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1

Interfacial interactions between natural RBC membranes and synthetic polymeric nanoparticles  

NASA Astrophysics Data System (ADS)

The unique structural features and stealth properties of a recently developed red blood cell membrane-cloaked nanoparticle (RBC-NP) platform raise curiosity over the interfacial interactions between natural cellular membranes and polymeric nanoparticle substrates. Herein, several interfacial aspects of the RBC-NPs are examined, including completeness of membrane coverage, membrane sidedness upon coating, and the effects of polymeric particles' surface charge and surface curvature on the membrane cloaking process. The study shows that RBC membranes completely cover negatively charged polymeric nanoparticles in a right-side-out manner and enhance the particles' colloidal stability. The membrane cloaking process is applicable to particle substrates with a diameter ranging from 65 to 340 nm. Additionally, the study reveals that both surface glycans on RBC membranes and the substrate properties play a significant role in driving and directing the membrane-particle assembly. These findings further the understanding of the dynamics between cellular membranes and nanoscale substrates and provide valuable information toward future development and characterization of cellular membrane-cloaked nanodevices.The unique structural features and stealth properties of a recently developed red blood cell membrane-cloaked nanoparticle (RBC-NP) platform raise curiosity over the interfacial interactions between natural cellular membranes and polymeric nanoparticle substrates. Herein, several interfacial aspects of the RBC-NPs are examined, including completeness of membrane coverage, membrane sidedness upon coating, and the effects of polymeric particles' surface charge and surface curvature on the membrane cloaking process. The study shows that RBC membranes completely cover negatively charged polymeric nanoparticles in a right-side-out manner and enhance the particles' colloidal stability. The membrane cloaking process is applicable to particle substrates with a diameter ranging from 65 to 340 nm. Additionally, the study reveals that both surface glycans on RBC membranes and the substrate properties play a significant role in driving and directing the membrane-particle assembly. These findings further the understanding of the dynamics between cellular membranes and nanoscale substrates and provide valuable information toward future development and characterization of cellular membrane-cloaked nanodevices. Electronic supplementary information (ESI) available: Theoretical calculations and supporting figures. See DOI: 10.1039/c3nr06371b

Luk, Brian T.; Jack Hu, Che-Ming; Fang, Ronnie H.; Dehaini, Diana; Carpenter, Cody; Gao, Weiwei; Zhang, Liangfang

2014-02-01

2

TRM1, a YY1-like suppressor of rbcS-m3 expression in maize mesophyll cells  

Microsoft Academic Search

The genes rbcS and rbcL encode, respectively, the small and large subunits of the photosynthetic carbon dioxide fixation enzyme ribulose bisphosphate carboxylase\\/oxygenase. There is a single rbcL gene in each chloroplast chromosome; a family of rbcS genes is located in the nuclear genome. These two genes are not expressed in mesophyll cells but are in adjacent bundle-sheath cells of leaves

Tao Xu; Marc Purcell; Paola Zucchi; Tim Helentjaris; Lawrence Bogorad

2001-01-01

3

Laser diffractometer of RBC suspension  

NASA Astrophysics Data System (ADS)

The original optical diagnostic device for measuring the RBC membrane permeability and RBC charge is considered in this message. A blood microsample drips in the mixer filled with a solution of NaCl. The resultant RBC suspension trickles down the pipe into the drain vessel. The flat thin cell is fitted into the pipe. The optical channel consists of He-Ne laser whose beam goes through the flat cell perpendicularly to its sides and scatters by the RBC flowing through the thin cell. The scattered light falls on a frosted screen put in the focal plane of a lens. As the RBC concentration is more than 0.1% of suspension volume, RBC form two flows moving along slightly heparinized sides of the thin cell due to repel each other electrostatically. The two flows orient each other so that RBC round bases are perpendicular to the sides of the flat cell due to RBC dipole momentum. In this case RBC viewed from the side will form on the screen a visible diffraction ellipse with axes lengths related in the initial time as 4:1. The measurement of the rate of the changes of the lengths of the axes of the diffraction ellipse due to osmos made it possible to develop a number of original optical diagnostic techniques approved by clinical practice. The method of measuring the membrane permeability was approbated clinically by examining blood samples (50 mcl) of 30 patients suffering from heavy poisoning by alcohol and barbiturates before and after detoxifying treatment and allowed the use the method developed for diagnosis the degree of poisoning and choosing the appropriate detoxifying rehabilitation. Unlike the ectacytometer where the shear stress between two planes is constant, the device offered has an area in the center of the cell with zero shear stress. It is the area where RBC should go with the increasing shear stress in the cell. The electric charge of RBC prevent them from going to the central plane, loosing mutual orientation, and can be measured.

Nemtsev, Igor Z.

1996-05-01

4

The relationship of red cell membrane lipid content to red cell morphology and survival in patients with liver disease.  

PubMed

The relationship of red blood cell (RBC) membrane lipid content to RBC morphology and survival was studied in patients with liver diseases. An increase in RBC cholesterol and phospholipid was detected in most patients with hepatocellular disease or cholestatic jaundice but the alteration in RBC lipid content did not correlate with RBC survival. The main abnormality of RBC morphology observed was the presence of macrocytes and target cells. In a small proportion of patients (approximately 3%) with severe hepatocellular disease, significant numbers of severely deformed ("spur") cells were seen. In these patients haemolysis was moderately severe and the RBC lipid profile showed increased membrane cholesterol without a concomitant increase in phospholipids. It is concluded that only in patients with "spur" cell anaemia do the morphological alterations lead to premature removal of cells from the circulation. The cause of the shortened RBC survival in jaundiced patients without "spur" cells remains to be determined. PMID:1057918

Powell, L W; Halliday, J W; Knowles, B R

1975-04-01

5

[Effect of trehalose-loading on red blood cell membrane].  

PubMed

This study was purposed to evaluate the effect of trehalose-loading on physiological and biochemistry properties of red blood cell (RBC) membrane. The samples were divided into the control group (RBC without trehalose loading) and the test group (RBC with trehalose loading). Osmotic fragility reaction was used to determine the osmotic fragility change of loaded RBC membrane in NaCl solution of different osmotic concentration. Flow cytometry and deformeter were used to assay the integrality and deformability of the RBC, respectively. The results showed that the NaCl solution osmotic concentrations were 160 mOsm and 121.4 mOsm, respectively when the haemolysis rate was 50% of the control group and the test group. Flow cytometry data demonstrated that incubation of RBC in a hypertonic trehalose solution resulted in a fraction of cells with different complexity that attached to little Annexin V-FITC, and that it could be removed by washing and resuspending the RBC in an iso-osmotic (300 mOsm PBS) medium. The deformability of the loaded RBC descend, the statistical difference was significant between control and test groups (P < 0.01). It is concluded that the membrane physiological and biochemistry stability and membrane integrality of RBC in a hyper osmotic pressure can be retained after trehalose loading. PMID:23257456

Chen, Lin-Feng; Liu, Jing-Han; Zhuang, Yuan; Che, Ji; Wang, De-Qing; Li, Hui; Wang, Shan

2012-12-01

6

Red blood cell (RBC) survival determined in humans using RBCs labeled at multiple biotin densities  

PubMed Central

BACKGROUND Safe, accurate methods permitting simultaneous and/or repeated measurement of red blood cell (RBC) survival (RCS) are important to investigate pathophysiology and therapy of anemia. Methods using chromium 51 (51Cr) -labeled RBCs are unacceptable for infants, children, and pregnant women. We report RCS measured in vivo using RBCs labeled with several densities of biotin (BioRBCs). STUDY DESIGN AND METHODS Aliquots of autologous RBCs from eight healthy adult subjects were labeled separately at four discrete biotin densities, mixed, and infused. The proportion of each population of BioRBCs circulating was determined serially by flow cytometry over 20 weeks. For each population, RCS was assessed by the following: 1) post-transfusion BioRBC recovery at 24 hour (PTR24); 2) time to decrease to 50% of the enrichment at 24 hours (T50); and 3) mean potential lifespan (MPL). RESULTS Among the four BioRBC densities, no significant differences in PTR24 were observed. T50 and MPL were similar for the two lowest BioRBC densities. In contrast, the two highest BioRBC densities demonstrated progressively decreased T50 and MPL. CONCLUSION RBCs labeled at four biotin densities can be used to independently and accurately measure PTR24 and two lowest biotin densities can accurately quantitate long-term RCS. This method provides a tool for investigating anemia in infants, fetuses, and pregnant women with the following advantages over the standard 51Cr method: 1) study subjects are not exposed to radiation; 2) small blood volumes (e.g., 20 ?L) are required; and 3) multiple independent RCS measurements can be made simultaneously in the same individual. PMID:21062290

Mock, Donald M.; Matthews, Nell I.; Zhu, Shan; Strauss, Ronald G.; Schmidt, Robert L.; Nalbant, Demet; Cress, Gretchen A.; Widness, John A.

2010-01-01

7

Light-regulated and cell-specific expression of tomato rbcS-gusA and rice rbcS-gusA fusion genes in transgenic rice  

Microsoft Academic Search

~~ A previously isolated rice (Oryza sativa) rbcS gene was further characterized. This analysis revealed specific sequences in the 5' regulatory region of the rice rbcS gene that are conserved in rbcS genes of other monocotyledonous species. In transgenic rice plants, we examined the expression of the 8-glucuronidase (gusA) re- porter gene directed by the 2.8-kbpromoter region of the rice

Junko Kyozuka; David McElroy; Takahiko Hayakawa; Yong Xie; Ray Wu; Ko Shimamoto

1993-01-01

8

SLE serum deposits C4d on red blood cells, decreases red blood cell membrane deformability, and promotes nitric oxide production  

PubMed Central

Objective Systemic lupus erythematosus (SLE) is characterized by intravascular activation of the complement system and deposition of complement fragments (C3 and C4) on plasma membranes of circulating cells, including red blood cells (RBC). The aim of this study was to address whether this process affects the biophysical properties of RBC. Methods Serum and red blood cells were isolated from patients with SLE, and healthy controls. RBC from healthy O Rh negative individuals were incubated with SLE or control serum. We used flow cytometry to assess complement fragment deposition on RBC. RBC membrane deformability was measured using 2D microchannel arrays. Protein phosphorylation levels were quantified by western blot. Results Incubation of healthy donor RBC with sera from patients with SLE but not control sera led to deposition of C4 fragments on the RBC. Complement decorated RBC exhibited significant decrease in both membrane deformability and flickering. Sera from SLE patients triggered a transitory Ca++ influx in RBC that was associated with decreased phosphorylation of ?-spectrin, and increased phosphorylation of band 3, two key proteins of RBC cytoskeleton. Finally, SLE but not control sera led to the production of nitric oxide (NO) by RBC. Conclusion Our data suggest that complement activation in patients with SLE leads to calcium dependent cytosketeletal changes in RBC that render them less deformable, likely impairing their flow through capillaries. This phenomenon may negatively impact the delivery of oxygen to the tissues. PMID:21280005

Ghiran, Ionita C.; Zeidel, Mark L.; Shevkoplyas, Sergey S.; Burns, Jennie M.; Tsokos, George C.; Kyttaris, Vasileios C.

2010-01-01

9

Interaction of injectable neurotropic drugs with the red cell membrane.  

PubMed

The normal red blood cell (RBC) shape is a biconcave discocyte. An intercalation of a drug in the outer half of the membrane lipid bilayer leads to echinocytosis, an intercalation in the inner half to stomatocytosis. We have used the shape transforming capacity of RBCs as a model to analyse the membrane interaction potential of various neurotropic drugs. Chlorpromazine, clomipramine, citalopram, clonazepam, and diazepam induced a reversible stomatocytosis, phenytoin induced echinocytosis, while the anticonvulsants levetiracetam, valproic acid and phenobarbital had no effect. This diversity of RBC shape transformations suggests that the pharmacological action is not linked to the membrane interaction. We conclude that this simple RBC shape transformation assay could be a useful tool to screen for potential drug interactions with cell membranes. PMID:24997296

Reinhart, Walter H; Lubszky, Szabina; Thöny, Sandra; Schulzki, Thomas

2014-10-01

10

Light scattering of human red blood cells during metabolic remodeling of membrane  

E-print Network

We present the light scattering properties of individual human red blood cells (RBCs). We show that both the RBC static and dynamic scattering signals are altered by adenosine 5’-triphosphate (ATP)-driven membrane metabolic ...

Park, YongKeun

11

Pf155/RESA protein influences the dynamic microcirculatory behavior of ring-stage Plasmodium falciparum infected red blood cells  

E-print Network

Proteins exported by Plasmodium falciparum to the red blood cell (RBC) membrane modify the structural properties of the parasitized RBC (Pf-RBC). Although quasi-static single cell assays show reduced ring-stage Pf-RBCs ...

Diez-Silva, Monica

12

Contribution of membrane permeability and unstirred layer diffusion to nitric oxide-red blood cell interaction  

PubMed Central

Nitric oxide (NO) consumption by red blood cell (RBC) hemoglobin (Hb) in vasculature is critical in regulating the vascular tone. The paradox of NO production at endothelium in close proximity of an effective NO scavenger Hb in RBCs is mitigated by lower NO consumption by RBCs compared to that of free Hb due to transport resistances including membrane resistance, extra- and intra- cellular resistances for NO biotransport to the RBC. Relative contribution of each transport resistance on NO-RBC interactions is still not clear. We developed a mathematical model of NO transport to a single RBC to quantify the contributions from individual transport barriers by analyzing the effect of RBC membrane permeability (Pm), hematocrit (Hct) and NO-Hb reaction rate constants on NO-RBC interactions. Our results indicated that intracellular diffusion of NO was not a rate limiting step for NO-RBC interactions. The extracellular diffusion contributed 70–90% of total transport resistance for Pm >1 cm/s whereas membrane resistance accounts for 50–75% of total transport resistance for Pm < 0.1 cm/s. We propose a narrow Pm range of 0.21–0.44 cm/s for 10–45% Hct, respectively, below which membrane resistance is more significant and above which extracellular diffusion is a dominating transport resistance for NO-RBC interactions. PMID:23116664

Deonikar, Prabhakar; Kavdia, Mahendra

2012-01-01

13

Composite fuel cell membranes  

DOEpatents

A bilayer or trilayer composite ion exchange membrane is described suitable for use in a fuel cell. The composite membrane has a high equivalent weight thick layer in order to provide sufficient strength and low equivalent weight surface layers for improved electrical performance in a fuel cell. In use, the composite membrane is provided with electrode surface layers. The composite membrane can be composed of a sulfonic fluoropolymer in both core and surface layers.

Plowman, K.R.; Rehg, T.J.; Davis, L.W.; Carl, W.P.; Cisar, A.J.; Eastland, C.S.

1997-08-05

14

Composite fuel cell membranes  

DOEpatents

A bilayer or trilayer composite ion exchange membrane suitable for use in a fuel cell. The composite membrane has a high equivalent weight thick layer in order to provide sufficient strength and low equivalent weight surface layers for improved electrical performance in a fuel cell. In use, the composite membrane is provided with electrode surface layers. The composite membrane can be composed of a sulfonic fluoropolymer in both core and surface layers.

Plowman, Keith R. (Lake Jackson, TX); Rehg, Timothy J. (Lake Jackson, TX); Davis, Larry W. (West Columbia, TX); Carl, William P. (Marble Falls, TX); Cisar, Alan J. (Cypress, TX); Eastland, Charles S. (West Columbia, TX)

1997-01-01

15

Transformation of membrane nanosurface of red blood cells under hemin action  

NASA Astrophysics Data System (ADS)

Hemin is the product of hemoglobin oxidation. Some diseases may lead to a formation of hemin. The accumulation of hemin causes destruction of red blood cells (RBC) membranes. In this study the process of development of topological defects of RBC membranes within the size range from nanoscale to microscale levels is shown. The formation of the grain-like structures in the membrane (``grains'') with typical sizes of 120-200 nm was experimentally shown. The process of formation of ``grains'' was dependent on the hemin concentration and incubation time. The possible mechanism of membrane nanostructure alterations is proposed. The kinetic equations of formation and transformation of small and medium topological defects were analyzed. This research can be used to study the cell intoxication and analyze the action of various agents on RBC membranes.

Kozlova, Elena; Chernysh, Alexander; Moroz, Victor; Gudkova, Olga; Sergunova, Victoria; Kuzovlev, Artem

2014-08-01

16

Plant cell membranes  

SciTech Connect

The contents of this book are: Cells, Protoplasts, Vacuoles and Liposomes; Tonoplasts; Nuclei, Endolplasmic Reticulum, and Plasma Membrane; Peroxisomes; Plastids; Teneral Physical and Biochemical Methods; and Mitochondira.

Packer, L.; Douce, R.

1987-01-01

17

Electroporation of cell membranes.  

PubMed Central

Electric pulses of intensity in kilovolts per centimeter and of duration in microseconds to milliseconds cause a temporary loss of the semipermeability of cell membranes, thus leading to ion leakage, escape of metabolites, and increased uptake by cells of drugs, molecular probes, and DNA. A generally accepted term describing this phenomenon is "electroporation." Other effects of a high-intensity electric field on cell membranes include membrane fusions, bleb formation, cell lysis... etc. Electroporation and its related phenomena reflect the basic bioelectrochemistry of cell membranes and are thus important for the study of membrane structure and function. These phenomena also occur in such events as electric injury, electrocution, and cardiac procedures involving electric shocks. Electroporation has found applications in: (a) introduction of plasmids or foreign DNA into living cells for gene transfections, (b) fusion of cells to prepare heterokaryons, hybridoma, hybrid embryos... etc., (c) insertion of proteins into cell membranes, (d) improving drug delivery and hence effectiveness in chemotherapy of cancerous cells, (e) constructing animal model by fusing human cells with animal tissues, (f) activation of membrane transporters and enzymes, and (g) alteration of genetic expression in living cells. A brief review of mechanistic studies of electroporation is given. PMID:1912274

Tsong, T Y

1991-01-01

18

Tension of red blood cell membrane in simple shear flow.  

PubMed

When a red blood cell (RBC) is subjected to an external flow, it is deformed by the hydrodynamic forces acting on its membrane. The resulting elastic tensions in the membrane play a key role in mechanotransduction and govern its rupture in the case of hemolysis. In this study, we analyze the motion and deformation of an RBC in a simple shear flow and the resulting elastic tensions on the membrane. The large deformation of the red blood cell is modelled by coupling a finite element method to solve the membrane mechanics and a boundary element method to solve the flows of the internal and external liquids. Depending on the capillary number Ca, ratio of the viscous to elastic forces, we observe three kinds of RBC motion: tumbling at low Ca, swinging at larger Ca, and breathing at the transitions. In the swinging regime, the region of the high principal tensions periodically oscillates, whereas that of the high isotropic tensions is almost unchanged. Due to the strain-hardening property of the membrane, the deformation is limited but the membrane tension increases monotonically with the capillary number. We have quantitatively compared our numerical results with former experimental results. It indicates that a membrane isotropic tension O(10{-6} N/m) is high enough for molecular release from RBCs and that the typical maximum membrane principal tension for haemolysis would be O(10{-4} N/m). These findings are useful to clarify not only the membrane rupture but also the mechanotransduction of RBCs. PMID:23214889

Omori, T; Ishikawa, T; Barthès-Biesel, D; Salsac, A-V; Imai, Y; Yamaguchi, T

2012-11-01

19

RBC-NOS-Dependent S-Nitrosylation of Cytoskeletal Proteins Improves RBC Deformability  

PubMed Central

Background Red blood cells (RBC) possess a nitric oxide synthase (RBC-NOS) whose activation depends on the PI3-kinase/Akt kinase pathway. RBC-NOS-produced NO exhibits important biological functions like maintaining RBC deformability. Until now, the cellular target structure for NO, to exert its influence on RBC deformability, remains unknown. In the present study we analyzed the modification of RBC-NOS activity by pharmacological treatments, the resulting influence on RBC deformability and provide first evidence for possible target proteins of RBC-NOS-produced NO in the RBC cytoskeletal scaffold. Methods/Findings Blood from fifteen male subjects was incubated with the NOS substrate L-arginine to directly stimulate enzyme activity. Direct inhibition of enzyme activity was induced by L-N5-(1-Iminoethyl)-ornithin (L-NIO). Indirect stimulation and inhibition of RBC-NOS were achieved by applying insulin and wortmannin, respectively, substances known to affect PI3-kinase/Akt kinase pathway. The NO donor sodium nitroprusside (SNP) and the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) were additionally applied as NO positive and negative controls, respectively. Immunohistochemical staining was used to determine phosphorylation and thus activation of RBC-NOS. As a marker for NO synthesis nitrite was measured in plasma and RBCs using chemiluminescence detection. S-nitrosylation of erythrocyte proteins was determined by biotin switch assay and modified proteins were identified using LC-MS. RBC deformability was determined by ektacytometry. The data reveal that activated RBC-NOS leads to increased NO production, S-nitrosylation of RBC proteins and RBC deformability, whereas RBC-NOS inhibition resulted in contrary effects. Conclusion/Significance This study first-time provides strong evidence that RBC-NOS-produced NO modifies RBC deformability through direct S-nitrosylation of cytoskeleton proteins, most likely ?- and ?-spectrins. Our data, therefore, gain novel insights into biological functions of RBC-NOS by connecting impaired RBC deformability abilities to specific posttranslational modifications of RBC proteins. By identifying likely NO-target proteins in RBC, our results will stimulate new therapeutic approaches for patients with microvascular disorders. PMID:23424675

Grau, Marijke; Pauly, Sebastian; Ali, Jamal; Walpurgis, Katja; Thevis, Mario; Bloch, Wilhelm; Suhr, Frank

2013-01-01

20

Red/far-red and blue light-responsive regions of maize rbcS-m3 are active in bundle sheath and mesophyll cells, respectively.  

PubMed Central

Leaves of the C4 plant maize have two major types of photosynthetic cells: a ring of five large bundle sheath cells (BSC) surrounds each vascular bundle and smaller mesophyll cells (MC) lie between the cylinders of bundle sheath cells. The enzyme ribulose bisphosphate carboxylase/oxygenase is encoded by nuclear rbcS and chloroplast rbcL genes. It is not present in MC but is abundant in adjacent BSC of green leaves. As reported previously, the separate regions of rbcS-m3, which are required for stimulating transcription of the gene in BSC and for suppressing expression of reporter genes in MC, were identified by an in situ expression assay; expression was not suppressed in MC until after leaves of dark-grown seedlings had been illuminated for 24 h. Now we have found that transient expression of rbcS-m3 reporter genes is stimulated in BSC via a red/far-red reversible phytochrome photoperception and signal transduction system but that blue light is required for suppressing rbcS-m3 reporter gene expression in MC. Blue light is also required for the suppression system to develop in MC. Thus, the maize gene rbcS-m3 contains certain sequences that are responsive to a phytochrome photoperception and signal transduction system and other regions that respond to a UVA/blue light photoperception and signal transduction system. Various models of "coaction" of plant photoreceptors have been advanced; these observations show the basis for one type of coaction. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:8524792

Purcell, M; Mabrouk, Y M; Bogorad, L

1995-01-01

21

Optical Trapping Techniques Applied to the Study of Cell Membranes  

NASA Astrophysics Data System (ADS)

Optical tweezers allow for manipulating micron-sized objects using pN level optical forces. In this work, we use an optical trapping setup to aid in three separate experiments, all related to the physics of the cellular membrane. In the first experiment, in conjunction with Brian Henslee, we use optical tweezers to allow for precise positioning and control of cells in suspension to evaluate the cell size dependence of electroporation. Theory predicts that all cells porate at a transmembrane potential VTMof roughly 1 V. The Schwann equation predicts that the transmembrane potential depends linearly on the cell radius r, thus predicting that cells should porate at threshold electric fields that go as 1/r. The threshold field required to induce poration is determined by applying a low voltage pulse to the cell and then applying additional pulses of greater and greater magnitude, checking for poration at each step using propidium iodide dye. We find that, contrary to expectations, cells do not porate at a constant value of the transmembrane potential but at a constant value of the electric field which we find to be 692 V/cm for K562 cells. Delivering precise dosages of nanoparticles into cells is of importance for assessing toxicity of nanoparticles or for genetic research. In the second experiment, we conduct nano-electroporation—a novel method of applying precise doses of transfection agents to cells—by using optical tweezers in conjunction with a confocal microscope to manipulate cells into contact with 100 nm wide nanochannels. This work was done in collaboration with Pouyan Boukany of Dr. Lee's group. The small cross sectional area of these nano channels means that the electric field within them is extremely large, 60 MV/m, which allows them to electrophoretically drive transfection agents into the cell. We find that nano electroporation results in excellent dose control (to within 10% in our experiments) compared to bulk electroporation. We also find that, unlike bulk electroporation, nano-electroporation directly injects nanoparticles, such as quantum dots, to the cell interior, bypassing the cell membrane without the need for endocytosis. The aging of RBC's can render them rigid, an issue for the survivability of transfusion patients. This rigidity can be assessed by examining the fluctuations in the cell membrane. In the third experiment, we use back focal plane detection—an interferometric detection scheme using an optical tweezers setup—to measure the membrane fluctuations of RBC's and K562 cells. Membrane fluctuations have long been observed in RBC's and a well developed theory exists linking them to the cells internal viscosity ?, the membrane bending modulus k and the surface tension of the membrane ?. We use back focal plane detection to measure the effect of ascorbic acid treatment on RBC aging and find no improvement in cell flexibility. K562 cells differ from RBC's in that they possess an actin cortex which the membrane attaches to. We demonstrate that K562 cells exhibit as much as an order of magnitude more variation in their fluctuations than RBC's do.

Morss, Andrew J.

22

IgG red blood cell autoantibodies in autoimmune hemolytic anemia bind to epitopes on red blood cell membrane band 3 glycoprotein  

SciTech Connect

Red blood cell (RBC) autoantibodies from patients with IgG warm-type autoimmune hemolytic anemia were labeled with iodine 125 and their RBC binding behavior characterized. Epitope-bearing RBC membrane polypeptides were identified after autoantibody immunoprecipitation of labeled membranes and immunoblotting. Immunoaffinity isolation of labeled membrane proteins with 12 different IgG hemolytic autoantibodies with protein A-agarose revealed a major polypeptide at Mr 95 to 110 kd, which coelectrophoresed on sodium dodecylsulfate-polyacrylamide gel electrophoresis with a membrane component isolated with sheep IgG anti-band 3. Immunoprecipitation studies with chymotrypsinized RBCs resulted in the recovery of two labeled membrane polypeptides with molecular weights characteristically resulting from the chymotryptic fragmentation of band 3. Immunoblotting with sheep IgG anti-band 3 of the immunoprecipitated polypeptides confirmed that hemolytic autoantibody binding led to recovery of band 3 or its fragments. Two 125I-labeled IgG hemolytic autoantibodies showed binding behavior consistent with epitope localization on band 3. The labeled RBC autoantibodies bound immunospecifically to all types of human RBC tested, including those of rare Rh type (Rh-null, D--) at a site density of approximately 10(6) per RBC. The 125I-IgG in two labeled autoantibodies was 84% and 92% adsorbable by human and higher nonhuman primate RBCs. Antigen-negative animal RBC bound less than 10%, consistent with immunospecific RBC binding. IgG-1 was the major subclass in five autoantibodies tested; one of six fixed complement; and autoantibody IgG appeared polyclonal by isoelectric focusing. We conclude that IgG eluted from RBCs of patients with autoimmune hemolytic anemia consists predominantly of a single totally RBC-adsorbable antibody population that binds to antigenic determinants on band 3.

Victoria, E.J.; Pierce, S.W.; Branks, M.J.; Masouredis, S.P. (Univ. of California, San Diego (USA))

1990-01-01

23

In vivo pharmaco-proteomic analysis of hydroxyurea induced changes in the sickle red blood cell membrane proteome.  

PubMed

Hydroxyurea (HU) is an effective drug for the treatment of sickle cell disease (SCD). The main clinical benefit of HU is thought to derive from its capacity to increase fetal hemoglobin (HbF) production. However, other effects leading to clinical benefit, such as improved blood rheology, have been suggested. In order to understand HU-induced changes at the proteomic level, we profiled sickle RBC membranes from of HU-treated and untreated patients. Our previous in vitro profiling studies on sickle RBC membranes identified a significant increase in predominantly anti-oxidant enzymes, protein repair and degradation components and a few RBC cytoskeletal proteins. In the present study, using 2D-DIGE (Two-Dimensional Difference In-Gel Electrophoresis) and tandem mass spectrometry, we detected 32 different proteins that significantly changed in abundance in the HU treatment group. The proteins that significantly increased in abundance were mostly membrane skeletal components involved in the regulation of RBC shape and flexibility, and those showing a significant decrease were components of the protein repair and degradation machinery. RBC palmitoylated membrane protein 55 (p55) is significantly increased in abundance at low (in vitro) and high (in vivo) concentrations of HU. Palmitoylated p55 may be an important target of HU-dependent regulation of the sickle RBC membrane, consistent with our earlier in vitro studies. PMID:19914412

Ghatpande, Swati S; Choudhary, Pankaj K; Quinn, Charles T; Goodman, Steven R

2010-01-01

24

Cell Membranes Tutorial  

NSDL National Science Digital Library

New from The Biology Project of the University of Arizona, this online tutorial "introduces the dynamic complexes of proteins, carbohydrates, and lipids that comprise cell membranes," and relates how membranes "are important for regulating ion and molecular traffic flow between cells." Each section of this Web site takes the form of a multiple choice question. Answer the question correctly, and a brief explanation of each answer choice will be displayed. Answer the question incorrectly, and a short but helpful tutorial with colorful diagrams will help get you on the right track. This would be an valuable Web site for students wishing to test themselves on cell membrane structure and function, but would not be especially useful for those new to the subject.

2002-01-01

25

Cell Membranes Tutorial  

NSDL National Science Digital Library

New from The Biology Project of the University of Arizona, this online tutorial introduces the dynamic complexes of proteins, carbohydrates, and lipids that comprise cell membranes, and relates how membranes are important for regulating ion and molecular traffic flow between cells. Each section of this Web site takes the form of a multiple choice question. Answer the question correctly, and a brief explanation of each answer choice will be displayed. Answer the question incorrectly, and a short but helpful tutorial with colorful diagrams will help get you on the right track. This would be an valuable Web site for students wishing to test themselves on cell membrane structure and function, but would not be especially useful for those new to the subject.

2002-01-01

26

Red blood cell membrane concentration of cis-palmitoleic and cis-vaccenic acids and risk of coronary heart disease.  

PubMed

Although previous studies have suggested associations between plasma palmitoleic acid and coronary heart disease (CHD) risk factors, including blood pressure, inflammation, and insulin resistance, little is known about the relation of palmitoleic acid and CHD. This ancillary study of the Physicians' Health Study was designed to examine whether red blood cell (RBC) membrane cis-palmitoleic acid and cis-vaccenic acid-2 fatty acids that can be synthesized endogenously-are associated with CHD risk. We used a risk set sampling method to prospectively select 1,000 incident CHD events and 1,000 matched controls. RBC membrane fatty acids were measured using gas chromatography. The CHD cases were ascertained using an annual follow-up questionnaire and validated by an End Point Committee through a review of the medical records. In a conditional logistic regression analysis adjusting for demographics, anthropometric, lifestyle factors, and co-morbidity, the odds ratios and 95% confidence intervals (CIs) for CHD were 1.0 (referent), 1.29 (95% CI 0.95 to 1.75), 1.08 (95% CI 0.78 to 1.51), 1.25 (95% CI 0.90 to 1.75), and 1.48 (95% CI 1.03 to 2.14) across consecutive quintiles of RBC membrane cis-palmitoleic acid (p for trend = 0.041). The odds ratio associated with each SD higher RBC membrane cis-palmitoleic acid level was 1.19 (95% CI 1.06 to 1.35) in a multivariate-adjusted model. Finally, RBC membrane cis-vaccenic acid was inversely associated with CHD risk (odds ratio 0.79, 95% CI 0.69 to 0.91, per SD increase). In conclusion, our data showed a positive association between RBC membrane cis-palmitoleic acid and CHD risk in male physicians. Furthermore, RBC membrane cis-vaccenic acid was inversely related to CHD. PMID:22579341

Djoussé, Luc; Matthan, Nirupa R; Lichtenstein, Alice H; Gaziano, John M

2012-08-15

27

Expression of both N- and C-terminal GFP tagged huCD36 and their discrepancy in OxLDL and pRBC binding on CHO cells  

PubMed Central

CD36, an 88 kDa membrane glycoprotein, is found in several cell types and it has been characterized to have two hydrophobic domains at their N- and C-termini which are essential for protein folding and targeting. In this study, we first tagged the green fluorescent protein (GFP) to both the N- and C-termini of huCD36 and investigated their cellular expression and influences on lipoprotein and plasmodium falciparium parasitized erythrocytes (pRBC) binding. Our work revealed that huCD36 proteins are expressed normally irrespective of the GFP tag presence at either the N- or C-termini. However, the two recombinant proteins showed discrepancy in uptake and surface-binding of OxLDL but they did not affect pRBC binding. These results suggested that the interaction between oxLDL and CD36 could be blocked using recombinant proteins and this may be useful in potential control of the trafficking of modified lipoproteins into monocytes leading to atherogenesis. PMID:17888147

Zhang, Jianshe; Crandall, Ian

2007-01-01

28

Expression of both N- and C-terminal GFP tagged huCD36 and their discrepancy in OxLDL and pRBC binding on CHO cells.  

PubMed

CD36, an 88 kDa membrane glycoprotein, is found in several cell types and it has been characterized to have two hydrophobic domains at their N- and C-termini which are essential for protein folding and targeting. In this study, we first tagged the green fluorescent protein (GFP) to both the N- and C-termini of huCD36 and investigated their cellular expression and influences on lipoprotein and plasmodium falciparium parasitized erythrocytes (pRBC) binding. Our work revealed that huCD36 proteins are expressed normally irrespective of the GFP tag presence at either the N- or C-termini. However, the two recombinant proteins showed discrepancy in uptake and surface-binding of OxLDL but they did not affect pRBC binding. These results suggested that the interaction between oxLDL and CD36 could be blocked using recombinant proteins and this may be useful in potential control of the trafficking of modified lipoproteins into monocytes leading to atherogenesis. PMID:17888147

Zhang, Jianshe; Crandall, Ian

2007-01-01

29

Cell Membrane Color Sheet and Build a Cell Membrane  

NSDL National Science Digital Library

Students color-code a schematic of a cell and its cell membrane structures. Then they complete the "Build-a-Membrane" activity found at http://learn.genetics.utah.edu. This reinforces their understanding of the structure and function of animal cells, and shows them the importance of being able to construct a tangible model of something that is otherwise difficult to see.

Vu Bioengineering Ret Program

30

Two-dimensional strain-hardening membrane model for large deformation behavior of multiple red blood cells in high shear conditions  

PubMed Central

Background Computational modeling of Red Blood Cell (RBC) flow contributes to the fundamental understanding of microhemodynamics and microcirculation. In order to construct theoretical RBC models, experimental studies on single RBC mechanics have presented a material description for RBC membranes based on their membrane shear, bending and area moduli. These properties have been directly employed in 3D continuum models of RBCs but practical flow analysis with 3D models have been limited by their computationally expensive nature. As such, various researchers have employed 2D models to efficiently and qualitatively study microvessel flows. Currently, the representation of RBC dynamics using 2D models is a limited methodology that breaks down at high shear rates due to excessive and unrealistic stretching. Methods We propose a localized scaling of the 2D elastic moduli such that it increases with RBC local membrane strain, thereby accounting for effects such as the Poisson effect and membrane local area incompressibility lost in the 2D simplification. Validation of our 2D Large Deformation (2D-LD) RBC model was achieved by comparing the predicted RBC deformation against the 3D model from literature for the case of a single RBC in simple shear flow under various shear rates (dimensionless shear rate G?=?0.05, 0.1, 0.2, 0.5). The multi-cell flow of RBCs (38% Hematocrit) in a 20 ?m width microchannel under varying shear rates (50, 150, 150 s-1) was then simulated with our proposed model and the popularly-employed 2D neo-Hookean model in order to evaluate the efficacy of our proposed 2D-LD model. Results The validation set indicated similar RBC deformation for both the 2D-LD and the 3D models across the studied shear rates, highlighting the robustness of our model. The multi-cell simulation indicated that the 2D neo-Hookean model predicts noodle-like RBC shapes at high shear rates (G?=?0.5) whereas our 2D-LD model maintains sensible RBC deformations. Conclusion The ability of the 2D-LD model to limit RBC strain even at high shear rates enables this proposed model to be employed in practical simulations of high shear rate microfluidic flows such as blood separation channels. PMID:24885482

2014-01-01

31

Red blood cell (RBC) transfusion rates among US chronic dialysis patients during changes to Medicare end-stage renal disease (ESRD) reimbursement systems and erythropoiesis stimulating agent (ESA) labels  

PubMed Central

Background Several major ESRD-related regulatory and reimbursement changes were introduced in the United States in 2011. In several large, national datasets, these changes have been associated with decreases in erythropoiesis stimulating agent (ESA) utilization and hemoglobin concentrations in the ESRD population, as well as an increase in the use of red blood cell (RBC) transfusions in this population. Our objective was to examine the use of RBC transfusion before and after the regulatory and reimbursement changes implemented in 2011 in a prevalent population of chronic dialysis patients in a large national claims database. Methods Patients in the Truven Health MarketScan Commercial and Medicare Databases with evidence of chronic dialysis were selected for the study. The proportion of chronic dialysis patients who received any RBC transfusion and RBC transfusion event rates per 100 patient-months were calculated in each month from January 1, 2007 to March 31, 2012. The results were analyzed overall and stratified by primary health insurance payer (commercial payer or Medicare). Results Overall, the percent of chronic dialysis patients with RBC transfusion and RBC transfusion event rates per 100 patient-months increased between January 2007 and March 2012. When stratified by primary health insurance payer, it appears that the increase was driven by the primary Medicare insurance population. While the percent of patients with RBC transfusion and RBC transfusion event rates did not increase in the commercially insured population between 2007 and 2012 they did increase in the primary Medicare insurance population; the majority of the increase occurred in 2011 during the same time frame as the ESRD-related regulatory and reimbursement changes. Conclusions The regulatory and reimbursement changes implemented in 2011 may have contributed to an increase in the use of RBC transfusions in chronic dialysis patients in the MarketScan dataset who were covered by Medicare plus Medicare supplemental insurance. PMID:25015348

2014-01-01

32

Evaluation of Red Cell Membrane Cytoskeletal Disorders Using a Flow Cytometric Method in South Iran  

PubMed Central

Objective: The diagnosis of hereditary red blood cell (RBC) membrane disorders, and in particular hereditary spherocytosis (HS) and Southeast Asian ovalocytosis (SAO), is based on clinical history, RBC morphology, and other conventional tests such as osmotic fragility. However, there are some milder cases of these disorders that are difficult to diagnose. The application of eosin-5’-maleimide (EMA) was evaluated for screening of RBC membrane defects along with some other anemias. We used EMA dye, which binds mostly to band 3 protein and to a lesser extent some other membrane proteins, for screening of some membrane defects such as HS. Materials and Methods: Fresh RBCs from hematologically normal controls and patients with HS, SAO, hereditary elliptocytosis, hereditary spherocytosis with pincered cells, severe iron deficiency, thalassemia minor, and autoimmune hemolytic anemia were stained with EMA dye and analyzed for mean fluorescent intensity (MFI) using a flow cytometer. Results: RBCs from patients with HS and iron deficiency showed a significant reduction in MFI compared to those from normal controls (p<0.0001 and p<0.001, respectively), while macrocytic RBCs showed a significant increase in MFI (p<0.01). A significant correlation was shown between mean corpuscular volume and MFI, with the exceptions of HS and thalassemia minor. Conclusion: Our results showed that the flow cytometric method could be a reliable diagnostic method for screening and confirmation, with higher sensitivity and specificity (95% and 93%, respectively) than conventional routine tests for HS patients prior to further specific membrane protein molecular tests. PMID:24764726

Golafshan, Habib Alah; Ranjbaran, Reza; Kalantari, Tahereh; Moezzi, Leili; Karimi, Mehran; Behzad- Behbahani, Abbas; Aboualizadeh, Farzaneh; Sharifzadeh, Sedigheh

2014-01-01

33

Enhancing effect of radioresistant spleen cells on the primary immune response against sheep RBC by mouse spleen cells in vitro.  

PubMed

Irradiated spleen cells cultured for 3 days, caused a stimulation of the primary in vitro immune response by normal spleen cells. These irradiated spleen cells were fractionated by velocity sedimentation and the fractions were tested for their stimulating activity. Only the macrophage enriched fractions were found to cause stimulation. The macrophages in these fractions were stuffed with erythrocytes and dead cells. The fractions enriched in thymus derived cells, had no effect on the immune response. Irradiated spleen cells cultured for 24 hours caused inhibition. It has not yet been determined whether this inhibition was due to some transient change in the macrophage population during incubation. The stimulating effect by the irradiated spleen cells from SPF mice was strongly reduced, which at least partly could be ascribed to the naturally occurring low number of macrophages in the spleens of these mice. PMID:1266673

Lubbe, F H; Zaalberg, O B

1976-01-01

34

Microfluidics analysis of red blood cell membrane viscoelasticity.  

PubMed

In this work, a microfluidic system to investigate the flow behavior of red blood cells in a microcirculation-mimicking network of PDMS microchannels with thickness comparable to cell size is presented. We provide the first quantitative description of cell velocity and shape as a function of the applied pressure drop in such devices. Based on these results, a novel methodology to measure cell membrane viscoelastic properties in converging/diverging flow is developed, and the results are in good agreement with data from the literature. In particular, in the diverging channel the effect of RBC surface viscosity is dominant with respect to shear elasticity. Possible applications include measurements of cell deformability in pathological samples, where reliable methods are still lacking. PMID:21076756

Tomaiuolo, Giovanna; Barra, Mario; Preziosi, Valentina; Cassinese, Antonio; Rotoli, Bruno; Guido, Stefano

2011-02-01

35

The Effect of Alcohols on Red Blood Cell Mechanical Properties and Membrane Fluidity Depends on Their Molecular Size  

PubMed Central

The role of membrane fluidity in determining red blood cell (RBC) deformability has been suggested by a number of studies. The present investigation evaluated alterations of RBC membrane fluidity, deformability and stability in the presence of four linear alcohols (methanol, ethanol, propanol and butanol) using ektacytometry and electron paramagnetic resonance (EPR) spectroscopy. All alcohols had a biphasic effect on deformability such that it increased then decreased with increasing concentration; the critical concentration for reversal was an inverse function of molecular size. EPR results showed biphasic changes of near-surface fluidity (i.e., increase then decrease) and a decreased fluidity of the lipid core; rank order of effectiveness was butanol > propanol > ethanol > methanol, with a significant correlation between near-surface fluidity and deformability (r = 0.697; p<0.01). The presence of alcohol enhanced the impairment of RBC deformability caused by subjecting cells to 100 Pa shear stress for 300 s, with significant differences from control being observed at higher concentrations of all four alcohols. The level of hemolysis was dependent on molecular size and concentration, whereas echinocytic shape transformation (i.e., biconcave disc to crenated morphology) was observed only for ethanol and propanol. These results are in accordance with available data obtained on model membranes. They document the presence of mechanical links between RBC deformability and near-surface membrane fluidity, chain length-dependence of the ability of alcohols to alter RBC mechanical behavior, and the biphasic response of RBC deformability and near-surface membrane fluidity to increasing alcohol concentrations. PMID:24086751

Sonmez, Melda; Ince, Huseyin Yavuz; Yalcin, Ozlem; Ajdzanovic, Vladimir; Spasojevic, Ivan; Meiselman, Herbert J.; Baskurt, Oguz K.

2013-01-01

36

Radiation effects on cell membranes  

Microsoft Academic Search

Summary The recent developments in the field of membrane biology of eukaryotic cells result in revival of relevant radiobiological studies. The spatial relations and chemical nature of membrane components provide rather sensitive targets. Experimental data are presented concerning the effects of relatively low doses of X-irradiation and low concentration of tritiated water (HTO) on variou receptor function - concanavalin A,

G. J. Köteles

1982-01-01

37

Responses of red blood cell-membrane systems: temperature and calcium effects on volume, deformability, and osmotic fragility as studied by resistive pulse spectroscopy  

SciTech Connect

The effects exerted by temperature and calcium on red blood cells were studied using resistive pulse spectroscopy (RPS). A new RPS protocol is presented which enables cell volume and shape to be determined more accurately than previously possible. Repair processes of the RBC membrane following osmotic hemolysis were examined. 140 references, 44 figures, 6 tables.

Richieri, G.V.

1984-04-01

38

Dielectric breakdown of cell membranes.  

PubMed

With human and bovine red blood cells and Escherichia coli B, dielectric breakdown of cell membranes could be demonstrated using a Coulter Counter (AEG-Telefunken, Ulm, West Germany) with a hydrodynamic focusing orifice. In making measurements of the size distributions of red blood cells and bacteria versus increasing electric field strength and plotting the pulse heights versus the electric field strength, a sharp bend in the otherwise linear curve is observed due to the dielectric breakdown of the membranes. Solution of Laplace's equation for the electric field generated yields a value of about 1.6 V for the membrane potential at which dielectric breakdown occurs with modal volumes of red blood cells and bacteria. The same value is also calculated for red blood cells by applying the capacitor spring model of Crowley (1973. Biophys. J. 13:711). The corresponding electric field strength generated in the membrane at breakdown is of the order of 4 . 10(6) V/cm and, therefore, comparable with the breakdown voltages for bilayers of most oils. The critical detector voltage for breakdown depends on the volume of the cells. The volume-dependence predicted by Laplace theory with the assumption that the potential generated across the membrane is independent of volume, could be verified experimentally. Due to dielectric breakdown the red blood cells lose hemoglobin completely. This phenomenon was used to study dielectric breakdown of red blood cells in a homogeneous electric field between two flat platinum electrodes. The electric field was applied by discharging a high voltage storage capacitor via a spark gap. The calculated value of the membrane potential generated to produce dielectric breakdown in the homogeneous field is of the same order as found by means of the Coulter Counter. This indicates that mechanical rupture of the red blood cells by the hydrodynamic forces in the orifice of the Coulter Counter could also be excluded as a hemolysing mechanism. The detector voltage (or the electric field strength in the orifice) depends on the membrane composition (or the intrinsic membrane potential) as revealed by measuring the critical voltage in E. coli B harvested from the logarithmic and stationary growth phases. The critical detector voltage increased by about 30% for a given volume on reaching the stationary growth phase. PMID:4611517

Zimmermann, U; Pilwat, G; Riemann, F

1974-11-01

39

Dielectric Breakdown of Cell Membranes  

PubMed Central

With human and bovine red blood cells and Escherichia coli B, dielectric breakdown of cell membranes could be demonstrated using a Coulter Counter (AEG-Telefunken, Ulm, West Germany) with a hydrodynamic focusing orifice. In making measurements of the size distributions of red blood cells and bacteria versus increasing electric field strength and plotting the pulse heights versus the electric field strength, a sharp bend in the otherwise linear curve is observed due to the dielectric breakdown of the membranes. Solution of Laplace's equation for the electric field generated yields a value of about 1.6 V for the membrane potential at which dielectric breakdown occurs with modal volumes of red blood cells and bacteria. The same value is also calculated for red blood cells by applying the capacitor spring model of Crowley (1973. Biophys. J. 13:711). The corresponding electric field strength generated in the membrane at breakdown is of the order of 4 · 106 V/cm and, therefore, comparable with the breakdown voltages for bilayers of most oils. The critical detector voltage for breakdown depends on the volume of the cells. The volume-dependence predicted by Laplace theory with the assumption that the potential generated across the membrane is independent of volume, could be verified experimentally. Due to dielectric breakdown the red blood cells lose hemoglobin completely. This phenomenon was used to study dielectric breakdown of red blood cells in a homogeneous electric field between two flat platinum electrodes. The electric field was applied by discharging a high voltage storage capacitor via a spark gap. The calculated value of the membrane potential generated to produce dielectric breakdown in the homogeneous field is of the same order as found by means of the Coulter Counter. This indicates that mechanical rupture of the red blood cells by the hydrodynamic forces in the orifice of the Coulter Counter could also be excluded as a hemolysing mechanism. The detector voltage (or the electric field strength in the orifice) depends on the membrane composition (or the intrinsic membrane potential) as revealed by measuring the critical voltage in E. coli B harvested from the logarithmic and stationary growth phases. The critical detector voltage increased by about 30% for a given volume on reaching the stationary growth phase. PMID:4611517

Zimmermann, U.; Pilwat, G.; Riemann, F.

1974-01-01

40

Metabolic remodeling of the human red blood cell membrane  

E-print Network

The remarkable deformability of the human red blood cell (RBC) results from the coupled dynamic response of the phospholipid bilayer and the spectrin molecular network. Here we present quantitative connections between ...

Suresh, Subra

41

Rabbit IgG Antibodies against Cord Red Blood Cell Membranes Bind to Complement Receptor 1 (CD35)  

Microsoft Academic Search

We have previously shown that a subpopulation of cord\\/fetal red blood cells (RBC) binds rabbit IgG antibodies raised against cord RBC and absorbed on adult RBC (F-IgG), while control IgG, raised against and absorbed on adult RBC (A-IgG), fails to do so. In the present study, F-IgG maintained its binding to cord RBC surface antigens following absorption on spectrin but

Anna Lisa Giuliani; Roberto Pora; Marina Verenini; Lorenza Unis; Giuseppe Graldi; Luisa Ferrari; Francesco Lanza; Edith Wiener; Hans U. Lutz; Fortunato Vesce; Gilberto Berti

1998-01-01

42

The Cell Membrane and Nanotechnology  

NSDL National Science Digital Library

This activity is from the Wisconsin Online Resource Center, which is a digital library of web-based learning objects. Barbara Liang created this resource, and it examines nanotechnology applications that are based on cell membrane structure and function. The brief activity contains animated illustrations and interactives that help students grasp nanotechnology concepts.

Liang, Barbara

2010-11-16

43

Tropomodulin 1-null mice have a mild spherocytic elliptocytosis with appearance of tropomodulin 3 in red blood cells and disruption of the membrane skeleton.  

PubMed

The short actin filaments in the red blood cell (RBC) membrane skeleton are capped at their pointed ends by tropomodulin 1 (Tmod1) and coated with tropomyosin (TM) along their length. Tmod1-TM control of actin filament length is hypothesized to regulate spectrin-actin lattice organization and membrane stability. We used a Tmod1 knockout mouse to investigate the in vivo role of Tmod1 in the RBC membrane skeleton. Western blots of Tmod1-null RBCs confirm the absence of Tmod1 and show the presence of Tmod3, which is normally not present in RBCs. Tmod3 is present at only one-fifth levels of Tmod1 present on wild-type membranes, but levels of actin, TMs, adducins, and other membrane skeleton proteins remain unchanged. Electron microscopy shows that actin filament lengths are more variable with spectrin-actin lattices displaying abnormally large and more variable pore sizes. Tmod1-null mice display a mild anemia with features resembling hereditary spherocytic elliptocytosis, including decreased RBC mean corpuscular volume, cellular dehydration, increased osmotic fragility, reduced deformability, and heterogeneity in osmotic ektacytometry. Insufficient capping of actin filaments by Tmod3 may allow greater actin dynamics at pointed ends, resulting in filament length redistribution, leading to irregular and attenuated spectrin-actin lattice connectivity, and concomitant RBC membrane instability. PMID:20585041

Moyer, Jeannette D; Nowak, Roberta B; Kim, Nancy E; Larkin, Sandra K; Peters, Luanne L; Hartwig, John; Kuypers, Frans A; Fowler, Velia M

2010-10-01

44

Cell handling using microstructured membranes  

PubMed Central

Gentle and precise handling of cell suspensions is essential for scientific research and clinical diagnostic applications. Although different techniques for cell analysis at the micro-scale have been proposed, many still require that preliminary sample preparation steps be performed off the chip. Here we present a microstructured membrane as a new microfluidic design concept, enabling the implementation of common sample preparation procedures for suspensions of eukaryotic cells in lab-on-a-chip devices. We demonstrate the novel capabilities for sample preparation procedures by the implementation of metered sampling of nanoliter volumes of whole blood, concentration increase up to three orders of magnitude of sparse cell suspension, and circumferentially uniform, sequential exposure of cells to reagents. We implemented these functions by using microstructured membranes that are pneumatically actuated and allowed to reversibly decouple the flow of fluids and the displacement of eukaryotic cells in suspensions. Furthermore, by integrating multiple structures on the same membrane, complex sequential procedures are possible using a limited number of control steps. PMID:16511616

Irimia, Daniel

2013-01-01

45

Marathon Running Fails to Influence RBC Survival Rates in Iron-Replete Women.  

ERIC Educational Resources Information Center

This study used radiolabeling to measure red blood cell (RBC) survival rates in six iron-replete female marathon runners, and urinary tests were conducted to search for secondary evidence of RBC damage. The hypothesized RBC fragmentation was not disclosed. (Author/MT)

Steenkamp, Irene; And Others

1986-01-01

46

Defected red blood cell membranes and direct correlation with the uraemic milieu: the connection with the decreased red blood cell lifespan observed in haemodialysis patients  

NASA Astrophysics Data System (ADS)

Together with impaired production of erythropoietin and iron deficiency, the decreased lifespan of red blood cells (RBCs) is a main factor contributing to the chronic anaemia observed in haemodialysis (HD) patients. Atomic force microscopy is employed in this work to thoroughly survey the membrane of intact RBCs (iRBCs) of HD patients in comparison to those of healthy donors, aiming to obtain direct information on the structural status of RBCs that can be related to their decreased lifespan. We observed that the iRBC membrane of the HD patients is overpopulated with extended circular defects, termed ‘orifices’, that have typical dimension ranging between 0.2 and 1.0 ?m. The ‘orifice’ index—that is, the mean population of ‘orifices’ per top membrane surface—exhibits a pronounced relative increase of order 54 ± 12% for the HD patients as compared to healthy donors. Interestingly, for the HD patients, the ‘orifice’ index, which relates to the structural status of the RBC membrane, correlates strongly with urea concentration, which is a basic index of the uraemic milieu. Thus, these results indicate that the uraemic milieu downgrades the structural status of the RBC membrane, possibly triggering biochemical processes that result in their premature elimination from the circulation. This process could decrease the lifespan of RBCs, as observed in HD patients.

Stamopoulos, D.; Grapsa, E.; Manios, E.; Gogola, V.; Bakirtzi, N.

2012-12-01

47

Tropomodulin 1-null mice have a mild spherocytic elliptocytosis with appearance of tropomodulin 3 in red blood cells and disruption of the membrane skeleton  

Microsoft Academic Search

The short actin filaments in the red blood cell (RBC) membrane skeleton are capped at their pointed ends by tropomodulin 1 (Tmod1) and coated with tropomyosin (TM) along their length. Tmod1-TM control of actin filament length is hypothesized to regulate spectrin-actin lattice organization and membrane stability. We used a Tmod1 knockout mouse to investigate the in vivo role of Tmod1

J. D. Moyer; R. B. Nowak; N. E. Kim; S. K. Larkin; L. L. Peters; J. Hartwig; F. A. Kuypers; V. M. Fowler

2010-01-01

48

Sulfonated polysulfone ionomer membranes for fuel cells  

Microsoft Academic Search

Sulfonated polysulfone (SPSU) membranes with different sulfonation levels have been prepared and evaluated as proton exchange membranes in polymer electrolyte fuel cells (PEFC). The membranes have been characterized by ion-exchange capacity (IEC), thermal analysis, proton conductivity and single cell performance. The introduction of sulfonic groups in the base polymer produces an increase in glass transition temperature (Tg) from 190 to

F. Lufrano; I. Gatto; P. Staiti; V. Antonucci; E. Passalacqua

2001-01-01

49

Lateral organization of membranes and cell shapes.  

PubMed Central

The relations among membrane structure, mechanical properties, and cell shape have been investigated. The fluid mosaic membrane models used contains several components that move freely in the membrane plane. These components interact with each other and determine properties of the membrane such as curvature and elasticity. A free energy equation is postulated for such a multicomponent membrane and the condition of free energy minimum is used to obtain differential equations relating the distribution of membrane components and the local membrane curvature. The force that moves membrane components along the membrane in a variable curvature field is calculated. A change in the intramembrane interactions can bring about phase separation or particle clustering. This, in turn, may strongly affect the local curvature. The numerical solution of the set of equations for the two dimensional case allows determination of the cell shape and the component distribution along the membrane. The model has been applied to describe certain erythrocytes shape transformations. PMID:7284547

Markin, V S

1981-01-01

50

Following-up changes in red blood cell deformability and membrane stability in the presence of PTFE graft implanted into the femoral artery in a canine model  

NASA Astrophysics Data System (ADS)

It is known that a moderate mechanical stress can even improve the red blood cells' (RBC) micro-rheological characteristics, however, a more significant stress causes deterioration in the deformability. In this study, we aimed to investigate the effect of the presence of artificial graft on the RBC deformability and membrane stability in beagles. In the Control group only anesthesia was induced and in the postoperative (p.o.) period blood samplings were carried out. In the Grafted group under general anesthesia, the left femoral artery was isolated, from which a 3.5 cm segment was resected and a PTFE graft (O.D.: 3 mm) of equal in length was implanted into the gap. On the 1st, 3rd, 5th, 7th and 14th p.o. days blood was collected the cephalic veins and RBC deformability was determined ektacytometry (LoRRca MaxSis Osmoscan). Membrane stability test consisted of two deformability measurements before and after the cells were being exposed to mechanical stress (60 or 100 Pa for 300 seconds). Compared to the Control group and the baseline values the red blood cell deformability showed significant deterioration on the 3rd, 5th and mainly on the 7th postoperative day after the graft implantation. The membrane stability of erythrocyte revealed marked inter-group difference on the 3rd, 5th and 7th day: in the Grafted group the deformability decreased and during the membrane stability test smaller difference was observed between the states before and after shearing. We concluded that the presence of a PTFE graft in the femoral artery may cause changes in RBC deformability in the first p.o. week. RBC membrane stability investigation shows a lower elongation index profile for the grafted group and a narrowed alteration in the deformability curves due to mechanical stress.

Toth, Csaba; Kiss, Ferenc; Klarik, Zoltan; Gergely, Eszter; Toth, Eniko; Peto, Katalin; Vanyolos, Erzsebet; Miko, Iren; Nemeth, Norbert

2014-05-01

51

General coarse-grained red blood cell models: I. Mechanics  

E-print Network

We present a rigorous procedure to derive coarse-grained red blood cell (RBC) models, which lead to accurate mechanical properties of realistic RBCs. Based on a semi-analytic theory linear and non-linear elastic properties of the RBC membrane can be matched with those obtained in optical tweezers stretching experiments. In addition, we develop a nearly stress-free model which avoids a number of pitfalls of existing RBC models, such as non-biconcave equilibrium shape and dependence of RBC mechanical properties on the triangulation quality. The proposed RBC model is suitable for use in many existing numerical methods, such as Lattice Boltzmann, Multiparticle Collision Dynamics, Immersed Boundary, etc.

Dmitry A. Fedosov; Bruce Caswell; George E. Karniadakis

2009-05-01

52

Tracking microdomain dynamics in cell membranes  

PubMed Central

Studies of the diffusion of proteins and lipids in the plasma membrane of cells have long pointed to the presence of membrane domains. A major challenge in the field of membrane biology has been to characterize the various cellular structures and mechanisms that impede free diffusion in cell membranes and determine the consequences that membrane compartmentalization has on cellular biology. In this review, we will provide a brief summary of the classes of domains that have been characterized to date, focusing on recent efforts to identify the properties of lipid rafts in cells through measurements of protein and lipid diffusion. PMID:19041847

Day, Charles A.; Kenworthy, Anne K.

2009-01-01

53

The Proton Exchange Membrane (PEM) Fuel Cell  

NSDL National Science Digital Library

This page is an introduction to the Proton Exchange Membrane (PEM) fuel cell. It uses flash animation to explain in greater detail what the PEM fuel cell consists of and how it works. The website has an introductory animation which is followed by more in depth description of the proton exchange membrane fuel cell.

2012-09-13

54

Polymer electrolyte membrane assembly for fuel cells  

NASA Technical Reports Server (NTRS)

An electrolyte membrane for use in a fuel cell can contain sulfonated polyphenylether sulfones. The membrane can contain a first sulfonated polyphenylether sulfone and a second sulfonated polyphenylether sulfone, wherein the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone have equivalent weights greater than about 560, and the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone also have different equivalent weights. Also, a membrane for use in a fuel cell can contain a sulfonated polyphenylether sulfone and an unsulfonated polyphenylether sulfone. Methods for manufacturing a membrane electrode assemblies for use in fuel cells can include roughening a membrane surface. Electrodes and methods for fabricating such electrodes for use in a chemical fuel cell can include sintering an electrode. Such membranes and electrodes can be assembled into chemical fuel cells.

Yen, Shiao-Ping S. (Inventor); Kindler, Andrew (Inventor); Yavrouian, Andre (Inventor); Halpert, Gerald (Inventor)

2000-01-01

55

Polymer electrolyte membrane assembly for fuel cells  

NASA Technical Reports Server (NTRS)

An electrolyte membrane for use in a fuel cell can contain sulfonated polyphenylether sulfones. The membrane can contain a first sulfonated polyphenylether sulfone and a second sulfonated polyphenylether sulfone, wherein the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone have equivalent weights greater than about 560, and the first sulfonated polyphenylether and the second sulfonated polyphenylether sulfone also have different equivalent weights. Also, a membrane for use in a fuel cell can contain a sulfonated polyphenylether sulfone and an unsulfonated polyphenylether sulfone. Methods for manufacturing a membrane electrode assemblies for use in fuel cells can include roughening a membrane surface. Electrodes and methods for fabricating such electrodes for use in a chemical fuel cell can include sintering an electrode. Such membranes and electrodes can be assembled into chemical fuel cells.

Yen, Shiao-Ping S. (Inventor); Kindler, Andrew (Inventor); Yavrouian, Andre (Inventor); Halpert, Gerald (Inventor)

2002-01-01

56

Advanced composite polymer electrolyte fuel cell membranes  

SciTech Connect

A new type of reinforced composite perfluorinated polymer electrolyte membrane, GORE-SELECT{trademark} (W.L. Gore & Assoc.), is characterized and tested for fuel cell applications. Very thin membranes (5-20 {mu}m thick) are available. The combination of reinforcement and thinness provides high membrane, conductances (80 S/cm{sup 2} for a 12 {mu}m thick membrane at 25{degrees}C) and improved water distribution in the operating fuel cell without sacrificing longevity or durability. In contrast to nonreinforced perfluorinated membranes, the x-y dimensions of the GORE-SELECT membranes are relatively unaffected by the hydration state. This feature may be important from the viewpoints of membrane/electrode interface stability and fuel cell manufacturability.

Wilson, M.S.; Zawodzinski, T.A.; Gottesfeld, S.; Kolde, J.A.; Bahar, B.

1995-09-01

57

Detecting Microdomains in Intact Cell Membranes  

NASA Astrophysics Data System (ADS)

Current models for cellular plasma membranes focus on spatial heterogeneity and how this heterogeneity relates to cell function. In particular, putative lipid raft membrane domains have been postulated to exist based in large part on the results that a significant fraction of the membrane is detergent insoluble and that molecules facilitating key membrane processes like signal transduction are often found in the detergent-resistant membrane fraction. Yet, the in vivo existence of lipid rafts remains extremely controversial because, despite being sought for more than a decade, evidence for their presence in intact cell membranes is inconclusive. In this review, a variety of experimental techniques that have been or might be used to look for lipid microdomains in intact cell membranes are described. Experimental results are highlighted and the strengths and limitations of different techniques for microdomain identification and characterization are assessed.

Lagerholm, B. Christoffer; Weinreb, Gabriel E.; Jacobson, Ken; Thompson, Nancy L.

2005-05-01

58

Fuel cell ion-exchange membrane investigation  

NASA Technical Reports Server (NTRS)

The present deficiencies in the fluorocarbon sulfonic acid membrane used as the solid polymer electrolyte in the H2/O2 fuel cell are studied. Considered are: Adhesives selection, elastomeric formulations, scavenger exploration, and membrane characterization. The significant data are interpreted and recommendations are given for both short and long range further investigations in two of the four major areas: membrane adhesives and membrane stabilization.

Toy, M. S.

1972-01-01

59

Live cell imaging of membrane / cytoskeleton interactions and membrane topology  

PubMed Central

We elucidate the interaction between actin and specific membrane components, using real time live cell imaging, by delivering probes that enable access to components, that cannot be accessed genetically. We initially investigated the close interplay between Phosphatidylinositol 4,5-bisphosphate (PIP2) and the F-actin network. We show that, during the early stage of cell adhesion, PIP2 forms domains within the filopodia membrane. We studied these domains alongside cell spreading and observed that these very closely follow the actin tread-milling. We show that this mechanism is associated with an active transport of PIP2 rich organelles from the cell perinuclear area to the edge, along actin fibers. Finally, mapping other phospholipids and membrane components we observed that the PIP2 domains formation is correlated with sphingosine and cholesterol rafts. PMID:25205456

Chierico, Luca; Joseph, Adrian S.; Lewis, Andrew L.; Battaglia, Giuseppe

2014-01-01

60

Live cell imaging of membrane / cytoskeleton interactions and membrane topology  

NASA Astrophysics Data System (ADS)

We elucidate the interaction between actin and specific membrane components, using real time live cell imaging, by delivering probes that enable access to components, that cannot be accessed genetically. We initially investigated the close interplay between Phosphatidylinositol 4,5-bisphosphate (PIP2) and the F-actin network. We show that, during the early stage of cell adhesion, PIP2 forms domains within the filopodia membrane. We studied these domains alongside cell spreading and observed that these very closely follow the actin tread-milling. We show that this mechanism is associated with an active transport of PIP2 rich organelles from the cell perinuclear area to the edge, along actin fibers. Finally, mapping other phospholipids and membrane components we observed that the PIP2 domains formation is correlated with sphingosine and cholesterol rafts.

Chierico, Luca; Joseph, Adrian S.; Lewis, Andrew L.; Battaglia, Giuseppe

2014-09-01

61

ACTIVATED GRANULOCYTE INDUCED ALTERATIONS IN RED BLOOD CELLS AND PROTECTION BY ANTIOXIDANT ENZYMES  

Microsoft Academic Search

Activated leukocytes generate oxygen free radicals and cause injury in a variety of surrounding cells. Red blood cells (RBC) are among the most susceptible cells to this injury. Deformability, lipid peroxidation and membrane proteins were investigated in RBC after incubation with activated granulocytes (2 hours, at 37 °C), obtained from guinea pigs with experimental sepsis. A second group of experiments

Oguz K. Baskurt

62

Functional dynamics of cell surface membrane proteins  

NASA Astrophysics Data System (ADS)

Cell surface receptors are integral membrane proteins that receive external stimuli, and transmit signals across plasma membranes. In the conventional view of receptor activation, ligand binding to the extracellular side of the receptor induces conformational changes, which convert the structure of the receptor into an active conformation. However, recent NMR studies of cell surface membrane proteins have revealed that their structures are more dynamic than previously envisioned, and they fluctuate between multiple conformations in an equilibrium on various timescales. In addition, NMR analyses, along with biochemical and cell biological experiments indicated that such dynamical properties are critical for the proper functions of the receptors. In this review, we will describe several NMR studies that revealed direct linkage between the structural dynamics and the functions of the cell surface membrane proteins, such as G-protein coupled receptors (GPCRs), ion channels, membrane transporters, and cell adhesion molecules.

Nishida, Noritaka; Osawa, Masanori; Takeuchi, Koh; Imai, Shunsuke; Stampoulis, Pavlos; Kofuku, Yutaka; Ueda, Takumi; Shimada, Ichio

2014-04-01

63

Reincorporated plasma membrane Ca2+-ATPase can mediate B-Type Ca2+ channels observed in native membrane of human red blood cells.  

PubMed

Recently, we reported indirect evidence that plasma membrane Ca2+-ATPase (PMCA) can mediate B-type Ca2+ channels of cardiac myocytes. In the present study, in order to bring more direct evidence, purified PMCA from human red blood cells (RBC) was reconstituted into giant azolectin liposomes amenable to the patch-clamp technique. Purified RBC PMCA was used because it is available pure in larger quantity than cardiac PMCA. The presence of B-type Ca2+ channels was first investigated in native membranes of human RBC. They were detected and share the characteristics of cardiac myocytes. They spontaneously appeared in scarce short bursts of activity, they were activated by chlorpromazine (CPZ) with an EC50 of 149 mmole/l or 1 mmole/l vanadate, and then switched off by 10 mmole/l eosin or dose-dependently blocked by 1-5 mmole/l ATP. Independent of membrane potential, the channel gating exhibited complex patterns of many conductance levels, with three most often observed conductance levels of 22, 47 and 80 pS. The activation by vanadate suggests that these channels could play a role in the influx of extracellular Ca2+ involved in the vanadate-induced Gardos effect. In PMCA-reconstituted proteoliposomes, nearly half of the ATPase activity was retained and clear "channel-like" openings of Ba2+- or Ca2+-conducting channels were detected. Channel activity could be spontaneously present, lasting the patch lifetime or, when previously quiescent, activity could be induced by application of 50 mmole/l CPZ only in presence of 25 U/ml calmodulin (CaM), or by application of 1 mmole/l vanadate alone. Eosin (10 mmole/l) and ATP (5 mmole/l) significantly reduced spontaneous activity. Channel gating characteristics were similar to those of RBC, with main conductance levels of 21, 40 and 72 pS. The lack of direct activation by CPZ alone might be attributed to a purification-induced modification or absence of unidentified regulatory component(s) of PMCA. Despite a few differences in results between RBC and reincorporated PMCA, most probably attributable to the decrease in ATPase activity following the procedure of reincorporation, the present experimental conditions appear to reveal a channel-mode of the PMCA that shares many similarities with the B-type Ca2+ channel. PMID:12163977

Pinet, C; Antoine, S; Filoteo, A G; Penniston, J T; Coulombe, A

2002-06-01

64

Membrane proteomic analysis of pancreatic cancer cells  

PubMed Central

Background Pancreatic cancer is one of the most aggressive human tumors due to its high potential of local invasion and metastasis. The aim of this study was to characterize the membrane proteomes of pancreatic ductal adenocarcinoma (PDAC) cells of primary and metastatic origins, and to identify potential target proteins related to metastasis of pancreatic cancer. Methods Membrane/membrane-associated proteins were isolated from AsPC-1 and BxPC-3 cells and identified with a proteomic approach based on SDS-PAGE, in-gel tryptic digestion and liquid chromatography with tandem mass spectrometry (LC-MS/MS). X! Tandem was used for database searching against the SwissProt human protein database. Results We identified 221 & 208 proteins from AsPC-1 and BxPC-3 cells, respectively, most of which are membrane or membrane-associated proteins. A hundred and nine proteins were found in both cell lines while the others were present in either AsPC-1 or BxPC-3 cells. Differentially expressed proteins between two cell lines include modulators of cell adhesion, cell motility or tumor invasion as well as metabolic enzymes involved in glycolysis, tricarboxylic acid cycle, or nucleotide/lipid metabolism. Conclusion Membrane proteomes of AsPC-1 (metastatic) and BxPC-3 (primary) cells are remarkably different. The differentially expressed membrane proteins may serve as potential targets for diagnostic and therapeutic interventions. PMID:20831833

2010-01-01

65

Nitrite enhances RBC hypoxic ATP synthesis and the release of ATP into the vasculature: a new mechanism for nitrite-induced vasodilation.  

PubMed

A role for nitric oxide (NO) produced during the reduction of nitrite by deoxygenated red blood cells (RBCs) in regulating vascular dilation has been proposed. It has not, however, been satisfactorily explained how this NO is released from the RBC without first reacting with the large pools of oxyhemoglobin and deoxyhemoglobin in the cell. In this study, we have delineated a mechanism for nitrite-induced RBC vasodilation that does not require that NO be released from the cell. Instead, we show that nitrite enhances the ATP release from RBCs, which is known to produce vasodilation by several different methods including the interaction with purinergic receptors on the endothelium that stimulate the synthesis of NO by endothelial NO synthase. This mechanism was established in vivo by measuring the decrease in blood pressure when injecting nitrite-reacted RBCs into rats. The observed decrease in blood pressure was not observed if endothelial NO synthase was inhibited by N(omega)-nitro-L-arginine methyl ester (L-NAME) or when any released ATP was degraded by apyrase. The nitrite-enhanced ATP release was shown to involve an increased binding of nitrite-modified hemoglobin to the RBC membrane that displaces glycolytic enzymes from the membrane, resulting in the formation of a pool of ATP that is released from the RBC. These results thus provide a new mechanism to explain nitrite-induced vasodilation. PMID:19700624

Cao, Zeling; Bell, Jeffrey B; Mohanty, Joy G; Nagababu, Enika; Rifkind, Joseph M

2009-10-01

66

Moderate Exercise Promotes Human RBC-NOS Activity, NO Production and Deformability through Akt Kinase Pathway  

PubMed Central

Background Nitric oxide (NO) produced by nitric oxide synthase (NOS) in human red blood cells (RBCs) was shown to depend on shear stress and to exhibit important biological functions, such as inhibition of platelet activation. In the present study we hypothesized that exercise-induced shear stress stimulates RBC-NOS activation pathways, NO signaling, and deformability of human RBCs. Methods/Findings Fifteen male subjects conducted an exercise test with venous blood sampling before and after running on a treadmill for 1 hour. Immunohistochemical staining as well as western blot analysis were used to determine phosphorylation and thus activation of Akt kinase and RBC-NOS as well as accumulation of cyclic guanylyl monophosphate (cGMP) induced by the intervention. The data revealed that activation of NO upstream located enzyme Akt kinase was significantly increased after the test. Phosphorylation of RBC-NOSSer1177 was also significantly increased after exercise, indicating activation of RBC-NOS through Akt kinase. Total detectable RBC-NOS content and phosphorylation of RBC-NOSThr495 were not affected by the intervention. NO production by RBCs, determined by DAF fluorometry, and RBC deformability, measured via laser-assisted-optical-rotational red cell analyzer, were also significantly increased after the exercise test. The content of the NO downstream signaling molecule cGMP increased after the test. Pharmacological inhibition of phosphatidylinositol 3 (PI3)-kinase/Akt kinase pathway led to a decrease in RBC-NOS activation, NO production and RBC deformability. Conclusion/Significance This human in vivo study first-time provides strong evidence that exercise-induced shear stress stimuli activate RBC-NOS via the PI3-kinase/Akt kinase pathway. Actively RBC-NOS-produced NO in human RBCs is critical to maintain RBC deformability. Our data gain insights into human RBC-NOS regulation by exercise and, therefore, will stimulate new therapeutic exercise-based approaches for patients with microvascular disorders. PMID:23049912

Suhr, Frank; Brenig, Julian; Muller, Rebecca; Behrens, Hilke; Bloch, Wilhelm; Grau, Marijke

2012-01-01

67

Red cell membrane: past, present, and future  

PubMed Central

As a result of natural selection driven by severe forms of malaria, 1 in 6 humans in the world, more than 1 billion people, are affected by red cell abnormalities, making them the most common of the inherited disorders. The non-nucleated red cell is unique among human cell type in that the plasma membrane, its only structural component, accounts for all of its diverse antigenic, transport, and mechanical characteristics. Our current concept of the red cell membrane envisions it as a composite structure in which a membrane envelope composed of cholesterol and phospholipids is secured to an elastic network of skeletal proteins via transmembrane proteins. Structural and functional characterization of the many constituents of the red cell membrane, in conjunction with biophysical and physiologic studies, has led to detailed description of the way in which the remarkable mechanical properties and other important characteristics of the red cells arise, and of the manner in which they fail in disease states. Current studies in this very active and exciting field are continuing to produce new and unexpected revelations on the function of the red cell membrane and thus of the cell in health and disease, and shed new light on membrane function in other diverse cell types. PMID:18988878

Gallagher, Patrick G.

2008-01-01

68

Mitochondrial Membrane Potential in Aging Cells  

Microsoft Academic Search

Decreased mitochondrial membrane potential (??M) has been found in a variety of aging cell types from several mammalian species. The physiological significance and mechanisms of the decreased ??M in aging are not well understood. This review considers the generation of ??M and its role in ATP generation together with factors that modify ??M with emphasis on mitochondrial membrane permeability, particularly

Mary M. Sugrue; William G. Tatton

2001-01-01

69

Specific binding of Thiobacillus ferrooxidans RbcR to the intergenic sequence between the rbc operon and the rbcR gene.  

PubMed Central

The presence of two sets (rbcL1-rbcS1 and rbcL2-rbcS2) of rbc operons has been demonstrated in Thiobacillus ferrooxidans Fe1 (T. Kusano, T. Takeshima, C. Inoue, and K. Sugawara, J. Bacteriol. 173:7313-7323, 1991). A possible regulatory gene, rbcR, 930 bp long and possibly translated into a 309-amino-acid protein, was found upstream from the rbcL1 gene as a single copy. The gene is located divergently to rbcL1 with a 144-bp intergenic sequence. As in the cases of the Chromatium vinosum RbcR and Alcaligenes eutrophus CfxR, T. ferrooxidans RbcR is thought to be a new member of the LysR family, and these proteins share 46.5 and 42.8% identity, respectively. Gel mobility shift assays showed that T. ferrooxidans RbcR, produced in Escherichia coli, binds specifically to the intergenic sequence between rbcL1 and rbcR. Footprinting and site-directed mutagenesis experiments further demonstrated that RbcR binds to overlapping promoter elements of the rbcR and rbcL1 genes. The above data strongly support the participation of RbcR in regulation of the rbcL1-rbcS1 operon and the rbcR gene in T. ferrooxidans. Images PMID:8432695

Kusano, T; Sugawara, K

1993-01-01

70

Diffuse charge effects in fuel cell membranes  

E-print Network

It is commonly assumed that electrolyte membranes in fuel cells are electrically neutral, except in unsteady situations, when the double-layer capacitance is heuristically included in equivalent circuit calculations. Indeed, ...

Biesheuvel, P. M.

71

Alternate Fuel Cell Membranes for Energy Independence  

SciTech Connect

The overall objective of this project was the development and evaluation of novel hydrocarbon fuel cell (FC) membranes that possess high temperature performance and long term chemical/mechanical durability in proton exchange membrane (PEM) fuel cells (FC). The major research theme was synthesis of aromatic hydrocarbon polymers of the poly(arylene ether sulfone) (PAES) type containing sulfonic acid groups tethered to the backbone via perfluorinated alkylene linkages and in some cases also directly attached to the phenylene groups along the backbone. Other research themes were the use of nitrogen-based heterocyclics instead of acid groups for proton conduction, which provides high temperature, low relative humidity membranes with high mechanical/thermal/chemical stability and pendant moieties that exhibit high proton conductivities in the absence of water, and synthesis of block copolymers consisting of a proton conducting block coupled to poly(perfluorinated propylene oxide) (PFPO) blocks. Accomplishments of the project were as follows: 1) establishment of a vertically integrated program of synthesis, characterization, and evaluation of FC membranes, 2) establishment of benchmark membrane performance data based on Nafion for comparison to experimental membrane performance, 3) development of a new perfluoroalkyl sulfonate monomer, N,N-diisopropylethylammonium 2,2-bis(p-hydroxyphenyl) pentafluoropropanesulfonate (HPPS), 4) synthesis of random and block copolymer membranes from HPPS, 5) synthesis of block copolymer membranes containing high-acid-concentration hydrophilic blocks consisting of HPPS and 3,3'-disulfonate-4,4'-dichlorodiphenylsulfone (sDCDPS), 6) development of synthetic routes to aromatic polymer backbones containing pendent 1H-1,2,3-triazole moieties, 7) development of coupling strategies to create phase-separated block copolymers between hydrophilic sulfonated prepolymers and commodity polymers such as PFPO, 8) establishment of basic performance properties of experimental membranes, 9) fabrication and FC performance testing of membrane electrode assemblies (MEA) from experimental membranes, and 10) measurement of ex situ and in situ membrane durability of experimental membranes. Although none of the experimental hydrocarbon membranes that issued from the project displayed proton conductivities that met DOE requirements, the project contributed to our basic understanding of membrane structure-property relationships in a number of key respects. An important finding of the benchmark studies is that physical degradation associated with humidity and temperature variations in the FC tend to open new fuel crossover pathways and act synergistically with chemical degradation to accelerate overall membrane degradation. Thus, for long term membrane survival and efficient fuel utilization, membranes must withstand internal stresses due to humidity and temperature changes. In this respect, rigid aromatic hydrocarbon fuel cell membranes, e.g. PAES, offer an advantage over un-modified Nafion membranes. The benchmark studies also showed that broadband dielectric spectroscopy is a potentially powerful tool in assessing shifts in the fundamental macromolecular dynamics caused by Nafion chemical degradation, and thus, this technique is of relevance in interrogating proton exchange membrane durability in fuel cells and macromolecular dynamics as coupled to proton migration, which is of fundamental relevance in proton exchange membranes in fuel cells. A key finding from the hydrocarbon membrane synthesis effort was that rigid aromatic polymers containing isolated ion exchange groups tethered tightly to the backbone (short tether), such as HPPS, provide excellent mechanical and durability properties but do not provide sufficient conductivity, in either random or block configuration, when used as the sole ion exchange monomer. However, we continue to hypothesize that longer tethers, and tethered groups spaced more closely within the hydrophilic chain elements of the polymer, will yield highly conductive materials with excellent mech

Storey, Robson, F.; Mauritz, Kenneth, A.; Patton, Derek, L.; Savin, Daniel, A.

2012-12-18

72

Characterization of melanoma cell membrane tumor-associated antigens using xenoserum, alloserum, and autoserum: I. immunofluorescence.  

PubMed

Xenoantiserum, alloantiserum, and autoantiserum prepared against human melanoma cells from cell lines maintained in tissue culture were evaluated by indirect immunofluorescence (ind IF) for their content of antibodies reactive with melanoma cell membrane tumor-associated antigens (TAA). Following absorptions which removed all detectable anti-human species, anti-RBC, and anti-HLA antigen activity, the antisera were tested against a panel of human cell lines. Three apparently distinct melanoma-associated cell membrane antigens were detected. The first of these was present on all human cells maintained in tissue culture including cells of both malignant and nonmalignant origin. The second antigen was expressed on all cells of malignant origin and also by fetal fibroblasts. The third antigen was detectable only on melanoma cells and was expressed by a majority of the melanomas tested. No evidence was obtained to suggest the presence of melanoma TAA unique to a single melanoma cell line. Marked differences were observed in the antigenic profile detected by the three antisera. PMID:7003264

Mutzner, P A; Stuhlmiller, G M; Seigler, H F

1980-01-01

73

Toxic effects of Litsea elliptica Blume essential oil on red blood cells of Sprague-Dawley rats.  

PubMed

Litsea elliptica Blume leaves have been traditionally used as medicinal herbs because of its antimutagenicity, chemopreventative and insecticidal properties. In this study, the toxic effects of L. elliptica essential oil against Sprague-Dawley rat's red blood cells (RBCs) were evaluated. L. elliptica essential oil was given by oral gavage 5 times per week for 3 treated groups in the doses of 125, 250, and 500 mg/(kg body weight), respectively, and the control group received distilled water. Full blood count, RBC osmotic fragility, RBC morphological changes, and RBC membrane lipid were analyzed 28 d after the treatment. Although L. elliptica essential oil administration had significantly different effects on hemoglobin (Hb), mean cell hemoglobin concentration (MCHC), mean cell volume (MCV), and mean cell hemoglobin (MCH) in the experimental groups as compared to the control group (P<0.05), the values were still within the normal range. L. elliptica induced morphological changes of RBC into the form of echinocyte. The percentage of echinocyte increased significantly among the treated groups in a dose-response manner (P<0.001). The concentrations of RBC membrane phospholipids and cholesterol of all treated groups were significantly lower than those of control group (P<0.001). However, the RBC membrane osmotic fragility and total proteins of RBC membrane findings did not differ significantly between control and treated groups (P>0.05). It is concluded that structural changes in the RBC membrane due to L. elliptica essential oil administration did not cause severe membrane damage. PMID:19882755

Taib, Izatus Shima; Budin, Siti Balkis; Siti Nor Ain, Seri Maseran; Mohamed, Jamaludin; Louis, Santhana Raj; Das, Srijit; Sallehudin, Sulaiman; Rajab, Nor Fadilah; Hidayatulfathi, Othman

2009-11-01

74

Chronic kidney disease predicts impaired membrane microviscosity of red blood cells in hypertensive and normotensive subjects.  

PubMed

Current evidence indicates that abnormalities in physical properties of the cell membranes may be strongly linked to hypertension and other circulatory disorders. Recent studies have shown that chronic kidney disease (CKD) might be a risk factor for cardiovascular and cerebrovascular outcomes. The purpose of the present study was to examine the possible relationship between kidney function and membrane fluidity (a reciprocal value of membrane microviscosity) of red blood cells (RBCs) in hypertensive and normotensive subjects using an electron spin resonance (ESR) and spin-labeling method. The order parameter (S) for the ESR spin-label agent (5-nitroxide stearate) in RBC membranes was significantly higher in hypertensive subjects than in normotensive subjects, indicating that membrane fluidity was decreased in hypertension. The order parameter (S) of RBCs was inversely correlated with estimated glomerular filtration rate (eGFR), suggesting that a decreased eGFR value might be associated with reduced membrane fluidity of RBCs. Multivariate regression analysis also demonstrated that, after adjustment for general risk factors, eGFR might be a significant predictor of membrane fluidity of RBCs. The reduced levels of both membrane fluidity of RBCs and eGFR were associated with increased plasma 8-iso-prostaglandin F2? (an index of oxidative stress) and decreased plasma nitric oxide (NO)-metabolites, suggesting that kidney function could be a determinant of membrane microviscosity of RBCs, at least in part, via oxidative stress- and NO-dependent mechanisms. The ESR study suggests that CKD might have a close correlation with impaired rheologic behavior of RBCs and microcirculatory disorders in hypertensive subjects. PMID:23774239

Tsuda, Kazushi

2013-01-01

75

Protective effects of stem bark of Harungana madgascariensis on the red blood cell membrane  

PubMed Central

Background Anemia is a condition that has multiple origins. One such origin is the destruction of red blood cells’ (RBCs) membrane induced by free radicals. Treatment of anemia could therefore be enhanced by the use of free radicals’ scavengers potentially found in some medicinal plants. In this study, the protective effect of Harungana madagascariensis on the RBCs’ membrane physiology was investigated in vitro and in vivo. Methods In vitro hemolytic anemia was induced by incubation of fresh human RBCs with carbontetrachloride (CCl4) in Olive oil (Oo). Relaxation times of protons excited at 20 MHz (Carr-Purcell-Meiboom-Gill pulse sequence) in the absence or presence of paramagnetic Mn2+ ions (T2i for “extracellular” water and T2a for “intracellular” water, respectively) were determined at several temperatures (25–37°C) via Nuclear Magnetic Resonance (NMR) on a Bruker Minispec spectrometer. Water exchange times (Te) were consequently calculated using the Conlon-Outhred equation: 1/Te = (1/T2a) – (1/T2i). Morphological characteristics (mean cell volume, V, and cell surface area, A) were determined by photonic microscopy and the RBCs’ diffusional water permeability (Pd) was calculated as Pd = (1/Te)*(Va/A), where Va is the aqueous volume in the RBC and is about 0.7 of the cell volume (V). The activation energy of the diffusional process (Ea) for the respective temperature range was estimated using the Arrhenius modified equation k = A(T/T0)n*e-Ea/RT. Inhibition of the water diffusion induced by incubation with para-chloro-mercuribenzoic acid (PCMB) at 25, 30 and 37°C was calculated as I(%) = [(Pd control – Pd sample)/Pd control]*100. To investigate the protective influence of the extract on the RBC membrane, inhibition of the water permeability was evaluated on membranes pre-incubated with the Harungana madagascariensis extract. Male rats were used in in vivo investigations. Malondialdehyde (MDA) and cholesterol in the RBC membrane were estimated by induction of lipid peroxidation while the antioxidant properties of catalase (CAT) and superoxide dismutase (SOD) on the membrane were evaluated in regard to their antioxidant properties on the membrane. Results T2a significantly decreased at each temperature. Te results were higher in both RBCs and RBCs + extract groups incubated with PCMB compared to non-incubated controls, but differences were not statistically significant. A high percentage (73.81 ± 7.22) of RBCs pre-incubated with the extract presented the regular biconcave shape. Inhibition by PCMB of the RBCs’ membrane water permeability was increased at 30°C and decreased in the presence of extract (25°C and 37°C), while Ea decreased from 30.52 ± 1.3 KJ/mol to 25.49 ± 1.84 KJ/mol. Presence of the Harungana madagascariensis extract normalized the SOD and CAT activities as well as the MDA and membrane cholesterol concentrations altered by the CCl4-induced oxidative stress. Conclusion Harungana madagascariensis could protect the RBCs’ membrane through its antioxidative properties. PMID:23663227

2013-01-01

76

Asymptomatic elevation of the hyperchromic red blood cell subpopulation is associated with decreased red cell deformability.  

PubMed

Hyperchromasia of the red blood cells (RBC), defined as an elevation of the hyperchromic subpopulation, has been described for various medical conditions. However, neither the association of hyperchromasia with an altered RBC membrane nor with other medical conditions has been investigated in a systematic way so far. Since the percentage of hyperchromic RBC is measured on a routine basis by many hematologic laboratories, we evaluated the predictive value of this parameter for the detection of RBC disorders. An extensive workup of all patients undergoing standard hematogram during a period of 6 months at our institution with a fraction of hyperchromic RBC larger than 10 % was collected by reviewing the medical history and performing osmotic gradient ektacytometry on RBC from a part of these patients. Thirty-two thousand two hundred twenty-six individuals were screened; of which, 162 (0.5 %) showed more than 10 % hyperchromic RBC. All of the patients examined by ektacytometry featured abnormal membrane deformability. Hereditary spherocytosis was found in 19 out of these 32 patients, in most cases unknown to the patient and currently asymptomatic. Another 17.9 % of the patients with an elevated subpopulation of hyperchromic RBC suffered from viral infection (human immunodeficiency virus, hepatitis). Our study shows that an elevated proportion of hyperchromic erythrocytes larger than 10 % is associated with both hereditary and acquired RBC membrane disorders and further follow-up should be considered. PMID:22526368

Deuel, Jeremy W; Lutz, Hans U; Misselwitz, Benjamin; Goede, Jeroen S

2012-09-01

77

Temporal sequence of major biochemical events during Blood Bank storage of packed red blood cells  

PubMed Central

Background. We used sensitive spectroscopic techniques to measure changes in Band 3 oligomeric state during storage of packed red blood cells (RBC); these changes were compared to metabolic changes, RBC morphology, cholesterol and membrane protein loss, phospholipid reorganisation of the RBC membrane, and peroxidation of membrane lipid. The aim of the study was to temporally sequence major biochemical events occurring during cold storage, in order to determine which changes may underlie the structural defects in stored RBC. Materials and methods. Fifteen RBC units were collected from normal volunteers and stored under standard blood bank conditions; both metabolic changes and lipid parameters were measured by multiple novel assays including a new mass spectrometric measurement of isoprostane (lipid peroxidation) and flow cytometric assessment of CD47 expression. Band 3 oligomeric state was assessed by time-resolved phosphorescence anisotropy, and RBC morphology by microscopy of glutaraldehyde-fixed RBC. Results. Extracellular pH decreased and extracellular potassium increased rapidly during cold storage. Band 3 on the RBC membrane aggregated into large oligomers early in the storage period and coincident with changes in RBC morphology. Membrane lipid changes, including loss of unesterified cholesterol, lipid peroxidation and expression of CD47, also changed early during the storage period. In contrast loss of acetylcholinesterase activity and haemolysis of RBC occurred late during storage. Discussion. Our results demonstrate that changes in the macromolecular organisation of membrane proteins on the RBC occur early in storage and suggest that lipid peroxidation and/or oxidative damage to the membrane are responsible for irreversible morphological changes and loss of function during red cell storage. PMID:22507860

Karon, Brad S.; van Buskirk, Camille M.; Jaben, Elizabeth A.; Hoyer, James D.; Thomas, David D.

2012-01-01

78

Conjugated polymer nanoparticles for cell membrane imaging.  

PubMed

The outstanding optical properties and biocompatibility of fluorescent conjugated polymer nanoparticles (CPNs) make them favorable for bioimaging application. However, few CPNs could achieve stable cell membrane labeling due to cell endocytosis. In this work, conjugated polymer nanoparticles (PFPNP-PLE) encapsulated with PFP and PLGA-PEG-N3 in the matrix and functionalized with the small-molecule drug plerixafor (PLE) on the surface were prepared by a mini-emulsion method. PFPNP-PLE exhibits excellent photophysical properties, low cytotoxicity, and specific cytomembrane location, which makes it a potential cell membrane labeling reagent with blue fluorescence emission, an important component for multilabel/multicolor bioimaging. PMID:25200372

Li, Meng; Nie, Chenyao; Feng, Liheng; Yuan, Huanxiang; Liu, Libing; Lv, Fengting; Wang, Shu

2014-11-01

79

Basement Membranes: Cell Scaffoldings and Signaling Platforms  

PubMed Central

Basement membranes are widely distributed extracellular matrices that coat the basal aspect of epithelial and endothelial cells and surround muscle, fat, and Schwann cells. These extracellular matrices, first expressed in early embryogenesis, are self-assembled on competent cell surfaces through binding interactions among laminins, type IV collagens, nidogens, and proteoglycans. They form stabilizing extensions of the plasma membrane that provide cell adhesion and that act as solid-phase agonists. Basement membranes play a role in tissue and organ morphogenesis and help maintain function in the adult. Mutations adversely affecting expression of the different structural components are associated with developmental arrest at different stages as well as postnatal diseases of muscle, nerve, brain, eye, skin, vasculature, and kidney. PMID:21421915

Yurchenco, Peter D.

2011-01-01

80

Evaluation of Cell Membrane Electro-  

E-print Network

. Bleomycin at a 5-nM concentration causes no statisti- cally significant effect on cell survival blue (14) and lucifer yellow (6). The latter two methods, however, have considerable weaknesses. Namely a quantitative evaluation. Lucifer yellow fluoresces both inside and outside the cell, and thus the cell

Ljubljana, University of

81

Erythrocyte membrane is an alternative coating to polyethylene glycol for prolonging the circulation lifetime of gold nanocages for photothermal therapy.  

PubMed

Gold nanocages (AuNCs), which have tunable near-infrared (NIR) absorption and intrinsically high photothermal conversion efficiency, have been actively investigated as photothermal conversion agents for photothermal therapy (PTT). The short blood circulation lifetime of AuNCs, however, limits their tumor uptake and thus in vivo applications. Here we show that such a limitation can be overcome by cloaking AuNCs with red blood cell (RBC) membranes, a natural stealth coating. The fusion of RBC membranes over AuNC surface does not alter the unique porous and hollow structures of AuNCs, and the resulting RBC-membrane-coated AuNCs (RBC-AuNCs) exhibit good colloidal stability. Upon NIR laser irradiation, the RBC-AuNCs demonstrate in vitro photothermal effects and selectively ablate cancerous cells within the irradiation zone as do the pristine biopolymer-stealth-coated AuNCs. Moreover, the RBC-AuNCs exhibit significantly enhanced in vivo blood retention and circulation lifetime compared to the biopolymer-stealth-coated counterparts, as demonstrated using a mouse model. With integrated advantages of photothermal effects from AuNCs and long blood circulation lifetime from RBCs, the RBC-AuNCs demonstrate drastically enhanced tumor uptake when administered systematically, and mice that received PPT cancer treatment modulated by RBC-AuNCs achieve 100% survival over a span of 45 days. Taken together, our results indicate that the long circulating RBC-AuNCs may facilitate the in vivo applications of AuNCs, and the RBC-membrane stealth coating technique may pave the way to improved efficacy of PPT modulated by noble metal nanoparticles. PMID:25286086

Piao, Ji-Gang; Wang, Limin; Gao, Feng; You, Ye-Zi; Xiong, Yujie; Yang, Lihua

2014-10-28

82

Integration of Cell Membranes and Nanotube Transistors  

E-print Network

Integration of Cell Membranes and Nanotube Transistors Keith Bradley, Alona Davis, Jean. As the nanoelectronic device, we use a nanotube network transistor, which incorporates many individual nanotubes as transistors, and that the two systems interact. Further, we use the interaction to study the charge

Gruner, George

83

Membrane electrode assembly for a fuel cell  

NASA Technical Reports Server (NTRS)

A catalyst ink for a fuel cell including a catalytic material and poly(vinylidene fluoride). The ink may be applied to a substrate to form an electrode, or bonded with other electrode layers to form a membrane electrode assembly (MEA).

Prakash, Surya (Inventor); Narayanan, Sekharipuram R. (Inventor); Atti, Anthony (Inventor); Olah, George (Inventor); Smart, Marshall C. (Inventor)

2006-01-01

84

Strategy of red blood cells immobilisation onto a gold electrode: Characterization by electrochemical impedance spectroscopy and quartz crystal microbalance  

Microsoft Academic Search

This study describes the grafting of red blood cells (RBC) onto a gold electrode. The erythrocytes were immobilised using antigen\\/antibody crosslinking based on the bonding of anti-D with the corresponding antigen of the RBC membrane that is shared by all erythrocytes from the positive rhesus group (O+). To optimise the reproducibility of the modified electrode and to avoid nonspecific interactions,

C. Ribaut; K. Reybier; B. Torbiero; J. Launay; A. Valentin; O. Reynes; P.-L. Fabre; F. Nepveu

2008-01-01

85

Shedding of phosphatidylserine from developing erythroid cells involves microtubule depolymerization and affects membrane lipid composition.  

PubMed

Phosphatidylserine (PS), which is normally localized in the cytoplasmic leaflet of the membrane, flip-flops to the external leaflet during aging of, or trauma to, cells. A fraction of this PS undergoes shedding into the extracellular milieu. PS externalization and shedding change during maturation of erythroid cells and affect the functioning, senescence and elimination of mature RBCs. Several lines of evidence suggest dependence of PS shedding on intracellular Ca concentration as well as on interaction between plasma membrane phospholipids and microtubules (MTs), the key components of the cytoskeleton. We investigated the effect of Ca flux and MT assembly on the distribution of PS across, and shedding from, the membranes of erythroid precursors. Cultured human and murine erythroid precursors were treated with the Ca ionophore A23187, the MT assembly enhancer paclitaxel (Taxol) or the inhibitor colchicine. PS externalization and shedding were measured by flow cytometry and the cholesterol/phospholipids in RBC membranes and supernatants, by ¹H-NMR. We found that treatment with Taxol or colchicine resulted in a marked increase in PS externalization, while shedding was increased by colchicine but inhibited by Taxol. These results indicate that PS externalization is mediated by Ca flux, and PS shedding by both Ca flux and MT assembly. The cholesterol/phospholipid ratio in the membrane is modified by PS shedding; we now show that it was increased by colchicine and A23187, while taxol had no effect. In summary, the results indicate that the Ca flux and MT depolymerization of erythroid precursors mediate their PS externalization and shedding, which in turn changes their membrane composition. PMID:22825717

Freikman, Inna; Ringel, Israel; Fibach, Eitan

2012-12-01

86

Ligation of complement receptor 1 increases erythrocyte membrane deformability  

PubMed Central

Microbes as well as immune complexes and other continuously generated inflammatory particles are efficiently removed from the human circulation by red blood cells (RBCs) through a process called immune-adherence clearance. During this process, RBCs use complement receptor 1 (CR1, CD35) to bind circulating complement-opsonized particles and transfer them to resident macrophages in the liver and spleen for removal. We here show that ligation of RBC CR1 by antibody and complement-opsonized particles induces a transient Ca++ influx that is proportional to the RBC CR1 levels and is inhibited by T1E3 pAb, a specific inhibitor of TRPC1 channels. The CR1-elicited RBC Ca++ influx is accompanied by an increase in RBC membrane deformability that positively correlates with the number of preexisting CR1 molecules on RBC membranes. Biochemically, ligation of RBC CR1 causes a significant increase in phosphorylation levels of ?-spectrin that is inhibited by preincubation of RBCs with DMAT, a specific casein kinase II inhibitor. We hypothesize that the CR1-dependent increase in membrane deformability could be relevant for facilitating the transfer of CR1-bound particles from the RBCs to the hepatic and splenic phagocytes. PMID:20861458

Glodek, Aleksandra M.; Mirchev, Rossen; Golan, David E.; Khoory, Joseph A.; Burns, Jennie M.; Shevkoplyas, Sergey S.; Nicholson-Weller, Anne

2010-01-01

87

Ligation of complement receptor 1 increases erythrocyte membrane deformability.  

PubMed

Microbes as well as immune complexes and other continuously generated inflammatory particles are efficiently removed from the human circulation by red blood cells (RBCs) through a process called immune-adherence clearance. During this process, RBCs use complement receptor 1 (CR1, CD35) to bind circulating complement-opsonized particles and transfer them to resident macrophages in the liver and spleen for removal. We here show that ligation of RBC CR1 by antibody and complement-opsonized particles induces a transient Ca(++) influx that is proportional to the RBC CR1 levels and is inhibited by T1E3 pAb, a specific inhibitor of TRPC1 channels. The CR1-elicited RBC Ca(++) influx is accompanied by an increase in RBC membrane deformability that positively correlates with the number of preexisting CR1 molecules on RBC membranes. Biochemically, ligation of RBC CR1 causes a significant increase in phosphorylation levels of ?-spectrin that is inhibited by preincubation of RBCs with DMAT, a specific casein kinase II inhibitor. We hypothesize that the CR1-dependent increase in membrane deformability could be relevant for facilitating the transfer of CR1-bound particles from the RBCs to the hepatic and splenic phagocytes. PMID:20861458

Glodek, Aleksandra M; Mirchev, Rossen; Golan, David E; Khoory, Joseph A; Burns, Jennie M; Shevkoplyas, Sergey S; Nicholson-Weller, Anne; Ghiran, Ionita C

2010-12-23

88

Aging of cell membranes: facts and theories.  

PubMed

This chapter is intended to outline the main results of a research trend realized by the author during the last 45 years, focused on the main role played by the cell membrane in the aging process. It is a very wide field; therefore, the reader cannot expect in this limited space a detailed description, but will be given a wide, interdisciplinary insight into the main facts and theories regarding cellular aging. The central idea described here is the concept called the membrane hypothesis of aging (MHA). The history, the chemical roots, physicochemical facts, biophysical processes, as well as the obligatory biochemical consequences are all touched in by indicating the most important sources of detailed knowledge for those who are more interested in the basic biology of the aging process. This chapter covers also the available anti-aging interventions on the cell membrane by means of the centrophenoxine treatment based on the MHA. It also briefly interprets the possibilities of a just developing anti-aging method by using the recombinant human growth hormone, essential basis of which is the species specificity, and the general presence of receptors of this hormone in the plasma membrane of all types of cells. PMID:24862015

Zs-Nagy, Imre

2014-01-01

89

Catalytic membranes for fuel cells  

DOEpatents

A fuel cell of the present invention comprises a cathode and an anode, one or both of the anode and the cathode including a catalyst comprising a bundle of longitudinally aligned graphitic carbon nanotubes including a catalytically active transition metal incorporated longitudinally and atomically distributed throughout the graphitic carbon walls of said nanotubes. The nanotubes also include nitrogen atoms and/or ions chemically bonded to the graphitic carbon and to the transition metal. Preferably, the transition metal comprises at least one metal selected from the group consisting of Fe, Co, Ni, Mn, and Cr.

Liu, Di-Jia (Naperville, IL); Yang, Junbing (Bolingbrook, IL); Wang, Xiaoping (Naperville, IL)

2011-04-19

90

The Tripartite Type III Secreton of Shigella flexneri Inserts IpaB and IpaC into Host Membranes  

Microsoft Academic Search

Bacterial type III secretion systems serve to translocate proteins into eukaryotic cells, requiring a secreton and a translocator for proteins to pass the bacterial and host membranes. We used the contact hemolytic activity of Shigella flexneri to investigate its putative translocator. Hemolysis was caused by forma- tion of a 25-Å pore within the red blood cell (RBC) membrane. Of the

Ariel Blocker; Pierre Gounon; Eric Larquet; Kirsten Niebuhr; Véronique Cabiaux; Claude Parsot; Philippe Sansonetti

1999-01-01

91

Sputter-deposited fuel cell membranes and electrodes  

NASA Technical Reports Server (NTRS)

A method for preparing a membrane for use in a fuel cell membrane electrode assembly includes the steps of providing an electrolyte membrane, and sputter-depositing a catalyst onto the electrolyte membrane. The sputter-deposited catalyst may be applied to multiple sides of the electrolyte membrane. A method for forming an electrode for use in a fuel cell membrane electrode assembly includes the steps of obtaining a catalyst, obtaining a backing, and sputter-depositing the catalyst onto the backing. The membranes and electrodes are useful for assembling fuel cells that include an anode electrode, a cathode electrode, a fuel supply, and an electrolyte membrane, wherein the electrolyte membrane includes a sputter-deposited catalyst, and the sputter-deposited catalyst is effective for sustaining a voltage across a membrane electrode assembly in the fuel cell.

Narayanan, Sekharipuram R. (Inventor); Jeffries-Nakamura, Barbara (Inventor); Chun, William (Inventor); Ruiz, Ron P. (Inventor); Valdez, Thomas I. (Inventor)

2001-01-01

92

Change dynamics of RBC morphology after injection glucose for diabetes by diffraction phase microscope  

NASA Astrophysics Data System (ADS)

Experimental setup of diffraction phase microscope (DPM) with double low-coherence lighting system is presented in the paper. Algorithm of interference picture processing and optical thickness, height, volume and mean cells volume (MCV) of RBC calculating is shown. We demonstrate results of experiments with blood smears and ability of the method to calculate 3D model of the biological cells shape. Investigation change dynamics of RBC morphology after injection glucose for diabetes by DPM is shown in the paper.

Talaykova, N. A.; Kalyanov, A. L.; Lychagov, V. V.; Ryabukho, V. P.; Malinova, L. I.

2013-11-01

93

Particle method for computer simulation of red blood cell motion in blood flow.  

PubMed

A particle method for the computer simulation of blood flow was proposed to analyze the motion of a deformable red blood cell (RBC) in flowing blood plasma. The RBC and plasma were discretized by particles that have the characteristics of an elastic membrane and a viscous fluid, respectively. The membrane particles were connected to their neighboring membrane particles by springs, and the motion of the particles was determined on the basis of the minimum energy principle. The incompressible flow of plasma that was expressed by the motion of the fluid particles was determined by the moving-particle semi-implicit (MPS) method. The RBC motion and plasma flow were weakly coupled. The two-dimensional simulation of blood flow between parallel plates demonstrated the capability of the proposed method to express the blood flow phenomena observed in experiments, such as the downstream motion of the RBC and the deformation of the RBC into a parachute shape. PMID:16879895

Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, Takami

2006-08-01

94

Dynamics of photoinduced cell plasma membrane injury.  

PubMed Central

We have developed a video microscopy system designed for real-time measurement of single cell damage during photolysis under well defined physicochemical and photophysical conditions. Melanoma cells cultured in vitro were treated with the photosensitizer (PS), tin chlorin e6 (SnCe6) or immunoconjugate (SnCe6 conjugated to a anti-ICAM monoclonal antibody), and illuminated with a 10 mW He/Ne laser at a 630 nm wavelength. Cell membrane integrity was assessed using the vital dye calcein-AM. In experiments in which the laser power density and PS concentration were varied, it was determined that the time lag before cell rupture was inversely proportional to the estimated singlet oxygen flux to the cell surface. Microscopic examination of the lytic event indicated that photo-induced lysis was caused by a point rupture of the plasma membrane. The on-line nature of this microscopy system offers an opportunity to monitor the dynamics of the cell damage process and to gain insights into the mechanism governing photolytic cell injury processes. Images FIGURE 2 FIGURE 3 FIGURE 6 FIGURE 7 PMID:7612864

Thorpe, W P; Toner, M; Ezzell, R M; Tompkins, R G; Yarmush, M L

1995-01-01

95

Focus on the physics of the cell membrane  

NASA Astrophysics Data System (ADS)

This focus issue on membrane biophysics presents a collection of papers illustrating new developments in modern biophysical research on cell membranes. The work described here addresses questions from a broad range of areas, including cell adhesion, membrane trafficking and activation of cells of the immune system. It also presents recent views on membrane mechanics, the effect of electric fields, as well as on the interplay of mechanics and chemistry and organization at many different scales.

Bassereau, Patricia; Phillips, Rob; Schwille, Petra

2012-05-01

96

Different activities of the reovirus FAST proteins and influenza hemagglutinin in cell-cell fusion assays and in response to membrane curvature agents  

SciTech Connect

The reovirus fusion-associated small transmembrane (FAST) proteins evolved to induce cell-cell, rather than virus-cell, membrane fusion. It is unclear whether the FAST protein fusion reaction proceeds in the same manner as the enveloped virus fusion proteins. We now show that fluorescence-based cell-cell and cell-RBC hemifusion assays are unsuited for detecting lipid mixing in the absence of content mixing during FAST protein-mediated membrane fusion. Furthermore, membrane curvature agents that inhibit hemifusion or promote pore formation mediated by influenza hemagglutinin had no effect on p14-induced cell-cell fusion, even under conditions of limiting p14 concentrations. Standard assays used to detect fusion intermediates induced by enveloped virus fusion proteins are therefore not applicable to the FAST proteins. These results suggest the possibility that the nature of the fusion intermediates or the mechanisms used to transit through the various stages of the fusion reaction may differ between these distinct classes of viral fusogens.

Clancy, Eileen K.; Barry, Chris; Ciechonska, Marta [Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, B3H 1X5 (Canada); Duncan, Roy, E-mail: roy.duncan@dal.c [Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, B3H 1X5 (Canada); Department of Pediatrics, Dalhousie University, Halifax, Nova Scotia, B3H 1X5 (Canada)

2010-02-05

97

Analysis of red blood cell deformation under fast shear flow for better estimation of hemolysis.  

PubMed

We examined the deformation behavior of a red blood cell (RBC) in various flow fields to determine whether the extent of RBC deformation is correlated with the shear stress used as a hemolysis index. The RBC model was introduced to a simple shear flow (Couette flow) and to slightly complex flows (unsteady shear flows and stenosed flows). The RBC deformation was assessed by the maximum first principal strain over the RBC membrane and compared with the shear stress. Although the results were consistent under steady Couette flow, this was not the case under unsteady Couette flow or stenosed flow due to the viscoelastic nature of the RBC deformation caused by fluid forces. These results suggest that there is a limitation in accurately estimating the mechanical damage of RBCs solely from a macroscopic flow field, indicating the necessity of taking into account the dynamic deformation of RBCs to provide a better estimation of hemolysis. PMID:23949912

Nakamura, Masanori; Bessho, Sadao; Wada, Shigeo

2014-01-01

98

Micropatterning cells on permeable membrane filters.  

PubMed

Epithelium is abundantly present in the human body as it lines most major organs. Therefore, ensuring the proper function of epithelium is pivotal for successfully engineering whole organ replacements. An important characteristic of mature epithelium is apical-basal polarization which can be obtained using the air-liquid interface (ALI) culture system. Micropatterning is a widely used bioengineering strategy to spatially control the location and organization of cells on tissue culture substrates. Micropatterning is therefore an interesting method for generating patterned epithelium. Enabling micropatterning of epithelial cells however requires micropatterning methods that are designed to (i) be compatible with permeable membranes substrates and (ii) allow prolonged culture of patterned cells, both of which are required for appropriate epithelial apical-basal polarization. Here, we describe a number of methods we have developed for generating monoculture as well as coculture of epithelial cells that are compatible with ALI culture. PMID:24560510

Javaherian, Sahar; Paz, Ana C; McGuigan, Alison P

2014-01-01

99

Fluorescence imaging of membrane dynamics in living cells  

NASA Astrophysics Data System (ADS)

Methods of wide-field fluorescence microscopy for measuring membrane dynamics of living cells are described, including spectral imaging as well as anisotropy imaging of the membrane marker 6-dodecanoyl-2-dimethylamino naphthalene (laurdan). Plasma membranes are selected by illumination with an evanescent electromagnetic field and distinguished from intracellular membranes assessed by whole-cell illumination. While fluorescence spectra of laurdan appeared red-shifted with decreasing membrane stiffness, fluorescence anisotropy and rotational correlation times were reduced with increasing membrane fluidity. Membrane stiffness was found to increase with decreasing temperature and increasing amounts of cholesterol and was always higher for the plasma membrane than for intracellular membranes. These effects may have some clinical relevance in the research of drug resistance or cell aging.

Weber, Petra; Wagner, Michael; Schneckenburger, Herbert

2010-07-01

100

Nanosecond electric pulses cause mitochondrial membrane permeabilization in Jurkat cells.  

PubMed

Nanosecond, high-voltage electric pulses (nsEP) induce permeabilization of the plasma membrane and the membranes of cell organelles, leading to various responses in cells including cytochrome c release from mitochondria and caspase activation associated with apoptosis. We report here evidence for nsEP-induced permeabilization of mitochondrial membranes in living cells. Using three different methods with fluorescence indicators-rhodamine 123 (R123), tetramethyl rhodamine ethyl ester (TMRE), and cobalt-quenched calcein-we have shown that multiple nsEP (five pulses or more, 4?ns duration, 10?MV/m, 1?kHz repetition rate) cause an increase of the inner mitochondrial membrane permeability and an associated loss of mitochondrial membrane potential. These effects could be a consequence of nsEP permeabilization of the inner mitochondrial membrane or the activation of mitochondrial membrane permeability transition pores. Plasma membrane permeabilization (YO-PRO-1 influx) was detected in addition to mitochondrial membrane permeabilization. PMID:21953203

Batista Napotnik, Tina; Wu, Yu-Hsuan; Gundersen, Martin A; Miklav?i?, Damijan; Vernier, P Thomas

2012-04-01

101

Origin of subdiffusion of water molecules on cell membrane surfaces  

NASA Astrophysics Data System (ADS)

Water molecules play an important role in providing unique environments for biological reactions on cell membranes. It is widely believed that water molecules form bridges that connect lipid molecules and stabilize cell membranes. Using all-atom molecular dynamics simulations, we show that translational and rotational diffusion of water molecules on lipid membrane surfaces exhibit subdiffusion and aging. Moreover, we provide evidence that both divergent mean trapping time (continuous-time random walk) and long-correlated noise (fractional Brownian motion) contribute to this subdiffusion. These results suggest that subdiffusion on cell membranes causes the water retardation, an enhancement of cell membrane stability, and a higher reaction efficiency.

Yamamoto, Eiji; Akimoto, Takuma; Yasui, Masato; Yasuoka, Kenji

2014-04-01

102

Origin of subdiffusion of water molecules on cell membrane surfaces  

E-print Network

Water molecules play an important role in providing unique environments for biological reactions on cell membranes. It is widely believed that water molecules form bridges that connect lipid molecules and stabilize cell membranes. Using all-atom molecular dynamics simulations, we show that translational and rotational diffusion of water molecules on lipid membrane surfaces exhibit subdiffusion. Moreover, we provide evidence that both divergent mean trapping time (continuous-time random walk) and long-correlated noise (fractional Brownian motion) contribute to this subdiffusion. These results suggest that subdiffusion on cell membranes causes the water retardation, an enhancement of cell membrane stability, and a higher reaction efficiency.

Yamamoto, Eiji; Yasui, Masato; Yasuoka, Kenji

2014-01-01

103

Polymer synthesis toward fuel cell membrane materials  

NASA Astrophysics Data System (ADS)

Fuel cells are a promising technology that will be part of the future energy landscape. New membranes for alkaline and proton exchange membrane fuel cells are needed to improve the performance, simplify the system, and reduce cost. Polymer chemistry can be applied to develop new polymers and to assemble polymers into improved membranes that need less water, have increased performance and are less expensive, thereby removing the deficiencies of current membranes. Nucleophilic aromatic substitution polymerization typically produces thermally stable engineering polymers that can be easily functionalized. New functional monomers were developed to explore new routes to novel functional polymers. Sulfonamides were discovered as new activating groups for polymerization of high molecular weight thermooxidatively stable materials with sulfonic acid latent functionality. While the sulfonamide functional polymers could be produced, the sulfonamide group proved to be too stable to convert into a sulfonic acid after reaction. The reactivity of 2-aminophenol was investigated to search for a new class of ion conducting polymer materials. Both the amine and the phenol groups are found to be reactive in a nucleophilic aromatic substitution, however not to the extent to allow the formation of high molecular weight polymer materials. Layer-by-layer films were assembled from aqueous solutions of poly(styrene sulfonate) and trimethylammonium functionalized poly(phenylene oxide). The deposition conditions were adjusted to increase the free charge carrier content, and chloride conductivites reached almost 30 mS/cm for the best films. Block and random poly(phenylene oxide) copolymers were produced from 2,6-dimethylphenol and 2,6-diphenylphenol and the methyl substituted repeat units were functionalized with trimethylammonium bromide. The block copolymers displayed bromide conductivities up to 26 mS/cm and outperformed the random copolymers, indicating that morphology has an effect on ion transport.

Rebeck, Nathaniel T.

104

Altered Erythrocyte Membrane Protein Composition in Chronic Kidney Disease Stage 5 Patients under Haemodialysis and Recombinant Human Erythropoietin Therapy  

Microsoft Academic Search

Our aim was to evaluate red blood cell (RBC) membrane protein composition in chronic kidney disease (CKD) stage 5 patients under haemodialysis (HD) and recombinant human erythropoietin (rhEPO) therapy, and its linkage to rhEPO hyporesponsiveness. We evaluated in 63 CKD stage 5 patients (32 responders and 31 non-responders to rhEPO therapy) and in 26 healthy controls RBC count, haematocrit, haemoglobin

Elísio Costa; Susana Rocha; Petronila Rocha-Pereira; Elisabeth Castro; Vasco Miranda; Maria do Sameiro Faria; Alfredo Loureiro; Alexandre Quintanilha; Luís Belo; Alice Santos-Silva

2008-01-01

105

Measurement of the nonlinear elasticity of red blood cell membranes  

E-print Network

The membranes of human red blood cells (RBCs) are a composite of a fluid lipid bilayer and a triangular network of semiflexible filaments (spectrin). We perform cellular microrheology using the dynamic membrane fluctuations ...

Park, YongKeun

106

Computational Modeling and Optimization of Proton Exchange Membrane Fuel Cells  

E-print Network

Computational Modeling and Optimization of Proton Exchange Membrane Fuel Cells by Marc Secanell and Optimization of Proton Exchange Membrane Fuel Cells by Marc Secanell Gallart Bachelor in Engineering cells. In this thesis, a computational framework for fuel cell analysis and optimization is presented

Victoria, University of

107

Interaction between Cell Penetrating pVEC and cell membranes  

NASA Astrophysics Data System (ADS)

Vascular Endothelial Cadherin (VEC) is a transmembrane-spanning glycoprotein that belongs to the family of cell adhesion molecules and plays an active role in control of vascular permeability and angiogenesis. PVEC, an 18 amino acid domain, has been shown to be able to traverse cell membranes with attached macromolecules. pVEC is an amphiphilic molecule with a high content of basic amino acids resulting in a net positive charge. Electrostatic and hydrophobic interactions can perturb membrane self-assembly and stability and are likely to be responsible for peptide uptake. We use synchrotron x-ray scattering and confocal microscopy to examine the phase behavior of the pVEC lipid system, and its relation to membrane permeation mechanisms.

Mishra, Abhijit; Hwee Lai, Ghee; Schmidt, Nathan; Wong, Gerard

2011-03-01

108

Dynamics of a vesicle as a cell mimic: Effects of interior structure, cross-membrane transport, and interaction with filaments  

E-print Network

, 28, 33, 46]. The membrane encapsulates cellular content such as the spectrin-actin cytoskeletal. On the sub-cellular scale, the RBC has a membrane skeleton comprised of a sprectin and actin network will cause the spectrin proteins to dissociate from the actin. These topological defects in the spectrin-actin

Young, Yuan N.

109

Dielectrophoretic discrimination of bovine red blood cell starvation age by buffer selection and membrane  

E-print Network

Dielectrophoretic discrimination of bovine red blood cell starvation age by buffer selection and discrimination of bovine red blood cell bRBC star- vation age. The buffer composition is selected such that two with a glutaraldehyde cross-linking cell fixation reaction, which allows for sensitive dielectrophoretic analysis

Chang, Hsueh-Chia

110

Computational analysis of dynamic interaction of two red blood cells in a capillary.  

PubMed

The dynamic interaction of two red blood cells (RBCs) in a capillary is investigated computationally by the two-fluid model, including their deformable motion and interaction. For characterization of the deformation, the RBC membrane is treated as a curved two-dimensional shell with finite thickness by the shell model, and allowed to undergo the stretching strain and bending deformation. Moreover, a Morse potential is adopted to model the intercellular interaction for the aggregation behavior, which is characterized as the weak attraction at far distance and strong repulsion at near distance. For validation of the present technique, the dynamic interaction of two RBCs in static blood plasma is simulated firstly, where the RBCs aggregate slowly until a balanced configuration is achieved between the deformation and aggregation forces. The balanced configuration is in good agreement with the results reported previously. Three important effects on the dynamic behavior of RBCs are then analyzed, and they are the initial RBC shape, RBC deformability, and the intercellular interaction strength. It is found that the RBC is less deformed into a well-known parachute shape when the initial RBC shape is larger. Similarly, if the elastic shear modulus and bending stiffness of RBC membrane increase, the RBC resistance to deformation becomes higher, such that the RBC is less deformed. The simulation results also demonstrate that the RBC deformability strongly depends on the intercellular interaction strength. The RBCs deform more easily as the intercellular interaction strength increases. PMID:24590262

Li, Hua; Ye, Ting; Lam, K Y

2014-07-01

111

Membrane thickness is an important variable in membrane scaffolds: Influence of chitosan membrane structure on the behavior of cells  

PubMed Central

Cell and tissue responses to polymeric materials are orchestrated in part by the conformations of adsorbed plasma proteins. Thus, the chemical properties of a polymer membrane that govern protein adsorption behaviour can play an important role in determining the biological properties of tissue engineered scaffolds derived from that polymer. In this study, we explored the role of membrane thickness as a factor influencing cell adhesion and proliferation on chitosan membranes with and without covalently-attached glycosaminoglycans. Rat mesenchymal stem cells cultured on chitosan membranes of various thicknesses demonstrated significantly improved cell adhesion, spreading and proliferation as membrane thickness was increased. Hepatocytes displayed increased spreading on the substrate with increasing membrane thickness similar to MSCs. Increased thickness reduced the overall crystallinity of the membrane, and the data indicate that the improved cellular responses were likely due to enhanced adsorption of serum vitronectin, presumably due to reduced membrane crystallinity. These results demonstrate that membrane thickness is an important design variable that can be manipulated in chitosan-based scaffolds to achieve enhanced cell spreading, proliferation and function. PMID:19925888

Uygun, Basak E.; Bou-Akl, Therese; Albanna, Mohammad

2009-01-01

112

Cholesterol:phospholipid ratio is elevated in platelet plasma membrane in patients with hypertension.  

PubMed

The cholesterol:phospholipid ratio was measured in platelet plasma membrane, red blood cell (RBC) membranes, low density lipoprotein (LDL) and whole plasma in patients with primary hypertension and in matched normal controls. The cholesterol:phospholipid ratio was raised in the platelet membrane from hypertensive patients compared with that from normal controls (0.65 +/- 0.03 vs 0.53 +/- 0.02: mean +/- SEM; P less than 0.01). The ratio observed in RBC membranes, LDL and whole blood was similar in the two groups. If this abnormality in the lipid composition of platelet plasma membrane is present in other cells it could account for some of the changes in cell membrane function that have been described in hypertension. PMID:2362260

Benjamin, N; Robinson, B F; Graham, J G; Wilson, R B

1990-06-01

113

The membrane proteome of the mouse lens fiber cell  

PubMed Central

Purpose Fiber cells of the ocular lens are bounded by a highly specialized plasma membrane. Despite the pivotal role that membrane proteins play in the physiology and pathophysiology of the lens, our knowledge of the structure and composition of the fiber cell plasma membrane remains fragmentary. In the current study, we utilized mass spectrometry-based shotgun proteomics to provide a comprehensive survey of the mouse lens fiber cell membrane proteome. Methods Membranes were purified from young mouse lenses and subjected to MudPIT (Multidimensional protein identification technology) analysis. The resulting proteomic data were analyzed further by reference to publically available microarray databases. Results More than 200 membrane proteins were identified by MudPIT, including Type I, Type II, Type III (multi-pass), lipid-anchored, and GPI-anchored membrane proteins, in addition to membrane-associated cytoskeletal elements and extracellular matrix components. The membrane proteins of highest apparent abundance included Mip, Lim2, and the lens-specific connexin proteins Gja3, Gja8, and Gje1. Significantly, many proteins previously unsuspected in the lens were also detected, including proteins with roles in cell adhesion, solute transport, and cell signaling. Conclusions The MudPIT technique constitutes a powerful technique for the analysis of the lens membrane proteome and provides valuable insights into the composition of the lens fiber cell unit membrane. PMID:19956408

Wilmarth, Phillip A.; David, Larry L.

2009-01-01

114

Effects of vitamin E supplementation on blood antioxidants levels in patients with Behçet’s disease 1 1 Abbreviations: ASO, anti-streptolysin-o; BD, Behçet’s disease; CRP, C reactive protein; ESR, erythrocyte sedimentation rate; GSH, reduced glutathione; GSH-Px, glutathione peroxidase; Lp (a), lipoprotein a; MDA, malondialdehyde; RBC, red blood cells; RF, rheumatoid factor; ROS, reactive oxygen species; SOD, superoxide dismutase; WBC, white blood cells  

Microsoft Academic Search

Behçet’s disease (BD) is known for many years, yet its etiology remains unknown. In BD, the increased production of reactive oxygen species from activated neutrophils may reduce concentrations of antioxidant vitamins and enzymes in plasma and red blood cells (RBC). Vitamin E is an important fat soluble antioxidant and its role on antioxidant parameters of BD is unclear. The study

Ibrahim Kökçam; Mustafa Naz?ro?lu

2002-01-01

115

CO2-SELECTIVE MEMBRANE FOR FUEL CELL APPLICATIONS.  

E-print Network

??We have developed CO2-selective membranes to purified hydrogen and nitrogenfor fuel cell processes. Hydrogen purification impacts other industries such as ammoniaproduction and flue gas purification… (more)

El-Azzami, Louei Abdel Raouf

2006-01-01

116

Stabilization/destabilization of cell membranes by multivalent ions: Implications for membrane fusion and division  

E-print Network

We propose a mechanism for the stabilization/destabilization of cell membranes by multivalent ions with an emphasis on its implications for the division and fusion of cells. We find that multivalent cations preferentially adsorbed onto a membrane dramatically changes the membrane stability. They not only reduce the surface charge density of the membrane but also induce a repulsive barrier to pore growth. While both of these effects lead to enhanced membrane stability against vesiculation and pore growth, the repulsive barrier arises from correlated fluctuations of the adsorbed cations and favors closure of a pore. Finally, the addition of a small amount of multivalent anions can reverse the membrane stabilization, providing an effective way to regulate membrane stability.

Bae-Yeun Ha

2000-05-31

117

Red blood cell deformability and alcohol dependence in humans.  

PubMed

Studies of DPH fluorescence polarization and deformability have shown that alcohol induces rigidification of the red blood cell (RBC) membrane. We investigated a possible link between RBC membrane fluidity and deformability by studying both parameters simultaneously in samples from alcohol-dependent patients (group 1, N = 19), social drinkers (group 2, N = 12) and long-term abstaining alcoholics (group 3, N = 8). The active drinkers showed disturbances of several RBC membrane parameters, including abnormal microorganization of the membrane surface, a decrease in sialic acid content, and resistance to the fluidizing effect of ethanol, that were not completely corrected in the abstinent alcoholics. The RBC transit time was significantly longer in the active drinkers than in the abstainers but not the social drinkers. There were no significant differences between the groups with regard to membrane lipid core fluidity. The main abnormality (fluidization) in RBC from the active alcoholics involved the polar surface of the membrane (probed using TMA-DPH), and correlated with the decrease in sialic acid content but not with RBC deformability. PMID:8003118

Beaugé, F; Niel, E; Hispard, E; Perrotin, R; Thepot, V; Boynard, M; Nalpas, B

1994-01-01

118

ALTERNATIVE RBC (ROTATING BIOLOGICAL CONTACTOR) DESIGN - SECOND ORDER KINETICS  

EPA Science Inventory

This paper presents an alternative method for designing rotating biological contactors (RBC) for use as a secondary treatment operation. The method uses a combination of chemical kinetics, good engineering practice, operational simplicity, and cost effectiveness to design a RBC s...

119

Evaluation of membranes for use in on-line cell separation during mammalian cell perfusion processes  

Microsoft Academic Search

In this study two microporous hollow fibre membranes were evaluated for their use as cell retention device in continuous perfusion systems. A chemically modified permanent hydrophillic PTFE membrane and a hydrophilized PP membrane were tested. To investigate the filtration characteristics under process conditions each membrane was tested during a long term perfusion cultivation of a hybridoma cell line. In both

Heino Btintemeyer; Christoph Btihme; Jtirgen Lehmann

1994-01-01

120

Exo70 Generates Membrane Curvature for Morphogenesis and Cell Migration  

PubMed Central

Dynamic shape changes of the plasma membrane are fundamental to many processes ranging from morphogenesis and cell migration to phagocytosis and viral propagation. Here we demonstrate that Exo70, a component of the exocyst complex, induces tubular membrane invaginations towards the lumen of synthetic vesicles in vitro and generates protrusions on the surface of cells. Biochemical analyses using Exo70 mutants and independent molecular dynamics simulations based on Exo70 structure demonstrate that Exo70 generates negative membrane curvature through an oligomerization-based mechanism. In cells, the membrane-deformation function of Exo70 is required for protrusion formation and directional cell migration. Exo70 thus represents a membrane-bending protein that may couple actin dynamics and plasma membrane remodeling for morphogenesis. PMID:23948253

Zhao, Yuting; Liu, Jianglan; Yang, Changsong; Capraro, Benjamin R.; Baumgart, Tobias; Bradley, Ryan P.; Ramakrishnan, N.; Xu, Xiaowei; Radhakrishnan, Ravi; Svitkina, Tatyana; Guo, Wei

2013-01-01

121

Journal of Biomechanics 31 (1998) 151--156 A possible physical mechanism of red blood cell vesiculation obtained  

E-print Network

erythrocyte; Vesiculation; pH; Membrane skeleton 1. Introduction The human red blood cell (RBC) hasJournal of Biomechanics 31 (1998) 151--156 A possible physical mechanism of red blood cell form 25 November 1997 Abstract The membrane of human red blood cells is essentially composed of two

Iglic, Ales

122

New ETFE-based membrane for direct methanol fuel cell  

Microsoft Academic Search

The investigated membranes are based on 35?? m thick commercial poly(ethylene-alt-tetrafluoroethylene) (ETFE) films. The films were made proton conductive by means of irradiation treatment followed by sulfonation. These membranes have exceptionally low water uptake and excellent dimensional stability. The new membranes are investigated widely in a laboratory-scale direct methanol fuel cell (DMFC). The temperature range used in the fuel cell

V. Saarinen; T. Kallio; M. Paronen; P. Tikkanen; E. Rauhala; K. Kontturi

2005-01-01

123

Direct ethanol fuel cells using an anion exchange membrane  

Microsoft Academic Search

Direct ethanol fuel cells (DEFCs) with a PtRu anode and a Pt cathode were prepared using an anion exchange membrane (AEM) as an electrolyte instead of a cation exchange membrane (CEM), as in conventional polymer electrolyte fuel cells. The maximum power density of DEFCs significantly increased from 6mWcm?2 to 58mWcm?2 at room temperature and atmospheric pressure when the electrolyte membrane

Naoko Fujiwara; Zyun Siroma; Shin-ichi Yamazaki; Tsutomu Ioroi; Hiroshi Senoh; Kazuaki Yasuda

2008-01-01

124

Membrane Compartmentation Is Required for Efficient T Cell Activation  

Microsoft Academic Search

The plasma membrane of mammalian cells contains detergent-resistant membrane rafts enriched in glycosphingolipids and cholesterol. Although several important signaling molecules have been found in such rafts, evidence documenting a functional role for their localization has been scarce. Using a fractionation scheme that preserves tyrosine phosphorylation, we show that T cell activation leads to a striking compartmentation in the rafts of

Ramnik Xavier; Todd Brennan; Qingqin Li; Christine McCormack; Brian Seed

1998-01-01

125

Cell evolution and the problem of membrane topology  

Microsoft Academic Search

Cells somehow evolved from primordial chemistry and their emergence depended on the co-evolution of the cytoplasm, a genetic system and the cell membrane. It is widely believed that the cytoplasm evolved inside a primordial lipid vesicle, but here I argue that the earliest cytoplasm could have co-evolved to high complexity outside a vesicle on the membrane surface. An invagination of

Gareth Griffiths

2007-01-01

126

A new membrane fractionation process based on the combination of hybrid membrane cells and differential diffusion of two solutes  

Microsoft Academic Search

A new membrane fractionation process based on the combination of hybrid membrane cells and differential diffusion of two solutes was studied by numerical methods. The hybrid membrane cell comprises semipermeable and fully-permeable membrane sub-sections. While the semi-permeable membranes are permeable to the solvent and impermeable to both solutes, the fully-permeable membranes are permeable to all components of the solution, including

S. I. S. Pinto; T. M. G. T. Rocha; J. M. Miranda; J. B. L. M. Campos

2009-01-01

127

Membrane Nanowaves in Single and Collective Cell Migration  

PubMed Central

We report the characterization of three-dimensional membrane waves for migrating single and collective cells and describe their propagation using wide-field optical profiling technique with nanometer resolution. We reveal the existence of small and large membrane waves the amplitudes of which are in the range of ?3–7 nm to ?16–25 nm respectively, through the cell. For migrating single-cells, the amplitude of these waves is about 30 nm near the cell edge. Two or more different directions of propagation of the membrane nanowaves inside the same cell can be observed. After increasing the migration velocity by BMP-2 treatment, only one wave direction of propagation exists with an increase in the average amplitude (more than 80 nm near the cell edge). Furthermore for collective-cell migration, these membrane nanowaves are attenuated on the leader cells and poor transmission of these nanowaves to follower cells was observed. After BMP-2 treatment, the membrane nanowaves are transmitted from the leader cell to several rows of follower cells. Surprisingly, the vast majority of the observed membrane nanowaves is shared between the adjacent cells. These results give a new view on how single and collective-cells modulate their motility. This work has significant implications for the therapeutic use of BMPs for the regeneration of skin tissue. PMID:24846182

Zouani, Omar F.; Gocheva, Veronika; Durrieu, Marie-Christine

2014-01-01

128

Live-cell imaging of receptors around postsynaptic membranes.  

PubMed

This protocol describes how to image the trafficking of glutamate receptors around excitatory postsynaptic membrane formed on an adhesion protein-coated glass surface. The protocol was developed to clarify how receptors move during the induction of synaptic plasticity. Dissociated neurons are cultured on a coverslip coated with neurexin, which induces the formation of postsynaptic membrane-like structures on the glass surface. A glutamate receptor tagged with a fluorescent protein is then transfected into neurons, and it is observed with total internal reflection fluorescence microscopy. The whole process takes about 3 weeks. Changes in the amount of cell-surface receptors caused by neuronal activities can be quantified, and individual exocytosis events of receptors can be clearly observed around the pseudo-postsynaptic membrane. This protocol has potential applications for studies of movements of membrane proteins around other specialized regions of the cell membrane, such as the inhibitory postsynaptic membrane, the presynaptic membrane or the immunological synapses. PMID:24336472

Tanaka, Hiromitsu; Fujii, Shumpei; Hirano, Tomoo

2014-01-01

129

Red Blood Cell Membrane Dynamics during Malaria Parasite Egress  

PubMed Central

Precisely how malaria parasites exit from infected red blood cells to further spread the disease remains poorly understood. It has been shown recently, however, that these parasites exploit the elasticity of the cell membrane to enable their egress. Based on this work, showing that parasites modify the membrane’s spontaneous curvature, initiating pore opening and outward membrane curling, we develop a model of the dynamics of the red blood cell membrane leading to complete parasite egress. As a result of the three-dimensional, axisymmetric nature of the problem, we find that the membrane dynamics involve two modes of elastic-energy release: 1), at short times after pore opening, the free edge of the membrane curls into a toroidal rim attached to a membrane cap of roughly fixed radius; and 2), at longer times, the rim radius is fixed, and lipids in the cap flow into the rim. We compare our model with the experimental data of Abkarian and co-workers and obtain an estimate of the induced spontaneous curvature and the membrane viscosity, which control the timescale of parasite release. Finally, eversion of the membrane cap, which liberates the remaining parasites, is driven by the spontaneous curvature and is found to be associated with a breaking of the axisymmetry of the membrane. PMID:23260049

Callan-Jones, Andrew; Albarran Arriagada, Octavio Eduardo; Massiera, Gladys; Lorman, Vladimir; Abkarian, Manouk

2012-01-01

130

Sustainable Energy Systems Lab: Proton Exchange Membrane Fuel Cell  

NSDL National Science Digital Library

This lab introduces the operation of a proton exchange membrane fuel cell. Students will become familiar with a Simulink model of a proton exchange membrane fuel cell, obtain the nonlinear voltage-current and power-current characteristics for a typical fuel cell, determine the maximum power point and obtain a linear voltage equation for the fuel cell as a function of the current. This document may be downloaded in Microsoft Word file format.

2012-10-08

131

Characterization of a graphene oxide membrane fuel cell  

NASA Astrophysics Data System (ADS)

The electrical, mechanical, and compositional characterization of a graphene oxide membrane is presented, and its application as an electrolyte material in a polymer electrolyte membrane fuel cell is explored. Self-supporting graphene oxide membranes were prepared by a simple vacuum filtration process and, for the first time, characterized as the electrolyte in a fuel cell operating in an elevated temperature range (30-80 °C), with a maximum power density of ?34 mW cm-2, approaching that of a Nafion electrolyte based cell prepared and tested under similar conditions. Evidence for partial membrane reduction was found at higher temperatures and is believed to originate from more easily released, higher energy oxide groups, such as epoxides. We also discuss the morphology, the mechanical properties, chemical composition, and electrical conductivity of the graphene oxide membranes, with comparisons made to conventional Nafion membranes.

Bayer, T.; Bishop, S. R.; Nishihara, M.; Sasaki, K.; Lyth, S. M.

2014-12-01

132

Synthesis of basement membrane collagen by cultured human endothelial cells  

PubMed Central

Studies were performed to determine if cultured human endothelial cells synthesized basement membrane collagen. In culture, endothelial cells were attached to grossly visible membranous structures which on light microscopy were composed of ribbons of dense, amorphous material. On transmission electron microscopy, these membranous structures consisted of amorphous basement membrane, and material morphologically similar to microfibrils and elastic fibers. By immunofluorescence microscopy, these membranous structures stained brightly with antisera to human glomerular basement membrane. Cultured endothelial cells incorporated [3H]proline into protein; 18% of the incorporated [3H]proline was solubilized by purified collagenase. When endothelial cells were cultured with [14C]proline, 7.1% of the incorporated counts were present as [14C]hydroxyproline. Cultured endothelial cells were labeled with [3H]glycine and [3H]proline and digested with pepsin. The resulting fractions on analysis by SDS-polyacrylamide gel electrophoresis contained two radioactive protein peaks of mol wt 94,200 and 120,500. Both these peaks disappeared after digestion with purified collagenase. The peak of mol wt 120,500 corresponds to that of alpha1 (IV) collagen; the peak of the mol wt 94,200 probably corresponds to that of alpha1 (III) collagen. Thus, cultured human endothelial cells synthesize material which is morphologically and immunologically like amorphous basement membrane and biochemically like basement membrane collagen. Cultured endothelial cells probably also synthesize material which is morphologically similar to microfibrils and elastic fibers. PMID:58957

1976-01-01

133

Membranous basal cell adenoma arising in the eyelid  

PubMed Central

Basal cell adenoma (BCA) is a specific entity that lacks the myxochondroid stromal component of pleomorphic adenoma. Membranous basal cell adenoma is a rare variant of BCA, which is characteristic by abundant eosinophilicextracellular hyaline material deposited either inside or at the periphery of the epithelial islands. Herin we describe the first case of membranous BCA arising in the upper eyelid in a 38-year-old woman. A well-demarcated nodule arising in the eyelid was composed of isomorphic basaloid cells organized with a prominent basal cell layer and distinct basement membrane-like material. Immunohistochemically, S100 protein and p63 highlighted the basal aspect of the peripheral epithelial cells, while CK7 expressed on the luminal cells. A diagnosis of membranous basal cell adenoma of the eyelid was made. At follow-up for 2 years and 3 months later, there was no evidence of recurrence. Further pathological characteristics of this disease are discussed. PMID:25120843

Huang, Yong; Yang, Min; Ding, Jianhui

2014-01-01

134

A Hybrid Microbial Fuel Cell Membrane Bioreactor with a Conductive Ultrafiltration Membrane Biocathode for Wastewater Treatment  

E-print Network

Biocathode for Wastewater Treatment Lilian Malaeb,,§ Krishna P. Katuri,,§ Bruce E. Logan, Husnul Maab, S. P-biocathode microbial fuel cell- membrane bioreactor (MFC-MBR) system was developed to achieve simultaneous wastewater and the membrane for wastewater filtration. The MFC-MBR used an air-biocathode, and it was shown to have good

135

Inorganic–Polymer Composite Membranes for Proton Exchange Membrane Fuel Cells  

Microsoft Academic Search

Composite membranes consisting primarily of a polymer and an inorganic proton conducting particle or a proton conducting polymer containing inorganic particles for use as proton exchange membranes in low and intermediate temperature fuel cells are reviewed. The chemistry of major inorganic additives that have been used is described in terms of their structure and intrinsic ability to conduct protons. Composites

Andrew M. Herring

2006-01-01

136

Cell membrane potentials induced during exposure to EMP fields  

SciTech Connect

Internal current densities and electric fields induced in the human body during exposure to EMP fields are reviewed and used to predict resulting cell membrane potentials. Using several different approaches, membrane potentials of about 100 mV are predicted. These values are comparable to the static membrane potentials maintained by cells as a part of normal physiological function, but the EMP-induced potentials persist for only about 10 ns. Possible biological implications of EMP-induced membrane potentials including conformational changes and electroporation are discussed.

Gailey, P.C.; Easterly, C.E.

1994-09-01

137

Proteomics and Phosphoproteomics Analysis of Human Lens Fiber Cell Membranes  

PubMed Central

Purpose. The human lens fiber cell insoluble membrane fraction contains important membrane proteins, cytoskeletal proteins, and cytosolic proteins that are strongly associated with the membrane. The purpose of this study was to characterize the lens fiber cell membrane proteome and phosphoproteome from human lenses. Methods. HPLC-mass spectrometry–based multidimensional protein identification technology (MudPIT), without or with phosphopeptide enrichment, was applied to study the proteome and phosphoproteome of lens fiber cell membranes, respectively. Results. In total, 951 proteins were identified, including 379 integral membrane and membrane-associated proteins. Enriched gene categories and pathways based on the proteomic analysis include carbohydrate metabolism (glycolysis/gluconeogenesis, pentose phosphate pathway, pyruvate metabolism), proteasome, cell-cell signaling and communication (GTP binding, gap junction, focal adhesion), glutathione metabolism, and actin regulation. The combination of TiO2 phosphopeptide enrichment and MudPIT analysis revealed 855 phosphorylation sites on 271 proteins, including 455 phosphorylation sites that have not been previously identified. PKA, PKC, CKII, p38MAPK, and RSK are predicted as the major kinases for phosphorylation on the sites identified in the human lens membrane fraction. Conclusions. The results presented herein significantly expand the characterized proteome and phosphoproteome of the human lens fiber cell and provide a valuable reference for future research in studies of lens development and disease. PMID:23349431

Wang, Zhen; Han, Jun; David, Larry L.; Schey, Kevin L.

2013-01-01

138

Functional Implications of Plasma Membrane Condensation for T Cell Activation  

PubMed Central

The T lymphocyte plasma membrane condenses at the site of activation but the functional significance of this receptor-mediated membrane reorganization is not yet known. Here we demonstrate that membrane condensation at the T cell activation sites can be inhibited by incorporation of the oxysterol 7-ketocholesterol (7KC), which is known to prevent the formation of raft-like liquid-ordered domains in model membranes. We enriched T cells with 7KC, or cholesterol as control, to assess the importance of membrane condensation for T cell activation. Upon 7KC treatment, T cell antigen receptor (TCR) triggered calcium fluxes and early tyrosine phosphorylation events appear unaltered. However, signaling complexes form less efficiently on the cell surface, fewer phosphorylated signaling proteins are retained in the plasma membrane and actin restructuring at activation sites is impaired in 7KC-enriched cells resulting in compromised downstream activation responses. Our data emphasizes lipids as an important medium for the organization at T cell activation sites and strongly indicates that membrane condensation is an important element of the T cell activation process. PMID:18509459

Quinn, Carmel M.; Engelhardt, Karin; Williamson, David; Grewal, Thomas; Jessup, Wendy; Harder, Thomas; Gaus, Katharina

2008-01-01

139

Detecting Nanodomains in Living Cell Membrane by Fluorescence Correlation Spectroscopy  

NASA Astrophysics Data System (ADS)

Cell membranes actively participate in numerous cellular functions. Inasmuch as bioactivities of cell membranes are known to depend crucially on their lateral organization, much effort has been focused on deciphering this organization on different length scales. Within this context, the concept of lipid rafts has been intensively discussed over recent years. In line with its ability to measure diffusion parameters with great precision, fluorescence correlation spectroscopy (FCS) measurements have been made in association with innovative experimental strategies to monitor modes of molecular lateral diffusion within the plasma membrane of living cells. These investigations have allowed significant progress in the characterization of the cell membrane lateral organization at the suboptical level and have provided compelling evidence for the in vivo existence of raft nanodomains. We review these FCS-based studies and the characteristic structural features of raft nanodomains. We also discuss the findings in regards to the current view of lipid rafts as a general membrane-organizing principle.

He, Hai-Tao; Marguet, Didier

2011-05-01

140

Numerical modeling of motion trajectory and deformation behavior of a cell in a nonuniform electric field  

PubMed Central

The motion trajectory and deformation behavior of a neutral red blood cell (RBC) in a microchannel subjected to an externally applied nonuniform electric field are numerically investigated, where both the membrane mechanical force and the dielectrophoresis (DEP) force are considered. The simulation results demonstrate that the DEP force is significantly influenced by several factors, namely, the RBC size, electrode potential, electric frequency, RBC permittivity, and conductivity, which finally results in the different behaviors of the cell motion and deformation in the nonuniform electric field. PMID:21523249

Li, Hua; Ye, Ting; Lam, K. Y.

2011-01-01

141

Toxic effects of Litsea elliptica Blume essential oil on red blood cells of Sprague-Dawley rats*  

PubMed Central

Litsea elliptica Blume leaves have been traditionally used as medicinal herbs because of its antimutagenicity, chemopreventative and insecticidal properties. In this study, the toxic effects of L. elliptica essential oil against Sprague-Dawley rat’s red blood cells (RBCs) were evaluated. L. elliptica essential oil was given by oral gavage 5 times per week for 3 treated groups in the doses of 125, 250, and 500 mg/(kg body weight), respectively, and the control group received distilled water. Full blood count, RBC osmotic fragility, RBC morphological changes, and RBC membrane lipid were analyzed 28 d after the treatment. Although L. elliptica essential oil administration had significantly different effects on hemoglobin (Hb), mean cell hemoglobin concentration (MCHC), mean cell volume (MCV), and mean cell hemoglobin (MCH) in the experimental groups as compared to the control group (P<0.05), the values were still within the normal range. L. elliptica induced morphological changes of RBC into the form of echinocyte. The percentage of echinocyte increased significantly among the treated groups in a dose-response manner (P<0.001). The concentrations of RBC membrane phospholipids and cholesterol of all treated groups were significantly lower than those of control group (P<0.001). However, the RBC membrane osmotic fragility and total proteins of RBC membrane findings did not differ significantly between control and treated groups (P>0.05). It is concluded that structural changes in the RBC membrane due to L. elliptica essential oil administration did not cause severe membrane damage. PMID:19882755

Taib, Izatus Shima; Budin, Siti Balkis; Siti Nor Ain, Seri Maseran; Mohamed, Jamaludin; Louis, Santhana Raj; Das, Srijit; Sallehudin, Sulaiman; Rajab, Nor Fadilah; Hidayatulfathi, Othman

2009-01-01

142

Alternative Sources of Adult Stem Cells: Human Amniotic Membrane  

Microsoft Academic Search

\\u000a Human amniotic membrane is a highly promising cell source for tissue engineering. The cells thereof, human amniotic epithelial\\u000a cells (hAEC) and human amniotic mesenchymal stromal cells (hAMSC), may be immunoprivileged, they represent an early developmental\\u000a status, and their application is ethically uncontroversial. Cell banking strategies may use freshly isolated cells or involve\\u000a in vitro expansion to increase cell numbers. Therefore,

Susanne Wolbank; Martijn van Griensven; Regina Grillari-Voglauer; Anja Peterbauer-Scherb

2010-01-01

143

Evidence for water channels in renal proximal tubule cell membranes  

Microsoft Academic Search

Summary Water transport mechanisms in rabbit proximal convoluted cell membranes were examined by measurement of: (1) osmotic (Pf) and diffusional (Pd) water permeabilities, (2) inhibition ofPf by mercurials, and (3) activation energies (Ea) forPf.Pf was measured in PCT brush border (BBMV) and basolateral membrane (BLMV) vesicles, and in viable PCT cells by stopped-flow light scattering;Pd was measured in PCT cells

Mary M. Meyer; A. S. Verkman

1987-01-01

144

Models of dynamic extraction of lipid tethers from cell membranes  

NASA Astrophysics Data System (ADS)

When a ligand that is bound to an integral membrane receptor is pulled, the membrane and the underlying cytoskeleton can deform before either the membrane delaminates from the cytoskeleton or the ligand detaches from the receptor. If the membrane delaminates from the cytoskeleton, it may be further extruded and form a membrane tether. We develop a phenomenological model for this process by assuming that deformations obey Hooke's law up to a critical force at which the cell membrane locally detaches from the cytoskeleton and a membrane tether forms. We compute the probability of tether formation and show that tethers can be extruded only within an intermediate range of force loading rates and pulling velocities. The mean tether length that arises at the moment of ligand detachment is computed as are the force loading rates and pulling velocities that yield the longest tethers.

Nowak, Sarah A.; Chou, Tom

2010-06-01

145

Models of dynamic extraction of lipid tethers from cell membranes.  

PubMed

When a ligand that is bound to an integral membrane receptor is pulled, the membrane and the underlying cytoskeleton can deform before either the membrane delaminates from the cytoskeleton or the ligand detaches from the receptor. If the membrane delaminates from the cytoskeleton, it may be further extruded and form a membrane tether. We develop a phenomenological model for this process by assuming that deformations obey Hooke's law up to a critical force at which the cell membrane locally detaches from the cytoskeleton and a membrane tether forms. We compute the probability of tether formation and show that tethers can be extruded only within an intermediate range of force loading rates and pulling velocities. The mean tether length that arises at the moment of ligand detachment is computed as are the force loading rates and pulling velocities that yield the longest tethers. PMID:20453295

Nowak, Sarah A; Chou, Tom

2010-01-01

146

Mechanisms of gold nanoparticle mediated ultrashort laser cell membrane perforation  

NASA Astrophysics Data System (ADS)

The gold nanoparticle (AuNP) mediated ultrashort laser cell membrane perforation has been proven as an efficient delivery method to bring membrane impermeable molecules into the cytoplasm. Nevertheless, the underlying mechanisms have not been fully determined yet. Different effects may occur when irradiating a AuNP with ultrashort laser pulses and finally enable the molecule to transfer. Depending on the parameters (pulse length, laser fluence and wavelength, particle size and shape, etc.) light absorption or an enhanced near field scattering can lead to perforation of the cell membrane when the particle is in close vicinity. Here we present our experimental results to clarify the perforation initiating mechanisms. The generation of cavitation and gas bubbles due to the laser induced effects were observed via time resolved imaging. Additionally, pump-probe experiments for bubble detection was performed. Furthermore, in our patch clamp studies a depolarization of the membrane potential and the current through the membrane of AuNP loaded cell during laser treatment was detected. This indicates an exchange of extra- and intra cellular ions trough the perforated cell membrane for some milliseconds. Additionally investigations by ESEM imaging were applied to study the interaction of cells and AuNP after co incubation. The images show an attachment of AuNP at the cell membrane after several hours of incubation. Moreover, images of irradiated and AuNP loaded cells were taken to visualize the laser induced effects.

Schomaker, M.; Baumgart, J.; Motekaitis, D.; Heinemann, D.; Krawinkel, J.; Pangalos, M.; Bintig, W.; Boulais, E.; Lachaine, R.; St.-Louis Lalonde, B.; Ngezahayo, A.; Meunier, M.; Heisterkamp, A.

2011-03-01

147

Human hepatocytes and endothelial cells in organotypic membrane systems.  

PubMed

The realization of organotypic liver model that exhibits stable phenotype is a major challenge in the field of liver tissue engineering. In this study we developed liver organotypic co-culture systems by using synthetic and biodegradable membranes with primary human hepatocytes and human umbilical vein endothelial cells (HUVEC). Synthetic membranes prepared by a polymeric blend constituted of modified polyetheretherketone (PEEK-WC) and polyurethane (PU) and biodegradable chitosan membranes were developed by phase inversion technique and used in homotypic and organotypic culture systems. The morphological and functional characteristics of cells in the organotypic co-culture membrane systems were evaluated in comparison with homotypic cultures and traditional systems. Hepatocytes in the organotypic co-culture systems exhibit compact polyhedral cells with round nuclei and well demarcated cell-cell borders like in vivo, as a result of heterotypic interaction with HUVECs. In addition HUVECs formed tube-like structures directly through the interactions with the membranes and hepatocytes and indirectly through the secretion of ECM proteins which secretion improved in the organotypic co-culture membrane systems. The heterotypic cell-cell contacts have beneficial effect on the hepatocyte albumin production, urea synthesis and drug biotransformation. The developed organotypic co-culture membrane systems elicit liver specific functions in vitro and could be applied for the realization of engineered liver tissues to be used in tissue engineering, drug metabolism studies and bioartificial liver devices. PMID:21871658

Salerno, Simona; Campana, Carla; Morelli, Sabrina; Drioli, Enrico; De Bartolo, Loredana

2011-12-01

148

Modifications in Erythrocyte Membrane Zeta Potential by Plasmodium falciparum Infection  

PubMed Central

The zeta potential (ZP) is an electrochemical property of cell surfaces that is determined by the net electrical charge of molecules exposed at the surface of cell membranes. Membrane proteins contribute to the total net electrical charge of cell surfaces and can alter ZP through variation in their copy number and changes in their intermolecular interactions. Plasmodium falciparum extensively remodels its host red blood cell (RBC) membrane by placing ‘knob’-like structures at the cell surface. Using an electrophoretic mobility assay, we found that the mean ZP of human RBCs was ?15.7 mV. In RBCs infected with P. falciparum trophozoites (‘iRBCs’), the mean ZP was significantly lower (?14.6 mV, p<0.001). Removal of sialic acid from the cell surface by neuraminidase treatment significantly decreased the ZP of both RBCs (?6.06 mV) and iRBCs (?4.64 mV). Parasite-induced changes in ZP varied by P. falciparum clone and the presence of knobs on the iRBC surface. Variations in ZP values were accompanied by altered binding of iRBCs to human microvascular endothelial cells (MVECs). These data suggest that parasite-derived knob proteins contribute to the ZP of iRBCs, and that electrostatic and hydrophobic interactions between iRBC and MVEC membranes are involved in cytoadherence. PMID:22459624

Tokumasu, Fuyuki; Ostera, Graciela R.; Amaratunga, Chanaki; Fairhurst, Rick M.

2012-01-01

149

Erythrocyte NADPH oxidase activity modulated by Rac GTPases, PKC, and plasma cytokines contributes to oxidative stress in sickle cell disease  

PubMed Central

Chronic inflammation has emerged as an important pathogenic mechanism in sickle cell disease (SCD). One component of this inflammatory response is oxidant stress mediated by reactive oxygen species (ROS) generated by leukocytes, endothelial cells, plasma enzymes, and sickle red blood cells (RBC). Sickle RBC ROS generation has been attributed to sickle hemoglobin auto-oxidation and Fenton chemistry reactions catalyzed by denatured heme moieties bound to the RBC membrane. In this study, we demonstrate that a significant part of ROS production in sickle cells is mediated enzymatically by NADPH oxidase, which is regulated by protein kinase C, Rac GTPase, and intracellular Ca2+ signaling within the sickle RBC. Moreover, plasma from patients with SCD and isolated cytokines, such as transforming growth factor ?1 and endothelin-1, enhance RBC NADPH oxidase activity and increase ROS generation. ROS-mediated damage to RBC membrane components is known to contribute to erythrocyte rigidity and fragility in SCD. Erythrocyte ROS generation, hemolysis, vaso-occlusion, and the inflammatory response to tissue damage may therefore act in a positive-feedback loop to drive the pathophysiology of sickle cell disease. These findings suggest a novel pathogenic mechanism in SCD and may offer new therapeutic targets to counteract inflammation and RBC rigidity and fragility in SCD. PMID:23349388

Pushkaran, Suvarnamala; Konstantinidis, Diamantis G.; Koochaki, Sebastian; Malik, Punam; Mohandas, Narla; Zheng, Yi; Joiner, Clinton H.; Kalfa, Theodosia A.

2013-01-01

150

Simulated Red Blood Cell Motion in Microvessel Bifurcations: Effects of Cell-Cell Interactions on Cell Partitioning  

PubMed Central

Partitioning of red blood cell (RBC) fluxes between the branches of a diverging microvessel bifurcation is generally not proportional to the flow rates, as RBCs preferentially enter the higher-flow branch. A two-dimensional model for RBC motion and deformation is used to investigate the effects of cell-cell mechanical interactions on RBC partitioning in bifurcations. The RBC membrane and cytoplasm are represented by sets of viscoelastic elements immersed in a low Reynolds number flow. Several types of two-cell interactions that can affect partitioning are found. In the most frequent interactions, a `trade-off' occurs, in which a cell entering one branch causes a following cell to enter the other branch. Other types of interactions include `herding,' where the leading cell is caused to enter the same branch as the following cell, and `following,' where the trailing cell is caused to enter the same branch as the leading cell. The combined effect of these cell-cell interactions is a tendency towards more uniform partitioning, which results from the trade-off effect but is reduced by the herding and following effects. With increasing hematocrit, the frequency of interactions increases, and more uniform partitioning results. This prediction is consistent with experimental observations on how hematocrit affects RBC partitioning. PMID:23555330

Barber, Jared O.; Restrepo, Juan M.; Secomb, Timothy W.

2013-01-01

151

Effect of Processing and Storage on RBC function in vivo  

PubMed Central

Red Blood Cell (RBC) transfusion is indicated to improve oxygen delivery to tissue, and for no other purpose. We have come to appreciate that donor RBCs are fundamentally altered during processing and storage, in a fashion that both impairs oxygen transport efficacy and introduces additional risk by perturbing both immune and coagulation systems. The protean biophysical and physiologic changes in RBC function arising from storage are termed the ‘storage lesion’; many have been understood for some time; for example, we know that the oxygen affinity of stored blood rises during the storage period1 and that intracellular allosteric regulators, notably 2,3-bisphosphoglyceric acid (DPG) and ATP, are depleted during storage. Our appreciation of other storage lesion features has emerged with improved understanding of coagulation, immune and vascular signaling systems. Herein we review key features of the ‘storage lesion’. Additionally, we call particular attention to the newly appreciated role of RBCs in regulating linkage between regional blood flow and regional O2 consumption by regulating the bioavailability of key vasoactive mediators in plasma, as well as discuss how processing and storage disturbs this key signaling function and impairs transfusion efficacy. PMID:22818545

Doctor, Allan; Spinella, Phil

2012-01-01

152

Radiation Interaction with Therapeutic Drugs and Cell Membranes  

NASA Astrophysics Data System (ADS)

This transient permeabilized state of the cell membrane, named the ``cell electroporation'' (CE) can be used to increase cells uptake of drugs that do not readily pass cell membrane, thus enabling their cytotoxicity. The anticancer drugs, such as bleomycin (BL) and cisplatin, are the most candidates for the combined use with ionizing and non-ionizing radiation fields. The methods and installations for the cell electroporation by electron beam (EB) and microwave (MW) irradiation are presented. The viability tests of the human leukocytes under EB and MW exposure with/without the BL in the cell cultures are discussed.

Martin, Diana I.; Manaila, Elena N.; Moisescu, Mihaela I.; Savopol, Tudor D.; Kovacs, Eugenia A.; Cinca, Sabin A.; Matei, Constantin I.; Margaritescu, Irina D.; Iacob, Nicusor I.; Ighigeanu, Daniel I.; Craciun, Gabriela D.

2007-04-01

153

Peptides released from reovirus outer capsid form membrane pores that recruit virus particles  

PubMed Central

Nonenveloped animal viruses must disrupt or perforate a cell membrane during entry. Recent work with reovirus has shown formation of size-selective pores in RBC membranes in concert with structural changes in capsid protein ?1. Here, we demonstrate that ?1 fragments released from reovirus particles are sufficient for pore formation. Both myristoylated N-terminal fragment ?1N and C-terminal fragment ? are released from particles. Both also associate with RBC membranes and contribute to pore formation in the absence of particles, but ?1N has the primary and sufficient role. Particles with a mutant form of ?1, unable to release ?1N or form pores, lack the ability to associate with membranes. They are, however, recruited by pores preformed with peptides released from wild-type particles or with synthetic ?1N. The results provide evidence that docking to membrane pores by virus particles may be a next step in membrane penetration after pore formation by released peptides. PMID:18369316

Ivanovic, Tijana; Agosto, Melina A; Zhang, Lan; Chandran, Kartik; Harrison, Stephen C; Nibert, Max L

2008-01-01

154

Wisconsin Online Resource Center: Construction of the Cell Membrane  

NSDL National Science Digital Library

Hosted by the Wisconsin Online Resource Center, this fun and informative web-based tutorial on the Construction of the Cell Membrane was created by Barbara Liang and Chad Blohowiak. Although the site content is geared for an older audience, the tutorial is so clear and easy to navigate that younger students curious about cells will enjoy it as well. Through the process of building the molecular structure of an animated cell membrane, site visitors will learn "the makeup and the basis for cell membrane function." The 23-page tutorial is fairly brief and interactive with questions and assignments such as placing the fibrous receptor or glycoprotein into the cell membrane. This site also has link for downloading the required software plug-in.

Blohowiak, Chad; Liang, Barbara

155

Layer-by-layer cell membrane assembly.  

PubMed

Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo. PMID:24153375

Matosevic, Sandro; Paegel, Brian M

2013-11-01

156

Layer-by-layer cell membrane assembly  

NASA Astrophysics Data System (ADS)

Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo.

Matosevic, Sandro; Paegel, Brian M.

2013-11-01

157

Apical Membrane Potassium Conductance in Guinea Pig Gallbladder Epithelial Cells,  

National Technical Information Service (NTIS)

The fractional resistance of the apical membrane (fRa) of guinea pig gallbladder epithelial cells was observed to vary with changes in apical membrane potential (Va). Depolarizing Va from a base-line potential of -60 to -30 mV decreased fRa from 0.79 + or...

P. J. Gunter-Smith

1988-01-01

158

Membrane protein dynamics and functional implications in mammalian cells.  

PubMed

The organization of the plasma membrane is both highly complex and highly dynamic. One manifestation of this dynamic complexity is the lateral mobility of proteins within the plane of the membrane, which is often an important determinant of intermolecular protein-binding interactions, downstream signal transduction, and local membrane mechanics. The mode of membrane protein mobility can range from random Brownian motion to immobility and from confined or restricted motion to actively directed motion. Several methods can be used to distinguish among the various modes of protein mobility, including fluorescence recovery after photobleaching, single-particle tracking, fluorescence correlation spectroscopy, and variations of these techniques. Here, we present both a brief overview of these methods and examples of their use to elucidate the dynamics of membrane proteins in mammalian cells-first in erythrocytes, then in erythroblasts and other cells in the hematopoietic lineage, and finally in non-hematopoietic cells. This multisystem analysis shows that the cytoskeleton frequently governs modes of membrane protein motion by stably anchoring the proteins through direct-binding interactions, by restricting protein diffusion through steric interactions, or by facilitating directed protein motion. Together, these studies have begun to delineate mechanisms by which membrane protein dynamics influence signaling sequelae and membrane mechanical properties, which, in turn, govern cell function. PMID:24210428

Alenghat, Francis J; Golan, David E

2013-01-01

159

Membrane Protein Dynamics and Functional Implications in Mammalian Cells  

PubMed Central

The organization of the plasma membrane is both highly complex and highly dynamic. One manifestation of this dynamic complexity is the lateral mobility of proteins within the plane of the membrane, which is often an important determinant of intermolecular protein-binding interactions, downstream signal transduction, and local membrane mechanics. The mode of membrane protein mobility can range from random Brownian motion to immobility and from confined or restricted motion to actively directed motion. Several methods can be used to distinguish among the various modes of protein mobility, including fluorescence recovery after photobleaching, single-particle tracking, fluorescence correlation spectroscopy, and variations of these techniques. Here, we present both a brief overview of these methods and examples of their use to elucidate the dynamics of membrane proteins in mammalian cells—first in erythrocytes, then in erythroblasts and other cells in the hematopoietic lineage, and finally in non-hematopoietic cells. This multisystem analysis shows that the cytoskeleton frequently governs modes of membrane protein motion by stably anchoring the proteins through direct-binding interactions, by restricting protein diffusion through steric interactions, or by facilitating directed protein motion. Together, these studies have begun to delineate mechanisms by which membrane protein dynamics influence signaling sequelae and membrane mechanical properties, which, in turn, govern cell function. PMID:24210428

Alenghat, Francis J.; Golan, David E.

2014-01-01

160

Modified SPEEK membranes for direct ethanol fuel cell  

Microsoft Academic Search

Membranes with low ethanol crossover were prepared aiming their application for direct ethanol fuel cell (DEFC). They were based on (1) sulfonated poly(ether ether ketone) (SPEEK) coated with carbon molecular sieves (CMS) and (2) on SPEEK\\/PI homogeneous blends. The membranes were characterized concerning their water and ethanol solution uptake, water and ethanol permeability in pervaporation experiments and their performance in

Husnul Maab; Suzana Pereira Nunes

2010-01-01

161

MRI Application for Clarifying Fuel Cell Performance with Variation of Polymer Electrolyte Membranes: Comparison of Water Content of a Hydrocarbon Membrane and a Perfluorinated Membrane  

Microsoft Academic Search

.  Magnetic resonance imaging (MRI) is applied to clarify a dominating factor on variation of fuel cell performance with two\\u000a types of polymer electrolyte membranes, a hydrocarbon membrane and a perfluorinated membrane. MRI results revealed that the\\u000a hydrocarbon membrane showed a water content higher than that of the perfluorinated membrane, responsible for a better fuel\\u000a cell performance due to decrease of

S. Tsushima; S. Hirai; K. Kitamura; M. Yamashita; S. Takase

2007-01-01

162

Thermodynamic and fluid properties of cells, tissues and membranes  

NASA Astrophysics Data System (ADS)

This dissertation studies cellular rearrangements in tissues and attempts to establish the role of physical properties of cells, tissues and membranes in several biological phenomena. Using experiments and statistical mechanical modeling, we study cell sorting, tissue engulfment, single cell motion and membrane fluctuations. When cells of two different types are mixed together, they sort out, with the less cohesive tissue surrounding the more cohesive one. This sorting out resembles the phase separation of a mixture of immiscible liquids. We have measured the rate of sorting in tissues and compared it with a cellular automaton based model of cell aggregates. We have also established that cell sorting agrees well with the theory for phase separating fluids. Engulfment is the spreading of one type of tissue over the surface of another tissue placed adjacent to it. Differences in adhesion cause an imbalance of surface tension forces which drives tissue spreading. We have quantitatively studied engulfment between different tissue types and compared the experimental rate with results from computer simulations and a liquid model. Our results suggest that simple physical principles can model tissue motion. Studying the motion of single cells in aggregates is important to understanding the overall pattern formation in tissues. We characterized cell motion in different types of adhesive aggregates to elucidate the role of adhesion in cell motion. We also observed that the cells exhibited a novel type of statistics including correlations and collective motion. Membrane deformations of cells played a negligible role in large scale cell motion. Our results indicate the importance of correlated motion for cells to move long distances in tissues. At the single cell level, tension of the cell membrane and intracellular membrane can play an important role in cell shape changes, regulation of cell motility and membrane dynamics. We used optical tweezers to measure the membrane tension of tubulo-vesicular networks obtained from Golgi and Endoplasmic Reticulum (ER) membranes within cells. As expected on the basis of some previous experiments, the ER has a higher membrane tension than the Golgi.

Upadhyaya, Arpita

2000-10-01

163

Membrane stress increases cation permeability in red cells.  

PubMed

The human red cell is known to increase its cation permeability when deformed by mechanical forces. Light-scattering measurements were used to quantitate the cell deformation, as ellipticity under shear. Permeability to sodium and potassium was not proportional to the cell deformation. An ellipticity of 0.75 was required to increase the permeability of the membrane to cations, and flux thereafter increased rapidly as the limits of cell extension were reached. Induction of membrane curvature by chemical agents also did not increase cation permeability. These results indicate that membrane deformation per se does not increase permeability, and that membrane tension is the effector for increased cation permeability. This may be relevant to some cation permeabilities observed by patch clamping. PMID:7858123

Johnson, R M

1994-11-01

164

Perceptual Grouping of Membrane Signals in Cell-based Assays  

SciTech Connect

Membrane proteins organize themselves in a linear fashion where adjacent cells are attached together along the basal-lateral region. Their intensity distributions are often heterogeneous and may lack specificity. Grouping of these linear structures can aid in segmentation and quantitative representation of protein localization. However, quantitative analysis of these signals is often hindered by noise, variation in scale, and perceptual features. This paper introduces an iterative voting method for inferring the membrane signal as it relates to continuity. A unique aspect of this technique is in the topography of the voting kernel, which is refined and reoriented iteratively. The technique can cluster and group membrane signals along the tangential direction. It has an excellent noise immunity and is tolerant to perturbations in scale. Application of this technique to quantitative analysis of cell-cell adhesion mediated by integral cell membrane proteins is demonstrated.

Chang, Hang; Andarawewa, Punya Kumari; Han, Ju; Barcellos-Hoff,Mary Helen; Parvin, Bahram

2007-02-02

165

Cell-free system for synthesizing membrane proteins cell free method for synthesizing membrane proteins  

DOEpatents

The invention provides an in vitro method for producing proteins, membrane proteins, membrane-associated proteins, and soluble proteins that interact with membrane-associated proteins for assembly into an oligomeric complex or that require association with a membrane for proper folding. The method comprises, supplying intracytoplasmic membranes from organisms; modifying protein composition of intracytoplasmic membranes from organism by modifying DNA to delete genes encoding functions of the organism not associated with the formation of the intracytoplasmic membranes; generating appropriate DNA or RNA templates that encode the target protein; and mixing the intracytoplasmic membranes with the template and a transcription/translation-competent cellular extract to cause simultaneous production of the membrane proteins and encapsulation of the membrane proteins within the intracytoplasmic membranes.

Laible, Philip D; Hanson, Deborah K

2013-06-04

166

Numerical and Experimental Study on the Development of Electric Sensor as for Measurement of Red Blood Cell Deformability in Microchannels  

PubMed Central

A microsensor that can continuously measure the deformability of a single red blood cell (RBC) in its microchannels using microelectrodes is described in this paper. The time series of the electric resistance is measured using an AC current vs. voltage method as the RBC passes between counter-electrode-type micro-membrane sensors attached to the bottom wall of the microchannel. The RBC is deformed by the shear flow created in the microchannel; the degree of deformation depends on the elastic modulus of the RBC. The resistance distribution, which is unique to the shape of the RBC, is analyzed to obtain the deformability of each cell. First, a numerical simulation of the electric field around the electrodes and RBC is carried out to evaluate the influences of the RBC height position, channel height, distance between the electrodes, electrode width, and RBC shape on the sensor sensitivity. Then, a microsensor was designed and fabricated on the basis of the numerical results. Resistance measurement was carried out using samples of normal RBCs and rigidified (Ca2+–A23186 treated) RBCs. Visualization measurement of the cells' behavior was carried out using a high-speed camera, and the results were compared with those obtained above to evaluate the performance of the sensor. PMID:23112616

Tatsumi, Kazuya; Katsumoto, Yoichi; Fujiwara, Ryoji; Nakabe, Kazuyoshi

2012-01-01

167

Amniotic membrane transplantation for partial limbal stem cell deficiency  

Microsoft Academic Search

AIMTo examine the efficacy, safety, and long term outcomes of amniotic membrane transplantation for corneal surface reconstruction in cases of partial limbal stem cell deficiency.METHODS17 eyes of 15 patients with partial limbal stem cell deficiency underwent superficial keratectomy of the conjunctivalised corneal surface followed by amniotic membrane transplantation. Cases were followed up for at least a year.RESULTSAll eyes exhibited a

David F Anderson; Pierre Ellies; Renato T F Pires; Scheffer C G Tseng

2001-01-01

168

Basement Membrane Matrix (BME) has Multiple Uses with Stem Cells  

Microsoft Academic Search

The utilization of basement membrane matrix has helped to overcome many of the obstacles associated with stem cell research.\\u000a Initially, there were several problems with investigating stem cells, including difficult extraction from tissues, the need\\u000a for feeder layers, poor survival, minimal proliferation, limited differentiation in vitro, and inadequate survival when injected\\u000a or transplanted in vivo. Given that the basement membrane

Irina Arnaoutova; Jay George; Hynda K. Kleinman; Gabriel Benton

169

Actin-propelled Invasive Membrane Protrusions Promote Fusogenic Protein Engagement During Cell-Cell Fusion  

PubMed Central

Cell-cell fusion is critical for the conception, development and physiology of multicellular organisms. Although cellular fusogenic proteins and the actin cytoskeleton are implicated in cell-cell fusion, whether and how they coordinate to promote plasma membrane fusion remain unclear. Here, we reconstituted a high-efficiency, inducible cell-fusion culture system in the normally non-fusing Drosophila S2R+ cells. Both fusogenic proteins and actin cytoskeletal rearrangements were necessary for cell fusion, and, in combination, were sufficient to impart fusion competence. Localized actin polymerization triggered by specific cell-cell or cell-matrix adhesion molecules propelled invasive cell membrane protrusions, which, in turn, promoted fusogenic protein engagement and plasma membrane fusion. This de novo cell-fusion culture system reveals a general role for actin-propelled invasive membrane protrusions in driving fusogenic protein engagement during cell-cell fusion. PMID:23470732

Shilagardi, Khurts; Li, Shuo; Luo, Fengbao; Marikar, Faiz; Duan, Rui; Jin, Peng; Kim, Ji Hoon; Murnen, Katherine; Chen, Elizabeth H.

2013-01-01

170

The principle of membrane fusion in the cell (nobel lecture).  

PubMed

Cells contain small membrane-enclosed vesicles which transport many kinds of cargo between the compartments of the cell. The result is a choreographed program of secretory, biosynthetic, and endocytic protein traffic that serves the cell's internal physiologic needs. PMID:25087728

Rothman, James Edward

2014-11-17

171

Controlled permeation of cell membrane by single bubble acoustic cavitation  

PubMed Central

Sonoporation is the membrane disruption generated by ultrasound and has been exploited as a non-viral strategy for drug and gene delivery. Acoustic cavitation of microbubbles has been recognized to play an important role in sonoporation. However, due to the lack of adequate techniques for precise control of cavitation activities and real-time assessment of the resulting sub-micron process of sonoporation, limited knowledge has been available regarding the detail processes and correlation of cavitation with membrane disruption at the single cell level. In the current study, we developed a combined approach including optical, acoustic, and electrophysiological techniques to enable synchronized manipulation, imaging, and measurement of cavitation of single bubbles and the resulting cell membrane disruption in real-time. Using a self-focused femtosecond laser and high frequency (7.44 MHz) pulses, a single microbubble was generated and positioned at a desired distance from the membrane of a Xenopus oocyte. Cavitation of the bubble was achieved by applying a low frequency (1.5 MHz) ultrasound pulse (duration 13.3 or 40 µs) to induce bubble collapse. Disruption of the cell membrane was assessed by the increase in the transmembrane current (TMC) of the cell under voltage clamp. Simultaneous high-speed bright field imaging of cavitation and measurements of the TMC were obtained to correlate the ultrasound-generated bubble activities with the cell membrane poration. The change in membrane permeability was directly associated with the formation of a sub-micrometer pore from a local membrane rupture generated by bubble collapse or bubble compression depending on ultrasound amplitude and duration. The impact of the bubble collapse on membrane permeation decreased rapidly with increasing distance (D) between the bubble (diameter d) and the cell membrane. The effective range of cavitation impact on membrane poration was determined to be D/d = 0.75. The maximum mean radius of the pores was estimated from the measured TMC to be 0.106 ± 0.032 µm (n = 70) for acoustic pressure of 1.5 MPa (duration 13.3 µs), and increased to 0.171 ± 0.030 µm (n = 125) for acoustic pressure of 1.7 MPa and to 0.182 ± 0.052 µm (n=112) for a pulse duration of 40 µs (1.5 MPa). These results from controlled cell membrane permeation by cavitation of single bubbles revealed insights and key factors affecting sonoporation at the single cell level. PMID:21945682

Zhou, Y.; Yang, K.; Cui, J.; Ye, J. Y.; Deng, C. X.

2011-01-01

172

Proton conducting membranes for high temperature fuel cells with solid state water free membranes  

NASA Technical Reports Server (NTRS)

A water free, proton conducting membrane for use in a fuel cell is fabricated as a highly conducting sheet of converted solid state organic amine salt, such as converted acid salt of triethylenediamine with two quaternized tertiary nitrogen atoms, combined with a nanoparticulate oxide and a stable binder combined with the converted solid state organic amine salt to form a polymeric electrolyte membrane. In one embodiment the membrane is derived from triethylenediamine sulfate, hydrogen phosphate or trifiate, an oxoanion with at least one ionizable hydrogen, organic tertiary amine bisulfate, polymeric quaternized amine bisulfate or phosphate, or polymeric organic compounds with quaternizable nitrogen combined with Nafion to form an intimate network with ionic interactions.

Narayanan, Sekharipuram R. (Inventor); Yen, Shiao-Pin S. (Inventor)

2006-01-01

173

Turgor Pressure Sensing in Plant Cell Membranes 1  

PubMed Central

Experimental evidence is reviewed which shows that the cell membrane is compressible by both mechanical and electrical forces. Calculations are given which show that significant changes in the thickness of cell membranes can occur as a result of (a) direct compression due to the turgor pressure; (b) indirect effects due to the stretching of the cell wall; and (c) the stresses induced by the electric field in the membrane. Such changes in the membrane thickness may provide the pressure-transducing mechanism required for osmoregulation and growth. An important feature of the model is that this pressure transduction can occur not only in the plasmalemma (where there is a pressure gradient), but also in the tonoplast. PMID:16659734

Coster, Hans G. L.; Steudle, Ernst; Zimmermann, Ulrich

1976-01-01

174

Elastic Membrane Heterogeneity of Living Cells Revealed by Stiff Nanoscale Membrane Domains  

PubMed Central

Many approaches have been developed to characterize the heterogeneity of membranes in living cells. In this study, the elastic properties of specific membrane domains in living cells are characterized by atomic force microscopy. Our data reveal the existence of heterogeneous nanometric scale domains with specific biophysical properties. We focused on glycosylphosphatidylinositol (GPI)-anchored proteins, which play an important role in membrane trafficking and cell signaling under both physiological and pathological conditions and which are known to partition preferentially into cholesterol-rich microdomains. We demonstrate that these GPI-anchored proteins reside within domains that are stiffer than the surrounding membrane. In contrast, membrane domains containing the transferrin receptor, which does not associate with cholesterol-rich regions, manifest no such feature. The heightened stiffness of GPI domains is consistent with existing data relating to the specific condensation of lipids and the slow diffusion rates of lipids and proteins therein. Our quantitative data may forge the way to unveiling the links that exist between membrane stiffness, molecular diffusion, and signaling activation. PMID:17981897

Roduit, Charles; van der Goot, F. Gisou; De Los Rios, Paolo; Yersin, Alexandre; Steiner, Pascal; Dietler, Giovanni; Catsicas, Stefan; Lafont, Frank; Kasas, Sandor

2008-01-01

175

Membrane Targeting of P-type ATPases in Plant Cells  

SciTech Connect

How membrane proteins are targeted to specific subcellular locations is a very complex and poorly understood area of research. Our long-term goal is to use P-type ATPases (ion pumps), in a model plant system Arabidopsis, as a paradigm to understand how members of a family of closely related membrane proteins can be targeted to different subcellular locations. The research is divided into two specific aims. The first aim is focused on determining the targeting destination of all 10 ACA-type calcium pumps (Arabidopsis Calcium ATPase) in Arabidopsis. ACAs represent a plant specific-subfamily of plasma membrane-type calcium pumps. In contrast to animals, the plant homologs have been found in multiple membrane systems, including the ER (ACA2), tonoplast (ACA4) and plasma membrane (ACA8). Their high degree of similarity provides a unique opportunity to use a comparative approach to delineate the membrane specific targeting information for each pump. One hypothesis to be tested is that an endomembrane located ACA can be re-directed to the plasma membrane by including targeting information from a plasma membrane isoform, ACA8. Our approach is to engineer domain swaps between pumps and monitor the targeting of chimeric proteins in plant cells using a Green Fluorescence Protein (GFP) as a tag. The second aim is to test the hypothesis that heterologous transporters can be engineered into plants and targeted to the plasma membrane by fusing them to a plasma membrane proton pump. As a test case we are evaluating the targeting properties of fusions made between a yeast sodium/proton exchanger (Sod2) and a proton pump (AHA2). This fusion may potentially lead to a new strategy for engineering salt resistant plants. Together these aims are designed to provide fundamental insights into the biogenesis and function of plant cell membrane systems.

Jeffrey F. Harper, Ph.D.

2004-06-30

176

Effect of gas diffusion layer and membrane properties in an annular proton exchange membrane fuel cell  

NASA Astrophysics Data System (ADS)

A complete three-dimensional and single phase computational dynamics model for annular proton exchange membrane (PEM) fuel cell is used to investigate the effect of changing gas diffusion layer and membrane properties on the performances, current density and gas concentration. The proposed model is a full cell model, which includes all the parts of the PEM fuel cell, flow channels, gas diffusion electrodes, catalyst layers and the membrane. Coupled transport and electrochemical kinetics equations are solved in a single domain; therefore no interfacial boundary condition is required at the internal boundaries between cell components. This computational fluid dynamics code is used as the direct problem solver, which is used to simulate the two-dimensional mass, momentum and species transport phenomena as well as the electron- and proton-transfer process taking place in a PEMFC that cannot be investigated experimentally. The results show that by increasing the thickness and decreasing the porosity of GDL the performance of the cell enhances that it is different with planner PEM fuel cell. Also the results show that by decreasing the thickness of the membrane the performance of the cell increases.

Khazaee, I.; Ghazikhani, M.; Esfahani, M. Nasr

2012-01-01

177

A new class of partially fluorinated fuel cell membranes  

SciTech Connect

A series of differently crosslinked FEP-g-polystyrene proton exchange membranes has been synthesized by the pre-irradiation grafting method. Divinylbenzene (DVB) and/or triallyl cyanurate (TAC) were used as crosslinkers in the membranes. It was found, that the physical properties of the membranes, such as water-uptake and specific resistance are strongly influenced by the nature of the crosslinker. Generally it can be stated, that DVB decreases water-uptake and increases specific resistance, on the other hand TAC increases swelling and decreases specific resistance to values as low as 5.0 {Omega}cm at 60 C. The membranes were tested in H{sub 2}/O{sub 2} fuel cells for stability and performance. It was found, that thick (170 {mu}m) DBV crosslinked membranes showed stable operation for 1,400 hours at temperatures up to 80 C. The highest power density in the fuel cell was found for the DVB and TAC double crosslinked membrane, it exceeded the value of a cell with a Nafion{reg_sign} 117 membrane by more than 60%.

Buechi, F.N.; Gupta, B.; Halim, J.; Haas, O.; Scherer, G.G. [Paul Scherrer Inst., Villigen-PSI (Switzerland)

1994-12-31

178

Imaging cell membrane injury and subcellular processes involved in repair.  

PubMed

The ability of injured cells to heal is a fundamental cellular process, but cellular and molecular mechanisms involved in healing injured cells are poorly understood. Here assays are described to monitor the ability and kinetics of healing of cultured cells following localized injury. The first protocol describes an end point based approach to simultaneously assess cell membrane repair ability of hundreds of cells. The second protocol describes a real time imaging approach to monitor the kinetics of cell membrane repair in individual cells following localized injury with a pulsed laser. As healing injured cells involves trafficking of specific proteins and subcellular compartments to the site of injury, the third protocol describes the use of above end point based approach to assess one such trafficking event (lysosomal exocytosis) in hundreds of cells injured simultaneously and the last protocol describes the use of pulsed laser injury together with TIRF microscopy to monitor the dynamics of individual subcellular compartments in injured cells at high spatial and temporal resolution. While the protocols here describe the use of these approaches to study the link between cell membrane repair and lysosomal exocytosis in cultured muscle cells, they can be applied as such for any other adherent cultured cell and subcellular compartment of choice. PMID:24686523

Defour, Aurelia; Sreetama, S C; Jaiswal, Jyoti K

2014-01-01

179

Fuel cell electrolyte membrane with basic polymer  

DOEpatents

The present invention is an electrolyte membrane comprising an acid and a basic polymer, where the acid is a low-volatile acid that is fluorinated and is either oligomeric or non-polymeric, and where the basic polymer is protonated by the acid and is stable to hydrolysis.

Larson, James M. (Saint Paul, MN); Pham, Phat T. (Little Canada, MN); Frey, Matthew H. (Cottage Grove, MN); Hamrock, Steven J. (Stillwater, MN); Haugen, Gregory M. (Edina, MN); Lamanna, William M. (Stillwater, MN)

2010-11-23

180

Fuel cell electrolyte membrane with basic polymer  

DOEpatents

The present invention is an electrolyte membrane comprising an acid and a basic polymer, where the acid is a low-volatile acid that is fluorinated and is either oligomeric or non-polymeric, and where the basic polymer is protonated by the acid and is stable to hydrolysis.

Larson, James M.; Pham, Phat T.; Frey, Matthew H.; Hamrock, Steven J.; Haugen, Gregory M.; Lamanna, William M.

2012-12-04

181

Numerical analysis of a red blood cell flowing through a thin micropore.  

PubMed

Red blood cell (RBC) deformability plays a key role in microcirculation, especially in vessels that have diameters even smaller than the nominal cell size. In this study, we numerically investigate the dynamics of an RBC in a thin micropore. The RBC is modeled as a capsule with a thin hyperelastic membrane. In a numerical simulation, we employ a boundary element method for fluid mechanics and a finite element method for membrane mechanics. The resulting RBC deformation towards the flow direction is suppressed considerably by increased cytoplasm viscosity, whereas the gap between the cell membrane and solid wall becomes smaller with higher cytoplasm viscosity. We also measure the transit time of the RBC and find that nondimensional transit time increases nonlinearly with respect to the viscosity ratio, whereas it is invariant to the capillary number. In conclusion, cytoplasmic viscosity plays a key role in the dynamics of an RBC in a thin pore. The results of this study will be useful for designing a microfluidic device to measure cytoplasmic viscosity. PMID:24580321

Omori, Toshihiro; Hosaka, Haruki; Imai, Yohsuke; Yamaguchi, Takami; Ishikawa, Takuji

2014-01-01

182

Numerical analysis of a red blood cell flowing through a thin micropore  

NASA Astrophysics Data System (ADS)

Red blood cell (RBC) deformability plays a key role in microcirculation, especially in vessels that have diameters even smaller than the nominal cell size. In this study, we numerically investigate the dynamics of an RBC in a thin micropore. The RBC is modeled as a capsule with a thin hyperelastic membrane. In a numerical simulation, we employ a boundary element method for fluid mechanics and a finite element method for membrane mechanics. The resulting RBC deformation towards the flow direction is suppressed considerably by increased cytoplasm viscosity, whereas the gap between the cell membrane and solid wall becomes smaller with higher cytoplasm viscosity. We also measure the transit time of the RBC and find that nondimensional transit time increases nonlinearly with respect to the viscosity ratio, whereas it is invariant to the capillary number. In conclusion, cytoplasmic viscosity plays a key role in the dynamics of an RBC in a thin pore. The results of this study will be useful for designing a microfluidic device to measure cytoplasmic viscosity.

Omori, Toshihiro; Hosaka, Haruki; Imai, Yohsuke; Yamaguchi, Takami; Ishikawa, Takuji

2014-01-01

183

Rotating Biological Contactors (RBC's). Student Manual. Biological Treatment Process Control.  

ERIC Educational Resources Information Center

This student manual provides the textual material for a unit on rotating biological contactors (RBC's). Topic areas considered include: (1) flow patterns of water through RBC installations; (2) basic concepts (shaft and stage); (3) characteristics of biomass; (4) mechanical features (bearings, mechanical drive systems, and air drive systems); (5)…

Zickefoose, Charles S.

184

Role of Rab GTPases in Membrane Traffic and Cell Physiology  

PubMed Central

Intracellular membrane traffic defines a complex network of pathways that connects many of the membrane-bound organelles of eukaryotic cells. Although each pathway is governed by its own set of factors, they all contain Rab GTPases that serve as master regulators. In this review, we discuss how Rabs can regulate virtually all steps of membrane traffic from the formation of the transport vesicle at the donor membrane to its fusion at the target membrane. Some of the many regulatory functions performed by Rabs include interacting with diverse effector proteins that select cargo, promoting vesicle movement, and verifying the correct site of fusion. We describe cascade mechanisms that may define directionality in traffic and ensure that different Rabs do not overlap in the pathways that they regulate. Throughout this review we highlight how Rab dysfunction leads to a variety of disease states ranging from infectious diseases to cancer. PMID:21248164

HUTAGALUNG, ALEX H.; NOVICK, PETER J.

2013-01-01

185

Towards fuel cell membranes with improved lifetime: Aquivion® Perfluorosulfonic Acid membranes containing immobilized radical scavengers  

NASA Astrophysics Data System (ADS)

A facile synthesis, based on a wet impregnation technique and a thermal treatment, of a novel silica-supported cerium-oxide-based radical scavenger bearing sulfonic acid functionalities is presented. This material is loaded as a filler in ePTFE reinforced membranes (called R79-02S) prepared starting from Aquivion® Perfluoro-Sulfonic Acid (PFSA) dispersions. The aim is to mitigate the peroxy radicals attack to the polymeric membrane under fuel cell operating conditions. These membranes show much longer (7 times more) life-time in Accelerated Stress Tests (AST) and reduced fluoride release (about one half) in Fenton's tests than the radical scavenger-free membrane without any loss in electrochemical performance. Scavenger-free Aquivion® PFSA-based membrane durability is about 200 h in AST whereas the same membrane containing the newly developed radical scavenger exceeds 1400 h. These results confirm the stability of the modified membranes and the excellent activity of the composite scavenger in mitigating the polymer electrolyte degradation.

D'Urso, C.; Oldani, C.; Baglio, V.; Merlo, L.; Aricò, A. S.

2014-12-01

186

Attachment of killed Mycoplasma gallisepticum cells and membranes to erythrocytes  

SciTech Connect

To correlate viability with attachment capacity, Mycoplasma gallisepticum cells harvested at different growth phases and treated by various agents were tested for their capacity to attach to human erythrocytes. The results show that viability per se is not essential for M. gallisepticum attachment to erythrocytes, as cells killed by ultraviolet irradiation and membranes isolated by lysing M. gallisepticum cells by various means retained attachment capacity. However, treatment of the mycoplasmas by protein-denaturing agents, such as heart, glutaraldehyde, or prolonged exposure to low pH, drastically affected or even abolished attachment, supporting the protein nature of the mycoplasma membrane components responsible for specific binding to the sialoglycoprotein receptors on the erythrocytes.

Banai, M.; Kahane, I.; Feldner, J.; Razin, S.

1981-11-01

187

Prevalence and Specificity of RBC Alloantibodies in Indian Patients Attending a Tertiary Care Hospital  

PubMed Central

Background. Red blood cell (RBC) alloimmunization results from genetic disparity of RBC antigens between donor and recipients. Data about alloimmunization rate in general patient population is scarce especially from resource limited countries. We undertook this study to determine prevalence and specificity of RBC alloantibodies in patients admitted in various clinical specialties at a tertiary care hospital in North India. Methods. Antibody screening was carried out in 11,235 patients on automated QWALYS 3 platform (Diagast, Loos, France). Antibody identification was carried out with an 11-cell identification panel (ID-Diapanel, Diamed GmbH, Switzerland). Results. The overall incidence of RBC alloimmunization in transfused patients was 1.4% (157/11235), with anti-E being the most common specificity (36.3%), followed by anti-D (16%), anti-c (6.4%), anti-c + E (6.4%), anti-C + D (5.1%), and anti-K (4.5%). The highest incidence of alloimmunization was observed in hematology/oncology patients (1.9%), whereas in other specialties the range was 0.7–1%. Conclusion. As alloimmunization complicates the transfusion outcomes, authors recommend pretransfusion antibody screening and issue of Rh and Kell matched blood to patients who warrant high transfusion requirements in future. PMID:25386192

Zaman, Shamsuz; Chaurasia, Rahul; Chatterjee, Kabita; Thapliyal, Rakesh Mohan

2014-01-01

188

Spring-network-based model of a red blood cell for simulating mesoscopic blood flow.  

PubMed

We developed a mechanical model of a red blood cell (RBC) that is capable of expressing its characteristic behaviors in shear flows. The RBC was modeled as a closed shell membrane consisting of spring networks in the framework of the energy minimum concept. The fluid forces acting on RBCs were modeled from Newton's viscosity law and the conservation of momentum. In a steady shear flow, the RBC model exhibited various behaviors, depending on the shear rate; it tumbled, tank-treaded, or both. The transition from tumbling to tank-treading occurred at a shear rate of 20 s(?-?1). The simulation of an RBC in steady and unsteady parallel shear flows (Couette flows) showed that the deformation parameters of the RBC were consistent with experimental results. The RBC in Poiseuille flow migrated radially towards the central axis of the flow channel. Axial migration became faster with an increase in the viscosity of the media, qualitatively consistent with experimental results. These results demonstrate that the proposed model satisfies the essential conditions for simulating RBC behavior in blood flow. Finally, a large-scale RBC flow simulation was implemented to show the capability of the proposed model for analyzing the mesoscopic nature of blood flow. PMID:23293072

Nakamura, Masanori; Bessho, Sadao; Wada, Shigeo

2013-01-01

189

Water Visualization and Flooding in Polymer Electrolyte Membrane Fuel Cells  

E-print Network

Water Visualization and Flooding in Polymer Electrolyte Membrane Fuel Cells Brian Holsclaw West and conditions Used in commercial designs Channels can be easily clogged by water ­ flooding Need water or larger design No channels for flooding Vertical inlet/outlet allows cell to auto-drain water Water can

Petta, Jason

190

Tetraspanins regulate the protrusive activities of cell membrane  

Microsoft Academic Search

Tetraspanins have gained increased attention due to their functional versatility. But the universal cellular mechanism that governs such versatility remains unknown. Herein we present the evidence that tetraspanins CD81 and CD82 regulate the formation and\\/or development of cell membrane protrusions. We analyzed the ultrastructure of the cells in which a tetraspanin is either overexpressed or ablated using transmission electron microscopy.

Rafijul Bari; Qiusha Guo; Bing Xia; Yanhui H. Zhang; Eldon E. Giesert; Shoshana Levy; Jie J. Zheng; Xin A. Zhang

191

Carbon monoxide poisoning of proton-exchange membrane fuel cells  

Microsoft Academic Search

The platinum-alloy catalyst used in proton-exchange membrane (PEM) fuel cell anodes is highly susceptible to carbon monoxide (CO) poisoning. CO reduces the catalyst activity by blocking active catalyst sites normally available for hydrogen chemisorption and dissociation. The reaction kinetics at the anode catalyst surface can be used to estimate the decrease in cell voltage due to various levels of CO

Aida Rodrigues; John C. Amphlett; Ronald F. Mann; Brant A. Peppley; Pierre R. Roberge

1997-01-01

192

Probing T cell membrane organization using dimeric MHCIg complexes  

E-print Network

organization; Binding assay; Lipid rafts; Fusion constructs; Crosslinks; Clusters; Sensitivity 1. IntroductionReview Probing T cell membrane organization using dimeric MHC­Ig complexes Tarek M. Fahmy, Joan G of T cells using dimeric major histocompatibility complexes (MHC), MHC­Ig. MHC­Ig complexes are useful

Fahmy, Tarek

193

Anion selective membrane. [ion exchange resins and ion exchange membrane electrolytes for electrolytic cells  

NASA Technical Reports Server (NTRS)

Experimental anion permselective membranes were prepared and tested for their suitability as cell separators in a chemical redox power storage system being developed at NASA-Lewis Research Center. The goals of long-term (1000 hr) oxidative and thermal stability at 80 C in FeCl3 and CrCl3 electrolytes were met by most of the weak base and strong base amino exchange groups considered in the program. Good stability is exhibited by several of the membrane substrate resins. These are 'styrene' divinylbenzene copolymer and PVC film. At least four membrane systems produce strong flexible films with electrochemical properties (resistivity, cation transfer) superior to those of the 103QZL, the most promising commercial membrane. The physical and chemical properties of the resins are listed.

Alexander, S. S.; Geoffroy, R. R.; Hodgdon, R. B.

1975-01-01

194

Composite polymer membranes for proton exchange membrane fuel cells operating at elevated temperatures and reduced humidities  

NASA Astrophysics Data System (ADS)

Proton Exchange Membrane Fuel Cells (PEMFCs) are the leading candidate in the fuel cell technology due to the high power density, solid electrolyte, and low operational temperature. However, PEMFCs operating in the normal temperature range (60-80°C) face problems including poor carbon monoxide tolerance and heat rejection. The poisoning effect can be significantly relieved by operating the fuel cell at elevated temperature, which also improves the heat rejection and electrochemical kinetics. Low relative humidity (RH) operation is also desirable to simplify the reactant humidification system. However, at elevated temperatures, reduced RH PEMFC performance is seriously impaired due to irreversible water loss from presently employed state-of-the-art polymer membrane, Nafion. This thesis focuses on developing polymer electrolyte membranes with high water retention ability for operation in elevated temperature (110-150°C), reduced humidity (˜50%RH) PEMFCs. One approach is to alter Nafion by adding inorganic particles such as TiO2, SiO2, Zr(HPO 4)2, etc. While the presence of these materials in Nafion has proven beneficial, a reduction or no improvement in the PEMFC performance of Nafion/TiO2 and Nafion/Zr(HPO4)2 membranes is observed with reduced particle sizes or increased particle loadings in Nafion. It is concluded that the PEMFC performance enhancement associated with addition of these inorganic particles was not due to the particle hydrophilicity. Rather, the particle, partially located in the hydrophobic region of the membrane, benefits the cell performance by altering the membrane structure. Water transport properties of some Nafion composite membranes were investigated by NMR methods including pulsed field gradient spin echo diffusion, spin-lattice relaxation, and spectral measurements. Compared to unmodified Nafion, composite membranes materials exhibit longer longitudinal relaxation time constant T1. In addition to the Nafion material, sulfonated styrene-ethylene/butylene-styrene triblock copolymer (sSEBS) was investigated as an alternate membrane candidate. sSEBS was modified through introduction of polymer crosslinks using benzephenone as a photoinitiator and addition of a titania co-phase. A photocrosslinked membrane initially containing 15% benzophenone and 3% titania laminated with a 10 mum Nafion layer was found to produce the best PEMFC performance (120°C, 50%RH).

Zhang, Tao

195

Bipolar membranes in forward bias region for fuel cell reactors  

Microsoft Academic Search

Three bipolar membranes, two home-made composed of commercial cation (DuPont) and anion (FuMA-Tech) exchange membranes (called Nafion\\/FT-FAA and Nafion\\/FT-FAS) and a commercial one, BP-1 from FuMA-Tech, were investigated in order to characterize their suitability to use in a H2\\/O2 fuel cell intended to produce hydrogen peroxide on the cathode instead of water. The Nafion\\/FT-FAA and Nafion\\/FT-FAS membranes were prepared using

Elena Lobyntseva; Tanja Kallio; Kyösti Kontturi

2006-01-01

196

Membrane proteins of dense lysosomes from Chinese hamster ovary cells  

SciTech Connect

In this work membrane proteins from lysosomes were studied in order to gain more information on the biogenesis and intracellular sorting of this class of membrane proteins. Membrane proteins were isolated from a purified population of lysosomes. These proteins were then examined for various co- and post-translational modifications which could serve as potential intracellular sorting signals. Biochemical analysis using marker enzymatic activities detected no plasma membrane, Golgi, endoplasmic reticulum, peroxisomes, mitochondria, or cytosol. Analysis after incorporation of ({sup 3}H)thymidine or ({sup 3}H)uridine detected no nuclei or ribosomes. A fraction containing integral membrane proteins was obtained from the dense lysosomes by extraction with Triton X-114. Twenty-three polypeptides which incorporated both ({sup 35}S)methionine and ({sup 3}H)leucine were detected by SDS PAGE in this membrane fraction, and ranged in molecular weight from 30-130 kDa. After incorporation by cells of various radioactive metabolic precursors, the membrane fraction from dense lysosomes was examined and was found to be enriched in mannose, galactose, fucose, palmitate, myristate, and sulfate, but was depleted in phosphate. The membrane fraction from dense lysosomes was then analyzed by SDS PAGE to determine the apparent molecular weights of modified polypepties.

Chance, S.C.

1987-01-01

197

Membrane and MEA Development in Polymer Electrolyte Fuel Cells  

Microsoft Academic Search

\\u000a The polymer electrolyte fuel cell (PEFC) is based on Nafion polymer membranes operating at a temperature of 80°C. The main\\u000a characteristics (structure and properties) and problems of Nafion-based PEFC technology are discussed. The primary drawbacks\\u000a of Nafion membranes are poor conductivity at low relative humidities (and consequently at temperatures >100°C and ambient\\u000a pressure) and large crossover of methanol in direct

Panagiotis Trogadas; Vijay Ramani

2009-01-01

198

Computational fluid dynamics modeling of proton exchange membrane fuel cells  

Microsoft Academic Search

A transient, multi-dimensional model has been developed to simulate proton exchange membrane (PEM) fuel cells. The model accounts simultaneously for electrochemical kinetics, current distribution, hydrodynamics and multi-component transport. A single set of conservation equations valid for flow channels, gas-diffusion electrodes, catalyst layers and the membrane region are developed and numerically solved using a finite-volume-based computational fluid dynamics (CFD) technique. The

SUKKEE UM; C.-Y. Wang; KEN S. CHEN

2000-01-01

199

Nanodomain stabilization dynamics in plasma membranes of biological cells  

NASA Astrophysics Data System (ADS)

We discover that a synergistically amplifying role of stabilizing membrane proteins and continuous lipid recycling can explain the physics governing the stability, polydispersity, and dynamics of lipid raft domains in plasma membranes of biological cells. We establish the conjecture using a generalized order parameter based on theoretical formalism, endorsed by detailed scaling arguments and domain mapping. Quantitative agreements with morphological distributions of raft complexes, as obtained from Förster resonance energy transfer based visualization, support the present theoretical conjecture.

Das, Tamal; Maiti, Tapas K.; Chakraborty, Suman

2011-02-01

200

Development of structured polymer electrolyte membranes for fuel cell applications  

Microsoft Academic Search

The objective of this research was to explore structure-property relationships to develop the understanding needed for introduction of superior PEM materials. Polymer electrolyte membranes based on sulfonated poly(ether ketone ketone) (SPEKK) were fabricated using N-methyl pyrrolidone as casting solvent. The membranes were characterized in terms of properties that were relevant to fuel cell applications, such as proton conductivity, methanol permeability,

Jeffrey Gasa

2006-01-01

201

Cell volume and membrane stretch independently control K+ channel activity  

PubMed Central

A number of potassium channels including members of the KCNQ family and the Ca2+ activated IK and SK, but not BK, are strongly and reversibly regulated by small changes in cell volume. It has been argued that this general regulation is mediated through sensitivity to changes in membrane stretch. To test this hypothesis we have studied the regulation of KCNQ1 and BK channels after expression in Xenopus oocytes. Results from cell-attached patch clamp studies (?50 ?m2 macropatches) in oocytes expressing BK channels demonstrate that the macroscopic volume-insensitive BK current increases with increasing negative hydrostatic pressure (suction) applied to the pipette. Thus, at a pipette pressure of ?5.0 ± 0.1 mmHg the increase amounted to 381 ± 146% (mean ±s.e.m., n= 6, P < 0.025). In contrast, in oocytes expressing the strongly volume-sensitive KCNQ1 channel, the current was not affected by membrane stretch. The results indicate that (1) activation of BK channels by local membrane stretch is not mimicked by membrane stress induced by cell swelling, and (2) activation of KCNQ1 channels by cell volume increase is not mediated by local tension in the cell membrane. We conclude that stretch and volume sensitivity can be considered two independent regulatory mechanisms. PMID:19289549

Hammami, Sofia; Willumsen, Niels J; Olsen, Hervør L; Morera, Francisco J; Latorre, Ramón; Klaerke, Dan A

2009-01-01

202

Membrane distribution of sodium-hydrogen and chloride-bicarbonate exchangers in crypt and villus cell membranes from rabbit ileum.  

PubMed Central

Present evidence suggests that in the small intestine, villus cells are primarily absorptive and crypt cells are primarily secretory. In order to further confirm that there are differences in transport properties between villus and crypt cells, we have separated villus from crypt cells, using calcium chelations techniques, and determined the distribution of Na:H and Cl:HCO3 exchange activity on brush border membrane and basolateral membrane preparations from these two cell populations. Separation of cells was determined utilizing alkaline phosphatase and maltase activity as a marker of villus cells and thymidine kinase activity as a marker of crypt cells. Utilizing these techniques, we were able to sequentially collect cells along the villus-crypt axis. Na-stimulated glucose and alanine uptake in brush border membrane vesicles diminished from the villus to the crypt region in the sequentially collected cells fractions, further suggesting separation of these cells. Brush border and basolateral membranes were then prepared from cells from the villus and crypt areas, utilizing a continuous sucrose gradient. In the villus cells, Na:H exchange activity was found associated with both the brush border and basolateral membrane, whereas, in crypt cells, Na:H exchange activity was only found on the basolateral membrane. Cl:HCO3 exchange activity was found only on the brush border membrane, in both villus and crypt cells. These studies suggest functional heterogeneity in ion transport between villus and crypt cells. PMID:2848868

Knickelbein, R G; Aronson, P S; Dobbins, J W

1988-01-01

203

Evaluation of membranes for use in on-line cell separation during mammalian cell perfusion processes.  

PubMed

In this study two microporous hollow fibre membranes were evaluated for their use as cell retention device in continuous perfusion systems. A chemically modified permanent hydrophillic PTFE membrane and a hydrophilized PP membrane were tested. To investigate the filtration characteristic under process conditions each membrane was tested during a long term perfusion cultivation of a hybridoma cell line. In both cultivations the conditions influencing membrane filtration (e.g. transmembrane flux) were kept constant. Filtration behaviour was investigated by monitoring transmembrane pressure and protein permeability. Transmembrane pressure was measured on-line with an autoclavable piezo-resistive pressure sensor. Protein permeability was determined by quantitative evaluation of unreduced, Coomassie stained SDS-PAGE. The membrane fouling process influences the filtration characteristic of both membranes in a different way. After fermentation the PP membrane was blocked by a thick gel layer located in the big outer pores of the asymmetric membrane structure. The hydraulic resistance was higher but the protein permeability was slightly better than of the PTFE membrane. For this reason the PP membrane should be preferred. On the other hand, transmembrane pressure decreases slower when the PTFE membrane is used, which favours this membrane for long term cultivations, especially when low molecular weight proteins (< 30 KD) are produced. PMID:7765937

Büntemeyer, H; Böhme, C; Lehmann, J

1994-01-01

204

The protective effect of aqueous extracts of roselle (Hibiscus sabdariffa L. UKMR-2) against red blood cell membrane oxidative stress in rats with streptozotocin-induced diabetes  

PubMed Central

OBJECTIVES: The aim of this study was to investigate the protective effects of aqueous extracts of roselle (Hibiscus sabdariffa L. UKMR-2) against red blood cell (RBC) membrane oxidative stress in rats with streptozotocin-induced diabetes. METHODS: Forty male Sprague-Dawley rats weighing 230-250 g were randomly divided into four groups (n?=?10 rats each): control group (N), roselle-treated control group, diabetic group, and roselle-treated diabetic group. Roselle was administered by force-feeding with aqueous extracts of roselle (100 mg/kg body weight) for 28 days. RESULTS: The results demonstrated that the malondialdehyde levels of the red blood cell membranes in the diabetic group were significantly higher than the levels in the roselle-treated control and roselle-treated diabetic groups. The protein carbonyl level was significantly higher in the roselle-treated diabetic group than in the roselle-treated control group but lower than that in the diabetic group. A significant increase in the red blood cell membrane superoxide dismutase enzyme was found in roselle-treated diabetic rats compared with roselle-treated control rats and diabetic rats. The total protein level of the red blood cell membrane, osmotic fragility, and red blood cell morphology were maintained. CONCLUSION: The present study demonstrates that aqueous extracts of roselle possess a protective effect against red blood cell membrane oxidative stress in rats with streptozotocin-induced diabetes. These data suggest that roselle can be used as a natural antioxidative supplement in the prevention of oxidative damage in diabetic patients. PMID:24212844

Mohamed, Jamaludin; Shing, Saw Wuan; Md Idris, Muhd Hanis; Budin, Siti Balkis; Zainalabidin, Satirah

2013-01-01

205

Indole prevents Escherichia coli cell division by modulating membrane potential  

PubMed Central

Indole is a bacterial signalling molecule that blocks E. coli cell division at concentrations of 3–5 mM. We have shown that indole is a proton ionophore and that this activity is key to the inhibition of division. By reducing the electrochemical potential across the cytoplasmic membrane of E. coli, indole deactivates MinCD oscillation and prevents formation of the FtsZ ring that is a prerequisite for division. This is the first example of a natural ionophore regulating a key biological process. Our findings have implications for our understanding of membrane biology, bacterial cell cycle control and potentially for the design of antibiotics that target the cell membrane. PMID:22387460

Chimerel, Catalin; Field, Christopher M.; Pinero-Fernandez, Silvia; Keyser, Ulrich F.; Summers, David K.

2012-01-01

206

Basement membranes and artificial substrates in cell transplantation  

Microsoft Academic Search

This article will concentrate largely on the current developments in the area of cell transplantations presented at the 1st Workshop for Cell Transplantation in Age-related Macular Degeneration. In particular, this brief review will address our current understanding of the role of cell–matrix interactions by covering the pathobiology of normal ageing Bruch’s membrane; some of the problems faced at the time

Carl Sheridan; Rachel Williams; Ian Grierson

2004-01-01

207

Cell surface energy and membrane associated actin in lymphocytes  

Microsoft Academic Search

We have shown previously that membrane associated actin correlates with the migratory abilities of lymphocytes during recirculation,\\u000a and that cell surface energy correlates with the adhesiveness of lymphocytes to other cells. In this study, measurements of\\u000a actin content and cell surface energy have been made for various lymphocyte subpopulations to examine the possibility that\\u000a recirculation ability may be related to

Bernard Mely-Goubert; Donald Bellgrau; Donald F. Gerson

1988-01-01

208

PROTEIN STRUCTURE: Pumping Iron Through Cell Membranes  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. Despite their importance in various cellular functions, the three-dimensional structure at atomic resolution has been determined for only a few membrane proteins. In his Perspective, Braun discusses results reported in the same issue by Ferguson et al. in which the crystal structure of FhuA, an iron transporter protein, has been determined at high resolution. This and related proteins may be the general model for a large class of iron-transporting molecules.

Volkmar Braun (Universität Tüebingen;Department of Mikrobiologie/Membranphysiologie)

1998-12-18

209

Dielectrophoretic discrimination of bovine red blood cell starvation age by buffer selection and membrane cross-linking  

Microsoft Academic Search

We report an interesting buffer electric relaxation time tuning technique, coupled with a glutaraldehyde cross-linking cell fixation reaction, which allows for sensitive dielectrophoretic analysis and discrimination of bovine red blood cell (bRBC) starvation age. The buffer composition is selected such that two easily accessible dielectrophoretic crossover frequencies (cof) exist. Low concentration glutaraldehyde fixation was observed to produce a threefold decrease

Jason E. Gordon; Zachary Gagnon; Hsueh-Chia Chang

2007-01-01

210

Application of graphene membrane in micro-Golay cell array  

NASA Astrophysics Data System (ADS)

We report the design, simulation, and fabrication of a miniaturized Golay cell array, implemented with monolayer graphene suspended over a TEM grid as the deflecting membrane. Currently, ultra-thin membranes for Golay cell applications suffer diminishing responsivity as the lateral dimensions are reduced to the microscopic scale. We propose graphene as the ideal membrane material for micro-Golay cell arrays, whereby the minimal elastic stiffness of atomically thin graphene allows membranes to be scaled to microscopic dimensions. We examine how graphene's unique material parameters, such as high mobility, negligible gas permeability, and supreme strength, offer ease of fabrication and improved performance over existing technology. Simulations of graphene membrane deflection versus temperature are presented, with an analysis of the optimal geometry for maximum sensitivity. Cavities with all spatial dimensions under 100 ?m are predicted to provide sensitivities of hundreds of nanometres per Kelvin, in good competition with existing research on devices many times larger. Up to a four-fold increase in responsivity of 400 nm/K is predicted for a graphene cell of the same dimensions as current technology, and a three-fold increase for a cell one quarter the diameter. These predictions permit an increased detector density in a focal plane array application while still providing improved responsivity. Furthermore, our fabrication method permits the construction of arrays consisting of thousands of devices, avoiding individual cell assembly and including built-in electrical contacts due to the conductive nature of graphene. We also present a theoretical analysis of interferometric optical read-out of membrane deflection.

Ledwosinska, Elizabeth; Szkopek, Thomas; Guermoune, Abdeladim; Siaj, Mohamed

2012-02-01

211

Optimization of a proton exchange membrane fuel cell membrane electrode assembly  

Microsoft Academic Search

A computational framework for fuel cell analysis and optimization is presented as an innovative alternative to the time consuming\\u000a trial-and-error process currently used for fuel cell design. The framework is based on a two-dimensional through-the-channel\\u000a isothermal, isobaric and single phase membrane electrode assembly (MEA) model. The model input parameters are the manufacturing\\u000a parameters used to build the MEA: platinum loading,

Marc Secanell; Ron Songprakorp; Ned Djilali; Afzal Suleman

2010-01-01

212

Physical membrane displacement: Reconstitution in a cell-free system and relationship to cell growth +  

Microsoft Academic Search

Summary Physical membrane displacement is a process common to all forms of vesicle budding as well as cell enlargement and pleomorphic shape changes. Cell-free reconstitution of membrane budding has been achieved with transitional endoplasmic reticulum fractions from both plants and animals where 50 to 70 nm transition vesicles have been observed to bud from the part-rough, part-smooth membrane elements that

D. J. Morré

1994-01-01

213

Combined Biological/Chemical Treatment in RBC (Rotating Biological Contactors) Plants.  

National Technical Information Service (NTIS)

Combined biological/chemical treatment can be obtained in RBC plants by adding precipitant before or into the RBC tank (Simultaneous precipitation), after the RBC-tank and before a flocculation/sedimentation system (Combined precipitation) or with separat...

H. Oedegaard

1982-01-01

214

Oncostatin M regulates membrane traffic and stimulates bile canalicular membrane biogenesis in HepG2 cells  

PubMed Central

Hepatocytes are the major epithelial cells of the liver and they display membrane polarity: the sinusoidal membrane representing the basolateral surface, while the bile canalicular membrane is typical of the apical membrane. In polarized HepG2 cells an endosomal organelle, SAC, fulfills a prominent role in the biogenesis of the canalicular membrane, reflected by its ability to sort and redistribute apical and basolateral sphingolipids. Here we show that SAC appears to be a crucial target for a cytokine-induced signal transduction pathway, which stimulates membrane transport exiting from this compartment promoting apical membrane biogenesis. Thus, oncostatin M, an IL-6-type cytokine, stimulates membrane polarity development in HepG2 cells via the gp130 receptor unit, which activates a protein kinase A-dependent and sphingomyelin-marked membrane transport pathway from SAC to the apical membrane. To exert its signal transducing function, gp130 is recruited into detergent-resistant membrane microdomains at the basolateral membrane. These data provide a clue for a molecular mechanism that couples the biogenesis of an apical plasma membrane domain to the regulation of intracellular transport in response to an extracellular, basolaterally localized stimulus. PMID:12456648

van der Wouden, Johanna M.; van IJzendoorn, Sven C.D.; Hoekstra, Dick

2002-01-01

215

Filter-exchange PGSE NMR determination of cell membrane permeability  

NASA Astrophysics Data System (ADS)

A new PGSE NMR sequence is introduced for measuring diffusive transport across the plasma membrane of living cells. A "diffusion filter" and a variable mixing time precedes a standard PGSE block for diffusion encoding of the NMR signal. The filter is a PGSE block optimized for selectively removing the magnetization of the extracellular water. With increasing mixing time the intra- and extracellular components approach their equilibrium fractional populations. The rate of exchange can be measured using only a few minutes of instrument time. Water exchange over the plasma membrane of starved yeast cells is studied in the temperature range +5 to +32 °C.

Åslund, Ingrid; Nowacka, Agnieszka; Nilsson, Markus; Topgaard, Daniel

2009-10-01

216

Amniotic Fluid and Amniotic Membrane Stem Cells: Marker Discovery  

PubMed Central

Amniotic fluid (AF) and amniotic membrane (AM) have been recently characterized as promising sources of stem or progenitor cells. Both not only contain subpopulations with stem cell characteristics resembling to adult stem cells, such as mesenchymal stem cells, but also exhibit some embryonic stem cell properties like (i) expression of pluripotency markers, (ii) high expansion in vitro, or (iii) multilineage differentiation capacity. Recent efforts have been focused on the isolation and the detailed characterization of these stem cell types. However, variations in their phenotype, their heterogeneity described by different groups, and the absence of a single marker expressed only in these cells may prevent the isolation of a pure homogeneous stem cell population from these sources and their potential use of these cells in therapeutic applications. In this paper, we aim to summarize the recent progress in marker discovery for stem cells derived from fetal sources such as AF and AM, using novel methodologies based on transcriptomics, proteomics, or secretome analyses. PMID:22701492

Roubelakis, Maria G.; Trohatou, Ourania; Anagnou, Nicholas P.

2012-01-01

217

The role of cell membranes in the regulation of lignification in pine cells  

NASA Technical Reports Server (NTRS)

The identity of pine cell membranes bearing PAL enzyme activity, the isolation of a plasma membrane preparation from pine cells for testing as a regulatory barrier in lignification, and the measurement of the geopotential effect in pine stems are presented. A model to describe and predict the interaction of gravity and lignification of higher plants was developed.

Hendrix, D. L.

1978-01-01

218

Mechanistic Diversity of Cytokine Receptor Signaling Across Cell Membranes  

NSDL National Science Digital Library

This STKE Review addresses the issue of how signals get across biological membranes to initiate signal transduction pathways inside the cell. Extracellular ligands bind to their specific membrane receptors and mediate signal transduction by two general mechanisms. In the first, "Vertical Signaling," changes in a preassembled transmembrane receptor structure are relayed to bring about changes on the other side of the membrane, and this often occurs extremely quickly. Such changes may lead to opening of ion channels, or may be detected by other proteins that are specific to a particular activated receptor structure. In the second, "Horizontal Signaling," ligand binding induces a change in the association of receptors in the plane of the membrane. This mechanism predominates in cytokine signaling, in which signaling is slower, and often leads to regulation of transcription of specific genes. We focus here on the surprising diversity in the ways horizontal signaling controls the activation state of receptor proteins.

Robert M. Stroud (University of California; REV); James A. Wells (Sunesis Pharmaceuticals; REV)

2004-05-04

219

Radiation effects on membranes - 1. Cellular permeability and cell survival  

SciTech Connect

The effect of various doses of ..gamma.. radiation (5-60 krad) on the membrane permeability and cell survival of Candida albicans, a pathogenic yeast, was investigated. A reduction in the cell survival and in the accumulation of amino acids (proline, glycine, lysine, and glutamic acid) was observed following irradiation. The rate of oxygen uptake, which is often associated with transport, was also reduced. There was no damage to available sulfhydryl groups following the exposure of cells to various doses of ..gamma.. radiation. The membrane lipid composition of C. albicans cells can be altered by growing them in alkanes of varying chain lengths. The effects of such altered lipid composition on radiosensitivity was examined. It was observed that C. albicans cells with altered lipid content acquire resistance to ..gamma.. radiation.

Khare, S.; Jayakumar, A.; Trivedi, A.; Kesavan, P.C.; Prasad, R.

1982-05-01

220

Inorganic Nanoporous Membranes for Immunoisolated Cell-Based Drug Delivery  

PubMed Central

Materials advances enabled by nanotechnology have brought about promising approaches to improve the encapsulation mechanism for immunoisolated cell-based drug delivery. Cell-based drug delivery is a promising treatment for many diseases but has thus far achieved only limited clinical success. Treatment of insulin dependent diabetes mellitus (IDDM) by transplantation of pancreatic ?-cells represents the most anticipated application of cell-based drug delivery technology. This review outlines the challenges involved with maintaining transplanted cell viability and discusses how inorganic nanoporous membranes may be useful in achieving clinical success. PMID:20384222

Mendelsohn, Adam; Desai, Tejal

2014-01-01

221

Evidence for Bidirectional Endocannabinoid Transport across Cell Membranes*  

PubMed Central

Despite extensive research on the trafficking of anandamide (AEA) across cell membranes, little is known about the membrane transport of other endocannabinoids, such as 2-arachidonoylglycerol (2-AG). Previous studies have provided data both in favor and against a cell membrane carrier-mediated transport of endocannabinoids, using different methodological approaches. Because AEA and 2-AG undergo rapid and almost complete intracellular hydrolysis, we employed a combination of radioligand assays and absolute quantification of cellular and extracellular endocannabinoid levels. In human U937 leukemia cells, 100 nm AEA and 1 ?m 2-AG were taken up through a fast and saturable process, reaching a plateau after 5 min. Employing differential pharmacological blockage of endocannabinoid uptake, breakdown, and interaction with intracellular binding proteins, we show that eicosanoid endocannabinoids harboring an arachidonoyl chain compete for a common membrane target that regulates their transport, whereas other N-acylethanolamines did not interfere with AEA and 2-AG uptake. By combining fatty acid amide hydrolase or monoacyl glycerol lipase inhibitors with hydrolase-inactive concentrations of the AEA transport inhibitors UCM707 (1 ?m) and OMDM-2 (5 ?m), a functional synergism on cellular AEA and 2-AG uptake was observed. Intriguingly, structurally unrelated AEA uptake inhibitors also blocked the cellular release of AEA and 2-AG. We show, for the first time, that UCM707 and OMDM-2 inhibit the bidirectional movement of AEA and 2-AG across cell membranes. Our findings suggest that a putative endocannabinoid cell membrane transporter controls the cellular AEA and 2-AG trafficking and metabolism. PMID:22879589

Chicca, Andrea; Marazzi, Janine; Nicolussi, Simon; Gertsch, Jurg

2012-01-01

222

Isolation of plasma membranes from cultured glioma cells and application to evaluation of membrane sphingomyelin turnover  

SciTech Connect

A rapid and reliable method for the isolation of plasma membranes and microsomes of high purity and yield from cultured glioma cells is described. The procedure involves disruption by N2 cavitation, preliminary separation by centrifugation in Tricine buffer, and final separation on a gradient formed from 40% Percoll at pH 9.3. Enzyme and chemical markers indicated greater than 60% yield with six- to eightfold enrichment for plasma membranes and greater than 25% yield with three- to fourfold enrichment for a microsomal fraction consisting mainly of endoplasmic reticulum. The final fractions were obtained with high reproducibility in less than 1 h from the time of cell harvesting. Application of this procedure to human fibroblasts in culture is assessed. The isolation procedure was applied to investigations of synthesis and turnover of sphingomyelin and phosphatidylcholine in plasma membranes of glioma cells following incubation for 4-24 h with (methyl-/sup 3/H)choline. These studies indicated that radioactivity from phosphatidylcholine synthesized in microsomes from exogenous choline may serve as a precursor of the head-group of sphingomyelin accumulating in the plasma membrane.

Cook, H.W.; Palmer, F.B.; Byers, D.M.; Spence, M.W.

1988-11-01

223

Membrane with internal passages to permit fluid flow and an electrochemical cell containing the same  

NASA Technical Reports Server (NTRS)

The invention provides an improved proton exchange membrane for use in electrochemical cells having internal passages parallel to the membrane surface, an apparatus and process for making the membrane, membrane and electrode assemblies fabricated using the membrane, and the application of the membrane and electrode assemblies to a variety of devices, both electrochemical and otherwise. The passages in the membrane extend from one edge of the membrane to another and allow fluid flow through the membrane and give access directly to the membrane for purposes of hydration.

Cisar, Alan J. (Inventor); Gonzalez-Martin, Anuncia (Inventor); Hitchens, G. Duncan (Inventor); Murphy, Oliver J. (Inventor)

1997-01-01

224

Desmosome Assembly and Cell-Cell Adhesion Are Membrane Raft-dependent Processes  

PubMed Central

The aim of our study was to investigate the association of desmosomal proteins with cholesterol-enriched membrane domains, commonly called membrane rafts, and the influence of cholesterol on desmosome assembly in epithelial Madin-Darby canine kidney cells (clone MDc-2). Biochemical analysis proved an association of desmosomal cadherin desmocollin 2 (Dsc2) in cholesterol-enriched fractions that contain membrane raft markers caveolin-1 and flotillin-1 and the novel raft marker ostreolysin. Cold detergent extraction of biotinylated plasma membranes revealed that ?60% of Dsc2 associates with membrane rafts while the remainder is present in nonraft and cholesterol-poor membranes. The results of immunofluorescence microscopy confirmed colocalization of Dsc2 and ostreolysin. Partial depletion of cholesterol with methyl-?-cyclodextrin disturbs desmosome assembly, as revealed by sequential recordings of live cells. Moreover, cholesterol depletion significantly reduces the strength of cell-cell junctions and partially releases Dsc2 from membrane rafts. Our data indicate that a pool of Dsc2 is associated with membrane rafts, particularly with the ostreolysin type of membrane raft, and that intact membrane rafts are necessary for desmosome assembly. Taken together, these data suggest cholesterol as a potential regulator that promotes desmosome assembly. PMID:21071449

Resnik, Natasa; Sepcic, Kristina; Plemenitas, Ana; Windoffer, Reinhard; Leube, Rudolf; Veranic, Peter

2011-01-01

225

CD2 Promotes Human Natural Killer Cell Membrane Nanotube Formation  

PubMed Central

Membrane nanotubes are thin membranous projections that physically connect two cells. While nanotubes have been studied in human natural killer (NK) cells and are implicated in aiding NK cell cytotoxic function, requirements for their formation to susceptible target cells remain incompletely understood. Here we demonstrate that the CD2-CD58/48 receptor-ligand interaction promotes and is required for nanotube formation in human NK cells. In the CD2? NK cell line YTS, a stable CD2 expression variant enabled effective nanotube formation, and was associated with better cytotoxic function. Importantly, only interactions between an NK cell and a susceptible target cell were associated with multiple nanotubes and the number of nanotubes was inversely correlated with their length. Quantitative live cell fluorescence microscopy of CD2 nanotubes revealed time-dependent enrichment and localization of CD2 to the nanotube tip, and blocking CD2 receptor-ligand interactions prevented nanotube formation. Increased nanotube formation was not simply a feature of receptor-ligand pairing, as a KIR-MHC interaction in the same cell line system failed to promote nanotube formation. Additionally, blocking LFA-1-ICAM and 2B4-CD48 receptor-ligand interactions failed to inhibit nanotube formation. Thus only specific receptor-ligand pairs promote nanotubes. CD2 also promoted nanotube formation in ex vivo NK cells suggesting that CD2 plays a crucial role in the generation of nanotubes between an NK cell and its target. PMID:23112830

Comerci, Colin J.; Mace, Emily M.; Banerjee, Pinaki P.; Orange, Jordan S.

2012-01-01

226

Autophagy modulates cell migration and ?1 integrin membrane recycling  

PubMed Central

Cell migration is dependent on a series of integrated cellular events including the membrane recycling of the extracellular matrix receptor integrins. In this paper, we investigate the role of autophagy in regulating cell migration. In a wound-healing assay, we observed that autophagy was reduced in cells at the leading edge than in cells located rearward. These differences in autophagy were correlated with the robustness of MTOR activity. The spatial difference in the accumulation of autophagic structures was not detected in rapamycin-treated cells, which had less migration capacity than untreated cells. In contrast, the knockdown of the autophagic protein ATG7 stimulated cell migration of HeLa cells. Accordingly, atg3?/? and atg5?/? MEFs have greater cell migration properties than their wild-type counterparts. Stimulation of autophagy increased the co-localization of ?1 integrin-containing vesicles with LC3-stained autophagic vacuoles. Moreover, inhibition of autophagy slowed down the lysosomal degradation of internalized ?1 integrins and promoted its membrane recycling. From these findings, we conclude that autophagy regulates cell migration, a central mechanism in cell development, angiogenesis, and tumor progression, by mitigating the cell surface expression of ?1 integrins. PMID:24036548

Tuloup-Minguez, Veronique; Hamai, Ahmed; Greffard, Anne; Nicolas, Valerie; Codogno, Patrice; Botti, Joelle

2013-01-01

227

Dipole relaxation in erythrocyte membrane: involvement of spectrin skeleton.  

PubMed

Polarization of spectrin-actin undermembrane skeleton of red blood cell (RBC) plasma membranes was studied by impedance spectroscopy. Relatedly, dielectric spectra of suspensions that contained RBCs of humans, mammals (bovine, horse, dog, cat) and birds (turkey, pigeon, duck), and human RBC ghost membranes were continuously obtained during heating from 20 to 70°C. Data for the complex admittance and capacitance were used to derive the suspension resistance, R, and capacitance, C, as well as the energy loss as a function of temperature. As in previous studies, two irreversible temperature-induced transitions in the human RBC plasma membrane were detected at 49.5°C and at 60.7°C (at low heating rate). The transition at 49.5°C was evident from the abrupt changes in R, and C and the fall in the energy loss, due to dipole relaxation. For the erythrocytes of indicated species the changes in R and C displayed remarkable and similar frequency profiles within the 0.05-13MHz domain. These changes were subdued after cross-linking of membranes by diamide (0.3-1.3mM) and glutaraldehyde (0.1-0.4%) and at the presence of glycerol (10%). Based on the above results and previous reports, the dielectric changes at 49.5°C were related to dipole relaxation and segmental mobility of spectrin cytoskeleton. The results open the possibility for selective dielectric thermolysis of cell cytoskeleton. PMID:22513264

Ivanov, I T; Paarvanova, B; Slavov, T

2012-12-01

228

Extracellular Heme Uptake and the Challenges of Bacterial Cell Membranes  

PubMed Central

In bacteria, the fine balance of maintaining adequate iron levels while preventing the deleterious effects of excess iron has led to the evolution of sophisticated cellular mechanisms to obtain, store, and regulate iron. Iron uptake provides a significant challenge given its limited bioavailability and need to be transported across the bacterial cell wall and membranes. Pathogenic bacteria have circumvented the iron-availability issue by utilizing the hosts' heme-containing proteins as a source of iron. Once internalized, iron is liberated from the porphyrin enzymatically for cellular processes within the bacterial cell. Heme, a lipophilic and toxic molecule, poses a significant challenge in terms of transport given its chemical reactivity. As such, pathogenic bacteria have evolved sophisticated membrane transporters to coordinate, sequester, and transport heme. Recent advances in the biochemical and structural characterization of the membrane-bound heme transport proteins are discussed in the context of ligand coordination, protein–protein interaction, and heme transfer. PMID:23046657

Smith, Aaron D.; Wilks, Angela

2013-01-01

229

Electrospun fiber membranes enable proliferation of genetically modified cells  

PubMed Central

Polycaprolactone (PCL) and its blended composites (chitosan, gelatin, and lecithin) are well-established biomaterials that can enrich cell growth and enable tissue engineering. However, their application in the recovery and proliferation of genetically modified cells has not been studied. In the study reported here, we fabricated PCL-biomaterial blended fiber membranes, characterized them using physicochemical techniques, and used them as templates for the growth of genetically modified HCT116-19 colon cancer cells. Our data show that the blended polymers are highly miscible and form homogenous electrospun fiber membranes of uniform texture. The aligned PCL nanofibers support robust cell growth, yielding a 2.5-fold higher proliferation rate than cells plated on standard plastic plate surfaces. PCL-lecithin fiber membranes yielded a 2.7-fold higher rate of proliferation, while PCL-chitosan supported a more modest growth rate (1.5-fold higher). Surprisingly, PCL-gelatin did not enhance cell proliferation when compared to the rate of cell growth on plastic surfaces. PMID:23467983

Borjigin, Mandula; Eskridge, Chris; Niamat, Rohina; Strouse, Bryan; Bialk, Pawel; Kmiec, Eric B

2013-01-01

230

Electrospun fiber membranes enable proliferation of genetically modified cells.  

PubMed

Polycaprolactone (PCL) and its blended composites (chitosan, gelatin, and lecithin) are well-established biomaterials that can enrich cell growth and enable tissue engineering. However, their application in the recovery and proliferation of genetically modified cells has not been studied. In the study reported here, we fabricated PCL-biomaterial blended fiber membranes, characterized them using physicochemical techniques, and used them as templates for the growth of genetically modified HCT116-19 colon cancer cells. Our data show that the blended polymers are highly miscible and form homogenous electrospun fiber membranes of uniform texture. The aligned PCL nanofibers support robust cell growth, yielding a 2.5-fold higher proliferation rate than cells plated on standard plastic plate surfaces. PCL-lecithin fiber membranes yielded a 2.7-fold higher rate of proliferation, while PCL-chitosan supported a more modest growth rate (1.5-fold higher). Surprisingly, PCL-gelatin did not enhance cell proliferation when compared to the rate of cell growth on plastic surfaces. PMID:23467983

Borjigin, Mandula; Eskridge, Chris; Niamat, Rohina; Strouse, Bryan; Bialk, Pawel; Kmiec, Eric B

2013-01-01

231

EVALUATION OF THE RBC PROCESS FOR MUNICIPAL WASTEWATER TREATMENT  

EPA Science Inventory

The major objective of this study was to operate a full scale rotating biological contactor (RBC) to determine if it could produce an effluent that would meet the definition of a secondary effluent (BOD ...

232

Creatine kinase, cell membrane and Duchenne muscular dystrophy  

Microsoft Academic Search

In 1958 Professor Setsuro Ebashi found that serum creatine kinase activity is increased in patients suffering from various muscular dystrophies, especially Duchenne muscular dystrophy (DMD). He and others proposed that creatine kinase passes through the cell membrane as it is released from DMD muscle fibers.

Eijiro Ozawa; Yasuko Hagiwara; Mikiharu Yoshida

1999-01-01

233

Applications of proton exchange membrane fuel cell systems  

Microsoft Academic Search

Proton exchange membrane fuel cells (PEMFCs) have recently passed the test or demonstration phase and have partially reached the commercialization stage due to the impressive worldwide research effort. Despite the currently promising achievements and the plausible prospects of PEMFCs, there are many challenges remaining that need to be overcome before PEMFCs can successfully and economically substitute for the various traditional

Jung-Ho Wee

2007-01-01

234

Tetrazole-based, anhydrous proton exchange membranes for fuel cells.  

PubMed

A tetrazole-based polymer electrolyte membrane showed high conductivity at 20-120°C under dry conditions, offering the potential to dramatically simplify fuel cells for many applications over a wide temperature range without the need for cumbersome humidification and pressurization. PMID:24591010

Song, Min-Kyu; Li, Huiping; Li, Jinhuan; Zhao, Dan; Wang, Jenghan; Liu, Meilin

2014-02-26

235

Reconstitution of synaptic vesicle biogenesis from PC12 cell membranes.  

PubMed

Neuroendocrine PC12 cells contain small microvesicles that closely resemble synaptic vesicles in their physical and chemical properties. Two defining characteristics of synaptic vesicles are their homogeneous size and their unique protein composition. Since synaptic vesicles arise by endocytosis from the plasma membrane, nerve terminals and PC12 cells must contain the molecular machinery to sort synaptic vesicles from other membrane proteins and pinch off vesicles of the correct diameter from a precursor compartment. A cell-free reconstitution system was developed that generates vesicles from PC12 membrane precursors in the presence of ATP and brain cytosol and is temperature dependent. At 15 degrees C, surface-labeled synaptic vesicle proteins accumulate in a donor compartment, while labeled synaptic vesicles cannot be detected. The block of synaptic vesicle formation at 15 degrees C enables the use of the monoclonal antibody, KT3, a specific marker for the epitope-tagged synaptic vesicle protein, VAMP-TAg, to label precursors in the synaptic vesicle biogenesis pathway. From membranes labeled in vivo at 15 degrees C, vesicles generated in vitro at 37 degreesC had the sedimentation characteristics of neuroendocrine synaptic vesicles on glycerol velocity gradients, and excluded the transferrin receptor. Therefore, vesiculation and sorting can be studied in this cell-free system. PMID:9790861

Clift-O'Grady, L; Desnos, C; Lichtenstein, Y; Faúndez, V; Horng, J T; Kelly, R B

1998-10-01

236

Apoptosis method for biomimetic artificial cell membranes employing nanophotonic theranostics  

NASA Astrophysics Data System (ADS)

Colloidal biomimetic disc shaped metallic gold shells with a uniform size distribution were synthesized using red blood cells as sacrificial templates. Red blood cells do not reproduce by dividing; hence they are truly colloidal particles. They are almost completely filled with hemoglobin allowing for an extremely dynamic work cycle with long intercellular vacations separated by self-destructive workloads on the cell surface. This method of exchange is emulated in the presented research. The colloidal disc shaped gold shells were coated with multiple layers of 50nm fluorescent polystyrene spheres followed by chemical removal of the gold core. This process yielded hollow synthetic biomimetic membranes with a strong optical signature that are diffusely permeable to water and impervious to particles larger than a few nanometers. Currently, the most successful synthetic intravascular oxygen carrying materials are perfluorocarbons; however, they break down quickly in roughly 50 hours from overexposure to their in vivo workload. The meso-porous membrane cages will be filled with hundreds of fibrous spheroid conglomerates composed of perfluorocarbon chains that can protrude through the meso-porous membrane as they thermally jostle about the cage. This is to statistically limit the exposure time of individual polymer strands to the self-destructive work at the surface and hopefully will greatly increase the effective functioning lifetime of the perfluorocarbon-based synthetic red blood cell. The artificial membranes are intentionally designed to be weak allowing them to flex under normal pressures and to hopefully burst under more extreme conditions such as blockage.

Gilleland, Cody L.; Waters, Brian D.; Jarvis, Brandon; Schaefers, Justin K.; Renfro, Tim; Gutierrez, Jose; Ussery, Geoffrey; Cavanah, Taylor; Glosser, R.; Landon, Preston B.

2005-08-01

237

Polymer electrolyte membrane fuel cells for communication applications  

Microsoft Academic Search

An advanced portable power source using a 50Watt (PPS-50) polymer electrolyte membrane cell EMFC) system was developed by Ball Aerospace under the US Army, Defense Advanced Research Project Agency (DARPA) and the Office Special Technology (OST) joint program. The PEMFC system was designed as required for commercial and military applications. The system as evaluated extensively under different environmental temperatures and

Deryn Chu; R. Jiang; K. Gardner; R. Jacobs; J. Schmidt; T. Quakenbush; J. Stephens

2001-01-01

238

Membrane Transport Chloride Transport Across Vesicle and Cell  

E-print Network

unilamellar vesicles using a chloride-selective electrode. More specifically, 30 mm unilamellar vesicles (200 the formation of an ion pair.[4a­g] Anion transport by purely electroneutral systems is still quite rare.[4j ions across liposomal membranes and also across live cells grown as polarized epithelia. Receptors 2

Smith, Bradley D.

239

Hereditary red cell membrane disorders and laboratory diagnostic testing.  

PubMed

This overview describes two groups of nonimmune hereditary hemolytic anemias caused by defects in membrane proteins located in distinct layers of the red cell membrane. Hereditary spherocytosis (HS), hereditary elliptocytosis (HE), and hereditary pyropoikilocytosis (HPP) represent disorders of the red cell cytoskeleton. Hereditary stomatocytoses represents disorders of cation permeability in the red cell membrane. The current laboratory screening tests for HS are the osmotic fragility test, acid glycerol lysis time test (AGLT), cryohemolysis test, and eosin-5'-maleimide (EMA)-binding test. For atypical HS, SDS-polyacrylamide gel electrophoresis of erythrocyte membrane proteins is carried out to confirm the diagnosis. The diagnosis of HE/HPP is based on abnormal red cell morphology and the detection of protein 4.1R deficiency or spectrin variants using gel electrophoresis. None of screening tests can detect all HS cases. Some testing centers (a survey of 25 laboratories) use a combination of tests (e.g., AGLT and EMA). No specific screening test for hereditary stomatocytoses is available. The preliminary diagnosis is based on presenting a compensated hemolytic anemia, macrocytosis, and a temperature or time dependent pseudohyperkalemia in some patients. Both the EMA-binding test and the osmotic fragility test may help in differential diagnosis of HS and hereditary stomatocytosis. PMID:23480868

King, M-J; Zanella, A

2013-06-01

240

Carbon monoxide poisoning of proton exchange membrane fuel cells  

Microsoft Academic Search

SUMMARY Proton exchange membrane fuel cell (PEMFC) performance degrades when carbon monoxide (CO) is present in the fuel gas; this is referred to as CO poisoning. This paper investigates CO poisoning of PEMFCs by reviewing work on the electrochemistry of CO and hydrogen, the experimental performance of PEMFCs exhibiting CO poisoning, methods to mitigate CO poisoning and theoretical models of

J. J. Baschuk; Xianguo Li

2001-01-01

241

CAPSTONE SENIOR DESIGN - SUPRAMOLECULAR PROTON EXCHANGE MEMBRANES FOR FUEL CELLS  

EPA Science Inventory

In order to assume a leading role in the burgeoning hydrogen economy, new infrastructure will be required for fuel cell manufacturing and R&D capabilities. The objective of this proposal is the development of a new generation of advanced proton exchange membrane (PEM) technol...

242

Alterations in cell membrane properties caused by perfluorinated compounds  

Microsoft Academic Search

The recent detection of perfluorinated compounds (PFCs) in wildlife from even remote locations has spurred interest in the environmental occurrence and effects of these chemicals. While the global distribution of PFCs is increasingly understood, there is still little information available on their effects on wildlife. The amphiphillic nature of PFCs suggests that their effects could be primarily on cell membranes.

Wen yue Hu; Paul D Jones; Wim DeCoen; Louis King; Pamela Fraker; John Newsted; John P Giesy

2003-01-01

243

Tannic acid effect on membrane of cell surface origin in guinea pig megakaryocytes and platelets.  

PubMed

Plasma membranes in isolated guinea pig megakaryocytes and washed platelets are poorly stained with the usual methods used to outline cell membranes. The addition of tannic acid and calcium to the initial fixative is useful to enhance electron density of all surface-derived membrane systems in these cells. The method described here shows that the increased electron denisty of membrane after fixation in the presence of tannic acid occurs both at the cell surface and along the invaginated membrane systems. PMID:58024

Fedorko, M E; Levine, R F

1976-04-01

244

Voltage Clamp Analysis of Two Inward Current Mechanisms in the Egg Cell Membrane of a Starfish  

Microsoft Academic Search

Ionic mechanisms of excitation were studied in the immature egg cell membrane of a starfish, Mediaster aequalis, by analyzing membrane currents during voltage clamp. The cell membrane shows two different inward current mechanisms. One is activated at a membrane potential of --55 ,~ --50 mV and the other at --7 ~-~ --6 mV. They are referred to as channels I

SUSUMU HAGIWARA; SEIJI OZAWA; OLAV SAND

2009-01-01

245

VIEW OF RBC (REFINED BICARBONATE) BUILDING LOOKING NORTHEAST. DEMOLITION IN ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

VIEW OF RBC (REFINED BICARBONATE) BUILDING LOOKING NORTHEAST. DEMOLITION IN PROGRESS. "ARM & HAMMER BAKING SODA WAS MADE HERE FOR OVER 50 YEARS AND THEN SHIPPED ACROSS THE STREET TO THE CHURCH & DWIGHT PLANT ON WILLIS AVE. (ON THE RIGHT IN THIS PHOTO). LAYING ON THE GROUND IN FRONT OF C&D BUILDING IS PART OF AN RBC DRYING TOWER. - Solvay Process Company, Refined Bicarbonate Building, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

246

Amniotic membrane transplantation for partial limbal stem cell deficiency  

Microsoft Academic Search

Aim—To examine the eYcacy, safety, and long term outcomes of amniotic mem- brane transplantation for corneal surface reconstruction in cases of partial limbal stem cell deficiency. Methods—17 eyes of 15 patients with par- tial limbal stem cell deficiency underwent superficial keratectomy of the conjuncti- valised corneal surface followed by amni- otic membrane transplantation. Cases were followed up for at least

David F Anderson; Pierre Ellies; Renato T F Pires; ScheVer C G Tseng

247

Continuous monitoring of mitochondrial membrane potential in hepatocyte cell suspensions  

Microsoft Academic Search

We report a simple fluorometric method for the continuous monitoring of mitochondrial membrane potential and cell viability in suspensions of hepatocytes exposed in vitro to cytotoxic agents. Suspensions of freshly isolated hepatocytes (106 cells\\/mL) preloaded with rhodamine 123 (Rh 123, 100 ?mol\\/L) are transferred to a thermostatically controlled mixed cuvette to which the desired cytotoxic agent is added. Rh 123

Carlos M. Palmeira; Antonio J. M. Moreno; Vitor M. C. Madeira; Kendall B. Wallace

1996-01-01

248

Effect of BCD Plasma on a Bacteria Cell Membrane  

NASA Astrophysics Data System (ADS)

Abstract Cell membrane rupture is considered to be one of the probable mechanisms for bacterial inactivation using barrier corona discharge (BCD) plasma. In this paper, the effect of the BCD plasma on the Escherichia coli (E. coli) bacteria cell wall was investigated through two analytical methods; Adenosine-5'-triphosphate (ATP) assay and Atomic Force Microscopy (AFM). The ATP assay results indicate an increase in the ATP content of samples which were exposed to the BCD plasma. This implies the bacteria cell rupture. Moreover, AFM images confirm a serious damage of the bacteria cell wall under the influence of the bactericidal agents of the plasma.

Nasrin, Navabsafa; Hamid, Ghomi; Maryam, Nikkhah; Soheila, Mohades; Hossein, Dabiri; Saeed, Ghasemi

2013-07-01

249

Shear stress-induced improvement of red blood cell deformability.  

PubMed

Classically, it is known that red blood cell (RBC) deformability is determined by the geometric and material properties of these cells. Experimental evidence accumulated during the last decade has introduced the concept of active regulation of RBC deformability. This regulation is mainly related to altered associations between membrane skeletal proteins and integral proteins, with the latter serving to anchor the skeleton to the lipid matrix. It has been hypothesized that shear stress induces alterations of RBC deformability: the current study investigated the dynamics of the transient improvement in deformability induced by shear stress at physiologically-relevant levels. RBC were exposed to various levels of shear stress (SS) in a Couette type shearing system that is part of an ektacytometer, thus permitting the changes in RBC deformability during the application of SS to be monitored. Initial studies showed that there is an increase in deformability of the RBC subjected to SS in the range of 5-20 Pa, with kinetics characterized by time constants of a few seconds. Such improvement in deformability, expressed by an elongation index (EI), was faster with higher levels of SS and hence yielded shorter time constants: absolute values of EI increased by 3-8% of the starting level. Upon the removal of the shear stress, this response by RBC was reversible with a slower time course compared to the increase in EI during application of SS. Increased calcium concentration in the RBC suspending medium prevented the improvement of deformability. It is suggested that the improvement of RBC deformability by shear forces may have significant effects on blood flow dynamics, at least in tissues supplied by blood vessels with impaired vasomotor reserve, and may therefore serve as a compensating mechanism for the maintenance of adequate microcirculatory perfusion. PMID:23863281

Meram, Ece; Yilmaz, Bahar D; Bas, Ceren; Atac, Nazl?; Yalcin, O; Meiselman, Herbert J; Baskurt, Oguz K

2013-01-01

250

Erythrocyte membrane model with explicit description of the lipid bilayer and the spectrin network.  

PubMed

The membrane of the red blood cell (RBC) consists of spectrin tetramers connected at actin junctional complexes, forming a two-dimensional (2D) sixfold triangular network anchored to the lipid bilayer. Better understanding of the erythrocyte mechanics in hereditary blood disorders such as spherocytosis, elliptocytosis, and especially, sickle cell disease requires the development of a detailed membrane model. In this study, we introduce a mesoscale implicit-solvent coarse-grained molecular dynamics (CGMD) model of the erythrocyte membrane that explicitly describes the phospholipid bilayer and the cytoskeleton, by extending a previously developed two-component RBC membrane model. We show that the proposed model represents RBC membrane with the appropriate bending stiffness and shear modulus. The timescale and self-consistency of the model are established by comparing our results with experimentally measured viscosity and thermal fluctuations of the RBC membrane. Furthermore, we measure the pressure exerted by the cytoskeleton on the lipid bilayer. We find that defects at the anchoring points of the cytoskeleton to the lipid bilayer (as in spherocytes) cause a reduction in the pressure compared with an intact membrane, whereas defects in the dimer-dimer association of a spectrin filament (as in elliptocytes) cause an even larger decrease in the pressure. We conjecture that this finding may explain why the experimentally measured diffusion coefficients of band-3 proteins are higher in elliptocytes than in spherocytes, and higher than in normal RBCs. Finally, we study the effects that possible attractive forces between the spectrin filaments and the lipid bilayer have on the pressure applied on the lipid bilayer by the filaments. We discover that the attractive forces cause an increase in the pressure as they diminish the effect of membrane protein defects. As this finding contradicts with experimental results, we conclude that the attractive forces are moderate and do not impose a complete attachment of the filaments to the lipid bilayer. PMID:25099803

Li, He; Lykotrafitis, George

2014-08-01

251

Membrane protein synthesis in cell-free systems: from bio-mimetic systems to bio-membranes.  

PubMed

When taking up the gauntlet of studying membrane protein functionality, scientists are provided with a plethora of advantages, which can be exploited for the synthesis of these difficult-to-express proteins by utilizing cell-free protein synthesis systems. Due to their hydrophobicity, membrane proteins have exceptional demands regarding their environment to ensure correct functionality. Thus, the challenge is to find the appropriate hydrophobic support that facilitates proper membrane protein folding. So far, various modes of membrane protein synthesis have been presented. Here, we summarize current state-of-the-art methodologies of membrane protein synthesis in biomimetic-supported systems. The correct folding and functionality of membrane proteins depend in many cases on their integration into a lipid bilayer and subsequent posttranslational modification. We highlight cell-free systems utilizing the advantages of biological membranes. PMID:24931371

Sachse, Rita; Dondapati, Srujan K; Fenz, Susanne F; Schmidt, Thomas; Kubick, Stefan

2014-08-25

252

Anionexchange membrane direct ethanol fuel cells: Status and perspective  

Microsoft Academic Search

Direct ethanol fuel cells (DEFCs) are a promising carbon-neutral and sustainable power source for portable, mobile, and stationary\\u000a applications. However, conventional DEFCs that use acid proton-exchange membranes (typically Nafion type) and platinum-based\\u000a catalysts exhibit low performance (i.e., the state-of-the-art peak power density is 79.5 mW\\/cm2 at 90°C). Anionexchange membrane (AEM) DEFCs that use low-cost AEM and non-platinum catalysts have recently

T. S. Zhao; Y. S. Li; S. Y. Shen

2010-01-01

253

Block copolymers for alkaline fuel cell membrane materials  

NASA Astrophysics Data System (ADS)

Alkaline fuel cells (AFCs) using anion exchange membranes (AEMs) as electrolyte have recently received considerable attention. AFCs offer some advantages over proton exchange membrane fuel cells, including the potential of non-noble metal (e.g. nickel, silver) catalyst on the cathode, which can dramatically lower the fuel cell cost. The main drawback of traditional AFCs is the use of liquid electrolyte (e.g. aqueous potassium hydroxide), which can result in the formation of carbonate precipitates by reaction with carbon dioxide. AEMs with tethered cations can overcome the precipitates formed in traditional AFCs. Our current research focuses on developing different polymer systems (blend, block, grafted, and crosslinked polymers) in order to understand alkaline fuel cell membrane in many aspects and design optimized anion exchange membranes with better alkaline stability, mechanical integrity and ionic conductivity. A number of distinct materials have been produced and characterized. A polymer blend system comprised of poly(vinylbenzyl chloride)-b-polystyrene (PVBC-b-PS) diblock copolymer, prepared by nitroxide mediated polymerization (NMP), with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) or brominated PPO was studied for conversion into a blend membrane for AEM. The formation of a miscible blend matrix improved mechanical properties while maintaining high ionic conductivity through formation of phase separated ionic domains. Using anionic polymerization, a polyethylene based block copolymer was designed where the polyethylene-based block copolymer formed bicontinuous morphological structures to enhance the hydroxide conductivity (up to 94 mS/cm at 80 °C) while excellent mechanical properties (strain up to 205%) of the polyethylene block copolymer membrane was observed. A polymer system was designed and characterized with monomethoxy polyethylene glycol (mPEG) as a hydrophilic polymer grafted through substitution of pendent benzyl chloride groups of a PVBC-b-PS. The incorporation of the hydrophilic polymer allows for an investigation of the effect of hydration on ionic conductivity, resulting in the increase in membrane water affinity, enhancement of conductivity and reduced dependence of conductivity on relative humidity. A study of crosslinking of block copolymers was done wherein the crosslinking occurs in the non-matrix phase in order to maintain mechanical properties. The formation of a cationic crosslinked structure improves the mechanical integrity of the membrane in water while showing little deleterious effect on ionic conductivity and mechanical properties.

Li, Yifan

254

A Novel Unitized Regenerative Proton Exchange Membrane Fuel Cell  

NASA Technical Reports Server (NTRS)

A difficulty encountered in designing a unitized regenerative proton exchange membrane (PEM) fuel cell lies in the incompatibility of electrode structures and electrocatalyst materials optimized for either of the two functions (fuel cell or electrolyzer) with the needs of the other function. This difficulty is compounded in previous regenerative fuel cell designs by the fact that water, which is needed for proton conduction in the PEM during both modes of operation, is the reactant supplied to the anode in the electrolyzer mode of operation and the product formed at the cathode in the fuel cell mode. Drawbacks associated with existing regenerative fuel cells have been addressed. In a first innovation, electrodes function either as oxidation electrodes (hydrogen ionization or oxygen evolution) or as reduction electrodes (oxygen reduction or hydrogen evolution) in the fuel cell and electrolyzer modes, respectively. Control of liquid water within the regenerative fuel cell has been brought about by a second innovation. A novel PEM has been developed with internal channels that permit the direct access of water along the length of the membrane. Lateral diffusion of water along the polymer chains of the PEM provides the water needed at electrode/PEM interfaces. Fabrication of the novel single cell unitized regenerative fuel cell and results obtained on testing it are presented.

Murphy, O. J.; Cisar, A. J.; Gonzalez-Martin, A.; Salinas, C. E.; Simpson, S. F.

1996-01-01

255

Time-dependent surface adhesive force and morphology of RBC measured by AFM  

Microsoft Academic Search

Atomic force microscopy (AFM) is a rapidly developing tool recently introduced into the evaluation of the age of bloodstains, potentially providing legal medical experts useful information for forensic investigation. In this study, the time-dependent, morphological changes of red blood cells (RBC) under three different conditions (including controlled, room-temperature condition, uncontrolled, outdoor-environmental condition, and controlled, low-temperature condition) were observed by AFM,

Yangzhe Wu; Yi Hu; Jiye Cai; Shuyuan Ma; Xiaoping Wang; Yong Chen; Yunlong Pan

2009-01-01

256

Capacitance-Voltage Measurement of Transporting Function at Cell Membrane  

NASA Astrophysics Data System (ADS)

In this paper, we report the detection of transporting function at cell membrane using capacitance-voltage (CV) measurement. The detection principle of our devices is based on the field-effect of electrostatic interaction between charged species at cell membrane in solution and surface electrons in silicon crystal through the gate insulator of Si3N4/SiO2 thin double-layer. We designed an oocyte-based field-effect capacitor, on which a Xenopus laevis oocyte was fixed. The transporter of human organic anion transporting peptide C (hOATP-C) was expressed at oocyte membrane by induction of cRNA. The electrical phenomena such as ion or molecular charge flux at the interface between cell membrane and gate surface could be detected as the change of flat band voltage in CV characteristics. The flat band voltage shift decreased with incubation time after introduction of substrate into the oocyte-based field-effect capacitor. The electrical signal is due to the change of charge flux from the oocyte at the gate surface inspired by transporter-substrate binding. The platform based on the oocyte-based field-effect capacitor is suitable for a simple and non-invasive detection system in order to analyze function of transporters related to drug efficacy.

Sakata, Toshiya; Miyahara, Yuji

257

Cell Component Accelerated Stress Test and Polarization Curve Protocols for Polymer Electrolyte Membrane Fuel Cells  

NSDL National Science Digital Library

This document contains test protocols to determine the performance and durability of fuel cell components such as electrocatalysts and supports, membranes, and membrane electrode assemblies (MEAs). These protocols were established with the intent to be used as a common industry standard when assessing durability of different polymer electrolyte membranes (PEM) in fuel cells for automotive applications and to be compared against DOE and FreedomCar targets. The resulting data may also help to model the performance of the fuel cell under variable load conditions and the effects of ageing on performance.

United States Driving Research and Innovation for Vehicle Efficiency and Energy Sustainability (USDRIVE)

258

Creating Transient Cell Membrane Pores Using a Standard Inkjet Printer  

PubMed Central

Bioprinting has a wide range of applications and significance, including tissue engineering, direct cell application therapies, and biosensor microfabrication.1-10 Recently, thermal inkjet printing has also been used for gene transfection.8,9 The thermal inkjet printing process was shown to temporarily disrupt the cell membranes without affecting cell viability. The transient pores in the membrane can be used to introduce molecules, which would otherwise be too large to pass through the membrane, into the cell cytoplasm.8,9,11 The application being demonstrated here is the use of thermal inkjet printing for the incorporation of fluorescently labeled g-actin monomers into cells. The advantage of using thermal ink-jet printing to inject molecules into cells is that the technique is relatively benign to cells.8, 12 Cell viability after printing has been shown to be similar to standard cell plating methods1,8. In addition, inkjet printing can process thousands of cells in minutes, which is much faster than manual microinjection. The pores created by printing have been shown to close within about two hours. However, there is a limit to the size of the pore created (~10 nm) with this printing technique, which limits the technique to injecting cells with small proteins and/or particles. 8,9,11 A standard HP DeskJet 500 printer was modified to allow for cell printing.3, 5, 8 The cover of the printer was removed and the paper feed mechanism was bypassed using a mechanical lever. A stage was created to allow for placement of microscope slides and coverslips directly under the print head. Ink cartridges were opened, the ink was removed and they were cleaned prior to use with cells. The printing pattern was created using standard drawing software, which then controlled the printer through a simple print command. 3T3 fibroblasts were grown to confluence, trypsinized, and then resuspended into phosphate buffered saline with soluble fluorescently labeled g-actin monomers. The cell suspension was pipetted into the ink cartridge and lines of cells were printed onto glass microscope cover slips. The live cells were imaged using fluorescence microscopy and actin was found throughout the cytoplasm. Incorporation of fluorescent actin into the cell allows for imaging of short-time cytoskeletal dynamics and is useful for a wide range of applications.13-15 PMID:22453577

Owczarczak, Alexander B.; Shuford, Stephen O.; Wood, Scott T.; Deitch, Sandra; Dean, Delphine

2012-01-01

259

Modulation of membrane composition of swine vascular smooth muscle cells by homologous lipoproteins in culture.  

PubMed

Swine vascular smooth muscle cells were exposed to homologous low-density or high-density lipoprotein fractions for 24 h. Total cell membranes were isolated from the post-nuclear supernatant of the cell homogenates, fractionated by sucrose denisty gradient centrifugation and characterized by enzyme assays. The membrane fraction with the lowest density was enriched in plasma membrane marker enzymes. Cholesterol analysis showed that cells exposed to low-density lipoprotein had higher cholesterol-to-protein ratios in total cells, total cell membranes and individual membrane fractions than had the cells exposed to high-density lipoproteins. Cholesterol-to-phospholipid ratios of the plasma membrane-enriched fraction from cells exposed to low-density lipoprotein were higher than the same membrane fraction of cells exposed to high-density lipoprotein. Studies with iodinated lipoproteins showed that these compositional changes could not be due to lipoprotein contamination. Membrane microviscosity was determined by fluorescence depolarization with diphenylhextriene and the microviscosity of the plasma membrane-enriched fraction was different in the cells exposed to the two different lipoprotein fractions. This difference in membrane microviscosity was significant only when the medium cholesterol content was 40 micrograms per ml or greater; cells exposed to low-density lipoprotein gave membranes with higher microviscosity. These results demonstrate that the properties of vascular smooth muscle cell membranes are influcenced by exposure of the cells to homologous lipoprotein fractions. PMID:7407139

Kuehl, K S; Yeroushalmy, S; Holloway, P W

1980-08-14

260

A novel unitized regenerative proton exchange membrane fuel cell  

NASA Technical Reports Server (NTRS)

A difficulty encountered in designing a unitized regenerative proton exchange membrane (PEM) fuel cell lies in the incompatibility of electrode structures and electrocatalyst materials optimized for either of the two functions (fuel cell or electrolyzer) with the needs of the other function. This difficulty is compounded in previous regenerative fuel cell designs by the fact that water, which is needed for proton conduction in the PEM during both modes of operation, is the reactant supplied to the anode in the electrolyzer mode of operation and the product formed at the cathode in the fuel cell mode. Drawbacks associated with existing regenerative fuel cells have been addressed in work performed at Lynntech. In a first innovation, electrodes function either as oxidation electrodes (hydrogen ionization or oxygen evolution) or as reduction electrodes (oxygen reduction or hydrogen evolution) in the fuel cell and electrolyzer modes, respectively. Control of liquid water within the regenerative fuel cell has been brought about by a second innovation. A novel PEM has been developed with internal channels that permit the direct access of water along the length of the membrane. Lateral diffusion of water along the polymer chains of the PEM provides the water needed at electrode/PEM interfaces. Fabrication of the novel unitized regenerative fuel cell and results obtained on testing it will be presented.

Murphy, O. J.; Cisar, A. J.; Gonzalez-Martin, A.; Salinas, C. E.; Simpson, S. F.

1995-01-01

261

Multiscale Modeling of Red Blood Cell Mechanics and Blood Flow in Malaria  

E-print Network

Multiscale Modeling of Red Blood Cell Mechanics and Blood Flow in Malaria Dmitry A. Fedosov1 Abstract Red blood cells (RBCs) infected by a Plasmodium parasite in malaria may lose their membrane. In the present work, we simulate infected RBCs in malaria using a multiscale RBC model based on the dissipative

Suresh, Subra

262

Myosin-X facilitates Shigella-induced membrane protrusions and cell-to-cell spread  

PubMed Central

Summary The intracellular pathogen Shigella flexneri forms membrane protrusions to spread from cell to cell. As protrusions form, myosin-X (Myo10) localizes to Shigella. Electron micrographs of immunogold-labelled Shigella-infected HeLa cells reveal that Myo10 concentrates at the bases and along the sides of bacteria within membrane protrusions. Time-lapse video microscopy shows that a full-length Myo10 GFP-construct cycles along the sides of Shigella within the membrane protrusions as these structures progressively lengthen. RNAi knock-down of Myo10 is associated with shorter protrusions with thicker stalks, and causes a >80% decrease in confluent cell plaque formation. Myo10 also concentrates in membrane protrusions formed by another intracellular bacteria, Listeria, and knock-down of Myo10 also impairs Listeria plaque formation. In Cos7 cells (contain low concentrations of Myo10), the expression of full-length Myo10 nearly doubles Shigella-induced protrusion length, and lengthening requires the head domain, as well as the tail-PH domain, but not the FERM domain. The GFP-Myo10-HMM domain localizes to the sides of Shigella within membrane protrusions and the GFP-Myo10-PH domain localizes to host cell membranes. We conclude that Myo10 generates the force to enhance bacterial-induced protrusions by binding its head region to actin filaments and its PH tail domain to the peripheral membrane. PMID:23083060

Li, Wei; Dhillon, Jess; Bohil, Aparna B.; Cheney, Richard E.; Hartwig, John H.; Southwick, Frederick S.

2014-01-01

263

Near-Critical Fluctuations and Cytoskeleton-Assisted Phase Separation Lead to Subdiffusion in Cell Membranes  

PubMed Central

We address the relationship between membrane microheterogeneity and anomalous subdiffusion in cell membranes by carrying out Monte Carlo simulations of two-component lipid membranes. We find that near-critical fluctuations in the membrane lead to transient subdiffusion, while membrane-cytoskeleton interaction strongly affects phase separation, enhances subdiffusion, and eventually leads to hop diffusion of lipids. Thus, we present a minimum realistic model for membrane rafts showing the features of both microscopic phase separation and subdiffusion. PMID:21190659

Ehrig, Jens; Petrov, Eugene P.; Schwille, Petra

2011-01-01

264

Extra- and intracellular unstirred layer effects in measurements of CO2 diffusion across membranes - a novel approach applied to the mass spectrometric 18O technique for red blood cells  

PubMed Central

We have developed an experimental approach that allows us to quantify unstirred layers around cells suspended in stirred solutions. This technique is applicable to all types of transport measurements and was applied here to the 18O technique used to measure CO2 permeability of red cells . We measure in well-stirred red cell (RBC) suspensions of various viscosities adjusted by adding different amounts of 60 kDa dextran. Plotting vs. viscosity ? gives a linear relation, which can be extrapolated to ?= 0. Theoretical hydrodynamics predicts that extracellular unstirred layers vanish at zero viscosity when stirring is maintained, and thus this extrapolation gives us an estimate of the free from extracellular unstirred layer artifacts. The extrapolated value is found to be 0.16 cm s?1 instead of the experimental value in saline of 0.12 cm s?1 (+30%). This effect corresponds to an unstirred layer thickness of 0.5 ?m. In addition, we present a theoretical approach modelling the actual geometrical and physico-chemical conditions of 18O exchange in our experiments. It confirms the role of an extracellular unstirred layer in the determination of . Also, it allows us to quantify the contribution of the so-called intracellular unstirred layer, which results from the fact that in these transport measurements – as in all such measurements in general – the intracellular space is not stirred. The apparent thickness of this intracellular unstirred layer is about 1/4–1/3 of the maximal intracellular diffusion distance, and correction for it results in a true of the RBC membrane of 0.20 cm s?1. Thus, the order of magnitude of this is unaltered compared to our previous reports. Discussion of the available evidence in the light of these results confirms that CO2 channels exist in red cell and other membranes, and that of red cell membranes in the absence of these channels is quite low. PMID:19139045

Endeward, Volker; Gros, Gerolf

2009-01-01

265

Tetraspanins regulate the protrusive activities of cell membrane  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Tetraspanins regulate microvillus formation. Black-Right-Pointing-Pointer Tetraspanin CD81 promotes microvillus formation. Black-Right-Pointing-Pointer Tetraspanin CD82 inhibits microvillus formation. Black-Right-Pointing-Pointer Based on this study, we extrapolated a general cellular mechanism for tetraspanins. Black-Right-Pointing-Pointer Tetraspanins engage various functions by regulating membrane protrusion morphogenesis. -- Abstract: Tetraspanins have gained increased attention due to their functional versatility. But the universal cellular mechanism that governs such versatility remains unknown. Herein we present the evidence that tetraspanins CD81 and CD82 regulate the formation and/or development of cell membrane protrusions. We analyzed the ultrastructure of the cells in which a tetraspanin is either overexpressed or ablated using transmission electron microscopy. The numbers of microvilli on the cell surface were counted, and the radii of microvillar tips and the lengths of microvilli were measured. We found that tetraspanin CD81 promotes the microvillus formation and/or extension while tetraspanin CD82 inhibits these events. In addition, CD81 enhances the outward bending of the plasma membrane while CD82 inhibits it. We also found that CD81 and CD82 proteins are localized at microvilli using immunofluorescence. CD82 regulates microvillus morphogenesis likely by altering the plasma membrane curvature and/or the cortical actin cytoskeletal organization. We predict that membrane protrusions embody a common morphological phenotype and cellular mechanism for, at least some if not all, tetraspanins. The differential effects of tetraspanins on microvilli likely lead to the functional diversification of tetraspanins and appear to correlate with their functional propensity.

Bari, Rafijul [Cancer Center and Department of Medicine, University of Tennessee, Memphis, TN (United States)] [Cancer Center and Department of Medicine, University of Tennessee, Memphis, TN (United States); Guo, Qiusha [Cancer Center and Department of Medicine, University of Tennessee, Memphis, TN (United States) [Cancer Center and Department of Medicine, University of Tennessee, Memphis, TN (United States); Zhongnan Hospital, Wuhan University, Wuhan (China); Xia, Bing [Zhongnan Hospital, Wuhan University, Wuhan (China)] [Zhongnan Hospital, Wuhan University, Wuhan (China); Zhang, Yanhui H. [Cancer Center and Department of Medicine, University of Tennessee, Memphis, TN (United States)] [Cancer Center and Department of Medicine, University of Tennessee, Memphis, TN (United States); Giesert, Eldon E. [Department of Ophthalmology, University of Tennessee, Memphis, TN (United States)] [Department of Ophthalmology, University of Tennessee, Memphis, TN (United States); Levy, Shoshana [Department of Medicine, Stanford University, Palo Alto, CA (United States)] [Department of Medicine, Stanford University, Palo Alto, CA (United States); Zheng, Jie J. [Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN (United States)] [Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN (United States); Zhang, Xin A., E-mail: xzhang@uthsc.edu [Cancer Center and Department of Medicine, University of Tennessee, Memphis, TN (United States)

2011-12-02

266

Muscarinic receptor size on smooth muscle cells and membranes  

SciTech Connect

The loss of (/sup 3/H)quinuclidinyl benzilate ((/sup 3/H)QNB) binding following high-energy radiation was used to compare the muscarinic receptor size on single smooth muscle cells isolated by collagenase digestion from the canine stomach and on plasma membranes derived from intact gastric smooth muscle without exposure to exogenous proteolysis. Radiation inactivation of galactose oxidase (68 kdaltons), yeast alcohol dehydrogenase (160 kdaltons), and pyruvate kinase (224 kdaltons) activities were used as molecular-weight standards. Radiation inactivation of (/sup 3/H)QNB binding to rat brain membranes, which gave a target size of 86 kdaltons, served as an additional control. In isolated smooth muscle cells, the calculated size of the muscarinic receptor was 80 +/- 8 kdaltons. In contrast, in a smooth muscle enriched plasma membrane preparation, muscarinic receptor size was significantly smaller at 45 +/- 3 kdaltons. Larger molecular sizes were obtained either in the presence of protease inhibitors (62 +/- 4 kdaltons) or by using a crude membrane preparation of gastric smooth muscle 86 +/- 7 kdaltons).

Collins, S.M.; Jung, C.Y.; Grover, A.K.

1986-08-01

267

Membrane Domains Based on Ankyrin and Spectrin Associated with Cell–Cell Interactions  

PubMed Central

Nodes of Ranvier and axon initial segments of myelinated nerves, sites of cell–cell contact in early embryos and epithelial cells, and neuromuscular junctions of skeletal muscle all perform physiological functions that depend on clustering of functionally related but structurally diverse ion transporters and cell adhesion molecules within microdomains of the plasma membrane. These specialized cell surface domains appeared at different times in metazoan evolution, involve a variety of cell types, and are populated by distinct membrane-spanning proteins. Nevertheless, recent work has shown that these domains all share on their cytoplasmic surfaces a membrane skeleton comprised of members of the ankyrin and spectrin families. This review will summarize basic features of ankyrins and spectrins, and will discuss emerging evidence that these proteins are key players in a conserved mechanism responsible for assembly and maintenance of physiologically important domains on the surfaces of diverse cells. PMID:20457566

Bennett, Vann; Healy, Jane

2009-01-01

268

Mechanical properties of stored red blood cells using optical tweezers  

NASA Astrophysics Data System (ADS)

We have developed a method for measuring the red blood cell (RBC) membrane overall elasticity ? by measuring the deformation of the cells when dragged at a constant velocity through a plasma fluid by an optical tweezers. The deformability of erythrocytes is a critical determinant of blood flow in the microcirculation. We tested our method and hydrodynamic models, which included the presence of two walls, by measuring the RBC deformation as a function of drag velocity and of the distance to the walls. The capability and sensitivity of this method can be evaluated by its application to a variety of studies, such as, the measurement of RBC elasticity of sickle cell anemia patients comparing homozygous (HbSS), including patients taking hydroxyrea (HU) and heterozygous (HbAS) with normal donors and the RBC elasticity measurement of gamma irradiated stored blood for transfusion to immunosupressed patients as a function of time and dose. These studies show that the technique has the sensitivity to discriminate heterozygous and homozygous sickle cell anemia patients from normal donors and even follow the course of HU treatment of Homozygous patients. The gamma irradiation studies show that there is no significant change in RBC elasticity over time for up to 14 days of storage, regardless of whether the unit was irradiated or not, but there was a huge change in the measured elasticity for the RBC units stored for more than 21 days after irradiation. These finds are important for the assessment of stored irradiated RBC viability for transfusion purposes because the present protocol consider 28 storage days after irradiation as the limit for the RBC usage.

Fontes, Adriana; Alexandre de Thomaz, Andre; de Ysasa Pozzo, Liliana; de Lourdes Barjas-Castro, Maria; Brandao, Marcelo M.; Saad, Sara T. O.; Barbosa, Luiz Carlos; Cesar, Carlos Lenz

2005-08-01

269

Evaluation of stem cell components in retrocorneal membranes.  

PubMed

The purpose of this study was to elucidate the origin and cellular composition of retrocorneal membranes (RCMs) associated with chemical burns using immunohistochemical staining for primitive cell markers. Six cases of RCMs were collected during penetrating keratoplasty. We examined RCMs with hematoxylin and eosin (H&E), periodic acid-Schiff (PAS) staining and immunohistochemical analysis using monoclonal antibodies against hematopoietic stem cells (CD34, CD133, c-kit), mesenchymal stem cells (beta-1-integrin, TGF-?, vimentin, hSTRO-1), fibroblasts (FGF-?, ?-smooth muscle actin), and corneal endothelial cells (type IV collagen, CD133, VEGF, VEGFR1). Histologic analysis of RCMs revealed an organized assembly of spindle-shaped cells, pigment-laden cells, and thin collagenous matrix structures. RCMs were positive for markers of mesenchymal stem cells including beta-1-integrin, TGF-?, vimentin, and hSTRO-1. Fibroblast markers were also positive, including FGF-? and ?-smooth muscle actin (SMA). In contrast, immunohistochemical staining was negative for hematopoietic stem cell markers including CD34, CD133 and c-kit as well as corneal endothelial cell markers such as type IV collagen, CD133 except VEGF and VEGFR1. Pigment-laden cells did not stain with any antibodies. The results of this study suggest that RCMs consist of a thin collagen matrix and fibroblast-like cells and may be a possible neogenetic structure produced from a lineage of bone marrow-derived mesenchymal stem cells. PMID:24932088

Lee, Seok Hyun; Kim, Kyoung Woo; Kim, Mi Kyung; Chun, Yeoun Sook; Kim, Jae Chan

2014-06-01

270

From artificial red blood cells, oxygen carriers, and oxygen therapeutics to artificial cells, nanomedicine, and beyond  

PubMed Central

The first experimental artificial red blood cells have all three major functions of red blood cells (rbc). However, the first practical one is a simple polyhemoglobin (PolyHb) that only has an oxygen-carrying function. This is now in routine clinical use in South Africa and Russia. An oxygen carrier with antioxidant functions, PolyHb-catalase-superoxide dismutase, can fulfill two of the three functions of rbc. Even more complete is one with all three functions of rbc in the form of PolyHb-catalase-superoxide dismutase-carbonic anhydrase. The most advanced ones are nanodimension artificial rbc with either PEG-lipid membrane or PEG-PLA polymermembrane. Extensions in to oxygen therapeutics include a PolyHb-tyrosinase that suppresses the growth of melanoma in a mice model. Another is a PolyHb-fibrinogen that is an oxygen carrier with platelet-like function. Research has now extended well beyond the original research on artificial rbc into many areas of artificial cells. These include nanoparticles, nanotubules, lipid vesicles, liposomes, polymer-tethered lipid vesicles, polymersomes, microcapsules, bioencapsulation, nanocapules, macroencapsulation, synthetic cells, and others. These are being used in nanotechnology, nanomedicine, regenerative medicine, enzyme/gene therapy, cell/stem cell therapy, biotechnology, drug delivery, hemoperfusion, nanosensers, and even by some groups in agriculture, industry, aquatic culture, nanocomputers, and nanorobotics. PMID:22409281

Chang, Thomas M. S.

2013-01-01

271

Development of structured polymer electrolyte membranes for fuel cell applications  

NASA Astrophysics Data System (ADS)

The objective of this research was to explore structure-property relationships to develop the understanding needed for introduction of superior PEM materials. Polymer electrolyte membranes based on sulfonated poly(ether ketone ketone) (SPEKK) were fabricated using N-methyl pyrrolidone as casting solvent. The membranes were characterized in terms of properties that were relevant to fuel cell applications, such as proton conductivity, methanol permeability, and swelling properties, among others. It was found in this study that the proton conductivity of neat SPEKK membranes could reach the conductivity of commercial membranes such as NafionRTM. However, when the conductivity of SPEKK was comparable to NafionRTM, the swelling of SPEKK in water was quite excessive. The swelling problem was remedied by modifying the microstructure of SPEKK using different techniques. One of them involved blending of lightly sulfonated PEKK with highly acidic particles (sulfonated crosslinked polystyrene-SXLPS). Low sulfonation level of SPEKK was used to reduce the swelling of the membrane in water and the role of the highly acidic particles was to enhance the proton conductivity of the membrane. Because of the residual crystallinity in SPEKK with low sulfonation levels (IEC < 1 meq/g), the composite membranes exhibited excellent dimensional stability in water at elevated temperatures (30-90 °C). Also, the resistance to swelling of these composite membranes in methanol-water mixtures was far better than NafionRTM, and so was the methanol permeability. Another technique explored was blending with non-conductive polymers (poly(ether imide) and poly(ether sulfone)) to act as mechanical reinforcement. It was found that miscibility behavior of the blends had a significant impact on the transport and swelling properties of these blends, which could be explained by the blend microstructure. The miscibility behavior was found to be strongly dependent on the sulfonation level of SPEKK. The conductivities of the blends were enhanced by as much as two orders of magnitude when the morphology was modified by electric field. The last approach was ionic crosslinking of the sulfonate groups in SPEKK using divalent cations, specifically barium ions. The crosslinking treatment has greatly improved the thermal stability of the membranes in both dry and wet conditions.

Gasa, Jeffrey

272

Morphology matters in immune cell chemotaxis: membrane asymmetry affects amplification  

NASA Astrophysics Data System (ADS)

A key mediator of eukaryotic chemotaxis is the asymmetric accumulation of phosphatidylinositol-3,4,5-triphosphate (PIP3) on the cell membrane. Recent work has focused on understanding how a shallow external gradient of chemoattractant leads to an amplified internal gradient of PIP3. In this paper we dissect what fraction of this amplification is derived biochemically by the signal transduction network and how much arises entirely from the effects of cell morphology. Here we identify and formalize the role of morphology in signal detection and demonstrate its effects through simulation and experiments. Our key result is that an asymmetric distribution of membrane accounts for approximately one-half of the measured amplification from ligand concentration to PIP3 production. We also show that the underlying biochemical network behaves as a linear amplifier in the micropipette assay.

Onsum, Matthew David; Wong, Kit; Herzmark, Paul; Bourne, Henry R.; Arkin, Adam Paul

2006-09-01

273

Lysosomotropic agents: impact on lysosomal membrane permeabilization and cell death.  

PubMed

Lysosomes are acidic organelles essential for degradation, signalling and cell homoeostasis. In addition, they play a key role in cell death. Permeabilization of the lysosomal membrane and release of hydrolytic enzymes to the cytosol accompanies apoptosis signalling in several systems. The regulatory mechanism of lysosomal stability is, however, poorly understood. Lipophilic or amphiphilic compounds with a basic moiety will become protonated and trapped within lysosomes, and such lysosomotropic behaviour is also found in many pharmacological drugs. The natural sphingolipid sphingosine exhibits lysosomotropic detergent ability and is an endogenous candidate for controlling lysosomal membrane permeabilization. The lysosomotropic properties of certain detergents might be of use in lysosome-targeting anticancer drugs and drug delivery system in the future. The present review summarizes the current knowledge on the targeting and permeabilizing properties of lysosomotropic detergents from a cellular and physicochemical perspective. PMID:25233432

Villamil Giraldo, Ana M; Appelqvist, Hanna; Ederth, Thomas; Ollinger, Karin

2014-10-01

274

Adaptive evolution of rbcL in Conocephalum (Hepaticae, bryophytes).  

PubMed

An excess of nonsynonymous substitutions over synonymous ones has been regarded as an important indicator of adaptive evolution or positive selection at the molecular level. We now report such a case for rbcL sequences among cryptic species in Conocephalum (Hepaticae, Bryophytes). This finding can be regarded as evidence of adaptive evolution in several cryptic species (especially in F and JN types) within the genus. Bryophytes are small land plants with simple morphology. We can therefore expect the existence of several biologically distinct units or cryptic species within each morphological species. In our previous study, we found three rbcL types in Asian Conocephalum japonicum (Thunb.) Grolle and also found evidence strongly suggesting that the three types are reproductively isolated cryptic species. Additionally, we examined rbcL sequence variation in six cryptic species of C. conicum (L.) Dumort. previously recognized by allozyme analyses. As a result, we were able to discriminate the six cryptic species based only on their rbcL sequences. We were able to show that rbcL sequence variation is also useful in finding cryptic species of C. conicum. PMID:19100313

Miwa, Hidetsugu; Odrzykoski, Ireneusz J; Matsui, Atsushi; Hasegawa, Masami; Akiyama, Hiroyuki; Jia, Yu; Sabirov, Renat; Takahashi, Hideki; Boufford, David E; Murakami, Noriaki

2009-07-15

275

Yield Strength of Human Erythrocyte Membranes to Impulsive Stretching  

PubMed Central

Deformability while remaining viable is an important mechanical property of cells. Red blood cells (RBCs) deform considerably while flowing through small capillaries. The RBC membrane can withstand a finite strain, beyond which it ruptures. The classical yield areal strain of 2–4% for RBCs is generally accepted for a quasi-static strain. It has been noted previously that this threshold strain may be much larger with shorter exposure duration. Here we employ an impulse-like forcing to quantify this yield strain of RBC membranes. In the experiments, RBCs are stretched within tens of microseconds by a strong shear flow generated from a laser-induced cavitation bubble. The deformation of the cells in the strongly confined geometry is captured with a high-speed camera and viability is successively monitored with fluorescence microscopy. We find that the probability of cell survival is strongly dependent on the maximum strain. Above a critical areal strain of ?40%, permanent membrane damage is observed for 50% of the cells. Interestingly, many of the cells do not rupture immediately and exhibit ghosting, but slowly obtain a round shape before they burst. This observation is explained with structural membrane damage leading to subnanometer-sized pores. The cells finally lyse from the colloidal osmotic pressure imbalance. PMID:23972839

Li, Fenfang; Chan, Chon U; Ohl, Claus Dieter

2013-01-01

276

CFD-based modelling of proton exchange membrane fuel cells  

Microsoft Academic Search

A comprehensive non-isothermal, 3D computational model for proton exchange membrane (PEM) fuel cells has been developed, and implemented into a computational fluid dynamic (CFD) code. The model allows parallel computing, thus making it practical to perform well-resolved simulations for large computational domains. The model accounts for convective and diffusive transport and allows prediction of the concentration of species. Distributed heat

B. R. Sivertsen; N. Djilali

2005-01-01

277

Sulfonated polynaphthylimides as proton-conducting membranes for fuel cells  

NASA Astrophysics Data System (ADS)

The main achievements in the field of synthesis of sulfonated polynaphthylimides and their precursors, namely, sulfonated aromatic diamines, are analysed. The relationship between the structure of sulfonated polynaphthylimides and their physicochemical characteristics such as chemical and thermal stability, moisture uptake, ion-exchange capacity and proton conductivity is studied. The prospects of using polynaphthylimides containing pendant sulfo groups for the development of proton-conducting polymeric electrolyte membranes for fuel cells are demonstrated.

Rusanov, Aleksandr L.; Bulycheva, E. G.; Bugaenko, M. G.; Voytekunas, V. Yu; Abadie, M. J.

2009-01-01

278

Stimulation of Erythrocyte Cell Membrane Scrambling by Mushroom Tyrosinase  

PubMed Central

Background: Mushroom tyrosinase, a copper containing enzyme, modifies growth and survival of tumor cells. Mushroom tyrosinase may foster apoptosis, an effect in part due to interference with mitochondrial function. Erythrocytes lack mitochondria but are able to undergo apoptosis-like suicidal cell death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine-exposure at the erythrocyte surface. Signaling involved in the triggering of eryptosis include increase of cytosolic Ca2+-activity ([Ca2+]i) and activation of sphingomyelinase with subsequent formation of ceramide. The present study explored, whether tyrosinase stimulates eryptosis. Methods: Cell volume has been estimated from forward scatter, phosphatidylserine-exposure from annexin V binding, [Ca2+]i from Fluo3-fluorescence, and ceramide abundance from binding of fluorescent antibodies in flow cytometry. Results: A 24 h exposure to mushroom tyrosinase (7 U/mL) was followed by a significant increase of [Ca2+]i, a significant increase of ceramide abundance, and a significant increase of annexin-V-binding. The annexin-V-binding following tyrosinase treatment was significantly blunted but not abrogated in the nominal absence of extracellular Ca2+. Tyrosinase did not significantly modify forward scatter. Conclusions: Tyrosinase triggers cell membrane scrambling, an effect, at least partially, due to entry of extracellular Ca2+ and ceramide formation. PMID:24647148

Frauenfeld, Leonie; Alzoubi, Kousi; Abed, Majed; Lang, Florian

2014-01-01

279

Amniotic membrane transplantation for partial limbal stem cell deficiency  

PubMed Central

AIM—To examine the efficacy, safety, and long term outcomes of amniotic membrane transplantation for corneal surface reconstruction in cases of partial limbal stem cell deficiency.?METHODS—17 eyes of 15 patients with partial limbal stem cell deficiency underwent superficial keratectomy of the conjunctivalised corneal surface followed by amniotic membrane transplantation. Cases were followed up for at least a year.?RESULTS—All eyes exhibited a stable, intact corneal epithelial surface after a mean follow up period of 25.8 months with no eyes developing recurrent erosion or persistent epithelial defect. The mean time to re-epithelialisation was 22.8 days. Overall improvement in visual acuity was observed in 92.9% of 14 eyes with visual potential. Of those, five eyes gained six or more lines, two eyes gained between four and five lines, six eyes gained between one and three lines, and one eye lost three lines of Snellen acuity. Pain and photophobia were abolished in 86% of cases and substantially reduced in 14%, with all eyes exhibiting decreased vascularisation and inflammation at final follow up.?CONCLUSIONS—Amniotic membrane transplantation appears to be a safe and effective method of restoring a stable corneal epithelium for cases of partial limbal stem cell deficiency and can be considered as an alternative to limbal autograft or allograft.?? PMID:11316719

Anderson, D.; Ellies, P.; Pires, R.; Tseng, S.

2001-01-01

280

Size-based chromatography of signaling clusters in a living cell membrane.  

PubMed

Here we introduce a form of chromatography that can be imposed on the membrane of a living cell. A cell-cell signaling interaction is reconstituted in a hybrid live cell-supported membrane junction. The chromatographic material consists of a hexagonally ordered array of gold nanoparticles (nanodot array), which is fabricated onto the underlying substrate. While individual membrane components move freely throughout the array, the movement of larger assemblies is impeded if they exceed the physical dimensions of the array. This tactile approach to probing membrane structures in living cells reveals organizational aspects of the membrane environment unobservable by other techniques. PMID:24655064

Caculitan, Niña G; Kai, Hiroyuki; Liu, Eulanca Y; Fay, Nicole; Yu, Yan; Lohmüller, Theobald; O'Donoghue, Geoff P; Groves, Jay T

2014-05-14

281

Ambidextrous binding of cell and membrane bilayers by soluble matrix metalloproteinase-12.  

PubMed

Matrix metalloproteinases (MMPs) regulate tissue remodelling, inflammation and disease progression. Some soluble MMPs are inexplicably active near cell surfaces. Here we demonstrate the binding of MMP-12 directly to bilayers and cellular membranes using paramagnetic NMR and fluorescence. Opposing sides of the catalytic domain engage spin-labelled membrane mimics. Loops project from the ?-sheet interface to contact the phospholipid bilayer with basic and hydrophobic residues. The distal membrane interface comprises loops on the other side of the catalytic cleft. Both interfaces mediate MMP-12 association with vesicles and cell membranes. MMP-12 binds plasma membranes and is internalized to hydrophobic perinuclear features, the nuclear membrane and inside the nucleus within minutes. While binding of TIMP-2 to MMP-12 hinders membrane interactions beside the active site, TIMP-2-inhibited MMP-12 binds vesicles and cells, suggesting compensatory rotation of its membrane approaches. MMP-12 association with diverse cell membranes may target its activities to modulate innate immune responses and inflammation. PMID:25412686

Koppisetti, Rama K; Fulcher, Yan G; Jurkevich, Alexander; Prior, Stephen H; Xu, Jia; Lenoir, Marc; Overduin, Michael; Van Doren, Steven R

2014-01-01

282

Quantitative analysis of cell surface membrane proteins using membrane-impermeable chemical probe coupled with 18O labeling  

PubMed Central

We report a mass spectrometry-based strategy for quantitative analysis of cell surface membrane proteome changes. The strategy includes enrichment of surface membrane proteins using a membrane-impermeable chemical probe followed by stable isotope 18O labeling and LC-MS analysis. We applied this strategy for enriching membrane proteins expressed by Shewanella oneidensis MR-1, a gram-negative bacterium with known metal-reduction capability via extracellular electron transfer between outer membrane proteins and extracellular electron receptors. LC/MS/MS analysis resulted in the identification of about 400 proteins with 79% of them being predicted to be membrane localized. Quantitative aspects of the membrane enrichment were shown by peptide level 16O and 18O labeling of proteins from wild-type and mutant cells (generated from deletion of a type II secretion protein, GspD) prior to LC-MS analysis. Using a chemical probe labeled pure protein as an internal standard for normalization, the quantitative data revealed reduced abundances in ?gspD mutant cells of many outer membrane proteins including the outer membrane c-cype cytochromes OmcA and MtrC, in agreement with previously investigation demonstrating that these proteins are substrates of the type II secretion system. PMID:20380418

Zhang, Haizhen; Brown, Roslyn N.; Qian, Wei-Jun; Monroe, Matthew E.; Purvine, Samuel O.; Moore, Ronald J.; Gritsenko, Marina A.; Shi, Liang; Romine, Margaret F; Fredrickson, James K.; Pasa-Tolic, Ljiljana; Smith, Richard D.; Lipton, Mary S.

2010-01-01

283

Stimulation of erythrocyte cell membrane scrambling by methyldopa.  

PubMed

Methyldopa is used for treatment of hypertension in pregnancy. Side effects of methyldopa include anemia, which could result from decreased formation or accelerated death of circulating erythrocytes. Several drugs cause anemia by triggering of suicidal erythrocyte death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling, the latter leading to phosphatidylserine exposure at the erythrocyte surface. Stimulators of erythrocyte membrane scrambling include increased cytosolic Ca(2+) concentration ([Ca(2+)](i)) and ceramide. Phosphatidylserine-exposing cells are rapidly cleared from circulating blood. The present study explored whether eryptosis could be triggered by methyldopa. Erythrocytes from healthy volunteers were exposed to methyldopa, and phosphatidylserine exposure (annexin A5 binding), cell volume (forward scatter), [Ca(2+)](i) (Fluo3-dependent fluorescence), and ceramide formation (anti-ceramide-fluorescein isothiocyanate antibody) were determined by flow cytometry. Methyldopa (6 microg/ml) did not increase [Ca(2+)](i) but led to stimulation of ceramide formation resulting in significant phosphatidylserine exposure and, at higher concentrations, to cell shrinkage. Methyldopa further decreased the GSH/GSSG ratio, pointing to oxidative stress. The scavenger N-acetyl-L-cysteine significantly blunted methyldopa-induced eryptosis. Clearance of erythrocytes from circulating blood was significantly accelerated by treatment with methyldopa. The present observations disclose a novel action of methyldopa, which may well contribute to drug-induced anemia. PMID:18772603

Mahmud, Hasan; Föller, Michael; Lang, Florian

2008-01-01

284

Better Proton-Conducting Polymers for Fuel-Cell Membranes  

NASA Technical Reports Server (NTRS)

Polyoxyphenylene triazole sulfonic acid has been proposed as a basis for development of improved proton-conducting polymeric materials for solid-electrolyte membranes in hydrogen/air fuel cells. Heretofore, the proton-conducting membrane materials of choice have been exemplified by a family of perfluorosulfonic acid-based polymers (Nafion7 or equivalent). These materials are suitable for operation in the temperature of 75 to 85 C, but in order to reduce the sizes and/or increase the energy-conversion efficiencies of fuel-cell systems, it would be desirable to increase temperatures to as high as 120 C for transportation applications, and to as high as 180 C for stationary applications. However, at 120 C and at relative humidity values below 50 percent, the loss of water from perfluorosulfonic acid-based polymer membranes results in fuel-cell power densities too low to be of practical value. Therefore, membrane electrolyte materials that have usefully high proton conductivity in the temperature range of 180 C at low relative humidity and that do not rely on water for proton conduction at 180 C would be desirable. The proposed polyoxyphenylene triazole sulfonic acid-based materials have been conjectured to have these desirable properties. These materials would be free of volatile or mobile acid constituents. The generic molecular structure of these materials is intended to exploit the fact, demonstrated in previous research, that materials that contain ionizable acid and base groups covalently attached to thermally stable polymer backbones exhibit proton conduction even in the anhydrous state.

Narayan, Sri; Reddy, Prakash

2012-01-01

285

Mathematical and Computational Modeling of Polymer Exchange Membrane Fuel Cells  

NASA Astrophysics Data System (ADS)

In this thesis a comprehensive review of fuel cell modeling has been given and based on the review, a general mathematical fuel cell model has been developed in order to understand the physical phenomena governing the fuel cell behavior and in order to contribute to the efforts investigating the optimum performance at different operating conditions as well as with different physical parameters. The steady state, isothermal model presented here accounts for the combined effects of mass and species transfer, momentum conservation, electrical current distribution through the gas channels, the electrodes and the membrane, and the electrochemical kinetics of the reactions in the anode and cathode catalyst layers. One of the important features of the model is that it proposes a simpler modified pseudo-homogeneous/agglomerate catalyst layer model which takes the advantage of the simplicity of pseudo-homogenous modeling while taking into account the effects of the agglomerates in the catalyst layer by using experimental geometric parameters published. The computation of the general mathematical model can be accomplished in 3D, 2D and 1D with the proper assumptions. Mainly, there are two computational domains considered in this thesis. The first modeling domain is a 2D Membrane Electrode Assembly (MEA) model including the modified agglomerate/pseudo-homogeneous catalyst layer modeling with consistent treatment of water transport in the MEA while the second domain presents a 3D model with different flow filed designs: straight, stepped and tapered. COMSOL Multiphysics along with Batteries and Fuel Cell Module have been used for 2D & 3D model computations while ANSYS FLUENT PEMFC Module has been used for only 3D two-phase computation. Both models have been validated with experimental data. With 2D MEA model, the effects of temperature and water content of the membrane as well as the equivalent weight of the membrane on the performance have been addressed. 3D COMSOL simulation results showed that the fuel performance can be improved by using flow field designs alleviating the reactant depletion along the channels and supplying more uniform reactant distribution. Stepped flow field was found to show better performance when compared to straight and tapered ones. ANSYS FLUENT model is evaluated in terms of predicting the two phase flow in the fuel cell components. It is proposed that it is not capable of predicting the entire fuel cell polarization due to the lack of agglomerate catalyst layer modeling and well-established two-phase flow modeling. Along with the comprehensive modeling efforts, also an analytical model has been computed by using MathCAD and it is found that this simpler model is able to predict the performance in a general trend according to the experimental data obtained for a new novel membrane. Therefore, it can be used for robust prediction of the cell performance at different operating conditions such as temperature and pressure, and the electrochemical properties such as the catalyst loading, the exchange current density and the diffusion coefficients of the reactants. In addition to the modeling efforts, this thesis also presents a very comprehensive literature review on the models developed in the literature so far, the modeling efforts in fuel cell sandwich including membrane, catalyst layer and gas diffusion layer and fuel cell model properties. Moreover, a summary of possible directions of research in fuel cell analysis and computational modeling has been presented.

Ulusoy, Sehribani

286

Relationship Between the Membrane Envelope of Rhizobial Bacteroids and the Plasma Membrane of the Host Cell as Demonstrated by Histochemical Localization of Adenyl Cyclase  

PubMed Central

By using adenyl cyclase as a marker enzyme, the relationship between the membrane envelope of the bacteroids of rhizobia and the plasma membrane of the host cell was demonstrated histochemically. Electron-dense deposits were found on the outer surface of the plasma membrane of the host cell and on the inner surface of the membrane envelopes of the bacteroids, but not in vacuole membranes, endoplasmic reticula, Golgi apparatus, and mitochondrial membranes. The results suggest that the membrane envelopes of the bacteroids are closely related to the host plasma membrane, and that entry of the bacteroids into the cytoplasm is in a manner similar to endocytosis. Images PMID:4854087

Tu, J. C.

1974-01-01

287

Cell Spreading and Lamellipodial Extension Rate Is Regulated by Membrane Tension  

Microsoft Academic Search

Cell spreading and motility require the ex- tension of the plasma membrane in association with the assembly of actin. In vitro, extension must overcome re- sistance from tension within the plasma membrane. We report here that the addition of either amphiphilic com- pounds or fluorescent lipids that expanded the plasma membrane increased the rate of cell spreading and lamellipodial extension,

Drazen Raucher; Michael P. Sheetz

2000-01-01

288

Dipolar interactions could be important for the formation of lipid rafts on cell membranes  

Microsoft Academic Search

Lipid rafts are cholesterol rich regions on cell membranes, and have been hypothesized to be important for signaling. We use field theory to examine the formation of lipid rafts in an idealized cell membrane. We find that it is difficult to reconcile the measured size of lipid raft domains with a mechanism that relies only on coupling between membrane shape

Jian Liu; Shuyan Qi; Arup K. Chakraborty

2004-01-01

289

Water free proton conducting membranes based on poly-4-vinylpyridinebisulfate for fuel cells  

NASA Technical Reports Server (NTRS)

Disclosed are methods for forming a water-free electrolyte membrane useful in fuel cells. Also provided is a water-free electrolyte membrane comprising a quaternized amine salt including poly-4-vinylpyridinebisulfate, a poly-4-vinylpyridinebisulfate silica composite, and a combination thereof and a fuel cell comprising the membrane.

Narayanan, Sekharipuram R. (Inventor); Yen, Shiao-Pin S. (Inventor)

2007-01-01

290

HIV Fusion Peptide Penetrates, Disorders, and Softens T-Cell Membrane Mimics  

E-print Network

HIV Fusion Peptide Penetrates, Disorders, and Softens T-Cell Membrane Mimics Stephanie Tristram of N-terminal gp41 fusion peptide (FP) of human immunodeficiency virus type 1 (HIV-1) with model membranes in order to elucidate how FP leads to fusion of HIV and T-cell membranes. FP constructs were (i

Weliky, David

291

Proton exchange membrane fuel cells: water permeation through Nafion(R) membranes.  

E-print Network

??Water permeation through Nafion® membranes and catalyst-coated membranes are measured. Three types of water permeability measurements are conducted in order to systematically study the effect… (more)

Adachi, Makoto

2010-01-01

292

Influence of estrogenic pesticides on membrane integrity and membrane transfer of monosaccharide into the human red cell  

SciTech Connect

Some natural and synthetic estrogens inhibit carrier-mediated transport of glucose into human red blood cells and membrane vesicles from the placenta. The inhibitory action of these estrogens on transport appears to be a direct effect at the membrane and does not involve receptor binding and protein synthesis. It is not clear, however, whether such inhibition is a common feature among estrogenic agents. Several chlorinated hydrocarbon pesticides have been shown to possess estrogenic activity. These pesticides could have inhibitory effects on the human sodium-independent glucose transporter. Owing to the apparent importance of this membrane transporter in human tissues, direct interaction of hormones and xenobiotics with the glucose transporter is of fundamental significance. Some pesticides have been shown to alter membrane structure directly and alter the passive permeability of membranes. Whether the estrogenic pesticides influence passive diffusion of sugars across membranes has not been established. Finally, preliminary observations have suggested that some estrogens and pesticides have lytic effects on intact cells. Consequently, this study focuses on the ability of several estrogens and estrogenic pesticides to disrupt the cell membrane, influence the monosaccharide transporter, and alter the rate of monosaccharide permeation through the membrane by simple diffusion.

Ingermann, R.L. (Univ. of Idaho, Moscow (USA))

1989-09-01

293

Effects of open-circuit operation on membrane and catalyst layer degradation in proton exchange membrane fuel cells  

Microsoft Academic Search

Durability issues have been attracting a great deal of attention in hydrogen\\/air proton exchange membrane (PEM) fuel cell research. In the present work, membrane electrode assembly (MEA) degradation under open circuit (OC) conditions was carried out for more than 250h. By means of several on-line electrochemical measurements, the performance of the fuel cell was analysed at different times during the

Shengsheng Zhang; Xiao-Zi Yuan; Jason Ng Cheng Hin; Haijiang Wang; Jinfeng Wu; K. Andreas Friedrich; Mathias Schulze

2010-01-01

294

Noncontact microsurgery of cell membranes using femtosecond laser pulses for optoinjection of specified substances into cells  

NASA Astrophysics Data System (ADS)

IR femtosecond laser pulses were used for microsurgery of a cell membrane aimed at local and short-duration change in its permeability and injection of specified extracellular substances into the cells. The possibility of noncontact laser delivery of the propidium iodide fluorescent dye and the pEGFP plasmid, encoding the green fluorescent protein, into the cells with preservation of the cell viability was demonstrated.

Il'ina, I. V.; Ovchinnikov, A. V.; Chefonov, O. V.; Sitnikov, D. S.; Agranat, Mikhail B.; Mikaelyan, A. S.

2013-04-01

295

Noncontact microsurgery of cell membranes using femtosecond laser pulses for optoinjection of specified substances into cells  

SciTech Connect

IR femtosecond laser pulses were used for microsurgery of a cell membrane aimed at local and short-duration change in its permeability and injection of specified extracellular substances into the cells. The possibility of noncontact laser delivery of the propidium iodide fluorescent dye and the pEGFP plasmid, encoding the green fluorescent protein, into the cells with preservation of the cell viability was demonstrated. (extreme light fields and their applications)

Il'ina, I V; Ovchinnikov, A V; Chefonov, O V; Sitnikov, D S; Agranat, Mikhail B; Mikaelyan, A S

2013-04-30

296

Process for recycling components of a PEM fuel cell membrane electrode assembly  

DOEpatents

The membrane electrode assembly (MEA) of a PEM fuel cell can be recycled by contacting the MEA with a lower alkyl alcohol solvent which separates the membrane from the anode and cathode layers of the assembly. The resulting solution containing both the polymer membrane and supported noble metal catalysts can be heated under mild conditions to disperse the polymer membrane as particles and the supported noble metal catalysts and polymer membrane particles separated by known filtration means.

Shore, Lawrence (Edison, NJ)

2012-02-28

297

Carbon monoxide poisoning of proton-exchange membrane fuel cells  

SciTech Connect

The platinum-alloy catalyst used in proton-exchange membrane (PEM) fuel cell anodes is highly susceptible to carbon monoxide (CO) poisoning. CO reduces the catalyst activity by blocking active catalyst sites normally available for hydrogen chemisorption and dissociation. The reaction kinetics at the anode catalyst surface can be used to estimate the decrease in cell voltage due to various levels of CO contamination in the inlet fuel streams on PEM fuel cell performance have been reviewed and analyzed in an attempt to further understand the electrochemical properties of the CO adsorption process. A fuel cell performance model of bipolar, Nafion 117 PEM fuel cell stack has been developed which predicts equilibrium cell output voltage as a function of current density and partial pressure of CO. The model contains both empirical and mechanistic parameters and evolved from a steady-state electrochemical model for a PEM fuel cell fed with a CO-free anode gas. Reaction kinetics and equilibrium surface coverage have been incorporated into the electrochemical model to predict the decrease in fuel cell performance at equilibrium. The effects of CO were studied at various concentrations of CO in hydrogen as the anode feed gas. Literature data were used to develop the model parameters and the resulting model is used to compare the model-predicted voltages, with and without CO, to data found in the literature.

Rodrigues, A.; Amphlett, J.C.; Mann, R.F.; Peppley, B.A.; Roberge, P.R. [Royal Military Coll. of Canada, Kingston, Ontario (Canada). Dept. of Chemistry and Chemical Engineering

1997-12-31

298

Reduced diversity of the human erythrocyte membrane sialic acids in polycythemia vera. Absence of N-glycolylneuraminic acid and characterisation of N-acetylneuraminic acid 1,7 lactone.  

PubMed

Sialic acids from the erythrocyte (RBC) membrane of a patient suffering from polycythemia vera, a malignant orphan disorder of hematopoietic cells, was studied using GC/MS. We found that the sialic acid diversity of these membranes was drastically reduced since only four entities were identified: Neu5Ac (91.5%) and its 1,7 lactone Neu5Ac1,7L (7.5%) which is absent in normal RBC, Neu4,5Ac(2) (0.50%) and Neu4,5Ac(2) 9Lt (0.50%); in normal RBC, Neu5,7Ac(2), Neu5,9Ac(2), Neu5Ac9Lt, Neu5Ac8S and Neu, as well as traces of Kdn, were also present. Neu5Gc and its O-alkylated or O-acetylated derivatives, which are considered by various authors as cancer markers, were not detected. PMID:17188794

Bratosin, Daniela; Palii, Carmen; Moicean, Andreea Delia; Zanetta, Jean-Pierre; Montreuil, Jean

2007-03-01

299

Characteristics of Subfreezing Operation of Polymer Electrolyte Membrane Fuel Cells  

NASA Astrophysics Data System (ADS)

Polymer Electrolyte Membrane (PEM) Fuel Cells are capable of high efficiency operation, and are free of NOx, SOx, and CO2 emissions when using hydrogen fuel, and ideally suited for use in transportation applications due to their high power density and low operating temperatures. However, under subfreezing conditions which may be encountered during winter seasons in some areas, product water will freeze within the membrane, cathode side catalyst layer and gas diffusion media, leading to voltage loss and operation failure. Experiments were undertaken in order to characterize the amount and location of water during fuel cell operation. First, in-situ neutron radiography was undertaken on the fuel cells at a normal operating temperature for various operating current densities, inlet relative humidities, and diffusion media hydrophobicities. It was found that more hydrophobic cathode microporous layer (MPL) or hydrophilic anode MPL may result in a larger amount of water transporting back to the anode. The water profiles along the channels were measured and the point of liquid water emergence, where two phase flow begins, was compared to previous models. Secondly, under subfreezing temperatures, neutron imaging showed that water ice product accumulates because of lack of a water removal mechanism. Water was observed under both the lands and channels, and increased almost linearly with time. It is found that most ice exists in the cathode side. With evidence from experimental observation, a cold start model was developed and explained, following existing approaches in the literature. Three stages of cold start are explained: membrane saturation, ice storage in catalyst layer pores, and then ice melting. The voltage losses due to temperature change, increased transport resistance, and reduced electrochemical surface area. The ionic conductivity of the membrane at subfreezing temperatures was modeled. Voltage evolution over time for isothermal cold starts was predicted and validated against experimental data. The ice coverage coefficient was shown to be a key variable in matching with experimental data. From model analysis, it appears that the coulombs of charge passed before operation failure is an important parameter characterizing PEM fuel cell cold start. To investigate the coulombs of charge and its determining factors, PEM fuel cells were constructed to measure the effects of membrane configuration (thickness and initial state), catalyst layer configuration (thickness and ionomer-carbon ratio), current density, and temperature on the quantity. It was found that subfreezing temperature, ionomer-catalyst ratio, and catalyst-layer thickness significantly affect the amount of charge transferred before operational failure, whereas the membrane thickness and initial hydration level have limited effect for the considered cases. In addition, degradation of the catalyst layer was observed and quantified. These results improve the fundamental understanding of characteristics of subfreezing operation and thus are valuable for automobile applications of PEM fuel cells. The model directly relates the material properties to voltage loss, and predicts voltage evolution, thus providing a way for material optimization and diagnostics. Additionally, insights into component design and operating conditions can be used to better optimize the fuel cell for cold start-up of the vehicle.

Mishler, Jeffrey Harris

300

Direct liquid-feed fuel cell with membrane electrolyte and manufacturing thereof  

NASA Technical Reports Server (NTRS)

An improved direct liquid-feed fuel cell having a solid membrane electrolyte for electrochemical reactions of an organic fuel. Improvements in interfacing of the catalyst layer and the membrane and activating catalyst materials are disclosed.

Narayanan, Sekharipuram (Inventor); Surampudi, Subbarao (Inventor); Halpert, Gerald (Inventor)

1999-01-01

301

Redox activity and peroxidase activity associated with the plasma membrane of guard-cell protoplasts  

Microsoft Academic Search

Redox systems have been reported in the plasma membrane of numerous cell types and in cells from various species of higher plant. A search for a redox system in the plasma membrane of guard cells was therefore made in efforts to explain how blue light stimulates stomatal opening, a process which is coupled to guard cell H+ efflux and K+

O. Pantoja; C. M. Willmer

1988-01-01

302

Laminin and Bullous Pemphigoid Antigen Are Distinct Basement Membrane Proteins Synthesized by Epidermal Cells  

Microsoft Academic Search

We sought to determine if laminin, a high molecular weight glycoprotein of basement membrane, is synthesized by epidermal cells and whether it is distinct from bullous pemphigoid (BP) antigen, another high molecular weight-protein of basement membrane. By indirect immunofluorescence we detected laminin in cultures of Pam cells (a mouse keratinocyte cell line) and normal human epidermal cells. To directly demonstrate

John R. Stanley; Pamela Hawley-Nelson; Mina Yaar; George H. Martin; Stephen I. Katz

1982-01-01

303

Role molecular signaling pathways in changes of red blood cell deformability.  

PubMed

This study was designed to investigate the dependency of the red blood cell deformability upon activation of extra- and intracellular signaling pathways. Exposures of red blood cells (RBCs) to catecholamines and to insulin led to positive change in the RBC deformability. When forskolin, a stimulator of adenylyl cyclase (AC), was added to RBC suspension, the RBC deformability was increased. Somewhat more significant deformability rise appeared after RBC incubation with dB-AMP. The inhibitors of phosphodiesterase (PDE) activity increased red cell deformability. These results revealed a considerable role of the AC-cAMP signaling system in the regulation of red blood cell deformability. The rise of the red blood cell Ca(2+) influx, stimulated by mechanical loading or A23187 was accompanied by a marked lowering of RBC deformability. At the same time blocking of Ca(2+) entry into RBC by verapamil or Ca(2+) chelating by EGTA led to significant deformability rise. The comparison of the effect of the different protein kinases on the red blood cell deformability showed that it was altered more considerable under PKA activation by forskolin or dB-cAMP than by other protein kinases. There was a lesser but quite statistically significant effect of tyrosine protein kinase (TPK) on RBC microrheology. Whereas the microrheological effect of PKC was not so considerable. The problem of the short-term regulation of red blood cell microrheology is examined. The latter includes: the modes of activation of extra- and intracellular molecular signaling pathways, ligand - receptor interaction, second messengers, membrane protein phosphorylation. On the whole the total data clearly show that the red cell deformability changes are connected with activation of different extra - and intracellular signaling pathways. It seems reasonable to suppose that red blood cell deformability changes were mainly associated with activation of the AC-cAMP-PKA pathway, and with decrease of Ca(2+) entry into cells. PMID:22951624

Muravyov, Alexei V; Tikhomirova, Irina A

2013-01-01

304

Proton-induced endocytosis is dependent on cell membrane fluidity, lipid-phase order and the membrane resting potential.  

PubMed

Recently it has been shown that decreasing the extracellular pH of cells stimulates the formation of inward membrane invaginations and vesicles, accompanied by an enhanced uptake of macromolecules. This type of endocytosis was coined as proton-induced uptake (PIU). Though the initial induction of inward membrane curvature was rationalized in terms of proton-based increase of charge asymmetry across the membrane, the dependence of the phenomenon on plasma membrane characteristics is still unknown. The present study shows that depolarization of the membrane resting potential elevates PIU by 25%, while hyperpolarization attenuates it by 25%. Comparison of uptake in suspended and adherent cells implicates that the resting-potential affects PIU through remodeling the actin-cytoskeleton. The pH at the external interface of the cell membrane rather than the pH gradient across it determines the extent of PIU. PIU increases linearly upon temperature increase in the range of 4-36°C, in correlation with the membrane fluidity. The plasma membrane fluidity and the lipid phase order are modulated by enriching the cell's membrane with cholesterol, tergitol, dimethylsulfoxide, 6-ketocholestanol and phloretin and by cholesterol depletion. These treatments are shown to alter the extent of PIU and are better correlated with membrane fluidity than with the lipid phase order. We suggest that the lipid phase order and fluidity influence PIU by regulating the lipid order gradient across the perimeter of the lipid-condensed microdomains (rafts) and alter the characteristic tension line that separates the higher ordered lipid-domains from the lesser ordered ones. PMID:23911577

Ben-Dov, Nadav; Korenstein, Rafi

2013-11-01

305

A Simple Alkaline Method for Decellularizing Human Amniotic Membrane for Cell Culture  

PubMed Central

Human amniotic membrane is a standard substratum used to culture limbal epithelial stem cells for transplantation to patients with limbal stem cell deficiency. Various methods were developed to decellularize amniotic membrane, because denuded membrane is poorly immunogenic and better supports repopulation by dissociated limbal epithelial cells. Amniotic membrane denuding usually involves treatment with EDTA and/or proteolytic enzymes; in many cases additional mechanical scraping is required. Although ensuring limbal cell proliferation, these methods are not standardized, require relatively long treatment times and can result in membrane damage. We propose to use 0.5 M NaOH to reliably remove amniotic cells from the membrane. This method was used before to lyse cells for DNA isolation and radioactivity counting. Gently rubbing a cotton swab soaked in NaOH over the epithelial side of amniotic membrane leads to nearly complete and easy removal of adherent cells in less than a minute. The denuded membrane is subsequently washed in a neutral buffer. Cell removal was more thorough and uniform than with EDTA, or EDTA plus mechanical scraping with an electric toothbrush, or n-heptanol plus EDTA treatment. NaOH-denuded amniotic membrane did not show any perforations compared with mechanical or thermolysin denuding, and showed excellent preservation of immunoreactivity for major basement membrane components including laminin ?2, ?1-?3 chains, ?1/?2 and ?6 type IV collagen chains, fibronectin, nidogen-2, and perlecan. Sodium hydroxide treatment was efficient with fresh or cryopreserved (10% dimethyl sulfoxide or 50% glycerol) amniotic membrane. The latter method is a common way of membrane storage for subsequent grafting in the European Union. NaOH-denuded amniotic membrane supported growth of human limbal epithelial cells, immortalized corneal epithelial cells, and induced pluripotent stem cells. This simple, fast and reliable method can be used to standardize decellularized amniotic membrane preparations for expansion of limbal stem cells in vitro before transplantation to patients. PMID:24236148

Saghizadeh, Mehrnoosh; Winkler, Michael A.; Kramerov, Andrei A.; Hemmati, David M.; Ghiam, Chantelle A.; Dimitrijevich, Slobodan D.; Sareen, Dhruv; Ornelas, Loren; Ghiasi, Homayon; Brunken, William J.; Maguen, Ezra; Rabinowitz, Yaron S.; Svendsen, Clive N.; Jirsova, Katerina; Ljubimov, Alexander V.

2013-01-01

306

Adaptive evolution of rbcL in Conocephalum (Hepaticae, bryophytes)  

Microsoft Academic Search

An excess of nonsynonymous substitutions over synonymous ones has been regarded as an important indicator of adaptive evolution or positive selection at the molecular level. We now report such a case for rbcL sequences among cryptic species in Conocephalum (Hepaticae, Bryophytes). This finding can be regarded as evidence of adaptive evolution in several cryptic species (especially in F and JN

Hidetsugu Miwa; Ireneusz J. Odrzykoski; Atsushi Matsui; Masami Hasegawa; Hiroyuki Akiyama; Yu Jia; Renat Sabirov; Hideki Takahashi; David E. Boufford; Noriaki Murakami

2009-01-01

307

Percolation in a Proton Exchange Membrane Fuel Cell Catalyst Layer  

SciTech Connect

Water management in the catalyst layers of proton exchange membrane fuel cells (PEMFC) is confronted by two issues, flooding and dry out, both of which result in improper functioning of the fuel cell and lead to poor performance and degradation. At the present time, the data that has been reported about water percolation and wettability within a fuel cell catalyst layer is limited. A method and apparatus for measuring the percolation pressure in the catalyst layer has been developed based upon an experimental apparatus used to test water percolation in porous transport layers (PTL). The experimental setup uses a pseudo Hele-Shaw type testing where samples are compressed and a fluid is injected into the sample. Testing the samples gives percolation pressure plots which show trends in increasing percolation pressure with an increase in flow rate. A decrease in pressure was seen as percolation occurred in one sample, however the pressure only had a rising effect in the other sample.

Stacy, Stephen; Allen, Jeffrey

2012-07-01

308

Cell-Specific Aptamer Probes for Membrane Protein Elucidation in Cancer Cells  

E-print Network

approaches to cancer, and markedly improve our understanding of cancer biology. Keywords: Biomarker · AptamerCell-Specific Aptamer Probes for Membrane Protein Elucidation in Cancer Cells Dihua Shangguan* Department of Chemistry, Department of Physiology and Functional Genomics, Department of Pathology

Tan, Weihong

309

Surface-enhanced Raman imaging of red blood cell membrane with highly uniform active substrates obtained using block copolymers self-assembly  

NASA Astrophysics Data System (ADS)

In this communication, we discuss the application of ordered, ultrahigh-density templates of nano-textured Ag-particles obtained by self-assembling of inorganic-containing polystyrene-block-poly(4-vinylpyridine) copolymer (PS-b-P4VP) micelles, for the spectroscopic surface-enhanced Raman imaging in-vitro of red blood cells (RBCs) and its capability to identify the vibrational fingerprint of the plasma membrane of the cell physisorbed to the SERS substrate. Hexagonal arrays of PS-b-P4VP micelles, with selective inclusion of Ag nanoparticles (NPs) in the polar core, prepared by in situ reduction of a suitable precursor, are obtained by polymer self-assembly upon fast solvent evaporation during spin coating on the supporting substrate. UV irradiation and/or plasma oxygen treatment remove the polymer matrix leaving immobilized nano-islands of Ag-NPs. Such a kind of SERS-active substrate consists of a reproducible and uniform twodimensional hexagonal array of silver clusters with a diameter ranging from 25 to 30 nm (single particles having typically diameters of 5 nm) and nano-island gap distances of the order of 5-8 nm on silicon and 15 nm on glass , while giving rise to high enhancement factors and addressing the issue of SERS reproducibility. The basic substrate supporting the plasmonic coating used in this work is either of silicon or glass. This last allows working in back scattering configuration permitting real time monitoring, via microscopy, of the RBCs on which Raman measurements are being carried out. The template is thus applied for surface-enhanced Raman analysis of the red blood cell (RBC) membrane in confocal micro-Raman configuration demonstrating to have SERS imaging potential thanks to the uniformity of the nano-textured substrate. The first experimental evidence of SERS imaging of a red blood cell membrane in-vitro is demonstrated.

Zito, Gianluigi; Malafronte, Anna; Dochshanov, Alden; Rusciano, Giulia; Auriemma, Finizia; Pesce, Giuseppe; De Rosa, Claudio; Sasso, Antonio

2013-05-01

310

Cell-free synthesis of membrane subunits of ATP synthase in phospholipid bicelles: NMR shows subunit a fold similar to the protein in the cell membrane  

PubMed Central

NMR structure determination of large membrane proteins is hampered by broad spectral lines, overlap, and ambiguity of signal assignment. Chemical shift and NOE assignment can be facilitated by amino acid selective isotope labeling in cell-free protein synthesis system. However, many biological detergents are incompatible with the cell-free synthesis, and membrane proteins often have to be synthesized in an insoluble form. We report cell-free synthesis of subunits a and c of the proton channel of Escherichia coli ATP synthase in a soluble form in a mixture of phosphatidylcholine derivatives. In comparison, subunit a was purified from the cell-free system and from the bacterial cell membranes. NMR spectra of both preparations were similar, indicating that our procedure for cell-free synthesis produces protein structurally similar to that prepared from the cell membranes. PMID:22162071

Uhlemann, Eva-Maria E; Pierson, Hannah E; Fillingame, Robert H; Dmitriev, Oleg Y

2012-01-01

311

Evidence for Transfer of Membranes from Mesenchymal Stem Cells to HL-1 Cardiac Cells  

PubMed Central

This study examined the interaction of mouse bone marrow mesenchymal stem cells (MSC) with cardiac HL-1 cells during coculture by fluorescent dye labeling and then flow cytometry. MSC were layered onto confluent HL-1 cell cultures in a 1?:?4 ratio. MSC gained gap junction permeant calcein from HL-1 cells after 4 hours which was partially reduced by oleamide. After 20 hours, 99% MSC gained calcein, unaffected by oleamide. Double-labeling HL-1 cells with calcein and the membrane dye DiO resulted in transfer of both calcein and DiO to MSC. When HL-1 cells were labeled with calcein and MSC with DiO, MSC gained calcein while HL-1 cells gained DiO. Very little fusion was observed since more than 90% Sca-1 positive MSC gained DiO from HL-1 cells while less than 9% gained gap junction impermeant CMFDA after 20 hours with no Sca-1 transfer to HL-1 cells. Time dependent transfer of membrane DiD was observed from HL-1 cells to MSC (100%) and vice versa (50%) after 20 hours with more limited transfer of CMFDA. These results demonstrate that MSC and HL-1 cells exchange membrane components which may account for some of the beneficial effect of MSC in the heart after myocardial infarction. PMID:25295065

Boomsma, Robert A.; Geenen, David L.

2014-01-01

312

Evidence for Transfer of Membranes from Mesenchymal Stem Cells to HL-1 Cardiac Cells.  

PubMed

This study examined the interaction of mouse bone marrow mesenchymal stem cells (MSC) with cardiac HL-1 cells during coculture by fluorescent dye labeling and then flow cytometry. MSC were layered onto confluent HL-1 cell cultures in a 1?:?4 ratio. MSC gained gap junction permeant calcein from HL-1 cells after 4 hours which was partially reduced by oleamide. After 20 hours, 99% MSC gained calcein, unaffected by oleamide. Double-labeling HL-1 cells with calcein and the membrane dye DiO resulted in transfer of both calcein and DiO to MSC. When HL-1 cells were labeled with calcein and MSC with DiO, MSC gained calcein while HL-1 cells gained DiO. Very little fusion was observed since more than 90% Sca-1 positive MSC gained DiO from HL-1 cells while less than 9% gained gap junction impermeant CMFDA after 20 hours with no Sca-1 transfer to HL-1 cells. Time dependent transfer of membrane DiD was observed from HL-1 cells to MSC (100%) and vice versa (50%) after 20 hours with more limited transfer of CMFDA. These results demonstrate that MSC and HL-1 cells exchange membrane components which may account for some of the beneficial effect of MSC in the heart after myocardial infarction. PMID:25295065

Boomsma, Robert A; Geenen, David L

2014-01-01

313

The Tripartite Type III Secreton of Shigella flexneri Inserts Ipab and Ipac into Host Membranes  

PubMed Central

Bacterial type III secretion systems serve to translocate proteins into eukaryotic cells, requiring a secreton and a translocator for proteins to pass the bacterial and host membranes. We used the contact hemolytic activity of Shigella flexneri to investigate its putative translocator. Hemolysis was caused by formation of a 25-Å pore within the red blood cell (RBC) membrane. Of the five proteins secreted by Shigella upon activation of its type III secretion system, only the hydrophobic IpaB and IpaC were tightly associated with RBC membranes isolated after hemolysis. Ipa protein secretion and hemolysis were kinetically coupled processes. However, Ipa protein secretion in the immediate vicinity of RBCs was not sufficient to cause hemolysis in the absence of centrifugation. Centrifugation reduced the distance between bacterial and RBC membranes beyond a critical threshold. Electron microscopy analysis indicated that secretons were constitutively assembled at 37°C before any host contact. They were composed of three parts: (a) an external needle, (b) a neck domain, and (c) a large proximal bulb. Secreton morphology did not change upon activation of secretion. In mutants of some genes encoding the secretion machinery the organelle was absent, whereas ipaB and ipaC mutants displayed normal secretons. PMID:10545510

Blocker, Ariel; Gounon, Pierre; Larquet, Eric; Niebuhr, Kirsten; Cabiaux, Veronique; Parsot, Claude; Sansonetti, Philippe

1999-01-01

314

CR1-mediated ATP Release by Human Red Blood Cells Promotes CR1 Clustering and Modulates the Immune Transfer Process*  

PubMed Central

Humans and other higher primates are unique among mammals in using complement receptor 1 (CR1, CD35) on red blood cells (RBC) to ligate complement-tagged inflammatory particles (immune complexes, apoptotic/necrotic debris, and microbes) in the circulation for quiet transport to the sinusoids of spleen and liver where resident macrophages remove the particles, but allow the RBC to return unharmed to the circulation. This process is called immune-adherence clearance. In this study we found using luminometric- and fluorescence-based methods that ligation of CR1 on human RBC promotes ATP release. Our data show that CR1-mediated ATP release does not depend on Ca2+ or enzymes previously shown to mediate an increase in membrane deformability promoted by CR1 ligation. Furthermore, ATP release following CR1 ligation increases the mobility of the lipid fraction of RBC membranes, which in turn facilitates CR1 clustering, and thereby enhances the binding avidity of complement-opsonized particles to the RBC CR1. Finally, we have found that RBC-derived ATP has a stimulatory effect on phagocytosis of immune-adherent immune complexes. PMID:24022490

Melhorn, Mark I.; Brodsky, Abigail S.; Estanislau, Jessica; Khoory, Joseph A.; Illigens, Ben; Hamachi, Itaru; Kurishita, Yasutaka; Fraser, Andrew D.; Nicholson-Weller, Anne; Dolmatova, Elena; Duffy, Heather S.; Ghiran, Ionita C.

2013-01-01

315

Cytoskeleton confinement and tension of red blood cell membranes.  

PubMed

We analyze theoretically both the static and dynamic fluctuation spectra of the red blood cell in a unified manner, using a simple model of the composite membrane. In this model, the two-dimensional spectrin network that forms the cytoskeleton is treated as a rigid shell, located at a fixed, average distance from the lipid bilayer. The cytoskeleton thereby confines both the static and dynamic fluctuations of the lipid bilayer. The sparse connections of the cytoskeleton and bilayer induce a surface tension, for wavelengths larger than the bilayer persistence length. The predictions of the model give a consistent account for both the wave vector and frequency dependence of the experimental data. PMID:12857343

Gov, N; Zilman, A G; Safran, S

2003-06-01

316

2011 Alkaline Membrane Fuel Cell Workshop Final Report  

SciTech Connect

A workshop addressing the current state-of-the-art in alkaline membrane fuel cells (AMFCs) was held May 8-9, 2011, at the Crystal Gateway Marriott in Arlington, Virginia. This workshop was the second of its kind, with the first being held December 11-13, 2006, in Phoenix, Arizona. The 2011 workshop and associated workshop report were created to assess the current state of AMFC technology (taking into account recent advances), investigate the performance potential of AMFC systems across all possible power ranges and applications, and identify the key research needs for commercial competitiveness in a variety of areas.

Pivovar, B.

2012-02-01

317

Grafted polyelectrolyte membranes for lithium batteries and fuel cells  

SciTech Connect

Polyelectrolyte materials have been developed for lithium battery systems in response to the severe problems due to salt concentration gradients that occur in composite electrodes (aka membrane-electrode assemblies). Comb branch polymer architectures are described which allow for grafting of appropriate anions on to the polymer and also for cross-linking to provide for appropriate mechanical properties. The interactions of the polymers with the electrode surfaces are critical for the performance of the system and some of the structural features that influence this will be described. Parallels with the fuel cell MEA structures exist and will also be discussed.

Kerr, John B.

2003-06-24

318

Effective Temperature of Red Blood Cell Membrane Fluctuations  

E-print Network

Biologically driven non-equilibrium fluctuations are often characterized by their non-Gaussianity or by an "effective temperature", which is frequency dependent and higher than the ambient temperature. We address these two measures theoretically by examining a randomly kicked "particle", with a variable number of kicking "motors", and show how these two indicators of non-equilibrium behavior can contradict. Our results are compared with new experiments on shape fluctuations of red-blood cell membranes, and demonstrate how the physical nature of the motors in this system can be revealed using these global measures of non-equilibrium.

Eyal Ben-Isaac; YongKeun Park; Gabriel Popescu; Frank L. H. Brown; Nir S. Gov; Yair Shokef

2011-02-22

319

Red Blood Cell Osmotic Fragility in Chronically Hemodialyzed Patients  

Microsoft Academic Search

Chronic renal failure induces anemia and a short erythrocyte life span. Red blood cell (RBC) osmotic fragility is the resistance of RBC hemolysis to osmotic changes that is used to evaluate RBC friability. To find the cause of shortened red cell survival in uremic patients, we evaluated the RBC osmotic fragility in 57 chronic hemodialyzed patients. Each patient had received

San-Giang Wu; Fu-Rong Jeng; Shu-Yi Wei; Chin-Zung Su; Tieh-Chi Chung; Wen-Jou Chang; Hsueh-Wen Chang

1998-01-01

320

The actin homologue MreB organizes the bacterial cell membrane  

PubMed Central

The eukaryotic cortical actin cytoskeleton creates specific lipid domains, including lipid rafts, which determine the distribution of many membrane proteins. Here we show that the bacterial actin homologue MreB displays a comparable activity. MreB forms membrane-associated filaments that coordinate bacterial cell wall synthesis. We noticed that the MreB cytoskeleton influences fluorescent staining of the cytoplasmic membrane. Detailed analyses combining an array of mutants, using specific lipid staining techniques and spectroscopic methods, revealed that MreB filaments create specific membrane regions with increased fluidity (RIFs). Interference with these fluid lipid domains (RIFs) perturbs overall lipid homeostasis and affects membrane protein localization. The influence of MreB on membrane organization and fluidity may explain why the active movement of MreB stimulates membrane protein diffusion. These novel MreB activities add additional complexity to bacterial cell membrane organization and have implications for many membrane-associated processes. PMID:24603761

Strahl, Henrik; Burmann, Frank; Hamoen, Leendert W.

2014-01-01

321

[Progress with research on the permeability characteristics of reproductive cell membranes].  

PubMed

The successful cryopreservation of reproductive cells has important practical significance in many fields. In order to improve the recovery rate and viability of cryopreserved cells, it is necessary to study the permeability characteristics of cell membrane to both water and cryoprotectant. In this paper we review the studies on membrane permeability of animal reproductive cell for the recent years. We firstly list the typical permeability data of spermatozoa and oocyte membrane for water and cryoprotectant. We then analyze the effects of these characteristics on the design of cryopreservation protocol. We also introduce the latest experimental methods to measure the cell membrane permeability. PMID:22616195

Zhou, Zheng; Chen, Guangming; Zhang, Shaozhi

2012-04-01

322

Polymeric nanoparticles of different sizes overcome the cell membrane barrier.  

PubMed

Polymeric nanoparticles have tremendous potential either as carriers or markers in treatment for diseases or as diagnostics in biomedical applications. Finding the optimal conditions for effective intracellular delivery of the payload to the location of interest is still a big challenge. The particles have to overcome the barrier of the cell membrane. Here, we investigated the uptake in HeLa cells of fluorescent polystyrene particles with different size and surface charge. Particles stabilized with the nonionic surfactant Lutensol AT50® (132 nm, 180 nm, 242 nm, 816 nm, 846 nm diameter) were synthesized via dispersion polymerization. Cationic particles (120 nm, 208 nm, 267 nm, 603 nm diameter) were obtained by a combination of miniemulsion and seed dispersion polymerization using cationic surfactant (cetyltrimethylammonium chloride (CTMA-Cl). The particle uptake into HeLa cells was studied by confocal laser scanning microscopy and flow cytometry. Nonionic particles were - independent of their size - taken up by cells only at a barely detectable level, thus aggravating a quantitative comparison. The uptake of positively charged particles was substantially higher and therefore enabling further investigation keeping constant one of these parameters: either material amount or particles number or total interaction surface area. It was found that the uptake rather depends on the total amount of polymeric material present in the media than on the number of particles. The total particle's surface area does not correlate linearly with the uptake, thus indicating that there is no direct dependency between the total surface area and the cellular endocytotic process to overcome the biobarrier "cell membrane." A potentially novel uptake mechanism is found which can be described as an excavator shovel like mechanism. It is a kind of macropinocytosis dependent on actin filaments as well as dynamin, but is clathrin-independent. PMID:23422734

Lerch, Simone; Dass, Martin; Musyanovych, Anna; Landfester, Katharina; Mailänder, Volker

2013-06-01

323

DEVELOPMENT OF NOVEL ELECTROCATALYST FOR PROTON EXCHANGE MEMBRANE FUEL CELLS  

SciTech Connect

Proton-exchange membrane fuel cell (PEMFC) is one of the strongest contenders as a power source for space & electric vehicle applications. Platinum catalyst is used for both fuel and air electrodes in PEMFCs. CO contamination of H{sub 2} greatly affects electrocatalysts used at the anode of polymer electrolyte fuel cells and decrease the cell performance. Pt-Ru catalyst had been recognized to alleviate this problem by showing better tolerance to CO poisoning than only Pt catalyst. This irreversible poisoning of the anode can be happened even in concentrations as little as a few ppm, and therefore, require expensive scrubbing to reduce the contaminant concentration to acceptable level. In order to commercialize this environmentally sound source of energy/power system, development of suitable impurity tolerant catalyst is needed. This project will develop novel electrocatalysts for the PEMFCs and demonstrate the feasibility of a H{sub 2}/O{sub 2} fuel cell base on these materials. This project, if successful, will reduce the costs due to reduce Pt catalyst loading or use non-precious metals. It will increase the PEM fuel cell performance by increasing catalyst tolerance to methanol oxidation intermediate products (CO) and fuel impurities (H{sub 2}S), which will generate substantial interest for commercialization of the PEM fuel cell technology.

Shamsuddin Ilias

2000-01-19

324

Cooperative binding of Annexin A5 to phosphatidylserine on apoptotic cell membranes  

NASA Astrophysics Data System (ADS)

Healthy cells exhibit an asymmetric plasma membrane with phosphatidylserine (PS) located on the cytoplasmic leaflet of the plasma membrane bilayer. Annexin A5-FITC, a PS binding protein, is commonly used to evaluate apoptosis in flow cytometry. PS exposed by apoptotic cells serves as a major ‘eat-me’ signal for phagocytes. Although exposition of PS has been observed after alternative stimuli, no clearance of viable, PS exposing cells has been detected. Thus, besides PS exposure, membranes of viable and apoptotic cells might exhibit specific characteristics. Here, we show that Annexin A5 binds in a cooperative manner to different types of dead cells. Shrunken apoptotic cells thereby showed the highest Hill coefficient values. Contrarily, parafomaldehyde fixation of apoptotic cells completely abrogates the cooperativity effect seen with dead and dying cells. We tend to speculate that the cooperative binding of Annexin A5 to the membranes of apoptotic cells reflects higher fluidity of the exposed membranes facilitating PS clustering.

Janko, Christina; Jeremic, Ivica; Biermann, Mona; Chaurio, Ricardo; Schorn, Christine; Muñoz, Luis E.; Herrmann, Martin

2013-12-01

325

Effects of cholesterol on nano-mechanical properties of the living cell plasma membrane  

PubMed Central

In this study, we investigated the effects of membrane cholesterol content on the mechanical properties of cell membranes by using optical tweezers. We pulled membrane tethers from human embryonic kidney cells using single and multi-speed protocols, and obtained time-resolved tether forces. We quantified various mechanical characteristics including the tether equilibrium force, bending modulus, effective membrane viscosity, and plasma membrane-cytoskeleton adhesion energy, and correlated them to the membrane cholesterol level. Decreases in cholesterol concentration were associated with increases in the tether equilibrium force, tether stiffness, and adhesion energy. Tether diameter and effective viscosity increased with increasing cholesterol levels. Disruption of cytoskeletal F-actin significantly changed the tether diameters in both non-cholesterol and cholesterol-manipulated cells, while the effective membrane viscosity was unaffected by F-actin disruption. The findings are relevant to inner ear function where cochlear amplification is altered by changes in membrane cholesterol content. PMID:23227105

Khatibzadeh, Nima; Gupta, Sharad; Farrell, Brenda; Brownell, William E.; Anvari, Bahman

2012-01-01

326

RELATION BETWEEN EPSTEIN-BARR VIRAL AND CELL MEMBRANE IMMUNOFLUORESCENCE OF BURKITT TUMOR CELLS  

PubMed Central

A comparison was made of the immunofluorescence tests for detection of cell membrane and Epstein-Barr virus antigens in cells from Burkitt tumor biopsies or continuous cultures derived therefrom. On the whole, cell membrane fluorescence in established lines appeared to depend not only upon the presence of EBV but to a considerable degree also upon the extent of the persistent viral infection. There was no constant relationship, however, between the results of the two tests and exceptions to the rule were noted. These observations indicate that different antigens are involved in the two tests. Biopsy cells in general and young cultures may reveal strong MIF activity but few, if any, EBV-positive cells. The reverse, the presence of relatively large numbers of EBV antigen-containing cells in the absence of significant MIF reactions, was also noted on occasion in a few established cultures. The possible interpretations of these findings have been discussed. PMID:4878906

Klein, G.; Pearson, G.; Nadkarni, J. S.; Nadkarni, J. J.; Klein, E.; Henle, G.; Henle, W.; Clifford, P.

1968-01-01

327

Cell-Culture Reactor Having a Porous Organic Polymer Membrane  

NASA Technical Reports Server (NTRS)

A method for making a biocompatible polymer article using a uniform atomic oxygen treatment is disclosed. The substrate may be subsequently optionally grated with a compatibilizing compound. Compatibilizing compounds may include proteins, phosphory1choline groups, platelet adhesion preventing polymers, albumin adhesion promoters, and the like. The compatibilized substrate may also have a living cell layer adhered thereto. The atomic oxygen is preferably produced by a flowing afterglow microwave discharge, wherein the substrate resides in a sidearm out of the plasma. Also, methods for culturing cells for various purposes using the various membranes are disclosed as well. Also disclosed are porous organic polymers having a distributed pore chemistry (DPC) comprising hydrophilic and hydrophobic regions, and a method for making the DPC by exposing the polymer to atomic oxygen wherein the rate of hydrophilization is greater than the rate of mass loss.

Koontz, Steven L. (Inventor)

2000-01-01

328

ATP and ADP hydrolysis in cell membranes from rat myometrium.  

PubMed

Extracellular nucleotides affect female reproductive functions, fertilization, and pregnancy. The aim of this study was to investigate biochemical characteristics of ATP and ADP hydrolysis and identify E-NTPDases in myometrial cell membranes from Wistar albino rats. The apparent K (m) values were 506.4 ± 62.1 and 638.8 ± 31.3 ?M, with a calculated V (max) (app) of 3,973.0 ± 279.5 and 2,853.9 ± 79.8 nmol/min/mg for ATP and ADP, respectively. The enzyme activity described here has common properties characteristic for NTPDases: divalent cation dependence; alkaline pH optimum for both substrates, insensitivity to some of classical ATPase inhibitors (ouabain, oligomycine, theophylline, levamisole) and significant inhibition by suramine and high concentration of sodium azides (5 mM). According to similar apparent K(m) values for both substrates, the ATP/ADP hydrolysis ratio, and Chevillard competition plot, NTPDase1 is dominant ATP/ADP hydrolyzing enzyme in myometrial cell membranes. RT-PCR analysis revealed expression of three members of ectonucleoside triphosphate diphosphohydrolase family (NTPDase 1, 2, and 8) in rat uterus. These findings may further elucidate the role of NTPDases and ATP in reproductive physiology. PMID:22956447

Miloševi?, Maja; Petrovi?, Snježana; Veli?kovi?, Nataša; Grkovi?, Ivana; Ignjatovi?, Marija; Horvat, Anica

2012-12-01

329

Serum iron metabolism and erythropoiesis in patients with myelodysplastic syndrome not receiving RBC transfusions.  

PubMed

Dysregulation of hepcidin, a key iron regulating hormone, is important in the pathogenesis of iron overload in patients with myelodysplatic syndrome (MDS). However, most studies of hepcidin levels are complicated by concomitant RBC transfusions. To evaluate the relationship between iron metabolism and erythropoiesis, we measured serum levels of hepcidin, growth-differentiation factor-15 (GDF15) and other markers of erythropoiesis in 107 subjects with MDS not receiving RBC transfusions. Patients with MDS had significantly higher levels of hepcidin than normals. However, their hepcidin-ferritin ratio was markedly decreased compared to normals (P<0.001) and varied substantially between MDS subtypes (P=0.011). GDF15 levels positively correlated with percent of bone marrow erythroblasts (P<0.001), soluble transferrin receptor (sTfR) (P=0.018), and also with transferrin saturation (ISAT) (P=0.038). The hepcidin-ferritin ratio negatively correlated with serum erythropoietin (EPO) levels (P<0.001), and also with GDF15 levels (P=0.014). Colony forming cells (CFC) were evaluated in 70 subjects. Those with serum ferritin (SF) levels <500 ng/ml had significantly more BFU-E than subjects with SF ? 500 ng/L (P=0.007), but numbers of granulocyte/macrophage-colony-forming cells (CFU-GM) were similar (P=0.190). Our data indicate serum hepcidin levels are inappropriately low in patients MDS not receiving RBC transfusions. GDF15 levels correlated with low hepcidin levels and may contribute to iron overload in this setting. Iron overload may in turn suppress erythropoiesis by imparing the proliferative capacity of the erythroid progenitor cells. PMID:24598841

Cui, Rui; Gale, Robert Peter; Zhu, Guoqing; Xu, Zefeng; Qin, Tiejun; Zhang, Yue; Huang, Gang; Li, Bing; Fang, Liwei; Zhang, Hongli; Pan, Lijuan; Hu, Naibo; Qu, Shiqiang; Xiao, Zhijian

2014-05-01

330

DEVELOPMENT OF NOVEL ELECTROCATALYSTS FOR PROTON EXCHANGE MEMBRANE FUEL CELLS  

SciTech Connect

The Proton Exchange Membrane Fuel Cell (PEMFC) is one of the most promising power sources for stand-alone utility and electric vehicle applications. Platinum (Pt) Catalyst is used for both fuel and air electrodes in PEMFCs. However, carbon monoxide (CO) contamination of H{sub 2} greatly affects electro catalysts used at the anode of PEMFCs and decreases cell performance. The irreversible poisoning of the anode can occur even in CO concentrations as low as few parts per million (ppm). In this work, we have synthesized several novel elctrocatalysts (Pt/C, Pt/Ru/C, Pt/Mo/C, Pt/Ir and Pt/Ru/Mo) for PEMFCs. These catalysts have been tested for CO tolerance in the H{sub 2}/air fuel cell, using CO concentrations in the H{sub 2} fuel that varies from 10 to 100 ppm. The performance of the electrodes was evaluated by determining the cell potential against current density. The effects of catalyst composition and electrode film preparation method on the performance of PEM fuel cell were also studied. It was found that at 70 C and 3.5 atm pressure at the cathode, Pt-alloy catalyst (10 wt% Pt/Ru/C, 20 wt% Pt/Mo/C) were more CO tolerant than the 20 wt% Pt/C catalyst alone. It was also observed that spraying method was better than the brushing technique for the preparation of electrode film.

Shamsuddin Ilias

2002-06-11

331

Alloantibodies to a paternally derived RBC KEL antigen lead to hemolytic disease of the fetus/newborn in a murine model.  

PubMed

Exposure to nonself red blood cell (RBC) antigens, either from transfusion or pregnancy, may result in alloimmunization and incompatible RBC clearance. First described as a pregnancy complication 80 years ago, hemolytic disease of the fetus and newborn (HDFN) is caused by alloimmunization to paternally derived RBC antigens. Despite the morbidity/mortality of HDFN, women at risk for RBC alloimmunization have few therapeutic options. Given that alloantibodies to antigens in the KEL family are among the most clinically significant, we developed a murine model with RBC-specific expression of the human KEL antigen to evaluate the impact of maternal/fetal KEL incompatibility. After exposure to fetal KEL RBCs during successive pregnancies with KEL-positive males, 21 of 21 wild-type female mice developed anti-KEL alloantibodies; intrauterine fetal anemia and/or demise occurred in a subset of KEL-positive pups born to wild type, but not agammaglobulinemic mothers. Similar to previous observations in humans, pregnancy-associated alloantibodies were detrimental in a transfusion setting, and transfusion-associated alloantibodies were detrimental in a pregnancy setting. This is the first pregnancy-associated HDFN model described to date, which will serve as a platform to develop targeted therapies to prevent and/or mitigate the dangers of RBC alloantibodies to fetuses and newborns. PMID:23801629

Stowell, Sean R; Henry, Kate L; Smith, Nicole H; Hudson, Krystalyn E; Halverson, Greg R; Park, Jaekeun C; Bennett, Ashley M; Girard-Pierce, Kathryn R; Arthur, C Maridith; Bunting, Silvia T; Zimring, James C; Hendrickson, Jeanne E

2013-08-22

332

Alloantibodies to a paternally derived RBC KEL antigen lead to hemolytic disease of the fetus/newborn in a murine model  

PubMed Central

Exposure to nonself red blood cell (RBC) antigens, either from transfusion or pregnancy, may result in alloimmunization and incompatible RBC clearance. First described as a pregnancy complication 80 years ago, hemolytic disease of the fetus and newborn (HDFN) is caused by alloimmunization to paternally derived RBC antigens. Despite the morbidity/mortality of HDFN, women at risk for RBC alloimmunization have few therapeutic options. Given that alloantibodies to antigens in the KEL family are among the most clinically significant, we developed a murine model with RBC-specific expression of the human KEL antigen to evaluate the impact of maternal/fetal KEL incompatibility. After exposure to fetal KEL RBCs during successive pregnancies with KEL-positive males, 21 of 21 wild-type female mice developed anti-KEL alloantibodies; intrauterine fetal anemia and/or demise occurred in a subset of KEL-positive pups born to wild type, but not agammaglobulinemic mothers. Similar to previous observations in humans, pregnancy-associated alloantibodies were detrimental in a transfusion setting, and transfusion-associated alloantibodies were detrimental in a pregnancy setting. This is the first pregnancy-associated HDFN model described to date, which will serve as a platform to develop targeted therapies to prevent and/or mitigate the dangers of RBC alloantibodies to fetuses and newborns. PMID:23801629

Stowell, Sean R.; Henry, Kate L.; Smith, Nicole H.; Hudson, Krystalyn E.; Halverson, Greg R.; Park, Jaekeun C.; Bennett, Ashley M.; Girard-Pierce, Kathryn R.; Arthur, C. Maridith; Bunting, Silvia T.; Zimring, James C.

2013-01-01

333

Single cell membrane poration by bubble-induced microjets in a microfluidic chip.  

PubMed

This paper demonstrates membrane poration of a single suspension cell due to a fast liquid microjet. The jet is formed during the collapse of a laser induced bubble created at a variable stand-off distance from the target cell. The cell is trapped by a converging structure within a microfluidic chip. The asymmetrical growth and collapse of the cavitation bubble next to the cell lead to the microjetting, which deforms and porates the cell membrane. In the experiments, the membrane porations of myeloma cells are probed with the uptake of trypan blue. Time-resolved studies of the diffusion of trypan blue show a marked dependency on the bubble dynamics, i.e. the stand-off distance. The penetration length of the dye increases with shorter distances. Numerical simulations of the diffusion process agree with larger pores formed on the cell membrane. This method allows for a fast, repeatable, and localized rupture of membranes of individual cells in suspension. PMID:23364762

Li, Z G; Liu, A Q; Klaseboer, E; Zhang, J B; Ohl, C D

2013-03-21

334

Secondary Structure of Cell-Penetrating Peptides Controls Membrane Interaction and Insertion  

E-print Network

Secondary Structure of Cell-Penetrating Peptides Controls Membrane Interaction and Insertion Emelía permeability of the biological membranes. In order to enhance their cell delivery, short amphipathic peptides called cell-penetrating peptides (CPPs) have been intensively developed for the last two decades. CPPs

Boyer, Edmond

335

Cell Sorting Experiments Link Persistent Mitochondrial DNA Damage with Loss of Mitochondrial Membrane Potential and  

E-print Network

in the fraction of cells with low mitochondrial membrane potential ( m). Further analysis also showed increased Membrane Potential and Apoptotic Cell Death* Received for publication, August 27, 2002, and in revised formCell Sorting Experiments Link Persistent Mitochondrial DNA Damage with Loss of Mitochondrial

Santos, Janine H.

336

Quantitative assay by flow cytometry of the mitochondrial membrane potential in intact cells  

Microsoft Academic Search

Mitochondrial membrane potential, in situ, is an important indicator of mitochondrial function and dysfunction. Because of recent interest in the role of mitochondria in signaling, cell injury and cell death, there is a need for a convenient, sensitive and accurate method for the measurement of the mitochondrial membrane potential, ??m, in situ, in a heterogeneous cell population. We have adapted

Hagai Rottenberg; Shaolong Wu

1998-01-01

337

Refractive index maps and membrane dynamics of human red blood cells parasitized  

E-print Network

Refractive index maps and membrane dynamics of human red blood cells parasitized by Plasmodium to the host red blood cells (RBCs). To study these modifications, we investigate two intrinsic indicators for identifying, through cell membrane dynamics, pathological states that cause or accompany human diseases

Suresh, Subra

338

Surface-dependent Coagulation Enzymes FLOW KINETICS OF FACTOR Xa GENERATION ON LIVE CELL MEMBRANES*  

E-print Network

Surface-dependent Coagulation Enzymes FLOW KINETICS OF FACTOR Xa GENERATION ON LIVE CELL MEMBRANES of the extrinsic coagula- tion pathway on live cell membranes were examined under flow conditions. Generation of activated coagula- tion factor X (fXa) was measured on spherical monolay- ers of epithelial cells

Chou, Tom

339

Continuous monitoring of membrane protein micro-domain association during cell signaling  

E-print Network

Central to understanding membrane bound cell signaling is to quantify how the membrane ultra-structure consisting of transient spatial domains modulates signaling and how the signaling influences this ultra-structure. Yet, measuring the association of membrane proteins with domains in living, intact cells poses considerable challenges. Here, we describe a non-destructive method to quantify protein-lipid domain and protein cytoskeleton interactions in single, intact cells enabling continuous monitoring of the protein domains interaction over time during signaling.

Heng Huang; Arnd Pralle

2011-01-26

340

Designing Therapies against Experimental Visceral Leishmaniasis by Modulating the Membrane Fluidity of Antigen-Presenting Cells  

Microsoft Academic Search

Received 16 January 2009\\/Returned for modification 2 March 2009\\/Accepted 6 March 2009 The membrane fluidity of antigen-presenting cells (APCs) has a significant bearing on T-cell-stimulating ability and is dependent on the cholesterol content of the membrane. The relationship, if any, between membrane fluidity and defective cell-mediated immunity in visceral leishmaniasis has been investigated. Systemic administration of cholesterol by liposome delivery

Subha Banerjee; June Ghosh; Subha Sen; Rajan Guha; Ranjan Dhar; Moumita Ghosh; Sanchita Datta; Bikramjit Raychaudhury; Kshudiram Naskar; Arun Kumar Haldar; C. S. Lal; K. Pandey; V. N. R. Das; P. Das; S. Roy

2009-01-01

341

Gastric mucosal cell homeostatic physiome. Critical role of ER-initiated membranes restitution in the fidelity of cell function renewal.  

PubMed

Homeostatic cell physiology is preserved through the fidelity of the cell membranes restitution. The task is accomplished through the assembly of the precisely duplicated segments of the cell membranes, and transport to the site of their function. Here we examined the mechanism that initiates and directs the restitution of the intra- and extracellular membranes of gastric mucosal cell. The homeostatic restitution of gastrointestinal epithelial cell membrane components was investigated by studying the lipidomic processes in endoplasmic reticulum (ER) and Golgi. The biomembrane lipid synthesis during the formation of transport vesicles in the systems containing isolated organelle and the cell-specific cytosol (Cyt) from rat gastric mucosal epithelial cells was assessed. The results revealed that lipids of ER transport vesicle and the transmembrane and intravesicular cargo are delivered en bloc to the point of destination. En bloc delivery of proteins, incorporated into predetermined in ER lipid environment, ensures fidelity of the membrane modification in Golgi and the restitution of the lipid and protein elements that are consistent with the organelle and the cell function. The mechanism that maintains apical membrane restitution is mediated through the synthesis of membrane segments containing ceramide (Cer). The Cer-containing membranes and protein cargo are further specialized in Golgi. The portion of the vesicles destined for apical membrane renewal contains glycosphingolipids and phosphatidylinositol 3-phosphate. The vesicles containing phosphatidylinositol 4-phosphate are directed to endosomes. Our findings revealed that the preservation of the physiological equilibrium in cell structure and function is attributed to (1) a complete membrane segment synthesis in ER, (2) its transport in the form of ER-transport vesicle to Golgi, (3) the membrane components-defined maturation of lipids and proteins in Golgi, and (4) en bloc transfer of the new segment of the membrane to the cell apical membrane or intracellular organelle. PMID:15613747

Slomiany, A; Sano, S; Grabska, M; Yamaki, K; Slomiany, B L

2004-12-01

342

Gallbladder visualization during technetium-99m RBC blood pool imaging. Case report and literature review  

SciTech Connect

Gallbladder visualization occurred after a Tc-99m red blood cell (RBC) cardiac gated blood pool scan. To date, seven cases of gallbladder visualization after the intravenous injection of Tc-99m RBCs have been reported. In the previous six patients the gallbladder was visualized incidentally during a search for gastrointestinal (GI) bleeding. All of the patients were anemic, six of seven had chronic renal failure, and five of seven had received multiple blood transfusions. When interpreting GI bleeding scans in patients with anemia and renal failure, awareness of the possibility of gallbladder visualization in the delayed images is important to avoid false-positive results. 3 references.

Kotlyarov, E.V.; Mattay, V.S.; Reba, R.C.

1988-07-01

343

Cross-linked, ETFE-derived and radiation grafted membranes for anion exchange membrane fuel cell applications  

Microsoft Academic Search

To develop a series of cross-linked anion exchange membranes for application in fuel cells, poly(ethylene-co-tetrafluoroethylene) (ETFE) films was radiation grafted with vinyl benzyl chloride (VBC), followed by quaternization and crosslinking with 1,4-Diazabicyclo[2,2,2]octane (DABCO), alkylation with p-Xylylenedichloride (DCX), and quaternization again with trimethylamine (TMA). These anion exchange membranes were characterized in terms of water uptake, ion-exchange capacity, ionic conductivity as well

Jun Fang; Yi-xu Yang; Xiao-huan Lu; Mei-ling Ye; Wei Li; Yan-mei Zhang

344

Isolation of Mesenchymal Stem Cells with Neurogenic Potential from the Mesoderm of the Amniotic Membrane  

Microsoft Academic Search

The amniotic membrane has been clinically applied as a therapeutic material in wound covering and corneal surface reconstruction. Recently, mesenchymal stem cells (MSCs) have been isolated from the placenta, specifically from the amniotic membrane. However, the localization of MSCs in the amniotic membrane has not been determined. In this study, term placenta was collected, and we performed immunohistochemical staining techniques

Yu-Jen Chang; Shiaw-Min Hwang; Ching-Ping Tseng; Fu-Chou Cheng; Shih-Hung Huang; Lee-Feng Hsu; Li-Wen Hsu; Ming-Song Tsai

2010-01-01

345

Influence of electrolytes and membranes on cell operation for syn-gas production  

Microsoft Academic Search

The impact of membrane type and electrolyte composition for the electrochemical generation of synthesis gas (CO + H2) using a Ag gas diffusion electrode are presented. Changing from a cation exchange membrane to an anion exchange membrane (AEM) extended the cell operational time at low Ecell values (up to 4x) without impacting product composition. The use of KOH as the

Eric J. Dufek; Tedd E. Lister; Michael E. McIlwain

2012-01-01

346

Membrane-based electrolyte sheets for facile fabrication of flexible dye-sensitized solar cells  

Microsoft Academic Search

New electrolyte sheets based on porous polyethylene membranes for flexible dye-sensitized solar cells have been developed. Ionic liquid electrolytes are accommodated in commercial polyethylene membranes to form the electrolyte sheets. The morphology of membranes and iodine concentrations in ionic liquid are varied. The electrochemical measurement results show that the morphology, pore structure, and iodine concentration affect mass transport in electrolyte

Jiake Chen; Hong Lin; Xin Li; Xiaochong Zhao; Feng Hao; Siming Dong

2011-01-01

347

Alkali doped polybenzimidazole membrane for high performance alkaline direct ethanol fuel cell  

Microsoft Academic Search

An anion exchange membrane for alkaline direct ethanol fuel cell (ADEFC) was prepared by doping KOH in polybenzimidazole (PBI) membrane. The distributions of nitrogen, oxygen and potassium in the membrane were analyzed by means of XRD and SEM-EDX, respectively. It was found that free or combined KOH molecules may exist in the PBI matrix, which was helpful for the ionic

Hongying Hou; Gongquan Sun; Ronghuan He; Zhimou Wu; Baoying Sun

2008-01-01

348

Direct deposit of catalyst on the membrane of direct feed fuel cells  

NASA Technical Reports Server (NTRS)

An improved direct liquid-feed fuel cell having a solid membrane electrolyte for electrochemical reactions of an organic fuel. Catalyst utilization and catalyst/membrane interface improvements are disclosed. Specifically, the catalyst layer is applied directly onto the membrane electrolyte.

Chun, William (Inventor); Narayanan, Sekharipuram R. (Inventor); Jeffries-Nakamura, Barbara (Inventor); Valdez, Thomas I. (Inventor); Linke, Juergen (Inventor)

2001-01-01

349

Passive Ca 2+ Transport and Ca 2+ Dependent K + Transport in Plasmodium falciparum Infected Red Cells  

Microsoft Academic Search

.   Previous reports have indicated that Plasmodium falciparum-infected red cells (pRBC) have an increased Ca2+ permeability. The magnitude of the increase is greater than that normally required to activate the Ca2+-dependent K+ channel (K\\u000a \\u000a \\u000a \\u000a Ca\\u000a \\u000a channel) of the red cell membrane. However, there is evidence that this channel remains inactive in pRBC. To clarify this\\u000a discrepancy, we have reassessed both

H. M. Staines; W. Chang; J. C. Ellory; T. Tiffert; K. Kirk; V. L. Lew

1999-01-01

350

Water-Free Proton-Conducting Membranes for Fuel Cells  

NASA Technical Reports Server (NTRS)

Poly-4-vinylpyridinebisulfate (P4VPBS) is a polymeric salt that has shown promise as a water-free proton-conducting material (solid electrolyte) suitable for use in membrane/electrode assemblies in fuel cells. Heretofore, proton-conducting membranes in fuel cells have been made from perfluorinated ionomers that cannot conduct protons in the absence of water and, consequently, cannot function at temperatures >100 C. In addition, the stability of perfluorinated ionomers at temperatures >100 C is questionable. However, the performances of fuel cells of the power systems of which they are parts could be improved if operating temperatures could be raised above 140 C. What is needed to make this possible is a solid-electrolyte material, such as P4VPBS, that can be cast into membranes and that both retains proton conductivity and remains stable in the desired higher operating temperature range. A family of solid-electrolyte materials different from P4VPBS was described in Anhydrous Proton-Conducting Membranes for Fuel Cells (NPO-30493), NASA Tech Briefs, Vol. 29, No. 8 (August 2005), page 48. Those materials notably include polymeric quaternized amine salts. If molecules of such a polymeric salt could be endowed with flexible chain structures, it would be possible to overcome the deficiencies of simple organic amine salts that must melt before being able to conduct protons. However, no polymeric quaternized amine salts have yet shown to be useful in this respect. The present solid electrolyte is made by quaternizing the linear polymer poly- 4-vinylpyridine (P4VP) to obtain P4VPBS. It is important to start with P4VP having a molecular weight of 160,000 daltons because P4VPBS made from lower-molecular-weight P4VP yields brittle membranes. In an experimental synthesis, P4VP was dissolved in methanol and then reacted with an excess of sulfuric acid to precipitate P4VPBS. The precipitate was recovered, washed several times with methanol to remove traces of acid, and dried to a white granular solid. In another synthesis, nanoparticles of silica rich with surface hydroxyl groups were added to P4VP in methanol solution, which was then reacted with excess sulfuric acid to precipitate granules of a composite that most probably had the composition (P4VPBS)-SiO2-SiO(HSO4)2. The granular P4VPBS produced in the first-mentioned synthesis was dissolved in water to make a glue-like, turbid solution; the granular P4VPBS/silica composite produced in the second-mentioned synthesis was mixed with water to make a turbid, glue-like suspension. The proportions of polymer salt to water in such preparations can be varied; it was found that approximately equal parts of water and polymer salt yield a solution or suspension amenable to further processing.

Narayanan, Sekharipuram; Yen, Shiao-Pin

2007-01-01

351

Rapid micropatterning of cell lines and human pluripotent stem cells on elastomeric membranes.  

PubMed

Tissue function during development and in regenerative medicine completely relies on correct cell organization and patterning at micro and macro scales. We describe a rapid method for patterning mammalian cells including human embryonic stem cells (HESCs) and induced pluripotent stem cells (iPSCs) on elastomeric membranes such that micron-scale control of cell position can be achieved over centimeter-length scales. Our method employs surface engineering of hydrophobic polydimethylsiloxane (PDMS) membranes by plasma polymerization of allylamine. Deposition of plasma polymerized allylamine (ppAAm) using our methods may be spatially restricted using a micro-stencil leaving faithful hydrophilic ppAAm patterns. We employed airbrushing to create aerosols which deposit extracellular matrix (ECM) proteins (such as fibronectin and Matrigel™) onto the same patterned ppAAm rich regions. Cell patterns were created with a variety of well characterized cell lines (e.g., NIH-3T3, C2C12, HL1, BJ6, HESC line HUES7, and HiPSC line IPS2). Individual and multiple cell line patterning were also achieved. Patterning remains faithful for several days and cells are viable and proliferate. To demonstrate the utility of our technique we have patterned cells in a variety of configurations. The ability to rapidly pattern cells at high resolution over macro scales should aid future tissue engineering efforts for regenerative medicine applications and in creating in vitro stem cell niches. PMID:22511037

Paik, Isha; Scurr, David J; Morris, Bryan; Hall, Graham; Denning, Chris; Alexander, Morgan R; Shakesheff, Kevin M; Dixon, James E

2012-10-01

352

DEVELOPMENT OF NOVEL ELECTROCATALYSTS FOR PROTON EXCHANGE MEMBRANE FUEL CELLS  

SciTech Connect

Fuel cells are electrochemical devices that convert the available chemical free energy directly into electrical energy, without going through heat exchange process. Of all different types of fuel cells, the Proton Exchange Membrane Fuel Cell (PEMFC) is one of the most promising power sources for stand-alone utility and electric vehicle applications. Platinum (Pt) Catalyst is used for both fuel and air electrodes in PEMFCs. However, carbon monoxide (CO) contamination of H{sub 2} greatly affects electro catalysts used at the anode of PEMFCs and decreases cell performance. The irreversible poisoning of the anode can occur even in CO concentrations as low as few parts per million (ppm). In this work, we have synthesized several novel elctrocatalysts (Pt/C, Pt/Ru/C, Pt/Mo/C, Pt/Ir and Pt/Ru/Mo) for PEMFCs. These catalysts have been tested for CO tolerance in the H{sub 2}/air fuel cell, using CO concentrations in the H{sub 2} fuel that varies from 10 to 100 ppm. The performance of the electrodes was evaluated by determining the cell potential against current density. The effects of catalyst composition and electrode film preparation method on the performance of PEM fuel cell were also studied. It was found that at 70 C and 3.5 atm pressure at the cathode, Pt-alloy catalyst (10 wt% Pt/Ru/C, 20 wt% Pt/Mo/C) were more CO tolerant than the 20 wt% Pt/C catalyst alone. It was also observed that spraying method was better than the brushing technique for the preparation of electrode film.

Shamsuddin Ilias

2003-04-24

353

Elution and uncoating of Coxsackievirus B3 by isolated HeLa cell plasma membranes.  

PubMed Central

Plasma membranes isolated from HeLa cells on discontinuous sucrose gradients were assayed for their capacity to elute and uncoat coxsackievirus B3 at 37 C. Because the viral receptors are limited to the surface of HeLa cells, the addition of radioactively labeled virus to the cells prior to cell homogenization provided a useful marker for locating the plasma membranes during the fractionation procedure. Four bands were formed on the discontinuous sucrose gradients with approximately 70% or more of the membrane-associated viral label being recovered in the most dense bands, designated as bands 3 and 4. Bands 3 and 4 also possessed the plasma membrane marker enzymes, Na+, K+ adenosine triphosphatase and 5'-nucleotidase and revealed typical structures characteristic of plasma membranes as revealed by electron microscopy. Pelleted and washed membranes from band 3 both eluted and uncoated B3 32P-labeled virus, whereas membranes from band 4 eluted virus but failed to uncoat it. The membranes from band 4 were shown to inhibit the viral uncoating activity when mixed with membranes of band 3. Characteristically, unfractionated homogenates of cell membranes eluted but did not uncoat virus. The finding of a naturally occurring inhibitor of virus uncoating provides for the first time a way to distinguish between the membrane activities of virus elution and virus uncoating. The inhibitor remains to be characterized. Images PMID:123011

Roesing, T G; Toselli, P A; Crowell, R L

1975-01-01

354

Computational Estimates of Membrane Flow and Tension Gradient in Motile Cells  

PubMed Central

All parts of motile cells, including the plasma membrane, have to translocate in the direction of locomotion. Both directed intracellular membrane transport coupled with polarized endo- and exocytosis and fluid flow in the plane of the plasma membrane can contribute to this overall plasma membrane translocation. It remains unclear how strong a force is required to generate this flow. We numerically solve Stokes equations for the viscous membrane flow across a flat plasma membrane surface in the presence of transmembrane proteins attached to the cytoskeleton and find the membrane tension gradient associated with this flow. This gradient is sensitive to the size and density of the transmembrane proteins attached to the cytoskeleton and can become significant enough to slow down cell movement. We estimate the influence of intracellular membrane transport and actin growth and contraction on the tension gradient, and discuss possible ‘tank tread’ flow at ventral and dorsal surfaces. PMID:24465414

Fogelson, Ben; Mogilner, Alex

2014-01-01

355

Cell-autonomous defense, re-organization and trafficking of membranes in plant-microbe interactions.  

PubMed

Plant cells dynamically change their architecture and molecular composition following encounters with beneficial or parasitic microbes, a process referred to as host cell reprogramming. Cell-autonomous defense reactions are typically polarized to the plant cell periphery underneath microbial contact sites, including de novo cell wall biosynthesis. Alternatively, host cell reprogramming converges in the biogenesis of membrane-enveloped compartments for accommodation of beneficial bacteria or invasive infection structures of filamentous microbes. Recent advances have revealed that, in response to microbial encounters, plasma membrane symmetry is broken, membrane tethering and SNARE complexes are recruited, lipid composition changes and plasma membrane-to-cytoskeleton signaling is activated, either for pre-invasive defense or for microbial entry. We provide a critical appraisal on recent studies with a focus on how plant cells re-structure membranes and the associated cytoskeleton in interactions with microbial pathogens, nitrogen-fixing rhizobia and mycorrhiza fungi. PMID:25168837

Dörmann, Peter; Kim, Hyeran; Ott, Thomas; Schulze-Lefert, Paul; Trujillo, Marco; Wewer, Vera; Hückelhoven, Ralph

2014-12-01

356

Gadolinium blocks membrane permeabilization induced by nanosecond electric pulses and reduces cell death  

PubMed Central

It has been widely accepted that nanosecond electric pulses (nsEP) are distinguished from micro-and millisecond duration pulses by their ability to cause intracellular effects and cell death with reduced effects on the cell plasma membrane. However, we found that nsEP-induced cell death is most likely mediated by the plasma membrane disruption. We showed that nsEP can cause long-lasting (minutes) increase in plasma membrane electrical conductance and disrupt electrolyte balance, followed by water uptake, cell swelling and blebbing. These effects of plasma membrane permeabilization could be blocked by Gd3+ in a dose-dependent manner, with a threshold at sub-micromolar concentrations. Consequently, Gd3+ protected cells from nsEP-induced cell death, thereby pointing to plasma membrane permeabilization as a likely primary mechanism of lethal cell damage. PMID:20097138

André, Franck M.; Rassokhin, Mikhail A.; Bowman, Angela M.; Pakhomov, Andrei G.

2009-01-01

357

Smoking and fluidity of erythrocyte membranes: a high resolution scanning electron and atomic force microscopy investigation.  

PubMed

Smoking affects the general health of an individual, however, the red blood cells (RBCs) and their architecture are particularly vulnerable to inhaled toxins related to smoking. Smoking is one of the lifestyle diseases that are responsible for the most deaths worldwide and an individual who smokes is exposed to excessive amounts of oxidants and toxins which generate up to 10(18) free radicals in the human body. Recently, it was reported that smoking decreases RBC membrane fluidity. Here we confirm this and we show changes visible in the topography of RBC membranes, using scanning electron microscopy (SEM). RBC membranes show bubble formation of the phospholipid layer, as well as balloon-like smooth areas; while their general discoid shapes are changed to form pointed extensions. We also investigate membrane roughness using atomic force microscopy (AFM) and these results confirm SEM results. Due to the vast capability of RBCs to be adaptable, their state of well-being is a major indication for the general health status of an individual. We conclude that these changes, using an old technique in a novel application, may provide new insights and new avenues for future improvements in clinical medicine pertaining to conditions like COPD. PMID:23973530

Pretorius, Etheresia; du Plooy, Jeanette N; Soma, Prashilla; Keyser, Ina; Buys, Antoinette V

2013-11-30

358

Hybrid Nafion–silica membranes doped with heteropolyacids for application in direct methanol fuel cells  

Microsoft Academic Search

Nafion–silica composite membranes doped with phosphotungstic and silicotungstic acids have been investigated for application in direct methanol fuel cells at high temperature (145°C). The phosphotungstic acid-based membrane showed better electrochemical characteristics at high current densities with respect to both silicotungstic acid-modified membrane and silica–Nafion membrane. A maximum power density of 400 mW cm?2 was obtained at 145°C in the presence

P Staiti; A. S Aricò; V Baglio; F Lufrano; E Passalacqua; V Antonucci

2001-01-01

359

Lipid A binding sites in membranes of macrophage tumor cells  

SciTech Connect

Lipopolysaccharide affects a variety of eukaryotic cells and mammalian organisms. These actions are involved in the pathogenesis of Gram-negative septicemia. Many of the actions of lipopolysaccharide are believed to be caused by its active moiety, lipid A. Our laboratory has previously identified a bioactive lipid A precursor, termed lipid IVA, which can be labeled with 32P of high specific activity and purified. In this work we have used the labeled probe, 4'-32P-lipid IVA, to develop a novel assay for the specific binding of lipid IVA to whole cells. We have also demonstrated its use in a ligand blotting assay of immobilized cellular proteins. Using the whole cell assay, we show that 4'-32P-lipid IVA specifically binds to RAW 264.7 macrophage-like cultured cells. The binding is saturable, is inhibited with excess unlabeled lipid IVA, and is proteinase K-sensitive. It displays cellular and pharmacological specificity. Using the ligand blotting assay, we show that several RAW 264.7 cell proteins can bind 4'-32P-lipid IVA. The two principal binding proteins have Mr values of 31 and 95 kDa, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fractionation studies indicate that the 31-kDa protein is enriched in the nuclear fraction and may be a histone, whereas the 95-kDa protein is enriched in the membrane fraction. The binding assays that we have developed should lead to a clearer understanding of lipid A/animal cell interactions.

Hampton, R.Y.; Golenbock, D.T.; Raetz, C.R.

1988-10-15

360

In situ single molecule imaging of cell membranes: linking basic nanotechniques to cell biology, immunology and medicine  

NASA Astrophysics Data System (ADS)

The cell membrane, which consists of a viscous phospholipid bilayer, different kinds of proteins and various nano/micrometer-sized domains, plays a very important role in ensuring the stability of the intracellular environment and the order of cellular signal transductions. Exploring the precise cell membrane structure and detailed functions of the biomolecules in a cell membrane would be helpful to understand the underlying mechanisms involved in cell membrane signal transductions, which could further benefit research into cell biology, immunology and medicine. The detection of membrane biomolecules at the single molecule level can provide some subtle information about the molecular structure and the functions of the cell membrane. In particular, information obtained about the molecular mechanisms and other information at the single molecule level are significantly different from that detected from a large amount of biomolecules at the large-scale through traditional techniques, and can thus provide a novel perspective for the study of cell membrane structures and functions. However, the precise investigations of membrane biomolecules prompts researchers to explore cell membranes at the single molecule level by the use of in situ imaging methods, as the exact conformation and functions of biomolecules are highly controlled by the native cellular environment. Recently, the in situ single molecule imaging of cell membranes has attracted increasing attention from cell biologists and immunologists. The size of biomolecules and their clusters on the cell surface are set at the nanoscale, which makes it mandatory to use high- and super-resolution imaging techniques to realize the in situ single molecule imaging of cell membranes. In the past few decades, some amazing imaging techniques and instruments with super resolution have been widely developed for molecule imaging, which can also be further employed for the in situ single molecule imaging of cell membranes. In this review, we attempt to summarize the characteristics of these advanced techniques for use in the in situ single molecule imaging of cell membranes. We believe that this work will help to promote the technological and methodological developments of super-resolution techniques for the single molecule imaging of cell membranes and help researchers better understand which technique is most suitable for their future exploring of membrane biomolecules; ultimately promoting further developments in cell biology, immunology and medicine.

Pi, Jiang; Jin, Hua; Yang, Fen; Chen, Zheng W.; Cai, Jiye

2014-10-01

361

Six cell 'single cell' stack diagnostics and membrane electrode assembly evaluation  

SciTech Connect

Polymer electrolyte fuel cells are promising candidates as energy conversion devices in applications from portable power to stationary applications or electric vehicles. In order to achieve practical voltage, power and energy density, stacks are employed for almost all applications. Here, we present a six-cell 'single cell' stack in which individual cells can be isolated from the stack by current carrying leads found within each of the bipolar plates. The current carrying leads allow individual cells to be isolated from the rest of the stack, so that cells can either be tested together or independently. The design of the stack, utility for specific applications, including stack diagnostics and membrane electrode assembly (MEA) testing, and some experimental results, obtained using the stack, are presented. Special focus is given in this paper to the area of direct methanol fuel cell (DMFC) stacks, however the equipment and many of the experimental results presented are appropriate for other fuel cell systems.

Pivovar, B. S. (Bryan Scott); Le Scornet, F. (Francois); Eickes, C. (Christian); Zawodzinski, C. (Christine); Purdy, G. M. (Geraldine M.); Wilson, M. S. (Mahlon S.); Zelenay, P. (Piotr)

2002-01-01

362

Interactions between the HIV TAT domain and cell membranes  

NASA Astrophysics Data System (ADS)

Biologically active molecules such as proteins and oligonucleotides can be transduced into cells with high efficiency when covalently linked to a Protein Transduction Domain (PTD), such as the TAT domain in the HIV virus. All PTDs have a high content of basic amino acids resulting in a net positive charge. Electrostatic interactions between cationic PTDs and the negatively charged phospholipids that constitute the plasma membrane seem to be responsible for peptide uptake, but no detailed structural studies exist. We present recent results on the structures of self-assembled complexes of the cationic TAT domain and anionic lipid bilayers using synchrotron x-ray scattering and electron microscopy, and examine possible mechanisms of the anomalous transduction.

Mishra, Abhijit; Wong, Gerard

2005-03-01

363

Plasma Membrane Lesions In Anthracycline-Resistant Tumor Cells Probed Using A Fluorescent Dye  

NASA Astrophysics Data System (ADS)

Human cancer cells selected for resistance to several structurally unrelated cytotoxic drugs are known to display plasma membrane alterations such as amplified levels of a variety of glycoproteins, modifications in lipid composition, alterations in membrane fluidity and increased cellular fragility to osmotic shock. We have studied the plasma membrane fluidity of HL60 human leukemia cells and MCF-7 human breast cancer cells that have been selected for acquired resistance against the cytocidal effects of the anthracycline anticancer drug Adriamycin. Fluidity measurements were accomplished by evaluating the fluorescence anisotropy of the plasma membrane specific probe trimethylamino-1,6-dipihenylhexatriene (TMA.DPH) bound to whole, living cells. TMA.DPH anisotropy values for MCF-7 sensitive and 12-fold resistant cells were 0.306 and 0.285, respectively, while anisotropy values for HL-60 sensitive and 80-fold resistant cells lines were 0.310 and 0.295, respectively. In all cases, cell viability exceeded 97% and anisotropy values were subject to a day-to-day uncertainty of +/-2%. Our results demonstrate that increased plasma membrane fluidity apparently accompanies the development of resistance in both cell lines. Because it is known that increased membrane fluidity results in significantly decreased Adriamycin binding in artificial membrane systems, we propose here that decreased drug associations with fluidized, plasma membrane lipid bilayer regions may be a mechanism which contributes, in part, to the reduced rates of drug accumulation observed in HL60 and MCF-7 cells resistant to Adriamycin.

Burke, Thomas G.; Doroshow, James H.

1989-06-01

364

A novel Bruch's membrane-mimetic electrospun substrate scaffold for human retinal pigment epithelium cells.  

PubMed

Various artificial membranes have been used as scaffolds for retinal pigment epithelium cells (RPE) for monolayer reconstruction, however, long-term cell viability and functionality are still largely unknown. This study aimed to construct an ultrathin porous nanofibrous film to mimic Bruch's membrane, and in particular to investigate human RPE cell responses to the resultant substrates. An ultrathin porous nanofibrous membrane was fabricated by using regenerated wild Antheraea pernyi silk fibroin (RWSF), polycaprolactone (PCL) and gelatin (Gt) and displayed a thickness of 3-5 ?m, with a high porosity and an average fiber diameter of 166 ± 85 nm. Human RPE cells seeded on the RWSF/PCL/Gt membranes showed a higher cell growth rate (p < 0.05), and a typical expression pattern of RPE signature genes, with reduced expression of inflammatory mediators. With long-term cultivation on the substrates, RPE cells exhibited characteristic polygonal morphology and development of apical microvilli. Immunocytochemisty demonstrated RPE-specific expression profiles in cells after 12-weeks of co-culture on RWSF/PCL/Gt membranes. Interestingly, the cells on the RWSF/PCL/Gt membranes functionally secreted polarized PEDF and phagocytosed labeled porcine POS. Furthermore, RWSF/PCL/Gt membranes transplanted subsclerally exhibited excellent biocompatibility without any evidence of inflammation or rejection. In conclusion, we established a novel RWSF-based substrate for growth of RPE cells with excellent cytocompatibility in vitro and biocompatibility in vivo for potential use as a prosthetic Bruch's membrane for RPE transplantation. PMID:25220295

Xiang, Ping; Wu, Kun-Chao; Zhu, Ying; Xiang, Lue; Li, Chong; Chen, Deng-Long; Chen, Feng; Xu, Guotong; Wang, Aijun; Li, Min; Jin, Zi-Bing

2014-12-01

365

Thylakoid Membrane Maturation and PSII Activation Are Linked in Greening Synechocystis sp. PCC 6803 Cells1  

PubMed Central

Thylakoid membranes are typical and essential features of both chloroplasts and cyanobacteria. While they are crucial for phototrophic growth of cyanobacterial cells, biogenesis of thylakoid membranes is not well understood yet. Dark-grown Synechocystis sp. PCC 6803 cells contain only rudimentary thylakoid membranes but still a relatively high amount of phycobilisomes, inactive photosystem II and active photosystem I centers. After shifting dark-grown Synechocystis sp. PCC 6803 cells into the light, “greening” of Synechocystis sp. PCC 6803 cells, i.e. thylakoid membrane formation and recovery of photosynthetic electron transport reactions, was monitored. Complete restoration of a typical thylakoid membrane system was observed within 24 hours after an initial lag phase of 6 to 8 hours. Furthermore, activation of photosystem II complexes and restoration of a functional photosynthetic electron transport chain appears to be linked to the biogenesis of organized thylakoid membrane pairs. PMID:23922268

Barthel, Sandra; Bernat, Gabor; Seidel, Tobias; Rupprecht, Eva; Kahmann, Uwe; Schneider, Dirk

2013-01-01

366

Thylakoid membrane maturation and PSII activation are linked in greening Synechocystis sp. PCC 6803 cells.  

PubMed

Thylakoid membranes are typical and essential features of both chloroplasts and cyanobacteria. While they are crucial for phototrophic growth of cyanobacterial cells, biogenesis of thylakoid membranes is not well understood yet. Dark-grown Synechocystis sp. PCC 6803 cells contain only rudimentary thylakoid membranes but still a relatively high amount of phycobilisomes, inactive photosystem II and active photosystem I centers. After shifting dark-grown Synechocystis sp. PCC 6803 cells into the light, "greening" of Synechocystis sp. PCC 6803 cells, i.e. thylakoid membrane formation and recovery of photosynthetic electron transport reactions, was monitored. Complete restoration of a typical thylakoid membrane system was observed within 24 hours after an initial lag phase of 6 to 8 hours. Furthermore, activation of photosystem II complexes and restoration of a functional photosynthetic electron transport chain appears to be linked to the biogenesis of organized thylakoid membrane pairs. PMID:23922268

Barthel, Sandra; Bernát, Gábor; Seidel, Tobias; Rupprecht, Eva; Kahmann, Uwe; Schneider, Dirk

2013-10-01

367

Cell membrane mediated (-)-epicatechin effects on upstream endothelial cell signaling: evidence for a surface receptor.  

PubMed

The consumption of cacao-derived products, particularly in the form of dark chocolate is known to provide beneficial cardiovascular effects in normal individuals and in those with vascular dysfunction (reduced nitric oxide [NO] bioavailability and/or synthesis). Upstream mechanisms by which flavonoids exert these effects are poorly understood and may involve the participation of cell membrane receptors. We previously demonstrated that the flavanol (-)-epicatechin (EPI) stimulates NO production via Ca(+2)-independent eNOS activation/phosphorylation. We wished to investigate the plausible participation of a cell surface receptor using a novel cell-membrane impermeable EPI-Dextran conjugate (EPI-Dx). Under Ca(2+)-free conditions, human coronary artery endothelial cells (HCAEC) were treated for 10min with EPI or EPI-Dx at equimolar concentrations (100nM). Results demonstrate that both EPI and EPI-Dx induced the phosphorylation/activation of PI3K, PDK-1, AKT and eNOS. Interestingly, EPI-Dx effects were significantly higher in magnitude than those of EPI alone. The capacity of EPI-Dx to stimulate cell responses supports the existence of an EPI cell membrane receptor mediating eNOS activation. PMID:24794111

Moreno-Ulloa, Aldo; Romero-Perez, Diego; Villarreal, Francisco; Ceballos, Guillermo; Ramirez-Sanchez, Israel

2014-06-15

368

Characterization of the Small Exported Plasmodium falciparum Membrane Protein SEMP1  

PubMed Central

Survival and virulence of the human malaria parasite Plasmodium falciparum during the blood stage of infection critically depend on extensive host cell refurbishments mediated through export of numerous parasite proteins into the host cell. The parasite-derived membranous structures called Maurer's clefts (MC) play an important role in protein trafficking from the parasite to the red blood cell membrane. However, their specific function has yet to be determined. We identified and characterized a new MC membrane protein, termed small exported membrane protein 1 (SEMP1). Upon invasion it is exported into the RBC cytosol where it inserts into the MCs before it is partly translocated to the RBC membrane. Using conventional and conditional loss-of-function approaches we showed that SEMP1 is not essential for parasite survival, gametocytogenesis, or PfEMP1 export under culture conditions. Co-IP experiments identified several potential interaction partners, including REX1 and other membrane-associated proteins that were confirmed to co-localize with SEMP1 at MCs. Transcriptome analysis further showed that expression of a number of exported parasite proteins was up-regulated in SEMP1-depleted parasites. By using Co-IP and transcriptome analysis for functional characterization of an exported parasite protein we provide a new starting point for further detailed dissection and characterisation of MC-associated protein complexes. PMID:25062022

Dietz, Olivier; Rusch, Sebastian; Brand, Francoise; Mundwiler-Pachlatko, Esther; Gaida, Annette; Voss, Till; Beck, Hans-Peter

2014-01-01

369

DEVELOPMENT OF NOVEL ELECTROCATALYSTS FOR PROTON EXCHANGE MEMBRANE FUEL CELLS  

SciTech Connect

Proton Exchange Membrane Fuel Cell (PEMFC) is one of the most promising power sources for space and electric vehicle applications. Platinum (Pt) catalyst is used for both fuel and air electrodes in PEMFCs. The carbon monoxide (CO) contamination of H{sub 2} greatly affects electrocatalysts used at the anode of PEMFCs and decrease the cell performance. This irreversible poisoning of the anode can happen even in CO concentrations as low as few ppm, and therefore, require expensive scrubbing of the H{sub 2}-fuel to reduce the contaminant concentration to acceptable level. In order to commercialize this environmentally sound source of energy/power system, development of suitable CO-tolerant catalyst is needed. In this work, we have synthesized several novel electrocatalysts (Pt/C, Pt/Ru/C Pt/Mo/C, Pt/Ir and Pt/Ru/Mo) for PEMFCs. These catalysts have been tested for CO tolerance in the H{sub 2}/air fuel cell. The concentration of CO in the H{sub 2} fuel varied from 10 ppm to 100 ppm. The performance of the electrodes was evaluated by determining the cell potential against current density. The effect of temperature, catalyst compositions, and electrode film preparation methods on the performance of PEM fuel cell has also been studied. It was found that at 70 C and 3.5 atm pressure at the cathode, Pt-alloy catalysts (10 wt % Pt/Ru/C, 20 wt % Pt/Mo/C) were more CO-tolerant than 20 wt % Pt catalyst alone. It was also observed that spraying method is better for the preparation of electrode film than the brushing technique. Some of these results are summarized in this report.

Shamsuddin Ilias

2001-07-06

370

Control of membrane permeability in animal cells by divalent cations  

SciTech Connect

The permeability of several cell lines, including HeLa, L929, 3T6 and T3, to various compounds is affected by the concentration of divalent cations in the culture medium. In the absence of Mg/sup 2 +/ ions but with 4-8 mM CaCl/sub 2/ in the medium, HeLa and L929 cells become permeabilized, as measured by the entry of the aminoglycoside antibiotic hygromycin B. However, 33 and 3T6 cells become much more permeable when calcium and magnesium are both absent from the medium. Addition of Mg/sup 2 +/ above 2 mM abolishes the permeabilization induced by Ca/sup 2 +/. Basic pH favors permeabilization, whereas acidic pH inhibits the entry of hygromycin B. Increased entry of macromolecules, such as the toxin alpha-sarcin, horseradish peroxidase (HRP) and luciferase, is also observed under permeabilization conditions, suggesting that this method could be of general use, since it is not harmful to cells and is fully reversible. Exit of /sup 86/Rb/sup +/ ions and (/sup 3/H)uridine-labelled nucleotides was also assayed. The authors did not observe increased release of these compounds from preloaded cells under various calcium concentrations. Finally, the effects of several inhibitors of endocytosis and other membrane functions on the permeabilization process were also analyzed. The entry of alpha-sarcin was not affected by nifedipine, dibucaine or mepacrine, but was partially inhibited by NH/sub 4/Cl, amantadine and chloroquine.

Otero, M.J.; Carrasco, L.

1987-04-01

371

Membrane properties of solitary horizontal cells isolated from goldfish retina.  

PubMed Central

1. Solitary horizontal cells were obtained by dissociating the adult goldfish retina using the enzyme papain. The cells were identified on morphological grounds and could be kept in culture for over a week. 2. Solitary horizontal cells, penetrated with micro-electrodes, had resting potentials of about -75 mV in normal solution. When external K+ concentration was changed, the membrane potential varied from EK calculated from the Nernst equation. 3. All solitary horizontal cells tested showed an action potential in response to superthreshold depolarizing current pulses. The action potential had an overshoot of about +20 mV and a plateau potential lasting for several seconds. 4. The action potential appeared to be Ca-dependent for the following reasons: (a) TTX or low [Na+] did not affect the action potential, (b) Sr2+, Ba2+ or high [Ca2+] enhanced the action potential, while (c) Co2+ or high [Mg2+] blocked it. No regenerative activity has been observed in horizontal cells in the retina but it is possible that the regenerative mechanism is suppressed normally. 5. A role for K+ was indicated by an increase in the duration and amplitude of the action potential on the application of tetraethylammonium. 6. The steady-state current--voltage (I--V) curve, measured by applying constant current pulses, was S-shaped (current on the abscissa) and composed of inward- and outward-going rectifying regions and a transitional region between them. A similar non-linear I--V relationship has been reported in vivo. 7. The transitional region was characterized by a sudden potential jump and hysteresis, suggesting the presence of a 'negative resistance'. This potential jump appeared not to be produced by the Ca-conductance mechanism mentioned above, since similar jumps were observed in the presence of Co2+. Images Plate 1 PMID:7338808

Tachibana, M

1981-01-01

372

Autophagy machinery mediates macroendocytic processing and entotic cell death by targeting single membranes  

Microsoft Academic Search

Autophagy normally involves the formation of double-membrane autophagosomes that mediate bulk cytoplasmic and organelle degradation. Here we report the modification of single-membrane vacuoles in cells by autophagy proteins. LC3 (Light chain 3) a component of autophagosomes, is recruited to single-membrane entotic vacuoles, macropinosomes and phagosomes harbouring apoptotic cells, in a manner dependent on the lipidation machinery including ATG5 and ATG7,

Oliver Florey; Sung Eun Kim; Cynthia P. Sandoval; Cole M. Haynes; Michael Overholtzer

2011-01-01

373

Poliovirus 2C Protein Determinants of Membrane Binding and Rearrangements in Mammalian Cells  

Microsoft Academic Search

Poliovirus protein 2C is a 329-amino acid-protein that is essential for viral RNA synthesis and may perform multiple functions. In infected cells, it is associated with virus-specific membrane vesicles. Recombinant 2C protein expressed in transfected cells has been shown to associate with and induce rearrangement of the intracellular membrane network. This study was designed to map the determinants of membrane

NATALYA L. TETERINA; ALEXANDER E. GORBALENYA; DENISE EGGER; KURT BIENZ

1997-01-01

374

Nafion–TiO 2 hybrid membranes for medium temperature polymer electrolyte fuel cells (PEFCs)  

Microsoft Academic Search

A nanocomposite re-cast Nafion hybrid membrane containing titanium oxide calcined at T=400°C as an inorganic filler was developed in order to work at medium temperature in polymer electrolyte fuel cells (PEFCs) maintaining a suitable membrane hydration under fuel cell operative critical conditions. Nanometre TiO2 powder was synthesized via a sol–gel procedure by a rapid hydrolysis of Ti(OiPr)4. The membrane was

A. Saccà; A. Carbone; E. Passalacqua; A. D’Epifanio; S. Licoccia; E. Traversa; E. Sala; F. Traini; R. Ornelas

2005-01-01

375

Permeability issues in whole-cell bioprocesses and cellular membrane engineering  

Microsoft Academic Search

Nutrient uptake and waste excretion are among the many important functions of the cellular membrane. While permitting nutrients\\u000a into the cell, the cellular membrane system evolves to guide against noxious agents present in the environment from entering\\u000a the intracellular milieu. The semipermeable nature of the membrane is at odds with biomolecular engineers in their endeavor\\u000a of using microbes as cell

Rachel Ruizhen Chen

2007-01-01

376

Investigation of grafted ETFE-based polymer membranes as alternative electrolyte for direct methanol fuel cells  

Microsoft Academic Search

Low cost ethylene–tetrafluoroethylene (ETFE)-based grafted membranes have been prepared by a process based on electron beam irradiation, subsequent grafting, cross-linking and sulfonation procedure. Two different grafted membranes varying by their grafting and cross-linking levels have been investigated for applications in direct methanol fuel cells (DMFCs) operating between 90 and 130°C. DMFC assemblies based on these membranes showed cell resistance and

A. S. Aricò; V. Baglio; A. Di Blasi; V. Antonucci; J. Brunea; A. Chapotot; A. Bozzi; J. Schoemans

2003-01-01

377

Investigation of the performance and water transport of a polymer electrolyte membrane (pem) fuel cell  

E-print Network

Fuel cell performance was obtained as functions of the humidity at the anode and cathode sites, back pressure, flow rate, temperature, and channel depth. The fuel cell used in this work included a membrane and electrode assembly (MEA) which...

Park, Yong Hun

2009-05-15

378

Migration of Retinal Cells through a Perforated Membrane: Implications for a  

E-print Network

Migration of Retinal Cells through a Perforated Membrane: Implications for a High cells. This is a report of a phenomenon of retinal cellular migration into a perforated membrane the migration. RESULTS. Retinal tissue in vitro grew within 3 days through perforations of greater than 5 m

Palanker, Daniel

379

The anomalous rectification and cation selectivity of the membrane of a starfish egg cell  

Microsoft Academic Search

Summary The cation selectivity and its relation to the inward-going rectification of the immature egg cell membrane of a starfish,Nordora punctiformis, were studied and the following results were obtained. (1) When the external saline contains usual ion species the cell membrane at rest is predominantly permeable to K ions. The K chord conductancegk depends on the electrochemical potential of K

Susumu Hagiwara; Kunitaro Takahashi

1974-01-01

380

Nitrogen Front Evolution in Purged Polymer Electrolyte Membrane Fuel Cell with Dead-Ended Anode  

E-print Network

Nitrogen Front Evolution in Purged Polymer Electrolyte Membrane Fuel Cell with Dead-Ended Anode and experimentally verify the evolution of liquid water and nitrogen fronts along the length of the anode channel in a proton exchange membrane fuel cell operating with a dead-ended anode that is fed by dry hydrogen

Stefanopoulou, Anna

381

Increased phorbol 12,13-dibutyrate (PDBu) receptor function associated with sickle red cell membrane ghosts  

SciTech Connect

The biological receptor for tumor-promoting phorbol esters has been identified as the CaS /phospholipid dependent enzyme, protein kinase C. In the red cell, this enzyme is mainly cytosolic but becomes translocated to the membrane if the cellular CaS is allowed to rise. Since cellular CaS in sickle red cells is high, it was reasoned that this enzyme may become more membrane-bound. In fact, the authors noticed a four-fold increase in the binding of TH-PDBu by membrane ghosts isolated from sickle red cells compared to normal red cells (pmoles PDBu bound/mg protein; normal = 0.3 vs sickle cell = 1.4). Attempts to assay the enzyme directly as phospholipid-activated TSP incorporation into the acid-precipitable membrane proteins also indicated a two-fold increase in the radiolabelling of sickle cell membrane ghosts. Autophosphorylation of membrane proteins and analysis of the phosphorylation profile by SDS-PAGE and autoradiography revealed phosphorylation predominantly of bands 3, 4.1 and 4.9 which are known protein kinase C substrates for the red cell enzyme. The increased membrane-associated protein kinase C in sickle red cells may have a bearing on the altered membrane properties reported in this condition.

Ramachandran, M.; Nair, C.N.; Abraham, E.C.

1987-05-01

382

Heat and Mass Transport in Proton Exchange Membrane Fuel Cells---A Review  

Microsoft Academic Search

This review brings out those aspects of the development of proton exchange membrane (PEM) fuel cells over the last two to three decades that are of interest to the heat and mass transfer community. Because the heat transport and mass transport in proton exchange membrane fuel cells are very important from the efficiency point of view, an emphasis is given

Sarit K. Das; Annasaheb S. Bansode

2009-01-01

383

Membrane potential and ion transport in lung epithelial type II cells  

SciTech Connect

The alveolar type II pneumocyte is critically important to the function and maintenance of pulmonary epithelium. To investigate the nature of the response of type II cells to membrane injury, and describe a possible mechanism by which these cells regulate surfactant secretion, the membrane potential of isolated rabbit type II cells was characterized. This evaluation was accomplished by measurements of the accumulation of the membrane potential probes: (/sup 3/H)triphenylmethylphosphonium ((/sup 3/H)TPMP/sup +/), rubidium 86, and the fluorescent dye DiOC/sub 5/. A compartmental analysis of probe uptake into mitochondrial, cytoplasmic, and non-membrane potential dependent stores was made through the use of selective membrane depolarizations with carbonycyanide M-chlorophenylhydrazone (CCCP), and lysophosphatidylcholine (LPC). These techniques and population analysis with flow cytometry, permitted the accurate evaluation of type II cell membrane potential under control conditions and under conditions which stimulated cell activity. Further analysis of ion transport by cells exposed to radiation or adrenergic stimulation revealed a common increase in Na/sup +//K/sup +/ ATPase activity, and an increase in sodium influx across the plasma membrane. This sodium influx was found to be a critical step in the initiation of surfactant secretion. It is concluded that radiation exposure as well as other pulmonary toxicants can directly affect the membrane potential and ionic regulation of type II cells. Ion transport, particularly of sodium, plays an important role in the regulation of type II cell function.

Gallo, R.L.

1986-01-01

384

Hostile Takeover by Plasmodium: Reorganization of Parasite and Host Cell Membranes during Liver Stage  

E-print Network

Hostile Takeover by Plasmodium: Reorganization of Parasite and Host Cell Membranes during Liver, called merosomes, which are delivered directly into liver sinusoids. However, it was unclear whether by Plasmodium: Reorganization of Parasite and Host Cell Membranes during Liver Stage Egress. PLoS Pathog 7(9): e

Arnold, Jonathan

385

Actin disassembly 'clock' and membrane tension determine cell shape and turning: a mathematical model  

E-print Network

Actin disassembly 'clock' and membrane tension determine cell shape and turning: a mathematical that terms and conditions apply. View the table of contents for this issue, or go to the journal homepage.1088/0953-8984/22/19/194118 Actin disassembly `clock' and membrane tension determine cell shape and turning: a mathematical model

Mogilner, Alex

386

Three steps in the anode reaction of the polymer electrolyte membrane fuel cell. Effect of CO  

E-print Network

Three steps in the anode reaction of the polymer electrolyte membrane fuel cell. Effect of CO Anne in the polymer electrolyte membrane fuel cell (PEMFC) using electrochemical impedance spectroscopy (EIS.0 °C or 50.0 ± 0.1 °C. Bias voltages of 0 and 0.05 V were used. Three steps were revealed

Kjelstrup, Signe

387

Understanding external forces acting on cells control lipid membrane structure and dynamics  

E-print Network

Understanding external forces acting on cells control lipid membrane structure and dynamics to understanding how they regulate signaling at the cell surface. Structural features of lipid membranes such as lipid rafts and protein complexes are often much smaller than that can be resolved using traditional

Bjørnstad, Ottar Nordal

388

"NEW MEMBRANE" FORMATION IN AMOEBA PROTEUS UPON INJURY OF INDIVIDUAL CELLS  

PubMed Central

Changes in the plasma membrane complex following the injury of single cells of Amoeba proteus were examined with the electron microscope. Two types of injury were employed in this study; cells were either pinched ("cut") in half or speared with a glass microneedle, and quickly fixed. Speared cells, when fixed in the presence of the ruthenium violet (a derivative of ruthenium red), revealed the presence of an extra trilaminar structure outside of each cell. This structure, called the "new membrane," was separated from the plasma membrane complex by a distance of less than a micron. The trilaminar structure of the new membrane strikingly resembled the image of the plasma membrane in all cells examined, except for its increased width (30%). This new membrane appeared nearly to surround the injured amebae. Attempts were made to demonstrate the possible origin of the new membrane, its reality, and its sensitivity to calcium. Also, some evidence is shown concerning the role of the small dense droplets (100–1200 A in diameter) normally present in the cytoplasm of amebae. Their frequent contact with the plasma membrane of the cell as the result of injury is interpreted as indicating their involvement in the formation and expansion of the plasma membrane. PMID:4103955

Szubinska, Barbara

1971-01-01

389

Influence of the membrane ion exchange capacity on the catalyst layer of proton exchange membrane fuel cell  

NASA Astrophysics Data System (ADS)

This work investigated the effect of ion exchange capacity (IEC) of polymer electrolyte membranes (PEM) on the PEM fuel cell cathode catalyst layer. A series of radiation grafted ethylene tetrafluoroethylene-g-polystyrene sulfonic acid (ETFE-g-PSSA) membranes was used to provide a systematic variation of IEC. A method to fabricate gas diffusion electrodes (GDEs) was adapted and custom-made GDEs with known compositions were prepared. Oxygen electrochemistry, mass transport properties, water absorption behaviour and proton conductivity were studied in relation to the IEC. Electrochemical characterization including cyclic voltammetry, electrochemical impedance spectroscopy and linear sweep voltammetry were employed. The agglomerate model for cathodes was adapted and used to extract mass transport parameters from experimental results. Prior to investigation in fuel cell systems, studies were performed in a half-fuel cell, which simplified complicating parameters associated with fuel cell operation. It was found that membranes with higher IEC resulted in a higher active surface area of electrode. In contrast, they exhibited lower oxygen reduction performance. The extracted effective diffusion coefficient of oxygen and O2 solubility in the catalyst layer was used to estimate the extent of flooding, which revealed that ˜67--70% of void space was filled with water. The membrane's IEC regulates the extent of flooding of the cathode, which in turn affects its electrochemical characteristics. The investigation under operating fuel cell conditions revealed an increase in fuel cell performance with increasing IEC---a contradicting trend to that found for the half-fuel cell. This is explained by the interplay of electroosmotic flux and hydraulic counterflux in the membrane which affects water management in the membrane electrode assembly (MEA). The influence was most significant in the cathode catalyst layer, where it affects mass transport and electrochemical characteristics. It was found that the higher IEC facilitated better water management in MEAs. Comparing results obtained with half fuel cell and fuel cell systems revealed insights into the state of hydration and effective use of Pt in the catalyst layer. The two types of measurements provide a convenient approach to study the interplay of different mechanisms of water flux in the membrane.

Navessin, Titichai

390

Na+-dependent transport of taurine by membrane vesicles of neuroblastoma x glioma hybrid cells.  

PubMed

The transport of taurine into membrane vesicles prepared from neuroblastoma x glioma hybrid cells 108CC5 was studied. A great part of the taurine uptake by the membrane preparation is due to the transport into an osmotically sensitive space of membrane vesicles. Taurine uptake by membrane vesicles is an active transport driven by the concentration gradient of Na+ across the membrane (outside concentration greater than inside). The Km value of 36 microM for Na+-dependent taurine uptake indicates a high-affinity transport system. The rate of taurine transport by the membrane vesicles is enhanced by the K+ gradient (inside concentration greater than outside) and the K+ ionophore valinomycin. Taurine transport is inhibited by several structural analogs of taurine: hypotaurine, beta-alanine, and taurocyamine. All these results indicate that the taurine transport system of the membrane vesicles displays properties almost identical to those of intact neuroblastoma X glioma hybrid cells. PMID:3598583

Yuasa, S; Hamprecht, B

1987-08-01

391

Effect of ingested titanium dioxide nanoparticles on the digestive gland cell membrane of terrestrial isopods.  

PubMed

The aim of this study was to find out whether ingested titanium dioxide nanoparticles (nano-TiO(2)) cause cell membrane damage by direct contact or by lipid peroxidation. We assessed lipid peroxidation and digestive gland cell membrane stability of animals fed on food dosed with nano-TiO(2). Conventional toxicity measures were completed to determine if cellular effects are propagated to higher levels of biological complexity. An invertebrate model organism (Porcellio scaber, Isopoda, Crustacea) was fed with food containing nanosized TiO(2) and the result confirmed that at higher exposure concentrations after 3 d exposure, nano-TiO(2) destabilized cell membranes but lipid peroxidation was not detected. Oxidative stress as evidenced by lipid peroxidation was observed at longer exposure durations and high exposure doses. These data suggest that cell membranes are destabilized by direct interactions between nanoparticles and cell membrane, not solely via oxidative stress. PMID:22189379

Valant, Janez; Drobne, Damjana; Novak, Sara

2012-03-01

392

Novel pore-filled polyelectrolyte composite membranes for cathodic microbial fuel cell application  

NASA Astrophysics Data System (ADS)

Novel pore-filled polyelectrolyte membrane (PEM) was produced using track etched polycarbonate (PC) as porous substrate and poly(vinyl alcohol) (PVA) as pore filling material. PVA in PC pores was stabilized through cross-linking of PVA matrix with glutaraldehyde (GA). Cross-link time was varied from 24 h to 96 h while keeping the membranes in GA solution. Pore sizes of substrate PC membrane tested were 0.01, 0.1 and 0.2 ?m. The membranes were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Ionic conductivity, water uptake, contact angle and gel content have been measured to determine membranes performance. The ionic crossover (iron ions and protons) through membranes was studied in a complete fuel cell. The single-cell performance of membrane was tested in a cathodic microbial fuel cell (MFC, Biogenerator). The physiochemical properties and membranes fuel cell performance were highly depended on the cross-link density of PVA matrices. Membranes cross-liked with GA for 72 h showed maximum gel content and their peak power density has reached 110 mW cm-2 at current density of 378 mA cm-2. Among all, membrane cross-linked for 72 h was studied for continuous long-term stability, which showed consistency for application in MFC.

Gohil, J. M.; Karamanev, D. G.

2013-12-01

393

Erythrocyte swelling and membrane hole formation in hypotonic media as studied by conductometry.  

PubMed

Hypoosmotic swelling of erythrocytes and the formation of membrane holes were studied by measuring the dc conductance (G). In accordance with the theoretical predictions, these processes are manifested by a decrease in G followed by its increase. Thus, unlike the conventional osmotic fragility test, the proposed methodological approach allows investigations of both the kinetics of swelling and the erythrocyte fragility. It is shown that the initial rate of swelling and the equilibrium size of the cells are affected by the tonicity of a hypotonic solution and the membrane rheological properties. Because the rupture of biological membranes is a stochastic process, a time-dependent increase in the conductance follows an integral distribution function of the membrane lifetime. The main conclusion which stems from reported results is that information about rheological properties of red blood cell (RBC) membranes and the resistivity of RBCs to a certain osmotic shock may be extracted from conductance signals. PMID:23343529

Pribush, A; Meyerstein, D; Hatskelzon, L; Kozlov, V; Levi, I; Meyerstein, N

2013-02-01

394

Cell volume and plasma membrane osmotic water permeability in epithelial cell layers measured by interferometry.  

PubMed Central

The development of strategies to measure plasma membrane osmotic water permeability (Pf) in epithelial cells has been motivated by the identification of a family of molecular water channels. A general approach utilizing interferometry to measure cell shape and volume was developed and applied to measure Pf in cell layers. The method is based on the cell volume dependence of optical path length (OPL) for a light beam passing through the cell. The small changes in OPL were measured by interferometry. A mathematical model was developed to relate the interference signal to cell volume changes for cells of arbitrary shape and size. To validate the model, a Mach-Zehnder interference microscope was used to image OPL in an Madin Darby Canine Kidney (MDCK) cell layer and to reconstruct the three-dimensional cell shape (OPL resolution < lambda/25). As predicted by the model, a doubling of cell volume resulted in a change in OPL that was proportional to the difference in refractive indices between water and the extracellular medium. The time course of relative cell volume in response to an osmotic gradient was computed from serial interference images. To measure cell volume without microscopy and image analysis, a Mach-Zehnder interferometer was constructed in which one of two interfering laser beams passed through a flow chamber containing the cell layer. The interference signal in response to an osmotic gradient was analyzed to quantify the time course of relative cell volume. The calculated MDCK cell plasma membrane Pf of 6.1 x 10(-4) cm/s at 24 degrees C agreed with that obtained by interference microscopy and by a total internal reflection fluorescence method. Interferometry was also applied to measure the apical plasma membrane water permeability of intact toad urinary bladder; Pf increased fivefold after forskolin stimulation to 0.04 cm/s at 23 degrees C. These results establish and validate the application of interferometry to quantify cell volume and osmotic water permeability in cell layers. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 6 PMID:8968620

Farinas, J; Verkman, A S

1996-01-01

395

Red blood cells serve as intravascular carriers of myeloperoxidase.  

PubMed

Myeloperoxidase (MPO) is a heme enzyme abundantly expressed in polymorphonuclear neutrophils. MPO is enzymatically capable of catalyzing the generation of reactive oxygen species (ROS) and the consumption of nitric oxide (NO). Thus MPO has both potent microbicidal and, upon binding to the vessel wall, pro-inflammatory properties. Interestingly, MPO - a highly cationic protein - has been shown to bind to both endothelial cells and leukocyte membranes. Given the anionic surface charge of red blood cells, we investigated binding of MPO to erythrocytes. Red blood cells (RBCs) derived from patients with elevated MPO plasma levels showed significantly higher amounts of MPO by flow cytometry and ELISA than healthy controls. Heparin-induced MPO-release from patient-derived RBCs was significantly increased compared to controls. Ex vivo experiments revealed dose and time dependency for MPO-RBC binding, and immunofluorescence staining as well as confocal microscopy localized MPO-RBC interaction to the erythrocyte plasma membrane. NO-consumption by RBC-membrane fragments (erythrocyte "ghosts") increased with incrementally greater concentrations of MPO during incubation, indicating preserved catalytic MPO activity. In vivo infusion of MPO-loaded RBCs into C57BL/6J mice increased local MPO tissue concentrations in liver, spleen, lung, and heart tissue as well as within the cardiac vasculature. Further, NO-dependent relaxation of aortic rings was altered by RBC bound-MPO and systemic vascular resistance significantly increased after infusion of MPO-loaded RBCs into mice. In summary, we find that MPO binds to RBC membranes in vitro and in vivo, is transported by RBCs to remote sites in mice, and affects endothelial function as well as systemic vascular resistance. RBCs may avidly bind circulating MPO, and act as carriers of this leukocyte-derived enzyme. PMID:24976018

Adam, Matti; Gajdova, Silvie; Kolarova, Hana; Kubala, Lukas; Lau, Denise; Geisler, Anne; Ravekes, Thorben; Rudolph, Volker; Tsao, Philip S; Blankenberg, Stefan; Baldus, Stephan; Klinke, Anna

2014-09-01

396

High power density proton exchange membrane fuel cells  

NASA Technical Reports Server (NTRS)

Proton exchange membrane (PEM) fuel cells use a perfluorosulfonic acid solid polymer film as an electrolyte which simplifies water and electrolyte management. Their thin electrolyte layers give efficient systems of low weight, and their materials of construction show extremely long laboratory lifetimes. Their high reliability and their suitability for use in a microgravity environment makes them particularly attractive as a substitute for batteries in satellites utilizing high-power, high energy-density electrochemical energy storage systems. In this investigation, the Dow experimental PEM (XUS-13204.10) and unsupported high platinum loading electrodes yielded very high power densities, of the order of 2.5 W cm(exp -2). A platinum black loading of 5 mg per cm(exp 2) was found to be optimum. On extending the three-dimensional reaction zone of fuel cell electrodes by impregnating solid polymer electrolyte into the electrode structures, Nafion was found to give better performance than the Dow experimental PEM. The depth of penetration of the solid polymer electrolyte into electrode structures was 50-70 percent of the thickness of the platinum-catalyzed active layer. However, the degree of platinum utilization was only 16.6 percent and the roughness factor of a typical electrode was 274.

Murphy, Oliver J.; Hitchens, G. Duncan; Manko, David J.

1993-01-01

397

Sutureless Amniotic Membrane Transplantation for Partial Limbal Stem Cell Deficiency  

PubMed Central

PURPOSE To evaluate the results of sutureless amniotic membrane (AM) transplantation using fibrin glue for reconstructing corneal surfaces with partial limbal stem cell deficiency (LSCD). DESIGN Retrospective noncomparative interventional case series. METHODS Eleven eyes of nine patients that had LSCD with 120 degrees to almost 360 degrees of limbal involvement underwent superficial keratectomy to remove the conjunctivalized pannus followed by AM transplantation using fibrin glue. Additional sutureless AM patch (ProKera; Bio-Tissue, Inc, Miami, Florida, USA) was used in seven patients, and mitomycin C was applied on the cornea in four eyes and during fornix reconstruction in seven eyes. The surgery was repeated in three eyes for residual pannus. RESULTS During a mean follow-up of 14.2 ± 7.7 months (range, six to 26 months), all eyes maintained a smooth and stable corneal epithelial surface without recurrent erosion or persistent epithelial defect, and showed less stromal cloudiness and vascularization. Best-corrected visual acuity improved in nine eyes (81.8%). Corneal epithelialization proceeded by epithelial growth over AM (n = 4), accompanied by dissolution of AM (n = 4) or a combination of both (n = 3). No complication was noted regarding initial or repeated uses of fibrin glue. CONCLUSION AM transplantation using fibrin glue appears to be a safe and effective method of restoring a stable corneal epithelium for cases with partial LSCD. This approach avoids the need of transplanting limbal epithelial stem cells. PMID:18329626

KHEIRKHAH, AHMAD; CASAS, VICTORIA; RAJU, VADREVU K.; TSENG, SCHEFFER C. G.

2010-01-01