefore, it is of interest to screen channel proteins with the arsenic complex in the different combination of arsenic, GSH (glutathione) and arsenic, selenium using docking methods. The mode of arsenic removal. The complex structure revealed the mode of arsenic binding efficiency with the receptor aquaporine 9 and ABCC1 channel protein. This provides insights to understand the mechanism of arsenic efflux. These inferences find application in the design, identification and development of novel nutracetucal or any other formulation useful in the balance of arsenic efflux.

  19. Presence of an Active Efflux System in the Fluoroquinolones Resistance of Mycoplasma Hominis

    Institute of Scientific and Technical Information of China (English)

    姚艳冰; 吴移谋; 朱翠明; 曾铁兵; 曾焱华

    2003-01-01

    Objective: To investigate the possible presence of an active efflux system in resistance to fluoroqninolones in Mycoplasma hominis. Methods: The resistant strains of M. hominis were selected from one hundred and three clinical strains of M. homlnls by broth microdilution method. The ac-cumulation of ciprofloxacin in M. hominis and the in-fluence of carbonyl cyanide m-chlorophenyl- hydrazone (CCCP) and reserpine were measured by a fluores-cence method. Results: Two resistant strains and two susceptible strains of M. hominis were selected in vitro. The accu-mulation of ciprofloxacin for resistant strains is lower than that of susceptible strains. CCCP and reserpine had different influence on clinical strains of M.hominis. Reserpine could dramatically increase the accumulation of ciprofloxacin, however CCCP had a little effect on it. Conclusion: These results suggest that the pres-ence of an active efflux system implicated in the fluoroouinolones-resistant in M. hominis.

  20. Critical conditions during unsteady efflux of two-phase medium following the pipeline break

    International Nuclear Information System (INIS)

    Unsteady efflux of two-phase medium following the pipeline break has been studied. The experiments with saturated and underheated water at the pressure of 32 bar were carried out on the pipe with 102.3 mm diameter and 3 m length. The liquid underheating, reaching 14 deg C under the experimental conditions and parameter variation dynamics have been analyzed. A comparison with the quasi-stationary methods is given. The theoretical analysis of the unsteady efflux is made on the basis of the two-phase homogeneous equilibrium model. Numerical solution of the difference equations has been made along the characteristic directions by the Godynov layer method. The comparison of the calculated and experimental results gives a satisfactory agreement during the main unsealing period

  1. Sediment CO2 efflux from cleared and intact temperate mangrove and tidal flat habitat

    Science.gov (United States)

    Bulmer, Richard; Lundquist, Carolyn; Schwendenmann, Luitgard

    2015-04-01

    Temperate mangroves in Southern Australia and New Zealand have been increasing in extent over the past 50 years, whereas tropical mangroves have declined by 30-50% over a similar time frame to support development of aquaculture, land development and timber production. Tropical mangroves are understood to be an important carbon sink and carbon emissions following clearance are estimated to be significant; comparable or greater than clearance of many terrestrial forest systems. As temperate mangrove clearance is proposed and has already occurred at some locations, it is important to determine potential carbon emissions from temperate mangroves, as well as exploring the factors which may influence emission rates. Here, we investigated the impact of temperate mangrove clearance on CO2 efflux from the sediment to the atmosphere along with a range of other biotic and abiotic factors. Higher CO2 efflux rates were observed within cleared (1.34

  2. The Slow Flow Model of Dust Efflux in Local Star-Forming Galaxies

    CERN Document Server

    Zahid, H Jabran; Kudritzki, Rolf; Kewley, Lisa; Dave, Romeel; Geller, Margaret

    2013-01-01

    We develop a dust efflux model of radiation pressure acting on dust grains which successfully reproduces the relation between stellar mass, dust opacity and star formation rate observed in local star-forming galaxies. The dust content of local star-forming galaxies is set by the competition between the physical processes of dust production and dust loss in our model. The dust loss rate is proportional to the dust opacity and star formation rate. Observations of the relation between stellar mass and star formation rate at several epochs imply that the majority of local star-forming galaxies are best characterized as having continuous star formation histories. Dust loss is a consequence of sustained interaction of dust with the radiation field generated by continuous star formation. Dust efflux driven by radiation pressure rather than dust destruction offers a more consistent physical interpretation of the dust loss mechanism. By comparing our model results with the observed relation between stellar mass, dust ...

  3. Efflux of potassium ion is an important reason of HL-60 cells apoptosis induced by tachyplesin

    Institute of Scientific and Technical Information of China (English)

    Hai-tao ZHANG; Jun WU; Hai-feng ZHANG; Qi-feng ZHU

    2006-01-01

    Aim: To investigate the role of intercellular potassium in tachyplesin-induced HL-60 cells apoptosis. Methods: The concentration of intercellular potassium, cell volume and mitochondrial membrane potential were examined by flow cytometry. Results: The concentration of intercellular potassium reduced in a time-dependent manner in tachyplesin-treated HL-60 cells. In addition, the loss of mitochondrial membrane potential was tightly coupled with the shrinkage of cell volume. Different caspase inhibitors protected against DNA degradation but did not prevent the loss of HL-60 cell viability induced by tachyplesin. Ba2+, which was a kind of blocker of volume-regulatory K+ channels, increased the viability of tachyplesin-treated HL-60 cells and maintained mitochondrial membrane potential and cell volume. Conclusion: Efflux of K+ was an important reason for apoptosis in tachyplesin-treated HL-60 cells. Efflux of K+ affected the viability of tachyplesin-treated HL-60 cells independent of the process of caspase activation.

  4. Evidence for regulation of polar auxin transport at the efflux carrier in maize coleoptile sections

    Energy Technology Data Exchange (ETDEWEB)

    Vesper, M.J. (Univ. of Dayton, OH (USA))

    1989-04-01

    Previously we have shown that conditions which result in an increased auxin-induced growth response in maize (Zea mays L.) coleoptile sections also result in a decrease in the velocity of polar auxin transport. Coleoptile sections given conditions which result in slower transport of IAA have different kinetics for net IAA accumulation compared to sections given conditions which result in faster transport. In further experiments, sections were loaded with 30 nM ({sup 3}H)IAA in the presence of increasing unlabeled IAA at low pH. Efflux of ({sup 3}H)IAA was then followed as a function of unlabeled IAA. Saturation of efflux appears to occur at a lower conc. of IAA in sections showing slower transport.

  5. 药用辅料抑制P-糖蛋白外排泵的研究进展%Progress in Pharmaceutical Excipients with Function of Inhibition of P-glycoprotein Mediated Efflux

    Institute of Scientific and Technical Information of China (English)

    崔升淼; 叶珍珍; 张建; 廖华卫

    2012-01-01

    P-糖蛋白(P-glycoprotein,P-gp)是一种ATP依赖性药物外排泵,广泛分布在机体的各个组织中,可降低某些药物的生物利用度,同时也是引起肿瘤细胞产生多药耐药的重要原因之一.一些药用辅料可抑制P-gp的外排作用,同时具有低毒、无药理活性和安全性高的优点.本文着重综述了对P-gp外排具有抑制作用的3类药用辅料(非离子型表面活性剂、聚合物和脂质)的研究进展,并简单介绍了P-gp的结构、功能和研究模型等.%P-Glycoprotein (P-gp) is an ATP-dependent efflux pump that is expressed in various tissues. It can reduce the bioavailability of some drugs, and it is also one of the important causes for multidrug resistance of tumor cells. Some pharmaceutical excipients can inhibit P-gp mediated efflux, and they simultaneously have the advantages of low toxicity, no pharmacological activity and high safety. This paper emphasizes on the progress of three kinds of pharmaceutical excipients (non-ionic surfactants, polymers and lipids) with the function of inhibition of P-gy mediated efflux. Meanwhile the structure, function and research model of P-gp are briefly introduced.

  6. Characterization of Zebrafish Abcc4 as an Efflux Transporter of Organochlorine Pesticides

    OpenAIRE

    Xing Lu; Yong Long; Li Lin; Rongze Sun; Shan Zhong; Zongbin Cui

    2014-01-01

    DDT and lindane are highly toxic organochlorine pesticides and posing adverse effects on the environment and public health due to their frequent usage in developing countries. ABCC4/MRP4 is an organic anion transporter that mediates cellular efflux of a wide range of exogenous and endogenous compounds such as cyclic nucleotides and anti-cancer drugs; however, it remains unclear whether ABCC4 and its orthologs function in the detoxification of organochlorine pesticides. Here, we demonstrated t...

  7. Direct assessment of P-glycoprotein efflux to determine tumor response to chemotherapy

    OpenAIRE

    Patwardhan, Gauri; Gupta, Vineet; Huang, Juowen; Gu, Xin; Liu, Yong-Yu

    2010-01-01

    Multidrug resistance is a major impediment to the success of cancer chemotherapy. The overproduced P-glycoprotein that extrudes anticancer drugs from cells, is the most common mechanism detected in multidrug-resistant cancers. Direct measurement of cellular efflux of tumors in vivo, rather than estimation of MDR1 mRNA and P-glycoprotein levels in samples stored or embedded, can functionally characterize the mechanism of drug resistance and determine the choice of anticancer drugs for cancer p...

  8. Multidrug Efflux Transporters Limit Accumulation of Inorganic, but Not Organic, Mercury in Sea Urchin Embryos

    OpenAIRE

    BOŠNJAK, IVANA; Uhlinger, Kevin R.; Heim, Wesley; Smital, Tvrtko; Franekić-Čolić, Jasna; Coale, Kenneth; Epel, David; Hamdoun, Amro

    2009-01-01

    Mercuric compounds are persistent global pollutants that accumulate in marine organisms and in humans who consume them. While the chemical cycles and speciation of mercury in the oceans are relatively well described, the cellular mechanisms that govern which forms of mercury accumulate in cells and why they persist are less understood. In this study we examined the role of multidrug efflux transport in the differential accumulation of inorganic (HgCl2) and organic (CH3HgCl) mercury in sea urc...

  9. Active efflux of ciprofloxacin from J774 macrophages through an MRP-like transporter

    OpenAIRE

    Michot, Jean-Michel; Van Bambeke, Françoise; Mingeot-Leclercq, Marie-Paule; Tulkens, Paul M.

    2004-01-01

    The accumulation and efflux kinetics of ciprofloxacin have been examined by using murine J774 macrophages. Accumulation (at equilibrium) was increased (three- to fourfold) (i) when cells were incubated with high extracellular drug concentrations (typically 200 mg/liter) as opposed to clinically meaningful concentrations (10 mg/liter or lower), (ii) during ATP- depletion and at acid pH, and (iii) during coincubation with probenecid, gemfibrozil and the preferential multidrug resistance-related...

  10. The cryptic tetracycline resistance determinant on Tn4400 mediates tetracycline degradation as well as tetracycline efflux.

    OpenAIRE

    Park, B. H.; Levy, S. B.

    1988-01-01

    Escherichia coli containing the cryptic tetracycline resistance determinant (class F) from the Bacteroides fragilis transposon Tn4400 on plasmid pGAT400 expressed a detoxification of tetracycline as well as an active efflux of tetracycline. This finding concurs with the report of detoxification for a related tetracycline resistance determinant from B. fragilis on Tn4351 (B. S. Speer and A. Salyers, J. Bacteriol. 170:1423-1429, 1987), which specifies a 10-fold-higher resistance than Tn4400. In...

  11. Energy-dependent efflux mediated by class L (tetL) tetracycline resistance determinant from streptococci.

    OpenAIRE

    McMurry, L M; Park, B. H.; Burdett, V; Levy, S. B.

    1987-01-01

    The class L (TetL) tetracycline resistance determinant from streptococci specified resistance and an energy-dependent decreased accumulation of tetracycline in both Streptococcus faecalis and Escherichia coli. Using E. coli, we showed that the reduced uptake resulted from active efflux. The streptococcal class M determinant, known to render the protein synthesis machinery of S. faecalis resistant to tetracycline inhibition, did not alter tetracycline transport in either host.

  12. NADP redox state and mitochondrial Ca2+ efflux: a controversial issue.

    Science.gov (United States)

    Vercesi, A E; Pereira-da-Silva, L

    1984-01-01

    It has been shown that Ca2+ efflux from respiring liver mitochondria is promoted by the oxidized steady state of mitochondrial pyridine nucleotides (NAD(P)), whereas Ca2+ retention is favored by a more reduced state (Lehninger, A.L., Vercesi, A.E. and Bababunmi, E.A., Proceedings of the National Academy of Sciences USA, 75, 1690-1694, 1978). The physiological relevance and the molecular mechanism responsible for the process are controversial and are discussed here. PMID:6529616

  13. Using O2 to study the relationships between soil CO2 efflux and soil respiration

    Science.gov (United States)

    Angert, A.; Yakir, D.; Rodeghiero, M.; Preisler, Y.; Davidson, E. A.; Weiner, T.

    2015-04-01

    Soil respiration is the sum of respiration processes in the soil and is a major flux in the global carbon cycle. It is usually assumed that the CO2 efflux is equal to the soil respiration rate. Here we challenge this assumption by combining measurements of CO2 with high-precision measurements of O2. These measurements were conducted on different ecosystems and soil types and included measurements of air samples taken from the soil profile of three Mediterranean sites: a temperate forest and two alpine forests. Root-free soils from the alpine sites were also incubated in the lab. We found that the ratio between the CO2 efflux and the O2 influx (defined as apparent respiratory quotient, ARQ) was in the range of 0.14 to 1.23 and considerably deviated from the value of 0.9 ± 0.1 expected from the elemental composition of average plants and soil organic matter. At the Mediterranean sites, these deviations are explained as a result of CO2 dissolution in the soil water and transformation to bicarbonate ions in these high-pH soils, as well as by carbonate mineral dissolution and precipitation processes. Thus, a correct estimate of the short-term, chamber-based biological respiratory flux in such soils can only be made by dividing the measured soil CO2 efflux by the average (efflux-weighted) soil profile ARQ. Applying this approach to a semiarid pine forest resulted in an estimated short-term biological respiration rate that is 3.8 times higher than the chamber-measured surface CO2. The ARQ values often observed in the more acidic soils were unexpectedly low (exchange fluxes and biological soil respiration.

  14. Retinoid regulated macrophage cholesterol efflux involves the steroidogenic acute regulatory protein

    OpenAIRE

    Manna, Pulak R.

    2016-01-01

    Elimination of excess cholesteryl esters from macrophage-derived foam cells is known to be a key process in limiting plaque stability and progression of atherosclerotic lesions. We have recently demonstrated that regulation of retinoid mediated cholesterol efflux is influenced by liver X receptor (LXR) signaling in mouse macrophages (Manna, P.R. et al., 2015, Biochem. Biophys. Res. Commun., 464:312-317). The data presented in this article evaluate the importance of the steroidogenic acute reg...

  15. Hydrogen peroxide efflux from muscle mitochondria underestimates matrix superoxide production: a correction using glutathione depletion

    OpenAIRE

    Treberg, Jason R.; Quinlan, Casey L.; Brand, Martin D.

    2010-01-01

    The production of H2O2 by isolated mitochondria is frequently used as a measure of mitochondrial superoxide formation. Matrix superoxide dismutase quantitatively converts matrix superoxide to H2O2. However, matrix enzymes such as the glutathione peroxidases can consume H2O2 and compete with efflux of H2O2, causing an underestimate of superoxide production. To assess this underestimate we depleted matrix glutathione in rat skeletal muscle mitochondria by more than 90% by pretreatment with 1-ch...

  16. Conservation of the multidrug resistance efflux gene oprM in Pseudomonas aeruginosa.

    OpenAIRE

    BIANCO, N.; Neshat, S; Poole, K

    1997-01-01

    An intragenic probe derived from the multidrug resistance gene oprM hybridized with genomic DNA from all 20 serotypes of Pseudomonas aeruginosa and from all 34 environmental and clinical isolates tested, indicating that the MexA-MexB-OprM multidrug efflux system is highly conserved in this organism. The oprM probe also hybridized with genomic DNA from Pseudomonas aureofaciens, Pseudomonas chlororaphis, Pseudomonas syringae, Burkholderia pseudomallei, and Pseudomonas putida, suggesting that ef...

  17. Mast Cells and HDL Studies on Cholesterol Efflux and Reverse Cholesterol Transport

    OpenAIRE

    Kareinen, Ilona

    2015-01-01

    Atherosclerosis is an inflammatory disease characterized by the accumulation of cholesterol in the arterial intima and consequently the formation of atherosclerotic plaques. Formation of these plaques is initiated by the appearance of macrophage foam cell in the arterial intima. Foam cells are formed as excessive cholesterol accumulates in the cytosol of macrophages and finally the net influx exceeds the efflux of cholesterol. Excessive accumulation of chemically modified cholesterol in foam ...

  18. Modulation of drug efflux by aloe materials: An In Vitro investigation across rat intestinal tissue

    OpenAIRE

    Beneke Carien; Viljoen Alvaro; Hamman Josias

    2013-01-01

    Background: Clinically, significant herb-drug interactions have been previously documented and can be pharmacodynamic and/or pharmacokinetic in nature. Pharmacokinetic interactions have been attributed to induction or inhibition of either metabolic enzymes or efflux transporters. Objective: The effect of gel and whole leaf materials from 3 different aloe species namely Aloe ferox, Aloe marlothii, and Aloe vera as well as polysaccharides precipitated from the A. vera materials o...

  19. Sediment properties and CO2 efflux from intact and cleared temperate mangrove forests

    OpenAIRE

    R. H. Bulmer; Lundquist, C. J.; Schwendenmann, L.

    2015-01-01

    Temperate mangrove forests in New Zealand have increased in area over recent decades. Expansion of temperate mangroves in New Zealand is associated with perceived loss of other estuarine habitats, and decreased recreational and amenity values, resulting in clearing of mangrove forests. In the tropics, changes in sediment characteristics and carbon efflux have been reported following mangrove clearance. This is the first study in temperate mangrove (Avicennia marina) forests ...

  20. Dopamine efflux in response to ultraviolet radiation in addicted sunbed users.

    Science.gov (United States)

    Aubert, Pamela M; Seibyl, John P; Price, Julianne L; Harris, Thomas S; Filbey, Francesca M; Jacobe, Heidi; Devous, Michael D; Adinoff, Bryon

    2016-05-30

    Compulsive tanning despite awareness of ultraviolet radiation (UVR) carcinogenicity may represent an "addictive" behavior. Many addictive disorders are associated with alterations in dopamine (D2/D3) receptor binding and dopamine reactivity in the brain's reward pathway. To determine if compulsive tanners exhibited neurobiologic responses similar to other addictive disorders, this study assessed basal striatal D2/D3 binding and UVR-induced striatal dopamine efflux in ten addicted and ten infrequent tanners. In a double-blind crossover trial, UVR or sham UVR was administered in separate sessions during brain imaging with single photon emission computerized tomography (SPECT). Basal D2/D3 receptor density and UVR-induced dopamine efflux in the caudate were assessed using (123)I-iodobenzamide ((123)I-IBZM) binding potential non-displaceable (BPnd). Basal BPnd did not significantly differ between addicted and infrequent tanners. Whereas neither UVR nor sham UVR induced significant changes in bilateral caudate BPnd in either group, post-hoc analyses revealed left caudate BPnd significantly decreased (reflecting increased dopamine efflux) in the addicted tanners - but not the infrequent tanners - during the UVR session only. Bilateral ∆BPnd correlated with tanning severity only in the addicted tanners. These preliminary findings are consistent with a stronger neural rewarding response to UVR in addicted tanners, supporting a cutaneous-neural connection driving excessive sunbed use. PMID:27085608

  1. Silicon efflux transporters isolated from two pumpkin cultivars contrasting in Si uptake.

    Science.gov (United States)

    Mitani-Ueno, Namiki; Yamaji, Naoki; Ma, Jian Feng

    2011-07-01

    The accumulation of silicon (Si) differs greatly with plant species and cultivars due to different ability of the roots to take up Si. In Si accumulating plants such as rice, barley and maize, Si uptake is mediated by the influx (Lsi1) and efflux (Lsi2) transporters. Here we report isolation and functional analysis of two Si efflux transporters (CmLsi2-1 and CmLsi2-2) from two pumpkin (Cucurbita moschata Duch.) cultivars contrasting in Si uptake. These cultivars are used for rootstocks of bloom and bloomless cucumber, respectively. Different from mutations in the Si influx transporter CmLsi1, there was no difference in the sequence of either CmLsi2 between two cultivars. Both CmLsi2-1 and CmLsi2-2 showed an efflux transport activity for Si and they were expressed in both the roots and shoots. These results confirm our previous finding that mutation in CmLsi1, but not in CmLsi2-1 and CmLsi2-2 are responsible for bloomless phenotype resulting from low Si uptake.

  2. Lactose uptake driven by galactose efflux in Streptococcus thermophilus: Evidence for a galactose-lactose antiporter

    International Nuclear Information System (INIS)

    Galactose-nonfermenting (Gal-) Streptococcus thermophilus TS2 releases galactose into the extracellular medium when grown in medium containing excess lactose. Starved and de-energized Gal- cells, however, could be loaded with galactose to levels approximately equal to the extracellular concentration (0 to 50 mM). When loaded cells were separated from the medium and resuspended in fresh broth containing 5 mM lactose, galactose efflux occurred. De-energized, galactose-loaded cells, resuspended in buffer or medium, accumulated [14C]lactose at a greater rate and to significantly higher intracellular concentrations than unloaded cells. Uptake of lactose by loaded cells was inhibited more than that by unloaded cells in the presence of extracellular galactose, indicating that a galactose gradient was involved in the exchange system. When de-energized, galactose-loaded cells were resuspended in carbohydrate-free medium at pH 6.7, a proton motive force (Δp) of 86 to 90 mV was formed, whereas de-energized, nonloaded cells maintained a Δp of about 56 mV. However, uptake of lactose by loaded cells occurred when the proton motive force was abolished by the addition of an uncoupler or in the presence of a proton-translocating ATPase inhibitor. These results support the hypothesis that galactose efflux in Gal- S. thermophilus is electrogenic and that the exchange reaction (lactose uptake and galactose efflux) probably occurs via an antiporter system

  3. Escherichia coli tetracycline efflux determinants in relation to tetracycline residues in chicken

    Institute of Scientific and Technical Information of China (English)

    Al-Bahry SN; Al-Mashani BM; Al-Ansari AS; Elshafie AE; Mahmoud IY

    2013-01-01

    Objective: To screen for Escherichia coli (E. coli) resistant to tetracycline, followed by identification of tet efflux genes by polymerase chain reaction (PCR). In addition, detection of tetracycline residues in chicken livers and kidneys were conducted using high performance liquid chromatography-tandem quadrupole mass spectrometry (HPLC-MS-MS). Methods:Strains of E. coli were isolated from samples of chicken colon and screened for tetracycline resistance. Tetracycline genes conferring resistance (Tcr) were detected by polymerase chain reaction (PCR). Most of the isolates were resistant to tetracycline (97.9%). Results: PCR analysis indicated that Tcr E. coli R-plasmids contained tet(A), tet(B) and a combination of both efflux genes. None of the isolates contained other efflux tet genes tet (C, D, E and Y). High performance liquid chromatography-tandem quadrupole mass spectrometry (HPLC-MS-MS), a sensitive technique, was used to detect residues of chlortetracycline (CTC), oxytetracycline (OTC), doxycycline (DC) in chicken livers and kidneys. The samples containing tetracycline residues were at 0.13-0.65 pg/μL levels. Conclusions: Tetracycline and other antibiotics are commonly used in the poultry and meat production industry for prevention of microbial infections. Multiple antibiotic resistant bacteria in Oman have increased to alarming levels, threatening public health, domestic and may have adverse effect on environment.

  4. Silicon efflux transporters isolated from two pumpkin cultivars contrasting in Si uptake

    Science.gov (United States)

    Mitani-Ueno, Namiki; Yamaji, Naoki

    2011-01-01

    The accumulation of silicon (Si) differs greatly with plant species and cultivars due to different ability of the roots to take up Si. In Si accumulating plants such as rice, barley and maize, Si uptake is mediated by the influx (Lsi1) and efflux (Lsi2) transporters. Here we report isolation and functional analysis of two Si efflux transporters (CmLsi2-1 and CmLsi2-2) from two pumpkin (Cucurbita moschata Duch.) cultivars contrasting in Si uptake. These cultivars are used for rootstocks of bloom and bloomless cucumber, respectively. Different from mutations in the Si influx transporter CmLsi1, there was no difference in the sequence of either CmLsi2 between two cultivars. Both CmLsi2-1 and CmLsi2-2 showed an efflux transport activity for Si and they were expressed in both the roots and shoots. These results confirm our previous finding that mutation in CmLsi1, but not in CmLsi2-1 and CmLsi2-2 are responsible for bloomless phenotype resulting from low Si uptake. PMID:21617377

  5. Escherichia coli tetracycline efflux determinants in relation to tetracycline residues in chicken

    Institute of Scientific and Technical Information of China (English)

    Al-Bahry; SN; Al-Mashani; BM; Al-Ansari; AS; Elshafie; AE; Mahmoud; IY

    2013-01-01

    Objective:To screen for Escherichia coli(E.coli)resistant to tetracycline,followed by identification of tet efflux genes by polymerase chain reaction(PCR).In addition,detection of tetracycline residues in chicken livers and kidneys were conducted using high performance liquid chromatography-tandem quadrupole mass spectrometry(HPLC-MS-MS).Methods:Strains of E.coli were isolated from samples of chicken colon and screened for tetracycline resistance.Tetracycline genes conferring resistance(Tc~r)were detected by polymerase chain reaction(PCR).Most of the isolates were resistant to tetracycline(97.9%).Results:PCR analysis indicated that Tc~r E.coli R-plasmids contained tet(A),tet(B)and a combination of both efflux genes.None of the isolates contained other efflux tet genes tet(C,D,E and Y).High performance liquid chromatography-tandem quadrupole mass spectrometry(HPLC-MS-MS),a sensitive technique,was used to detect residues of chlortetracycline(CTC),oxytetracyeline(OTC),doxveycline(DC)in chicken livers and kidneys.The samples containing tetracycline residues were at 0.13-0.65pg/μL levels.Conclusions:Tetracycline and other antibiotics are commonly used in the poultry and meat production industry for prevention of microbial infections.Multiple antibiotic resistant bacteria in Oman have increased to alarming levels,threatening public health,domestic and may have adverse effect on environment.

  6. Isolation and functional analysis of a Brassica juncea gene encoding a component of auxin efflux carrier

    Institute of Scientific and Technical Information of China (English)

    WEI; MIN; NI; XIAO; YA; CHEN; ZHI; HONG; XU; HONG; WEI; XUE

    2002-01-01

    Polar auxin transport plays a divergent role in plant growth and developmental processes including rootand embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsispin gene family was believed to encode a component of auxin efflux carrier (Galweiler et al, 1998). Basedon the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpinl), whichencoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level withAtPIN1 and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homologyto AtPIN3). Hydrophobic analysis showed similar structures between BjPIN1 and AtPIN proteins. Presenceof 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp)in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blotanalysis indicated that Bjpinl was expressed in most of the tissues tested, with a relatively higher levelof transcript in flowers and a lower level in root tissues. Promoter-reporter gene fusion studies furtherrevealed the expression of Bjpinl in the mature pollen grains, young seeds, root tip, leaf vascular tissue andtrace bundle, stem epidermis, cortex and vascular cells. BjPIN1 was localized on the plasma membraneas demonstrated through fusion expression of green fluorescent protein (GFP). Auxin efflux carrier activitywas elevated in transgenic Arabidopsis expressing BjPIN1.

  7. Bypassing P-Glycoprotein Drug Efflux Mechanisms: Possible Applications in Pharmacoresistant Schizophrenia Therapy

    Directory of Open Access Journals (Sweden)

    Famida G. Hoosain

    2015-01-01

    Full Text Available The efficient noninvasive treatment of neurodegenerative disorders is often constrained by reduced permeation of therapeutic agents into the central nervous system (CNS. A vast majority of bioactive agents do not readily permeate into the brain tissue due to the existence of the blood-brain barrier (BBB and the associated P-glycoprotein efflux transporter. The overexpression of the MDR1 P-glycoprotein has been related to the occurrence of multidrug resistance in CNS diseases. Various research outputs have focused on overcoming the P-glycoprotein drug efflux transporter, which mainly involve its inhibition or bypassing mechanisms. Studies into neurodegenerative disorders have shown that the P-glycoprotein efflux transporter plays a vital role in the progression of schizophrenia, with a noted increase in P-glycoprotein function among schizophrenic patients, thereby reducing therapeutic outcomes. In this review, we address the hypothesis that methods employed in overcoming P-glycoprotein in cancer and other disease states at the level of the BBB and intestine may be applied to schizophrenia drug delivery system design to improve clinical efficiency of drug therapies. In addition, the current review explores polymers and drug delivery systems capable of P-gp inhibition and modulation.

  8. Retinoid regulated macrophage cholesterol efflux involves the steroidogenic acute regulatory protein.

    Science.gov (United States)

    Manna, Pulak R

    2016-06-01

    Elimination of excess cholesteryl esters from macrophage-derived foam cells is known to be a key process in limiting plaque stability and progression of atherosclerotic lesions. We have recently demonstrated that regulation of retinoid mediated cholesterol efflux is influenced by liver X receptor (LXR) signaling in mouse macrophages (Manna, P.R. et al., 2015, Biochem. Biophys. Res. Commun., 464:312-317). The data presented in this article evaluate the importance of the steroidogenic acute regulatory protein (StAR) in retinoid mediated macrophage cholesterol efflux. Overexpression of StAR in mouse RAW 264.7 macrophages increased the effects of both all-trans retinoic acid (atRA) and 9-cis RA on cholesterol efflux, suggesting StAR enhances the efficacy of retinoic acid receptor (RAR) and/or retinoid X receptor (RXR) ligands. Additional data revealed that atRA enhances (Bu)2cAMP induced StAR and ATP-binding cassette transporter A1 protein levels. Treatment of macrophages transfected with an LXRE reporter plasmid (pLXREx3-Luc) was found to induce the effects of RAR and RXR analogs on LXR activity. PMID:27081671

  9. Summer storms trigger soil N2O efflux episodes in forested catchments

    Science.gov (United States)

    Enanga, E. M.; Creed, I. F.; Casson, N. J.; Beall, F. D.

    2016-01-01

    Climate change and climate-driven feedbacks on catchment hydrology and biogeochemistry have the potential to alter the aquatic versus atmospheric fate of nitrogen (N) in forests. This study investigated the hypothesis that during the forest growth season, topography redistributes water and water-soluble precursors (i.e., dissolved organic carbon and nitrate) for the formation of gaseous N species. Soil nitrous oxide (N2O) and nitrogen (N2) efflux and soil physical and chemical properties were measured in a temperate forest in Central Ontario, Canada from 2005 to 2010. Hotspots and hot moments of soil N2O and N2 efflux were observed in topographic positions that accumulate precipitation, which likely triggered the formation of redox conditions and in turn intercepted the conversion of nitrate N flowing to the stream by transforming it to N2O and N2. There was a strong relationship between precipitation and N2O efflux (y = 0.44x1.22, r2 = 0.618, p greenhouse gases.

  10. Akt inhibition promotes ABCA1-mediated cholesterol efflux to ApoA-I through suppressing mTORC1.

    Directory of Open Access Journals (Sweden)

    Fumin Dong

    Full Text Available ATP-binding cassette transporter A1 (ABCA1 plays an essential role in mediating cholesterol efflux to apolipoprotein A-I (apoA-I, a major housekeeping mechanism for cellular cholesterol homeostasis. After initial engagement with ABCA1, apoA-I directly interacts with the plasma membrane to acquire cholesterol. This apoA-I lipidation process is also known to require cellular signaling processes, presumably to support cholesterol trafficking to the plasma membrane. We report here that one of major signaling pathways in mammalian cells, Akt, is also involved. In several cell models that express ABCA1 including macrophages, pancreatic beta cells and hepatocytes, inhibition of Akt increases cholesterol efflux to apoA-I. Importantly, Akt inhibition has little effect on cells expressing non-functional mutant of ABCA1, implicating a specific role of Akt in ABCA1 function. Furthermore, we provide evidence that mTORC1, a major downstream target of Akt, is also a negative regulator of cholesterol efflux. In cells where mTORC1 is constitutively activated due to tuberous sclerosis complex 2 deletion, cholesterol efflux to apoA-I is no longer sensitive to Akt activity. This suggests that Akt suppresses cholesterol efflux through mTORC1 activation. Indeed, inhibition of mTORC1 by rapamycin or Torin-1 promotes cholesterol efflux. On the other hand, autophagy, one of the major pathways of cholesterol trafficking, is increased upon Akt inhibition. Furthermore, Akt inhibition disrupts lipid rafts, which is known to promote cholesterol efflux to apoA-I. We therefore conclude that Akt, through its downstream targets, mTORC1 and hence autophagy, negatively regulates cholesterol efflux to apoA-I.

  11. Seasonal and spatial variability in soil CO2 efflux rates for a central Siberian Pinus sylvestris forest

    International Nuclear Information System (INIS)

    Rates of CO2 efflux from the floor of a central Siberian Scots pine (Pinus sylvestris) forest were measured using a dynamic closed chamber system and by a eddy covariance system placed 2.5 m above the forest floor. Measurements were undertaken for a full growing season: from early May to early October 1999. Spatial variability as determined by the chamber measurements showed the rate of CO2 efflux to depend on location, with rates from relatively open areas ('glades') only being about 50% those observed below or around trees. This was despite generally higher temperatures in the glade during the day. A strong relationship between CO2 efflux rate and root density was observed in early spring, suggesting that lower rates in open areas may have been attributable to fewer roots there. Continuous measurements with the eddy covariance system provided good temporal coverage. This method, however, provided estimates of ground CO2 efflux rate rates that were about 50% lower than chamber measurements that were undertaken in areas considered to be representative of the forest as a whole. An examination of the seasonal pattern of soil CO2 efflux rates suggests that much of the variability in CO2 efflux rate could be accounted for by variations in soil temperature. Nevertheless, there were also some indications that the soil water deficits served to reduce soil CO2 efflux rates during mid-summer. Overall the sensitivity of CO2 efflux rate to temperature seems to be greater for this boreal ecosystem than has been the case for most other studies

  12. PKC phosphorylates residues in the N-terminal of the DA transporter to regulate amphetamine-induced DA efflux.

    Science.gov (United States)

    Wang, Qiang; Bubula, Nancy; Brown, Jason; Wang, Yunliang; Kondev, Veronika; Vezina, Paul

    2016-05-27

    The DA transporter (DAT), a phosphoprotein, controls extracellular dopamine (DA) levels in the central nervous system through transport or reverse transport (efflux). Multiple lines of evidence support the claim that PKC significantly contributes to amphetamine-induced DA efflux. Other signaling pathways, involving CaMKII and ERK, have also been shown to regulate DAT mediated efflux. Here we assessed the contribution of putative PKC residues (S4, S7, S13) in the N-terminal of the DAT to amphetamine-induced DA efflux by transfecting DATs containing different serine to alanine (S-A) point mutations into DA pre-loaded HEK-293 cells and incubating these cells in amphetamine (2μM). The effects of a S-A mutation at the non-PKC residue S12 and a threonine to alanine (T-A) mutation at the ERK T53 residue were also assessed for comparison. WT-DATs were used as controls. In an initial experiment, we confirmed that inhibiting PKC with Go6976 (130nM) significantly reduced amphetamine-induced DA efflux. In subsequent experiments, cells transfected with the S4A, S12A, S13A, T53A and S4,7,13A mutants showed a reduction in amphetamine-induced DA efflux similar to that observed with Go6976. Interestingly, cells transfected with the S7A mutant, identified by some as a PKC-PKA residue, showed unperturbed WT-DAT levels of amphetamine-induced DA efflux. These results indicate that phosphorylation by PKC of select residues in the DAT N-terminal can regulate amphetamine-induced efflux. PKC can act either independently or in concert with other kinases such as ERK to produce this effect.

  13. Novel limiter pump topologies

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, J.H.

    1981-01-01

    The use of limiter pumps as the principle plasma exhaust system of a magnetic confinement fusion device promises significant simplification, when compared to previously investigating divertor based systems. Further simplifications, such as the integration of the exhaust system with a radio frequency heating system and with the main reactor shield and structure are investigated below. The integrity of limiters in a reactor environment is threatened by many mechanisms, the most severe of which may be erosion by sputtering. Two novel topolgies are suggested which allow high erosion without limiter failure.

  14. Centrifugal pumps and allied machinery

    CERN Document Server

    Anderson, HH

    1994-01-01

    This book will be of vital interest to all engineers and designers concerned with centrifugal pumps and turbines. Including statistical information derived from 20000 pumps and 700 turbines with capacities of 5gpm to 5000000gpm, this book offers the widest range and scope of information currently available. Statistical analyses suggest practical methods of increasing pump performance and provide valuable data for new design aspects.

  15. Spin pumping through quantum dots

    OpenAIRE

    Rojek, Stephan; Governale, Michele; König, Jürgen

    2013-01-01

    We propose schemes for generating spin currents into a semiconductor by adiabatic or non-adiabatic pumping of electrons through interacting quantum dots. The appeal of such schemes lies in the possibility to tune the pumping characteristics via gate voltages that control the properties of the quantum dot. The calculations are based on a systematic perturbation expansion in the tunnel-coupling strength and the pumping frequency, expressed within a diagrammatic real-time technique. Special focu...

  16. Research on synchronous gear pump

    Institute of Scientific and Technical Information of China (English)

    LUAN Zhen-hui

    2010-01-01

    Based on a comprehensive analysis of the structure and existing problems of the gear pump, provided a structure principle of a synchronous gear pump. The discussions focused on the working principle, construction features and finite element analysis of the hydraulic gear. The research indicates that the new pump has such advantages as lower noise, better distributed flow and a high work pressure, and it can be widely used in hydraulic systems.

  17. Pump cavitation and inducer design

    International Nuclear Information System (INIS)

    Details of past work on sodium pump development and cavitation studies executed mainly for SNR 300 were reported earlier. Among the requirements for large sodium pumps are long life (200000 hours up to 300000 hours) and small size of impeller and pump, fully meeting the process and design criteria. These criteria are the required 'Q, H, r characteristics' in combination with a low NPSH value and the avoidance of cavitation damage to the pump. The pump designer has to develop a sound hydraulic combination consisting of suction arrangement, impeller design and diffuser. On the other hand the designer is free to choose an optimal pump speed. The pump speed in its turn influences the rotor dynamic pump design and the pump drive. The introduction of the inducer as an integral part of the pump design is based on following advantages: no tip cavitation; (possible) cavitation bubbles move to the open centre due to centrifugal forces on the fluid; the head of the inducer improves the inlet conditions of the impeller. The aim of an inducer is the increase in the suction specific speed (SA value) of a pump whereby the inducer functions as a pressure source improving the impeller inlet conditions. With inducer-impeller combinations values up to SA=15000 are realistic. With the use of an inducer the overall pump sizes can be reduced with Ca. 30%. Pumps commonly available have SA values up to a maximum of ca. 10000. A development programme was executed for SNR 300 in order to reach an increase of the suction specific speed of the impeller from SA 8200 to SA 11000. Further studies to optimize pumps design for the follow up line introduced the 'inducer acting as a pre-impeller' development. This programme was executed in the period 1979-1981. At the FDO premises a scale 1 2.8 inducer impeller combination with a suction specific speed SA=15000 was developed, constructed and tested at the water test rig. This water test rig is equipped with a perspex pipe allowing also visualisation

  18. Soil CO2 efflux in a sand grassland: contribution by root, mycorrhizal and basal respiration components

    Science.gov (United States)

    Papp, Marianna; Balogh, János; Pintér, Krisztina; Cserhalmi, Dóra; Nagy, Zoltán

    2014-05-01

    Grasslands play an important role in global carbon cycle because of their remarkable extension and carbon storage capacity. Soil respiration takes a major part in the carbon cycle of the ecosystems; ratio of its autotrophic and heterotrophic components is important also when considering their sensitivity to environmental drivers. The aim of the study was to estimate the contribution by root, mycorrhizal and basal components to total soil CO2 efflux. The study was carried out in the semi-arid sandy grassland dominated by Festuca pseudovina at the Kiskunság National Park in Hungary (Bugac site) where C-flux measurements have been going on since 2002. The soil CO2 effluxes were measured in the following treatments: a./ control, b./ root-exclusion, c./ root and mycorrhiza exclusion by using 80 cm long 15 cm inner diameter PVC tubes and micro-pore inox meshes. Inox mesh was used to exclude roots, but let the mycorrhiza filaments to grow into the tubes. 10 soil cores were excavated, sieved, then root-free soil was packed back layer by layer into the cores giving 6 and 4 repetitions in b and c treatments respectively. Basal respiration is referred to as the heterotrophic respiration without influence of roots or mycorrhiza. Difference between root-exclusion and root and mycorrhiza exclusion treatment gave the value of mycorrhizal respiration and control (non-disturbed) plots the total soil CO2 efflux. The contribution by the above components was evaluated. Soil CO2 efflux was measured continuously by using an automated open system of 10 soil respiration chambers. Data was collected in every two hours from each treatment (one of the chambers recorded basal respiration, 3 chambers were settled on root-excluded treatments and 6 chambers measured control plots). Chambers were moved in every 2 weeks between the repetitions of the treatments. Soil CO2 efflux (mycorrhiza-free, root free, control) data were fitted using a soil respiration model, where soil temperature, soil

  19. Using O2 to study the relationships between soil CO2 efflux and soil respiration

    Directory of Open Access Journals (Sweden)

    A. Angert

    2014-08-01

    Full Text Available Soil respiration, is the sum of respiration processes in the soil, and is a major flux in the global carbon cycle. It is usually assumed that the CO2 efflux is equal to the soil respiration rate. Here we challenge this assumption by combining measurements of CO2 with high-precision measurements of O2. These measurements were conducted on different ecosystems and soil types, and included measurements of air-samples taken from the soil profile of three Mediterranean sites, a temperate forest, and two alpine forests. Root-free soils from the alpine sites were also incubated at the lab. We found that the ratio between the CO2 efflux to the O2 influx (which we defined as apparent respiratory quotient, ARQ was in the range of 0.14 to 1.23, which strongly deviates from 0.9 ± 0.1, which is the ratio expected from the elemental composition of average plants and soil organic matter. At the Mediterranean sites these deviations were explained as a result of CO2 dissolution in the soil water and transformation to bi-carbonate in these high pH soils, and by carbonates dissolution and precipitation processes. Thus, correct estimate of the short-term, chamber-based biological respiratory flux in such soils can only be made by dividing the measured CO2 efflux by the average (efflux weighted soil profile ARQ. We demonstrated that applying this approach to a semiarid pine forest resulted in estimated short-term respiration rate 3.8 times higher than the chamber-measured surface CO2 efflux (8.8 μmol CO2 m−2 s−1 instead of 2.3 μmol CO2 m−2 s−1, at the time of measurement. The ARQ values that were often found for the more acidic soils were lower than 0.7, and hence surprising. These values might be the result of the oxidation of reduced iron, which could previously form during times of high soil moisture and local anaerobic conditions inside aggregates. Further research is needed to confirm that low ARQ found in non-calcareous soils, is the result of this

  20. The terrestrial silica pump.

    Directory of Open Access Journals (Sweden)

    Joanna C Carey

    Full Text Available Silicon (Si cycling controls atmospheric CO(2 concentrations and thus, the global climate, through three well-recognized means: chemical weathering of mineral silicates, occlusion of carbon (C to soil phytoliths, and the oceanic biological Si pump. In the latter, oceanic diatoms directly sequester 25.8 Gton C yr(-1, accounting for 43% of the total oceanic net primary production (NPP. However, another important link between C and Si cycling remains largely ignored, specifically the role of Si in terrestrial NPP. Here we show that 55% of terrestrial NPP (33 Gton C yr(-1 is due to active Si-accumulating vegetation, on par with the amount of C sequestered annually via marine diatoms. Our results suggest that similar to oceanic diatoms, the biological Si cycle of land plants also controls atmospheric CO(2 levels. In addition, we provide the first estimates of Si fixed in terrestrial vegetation by major global biome type, highlighting the ecosystems of most dynamic Si fixation. Projected global land use change will convert forests to agricultural lands, increasing the fixation of Si by land plants, and the magnitude of the terrestrial Si pump.

  1. The terrestrial silica pump.

    Science.gov (United States)

    Carey, Joanna C; Fulweiler, Robinson W

    2012-01-01

    Silicon (Si) cycling controls atmospheric CO(2) concentrations and thus, the global climate, through three well-recognized means: chemical weathering of mineral silicates, occlusion of carbon (C) to soil phytoliths, and the oceanic biological Si pump. In the latter, oceanic diatoms directly sequester 25.8 Gton C yr(-1), accounting for 43% of the total oceanic net primary production (NPP). However, another important link between C and Si cycling remains largely ignored, specifically the role of Si in terrestrial NPP. Here we show that 55% of terrestrial NPP (33 Gton C yr(-1)) is due to active Si-accumulating vegetation, on par with the amount of C sequestered annually via marine diatoms. Our results suggest that similar to oceanic diatoms, the biological Si cycle of land plants also controls atmospheric CO(2) levels. In addition, we provide the first estimates of Si fixed in terrestrial vegetation by major global biome type, highlighting the ecosystems of most dynamic Si fixation. Projected global land use change will convert forests to agricultural lands, increasing the fixation of Si by land plants, and the magnitude of the terrestrial Si pump. PMID:23300825

  2. Lasers with nuclear pumping

    CERN Document Server

    Melnikov, S P; Sizov, A N; Miley, George H

    2015-01-01

    This book covers the history of lasers with nuclear pumping (Nuclear Pumped Lasers, NPLs). This book showcases the most important results and stages of NPL development in The Russian Federal Nuclear Center (VNIIEF) as well as other Russian and international laboratories, including laboratories in the United States. The basic science and technology behind NPLs along with potential applications are covered throughout the book. As such, this book: ·         Contains a historical overview of the extensive information developed over the past 40 years of work on NPLs ·         Covers the most important results and stages of NPL development, not just in the Russian Federal Nuclear Center, VNIIEF, but also in other laboratories in Russia, the United States , and some other scattered international laboratories ·         Systematizes the fragmented information accumulated over these years of very active research and development As the first comprehensive discussion of NPLs, students, research...

  3. Work plan, AP-102 mixer pump removal and pump replacement

    International Nuclear Information System (INIS)

    The objective of this work plan is to plan the steps and estimate the costs required to remove the failed AP-102 mixer pump, and to plan and estimate the cost of the necessary design and specification work required to order a new, but modified, mixer pump including the pump and pump pit energy absorbing design. The main hardware required for the removal of the mixer is as follows: a flexible receiver and blast shield; a metal container for the pulled mixer pump; and a trailer and strongback to haul and manipulate the container. Additionally: a gamma scanning device will be needed to detect the radioactivity emanating from the mixer as it is pulled from the tank; a water spray system will be required to remove tank waste from the surface of the mixer as it is pulled from the AP-102 tank; and a lifting yoke to lift the mixer from the pump pit (the SY-101 Mixer Lifting Yoke will be used). A ''green house'' will have to be erected over the AP-102 pump pit and an experienced Hoisting and Rigging crew must be assembled and trained in mixer pump removal methods before the actual removal is undertaken

  4. Heat-Powered Pump for Liquid Metals

    Science.gov (United States)

    Campana, R. J.

    1986-01-01

    Proposed thermoelectromagnetic pump for liquid metal powered by waste heat; needs no battery, generator, or other external energy source. Pump turns part of heat in liquid metal into pumping energy. In combination with primary pump or on its own, thermoelectric pump circulates coolant between reactor and radiator. As long as there is decay heat to be removed, unit performs function.

  5. About Variable Speed Heating and Cooling Pumps

    OpenAIRE

    Cătălin Popovici; Jan Ignat

    2009-01-01

    The present work has the purpose of underlying the advantages of variable speed heating and cooling pumps use for the perspective of general and particular pumping costs and efficiency. The study approaches comparisons between constant flow pumps and variable flow pumps in different given situations and comparatively analyses the pumping costs.

  6. Pump rod forces due to hydrodynamic effects in piston pumps

    Energy Technology Data Exchange (ETDEWEB)

    Verheij, F.

    1986-10-01

    A mathematical model has been set up to describe flow and pressure fluctuations in a pump system of a wind pump for single acting piston pumps. With this, hydrodynamic forces acting on the pump rod can be calculated. Hydrodynamic forces make an important contribution to the total pump rod force. Experiments have been performed on a laboratory version of the so-called Tanzania pump. Different air volumes of the delivery airchamber, different delivery heads and different rotational speeds were chosen to obtain enough information to check the validity of the model. For the measuring and the elaboration of the measurements, computer programs were developed using a new data acquisition system. This new system operates very satisfactorily. A new magneto-inductive flow meter has been installed. However there are still incertainties as to the reliability of this sensor. Simple analytical expressions using Fourier transform analysis methods were obtained for the pressure and flow fluctuations in the pump system, from which the forces acting on the pump rod can be calculated. Comparison between theoretical and experimental results suggest that the pressure fluctuations are predicted correctly by theory. This is yet not the case in comparing theory and experiment with regards to the flow fluctuations. Apart from the irreliability of the flow meter, this could also be due to the complex flow in and out of the airchamber that is not correctly modelled in theory. There is certainly need for further analysis of the measurements possibly supplemented by a new set of measurements. However, design rules already can be derived from the results obtained so far. A good sizing of the airchamber in relation to the stroke volume of the pump keeps the pressure fluctuations, and so the fluctuating hydrodynamic forces acting on the pump rod, within bounds. 13 refs.

  7. High Temperature Thermoacoustic Heat Pump

    Energy Technology Data Exchange (ETDEWEB)

    Tijani, H.; Spoelstra, S. [ECN Biomass and Energy Efficiency, Petten (Netherlands)

    2012-07-15

    Thermoacoustic technology can provide new types of heat pumps that can be deployed in different applications. Thermoacoustic heat pumps can for example be applied in dwellings to generate cooling or heating. Typically, space and water heating makes up about 60% of domestic and office energy consumption. The application of heat pumps can contribute to achieve energy savings and environmental benefits by reducing CO2 and NOx emissions. This paper presents the study of a laboratory scale thermoacoustic-Stirling heat pump operating between 10C and 80C which can be applied in domestics and offices. The heat pump is driven by a thermoacoustic-Stirling engine. The experimental results show that the heat pump pumps 250 W of heat at 60C at a drive ratio of 3.6 % and 200 W at 80C at a drive ratio of 3.5 %. The performance for both cases is about 40% of the Carnot performance. The design, construction, and performance measurements of the heat pump will be presented and discussed.

  8. Multi-path peristaltic pump

    Science.gov (United States)

    Chandler, Joseph A. (Inventor)

    1986-01-01

    The instant invention is directed to a peristaltic pump for critical laboratory or hospital applications requiring precise flow rates over an extended period of time. Within the cylindrical barrel pump housing is a single-piece, molded, elastometric, cylindrical liner with a multiplicity of flattened helical channels created therein from one end of the liner to the other. Three cylindrical rollers rotate about the center axis of the pump around the inside surface of the liner selectively compressing the liner, and hence the helical channels between the rollers and the barrel housing, creating a pumping action by forcing trapped fluid in the helical channels axially from one end of the liner to the opposite end. The novelty of the invention appears to lie in the provision of the special liner with multiple helical channels as the pumping chamber, rather than the standard single elastomeric tubing which is squeezed repeatedly by rollers to move the liquid through a typical peristaltic pump. Large, repeated deflections on the standard tubing causes a permanent set in the tubing, thus either changing the flow rate, or requiring a new section of tubing to be positioned in the pump head. Further, this configuration minimizes the amount of outflow pulsation which is characteristic of a typical single tubing peristaltic pump.

  9. Threshold values of autoresonant pumping

    OpenAIRE

    Kiselev, O. M.

    2013-01-01

    There exists stable growing solution of primary resonant equation for a autoresonant pumping with decreasing amplitude. The primary term of asymptotics is $O(\\sqrt{t})$ and does not depend on order of the force from some interval. We point to the interval for the amplitude of the pumping for which the growing stable solution exists.

  10. Centrifugal pumps for rocket engines

    Science.gov (United States)

    Campbell, W. E.; Farquhar, J.

    1974-01-01

    The use of centrifugal pumps for rocket engines is described in terms of general requirements of operational and planned systems. Hydrodynamic and mechanical design considerations and techniques and test procedures are summarized. Some of the pump development experiences, in terms of both problems and solutions, are highlighted.

  11. Ion-Pumping Microbial Rhodopsins

    Directory of Open Access Journals (Sweden)

    Hideki eKandori

    2015-09-01

    Full Text Available Rhodopsins are light-sensing proteins used in optogenetics. The word rhodopsin originates from the Greek words rhodo and opsis, indicating rose and sight, respectively. Although the classical meaning of rhodopsin is the red-colored pigment in our eyes, the modern meaning of rhodopsin encompasses photoactive proteins containing a retinal chromophore in animals and microbes. Animal and microbial rhodopsins possess 11-cis and all-trans retinal, respectively, to capture light in seven transmembrane α-helices, and photoisomerizations into all-trans and 13-cis forms, respectively, initiate each function. Ion-transporting proteins can be found in microbial rhodopsins, such as light-gated channels and light-driven pumps, which are the main tools in optogenetics. Light-driven pumps, such as archaeal H+ pump bacteriorhodopsin (BR and Cl- pump halorhodopsin (HR, were discovered in the 1970s, and their mechanism has been extensively studied. On the other hand, different kinds of H+ and Cl- pumps have been found in marine bacteria, such as proteorhodopsin (PR and Fulvimarina pelagi rhodopsin (FR, respectively. In addition, a light-driven Na+ pump was found, Krokinobacter eikastus rhodopsin 2 (KR2. These light-driven ion-pumping microbial rhodopsins are classified as DTD, TSA, DTE, NTQ and NDQ rhodopsins for BR, HR, PR, FR and KR2, respectively. Recent understanding of ion-pumping microbial rhodopsins is reviewed in this paper.

  12. SOLAR PUMPED LASER MICROTHRUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Rubenchik, A M; Beach, R; Dawson, J; Siders, C W

    2010-02-05

    The development of microsatellites requires the development of engines to modify their orbit. It is natural to use solar energy to drive such engines. For an unlimited energy source the optimal thruster must use a minimal amount of expendable material to minimize launch costs. This requires the ejected material to have the maximal velocity and, hence, the ejected atoms must be as light as possible and be ejected by as high an energy density source as possible. Such a propulsion can be induced by pulses from an ultra-short laser. The ultra-short laser provides the high-energy concentration and high-ejected velocity. We suggest a microthruster system comprised of an inflatable solar concentrator, a solar panel, and a diode-pumped fiber laser. We will describe the system design and give weight estimates.

  13. Nanowire liquid pumps

    Science.gov (United States)

    Huang, Jian Yu; Lo, Yu-Chieh; Niu, Jun Jie; Kushima, Akihiro; Qian, Xiaofeng; Zhong, Li; Mao, Scott X.; Li, Ju

    2013-04-01

    The ability to form tiny droplets of liquids and control their movements is important in printing or patterning, chemical reactions and biological assays. So far, such nanofluidic capabilities have principally used components such as channels, nozzles or tubes, where a solid encloses the transported liquid. Here, we show that liquids can flow along the outer surface of solid nanowires at a scale of attolitres per second and the process can be directly imaged with in situ transmission electron microscopy. Microscopy videos show that an ionic liquid can be pumped along tin dioxide, silicon or zinc oxide nanowires as a thin precursor film or as beads riding on the precursor film. Theoretical analysis suggests there is a critical film thickness of ~10 nm below which the liquid flows as a flat film and above which it flows as discrete beads. This critical thickness is the result of intermolecular forces between solid and liquid, which compete with liquid surface energy and Rayleigh-Plateau instability.

  14. Electric fluid pump

    Science.gov (United States)

    Van Dam, Jeremy Daniel; Turnquist, Norman Arnold; Raminosoa, Tsarafidy; Shah, Manoj Ramprasad; Shen, Xiaochun

    2015-09-29

    An electric machine is presented. The electric machine includes a hollow rotor; and a stator disposed within the hollow rotor, the stator defining a flow channel. The hollow rotor includes a first end portion defining a fluid inlet, a second end portion defining a fluid outlet; the fluid inlet, the fluid outlet, and the flow channel of the stator being configured to allow passage of a fluid from the fluid inlet to the fluid outlet via the flow channel; and wherein the hollow rotor is characterized by a largest cross-sectional area of hollow rotor, and wherein the flow channel is characterized by a smallest cross-sectional area of the flow channel, wherein the smallest cross-sectional area of the flow channel is at least about 25% of the largest cross-sectional area of the hollow rotor. An electric fluid pump and a power generation system are also presented.

  15. Pump it up

    Science.gov (United States)

    Maffli, Luc; O'Brien, Benjamin; Rosset, Samuel; Shea, Herbert

    2012-04-01

    We report on the use of zipping actuation applied to dielectric elastomer actuators to microfabricate mm-sized pumps. The zipping actuators presented here use electrostatic attraction to deform an elastomeric membrane by pulling it into contact with a rigid counter electrode. We present several actuation schemes using either conventional DEA actuation, zipping, or a combination of both in order to realize microfluidic devices. A zipping design in which the electric field is applied across the elastomer membrane was explored theoretically and experimentally. Single zipping chambers and a micropump body made of a three chambers connected by an embedded channel were wet-etched into a silicon wafer and subsequently covered by a gold-implanted silicone membrane. We measured static deflections of up to 300 μm on chambers with square openings of 1.8 and 2.6 mm side, in very good agreement with our model.

  16. Stochastic thermodynamics of hidden pumps

    Science.gov (United States)

    Esposito, Massimiliano; Parrondo, Juan M. R.

    2015-05-01

    We show that a reversible pumping mechanism operating between two states of a kinetic network can give rise to Poisson transitions between these two states. An external observer, for whom the pumping mechanism is not accessible, will observe a Markov chain satisfying local detailed balance with an emerging effective force induced by the hidden pump. Due to the reversibility of the pump, the actual entropy production turns out to be lower than the coarse-grained entropy production estimated from the flows and affinities of the resulting Markov chain. Moreover, in presence of a large time scale separation between the fast-pumping dynamics and the slow-network dynamics, a finite current with zero dissipation may be produced. We make use of these general results to build a synthetase-like kinetic scheme able to reversibly produce high free-energy molecules at a finite rate and a rotatory motor achieving 100% efficiency at finite speed.

  17. Heat pumps in industry. Pt. 2: Applications

    Energy Technology Data Exchange (ETDEWEB)

    Lazzarin, R.M. [Padova Univ., Vicenza (Italy). Ist. di Ingegneria Gestionale

    1995-04-01

    A selection of applications of heat pumps in industry is described, reporting plant lay-outs and performances. The selection includes compression heat pumps at different temperatures, vapour recompression systems, absorption heat pumps and heat transformers. (author)

  18. Automatic Control of Water Pumping Stations

    Institute of Scientific and Technical Information of China (English)

    Muhannad Alrheeh; JIANG Zhengfeng

    2006-01-01

    Automatic Control of pumps is an interesting proposal to operate water pumping stations among many kinds of water pumping stations according to their functions.In this paper, our pumping station is being used for water supply system. This paper is to introduce the idea of pump controller and the important factors that must be considering when we want to design automatic control system of water pumping stations. Then the automatic control circuit with the function of all components will be introduced.

  19. Precipitation pulse dynamics of carbon sequestration and efflux in highly weatherable soils

    Science.gov (United States)

    Barron-Gafford, G.; Minor, R.; Van Haren, J. L.; Dontsova, K.; Troch, P. A.

    2013-12-01

    Soils are the primary pool for terrestrial carbon on Earth, and loss of that carbon to the atmosphere or hydrosphere represents a significant efflux that can impact a host of other downstream processes. Soil respiration (Rsoil), the efflux of CO2 to the atmosphere, represents the major pathway by which carbon is lost from the soil system in more weathered soils. However, in newly formed soils, chemical weathering can significantly deplete soil CO2 concentrations. As vegetation colonizes these soils, multiple interacting and contradictory pathways evolve such that soil CO2 concentrations increase in response to plant inputs but are decreased through chemical reactions. Furthermore, abiotic drivers of soil temperature and moisture likely differentially affect these processes. Understanding the bio-geo-chemical drivers and feedbacks associated with soil CO2 production and efflux in the critical zone necessitates an integrated science approach, drawing on input from plant physiologists, bio- and geochemists, and hydrologists. Here, we created a series of 1-meter deep mesocosms filled with granular basalt that supported either a woody mesquite shrub, a bunchgrass, or was left as bare soil. Use of multiple plant functional types allowed us to explore the impacts of plant structure (primarily rooting profiles) on critical zone function in terms of water and carbon exchange surrounding precipitation pulse dynamics. Each mesocosm was outfitted with an array of soil moisture, temperature, water potential, and CO2 concentration sensors at the near-surface, 30, 55, and 80cm depths to quantify patterns of soil moisture and respiratory CO2 efflux in response to rainfall events of varying magnitude and intervening periods of drought. Five replicates of each were maintained under current ambient or projected (+4oC) air temperatures. In addition, we used minirhizotrons to quantify the response of roots to episodic rainfall and confirm differences among plant types and collected

  20. Rapid Sediment Accumulation Results in High Methane Effluxes from Coastal Sediments

    Science.gov (United States)

    Lenstra, Wytze; Jong, Dirk; Meysman, Filip J. R.; Sapart, Célia J.; van der Veen, Carina; Röckmann, Thomas; Gonzalez, Santiago; Slomp, Caroline P.

    2016-01-01

    Globally, the methane (CH4) efflux from the ocean to the atmosphere is small, despite high rates of CH4 production in continental shelf and slope environments. This low efflux results from the biological removal of CH4 through anaerobic oxidation with sulfate in marine sediments. In some settings, however, pore water CH4 is found throughout the sulfate-bearing zone, indicating an apparently inefficient oxidation barrier for CH4. Here we demonstrate that rapid sediment accumulation can explain this limited capacity for CH4 removal in coastal sediments. In a saline coastal reservoir (Lake Grevelingen, The Netherlands), we observed high diffusive CH4 effluxes from the sediment into the overlying water column (0.2–0.8 mol m-2 yr-1) during multiple years. Linear pore water CH4 profiles and the absence of an isotopic enrichment commonly associated with CH4 oxidation in a zone with high rates of sulfate reduction (50–170 nmol cm-3 d-1) both suggest that CH4 is bypassing the zone of sulfate reduction. We propose that the rapid sediment accumulation at this site (~ 13 cm yr-1) reduces the residence time of the CH4 oxidizing microorganisms in the sulfate/methane transition zone (< 5 years), thus making it difficult for these slow growing methanotrophic communities to build-up sufficient biomass to efficiently remove pore water CH4. In addition, our results indicate that the high input of organic matter (~ 91 mol C m-2 yr-1) allows for the co-occurrence of different dissimilatory respiration processes, such as (acetotrophic) methanogenesis and sulfate reduction in the surface sediments by providing abundant substrate. We conclude that anthropogenic eutrophication and rapid sediment accumulation likely increase the release of CH4 from coastal sediments. PMID:27560511

  1. Efflux of glutathione and glutathione complexes from human erythrocytes in response to inorganic arsenic exposure.

    Science.gov (United States)

    Yildiz, Deniz; Cakir, Yeliz

    2012-12-01

    The objective of the present study was to investigate if arsenic exposure results in glutathione efflux from human erythrocytes. Arsenite significantly depleted intracellular nonprotein thiol level in a time- and concentration-dependent manner. The intracellular nonprotein thiol level was decreased to 0.767 ± 0.0017 μmol/ml erythrocyte following exposure to 10 mM of arsenite for 4 h. Extracellular nonprotein thiol level was increased concomitantly with the intracellular decrease and reached to 0.481 ± 0.0005 μmol/ml erythrocyte in 4 h. In parallel with the change in extracellular nonprotein thiol levels, significant increases in extracellular glutathione levels were detected. Extracellular glutathione levels reached to 0.122 ± 0.0013, 0.226 ± 0.003, and 0.274 ± 0.004 μmol/ml erythrocyte with 1, 5, and 10 mM of arsenite, respectively. Dimercaptosuccinic acid treatment of supernatants significantly increased the glutathione levels measured in the extracellular media. Utilization of MK571 and verapamil, multidrug resistance-associated protein 1 and Pgp inhibitors, decreased the rate of glutathione efflux from erythrocytes suggesting a role for these membrane transporters in the process. The results of the present study indicate that human erythrocytes efflux glutathione in reduced free form and in conjugated form or forms that can be recovered with dimercaptosuccinic acid when exposed to arsenite. PMID:22890881

  2. Impacts of ABCB1 (G1199A) polymorphism on resistance, uptake, and efflux to steroid drugs.

    Science.gov (United States)

    Peng, Rui; Zhang, Hong; Zhang, Ying; Wei, Dan-Yun

    2016-10-01

    1. P-glycoprotein (P-gp) substrates, including steroid drugs, involve in the inter-individual differences in resistant phenotype. This study was performed to evaluate whether G1199A polymorphism in ABCB1 gene can alter the sensitivity, accumulation, and transepithelial efflux to steroids in LLC-PK1 cells. 2. The stable recombinant LLC-PK1 cell lines transfected with ABCB1 1199G and ABCB1 1199A were used to assess the sensitivity, accumulation, and transepithelial permeability to steroids. 3. The cells transfected with 1199A allele displayed stronger resistance to aldosterone, dexamethasone, and cortisol (2.5-, 2.0-, and 1.6-fold, respectively) than cells overexpressing 1199G allele, while the two types of recombinant cells showed a similar resistance to corticosterone. The accumulation of aldosterone, dexamethasone, and cortisol in recombinant 1199A cells were significantly decreased when compared to 1199G cells (2.9-, 4.4-, and 3.9-fold, respectively). The net efflux ratios of P-gp-mediated aldosterone, dexamethasone, and cortisol in cells expressing 1199A allele were apparently greater than cells transfected with 1199G allele (3.3-, 3.5-, and 4.0-fold, respectively). 4. The impacts of ABCB1 (G1199A) single nucleotide polymorphism on the efflux of P-gp substrates presented as drug-specific. Overall, the transport ability of P-gp-dependent steroid drugs in recombinant model overexpressing variant 1199A allele is stronger in comparison to cells overexpressing wild-type 1199G allele. Therefore, the ABCB1 (G1199A) polymorphism may affect effective steroids concentration in target cells by regulating the drug transport and distribution. PMID:26822676

  3. Monocytes from HIV+ individuals show impaired cholesterol efflux and increased foam cell formation after transendothelial migration

    Science.gov (United States)

    MAISA, Anna; HEARPS, Anna C.; ANGELOVICH, Thomas A.; PEREIRA, Candida F.; ZHOU, Jingling; SHI, Margaret D.Y.; PALMER, Clovis S.; MULLER, William A.; CROWE, Suzanne M.; JAWOROWSKI, Anthony

    2016-01-01

    Design HIV+ individuals have an increased risk of atherosclerosis and cardiovascular disease which is independent of antiretroviral therapy and traditional risk factors. Monocytes play a central role in the development of atherosclerosis, and HIV-related chronic inflammation and monocyte activation may contribute to increased atherosclerosis, but the mechanisms are unknown. Methods Using an in vitro model of atherosclerotic plaque formation, we measured the transendothelial migration of purified monocytes from age-matched HIV+ and uninfected donors and examined their differentiation into foam cells. Cholesterol efflux and the expression of cholesterol metabolism genes were also assessed. Results Monocytes from HIV+ individuals showed increased foam cell formation compared to controls (18.9% vs 0% respectively, p=0.004) and serum from virologically suppressed HIV+ individuals potentiated foam cell formation by monocytes from both uninfected and HIV+ donors. Plasma TNF levels were increased in HIV+ vs control donors (5.9 vs 3.5 pg/ml, p=0.02) and foam cell formation was inhibited by blocking antibodies to TNF receptors, suggesting a direct effect on monocyte differentiation to foam cells. Monocytes from virologically suppressed HIV+ donors showed impaired cholesterol efflux and decreased expression of key genes regulating cholesterol metabolism, including the cholesterol transporter ABCA1 (p=0.02). Conclusions Monocytes from HIV+ individuals show impaired cholesterol efflux and are primed for foam cell formation following trans-endothelial migration. Factors present in HIV+ serum, including elevated TNF levels, further enhance foam cell formation. The pro-atherogenic phenotype of monocytes persists in virologically suppressed HIV+ individuals and may contribute mechanistically to increased atherosclerosis in this population. PMID:26244384

  4. Identification and characterization of silicon efflux transporters in horsetail (Equisetum arvense).

    Science.gov (United States)

    Vivancos, Julien; Deshmukh, Rupesh; Grégoire, Caroline; Rémus-Borel, Wilfried; Belzile, François; Bélanger, Richard R

    2016-08-01

    Silicon (Si) is a beneficial element to plants, and its absorption via transporters leads to protective effects against biotic and abiotic stresses. In higher plants, two groups of root transporters for Si have been identified: influx transporters (Lsi1) and efflux transporters (Lsi2). Lsi1 transporters belong to the NIPIII aquaporins, and functional Lsi1s have been found in many plants species. Much less is known about Lsi2s that have been characterized in only a few species. Horsetail (Equisetum arvense), known among the highest Si accumulators in the plant kingdom, is a valuable model to study Si absorption and deposition. In this study, we first analyzed discrete Si deposition patterns in horsetail shoots, where ubiquitous silicification differs markedly from that of higher plants. Then, using the sequenced horsetail root transcriptome, two putative Si efflux transporter genes, EaLsi2-1 and EaLsi2-2, were identified. These genes share low sequence similarity with their homologues in higher plants. Further characterisation of EaLsi2-1 in transient expression assay using Nicotiana benthamiana epidermal cells confirmed transmembrane localization. In order to determine their functionality, the EaLsi2-1 was expressed in Xenopus oocytes, confirming that the translated protein was efficient for Si efflux. Both genes were equally expressed in roots and shoots, but interestingly, showed a much higher expression in the shoots than in the roots in contrast to Lsi2s found in other plants, a result consistent with the specific anatomy of horsetail and its rank as one of the highest Si accumulators among plant species. PMID:27344403

  5. Seasonality in a boreal forest ecosystem affects the use of soil temperature and moisture as predictors of soil CO2 efflux

    OpenAIRE

    S. M. Niinistö; Kellomäki, S.; J. Silvola

    2011-01-01

    Our objectives were to identify factors related to temporal variation of soil CO2 efflux in a boreal pine forest and to evaluate simple predictive models of temporal variation of soil CO2 efflux. Soil CO2 efflux was measured with a portable chamber in a Finnish Scots pine forest for three years, with a fourth year for model evaluation. Plot averages for soil CO2 efflux ranged from 0.04 to 0.90 g CO2 m−2 h−1 during the snow-free period, i.e. May–October, and from 0.04 to 0.13...

  6. Seasonality in a boreal forest ecosystem affects the use of soil temperature and moisture as predictors of soil CO2 efflux

    OpenAIRE

    Kellomäki, S.; J. Silvola; S. M. Niinistö

    2011-01-01

    Our objectives were to identify factors related to temporal variation of soil CO2 efflux in a boreal pine forest and to evaluate simple predictive models of temporal variation of soil CO2 efflux. Soil CO2 efflux was measured with a portable chamber in a Finnish Scots pine forest for three years, with a fourth year for model evaluation. Plot averages for soil CO2 efflux ranged from 0.04 to 0.90 g CO2 m−2 h−1 during the snow-free period, i.e. May–October, and from 0.04 to 0.13 g CO2 m−2 h−1 in ...

  7. Hepatic calcium efflux during cytochrome P-450-dependent drug oxidations at the endoplasmic reticulum in intact liver.

    Science.gov (United States)

    Sies, H; Graf, P; Estrela, J M

    1981-06-01

    During metabolism of (type I) drugs by cytochrome P-450-dependent monooxygenase of the endoplasmic reticulum, the NADPH/NADP+ ratio in rat liver selectively decreases to approximately one-half of the control values, whereas the NADH/NAD+ ratio remains practically unaffected [Sies, H. & Brauser, B. (1970) Eur. J. Biochem. 15, 521-540]. In view of the observations with isolated mitochondria [Lehninger, A. L., Vercesi, A. & Bababunmi, E. A. (1978) Proc. Natl. Acad. Sci. USA 75, 1690-1694] of stimulated Ca2+ efflux upon nicotinamide nucleotide oxidation, the selective oxidation of NADPH in cytosol and mitochondria during drug oxidations was considered a useful experimental tool for the determination of whether the oxidation of NADPH or of NADH is responsible for Ca2+ efflux. With perfused livers from phenobarbital-treated rats, Ca2+ efflux was demonstrated, amounting to 8 nmol/min per gram of liver (wet weight), with aminopyrine, ethylmorphine, or hexobarbital as drug substrates. Drug-associated Ca2+ release was diminished when the inhibitor metyrapone was also present, or when drug oxidation was suppressed during N2 anoxia or in the presence of antimycin A in livers from fasted rats. Ca2+ efflux was elicited also by infusion of the thiol oxidant diamide, and by t-butyl hydroperoxide. However whereas Ca2+ efflux elicited by these compounds was restricted upon addition of the thiol dithioerythritol, there was little, if any, sensitivity of the drug-associated Ca2+ efflux to the thiol. Further mitochondrial oxidation of NADPH by addition of ammonium chloride had no effect on drug-associated Ca2+ efflux. Prior addition of the alpha-agonist phenylephrine suppressed the Ca2+ release by drug addition. While the molecular mechanism involved in Ca2+ efflux from liver mitochondria and from hepatocytes as well as the regulatory significance are not yet known, it is concluded from the present experiments that in case of nicotinamide nucleotide-linked Ca2+ efflux the oxidation of

  8. AcrB-AcrA Fusion Proteins That Act as Multidrug Efflux Transporters

    OpenAIRE

    Hayashi, Katsuhiko; Nakashima, Ryosuke; Sakurai, Keisuke; Kitagawa, Kimie; Yamasaki, Seiji; Nishino, Kunihiko; Yamaguchi, Akihito

    2015-01-01

    The AcrAB-TolC system in Escherichia coli is an intrinsic RND-type multidrug efflux transporter that functions as a tripartite complex of the inner membrane transporter AcrB, the outer membrane channel TolC, and the adaptor protein AcrA. Although the crystal structures of each component of this system have been elucidated, the crystal structure of the whole complex has not been solved. The available crystal structures have shown that AcrB and TolC function as trimers, but the number of AcrA m...

  9. Control of cellular cholesterol efflux by the nuclear oxysterol receptor LXRα

    OpenAIRE

    Venkateswaran, Asha; Laffitte, Bryan A.; Joseph, Sean B.; Mak, Puiying A.; Wilpitz, Damien C.; Edwards, Peter A.; Tontonoz, Peter

    2000-01-01

    LXRα is a nuclear receptor that has previously been shown to regulate the metabolic conversion of cholesterol to bile acids. Here we define a role for this transcription factor in the control of cellular cholesterol efflux. We demonstrate that retroviral expression of LXRα in NIH 3T3 fibroblasts or RAW264.7 macrophages and/or treatment of these cells with oxysterol ligands of LXR results in 7- to 30-fold induction of the mRNA encoding the putative cholesterol/phospholi...

  10. A Combination of Varying Column Pressure and Total Reflux—Total Efflux in Batch Distillation Operation

    Institute of Scientific and Technical Information of China (English)

    ZHANGWeijiang; QUHongmei; 等

    2002-01-01

    A novel operation of batch distillation-combination of varying colum pressure and total reflux-total efflux is studied experimentally. In the operation, the product is accumulated at the top of the column under total reflux and then drained off completely, and the column pressure is varying in the whole process. This process has been industrialized successfully with large profits. The conventional mode of batch distillation is improved by this method effectively: the separation eficiency and the yield of product are increased greatly, the operation time is shortened and the production cost is cut down. Moreover, the amount of condensation water is decreased and the over-high reboiler temperature is lowered.

  11. Reynolds-Averaged Navier-Stokes Analysis of Zero Efflux Flow Control over a Hump Model

    Science.gov (United States)

    Rumsey, Christopher L.

    2006-01-01

    The unsteady flow over a hump model with zero efflux oscillatory flow control is modeled computationally using the unsteady Reynolds-averaged Navier-Stokes equations. Three different turbulence models produce similar results, and do a reasonably good job predicting the general character of the unsteady surface pressure coefficients during the forced cycle. However, the turbulent shear stresses are underpredicted in magnitude inside the separation bubble, and the computed results predict too large a (mean) separation bubble compared with experiment. These missed predictions are consistent with earlier steady-state results using no-flow-control and steady suction, from a 2004 CFD validation workshop for synthetic jets.

  12. Internal respiration of Amazon tree stems greatly exceeds external CO2 efflux

    Directory of Open Access Journals (Sweden)

    J. Q. Chambers

    2012-08-01

    Full Text Available Respiration in tree stems is an important component of forest carbon balance. The rate of CO2 efflux from the stem has often been assumed to be a measure of stem respiration. However, recent work in temperate forests has demonstrated that stem CO2 efflux can either overestimate or underestimate respiration rate, because of emission or removal of CO2 by transport in xylem water. Here we used the ratio between CO2 efflux and O2 influx in stems of tropical forest trees to better understand respiration in an ecosystem that plays a key role in the global carbon cycle. This ratio, which we defined here as apparent respiratory quotient (ARQ, is expected to equal 1.0 if carbohydrates are the substrate for respiration, and the net transport of CO2 in the xylem water is negligible. However, using a stem chamber approach to quantifying ARQ we found values of 0.66 ± 0.18. These low ARQ values indicate that a large portion of respired CO2 (~35% is not emitted locally, and is probably transported upward in the stem. ARQ values of 0.21 ± 0.10 were found for the steady-state gas concentration within the tree, sampled by in-stem equilibration probes. These lower values may result from the proximity to the xylem water stream. In contrast, we found ARQ values of 1.00 ± 0.13 for soil respiration. Our results indicate, for the first time, the existence of a~considerable internal flux of CO2in the stem of tropical trees. If the transported CO2 is used in the canopy as a substrate for photosynthesis, it could account for several percent of the C fixed by the tree, and perhaps serve as a mechanism that buffers the response of the tree to changing CO2 levels. Our results also indicate, in agreement with previous work, that the widely used CO2 efflux approach for determining stem respiration is unreliable. We demonstrate here a field applicable approach for measuring the O2 uptake rate, which we suggest to be a more appropriate method to estimate stem respiration

  13. Greenhouse gas efflux from an impacted Malaysian tropical peat swamp (Invited)

    Science.gov (United States)

    Waldron, S.; Vihermaa, L. E.; Evers, S.; Garnett, M.; Newton, J.; Padfield, R.

    2013-12-01

    Tropical peatlands constitute ~11% of global peatland area and ~12% of the global peat C pool. Malaysia alone contains 10% of tropical peats. Due to rising global demands for food and biofuels, SE-Asia peat swamp forest ecosystems are threatened by increasing amounts of drainage, fire and conversion to plantation. These processes can change the GHG emissions and thus net ecosystem C balance. However, in comparison to temperate and boreal peatlands, there is a lack of data on terrestrial-aquatic-atmospheric carbon transfer from tropical peatlands, both those that are little disturbed and those facing anthropogenic pressures. Lateral transport of soil-respired carbon, and fluvial respiration or UV-oxidation of terrestrial DOC primes atmospheric carbon dioxide efflux. We now know that DOC lost from disturbed tropical peat swamp forests can be centuries to millennia old and originates deep within the peat column - this carbon may fuel efflux of old carbon dioxide and so anthropogenic land-use change renders the older, slower carbon cycles shorter and faster. Currently we have no knowledge of how significant ';older-slower' terrestrial-aquatic-atmospheric cycles are in disturbed tropical peatlands. Further, in some areas for commercial reasons, or by conservation bodies trying to minimise peat habitat loss, logged peats have been left to regenerate. Consequently, unpicking the legacy of multiple land uses on magnitude, age and source of GHG emissions is challenging but required to support land management decisions and projections of response to a changing climate. Here, we present the results of our first field campaign in July 2013 to the Raja Musa and Sungai Karang Peat Swamp Forest Reserves in North Selangor, Malaysia. This is one of Malaysia's largest oceanic peat swamps, and has been selectively logged and drained for 80 years, but is now subject to a 30 year logging ban to aid forest regeneration and build up wood stocks. From sites subject to different land use

  14. Complexation of arsenite with phytochelatins reduces arsenite efflux and translocation from roots to shoots in Arabidopsis.

    Science.gov (United States)

    Liu, Wen-Ju; Wood, B Alan; Raab, Andrea; McGrath, Steve P; Zhao, Fang-Jie; Feldmann, Jörg

    2010-04-01

    Complexation of arsenite [As(III)] with phytochelatins (PCs) is an important mechanism employed by plants to detoxify As; how this complexation affects As mobility was little known. We used high-resolution inductively coupled plasma-mass spectrometry and accurate mass electrospray ionization-mass spectrometry coupled to HPLC to identify and quantify As(III)-thiol complexes and free thiol compounds in Arabidopsis (Arabidopsis thaliana) exposed to arsenate [As(V)]. As(V) was efficiently reduced to As(III) in roots. In wild-type roots, 69% of As was complexed as As(III)-PC4, As(III)-PC3, and As(III)-(PC2)2. Both the glutathione (GSH)-deficient mutant cad2-1 and the PC-deficient mutant cad1-3 were approximately 20 times more sensitive to As(V) than the wild type. In cad1-3 roots, only 8% of As was complexed with GSH as As(III)-(GS)3 and no As(III)-PCs were detected, while in cad2-1 roots, As(III)-PCs accounted for only 25% of the total As. The two mutants had a greater As mobility, with a significantly higher accumulation of As(III) in shoots and 4.5 to 12 times higher shoot-to-root As concentration ratio than the wild type. Roots also effluxed a substantial proportion of the As(V) taken up as As(III) to the external medium, and this efflux was larger in the two mutants. Furthermore, when wild-type plants were exposed to l-buthionine sulfoximine or deprived of sulfur, both As(III) efflux and root-to-shoot translocation were enhanced. The results indicate that complexation of As(III) with PCs in Arabidopsis roots decreases its mobility for both efflux to the external medium and for root-to-shoot translocation. Enhancing PC synthesis in roots may be an effective strategy to reduce As translocation to the edible organs of food crops.

  15. Pumping of titanium sapphire laser

    Science.gov (United States)

    Jelínková, H.; Vaněk, P.; Valach, P.; Hamal, K.; Kubelka, J.; Škoda, V.; Jelínek, M.

    1993-02-01

    Two methods of Ti:Sapphire pumping for the generation of tunable laser radiation in the visible region were studied. For coherent pumping, the radiation of the second harmonic of a Nd:YAP laser was used and a maximum output energy of E out=4.5 mJ was reached from the Ti:Sapphire laser. For noncoherent pumping, two different lengths of flashlamp pulses were used and a maximum of E out=300 mJ was obtained. Preliminary estimations of the wavelength range of tunability were made.

  16. Solar pumped solid state lasers

    International Nuclear Information System (INIS)

    Results are presented for direct solar pumping of a Nd:YAG rod laser. Stable CW output of more than 60 watts was obtained with slope efficiencies exceeding 2%. Results are consistent with predictions based on a simple solar laser model the authors have developed. Using this model, performance projections and design concepts for higher power and higher efficiency solar-pumped solid state lasers are presented. It is shown that existing laser materials with broadband absorption characteristics (e.g., alexandrite and Nd:Cr:GSGG) can have better than 10% overall conversion efficiencies when solar pumped. The utility of solar lasers for various laser applications in space is briefly discussed

  17. Novel Characteristics of Valveless Pumping

    DEFF Research Database (Denmark)

    Timmermann, Stine; Ottesen, Johnny T.

    2009-01-01

    This study investigates the occurrence of valveless pumping in a fluidfilled system consisting of two open tanks connected by an elastic tube. We show that directional flow can be achieved by introducing a periodic pinching applied at an asymmetrical location along the tube, and that the flow...... direction depends on the pumping frequency. We propose a relation between wave propagation velocity, tube length, and resonance frequencies associated with shifts in the pumping direction using numerical simulations. The eigenfrequencies of the system are estimated from the linearized system, and we show...

  18. Proper Sizing of Circulation Pumps

    DEFF Research Database (Denmark)

    Tommerup, Henrik M.; Nørgaard, Jørgen

    2007-01-01

    , but the results can be applied to Europe in general. Despite the small sample of houses involved in the test, 15 houses, some rather safe conclusions can be drawn from the results, which showed that newly developed pumps with power consumption around 5-8 W, can perform the task of circulating the water...... as well as their pollution during operation. Policy measures are proposed of how to ensure that in the future only such energy saving pumps are installed. Furthermore, on the basis of the historic experiences with circulation pumps some con¬clusions are drawn on how to investigate, develop and market new...

  19. Heat pumps for the home

    CERN Document Server

    Cantor, John

    2013-01-01

    In recent years, heat pumps have emerged as a promising new form of technology with a relatively low environmental impact. Moreover, they have presented householders with an opportunity to reduce their heating bills. Heat pumps can heat a building by 'pumping' heat from either the ground or the air outside: an intriguing process which utilizes principles that are somewhat analogous to those employed in the domestic refrigerator. Armed with the practical information contained in these pages, homeowners will have the necessary knowledge to take advantage of this potentially low-carbon t

  20. Chemically driven electron tunnelling pumps

    CERN Document Server

    Goychuk, I

    2006-01-01

    The simplest mechanism for molecular electron pumps is discussed which is based on nonadiabatic electron tunnelling and nonequilibrium conformational fluctuations. Such fluctuations can be induced, e.g. by random binding of negatively charged ATP molecules to the electron-transferring molecular complex, their subsequent hydrolysis and the products dissociation. The pumping rate can be controlled by the ATP concentration in solution. Depending on the model parameters there may exist a critical ATP concentration for the pump to function. Alternatively, nonequilibrium fluctuations can be induced by externally applied stochastic electric fields. For realistically chosen parameters, the mechanism is shown to be robust and highly efficient.