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Articles 421 - 450 of 455

Full-Text Articles in Dentistry

4th Annual Pacific Research Day Abstracts, University Of The Pacific May 2002

4th Annual Pacific Research Day Abstracts, University Of The Pacific

Excellence Day

No abstract provided.

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Enhanced Gene Delivery In Vitro And In Vivo By Improved Transferrin-Lipoplexes, Conchita Tros De Ilarduya, M. A. Arangoa, M. J. Moreno-Aliaga, Nejat Düzgüneş Apr 2002

Enhanced Gene Delivery In Vitro And In Vivo By Improved Transferrin-Lipoplexes, Conchita Tros De Ilarduya, M. A. Arangoa, M. J. Moreno-Aliaga, Nejat Düzgüneş

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Cationic liposomes and the complexes they form with DNA (lipoplexes) constitute the most promising alternative to the use of viral vectors for gene therapy. One of the limitations to their application in vivo, however, is the inhibition of gene delivery by serum. In a previous study, we demonstrated that transferrin (Tf)-lipoplexes were superior to plain lipoplexes in transfecting HeLa cells in the presence of high concentrations of serum. With the goal of obtaining efficient gene expression in vivo, we evaluated the efficacy of Tf-lipoplexes (containing DOTAP and cholesterol) in transfecting primary hepatocytes and adipocytes in the presence of high serum …

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Fluorescent Probes For Monitoring Virus Fusion Kinetics: Comparative Evaluation Of Reliability, Isabel Nunes-Correia, Ana Eulálio, Shlomo Nir, Nejat Düzgüneş, João Ramalho-Santos, Maria C. Pedroso De Lima Mar 2002

Fluorescent Probes For Monitoring Virus Fusion Kinetics: Comparative Evaluation Of Reliability, Isabel Nunes-Correia, Ana Eulálio, Shlomo Nir, Nejat Düzgüneş, João Ramalho-Santos, Maria C. Pedroso De Lima

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Fluorescence assays for viral membrane fusion employ lipidic probes whose kinetics of fluorescence dequenching should mimic the actual kinetics of membrane merging. We examined the fusion of influenza virus with CEM cells, erythrocyte ghosts or liposomes by monitoring the fluorescence dequenching of each one of the three probes, octadecylrhodamine B chloride (R18), N-(lissamine rhodamine B sulfonyl)phosphatidylethanolamine (Rh-PE), or rac-2,3-dioleoylglycerol ester of rhodamine B (DORh-B), inserted into the virus membrane. Experimental conditions were designed to allow a clear distinction between membrane mixing and non-specific probe transfer. Fluorescence dequenching observed with Rh-PE was much slower than with R18, unless a particular experimental …

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On The Mechanisms Of Internalization And Intracellular Delivery Mediated By Ph-Sensitive Liposomes, Sérgio Simões, Vladimir Slepushkin, Nejat Düzgüneş, Maria C. Pedroso De Lima Nov 2001

On The Mechanisms Of Internalization And Intracellular Delivery Mediated By Ph-Sensitive Liposomes, Sérgio Simões, Vladimir Slepushkin, Nejat Düzgüneş, Maria C. Pedroso De Lima

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We investigated the molecular mechanisms by which pH-sensitive liposomes surpass the cytoplasmic and endosomal membranes to deliver their aqueous contents into the cytoplasm. Various liposome formulations were evaluated for their efficacy to mediate intracellular delivery of encapsulated material, including a novel sterically stabilized pH-sensitive formulation ((DOPE:CHEMS:DSPE-PEG2000 (6:4:0.3)) that was previously developed in our laboratories. In an attempt to fully characterize the nature of liposome-cell interactions different approaches based on a dual-labeling fluorescence assay were used. Our results indicate that the efficacy of interaction of pH-sensitive liposomes, both plain and sterically stabilized, with cells is strongly determined by the inclusion of …

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3rd Annual Pacific Research Day Abstracts, University Of The Pacific May 2001

3rd Annual Pacific Research Day Abstracts, University Of The Pacific

Excellence Day

No abstract provided.

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2nd Annual Pacific Research Day Abstracts, University Of The Pacific May 2000

2nd Annual Pacific Research Day Abstracts, University Of The Pacific

Excellence Day

No abstract provided.

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Human Serum Albumin Enhances Dna Transfection By Lipoplexes And Confers Resistance To Inhibition By Serum, Sérgio Simões, Vladimir Slepushkin, Pedro Pires, Rogério Gaspar, Maria C. Pedroso De Lima, Nejat Düzgüneş Feb 2000

Human Serum Albumin Enhances Dna Transfection By Lipoplexes And Confers Resistance To Inhibition By Serum, Sérgio Simões, Vladimir Slepushkin, Pedro Pires, Rogério Gaspar, Maria C. Pedroso De Lima, Nejat Düzgüneş

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Cationic liposome-DNA complexes ('lipoplexes') are used as gene delivery vehicles and may overcome some of the limitations of viral vectors for gene therapy applications. The interaction of highly positively charged lipoplexes with biological macromolecules in blood and tissues is one of the drawbacks of this system. We examined whether coating cationic liposomes with human serum albumin (HSA) could generate complexes that maintained transfection activity. The association of HSA with liposomes composed of 1,2-dioleoyl-3-(trimethylammonium) propane and dioleoylphosphatidylethanolamine, and subsequent complexation with the plasmid pCMVluc greatly increased luciferase expression in epithelial and lymphocytic cell lines above that obtained with plain lipoplexes. The …

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Efficient Gene Transfer By Transferrin Lipoplexes In The Presence Of Serum, Conchita Tros De Ilarduya, Nejat Düzgüneş Feb 2000

Efficient Gene Transfer By Transferrin Lipoplexes In The Presence Of Serum, Conchita Tros De Ilarduya, Nejat Düzgüneş

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Cationic lipids are being used increasingly as reagents for gene delivery both in vitro and in vivo. One of the limitations to the application of cationic lipid-DNA complexes (lipoplexes) in vivo is the inhibition of gene delivery by serum. In this study, we have shown that transferrin (Tf)-lipoplexes, which had transferrin adsorbed at their surface via electrostatic interactions, are much more effective than plain lipoplexes in transfecting cells in the presence of relatively high concentrations (up to 60%) of fetal bovine serum (FBS). Serum even enhanced transfection by Tf-lipoplexes composed of 1,2-dioleoyl-3-(trimethylammonium) propane (DOTAP)/dioleoylphosphatidylethanolamine (DOPE)/pCMVLacZ at high lipid/DNA (+/-) charge …

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Mechanisms Of Gene Transfer Mediated By Lipoplexes Associated With Targeting Ligands Or Ph-Sensitive Peptides, Sérgio Simões, Vladimir Slepushkin, Pedro Pires, Rogério Gaspar, Maria C. Pedroso De Lima, Nejat Düzgüneş Nov 1999

Mechanisms Of Gene Transfer Mediated By Lipoplexes Associated With Targeting Ligands Or Ph-Sensitive Peptides, Sérgio Simões, Vladimir Slepushkin, Pedro Pires, Rogério Gaspar, Maria C. Pedroso De Lima, Nejat Düzgüneş

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Association of a targeting ligand such as transferrin, or an endosome disrupting peptide such as GALA, with cationic liposome-DNA complexes ('lipoplexes') results in a significant enhancement of transfection of several cell types. Although these strategies can overcome some of the barriers to gene delivery by lipoplexes, the mechanisms by which they actually enhance transfection is not known. In studies designed to establish the targeting specificity of transferrin, we found that apo-transferrin enhances transfection to the same extent as transferrin, indicating that internalization of the lipoplexes is mostly independent of transferrin receptors. These observations were reinforced by results obtained from competitive …

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Interaction Of Cationic Liposomes And Their Dna Complexes With Monocytic Leukemia Cells, Pedro Pires, Sérgio Simões, Shlomo Nir, Rogério Gaspar, Nejat Düzgüneş, Maria C. Pedroso De Lima Apr 1999

Interaction Of Cationic Liposomes And Their Dna Complexes With Monocytic Leukemia Cells, Pedro Pires, Sérgio Simões, Shlomo Nir, Rogério Gaspar, Nejat Düzgüneş, Maria C. Pedroso De Lima

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Cationic liposomes complexed with DNA have been used extensively as non-viral vectors for the intracellular delivery of reporter or therapeutic genes in culture and in vivo. We examined the relationship between the characteristics of the lipoplexes, their mode of interaction with monocytic THP-1 cells and their ability to transfect these cells. We determined the size and ζ potential of cationic liposomes (composed of 1,2-dioleoyl-3-(trimethylammonium) propane (DOTAP) and its mixtures with neutral lipids), and lipoplexes at different (+/-) charge ratios. As the (+/-) charge ratio of the lipoplexes decreased to (1/1), a significant reduction in ζ potential and an increase in …

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Transfection Of Human Macrophages By Lipoplexes Via The Combined Use Of Transferrin And Ph-Sensitive Peptides, Sérgio Simões, Vladimir Slepushkin, Elizabeth Pretzer, Paul Dazin, Rogério Gaspar, Maria C. Pedroso De Lima, Nejat Düzgüneş Jan 1999

Transfection Of Human Macrophages By Lipoplexes Via The Combined Use Of Transferrin And Ph-Sensitive Peptides, Sérgio Simões, Vladimir Slepushkin, Elizabeth Pretzer, Paul Dazin, Rogério Gaspar, Maria C. Pedroso De Lima, Nejat Düzgüneş

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The crucial function of macrophages in a variety of biological processes and pathologies render these cells important targets for gene therapeutic interventions. Commonly used synthetic gene delivery vectors have not been successful in transfecting these non-dividing cells. A combination strategy involving cationic liposomes to condense and carry DNA, transferrin to facilitate cellular uptake, and the pH-sensitive peptide GALA to promote endosome destabilization, resulted in significant expression of a luciferase gene. Transfection of macrophages was dependent on the degree of differentiation of the cells. The quaternary complexes of cationic liposomes, DNA, transferrin, and GALA exhibited a net negative charge, which may …

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Delivery Of An Anti-Hiv-1 Ribozyme Into Hiv-Infected Cells Via Cationic Liposomes, Krystyna Konopka, John J. Rossi, Piotr Swiderski, Vladimir A. Slepushkin, Nejat Düzgüneş Jun 1998

Delivery Of An Anti-Hiv-1 Ribozyme Into Hiv-Infected Cells Via Cationic Liposomes, Krystyna Konopka, John J. Rossi, Piotr Swiderski, Vladimir A. Slepushkin, Nejat Düzgüneş

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Cationic liposome-mediated intracellular delivery of a fluorescein-labeled chimeric DNA-RNA ribozyme targeted to the HIV-1 5' LTR was investigated, using THP-1, THP-1/HIV-1(IIIB) or HeLa/LAV cells. Different fluorescence patterns were observed when the cells were exposed to Lipofectamine, Lipofectin or DMRIE:DOPE (1:1) complexed to the ribozyme. With Lipofectamine intense cell-associated fluorescence was found. Incubation with Lipofectin resulted in less intense diffuse fluorescence, while with DMRIE an intense but sporadic fluorescence was observed. Differentiated THP-1/HIV-1(IIIB) cells were more susceptible to killing by liposome-ribozyme complexes than THP-1 cells. Under non-cytotoxic conditions (a 4-h treatment) complexes of 5, 10 or 15 μM Lipofectin or DOTAP:DOPE …

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Gene Delivery By Negatively Charged Ternary Complexes Of Dna, Cationic Liposomes And Transferrin Or Fusigenic Peptides, Sérgio Simões, Vladimir Slepushkin, R. Caspar, Maria C. Pedroso De Lima, Nejat Düzgüneş Jan 1998

Gene Delivery By Negatively Charged Ternary Complexes Of Dna, Cationic Liposomes And Transferrin Or Fusigenic Peptides, Sérgio Simões, Vladimir Slepushkin, R. Caspar, Maria C. Pedroso De Lima, Nejat Düzgüneş

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Potential problems with the use of viral vectors for gene therapy necessitate the development of efficient nonviral vectors. The association of transferrin, or the pH-sensitive peptide GALA, with cationic liposomes composed of 1,2-dioleoyl-3-(trimethylammonium) propane and its equimolar mixture with dioleoylphosphatidylethanolamine, under conditions where the liposome/DNA complex is negatively charged, drastically increased luciferase expression from pCMVluc. The percentage of cells transfected, measured by β-galactosidase expression, was also increased by about 10-fold. The zeta potential of the ternary complexes was lower than that of the liposome/DNA complexes. Transfection activity of positively charged complexes was also enhanced by association with transferrin, GALA or …

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Cationic Liposome-Mediated Expression Of Hiv-Regulated Luciferase And Diphtheria Toxin A Genes In Hela Cells Infected With Or Expressing Hiv, Krystyna Konopka, Gail S. Harrison, Philip L. Felgner, Nejat Düzgüneş Apr 1997

Cationic Liposome-Mediated Expression Of Hiv-Regulated Luciferase And Diphtheria Toxin A Genes In Hela Cells Infected With Or Expressing Hiv, Krystyna Konopka, Gail S. Harrison, Philip L. Felgner, Nejat Düzgüneş

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HIV-regulated expression of the diphtheria toxin A fragment gene (HIV-DT-A) is a potential gene therapy approach to AIDS. Since cationic liposomes are safe and non-immunogenic for in vivo gene delivery, we examined whether LipofectAMINE or DMRIE reagent could mediate the transfection of HIV-DT-A (pTHA43) or the HIV-regulated luciferase gene (pLUCA43) into HIV-infected or uninfected HeLa cells. pLUCA43 was expressed at a 103-fold higher level in HeLa/LAV cells than in uninfected HeLa cells, while the extent of expression of RSV-regulated luciferase was the same in both cell lines. Co-transfection of HeLa cells with pTHA43 and the proviral HIV clone, HXBΔBgl, resulted …

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Sterically Stabilized Ph-Sensitive Liposomes. Intracellular Delivery Of Aqueous Contents And Prolonged Circulation In Vivo, Vladimir A. Slepushkin, Sérgio Simões, Paul Dazin, Mary S. Newman, Luke S. Guo, Maria C. Pedroso De Lima, Nejat Düzgüneş Feb 1997

Sterically Stabilized Ph-Sensitive Liposomes. Intracellular Delivery Of Aqueous Contents And Prolonged Circulation In Vivo, Vladimir A. Slepushkin, Sérgio Simões, Paul Dazin, Mary S. Newman, Luke S. Guo, Maria C. Pedroso De Lima, Nejat Düzgüneş

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Liposomes that destabilize at mildly acidic pH are efficient tools for delivering water-soluble drugs into the cell cytoplasm. However, their use in vivo is limited because of their rapid uptake from circulation by the reticuloendothelial system. Lipid-anchored polyethylene glycol (PEG-PE) prolongs the circulation time of liposomes by steric stabilization. We have found that addition of PEG-PE to the membrane of pH-sensitive liposomes composed of cholesteryl hemisuccinate (CHEMS) and dioleoylphosphatidylethanolamine (DOPE) confers steric stability to these vesicles. This modification significantly decreases the pH-dependent release of a charged water-soluble fluorophore, calcein, from liposomes suspended in buffer or cell culture medium. However, the …

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Human Immunodeficiency Virus Type-1 (Hiv-1) Infection Increases The Sensitivity Of Macrophages And Thp-1 Cells To Cytotoxicity By Cationic Liposomes, Krystyna Konopka, Elizabeth Pretzer, Philip L. Felgner, Nejat Düzgüneş Jul 1996

Human Immunodeficiency Virus Type-1 (Hiv-1) Infection Increases The Sensitivity Of Macrophages And Thp-1 Cells To Cytotoxicity By Cationic Liposomes, Krystyna Konopka, Elizabeth Pretzer, Philip L. Felgner, Nejat Düzgüneş

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Cationic liposomes may be valuable for the delivery of anti-sense oligonucleotides, ribozymes, and therapeutic genes into human immunodeficiency virus type 1 (HIV-1)-infected and uninfected cells. We evaluated the toxicity of three cationic liposomal preparations, Lipofectamine, Lipofectin, and 1,2-dimyristyloxypropyl-3-dimethyl-hydroxyethyl ammonium bromide (DMRIE) reagent, to HIV-infected and uninfected cells. Monocyte/macrophages were infected with HTV-1(BaL) and treated with liposomes in medium containing 20% fetal bovine serum (FBS) for 4 h or 24 h at 37°C. Uninfected monocytic THP-1 cells and chronically infected THP-1/HIV-1(IIIB) cells were treated with phorbol 12-myristate 13-acetate (PMA) and exposed to liposomes in the presence of 10% FBS. Toxicity was …

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Treatment Of Intracellular Mycobacterium Avium Complex Infection By Free And Liposome-Encapsulated Sparfloxacin, Nejat Düzgüneş, Diana L. Flasher, M. Venkata Reddy, Julieta Luna-Herrera, Pattisapu R.J. Gangadharam Jan 1996

Treatment Of Intracellular Mycobacterium Avium Complex Infection By Free And Liposome-Encapsulated Sparfloxacin, Nejat Düzgüneş, Diana L. Flasher, M. Venkata Reddy, Julieta Luna-Herrera, Pattisapu R.J. Gangadharam

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Mycobacterium avium-M. intracellulare complex (MAC) is the most frequent cause of opportunistic bacterial infection in patients with AIDS. Previous studies have indicated that liposome-encapsulated aminoglycosides are highly effective in treating MAC infections in mice. We investigated whether the fluoroquinolone sparfloxacin is effective in treating MAC infection in the murine macrophage-like cell line J774. Sparfloxacin was encapsulated in the membrane phase of multilamellar liposomes composed of phosphatidylglycerol-phosphatidylcholine-cholesterol (1:1:1 molar ratio). MAC-infected macrophages were treated for either 24 h or 4 days with free or liposome-encapsulated sparfloxacin. Treatment with free or liposome- encapsulated sparfloxacin (6 μg/ml) for 24 h resulted in the …

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Target Cell Membrane Sialic Acid Modulates Both Binding And Fusion Activity Of Influenza Virus, Maria C. Pedroso De Lima, João Ramalho-Santos, Diana L. Flasher, Vladimir A. Slepushkin, Shlomo Nir, Nejat Düzgüneş Jun 1995

Target Cell Membrane Sialic Acid Modulates Both Binding And Fusion Activity Of Influenza Virus, Maria C. Pedroso De Lima, João Ramalho-Santos, Diana L. Flasher, Vladimir A. Slepushkin, Shlomo Nir, Nejat Düzgüneş

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Influenza virus binds to cell surface sialic acid receptors, and following endocytosis fuses with the endosome membrane at low pH. Whether sialic acid plays a role in the virus-cell membrane fusion step is not known. We investigated the effect of the removal of cell membrane sialic acid on the fusion activity of influenza virus (A/PR/8/34 strain) toward human T lymphocytic leukemia (CEM) cells at low pH. Fusion was monitored by fluorescence dequenching of octadecylrhodamine incorporated in the virus membrane. Removal of sialic acid by neuraminidase resulted in a drastic reduction in both viral binding and fusion. The association of the …

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A Monoclonal Antibody To The Gp120-Cd4 Complex Has Differential Effects On Hiv-Induced Syncytium Formation And Viral Infectivity, Krystyna Konopka, Elizabeth Pretzer, F. Celada, Nejat Düzgüneş Jan 1995

A Monoclonal Antibody To The Gp120-Cd4 Complex Has Differential Effects On Hiv-Induced Syncytium Formation And Viral Infectivity, Krystyna Konopka, Elizabeth Pretzer, F. Celada, Nejat Düzgüneş

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A murine monoclonal antibody (MAb F-91-55) raised against the complex of soluble CD4 and human immunodeficiency virus type 1 (HIV-1) gp120 had previously been found to inhibit syncytium formation without inhibiting the interaction of CD4 with gp120, and its binding site was localized within the first two domains (D1/D2) of CD4. We investigated whether this antibody inhibited the infectivity of HIV-1 in the CD4+ T cell lines A3.01, Sup-T1 and H9. We also examined the effect of the antibody on syncytium formation between these cells and chronically infected H9 cells. Syncytium formation was found to depend critically on the incubation …

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Therapy Of Mycobacterium Avium Complex Infections In Beige Mice With Streptomycin Encapsulated In Sterically Stabilized Liposomes, Pattisapu R.J. Gangadharam, D. R. Ashtekar, Diana L. Flasher, Nejat Düzgüneş Jan 1995

Therapy Of Mycobacterium Avium Complex Infections In Beige Mice With Streptomycin Encapsulated In Sterically Stabilized Liposomes, Pattisapu R.J. Gangadharam, D. R. Ashtekar, Diana L. Flasher, Nejat Düzgüneş

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Mycobacterium avium complex (MAC) causes serious opportunistic infections in AIDS patients. Previous studies with MAC-infected beige mice have indicated that weekly administration of liposome-encapsulated streptomycin can reduce significantly the CFU in the liver and spleen. We examined whether streptomycin encapsulated in recently developed sterically stabilized liposomes with prolonged circulation times would have a therapeutic effect in this animal model. Two liposome types with prolonged circulation (polyethyleneglycol-distearoylphosphatidylethanolamine [PEG-DSPE]- distearoylphosphatidylcholine [DSPC]-cholesterol [chol] or phosphatidylinositol [PI]-DSPC-chol) and conventional liposomes (phosphatidylglycerol [PG]-phosphatidylcholine [PC]-chol) encapsulating streptomycin and administered twice weekly were bactericidal to MAC strain 101 in the spleen when the level of infection after …

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A Common Mechanism For Influenza Virus Fusion Activity And Inactivation, João Ramalho-Santos, Shlomo Nir, Nejat Düzgüneş, Arsélio Pato De Carvalho, Maria Conceição Pedroso De Lima Mar 1993

A Common Mechanism For Influenza Virus Fusion Activity And Inactivation, João Ramalho-Santos, Shlomo Nir, Nejat Düzgüneş, Arsélio Pato De Carvalho, Maria Conceição Pedroso De Lima

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The fusion of influenza virus (A/PR/8/34 strain) with PC-12 cells was monitored by a fluorescence assay, and the results were analyzed with a mass-action model which could explain and predict the kinetics of fusion. The model accounted explicitly for the reduction in the fusion rate constant upon exposure of the virus to low pH, either for the virus alone in suspension or for the virus bound to the cells. When the pH was lowered without previous viral attachment to cells, an optimal fusion activity was detected at pH 5.2. When the virus was prebound to the cells, however, reduction of …

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Simian Immunodeficiency Virus (Siv(Mac)251) Membrane Lipid Mixing With Human Cd4+ And Cd4- Cell Lines In Vitro Does Not Necessarily Result In Internalization Of The Viral Core Proteins And Productive Infection, L. Stamatatos, Nejat Düzgüneş Jan 1993

Simian Immunodeficiency Virus (Siv(Mac)251) Membrane Lipid Mixing With Human Cd4+ And Cd4- Cell Lines In Vitro Does Not Necessarily Result In Internalization Of The Viral Core Proteins And Productive Infection, L. Stamatatos, Nejat Düzgüneş

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The cell binding site of simian immunodeficiency virus (SIV) is believed to be the CD4 molecule. Several CD4+ cell lines are, however, resistant to infection by SIV(mac)251 in vitro and additional cell membrane molecules have been implicated in SIV(mac)251 entry. We investigated the binding, envelope fusion and entry of the viral core proteins (p27) of SIV(mac)251 into two human CD4+ cell lines (H9 and Sup-T1) which are infectible, and one CD4+ (A3.01) and two CD4- cell lines (K562 and Raji) that are resistant to infection. The fusion of the viral and cellular membranes was monitored by a fluorescence assay for …

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Anionic Liposomes Inhibit Human Immunodeficiency Virus Type 1 (Hiv-1) Infectivity In Cd4+ A3.01 And H9 Cells, Krystyna Konopka, B. R. Davis, C. E. Larsen, Nejat Düzgüneş Jan 1993

Anionic Liposomes Inhibit Human Immunodeficiency Virus Type 1 (Hiv-1) Infectivity In Cd4+ A3.01 And H9 Cells, Krystyna Konopka, B. R. Davis, C. E. Larsen, Nejat Düzgüneş

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Immunodeficiency viruses undergo fusion with liposomes containing anionic phospholipids (Larsen et al., 1990). We have investigated the effect of liposomes composed of cardiolipin, phosphatidylserine or phosphatidylinositol, on the infectivity of three strains of HIV-1 in A3.01 and H9 cells, measured by p24 (gag) production in the medium. The infectivity of HIV-1 in A3.01 or H9 cells was inhibited by the presence of cardiolipin liposomes during a 2 h infection period, with IC50's of 23.0, 4.8, and 5.0 μM phospholipid, respectively, for the different strains. Liposomes composed of phosphatidylserine or phosphatidylinositol were ineffective under similar conditions. However, prolonged pre-incubation of the …

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Fusion Activity And Inactivation Of Influenza Virus: Kinetics Of Low Ph-Induced Fusion With Cultured Cells, Nejat Düzgüneş, Maria C. Pedroso De Lima, L. Stamatatos, D. Flasher, D. R. Alford, Daniel S. Friend, S. Nir Jan 1992

Fusion Activity And Inactivation Of Influenza Virus: Kinetics Of Low Ph-Induced Fusion With Cultured Cells, Nejat Düzgüneş, Maria C. Pedroso De Lima, L. Stamatatos, D. Flasher, D. R. Alford, Daniel S. Friend, S. Nir

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The kinetics of fusion of influenza virus (A/PR/8/34) with human promyelocytic leukaemia (HL-60), human T lymphocytic leukaemia (CEM) and murine lymphoma (S49) cells were investigated. Fusion was demonstrated by electron microscopy, and monitored by fluorescence dequenching of octadecylrhodamine incorporated in the virus membrane. Rapid fusion was induced upon mild acidification of the medium. At pH 5, all virus particles were capable of fusing with the cells. The initial rate and the extent of fusion were maximal between pH 4.9 and 5.2 and declined sharply below and above this range. The rate constants of adhesion of influenza virus to cells or …

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Efficacies Of Liposome-Encapsulated Streptomycin And Ciprofloxacin Against Mycobacterium Avium-M. Intracellulare Complex Infections In Human Peripheral Blood Monocyte/Macrophages, S. Majumdar, Diana L. Flasher, Daniel S. Friend, P. Nassos, D. Yajko, W. K. Hadley, Nejat Düzgüneş Jan 1992

Efficacies Of Liposome-Encapsulated Streptomycin And Ciprofloxacin Against Mycobacterium Avium-M. Intracellulare Complex Infections In Human Peripheral Blood Monocyte/Macrophages, S. Majumdar, Diana L. Flasher, Daniel S. Friend, P. Nassos, D. Yajko, W. K. Hadley, Nejat Düzgüneş

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Current treatments of disseminated infection caused by the Mycobacterium avium-M. intracellulare complex (MAC) are generally ineffective. Liposome- mediated delivery of antibiotics to MAC-infected tissues in vivo can enhance the efficacy of the drugs (N. Duzgunes, V. K. Perumal, L. Kesavalu, J. A. Goldstein, R. J. Debs, and P. R. J. Gangadharam, Antimicrob. Agents Chemother. 32:1404-1411, 1988; N. Duzgunes, D. A. Ashtekar, D. L. Flasher, N. Ghori, R. J. Debs, D. S. Friend, and P. R. J. Gangadharam, J. Infect. Dis. 164:143-151, 1991). We investigated the therapeutic efficacies of liposome- encapsulated streptomycin and ciprofloxacin against growth of the MAC inside human …

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Enhancement Of Human Immunodeficiency Virus Type 1 Infection By Cationic Liposomes: The Role Of Cd4, Serum And Liposome-Cell Interactions, Krystyna Konopka, L. L. Stamatatos, C. E. Larsen, B. R. Davis, Nejat Düzgüneş Jan 1991

Enhancement Of Human Immunodeficiency Virus Type 1 Infection By Cationic Liposomes: The Role Of Cd4, Serum And Liposome-Cell Interactions, Krystyna Konopka, L. L. Stamatatos, C. E. Larsen, B. R. Davis, Nejat Düzgüneş

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We have reported previously the enhancement of the infectivity of human immunodeficiency virus type 1 (HIV- 1) by liposomes composed of the cationic lipid N[2,3-(dioleyloxy) propyl]-N,N,N-trimethylammonium chloride (DOTMA). To determine the mechanism by which this process occurs, we have investigated the role of CD4, serum concentration and liposome-cell interactions in the DOTMA-mediated stimulation of HIV-1 infection of A3.01 cells. Serum alone significantly inhibited the binding and infectivity of HIV-1, but DOTMA-mediated enhancement of infectivity was more pronounced in the presence of serum than in its absence. HIV-1 binding to cells was increased in the presence of DOTMA liposomes, DEAE-dextran and …

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Liposomes Modulate Human Immunodeficiency Virus Infectivity, Krystyna Konopka, B. R. Davis, C. E. Larsen, D. R. Alford, Robert J. Debs, Nejat Düzgüneş Jan 1990

Liposomes Modulate Human Immunodeficiency Virus Infectivity, Krystyna Konopka, B. R. Davis, C. E. Larsen, D. R. Alford, Robert J. Debs, Nejat Düzgüneş

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We have investigated the effects of the fusion of liposomes with human immunodeficiency virus type 1 (HIV-1(LVA)) on the ability of the virus to infect CD4+ and CD4- cells. Fluorescence dequenching measurements indicated that HIV-1 fuses with liposomes composed of either cardiolipin (CL) or N-[2,3-(dioleyloxy) propyl]-N,N,N-trimethyl ammonium chloride (DOTMA) but not appreciably with dioleoylphosphatidylcholine (DOPC) liposomes. Pre-incubation of HIV-1 with DOTMA liposomes enhanced virus production (measured by p24 gag antigen production in the culture medium and in situ) in CD4+ A3.01 and H9 cells in a concentration-dependent manner, but did not mediate the infection of the CD4- cell line, K562. …

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Fusion Of Simian Immunodeficiency Virus With Liposomes And Erythrocyte Ghost Membranes: Effects Of Lipid Composition, Ph And Calcium, Charles E. Larsen, D. R. Alford, L. J.T. Young, T. P. Mcgraw, Nejat Düzgüneş Jan 1990

Fusion Of Simian Immunodeficiency Virus With Liposomes And Erythrocyte Ghost Membranes: Effects Of Lipid Composition, Ph And Calcium, Charles E. Larsen, D. R. Alford, L. J.T. Young, T. P. Mcgraw, Nejat Düzgüneş

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Simian immunodeficiency virus from macaques (SIV(mac)) is closely related in its structure and biological activity to human immunodeficiency virus, and is the best animal model for the acquired immunodeficiency syndrome. We investigated the kinetics of membrane fusion between SIV(mac) and phospholipid vesicles and the effects of various parameters on this process. Purified SIV(mac) was labelled with octadecyl rhodamine B chloride, and fusion was continuously monitored as the dilution of the probe in target membranes. These studies show that SIV(mac) fusion is strongly dependent upon the liposome composition. Fusion with pure cardiolipin (CL) liposomes is significantly faster than with CL/dioleoylphosphatidylcholine (DOPC) …

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Enhanced Effect Of Liposome-Encapsulated Amikacin On Mycobacterium Avium-M. Intracellulare Complex Infection In Beige Mice, Nejat Düzgüneş, Veluchamy K. Perumal, L. Kesavalu, Jayne A. Goldstein, Robert J. Debs, Pattisapu R.J. Gangadharam Jan 1988

Enhanced Effect Of Liposome-Encapsulated Amikacin On Mycobacterium Avium-M. Intracellulare Complex Infection In Beige Mice, Nejat Düzgüneş, Veluchamy K. Perumal, L. Kesavalu, Jayne A. Goldstein, Robert J. Debs, Pattisapu R.J. Gangadharam

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We examined the therapeutic effects of free and liposome-encapsulated amikacin on Mycobacterium avium-M. intracellulare complex infection by using the beige-mouse model of the disease. In the first series of studies, intravenous administration of four weekly doses of 5 mg of amikacin per kg encapsulated in large (approximately 0.4-μm diameter), unilamellar liposomes arrested the growth of M. avium-M. intracellulare complex organisms in the liver, as measured by CFU counts. M. avium-M. intracellulare complex levels in untreated animals and in those treated with the same dose of free amikacin increased by several orders of magnitude over 8 weeks. Liposome-encapsulated amikacin was also …

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La3+-Induced Fusion Of Phosphatidylserine Liposomes. Close Approach, Intermembrane Intermediates, And The Electrostatic Surface Potential, Joe Bentz, D. R. Alford, J. Cohen, Nejat Düzgüneş Jan 1988

La3+-Induced Fusion Of Phosphatidylserine Liposomes. Close Approach, Intermembrane Intermediates, And The Electrostatic Surface Potential, Joe Bentz, D. R. Alford, J. Cohen, Nejat Düzgüneş

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The fusion of large unilamellar phosphatidylserine liposomes (PS LUV) induced by La3+ has been monitored using the 1-aminoapthalene-3,6,8-trisulfonic acid/p-xylenebis(pyridinium bromide) (ANTS/DPX) fluorescence assay for the mixing of aqueous contents. The fusion event is extensive and nonleaky, with up to 95% mixing of contents in the fused liposomes. However, addition of excess EDTA leads to disruption of the fusion products in a way that implies the existence of metastable intermembrane contact sites. The maximal fusion activity occurs between 10 and 100 microM La3+ and fusion can be terminated rapidly, without loss of contents, by the addition of excess La3+, e.g., 1 …

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