Note: This page contains sample records for the topic cell rbc membrane from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Less is more: removing membrane attachments stiffens the RBC cytoskeleton  

NASA Astrophysics Data System (ADS)

The polymerized network of the cytoskeleton of the red-blood cell (RBC) contains different protein components that maintain its overall integrity and attachment to the lipid bilayer. One of these key components is the band 3 ankyrin complex that attaches the spectrin filaments to the fluid bilayer. Defects in this particular component result in the shape transformation called spherocytosis, through the shedding of membrane nano-vesicles. We show here that this transition and membrane shedding can be explained through the increased stiffness of the network when the band 3 ankyrin complexes are removed. ATP-induced transient dissociations lead to network softening, which offsets the stiffening to some extent, and causes increased fragility of these mutant cells, as is observed.

Gov, Nir S.

2007-11-01

2

PERSPECTIVE: Fractional order models of viscoelasticity as an alternative in the analysis of red blood cell (RBC) membrane mechanics  

NASA Astrophysics Data System (ADS)

New lumped-element models of red blood cell mechanics can be constructed using fractional order generalizations of springs and dashpots. Such 'spring-pots' exhibit a fractional order viscoelastic behavior that captures a wide spectrum of experimental results through power-law expressions in both the time and frequency domains. The system dynamics is fully described by linear fractional order differential equations derived from first order stress-strain relationships using the tools of fractional calculus. Changes in the composition or structure of the membrane are conveniently expressed in the fractional order of the model system. This approach provides a concise way to describe and quantify the biomechanical behavior of membranes, cells and tissues.

Craiem, Damian; Magin, Richard L.

2010-03-01

3

Fractional order models of viscoelasticity as an alternative in the analysis of red blood cell (RBC) membrane mechanics.  

PubMed

New lumped-element models of red blood cell mechanics can be constructed using fractional order generalizations of springs and dashpots. Such 'spring-pots' exhibit a fractional order viscoelastic behavior that captures a wide spectrum of experimental results through power-law expressions in both the time and frequency domains. The system dynamics is fully described by linear fractional order differential equations derived from first order stress-strain relationships using the tools of fractional calculus. Changes in the composition or structure of the membrane are conveniently expressed in the fractional order of the model system. This approach provides a concise way to describe and quantify the biomechanical behavior of membranes, cells and tissues. PMID:20090192

Craiem, Damian; Magin, Richard L

2010-01-20

4

Fractional order models of viscoelasticity as an alternative in the analysis of red blood cell (RBC) membrane mechanics  

PubMed Central

New lumped-element models of red blood cell mechanics can be constructed using fractional order generalizations of springs and dashpots. Such ‘spring-pots’ exhibit a fractional order viscoelastic behavior that captures a wide spectrum of experimental results through power-law expressions in both the time and frequency domains. The system dynamics is fully described by linear fractional order differential equations derived from first order stress–strain relationships using the tools of fractional calculus. Changes in the composition or structure of the membrane are conveniently expressed in the fractional order of the model system. This approach provides a concise way to describe and quantify the biomechanical behavior of membranes, cells and tissues.

Craiem, Damian; Magin, Richard L

2011-01-01

5

Less is more: removing membrane attachments stiffens the RBC cytoskeleton  

Microsoft Academic Search

The polymerized network of the cytoskeleton of the red-blood cell (RBC) contains different protein components that maintain its overall integrity and attachment to the lipid bilayer. One of these key components is the band 3–ankyrin complex that attaches the spectrin filaments to the fluid bilayer. Defects in this particular component result in the shape transformation called spherocytosis, through the shedding

Nir S Gov

2007-01-01

6

Less is more: removing membrane attachments stiffens the RBC cytoskeleton  

Microsoft Academic Search

The polymerized network of the cytoskeleton of the red-blood cell (RBC) contains different protein components that maintain its overall integrity and attachment to the lipid bilayer. One of these key components is the band 3 ankyrin complex that attaches the spectrin filaments to the fluid bilayer. Defects in this particular component result in the shape transformation called spherocytosis, through the

Nir S. Gov

2007-01-01

7

Comparative analysis of RBC membrane lipids in thalassemia, and iron deficiency anemia in relation to hypochromia and oxidant injury  

Microsoft Academic Search

The effect of an intrinsic defect in the red cell and pronounced hypochromia on oxidative damage to RBC membrane lipids was\\u000a compared in beta-thalassemia and iron deficiency anemia (IDA), which have a varied etiology but equivalent low hemogiobin\\u000a content. The study was planned to correlate the etiology of the disorders to the severity of lipid imbalance and RBC hemolysis\\u000a in

S. P. Sanghani; V. A. Haldankar; K. K. Shalia; S. K. Bichlle

2001-01-01

8

A band 3-based macrocomplex of integral and peripheral proteins in the RBC membrane  

SciTech Connect

We have studied the membrane proteins of band 3 anion exchanger (AE1)-deficient mouse and human red blood cells. It has been shown previously that proteins of the band 3 complex are reduced or absent in these cells. In this study we show that proteins of the Rh complex are also greatly reduced (Rh-associated glycoprotein, Rh polypeptides, CD47, glycophorin B) or absent (LW). These observations suggest that the Rh complex is associated with the band 3 complex in healthy RBCs. Mouse band 3 RBCs differed from the human band 3-deficient RBCs in that they retained CD47. Aquaporin 1 was reduced, and its glycosylation was altered in mouse and human band 3-deficient RBCs. Proteins of the glycophorin complex, and other proteins with independent cytoskeletal interactions, were present in normal or increased amounts. To obtain direct evidence for the association of the band 3 and the Rh protein complexes in the RBC, we examined whether Rh complex proteins were coimmunoprecipitated with band 3 from membranes. RhAG and Rh were found to be efficiently coimmunoprecipitated with band 3 from deoxycholate-solubilized membranes. Results suggest that band 3 forms the core of a macrocomplex of integral and peripheral RBC membrane proteins. The presence of these proteins in a single structural Macrocomplex makes it likely that they have linked functional or regulatory roles. We speculate that this macrocomplex may function as an integrated CO2/O2 gas exchange unit (metabolon) in the erythrocyte.

Bruce, Lesley J.; Beckmann, Roland; Ribeiro, M. Leticia; Peters, Luanne L.; Chasis, Joel A.; Delaunay, Jean; Mohandas, Narla; Anstee, David J.; Tanner, Michael J.A.

2003-06-18

9

RBC membrane composition in insulin dependent diabetes mellitus in context of oxidative stress.  

PubMed

Glyco-oxidation is considered as a source of permanent, cumulative, oxidative damage to long lived proteins in ageing and in diabetes. Although RBC depends solely on glucose for energy purpose, hyperglycemic state glycosylates hemoglobin, creates oxidative stress and puts the cellular components at risk. In view of this, RBC membrane composition was analyzed in diabetic patients. The results were compared with healthy age and sex matched control groups. When RBC membrane components such as protein, sialic acid, phospholipids and cholesterol were determined in insulin dependent diabetes mellitus, a significant rise in phospholipids and cholesterol and significant fall in sialic acid and protein content was noted. RBC membrane composition showed pronounced alterations in insulin dependent diabetes mellitus. These changes were accompanied by higher levels of lipid peroxidation products like Malondialdehyde. PMID:23105758

Vahalkar, Gauri S; Haldankar, Vijaya A

2008-10-01

10

Cation specificity of propranolol-induced changes in RBC membrane permeability: comparative effects in human, dog and cat erythrocytes.  

PubMed

Propranolol, in the presence of calcium, causes marked K efflux from human red blood cells (high K, low Na). The studies reported here indicate this effect of propranolol is specific for K and does not represent a nonspecific permeability increase for intracellular cations to leave the cell. Amphotericin-treated human RBC's (high Na, low K) and dog RBC's (high Na, low K) both gain K and increase in size when incubated in a K-medium containing propranolol and calcium. No effect was noted when cat RBC's (high Na, low K) were similarly treated. Propranolol, independent of added calcium, also inhibited the normally increased Na efflux observed when dog RBC's are suspended in K-medium. These species differences in response to propranolol thus may serve as a focus for elucidating the mechanism by which this drug alters normal membrane physiology. The unique drug effect on Na permeability of canine erythrocytes also may be a useful probe for the study of dog RBC volume regulation. PMID:558987

Müller-Soyano, A; Glader, B E

1977-05-01

11

RBC count  

MedlinePLUS

... Dehydration (such as from severe diarrhea) Kidney tumor (renal cell carcinoma) Low blood oxygen levels (hypoxia) Pulmonary fibrosis Polycythemia vera Your RBC count will increase for several weeks ...

12

Proteomic analysis of RBC membrane protein degradation during blood storage.  

PubMed

Two-dimensional gel electrophoresis and mass spectrometry were used to identify protein profile changes in red blood cell membranes stored over time under atmospheric oxygen, in the presence or absence of protease inhibitors. New spots with lower molecular masses, ranging between 7 and 15 kDa were observed during the first 7 days storage, while over time, further fragments and high-molecular-mass aggregates appeared, seen as a smearing in the upper part of the gel. Some of the protein changes turned out to be shifts in isoelectric point, as a consequence of chemical oxidations. All these new spots were generated as a result of protein attack by reactive oxygen species (ROS). Protein identification revealed that most of the modified proteins are located in the cytoskeleton. During the first 7 days of storage, oxidative degradation was observed prevalently in band 4.2, to a minor extent in bands 4.1 and 3, and in spectrin. After 14 days, there were new fragments from beta-actin, glyceraldehyde-3-phosphate dehydrogenase, band 4.9, and ankyrin, among others. Preliminary protein-protein cross-linked products, involving alpha and beta spectrin, were also detected. The cross-linked products increased over time. Protein degradation was greatly reduced when oxygen was removed and blood was stored under helium. Interestingly, very few spots were related to enzyme activity, and they were more numerous when oxygen was present, suggesting that some proteases may be oxygen-dependent. PMID:17585793

D'Amici, Gian Maria; Rinalducci, Sara; Zolla, Lello

2007-06-22

13

Comparative analysis of RBC membrane lipids in thalassemia, and iron deficiency anemia in relation to hypochromia and oxidant injury.  

PubMed

The effect of an intrinsic defect in the red cell and pronounced hypochromia on oxidative damage to RBC membrane lipids was compared in beta-thalassemia and iron deficiency anemia (IDA), which have a varied etiology but equivalent low hemogiobin content. The study was planned to correlate the etiology of the disorders to the severity of lipid imbalance and RBC hemolysis in membranes of both the conditions. Results indicated a fall of lysophosphatidylcholine(LPC), phosphatidylethanolamine(PE) and the unsaturated to saturated fatty acid ratio in both conditions, while phosphatidylcholine(PC) increased only in thalassemia. However, irrespective of the disease, sphingomyelin(SM), total cholesterol and phospholipid levels elevated and the hydrogen peroxide stress test indicated increased susceptibility of both pathologic RBCs to peroxidation. Present findings indicate that IDA and thalassemla, allow for considerable amounts of oxidative damage to membrane lipids, irrespective of their etiologles, and thus point hypochromia as an important contributor for inducing lipid imbalance and RBC hemolysis. PMID:23105304

Sanghani, S P; Haldankar, V A; Shalia, K K; Bichlle, S K

2001-01-01

14

Determination of RBC membrane and serum lipid composition in trinidadian type II diabetics with and without nephropathy  

PubMed Central

Aim: The rheological properties of erythrocytes are impaired in diabetes mellitus, especially because of changes in their membrane lipid composition.The aim of this study was to determine and examine the relationship between red blood cell (RBC) membrane and serum lipid composition in type II diabetes subjects with and without nephropathy. Methods: Trinidadian subjects aged 18–65 years were recruited for the study regardless of gender and ethnicity. Fasting blood samples were collected from 60 subjects of whom 20 were healthy individuals, 20 had type II diabetes without complications, and 20 were type II diabetics with nephropathy. Weight, height, waist/hip ratio, and blood pressure were recorded. All the blood samples were analysed to determine the serum lipid concentration, membrane lipid composition and plasma glucose concentration. Results: The body mass index and the systolic blood pressure of the diabetics (28.17 ± 4.98 kg/m2, 153.21 ± 22.10 mmHg) and those with nephropathy (25.87 ± 4.68, 158.60 ± 22.49 mmHg) were higher when compared with controls (24.67 ± 5.18, 119.15 ± 13.03 mmHg). The diabetic (175.89 ± 102.73 ?g/mgprotein) and diabetic nephropathy (358.80 ± 262.66) subjects showed significantly higher levels of RBC membrane cholesterol compared with controls (132.27 ± 66.47). The membrane phospholipids, protein and Na+/K+ATPase concentrations were altered in diabetics and diabetic nephropathy patients when compared with controls. The trends of increased serum cholesterol and decreased high-density lipoprotein in diabetics and diabetic nephropathy patients were noted as compared with controls but they are not significant as expected. The low-density lipoprotein cholesterol was significantly higher in diabetics when compared with diabetic nephropathy and control subjects. Conclusions: Our data suggest that there is a relationship between RBC membrane and serum lipid composition in subjects with type II diabetes with and without nephropathy. This relationship shows that diet and lifestyle plays a significant role in the alterations of the lipids both in serum and RBC membrane. The membrane and serum lipid composition may be used as possible indicators for type II diabetic patients with and without nephropathy to control their diet in the beginning stages to prevent them from further complications.

Nayak, B Shivananda; Beharry, Vishi Y; Armoogam, Shivani; Nancoo, Melinda; Ramadhin, Kevin; Ramesar, Kiron; Ramnarine, Ciara; Singh, Anandi; Singh, Anisha; Nwachi, Kingsley Uche; Teelucksing, Surujpaul; Mathura, Ramesh; Roberts, Lesley

2008-01-01

15

Increased anticoagulant osmolality improves separation of leukocytes from red blood cells (RBC)  

Microsoft Academic Search

Background: The bottom-and-top (BAT) procedure separates the buffy coat (BC) from plasma and red blood cells (RBC). The contents of mononuclear cells (MNC) remaining in the RBC are about 1×106 cells\\/unit, whereas the granulocytes are removed less effectively, 500–800×106 or more remaining in the RBC unit. The aim was to improve the separation efficacy by collecting the blood in an

F Knutson; H Lööf; C. F Högman

1999-01-01

16

Heterogeneity of human red blood cell membrane: Co-existence of heavy and light membranes  

Microsoft Academic Search

The exact chemical composition of the red blood cell (RBC) membrane may vary depending on the methods used to isolate the membrane. We provide evidence here that RBC membrane can be fractionated by differential centrifugation and\\/or density gradient centrifugation into two distinct types, designated as ‘heavy membrane’ (HM) and ‘light membrane’ (LM). The amount of LM is twice that of

Salil K. Das; Shyamali Mukherjee

1999-01-01

17

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

18

Reduced expression of CD47 during murine red blood cell (RBC) senescence and its role in RBC clearance from the circulation  

Microsoft Academic Search

BACKGROUND: Almost 2 percent of murine blood red blood cells (RBCs) are destroyed each day and are replaced by fresh RBCs generated through the process of erythropoiesis. RBCs to be destroyed are phagocy- tosed by macrophages in the reticuloendothelial system, especially in the spleen. CD47 molecules on RBCs may regulate the susceptibility of RBC to destruction by phagocytosis because its

Sanjay Khandelwal; Nico van Rooijen

2007-01-01

19

Adiabatic compressibility of red blood cell membrane: influence of skeleton  

Microsoft Academic Search

Measurements of ultrasound velocity and density were used for determination of the adiabatic compressibility of red blood cells (RBC) during detachment of the membrane skeleton. Skeleton detachment was induced by addition of nystatin into a low ionic strength RBC suspension resulting in an increase (10%) of the ultrasound velocity concentration increment, [u], while the specific volume of cells, ?V, did

Tibor Hianik; Peter Rybár; Ingolf Bernhardt

2000-01-01

20

[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, resectively. 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

21

Detection and characterization of red blood cell (RBC) aggregation with photoacoustics  

NASA Astrophysics Data System (ADS)

Red blood cells (RBCs) aggregate in the presence of increased plasma fibrinogen and low shear forces during blood flow. RBC aggregation has been observed in deep vein thrombosis, sepsis and diabetes. We propose using photoacoustics (PA) as a non-invasive imaging modality to detect RBC aggregation. The theoretical and experimental feasibility of PA for detecting and characterizing aggregation was assessed. A simulation study was performed to generate PA signals from non-aggregated and aggregated RBCs using a frequency domain approach and to study the PA signals' dependence on hematocrit and aggregate size. The effect of the finite bandwidth nature of transducers on the PA power spectra was also investigated. Experimental confirmation of theoretical results was conducted using porcine RBC samples exposed to 1064 nm optical wavelength using the Imagio Small Animal PA imaging system (Seno Medical Instruments, Inc., San Antonio, TX). Aggregation was induced with Dextran-70 (Sigma-Aldrich, St. Louis, MO) and the effect of hematocrit and aggregation level was investigated. The theoretical and experimental PA signal amplitude increased linearly with increasing hematocrit. The theoretical dominant frequency content of PA signals shifted towards lower frequencies (<30 MHz) and 9 dB enhancements in spectral power were observed as the size of aggregates increased compared to non-aggregating RBCs. Calibration of the PA spectra with the transducer response obtained from a 200 nm gold film was performed to remove system dependencies. Analysis of the spectral parameters from the calibrated spectra suggested that PA can assess the degree of aggregation at multiple hematocrit and aggregation levels.

Hysi, Eno; Saha, Ratan K.; Rui, Min; Kolios, Michael C.

2012-02-01

22

Hyperglycemia can cause membrane lipid peroxidation and osmotic fragility in human red blood cells.  

PubMed

The present study has examined the effect of elevated glucose levels on membrane lipid peroxidation and osmotic fragility in human red blood cells (RBC). Defibrinated whole blood or RBC were incubated with varying concentrations of glucose at 37 degrees C for 24 h. RBC incubated with elevated levels of glucose showed a significantly increased membrane lipid peroxidation when compared with control RBC. A significant positive correlation was observed between the extent of glucose-induced membrane lipid peroxidation and the osmotic fragility of treated RBC. Glucose-induced membrane lipid peroxidation and osmotic fragility were blocked when RBC were pretreated with fluoride, an inhibitor of glucose metabolism; with vitamin E, an antioxidant; with para-chloromercurobenzoate and metyrapone, inhibitors of the cytochrome P-450 system; or with dimethylfurane, diphenylamine, and thiourea, scavengers of oxygen radicals. RBC treated with elevated glucose concentrations also showed an increase in NADPH levels. Exogenous addition of NADPH to normal RBC lysate induced membrane lipid peroxidation similar to that observed in the glucose-treated RBC. These data suggest that elevated glucose levels can cause the peroxidation of membrane lipids in human RBC. PMID:2592379

Jain, S K

1989-12-15

23

Red blood cell membrane integrity in primary open angle glaucoma: ex vivo and in vitro studies  

Microsoft Academic Search

Purpose There is increasing evidence that abnormal perfusion of the optic nerve head is an important factor involved in the pathophysiology of glaucoma. Transport and distribution of oxygen to the tissues takes place through the erythrocyte membrane. Red blood cell (RBC) acetylcholinesterase (AChE) is a marker of RBC membrane integrity. The aim of this study was to find out whether

L Zabala; C Saldanha; J Martins E Silva; P Souza-Ramalho

1999-01-01

24

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

Microsoft Academic Search

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

E. J. Victoria; S. W. Pierce; M. J. Branks; S. P. Masouredis

1990-01-01

25

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.

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

2010-01-01

26

Light-dependent developmental control of rbcS gene expression in epidermal cells of maize leaves  

Microsoft Academic Search

Regulatory elements of the maize rbcS-m3 gene (a member of the family of genes encoding the small subunit of ribulose bisphosphate carboxylase) that are sufficient for expression of the ß-glucuronidase (gusA) gene in photosynthetic tissue lead to relatively weak expression of the reporter gene in epidermal cells of green maize leaves when delivered by ballistic gene transfer methods. However, epidermal

Roland Bilang; Lawrence Bogorad

1996-01-01

27

Direct Measurement of the Area Expansion and Shear Moduli of the Human Red Blood Cell Membrane Skeleton  

Microsoft Academic Search

The area expansion and the shear moduli of the free spectrin skeleton, freshly extracted from the membrane of a human red blood cell (RBC), are measured by using optical tweezers micromanipulation. An RBC is trapped by three silica beads bound to its membrane. After extraction, the skeleton is deformed by applying calibrated forces to the beads. The area expansion modulus

Guillaume Lenormand; Sylvie Hénon; Alain Richert; Jacqueline Siméon; François Gallet

2001-01-01

28

Elastic properties of the red blood cell membrane that determine echinocyte deformability  

Microsoft Academic Search

The natural biconcave shape of red blood cells (RBC) may be altered by injury or environmental conditions into a spiculated form (echinocyte). An analysis is presented of the effect of such a transformation on the resistance of RBC to entry into capillary sized cylindrical tubes. The analysis accounts for the elasticity of the membrane skeleton in dilation and shear, and

D. Kuzman; S. Svetina; R. E. Waugh; B. Žekš

2004-01-01

29

Role of Surface Electric Charge in Red Blood Cell Interactions  

Microsoft Academic Search

The role of the surface charge of human red blood cells (RBC's) in affecting RBC aggregation by macromolecules was studied by comparing the behavior of normal RBC's with that of RBC's treated with neuraminidase, which removes the sialic acids from the cell membrane and reduces the zeta potential. RBC aggregation in dextrans with different molecular weights (Dx 20, Dx 40,

KUNG-MING JAN; SHU CHIEN

2010-01-01

30

Alterations in human red blood cell membrane properties induced by the lipopolysaccharide from Proteus mirabilis S1959  

Microsoft Academic Search

The effect of lipopolysaccharide (LPS, endotoxin), isolated from Proteus mirabilis S1959 strain, on red blood cell (RBC) membranes in whole cells as well as on isolated membranes was studied. Lipid membrane fluidity, conformational state of membrane proteins and the osmotic fragility of RBCs were examined using electron paramagnetic resonance spectroscopy and spectrophotometric method. Lipid membrane fluidity was determined using three

Krzysztof Gwozdzinski; Anna Pieniazek; Beata Sudak; Wieslaw Kaca

2003-01-01

31

Lipopolysaccharide from Proteus mirabilis O29 induces changes in red blood cell membrane lipids and proteins  

Microsoft Academic Search

Alterations in red blood cell (RBC) plasma membranes, i.e. in lipids and proteins, and osmotic fragility of these cells after treatment with Proteus mirabilis O29 endotoxin (lipolysaccharide (LPS)) were examined using a spin labelling method. At the highest concentration of LPS, insignificantly decreased fluidity of membrane lipids was observed. Changes in conformation of membrane proteins were determined by two covalently

Krzysztof Gwo?dzi?ski; Anna Pieni; Wies?aw Kaca

2003-01-01

32

Interaction of mesoporous silica nanoparticles with human red blood cell membranes: size and surface effects.  

PubMed

The interactions of mesoporous silica nanoparticles (MSNs) of different particle sizes and surface properties with human red blood cell (RBC) membranes were investigated by membrane filtration, flow cytometry, and various microscopic techniques. Small MCM-41-type MSNs (?100 nm) were found to adsorb to the surface of RBCs without disturbing the membrane or morphology. In contrast, adsorption of large SBA-15-type MSNs (?600 nm) to RBCs induced a strong local membrane deformation leading to spiculation of RBCs, internalization of the particles, and eventual hemolysis. In addition, the relationship between the degree of MSN surface functionalization and the degree of its interaction with RBC, as well as the effect of RBC-MSN interaction on cellular deformability, were investigated. The results presented here provide a better understanding of the mechanisms of RBC-MSN interaction and the hemolytic activity of MSNs and will assist in the rational design of hemocompatible MSNs for intravenous drug delivery and in vivo imaging. PMID:21294526

Zhao, Yannan; Sun, Xiaoxing; Zhang, Guannan; Trewyn, Brian G; Slowing, Igor I; Lin, Victor S-Y

2011-02-04

33

Effects of Membrane Partitioning and Other Physical Chemical Properties on the Apparent Potency of “Membrane Active” Compounds Evaluated Using Red Blood Cell Lysis Assays  

Microsoft Academic Search

The membrane-destabilizing properties of Amphotericin B and Zwittergent were used as benchmark compounds for examining in detail their membrane-altering effects in a series of human red blood cell lysis assays. The procedures included examining dose responses and the effects of different cell concentrations on potency in rbc lysis assays. In order to enhance detection of subtle membrane effects, we also

Darryl Chapman; Stephen Buxser

2002-01-01

34

Familial aggregation of red blood cell membrane fatty acid composition: the Kibbutzim Family Study  

Microsoft Academic Search

The fatty acid composition of membranes plays an important role in health and diseases. Whether genetic factors play a role in interindividual variability in membrane fatty acid levels has received limited attention. Using variance decomposition methods, we estimated the heritability of red blood cell (RBC) membrane fatty acids in an unselected population sample of 80 families (205 male and 212

Rozenn N. Lemaitre; David S. Siscovick; Elliot M. Berry; Jeremy D. Kark; Yechiel Friedlander

2008-01-01

35

Comparative analysis of RBC membrane fatty acids, proteins and glycophorin in patients with heterozygous beta thalassemia and iron deficiency anemia.  

PubMed

Membrane lipid and protein composition was compared in erythrocytes from iron deficiency anemia (IDA) and heterozygous beta thalassemia patients. The study was planned to correlate the influence of iron deficiency with the intrinsic defect of the heterozygous condition on the membrane structural integrity as well as to investigate whether there are differences in membrane changes between the two conditions. Results indicate high levels of saturated fatty acids and low unsaturated fatty acids in both disorders although arachidonic acid and the unsaturation index were lower in heterozygous thalassemia than IDA. Nevertheless, neither of the conditions provoked any alterations in membrane protein or glycophorin suggesting alterations in the lipid moiety only. Present findings indicate that irrespective to the etiology, both, iron deficiency and the heterozygous condition show a common pattern of lipid derangement, which may in turn result in increased membrane rigidity and decreased cellular deformability. PMID:23105609

Sanghani, S P; Haldankar, V A

2006-09-01

36

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.

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

2013-01-01

37

Composite fuel cell membranes  

Microsoft Academic Search

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

Keith R. Plowman; Timothy J. Rehg; Larry W. Davis; William P. Carl; Alan J. Cisar; Charles S. Eastland

1997-01-01

38

Palmitoylation of MPP1 (Membrane-palmitoylated Protein 1)/p55 Is Crucial for Lateral Membrane Organization in Erythroid Cells*  

PubMed Central

S-Acylation of proteins is a ubiquitous post-translational modification and a common signal for membrane association. The major palmitoylated protein in erythrocytes is MPP1, a member of the MAGUK family and an important component of the ternary complex that attaches the spectrin-based skeleton to the plasma membrane. Here we show that DHHC17 is the only acyltransferase present in red blood cells (RBC). Moreover, we give evidence that protein palmitoylation is essential for membrane organization and is crucial for proper RBC morphology, and that the effect is specific for MPP1. Our observations are based on the clinical cases of two related patients whose RBC had no palmitoylation activity, caused by a lack of DHHC17 in the membrane, which resulted in a strong decrease of the amount of detergent-resistant membrane (DRM) material. We confirmed that this loss of detergent-resistant membrane was due to the lack of palmitoylation by treatment of healthy RBC with 2-bromopalmitic acid (2-BrP, common palmitoylation inhibitor). Concomitantly, fluorescence lifetime imaging microscopy (FLIM) analyses of an order-sensing dye revealed a reduction of membrane order after chemical inhibition of palmitoylation in erythrocytes. These data point to a pathophysiological relationship between the loss of MPP1-directed palmitoylation activity and perturbed lateral membrane organization.

Lach, Agnieszka; Grzybek, Michal; Heger, Elzbieta; Korycka, Justyna; Wolny, Marcin; Kubiak, Jakub; Kolondra, Adam; Boguslawska, Dzamila M.; Augoff, Katarzyna; Majkowski, Michal; Podkalicka, Joanna; Kaczor, Jakub; Stefanko, Adam; Kuliczkowski, Kazimierz; Sikorski, Aleksander F.

2012-01-01

39

Liposomes alter thermal phase behavior and composition of red blood cell membranes.  

PubMed

Unilamellar liposomes composed of natural phospholipids provide a new promising class of protective agents for hypothermic storage, cryopreservation, or freeze-drying of red blood cells (RBCs). In this study, FTIR spectroscopy, MALDI-TOF MS, and colorimetric assays were used to investigate the effects of liposomes composed of a homologous series of linear saturated phosphatidylcholine phospholipids (18:0; 16:0; 14:0; 12:0) on RBC membranes. RBCs were incubated with liposomes at 37°C and both the liposomal and the RBC fraction were analyzed after incubation. FTIR studies showed that liposomes composed of short acyl chain length lipids cause an increase in RBC membrane conformational disorder at suprazero temperatures, whereas long acyl chain length lipids were found to have little effects. The increased lipid conformational disorder in the RBC membranes coincided with a decrease in the cholesterol-to-phospholipid ratio. The opposite effects were found in the liposomes after incubation with RBCs. MALDI-TOF MS analysis showed the presence of short acyl chain length lipids (14:0 and 12:0) in RBC membranes after incubation, which was not observed after incubation with liposomes containing long acyl chain length lipids (18:0 and 16:0). Liposomes alter RBC membrane properties by cholesterol depletion and lipid addition. PMID:20883663

Stoll, Christoph; Stadnick, Hart; Kollas, Oliver; Holovati, Jelena L; Glasmacher, Birgit; Acker, Jason P; Wolkers, Willem F

2010-09-29

40

Composite fuel cell membranes  

Microsoft Academic Search

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

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

1997-01-01

41

Determination of red blood cell shape recovery time constant in a couette system by the analysis of light reflectance and ektacytometry  

Microsoft Academic Search

Red blood cell (RBC) shape change under shear is generally reversible, with the time course of shape recovery a function of the elastic and viscous properties of the RBC membrane. RBC shape recovery can be investigated, using several different techniques, to provide information about the membrane material properties that are not directly accessible by frequently used methods to assess RBC

O. K. Baskurt; H. J. Meiselman

1996-01-01

42

Protein kinase C and calmodulin effects on the plasma membrane Ca2+ATPase from excitable and nonexcitable cells  

Microsoft Academic Search

We have purified Ca2+-ATPase from synaptosomal membranes (SM)1 from ratcerebellum by calmodulin affinity chromatography. The enzyme was identifiedas plasma membrane Ca2+-ATPase by its interaction with calmodulin andmonoclonal antibodies produced against red blood cell (RBC) Ca2+-ATPase, andby thapsigargin insensitivity. The purpose of the study was to establishwhether two regulators of the RBC Ca2+-ATPase, calmodulin and protein kinaseC (PKC), affect the Ca2+-ATPase

Danuta Kosk-Kosicka; Ludmi?a Zyli?ska

1997-01-01

43

Extracellular Methemoglobin Mediated Early ROS Spike Triggers Osmotic Fragility and RBC Destruction: An Insight into the Enhanced Hemolysis During Malaria.  

PubMed

Malaria infection is known to cause severe hemolysis due to production of abnormal RBCs and enhanced RBC destruction through apoptosis. Infected RBC lysis exposes uninfected RBC to the large amount of pro-oxidant molecules such as methemoglobin. Methemoglobin (MetHb) exposure dose dependently makes RBCs susceptible to osmotic stress and causes hemolysis. MetHb mediated oxidative stress in RBC correlated well with osmotic fragility and hemolysis. Interestingly, a reactive oxygen species (ROS) spike at 15 min was responsible for the observed effects on RBC cells. Two natural antioxidants N-acetyl cysteine and mannitol protected the RBC from MetHb-mediated defects, which clearly indicated involvement of oxidative stress in the process. MetHb due to its pseudo-peroxidase activity produces ROS in the external microenvironment. Therefore, classical peroxidase inhibitors were tested to probe peroxidase activity mediated ROS production with defects in RBCs. Clotrimazole (CLT), which irreversibly inactivates the MetHb (CLT-MetHb) and abolishes peroxidase activity, did not produce significant ROS outside RBC and was inefficient to cause osmotic fragility and hemolysis. Hence, initiating a chain reaction, MetHb released from ruptured RBC produces significant ROS in the external microenvironment to make RBC membrane leaky and enhanced hemolysis. Together data presented in the current work explored the role of MetHb in accelerated humorless during malaria which could be responsible for severe outcomes of pathological disorders. PMID:23543627

Balaji, S N; Trivedi, Vishal

2011-11-08

44

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

45

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

46

Red blood cell membrane viscoelasticity, agglutination and zeta potential measurements with double optical tweezers  

NASA Astrophysics Data System (ADS)

The red blood cell (RBC) viscoelastic membrane contains proteins and glycolproteins embedded in, or attached, to a fluid lipid bilayer and are negatively charged, which creates a repulsive electric (zeta) potential between the cells and prevents their aggregation in the blood stream. There are techniques, however, to decrease the zeta potential to allow cell agglutination which are the basis of most of the tests of antigen-antibody interactions in blood banks. This report shows the use of a double optical tweezers to measure RBC membrane viscosity, agglutination and zeta potential. In our technique one of the optical tweezers trap a silica bead that binds strongly to a RBC at the end of a RBCs rouleaux and, at the same time, acts as a pico-Newton force transducer, after calibration through its displacement from the equilibrium position. The other optical tweezers trap the RBC at the other end. To measure the membrane viscosity the optical force is measured as a function of the velocity between the RBCs. To measure the adhesion the tweezers are slowly displaced apart until the RBCs disagglutination happens. The RBC zeta potential is measured in two complimentary ways, by the force on the silica bead attached to a single RBC in response to an applied electric field, and the conventional way, by the measurement of terminal velocity of the RBC after released from the optical trap. These two measurements provide information about the RBC charges and, also, electrolytic solution properties. We believe this can improve the methods of diagnosis in blood banks.

Fontes, Adriana; Fernandes, Heloise P.; Barjas-Castro, Maria L.; de Thomaz, André A.; de Ysasa Pozzo, Liliana; Barbosa, Luiz C.; Cesar, Carlos L.

2006-03-01

47

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.

Tsong, T Y

1991-01-01

48

Effects of lead on red blood cell membrane proteins  

Microsoft Academic Search

Summary The effects of lead on red blood cell (RBC) membrane proteins were studied in two groups of workers with different lead exposure levels: Group 1 (6 subjects employed in a battery plant) with a mean blood lead of 40.1 (SD = 3.7) µg\\/100 ml; Group II(5 workers employed in different industries) with a mean blood lead of 60.6 (SD

P. Apostoli; L. Romeo; M. C. De Matteis; M. Menegazzi; G. Faggionato; L. Vettore

1988-01-01

49

Fibrinogen interaction with the red blood cell membrane.  

PubMed

A brief review of the fibrinogen molecule composition and structure is presented like as an introduction to the effects of this plasma protein on the red blood cell hemorheoplogical properties namely erythrocyte aggregation tendency and deformability ability. The protein membrane RBC target for fibrinogen is also highlight as well as the erythrocyte signal transduction pathway associated with nitric oxide mobilization resulting from its binding. PMID:22960295

Saldanha, Carlota

2013-01-01

50

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

2012-11-29

51

A Comparison of Multi-scale and Low-Dimensional Models of Red Blood Cells  

Microsoft Academic Search

A new low-dimensional dissipative particle dynamics (DPD) model of the red blood cell (LD-RBC) is tested against a multi-scale RBC (MS-RBC) model known to accurately capture the mechanical response of single human RBCs in a number of static and dynamic experiments. The MS-RBC model represents the RBC membrane with hundreds or even thousands of DPD-particles and includes membrane viscosity. In

Wenxiao Pan; Dmitry Fedosov; Bruce Caswell; George Karniadakis

2010-01-01

52

Competition between Na + and Li + for Unsealed and Cytoskeleton-Depleted Human Red Blood Cell Membrane: A 23Na Multiple Quantum Filtered and 7Li NMR Relaxation Study  

Microsoft Academic Search

Evidence for competition between Li+ and Na+ for binding sites of human unsealed and cytoskeleton-depleted human red blood cell (csdRBC) membranes was obtained from the effect of added Li+ upon the 23Na double quantum filtered (DQF) and triple quantum filtered (TQF) NMR signals of Na+-containing red blood cell (RBC) membrane suspensions. We found that, at low ionic strength, the observed

Chandra Srinivasan; Nicole Minadeo; Jason Toon; Daniel Graham; Duarte Mota de Freitas; Carlos F. G. C. Geraldes

1999-01-01

53

Measurement of the nonlinear elasticity of red blood cell membranes  

NASA Astrophysics Data System (ADS)

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 of the RBCs to extract the elastic moduli of this composite membrane. By applying known osmotic stresses, we measure the changes in the elastic constants under imposed strain and thereby determine the nonlinear elastic properties of the membrane. We find that the elastic nonlinearities of the shear modulus in tensed RBC membranes can be well understood in terms of a simple wormlike chain model. Our results show that the elasticity of the spectrin network can mostly account for the area compression modulus at physiological osmolality, suggesting that the lipid bilayer has significant excess area. As the cell swells, the elastic contribution from the now tensed lipid membrane becomes dominant.

Park, Yongkeun; Best, Catherine A.; Kuriabova, Tatiana; Henle, Mark L.; Feld, Michael S.; Levine, Alex J.; Popescu, Gabriel

2011-05-01

54

Measurement of the nonlinear elasticity of red blood cell membranes.  

PubMed

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 of the RBCs to extract the elastic moduli of this composite membrane. By applying known osmotic stresses, we measure the changes in the elastic constants under imposed strain and thereby determine the nonlinear elastic properties of the membrane. We find that the elastic nonlinearities of the shear modulus in tensed RBC membranes can be well understood in terms of a simple wormlike chain model. Our results show that the elasticity of the spectrin network can mostly account for the area compression modulus at physiological osmolality, suggesting that the lipid bilayer has significant excess area. As the cell swells, the elastic contribution from the now tensed lipid membrane becomes dominant. PMID:21728589

Park, YongKeun; Best, Catherine A; Kuriabova, Tatiana; Henle, Mark L; Feld, Michael S; Levine, Alex J; Popescu, Gabriel

2011-05-27

55

Antigens protected functional red blood cells by the membrane grafting of compact hyperbranched polyglycerols.  

PubMed

Red blood cell (RBC) transfusion is vital for the treatment of a number of acute and chronic medical problems such as thalassemia major and sickle cell anemia. Due to the presence of multitude of antigens on the RBC surface (~308 known antigens), patients in the chronic blood transfusion therapy develop alloantibodies due to the miss match of minor antigens on transfused RBCs. Grafting of hydrophilic polymers such as polyethylene glycol (PEG) and hyperbranched polyglycerol (HPG) forms an exclusion layer on RBC membrane that prevents the interaction of antibodies with surface antigens without affecting the passage of small molecules such as oxygen, glucose, and ions. At present no method is available for the generation of universal red blood donor cells in part because of the daunting challenge presented by the presence of large number of antigens (protein and carbohydrate based) on the RBC surface and the development of such methods will significantly improve transfusion safety, and dramatically improve the availability and use of RBCs. In this report, the experiments that are used to develop antigen protected functional RBCs by the membrane grafting of HPG and their characterization are presented. HPGs are highly biocompatible compact polymers, and are expected to be located within the cell glycocalyx that surrounds the lipid membrane and mask RBC surface antigens. PMID:23328980

Chapanian, Rafi; Constantinescu, Iren; Brooks, Donald E; Scott, Mark D; Kizhakkedathu, Jayachandran

2013-01-02

56

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.

57

Regulation of the Complement-Mediated Elimination of Red Blood Cells Modified with Biotin and Streptavidin  

Microsoft Academic Search

Red blood cells (RBC) modified with biotin and streptavidin (SA) present an interesting potential drug delivery system. Biotinylation and SA attachment, however, alter the biocompatibility of RBC. We have reported that polyvalent SA attachment induces lysis of biotinylated RBC (b-RBC) by homologous complement via the alternative pathway. Lysis occurs due to inactivation of the membrane regulators of complement, DAF and

Vladimir R. Muzykantov; Juan C. Murciano; Ronald P. Taylor; Elena N. Atochina; Angel Herraez

1996-01-01

58

Time-resolved fluorometry of red blood cell membrane conformational changes in a population exposed to low-dose radiation  

NASA Astrophysics Data System (ADS)

Using subnanosecond laser spectrofluorometry the spectral and polarization time-resolved characteristics of 1-phenylnaphthylamine (1-AN) fluorescent probe in phospholipid bilayer and red blood cell (RBC) membranes have been studied. It is shown that the electronic spectra of probe in model membranes inhomogeneously broadened. Inhomogeneous broadening affect significantly the spectroscopic properties of probe in membranes, such as the time-dependent fluorescence Stokes shift, the dependence of the fluorescence instantaneous spectra and fluorescence kinetics on excitation wavelength. The obtained results prove the existence of the earlier unknown effect of the wavelength- dependent rotation of a probe in phospholipid bilayer and RBC membranes.

Nemkovich, Nicolai A.; Kozlovski, Alexander S.; Rubinov, Anatoly N.; Neumerzhicki, V. A.

1994-01-01

59

Deferiprone (Ll) Chelates Pathologic Iron Deposits From Membranes of Intact Thalassemic and Sickle Red Blood Cells Both In Vitro and In Vivo  

Microsoft Academic Search

Red blood cell (RBC) membranes from patients with the thal- assemic and sickle hemoglobinopathies carry abnormal de- posits of iron presumed to mediate a variety of oxidative- induced membrane dysfunctions. We hypothesized that the oral iron chelator deferiprone (LI), which has an enhanced capacity to permeate cell membranes, might be useful in chelating these pathologic iron deposits from intact RBCs.

Oded Shalev; Tanya Repka; Ada Goldfarb; Leonid Grinberg; Ayala Abrahamov; Nancy F. Olivieri; Eliezer A. Rachmilewitz; Robert P. Hebbel

2008-01-01

60

Depletion of Omega3 Fatty Acid Levels in Red Blood Cell Membranes of Depressive Patients  

Microsoft Academic Search

Background: It has been hypothesized that depletion of cell membrane n3 polyunsaturated fatty acids (PUFA), particularly docosahexanoic acid (DHA), may be of etiological importance in depression.Methods: We measured the fatty acid composition of phospholipid in cell membranes from red blood cells (RBC) of 15 depressive patients and 15 healthy control subjects.Results: Depressive patients showed significant depletions of total n3 PUFA

Malcolm Peet; Brendan Murphy; Janet Shay; David Horrobin

1998-01-01

61

Polarizability of red blood cells with an anisotropic membrane  

NASA Astrophysics Data System (ADS)

We predict the complex polarizability of a realistic model of a red blood cell (RBC), with an inhomogeneous dispersive and anisotropic membrane. In this model, the frequency-dependent complex electrical parameters of the individual cell layers are described by the Debye equation while the dielectric anisotropy of the cell membrane is taken into account by the different permittivities along directions normal and tangential to the membrane surface. The realistic shape of the RBC is described in terms of the Jacobi elliptic functions. To calculate the polarizability, we evoke the effective dipole moment method to determine the cell internal electric field distribution, employing an adaptive finite-element numerical approach. We have furthermore investigated the influence of the anisotropic membrane and dispersive electrical parameters of each individual cell layer on the total complex polarizability. Our findings suggest that the individual layer contribution depends on two factors: the volume of the layer and the associated induced electric field, which in turn is influenced by other layers of the cell. These results further show that the average polarizability spectra of the cell are significantly impacted by the anisotropy and associated dispersion of the cellular compartments.

Sebastián, José Luis; Muñoz, Sagrario; Sancho, Miguel; Martínez, Genoveva; Kaler, Karan V. I. S.

2010-02-01

62

Omega3 polyunsaturated fatty acid levels in the diet and in red blood cell membranes of depressed patients  

Microsoft Academic Search

Background: There is a hypothesis that lack of n-3 polyunsaturated fatty acids (PUFAs) is of aetiological importance in depression. Docosahexaenoic acid, a member of the n-3 PUFA family, is a crucial component of synaptic cell membranes. The aim of this study was to measure RBC membrane fatty acids in a group of depressed patients relative to a well matched healthy

Rhian Edwards; Malcolm Peet; Janet Shay; David Horrobin

1998-01-01

63

Effective surface tension of red blood cell membranes induced by cytoskeleton meshworks  

Microsoft Academic Search

The membrane of red blood cell (RBC) consists of a lipid bilayer and a two dimensional cytoskeleton meshwork underneath. Its elastic properties are therefore different from a simple lipid bilayer. We introduced a simple entropic spring model to study the meshwork. In this model, adjacent nodes of the meshwork interact with each other through the link of an entropic spring.

Rui Zhang; Frank Brown

2007-01-01

64

MEMBRANES OF ANIMAL CELLS  

PubMed Central

Turnover studies of the surface membrane and of cell particulate matter of L cells in tissue culture in logarithmic and plateau phase of growth have been made. The rate of incorporation of isotope into these fractions and the rate of fall of specific activities of labeled L-cell fractions have been observed. The following interpretation of the data appears most likely although other interpretations are possible. Growing and nongrowing cells synthesize approximately similar amounts of surface membrane and particulate material. In the growing cell the material is incorporated with net increases in substance. There is relatively little turnover. In the nongrowing cell newly synthesized material is incorporated, but a corresponding amount of material is eliminated so that there is turnover without net increase of substance. Our results suggest that there is no gross differential turnover between the protein, lipid, and carbohydrate of the surface membrane under the conditions of our experiments. Metabolic inhibitors or omission of amino acids in the culture medium lead to a decrease in synthesis of surface membrane and cell particulates and cause an equivalent decrease in the rate of degradation of surface membrane and of particulates; therefore the synthetic and degradative aspects of turnover appear to be coupled. As cultures of nongrowing cells in suspension or on a glass surface age, their synthetic and turnover capacities diminish. Our results suggest that the cell may exist in a nongrowing state with a level of synthesis similar to that of a growing cell. It can exist in this state with a high level of turnover.

Warren, L.; Glick, M. C.

1968-01-01

65

Effects of dietary supplementation of saturated fatty acids and of n?6 or n?3 polyunsaturated fatty acids on plasma and red blood cell membrane phospholipids and deformability in weanling guinea pigs  

Microsoft Academic Search

The fatty acid composition of plasma cholesteryl esters, plasma phospholipids, red blood cell (RBC) membrane phosphatidylcholine\\u000a (corresponding to the outer membrane leaflet), and phosphatidylethanolamine (corresponding to the inner membrane leaflet)\\u000a was investigated in weanling guinea pigs fed with diets of cacao (saturated fatty acids), sunflower oil [n?6 polyunsaturated\\u000a fatty acids (PUFA)] or fish oil (n?3 PUFA) for 20 wk. RBC

Johannes M. B. Pöschl; Karl Paul; Michael Leichsenring; Shan R. Han; Matthias Pfisterer; Hans J. Bremer; Otwin Linderkamp

1999-01-01

66

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

67

Effects of Oral Supplementation of Vitamin E on Fragility of RBC in Hemolytic Anemic Patients with G6PD Deficiency  

Microsoft Academic Search

Background: Vitamin E has role in maintaining the integrity of red cell membrane by preventing oxidation of polyunsaturated fatty acids and thereby protects cells from oxidative stress- induced lysis in G6PD deficiency, which can be reflected by changes in osmotic fragility of RBC and some absolute values like MCV, MCH & MCHC. Objective: To observe the effects of vitamin E

Nayma Sultana; Noorzahan Begum; Shelina Begum; Sultana Ferdousi; Taskina Ali

2008-01-01

68

Role of enzyme-treated cells in RBC antibody screening using the gel test: a study of anti-RH1, -RH2, and -RH3 antibodies.  

PubMed

The role of enzyme-treated cells (ETCs) in red blood cell (RBC) antibody screening has been the subject of controversy, and its place in the clinical routine remains to be determined. In this work, plasma samples containing anti-RH1 (anti-D; N = 10), anti-RH2 (anti-C; N = 10), or anti-RH3 (anti-E; N = 10) antibodies were studied. The samples were diluted in nonbuffered or buffered normal saline, as well as in a pool of AB plasma samples. Titers and scores were determined by means of the gel test, using the indirect antiglobulin test (IAT) as well as ETCs, with R(0)r, r'r, or r''r test cells. Our results showed that compared to the IAT, ETCs allowed a clearer detection of anti-RH2 and anti-RH3, but not of anti-RH1 antibodies. Based on our study, it is not clear whether the ETC phase of the gel test should be maintained for RBC antibody screening. PMID:17385674

Conne, Jocelyne; Schneider, Philippe; Tissot, Jean-Daniel

2007-01-01

69

Fuel cell membrane humidification  

DOEpatents

A polymer electrolyte membrane fuel cell assembly has an anode side and a cathode side separated by the membrane and generating electrical current by electrochemical reactions between a fuel gas and an oxidant. The anode side comprises a hydrophobic gas diffusion backing contacting one side of the membrane and having hydrophilic areas therein for providing liquid water directly to the one side of the membrane through the hydrophilic areas of the gas diffusion backing. In a preferred embodiment, the hydrophilic areas of the gas diffusion backing are formed by sewing a hydrophilic thread through the backing. Liquid water is distributed over the gas diffusion backing in distribution channels that are separate from the fuel distribution channels.

Wilson, Mahlon S. (Los Alamos, NM)

1999-01-01

70

Abnormal transbilayer distribution of phospholipids in red blood cell membranes in schizophrenia.  

PubMed

Abnormalities in membrane lipids have been repeatedly reported in patients with schizophrenia. These abnormalities include decreased phosphatidylethanolamine (PE) and n-3 and n-6 polyunsaturated fatty acids in peripheral and brain cell membranes. The present study investigates the hypothesis of an overrepresentation of PE in the external leaflet of the red blood cell (RBC) membrane in patients with schizophrenia. The assumption was that this modification of PE asymmetrical distribution could explain the reported lipid membrane abnormalities. Phosphatidylethanolamine located in the external leaflet was specifically labeled in RBC membranes from 65 medicated patients with schizophrenia and 38 healthy controls. Labeled (external) and non-labeled (internal) PE and their respective fatty acid composition were analyzed by mass spectrometry. A significant increase in the percentage of external leaflet PE was found in RBC membranes in 63.1% of the patients. In this subgroup, a significant depletion of n-3 and n-6 polyunsaturated fatty acids from internally located PE was also observed. Age, sex and antipsychotic treatment were not associated with the transbilayer membrane distribution of PE. Potential mechanisms underlying these abnormalities may involve membrane phospholipid transporters or degradative enzymes involved in phospholipid metabolism. The anomaly described could characterize a subgroup among patients with schizophrenia. PMID:19646766

Nuss, Philippe; Tessier, Cedric; Ferreri, Florian; De Hert, Marc; Peuskens, Joseph; Trugnan, Germain; Masliah, Joelle; Wolf, Claude

2009-07-30

71

Sialoglycosylation of RBC in visceral leishmaniasis leads to enhanced oxidative stress, calpain-induced fragmentation of spectrin and hemolysis.  

PubMed

Visceral leishmaniasis (VL) caused by the intracellular parasite Leishmania donovani accounts for an estimated 12 million cases of human infection. It is almost always associated with anemia, which severely complicates the disease course. However, the pathological processes leading to anemia in VL have thus far not been adequately characterized to date. In studying the glycosylation patterns of peripheral blood cells we found that the red blood cells (RBC) of VL patients (RBC(VL)) express eight 9-O-acetylated sialoglycoproteins (9-O-AcSGPs) that are not detected in the RBC of healthy individuals (RBC(N)). At the same time, the patients had high titers of anti-9-O-AcSGP IgG antibodies in their sera. These two conditions appear to be linked and related to the anemic state of the patients, as exposure of RBC(VL) but not RBC(N) to anti-9-O-AcSGPs antibodies purified from patient sera triggered a series of responses. These included calcium influx via the P/Q-type but not L-type channels, activation of calpain I, proteolysis of spectrin, enhanced oxidative stress, lipid peroxidation, externalization of phosphatidyl serine with enhanced erythrophagocytosis, enhanced membrane fragility and, finally, hemolysis. Taken together, this study suggests that the enhanced hemolysis is linked to an impairment of membrane integrity in RBC(VL) which is mediated by ligand-specific interaction of surface 9-O-AcSGPs. This affords a potential explanation for the structural and functional features of RBC(VL) which are involved in the hemolysis related to the anemia which develops in VL patients. PMID:22860118

Samanta, Sajal; Ghoshal, Angana; Bhattacharya, Kaushik; Saha, Bibhuti; Walden, Peter; Mandal, Chitra

2012-07-31

72

Measurement of RBC deformation and velocity in capillaries in vivo  

Microsoft Academic Search

Red blood cells (RBC) become deformed while flowing through capillaries. We captured images of blood flow in capillaries and of RBC in the rat mesentery using a high-speed camera at 2000 frames\\/s and then directly measured and estimated the deformation and velocity of RBC in a non-uniform capillary. The distribution of the capillary diameter was determined by image processing. We applied

Jae Hong Jeong; Yasusiko Sugii; Motomu Minamiyama; Koji Okamoto

2006-01-01

73

Rh proteins: Key structural and functional components of the red cell membrane  

Microsoft Academic Search

Rh (Rhesus) proteins (D, CcEe) are expressed in red cells (RBC) in association with other membrane proteins (RhAG, LW, CD47 and GPB). By interacting with the spectrin-based skeleton through protein 4.2 and ankyrin, the Rh complex contributes to the maintenance of the mechanical properties of the erythrocyte membrane. The RH system is one of the most immunogenic and polymorphic human

Caroline Le Van Kim; Yves Colin; Jean-Pierre Cartron

2006-01-01

74

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

NASA Astrophysics Data System (ADS)

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 remodeling. To measure the light scattering signal from individual RBCs, we use diffraction phase microscopy together with a Fourier transform light scattering technique. RBC cytosolic ATPs are both chemically and metabolically depleted, and the corresponding scattering signals are compared with the light scattering signal of normal RBCs having physiologic levels of ATP.

Park, Yongkeun; Best-Popescu, Catherine A.; Dasari, Ramachandra R.; Popescu, Gabriel

2011-01-01

75

Cyclosporin A-Associated Changes in Red Blood Cell Membrane Composition, Deformability, Blood and Plasma Viscosity in Rats  

Microsoft Academic Search

Most of the studies concerning the effects of cyclosporin A (Cs A) on red blood cell (RBC) rheology were carried out in human transplant recipients who may still have residual insufficiency and concomitant administration of other immunosuppressive and antihypertensive drugs. The aim of this study is to evaluate the effects of Cs A on red cell rheology and membrane composition

Evin Ademoglu; Sule Tamer; Isil Albeniz; Cahide Gokkusu; Sevda Tanrikulu

2004-01-01

76

Membrane Compartmentalization in Southeast Asian Ovalocytosis Red Blood Cells  

PubMed Central

Summary Red blood cells (RBCs) from individuals with Southeast Asian ovalocytosis (SAO) contain a mutant band 3 protein that causes the formation of unique linear oligomers in the RBC membrane. We used single-particle tracking to measure the lateral diffusion of individual glycophorin C (GPC), band 3, and CD58 proteins in membranes of intact SAO RBCs and normal RBCs (nRBCs). GPC, an integral protein that binds with high affinity to the RBC membrane skeleton, showed oscillatory motion within confinement areas that were smaller in SAO RBCs than in nRBCs. The additional confinement in SAO RBCs could be due to membrane stiffening associated with the SAO phenotype. Band 3 in both SAO RBCs and nRBCs also showed confined motion over short times (ms) and distances (nm), and the area of confinement was smaller in SAO RBCs than in nRBCs. These data presumably reflect the constraints imposed by band 3 oligomerization. Similarly, the glycosylphosphatidylinositol-linked protein CD58 showed loosely confined diffusion in nRBCs and a substantially higher degree of confinement in SAO RBCs. Restricted protein mobility could contribute to the altered adherence of parasite-infected RBCs to vascular endothelium that is thought to protect individuals with SAO from severe manifestations of malaria.

Mirchev, Rossen; Lam, Alexander; Golan, David E.

2011-01-01

77

Nitric Oxide Red Blood Cell Membrane Permeability at high and low Oxygen Tension  

PubMed Central

Red blood cell (RBC) encapsulated hemoglobin in the blood scavenges nitric oxide (NO) much more slowly than cell-free hemoglobin would. Part of this reduced NO scavenging has been attributed to an intrinsic membrane barrier to diffusion of NO through the RBC membrane. Published values for the permeability of RBCs to NO vary over several orders of magnitude. Recently, the rate that RBCs scavenge NO has been shown to depend on the hematocrit (percentage volume of RBCs) and oxygen tension. The difference in rate constants was hypothesized to be due to oxygen modulation of the RBC membrane permeability, but also could have been due to the difference in bimolecular rate constants for the reaction of NO and oxygenated vs deoxygenated hemoglobin. Here we model NO scavenging by RBCs under previously published experimental conditions. A finite-element based computer program model is constrained by published values for the reaction rates of NO with oxygenated and deoxygenated hemoglobin as well as RBC NO scavenging rates. We find that the permeability of RBCs to NO under oxygenated conditions is between 4,400 ?m/s and 5,100 ?m/s while the permeability under deoxygenated conditions is greater than 64,000 ?m/s. The permeability changes by a factor of 10 or more upon oxygenation of anoxic RBCs. These results may have important implications with respect to NO import or export in physiology.

Huang, Kris T.; Huang, Zhi; Kim-Shapiro, Daniel B.

2007-01-01

78

Continuum modeling of cell membranes  

Microsoft Academic Search

In this paper, we develop a finite-deformation model for cell membranes with a view toward characterizing the local mechanical response of membranes in atomic force microscope (AFM) experiments. The membrane is modeled as a 2-D fluid continuum endowed with bending resistance. The general theory is used to obtain equations that describe axisymmetric equilibrium states. The membrane is assumed to enclose

Eveline Baesu; R. E. Rudd; J. Belak; M. McElfresh

2004-01-01

79

Time-resolved fluorometry of red blood cell membrane conformational changes in a population exposed to low-dose radiation  

Microsoft Academic Search

Using subnanosecond laser spectrofluorometry the spectral and polarization time-resolved characteristics of 1-phenylnaphthylamine (1-AN) fluorescent probe in phospholipid bilayer and red blood cell (RBC) membranes have been studied. It is shown that the electronic spectra of probe in model membranes inhomogeneously broadened. Inhomogeneous broadening affect significantly the spectroscopic properties of probe in membranes, such as the time-dependent fluorescence Stokes shift, the

Nicolai A. Nemkovich; Alexander S. Kozlovski; Anatoly N. Rubinov; V. A. Neumerzhicki

1994-01-01

80

Influence of moxaverine hydrochloride on membrane curvature and microsieve filterability of red cells after exposure to hyperosmolarity and lactacidosis.  

PubMed

Using a combination of novel techniques to assess quantitatively the shape and the filterability of red blood cells (RBC) after exposure to stress conditions (400 mosmol/l, lactacidosis, pH 6.8), the effects of 1-benzyl-3-ethyl-6,7-dimethoxy-isoquinoline hydrochloride (moxaverine-HCl, Kollateral) were tested. The shape of freely suspended RBC was quantified using the tangent count procedure. The filterability (microrheological performance) of leukocyte-free RBC suspensions was determined by computer-assisted conductometry using novel precision metal microsieves with uniform pore diameter of 4.2 micron. Moxaverine, when present in doses between 10(-5) und 10(-2) mol/l while the RBC are stressed, restored both the normal discoid red cell configuration and the microrheological performance when tested under low shear stresses. The data show that moxaverine, a papaverine derivative, hitherto considered as a classical vasodilator exerts protective effects on RBC membrane curvature and whole cell microrheological behavior (performance). The protective effects manifest themselves when the RBC's are exposed to abnormal biochemical conditions such as they might occur in poststenotic areas, where hypoxic ischemia is known to lead to a combination of hyperosmolarity and lactacidosis which modify the RBCs. PMID:3415714

Schmid-Schönbein, H; Schröder, S; Grebe, R; Artmann, G; Eschweiler, H; Teitel, P

1988-05-01

81

The cell membrane and receptors  

Microsoft Academic Search

The cell membrane, the plasmalemma, separates the intracellular fluid (ICF) from the surrounding extracellular fluid (ECF), and acts as an interface between the cell's environment and its contents. Because the ICF and ECF differ in composition, the cell membrane must act as a barrier; however, the metabolism of the cell requires the entry of raw materials and the exit of

James Waterhouse

2004-01-01

82

Lateral Diffusion of Membrane Proteins at Cell Membrane  

Microsoft Academic Search

The cell membrane is an important organ of living cells, which has a complex structure influenced by the interaction between membrane proteins and cell membrane. On the basis of fluid motion and diffusion interaction, a simple model is proposed to evaluate quantitatively the effects of the protein size and membrane fluid velocity on the lateral diffusion of membrane proteins at

Lei Fan; Tian You Fan

2010-01-01

83

The effect of alcohols on red blood cell mechanical properties and membrane fluidity depends on their molecular size.  

PubMed

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; Ajdžanovi?, Vladimir; Spasojevi?, Ivan; Meiselman, Herbert J; Baskurt, Oguz K

2013-09-23

84

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.

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

2013-01-01

85

Characterization and Comparison of the Red Blood Cell Membrane Damage in Severe Human a- and f3Thalassemia  

Microsoft Academic Search

The aim of the present work was to understand the patho- physiology of the severe human thalassemias as represented by pthalassemia intermedia and hemoglobin (Hb) H (a- thalassemia) disease. We have previously shown that the material properties of the red blood cell (RBC) and its membrane differ in severe a- and p-thalassemia, and we now show that this difference is

R. Advani; S. Sorenson; E. Shinar; W. Lande; E. Rachmilewitz; S. L. Schrier

1992-01-01

86

Deferiprone (L1) chelates pathologic iron deposits from membranes of intact thalassemic and sickle red blood cells both in vitro and in vivo.  

PubMed

Red blood cell (RBC) membranes from patients with the thalassemic and sickle hemoglobinopathies carry abnormal deposits of iron presumed to mediate a variety of oxidative-induced membrane dysfunctions. We hypothesized that the oral iron chelator deferiprone (L1), which has an enhanced capacity to permeate cell membranes, might be useful in chelating these pathologic iron deposits from intact RBCs. We tested this hypothesis in vitro by incubating L1 with RBCs from 15 patients with thalassemia intermedia and 6 patients with sickle cell anemia. We found that removal of RBC membrane free iron by L1 increased both as a function of time of incubation and L1 concentration. Thus, increasing the time of incubation of thalassemic RBCs with 0.5 mmol/L L1 from 0.5 to 6 hours, enhanced removal of their membrane free iron from 18% +/- 9% to 96% +/- 4%. Dose-response studies showed that incubating thalassemic RBC for 2 hours with L1 concentrations ranging from 0.125 to 0.5 mmol/L resulted in removal of membrane free iron from 28% +/- 15% to 68% +/- 11%. Parallel studies with sickle RBCs showed a similar pattern in time and dose responses. Deferoxamine (DFO), on the other hand, was ineffective in chelating membrane free iron from either thalassemic or sickle RBCs regardless of dose (maximum, 0.333 mmol/L) or time of incubation (maximum, 24 hours). In vivo efficacy of L1 was shown in six thalassemic patients whose RBC membrane free iron decreased by 50% +/- 29% following a 2-week course of L1 at a daily dose of 25 mg/kg. As the dose of L1 was increased to 50 mg/kg/d (n = 5), and then to 75 mg/kg/d (n = 4), 67% +/- 14% and 79% +/- 11%, respectively, of their RBC membrane free iron was removed. L1 therapy--both in vitro and in vivo--also significantly attenuated the malondialdehyde response of thalassemic RBC membranes to in vitro stimulation with peroxide. Remarkably, the heme content of RBC membranes from L1-treated thalassemic patients decreased by 28% +/- 10% during the 3-month study period. These results indicate that L1 can remove pathologic deposits of chelatable iron from thalassemic and sickle RBC membranes, a therapeutic potential not shared by DFO. Furthermore, membrane defects possibly mediated by catalytic iron, such as lipid peroxidation and hemichrome formation, may also be alleviated, at least in part, by L1. PMID:7655028

Shalev, O; Repka, T; Goldfarb, A; Grinberg, L; Abrahamov, A; Olivieri, N F; Rachmilewitz, E A; Hebbel, R P

1995-09-01

87

Lateral Diffusion of Membrane Proteins at Cell Membrane  

NASA Astrophysics Data System (ADS)

The cell membrane is an important organ of living cells, which has a complex structure influenced by the interaction between membrane proteins and cell membrane. On the basis of fluid motion and diffusion interaction, a simple model is proposed to evaluate quantitatively the effects of the protein size and membrane fluid velocity on the lateral diffusion of membrane proteins at the cell membrane. The study shows that the diffusion coefficient is a dominant factor on the lateral diffusion.

Fan, Lei; Fan, Tian You

88

Autoxidation and effects of pro- and antioxidants in lyophilized red blood cell membranes  

Microsoft Academic Search

Oxygen uptake and effects of pro- and antioxidants have been compared at 80 C in lyophilized red blood cell (RBC) bilayer\\u000a membranes (ghosts). In this dry and relatively immobile system, catalytic metals have pronounced effects. When ghosts are\\u000a prepared in the usual manner, in phosphate buffer, hypotonic saline, or deionized water (DI), oxygen uptake is extremely slow\\u000a and limited unless:

W. L. Porter; A. S. Henick; F. Murphy; R. Colgan; G. Porfert

1978-01-01

89

Liposomes alter thermal phase behavior and composition of red blood cell membranes  

Microsoft Academic Search

Unilamellar liposomes composed of natural phospholipids provide a new promising class of protective agents for hypothermic storage, cryopreservation, or freeze-drying of red blood cells (RBCs). In this study, FTIR spectroscopy, MALDI-TOF MS, and colorimetric assays were used to investigate the effects of liposomes composed of a homologous series of linear saturated phosphatidylcholine phospholipids (18:0; 16:0; 14:0; 12:0) on RBC membranes.

Christoph Stoll; Hart Stadnick; Oliver Kollas; Jelena L. Holovati; Birgit Glasmacher; Jason P. Acker; Willem F. Wolkers

2011-01-01

90

Membrane skeletal protein S-glutathionylation and hemolysis in human red blood cells  

Microsoft Academic Search

In this work, protein–glutathione mixed disulfide formation in human red blood cells (RBCs) was evaluated in vitro by using the thiol-specific reagent diamide. We investigated what mechanism could lead to S-glutathionylation of membrane skeletal proteins, what are the main target proteins, and the correlation between protein S-glutathionylation and RBC hemolysis. Diamide caused a decrease in the reduced form of glutathione

Ranieri Rossi; Daniela Giustarini; Aldo Milzani; Isabella Dalle-Donne

2006-01-01

91

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

92

Investigating effects of nano-particles infiltration on mechanical properties of cell membrane using atomic force microscopy  

NASA Astrophysics Data System (ADS)

In this paper, we introduce our finding of the effects of C60 nanoparticles (NP) infiltration on mechanical properties of cell and its membrane. Atomic force microscopy (AFM) is used to perform indentation on both normal and C60 infiltrated red blood cells (RBC) to gain data of mechanical characteristics of the membrane. Our results show that the mechanical properties of human RBC membrane seem to be altered due to the presence of C60 NPs. The resistance and ultimate strength of the C60 infiltrated RBC membrane significantly decrease. We also explain the mechanism of how C60 NPs infiltration changes the mechanical properties of the cell membrane by predicting the structural change of the lipid bilayer caused by the C60 infiltration at molecular level and analyze the interactions among molecules in the lipid bilayer. The potential hazards and application of the change in mechanical characteristics of the RBCs membrane are also discussed. Nanotoxicity of C60 NPs may be significant for some biological cells.

Zhang, XiaoYue; Zhang, Yong; Zheng, Yue; Wang, Biao

2012-06-01

93

Cell micromanipulation: Influence of an ionic contrast medium on the erythrocyte membrane elasticity modulus  

NASA Astrophysics Data System (ADS)

The effect of ioxitalamate, a radiological contrast medium, on red blood cell (RBC) elastic properties has been studied. Individual red blood cells are gently aspirated by an accurately controlled pressure into the tip of a glass micropipette. Cells are deformed with a well-defined force produced by a very small suction pressure. An elasticity shear modulus is then deduced. At a concentration isoosmotic to plasma, the elasticity shear modulus remains normal. At a concentration hyperosmotic to plasma the elasticity shear modulus is significantly higher than the one obtained for cells suspended in either isoosmotic or hyperosmotic buffer. It can be concluded that the effect of ioxitalamate at a volume ratio of 20% on elastic properties of RBC is related to membrane changes and not to the increase in osmolality.

Bucherer, C.; Lacombe, C.; Lelievre, J. C.

1991-05-01

94

Effective surface tension of red blood cell membranes induced by cytoskeleton meshworks  

NASA Astrophysics Data System (ADS)

The membrane of red blood cell (RBC) consists of a lipid bilayer and a two dimensional cytoskeleton meshwork underneath. Its elastic properties are therefore different from a simple lipid bilayer. We introduced a simple entropic spring model to study the meshwork. In this model, adjacent nodes of the meshwork interact with each other through the link of an entropic spring. We run Monte Carlo and Brownian dynamics simulations, and developed some simple analytical theories to understand the simulation results. For a complete meshwork, we found that the cytoskeleton meshwork produced an effective surface tension to the RBC membrane, as far as the height fluctuation of the membrane is considered. This surface tension depends on the wave length of the fluctuation, and shows a crossover at the wave length of the average mesh size. We also studied the case when a fraction of randomly chosen links are disconnected from the nodes, possibly with the help of ATP. In this case, the surface tension changes with the fraction of connected links. Most interestingly, we found a percolation phase transition of the surface tension at long wave length limit. We discussed the experimental results related to our theory. Our model may improve the understanding of certain functions the RBC membrane related to its elastic properties.

Zhang, Rui; Brown, Frank

2007-03-01

95

Metabolic remodeling of the human red blood cell membrane measured by quantitative phase microscopy  

NASA Astrophysics Data System (ADS)

We have quantitatively and systemically measured the morphologies and dynamics of fluctuations in human RBC membranes using a full-field laser interferometry technique that accurately measures dynamic membrane fluctuations. We present conclusive evidence that the presence of adenosine 5'-triphosphate (ATP) facilitates nonequilibrium dynamic fluctuations in the RBC membrane and that these fluctuations are highly correlated with specific regions in the biconcave shape of RBCs. Spatial analysis reveals that these nonequilibrium membrane fluctuations are enhanced at the scale of the spectrin mesh size. Our results indicate the presence of dynamic remodeling in the RBC membrane cortex powered by ATP, which results in nonequilibrium membrane fluctuations.

Park, Yongkeun; Best, Catherine; Auth, Thorsten; Gov, Nir S.; Safran, Samuel; Popescu, Gabriel

2011-02-01

96

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

Microsoft Academic Search

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

1984-01-01

97

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

98

Effects of Fibrinogen on RBC Aggregation and Rouleux Formation  

NASA Astrophysics Data System (ADS)

We employ dissipative particle dynamics (DPD) to study human blood rheology. Specifically, using a multi-scale (MS-RBC) and low-dimensional model (LD-RBC) for modeling red blood cells (RBCs), we study the role of fibrinogen inter-cellular forces in the formation of rouleaux structures at low shear rates. In particular, both models verify that RBC aggregation into rouleaux determines non-Newtonian response and they also predict a non-zero yield stress whose value depends on the fibrinogen concentration.

Fedosov, Dmitry; Pan, Wenxiao; Caswell, Bruce; Gompper, Gerhard; Karniadakis, George

2010-11-01

99

Incorporation of the hydrophobic probe N-t-BOC-L-tyrosine tert-butyl ester to red blood cell membranes to study peroxynitrite-dependent reactions.  

PubMed

We have previously demonstrated that red blood cells (RBC) are an important sink of intravascularly generated peroxynitrite even in the presence of physiological concentrations of CO2 or other plasmatic biotargets. Once inside erythrocytes, peroxynitrite reacts fast with oxyhemoglobin (oxyHb; k2=2 x 10(4) M(-1) s(-1) at 37 degrees C and pH 7.4) and isomerizes to nitrate. Herein, we investigated whether, in spite of the fast diffusion and consumption of extracellularly added peroxynitrite by intraerythrocytic oxyHb, peroxynitrite-dependent radical processes could occur at the RBC membrane, focusing on tyrosine nitration. For this purpose, the hydrophobic tyrosine analogue N-t-BOC-L-tyrosine tert-butyl ester (BTBE) was successfully incorporated for the first time to a biological membrane, that is, RBC membrane, with incorporation yields approximately 1-3 x 10(7) molecules per RBC. The membrane integrity of BTBE-containing RBC was not significantly altered after BTBE incorporation as demonstrated by permeability studies. The probe was then used to study peroxynitrite-dependent reactions. The addition of peroxynitrite to BTBE-containing RBC suspensions resulted in BTBE nitration and dimerization to 3-nitro-BTBE and 3,3'-di-BTBE, respectively, indicative of peroxynitrite-derived radicals reactions in the membrane. Peroxynitrite addition to RBC also caused tyrosine nitration of membrane-associated proteins. The free radical nature of the process was also shown by the detection of protein-derived radicals by DMPO-immunospin trapping. While the presence of extracellular CO2 was potently inhibitory of intracellular oxyHb oxidation, membrane protein and BTBE nitration by peroxynitrite at RBC membrane, in spite of the significant peroxynitrite scavenging activity of oxyHb inside the RBC. PMID:17941688

Romero, Natalia; Peluffo, Gonzalo; Bartesaghi, Silvina; Zhang, Hao; Joseph, Joy; Kalyanaraman, Balaraman; Radi, Rafael

2007-10-18

100

Disorders of red cell membrane.  

PubMed

Studies during the last three decades have enabled the development of detailed molecular insights into the structural basis of altered function in various inherited red cell membrane disorders. This review highlights our current understanding of molecular and mechanistic insights into various inherited red cell membrane disorders involving either altered membrane structural organization (hereditary spherocytosis, hereditary elliptocytosis and hereditary ovalocytosis) or altered membrane transport function (hereditary stomatocytosis). The molecular basis for the vast majority of cases of hereditary spherocytosis, elliptocytosis and ovalocytosis have been fully defined while little progress has been made in defining the molecular basis for hereditary stomatocytosis. Mutations in a number of distinct genes account for hereditary spherocytosis and elliptocytosis, while a single genetic defect accounts for all cases of hereditary ovalocytosis. Based on these molecular insights, a comprehensive understanding of the structural basis for altered membrane function has been developed. Loss of vertical linkage between membrane skeleton and lipid bilayer leads to membrane loss in hereditary spherocytosis, while weakening of lateral linkages between skeletal proteins leads to membrane fragmentation and surface area loss in hereditary elliptocytosis. Importantly, the severity of anaemia in both these disorders is directly related to extent of membrane surface area loss. Splenectomy results in amelioration of anaemia. PMID:18341630

An, Xiuli; Mohandas, Narla

2008-03-12

101

The Molecules of the Cell Membrane.  

ERIC Educational Resources Information Center

|Cell membrane molecules form a simple, two-dimensional liquid controlling what enters and leaves the cell. Discusses cell membrane molecular architecture, plasma membranes, epithelial cells, cycles of endocytosis and exocytosis, and other topics. Indicates that some cells internalize, then recycle, membrane area equivalent to their entire surface…

Bretscher, Mark S.

1985-01-01

102

Predicting dynamics and rheology of blood flow: A comparative study of multiscale and low-dimensional models of red blood cells  

Microsoft Academic Search

We compare the predictive capability of two mathematical models for red blood cells (RBCs) focusing on blood flow in capillaries and arterioles. Both RBC models as well as their corresponding blood flows are based on the dissipative particle dynamics (DPD) method, a coarse-grained molecular dynamics approach. The first model employs a multiscale description of the RBC (MS-RBC), with its membrane

Wenxiao Pan; Dmitry A. Fedosov; Bruce Caswell; George Em Karniadakis

2011-01-01

103

Effects of age-dependent membrane transport changes on the homeostasis of senescent human red blood cells  

PubMed Central

Little is known about age-related changes in red blood cell (RBC) membrane transport and homeostasis. We investigated first whether the known large variation in plasma membrane Ca2+ (PMCA) pump activity was correlated with RBC age. Glycated hemoglobin, Hb A1c, was used as a reliable age marker for normal RBCs. We found an inverse correlation between PMCA strength and Hb A1c content, indicating that PMCA activity declines monotonically with RBC age. The previously described subpopulation of high-Na+, low-density RBCs had the highest Hb A1c levels, suggesting it represents a late homeostatic condition of senescent RBCs. Thus, the normal densification process of RBCs with age must undergo late reversal, requiring a membrane permeability increase with net NaCl gain exceeding KCl loss. Activation of a nonselective cation channel, Pcat, was considered the key link in this density reversal. Investigation of Pcat properties showed that its most powerful activator was increased intracellular Ca2+. Pcat was comparably selective to Na+, K+, choline, and N-methyl-D-glucamine, indicating a fairly large, poorly selective cation permeability pathway. Based on these observations, a working hypothesis is proposed to explain the mechanism of progressive RBC densification with age and of the late reversal to a low-density condition with altered ionic gradients.

Daw, Nuala; Etzion, Zipora; Tiffert, Teresa; Muoma, Adaeze; Vanagas, Laura; Bookchin, Robert M.

2007-01-01

104

Thylakoid dismantling of damaged unfunctional chloroplasts modulates the Cab and RbcS gene expression in wheat leaves.  

PubMed

Thylakoid membrane dismantling and Lhcb and RbcS nuclear gene expression have been analysed in leaves of wheat plants grown in high fluence rate light and deprived of photoprotective carotenoids by treatments with the two bleaching herbicides, either norflurazon or amitrole. The Lhcb transcript was not detectable in cells of norflurazon-supplied leaves, having chloroplasts totally devoid of both inner membranes and pigments. In contrast, a substantial amount of Lhcb mRNA could be found in cells of amitrole-treated leaves, whose severely damaged organelles still contained few strikingly altered and photosynthetically unfunctional thylakoids, as well as chlorophyll traces. A possible relationship between chlorophyll synthesis and Lhcb expression, with the transcript level depending on the rate of pigment production in photodamaged chloroplasts is discussed. Also the RbcS expression was linked to the chloroplast membrane photodamage. However, a detectable level of transcript was still produced in norflurazon-treated cells, despite complete thylakoid demolition. Thus, the wheat cell behaviour had to be placed between that of species, such as maize, in which the RbcS expression is broken off in these conditions, and that of species, such as pea, in which it is slightly lowered. Interestingly, the dramatically photodamaged chloroplasts still maintained the ability to synthesize proteins and this allowed SSU and LSU Rubisco subunits to be found in the organelles of both norflurazon- and amitrole-treated plants. PMID:14975404

La Rocca, Nicoletta; Barbato, Roberto; Bonora, Angelo; Dalla Valle, Luisa; De Faveri, Stefania; Rascio, Nicoletta

2004-02-20

105

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

2010-06-28

106

Maize rbcS promoter activity depends on sequence elements not found in dicot rbcS promoters.  

PubMed

Although the molecular mechanisms of dicot photosynthetic gene regulation have been pursued actively, comparable studies of monocot regulation have been slow to come forth. We show here that monocot (maize and wheat) but not dicot (pea, tobacco, and Arabidopsis) ribulose-1,5-bisphosphate carboxylase small subunit (rbcS) gene promoters are active in maize mesophyll protoplasts. The evolutionarily conserved GT and G boxes of dicot rbcS promoters are not essential for light-responsive expression in monocot leaf cells. Instead, at least six constitutive and light-sensitive regulatory elements are likely important for maize rbcS expression. Synergism between upstream and downstream promoter elements is required. Whereas in dicots, light triggers coupled leaf development and photosynthetic gene expression, in monocots, light regulation of rbcS is uncoupled from leaf development. Light regulation of maize rbcS may be divided into direct and indirect contributions mediated by different regulatory elements. Because wheat and maize rbcS promoters show sequence homologies and similar expression patterns in monocot and dicot leaf cells, it appears likely that monocots share conserved regulatory elements irrespective of whether they utilize the C3 or C4 pathway for carbon fixation. PMID:1822995

Schäffner, A R; Sheen, J

1991-09-01

107

Multiple stages of detergent-erythrocyte membrane interaction—A spin label study  

Microsoft Academic Search

The various stages of the interaction between the detergent Triton X-100 (TTX-100) and membranes of whole red blood cells (RBC) were investigated in a broad range of detergent concentrations. The interaction was monitored by RBC hemolysis–assessed by release of intracellular hemoglobin (Hb) and inorganic phosphate–and by analysis of EPR spectra of a fatty acid spin probe intercalated in whole RBC

Paulo S. C. Preté; Cleyton C. Domingues; Nilce C. Meirelles; Sônia V. P. Malheiros; Félix M. Goñi; Eneida de Paula; Shirley Schreier

2011-01-01

108

The effect of curvature on the undulation spectrum of Red Blood Cell membranes  

NASA Astrophysics Data System (ADS)

The human red blood cell (RBC) membrane has a composite structure of a fluid lipid bilayer tethered to an elastic 2D spectrin network. The study of the mechanical properties of RBCs is crucial to our understanding of their ability withstand large amplitude deformations during their passage through the microvasculature. The linear mechanical response of this composite membrane can be measured by observing its undulatory dynamics in thermal equilibrium, i.e. microrheology. Previous models of these dynamics postulated an effective surface tension. In this talk, we show that surface tension is not necessary. Rather, the coupling of membrane bending to spectrin network compression by curvature can account for the observed dynamics. We use a simplified theoretical model to describe the undulatory dynamics of RBCs, measured experimentally by the Popescu group.ootnotetextG. Popescu et al. ``Imaging red blood cell dynamics by quantitative phase microscopy, Blood Cells, Molecules, and Diseases, (2008), in print'' Analyzing their data using our model, we observe dramatic changes in RBC membrane elasticity associated with cells' morphological transition from discocytes to echinocyte to spherocyte.

Kuriabova, Tatiana; Henle, Mark L.; Levine, Alex J.

2009-03-01

109

[Alterations in erythrocyte membrane. Effect of neutrophil activation].  

PubMed

White blood cells, especially polymorphonuclear neutrophils (PMN), are known to alter some hemorheological parameters. Most of in vitro results have been obtained with passive PMN. Stimulated PMN also lead to other hemorheological changes. In our study, we have firstly activated PMN with opsonized zymosan and collected a PMN-free supernatant after 30 minutes activation. This supernatant was secondarily incubated with erythrocytes either in whole blood or in suspension. After 10 minutes incubation, hemorheological parameters were evaluated: 1) red blood deformability (RBC) (Ektacytometer* Technicon), 2) RBC filtration (Hemorheometer MK 1), 3) RBC aggregation (Erythroaggregometer* Sefam), 4) Plasmatic and whole blood viscosities (Low Shear 30* Contraves). Our results show that activated PMN-supernatant increases rigidity index (IR) of RBC in suspensions (IR of RBC control = 14.59 +/- 3.30 towards RI of incubated RBC = 22.91 +/- 7.06 p less than 0.001). Other rheological parameters remain unchanged. Activated PMN suspenatant influence on RBC is slight but could suggest of an alteration of RBC membrane. With an in vitro model of washed platelets aggregation, we have previously demonstrated that proaggregant activity of PMN supernatant was inhibited by specific Platelet-Activating Factor (PAF-acether) antagonists: BN 52021, BN 50723, Web 2086. We have so compared both effects of activated PMN-supernatant and synthetic PAF-acether on RBC membrane fluidity. Membrane fluidity was studied by fluorescence polarization of 4 probes embedded at different deep in the membrane of intact RBC. Similar modifications of RBC membrane fluidity are observed with either synthetic PAF-acether or PMN supernatant.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1940654

Petitfrere, E; Nguyen, P; Mailliot, J L; Culioli-Pickel, B; Potron, G

1991-01-01

110

Pervaporation membranes in direct methanol fuel cells  

Microsoft Academic Search

The membranes in direct methanol fuel cells must both conduct protons and serve as a barrier for methanol. Nafion, the most common fuel cell membrane, is an excellent conductor but a poor barrier. Polyvinyl alcohol pervaporation membranes are good methanol barriers but poor conductors. These and most other pervaporation membranes offer no significant advantages over Nafion in methanol fuel cell

Bryan S. Pivovar; Yuxin Wang; E. L. Cussler

1999-01-01

111

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.

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

1974-01-01

112

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

113

Wrinkled Membrane Morphology of Biological Cell  

NASA Astrophysics Data System (ADS)

Membranes of many biological cells possess a wrinkled surface topology that, in some instance, serves as a reservoir for providing large surface area and membrane expansion during osmotic swelling. We consider and model the development of the wrinkled morphology to result from buckling instabilities which occur during the membrane growth. In particular, we examine the wrinkled membrane morphology of white blood cell experimentally and numerically. Our results show that the deformation mismatch between the membrane and the cytoskeleton during membrane growth triggers buckling of the membrane. This behavior of the wrinkled topology enables expansion of the cell during swelling and reveals interesting details on the role of the membrane topology.

Wang, Lifeng; Castro, Carlos; Boyce, Mary

2010-03-01

114

Dynamics of Interaction of RBC with optical tweezers  

NASA Astrophysics Data System (ADS)

It has recently been shown that a red blood cell (RBC) can be used as optically driven motor. The mechanism for rotation is however not fully understood. While the dependence on osmolarity of the buffer led us to conclude that the osmolarity dependent changes in shape of the cell are responsible for the observed rotation, role of ion gradients and folding of RBC to a rod shape has been invoked by Dharmadhikari et al to explain their observations. In this paper we report results of studies undertaken to understand the dynamics of a RBC when it is optically tweezed. The results obtained support our earlier conjecture that osmolarity dependent changes in shape of the cell are responsible for the observed rotation.

Mohanty, Samarendra K.; Mohanty, Khyati S.; Gupta, Pradeep Kumar

2005-06-01

115

Faster lactate transport across red blood cell membrane in sickle cell trait carriers.  

PubMed

The physical and physiological behavior of sickle cell trait carriers (AS) is somewhat equivocal under strenuous conditions, although this genetic abnormality is generally considered to be a benign disorder. The occurrence of incidents and severe injuries in AS during exercise might be explained, in part, by the lactic acidosis due to a greater lactate influx into AS red blood cells (RBCs). In the present study, the RBC lactate transport activity via the different pathways was compared between AS and individuals with normal hemoglobin (AA). Sixteen Caribbean students, nine AS and seven AA, performed a progressive and maximal exercise test to determine maximal oxygen consumption. Blood samples were obtained at rest to assess haematological parameters and RBC lactate transport activity. Lactate influxes [total lactate influx and monocarboxylate transporter (MCT-1)-mediated lactate influx] into erythrocytes were measured at four external [14C]-labeled lactate concentrations (1.6, 8.1, 41, and 81.1 mM). The two groups had similar maximal oxygen consumption. Total lactate influx and lactate influx via the MCT-1 pathway were significantly higher in AS compared with AA at 1.6, 41, and 81.1 mM. The maximal lactate transport capacity for MCT-1 was higher in AS than in AA. Although AS and AA had the same maximal aerobic physical fitness, the RBCs from the sickle cell trait carriers took up more lactate at low and high concentrations than the RBCs from AA individuals. The higher MCT-1 maximal lactate transport capacity found in AS suggests greater content or greater activity of MCT-1 in AS RBC membranes. PMID:16239612

Sara, Fagnété; Fagnété, Sara; Connes, Philippe; Philippe, Connes; Hue, Olivier; Olivier, Hue; Montout-Hedreville, Mona; Mona, Montout-Hedreville; Etienne-Julan, Maryse; Maryse, Etienne-Julan; Hardy-Dessources, Marie-Dominique; Marie-Dominique, Hardy-Dessources

2005-10-20

116

Changes in serum and red blood cell membrane lipids in patients treated with interferon ribavirin for chronic hepatitis C  

Microsoft Academic Search

One of the side effects by interferon ribavirin (I\\/R) treatment is haemolytic anemia, causing some patients to discontinue I\\/R treatment. The exact mechanism of I\\/R-induced anemia is unknown. The aim of this study is to evaluate the effects of I\\/R treatment on the serum lipid and red blood cell (RBC) membrane lipid profiles of patients with chronic hepatitis C (CHC)

H. Tanaka; M. Miyano; H. Ueda; K. Fukui; M. Ichinose

2005-01-01

117

Elasticities and stabilities: lipid membranes vs cell membranes  

Microsoft Academic Search

A cell membrane can be simply regarded as composite material consisting of lipid bilayer, membrane cytoskeleton beneath lipid bilayer, and proteins embedded in lipid bilayer and linked with membrane cytoskeleton if one only concerns its mechanical properties. In this Chapter, above all, the authors give a brief introduction to some important work on mechanical properties of lipid bilayers following Helfrich's

Z. C. Tu; R. An; Z. C. Ou-Yang

2005-01-01

118

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

119

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.  

PubMed

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. PMID:23124094

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

2012-11-02

120

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

121

Amphiphile induced echinocyte-spheroechinocyte transformation of red blood cell shape  

Microsoft Academic Search

A possible physical explanation of the echinocyte-spheroechinocyte red blood cell (RBC) shape transformation induced by the\\u000a intercalation of amphiphilic molecules into the outer layer of the RBC plasma membrane bilayer is given. The stable RBC shape\\u000a is determined by the minimization of the membrane elastic energy, consisting of the bilayer bending energy, the bilayer relative\\u000a stretching energy and the skeleton

A. Igli?; Veronika Kralj-Igli?; Henry Hägerstrand

1998-01-01

122

Experience with eosin-5'-maleimide as a diagnostic tool for red cell membrane cytoskeleton disorders.  

PubMed

The diagnosis of hereditary spherocytosis (HS) is based on red cell morphology and other conventional tests such as osmotic fragility, autohemolysis and acidified glycerol lysis. However, milder cases are at times difficult to diagnose. Confirmation by red blood cell (RBC) membrane protein analysis is not possible in most laboratories. Recently, a flow cytometric method has been described for quantitating the fluorescence intensity of intact red cells after incubation with the dye eosin-5'-maleimide (EMA), which binds specifically to the anion transport protein (band-3) at lysine-430. This has been shown to be an effective screening test for red cell membrane disorders. We evaluated the usefulness of this approach for screening membrane protein disorders such as HS and hereditary elliptocytosis (HE) and its value in discriminating this group from other hemolytic anemias, such as glucose-6-phosphate dehydrogenase (G6PD) deficiency, beta-thalassemia trait, sickle cell anemia and autoimmune hemolytic anemia. Fluorescence intensity, expressed in mean channel fluorescence (MCF) units, was determined using a Becton Dickinson FACS Caliber flow cytometer. Membrane protein analysis was carried out by sodium dodecyl sulfate-polyacrylamide gel eletrophoresis (SDS-PAGE). RBCs from patients with HS and HE gave significantly lower MCF values (P < 0.001) than the normal control group and other patient groups. The diagnosis of HS in four cases was confirmed by RBC membrane protein electrophoresis and all showed a deficiency of spectrin. The advantage of the EMA dye method are its specificity for membrane disorders, as well as being a simple, user-friendly and rapid method which is inexpensive, provided a flow cytometer is available. PMID:14641141

Kedar, P S; Colah, R B; Kulkarni, S; Ghosh, K; Mohanty, D

2003-12-01

123

Reliability of membrane test cell measurements  

Microsoft Academic Search

Membrane test cells are extensively used for quality assurance, screening tests and in many research projects. However, many practitioners will agree that test cell results may vary considerably and their accuracy can be inadequate for scale-up to larger membrane units. The reliability of test cells is, besides other factors, influenced by small-scale variations of membrane material properties. The performance of

T. Schipolowski; A. Je?owska; G. Wozny

2006-01-01

124

Membrane degradation mechanisms in polymer electrolyte membrane fuel cells  

NASA Astrophysics Data System (ADS)

Membrane degradation and failure is one of the most important factors limiting the lifetime of polymer electrolyte membrane fuel cells (PEMFCs). Increasing the membrane life by developing degradation mitigation strategies in the cell or developing a new membrane with improved life requires a detailed understanding of the membrane degradation mechanism during operation in a PEMFC. An in-situ and nondestructive technique, which relies on the measurement of the membrane degradation rate in a fuel cell, was used to study the chemical/electrochemical mode of membrane degradation. NafionRTM membrane was used for the degradation study and fluoride emission rate (FER) as measured from the fuel cell effluent water analysis was used as a quantitative indicator of the membrane degradation rate. The degradation mechanism was studied by a detailed investigation of the effect of reactants, catalyst properties (location, potential, catalyst type, interaction with O2 and H2O), cell current, membrane thickness, NafionRTM counterion, and direction of water movement on the membrane degradation rate. Based on the experimental findings it is shown that commonly known membrane degradation mechanisms involving formation of active oxygen species from H 2O2 decomposition or the direct formation of active oxygen species in the oxygen reduction reaction are not the dominating membrane degradation mechanisms in PEMFCs. It is proposed that molecular H2 and O 2 react on the surface of Pt catalyst to form the membrane degrading species. Depending upon the catalyst location the source of H2 or O2 or both is from the reactant crossover through the membrane. The reaction mechanism is chemical in nature and depends upon the catalyst surface properties and the relative concentrations of H2 and O 2 at the catalyst. The membrane degradation rate also depends on the residence time of the species in the membrane and the reaction volume i.e. the membrane thickness. Thus, the membrane degradation may not be limited only to the polymer surface in contact with Pt catalyst. The sulfonic acid groups in the NafionRTM side chain are key to the mechanism by which the radical species attack the polymer.

Mittal, Vishal Onkarmal

125

Detecting Microdomains in Intact Cell Membranes  

Microsoft Academic Search

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

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

2005-01-01

126

The proteomics of plant cell membranes  

Microsoft Academic Search

Membrane proteins are involved in many different functions depending on their location in the cell. Characterization of the membrane proteome can bring new insights to the function of different plant membrane systems and the subcellular compartments where the proteins are found. Plant membrane pro- teomics can also provide valuable information about plant-specific biological processes. Despite recent ad- vances in the

Setsuko Komatsu; Hirosato Konishi; Makoto Hashimoto

2010-01-01

127

Competition between Na+ and Li+ for Unsealed and Cytoskeleton-Depleted Human Red Blood Cell Membrane: A 23Na Multiple Quantum Filtered and 7Li NMR Relaxation Study  

NASA Astrophysics Data System (ADS)

Evidence for competition between Li+ and Na+ for binding sites of human unsealed and cytoskeleton-depleted human red blood cell (csdRBC) membranes was obtained from the effect of added Li+ upon the 23Na double quantum filtered (DQF) and triple quantum filtered (TQF) NMR signals of Na+-containing red blood cell (RBC) membrane suspensions. We found that, at low ionic strength, the observed quenching effect of Li+ on the 23Na TQF and DQF signal intensity probed Li+/Na+ competition for isotropic binding sites only. Membrane cytoskeleton depletion significantly decreased the isotropic signal intensity, strongly affecting the binding of Na+ to isotropic membrane sites, but had no effect on Li+/Na+ competition for those sites. Through the observed 23Na DQF NMR spectra, which allow probing of both isotropic and anisotropic Na+ motion, we found anisotropic membrane binding sites for Na+ when the total ionic strength was higher than 40 mM. This is a consequence of ionic strength effects on the conformation of the cytoskeleton, in particular on the dimer-tetramer equilibrium of spectrin. The determinant involvement of the cytoskeleton in the anisotropy of Na+ motion at the membrane surface was demonstrated by the isotropy of the DQF spectra of csdRBC membranes even at high ionic strength. Li+ addition initially quenched the isotropic signal the most, indicating preferential Li+/Na+ competition for the isotropic membrane sites. High ionic strength also increased the intensity of the anisotropic signal, due to its effect on the restructuring of the membrane cytoskeleton. Further Li+ addition competed with Na+ for those sites, quenching the anisotropic signal. 7Li T1 relaxation data for Li+-containing suspensions of unsealed and csdRBC membranes, in the absence and presence of Na+ at low ionic strength, showed that cytoskeleton depletion does not affect the affinity of Na+ for the RBC membrane, but increases the affinity of Li+ by 50%. This clearly indicates that cytoskeleton depletion favors Li+ relative to Na+ binding, and thus Li+/Na+ competition for its isotropic sites. Thus, this relaxation technique proves to be very sensitive to alkali metal binding to the membrane, detecting a more pronounced steric hindrance effect of the cytoskeleton network to binding of the larger hydrated Li+ ion to the membrane phosphate groups.

Srinivasan, Chandra; Minadeo, Nicole; Toon, Jason; Graham, Daniel; Mota de Freitas, Duarte; Geraldes, Carlos F. G. C.

1999-09-01

128

Elasticities and stabilities: lipid membranes vs cell membranes  

Microsoft Academic Search

A cell membrane can be simply regarded as composite material consisting of\\u000alipid bilayer, membrane cytoskeleton beneath lipid bilayer, and proteins\\u000aembedded in lipid bilayer and linked with membrane cytoskeleton if one only\\u000aconcerns its mechanical properties. In this Chapter, above all, the authors\\u000agive a brief introduction to some important work on mechanical properties of\\u000alipid bilayers following Helfrich's

Z. C. Tu; R. An; Z. C. Ou-Yang

2005-01-01

129

Curling and local shape changes of red blood cell membranes driven by cytoskeletal reorganization.  

PubMed

Human red blood cells (RBCs) lack the actin-myosin-microtubule cytoskeleton that is responsible for shape changes in other cells. Nevertheless, they can display highly dynamic local deformations in response to external perturbations, such as those that occur during the process of apical alignment preceding merozoite invasion in malaria. Moreover, after lysis in divalent cation-free media, the isolated membranes of ruptured ghosts show spontaneous inside-out curling motions at the free edges of the lytic hole, leading to inside-out vesiculation. The molecular mechanisms that drive these rapid shape changes are unknown. Here, we propose a molecular model in which the spectrin filaments of the RBC cortical cytoskeleton control the sign and dynamics of membrane curvature depending on whether the ends of the filaments are free or anchored to the bilayer. Computer simulations of the model reveal that curling, as experimentally observed, can be obtained either by an overall excess of weakly-bound filaments throughout the cell, or by the flux of such filaments toward the curling edges. Divalent cations have been shown to arrest the curling process, and Ca2+ ions have also been implicated in local membrane deformations during merozoite invasion. These effects can be replicated in our model by attributing the divalent cation effects to increased filament-membrane binding. This process converts the curl-inducing loose filaments into fully bound filaments that arrest curling. The same basic mechanism can be shown to account for Ca2+-induced local and dynamic membrane deformations in intact RBCs. The implications of these results in terms of RBC membrane dynamics under physiological, pathological, and experimental conditions is discussed. PMID:20682258

Kabaso, Doron; Shlomovitz, Roie; Auth, Thorsten; Lew, Virgilio L; Gov, Nir S

2010-08-01

130

Cell Plasma Membranes and Phase Transitions  

Microsoft Academic Search

Cell plasma membrane phaseplays a large role in membrane trafficking and signaling. The rolethat membrane phase plays in cell\\u000a function, current hypothesesconcerning the size and time duration of the phase transitions, andthe role in disease are discussed.

Mark M. Banaszak Holl

131

Junctional membrane uncoupling. Permeability transformations at a cell membrane junction.  

PubMed

The permeability of the membrane surfaces where cells are in contact (junctional membranes) in Chironomus salivary glands depends on Ca(++) and Mg(++). When the concentration of these ions at the junctional membranes is raised sufficiently, these normally highly permeable membranes seal off; their permeability falls one to three orders, as they approach the nonjunctional membranes in conductance. This permeability transformation is achieved in three ways: (a) by iontophoresis of Ca(++) into the cell; (b) by entry of Ca(++) and/or Mg(++) from the extracellular fluid into the cell through leaks in the cell surface membrane (e.g., injury); or (c) by entry of these ions through leaks arising, probably primarily in the perijunctional insulation, due to trypsin digestion, anisotonicity, alkalinity, or chelation. Ca(++) and Mg(++) appear to have three roles in the junctional coupling processes: (a) in the permeability of the junctional membranes; (b) in the permeability of the perijunctional insulation; and (c) a role long known- in the mechanical stability of the cell junction. The two latter roles may well be closely interdependent, but the first is clearly independent of the others. PMID:6050971

Loewenstein, W R; Nakas, M; Socolar, S J

1967-08-01

132

Influence of network topology on the elasticity of the red blood cell membrane skeleton.  

PubMed Central

A finite-element network model is used to investigate the influence of the topology of the red blood cell membrane skeleton on its macroscopic mechanical properties. Network topology is characterized by the number of spectrin oligomers per actin junction (phi a) and the number of spectrin dimers per self-association junction (phi s). If it is assumed that all associated spectrin is in tetrameric form, with six tetramers per actin junction (i.e., phi a = 6.0 and phi s = 2.0), then the topology of the skeleton may be modeled by a random Delaunay triangular network. Recent images of the RBC membrane skeleton suggest that the values for these topological parameters are in the range of 4.2 < phi a < 5.5 and 2.1 < phi s < 2.3. Model networks that simulate these realistic topologies exhibit values of the shear modulus that vary by more than an order of magnitude relative to triangular networks. This indicates that networks with relatively sparse nontriangular topologies may be needed to model the RBC membrane skeleton accurately. The model is also used to simulate skeletal alterations associated with hereditary spherocytosis and Southeast Asian ovalocytosis. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 11 FIGURE 12 FIGURE 13 FIGURE 14

Hansen, J C; Skalak, R; Chien, S; Hoger, A

1997-01-01

133

Rapid flow cytometric test using eosin-5-maleimide for diagnosis of red blood cell membrane disorders.  

PubMed

Conventional diagnosis of hereditary red blood cell (RBC) membrane disorders, in particular hereditary spherocytosis (HS), is labor intensive, time consuming and requires at least 2 ml of blood, which might be impractical in neonatal period. We evaluated the use of eosin-5-maleimide (EMA), a dye that reacts covalently with lysine-430 on the first extracellular loop of band 3 protein, for rapid screening test of patients with HS and Southeast Asian Ovalocytosis (SAO). Fresh RBCs from 142 healthy controls, 50 HS, 17 SAO, 29 hereditary elliptocytosis, 5 autoimmune hemolytic anemia, 66 patients with beta-thalassemia/HbE, 31 cases with alpha-thalassemia (HbH disease) and 4 cases with pyruvate kinase deficiency were stained with EMA, and analyzed for their mean channel fluorescence (MCF) using a flow cytometer. RBCs from patients with HS and SAO expressed a greater degree of reduction in MCF compared to those from normal controls and other hemolytic diseases. These findings showed that the fluorescence flow cytometric-based method is a simple, sensitive and reliable diagnostic test for RBC membrane disorders using a small volume of blood, and results could be obtained within 2 hours. Such method could serve as a first line screening for the diagnosis of HS and SAO in routine hematology before further specific membrane protein electrophoresis and molecular diagnosis are employed. PMID:19842445

Tachavanich, Kalaya; Tanphaichitr, Voravarn S; Utto, Wiyakan; Viprakasit, Vip

2009-05-01

134

Computational analysis on the mechanical interaction between a thrombus and red blood cells: possible causes of membrane damage of red blood cells at microvessels.  

PubMed

Previous studies investigating thrombus formation have not focused on the physical interaction between red blood cells (RBCs) and thrombus, although they have been speculated that some pathological conditions such as microangiopathic hemolytic anemia (MAHA) stem from interactions between RBCs and thrombi. In this study, we investigated the mechanical influence of RBCs on primary thrombi during hemostasis. We also explored the mechanics and aggravating factors of intravascular hemolysis. Computer simulations of primary thrombogenesis in the presence and the absence of RBCs demonstrated that RBCs are unlikely to affect the thrombus height and coverage, although their presence may change microvessel hemodynamics and platelet transportation to the injured wall. Our results suggest that intravascular hemolysis owing to RBC membrane damage would be promoted by three hemodynamic factors: (1) dispersibility of platelet thrombi, because more frequent spatial thrombus formation decreases the time available for an RBC to recover its shape and enforces more severe deformation; (2) platelet thrombus stiffness, because a stiffer thrombus increases the degree of RBC deformation upon collision; and (3) vessel size and hemocyte density, because a smaller vessel diameter and higher hemocyte density decrease the room for RBCs to escape as they come closer to a thrombus, thereby enhancing thrombus-RBC interactions. PMID:22356820

Kamada, Hiroki; Imai, Yohsuke; Nakamura, Masanori; Ishikawa, Takuji; Yamaguchi, Takami

2012-02-21

135

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.

Day, Charles A.; Kenworthy, Anne K.

2009-01-01

136

Red blood cell membrane defects.  

PubMed

We present an overview of the currently known molecular basis of red cell membrane disorders. A detailed discussion of the structure of the red cell membrane and the pathophysiology and clinical aspects of its disorders is reported. Generally speaking, hereditary spherocytosis (HS) results from a loss of erythrocyte surface area. The mutations of most cases of HS are located in the following genes: ANK1, SPTB, SLC4A1, EPB42 and SPTA1, which encode for ankyrin, spectrin beta-chain, the anion exchanger 1 (band 3), protein 4.2 and spectrin alpha-chain, respectively. Hereditary elliptocytosis (HE) reflects a diminished elasticity of the skeleton. Its aggravated form, hereditary pyropoikilocytosis (HPP), implies that the skeleton undergoes further destabilization. The mutations responsible for HE and HPP, lie in the SPTA1 and SPTB gene, and in the EPB41 gene encoding protein 4.1. Allele alpha LELY is a common polymorphic allele, which plays the role of an aggravating factor when it occurs in trans of an elliptocytogenic allele of the SPTA1 gene. Southeast Asian ovalocytosis derives from a change in band 3. The genetic disorders of membrane permeability to monovalent cations required a positional cloning approach. In this respect, channelopathies represent a new frontier in the field. Dehydrated hereditary stomatocytosis (DHS) was shown to belong to a pleiotropic syndrome: DHS + fetal edema + pseudohyperkalemia, which maps 16q23-24. Splenectomy is strictly contraindicated in DHS and another disease of the same class, overhydrated hereditary stomatocytosis, because it increases the risk of thromboembolic accidents. PMID:14692233

Iolascon, Achille; Perrotta, Silverio; Stewart, Gordon W

2003-03-01

137

Membrane lipids and cell death: an overview  

Microsoft Academic Search

In this article we overview major aspects of membrane lipids in the complex area of cell death, comprising apoptosis and various forms of programmed cell death. We have focused here on glycerophospholipids, the major components of cellular membranes. In particular, we present a detailed appraisal of mitochondrial lipids that attract increasing interest in the field of cell death, while the

Ileana M. Cristea; Mauro Degli Esposti

2004-01-01

138

Red cell membrane Na+ transport systems in hereditary spherocytosis: relevance to understanding the increased Na+ permeability.  

PubMed

Red blood cells (RBCs) in hereditary spherocytosis (HS) show high sodium (Na+) and potassium (K+) movement across the membrane, resulting in dehydration. In general, these abnormal cation fluxes have been interpreted as "increased leaks" due to passive or electrodiffusional permeability of the RBC membrane. A study to elucidate the contribution of concomitant ouabain-resistant pathways (Na-K-2Cl cotransport and Na-Li countertransport) to abnormal Na+ permeability present in RBCs of subjects with HS has been undertaken. Accordingly, erythrocyte Na+ and K+ content and transmembrane cation movements via the Na-K pump, Na-K-2Cl cotransport, Na-Li countertransport, and Na+ passive diffusion, were measured in 25 non-splenectomized patients with HS and compared with the results obtained from the study of 11 patients with congenital non-spherocytic haemolytic anaemia (CNSHA) due to hereditary elliptocytosis (7 cases) and RBC enzyme defects (4 cases) and of 30 normal controls. Compared to the controls, patients with HS exhibited a highly significant (P<0.001) increase in all the Na+ transmembrane movements via passive diffusion (411+/-243 vs 105+/-40), Na-K pump (2615+/-970 vs 1874+/-359), Na-K-2Cl cotransport (males: 371+/-138 vs 190+/-42; females: 401+/-134 vs 104+/-44) and Na-Li countertransport (207+/-131 vs 98+/-41). This was associated with increased Na+ and decreased K+ content, resulting in a reduction of total cation (Na+ + K+) RBC concentration. Furthermore, significant correlations were also found between the patients' RBC cationic content and the mean corpuscular haemoglobin concentration (MCHC) (r=0.51, P<0.05) and between the Na+ passive leak and the haematocrit value (r=-0.44, P<0.05). In the patients with CNSHA, a less significant (P<0.01) increase of active (Na-K pump) and passive (leak) transmembrane permeability to Na+ was associated with normal transmembrane movements via Na-K-2Cl cotransport and Na-Li countertransport. The present study demonstrates that in HS, RBCs are characterized by a variable, but always significant increase of all the membrane transport systems leading to the extrusion of Na+, and that these abnormalities, regardless of their relation to membrane structural defects, may probably be valuable for the differential diagnosis between HS and other congenital defects of RBCs. PMID:11669303

Vives Corrons, J L; Besson, I

2001-09-01

139

Vesicle Trafficking and Cell Surface Membrane Patchiness  

Microsoft Academic Search

Membrane proteins and lipids often appear to be distributed in patches on the cell surface. These patches are often assumed to be membrane domains, arising from specific molecular associations. However, a computer simulation (Gheber and Edidin, 1999) shows that membrane patchiness may result from a combination of vesicle trafficking and dynamic barriers to lateral mobility. The simulation predicts that the

Qing Tang; Michael Edidin

2001-01-01

140

Resistance of cell membranes to different detergents  

Microsoft Academic Search

Partial resistance of cell membranes to solubilization with mild detergents and the analysis of isolated detergent-resistant membranes (DRMs) have been used operationally to define membrane domains. Given the multitude of detergents used for this purpose, we sought to investigate whether extraction with different detergents might reflect the same underlying principle of domain formation. We therefore compared the protein and lipid

Sebastian Schuck; Masanori Honsho; Kim Ekroos; Andrej Shevchenko; Kai Simons

2003-01-01

141

High electrical field effects on cell membranes  

Microsoft Academic Search

Electrical charging of lipid membranes causes electroporation with sharp membrane conductance increases. Several recent observations, especially at very high field strength, are not compatible with the simple electroporation picture. Here we present several relevant experiments on cell electrical responses to very high external voltages. We hypothesize that, not only are aqueous pores created within the lipid membranes, but that nanoscale

U. Pliquett; R. P. Joshi; V. Sridhara; K. H. Schoenbach

2007-01-01

142

Viscoelastic Properties of Red Cell Membrane in Hereditary Elliptocytosis  

Microsoft Academic Search

The viscoelastic properties of the RBC membrane are in part determined by a submembrane network of proteins consisting of spectrin afi heterodimers (SpD) assembled head-to-head to form spectrin tetramers (SpT) and spec- trin oligomers (SpO). SpT, in turn, are connected into a two-dimensional network by the linkage of distal ends of SpT to protein 4.1 and actin. With the micropipette

S. Chien

1989-01-01

143

Determination of red blood cell membrane viscosity from rheoscopic observations of tank-treading motion.  

PubMed Central

Measurements of the dimensions and membrane rotational frequency of individual erythrocytes steadily tank-treading in a rheoscope are used to deduce the surface shear viscosity of the membrane. The method is based on an integral energy principle which says that the power supplied to the tank-treading cell by the suspending fluid is equal to the rate at which energy is dissipated by viscous action in the membrane and cytoplasm. The integrals involved are formulated with the aid of an idealized mathematical model of the tank-treading red blood cell (RBC) (Keller and Skalak, 1982, J. Fluid Mech., 120:24-27) and evaluated numerically. The outcome is a surface-averaged value of membrane viscosity which is representative of a finite interval of membrane shear rate. The numerical values computed show a clear shear-thinning characteristic as well as a significant augmentation of viscosity with cell age and tend toward agreement with those determined for the rapid phase of shape recovery in micropipettes (Chien, S., K.-L. P. Sung, R. Skalak, S. Usami, and A. Tozeren, 1978, Biophys. J., 24:463-487). The computations also indicate that the rate of energy dissipation in the membrane is always substantially greater than that in the cytoplasm. Images FIGURE 2

Tran-Son-Tay, R; Sutera, S P; Rao, P R

1984-01-01

144

Advanced composite polymer electrolyte fuel cell membranes  

Microsoft Academic Search

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 microns thick) are available. The combination of reinforcement and thinness provides high membrane, conductances (80 S\\/cm(exp 2) for a 12-micron thick membrane at 25 degrees C) and improved water distribution in the operating

Mahlon S. Wilson; Thomas A. Zawodzinski; Shimshon Gottesfeld; Jeffrey A. Kolde; Bamdad Bahar

1995-01-01

145

Development of ionomer membranes for fuel cells  

Microsoft Academic Search

In this contribution an overview is given about the state-of-the-art at the membrane development for proton-conductive polymer (composite) membranes for the application membrane fuel cells, focusing on the membrane developments in this field performed at ICVT.For preparation of the polymers, processes have been developed for sulfonated arylene main-chain polymers as well as for arylene main-chain polymers containing basic N-containing groups,

Jochen A. Kerres

2001-01-01

146

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

147

Dicarboxylic acids with limited numbers of hydrocarbons stabilize cell membrane and increase osmotic resistance in rat erythrocytes.  

PubMed

We examined the effect of dicarboxylic acids having 0 to 6 hydrocarbons and their corresponding monocarboxylic or tricarboxylic acids in changing the osmotic fragility (OF) in rat red blood cells (RBCs). Malonic, succinic, glutaric and adipic acids, which are dicarboxylic acids with 1, 2, 3 and 4 straight hydrocarbons located between two carboxylic groups, decreased the OF in a concentration-dependent manner. Other long-chain dicarboxylic acids did not change the OF in rat RBCs. The benzoic acid derivatives, isophthalic and terephthalic acids, but not phthalic acid, decreased the OF in a concentration-dependent manner. Benzene-1,2,3-tricarboxylic acid, but not benzene-1,3,5-tricarboxylic acid, also decreased the OF in rat RBCs. On the other hand, monocarboxylic acids possessing 2 to 7 straight hydrocarbons and benzoic acid increased the OF in rat RBCs. In short-chain dicarboxylic acids, a limited number of hydrocarbons between the two carboxylic groups are thought to form a V- or U-shaped structure and interact with phospholipids in the RBC membrane. In benzene dicarboxylic and tricarboxylic acids, a part of benzene nucleus between the two carboxylic groups is thought to enter the plasma membrane and act on acyl-chain in phospholipids in the RBC membrane. For dicarboxylic and tricarboxylic acids, limited numbers of hydrocarbons in molecules are speculated to enter the RBC membrane with the hydrophilic carboxylic groups remaining outside, stabilizing the structure of the cell membrane and resulting in an increase in osmotic resistance in rat RBCs. PMID:23770357

Mineo, Hitoshi; Amita, Nozomi; Kawawake, Megumi; Higuchi, Ayaka

2013-06-14

148

Emerging Role for Use of Liposomes in the Biopreservation of Red Blood Cells  

PubMed Central

Summary Biopreservation is the process of maintaining the integrity and functionality of cells held outside the native environment for extended storage times. The development of red blood cell (RBC) biopreservation techniques that maintain in vitro RBC viability and function represents the foundation of modern blood banking. The biopreservation of RBCs for clinical use can be categorized based on the techniques used to achieve biologic stability, including hypothermic storage and cryopreservation. This review will examine the emerging role of liposomes in the RBC biopreservation, including the incorporation of liposomes into RBC membranes as an effective approach for minimizing RBC hypothermic storage membrane lesion and use of liposomes as a permeabilization strategy for the intracellular accumulation of novel intracellular cryoprotectants. Integration of current biopreservation research with blood banking practices offers enormous potential for future improvements of safety and efficacy of RBC transfusion.

Holovati, Jelena L.; Acker, Jason P.

2011-01-01

149

Proton Exchange Membranes for Fuel Cells  

SciTech Connect

Proton exchange membrane, also known as polymer electrolyte membrane, fuel cells (PEMFCs) offer the promise of efficient conversion of chemical energy of fuel, such as hydrogen or methanol, into electricity with minimal pollution. Their widespread use to power zero-emission automobiles as part of a hydrogen economy can contribute to enhanced energy security and reduction in greenhouse gas emissions. However, the commercial viability of PEMFC technology is hindered by high cost associated with the membrane electrode assembly (MEA) and poor membrane durability under prolonged operation at elevated temperature. Membranes for automotive fuel cell applications need to perform well over a period comparable to the life of an automotive engine and under heavy load cycling including start-stop cycling under sub-freezing conditions. The combination of elevated temperature, changes in humidity levels, physical stresses and harsh chemical environment contribute to membrane degradation. Perfluorinated sulfonic acid (PFSA)-based membranes, such as Nafion®, have been the mainstay of PEMFC technology. Their limitations, in terms of cost and poor conductivity at low hydration, have led to continuing research into membranes that have good proton conductivity at elevated temperatures above 120 °C and under low humidity conditions. Such membranes have the potential to avoid catalyst poisoning, simplify fuel cell design and reduce the cost of fuel cells. Hydrocarbon-based membranes are being developed as alternatives to PFSA membranes, but concerns about chemical and mechanical stability and durability remain. Novel anhydrous membranes based on polymer gels infused with protic ionic liquids have also been recently proposed, but considerable fundamental research is needed to understand proton transport in novel membranes and evaluate durability under fuel cell operating conditions. In order to advance this promising technology, it is essential to rationally design the next generation of PEMs based on an understanding of chemistry, membrane morphology and proton transport obtained from experiment, theory and computer simulation.

Devanathan, Ramaswami

2010-11-01

150

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

151

Lipid microdomains in cell surface membranes  

Microsoft Academic Search

Lipid microdomains within cell membranes are detected by a variety of experimental techniques, each of which characterizes microdomains on a different time and spatial scale. The sum of the data on lipid microdomains has yet to be integrated into a single model of cell membrane structure. Indeed, one highlight of the past year is a new analysis of experimental results

Michael Edidin

1997-01-01

152

Interaction of Defensins with Model Cell Membranes  

NASA Astrophysics Data System (ADS)

Antimicrobial peptides (AMPs) comprise a key component of innate immunity for a wide range of multicellular organisms. For many AMPs, activity comes from their ability to selectively disrupt and lyse bacterial cell membranes. There are a number of proposed models for this action, but the detailed molecular mechanism of selective membrane permeation remains unclear. Theta defensins are circularized peptides with a high degree of selectivity. We investigate the interaction of model bacterial and eukaryotic cell membranes with theta defensins RTD-1, BTD-7, and compare them to protegrin PG-1, a prototypical AMP, using synchrotron small angle x-ray scattering (SAXS). The relationship between membrane composition and peptide induced changes in membrane curvature and topology is examined. By comparing the membrane phase behavior induced by these different peptides we will discuss the importance of amino acid composition and placement on membrane rearrangement.

Sanders, Lori K.; Schmidt, Nathan W.; Yang, Lihua; Mishra, Abhijit; Gordon, Vernita D.; Selsted, Michael E.; Wong, Gerard C. L.

2009-03-01

153

Cytochemical Properties of Osteoblast Cell Membrane Domains.  

National Technical Information Service (NTIS)

The interactions of osteoblasts with one another and with the extracellular milieu are of vital importance for cell function. These interactions are mediated by cell membrane-associated components. In the present work, we studied the distribution of sever...

L. P. Watson Y. H. Kang M. C. Falk

1989-01-01

154

Detrended fluctuation analysis of membrane flickering in discocyte and spherocyte red blood cells using quantitative phase microscopy  

NASA Astrophysics Data System (ADS)

Dynamic analyses of vibrational motion in cell membranes provide a lot of information on the complex dynamic motilities of a red blood cell (RBC). Here, we present the correlation properties of membrane fluctuation in discocyte and spherocyte RBCs by using quantitative phase microscopy (QPM). Since QPM can provide nanometer sensitivity in thickness measurement within a millisecond time scale, we were able to observe the membrane flicking of an RBC in nanometer resolution up to the bandwidth of 50 Hz. The correlation properties of the vibrational motion were analyzed with the detrended fluctuation analysis (DFA) method. Fractal scaling exponent ? in the DFA method was calculated for the vibrational motion of a cell surface at various surface points for normal discocyte and abnormal spherocyte RBCs. Measured ? values for normal RBCs are distributed between 0.7 and 1.0, whereas those for abnormal spherocyte RBCs are within a range from 0.85 to 1.2. We have also verified that the vibrational motion of background fluid outside of a cell has an ? value close to 0.5, which is a typical property of an uncorrelated white noise.

Lee, Seungrag; Yong Lee, Ji; Park, Chang-Soo; Young Kim, Dug

2011-07-01

155

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

2012-04-18

156

Imaging of membrane systems and membrane traffic in living cells.  

PubMed

Eukaryotic cells are composed of an intricate system of internal membranes that are organized into different compartments--including the endoplasmic reticulum (ER), the nuclear envelope, the Golgi complex (GC), lysosomes, endosomes, caveolae, mitochondria, and peroxisomes--that perform specialized tasks within the cell. The localization and dynamics of intracellular compartments are now being studied in living cells because of the availability of green fluorescent protein (GFP)-fusion proteins and recent advances in fluorescent microscope imaging systems. Results using these techniques are revealing how intracellular compartments maintain their steady-state organization and distributions, how they undergo growth and division, and how they transfer protein and lipid components between themselves through the formation and trafficking of membrane transport intermediates. This article describes methods using GFP-fusion proteins to visualize the behavior of organelles and to track membrane-bound transport intermediates moving between them. Practical issues related to the construction and expression of GFP-fusion proteins are discussed first. These are essential for optimizing the brightness and expression levels of GFP-fusion proteins so that intracellular membrane-bound structures containing these fusion proteins can be readily visualized. Next, techniques for performing time-lapse imaging using a confocal laser-scanning microscope (CLSM) are detailed, including the use of photobleaching to highlight organelles and transport intermediates. Methods for the acquisition and analysis of data are then discussed. Finally, commonly used and exciting new approaches for perturbing membrane traffic are outlined. PMID:22046036

Snapp, Erik Lee; Lajoie, Patrick

2011-11-01

157

?-Adrenergic agonists regulate cell membrane fluctuations of human erythrocytes  

PubMed Central

Mechanical fluctuations of the cell membrane (CMFs) in human erythrocytes reflect the bending deformability of the membrane-skeleton complex. These fluctuations were monitored by time-dependent light scattering from a small area (?0.25 ?m2) of the cell surface by a method based on point dark field microscopy.Exposure of red blood cells (RBCs) to adrenaline (epinephrine) and isoproterenol (isoprenaline) resulted in up to a 45 % increase in the maximal fluctuation amplitude and up to a 35 % increase in the half-width of the amplitude distribution. The power spectra of membrane fluctuations of control and treated cells revealed that adrenaline stimulated only the low frequency component (0.3-3 Hz). Analysis of the dose-response curves of ?-adrenergic agonists yielded an EC50 of 5 × 10?9 and 1 × 10?11 M for adrenaline and isoproterenol, respectively. Propranolol had an inhibitory effect on the stimulatory effect of isoproterenol. These findings show a potency order of propranolol > isoproterenol > adrenaline.The stimulatory effect of adrenaline was a temporal one, reaching its maximal level after 20-30 min but being abolished after 60 min. However, in the presence of 3-isobutyl-1-methylxanthine, a partial stimulatory effect was maintained even after 60 min. Pentoxifylline and 8-bromo-cAMP elevated CMFs. However, exposure of ATP-depleted erythrocytes to adrenaline or 8-bromo-cAMP did not yield any elevation in CMFs. These findings suggest that the ?-agonist effect on CMFs is transduced via a cAMP-dependent pathway.Deoxygenation decreased CMFs and filterability of erythrocytes by ?30 %. The stimulatory effect of isoproterenol on CMFs was 2.2-fold higher in deoxygenated RBCs than in oxygenated cells.Exposure of RBCs to adrenaline resulted in a concentration-dependent increase in RBC filterability, demonstrating a linear relationship between CMFs and filterability, under the same exposure conditions to adrenaline. These findings suggest that ?-adrenergic agonists may improve passage of erythrocytes through microvasculature, enhancing oxygen delivery to tissues, especially under situations of reduced oxygen tension for periods longer than 20 min.

Tuvia, Shmuel; Moses, Ayelet; Gulayev, Nathan; Levin, Shlomo; Korenstein, Rafi

1999-01-01

158

Drag reducing polymers improve tissue perfusion via modification of the RBC traffic in microvessels.  

PubMed

This paper reports a novel, physiologically significant, microfluidic phenomenon generated by nanomolar concentrations of drag-reducing polymers (DRP) dissolved in flowing blood, which may explain previously demonstrated beneficial effects of DRP on tissue perfusion. In microfluidic systems used in this study, DRP additives were found to significantly modify traffic of red blood cells (RBC) into microchannel branches as well as reduce the near-wall cell-free layer, which normally is found in microvessels with a diameter smaller than 0.3 mm. The reduction in plasma layer size led to attenuation of the so-called "plasma skimming" effect at microchannel bifurcations, increasing the number of RBC entering branches. In vivo, these changes in RBC traffic may facilitate gas transport by increasing the near vessel wall concentration of RBC and capillary hematocrit. In addition, an increase in near-wall viscosity due to the redirection of RBC in this region may potentially decrease vascular resistance as a result of increased wall shear stress, which promotes endothelium mediated vasodilation. These microcirculatory phenomena can explain the previously reported beneficial effects of DRP on hemodynamics in vivo observed in many animal studies. We also report here our finding that DRP additives reduce flow separations at microchannel expansions, deflecting RBC closer to the wall and eliminating the plasma recirculation zone. Although the exact mechanism of the DRP effects on RBC traffic in microchannels is yet to be elucidated, these findings may further DRP progress toward clinical use. PMID:19721190

Marhefka, J N; Zhao, R; Wu, Z J; Velankar, S S; Antaki, J F; Kameneva, M V

2009-01-01

159

Drag reducing polymers improve tissue perfusion via modification of the RBC traffic in microvessels  

PubMed Central

This paper reports a novel, physiologically significant, microfluidic phenomenon generated by nanomolar concentrations of drag-reducing polymers (DRP) dissolved in flowing blood, which may explain previously demonstrated beneficial effects of DRP on tissue perfusion. In microfluidic systems used in this study, DRP additives were found to significantly modify traffic of red blood cells (RBC) into microchannel branches as well as reduce the near-wall cell-free layer, which normally is found in microvessels with a diameter smaller than 0.3 mm. The reduction in plasma layer size led to attenuation of the so-called “plasma skimming” effect at microchannel bifurcations, increasing the number of RBC entering branches. In vivo, these changes in RBC traffic may facilitate gas transport by increasing the near vessel wall concentration of RBC and capillary hematocrit. In addition, an increase in near-wall viscosity due to the redirection of RBC in this region may potentially decrease vascular resistance as a result of increased wall shear stress, which promotes endothelium mediated vasodilation. These microcirculatory phenomena may explain the previously reported beneficial effects of DRP on hemodynamics in vivo observed in many animal studies. We also report here our finding that DRP additives reduce flow separations at microchannel expansions, deflecting RBC closer to the wall and eliminating the plasma recirculation zone. Although the exact mechanism of the DRP effects on RBC traffic in microchannels is yet to be elucidated, these findings may further DRP progress toward clinical use.

Marhefka, J.N.; Zhao, R.; Wu, Z.; Velankar, S.S.; Antaki, J.F.; Kameneva, M.V.

2011-01-01

160

Measurement of RBC Velocities in the Rat Pial Arteries with an Image-Intensified High-Speed Video Camera System  

Microsoft Academic Search

The mean centerline red blood cell (RBC) velocity of the rat pial artery was measured using an image-intensified high-speed (1000 frames\\/s) video camera system and RBCs labeled with fluorescein isothiocyanate (FITC). Some investigations measuring RBC velocity have been made in most organs, but the RBC velocity of the pial artery has not yet been measured with this system using FITC

Mami Ishikawa; Eiichi Sekizuka; Katsuyoshi Shimizu; Noriyuki Yamaguchi; Takeshi Kawase

1998-01-01

161

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.

Gallagher, Patrick G.

2008-01-01

162

Sickle cell membranes and oxidative damage.  

PubMed Central

Sickle erythrocytes and their membranes are susceptible to endogenous free-radical-mediated oxidative damage which correlates with the proportion of irreversibly sickled cells. The suppression of incubation-induced oxidative stress by antioxidants, free radical scavengers and an iron chelator suggest that oxidation products of membrane-bound haemoglobin contribute towards the pathology of the disease.

Rice-Evans, C; Omorphos, S C; Baysal, E

1986-01-01

163

Proton Exchange Membranes for Fuel Cells  

Microsoft Academic Search

Proton exchange membrane, also known as polymer electrolyte membrane, fuel cells (PEMFCs) offer the promise of efficient conversion of chemical energy of fuel, such as hydrogen or methanol, into electricity with minimal pollution. Their widespread use to power zero-emission automobiles as part of a hydrogen economy can contribute to enhanced energy security and reduction in greenhouse gas emissions. However, the

Devanathan

2010-01-01

164

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

165

Membrane elastic properties and cell function.  

PubMed

Recent studies indicate that the cell membrane, interacting with its attached cytoskeleton, is an important regulator of cell function, exerting and responding to forces. We investigate this relationship by looking for connections between cell membrane elastic properties, especially surface tension and bending modulus, and cell function. Those properties are measured by pulling tethers from the cell membrane with optical tweezers. Their values are determined for all major cell types of the central nervous system, as well as for macrophage. Astrocytes and glioblastoma cells, which are considerably more dynamic than neurons, have substantially larger surface tensions. Resting microglia, which continually scan their environment through motility and protrusions, have the highest elastic constants, with values similar to those for resting macrophage. For both microglia and macrophage, we find a sharp softening of bending modulus between their resting and activated forms, which is very advantageous for their acquisition of phagocytic functions upon activation. We also determine the elastic constants of pure cell membrane, with no attached cytoskeleton. For all cell types, the presence of F-actin within tethers, contrary to conventional wisdom, is confirmed. Our findings suggest the existence of a close connection between membrane elastic constants and cell function. PMID:23844071

Pontes, Bruno; Ayala, Yareni; Fonseca, Anna Carolina C; Romão, Luciana F; Amaral, Rac?ele F; Salgado, Leonardo T; Lima, Flavia R; Farina, Marcos; Viana, Nathan B; Moura-Neto, Vivaldo; Nussenzveig, H Moysés

2013-07-03

166

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.

2013-01-01

167

[Cell membrane changes and skin diseases].  

PubMed

Biological membranes are laminar bilayers of lipoids with thermolabile biophysical properties. Changing temperatures not only result in altered polarity and permeability of the membranes, but also in changes of the various membrane receptors (e.g. histamine and beta-adrenergic receptors) and the cell makers. In healthy persons, lower temperatures (25 degrees) lead to elevated suppressor properties, and the T4 ratio is below 1.0. At 37 and 41 degrees C, there is a growing number of helper cells, and the T4/T8 ratio becomes normal again. In psoriatic patients, the number of helper cells does not change with the temperature. We also found some evidence for changes of the cell membranes in atopic dermatitis and chronic urticaria. PMID:2907212

Rácz, I

1988-10-15

168

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

169

Membrane Reserves and Hypotonic Cell Swelling  

Microsoft Academic Search

To accommodate expanding volume (V) during hyposmotic swelling, animal cells change their shape and increase surface area\\u000a (SA) by drawing extra membrane from surface and intracellular reserves. The relative contributions of these processes, sources\\u000a and extent of membrane reserves are not well defined. In this study, the SA and V of single substrate-attached A549, 16HBE14o?, CHO and NIH 3T3 cells

Nicolas Groulx; Francis Boudreault; Sergei N. Orlov; Ryszard Grygorczyk

2006-01-01

170

Photothermal nanoblade for patterned cell membrane cutting.  

PubMed

We report a photothermal nanoblade that utilizes a metallic nanostructure to harvest short laser pulse energy and convert it into a highly localized and specifically shaped explosive vapor bubble. Rapid bubble expansion and collapse punctures a lightly-contacting cell membrane via high-speed fluidic flows and induced transient shear stress. The membrane cutting pattern is controlled by the metallic nanostructure configuration, laser pulse polarization, and energy. Highly controllable, sub-micron sized circular hole pairs to half moon-like, or cat-door shaped, membrane cuts were realized in glutaraldehyde treated HeLa cells. PMID:21164656

Wu, Ting-Hsiang; Teslaa, Tara; Teitell, Michael A; Chiou, Pei-Yu

2010-10-25

171

Photothermal nanoblade for patterned cell membrane cutting  

PubMed Central

We report a photothermal nanoblade that utilizes a metallic nanostructure to harvest short laser pulse energy and convert it into a highly localized and specifically shaped explosive vapor bubble. Rapid bubble expansion and collapse punctures a lightly-contacting cell membrane via high-speed fluidic flows and induced transient shear stress. The membrane cutting pattern is controlled by the metallic nanostructure configuration, laser pulse polarization, and energy. Highly controllable, sub-micron sized circular hole pairs to half moon-like, or cat-door shaped, membrane cuts were realized in glutaraldehyde treated HeLa cells.

Wu, Ting-Hsiang; Teslaa, Tara; Teitell, Michael A.; Chiou, Pei-Yu

2010-01-01

172

Durability of PEM Fuel Cell Membranes  

NASA Astrophysics Data System (ADS)

Durability is still a critical limiting factor for the commercialization of polymer electrolyte membrane (PEM) fuel cells, a leading energy conversion technology for powering future hydrogen fueled automobiles, backup power systems (e.g., for base transceiver station of cellular networks), portable electronic devices, etc. Ionic conducting polymer (ionomer) electrolyte membranes are the critical enabling materials for the PEM fuel cells. They are also widely used as the central functional elements in hydrogen generation (e.g., electrolyzers), membrane cell for chlor-alkali production, etc. A perfluorosulfonic acid (PFSA) polymer with the trade name Nafion® developed by DuPont™ is the most widely used PEM in chlor-alkali cells and PEM fuel cells. Similar PFSA membranes have been developed by Dow Chemical, Asahi Glass, and lately Solvay Solexis. Frequently, such membranes serve the dual function of reactant separation and selective ionic conduction between two otherwise separate compartments. For some applications, the compromise of the "separation" function via the degradation and mechanical failure of the electrolyte membrane can be the life-limiting factor; this is particularly the case for PEM in hydrogen/oxygen fuel cells.

Huang, Xinyu; Reifsnider, Ken

173

Lysophosphatidylcholine cell depolarization: increased membrane permeability for use in the determination of cell membrane potentials  

SciTech Connect

Current techniques for the determination of cellular membrane potentials based on the uptake of a radiolabeled lipophilic cation, (3H)triphenylmethylphosphonium, and the cyanine dye, DiOC5(3), were analyzed in terms of the proportions of these probes which are accumulated due to potential-dependent and potential-independent forces. Measurements were made of probe uptake in two model systems: rabbit type II pneumocytes and human promyelocytic HL60 cells. For both cell types, the membrane potential-independent component of triphenylmethylphosphonium uptake was found to be a function of several variables, including the length of exposure of the cells to the transport facilitator tetraphenylboron, the concentration of tetraphenylboron, and the integrity of the cell membrane. To accurately determine the magnitude of the potential-independent component of probe uptake by type II and HL60 cells, the cell-permeabilizing agent lysophosphatidylcholine was used. The ability of lysophosphatidylcholine to depolarize cell membranes and accurately predict membrane potential-independent accumulation was found to be equal to or superior to several other techniques commonly used to achieve membrane depolarization (e.g. gramicidin, valinomycin plus high external potassium). Lysophosphatidylcholine cell treatment was found to be a simple, rapid, and accurate technique to increase cell membrane permeability and allow equilibration of intra- and extracellular ions. The method is shown to be useful for determining membrane potential-independent accumulation of both radiolabeled and fluorescent probes of membrane potential.

Gallo, R.L.; Wersto, R.P.; Notter, R.H.; Finkelstein, J.N.

1984-12-01

174

Mechanical Properties of the Red Cell Membrane  

PubMed Central

The technique of Mitchison and Swann (1954) was modified for determining the resistance to deformation, or “stiffness,” of the red cell membrane and the pressure gradient across the cell wall. It requires a measure of the pressure needed to suck a portion of the cell into a micropipette. Stiffness of hypertonically crenated cells was less than that of biconcave discs or hypotonically swollen cells. Crenated cells showed zero pressure gradient and a stiffness, probably due to pure bending, equivalent to 0.007 ± 0.001 (SE) dynes/cm. Normal and swollen cells showed a pressure gradient of 2.3 ± 0.8 (SE) mm H2O and a stiffness, due to bending and tension in the membrane, equivalent to 0.019 ± 0.002 (SE) dynes/cm. No difference in stiffness was found between the rim and the biconcavity of the cell or between biconcave discs and hypotonically swollen cells. Micromanipulation showed that the membrane can withstand large bending strains but limited tangential strains (stretching). These results have significant implications in any theory explaining the cell shape. For example, the data give no indication that the physical properties of the membrane are different at the rim from those of the biconcavities, and the existence of a positive pressure in the normal cell is established. ImagesFigure 1Figure 8Figure 11Figure 12

Rand, R. P.; Burton, A. C.

1964-01-01

175

Vesicle trafficking and cell surface membrane patchiness.  

PubMed Central

Membrane proteins and lipids often appear to be distributed in patches on the cell surface. These patches are often assumed to be membrane domains, arising from specific molecular associations. However, a computer simulation (Gheber and Edidin, 1999) shows that membrane patchiness may result from a combination of vesicle trafficking and dynamic barriers to lateral mobility. The simulation predicts that the steady-state patches of proteins and lipids seen on the cell surface will decay if vesicle trafficking is inhibited. To test this prediction, we compared the apparent sizes and intensities of patches of class I HLA molecules, integral membrane proteins, before and after inhibiting endocytic vesicle traffic from the cell surface, either by incubation in hypertonic medium or by expression of a dominant-negative mutant dynamin. As predicted by the simulation, the apparent sizes of HLA patches increased, whereas their intensities decreased after endocytosis and vesicle trafficking were inhibited.

Tang, Q; Edidin, M

2001-01-01

176

Membrane reserves and hypotonic cell swelling.  

PubMed

To accommodate expanding volume (V) during hyposmotic swelling, animal cells change their shape and increase surface area (SA) by drawing extra membrane from surface and intracellular reserves. The relative contributions of these processes, sources and extent of membrane reserves are not well defined. In this study, the SA and V of single substrate-attached A549, 16HBE14o(-), CHO and NIH 3T3 cells were evaluated by reconstructing cell three-dimensional topology based on conventional light microscopic images acquired simultaneously from two perpendicular directions. The size of SA reserves was determined by swelling cells in extreme 98% hypotonic (approximately 6 mOsm) solution until membrane rupture; all cell types examined demonstrated surprisingly large membrane reserves and could increase their SA 3.6 +/- 0.2-fold and V 10.7 +/- 1.5-fold. Blocking exocytosis (by N-ethylmaleimide or 10 degrees C) reduced SA and V increases of A549 cells to 1.7 +/- 0.3-fold and 4.4 +/- 0.9-fold, respectively. Interestingly, blocking exocytosis did not affect SA and V changes during moderate swelling in 50% hypotonicity. Thus, mammalian cells accommodate moderate (<2-fold) V increases mainly by shape changes and by drawing membrane from preexisting surface reserves, while significant endomembrane insertion is observed only during extreme swelling. Large membrane reserves may provide a simple mechanism to maintain membrane tension below the lytic level during various cellular processes or acute mechanical perturbations and may explain the difficulty in activating mechanogated channels in mammalian cells. PMID:17598067

Groulx, Nicolas; Boudreault, Francis; Orlov, Sergei N; Grygorczyk, Ryszard

2007-06-26

177

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.

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

2010-01-01

178

Preparation of cell membranes for high resolution imaging by AFM  

Microsoft Academic Search

Studies of cell membrane structure by atomic force microscopy (AFM) have been limited because of the softness of cell membranes. Here, we utilize a new technique of sample preparation to lay red blood cell membranes on the top of a mica surface to obtain high resolution images by in-situ AFM on both sides of cell membranes. Our results indicate that

Hongda Wang; Xian Hao; Yuping Shan; Junguang Jiang; Mingjun Cai; Xin Shang

2010-01-01

179

Fixed charge in the cell membrane  

PubMed Central

1. Focal electric field was generated by passing a current of 5 × 10-7 to 1 × 10-5 A from a micropipette into the culture medium. Movement of cells at a distance of 5-50 ? from the electrode tip was observed. In case of cells embedded in the culture only local deformation of the membrane was observed. 2. The cell species explored included neurones, glia, muscle fibres, connective cells, malignant cells and erythrocytes. All cells responded in a similar manner to the electric field, and the current required was in the same range. 3. Cells were attracted to a positive micropipette and repelled from a negative one: the only exception was observed in certain malignant cells which moved in the opposite direction. 4. Movement and membrane deformation could be obtained with electrodes filled with various concentrated and isotonic solutions. The composition of the culture medium also had no qualitative influence on these effects. 5. Metabolic poisons or rupture of the cell membrane had no effect on the movement. Isolated membrane fragments showed movement similar to that of intact cells. 6. The possibility of artifacts due to proximity of the focal electrode is considered. It is shown that electro-osmosis cannot account for the present observations. Some other artifacts are also excluded. 7. It is proposed that the most satisfactory way to account for the present observations is by a membrane carrying negative fixed charge of the order of 2·5 × 103 e.s.u./cm2. Some physiological consequences of presence of negative charge in the membrane are briefly discussed. ImagesFig. 1Fig. 2Fig. 3

Elul, R.

1967-01-01

180

Modeling and simulation of microfluid effects on deformation behavior of a red blood cell in a capillary.  

PubMed

A modified SIMPER algorithm is developed for analysis of microfluid effects on the motion and deformation of a red blood cell (RBC) in a capillary. With consideration of very small Reynolds number in microfluidics, this algorithm not only speeds up the convergence of the momentum equations by combining the advantages of the SIMPLEC and SIMPLER algorithms together, but also satisfies the continuity equation with higher accuracy by integrating a fine adjustment technique. In order to validate the modified SIMPLER algorithm, the behavior of RBC in a capillary is simulated at different velocities. When the mean RBC velocity is 0.1mm/s, the RBC exhibits a characteristic parachute shape in the steady state, which agrees well with the numerical results previously reported. Apart from that, a quantitative validation with the experimental data is performed by examining the relationship between the mean velocity and deformation index of the RBC, showing an excellent agreement. The effects of crucial parameters are investigated systematically on the motion and deformation of the RBC, including the RBC radius, elastic modulus and bending stiffness of RBC membrane, initial velocity of suspending fluid, as well as the density and viscosity ratios of the suspending fluid to RBC. The simulation results demonstrate that all of the parameters have influences on the RBC behavior by changing the interaction between the RBC and suspending fluid. PMID:20643152

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

2010-07-16

181

Adenosinetriphosphatase Activity in the Cell Membranes of Kidney Tubule Cells  

Microsoft Academic Search

This cytochemical study demonstrates high levels of apparent ATPase ac- tivity in the infolded cell membranes of the proximal tubules (dog, rat, human, mouse, monkey, and opossum) and ascending loops of Henle (dog, rat, human and, to a variable degree, mouse). Electron microscopy has shown (see Rhodin (1)) that these membranes separate adjacent cells where they interlock with one another

HERMAN W. SPATER; ALEX B. NOVIKOFF; BERTHA MASEK

1958-01-01

182

Membrane-cell developments ease electrochemistry scaleup  

Microsoft Academic Search

This paper examines Steetley Engineering Limited's addition of a production-size cell to its dished electrode membrane line. The basic cell unit has a 1-m² electrode area, compared with the 0.25-m² pilot-plant size and 0.05-m² lab size the company began offering in 1983. An electro Prod cell for production applications was also introduced. Both cells are assembled in a manner similar

H. C. Short; R. Skole

1985-01-01

183

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.

Yurchenco, Peter D.

2011-01-01

184

Membranes in the plant cell  

Microsoft Academic Search

Summary 1.Existing evidence for the formation of morphological membranes at protoplasmic surfaces in the living plant protoplast is reviewed and judged inadequate.2.Cases from the literature and from the author's work are cited to show that micromanipulation may be employed in the investigation of this problem without perceptible disturbance of the normal condition of the protoplast.3.Investigation of plasmolyzed and unplasmolyzed protoplasts

Janet Q. Plowe

1931-01-01

185

Plasma cell membranes of the rat kidney  

Microsoft Academic Search

A fraction enriched with plasma cell membranes (PMF) was isolated from rat kidney homogenate by differential centrifugation. Before NaJ treatment electron micrographs of the preparation showed a membraneous fraction with only a small contamination of mitochondria. After treatment with NaJ the residual PMF exhibited a low microsomal glucose 6-phosphatase activity. Marker enzymes of other subcellular fractions were not detected. The

H. Ebel; N. G. Santo; K. Hierholzer

1971-01-01

186

Organization of the cell membrane in Euglena  

Microsoft Academic Search

Summary The cell membrane ofEuglena gracilis has been investigated with the freeze-fracture technique. When split, this membrane produces two fracture faces which are striking in their non-complementarity. The P fracture face is covered with a high density of 110 Å (average diameter) particles, while the E face is made up of a complex series of striations occurring at regular angles

K. R. Miller; Gayle J. Miller

1978-01-01

187

The hemolysis kinetics of psoriatic red blood cells  

Microsoft Academic Search

Psoriasis has been reported to be associated with several red blood cell (RBC) membrane alterations including: a membrane fluidity decrease, a significant elevation of Na+-K+and quantitative changes of erythrocyte membrane proteins that may indicate red cell cytoskeleton impairment. The aim of the present study was to analyse the hemolytic behaviour of psoriatic RBCs. The osmotic behaviour of RBCs was examined

A. Górnicki

2008-01-01

188

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...

189

Full-length CD4 electroinserted in the erythrocyte membrane as a long-lived inhibitor of infection by human immunodeficiency virus  

SciTech Connect

Recombinant full-length CD4 expressed in Spodoptera frugiperda 9 cells with the baculovirus system was electroinserted in erythrocyte (RBC) membranes. Of the inserted CD4, 70% was correctly oriented as shown by fluorescence quenching experiments with fluorescein-labeled CD4. The inserted CD4 displayed the same epitopes as the naturally occurring CD4 in human T4 cells. Double-labeling experiments ({sup 125}I-CD4 and {sup 51}Cr-RBC) showed that the half-life of CD4 electroinserted in RBC membrane in rabbits was approximately 7 days. Using the fluorescence dequenching technique with octadecylrhodamine B-labeled human immunodeficiency virus (HIV)-1, the authors showed fusion of the HIV envelope with the plasma membrane of RBC-CD4, whereas no such fusion could be detected with RBC. The dequenching efficiency of RBC-CD4 is the same as that of CEM cells. Exposure to anti-CD4 monoclonal antibody OKT4A, which binds to the CD4 region that attaches to envelope glycoprotein gp120, caused a significant decrease in the dequenching of fluorescence. In vitro infectivity studies showed that preincubation of HIV-1 with RBC-CD4 reduced by 80-90% the appearance of HIV antigens in target cells, the amount of viral reverse transcriptase, and the amount of p24 core antigen produced by the target cells. RBC-CD4, but not RBCs, aggregated with chronically HIV-1-infected T cells and caused formation of giant cells. These data show that the RBC-CD4 reagent is relatively long lived in circulation and efficient in attaching to HIV-1 and HIV-infected cells, and thus it may have value as a therapeutic agent against AIDS.

Zeira, M.; Volsky, D.J. (Columbia Univ., New York, NY (United States)); Tosi, P.F.; Mouneimne, Y.; Lazarte, J.; Sneed, L.; Nicolau, C. (Texas A and M Univ., College Station (United States))

1991-05-15

190

Studies in erythropoiesis: the influence of the glycocalyx of the red cell membrane  

SciTech Connect

The possible existence of a correlation between the removal from the circulation of aged cells and the production of new RBCs was investigated. An erythropoietic influence was found to be associated with the glycocalyx of the erythrocyte membrane. The influencing factor, presumably a desialated glycopeptide, asialoglycophorin, appeared to be masked on the young RBC by an amino ketosugar, sialic acid. Ostensibly during the aging process, an increasing amount of sialic acid becomes removed from the membrane to expose the underlying erythropoietic message. Sialic acid was removed enzymatically in vitro from the membranes of erythrocytes by incubation with neuraminidase from Clostridium Perfringens. Erythropoietic activity was assayed by measuring iron-59 uptake after injection or transfusion of test material into exhypoxic mice. The amount of erythropoietic activity was found to be directly related to the number of desialated erythrocytes transfused and to the degree of desialation of the transfused erythrocytes. Asialoglycophorin was shown to be an erythrocyte stimulating factor following its isolation from the membrane and subsequent injection into test mice. Both mouse and human asialoglycophorin were found to be stimulatory.

Franco, M.W.

1980-01-01

191

Cell membrane destabilizes progressively during repetitive mechanical rupture events  

Microsoft Academic Search

The postfusion oscillation cycle method of electrofused cells was applied to red blood cell membranes to induce repetitive membrane ruptures and test the mechanical membrane resistance against sequential events of membrane strain and rupture. After producing doublets from pairs of electrofused cells, they entered the oscillation cycle, providing a sequence of at least four consecutive colloidosmotic-driven rupture events. Different gradations

Martin Baumann

2002-01-01

192

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

193

Cell motility through plasma membrane blebbing  

PubMed Central

Plasma membrane blebs are dynamic cytoskeleton-regulated cell protrusions that have been implicated in apoptosis, cytokinesis, and cell movement. Influencing Rho–guanosine triphosphatase activities and subsequent actomyosin dynamics appears to constitute a core component for bleb formation. In this paper, we discuss recent evidence in support of a central role of nonapoptotic membrane blebbing for cell migration and cancer cell invasion as well as advances in our understanding of the underlying molecular mechanisms. Based on these studies, we propose that in a physiological context, bleb-associated cell motility reflects a cell's response to reduced substratum adhesion. The importance of blebbing as a functional protrusion is underscored by the existence of multiple molecular mechanisms that govern actin-mediated bleb retraction.

Fackler, Oliver T.; Grosse, Robert

2008-01-01

194

Structure and properties of cell membranes. Volume 3: Methodology and properties of membranes  

Microsoft Academic Search

This book covers the topics: Quantum chemical approach to study the mechanisms of proton translocation across membranes through protein molecules; monomolecular films as biomembrane models; planar lipid bilayers in relation to biomembranes; relation of liposomes to cell membranes; reconstitution of membrane transport systems; structure-function relationships in cell membranes as revealed by X-ray techniques; structure-function relationships in cell membranes as revealed

Benga

1985-01-01

195

Blend Concepts for Fuel Cell Membranes  

NASA Astrophysics Data System (ADS)

Differently cross-linked blend membranes were prepared from commercial arylene main-chain polymers from the classes of poly(ether-ketones) and poly(ethersulfones) modified with sulfonate groups, sulfinate cross-linking groups and basic N-groups. The following membrane types have been prepared: (a) van-der Waals/dipole-dipole blends by mixing a polysulfonate with unmodified PSU. This membrane type showed a heterogeneous morphology, leading to extreme swelling and even dissolution of the sulfonated component at elevated temperatures. (b) Hydrogen bridge blends by mixing a polysulfonate with a polyamide or polyetherimide. This membrane type showed a partially heterogeneous morphology, also leading to extreme swelling/dissolution of the sulfonated blend component at elevated temperatures. (c) Acid-base blends by mixing a polysulfonate with a polymeric N-base (self-developed/commercial). With this membrane type, we could reach a wide variability of properties by variation of different parameters. Membranes showing excellent stability and good fuel cell performance up to 100°C (PEFC) and 130°C (DMFC) were obtained. (d) Covalently cross-linked (blend) membranes by either mixing of a polysulfonate with a polysulfinate or by preparation of a polysulfinatesulfonate, followed by reaction of the sulfinate groups in solution with a dihalogeno compound under S-alkylation. Membranes were prepared that showed effective suppression of swelling without H+-conductivity loss. The membranes showed good PEFC (up to 100°C) and DMFC (up to 130°C) performance. (e) Covalent-ionically cross-linked blend membranes by mixing polysulfonates with polysulfinates and polybases or by mixing a polysulfonate with a polymer carrying both sulfinate and basic N-groups. The covalent-ionically cross-linked membranes were tested in DMFC up to 110°C and showed a good performance. (f) Differently cross-linked organic-inorganic blend composite membranes via different procedures. The best results were obtained with blend membranes having a layered zirconium phosphate “ZrP” phase: They were transparent, and showed good H+;-conductivity and stability. Application of one of these composite membranes to a PEFC yielded good performance up to T=115°C.

Kerres, Jochen

196

The application of Dow Chemical's perfluorinated membranes in proton-exchange membrane fuel cells  

Microsoft Academic Search

Dow Chemical's research activities in fuel cells revolve around the development of perfluorosulfonic acid membranes useful as the proton transport medium and separator. Some of the performance characteristics which are typical for such membranes are outlined. The results of tests utilizing a new experimental membrane useful in proton-exchange membrane fuel cells are presented. The high voltage at low current densities

G. A. Eisman

1989-01-01

197

Glycosphingolipid Domains on Cell Plasma Membrane  

Microsoft Academic Search

In this study we analyzed by immunofluorescence, laser confocal microscopy, immunoelectron microscopy and label fracture technique the ganglioside distribution on the plasma membrane of several different cell types: human peripheral blood lymphocytes (PBL), Molt-4 lymphoid cells, and NIH 3T3 fibroblasts, which mainly express monosialoganglioside GM3, and murine NS20Y neuroblastoma cells, which have been shown to express a high amount of

Maurizio Sorice; Tina Garofalo; Roberta Misasi; Vincenza Dolo; Giuseppe Lucania; Tiziana Sansolini; Isabella Parolini; Massimo Sargiacomo; Maria Rosaria Torrisi; Antonio Pavan

1999-01-01

198

Hereditary spherocytosis, elliptocytosis, and other red cell membrane disorders.  

PubMed

Hereditary spherocytosis and elliptocytosis are the two most common inherited red cell membrane disorders resulting from mutations in genes encoding various red cell membrane and skeletal proteins. Red cell membrane, a composite structure composed of lipid bilayer linked to spectrin-based membrane skeleton is responsible for the unique features of flexibility and mechanical stability of the cell. Defects in various proteins involved in linking the lipid bilayer to membrane skeleton result in loss in membrane cohesion leading to surface area loss and hereditary spherocytosis while defects in proteins involved in lateral interactions of the spectrin-based skeleton lead to decreased mechanical stability, membrane fragmentation and hereditary elliptocytosis. The disease severity is primarily dependent on the extent of membrane surface area loss. Both these diseases can be readily diagnosed by various laboratory approaches that include red blood cell cytology, flow cytometry, ektacytometry, electrophoresis of the red cell membrane proteins, and mutational analysis of gene encoding red cell membrane proteins. PMID:23664421

Da Costa, Lydie; Galimand, Julie; Fenneteau, Odile; Mohandas, Narla

2013-05-09

199

Membrane fluidity sensoring microbial fuel cell.  

PubMed

A study has been performed to examine the effect of temperature and ethanolic stresses on the coulombic efficiency of a microbial fuel cell. The conventional-type fuel cell containing Gram-negative bacteria, Proteus vulgaris, was investigated as a model system. From current output measurements, it was found that the coulombic yields were altered by environmental stresses such as temperature shock or ethanol treatment to the bacteria. While high-temperature or ethanolic shock led to a remarkable decrement in coulombic output, the low-temperature shock induced a slight increase in microbial fuel cell efficiency. These results indicate that the membrane fluidity is affected considerably by environmental stress, which in turn affects the electron transfer process through the bacterial cell membrane to and from the electrode. This interpretation was confirmed by the cyclic voltammetric study of a mediator on an electrode surface modified with the lipids extracted from the membrane of P. vulgaris under the given stress. Markedly different electrochemical behaviors were observed depending on the environmental stress. A reciprocal relationship between coulomb output and the ratio of saturation/unsaturation of fatty acids has been observed. This is the first report, to our knowledge, that the structural adaptation of membrane fatty acids in response to the environmental shock can regulate the coulombic efficiency of a microbial fuel cell. PMID:12699828

Choi, Youngjin; Jung, Eunkyoung; Kim, Sunghyun; Jung, Seunho

2003-04-01

200

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

2012-07-24

201

Compartmental Hollow Fiber Capillary Membrane-Based Bioreactor Technology for In Vitro Studies on Red Blood Cell Lineage Direction of Hematopoietic Stem Cells  

PubMed Central

Continuous production of red blood cells (RBCs) in an automated closed culture system using hematopoietic stem cell (HSC) progenitor cell populations is of interest for clinical application because of the high demand for blood transfusions. Previously, we introduced a four-compartment bioreactor that consisted of two bundles of hollow fiber microfiltration membranes for transport of culture medium (forming two medium compartments), interwoven with one bundle of hollow fiber membranes for transport of oxygen (O2), carbon dioxide (CO2), and other gases (forming one gas compartment). Small-scale prototypes were developed of the three-dimensional (3D) perfusion cell culture systems, which enable convection-based mass transfer and integral oxygenation in the cell compartment. CD34+ HSC were isolated from human cord blood units using a magnetic separation procedure. Cells were inoculated into 2- or 8-mL scaled-down versions of the previously designed 800-mL cell compartment devices and perfused with erythrocyte proliferation and differentiation medium. First, using the small-scale 2-mL analytical scale bioreactor, with an initial seeding density of 800,000 cells/mL, we demonstrated approximately 100-fold cell expansion and differentiation after 7 days of culture. An 8-mL laboratory-scale bioreactor was then used to show pseudocontinuous production by intermediately harvesting cells. Subsequently, we were able to use a model to demonstrate semicontinuous production with up to 14,288-fold expansion using seeding densities of 800,000 cells/mL. The down-scaled culture technology allows for expansion of CD34+ cells and stimulating these progenitors towards RBC lineage, expressing approximately 40% CD235+ and enucleation. The 3D perfusion technology provides an innovative tool for studies on RBC production, which is scalable.

Housler, Greggory J.; Miki, Toshio; Schmelzer, Eva; Pekor, Christopher; Zhang, Xiaokui; Kang, Lin; Voskinarian-Berse, Vanessa; Abbot, Stewart; Zeilinger, Katrin

2012-01-01

202

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

203

Red Cell Lead, Whole Blood Lead, and Red Cell Enzymes*  

PubMed Central

Simultaneous assay of blood lead (Pb-B) and red cell lead (Pb-Rbc) in 123 samples from 104 urban and suburban students, ages 10–18, shows the ratio of concentration (Pb-Rbc)/(Pb-B) to increase as the hematocrit decreases. On direct assay in 40 samples, plasma lead (Pb-P) was fixed in a narrow range. In 28 students with Pb-Rbc >40 ?g/100 ml, the mean red cell 2,3-diphosphoglycerate (2,3-DPG) was 6.05±0.28 (±S.E.), significantly higher (P<.025) than the 5.25±0.18 of 51 students with Pb-Rbc<40 ?g/100 ml, although hemoglobin values were comparable (13.83±0.31 versus 13.55±0.20). Analysis of the individual population groups showed this correlation of Pb-Rbc with 2,3-DPG to be primarily related to the intercorrelation of each parameter with hemoglobin. Rbc membrane Na/K ATPase, as per cent of total membrane ATPase, had a median value of 60% in 48 subjects. Na/K ATPase below 60% was found in 10 (77%) of the 13 students with Pb-Rbc?40 ?g/100 ml, but in only 14 of the 35 with Pb-Rbc<40 ?g/100 ml (?2=5.1, df=1, P<0.05). Correlation of significant enzyme changes with Pb-Rbc, but not with Pb-B in the normal urban range of Pb-B<35 ?g/100 ml suggests Pb-Rbc, increased in anemia, to be a critical factor in the hematotoxicity of lead.

Angle, Carol R.; McIntire, Matilda S.

1974-01-01

204

Membrane curvature and mechanisms of dynamic cell membrane remodelling  

Microsoft Academic Search

Membrane curvature is no longer seen as a passive consequence of cellular activity but an active means to create membrane domains and to organize centres for membrane trafficking. Curvature can be dynamically modulated by changes in lipid composition, the oligomerization of curvature scaffolding proteins and the reversible insertion of protein regions that act like wedges in membranes. There is an

Jennifer L. Gallop; Harvey T. McMahon

2005-01-01

205

Functional imaging of microdomains in cell membranes  

Microsoft Academic Search

The presence of microdomains or rafts within cell membranes is a topic of intense study and debate. The role of these structures\\u000a in cell physiology, however, is also not yet fully understood with many outstanding problems. This problem is partly based\\u000a on the small size of raft structures that presents significant problems to their in vivo study, i.e., within live

James Duggan; Ghadir Jamal; Mark Tilley; Ben Davis; Graeme McKenzie; Kelly Vere; Michael G. Somekh; Paul O’Shea; Helen Harris

2008-01-01

206

Membrane-cell developments ease electrochemistry scaleup  

SciTech Connect

This paper examines Steetley Engineering Limited's addition of a production-size cell to its dished electrode membrane line. The basic cell unit has a 1-m/sup 2/ electrode area, compared with the 0.25-m/sup 2/ pilot-plant size and 0.05-m/sup 2/ lab size the company began offering in 1983. An electro Prod cell for production applications was also introduced. Both cells are assembled in a manner similar to a plate-and-frame filter press. An illustration is provided in the paper to clarify the assembly.

Short, H.C.; Skole, R.

1985-03-04

207

Sodium selectivity of Reissner's membrane epithelial cells  

PubMed Central

Background Sodium absorption by Reissner's membrane is thought to contribute to the homeostasis of the volume of cochlear endolymph. It was previously shown that the absorptive transepithelial current was blocked by amiloride and benzamil. The most commonly-observed target of these drugs is the epithelial sodium channel (ENaC), which is composed of the three subunits ?-,?- and ?-ENaC. However, other less-selective cation channels have also been observed to be sensitive to benzamil and amiloride. The aim of this study was to determine whether Reissner's membrane epithelial cells could support parasensory K+ absorption via amiloride- and benzamil-sensitive electrogenic pathways. Results We determined the molecular and functional expression of candidate cation channels with gene array (GEO GSE6196), RT-PCR, and whole-cell patch clamp. Transcript expression analysis of Reissner's membrane detected no amiloride-sensitive acid-sensing ion channels (ASIC1a, ASIC2a, ASIC2b) nor amiloride-sensitive cyclic-nucleotide gated channels (CNGA1, CNGA2, CNGA4, CNGB3). By contrast, ?-,?- and ?-ENaC were all previously reported as present in Reissner's membrane. The selectivity of the benzamil-sensitive cation currents was observed in whole-cell patch clamp recordings under Cl--free conditions where cations were the only permeant species. The currents were carried by Na+ but not K+, and the permeability of Li+ was greater than that of Na+ in Reissner's membrane. Complete replacement of bath Na+ with the inpermeable cation NMDG+ led to the same inward current as with benzamil in a Na+ bath. Conclusions These results are consistent with the amiloride/benzamil-sensitive absorptive flux of Reissner's membrane mediated by a highly Na+-selective channel that has several key characteristics in common with ???-ENaC. The amiloride-sensitive pathway therefore absorbs only Na+ in this epithelium and does not provide a parasensory K+ efflux route from scala media.

2011-01-01

208

Low concentration of extracellular hemoglobin affects shape of RBC in low ion strength sucrose solution.  

PubMed

When red blood cells (RBCs) are placed in isotonic sucrose solution with low chloride content dynamic shape response is observed. Generally, it consists of three phases: i) fast spherulation (phase 1), ii) restoration of shape close to discoid one (phase 2), followed by a second slower spherulation in stomatocyte direction (phase 3). This morphological transformation (morphological response (MR)) is rather a fast process, usually comprises 1-2 min interval with disc retransformation time within 20-30 s. We have found that low concentration of extracellular hemoglobin (Hb) in the range 14-44 nM derived from cell lysate significantly accelerated MR at any stage of process. Increasing NaCl concentration up to 10 mM completely eliminated any influence of Hb. Other inhibitors EDTA and chlorpromazine while retarding some phases of MR did not prevent its activation by Hb. It was established that at conditions of low ionic strength Hb strongly binds to native RBC membrane. The number of binding sites was found to be 1-1.6x10(6) molecules per cell and the equilibrium dissociation constant was less than 2x10(-8) M. After heat denaturation of Hb at 70-72 degrees C an ability of Hb to affect MR was lost. Our data provide evidence that extracellular Hb could be involved in shape regulation of red blood cells at least in low ionic strength solutions. PMID:19186113

Rudenko, Sergey V

2009-01-08

209

Collective charge excitations along cell membranes  

NASA Astrophysics Data System (ADS)

A significant part of the thin layers of counter-ions adjacent to the exterior and interior surfaces of a cell membrane form quasi-two-dimensional (2D) layers of mobile charge. Collective charge density oscillations, known as plasmon modes, in these 2D charged systems of counter-ions are predicted in the present paper. This is based on a calculation of the self-consistent response of this system to a fast electric field fluctuation. The possibility that the membrane channels might be using these excitations to carry out fast communication is suggested and experiments are proposed to reveal the existence of such excitations.

Manousakis, E.

2005-07-01

210

Comparative Membrane Extraction Methods for Identifying Membrane Proteome of SW900 Squamous Lung Cancer Cell Line  

Microsoft Academic Search

Although several methods for extracting and handling membrane proteins for proteomics experiments have been reported, the direct comparison of different methods has never been clarified for the identifying membrane proteome in lung cancer cell lines. This study was purposed to find a protocol suitable for membrane protein extraction and to identify the membrane proteome in lung cancer. Three detergent-based extraction

Suree Phutrakul; Shui-Tein Chen

211

Measurement of red blood cell mechanics during morphological changes  

PubMed Central

The human red blood cell (RBC) membrane, a fluid lipid bilayer tethered to an elastic 2D spectrin network, provides the principal control of the cell’s morphology and mechanics. These properties, in turn, influence the ability of RBCs to transport oxygen in circulation. Current mechanical measurements of RBCs rely on external loads. Here we apply a noncontact optical interferometric technique to quantify the thermal fluctuations of RBC membranes with 3 nm accuracy over a broad range of spatial and temporal frequencies. Combining this technique with a new mathematical model describing RBC membrane undulations, we measure the mechanical changes of RBCs as they undergo a transition from the normal discoid shape to the abnormal echinocyte and spherical shapes. These measurements indicate that, coincident with this morphological transition, there is a significant increase in the membrane’s shear, area, and bending moduli. This mechanical transition can alter cell circulation and impede oxygen delivery.

Park, YongKeun; Best, Catherine A.; Badizadegan, Kamran; Dasari, Ramachandra R.; Feld, Michael S.; Kuriabova, Tatiana; Henle, Mark L.; Levine, Alex J.; Popescu, Gabriel

2010-01-01

212

Membrane protein expression: no cells required.  

PubMed

Structural and functional studies of membrane proteins have been severely hampered by difficulties in producing sufficient quantities of properly folded protein products. It is well established that cell-based expression of membrane proteins is generally problematic and frequently results in low yield, cell toxicity, protein aggregation and misfolding. Owing to its inherent open nature, cell-free protein expression has become a highly promising tool for the fast and efficient production of these difficult-to-express proteins. Here we review the most recent advances in this field, underscoring the potentials and weaknesses of the newly developed approaches and place specific emphasis on the use of nanolipoprotein particles (NLPs or nanodiscs). PMID:19616329

Katzen, Federico; Peterson, Todd C; Kudlicki, Wieslaw

2009-07-16

213

Membrane catalyst layer for fuel cells  

DOEpatents

A gas reaction fuel cell incorporates a thin catalyst layer between a solid polymer electrolyte (SPE) membrane and a porous electrode backing. The catalyst layer is preferably less than about 10 {mu}m in thickness with a carbon supported platinum catalyst loading less than about 0.35 mgPt/cm{sup 2}. The film is formed as an ink that is spread and cured on a film release blank. The cured film is then transferred to the SPE membrane and hot pressed into the surface to form a catalyst layer having a controlled thickness and catalyst distribution. The layer has adequate gas permeability so that cell performance is not affected and has a density and particle distribution effective to optimize proton access to the catalyst and electronic continuity for electron flow from the half-cell reaction occurring at the catalyst.

Wilson, M.S.

1991-02-19

214

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

215

Numerical study of a hybrid membrane cell with semi and fully permeable membrane sub-sections  

Microsoft Academic Search

Hybrid membrane cells with up to 128 sections, each one comprising a fully and a semi-permeable membrane sub-section and, the limit case of a cell with an infinite number of membrane sections were studied by numerical methods. These hybrid cells separate a feed stream into two parts: a solvent stream which crosses the semi-permeable membranes and a concentrate stream which

J. M. Miranda; J. B. L. M. Campos

2007-01-01

216

Noncontact microsurgery of living cell membrane using femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Near-infrared femtosecond laser pulses were applied to initiate reversible permeabilization of cell membrane and inject extrinsic substances into the target cells. Successful laser-based injection of a membrane impermeable dye, as well as plasmid DNA was demonstrated.

Ilina, I. V.; Ovchinnikov, A. V.; Sitnikov, D. S.; Chefonov, O. V.; Agranat, M. B.; Mikaelyan, A. S.

2013-06-01

217

Regulation of Photosynthesis during Leaf Development in RbcS Antisense DNA Mutants of Tobacco.  

PubMed Central

We have previously characterized RbcS antisense DNA mutants of tobacco that have drastic reductions in their content of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; S.R. Rodermel, M.S. Abbott, L. Bogorad [1988] Cell 55: 673-681). In this report we examine the impact of Rubisco loss on photosynthesis during tobacco (Nicotiana tabacum) leaf development. Photosynthetic capacities are depressed in the antisense leaves, but the patterns of change in photosynthetic rates during the development of these leaves are similar to those in wild-type plants: after attaining a maximum in young leaves, photosynthetic capacities undergo a prolonged senescence decline in older leaves. The alterations in photosynthetic capacities in both the wild type and mutant are closely correlated with changes in Rubisco activity and content. During wild-type leaf development, Rubisco accumulation is regulated by coordinate changes in RbcS and rbcL transcript accumulation, whereas in the antisense leaves, Rubisco content is a function of RbcS, but not rbcL, transcript abundance. This indicates that large subunit protein production is controlled posttranscriptionally in the mutants. The antisense leaves accumulate near-normal levels of chlorophyll and representative photosynthetic proteins throughout development, suggesting that photosynthetic gene expression is not feedback regulated by Rubisco abundance. Considered together, the data in this paper indicate that leaf developmental programs are generally insensitive to sharp reductions in Rubisco content and emphasize the metabolic plasticity of plant cells in achieving optimal photosynthetic rates.

Jiang, C. Z.; Rodermel, S. R.

1995-01-01

218

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.

Doctor, Allan; Spinella, Phil

2012-01-01

219

Optical Measurement of Cell Membrane Tension  

NASA Astrophysics Data System (ADS)

Using a novel noncontact technique based on optical interferometry, we quantify the nanoscale thermal fluctuations of red blood cells (RBCs) and giant unilamellar vesicles (GUVs). The measurements reveal a nonvanishing tension coefficient for RBCs, which increases as cells transition from a discocytic shape to a spherical shape. The tension coefficient measured for GUVs is, however, a factor of 4 24 smaller. By contrast, the bending moduli for cells and vesicles have similar values. This is consistent with the cytoskeleton confinement model, in which the cytoskeleton inhibits membrane fluctuations [Gov et al., Phys. Rev. Lett. 90, 228101, (2003)PRLTAO0031-900710.1103/PhysRevLett.90.228101].

Popescu, Gabriel; Ikeda, Takahiro; Goda, Keisuke; Best-Popescu, Catherine A.; Laposata, Michael; Manley, Suliana; Dasari, Ramachandra R.; Badizadegan, Kamran; Feld, Michael S.

2006-11-01

220

Elevated intracellular Ca2+ reveals a functional membrane nucleotide pool in intact human red blood cells  

PubMed Central

Elevated intracellular calcium generates rapid, profound, and irreversible changes in the nucleotide metabolism of human red blood cells (RBCs), triggered by the adenosine triphosphatase (ATPase) activity of the powerful plasma membrane calcium pump (PMCA). In the absence of glycolytic substrates, Ca2+-induced nucleotide changes are thought to be determined by the interaction between PMCA ATPase, adenylate kinase, and AMP-deaminase enzymes, but the extent to which this three-enzyme system can account for the Ca2+-induced effects has not been investigated in detail before. Such a study requires the formulation of a model incorporating the known kinetics of the three-enzyme system and a direct comparison between its predictions and precise measurements of the Ca2+-induced nucleotide changes, a precision not available from earlier studies. Using state-of-the-art high-performance liquid chromatography, we measured the changes in the RBC contents of ATP, ADP, AMP, and IMP during the first 35 min after ionophore-induced pump-saturating Ca2+ loads in the absence of glycolytic substrates. Comparison between measured and model-predicted changes revealed that for good fits it was necessary to assume mean ATPase Vmax values much higher than those ever measured by PMCA-mediated Ca2+ extrusion. These results suggest that the local nucleotide concentrations generated by ATPase activity at the inner membrane surface differed substantially from those measured in bulk cell extracts, supporting previous evidence for the existence of a submembrane microdomain with a distinct nucleotide metabolism.

Tiffert, Teresa

2011-01-01

221

Fuel cell membranes and crossover prevention  

SciTech Connect

A membrane electrode assembly for use with a direct organic fuel cell containing a formic acid fuel includes a solid polymer electrolyte having first and second surfaces, an anode on the first surface and a cathode on the second surface and electrically linked to the anode. The solid polymer electrolyte has a thickness t:.gtoreq..times..times..times..times. ##EQU00001## where C.sub.f is the formic acid fuel concentration over the anode, D.sub.f is the effective diffusivity of the fuel in the solid polymer electrolyte, K.sub.f is the equilibrium constant for partition coefficient for the fuel into the solid polymer electrolyte membrane, I is Faraday's constant n.sub.f is the number of electrons released when 1 molecule of the fuel is oxidized, and j.sub.f.sup.c is an empirically determined crossover rate of fuel above which the fuel cell does not operate.

Masel, Richard I. (Champaign, IL); York, Cynthia A. (Newington, CT); Waszczuk, Piotr (White Bear Lake, MN); Wieckowski, Andrzej (Champaign, IL)

2009-08-04

222

Molecular Basis of Red Cell Membrane Disorders  

Microsoft Academic Search

We will consider an array of genetic disorders of the red cell membrane. Some affect well-known genes. The mutations of most cases of hereditary spherocytosis (HS) are located in the following genes: ANK1, SPTB, SLC4A1, EPB42 and SPTA1, which encode ankyrin, spectrin ?-chain, the anion exchanger 1 (band 3), protein 4.2 and spectrin ?-chain, respectively. A dominant form of distal

Jean Delaunay

2002-01-01

223

Application of Dow Chemical's Perfluorinated Membranes in Proton-Exchange Membrane Fuel Cells. (Abstract Only).  

National Technical Information Service (NTIS)

Dow Chemical's research activities in fuel cell devices revolves around the development and subsequent investigation of the perfluorinated inomeric membrane separator useful in proton-exchange membrane systems. Work is currently focusing on studying the e...

G. A. Eisman

1989-01-01

224

Application of Dow Chemical's Perfluorinated Membranes in Proton-Exchange Membrane Fuel Cells.  

National Technical Information Service (NTIS)

Dow Chemical's research activities in fuel cells revolve around the development of perfluorosulfonic acid membranes useful as the proton transport medium and separator. Some of the performance characteristics which are typical for such membranes are outli...

G. A. Eisman

1989-01-01

225

Bioluminescence Assay for Detecting Cell Surface Membrane Protein Expression  

PubMed Central

Abstract We have developed a method to measure the amounts of cell surface-expressed membrane proteins with bioluminescence. Dinoflagellate luciferase was expressed on the surface of a mammalian cell as a chimeric fusion protein with a membrane protein of interest. Using a membrane-impermeable substrate to quantify the membrane-displayed luciferase, the expression of the membrane protein on the cell surface was determined. By inclusion of a quenching step for the luminescent activity of luciferase on the cell surface, we were able to monitor the membrane protein expression kinetics by measuring the luminescence recovery from the cell surface after quenching. The reported methods provide a convenient way to monitor the kinetics of expression and transport of membrane proteins to the cell surface. It is applicable to the high-throughput analysis of drugs or drug candidates concerning their effects on membrane protein expression.

Kato, Mieko; Chiba, Tomoki; Li, Min

2011-01-01

226

Membrane catalyst layer for fuel cells  

DOEpatents

A gas reaction fuel cell incorporates a thin catalyst layer between a solid polymer electrolyte (SPE) membrane and a porous electrode backing. The catalyst layer is preferably less than about 10 .mu.m in thickness with a carbon supported platinum catalyst loading less than about 0.35 mgPt/cm.sup.2. The film is formed as an ink that is spread and cured on a film release blank. The cured film is then transferred to the SPE membrane and hot pressed into the surface to form a catalyst layer having a controlled thickness and catalyst distribution. Alternatively, the catalyst layer is formed by applying a Na.sup.+ form of a perfluorosulfonate ionomer directly to the membrane, drying the film at a high temperature, and then converting the film back to the protonated form of the ionomer. The layer has adequate gas permeability so that cell performance is not affected and has a density and particle distribution effective to optimize proton access to the catalyst and electronic continuity for electron flow from the half-cell reaction occurring at the catalyst.

Wilson, Mahlon S. (Los Alamos, NM)

1993-01-01

227

Correlation of cell membrane dynamics and cell motility  

PubMed Central

Background Essential events of cell development and homeostasis are revealed by the associated changes of cell morphology and therefore have been widely used as a key indicator of physiological states and molecular pathways affecting various cellular functions via cytoskeleton. Cell motility is a complex phenomenon primarily driven by the actin network, which plays an important role in shaping the morphology of the cells. Most of the morphology based features are approximated from cell periphery but its dynamics have received none to scant attention. We aim to bridge the gap between membrane dynamics and cell states from the perspective of whole cell movement by identifying cell edge patterns and its correlation with cell dynamics. Results We present a systematic study to extract, classify, and compare cell dynamics in terms of cell motility and edge activity. Cell motility features extracted by fitting a persistent random walk were used to identify the initial set of cell subpopulations. We propose algorithms to extract edge features along the entire cell periphery such as protrusion and retraction velocity. These constitute a unique set of multivariate time-lapse edge features that are then used to profile subclasses of cell dynamics by unsupervised clustering. Conclusions By comparing membrane dynamic patterns exhibited by each subclass of cells, correlated trends of edge and cell movements were identified. Our findings are consistent with published literature and we also identified that motility patterns are influenced by edge features from initial time points compared to later sampling intervals.

2011-01-01

228

The Bo-RBC-SCID mouse model for evaluating the efficacy of anti-theilerial drugs.  

PubMed

We have previously developed a mouse model which allowed the proliferation of Theileria sergenti in severe combined immunodeficiency (SCID) mice with circulating bovine erythrocytes (Bo-RBC). In the present study, this model was utilized to test the efficacy of anti-theilerial drugs. Bo-RBC-SCID mice were created by giving periodic transfusions of T. sergenti-free Bo-RBC, and subsequently infecting with T. sergenti. Three anti-protozoal compounds, Pamaquine (Yamanouchi Pharmaceutical Co. Ltd), Ganaseg (Japan CIBA-GEIGY Ltd) and Buparvaquone (Coopers Animal Health Ltd), were subcutaneously administered into the mice at doses recommended for cattle therapy. Blood examinations demonstrated that all three drugs significantly reduced the level of parasitemia although Ganaseg was effective only at a dose five times higher than that recommended for cattle therapy. Administration of the drugs neither caused any sign of acute toxicity nor changed the rate of Bo-RBC in the SCID mice's circulating blood cells. The results indicate that the Bo-RBC-SCID mouse model may offer a useful in vivo system for evaluating the efficacy of anti-protozoal drugs against T. sergenti. PMID:8468129

Hagiwara, K; Tsuji, M; Ishihara, C; Tajima, M; Kurosawa, T; Iwai, H; Takahashi, K

1993-02-01

229

DePEGylation studies: PEG-RBC stability in conditions consistent with massive transfusion.  

PubMed

Each year the United States population receives an estimated 12 to 14 million units of packed red blood cells (RBCs) and whole blood. It is estimated that 33% of transfusions associated with trauma are with unmatched type O RBCs (UORBC). UORBCs have been proven effective and relatively safe however, by masking RBC surface antigens the risk of transfusion reaction may be further decreased. It is, therefore, important to evaluate and validate the stability of antigen masked RBCs, which may play a part in avoiding transfusion reactions. These antigen-masked RBCs would be regularly subjected to abnormal in vivo conditions commonly associated with massive transfusion such as lactic acidosis, bacteremia, and in vitro irradiation, which is frequently used to sterilize and decrease T Lymphocyte counts in RBC units before transfusion. This study compared two methods of masking RBC antigens by PEGylation: maleimide-PEGylation and cyanuric chloride-PEGylation. RBC PEGylation effectively masks the Rh(D) antigen and PEG-RBC bond stability was evaluated by comparison of pre and post exposure agglutination with anti-D sera. While the stability of maleimide-PEG-RBCs remained unaffected, the cyanuric chloride-PEG-RBCs remained stable in the bacteremia and irradiation studies, but critical concentrations of lactic acid caused dePEGylation. Further studies are warranted to ensure in vivo stability. PMID:22288221

Moore, M Scott; Okelberry, Eric; Cordingley, Krystle; Drake, Alex; Robinett, Zachary

2011-01-01

230

Adenosinetriphosphatase Activity in the Cell Membranes of Kidney Tubule Cells  

PubMed Central

This cytochemical study demonstrates high levels of apparent ATPase activity in the infolded cell membranes of the proximal tubules (dog, rat, human, mouse, monkey, and opossum) and ascending loops of Henle (dog, rat, human and, to a variable degree, mouse). Electron microscopy has shown (see Rhodin (1)) that these membranes separate adjacent cells where they interlock with one another by multiple cytoplasmic lamellae containing oriented mitochondria. The significance of the high ATPase activity is considered in relation to possible movements of the membranes and to "active transport" believed to occur there. In the rat, enzyme activity in the proximal tubule membranes does not survive formol-calcium fixation, and it is therefore necessary to use unfixed sections for its demonstration. However, in edematous rats with experimental nephrosis (induced by the injection of aminonucleoside or with antikidney serum) marked ATPase activity is exhibited in these membranes even after formol-calcium fixation. When proximal tubule or Henle loop cells of the dog acquire an altered metabolism, as indicated by accumulated lipide spheres or by "droplets," the infolded ATPase-rich membranes are no longer demonstrable.

Spater, Herman W.; Novikoff, Alex B.; Masek, Bertha

1958-01-01

231

Sialoglycosylation of RBC in Visceral Leishmaniasis Leads to Enhanced Oxidative Stress, Calpain-Induced Fragmentation of Spectrin and Hemolysis  

PubMed Central

Visceral leishmaniasis (VL) caused by the intracellular parasite Leishmania donovani accounts for an estimated 12 million cases of human infection. It is almost always associated with anemia, which severely complicates the disease course. However, the pathological processes leading to anemia in VL have thus far not been adequately characterized to date. In studying the glycosylation patterns of peripheral blood cells we found that the red blood cells (RBC) of VL patients (RBCVL) express eight 9-O-acetylated sialoglycoproteins (9-O-AcSGPs) that are not detected in the RBC of healthy individuals (RBCN). At the same time, the patients had high titers of anti-9-O-AcSGP IgG antibodies in their sera. These two conditions appear to be linked and related to the anemic state of the patients, as exposure of RBCVL but not RBCN to anti-9-O-AcSGPs antibodies purified from patient sera triggered a series of responses. These included calcium influx via the P/Q-type but not L-type channels, activation of calpain I, proteolysis of spectrin, enhanced oxidative stress, lipid peroxidation, externalization of phosphatidyl serine with enhanced erythrophagocytosis, enhanced membrane fragility and, finally, hemolysis. Taken together, this study suggests that the enhanced hemolysis is linked to an impairment of membrane integrity in RBCVL which is mediated by ligand-specific interaction of surface 9-O-AcSGPs. This affords a potential explanation for the structural and functional features of RBCVL which are involved in the hemolysis related to the anemia which develops in VL patients.

Samanta, Sajal; Ghoshal, Angana; Bhattacharya, Kaushik; Saha, Bibhuti; Walden, Peter; Mandal, Chitra

2012-01-01

232

Changes in red blood cell membrane structure in type 2 diabetes: a scanning electron and atomic force microscopy study  

PubMed Central

Red blood cells (RBCs) are highly deformable and possess a robust membrane that can withstand shear force. Previous research showed that in diabetic patients, there is a changed RBC ultrastructure, where these cells are elongated and twist around spontaneously formed fibrin fibers. These changes may impact erythrocyte function. Ultrastructural analysis of RBCs in inflammatory and degenerative diseases can no longer be ignored and should form a fundamental research tool in clinical studies. Consequently, we investigated the membrane roughness and ultrastructural changes in type 2 diabetes. Atomic force microscopy (AFM) was used to study membrane roughness and we correlate this with scanning electron microscopy (SEM) to compare results of both the techniques with the RBCs of healthy individuals. We show that the combined AFM and SEM analyses of RBCs give valuable information about the disease status of patients with diabetes. Effectiveness of treatment regimes on the integrity, cell shape and roughness of RBCs may be tracked, as this cell’s health status is crucial to the overall wellness of the diabetic patient.

2013-01-01

233

A Comparison of Multi-scale and Low-Dimensional Models of Red Blood Cells  

NASA Astrophysics Data System (ADS)

A new low-dimensional dissipative particle dynamics (DPD) model of the red blood cell (LD-RBC) is tested against a multi-scale RBC (MS-RBC) model known to accurately capture the mechanical response of single human RBCs in a number of static and dynamic experiments. The MS-RBC model represents the RBC membrane with hundreds or even thousands of DPD-particles and includes membrane viscosity. In contrast, the LD-RBC is constructed as a closed torus-like ring of only 10 large, hard DPD-particles previously employed to represent a colloidal suspension. Except for channel sizes comparable to RBC diameters, suspensions of LD-RBCs also capture the essential hydrodynamics of blood flow in vessels as faithfully as do suspensions of MS-RBCs. In particular, the LD-RBC is in agreement with the experimental data for the apparent viscosity of blood and its cell-free layer over a wide range of hematocrits.

Pan, Wenxiao; Fedosov, Dmitry; Caswell, Bruce; Karniadakis, George

2010-11-01

234

Fuel cell membrane hydration and fluid metering  

DOEpatents

A hydration system includes fuel cell fluid flow plate(s) and injection port(s). Each plate has flow channel(s) with respective inlet(s) for receiving respective portion(s) of a given stream of reactant fluid for a fuel cell. Each injection port injects a portion of liquid water directly into its respective flow channel in order to mix its respective portion of liquid water with the corresponding portion of the stream. This serves to hydrate at least corresponding part(s) of a given membrane of the corresponding fuel cell(s). The hydration system may be augmented by a metering system including flow regulator(s). Each flow regulator meters an injecting at inlet(s) of each plate of respective portions of liquid into respective portion(s) of a given stream of fluid by corresponding injection port(s).

Jones, Daniel O. (Glenville, NY); Walsh, Michael M. (Fairfield, CT)

1999-01-01

235

Erythrocyte plasma membrane-bound ERK1/2 activation promotes ICAM-4-mediated sickle red cell adhesion to endothelium  

PubMed Central

The core pathology of sickle cell disease (SCD) starts with the erythrocyte (RBC). Aberration in MAPK/ERK1/2 signaling, which can regulate cell adhesion, occurs in diverse pathologies. Because RBCs contain abundant ERK1/2, we predicted that ERK1/2 is functional in sickle (SS) RBCs and promotes adherence, a hallmark of SCD. ERK1/2 remained active in SS but not normal RBCs. ?2-adrenergic receptor stimulation by epinephrine can enhance ERK1/2 activity only in SS RBCs via PKA- and tyrosine kinase p72syk-dependent pathways. ERK signaling is implicated in RBC ICAM-4 phosphorylation, promoting SS RBC adhesion to the endothelium. SS RBC adhesion and phosphorylation of both ERK and ICAM-4 all decreased with continued cell exposure to epinephrine, implying that activation of ICAM-4–mediated SS RBC adhesion is temporally associated with ERK1/2 activation. Furthermore, recombinant ERK2 phosphorylated ?- and ?-adducins and dematin at the ERK consensus motif. Cytoskeletal protein 4.1 also showed dynamic phosphorylation but not at the ERK consensus motif. These results demonstrate that ERK activation induces phosphorylation of cytoskeletal proteins and the adhesion molecule ICAM-4, promoting SS RBC adhesion to the endothelium. Thus, blocking RBC ERK1/2 activation, such as that promoted by catecholamine stress hormones, could ameliorate SCD pathophysiology.

Whalen, Erin J.; Soderblom, Erik J.; Alexander, Susan C.; Thompson, J. Will; Dubois, Laura G.; Moseley, M. Arthur; Telen, Marilyn J.

2012-01-01

236

Erythrocyte plasma membrane-bound ERK1/2 activation promotes ICAM-4-mediated sickle red cell adhesion to endothelium.  

PubMed

The core pathology of sickle cell disease (SCD) starts with the erythrocyte (RBC). Aberration in MAPK/ERK1/2 signaling, which can regulate cell adhesion, occurs in diverse pathologies. Because RBCs contain abundant ERK1/2, we predicted that ERK1/2 is functional in sickle (SS) RBCs and promotes adherence, a hallmark of SCD. ERK1/2 remained active in SS but not normal RBCs. ?(2)-adrenergic receptor stimulation by epinephrine can enhance ERK1/2 activity only in SS RBCs via PKA- and tyrosine kinase p72(syk)-dependent pathways. ERK signaling is implicated in RBC ICAM-4 phosphorylation, promoting SS RBC adhesion to the endothelium. SS RBC adhesion and phosphorylation of both ERK and ICAM-4 all decreased with continued cell exposure to epinephrine, implying that activation of ICAM-4-mediated SS RBC adhesion is temporally associated with ERK1/2 activation. Furthermore, recombinant ERK2 phosphorylated ?- and ?-adducins and dematin at the ERK consensus motif. Cytoskeletal protein 4.1 also showed dynamic phosphorylation but not at the ERK consensus motif. These results demonstrate that ERK activation induces phosphorylation of cytoskeletal proteins and the adhesion molecule ICAM-4, promoting SS RBC adhesion to the endothelium. Thus, blocking RBC ERK1/2 activation, such as that promoted by catecholamine stress hormones, could ameliorate SCD pathophysiology. PMID:22147898

Zennadi, Rahima; Whalen, Erin J; Soderblom, Erik J; Alexander, Susan C; Thompson, J Will; Dubois, Laura G; Moseley, M Arthur; Telen, Marilyn J

2011-12-06

237

Application of optical trapping for detection of Calcium induced morphological changes of red blood cells  

Microsoft Academic Search

This work investigates an optical trap based method for detection of structural changes of the red blood cell (RBC) membrane affected by Ca2+ ions. Individual cells are immobilized by use of optical tweezers and are monitored live while the concentration of Ca2+ ions in the buffer is changed simultaneously. Ca2+ ions affect cells' membrane morphology, which results in the change

Ali-Reza Moradi; Mohammad Kutub Ali; Mehdi Daneshpanah; Arun Anand; Bahram Javidi

2010-01-01

238

Cell membrane potentials induced during exposure to EMP fields  

Microsoft Academic Search

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

P. C. Gailey; C. E. Easterly

1994-01-01

239

The membrane proteome of the mouse lens fiber cell  

Microsoft Academic Search

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

Steven Bassnett; Phillip A. Wilmarth; Larry L. David

2009-01-01

240

Permeability of a Cell Membrane Junction  

PubMed Central

The ion permeability of the membrane junctions between Chironomus salivary gland cells is strongly depressed by treatments that are generally known to inhibit energy metabolism. These treatments include prolonged cooling at 6°–8°C, and exposure to dinitrophenol, cyanide, oligomycin, and N-ethylmaleimide. Intracellular injection of ATP appears to prevent depression of junctional permeability by dinitrophenol or to reverse it. Ouabain, azide, p-chloromercuriphenylsulfonic acid, reserpine, and acetazolamide fail to depress junctional permeability. Thus the ion permeability of the junctional membranes appears to depend on energy provided by oxidative phosphorylation. Possible energy-linked processes for maintaining junctional permeability are discussed, including processes involving transport of permeability-modifying species such as Ca++.

Politoff, A. L.; Socolar, S. J.; Loewenstein, W. R.

1969-01-01

241

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

242

Effect of Hydroperoxides on Red Blood Cell Membrane Mechanical Properties  

Microsoft Academic Search

We investigate the effect of oxidative stress on red blood cell membrane mechanical properties in vitro using detailed analysis of the membrane thermal fluctuation spectrum. Two different oxidants, the cytosol-soluble hydrogen peroxide and the membrane-soluble cumene hydroperoxide, are used, and their effects on the membrane bending elastic modulus, surface tension, strength of confinement due to the membrane skeleton, and 2D shear

2011-01-01

243

Durable, Low-Cost, Improved Fuel Cell Membranes.  

National Technical Information Service (NTIS)

The development of low cost, durable membranes and membranes electrode assemblies (MEAs) that operate under reduced relative humidity (RH) conditions remain a critical challenge for the successful introduction of fuel cells into mass markets. It was the g...

C. Roger D. Mountz T. Zhang W. He

2011-01-01

244

Preparation of cell membranes for high resolution imaging by AFM.  

PubMed

Studies of cell membrane structure by atomic force microscopy (AFM) have been limited because of the softness of cell membranes. Here, we utilize a new technique of sample preparation to lay red blood cell membranes on the top of a mica surface to obtain high resolution images by in-situ AFM on both sides of cell membranes. Our results indicate that the location of oligosaccharides and proteins in red blood cell membranes might be different from the current membrane model. The inner membrane leaflet is covered by dense proteins with fewer free lipids than expected. In contrast, the outer membrane leaflet is quite smooth; oligosaccharides and peptides supposed to protrude out of the outer membrane leaflet surface might be actually hidden in the middle of hydrophilic lipid heads; transmembrane proteins might form domains in the membranes revealed by PNGase F and trypsin digestion. Our result could be significant to interpret some functions about red blood cell membranes and guide to heal the blood diseases related to cell membranes. PMID:20097008

Wang, Hongda; Hao, Xian; Shan, Yuping; Jiang, Junguang; Cai, Mingjun; Shang, Xin

2010-01-04

245

The plasma membrane lipid composition affects fusion between cells and model membranes  

Microsoft Academic Search

Investigations were carried out on the effect of plasma membrane lipid modifications on the fusogenic capacity of control and ras-transformed fibroblasts. The plasma membrane lipid composition was modified by treatment of cells with exogenous phospholipases C and D, sphingomyelinase and cyclodextrin. The used enzymes hydrolyzed definite membrane lipids thus inducing specific modifications of the lipid composition while cyclodextrin treatment reduced

Roumen Pankov; Tania Markovska; Peter Antonov; Lidia Ivanova; Albena Momchilova

2006-01-01

246

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.

247

Membrane Purification Cell for Aluminum Recycling  

SciTech Connect

Recycling mixed aluminum scrap usually requires adding primary aluminum to the scrap stream as a diluent to reduce the concentration of non-aluminum constituents used in aluminum alloys. Since primary aluminum production requires approximately 10 times more energy than melting scrap, the bulk of the energy and carbon dioxide emissions for recycling are associated with using primary aluminum as a diluent. Eliminating the need for using primary aluminum as a diluent would dramatically reduce energy requirements, decrease carbon dioxide emissions, and increase scrap utilization in recycling. Electrorefining can be used to extract pure aluminum from mixed scrap. Some example applications include producing primary grade aluminum from specific scrap streams such as consumer packaging and mixed alloy saw chips, and recycling multi-alloy products such as brazing sheet. Electrorefining can also be used to extract valuable alloying elements such as Li from Al-Li mixed scrap. This project was aimed at developing an electrorefining process for purifying aluminum to reduce energy consumption and emissions by 75% compared to conventional technology. An electrolytic molten aluminum purification process, utilizing a horizontal membrane cell anode, was designed, constructed, operated and validated. The electrorefining technology could also be used to produce ultra-high purity aluminum for advanced materials applications. The technical objectives for this project were to: - Validate the membrane cell concept with a lab-scale electrorefining cell; - Determine if previously identified voltage increase issue for chloride electrolytes holds for a fluoride-based electrolyte system; - Assess the probability that voltage change issues can be solved; and - Conduct a market and economic analysis to assess commercial feasibility. The process was tested using three different binary alloy compositions (Al-2.0 wt.% Cu, Al-4.7 wt.% Si, Al-0.6 wt.% Fe) and a brazing sheet scrap composition (Al-2.8 wt.% Si-0.7 wt.% Fe-0.8 wt.% Mn),. Purification factors (defined as the initial impurity concentration divided by the final impurity concentration) of greater than 20 were achieved for silicon, iron, copper, and manganese. Cell performance was measured using its current and voltage characteristics and composition analysis of the anode, cathode, and electrolytes. The various cells were autopsied as part of the study. Three electrolyte systems tested were: LiCl-10 wt. % AlCl3, LiCl-10 wt. % AlCl3-5 wt.% AlF3 and LiF-10 wt.% AlF3. An extended four-day run with the LiCl-10 wt.% AlCl3-5 wt.% AlF3 electrolyte system was stable for the entire duration of the experiment, running at energy requirements about one third of the Hoopes and the conventional Hall-Heroult process. Three different anode membranes were investigated with respect to their purification performance and survivability: a woven graphite cloth with 0.05 cm nominal thickness & > 90 % porosity, a drilled rigid membrane with nominal porosity of 33%, and another drilled rigid graphite membrane with increased thickness. The latter rigid drilled graphite was selected as the most promising membrane design. The economic viability of the membrane cell to purify scrap is sensitive to primary & scrap aluminum prices, and the cost of electricity. In particular, it is sensitive to the differential between scrap and primary aluminum price which is highly variable and dependent on the scrap source. In order to be economically viable, any scrap post-processing technology in the U.S. market must have a total operating cost well below the scrap price differential of $0.20-$0.40 per lb to the London Metal Exchange (LME), a margin of 65%-85% of the LME price. The cost to operate the membrane cell is estimated to be < $0.24/lb of purified aluminum. The energy cost is estimated to be $0.05/lb of purified aluminum with the remaining costs being repair and maintenance, electrolyte, labor, taxes and depreciation. The bench-scale work on membrane purification cell process has demonstrated technological advantages and subs

David DeYoung; James Wiswall; Cong Wang

2011-11-29

248

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.

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

2009-01-01

249

Cell membrane structure of human giant-celled glioblastoma  

Microsoft Academic Search

A giant-cell glioblastoma was examined by electron microscopy and by the freeze-fracture technique. The cell membranes bordering the extensive extracellular space often showed complicated undulations and peripheral vacuoles as well as occasional microvilli or filopodia. The undulations were mainly composed of plasmalemmal vesicles as well as of large (400–800 nm in diameter) and small (30–50 nm in diameter) localized protrusions

Eiichi Tani; Masaru Nakano; Tetsuya Itagaki; Toyokazu Fukumori

1978-01-01

250

The influence of saponins on cell membrane cholesterol.  

PubMed

We studied the influence of structurally different saponins on the cholesterol content of cellular membranes. Therefore a cell culture model using ECV-304 urinary bladder carcinoma cells was developed. To measure the cholesterol content we used radiolabeled (3)H-cholesterol which is chemically and physiologically identical to natural cholesterol. The cells were pre-incubated with (3)H-cholesterol and after a medium change, they were treated with saponins to assess a saponin-induced cholesterol liberation from the cell membrane. In another experiment the cells were pre-incubated with saponins and after a medium change, they were treated with (3)H-cholesterol to assess a saponin-induced inhibition of cholesterol uptake into the cell membrane. Furthermore, the membrane toxicity of all applied saponins was analyzed using extracellular LDH quantification and the general cytotoxicity was analyzed using a colorimetric MTT-assay and DNA quantification. Our results revealed a correlation between membrane toxicity and general cytotoxicity. We also compared the results from the experiments on the saponin-induced cholesterol liberation as well as the saponin-induced inhibition of cholesterol uptake with the membrane toxicity. A significant reduction in the cell membrane cholesterol content was noted for those saponins who showed membrane toxicity (IC50 <60?M). These potent membrane toxic saponins either liberated (3)H-cholesterol from intact cell membranes or blocked the integration of supplemented (3)H-cholesterol into the cell membrane. Saponins with little influence on the cell membrane (IC50 >100?M) insignificantly altered the cell membrane cholesterol content. The results suggested that the general cytotoxicity of saponins is mainly dependent on their membrane toxicity and that the membrane toxicity might be caused by the loss of cholesterol from the cell membrane. We also analyzed the influence of a significantly membrane toxic saponin on the cholesterol content of intracellular membranes such as those of endosomes and lysosomes. In these experiments ECV-304 cells were either incubated with (3)H-cholesterol or with (3)H-cholesterol and 5?M saponin. After isolation of the endosomes/lysosomes their (3)H-cholesterol content was measured. A significant influence of the saponins on the cholesterol content of endosomal/lysosomal membranes was not detected. PMID:24084294

Böttger, Stefan; Melzig, Matthias F

2013-09-14

251

Measurement of red blood cell mechanics during morphological changes  

NASA Astrophysics Data System (ADS)

The human red blood cell (RBC) membrane, a fluid lipid bilayer tethered to an elastic 2D spectrin network, provides the principal control of the cell's morphology and mechanics. These properties, in turn, influence the ability of RBCs to transport oxygen in circulation. Current mechanical measurements of RBCs rely on external loads. Here we apply a Noncontact optical interferometric technique to quantify the thermal fluctuations of RBC membranes with 3 nm accuracy over a broad range of spatial and temporal frequencies. Combining this technique with a new mathematical model describing RBC membrane undulations, we measure the mechanical changes of RBCs as they undergo a transition from the normal discoid shape to the abnormal echinocyte and spherical shapes. These measurements indicate that, coincident with this morphological transition, there is a significant increase in the membrane's shear and bending moduli. This mechanical transition can alter cell circulation and impede oxygen delivery.

Popescu, Gabriel; Park, Yongkeun; Best, Catherine; Dasari, Ramachandra; Feld, Michael; Kuriabova, Tatiana; Henle, Mark; Levine, Alex

2010-03-01

252

Kinetics and mechanism of cell membrane electrofusion.  

PubMed Central

A new quantitative approach to study cell membrane electrofusion has been developed. Erythrocyte ghosts were brought into close contact using dielectrophoresis and then treated with one square or even exponentially decaying fusogenic pulse. Individual fusion events were followed by lateral diffusion of the fluorescent lipid analogue 1,1'-dihexadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil) from originally labeled to unlabeled adjacent ghosts. It was found that ghost fusion can be described as a first-order rate process with corresponding rate constants; a true fusion rate constant, k(f), for the square waveform pulse and an effective fusion rate constant, k(ef), for the exponential pulse. Compared with the fusion yield, the fusion rate constants are more fundamental characteristics of the fusion process and have implications for its mechanisms. Values of k(f) for rabbit and human erythrocyte ghosts were obtained at different electric field strength and temperatures. Arrhenius k(f) plots revealed that the activation energy of ghost electrofusion is in the range of 6-10 kT. Measurements were also made with the rabbit erythrocyte ghosts exposed to 42 degrees C for 10 min (to disrupt the spectrin network) or 0.1-1.0 mM uranyl acetate (to stabilize the bilayer lipid matrix of membranes). A correlation between the dependence of the fusion and previously published pore-formation rate constants for all experimental conditions suggests that the cell membrane electrofusion process involve pores formed during reversible electrical breakdown. A statistical analysis of fusion products (a) further supports the idea that electrofusion is a stochastic process and (b) shows that the probability of ghost electrofusion is independent of the presence of Dil as a label as well as the number of fused ghosts.

Abidor, I G; Sowers, A E

1992-01-01

253

Exocytosis and Endocytosis in Neuroendocrine Cells: Inseparable Membranes!  

PubMed Central

Although much has been learned concerning the mechanisms of secretory vesicle formation and fusion at donor and acceptor membrane compartments, relatively little attention has been paid toward understanding how cells maintain a homeostatic membrane balance through vesicular trafficking. In neurons and neuroendocrine cells, release of neurotransmitters, neuropeptides, and hormones occurs through calcium-regulated exocytosis at the plasma membrane. To allow recycling of secretory vesicle components and to preserve organelles integrity, cells must initiate and regulate compensatory membrane uptake. This review relates the fate of secretory granule membranes after full fusion exocytosis in neuroendocrine cells. In particular, we focus on the potential role of lipids in preserving and sorting secretory granule membranes after exocytosis and we discuss the potential mechanisms of membrane retrieval.

Houy, Sebastien; Croise, Pauline; Gubar, Olga; Chasserot-Golaz, Sylvette; Tryoen-Toth, Petra; Bailly, Yannick; Ory, Stephane; Bader, Marie-France; Gasman, Stephane

2013-01-01

254

Proteomic identification of erythrocyte membrane protein deficiency in hereditary spherocytosis  

Microsoft Academic Search

Hereditary spherocytosis (HS) is the most common congenital hemolytic anemia in Caucasians, with an estimated prevalence ranging\\u000a from 1:2000 to 1:5000. The molecular defect in one of the erythrocytes (RBC) membrane proteins underlying HS like; spectrin-?,\\u000a spectrin-?, ankyrin, band 3 and protein 4.2 that lead to membrane destabilization and vesiculation, may change the RBCs into\\u000a denser and more rigid cells

Selen Peker; Nejat Akar; Duygu Ozel Demiralp

255

Nano thermo-hydrodynamics method for investigating cell membrane fluidity  

Microsoft Academic Search

As a barrier to compartmentalize cells, membranes form the interface between a cell and its surroundings. The essential function\\u000a of a membrane is to maintain a relatively stable environment in the cell, exchange substances selectively and transfer energy\\u000a and information continually from the outside. It is intriguing that above the phase transition temperature, the membrane lipid\\u000a molecule will have three

Yang Yang; Jing Liu

2008-01-01

256

Apparatus for exposing cell membranes to rapid temperature transients  

Microsoft Academic Search

We seek to determine whether cell membranes contain sensors that trigger a downstream response to temperature excursions. To do this, we have developed a novel apparatus for exposing a cell membrane to an extremely rapid temperature excursion in the nanosecond range. Cells are plated on a gold surface that is back-heated by a pulsed laser and cooled by conduction of

B. Steel; M. M. Bilek; C. G. dos Remedios; D. R. McKenzie

2004-01-01

257

Integrated system of fuel cell for polymer electrolyte membrane  

Microsoft Academic Search

The polymer electrolyte membrane fuel cell (PEMFC) is an ionic conducting electrolyte polymer membrane. The factors which influence the performance of PEMFC include relative humidity, reaction temperature, gas inlet temperature, gas inlet pressure, and hydrogen and air flow rate. The safety control methodology strongly depends on the fuel cell operation voltage and current. In order to run the fuel cell

Jenn-Kun Kuo; Yuan-Yao Hsu; Shiuh Ming Chang

2011-01-01

258

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

PubMed

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 Ca(2+) 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

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

2013-01-24

259

Predicting dynamics and rheology of blood flow: A comparative study of multiscale and low-dimensional models of red blood cells  

SciTech Connect

In this work we compare the predictive capability of two mathematical models for red blood cells (RBCs) focusing on blood flow in capillaries and arterioles. Both RBC models as well as their corresponding blood flows are based on the dissipative particle dynamics (DPD) method, a coarse-grained molecular dynamics approach. The first model employs a multiscale description of the RBC (MS-RBC), with its membrane represented by hundreds or even thousands of DPD-particles connected by springs into a triangular network in combination with out-of-plane elastic bending resistance. Extra dissipation within the network accounts for membrane viscosity, while the characteristic biconcave RBC shape is achieved by imposition of constraints for constant membrane area and constant cell volume. The second model is based on a low-dimensional description (LD-RBC) constructed as a closed torus-like ring of only 10 large DPD colloidal particles. They are connected into a ring by worm-like chain (WLC) springs combined with bending resistance. The LD-RBC model can be fitted to represent the entire range of nonlinear elastic deformations as measured by optical-tweezers for healthy and for infected RBCs in malaria. MS-RBCs suspensions model the dynamics and rheology of blood flow accurately for any size vessel but this approach is computationally expensive above 100 microns. Surprisingly, the much more economical suspensions of LD-RBCs also capture the blood flow dynamics and rheology accurately except for vessels with sizes comparable to RBC diameter. In particular, the LD-RBC suspensions are shown to properly capture the experimental data for the apparent viscosity of blood and its cell-free layer (CFL) in tube flow. Taken together, these findings suggest a hierarchical approach in modeling blood flow in the arterial tree, whereby the MS-RBC model should be employed for capillaries and arterioles below 100 microns, the LD-RBC model for arterioles, and the continuum description for arteries.

Pan, Wenxiao; Fedosov, Dmitry A.; Caswell, Bruce; Karniadakis, George E.

2011-05-27

260

How to measure slow diffusion in yeast cell membranes  

NASA Astrophysics Data System (ADS)

Here we present two complementary methods for accurate diffusion measurements in yeast cell membranes. Fluorescence spreading after photobleaching analyzes the blurring of an initially sharp border between bleached and unbleached parts of the membrane. Two-focus scanning fluorescence correlation spectroscopy requires only a low concentration of labeled fluorophores and allows for very long measurement times due to correction for instabilities necessary to probe the slow diffusion in yeast plasma membranes. We apply these techniques to study the dynamics of different transmembrane proteins in the plasma membrane of the yeast Saccharomyces cerevisiae. The differences in the diffusion coefficients support the idea of co-existing membrane microdomains in the yeast plasma membrane.

Ries, Jonas; Klose, Christian; Walch-Solimena, Christiane; Schwille, Petra

2008-05-01

261

The plasma membrane lipid composition affects fusion between cells and model membranes.  

PubMed

Investigations were carried out on the effect of plasma membrane lipid modifications on the fusogenic capacity of control and ras-transformed fibroblasts. The plasma membrane lipid composition was modified by treatment of cells with exogenous phospholipases C and D, sphingomyelinase and cyclodextrin. The used enzymes hydrolyzed definite membrane lipids thus inducing specific modifications of the lipid composition while cyclodextrin treatment reduced significantly the level of cholesterol. The cells with modified membranes were used for assessment of their fusogenic capacity with model membranes with a constant lipid composition. Treatment with phospholipases C and D stimulated the fusogenic potential of both cell lines whereas the specific reduction of either sphingomyelin or cholesterol induced the opposite effect. The results showed that all modifications of the plasma membrane lipid composition affected the fusogenic capacity irrespective of the initial differences in the membrane lipid composition of the two cell lines. These results support the notion that the lipid composition plays a significant role in the processes of membrane-membrane fusion. This role could be either direct or through modulation of the activity of specific proteins which regulate membrane fusion. PMID:17098217

Pankov, Roumen; Markovska, Tania; Antonov, Peter; Ivanova, Lidia; Momchilova, Albena

2006-11-13

262

Preparation of basal cell membranes for scanning probe microscopy.  

PubMed

Scanning probe microscopy has the potential for investigating membranes in a physiological environment. We prepared with a lysis-squirting protocol basal cell membranes, that are suitable for scanning probe microscopy. Investigations using atomic force microscopy under liquid revealed cellular filaments which correlated perfectly with fluorescently stained actin filaments. Globular structures with a diameter as little as 10 nm could be resolved by stripping cytoplasmic components from the membranes. Therefore, cytoplasmic sides of supported basal cell membranes prove useful to gain high resolution with scanning probe microscopy in studies of plasma membrane associated structures and processes under buffer solution. PMID:9781674

Ziegler, U; Vinckier, A; Kernen, P; Zeisel, D; Biber, J; Semenza, G; Murer, H; Groscurth, P

1998-10-01

263

Membrane fouling in microfiltration used for cell harvesting  

NASA Astrophysics Data System (ADS)

In the present study the membrane fouling in microfiltration used for cell harvesting in a deadend system has been investigated. Experimental results were analysed in terms of existing membrane filtration models and membrane resistances. The cake filtration model (CFM) and standard blocking model (SBM) have been considered in this study. Various membrane resistances were determined at different processing time, feed concentration and stirring speed. Resistances to permeation in this system include filter medium, pore blocking, adsorption, cake layer and concentration polarization.

Kaghazchi, Tahereh; Zokaee, Farzin; Zare, Abbas

2001-03-01

264

Silver--zinc electric storage cells. [semipermeable membrane as separator  

Microsoft Academic Search

A rechargeable silver--zinc electric storage cell is described which comprises a casing enclosing a silver electrode and a zinc electrode, a separator comprising an imperforate semi-permeable membrane disposed between the electrodes, and an electrolyte. The membrane is sealed to the casing so that the only ion path between the electrodes is through the membrane. The imperforate semi-permeable membrane comprises a

H. T. Mote; L. Hajdu; B. Ronay

1974-01-01

265

Microspectrofluorometry and polarization microscopy of membrane dynamics in living cells  

NASA Astrophysics Data System (ADS)

Membrane dynamics of human glioblastoma cells were investigated using the intercalating fluorescence marker 6-dodecanoyl-2-dimethylamino naphthalene (laurdan). In particular its generalized polarization (GP), which describes a spectral shift depending on the phase of membrane lipids, was used as a measure of membrane stiffness, whereas its fluorescence lifetime ? and its rotational diffusion time tr were used to characterize membrane fluidity. Upon excitation with linearly polarized pulsed laser light the parallel and perpendicular components of fluorescence from the sample were measured simultaneously using an imaging device with polarization sensitivity. So far, membrane dynamics depended on temperature and cell age as well as the on intracellular amount of cholesterol. In addition, the plasma membrane (assessed by illumination with an evanescent electromagnetic wave) appeared to be stiffer than intracellular membranes (assessed by epiillumination of the cells).

Wagner, Michael; Weber, Petra; Schneckenburger, Herbert

2006-05-01

266

Neither a Nitric Oxide Donor Nor Potassium Channel Blockage Inhibit RBC Mechanical Damage Induced by a Roller Pump  

PubMed Central

Red blood cells (RBC) are exposed to various levels of shear stresses when they are exposed to artificial flow environments, such as extracorporeal flow circuits and hemodialysis equipment. This mechanical trauma affects RBC and the resulting effect is determined by the magnitude of shear forces and exposure time. It has been previously demonstrated that nitric oxide (NO) donors and potassium channel blockers could prevent the sub-hemolytic damage to RBC, when they are exposed to 120 Pa shear stress in a Couette shearing system. This study aimed at testing the effectiveness of NO donor sodium nitroprussid (SNP, 10-4 M) and non-specific potassium channel blocker tetraethylammonium (TEA, 10-7 M) in preventing the mechanical damage to RBC in a simple flow system including a roller pump and a glass capillary of 0.12 cm diameter. RBC suspensions were pumped through the capillary by the roller pump at a flow rate that maintains 200 mmHg hydrostatic pressure at the entrance of the capillary. An aliquot of 10 ml of RBC suspension of 0.4 L/L hematocrit was re-circulated through the capillary for 30 minutes. Plasma hemoglobin concentrations were found to be significantly increased (~7 folds compared to control aliquot which was not pumped through the system) and neither SNP nor TEA prevented this hemolysis. Alternatively, RBC deformability assessed by laser diffraction ektacytometry was not altered after 30 min of pumping and both SNP and TEA had no effect on this parameter. The results of this study indicated that, in contrast with the findings in RBC exposed to a well-defined magnitude of shear stress in a Couette shearing system, the mechanical damage induced by a roller pump could not be prevented by NO donor or potassium channel blocker.

Ulker, Pinar; Meiselman, Herbert J; Baskurt, Oguz K

2008-01-01

267

Membrane glycoproteins of differentiating skeletal muscle cells  

SciTech Connect

The composition of N-linked glycoprotein oligosaccharides was studied in myoblasts and myotubes of the C2 muscle cell line. Oligosaccharides were radioactively labelled for 15 hr with (TH) mannose and plasma membranes isolated. Ten glycopeptides were detected by SDS-PAGE and fluorography. The extent of labelling was 4-6 fold greater in myoblasts vs myotubes. A glycopeptide of Mr > 100,000 was found exclusively in myoblast membranes. Lectin chromatography revealed that the proportion of tri-, tetranntenary, biantennary and high mannose chains was similar throughout differentiation. The high mannose chain fraction was devoid of hybrid chains. The major high mannose chain contained nine mannose residues. The higher level of glycopeptide labelling in myoblasts vs myotubes corresponded to a 5-fold greater rate of protein synthesis. Pulse-chase experiments were used to follow the synthesis of the Dol-oligosaccharides. Myoblasts and myotubes labelled equivalently the glucosylated tetradecasaccharide but myoblasts labelled the smaller intermediates 3-4 greater than myotubes. Myoblasts also exhibited a 2-3 fold higher Dol-P dependent glycosyl transferase activity for chain elongation and Dol-sugar synthesis. Together these results show that the degree of protein synthesis and level of Dol-P are contributing factors in the higher capacity of myoblasts to produce N-glycoproteins compared to myotubes.

Miller, K.R.; Remy, C.N.; Smith, P.B.

1987-05-01

268

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

269

Reversal of anemia with allogenic RBC transfusion prevents post-cardiopulmonary bypass acute kidney injury in swine  

PubMed Central

Anemia during cardiopulmonary bypass (CPB) is strongly associated with acute kidney injury in clinical studies; however, reversal of anemia with red blood cell (RBC) transfusions is associated with further renal injury. To understand this paradox, we evaluated the effects of reversal of anemia during CPB with allogenic RBC transfusion in a novel large-animal model of post-cardiac surgery acute kidney injury with significant homology to that observed in cardiac surgery patients. Adult pigs undergoing general anesthesia were allocated to a Sham procedure, CPB alone, Sham+RBC transfusion, or CPB+RBC transfusion, with recovery and reassessment at 24 h. CPB was associated with dilutional anemia and caused acute kidney injury in swine characterized by renal endothelial dysfunction, loss of nitric oxide (NO) bioavailability, vasoconstriction, medullary hypoxia, cortical ATP depletion, glomerular sequestration of activated platelets and inflammatory cells, and proximal tubule epithelial cell stress. RBC transfusion in the absence of CPB also resulted in renal injury. This was characterized by endothelial injury, microvascular endothelial dysfunction, platelet activation, and equivalent cortical tubular epithelial phenotypic changes to those observed in CPB pigs, but occurred in the absence of severe intrarenal vasoconstriction, ATP depletion, or reductions in creatinine clearance. In contrast, reversal of anemia during CPB with RBC transfusion prevented the reductions in creatinine clearance, loss of NO bioavailability, platelet activation, inflammation, and epithelial cell injury attributable to CPB although it did not prevent the development of significant intrarenal vasoconstriction and endothelial dysfunction. In conclusion, contrary to the findings of observational studies in cardiac surgery, RBC transfusion during CPB protects pigs against acute kidney injury. Our study underlines the need for translational research into indications for transfusion and prevention strategies for acute kidney injury.

Patel, Nishith N.; Lin, Hua; Toth, Tibor; Welsh, Gavin I.; Jones, Ceri; Ray, Paramita; Satchell, Simon C.; Sleeman, Philippa; Angelini, Gianni D.

2011-01-01

270

Fluorescence and polarization imaging of membrane dynamics in living cells  

NASA Astrophysics Data System (ADS)

Methods of wide field fluorescence microscopy for measuring membrane dynamics in living cells are described. These methods are based on laser pulse excitation of the membrane marker 6-dodecanoyl-2-dimethylamino naphthalene (laurdan) whose emission spectra, fluorescence decay kinetics and anisotropies are sensitive to membrane stiffness and fluidity. 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 relaxation times were reduced with increasing membrane fluidity. Membrane stiffness was found to increase with decreasing temperature and increasing amounts of cholesterol. In addition, membrane stiffness of the plasma membrane was always higher than that of intracellular membranes. These effects may have some influence on pathogenesis of certain diseases, uptake of pharmaceutical agents or cell aging. Present experiments are limited to fluorescence microscopy with total internal reflection (TIR) or epi-illumination, but corresponding methods can also be used for screening of larger cell collectives, e.g. in microtiter plates.

Wagner, M.; Weber, P.; Bruns, T.; Strauss, W. S. L.; Schneckenburger, H.

2009-02-01

271

Exo70 generates membrane curvature for morphogenesis and cell migration.  

PubMed

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 toward 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

2013-08-12

272

Process Engineering and Economic Evaluations of Diaphragm and Membrane Chlorine Cell Technologies. Final Report.  

National Technical Information Service (NTIS)

The chlor-alkali manufacturing technologies of (1), diaphragm cells (2), current technology membrane cells (3), catalytic cathode membrane cells (4), oxygen-cathode membrane cells and to a lesser extent several other related emerging processes are studied...

1980-01-01

273

Allogeneic Stimulation of Cytotoxic T Cells by Supported Planar Membranes  

NASA Astrophysics Data System (ADS)

Phospholipid vesicles containing the transmembrane protein H-2Kk spontaneously fuse to form planar membranes when incubated on treated glass surfaces. Pattern photobleaching of fluorescent lipid probes indicates that these planar membranes are continuous and that the lipids are as mobile as they are in conventional fluid bilayers or monolayers. H-2Kk molecules in these planar membranes are immobile. These membranes stimulate cytotoxic T lymphocytes when cultured with immune spleen cells. The response to H-2Kk in planar membranes is greatly enhanced by the addition of supernatant from concanavalin A-stimulated spleen cells, indicating that relatively little antigen processing or presentation by accessory cells occurs. Cytotoxic T cells induced by purified alloantigen are found to be as susceptible to antibody blockade as are effectors from conventional mixed lymphocyte culture, where the antibody is directed against a T-cell surface antigen reputed to strengthen target cell adhesion through an interaction independent of major histocompatibility antigens.

Brian, Adrienne A.; McConnell, Harden M.

1984-10-01

274

Molecular Forces Governing Non-Electrolyte Permeation through Cell Membranes  

Microsoft Academic Search

The relations between the chemical structure of non-electrolytes and their ability to permeate cell membranes are analysed at the level of molecular forces, using the measurements of reflexion coefficients in gall-bladder epithelial cells tabulated in the preceding paper. Stronger solute: water forces and weaker solute: membrane forces are associated with lower permeating power. The portions of the membrane controlling non-electrolyte

Jared M. Diamond; Ernest M. Wright

1969-01-01

275

Organic-Inorganic Membranes for Fuel Cell Application  

NASA Astrophysics Data System (ADS)

Organic-inorganic membranes are worldwide under investigation with the purpose of achieving reduced methanol crossover for direct methanol fuel cell (DMFC) and increasing the proton conductivity at temperatures higher than 100°C in hydrogen fuel cells. The advantages and disadvantages of these membranes are discussed here with membrane examples containing aerosol, layered silicates, and modified silica as passive fillers as well as zirconium phosphate and heteropolyacids as conductive fillers.

Nunes, Suzana Pereira

276

An ESR study of pathologic red blood cell membranes (RBCM).  

PubMed

A comparative study of red blood cell membranes from normal subjects and beta-thalassemia and sickle cell anemia patients was performed by spin labeling at the lipidic and protein phase. The results show that the quantity of bound spin label is the same for sickle, thalassemic, and normal membranes. The data from 5-doxyl stearic acid suggest an increase in fluidity for the thalassemic membrane. PMID:2175007

Perussi, J R; Costa, F F; Baffa, O; Zago, M A; Tinto, M H; Tabak, M

1990-10-01

277

Surface functionalization of gold nanoparticles with red blood cell membranes.  

PubMed

Gold nanoparticles are enclosed in cellular membranes derived from natural red blood cells (RBCs) by a top-down approach. The gold nanoparticles exhibit a complete membrane surface layer and biological characteristics of the source cells. The combination of inorganic gold nanoparticles with biological membranes is a compelling way to develop biomimetic gold nanostructures for future applications, such as those requiring evasion of the immune system. PMID:23712782

Gao, Weiwei; Hu, Che-Ming J; Fang, Ronnie H; Luk, Brian T; Su, Jing; Zhang, Liangfang

2013-05-27

278

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

279

Effect of EMP fields on cell membrane potentials  

SciTech Connect

A simple model is presented for cell membrane potentials induced during exposure to electromagnetic pulse (EMP). Using calculated values of internal electric field strength induced during EMP exposure, the model predicts that cell membrane potentials of about 100 mV may be induced for time frames on the order of 10 ns. Possible biological effects of these potentials including electroporation area discussed.

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

1993-06-01

280

Patterns of Nonelectrolyte Permeability in Human Red Blood Cell Membrane  

Microsoft Academic Search

The permeability of human red cell membrane to 90 different molecules has been measured. These solutes cover a wide spectrum of non- electrolytes with varying chemical structure, chain length, lipid solubility, chemical reactive group, ability to form hydrogen bonds, and other properties. In general, the present study suggests that the permeability of red cell membrane to a large solute is

P. Naccache; R. I. SHA' AFI

1973-01-01

281

Cell membrane receptors for cardiac glycosides in the heart  

Microsoft Academic Search

Summary Cell membranes contain special binding proteins for hormones and drugs. These binding sites (“receptors”) located on the outside surface are linked to or are part of an enzyme facing the inner side of the membrane and are transducing and probably amplifying the information carried by the pharmacological agent to the cell.

E. Erdmann

1977-01-01

282

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

283

THE ENZYMATIC IODINATION OF THE RED CELL MEMBRANE  

Microsoft Academic Search

An enzymatic iodination procedure utilizing lactoperoxidase (LPO), radioactive iodide, and hydrogen peroxide generated by a glucose oxidase-glucose system has been described and utilized for a study of the red cell membrane . 97 % of the incorporated isotope is in the erythrocyte ghost and 3 % is associated with hemoglobin . No significant labeling of the red cell membrane occurs

ANN L. HUBBARD; ZANVIL A. COHN

1972-01-01

284

Effect of EMP fields on cell membrane potentials  

Microsoft Academic Search

A simple model is presented for cell membrane potentials induced during exposure to elecrromagnetic Duke EMPL Usinp calculated values of intemal electric field strength induced durinn EMP mosure. the model medias that cell membrane potentials of about 100 mV may be induced for rime frames on the order of 10 ns. Possible bioloaical effects of these Dotentiah includinn electrouoration are

Paul C. Gailey; Clay E. Easterly

1993-01-01

285

Mathematical modeling of proton exchange membrane fuel cells  

Microsoft Academic Search

A one-dimensional non-isothermal model of a proton exchange membrane (PEM) fuel cell has been developed to investigate the effect of various design and operating conditions on the cell performance, thermal response and water management, and to understand the underlying mechanism. The model includes variable membrane hydration, ternary gas mixtures for both reactant streams, phase change of water in the electrodes

Andrew Rowe; Xianguo Li

2001-01-01

286

Membrane electrode assemblies for unitised regenerative polymer electrolyte fuel cells  

Microsoft Academic Search

Membrane electrode assemblies for regenerative polymer electrolyte fuel cells were made by hot pressing and sputtering. The different MEAs are examined in fuel cell and water electrolysis mode at different pressure and temperature conditions. Polarisation curves and ac impedance spectra are used to investigate the influence of the changes in coating technique. The hydrogen gas permeation through the membrane is

U. Wittstadt; E. Wagner; T. Jungmann

2005-01-01

287

Chloride conductance of the Amphiuma red cell membrane  

Microsoft Academic Search

Summary Like most other red cells, the giant erythrocytes ofAmphiuma means possess a system for rapid exchange of chloride across the membrane. Also, there are indications that the net transport of chloride in these cells is slow. The size ofAmphiuma erythrocytes allows direct measurements of membrane potential with microelectrodes. The present work exploits the possibility that such measurements can be

U. V. Lassen; L. Pape; B. Vestergaard-Bogind

1978-01-01

288

The functional activity of cell membranes in multiple sclerosis  

Microsoft Academic Search

The approach of the present study was determined by the marked interest in recent years in the problems of the pathogenesis of a number of diseases from the perspectives of the pathological chemistry of cell membranes. Studies devoted to the investigation of the structure and function of cell membranes in progressive muscular dystrophies [2, 15], disturbances in cerebral circulation [8,

P. V. Predtechenskaya; A. P. Ierusalimskii

1993-01-01

289

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

290

Novel Unitized Regenerative Proton Exchange Membrane Fuel Cell.  

National Technical Information Service (NTIS)

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) ...

O. J. Murphy A. J. Cisar A. Gonzalez-martin C. E. Salinas S. F. Simpson

1995-01-01

291

Cell membrane thermal gradients induced by electromagnetic fields  

NASA Astrophysics Data System (ADS)

While electromagnetic fields induce structural changes in cell membranes, particularly electroporation, much remains to be understood about membrane level temperature gradients. For instance, microwaves induce cell membrane temperature gradients (?T) and bioeffects with little bulk temperature change. Recent calculations suggest that nanosecond pulsed electric fields (nsPEFs) may also induce such gradients that may additionally impact the electroporation threshold. Here, we analytically and numerically calculate the induced ?T as a function of pulse duration and pulse repetition rate. We relate ?T to the thermally induced cell membrane electric field (Em) by assuming the membrane behaves as a thermoelectric such that Em ~ ?T. Focusing initially on applying nsPEFs to a uniform membrane, we show that reducing pulse duration and increasing pulse repetition rate (or using higher frequency for alternating current (AC) fields) maximizes the magnitude and duration of ?T and, concomitantly, Em. The maximum ?T initially occurs at the interface between the cell membrane and extracellular fluid before becoming uniform across the membrane, potentially enabling initial molecular penetration and subsequent transport across the membrane. These results, which are equally applicable to AC fields, motivate further studies to elucidate thermoelectric behavior in a model membrane system and the coupling of the Em induced by ?T with that created directly by the applied field.

Garner, Allen L.; Deminsky, Maxim; Bogdan Neculaes, V.; Chashihin, V.; Knizhnik, Andrey; Potapkin, Boris

2013-06-01

292

The Role of Cell Membranes in the Regulation of Lignification in Pine Cells.  

National Technical Information Service (NTIS)

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 presente...

D. L. Hendrix

1978-01-01

293

Molecular basis of red cell membrane disorders.  

PubMed

We will consider an array of genetic disorders of the red cell membrane. Some affect well-known genes. The mutations of most cases of hereditary spherocytosis (HS) are located in the following genes: ANK1, SPTB, SLC4A1, EPB42 and SPTA1, which encode ankyrin, spectrin beta-chain, the anion exchanger 1 (band 3), protein 4.2 and spectrin alpha-chain, respectively. A dominant form of distal renal tubular acidosis also stems from distinct mutations in the SLC4A1 gene. The mutations responsible for hereditary elliptocytosis (HE) and its aggravated form, poikilocytosis (HP), lie in the SPTA1 and SPTB gene, already mentioned, and in the EPB41 gene encoding protein 4.1. Whereas in HS, the SPTA1 and SPTB gene mutations tend to abolish the synthesis of the corresponding chains, in HE/HP, they hinder spectrin tetramerization. Allele alpha(LELY) is a common polymorphic allele which plays the role of an aggravating factor when it occurs in trans of an elliptocytogenic allele of the SPTA1 gene. Southeast Asian ovalocytosis results from a 27- nucleotide deletion in the SLC4A1 gene. Besides these conditions in which the mutations were reached from known alterations in the proteins, other conditions required a positional cloning approach. Such are the genetic disorders of membrane permeability to monovalent cations. Knowledge is the most advanced as regards dehydrated hereditary stomatocytois (DHS). DHS was shown to belong to a pleiotropic syndrome: DHS + fetal edema + pseudohyperkalemia, which maps to 16q23-24. Concerning DHS and another disease of the same class, overhydrated hereditary stomatocytosis, splenectomy almost certainly appears to elicit thromboembolic accidents. PMID:12432217

Delaunay, Jean

2002-01-01

294

Lactobacillus casei combats acid stress by maintaining cell membrane functionality.  

PubMed

Lactobacillus casei strains have traditionally been recognized as probiotics and frequently used as adjunct culture in fermented dairy products where lactic acid stress is a frequently encountered environmental condition. We have investigated the effect of lactic acid stress on the cell membrane of L. casei Zhang [wild type (WT)] and its acid-resistant mutant Lbz-2. Both strains were grown under glucose-limiting conditions in chemostats; following challenge by low pH, the cell membrane stress responses were investigated. In response to acid stress, cell membrane fluidity decreased and its fatty acid composition changed to reduce the damage caused by lactic acid. Compared with the WT, the acid-resistant mutant exhibited numerous survival advantages, such as higher membrane fluidity, higher proportions of unsaturated fatty acids, and higher mean chain length. In addition, cell integrity analysis showed that the mutant maintained a more intact cellular structure and lower membrane permeability after environmental acidification. These results indicate that alteration in membrane fluidity, fatty acid distribution, and cell integrity are common mechanisms utilized by L. casei to withstand severe acidification and to reduce the deleterious effect of lactic acid on the cell membrane. This detailed comparison of cell membrane responses between the WT and mutant add to our knowledge of the acid stress adaptation and thus enable new strategies to be developed aimed at improving the industrial performance of this species under acid stress. PMID:22366811

Wu, Chongde; Zhang, Juan; Wang, Miao; Du, Guocheng; Chen, Jian

2012-02-26

295

Microfabricated electroporation chip for single cell membrane permeabilization  

Microsoft Academic Search

Silicon microfabrication technology was used to develop a chip that can incorporate a live biological cell in its electrical circuit and thereby induce controlled electroporation in the cell. Electroporation employs electrical pulses applied across a cell for cell membrane permeabilization. Commonly used in biotechnology for genetic engineering of cells in a batch, this chip is the first microfabricated device in

Yong Huang; Boris Rubinsky

2001-01-01

296

Axially resolved polarisation microscopy of membrane dynamics in living cells  

NASA Astrophysics Data System (ADS)

Membrane dynamics has a large impact on cellular uptake and release of various metabolites or pharmaceutical agents. For a deeper understanding of the cellular processes involved, we used U373-MG human glioblastoma cells as a model system. As conventional microscopy does not permit to investigate individual layers in living cells, we used structured illumination techniques and total internal reflection fluorescence microscopy (TIRFM) to analyse the plasma membrane and intracellular membranes of living cells selectively. Optical image sections provide a high resolution and the possibility of 3D reconstruction. Membranes of living cells were characterized by the membrane marker 6-dodecanoyl-2-dimethylamino naphthalene (laurdan). Due to its spectral and kinetic properties this fluorescence marker appears appropriate for measuring membrane stiffness and fluidity. After excitation with linearly polarized laser pulses, membrane fluidity of human glioblastoma cells was determined by measurements of steady-state and time-resolved fluorescence anisotropy r(t), since with increasing viscosity of the environment, the rotation of an excited molecule is impeded. The corresponding time constant ?r of molecular relaxation decreased with temperature and increased with the amount of cholesterol. In addition, fluorescence anisotropy r(t) values of the plasma membrane were larger than the values of intracellular membranes for all temperatures in the range of 16°C<=T<=41°C.

Wagner, Michael; Weber, Petra; Schneckenburger, Herbert

2007-06-01

297

Ca binding to the human red cell membrane: Characterization of membrane preparations and binding sites  

Microsoft Academic Search

Summary Inside out and right side out vesicles were used to study the sidedness of Ca binding to the human red cell membrane. It was shown that these vesicles exhibited only a limited permeability to Ca, enabling the independent characterization of Ca binding to the extracellular and cytoplasmic membrane surfaces. Ca binding was studied in 10 mM Tris HCl at

Carl M. Cohen; A. K. Solomon

1976-01-01

298

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

299

Evaluating the interfacial reaction kinetics of the bipolar membrane interface in the bipolar membrane fuel cell.  

PubMed

A reaction kinetic model of the bipolar membrane interface in the bipolar membrane fuel cell (BPMFC) was proposed based on the p-n junction theory and chemical reaction kinetics. It verified the self-humidification feasibility of the BPMFC successfully. PMID:23744271

Peng, Sikan; Lu, Shanfu; Zhang, Jin; Sui, Pang-Chieh; Xiang, Yan

2013-06-06

300

Novel Fusogenic Liposomes for Fluorescent Cell Labeling and Membrane Modification.  

PubMed

Efficient delivery of biomolecules into membranes of living cells as well as cell surface modifications are major biotechnological challenges. Here, novel liposome systems based on neutral and cationic lipids in combination with lipids modified by aromatic groups are introduced for such applications. The fusion efficiency of these liposome systems was tested on single cells in culture like HEK293, myofibroblasts, cortical neurons, human macrophages, smooth muscle cells, and even on tissue. Fusogenic liposomes enabled highly efficient incorporation of molecules into mammalian cell membranes within 1 to 30 min at fully unchanged cell growth conditions and did not affect cell behavior. We hypothesize that membrane fusions were induced in all cases by the interaction of the positively charged lipids and the delocalized electron system of the aromatic group generating local dipoles and membrane instabilities. Selected applications ranging from basic research to biotechnology are envisaged here. PMID:20184308

Csisza?r, Agnes; Hersch, Nils; Dieluweit, Sabine; Biehl, Ralf; Merkel, Rudolf; Hoffmann, Bernd

2010-02-25

301

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

302

Coherence properties of red blood cell membrane motions  

NASA Astrophysics Data System (ADS)

We use a highly sensitive, noncontact, optical interferometric technique to quantify the red blood cell membrane fluctuations at the nanometer and millisecond scales. The results reveal significant properties of both temporal and spatial coherence associated with the membrane dynamics. We show that these correlations can be accounted for by the viscoelastic properties of the cell membrane. From this measurement, we extract the loss and storage moduli associated with the membrane and find a crossover frequency at which the buffer viscosity seems to become dominant.

Popescu, Gabriel; Park, Yongkeun; Dasari, Ramachandra R.; Badizadegan, Kamran; Feld, Michael S.

2007-09-01

303

Cell Membranes Under Hydrostatic Pressure Subjected to Micro-Injection  

NASA Astrophysics Data System (ADS)

The work is concerned with the determination of the mechanical behaviour of cell membranes under uniform hydrostatic pressure subject to micro-injections. For that purpose, assuming that the shape of the deformed cell membrane is axisymmetric a variational statement of the problem is developed on the ground of the so-called spontaneous curvature model. In this setting, the cell membrane is regarded as an axisymmetric surface in the three-dimensional Euclidean space providing a stationary value of the shape energy functional under the constraint of fixed total area and fixed enclosed volume. The corresponding Euler-Lagrange equations and natural boundary conditions are derived, analyzed and used to express the forces and moments in the membrane. Several examples of such surfaces representing possible shapes of cell membranes under pressure subjected to micro injection are determined numerically.

Vassilev, Vassil M.; Kostadinov, Kostadin G.; Mladenov, Ivaïlo M.; Shulev, Assen A.; Stoilov, Georgi I.; Djondjorov, Peter A.

2011-04-01

304

Red cell membrane lipid peroxidation and hemolysis secondary to phototherapy.  

PubMed

The exposure of red cells to phototherapy light in the presence of a sensitizer (bilirubin) resulted in oxidative injury to the red cell membrane as manifested by a significant increase in the concentration of the products of lipid peroxidation (TBA reactants and diene conjugation) in the membrane and hemolysis. To induce a photo-oxidized membrane injury, the sensitizer (bilirubin) has to be membrane bound. Thus, by altering the availability of free bilirubin in the red cell suspension through changes in the molar concentration ratio of bilirubin to albumin, one is able to regulate the occurrence and extent of the oxidative red cell membrane injury. The clinical implications of these findings are discussed. PMID:4003061

Ostrea, E M; Cepeda, E E; Fleury, C A; Balun, J E

1985-05-01

305

Membrane trafficking in guard cells during stomatal movement  

PubMed Central

Pairs of guard cells form small pores called stoma in the epidermis, and the reversible swelling and shrinking of these guard cells regulate the stomatal apertures. The well-documented changes in guard cell volume have been associated with their vacuolar structures. To investigate the contribution of the guard cell vacuoles to stomatal movement, the dynamics of these vacuolar structures were recently monitored during stomatal movement in vacuolar-membrane visualized Arabidopsis plants. Calculation of the vacuolar volume and surface area after reconstruction of three-dimensional images revealed a decrease in the vacuolar volume but an increase in the vacuolar surface area upon stomatal closure. These results implied the possible acceleration of membrane trafficking to the vacuole upon stomatal closure and membrane recycling from the vacuole to the plasma membrane upon stomatal opening. To clarify and quantify membrane trafficking during stomatal movement, we describe in this addendum our development of an improved image processing system.

Kutsuna, Natsumaro; Hasezawa, Seiichiro; Tanaka, Yoko

2008-01-01

306

Beta-adrenergic agonists regulate cell membrane fluctuations of human erythrocytes.  

PubMed

1. Mechanical fluctuations of the cell membrane (CMFs) in human erythrocytes reflect the bending deformability of the membrane-skeleton complex. These fluctuations were monitored by time-dependent light scattering from a small area ( approximately 0. 25 microm2) of the cell surface by a method based on point dark field microscopy. 2. Exposure of red blood cells (RBCs) to adrenaline (epinephrine) and isoproterenol (isoprenaline) resulted in up to a 45 % increase in the maximal fluctuation amplitude and up to a 35 % increase in the half-width of the amplitude distribution. The power spectra of membrane fluctuations of control and treated cells revealed that adrenaline stimulated only the low frequency component (0.3-3 Hz). Analysis of the dose-response curves of beta-adrenergic agonists yielded an EC50 of 5 x 10-9 and 1 x 10-11 M for adrenaline and isoproterenol, respectively. Propranolol had an inhibitory effect on the stimulatory effect of isoproterenol. These findings show a potency order of propranolol > isoproterenol > adrenaline. 3. The stimulatory effect of adrenaline was a temporal one, reaching its maximal level after 20-30 min but being abolished after 60 min. However, in the presence of 3-isobutyl-1-methylxanthine, a partial stimulatory effect was maintained even after 60 min. Pentoxifylline and 8-bromo-cAMP elevated CMFs. However, exposure of ATP-depleted erythrocytes to adrenaline or 8-bromo-cAMP did not yield any elevation in CMFs. These findings suggest that the beta-agonist effect on CMFs is transduced via a cAMP-dependent pathway. 4. Deoxygenation decreased CMFs and filterability of erythrocytes by approximately 30 %. The stimulatory effect of isoproterenol on CMFs was 2.2-fold higher in deoxygenated RBCs than in oxygenated cells. 5. Exposure of RBCs to adrenaline resulted in a concentration-dependent increase in RBC filterability, demonstrating a linear relationship between CMFs and filterability, under the same exposure conditions to adrenaline. These findings suggest that beta-adrenergic agonists may improve passage of erythrocytes through microvasculature, enhancing oxygen delivery to tissues, especially under situations of reduced oxygen tension for periods longer than 20 min. PMID:10200425

Tuvia, S; Moses, A; Gulayev, N; Levin, S; Korenstein, R

1999-05-01

307

Membrane transport of anandamide through resealed human red blood cell membranes.  

PubMed

The use of resealed red blood cell membranes (ghosts) allows the study of the transport of a compound in a nonmetabolizing system with a biological membrane. Transmembrane movements of anandamide (N-arachidonoylethanolamine, arachidonoylethanolamide) have been studied by exchange efflux experiments at 0 degrees C and pH 7.3 with albumin-free and albumin-filled human red blood cell ghosts. The efflux kinetics is biexponential and is analyzed in terms of compartment models. The distribution of anandamide on the membrane inner to outer leaflet pools is determined to be 0.275 +/- 0.023, and the rate constant of unidirectional flux from inside to outside is 0.361 +/- 0.023 s(-1). The rate constant of unidirectional flux from the membrane to BSA in the medium ([BSA]o) increases with the square root of [BSA]o in accordance with the theory of an unstirred layer around ghosts. Anandamide passed through the red blood cell membrane very rapidly, within seconds. At a molar ratio of anandamide to BSA of <1, membrane binding of anandamide increases with increasing temperatures between 0 degrees C and 37 degrees C, and the equilibrium dissociation constants are in the nanomolar range. The nature of membrane binding and the mechanism of membrane translocation are discussed. PMID:15930521

Bojesen, Inge N; Hansen, Harald S

2005-06-01

308

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

2010-05-07

309

Time-resolved molecular transport across living cell membranes.  

PubMed

It is shown that the nonlinear optical phenomenon known as second-harmonic generation can be used for label-free, time-resolved study of the transport of molecules through living cell membranes. The adsorption and transport of a 300-Da molecular-mass hydrophobic ion at the Escherichia coli membrane is observed. Remarkably, at low ion concentrations, the second-harmonic generation technique clearly exposes a multistep molecular transport process: Transport of the molecular ion across the outer and cytoplasmic membranes of the Gram-negative bacteria is recorded, in sequence, in time. Fitting of the data to a multiprocess kinematic model reveals that the transport of this hydrophobic ion through the outer membrane is much faster than through the cytoplasmic membrane, likely reflecting the effectiveness of ion transport porins. The observations illustrate an experimental means for studying the interactions of small molecules with cell membranes. PMID:23332066

Zeng, Jia; Eckenrode, Heather M; Dounce, Susan M; Dai, Hai-Lung

2013-01-08

310

Hydrodynamic extrusion of membrane nanotubes: the role of the cytoskeleton  

NASA Astrophysics Data System (ADS)

We have investigated membrane-cytoskeleton adhesion properties by extrusion of tubes from tethered vesicles and cells using hydrodynamic flows. Our experimental results show that impermeable membranes (giant vesicles) act as entropic springs, i.e. the extruded tubes reach a stationary length, whereas porous membranes (vesicles decorated with pores) lead to tubes, which extrude at constant velocity without reaching a stationary length. On the other hand, experiments on red blood cells (RBC) suggest that the dynamics of extruded tubes is dominated by the detachment of the membrane from the cytoskeleton and the flow of lipids through the binding membrane proteins. We have estimated the membrane-cytoskeleton binding energy and the viscosity of the membrane for RBC-s. Tube extrusion from other cell types (S180, MDCK, BON) show phenomena such as healing time for the membrane-cytoskeleton rebinding, and cell aging (breakage of the tube after a few consecutive extrusions). We will discuss how these phenomena depend on the properties of the cytoskeleton and on the presence of cell adhesion molecules.

Guevorkian, Karine; Borghi, Nicolas; Kremer, Séastien; Buguin, Axel; Brochard, Françise

2007-03-01

311

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

312

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

2011-08-25

313

Improved Membrane Materials for PEM Fuel Cell Application  

SciTech Connect

The overall goal of this project is to collect and integrate critical structure/property information in order to develop methods that lead to significant improvements in the durability and performance of polymer electrolyte membrane fuel cell (PEMFC) materials. This project is focused on the fundamental improvement of PEMFC membrane materials with respect to chemical, mechanical and morphological durability as well as the development of new inorganically-modified membranes.

Kenneth A. Mauritz; Robert B. Moore

2008-06-30

314

Preparation and properties of thyroid cell membranes  

Microsoft Academic Search

Summary Calf and human thyroids have been disrupted by nitrogen microcavitation, and the thyroid membranes prepared by repeated centrifugation in low ionic strength buffers. Two classes of membranes were prepared by centrifugation on a discontinuous gradient of ficoll. A lighter fraction was comprised of somewhat larger vesicles; they were higher in Na+-K+-activated ATPase, phosphodiesterase, and 5'-nucleotidase than was the heavier

John B. Stanbury; Janice V. Wicken; Mary Ann Lafferty

1969-01-01

315

Influence of Desialylation on the Interaction of Red Blood Cells with a Hemotoxic Partly Quaternized Tertiary Polyamine  

Microsoft Academic Search

Partly quaternized poly[thio-1-(N,N-diethyl-aminomethyl) ethylene] polycations (Q-P(TDAE)x) interact electrostatically with the membrane of human red blood cells (RBC) and are highly toxic when given intravenously (i.v.). In order to study the influence of sialic acid negative charges on the hemagglutination and hemolysis induced by Q-P(TDAE)11, RBC were desialylated using neuraminidase. Desialylation had little influence on Q-P(TDAE)11-induced agglutination. It was concluded that

Élisabeth Moreau; Pascal Chapon; Michel Vert; Dominique Domurado

2000-01-01

316

Effect of Hydroperoxides on Red Blood Cell Membrane Mechanical Properties  

PubMed Central

We investigate the effect of oxidative stress on red blood cell membrane mechanical properties in vitro using detailed analysis of the membrane thermal fluctuation spectrum. Two different oxidants, the cytosol-soluble hydrogen peroxide and the membrane-soluble cumene hydroperoxide, are used, and their effects on the membrane bending elastic modulus, surface tension, strength of confinement due to the membrane skeleton, and 2D shear elastic modulus are measured. We find that both oxidants alter significantly the membrane elastic properties, but their effects differ qualitatively and quantitatively. While hydrogen peroxide mainly affects the elasticity of the membrane protein skeleton (increasing the membrane shear modulus), cumene hydroperoxide has an impact on both membrane skeleton and lipid bilayer mechanical properties, as can be seen from the increased values of the shear and bending elastic moduli. The biologically important implication of these results is that the effects of oxidative stress on the biophysical properties, and hence the physiological functions, of the cell membrane depend on the nature of the oxidative agent. Thermal fluctuation spectroscopy provides a means of characterizing these different effects, potentially in a clinical milieu.

Hale, John P.; Winlove, C. Peter; Petrov, Peter G.

2011-01-01

317

Effect of hydroperoxides on red blood cell membrane mechanical properties.  

PubMed

We investigate the effect of oxidative stress on red blood cell membrane mechanical properties in vitro using detailed analysis of the membrane thermal fluctuation spectrum. Two different oxidants, the cytosol-soluble hydrogen peroxide and the membrane-soluble cumene hydroperoxide, are used, and their effects on the membrane bending elastic modulus, surface tension, strength of confinement due to the membrane skeleton, and 2D shear elastic modulus are measured. We find that both oxidants alter significantly the membrane elastic properties, but their effects differ qualitatively and quantitatively. While hydrogen peroxide mainly affects the elasticity of the membrane protein skeleton (increasing the membrane shear modulus), cumene hydroperoxide has an impact on both membrane skeleton and lipid bilayer mechanical properties, as can be seen from the increased values of the shear and bending elastic moduli. The biologically important implication of these results is that the effects of oxidative stress on the biophysical properties, and hence the physiological functions, of the cell membrane depend on the nature of the oxidative agent. Thermal fluctuation spectroscopy provides a means of characterizing these different effects, potentially in a clinical milieu. PMID:22004746

Hale, John P; Winlove, C Peter; Petrov, Peter G

2011-10-19

318

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

2013-09-29

319

Physicochemical factors affecting the E. coli removal in a rotating biological contactor (RBC) treating UASB effluent  

Microsoft Academic Search

The removal mechanism of E. coli from UASB effluent using a Rotating Biological Contractor (RBC) has been investigated. Preliminary batch experiments in a RBC indicate a first-order removal kinetics. Variation in the dissolved oxygen concentration and E. coli counts over the depth of the RBC has been recorded and indicates that the RBC is not a completely mixed reactor. Therefore

Ahmed Tawfik; Bram Klapwijk; Joost Van Buuren; Fatma El-Gohary; Gatze Lettinga

2004-01-01

320

Cytoskeletal control of the red-blood cell membrane  

NASA Astrophysics Data System (ADS)

We have shown (Physical Review Letters, 90, 228101 (2003)) that the thermal fluctuations of red blood cells can be accounted for by a model of a nearly-free, but confined bilayer membrane with a finite tension; both the confinement and tension arise from the coupling of the membrane with the cytoskeleton. Recently, we have shown that these relatively gentle effects of the cytoskeleton-membrane couplings on the membrane fluctuations are due to the dilute nature of the coupling molecules. To quantify this, we predict the fluctuation amplitude for a microscopic model of the inhomogeneous coupling of a fluid membrane and a fixed cytoskeleton. The coupling is modeled as periodic and harmonic, and we consider the linear response of the membrane. We find that there is indeed, an effective surface tension and confinement of such a membrane, in accord with our phenomenological model, and relate these quantities to the strength and periodicity of the microscopic coupling. We also find, surprisingly, that the membrane can develop a spontaneous breaking of the cytoskeleton symmetry, at low confinements. Finally we address the role of ATP activity on the cytoskeleton-driven fluctuations and the equilibrium shape of the cell. We examine in detail the role of spectrin disconnections as the main ATP-activated network defects on the global cell shape and membrane fluctuations.

Gov, Nir; Safran, Sam

2004-03-01

321

Direct measurements of membrane potential and membrane resistance of human red cells  

PubMed Central

1. In order to evaluate the membrane potentials calculated from the distribution of chloride ions in human red cells and plasma, it is desirable to have a direct measurement of the transmembrane potential of these cells. 2. A method has been devised for introducing a capillary micro-electrode into human red cells. The method allows simultaneous measurements of potential and membrane resistance with only one micro-electrode located in the cell. 3. Upon impalement of single cells in plasma, a scatter of membrane potentials and of resistance values was obtained. The potential drop never exceeded -14 mV and the maximum resistances were about 7 ?. cm2. Positive potentials were obtained on impalement of red cell aggregates. 4. Arguments are given to support the view that it is in these cells which suffer least damage from the impalement that maximum values of membrane potentials and resistances are observed. The errors caused by the change in the liquid junction during the impalement have been estimated. 5. As judged from this study, it seems permissible under normal conditions to calculate the membrane potential of the red cell from the chloride concentrations in plasma and in intracellular water.

Lassen, U. V.; Sten-Knudsen, O.

1968-01-01

322

Membrane ultrastructure preservation and membrane potentials after isolation of rabbit retinal glial (Müller) cells by papain.  

PubMed

Enzymatically isolated retinal glial (Müller) cells have been the subject of many electrophysiological studies. Local high membrane conductivities for potassium ions have been speculated to correspond with local occurrence of orthogonal arrays of intramembranous particles (OAP) observed in freeze-fracture replicas of retinal Müller cells in situ. We studied whether such OAP are preserved after enzymatic digestion of the retinal tissue which is necessary for isolation of living cells for electrophysiology. We found that strong papain digestion leads not only to disturbances in the cell's ultrastructure as seen in ultrathin sections but evokes both a redistribution of intramembranous particles and a disappearance of OAP as seen in the freeze-fracture replica. Furthermore, such isolated cells have low membrane potentials and lose their topographical specialization in K+ conductance. If, however, the retinae were exposed to papain as short as possible to get just some isolated cells, their cytoplasmic and membranous ultrastructure was preserved very well, and high resting membrane potentials were recorded in cells with marked regional specialization of membrane conductivity. Our results show that indeed sites of high K+ conductance may correspond with the occurrence of OAP, even in isolated cells. PMID:2385140

Reichenbach, A; Wolburg, H; Richter, W; Eberhardt, W

1990-06-01

323

Radiation Interaction with Therapeutic Drugs and Cell Membranes  

SciTech Connect

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.; Matei, Constantin I.; Iacob, Nicusor I.; Ighigeanu, Daniel I.; Craciun, Gabriela D. [Accelerators Laboratory, National Institute for Lasers, Plasma and Radiation Physics, 409, Atomistilor St., 077125 Magurele (Romania); Moisescu, Mihaela I.; Savopol, Tudor D.; Kovacs, Eugenia A. [Carol Davila University of Medicine and Pharmacy, 8, Eroii Sanitari St., 050474 Bucharest (Romania); Cinca, Sabin A. [Oncology Institute Prof. A. Trestioreanu, 252, Fundeni St., 022328 Bucharest (Romania); Margaritescu, Irina D. [Military Clinical Hospital, 88, Mircea Vulcanescu St., 010825 Bucharest (Romania)

2007-04-23

324

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

325

Automated membrane test cell apparatus and method for so using  

SciTech Connect

An automated electrolytic membrane test cell apparatus adaptable for the purpose of accurately measuring cationic transport and water transport numbers for membranes used in chlor-alkali cells under operating conditions similar to those used in such cells is disclosed. The apparatus comprises a test cell, said test cell being adapted to hold a permselective membrane sealingly supported therein so as to create separate anode and cathode compartments, each of said compartments having a suitable electrode, and heating electrolyte inlet and outlet means attached thereto. The apparatus further comprises means to select one of a plurality of anolyte and catholyte test solutions and control means adapted to control the electrolysis, circulation and heating of said solutions and the generation of all test samples needed to perform the measurements necessary to calculate said transport numbers. When used in conjunction with radioactive tracer techniques, considerably improvements are possible in the accuracy and ease with which transport phenomena in said membrane can be studied.

Yeager, H.L.; Malinsky, J.D.

1984-11-20

326

Large deformation of red blood cell ghosts in a simple shear flow  

Microsoft Academic Search

The membrane of the red blood cell RBC is easily deformed by shearing forces while maintaining its local area nearly unchanged. This type of response is due to the struc- ture of the membrane which is composed of a lipid bilayer supported by a scaffolding of cytoskeletal proteins. Normal human RBCs in quiescent plasma assume a biconcave dis- coid shape

C. D. Eggletona

327

T cell antigen recognition at the cell membrane  

PubMed Central

T cell antigen receptors (TCR) on the surface of T cells bind specifically to particular peptide bound major histocompatibility complexes (pMHC) presented on the surface of antigen presenting cells (APC). This interaction is a key event in T cell antigen recognition and activation. Most studies have used surface plasmon resonance (SPR) to measure the in vitro binding kinetics of TCR-pMHC interactions in solution using purified proteins. However, these measurements are not physiologically precise, as both TCRs and pMHCs are membrane-associated molecules which are regulated by their cellular environments. Recently, single-molecule förster resonance energy transfer (FRET) and single-molecule mechanical assays were used to measure the in situ binding kinetics of TCR-pMHC interactions on the surface of live T cells. These studies have provided exciting insights into the biochemical basis of T cell antigen recognition and suggest that TCRs serially engage with a small number of antigens with very fast kinetics in order to maximize TCR signaling and sensitivity.

Huang, Jun; Meyer, Christina; Zhu, Cheng

2012-01-01

328

Computer Simulations of Protein Diffusion in Compartmentalized Cell Membranes  

Microsoft Academic Search

The diffusion of proteins in the cell membrane is investigated using computer simulations of a two-dimensional model. The membrane is assumed to be divided into compartments, with adjacent compartments separated by a barrier of stationary obstacles. Each compartment contains traps represented by stationary attractive disks. Depending on their size, these traps are intended to model either smaller compartments or binding

Bong June Sung; Arun Yethiraj

2009-01-01

329

Alkaline fuel cell membranes from xylylene block ionenes  

Microsoft Academic Search

A new class of anion-exchange membranes, based on xylylene ionene segmented block copolymers, has been fabricated and characterized for possible use in alkaline fuel cells. The ionene materials were composed of non-polar blocks which, in principle, conferred mechanical strength and water swelling control to the membrane, and polar blocks with quaternary dibenzyl dimethyl ammonium groups located on the polymer backbone

Kyung Min Lee; Ryszard Wycisk; Morton Litt; Peter N. Pintauro

2011-01-01

330

Cytoskeletal control of the red-blood cell membrane  

Microsoft Academic Search

We have shown (Physical Review Letters, 90, 228101 (2003)) that the thermal fluctuations of red blood cells can be accounted for by a model of a nearly-free, but confined bilayer membrane with a finite tension; both the confinement and tension arise from the coupling of the membrane with the cytoskeleton. Recently, we have shown that these relatively gentle effects of

Nir Gov; Sam Safran

2004-01-01

331

Molecular Engine for Transporting Drugs Across Cell Membranes  

Microsoft Academic Search

A molecular engine has been developed from first principles to transport drugs from endosomes to the cytosol of cells. The engine is powered by the pH differential across the endosomal membrane, does not disrupt the endosomal membrane, and is disassembled into innocuous components after carrying out its transport function.

James Summerton; Dwight Weller

1997-01-01

332

Aquaporins: water channel proteins of the cell membrane  

Microsoft Academic Search

Aquaporins (AQP) are integral membrane proteins that serve as channels in the transfer of water, and in some cases, small solutes across the membrane. They are conserved in bacteria, plants, and animals. Structural analyses of the molecules have revealed the presence of a pore in the center of each aquaporin molecule. In mammalian cells, more than 10 isoforms (AQP0–AQP10) have

Kuniaki Takata; Toshiyuki Matsuzaki; Yuki Tajika

2004-01-01

333

Membrane associated proteoglycans in rat testicular peritubular cells  

Microsoft Academic Search

Confluent testicular peritubular cells derived from immature rats were used to study membrane associated proteoglycans (PG) Peripheral material (heparin releasable), membrane and intracellular material (Triton X-100 releasable) were collected, purified by anion exchange chromatography then characterized by gel filtration and by hydrophobic interaction chromatography, followed by enzymatic digestion and chemical treatment. The peripheral material was constituted of two populations of

Lahcen Bichoualne; Bénédicte Thiébot; Monique Langris; Pierre Barbey; Hamid Oulhaj; Jean Bocquet

1994-01-01

334

Membrane-electrode assemblies for electrochemical cells  

DOEpatents

A combination, unitary, membrane and electrode assembly with a solid polymer electrolyte membrane, and first and second electrodes at least partially embedded in opposed surfaces of the membrane. The electrodes each comprise a respective group of finely divided carbon particles, very finely divided catalytic particles supported on internal and external surfaces of the carbon particles and a proton conductive material intermingled with the catalytic and carbon particles. A first group of finely divided carbon particles forming the first electrode has greater water attraction and retention properties, and is more hydrophilic than a second group of carbon particles forming the second electrode. In a preferred method, the membrane electrode assembly of the invention is prepared by forming a slurry of proton conductive material and at least one group of the carbon and catalyst particles. The slurry is applied to the opposed surfaces of the membrane and heated while being pressed to the membrane for a time and at a temperature and compressive load sufficient to embed at least a portion of the particles into the membrane.

Swathirajan, Sundararajan (Troy, MI); Mikhail, Youssef M. (Sterling Heights, MI)

1993-01-01

335

Blend Concepts for Fuel Cell Membranes  

Microsoft Academic Search

\\u000a Differently cross-linked blend membranes were prepared from commercial arylene main-chain polymers from the classes of poly(ether-ketones)\\u000a and poly(ethersulfones) modified with sulfonate groups, sulfinate cross-linking groups and basic N-groups. The following membrane\\u000a types have been prepared: (a) van-der Waals\\/dipole-dipole blends by mixing a polysulfonate with unmodified PSU. This membrane\\u000a type showed a heterogeneous morphology, leading to extreme swelling and even dissolution

Jochen Kerres

2009-01-01

336

99mTc-RBC Scintigraphy for diagnosis of intestinal stromal tumor hemorrhage: a case report  

PubMed Central

Background Gastrointestinal stromal tumors (GISTs) are rare and our understanding of the natural history and optimal treatment of GISTs are continually evolving. They are characterized by a remarkable cellular variability and their malignant potential is sometimes difficult to predict. Case presentation We report the case of intestinal stromal tumor in a 44 years old patient with a long history of anemia and recurrent hemafecia. By using 99mTc-labeled red blood cell (99mTc-RBC) scintigraphy, extensive tracer accumulation in the jejunum was detected. Immunohistochemically, the tumor strongly expresses the KIT (CD117) protein. The intestinal tumor was successfully resected with a postoperative favorable outcome. Conclusion 99mTc-RBC scintigraphy is an established technique for the identification and localization of gastrointestinal bleeding. Abdominal scintigraphy appears to be a valuable supplement to conventional diagnostic methods for the diagnosis of gastrointestinal stromal tumor hemorrhage.

Wang, Jiang; Zhao, Rong

2012-01-01

337

Thrombelastographic evaluation of the influence of 2-RBC apheresis on donor's coagulation system.  

PubMed

Rotation thrombelastogram (ROTEM®/TEG®) assays allow rapid global assessment of hemostatic function using whole blood. Since published data about the effects of automated red cell collection on coagulation system are scarce, we aimed to investigate the effects of 2-RBC apheresis on donor's coagulation system using ROTEM® assays. In INTEM assay, CFT was significantly shortened 24h after apheresis compared with baseline value (p<0.05) and MCF was significantly prolonged immediately after apheresis and 24h after apheresis compared with baseline value (p<0.05 and p<0.01, respectively). In EXTEM assay, CFT was significantly prolonged immediately after apheresis and 24h after apheresis compared with baseline value (p=0.001 and p<0.001, respectively) and MCF was significantly prolonged 24h after apheresis compared with baseline value (p<0,001). Our results demonstrate thromboelastographic signs of hypercoagulability in donors undergoing 2-RBC apheresis. PMID:23660469

Akay, Olga Meltem; Karagulle, Mustafa; Kus, Gokhan; Mutlu, Fezan Sah?n; Gunduz, Eren

2013-05-06

338

Characterization of an rbcS gene from Nicotiana plumbaginifolia and expression of an rbc SCAT chimeric gene in homologous and heterologous nuclear background  

Microsoft Academic Search

We have cloned a gene (rbcS-8B) encoding the small subunit of ribulose bisphosphate carboxylase from Nicotiana plumbaginifolia and analyzed it with respect to structure and expression. The nucleotide sequence of the rbcS-8B coding region is highly conserved when compared to rbcS sequences from N. tabacum and N. sylvestris. The first two of the three Nicotiana rbcS introns are also well

Carsten Poulsen; Robert Fluhr; John M. Kauffman; Marc Boutry; Nam-Hai Chua

1986-01-01

339

Mechanical and water sorption properties of nafion and composite nafion/titanium dioxide membranes for polymer electrolyte membrane fuel cells  

NASA Astrophysics Data System (ADS)

The mechanical properties of the membranes used in polymer electrolyte membrane fuel cells are important to the performance and longevity of the cell. The speed and extent of membrane water uptake depend on the membrane's viscoelastic mechanical properties, which are themselves dependent on membrane hydration, and increased hydration improves membrane proton conductivity and fuel cell performance. Membrane mechanical properties also affect durability and cell longevity, preventing membrane failure from stresses induced by changing temperature and water content during operational cycling. Further, membrane creep and stress-relaxation can change the extent of membrane/electrode contact, also changing cell behavior. New composite membrane materials have exhibited superior performance in fuel cells, and it is suspected that improved mechanical properties are responsible. Studies of polymer electrolyte membrane (PEM) fuel cell dynamics using Nafion membranes have demonstrated the importance of membrane mechanical properties, swelling and water-absorption behavior to cell performance. Nonlinear and delayed dynamic responses to changing operating parameters were unexpected, but reminiscent of polymer viscoelastic behavior and water sorption dynamics, illustrating the need to better understand membrane properties to design and operate fuel cells. Further, Nafion/TiO2 composite membranes developed by the Princeton Chemistry Department improve fuel cell performance, which may be due to changes in membrane microstructure and enhanced mechanical properties. Mechanical properties, stress-relaxation behavior, water sorption and desorption rates and pressures exerted during hydration by a confined membrane have been measured for Nafion and for Nafion/TiO2 composite membranes. Mechanical properties, including the Young's modulus and limits of elastic deformation are dependent on temperature and membrane water content. The Young's modulus decreases with increasing water content and temperature, is less temperature-dependent in hydrated membranes than dry membranes and is slightly higher in the composite membranes. Stress-relaxation also follows two distinct behaviors depending on its temperature, humidity and degree of strain. The water sorption and desorption dynamics are not controlled by diffusion rates but by interfacial mass transport resistance and, during sorption, by the kinetics of swelling and stress-relaxation. Pressure exerted by a swelling membrane scales with membrane thickness, is slightly higher for the composite membranes and is relevant to fuel cell design.

Satterfield, May Barclay

340

The anti-angiogenic peptide anginex disrupts the cell membrane.  

PubMed

Anginex is a synthetic beta-sheet peptide with anti-angiogenic and anti-tumor activity. When added to cultured endothelial cells at concentrations ranging from 2.5 microM to 25 microM, anginex induced cell death, which was reflected by a strong increase of subdiploid cells and fragments, loss of cellular ATP, and LDH release. Cytotoxicity remained the same whether cells were treated with anginex at 4 degrees C or at 37 degrees C. At low temperatures, fluorescein-conjugated anginex accumulated on the endothelial surface, but did not reach into the cytoplasm, indicating that the cell membrane is the primary target for the peptide. Within minutes of treatment, anginex caused endothelial cells to take up propidium iodide and undergo depolarization, both parameters characteristic for permeabilization of the cell membrane. This process was amplified when cells were activated with hydrogen peroxide. Red blood cell membranes were essentially unaffected by anginex. Anginex bound lipid bilayers with high affinity and with a clear preference for anionic over zwitterionic phospholipids. Structural studies by circular dichroism and solid-state nuclear magnetic resonance showed that anginex forms a beta-sheet and adopts a unique and highly ordered conformation upon binding to lipid membranes. This is consistent with lipid micellization or the formation of pore-forming beta-barrels. The data suggest that the cytotoxicity of anginex stems from its ability to target and disrupt the endothelial cell membrane, providing a possible explanation for the angiostatic activity of the peptide. PMID:16403516

Pilch, Jan; Franzin, Carla M; Knowles, Lynn M; Ferrer, Fernando J; Marassi, Francesca M; Ruoslahti, Erkki

2005-12-20

341

Analysis of RBC damage using laser tweezers Raman spectroscopy (LTRS) during femtosecond laser optical trapping  

NASA Astrophysics Data System (ADS)

We monitored cell viability and damage under femtosecond laser irradiation using aser weezers Raman pectroscopy (LTRS) which is becoming a powerful tool for the analysis of biological materials. Femtosecond lasers are more frequently used as a light source for optical tweezers since they enable nonlinear optical phenomena such as two-photon absorption or second harmonic generation trapping. Femtosecond laser optical trapping similar to thee CW laser optical trapping except that optical damage can be easily induced due to extremely high peak power of femtosecond pulses. We monitored the Raman signal changes as a marker for optical damage. We used red blood cell (RBC) as a target sample and first used the CW laser beams to trap the RBC from the bottom of the chamber. After the trapped RBC is moved to a desired depth, we switched the laser mode to mode-locked mode and monitored the Raman signals as a function of the laser irradiation time. It was observed that the Raman shift at 1543 cm-1 may be a good marker for optical damage both for CW and femtosecond laser trapping.

Ju, Sung-bin; Pyo, Jin-woo; Jang, Jae-young; Lee, Seungduk; Kim, Beop-Min

2008-03-01

342

Dynamics of cell membrane permeability changes at supraphysiological temperatures.  

PubMed Central

A quantitative fluorescent microscopy system was developed to characterize, in real time, the effects of supraphysiological temperatures between 37 degrees and 70 degrees C on the plasma membrane of mouse 3T3 fibroblasts and isolated rat skeletal muscle cells. Membrane permeability was assessed by monitoring the leakage as a function of time of the fluorescent membrane integrity probe calcein. The kinetics of dye leakage increased with increasing temperature in both the 3T3 fibroblasts and the skeletal muscle cells. Analytical solutions derived from a two-compartment transport model showed that, for both cell types, a time-dependent permeability assumption provided a statistically better fit of the model predictions to the data than a constant permeability assumption. This finding suggests that the plasma membrane integrity is continuously being compromised while cells are subjected to supraphysiological temperatures. Images FIGURE 1 FIGURE 2 FIGURE 3

Bischof, J C; Padanilam, J; Holmes, W H; Ezzell, R M; Lee, R C; Tompkins, R G; Yarmush, M L; Toner, M

1995-01-01

343

[Membrane contacts of endoplasmic reticulum with plasmalemma in plant cells].  

PubMed

Close contacts of endoplasmatic reticulum membrane with plasmalemma have been shown in common wheat root cells by means of electron microscopy. Qualitative analogy of these contacts with high-permeable intercellular contacts in animals has been preliminary established. PMID:20352693

Velikanov, G A; Ponomareva, A A; Belova, L P; Levanov, V Iu

2010-01-01

344

Subnanosecond electric pulses cause membrane permeabilization and cell death.  

PubMed

Subnanosecond electric pulses (200 ps) at electric field intensities on the order of 20 kV/cm cause the death of B16.F10 murine melanoma cells when applied for minutes with a pulse repetition rate of 10 kHz. The lethal effect of the ultrashort pulses is found to be caused by a combination of thermal effects and electrical effects. Studies on the cellular level show increased transport across the membrane at much lower exposure times or number of pulses. Exposed to 2000 pulses, NG108 cells exhibit an increase in membrane conductance, but only allow transmembrane currents to flow, if the medium is positively biased with respect to the cell interior. This means that the cell membrane behaves like a rectifying diode. This increase in membrane conductance is a nonthermal process, since the temperature rise due to the pulsing is negligible. PMID:21303739

Xiao, Shu; Guo, Siqi; Nesin, Vasyl; Heller, Richard; Schoenbach, Karl H

2011-02-07

345

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

346

Alteration of the Erythrocyte Membrane Skeletal Ultrastructure in Hereditary Spherocytosis, Hereditary Elliptocytosis, and Pyropoikilocytosis  

Microsoft Academic Search

HE INNER SIDE of the human erythrocyte membrane T is laminated by a protein network that is principally composed of spectrin, actin, and proteins 4.1 and 4.9.',2 Recent electron microscopic studies of red blood cell (RBC) membrane skeletal preparations, which have been uniformly extended to permit visualization of the individual skeletal subunits and their connections, showed a two-dimensional regularly ordered

Shih-Chun Liu; Laura H. Derick; Peter Agre; Jiri Palek

347

Membrane Composition Tunes the Outer Hair Cell Motor  

NASA Astrophysics Data System (ADS)

Cholesterol and docosahexaenoic acid (DHA), an ?-3 fatty acid, affect membrane mechanical properties in different ways and modulate the function of membrane proteins. We have probed the functional consequence of altering cholesterol and DHA levels in the membranes of OHCs and prestin expressing HEK cells. Large, dynamic and reversible changes in prestin-associated charge movement and OHC motor activity result from altering the concentration of membrane cholesterol. Increasing membrane cholesterol shifts the q/V function ~ 50 mV in the hyperpolarizing direction, possibly a response related to increases in membrane stiffness. The voltage shift is linearly related to total membrane cholesterol. Increasing cholesterol also decreases the total charge moved in a linear fashion. Decreasing membrane cholesterol shifts the q/V function ~ 50 mV in the depolarizing direction with little or no effect on the amount of charge moved. In vivo increases in membrane cholesterol transiently increase but ultimately lead to decreases in DPOAE. Docosahexaenoic acid shifts the q/V function in the hyperpolarizing direction < 15 mV and increases total charge moved. Tuning of cochlear function by membrane cholesterol contributes to the exquisite temporal and frequency processing of mammalian hearing by optimizing the cochlear amplifier.

Rajagopalan, L.; Sfondouris, J.; Oghalai, J. S.; Pereira, F. A.; Brownell, W. E.

2009-02-01

348

Modeling of interactions between nanoparticles and cell membranes  

NASA Astrophysics Data System (ADS)

Rapid development of nanotechnology and ability to manufacture materials and devices with nanometer feature size leads to exciting innovations in many areas including the medical and electronic fields. However, the possible health and environmental impacts of manufactured nanomaterials are not fully known. Recent experimental reports suggest that some of the manufactured nanomaterials, such as fullerenes and carbon nanotubes, are highly toxic even in small concentrations. The goal of the current work is to understand the mechanisms responsible for the toxicity of nanomaterials. In the current study coarse-grained molecular dynamics simulations are employed to investigate the interactions between NPs and cellular membranes at a molecular level. One of the possible toxicity mechanisms of the nanomaterials is membrane disruption. Possibility of membrane disruption exposed to the manufactured nanomaterials are examined by considering chemical reactions and non-reactive physical interactions as chemical as well as physical mechanisms. Mechanisms of transport of carbon-based nanoparticles (fullerene and its derivative) across a phospholipid bilayer are investigated. The free energy profile is obtained using constrained simulations. It is shown that the considered nanoparticles are hydrophobic and therefore they tend to reside in the interior of the lipid bilayer. In addition, the dynamics of the membrane fluctuations is significantly affected by the nanoparticles at the bilayer-water interface. The hydrophobic interaction between the particles and membrane core induces the strong coupling between the nanoparticle motion and membrane deformation. It is observed that the considered nanoparticles affect several physical properties of the membrane. The nanoparticles embedded into the membrane interior lead to the membrane softening, which becomes more significant with increase in CNT length and concentration. The lateral pressure profile and membrane energy in the membrane containing the nanoparticles exhibit localized perturbation around the nanoparticle. The nanoparticles are not likely to affect membrane protein function by the weak perturbation of the internal stress in the membrane. Due to the short-ranged interactions between the nanoparticles, the nanoparticles would not form aggregates inside membranes. The effect of lipid peroxidation on cell membrane deformation is assessed. The peroxidized lipids introduce a perturbation to the internal structure of the membrane leading to higher amplitude of the membrane fluctuations. Higher concentration of the peroxidized lipids induces more significant perturbation. Cumulative effects of lipid peroxidation caused by nanoparticles are examined for the first time. The considered amphiphilic particle appears to reduce the perturbation of the membrane structure at its equilibrium position inside the peroxidized membrane. This suggests a possibility of antioxidant effect of the nanoparticle.

Ban, Young-Min

349

Abnormal Phospholipid Metabolism in Spur Cell Anemia: Decreased Fatty Acid Incorporation Into Phosphatidylethanolamine and Increased Incorporation Into Acylcarnitine in Spur Cell Anemia Erythrocytes  

Microsoft Academic Search

Spur cell anemia is a hemolytic anemia seen in severe alco- holic cirrhosis that is characterized by unusual morphology and a decreased ratio of phospholipids to cholesterol in the erythrocyte membrane. We hypothesized that defective phospholipid repair may contribute to the red blood cell (RBC) phospholipid abnormalities of spur cell anemia. There- fore, we compared RBCs from normal control subjects

David W. Allen; Nancy Manning

1994-01-01

350

Cytotopographical specialization of enzymatically isolated rabbit retinal Müller (glial) cells: K+ conductivity of the cell membrane.  

PubMed

Müller (radial glial) cells were isolated from rabbit retinae by means of papaine and mechanical dissociation. Regional membrane properties of these cells were studied by intracellular microelectrode recordings of potential responses to local application of high K+ solutions. When different parts of the cell membrane were exposed to high K+, the amplitude of the depolarizing responses varied greatly, indicating a strong regional specialization of the membrane properties. Using morphometrical data of isolated rabbit Müller cells, and a simple circuit model, we calculated the endfoot membrane to constitute more than 80% of the total K+ conductance of the cell; the specific resistivity of the endfoot membrane was about 400 omega cm2, i.e., more than 40 times less than that of the membrane of the vitread process, which is immediately adjacent. This kind of regional membrane specialization seems to be optimized in respect to the Müller cells' ability to carry spatial buffering K+ currents. PMID:2976038

Reichenbach, A; Eberhardt, W

1988-01-01

351

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

352

Selective and Asymmetric Molecular Transport Across Electroporated Cell Membranes  

Microsoft Academic Search

Transport of a divalent cation (Ca2+) and three DNA indicators [ethidium bromide (EB), propidium iodide (PI), and ethidium homodimer (EthD-1)] across electroporated membranes of several mammalian cell lines was found to be selective and asymmetrical. In low salt medium, Ca2+ and EB were preferentially transported across the anode-facing cell membrane while PI and EthD-1 predominately entered at the site facing

Ephrem Tekle; R. Dean Astumian; P. Boon Chock

1994-01-01

353

A biophotonic study of live, flowing red blood cells in an optical trap  

NASA Astrophysics Data System (ADS)

We investigate the physics of an optically trapped red blood cell under physiological conditions. When a single, live red blood cell, is placed in an optical trap, the normal biconcave disk shaped cell is observed to undergo a folding action and thereby take up a rod like shape. If such an RBC has any shape anisotropies due to perturbation through malarial infection or hyperosmotic stress, it is observed to rotate in the linearly polarised laser field. Finally when such an optically trapped RBC is exposed to a shear flow, a tank treading like behaviour of the red blood cell membrane is visualised (wherein the RBC membrane revolves around the central body of the cell). The tank treading motion of a red blood cell held stationary in the optical trap allows for the dynamics to be viewed in a prolonged manner without the usage of earlier constraints such fast imaging system.

Basu, H.; Dharmadhikari, A. K.; Dharmadhikari, J. A.; Sharma, S.; Mathur, D.

2010-12-01

354

Fibronectin coating of oxygenator membranes enhances endothelial cell attachment  

PubMed Central

Background Extracorporeal membrane oxygenation (ECMO) can replace the lungs’ gas exchange capacity in refractory lung failure. However, its limited hemocompatibility, the activation of the coagulation and complement system as well as plasma leakage and protein deposition hamper mid- to long-term use and have constrained the development of an implantable lung assist device. In a tissue engineering approach, lining the blood contact surfaces of the ECMO device with endothelial cells might overcome these limitations. As a first step towards this aim, we hypothesized that coating the oxygenator’s gas exchange membrane with proteins might positively influence the attachment and proliferation of arterial endothelial cells. Methods Sheets of polypropylene (PP), polyoxymethylpentene (TPX) and polydimethylsiloxane (PDMS), typical material used for oxygenator gas exchange membranes, were coated with collagen, fibrinogen, gelatin or fibronectin. Tissue culture treated well plates served as controls. Endothelial cell attachment and proliferation were analyzed for a period of 4 days by microscopic examination and computer assisted cell counting. Results Endothelial cell seeding efficiency is within range of tissue culture treated controls for fibronectin treated surfaces only. Uncoated membranes as well as all other coatings lead to lower cell attachment. A confluent endothelial cell layer develops on fibronectin coated PDMS and the control surface only. Conclusions Fibronectin increases endothelial cells’ seeding efficiency on different oxygenator membrane material. PDMS coated with fibronectin shows sustained cell attachment for a period of four days in static culture conditions.

2013-01-01

355

Hydroxycarbamide-induced changes in E/beta thalassemia red blood cells.  

PubMed

In thalassemia, fetal hemoglobin (HbF) augmentation with hydroxycarbamide (also known as hydroxyurea) is not always successful. The expected parallel effects on red cell (RBC) membrane deformability, cell hydration, and membrane phospholipid organization, all important for extending RBC life span and increasing Hb, have been infrequently examined. We analyzed these characteristics in 15 nontransfused E/beta(0) thalassemia patients treated with HU (mean 10.2 months). Membrane deformability and cell hydration mildly improved in association with increased HbF levels approaching statistical significance (r = 0.51, P = 0.06). All measures improved considerably in splenctomized patients. These findings underscore the disappointing results of hydroxyurea treatment in clinical trials and the importance of examining the effect on RBC characteristics for the development and understanding of HbF-enhancing agents. PMID:18821710

Singer, Sylvia T; Vichinsky, Elliott P; Larkin, Sandra; Olivieri, Nancy; Sweeters, Nancy; Kuypers, Frans A

2008-11-01

356

Materials issues in polymer electrolyte membrane fuel cells  

Microsoft Academic Search

Fuel cells have the potential to reduce the nation's energy use through increased energy conversion efficiency and dependence on imported petroleum by the use of hydrogen from renewable resources. The US DOE Fuel Cell subprogram emphasizes polymer electrolyte membrane (PEM) fuel cells as replacements for internal combustion engines in light-duty vehicles to support the goal of reducing oil use in

N. L. Garland; T. G. Benjamin; J. P. Kopasz

2008-01-01

357

Cell membranes: The electromagnetic environment and cancer promotion  

Microsoft Academic Search

Use of weak electromagnetic fields to study the sequence and energetics of events that couple humoral stimuli from surface receptor sites to the cell interior has identified cell membranes as a primary site of interaction, with these low frequency fields. Field modulation of cell surface chemical events indicates a major amplification of initial weak triggers associated with binding of hormones,

W. R. Adey

1988-01-01

358

A novel unitized regenerative proton exchange membrane fuel cell  

Microsoft Academic Search

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

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

1995-01-01

359

Computational modeling and optimization of proton exchange membrane fuel cells  

Microsoft Academic Search

Improvements in performance, reliability and durability as well as reductions in production costs, remain critical prerequisites for the commercialization of proton exchange membrane fuel cells. In this thesis, a computational framework for fuel cell analysis and optimization is presented as an innovative alternative to the time consuming trial-and-error process currently used for fuel cell design. The framework is based on

Marc Secanell Gallart

2007-01-01

360

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.

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

2011-01-01

361

Dynamic continuity of cytoplasmic and membrane compartments between plant cells  

PubMed Central

Fluorescence photobleaching was employed to examine the intercellular movement of fluorescein and carboxyfluorescein between contiguous soybean root cells (SB-1 cell line) growing in tissue culture. Results of these experiments demonstrated movement of these fluorescent probes between cytoplasmic (symplastic) compartments. This symplastic transport was inhibited with Ca2+ in the presence of ionophore A23187, and also with the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Both of these agents have previously been demonstrated to inhibit gap junction-mediated cell-cell communication in animal cells. In a companion experiment, a fluorescent phospholipid analogue, N-4- nitrobenzo-2-oxa-1,3-diazole phosphatidylcholine (NBD-PC), was incorporated into soybean cell membranes to examine whether dynamic membrane continuity existed between contacting cells, a transport route not existing between animal cells. Photobleaching single soybean cells growing in a filamentous strand demonstrated that phospholipid did exchange between contiguous cells.

1988-01-01

362

Redistribution of membrane proteins in isolated mouse intestinal epithelial cells  

PubMed Central

Single mouse intestinal epithelial cells (IEC) may be isolated by the use of a combination of methods used for the isolation of IEC from other species. Isolated cells remain viable for several hours. The membrane integral enzymes alkaline phosphatase and leucine aminopeptidase of isolated IEC are localized to the brush borders of IEC in tissue and in most newly isolated IEC. With time, both enzymes are found distributed over the entire cell surface. Redistribution appears to occur by diffusion in the plane of the membrane. It is slowed, but not blocked, if cells are maintained at 0 degrees C instead of at 37 degrees C, and it is not blocked by fixation in 0.5-3% paraformaldehyde. Drugs that alter cell membrane potential or that affect cell levels of ATP enhance the rate of redistribution of the enzymes.

1980-01-01

363

Identification of laminin binding proteins in cell membranes of a human colon adenocarcinoma cell line  

Microsoft Academic Search

The invasion of malignant cells through the basement membrane is a critical step in local infiltration and metastasis. Adhesion and invasion of malignant cells may be modulated by their receptor mediated binding to the basement membrane glycoprotein laminin. We studied the specific adhesion of human colon adenocarcinoma derived HT 29 cells to laminin and its proteolytic fragments. The major cell

A Stallmach; D Schuppan; J Dax; C Hanski; E O Riecken

1990-01-01

364

Toward mechanical manipulations of cell membranes and membrane proteins using an atomic force microscope  

Microsoft Academic Search

Recent advances in the use of the atomic force microscope (AFM) for manipulating cell membranes and membrane proteins are\\u000a reviewed. Early pioneering work on measurements of the magnitude of the force required to create indentations with defined\\u000a depth on their surfaces and to separate interacting pairs of avidin-biotin, antigen-antibody, and complementary DNA pairs\\u000a formed the basis of this field. The

Atsushi Ikai; Rehana Afrin

2003-01-01

365

Roles of adiponectin and oxidative stress in the regulation of membrane microviscosity of red blood cells in hypertensive men-an electron spin resonance study.  

PubMed

This study was undertaken to investigate possible relationships among plasma adiponectin, 8-iso-prostaglandin F2? (8-iso-PG F2?: an index of oxidative stress), and membrane fluidity (a reciprocal value of microviscosity) in hypertensive and normotensive men using an electron spin resonance-method. The order parameter (S) for the spin-label agent (5-nitroxide stearate) in red blood cell (RBC) membranes was higher in hypertensive men than in normotensive men, indicating that membrane fluidity was decreased in hypertension. Plasma adiponectin and NO metabolites levels were lower in hypertensive men than in normotensive men. In contrast, plasma 8-iso-PG F2? levels were increased in hypertensive men compared with normotensive men. Plasma adiponectin concentration was correlated with plasma NO-metabolites, and inversely correlated with plasma 8-iso-PG F2?. The order parameter (S) of RBCs was inversely correlated with plasma adiponectin and plasma NO metabolite levels, and positively correlated with plasma 8-iso-PG F2?, suggesting that the reduced membrane fluidity of RBCs might be associated with hypoadiponectinemia, endothelial dysfunction, and increased oxidative stress. In a multivariate regression analysis, adiponectin and 8-iso-PG F2? were significant determinants of membrane fluidity of RBCs after adjustment for general risk factors. These results suggest that adiponectin and oxidative stress might have a close correlation with rheologic behavior and microcirculation in hypertension. PMID:20871823

Tsuda, Kazushi

2010-09-02

366

Roles of Adiponectin and Oxidative Stress in the Regulation of Membrane Microviscosity of Red Blood Cells in Hypertensive Men--An Electron Spin Resonance Study  

PubMed Central

This study was undertaken to investigate possible relationships among plasma adiponectin, 8-iso-prostaglandin F2? (8-iso-PG F2?: an index of oxidative stress), and membrane fluidity (a reciprocal value of microviscosity) in hypertensive and normotensive men using an electron spin resonance-method. The order parameter (S) for the spin-label agent (5-nitroxide stearate) in red blood cell (RBC) membranes was higher in hypertensive men than in normotensive men, indicating that membrane fluidity was decreased in hypertension. Plasma adiponectin and NO metabolites levels were lower in hypertensive men than in normotensive men. In contrast, plasma 8-iso-PG F2? levels were increased in hypertensive men compared with normotensive men. Plasma adiponectin concentration was correlated with plasma NO-metabolites, and inversely correlated with plasma 8-iso-PG F2?. The order parameter (S) of RBCs was inversely correlated with plasma adiponectin and plasma NO metabolite levels, and positively correlated with plasma 8-iso-PG F2?, suggesting that the reduced membrane fluidity of RBCs might be associated with hypoadiponectinemia, endothelial dysfunction, and increased oxidative stress. In a multivariate regression analysis, adiponectin and 8-iso-PG F2? were significant determinants of membrane fluidity of RBCs after adjustment for general risk factors. These results suggest that adiponectin and oxidative stress might have a close correlation with rheologic behavior and microcirculation in hypertension.

Tsuda, Kazushi

2011-01-01

367

Influence of hydrogen ion concentration on refractive index value in red blood cells of diabetes patients  

Microsoft Academic Search

Since hyperglycaemia changes fluidity of erythrocyte cell membrane and impair cell deformability, our goal was to characterize light refractive properties of haemoglobin and red blood cells (RBC) in diabetes patients. Microscopic investigation was carried out on intact and in methanol fixed RBCs of diabetes patients with long-term hyperglycaemia (glycosylated haemoglobin > 7,5%). Interference microscopy was used for refractive index (RI)

Gunta Mazarevica; Talivaldis Freivalds; Antra Jurka

2002-01-01

368

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.

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

369

Elastic membrane heterogeneity of living cells revealed by stiff nanoscale membrane domains.  

PubMed

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

2007-11-02

370

Oxime Reactivation of RBC Acetylcholinesterases for Biomonitoring  

Microsoft Academic Search

.   A low-variability method to reactivate blood cholinesterases (ChEs) after prior exposure of mammals, including humans, to\\u000a ChE-inhibiting organophosphate esters (OPs) is presented. A concentration of 10 mM pyridine 2-aldoxime methochloride (2-PAM\\u000a Cl) was incubated with intact red blood cells (RBCs) and assayed virtually free of interfering oxime and hemoglobin (Hb).\\u000a Variability was decreased by reducing the number of washing

M. E. Hansen; B. W. Wilson

1999-01-01

371

Simultaneous manipulation and detection of living cell membrane dynamics  

NASA Astrophysics Data System (ADS)

We report a novel optical-tweezers-based method to study the membrane motion at the leading edge of biological cells with nanometer spatial and microsecond temporal resolution. A diffraction-limited laser spot was positioned at the leading edge of a cell, and the forward scattered light was imaged on a quadrant photodiode that served as a position sensitive device. The universality of this technique is demonstrated with different cell types. We investigated the membrane motion at the leading edge of red blood cells in detail and showed that this technique can achieve simultaneous manipulation and detection of cellular edge dynamics with unprecedented precision.

Gögler, Michael; Betz, Timo; Alfons Käs, Josef

2007-07-01

372

Recent developments in proton exchange membranes for fuel cells  

SciTech Connect

Proton exchange membranes (PEMs) that operate at temperatures above 120 °C are needed to avoid catalyst poisoning, speed up electrochemical reactions, simplify the design and reduce the cost of fuel cells. This review summarizes developments in PEMs over the last five years. In order to design new membranes for elevated temperature operation, one must understand the chemistry, morphology and dynamics of protons and small molecules in existing membranes. The integration of experiments with modeling and simulation can shed light on the hierarchical structure of the membrane and dynamical processes associated with molecular transport. Based on such a fundamental understanding, membranes can be modified by controlling the polymer chemistry and architecture or adding inorganic fillers that can retain water under low relative humidity conditions. In addition, the development of anhydrous membranes based on phosphoric acid doped polymers, ionic liquid-infused polymer gels and solid acids can enable fuel cell operation above 150 °C. Considerable work remains to be done to identify proton transport mechanisms in novel membranes and evaluate membrane durability under real world operating conditions.

Devanathan, Ramaswami

2008-07-23

373

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

374

Cdc42 localization and cell polarity depend on membrane traffic  

PubMed Central

Cell polarity is essential for cell division, cell differentiation, and most differentiated cell functions including cell migration. The small G protein Cdc42 controls cell polarity in a wide variety of cellular contexts. Although restricted localization of active Cdc42 seems to be important for its distinct functions, mechanisms responsible for the concentration of active Cdc42 at precise cortical sites are not fully understood. In this study, we show that during directed cell migration, Cdc42 accumulation at the cell leading edge relies on membrane traffic. Cdc42 and its exchange factor ?PIX localize to intracytosplasmic vesicles. Inhibition of Arf6-dependent membrane trafficking alters the dynamics of Cdc42-positive vesicles and abolishes the polarized recruitment of Cdc42 and ?PIX to the leading edge. Furthermore, we show that Arf6-dependent membrane dynamics is also required for polarized recruitment of Rac and the Par6–aPKC polarity complex and for cell polarization. Our results demonstrate influence of membrane dynamics on the localization and activation of Cdc42 and consequently on directed cell migration.

Osmani, Nael; Peglion, Florent; Chavrier, Philippe

2010-01-01

375

Localization and Conditional Redundancy of Regulatory Elements in rbcS-3A, a Pea Gene Encoding the Small Subunit of Ribulose-bisphosphate Carboxylase  

Microsoft Academic Search

Expression of the pea rbcS-3A gene, one of a family of genes encoding the small subunit of ribulose-bisphosphate carboxylase [EC 4.1.1.39], is regulated by light and is restricted to chloroplast-containing cells. We analyzed the effects of light and development on rbcS-3A expression in transgenic plants. Two highly conserved sequences (``boxes'' II and III) around nucleotide position -150 (relative to the

Cris Kuhlemeier; Maria Cuozzo; Pamela J. Green; Elisabeth Goyvaerts; Kathy Ward; Nam-Hai Chua

1988-01-01

376

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

2012-03-29

377

Fuel cell electrolyte membrane with basic polymer  

SciTech Connect

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

378

Fuel cell electrolyte membrane with basic polymer  

SciTech Connect

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

379

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

380

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.

HUTAGALUNG, ALEX H.; NOVICK, PETER J.

2013-01-01

381

Efficient and Specific Analysis of Red Blood Cell Glycerophospholipid Fatty Acid Composition  

PubMed Central

Background Red blood cell (RBC) n-3 fatty acid status is related to various health outcomes. Accepted biological markers for the fatty acid status determination are RBC phospholipids, phosphatidylcholine, and phosphatidyletholamine. The analysis of these lipid fractions is demanding and time consuming and total phospholipid n-3 fatty acid levels might be affected by changes of sphingomyelin contents in the RBC membrane during n-3 supplementation. Aim We developed a method for the specific analysis of RBC glycerophospholipids. The application of the new method in a DHA supplementation trial and the comparison to established markers will determine the relevance of RBC GPL as a valid fatty acid status marker in humans. Methods Methyl esters of glycerophospholipid fatty acids are selectively generated by a two step procedure involving methanolic protein precipitation and base-catalysed methyl ester synthesis. RBC GPL solubilisation is facilitated by ultrasound treatment. Fatty acid status in RBC glycerophospholipids and other established markers were evaluated in thirteen subjects participating in a 30 days supplementation trial (510 mg DHA/d). Outcome The intra-assay CV for GPL fatty acids ranged from 1.0 to 10.5% and the inter-assay CV from 1.3 to 10.9%. Docosahexaenoic acid supplementation significantly increased the docosahexaenoic acid contents in all analysed lipid fractions. High correlations were observed for most of the mono- and polyunsaturated fatty acids, and for the omega-3 index (r?=?0.924) between RBC phospholipids and glycerophospholipids. The analysis of RBC glycerophospholipid fatty acids yields faster, easier and less costly results equivalent to the conventional analysis of RBC total phospholipids.

Klem, Sabrina; Klingler, Mario; Demmelmair, Hans; Koletzko, Berthold

2012-01-01

382

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.

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

2013-01-01

383

Electrical Resistance of Cell Membranes of Avena coleoptiles.  

PubMed

The cell membrane resistance to direct current was measured in single cells for the first time in a higher plant tissue, oat coleoptiles (Avena sativa). On the assumption that the current density over the cell surface was uniform, a mean value of about 1300 ohm-cm(2) was found for cells in an external nutrient medium containing 1 mmole each of K(+), Na(+), and Ca(++) per liter. As expected, either decreasing K(+) concentration or increasing Ca(++) concentration increased the resistance. PMID:17807848

Higinbotham, N; Hope, A B; Findlay, G P

1964-03-27

384

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

385

Determination of apical membrane polarity in mammary epithelial cell cultures: the role of cell-cell, cell-substratum, and membrane-cytoskeleton interactions.  

PubMed

The membrane glycoprotein, PAS-O, is a major differentiation antigen on mammary epithelial cells and is located exclusively in the apical domain of the plasma membrane. We have used 734B cultured human mammary carcinoma cells as a model system to study the role of tight junctions, cell-substratum contacts, and submembraneous cytoskeletal elements in restricting PAS-O to the apical membrane. Immunofluorescence and immunoelectronmicroscopy experiments demonstrated that while tight junctions demarcate PAS-O distribution in confluent cultures, apical polarity could be established at low culture densities when cells could not form tight junctions with neighboring cells. In such cultures the boundary between apical and basal domains was observed at the point of cell contact with the substratum. Immunocytochemical analysis of these cell-substratum contacts revealed the absence of a characteristic basement membrane containing laminin, collagen (IV), and heparan sulfate proteoglycan. However, serum-derived vitronectin was associated with the basal cell surface and the cells were shown to express the vitronectin receptor on their basolateral membranes. Additionally, treatment of cultures with antibodies against the vitronectin receptor caused cell detachment. We suggest, then, that interactions between vitronectin and its receptor, are responsible for establishment of membrane domains in the absence of tight junctions. The role of cytoskeletal elements in restricting PAS-O distribution was examined by treating cultures with cytochalasin D, colchicine, or acrylamide. Cytochalasin D led to a redistribution of PAS-O while colchicine and acrylamide did not. We hypothesize that PAS-O is restricted to the apical membrane by interactions with a microfilament network and that the cytoskeletal organization is dependent upon cell-cell and cell-substratum interactions. PMID:1692284

Parry, G; Beck, J C; Moss, L; Bartley, J; Ojakian, G K

1990-06-01

386

Cytokines Modulate Expression of Cell-Membrane Complement Inhibitory Proteins in Human Lung Cancer Cell Lines  

Microsoft Academic Search

Human lung cancers overexpress several cell-membrane complement inhibitory proteins (CIP). These complement inhibitory proteins are membrane cofactor protein (CD46), decay-accelerating factor (DAF; CD55), and CD59 (protectin). These cell-membrane proteins have a wide normal tissue distribution, are known to protect normal host cells from homologous complement-mediated lysis, and are thought to facil- itate tumor escape from immunosurveillance. To study whether proinflammatory

Shabtai Varsano; Ludmila Rashkovsky; Hava Shapiro; Judith Radnay

387

Mild spherocytosis and altered red cell ion transport in protein 4. 2-null mice  

Microsoft Academic Search

Protein 4.2 is a major component of the red blood cell (RBC) membrane skeleton. We used targeted mutagenesis in embryonic stem (ES) cells to elucidate protein 4.2 functions in vivo. Protein 4. 2-null (4.2(-\\/-)) mice have mild hereditary spherocytosis (HS). Scanning electron microscopy and ektacytometry confirm loss of membrane surface in 4.2(-\\/-) RBCs. The membrane skeleton architecture is intact, and

Luanne L. Peters; Hitesh K. Jindel; Babette Gwynn; Cathy Korsgren; Kathryn M. John; Samuel E. Lux; Narla Mohandas; Carl M. Cohen; Michael R. Cho; David E. Golan; Carlo Brugnara

1999-01-01

388

Fluorescent sterols as tools in membrane biophysics and cell biology.  

PubMed

Cholesterol is an important constituent of cellular membranes playing a fundamental role in many biological processes. This sterol affects membrane permeability, lateral lipid organization, signal transduction and membrane trafficking. Intracellular sterol transport modes and pathways as well as the regulation of sterol metabolism and disposition in various tissues are areas of intense research. Progress is intimately linked to development and use of appropriate analogs, which closely mimic the properties of cholesterol while allowing to be detected by spectroscopic or microscopic methods. This review provides an overview of various fluorescent sterols used in membrane biophysics and cell biology including analogs of cholesterol and cholesteryl esters. Attention is paid to the natural fluorescent sterol dehydroergosterol (DHE). A survey of the many applications of DHE in biological research is presented. Special emphasis is on recent developments in fluorescence microscopy instrumentation to visualize DHE as an intrinsically fluorescent analog of cholesterol in living cells. PMID:17241621

Wüstner, Daniel

2006-12-30

389

Nonlinear electro-mechanobiological behavior of cell membrane during electroporation  

NASA Astrophysics Data System (ADS)

A nonlinear electroporation (EP) model is proposed to study the electro-mechanobiological behavior of cell membrane during EP, by taking the nonlinear large deformation of the membrane into account. The proposed model predicts the critical transmembrane potential and the activation energy for EP, the equilibrium pore size, and the resealing process of the pore. Single-cell EP experiments using a micro EP chip were conducted on chicken red blood cells at different temperatures to determine the activation energy and the critical transmembrane potential for EP. The experimental results are in good agreement with the theoretical predictions.

Deng, Peigang; Lee, Yi-Kuen; Lin, Ran; Zhang, Tong-Yi

2012-07-01

390

Attachment of killed Mycoplasma gallisepticum cells and membranes to erythrocytes.  

PubMed Central

To correlate viability with attachment capacity, Mycoplasma gallisepticum cell 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 anmd 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

1981-01-01

391

Microrheology of red blood cell membranes using dynamic scattering microscopy.  

PubMed

We employ a novel optical technique, dynamic scattering microscopy (DSM), to extract the frequency dependence of the viscoelastic modulus associated with the red blood cell membrane. This approach applies the principle of dynamic light scattering to micro beads attached to the red blood cell membrane in thermal fluctuation. This allows for highthroughput characterization of a large number of cells simultaneously, which represents a significant advantage over current methods. The results in terms of the effective loss and storage moduli indicate the generic behavior of a viscoelastic material, characterized by power laws with exponents between 0 and 1. PMID:19550991

Amin, M Shahrooz; Park, Yougkeun; Lue, Niyom; Dasari, Ramachandra R; Badizadegan, Kamran; Feld, Michael S; Popescu, Gabriel

2007-12-10

392

Membrane currents and the resting membrane potential in cultured bovine pulmonary artery endothelial cells.  

PubMed Central

1. We have used the whole-cell patch-clamp technique to characterize the ionic conductances that determine the resting membrane potential in cultured endothelial cells from calf pulmonary artery (CPAE cells). 2. Resting membrane potentials were scattered between -88 and +5 mV with a mean +/- S.E.M. of -26 +/- 3 mV (n = 104). 3. The most prominent membrane current in resting cells was an inwardly rectifying K+ current. This current showed Na(+)-dependent inactivation and was efficiently blocked by external Ba2+ (EC50 = 2.2 microM), but was relatively insensitive to quinine, quinidine and TEA. 4. Hypertonic cell shrinkage inhibited an outwardly rectifying Cl- current, which was also efficiently blocked by 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB; 100 microM), quinine (500 microM) and quinidine (500 microM). 5. A linear, time-independent background current remained after elimination of these two currents. This current was dependent on extracellular monovalent cations with a permeability sequence of Cs+ > Na+ > Li+ >> N-methyl-D-glucamine. It was partially blocked by millimolar concentrations of the divalent cations Ca2+, Ni2+ and Ba2+. Gd3+ (200 microM) had no significant effect on this background current. 6. Continuous measurements of the membrane potential confirm that the three described conductances are the major determinants of the membrane potential. Due to the low slope conductance in the region between -70 and 0 mV, small changes in one of the current components can evoke large depolarizations or hyperpolarizations, which explains the large scattering of the resting membrane potentials.

Voets, T; Droogmans, G; Nilius, B

1996-01-01

393

Nonlinear Behavior of Fuel Cell Membrane Assemblies  

Microsoft Academic Search

Fuel cells are composite material systems. A schematic diagram of a polymer-based fuel cell is shown in Fig. 1 Figure 1. Schematic diagram of a PEM cell. There are a variety of degradation and failure modes associated with the operation of fuel cells. Predicting the voltage-current output of the fuel cell typically requires that coupled multi-physics equations be solved to

K. Reifsnider; X. Huang; G. Ju

394

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

395

Phospholipids undergo hop diffusion in compartmentalized cell membrane  

Microsoft Academic Search

he diffusion rate of lipids in the cell membrane is reduced by a factor of 5-100 from that in artificial bilayers. This slowing mechanism has puzzled cell biologists for the last 25 yr. Here we address this issue by studying the movement of unsaturated phospholipids in rat kidney fibroblasts at the single molecule level at the temporal resolution of 25

Takahiro Fujiwara; Ken Ritchie; Hideji Murakoshi; Ken Jacobson; Akihiro Kusumi

2002-01-01

396

Challenges and future developments in proton exchange membrane fuel cells  

Microsoft Academic Search

Fuel cell system is an advanced power system for the future that is sustainable, clean and environmental friendly. The importance of fuel cell as the future power system is discussed in the light of future fossil fuel depletion, impending international law on green house gases control and the national renewable energy policy. The modern development of the proton exchange membrane

Kamaruzzaman Sopian; Wan Ramli Wan Daud

2006-01-01

397

Membrane nanotubes: dynamic long-distance connections between animal cells  

Microsoft Academic Search

Membrane nanotubes are transient long-distance connections between cells that can facilitate intercellular communication (for example, by trafficking vesicles or transmitting calcium-mediated signals), but they can also contribute to pathologies (for example, by directing the spread of viruses). Recent data have revealed considerable heterogeneity in their structures, processes of formation and functional properties, in part dependent on the cell types involved.

Stefanie Sowinski; Daniel M. Davis

2008-01-01

398

Structural changes in cell membranes after ionizing electromagnetic field exposure  

Microsoft Academic Search

Ionizing radiation damages chemical structures in biological tissues mainly through the generation of reactive oxygen intermediates (ROI). Consequences on the cell's transcriptional mechanisms are widely investigated but cannot account for the rapid lethal effects in victims of accidental high-dose radiation exposure. ROI-mediated structural damage of cell membranes through lipid peroxidation can lead to increased ion permeability followed by the loss

Jurgen Hannig; Raphael C. Lee

2000-01-01

399

ERM proteins in cell adhesion and membrane dynamics  

Microsoft Academic Search

Ezrin, radixin and moesin, collectively known as the ERM proteins, are a group of closely related membrane–cytoskeleton linkers that regulate cell adhesion and cortical morphogenesis. ERM proteins can self-associate through intra- and inter-molecular interactions, and these interactions mask several binding sites on the proteins. ERM activation involves unfolding of the molecule, and allows the protein to bind to plasma membrane

Paul Mangeat; Christian Roy; Marianne Martin

1999-01-01

400

Cranin: A Laminin-Binding Protein of Cell Membranes  

Microsoft Academic Search

We report that a 120-kDa glycoprotein is the predominant laminin-binding protein detected within plasma membranes of rodent NG108-15 neural hybrid cells, embryonic chicken brain, and mouse 3T3 fibroblasts. This protein was detected when membrane extracts were separated by PAGE, transferred to nitrocellulose, and incubated with laminin at concentrations as low as 2.8 × 10-11 M, under conditions of physiological ionic

Neil R. Smalheiser; Nancy B. Schwartz

1987-01-01

401

Durable, Low-cost, Improved Fuel Cell Membranes  

Microsoft Academic Search

The development of low cost, durable membranes and membranes electrode;\\u000aassemblies (MEAs) that operate under reduced relative humidity (RH) conditions;\\u000aremain a critical challenge for the successful introduction of fuel cells into mass;\\u000amarkets. It was the goal of the team lead by Arkema, Inc. to address these;\\u000ashortages. Thus, this project addresses the following technical barriers from the;\\u000afuel

Chris Roger; David Mountz; Wensheng He; Tao Zhang

2011-01-01

402

THE MOVEMENT OF PYRIDINIUM ALDOXIMES ACROSS THE RED CELL MEMBRANE  

Microsoft Academic Search

The movement of 2 PAM chloride (2-hydroxyiminomethyl-1-methylpyridinium chloride) across the rabbit red cell membrane was examined. The rate of uptake and efflux of the oxime through the membrane was proportional to the concentration gradient and appeared to be a process of non-assisted diffusion. The uptake was affected by factors such as the pH and ionic strength of the medium which

TEB Keen

1973-01-01

403

Water-soluble proteins of the human red cell membrane  

Microsoft Academic Search

Summary Procedures were developed for preparation of red cell membranes almost free of hemoglobin but with minimal loss of membrane proteins. Two water-soluble protein fractions are described, each constituting about 25% of the ghost protein. The first is ionically bonded and can be solubilized in water rapidly at pH 7.0 and more slowly at higher ionic strength solutions, with a

J. Th. Hoogeveen; R. Juliano; J. Coleman; A. Rothstein

1970-01-01

404

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

405

Degradation process of fuel cell membrane observed by positron  

NASA Astrophysics Data System (ADS)

To investigate degradation process due to radicals in fuel cell membrane by means of positron annihilation spectroscopy, three kinds of radicals, HO•, H• and O2•- are produced through water radiolysis. The results show that the cluster structure and proton conductivity was greatly affected by reductive radicals. This is because the oxidative radical is responsible for the dissociation of sulfonic group, whereas the reductive radical breaks down the cluster in the membrane and disrupts proton conduction, which is consistent with solution analysis.

Honda, Y.; Aoyagi, Y.; Tojo, S.; Watanabe, G.; Akiyama, Y.; Nishijima, S.

2013-06-01

406

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

407

Rapid and opposite effects of cortisol and estradiol on human erythrocyte NA +,K +-atpase activity: Relationship to steroid intercalation into the cell membrane  

Microsoft Academic Search

We determined whether two naturally occurring steroids, cortisol and 17?-estradiol (E2), can rapidly modulate the activity of an important membrane protein, human erythrocyte (RBC) Na+,K+-ATPase, an enzyme that does not bind either hormone directly. We also determined the membrane binding locations for cortisol and E2 and their effects on membrane molecular structure and fluidity. Direct application of both steroids to

Gil A. Golden; R. Preston Mason; Thomas N. Tulenko; George S. Zubenko; Robert T. Rubin

1999-01-01

408

Decreased cell membrane magnesium in some essential hypertension patients.  

PubMed

The concentrations of total ([T-Mg]), ultrafilterable ([UF-Mg]), and protein-bound or nonfilterable ([NF-Mg]) magnesium were measured in the plasma and in the intracellular compartment of blood from 8 essential hypertensive patients and 9 normotensive subjects. In the former, [T-Mg] was unchanged in the plasma but decreased in whole blood due to decreases of both [UF-Mg] and [NF-MG]; [UF-Mg] was increased in plasma but decreased intracellularly while [NF-Mg] was decreased in plasma and unchanged intracellularly. These concentrations correlated significantly with the average blood pressures. Decreased Mg binding to the erythrocyte membrane was also observed in 13 additional essential hypertensive patients. This decreased binding may well be responsible for the decreased intracellular [UF-Mg] in the blood of such patients. The cause of the decreased Mg binding to the erythrocyte membrane is unknown, but the binding is returned to normal by incubating erythrocytes from essential hypertensive patients with blood plasma from normotensive subjects. Decreased Mg binding to cell membranes must also occur in frankly Mg-deficient patients, some of whom, as a consequence of the primary deficiency of this mineral, are hypertensive. Normal Mg binding to erythrocyte membranes was observed in two patients with hypertension indicating that hypertension per se does not cause decreased Mg binding to cell membranes. These observations suggest that decreased Mg binding to cell membranes may be an important contributing factor in some cases of essential hypertension. PMID:2022073

Mattingly, M T; Brzezinski, W A; Wells, I C

1991-01-01

409

Fluorescence lifetime imaging (FLIM) of membrane markers in living cells  

NASA Astrophysics Data System (ADS)

An experimental setup for fluorescence lifetime imaging (FLIM) has been combined with total internal reflection fluorescence microscopy (TIRFM) in order to detect various membrane markers within living cells. The method is established using T47D human breast cancer cells transfected by a plasmid encoding for a membrane associated yellow fluorescent protein (EYFPmem). For further measurements the mitochondrial marker rhodamine 123 (R123) as well as the membrane marker laurdan are used. With increasing concentration R123 is accumulated outside the mitochondria, in particular within the plasma membrane, whereas mitochondrial fluorescence is quenched. Fluorescence lifetime of laurdan can be used to probe membrane dynamics, in particular the phase of membrane lipids. These lipids are in a rigid gel phase at temperatures around 24°C, whereas the gel phases and a liquid crystalline phase coexist at T >= 30°C. This phase pattern also depends on the age and the growth phase of the cells and may play a role in the uptake of pharmaceutical agents.

Schneckenburger, Herbert; Wagner, Michael; Kretzschmar, Martina; Strauss, Wolfgang S.; Sailer, Reinhard

2003-10-01

410

Cell surface accumulation of overexpressed hamster lysosomal membrane glycoproteins.  

PubMed

We cloned and sequenced cDNAs encoding two lysosomal membrane glycoproteins, lgp-A and lgp-B, from Chinese hamster ovary cells. The deduced amino acid sequences of these proteins are similar to those of the other known members of this conserved family (also known as "LAMP" proteins). We used the cDNAs to generate stable lines of hamster lgp-expressing mouse NIH-3T3 cells, rat NRK cells, and monkey CV-1 cells. We also generated hybridomas that secrete antibodies specific for hamster lgp-A and lgp-B, enabling us to distinguish foreign from endogenous lgps in a wider variety of transfected cell lines. One line of mouse NIH-3T3 cells that expresses hamster lgp-B was studied in detail. Whereas most of the hamster lgp-B appeared to be transported to lysosomes in these cells, butyrate-induced overexpression resulted in the accumulation of a significant proportion of the total on the plasma membrane. In addition, overexpression of this foreign lgp-B also resulted in the appearance of the endogenous mouse lgp-A and lgp-B on the plasma membrane. Characterization of this accumulation suggested that it resulted from competition for one or more limited components in the transport pathway(s) to lysosomes. Endocytosis from the plasma membrane appeared to be one step that was saturable. PMID:8867788

Uthayakumar, S; Granger, B L

1995-01-01

411

Polymer-zeolite nanocomposite membranes for proton exchange membrane fuel cells  

NASA Astrophysics Data System (ADS)

Proton exchange membrane fuel cells (PEMFCs) have recently received a great deal of attention for their potential as compact, high efficiency power sources for portable, distributed generation, and transportation applications. Unfortunately, current proton exchange membrane (PEM) technology hinders fuel cell performance by limiting fuel cell operation temperature and methanol feed concentration in direct methanol fuel cells (DMFCs). Nafion-zeolite nanocomposite membranes that take advantage of the hydrophilicity, selectivity, and proton conductivity of zeolite nanocrystals have been developed to address these problems. All known zeolite topologies were evaluated as potential additives to Nafion proton exchange membranes. Zeolites Y and beta were determined to have great potential as additives due to their low framework density, three dimensional pore structure, and high hydrophilicity. Zeolite Y nanocrystal syntheses were optimized to enhance yield and produce smaller crystal size. Significant improvement of the acid stability of the zeolite Y nanocrystals was not achieved with both ammonium hexafluorosilicate treatments and direct high silica nanocrystal synthesis. However, control of zeolite Y nanocrystal framework Si/Al ratio was demonstrated in the range of SiO2/Al2O3 = 4.38 to 5.84 by manipulating the tetramethylammonium structure directing agent hydroxide content. Zeolite beta nanocrystals were investigated due to their inherent high silica content and high acid stability. Zeolite beta nanocrystals were hydrothermally synthesized with and without phenethyl (called PE-BEA and BEA respectively) organic functional groups. Sulfonic acid functionalized zeolite beta (SAPE-BEA) was generated by treating the PE-BEA nanocrystals with a concentrated sulfuric acid post synthesis treatment. SAPE-BEA samples demonstrated proton conductivities up to 0.01 S/cm at room temperature under water-saturated conditions using a newly developed characterization technique. With optimization, acid functionalized zeolite materials could possibly perform as competent stand-alone proton conducting materials with the proper engineering. BEA and SAPE-BEA zeolite nanocrystals mixed with suspensions of Nafion were cast into nanocomposite membranes. DMFC membrane electrode assemblies (MEAs) prepared with a 2.5wt% SAPE-BEA nanocomposite membrane delivered twice the peak power of a MEA with a commercial Nafion 117 membrane. Membrane performance improvements of this magnitude could ultimately lead to DMFC cost and size reductions that make the technology commercially viable for a variety of applications.

Holmberg, Brett Anderson

412

Bending undulations and elasticity of the erythrocyte membrane: effects of cell shape and membrane organization  

Microsoft Academic Search

The undulatory excitations (flickering) of human and camel erythrocytes were evaluated by employing the previously used flicker spectroscopy and by local measurements of the autocorrelation function K (t) of the cell thickness fluctuations using a dynamic image processing technique. By fitting theoretical and experimental flicker spectra relative values of the bending elastic modulus Kc of the membrane and of the

K. Zeman; H. Engelhard; E. Sackmann

1990-01-01

413

Thermal Destruction on the Nanoscale: Cell Membrane Hyperthermia with Functionalized Magnetic Nanoparticles  

Microsoft Academic Search

A new mode of hyperthermia, namely hyperthermia with magnetic nanoparticles (MNPs) at the cell membrane, is proposed and analyzed. Clusters of MNPs being positioned on the cell membrane and subjected to an alternative magnetic field are able to significantly elevate the temperature of the cell membrane and to compromise the cellular integrity. A simple model of membrane heating with MNP

Oleg Lunov; Vitalii Zablotskii; José Martín Pastor; José Ignacio Pérez-Landazábal; Cristina Gómez-Polo; Tatiana Syrovets; Thomas Simmet

2010-01-01

414

Chapter Three On the Prospects for Phosphonated Polymers as Proton-Exchange Fuel Cell Membranes  

Microsoft Academic Search

One of the major challenges in advancing polymer electrolyte membrane fuel cell technology lies currently in the development of new durable polymeric membranes that will allow fuel cell operation at high temperatures without extensive humidification requirements. Access to these membranes promises important benefits concerning the complexity, cost and performance of the fuel cell system. In this context, membranes functionalized with

Benoît Lafitte; Patric Jannasch

2007-01-01

415

Membrane perturbing activity of beta-adrenoceptor blocking drugs in isolated rat mast cells  

Microsoft Academic Search

Beta-adrenoceptor blocking (BAB) drugs perturb the membranes of isolated rat mast cells. Membrane fluidisation was temperature dependent and was determined by the liposolubility of the BAB drugs. The secretory index, evaluated as the ratio between histamine liberation and degranulation, correlated with the membrane order parameter of the mast cell membranes. The rank order of potency for mast cell activation and

B. Nosál; K. Drábiková; J. Pe?ivová; K. Ondriaš

1989-01-01

416

Shedding of membrane vesicles by tumor and endothelial cells.  

PubMed

Shedding of membrane vesicles is a vital phenomenon frequently observed in tumor cells and suggested to be involved in several aspects of tumor progression. Our previous studies have shown that human breast tumor cells rapidly shed membrane vesicles containing matrix metalloproteinases (MMPs). In this study we present that human umbilical vein endothelial cells (HUVEC) as well as different tumor cell lines (human ovarian cancer, CABA I and A2780, and hepatocarcinoma cell line, SK-Hep 1) shed vesicles in the extracellular medium. These vesicles carry MMPs and their inhibitors TIMPs. We conclude that tumor and endothelial cells shed MMP-containing vesicles and this may represent a mechanism for regulating focalized proteolytic activity and a way to interact with microenvironment during tumor angiogenesis. PMID:16101030

Dolo, V; D'Ascenzo, S; Giusti, I; Millimaggi, D; Taraboletti, G; Pavan, A

2005-01-01

417