Pseudolocal tomography

DOEpatents

Katsevich, A.J.; Ramm, A.G.

1996-07-23

Local tomographic data is used to determine the location and value of a discontinuity between a first internal density of an object and a second density of a region within the object. A beam of radiation is directed in a predetermined pattern through the region of the object containing the discontinuity. Relative attenuation data of the beam is determined within the predetermined pattern having a first data component that includes attenuation data through the region. The relative attenuation data is input to a pseudo-local tomography function, where the difference between the internal density and the pseudo-local tomography function is computed across the discontinuity. The pseudo-local tomography function outputs the location of the discontinuity and the difference in density between the first density and the second density. 7 figs.

Co-immobilization of adhesive peptides and VEGF within a dextran-based coating for vascular applications.

PubMed

Noel, Samantha; Fortier, Charles; Murschel, Frederic; Belzil, Antoine; Gaudet, Guillaume; Jolicoeur, Mario; De Crescenzo, Gregory

2016-06-01

Multifunctional constructs providing a proper environment for adhesion and growth of selected cell types are needed for most tissue engineering and regenerative medicine applications. In this context, vinylsulfone (VS)-modified dextran was proposed as a matrix featuring low-fouling properties as well as multiple versatile moieties. The displayed VS groups could indeed react with thiol, amine or hydroxyl groups, be it for surface grafting, crosslinking or subsequent tethering of biomolecules. In the present study, a library of dextran-VS was produced, grafted to aminated substrates and characterized in terms of degree of VS modification (%VS), cell-repelling properties and potential for the oriented grafting of cysteine-tagged peptides. As a bioactive coating of vascular implants, ECM peptides (e.g. RGD) as well as vascular endothelial growth factor (VEGF) were co-immobilized on one of the most suitable dextran-VS coating (%VS=ca. 50% of saccharides units). Both RGD and VEGF were efficiently tethered at high densities (ca. 1nmol/cm(2) and 50fmol/cm(2), respectively), and were able to promote endothelial cell adhesion as well as proliferation. The latter was enhanced to the same extent as with soluble VEGF and proved selective to endothelial cells over smooth muscle cells. Altogether, multiple biomolecules could be efficiently incorporated into a dextran-VS construct, while maintaining their respective biological activity. This work addresses the need for multifunctional coatings and selective cell response inherent to many tissue engineering and regenerative medicine applications, for instance, vascular graft. More specifically, a library of dextrans was first generated through vinylsulfone (VS) modification. Thoroughly selected dextran-VS provided an ideal platform for unbiased study of cell response to covalently grafted biomolecules. Considering that processes such as healing and angiogenesis require multiple factors acting synergistically, vascular endothelial growth factor (VEGF) was then co-immobilized with the cell adhesive RGD peptide within our dextran coating through a relevant strategy featuring orientation and specificity. Altogether, both adhesive and proliferative cues could be incorporated into our construct with additive, if not synergetic, effects. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Generalized local emission tomography

DOEpatents

Katsevich, Alexander J.

1998-01-01

Emission tomography enables locations and values of internal isotope density distributions to be determined from radiation emitted from the whole object. In the method for locating the values of discontinuities, the intensities of radiation emitted from either the whole object or a region of the object containing the discontinuities are inputted to a local tomography function .function..sub..LAMBDA..sup.(.PHI.) to define the location S of the isotope density discontinuity. The asymptotic behavior of .function..sub..LAMBDA..sup.(.PHI.) is determined in a neighborhood of S, and the value for the discontinuity is estimated from the asymptotic behavior of .function..sub..LAMBDA..sup.(.PHI.) knowing pointwise values of the attenuation coefficient within the object. In the method for determining the location of the discontinuity, the intensities of radiation emitted from an object are inputted to a local tomography function .function..sub..LAMBDA..sup.(.PHI.) to define the location S of the density discontinuity and the location .GAMMA. of the attenuation coefficient discontinuity. Pointwise values of the attenuation coefficient within the object need not be known in this case.

Insights from diversified anti-angiogenic models: Role of β-interferon inducer DEAE-Dextran.

PubMed

Bakrania, Anita K; Variya, Bhavesh C; Patel, Snehal S

2018-04-17

Angiogenesis, the physiological process involving growth of new blood vessels from preexisting vessels, is essential for organ growth and repair. However, the imbalance in angiogenesis contributes to copious pathologies including cancer. Preceding the development of anti-angiogenic or proangiogenic agents, its evaluation is equally imperative; hence, precise and adequate models required. Valid mammalian models are expensive, time-consuming and not easy to set up, instigating legal and ethical aspects making it necessary to establish models with satisfactory activity and limited drawbacks. We investigated the activity of DEAE-Dextran on diversified models viz. in vitro cell migration assay, ex vivo aortic ring assay, in vitro chick yolk sac membrane assay and in vivo matrigel plug xenograft model corroborating its anti-angiogenic potential and establishing the best means of evaluation. Assorted models were reproducible and correlative to one another. DEAE-Dextran exhibited excellent anti-angiogenic effect in cell migration assay over a duration of 24 h compared to the vehicle control fibroblast cell line and aortic ring possessed an alleviated rate of sprouting when treated with DEAE-Dextran with contrast to vehicle control aorta. Similarly, decreased vascular density was observed in DEAE-Dextran treated chick embryos implicating potency of the β-interferon inducer. Augmenting to these results, the matrigel plugs also mitigated vascular net as well as reduced levels of angiogenic marker CD31. Substantially, DEAE-Dextran leads to anti-tumor activity through anti-angiogenic action and a combination of in vitro and in vivo model is vital for the judgement of anti-angiogenic potential since an in vitro model exempts mammalian-culture considerations. Copyright © 2018 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Characterization of the dextran-binding domain in the glucan-binding protein C of Streptococcus mutans.

PubMed

Takashima, Y; Fujita, K; Ardin, A C; Nagayama, K; Nomura, R; Nakano, K; Matsumoto-Nakano, M

2015-10-01

Streptococcus mutans produces multiple glucan-binding proteins (Gbps), among which GbpC encoded by the gbpC gene is known to be a cell-surface-associated protein involved in dextran-induced aggregation. The purpose of the present study was to characterize the dextran-binding domain of GbpC using bioinformatics analysis and molecular techniques. Bioinformatics analysis specified five possible regions containing molecular binding sites termed GB1 through GB5. Next, truncated recombinant GbpC (rGbpC) encoding each region was produced using a protein expression vector and five deletion mutant strains were generated, termed CDGB1 through CDGB5 respectively. The dextran-binding rates of truncated rGbpC that included the GB1, GB3, GB4 and GB5 regions in the upstream sequences were higher than that of the construct containing GB2 in the downstream region. In addition, the rates of dextran-binding for strains CDGB4 and CD1, which was entire gbpC deletion mutant, were significantly lower than for the other strains, while those of all other deletion mutants were quite similar to that of the parental strain MT8148. Biofilm structures formed by CDGB4 and CD1 were not as pronounced as that of MT8148, while those formed by other strains had greater density as compared to that of CD1. Our results suggest that the dextran-binding domain may be located in the GB4 region in the interior of the gbpC gene. Bioinformatics analysis is useful for determination of functional domains in many bacterial species. © 2015 The Society for Applied Microbiology.

Radiation synthesis of biocompatible hydrogels of dextran methacrylate

NASA Astrophysics Data System (ADS)

Szafulera, Kamila; Wach, Radosław A.; Olejnik, Alicja K.; Rosiak, Janusz M.; Ulański, Piotr

2018-01-01

The aim of this work was to synthesize biocompatible dextran-based hydrogels through crosslinking initiated by ionizing radiation. A series of derivatives of dextran has been synthesized by coupling of methacrylated glycidyl to the structure of this polysaccharide, yielding dextran methacrylate (Dex-MA) of the degree of methacrylate substitution (DS) up to 1.13 as characterised by FTIR and NMR spectroscopy. Chemically crosslinked hydrogels were formed by electron-beam irradiation of Dex-MA in aqueous solution in the absence of low-molecular-weight additives such as catalysts, monomers or crosslinking agents. Crosslinking of Dex-MA in aqueous solutions of 20 g/l and above was an efficient process, the gels were formed at doses as low as 0.5 kGy (experiments conducted up to 100 kGy) and were characterised by high content of insoluble fraction (70-100%). Due to high crosslinking density the equilibrium degree of swelling of fabricated gels was controlled principally by the initial concentration of Dex-MA solution subjected to irradiation, and it was in the range of 20 to over 100 g of water absorbed by gram of gel. Cytocompatibility of hydrogels was examined using XTT assay through evaluation of the cell viability being in indirect contact with hydrogels. The results indicated that hydrogels of Dex-MA of the average DS below 1 were not cytotoxic. Altogether, our data demonstrate that irradiation of methacrylated dextran in aqueous solution is an efficient method of fabrication of biocompatible hydrogels, which applications in regeneration medicine are anticipated.

Derivative discontinuity and exchange-correlation potential of meta-GGAs in density-functional theory.

PubMed

Eich, F G; Hellgren, Maria

2014-12-14

We investigate fundamental properties of meta-generalized-gradient approximations (meta-GGAs) to the exchange-correlation energy functional, which have an implicit density dependence via the Kohn-Sham kinetic-energy density. To this purpose, we construct the most simple meta-GGA by expressing the local exchange-correlation energy per particle as a function of a fictitious density, which is obtained by inverting the Thomas-Fermi kinetic-energy functional. This simple functional considerably improves the total energy of atoms as compared to the standard local density approximation. The corresponding exchange-correlation potentials are then determined exactly through a solution of the optimized effective potential equation. These potentials support an additional bound state and exhibit a derivative discontinuity at integer particle numbers. We further demonstrate that through the kinetic-energy density any meta-GGA incorporates a derivative discontinuity. However, we also find that for commonly used meta-GGAs the discontinuity is largely underestimated and in some cases even negative.

Derivative discontinuity and exchange-correlation potential of meta-GGAs in density-functional theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eich, F. G., E-mail: eichf@missouri.edu; Hellgren, Maria

2014-12-14

We investigate fundamental properties of meta-generalized-gradient approximations (meta-GGAs) to the exchange-correlation energy functional, which have an implicit density dependence via the Kohn-Sham kinetic-energy density. To this purpose, we construct the most simple meta-GGA by expressing the local exchange-correlation energy per particle as a function of a fictitious density, which is obtained by inverting the Thomas-Fermi kinetic-energy functional. This simple functional considerably improves the total energy of atoms as compared to the standard local density approximation. The corresponding exchange-correlation potentials are then determined exactly through a solution of the optimized effective potential equation. These potentials support an additional bound state andmore » exhibit a derivative discontinuity at integer particle numbers. We further demonstrate that through the kinetic-energy density any meta-GGA incorporates a derivative discontinuity. However, we also find that for commonly used meta-GGAs the discontinuity is largely underestimated and in some cases even negative.« less

Comparison of two sperm processing techniques for low complexity assisted fertilization: sperm washing followed by swim-up and discontinuous density gradient centrifugation.

PubMed

Fácio, Cássio L; Previato, Lígia F; Machado-Paula, Ligiane A; Matheus, Paulo Cs; Araújo, Edilberto

2016-12-01

This study aimed to assess and compare sperm motility, concentration, and morphology recovery rates, before and after processing through sperm washing followed by swim-up or discontinuous density gradient centrifugation in normospermic individuals. Fifty-eight semen samples were used in double intrauterine insemination procedures; 17 samples (group 1) were prepared with sperm washing followed by swim-up, and 41 (group 2) by discontinuous density gradient centrifugation. This prospective non-randomized study assessed seminal parameters before and after semen processing. A dependent t-test was used for the same technique to analyze seminal parameters before and after semen processing; an independent t-test was used to compare the results before and after processing for both techniques. The two techniques produced decreases in sample concentration (sperm washing followed by swim-up: P<0.000006; discontinuous density gradient centrifugation: P=0.008457) and increases in motility and normal morphology sperm rates after processing. The difference in sperm motility between the two techniques was not statistically significant. Sperm washing followed by swim-up had better morphology recovery rates than discontinuous density gradient centrifugation (P=0.0095); and the density gradient group had better concentration recovery rates than the swim-up group (P=0.0027). The two methods successfully recovered the minimum sperm values needed to perform intrauterine insemination. Sperm washing followed by swim-up is indicated for semen with high sperm concentration and better morphology recovery rates. Discontinuous density gradient centrifugation produced improved concentration recovery rates.

Fundamental gaps with approximate density functionals: The derivative discontinuity revealed from ensemble considerations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraisler, Eli; Kronik, Leeor

2014-05-14

The fundamental gap is a central quantity in the electronic structure of matter. Unfortunately, the fundamental gap is not generally equal to the Kohn-Sham gap of density functional theory (DFT), even in principle. The two gaps differ precisely by the derivative discontinuity, namely, an abrupt change in slope of the exchange-correlation energy as a function of electron number, expected across an integer-electron point. Popular approximate functionals are thought to be devoid of a derivative discontinuity, strongly compromising their performance for prediction of spectroscopic properties. Here we show that, in fact, all exchange-correlation functionals possess a derivative discontinuity, which arises naturallymore » from the application of ensemble considerations within DFT, without any empiricism. This derivative discontinuity can be expressed in closed form using only quantities obtained in the course of a standard DFT calculation of the neutral system. For small, finite systems, addition of this derivative discontinuity indeed results in a greatly improved prediction for the fundamental gap, even when based on the most simple approximate exchange-correlation density functional – the local density approximation (LDA). For solids, the same scheme is exact in principle, but when applied to LDA it results in a vanishing derivative discontinuity correction. This failure is shown to be directly related to the failure of LDA in predicting fundamental gaps from total energy differences in extended systems.« less

Differences in the protein composition of bovine retinal rod outer segment disk and plasma membranes isolated by a ricin-gold-dextran density perturbation method

PubMed Central

1987-01-01

The plasma membrane and disk membranes of bovine retinal rod outer segments (ROS) have been purified by a novel density-gradient perturbation method for analysis of their protein compositions. Purified ROS were treated with neuraminidase to expose galactose residues on plasma membrane-specific glycoproteins and labeled with ricin-gold-dextran particles. After the ROS were lysed in hypotonic buffer, the plasma membrane was dissociated from the disks by either mild trypsin digestion or prolonged exposure to low ionic strength buffer. The dense ricin-gold-dextran-labeled plasma membrane was separated from disks by sucrose gradient centrifugation. Electron microscopy was used to follow this fractionation procedure. The dense red pellet primarily consisted of inverted plasma membrane vesicles containing gold particles; the membrane fraction of density 1.13 g/cc consisted of unlabeled intact disks and vesicles. Ricin-binding studies indicated that the plasma membrane from trypsin-treated ROS was purified between 10-15-fold. The protein composition of plasma membranes and disks was significantly different as analyzed by SDS gels and Western blots labeled with lectins and monoclonal antibodies. ROS plasma membrane exhibited three major proteins of 36 (rhodopsin), 38, and 52 kD, three ricin-binding glycoproteins of 230, 160, and 110 kD, and numerous minor proteins in the range of 14-270 kD. In disk membranes rhodopsin appeared as the only major protein. A 220-kD concanavalin A-binding glycoprotein and peripherin, a rim-specific protein, were also present along with minor proteins of 43 and 57-63 kD. Radioimmune assays indicated that the ROS plasma membrane contained about half as much rhodopsin as disk membranes. PMID:2447095

Contribution of strong discontinuities to the power spectrum of the solar wind.

PubMed

Borovsky, Joseph E

2010-09-10

Eight and a half years of magnetic field measurements (2(22) samples) from the ACE spacecraft in the solar wind at 1 A.U. are analyzed. Strong (large-rotation-angle) discontinuities in the solar wind are collected and measured. An artificial time series is created that preserves the timing and amplitudes of the discontinuities. The power spectral density of the discontinuity series is calculated and compared with the power spectral density of the solar-wind magnetic field. The strong discontinuities produce a power-law spectrum in the "inertial subrange" with a spectral index near the Kolmogorov -5/3 index. The discontinuity spectrum contains about half of the power of the full solar-wind magnetic field over this "inertial subrange." Warnings are issued about the significant contribution of discontinuities to the spectrum of the solar wind, complicating interpretation of spectral power and spectral indices.

Towards increased selectivity of drug delivery to cancer cells: development of a LDL-based nanodelivery system for hydrophobic photosensitizers

NASA Astrophysics Data System (ADS)

Buzova, Diana; Huntosova, Veronika; Kasak, Peter; Petrovajova, Dana; Joniova, Jaroslava; Dzurova, Lenka; Nadova, Zuzana; Sureau, Franck; Midkovsky, Pavol; Jancura, Daniel

2012-10-01

Low-density lipoproteins (LDL), a natural in vivo carrier of cholesterol in the vascular system, play a key role in the delivery of hydrophobic photosensitizers (pts) to tumor cells in photodynamic therapy (PDT) of cancer. To make this delivery system even more efficient, we have constructed a nano-delivery system by coating of LDL surface by polyethylene glycol (PEG) and dextran. Fluorescence spectroscopy and confocal fluorescence imaging were used to characterize redistribution of hypericin (Hyp), a natural potent pts, loaded in LDL/PEG and LDL/dextran complexes to free LDL molecules as well as to monitor cellular uptake of Hyp by U87-MG cells. It was shown than the redistribution process of Hyp between LDL molecules is significantly suppressed by dextran coating of LDL surface. On the other hand, PEG does not significantly influence this process. The modification of LDL molecules by the polymers does not inhibit their recognition by cellular LDL receptors. U-87 MG cellular uptake of Hyp loaded in LDL/PEG and LDL/dextran complexes appears to be similar to that one observed for Hyp transported by unmodified LDL particles. It is proposed that by polymers modified LDL molecules could be used as a basis for construction of a drug transport system for targeted delivery of hydrophobic drugs to cancer cells expressing high level of LDL receptors.

Chemical Synthesis and Evaluation of a Disialic Acid-Containing Dextran Polymer as an Inhibitor for the Interaction between Siglec 7 and Its Ligand.

PubMed

Yamaguchi, Sho; Yoshimura, Atsushi; Yasuda, Yu; Mori, Airi; Tanaka, Hiroshi; Takahashi, Takashi; Kitajima, Ken; Sato, Chihiro

2017-07-04

A new sialic acid (Sia)-containing glycopolymer-a fluorescent probe with high-density disialic acid (diSia) on the surface of polysaccharide dextran (diSia-Dex)-was synthesized as a key molecule to regulate the Sia recognition lectins, Siglecs, that are involved in the immune system. According to our original methods, diSia was synthesized by α-selective sialylation, and a dextran template possessing terminal acetylenes and amino groups was prepared. A diSia and a fluorescent molecule were subsequently introduced to surface-modified dextran by Hüisgen reaction and amidation, respectively. The modulatory activity of Siglec7 was evaluated by using synthetic probes. DiSia-Dex showed high binding avidity toward Siglec7, with a K D value of 5.87×10 -10  m, and a high inhibitory activity for the interaction between Siglec7 and a ligand (GD3), with a IC 50 value of 1.0 nm. Notably, diSia-Dex was able to release Siglec7 from the pre-existing Siglec7-GD3 complex, possibly due to its unique properties of a slow dissociation rate and a high association rate. Together, these data show that diSia-Dex can be widely applicable as a modulator of Siglec7 functions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

An intrinsically shielded hydrogel for the adsorptive recovery of lysozyme.

PubMed

Wang, Lu; Zhang, Rongsheng; Eisenthal, Robert; Hubble, John

2006-07-01

The present paper addresses the selective recovery of lysozyme from egg white using CM-dextran (carboxymethyldextran)-based hydrogels containing Cibacron Blue as an affinity ligand and co-immobilized BSA intended to act as a shielding agent to reduce non-specific adsorption. Initial studies using pure lysozyme were conducted that indicated that the adsorption capacity increased with ligand density and that adsorption was well described by a Langmuir-type isotherm. The inclusion of BSA as a putative shielding agent did not decrease the adsorption capacity for lysozyme in single-adsorbate experiments. To assess the effectiveness of the shielding strategy, subsequent experiments were conducted with both defined lysozyme/ovalbumin mixtures and hen's-egg white. From these studies, the optimal operating conditions for lysozyme recovery have been determined. These include: optimal initial egg-white concentration [a 10% (v/v) solution of native egg white in the chosen buffer], affinity-ligand density (1.86 mM) and ligand-to-shielding-agent ratio (4:1). The purity of lysozyme obtained from egg white was improved from 69% with a non-shielded hydrogel to 94% with an intrinsically shielded hydrogel. Finally, the possibility of using a protein, rather than dextran-backbone-based, hydrogel was investigated. It was found that BSA could take the place of CM-dextran as the gel backbone in a simplified synthesis, producing a gel which also proved effective for lysozyme recovery with a 30% lysozyme in egg-white solution purified to approx. 92% in a single adsorption-desorption cycle.

Numerical Simulations of Shock Wave Refraction at Inclined Gas Contact Discontinuity

ERIC Educational Resources Information Center

Bulat, Pavel V.; Volkov, Konstantin N.

2016-01-01

When a shock wave interacts with a contact discontinuity, there may appear a reflected rarefaction wave, a deflected contact discontinuity and a refracted supersonic shock. The numerical simulation of shock wave refraction at a plane contact discontinuity separating gases with different densities is performed. Euler equations describing inviscid…

Influence of molecular structure on the tolerogenicity of bacterial dextrans. I. The alpha1--6-linked epitope of dextran B512.

PubMed Central

Howard, J G; Vicari, G; Courtenay, B M

1975-01-01

Native dextran B512 is a near-linear glucose polymer with 96 per cent alpha1--6 and 4 per cent alpha1--3 linkages and a molecular weight (mol. wt) of 8 X 10(7). Sheep RBC sensitized with its O-stearoyl derivative (prepared by a modified method) have been used satisfactorily in direct PFC assays. B512 immunizes BALB/c mice optimally with doses of 1--10 mug and produces B-cell tolerance with 1 mg upwards. The specificity of the response determined by PFC inhibition analysis, is directed towards an alpha1--6-linked epitope. High dose tolerance is not preceded by immunity and is stable on cell transfer to irradiated recipients in which responsiveness becomes perceptible after 4--6 weeks. Progressive depolymerization of this polysaccharide reduces immunogenicity and tolerogenicity, both of which are extinguished when the mol. wt falls to 2 X 10(4). Optimal immunization with B512 is succeeded by partial tolerance (previously characterized by analogous levan experiments as a B-cell exhaustion process). The tolerance threshold dose of B512 is reduced 1000-fold during immunosuppression with cyclophosphamide. PFC inhibition studies supported the contention that tolerogenicity of polysaccharides is influenced by their overall binding capacities. A direct relationship between inhibitory and tolerogenic activities was found both with B512 fractions of varying mol. wt and with heterologous dextrans. The similarities between B512 and levan argue against the association of a highly branched structure with greater tolerogenicity. The effect of reducing the percentage of alpha1--6 linkages in dextrans suggests, however, that epitope density probably plays a contributory role in determining the outcome of interaction between polysaccharides and B cells. PMID:52612

Effective homogeneity of the exchange-correlation and non-interacting kinetic energy functionals under density scaling.

PubMed

Borgoo, Alex; Teale, Andrew M; Tozer, David J

2012-01-21

Correlated electron densities, experimental ionisation potentials, and experimental electron affinities are used to investigate the homogeneity of the exchange-correlation and non-interacting kinetic energy functionals of Kohn-Sham density functional theory under density scaling. Results are presented for atoms and small molecules, paying attention to the influence of the integer discontinuity and the choice of the electron affinity. For the exchange-correlation functional, effective homogeneities are highly system-dependent on either side of the integer discontinuity. By contrast, the average homogeneity-associated with the potential that averages over the discontinuity-is generally close to 4/3 when the discontinuity is computed using positive affinities for systems that do bind an excess electron and negative affinities for those that do not. The proximity to 4/3 becomes increasingly pronounced with increasing atomic number. Evaluating the discontinuity using a zero affinity in systems that do not bind an excess electron instead leads to effective homogeneities on the electron abundant side that are close to 4/3. For the non-interacting kinetic energy functional, the effective homogeneities are less system-dependent and the effect of the integer discontinuity is less pronounced. Average values are uniformly below 5/3. The study provides information that may aid the development of improved exchange-correlation and non-interacting kinetic energy functionals. © 2012 American Institute of Physics

Assessment of Dextran Antigenicity of Intravenous Iron Preparations with Enzyme-Linked Immunosorbent Assay (ELISA).

PubMed

Neiser, Susann; Koskenkorva, Taija S; Schwarz, Katrin; Wilhelm, Maria; Burckhardt, Susanna

2016-07-21

Intravenous iron preparations are typically classified as non-dextran-based or dextran/dextran-based complexes. The carbohydrate shell for each of these preparations is unique and is key in determining the various physicochemical properties, the metabolic pathway, and the immunogenicity of the iron-carbohydrate complex. As intravenous dextran can cause severe, antibody-mediated dextran-induced anaphylactic reactions (DIAR), the purpose of this study was to explore the potential of various intravenous iron preparations, non-dextran-based or dextran/dextran-based, to induce these reactions. An IgG-isotype mouse monoclonal anti-dextran antibody (5E7H3) and an enzyme-linked immunosorbent assay (ELISA) were developed to investigate the dextran antigenicity of low molecular weight iron dextran, ferumoxytol, iron isomaltoside 1000, ferric gluconate, iron sucrose and ferric carboxymaltose, as well as isomaltoside 1000, the isolated carbohydrate component of iron isomaltoside 1000. Low molecular weight iron dextran, as well as dextran-based ferumoxytol and iron isomaltoside 1000, reacted with 5E7H3, whereas ferric carboxymaltose, iron sucrose, sodium ferric gluconate, and isolated isomaltoside 1000 did not. Consistent results were obtained with reverse single radial immunodiffusion assay. The results strongly support the hypothesis that, while the carbohydrate alone (isomaltoside 1000) does not form immune complexes with anti-dextran antibodies, iron isomaltoside 1000 complex reacts with anti-dextran antibodies by forming multivalent immune complexes. Moreover, non-dextran based preparations, such as iron sucrose and ferric carboxymaltose, do not react with anti-dextran antibodies. This assay allows to assess the theoretical possibility of a substance to induce antibody-mediated DIARs. Nevertheless, as this is only one possible mechanism that may cause a hypersensitivity reaction, a broader set of assays will be required to get an understanding of the mechanisms that may lead to intravenous iron-induced hypersensitivity reactions.

More complications in patients with septic shock treated with dextran compared with crystalloids.

PubMed

Rasmussen, Anders Mølgaard; Jakobsen, Rasmus; Strøm, Thomas; Carlsson, Marcela; Dahler-Eriksen, Bjarne; Toft, Palle

2015-02-01

In recent years, the safety-profile of synthetic colloids has been questioned. The purpose of the present study was to elucidate the safety-profile of the colloid dextran-70 in relation to acute kidney injury (AKI) and death. We conducted a retrospective, observational study of patients admitted to our intensive care unit with septic shock and treated with dextran-70 in the period from 1 January 2009 to 31 December 2009. The controls were included from 1 March 2012 to 28 February 2013 when dextran-70 was replaced with crystalloids. There were 91 patients in the dextran group and 150 patients in the non-dextran group. The urinary output was 17.93 ml/kg/24 h in the dextran group and 27.87 in the non-dextran group (p < 0.05). Continuous renal replacement therapy (CRRT) was used in 48% in the dextran group and in 23% in the non-dextran group (p < 0.05). Major bleeding episodes occurred in 32% in the dextran group compared with 15% in the control group (p < 0.05). The 90-day mortality was 42% in the dextran group and 35% in the non-dextran group (p = 0.08). Patients in the dextran group had significantly more bleeding episodes, a higher need for CRRT and a lower urinary output than patients in the non-dextran group. Due to study design, it cannot be concluded that the use of dextran-70 is causally related to the development of AKI.

Density Affects the Nature of the Hexatic-Liquid Transition in Two-Dimensional Melting of Soft-Core Systems

NASA Astrophysics Data System (ADS)

Zu, Mengjie; Liu, Jun; Tong, Hua; Xu, Ning

2016-08-01

We find that both continuous and discontinuous hexatic-liquid transitions can happen in the melting of two-dimensional solids of soft-core disks. For three typical model systems, Hertzian, harmonic, and Gaussian-core models, we observe the same scenarios. These systems exhibit reentrant crystallization (melting) with a maximum melting temperature Tm happening at a crossover density ρm. The hexatic-liquid transition at a density smaller than ρm is discontinuous. Liquid and hexatic phases coexist in a density interval, which becomes narrower with increasing temperature and tends to vanish approximately at Tm. Above ρm, the transition is continuous, in agreement with the Kosterlitz-Thouless-Halperin-Nelson-Young theory. For these soft-core systems, the nature of the hexatic-liquid transition depends on density (pressure), with the melting at ρm being a plausible transition point from discontinuous to continuous hexatic-liquid transition.

Assessment of Dextran Antigenicity of Intravenous Iron Preparations with Enzyme-Linked Immunosorbent Assay (ELISA)

PubMed Central

Neiser, Susann; Koskenkorva, Taija S.; Schwarz, Katrin; Wilhelm, Maria; Burckhardt, Susanna

2016-01-01

Intravenous iron preparations are typically classified as non-dextran-based or dextran/dextran-based complexes. The carbohydrate shell for each of these preparations is unique and is key in determining the various physicochemical properties, the metabolic pathway, and the immunogenicity of the iron-carbohydrate complex. As intravenous dextran can cause severe, antibody-mediated dextran-induced anaphylactic reactions (DIAR), the purpose of this study was to explore the potential of various intravenous iron preparations, non-dextran-based or dextran/dextran-based, to induce these reactions. An IgG-isotype mouse monoclonal anti-dextran antibody (5E7H3) and an enzyme-linked immunosorbent assay (ELISA) were developed to investigate the dextran antigenicity of low molecular weight iron dextran, ferumoxytol, iron isomaltoside 1000, ferric gluconate, iron sucrose and ferric carboxymaltose, as well as isomaltoside 1000, the isolated carbohydrate component of iron isomaltoside 1000. Low molecular weight iron dextran, as well as dextran-based ferumoxytol and iron isomaltoside 1000, reacted with 5E7H3, whereas ferric carboxymaltose, iron sucrose, sodium ferric gluconate, and isolated isomaltoside 1000 did not. Consistent results were obtained with reverse single radial immunodiffusion assay. The results strongly support the hypothesis that, while the carbohydrate alone (isomaltoside 1000) does not form immune complexes with anti-dextran antibodies, iron isomaltoside 1000 complex reacts with anti-dextran antibodies by forming multivalent immune complexes. Moreover, non-dextran based preparations, such as iron sucrose and ferric carboxymaltose, do not react with anti-dextran antibodies. This assay allows to assess the theoretical possibility of a substance to induce antibody-mediated DIARs. Nevertheless, as this is only one possible mechanism that may cause a hypersensitivity reaction, a broader set of assays will be required to get an understanding of the mechanisms that may lead to intravenous iron-induced hypersensitivity reactions. PMID:27455240

Discontinuous functional for linear-response time-dependent density-functional theory: The exact-exchange kernel and approximate forms

NASA Astrophysics Data System (ADS)

Hellgren, Maria; Gross, E. K. U.

2013-11-01

We present a detailed study of the exact-exchange (EXX) kernel of time-dependent density-functional theory with an emphasis on its discontinuity at integer particle numbers. It was recently found that this exact property leads to sharp peaks and step features in the kernel that diverge in the dissociation limit of diatomic systems [Hellgren and Gross, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.85.022514 85, 022514 (2012)]. To further analyze the discontinuity of the kernel, we here make use of two different approximations to the EXX kernel: the Petersilka Gossmann Gross (PGG) approximation and a common energy denominator approximation (CEDA). It is demonstrated that whereas the PGG approximation neglects the discontinuity, the CEDA includes it explicitly. By studying model molecular systems it is shown that the so-called field-counteracting effect in the density-functional description of molecular chains can be viewed in terms of the discontinuity of the static kernel. The role of the frequency dependence is also investigated, highlighting its importance for long-range charge-transfer excitations as well as inner-shell excitations.

Direct recognition of superparamagnetic nanocrystals by macrophage scavenger receptor SR-AI.

PubMed

Chao, Ying; Karmali, Priya P; Mukthavaram, Rajesh; Kesari, Santosh; Kouznetsova, Valentina L; Tsigelny, Igor F; Simberg, Dmitri

2013-05-28

Scavenger receptors (SRs) are molecular pattern recognition receptors that have been shown to mediate opsonin-independent uptake of therapeutic and imaging nanoparticles, underlying the importance of SRs in nanomedicine. Unlike pathogens, engineered nanomaterials offer great flexibility in control of surface properties, allowing addressing specific questions regarding the molecular mechanisms of nanoparticle recognition. Recently, we showed that SR-type AI/II mediates opsonin-independent internalization of dextran superparamagnetic iron oxide (SPIO) nanoparticles via positively charged extracellular collagen-like domain. To understand the mechanism of opsonin-independent SPIO recognition, we tested the binding and uptake of nanoparticles with different surface coatings by SR-AI. SPIO coated with 10 kDa dextran was efficiently recognized and taken up by SR-AI transfected cells and J774 macrophages, while SPIO with 20 kDa dextran coating or cross-linked dextran hydrogel avoided the binding and uptake. Nanoparticle negative charge density and zeta-potential did not correlate with SR-AI binding/uptake efficiency. Additional experiments and computer modeling revealed that recognition of the iron oxide crystalline core by the positively charged collagen-like domain of SR-AI is sterically hindered by surface polymer coating. Importantly, the modeling revealed a strong complementarity between the surface Fe-OH groups of the magnetite crystal and the charged lysines of the collagen-like domain of SR-AI, suggesting a specific recognition of SPIO crystalline surface. These data provide an insight into the molecular recognition of nanocrystals by innate immunity receptors and the mechanisms whereby polymer coatings promote immune evasion.

Dextran as a Generally Applicable Multivalent Scaffold for Improving Immunoglobulin-Binding Affinities of Peptide and Peptidomimetic Ligands

PubMed Central

2015-01-01

Molecules able to bind the antigen-binding sites of antibodies are of interest in medicine and immunology. Since most antibodies are bivalent, higher affinity recognition can be achieved through avidity effects in which a construct containing two or more copies of the ligand engages both arms of the immunoglobulin simultaneously. This can be achieved routinely by immobilizing antibody ligands at high density on solid surfaces, such as ELISA plates, but there is surprisingly little literature on scaffolds that routinely support bivalent binding of antibody ligands in solution, particularly for the important case of human IgG antibodies. Here we show that the simple strategy of linking two antigens with a polyethylene glycol (PEG) spacer long enough to span the two arms of an antibody results in higher affinity binding in some, but not all, cases. However, we found that the creation of multimeric constructs in which several antibody ligands are displayed on a dextran polymer reliably provides much higher affinity binding than is observed with the monomer in all cases tested. Since these dextran conjugates are simple to construct, they provide a general and convenient strategy to transform modest affinity antibody ligands into high affinity probes. An additional advantage is that the antibody ligands occupy only a small number of the reactive sites on the dextran, so that molecular cargo can be attached easily, creating molecules capable of delivering this cargo to cells displaying antigen-specific receptors. PMID:25073654

Creating biomimetic polymeric surfaces by photochemical attachment and patterning of dextran

PubMed Central

Ferrer, M. Carme Coll; Yang, Shu; Eckmann, David M.; Composto, Russell J.

2010-01-01

In this work, we report the preparation of photoactive dextran and demonstrate its utility by photochemically attaching it onto various polymeric substrates. The attachment of homogeneous and patterned dextran films was performed on polyurethane and polystyrene, with detailed analysis of surface morphology, swelling behavior, and the protein resistance of these substrates. The described photoactive dextran and attachment procedure is applicable to a wide variety of substrates while accommodating surfaces with complex surface and geometries. Dextran with azide content between 22 to 0.3 wt% was produced by esterification with p-azidobenzoic acid. Dextran (1.2 wt% azide) was photografted onto plasma oxidized polyurethane and polystyrene and displayed thicknesses of 5 ± 3 nm and 7 ± 3 nm, respectively. The patterned dextran on oxidized polyurethane was patchy with a nominal height difference between dextranized and non-dextranized regions. The azidated dextran on oxidized polystyrene exhibited a distinct step in height. In the presence of PBS buffer, the dextranized regions became smoother and more uniform without affecting the height difference at the oxidized polyurethane boundary. However, the dextranized regions on oxidized polyurethane were observed to swell by a factor of 3 relative to the dried thickness. These dissimilarities were attributed to hydrogen bonding between the dextran and oxidized polyurethane and were confirmed by the photoimmobiliization in the presence of LiCl. The resulting surface was the smoothest of all the azidated dextran samples (RRMS = 1 ± 0.3 nm) and swelled up to 2 times its dried thickness in PBS buffer. The antifouling properties of dextran functionalized surfaces were verified by the selective adsorption of FITC-labeled human albumin only on the non-dextranized regions of the patterned polyurethane and polystyrene substrates. PMID:20712352

Natural Tissue Microenvironmental Conditions Modulate Adhesive Material Performance

PubMed Central

Oliva, Nuria; Shitreet, Sagi; Abraham, Eytan; Stanley, Butch; Edelman, Elazer R.; Artzi, Natalie

2015-01-01

We designed and optimized tissue-responsive adhesive materials by matching material and tissue properties. A two-component material based on dextran aldehyde and dendrimer amine provides a cohesive gel through aldehyde–amine cross-linking and an adhesive interface created by a dextran aldehyde-selective reaction with tissue amines. By altering aldehyde–amine chemistry, we examined how variations in tissue surfaces (serosal amine density in the duodenum, jejunum, and ileum) affect interactions with adhesive materials of varied compositions (aldehyde content). Interestingly, the same adhesive formulation reacts differentially with the three regions of the small intestine as a result of variation in the tissue amine density along the intestinal tract, affecting the tissue–material interfacial morphology, adhesion strength, and adhesive mechanical properties. Whereas tissues provide chemical anchors for interaction with materials, we were able to tune the adhesion strength for each section of the small intestine tissue by altering the adhesive formulation using a two-component material with flexible variables aimed at controlling the aldehyde/amine ratio. This tissue-specific approach should be applied to the broad spectrum of biomaterials, taking into account specific microenvironmental conditions in material design. PMID:23046479

Protein resistance of dextran and dextran-PEG copolymer films

PubMed Central

Kozak, Darby; Chen, Annie; Bax, Jacinda; Trau, Matt

2011-01-01

The protein resistance of dextran and dextran-poly(ethylene glycol) (PEG) copolymer films was examined on an organosilica particle-based assay support. Comb-branched dextran-PEG copolymer films were synthesized in a two step process using the organosilica particle as a solid synthetic support. Particles modified with increasing amounts (0.1-1.2 mg m−2) of three molecular weights (10 000, 66 900, 400 000 g mol−1) of dextran were found to form relatively poor protein-resistant films compared to dextran-PEG copolymers and previously studied PEG films. The efficacy of the antifouling polymer films was found to be dependent on the grafted amount and its composition, with PEG layers being the most efficient, followed by dextran-PEG copolymers, and dextran alone being the least efficient. Immunoglobulin gamma (IgG) adsorption decreased from ~ 5 to 0.5 mg m−2 with increasing amounts of grafted dextran, but bovine serum albumin (BSA) adsorption increased above monolayer coverage (to ~2 mg m−2) indicating ternary adsorption of the smaller protein within the dextran layer. PMID:21614699

Efficient fabrication of high-capacity immobilized metal ion affinity chromatographic media: The role of the dextran-grafting process and its manipulation.

PubMed

Zhao, Lan; Zhang, Jingfei; Huang, Yongdong; Li, Qiang; Zhang, Rongyue; Zhu, Kai; Suo, Jia; Su, Zhiguo; Zhang, Zhigang; Ma, Guanghui

2016-03-01

Novel high-capacity Ni(2+) immobilized metal ion affinity chromatographic media were prepared through the dextran-grafting process. Dextran was grafted to an allyl-activated agarose-based matrix followed by functionalization for the immobilized metal ion affinity chromatographic media. With elaborate regulation of the allylation degree, dextran was completely or partly grafted to agarose microspheres, namely, completely dextran-grafted agarose microspheres and partly dextran-grafted ones, respectively. Confocal laser scanning microscope results demonstrated that a good adjustment of dextran-grafting degree was achieved, and dextran was distributed uniformly in whole completely dextran-grafted microspheres, while just distributed around the outside of the partly dextran-grafted ones. Flow hydrodynamic properties were improved greatly after the dextran-grafting process, and the flow velocity increased by about 30% compared with that of a commercial chromatographic medium (Ni Sepharose FF). A significant improvement of protein binding performance was also achieved by the dextran-grafting process, and partly dextran-grafted Ni(2+) chelating medium had a maximum binding capacity for His-tagged lactate dehydrogenase about 2.5 times higher than that of Ni Sepharose FF. The results indicated that this novel chromatographic medium is promising for applications in high-efficiency and large-scale protein purification. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tumor targeting of gene expression through metal-coordinated conjugation with dextran.

PubMed

Hosseinkhani, Hossein; Aoyama, Teruyoshi; Ogawa, Osamu; Tabata, Yasuhiko

2003-03-07

Tumor targeting of plasmid DNA was achieved through the conjugation of dextran derivatives with chelate residues based on metal coordination. Diethylenetriamine pentaacetic acid (DTPA), spermidine (Sd), and spermine (Sm) were chemically introduced to the hydroxyl groups of dextran to obtain dextran-DTPA, dextran-Sd and dextran-Sm derivatives. Conjugation of the dextran derivative by Zn(2+) coordination decreased the apparent size of the plasmid DNA, depending on the derivative type. The negative zeta potential of plasmid DNA became almost 0 mV after Zn(2+)-coordinated conjugation with dextran-Sm. When the dextran derivative-plasmid DNA conjugates with Zn(2+) coordination were intravenously injected subcutaneously into mice bearing Meth-AR-1 fibrosarcoma, the dextran-Sm-plasmid DNA conjugate significantly enhanced the level of gene expression in the tumor, in contrast to the conjugate of other dextran derivatives and free plasmid DNA. The enhanced gene expression produced by the Zn(2+)-coordinated dextran-Sm-plasmid DNA conjugate was specific to the tumor, whereas a simple mixture of dextran-Sm and plasmid DNA was not effective. The level of gene expression depended on the percentage of chelate residues introduced, the mixing weight ratio of the plasmid DNA/Sm residue used for conjugate preparation, and the plasmid DNA dose. A fluorescent microscopic study revealed that localization of plasmid DNA in the tumor tissue was observed only after injection of the dextran-Sm-plasmid DNA conjugate with Zn(2+) coordination. In addition, the gene expression induced by the conjugate lasted for more than 10 days after the injection. We conclude that Zn(2+)-coordinated dextran-Sm conjugation is a promising way to enable plasmid DNA to target the tumor in gene expression as well as to prolong the duration of gene expression.

Immunogenic properties of alpha (1----6) dextran, its protein conjugates, and conjugates of its breakdown products in mice.

PubMed

Mäkelä, O; Péterfy, F; Outschoorn, I G; Richter, A W; Seppälä, I

1984-06-01

Mice were immunized with alpha (1-6) dextran, either as such or coupled to protein carriers, and their anti-dextran response was measured by a solid-phase radioimmunoassay and the Farr assay. Like earlier investigators we found that protein-conjugated dextran was more antigenic than plain dextran. Our novel findings were that (1) a standard dose (30 micrograms of dextran per injection) coupled to strongly antigenic protein (chicken serum albumin (CSA) was three times more antigenic than dextran coupled to weakly antigenic bovine serum albumin (BSA); (2) dextrans of low molecular weight (1000-10,000 daltons) coupled to CSA induced at least ten times stronger secondary responses than did a similarly coupled macromolecular dextran (5-40 million daltons); (3) variation of the CHO/protein ratio from 0.3 to 1 had little effect on the antigenicity of the dextran. Increase of the ratio from one appeared to decrease immunogenicity when BSA was the carrier but not when CSA was the carrier.

Molecular self assembly of mixed comb-like dextran surfactant polymers for SPR virus detection.

PubMed

Mai-Ngam, Katanchalee; Kiatpathomchai, Wansika; Arunrut, Narong; Sansatsadeekul, Jitlada

2014-11-04

The synthesis of two comb-like dextran surfactant polymers, that are different in their dextran molecular weight (MW) distribution and the presence of carboxylic groups, and their characterization are reported. A bimodal carboxylic dextran surfactant polymer consists of poly(vinyl amine) (PVAm) backbone with carboxyl higher MW dextran, non-functionalized lower MW dextran and hydrophobic hexyl branches; while a monomodal dextran surfactant polymer is PVAm grafted with non-functionalized lower MW dextran and hexyl branches. Layer formation of non-covalently attached dextran chains with bimodal MW distributions on a surface plasmon resonance (SPR) chip was investigated from the perspective of mixed physisorption of the bimodal and monomodal surfactant polymers. Separation distances between the carboxylic longer dextran side chains within the bimodal surfactant polymer and between the whole bimodal surfactant molecules on the chip surface could be well-controlled. SPR analysis of shrimp yellow head virus using our mixed surfactant chips showed dependence on synergetic adjustment of these separation distances. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dextran Nanoparticle Synthesis and Properties

PubMed Central

Wasiak, Iga; Kulikowska, Aleksandra; Janczewska, Magdalena; Michalak, Magdalena; Cymerman, Iwona A.; Nagalski, Andrzej; Kallinger, Peter; Szymanski, Wladyslaw W.; Ciach, Tomasz

2016-01-01

Dextran is widely exploited in medical products and as a component of drug-delivering nanoparticles (NPs). Here, we tested whether dextran can serve as the main substrate of NPs and form a stable backbone. We tested dextrans with several molecular masses under several synthesis conditions to optimize NP stability. The analysis of the obtained nanoparticles showed that dextran NPs that were synthesized from 70 kDa dextran with a 5% degree of oxidation of the polysaccharide chain and 50% substitution with dodecylamine formed a NP backbone composed of modified dextran subunits, the mean diameter of which in an aqueous environment was around 100 nm. Dextran NPs could be stored in a dry state and reassembled in water. Moreover, we found that different chemical moieties (e.g., drugs such as doxorubicin) can be attached to the dextran NPs via a pH-dependent bond that allows release of the drug with lowering pH. We conclude that dextran NPs are a promising nano drug carrier. PMID:26752182

Dextran Nanoparticle Synthesis and Properties.

PubMed

Wasiak, Iga; Kulikowska, Aleksandra; Janczewska, Magdalena; Michalak, Magdalena; Cymerman, Iwona A; Nagalski, Andrzej; Kallinger, Peter; Szymanski, Wladyslaw W; Ciach, Tomasz

2016-01-01

Dextran is widely exploited in medical products and as a component of drug-delivering nanoparticles (NPs). Here, we tested whether dextran can serve as the main substrate of NPs and form a stable backbone. We tested dextrans with several molecular masses under several synthesis conditions to optimize NP stability. The analysis of the obtained nanoparticles showed that dextran NPs that were synthesized from 70 kDa dextran with a 5% degree of oxidation of the polysaccharide chain and 50% substitution with dodecylamine formed a NP backbone composed of modified dextran subunits, the mean diameter of which in an aqueous environment was around 100 nm. Dextran NPs could be stored in a dry state and reassembled in water. Moreover, we found that different chemical moieties (e.g., drugs such as doxorubicin) can be attached to the dextran NPs via a pH-dependent bond that allows release of the drug with lowering pH. We conclude that dextran NPs are a promising nano drug carrier.

Structural and biocompatibility properties of dextran from Weissella cibaria JAG8 as food additive.

PubMed

Tingirikari, Jagan Mohan Rao; Kothari, Damini; Shukla, Rishikesh; Goyal, Arun

2014-09-01

Dextran produced from Weissella cibaria JAG8 was purified and characterized. The molecular mass of dextran as determined by the gel filtration and copper bicinchoninate method was approximately, 800 kDa. Monosaccharide analysis revealed that the polysaccharide comprised only glucose units. Dynamic light scattering study confirmed the mono-disperse nature of dextran with hydrodynamic radius of 900 nm. Surface morphology study of dextran by scanning electron microscopy showed the porous web like structure. Cytotoxicity studies on human cervical cancer (HeLa) cell line showed non-toxic and biocompatible nature of dextran. The relative browning for dextran from W. cibaria JAG8 was similar to commercial prebiotic Nutraflora P-95 and 3-fold lower than Raftilose P-95. Synthesis of dextran by dextransucrase treated, sucrose-supplemented skimmed milk revealed the promising potential of dextran as a food additive.

Superior prebiotic and physicochemical properties of novel dextran from Weissella cibaria JAG8 for potential food applications.

PubMed

Tingirikari, Jagan Mohan Rao; Kothari, Damini; Goyal, Arun

2014-09-01

The dextran produced by dextransucrase from Weissella cibaria JAG8 was subjected to physicochemical characterization and assessment of its prebiotic potential. Dextran displayed a solubility of 24.5% and a water holding capacity of 352%. The emulsion and flocculation activity of dextran were 89% and 92%, respectively. The degradation temperature (Td) of dextran was 353 °C. Dextran exhibited 33- and 12-fold less hydrolysis than inulin, in simulated gastric juice (pH 1.0) and α-amylase (pH 7.0), respectively. Dextran stimulated the growth of probiotic bacteria such as Bifidobacterium animalis subspecies lactis, Bifidobacterium infantis and Lactobacillus acidophilus significantly and was comparable to that of commercial inulin. However, the growth of E. coli was not enhanced by dextran or inulin. The dextran used in this study can be used as a potential prebiotic for health benefits.

Isolation of Intact Chloroplasts from Euglena gracilis by Zonal Centrifugation 1

PubMed Central

Vasconcelos, Aurea; Pollack, Marilyn; Mendiola, Leticia R.; Hoffmann, H.-P.; Brown, D. H.; Price, C. A.

1971-01-01

Chloroplasts were separated from Euglena gracilis by zonal centrifugation at low speed in density gradients of Ficoll or dextran. The chloroplasts were intact by the criteria of ultrastructure and their content of ribulose diphosphate carboxylase and soluble protein. The chloroplasts also contained ribosomes and ribosomal RNA uncontaminated by the corresponding cytoplasmic particles. Images PMID:16657599

Dextran-encapsulated photoluminescent gold nanoclusters: synthesis and application

NASA Astrophysics Data System (ADS)

Chiu, Wei-Ju; Chen, Wei-Yu; Lai, Hong-Zheng; Wu, Ching-Yi; Chiang, Hsiang-Lin; Chen, Yu-Chie

2014-07-01

Dextrans are widely used as additives in food, pharmaceutical, and cosmetics because of their hydrophilicity, biocompatibility, and low toxicity. These features allow the use of dextrans to modify the surface of nanoparticles to improve cell compatibility for biomedical applications. Additionally, dextran molecules covalently bound with fluorescent dyes are frequently used as tracers in animal studies. These facts show that dextrans are useful compounds for biomedicine-related applications and research. Our aim was to explore a facile way to generate dextran-derived nanoparticles with photoluminescent property for the use in fluorescence imaging of bacteria and cancer cells. Dextran-encapsulated gold nanoclusters (AuNCs@dextran) were generated through a one-pot reaction by stirring dextrans and aqueous tetrachloroauric acid overnight. The generated AuNCs exhibit bright and green photoluminescence under the illumination of an ultraviolet lamp ( λ max = 365 nm), and high cell biocompatibility was found as well. Therefore, the generated AuNCs can be used as fluorescence tracers and nanoprobes. We explored the suitability of AuNCs@dextran as labeling agents for bacteria, such as Staphylococcus aureus and Escherichia coli. After the bacteria were labeled by AuNCs@dextran, they became quite visible under a fluorescence microscope. Additionally, we demonstrated that nanocomposites composed of AuNCs@dextran and silica beads can be readily internalized by cancer cells. The nanocomposites can be readily detected in the cells through their photoluminescence, suggesting possible applications in drug delivery and fluorescence imaging.

Quantitative Correlation between Infectivity and Gp120 Density on HIV-1 Virions Revealed by Optical Trapping Virometry*

PubMed Central

DeSantis, Michael C.; Kim, Jin H.; Song, Hanna; Klasse, Per Johan

2016-01-01

The envelope glycoprotein (Env) gp120/gp41 is required for HIV-1 infection of host cells. Although in general it has been perceived that more Env gives rise to higher infectivity, the precise quantitative dependence of HIV-1 virion infectivity on Env density has remained unknown. Here we have developed a method to examine this dependence. This method involves 1) production of a set of single-cycle HIV-1 virions with varied density of Env on their surface, 2) site-specific labeling of Env-specific antibody Fab with a fluorophore at high efficiency, and 3) optical trapping virometry to measure the number of gp120 molecules on individual HIV-1 virions. The resulting gp120 density per virion is then correlated with the infectivity of the virions measured in cell culture. In the presence of DEAE-dextran, the polycation known to enhance HIV-1 infectivity in cell culture, virion infectivity follows gp120 density as a sigmoidal dependence and reaches an apparent plateau. This quantitative dependence can be described by a Hill equation, with a Hill coefficient of 2.4 ± 0.6. In contrast, in the absence of DEAE-dextran, virion infectivity increases monotonically with gp120 density and no saturation is observed under the experimental conditions. These results provide the first quantitative evidence that Env trimers cooperate on the virion surface to mediate productive infection by HIV-1. Moreover, as a result of the low number of Env trimers on individual virions, the number of additional Env trimers per virion that is required for the optimal infectivity will depend on the inclusion of facilitating agents during infection. PMID:27129237

Low molecular weight dextran provides similar optical coherence tomography coronary imaging compared to radiographic contrast media.

PubMed

Frick, Kyle; Michael, Tesfaldet T; Alomar, Mohammed; Mohammed, Atif; Rangan, Bavana V; Abdullah, Shuaib; Grodin, Jerrold; Hastings, Jeffrey L; Banerjee, Subhash; Brilakis, Emmanouil S

2014-11-01

Optical coherence tomography (OCT) coronary imaging requires displacement of red blood cells from the vessel lumen. This is usually accomplished using radiographic contrast. Low molecular weight dextran has low cost and is safe in low volumes. In the present study, we compared dextran with contrast for coronary OCT imaging. Fifty-one vessels in 26 patients were sequentially imaged using manual injection of radiographic contrast (iodixanol) and dextran. OCT images were analyzed at 1 mm intervals to determine the image clarity (defined as a visible lumen border > 270°) and to measure the lumen area and lumen diameter. To correct for the refractive index of dextran, the dextran area measurements were multiplied by 1.117 and the dextran length measurements were multiplied by 1.057. A total of 3,418 cross-sections (1,709 with contrast and 1,709 with dextran) were analyzed. There were no complications related to OCT imaging or to contrast or dextran administration. Clear image segments were observed in 97.0% vs. 96.7% of the cross-sections obtained with contrast and dextran, respectively (P = 0.45). The mean lumen areas were also similar: 6.69 ± 1.95 mm(2) with iodixanol vs. 7.06 ± 2.06 mm(2) with dextran (correlation coefficient 0.984). The image quality and measurements during OCT image acquisition are similar for dextran and contrast. Dextran could be used instead of contrast for OCT imaging, especially in patients in whom contrast load minimization is desired. © 2013 Wiley Periodicals, Inc.

Molecular recognition between insulin and dextran encapsulated gold nanoparticles.

PubMed

Lee, Kai-Chieh; Chiang, Hsiang-Ling; Chiu, Wei-Ru; Chen, Yu-Chie

2016-11-01

Insulin is a peptide hormone that can regulate the metabolism of carbohydrates and lipids. This hormone is closely related to glucose-uptake in cells and can control blood glucose levels. Dextran is a polysaccharide composed of glucose units. In this study, we discovered that dextran-encapsulated gold nanoparticles (AuNPs@Dextran) and nanoclusters (AuNCs@Dextran) can be used to recognize insulin. The dissociation constant of insulin toward AuNPs@Dextran was estimated to be ∼5.3 × 10 -6  M. The binding site on insulin toward the dextran on the nanoprobes was explored as well. It was found that the sequence of numbers 1-22 on the insulin B chain can interact with the dextran encapsulated nanoprobes. Additionally, we also demonstrated that the dextran-encapsulated nanoprobes could be used as concentration probes to selectively enrich trace amounts of insulin (∼1 pM) from serum samples. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Semi-quantitative assessments of dextran toxicity on corneal endothelium: conceptual design of a predictive algorithm.

PubMed

Filev, Filip; Oezcan, Ceprail; Feuerstacke, Jana; Linke, Stephan J; Wulff, Birgit; Hellwinkel, Olaf J C

2017-03-01

Dextran is added to corneal culture medium for at least 8 h prior to transplantation to ensure that the cornea is osmotically dehydrated. It is presumed that dextran has a certain toxic effect on corneal endothelium but the degree and the kinetics of this effect have not been quantified so far. We consider that such data regarding the toxicity of dextran on the corneal endothelium could have an impact on scheduling and logistics of corneal preparation in eye banking. In retrospective statistic analyses, we compared the progress of corneal endothelium (endothelium cell loss per day) of 1334 organ-cultured corneal explants in media with and without dextran. Also, the influence of donor-age, sex and cause of death on the observed dextran-mediated effect on endothelial cell counts was studied. Corneas cultured in dextran-free medium showed a mean endothelium cell count decrease of 0.7% per day. Dextran supplementation led to a mean endothelium cell loss of 2.01% per day; this reflects an increase by the factor of 2.9. The toxic impact of dextran was found to be time dependent; while the prevailing part of the effect was observed within the first 24 h after dextran-addition. Donor age, sex and cause of death did not seem to have an influence on the dextran-mediated toxicity. Based on these findings, we could design an algorithm which approximately describes the kinetics of dextran-toxicity. We reproduced the previously reported toxic effect of dextran on the corneal endothelium in vitro. Additionally, this is the first work that provides an algorithmic instrument for the semi-quantitative calculation of the putative endothelium cell count decrease in dextran containing medium for a given incubation time and could thus influence the time management and planning of corneal transplantations.

Acute and chronic exposure of rat intestinal mucosa to dextran promotes SGLTI-mediated glucose transport.

PubMed

Debnam, E S; Denholm, E E; Grimble, G K

1998-08-01

The intestinal handling of dextran, an alpha-1,6-linked glucose polymer, is poor compared with starch, and some ingested dextran might therefore reach the lower small intestine. As luminal sugar up-regulates SGLT1 (sodium-dependent glucose transporter) locally, we report the effects of a dextran-enriched diet on jejunal and ileal brush border membrane (BBM) glucose uptake. Rats were maintained on a diet containing 65% maltodextrin or 32.5% maltodextrin + 32.5% dextran (10 kD or 40 kD) for 8-10 days, and the kinetics of phlorizin-sensitive [3H]-glucose uptake by purified BBM vesicles was determined. Ingestion of 40-kD but not 10-kD dextran increased Vmax for jejunal and ileal glucose uptake (+64.3% and +61.8% respectively, both P < 0.02). The transport response to 40-kD dextran was in keeping with lower levels of expired H2 at the end of the feeding period. High-performance liquid chromatography (HPLC) analysis of luminal contents indicated extensive hydrolysis of ingested dextran. Finally, 3-h jejunal exposure to 40-kD dextran in vivo increased the Vmax for glucose uptake by jejunal BBM. It is likely that increased SGLT1-mediated glucose uptake after short or longer term mucosal exposure to dextran results from luminal dextran per se or a hydrolysis product. The clinical implications of this up-regulation are discussed.

Dextran Utilization During Its Synthesis by Weissella cibaria RBA12 Can Be Overcome by Fed-Batch Fermentation in a Bioreactor.

PubMed

Baruah, Rwivoo; Deka, Barsha; Kashyap, Niharika; Goyal, Arun

2018-01-01

Weissella cibaria RBA12 produced a maximum of 9 mg/ml dextran (with 90% efficiency) using shake flask culture under the optimized concentration of medium components viz. 2% (w/v) of each sucrose, yeast extract, and K 2 HPO 4 after incubation at optimized conditions of 20 °C and 180 rpm for 24 h. The optimized medium and conditions were used for scale-up of dextran production from Weissella cibaria RBA12 in 2.5-l working volume under batch fermentation in a bioreactor that yielded a maximum of 9.3 mg/ml dextran (with 93% efficiency) at 14 h. After 14 h, dextran produced was utilized by the bacterium till 18 h in its stationary phase under sucrose depleted conditions. Dextran utilization was further studied by fed-batch fermentation using sucrose feed. Dextran on production under fed-batch fermentation in bioreactor gave 35.8 mg/ml after 32 h. In fed-batch mode, there was no decrease in dextran concentration as observed in the batch mode. This showed that the utilization of dextran by Weissella cibaria RBA12 is initiated when there is sucrose depletion and therefore the presence of sucrose can possibly overcome the dextran hydrolysis. This is the first report of utilization of dextran, post-sucrose depletion by Weissella sp. studied in bioreactor.

Production & Characterization of a Unique Dextran from an Indigenous Leuconostoc mesenteroides CMG713

PubMed Central

Sarwat, Farwa; Qader, Shah Ali Ul; Aman, Afsheen; Ahmed, Nuzhat

2008-01-01

On the basis of high enzyme activity a newly isolated strain of L. mesenteroides CMG713 was selected for dextran production. For maximum yield of dextran, effects of various parameters such as pH, temperature, sucrose concentration and incubation period were studied. L. mesenteroides CMG713 produced maximum dextran after 20 hours of incubation at 30ºC with 15% sucrose at pH 7.0. The molecular mass distribution of dextran produced by this strain showed that its molecular mass was about 2.0 million Da. Dextran analysis by 13C-NMR spectrometry showed no signals corresponding to any other linkages except α-(1→6) glycosidic linkage in the main chain, which has not been reported before. Physico-chemical properties of this unique dextran were also studied. These optimised conditions could be used for the commercial production of this unique high molecular weight dextran, which have significant industrial perspectives. PMID:18953402

Discontinuous Galerkin finite element method for solving population density functions of cortical pyramidal and thalamic neuronal populations.

PubMed

Huang, Chih-Hsu; Lin, Chou-Ching K; Ju, Ming-Shaung

2015-02-01

Compared with the Monte Carlo method, the population density method is efficient for modeling collective dynamics of neuronal populations in human brain. In this method, a population density function describes the probabilistic distribution of states of all neurons in the population and it is governed by a hyperbolic partial differential equation. In the past, the problem was mainly solved by using the finite difference method. In a previous study, a continuous Galerkin finite element method was found better than the finite difference method for solving the hyperbolic partial differential equation; however, the population density function often has discontinuity and both methods suffer from a numerical stability problem. The goal of this study is to improve the numerical stability of the solution using discontinuous Galerkin finite element method. To test the performance of the new approach, interaction of a population of cortical pyramidal neurons and a population of thalamic neurons was simulated. The numerical results showed good agreement between results of discontinuous Galerkin finite element and Monte Carlo methods. The convergence and accuracy of the solutions are excellent. The numerical stability problem could be resolved using the discontinuous Galerkin finite element method which has total-variation-diminishing property. The efficient approach will be employed to simulate the electroencephalogram or dynamics of thalamocortical network which involves three populations, namely, thalamic reticular neurons, thalamocortical neurons and cortical pyramidal neurons. Copyright © 2014 Elsevier Ltd. All rights reserved.

Ultrasound enhances in vivo tumor expression of plasmid DNA by PEG-introduced cationized dextran.

PubMed

Hosseinkhani, Hossein; Tabata, Yasuhiko

2005-11-28

This study is an investigation to experimentally confirm whether or not ultrasound (US) irradiation is effective in enhancing the in vivo gene expression of plasmid DNA in tumor. Dextran was cationized by introducing spermine to the hydroxyl groups to allow to polyionically complex with a plasmid DNA. The cationized dextran prepared was additionally modified with poly(ethylene glycol) (PEG) molecules which have an active ester and methoxy groups at each terminal, to obtain cationized dextran with different percentages of PEG introduced. Various cationized dextrans with or without PEG introduction were mixed with a plasmid DNA of LacZ to form cationized dextran-plasmid DNA complexes. Electrophoretical examination revealed that the plasmid DNA was complexed both with the cationized dextran and PEG-introduced cationized dextran, irrespective of the PEG introduction percentage, although the higher N/P ratio was needed for plasmid DNA complexation with the latter. By complexation with the cationized dextran, the zeta potential of plasmid DNA was changed to be positive. The charge of PEG-introduced cationized dextran-plasmid DNA complexes became close to 0 mV as their percentage of PEG introduced increased, although the molecular size was about 250 nm, irrespective of the PEG introduction. When cationized dextran-plasmid DNA complexes with or without PEG introduction were intravenously injected to mice carrying a subcutaneous Meth-AR-1 fibrosarcoma mass and the subsequent US irradiation to the tumor mass percutaneously, the PEG-introduced cationized dextran-plasmid DNA complex plus US irradiation enhanced the tumor level of gene expression to a significantly high extent compared with the cationized dextran-plasmid DNA complex and free plasmid DNA with or without US irradiation. The enhanced level depended on the time period and timing of US irradiation. Fluorescent microscopic studies revealed that the localization of plasmid DNA and the gene expression were observed in the tumor tissue injected with the PEG-introduced cationized dextran-plasmid DNA complex plus the subsequent US irradiation. We conclude that complexation with the PEG-introduced cationized dextran combined with US irradiation is a promising way to target the plasmid DNA to the tumor for gene expression.

Role of β-Interferon Inducer (DEAE-Dextran) in Tumorigenesis by VEGF and NOTCH1 Inhibition along with Apoptosis Induction.

PubMed

Bakrania, Anita K; Variya, Bhavesh C; Patel, Snehal S

2017-01-01

As a novel target for breast cancer, interferon inducers have found its role as anti-angiogenic agents with diethylaminoethyl dextran (DEAE-Dextran) being a molecule used for centuries as a transfection agent. Our results herein offer an explanation for the emergence of DEAE-Dextran as an anti-tumor agent for TNBC with in-depth mechanistic approach as an anti-angiogenic molecule. DEAE-Dextran has found to possess cytotoxic activity demonstrated during the various in vitro cytotoxicity assays; moreover, as an anti-oxidant, DEAE-Dextran has shown to possess excellent reactive oxygen species scavenging activity. The interferon inducing capacity of DEAE-Dextran was determined qualitatively as well as quantitatively specifically demonstrating overexpression of β-interferon. As a measure of anti-proliferative activity, DEAE-Dextran exhibited reduced ki67, p53, and PCNA levels. Also, overexpression of CK5/6 and p63 in DEAE-Dextran treated animals indicated improvement in breast cell morphology along with an improvement in cell-cell adhesion by virtue of upregulation of β-catenin and E-cadherin. Anti-angiogenic property of DEAE-Dextran was concluded by the downregulation of CD31, VEGF, and NOTCH1 both in vivo and in vitro . Further, apoptosis due to DEAE-Dextran, initially determined by downregulation of Bcl2, was confirmed with flow cytometry. Overall, results are defensive of DEAE-Dextran as an emerging anti-tumor agent with mechanisms pertaining to β-interferon induction with probable VEGF and NOTCH1 inhibition as well as apoptosis which still needs to be studied in further depth.

Role of β-Interferon Inducer (DEAE-Dextran) in Tumorigenesis by VEGF and NOTCH1 Inhibition along with Apoptosis Induction

PubMed Central

Bakrania, Anita K.; Variya, Bhavesh C.; Patel, Snehal S.

2017-01-01

As a novel target for breast cancer, interferon inducers have found its role as anti-angiogenic agents with diethylaminoethyl dextran (DEAE-Dextran) being a molecule used for centuries as a transfection agent. Our results herein offer an explanation for the emergence of DEAE-Dextran as an anti-tumor agent for TNBC with in-depth mechanistic approach as an anti-angiogenic molecule. DEAE-Dextran has found to possess cytotoxic activity demonstrated during the various in vitro cytotoxicity assays; moreover, as an anti-oxidant, DEAE-Dextran has shown to possess excellent reactive oxygen species scavenging activity. The interferon inducing capacity of DEAE-Dextran was determined qualitatively as well as quantitatively specifically demonstrating overexpression of β-interferon. As a measure of anti-proliferative activity, DEAE-Dextran exhibited reduced ki67, p53, and PCNA levels. Also, overexpression of CK5/6 and p63 in DEAE-Dextran treated animals indicated improvement in breast cell morphology along with an improvement in cell–cell adhesion by virtue of upregulation of β-catenin and E-cadherin. Anti-angiogenic property of DEAE-Dextran was concluded by the downregulation of CD31, VEGF, and NOTCH1 both in vivo and in vitro. Further, apoptosis due to DEAE-Dextran, initially determined by downregulation of Bcl2, was confirmed with flow cytometry. Overall, results are defensive of DEAE-Dextran as an emerging anti-tumor agent with mechanisms pertaining to β-interferon induction with probable VEGF and NOTCH1 inhibition as well as apoptosis which still needs to be studied in further depth. PMID:29311933

Asymmetry of nonlinear interactions of solar MHD discontinuities with the bow shock

NASA Astrophysics Data System (ADS)

Grib, S. A.; Pushkar, E. A.

2006-07-01

Oblique interaction between the solar fast shock wave, which is a typical nonstationary strong discontinuity in the interplanetary space, and the bow shock front upstream of an Earth-type planetary magnetosphere is studied. Attention has been paid to the qualitative and quantitative (with respect to the proton density distribution) dawn-dusk (or morning-evening) asymmetry of the discontinuities refracted into the magnetosheath, which originates in the ecliptic plane on different sides of the Sun-Earth line. The results under discussion have been corroborated experimentally by the gas-kinetic pattern of the bow-shock front and the WIND and ISEE 3 spacecraft measurements of the plasma density.

Sequential limiting in continuous and discontinuous Galerkin methods for the Euler equations

NASA Astrophysics Data System (ADS)

Dobrev, V.; Kolev, Tz.; Kuzmin, D.; Rieben, R.; Tomov, V.

2018-03-01

We present a new predictor-corrector approach to enforcing local maximum principles in piecewise-linear finite element schemes for the compressible Euler equations. The new element-based limiting strategy is suitable for continuous and discontinuous Galerkin methods alike. In contrast to synchronized limiting techniques for systems of conservation laws, we constrain the density, momentum, and total energy in a sequential manner which guarantees positivity preservation for the pressure and internal energy. After the density limiting step, the total energy and momentum gradients are adjusted to incorporate the irreversible effect of density changes. Antidiffusive corrections to bounds-compatible low-order approximations are limited to satisfy inequality constraints for the specific total and kinetic energy. An accuracy-preserving smoothness indicator is introduced to gradually adjust lower bounds for the element-based correction factors. The employed smoothness criterion is based on a Hessian determinant test for the density. A numerical study is performed for test problems with smooth and discontinuous solutions.

Magnetic catechin-dextran conjugate as targeted therapeutic for pancreatic tumour cells.

PubMed

Vittorio, Orazio; Voliani, Valerio; Faraci, Paolo; Karmakar, Biswajit; Iemma, Francesca; Hampel, Silke; Kavallaris, Maria; Cirillo, Giuseppe

2014-06-01

Catechin-dextran conjugates have recently attracted a lot of attention due to their anticancer activity against a range of cancer cells. Magnetic nanoparticles have the ability to concentrate therapeutically important drugs due to their magnetic-spatial control and provide opportunities for targeted drug delivery. Enhancement of the anticancer efficiency of catechin-dextran conjugate by functionalisation with magnetic iron oxide nanoparticles. Modification of the coating shell of commercial magnetic nanoparticles (Endorem) composed of dextran with the catechin-dextran conjugate. Catechin-dextran conjugated with Endorem (Endo-Cat) increased the intracellular concentration of the drug and it induced apoptosis in 98% of pancreatic tumour cells placed under magnetic field. The conjugation of catechin-dextran with Endorem enhances the anticancer activity of this drug and provides a new strategy for targeted drug delivery on tumour cells driven by magnetic field. The ability to spatially control the delivery of the catechin-dextran by magnetic field makes it a promising agent for further application in cancer therapy.

Preparation, characterization and dynamical mechanical properties of dextran-coated iron oxide nanoparticles (DIONPs).

PubMed

Can, Hatice Kaplan; Kavlak, Serap; ParviziKhosroshahi, Shahed; Güner, Ali

2018-03-01

Dextran-coated iron oxide nanoparticles (DIONPs) with appropriate surface chemistry exhibit many interesting properties that can be exploited in a variety of biomedical applications such as magnetic resonance imaging (MRI) contrast enhancement, tissue repair, hyperthermia, drug delivery and in cell separation. This paper reports the experimental detail for preparation, characterization and investigation of thermal and dynamical mechanical characteristics of the dextran-coated Fe 3 O 4 magnetic nanoparticles. In our work, DIONPs were prepared in a 1:2 ratio of Fe(II) and Fe(III) salt in the HCl solution with NaOH at given temperature. The obtained dextran-coated iron-oxide nanoparticles structure-property correlation was characterized by spectroscopic methods; attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and XRD. Coating dextran on the iron-oxide proof of important peaks can be seen from the ATR-FTIR. Dramatic crystallinity increment can be observed from the XRD pattern of the iron-oxide dextran nanoparticles. The thermal analysis was examined by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). Dynamical mechanical properties of dextran nanoparticles were analysed by dynamic mechanical analysis (DMA). Thermal stability of the iron oxide dextran nanoparticles is higher than that of the dextran.

The impact of the molecular weight of dextran on formation of whey protein isolate (WPI)-dextran conjugates in fibers produced by needleless electrospinning after annealing.

PubMed

Turan, Deniz; Gibis, Monika; Gunes, Gurbuz; Baier, Stefan K; Weiss, Jochen

2018-04-25

The conjugation reaction of electrospun fibers of a mixture of whey protein isolate (WPI) and dextran using different molecular weights (40, 70, and 100 kDa) and mixing ratios was studied. This study includes the electrospinnability of a mixture of WPI and dextran, and the conjugation reaction between them via the initial stage of the Maillard reaction. The WPI-dextran fibers were characterized using optical and transmission electron microscopy. The covalent attachment of dextran to WPI was confirmed using sodium-dodecyl-sulfate-polyacrylamide gel-electrophoresis with protein and glycoprotein staining. Both 70 and 100 kDa of dextran and WPI at mixing ratios of 2 : 1 and 3 : 1 in phosphate buffer (30 mM, pH 6.5) were electrospun using needleless electrospinning. The solution concentration of the mixture was 50 wt% (33.3/37.5 wt% for dextran/16.5/12.5 wt% for WPI). The optimal conjugation conditions chosen from the experiments were a mixture of dextran (70 kDa)-WPI at 3 : 1 (75% relative humidity, 60 °C, 48 h).

Eudragit-coated dextran microspheres of 5-fluorouracil for site-specific delivery to colon.

PubMed

Rai, Gopal; Yadav, Awesh K; Jain, Narendra K; Agrawal, Govind P

2016-01-01

Objective of the present investigation was to prepare and evaluate the potential of enteric coated dextran microspheres for colon targeting of 5-fluorouracil (5-FU). Dextran microspheres were prepared by emulsification-crosslinking method and the formulation variables studied included different molecular weights of dextran, drug:polymer ratio, volume of crosslinking agent, stirring speed and time. Enteric coating (Eudragit S-100) of dextran microspheres was performed by oil-in-oil solvent evaporation method using different coat:core ratios (4:1 or 8:1). Uncoated and coated dextran microspheres were characterized by particle size, surface morphology, entrapment efficiency, DSC, in vitro drug release in the presence of dextranase and 2% rat cecal contents. The release study of 5-FU from coated dextran microspheres was pH dependent. No release was observed at acidic pH; however, the drug was released quickly where Eudragit starts solublizing there was continuous release of drug from the microspheres. Organ distribution study was suggested that coated dextran microspheres retard the release of drug in gastric and intestinal pH environment and released of drug from microspheres in colon due to the degradation of dextran by colonic enzymes.

Low cytotoxic tissue adhesive based on oxidized dextran and epsilon-poly-L-lysine.

PubMed

Hyon, Suong-Hyu; Nakajima, Naoki; Sugai, Hajime; Matsumura, Kazuaki

2014-08-01

A novel adhesive hydrogel consisting of dextran and epsilon-poly(L-lysine) (dextran-PL) with multiple biomedical applications was developed. Periodate oxidation in aqueous media almost stoichiometrically introduces aldehyde groups in dextran molecules, and aldehyde dextran can react with the primary amino groups in epsilon-PL (ɛ-PL) at neutral pH to form a hydrogel. The gelation time of the hydrogel can be easily controlled by the extent of oxidation in dextran and of the acylation in ɛ-PL by anhydrides. The shear adhesion strength of dextran-PL was 10 times higher than that of fibrin glue, when wet collagen sheets were selected as test specimens. The cytotoxicity of aldehyde dextran and ɛ-PL were 1000 times lower than that of glutaraldehyde and poly(allylamine). The considerably low cytotoxicity of aldehyde dextran could be ascribed to its low reactivity with amine species when compared with glutaraldehyde. In contrast, a high reactivity of amino groups in ɛ-PL was observed when compared with glycine, L-lysine, and gelatin, which could be explained by their poor dissociation at neutral pH, thus leading to low cytotoxicity. © 2013 Wiley Periodicals, Inc.

Mechanisms of the ultrasound-mediated intracellular delivery of liposomes and dextrans.

PubMed

Afadzi, Mercy; Strand, Sabina P; Nilssen, Esben A; Måsøy, Svein-Erik; Johansen, Tonni F; Hansen, Rune; Angelsen, Bjørn A; de L Davies, Catharina

2013-01-01

The mechanism involved in the ultrasoundenhanced intracellular delivery of fluorescein-isothiocyanate (FITC)-dextran (molecular weight 4 to 2000 kDa) and liposomes containing doxorubicin (Dox) was studied using HeLa cells and an ultrasound transducer at 300 kHz, varying the acoustic power. The cellular uptake and cell viability were measured using flow cytometry and confocal microscopy. The role of endocytosis was investigated by inhibiting clathrin- and caveolae-mediated endocytosis, as well as macropinocytosis. Microbubbles were found to be required during ultrasound treatment to obtain enhanced cellular uptake. The percentage of cells internalizing Dox and dextran increased with increasing mechanical index. Confocal images and flow cytometric analysis indicated that the liposomes were disrupted extracellularly and that released Dox was taken up by the cells. The percentage of cells internalizing dextran was independent of the molecular weight of dextrans, but the amount of the small 4-kDa dextran molecules internalized per cell was higher than for the other dextrans. The inhibition of endocytosis during ultrasound exposure resulted in a significant decrease in cellular uptake of dextrans. Therefore, the improved uptake of Dox and dextrans may be a result of both sonoporation and endocytosis.

Dual-Energy Micro-Computed Tomography Imaging of Radiation-Induced Vascular Changes in Primary Mouse Sarcomas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moding, Everett J.; Clark, Darin P.; Qi, Yi

2013-04-01

Purpose: To evaluate the effects of radiation therapy on primary tumor vasculature using dual-energy (DE) micro-computed tomography (micro-CT). Methods and Materials: Primary sarcomas were generated with mutant Kras and p53. Unirradiated tumors were compared with tumors irradiated with 20 Gy. A liposomal-iodinated contrast agent was administered 1 day after treatment, and mice were imaged immediately after injection (day 1) and 3 days later (day 4) with DE micro-CT. CT-derived tumor sizes were used to assess tumor growth. After DE decomposition, iodine maps were used to assess tumor fractional blood volume (FBV) at day 1 and tumor vascular permeability at daymore » 4. For comparison, tumor vascularity and vascular permeability were also evaluated histologically by use of CD31 immunofluorescence and fluorescently-labeled dextrans. Results: Radiation treatment significantly decreased tumor growth from day 1 to day 4 (P<.05). There was a positive correlation between CT measurement of tumor FBV on day 1 and extravasated iodine on day 4 with microvascular density (MVD) on day 4 (R{sup 2}=0.53) and dextran accumulation (R{sup 2}=0.63) on day 4, respectively. Despite no change in MVD measured by histology, tumor FBV significantly increased after irradiation as measured by DE micro-CT (0.070 vs 0.091, P<.05). Both dextran and liposomal-iodine accumulation in tumors increased significantly after irradiation, with dextran fractional area increasing 5.2-fold and liposomal-iodine concentration increasing 4.0-fold. Conclusions: DE micro-CT is an effective tool for noninvasive assessment of vascular changes in primary tumors. Tumor blood volume and vascular permeability increased after a single therapeutic dose of radiation treatment.« less

Dextran loading protects macrophages from lipid peroxidation and induces a Keap1/Nrf2/ARE-dependent antioxidant response.

PubMed

Chechushkov, Anton; Zaitseva, Natalia; Vorontsova, Elena; Kozhin, Petr; Menshchikova, Elena; Shkurupiy, Vyacheslav

2016-12-01

Linear dextrans are often proposed as drug delivery systems with milder adverse effects and lower effective drug concentrations. Linear dextrans are polysaccharides that can potentially be used to load macrophages with drugs to transport them to a site of inflammation. Recently, it was reported that dextrans may exert a protective effect vis-à-vis drug cytotoxicity and during wound healing. The aim of the current work was to evaluate molecular mechanisms of action of dextrans that may be relevant to the cytoprotective effects. We determined the effect of treatment with 40- or 70-kDa dextran on production of reactive oxygen species, lipid peroxidation, and lysosomal pH in the J774 macrophage cell line. In addition, induction of Keap1/Nrf2/ARE and autophagic activity were evaluated. Dextrans of both molecular weights protected the cells from oxidative stress induced by cumene hydroperoxide and from lysosomal stress induced by ammonium chloride. The effect was associated with induction of the Keap1/Nrf2/ARE signaling pathway. Furthermore, dextran stimulated autophagy in a dose-dependent manner but inhibited the autophagosome-lysosome fusion in a time-dependent manner. This study shows possible cytoprotective effects of dextran under oxidative stress, and these findings may be used for the development of novel (dextran-based) drug delivery approaches. Copyright © 2016 Elsevier Inc. All rights reserved.

β-CD-dextran polymer for efficient sequestration of cholesterol from phospholipid bilayers: Mechanistic and safe-toxicity investigations.

PubMed

Stelzl, Dominik; Nielsen, Thorbjørn Terndrup; Hansen, Terkel; di Cagno, Massimiliano

2015-12-30

The aim of this work was to investigate the suitability of β-cyclodextrin-dextran (BCD-dextran) polymer as cholesterol sequestering agent in vitro. For this purpose, BCD-dextran-cholesterol complexation was studied by phase solubility studies as well as with a specifically designed in vitro model based on giant unilamellar vesicles (GUVs) to evaluate the ability of this polymer to sequestrate cholesterol from phospholipid bilayers. Cholesterol-sequestering ability of BCD-dextran was also investigated on different cell lines relevant for the hematopoietic system and results were correlated to cells toxicity. BCD-dextran polymer was capable of extracting significant amount of cholesterol from phospholipid bilayers and to a higher extent in comparison to available β-cyclodextrins (BCDs). The ability of BCD-dextran in sequestering cholesterol resulted also very high on cell lines relevant for the hematopoietic system. Moreover, BCD-dextran resulted less toxic on cell cultures due to higher selectivity in sequestering cholesterol in comparison to MBCD (that sequestrated also significant amounts of cholesteryl esters). In conclusion, BCD-dextran resulted an extremely efficient cholesterol-sequestering agent and BCD-dextran resulted more selective to cholesterol extraction in comparison to other BCDs (therefore of lower cytotoxicity). This phenomenon might play a key role to develop an efficient treatment for hypercholesterolemia based on cholesterol segregation. Copyright © 2015 Elsevier B.V. All rights reserved.

Protective effect of dextrans on glucose oxidase denaturation and inactivation.

PubMed

Altikatoglu, Melda; Basaran-Elalmis, Yeliz

2012-08-01

In the present study, the stabilizing effect of dextrans as additives on the denaturation and inactivation of glucose oxidase (GOD) was investigated. Three different molecular weighted dextrans (M(w) 17.5, 75, 188 kD) were used with different concentrations. Dramatically increased enzyme activities were measured after one hour of incubation of enzyme with additives between 25-40°C in water bath. Highest activity value was measured with 75 kDa molecular weighted dextran (in concentration 30% w/v) at pH 5. Dextran as an additive supplied a long shelf-life to the enzyme at 4°C. In the presence of the 75 kDa dextran, the enzyme was more stable and its activity was increased 2.7-fold at 30°C. In addition, dextran protected GOD against inactivation by a n-heptane/aqueous buffer-stirred system.

Targeting the C-type lectins-mediated host-pathogen interactions with dextran.

PubMed

Pustylnikov, Sergey; Sagar, Divya; Jain, Pooja; Khan, Zafar K

2014-01-01

Dextran, the α-1,6-linked glucose polymer widely used in biology and medicine, promises new applications. Linear dextran applied as a blood plasma substitute demonstrates a high rate of biocompatibility. Dextran is present in foods, drugs, and vaccines and in most cases is applied as a biologically inert substance. In this review we analyze dextran's cellular uptake principles, receptor specificity and, therefore, its ability to interfere with pathogen-lectin interactions: a promising basis for new antimicrobial strategies. Dextran-binding receptors in humans include the DC-SIGN (dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin) family receptors: DC-SIGN (CD209) and L-SIGN (the liver and lymphatic endothelium homologue of DC-SIGN), the mannose receptor (CD206), and langerin. These receptors take part in the uptake of pathogens by dendritic cells and macrophages and may also participate in the modulation of immune responses, mostly shown to be beneficial for pathogens per se rather than host(s). It is logical to predict that owing to receptor-specific interactions, dextran or its derivatives can interfere with these immune responses and improve infection outcome. Recent data support this hypothesis. We consider dextran a promising molecule for the development of lectin-glycan interaction-blocking molecules (such as DC-SIGN inhibitors) that could be applied in the treatment of diseases including tuberculosis, influenza, hepatitis B and C, human immunodeficiency virus infection and AIDS, etc. Dextran derivatives indeed change the pathology of infections dependent on DC-SIGN and mannose receptors. Complete knowledge of specific dextran-lectin interactions may also be important for development of future dextran applications in biological research and medicine.

Fermented Herbal Formulas KIOM-MA128 Ameliorate IL-6-Induced Intestinal Barrier Dysfunction in Colon Cancer Cell Line

PubMed Central

Park, Kwang Il; Kim, Dong Gun; Lee, Bo Hyoung

2016-01-01

Inflammatory bowel disease (IBD) comprises Crohn's disease (CD) and ulcerative colitis (UC). IBD increases the risk of colorectal cancer (CRC), depending on the extent and duration of intestinal inflammation. Increased IL-6 expression has been reported in IBD patients, which may be associated with intestinal barrier function through discontinuous tight junction (TJ). KIOM-MA is a specific agent for allergic diseases and cancer, and it is composed of several plants; these herbs have been used in traditional oriental medicine. We fermented KIOM-MA, the product of KIOM-MA128, using probiotics to improve the therapeutic efficacy via the absorption and bioavailability of the active ingredients. In this study, we demonstrated that KIOM-MA/MA128 exhibited anticolitis effects via the modulation of TJ protein. Interleukin-6 resulted in a dose-dependent decrease in the TER and an increase in the FITC-dextran permeability; however, pretreatment with 400 µg/ml KIOM-MA/MA128 resulted in a significant increase in the TER and a decrease in the FITC-dextran permeability via IL-6 induction. Furthermore, protein and mRNA TJ levels remained stable after pretreatment with 400 µg/ml KIOM-MA/MA128. Moreover, KIOM-MA/MA128 suppressed the expression of PLCγ1 and PKC. Taken together, these findings suggest novel information and clue of the anticolitis effects of KIOM-MA128 via regulation of tight junction. PMID:27980357

Fermented Herbal Formulas KIOM-MA128 Ameliorate IL-6-Induced Intestinal Barrier Dysfunction in Colon Cancer Cell Line.

PubMed

Park, Kwang Il; Kim, Dong Gun; Lee, Bo Hyoung; Ma, Jin Yeul

2016-01-01

Inflammatory bowel disease (IBD) comprises Crohn's disease (CD) and ulcerative colitis (UC). IBD increases the risk of colorectal cancer (CRC), depending on the extent and duration of intestinal inflammation. Increased IL-6 expression has been reported in IBD patients, which may be associated with intestinal barrier function through discontinuous tight junction (TJ). KIOM-MA is a specific agent for allergic diseases and cancer, and it is composed of several plants; these herbs have been used in traditional oriental medicine. We fermented KIOM-MA, the product of KIOM-MA128, using probiotics to improve the therapeutic efficacy via the absorption and bioavailability of the active ingredients. In this study, we demonstrated that KIOM-MA/MA128 exhibited anticolitis effects via the modulation of TJ protein. Interleukin-6 resulted in a dose-dependent decrease in the TER and an increase in the FITC-dextran permeability; however, pretreatment with 400  µ g/ml KIOM-MA/MA128 resulted in a significant increase in the TER and a decrease in the FITC-dextran permeability via IL-6 induction. Furthermore, protein and mRNA TJ levels remained stable after pretreatment with 400  µ g/ml KIOM-MA/MA128. Moreover, KIOM-MA/MA128 suppressed the expression of PLC γ 1 and PKC. Taken together, these findings suggest novel information and clue of the anticolitis effects of KIOM-MA128 via regulation of tight junction.

Molecular weight kinetics and chain scission models for dextran polymers during ultrasonic degradation.

PubMed

Pu, Yuanyuan; Zou, Qingsong; Hou, Dianzhi; Zhang, Yiping; Chen, Shan

2017-01-20

Ultrasonic degradation of six dextran samples with different initial molecular weights (IMW) has been performed to investigate the degradation behavior and chain scission mechanism of dextrans. The weight-average molecular weight (Mw) and polydispersity index (D value) were monitored by High Performance Gel Permeation Chromatography (HPGPC). Results showed that Mw and D value decreased with increasing ultrasonic time, resulting in a more homologous dextran solution with lower molecular weight. A significant degradation occurred in dextrans with higher IMW, particularly at the initial stage of the ultrasonic treatment. The Malhotra model was found to well describe the molecular weight kinetics for all dextran samples. Experimental data was fitted into two chain scission models to study dextran chain scission mechanism and the model performance was compared. Results indicated that the midpoint scission model agreed well with experimental results, with a linear regression factor of R 2 >0.99. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structural analysis and biomedical applications of dextran produced by a new isolate Pediococcus pentosaceus screened from biodiversity hot spot Assam.

PubMed

Patel, Seema; Kasoju, Naresh; Bora, Utpal; Goyal, Arun

2010-09-01

Dextran produced by a natural isolate of Pediococcus pentosaceus, screened from Assam, in the Northeastern region of India, was estimated, purified, structure characterised and functionality analysed. The dextran concentration in the cell free supernatant of the isolate P. pentosaceus was 10.2mg/ml. FT-IR analysis revealed the hydroxyl and carboxyl functional groups present in the dextran. (1)H NMR and (13)C NMR spectral data revealed that the dextran has a linear backbone of alpha-(1-->6) linked D-glucose residues. The decrease in viscosity of dextran solution with the increase in shear rate, threw light on its typical non-Newtonian pseudoplastic behaviour. The cytotoxicity tests on human cervical cancer (HeLa) cell line was studied which showed the dextran is non-toxic and biocompatible, rendering it safe for drug delivery, tissue engineering and various other biomedical applications. (c) 2010 Elsevier Ltd. All rights reserved.

High impact of in situ dextran coating on biocompatibility, stability and magnetic properties of iron oxide nanoparticles.

PubMed

Shaterabadi, Zhila; Nabiyouni, Gholamreza; Soleymani, Meysam

2017-06-01

Biocompatible ferrofluids based on dextran coated iron oxide nanoparticles were fabricated by conventional co-precipitation method. The experimental results show that the presence of dextran in reaction medium not only causes to the appearance of superparamagnetic behavior but also results in significant suppression in saturation magnetization of dextran coated samples. These results can be attributed to size reduction originated from the role of dextran as a surfactant. Moreover, weight ratio of dextran to magnetic nanoparticles has a remarkable influence on size and magnetic properties of nanoparticles, so that the sample prepared with a higher weight ratio of dextran to nanoparticles has the smaller size and saturation magnetization compare with the other samples. In addition, the ferrofluids containing such nanoparticles have an excellent stability at physiological pH for several months. Furthermore, the biocompatibility studies reveal that surface modification of nanoparticles by dextran dramatically decreases the cytotoxicity of bare nanoparticles and consequently improves their potential application for diagnostic and therapeutic purposes. Copyright © 2017 Elsevier B.V. All rights reserved.

Functional food applications of dextran from Weissella cibaria RBA12 from pummelo (Citrus maxima).

PubMed

Baruah, Rwivoo; Maina, Ndegwa H; Katina, Kati; Juvonen, Riikka; Goyal, Arun

2017-02-02

Weissella cibaria RBA12 isolated from pummelo from Northeast India produces a dextran composed of 97% α-(1→6) linkages in the main chain and 3% α-(1→3) branched linkages. The in vitro prebiotic activity of dextran-RBA12 was explored. Dextran-RBA12 displayed enhanced growth of probiotic Bifidobacterium and Lactobacillus spp., and controlled growth of non-probiotic enteric bacteria. Dextran-RBA12 showed superior resistance to physiological barriers with a maximum hydrolysis of 0.51%, 0.31% and 0.24% by artificial gastric juice, α-amylase and intestinal fluid, respectively, whereas compared to maximum hydrolysis of 25.23%, 19.13% and 6%, respectively after 5h of incubation shown by commercial prebiotic inulin. The production of dextran from Weissella cibaria RBA12 in sourdough prepared from whole wheat flour, wheat bran and rye bran showed the highest dextran of 3.26±0.12% d.w. in rye bran. The overall study summarized that dextran-RBA12 can be used as a prebiotic and also can be easily produced in sourdough. Copyright © 2016 Elsevier B.V. All rights reserved.

Enhanced binding by dextran-grafting to Protein A affinity chromatographic media.

PubMed

Zhao, Lan; Zhu, Kai; Huang, Yongdong; Li, Qiang; Li, Xiunan; Zhang, Rongyue; Su, Zhiguo; Wang, Qibao; Ma, Guanghui

2017-04-01

Dextran-grafted Protein A affinity chromatographic medium was prepared by grafting dextran to agarose-based matrix, followed by epoxy-activation and Protein A coupling site-directed to sulfhydryl groups of cysteine molecules. An enhancement of both the binding performance and the stability was achieved for this dextran-grafted Protein A chromatographic medium. Its dynamic binding capacity was 61 mg immunoglobulin G/mL suction-dried gel, increased by 24% compared with that of the non-grafted medium. The binding capacity of dextran-grafted medium decreased about 7% after 40 cleaning-in-place cycles, much lower than that of the non-grafted medium as decreased about 15%. Confocal laser scanning microscopy results showed that immunoglobulin G was bound to both the outside and the inside of dextran-grafted medium faster than that of non-grafted one. Atomic force microscopy showed that this dextran-grafted Protein A medium had much rougher surface with a vertical coordinate range of ±80 nm, while that of non-grafted one was ±10 nm. Grafted dextran provided a more stereo surface morphology and immunoglobulin G molecules were more easily to be bound. This high-performance dextran-grafted Protein A affinity chromatographic medium has promising applications in large-scale antibody purification. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of monoclonal antibody-based sandwich ELISA for detection of dextran.

PubMed

Wang, Sheng-Yu; Li, Zhe; Wang, Xian-Jiang; Lv, Sha; Yang, Yun; Zeng, Lian-Qiang; Luo, Fang-Hong; Yan, Jiang-Hua; Liang, Da-Feng

2014-10-01

Dextran as anti-nutritional factor is usually a result of bacteria activity and has associated serial problems during the process stream in the sugar industry and in medical therapy. A sensitive method is expected to detect dextran quantitatively. Here we generated four monoclonal antibodies (MAbs) against dextran using dextran T40 conjugated with bovine serum albumin (BSA) as immunogen in our lab following hybridoma protocol. Through pairwise, an MAb named D24 was determined to be conjugated with horseradish peroxidase (HRP) and was used in the establishment of a sensitive sandwich enzyme-linked immunosorbent assay (ELISA) method for determination of dextran, in which MAb D9 was chosen as a capture antibody. The detection limit and working scope of the developed sandwich ELISA method were 3.9 ng/mL and 7.8-500 ng/mL with a correlation coefficient of 0.9909. In addition, the cross-reaction assay demonstrated that the method possessed high specificity with no significant cross-reaction with dextran-related substances, and the recovery rate ranged from 96.35 to 102.00%, with coefficient of variation ranging from 1.58 to 6.94%. These results indicated that we developed a detection system of MAb-based sandwich ELISA to measure dextran and this system should be a potential tool to determine dextran levels.

Pulmonary permeability assessed by fluorescent-labeled dextran instilled intranasally into mice with LPS-induced acute lung injury.

PubMed

Chen, Honglei; Wu, Shaoping; Lu, Rong; Zhang, Yong-guo; Zheng, Yuanyuan; Sun, Jun

2014-01-01

Several different methods have been used to assess pulmonary permeability in response to acute lung injury (ALI). However, these methods often involve complicated procedures and algorithms that are difficult to precisely control. The purpose of the current study is to establish a feasible method to evaluate alterations in lung permeability by instilling fluorescently labeled dextran (FITC-Dextran) intranasally. For the mouse model of direct ALI, lipopolysaccharide (LPS) was administered intranasally. FITC-Dextran was instilled intranasally one hour before the mice were euthanized. Plasma fluorescence intensities from the LPS group were significantly higher than in the control group. To determine the reliability and reproducibility of the procedure, we also measured the lung wet-to-dry weight ratio, the protein concentration of the bronchoalveolar lavage fluid, tight and adherens junction markers and pathological changes. Consistent results were observed when the LPS group was compared with the control group. Simultaneously, we found that the concentration of plasma FITC-Dextran was LPS dose-dependent. The concentration of plasma FITC-Dextran also increased with initial intranasal FITC-Dextran doses. Furthermore, increased fluorescence intensity of plasma FITC-Dextran was found in the intraperitoneally LPS-induced ALI model. In conclusion, the measurement of FITC-Dextran in plasma after intranasal instillation is a simple, reliable, and reproducible method to evaluate lung permeability alterations in vivo. The concentration of FITC-Dextran in the plasma may be useful as a potential peripheral biomarker of ALI in experimental clinical studies.

In vivo administration of fluorescent dextrans for the specific and sensitive localization of brain vascular pericytes and their characterization in normal and neurotoxin exposed brains.

PubMed

Sarkar, Sumit; Schmued, Larry

2012-06-01

We have aimed to develop novel histochemical markers for the labeling of brain pericytes and characterize their morphology in the normal and the excitotoxin-exposed brain, as this class of cells has received little attention until recently. Pericyte labeling was accomplished by the intracerebroventricular injection of certain fluorescent dextran conjugates, such as Fluoro-Gold-dextran, FR-dextran, FITC-dextran and Fluoro-Turquoise (FT)-dextran. 1-7 days after the tracer injection, extensive labeling of vascular pericytes was seen throughout the entire brain. These cells were found distal to the endothelial cells and exhibited large dye containing vacuoles. The morphology of the pericytes was somewhat variable, exhibiting round or amoeboid shapes within larger intracellular vesicles, while those wrapping around capillaries exhibited a more elongated appearance with finger-like projections. The use of FG-dextran resulted in bluish yellow fluorescently labeled pericytes, while FR-dextran resulted in red fluorescent labeled pericytes, FITC-dextran exhibited green fluorescent pericytes and FT-dextran showed fluorescent blue pericytes in the brain. We have used these tracers to study possible changes in morphology and pericyte number following kainic acid insult, observing that the number of pericytes in the injured or lesioned areas of the brain is dramatically reduced compared to the non-injured areas. These novel fluorochromes should be of use for studies involving the detection and localization of pericytes in both normal and pathological brain tissues. Published by Elsevier B.V.

The use of chitosan-dextran gel shows anti-inflammatory, antibiofilm, and antiproliferative properties in fibroblast cell culture.

PubMed

Paramasivan, Sathish; Jones, Damien; Baker, Leonie; Hanton, Lyall; Robinson, Simon; Wormald, Peter J; Tan, Lorwai

2014-01-01

Chitosan-dextran gel has been used as an antihemostatic agent and antiadhesive agent after endoscopic sinus surgery. Because Staphylococcus aureus biofilms have been implicated in recalcitrant chronic rhinosinusitis, this study aimed to further investigate the (i) anti-inflammatory, (ii) bacterial biofilm inhibition, (iii) antiproliferative effects, and (iv) wound-healing properties of chitosan and chitosan-dextran gel. Fibroblasts were isolated from human nasal tissue and were used to determine the effects of chitosan and chitosan-dextran gel on (i) cell proliferation, (ii) wound healing, (iii) inflammation in fibroblast cultures challenged with superantigens S. aureus enterotoxin B (SEB) and toxic shock syndrome toxin (TSST), and (iv) on S. aureus biofilms. Chitosan was highly effective at reducing IL-8 expression after TSST and SEB challenge. Chitosan was also effective at reducing IL-8 expression of nonchallenged fibroblasts showing its anti-inflammatory effects on fibroblasts in a diseased state. Chitosan-dextran gel showed strong antibiofilm properties at 50% (v/v) concentration in vitro. Dextran, on its own, showed antibiofilm properties at 1.25% (w/v) concentration. Chitosan, on its own, reduced proliferation of fibroblasts to 82% of control proliferation and chitosan-dextran gel reduced proliferation of the fibroblasts to 0.04% of control proliferation. Relative to the no treatment controls, chitosan-dextran gel significantly delayed the wound-healing rate over the first 48 hours of the experiment. Chitosan-dextran gel reduced fibroblast proliferation and wound-healing time, showing a possible mechanism of reducing adhesions in the postsurgical period. Chitosan reduced IL-8 levels, showing its anti-inflammatory properties. Chitosan-dextran gel and dextran treatment showed antibiofilm properties in our model.

In Vitro Fermentation of Linear and α-1,2-Branched Dextrans by the Human Fecal Microbiota▿

PubMed Central

Sarbini, Shahrul R.; Kolida, Sofia; Naeye, Thierry; Einerhand, Alexandra; Brison, Yoann; Remaud-Simeon, Magali; Monsan, Pierre; Gibson, Glenn R.; Rastall, Robert A.

2011-01-01

The role of structure and molecular weight in fermentation selectivity in linear α-1,6 dextrans and dextrans with α-1,2 branching was investigated. Fermentation by gut bacteria was determined in anaerobic, pH-controlled fecal batch cultures after 36 h. Inulin (1%, wt/vol), which is a known prebiotic, was used as a control. Samples were obtained at 0, 10, 24, and 36 h of fermentation for bacterial enumeration by fluorescent in situ hybridization and short-chain fatty acid analyses. The gas production of the substrate fermentation was investigated in non-pH-controlled, fecal batch culture tubes after 36 h. Linear and branched 1-kDa dextrans produced significant increases in Bifidobacterium populations. The degree of α-1,2 branching did not influence the Bifidobacterium populations; however, α-1,2 branching increased the dietary fiber content, implying a decrease in digestibility. Other measured bacteria were unaffected by the test substrates except for the Bacteroides-Prevotella group, the growth levels of which were increased on inulin and 6- and 70-kDa dextrans, and the Faecalibacterium prausnitzii group, the growth levels of which were decreased on inulin and 1-kDa dextrans. A considerable increase in short-chain fatty acid concentration was measured following the fermentation of all dextrans and inulin. Gas production rates were similar among all dextrans tested but were significantly slower than that for inulin. The linear 1-kDa dextran produced lower total gas and shorter time to attain maximal gas production compared to those of the 70-kDa dextran (branched) and inulin. These findings indicate that dextrans induce a selective effect on the gut flora, short-chain fatty acids, and gas production depending on their length. PMID:21666027

Discontinuity of the exchange-correlation potential and the functional derivative of the noninteracting kinetic energy as the number of electrons crosses integer boundaries in Li, Be, and B.

PubMed

Morrison, Robert C

2015-01-07

Accurate densities were determined from configuration interaction wave functions for atoms and ions of Li, Be, and B with up to four electrons. Exchange-correlation potentials, Vxc(r), and functional derivatives of the noninteracting kinetic energy, δK[ρ]/δρ(r), obtained from these densities were used to examine their discontinuities as the number of electrons N increases across integer boundaries for N = 1, N = 2, and N = 3. These numerical results are consistent with conclusions that the discontinuities are characterized by a jump in the chemical potential while the shape of Vxc(r) varies continuously as an integer boundary is crossed. The discontinuity of the Vxc(r) is positive, depends on the ionization potential, electron affinity, and orbital energy differences, and the discontinuity in δK[ρ]/δρ(r) depends on the difference between the energies of the highest occupied and lowest unoccupied orbitals. The noninteracting kinetic energy and the exchange correlation energy have been computed for integer and noninteger values of N between 1 and 4.

Periodate oxidation of nanoscaled magnetic dextran composites

NASA Astrophysics Data System (ADS)

Hong, Xia; Guo, Wei; Yuan, Hang; Li, Jun; Liu, Yanmei; Ma, Lan; Bai, Yubai; Li, Tiejin

2004-02-01

Highly hydrophilic, uniform and nontoxic magnetic fluids consisting of magnetite (Fe 3O 4) and dextran were prepared. A periodate oxidation method was used to further activate the magnetic dextran, forming magnetic polyaldehyde-dextran, which could be conjugated to biomolecules such as proteins or antibodies. Oxidated Magnetic dextran composites were characterized by TEM, XRD and SQUID magnetometry. Moreover, a flexible, rapid and simple method to detect aldehydes was introduced to the magnetic composite system by utilizing 2,4-dinitrophenylhydrazine reagent. The result of the quantitative analysis of aldehyde was given by thermogravimetric analysis and elemental analysis.

Effects of Liposomal Compositions with Oxidized Dextrans on Functional Activity of U937 Macrophage-Like Cells In Vitro.

PubMed

Kozhin, P M; Chechushkov, A V; Zaitseva, N S; Lemza, A E; Men'shchikova, E B; Troitskii, A V; Shkurupy, V A

2015-11-01

We studied the effects of liposomal pharmaceutical compositions with oxidized dextrans on functional activity of U937 monocyte/macrophage-like cells. Liposomes in the emulsion contained oxidized dextran with a molecular weights of 40 kDa or 70 kDa or isonicotinic acid hydrazide (INAH) conjugated with oxidized dextran (40 kDa). Cell viability was evaluated by MTT test; mitochondrial transmembrane potential and production of superoxide anion and H2O2 were studied by fluorescent methods. The studied compositions exhibited no cytotoxic effect and even improved cell viability and mitochondrial respiration. Liposomes with oxidized 40 kDa dextran, including those with INAH-conjugated dextran, inhibited production of superoxide anion, but increased H2O2 generation.

An oscillation free shock-capturing method for compressible van der Waals supercritical fluid flows

DOE PAGES

Pantano, C.; Saurel, R.; Schmitt, T.

2017-02-01

Numerical solutions of the Euler equations using real gas equations of state (EOS) often exhibit serious inaccuracies. The focus here is the van der Waals EOS and its variants (often used in supercritical fluid computations). The problems are not related to a lack of convexity of the EOS since the EOS are considered in their domain of convexity at any mesh point and at any time. The difficulties appear as soon as a density discontinuity is present with the rest of the fluid in mechanical equilibrium and typically result in spurious pressure and velocity oscillations. This is reminiscent of well-knownmore » pressure oscillations occurring with ideal gas mixtures when a mass fraction discontinuity is present, which can be interpreted as a discontinuity in the EOS parameters. We are concerned with pressure oscillations that appear just for a single fluid each time a density discontinuity is present. As a result, the combination of density in a nonlinear fashion in the EOS with diffusion by the numerical method results in violation of mechanical equilibrium conditions which are not easy to eliminate, even under grid refinement.« less

An oscillation free shock-capturing method for compressible van der Waals supercritical fluid flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pantano, C.; Saurel, R.; Schmitt, T.

Numerical solutions of the Euler equations using real gas equations of state (EOS) often exhibit serious inaccuracies. The focus here is the van der Waals EOS and its variants (often used in supercritical fluid computations). The problems are not related to a lack of convexity of the EOS since the EOS are considered in their domain of convexity at any mesh point and at any time. The difficulties appear as soon as a density discontinuity is present with the rest of the fluid in mechanical equilibrium and typically result in spurious pressure and velocity oscillations. This is reminiscent of well-knownmore » pressure oscillations occurring with ideal gas mixtures when a mass fraction discontinuity is present, which can be interpreted as a discontinuity in the EOS parameters. We are concerned with pressure oscillations that appear just for a single fluid each time a density discontinuity is present. As a result, the combination of density in a nonlinear fashion in the EOS with diffusion by the numerical method results in violation of mechanical equilibrium conditions which are not easy to eliminate, even under grid refinement.« less

Vincristine sulfate loaded dextran microspheres amalgamated with thermosensitive gel offered sustained release and enhanced cytotoxicity in THP-1, human leukemia cells: In vitro and in vivo study.

PubMed

Thakur, Vivek; Kush, Preeti; Pandey, Ravi Shankar; Jain, Upendra Kumar; Chandra, Ramesh; Madan, Jitender

2016-04-01

Vincristine sulfate (VCS) is a drug of choice for the treatment of childhood and adult acute lymphocytic leukemia, Hodgkin's, non-Hodgkin's lymphoma as well as solid tumors including sarcomas. However, poor biopharmaceutical and pharmacokinetic traits of VCS like short serum half-life (12 min), high dosing frequency (1.4 mg/m(2) per week for 4 weeks) and extensive protein binding (75%) limit the clinical potential of VCS in cancer therapy. In present investigation, injectable vincristine sulfate loaded dextran microspheres (VCS-Dextran-MSs) were prepared and amalgamated with chitosan-β-glycerophosphate gel (VCS-Dextran-MSs-Gel) to surmount the biopharmaceutical and pharmacokinetic limitations of VCS that consequently induced synergistic sustained release pattern of the drug. Particle size and zeta-potential of VCS-Dextran-MSs were measured to be 6.8 ± 2.4 μm and -18.3 ± 0.11 mV along with the encapsulation efficiency of about 60.4 ± 4.5%. Furthermore, VCS-Dextran-MSs and VCS-Dextran-MSs-Gel exhibited slow release pattern and 94.7% and 95.8% of the drug was released in 72 h and 720 h, respectively. Results from cell viability assay and pharmacokinetic as well as histopathological analysis in mice indicated that VCS-Dextran-MSs-Gel offers superior therapeutic potential and higher AUClast than VCS-Dextran-MSs and drug solution. In conclusion, VCS-Dextran-MSs-Gel warrants further preclinical tumor growth study to scale up the technology. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Discontinuities and Penetrations on the Shielding Efficacy of High Temperature Superconducting Magnetic Shields

NASA Astrophysics Data System (ADS)

Hatwar, R.; Kvitkovic, J.; Herman, C.; Pamidi, S.

2015-12-01

High Temperature Superconducting (HTS) materials have been demonstrated to be suitable for applications in shielding of both DC and AC magnetic fields. Magnetic shielding is required for protecting sensitive instrumentation from external magnetic fields and for preventing the stray magnetic fields produced by high power density equipment from affecting neighbouring devices. HTS shields have high current densities at relatively high operating temperatures (40-77 K) and can be easily fabricated using commercial HTS conductor. High current densities in HTS materials allow design and fabrication of magnetic shields that are lighter and can be incorporated into the body and skin of high power density devices. HTS shields are particularly attractive for HTS devices because a single cryogenic system can be used for cooling the device and the associated shield. Typical power devices need penetrations for power and signal cabling and the penetrations create discontinuities in HTS shields. Hence it is important to assess the effect of the necessary discontinuities on the efficacy of the shields and the design modifications necessary to accommodate the penetrations.

Inverse problems for torsional modes.

USGS Publications Warehouse

Willis, C.

1984-01-01

Considers a spherically symmetric, non-rotating Earth consisting of an isotropic, perfect elastic material where the density and the S-wave velocity may have one or two discontinuities in the upper mantle. Shows that given the velocity throughout the mantle and the crust and given the density in the lower mantle, then the freqencies of the torsional oscillations of one angular order (one torsional spectrum), determine the density in the upper mantle and in the crust uniquely. If the velocity is known only in the lower mantle, then the frequencies of the torsional oscillations of two angular orders uniquely determine both the density and the velocity in the upper mantle and in the crust. In particular, the position and size of the discontinuities in the density and velocity are uniquely determined by two torsional spectra.-Author

Preparation of synaptic plasma membrane and postsynaptic density proteins using a discontinuous sucrose gradient.

PubMed

Bermejo, Marie Kristel; Milenkovic, Marija; Salahpour, Ali; Ramsey, Amy J

2014-09-03

Neuronal subcellular fractionation techniques allow the quantification of proteins that are trafficked to and from the synapse. As originally described in the late 1960's, proteins associated with the synaptic plasma membrane can be isolated by ultracentrifugation on a sucrose density gradient. Once synaptic membranes are isolated, the macromolecular complex known as the post-synaptic density can be subsequently isolated due to its detergent insolubility. The techniques used to isolate synaptic plasma membranes and post-synaptic density proteins remain essentially the same after 40 years, and are widely used in current neuroscience research. This article details the fractionation of proteins associated with the synaptic plasma membrane and post-synaptic density using a discontinuous sucrose gradient. Resulting protein preparations are suitable for western blotting or 2D DIGE analysis.

Injectable dextran hydrogels fabricated by metal-free click chemistry for cartilage tissue engineering.

PubMed

Wang, Xiaoyu; Li, Zihan; Shi, Ting; Zhao, Peng; An, Kangkang; Lin, Chao; Liu, Hongwei

2017-04-01

Injectable dextran-based hydrogels were prepared for the first time by bioorthogonal click chemistry for cartilage tissue engineering. Click-crosslinked injectable hydrogels based on cyto-compatible dextran (Mw=10kDa) were successfully fabricated under physiological conditions by metal-free alkyne-azide cycloaddition (click) reaction between azadibenzocyclooctyne-modified dextran (Dex-ADIBO) and azide-modified dextran (Dex-N 3 ). Gelation time of these dextran hydrogels could be regulated in the range of approximately 1.1 to 10.2min, depending on the polymer concentrations (5% or 10%) and ADIBO substitution degree (DS, 5 or 10) of Dex-ADIBO. Rheological analysis indicated that the dextran hydrogels were elastic and had storage moduli from 2.1 to 6.0kPa with increasing DS of ADIBO from 5 to 10. The in vitro tests revealed that the dextran hydrogel crosslinked from Dex-ADIBO DS 10 and Dex-N 3 DS 10 at a polymer concentration of 10% could support high viability of individual rabbit chondrocytes and the chondrocyte spheroids encapsulated in the hydrogel over 21days. Individual chondrocytes and chondrocyte spheroids in the hydrogel could produce cartilage matrices such as collagen and glycosaminoglycans. However, the chondrocyte spheroids produced a higher content of matrices than individual chondrocytes. This study indicates that metal-free click chemistry is effective to produce injectable dextran hydrogels for cartilage tissue engineering. Copyright © 2016 Elsevier B.V. All rights reserved.

Methyl-DEAE-dextran: a candidate biomaterial.

PubMed

Zambito, Ylenia; Baggiani, Andrea; Carelli, Vera; Serafini, Maria Francesca; Di Colo, Giacomo

2004-01-01

The full quaternisation of DEAE-dextran was successfully attempted and an application of the quaternised product was suggested. Commercial DEAE-dextran was reacted with iodomethane at 60 degrees C in the presence of NaOH. The raw product was purified by dialysis, during which the iodide ion was replaced by chloride. N-methylation and O-methylation resulted from the reaction. A second methylation step produced no further changes in the molecule. Alkalimetry indicated the absence of amino groups in the methylated polymer molecule, thus testifying to a complete quaternisation. N-acetylcysteine (AcCy) was neutralised with the polymer in the hydroxide form, thus obtaining the methyl DEAE-dextran salt of AcCy (Me-DEAE-dextran/AcCy), whereby an ophthalmic formulation for the treatment of the dry eye syndrome was prepared. For comparison, the neutral AcCy salt of commercial DEAE-dextran (DEAE-dextran/AcCy) was prepared. The AcCy content in Me-DEAE-dextran/AcCy was higher than in DEAE-dextran/AcCy (23 vs 13%), while the viscosity of a solution containing the salt concentration corresponding to the therapeutic AcCy concentration (4%w/v) was lower with the former compared to the latter salt (20.5 vs 23.9 mPa s). Both solutions were ipotonic (245 mOsm/kg), whereas the commercial Tirocular is strongly hypertonic (900 mOsm/kg) and irritant.

Self-degradation of tissue adhesive based on oxidized dextran and poly-L-lysine.

PubMed

Matsumura, Kazuaki; Nakajima, Naoki; Sugai, Hajime; Hyon, Suong-Hyu

2014-11-26

We have developed a low-toxicity bioadhesive based on oxidized dextran and poly-L-lysine. Here, we report that the mechanical properties and degradation of this novel hydrogel bioadhesive can be controlled by changing the extent of oxidation of the dextran and the type or concentration of the anhydride species in the acylated poly-L-lysine. The dynamic moduli of the hydrogels can be controlled from 120 Pa to 20 kPa, suggesting that they would have mechanical compatibility with various tissues, and could have applications as tissue adhesives. Development of the hydrogel color from clear to brown indicates that the reaction between the dextran aldehyde groups and the poly-L-lysine amino groups may be induced by a Maillard reaction via Schiff base formation. Degradation of the aldehyde dextran may begin by reaction of the amino groups in the poly-L-lysine. The gel degradation can be ascribed to degradation of the aldehyde dextran in the hydrogel, although the aldehyde dextran itself is relatively stable in water. The oxidized dextran and poly-L-lysine, and the degraded hydrogel showed low cytotoxicities. These findings indicate that a hydrogel consisting of oxidized dextran and poly-L-lysine has low toxicity and a well-controlled degradation rate, and has potential clinical applications as a bioadhesive. Copyright © 2014 Elsevier Ltd. All rights reserved.

Preparation and Characteristic of Dextran-BSA Antibody and Establishment of its ELISA Immunoassay.

PubMed

Xie, Zhen-ming; Yu, Lin; Fang, Li-sha

2015-01-01

The enzyme-linked immunosorbent assay (ELISA) is a potential tool for the determination of dextran. In this study, dextran neoglycoprotein antigens were prepared by Reductive Amination method, and were confirmed by SDS-PAGE and free amino detection. The impact factors such as different oxidation degree of dextran, the conjugate reaction time to BSA were investigated. The best preparation conditions were obtained (n(dextran)/n(oxidant) of NaIO4 = 1/120, the reaction time of 24 h), and the antigen with best combination with standard was obtained. The antigens interacted with standard antibody and were evaluated through ELISA. The immunogen was immunized with white rabbits to obtained antibody, respectively. A general and broad class-specific ELISA immunoassay was developed for dextran detection according to ELISA theory. The optimized conditions of assay used coating antigen at 10 μg/mL, reaction time of antibody and rabbit-anti-bovine IgG in 45 min, blocking reagents with 5% calf serum. The developed ELISA detection method with good linear and accuracy was put to use for quantitative analysis of dextran T40 in commercial sugarpractical for detection of dextran.

Qualitative and quantitative analysis of branches in dextran using high-performance anion exchange chromatography coupled to quadrupole time-of-flight mass spectrometry.

PubMed

Yi, Lin; Ouyang, Yilan; Sun, Xue; Xu, Naiyu; Linhardt, Robert J; Zhang, Zhenqing

2015-12-04

Dextran, a family of natural polysaccharides, consists of an α (1→6) linked-glucose main (backbone) chain having a number of branches. The determination of the types and the quantities of branches in dextran is important in understanding its various biological roles. In this study, a hyphenated method using high-performance anion exchange chromatography (HPAEC) in parallel with pulsed amperometric detection (PAD) and mass spectrometry (MS) was applied to qualitative and quantitative analysis of dextran branches. A rotary cation-exchange cartridge array desalter was used for removal of salt from the HPAEC eluent making it MS compatible. MS and MS/MS were used to provide structural information on the enzymatically prepared dextran oligosaccharides. PAD provides quantitative data on the ratio of enzyme-resistant, branched dextran oligosaccharides. Both the types and degree of branching found in a variety of dextrans could be simultaneously determined online using this method. Copyright © 2015 Elsevier B.V. All rights reserved.

Challenges in analysis of high-molar mass dextrans: comparison of HPSEC, AsFlFFF and DOSY NMR spectroscopy.

PubMed

Maina, Ndegwa Henry; Pitkänen, Leena; Heikkinen, Sami; Tuomainen, Päivi; Virkki, Liisa; Tenkanen, Maija

2014-01-01

Dilute solutions of various dextran standards, a high-molar mass (HMM) commercial dextran from Leuconostoc spp., and HMM dextrans isolated from Weissella confusa and Leuconostoc citreum were analyzed with high-performance size-exclusion chromatography (HPSEC), asymmetric flow field-flow fractionation (AsFlFFF), and diffusion-ordered NMR spectroscopy (DOSY). HPSEC analyses were performed in aqueous and dimethyl sulfoxide (DMSO) solutions, while only aqueous solutions were utilized in AsFlFFF and DOSY. The study showed that all methods were applicable to dextran analysis, but differences between the aqueous and DMSO-based solutions were obtained for HMM samples. These differences were attributed to the presence of aggregates in aqueous solution that were less prevalent in DMSO. The study showed that DOSY provides an estimate of the size of HMM dextrans, though calibration standards may be required for each experimental set-up. To our knowledge, this is the first study utilizing these three methods in analyzing HMM dextrans. Copyright © 2013 Elsevier Ltd. All rights reserved.

The Application of a Modified d-ROMs Test for Measurement of Oxidative Stress and Oxidized High-Density Lipoprotein

PubMed Central

Ito, Fumiaki; Ito, Tomoyuki; Suzuki, Chinatsu; Yahata, Tomoyo; Ikeda, Kazuyuki; Hamaoka, Kenji

2017-01-01

Reactive oxygen species (ROS) are involved in the initiation and progression of atherosclerosis. ROS-derived hydroperoxides, as an indicator of ROS production, have been measured by using the diacron reactive oxygen metabolites (d-ROMs) test, which requires iron-containing transferrin in the reaction mixture. In this study we developed a modified d-ROMs test, termed the Fe-ROMs test, where iron ions were exogenously added to the reaction mixture. This modification is expected to exclude the assay variation that comes from different blood iron levels in individuals. In addition, this Fe-ROMs test was helpful for determining the class of plasma lipoproteins that are hydroperoxidized. Low-density lipoprotein/very low-density lipoprotein (LDL/VLDL) and high-density lipoprotein (HDL) were purified by use of an LDL/VLDL purification kit and the dextran sulfate-Mg2+ precipitation method, respectively; their hydroperoxide contents were assessed by performing the Fe-ROMs test. The majority of the hydroperoxides were detected only in the HDL fraction, not in the LDL/VLDL. Further detailed analysis of HDLs by size-exclusion high-performance liquid chromatography revealed that the hydroperoxide-containing molecules were small-sized HDLs. Because HDL was shown to be the principal vehicle for the plasma hydroperoxides, this Fe-ROMs test is a beneficial method for the assessment of oxidized-HDL levels. Indeed, Fe-ROMs levels were strongly associated with the levels of oxidized HDL, which were determined by performing the malondialdehyde-modified HDL enzyme immunoassay. In conclusion, the Fe-ROMs test using plasma itself or the HDL fraction after dextran sulfate-Mg2+ precipitation is useful to assess the functionality of HDL, because the oxidation of HDL impairs its antiatherogenic capacity. PMID:28230785

The Application of a Modified d-ROMs Test for Measurement of Oxidative Stress and Oxidized High-Density Lipoprotein.

PubMed

Ito, Fumiaki; Ito, Tomoyuki; Suzuki, Chinatsu; Yahata, Tomoyo; Ikeda, Kazuyuki; Hamaoka, Kenji

2017-02-21

Reactive oxygen species (ROS) are involved in the initiation and progression of atherosclerosis. ROS-derived hydroperoxides, as an indicator of ROS production, have been measured by using the diacron reactive oxygen metabolites (d-ROMs) test, which requires iron-containing transferrin in the reaction mixture. In this study we developed a modified d-ROMs test, termed the Fe-ROMs test, where iron ions were exogenously added to the reaction mixture. This modification is expected to exclude the assay variation that comes from different blood iron levels in individuals. In addition, this Fe-ROMs test was helpful for determining the class of plasma lipoproteins that are hydroperoxidized. Low-density lipoprotein/very low-density lipoprotein (LDL/VLDL) and high-density lipoprotein (HDL) were purified by use of an LDL/VLDL purification kit and the dextran sulfate-Mg 2+ precipitation method, respectively; their hydroperoxide contents were assessed by performing the Fe-ROMs test. The majority of the hydroperoxides were detected only in the HDL fraction, not in the LDL/VLDL. Further detailed analysis of HDLs by size-exclusion high-performance liquid chromatography revealed that the hydroperoxide-containing molecules were small-sized HDLs. Because HDL was shown to be the principal vehicle for the plasma hydroperoxides, this Fe-ROMs test is a beneficial method for the assessment of oxidized-HDL levels. Indeed, Fe-ROMs levels were strongly associated with the levels of oxidized HDL, which were determined by performing the malondialdehyde-modified HDL enzyme immunoassay. In conclusion, the Fe-ROMs test using plasma itself or the HDL fraction after dextran sulfate-Mg 2+ precipitation is useful to assess the functionality of HDL, because the oxidation of HDL impairs its antiatherogenic capacity.

Squishy nanotraps: hybrid cellulose nanocrystal-zirconium metallogels for controlled trapping of biomacromolecules.

PubMed

Sheikhi, A; van de Ven, T G M

2017-08-11

A brick-and-mortar-like ultrasoft nanocomposite metallogel is formed by crosslinking cellulose nanocrystals (CNC) with ammonium zirconium carbonate (AZC) to trap and reconfigure dextran, a model biomacromolecule. The bricks (CNC) reinforce the metallogel, compete with dextran in reacting with AZC, and decouple long-time dextran dynamics from network formation, while the mortar (AZC) imparts bimodality to the dextran diffusion.

Dextransucrase and the mechanism for dextran biosynthesis.

PubMed

Robyt, John F; Yoon, Seung-Heon; Mukerjea, Rupendra

2008-12-08

Remaud-Simeon and co-workers [Moulis, C.; Joucla, G.; Harrison, D.; Fabre, E.; Potocki-Veronese, G.; Monsan, P.; Remaud-Simeon, M. J. Biol. Chem., 2006, 281, 31254-31267] have recently proposed that a truncated Escherichia coli recombinant B-512F dextransucrase uses sucrose and the hydrolysis product of sucrose, D-glucose, as initiator primers for the nonreducing-end synthesis of dextran. Using (14)C-labeled D-glucose in a dextransucrase-sucrose digest, it was found that <0.02% of the D-glucose appears in a dextran of M(n) 84,420, showing that D-glucose is not an initiator primer, and when the dextran was treated with 0.01 M HCl at 80 degrees C for 90 min and a separate sample with invertase at 50 degrees C for 24h, no D-fructose was formed, indicating that sucrose is not present at the reducing-end of dextran, showing that sucrose also was not an initiator primer. It is further shown that both d-glucose and dextran are covalently attached to B-512FMC dextransucrase at the active site during polymerization. A pulse reaction with [(14)C]-sucrose and a chase reaction with nonlabeled sucrose, followed by dextran isolation, reduction, and acid hydrolysis, gave (14)C-glucitol in the pulsed dextran, which was significantly decreased in the chased dextran, showing that the D-glucose moieties of sucrose are added to the reducing-ends of the covalently linked growing dextran chains. The molecular size of dextran is shown to be inversely proportional to the concentration of the enzyme, indicating a highly processive mechanism in which D-glucose is rapidly added to the reducing-ends of the growing chains, which are extruded from the active site of dextransucrase. It is also shown how the three conserved amino acids (Asp551, Glu589, and Asp 622) at the active sites of glucansucrases participate in the polymerization of dextran and related glucans from a single active site by the addition of the D-glucose moiety of sucrose to the reducing-ends of the covalently linked glucan chains in a two catalytic-site, insertion mechanism.

Intraoperative use of dextran is associated with cardiac complications after carotid endarterectomy

PubMed Central

Farber, Alik; Tan, Tze-Woei; Rybin, Denis; Kalish, Jeffrey A.; Hamburg, Naomi M.; Doros, Gheorghe; Goodney, Philip P.; Cronenwett, Jack L.

2013-01-01

Objective Although dextran has been theorized to diminish the risk of stroke associated with carotid endarterectomy (CEA), variation exists in its use. We evaluated outcomes of dextran use in patients undergoing CEA to clarify its utility. Methods We studied all primary CEAs performed by 89 surgeons within the Vascular Study Group of New England database (2003–2010). Patients were stratified by intraoperative dextran use. Outcomes included perioperative death, stroke, myocardial infarction (MI), and congestive heart failure (CHF). Group and propensity score matching was performed for risk-adjusted comparisons, and multivariable logistic and gamma regressions were used to examine associations between dextran use and outcomes. Results There were 6641 CEAs performed, with dextran used in 334 procedures (5%). Dextran-treated and untreated patients were similar in age (70 years) and symptomatic status (25%). Clinical differences between the cohorts were eliminated by statistical adjustment. In crude, group-matched, and propensity-matched analyses, the stroke/death rate was similar for the two cohorts (1.2%). Dextran-treated patients were more likely to suffer postoperative MI (crude: 2.4% vs 1.0%; P = .03; group-matched: 2.4% vs 0.6%; P = .01; propensity-matched: 2.4% vs 0.5%; P = .003) and CHF (2.1% vs 0.6%; P = .01; 2.1% vs 0.5%; P = .01; 2.1% vs 0.2%; P < .001). In multivariable analysis of the crude sample, dextran was associated with a higher risk of postoperative MI (odds ratio, 3.52; 95% confidence interval, 1.62–7.64) and CHF (odds ratio, 5.71; 95% confidence interval, 2.35–13.89). Conclusions Dextran use was not associated with lower perioperative stroke but was associated with higher rates of MI and CHF. Taken together, our findings suggest limited clinical utility for routine use of intraoperative dextran during CEA. PMID:23337295

Iron Dextran Injection

MedlinePlus

Iron dextran injection is used to treat iron-deficiency anemia (a lower than normal number of red blood cells ... treated with iron supplements taken by mouth. Iron dextran injection is in a class of medications called ...

In vivo cleavage rate of a dextran-bound magnetic resonance imaging contrast agent: preparation and intravascular pharmacokinetic characteristics in the rabbit.

PubMed

Hals, Petter Arnt; Sontum, Per Christian; Holtz, Eckart; Klaveness, Jo; Rongved, Pål

2013-02-01

Earlier described dextran-based contrast agents for magnetic resonance imaging (MRI) comprising the gadolinium chelate diethylenetriamine pentaacetic acid (GdDTPA, 1) have shown significantly shorter in vivo contrast duration in rat than what would be expected from the initial average molecular weight (Mw) of the dextran fraction (71.4 kD). To investigate this further, four dextran fractions with given initial average molecular weight (Mw) of 10.4, 41.0, 71.4 and 580 kD were used as starting material to prepare products 2-5 where one of the carboxylic acid functionalities in GdDTPA was used as a direct covalent ester linker to hydroxyl groups in dextrans. A fifth derivative (6) was an amide-ester bound β-alanine-DTPAGd conjugate with dextran having Mw 71.4 kD. The reference compound GdDTPA (1) and gadoliniumlabelled dextran derivatives 2-6 were injected intravenously in rabbits. Pharmacokinetic parameters showed that when GdDTPA is ester-bound directly to dextran hydroxyls, the cleavage rates of 2-5 were only moderately dependent on the molecular weights of the dextrans, having blood pool half-lives comparable to the low-molecular reference compound (t 1/2,β 0.3 - 0.5 hrs.). Presence of a β-alanine spacer in 6 prolonged the plasma half-life t 1/2,β to 6.9 hours, rendering a blood residence time suitable for blood pool slow release of GdDTPA. Biological cleavage regenerates the clinically acceptable carrier dextran and the β-alanine derivative of GdDTPA, pointing at a clinically acceptable product class for blood-pool contrast in MRI.

Controlled release of β-carotene in β-lactoglobulin-dextran-conjugated nanoparticles' in vitro digestion and transport with Caco-2 monolayers.

PubMed

Yi, Jiang; Lam, Tina I; Yokoyama, Wallace; Cheng, Luisa W; Zhong, Fang

2014-09-03

Undesirable aggregation of nanoparticles stabilized by proteins may occur at the protein's isoelectric point when the particle has zero net charge. Stability against aggregation of nanoparticles may be improved by reacting free amino groups with reducing sugars by the Maillard reaction. β-Lactoglobulin (BLG)-dextran conjugates were characterized by SDS-PAGE and CD. Nanoparticles (60-70 nm diameter) of β-carotene (BC) encapsulated by BLG or BLG-dextran were prepared by the homogenization-evaporation method. Both BLG and BLG-dextran nanoparticles appeared to be spherically shaped and uniformly dispersed by TEM. The stability and release of BC from the nanoparticles under simulated gastrointestinal conditions were evaluated. Dextran conjugation prevented the flocculation or aggregation of BLG-dextran particles at pH ∼4-5 compared to very large sized aggregates of BLG nanoparticles. The released contents of BC from BLG and BLG-dextran nanoparticles under acidic gastric conditions were 6.2 ± 0.9 and 5.4 ± 0.3%, respectively. The release of BC from BLG-dextran nanoparticles by trypsin digestion was 51.8 ± 4.3% of total encapsulated BC, and that from BLG nanoparticles was 60.9 ± 2.9%. Neither BLG-BC nanoparticles nor the Maillard-reacted BLG-dextran conjugates were cytotoxic to Caco-2 cells, even at 10 mg/mL. The apparent permeability coefficient (Papp) of Caco-2 cells to BC was improved by nanoencapsulation, compared to free BC suspension. The results indicate that BC-encapsulated β-lactoglobulin-dextran-conjugated nanoparticles are more stable to aggregation under gastric pH conditions with good release and permeability properties.

Ultraviolet A: Visible spectral absorbance of the human cornea after transepithelial soaking with dextran-enriched and dextran-free riboflavin 0.1% ophthalmic solutions.

PubMed

Lombardo, Marco; Micali, Norberto; Villari, Valentina; Serrao, Sebastiano; Pucci, Giuseppe; Barberi, Riccardo; Lombardo, Giuseppe

2015-10-01

To evaluate the stromal concentration of 2 commercially available transepithelial riboflavin 0.1% solutions in human donor corneas with the use of spectrophotometry. University of Calabria, Rende, Italy. Experimental study. The absorbance spectra of 12 corneal tissues were measured in the 330 to 700 nm wavelength range using a purpose-designed spectrophotometry setup before and after transepithelial corneal soaking with a 15% dextran-enriched riboflavin 0.1% solution (n = 6) or a hypotonic dextran-free riboflavin 0.1% solution (n = 6). Both ophthalmic solutions contained ethylenediaminetetraacetic acid and trometamol as enhancers. In addition, 4 deepithelialized corneal tissues underwent stromal soaking with a 20% dextran-enriched riboflavin 0.1% solution and were used as controls. All the riboflavin solutions were applied topically for 30 minutes. The stromal concentration of riboflavin was quantified by analysis of absorbance spectra of the cornea collected before and after application of each solution. The mean stromal riboflavin concentration was 0.012% ± 0.003% (SD), 0.0005% ± 0.0003% (P < .001), and 0.004% ± 0.001% (P < .01) in tissues soaked with 20% dextran-enriched, 15% dextran-enriched, and hypotonic dextran-free solutions, respectively. The difference of stromal riboflavin concentration between the 2 transepithelial solutions was statistically significant (P < .01). Dextran-enriched solutions required complete corneal deepithelialization to permit effective stromal soaking with riboflavin. Nevertheless, riboflavin in hypotonic dextran-free solution with enhancers permeates across stroma through an intact epithelium. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

The ligand-binding profile of HARE: hyaluronan and chondroitin sulfates A, C, and D bind to overlapping sites distinct from the sites for heparin, acetylated low-density lipoprotein, dermatan sulfate, and CS-E.

PubMed

Harris, Edward N; Weigel, Paul H

2008-08-01

The hyaluronic acid receptor for endocytosis (HARE)/ Stabilin-2 is the primary systemic scavenger receptor for hyaluronan (HA), the chondroitin sulfates (CS), dermatan sulfate (DS), and nonglycosaminoglycan (GAG) ligands such as acetylated low-density lipoprotein (AcLDL), pro-collagen propeptides, and advanced glycation end products. We recently discovered that HARE is also a systemic scavenger receptor for heparin (Hep) (Harris EN, Weigel JA, Weigel PH. 2008. The human hyaluronan receptor for endocytosis [HARE/Stabilin-2] is a systemic clearance receptor for heparin. J Biol Chem. 283:17341-17350). Our goal was to map the binding sites of eight different ligands within HARE. We used biotinylated GAGs and radio-iodinated streptavidin or AcLDL to assess the binding activities of ligands directly or indirectly (by competition with unlabeled ligands) in endocytosis assays using stable cell lines expressing the 315 or 190 kDa HA receptor for endocytosis (315- or 190-HARE) isoforms, and ELISA-like assays, with purified recombinant soluble 190-HARE ecto-domain. For example, Hep binding to HARE was competed by DS, CS-E, AcLDL, and dextran sulfate, but not by other CS types, HA, dextran, or heparosan. (125)I-AcLDL binding to HARE was partially competed by Hep and dextran sulfate, but not competed by HA. Two ligands, DS and CS-E, competed with both Hep and HA to some degree. Hep and HA binding or endocytosis is mutually inclusive; binding of these two GAGs occurs with functionally separate, noncompetitive, and apparently noninteracting domains. Thus, HARE binds to HA and Hep simultaneously. Although the domain(s) responsible for Hep binding remains unknown, the Link domain was required for HARE binding to HA, CS-A, CS-C, and CS-D. These results enable us to outline, for the first time, a binding activity map for multiple ligands of HARE.

The ligand-binding profile of HARE: hyaluronan and chondroitin sulfates A, C, and D bind to overlapping sites distinct from the sites for heparin, acetylated low-density lipoprotein, dermatan sulfate, and CS-E

PubMed Central

Harris, Edward N.; Weigel, Paul H.

2008-01-01

The hyaluronic acid receptor for endocytosis (HARE)/ Stabilin-2 is the primary systemic scavenger receptor for hyaluronan (HA), the chondroitin sulfates (CS), dermatan sulfate (DS), and nonglycosaminoglycan (GAG) ligands such as acetylated low-density lipoprotein (AcLDL), pro-collagen propeptides, and advanced glycation end products. We recently discovered that HARE is also a systemic scavenger receptor for heparin (Hep) (Harris EN, Weigel JA, Weigel PH. 2008. The human hyaluronan receptor for endocytosis [HARE/Stabilin-2] is a systemic clearance receptor for heparin. J Biol Chem. 283:17341–17350). Our goal was to map the binding sites of eight different ligands within HARE. We used biotinylated GAGs and radio-iodinated streptavidin or AcLDL to assess the binding activities of ligands directly or indirectly (by competition with unlabeled ligands) in endocytosis assays using stable cell lines expressing the 315 or 190 kDa HA receptor for endocytosis (315- or 190-HARE) isoforms, and ELISA-like assays, with purified recombinant soluble 190-HARE ecto-domain. For example, Hep binding to HARE was competed by DS, CS-E, AcLDL, and dextran sulfate, but not by other CS types, HA, dextran, or heparosan. 125I-AcLDL binding to HARE was partially competed by Hep and dextran sulfate, but not competed by HA. Two ligands, DS and CS-E, competed with both Hep and HA to some degree. Hep and HA binding or endocytosis is mutually inclusive; binding of these two GAGs occurs with functionally separate, noncompetitive, and apparently noninteracting domains. Thus, HARE binds to HA and Hep simultaneously. Although the domain(s) responsible for Hep binding remains unknown, the Link domain was required for HARE binding to HA, CS-A, CS-C, and CS-D. These results enable us to outline, for the first time, a binding activity map for multiple ligands of HARE. PMID:18499864

Use of dextran nanoparticle: A paradigm shift in bacterial exopolysaccharide based biomedical applications.

PubMed

Banerjee, Aparna; Bandopadhyay, Rajib

2016-06-01

This review is a concise compilation of all the major researches on dextran nanoparticle based biomedical applications. Dextran is a highly biocompatible and biodegradable neutral bacterial exopolysaccharide with simple repeating glucose subunits. It's simple yet unique biopolymeric nature made it highly suitable as nanomedicine, nanodrug carrier, and cell imaging system or nanobiosensor. Most importantly, it is extremely water soluble and shows no post drug delivery cellular toxicity. Complete metabolism of dextran is possible inside body thus possibility of renal failure is minimum. Dextran based nanoparticles have superior aqueous solubility, high cargo capacity and intrinsic viscosity, and short storage period. The main focus area of this review is- past and present of major biomedical applications of dextran based nanomaterials thus showing a paradigm shift in bacterial exopolysaccharide based nanobiotechnology. Copyright © 2016 Elsevier B.V. All rights reserved.

Dextran vesicular carriers for dual encapsulation of hydrophilic and hydrophobic molecules and delivery into cells.

PubMed

Pramod, P S; Takamura, Kathryn; Chaphekar, Sonali; Balasubramanian, Nagaraj; Jayakannan, M

2012-11-12

Dextran vesicular nanoscaffolds were developed based on polysaccharide and renewable resource alkyl tail for dual encapsulation of hydrophilic and hydrophobic molecules (or drugs) and delivery into cells. The roles of the hydrophobic segments on the molecular self-organization of dextran backbone into vesicles or nanoparticles were investigated in detail. Dextran vesicles were found to be a unique dual carrier in which water-soluble molecules (like Rhodamine-B, Rh-B) and polyaromatic anticancer drug (camptothecin, CPT) were selectively encapsulated in the hydrophilic core and hydrophobic layer, respectively. The dextran vesicles were capable of protecting the plasma-sensitive CPT lactone pharmacophore against the hydrolysis by 10× better than the CPT alone in PBS. The aliphatic ester linkage connecting the hydrophobic tail with dextran was found to be cleaved by esterase under physiological conditions for fast releasing of CPT or Rh-B. Cytotoxicity of the dextran vesicle and its drug conjugate were tested on mouse embryonic fibroblast cells (MEFs) using MTT assay. The dextran vesicular scaffold was found to be nontoxic to living cells. CPT loaded vesicles were found to be 2.5-fold more effective in killing fibroblasts compared to that of CPT alone in PBS. Confocal microscopic images confirmed that both Rh-B and CPT loaded vesicles to be taken up by fibroblasts compared to CPT alone, showing a distinctly perinuclear localization in cells. The custom designed dextran vesicular provides new research opportunities for dual loading and delivering of hydrophilic and hydrophobic drug molecules.

The Role of Dextran Coatings on the Cytotoxicity Properties of Ceria Nanoparticles Toward Bone Cancer Cells

NASA Astrophysics Data System (ADS)

Yazici, Hilal; Alpaslan, Ece; Webster, Thomas J.

2015-04-01

Cerium oxide nanoparticles have demonstrated great potential as antioxidant and radioprotective agents for nanomedicine applications especially for cancer therapy. The surface chemistry of nanoparticles is an important property that has a significant effect on their performance in biological applications including cancer diagnosis, cancer treatment, and bacterial infection. Recently, various nanosized cerium oxide particles with different types of polymer coatings have been developed to improve aqueous solubility and allow for surface functionalization for distinct applications. In this study, the role of ceria nanoparticles coated with dextran on the cytotoxicity properties of bone cancer cells was shown. Specifically, 0.1 M and 0.01 M dextran-coated, <5-nm ceria nanoparticles, were synthesized. The cytotoxicity of 0.1 M and 0.01 M dextran-coated ceria nanoparticles was evaluated against osteosarcoma cells. A change in cell viability was observed when treating osteosarcoma cells with 0.1 M dextran-coated ceria nanoparticles in the 250 -1000 μg/mL concentration range. In contrast, minimal toxicity to bone cancer cells was observed for the 0.01 M dextran coating after 3 days compared with the 0.1 M dextran coating. These results indicated that surface dextran functionalization had a positive impact on the cytotoxicity of cerium oxide nanoparticles against osteosarcoma cells.

Cloning and characterization of a Weissella confusa dextransucrase and its application in high fibre baking.

PubMed

Kajala, Ilkka; Shi, Qiao; Nyyssölä, Antti; Maina, Ndegwa Henry; Hou, Yaxi; Katina, Kati; Tenkanen, Maija; Juvonen, Riikka

2015-01-01

Wheat bran offers health benefits as a baking ingredient, but is detrimental to bread textural quality. Dextran production by microbial fermentation improves sourdough bread volume and freshness, but extensive acid production during fermentation may negate this effect. Enzymatic production of dextran in wheat bran was tested to determine if dextran-containing bran could be used in baking without disrupting bread texture. The Weissella confusa VTT E-90392 dextransucrase gene was sequenced and His-tagged dextransucrase Wc392-rDSR was produced in Lactococcus lactis. Purified enzyme was characterized using (14)C-sucrose radioisotope and reducing value-based assays, the former yielding K(m) and V(max) values of 14.7 mM and 8.2 μmol/(mg ∙ min), respectively, at the pH optimum of 5.4. The structure and size of in vitro dextran product was similar to dextran produced in vivo. Dextran (8.1% dry weight) was produced in wheat bran in 6 h using Wc392-rDSR. Bran with and without dextran was used in wheat baking at 20% supplementation level. Dextran presence improved bread softness and neutralized bran-induced volume loss, clearly demonstrating the potential of using dextransucrases in bran bioprocessing for use in baking.

Cloning and Characterization of a Weissella confusa Dextransucrase and Its Application in High Fibre Baking

PubMed Central

Kajala, Ilkka; Shi, Qiao; Nyyssölä, Antti; Maina, Ndegwa Henry; Hou, Yaxi; Katina, Kati; Tenkanen, Maija; Juvonen, Riikka

2015-01-01

Wheat bran offers health benefits as a baking ingredient, but is detrimental to bread textural quality. Dextran production by microbial fermentation improves sourdough bread volume and freshness, but extensive acid production during fermentation may negate this effect. Enzymatic production of dextran in wheat bran was tested to determine if dextran-containing bran could be used in baking without disrupting bread texture. The Weissella confusa VTT E-90392 dextransucrase gene was sequenced and His-tagged dextransucrase Wc392-rDSR was produced in Lactococcus lactis. Purified enzyme was characterized using 14C-sucrose radioisotope and reducing value-based assays, the former yielding K m and V max values of 14.7 mM and 8.2 μmol/(mg∙min), respectively, at the pH optimum of 5.4. The structure and size of in vitro dextran product was similar to dextran produced in vivo. Dextran (8.1% dry weight) was produced in wheat bran in 6 h using Wc392-rDSR. Bran with and without dextran was used in wheat baking at 20% supplementation level. Dextran presence improved bread softness and neutralized bran-induced volume loss, clearly demonstrating the potential of using dextransucrases in bran bioprocessing for use in baking. PMID:25603169

Comparison of microdialysis sampling perfusion fluid components on the foreign body reaction in rat subcutaneous tissue.

PubMed

Keeler, Geoffrey D; Durdik, Jeannine M; Stenken, Julie A

2014-06-16

Microdialysis sampling is a commonly used technique for collecting solutes from the extracellular space of tissues in laboratory animals and humans. Large molecular weight solutes can be collected using high molecular weight cutoff (MWCO) membranes (100kDa or greater). High MWCO membranes require addition of high molecular weight dextrans or albumin to the perfusion fluid to prevent fluid loss via ultrafiltration. While these perfusion fluid additives are commonly used during microdialysis sampling, the tissue response to the loss of these compounds across the membrane is poorly understood. Tissue reactions to implanted microdialysis sampling probes containing different microdialysis perfusion fluids were compared over a 7-day time period in rats. The base perfusion fluid was Ringer's solution supplemented with either bovine serum albumin (BSA), rat serum albumin (RSA), Dextran-70, or Dextran-500. A significant inflammatory response to Dextran-70 was observed. No differences in the tissue response between BSA and RSA were observed. Among these agents, the BSA, RSA, and Dextran-500 produced a significantly reduced inflammatory response compared to the Dextran-70. This work demonstrates that use of Dextran-70 in microdialysis sampling perfusion fluids should be eliminated and replaced with Dextran-500 or other alternatives. Copyright © 2013 Elsevier B.V. All rights reserved.

Enteric-coated epichlorohydrin crosslinked dextran microspheres for site-specific delivery to colon.

PubMed

Rai, Gopal; Yadav, Awesh K; Jain, Narendra K; Agrawal, Govind P

2015-01-01

Enteric-coated epichlorohydrin crosslinked dextran microspheres containing 5-Fluorouracil (5-FU) for colon drug delivery was prepared by emulsification-crosslinking method. The formulation variables studied includes different molecular weights of dextran, volume of crosslinking agent, stirring speed, time and temperature. Dextran microspheres showed mean entrapment efficiencies ranging between 77 and 87% and mean particle size ranging between 10 and 25 µm. About 90% of drug was released from uncoated dextran microspheres within 8 h, suggesting the fast release and indicated the drug loaded in uncoated microspheres, released before they reached colon. Enteric coating (Eudragit-S-100 and Eudragit-L-100) of dextran microspheres was performed by oil-in-oil solvent evaporation method. The release study of 5-FU from coated dextran microspheres was complete retardation in simulated gastric fluid (pH 1.2) and once the coating layer of enteric polymer was dissolved at higher pH (7.4 and 6.8), a controlled release of the drug from the microspheres was observed. Further, the release of drug was found to be higher in the presence of dextranase and rat caecal contents, indicating the susceptibility of dextran microspheres to colonic enzymes. Organ distribution and pharmacokinetic study in albino rats was performed to establish the targeting potential of optimized formulation in the colon.

Persistent Epithelial Defects and Corneal Opacity After Collagen Cross-Linking With Substitution of Dextran (T-500) With Dextran Sulfate in Compounded Topical Riboflavin.

PubMed

Höllhumer, Roland; Watson, Stephanie; Beckingsale, Peter

2017-03-01

Collagen cross-linking (CXL) is a commonly performed procedure to prevent the progression of keratoconus. Riboflavin is an essential part of the procedure, which facilitates both the cross-linking process and protection of intraocular structures. Dextran can be added to riboflavin to create an isotonic solution. This case report highlights the importance of compounding riboflavin with the correct dextran solution. A retrospective case series. Six eyes of 4 male patients with keratoconus aged from 20 to 38 years underwent CXL with substitution of 20% dextran (T-500) with 20% dextran sulfate in a compounded riboflavin 0.1% solution. Postoperatively, persistent corneal epithelial defects, stromal haze, and then scarring occurred. Corneal transplantation was performed for visual rehabilitation but was complicated by graft rejection followed by failure (n = 1 eye), dehiscence (n = 4), cataract (n = 2), post-laser ablation haze (n = 1), and steroid-induced glaucoma (n = 2). The visual outcome was <6/18 in all 6 cases because of irregular astigmatism and stromal haze. Thinning, vascularization, and scarring of the residual host tissue were noted. Substitution of dextran (T-500) with dextran sulfate in riboflavin solutions during CXL results in loss of vision from permanent corneal opacity. Residual host changes may compromise the results of corneal transplantation.

The molecular mass of dextran used to modify magnetite nanoparticles affects insulin amyloid aggregation

NASA Astrophysics Data System (ADS)

Siposova, Katarina; Pospiskova, Kristyna; Bednarikova, Zuzana; Safarik, Ivo; Safarikova, Mirka; Kubovcikova, Martina; Kopcansky, Peter; Gazova, Zuzana

2017-04-01

Protein transformation from its soluble state into amyloid aggregates is associated with amyloid-related diseases. Amyloid deposits of insulin fibrils have been found in the sites of subcutaneous insulin application in patients with prolonged diabetes. Using atomic force microscopy and ThT fluorescence assay we have investigated the interference of insulin amyloid aggregation with superparamagnetic Fe3O4-based nanoparticles (SPIONs) coated with dextran (DEX); molecular mass of dextran was equal to 15-20, 40 or 70 kDa. The obtained data indicate that all three types of dextran coated nanoparticles (NP-FeDEXs) are able to inhibit insulin fibrillization and to destroy amyloid fibrils. The extent of anti-amyloid activities depends on the properties of NP-FeDEXs, mainly on the size of nanoparticles which is determined by molecular mass of dextran molecules. The most effective inhibiting activity was observed for the smallest nanoparticles coated with 15-20 kDa dextran. Contrary, the highest destroying activity was observed for the largest NP-FeDEX (70 kDa dextran).

Diffusing colloidal probes of protein-carbohydrate interactions.

PubMed

Eichmann, Shannon L; Meric, Gulsum; Swavola, Julia C; Bevan, Michael A

2013-02-19

We present diffusing colloidal probe measurements of weak, multivalent, specific protein-polysaccharide interactions mediated by a competing monosaccharide. Specifically, we used integrated evanescent wave and video microscopy methods to monitor the three-dimensional Brownian excursions of conconavilin A (ConA) decorated colloids interacting with dextran-functionalized surfaces in the presence of glucose. Particle trajectories were interpreted as binding lifetime histograms, binding isotherms, and potentials of mean force. Binding lifetimes and isotherms showed clear trends of decreasing ConA-dextran-specific binding with increasing glucose concentration, consistent with expectations. Net potentials were accurately captured by superposition of a short-range, glucose-independent ConA-dextran repulsion and a longer-range, glucose-dependent dextran bridging attraction modeled as a harmonic potential. For glucose concentrations greater than 100 mM, the net ConA-dextran potential was found to have only a nonspecific repulsion, similar to that of bovine serum albumin (BSA) decorated colloids over dextran determined in control experiments. Our results demonstrate the first use of optical microscopy methods to quantify the connections between potentials of mean force and the binding behavior of ConA-decorated colloids on dextran-functionalized surfaces.

Phase partitioning in space and on earth

NASA Technical Reports Server (NTRS)

Van Alstine, James M.; Karr, Laurel J.; Snyder, Robert S.; Matsos, Helen C.; Curreri, Peter A.; Harris, J. Milton; Bamberger, Stephan B.; Boyce, John; Brooks, Donald E.

1987-01-01

The influence of gravity on the efficiency and quality of the impressive separations achievable by bioparticle partitioning is investigated by demixing polymer phase systems in microgravity. The study involves the neutral polymers dextran and polyethylene glycol, which form a two-phase system in aqueous solution at low concentrations. It is found that demixing in low-gravity occurs primarily by coalescence, whereas on earth the demixing occurs because of density differences between the phases.

Formation of polyelectrolyte complexes with diethylaminoethyl dextran: charge ratio and molar mass effect.

PubMed

Le Cerf, Didier; Pepin, Anne Sophie; Niang, Pape Momar; Cristea, Mariana; Karakasyan-Dia, Carole; Picton, Luc

2014-11-26

The formation of polyelectrolyte complexes (PECs) between carboxymethyl pullulan and DEAE Dextran, was investigated, in dilute solution, with emphasis on the effect of charge density (molar ratio or pH) and molar masses. Electrophoretic mobility measurements have evidenced that insoluble PECs (neutral electrophoretic mobility) occurs for charge ratio between 0.6 (excess of polycation) and 1 (stoichiometry usual value) according to the pH. This atypical result is explained by the inaccessibility of some permanent cationic charge when screened by pH dependant cationic ones (due to the Hoffman alkylation). Isothermal titration calorimetry (ITC) indicates an endothermic formation of PEC with a binding constant around 10(5) L mol(-1). Finally asymmetrical flow field flow fractionation coupled on line with static multi angle light scattering (AF4/MALS) evidences soluble PECs with very large average molar masses and size around 100 nm, in agreement with scrambled eggs multi-association between various polyelectrolyte chains. Copyright © 2014 Elsevier Ltd. All rights reserved.

EnVision+, a new dextran polymer-based signal enhancement technique for in situ hybridization (ISH).

PubMed

Wiedorn, K H; Goldmann, T; Henne, C; Kühl, H; Vollmer, E

2001-09-01

Seventy paraffin-embedded cervical biopsy specimens and condylomata were tested for the presence of human papillomavirus (HPV) by conventional in situ hybridization (ISH) and ISH with subsequent signal amplification. Signal amplification was performed either by a commercial biotinyl-tyramide-based detection system [GenPoint (GP)] or by the novel two-layer dextran polymer visualization system EnVision+ (EV), in which both EV-horseradish peroxidase (EV-HRP) and EV-alkaline phosphatase (EV-AP) were applied. We could demonstrate for the first time, that EV in combination with preceding ISH results in a considerable increase in signal intensity and sensitivity without loss of specificity compared to conventional ISH. Compared to GP, EV revealed a somewhat lower sensitivity, as measured by determination of the integrated optical density (IOD) of the positively stained cells. However, EV is easier to perform, requires a shorter assay time, and does not raise the background problems that may be encountered with biotinyl-tyramide-based amplification systems. (J Histochem Cytochem 49:1067-1071, 2001)

Development of poly-l-lysine-coated calcium-alginate microspheres encapsulating fluorescein-labeled dextrans

NASA Astrophysics Data System (ADS)

Charron, Luc; Harmer, Andrea; Lilge, Lothar

2005-09-01

A technique to produce fluorescent cell phantom standards based on calcium alginate microspheres with encapsulated fluorescein-labeled dextrans is presented. An electrostatic ionotropic gelation method is used to create the microspheres which are then exposed to an encapsulation method using poly-l-lysine to trap the dextrans inside. Both procedures were examined in detail to find the optimal parameters producing cell phantoms meeting our requirements. Size distributions favoring 10-20 microns microspheres were obtained by varying the high voltage and needle size parameters. Typical size distributions of the samples were centered at 150 μm diameter. Neither the molecular weight nor the charge of the dextrans had a significant effect on their retention in the microspheres, though anionic dextrans were chosen to help in future capillary electrophoresis work. Increasing the exposure time of the microspheres to the poly-l-lysine solution decreased the leakage rates of fluorescein-labeled dextrans.

Clinical effectiveness analysis of dextran 40 plus dexamethasone on the prevention of fat embolism syndrome.

PubMed

Liu, Xi-Ming; Huang, Jin-Cheng; Wang, Guo-Dong; Lan, Sheng-Hui; Wang, Hua-Song; Pan, Chang-Wu; Zhang, Ji-Ping; Cai, Xian-Hua

2014-01-01

This study aims to investigate the clinical efficacy of Dextran 40 plus dexamethasone on the prevention of fat embolism syndrome (FES) in high-risk patients with long bone shaft fractures. According to the different preventive medication, a total of 1837 cases of long bone shaft fracture patients with injury severity score (ISS) > 16 were divided into four groups: dextran plus dexamethasone group, dextran group, dexamethasone group and control group. The morbidity and mortality of FES in each group were analyzed with pairwise comparison analysis. There were totally 17 cases of FES and 1 case died. The morbidity of FES was 0.33% in dextran plus dexamethasone group and significantly lowers than that of other groups (P < 0.05). There was no significant difference among other groups (P > 0.05). Conclusion from our data is dextran 40 plus dexamethasone can effectively prevent long bone shaft fractures occurring in high-risk patients with FES.

The use of dextran post free tissue transfer.

PubMed

Ridha, H; Jallali, N; Butler, P E

2006-01-01

Dextran has been used in microsurgery to reduce the risk of free tissue transfer loss. A number of regimens which vary considerably in dosage and timing have been published in the literature. Using a postal questionnaire, a survey was conducted to delineate the current practise of UK plastic surgeons. Data were received from 161 plastic surgeons in 51 units (response rate of 61%). Forty-five percent of microsurgeons routinely use dextran post-operatively whilst 29% use alternative thromboprophylaxis. The indications, post-operative regimes and duration of administration of dextran vary significantly amongst surgeons and units. The reported success rates of free tissue transfer and digital replants were 97 and 85.1%, respectively, and was not significantly affected by the use of dextran. We conclude that there is considerable variation amongst UK plastic surgeons regarding thromboprophylaxis post microsurgery. Our data suggest that the use of dextrans does not affect free tissue transfer success rates.

Rye bran as fermentation matrix boosts in situ dextran production by Weissella confusa compared to wheat bran.

PubMed

Kajala, Ilkka; Mäkelä, Jari; Coda, Rossana; Shukla, Shraddha; Shi, Qiao; Maina, Ndegwa Henry; Juvonen, Riikka; Ekholm, Päivi; Goyal, Arun; Tenkanen, Maija; Katina, Kati

2016-04-01

The consumption of fiber-rich foods such as cereal bran is highly recommended due to its beneficial health effects. Pre-fermentation of bran with lactic acid bacteria can be used to improve the otherwise impaired flavor and textural qualities of bran-rich products. These positive effects are attributed to enzymatic modification of bran components and the production of functional metabolites like organic acids and exopolysaccharides such as dextrans. The aim of this study was to investigate dextran production in wheat and rye bran by fermentation with two Weissella confusa strains. Bran raw materials were analyzed for their chemical compositions and mineral content. Microbial growth and acidification kinetics were determined from the fermentations. Both strains produced more dextran in rye bran in which the fermentation-induced acidification was slower and the acidification lag phase longer than in wheat bran. Higher dextran production in rye bran is expected to be due to the longer period of optimal pH for dextran synthesis during fermentation. The starch content of wheat bran was higher, which may promote isomaltooligosaccharide formation at the expense of dextran production. W. confusa Cab3 produced slightly higher amounts of dextran than W. confusa VTT E-90392 in all raw materials. Fermentation with W. confusa Cab3 also resulted in lower residual fructose content which has technological relevance. The results indicate that wheat and particularly rye bran are promising matrices for producing technologically significant amounts of dextran, which facilitates the use of nutritionally valuable raw bran in food applications.

The low molecular weight Dextran 40 inhibits the adhesion of T lymphocytes to endothelial cells

PubMed Central

TERMEER, C C; WEISS, J M; SCHÖPF, E; VANSCHEIDT, W; SIMON, J C

1998-01-01

Dextrans are complex colloidal macromolecules widely used as haemorrheologic substances and anti-thrombotic agents. Here we describe a novel function of Dextran 40 by demonstrating an inhibition of T lymphocyte adhesion to endothelial cells (EC). We applied an established microassay in which constitutive and tumour necrosis factor-alpha (TNF-α)-induced binding of mouse T lymphoma cells (TK-1) to mouse endothelioma (eEND.2) cells is mediated by the interaction of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on EC with their counter-receptors the LFA-1 heterodimer (CD11a/CD18) and VLA-4 on T cells. Dextran 40 in therapeutically achievable levels (2–32 mg/ml) reduced both constitutive and TNF-α-stimulated TK-1 adhesion to eEND.2. Selective preincubation of eEND.2 or TK-1 revealed that Dextran 40 acted exclusively on the T cells. To explore further the mechanisms by which Dextran 40 interfered with TK-1 adhesion, their LFA-1 and VLA-4 expression was analysed by FACS. The surface expression levels of neither receptor were affected by Dextran 40. However, confocal microscopy revealed that Dextran 40 interfered with the activation-dependent capping and clustering of LFA-1 and VLA-4 on the surface of TK-1. We conclude that Dextran 40 inhibits the capacity of TK-1 T cells to adhere to eEND.2 endothelial cells and thus may be useful for therapeutic intervention in diseases associated with enhanced T lymphocyte binding to microvascular endothelium. PMID:9844053

Preparation and characterization of magnetic nanoparticles containing Fe(3)O(4)-dextran-anti-β-human chorionic gonadotropin, a new generation choriocarcinoma-specific gene vector.

PubMed

Jingting, Cai; Huining, Liu; Yi, Zhang

2011-01-01

To evaluate the feasibility of using magnetic iron oxide (Fe(3)O(4))-dextran-anti-β-human chorionic gonadotropin (HCG) nanoparticles as a gene vector for cellular transfections. Fe(3)O(4)-dextran-anti-β-HCG nanoparticles were synthesized by chemical coprecipitation. The configuration, diameter, and iron content of the nanoparticles were detected by transmission electron microscopy (TEM), light scatter, and atomic absorption spectrophotometry. A3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide assay was used to evaluate the cytotoxicity of Fe(3)O(4)-dextran-anti-β-HCG nanoparticles. Enzyme-linked immunosorbent assay and indirect immunofluorescence were used to evaluate immunoreactivity. The efficiency of absorbing DNA and resisting deoxyribonuclease I (DNase I) digestion when bound to Fe(3)O(4)-dextran-anti-β-HCG nanoparticles was examined by agarose gel electrophoresis. The ability of Fe(3)O(4)-dextran-anti-β-HCG nanoparticles to absorb heparanase antisense oligodeoxynucleotides (AS-ODN) nanoparticles in different cell lines was evaluated by flow cytometry. The tissue distribution of heparanase AS-ODN magnetic nanoparticles in choriocarcinoma tumors transplanted in nude mice was detected by atomic absorption spectrophotometry. TEM demonstrated that the shape of nanoparticles is irregular. Light scatter revealed nanoparticles with a mean diameter of 75.5 nm and an iron content of 37.5 μg/mL. No cytotoxicity was observed when the concentration of Fe(3)O(4)-dextran-anti-β-HCG nanoparticles was <37.5 μg/mL. Fe(3)O(4)-dextran nanoparticles have a satisfactory potential to combine with β-HCG antibody. Agarose gel electrophoresis analysis of binding experiments showed that after treatment with sodium periodate, Fe(3)O(4)-dextran-anti-β-HCG nanoparticles have a satisfactory potential to absorb DNA, and the protection experiment showed that nanoparticles can effectively protect DNA from DNase I digestion. Aldehyde Fe(3)O(4)-dextran-anti-β-HCG nanoparticles can transfect reporter genes, and the transfection efficiency of these nanoparticles is greater than that of liposomes (P < 0.05). Fe(3)O(4)-dextran-anti-β-HCG nanoparticles can concentrate in choriocarcinoma cells and in transplanted choriocarcinoma tumors. The results confirm that Fe(3)O(4)-dextran-anti-β-HCG nanoparticles have potential as a secure, effective, and choriocarcinoma-specific targeting gene vector.

Effect of dextran-70 on outcome in severe sepsis; a propensity-score matching study.

PubMed

Bentzer, Peter; Broman, Marcus; Kander, Thomas

2017-07-06

Albumin may be beneficial in patients with septic shock but availability is limited and cost is high. The objective of the present study was to investigate if the use of dextran-70 in addition to albumin and crystalloids influences organ failure or mortality in patients with severe sepsis or septic shock. Patients with severe sepsis or septic shock (n = 778) admitted to a university hospital intensive care unit (ICU) between 2007 and 2015 that received dextran-70 during resuscitation were propensity score matched to controls at a 1 to 1 ratio. Outcomes were highest acute kidney injury network (AKIN) score the first 10 days in the ICU, use of renal replacement therapy, days alive and free of organ support the first 28 days after admission to ICU, mortality and events of severe bleeding. Outcomes were assessed using paired hypothesis testing. Propensity score matching resulted in two groups of patients with 245 patients in each group. The dextran group received a median volume of 1483 ml (interquartile range, 1000-2000 ml) of dextran-70 during the ICU stay. Highest AKIN score did not differ between the control- and dextran groups (1 (0-3) versus 2 (0-3), p = 0.06). Incidence of renal replacement therapy in the control- and dextran groups was similar (19% versus 22%, p = 0.42, absolute risk reduction -2.9% [95% CI: -9.9 to 4.2]). Days alive and free of renal replacement, vasopressors and mechanical ventilation did not differ between the control- and dextran groups. The 180-day mortality was 50.2% in the control group and 41.6% in the dextran group (p = 0.046, absolute risk reduction 8.6% [-0.2 to 17.4]). Fraction of patients experiencing a severe bleeding in the first 10 days in the ICU did not differ between the control and dextran groups (14% versus 18%, p = 0.21). There is a paucity of high quality data regarding effects of dextran solutions on outcome in sepsis. In the present study, propensity score matching was used in attempt to reduce bias. No evidence to support a detrimental effect of dextran-70 on mortality or on organ failures in patients with severe sepsis or septic shock could be detected.

Inhibitory effects of carbohydrates on histamine release and mast cell disruption by dextran

PubMed Central

Beraldo, W. T.; Da Silva, W. dias; Fernandes, A. D. Lemos

1962-01-01

Alloxan diabetic rats failed to show the skin reaction (blue spot) evoked by dextran, whereas the effects produced by histamine and compound 48/80 were not altered. When dextran and glucose were injected simultaneously into the skin the reaction was inhibited. In vitro, mast cell alterations produced by dextran occurred simultaneously with histamine release; both processes were inhibited by glucose, other carbohydrates related to glucose, and inhibitors of anaphylaxis. These experiments suggest that dextran releases histamine by a mechanism similar to that found with 48/80 and anaphylaxis in the rat. The inhibitory effect of carbohydrates may be understood on the basis of a competitive mechanism. ImagesFig. 1Fig. 2 PMID:13967594

Preparation and characterization of a dextran-amylase conjugate.

PubMed

Marshall, J J

1976-07-01

Bacillus amyloliquefaciens alpha-amylase was attached to dextran after activation of the polysaccharide by using a modification of the cyanogen bromide method. The soluble dextran-amylase conjugate was purified by molecular-sieve chromatography. The conjugated enzyme has greater stability than the unmodified enzyme at low pH values, during heat treatment, and on removal of calcium ions with a chelating agent. Attachment of dextran to alpha-amylase did not alter the Michaelis constant of the enzyme acting on starch. The polysaccharide-enzyme conjugate probably consists of a cross-linked aggregate of many dextran and many enzyme molecules, in which a proportion of the enzyme molecules, although not inactivated, are unable to express their activity, except after dextranase treatment.

The role of density discontinuity in the inviscid instability of two-phase parallel flows

NASA Astrophysics Data System (ADS)

Behzad, M.; Ashgriz, N.

2014-02-01

We re-examine the inviscid instability of two-phase parallel flows with piecewise linear velocity profiles. Although such configuration has been theoretically investigated, we employ the concept of waves resonance to physically interpret the instability mechanism as well as the essential role of density discontinuity in the flow. Upon performing linear stability analysis, we demonstrate the existence of neutrally stable "density" and "density-vorticity" waves which are emerged due to the density jump in the flow, in addition to the well-known vorticity waves. Such waves are capable of resonating with each other to form unstable modes in the flow. Although unstable modes in this study are classified as the "shear instability" type, we demonstrate that they are not necessarily of the Rayleigh type. The results also show that the density can have both stabilizing and destabilizing effects on the flow stability. We verify that the difference in the resonating pair of neutral waves leads to such distinct behavior of the density variation.

Derivatization of Dextran for Multiply Charged Ion Formation and Electrospray Ionization Time-of-Flight Mass Spectrometric Analysis

NASA Astrophysics Data System (ADS)

Tapia, Jesus B.; Hibbard, Hailey A. J.; Reynolds, Melissa M.

2017-10-01

We present the use of a simple, one-pot derivatization to allow the polysaccharide dextran to carry multiple positive charges, shifting its molecular weight distribution to a lower m/ z range. We performed this derivatization because molecular weight measurements of polysaccharides by mass spectrometry are challenging because of their lack of readily ionizable groups. The absence of ionizable groups limits proton abstraction and suppresses proton adduction during the ionization process, producing mass spectra with predominantly singly charged metal adduct ions, thereby limiting the detection of large polysaccharides. To address this challenge, we derivatized dextran T1 (approximately 1 kDa) by attaching ethylenediamine, giving dextran readily ionizable, terminal amine functional groups. The attached ethylenediamine groups facilitated proton adduction during the ionization process in positive ion mode. Using the low molecular weight dextran T1, we tracked the number of ethylenediamine attachments by measuring the mass shift from underivatized to derivatized dextran T1. Using electrospray ionization time-of-flight mass spectrometry, we observed derivatized dextran chains ranging from two to nine glucose residues with between one and four attachments/charges. Our success in shifting derivatized dextran T1 toward the low m/ z range suggests potential for this derivatization as a viable route for analysis of high molecular weight polysaccharides using electrospray ionization time-of-flight mass spectrometry. [Figure not available: see fulltext.

Permeabilization of the plasma membrane of L1210 mouse leukemia cells using lithotripter shock waves.

PubMed

Gambihler, S; Delius, M; Ellwart, J W

1994-09-01

Permeabilization of L1210 cells by lithotripter shock waves in vitro was monitored by evaluating the accumulation of fluorescein-labeled dextrans with a relative molecular mass ranging from 3,900-2,000,000. Incubation with labeled dextran alone caused a dose- and time-dependent increase in cellular fluorescence as determined by flow cytometry, with a vesicular distribution pattern in the cells consistent with endocytotic uptake. Shock wave exposure prior to incubation with labeled dextran revealed similar fluorescence intensities compared to incubation with labeled dextran alone. When cells were exposed to shock waves in the presence of labeled dextran, mean cellular fluorescence was further increased, indicating additional internalization of the probe. Confocal laser scanning microscopy confirmed intracellular fluorescence of labeled dextran with a diffuse distribution pattern. Fluorescence-activated cell sorting with subsequent determination of proliferation revealed that permeabilized cells were viable and able to proliferate. Permeabilization of the membrane of L1210 cells by shock waves in vitro allowed loading of dextrans with a relative molecular mass up to 2,000,000. Permeabilization of tumor cells by shock waves provides a useful tool for introducing molecules into cells which might be of interest for drug targeting in tumor therapy in vivo.

Optimization of dextran production by Leuconostoc mesenteroides NRRL B-512 using cheap and local sources of carbohydrate and nitrogen.

PubMed

Behravan, Javad; Bazzaz, B Seddigheh Fazly; Salimi, Zohreh

2003-12-01

Using pure components for the fermentation medium in dextran production imposes high costs on the industry. In the present study, the economic production of dextran using local and cheap sources of carbohydrate and nitrogen was investigated. Different concentrations of molasses and wheat-bran extract, after filtration, steam sterilization and pH adjustment, were inoculated with a fresh suspension of Leuconostoc mesenteroides. Cultures were incubated, and then diluted with an equal volume of ethanol. The bacteria were pelleted, and an aliquot of the supernatant was diluted with ethanol and dextran was precipitated. The supernatant was removed and the precipitate was dissolved in a minimal volume of water. Activated charcoal was added and the solution was boiled. The solution was filtered and protein impurities removed by 2-methylbutan-2-ol/chloroform extraction. Dextran was again precipitated with cold ethanol as described above, and the precipitate was dried in a desiccator. Optimum conditions and composition of culture media for dextran production using sugar-beet molasses and wheat bran were determined. The best results were obtained when 20% (w/v) molasses and 15% (w/v) wheat bran were used. The optimal initial pH for dextran production was 7.5.

Fabrication and characterization of iron oxide dextran composite layers

NASA Astrophysics Data System (ADS)

Iconaru, S. L.; Predoi, S. A.; Beuran, M.; Ciobanu, C. S.; Trusca, R.; Ghita, R.; Negoi, I.; Teleanu, G.; Turculet, S. C.; Matei, M.; Badea, Monica; Prodan, A. M.

2018-02-01

Super paramagnetic iron oxide nanoparticles such as maghemite have been shown to exhibit antimicrobial properties [1-5]. Moreover, the iron oxide nanoparticles have been proposed as a potential magnetically controllable antimicrobial agent which could be directed to a specific infection [3-5]. The present research has focused on studies of the surface and structure of iron oxide dextran (D-IO) composite layers surface and structure. These composite layers were deposited on Si substrates. The structure of iron oxide dextran composite layers was investigated by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) while the surface morphology was evaluated by Scanning Electron Microscopy (SEM). The structural characterizations of the iron oxide dextran composite layers revealed the basic constituents of both iron and dextran structure. Furthermore, the in vitro evaluation of the antifungal effect of the complex layers, which have been shown revealed to be active against C. albicans cells at distinct intervals of time, is exhibited. Our research came to confirm the fungicidal effect of iron oxide dextran composite layers. Also, our results suggest that iron oxide dextran surface may be used for medical treatment of biofilm associated Candida infections.

Dextrans produced by lactic acid bacteria exhibit antiviral and immunomodulatory activity against salmonid viruses.

PubMed

Nácher-Vázquez, Montserrat; Ballesteros, Natalia; Canales, Ángeles; Rodríguez Saint-Jean, Sylvia; Pérez-Prieto, Sara Isabel; Prieto, Alicia; Aznar, Rosa; López, Paloma

2015-06-25

Viral infections in the aquaculture of salmonids can lead to high mortality and substantial economic losses. Thus, there is industrial interest in new molecules active against these viruses. Here we describe the production, purification, and the physicochemical and structural characterization of high molecular weight dextrans synthesized by Lactobacillus sakei MN1 and Leuconostoc mesenteroides RTF10. The purified dextrans, and commercial dextrans with molecular weights ranging from 10 to 2000kDa, were assayed in infected BF-2 and EPC fish cell-line monolayers for antiviral activity. Only T2000 and dextrans from MN1 and RTF10 had significant antiviral activity. This was similar to results obtained against infectious pancreatic necrosis virus. However the dextran from MN1 showed ten-fold higher activity against hematopoietic necrosis virus than T2000. In vivo assays using the MN1 polymer confirmed the in vitro results and revealed immunomodulatory activity. These results together with the high levels of dextran production (2gL(-1)) by Lb. sakei MN1, indicate the compounds potential utility as an antiviral agent in aquaculture. Copyright © 2015 Elsevier Ltd. All rights reserved.

Automated Continuous Distraction Osteogenesis May Allow Faster Distraction Rates: A Preliminary Study

PubMed Central

Peacock, Zachary S.; Tricomi, Brad; Murphy, Brian; Magill, John; Kaban, Leonard B.; Troulis, Maria

2013-01-01

Purpose To determine if automated continuous distraction osteogenesis at rates > 1mm/day would result in clinical and radiographic bone formation in a minipig model. Materials and Methods An automated, continuous, curvilinear distraction device was placed across a mandibular osteotomy in 10 minipigs. After 12 mm of distraction and 24 days fixation, animals were sacrificed and bone healing evaluated. The continuous distraction rates were 1.5 (n=5) and 3 mm/day (n=5). A semiquantitative scale was used to assess ex-vivo clinical appearance of the distraction gap (3= osteotomy not visible; 2= <50%; 1= >50%; 0= 100% visible); stability (3 = no mobility; 2 and 1 = mobility in 2 or 1 plane respectively; 0= mobility in 3 planes); radiographic density (4 = 100% gap opaque, 3= >75%, 2 = 50% – 75%, 1= <50%, or 0 = radiolucent). Groups of 4 minipigs distracted discontinuously at 1, 2, and 4 mm/day served as controls. Results The continuous DO 1.5 mm/day group had significantly higher scores for appearance and radiographic density compared to the discontinuous 4 mm/day group. The continuous DO 3mm/day group had significantly higher scores for appearance and radiographic density compared to the discontinuous 4 mm/day group, and higher stability compared to the discontinuous 2 and 4 mm/day groups. Conclusions Results of this preliminary study indicate that continuous DO at rates of 1.5 and 3.0 mm/day produces better bone formation when compared to discontinuous DO at rates faster than 1mm/day. PMID:23499159

Molecular Imaging Probes for Positron Emission Tomography and Optical Imaging of Sentinel Lymph Node and Tumor

NASA Astrophysics Data System (ADS)

Qin, Zhengtao

Molecular imaging is visualizations and measurements of in vivo biological processes at the molecular or cellular level using specific imaging probes. As an emerging technology, biocompatible macromolecular or nanoparticle based targeted imaging probes have gained increasing popularities. Those complexes consist of a carrier, an imaging reporter, and a targeting ligand. The active targeting ability dramatically increases the specificity. And the multivalency effect may further reduce the dose while providing a decent signal. In this thesis, sentinel lymph node (SLN) mapping and cancer imaging are two research topics. The focus is to develop molecular imaging probes with high specificity and sensitivity, for Positron Emission Tomography (PET) and optical imaging. The objective of this thesis is to explore dextran radiopharmaceuticals and porous silicon nanoparticles based molecular imaging agents. Dextran polymers are excellent carriers to deliver imaging reporters or therapeutic agents due to its well established safety profile and oligosaccharide conjugation chemistry. There is also a wide selection of dextran polymers with different lengths. On the other hand, Silicon nanoparticles represent another class of biodegradable materials for imaging and drug delivery. The success in fluorescence lifetime imaging and enhancements of the immune activation potency was briefly discussed. Chapter 1 begins with an overview on current molecular imaging techniques and imaging probes. Chapter 2 presents a near-IR dye conjugated probe, IRDye 800CW-tilmanocept. Fluorophore density was optimized to generate the maximum brightness. It was labeled with 68Ga and 99mTc and in vivo SLN mapping was successfully performed in different animals, such as mice, rabbits, dogs and pigs. With 99mTc labeled IRDye 800CW-tilmanocept, chapter 3 introduces a two-day imaging protocol with a hand-held imager. Chapter 4 proposed a method to dual radiolabel the IRDye 800CW-tilmanocept with both 68Ga and 99mTc. Chapter 5 introduces a 68Ga metal chelating bioorthogonal tetrazine dextran probe for multistep imaging of a colon cancer. Chapter 6 presents the synthesis and in vivo evaluation of a Hepatocellular Carcinoma targeting PET probe 68Ga-Insulin-Dextran. Chapter 7 discusses a novel method to prepare silicon nanoparticles with great yield and size control. The last chapter 8 concludes all probes developed in this thesis and their clinical relevance.

Automated extraction and analysis of rock discontinuity characteristics from 3D point clouds

NASA Astrophysics Data System (ADS)

Bianchetti, Matteo; Villa, Alberto; Agliardi, Federico; Crosta, Giovanni B.

2016-04-01

A reliable characterization of fractured rock masses requires an exhaustive geometrical description of discontinuities, including orientation, spacing, and size. These are required to describe discontinuum rock mass structure, perform Discrete Fracture Network and DEM modelling, or provide input for rock mass classification or equivalent continuum estimate of rock mass properties. Although several advanced methodologies have been developed in the last decades, a complete characterization of discontinuity geometry in practice is still challenging, due to scale-dependent variability of fracture patterns and difficult accessibility to large outcrops. Recent advances in remote survey techniques, such as terrestrial laser scanning and digital photogrammetry, allow a fast and accurate acquisition of dense 3D point clouds, which promoted the development of several semi-automatic approaches to extract discontinuity features. Nevertheless, these often need user supervision on algorithm parameters which can be difficult to assess. To overcome this problem, we developed an original Matlab tool, allowing fast, fully automatic extraction and analysis of discontinuity features with no requirements on point cloud accuracy, density and homogeneity. The tool consists of a set of algorithms which: (i) process raw 3D point clouds, (ii) automatically characterize discontinuity sets, (iii) identify individual discontinuity surfaces, and (iv) analyse their spacing and persistence. The tool operates in either a supervised or unsupervised mode, starting from an automatic preliminary exploration data analysis. The identification and geometrical characterization of discontinuity features is divided in steps. First, coplanar surfaces are identified in the whole point cloud using K-Nearest Neighbor and Principal Component Analysis algorithms optimized on point cloud accuracy and specified typical facet size. Then, discontinuity set orientation is calculated using Kernel Density Estimation and principal vector similarity criteria. Poles to points are assigned to individual discontinuity objects using easy custom vector clustering and Jaccard distance approaches, and each object is segmented into planar clusters using an improved version of the DBSCAN algorithm. Modal set orientations are then recomputed by cluster-based orientation statistics to avoid the effects of biases related to cluster size and density heterogeneity of the point cloud. Finally, spacing values are measured between individual discontinuity clusters along scanlines parallel to modal pole vectors, whereas individual feature size (persistence) is measured using 3D convex hull bounding boxes. Spacing and size are provided both as raw population data and as summary statistics. The tool is optimized for parallel computing on 64bit systems, and a Graphic User Interface (GUI) has been developed to manage data processing, provide several outputs, including reclassified point clouds, tables, plots, derived fracture intensity parameters, and export to modelling software tools. We present test applications performed both on synthetic 3D data (simple 3D solids) and real case studies, validating the results with existing geomechanical datasets.

Comparison of Corneal Riboflavin Gradients Using Dextran and HPMC Solutions.

PubMed

Ehmke, Tobias; Seiler, Theo G; Fischinger, Isaak; Ripken, Tammo; Heisterkamp, Alexander; Frueh, Beatrice E

2016-12-01

To determine the riboflavin concentration gradient in the anterior corneal stroma when using hydroxypropyl methylcellulose (HPMC) or dextran as the carrier agent. Four different groups of porcine corneas (5 each) were compared regarding the riboflavin concentration in the anterior stroma. Prior to all experiments, stable hydration conditions were established for the corresponding solution. The dextran groups were treated with 0.1% riboflavin in 20% dextran for 10 and 30 minutes and the HPMC groups with 0.1% riboflavin in 1.1% HPMC for 10 and 30 minutes. After imbibition, nonlinear microscopy and consecutive image analysis were used to determine two-photon fluorescence intensities. To determine the riboflavin concentration, corneas were saturated and measured a second time by two-photon microscopy. With this measurement, a proper correction for absorption and scattering could be performed. Ultraviolet-A (UVA) transmission was measured after the application time for each group. Riboflavin concentration decreased with increasing depth and increased with longer application times in all groups. Comparing the dextran for 30 minutes and HPMC for 10 minutes groups, a significantly higher stromal riboflavin concentration was found within the most anterior 70 µm in the dextran group for 30 minutes, whereas deeper than 260 µm HPMC-assisted imbibition for 10 minutes yielded higher concentrations. In dextran-treated corneas, values obtained from pachymetry were substantially reduced, whereas HPMC-assisted imbibition led to a decent swelling. UVA transmission values were higher in dextran-assisted imbibition than in HPMC-assisted imbibition. Stromal riboflavin gradients are similar when applied in dextran for 30 minutes and HPMC for 10 minutes. When using HPMC solutions, a shallower cross-linked volume is expected due to a higher corneal hydration. [J Refract Surg. 2016;32(12):798-802.]. Copyright 2016, SLACK Incorporated.

Potential of novel dextran oligosaccharides as prebiotics for obesity management through in vitro experimentation.

PubMed

Sarbini, Shahrul R; Kolida, Sofia; Deaville, Eddie R; Gibson, Glenn R; Rastall, Robert A

2014-10-28

The energy-salvaging capacity of the gut microbiota from dietary ingredients has been proposed as a contributing factor for the development of obesity. This knowledge generated interest in the use of non-digestible dietary ingredients such as prebiotics to manipulate host energy homeostasis. In the present study, the in vitro response of obese human faecal microbiota to novel oligosaccharides was investigated. Dextrans of various molecular weights and degrees of branching were fermented with the faecal microbiota of healthy obese adults in pH-controlled batch cultures. Changes in bacterial populations were monitored using fluorescent in situ hybridisation and SCFA concentrations were analysed by HPLC. The rate of gas production and total volume of gas produced were also determined. In general, the novel dextrans and inulin increased the counts of bifidobacteria. Some of the dextrans were able to alter the composition of the obese human microbiota by increasing the counts of Bacteroides-Prevotella and decreasing those of Faecalibacterium prausnitzii and Ruminococcus bromii/R. flavefaciens. Considerable increases in SCFA concentrations were observed in response to all substrates. Gas production rates were similar during the fermentation of all dextrans, but significantly lower than those during the fermentation of inulin. Lower total gas production and shorter time to attain maximal gas production were observed during the fermentation of the linear 1 kDa dextran than during the fermentation of the other dextrans. The efficacy of bifidobacteria to ferment dextrans relied on the molecular weight and not on the degree of branching. In conclusion, there are no differences in the profiles between the obese and lean human faecal fermentations of dextrans.

Targeting the C-type Lectins-Mediated Host-Pathogen Interactions with Dextran

PubMed Central

Pustylnikov, Sergey; Sagar, Divya; Jain, Pooja; Khan, Zafar K.

2017-01-01

Dextran, the α-1,6-linked glucose polymer widely used in biology and medicine, promises new applications. Linear dextran applied as a blood plasma substitute demonstrates a high rate of biocompatibility. Dextran is present in foods, drugs, and vaccines and in most cases is applied as a biologically inert substance. In this review we analyze dextran’s cellular uptake principles, receptor specificity and, therefore, its ability to interfere with pathogen–lectin interactions: a promising basis for new antimicrobial strategies. Dextran-binding receptors in humans include the DC-SIGN (dendritic cell–specific intercellular adhesion molecule 3-grabbing nonintegrin) family receptors: DC-SIGN (CD209) and L-SIGN (the liver and lymphatic endothelium homologue of DC-SIGN), the mannose receptor (CD206), and langerin. These receptors take part in the uptake of pathogens by dendritic cells and macrophages and may also participate in the modulation of immune responses, mostly shown to be beneficial for pathogens per se rather than host(s). It is logical to predict that owing to receptor-specific interactions, dextran or its derivatives can interfere with these immune responses and improve infection outcome. Recent data support this hypothesis. We consider dextran a promising molecule for the development of lectin–glycan interaction-blocking molecules (such as DC-SIGN inhibitors) that could be applied in the treatment of diseases including tuberculosis, influenza, hepatitis B and C, human immunodeficiency virus infection and AIDS, etc. Dextran derivatives indeed change the pathology of infections dependent on DC-SIGN and mannose receptors. Complete knowledge of specific dextran–lectin interactions may also be important for development of future dextran applications in biological research and medicine. PMID:25224349

Biophysical properties of carboxymethyl derivatives of mannan and dextran.

PubMed

Korcová, Jana; Machová, Eva; Filip, Jaroslav; Bystrický, Slavomír

2015-12-10

Mannan from Candida albicans, dextran from Leuconostoc spp. and their carboxymethyl (CM)-derivatives were tested on antioxidant and thrombolytic activities. As antioxidant tests, protection of liposomes against OH radicals and reducing power assay were used. Dextran and mannan protected liposomes in dose-dependent manner. Carboxymethylation significantly increased antioxidant properties of both CM-derivatives up to concentration of 10mg/mL, higher concentrations did not change the protection of liposomes. The reducing power of CM-mannan (DS 0.92) was significantly lower (P<0.05) than underivatized mannan. No reductive activity was found for dextran and CM-dextran. All CM-derivatives demonstrated statistically significant increasing activity compared with underivatized polysaccharides. The highest thrombolytic activity was found using CM-mannan (DS 0.92). The clot lysis here amounted to 68.78 ± 6.52% compared with 0.9% NaCl control (18.3 ± 6.3%). Three-dimensional surface profiles of mannan, dextran, and their CM-derivatives were compared by atomic force microscopy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dextran synthesized by Leuconostoc mesenteroides BD1710 in tomato juice supplemented with sucrose.

PubMed

Han, Jin; Hang, Feng; Guo, Benheng; Liu, Zhenmin; You, Chunpin; Wu, Zhengjun

2014-11-04

The characteristics of the growth of Leuconostoc mesenteroides BD1710 and the synthesis of dextran in tomato juice supplemented with 15% sucrose were assayed. L. mesenteroides BD1710 could synthesize approximately 32 g L(-1) dextran in the tomato-juice-sucrose medium when cultured at 28 °C for 48 h, which was on the same level as the dextran yield in a chemically defined medium. The viscosity of the cultured tomato-juice-sucrose medium with various dextran contents was also measured. The results of the monosaccharide composition, molecular-weight distribution, Fourier transform infrared spectra (FTIR) and nuclear magnetic resonance spectra (NMR) showed that the polysaccharide synthesized by L. mesenteroides BD1710 in the tomato-juice-sucrose medium was dextran with a peak molecular weight of 6.35 × 10(5)Da, a linear backbone composed of consecutive α-(1 → 6)-linked d-glucopyranosyl units and approximately 6% α-(1 → 3) branches. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dextran: Influence of Molecular Weight in Antioxidant Properties and Immunomodulatory Potential.

PubMed

Soeiro, Vinicius C; Melo, Karoline R T; Alves, Monique G C F; Medeiros, Mayara J C; Grilo, Maria L P M; Almeida-Lima, Jailma; Pontes, Daniel L; Costa, Leandro S; Rocha, Hugo A O

2016-08-19

Dextrans (α-d-glucans) extracted from Leuconostoc mesenteroides, with molecular weights (MW) of 10 (D10), 40 (D40) and 147 (D147) kDa, were evaluated as antioxidant, anticoagulant and immunomodulatory drugs for the first time. None presented anticoagulant activity. As for the antioxidant and immunomodulatory tests, a specific test showed an increase in the dextran activity that was proportional to the increase in molecular weight. In a different assay, however, activity decreased or showed no correlation to the MW. As an example, the reducing power assay showed that D147 was twice as potent as other dextrans. On the other hand, all three samples showed similar activity (50%) when it came to scavenging the OH radical, whereas only the D10 sample showed sharp activity (50%) when it came to scavenging the superoxide ion. D40 was the single dextran that presented with immunomodulatory features since it stimulated the proliferation (~50%) of murine macrophages (RAW 264.7) and decreased the release of nitric oxide (~40%) by the cells, both in the absence and presence of lipopolysaccharides (LPS). In addition, D40 showed a greater scavenging activity (50%) for the hydrogen peroxide, which caused it to also be the more potent dextran when it came to inhibiting lipid peroxidation (70%). These points toward dextrans with a 40 kDa weight as being ideal for antioxidant and immunomodulatory use. However, future studies with the D40 and other similarly 40 kDa dextrans are underway to confirm this hypothesis.

Dextran: Influence of Molecular Weight in Antioxidant Properties and Immunomodulatory Potential

PubMed Central

Soeiro, Vinicius C.; Melo, Karoline R. T.; Alves, Monique G. C. F.; Medeiros, Mayara J. C.; Grilo, Maria L. P. M.; Almeida-Lima, Jailma; Pontes, Daniel L.; Costa, Leandro S.; Rocha, Hugo A. O.

2016-01-01

Dextrans (α-d-glucans) extracted from Leuconostoc mesenteroides, with molecular weights (MW) of 10 (D10), 40 (D40) and 147 (D147) kDa, were evaluated as antioxidant, anticoagulant and immunomodulatory drugs for the first time. None presented anticoagulant activity. As for the antioxidant and immunomodulatory tests, a specific test showed an increase in the dextran activity that was proportional to the increase in molecular weight. In a different assay, however, activity decreased or showed no correlation to the MW. As an example, the reducing power assay showed that D147 was twice as potent as other dextrans. On the other hand, all three samples showed similar activity (50%) when it came to scavenging the OH radical, whereas only the D10 sample showed sharp activity (50%) when it came to scavenging the superoxide ion. D40 was the single dextran that presented with immunomodulatory features since it stimulated the proliferation (~50%) of murine macrophages (RAW 264.7) and decreased the release of nitric oxide (~40%) by the cells, both in the absence and presence of lipopolysaccharides (LPS). In addition, D40 showed a greater scavenging activity (50%) for the hydrogen peroxide, which caused it to also be the more potent dextran when it came to inhibiting lipid peroxidation (70%). These points toward dextrans with a 40 kDa weight as being ideal for antioxidant and immunomodulatory use. However, future studies with the D40 and other similarly 40 kDa dextrans are underway to confirm this hypothesis. PMID:27548151

Local Existence of MHD Contact Discontinuities

NASA Astrophysics Data System (ADS)

Morando, Alessandro; Trakhinin, Yuri; Trebeschi, Paola

2018-05-01

We prove the local-in-time existence of solutions with a contact discontinuity of the equations of ideal compressible magnetohydrodynamics (MHD) for two dimensional planar flows provided that the Rayleigh-Taylor sign condition {[partial p/partial N] <0 } on the jump of the normal derivative of the pressure is satisfied at each point of the initial discontinuity. MHD contact discontinuities are characteristic discontinuities with no flow across the discontinuity for which the pressure, the magnetic field and the velocity are continuous whereas the density and the entropy may have a jump. This paper is a natural completion of our previous analysis (Morando et al. in J Differ Equ 258:2531-2571, 2015) where the well-posedness in Sobolev spaces of the linearized problem was proved under the Rayleigh-Taylor sign condition satisfied at each point of the unperturbed discontinuity. The proof of the resolution of the nonlinear problem given in the present paper follows from a suitable tame a priori estimate in Sobolev spaces for the linearized equations and a Nash-Moser iteration.

Time-dependent density-functional theory with optimized effective potential and self-interaction correction and derivative discontinuity for the treatment of double ionization of He and Be atoms in intense laser fields

NASA Astrophysics Data System (ADS)

Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

2013-05-01

We present a self-interaction-free time-dependent density-functional theory (TDDFT) for the treatment of double-ionization processes of many-electron systems. The method is based on the extension of the Krieger-Li-Iafrate (KLI) treatment of the optimized effective potential (OEP) theory and the incorporation of an explicit self-interaction correction (SIC) term. In the framework of the time-dependent density functional theory, we have performed three-dimensional (3D) calculations of double ionization of He and Be atoms by intense near-infrared laser fields. We make use of the exchange-correlation potential with the integer discontinuity which improves the description of the double-ionization process. We found that a proper description of the double ionization requires the TDDFT exchange-correlation potential with the discontinuity with respect to the variation of the total particle number (TPN). The results for the intensity-dependent rates of double ionization of He and Be atoms are presented.

Numerical Homogenization of Jointed Rock Masses Using Wave Propagation Simulation

NASA Astrophysics Data System (ADS)

Gasmi, Hatem; Hamdi, Essaïeb; Bouden Romdhane, Nejla

2014-07-01

Homogenization in fractured rock analyses is essentially based on the calculation of equivalent elastic parameters. In this paper, a new numerical homogenization method that was programmed by means of a MATLAB code, called HLA-Dissim, is presented. The developed approach simulates a discontinuity network of real rock masses based on the International Society of Rock Mechanics (ISRM) scanline field mapping methodology. Then, it evaluates a series of classic joint parameters to characterize density (RQD, specific length of discontinuities). A pulse wave, characterized by its amplitude, central frequency, and duration, is propagated from a source point to a receiver point of the simulated jointed rock mass using a complex recursive method for evaluating the transmission and reflection coefficient for each simulated discontinuity. The seismic parameters, such as delay, velocity, and attenuation, are then calculated. Finally, the equivalent medium model parameters of the rock mass are computed numerically while taking into account the natural discontinuity distribution. This methodology was applied to 17 bench fronts from six aggregate quarries located in Tunisia, Spain, Austria, and Sweden. It allowed characterizing the rock mass discontinuity network, the resulting seismic performance, and the equivalent medium stiffness. The relationship between the equivalent Young's modulus and rock discontinuity parameters was also analyzed. For these different bench fronts, the proposed numerical approach was also compared to several empirical formulas, based on RQD and fracture density values, published in previous research studies, showing its usefulness and efficiency in estimating rapidly the Young's modulus of equivalent medium for wave propagation analysis.

Effect of Sulfation and Molecular Weight on Anticoagulant Activity of Dextran.

PubMed

Drozd, N N; Logvinova, Yu S; Torlopov, M A; Udoratina, E V

2017-02-01

Sulfation (to 2.8) of dextrans with molecular weight of 150 and 20 kDa was followed by the appearance of anticoagulant activity that increased with decreasing their molecular weight and did not depend on antithrombin, plasma inhibitor of serine proteases of the blood coagulation system. Antithrombin activity of dextran sulfate with a molecular weight of 20 kDa reached 12.6-15.3 U/mg. Dextran sulfates with molecular weights of 20 and 150 kDa did not potentiate ADP-induced human platelet aggregation.

Electron-beam generated porous dextran gels: experimental and quantum chemical studies.

PubMed

Naumov, Sergej; Knolle, Wolfgang; Becher, Jana; Schnabelrauch, Matthias; Reichelt, Senta

2014-06-01

The aim of this work was to investigate the reaction mechanism of electron-beam generated macroporous dextran cryogels by quantum chemical calculation and electron paramagnetic resonance measurements. Electron-beam radiation was used to initiate the cross-linking reaction of methacrylated dextran in semifrozen aqueous solutions. The pore morphology of the resulting cryogels was visualized by scanning electron microscopy. Quantum chemical calculations and electron paramagnetic resonance studies provided information on the most probable reaction pathway and the chain growth radicals. The most probable reaction pathway was a ring opening reaction and the addition of a C-atom to the double-bond of the methacrylated dextran molecule. First detailed quantum chemical calculation on the reaction mechanism of electron-beam initiated cross-linking reaction of methacrylated dextran are presented.

Synthesis and characterization of dextran-coated iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Predescu, Andra Mihaela; Matei, Ecaterina; Berbecaru, Andrei Constantin; Pantilimon, Cristian; Drăgan, Claudia; Vidu, Ruxandra; Predescu, Cristian; Kuncser, Victor

2018-03-01

Synthesis and characterization of iron oxide nanoparticles coated with a large molar weight dextran for environmental applications are reported. The first experiments involved the synthesis of iron oxide nanoparticles which were coated with dextran at different concentrations. The synthesis was performed by a co-precipitation technique, while the coating of iron oxide nanoparticles was carried out in solution. The obtained nanoparticles were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectrometry, Fourier transform infrared spectroscopy and superconducting quantum interference device magnetometry. The results demonstrated a successful coating of iron oxide nanoparticles with large molar weight dextran, of which agglomeration tendency depended on the amount of dextran in the coating solution. SEM and TEM observations have shown that the iron oxide nanoparticles are of about 7 nm in size.

The effect of the size of fluorescent dextran on its endocytic pathway.

PubMed

Li, Lei; Wan, Tao; Wan, Min; Liu, Bei; Cheng, Ran; Zhang, Rongying

2015-05-01

Fluorescent dextrans are commonly used as macropinocytic probes to study the properties of endocytic cargoes; however, the effect of the size of dextrans on endocytic mechanisms has not been carefully analyzed. By using chemical and siRNA inhibition of individual endocytic pathways, we evaluated the internalization of two commonly used dextrans, Dex10 (dextran 10 kDa) and Dex70 (dextran 70 kDa), in mammalian HeLa cells and Caenorhabditis elegans coelomocytes. We revealed that Dex70 enters these two cell types predominantly via clathrin- and dynamin-independent and amiloride-sensitive macropinocytosis process; Dex10, on the other hand, enters the two cell types through clathrin-/dynamin-dependent micropinocytosis in addition to macropinocytosis. In addition, although different-sized dextrans follow different endocytic processes, they share common post-endocytic events. Herein, though straightforward, our studies support that the size of nanomaterials could play a paramount role in their inclusion into endocytic vesicles and suggest that care should be taken while selecting endocytic pathway markers. Based on our results, we propose that Dex70 is a better probe for macropinocytosis, whereas Dex10 and smaller molecules are better for probing general fluid-phase endocytosis, which includes macropinocytic and micropinocytic processes. © 2015 International Federation for Cell Biology.

On the Stability of Strange Dwarf Hybrid Stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alford, Mark G.; Harris, Steven P.; Sachdeva, Pratik S., E-mail: harrissp@wustl.edu

2017-10-01

We investigate the stability of “strange dwarfs”: white-dwarf-sized stars with a density discontinuity between a small dense core of quark matter and a thick low-density mantle of degenerate electrons. Previous work on strange dwarfs suggested that such a discontinuity could stabilize stars that would have been classified as unstable by the conventional criteria based on extrema in the mass–radius relation. We investigate the stability of such stars by numerically solving the Sturm–Liouville equations for the lowest-energy modes of the star. We find that the conventional criteria are correct, and strange dwarfs are not stable.

21 CFR 520.1182 - Iron dextran suspension.

Code of Federal Regulations, 2013 CFR

2013-04-01

... dose dispenser. (2) Indications for use. For the prevention of iron deficiency anemia in baby pigs. (3... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Iron dextran suspension. 520.1182 Section 520.1182... DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1182 Iron dextran suspension...

21 CFR 520.1182 - Iron dextran suspension.

Code of Federal Regulations, 2011 CFR

2011-04-01

... dose dispenser. (2) Indications for use. For the prevention of iron deficiency anemia in baby pigs. (3... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Iron dextran suspension. 520.1182 Section 520.1182... DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1182 Iron dextran suspension...

21 CFR 520.1182 - Iron dextran suspension.

Code of Federal Regulations, 2012 CFR

2012-04-01

... dose dispenser. (2) Indications for use. For the prevention of iron deficiency anemia in baby pigs. (3... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Iron dextran suspension. 520.1182 Section 520.1182... DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1182 Iron dextran suspension...

21 CFR 520.1182 - Iron dextran suspension.

Code of Federal Regulations, 2010 CFR

2010-04-01

... dose dispenser. (2) Indications for use. For the prevention of iron deficiency anemia in baby pigs. (3... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Iron dextran suspension. 520.1182 Section 520.1182... DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1182 Iron dextran suspension...

21 CFR 520.1182 - Iron dextran suspension.

Code of Federal Regulations, 2014 CFR

2014-04-01

... dose dispenser. (2) Indications for use. For the prevention of iron deficiency anemia in baby pigs. (3... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Iron dextran suspension. 520.1182 Section 520.1182... DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1182 Iron dextran suspension...

Roles of dextrans on improving lymphatic drainage for liposomal drug delivery system.

PubMed

Feng, Linglin; Zhang, Lei; Liu, Min; Yan, Zhiqiang; Wang, Chenyu; Gu, Bing; Liu, Yu; Wei, Gang; Zhong, Gaoren; Lu, Weiyue

2010-04-01

Our aim was to develop a novel liposomal drug delivery system containing dextrans to reduce undesirable retention of antineoplastic agents and thus alleviate local tissue damage. At the cell level, diethylaminoethyl-dextran (DEAE-Dx) showed the strongest inhibiting effect on liposome uptake by macrophages among tested dextrans. The distribution of radiolabeled liposomes mixed with dextrans in injection site and draining lymph node was investigated in rats after subcutaneous injection. DEAE-Dx substantially reduced the undesired local retention and promoted the draining of liposome into lymphatics, which was further confirmed by confocal microscopy images revealing the substantial prevention of rhodamine B-labelled liposome sequestration by macrophages in normal lymph node in rats. Pharmacokinetic data indicated the accelerated drainage of liposome through lymphatics back to systemic circulation by mixing with DEAE-Dx. In the toxicological study in rabbits, DEAE-Dx alleviated the local tissue damage caused by liposomal doxorubicin. In conclusion, dextrans, particularly DEAE-Dx, could efficiently enhanced liposomes drainage into lymphatics, which proves themselves as promising adjuvants for lymphatic-targeted liposomal drug delivery system.

Fabrication of curcumin-loaded bovine serum albumin (BSA)-dextran nanoparticles and the cellular antioxidant activity.

PubMed

Fan, Yuting; Yi, Jiang; Zhang, Yuzhu; Yokoyama, Wallace

2018-01-15

Bovine serum albumin (BSA)-dextran conjugate was prepared with glycation. Self-assembly nanoparticles were synthesized with a green, and facile approach. The effects of dry-heating time on the fabrication and characteristics of BSA-dextran conjugate nanoparticles were examined. Stable nanoparticles (<200nm) were formed after only 6h dry-heating because enough dextran was grafted onto the BSA to provide significant steric hindrance. Particle size decreased with the increase of dry-heating time and the lowest particle size (51.2nm) was obtained after 24h dry-heating. The nanoparticles were stable in a wide pH range (pH 2.0-7.0). The particle size of nanoparticles increased to 115nm after curcumin incorporation and was stable even after one-month storage. TEM results demonstrated that curcumin-loaded nanoparticles displayed a spherical structure and were homogeneously dispersed. Curcumin in BSA-dextran nanoparticle showed better stability, compared to free curcumin. In addition, BSA-dextran nanoparticles can improve the cellular antioxidant activity of curcumin in Caco-2 cells. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hindered Diffusion in Polymeric Solutions Studied by Fluorescence Correlation Spectroscopy

PubMed Central

Zustiak, Silviya P.; Nossal, Ralph; Sackett, Dan L.

2011-01-01

Diffusion of molecules in the crowded and charged interior of the cell has long been of interest for understanding cellular processes. Here, we introduce a model system of hindered diffusion that includes both crowding and binding. In particular, we obtained the diffusivity of the positively charged protein, ribonuclease A (RNase), in solutions of dextrans of various charges (binding) and concentrations (crowding), as well as combinations of both, in a buffer of physiological ionic strength. Using fluorescence correlation spectroscopy, we observed that the diffusivity of RNase was unaffected by the presence of positively charged or neutral dextrans in the dilute regime but was affected by crowding at higher polymer concentrations. Conversely, protein diffusivity was significantly reduced by negatively charged dextrans, even at 0.4 μM (0.02% w/v) dextran. The diffusivity of RNase decreased with increasing concentrations of negative dextran, and the amount of bound RNase increased until it reached a plateau of ∼80% bound RNase. High salt concentrations were used to establish the electrostatic nature of the binding. Binding of RNase to the negatively charged dextrans was further confirmed by ultrafiltration. PMID:21723836

Evidence for Central Venous Pressure Resetting During Initial Exposure to Microgravity

DTIC Science & Technology

2001-12-01

to 10° HDT. During each experimental condition, water and food were provided ad libitum and intake amounts were recorded. A standard monkey diet ...biscuit (LabDiet) of ;3.5 g with a caloric density equal to 4 kcal/g (69% carbohy- drate, 13% fat, 18% protein) was used as the primary food source...effect of Dextran on water filtration from renal tubules to tubular capillar- ies, consequently reducing urine formation in a hypo - volemic state of HDT

Crystallization and preliminary X-ray analysis of Streptococcus mutans dextran glucosidase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saburi, Wataru; Hondoh, Hironori, E-mail: hondoh@abs.agr.hokudai.ac.jp; Unno, Hideaki

2007-09-01

Dextran glucosidase from S. mutans was crystallized using the hanging-drop vapour-diffusion method. The crystals diffracted to 2.2 Å resolution. Dextran glucosidase from Streptococcus mutans is an exo-hydrolase that acts on the nonreducing terminal α-1,6-glucosidic linkage of oligosaccharides and dextran with a high degree of transglucosylation. Based on amino-acid sequence similarity, this enzyme is classified into glycoside hydrolase family 13. Recombinant dextran glucosidase was purified and crystallized by the hanging-drop vapour-diffusion technique using polyethylene glycol 6000 as a precipitant. The crystals belong to the orthorhombic space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 72.72, b = 86.47, cmore » = 104.30 Å. A native data set was collected to 2.2 Å resolution from a single crystal.« less

Properties of chymotrypsin bound covalently to dextran.

PubMed

Zlateva, T P; Krysteva, M; Balajthy, Z; Elödi, P

1988-01-01

The kinetic properties dextran-chymotrypsin conjugate were studied by means of low molecular weight substrates. It was found that KM, kcat and kcat/KM of dextran chymotrypsin for the hydrolysis of benzoyl-L-tyrosine-ethyl-ester did not differ substantially from those of the free enzyme. However, the data found for kcat of dextran-chymotrypsin and free chymotrypsin assayed for the hydrolysis of three tripeptidyl-p-nitroanilide D-Arg-Val-Trp-pNA, D-Arg-Val-Tyr-pNA, Z-Phe-Pro-Phe-pNA, were definitely different. The inhibition of the modified chymotrypsin with soybean trypsin inhibitor was found to be less pronounced than that with the free enzyme. The effect of potassium and magnesium salts on the inactivation of both enzymes was also studied. The effect of dextran matrix on the catalytic properties and the conformational stability of modified chymotrypsin is discussed.

Dextran Preserves Native Corneal Structure During Decellularization.

PubMed

Lynch, Amy P; Wilson, Samantha L; Ahearne, Mark

2016-06-01

Corneal decellularization has become an increasingly popular technique for generating scaffolds for corneal regeneration. Most decellularization procedures result in tissue swelling, thus limiting their application. Here, the use of a polysaccharide, dextran, to reduce swelling and conserve the native corneal structure during decellularization was investigated. Corneas were treated with 1% Triton X-100, 0.5% sodium dodecyl sulfate, and nucleases under constant rotation followed by extensive washing. To reduce swelling, decellularization solutions were supplemented with 5% dextran either throughout the whole decellularization process or during the washing cycles only. Quantitative analysis of DNA content showed a 96% reduction after decellularization regardless of the addition of dextran. Dextran resulted in a significant reduction in swelling from 3.85 ± 0.43 nm without to 1.94 ± 0.29-2.01 ± 0.37 nm (p < 0.05) remaining at similar dimensions to the native tissue (1.73 ± 0.23 nm). Tissue transparency was restored to all decellularized corneas following submersion in glycerol. Transmission electron microscopy (TEM) analysis found that dextran must be present throughout the decellularization protocol to preserve the native corneal architecture, anisotropy analysis demonstrated comparable results (0.22 ± 0.03) to the native cornea (0.24 ± 0.02), p > 0.05. Dextran can counteract the detrimental effects of decellularizing agents on the biomechanical properties of the tissue resulting in similar compressive moduli (mean before decellularization: 5.40 ± 1.18 kPa; mean after decellularization with dextran: 5.64 ± 1.34 kPa, p > 0.05). Cells remained viable in the presence of decellularized scaffolds. The findings of this study indicate that dextran not only prevents significant corneal swelling during decellularization but also enhances the maintenance of the native corneal ultrastructure.

Soy protein supports cardiovascular health by downregulating hydroxymethylglutaryl-coenzyme A reductase and sterol regulatory element-binding protein-2 and increasing antioxidant enzyme activity in rats with dextran sodium sulfate-induced mild systemic inflammation.

PubMed

Marsh, Tanya G; Straub, Rachel K; Villalobos, Fatima; Hong, Mee Young

2011-12-01

Animal and human studies have indicated that the presence of soy in the diet improves cardiovascular health. Inflammation plays a pivotal role in the progression of cardiovascular disease (CVD). However, little is known about how dextran sodium sulfate (DSS)-induced systemic inflammation impacts overall heart health and, correspondingly, how soy protein modulates risk of CVD development in DSS-induced systemic inflammation. We hypothesized that soy protein-fed rats would have a lower risk of CVD by beneficial alteration of gene expression involving lipid metabolism and antioxidant capacity in DSS-induced systemic inflammation. Forty Sprague-Dawley rats were divided into 4 groups: casein, casein + DSS, soy protein, and soy protein + DSS. After 26 days, inflammation was induced in one group from each diet by incorporating 3% DSS in drinking water for 48 hours. Soy protein-fed rats had lower final body weights (P = .010), epididymal fat weights (P = .049), total cholesterol (P < .001), and low-density lipoprotein cholesterol (P < .001). In regard to gene expression, soy protein-fed rats had lower sterol regulatory element-binding protein-2 (P = .032) and hydroxymethylglutaryl-coenzyme A reductase (P = .028) levels and higher low-density lipoprotein receptor levels (P = .036). Antioxidant enzyme activity of superoxide dismutase and catalase was higher among the soy protein groups (P = .037 and P = .002, respectively). These results suggest that soy protein positively influences cardiovascular health by regulating serum lipids through modified expression of sterol regulatory element-binding protein-2 and its downstream genes (ie, hydroxymethylglutaryl-coenzyme A reductase and low-density lipoprotein receptor) and by promoting the antioxidant enzyme activity of superoxide dismutase and catalase. Copyright © 2011 Elsevier Inc. All rights reserved.

Correlation of transarterial transport of various dextrans with their physicochemical properties.

PubMed

Elmalak, O; Lovich, M A; Edelman, E

2000-11-01

Local vascular drug delivery provides elevated concentrations of drug in the target tissue while minimizing systemic side effects. To better characterize local pharmacokinetics we examined the arterial transport of locally applied dextran and dextran derivatives in vivo. Using a two-compartment pharmacokinetic model to correct the measured transmural flux of these compounds for systemic redistribution and elimination as delivered from a photopolymerizable hydrogel surrounding rat carotid arteries, we found that the diffusivities and the transendothelial permeabilities were strongly dependent on molecular weight and charge. For neutral dextrans, the effective diffusive resistance in the media increased with molecular weight approximately 4.1-fold between the molecular weights of 10 and 282 kDa. Similarly, endothelial resistance increased 28-fold over the same molecular weight range. The effective medial diffusive resistance was unaffected by cationic charge as such molecules moved identically to neutral compounds, but increased approximately 40% when dextrans were negatively charged. Transendothelial resistance was 20-fold lower for the cationic dextrans, and 11-fold higher for the anionic dextrans, when both were compared to neutral counterparts. These results suggest that, while low molecular weight drugs will rapidly traverse the arterial wall with the endothelium posing a minimal barrier, the reverse is true for high molecular weight agents. With these data, the deposition and distribution of locally released vasotherapeutic compounds might be predicted based upon chemical properties, such as molecular weight and charge.

Temperature-responsive electrospun nanofibers for ‘on–off’ switchable release of dextran

PubMed Central

Kim, Young-Jin; Ebara, Mitsuhiro; Aoyagi, Takao

2012-01-01

We propose a new type of ‘smart’ nanofiber (NF) with dynamically and reversibly tunable properties for the ‘on–off’ controlled release of the polysaccharide dextran. The fibers are produced by electrospinning copolymers of N-isopropylacrylamide (NIPAAm) and N-hydroxymethylacrylamide (HMAAm). The OH groups of HMAAm are subsequently crosslinked by thermal curing. The copolymers were successfully fabricated into a well-defined nanofibrous structure with a diameter of about 600–700 nm, and the fibers preserved their morphology even after thermal curing. The resulting crosslinked NFs showed rapid and reversible volume changes in aqueous media in response to cycles of temperature alternation. The fibrous morphology was maintained for the crosslinked NFs even after the cycles of temperature alternation, while non-crosslinked NFs collapsed and dispersed quickly in the aqueous solution. Dextran-containing NFs were prepared by electrospinning the copolymers blended with fluorescein isothiocyanate (FITC)-dextran, and the ‘on–off’ switchable release of FITC-dextran from the crosslinked NFs was observed. Almost all the FITC-dextran was released from the NFs after six heating cycles, whereas only a negligible amount of FITC-dextran was evolved during the cooling process. The reported incorporation of smart properties into NFs takes advantage of their extremely large surface area and porosity and is expected to provide a simple platform for on–off drug delivery. PMID:27877530

Spray drying of silica microparticles for sustained release application with a new sol-gel precursor.

PubMed

Wang, Bifeng; Friess, Wolfgang

2017-10-30

A new precursor, tetrakis(2-methoxyethyl) orthosilicate (TMEOS) was used to fabricate microparticles for sustained release application, specifically for biopharmaceuticals, by spray drying. The advantages of TMEOS over the currently applied precursors are its water solubility and hydrolysis at moderate pH without the need of organic solvents or catalyzers. Thus a detrimental effect on biomolecular drug is avoided. By generating spray-dried silica particles encapsulating the high molecular weight model compound FITC-dextran 150 via the nano spray dryer Büchi-90, we demonstrated how formulation parameters affect and enable control of drug release properties. The implemented strategies to regulate release included incorporating different quantities of dextrans with varying molecular weight as well as adjusting the pH of the precursor solution to modify the internal microstructures. The addition of dextran significantly altered the released amount, while the release became faster with increasing dextran molecular weight. A sustained release over 35days could be achieved with addition of 60 kD dextran. The rate of FITC-Dextran 150 release from the dextran 60 containing particles decreased with higher precursor solution pH. In conclusion, the new precursor TMEOS presents a promising alternative sol-gel technology based carrier material for sustained release application of high molecular weight biopharmaceutical drugs. Copyright © 2017 Elsevier B.V. All rights reserved.

Repeated dose 28-day oral toxicity study of DEAE-Dextran in mice: An advancement in safety chemotherapeutics.

PubMed

Bakrania, Anita K; Variya, Bhavesh C; Madan, Prem; Patel, Snehal S

2017-08-01

Cancer has emerged as a global threat with challenges for safe chemotherapeutics. Most of the currently available anti-cancer drugs exhibit significant toxicity. Amongst novel agents, interferons have exhibited anti-proliferative and cytoprotective roles. However, due to stability drawbacks of interferons, we have identified an interferon inducer DEAE-Dextran, which resolves the stability issues. Based on the previous history of toxicity pertaining to the current chemotherapeutic agents, it is equally essential to determine the safety of DEAE-Dextran. In the present study, repeated dose 28 day oral toxicity of DEAE-Dextran has been evaluated in accordance to OECD-407. We found absence of any CNS behavioral changes related to self-mutilation, walking backwards, aggressiveness on handling or tonic-clonic seizures during the 28 day study. Neither the motor activity nor grip strength was altered during the treatment duration with DEAE-Dextran implying absence of any effect on the skeletal muscles. Interestingly, we also found that treatment with DEAE-Dextran did not present any significant cardiac, hepatic, renal, gastrointestinal, lymphatic or reproductive system toxicity or alteration in the body's normal physiology based upon the various organ function tests. Henceforth, it may be concluded that DEAE-Dextran is a safe anti-cancer agent devoid of any sub-acute toxicity. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of Au-dextran NPs as anti-tumor agent against EAC and solid tumor in mice by biochemical evaluations and histopathological investigations.

PubMed

Medhat, Dalia; Hussein, Jihan; El-Naggar, Mehrez E; Attia, Mohamed F; Anwar, Mona; Latif, Yasmine Abdel; Booles, Hoda F; Morsy, Safaa; Farrag, Abdel Razik; Khalil, Wagdy K B; El-Khayat, Zakaria

2017-07-01

Dextran-capped gold nanoparticles (Au-dextran NPs) were prepared exploiting the natural polysaccharide polymer as both reducing and stabilizing agent in the synthesis process, aiming at studying their antitumor effect on solid carcinoma and EAC-bearing mice. To this end, Au-dextran NPs were designed via simple eco-friendly chemical reaction and they were characterized revealing the monodispersed particles with narrow distributed size of around 49nm with high negative charge. In vivo experiments were performed on mice. Biochemical analysis of liver and kidney functions and oxidation stress ratio in addition to histopathological investigations of such tumor tissues were done demonstrating the potentiality of Au-dextran NPs as antitumor agent. The obtained results revealed that EAC and solid tumors caused significant increase in liver and kidney functions, liver oxidant parameters, alpha feto protein levels and diminished liver antioxidant accompanied by positive expression of tumor protein p53 of liver while the treatment with Au-dextran NPs for both types caused improvement in liver and kidney functions, increased liver antioxidant, increased the expression level of B-cell lymphoma 2 gene and subsequently suppressed the apoptotic pathway. As a result, the obtained data provides significant antitumor effects of the Au-dextran NPs in both Ehrlich ascites and solid tumor in mice models. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Levobupivacaine-dextran mixture for transversus abdominis plane block and rectus sheath block in patients undergoing laparoscopic colectomy: a randomised controlled trial.

PubMed

Hamada, T; Tsuchiya, M; Mizutani, K; Takahashi, R; Muguruma, K; Maeda, K; Ueda, W; Nishikawa, K

2016-04-01

We performed a randomised controlled double-blinded study of patients having laparoscopic colectomy with bilateral transversus abdominis plane block plus rectus sheath block, comparing a control group receiving 80 ml levobupivacaine 0.2% in saline with a dextran group receiving 80 ml levobupivacaine 0.2% in 8% low-molecular weight dextran. Twenty-seven patients were studied in each group. The mean (SD) maximum plasma concentration of levobupivacaine in the control group (1410 (322) ng.ml(-1) ) was higher than the dextran group (1141 (287) ng.ml(-1) ; p = 0.004), and was reached more quickly (50.6 (30.2) min vs 73.2 (24.6) min; p = 0.006). The area under the plasma concentration-time curve from 0 min to 240 min in the control group (229,124 (87,254) ng.min.ml(-1) ) was larger than in the dextran group (172,484 (50,502) ng.min.ml(-1) ; p = 0.007). The median (IQR [range]) of the summated numerical pain rating score at rest during the first postoperative 24 h in the control group (16 (9-20 [3-31]) was higher than in the dextran group (8 (2-11 [0-18]); p = 0.0001). In this study, adding dextran to levobupivacaine decreased the risk of levobupivacaine toxicity while providing better analgesia. © 2016 The Association of Anaesthetists of Great Britain and Ireland.

77 FR 50121 - Hospira, Inc.; Withdrawal of Approval of a New Drug Application for DEXTRAN 70

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-20

..., Center for Biologics Evaluation and Research (HFM-17), Food and Drug Administration, 1401 Rockville Pike... and Research, by the Commissioner of Food and Drugs, approval of NDA 080- 819, DEXTRAN 70 [6% Dextran... DEPARTMENT OF HEALTH AND HUMAN SERVICES Food and Drug Administration [Docket No. FDA-2012-N-0840...

Effects of immersion solution on corneal tissue strip hydration and thickness during thermal shrinkage

NASA Astrophysics Data System (ADS)

Borja, David; Manns, Fabrice; Lamar, Peggy D.; Rosen, Alexander; Parel, Jean-Marie A.

2003-07-01

Purpose: To assess the effects of immersion solutions with different Dextran concentrations on the hydration of cornea tissue strips at normal body temperature. Methods: A 20% Dextran-BSS solution was injected via a self sealing limbal-transcorneal tunnel incision using a 30ga needle into the anterior chamber of human donor eyes until the globe was hard. The eyes were then immersed cornea down overnight in the same solution. Corneal thickness was measured by ultrasound pachymetry after the eyes were re-inflated and at regular intervals to assess dehydration. When the central cornea thickness reached 400-500μm corneal buttons were removed using a 10mm trephine. The buttons were then cut into 6x6mm strips using a custom-made jig and immediately immersed in solutions of Dextran (15 to 20% in increments of 2.5%) at 35degC. The edge thickness of the immersed strip was measured every 5 min for one hour using an optical comparator (Topcon, Japan) modified for tissue shadowphotogrammetry. Results: For five Florida Lions Eye Bank donated eyes after one hour in the Dextran solution the mean final measured thickness of corneas in 20%, 17.5% and 15% Dextran-BSS solutions were 570 (+/-75) μm, 680 (+/-70) μm, and 1080 (+/-95) μm respectively. These measured thicknesses changes correspond to an average swelling of 1.2, 1.4 and 2.2 times the initial thickness of each cornea strip in the 20%, 17.5% and 15% Dextran-BSS solutions respectively. Conclusion: We will conduct experiments at higher Dextran concentrations but our current results indicate that 20% Dextran-BSS solution was the best solution tested at keeping corneal tissue strips at or close to physiological thickness.

Phospatidylserine or ganglioside--which of anionic lipids determines the effect of cationic dextran on lipid membrane?

PubMed

Hąc-Wydro, Katarzyna; Wydro, Paweł; Cetnar, Andrzej; Włodarczyk, Grzegorz

2015-02-01

In this work the influence of cationic polymer, namely diethylaminoethyl DEAE-dextran on model lipid membranes was investigated. This polymer is of a wide application as a biomaterial and a drug carrier and its cytotoxicity toward various cancer cells was also confirmed. It was suggested that anticancer effect of cationic dextran is connected with the binding of the polymer to the negatively charged sialic acid residues overexpressed in cancer membrane. This fact encouraged us to perform the studies aimed at verifying whether the effect of cationic DEAE-dextran on membrane is determined only by the presence of the negatively charged lipid in the system or the kind of anionic lipid is also important. To reach this goal systematic investigations on the effect of dextran on various one-component lipid monolayers and multicomponent hepatoma cell model membranes differing in the level and the kind of anionic lipids (phosphatidylserine, sialic acid-containing ganglioside GM3 or their mixture) were done. As evidenced the results the effect of DEAE-dextran on the model system is determined by anionic lipid-polymer electrostatic interactions. However, the magnitude of the effect of cationic polymer is strongly dependent on the kind of anionic lipid in the model system. Namely, the packing and ordering of the mixtures containing ganglioside GM3 were more affected by DEAE-dextran than phosphatidylserine-containing monolayers. Although the experiments were done on model systems and therefore further studies are highly needed, the collected data may indicate that ganglioside may be important in the differentiation of the effect of cationic dextran on membranes. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of 0.3% Hydroxypropyl Methylcellulose/Dextran Versus 0.18% Sodium Hyaluronate in the Treatment of Ocular Surface Disease in Glaucoma Patients: A Randomized, Double-Blind, and Controlled Study.

PubMed

Prabhasawat, Pinnita; Ruangvaravate, Ngamkae; Tesavibul, Nattaporn; Thewthong, Maneerat

2015-01-01

To compare the efficacy and safety of 0.3% hydroxypropyl methylcellulose/dextran (HPMC/dextran) and 0.18% sodium hyaluronate (SH) in the treatment of ocular surface disease in patients using antiglaucoma drugs containing preservatives. This was a double-blind, randomized, parallel-group study in 70 glaucoma patients with Ocular Surface Disease Index (OSDI) score greater than 20 points and/or presence of ocular signs. Patients were randomized to receive either preservative-free 0.3% HPMC/dextran (n=35) or preservative-free 0.18% SH (n=35). Treatment was 1 drop in each eye, 4 times a day. Data were collected at baseline, at day 7 and day 28. The groups were homogeneous at baseline. At day 28, both treatments showed significant improvements (P<0.05) in the mean OSDI score, lid skin and lid margin inflammation, conjunctival injection, and expressibility of meibomian glands, corneal staining score, fluorescein tear breakup time (FBUT), and Schirmer I test. However, the mean OSDI score, lid margin inflammation and conjunctival injection showed significant improvements (P<0.05) in the SH group at days 7 and 28, compared to the HPMC/dextran group. FBUT and the Schirmer I test also showed significant improvements (P<0.05) in the SH group compared to the HPMC/dextran group, at day 28. No adverse reactions were observed in either group. Preservative-free artificial tear, 0.3% HPMC/dextran, and 0.18% SH, caused a significant relief of the ocular surface disease in glaucoma patients. However, 0.18% SH led to a greater improvement in ocular signs and symptoms than 0.3% HPMC/dextran.

Probing Conformational Change of Bovine Serum Albumin–Dextran Conjugates under Controlled Dry Heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Shuqin; Li, Yunqi; Zhao, Qin

2015-04-29

The time-dependent conformational change of bovine serum album (BSA) during Maillard reaction with dextran under controlled dry heating has been studied by small-angle X-ray scattering, fluorescence spectroscopy, dynamic light scattering, and circular dichroism analysis. Through the research on the radii of gyration (R g), intrinsic fluorescence, and secondary structure, conjugates with dextran coating were found to inhibit BSA aggregation and preserve the secondary structure of native BSA against long-time heat treatment during Maillard reaction. The results suggested that the hydrophilic dextran was conjugated to the compact protein surface and enclosed it and more dextran chains were attached to BSA withmore » the increase of the heating time. The study presented here will be beneficial to the understanding of the conformational evolution of BSA molecules during the dry-heating Maillard reaction and to the control of the protein–polysaccharide conjugate structure.« less

Antigen size and charge in immune complex glomerulonephritis. II. Passive induction of immune deposits with dextran-anti-dextran immune complexes.

PubMed Central

Isaacs, K. L.; Miller, F.

1983-01-01

Utilizing dextrans of restricted sizes (10,000, 70,000, 500,000 daltons), modified with regard to charge (neutral, polycationic, polyanionic) and an anti-dextran murine IgA myeloma, W3129, the authors have examined a model that may be used in the study of the combined effect of size and charge on renal deposition of immune complexes. Polycationic DEAE dextran complexes, using the 10,000 dalton antigen, showed a mesangiocapillary pattern of deposition. The other antigens showed focal to diffuse mesangial localization of varying degree. This indicates the potential usefulness of this system in examining the factors important in glomerular immune injury. The relevance to other observations, importance of polysaccharide antigens, and role in circulating versus in situ or "planted" immune complex models are considered. Images Figure 3 Figure 4 Figure 5 Figure 6 PMID:6190406

Surface functionalization of magnetic nanoparticles formed by self-associating hydrophobized oxidized dextrans

NASA Astrophysics Data System (ADS)

Farber, Shimon; Ickowicz, Diana E.; Melnik, Kristie; Yudovin-Farber, Ira; Recko, Daniel; Rampersaud, Arfaan; Domb, Abraham J.

2014-06-01

Magnetic iron oxide nanoparticles surface covered with oleic acid layer followed by a second layer of hydrophobized oxidized dextran aldehyde were prepared and tested for physico-chemical properties and ligand- and cell-specific binding. It was demonstrated that oleic acid-iron oxide nanoparticles coated with an additional layer of hydrophobized oxidized dextran were dispersible in buffer solutions and possess surface aldehyde active groups available for further binding of ligands or markers via imine or amine bond formation. Hydrophobized dextrans were synthesized by periodate oxidation and conjugation of various alkanamines to oxidized dextran by imination. Physico-chemical properties, as separation using magnetic field, magnetite concentration, and particle diameter, of the prepared magnetic samples are reported. The biotin-binding protein, neutravidin, was coupled to the particle surface by a simple reductive amination procedure. The particles were used for specific cell separation with high specificity.

Engineering dextran-based scaffolds for drug delivery and tissue repair

PubMed Central

Sun, Guoming; Mao, Jeremy J

2015-01-01

Owing to its chemically reactive hydroxyl groups, dextran can be modified with different functional groups to form spherical, tubular and 3D network structures. The development of novel functional scaffolds for efficient controlled release and tissue regeneration has been a major research interest, and offers promising therapeutics for many diseases. Dextran-based scaffolds are naturally biodegradable and can serve as bioactive carriers for many protein biomolecules. The reconstruction of the in vitro microenvironment with proper signaling cues for large-scale tissue regenerative scaffolds has yet to be fully developed, and remains a significant challenge in regenerative medicine. This paper will describe recent advances in dextran-based polymers and scaffolds for controlled release and tissue engineering. Special attention is given to the development of dextran-based hydrogels that are precisely manipulated with desired structural properties and encapsulated with defined angiogenic growth factors for therapeutic neovascularization, as well as their potential for wound repair. PMID:23210716

Antimicrobial activity of chemically modified dextran derivatives.

PubMed

Tuchilus, Cristina G; Nichifor, Marieta; Mocanu, Georgeta; Stanciu, Magdalena C

2017-04-01

Cationic amphiphilic dextran derivatives with a long alkyl group attached to the reductive end of the polysaccharide chain and quaternary ammonium groups attached as pendent groups to the main dextran backbone were synthesized and tested for their antimicrobial properties against several bacteria and fungi strains. Dependence of antimicrobial activity on both polymer chemical composition (dextran molar mass, length of end alkyl group and chemical structure of ammonium groups) and type of microbes was highlighted by disc-diffusion method (diameter of inhibition zone) and broth microdilution method (minimum inhibitory concentrations). Polymers had antimicrobial activity for all strains studied, except for Pseudomonas aeruginosa ATCC 27853. The best activity against Staphylococcus aureus (Minimun Inhibitory Concentration 60μg/mL) was provided by polymers obtained from dextran with lower molecular mass (Mn=4500), C 12 H 25 or C 18 H 37 end groups, and N,N-dimethyl-N-benzylammonium pendent groups. Copyright © 2017 Elsevier Ltd. All rights reserved.

The derivative discontinuity of the exchange-correlation functional.

PubMed

Mori-Sánchez, Paula; Cohen, Aron J

2014-07-28

The derivative discontinuity is a key concept in electronic structure theory in general and density functional theory in particular. The electronic energy of a quantum system exhibits derivative discontinuities with respect to different degrees of freedom that are a consequence of the integer nature of electrons. The classical understanding refers to the derivative discontinuity of the total energy as a function of the total number of electrons (N), but it can also manifest at constant N. Examples are shown in models including several hydrogen systems with varying numbers of electrons or nuclear charge (Z), as well as the 1-dimensional Hubbard model (1DHM). Two sides of the problem are investigated: first, the failure of currently used approximate exchange-correlation functionals in DFT and, second, the importance of the derivative discontinuity in the exact electronic structure of molecules, as revealed by full configuration interaction (FCI). Currently, all approximate functionals, including hybrids, miss the derivative discontinuity, leading to basic errors that can be seen in many ways: from the complete failure to give the total energy of H2 and H2(+), to the missing gap in Mott insulators such as stretched H2 and the thermodynamic limit of the 1DHM, or a qualitatively incorrect density in the HZ molecule with two electrons and incorrect electron transfer processes. Description of the exact particle behaviour of electrons is emphasised, which is key to many important physical processes in real systems, especially those involving electron transfer, and offers a challenge for the development of new exchange-correlation functionals.

Dynamics of Intense Currents in the Solar Wind

NASA Astrophysics Data System (ADS)

Artemyev, Anton V.; Angelopoulos, Vassilis; Halekas, Jasper S.; Vinogradov, Alexander A.; Vasko, Ivan Y.; Zelenyi, Lev M.

2018-06-01

Transient currents in the solar wind are carried by various magnetic field discontinuities that contribute significantly to the magnetic field fluctuation spectrum. Internal instabilities and dynamics of these discontinuities are believed to be responsible for magnetic field energy dissipation and corresponding charged particle acceleration and heating. Accurate modeling of these phenomena requires detailed investigation of transient current formation and evolution. By examining such evolution using a unique data set compiled from observations of the same solar wind flow by two spacecraft at Earth’s and Mars’s orbits, we show that it consists of several processes: discontinuity thinning (decrease in thickness normalized by the ion inertial length), intensification of currents normalized to the proton thermal current (i.e., the product of proton charge, density, and thermal velocity), and increase in the compressional component of magnetic field variations across discontinuities. The significant proton temperature variation around most observed discontinuities indicates possible proton heating. Plasma velocity jumps across the discontinuities are well correlated with Alfvén velocity changes. We discuss possible explanations of the observed discontinuity evolution. We also compare the observed evolution with predictions of models describing discontinuity formation due to Alfvén wave steepening. Our results show that discontinuity modeling likely requires taking into account both the effects of nonlinear Alfvén wave dynamics and solar wind expansion.

Preparation of self-assembled microspheres and their potential for drug delivery.

PubMed

Mellors, Rachel; Benzeval, Ian; Eisenthal, Robert; Hubble, John

2010-01-01

Dextran solutions intended for use as plasma extenders have been observed to form insoluble precipitates. Earlier studies of precipitation have shown that in solutions of 50% and 60% w/w of dextran molecular mass 6000 g mol(-1) beaded precipitates are formed over a two-week period. This study considers dextran precipitation over a wider molecular mass range and the kinetics, of formation, morphology and potential utility of these precipitates is investigated. Results show precipitation occurs over the dextran molecular mass range 6000-17,000 g mol(-1), with lower molecular mass material showing more rapid precipitation. As bead formation is accompanied by an increase in turbidity, formation kinetics were quantified spectrophotometrically confirming that precipitation rates were inversely proportional to molecular mass. The utility of these precipitates for drug delivery applications was assessed using bovine serum albumin as a protein drug analogue. The results showed that the inclusion of protein did not prevent bead formation and that entrapped protein was subsequently released from dextran beads in a time dependant manner. This suggests that dextran beads of this type may find application in the drug delivery area, as they combine the advantages of mild entrapment conditions with the use of an unmodified clinically approved polymer.

Real-world data to assess changes in low-density lipoprotein cholesterol and predicted cardiovascular risk after ezetimibe discontinuation post reporting of the Ezetimibe and Simvastatin in Hypercholesterolemia Enhances Atherosclerosis Regression trial.

PubMed

Bays, Harold E; Patel, Mehul D; Mavros, Panagiotis; Ramey, Dena R; Tomassini, Joanne E; Tershakovec, Andrew M; Baxter, Carl A

The 2008 Ezetimibe and Simvastatin in Hypercholesterolemia Enhances Atherosclerosis Regression (ENHANCE) study demonstrated ezetimibe + simvastatin vs simvastatin alone had a neutral effect on the surrogate endpoint of carotid intima-media thickness. Subsequent media portrayal of the study prompted ezetimibe discontinuation in many patients. The objective of the study was to assess the impact of ENHANCE reporting on ezetimibe discontinuation, low-density lipoprotein cholesterol (LDL-C) changes, and potential cardiovascular disease (CVD) risk. This analysis used claims data in a retrospective, observational study of patients receiving ezetimibe + statin and compared LDL-C for patients who discontinued ezetimibe (n = 970) vs those who continued ezetimibe + statins (n = 3706) after ENHANCE results disclosure. Change in relative CVD risk was estimated from the absolute LDL-C difference between groups per the Cholesterol Treatment Trialists' meta-analysis of statin trials. The rate of ezetimibe discontinuation was 2% in the 6 months before and 21% in the 6 months after reporting of ENHANCE results. Among patients who ultimately discontinued vs continued ezetimibe, respective mean LDL-C levels were 79.8 and 78.3 mg/dL 6 months before reporting of the ENHANCE results and 93.5 and 78.1 mg/dL 6 months after reporting of ENHANCE. Predictive application of the Cholesterol Treatment Trialists' meta-analysis suggested the 13.9 mg/dL increase in mean LDL-C translated to a 9.4% increase in relative CVD risk for those who discontinued ezetimibe. After reporting of the neutral ENHANCE results, ezetimibe discontinuation rate increased, LDL-C levels increased, and predicted CVD risk increased among those who discontinued ezetimibe. Characterization of clinical outcomes regarding lipid-altering agents based on surrogate biomarker studies not designed to assess CVD outcomes may be misleading, potentially placing patients at increased CVD risk. Copyright © 2017 National Lipid Association. Published by Elsevier Inc. All rights reserved.

Strong-field ionization of Li and Be: a time-dependent density functional theory with self-interaction correction

NASA Astrophysics Data System (ADS)

Telnov, Dmitry A.; Heslar, John T.; Chu, Shih-I.

2011-11-01

In the framework of the time-dependent density functional theory, we have performed 3D calculations of multiphoton ionization of Li and Be atoms by strong near-infrared laser fields. The results for the intensity-dependent probabilities of single and double ionization are presented. We make use of the time-dependent Krieger-Li-Iafrate exchange-correlation potential with self-interaction correction (TD-KLI-SIC). Such a potential possesses an integer discontinuity which improves description of the ionization process. However, we have found that the discontinuity of the TD-KLI-SIC potential is not sufficient to reproduce characteristic feature of double ionization.

β-Cyclodextrin-dextran polymers for the solubilization of poorly soluble drugs.

PubMed

di Cagno, Massimiliano; Terndrup Nielsen, Thorbjørn; Lambertsen Larsen, Kim; Kuntsche, Judith; Bauer-Brandl, Annette

2014-07-01

The aim of this study was to assess the potential of novel β-cyclodextrin (βCD)-dextran polymers for drug delivery. The size distribution of βCD-dextrans (for eventual parenteral administration), the influence of the dextran backbones on the stability of the βCD/drug complex, the solubilization efficiency of poorly soluble drugs and drug release properties were investigated. Size analysis of different βCD-dextrans was measured by size exclusion chromatography (SEC) and asymmetrical flow field-flow fractionation (AF4). Stability of drug/βCD-dextrans was assessed by isothermal titration calorimetry (ITC) and molar enthalpies of complexation and equilibrium constants compared to some commercially available βCD derivatives. For evaluation of the solubilization efficiency, phase-solubility diagrams were made employing hydrocortisone (HC) as a model of poorly soluble drugs, whereas reverse dialysis was used to detect potential drug supersaturation (increased molecularly dissolved drug concentration) as well as controlled release effects. Results indicate that all investigated βCD-polymers are of appropriate sizes for parenteral administration. Thermodynamic results demonstrate that the presence of the dextran backbone structure does not affect the stability of the βCD/drug complex, compared to native βCD and commercially available derivatives. Solubility studies evidence higher solubilizing abilities of these new polymers in comparison to commercially available βCDs, but no supersaturation states were induced. Moreover, drug release studies evidenced that diffusion of HC was influenced by the solubilization induced by the βCD-derivatives. Copyright © 2014 Elsevier B.V. All rights reserved.

Delivery of macromolecules into the endothelium of whole ex vivo human cornea by femtosecond laser-activated carbon nanoparticles.

PubMed

Jumelle, Clotilde; Mauclair, Cyril; Houzet, Julien; Bernard, Aurélien; He, Zhiguo; Forest, Fabien; Perrache, Chantal; Gain, Philippe; Thuret, Gilles

2016-08-01

The targeted delivery of drugs or genes into corneal endothelial cells (ECs) during eye banking could help improve graft quality and quantity. Physical methods raising less safety concerns than viral ones, we previously adapted, for in vitro ECs, a recent innovative technique of drug delivery based on the activation of carbon nanoparticles (CNPs) by a femtosecond laser (fsL). The aim of the present pilot study was to adapt this method to enable molecule delivery into the intact endothelium of ex vivo human corneas. ECs from 40 organ-cultured corneas were perforated by photoacoustic reaction induced by irradiation of CNPs by a fsL. This enabled intracellular delivery of Alexa Fluor 488 dextran, a 4000 Da fluorescent macromolecule. The influence of increasing laser fluences (15, 20, 30 and 40 mJ/cm(2)) and of protective additives (ROCK inhibitor and poloxamer 407) on delivery and mortality rates was quantified using ImageJ. No dextran was delivered with a fluence lower than 20 mJ/cm(2). Dextran was delivered into 3% (range 0%-7%) of cells at 20 mJ/cm(2), 7% (range 2%-12%) at 30 mJ/cm(2) and reaching a median 13% (range 3%-24%) for 40 mJ/cm(2), showing that dextran uptake by ECs increased significantly with fluence. Induced mortality varied from 0% to 53% irrespective of fluence, but likely to be related with the endothelial status (EC density and morphometry, donor age, storage duration and presence of Descemet's folds). ROCK inhibitor slightly increased uptake efficiency, unlike poloxamer. However, none of them decreased the mortality induced by laser. This study shows that a macromolecule can be delivered specifically into ECs of a whole organ-cultured human cornea, using fsL-activated CNPs. The delivery rate was relatively high for a non-viral method. Further optimisation is required to understand and reduce variability in cell mortality. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Evaluation of changes in serum chemistry in association with feed withdrawal or high dose oral gavage with Dextran Sodium Sulfate (DSS) induced gut leakage in broiler chickens

USDA-ARS?s Scientific Manuscript database

Dextran sodium sulfate (DSS) has been shown to be effective at inducing enteric inflammation in broiler chickens, resulting in increased leakage of orally administered fluorescein isothiocyanate dextran to circulation. In a previous study, two doses of DSS (0.45g/dose) administered as oral gavage re...

Action of polysaccharides of similar average mass but differing molecular volume and charge on fluid drainage through synovial interstitium in rabbit knees

PubMed Central

Scott, D; Coleman, P J; Mason, R M; Levick, J R

2000-01-01

Hyaluronan (HA), an anionic polysaccharide of synovial fluid, attenuates fluid loss from joints as joint pressure is raised (‘outflow buffering’). The buffering is thought to depend on the expanded molecular domain of the polymer, which causes reflection by synovial extracellular matrix, leading to flow-dependent concentration polarization. We therefore assessed the effects of polysaccharides of differing average molecular volume and charge. Trans-synovial fluid drainage(Q̇s) was measured at controlled joint fluid pressure (Pj) in knees of anaesthetized rabbits. The joints were infused with polydisperse HA of weight-average mass 2100 kDa (4 mg ml−1, n = 17), with polydisperse neutral dextran of similar average mass (2000 kDa; n = 7) or with Ringer solution vehicle (n = 2). The role of polymer charge was assessed by infusions of neutral or sulphated dextran of average molecular mass 500 kDa (n = 6). When HA was present, Q̇s increased little with pressure, forming a virtual plateau of ∼4 μl min−1 from 10 to 25 cmH2O. Neutral dextran 2000 failed to replicate this effect. Instead, Q̇s increased steeply with Pj, reaching eight times the HA value by 20 cmH2O (P = 0.0001, ANOVA). Dextran 2000 reduced flows in comparison with Ringer solution. Analysis of the aspirated joint fluid showed that 31 ± 0.07 % (s.e.m.) of dextran 2000 in the filtrand was reflected by synovium, compared with ≥ 79 % for HA. The viscometric molecular radius of the dextran, ∼31 nm, was smaller than that of HA (101–181 nm), as was its osmotic pressure. Anionic dextran 500 failed to buffer fluid drainage, but it reduced fluid escape and synovial conductance dQ̇s/dPj more than neutral dextran 500 (P < 0.0001, ANOVA). The anionic charge increased the molecular volume and viscosity of dextran 500. The results support the hypothesis that polymer molecular volume influences its reflection by interstitial matrix and outflow buffering. Polymer charge influences flow through an effect on viscosity and possibly electrostatic interactions with negatively charged interstitial matrix. PMID:11060134

Characterization of the swelling-induced alkalinization of endocytotic vesicles in fluorescein isothiocyanate-dextran-loaded rat hepatocytes.

PubMed Central

Schreiber, R; Häussinger, D

1995-01-01

Short-term cultivated rat hepatocytes were allowed to endocytose fluorescein isothiocyanate (FITC)-coupled dextran and the apparent vesicular pH (pHves) was measured by single-cell fluorescence. After 2 h of exposure to FITC-dextran, the apparent pH in the vesicular compartments accessible to endocytosed FITC-dextran was 6.01 +/- 0.05 (n = 39) in normo-osmotic media. Hypo-osmotic exposure increased, whereas hyper-osmotic exposure decreased apparent pHves. by 0.18 +/- 0.02 (n = 26) and 0.12 +/- 0.01 (n = 23) respectively. Incubation of the cells with unlabelled dextran for 2h before a 2-h FITC-dextran exposure had no effect on apparent pHves and its osmosensitivity. When, however, hepatocytes were exposed to unlabelled dextran for 5 h after a 2 h exposure to FITC-dextran, in order to allow transport of endocytosed FITC-dextran to late endocytotic/lysosomal compartments, apparent pHves. decreased to 5.38 +/- 0.04 (n = 12) and the apparent pH in the vesicular compartment containing the dye was no longer sensitive to aniso-osmotic exposure. These findings indicate that the osomosensitivity of pHves. is apparently restricted to early endocytotic compartments. Aniso-osmotic regulation of apparent pHves. in freshly FITC-loaded hepatocytes was not accompanied by aniso-osmolarity-induced changes of the cytosolic free calcium concentration, and neither vasopressin nor extracellular ATP, which provoked a marked Ca2+ signal, affected apparent pHves. Dibutyryl-cyclic AMP (cAMP) or vanadate (0.5 mmol/l) were without effect on apparent pHves. and its osmosensitivity. However, pertussis toxin-treatment or genistein (but not daidzein) or the erbstatin analogue methyl 2,5-dihydroxycinnamate fully abolished the osmo-sensitivity of apparent pHves., but did not affect apparent pHves. It is concluded that regulation of pHves. by cell volume occurs in early endocytotic compartments, but probably not in lysosomes, and is mediated by a G-protein and tyrosine kinase-dependent, but Ca2+- and cAMP-independent mechanism. PMID:7542446

Nonlinear theory of magnetohydrodynamic flows of a compressible fluid in the shallow water approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klimachkov, D. A., E-mail: klimchakovdmitry@gmail.com; Petrosyan, A. S., E-mail: apetrosy@iki.rssi.ru

2016-09-15

Shallow water magnetohydrodynamic (MHD) theory describing incompressible flows of plasma is generalized to the case of compressible flows. A system of MHD equations is obtained that describes the flow of a thin layer of compressible rotating plasma in a gravitational field in the shallow water approximation. The system of quasilinear hyperbolic equations obtained admits a complete simple wave analysis and a solution to the initial discontinuity decay problem in the simplest version of nonrotating flows. In the new equations, sound waves are filtered out, and the dependence of density on pressure on large scales is taken into account that describesmore » static compressibility phenomena. In the equations obtained, the mass conservation law is formulated for a variable that nontrivially depends on the shape of the lower boundary, the characteristic vertical scale of the flow, and the scale of heights at which the variation of density becomes significant. A simple wave theory is developed for the system of equations obtained. All self-similar discontinuous solutions and all continuous centered self-similar solutions of the system are obtained. The initial discontinuity decay problem is solved explicitly for compressible MHD equations in the shallow water approximation. It is shown that there exist five different configurations that provide a solution to the initial discontinuity decay problem. For each configuration, conditions are found that are necessary and sufficient for its implementation. Differences between incompressible and compressible cases are analyzed. In spite of the formal similarity between the solutions in the classical case of MHD flows of an incompressible and compressible fluids, the nonlinear dynamics described by the solutions are essentially different due to the difference in the expressions for the squared propagation velocity of weak perturbations. In addition, the solutions obtained describe new physical phenomena related to the dependence of the height of the free boundary on the density of the fluid. Self-similar continuous and discontinuous solutions are obtained for a system on a slope, and a solution is found to the initial discontinuity decay problem in this case.« less

Intravenous iron-dextran: studies on unsaturated iron-binding capacity

PubMed Central

Cox, J. S. G.; Moss, G. F.; Bremner, I.; Reason, Janet

1968-01-01

A method is described for measuring the plasma unsaturated iron-binding capacity in the presence of very high concentrations of iron as iron-dextran. The procedure utilizes 59Fe to label the apotransferrin with subsequent separation of ionic iron from transferrin-bound iron on an ion exchange or Sephadex G.25 column. The unsaturated iron-binding capacity has been measured in rabbits and dogs after intravenous injection of iron-dextran and in human subjects after total dose infusion of iron-dextran. No evidence of saturation of the unsaturated iron-binding capacity was found even when the plasma iron values were greater than 40,000 μg Fe/100 ml. PMID:5697365

Permeability of the Peritrophic Envelopes of Herbivorous Insects to Dextran Sulfate: a Test of the Polyanion Exclusion Hypothesis.

PubMed

MARTIN, M M.; BARBEHENN, R V.

1997-03-01

We tested the hypothesis that the permeability of the peritrophic envelope in herbivorous insects is greatly reduced for polyanions as a result of an extensive network of anionic sites in the proteoglycans of the matrix. 14C-Dextran sulfate (polyanionic, 8000 M(w)) and fluorescein isothiocyanate-labeled (FITC) dextran (monoanionic, 9400 M(w)) were introduced together into the endoperitrophic space of the midguts of Orgyia leucostigma (Lepidoptera) larvae and Melanoplus sanguinipes (Orthoptera) adults. In all cases more of the 14C-dextran sulfate permeated the peritrophic envelope than the FITC-dextran, the opposite of the result predicted by the polyanion exclusion hypothesis. We conclude that polyanion exclusion is not a mechanism that contributes significantly to the permeability properties of the peritrophic envelopes of these two species, or that explains the failure of tannic acid to cross the peritrophic envelopes of lepidopteran larvae. Copyright 1997 Elsevier Science Ltd. All rights reserved

Dextran hydrogels by crosslinking with amino acid diamines and their viscoelastic properties.

PubMed

O'Connor, Naphtali A; Jitianu, Mihaela; Nunez, Greisly; Picard, Quentin; Wong, Madeline; Akpatsu, David; Negrin, Adam; Gharbaran, Rajendra; Lugo, Daniel; Shaker, Sundus; Jitianu, Andrei; Redenti, Stephen

2018-05-01

Amine functionalized polysaccharide hydrogels such as those based on chitosan are widely examined as biomaterials. Here we set out to develop a facile procedure for developing such hydrogels by crosslinking dextran with amino acid diamines. The dextran-amino acid gels were formed by the addition of the amino acid diamines to a dextran and epichlorohydrin solution once it became homogeneous. This was demonstrated with three amino acid diamines, lysine, lysine methyl ester, and cystine dimethyl ester. Hydrogel networks with albumin entrapped were also demonstrated. These hydrogels were characterized by FTIR, SEM, rotational rheometry, swelling studies and cell biocompatibility analysis. These hydrogels showed the unexpected pH-responsive behavior of greater swelling at more basic pH, similar to that of an anionic hydrogel. This is uncharacteristic for amine functionalized gels as they typically exhibit cationic hydrogel behavior. All hydrogels showed similar biocompatibility to that of dextran crosslinked without amino acids. Copyright © 2018 Elsevier B.V. All rights reserved.

Microbial dextran-hydrolyzing enzymes: fundamentals and applications.

PubMed

Khalikova, Elvira; Susi, Petri; Korpela, Timo

2005-06-01

Dextran is a chemically and physically complex polymer, breakdown of which is carried out by a variety of endo- and exodextranases. Enzymes in many groups can be classified as dextranases according to function: such enzymes include dextranhydrolases, glucodextranases, exoisomaltohydrolases, exoisomaltotriohydrases, and branched-dextran exo-1,2-alpha-glucosidases. Cycloisomalto-oligosaccharide glucanotransferase does not formally belong to the dextranases even though its side reaction produces hydrolyzed dextrans. A new classification system for glycosylhydrolases and glycosyltransferases, which is based on amino acid sequence similarities, divides the dextranases into five families. However, this classification is still incomplete since sequence information is missing for many of the enzymes that have been biochemically characterized as dextranases. Dextran-degrading enzymes have been isolated from a wide range of microorganisms. The major characteristics of these enzymes, the methods for analyzing their activities and biological roles, analysis of primary sequence data, and three-dimensional structures of dextranases have been dealt with in this review. Dextranases are promising for future use in various scientific and biotechnological applications.

Transfection using DEAE-dextran.

PubMed

Gulick, T

2001-05-01

Transfection of cultured mammalian cells using diethylaminoethyl (DEAE)-dextran/DNA can be an attractive alternative to other transfection methods in many circumstances. The major advantages of the technique are its relative simplicity and speed, limited expense, and remarkably reproducible interexperimental and intraexperimental transfection efficiency. Disadvantages include inhibition of cell growth and induction of heterogeneous morphological changes in cells. Furthermore, the concentration of serum in the culture medium must be transiently reduced during the transfection. In general, DEAE-dextran DNA transfection is ideal for transient transfections with promoter/reporter plasmids in analyses of promoter and enhancer functions, and is suitable for overexpression of recombinant protein in transient transfections or for generation of stable cell lines using vectors designed to exist in the cell as episomes. This unit presents a general description of DEAE-dextran transfection, as well as two more specific protocols for typical experimental applications. The basic protocol is suitable for transfection of anchorage-dependent (attached) cells. For cells that grow in suspension, electroporation or lipofection is usually preferred, although DEAE-dextran-mediated transfection can be used.

Transfection using DEAE-dextran.

PubMed

Gulick, Tod

2003-08-01

Transfection of cultured mammalian cells using diethylaminoethyl (DEAE)-dextran/DNA can be an attractive alternative to other transfection methods in many circumstances. The major advantages of the technique are its relative simplicity and speed, limited expense, and remarkably reproducible interexperimental and intraexperimental transfection efficiency. Disadvantages include inhibition of cell growth and induction of heterogeneous morphological changes in cells. Furthermore, the concentration of serum in the culture medium must be transiently reduced during the transfection. In general, DEAE-dextran DNA transfection is ideal for transient transfections with promoter/reporter plasmids in analyses of promoter and enhancer functions, and is suitable for overexpression of recombinant protein in transient transfections or for generation of stable cell lines using vectors designed to exist in the cell as episomes. This unit presents a general description of DEAE-dextran transfection, as well as two more specific protocols for typical experimental applications. The basic protocol is suitable for transfection of anchorage-dependent (attached) cells. For cells that grow in suspension, electroporation or lipofection is usually preferred, although DEAE-dextran-mediated transfection can be used.

Transfection using DEAE-dextran.

PubMed

Gulick, T

2001-05-01

Transfection of cultured mammalian cells using diethylaminoethyl (DEAE)-dextran/DNA can be an attractive alternative to other transfection methods in many circumstances. The major advantages of the technique are its relative simplicity and speed, limited expense, and remarkably reproducible interexperimental and intraexperimental transfection efficiency. Disadvantages include inhibition of cell growth and induction of heterogeneous morphological changes in cells. Furthermore, the concentration of serum in the culture medium must be transiently reduced during the transfection. In general, DEAE-dextran DNA transfection is ideal for transient transfections with promoter/reporter plasmids in analyses of promoter and enhancer functions, and is suitable for overexpression of recombinant protein in transient transfections or for generation of stable cell lines using vectors designed to exist in the cell as episomes. This unit presents a general description of DEAE-dextran transfection, as well as two more specific protocols for typical experimental applications. The Basic Protocol is suitable for transfection of anchorage-dependent (attached) cells. For cells that grow in suspension, electroporation or lipofection is usually preferred, although DEAE-dextran-mediated transfection can be used.

The immune synapse clears and excludes molecules above a size threshold

PubMed Central

Cartwright, Adam N. R.; Griggs, Jeremy; Davis, Daniel M.

2014-01-01

Natural killer cells assess target cell health via interactions at the immune synapse (IS) that facilitates signal integration and directed secretion. Here we test whether the IS also functions as a gasket. Quantitative fluorescence microscopy of nanometer-scale dextrans within synapses formed by various effector-target cell conjugates reveal that molecules are excluded in a size-dependent manner at activating synapses. Dextran sized ≤4 nm move in and out of the IS, but access is significantly reduced (by >50%) for dextran sized 10–13 nm, and dextran ≥32 nm is almost entirely excluded. Depolymerization of F-actin abrogated exclusion. Unexpectedly, larger-sized dextrans are cleared as the IS assembles in a zipper-like manner. Monoclonal antibodies are also excluded from the IS but smaller single-domain antibodies are able to penetrate. Therefore, the IS can clear and exclude molecules above a size threshold, and drugs designed to target synaptic cytokines or cytotoxic proteins must fit these dimensions. PMID:25407222

Water soluble cationic dextran derivatives containing poly(amidoamine) dendrons for efficient gene delivery.

PubMed

Mai, Kaijin; Zhang, Shanshan; Liang, Bing; Gao, Cong; Du, Wenjun; Zhang, Li-Ming

2015-06-05

To develop new dextran derivatives for efficient gene delivery, the conjugation of poly(amidoamine) dendrons onto biocompatible dextran was carried out by a Cu(I)-catalyzed azide-alkyne cycloaddition, as confirmed by FTIR and (1)H NMR analyses. For resultant dextran conjugates with various generations of poly(amidoamine) dendrons, their buffering capacity and in vitro cytotoxicity were evaluated by acid-base titration and MTT tests, respectively. In particular, their physicochemical characteristics for the complexation with plasmid DNA were investigated by the combined analyses from agarose gel electrophoresis, zeta potential, particle size, transmission electron microscopy and fluorescence emission spectra. Moreover, their complexes with plasmid DNA were studied with respect to their transfection efficiency in human embryonic kidney (HEK293) cell lines. In the case of a higher generation of poly(amidoamine) dendrons, such a dextran conjugate was found to have much lower cytotoxicity and better gene delivery capability when compared to branched polyethylenimine (bPEI, 25kDa), a commonly used gene vector. Copyright © 2015 Elsevier Ltd. All rights reserved.

Intracellular degradation of microspheres based on cross-linked dextran hydrogels or amphiphilic block copolymers: A comparative Raman microscopy study

PubMed Central

van Manen, Henk-Jan; van Apeldoorn, Aart A; Verrijk, Ruud; van Blitterswijk, Clemens A; Otto, Cees

2007-01-01

Micro- and nanospheres composed of biodegradable polymers show promise as versatile devices for the controlled delivery of biopharmaceuticals. Whereas important properties such as drug release profiles, biocompatibility, and (bio)degradability have been determined for many types of biodegradable particles, information about particle degradation inside phagocytic cells is usually lacking. Here, we report the use of confocal Raman microscopy to obtain chemical information about cross-linked dextran hydrogel microspheres and amphiphilic poly(ethylene glycol)-terephthalate/poly(butylene terephthalate) (PEGT/PBT) microspheres inside RAW 264.7 macrophage phagosomes. Using quantitative Raman microspectroscopy, we show that the dextran concentration inside phagocytosed dextran microspheres decreases with cell incubation time. In contrast to dextran microspheres, we did not observe PEGT/PBT microsphere degradation after 1 week of internalization by macrophages, confirming previous studies showing that dextran microsphere degradation proceeds faster than PEGT/PBT degradation. Raman microscopy further showed the conversion of macrophages to lipid-laden foam cells upon prolonged incubation with both types of microspheres, suggesting that a cellular inflammatory response is induced by these biomaterials in cell culture. Our results exemplify the power of Raman microscopy to characterize microsphere degradation in cells and offer exciting prospects for this technique as a noninvasive, label-free optical tool in biomaterials histology and tissue engineering. PMID:17722552

Metallization and Biopatterning on Ultra-Flexible Substrates via Dextran Sacrificial Layers

PubMed Central

Tseng, Peter; Pushkarsky, Ivan; Di Carlo, Dino

2014-01-01

Micro-patterning tools adopted from the semiconductor industry have mostly been optimized to pattern features onto rigid silicon and glass substrates, however, recently the need to pattern on soft substrates has been identified in simulating cellular environments or developing flexible biosensors. We present a simple method of introducing a variety of patterned materials and structures into ultra-flexible polydimethylsiloxane (PDMS) layers (elastic moduli down to 3 kPa) utilizing water-soluble dextran sacrificial thin films. Dextran films provided a stable template for photolithography, metal deposition, particle adsorption, and protein stamping. These materials and structures (including dextran itself) were then readily transferrable to an elastomer surface following PDMS (10 to 70∶1 base to crosslinker ratios) curing over the patterned dextran layer and after sacrificial etch of the dextran in water. We demonstrate that this simple and straightforward approach can controllably manipulate surface wetting and protein adsorption characteristics of PDMS, covalently link protein patterns for stable cell patterning, generate composite structures of epoxy or particles for study of cell mechanical response, and stably integrate certain metals with use of vinyl molecular adhesives. This method is compatible over the complete moduli range of PDMS, and potentially generalizable over a host of additional micro- and nano-structures and materials. PMID:25153326

The Efficacy of Dextran-40 as a Venous Thromboembolism Prophylaxis Strategy in Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy.

PubMed

Foster, Jason M; Sleightholm, Richard; Watley, Duncan; Wahlmeier, Steven; Patel, Asish

2017-02-01

The incidence of venous thromboembolism (VTE) in peritoneal malignancies can approach 30 to 50 per cent without prophylaxis. Prophylaxis in cytoreductive surgeries (CRS) presents a challenge to preoperative heparin-based therapy because of an increased risk of coagulopathy and potential for bleeding. Herein, we report the large series of CRS and hyperthermic intraperitoneal chemotherapy receiving dextran-40 prophylaxis. Retrospective chart review of peritoneal malignancies patients undergoing CRS at University of Nebraska Medical Center identified 69 individuals who received dextran-40 between 2010 and 2013. The incidences of VTEs, perioperative bleeding, complications, morbidity, and mortality were determined in-hospital and at 90 days. Of the 69 patients treated, the 30-day VTE rate was 8.7 per cent, and no pulmonary embolisms, bleeding, anaphylactoid reaction, or mortality were observed with dextran usage. The specific VTE events included three upper extremity and three lower extremity VTEs. No additional VTE events were identified between 30 and 90 days. In conclusion, dextran-40 prophylaxis was not associated with any perioperative bleeding events, and the observed incidence of VTE was comparable to reported heparin-based prophylaxis in CRS/hyperthermic intraperitoneal chemotherapy patients. This data supports further exploration of dextran-40 as a VTE prophylactic agent in complex surgical oncology cases.

Quantitative monitoring of activity-dependent bulk endocytosis of synaptic vesicle membrane by fluorescent dextran imaging

PubMed Central

Clayton, Emma Louise; Cousin, Michael Alan

2012-01-01

Activity-dependent bulk endocytosis (ADBE) is the dominant synaptic vesicle (SV) retrieval mode in central nerve terminals during periods of intense neuronal activity. Despite this fact there are very few real time assays that report the activity of this critical SV retrieval mode. In this paper we report a simple and quantitative assay of ADBE using uptake of large flourescent dextrans as fluid phase markers. We show that almost all dextran uptake occurs in nerve terminals, using co-localisation with the fluorescent probe FM1-43. We also demonstrate that accumulated dextran cannot be unloaded by neuronal stimulation, indicating its specific loading into bulk endosomes and not SVs. Quantification of dextran uptake was achieved by using thresholding analysis to count the number of loaded nerve terminals, since monitoring the average fluorescence intensity of these nerve terminals did not accurately report the extent of ADBE. Using this analysis we showed that dextran uptake occurs very soon after stimulation and that it does not persist when stimulation terminates. Thus we have devised a simple and quantitative method to monitor ADBE in living neurones, which will be ideal for real time screening of small molecule inhibitors of this key SV retrieval mode. PMID:19766140

Gradient-dependent release of the model drug TRITC-dextran from FITC-labeled BSA hydrogel nanocarriers in the hair follicles of porcine ear skin.

PubMed

Tran, Ngo Bich Nga Nathalie; Knorr, Fanny; Mak, Wing Cheung; Cheung, Kwan Yee; Richter, Heike; Meinke, Martina; Lademann, Jürgen; Patzelt, Alexa

2017-07-01

Hair follicle research is currently focused on the development of drug-loaded nanocarriers for the targeting of follicular structures in the treatment of skin and hair follicle-related disorders. In the present study, a dual-label nanocarrier system was implemented in which FITC-labeled BSA hydrogel nanocarriers loaded with the model drug and dye TRITC-dextran were applied topically to porcine ear skin. Follicular penetration and the distribution of both dyes corresponding to the nanocarriers and the model drug in the follicular ducts subsequent to administration to the skin were investigated using confocal laser scanning microscopy. The release of TRITC-dextran from the particles was induced by washing of the nanocarriers, which were kept in a buffer containing TRITC-labeled dextran to balance out the diffusion of the dextran during storage, thereby changing the concentration gradient. The results showed a slightly but statistically significantly deeper follicular penetration of fluorescent signals corresponding to TRITC-dextran as opposed to fluorescence corresponding to the FITC-labeled particles. The different localizations of the dyes in the cross-sections of the skin samples evidenced the release of the model drug from the labeled nanoparticles. Copyright © 2016 Elsevier B.V. All rights reserved.

Redefining the properties of an osmotic agent in an intestinal-specific preservation solution

PubMed Central

Schlachter, Kimberly; Kokotilo, Matthew S; Carter, Jodi; Thiesen, Aducio; Ochs, Angela; Khadaroo, Rachel G; Churchill, Thomas A

2010-01-01

AIM: To investigate the effects of dextrans of various molecular weights (Mw) during a 12 h cold storage time-course on energetics, histology and mucosal infiltration of fluorescein isothiocyanate (FITC)-dextran. METHODS: Rodent intestines were isolated and received a standard University of Wisconsin vascular flush followed by intraluminal administration of a nutrient-rich preservation solution containing dextrans of varying Mw: Group D1, 73 kdal; Group D2, 276 kdal; Group D3, 534 kdal; Group D4, 1185 kdal; Group D5, 2400 kdal. RESULTS: Using FITC-labeled dextrans, fluorescent micrographs demonstrated varying degrees of mucosal infiltration; lower Mw (groups D1-D3: 73-534 kdal) dextrans penetrated the mucosa as early as 2 h, whereas the largest dextran (D5: 2400 kdal) remained captive within the lumen and exhibited no permeability even after 12 h. After 12 h, median injury grades ranged from 6.5 to 7.5 in groups D1-D4 (73-1185 kdal) representing injury of the regenerative cryptal regions and submucosa; this was in contrast to group D5 (2400 kdal) which exhibited villus denudation (with intact crypts) corresponding to a median injury grade of 4 (P < 0.05). Analysis of tissue energetics reflected a strong positive correlation between Mw and adenosine triphosphate (r2 = 0.809), total adenylates (r2 = 0.865) and energy charge (r2 = 0.667). CONCLUSION: Our data indicate that dextrans of Mw > 2400 kdal act as true impermeant agents during 12 h ischemic storage when incorporated into an intraluminal preservation solution. PMID:21128319

Influence of molecular shape, conformability, net surface charge, and tissue interaction on transscleral macromolecular diffusion.

PubMed

Srikantha, Nishanthan; Mourad, Fatma; Suhling, Klaus; Elsaid, Naba; Levitt, James; Chung, Pei Hua; Somavarapu, Satyanarayana; Jackson, Timothy L

2012-09-01

The purpose of this study was to investigate the influence of molecular shape, conformability, net surface charge and tissue interaction on transscleral diffusion. Unfixed, porcine sclera was clamped in an Ussing chamber. Fluorophore-labelled neutral albumin, neutral dextran, or neutral ficoll were placed in one hemi-chamber and the rate of transscleral diffusion was measured over 24 h using a spectrophotometer. Experiments were repeated using dextrans and ficoll with positive or negative net surface charges. Fluorescence recovery after photobleaching (FRAP) was undertaken to compare transscleral diffusion with diffusion through a solution. All molecules were 70 kDa. With FRAP, the diffusion coefficient (D) of neutral molecules was highest for albumin, followed by ficoll, then dextran (p < 0.0001). Positive dextrans diffused fastest, followed by negative, then neutral dextrans (p = 0.0004). Neutral ficoll diffused the fastest, followed by positive then negative ficoll (p = 0.5865). For the neutral molecules, transscleral D was highest for albumin, followed by dextran, then ficoll (p < 0.0001). D was highest for negative ficoll, followed by neutral, then positive ficoll (p < 0.0001). By contrast, D was highest for positive dextran, followed by neutral, then negative dextran (p = 0.0021). In conclusion, diffusion in free solution does not predict transscleral diffusion and the molecular-tissue interaction is important. Molecular size, shape, and charge may all markedly influence transscleral diffusion, as may conformability to a lesser degree, but their effects may be diametrically opposed in different molecules, and their influence on diffusion is more complex than previously thought. Each variable cannot be considered in isolation, and the interplay of all these variables needs to be tested, when selecting or designing drugs for transscleral delivery. Copyright © 2012 Elsevier Ltd. All rights reserved.

Porosity of porcine bladder acellular matrix: impact of ACM thickness.

PubMed

Farhat, Walid; Chen, Jun; Erdeljan, Petar; Shemtov, Oren; Courtman, David; Khoury, Antoine; Yeger, Herman

2003-12-01

The objectives of this study are to examine the porosity of bladder acellular matrix (ACM) using deionized (DI) water as the model fluid and dextran as the indicator macromolecule, and to correlate the porosity to the ACM thickness. Porcine urinary bladders from pigs weighing 20-50 kg were sequentially extracted in detergent containing solutions, and to modify the ACM thickness, stretched bladders were acellularized in the same manner. Luminal and abluminal ACM specimens were subjected to fixed static DI water pressure (10 cm); and water passing through the specimens was collected at specific time interval. While for the macromolecule porosity testing, the diffusion rate and direction of 10,000 MW fluoroescein-labeled dextrans across the ACM specimens mounted in Ussing's chambers were measured. Both experiments were repeated on the thin stretched ACM. In both ACM types, the fluid porosity in both directions did not decrease with increased test duration (3 h); in addition, the abluminal surface was more porous to fluid than the luminal surface. On the other hand, when comparing thin to thick ACM, the porosity in either direction was higher in the thick ACM. Macromolecule porosity, as measured by absorbance, was higher for the abluminal thick ACM than the luminal side, but this characteristic was reversed in the thin ACM. Comparing thin to thick ACM, the luminal side in the thin ACM was more porous to dextran than in the thick ACM, but this characteristic was reversed for the abluminal side. The porcine bladder ACM possesses directional porosity and acellularizing stretched urinary bladders may increase structural density and alter fluid and macromolecule porosity. Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 970-974, 2003

21 CFR 186.1275 - Dextrans.

Code of Federal Regulations, 2014 CFR

2014-04-01

... by bacterial fermentation of sucrose. Commercially available dextrans are synthesized from sucrose by Leuconostoc mesenteroides strain NRRL B-512(F). Partial depolymerization and purification of the fermented...

Enhancing Peripheral Nerve Regeneration with a Novel Drug-Delivering Nerve Conduit

DTIC Science & Technology

2015-10-01

data with the release of fluorescently labeled dextran that indicate the new device is sealed and able to release therapeutics in a controlled manner...accurately predict the release of fluorescently labeled dextran , with a similar diffusion coefficient to NGF, over a period of approximately 40 days...enables the release of NGF from the reservoir into the inner chamber. 7 Figure 2. Fluorescently labeled dextran (blue) was released from our PLGA nerve

Synthesis and film formation of furfuryl- and maleimido carbonic acid derivatives of dextran.

PubMed

Elschner, Thomas; Obst, Franziska; Stana-Kleinschek, Karin; Kargl, Rupert; Heinze, Thomas

2017-04-01

Carbonic acid derivatives of dextran possessing furfuryl- and maleimido moieties were synthesized and processed into thin films by spin coating. First, products with different degrees of substitution (DS) of up to 3.0 and substitution patterns were obtained and characterized by NMR- and FTIR spectroscopy, as well as elemental analysis. Thin films possessing maleimide groups were obtained by spin coating of maleimido dextran (furan-protected) and dextran furfuryl carbamate that was converted with bismaleimide. The removal of the protecting group (furan) on the thin film was monitored by QCM-D and compared with gravimetric analysis of the bulk material. Film morphology and wettability were determined by means of AFM and contact angle measurements. Copyright © 2016 Elsevier Ltd. All rights reserved.

Non-Gaussian PDF Modeling of Turbulent Boundary Layer Fluctuating Pressure Excitation

NASA Technical Reports Server (NTRS)

Steinwolf, Alexander; Rizzi, Stephen A.

2003-01-01

The purpose of the study is to investigate properties of the probability density function (PDF) of turbulent boundary layer fluctuating pressures measured on the exterior of a supersonic transport aircraft. It is shown that fluctuating pressure PDFs differ from the Gaussian distribution even for surface conditions having no significant discontinuities. The PDF tails are wider and longer than those of the Gaussian model. For pressure fluctuations upstream of forward-facing step discontinuities and downstream of aft-facing step discontinuities, deviations from the Gaussian model are more significant and the PDFs become asymmetrical. Various analytical PDF distributions are used and further developed to model this behavior.

Geometrically Nonlinear Field Fracture Mechanics and Crack Nucleation, Application to Strain Localization Fields in Al-Cu-Li Aerospace Alloys.

PubMed

Gupta, Satyapriya; Taupin, Vincent; Fressengeas, Claude; Jrad, Mohamad

2018-03-27

The displacement discontinuity arising between crack surfaces is assigned to smooth densities of crystal defects referred to as disconnections, through the incompatibility of the distortion tensor. In a dual way, the disconnections are defined as line defects terminating surfaces where the displacement encounters a discontinuity. A conservation statement for the crack opening displacement provides a framework for disconnection dynamics in the form of transport laws. A similar methodology applied to the discontinuity of the plastic displacement due to dislocations results in the concurrent involvement of dislocation densities in the analysis. Non-linearity of the geometrical setting is assumed for defining the elastic distortion incompatibility in the presence of both dislocations and disconnections, as well as for their transport. Crack nucleation in the presence of thermally-activated fluctuations of the atomic order is shown to derive from this nonlinearity in elastic brittle materials, without any algorithmic rule or ad hoc material parameter. Digital image correlation techniques applied to the analysis of tensile tests on ductile Al-Cu-Li samples further demonstrate the ability of the disconnection density concept to capture crack nucleation and relate strain localization bands to consistent disconnection fields and to the eventual occurrence of complex and combined crack modes in these alloys.

21 CFR 186.1275 - Dextrans.

Code of Federal Regulations, 2010 CFR

2010-04-01

... weight polysaccharides produced by bacterial fermentation of sucrose. Commercially available dextrans are... purification of the fermented mixture shall produce a product that is free of viable microorganisms. (b) The...

21 CFR 186.1275 - Dextrans.

Code of Federal Regulations, 2013 CFR

2013-04-01

... weight polysaccharides produced by bacterial fermentation of sucrose. Commercially available dextrans are... purification of the fermented mixture shall produce a product that is free of viable microorganisms. (b) The...

21 CFR 186.1275 - Dextrans.

Code of Federal Regulations, 2012 CFR

2012-04-01

... weight polysaccharides produced by bacterial fermentation of sucrose. Commercially available dextrans are... purification of the fermented mixture shall produce a product that is free of viable microorganisms. (b) The...

21 CFR 186.1275 - Dextrans.

Code of Federal Regulations, 2011 CFR

2011-04-01

... weight polysaccharides produced by bacterial fermentation of sucrose. Commercially available dextrans are... purification of the fermented mixture shall produce a product that is free of viable microorganisms. (b) The...

Simultaneous assessment of glomerular filtration and barrier function in live zebrafish

PubMed Central

Kotb, Ahmed M.; Müller, Tobias; Xie, Jing; Anand-Apte, Bela; Endlich, Nicole

2014-01-01

The zebrafish pronephros is a well-established model to study glomerular development, structure, and function. A few methods have been described to evaluate glomerular barrier function in zebrafish larvae so far. However, there is a need to assess glomerular filtration as well. In the present study, we extended the available methods by simultaneously measuring the intravascular clearances of Alexa fluor 647-conjugated 10-kDa dextran and FITC-conjugated 500-kDa dextran as indicators of glomerular filtration and barrier function, respectively. After intravascular injection of the dextrans, mean fluorescence intensities of both dextrans were measured in the cardinal vein of living zebrafish (4 days postfertilization) by confocal microscopy over time. We demonstrated that injected 10-kDa dextran was rapidly cleared from the circulation, became visible in the lumen of the pronephric tubule, quickly accumulated in tubular cells, and was detectably excreted at the cloaca. In contrast, 500-kDa dextran could not be visualized in the tubule at any time point. To check whether alterations in glomerular function can be quantified by our method, we injected morpholino oligonucleotides (MOs) against zebrafish nonmuscle myosin heavy chain IIA (zMyh9) or apolipoprotein L1 (zApol1). While glomerular filtration was reduced in zebrafish nonmuscle myosin heavy chain IIA MO-injected larvae, glomerular barrier function remained intact. In contrast, in zebrafish apolipoprotein L1 MO-injected larvae, glomerular barrier function was compromised as 500-kDa dextran disappeared from the circulation and became visible in tubular cells. In summary, we present a novel method that allows to simultaneously assess glomerular filtration and barrier function in live zebrafish. PMID:25298528

Molecules of various pharmacologically-relevant sizes can cross the ultrasound-induced blood-brain barrier opening in vivo

PubMed Central

Choi, James J.; Wang, Shougang; Tung, Yao-Sheng; Morrison, Barclay; Konofagou, Elisa E.

2009-01-01

Focused ultrasound (FUS) is hereby shown to noninvasively and selectively deliver compounds at pharmacologically relevant molecular weights through the opened blood-brain barrier (BBB). A complete examination on the size of the FUS-induced BBB opening, the spatial distribution of the delivered agents and its dependence on the agent's molecular weight were imaged and quantified using fluorescence microscopy. BBB opening in mice (n=13) was achieved in vivo after systemic administration of microbubbles and subsequent application of pulsed FUS (frequency: 1.525 MHz, peak-rarefactional pressure in situ: 569 kPa) to the left murine hippocampus through the intact skin and skull. BBB-impermeant, fluorescent-tagged dextrans at three distinct molecular weights spanning over several orders of magnitude were systemically administered and acted as model therapeutic compounds. First, dextrans of 3 and 70 kDa were delivered trans-BBB while 2000 kDa dextran was not. Second, compared to 70 kDa dextran, a higher concentration of 3 kDa dextran was delivered through the opened BBB. Third, the 3 and 70 kDa dextrans were both diffusely distributed throughout the targeted brain region. However, high concentrations of 70 kDa dextran appeared more punctated throughout the targeted region. In conclusion, FUS combined with microbubbles opened the BBB sufficiently to allow passage of compounds of at least 70 kDa, but not greater than 2000 kDa, into the brain parenchyma. This noninvasive and localized BBB opening technique could thus provide a unique means for the delivery of compounds of several magnitudes of kDa that include agents with shown therapeutic promise in vitro, but whose in vivo translation has been hampered by their associated BBB impermeability. PMID:19900750

Comparison of Dextran Perfusion and GSI-B4 Isolectin Staining in a Mouse Model of Oxygen-induced Retinopathy.

PubMed

Huang, Shaofen; Liang, Jiajian; Yam, Gary Hin-Fai; Lu, Zhihao; Pang, Chi Pui; Chen, Haoyu

2015-06-01

Oxygen-induced retinopathy (OIR) is a robust and widely used animal model for the study of retinal neovascularization (NV). Dextran perfusion and Griffonia simplicifolia isolectin B4 (GSI-B4) staining are two common methods for examining the occurrence and extent of OIR. This study provides a quantitative comparison of the two for OIR detection. At postnatal day 7 (PN7), fifteen C57BL/6J mice were exposed to a 75% hyperoxic condition for 5 days and then returned to room air conditions. At PN17, the mice received intravitreal injection of GSI-B4 Alexa Fluor 568 conjugate. After 10 hours, they were infused with FITC-dextran conjugate via the left ventricle. Retinal flat mounts were photographed by confocal microscopy. Areas with fluorescent signals and the total retinal areas were quantified by Image J software. Both GSI-B4 and dextran detected the peripheral neovascular area. The mean hyper fluorescence area was 0.33 ± 0.14% of whole retinal area determined by GSI-B4 staining and 0.25 ± 0.28% determined by dextran perfusion. The difference between the two measures was 0.08% (95% CI:-0.59%, 0.43%). The Pearson correlation coefficient between the two methods was 0.386,P =0.035. The mean coincidence rates were 14.3 ± 13.4% and 24.9 ± 18.5% for GSI-B4 and dextran staining, respectively. Both methods can complement each other in demonstrating and quantitatively evaluating retinal NV. A poor agreement was found between the two methods; GSI-B4 isolectin was more effective than FITC-dextran perfusion in evaluating the extent of retinal NV in a mouse model of OIR.

Optimization of peptide nucleic acid fluorescence in situ hybridization (PNA-FISH) for the detection of bacteria: The effect of pH, dextran sulfate and probe concentration.

PubMed

Rocha, Rui; Santos, Rita S; Madureira, Pedro; Almeida, Carina; Azevedo, Nuno F

2016-05-20

Fluorescence in situ hybridization (FISH) is a molecular technique widely used for the detection and characterization of microbial populations. FISH is affected by a wide variety of abiotic and biotic variables and the way they interact with each other. This is translated into a wide variability of FISH procedures found in the literature. The aim of this work is to systematically study the effects of pH, dextran sulfate and probe concentration in the FISH protocol, using a general peptide nucleic acid (PNA) probe for the Eubacteria domain. For this, response surface methodology was used to optimize these 3 PNA-FISH parameters for Gram-negative (Escherichia coli and Pseudomonas fluorescens) and Gram-positive species (Listeria innocua, Staphylococcus epidermidis and Bacillus cereus). The obtained results show that a probe concentration higher than 300nM is favorable for both groups. Interestingly, a clear distinction between the two groups regarding the optimal pH and dextran sulfate concentration was found: a high pH (approx. 10), combined with lower dextran sulfate concentration (approx. 2% [w/v]) for Gram-negative species and near-neutral pH (approx. 8), together with higher dextran sulfate concentrations (approx. 10% [w/v]) for Gram-positive species. This behavior seems to result from an interplay between pH and dextran sulfate and their ability to influence probe concentration and diffusion towards the rRNA target. This study shows that, for an optimum hybridization protocol, dextran sulfate and pH should be adjusted according to the target bacteria. Copyright © 2016 Elsevier B.V. All rights reserved.

Protelytic Regulation of the Intestinal Epithelial Barrier: Mechanisms and Interventions

DTIC Science & Technology

2015-09-01

group) during the course of the DSS protocol to assess gut permeability by serum FITC- dextran concentration after gavage and by ex vivo TEER...TEER and by the flux of 4kDa FITC conjugated dextran across monolayers (months 1-3) Year 1 and 2 summary - Preliminary data showed that after treatment...macromolecular FITC- dextran . We have been able to consistently induce barrier disruption of T84 cultures using IL-13 in combination with the

THE FORMATION OF ROTATIONAL DISCONTINUITIES IN COMPRESSIVE THREE-DIMENSIONAL MHD TURBULENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Liping; Feng, Xueshang; Zhang, Lei

Measurements of solar wind turbulence reveal the ubiquity of discontinuities. In this study we investigate how the discontinuities, especially rotational discontinuities (RDs), are formed in MHD turbulence. In a simulation of the decaying compressive three-dimensional (3D) MHD turbulence with an imposed uniform background magnetic field, we detect RDs with sharp field rotations and little variations of magnetic field intensity, as well as mass density. At the same time, in the de Hoffman–Teller frame, the plasma velocity is nearly in agreement with the Alfvén speed, and is field-aligned on both sides of the discontinuity. We take one of the identified RDsmore » to analyze its 3D structure and temporal evolution in detail. By checking the magnetic field and plasma parameters, we find that the identified RD evolves from the steepening of the Alfvén wave with moderate amplitude, and that steepening is caused by the nonuniformity of the Alfvén speed in the ambient turbulence.« less

Dextran-Catechin: An anticancer chemically-modified natural compound targeting copper that attenuates neuroblastoma growth

PubMed Central

Vittorio, Orazio; Brandl, Miriam; Cirillo, Giuseppe; Kimpton, Kathleen; Hinde, Elizabeth; Gaus, Katharina; Yee, Eugene; Kumar, Naresh; Duong, Hien; Fleming, Claudia; Haber, Michelle; Norris, Murray; Boyer, Cyrille; Kavallaris, Maria

2016-01-01

Neuroblastoma is frequently diagnosed at advanced stage disease and treatment includes high dose chemotherapy and surgery. Despite the use of aggressive therapy survival rates are poor and children that survive their disease experience long term side effects from their treatment, highlighting the need for effective and less toxic therapies. Catechin is a natural polyphenol with anti-cancer properties and limited side effects, however its mechanism of action is unknown. Here we report that Dextran-Catechin, a conjugated form of catechin that increases serum stability, is preferentially and markedly active against neuroblastoma cells having high levels of intracellular copper, without affecting non-malignant cells. Copper transporter 1 (CTR1) is the main transporter of copper in mammalian cells and it is upregulated in neuroblastoma. Functional studies showed that depletion of CTR1 expression reduced intracellular copper levels and led to a decrease in neuroblastoma cell sensitivity to Dextran-Catechin, implicating copper in the activity of this compound. Mechanistically, Dextran-Catechin was found to react with copper, inducing oxidative stress and decreasing glutathione levels, an intracellular antioxidant and regulator of copper homeostasis. In vivo, Dextran-Catechin significantly attenuated tumour growth in human xenograft and syngeneic models of neuroblastoma. Thus, Dextran-Catechin targets copper, inhibits tumour growth, and may be valuable in the treatment of aggressive neuroblastoma and other cancers dependent on copper for their growth. PMID:27374085

Simulation of the effect of hydrogen bonds on water activity of glucose and dextran using the Veytsman model.

PubMed

De Vito, Francesca; Veytsman, Boris; Painter, Paul; Kokini, Jozef L

2015-03-06

Carbohydrates exhibit either van der Waals and ionic interactions or strong hydrogen bonding interactions. The prominence and large number of hydrogen bonds results in major contributions to phase behavior. A thermodynamic framework that accounts for hydrogen bonding interactions is therefore necessary. We have developed an extension of the thermodynamic model based on the Veytsman association theory to predict the contribution of hydrogen bonds to the behavior of glucose-water and dextran-water systems and we have calculated the free energy of mixing and its derivative leading to chemical potential and water activity. We compared our calculations with experimental data of water activity for glucose and dextran and found excellent agreement far superior to the Flory-Huggins theory. The validation of our calculations using experimental data demonstrated the validity of the Veytsman model in properly accounting for the hydrogen bonding interactions and successfully predicting water activity of glucose and dextran. Our calculations of the concentration of hydrogen bonds using the Veytsman model were instrumental in our ability to explain the difference between glucose and dextran and the role that hydrogen bonds play in contributing to these differences. The miscibility predictions showed that the Veytsman model is also able to correctly describe the phase behavior of glucose and dextran. Copyright © 2014 Elsevier Ltd. All rights reserved.

Role of macromolecular crowding and salt ions on the structural-fluctuation of a highly compact configuration of carbonmonoxycytochrome c.

PubMed

Kumar, Rajesh; Sharma, Deepak; Jain, Rishu; Kumar, Sandeep; Kumar, Rajesh

2015-12-01

Carbonmonoxycytochrome c refolds to a native-like compact state (NCO-state), where the non-native Fe(2+)-CO interaction persists. Structural and molecular properties extracted from CD, fluorescence and NMR experiments reveal that the NCO-state shows the generic properties of molten globules. Slow thermal-dissociation of CO transforms the NCO-state to native-state (N-state), where the native Fe(2+)-M80 bond recovers. To determine the role of crowding agents and salt ions on the structural-fluctuation of NCO, the kinetic and thermodynamic parameters for CO-dissociation from NCO (NCO→N+CO) were measured at varying concentrations of crowding agents (dextran 70, dextran 40, ficoll 70) and salt ions (anion: ClO4(-), I(-), Br(-), NO3(-), Cl(-); cation: NH4(+), K(+), Na(+)). As [crowding agent] or [ion] is increased, the rate coefficient of CO-dissociation (kdiss) decreases exponentially. Furthermore, the extent of decrease in kdiss is found to be dependent on (i) size, charge density and charge dispersion of the ion, and (ii) size, shape, and viscosity of the crowding agent. Copyright © 2015 Elsevier B.V. All rights reserved.

Intraoperative corneal thickness measurements during corneal collagen cross-linking with isotonic riboflavin solution without dextran in corneal ectasia.

PubMed

Cınar, Yasin; Cingü, Abdullah Kürşat; Sahin, Alparslan; Türkcü, Fatih Mehmet; Yüksel, Harun; Caca, Ihsan

2014-03-01

Abstract Objective: To monitor the changes in corneal thickness during the corneal collagen cross-linking procedure by using isotonic riboflavin solution without dextran in ectatic corneal diseases. The corneal thickness measurements were obtained before epithelial removal, after epithelial removal, following the instillation of isotonic riboflavin solution without dextran for 30 min, and after 10 min of ultraviolet A irradiation. Eleven eyes of eleven patients with progressive keratoconus (n = 10) and iatrogenic corneal ectasia (n = 1) were included in this study. The mean thinnest pachymetric measurements were 391.82 ± 30.34 µm (320-434 µm) after de-epithelialization of the cornea, 435 ± 21.17 µm (402-472 µm) following 30 min instillation of isotonic riboflavin solution without dextran and 431.73 ± 20.64 µm (387-461 µm) following 10 min of ultraviolet A irradiation to the cornea. Performing corneal cross-linking procedure with isotonic riboflavin solution without dextran might not induce corneal thinning but a little swelling throughout the procedure.

Isolation of dextran-hydrolyzing intestinal bacteria and characterization of their dextranolytic activities.

PubMed

Kim, Jin Kyoung; Shin, So-Yeon; Moon, Jin Seok; Li, Ling; Cho, Seung Kee; Kim, Tae-Jip; Han, Nam Soo

2015-06-01

The aim of this study was to isolate dextran-hydrolyzing bacteria from the human intestines and to identify their dextranolytic enzymes. For this, dextranase-producing microorganisms were screened from fecal samples by using blue dextran-containing media. Colonies producing a decolorized zone were isolated and they were grouped using RAPD-PCR. 16S rRNA gene sequencing analysis revealed the isolates were Bacteroides (B.) thetaiotaomicron, B. ovatus, B. vulgatus, B. dorei, B. xylanisolvens, B. uniformis, and Veillonella (V.) rogosae. Thin layer chromatography analysis showed that the dextranases exhibit mainly endo-type activity and produce various oligosaccharides including isomaltose and isomaltotriose. Zymogram analysis demonstrated that enzymes localized mainly in the cell membrane fraction and the molecular weight was 50-70 kDa. When cultured in a dextran-containing medium, all strains isolated in this study produced short-chain fatty acids, with butyric acid as the major compound. This is the first study to report that human intestinal B. xylanisolvens, B. dorei, and V. rogosae metabolize dextran utilizing dextranolytic enzymes. © 2015 Wiley Periodicals, Inc.

“Click” Synthesis of Dextran Macrostructures for Combinatorial-Designed Self-Assembled Nanoparticles Encapsulating Diverse Anticancer Therapeutics

PubMed Central

Abeylath, Sampath C.; Amiji, Mansoor

2011-01-01

With the non-specific toxicity of anticancer drugs to healthy tissues upon systemic administration, formulations capable of enhanced selectivity in delivery to the tumor mass and cells are highly desirable. Based on the diversity of the drug payloads, we have investigated a combinatorial-designed strategy where the nano-sized formulations are tailored based on the physicochemical properties of the drug and the delivery needs. Individually functionalized C2 to C12 lipid-, thiol-, and poly(ethylene glycol) (PEG)-modified dextran derivatives were synthesized via “click” chemistry from O-pentynyl dextran and relevant azides. These functionalized dextrans in combination with anticancer drugs form nanoparticles by self-assembling in aqueous medium having PEG surface functionalization and intermolecular disulfide bonds. Using anticancer drugs with logP values ranging from −0.5 to 3.0, the optimized nanoparticles formulations were evaluated for preliminary cellular delivery and cytotoxic effects in SKOV3 human ovarian adenocarcinoma cells. The results show that with the appropriate selection of lipid-modified dextran, one can effectively tailor the self-assembled nano-formulation for intended therapeutic payload. PMID:21978947

Enzymatic and acidic degradation of high molecular weight dextran into low molecular weight and its characterizations using novel Diffusion-ordered NMR spectroscopy.

PubMed

Iqbal, Samina; Marchetti, Roberta; Aman, Afsheen; Silipo, Alba; Qader, Shah Ali Ul; Molinaro, Antonio

2017-10-01

Low molecular weight fractions were derived from native high molecular weight dextran produced by Leuconostoc mesenteroides KIBGE-IB26. Structural characterization of native and low molecular weight fractions obtained after acidic and enzymatic hydrolysis was done using FTIR and NMR spectroscopy. The molecular weight was estimated using Diffusion Ordered NMR spectroscopy. Native dextran (892kDa) is composed of α-(1→6) glycosidic linkage along with α-(1→3) branching. Major proportion of 528kDa dextran was obtained after prolong enzymatic hydrolysis however, an effective acidic treatment at pH-1.4 up to 02 and 04h of exposure resulted in the formation of 77kDa and 57kDa, respectively. The increment in pH from 1.4 to 1.8 lowered the hydrolysis efficiency and resulted in the formation of 270kDa dextran fraction. The results suggest that derived low molecular weight water soluble fractions can be utilized as a drug delivery carrier along with multiple application relating pharmaceutical industries. Copyright © 2017 Elsevier B.V. All rights reserved.

Structural analysis and characterization of dextran produced by wild and mutant strains of Leuconostoc mesenteroides.

PubMed

Siddiqui, Nadir Naveed; Aman, Afsheen; Silipo, Alba; Qader, Shah Ali Ul; Molinaro, Antonio

2014-01-01

An exopolysaccharide known as dextran was produced by Leuconostoc mesenteroides KIBGE-IB22 (wild) and L. mesenteroides KIBGE-IB22M20 (mutant). The structure was characterized using FTIR, (1)H NMR, (13)C NMR and 2D NMR spectroscopic techniques, whereas surface morphology was analyzed using SEM. A clear difference in the spectral chemical shift patterns was observed in both samples. All the spectral data indicated that the exopolysaccharide produced by KIBGE-IB22 is a mixture of two biopolymers. One was dextran in α-(1 → 6) configuration with a small proportion of α-(1 → 3) branching and the other was levan containing β-(2 → 6) fructan fructofuranosyl linkages. However, remarkably the mutant only produced dextran without any concomitant production of levan. Study suggested that the property of KIBGE-IB22M20, regarding improved production of high molecular weight dextran in a shorter period of fermentation time without any contamination of other exopolysaccharide, could be employed to make the downstream process more feasible and cost effective on large scale. Copyright © 2013 Elsevier Ltd. All rights reserved.

Dextran as a fast resorbable and mechanically stiff coating for flexible neural probes

NASA Astrophysics Data System (ADS)

Kil, D.; Brancato, L.; Puers, R.

2017-11-01

In this paper we report on the use of dextran as a temporary, fast dissolving stiff coating for flexible neural probes. Although polymer-based neural implants offer several advantages, compared to their rigid silicon counterparts, they pose significant challenges during implantation. Due to their extreme flexibility, they have the tendency to buckle under the axial load applied during insertion. The structural stiffness of the implants can be temporarily increased by applying a bioresorbable dextran coating which eases the penetration of neural tissue. For this application three types of dextran with different molecular weights are analysed. The dissolution rate of the coatings is reported as well as the increased bending stiffness resulting from the dextran coating of Parylene C neural probes. Based on these findings the dissolution rate can be linked to parameters such as molecular weight, coating thickness and the surface area exposed to the dissolution medium. The mechanical characterization yields information on how the structural stiffness of neural probes can be tuned by varying the dextran’s molecular weight and coating thickness.

Nonfouling Characteristics of Dextran-Containing Surfaces

PubMed Central

Martwiset, Surangkhana; Koh, Anna E.; Chen, Wei

2008-01-01

Hydroxyl groups in dextrans have been selectively oxidized to aldehyde groups by sodium periodate in a controlled fashion with percentage of conversion ranging from 6% to 100%. Dextrans (10 k, 70 k, 148 k, 500 k, and 2 000 kDa) and oxidized 10 k dextrans have been successfully grafted to functionalized silicon surfaces. The effect of molecular weight on protein adsorption is not nearly as striking as that of the extent of oxidation. When ∼ 25% of the hydroxyl groups have been converted to aldehyde groups, there is negligible protein adsorption on surfaces containing the oxidized polysaccharides. Conformations of grafted polymers depend strongly on their chemical structures, i.e. the relative amounts of –OH and –CHO groups. That the dependence of the chain conformation as well as the protein resistance on the balance of the hydrogen bond donors (-OH) and the acceptors (-OH and –CHO) implies the importance of chemical structure of surface molecules, specifically the interactions between surface and surrounding water molecules on protein adsorption. Oxidized dextrans are potential poly(ethylene glycol)-alternatives for nonfouling applications. PMID:16952261

Contributions of fluid convection and electrical migration to transport in cartilage: relevance to loading.

PubMed

Garcia, A M; Frank, E H; Grimshaw, P E; Grodzinsky, A J

1996-09-15

We have studied the contributions of diffusion, fluid flow and electrical migration to molecular transport through adult articular cartilage explants using neutral and charged solutes that were either radiolabeled (3H2O, [35S]sulfate, [3H]thymidine, [3H]raffinose, and a synthetic matrix metalloproteinase inhibitor) or fluorescently tagged (NSPA and Lissamine-dextran). In order to induce fluid flow within the cartilage matrix without mechanical deformation, electric current densities were applied across cartilage disks. These currents produced electroosmotic fluid velocities of 1-2 microns/s, magnitudes that have been reported to exist during joint loading in vivo. This fluid convection enhanced neutral solute flux relative to passive diffusion alone by a factor that increased with the size of the solute. While the enhancement factor for 3H2O was 2.3-fold, that for [3H]raffinose (594 Da) and similar sized neutral solutes was 10-fold, suggesting that the effect of fluid flow is important even for small solutes. The largest enhancement (25-fold) was seen for the neutral 10-kDa Lissamine-dextran, confirming that fluid convection is most important for large solutes. We also studied the electrophoretic contribution to solute flux, which is relevant to the presence of intratissue streaming potentials induced during loading in vivo. Using the negatively charged [35S]sulfate ion with a range of current densities, as much as a 10-fold enhancement in flux was observed. Values for the intrinsic transport properties of the solutes (e.g., diffusivity, electrical mobility, hydrodynamic hindrance factor) can be obtained from the data.

Reconciling Apparent Differences between the Responses of Humans and Other Animals to Crowding.

ERIC Educational Resources Information Center

Freedman, Jonathan L.

1979-01-01

In this article, research on nonhuman animals is reviewed to show that there is no discontinuity between humans and other animals. For both, high density is not necessarily harmful. Rather, the effect of high density depends on other factors in the situation. (Author)

Form and process in developing channels

Treesearch

Leslie M. Reid

1988-01-01

The topographic grain of a landscape is strongly influenced by the drainage density, and the drainage density reflects the balance between processes active on hillslopes and those in channels. This balance was explored by constructing sediment budgets for a sequence of stages in the development of a discontinuously incising channel.

Substructures of the mantle transition-zone discontinuities and compositional heterogeneities in the mid-mantle

NASA Astrophysics Data System (ADS)

Wei, S. S.; Shearer, P. M.

2017-12-01

The mantle transition-zone discontinuities are usually attributed to isochemical phase transformations of olivine and its high-pressure polymorphs. However, recent seismic observations have shown complexities in these discontinuities that cannot be explained by conventional models of thermal variations. Here we analyse SS precursor stacking results to investigate global mantle transition-zone properties. The precursor waveforms provide information on the seismic velocity and density profiles across and near the major mantle discontinuities. A sporadic low-velocity layer immediately above the 410-km discontinuity is observed worldwide, including East Asia, western North America, eastern South America, and 33-50% of the resolved Pacific Ocean. The 520-km discontinuity exhibits significant variations in its sharpness and depth, and occasionally appears to be split. Structures underlying the 660-km discontinuity show even larger complexities: a sub-discontinuity at 700-800 km depth is detected in some regions, of which some require a positive velocity gradient whereas others have a negative gradient. All of these lateral variations show no geographical correlation with discontinuity topography or tomographic models of seismic velocity, suggesting that they are not caused by regional thermal anomalies. Alternatively, our observations can be explained by compositional heterogeneities in the mid-mantle, including major minerals and volatile content, which may result in additional phase transformations and partial melting. These compositional heterogeneities should be taken into account in future geodynamic models of mantle convection and the deep water cycle.

Magnetic discontinuities in magnetohydrodynamic turbulence and in the solar wind.

PubMed

Zhdankin, Vladimir; Boldyrev, Stanislav; Mason, Joanne; Perez, Jean Carlos

2012-04-27

Recent measurements of solar wind turbulence report the presence of intermittent, exponentially distributed angular discontinuities in the magnetic field. In this Letter, we study whether such discontinuities can be produced by magnetohydrodynamic (MHD) turbulence. We detect the discontinuities by measuring the fluctuations of the magnetic field direction, Δθ, across fixed spatial increments Δx in direct numerical simulations of MHD turbulence with an imposed uniform guide field B(0). A large region of the probability density function (pdf) for Δθ is found to follow an exponential decay, proportional to exp(-Δθ/θ(*)), with characteristic angle θ(*)≈(14°)(b(rms)/B(0))(0.65) for a broad range of guide-field strengths. We find that discontinuities observed in the solar wind can be reproduced by MHD turbulence with reasonable ratios of b(rms)/B(0). We also observe an excess of small angular discontinuities when Δx becomes small, possibly indicating an increasing statistical significance of dissipation-scale structures. The structure of the pdf in this case closely resembles the two-population pdf seen in the solar wind. We thus propose that strong discontinuities are associated with inertial-range MHD turbulence, while weak discontinuities emerge from dissipation-range turbulence. In addition, we find that the structure functions of the magnetic field direction exhibit anomalous scaling exponents, which indicates the existence of intermittent structures.

Novel dextran derivatives with unconventional structure formed in an efficient one-pot reaction.

PubMed

Hotzel, Konrad; Heinze, Thomas

2016-11-03

An efficient one-pot synthesis of new dextran derivatives is described. The functional groups of β-alanine, i.e., the carboxyl- and amine group, are converted independently in one-step by iminium chloride to form products with a single substituent. The dextran N-[(dimethylamino)methylene]-β-alanine ester is formed selectively. The structure of the resulting polymers is unambiguously determined by means of NMR- and FTIR-spectroscopy and elemental analysis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Collider Bias in Trauma Comparative Effectiveness Research: The Stratification Blues for Systematic Reviews

DTIC Science & Technology

2015-05-01

of treatment and outcome, plagues randomised and observational trauma research. Of the seven trials of prehospital hypertonic saline in dextran (HSD...hypertonic saline in dextran (HSD) for hypovolaemic trauma patients [11–17] evaluated in systematic reviews [18–26], none found an overall between-group...containing either HSD (7.5% NaCl with 6% dextran -70) or the standard-of-care, i.e., lactated Ringer’s in the pilot [11]; normal saline (0.9%) in the pivotal

Intra-articular clearance of labeled dextrans from naive and arthritic rat knee joints.

PubMed

Mwangi, Timothy K; Berke, Ian M; Nieves, Eduardo H; Bell, Richard D; Adams, Samuel B; Setton, Lori A

2018-05-26

Determine the effects of arthritis on the trans-synovial clearance of small and large model compounds following local delivery to the knee joint in a rat model. Intra-articular delivery was studied in rat knee joints in an osteoarthritis model of joint instability (medial collateral ligament and meniscus transection model or MMT). Fluorescently-labeled 10 kDa or 500 kDa dextran was injected in the arthritic or unoperated control (naive) joints 3 weeks after surgical destabilization, and the temporal clearance pattern was evaluated via in vivo regional fluorescence imaging, dextran concentrations in plasma and draining lymph nodes, and by quantification of fluorescence in histological synovium sections. Together these data were used to evaluate the effect of osteoarthritis and solute size on the rate of drug clearance from the joint. Clearance of 10 kDa dextran from the joint space quantified using in vivo fluorescence imaging of the knee joint region was not significantly different between naive and MMT joints. In contrast, clearance of 500 kDa dextran was significantly reduced for MMT joints when compared to naive joints by fluorescence in vivo imaging. Drug accumulation in lymph nodes and plasma were lower for the 500 kDa dextran as compared to 10 kDa dextran, and lymph node levels were further reduced with the presence of osteoarthritis. Furthermore, synovium was significantly thicker in MMT joints than in naive joints and image analysis of joint tissue sections revealed different trans-synovial distributions of 10 and 500 kDa dextran. Large macromolecules were retained in the arthritic joint longer than in the healthy joint, while smaller molecules were cleared similarly in healthy and arthritic joints. In vivo fluorescence imaging, plasma and lymph node concentrations, and spatial distributions of drug fluorescence identified differences in higher molecular weight clearance between naive and arthritic disease states. Findings may relate to a thickening of synovium for joints with induced arthritis, and support the concept that intra-articular drug delivery effectiveness may vary with the state of joint pathology. Copyright © 2018 Elsevier B.V. All rights reserved.

An updated Lagrangian discontinuous Galerkin hydrodynamic method for gas dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Tong; Shashkov, Mikhail Jurievich; Morgan, Nathaniel Ray

Here, we present a new Lagrangian discontinuous Galerkin (DG) hydrodynamic method for gas dynamics. The new method evolves conserved unknowns in the current configuration, which obviates the Jacobi matrix that maps the element in a reference coordinate system or the initial coordinate system to the current configuration. The density, momentum, and total energy (ρ, ρu, E) are approximated with conservative higher-order Taylor expansions over the element and are limited toward a piecewise constant field near discontinuities using a limiter. Two new limiting methods are presented for enforcing the bounds on the primitive variables of density, velocity, and specific internal energymore » (ρ, u, e). The nodal velocity, and the corresponding forces, are calculated by solving an approximate Riemann problem at the element nodes. An explicit second-order method is used to temporally advance the solution. This new Lagrangian DG hydrodynamic method conserves mass, momentum, and total energy. 1D Cartesian coordinates test problem results are presented to demonstrate the accuracy and convergence order of the new DG method with the new limiters.« less

An updated Lagrangian discontinuous Galerkin hydrodynamic method for gas dynamics

DOE PAGES

Wu, Tong; Shashkov, Mikhail Jurievich; Morgan, Nathaniel Ray; ...

2018-04-09

Here, we present a new Lagrangian discontinuous Galerkin (DG) hydrodynamic method for gas dynamics. The new method evolves conserved unknowns in the current configuration, which obviates the Jacobi matrix that maps the element in a reference coordinate system or the initial coordinate system to the current configuration. The density, momentum, and total energy (ρ, ρu, E) are approximated with conservative higher-order Taylor expansions over the element and are limited toward a piecewise constant field near discontinuities using a limiter. Two new limiting methods are presented for enforcing the bounds on the primitive variables of density, velocity, and specific internal energymore » (ρ, u, e). The nodal velocity, and the corresponding forces, are calculated by solving an approximate Riemann problem at the element nodes. An explicit second-order method is used to temporally advance the solution. This new Lagrangian DG hydrodynamic method conserves mass, momentum, and total energy. 1D Cartesian coordinates test problem results are presented to demonstrate the accuracy and convergence order of the new DG method with the new limiters.« less

Communication: Two types of flat-planes conditions in density functional theory.

PubMed

Yang, Xiaotian Derrick; Patel, Anand H G; Miranda-Quintana, Ramón Alain; Heidar-Zadeh, Farnaz; González-Espinoza, Cristina E; Ayers, Paul W

2016-07-21

Using results from atomic spectroscopy, we show that there are two types of flat-planes conditions. The first type of flat-planes condition occurs when the energy as a function of the number of electrons of each spin, Nα and Nβ, has a derivative discontinuity on a line segment where the number of electrons, Nα + Nβ, is an integer. The second type of flat-planes condition occurs when the energy has a derivative discontinuity on a line segment where the spin polarization, Nα - Nβ, is an integer, but does not have a discontinuity associated with an integer number of electrons. Type 2 flat planes are rare-we observed just 15 type 2 flat-planes conditions out of the 4884 cases we tested-but their mere existence has implications for the design of exchange-correlation energy density functionals. To facilitate the development of functionals that have the correct behavior with respect to both fractional number of electrons and fractional spin polarization, we present a dataset for the chromium atom and its ions that can be used to test new functionals.

Synthesis and chromatographic characterization of dextran-coated zirconia high-performance liquid chromatographic stationary phases.

PubMed

Dunlap, C J; Carr, P W

1996-10-11

Porous zirconia particles made by the oil emulsion (OE) method and the polymerization-induced colloid aggregation (PICA) method have been coated with a small, carboxymethylated (approximately 5%) dextran polymer and crosslinked in place. The parameters of the coating process (dextran concentration, adsorption time and crosslinker concentration) have all been examined and an optimum value for each determined. The coated and uncoated materials were characterized by nitrogen sorptometry and size-exclusion chromatography (SEC) using solutes (polystyrenes and dextrans) of well-defined molecular masses. Nitrogen sorptometry results show that the PICA material has a much lower pore volume and smaller pore diameter than do the OE materials. Despite this, the elution volumes of the SEC probes change very little upon polymer coating the PICA material while the OE material shows a very large change upon coating.

Anticancer drug-based multifunctional nanogels through self-assembly of dextran-curcumin conjugates toward cancer theranostics.

PubMed

Nagahama, Koji; Sano, Yoshinori; Kumano, Takayuki

2015-06-15

Curcumin (CCM) has been received much attention in cancer theranostics because CCM exhibits both anticancer activity and strong fluorescence available for bio-imaging. However, CCM has never been utilized in clinical mainly due to its extremely low water solubility and its low cellular uptake into cancer cells. We fabricated novel CCM-based biodegradable nanoparticles through self-assembly of amphiphilic dextran-CCM conjugates. Significantly high CCM loading contents in the nanoparticles and the high water solubility were achieved. Importantly, the dextran-CCMs nanoparticles were effectively delivered into HeLa cells and exhibited strong fluorescence available for live-cell imaging, although the nanoparticles were not delivered into normal cells. Thus, the dextran-CCMs nanoparticles could be a promising for creation of novel CCM-based cancer theranostics with high efficacy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Recombinant domains III of Tick-Borne Encephalitis Virus envelope protein in combination with dextran and CpGs induce immune response and partial protectiveness against TBE virus infection in mice.

PubMed

Ershova, Anna S; Gra, Olga A; Lyaschuk, Alexander M; Grunina, Tatyana M; Tkachuk, Artem P; Bartov, Mikhail S; Savina, Darya M; Sergienko, Olga V; Galushkina, Zoya M; Gudov, Vladimir P; Kozlovskaya, Liubov I; Kholodilov, Ivan S; Gmyl, Larissa V; Karganova, Galina G; Lunin, Vladimir G; Karyagina, Anna S; Gintsburg, Alexander L

2016-10-07

E protein of tick-borne encephalitis virus (TBEV) and other flaviviruses is located on the surface of the viral particle. Domain III of this protein seems to be a promising component of subunit vaccines for prophylaxis of TBE and kits for diagnostics of TBEV. Three variants of recombinant TBEV E protein domain III of European, Siberian and Far Eastern subtypes fused with dextran-binding domain of Leuconostoc citreum KM20 were expressed in E. coli and purified. The native structure of domain III was confirmed by ELISA antibody kit and sera of patients with tick-borne encephalitis. Immunogenic and protective properties of the preparation comprising these recombinant proteins immobilized on a dextran carrier with CpG oligonucleotides as an adjuvant were investigated on the mice model. All 3 variants of recombinant proteins immobilized on dextran demonstrate specific interaction with antibodies from the sera of TBE patients. Thus, constructed recombinant proteins seem to be promising for TBE diagnostics. The formulation comprising the 3 variants of recombinant antigens immobilized on dextran and CpG oligonucleotides, induces the production of neutralizing antibodies against TBEV of different subtypes and demonstrates partial protectivity against TBEV infection. Studied proteins interact with the sera of TBE patients, and, in combination with dextran and CPGs, demonstrate immunogenicity and limited protectivity on mice compared with reference "Tick-E-Vac" vaccine.

In vitro evaluation of the effect of haemodilution with dextran 40 on coagulation profile as measured by thromboelastometry and multiple electrode aggregometry.

PubMed

Kam, Pca; Liou, Jpc; Yang, Kxf

2017-09-01

We evaluated the effects of haemodilution with either dextran 40 or 0.9% normal saline on coagulation in vitro using rotational thromboelastometry (ROTEM®, Pentapharm Co., Munich, Germany) and multiple electrode aggregometry (Multiplate® Platelet Function Analyser, Dynabyte, Munich, Germany). Venous blood samples obtained from 20 healthy volunteers were diluted in vitro with dextran 40 or normal saline by 5%, 10% and 15%. Fibrinogen concentration, ROTEM-EXTEM® (screening test for the extrinsic coagulation pathway), FIBTEM® (an EXTEM-based assay of the fibrin component of clot) parameters including coagulation time, clot formation time, alpha angle, maximum clot firmness and lysis index were measured in the undiluted sample and at each level of haemodilution. Dextran 40 at 15% haemodilution significantly prolonged coagulation time, clot formation time and significantly decreased the alpha angle and maximal clot firmness (EXTEM amplitude at five minutes [A5] and ten minutes [A10]) compared with normal saline. The FIBTEM assay (maximal clot firmness and FIBTEM A5 and A10) showed a marked decrease in maximal clot firmness at all dilutions suggesting impaired fibrinogen activity and a risk of bleeding. Multiple electrode aggregometry did not demonstrate any platelet dysfunction. Haemodilution with dextran 40 causes significant impairment in clot formation and strength compared to saline haemodilution and undiluted blood. At the levels of in vitro haemodilution designed to reflect the clinical use of dextran infusions, no significant fibrinolysis or platelet inhibition was observed.

Amphipathic dextran-doxorubicin prodrug micelles for solid tumor therapy.

PubMed

Jin, Rong; Guo, Xuelian; Dong, Lingli; Xie, Enyuan; Cao, Aoneng

2017-10-01

A group of micelles self-assembled from deoxycholic acid-doxorubicin-conjugated dextran (denoted as Dex-DCA-DOX) prodrugs were designed and prepared for pH-triggered drug release and cancer chemotherapy. These prodrugs could be successfully produced by chemically coupling hydrophobic deoxycholic acid (DCA) to dextran hydrazine (denoted as Dex-NHNH 2 ) and hydrazone linker formation between doxorubicin (DOX) and Dex-NHNH 2 . These Dex-DCA-DOX prodrugs self-assembled to form micelles under physiological conditions with varied particle sizes depending on molecular weight of dextran, degree of substitution (DS) of DCA and DOX. After optimization, Dex10k-DCA9-DOX5.5 conjugate comprising dextran of 10kDa, DCA of DS 9 and DOX loading content of 5.5wt%, formed the micelles with the smallest size (110nm). These prodrug micelles could slowly liberate DOX under physiological conditions but efficiently released the drug at an acidified endosomal pH by the hydrolysis of acid-labile hydrazone linker. In vitro cytotoxicity experiment indicated that Dex10k-DCA9-DOX5.5 micelles exerted marked antitumor activity against MCF-7 and SKOV-3 cancer cells. Besides, intravenous administration of the micelles afforded growth inhibition of SKOV-3 tumor bearing in nude mice at a dosage of 2.5mg per kg with anti-cancer efficacy comparable to free DOX-chemotherapy but low systemic toxicity. This study highlights the feasibility of bio-safe and efficient dextran-based prodrug micelles designed for cancer chemotherapy. Copyright © 2017 Elsevier B.V. All rights reserved.

Immune-mediated pure red cell aplasia in a domestic ferret.

PubMed

Malka, Shachar; Hawkins, Michelle G; Zabolotzky, Shanon M; Mitchell, Elizabeth B; Owens, Sean D

2010-09-15

An 8-month-old spayed female domestic ferret (Mustela putorius furo) was referred for examination to determine the cause of lethargy and severe anemia. Initial examination revealed that the ferret was lethargic but with appropriate mentation. The only other abnormal findings were severe pallor of the mucous membranes, nasal planum, and skin and a PCV of 8%. Pure red cell aplasia (PRCA) was diagnosed on the basis of cytologic evaluation of a bone marrow biopsy specimen. Medical treatment included blood transfusions, IM administration of iron dextran, oral administration of antimicrobials and gastrointestinal tract protectants, and SC administration of erythropoietin. Once PRCA was diagnosed, the ferret was orally administered prednisone, cyclosporine, and azathioprine. Nine months after onset of treatment, the PRCA was in remission and the ferret was doing well. Immunosuppressive treatment was discontinued at 14 months after onset of treatment, and 36 months after initial examination, the ferret appeared to be healthy. It is important that PRCA be considered as a differential diagnosis for a ferret with severe anemia. Prolonged immunosuppressive treatment was successful in the ferret described here.

Divergence of activity expansions: Is it actually a problem?

NASA Astrophysics Data System (ADS)

Ushcats, M. V.; Bulavin, L. A.; Sysoev, V. M.; Ushcats, S. Yu.

2017-12-01

For realistic interaction models, which include both molecular attraction and repulsion (e.g., Lennard-Jones, modified Lennard-Jones, Morse, and square-well potentials), the asymptotic behavior of the virial expansions for pressure and density in powers of activity has been studied taking power terms of high orders into account on the basis of the known finite-order irreducible integrals as well as the recent approximations of infinite irreducible series. Even in the divergence region (at subcritical temperatures), this behavior stays thermodynamically adequate (in contrast to the behavior of the virial equation of state with the same set of irreducible integrals) and corresponds to the beginning of the first-order phase transition: the divergence yields the jump (discontinuity) in density at constant pressure and chemical potential. In general, it provides a statistical explanation of the condensation phenomenon, but for liquid or solid states, the physically proper description (which can turn the infinite discontinuity into a finite jump of density) still needs further study of high-order cluster integrals and, especially, their real dependence on the system volume (density).

Anesthetic duration of lidocaine with 10% dextran is comparable to lidocaine with 1:160 000 epinephrine after intraosseous injection in the rabbit.

PubMed

Ito, Emiko; Ichinohe, Tatsuya; Shibukawa, Yoshiyuki; Aida, Hidetaka; Kaneko, Yuzuru

2007-09-01

To compare the effects of 10% dextran and epinephrine on intraosseous injection with lidocaine in rabbits. Twenty male Japanese white rabbits were used. The effect of intraosseous injection was evaluated using an electromyogram (EMG) of the digastric muscle after electrical pulp stimulation. Two percent lidocaine alone (L), 2% lidocaine containing 1:80000 epinephrine (LE8), 2% lidocaine containing 1:160 000 epinephrine (LE16), and 2% lidocaine containing 10% dextran (LD) were tested. Electromyogram recordings were repeated before and 30 seconds, 1, 2, 3, 4, 5, 7, 10, 12, 15, and 20 minutes after the intraosseous injection. Thereafter, recordings were repeated every 5 minutes until the EMG recovered to the control value. There was no difference in the onset time between the 4 groups. The order of the duration of maximum effect was LE8 >LE16 = LD >or=L. The order of the duration of anesthesia was LE8 >LE16 = LD >L. Ten percent dextran potentiates local anesthetic effects of 2% lidocaine in intraosseous injection. The potency of 10% dextran is comparable to 1:160 000 epinephrine.

One pot light assisted green synthesis, storage and antimicrobial activity of dextran stabilized silver nanoparticles.

PubMed

Hussain, Muhammad Ajaz; Shah, Abdullah; Jantan, Ibrahim; Tahir, Muhammad Nawaz; Shah, Muhammad Raza; Ahmed, Riaz; Bukhari, Syed Nasir Abbas

2014-12-03

Green synthesis of nanomaterials finds the edge over chemical methods due to its environmental compatibility. Herein, we report green synthesis of silver nanoparticles (Ag NPs) mediated with dextran. Dextran was used as a stabilizer and capping agent to synthesize Ag NPs using silver nitrate (AgNO3) under diffused sunlight conditions. UV-vis spectra of as synthesized Ag nanoparticles showed characteristic surface plasmon band in the range from ~405-452 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies showed spherical Ag NPs in the size regime of ~50-70 nm. Face centered cubic lattice of Ag NPs was confirmed by powder X-ray diffraction (PXRD). FT-IR spectroscopy confirmed that dextran not only acts as reducing agent but also functionalizes the surfaces of Ag NPs to make very stable dispersions. Moreover, on drying, the solution of dextran stabilized Ag NPs resulted in the formation of thin films which were found stable over months with no change in the plasmon band of pristine Ag NPs. The antimicrobial assay of the as synthesized Ag NPs showed remarkable activity. Being significantly active against microbes, the Ag NPs can be explored for antimicrobial medical devices.

The complex fluid dynamics of simple diffusion

NASA Astrophysics Data System (ADS)

Vold, Erik

2017-11-01

Diffusion as the mass transport process responsible for mixing fluids at the atomic level is often underestimated in its complexity. An initial discontinuity between two species of different atomic masses exhibits a mass density discontinuity under isothermal pressure equilibrium implying equal species molar densities. The self-consistent kinetic transport processes across such an interface leads to a zero sum of mass flux relative to the center of mass and so diffusion alone cannot relax an initially stationary mass discontinuity nor broaden the density profile at the interface. The diffusive mixing leads to a molar imbalance which drives a center of mass velocity which moves the heavier species toward the lighter species leading to the interfacial density relaxation. Simultaneously, the species non-zero molar flux modifies the pressure profile in a transient wave and in a local perturbation. The resulting center of mass velocity has two components; one, associated with the divergence of the flow, persists in the diffusive mixing region throughout the diffusive mixing process, and two, travelling waves at the front of the pressure perturbations propagate away from the mixing region. The momentum in these waves is necessary to maintain momentum conservation in the center of mass frame. Thus, in a number of ways, the diffusive mixing provides feedback into the small scale advective motions. Numerical methods which diffuse all species assuming P-T equilibrium may not recover the subtle dynamics of mass transport at an interface. Work performed by the LANS, LLC, under USDOE Contract No. DE-AC52-06NA25396, funded by the (ASC) Program.

Acute and Subacute Toxicity of 7.5% Hypertonic Saline/6% Dextran-70 (HSD) in Dogs

DTIC Science & Technology

1991-11-18

7.5% hypertonic saline/6% Dextran-70 in dogs . 1. Serum immunoglobulin and complement responses. J. Appl. Toxicol., in press. 26. G.M. Zaucha, D.F...Dextran-70 (HSD) in Dogs . I PuoiL UM. aucna, DW. Korte, Jr., CE. Wade 13a. TYPE OF REPORT 113b. TIME COVERED 114. DATE OF REPORT (Year, Month, Day) 15...dehydrogenase dogs . 19. ABSTRACT (Continue on reverse if necessary and identify by block number) HSD is currently being evaluated in our laboratory as

Translational Diffusion of Macromolecule-sized Solutes in Cytoplasm and Nucleus

PubMed Central

Seksek, Olivier; Biwersi, Joachim; Verkman, A.S.

1997-01-01

Fluorescence recovery after photobleaching (FRAP) was used to quantify the translational diffusion of microinjected FITC-dextrans and Ficolls in the cytoplasm and nucleus of MDCK epithelial cells and Swiss 3T3 fibroblasts. Absolute diffusion coefficients (D) were measured using a microsecond-resolution FRAP apparatus and solution standards. In aqueous media (viscosity 1 cP), D for the FITC-dextrans decreased from 75 to 8.4 × 10−7 cm2/s with increasing dextran size (4–2,000 kD). D in cytoplasm relative to that in water (D/Do) was 0.26 ± 0.01 (MDCK) and 0.27 ± 0.01 (fibroblasts), and independent of FITC-dextran and Ficoll size (gyration radii [RG] 40–300 Å). The fraction of mobile FITC-dextran molecules (fmob), determined by the extent of fluorescence recovery after spot photobleaching, was >0.75 for RG < 200 Å, but decreased to <0.5 for RG > 300 Å. The independence of D/Do on FITC-dextran and Ficoll size does not support the concept of solute “sieving” (size-dependent diffusion) in cytoplasm. Photobleaching measurements using different spot diameters (1.5–4 μm) gave similar D/Do, indicating that microcompartments, if present, are of submicron size. Measurements of D/Do and fmob in concentrated dextran solutions, as well as in swollen and shrunken cells, suggested that the low fmob for very large macromolecules might be related to restrictions imposed by immobile obstacles (such as microcompartments) or to anomalous diffusion (such as percolation). In nucleus, D/Do was 0.25 ± 0.02 (MDCK) and 0.27 ± 0.03 (fibroblasts), and independent of solute size (RG 40–300 Å). Our results indicate relatively free and rapid diffusion of macromolecule-sized solutes up to approximately 500 kD in cytoplasm and nucleus. PMID:9214387

Effects of controlled discontinuation of long-term used antipsychotics on weight and metabolic parameters in individuals with intellectual disability.

PubMed

de Kuijper, Gerda; Mulder, Hans; Evenhuis, Heleen; Visser, Frank; Hoekstra, Pieter J

2013-08-01

Antipsychotics are frequently prescribed agents in individuals with intellectual disability, often for behavioral symptoms. Efficacy of antipsychotics for this is ambiguous, so discontinuation should be considered. Weight gain and metabolic dysregulation are well-known adverse effects of antipsychotics which increase the risk of the metabolic syndrome. We performed a discontinuation study in 99 adults with intellectual disability, living in residential facilities who used antipsychotics for behavioral symptoms for more than 1 year. The aim of the present study was to investigate the effects of discontinuation of long-term used antipsychotics on weight, body mass index (BMI), and parameters of the metabolic syndrome and to investigate the influence of genetic polymorphisms and medication factors on these outcomes. Discontinuation of antipsychotics led to a mean decrease of 4 cm waist circumference, of 3.5 kg weight, 1.4 kg/m2 BMI, and 7.1 mm Hg systolic blood pressure. In those participants who had not completely discontinued use of antipsychotics we found a decrease in weight and BMI and an increase in fasting glucose. The presence of the C-allele of serotonin 5-hydroxytryptamine receptor polymorphism rs141334 was associated with higher waist circumference and higher plasma levels of triglycerides and lower levels of high-density lipoprotein. Achievement of complete discontinuation predicted a larger decrease in waist circumference and BMI. In conclusion, results of the study show the beneficial effects of discontinuation of long-term used antipsychotics on metabolic outcomes.

Exopolysaccharide hydrogels for corrosion inhibition

USDA-ARS?s Scientific Manuscript database

Exopolysaccharide production by micro-organisms have several industrial applications in food, pharmaceuticals, or other industries. Lactic acid bacteria such as Leuconostoc mesenteroides (LM) are endemic to the environment and produce extracellular polymeric glucans such as dextran. Dextrans cause s...

Effect of different culture media and deswelling agents on survival of human corneal endothelial and epithelial cells in vitro.

PubMed

Valtink, Monika; Donath, Patricia; Engelmann, Katrin; Knels, Lilla

2016-02-01

To examine the effects of media and deswelling agents on human corneal endothelial and epithelial cell viability using a previously developed screening system. The human corneal endothelial cell line HCEC-12 and the human corneal epithelial cell line HCE-T were cultured in four different corneal organ culture media (serum-supplemented: MEM +2 % FCS, CorneaMax®/CorneaJet®, serum-free: Human Endothelial-SFM, Stemalpha-2 and -3) with and without 6 % dextran T500 or 7 % HES 130/0.4. Standard growth media F99HCEC and DMEM/F12HCE-T served as controls. In additional controls, the stress inducers staurosporine or hydrogen peroxide were added. After 5 days in the test media, cell viability was assessed by flow cytometrically quantifying apoptotic and necrotic cells (sub-G1 DNA content, vital staining with YO-PRO-1® and propidium iodide) and intracellular reactive oxygen species (ROS). The MEM-based media were unable to support HCEC-12 and HCE-T survival under stress conditions, resulting in significantly increased numbers of apoptotic and necrotic cells. HCEC-12 survival was markedly improved in SFM-based media even under staurosporine or hydrogen peroxide. Likewise, HCE-T survival was improved in SFM with or without dextran. The media CorneaMax®, CorneaJet®, and CorneaMax® with HES supported HCEC-12 survival better than MEM-based media, but less well than SFM-based media. HCE-T viability was also supported by CorneaJet®, but not by CorneaMax® with or without HES. Stemalpha-based media were not suitable for maintaining viability of HCEC-12 or HCE-T in the applied cell culture system. The use of serum-supplemented MEM-based media for corneal organ culture should be discontinued in favour of serum-free media like SFM.

How the 410-km Discontinuity Reflects Mantle Water Content: Constraints from High-Pressure Experiments on Wadsleyite Single-Crystal Elasticity

NASA Astrophysics Data System (ADS)

Buchen, J.; Marquardt, H.; Boffa Ballaran, T.; Kawazoe, T.; Speziale, S.; Kurnosov, A.

2017-12-01

The olivine-wadsleyite phase transition gives rise to a seismic discontinuity at 410 km depth. By incorporating hydroxyl groups in its crystal structure, wadsleyite can store large amounts of water in the shallow transition zone. The velocity contrast across the 410-km seismic discontinuity has been widely used to deduce mantle mineralogy including estimates of the water content at depth. To interpret seismic observations in terms of mantle mineralogy and deep water cycling, the elastic properties of wadsleyite need to be determined at relevant pressures and temperatures. We performed simultaneous sound wave velocity and density measurements on iron-bearing wadsleyite single crystals at high pressures and first experiments at combined high pressures and high temperatures. When compared with previous work on hydrous iron-bearing wadsleyite with identical Fe/(Mg+Fe) ratio of 0.11, our results show that hydration of iron-bearing wadsleyite reduces the sound wave velocities at low pressures. At high pressures, in contrast, P-wave and S-wave velocities of hydrous and anhydrous iron-bearing wadsleyite cross over and become seismically indistinguishable at conditions of the transition zone. As a consequence, hydrated regions in the shallow transition zone cannot be detected by seismic tomography. Motivated by our experimental results, we modeled velocity, density, and acoustic impedance contrasts across the 410-km seismic discontinuity and found velocity contrasts to vary only slightly with hydration. Instead, we show that the impedance contrast caused by the olivine-wadsleyite phase transition and hence the reflectivity of the 410-km seismic discontinuity are more sensitive to hydration. Our findings give important constraints on the interpretation of seismic observations aiming to trace Earth's deep water cycle.

A new limiting procedure for discontinuous Galerkin methods applied to compressible multiphase flows with shocks and interfaces

NASA Astrophysics Data System (ADS)

Henry de Frahan, Marc T.; Varadan, Sreenivas; Johnsen, Eric

2015-01-01

Although the Discontinuous Galerkin (DG) method has seen widespread use for compressible flow problems in a single fluid with constant material properties, it has yet to be implemented in a consistent fashion for compressible multiphase flows with shocks and interfaces. Specifically, it is challenging to design a scheme that meets the following requirements: conservation, high-order accuracy in smooth regions and non-oscillatory behavior at discontinuities (in particular, material interfaces). Following the interface-capturing approach of Abgrall [1], we model flows of multiple fluid components or phases using a single equation of state with variable material properties; discontinuities in these properties correspond to interfaces. To represent compressible phenomena in solids, liquids, and gases, we present our analysis for equations of state belonging to the Mie-Grüneisen family. Within the DG framework, we propose a conservative, high-order accurate, and non-oscillatory limiting procedure, verified with simple multifluid and multiphase problems. We show analytically that two key elements are required to prevent spurious pressure oscillations at interfaces and maintain conservation: (i) the transport equation(s) describing the material properties must be solved in a non-conservative weak form, and (ii) the suitable variables must be limited (density, momentum, pressure, and appropriate properties entering the equation of state), coupled with a consistent reconstruction of the energy. Further, we introduce a physics-based discontinuity sensor to apply limiting in a solution-adaptive fashion. We verify this approach with one- and two-dimensional problems with shocks and interfaces, including high pressure and density ratios, for fluids obeying different equations of state to illustrate the robustness and versatility of the method. The algorithm is implemented on parallel graphics processing units (GPU) to achieve high speedup.

Functional analysis of truncated and site-directed mutagenesis dextransucrases to produce different type dextrans.

PubMed

Wang, Chao; Zhang, Hong-Bin; Li, Meng-Qi; Hu, Xue-Qin; Li, Yao

2017-07-01

Dextrans with distinct molecular size and structure are increasingly being used in the food and pharmaceutical industries. Dextran is produced by dextransucrase (DSR, EC2.4.5.1), which is produced by Leuconostoc mesenteroides. DSR belongs to glycosyl hydrolase family (GH70) and synthesizes branched α-glucan (dextran) with both 5% α(1-3) and 95% α(1-6) glycosidic linkages. The DSR gene dex-YG (Genebank, Accession No. DQ345760) was cloned from the wild strain Leuconostoc mesenteroides 0326. This study generated a series of C-terminally truncated variants of dextransucrase and substituting the amino-acid residues in the active site of DSR. With shorter length of DSR, its polysaccharide-synthesizing capability was impaired heavily, whereas oligosaccharide (acting as prebiotics)-synthesizing capability increased significantly, efficiently producing special sizes of dextran. All truncated mutant enzymes were active. Results demonstrated that the catalytic domain dextransucrase was likely in 800 aa or less. Based on the three-dimensional structure model of dextransucrase built through homology modeling methods, the DSR and its mutants with the acceptor substrate of maltose and donor substrate of sucrose were studied by molecular-docking method. Substituting these amino-acid residues significantly affected enzyme activities. Compared with the wild-type dextran, mutant enzymes catalyzed the synthesis of a-glucan with 1-9% α(1-3) and 90-98% α(1-6) branching linkages. Some mutants introduced a small amount of α(1-4) linkages and α(1-2) linkages. This strategy can be effectively used for the rational protein design of dextransucrase. Copyright © 2017 Elsevier Inc. All rights reserved.

Density-Functional Theory with Optimized Effective Potential and Self-Interaction Correction for the Double Ionization of He and Be Atoms

NASA Astrophysics Data System (ADS)

Heslar, John; Telnov, Dmitry; Chu, Shih-I.

2012-06-01

We present a self-interaction-free (SIC) time-dependent density-functional theory (TDDFT) for the treatment of double ionization processes of many-electron systems. The method is based on the Krieger-Li-Iafrate (KLI) treatment of the optimized effective potential (OEP) theory and the incorporation of an explicit self-interaction correction (SIC) term. In the framework of the time-dependent density functional theory, we have performed 3D calculations of double ionization of He and Be atoms by strong near-infrared laser fields. We make use of the exchange-correlation potential with the integer discontinuity which improves the description of the double ionization process. We found that proper description of the double ionization requires the TDDFT exchange-correlation potential with the discontinuity with respect to the variation of the spin particle numbers (SPN) only. The results for the intensity-dependent probabilities of single and double ionization are presented and reproduce the famous ``knee'' structure.

Comparing the Richtmyer-Meshkov instability of thermal and ion-species interfaces in two-fluid plasmas

NASA Astrophysics Data System (ADS)

Wheatley, Vincent; Bond, Daryl; Li, Yuan; Samtaney, Ravi; Pullin, Dale

2017-11-01

The Richtmyer-Meshkov instability (RMI) of a shock accelerated perturbed density interface is important in both inertial confinement fusion and astrophysics, where the materials involved are typically in the plasma state. Initial density interfaces can be due to either temperature or ion-species discontinuities. If the Atwood number of the interfaces and specific heat ratios of the fluids are matched, these two cases behave similarly when modeled using the equations of either hydrodynamics or magnetohydrodynamics. In the two-fluid ion-electron plasma model, however, there is a significant difference between them: In the thermal interface case, there is a discontinuity in electron density that is also subject to the RMI, while for the ion-species interface case there is not. It will be shown via ideal two-fluid plasma simulations that this causes substantial differences in the dynamics of the flow between the two cases. This work was partially supported by the KAUST Office of Sponsored Research under Award URF/1/2162-01.

Time-dependent uptake and trafficking of vesicles capturing extracellular S100B in cultured rat astrocytes.

PubMed

Lasič, Eva; Galland, Fabiana; Vardjan, Nina; Šribar, Jernej; Križaj, Igor; Leite, Marina Concli; Zorec, Robert; Stenovec, Matjaž

2016-10-01

Astrocytes, the most heterogeneous glial cells in the central nervous system, contribute to brain homeostasis, by regulating a myriad of functions, including the clearance of extracellular debris. When cells are damaged, cytoplasmic proteins may exit into the extracellular space. One such protein is S100B, which may exert toxic effects on neighboring cells unless it is removed from the extracellular space, but the mechanisms of this clearance are poorly understood. By using time-lapse confocal microscopy and fluorescently labeled S100B (S100B-Alexa 488 ) and fluorescent dextran (Dextran 546 ), a fluid phase uptake marker, we examined the uptake of fluorescently labeled S100B-Alexa 488 from extracellular space and monitored trafficking of vesicles that internalized S100B-Alexa 488 . Initially, S100B-Alexa 488 and Dextran 546 internalized with distinct rates into different endocytotic vesicles; S100B-Alexa 488 internalized into smaller vesicles than Dextran 546 . At a later stage, S100B-Alexa 488 -positive vesicles substantially co-localized with Dextran 546 -positive endolysosomes and with acidic LysoTracker-positive vesicles. Cell treatment with anti-receptor for advanced glycation end products (RAGE) antibody, which binds to RAGE, a 'scavenger receptor', partially inhibited uptake of S100B-Alexa 488 , but not of Dextran 546 . The dynamin inhibitor dynole 34-2 inhibited internalization of both fluorescent probes. Directional mobility of S100B-Alexa 488 -positive vesicles increased over time and was inhibited by ATP stimulation, an agent that increases cytosolic free calcium concentration ([Ca 2+ ] i ). We conclude that astrocytes exhibit RAGE- and dynamin-dependent vesicular mechanism to efficiently remove S100B from the extracellular space. If a similar process occurs in vivo, astroglia may mitigate the toxic effects of extracellular S100B by this process under pathophysiologic conditions. This study reveals the vesicular clearance mechanism of extracellular S100B in astrocytes. Initially, fluorescent S100B internalizes into smaller endocytotic vesicles than dextran molecules. At a later stage, both probes co-localize within endolysosomes. S100B internalization is both dynamin- and RAGE-dependent, whereas dextran internalization is dependent on dynamin. Vesicle internalization likely mitigates the toxic effects of extracellular S100B and other waste products. © 2016 International Society for Neurochemistry.

Evidence for presynaptically silent synapses in the immature hippocampus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoon, Jae Young; Choi, Sukwoo

Silent synapses show NMDA receptor (NMDAR)-mediated synaptic responses, but not AMPAR-mediated synaptic responses. A prevailing hypothesis states that silent synapses contain NMDARs, but not AMPARs. However, alternative presynaptic hypotheses, according to which AMPARs are present at silent synapses, have been proposed; silent synapses show slow glutamate release via a fusion pore, and glutamate spillover from the neighboring synaptic terminals. Consistent with these presynaptic hypotheses, the peak glutamate concentrations at silent synapses have been estimated to be ≪170 μM, much lower than those seen at functional synapses. Glutamate transients predicted based on the two presynaptic mechanisms have been shown to activate onlymore » high-affinity NMDARs, but not low-affinity AMPARs. Interestingly, a previous study has developed a new approach to distinguish between the two presynaptic mechanisms using dextran, an inert macromolecule that reduces the diffusivity of released glutamate: postsynaptic responses through the fusion pore mechanism, but not through the spillover mechanism, are potentiated by reduced glutamate diffusivity. Therefore, we reasoned that if the fusion pore mechanism underlies silent synapses, dextran application would reveal AMPAR-mediated synaptic responses at silent synapses. In the present study, we recorded AMPAR-mediated synaptic responses at the CA3-CA1 synapses in neonatal rats in the presence of blockers for NMDARs and GABAARs. Bath application of dextran revealed synaptic responses at silent synapses. GYKI53655, a selective AMPAR-antagonist, completely inhibited the unsilenced synaptic responses, indicating that the unsilenced synaptic responses are mediated by AMPARs. The dextran-mediated reduction in glutamate diffusivity would also lead to the activation of metabotropic glutamate receptors (mGluRs), which might induce unsilencing via the activation of unknown intracellular signaling. Hence, we determined whether mGluR-blockers alter the dextran-induced unsilencing. However, dextran application continued to produce significant synaptic unsilencing in the presence of a cocktail of the blockers for all subtypes of mGluRs. Our findings provide evidence that slowed glutamate diffusion produces synaptic unsilencing by enhancing the peak glutamate occupancy of pre-existing AMPARs, supporting the fusion pore mechanism of silent synapses. - Highlights: • Slowed glutamate diffusion by dextran reveals synaptic responses at silent synapses. • Unsilenced synaptic responses are mediated by AMPA receptors. • Dextran-induced unsilencing is independent of metabotropic glutamate receptors.« less

Densities and abundances of hot cometary ions in the coma of P/Halley

NASA Technical Reports Server (NTRS)

Neugebauer, M.; Goldstein, R.; Goldstein, B. E.; Fuselier, S. A.; Balsiger, H.; Ip, W.-H.

1991-01-01

On its flight by P/Halley, the Giotto spacecraft carried a High Energy Range Spectrometer (HERS) for measuring the properties of cometary ions picked up by the solar wind in the nearly collisionless regions of the coma. Preliminary estimates of the ion densities observed by HERS were reevaluated and extended; density profiles along the Giotto trajectory are presented for 13 values of ion mass/charge. Comparison with the physical-chemical model of the interaction of sunlight and the solar wind with the comet by other researchers reveals that, with the exception of protons and H2(+), all ion densities were at least an order of magnitude higher than predicted. The high ion densities cannot be explained on the basis of compression of the plasma, but require additional or stronger ionization mechanisms. Ratios of the densities of different ion species reveal an overabundance of carbonaceous material and an underabundance of H2(+) compared to the predictions of the Schmidt. While the densities of solar wind ions (H(+) and He(++)) changed sharply across a magnetic discontinuity located 1.35(10)(exp 5) km from the comet, this feature, which has been called both the 'cometopause' and the 'magnetic pileup boundary' was barely distinguishable in the density profiles of hot cometary ions. This result is consistent with the interpretation that the magnetic pileup boundary detected by Giotto was caused by a discontinuity in the solar wind and is not an intrinsic feature of the interaction of the solar wind with an active comet.

Self-Assembled Modified Soy Protein/Dextran Nanogel Induced by Ultrasonication as a Delivery Vehicle for Riboflavin.

PubMed

Jin, Bei; Zhou, Xiaosong; Li, Xiangzhong; Lin, Weiqin; Chen, Guangbin; Qiu, Riji

2016-03-15

A simple and green approach was developed to produce a novel nanogel via self-assembly of modified soy protein and dextran, to efficiently deliver riboflavin. First, modified soy protein was prepared by heating denaturation at 60 °C for 30 min or Alcalase hydrolysis for 40 min. Second, modified soy protein was mixed with dextran and ultrasonicated for 70 min so as to assemble nanogels. The modified soy protein-dextran nanogels were characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) and ζ-potential studies to confirm the formation of NGs. Transmission electron microscopy (TEM) revealed the NGs to be spherical with core-shell structures, in the range of 32-40 nm size. The nanogels were stable against various environmental conditions. Furthermore, the particle size of the nanogels hardly changed with the incorporation of riboflavin. The encapsulation efficiency of nanogels was found to be up to 65.9% at a riboflavin concentration of 250 μg/mL. The nanogels exhibited a faster release in simulated intestine fluid (SIF) compared with simulated gastric fluid (SGF). From the results obtained it can be concluded that modified soy protein-dextran nanogels can be considered a promising carrier for drugs and other bioactive molecule delivery purposes.

Tuning complement activation and pathway through controlled molecular architecture of dextran chains in nanoparticle corona.

PubMed

Coty, Jean-Baptiste; Eleamen Oliveira, Elquio; Vauthier, Christine

2017-11-05

The understanding of complement activation by nanomaterials is a key to a rational design of safe and efficient nanomedicines. This work proposed a systematic study investigating how molecular design of nanoparticle coronas made of dextran impacts on mechanisms that trigger complement activation. The nanoparticles used for this work consisted of dextran-coated poly(isobutylcyanoacrylate) (PIBCA) nanoparticles have already been thoroughly characterized. Their different capacity to trigger complement activation established on the cleavage of the protein C3 was also already described making these nanoparticles good models to investigate the relation between the molecular feature of their corona and the mechanism by which they triggered complement activation. Results of this new study show that complement activation pathways can be selected by distinct architectures formed by dextran chains composing the nanoparticle corona. Assumptions that explain the relation between complement activation mechanisms triggered by the nanoparticles and the nanoparticle corona molecular feature were proposed. These results are of interest to better understand how the design of dextran-coated nanomaterials will impact interactions with the complement system. It can open perspectives with regard to the selection of a preferential complement activation pathway or prevent the nanoparticles to activate the complement system, based on a rational choice of the corona configuration. Copyright © 2017 Elsevier B.V. All rights reserved.

Puberty is delayed in male mice with dextran sodium sulfate colitis out of proportion to changes in food intake, body weight, and serum levels of leptin.

PubMed

Deboer, Mark D; Li, Yongli

2011-01-01

In boys, inflammatory bowel disease often results in delayed puberty associated with decreased bone mineral density and decreased linear growth. Our goal was to investigate whether pubertal timing and levels of leptin differed between prepubertal male mice with colitis and food-restricted (FR) mice maintained at a similar weight. We induced colitis in 32-d-old male mice using dextran sodium sulfate (DSS), resulting in 10 d of worsening colitis. We followed up these mice for separation of the prepuce from the glans penis as a marker of pubertal progression. Compared with free-feeding control mice, DSS and FR mice had significantly lower weight on d 7-10 of treatment. DSS mice had later puberty than control and FR mice. DSS mice also had smaller testes, lower FSH levels, increased systemic cytokines, and increased colonic inflammation by histology. Leptin levels were similar between DSS and FR mice, whereas both had decreases in leptin compared with controls. We conclude that DSS colitis causes delayed puberty in sexually immature male mice beyond what is seen among FR mice of similar weight, food intake, and leptin levels. These experiments provide support for the hypothesis that pubertal delay in colitis is influenced by factors beyond poor weight gain alone.

Effect of preparation conditions on properties and permeability of chitosan-sodium hexametaphosphate capsules.

PubMed

Angelova, N; Hunkeler, D

2001-01-01

Capsules were obtained by interpolymer complexation between chitosan (polycation) and sodium hexametaphosphate (SMP, oligoanion). The effect of the preparation conditions on the capsule characteristics was evaluated. Specifically, the influence of variables such as pH, ionic strength, reagent concentration, and additives on the capsule permeability properties was investigated using dextran as a model permeant. The capsule membrane permeability was found to increase by decreasing the chitosan/SMP ratio as well as adding mannitol to the oligoanion recipient bath. Increasing the ionic strength or the pH of the initial chitosan solution was also found to enhance the membrane permeability, moving the membrane exclusion limit to higher values. Generally, the capsules prepared tinder all tested conditions had a relatively low permeability which rarely exceeded a molecular cut-off of 40 kD based on dextran standards. Furthermore, the diffusion rate showed a strong temporal dependence, indicating that the capsules prepared under various conditions exhibit different apparent pore size densities on the surface. The results indicated that, in order to obtain the desired capsule mass-transfer properties, the preparation conditions should be carefully considered and adjusted. Adding a polyol as well as low salt amount (less than 0.15%) is preferable as a means of modulating the diffusion characteristics, without disturbing the capsule mechanical stability.

Permeability and route of entry for lipid-insoluble molecules across brain barriers in developing Monodelphis domestica

PubMed Central

Ek, C Joakim; Habgood, Mark D; Dziegielewska, Katarzyna M; Potter, Ann; Saunders, Norman R

2001-01-01

We have studied the permeability of blood-brain barriers to small molecules such as [14C]sucrose, [3H]inulin, [14C]l-glucose and [3H]glycerol from early stages of development (postnatal day 6, P6) in South American opossums (Monodelphis domestica), using a litter-based method for estimating steady-state cerebrospinal fluid (CSF)/plasma and brain/plasma ratios of markers that were injected i.p.. Steady-state ratios for l-glucose, sucrose and inulin all showed progressive decreases during development. The rate of uptake of l-glucose into the brain and CSF, in short time course experiments (7–24 min) when age-related differences in CSF production can be considered negligible also decreased during development. These results indicate that there is a significant decrease in the permeability of brain barriers to small lipid-insoluble molecules during brain development. The steady-state blood/CSF ratio for 3000 Da lysine-fixable biotin-dextran following i.p. injection was shown to be consistent with diffusion from blood to CSF. It was therefore used to visualise the route of penetration for small lipid-insoluble molecules across brain barriers at P 0–30. The proportion of biotin-dextran-positive cells in the choroid plexuses declined in parallel with the age-related decline in permeability to the small-molecular-weight markers; the paracellular (tight junction) pathway for biotin-dextran appeared to be blocked, but biotin-dextran was easily detectable in the CSF. A transcellular route from blood to CSF was suggested by the finding that some choroid plexus epithelial cells contained biotin-dextran. Biotin-dextran was also taken up by cerebral endothelial cells in the youngest brains studied (P0), but in contrast to the CSF, could not be detected in the brain extracellular space (i.e. a significant blood-brain barrier to small-sized lipid-insoluble compounds was already present). However, in immature brains (P0–13) biotin-dextran was taken up by some cells in the brain. These cells generally had contact with the CSF, suggesting that it is likely to have been the 2source of their biotin-dextran. Since the quantitative permeability data suggest that biotin-dextran behaves similarly to the radiolabelled markers used in this study, it is suggested that these markers in the more immature brains were also present intracellularly. Thus, brain/plasma ratios may be a misleading indicator of blood-brain barrier permeability in very immature animals. The immunocytochemical staining for biotin-dextran in the CSF, in contrast to the lack of staining in the brain extracellular space, together with the quantitative permeability data showing that the radiolabelled markers penetrated more rapidly and to a much higher steady-state level in CSF than in the brain, suggests that lipid-insoluble molecules such as sucrose and inulin reach the immature brain predominantly via the CSF rather than directly across the very few blood vessels that are present at that time. PMID:11691876

Communication: Two types of flat-planes conditions in density functional theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Xiaotian Derrick; Patel, Anand H. G.; González-Espinoza, Cristina E.

Using results from atomic spectroscopy, we show that there are two types of flat-planes conditions. The first type of flat-planes condition occurs when the energy as a function of the number of electrons of each spin, N{sub α} and N{sub β}, has a derivative discontinuity on a line segment where the number of electrons, N{sub α} + N{sub β}, is an integer. The second type of flat-planes condition occurs when the energy has a derivative discontinuity on a line segment where the spin polarization, N{sub α} – N{sub β}, is an integer, but does not have a discontinuity associated withmore » an integer number of electrons. Type 2 flat planes are rare—we observed just 15 type 2 flat-planes conditions out of the 4884 cases we tested—but their mere existence has implications for the design of exchange-correlation energy density functionals. To facilitate the development of functionals that have the correct behavior with respect to both fractional number of electrons and fractional spin polarization, we present a dataset for the chromium atom and its ions that can be used to test new functionals.« less

PHYSICAL-CONSTRAINT-PRESERVING CENTRAL DISCONTINUOUS GALERKIN METHODS FOR SPECIAL RELATIVISTIC HYDRODYNAMICS WITH A GENERAL EQUATION OF STATE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Kailiang; Tang, Huazhong, E-mail: wukl@pku.edu.cn, E-mail: hztang@math.pku.edu.cn

The ideal gas equation of state (EOS) with a constant adiabatic index is a poor approximation for most relativistic astrophysical flows, although it is commonly used in relativistic hydrodynamics (RHD). This paper develops high-order accurate, physical-constraints-preserving (PCP), central, discontinuous Galerkin (DG) methods for the one- and two-dimensional special RHD equations with a general EOS. It is built on our theoretical analysis of the admissible states for RHD and the PCP limiting procedure that enforce the admissibility of central DG solutions. The convexity, scaling invariance, orthogonal invariance, and Lax–Friedrichs splitting property of the admissible state set are first proved with themore » aid of its equivalent form. Then, the high-order central DG methods with the PCP limiting procedure and strong stability-preserving time discretization are proved, to preserve the positivity of the density, pressure, specific internal energy, and the bound of the fluid velocity, maintain high-order accuracy, and be L {sup 1}-stable. The accuracy, robustness, and effectiveness of the proposed methods are demonstrated by several 1D and 2D numerical examples involving large Lorentz factor, strong discontinuities, or low density/pressure, etc.« less

Efficacy and safety of newly developed cross-linked dextran gel injection for glans penis augmentation with a novel technique

PubMed Central

Yang, Dae Yul; Ko, Kyungtae; Lee, Seong Ho; Moon, Du Geon; Kim, Jong Wook; Lee, Won Ki

2018-01-01

There is no safe and effective standard method for glans penis augmentation. Furthermore, there has been scant research on glans penis augmentation due to a poor understanding of glans anatomy, technical difficulty, and a lack of suitable substances for augmentation. Cross-linked dextran gel is a newly developed filler for soft-tissue augmentation. We evaluated the efficacy and safety of using a novel technique to inject cross-linked dextran gel for glans penis augmentation during a 24-week follow-up study. This prospective, single-arm, multicenter study enrolled twenty healthy adult men who underwent glans penis augmentation between June and August 2013. Cross-linked dextran gel was injected into the glans penis using a simple and easy technique. The sizes of the glans penis and individual satisfaction were assessed. Any adverse event was also reported. A total of 18 individuals were analyzed; two of them were lost to follow-up. The mean procedure time and injected volume were about 30 min and 6.6 ± 0.9 ml, respectively. The mean surface areas of the glans at baseline and 24 weeks were 20.0 ± 3.5 cm2 and 33.6 ± 5.4 cm2, respectively, representing a mean increase of 68.7% ± 14.0% (P < 0.001). Sixteen individuals (88.9%) were satisfied with the outcomes, and none were dissatisfied. There were no serious adverse events during the study. Cross-linked dextran gel injection for glans penis augmentation was easy and showed a significant augmentative effect on the glans penis, good durability, and was well tolerated without serious adverse events. Therefore, cross-linked dextran gel injection may be an effective, new technique for glans penis augmentation. PMID:28303807

Pore size assessment during corneal endothelial cells permeabilization by femtosecond laser activated carbon nanoparticles

NASA Astrophysics Data System (ADS)

Jumelle, C.; Mauclair, C.; Houzet, J.; Bernard, A.; He, Z.; Piselli, S.; Perrache, C.; Egaud, G.; Baubeau, E.; Gain, P.; Thuret, G.

2015-07-01

Corneal therapeutic molecules delivery represents a promising solution to maintain human corneal endothelial cells (HCECs) viability, but the difficulty is transport across cell membrane. A new delivery method published recently consists in ephemerally permeabilizing cell membranes using a photo-acoustic reaction produced by carbon nanoparticles (CNPs) and femtosecond laser (FsL). The aim of this work is to investigate the size of pores formed at cell membrane by this technique. To induce cell permeabilization, HCECs were put in contact with CNPs and irradiated with a 500 μm diameter Ti:Sa FsL focalized spot. Four sizes of marker molecules were delivered into HCECs to investigate pore sizes: calcein (1.2 nm), FITC-Dextran 4kDa (2.8 nm) and FITC-Dextran 70kDa (12 nm) and FITC-Dextran 2MDa (50 nm). Delivery of each molecule was assessed by flow cytometry, a technique able to measure their presence into cells. We showed that the delivery rate was dependent of their size. Calcein was delivered in 56.1±8.2% of HCECs, FITC-Dextran 4kDa in 42.2±3.5%, FITC-Dextran 70 kDa in 21.5±2.7% and finally FITC-Dextran 2MDa in 12.9±2.0%. It means that a large number of pores in the size ranging from 1.2 to 2.8 nm were formed. However, 12 nm and larger pores were almost half more infrequent. Pore sizes formed at cell membrane by the technique of cell permeabilization by FsL activated CNPs was investigated. The results indicated that the pore sizes are large enough for the efficient delivery of small, medium and big therapeutics molecules on HCECs by this technique.

Evaluation of self-dissolving needles containing low molecular weight heparin (LMWH) in rats.

PubMed

Ito, Yukako; Murakami, Aiko; Maeda, Tomohiro; Sugioka, Nobuyuki; Takada, Kanji

2008-02-12

Feasibility study of self-dissolving needles containing polysaccharide was performed. Low molecular weight heparin (LMWH) was used as a representative polysaccharide. Using chondroitin, dextran and dextrin as the base, self-dissolving needles (SDN) were prepared. The obtained SDNs were evaluated in rat absorption experiment, where pharmacological availability (PA) was calculated by comparing the plasma anti-Xa activity vs. time curves between SDNs and i.v. solution. After the insertion of SDNs to rats skin where the doses of LMWH were 25, 50 and 100 IU/kg, plasma samples were collected for 6h and anti-Xa activity was measured as the pharmacological index of LMWH. The anti-Xa level was maintained above 0.2 IU/ml, the therapeutic level, for about 2h at a dose of 100 IU/kg. Almost the same PAs of LMWH were obtained with dextran and dextrin SDNs, 97.7% and 102.3%, though lower PA was obtained with chondroitin SDN, 81.5%. In vitro dissolution experiment showed that LMWH was released from dextran, dextrin and chondroitin SDNs within 10 min. The T(50%)s were 0.84+/-0.06 min for dextran SDN, 1.07+/-0.12 min for chondroitin SDN and 2.11+/-0.31 min for dextrin SDN, respectively. Plasma anti-Xa activity vs. time profiles showed good dose-dependency in the 25-100 IU/kg range and high PAs were obtained, 90.0% for 25 IU/kg, 95.4% for 50 IU/kg and 97.7% for 100 IU/kg from dextran SDNs. Stability experiment was performed with dextran SDNs for 3 months. Above 97% of LMWH were remained in SDNs under three different conditions, -80, 4 and 40 degrees C. These results suggest the usefulness of SDN to polysaccharide drug.

Chemical Functionalization of Germanium with Dextran Brushes for Immobilization of Proteins Revealed by Attenuated Total Reflection Fourier Transform Infrared Difference Spectroscopy.

PubMed

Schartner, Jonas; Hoeck, Nina; Güldenhaupt, Jörn; Mavarani, Laven; Nabers, Andreas; Gerwert, Klaus; Kötting, Carsten

2015-07-21

Protein immobilization studied by attenuated total reflection Fourier transform infrared (ATR-FT-IR) difference spectroscopy is an emerging field enabling the study of proteins at atomic detail. Gold or glass surfaces are frequently used for protein immobilization. Here, we present an alternative method for protein immobilization on germanium. Because of its high refractive index and broad spectral window germanium is the best material for ATR-FT-IR spectroscopy of thin layers. So far, this technique was mainly used for protein monolayers, which lead to a limited signal-to-noise ratio. Further, undesired protein-protein interactions can occur in a dense layer. Here, the germanium surface was functionalized with thiols and stepwise a dextran brush was generated. Each step was monitored by ATR-FT-IR spectroscopy. We compared a 70 kDa dextran with a 500 kDa dextran regarding the binding properties. All surfaces were characterized by atomic force microscopy, revealing thicknesses between 40 and 110 nm. To analyze the capability of our system we utilized N-Ras on mono-NTA (nitrilotriacetic acid) functionalized dextran, and the amount of immobilized Ras corresponded to several monolayers. The protein stability and loading capacity was further improved by means of tris-NTA for immobilization. Small-molecule-induced changes were revealed with an over 3 times higher signal-to-noise ratio compared to monolayers. This improvement may allow the observation of very small and so far hidden changes in proteins upon stimulus. Furthermore, we immobilized green fluorescent protein (GFP) and mCherry simultaneously enabling an analysis of the surface by fluorescence microscopy. The absence of a Förster resonance energy transfer (FRET) signal demonstrated a large protein-protein distance, indicating an even distribution of the protein within the dextran.

Enhanced Reduction of Helicobacter pylori Load in Precolonized Mice Treated with Combined Famotidine and Urease-Binding Polysaccharides

PubMed Central

Icatlo, Faustino C.; Kimura, Nobutake; Goshima, Hideo; Kodama, Yoshikatsu

2000-01-01

The present study investigated the effect of a model urease-binding polysaccharide in combination with a histamine H2 receptor antagonist on Helicobacter pylori colonization in vivo. Euthymic hairless mice were treated daily with dextran sulfate via drinking water and/or famotidine via intragastric gavage starting at 1 week postchallenge with a CagA+ VacA+ (type 1) strain of H. pylori. Treatment of precolonized mice for 2 weeks with dextran sulfate combined with famotidine yielded a group mean bacterial load (per 100 mg of gastric tissue) of log10 1.04 CFU, which was significantly lower than those of the famotidine (log10 3.35 CFU, P < 0.01) and dextran sulfate (log10 2.45 CFU, P < 0.05) monotherapy groups and the infected nontreated group (log10 3.64 CFU, P < 0.01). Eradication was achieved after 2 weeks of treatment in 50% or more of the test mice using drug combinations (1 or 2 weeks of famotidine plus 2 weeks of dextran sulfate) versus none in the monotherapy and positive control groups. The enhanced activity of the drug combination may be related to the daily pattern of transient acid suppression by famotidine inducing periodic bacterial convergence to superficial mucus sites penetrated by dextran sulfate from the lumen. Increased urease-dextran sulfate avidity was observed in vitro in the presence of famotidine and may partly account for the enhanced activity. With potential utility in abbreviating treatment time and eradication of antibiotic-resistant strains, the use of urease-targeted polysaccharides concurrently with a gastric acid inhibitor warrants consideration as an additional component of the standard multidrug chemotherapy of H. pylori infection. PMID:10952600

Perilymph Kinetics of FITC-Dextran Reveals Homeostasis Dominated by the Cochlear Aqueduct and Cerebrospinal Fluid.

PubMed

Salt, A N; Gill, R M; Hartsock, J J

2015-06-01

Understanding how drugs are distributed in perilymph following local applications is important as local drug therapies are increasingly used to treat disorders of the inner ear. The potential contribution of cerebrospinal fluid (CSF) entry to perilymph homeostasis has been controversial for over half a century, largely due to artifactual contamination of collected perilymph samples with CSF. Measures of perilymph flow and of drug distribution following round window niche applications have both suggested a slow, apically directed flow occurs along scala tympani (ST) in the normal, sealed cochlea. In the present study, we have used fluorescein isothiocyanate-dextran as a marker to study perilymph kinetics in guinea pigs. Dextran is lost from perilymph more slowly than other substances so far quantified. Dextran solutions were injected from pipettes sealed into the lateral semicircular canal (SCC), the cochlear apex, or the basal turn of ST. After varying delays, sequential perilymph samples were taken from the cochlear apex or lateral SCC, allowing dextran distribution along the perilymphatic spaces to be quantified. Variability was low and findings were consistent with the injection procedure driving volume flow towards the cochlear aqueduct, and with volume flow during perilymph sampling driven by CSF entry at the aqueduct. The decline of dextran with time in the period between injection and sampling was consistent with both a slow volume influx of CSF (~30 nL/min) entering the basal turn of ST at the cochlear aqueduct and a CSF-perilymph exchange driven by pressure-driven fluid oscillation across the cochlear aqueduct. Sample data also allowed contributions of other processes, such as communications with adjacent compartments, to be quantified. The study demonstrates that drug kinetics in the basal turn of ST is complex and is influenced by a considerable number of interacting processes.

Characteristics of DEAE-dextran-MMA graft copolymer as a nonviral gene carrier.

PubMed

Onishi, Yasuhiko; Eshita, Yuki; Murashita, Aya; Mizuno, Masaaki; Yoshida, Jun

2007-09-01

A stable and soapless latex of diethylaminoethyl-dextran-methyl methacrylate (DEAE-dextran-MMA) graft copolymer (DDMC) has been developed for nonviral gene delivery vectors that are possible to autoclave. DDMC relatively easily formed a polyion complex between DNA and DDMC by the hydrophobic force of graft poly(MMA) depending on its large positive entropy change (DeltaS). DDMC has been confirmed as having a high protection facility for DNase by DNase degradation test.Transfection activity was determined using the beta-galactosidase assay, and a higher value of 16 times or more was confirmed for the DDMC samples in comparison with one of the starting DEAE-dextran hydrochloride samples. The resulting DDMC, having an amphiphilic domain so as to form a polymer micelle, should become a stable latex with a hydrophilic-hydrophobic microseparated domain. The complex of DDMC and plasmid DNA may be formed on the spherical structure of the amphiphilic microseparated domain of DDMC and have a good affinity to the cell membrane. The infrared absorption spectrum shift to a high-energy direction at around 3450 cm(-1), because of the complexes between DNA and DDMC, may cause the formation of more compact structures, not only by a coulomb force between the phosphoric acid of DNA and the DEAE group of DEAE-dextran copolymer but also by a force from the multi-intermolecule hydrogen bond in the backbone polymer DEAE-dextran and a hydrophobic force from the graft poly(MMA) in DDMC. It is thus concluded that DNA condensation may possibly have a high transfection efficiency via DDMC. The high efficiency of this graft copolymer, which is sterilized by an autoclave, may thus make it a valuable tool for safe gene delivery.

Hydroxyethyl starch as a substitute for dextran 40 for thawing peripheral blood progenitor cell products.

PubMed

Zhu, Fenlu; Heditke, Sarah; Kurtzberg, Joanne; Waters-Pick, Barbara; Hari, Parameswaran; Margolis, David A; Keever-Taylor, Carolyn A

2015-12-01

Removing DMSO post-thaw results in: reduced infusion reactions, improved recovery and stability of viable CD34+ cells. Validated methods use 5%-8.3% Dextran 40 with 2.5%-4.2% HSA for this purpose. Recent shortages of clinical grade Dextran require identification of suitable alternatives. PBPC were used to compare a standard 2X wash medium of 5 parts 10% Dextran 40 in saline (DEX) with 1 part 25% HSA (8.3% DEX/ 4.2% HSA) with Hydroxyethyl Starch (HES)-based solutions. Cells in replicate bags were diluted with an equal volume of wash solution, equilibrated 5 minutes, the bag filled with wash medium, pelleted and the supernatant expressed. Bags were restored to the frozen volume in wash medium and tested by single platform flow cytometry and CFU. Total viability, viable TNC, MNC, and CD34+ cell recovery, and CD34+ cell viability were compared immediately post-thaw and after 90 minutes. 5.2% HES/4.2% HSA did not differ from our standard in CD34 recovery or viability. Due to concerns that high concentrations of HES could affect renal function we tested 0.6% HES/2.5% HSA resulting in significantly poorer CD34 recovery and viability. Results improved using 2.4% HES/4.2% HSA and when 0.6% HES/4.2%HSA was used no significant differences were seen. CFU assays confirmed no differences between the standard dextran arm and HES at 2.4% or 0.6% so long as HSA was at 4.2%. We conclude that HES from 0.6% to 5.2% with 4.2% HSA is a suitable substitute for Dextran 40 as a reconstitution/washing medium for PBPC products. Copyright © 2015 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.

Particle flows to shape and voltage surface discontinuities in the electron sheath surrounding a high voltage solar array in LEO

NASA Technical Reports Server (NTRS)

Metz, Roger N.

1991-01-01

This paper discusses the numerical modeling of electron flows from the sheath surrounding high positively biased objects in LEO (Low Earth Orbit) to regions of voltage or shape discontinuity on the biased surfaces. The sheath equations are derived from the Two-fluid, Warm Plasma Model. An equipotential corner and a plane containing strips of alternating voltage bias are treated in two dimensions. A self-consistent field solution of the sheath equations is outlined and is pursued through one cycle. The electron density field is determined by numerical solution of Poisson's equation for the electrostatic potential in the sheath using the NASCAP-LEO relation between electrostatic potential and charge density. Electron flows are calculated numerically from the electron continuity equation. Magnetic field effects are not treated.

Emergence of currents as a transient quantum effect in nonequilibrium systems

NASA Astrophysics Data System (ADS)

Granot, Er'El; Marchewka, Avi

2011-09-01

Most current calculations are based on equilibrium or semi-equilibrium models. However, except for very special scenarios (like ring configuration), the current cannot exist in equilibrium. Moreover, unlike with equilibrium scenarios, there is no generic approach to confront out-of-equilibrium currents. In this paper we used recent studies on transient quantum mechanics to solve the current, which appears in the presence of very high density gradients and fast transients. It shows that the emerging current appears instantaneously, and although the density beyond the discontinuity is initially negligible the currents there have a finite value, and remain constant for a finite period. It is shown that this nonequilibrium effect can be measured in real experiments (such as cooled rubidium atoms), where the discontinuity is replaced with a finite width (hundreds of nanometers) gradient.

Single and double multiphoton ionization of Li and Be atoms by strong laser fields

NASA Astrophysics Data System (ADS)

Telnov, Dmitry; Heslar, John; Chu, Shih-I.

2011-05-01

The time-dependent density functional theory with self-interaction correction and proper asymptotic long-range potential is extended for nonperturbative treatment of multiphoton single and double ionization of Li and Be atoms by strong 800 nm laser fields. We make use of the time-dependent Krieger-Li-Iafrate (TDKLI) exchange-correlation potential with the integer discontinuity which improves the description of the double ionization process. However, we have found that the discontinuity of the TDKLI potential is not sufficient to reproduce the characteristic feature of double ionization. This may happen because the discontinuity of the TDKLI potential is related to the spin particle numbers only and not to the total particle number. Introducing a discontinuity with respect to the total particle number to the exchange-correlation potential, we were able to obtain the knee structure in the intensity dependence of the double ionization probability of Be. This work was partially supported by DOE and NSF and by NSC-Taiwan.

Differential proteomics analysis of the surface heterogeneity of dextran iron oxide nanoparticles and the implications for their in vivo clearance

PubMed Central

Simberg, Dmitri; Park, Ji-Ho; Karmali, Priya P.; Zhang, Wan-Ming; Merkulov, Sergei; McCrae, Keith; Bhatia, Sangeeta; Sailor, Michael; Ruoslahti, Erkki

2009-01-01

In order to understand the role of plasma proteins in the rapid liver clearance of dextran-coated superparamagnetic iron oxide (SPIO) in vivo, we analyzed the full repertoire of SPIO-binding blood proteins using novel two-dimensional differential mass spectrometry approach. The identified proteins showed specificity for surface domains of the nanoparticles: mannan-binding lectins bound to the dextran coating, histidine-rich glycoprotein and kininogen bound to the iron oxide part, and the complement lectin and contact clotting factors were secondary binders. Nanoparticle clearance studies in knockout mice suggested that these proteins, as well as several previously identified opsonins, do not play a significant role in the SPIO clearance. However, both the dextran coat and the iron oxide core remained accessible to specific probes after incubation of SPIO in plasma, suggesting that the nanoparticle surface could be available for recognition by macrophages, regardless of protein coating. These data provide guidance to rational design of bioinert, long-circulating nanoparticles. PMID:19394687

Differential proteomics analysis of the surface heterogeneity of dextran iron oxide nanoparticles and the implications for their in vivo clearance.

PubMed

Simberg, Dmitri; Park, Ji-Ho; Karmali, Priya P; Zhang, Wan-Ming; Merkulov, Sergei; McCrae, Keith; Bhatia, Sangeeta N; Sailor, Michael; Ruoslahti, Erkki

2009-08-01

In order to understand the role of plasma proteins in the rapid liver clearance of dextran-coated superparamagnetic iron oxide (SPIO) in vivo, we analyzed the full repertoire of SPIO-binding blood proteins using novel two-dimensional differential mass spectrometry approach. The identified proteins showed specificity for surface domains of the nanoparticles: mannan-binding lectins bound to the dextran coating, histidine-rich glycoprotein and kininogen bound to the iron oxide part, and the complement lectin and contact clotting factors were secondary binders. Nanoparticle clearance studies in knockout mice suggested that these proteins, as well as several previously identified opsonins, do not play a significant role in the SPIO clearance. However, both the dextran coat and the iron oxide core remained accessible to specific probes after incubation of SPIO in plasma, suggesting that the nanoparticle surface could be available for recognition by macrophages, regardless of protein coating. These data provide guidance to rational design of bioinert, long-circulating nanoparticles.

Sentinel lymph node mapping in melanoma with technetium-99m dextran.

PubMed

Neubauer, S; Mena, I; Iglesis, R; Schwartz, R; Acevedo, J C; Leon, A; Gomez, L

2001-06-01

The aim of this work is to evaluate the capability of Tc99m B Dextran as a lymphoscintigraphic agent in the detection of the sentinel node in skin lesions. Forty-one patients with melanomas (39) and Merkel cell tumors (2) had perilesional intradermal injection of Tc99m-Dextran 2 hours before surgery. Serial gamma camera images and a handheld gamma probe were used to direct sentinel node biopsy. In 39/41 patients, lymph channels and 52 sentinel nodes (one to three sentinel nodes/patient) could be visualized. In one patient, with a dorsal melanoma, no lymph channels or lymph nodes could be demonstrated on the images and only minimal radioactivity was found in the regional nodes with the probe. Another patient with a facial lesion failed to demonstrate lymph channels or nodes. No adverse reactions were observed. Tc99m-Dextran provided good definition of lymph channels and sentinel node localization, without the risks related to the use of potentially hazardous labeled materials of biological origin.

Optimal size for heating efficiency of superparamagnetic dextran-coated magnetite nanoparticles for application in magnetic fluid hyperthermia

NASA Astrophysics Data System (ADS)

Shaterabadi, Zhila; Nabiyouni, Gholamreza; Soleymani, Meysam

2018-06-01

Dextran-coated magnetite (Fe3O4) nanoparticles with average particle sizes of 4 and 19 nm were synthesized through in situ and semi-two-step co-precipitation methods, respectively. The experimental results confirm the formation of pure phase of magnetite as well as the presence of dextran layer on the surface of modified magnetite nanoparticles. The results also reveal that both samples have the superparamagnetic behavior. Furthermore, calorimetric measurements show that the dextran-coated Fe3O4 nanoparticles with an average size of 4 nm cannot produce any appreciable heat under a biologically safe alternating magnetic field used in hyperthermia therapy; whereas, the larger ones (average size of 19 nm) are able to increase the temperature of their surrounding medium up to above therapeutic range. In addition, measured specific absorption rate (SAR) values confirm that magnetite nanoparticles with an average size of 19 nm are very excellent candidates for application in magnetic hyperthermia therapy.

New biodegradable dextran-based hydrogels for protein delivery: Synthesis and characterization.

PubMed

Pacelli, Settimio; Paolicelli, Patrizia; Casadei, Maria Antonietta

2015-08-01

A new derivative of dextran grafted with polyethylene glycol methacrylate through a carbonate bond (DEX-PEG-MA) has been synthesized and characterized. The photo-crosslinking reaction of DEX-PEG-MA allowed the obtainment of biodegradable networks tested for their mechanical and release properties. The new hydrogels were compared with those made of dextran methacrylate (DEX-MA), often employed as drug delivery systems of small molecules. The inclusion of PEG as a spacer created additional interactions among the polymeric chains improving the extreme fragility and lack of hardness typical of gels made of DEX-MA. Moreover, the different behavior in terms of swelling and degradability of the networks was able to affect the release of a model macromolecule over time, making DEX-PEG-MA matrices suitable candidates for the delivery of high molecular weight peptides. Interestingly, the combination of the two dextran derivatives showed intermediate ability to modulate the release of high molecular weight macromolecules. Copyright © 2015 Elsevier Ltd. All rights reserved.

Separation of pharmacologically active nitrogen-containing compounds on silica gels modified with 6,10-ionene, dextran sulfate, and gold nanoparticles

NASA Astrophysics Data System (ADS)

Ioutsi, A. N.; Shapovalova, E. N.; Ioutsi, V. A.; Mazhuga, A. G.; Shpigun, O. A.

2017-12-01

New stationary phases for HPLC are obtained via layer-by-layer deposition of polyelectrolytes and studied: (1) silica gel modified layer-by-layer with 6,10-ionene and dextran sulfate (Sorbent 1); (2) silica gel twice subjected to the above modification (Sorbent 2); and (3) silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate (Sorbent 3). The effect the content of the organic solvent in the mobile phase and the concentration and pH of the buffer solution have on the chromatographic behavior of several pharmacologically active nitrogen-containing compounds is studied. The sorbents are stable during the process and allow the effective separation of beta-blockers, calcium channel blockers, alpha-agonists, and antihistamines. A mixture of caffeine, nadolol, tetrahydrozoline, pindolol, orphenadrine, doxylamine, carbinoxamine, and chlorphenamine is separated in 6.5 min on the silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate.

Recombination Between Guanidine-resistant and Dextran Sulfate-resistant Mutants of Type 1 Poliovirus

PubMed Central

Sergiescu, Dina; Aubert-Combiescu, Andrei; Crainic, Radu

1969-01-01

Mixed infection of monkey kidney cells with two mutants of the LSc2ab strain of poliovirus, one resistant to guanidine and the other resistant to both dextran sulfate and 2-(α-hydroxybenzyl)-benzimidazole (HBB), yielded progeny in which the number of guardexr particles exceeded by a factor of 7 to 10 the expected number of similar particles occurring through spontaneous mutation; recombination would explain the fairly high excess of doubly mutant particles that was obtained. Scoring of HBB resistance in 50 guardexr clones suggested that, during recombination, resistance to dextran sulfate is not associated with HBB resistance. Images PMID:4305674

Parameters optimization defined by statistical analysis for cysteine-dextran radiolabeling with technetium tricarbonyl core.

PubMed

Núñez, Eutimio Gustavo Fernández; Faintuch, Bluma Linkowski; Teodoro, Rodrigo; Wiecek, Danielle Pereira; da Silva, Natanael Gomes; Papadopoulos, Minas; Pelecanou, Maria; Pirmettis, Ioannis; de Oliveira Filho, Renato Santos; Duatti, Adriano; Pasqualini, Roberto

2011-04-01

The objective of this study was the development of a statistical approach for radiolabeling optimization of cysteine-dextran conjugates with Tc-99m tricarbonyl core. This strategy has been applied to the labeling of 2-propylene-S-cysteine-dextran in the attempt to prepare a new class of tracers for sentinel lymph node detection, and can be extended to other radiopharmaceuticals for different targets. The statistical routine was based on three-level factorial design. Best labeling conditions were achieved. The specific activity reached was 5 MBq/μg. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Biliary secretion of fluid-phase markers by the isolated perfused rat liver. Role of transcellular vesicular transport.

PubMed Central

Lake, J R; Licko, V; Van Dyke, R W; Scharschmidt, B F

1985-01-01

In these studies, we have used several approaches to systematically explore the contribution of transcellular vesicular transport (transcytosis) to the blood-to-bile movement of inert fluid-phase markers of widely varying molecular weight. First, under steady-state conditions, the perfused rat liver secreted even large markers in appreciable amounts. The bile-to-plasma (B/P) ratio of these different markers, including microperoxidase (B/P ratio = 0.06; mol wt = 1,879), insulin (B/P ratio = 0.09, mol wt = 5,000), horseradish peroxidase (B/P ratio = 0.04, mol wt = 40,000), and dextran (B/P ratio = 0.09, mol wt = 70,000), exhibited no clear ordering based on size alone, and when dextrans of two different sizes (40,000 and 70,000 mol wt) were studied simultaneously, the relative amounts of the two dextran species in bile were the same as in perfusate. Taurocholate administration produced a 71% increase in bile flow but little or no (0-20%) increase in the output of horseradish peroxidase, microperoxidase, inulin, and dextran. Second, under nonsteady-state conditions in which the appearance in or disappearance from bile of selected markers was studied after their abrupt addition to or removal from perfusate, erythritol reached a B/P ratio of 1 within 2 min. Microperoxidase and dextran appeared in bile only after a lag period of approximately 12 min and then slowly approached maximal values, whereas sucrose exhibited kinetically intermediate behavior. A similar pattern was observed after removal of greater than 95% of the marker from the perfusate. Erythritol rapidly reapproached a B/P ratio of 1, whereas the B/P ratio for sucrose, dextran, and microperoxidase fell much more slowly and exceeded 1 for a full 30 min after perfusate washout. Finally, electron microscopy and fluorescence microscopy of cultured hepatocytes demonstrated the presence of horseradish peroxidase and fluorescein-dextran, respectively, in intracellular vesicles, and fractionation of perfused liver homogenates revealed that at least 35-50% of sucrose, inulin, and dextran was associated with subcellular organelles. Collectively, these observations are most compatible with a transcytosis pathway that contributes minimally to the secretion of erythritol, but accounts for a substantial fraction of sucrose secretion and virtually all (greater than 95%) of the blood-to-bile transport of microperoxidase and larger markers. These findings have important implications with respect to current concepts of canalicular bile formation as well as with respect to the conventional use of solutes such as sucrose as markers of canalicular or paracellular pathway permeability. Images PMID:2411761

Effect of dielectric discontinuity on a spherical polyelectrolyte brush

NASA Astrophysics Data System (ADS)

Tergolina, Vinicius B.; dos Santos, Alexandre P.

2017-09-01

In this paper we perform molecular dynamics simulations of a spherical polyelectrolyte brush and counterions in a salt-free medium. The dielectric discontinuity on the grafted nanoparticle surface is taken into account by the method of image charges. Properties of the polyelectrolyte brush are obtained for different parameters, including valency of the counterions, radius of the nanoparticle, and the brush total charge. The monovalent counterions density profiles are obtained and compared with a simple mean-field theoretical approach. The theory allows us to obtain osmotic properties of the system.

Pentadecapeptide BPC 157 and anaphylactoid reaction in rats and mice after intravenous dextran and white egg administration.

PubMed

Duplancic, Bozidar; Stambolija, Vasilije; Holjevac, Jadranka; Zemba, Mladen; Balenovic, Igor; Drmic, Domagoj; Suran, Jelena; Radic, Bozo; Filipovic, Marinko; Blagaic, Alenka Boban; Brcic, Luka; Kolenc, Danijela; Grabarevic, Zeljko; Seiwerth, Sven; Sikiric, Predrag

2014-03-15

Anesthetized mice or rats received intravenously 6%, 10%, 20%, 40%, 60%, 80%, and 90% dextran and/or white egg (1ml/rat or 0.15ml/mouse) into their tails. Medication (/kg b.w., 5ml/kg) was given intraperitoneally (BPC 157 10µg, 1µg, 10ng, and 10pg/kg, chloropyramine 20mg/kg, and cimetidine 10mg/kg intraperitoneally, alone or in combination while controls received an equivolume of saline), immediately after challenge or, alternatively, at 5min after or 24 or 48h before challenge. The effect was assessed at 5, 10, 20 and 30min after dextran and/or white egg challenge. We commonly noted prominent edema involving the face, upper and lower lip, snout, paws and scrotum (presented with extreme cyanosis), poor respiration and the number of fatalities after dextran and/or white egg application. Contrary, BPC 157 regimens (10µg, 1µg, 10ng, and 10pg/kg) effectively, may both prevent anaphylactoid reactions that may arise from dextran and/or white egg application and furthermore, rescue already advanced reactions when given after the challenge. Chloropyramine and cimetidine given alone were only moderately effective. When given together with BPC 157, the observed effect correlates with the strong effect of BPC 157 given alone. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhancement of Chlamydia trachomatis infectious progeny by cultivation of HeLa 229 cells treated with DEAE-dextran and cycloheximide.

PubMed Central

Sabet, S F; Simmons, J; Caldwell, H D

1984-01-01

The effects of DEAE-dextran and cycloheximide on the infection of HeLa 229 cells with Chlamydia trachomatis serotype G were studied in terms of the number of cells infected and the yield of infectious progeny per infected cell. Pretreatment of the host cells with DEAE-dextran resulted in an increase in the number of infected cels but had no significant effect on the yield of infectious progeny per infected cell (burst size). In contrast, the addition of cycloheximide to the medium of infected cells had no significant effect on the number of infected cells but greatly enhanced the burst size. The burst size was calculated to be close to 500. The enhanced burst size was also observed in cells treated with DEAE-dextran and cycloheximide. In addition, there was an increase in the number of cells infected and an augmentation of the infectious progeny yield. Under the conditions of combined treatment, the yield of C. trachomatis serotype G cultivated in HeLa 229 cells was found to be approximately threefold higher than the yield of the organisms cultivated in McCoy cells. The results suggest that HeLa 229 cells treated with DEAE-dextran and cycloheximide offer a most suitable system for the high-yield cultivation of C. trachomatis organisms and possibly also for the diagnosis of infection with these organisms. Images PMID:6208215

Structural perturbations of azurin deposited on solid matrices as revealed by trp phosphorescence.

PubMed Central

Gabellieri, E; Strambini, G B

2001-01-01

The phosphorescence emission of Cd-azurin from Pseudomonas aeruginosa was used as a probe of possible perturbations in the dynamical structure of the protein core that may be induced by protein-sorbent and protein-protein interactions occurring when the macromolecule is deposited into amorphous, thin solid films. Relative to the protein in aqueous solution, the spectrum is unrelaxed and the phosphorescence decay becomes highly heterogeneous, the average lifetime increasing sharply with film thickness and upon its dehydration. According to the lifetime parameter, adsorption of the protein to the substrate is found to produce a multiplicity of partially unfolded structures, an influence that propagates for several protein layers from the surface. Among the substrates used for film deposition, hydrophilic silica, dextran, DEAE-dextran, dextran sulfate, and hydrophobic octodecylamine, the perturbation is smallest with dextran sulfate and largest with octodecylamine. The destabilizing effect of protein-protein interactions, as monitored on 50-layer-thick films, is most evident at a relative humidity of 75%. Stabilizing agents were incorporated to attenuate the deleterious effects of protein aggregation. Among them, the most effective in preserving a more native-like structure are the disaccharides sucrose and trehalose in dry films and the polymer dextran in wet films. Interestingly, the polymer was found to achieve maximum efficacy at sensibly lower additive/protein ratios than the sugars. PMID:11325742

VERSATILE, HIGH-RESOLUTION ANTEROGRADE LABELING OF VAGAL EFFERENT PROJECTIONS WITH DEXTRAN AMINES

PubMed Central

Walter, Gary C.; Phillips, Robert J.; Baronowsky, Elizabeth A.; Powley, Terry L.

2009-01-01

None of the anterograde tracers used to label and investigate vagal preganglionic neurons projecting to the viscera has proved optimal for routine and extensive labeling of autonomic terminal fields. To identify an alternative tracer protocol, the present experiment evaluated whether dextran conjugates, which have produced superior results in the CNS, might yield widespread and effective labeling of long, fine-caliber vagal efferents in the peripheral nervous system. The dextran conjugates that were evaluated proved reliable and versatile for labeling the motor neuron pool in its entirety, for single- and multiple-labeling protocols, for both conventional and confocal fluorescence microscopy, and for permanent labeling protocols for brightfield microscopy of the projections to the gastrointestinal (GI) tract. Using a standard ABC kit followed by visualization with DAB as the chromagen, Golgi-like labeling of the vagal efferent terminal fields in the GI wall was achieved with the biotinylated dextrans. The definition of individual terminal varicosities was so sharp and detailed that it was routinely practical to examine the relationship of putative vagal efferent contacts (by the criteria of high magnification light microscopy) with the dendritic and somatic architecture of counterstained neurons in the myenteric plexus. Overall, dextran conjugates provide high-definition labeling of an extensive vagal motor pool in the GI tract, and offer considerable versatility when multiple-staining protocols are needed to elucidate the complexities of the innervation of the gut. PMID:19056424

Synthesis of silver nanoparticles in the presence of diethylaminoethyl-dextran hydrochloride polymer and their SERS activity

NASA Astrophysics Data System (ADS)

Mikac, L.; Jurkin, T.; Štefanić, G.; Ivanda, Mile; Gotić, Marijan

2017-09-01

The silver nanoparticles (AgNPs) were synthesized upon γ-irradiation of AgNO3 precursor suspensions in the presence of diethylaminoethyl-dextran hydrochloride (DEAE-dextran) cationic polymer as a stabilizer. The dose rate of γ-irradiation was 32 kGy h-1, and absorbed doses were 30 and 60 kGy. The γ-irradiation of the precursor suspension at acidic or neutral pH conditions produced predominantly the silver(I) chloride (AgCl) particles, because of the poor solubility of AgCl already present in the precursor suspension. The origin of AgCl in the precursor suspension was due to the presence of chloride ions in DEAE-dextran hydrochloride polymer. The addition of ammonia to the precursor suspension dissolved the AgCl precipitate, and the γ-irradiation of such colourless suspension at alkali pH produced a stable aqueous suspension with rather uniform spherical AgNPs of approximately 30 nm in size. The size of AgNPs was controlled by varying the AgNO3/DEAE-dextran concentration in the suspensions. The surface-enhanced Raman scattering (SERS) activities of synthesized AgNPs were examined using organic molecules rhodamine 6G, pyridine and 4-mercaptobenzoic acid (4-MBA). The NaBH4 was used as SERS aggregation agent. The SERS results have shown that in the presence of synthesized AgNPs, it was possible to detect low concentration of tested compounds.

PROBLEM ON IRREGULAR 3-DIMENSIONAL DENSITY DISCONTINUITY SURFACES.

DTIC Science & Technology

method. The result is used to analyze the relation of linear correlation between the crustal thickness and the local Bouguer gravity anomaly, and good agreement is obtained in comparison with the actual statistical data. (Author)

Alternan Research at the National Center for Agricultural Utilization Research

USDA-ARS?s Scientific Manuscript database

The Northern Regional Research Laboratory (later the National Center for Agricultural Utilization Research, or NCAUR) began operations on December 16, 1940. By the late 1940’s, Dr. Allene Jeanes was leading a team in an extensive research program on dextrans. Dextrans are glucan polysaccharides th...

Alternan research at the National Center for Agricultural Utilization Research

USDA-ARS?s Scientific Manuscript database

The Northern Regional Research Laboratory (later the National Center for Agricultural Utilization Research, or NCAUR) began operations on December 16, 1940. By the late 1940’s, Dr. Allene Jeanes was leading a team in an extensive research program on dextrans. Dextrans are glucan polysaccharides th...

Insoluble Glucans from Planktonic and Biofilm Cultures of Mutants of Leuconostoc mesenteroides NRRL B-1355

USDA-ARS?s Scientific Manuscript database

Leuconostoc mesenteroides strain NRRL B-1355 produces the soluble exopolysaccharides alternan and dextran in planktonic cultures. Mutants of this strain are available that are deficient in the production of alternan, dextran, or both. Our recent work demonstrated that biofilms from all strains con...

What drives the Tibetan crust to the South East Asia? Role of upper mantle density discontinuities as inferred from the continental geoid anomalies

NASA Astrophysics Data System (ADS)

Rajesh, S.

2012-04-01

The Himalaya-Tibet orogen formed as a result of the northward convergence of India into the Asia over the past 55 Ma had caused the north south crustal shortening and Cenozoic upliftment of the Tibetan plateau, which significantly affected the tectonic and climatic framework of the Asia. Geodetic measurements have also shown eastward crustal extrusion of Tibet, especially along major east-southeast strike slip faults at a slip rate of 15-20 mm a-1 and around 40 mm a-1. Such continental scale deformations have been modeled as block rotation by fault boundary stresses developed due to the India-Eurasia collision. However, the Thin Sheet model explained the crustal deformation mechanism by considering varying gravitational potential energy arise out of varying crustal thickness of the viscous lithosphere. The Channel Flow model, which also suggests extrusion is a boundary fault guided flow along the shallow crustal brittle-ductile regime. Although many models have proposed, but no consensus in these models to explain the dynamics of measured surface geodetic deformation of the Tibetan plateau. But what remains conspicuous is the origin of driving forces that cause the observed Tibetan crustal flow towards the South East Asia. Is the crustal flow originated only because of the differential stresses that developed in the shallow crustal brittle-ductile regime? Or should the stress transfer to the shallow crustal layers as a result of gravitational potential energy gradient driven upper mantle flow also to be accounted. In this work, I examine the role of latter in the light of depth distribution of continental geoid anomalies beneath the Himalaya-Tibet across major upper mantle density discontinuities. These discontinuity surfaces in the upper mantle are susceptible to hold the plastic deformation that may occur as a result of the density gradient driven flow. The distribution of geoid anomalies across these density discontinuities at 220, 410 and 660 km depth in the upper mantle beneath the Himalaya-Tibet has been studied by analyzing the geoid undulation data obtained from various satellite geodetic missions along with the recent and old (EGM2008 and EGM2006) Earth Gravity models. Results show that the net geoid anomaly varies from -65 m to -20 m, which signify a density stratified upper mantle beneath the Himalaya-Tibet and the same has been confirmed from the results of regional seismic tomography studies. The density anomaly distribution beneath Tibet from 163 km depth to its upper mantle thickness of 1063 km show a strong NW-SE elliptically oriented positive geoid anomalies of magnitude around 40 meter. Asymmetric density anomaly gradient have been observed along the Himalayan arc from west to east as well as across the arc from north to south. This caused differential gravitational potential gradient and hence an elliptical flow structure of the Tibetan continental mantle along the resultant NW-SE direction, which is in concurrence with the observed present day direction of the Tibetan crustal flow. Thus the geoid anomalies distributed at various depth ranges show how the gradient in the upper mantle gravitational potential energy, especially across the deformed discontinuity surface, is significant in determining the transfer of deviatoric stresses and providing traction to the flow of crustal layers of the Tibetan Plateau. This suggests the viscous flow model could be a preferable choice, which could better accommodate the dynamics of the upper mantle, in explaining the crustal extrusion processes of the Tibetan Plateau.

Predictors of statin adherence, switching, and discontinuation in the USAGE survey: understanding the use of statins in America and gaps in patient education.

PubMed

Wei, Melissa Y; Ito, Matthew K; Cohen, Jerome D; Brinton, Eliot A; Jacobson, Terry A

2013-01-01

Although statins have been shown to reduce cardiovascular disease mortality, less than half of U.S. adults achieve their low-density lipoprotein cholesterol goal. In many patients initiated on a statin, adherence rates decrease over time. To characterize current and former statin users, identify reasons for the discontinuation or switching of statins, and identify factors associated with adherence. The USAGE survey is a cross-sectional, self-administered Internet-based survey of 10,138 U.S. adults fielded September to October 2011. The following statin users were identified and compared: adherent nonswitchers, adherent switchers, non-adherent switchers, and discontinuers. Univariate and multivariate models using a priori covariates for adherence and discontinuation were examined. Most participants were current statin users who adhered with their prescribed statin (82.5%, n = 8371). Former statin users or discontinuers (12%, n = 1220) cited muscle pain, a side effect, as the primary reason for discontinuation (60%), followed by cost (16%), and then perceived lack of efficacy (13%). Discontinuers were less satisfied with their physicians' explanation of cholesterol treatment, more likely to use the Internet to research statins, and less likely to undergo frequent cholesterol monitoring. Among adherent statin users, the primary reasons for switching were muscle side effects (33%) and cost (32%). Individuals at risk for non-adherence included those with low household income, those who experienced muscle pain as a side effect while on statin therapy, and those taking medication for cardiovascular disease. Statin-related muscle side effects are common and contribute significantly to rates of discontinuation, switching, and non-adherence. Improved physician patient communication about side effects and benefits of statins are necessary to improve both adherence and outcomes. Copyright © 2013 National Lipid Association. Published by Elsevier Inc. All rights reserved.

A Lagrangian discontinuous Galerkin hydrodynamic method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xiaodong; Morgan, Nathaniel Ray; Burton, Donald E.

Here, we present a new Lagrangian discontinuous Galerkin (DG) hydrodynamic method for solving the two-dimensional gas dynamic equations on unstructured hybrid meshes. The physical conservation laws for the momentum and total energy are discretized using a DG method based on linear Taylor expansions. Three different approaches are investigated for calculating the density variation over the element. The first approach evolves a Taylor expansion of the specific volume field. The second approach follows certain finite element methods and uses the strong mass conservation to calculate the density field at a location inside the element or on the element surface. The thirdmore » approach evolves a Taylor expansion of the density field. The nodal velocity, and the corresponding forces, are explicitly calculated by solving a multidirectional approximate Riemann problem. An effective limiting strategy is presented that ensures monotonicity of the primitive variables. This new Lagrangian DG hydrodynamic method conserves mass, momentum, and total energy. Results from a suite of test problems are presented to demonstrate the robustness and expected second-order accuracy of this new method.« less

A Lagrangian discontinuous Galerkin hydrodynamic method

DOE PAGES

Liu, Xiaodong; Morgan, Nathaniel Ray; Burton, Donald E.

2017-12-11

Here, we present a new Lagrangian discontinuous Galerkin (DG) hydrodynamic method for solving the two-dimensional gas dynamic equations on unstructured hybrid meshes. The physical conservation laws for the momentum and total energy are discretized using a DG method based on linear Taylor expansions. Three different approaches are investigated for calculating the density variation over the element. The first approach evolves a Taylor expansion of the specific volume field. The second approach follows certain finite element methods and uses the strong mass conservation to calculate the density field at a location inside the element or on the element surface. The thirdmore » approach evolves a Taylor expansion of the density field. The nodal velocity, and the corresponding forces, are explicitly calculated by solving a multidirectional approximate Riemann problem. An effective limiting strategy is presented that ensures monotonicity of the primitive variables. This new Lagrangian DG hydrodynamic method conserves mass, momentum, and total energy. Results from a suite of test problems are presented to demonstrate the robustness and expected second-order accuracy of this new method.« less

Chebyshev polynomial filtered subspace iteration in the discontinuous Galerkin method for large-scale electronic structure calculations

DOE PAGES

Banerjee, Amartya S.; Lin, Lin; Hu, Wei; ...

2016-10-21

The Discontinuous Galerkin (DG) electronic structure method employs an adaptive local basis (ALB) set to solve the Kohn-Sham equations of density functional theory in a discontinuous Galerkin framework. The adaptive local basis is generated on-the-fly to capture the local material physics and can systematically attain chemical accuracy with only a few tens of degrees of freedom per atom. A central issue for large-scale calculations, however, is the computation of the electron density (and subsequently, ground state properties) from the discretized Hamiltonian in an efficient and scalable manner. We show in this work how Chebyshev polynomial filtered subspace iteration (CheFSI) canmore » be used to address this issue and push the envelope in large-scale materials simulations in a discontinuous Galerkin framework. We describe how the subspace filtering steps can be performed in an efficient and scalable manner using a two-dimensional parallelization scheme, thanks to the orthogonality of the DG basis set and block-sparse structure of the DG Hamiltonian matrix. The on-the-fly nature of the ALB functions requires additional care in carrying out the subspace iterations. We demonstrate the parallel scalability of the DG-CheFSI approach in calculations of large-scale twodimensional graphene sheets and bulk three-dimensional lithium-ion electrolyte systems. In conclusion, employing 55 296 computational cores, the time per self-consistent field iteration for a sample of the bulk 3D electrolyte containing 8586 atoms is 90 s, and the time for a graphene sheet containing 11 520 atoms is 75 s.« less

Glass Formation of n-Butanol: Coarse-grained Molecular Dynamics Simulations Using Gay-Berne Potential Model

NASA Astrophysics Data System (ADS)

Xie, Gui-long; Zhang, Yong-hong; Huang, Shi-ping

2012-04-01

Using coarse-grained molecular dynamics simulations based on Gay-Berne potential model, we have simulated the cooling process of liquid n-butanol. A new set of GB parameters are obtained by fitting the results of density functional theory calculations. The simulations are carried out in the range of 290-50 K with temperature decrements of 10 K. The cooling characteristics are determined on the basis of the variations of the density, the potential energy and orientational order parameter with temperature, whose slopes all show discontinuity. Both the radial distribution function curves and the second-rank orientational correlation function curves exhibit splitting in the second peak. Using the discontinuous change of these thermodynamic and structure properties, we obtain the glass transition at an estimate of temperature Tg=120±10 K, which is in good agreement with experimental results 110±1 K.

Influence of system size on the properties of a fluid adsorbed in a nanopore: Physical manifestations and methodological consequences

DOE Office of Scientific and Technical Information (OSTI.GOV)

Puibasset, Joël, E-mail: puibasset@cnrs-orleans.fr; Kierlik, Edouard, E-mail: edouard.kierlik@upmc.fr; Tarjus, Gilles, E-mail: tarjus@lptl.jussieu.fr

Hysteresis and discontinuities in the isotherms of a fluid adsorbed in a nanopore in general hamper the determination of equilibrium thermodynamic properties, even in computer simulations. A way around this has been to consider both a reservoir of small size and a pore of small extent in order to restrict the fluctuations of density and approach a classical van der Waals loop. We assess this suggestion by thoroughly studying through Monte Carlo simulations and density functional theory the influence of system size on the equilibrium configurations of the adsorbed fluid and on the resulting isotherms. We stress the importance ofmore » pore-symmetry-breaking states that even for modest pore sizes lead to discontinuous isotherms and we discuss the physical relevance of these states and the methodological consequences for computing thermodynamic quantities.« less

Theory of charge density wave depinning by electromechanical effect

NASA Astrophysics Data System (ADS)

Quémerais, P.

2017-03-01

We discuss the first theory for the depinning of low-dimensional, incommensurate, charge density waves (CDWs) in the strong electron-phonon (e-p) regime. Arguing that most real CDWs systems invariably develop a gigantic dielectric constant (GDC) at very low frequencies, we propose an electromechanical mechanism which is based on a local field effect. At zero electric field and large enough e-p coupling the structures are naturally pinned by the lattice due to its discreteness, and develop modulation functions which are characterized by discontinuities. When the electric field is turned on, we show that it exists a finite threshold value for the electric field above which the discontinuities of the modulation functions vanish due to CDW deformation. The CDW is then free to move. The signature of this pinning/depinning transition as a function of the increasing electric field can be directly observed in the phonon spectrum by using inelastic neutrons or X-rays experiments.

Interactions Between Diet and the Intestinal Microbiota Alter Intestinal Permeability and Colitis Severity in Mice.

PubMed

Llewellyn, Sean R; Britton, Graham J; Contijoch, Eduardo J; Vennaro, Olivia H; Mortha, Arthur; Colombel, Jean-Frederic; Grinspan, Ari; Clemente, Jose C; Merad, Miriam; Faith, Jeremiah J

2018-03-01

It is not clear how the complex interactions between diet and the intestinal microbiota affect development of mucosal inflammation or inflammatory bowel disease. We investigated interactions between dietary ingredients, nutrients, and the microbiota in specific pathogen-free (SPF) and germ-free (GF) mice given more than 40 unique diets; we quantified individual and synergistic effects of dietary macronutrients and the microbiota on intestinal health and development of colitis. C56BL/6J SPF and GF mice were placed on custom diets containing different concentrations and sources of protein, fat, digestible carbohydrates, and indigestible carbohydrates (fiber). After 1 week, SPF and GF mice were given dextran sulfate sodium (DSS) to induce colitis. Disease severity was determined based on the percent weight change from baseline, and modeled as a function of the concentration of each macronutrient in the diet. In unchallenged mice, we measured intestinal permeability by feeding mice labeled dextran and measuring levels in blood. Feces were collected and microbiota were analyzed by 16S rDNA sequencing. We collected colons from mice and performed transcriptome analyses. Fecal microbiota varied with diet; the concentration of protein and fiber had the strongest effect on colitis development. Among 9 fiber sources tested, psyllium, pectin, and cellulose fiber reduced the severity of colitis in SPF mice, whereas methylcellulose increased severity. Increasing dietary protein increased the density of the fecal microbiota and the severity of colitis in SPF mice, but not in GF mice or mice given antibiotics. Psyllium fiber reduced the severity of colitis through microbiota-dependent and microbiota-independent mechanisms. Combinatorial perturbations to dietary casein protein and psyllium fiber in parallel accounted for most variation in gut microbial density and intestinal permeability in unchallenged mice, as well as the severity of DSS-induced colitis; changes in 1 ingredient could be offset by changes in another. In an analysis of the effects of different dietary components and the gut microbiota on mice with and without DSS-induced colitis, we found complex mixtures of nutrients affect intestinal permeability, gut microbial density, and development of intestinal inflammation. Copyright © 2018 AGA Institute. Published by Elsevier Inc. All rights reserved.

Transfection using DEAE-dextran.

PubMed

Selden, R F

2001-05-01

Two protocols for DEAE-dextran transfection of cells are provided in this unit. The Basic Protocol describes a procedure used to transfect adherent cells and the first Alternate Protocol presents a method used to transfect suspension cells. If an increase in transfection efficiency is needed, cells can be treated with chloroquine as described in the second Alternate Protocol.

Effect of varying molecular weight of dextran on acrylic-derivatized dextran and concanavalin A glucose-responsive materials for closed-loop insulin delivery.

PubMed

Sahota, Tarsem; Sawicka, Kirsty; Taylor, Joan; Tanna, Sangeeta

2011-03-01

Dextran methacrylate (dex-MA) and concanavalin A (con A)-methacrylamide were photopolymerized to produce covalently cross-linked glucose-sensitive gels for the basis of an implantable closed-loop insulin delivery device. The viscoelastic properties of these polymerized gels were tested rheologically in the non-destructive oscillatory mode within the linear viscoelastic range at glucose concentrations between 0 and 5% (w/w). For each cross-linked gel, as the glucose concentration was raised, a decrease in storage modulus, loss modulus and complex viscosity (compared at 1 Hz) was observed, indicating that these materials were glucose responsive. The higher molecular weight acrylic-derivatized dextrans [degree of substitution (DS) 3 and 8%] produced higher complex viscosities across the glucose concentration range. These studies coupled with in vitro diffusion experiments show that dex-MA of 70 kDa and DS (3%) was the optimum mass average molar mass to produce gels that show reduced component leach, glucose responsiveness, and insulin transport useful as part of a self-regulating insulin delivery device.

Macromolecular cross-linked enzyme aggregates (M-CLEAs) of α-amylase.

PubMed

Nadar, Shamraja S; Muley, Abhijeet B; Ladole, Mayur R; Joshi, Pranoti U

2016-03-01

Macromolecular cross-linked enzyme aggregates (M-CLEAs) of α-amylase were prepared by precipitation and subsequent cross-linking. The non-toxic, biodegradable, biocompatible, renewable polysaccharide based macromolecular cross-linkers viz. agar, chitosan, dextran, and gum arabic were used as a substitute for traditional glutaraldehyde to augment activity recovery toward macromolecular substrate. Macromolecular cross-linkers were prepared by periodate mediated controlled oxidation of polysaccharides. The effects of precipitating agent, concentration and different cross-linkers on activity recovery of α-amylase CLEAs were investigated. α-Amylase aggregated with ammonium sulphate and cross-linked by dextran showed 91% activity recovery, whereas glutaraldehyde CLEAs (G-CLEAs) exhibited 42% activity recovery. M-CLEAs exhibited higher thermal stability in correlation with α-amylase and G-CLEAs. Moreover, dextran and chitosan M-CLEAs showed same affinity for starch hydrolysis as of free α-amylase. The changes in secondary structures revealed the enhancements in structural and conformational rigidity attributed by cross-linkers. Finally, after five consecutive cycles dextran M-CLEAs retained 1.25 times higher initial activity than G-CLEAs. Copyright © 2015 Elsevier B.V. All rights reserved.

New shell crosslinked micelles from dextran with hydrophobic end groups and their interaction with bioactive molecules.

PubMed

Mocanu, Georgeta; Nichifor, Marieta; Stanciu, Magdalena C

2015-03-30

Micelles formed in aqueous solution by dextran with hydrophobic (alkyl) end-groups were stabilized through divinyl sulfone crosslinking of the dextran shell. The efficacy of the crosslinking reaction was influenced by the divinyl sulfone amount, the pH and micelle concentration. Crosslinked micelles with a moderate crosslinking degree were further functionalized by attachment of 10 and 17 moles% N-(2-hydroxypropyl)-N,N-dimethyl-N-benzylammonium chloride groups along the dextran chain. The size and shape of both crosslinked micelles and their cationic derivatives were analyzed by DLS and TEM. The prepared micelles were able to bind anionic diclofenac (60-370 mg/g), hydrophobic anionic indometacin (70-120 mg/g), and hydrophobic alpha-tocopherol (170-220 mg/g) or ergocalciferol (90-110 mg/g) by hydrophobic or/and electrostatic forces. The release experiments and the antioxidant activity of bound alpha-tocopherol highlighted the potential of the new nano-sized micelles mainly as carriers for prolonged and controlled delivery of hydrophobic drugs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Inositol and hepatic lipidosis. I. Effect of inositol supplementation and time from parturition on liver and serum lipids in dairy cattle.

PubMed

Gerloff, B J; Herdt, T H; Wells, W W; Liesman, J S; Emery, R S

1986-06-01

Percutaneous liver biopsies and blood samples were obtained from 80 multiparous dairy cows in nine Michigan herds. Biopsies and samples were obtained serially over the peripartum period. Thirty-nine cows received 17 g of supplemental myoinositol in the diet to test its use as a possible lipotropic substance and 41 received a placebo. Liver biopsies were assayed for triglyceride (TG) and total myoinositol content. Serum was assayed for dextran precipitable cholesterol and non-esterified fatty acids (NEFA). Inositol supplementation had no effect on any of the lipid variables. There was a significant herd effect on liver inositol, serum dextran precipitable cholesterol and NEFA concentrations. Serum NEFA and liver TG concentrations increased in the immediate postpartum period, while dextran precipitable cholesterol decreased. A significant herd X period interaction existed for liver TG and serum dextran precipitable cholesterol concentrations. Liver TG and serum NEFA concentrations were positively correlated. Excessive infiltration of bovine liver with lipid at calving appears to be an exaggerated manifestation of normal metabolic changes.

Synthesis and application of magnetite dextran-spermine nanoparticles in breast cancer hyperthermia.

PubMed

Avazzadeh, Reza; Vasheghani-Farahani, Ebrahim; Soleimani, Masoud; Amanpour, Saeid; Sadeghi, Mohsen

2017-09-01

Cancer treatment has been very challenging in recent decades. One of the most promising cancer treatment methods is hyperthermia, which increases the tumor temperature (41-45 °C). Magnetic nanoparticles have been widely used for selective targeting of cancer cells. In the present study, magnetic dextran-spermine nanoparticles, conjugated with Anti-HER2 antibody to target breast cancer cells were developed. The magnetic dextran-spermine nanoparticles (DMNPs) were prepared by ionic gelation, followed by conjugation of antibody to them using EDC-NHS method. Then the Prussian blue method was used to estimate the targeting ability and cellular uptake. Cytotoxicity assay by MTT showed that antibody-conjugated MNPs (ADMNPs) have no toxic effect on SKBR3 and human fibroblast cells. Finally, the hyperthermia was applied to show that synthesized ADMNPs, could increase the cancer cells temperature up to 45 °C and kill most of them without affecting normal cells. These observations proved that Anti-HER2 conjugated magnetic dextran-spermine nanoparticles can target and destroy cancer cells and are potentially suitable for cancer treatment.

Neurogenic plasma exudation mediates grain dust-induced tissue injury in vivo.

PubMed

Gao, X P; Von Essen, S; Rubinstein, I

1997-02-01

The purpose of this study was to determine whether an aqueous extract of grain sorghum dust (GDE) elicits neurogenic plasma exudation in the oral mucosa in vivo. Using intravital microscopy, we found that GDE elicited significant, concentration-dependent leaky site formation and an increase in clearance of fluorescein isothiocyanate-labeled dextran (FITC-dextran; mol mass 70 kDa) from the hamster cheek pouch (P < 0.05). The selective, nonpeptide neurokinin(1) (substance P) receptor antagonists, CP-96,345 and RP-67580, but not the 2R,3R enantiomer CP-96,344, significantly attenuated GDE-induced leaky site formation and increase in clearance of FITC-dextran (P < 0.05). Indomethacin had no significant effects on GDE-induced responses. CP-96,345 had no significant effects of adenosine-induced leaky site formation and increase in clearance of FITC-dextran from the cheek pouch. We conclude that GDE elicits neurogenic plasma exudation from the oral mucosa in vivo. We suggest that this process is one mechanism whereby grain sorghum dust elicits immediate oral mucosa inflammation in vivo.

Grain sorghum dust increases macromolecular efflux from the in situ nasal mucosa.

PubMed

Gao, X P

1998-04-01

The purpose of this study was to determine whether an aqueous extract of grain sorghum dust increases macromolecular efflux from the nasal mucosa in vivo and, if so, whether this response is mediated, in part, by substance P. Suffusion of grain sorghum dust extract on the in situ nasal mucosa of anesthetized hamsters elicits a significant increase in clearance of fluorescein isothiocyanate-labeled dextran (FITC-dextran; mol mass, 70 kDa; P < 0.05). This response is significantly attenuated by CP-96345 and RP-67580, two selective, but structurally distinct, nonpeptide neurokinin 1 (substance P)-receptor antagonists, but not by CP-96344, the 2R,3R enantiomer of CP-96345 (P < 0.05). CP-96345 has no significant effects on adenosine-induced increase in clearance of FITC-dextran from the in situ nasal mucosa. CP-96345 and RP-67580, but not CP-96344, significantly attenuate substance P-induced increases in clearance of FITC-dextran from the in situ nasal mucosa (P < 0.05). Collectively, these data suggest that grain sorghum dust elicits neurogenic plasma exudation from the in situ nasal mucosa.

Continuous monitoring of blood volume changes in humans

NASA Technical Reports Server (NTRS)

Hinghofer-Szalkay, H.; Greenleaf, J. E.

1987-01-01

Use of on-line high-precision mass densitometry for the continuous monitoring of blood volume changes in humans was demonstrated by recording short-term blood volume alterations produced by changes in body position. The mass density of antecubital venous blood was measured continuously for 80 min per session with 0.1 g/l precision at a flow rate of 1.5 ml/min. Additional discrete plasma density and hematocrit measurements gave linear relations between all possible combinations of blood density, plasma density, and hematocrit. Transient filtration phenomena were revealed that are not amenable to discontinuous measurements.

Transfusion of stored blood impairs host defenses against Gram-negative pathogens in mice.

PubMed

Prestia, Kevin; Bandyopadhyay, Sheila; Slate, Andrea; Francis, Richard O; Francis, Kevin P; Spitalnik, Steven L; Fidock, David A; Brittenham, Gary M; Hod, Eldad A

2014-11-01

Although human red blood cell (RBC) units may be refrigerator stored for up to 42 days, transfusion of older RBCs acutely delivers a large bolus of iron to mononuclear phagocytes. Similarly, iron dextran circulates in plasma for hours to days and is progressively cleared by mononuclear phagocytes, which return iron to plasma. Finally, malaria infection continuously delivers iron to macrophages by intra- and extravascular hemolysis. Studies suggest that iron administration increases infectious risk. To assess the effects of increased iron availability on susceptibility to infection, we infected mice with model Gram-negative intracellular or extracellular pathogens (Salmonella typhimurium or Escherichia coli, respectively), accompanied by RBC transfusion, iron dextran administration, or malarial coinfection. In our mouse models, transfusion of older RBCs exacerbates infection with both Gram-negative pathogens. Although iron dextran exacerbates E. coli infection to a similar extent as transfusion of corresponding amounts of iron, higher iron doses are required to produce comparable effects with S. typhimurium. Coinfection of mice with Plasmodium yoelii and S. typhimurium produces overwhelming Salmonella sepsis. Finally, treating mice with antibiotics abrogates the enhancing effect on E. coli infection of both older RBC transfusion and iron dextran administration. Transfusion of older RBCs exacerbates Gram-negative infection to a similar extent as malaria coinfection or iron dextran administration. Appropriate antibiotic therapy abrogates the effect of older RBC transfusions on infection with E. coli. Iron delivery to macrophages may be an underappreciated mechanism mediating, at least some, adverse effects of RBC transfusions. © 2014 AABB.

Ingenious pH-sensitive dextran/mesoporous silica nanoparticles based drug delivery systems for controlled intracellular drug release.

PubMed

Zhang, Min; Liu, Jia; Kuang, Ying; Li, Qilin; Zheng, Di-Wei; Song, Qiongfang; Chen, Hui; Chen, Xueqin; Xu, Yanglin; Li, Cao; Jiang, Bingbing

2017-05-01

In this work, dextran, a polysaccharide with excellent biocompatibility, is applied as the "gatekeeper" to fabricate the pH-sensitive dextran/mesoporous silica nanoparticles (MSNs) based drug delivery systems for controlled intracellular drug release. Dextran encapsulating on the surface of MSNs is oxidized by NaIO 4 to obtain three kinds of dextran dialdehydes (PADs), which are then coupled with MSNs via pH-sensitive hydrazone bond to fabricate three kinds of drug carriers. At pH 7.4, PADs block the pores to prevent premature release of anti-cancer drug doxorubicin hydrochloride (DOX). However, in the weakly acidic intracellular environment (pH∼5.5) the hydrazone can be ruptured; and the drug can be released from the carriers. The drug loading capacity, entrapment efficiency and release rates of the drug carriers can be adjusted by the amount of NaIO 4 applied in the oxidation reaction. And from which DOX@MSN-NH-N=C-PAD 10 is chosen as the most satisfactory one for the further in vitro cytotoxicity studies and cellular uptake studies. The results demonstrate that DOX@MSN-NH-N=C-PAD 10 with an excellent pH-sensitivity can enter HeLa cells to release DOX intracellular due to the weakly acidic pH intracellular and kill the cells. In our opinion, the ingenious pH-sensitive drug delivery systems have application potentials for cancer therapy. Copyright © 2017 Elsevier B.V. All rights reserved.

Dextran and protamine-based solid lipid nanoparticles as potential vectors for the treatment of X-linked juvenile retinoschisis.

PubMed

Delgado, Diego; del Pozo-Rodríguez, Ana; Solinís, Maria Ángeles; Avilés-Triqueros, Marcelino; Weber, Bernhard H F; Fernández, Eduardo; Gascón, Alicia R

2012-04-01

The goal of the present study was to analyze the potential application of nonviral vectors based on solid lipid nanoparticles (SLN) for the treatment of ocular diseases by gene therapy, specifically X-linked juvenile retinoschisis (XLRS). Vectors were prepared with SLN, dextran, protamine, and a plasmid (pCMS-EGFP or pCEP4-RS1). Formulations were characterized and the in vitro transfection capacity as well as the cellular uptake and the intracellular trafficking were studied in ARPE-19 cells. Formulations were also tested in vivo in Wistar rat eyes, and the efficacy was studied by monitoring the expression of enhanced green fluorescent protein (EGFP) after intravitreal, subretinal, and topical administration. The presence of dextran and protamine in the SLN improved greatly the expression of retinoschisin and EGFP in ARPE-19 cells. The nuclear localization signals of protamine, its ability to protect the DNA, and a shift in the entry mechanism from caveola-mediated to clathrin-mediated endocytosis promoted by the dextran, justify the increase in transfection. After ocular administration of the dextran-protamine-DNA-SLN complex to rat eyes, we detected the expression of EGFP in various types of cells depending on the administration route. Our vectors were also able to transfect corneal cells after topical application. We have demonstrated the potential usefulness of our nonviral vectors loaded with XLRS1 plasmid and provided evidence for their potential application for the management or treatment of degenerative retinal disorders as well as ocular surface diseases.

Development of Recombinant Human Growth Hormone (rhGH) sustained-release microspheres by a low temperature aqueous phase/aqueous phase emulsion method.

PubMed

Kang, Jian; Wu, Fei; Cai, Yunpeng; Xu, Mingxin; He, Mu; Yuan, Weien

2014-10-01

A novel method has been developed to protect Recombinant Human Growth Hormone (rhGH) in poly (lactic-co-glycolic acid) (PLGA) microspheres using an aqueous phase/aqueous phase emulsion and S/O/W multi-emulsion method. This method develops a novel rhGH sustained-release system, which is based on the combination of rhGH-loaded dextran microparticles and PLGA microspheres. The process to fabricate rhGH-loaded dextran microparticles involves an aqueous phase/aqueous phase emulsion system formed at the reduced temperature. RhGH was first dissolved in water together with dextran and polyethylene glycol, followed by stirring at the speed of 2000 rpm for 20-30s at 0°C, and then a freezing process could enable the dextran phase to separate from the continuous PEG phase and rhGH could preferentially be loaded with dextran. The sample after freezing and phase separation was then lyophilized to powder and washed with dichloromethane to remove the PEG. Once loaded in the dextran microparticles (1-4 μm in diameter), rhGH gained resistance to interface tensions and was encapsulated into PLGA microspheres without aggregation thereafter. RhGH released from PLGA microspheres was in a sustained manner with minimal burst and maximally reduced incomplete release in vitro. Single subcutaneous injection of rhGH-loaded PLGA microspheres to rats resulted in a stable plasma concentration for 30 days avoiding the drug concentration fluctuations after multiple injections of protein solutions. In a hypophysectomized rat model, the IGF-1 and bodyweight results showed that there were higher than the levels obtained for the sustained release formulation by W/O/W for 40 days. These results suggest that the microsphere delivery system had the potential to be an injectable depot for sustained-release of the biocompatible protein of rhGH. Copyright © 2014 Elsevier B.V. All rights reserved.

Nanoparticles of alkylglyceryl-dextran-graft-poly(lactic acid) for drug delivery to the brain: Preparation and in vitro investigation.

PubMed

Toman, Petr; Lien, Chun-Fu; Ahmad, Zeeshan; Dietrich, Susanne; Smith, James R; An, Qian; Molnár, Éva; Pilkington, Geoffrey J; Górecki, Darek C; Tsibouklis, John; Barbu, Eugen

2015-09-01

Poly(lactic acid), which has an inherent tendency to form colloidal systems of low polydispersity, and alkylglyceryl-modified dextran - a material designed to combine the non-immunogenic and stabilising properties of dextran with the demonstrated permeation enhancing ability of alkylglycerols - have been combined for the development of nanoparticulate, blood-brain barrier-permeating, non-viral vectors. To this end, dextran, that had been functionalised via treatment with epoxide precursors of alkylglycerol, was covalently linked to poly(lactic acid) using a carbodiimide cross-linker to form alkylglyceryl-modified dextran-graft-poly(lactic acid). Solvent displacement and electrospray methods allowed the formulation of these materials into nanoparticles having a unimodal size distribution profile of about 100-200nm and good stability at physiologically relevant pH (7.4). The nanoparticles were characterised in terms of hydrodynamic size (by Dynamic Light Scattering and Nanoparticle Tracking Analysis), morphology (by Scanning Electron Microscopy and Atomic Force Microscopy) and zeta potential, and their toxicity was evaluated using MTT and PrestoBlue assays. Cellular uptake was evidenced by confocal microscopy employing nanoparticles that had been loaded with the easy-to-detect Rhodamine B fluorescent marker. Transwell-model experiments employing mouse (bEnd3) and human (hCMEC/D3) brain endothelial cells revealed enhanced permeation (statistically significant for hCMEC/D3) of the fluorescent markers in the presence of the nanoparticles. Results of studies using Electric Cell Substrate Impedance Sensing suggested a transient decrease of the barrier function in an in vitro blood-brain barrier model following incubation with these nanoformulations. An in ovo study using 3-day chicken embryos indicated the absence of whole-organism acute toxicity effects. The collective in vitro data suggest that these alkylglyceryl-modified dextran-graft-poly(lactic acid) nanoparticles are promising candidates for in vivo evaluations that would test their capability to transport therapeutic actives to the brain. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Diffusion and clearance of superparamagnetic iron oxide nanoparticles infused into the rat striatum studied by MRI and histochemical techniques

NASA Astrophysics Data System (ADS)

Wang, F. H.; Kim, D. K.; Yoshitake, T.; Johansson, S. M.; Bjelke, B.; Muhammed, M.; Kehr, J.

2011-01-01

The purpose of the present study was to investigate, by MRI and histochemical techniques, the diffusion and clearance abilities of superparamagnetic iron oxide nanoparticles (SPION) coated with dextran (Dextran-SPION) and gold (Au-SPION) following their local infusions into the rat brain. In separate groups of anesthetized rats, the Dextran-SPION and Au-SPION were infused at concentrations of 0.01, 0.1, 1 and 5 µg Fe/0.5 µl and at the flow rate of 0.5 µl min - 1 into the left and right striata, respectively. Repetitive T2-weighted spin-echo MRI scans were performed at time intervals of 1, 6, 12, 24, 48, 72 h, and one, two and eight weeks after inoculation. Following infusion of Dextran-SPION (0.1 µg and 1 µg Fe), the maximal distribution volume was observed at about 12-24 h after inoculation and two weeks later the Fe signals were undetectable for the lower dose. On the other hand, Au-SPION remained tightly localized in the closest vicinity of the infusion site as revealed by unchanged MRI signal intensities and strong histochemical staining of Fe2 + and Fe3 + ions in the corresponding brain slices. Immunohistochemical staining of astrocytic and microglial reactions revealed that there were no marked differences in GFAP, VIM or OX-42 labeling observed between the nanoparticle types, however the astrocytic reaction was more pronounced in rats receiving nanoparticles compared to the control (aCSF-infused) rats. In conclusion, the present data demonstrate that the viral-sized Dextran-SPION were able to diffuse freely through the interstitial space of the brain being progressively cleared out from the infusion site within two weeks. Thus, Dextran-SPION could be beneficially used in MRI-guided diagnostic applications such as in experimental oncology or as labels and carriers for targeted drug delivery, whereas Au-SPION could be used for labeling and tracking the transplanted stem cells in experimental MRI.

Conjugation of metronidazole with dextran: a potential pharmaceutical strategy to control colonic distribution of the anti-amebic drug susceptible to metabolism by colonic microbes

PubMed Central

Kim, Wooseong; Yang, Yejin; Kim, Dohoon; Jeong, Seongkeun; Yoo, Jin-Wook; Yoon, Jeong-Hyun; Jung, Yunjin

2017-01-01

Metronidazole (MTDZ), the drug of choice for the treatment of protozoal infections such as luminal amebiasis, is highly susceptible to colonic metabolism, which may hinder its conversion from a colon-specific prodrug to an effective anti-amebic agent targeting the entire large intestine. Thus, in an attempt to control the colonic distribution of the drug, a polymeric colon-specific prodrug, MTDZ conjugated to dextran via a succinate linker (Dex-SA-MTDZ), was designed. Upon treatment with dextranase for 8 h, the degree of Dex-SA-MTDZ depolymerization (%) with a degree of substitution (mg of MTDZ bound in 100 mg of Dex-SA-MTDZ) of 7, 17, and 30 was 72, 38, and 8, respectively, while that of dextran was 85. Depolymerization of Dex-SA-MTDZ was found to be necessary for the release of MTDZ, because dextranase pretreatment ensures that de-esterification occurs between MTDZ and the dextran backbone. In parallel, Dex-SA-MTDZ with a degree of substitution of 17 was found not to release MTDZ upon incubation with the contents of the small intestine and stomach of rats, but it released MTDZ when incubated with rat cecal contents (including microbial dextranases). Moreover, Dex-SA-MTDZ exhibited prolonged release of MTDZ, which contrasts with drug release by small molecular colon-specific prodrugs, MTDZ sulfate and N-nicotinoyl-2-{2-(2-methyl-5-nitroimidazol-1-yl)ethyloxy}-d,l-glycine. These prodrugs were eliminated very rapidly, and no MTDZ was detected in the cecal contents. Consistent with these in vitro results, we found that oral gavage of Dex-SA-MTDZ delivered MTDZ (as MTDZ conjugated to [depolymerized] dextran) to the distal colon. However, upon oral gavage of the small molecular prodrugs, no prodrugs were detected in the distal colon. Collectively, these data suggest that dextran conjugation is a potential pharmaceutical strategy to control the colonic distribution of drugs susceptible to colonic microbial metabolism. PMID:28243064

Conjugation of metronidazole with dextran: a potential pharmaceutical strategy to control colonic distribution of the anti-amebic drug susceptible to metabolism by colonic microbes.

PubMed

Kim, Wooseong; Yang, Yejin; Kim, Dohoon; Jeong, Seongkeun; Yoo, Jin-Wook; Yoon, Jeong-Hyun; Jung, Yunjin

2017-01-01

Metronidazole (MTDZ), the drug of choice for the treatment of protozoal infections such as luminal amebiasis, is highly susceptible to colonic metabolism, which may hinder its conversion from a colon-specific prodrug to an effective anti-amebic agent targeting the entire large intestine. Thus, in an attempt to control the colonic distribution of the drug, a polymeric colon-specific prodrug, MTDZ conjugated to dextran via a succinate linker (Dex-SA-MTDZ), was designed. Upon treatment with dextranase for 8 h, the degree of Dex-SA-MTDZ depolymerization (%) with a degree of substitution (mg of MTDZ bound in 100 mg of Dex-SA-MTDZ) of 7, 17, and 30 was 72, 38, and 8, respectively, while that of dextran was 85. Depolymerization of Dex-SA-MTDZ was found to be necessary for the release of MTDZ, because dextranase pretreatment ensures that de-esterification occurs between MTDZ and the dextran backbone. In parallel, Dex-SA-MTDZ with a degree of substitution of 17 was found not to release MTDZ upon incubation with the contents of the small intestine and stomach of rats, but it released MTDZ when incubated with rat cecal contents (including microbial dextranases). Moreover, Dex-SA-MTDZ exhibited prolonged release of MTDZ, which contrasts with drug release by small molecular colon-specific prodrugs, MTDZ sulfate and N -nicotinoyl-2-{2-(2-methyl-5-nitroimidazol-1-yl)ethyloxy}-d,l-glycine. These prodrugs were eliminated very rapidly, and no MTDZ was detected in the cecal contents. Consistent with these in vitro results, we found that oral gavage of Dex-SA-MTDZ delivered MTDZ (as MTDZ conjugated to [depolymerized] dextran) to the distal colon. However, upon oral gavage of the small molecular prodrugs, no prodrugs were detected in the distal colon. Collectively, these data suggest that dextran conjugation is a potential pharmaceutical strategy to control the colonic distribution of drugs susceptible to colonic microbial metabolism.

Comparison of Changes in Central Corneal Thickness During Corneal Collagen Cross-Linking, Using Isotonic Riboflavin Solutions With and Without Dextran, in the Treatment of Progressive Keratoconus.

PubMed

Zaheer, Naima; Khan, Wajid Ali; Khan, Shama; Khan, M Abdul Moqeet

2018-03-01

To compare intraoperative changes in central corneal thickness (CCT) during corneal cross-linking, using 2 different isotonic riboflavin solutions either with dextran or with hydroxy propyl methylcellulose, in the treatment of progressive keratoconus. In this retrospective study, we analyzed records of corneal thickness measurements, taken during various steps of cross-linking. Cross-linking was performed using either isotonic riboflavin with dextran (group A) or isotonic riboflavin with hydroxy propyl methylcellulose (without dextran) (group B). CCT measurements were recorded before and after epithelial removal, after saturation with respective isotonic riboflavin solution, after use of hypotonic riboflavin in selected cases, and after ultraviolet A (UV-A) application. A mixed-way analysis of variance was conducted on CCT readings within each group and between both groups, and p < 0.05 was considered significant. In group A (100 cases), after saturation with isotonic riboflavin, CCT was decreased by a mean of 51.4 μm (12.1%). In 64%, CCT was <400 μm and additional hypotonic riboflavin was used. After UV-A irradiation, CCT was decreased by a mean of 46.7 μm (11.4%). In group B (100 cases), after saturation with isotonic riboflavin, CCT was increased by a mean of 109.4 μm (26.1%). After UV-A exposure, CCT was increased by a mean of 59.2 μm (11.2%). There was a substantial main effect for time on CCT during corneal cross-linking (CXL), p < 0.001, within both groups. The main effect comparing CCT readings between groups A and B was also significant, p < 0.001. During cross-linking, isotonic riboflavin with dextran causes a significant decrease in corneal thickness, whereas dextran-free isotonic riboflavin causes a significant increase in corneal thickness, thus facilitating the procedure.

Non-Viral Transfection Methods Optimized for Gene Delivery to a Lung Cancer Cell Line

PubMed Central

Salimzadeh, Loghman; Jaberipour, Mansooreh; Hosseini, Ahmad; Ghaderi, Abbas

2013-01-01

Background Mehr-80 is a newly established adherent human large cell lung cancer cell line that has not been transfected until now. This study aims to define the optimal transfection conditions and effects of some critical elements for enhancing gene delivery to this cell line by utilizing different non-viral transfection Procedures. Methods In the current study, calcium phosphate (CaP), DEAE-dextran, superfect, electroporation and lipofection transfection methods were used to optimize delivery of a plasmid construct that expressed Green Fluorescent Protein (GFP). Transgene expression was detected by fluorescent microscopy and flowcytometry. Toxicities of the methods were estimated by trypan blue staining. In order to evaluate the density of the transfected gene, we used a plasmid construct that expressed the Stromal cell-Derived Factor-1 (SDF-1) gene and measured its expression by real-time PCR. Results Mean levels of GFP-expressing cells 48 hr after transfection were 8.4% (CaP), 8.2% (DEAE-dextran), 4.9% (superfect), 34.1% (electroporation), and 40.1% (lipofection). Lipofection had the highest intense SDF-1 expression of the analyzed methods. Conclusion This study has shown that the lipofection and electroporation methods were more efficient at gene delivery to Mehr-80 cells. The quantity of DNA per transfection, reagent concentration, and incubation time were identified as essential factors for successful transfection in all of the studied methods. PMID:23799175

Hydrodynamical models of cometary H II regions

NASA Astrophysics Data System (ADS)

Steggles, H. G.; Hoare, M. G.; Pittard, J. M.

2017-04-01

We have modelled the evolution of cometary H II regions produced by zero-age main-sequence stars of O and B spectral types, which are driving strong winds and are born off-centre from spherically symmetric cores with power-law (α = 2) density slopes. A model parameter grid was produced that spans stellar mass, age and core density. Exploring this parameter space, we investigated limb-brightening, a feature commonly seen in cometary H II regions. We found that stars with mass M⋆ ≥ 12 M⊙ produce this feature. Our models have a cavity bounded by a contact discontinuity separating hot shocked wind and ionized ambient gas that is similar in size to the surrounding H II region. Because of early pressure confinement, we did not see shocks outside of the contact discontinuity for stars with M⋆ ≤ 40 M⊙, but the cavities were found to continue to grow. The cavity size in each model plateaus as the H II region stagnates. The spectral energy distributions of our models are similar to those from identical stars evolving in uniform density fields. The turn-over frequency is slightly lower in our power-law models as a result of a higher proportion of low-density gas covered by the H II regions.

Phase transitions in local equation-of-state approximation and anomalies of spatial charge profiles in non-uniform plasma

NASA Astrophysics Data System (ADS)

Chigvintsev, A. Yu; Zorina, I. G.; Noginova, L. Yu; Iosilevskiy, I. L.

2018-01-01

Impressive appearance of discontinuities in equilibrium spatial charge profiles in non-uniform Coulomb systems is under discussions in wide number of thermoelectrostatics problems. Such discontinuities are considered as peculiar micro-level manifestation of phase transitions and intrinsic macro-level non-ideality effects in local equation of state (EOS), which should be used for description of non-ideal ionic subsystem in frames of local-density (or “pseudofluid”, or “jellium” etc) approximation. Such discontinuities were discussed already by the authors for electronic subsystems. Special emphasis is made in present paper on the mentioned above non-ideality effects in non-uniform ionic subsystems, such as micro-ions profile within screening “cloud” around macro-ion in complex (dusty, colloid etc) plasmas, equilibrium charge profile in ionic traps or (and) in the neighborhood vicinity of “charged wall” etc). Multiphase EOS for simplified ionic model of classical charged hard spheres on uniformly compressible electrostatic compensating background was constructed and several illustrative examples of discussed discontinuous ionic profiles were calculated.

Preparative liquid column electrophoresis of T and B lymphocytes at gravity = 1

NASA Technical Reports Server (NTRS)

Van Oss, C. J.; Bigazzi, P. E.; Gillman, C. F.; Allen, R. E.

1974-01-01

Vertical liquid columns containing low-molecular-weight dextran density gradients can be used for preparative lymphocyte electrophoresis on earth, in simulation of zero gravity conditions. Another method that has been tested at 1 g, is the electrophoresis of lymphocytes in an upward direction in vertical columns. By both methods up to 100 million lymphocytes can be separated at one time in a 30-cm glass column of 8-mm inside diameter, at 12 V/cm, in two hours. Due to convection and sedimentation problems, the separation at 1 g is less than ideal, but it is expected that at zero gravity electrophoresis will probe to be a uniquely powerful cell separation tool.

Physicochemical stability and in vitro bioaccessibility of ß-carotene nanoemulsions stabilized with whey protein-dextran conjugates

USDA-ARS?s Scientific Manuscript database

In this study, ß-carotene (BC)-loaded nanoemulsions encapsulated with native whey protein isolate (WPI) and WPI-dextran (DT, 5 kDa, 20 kDa, and 70 kDa) conjugates were prepared and the effects of glycosylation with various molecular weight DTs on the physicochemical property, lipolysis, and BC bioac...

Homogeneous Bacterial Aerosols Produced with a Spinning-Disc Generator

PubMed Central

Harstad, J. Bruce; Filler, Melvin E.; Hushen, William T.; Decker, Herbert M.

1970-01-01

Aerosols composed of viable particles of a uniform size were produced with a commercial spinning-disc generator from aqueous suspensions of Bacillus subtilis var. niger spores containing various amounts of an inert material, dextran, to regulate aerosol particle size. Aerosols composed of single naked spores having an equivalent spherical diameter of 0.87 μm were produced from spore suspensions without dextran, whereas aerosols produced from suspensions containing 0.001, 0.01, 0.1, and 1% dextran had median diameters of 0.90, 1.04, 1.80, and 3.62 μm, respectively. Such aerosols, both homogeneous and viable, would be useful for calibrating air sampling devices, evaluating air filter systems, or for employment wherever aerosol behavior may be size-dependent. Images PMID:4989672

Investigation of Stable Atmospheric Stratification Effect on the Dynamics of Descending Vortex Pairs

DOT National Transportation Integrated Search

1979-02-01

The physics of vortex flows in stratified fluids is studied with the objective of determining the influence of stable stratification on the descent of aircraft vortex pairs. Vortex rings descending into linear and discontinuous density stratification...

ON INTERMITTENT TURBULENCE HEATING OF THE SOLAR WIND: DIFFERENCES BETWEEN TANGENTIAL AND ROTATIONAL DISCONTINUITIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Xin; Tu Chuanyi; He Jiansen

The intermittent structures in solar wind turbulence, studied by using measurements from the WIND spacecraft, are identified as being mostly rotational discontinuities (RDs) and rarely tangential discontinuities (TDs) based on the technique described by Smith. Only TD-associated current sheets (TCSs) are found to be accompanied with strong local heating of the solar wind plasma. Statistical results show that the TCSs have a distinct tendency to be associated with local enhancements of the proton temperature, density, and plasma beta, and a local decrease of magnetic field magnitude. Conversely, for RDs, our statistical results do not reveal convincing heating effects. These resultsmore » confirm the notion that dissipation of solar wind turbulence can take place in intermittent or locally isolated small-scale regions which correspond to TCSs. The possibility of heating associated with RDs is discussed.« less

Adverse events, bone mineral density and discontinuation associated with generic alendronate among postmenopausal women previously tolerant of brand alendronate: a retrospective cohort study

PubMed Central

2010-01-01

Background A rise in gastrointestinal (GI) adverse events (AEs) and a decline in bone mineral density (BMD) was observed in patients previously tolerant to brand alendronate shortly after generic versions were introduced in July 2005 to the Canadian market. The objective of our study was to quantify changes in AE rates and BMD scores, as well as associated alendronate discontinuation among patients before and after switch from brand to generic alendronate. Methods A chart review of postmenopausal women 50 years of age and older between 2003 and 2007 was conducted in two specialized tertiary care referral centers. Patients on alendronate both before and after July 2005 were included. The change in the number of AEs, changes in BMD and associated alendronate discontinuation was compared before and after the switch from brand to generic alendronate. Results 301 women with an average age of 67.6 years (standard deviation (SD) = 9.5) had a total of 47 AEs between July 2003 and December 2007 that resulted in discontinuation of the medication. There was a significant increase in the rate of AEs per patient-months-at-risk from 0.0001 before to 0.0044 after October 2005 (p < 0.001). The most common AEs were GI in nature (stomach pain, GI upset, nausea, and reflux). In addition, 23 patients discontinued alendronate due to BMD reduction after January 2006. In these patients, BMD scores were significantly reduced from their prior BMD measures (change of -0.0534, p < 0.001 for spine BMD and change of -0.0338, p = 0.01 for femur BMD). Among patients who discontinued due to BMD reduction, BMD was stable in the period prior to January 2006 (change of -0.0066, p = 0.5 for spine BMD and change of 0.0011, p = 0.9 for femur BMD); however, testing for reduction after January 2006 in BMD measures (one-sided T-test) revealed there was a significant reduction in BMD scores for both anatomic sites (change of -0.0321, p = .005 for spine, change of -0.0205, p = 0.05 for femur). Conclusions Patients who were previously stable on doses of brand alendronate experienced an increase in AEs causing discontinuation after introduction of automatic substitution to generic alendronate. In addition, reductions in BMD were observed in some patients who had stable BMDs before January 2006. Given the substantial increase in AEs, generic alendronate may not be as well tolerated as brand alendronate. PMID:20388226

Colorimetric device for measurement of transvascular fluid flux in blood-perfused organs.

PubMed

Oppenheimer, L; Richardson, W N; Bilan, D; Hoppensack, M

1987-01-01

The aim of this study was to develop a device capable of measuring transvascular fluid flux in blood-perfused organs. For any given blood flow through the organ (QT), transvascular flux (QF) can be considered as the fraction of QT exchange. Presumably, QF would change the background concentration of an impermeable tracer residing in the perfusate. Thus QF could be calculated from the relative changes in tracer concentration for any given QT. We have used Blue Dextran (1 g/l of blood) as the reference tracer. Because the minimum molecular weight of Blue Dextran is 2 X 10(6), we anticipated it to behave as an impermeable tracer in most organs. QF was simulated with continuous infusions of plasma, normal saline solution, and a 50% mixture of both. Changes in Blue Dextran concentration were continuously followed colorimetrically by changes in transmission of specific light at a wavelength of 632 nm. Because 632-nm light is affected by hematocrit and O2 saturation changes, two additional wavelengths were used: 815-nm, which is not affected by saturation or Blue Dextran concentration changes, was used to account for changes in hematocrit, and 887-nm specific light, which is not affected by Blue Dextran, served to correct for saturation changes. Red cells could not be used as the reference tracer because of the possibility of hematocrit changes independent of fluid flux (Fahraeus effect). The device so constructed proved capable of measuring rates of fluid infusion in the order of 0.1% of QT with a variability of 10% around the mean.

Nitrosative Stress and Apoptosis by Intravenous Ferumoxytol, Iron Isomaltoside 1000, Iron Dextran, Iron Sucrose, and Ferric Carboxymaltose in a Nonclinical Model.

PubMed

Toblli, J E; Cao, G; Giani, J F; Dominici, F P; Angerosa, M

2015-07-01

Iron is involved in the formation as well as in the scavenging of reactive oxygen and nitrogen species. Thus, iron can induce as well as inhibit both oxidative and nitrosative stress. It also has a key role in reactive oxygen and nitrogen species-mediated apoptosis. We assessed the differences in tyrosine nitration and caspase 3 expression in the liver, heart, and kidneys of rats treated weekly with intravenous ferumoxytol, iron isomaltoside 1000, iron dextran, iron sucrose and ferric carboxymaltose (40 mg iron/kg body weight) for 5 weeks. Nitrotyrosine was quantified in tissue homogenates by Western blotting and the distribution of nitrotyrosine and caspase 3 was assessed in tissue sections by immunohistochemistry. Ferric carboxymaltose and iron sucrose administration did not result in detectable levels of nitrotyrosine or significant levels of caspase 3 vs. control in any of the tissue studied. Nitrotyrosine and caspase 3 levels were significantly (p<0.01) increased in all assessed organs of animals treated with iron dextran and iron isomaltoside 1000, as well as in the liver and kidneys of ferumoxytol-treated animals compared to isotonic saline solution (control). Nitrotyrosine and caspase 3 levels were shown to correlate positively with the amount of Prussian blue-detectable iron(III) deposits in iron dextran- and iron isomaltoside 1000-treated rats but not in ferumoxytol-treated rats, suggesting that iron dextran, iron isomaltoside 1000 and ferumoxytol induce nitrosative (and oxidative) stress as well as apoptosis via different mechanism(s). © Georg Thieme Verlag KG Stuttgart · New York.

Radiation dose rate affects the radiosensitization of MCF-7 and HeLa cell lines to X-rays induced by dextran-coated iron oxide nanoparticles.

PubMed

Khoshgard, Karim; Kiani, Parvaneh; Haghparast, Abbas; Hosseinzadeh, Leila; Eivazi, Mohammad Taghi

2017-08-01

The aim of radiotherapy is to deliver lethal damage to cancerous tissue while preserving adjacent normal tissues. Radiation absorbed dose of the tumoral cells can increase when high atomic nanoparticles are present in them during irradiation. Also, the dose rate is an important aspect in radiation effects that determines the biological results of a given dose. This in vitro study investigated the dose-rate effect on the induced radiosensitivity by dextran-coated iron oxide in cancer cells. HeLa and MCF-7 cells were cultured in vitro and incubated with different concentrations of dextran-coated iron oxide nanoparticles. They were then irradiated with 6 MV photons at dose rates of 43, 185 and 370 cGy/min. The MTT test was used to obtain the cells' survival after 48 h of irradiations. Incubating the cells with the nanoparticles at concentrations of 10, 40 and 80 μg/ml showed no significant cytotoxicity effect. Dextran-coated iron oxide nanoparticles showed more radiosensitivity effect by increasing the dose rate and nanoparticles concentration. Radiosensitization enhancement factors of MCF-7 and HeLa cells at a dose-rate of 370 cGy/min and nanoparticles' concentration of 80 μg/ml were 1.21 ± 0.06 and 1.19 ± 0.04, respectively. Increasing the dose rate of 6 MV photons irradiation in MCF-7 and HeLa cells increases the radiosensitization induced by the dextran-coated iron nanoparticles in these cells.

Pathogenesis of Infection by Clinical and Environmental Strains of Vibrio vulnificus in Iron-Dextran-Treated Mice

PubMed Central

Starks, Angela M.; Schoeb, Trenton R.; Tamplin, Mark L.; Parveen, Salina; Doyle, Thomas J.; Bomeisl, Philip E.; Escudero, Gloria M.; Gulig, Paul A.

2000-01-01

Vibrio vulnificus is an opportunistic pathogen that contaminates oysters harvested from the Gulf of Mexico. In humans with compromising conditions, especially excess levels of iron in plasma and tissues, consumption of contaminated seafood or exposure of wounds to contaminated water can lead to systemic infection and disfiguring skin infection with extremely high mortality. V. vulnificus-associated diseases are noted for the rapid replication of the bacteria in host tissues, with extensive tissue damage. In this study we examined the virulence attributes of three virulent clinical strains and three attenuated oyster or seawater isolates in mouse models of systemic disease. All six V. vulnificus strains caused identical skin lesions in subcutaneously (s.c.) inoculated iron dextran-treated mice in terms of numbers of recovered CFU and histopathology; however, the inocula required for identical frequency and magnitude of infection were at least 350-fold higher for the environmental strains. At lethal doses, all strains caused s.c. skin lesions with extensive edema, necrosis of proximate host cells, vasodilation, and as many as 108 CFU/g, especially in perivascular regions. These data suggest that the differences between these clinical and environmental strains may be related to growth in the host or susceptibility to host defenses. In non-iron dextran-treated mice, strains required 105-fold-higher inocula to cause an identical disease process as with iron dextran treatment. These results demonstrate that s.c. inoculation of iron dextran-treated mice is a useful model for studying systemic disease caused by V. vulnificus. PMID:10992486

Interferon Inducers Against Infectious Diseases.

DTIC Science & Technology

1991-06-15

mouse there was little, if any, difference. b. PLL- Monosaccharide Grafts. The PLL-dextran grafts described above contain long polysaccharide chains...engrafted polysaccharides . Our research has resulted in the demonstration that effective IFN inducers can be formulated without using...Action of IC-(PLL-dextran) .............. 7. Induction of IFN in Mice by IC-(PLL- monosaccharides ). I 8. ICL-SCDS04; Compositions and IFN Titers

Ni-Fe2O4 nanoparticles as contrast agents for magnetic resonance imaging.

PubMed

Ahmad, Tanveer; Rhee, Ilsu; Hong, Sungwook; Chang, Yongmin; Lee, Jaejun

2011-07-01

Reported herein is the synthesis of a dextran coating on nickel ferrite (Ni-Fe2O4) nanoparticles via chemical coprecipitation. The aqueous solution of the synthesized nanoparticles showed good colloidal stability, and no precipitate was observed 20 months after the synthesis. The coated nanoparticles were found to be cylindrical in shape in the TEM images, and showed a uniform size distribution with an average length and diameter of 17 and 4 nm, respectively. The coated particles were evaluated as potential T1 and T2 contrast agents for MRI. The T1 and T2 relaxations of the hydrogen protons in the water molecules in an aqueous solution of dextran-coated Ni-Fe2O4 nanoparticles were studied. It was found that the T1 relaxivity for the aqueous solution of dextran-coated nanoparticles was slightly greater than that of a commercial Gd-DTPA-BMA contrast agent. The T2 relaxivity, however, was almost twice that of the commercial Gd-DTPA-BMA contrast agent. Animal experimentation also demonstrated that the dextran-coated Ni-Fe2O4 nanoparticles are suitable for use as either T1 or T2 contrast agents in MRI.

Protein Corona Composition of Superparamagnetic Iron Oxide Nanoparticles with Various Physico-Chemical Properties and Coatings

NASA Astrophysics Data System (ADS)

Sakulkhu, Usawadee; Mahmoudi, Morteza; Maurizi, Lionel; Salaklang, Jatuporn; Hofmann, Heinrich

2014-05-01

Because of their biocompatibility and unique magnetic properties, superparamagnetic iron oxide nanoparticles NPs (SPIONs) are recognized as some of the most prominent agents for theranostic applications. Thus, understanding the interaction of SPIONs with biological systems is important for their safe design and efficient applications. In this study, SPIONs were coated with 2 different polymers: polyvinyl alcohol polymer (PVA) and dextran. The obtained NPs with different surface charges (positive, neutral, and negative) were used as a model study of the effect of surface charges and surface polymer materials on protein adsorption using a magnetic separator. We found that the PVA-coated SPIONs with negative and neutral surface charge adsorbed more serum proteins than the dextran-coated SPIONs, which resulted in higher blood circulation time for PVA-coated NPs than the dextran-coated ones. Highly abundant proteins such as serum albumin, serotransferrin, prothrombin, alpha-fetoprotein, and kininogen-1 were commonly found on both PVA- and dextran-coated SPIONs. By increasing the ionic strength, soft- and hard-corona proteins were observed on 3 types of PVA-SPIONs. However, the tightly bound proteins were observed only on negatively charged PVA-coated SPIONs after the strong protein elution.

Macromolecular crowding effect upon in vitro enzyme kinetics: mixed activation-diffusion control of the oxidation of NADH by pyruvate catalyzed by lactate dehydrogenase.

PubMed

Balcells, Cristina; Pastor, Isabel; Vilaseca, Eudald; Madurga, Sergio; Cascante, Marta; Mas, Francesc

2014-04-17

Enzyme kinetics studies have been usually designed as dilute solution experiments, which differ substantially from in vivo conditions. However, cell cytosol is crowded with a high concentration of molecules having different shapes and sizes. The consequences of such crowding in enzymatic reactions remain unclear. The aim of the present study is to understand the effect of macromolecular crowding produced by dextran of different sizes and at diverse concentrations in the well-known reaction of oxidation of NADH by pyruvate catalyzed by L-lactate dehydrogenase (LDH). Our results indicate that the reaction rate is determined by both the occupied volume and the relative size of dextran obstacles with respect to the enzyme present in the reaction. Moreover, we analyzed the influence of macromolecular crowding on the Michaelis-Menten constants, vmax and Km. The obtained results show that only high concentrations and large sizes of dextran reduce both constants suggesting a mixed activation-diffusion control of this enzymatic reaction due to the dextran crowding action. From our knowledge, this is the first experimental study that depicts mixed activation-diffusion control in an enzymatic reaction due to the effect of crowding.

High level transient expression of a chloramphenicol acetyl transferase gene by DEAE-dextran mediated DNA transfection coupled with a dimethyl sulfoxide or glycerol shock treatment.

PubMed Central

Lopata, M A; Cleveland, D W; Sollner-Webb, B

1984-01-01

Using a plasmid containing the bacterial chloramphenicol acetyl transferase gene, we have assayed for transient expression of DNA introduced into mouse L cells by a variety of transfection conditions. High efficiency uptake and expression of this foreign DNA have been achieved by modifying the DEAE dextran mediated transfection procedure of McCutchan and Pagano (1) to include a shock with either dimethyl sulfoxide or glycerol. Inclusion of the shock step can increase expression of the transfected gene a surprising approximately 50 fold. With plasmid constructs that do not replicate after transfection, we can readily detect CAT activity in an overnight autoradiographic exposure from less than 0.1% of an extract from a 60 mm dish of transfected cells. We have determined the amounts of DNA, the amount and time course of DEAE-dextran and dimethyl sulfoxide treatments, the effects of additional DNA, and the time after transfection which yield maximal expression. Overall, this transfection protocol using DEAE-dextran coupled to a shock treatment is simple, straightforward, and gives consistently high levels of expression of the input DNA. Images PMID:6589587

Mechanism of introduction of exogenous genes into cultured cells using DEAE-dextran-MMA graft copolymer as non-viral gene carrier.

PubMed

Eshita, Yuki; Higashihara, Junko; Onishi, Masayasu; Mizuno, Masaaki; Yoshida, Jun; Takasaki, Tomohiko; Kubota, Naoji; Onishi, Yasuhiko

2009-07-23

Comparative investigations were carried out regarding the efficiency of introduction of exogenous genes into cultured cells using a cationic polysaccharide DEAE-dextran-MMA (methyl methacrylate ester) graft copolymer (2-diethylaminoethyl-dextran-methyl methacrylate graft copolymer; DDMC) as a nonviral carrier for gene introduction. The results confirmed that the gene introduction efficiency was improved with DDMC relative to DEAE-dextran. Comparative investigations were carried out using various concentrations of DDMC and DNA in the introduction of DNA encoding luciferase (pGL3 control vector; Promega) into COS-7 cells derived from African green monkey kidney cells. The complex formation reaction is thought to be directly proportional to the transformation rate, but the complex formation reaction between DDMC and DNA is significantly influenced by hydrophobic bonding strength along with hydrogen bonding strength and Coulomb forces due to the hydrophobicity of the grafted MMA sections. It is thought that the reaction is a Michaelis-Menten type complex formation reaction described by the following equation: Complex amount = K1 (DNA concentration)(DDMC concentration). In support of this equation, it was confirmed that the amount of formed complex was proportional to the RLU value.

Synthesis and Characterization of Water-soluble Conjugates of Cabazitaxel Hemiesters-Dextran.

PubMed

Parhizkar, Elahehnaz; Ahmadi, Fatemeh; Daneshamouz, Saeid; Mohammadi-Samani, Soliman; Sakhteman, Amirhossein; Parhizkar, Golnaz

2017-11-24

Cabazitaxel (CTX) is a second- generation taxane derivative, a class of potent anticancer drugs with very low water solubility. CTX is used in patients with resistant prostate cancer unresponsive to the first generation taxane, docetaxel. Currently marketed formulations of CTX contain high concentrations of surfactant and ethanol, which cause severe hypersensitivity reactions in patients. In order to increase its solubility, two hemiester analogs; CTX-succinate and CTX-glutarate were synthesized and characterized. To improve the solubility of hemiesters even more, dextran as a biocompatible polymer was also conjugated to hemiester analogs. MTT assay was performed on MCF-7 cell line to evaluate the cytotoxicity effect of hemiesters and conjugates. Based on the results, hemiester analogs increased water solubility of the drug up to about 3 and 8 fold. Conjugation to dextran enhanced the CTX solubility to more than 1500 fold. These conjugates released the conjugated CTX in less than 24 hours in a pH dependent manner and showed proper hemocompatibility characteristics. The hemiesters had approximately similar cytotoxicity in comparison with CTX and the dextran conjugates showed higher cytotoxicity effect on MCF-7 cell line. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Investigation of the Spatiotemporal Responses of Nanoparticles in Tumor Tissues with a Small-Scale Mathematical Model

PubMed Central

Chou, Cheng-Ying; Huang, Chih-Kang; Lu, Kuo-Wei; Horng, Tzyy-Leng; Lin, Win-Li

2013-01-01

The transport and accumulation of anticancer nanodrugs in tumor tissues are affected by many factors including particle properties, vascular density and leakiness, and interstitial diffusivity. It is important to understand the effects of these factors on the detailed drug distribution in the entire tumor for an effective treatment. In this study, we developed a small-scale mathematical model to systematically study the spatiotemporal responses and accumulative exposures of macromolecular carriers in localized tumor tissues. We chose various dextrans as model carriers and studied the effects of vascular density, permeability, diffusivity, and half-life of dextrans on their spatiotemporal concentration responses and accumulative exposure distribution to tumor cells. The relevant biological parameters were obtained from experimental results previously reported by the Dreher group. The area under concentration-time response curve (AUC) quantified the extent of tissue exposure to a drug and therefore was considered more reliable in assessing the extent of the overall drug exposure than individual concentrations. The results showed that 1) a small macromolecule can penetrate deep into the tumor interstitium and produce a uniform but low spatial distribution of AUC; 2) large macromolecules produce high AUC in the perivascular region, but low AUC in the distal region away from vessels; 3) medium-sized macromolecules produce a relatively uniform and high AUC in the tumor interstitium between two vessels; 4) enhancement of permeability can elevate the level of AUC, but have little effect on its uniformity while enhancement of diffusivity is able to raise the level of AUC and improve its uniformity; 5) a longer half-life can produce a deeper penetration and a higher level of AUC distribution. The numerical results indicate that a long half-life carrier in plasma and a high interstitial diffusivity are the key factors to produce a high and relatively uniform spatial AUC distribution in the interstitium. PMID:23565142

Preparation and characterization of dextran nanobubbles for oxygen delivery.

PubMed

Cavalli, R; Bisazza, A; Giustetto, P; Civra, A; Lembo, D; Trotta, G; Guiot, C; Trotta, M

2009-11-03

Dextran nanobubbles were prepared with a dextran shell and a perfluoropentan core in which oxygen was stored. To increase the stability polyvinylpirrolidone was also added to the formulation as stabilizing agent. Rhodamine B was used as fluorescent marker to obtain fluorescent nanobubbles. The nanobubble formulations showed sizes of about 500nm, a negative surface charge and a good capacity of loading oxygen, no hemolytic activity or toxic effect on cell lines. The fluorescent labelled nanobubbles could be internalized in Vero cells. Oxygen-filled nanobubbles were able to release oxygen in different hypoxic solutions at different time after their preparation in in vitro experiments. The oxygen release kinetics could be enhanced after nanobubble insonation with ultrasound at 2.5MHz. The oxygen-filled nanobubble formulations might be proposed for therapeutic applications in various diseases.

Amphiphilic Polysaccharide Block Copolymers for pH-Responsive Micellar Nanoparticles.

PubMed

Breitenbach, Benjamin B; Schmid, Ira; Wich, Peter R

2017-09-11

A full polysaccharide amphiphilic block copolymer was prepared from end group-functionalized dextrans using copper-mediated azide-alkyne click chemistry. Sufficient modification of the reducing end in both blocks was achieved by microwave-enhanced reductive amination in a borate-buffer/methanol solvent system. The combination of a hydrophilic dextran block with a hydrophobic acetalated dextran block results in an amphiphilic structure that turns water-soluble upon acid treatment. The material has a low critical micelle concentration and self-assembles in water to spherical micellar nanoparticles. The formed nanoparticles have a narrow size distribution below 70 nm in diameter and disassemble in slightly acidic conditions. The amphiphilic polysaccharide system shows low toxicity and can stabilize the hydrophobic model drug curcumin in aqueous solutions over extended time periods.

DEAE-Dextran in the treatment of primary hypercholesterolemia and/or hypercholesterolemia combined with hypertriglyceridemia. A multicentric randomized study on the efficacy of DEAE-Dextran compared with Cholestyramine.

PubMed

Fedele, F

2003-01-01

This study was carried out to verify the therapeutic homogeneity between DEAE-Dextran and Cholestyramine. Blood levels of total cholesterol, HDL, LDL and triglycerides were evaluated in 202 patients affected by dyslipidemia and treated with DEAD-D at 2.5 g/day or with Cholestyramine at 12 g/day for 30 days. At the end of treatment both drugs caused significant reduction of total cholesterol, LDL and triglycerides blood levels; DEAD-D was generally more effective than Cholestyramine, in particular on triglycerides values (30.6% and 13.7% of reduction respectively), and produced also a significant increase in HDL cholesterol, differently from Cholestyramine that was ineffective on this parameter.

Kinetic theory of shear thickening for a moderately dense gas-solid suspension: From discontinuous thickening to continuous thickening

NASA Astrophysics Data System (ADS)

Hayakawa, Hisao; Takada, Satoshi; Garzó, Vicente

2017-10-01

The Enskog kinetic theory for moderately dense gas-solid suspensions under simple shear flow is considered as a model to analyze the rheological properties of the system. The influence of the environmental fluid on solid particles is modeled via a viscous drag force plus a stochastic Langevin-like term. The Enskog equation is solved by means of two independent but complementary routes: (i) Grad's moment method and (ii) event-driven Langevin simulation of hard spheres. Both approaches clearly show that the flow curve (stress-strain rate relation) depends significantly on the volume fraction of the solid particles. In particular, as the density increases, there is a transition from the discontinuous shear thickening (observed in dilute gases) to the continuous shear thickening for denser systems. The comparison between theory and simulations indicates that while the theoretical predictions for the kinetic temperature agree well with simulations for densities φ ≲0.5 , the agreement for the other rheological quantities (the viscosity, the stress ratio, and the normal stress differences) is limited to more moderate densities (φ ≲0.3 ) if the inelasticity during collisions between particles is not large.

Kinetic theory of shear thickening for a moderately dense gas-solid suspension: From discontinuous thickening to continuous thickening.

PubMed

Hayakawa, Hisao; Takada, Satoshi; Garzó, Vicente

2017-10-01

The Enskog kinetic theory for moderately dense gas-solid suspensions under simple shear flow is considered as a model to analyze the rheological properties of the system. The influence of the environmental fluid on solid particles is modeled via a viscous drag force plus a stochastic Langevin-like term. The Enskog equation is solved by means of two independent but complementary routes: (i) Grad's moment method and (ii) event-driven Langevin simulation of hard spheres. Both approaches clearly show that the flow curve (stress-strain rate relation) depends significantly on the volume fraction of the solid particles. In particular, as the density increases, there is a transition from the discontinuous shear thickening (observed in dilute gases) to the continuous shear thickening for denser systems. The comparison between theory and simulations indicates that while the theoretical predictions for the kinetic temperature agree well with simulations for densities φ≲0.5, the agreement for the other rheological quantities (the viscosity, the stress ratio, and the normal stress differences) is limited to more moderate densities (φ≲0.3) if the inelasticity during collisions between particles is not large.

Improvement in bone mineral density after switching from tenofovir to abacavir in HIV-1-infected patients with low bone mineral density: two-centre randomized pilot study (OsteoTDF study).

PubMed

Negredo, Eugènia; Domingo, Pere; Pérez-Álvarez, Núria; Gutiérrez, Mar; Mateo, Gracia; Puig, Jordi; Escrig, Roser; Echeverría, Patricia; Bonjoch, Anna; Clotet, Bonaventura

2014-12-01

Tenofovir has been associated with a decrease in bone mineral density (BMD). However, data on changes in BMD after discontinuing tenofovir are lacking. We performed a two-centre randomized pilot study in virologically suppressed HIV-infected patients receiving tenofovir with osteopenia/osteoporosis (OsteoTDF study, ClinicalTrials.gov number NCT 01153217). Fifty-four patients were randomly assigned to switch from tenofovir to abacavir (n = 26) or to continue with tenofovir (n = 28). Changes in lumbar and total hip BMD were evaluated at Week 48 from baseline. Five patients discontinued the study (three from the tenofovir group and two from the abacavir group). No significant differences were detected between the groups at Week 48 (P = 0.229 for total hip and P = 0.312 for lumbar spine). However, hip BMD improved by 2.1% (95% CI -0.6 to 4.7) (P = 0.043) in the abacavir group and 0.7% (95% CI -0.9 to 2.4) (P = 0.372) in the tenofovir group. Lumbar spine BMD varied by -0.7% (95% CI -3.8 to 3.3) (P ≤ 0.001) in the abacavir group and -1.2% (95% CI -3.8 to 0.4) (P < 0.001) in the tenofovir group. Switching from tenofovir to abacavir led to a slight improvement in femoral BMD although no differences were detected between groups. Larger studies are necessary before firm recommendations can be made on the discontinuation of tenofovir in patients with a low BMD. © The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Demixing of aqueous polymer two-phase systems in low gravity

NASA Technical Reports Server (NTRS)

Bamberger, S.; Harris, J. M.; Baird, J. K.; Boyce, J.; Vanalstine, J. M.; Snyder, R. S.; Brooks, D. E.

1986-01-01

When polymers such as dextran and poly(ethylene glycol) are mixed in aqueous solution biphasic systems often form. On Earth the emulsion formed by mixing the phases rapidly demixes because of phase density differences. Biological materials can be purified by selective partitioning between the phases. In the case of cells and other particulates the efficiency of these separations appears to be somewhat compromised by the demixing process. To modify this process and to evaluate the potential of two-phase partitioning in space, experiments on the effects of gravity on phase emulsion demixing were undertaken. The behavior of phase systems with essentially identical phase densities was studied at one-g and during low-g parabolic aircraft maneuvers. The results indicate the demixing can occur rather rapidly in space, although more slowly than on Earth. The demixing process was examined from a theoretical standpoint by applying the theory of Ostwald ripening. This theory predicts demizing rates many orders of magnitude lower than observed. Other possible demixing mechanisms are considered.

DFT treatment of transport through Anderson junction: exact results and approximations

NASA Astrophysics Data System (ADS)

Burke, Kieron

2012-02-01

Since the pioneering break-junction experiments of Reed and Tour measuring the conductance of dithiolated benzene between gold leads, many researchers in physics and chemistry have been calculating conductance for such systems using density functional theory (DFT). Off resonance, the predicted current is often 10-100 times larger than that measured. This error is often ascribed to the application of ground-state DFT to a non-equilibrium problem. I will argue that, in fact, this is largely due to errors in the density functional approximations in popular use, rather than necessarily errors in the methodology. A stark illustration of this principle is the ability of DFT to reproduce the exact transmission through an Anderson junction at zero-temperature and weak bias, including the Kondo plateau, but only if the exact ground-state density functional is used. In fact, this case can be used to reverse-engineer the exact functional for this problem. Popular approximations can also be tested, including both smooth and discontinuous functionals of the density, as well as symmetry-broken approaches. [4pt] [1] Kondo effect given exactly by density functional theory, J. P. Bergfield, Z. Liu, K. Burke, and C. A. Stafford, arXiv:1106.3104; [0pt] [2] Broadening of the Derivative Discontinuity in Density Functional Theory, F. Evers, and P. Schmitteckert, arXiv:1106.3658; [0pt] [3] DFT-based transport calculations, Friedel's sum rule and the Kondo effect, P. Tr"oster, P. Schmitteckert, and F. Evers, arXiv:1106.3669; [0pt] [4] Towards a description of the Kondo effect using time-dependent density functional theory, G. Stefanucci, and S. Kurth, arXiv:1106.3728.

Retrogressive failures recorded in mass transport deposits in the Ursa Basin, Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Sawyer, Derek E.; Flemings, Peter B.; Dugan, Brandon; Germaine, John T.

2009-10-01

Clay-rich mass transport deposits (MTDs) in the Ursa Basin, Gulf of Mexico, record failures that mobilized along extensional failure planes and transformed into long runout flows. Failure proceeded retrogressively: scarp formation unloaded adjacent sediment causing extensional failure that drove successive scarp formation updip. This model is developed from three-dimensional seismic reflection data, core and log data from Integrated Ocean Drilling Project (IODP) Expedition 308, and triaxial shear experiments. MTDs are imaged seismically as low-amplitude zones above continuous, grooved, high-amplitude basal reflections and are characterized by two seismic facies. A Chaotic facies typifies the downdip interior, and a Discontinuous Stratified facies typifies the headwalls/sidewalls. The Chaotic facies contains discontinuous, high-amplitude reflections that correspond to flow-like features in amplitude maps: it has higher bulk density, resistivity, and shear strength, than bounding sediment. In contrast, the Discontinuous Stratified facies contains relatively dim reflections that abut against intact pinnacles of parallel-stratified reflections: it has only slightly higher bulk density, resistivity, and shear strength than bounding sediment, and deformation is limited. In both facies, densification is greatest at the base, resulting in a strong basal reflection. Undrained shear tests document strain weakening (sensitivity = 3). We estimate that failure at 30 meters below seafloor will occur when overpressure = 70% of the hydrostatic effective stress: under these conditions soil will liquefy and result in long runout flows.

Wave function continuity and the diagonal Born-Oppenheimer correction at conical intersections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meek, Garrett A.; Levine, Benjamin G., E-mail: levine@chemistry.msu.edu

2016-05-14

We demonstrate that though exact in principle, the expansion of the total molecular wave function as a sum over adiabatic Born-Oppenheimer (BO) vibronic states makes inclusion of the second-derivative nonadiabatic energy term near conical intersections practically problematic. In order to construct a well-behaved molecular wave function that has density at a conical intersection, the individual BO vibronic states in the summation must be discontinuous. When the second-derivative nonadiabatic terms are added to the Hamiltonian, singularities in the diagonal BO corrections (DBOCs) of the individual BO states arise from these discontinuities. In contrast to the well-known singularities in the first-derivative couplingsmore » at conical intersections, these singularities are non-integrable, resulting in undefined DBOC matrix elements. Though these singularities suggest that the exact molecular wave function may not have density at the conical intersection point, there is no physical basis for this constraint. Instead, the singularities are artifacts of the chosen basis of discontinuous functions. We also demonstrate that continuity of the total molecular wave function does not require continuity of the individual adiabatic nuclear wave functions. We classify nonadiabatic molecular dynamics methods according to the constraints placed on wave function continuity and analyze their formal properties. Based on our analysis, it is recommended that the DBOC be neglected when employing mixed quantum-classical methods and certain approximate quantum dynamical methods in the adiabatic representation.« less

Wave function continuity and the diagonal Born-Oppenheimer correction at conical intersections

NASA Astrophysics Data System (ADS)

Meek, Garrett A.; Levine, Benjamin G.

2016-05-01

We demonstrate that though exact in principle, the expansion of the total molecular wave function as a sum over adiabatic Born-Oppenheimer (BO) vibronic states makes inclusion of the second-derivative nonadiabatic energy term near conical intersections practically problematic. In order to construct a well-behaved molecular wave function that has density at a conical intersection, the individual BO vibronic states in the summation must be discontinuous. When the second-derivative nonadiabatic terms are added to the Hamiltonian, singularities in the diagonal BO corrections (DBOCs) of the individual BO states arise from these discontinuities. In contrast to the well-known singularities in the first-derivative couplings at conical intersections, these singularities are non-integrable, resulting in undefined DBOC matrix elements. Though these singularities suggest that the exact molecular wave function may not have density at the conical intersection point, there is no physical basis for this constraint. Instead, the singularities are artifacts of the chosen basis of discontinuous functions. We also demonstrate that continuity of the total molecular wave function does not require continuity of the individual adiabatic nuclear wave functions. We classify nonadiabatic molecular dynamics methods according to the constraints placed on wave function continuity and analyze their formal properties. Based on our analysis, it is recommended that the DBOC be neglected when employing mixed quantum-classical methods and certain approximate quantum dynamical methods in the adiabatic representation.

Wave function continuity and the diagonal Born-Oppenheimer correction at conical intersections.

PubMed

Meek, Garrett A; Levine, Benjamin G

2016-05-14

We demonstrate that though exact in principle, the expansion of the total molecular wave function as a sum over adiabatic Born-Oppenheimer (BO) vibronic states makes inclusion of the second-derivative nonadiabatic energy term near conical intersections practically problematic. In order to construct a well-behaved molecular wave function that has density at a conical intersection, the individual BO vibronic states in the summation must be discontinuous. When the second-derivative nonadiabatic terms are added to the Hamiltonian, singularities in the diagonal BO corrections (DBOCs) of the individual BO states arise from these discontinuities. In contrast to the well-known singularities in the first-derivative couplings at conical intersections, these singularities are non-integrable, resulting in undefined DBOC matrix elements. Though these singularities suggest that the exact molecular wave function may not have density at the conical intersection point, there is no physical basis for this constraint. Instead, the singularities are artifacts of the chosen basis of discontinuous functions. We also demonstrate that continuity of the total molecular wave function does not require continuity of the individual adiabatic nuclear wave functions. We classify nonadiabatic molecular dynamics methods according to the constraints placed on wave function continuity and analyze their formal properties. Based on our analysis, it is recommended that the DBOC be neglected when employing mixed quantum-classical methods and certain approximate quantum dynamical methods in the adiabatic representation.

Dynamical Phase Transition in Neutron Stars

NASA Astrophysics Data System (ADS)

Prasad, R.; Mallick, Ritam

2018-05-01

We have studied the dynamical evolution of the shock in a neutron star (NS). The conversion of nuclear to quark matter (QM) is assumed to take place at the shock discontinuity. The density and pressure discontinuity is studied both spatially and temporally as it starts near the center of the star and moves toward the surface. Polytropic equations of state (EoS), which mimic original nuclear and QM EoS, are used to study such dynamical phase transition (PT). Solving relativistic hydrodynamic equations for a spherically symmetric star, we study the PT, assuming a considerable density discontinuity near the center. We find that as the shock wave propagates outward, its intensity decreases with time; however, the shock velocity peaks up and reaches a value close to that of light. Such fast shock velocity indicates rapid PT in NS taking place on a timescale of some 10s of microseconds. Such a result is quite interesting, and it differs from previous calculations that the PT in NSs takes at least some 10s of milliseconds. Rapid PT can have significant observational significance, because such fast PT would imply rather strong gravitational wave (GW) signals that are rather short lived. Such short-lived GW signals would be accompanied with short-lived gamma-ray bursts and neutrino signals originating from the neutrino and gamma-ray generation from the PT of nuclear matter to QM.

Microvascular Physiologic and Anatomic Responses of the Guinea Pig to Experimental Arenavirus Infection

DTIC Science & Technology

1989-03-25

tumor necrosis factor results in dextran leaks and blot heorrhages. This may be important in the splanchnic pathogenesis of hemorrhagic fever. 20...Characterization of GP13 mesenteric microcirculatory module with measurement of microvascular blood flow, granulocyte adherence, and mesenteric local ...are measurable, and 4) topical tumor necrosis factor results in dextran leaks and blot hemorrhages. This may be important in the splanchnic

Dextran-shelled oxygen-loaded nanodroplets reestablish a normoxia-like pro-angiogenic phenotype and behavior in hypoxic human dermal microvascular endothelium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basilico, Nicoletta, E-mail: nicoletta.basilico@unimi.it; Magnetto, Chiara, E-mail: c.magnetto@inrim.it; D'Alessandro, Sarah, E-mail: sarah.dalessandro@unimi.it

In chronic wounds, hypoxia seriously undermines tissue repair processes by altering the balances between pro-angiogenic proteolytic enzymes (matrix metalloproteinases, MMPs) and their inhibitors (tissue inhibitors of metalloproteinases, TIMPs) released from surrounding cells. Recently, we have shown that in human monocytes hypoxia reduces MMP-9 and increases TIMP-1 without affecting TIMP-2 secretion, whereas in human keratinocytes it reduces MMP-2, MMP-9, and TIMP-2, without affecting TIMP-1 release. Provided that the phenotype of the cellular environment is better understood, chronic wounds might be targeted by new oxygenating compounds such as chitosan- or dextran-shelled and 2H,3H-decafluoropentane-cored oxygen-loaded nanodroplets (OLNs). Here, we investigated the effects ofmore » hypoxia and dextran-shelled OLNs on the pro-angiogenic phenotype and behavior of human dermal microvascular endothelium (HMEC-1 cell line), another cell population playing key roles during wound healing. Normoxic HMEC-1 constitutively released MMP-2, TIMP-1 and TIMP-2 proteins, but not MMP-9. Hypoxia enhanced MMP-2 and reduced TIMP-1 secretion, without affecting TIMP-2 levels, and compromised cell ability to migrate and invade the extracellular matrix. When taken up by HMEC-1, nontoxic OLNs abrogated the effects of hypoxia, restoring normoxic MMP/TIMP levels and promoting cell migration, matrix invasion, and formation of microvessels. These effects were specifically dependent on time-sustained oxygen diffusion from OLN core, since they were not achieved by oxygen-free nanodroplets or oxygen-saturated solution. Collectively, these data provide new information on the effects of hypoxia on dermal endothelium and support the hypothesis that OLNs might be used as effective adjuvant tools to promote chronic wound healing processes. - Highlights: • Hypoxia enhances MMP-2 and reduces TIMP-1 secretion by dermal HMEC-1 cell line. • Hypoxia compromises migration and matrix invasion abilities of HMEC-1. • Nontoxic dextran-shelled oxygen-loaded nanodroplets (OLNs) are uptaken by HMEC-1. • Dextran-shelled OLNs abrogate hypoxia effects on HMEC-1 pro-angiogenic phenotype. • Dextran-shelled OLNs abrogate hypoxia effects on HMEC-1 pro-angiogenic behavior.« less

Scattering apodizer for laser beams

DOEpatents

Summers, Mark A.; Hagen, Wilhelm F.; Boyd, Robert D.

1985-01-01

A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

Continental crust

USGS Publications Warehouse

Pakiser, L.C.

1964-01-01

The structure of the Earth’s crust (the outer shell of the earth above the M-discontinuity) has been intensively studied in many places by use of geophysical methods. The velocity of seismic compressional waves in the crust and in the upper mantle varies from place to place in the conterminous United States. The average crust is thick in the eastern two-thirds of the United States, in which the crustal and upper-mantle velocities tend to be high. The average crust is thinner in the western one-third of the United States, in which these velocities tend to be low. The concept of eastern and western superprovinces can be used to classify these differences. Crustal and upper-mantle densities probably vary directly with compressional-wave velocity, leading to the conclusion that isostasy is accomplished by the variation in densities of crustal and upper-mantle rocks as well as in crustal thickness, and that there is no single, generally valid isostatic model. The nature of the M-discontinuity is still speculative.

Scattering apodizer for laser beams

DOEpatents

Summers, M.A.; Hagen, W.F.; Boyd, R.D.

1984-01-01

A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

Suppressive Shields Structural Design and Analysis Handbook

DTIC Science & Technology

1977-11-18

of this disturbance to steepen as it passes through the air until it exhibits nearly discontinuous increases in pressure, density, and temperature ...sure. density, and temperature of the reflected wave are all in- creased above the values in the incident wave. The ove-nressure at the wall surface...limiting thickness of concrete at which per- foration will occur can be obtained from Fig. 3-18 and is a function of the coefficient C1, the fragment weight

Dopamine enhances duodenal epithelial permeability via the dopamine D5 receptor in rodent.

PubMed

Feng, X-Y; Zhang, D-N; Wang, Y-A; Fan, R-F; Hong, F; Zhang, Y; Li, Y; Zhu, J-X

2017-05-01

The intestinal barrier is made up of epithelial cells and intercellular junctional complexes to regulate epithelial ion transport and permeability. Dopamine (DA) is able to promote duodenal epithelial ion transport through D1-like receptors, which includes subtypes of D 1 (D 1 R) and D 5 (D 5 R), but whether D1-like receptors influence the duodenal permeability is unclear. FITC-dextran permeability, short-circuit current (I SC ), Western blot, immunohistochemistry and ELISA were used in human D 5 R transgenic mice and hyperendogenous enteric DA (HEnD) rats in this study. Dopamine induced a downward deflection in I SC and an increase in FITC-dextran permeability of control rat duodenum, which were inhibited by the D1-like receptor antagonist, SCH-23390. However, DA decreased duodenal transepithelial resistance (TER), an effect also reversed by SCH-23390. A strong immunofluorescence signal for D 5 R, but not D 1 R, was observed in the duodenum of control rat. In human D 5 R knock-in transgenic mice, duodenal mucosa displayed an increased basal I SC with high FITC-dextran permeability and decreased TER with a lowered expression of tight junction proteins, suggesting attenuated duodenal barrier function in these transgenic mice. D 5 R knock-down transgenic mice manifested a decreased basal I SC with lowered FITC-dextran permeability. Moreover, an increased FITC-dextran permeability combined with decreased TER and tight junction protein expression in duodenal mucosa were also observed in HEnD rats. This study demonstrates, for the first time, that DA enhances duodenal permeability of control rat via D 5 R, which provides new experimental and theoretical evidence for the influence of DA on duodenal epithelial barrier function. © 2016 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Hindered diffusion of high molecular weight compounds in brain extracellular microenvironment measured with integrative optical imaging.

PubMed

Nicholson, C; Tao, L

1993-12-01

This paper describes the theory of an integrative optical imaging system and its application to the analysis of the diffusion of 3-, 10-, 40-, and 70-kDa fluorescent dextran molecules in agarose gel and brain extracellular microenvironment. The method uses a precisely defined source of fluorescent molecules pressure ejected from a micropipette, and a detailed theory of the intensity contributions from out-of-focus molecules in a three-dimensional medium to a two-dimensional image. Dextrans tagged with either tetramethylrhodamine or Texas Red were ejected into 0.3% agarose gel or rat cortical slices maintained in a perfused chamber at 34 degrees C and imaged using a compound epifluorescent microscope with a 10 x water-immersion objective. About 20 images were taken at 2-10-s intervals, recorded with a cooled CCD camera, then transferred to a 486 PC for quantitative analysis. The diffusion coefficient in agarose gel, D, and the apparent diffusion coefficient, D*, in brain tissue were determined by fitting an integral expression relating the measured two-dimensional image intensity to the theoretical three-dimensional dextran concentration. The measurements in dilute agarose gel provided a reference value of D and validated the method. Values of the tortuosity, lambda = (D/D*)1/2, for the 3- and 10-kDa dextrans were 1.70 and 1.63, respectively, which were consistent with previous values derived from tetramethylammonium measurements in cortex. Tortuosities for the 40- and 70-kDa dextrans had significantly larger values of 2.16 and 2.25, respectively. This suggests that the extracellular space may have local constrictions that hinder the diffusion of molecules above a critical size that lies in the range of many neurotrophic compounds.

Stimulation of wound healing by positively charged dextran beads depends upon clustering of beads and cells in close proximity to the wound.

PubMed

Tawil, N J; Connors, D; Gies, D; Bennett, S; Gruskin, E; Mustoe, T

1999-01-01

We have previously shown that positively charged dextran (DEAE A25) increases wound breaking strength in linear incisions in rats and nonhuman primates at days 10-14 postwounding. In this article, we examined the cellular responses to different types of charged dextran beads (DEAE A50 and Cytodex-1) in culture studies and in rat incisional wounds. We show that Cytodex 1 and DEAE A50 beads also increased wound breaking strength in a rat linear incisional model. However, the increase was approximately 30-40% less than that observed in wounds treated with DEAE A25 beads. The main distinction between the three types of beads was the presence of bead clusters observed in tissue sections. Wounds treated with DEAE A25 beads formed distinct clusters while both Cytodex 1 and DEAE A50 beads clustered to a lesser extent or failed to cluster at all. We propose that the different types of charged dextran beads improve healing by promoting cell adhesion and encouraging proliferation in close proximity to the wound. We also hypothesize that the 30-40% improvement in wound breaking strength seen with DEAE A25 beads compared to other types of charged dextran beads (DEAE A50 and Cytodex-1) originates from the unique characteristic of DEAE A25 beads in forming cell-bead aggregates adjacent to the wounded area. This clustering, in turn, affects the distribution of cells infiltrating the wounded area (such as macrophages) during the healing process and, as a consequence, alters the distribution of matrix molecules and growth factors secreted by these cells.

Mass transfer of large molecules through collagen and collagen-silica hybrid membranes

NASA Astrophysics Data System (ADS)

Jofre-Lora, Pedro

Diabetes is a growing concern in the United States and around the world that must be addressed through new treatment options. Current standard treatment options of diabetes are limiting and have tremendous impacts on patient's lives. Emerging therapies, such as the implantation of encapsulated islets, are promising treatment options, but have not yet materialized due to unsolved problems with material properties. Hybrid silica-collagen membranes address some of these unsolved problems and are a promising material for cell encapsulation. However, the mass transfer properties of large molecules, such as insulin, TNF-alpha, IL1beta, and other important proteins in the etiology of diabetes, through these hybrid membranes are poorly characterized. In order to begin characterizing these properties, a device was constructed to accurately and efficiently measure the mass transfer of other similar large molecules, fluorescein isothiocyanate dextrans (FITC-dextran), through collagen-silica hybrid membranes. The device was used to measure diffusion coefficients of 4, 20, 40, and 150 kDa FITC-dextrans through non-silicified and silicified samples of 200 and 1000 Pa porcine skin collagen. Diffusion coefficients were found to be in the 10-7-10-6 cm2s -1 range, which is in agreement with previously published data for similar molecules through similar hydrogels. The effects of collagen stiffness, FITC-dextran molecular weight, and silicification treatment on diffusion were investigated. It was found that collagen stiffness and FITC-dextran molecular weight had a negative correlation with diffusion, whereas silicification treatment had no global impact on diffusion. The device created, and the results of this preliminary investigation, can be used to develop collagen-silica hybrid membranes as an alternative material for cell encapsulation in a forward-design manner.

Fabrication and characterization of ultrathin dextran layers: Time dependent nanostructure in aqueous environments revealed by OWLS.

PubMed

Saftics, Andras; Kurunczi, Sándor; Szekrényes, Zsolt; Kamarás, Katalin; Khánh, Nguyen Quoc; Sulyok, Attila; Bősze, Szilvia; Horvath, Robert

2016-10-01

Surface coatings of the polysaccharide dextran and its derivatives are key ingredients especially in label-free biosensors for the suppression of non-specific binding and for receptor immobilization. Nevertheless, the nanostructure of these ultrathin coatings and its tailoring by the variation of the preparation conditions have not been profoundly characterized and understood. In this work carboxymethylated dextran (CMD) was prepared and used for fabricating ultrathin surface coatings. A grafting method based on covalent coupling to aminosilane- and epoxysilane-functionalized surfaces was applied to obtain thin CMD layers. The carboxyl moiety of the CMD was coupled to the aminated surface by EDC-NHS reagents, while CMD coupling through epoxysilane molecules was performed without any additional reagents. The surface analysis following the grafting procedures consisted of X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared spectroscopy (ATR-IR), spectroscopic ellipsometry, atomic force microscopy (AFM) and optical waveguide lightmode spectroscopy (OWLS). The XPS and AFM measurements showed that the grafting resulted in a very thin dextran layer of a few nanometers. The OWLS method allowed devising the structure of the interfacial dextran layers by the evaluation of the optogeometrical parameters. The alteration in the nanostructure of the CMD layer with the chemical composition of the silane coverage and the pH of the grafting solution was revealed by in situ OWLS, specifically, lain down chains were found to be prevalent on the surface under neutral and basic conditions on epoxysilylated surfaces. The developed methodologies allowed to design and fabricate nanometer scale CMD layers with well-controlled surface structure, which are very difficult to characterize in aqueous environments using present instrumentations and highly hydrated surface layers. Copyright © 2016 Elsevier B.V. All rights reserved.

In-vitro and in-vivo assessment of dextran-appended cellulose acetate phthalate nanoparticles for transdermal delivery of 5-fluorouracil.

PubMed

Garg, Ashish; Rai, Gopal; Lodhi, Santram; Jain, Alok P; Yadav, Awesh K

2016-06-01

The aim of this research was transdermal delivery of 5-fluorouracil (5-FU) using dextran-coated cellulose acetate phthalate (CAP) nanoparticulate formulation. CAP nanoparticles were prepared using drug-polymer ratio (1:1 to 1:3) and surfactant ratio (2.5, 5 and 10%). Dextran coating was made using aminodextran. The results showed that the optimized CAP nanoparticles (CNs) and dextran-coated CAP nanoparticles represented core-corona nanoparticles with the mean diameter of 75 ± 3 and 79 ± 2 nm, respectively, and entrapment efficiency was 82.5 ± 0.06 and 78.2 ± 0.12, respectively. Dextran-coated nanoparticles (FDCNs) and CAP nanoparticles (FCNs) showed in vitro 5-FU release upto 31 h and 8 h, respectively. Moreover, the cumulative amount of 5-FU penetrated through excised skin from FDCNs was 2.94 folds than that of the FU cream. Concentration of 5-FU in epidermis and dermis were also studied. In dermis, concentration of 5-FU was found higher in case of FDCN formulation than plain FU cream. FDCNs were found more hemocompatible in comparison to FCNs. The hematological data recommended that FDCNs formulation was less immunogenic compared to FU creams formulation. In blood level study, FDCNs exhibited 153, 12, 16.66 and 16.24-fold higher values for area under the curve, Tmax, Cmax and mean residence time (MRT) compared with those of FU cream, respectively. The in-vitro cytotoxicity was assessed using the MCF-7 by the MTT test and was compared to the plain 5-FU solution. All the detailed evidence showed that FDCNs could provide a promising tuning as a transdermal delivery system of 5-FU.

Hindlimb heating increases vascular access of large molecules to murine tibial growth plates measured by in vivo multiphoton imaging

PubMed Central

Efaw, Morgan L.; Williams, Rebecca M.

2013-01-01

Advances in understanding the molecular regulation of longitudinal growth have led to development of novel drug therapies for growth plate disorders. Despite progress, a major unmet challenge is delivering therapeutic agents to avascular-cartilage plates. Dense extracellular matrix and lack of penetrating blood vessels create a semipermeable “barrier,” which hinders molecular transport at the vascular-cartilage interface. To overcome this obstacle, we used a hindlimb heating model to manipulate bone circulation in 5-wk-old female mice (n = 22). Temperatures represented a physiological range of normal human knee joints. We used in vivo multiphoton microscopy to quantify temperature-enhanced delivery of large molecules into tibial growth plates. We tested the hypothesis that increasing hindlimb temperature from 22°C to 34°C increases vascular access of large systemic molecules, modeled using 10, 40, and 70 kDa dextrans that approximate sizes of physiological regulators. Vascular access was quantified by vessel diameter, velocity, and dextran leakage from subperichondrial plexus vessels and accumulation in growth plate cartilage. Growth plate entry of 10 kDa dextrans increased >150% at 34°C. Entry of 40 and 70 kDa dextrans increased <50%, suggesting a size-dependent temperature enhancement. Total dextran levels in the plexus increased at 34°C, but relative leakage out of vessels was not temperature dependent. Blood velocity and vessel diameter increased 118% and 31%, respectively, at 34°C. These results demonstrate that heat enhances vascular carrying capacity and bioavailability of large molecules around growth plates, suggesting that temperature could be a noninvasive strategy for modulating delivery of therapeutics to impaired growth plates of children. PMID:24371019

SMU.940 regulates dextran-dependent aggregation and biofilm formation in Streptococcus mutans.

PubMed

Senpuku, Hidenobu; Yonezawa, Hideo; Yoneda, Saori; Suzuki, Itaru; Nagasawa, Ryo; Narisawa, Naoki

2018-02-01

The oral bacterium Streptococcus mutans is the principal agent in the development of dental caries. Biofilm formation by S. mutans requires bacterial attachment, aggregation, and glucan formation on the tooth surface under sucrose supplementation conditions. Our previous microarray analysis of clinical strains identified 74 genes in S. mutans that were related to biofilm morphology; however, the roles of almost all of these genes in biofilm formation are poorly understood. We investigated the effects of 21 genes randomly selected from our previous study regarding S. mutans biofilm formation, regulation by the complement pathway, and responses to competence-stimulating peptide. Eight competence-stimulating peptide-dependent genes were identified, and their roles in biofilm formation and aggregation were examined by mutational analyses of the S. mutansUA159 strain. Of these eight genes, the inactivation of the putative hemolysin III family SMU.940 gene of S. mutansUA159 promoted rapid dextran-dependent aggregation and biofilm formation in tryptic soy broth without dextrose (TSB) with 0.25% glucose and slightly reduced biofilm formation in TSB with 0.25% sucrose. The SMU.940 mutant showed higher expression of GbpC and gbpC gene than wild-type. GbpC is known to be involved in the dextran-dependent aggregation of S. mutans. An SMU.940-gbpC double mutant strain was constructed in the SMU.940 mutant background. The gbpC mutation completely abolished the dextran-dependent aggregation of the SMU.940 mutant. In addition, the aggregation of the mutant was abrogated by dextranase. These findings suggest that SMU.940 controls GbpC expression, and contributes to the regulation of dextran-dependent aggregation and biofilm formation. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Internal loading of an inhomogeneous compressible Earth with phase boundaries

NASA Technical Reports Server (NTRS)

Defraigne, P.; Dehant, V.; Wahr, J. M.

1996-01-01

The geoid and the boundary topography caused by mass loads inside the earth were estimated. It is shown that the estimates are affected by compressibility, by a radially varying density distribution, and by the presence of phase boundaries with density discontinuities. The geoid predicted in the chemical boundary case is 30 to 40 percent smaller than that predicted in the phase case. The effects of compressibility and radially varying density are likely to be small. The inner core-outer core topography for loading inside the mantle and for loading inside the inner core were computed.

Polyacetal Carboxylic Acids: a New Group of Antiviral Polyanions

PubMed Central

Claes, P.; Billiau, A.; De Clercq, E.; Desmyter, J.; Schonne, E.; Vanderhaeghe, H.; De Somer, P.

1970-01-01

Chlorite-oxidized oxypolysaccharides are polyacetal carboxylic acids. They inhibited the cytopathic effect of vesicular stomatitis virus in mouse embryo cell cultures challenged at low input multiplicity. After intraperitoneal injection of these compounds in mice, interferon appeared in the circulation. The compounds also protected mice against lethal mengovirus infection and against the development of experimental pox lesions on the tail. Chlorite-oxidized oxyamylose was antiviral only when at least 64% of the glucopyranose units were oxidized, an observation which suggested a correlation between charge density and antiviral effect. The antiviral activity was also influenced by the molecular weight, as demonstrated by the fact that chlorite-oxidized dextrans which had a high intrinsic viscosity were more active than those with low intrinsic viscosity. PMID:4314553

Detecting protein losing enteropathy by Tc-99m dextran scintigraphy: a novel experience.

PubMed

Kapoor, Seema; Ratan, Simmi K; Kashyap, Ravi; Mittal, S K; Rajeshwari, K; Rawat, H; Verma, Jyoti

2002-09-01

To evaluate protien using enteropathy by Tc-99m dextran scintigraphy. Methods for detecting protein loss from the intestine revolve around fecal nitrogen excretion, the clearance of alpha-1 antitrypsin in stools and by endoscopic biopsy. The diagnosis of protein-losing enteropathy (PLE) can also be established by a scintigraphic method that is noninvasive, simple and requires no patient preparation or motivation. This diagnostic modality can also delineate the site of protein loss, thereby offering a targeted approach, and if need be, surgery. Radiolabelling of a non-protein, noncolloidal, nonparticulate and biofriendly molecule like dextran with Technetium-99m for imaging enteric protein loss was utilized in imaging eight children with PLE. The results were encouraging. The authors advocate the use of this diagnostic tool in identifying patients with PLE, particularly in the pediatric age group.

Investigation of phosphatidylcholine enhancing FITC-insulin across buccal mucosa by confocal laser scanning microscopy

NASA Astrophysics Data System (ADS)

Tian, Weiqun; Su, Li; Zeng, Shaoqun; Luo, Qingming; Gao, Qiuhua; Xu, Huibi

2002-04-01

The aim was to characterize the transport of fluorescein isothiocyanate (FITC)-labeled dextran and insulin with different resoluble compounds for peptides and proteins through buccal mucosa. The penetration rate of insulin molecules through porcine buccal mucosa (a nonkeratinized epithelium, comparable to human buccal mucosa) was investigated by measuring transbuccal fluxes and by analyzing the distribution of the fluorescent probe in the rabbit buccal mucosa epithelium, using confocal laser scanning microscopy for visualizing permeation pathways. The confocal images of the distribution pattern of FITC-dextran and FITC-insulin showed that the paracellular route is the major pathway of FITC-dextran through buccal mucosa epithelium, the intra-cellular route is the major pathway of FITC-insulin through buccal mucosa epithelium. The permeation rate can be increased by co-administration of soybean phosphatidylcholine (SPC).

Mold Pectinase Modified with Dialdehyde Derivatives of Dextran and Cellulose.

PubMed

Kobayashi, M; Chiba, Y; Funane, K; Ohya, S; Kato, Y

1996-01-01

Chemical modification of mold pectinase with dextran- and cellulose-dialdehydes was examined to improve the enzyme characteristics. The modified pectinase with dextran-dialdehyde retained about 50% of the original activity, and more than 80% of the total amino groups were modified. HPLC gel filtration analysis showed an increase in molecular weight of the reaction product. Reaction with cellulose-dialdehyde provided an immobilized form of pectinase. The immobilized pectinase was resistant to both acidic and alkaline pHs, and also acquired heat stability at 60°C. The optimum pH of the modified enzyme shifted from pH 4.5 to 5.0-5.5, and this enzyme had higher activity at neutral pH regions than the native enzyme. A rather low recovery of immobilized enzyme (14.5%) should be improved by the combination with various methods hitherto established.

Alternative vaccine administration by powder injection: Needle-free dermal delivery of the glycoconjugate meningococcal group Y vaccine

PubMed Central

Schiffter, Heiko A.; Carlisle, Robert C.; Rollier, Christine S.; Prud’homme, Robert K.; Pollard, Andrew J.

2017-01-01

Powder-injectors use gas propulsion to deposit lyophilised drug or vaccine particles in the epidermal and sub epidermal layers of the skin. We prepared dry-powder (Tg = 45.2 ± 0.5°C) microparticles (58.1 μm) of a MenY-CRM197 glyconjugate vaccine (0.5% wt.) for intradermal needle-free powder injection (NFPI). SFD used ultrasound atomisation of the liquid vaccine-containing excipient feed, followed by lyophilisation above the glass transition temperature (Tg’ = − 29.9 ± 0.3°C). This resulted in robust particles (density~ 0.53 ±0.09 g/cm3) with a narrow volume size distribution (mean diameter 58.1 μm, and span = 1.2), and an impact parameter (ρvr ~ 11.5 kg/m·s) sufficient to breach the Stratum corneum (sc). The trehalose, manitol, dextran (10 kDa), dextran (150 kDa) formulation, or TMDD (3:3:3:1), protected the MenY-CRM197 glyconjugate during SFD with minimal loss, no detectable chemical degradation or physical aggregation. In a capsular group Y Neisseria meningitidis serum bactericidal assay (SBA) with human serum complement, the needle free vaccine, which contained no alum adjuvant, induced functional protective antibody responses in vivo of similar magnitude to the conventional vaccine injected by hypodermic needle and syringe and containing alum adjuvant. These results demonstrate that needle-free vaccination is both technically and immunologically valid, and could be considered for vaccines in development. PMID:28837693

Hybridization chain reaction amplification for highly sensitive fluorescence detection of DNA with dextran coated microarrays.

PubMed

Chao, Jie; Li, Zhenhua; Li, Jing; Peng, Hongzhen; Su, Shao; Li, Qian; Zhu, Changfeng; Zuo, Xiaolei; Song, Shiping; Wang, Lianhui; Wang, Lihua

2016-07-15

Microarrays of biomolecules hold great promise in the fields of genomics, proteomics, and clinical assays on account of their remarkably parallel and high-throughput assay capability. However, the fluorescence detection used in most conventional DNA microarrays is still limited by sensitivity. In this study, we have demonstrated a novel universal and highly sensitive platform for fluorescent detection of sequence specific DNA at the femtomolar level by combining dextran-coated microarrays with hybridization chain reaction (HCR) signal amplification. Three-dimensional dextran matrix was covalently coated on glass surface as the scaffold to immobilize DNA recognition probes to increase the surface binding capacity and accessibility. DNA nanowire tentacles were formed on the matrix surface for efficient signal amplification by capturing multiple fluorescent molecules in a highly ordered way. By quantifying microscopic fluorescent signals, the synergetic effects of dextran and HCR greatly improved sensitivity of DNA microarrays, with a detection limit of 10fM (1×10(5) molecules). This detection assay could recognize one-base mismatch with fluorescence signals dropped down to ~20%. This cost-effective microarray platform also worked well with samples in serum and thus shows great potential for clinical diagnosis. Copyright © 2016 Elsevier B.V. All rights reserved.

Permeability of Endothelial and Astrocyte Cocultures: In Vitro Blood–Brain Barrier Models for Drug Delivery Studies

PubMed Central

Li, Guanglei; Simon, Melissa J.; Cancel, Limary M.; Shi, Zhong-Dong; Ji, Xinying; Tarbell, John M.; Morrison, Barclay; Fu, Bingmei M.

2014-01-01

The blood–brain barrier (BBB) is a major obstacle for drug delivery to the brain. To seek for in vitro BBB models that are more accessible than animals for investigating drug transport across the BBB, we compared four in vitro cultured cell models: endothelial monoculture (bEnd3 cell line), coculture of bEnd3 and primary rat astrocytes (coculture), coculture with collagen type I and IV mixture, and coculture with Matrigel. The expression of the BBB tight junction proteins in these in vitro models was assessed using RT-PCR and immunofluorescence. We also quantified the hydraulic conductivity (Lp), transendothelial electrical resistance (TER) and diffusive solute permeability (P) of these models to three solutes: TAMRA, Dextran 10K and Dextran 70K. Our results show that Lp and P of the endothelial monoculture and coculture models are not different from each other. Compared with in vivo permeability data from rat pial microvessels, P of the endothelial monoculture and coculture models are not significantly different from in vivo data for Dextran 70K, but they are 2–4 times higher for TAMRA and Dextran 10K. This suggests that the endothelial monoculture and all of the coculture models are fairly good models for studying the transport of relatively large solutes across the BBB. PMID:20361260

Permeability of endothelial and astrocyte cocultures: in vitro blood-brain barrier models for drug delivery studies.

PubMed

Li, Guanglei; Simon, Melissa J; Cancel, Limary M; Shi, Zhong-Dong; Ji, Xinying; Tarbell, John M; Morrison, Barclay; Fu, Bingmei M

2010-08-01

The blood-brain barrier (BBB) is a major obstacle for drug delivery to the brain. To seek for in vitro BBB models that are more accessible than animals for investigating drug transport across the BBB, we compared four in vitro cultured cell models: endothelial monoculture (bEnd3 cell line), coculture of bEnd3 and primary rat astrocytes (coculture), coculture with collagen type I and IV mixture, and coculture with Matrigel. The expression of the BBB tight junction proteins in these in vitro models was assessed using RT-PCR and immunofluorescence. We also quantified the hydraulic conductivity (L (p)), transendothelial electrical resistance (TER) and diffusive solute permeability (P) of these models to three solutes: TAMRA, Dextran 10K and Dextran 70K. Our results show that L (p) and P of the endothelial monoculture and coculture models are not different from each other. Compared with in vivo permeability data from rat pial microvessels, P of the endothelial monoculture and coculture models are not significantly different from in vivo data for Dextran 70K, but they are 2-4 times higher for TAMRA and Dextran 10K. This suggests that the endothelial monoculture and all of the coculture models are fairly good models for studying the transport of relatively large solutes across the BBB.

Dextran based Polymeric Micelles as Carriers for Delivery of Hydrophobic Drugs.

PubMed

Mocanu, Georgeta; Nichifor, Marieta; Sacarescu, Liviu

2017-01-01

The improvement of drugs bioavailability, especially of the hydrophobic ones, by using various nanoparticles is a very exciting field of the modern research. The applicability of nano-sized shell crosslinked micelles based on dextran as supports for controlled release of several hydrophobic drugs (nystatin, rifampicin, resveratrol, and curcumin) was investigated by in vitro drug loading/release experiments. The synthesized crosslinked micelles were loaded with drugs of various hydrophobicities and their retention/release behavior was followed by dialysis procedure. Crosslinked micelles obtained from dextran with octadecyl end groups, with or without N-(2- hydroxypropyl)-N,N-dimethyl-N-benzylammonium chloride groups attached to the main dextran chains, could retain the drugs in amounts which increased with increasing drug hydrophobicity (water insolubility), as follows: 30-60 mg rifampicin/g, 70-100 mg nystatin/g, 120-144 mg resveratrol/g and 146-260 mg curcumin/g. The rate of drug release from the loaded micelles was also dependent on the drug hydrophobicity and was always slower than the free drug recovery. Antioxidant activity of curcumin and resveratrol released from the loaded micelles was preserved. The results highlighted the potential of the new nano-sized micelles as carriers for prolonged and controlled delivery of various hydrophobic drugs. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Effect of surface charge on the colloidal stability and in vitro uptake of carboxymethyl dextran-coated iron oxide nanoparticles

PubMed Central

Ayala, Vanessa; Herrera, Adriana P.; Latorre-Esteves, Magda; Torres-Lugo, Madeline

2013-01-01

Nanoparticle physicochemical properties such as surface charge are considered to play an important role in cellular uptake and particle–cell interactions. In order to systematically evaluate the role of surface charge on the uptake of iron oxide nanoparticles, we prepared carboxymethyl-substituted dextrans with different degrees of substitution, ranging from 38 to 5 groups per chain, and reacted them using carbodiimide chemistry with amine–silane-coated iron oxide nanoparticles with narrow size distributions in the range of 33–45 nm. Surface charge of carboxymethyl-substituted dextran-coated nano-particles ranged from −50 to 5 mV as determined by zeta potential measurements, and was dependent on the number of carboxymethyl groups incorporated in the dextran chains. Nanoparticles were incubated with CaCo-2 human colon cancer cells. Nanoparticle–cell interactions were observed by confocal laser scanning microscopy and uptake was quantified by elemental analysis using inductively coupled plasma mass spectroscopy. Mechanisms of internalization were inferred using pharmacological inhibitors for fluid-phase, clathrin-mediated, and caveola-mediated endocytosis. Results showed increased uptake for nanoparticles with greater negative charge. Internalization patterns suggest that uptake of the most negatively charged particles occurs via non-specific interactions. PMID:24470787

Highly Selective Photothermal Therapy by a Phenoxylated-Dextran-Functionalized Smart Carbon Nanotube Platform.

PubMed

Han, Seungmin; Kwon, Taeyun; Um, Jo-Eun; Haam, Seungjoo; Kim, Woo-Jae

2016-05-01

Near-infrared (NIR) photothermal therapy using biocompatible single-walled carbon nanotubes (SWNTs) is advantageous because as-produced SWNTs, without additional size control, both efficiently absorb NIR light and demonstrate high photothermal conversion efficiency. In addition, covalent attachment of receptor molecules to SWNTs can be used to specifically target infected cells. However, this technique interrupts SWNT optical properties and inevitably lowers photothermal conversion efficiency and thus remains major hurdle for SWNT applications. This paper presents a smart-targeting photothermal therapy platform for inflammatory disease using newly developed phenoxylated-dextran-functionalized SWNTs. Phenoxylated dextran is biocompatible and efficiently suspends SWNTs by noncovalent π-π stacking, thereby minimizing SWNT bundle formations and maintaining original SWNT optical properties. Furthermore, it selectively targets inflammatory macrophages by scavenger-receptor binding without any additional receptor molecules; therefore, its preparation is a simple one-step process. Herein, it is experimentally demonstrated that phenoxylated dextran-SWNTs (pD-SWNTs) are also biocompatible, selectively penetrate inflammatory macrophages over normal cells, and exhibit high photothermal conversion efficiency. Consequently, NIR laser-triggered macrophage treatment can be achieved with high accuracy by pD-SWNT without damaging receptor-free cells. These smart targeting materials can be a novel photothermal agent candidate for inflammatory disease. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Toxicity, toxicokinetics and biodistribution of dextran stabilized Iron oxide Nanoparticles for biomedical applications.

PubMed

Remya, N S; Syama, S; Sabareeswaran, A; Mohanan, P V

2016-09-10

Advancement in the field of nanoscience and technology has alarmingly raised the call for comprehending the potential health effects caused by deliberate or unintentional exposure to nanoparticles. Iron oxide magnetic nanoparticles have an increasing number of biomedical applications and hence a complete toxicological profile of the nanomaterial is therefore a mandatory requirement prior to its intended usage to ensure safety and to minimize potential health hazards upon its exposure. The present study elucidates the toxicity of in house synthesized Dextran stabilized iron oxide nanoparticles (DINP) in a regulatory perspective through various routes of exposure, its associated molecular, immune, genotoxic, carcinogenic effects and bio distribution profile. Synthesized ferrite nanomaterials were successfully coated with dextran (<25nm) and were physicochemically characterized and subjected to in vitro and in vivo toxicity evaluations. The results suggest that surface coating of ferrite nanoparticles with dextran helps in improvising particle stability in biological environments. The nanoparticles do not seem to induce oxidative stress mediated toxicological effects, nor altered physiological process or behavior changes or visible pathological lesions. Furthermore no anticipated health hazards are likely to be associated with the use of DINP and could be concluded that the synthesized DINP is nontoxic/safe to be used for biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

The Blume-Capel model on hierarchical lattices: Exact local properties

NASA Astrophysics Data System (ADS)

Rocha-Neto, Mário J. G.; Camelo-Neto, G.; Nogueira, E., Jr.; Coutinho, S.

2018-03-01

The local properties of the spin one ferromagnetic Blume-Capel model defined on hierarchical lattices with dimension two and three are obtained by a numerical recursion procedure and studied as functions of the temperature and the reduced crystal-field parameter. The magnetization and the density of sites in the configuration S = 0 state are carefully investigated at low temperature in the region of the phase diagram that presents the phenomenon of phase reentrance. Both order parameters undergo transitions from the ferromagnetic to the ordered paramagnetic phase with abrupt discontinuities that decrease along the phase boundary at low temperatures. The distribution of magnetization in a typical profile was determined on the transition line presenting a broad multifractal spectrum that narrows towards the fractal limit (single point) as the discontinuities of the order parameters grow towards a maximum. The amplitude of the order-parameter discontinuities and the narrowing of the multifractal spectra were used to delimit the low temperature interval for the possible locus of the tricritical point.

Assessment of 7.5% NaCl /6% Dextran-70 (HSD) Effects on Serum or Plasma Protein Determinations

DTIC Science & Technology

1990-12-26

determined by modified Lowry, dye-binding, and an automated biuret method, as well as by refractometry , before, and at various times following HSD...protein concentrations determined by the biuret assay or refractometry when dextran serum concentrations exceeded 1.2 g/dl. The in vivo studies... refractometry , before, and at various times following HSD infusion in both euvolemic and hemorrhaged animals. Other studies analyzed plasma protein

Analyzing Carbohydrate-Protein Interaction Based on Single Plasmonic Nanoparticle by Conventional Dark Field Microscopy.

PubMed

Jin, Hong-Ying; Li, Da-Wei; Zhang, Na; Gu, Zhen; Long, Yi-Tao

2015-06-10

We demonstrated a practical method to analyze carbohydrate-protein interaction based on single plasmonic nanoparticles by conventional dark field microscopy (DFM). Protein concanavalin A (ConA) was modified on large sized gold nanoparticles (AuNPs), and dextran was conjugated on small sized AuNPs. As the interaction between ConA and dextran resulted in two kinds of gold nanoparticles coupled together, which caused coupling of plasmonic oscillations, apparent color changes (from green to yellow) of the single AuNPs were observed through DFM. Then, the color information was instantly transformed into a statistic peak wavelength distribution in less than 1 min by a self-developed statistical program (nanoparticleAnalysis). In addition, the interaction between ConA and dextran was proved with biospecific recognition. This approach is high-throughput and real-time, and is a convenient method to analyze carbohydrate-protein interaction at the single nanoparticle level efficiently.

Use of HL cells for improved isolation and passage of Chlamydia pneumoniae.

PubMed Central

Cles, L D; Stamm, W E

1990-01-01

We compared growth of the recently discovered respiratory pathogen Chlamydia pneumoniae in McCoy, HeLa 229, BHK-21, and HL cells. When cells were not pretreated with DEAE-dextran, HL cells had significantly higher mean numbers of inclusion-forming units (IFUs) on initial inoculation than the other cell lines. When cells were pretreated with DEAE-dextran, HeLa 229 and HL cells had equivalent mean numbers of IFUs on initial inoculation. HL cells had strikingly higher mean numbers of IFUs in passage than HeLa 229, BHK-21, or McCoy cells. In addition, HL cells did not require pretreatment with DEAE-dextran and could be used from 2 to 4 days after seeding. We conclude that HL cells are an excellent cell culture system for laboratory propagation of C. pneumoniae and may be a more sensitive cell line for initial isolation. PMID:2191013

One-pot synthesis of magnetic nanoclusters enabling atherosclerosis-targeted magnetic resonance imaging.

PubMed

Kukreja, Aastha; Lim, Eun-Kyung; Kang, Byunghoon; Choi, Yuna; Lee, Taeksu; Suh, Jin-Suck; Huh, Yong-Min; Haam, Seungjoo

2014-01-01

In this study, dextran-encrusted magnetic nanoclusters (DMNCs) were synthesized using a one-pot solution phase method for detection of atherosclerosis by magnetic resonance imaging. Pyrenyl dextran was used as a surfactant because of its electron-stabilizing effect and its amphiphilic nature, rendering the DMNCs stable and water-dispersible. The DMNCs were 65.6±4.3 nm, had a narrow size distribution, and were superparamagnetic with a high magnetization value of 60.1 emu/g. Further, they showed biocompatibility and high cellular uptake efficiency, as indicated by a strong interaction between dextran and macrophages. In vivo magnetic resonance imaging demonstrated the ability of DMNCs to act as an efficient magnetic resonance imaging contrast agent capable of targeted detection of atherosclerosis. In view of these findings, it is concluded that DMNCs can be used as magnetic resonance imaging contrast agents to detect inflammatory disease.

Enzyme-resistant isomalto-oligosaccharides produced from Leuconostoc mesenteroides NRRL B-1426 dextran hydrolysis for functional food application.

PubMed

Kothari, Damini; Goyal, Arun

2016-07-01

The extracellular dextransucrase from Leuconostoc mesenteroides NRRL B-1426 was produced and purified using polyethylene glycol fractionation. In our earlier study, it was reported that L. mesenteroides dextransucrase synthesizes a high-molecular mass dextran (>2 × 10(6)  Da) with ∼85.5% α-(1→6) linear and ∼14.5% α-(1→3) branched linkages. Isomalto-oligosaccharides (IMOs) were synthesized through depolymerization of dextran by the action of dextranase. The degree of polymerization of IMOs was 2-10 as confirmed by mass spectrometry. The nuclear magnetic resonance spectroscopic analysis revealed the presence of α-(1→3) linkages in the synthesized IMOs. The IMOs were resistant to dextranase, α-glucosidase, and α-amylase, and therefore can have potential application as food additives in the functional foods. © 2015 International Union of Biochemistry and Molecular Biology, Inc.

The effects of 7.5% NaCl/6% dextran 70 on coagulation and platelet aggregation in humans

NASA Technical Reports Server (NTRS)

Hess, J. R.; Dubick, M. A.; Summary, J. J.; Bangal, N. R.; Wade, C. E.

1992-01-01

The combination solution of 7.5% NaCl/6% dextran 70 (HSD) administered IV gives hemodynamic improvement in the treatment of hemorrhagic hypotension. Since earlier dextran solutions were reported to interfere with blood coagulation, the effects of HSD on the prothrombin time (PT), the activated partial thromboplastin time (APTT), platelet aggregation, and platelet concentration were studied. The HSD mixed with human plasma (1:5 and 1:10) slightly prolonged PT, but had no effect on the APTT, compared with saline controls. The HSD also decreased human platelet aggregation at the 1:5 dilution. In separate mixing studies, the hypertonic saline component of HSD was associated with the prolongation of PT and decreased platelet aggregation. The data from these studies indicate that at its proposed therapeutic dose, HSD is expected to have minimal effect on blood coagulation.

The aerodynamic characteristics of eight very thick airfoils from tests in the variable density wind tunnel

NASA Technical Reports Server (NTRS)

Jacobs, Eastman N

1932-01-01

Report presents the results of wind tunnel tests on a group of eight very thick airfoils having sections of the same thickness as those used near the roots of tapered airfoils. The tests were made to study certain discontinuities in the characteristic curves that have been obtained from previous tests of these airfoils, and to compare the characteristics of the different sections at values of the Reynolds number comparable with those attained in flight. The discontinuities were found to disappear as the Reynolds number was increased. The results obtained from the large-scale airfoil, a symmetrical airfoil having a thickness ratio of 21 per cent, has the best general characteristics.

Interface structure in nanoscale multilayers near continuous-to-discontinuous regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pradhan, P. C.; Majhi, A.; Nayak, M., E-mail: mnayak@rrcat.gov.in

2016-07-28

Interfacial atomic diffusion, reaction, and formation of microstructure in nanoscale level are investigated in W/B{sub 4}C multilayer (ML) system as functions of thickness in ultrathin limit. Hard x-ray reflectivity (XRR) and x-ray diffuse scattering in conjunction with x-ray absorption near edge spectroscopy (XANES) in soft x-ray and hard x-ray regimes and depth profiling x-ray photoelectron spectroscopy (XPS) have been used to precisely evaluate detailed interfacial structure by systematically varying the individual layer thickness from continuous-to-discontinuous regime. It is observed that the interfacial morphology undergoes an unexpected significant modification as the layer thickness varies from continuous-to-discontinuous regime. The interfacial atomic diffusionmore » increases, the physical density of W layer decreases and that of B{sub 4}C layer increases, and further more interestingly the in-plane correlation length decreases substantially as the layer thickness varies from continuous-to-discontinuous regime. This is corroborated using combined XRR and x-ray diffused scattering analysis. XANES and XPS results show formation of more and more tungsten compounds at the interfaces as the layer thickness decreases below the percolation threshold due to increase in the contact area between the elements. The formation of compound enhances to minimize certain degree of disorder at the interfaces in the discontinuous region that enables to maintain the periodic structure in ML. The degree of interfacial atomic diffusion, interlayer interaction, and microstructure is correlated as a function of layer thickness during early stage of film growth.« less

What Maintains the Central North Pacific Genetic Discontinuity in Pacific Herring?

PubMed Central

Liu, Ming; Lin, Longshan; Gao, Tianxiang; Yanagimoto, Takashi; Sakurai, Yasunori; Grant, W. Stewart

2012-01-01

Pacific herring show an abrupt genetic discontinuity in the central North Pacific that represents secondary contact between refuge populations previously isolated during Pleistocene glaciations. Paradoxically, high levels of gene flow produce genetic homogeneity among ocean-type populations within each group. Here, we surveyed variability in mtDNA control-region sequences (463 bp) and nine microsatellite loci in Pacific herring from sites across the North Pacific to further explore the nature of the genetic discontinuity around the Alaska Peninsula. Consistent with previous studies, little divergence (ΦST  = 0.011) was detected between ocean-type populations of Pacific herring in the North West Pacific, except for a population in the Yellow Sea (ΦST  = 0.065). A moderate reduction in genetic diversity for both mtDNA and microsatellites in the Yellow Sea likely reflects founder effects during the last colonization of this sea. Reciprocal monophyly between divergent mtDNA lineages (ΦST  = 0.391) across the Alaska Peninsula defines the discontinuity across the North Pacific. However, microsatellites did not show a strong break, as eastern Bering Sea (EBS) herring were more closely related to NE Pacific than to NW Pacific herring. This discordance between mtDNA and microsatellites may be due to microsatellite allelic convergence or to sex-biased dispersal across the secondary contact zone. The sharp discontinuity between Pacific herring populations may be maintained by high-density blocking, competitive exclusion or hybrid inferiority. PMID:23300525

Microglia show altered morphology and reduced arborization in human brain during aging and Alzheimer's disease.

PubMed

Davies, Danielle S; Ma, Jolande; Jegathees, Thuvarahan; Goldsbury, Claire

2017-11-01

Changes in microglia function are involved in Alzheimer's disease (AD) for which ageing is the major risk factor. We evaluated microglial cell process morphologies and their gray matter coverage (arborized area) during ageing and in the presence and absence of AD pathology in autopsied human neocortex. Microglial cell processes were reduced in length, showed less branching and reduced arborized area with aging (case range 52-98 years). This occurred during normal ageing and without microglia dystrophy or changes in cell density. There was a larger reduction in process length and arborized area in AD compared to aged-matched control microglia. In AD cases, on average, 49%-64% of microglia had discontinuous and/or punctate Iba1 labeled processes instead of continuous Iba1 distribution. Up to 16% of aged-matched control microglia displayed discontinuous or punctate features. There was no change in the density of microglial cell bodies in gray matter during ageing or AD. This demonstrates that human microglia show progressive cell process retraction without cell loss during ageing. Additional changes in microglia occur with AD including Iba1 protein puncta and discontinuity. We suggest that reduced microglial arborized area may be an aging-related correlate of AD in humans. These variations in microglial cells during ageing and in AD could reflect changes in neural-glial interactions which are emerging as key to mechanisms involved in ageing and neurodegenerative disease. © 2016 International Society of Neuropathology.

The Progenitor Dependence of Core-collapse Supernovae from Three-dimensional Simulations with Progenitor Models of 12–40 M ⊙

NASA Astrophysics Data System (ADS)

Ott, Christian D.; Roberts, Luke F.; da Silva Schneider, André; Fedrow, Joseph M.; Haas, Roland; Schnetter, Erik

2018-03-01

We present a first study of the progenitor star dependence of the three-dimensional (3D) neutrino mechanism of core-collapse supernovae. We employ full 3D general-relativistic multi-group neutrino radiation-hydrodynamics and simulate the postbounce evolutions of progenitors with zero-age main sequence masses of 12, 15, 20, 27, and 40 M ⊙. All progenitors, with the exception of the 12 M ⊙ star, experience shock runaway by the end of their simulations. In most cases, a strongly asymmetric explosion will result. We find three qualitatively distinct evolutions that suggest a complex dependence of explosion dynamics on progenitor density structure, neutrino heating, and 3D flow. (1) Progenitors with massive cores, shallow density profiles, and high post-core-bounce accretion rates experience very strong neutrino heating and neutrino-driven turbulent convection, leading to early shock runaway. Accretion continues at a high rate, likely leading to black hole formation. (2) Intermediate progenitors experience neutrino-driven, turbulence-aided explosions triggered by the arrival of density discontinuities at the shock. These occur typically at the silicon/silicon–oxygen shell boundary. (3) Progenitors with small cores and density profiles without strong discontinuities experience shock recession and develop the 3D standing-accretion shock instability (SASI). Shock runaway ensues late, once declining accretion rate, SASI, and neutrino-driven convection create favorable conditions. These differences in explosion times and dynamics result in a non-monotonic relationship between progenitor and compact remnant mass.

Topical minoxidil fortified with finasteride: An account of maintenance of hair density after replacing oral finasteride.

PubMed

Chandrashekar, B S; Nandhini, T; Vasanth, Vani; Sriram, Rashmi; Navale, Shreya

2015-01-01

Finasteride acts by reducing dihydrotestosterone levels, thereby inhibiting miniaturization of hair follicles in patients with androgenetic alopecia (AGA). Oral finasteride is associated with side effects such as decreased libido, sexual dysfunction, and gynecomastia. The aim of the following study is to assess the efficacy of maintaining hair growth with 5% topical minoxidil fortified with 0.1% finasteride in patients with AGA after initial treatment with 5% topical minoxidil and oral finasteride for two years. A retrospective assessment was done in 50 male patients aged 20-40 years with AGA. All the patients had been initially treated with topical minoxidil and oral finasteride for a period of two years, after which the oral finasteride was replaced with topical minoxidil fortified with finasteride. Five of 50 patients had discontinued the treatment for a period of 8-12 months and were then resumed with only topical minoxidil fortified with finasteride. The patients' case sheets and photographs were reviewed by independent observers and the efficacy of minoxidil-finasteride combination was assessed. Of the 45 patients who underwent a continuous treatment for AGA, 84.44% maintained a good hair density with topical minoxidil-finasteride combinatio. Of the five patients who discontinued oral finasteride for 8-12 months, four demonstrated good improvement in hair density when treatment was resumed with topical minoxidil-finasteride combination. Topical finasteride can be considered for hair density maintenance after initial improvement with oral finasteride, thereby obviating the indefinite use of oral finasteride.

Effect of DEXTRAN-graft-POLYACRYLAMIDE Internal Structure on Flocculation Process Parameters

NASA Astrophysics Data System (ADS)

Bezugla, T.; Kutsevol, N.; Shyichuk, A.; Ziolkowska, D.

2008-08-01

Dextran-graft-Polyacrylamide copolymers (D-g-PAA) of brush-like architecture were tested as flocculation aids in the model kaolin suspensions. Due to expanded conformation the D-g-PAA copolymers are more effective flocculants than individual PAA with close molecular mass. The internal structure of D-g-PAA copolymers which is determined by number and length of grafted PAA chains, the distance between grafts, etc., has the significant influence on flocculation behavior of such polymers.

Abstracts of the International Conference on Hypertonic Resuscitation (5th) Held in Galveston, Texas on 3-5 June 1992

DTIC Science & Technology

1992-08-01

Dextran Metabolism in Dehydrated, Hemorrhaged Sheep Infused with Hypertonic Saline/Dextran (HSD). 3 J. Eaker (Davis, U.S.A.): Small Volume Intraosseous ...S. Majluf (Mexico City, Mexico): Eualuation of an Intraosseous Function versus Intrauenous and Central Catheter in Patients with Hemorrhagic Shock. W...between the traumatized brain parenchyma and the skull bone followed by closure of the cranium by dental cement. At 20 hrs later the animals were

Microparticles prepared from sulfenamide-based polymers

PubMed Central

D’Mello, Sheetal R.; Yoo, Jun; Bowden, Ned B.; Salem, Aliasger K.

2015-01-01

Polysulfenamides (PSN), with a SN linkage (RSNR2) along the polymer backbone, are a new class of biodegradable and biocompatible polymers. These polymers were unknown prior to 2012 when their synthesis and medicinally relevant properties were reported. The aim of this study was to develop microparticles as a controlled drug delivery system using polysulfenamide as the matrix material. The microparticles were prepared by a water-in-oil-in-water double emulsion solvent evaporation method. For producing drug-loaded particles, FITC-dextran was used as a model hydrophilic compound. At the optimal formulation conditions, the external morphology of the PSN microparticles was examined by scanning electron microscopy to show the formation of smooth-surfaced spherical particles with low polydispersity. The microparticles had a net negative surface charge (−23 mV) as analyzed by the zetasizer. The drug encapsulation efficiency of the particles and the drug loading were found to be dependent on the drug molecular weight, amount of FITC-dextran used in fabricating FITC-dextran loaded microparticles, concentration of PSN and surfactant, and volume of the internal and external water phases. FITC-dextran was found to be distributed throughout the PSN microparticles and was released in an initial burst followed by more continuous release over time. Confocal laser scanning microscopy was used to qualitatively observe the cellular uptake of PSN microparticles and indicated localization of the particles in both the cytoplasm and the nucleus. PMID:23862723

Intravenous ferric carboxymaltose for the treatment of iron deficiency anemia

PubMed Central

Friedrisch, João Ricardo; Cançado, Rodolfo Delfini

2015-01-01

Nutritional iron deficiency anemia is the most common deficiency disorder, affecting more than two billion people worldwide. Oral iron supplementation is usually the first choice for the treatment of iron deficiency anemia, but in many conditions, oral iron is less than ideal mainly because of gastrointestinal adverse events and the long course needed to treat the disease and replenish body iron stores. Intravenous iron compounds consist of an iron oxyhydroxide core, which is surrounded by a carbohydrate shell made of polymers such as dextran, sucrose or gluconate. The first iron product for intravenous use was the high molecular weight iron dextran. However, dextran-containing intravenous iron preparations are associated with an elevated risk of anaphylactic reactions, which made physicians reluctant to use intravenous iron for the treatment of iron deficiency anemia over many years. Intravenous ferric carboxymaltose is a stable complex with the advantage of being non-dextran-containing and a very low immunogenic potential and therefore not predisposed to anaphylactic reactions. Its properties permit the administration of large doses (15 mg/kg; maximum of 1000 mg/infusion) in a single and rapid session (15-minute infusion) without the requirement of a test dose. The purpose of this review is to discuss some pertinent issues in relation to the history, pharmacology, administration, efficacy, and safety profile of ferric carboxymaltose in the treatment of patients with iron deficiency anemia. PMID:26670403

Partial replacement of dietary linoleic acid with long chain n-3 polyunsaturated fatty acids protects against dextran sulfate sodium-induced colitis in rats.

PubMed

Tyagi, Anupama; Kumar, Uday; Santosh, Vadakattu Sai; Reddy, Suryam; Mohammed, Saazida Bhanu; Ibrahim, Ahamed

2014-12-01

Imbalances in the dietary n-6 and n-3 polyunsaturated fatty acids have been implicated in the increased prevalence of inflammatory bowel disease. This study investigated the effects of substitution of linoleic acid with long chain n-3 polyunsaturated fatty acids and hence decreasing n-6:n-3 fatty acid ratio on inflammatory response in dextran sulfate sodium induced colitis. Male weanling Sprague Dawley rats were fed diets with n-6:n-3 fatty acid in the ratios of 215,50,10 or 5 for 3 months and colitis was induced by administration of dextran sulfate sodium in drinking water during last 11 days. Decreasing the dietary n-6:n-3 fatty acid ratio to 10 and 5 significantly attenuated the severity of colitis as evidenced by improvements in clinical symptoms, reversal of shortening of colon length, reduced severity of anemia, preservation of colonic architecture as well as reduced colonic mucosal myeloperoxidase activity. This protection was associated with suppression of colonic mucosal proinflammatory mediators such as TNFα, IL-1β and nitric oxide. These findings suggest that long chain n-3 polyunsaturated fatty acids at a level of 3.0 g/kg diet (n-6:n-3 ratio of 10) prevents dextran sulfate sodium induced colitis by suppressing the proinflammatory mediators. Copyright © 2014 Elsevier Ltd. All rights reserved.

Inflammatory bowel disease causes reversible suppression of osteoblast and chondrocyte function in mice.

PubMed

Harris, Laura; Senagore, Patricia; Young, Vincent B; McCabe, Laura R

2009-05-01

Decreased bone density and stature can occur in pediatric patients with inflammatory bowel disease (IBD). Little is known about how IBD broadly impacts the skeleton. To evaluate the influence of an acute episode of IBD on growing bone, 4-wk-old mice were administered 5% dextran sodium sulfate (DSS) for 5 days to induce colitis and their recovery was monitored. During active disease and early recovery, trabecular bone mineral density, bone volume, and thickness were decreased. Cortical bone thickness, outer perimeter, and density were also decreased, whereas inner perimeter and marrow area were increased. These changes appear to maintain bone strength since measures of moments of inertia were similar between DSS-treated and control mice. Histological (static and dynamic), serum, and RNA analyses indicate that a decrease in osteoblast maturation and function account for changes in bone density. Unlike some conditions of bone loss, marrow adiposity did not increase. Similar to reports in humans, bone length decreased and correlated with decreases in growth plate thickness and chondrocyte marker expression. During disease recovery, mice experienced a growth spurt that led to their achieving final body weights and bone length, density, and gene expression similar to healthy controls. Increased TNF-alpha and decreased IGF-I serum levels were observed with active disease and returned to normal with recovery. Changes in serum TNF-alpha (increased) and IGF-I (decreased) paralleled changes in bone parameters and returned to normal values with recovery, suggesting a potential role in the skeletal response.

Agarose electrophoresis of DNA in discontinuous buffers, using a horizontal slab apparatus and a buffer system with improved properties.

PubMed

Zsolnai, A; Orbán, L; Chrambach, A

1993-03-01

Using a horizontal slab apparatus with a buffer in the reservoirs at the level of the gel ("sea-level electrophoresis"), the retrograde discontinuous buffer system reported by Wiltfang et al. for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of proteins was applied to DNA electrophoresis. This application yielded the advantages of an increased displacement rate of the moving boundary front and a decrease in the concentration of the counterion base in the resolving phase, which yielded reduced relative mobility values at equivalent gel concentrations and practicable low buffer concentrations. The change of relative mobilities (Rf) with a variation of field strength is decreased compared to that of the migration rate in the continuous Tris-boric-acid-EDTA (TBE) buffer and thus the robustness of the system is improved, as well as the efficiency of separation. The system of Wiltfang et al. has in common with previously described discontinuous DNA system, that it is able to stack DNA from dilute samples and is insensitive to sample components with lower net mobilities than DNA, such as acetate. However, the variance of Rf at constant current density in the discontinuous buffer system is not improved over that of the migration rate at constant field strength in the continuous TBE buffer.

Preparative electrophoresis of living lymphocytes

NASA Technical Reports Server (NTRS)

Vanoss, C. J.; Bigazzi, P. E.; Gillman, C. F.; Allen, R. E.

1974-01-01

Vertical liquid columns containing low molecular weight dextran density gradients can be used for preparative lymphocyte electrophoresis on earth, in simulation of 0 gravity conditions. Another method that has been tested at 1 G, is the electrophoresis of lymphocytes in a upward direction in vertical columns. By both methods up to 10 to the 7th power lymphocytes can be separated at one time in a 30 cm glass column of 8 mm inside diameter, at 12 v/cm, in 2 hours. Due to convection and sedimentation problems, the separation at 1 G is less than ideal, but it is expected that at 0 gravity electrophoresis will prove to be a uniquely powerful cell separation tool. The technical feasibility of electrophoresing inert particles at 0 G has been proven earlier, during the flight of Apollo 16.

Confinement effects on liquid oxygen flows in carbon nanotubes: A MD simulation study

NASA Astrophysics Data System (ADS)

Suga, Kazuhiko; Moritani, Rintaro; Mori, Yuki; Kaneda, Masayuki

2017-11-01

Molecular dynamics simulations are performed to investigate the liquid flow mechanism of diatomic molecules in armchair carbon nanotubes (CNTs). Oxygen molecules are considered as the fluid inside armchair (n,n) (n=6-20) CNTs at a temperature of 133[K] and a bulk density of 1680[kg /m3] for the liquid state. The velocity profiles and slip lengths are discussed considering the radial distributions of the fluid density by the finite difference-based velocity fitting method. It is shown that as the diameter of the CNT increases, the slip length and the flow rate enhancement generally become smaller while irregular tendencies (discontinuity points) are observed in the distribution profiles. Between the (7,7) and (8,8) CNTs, a steep drop can be seen in the profiles. Between the (9,9) and (11,11) CNTs, and between the (12,12) and (14,14) CNTs transitional profiles are observed. It is confirmed that those phenomena are caused by an instability of the fluid molecule cluster due to the discontinuous confinement of the CNTs. Professor.

Perilymph pharmacokinetics of marker applied through a cochlear implant in guinea pigs

PubMed Central

Hartsock, Jared; Gill, Ruth; Smyth, Daniel; Kirk, Jonathon; Verhoeven, Kristien

2017-01-01

Patients undergoing cochlear implantation could benefit from a simultaneous application of drugs into the ear, helping preserve residual low-frequency hearing and afferent nerve fiber populations. One way to apply drugs is to incorporate a cannula into the implant, through which drug solution is driven. For such an approach, perilymph concentrations achieved and the distribution in the ear over time have not previously been documented. We used FITC-labeled dextran as a marker, delivering it into perilymph of guinea pigs at 10 or 100 nL/min though a cannula incorporated into a cochlear implant with the outlet in the mid basal turn. After injections of varying duration (2 hours, 1 day or 7 days) perilymph was collected from the cochlear apex using a sequential sampling technique, allowing dextran levels and gradients along scala tympani to be quantified. Data were interpreted quantitatively using computer simulations of the experiments. For injections of 2 hours duration, dextran levels were critically influenced by the presence or absence of fluid leakage at the cochleostomy site. When the cochleostomy was fluid-tight, substantially higher perilymph levels were achieved at the injection site, with concentration declining along scala tympani towards the apex. Contrary to expectations, large dextran gradients along scala tympani persisted after 24 hours of sustained injection and were still present in some animals after 7 days injection. Functional changes associated with implantation and dextran delivery, and the histological state of the implant and cannula were also documented. The persistent longitudinal gradients of dextan along the ear were not readily explained by computer simulations of the experiments based on prior pharmacokinetic data. One explanation is that inner ear pharmacokinetics are altered in the period after cochlear implantation, possibly by a permeabilization of the blood-labyrinth barrier as part of the immune response to the implant. PMID:28817653

Dextran or Saline Can Replace Contrast for Intravascular Optical Coherence Tomography in Lower Extremity Arteries.

PubMed

Kendrick, Daniel E; Allemang, Matthew T; Gosling, Andre F; Nagavalli, Anil; Kim, Ann H; Nishino, Setsu; Parikh, Sahil A; Bezerra, Hiram G; Kashyap, Vikram S

2016-10-01

To examine the hypothesis that alternative flush media could be used for lower extremity optical coherence tomography (OCT) imaging in long lesions that would normally require excessive use of contrast. The OPTical Imaging Measurement of Intravascular Solution Efficacy (OPTIMISE) trial was a single-center, prospective study (ClinicalTrials.gov identifier NCT01743872) that enrolled 23 patients (mean age 68±11 years; 14 men) undergoing endovascular intervention involving the superficial femoral artery. Four flush media (heparinized saline, dextran, carbon dioxide, and contrast) were used in succession in random order for each image pullback. Quality was defined as ≥270° visualization of vessel wall layers from each axial image. Mean proportions (± standard deviation) of image quality for each flush medium were assessed using 1-way analysis of variance and are reported with the 95% confidence intervals (CI). Four OCT catheters failed, leaving 19 patients who completed the OCT imaging protocol; from this cohort, 51 highest quality runs were selected for analysis. Average vessel diameter was 3.99±1.01 mm. OCT imaging allowed 10- to 15-μm resolution of the lumen border, with diminishing quality as vessel diameter increased. Plaque characterization revealed fibrotic lesions. Mean proportions of image quality were dextran 87.2%±12% (95% CI 0.81 to 0.94), heparinized saline 74.3%±24.8% (95% CI 0.66 to 0.93), contrast 70.1%±30.5% (95% CI 0.52 to 0.88), and carbon dioxide 10.0%±10.4% (95% CI 0.00 to 0.26). Dextran, saline, and contrast provided better quality than carbon dioxide (p<0.001). OCT is feasible in peripheral vessels <5 mm in diameter. Dextran or saline flush media can allow lesion characterization, avoiding iodinated contrast. Carbon dioxide is inadequate for peripheral OCT imaging. Axial imaging may aid in enhancing durability of peripheral endovascular interventions. © The Author(s) 2016.

Patterns of the adsorption of bovine serum albumin on carboxymethyl dextran and carboxymethyl cellulose films

NASA Astrophysics Data System (ADS)

Paribok, I. V.; Solomyanskii, A. E.; Zhavnerko, G. K.

2016-02-01

Patterns of the adsorption of bovine serum albumin on carboxymethyl dextran and carboxymethyl cellulose films are studied by means of microcontact printing, atomic force microscopy, and quartz crystal microbalance. It is shown that both the charge of polysaccharide macromolecules and the technique for deposition of their films onto the surface (via adsorption from a solution or covalent cross-linking) are factors that determine the degree of nonspecific adsorption of the protein on such films.

The Interaction of Solar wind Discontinuities with the Earth's Bow Shock

NASA Technical Reports Server (NTRS)

Sibeck, David G.

2000-01-01

Funding from NASA Grant No. NAG54679 was received in three installments. The first year's installment amounted to only one month of salary support and was used to prepare survey plots. The second year's installment allowed us to complete two research papers concerning the interaction of solar wind discontinuities with the Earth's bow shock. In the first (published) paper, we reported that the discontinuities launch slow mode waves into the magnetosheath and the slow mode waves always propagate antisunward through the flank magnetosheath. Because the sunward/antisunward sense of the magnetosheath magnetic field reverses across local noon, so does the (north/south or east/west) sense of the velocity fluctuations associated with the waves. Wind, Geotail, and IMP-8 observations were used for this study. In the second study, we used Wind and Interball-1 observations to demonstrate that pressure pulses in the magnetosheath occur in pairs and that they bound pressure cavities and/or brief intervals of outward magnetopause motion. This paper is now in press. Funding from the third year's installment has been used to investigate the two aspects of the foreshock. Two manuscripts are now in preparation for submission to the Journal of Geophysical Research. The first reports that waves within the foreshock account for many instances of poor correlations between two solar wind monitors. Remaining cases of poor correlation occur during intervals of nearly constant IMF orientations and magnetic field strengths. While the former category pose a significant difficulty for space weather forecasts, the latter do not. The second study surveys IMP-8 observations of the foreshock. We find that diamagnetic cavities are common, particularly during periods of high solar wind velocity and low solar wind density. Plasma densities, temperatures, and magnetic field strengths fall during intervals of enhanced energetic particle fluxes. The cavities are bounded by regions of decelerated solar wind plasma and enhanced densities and magnetic field strengths.

Discontinuous finite element space-angle treatment of the first order linear Boltzmann transport equation with magnetic fields: Application to MRI-guided radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

St Aubin, J., E-mail: joel.st.aubin@albertahealthservices.ca; Keyvanloo, A.; Fallone, B. G.

Purpose: The advent of magnetic resonance imaging (MRI) guided radiotherapy systems demands the incorporation of the magnetic field into dose calculation algorithms of treatment planning systems. This is due to the fact that the Lorentz force of the magnetic field perturbs the path of the relativistic electrons, hence altering the dose deposited by them. Building on the previous work, the authors have developed a discontinuous finite element space-angle treatment of the linear Boltzmann transport equation to accurately account for the effects of magnetic fields on radiotherapy doses. Methods: The authors present a detailed description of their new formalism and comparemore » its accuracy to GEANT4 Monte Carlo calculations for magnetic fields parallel and perpendicular to the radiation beam at field strengths of 0.5 and 3 T for an inhomogeneous 3D slab geometry phantom comprising water, bone, and air or lung. The accuracy of the authors’ new formalism was determined using a gamma analysis with a 2%/2 mm criterion. Results: Greater than 98.9% of all points analyzed passed the 2%/2 mm gamma criterion for the field strengths and orientations tested. The authors have benchmarked their new formalism against Monte Carlo in a challenging radiation transport problem with a high density material (bone) directly adjacent to a very low density material (dry air at STP) where the effects of the magnetic field dominate collisions. Conclusions: A discontinuous finite element space-angle approach has been proven to be an accurate method for solving the linear Boltzmann transport equation with magnetic fields for cases relevant to MRI guided radiotherapy. The authors have validated the accuracy of this novel technique against GEANT4, even in cases of strong magnetic field strengths and low density air.« less

Super-resolving random-Gaussian apodized photon sieve.

PubMed

Sabatyan, Arash; Roshaninejad, Parisa

2012-09-10

A novel apodized photon sieve is presented in which random dense Gaussian distribution is implemented to modulate the pinhole density in each zone. The random distribution in dense Gaussian distribution causes intrazone discontinuities. Also, the dense Gaussian distribution generates a substantial number of pinholes in order to form a large degree of overlap between the holes in a few innermost zones of the photon sieve; thereby, clear zones are formed. The role of the discontinuities on the focusing properties of the photon sieve is examined as well. Analysis shows that secondary maxima have evidently been suppressed, transmission has increased enormously, and the central maxima width is approximately unchanged in comparison to the dense Gaussian distribution. Theoretical results have been completely verified by experiment.

Skeletal Health After Continuation, Withdrawal, or Delay of Alendronate in Men With Prostate Cancer Undergoing Androgen-Deprivation Therapy

PubMed Central

Greenspan, Susan L.; Nelson, Joel B.; Trump, Donald L.; Wagner, Julie M.; Miller, Megan E.; Perera, Subashan; Resnick, Neil M.

2008-01-01

Purpose Androgen-deprivation therapy (ADT) for prostate cancer is associated with bone loss and osteoporotic fractures. Our objective was to examine changes in bone density and turnover with sustained, discontinued, or delayed oral bisphosphonate therapy in men receiving ADT. Patients and Methods A total of 112 men with nonmetastatic prostate cancer receiving ADT were randomly assigned to alendronate 70 mg once weekly or placebo in a double-blind, partial-crossover trial with a second random assignment at year 2 for those who initially received active therapy. Outcomes included bone mineral density and bone turnover markers. Results Men initially randomly assigned to alendronate and randomly reassigned at year 2 to continue had additional bone density gains at the spine (mean, 2.3% ± 0.7) and hip (mean, 1.3% ± 0.5%; both P < .01); those randomly assigned to placebo in year 2 maintained density at the spine and hip but lost (mean, −1.9% ± 0.6%; P < .01) at the forearm. Patients randomly assigned to begin alendronate in year 2 experienced improvements in bone mass at the spine and hip, but experienced less of an increase compared with those who initiated alendronate at baseline. Men receiving alendronate for 2 years experienced a mean 6.7% (± 1.2%) increase at the spine and a 3.2% (± 1.5%) at the hip (both P < .05). Bone turnover remained suppressed. Conclusion Among men with nonmetastatic prostate cancer receiving ADT, once-weekly alendronate improves bone density and decreases turnover. A second year of alendronate provides additional skeletal benefit, whereas discontinuation results in bone loss and increased bone turnover. Delay in bisphosphonate therapy appears detrimental to bone health. PMID:18802155

Evaporation of freely suspended single droplets: experimental, theoretical and computational simulations

NASA Astrophysics Data System (ADS)

Hołyst, R.; Litniewski, M.; Jakubczyk, D.; Kolwas, K.; Kolwas, M.; Kowalski, K.; Migacz, S.; Palesa, S.; Zientara, M.

2013-03-01

Evaporation is ubiquitous in nature. This process influences the climate, the formation of clouds, transpiration in plants, the survival of arctic organisms, the efficiency of car engines, the structure of dried materials and many other phenomena. Recent experiments discovered two novel mechanisms accompanying evaporation: temperature discontinuity at the liquid-vapour interface during evaporation and equilibration of pressures in the whole system during evaporation. None of these effects has been predicted previously by existing theories despite the fact that after 130 years of investigation the theory of evaporation was believed to be mature. These two effects call for reanalysis of existing experimental data and such is the goal of this review. In this article we analyse the experimental and the computational simulation data on the droplet evaporation of several different systems: water into its own vapour, water into the air, diethylene glycol into nitrogen and argon into its own vapour. We show that the temperature discontinuity at the liquid-vapour interface discovered by Fang and Ward (1999 Phys. Rev. E 59 417-28) is a rule rather than an exception. We show in computer simulations for a single-component system (argon) that this discontinuity is due to the constraint of momentum/pressure equilibrium during evaporation. For high vapour pressure the temperature is continuous across the liquid-vapour interface, while for small vapour pressures the temperature is discontinuous. The temperature jump at the interface is inversely proportional to the vapour density close to the interface. We have also found that all analysed data are described by the following equation: da/dt = P1/(a + P2), where a is the radius of the evaporating droplet, t is time and P1 and P2 are two parameters. P1 = -λΔT/(qeffρL), where λ is the thermal conductivity coefficient in the vapour at the interface, ΔT is the temperature difference between the liquid droplet and the vapour far from the interface, qeff is the enthalpy of evaporation per unit mass and ρL is the liquid density. The P2 parameter is the kinetic correction proportional to the evaporation coefficient. P2 = 0 only in the absence of temperature discontinuity at the interface. We discuss various models and problems in the determination of the evaporation coefficient and discuss evaporation scenarios in the case of single- and multi-component systems.

Permeabilization and recovery of the stratum corneum in vivo: the synergy of photomechanical waves and sodium lauryl sulfate.

PubMed

Lee, S; McAuliffe, D J; Kollias, N; Flotte, T J; Doukas, A G

2001-01-01

Photomechanical waves render the stratum corneum permeable and allow macromolecules to diffuse into the epidermis and dermis. The aim of this study was to investigate the combined action of photomechanical waves and sodium lauryl sulfate, an anionic surfactant, for transdermal delivery. A single photomechanical wave was applied to the skin of rats in the presence of sodium lauryl sulfate. The sodium lauryl sulfate solution was removed and aqueous solutions of rhodamine-B dextran (40 kDa molecular weight) were applied to the skin at time points 2, 30, and 60 minutes post-exposure. The presence of rhodamine-B dextran in the skin was measured by fluorescence emission spectroscopy in vivo and fluorescence microscopy of frozen biopsies. The use of sodium lauryl sulfate delayed the recovery of the stratum corneum barrier and extended the time available for the diffusion of dextran through it. The combination of photomechanical waves and surfactants can enhance transdermal drug delivery. Copyright 2001 Wiley-Liss, Inc.

Test of the 'glymphatic' hypothesis demonstrates diffusive and aquaporin-4-independent solute transport in rodent brain parenchyma.

PubMed

Smith, Alex J; Yao, Xiaoming; Dix, James A; Jin, Byung-Ju; Verkman, Alan S

2017-08-21

Transport of solutes through brain involves diffusion and convection. The importance of convective flow in the subarachnoid and paravascular spaces has long been recognized; a recently proposed 'glymphatic' clearance mechanism additionally suggests that aquaporin-4 (AQP4) water channels facilitate convective transport through brain parenchyma. Here, the major experimental underpinnings of the glymphatic mechanism were re-examined by measurements of solute movement in mouse brain following intracisternal or intraparenchymal solute injection. We found that: (i) transport of fluorescent dextrans in brain parenchyma depended on dextran size in a manner consistent with diffusive rather than convective transport; (ii) transport of dextrans in the parenchymal extracellular space, measured by 2-photon fluorescence recovery after photobleaching, was not affected just after cardiorespiratory arrest; and (iii) Aqp4 gene deletion did not impair transport of fluorescent solutes from sub-arachnoid space to brain in mice or rats. Our results do not support the proposed glymphatic mechanism of convective solute transport in brain parenchyma.

Electric field mediated loading of macromolecules in intact yeast cells is critically controlled at the wall level.

PubMed

Ganeva, V; Galutzov, B; Teissié, J

1995-12-13

The mechanism of electric field mediated macromolecule transfer inside an intact yeast cell was investigated by observing, under a microscope, the fluorescence associated to cells after pulsation in a buffer containing two different hydrophilic fluorescent dyes. In the case of a small probe such as propidium iodide, a long lived permeabilized state was induced by the field as classically observed on wall free systems. Penetration of a 70 kDa FITC dextran was obtained only by using drastic conditions and only a very limited number of yeast cells which took up macromolecules remained viable. Most dextrans were trapped in the wall. A dramatic improvement in transfer of dextrans was observed when the cells were treated by dithiothreitol before pulsation. A cytoplasmic protein leakage was detected after the electric treatment suggesting that an irreversible damage took place in the walls of many pulsed cells. Electroloading of macromolecules in intact yeast cells appears to be controlled by a field induced short lived alteration of the envelope organization.

Proteomics Analysis Reveals Distinct Corona Composition on Magnetic Nanoparticles with Different Surface Coatings: Implications for Interactions with Primary Human Macrophages

PubMed Central

Vogt, Carmen; Pernemalm, Maria; Kohonen, Pekka; Laurent, Sophie; Hultenby, Kjell; Vahter, Marie; Lehtiö, Janne; Toprak, Muhammet S.; Fadeel, Bengt

2015-01-01

Superparamagnetic iron oxide nanoparticles (SPIONs) have emerged as promising contrast agents for magnetic resonance imaging. The influence of different surface coatings on the biocompatibility of SPIONs has been addressed, but the potential impact of the so-called corona of adsorbed proteins on the surface of SPIONs on their biological behavior is less well studied. Here, we determined the composition of the plasma protein corona on silica-coated versus dextran-coated SPIONs using mass spectrometry-based proteomics approaches. Notably, gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed distinct protein corona compositions for the two different SPIONs. Relaxivity of silica-coated SPIONs was modulated by the presence of a protein corona. Moreover, the viability of primary human monocyte-derived macrophages was influenced by the protein corona on silica-coated, but not dextran-coated SPIONs, and the protein corona promoted cellular uptake of silica-coated SPIONs, but did not affect internalization of dextran-coated SPIONs. PMID:26444829

Proteomics Analysis Reveals Distinct Corona Composition on Magnetic Nanoparticles with Different Surface Coatings: Implications for Interactions with Primary Human Macrophages.

PubMed

Vogt, Carmen; Pernemalm, Maria; Kohonen, Pekka; Laurent, Sophie; Hultenby, Kjell; Vahter, Marie; Lehtiö, Janne; Toprak, Muhammet S; Fadeel, Bengt

2015-01-01

Superparamagnetic iron oxide nanoparticles (SPIONs) have emerged as promising contrast agents for magnetic resonance imaging. The influence of different surface coatings on the biocompatibility of SPIONs has been addressed, but the potential impact of the so-called corona of adsorbed proteins on the surface of SPIONs on their biological behavior is less well studied. Here, we determined the composition of the plasma protein corona on silica-coated versus dextran-coated SPIONs using mass spectrometry-based proteomics approaches. Notably, gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed distinct protein corona compositions for the two different SPIONs. Relaxivity of silica-coated SPIONs was modulated by the presence of a protein corona. Moreover, the viability of primary human monocyte-derived macrophages was influenced by the protein corona on silica-coated, but not dextran-coated SPIONs, and the protein corona promoted cellular uptake of silica-coated SPIONs, but did not affect internalization of dextran-coated SPIONs.

Hyperthermia mediated by dextran-coated La0.7Sr0.3MnO3 nanoparticles: in vivo studies

PubMed Central

Haghniaz, Reihaneh; Umrani, Rinku D; Paknikar, Kishore M

2016-01-01

Purpose The aim of this study was to evaluate radiofrequency-induced dextran-coated lanthanum strontium manganese oxide nanoparticles-mediated hyperthermia to be used for tumor regression in mice. Materials and methods Nanoparticles were injected intra-tumorally in melanoma-bearing C57BL/6J mice and were subjected to radiofrequency treatment. Results Hyperthermia treatment significantly inhibited tumor growth (~84%), increased survival (~50%), and reduced tumor proliferation in mice. Histopathological examination demonstrated immense cell death in treated tumors. DNA fragmentation, increased terminal deoxynucleotidyl transferase-dUTP nick end labeling signal, and elevated levels of caspase-3 and caspase-6 suggested apoptotic cell death. Enhanced catalase activity suggested reactive oxygen species-mediated cell death. Enhanced expression of heat shock proteins 70 and 90 in treated tumors suggested the possible development of “antitumor immunity”. Conclusion The dextran-coated lanthanum strontium manganese oxide-mediated hyperthermia can be used for the treatment of cancer. PMID:27175076

Depression of fractional sodium reabsorption by the proximal tubule of the dog without sodium diuresis

PubMed Central

Howards, Stuart S.; Davis, Bernard B.; Knox, Franklyn G.; Wright, Fred S.; Berliner, Robert W.

1968-01-01

The effect of infusions of hyperoncotic solutions on fractional sodium reabsorption by the proximal tubule of the dog was studied by the recollection micropuncture method. Tubule fluid to plasma inulin concentration ratios were measured for identified proximal tubule segments before and after infusion of 25% albumin or dextran solutions. Results were compared with changes in fractional reabsorption during saline diuresis. Plasma volume increased 66% ± SE 5.8 after infusion of albumin solution and 94% ± SE 8.2 after infusion of dextran solution. Fractional sodium reabosorption by the proximal tubule was depressed after infusion of both of these hyperoncotic solutions. Nevertheless, changes in sodium excretion after infusion of albumin and dextran were small. In contrast, after infusions of isotonic sodium chloride solution, which increased plasma volume 61% ± SE 5.8, a decrease in fractional reabsorption of 50.7% ± SE 7.2 was associated with large changes in sodium excretion. PMID:5658588

Chromatography of Penicillins, Penicilloates, and Penicilloylamides on Dextran Gels

PubMed Central

Hyslop, Newton E.; Milligan, Richard J.

1974-01-01

The factors influencing the chromatographic behavior on dextran gels of penicillins and their derivatives were investigated by comparing elution profiles and partition coefficients (KD and KAV) of penicillins differing in side-chain structure and among penicillin derivatives of identical side-chain but different nuclear structure. Under the conditions of pH and ionic strength employed (pH 7.4, 0.145 M NaCl, 0.05 M PO4), side-chain adsorptive effects best explained the anomalous behavior of benzylpenicillin and of oxacillin and its chlorine-substituted analogues. Polar side-chain substituents, such as the amino group of ampicillin and the carboxyl group of carbenicillin, and cleavage of the β-lactam ring, exemplified by penicilloates and penicilloylamines, both appeared to interfere with side-chain-directed adsorption. The differential adsorption of penicillins and their derivatives to dextran gels is not only of theoretical interest relative to the mechanism of chromatography but of practical application to analytical and preparative procedures in penicillin chemistry. PMID:15825415

Dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux in vivo.

PubMed

Akhter, S R; Ikezaki, H; Gao, X P; Rubinstein, I

1999-05-01

The purpose of this study was to determine whether dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux from the in situ hamster cheek pouch and, if so, whether this response is specific. By using intravital microscopy, we found that an aqueous extract of grain sorghum dust elicited significant, concentration-dependent leaky site formation and increase in clearance of FITC-labeled dextran (FITC-dextran; mol mass, 70 kDa) from the in situ hamster cheek pouch (P < 0.05). This response was significantly attenuated by dexamethasone (10 mg/kg iv). Dexamethasone also attenuated substance P-induced leaky site formation and increase in clearance of FITC-dextran from the cheek pouch but had no significant effects on adenosine-induced responses. Dexamethasone had no significant effects on arteriolar diameter in the cheek pouch. On balance, these data indicate that dexamethasone attenuates grain sorghum dust extract- and substance P-induced increases in macromolecular efflux from the in situ hamster cheek pouch in a specific fashion.

Test of the 'glymphatic' hypothesis demonstrates diffusive and aquaporin-4-independent solute transport in rodent brain parenchyma

PubMed Central

Yao, Xiaoming; Dix, James A; Jin, Byung-Ju

2017-01-01

Transport of solutes through brain involves diffusion and convection. The importance of convective flow in the subarachnoid and paravascular spaces has long been recognized; a recently proposed ‘glymphatic’ clearance mechanism additionally suggests that aquaporin-4 (AQP4) water channels facilitate convective transport through brain parenchyma. Here, the major experimental underpinnings of the glymphatic mechanism were re-examined by measurements of solute movement in mouse brain following intracisternal or intraparenchymal solute injection. We found that: (i) transport of fluorescent dextrans in brain parenchyma depended on dextran size in a manner consistent with diffusive rather than convective transport; (ii) transport of dextrans in the parenchymal extracellular space, measured by 2-photon fluorescence recovery after photobleaching, was not affected just after cardiorespiratory arrest; and (iii) Aqp4 gene deletion did not impair transport of fluorescent solutes from sub-arachnoid space to brain in mice or rats. Our results do not support the proposed glymphatic mechanism of convective solute transport in brain parenchyma. PMID:28826498

TEMPERATURE-SENSITIVE DEXTRANSUCRASE SYNTHESIS BY A LACTOBACILLUS.

PubMed

DUNICAN, L K; SEELEY, H W

1963-11-01

Dunican, L. K. (Cornell University, Ithaca, New York), and H. W. Seeley, Jr. Temperature-sensitive dextransucrase synthesis by a lactobacillus. J. Bacteriol. 86:1079-1083. 1963.-Dextran synthesis was found to be temperature-dependent in Lactobacillus strain RWM-13. Dextran was not formed above 37 C, although growth of cells occurred up to 42 C. Logarithmically growing cells transferred from 30 C to 40 C ceased producing dextran while growth decreased nominally. An examination of the extracts of cells broken by sonic treatment showed that as the temperature of growth was increased above 37 C the production of dextransucrase decreased. By use of an inhibitor of invertase, 10(-4)m AgNO(3), it was shown that invertase replaced dextransucrase activity at temperatures above 37 C. In contrast to dextransucrase in Leuconostoc mesenteroides, the enzyme in Lactobacillus strain RWM-13 was constitutive and thus resembled that of Streptococcus bovis. Thermosensitivity of dextransucrase synthesis has not been observed in Leuconostoc or Streptococcus.

Structural characterization of the exopolysaccharides from water kefir.

PubMed

Fels, Lea; Jakob, Frank; Vogel, Rudi F; Wefers, Daniel

2018-06-01

Water kefir is a beverage which is produced by initiating fermentation of a fruit extract/sucrose solution with insoluble kefir grains. Exopolysaccharides that are formed from sucrose play a major role in the kefir grain formation, but the exopolysaccharides in the kefir beverage and the detailed structural composition of the whole kefir grains have not been studied yet. Therefore, kefir grains and the corresponding kefir beverage were analyzed for exopolysaccharides by multiple chromatographic approaches and two-dimensional NMR spectroscopy. Furthermore, different fractionation techniques were applied to obtain further information about the exopolysaccharides. The exopolysaccharide-fraction of the investigated kefir beverage was predominantly composed of O3- and O2-branched dextrans as well as lower amounts of levans. The insoluble dextrans from the kefir grains were mostly O3-branched and contained an elevated portion of 1,3-linked glucose units compared to the soluble dextrans. The structurally different exopolysaccharides in water kefir suggest the involvement of multiple bacteria. Copyright © 2018 Elsevier Ltd. All rights reserved.

Impact of Hydration Media on Ex Vivo Corneal Elasticity Measurements

PubMed Central

Dias, Janice; Ziebarth, Noël M.

2014-01-01

Objectives To determine the effect of hydration media on ex vivo corneal elasticity. Methods Experiments were conducted on forty porcine eyes retrieved from an abattoir (10 eyes each for PBS, BSS, Optisol, 15% Dextran). The epithelium was removed and the cornea was excised with an intact scleral rim and placed in 20% Dextran overnight to restore its physiological thickness. For each hydration media, corneas were evenly divided into two groups: one with an intact scleral rim and the other without. Corneas were mounted onto a custom chamber and immersed in a hydration medium for elasticity testing. While in each medium, corneal elasticity measurements were performed for 2 hours: at 5-minute intervals for the first 30 minutes and then 15-minute intervals for the remaining 90 minutes. Elasticity testing was performed using nanoindentation with spherical indenters and Young’s modulus was calculated using the Hertz model. Thickness measurements were taken before and after elasticity testing. Results The percentage change in corneal thickness and elasticity was calculated for each hydration media group. BSS, PBS, and Optisol showed an increase in thickness and Young’s moduli for corneas with and without an intact scleral rim. 15% Dextran exhibited a dehydrating effect on corneal thickness and provided stable maintenance of corneal elasticity for both groups. Conclusions Hydration media affects the stability of corneal thickness and elasticity measurements over time. 15% Dextran was most effective in maintaining corneal hydration and elasticity, followed by Optisol. PMID:25603443

UP-HILIC-MS/MS to Determine the Action Pattern of Penicillium sp. Dextranase.

PubMed

Yi, Lin; Sun, Xue; Du, Kenze; Ouyang, Yilan; Wu, Chengling; Xu, Naiyu; Linhardt, Robert J; Zhang, Zhenqing

2015-07-01

Investigation of the action pattern of enzymes acting on carbohydrates is challenging, as both the substrate and the digestion products are complex mixtures. Dextran and its enzyme-derived oligosaccharides are widely used for many industrial applications. In this work, a new method relying on ultra-performance hydrophilic interaction liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UP-HILIC-Q/TOF-MS/MS) was developed to analyze a complex mixture of dextran oligosaccharide products to determine the action pattern of dextranase. No derivatization of oligosaccharides was required and the impact of the α- and β-configurations of the native oligosaccharides on the chromatographic separation was eliminated. The 1→6, 1→3, 1→4 backbone linkages and the branch linkages of these oligosaccharides were all distinguished from diagnostic ions in their MS/MS spectra, including fragments corresponding to (0,2)A, (0,3)A, (0,4)A, B-H2O, (2,5)A, and (3,5)A. The sequences of the oligosaccharide products were similarly established. Thus, the complex oligosaccharide mixtures in dextran digestion products were profiled and identified using this method. The more enzyme-resistant structures in dextran were established using much less sample, labor, time, and uncertainty than in previous studies. This method provides an efficient, sensitive, and straightforward way to monitor the entire process of digestion, establish the action pattern of the dextranase from Penicillium sp., and to support the proper industrial application of dextranase.

Application of Controlled Shear Stresses on the Erythrocyte Membrane as a New Approach to Promote Molecule Encapsulation.

PubMed

Casagrande, Giustina; Arienti, Flavio; Mazzocchi, Arabella; Taverna, Francesca; Ravagnani, Fernando; Costantino, MariaLaura

2016-10-01

Human red blood cells (RBCs) have a remarkable capacity to undergo reversible membrane swelling. Resealed erythrocytes have been proposed as carriers and bioreactors to be used in the treatment of various diseases. This work is aimed at developing a setup allowing the encapsulation of test molecules into erythrocytes by inducing reversible pore formation on the RBC membrane through the application of controlled mechanical shear stresses. The designed setup consists of two reservoirs connected by a glass capillary. Each reservoir is connected to a compressor; during the tests, the reservoirs were in turn pressurized to promote erythrocyte flow through the capillary. The setup was filled with a suspension of erythrocytes, phosphate buffer, and FITC-dextran. Dextran was chosen as the diffusive molecule to check membrane pore dimensions. Samples of the suspension were withdrawn at scheduled times while the setup was operating. Flow cytometry and stereo-optical microscopy analyses were used to evaluate the erythrocyte dextran uptake. The setup was shown to be safe, well controlled, and adjustable. The outcomes of the experimental tests showed significant dextran uptake by RBCs up to 8%. Microscopy observations highlighted the formation of echinocytes in the analyzed samples. Erythrocytes from different donors showed different reactions to mechanical stresses. The experimental outcomes proved the possibility to encapsulate test molecules into erythrocytes by applying controlled mechanical shear stresses on the RBC membrane, encouraging further studies. Copyright © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Spleen deposition of Cryptococcus neoformans capsular glucuronoxylomannan in rodents occurs in red pulp macrophages and not marginal zone macrophages expressing the C-type lectin SIGN-R1.

PubMed

De Jesus, Magdia; Park, Chae Gyu; Su, Ya; Goldman, David L; Steinman, Ralph M; Casadevall, Arturo

2008-03-01

The fate of microbial polysaccharides in host tissues is an important consideration because these compounds are often immune modulators. Splenic marginal zone macrophages that express the C-type lectin receptor SIGN-R1, take up neutral polysaccharides such as dextran and the capsular polysaccharide of Streptococcus pneumoniae. Given that the major component of Cryptococcus neoformans capsular polysaccharide, glucuronoxylomannan (GXM), localizes in the spleen when injected intravenously, we investigated whether GXM uptake was mediated by splenic macrophages expressing the SIGN-R1 receptor in mice. No significant differences in the amount and location of GXM deposition were detected in the spleens of mice treated with a SIGN-R1 blocking antibody when compared to controls. Similarly, a blocking antibody to Dectin-1, a co-receptor of -SIGN-R1, had no effects on GXM distribution within the spleen. Histological examination of spleens from mice and rats injected with FITC-Dextran and GXM revealed no significant co-localization, with Dextran and GXM being found in marginal and red pulp macrophages, respectively. Hence we conclude that GXM was not deposited in marginal zone macrophages. However, GXM deposition was found in the red pulp. These results indicate that there is a selective localization of these polysaccharides to different receptors such as SIGN-R1 for FITC dextran in marginal zone and a to-be-identified receptor selectively expressed by red pulp macrophages for GXM.

Salt-induced inhibition of the precipitin reaction of concanavalin A with polysaccharides and glycoprotein.

PubMed

Salahuddin, A; Begum, R; Averill, B K

1984-06-15

The time course of the precipitin reactions of concanavalin A with glycogen, dextran and ovalbumin was investigated by a light-scattering method near 30 degrees C in 10 mM-Tris/HCl buffer, pH 7.4, containing neutral salts, i.e. NaCl, KCl, NaBr, KI and NaClO4. With 0.8 microM-lectin and 0.36 mg of glycogen/ml, the half-life, t 1/2, of the precipitin reaction was independent of salt concentration between 0.1 M and 1.5 M, and was the same (175s) in the presence of NaCl, KCl, NaBr and KI but was significantly (27%) higher in NaClO4. In contrast, the five salts caused significant to marked enhancement in t 1/2 for the reactions of concanavalin A with dextran and ovalbumin. Likewise, whereas the turbidity produced in 1 h as a result of lectin-glycogen precipitation remained unchanged, those measured for the binding of dextran and ovalbumin were decreased in the presence of three salts. The increase in t 1/2 and decrease in turbidity were found to be higher with NaClO4, followed by KI; NaBr produced moderate and NaCl (or KCl) small but generally significant inhibition of the precipitin reactions with dextran and ovalbumin. The results showed that the lectin-ligand precipitin reactions involve salt-sensitive polar interactions that are less pronounced with compactly folded ligands such as glycogen.

UP-HILIC-MS/MS to Determine the Action Pattern of Penicillium sp. Dextranase

NASA Astrophysics Data System (ADS)

Yi, Lin; Sun, Xue; Du, Kenze; Ouyang, Yilan; Wu, Chengling; Xu, Naiyu; Linhardt, Robert J.; Zhang, Zhenqing

2015-07-01

Investigation of the action pattern of enzymes acting on carbohydrates is challenging, as both the substrate and the digestion products are complex mixtures. Dextran and its enzyme-derived oligosaccharides are widely used for many industrial applications. In this work, a new method relying on ultra-performance hydrophilic interaction liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UP-HILIC- Q/TOF-MS/MS) was developed to analyze a complex mixture of dextran oligosaccharide products to determine the action pattern of dextranase. No derivatization of oligosaccharides was required and the impact of the α- and β-configurations of the native oligosaccharides on the chromatographic separation was eliminated. The 1→6, 1→3, 1→4 backbone linkages and the branch linkages of these oligosaccharides were all distinguished from diagnostic ions in their MS/MS spectra, including fragments corresponding to 0,2A, 0,3A, 0,4A, B-H2O, 2,5A, and 3,5A. The sequences of the oligosaccharide products were similarly established. Thus, the complex oligosaccharide mixtures in dextran digestion products were profiled and identified using this method. The more enzyme-resistant structures in dextran were established using much less sample, labor, time, and uncertainty than in previous studies. This method provides an efficient, sensitive, and straightforward way to monitor the entire process of digestion, establish the action pattern of the dextranase from Penicillium sp., and to support the proper industrial application of dextranase.

In situ measurement of airway surface liquid [K+] using a ratioable K+-sensitive fluorescent dye.

PubMed

Namkung, Wan; Song, Yuanlin; Mills, Aaron D; Padmawar, Prashant; Finkbeiner, Walter E; Verkman, A S

2009-06-05

The airway surface liquid (ASL) is the thin fluid layer lining airway surface epithelial cells, whose volume and composition are tightly regulated and may be abnormal in cystic fibrosis (CF). We synthesized a two-color fluorescent dextran to measure ASL [K(+)], TAC-Lime-dextran-TMR, consisting of a green-fluorescing triazacryptand K(+) ionophore-Bodipy conjugate, coupled to dextran, together with a red fluorescing tetramethylrhodamine reference chromophore. TAC-Lime-dextran-TMR fluorescence was K(+)-selective, increasing >4-fold with increasing [K(+)] from 0 to 40 mm. In well differentiated human airway epithelial cells, ASL [K(+)] was 20.8 +/- 0.3 mm and decreased by inhibition of the Na(+)/K(+) pump (ouabain), ENaC (amiloride), CF transmembrane conductance regulator (CFTR(inh)-172), or K(+) channels (TEA or XE991). ASL [K(+)] was increased by forskolin but not affected by Na(+)/K(+)/2Cl(-) cotransporter inhibition (bumetanide). Functional and expression studies indicated the involvement of [K(+)] channels KCNQ1, KCNQ3, and KCNQ5 as determinants of ASL [K(+)]. [K(+)] in CF cultures was similar to that in non-CF cultures, suggesting that abnormal ASL [K(+)] is not a factor in CF lung disease. In intact airways, ASL [K(+)] was also well above extracellular [K(+)]: 22 +/- 1 mm in pig trachea ex vivo and 16 +/- 1 mm in mouse trachea in vivo. Our results provide the first noninvasive measurements of [K(+)] in the ASL and indicate the involvement of apical and basolateral membrane ion transporters in maintaining a high ASL [K(+)].

EIGENMODES OF THREE-DIMENSIONAL MAGNETIC ARCADES IN THE SUN’S CORONA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hindman, Bradley W.; Jain, Rekha, E-mail: hindman@solarz.colorado.edu

We develop a model of coronal-loop oscillations that treats the observed bright loops as an integral part of a larger three-dimensional (3D) magnetic structure comprised of the entire magnetic arcade. We demonstrate that magnetic arcades within the solar corona can trap MHD fast waves in a 3D waveguide. This is accomplished through the construction of a cylindrically symmetric model of a magnetic arcade with a potential magnetic field. For a magnetically dominated plasma, we derive a governing equation for MHD fast waves and from this equation we show that the magnetic arcade forms a 3D waveguide if the Alfvén speedmore » increases monotonically beyond a fiducial radius. Both magnetic pressure and tension act as restoring forces, instead of just tension as is generally assumed in 1D models. Since magnetic pressure plays an important role, the eigenmodes involve propagation both parallel and transverse to the magnetic field. Using an analytic solution, we derive the specific eigenfrequencies and eigenfunctions for an arcade possessing a discontinuous density profile. The discontinuity separates a diffuse cylindrical cavity and an overlying shell of denser plasma that corresponds to the bright loops. We emphasize that all of the eigenfunctions have a discontinuous axial velocity at the density interface; hence, the interface can give rise to the Kelvin–Helmholtz instability. Further, we find that all modes have elliptical polarization with the degree of polarization changing with height. However, depending on the line of sight, only one polarization may be clearly visible.« less

Conservative discretization of the Landau collision integral

DOE PAGES

Hirvijoki, E.; Adams, M. F.

2017-03-28

Here we describe a density, momentum-, and energy-conserving discretization of the nonlinear Landau collision integral. The method is suitable for both the finite-element and discontinuous Galerkin methods and does not require structured meshes. The conservation laws for the discretization are proven algebraically and demonstrated numerically for an axially symmetric nonlinear relaxation problem using a finite-element implementation.

3-D direct current resistivity anisotropic modelling by goal-oriented adaptive finite element methods

NASA Astrophysics Data System (ADS)

Ren, Zhengyong; Qiu, Lewen; Tang, Jingtian; Wu, Xiaoping; Xiao, Xiao; Zhou, Zilong

2018-01-01

Although accurate numerical solvers for 3-D direct current (DC) isotropic resistivity models are current available even for complicated models with topography, reliable numerical solvers for the anisotropic case are still an open question. This study aims to develop a novel and optimal numerical solver for accurately calculating the DC potentials for complicated models with arbitrary anisotropic conductivity structures in the Earth. First, a secondary potential boundary value problem is derived by considering the topography and the anisotropic conductivity. Then, two a posteriori error estimators with one using the gradient-recovery technique and one measuring the discontinuity of the normal component of current density are developed for the anisotropic cases. Combing the goal-oriented and non-goal-oriented mesh refinements and these two error estimators, four different solving strategies are developed for complicated DC anisotropic forward modelling problems. A synthetic anisotropic two-layer model with analytic solutions verified the accuracy of our algorithms. A half-space model with a buried anisotropic cube and a mountain-valley model are adopted to test the convergence rates of these four solving strategies. We found that the error estimator based on the discontinuity of current density shows better performance than the gradient-recovery based a posteriori error estimator for anisotropic models with conductivity contrasts. Both error estimators working together with goal-oriented concepts can offer optimal mesh density distributions and highly accurate solutions.

Edge reconstruction in armchair phosphorene nanoribbons revealed by discontinuous Galerkin density functional theory.

PubMed

Hu, Wei; Lin, Lin; Yang, Chao

2015-12-21

With the help of our recently developed massively parallel DGDFT (Discontinuous Galerkin Density Functional Theory) methodology, we perform large-scale Kohn-Sham density functional theory calculations on phosphorene nanoribbons with armchair edges (ACPNRs) containing a few thousands to ten thousand atoms. The use of DGDFT allows us to systematically achieve a conventional plane wave basis set type of accuracy, but with a much smaller number (about 15) of adaptive local basis (ALB) functions per atom for this system. The relatively small number of degrees of freedom required to represent the Kohn-Sham Hamiltonian, together with the use of the pole expansion the selected inversion (PEXSI) technique that circumvents the need to diagonalize the Hamiltonian, results in a highly efficient and scalable computational scheme for analyzing the electronic structures of ACPNRs as well as their dynamics. The total wall clock time for calculating the electronic structures of large-scale ACPNRs containing 1080-10,800 atoms is only 10-25 s per self-consistent field (SCF) iteration, with accuracy fully comparable to that obtained from conventional planewave DFT calculations. For the ACPNR system, we observe that the DGDFT methodology can scale to 5000-50,000 processors. We use DGDFT based ab initio molecular dynamics (AIMD) calculations to study the thermodynamic stability of ACPNRs. Our calculations reveal that a 2 × 1 edge reconstruction appears in ACPNRs at room temperature.

Micro-Fluidic Diffusion Coefficient Measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forster, F.K.; Galambos, P.

1998-10-06

A new method for diffusion coefficient measurement applicable to micro-fluidics is pre- sented. The method Iltilizes an analytical model describing laminar dispersion in rect- anglllar ~llicro_channe]s. The Illethod ~vas verified throllgh measllremen~ of fllloresceill diffusivity in water and aqueolls polymer solutions of differing concentration. The diffll- sivity of flllorescein was measlmed as 0.64 x 10-gm2/s in water, 0.49 x 10-gm2/s in the 4 gm/dl dextran solution and 0.38 x 10-9n12/s in the 8 gnl/dl dextran solution.

One-step microwave synthesis of photoluminescent carbon nanoparticles from sodium dextran sulfate water solution

NASA Astrophysics Data System (ADS)

Kokorina, Alina A.; Goryacheva, Irina Y.; Sapelkin, Andrei V.; Sukhorukov, Gleb B.

2018-04-01

Photoluminescent (PL) carbon nanoparticles (CNPs) have been synthesized by one-step microwave irradiation from water solution of sodium dextran sulfate (DSS) as the sole carbon source. Microwave (MW) method is very simple and cheap and it provides fast synthesis of CNPs. We have varied synthesis time for obtaining high luminescent CNPs. The synthesized CNPs exhibit excitation-dependent photoluminescent. Final CNPs water solution has a blue- green luminescence. CNPs have low cytotoxicity, good photostability and can be potentially suitable candidates for bioimaging, analysis or analytical tests.

Response of a thin airfoil encountering strong density discontinuity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marble, F.E.

1993-12-01

Airfoil theory for unsteady motion has been developed extensively assuming the undisturbed medium to be of uniform density, a restriction accurate for motion in the atmosphere. In some instances, notably for airfoil comprising fan, compressor and turbine blade rows, the undisturbed medium may carry density variations or ``spots``, resulting from non-uniformities in temperature or composition, of a size comparable to the blade chord. This condition exists for turbine blades, immediately downstream of the main burner of a gas turbine engine where the density fluctuations of the order of 50 percent may occur. Disturbances of a somewhat smaller magnitude arise frommore » the ingestion of hot boundary layers into fans, and exhaust into hovercraft. Because these regions of non-uniform density convect with the moving medium, the airfoil experiences a time varying load and moment which the authors calculate.« less

Endophilin-1 regulates blood-brain barrier permeability via EGFR-JNK signaling pathway.

PubMed

Chen, Lin; Liu, Wenjing; Wang, Ping; Xue, Yixue; Su, Qingjie; Zeng, Chaosheng; Shang, Xiuli

2015-05-05

Endophilin-1 (Endo1), a multifunctional protein, is essential for synaptic vesicle endocytosis. However, the role and mechanism of endophilin-1 in blood-brain barrier (BBB) function are still unclear. This study was performed to determine whether endophilin-1 regulated BBB permeability via the EGFR-JNK signaling pathway. In the present study, we found that endophilin-1 over-expression in human cerebral microvascular endothelial cell (hCMEC/D3) increased BBB permeability and meanwhile reduced the expression levels of epidermal growth factor receptor (EGFR), phosphorylated c-Jun N-terminal kinase (p-JNK). While endophilin-1 knockdown led to the contrary results. After JNK inhibitor SP600125 was administered to the endophilin-1 silenced hCMEC/D3 cells, the transendothelial electrical resistance (TEER) value was decreased and the permeability coefficient values to 4kDa and 40kDa FITC-dextran were increased. Results observed by Transmission electron microscopy (TEM) showed that tight junctions (TJs) were opened. Moreover, immunofluorescence and Western blot assays revealed the discontinuous distribution of TJ-associated proteins ZO-1, occludin on cell-cell boundaries and a significant decrease in protein expressing levels. Therefore, these results indicated that endophilin-1 positively regulated BBB permeability via the EGFR-JNK signaling pathway in hCMEC/D3 cells, which would provide an experimental basis for further research on endophilin-1 mediated the opening of BBB. Copyright © 2015 Elsevier B.V. All rights reserved.

Low-index discontinuity terahertz waveguides

NASA Astrophysics Data System (ADS)

Nagel, Michael; Marchewka, Astrid; Kurz, Heinrich

2006-10-01

A new type of dielectric THz waveguide based on recent approaches in the field of integrated optics is presented with theoretical and experimental results. Although the guiding mechanism of the low-index discontinuity (LID) THz waveguide is total internal reflection, the THz wave is predominantly confined in the virtually lossless low-index air gap within a high-index dielectric waveguide due to the continuity of electric flux density at the dielectric interface. Attenuation, dispersion and single-mode confinement properties of two LID structures are discussed and compared with other THz waveguide solutions. The new approach provides an outstanding combination of high mode confinement and low transmission losses currently not realizable with any other metal-based or photonic crystal approach. These exceptional properties might enable the breakthrough of novel integrated THz systems or endoscopy applications with sub-wavelength resolution.

Ocular Penetration and Anti-inflammatory Activity of Ketorolac 0.45% and Bromfenac 0.09% Against Lipopolysaccharide-Induced Inflammation

PubMed Central

Galindo, Danielle; Villanueva, Linda; Nguyen, Cathy; Patel, Milan; Borbridge, Lisa; Attar, Mayssa; Schiffman, Rhett M.; Hollander, David A.

2011-01-01

Abstract Purpose Anti-inflammatory activity of topical nonsteroidal anti-inflammatory drugs is mediated by suppression of cyclooxygenase (COX) isoenzymes. This study compared ocular penetration and inflammation suppression of topical ketorolac 0.45% and bromfenac 0.09% ophthalmic solutions in a rabbit model. Methods At hour 0, 36 rabbits received ketorolac 0.45%, bromfenac 0.09%, or an artificial tear 3 times once every 20 min. Half of the rabbits in each group then received intravenous injections of lipopolysaccharide (LPS) and fluorescein isothiocyanate (FITC)–dextran at hour 1, and the other half at hour 10. Aqueous and iris-ciliary body (ICB) samples were collected in the former group at hour 2 (peak) and in the latter group at hour 11 (trough) An additional group of 6 animals received only FITC-dextran, and samples were collected 1 h later. Peak and trough nonsteroidal anti-inflammatory drug concentrations were compared with previously determined half-maximal inhibitory concentrations (IC50) for COX isoenzymes. Results Peak and trough aqueous and ICB concentrations of ketorolac were at least 7-fold or greater than those of bromfenac. At peak levels, both ketorolac 0.45% and bromfenac 0.09% significantly inhibited LPS-induced aqueous prostaglandin E2 and FITC-dextran elevation (P < 0.01). At trough, both study drugs significantly inhibited LPS-induced aqueous prostaglandin E2 elevation (P < 0.05), but only ketorolac 0.45% significantly reduced LPS-induced aqueous FITC-dextran elevation (P < 0.01). Aqueous and ICB ketorolac concentrations exceeded its IC50 for COX-1 and COX-2 at peak and trough. Aqueous and ICB bromfenac levels exceeded its IC50 for COX-2 at peak and trough, but not for COX-1 at trough aqueous levels and peak and trough ICB levels. Conclusions Both ketorolac 0.45% and bromfenac 0.09% effectively suppressed inflammation at peak. At trough, only ketorolac 0.45% effectively suppressed inflammation as measured by FITC-dextran leakage. The difference in inflammation suppression may be due to differences in tissue concentrations and/or greater COX-1 suppression by ketorolac 0.45%. PMID:21351868

Interactions between acidified dispersions of milk proteins and dextran or dextran sulfate.

PubMed

Pachekrepapol, U; Horne, D S; Lucey, J A

2014-09-01

Polysaccharides are often used to stabilize cultured milk products, although the nature of these interactions is not entirely clear. The objective of this study was to investigate phase behavior of milk protein dispersions with added dextran (DX; molecular weight = 2 × 10(6) Da) or dextran sulfate (DS; molecular weight = 1.4 × 10(6) Da) as examples of uncharged and charged polysaccharides, respectively. Reconstituted skim milk (5-20% milk solids, wt/wt) was acidified to pH 4.4, 4.6, 4.8, or 4.9 at approximately 0°C (to inhibit gelation) by addition of 3 N HCl. Dextran or DS was added to acidified milk samples to give concentrations of 0 to 2% (wt/wt) and 0 to 1% (wt/wt) polysaccharide, respectively. Milk samples were observed for possible phase separation after storage at 0°C for 1 and 24h. Possible gelation of these systems was determined by using dynamic oscillatory rheology. The type of interactions between caseins and DX or DS was probed by determining the total carbohydrate analysis of supernatants from phase-separated samples. At 5.0 to 7.5% milk solids, phase separation of milk samples occurred after 24h even without DX or DS addition, due to destabilization of caseins in these acidic conditions, and a stabilizing effect was observed when 0.7 or 1.0% DS was added. At higher milk solids content, phase separation was not observed without DX or DS addition. Similar results were observed at all pH levels. Gelation occurred in samples containing high milk solids (≥10%) with the addition of 1.0 to 2.0% DX or 0.4 to 1.0% DS. Based on carbohydrate analysis of supernatants, we believe that DX interacted with milk proteins through a type of depletion flocculation mechanism, whereas DS appeared to interact via electrostatic-type interactions with milk proteins. This study helps to explain how uncharged and charged stabilizers influence the texture of cultured dairy products. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Exact joint density-current probability function for the asymmetric exclusion process.

PubMed

Depken, Martin; Stinchcombe, Robin

2004-07-23

We study the asymmetric simple exclusion process with open boundaries and derive the exact form of the joint probability function for the occupation number and the current through the system. We further consider the thermodynamic limit, showing that the resulting distribution is non-Gaussian and that the density fluctuations have a discontinuity at the continuous phase transition, while the current fluctuations are continuous. The derivations are performed by using the standard operator algebraic approach and by the introduction of new operators satisfying a modified version of the original algebra. Copyright 2004 The American Physical Society

Curvature and frontier orbital energies in density functional theory

NASA Astrophysics Data System (ADS)

Kronik, Leeor; Stein, Tamar; Autschbach, Jochen; Govind, Niranjan; Baer, Roi

2013-03-01

Perdew et al. [Phys. Rev. Lett 49, 1691 (1982)] discovered and proved two different properties of exact Kohn-Sham density functional theory (DFT): (i) The exact total energy versus particle number is a series of linear segments between integer electron points; (ii) Across an integer number of electrons, the exchange-correlation potential may ``jump'' by a constant, known as the derivative discontinuity (DD). Here, we show analytically that in both the original and the generalized Kohn-Sham formulation of DFT, the two are in fact two sides of the same coin. Absence of a derivative discontinuity necessitates deviation from piecewise linearity, and the latter can be used to correct for the former, thereby restoring the physical meaning of the orbital energies. Using selected small molecules, we show that this results in a simple correction scheme for any underlying functional, including semi-local and hybrid functionals as well as Hartree-Fock theory, suggesting a practical correction for the infamous gap problem of DFT. Moreover, we show that optimally-tuned range-separated hybrid functionals can inherently minimize both DD and curvature, thus requiring no correction, and show that this can be used as a sound theoretical basis for novel tuning strategies.

Comparison of different interpolation operators including nonlinear subdivision schemes in the simulation of particle trajectories

NASA Astrophysics Data System (ADS)

Bensiali, Bouchra; Bodi, Kowsik; Ciraolo, Guido; Ghendrih, Philippe; Liandrat, Jacques

2013-03-01

In this work, we compare different interpolation operators in the context of particle tracking with an emphasis on situations involving velocity field with steep gradients. Since, in this case, most classical methods give rise to the Gibbs phenomenon (generation of oscillations near discontinuities), we present new methods for particle tracking based on subdivision schemes and especially on the Piecewise Parabolic Harmonic (PPH) scheme which has shown its advantage in image processing in presence of strong contrasts. First an analytic univariate case with a discontinuous velocity field is considered in order to highlight the effect of the Gibbs phenomenon on trajectory calculation. Theoretical results are provided. Then, we show, regardless of the interpolation method, the need to use a conservative approach when integrating a conservative problem with a velocity field deriving from a potential. Finally, the PPH scheme is applied in a more realistic case of a time-dependent potential encountered in the edge turbulence of magnetically confined plasmas, to compare the propagation of density structures (turbulence bursts) with the dynamics of test particles. This study highlights the difference between particle transport and density transport in turbulent fields.

Application of monotone integrated large eddy simulation to Rayleigh-Taylor mixing.

PubMed

Youngs, David L

2009-07-28

Rayleigh-Taylor (RT) instability occurs when a dense fluid rests on top of a light fluid in a gravitational field. It also occurs in an equivalent situation (in the absence of gravity) when an interface between fluids of different density is accelerated by a pressure gradient, e.g. in inertial confinement fusion implosions. Engineering models (Reynolds-averaged Navier-Stokes models) are needed to represent the effect of mixing in complex applications. However, large eddy simulation (LES) currently makes an essential contribution to understanding the mixing process and calibration or validation of the engineering models. In this paper, three cases are used to illustrate the current role of LES: (i) mixing at a plane boundary, (ii) break-up of a layer of dense fluid due to RT instability, and (iii) mixing in a simple spherical implosion. A monotone integrated LES approach is preferred because of the need to treat discontinuities in the flow, i.e. the initial density discontinuities or shock waves. Of particular interest is the influence of initial conditions and how this needs to be allowed for in engineering modelling. It is argued that loss of memory of the initial conditions is unlikely to occur in practical applications.

Preparation of immunomagnetic iron-dextran nanoparticles and application in rapid isolation of E.coli O157:H7 from foods

PubMed Central

Duan, Hui-Li; Shen, Zhi-Qiang; Wang, Xin-Wei; Chao, Fu-Huan; Li, Jun-Wen

2005-01-01

AIM: To prepare a kind of magnetic iron-dextran nanoparticles that was coated with anti-E.coli O157:H7 IgG, analyze its application conditions, and try to use it to isolate E.coli O157:H7 from foods. METHODS: Magnetic iron-dextran nanoparticles were prepared by the reaction of a mixture of ferric and ferrous ions with dextran polymers under alkaline conditions. The particles were coated with antiserum against E.coli O157:H7 by the periodate oxidation-borohydride reduction procedure. The oxidation time, amount of antibody coating the particles, amount of nanoparticles, incubation time and isolation time were varied to determine their effects on recovery of the organisms. Finally, the optimum conditions for isolating E.coli O157:H7 from food samples were established. RESULTS: E.coli O157:H7 can be isolated from samples within 15 min with the sensitivity of 101 CFU/mL or even less. In the presence of 108 CFU/mL of other organisms, the sensitivity is 101-102 CFU/mL. Nonspecific binding of other bacteria to the particles was not observed. Two and a half hours of enrichment is enough for the particles to detect the target from the food samples inoculated with 1 CFU/g. CONCLUSION: Isolation of target bacteria by immuno-magnetic nanoparticles is an efficient method with high sensitivity and specificity. The technique is so simple that it can be operated in lab and field even by untrained personnel. PMID:15968716

Role of dextran in maintaining adhesive and stiffness properties of prestripped DMEK lenticules.

PubMed

Parekh, Mohit; Ruzza, Alessandro; Di Mundo, Rosa; Ferrari, Stefano; Recchia, Giuseppina; Elbadawy, Hossein; Carbone, Giuseppe; Ponzin, Diego

2017-05-11

To investigate the adhesive and stiffness properties of prestripped Descemet membrane endothelial keratoplasty (DMEK) lenticules in different preservation conditions (with and without dextran). The study included 3 conditions: (C1) tissues collected from tissue culture media (TCM), stripped and preserved in TCM; (C2) tissues collected from transport media (TM) (TCM supplemented with 6% dextran T-500), stripped and preserved in TM; and (C3) tissues collected from TCM, stripped and preserved in TM. Using a hinge, 9.5-mm stripped DMEK lenticules were restored back on the stroma and preserved for 4 days at room temperature (RT) in different conditions as above. Nine tissues, 3 from each condition, were used to check the adhesive (fibronectin, laminin, and vitronectin) and elastic properties (fibrillin, elastin, and collagen VI) using different antibodies. Six tissues, 2 from each condition, were used to check the stiffness properties after preservation using atomic force microscopy (AFM) nanoindentation method. On the Descemet membrane, fibronectin was strongly expressed in C2 and C3, whereas laminin was intense in C2 postpreservation. Vitronectin was expressed in all the conditions. Elastic proteins were not expressed in either of the conditions apart from collagen VI, which was expressed on the posterior stroma. Atomic force microscopy showed higher stiffness in C3 and an insignificant but lower rigidity in C2 as compared to C1. The tissues from C2 showed expression of adherent proteins and lower stiffness. Dextran may be suitable in preservation of DMEK grafts before and after preparation. Less stiff tissues may help reduce manipulations required in the recipient eye during DMEK surgery.

A smart membrane based on an antigen-responsive hydrogel.

PubMed

Zhang, Rongsheng; Bowyer, Adrian; Eisenthal, Robert; Hubble, John

2007-07-01

Hydrogel membranes have been fabricated that incorporate antibody/antigen moieties. The permeability of large solutes through these membranes is dependent on the presence of soluble antigen that can compete with the internal interactions between antibody and antigen leading to an increase in gel mesh size. Specifically, the membrane's structure is based on a dextran backbone grafted with a fluorescein isothiocyanate (FITC) antigen and a sheep anti-FITC IgG antibody. The backbone is covalently cross-linked by conjugated divinyl sulfone (DVS) groups. The gel structure is additionally stabilized by affinity crosslinks formed by biospecific interactions between the bound IgG and FITC. FTIR spectra of the gel are consistent with formation of covalent bonds between cysteine groups in the IgG and DVS groups in the dextran. Results obtained using isothermal titration calorimetry (ITC) confirmed the competitive interaction binding between IgG-FITC-dextran and free sodium fluorescein at pH 5.0. Scanning electron microscopy (SEM) of samples prepared using cryofixation and cryofracturing techniques showed that observed changes in permeability correlate with free fluorescein-dependent structural changes in the gel. Three-dimensional images obtained from confocal laser scanning microscopy show that these changes occur throughout the gel and indicate that SEM results are not artifacts of sample preparation. The permeability of these gels, as shown by blue-dextran (12 kDa) diffusion, increases in response to the presence of free fluorescein of the external medium, which causes competitive displacement of the affinity cross-links. Sequential addition and removal of sodium fluorescein showed that these permeability changes are reversible. (c) 2006 Wiley Periodicals, Inc.

Convection-enhanced delivery of maghemite nanoparticles: Increased efficacy and MRI monitoring

PubMed Central

Perlstein, Benny; Ram, Zvi; Daniels, Dianne; Ocherashvilli, Aharon; Roth, Yiftach; Margel, Shlomo; Mardor, Yael

2008-01-01

Convection-enhanced drug delivery (CED) is a novel approach to delivering drugs into brain tissue. Drugs are delivered continuously via a catheter, enabling large volume distributions of high drug concentrations with minimum systemic toxicity. Previously we demonstrated that CED formation/extent of small molecules may be significantly improved by increasing infusate viscosities. In this study we show that the same methodology can be applied to monodispersed maghemite nanoparticles (MNPs). For this purpose we used a normal rat brain model and performed CED of MNPs over short infusion times. By adding 3% sucrose or 3%–6% polyethylene glycol (PEG; molecular weight 400) to saline containing pristine MNPs, we increased infusate viscosity and obtained increased CED efficacy. Further, we show that CED of dextran-coated MNPs (dextran-MNPs) resulted in increased efficacy over pristine MNPs (p < 0.007). To establish the use of MRI for reliable depiction of MNP distribution, CED of fluorescent dextran-MNPs was performed, demonstrating a significant correlation between the distributions as depicted by MRI and spectroscopic images (r2 = 0.74, p < 0.0002). MRI follow-up showed that approximately 80%–90% of the dextran-MNPs were cleared from the rat brain within 40 days of CED; the rest remained in the brain for more than 4 months. MNPs have been tested for applications such as targeted drug delivery and controlled drug release and are clinically used as a contrast agent for MRI. Thus, combining the CED method with the advantages of MNPs may provide a powerful tool to treat and monitor brain tumors. PMID:18316474

Automation of the anthrone assay for carbohydrate concentration determinations.

PubMed

Turula, Vincent E; Gore, Thomas; Singh, Suddham; Arumugham, Rasappa G

2010-03-01

Reported is the adaptation of a manual polysaccharide assay applicable for glycoconjugate vaccines such as Prevenar to an automated liquid handling system (LHS) for improved performance. The anthrone assay is used for carbohydrate concentration determinations and was scaled to the microtiter plate format with appropriate mixing, dispensing, and measuring operations. Adaptation and development of the LHS platform was performed with both dextran polysaccharides of various sizes and pneumococcal serotype 6A polysaccharide (PnPs 6A). A standard plate configuration was programmed such that the LHS diluted both calibration standards and a test sample multiple times with six replicate preparations per dilution. This extent of replication minimized the effect of any single deviation or delivery error that might have occurred. Analysis of the dextran polymers ranging in size from 214 kDa to 3.755 MDa showed that regardless of polymer chain length the hydrolysis was complete, as evident by uniform concentration measurements. No plate positional absorbance bias was observed; of 12 plates analyzed to examine positional bias the largest deviation observed was 0.02% percent relative standard deviation (%RSD). The high purity dextran also afforded the opportunity to assess LHS accuracy; nine replicate analyses of dextran yielded a mean accuracy of 101% recovery. As for precision, a total of 22 unique analyses were performed on a single lot of PnPs 6A, and the resulting variability was 2.5% RSD. This work demonstrated the capability of a LHS to perform the anthrone assay consistently and a reduced assay cycle time for greater laboratory capacity.

Synthesis and preparation of biodegradable hybrid dextran hydrogel incorporated with biodegradable curcumin nanomicelles for full thickness wound healing.

PubMed

Alibolandi, Mona; Mohammadi, Marzieh; Taghdisi, Seyed Mohammad; Abnous, Khalil; Ramezani, Mohammad

2017-10-30

There is a clinical need for a novel, more efficient therapy for full thickness wound healing. In the current study, curcumin encapsulated PEG-PLA [poly(lactide)-block-poly(ethylene glycol)] nanomicelles were incorporated into dextran hydrogel for a full thickness dermal wound healing application. To assess the application of the hydrogel as a therapeutic wound dressing, its morphology, swelling pattern, kinetics of degradation, and capacity to control curcumin release were evaluated. It was found that the prepared hybrid hydrogel had acceptable biocompatibility, incorporation capacity of curcumin nanomicelles, and mechanical properties. An in vitro release experiment also demonstrated the sustained release of curcumin from dextran hydrogel, which was first controlled by the diffusion of curcumin from hydrogel and continued through hydrogel matrix erosion at the terminal phase. An in vivo wound healing experiment was carried out using dressing hydrogels on full thickness wounds in BALB/c mice. An histological study demonstrated that the application of curcumin nanomicelles incorporated hydrogel could significantly augment the re-epithelialization of epidermis and collagen deposition in the wound area. Expression of CD31 and vimentin in wound tissue was investigated using immunohistochemistry tests on the eighth day post wounding. The results obtained demonstrated that curcumin nanomicelles incorporated hydrogel could significantly accelerate angiogenesis, fibroblast accumulation, and the process of wound healing. Together, the data indicate that the prepared hybrid curcumin PEG-PLA nanomicelles incorporated dextran hydrogel is a promising candidate for full thickness wound treatment that increases re-epithelialization, collagen deposition, angiogenesis, and tissue granulation. Copyright © 2017 Elsevier B.V. All rights reserved.

Lung damage and pulmonary uptake of serotonin in intact dogs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawson, C.A.; Christensen, C.W.; Rickaby, D.A.

1985-06-01

The authors examined the influence of glass bead embolization and oleic acid, dextran, and imipramine infusion on the pulmonary uptake of trace doses of (/sup 3/H)serotonin and the extravascular volume accessible to (/sup 14/C)antipyrine in anesthetized dogs. Embolization and imipramine decreased serotonin uptake by 53 and 61%, respectively, but no change was observed with oleic acid or dextran infusion. The extravascular volume accessible to the antipyrine was reduced by 77% after embolization and increased by 177 and approximately 44% after oleic acid and dextran infusion, respectively. The results suggest that when the perfused endothelial surface is sufficiently reduced, as withmore » embolization, the uptake of trace doses of serotonin will be depressed. In addition, decreases in serotonin uptake in response to imipramine in this study and in response to certain endothelial toxins in other studies suggest that serotonin uptake can reveal certain kinds of changes in endothelial function. However, the lack of a response to oleic acid-induced damage in the present study suggests that serotonin uptake is not sensitive to all forms of endothelial damage.« less

Deep in vivo two-photon imaging of blood vessels with a new dye encapsulated in pluronic nanomicelles

NASA Astrophysics Data System (ADS)

Maurin, Mathieu; Stéphan, Olivier; Vial, Jean-Claude; Marder, Seth R.; van der Sanden, Boudewijn

2011-03-01

Our purpose is to test if Pluronic® fluorescent nanomicelles can be used for in vivo two-photon imaging of both the normal and the tumor vasculature. The nanomicelles were obtained after encapsulating a hydrophobic two-photon dye: di-stryl benzene derivative, in Pluronic block copolymers. Their performance with respect to imaging depth, blood plasma staining, and diffusion across the tumor vascular endothelium is compared to a classic blood pool dye Rhodamin B dextran (70 kDa) using two-photon microscopy. Pluronic nanomicelles show, like Rhodamin B dextran, a homogeneous blood plasma staining for at least 1 h after intravenous injection. Their two-photon imaging depth is similar in normal mouse brain, using 10 times less injected mass. In contrast with Rhodamin B dextran, no extravasation is observed in leaky tumor vessels due to their large size: 20-100 nm. In conclusion, Pluronic nanomicelles can be used as a blood pool dye, even in leaky tumor vessels. The use of Pluronic block copolymers is a valuable approach for encapsulating two-photon fluorescent dyes that are hydrophobic and not suitable for intravenous injection.

Recovery of germanium-68 from irradiated targets

DOEpatents

Phillips, Dennis R.; Jamriska, Sr., David J.; Hamilton, Virginia T.

1993-01-01

A process for selective separation of germanium-68 from proton irradiated molybdenum targets is provided and includes dissolving the molybdenum target in a hydrogen peroxide solution to form a first ion-containing solution, contacting the first ion-containing solution with a cationic resin whereby ions selected from the group consisting of molybdenum, niobium, technetium, selenium, vanadium, arsenic, germanium, zirconium and rubidium remain in a second ion-containing solution while ions selected from the group consisting of rubidium, zinc, beryllium, cobalt, iron, manganese, chromium, strontium, yttrium and zirconium are selectively adsorbed by the first resin, adjusting the pH of the second ion-containing solution to within a range of from about 0.7 to about 3.0, adjusting the soluble metal halide concentration in the second ion-containing solution to a level adapted for subsequent separation of germanium, contacting the pH-adjusted, soluble metal halide-containing second ion-containing solution with a dextran-based material whereby germanium ions are separated by the dextran-based material, and recovering the germanium from the dextran-based material, preferably by distillation.

Pentynyl dextran as a support matrix for immobilization of serine protease subtilisin Carlsberg and its use for transesterification of N-acetyl-L-phenylalanine ethyl ester in organic media.

PubMed

Tahir, Muhammad Nazir; Cho, Eunae; Mischnick, Petra; Lee, Jae Yung; Yu, Jae-Hyuk; Jung, Seunho

2014-04-01

In this study, serine protease (subtilisin Carlsberg) was immobilized on pentynyl dextran (PyD, O-alkynyl ether of dextran, 1) and used for the transesterification of N-acetyl-L-phenylalanine ethyl ester (2) with different aliphatic (1-propanol, 1-butanol, 1-pentanol, 1-hexanol) and aromatic (benzyl alcohol, 2-phenyl ethanol, 4-phenyl-1-butanol) alcohols in tetrahydrofuran (THF). The effect of carbon chain length in aliphatic and aromatic alcohols on initial and average transesterification rate, transesterification activity of immobilized enzyme and yield of the reaction under selected reaction conditions was investigated. The transesterification reactivity of the enzyme and yield of the reaction increased as the chain length of the alcohols decreased. Furthermore, almost no change in yield was observed when the immobilized enzyme was repeatedly used for selected alcohols over six cycles. Intrinsic fluorescence analysis showed that the catalytic activity of the immobilized enzyme in THF was maintained due to retention of the tertiary structure of the enzyme after immobilization on PyD (1).

Visual and functional demonstration of growing Bax-induced pores in mitochondrial outer membranes

PubMed Central

Gillies, Laura A; Du, Han; Peters, Bjoern; Knudson, C. Michael; Newmeyer, Donald D.; Kuwana, Tomomi

2015-01-01

Bax induces mitochondrial outer membrane permeabilization (MOMP), a critical step in apoptosis in which proteins are released into the cytoplasm. To resolve aspects of the mechanism, we used cryo-electron microscopy (cryo-EM) to visualize Bax-induced pores in purified mitochondrial outer membranes (MOMs). We observed solitary pores that exhibited negative curvature at their edges. Over time, the pores grew to ∼100–160 nm in diameter after 60–90 min, with some pores measuring more than 300 nm. We confirmed these results using flow cytometry, which we used to monitor the release of fluorescent dextrans from isolated MOM vesicles. The dextran molecules were released gradually, in a manner constrained by pore size. However, the release rates were consistent over a range of dextran sizes (10–500 kDa). We concluded that the pores were not static but widened dramatically to release molecules of different sizes. Taken together, the data from cryo-EM and flow cytometry argue that Bax promotes MOMP by inducing the formation of large, growing pores through a mechanism involving membrane-curvature stress. PMID:25411335

Cytotoxicity control of silicon nanoparticles by biopolymer coating and ultrasound irradiation for cancer theranostic applications

NASA Astrophysics Data System (ADS)

Sviridov, A. P.; Osminkina, L. A.; Kharin, A. Yu; Gongalsky, M. B.; Kargina, J. V.; Kudryavtsev, A. A.; Bezsudnova, Yu I.; Perova, T. S.; Geloen, A.; Lysenko, V.; Timoshenko, V. Yu

2017-03-01

Silicon nanoparticles (SiNPs) prepared by mechanical grinding of luminescent porous silicon were coated with a biopolymer (dextran) and investigated as a potential theranostic agent for bioimaging and sonodynamic therapy. Transmission electron microscopy, photoluminescence and Raman scattering measurements of dextran-coated SiNPs gave evidence of their enhanced stability in water. In vitro experiments confirmed the lower cytotoxicity of the dextran-coated NPs in comparison with uncoated ones, especially for high concentrations of about 2 mg ml-1. Efficient uptake of the NPs by cancer cells was found using bioimaging in the optical transmittance and photoluminescence modes. Treatment of the cells with uptaken SiNPs by therapeutic ultrasound for 5-20 min resulted in a strong decrease in the number of living cells, while the total number of cells remained nearly unchanged. The obtained data indicate a ‘mild’ effect of the combined action of ultrasonic irradiation and SiNPs on cancer cells. The observed results reveal new opportunities for controlling the photoluminescent and sonosensitizing properties of silicon-based NPs for applications in the diagnostics and mild therapy of cancer.

Development of novel magnetic nanoparticles for hyperthermia cancer therapy

NASA Astrophysics Data System (ADS)

Cassim, Shiraz M.; Giustini, Andrew J.; Baker, Ian; Hoopes, P. Jack

2011-03-01

Advances in magnetic nanoparticle hyperthermia are opening new doors in cancer therapy. As a standalone or adjuvant therapy this new modality has the opportunity significantly advance thermal medicine. Major advantages of using magnetic magnetite (Fe3O4) nanoparticles are their highly localized power deposition and the fact that the alternating magnetic fields (AMF) used to excite them can penetrate deeply into the body without harmful effect. One limitation, however, which hinders the technology, is the problem of inductive heating of normal tissue by the AMF if the frequency and fields strength are not appropriately matched to the tissue. Restricting AMF amplitude and frequency limits the heat dose which can be selectively applied to cancerous tissue via the magnetic nanoparticle, thus lowering therapeutic effect. In an effort to address this problem, particles with optimized magnetic properties must be developed. Using particles with higher saturation magnetizations and coercivity will enhance hysteresis heating increasing particle power density at milder AMF strengths and frequencies. In this study we used oil in water microemulsions to develop nanoparticles with zero-valent Fe cores and magnetite shells. The superior magnetic properties of zero-valent Fe give these particles the potential for improved SAR over pure magnetite particles. Silane and subsequently dextran have been attached to the particle surface in order to provide a biocompatible surfactant coating. The heating capability of the particles was tested in-vivo using a mouse tumor model. Although we determined that the final stage of synthesis, purification of the dextran coated particles, permits significant corrosion/oxidation of the iron core to hematite, the particles can effectively heat tumor tissue. Improving the purification procedure will allow the generation Fe/Fe3O4 with superior SAR values.

Soil organic carbon pools and stocks in permafrost-affected soils on the tibetan plateau.

PubMed

Dörfer, Corina; Kühn, Peter; Baumann, Frank; He, Jin-Sheng; Scholten, Thomas

2013-01-01

The Tibetan Plateau reacts particularly sensitively to possible effects of climate change. Approximately two thirds of the total area is affected by permafrost. To get a better understanding of the role of permafrost on soil organic carbon pools and stocks, investigations were carried out including both discontinuous (site Huashixia, HUA) and continuous permafrost (site Wudaoliang, WUD). Three organic carbon fractions were isolated using density separation combined with ultrasonic dispersion: the light fractions (<1.6 g cm(-3)) of free particulate organic matter (FPOM) and occluded particulate organic matter (OPOM), plus a heavy fraction (>1.6 g cm(-3)) of mineral associated organic matter (MOM). The fractions were analyzed for C, N, and their portion of organic C. FPOM contained an average SOC content of 252 g kg(-1). Higher SOC contents (320 g kg(-1)) were found in OPOM while MOM had the lowest SOC contents (29 g kg(-1)). Due to their lower density the easily decomposable fractions FPOM and OPOM contribute 27% (HUA) and 22% (WUD) to the total SOC stocks. In HUA mean SOC stocks (0-30 cm depth) account for 10.4 kg m(-2), compared to 3.4 kg m(-2) in WUD. 53% of the SOC is stored in the upper 10 cm in WUD, in HUA only 39%. Highest POM values of 36% occurred in profiles with high soil moisture content. SOC stocks, soil moisture and active layer thickness correlated strongly in discontinuous permafrost while no correlation between SOC stocks and active layer thickness and only a weak relation between soil moisture and SOC stocks could be found in continuous permafrost. Consequently, permafrost-affected soils in discontinuous permafrost environments are susceptible to soil moisture changes due to alterations in quantity and seasonal distribution of precipitation, increasing temperature and therefore evaporation.

Analytical Computation of Effective Grid Parameters for the Finite-Difference Seismic Waveform Modeling With the PREM, IASP91, SP6, and AK135

NASA Astrophysics Data System (ADS)

Toyokuni, G.; Takenaka, H.

2007-12-01

We propose a method to obtain effective grid parameters for the finite-difference (FD) method with standard Earth models using analytical ways. In spite of the broad use of the heterogeneous FD formulation for seismic waveform modeling, accurate treatment of material discontinuities inside the grid cells has been a serious problem for many years. One possible way to solve this problem is to introduce effective grid elastic moduli and densities (effective parameters) calculated by the volume harmonic averaging of elastic moduli and volume arithmetic averaging of density in grid cells. This scheme enables us to put a material discontinuity into an arbitrary position in the spatial grids. Most of the methods used for synthetic seismogram calculation today receives the blessing of the standard Earth models, such as the PREM, IASP91, SP6, and AK135, represented as functions of normalized radius. For the FD computation of seismic waveform with such models, we first need accurate treatment of material discontinuities in radius. This study provides a numerical scheme for analytical calculations of the effective parameters for an arbitrary spatial grids in radial direction as to these major four standard Earth models making the best use of their functional features. This scheme can analytically obtain the integral volume averages through partial fraction decompositions (PFDs) and integral formulae. We have developed a FORTRAN subroutine to perform the computations, which is opened to utilization in a large variety of FD schemes ranging from 1-D to 3-D, with conventional- and staggered-grids. In the presentation, we show some numerical examples displaying the accuracy of the FD synthetics simulated with the analytical effective parameters.

Hall effects on the Walén relation in rotational discontinuities and Alfvén waves

NASA Astrophysics Data System (ADS)

Wu, B. H.; Lee, L. C.

2000-08-01

For Alfvénic fluctuations in magnetohydrodynamics (MHD) the perturbed transverse velocity Vt and magnetic field Bt can be related by the Walén relation, Vt = ±Bt/(μ0ρ)1/2 ≡;±VAt, where ρ is the plasma density, VAt is the transverse Alfvén velocity, and the plus (minus) sign is for antiparallel (parallel) propagation. However, observations of Vt and Bt for Alfvén waves and rotational discontinuities in the solar wind and at the magnetopause showed an obvious deviation from the relation. In this paper, modifications of the Walén relation for linear and nonlinear Alfvén waves and rotational discontinuities (RDs) are examined in the Hall-MHD formulation. Let Vit (≈ Vt) be the transverse ion velocity and Vet be the transverse electron velocity. It is found that Vit = ±Bt(z)/(μ0ρ1)1/2 = ±(ρ(z)/ρ1)1/2 VAt(z) and Vet = ±(ρ1/μ0)1/2Bt(z)/ρ(z) = ±(ρ1/ρ(z))1/2 VAt(z)for RDs in Hall-MHD, where ρ1 is the upstream plasma density. The ion and electron Walén ratios are defined as Ai = Vit/VAt and Ae = Vet/VAt, respectively. It is found in Hall-MHD that ?, AiAe = 1 and Ai < 1 (Ai > 1) for Alfvén waves and RDs with right-hand (left-hand) polarization. The Hall dispersive effect may modify the ion Walén ratio by ΔAi≈±0.14 for the magnetopause RDs and by ΔAi≈±0.07 for the interplanetary RDs.

Fourteen-Day Subacute Intravenous Toxicity Study of Hypertonic Saline/ Dextran 70 (Trade name) and its Constituents in New Zealand White Rabbits

DTIC Science & Technology

1989-11-01

of Hypertonic Saline/Dextran 70C and its Constituents in New Zealand White Rabbits," Toxicology Series 248, was audited on 20 October 1989. CAROLYNM...at tA "e a .6 L C C o L a L Lm .. .. a. a4 1 . . ao 3.&ow2 aCCa .0 00 c -C a- 4;. *; a 0O .. t x.T 2Cu u . u uu0 0 Uc L 01 2.:4A.1 4xa&C -I - -N .CA -e

Stabilizing Alginate Confinement and Polymer Coating of CO-Releasing Molecules Supported on Iron Oxide Nanoparticles To Trigger the CO Release by Magnetic Heating.

PubMed

Meyer, Hajo; Winkler, Felix; Kunz, Peter; Schmidt, Annette M; Hamacher, Alexandra; Kassack, Matthias U; Janiak, Christoph

2015-12-07

Maghemite (Fe2O3) iron oxide nanoparticles (IONPs) were synthesized, modified with covalent surface-bound CO-releasing molecules of a tri(carbonyl)-chlorido-phenylalaninato-ruthenium(II) complex (CORM), and coated with a dextran polymer. The time- and temperature-dependent CO release from this CORM-3 analogue was followed by a myoglobin assay. A new measurement method for the myoglobin assay was developed, based on confining "water-soluble" polymer-coated Dextran500k@CORM@IONP particles in hollow spheres of nontoxic and easily prepared calcium alginate. Dropping a mixture of Dextran500k@CORM@IONP and sodium alginate into a CaCl2 solution leads to stable hollow spheres of Ca(2+) cross-linked alginate which contain the Dextran500k@CORM@IONP particles. This "alginate-method" (i) protects CORM-3 analogues from rapid CO-displacement reactions with a protein, (ii) enables a spatial separation of the CORM from its surrounding myoglobin assay with the alginate acting as a CO-permeable membrane, and (iii) allows the use of substances with high absorptivity (such as iron oxide nanoparticles) in the myoglobin assay without interference in the optical path of the UV cell. Embedding the CORM@IONP nanoparticles in the alginate vessel represents a compartmentation of the reactive component and allows for close contact with, yet facile separation from, the surrounding myoglobin assay. The half-life of the CO release from Dextran500k@CORM@IONP particles surrounded by alginate was determined to be 890 ± 70 min at 20 °C. An acceleration of the CO release occurs at higher temperature with a half-life of 172 ± 27 min at 37 °C and 45 ± 7 min at 50 °C. The CO release can be triggered in an alternating current magnetic field (31.7 kA m(-1), 247 kHz, 39.9 mT) through local magnetic heating of the susceptible iron oxide nanoparticles. With magnetic heating at 20 °C in the bulk solution, the half-life of CO release from Dextran500k@CORM@IONP particles decreased to 155 ± 18 min without a noticeable temperature increase in the dispersion. At 37 and 50 °C, the half-life for the CO release triggered by local magnetic heating was 65 ± 5 min and 30 ± 3 min, respectively. Thus, at a physiological temperature of 37 °C, magnetic heating accelerates the CO release of the IONP-bound CORM by a factor of ∼ 2.6. The activation energy for CO release from a CORM-3 analogue was determined to be EA = 78 kJ/mol.

Keeping speed and distance for aligned motion

NASA Astrophysics Data System (ADS)

Farkas, Illés J.; Kun, Jeromos; Jin, Yi; He, Gaoqi; Xu, Mingliang

2015-01-01

The cohesive collective motion (flocking, swarming) of autonomous agents is ubiquitously observed and exploited in both natural and man-made settings, thus, minimal models for its description are essential. In a model with continuous space and time we find that if two particles arrive symmetrically in a plane at a large angle, then (i) radial repulsion and (ii) linear self-propelling toward a fixed preferred speed are sufficient for them to depart at a smaller angle. For this local gain of momentum explicit velocity alignment is not necessary, nor are adhesion or attraction, inelasticity or anisotropy of the particles, or nonlinear drag. With many particles obeying these microscopic rules of motion we find that their spatial confinement to a square with periodic boundaries (which is an indirect form of attraction) leads to stable macroscopic ordering. As a function of the strength of added noise we see—at finite system sizes—a critical slowing down close to the order-disorder boundary and a discontinuous transition. After varying the density of particles at constant system size and varying the size of the system with constant particle density we predict that in the infinite system size (or density) limit the hysteresis loop disappears and the transition becomes continuous. We note that animals, humans, drones, etc., tend to move asynchronously and are often more responsive to motion than positions. Thus, for them velocity-based continuous models can provide higher precision than coordinate-based models. An additional characteristic and realistic feature of the model is that convergence to the ordered state is fastest at a finite density, which is in contrast to models applying (discontinuous) explicit velocity alignments and discretized time. To summarize, we find that the investigated model can provide a minimal description of flocking.

Keeping speed and distance for aligned motion.

PubMed

Farkas, Illés J; Kun, Jeromos; Jin, Yi; He, Gaoqi; Xu, Mingliang

2015-01-01

The cohesive collective motion (flocking, swarming) of autonomous agents is ubiquitously observed and exploited in both natural and man-made settings, thus, minimal models for its description are essential. In a model with continuous space and time we find that if two particles arrive symmetrically in a plane at a large angle, then (i) radial repulsion and (ii) linear self-propelling toward a fixed preferred speed are sufficient for them to depart at a smaller angle. For this local gain of momentum explicit velocity alignment is not necessary, nor are adhesion or attraction, inelasticity or anisotropy of the particles, or nonlinear drag. With many particles obeying these microscopic rules of motion we find that their spatial confinement to a square with periodic boundaries (which is an indirect form of attraction) leads to stable macroscopic ordering. As a function of the strength of added noise we see--at finite system sizes--a critical slowing down close to the order-disorder boundary and a discontinuous transition. After varying the density of particles at constant system size and varying the size of the system with constant particle density we predict that in the infinite system size (or density) limit the hysteresis loop disappears and the transition becomes continuous. We note that animals, humans, drones, etc., tend to move asynchronously and are often more responsive to motion than positions. Thus, for them velocity-based continuous models can provide higher precision than coordinate-based models. An additional characteristic and realistic feature of the model is that convergence to the ordered state is fastest at a finite density, which is in contrast to models applying (discontinuous) explicit velocity alignments and discretized time. To summarize, we find that the investigated model can provide a minimal description of flocking.

Molecular transport through nanoporous silicon nitride membranes produced from self-assembling block copolymers.

PubMed

Montagne, Franck; Blondiaux, Nicolas; Bojko, Alexandre; Pugin, Raphaël

2012-09-28

To achieve fast and selective molecular filtration, membrane materials must ideally exhibit a thin porous skin and a high density of pores with a narrow size distribution. Here, we report the fabrication of nanoporous silicon nitride membranes (NSiMs) at the full wafer scale using a versatile process combining block copolymer (BCP) self-assembly and conventional photolithography/etching techniques. In our method, self-assembled BCP micelles are used as templates for creating sub-100 nm nanopores in a thin low-stress silicon nitride layer, which is then released from the underlying silicon wafer by etching. The process yields 100 nm thick free-standing NSiMs of various lateral dimensions (up to a few mm(2)). We show that the membranes exhibit a high pore density, while still retaining excellent mechanical strength. Permeation experiments reveal that the molecular transport rate across NSiMs is up to 16-fold faster than that of commercial polymeric membranes. Moreover, using dextran molecules of various molecular weights, we also demonstrate that size-based separation can be achieved with a very good selectivity. These new silicon nanosieves offer a relevant technological alternative to commercially available ultra- and microfiltration membranes for conducting high resolution biomolecular separations at small scales.

Differential Angiogenic Regulation of Experimental Colitis

PubMed Central

Chidlow, John H.; Langston, Will; Greer, James J.M.; Ostanin, Dmitry; Abdelbaqi, Maisoun; Houghton, Jeffery; Senthilkumar, Annamalai; Shukla, Deepti; Mazar, Andrew P.; Grisham, Matthew B.; Kevil, Christopher G.

2006-01-01

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders of the intestinal tract with unknown multifactorial etiology that, among other things, result in alteration and dysfunction of the intestinal microvasculature. Clinical observations of increased colon microvascular density during IBD have been made. However, there have been no reports investigating the physiological or pathological importance of angiogenic stimulation during the development of intestinal inflammation. Here we report that the dextran sodium sulfate and CD4+CD45RBhigh T-cell transfer models of colitis stimulate angiogenesis that results in increased blood vessel density concomitant with increased histopathology, suggesting that the neovasculature contributes to tissue damage during colitis. We also show that leukocyte infiltration is an obligatory requirement for the stimulation of angiogenesis. The angiogenic response during experimental colitis was differentially regulated in that the production of various angiogenic mediators was diverse between the two models with only a small group of molecules being similarly controlled. Importantly, treatment with the anti-angiogenic agent thalidomide or ATN-161 significantly reduced angiogenic activity and associated tissue histopathology during experimental colitis. Our findings identify a direct pathological link between angiogenesis and the development of experimental colitis, representing a novel therapeutic target for IBD. PMID:17148665

An iterative phase-space explicit discontinuous Galerkin method for stellar radiative transfer in extended atmospheres

NASA Astrophysics Data System (ADS)

de Almeida, Valmor F.

2017-07-01

A phase-space discontinuous Galerkin (PSDG) method is presented for the solution of stellar radiative transfer problems. It allows for greater adaptivity than competing methods without sacrificing generality. The method is extensively tested on a spherically symmetric, static, inverse-power-law scattering atmosphere. Results for different sizes of atmospheres and intensities of scattering agreed with asymptotic values. The exponentially decaying behavior of the radiative field in the diffusive-transparent transition region, and the forward peaking behavior at the surface of extended atmospheres were accurately captured. The integrodifferential equation of radiation transfer is solved iteratively by alternating between the radiative pressure equation and the original equation with the integral term treated as an energy density source term. In each iteration, the equations are solved via an explicit, flux-conserving, discontinuous Galerkin method. Finite elements are ordered in wave fronts perpendicular to the characteristic curves so that elemental linear algebraic systems are solved quickly by sweeping the phase space element by element. Two implementations of a diffusive boundary condition at the origin are demonstrated wherein the finite discontinuity in the radiation intensity is accurately captured by the proposed method. This allows for a consistent mechanism to preserve photon luminosity. The method was proved to be robust and fast, and a case is made for the adequacy of parallel processing. In addition to classical two-dimensional plots, results of normalized radiation intensity were mapped onto a log-polar surface exhibiting all distinguishing features of the problem studied.

A constrained Delaunay discretization method for adaptively meshing highly discontinuous geological media

NASA Astrophysics Data System (ADS)

Wang, Yang; Ma, Guowei; Ren, Feng; Li, Tuo

2017-12-01

A constrained Delaunay discretization method is developed to generate high-quality doubly adaptive meshes of highly discontinuous geological media. Complex features such as three-dimensional discrete fracture networks (DFNs), tunnels, shafts, slopes, boreholes, water curtains, and drainage systems are taken into account in the mesh generation. The constrained Delaunay triangulation method is used to create adaptive triangular elements on planar fractures. Persson's algorithm (Persson, 2005), based on an analogy between triangular elements and spring networks, is enriched to automatically discretize a planar fracture into mesh points with varying density and smooth-quality gradient. The triangulated planar fractures are treated as planar straight-line graphs (PSLGs) to construct piecewise-linear complex (PLC) for constrained Delaunay tetrahedralization. This guarantees the doubly adaptive characteristic of the resulted mesh: the mesh is adaptive not only along fractures but also in space. The quality of elements is compared with the results from an existing method. It is verified that the present method can generate smoother elements and a better distribution of element aspect ratios. Two numerical simulations are implemented to demonstrate that the present method can be applied to various simulations of complex geological media that contain a large number of discontinuities.

Shocks and cold fronts in merging and massive galaxy clusters: new detections with Chandra

NASA Astrophysics Data System (ADS)

Botteon, A.; Gastaldello, F.; Brunetti, G.

2018-06-01

A number of merging galaxy clusters show the presence of shocks and cold fronts, i.e. sharp discontinuities in surface brightness and temperature. The observation of these features requires an X-ray telescope with high spatial resolution like Chandra, and allows to study important aspects concerning the physics of the intracluster medium (ICM), such as its thermal conduction and viscosity, as well as to provide information on the physical conditions leading to the acceleration of cosmic rays and magnetic field amplification in the cluster environment. In this work we search for new discontinuities in 15 merging and massive clusters observed with Chandra by using different imaging and spectral techniques of X-ray observations. Our analysis led to the discovery of 22 edges: six shocks, eight cold fronts, and eight with uncertain origin. All the six shocks detected have M< 2 derived from density and temperature jumps. This work contributed to increase the number of discontinuities detected in clusters and shows the potential of combining diverse approaches aimed to identify edges in the ICM. A radio follow-up of the shocks discovered in this paper will be useful to study the connection between weak shocks and radio relics.

Ferroelectric switching of band alignments in LSMO/PZT/Co multiferroic tunnel junctions: an ab initio study.

PubMed

Imam, M; Stojić, N; Binggeli, N

2017-08-04

Band alignments in ferroelectric tunnel junctions (FTJs) are expected to play a critical role in determining the charge transport across the tunneling barrier. In general, however, the interface band discontinuities and their polarization dependence are not well known in these systems. Using a first-principles density-functional-theory approach, we explore the ferroelectric (FE) polarization dependence of the band alignments in [Formula: see text] (LSMO/PZT/Co) multiferroic tunnel junctions, for which recent experiments indicated an ON/OFF conductivity behavior upon switching the PZT FE polarization. Our results on the pseudomorphic defect-free LSMO/PZT/Co FTJs evidence a major FE switching effect on the band discontinuities at both interfaces. Based on the changes in the band alignments, we provide a possible explanation for the observed trends in the resistive switching.

Discontinuous model with semi analytical sheath interface for radio frequency plasma

NASA Astrophysics Data System (ADS)

Miyashita, Masaru

2016-09-01

Sumitomo Heavy Industries, Ltd. provide many products utilizing plasma. In this study, we focus on the Radio Frequency (RF) plasma source by interior antenna. The plasma source is expected to be high density and low metal contamination. However, the sputtering the antenna cover by high energy ion from sheath voltage still have been problematic. We have developed the new model which can calculate sheath voltage wave form in the RF plasma source for realistic calculation time. This model is discontinuous that electronic fluid equation in plasma connect to usual passion equation in antenna cover and chamber with semi analytical sheath interface. We estimate the sputtering distribution based on calculated sheath voltage waveform by this model, sputtering yield and ion energy distribution function (IEDF) model. The estimated sputtering distribution reproduce the tendency of experimental results.

Validation of DTI Tractography-Based Measures of Primary Motor Area Connectivity in the Squirrel Monkey Brain

PubMed Central

Gao, Yurui; Choe, Ann S.; Stepniewska, Iwona; Li, Xia; Avison, Malcolm J.; Anderson, Adam W.

2013-01-01

Diffusion tensor imaging (DTI) tractography provides noninvasive measures of structural cortico-cortical connectivity of the brain. However, the agreement between DTI-tractography-based measures and histological ‘ground truth’ has not been quantified. In this study, we reconstructed the 3D density distribution maps (DDM) of fibers labeled with an anatomical tracer, biotinylated dextran amine (BDA), as well as DTI tractography-derived streamlines connecting the primary motor (M1) cortex to other cortical regions in the squirrel monkey brain. We evaluated the agreement in M1-cortical connectivity between the fibers labeled in the brain tissue and DTI streamlines on a regional and voxel-by-voxel basis. We found that DTI tractography is capable of providing inter-regional connectivity comparable to the neuroanatomical connectivity, but is less reliable measuring voxel-to-voxel variations within regions. PMID:24098365

Photocontrolled Cargo Release from Dual Cross-Linked Polymer Particles.

PubMed

Tan, Shereen; Cui, Jiwei; Fu, Qiang; Nam, Eunhyung; Ladewig, Katharina; Ren, Jing M; Wong, Edgar H H; Caruso, Frank; Blencowe, Anton; Qiao, Greg G

2016-03-09

Burst release of a payload from polymeric particles upon photoirradiation was engineered by altering the cross-linking density. This was achieved via a dual cross-linking concept whereby noncovalent cross-linking was provided by cyclodextrin host-guest interactions, and irreversible covalent cross-linking was mediated by continuous assembly of polymers (CAP). The dual cross-linked particles (DCPs) were efficiently infiltrated (∼80-93%) by the biomacromolecule dextran (molecular weight up to 500 kDa) to provide high loadings (70-75%). Upon short exposure (5 s) to UV light, the noncovalent cross-links were disrupted resulting in increased permeability and burst release of the cargo (50 mol % within 1 s) as visualized by time-lapse fluorescence microscopy. As sunlight contains UV light at low intensities, the particles can potentially be incorporated into systems used in agriculture, environmental control, and food packaging, whereby sunlight could control the release of nutrients and antimicrobial agents.

Biotin-Tagged Polysaccharide Vesicular Nanocarriers for Receptor-Mediated Anticancer Drug Delivery in Cancer Cells.

PubMed

Deshpande, Nilesh Umakant; Jayakannan, Manickam

2018-06-15

Biotin-conjugated multi-stimuli-responsive polysaccharide vesicular nanocarriers are designed and developed, for the first time, to accomplish receptor-mediated endocytosis in cancer cells and to deliver anticancer drugs at the intracellular compartments. For this purpose, a new renewable hydrophobic unit was custom designed with redox-degradable disulphide and enzyme-biodegradable aliphatic ester chemical linkages and it was conjugated along with biotin on the dextran backbone. The dextran derivative self-assembled into nanovesicles of < 200 nm in size which were characterized by dynamic and static light scattering, electron and atomic force microscopes. Avidin-HABA assay established the high affinity of biotin-tagged dextran vesicles towards membrane-receptors up to 25 nM concentration. Doxorubicin-hydrochloride (DOX.HCl) loaded dextran vesicles exhibited stable formulation in PBS and FBS. Redox-degradation by glutathione (GSH) showed 60 % drug release whereas lysosomal esterase enzyme enabled > 98 % drug release in 12 h. Confocal microscope and flow cytometry assisted time-dependent cellular uptake studies revealed that the biotin-receptor over expressed cervical cancer cells (HeLa) exhibited larger drug accumulation through receptor-assisted endocytosis process. This process enabled the delivery of higher amount of DOX and significantly enhanced the killing in cancer cells (HeLa) compared to wild-type mouse embryonic fibroblast cells (WT-MEF, normal cells). Control experiments such as biotin pre-treatment in cancer cells and energy-suppressed cellular uptake at 4 C further supported the occurrence of receptor-mediated endocytosis by the biotin-tagged polymer vesicles. This report provides first insights into the targeted polysaccharide vesicle platform, and the proof-of-concept is successfully demonstrated in biotin receptors over expressed cervical cancer cells.