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Sample records for brush border membranes

  1. The Intestinal Brush Border Membrane in Diabetes

    PubMed Central

    Olsen, Ward A.; Korsmo, Helen

    1977-01-01

    Diabetes stimulates the functional activity of the intestinal brush border membrane with enhancement of both hydrolytic enzyme activity and membrane transport systems. To determine the mechanism of this effect, we studied the effects of streptozotocin diabetes on the metabolism of one membrane protein, sucrase-isomaltase, which increases its activity in diabetes. The protein was purified and an antiserum prepared. Sucrase-isomaltase from control and diabetic rats was immunologically identical as shown by Ouchterlony double-diffusion analysis of papain-solubilized mucosal proteins. The increase in sucrase enzyme activity in diabetic animals (31.0±1.4 U SEM 5 days after streptozotocin vs. 13.1±1.0 in controls) was the consequence of increased enzyme protein and not an alteration in catalytic efficiency as demonstrated by quantitative immunoprecipitin reactions. To account for increased sucrase-isomaltase protein in diabetes we studied papain-solubilized mucosal proteins labeled by injection of [14C]carbonate and [14C]leucine and analyzed incorporation into sucrase-isomaltase protein (anti-serum precipitable) and total protein (trichloroacetic acid precipitable). We found that diabetes did not affect the decay of labeled total protein, but prolonged the decay of labeled sucrase-isomaltase. t½ of sucrase-isomaltase was 4.4 h in control animals after [14C]carbonate injection and 8.8 and 10.2 h, respectively, 2 and 5 days after induction of streptozotocin diabetes. We obtained similar results in experiments with [14C]leucine with diabetes increasing t½ from 6 to 13.6 h. Diabetes did not appear to increase the rate of addition of sucrase-isomaltase to the brush border membrane, since it did not affect the 10- and 60-min incorporations of isotope into sucrase-isomaltase protein relative to incorporation into total protein and did not alter rate constants for synthesis calculated from the t½ and the change in enzyme mass over time. Thus, enhanced sucrase activity in

  2. Protein Mediators of Sterol Transport Across Intestinal Brush Border Membrane

    PubMed Central

    Brown, J. Mark; Yu, Liqing

    2012-01-01

    Dysregulation of cholesterol balance contributes significantly to atherosclerotic cardiovascular disease (ASCVD), the leading cause of death in the United States. The intestine has the unique capability to act as a gatekeeper for entry of cholesterol into the body, and inhibition of intestinal cholesterol absorption is now widely regarded as an attractive non-statin therapeutic strategy for ASCVD prevention. In this chapter we discuss the current state of knowledge regarding sterol transport across the intestinal brush border membrane. The purpose of this work is to summarize substantial progress made in the last decade in regards to protein-mediated sterol trafficking, and to discuss this in the context of human disease. PMID:20213550

  3. Electrogenicity of phosphate transport by renal brush-border membranes.

    PubMed Central

    Béliveau, R; Ibnoul-Khatib, H

    1988-01-01

    Phosphate uptake by rat renal brush-border membrane vesicles was studied under experimental conditions where transmembrane electrical potential (delta psi) could be manipulated. Experiments were performed under initial rate conditions to avoid complications associated with the dissipation of ion gradients. First, phosphate uptake was shown to be strongly affected by the nature of Na+ co-anions, the highest rates of uptake being observed with 100 mM-NaSCN (1.010 +/- 0.086 pmol/5 s per micrograms of protein) and the lowest with 50 mM-Na2SO4 (0.331 +/- 0.046 pmol/5 s per micrograms of protein). Anion substitution studies showed that potency of the effect of the co-anions was in the order thiocyanate greater than nitrate greater than chloride greater than isethionate greater than gluconate greater than sulphate, which correlates with the known permeability of the membrane to these anions and thus to the generation of transmembrane electrical potentials of decreasing magnitude (inside negative). The stimulation by ion-diffusion-induced potential was observed from pH 6.5 to 8.5, indicating that the transport of both monovalent and divalent phosphate was affected. In addition, inside-negative membrane potentials were generated by valinomycin-induced diffusion of K+ from K+-loaded vesicles and showed a 57% stimulation of phosphate uptake, at pH 7.5. Similar experiments with H+-loaded vesicles, in the presence of carbonyl cyanide m-chlorophenylhydrazone gave a 50% stimulation compared with controls. Inside-positive membrane potentials were also induced by reversal of the K+ gradient (outside greater than inside) in the presence of valinomycin and gave 58% inhibition of phosphate uptake. The membrane-potential dependency of phosphate uptake was finally analysed under thermodynamic equilibrium, and a stimulation by inside-negative potential was observed. The transport of phosphate was thus driven against a concentration gradient by a membrane potential, implicating the net

  4. Library of monoclonal antibodies against brush border membrane epithelial antigens

    SciTech Connect

    Behar, M.; Katz, A.; Silverman, M.

    1986-03-01

    A purified fraction of proximal tubule brush border membranes (BBM) was prepared from dog kidney and used to immunize mice. The standard technique of hybridoma production was followed as described by Kohler and Milstein. Production of antibodies was detected by indirect immunofluorescence on dog kidney slices and by immunodot against the purified fraction on nitrocellulose. Five hybrids exhibited anti BBM activity. These were cloned twice and yielded stable cell lines producing IgG type monoclonal antibodies against BBM. They were designated A/sub 1/, C/sub 7/, D/sub 3/, D/sub 7/ and H/sub 4/. As a family these five monoclonals have broad tissue specificity, i.e. positive staining of the surface mucosa of intestinal kidney proximal tubules. D/sub 3/ exhibits even broader specificity for epithelium reacting with bile canaliculi and choroid plexus. The authors have verified that at least 4/5 antibodies are directed against BBM protein as revealed by immunoprecipitation of solubilized BBM and detected by Coomassie blue staining or autoradiography of lactoperoxidase labelled BBM. Most interestingly all antibodies bind to the surface of LL CPK/sub 1/ cells, a continuous pig kidney cell line of undefined origin but exhibiting many characteristics of proximal tubule cells. The library of monoclonal antibodies obtained provide important probes with which to study membrane biogenesis and polarization in epithelial cells.

  5. Amiloride transport in rabbit renal brush-border membrane vesicles

    SciTech Connect

    Wright, S.H.; Wunz, T.M.

    1989-03-01

    Rabbit renal brush-border membrane vesicles (BBMV) were used to study amiloride transport across the luminal membrane of proximal tubular cells. An outwardly directed H+ gradient (pHi 6.0; pHo 7.5) stimulated 8 microM (/sup 14/C)-amiloride uptake into BBMV and supported a transient active accumulation of substrate consistent with the presence of an amiloride-H+ exchange process. Uptake was inhibited, in the presence or absence of a pH gradient, by 1 mM unlabeled amiloride or 20 mM tetraethylammonium (TEA). Amiloride transport was not directly affected by the presence of 100 mM Na+ in the extravesicular medium, suggesting that Na-H exchange did not mediate amiloride flux. Amiloride transport was a saturable process with a maximal flux (under pH gradient conditions) of 3 nmol.mg-1.min-1 and an apparent Kt of 8 microM. TEA acted as a competitive inhibitor of this process with an apparent Ki of approximately 80 microM, similar to the Kt of TEA transport via the TEA-H+ exchanger. Likewise, amiloride acted as a competitive inhibitor of TEA uptake with an apparent Ki of approximately 11 microM. Preloading BBMV with 1-2 mM TEA stimulated the rate of amiloride uptake and supported a transient active accumulation of amiloride. We conclude that amiloride and TEA are transported by a common pathway in BBMV, which involves a carrier-mediated exchange with H+ and which may play a role in the tubular secretion of these compounds.

  6. Riboflavin transport by rabbit renal brush border membrane vesicles.

    PubMed

    Yanagawa, N; Jo, O D; Said, H M

    1997-12-04

    The present study examined riboflavin (RF) uptake by isolated rabbit renal brush border membrane (BBM). RF uptake was linear for up to 30 s and leveled off thereafter reaching an equilibrium with longer incubation. Studies on RF uptake as a function of incubation medium osmolarity indicated that the uptake was the results of transport (61.4%) into the intravesicular space as well as binding (38.6%) to membrane surfaces. The process of RF uptake was saturable as a function of substrate concentration with an apparent Km of 25.7 +/- 7.6 microM and Vmax of 75.6 +/- 14.7 pmol/mg protein/10 s. cis-Addition of unlabeled RF and its structural analogues, lumiflavin and lumichrome, inhibited the uptake of [3H]RF significantly, indicating the involvement of a carrier-mediated process in RF uptake by renal BBM. RF uptake by renal BBM was partly Na+-dependent so that when Na+ was replaced by potassium, choline, lithium or tetramethylammonium, the RF uptake was reduced to ca. 60% of the control. This Na+-dependency was unlikely to be due to Na+-cotransport mechanism because RF uptake occurred without the characteristic 'overshoot' phenomenon as for other Na+-cotransport systems and the elimination of transmembrane Na+-gradient by preloading Na+ to the intravesicular space did not affect RF uptake. In contrast, removal of Na+ eliminated the binding component of RF uptake, suggesting the requirement of Na+ for RF binding to BBM. The RF uptake was not affected when extravesicular pH was varied within the physiological pH range of 6.5 to 8.5. No effect on BBM [3H]RF uptake was found when the transmembrane electrical potential was altered by either the presence of anions with different membrane permeability (Cl- = NO3- > SO4- > gluconate-) or by using nigericin (10 microg/mg protein) with an outwardly or inwardly directed transmembrane K+ gradient. The uptake of RF by BBM vesicles was, however, inhibited by probenecid and organic anion transport inhibitors, 4,4-diiso

  7. Binding of Escherichia coli heat-stable enterotoxin to rat intestinal cells and brush border membranes.

    PubMed Central

    Frantz, J C; Jaso-Friedman, L; Robertson, D C

    1984-01-01

    The association of heat-stable enterotoxin (STa) produced by enterotoxigenic Escherichia coli 431 with isolated rat intestinal epithelial cells and brush border membranes was characterized. Specific binding of strain 431 125I-STa to a single class of specific high-affinity receptors was saturable and temperature dependent and reached a maximum between 5 and 10 min. A 1,000-fold excess of unlabeled 431 STa competitively displaced 90 to 95% of radiolabeled enterotoxin bound to brush border membranes. In contrast, specific binding of 431 125I-STa to intestinal cells ranged from 40 to 65%. The number of STa-specific receptors on rat intestinal cells determined by Scatchard analysis was 47,520 +/- 14,352 (mean +/- standard error of the mean) per cell, with affinity constants (KaS) of 2.55 X 10(11)and 4.32 x 10(11) liters/mol determined for intestinal cells and brush border membranes, respectively. Villus intestinal cells appeared to possess about twice as many STa receptors as did crypt cells. Dissociation of specifically bound 431 125I-STa from intestinal cells and brush border membranes was minimal (2 to 5%). In addition, neither the rate nor the extent of dissociation was increased by a 1,000-fold excess of unlabeled homologous 431 Sta. Binding experiments with 431 125I-STa and brush border membranes showed that purified unlabeled STas from enterotoxigenic E. coli strains 667 (class 1 porcine enteropathogen), B-41 (bovine enteropathogen), and human strains 213C2 (Mexico) and 153961-2 (Dacca, Bangledesh) exhibited patterns of competitive inhibition similar to those of homologous unlabeled 431 STa (class 2 enteropathogen). A lipid extract which contained gangliosides and glycolipids exhibited dose-dependent competitive inhibition of heat-labile enterotoxin binding to brush border membranes but did not inhibit binding of 431 125I-STa. Purified heat-labile enterotoxin from strain 286C2 did not inhibit binding of 431 STa to brush border membranes. Pronase treatment of

  8. Calcium uptake by intestinal brush border membrane vesicles. Comparison with in vivo calcium transport.

    PubMed Central

    Schedl, H P; Wilson, H D

    1985-01-01

    In prior studies, we examined kinetics of steady state in vivo transepithelial calcium transport in rat and hamster. The present studies related calcium uptake by the brush border to in vivo transport. We measured calcium uptake by brush border membrane vesicles from the two species. In the rat, our prior in vivo studies had shown that (a) calcium transport was mediated, (b) no nonmediated component was detectable, and (c) Vmax was 2.5 times greater in proximal than distal small intestine. In brush border membrane vesicles from the rat, Vmax for the saturable component of calcium uptake was again 2.5 times greater in proximal than distal intestine. Contrasting with in vivo studies, a major nonsaturable component was present in vesicles from proximal and distal small intestine. In the hamster, our previous in vivo studies had shown (1) both mediated and nonmediated components of calcium transport, (2) greater nonmediated transport in proximal than distal small intestines, and (3) Vmax for calcium transport twice as great in distal as in proximal small intestine. In the present study with brush border membrane vesicles from hamster, Vmax for saturable calcium transport was again twice as great in distal as in proximal small intestine. However, nonsaturable calcium transport rates relative to saturable rates were much greater with vesicles than in in vivo studies, and were greater in vesicles from distal than proximal small intestine. Since rates of saturable calcium uptake by brush border membrane vesicles parallel corresponding in vivo mediated transport rates, we conclude that the segmental rates of calcium transport in rat and hamster could be determined by brush border function. PMID:2997294

  9. Reconstitution of the renal brush-border membrane sodium/phosphate co-transporter.

    PubMed Central

    Vachon, V; Delisle, M C; Laprade, R; Béliveau, R

    1991-01-01

    A simple and rapid procedure was developed for the reconstitution of Na(+)-dependent phosphate-transport activity from bovine kidney brush-border membranes. The phosphate transporter appears to be particularly sensitive to extraction conditions. To prevent its inactivation, the phosphate carrier was solubilized in a buffer containing its substrates, Na+ and phosphate, CHAPS, dithiothreitol, brush-border membrane lipids and glycerol. The uptake of phosphate by reconstituted vesicles was strongly stimulated by the presence of a transmembrane Na+ gradient. This stimulation was abolished when the Na+ gradient was dissipated by monensin. The affinity of the carrier for phosphate was similar in proteoliposomes and in brush-border membrane vesicles (apparent Kt = 40 microM). The transporter was also stimulated by the presence of a high concentration of phosphate on the trans side of the membrane. The reconstituted transport activity was inhibited by arsenate, a known inhibitor of phosphate transport. However, the bovine phosphate carrier, intact or reconstituted, was much less sensitive to inhibition by phosphonoformic and phosphonoacetic acids than were those of other species studied so far. SDS/PAGE revealed that only a small number of brush-border membrane proteins were incorporated into the proteoliposomes. This reconstitution procedure should be useful for the purification and identification of the carrier protein. Images Fig. 5. PMID:1832858

  10. Intestinal brush border membrane Na+/glucose cotransporter functions in situ as a homotetramer

    SciTech Connect

    Stevens, B.R.; Fernandez, A.; Hirayama, B.; Wright, E.M.; Kempner, E.S. )

    1990-02-01

    The functional unit molecular size of the intestinal brush border membrane-bound Na+/glucose cotransporter was determined by radiation inactivation. Purified brush border membrane vesicles preserved in cryoprotectant buffer were irradiated (-135 degrees C) with high-energy electrons from a 13-MeV (1 eV = 1.602 x 10(-19) J) linear accelerator at doses from 0 to 70 Mrad (1 rad = 0.01 Gy). After each dose, the cotransporter was investigated with respect to (i) Na(+)-dependent transport activity and (ii) immunologic blot analysis with antibodies against the cloned rabbit intestinal cotransporter. Increasing radiation decreased the maximal Na(+)-dependent cotransporter activity Jmax without affecting apparent Km. The size of the transporting functional unit was 290 +/- 5 kDa. Immunologic blot analysis of brush border membranes gave a single band of Mr 70,000, which decreased in intensity with increased radiation dose and gave a target size of 66 +/- 11 kDa. We conclude that activity of the intestinal Na+/glucose cotransporter in situ in the brush border membrane requires the simultaneous presence of four intact, independent, identical subunits arranged as a homotetramer.

  11. Calcium uptake by brush-border and basolateral membrane vesicles in chick duodenum

    SciTech Connect

    Takito, J.; Shinki, T.; Sasaki, T.; Suda, T. )

    1990-01-01

    Calcium uptake was compared between duodenal brush-border membrane vesicles (BBMV) and basolateral membrane vesicles (BLMV) isolated from vitamin D-deficient chicks and those injected with 625 ng of 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3). The uptake by BBMV in the 1 alpha,25-(OH)2D3-treated birds attained a maximum (280% of the control) at 12 h and was maintained at an elevated level (210%) at 24 h after the injection of the vitamin. In contrast, ATP-dependent calcium uptake by BLMV reached a maximum (185% of the control) at 6 h and decreased to the control level at 24 h. The kinetic analysis revealed that 1 alpha,25(OH)2D3 increased Vmax values without any changes in apparent Km values in both BBMV and BLMV. The activity of ATP-dependent calcium uptake was localized exclusively in the basolateral membrane, and the activity was inhibited by vanadate (IC50, 1 microM), but not by oligomycin, theophylline, calmodulin, trifluoperazine, or calbindin D28K. These results indicate that calcium transport through both the brush-border and basolateral membranes is involved in the 1 alpha,25(OH)2D3-dependent intestinal calcium absorption. The initiation of calcium absorption by 1 alpha,25(OH)2D3 appears to be due to an increase in the rate of calcium efflux at the basolateral membrane rather than the rate at the brush-border membrane.

  12. Cimetidine transport in isolated brush border membrane vesicles from bovine choroid plexus

    SciTech Connect

    Whittico, M.T.; Gang, Y.A.; Giacomini, K.M. )

    1990-11-01

    The purpose of this study was to elucidate the mechanisms involved in the transport of cimetidine across the brush border membrane of choroid plexus epithelium. Brush border membrane vesicles were prepared from bovine choroid plexus and the uptake of (3H)cimetidine was studied using the methods of rapid vacuum filtration and scintillation counting. Cimetidine accumulated in the vesicles with time reaching equilibrium within 2 hr. The amount of cimetidine taken up by the vesicles at equilibrium decreased with increasing extravesicular media osmolarity suggesting that cimetidine accumulates in an osmotically reactive intravesicular space. Binding of cimetidine to the membrane was estimated to be less than 18%. Michaelis-Menten studies demonstrated that cimetidine transport involved both a saturable and a nonsaturable component. The Vmax and Km (mean +/- S.E.) were 16.7 +/- 5.9 pmol/sec/mg protein and 58.1 +/- 3.1 microM, respectively, suggesting that cimetidine is transported across the choroid plexus brush border membrane with a lower affinity and a higher capacity than across the renal brush border membrane. The organic cation, quinidine (0.1 mM), and the amino acid, histidine (20 mM), both significantly reduced the initial, but not the equilibrium, uptake of cimetidine. However, high concentrations (5 mM) of more polar organic cations including tetraethylammonium, as well as of several organic anions including salicylate did not inhibit cimetidine transport. Studies with unlabeled cimetidine revealed a countertransport phenomenon. Attempts to drive the concentrative uptake of cimetidine with various ion gradients were unsuccessful. Of note was the fact that an outwardly directed proton gradient could significantly accelerate the uptake of cimetidine.

  13. Identification of Na+,Pi-binding protein in kidney and intestinal brush-border membranes.

    PubMed Central

    Debiec, H; Lorenc, R

    1988-01-01

    An Na+, Pi-binding protein has been extracted from kidney and intestinal brush-border membranes with an organic solvent and has been purified by Kieselghur and Sephadex LH-60 chromatography. The molecular mass of this protein has been estimated to be about 155 kDa as determined by gel-filtration chromatography on Sepharose 2B. Under denaturing conditions, polyacrylamide-gel electrophoresis revealed a monomer of molecular mass about 70 kDa. The protein has high specificity and high affinity for Pi [K0.5 (concentration at which half-maximal binding is observed) near 10 microM]. Na2+ binding also exhibits saturation behaviour, with a K0.5 near 7.5 mM. Pi binding is inhibited by known inhibitors of Pi transport in brush-border membrane vesicles. It appears that this protein could be involved in Na+/Pi co-transport across the renal and intestinal brush-border membranes. Images Fig. 6. Fig. 7. PMID:3196312

  14. Specific binding of lactoferrin to brush-border membrane: Ontogeny and effect of glycan chain

    SciTech Connect

    Davidson, L.A.; Loennerdal, B. )

    1988-04-01

    Bioavailability of iron from human milk is exceptionally high. It has been suggested that lactoferrin, the major iron-binding protein in human milk, may participate in this high iron bioavailability from milk. The authors examined the interaction of lactoferrin with the intestinal brush-border membrane using the rhesus monkeys as a model. Brush-border membrane vesicles were prepared from monkeys of various ages. Binding studies with {sup 59}Fe-labeled human and monkey lactoferrin were performed to examine interaction of lactoferrin with the brush-border membrane. Specific saturable binding of lactoferrin was found at all ages studied. The dissociation constant for lactoferrin-receptor binding was 9 {times} 10{sup {minus}6} M. In contrast, no binding of serum transferrin or bovine lactoferrin occurred. Removal of fucose from the lactoferrin glycans resulted in a significant decrease in binding. It was concluded that lactoferrin in milk may function in the process of iron absorption through interaction with a small intestinal receptor and that fucosylated glycans on the carbohydrate chain of lactoferrin are necessary for receptor recognition.

  15. Dietary fat effects on brush border membrane composition and enzyme activities in rat intestine.

    PubMed

    Kaur, M; Kaur, J; Ojha, S; Mahmood, A

    1996-01-01

    The effect of dietary fats on the chemical composition and enzyme activities has been studied in intestinal brush border membranes (BBM) or rats. Animals were given commercial rat pellet diet (RP) or semisynthetic diet rich in either saturated [coconut oil (CCO))] or polyunsaturated [n-6, corn oil (CO) or n-3, fish oil (FO)] fat at the 10% level for 5 weeks. The membrane cholesterol/phospholipid ratio was augmented in CO- or RP-fed rats. There was an increase in level of saturated fatty acids in BBM from CCO- or FO-fed animals. n-3 polyunsaturated fatty acid content was raised in FO-fed rats, while the proportion of linoleic acid and arachidonic acid was enhanced in animals given a CO diet. Membrane fluidity was in the order of CCO < RP = CO < FO. The membrane hexose content was high (p < 0.05) in the CCO group. Hexosamines were elevated (p < 0.05) in CCO- or FO-fed rat brush borders. Membrane fucose was unaltered, while sialic acid content was elevated in CO- (p < 0.05) and FO- (p < 0.01) fed vs. CCO-fed rats. Lectin binding to brush borders corroborated these findings. The activities of alkaline phosphatase, sucrase and lactase were augmented (p < 0.001) in CCO-fed animals. Leucine-aminopeptidase and sucrase activities were depressed by FO feeding. The activities of PNP-beta-glycosidases were the highest in FO-fed rats. These results indicate that dietary fat quality markedly affects microvillus membrane lipid composition, glycosylation and enzyme functions in rat intestine.

  16. Evidence for tripeptide/H+ co-transport in rabbit renal brush-border membrane vesicles.

    PubMed Central

    Tiruppathi, C; Kulanthaivel, P; Ganapathy, V; Leibach, F H

    1990-01-01

    L-Phe-L-Pro-L-Ala is a tripeptide which is hydrolysable almost exclusively by dipeptidyl peptidase IV in rabbit renal brush-border membrane vesicles. In order to delineate the mechanism of the transport of an intact tripeptide across the brush-border membrane, we studied the characteristics of the uptake of [3H]Phe-Pro-Ala in membrane vesicles in which the activity of dipeptidylpeptidase IV was completely inhibited by treatment with di-isopropyl fluorophosphate. In these vesicles, uptake of radiolabel from the tripeptide was found to be Na(+)-independent, but was greatly stimulated by an inwardly directed H+ gradient. The H(+)-gradient-dependent radiolabel uptake appeared to be an active process, because the time course of uptake exhibited an overshoot phenomenon. The process was also electrogenic, being stimulated by an inside-negative membrane potential. Under the uptake-measurement conditions there was no detectable hydrolysis of [3H]Phe-Pro-Ala in the incubation medium when di-isopropyl fluorophosphate-treated membrane vesicles were used. Analysis of intravesicular contents revealed that the radiolabel inside the vesicles was predominantly (greater than 90%) in the form of intact tripeptide. These data indicate that the uptake of radiolabel from [3H]Phe-Pro-Ala in the presence of an inwardly directed H+ gradient represents almost exclusively uptake of intact tripeptide. Uphill transport of the tripeptide was also demonstrable in the presence of an inwardly directed Na+ or K+ gradient, but only if nigericin was added to the medium. Under these conditions, nigericin, an ionophore for Na+, K+ and H+, was expected to generate a transmembrane H+ gradient. Uptake of Phe-Pro-Ala in the presence of a H+ gradient was inhibited by di- and tri-peptides, but not by free amino acids. It is concluded that tripeptide/H+ co-transport is the mechanism of Phe-Pro-Ala uptake in rabbit renal brush-border membrane vesicles. PMID:2160811

  17. Evidence for tripeptide/H+ co-transport in rabbit renal brush-border membrane vesicles.

    PubMed

    Tiruppathi, C; Kulanthaivel, P; Ganapathy, V; Leibach, F H

    1990-05-15

    L-Phe-L-Pro-L-Ala is a tripeptide which is hydrolysable almost exclusively by dipeptidyl peptidase IV in rabbit renal brush-border membrane vesicles. In order to delineate the mechanism of the transport of an intact tripeptide across the brush-border membrane, we studied the characteristics of the uptake of [3H]Phe-Pro-Ala in membrane vesicles in which the activity of dipeptidylpeptidase IV was completely inhibited by treatment with di-isopropyl fluorophosphate. In these vesicles, uptake of radiolabel from the tripeptide was found to be Na(+)-independent, but was greatly stimulated by an inwardly directed H+ gradient. The H(+)-gradient-dependent radiolabel uptake appeared to be an active process, because the time course of uptake exhibited an overshoot phenomenon. The process was also electrogenic, being stimulated by an inside-negative membrane potential. Under the uptake-measurement conditions there was no detectable hydrolysis of [3H]Phe-Pro-Ala in the incubation medium when di-isopropyl fluorophosphate-treated membrane vesicles were used. Analysis of intravesicular contents revealed that the radiolabel inside the vesicles was predominantly (greater than 90%) in the form of intact tripeptide. These data indicate that the uptake of radiolabel from [3H]Phe-Pro-Ala in the presence of an inwardly directed H+ gradient represents almost exclusively uptake of intact tripeptide. Uphill transport of the tripeptide was also demonstrable in the presence of an inwardly directed Na+ or K+ gradient, but only if nigericin was added to the medium. Under these conditions, nigericin, an ionophore for Na+, K+ and H+, was expected to generate a transmembrane H+ gradient. Uptake of Phe-Pro-Ala in the presence of a H+ gradient was inhibited by di- and tri-peptides, but not by free amino acids. It is concluded that tripeptide/H+ co-transport is the mechanism of Phe-Pro-Ala uptake in rabbit renal brush-border membrane vesicles.

  18. Proteomic evaluation of chicken brush-border membrane during the early posthatch period.

    PubMed

    Gilbert, Elizabeth R; Williams, Patricia M; Ray, William K; Li, Huifeng; Emmerson, Derek A; Wong, Eric A; Webb, Kenneth E

    2010-09-03

    The chicken small intestine undergoes structural and functional changes during the early posthatch period to accommodate the transition from a lipid-rich diet inside the egg to a carbohydrate- and protein-based diet. Many of the enterocyte brush-border membrane-associated proteins responsible for mediating changes in nutrient utilization are unknown. The objective of this study was to conduct a proteomic analysis of chicken small intestine during the early posthatch period. We isolated brush-border membrane at day of hatch and days 1, 3, 7, and 14 posthatch from the small intestine of 2 genetic lines of broilers that differ in growth performance, and performed 2D gel-electrophoresis. A total of 1693 spots were analyzed by matrix-assisted laser desorption/ionization-tandem time-of-flight mass spectrometry (MALDI-TOF/TOF). In total, 132 different proteins were identified and grouped according to biological function. Of these, there were 10 nutrient transporters, 9 digestive enzymes, and 17 proteins associated with cytoskeletal structure and microvilli organization. The remaining proteins were classified as basolateral membrane (3), endosomal/membrane trafficking (8), signaling (14), metabolic (33), degradative (5), stress-related (5), protein synthesis machinery/mitochondria/nucleus (19), immunologic (1), or unknown (8). Of the spots in which proteins were identified, there were 10 that showed an effect of broiler genetic line on protein spot density (P<0.001) and 19 spots showing a correlation of broiler genetic line x age (P<0.001). Identification of brush-border membrane-associated proteins is an important step in furthering our understanding of digestion and absorption in the chicken.

  19. Classical and channel-like urate transporters in rabbit renal brush border membranes.

    PubMed

    Knorr, B A; Beck, J C; Abramson, R G

    1994-03-01

    The precise mechanism by which urate is transported across rabbit renal proximal tubule luminal membranes has not been defined. To determine whether urate flux across this membrane represents simple diffusion or transport on specific carriers, urate uptake was examined in brush border membrane vesicles that were prepared by a Mg+(+)-aggregation technique and then exposed to CuCl2. Na(+)-independent, voltage sensitive urate transport was demonstrated in these Cu+(+)-exposed vesicles. Transport was trans-stimulated by urate and cis inhibited by pyrazinoic acid and oxonate. A small fraction of transported urate and urate in the extravesicular fluid was oxidized to allantoin. Kinetic analysis revealed the presence of two kinetically distinct transporters; a channel-like carrier that was inhibited by pyrazinoic acid and oxonate, and a high-affinity, classical, saturable carrier that was inhibited by higher concentrations of oxonate. These studies provide the first direct evidence for carrier-mediated urate transport in rabbit renal brush-border membranes and demonstrate that the rabbit transporter(s) share a number of properties with the urate uniporter in rat proximal tubule cell membranes.

  20. Facilitated diffusion of urate in avian brush-border membrane vesicles.

    PubMed

    Grassl, Steven M

    2002-10-01

    Membrane transport pathways mediating transcellular secretion of urate across the proximal tubule were investigated in brush-border membrane vesicles (BBMV) isolated from avian kidney. An inside-positive K diffusion potential induced a conductive uptake of urate to levels exceeding equilibrium. Protonophore-induced dissipation of membrane potential significantly reduced voltage-driven urate uptake. Conductive uptake of urate was inhibitor sensitive, substrate specific, and a saturable function of urate concentration. Urate uptake was trans-stimulated by urate and cis-inhibited by p-aminohippurate (PAH). Conductive uptake of PAH was cis-inhibited by urate. Urate uptake was unaffected by an outward alpha-ketoglutarate gradient. In the absence of a membrane potential, urate uptake was similar in the presence and absence of an imposed inside-alkaline pH gradient or an outward Cl gradient. These observations suggest a uniporter-mediated facilitated diffusion of urate as a pathway for passive efflux across the brush border membrane of urate-secreting proximal tubule cells.

  1. Chloride Uptake by Brush Border Membrane Vesicles Isolated from Rabbit Renal Cortex

    PubMed Central

    Warnock, David G.; Yee, Victoria J.

    1981-01-01

    Brush border membrane vesicles were isolated from rabbit renal cortex by Mg++-precipitation and differential centrifugation. 36Cl− and [3H]glucose uptakes were simultaneously determined by a rapid filtration technique. Lysis of the vesicles with distilled water abolished 90-95% of the radioactivity on the filters, suggesting that nearly all of the 36Cl− and [3H]glucose counts represented uptake into an osmotically reactive intravesicular space. Inwardly directed K+ gradients plus valinomycin stimulated 36Cl− uptake, demonstrating a conductive pathway for chloride uptake into brush-border membrane vesicles. 36Cl− uptake could also be stimulated by inwardly directed proton gradients (pHoutside < pHinside). This effect was seen in the absence of sodium, as well as in the presence of valinomycin when the vesicles had equal K+ concentrations inside and out. An “overshoot” phenomenon was observed when external 36Cl− was 2 mM and the external pH was lowered from 7.5 to 6.0 or to 4.5. The effect of the proton gradient was presumed to be different from the conductive mechanism because (a) the stimulation of 36Cl− uptake by inwardly directed K+ diffusion potentials was additive to the proton gradient effect, and (b) competition studies revealed statistically significant effects of thiocyanate on the conductive pathway, but not on the proton-driven pathway. HCl cotransport or anion exchange are electrically neutral mechanisms which could couple 36Cl− uptake to inwardly-directed proton gradients in a brush border membrane vesicle. If both electrically neutral and conductive path ways for chloride transport are present in the luminal membrane of the proximal tubule, then the mechanism as well as the direction of net chloride transport will be influenced by the nature of the accompanying cation transport process. PMID:7451645

  2. Enzymatic and transport characteristics of isolated snake renal brush-border membranes

    SciTech Connect

    Benyajati, S.; Dantzler, W.H. )

    1988-07-01

    Brush-border membranes (BBM) or proximal tubules were isolated from the kidney of the garter snake (Thamnophis sirtalis) by a procedure involving hypotonic lysis, Ca precipitation, and differential centrifugation. The isolated membranes were enriched 15-fold in brush-border enzyme activities (alkaline phosphatase, {gamma}-glutamyl transpeptidase) compared with whole kidney homogenates and were substantially free of other contaminating membranes. The yield of the BBM preparation was 40%. The BBM vesicular transport of several organic solutes was characterized by a rapid filtration technique at 25{degree}C. D-glucose, p-aminohippurate (PAH), and urate entered the same osmotically active space and binding was minimal. An uptake overshoot for 3-O-methyl-D-glucose by reptilian BBM was observed only in the presence of an inwardly directed NaCl gradient and was abolished by 0.1 mM phlorizin. Reptilian BBM exhibited Na-gradient-stimulated uptake of PAH (90 {mu}M) with an overshoot that was inhibited by other organic acids and by 4-acetamido-4{prime}-isothiocyanostilbene-2,2{prime}-disulfonic acid (SITS). In contrast, urate uptake appeared to be Na independent and not appreciably affected by other organic anions or SITS. The presence of specific transport systems for organic solutes in the isolated membrane preparation distinctly characterizes the BBM of reptilian kidney.

  3. Thyroid hormones increase Na -H exchange activity in renal brush border membranes

    SciTech Connect

    Kinsella, J.; Sacktor, B.

    1985-06-01

    Na -H exchange activity, i.e., amiloride-sensitive Na and H flux, in renal proximal tubule brush border (luminal) membrane vesicles was increased in the hyperthyroid rat and decreased in the hypothyroid rat, relative to the euthyroid animal. A positive correlation was found between Na -H exchange activity and serum concentrations of thyroxine (T4) and triiodothyronine (T3). The thyroid status of the animal did not alter amiloride-insensitive Na uptake. The rate of passive pH gradient dissipation was higher in membrane vesicles from hyperthyroid rats compared to the rate in vesicles from hypothyroid animals, a result which would tend to limit the increase in Na uptake in vesicles from hyperthyroid animals. Na -dependent phosphate uptake was increased in membrane vesicles from hyperthyroid rats; Na -dependent D-glucose and L-proline uptakes were not changed by the thyroid status of the animal. The effect of thyroid hormones in increasing the uptake of Na in the brush border membrane vesicle is consistent with the action of the hormones in enhancing renal Na reabsorption.

  4. Lanthanide-stimulated glucose and proline transport across rabbit intestinal brush-border membranes.

    PubMed

    Stevens, B R; Kneer, C

    1988-07-07

    Trivalent cations of the lanthanide series (La3+----Yb3+) stimulated uptake of proline or glucose in rabbit small intestinal brush-border membrane vesicles. The lanthanides stimulated uptake to an extent greater than Al3+, choline, and in many cases, Na+. A time-course of Er3+-stimulated glucose uptake gave initial rates and overshoots greater than Na+ stimulation. The best activators were Sm3+, Eu3+ and Tm3+, which stimulated proline initial uptakes by 400-600%, and stimulated glucose uptake by 120-150%, compared to Na+. The best lanthanide cotransport activators possessed high third ionization potentials.

  5. Characteristics of (+)-catechin and (-)-epicatechin transport across pig intestinal brush border membranes.

    PubMed

    Starp, Christiane; Alteheld, Birgit; Stehle, Peter

    2006-01-01

    (+)-Catechin and (-)-epicatechin are considered as disease preventive flavan-3-ols of foods like fruits, beverages and chocolate. We investigated mechanisms and kinetics of (+)-catechin and (-)-epicatechin uptake employing a validated in vitro model with isolated pig brush border membrane vesicles. Vesicles were isolated from pig small intestine employing the divalent cation method. Characterization (marker enzymes, electron microscopy) confirmed their purity and function. Transport studies with (+)-catechin and (-)-epicatechin under predefined conditions [presence/absence of sodium, pH gradient, temperature (8-37 degrees C), various initial substrate concentrations (2-20 mmol/l)] revealed a measurable transport (HPLC analyses) across the brush border membrane for both substrates. Catechin transport was stimulated by an outwardly directed H(+) gradient (pH(i) 5.5/pH(o) 7.5). The presence of an inwardly directed Na(+) gradient did not result in a transient overshoot in (+)-catechin and (-)-epicatechin uptake. At 37 degrees C, subtraction of diffusion from the total transport rate showed saturation kinetics. Our in vitro study indicate that both (+)-catechin and (-)-epicatechin are transported across the basolateral membrane using a dual transport system consisting of free diffusion (dominant at low concentrations) and carrier-mediated facilitated diffusion.

  6. Chloride ion transport into pig jejunal brush-border membrane vesicles.

    PubMed Central

    Forsyth, G W; Gabriel, S E

    1988-01-01

    1. This study was carried out to determine the types and activities of carrier proteins which transport the chloride ion in pig jejunal brush-border membranes, with an emphasis on studying the properties of chloride conductance activity in vesicles prepared from these membranes. 2. Sodium-chloride co-transport activity was not detected in this tissue. A sodium-proton antiport with typical amiloride sensitivity was present. An anion exchanger linking chloride to hydroxyl or bicarbonate ions was also found in the pig jejunal brush-border membrane vesicles. 3. Chloride conductance activity in this system was specifically dependent on the buffering agents used for vesicle preparation. Conductance activity could not be demonstrated in vesicles prepared in imidazolium acetate or in HEPES-Tris buffers. HEPES-tetramethylammonium buffering of vesicles in the chloride uptake system produced a significant conductance response to a potassium gradient plus valinomycin. 4. Chloride conductance showed saturable kinetics with respect to substrate concentration, with a Michaelis-Menten constant (Km) of approximately 116 mM and a maximum velocity (Vmax) of 132 nmol (mg protein)-1 min-1. 5. Preliminary screening of potential inhibitors of chloride conductance showed only minimal inhibitor effects of SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-sulphonic acid), anthracene-9-carboxylate, N-phenylanthranilate and piretanide. 6. The conductance activity in pig jejunal vesicles appears to have stringent buffer requirements, and to be relatively insensitive to the effects of reported conductance inhibitors. PMID:2466986

  7. Uptake mechanism of trientine by rat intestinal brush-border membrane vesicles.

    PubMed

    Tanabe, R; Kobayashi, M; Sugawara, M; Iseki, K; Miyazaki, K

    1996-05-01

    The uptake characteristics of trientine by rat intestinal brush-border membrane vesicles were studied. The uptake characteristics of trientine were similar to those of the physiological polyamines with respect to the excessive accumulation in vesicles, the pH dependency, the temperature dependency and the ineffectiveness of K+ diffusion potential (inside negative). The initial uptake of trientine was saturable with a K(m) value of 1.13 mM, which was larger than that of spermine and spermidine. Furthermore, the uptake rate of trientine was dose-dependently inhibited by spermine and spermidine. Spermine competitively inhibited the uptake of trientine with a Ki value of 18.6 microM, and it was close to the K(m) value for spermine (30.4 microM). These data suggested that the uptake of trientine was similar to that of spermine and spermidine in rat small intestinal brush-border membrane vesicles, and these polyamines seem to inhibit the absorption of trientine from the gastrointestinal tract.

  8. Aboral changes in D-glucose transport by human intestinal brush-border membrane vesicles.

    PubMed Central

    Bluett, M K; Abumrad, N N; Arab, N; Ghishan, F K

    1986-01-01

    D-Glucose transport was investigated in isolated brush-border membrane vesicles from human small intestine. Characteristics of D-glucose transport from the jejunum were compared with that in the mid and terminal ileum. Jejunal and mid-ileal D-glucose transport was Na+-dependent and electrogenic. The transient overshoot of jejunal D-glucose transport was significantly greater than corresponding values in mid-ileum. The terminal ileum did not exhibit Na+-dependent D-glucose transport, but did exhibit Na+-dependent taurocholate transport. Na+-glucose co-transport activity as measured by tracer-exchange experiments was greatest in the jejunum, and diminished aborally. We conclude that D-glucose transport in man is Na+-dependent and electrogenic in the proximal intestine and directly related to the activity of D-glucose-Na+ transporters present in the brush-border membranes. D-Glucose transport in the terminal ileum resembles colonic transport of D-glucose. PMID:3800877

  9. Characterization of the chloride conductance in porcine renal brush-border membrane vesicles.

    PubMed

    Krick, W; Dölle, A; Hagos, Y; Burckhardt, G

    1998-02-01

    The chloride conductance in brush-border membrane vesicles prepared from pig kidney cortex was investigated using a light-scattering assay, anion-diffusion-potential-dependent Na+-D-glucose cotransport and 36Cl- influx. K+-diffusion-potential-driven salt exit from, or entry into, the vesicles was slow in the presence of gluconate, SO42- and F-, intermediate with Cl- and Br-, and fast with I-, NO3-, and SCN-. Stimulation of Na+-D-glucose uptake followed a similar anion sequence. Conductive Cl- flux had a low activation energy and was inhibited by suphhydryl reagents, the stilbene disulphonates 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonate (SITS) and 4, 4'-diisothiocyanato-2,2'-disulphonate (DIDS), and the arylaminobenzoates diphenylamine-2-carboxylic acid (DPC) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). Intravesicular Ca2+ and extravesicular nucleotides were without effect on conductive Cl- flux. These characteristics tentatively exclude some known Cl- channels and leave members of the ClC family as possible candidates responsible for the Cl- conductance in brush-border membranes.

  10. Characterization of putrescine transport across the intestinal epithelium: study using isolated brush border and basolateral membrane vesicles of the enterocyte.

    PubMed

    Milovic, V; Stein, J; Piiper, A; Gerhard, R; Zeuzem, S; Caspary, W F

    1995-02-01

    Putrescine transport was investigated in isolated brush border and basolateral membrane vesicles prepared from the rabbit enterocyte. Brush border vesicles were oriented right-side-out and basolateral vesicles inside-out, forming a model representing uptake and extrusion across the intestinal epithelium. Putrescine transport across both membranes was initially rapid, and 66% of the equilibrium uptake was achieved within the first minute. According to osmoplots and measurements at 4 degrees C, 20% of total incorporation presented binding to the membrane. In order to estimate actual uptake into the vesicles, Km was calculated from the differences in putrescine incorporation at 37 degrees C and 4 degrees C, and was 12.7 mumol L-1 for brush border uptake and 38.2 mumol L-1 for basolateral extrusion. Putrescine uptake into brush border and basolateral membrane vesicles was not enhanced in the presence of an Na+ gradient. When Na+ was substituted with an uncharged solute, mannitol, putrescine incorporation was increased, indicating that putrescine uptake is not Na(+)-dependent and that cations might interfere with the carrier. Paraquat and methylglyoxalbis(guanylhydrazone), known to share the polyamine transport system, inhibited putrescine incorporation in both membrane vesicle preparations. Basolateral carrier showed significantly higher sensitivity to cations. We conclude that putrescine uptake across the apical membrane and extrusion across the basolateral membrane of the enterocyte are mediated by two different and independent carriers which differ in their electrical properties.

  11. Effect of amino acid intake on brush-border membrane uptake of sulfur amino acids.

    PubMed

    Chesney, R W; Gusowski, N; Padilla, M; Lippincott, S

    1986-07-01

    Alterations in the intake of sulfur amino acids (SAA) changes the rat renal brush-border membrane uptake of the beta-amino acid, taurine. A low-SAA diet enhances and a high-taurine diet reduces uptake (Chesney et al., Kidney Int. 24: 588-594, 1983). Neither the low-SAA diet nor the high-taurine diet alters the time course or concentration-dependent accumulation of the sulfur amino acids methionine and cystine or of inorganic sulfate. By contrast the uptake of beta-alanine, another beta-amino acid that competes with taurine, is greater in animals on the low-SAA diet. The high-taurine diet does not change beta-alanine uptake. The plasma levels of taurine are altered by dietary change, but not the values for methionine and cystine. This study indicates that renal adaptation is expressed for beta-alanine, a nonsulfur-containing beta-amino acid. By contrast, methionine, cystine, and sulfate, which participate in a variety of synthetic and conjugative processes, are not conserved by the renal brush-border surface following ingestion of either a low-methionine and -cystine diet or high-taurine diet.

  12. MPP+ is transported by the TEA(+)-H+ exchanger of renal brush-border membrane vesicles.

    PubMed

    Lazaruk, K D; Wright, S H

    1990-03-01

    Rabbit renal brush-border membrane vesicles (BBMV) were used to study the transport of the cationic neurotoxin, 1-methyl-4-phenylpyridinium (MPP+). An outwardly directed H(+)-gradient stimulated MPP+ uptake and led to the development of an active accumulation of MPP+ within the vesicles. H(+)-gradient driven MPP+ transport was saturable, with a maximal transport rate of 3 nmol.mg-1.min-1 and an apparent Michaelis constant (Kt) of 8 microM. MPP+ and tetraethylammonium (TEA) behaved as competitive inhibitors of one another's transport in renal BBMV, suggesting the presence of a common transport pathway for these organic cations. At an ambient pH of 7.5, preloading BBMV with MPP+ failed to stimulate TEA uptake, although trans TEA did stimulate MPP+ uptake. Increasing ambient pH to 8.5 (i.e., reducing competition between H+ and these organic cations for a common transport pathway) led to a clear reciprocal trans stimulation of TEA and MPP+ fluxes. With an equilibrium-shift protocol, a trans concentration of MPP+ energized uphill transport of TEA. We conclude that MPP+ and TEA share a common organic cation-H+ exchange pathway in the renal brush border, although turnover of an MPP(+)-loaded exchanger is slow compared with that for a TEA or H(+)-loaded exchanger.

  13. Truncated brush border myosin I affects membrane traffic in polarized epithelial cells.

    PubMed

    Durrbach, A; Raposo, G; Tenza, D; Louvard, D; Coudrier, E

    2000-05-01

    We investigate, in this study, the potential involvement of an acto-myosin-driven mechanism in endocytosis of polarized cells. We observed that depolymerization of actin filaments using latrunculin A decreases the rate of transferrin recycling to the basolateral plasma membrane of Caco-2 cells, and increases its delivery to the apical plasma membrane. To analyze whether a myosin was involved in endocytosis, we produced, in this polarized cell line, truncated, non-functional, brush border, myosin I proteins (BBMI) that we have previously demonstrated to have a dominant negative effect on endocytosis of unpolarized cells. These non-functional proteins affect the rate of transferrin recycling and the rate of transepithelial transport of dipeptidyl-peptidase IV from the basolateral plasma membrane to the apical plasma membrane. They modify the distribution of internalized endocytic tracers in apical multivesicular endosomes that are accessible to fluid phase tracers internalized from apical and basolateral plasma membrane domains. Altogether, these observations suggest that an acto-myosin-driven mechanism is involved in the trafficking of basolaterally internalized molecules to the apical plasma membrane.

  14. H+ V-ATPase-Energized Transporters in Brush Border Membrane Vesicles from Whole Larvae of Aedes Aegypti

    USDA-ARS?s Scientific Manuscript database

    Brush Border Membrane vesicles (BBMVs) from Whole larvae of Aedes aegypti (AeBBMVWs ) contain an H+ V-ATPase (V), a Na+/H+ antiporter, NHA1 (A) and a Na+-coupled, nutrient amino acid transporter, NAT8 (N), VAN for short. All V-ATPase subunits are present in the Ae. aegypti genome and in the vesicles...

  15. Tetraethylammonium transport in renal brush border membrane vesicles of the rabbit.

    PubMed

    Rafizadeh, C; Roch-Ramel, F; Schäli, C

    1987-01-01

    The mechanisms involved in the transport of tetraethylammonium (TEA) in the rabbit renal brush border were investigated by using membrane vesicles. Transport of [14C]TEA (0.2 mM) was measured by a rapid filtration method. We have reported previously that an imposed pH gradient (pHi = 6, pHo = 7.4) stimulates the uptake of TEA markedly, yielding a transient overshoot of 200% above the equilibrium value. Here we demonstrate that an overshoot of similar magnitude can also be obtained in the presence of indirectly induced proton gradients, via the naturally occurring Na+/H+ exchanger or via the artificial K+/H+ exchanger nigericin. The TEA exchange mechanism is shown to be electroneutral, temperature-dependent and saturable [Km, 0.328 (CL for P less than .05: 0.250-0.425) mM; Vmax, 2.13 (CL for P less than .05: 1.98-2.32) nmole/mg of protein X 15 sec]. Other organic cations interact with this exchange mechanism: mepiperphenidol and morphine both cis-inhibited and trans-stimulated TEA uptake. Quinine, which was the most potent inhibitor of TEA uptake (57% inhibition at 10(-5) M), did not trans-stimulate. The mechanism appears to be specific for organic cations inasmuch as the organic anion p-aminohippurate did not cis-inhibit or trans-stimulate TEA uptake. These results demonstrate the presence of a H+/TEA exchange mechanism in the rabbit renal brush border membrane showing many similarities with that shown to be present in the rat.

  16. L-canavanine inhibits L-arginine uptake by broiler chicken intestinal brush border membrane vesicles.

    PubMed

    Rueda, E; Michelangeli, C; Gonzalez-Mujica, F

    2003-09-01

    1. Intestinal brush border membrane vesicles (BBMV) were prepared from 3-week-old broiler chickens. 2. Electron microscopy of the BBMV fraction showed single membrane vesicles of different sizes with no electron dense material inside. No other organelles were observed. The sucrase and maltase activities were enriched by factors of 16 and 18, respectively, in the BBMV fraction in comparison with the homogenate. On the other hand, the Na+/K+-ATPase sensitivity to ouabain was increased by a factor of 0.8. 3. The BBMV showed a maximum L-[14C]-arginine uptake (944.9 +/- 22.9 pmoles/mg protein) at 45 s and thereafter it declined slowly. In the presence of 0.5 mM L-canavanine, the L-[14C]-arginine uptake by BBMV was reduced by 43.6% at 45 s. 4. It is concluded that L-canavanine inhibits L-arginine Na+-dependent transport across the enterocyte apical membrane in a highly purified intestinal BBMV from broiler chickens.

  17. Preparation and characterization of reconstructed small intestinal brush border membranes for surface plasmon resonance analysis.

    PubMed

    Cho, Sungpil; Park, Jae Hyung; Yu, Jaehoon; Lee, Yong-Kyu; Byun, Youngro; Chung, Hesson; Kwon, Ick Chan; Jeong, Seo Young

    2004-01-01

    To prepare the surface generated by small intestinal brush border membrane vesicles (BBMVs) for the surface plasmon resonance (SPR) analysis, which allows the real-time measurement of binding events occurring on the intestinal membrane. BBMVs were isolated from Sprague-Dawley rats, suspended in HEPES-buffered saline, and flowed over the surface of a SPR sensor chip composed of dextran derivatives modified with lipophilic residues. The surface coverage was determined from binding of bovine serum albumin to BBMV-immobilized sensor chip. The performance of BBMVs immobilized was evaluated by their interaction with otilonium bromide and bile salts. The stable BBMV surface was achieved when BBMV suspension was flowed over the sensor chip for 8 h at a rate of 2 microl/min. The flow of otilonium bromide resulted in an increased SPR signal because of its binding to calcium channel, which is known to be distributed over the gastrointestinal tact. When bile salts were flowed over ileal and duodenal BBMV surfaces, respectively, a slightly higher SPR signal was observed in the ileal BBMV surface, indicating the specific interaction of bile salts with bile acid transporters. BBMV surfaces may be useful for the estimation of binding events on the intestinal membrane by SPR analysis, especially for the drugs that are orally administrated.

  18. Taurocholate transport by brush-border membrane vesicles from the developing rabbit ileum: Structure/function relationships

    SciTech Connect

    Schwarz, S.M.; Watkins, J.B.; Ling, S.C. )

    1990-05-01

    To examine the ontogenesis of bile acid transport in the rabbit ileum, brush-border membrane vesicles (12- to 20-fold purified) were prepared from 14- to 49-day-old animals. Taurocholate uptake was characterized by the emergence of secondary active, Na(+)-dependent transport at the start of weaning (21 days). Transient intravesicular accumulation (overshoot) of taurocholate occurred at 5-10 s of incubation, and the overshoot maximum increased significantly from 21 days (349.2 +/- 22.4 nmol/mg protein) to 35 days (569.0 +/- 84.3 nmol/mg protein; p less than 0.001), without further increase at maturity (49 days, not equal to 607.6 +/- 136.7 nmol/mg protein). No significant taurocholate active uptake component was noted at 14 days; however, ileal vesicles from sucklings showed carrier-mediated, Na+ D-glucose cotransport. In greater than or equal to 35-day-old rabbits, osmolarity studies at 20 s of incubation showed that only approximately 12% of (14C)taurocholate uptake was secondary to bile acid-to-membrane binding. Conversely, at 20 min, greater than 95% of radiolabel incorporation represented solute bound to the external and/or internal membrane surface. Arrhenius plots establish brush-border membrane taurocholate uptake as an intrinsic, lipid-dependent process, with a slope discontinuity between 24 and 28 degrees C, similar to the membrane lipid thermotropic transition region. Steady-state fluorescence polarization studies (1,6-diphenyl-1,3,5-hexatriene) demonstrate a temporal association between the maturation of taurocholate uptake and age-related decreases in ileal brush-border membrane fluidity. These data indicate that maturation of bile acid secondary active transport in the rabbit ileum may be regulated, at least in part, by changes in brush-border membrane lipid dynamics.

  19. Sulfate uptake by crustacean hepatopancreatic brush border membrane vesicles. [Homarus americanus

    SciTech Connect

    Gerencser, G.A.; Cattey, M.A; Ahearn, G.A. Univ. of Hawaii, Honolulu )

    1990-02-26

    Purified brush border membrane vesicles (BBMV) were prepared from Atlantic lobster (Homarus americanus) hepatopancreas using differential centrifugation and Mg{sup +2} precipitation techniques. Uptake of 0.1 mM {sup 35}SO{sub 4}{sup {minus}2} was stimulated by pre-loading vesicles with Cl{sup {minus}} leading to a transient accumulation of isotope more than twice that at equilibrium. Pre-loading with HCO{sub 3}{sup {minus}} or gluconate had no effect on sulfate uptake. No stimulation of {sup 35}SO{sub 4}{sup {minus}2} was observed in the presence of inwardly directed Na{sup +} or tetramethylammonium{sup +} gradients. Uptake of the divalent anion was strongly stimulated by inwardly directed proton gradients (pH{sub o} < pH{sub i}) and markedly inhibited by outwardly directed proton gradients (pH{sub o} > pH{sub i}). {sup 35}SO{sub 4}{sup {minus}2}/Cl{sup {minus}} exchange was enhanced by imposing a transmembrane inside positive K{sup +} diffusion potential and inhibited by a membrane potential of the opposite polarity (K{sup +}/valinomycin). Results suggest the presence of a proton-dependent, electrogenic anion antiport mechanism in BBMV isolated from the crustacean hepatopancreas.

  20. Heparin blocks /sup 125/I-calmodulin internalization by isolated rat renal brush border membrane vesicles

    SciTech Connect

    Meezan, E.; Elgavish, A.; Roden, L.; Wallace, R.W.

    1986-03-05

    /sup 125/I-Calmodulin is internalized by isolated rat renal brush border membrane vesicles (BBV) in a time, temperature and calcium dependent manner. Internalization of /sup 125/I-calmodulin into the osmotically sensitive space of BBV was distinguished from binding of the ligand to the outer BBV surface by examining the interaction of ligand and BBV at different medium osmolarities (300-1100 mosm), uptake was inversely proportional to medium osmolarity. Internalized /sup 125/I-calmodulin was intact and Western blots of solubilized BBV with /sup 125/I-calmodulin demonstrated the presence of several calmodulin-binding proteins of 143, 118, 50, 47.5, 46.5 and 35 kilodaltons which could represent potential intravesicular binding sites for the ligand. Heparin and the related glycosaminoglycan heparin sulfate both showed a dose-dependent inhibition (0.5-50 ..mu..g/ml) of /sup 125/I-calmodulin uptake by BBV, but other sulfated and nonsulfated glycosaminoglycans including chondroitin sulfates, keratan sulfate and hyaluronic acid showed little or no inhibitory effect. Desulfation of heparin virtually abolished the inhibition of uptake while depolymerization reduced it. Heparin did not block the binding of /sup 125/I-calmodulin to BBV proteins as assessed by Western blotting technique suggesting its effect was on internalization of the ligand rather than on its association with internal membrane proteins.

  1. Effect of alpha interferon on glucose and alanine transport by rat renal brush border membrane vesicles

    SciTech Connect

    Batuman, V.; Chadha, I. New Jersey Medical School, Newark )

    1990-01-01

    To investigate the pathogenetic mechanisms of interferon nephrotoxicity, we studied the effect of recombinant interferon alfa-2b on the uptake of {sup 14}C-D-glucose and {sup 14}C-L-alanine by rat renal brush-border-membrane vesicles. Interferon significantly inhibited 20 sec. sodium-dependent and 5 and 10 min. equilibrium uptake of both glucose and alanine. The inhibitory effect was dose dependent with maximum effect achieved at interferon concentration of 5 {times} 10{sup {minus}8}M in the uptake media. The half-maximal inhibitory concentrations, IC{sub 50}, of interferon on glucose uptake was 1.8 {times} 10{sup {minus}8}M, and 5.4 {times} 10{sup {minus}9}M on alanine uptake. Dixon plot analysis of uptake data was consistent with pure non-competitive inhibition. The inhibition constants, K{sub i}, 1.5 {times} 10{sup {minus}8}M for glucose uptake, and 7.3 {times} 10{sup {minus}9}M for alanine uptake, derived from Dixon plots were in close agreement with the IC{sub 50}s calculated from the semilog dose response curves. These observations reveal that direct interactions at the proximal tubule cell membrane are involved in the pathogenesis of interferon nephrotoxicity, and that its mechanism of nephrotoxicity is similar to that of other low molecular weight proteins.

  2. Effect of arginine modification on kidney brush-border-membrane transport activity.

    PubMed

    Strevey, J; Brunette, M G; Béliveau, R

    1984-11-01

    The effect of phenylglyoxylation on brush-border-membrane functions was studied with membrane vesicles from rat kidney cortex. Na+-gradient-dependent uptake of phosphate, glucose and alanine was inhibited by 65, 88 and 70% by pre-incubation of vesicles with 50 mM-phenylglyoxal for 2 min. The inhibition showed a dependency for alkaline pH. Borate co-operativity in butanedione inactivation was used to prove that inhibition was caused by arginine modification. Intravesicular volumes, alkaline phosphatase, aminopeptidase M and Na+-H+ exchange were not affected by phenylglyoxal treatment. Inhibition of phosphate uptake was studied in more detail and showed that the chemical modification introduced by phenylglyoxal inhibited the overshoot of phosphate uptake caused by the Na+ gradient, and decreased the apparent maximal velocity of the phosphate-transport system in its interaction with Na+. Phosphate uptake measured in the absence of Na+ was not affected by phenylglyoxal. Shunting of the transmembrane electrical potential with K+ and valinomycin had no effect on phenylglyoxal inhibition, proving that the alteration of transmembrane electrical potential could not be responsible for this effect. Phenylglyoxal had no ionophoric effect on the Na+ gradients studied (1-100 mM). Na+ efflux was also unaffected by phenylglyoxal treatment. Na+, harmaline and amiloride were ineffective in protecting against phenylglyoxal inhibition, suggesting that the site modified was not an Na+-binding site. These results indicate the involvement of highly reactive arginine residues in phosphate, glucose and alanine uptake.

  3. Effect of arginine modification on kidney brush-border-membrane transport activity.

    PubMed Central

    Strevey, J; Brunette, M G; Béliveau, R

    1984-01-01

    The effect of phenylglyoxylation on brush-border-membrane functions was studied with membrane vesicles from rat kidney cortex. Na+-gradient-dependent uptake of phosphate, glucose and alanine was inhibited by 65, 88 and 70% by pre-incubation of vesicles with 50 mM-phenylglyoxal for 2 min. The inhibition showed a dependency for alkaline pH. Borate co-operativity in butanedione inactivation was used to prove that inhibition was caused by arginine modification. Intravesicular volumes, alkaline phosphatase, aminopeptidase M and Na+-H+ exchange were not affected by phenylglyoxal treatment. Inhibition of phosphate uptake was studied in more detail and showed that the chemical modification introduced by phenylglyoxal inhibited the overshoot of phosphate uptake caused by the Na+ gradient, and decreased the apparent maximal velocity of the phosphate-transport system in its interaction with Na+. Phosphate uptake measured in the absence of Na+ was not affected by phenylglyoxal. Shunting of the transmembrane electrical potential with K+ and valinomycin had no effect on phenylglyoxal inhibition, proving that the alteration of transmembrane electrical potential could not be responsible for this effect. Phenylglyoxal had no ionophoric effect on the Na+ gradients studied (1-100 mM). Na+ efflux was also unaffected by phenylglyoxal treatment. Na+, harmaline and amiloride were ineffective in protecting against phenylglyoxal inhibition, suggesting that the site modified was not an Na+-binding site. These results indicate the involvement of highly reactive arginine residues in phosphate, glucose and alanine uptake. PMID:6508741

  4. Effect of insulin on D-glucose transport by human placental brush border membranes.

    PubMed

    Brunette, M G; Lajeunesse, D; Leclerc, M; Lafond, J

    1990-02-12

    We studied the effect of insulin on the uptake of D-glucose by human placental brush border membranes (BBM) in vitro. D-glucose transport through placental BBM is a Na(+)-independent transport, inhibited by 0.5 mM phloretin. Increasing the substrate concentration from 1 to 50 mM resulted in an increase in glucose uptake according to an S-shaped relationship. Hill plot analysis suggests that at least two molecules of D-glucose are transported at the same time by the carrier. Preincubation of the placental tissue with insulin for 45 min at 22 degrees C significantly enhanced the D-glucose influx into the membrane vesicles, without influencing the slope of the Hill plot. A dose-response curve of the effect of insulin revealed that although the effect was already significant at 10(-9) M, the maximal activity was reached at 10(-8) M. The influence of insulin on D-glucose uptake was present only when preincubation of the placental tissue with the hormone was performed in the presence of Mn2+. Incubation of placental tissue with 10(-8) M insulin did not influence D-glucose efflux from the BBM vesicles. Finally, direct incubation of the membranes with insulin had no effect on the glucose influx into these membrane vesicles. We conclude that insulin, at physiological concentrations, enhances glucose uptake by the BBM, and that such a regulation might contribute to the glucose homeostasis in the fetal circulation, independent of the maternal variations in glycemia.

  5. Sulphate-ion/sodium-ion co-transport by brush-border membrane vesicles isolated from rat kidney cortex

    PubMed Central

    Lücke, Heinrich; Stange, Gertraud; Murer, Heini

    1979-01-01

    Uptake of SO42− into brush-border membrane vesicles isolated from rat kindey cortex by a Ca2+-precipitation method was investigated by using a rapid-filtration technique. Uptake of SO42− by the vesicles was osmotically sensitive and represented transport into an intra-vesicular space. Transport of SO42− by brush-border membranes was stimulated in the presence of Na+, compared with the presence of K+ or other univalent cations. A typical `overshoot' phenomenon was observed in the presence of an NaCl gradient (100mm-Na+ outside/zero mm-Na+ inside). Radioactive-SO42− exchange was faster in the presence of Na+ than in the presence of K+. Addition of gramicidin-D, an ionophore for univalent cations, decreased the Na+-gradient-driven SO42− uptake. SO42− uptake was only saturable in the presence of Na+. Counter-transport of Na+-dependent SO42− transport was shown with MoO42− and S2O32−, but not with PO42−. Changing the electrical potential difference across the vesicle membrane by establishing different diffusion potentials (anion replacement; K+ gradient±valinomycin) was not able to alter Na+-dependent SO42− uptake. The experiments indicate the presence of an electroneutral Na+/SO42−-co-transport system in brush-border membrane vesicles isolated from rat kidney cortex. PMID:91368

  6. Cimetidine transport in rabbit renal cortical brush-border membrane vesicles.

    PubMed

    McKinney, T D; Kunnemann, M E

    1987-03-01

    Cimetidine is an organic cation and commonly prescribed drug that is eliminated primarily by proximal renal tubular secretion. The present studies evaluated cimetidine transport in rabbit renal cortical brush-border membrane vesicles (BBMV). [3H]Cimetidine uptake varied inversely with media osmolarity and was stimulated with uphill transport above equilibrium values (overshoot) produced by an initial proton gradient directed from the vesicle interior outwardly. Uphill transport occurred earlier and was of greater magnitude at 25 degrees C than at 5 degrees C. pH-stimulated [3H]cimetidine uptake was inhibited by excess nonradiolabeled cimetidine, quinidine, and procainamide but was affected little by probenecid. Tetraethylammonium inhibited cimetidine uptake in the presence and absence of an initial proton gradient, indicating that nonionic diffusion and simple diffusion cannot totally account for cimetidine transport in BBMV. The protonophore carbonyl cyanide trifluoromethoxyphenylhydrazone (FCCP) inhibited pH-stimulated cimetidine uptake but had no effect on uptake occurring in the absence of an initial pH gradient. Preloading BBMV with an excess of procainamide enhanced cimetidine uptake. However, in the presence of FCCP, the combination of FCCP and valinomycin, or nigericin the effect of preloading with procainamide was diminished, suggesting that the apparent countertransport of cimetidine produced by procainamide was indirect and due to generation of a transvesicular proton gradient. These results are consistent with the hypothesis that cimetidine is transported across BBMV by organic cation-proton exchange.

  7. Cimetidine transport in rabbit renal cortical brush-border membrane vesicles

    SciTech Connect

    McKinney, T.D.; Kunnemann, M.E.

    1987-03-01

    Cimetidine is an organic cation and commonly prescribed drug that is eliminated primarily by proximal renal tubular secretion. The present studies evaluated cimetidine transport in rabbit renal cortical brush-border membrane vesicles (BBMV). (/sup 3/H)Cimetidine uptake varied inversely with media osmolarity and was stimulated with uphill transport above equilibrium values (overshoot) produced by an initial proton gradient directed from the vesicle interior outwardly. Uphill transport occurred earlier and was of greater magnitude at 25/sup 0/C than at 5/sup 0/C. pH-stimulated (/sup 3/H)cimetidine uptake was inhibited by excess nonradiolabeled cimetidine, quinidine, and procainamide but was affected little by probenecid. Tetraethylammonium inhibited cimetidine uptake in the presence and absence of an initial proton gradient, indicating that nonionic diffusion and simple diffusion cannot totally account for cimetidine transport in BBMV. Preloading BBMV with an excess of procainamide enhanced cimetidine uptake. These results are consistent with the hypothesis that cimetidine is transported across BBMV by organic cation-proton exchange.

  8. Possible degradative process of cholecystokinin analogs in rabbit jejunum brush-border membrane vesicles.

    PubMed

    Su, Sheng-Fang; Amidon, Gordon L; Lee, Hye J

    2002-11-22

    Our recent work on the intestinal metabolism and absorption of cholecystokinin analogs, sulfated C-terminal octapeptide (CCK8; Asp-Tyr(SO(3)H)-Met-Gly-Trp-Met-Asp-Phe(NH(2)) = DY(SO(3)H)MGWMDF(NH(2))) and tetrapeptide (CCK4; Trp-Met-Asp-Phe(NH(2)) = WMDF(NH(2))), was extended to investigate the degradative process of these analogs using rabbit jejunum brush-border membrane vesicles and to find a better enzyme-inhibitor system for intestinal absorption of peptide drugs. Various enzyme inhibitors and a lower pH buffer were applied to discover the major enzyme(s) involved in each process. Metabolic pathways showing degradative processes were proposed for both analogs. The major cleavage site occurs at the W(1)-M(2) for CCK4. At least three metabolic pathways occur independently for CCK8 and appear at peptides bonds between G(4)-W(5), M(6)-D(7), and D(7)-F(NH(2))(8). Many different enzymes of aminopeptidase, endopeptidase, angiotensin-converting enzyme, metalloenzyme, and others were involved in each process. Identification of more specific yet safe enzyme inhibitors and co-administration of various these inhibitors may lead to further enhancement in intestinal peptide absorption when administered orally.

  9. Transport of citrate across renal brush border membrane: effects of dietary acid and alkali loading

    SciTech Connect

    Jenkins, A.D.; Dousa, T.P.; Smith, L.H.

    1985-10-01

    Dietary acid or alkali loading was given to rats by providing 150 mM NH4Cl or 150 mM NaHCO3 in place of drinking water for 6 days; control animals received 150 mM NaCl. After 6 days, the citrate clearance was 0.04 +/- 0.01 ml/min (mean +/- SE) in the acid-loaded group, 0.9 +/- 0.1 ml/min in the control group, and 2.5 +/- 0.2 ml/min in the alkali-loaded group. At the end of the experiment, the rats were killed, and the Na gradient-dependent citrate uptake was measured in brush border membrane (BBM) vesicles prepared from each group. At 0.3 min, the ( UC)citrate uptake was 198 +/- 8 pmol/mg protein (mean +/- SE) in the acid-loaded group, 94 +/- 16 pmol/mg protein in the control group, and 94 +/- 13 pmol/mg protein in the alkali-loaded group. The rate of Na -independent (NaCl in medium replaced by KCl) ( UC)-citrate uptake by BBM vesicles was the same for acid-loaded, control, and alkali-loaded animals. Thus, the increased capacity of the proximal tubular BBM to transport citrate from the tubular lumen into the cell interior may be an important factor that contributes to decreased urinary citrate in the presence of metabolic acidosis induced by chronic dietary acid loading.

  10. Intestinal assimilation of a proline-containing tetrapeptide. Role of a brush border membrane postproline dipeptidyl aminopeptidase IV.

    PubMed Central

    Morita, A; Chung, Y C; Freeman, H J; Erickson, R H; Sleisenger, M H; Kim, Y S

    1983-01-01

    The mechanism of hydrolysis and absorption of a proline-containing tetrapeptide, Leu-Pro-Gly-Gly (10 mM) by rat intestine was examined in vivo by using jejunal perfusion methods. The peptide substrate and hydrolysis products were analyzed by use of an automated amino acid analyzer. Leucine, proline, and glycine were absorbed by the intestine at a significantly higher rate from the tetrapeptide than from an equivalent amino acid mixture. The analysis of the hydrolytic products in the lumen during in vivo perfusion of the tetrapeptide showed that two dipeptides, Leu-Pro and Gly-Gly, were the major products. These two dipeptides were also the major hydrolytic products when a purified rat intestinal brush border membrane preparation was incubated with Leu-Pro-Gly-Gly. The rate of hydrolysis of the tetrapeptide was much higher than that for several other proline-containing peptides (Leu-Pro, Pro-Leu, and Pro-Gly-Gly) that were tested. Studies using Gly-Pro-beta-naphthylamide, a specific substrate for postproline dipeptidyl aminopeptidase IV, showed that this enzyme is mainly localized to the brush border membrane and is responsible for the hydrolysis of the tetrapeptide into the two dipeptides Leu-Pro and Gly-Gly. Thus, brush border membrane dipeptidyl aminopeptidase IV very likely plays an important role at the intestinal mucosal cell surface in the final stages of digestion of proline-containing peptides. PMID:6135710

  11. Effect of chronic (4 weeks) ingestion of ethanol on transport of proline into intestinal brush border membrane vesicles

    SciTech Connect

    Beesley, R.C.; Jones, T.D.

    1986-03-01

    Hamsters were separated into two groups and fed liquid diets ad lib. Controls were given a diet similar to that described by DeCarli and Lieber while alcoholics received the same diet containing 5% ethanol isocalorically substituted for sucrose. The volume of diet consumed daily and the gain in body weights of alcoholics were not significantly different from those of controls. After four weeks the animals were sacrificed and the upper third of the small intestine was used to prepare brush border membrane vesicles. In the presence of a Na/sup +/ gradient, uptake of proline into vesicles prepared from both groups was rapid, reaching a maximum accumulation in 1 to 2 min and then decreasing to the equilibrium level. To normalize the results, the amount of proline take up at each time point was divided by the amount present at equilibrium. From the normalized data it was concluded that both the rate of uptake and the maximum accumulation of proline into brush border membrane vesicles isolated from alcoholics were significantly less than those obtained with vesicles from controls. These results suggest that chronic ingestion of ethanol results in a reduction in Na/sup +/-dependent transport of proline across the brush border membrane and, thus, may contribute to the malnutrition which is frequently associated with chronic alcoholism.

  12. Sulfate transport by chick renal tubule brush-border and basolateral membranes

    SciTech Connect

    Renfro, J.L.; Clark, N.B.; Metts, R.E.; Lynch, M.A.

    1987-01-01

    Brush-border and basolateral membrane vesicles (BBMV and BLMV, respectively) were prepared from chick kidney by a calcium precipitation method and by centrifugation on an 8% Percoll self-generating gradient, respectively. In BBMV a 100-mM Na gluconate gradient, out>in, caused concentrative (/sup 35/S) sulfate uptake approximately fivefold greater at 1 min than at 60 min (equilibrium) whether or not the membranes were short-circuited with 100 mM K gluconate, in=out, plus 20 ..mu..g valinomycin/mg protein. A 48-mM HCO/sub 3//sup -/ gradient, in>out, stimulated a 2.5-fold higher uptake at 1 min than at 60 min, and short circuiting as above had no effect on the magnitude of this response. Imposition of a H/sup +/ gradient caused concentrative uptake fourfold higher at 1 min than at equilibrium. Short circuiting as above or addition of 0.1 mM carbonyl cyanide m-chlorophenylhydrazone (CCCP) significantly inhibited the pH gradient effect. Creation of an inside positive electrical potential with 100 mM K gluconate, out>in, plus valinomycin, also caused concentrative sulfate uptake. Based on inhibitor/competitor effects, these are distinct sulfate transport processes. In chick BLMV, imposition of an HCO/sub 3//sup -/ gradient, in>out, produced concentrative sulfate uptake. 4-Acetamido-4'-isothiocyanostilbene 2,2'-disulfonic acid disodium at 0.1 mM was an effective inhibitor of BLMV bicarbonate-sulfate exchange.

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

    PubMed Central

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

    2016-01-01

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

  14. Inhibition of beta-amino acid transport by diamide does not involve the brush border membrane surface

    SciTech Connect

    Chesney, R.W.; Gusowski, N.; Albright, P.

    1985-01-01

    Diamide (dicarboxylic acid bis-(N,N-dimethylamide) has been shown in previous studies to block the uptake of the beta-amino acid taurine at its high affinity transport site in rat renal cortex slices. Diamide may act by increasing the efflux of taurine from the slice. Studies performed in rat slices again indicate enhanced efflux over 8-12 minutes. The time course of reduced glutathione (GSH) depletion from renal cortex is similar, indicating a potential interaction between GSH depletion and inhibition of taurine accumulation. The effect of 9 mM diamide on the Na+ -dependent accumulation of taurine (10 and 250 microM) by brush border membrane vesicles was examined, and the taurine uptake value both initially and at equilibrium was the same in the presence and absence of diamide. Isolation of the brush border surface and subsequent transport studies of taurine are not influenced by diamide. Thus, diamide inhibition of taurine uptake does not involve physiochemical alteration of the membrane surface where active amino acid transport occurs, despite the thiol-oxidizing properties of this agent. Further, these studies suggest that diamide either acts at the basolateral surface, rather than the brush border surface of rat renal cortex or requires the presence of an intact tubule, capable of metabolism, prior to its inhibitory action.

  15. Sodium/proton antiport in brush-border-membrane vesicles isolated from rat small intestine and kidney.

    PubMed

    Murer, H; Hopfer, U; Kinne, R

    1976-03-15

    Studies on proton and Na+ transport by isolated intestinal and renal brush-border-membrane vesicles were carried out to test for the presence of an Na+/H+-exchange system. Proton transport was evaluated as proton transfer from the intravesicular space to the incubation medium by monitoring pH changes in the membrane suspension induced by sudden addition of cations. Na+ transport was determined as Na+ uptake into the vesicles by filtration technique. A sudden addition of sodium salts (but not choline) to the membrane suspension provokes an acidification of the incubation medium which is abolished by the addition of 0.5% Triton X-100. Pretreatment of the membranes with Triton X-100 prevents the acidification. The acidification is also not observed if the [K+] and proton conductance of the membranes have been increased by the simultaneous addition of valinomycin and carbonyl cyanide p-trifluoromethoxyphenylhydrazone to the K+-rich incubation medium. Either valinomycin or carbonyl cyanide p-trifluoromethoxyphenylhydrazone when added alone do not alter the response of the membranes to the addition of Na+. Na+ uptake by brush-border microvilli is enhanced in the presence of a proton gradient directed from the intravesicular space to the incubation medium. Under these conditions a transient accumulation of Na+ inside the vesicles is observed. It is concluded that intestinal and renal brush-border membranes contain a NA+/H+ antiport system which catalyses an electroneutral exchange of Na+ against protons and consequently can produce a proton gradient in the presence of a concentration difference for Na+. This system might be involved in the active proton secretion of the small intestine and the proximal tubule of the kidney.

  16. Hypothyroidism increases osmotic water permeability (Pf) in the developing renal brush border membrane.

    PubMed

    Mulder, Jaap; Haddad, Maha N; Vernon, Kimberly; Baum, Michel; Quigley, Raymond

    2003-06-01

    The osmotic water permeability (Pf) of the rabbit proximal tubule brush border membrane vesicles (BBMV) increases during maturation and is mediated by an increase in aquaporin-1 (AQP1) protein expression. Serum thyroid hormone levels increase after birth and have been shown to play a role in the maturation of other renal transport functions. We examined the hypothesis that thyroid hormone plays a role in the maturational increase in osmotic water permeability. Hypothyroidism was induced by addition of 0.1% propylthiouracil (PTU) to the drinking water of pregnant rabbits (starting 9 d before delivery) and was continued until the rabbits were studied as adults (9-11 wk). Some animals received thyroid hormone replacement by daily injection with triiodothyronine (T3; 10 microg/100 g body weight) for three days before study. Pf was found to be higher in BBMV from hypothyroid (82.7 +/- 5.5 microm/s) than from euthyroid (60.6 +/- 4.0 microm/s) and T3-replacement rabbits (69.0 +/- 5.0 microm/s) (p < 0.05). The activation energy (Ea; in kcal/deg.mol) of Pf was not different among the three experimental groups (euthyroid 5.6 +/- 0.9, hypothyroid 4.9 +/- 0.8, T3-replacement 5.0 +/- 1.0; p = NS), nor was the percentage mercury inhibition of Pf (euthyroid 66.5 +/- 5.3, hypothyroid 74.2 +/- 3.2 and T3-replacement 73.1 +/- 4.3; p = NS). AQP1 expression, measured by immunoblotting, was highest in BBMV from hypothyroid rabbits (p < 0.05). Membrane fluidity, measured as steady-state generalized polarization (GP) of Laurdan, which is inversely related to membrane fluidity, was significantly different between the three groups (GP: euthyroid 0.307 +/- 0.004, hypothyroid 0.271 +/- 0.004 and T3-replacement 0.287 +/- 0.003; for all p < 0.05). These data demonstrate that the maturational increase in thyroid hormone levels is not responsible for the maturational increase in water transport. Surprisingly, congenital hypothyroidism in rabbits is associated with an increased Pf when rabbits

  17. Effect of external abdominal irradiation on intestinal morphology and brush border membrane enzyme and lipid composition

    SciTech Connect

    Keelan, M.; Cheeseman, C.; Walker, K.; Thomson, A.B.

    1986-01-01

    Previous studies have shown that external abdominal irradiation is associated with alterations in intestinal morphology and function. The activity of the jejunal brush border membrane (BBM) enzyme markers sucrase (S) and alkaline phosphate (AP) were not altered by 600 rad irradiation in the rat. In contrast, ileal BBM, AP, and AP/S were increased 3, 7/8, and 28 days postirradiation. The total lipid composition of the jejunal BBM was lower than in control animals only at 3 days postirradiation; this was due to a decrease in the total free fatty acid content. In addition to a lower total free fatty acid content, the ileal BBM contained an increased amount of total phospholipid (PL) which resulted in an increased phospholipid/cholesterol ratio at 3 days following irradiation. Variations in the BBM phospholipid composition occurred in both jejunum and ileum. In the jejunal BBM, the phospholipid composition changes did not alter the choline or amine phospholipid content; therefore, the choline/amine phospholipid ratio was unaffected by irradiation at 600 rad. In the ileal BBM, the phosphatidyl ethanolamine was increased at 3, 7/8, 14, and 28 days following irradiation. The choline/amine phospholipid ratio was not altered in the ileal BBM due to concomitant increases in lecithin content. Jejunal villus height, villus surface area, and the number of cells per villus were decreased at 3 days postirradiation, but increased by day 7/8 and 14 postirradiation to levels much higher than observed in control jejunal villi. The mucosal surface area was decreased at 3 and 7/8 days following irradiation but returned to control values by Day 14. Jejunal microvillus morphology was unaffected by irradiation. Few significant changes were observed in ileal villus morphology following irradiation at 600 rad. (Abstract Truncated)

  18. Effects of uricosuric and antiuricosuric agents on urate transport in human brush-border membrane vesicles.

    PubMed

    Roch-Ramel, F; Guisan, B; Diezi, J

    1997-02-01

    Inhibition of [14C]-urate uptake by uricosuric and antiuricosuric agents was investigated in human brush-border membrane vesicles, urate being transported either by anion exchange mechanisms or by voltage sensitive pathway. The IC50 for drugs on [14C]-urate uptake in vesicles loaded with 1 mM cold urate or with 5 mM lactate was, respectively: 0.7 and 0.3 microM for benzbromarone; 6 and 4 microM for salicylate; 133 and 13 microM for losartan; 520 and 190 microM for sulfinpyrazone and 807 and 150 microM, for probenecid. The IC50 ratio for [14C]-urate uptake in exchange for cold urate or for lactate varied from about 1 for salicylate to 10 for losartan, supporting the hypothesis that two distinct anion exchangers are involved in urate transport. Application of Hill equation revealed that urate/anion exchangers have more than one binding site, possibly two binding sites with high cooperativity, for benzbromarone and sulfinpyrazone, but only one for probenecid, salicylate and losartan. The uricosuric diuretic, tienilic acid was 10 to 50 times more potent than hydrochlorothiazide, chlorothiazide and furosemide, for inhibiting [14C]-urate uptake in exchange for cold urate. This higher potency is the reason of its uricosuric properties. All uricosuric agents, as well as the antiuricosuric agents, pyrazinoate and ethambutol, had a much lower potency for inhibiting [14C]-urate uptake through the voltage sensitive pathway (apical secretory step) than through the urate/anion exchangers. This suggests that antiuricosuria, induced by pyrazinoate and ethambutol, as well as by low concentrations of uricosuric agents, does not result from an inhibition of the apical voltage sensitive pathway.

  19. Proline transport by brush-border membrane vesicles of lobster antennal glands

    SciTech Connect

    Behnke, R.D.; Wong, R.K.; Huse, S.M.; Reshkin, S.J.; Ahearn, G.A. )

    1990-02-01

    Purified brush-border membrane vesicles (BBMV) of lobster antennal gland labyrinth and bladder were separately formed by a magnesium precipitation technique. L-(3H)proline uptake was stimulated by a transmembrane NaCl gradient (outside (o) greater than inside (i)) to a greater extent in BBMV from labyrinth than those from the bladder. Detailed study of the labyrinth proline-transport processes revealed a specific dependence on NaCl, with negligible stimulatory effects by NaSCN, Na-gluconate, or KCl. A transmembrane proton gradient (o greater than i) was without stimulatory effect on proline transport. A transmembrane potential difference alone, in the presence of equilibrated NaCl and L-(3H)proline, led to net influx of the labeled amino acid, suggesting that the uptake process was electrogenic and capable of bringing about the net transfer of positive charge to the vesicle interior. Although a transmembrane Na gradient alone, in the presence of equilibrated Cl and L-(3H)proline, was able to bring about the net influx of the amino acid, a transmembrane Cl gradient alone under Na- and L-(3H)proline-equilibrated conditions was not, suggesting that only the Na gradient could energize the carrier process through cotransport, while the anion served an essential activating role. Proline influx by these vesicles occurred by the combination of at least one saturable Michaelis-Menten carrier system (apparent Kt = 0.37 mM; apparent JM = 1.19 nmol.mg protein-1.10 s-1) and apparent diffusion (P = 0.33 nmol.mg protein-1.10 s-1.mM-1). Static head analysis of the transport process suggested a cotransport stoichiometry of 2 Na:1 proline with essential activation by Cl ion.

  20. Paraquat2+/H+ exchange in isolated renal brush-border membrane vesicles.

    PubMed

    Wright, S H; Wunz, T M

    1995-11-22

    The mechanism(s) by which paraquat (1,1'-dimethyl-4,4'-bipyridinium), a divalent organic cation (OC) and proximal tubule nephrotoxicant, crosses renal cell membranes is unclear. The structurally-related monovalent OC, 1-methyl-4-phenylpyridinium (MPP+), crosses the renal brush border via OC/H+ exchange using the same pathway by which tetraethylammonium (TEA) is transported. We examined whether paraquat shares the TEA(MPP+)/H+ exchanger by examining 14C-paraquat transport in rabbit renal BBMV. Compared to a pH equilibrium condition (pH 7.5in:7.5o), an H-gradient (pH 6in:7.5o) stimulated the 5 s and 60 s uptakes of 230 microM paraquat by 51% and 108%, respectively, and this stimulation was blocked by both 20 mM unlabeled paraquat and TEA. Pre-loading BBMV with 2 mM unlabeled TEA (under conditions of pH equilibrium) stimulated by 3-fold the 60 s uptake of 120 microM paraquat and by 5 min produced a transient intravesicular accumulation of paraquat that exceeded equilibrium (2 h) uptake by 45%. The presence of 200 microM paraquat in the extravesicular solution competitively inhibited H-gradient-stimulated transport of 14C-TEA in renal BBMV, increasing the apparent Kt for TEA transport from 169 microM to 379 microM, without significantly influencing the Jmax (16.0 vs. 15.4 nmol mg-1 min-1). The calculated Ki for paraquat (presumably equal to its Kt for transport) after transport was between 160 and 220 microM (depending upon the method of estimation). Significantly, the Kt for MPP+/H exchange is 12 microM, suggesting that the affinity of the exchanger is profoundly influenced by the presence on paraquat of a second positive charge. We conclude that renal transport of paraquat involves the OC/H+ exchanger of proximal cell luminal membranes and that this pathway may play a role in the renal secretion of polyvalent organic cations.

  1. Uptake of 75Se-selenite by brush border membrane vesicles from chick duodenum stimulated by vitamin D.

    PubMed

    Mykkanen, H M; Wasserman, R H

    1989-02-01

    Brush border membrane vesicles were isolated from mucosal homogenates of duodena from normal, rachitic and vitamin D-treated rachitic chicks using a discontinuous sucrose gradient, and further purified by glycerol gradient centrifugation. In vitro uptake of 75Se-selenite by purified brush border membrane vesicles was studied using a rapid filtration technique. The time course of 75Se uptake was non-linear; rapid initial binding was followed by a gradual decrease in the rate of uptake until an equilibrium value was reached at 60-120 min. The initial binding at 36 s was not affected by selenite concentration in the incubation buffer, while the fractional rate of uptake between the 36 s and 2 min time periods was clearly lower with 1 mM Se than with 4-100 microM Se. 75Se uptake did not show any dependency on the external Na-gradient, nor could it be inhibited by other anions (arsenate, phosphate). Treatment of rachitic chicks either with cholecalciferol (500 Iu, 72 h) or with 1,25(OH)2-cholecalciferol (0.5 microgram given 16 h prior to isolation of the vesicles) significantly enhanced 75Se uptake. A threefold excess of mannitol in the outside buffer reduced 75Se uptake by vesicles from vitamin D-deficient and D-treated chicks 60% and 35% respectively, but had no effect on vesicles from vitamin D-treated chicks preloaded with 75Se. Neither saponin treatment nor excess cold selenite could release the label from the vesicles preloaded with 75Se. These data are compatible with the hypothesis that selenite easily crosses the brush border membrane into the intravesicular space and, once inside, is tightly bound by the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Uptake of /sup 75/Se-selenite by brush border membrane vesicles from chick duodenum stimulated by vitamin D

    SciTech Connect

    Mykkanen, H.M.; Wasserman, R.H.

    1989-02-01

    Brush border membrane vesicles were isolated from mucosal homogenates of duodena from normal, rachitic and vitamin D-treated rachitic chicks using a discontinuous sucrose gradient, and further purified by glycerol gradient centrifugation. In vitro uptake of 75Se-selenite by purified brush border membrane vesicles was studied using a rapid filtration technique. The time course of 75Se uptake was non-linear; rapid initial binding was followed by a gradual decrease in the rate of uptake until an equilibrium value was reached at 60-120 min. The initial binding at 36 s was not affected by selenite concentration in the incubation buffer, while the fractional rate of uptake between the 36 s and 2 min time periods was clearly lower with 1 mM Se than with 4-100 microM Se. 75Se uptake did not show any dependency on the external Na-gradient, nor could it be inhibited by other anions (arsenate, phosphate). Treatment of rachitic chicks either with cholecalciferol (500 Iu, 72 h) or with 1,25(OH)2-cholecalciferol (0.5 microgram given 16 h prior to isolation of the vesicles) significantly enhanced 75Se uptake. A threefold excess of mannitol in the outside buffer reduced 75Se uptake by vesicles from vitamin D-deficient and D-treated chicks 60% and 35% respectively, but had no effect on vesicles from vitamin D-treated chicks preloaded with 75Se. Neither saponin treatment nor excess cold selenite could release the label from the vesicles preloaded with 75Se. These data are compatible with the hypothesis that selenite easily crosses the brush border membrane into the intravesicular space and, once inside, is tightly bound by the membrane.

  3. Effect of lipid peroxidation on membrane-bound Ca2+-ATPase activity of the intestinal brush-border membranes.

    PubMed

    Ohta, A; Mohri, T; Ohyashiki, T

    1989-09-04

    We have studied lipid peroxidation and Ca2+-ATPase activity of the porcine intestinal brush-border membranes using a oxygen-radical-generating system consisting of dithiothreitol (DTT)/Fe2+ and tert-butyl hydroperoxide (t-BuOOH). The rates of lipid peroxidation were measured by formation of thiobarbituric acid-reactive substances (TBAR) and conjugated diene. Incubation of the membranes with DTT/Fe2+ in the absence and presence of t-BuOOH resulted in a slight (about 20%) and a marked (about 50%) inhibition of Ca2+-ATPase activity, respectively. The degree of inhibition was dependent on the hydroperoxide concentration. Addition of thiourea effectively protected Ca2+-ATPase activity but catalase and superoxide dismutase showed a slight and no effect on protection of the ATPase activity, respectively. Results of kinetic studies on the ATPase activity with varying ATP and Ca2+ concentrations revealed that the decrease in the enzyme activity by treatment with these oxidizing agents is mainly due to decrease of the Vmax value. Modification of SH groups in the membrane proteins by thiol group reagents such as N-ethylmaleimide, monoiodoacetate and monoiodacetamide did not induce the inhibition of Ca2+-ATPase activity. From these results, it is suggested that inhibition of the ATPase activity of the membranes by treatment with DTT/Fe2+ in the presence and absence of t-BuOOH is dependent on lipid peroxidation and that oxidative modification of SH groups may not be directly involved to the loss of the ATPase activity. In addition, results of the fluorescence anisotropy measurements of pyrene-labeled membranes suggested that change in the Ca2+-ATPase activity is partly related to a decrease in the membrane lipid fluidity.

  4. Vitamin D. Its effect on the protein composition and core material structure of the chick intestinal brush-border membrane.

    PubMed

    Putkey, J A; Norman, A W

    1983-07-25

    Vitamin D3 is known to stimulate the absorption of calcium across the asymmetric intestinal epithelial cells. Efforts to elucidate the mechanism of stimulation of intestinal calcium transport by vitamin D are now focused on evaluating the protein composition and topology of the brush-border membrane and its associated core material. Intestinal brush-border membranes were isolated from vitamin D-replete and vitamin D-deficient chicks. Core material proteins were isolated, by sedimentation, from brush-border membranes which were solubilized with Triton X-100. As determined by polyacrylamide gel electrophoresis, dietary vitamin D3 treatment caused no change in the relative amounts of five major core material proteins with Mr = 101,000, 94,000, 67,000, 42,000 (actin), and 17,000. In contrast, dietary vitamin D3 treatment caused a significant reduction in the levels of two proteins with Mr = 111,000 (sucrase) and 83,000, and an increase in the levels of a protein with Mr = 78,000 (possibly a subunit of alkaline phosphatase). The Mr = 111,000, 83,000, and 78,000 proteins are readily solubilized by Triton X-100 and are located on the extracellular surface of the brush-border membrane, as judged by [125I]diazoiodosulfanilic acid and lactoperoxidase 125I labeling. A significant vitamin D-dependent difference was found with respect to iodination of isolated core material as evidenced by the 125I labeling patterns of the Mr = 42,000 protein (actin). The Mr = 42,000 protein was labeled two to three times more extensively when associated with core material derived from vitamin D-deficient chicks as compared to vitamin D-replete chicks. Increasing the salt concentration (0-125 mM KCl) present during core material isolation from either vitamin D-replete or vitamin D-deficient chicks yields core material actin which is more susceptible to iodination by both [125I]diazoiodosulfanilic acid and lactoperoxidase. This increase in the extent of actin iodination is coupled to a salt

  5. A protein complex in the brush-border membrane explains a Hartnup disorder allele.

    PubMed

    Kowalczuk, Sonja; Bröer, Angelika; Tietze, Nadine; Vanslambrouck, Jessica M; Rasko, John E J; Bröer, Stefan

    2008-08-01

    Protein absorption in the intestine is mediated by proteases and brush-border peptidases together with peptide and amino acid transporters. Neutral amino acids are generated by a variety of aminopeptidases and carboxypeptidases and are subsequently taken up by the amino acid transporter B(0)AT1 (SLC6A19), which is mutated in Hartnup disorder. Coexpression of B(0)AT1 together with the brush-border carboxypeptidase angiotensin-converting enzyme 2 (ACE2) in Xenopus laevis oocytes led to a dramatic increase of transporter expression at the oocyte surface. Other members of the SLC6 family were not stimulated by coexpression with ACE2. Addition of a peptide containing a carboxyterminal leucine residue to ACE2- and B(0)AT1-coexpressing oocytes caused inward currents due to Na(+)-leucine cotransport, demonstrating the formation of a metabolic complex. Coexpression of the Hartnup disorder causing mutation B(0)AT1(R240Q) showed reduced interaction with ACE2 and its renal paralogue collectrin. This would result in reduced surface expression in both kidney and intestine, thereby explaining the onset of the disorder in individuals carrying this mutation.

  6. Microbial sphingomyelinase induces RhoA-mediated reorganization of the apical brush border membrane and is protective against invasion

    PubMed Central

    Saslowsky, David E.; Thiagarajah, Jay R.; McCormick, Beth A.; Lee, Jean C.; Lencer, Wayne I.

    2016-01-01

    The apical brush border membrane (BBM) of intestinal epithelial cells forms a highly structured and dynamic environmental interface that serves to regulate cellular physiology and block invasion by intestinal microbes and their products. How the BBM dynamically responds to pathogenic and commensal bacterial signals can define intestinal homeostasis and immune function. We previously found that in model intestinal epithelium, the conversion of apical membrane sphingomyelin to ceramide by exogenous bacterial sphingomyelinase (SMase) protected against the endocytosis and toxicity of cholera toxin. Here we elucidate a mechanism of action by showing that SMase induces a dramatic, reversible, RhoA-dependent alteration of the apical cortical F-actin network. Accumulation of apical membrane ceramide is necessary and sufficient to induce the actin phenotype, and this coincides with altered membrane structure and augmented innate immune function as evidenced by resistance to invasion by Salmonella. PMID:26864627

  7. Role of calcium and calmodulin in the regulation of the rabbit ileal brush-border membrane Na+/H+ antiporter.

    PubMed

    Emmer, E; Rood, R P; Wesolek, J H; Cohen, M E; Braithwaite, R S; Sharp, G W; Murer, H; Donowitz, M

    1989-06-01

    In rabbit ileum, Ca2+/calmodulin (CaM) appears to be involved in physiologically inhibiting the linked NaCl absorptive process, since inhibitors of Ca2+/CaM stimulate linked Na+ and Cl- absorption. The role of Ca2+/CaM-dependent phosphorylation in regulation of the brush-border Na+/H+ antiporter, which is believed to be part of the neutral linked NaCl absorptive process, was studied using purified brush-border membrane vesicles, which contain both the Na+/H+ antiporter and Ca2+/CaM-dependent protein kinase(s) and its phosphorprotein substrates. Rabbit ileal villus cell brush-border membrane vesicles were prepared by Mg precipitation and depleted of ATP. Using a freezethaw technique, the ATP-depleted vesicles were loaded with Ca2+, CaM, ATP and an ATP-regenerating system consisting of creatine kinase and creatine phosphate. The combination of Ca2+/CaM and ATP inhibited Na+/H+ exchange by 45 +/- 13%. This effect was specific since Ca2+/CaM and ATP did not alter diffusive Na+ uptake, Na+-dependent glucose entry, or Na+ or glucose equilibrium volumes. The inhibition of the Na+/H+ exchanger by Ca2+/CaM/ATP was due to an effect on the Vmax and not on the Km for Na+. In the presence of CaM and ATP, Ca2+ caused a concentration-dependent inhibition of Na+ uptake, with an effect 50% of maximum occurring at 120 nM. This Ca2+ concentration dependence was similar to the Ca2+ concentration dependence of Ca2+/CaM-dependent phosphorylation of specific proteins in the vesicles. The Ca2+/CaM/ATP-inhibition of Na+/H+ exchange was reversed by W13, a Ca2+/CaM antagonist, but not by a hydrophobic control, W12, or by H-7, a protein kinase C antagonist. We conclude that Ca2+, acting through CaM, regulates ileal brush-border Na+/H+ exchange, and that this may be involved in the regulation of neutral linked NaCl absorption.

  8. High affinity 3H-Phe uptake by brush border membrane vesicles from whole larvae of Aedes aegypti (AaBMVw)

    USDA-ARS?s Scientific Manuscript database

    Brush border membrane vesicles from whole Aedes aegypti larvae (AaBBMVw) are confirmed to be valid preparations for membrane transport studies. The Abdul-Rauf and Ellar method was used to isolate AaBBMVw that were frozen, stored for several months, transported to a distant site, thawed and used to s...

  9. Phosphorylation of adenosine in renal brush-border membrane vesicles by an exchange reaction catalysed by adenosine kinase.

    PubMed Central

    Sayós, J; Solsona, C; Mallol, J; Lluis, C; Franco, R

    1994-01-01

    Uptake of [3H]adenosine in brush-border membrane (BBM) vesicles from either rat or pig kidney leads to an accumulation of intravesicular [3H]AMP. The lack of significant levels of ATP and the presence of AMP in BBM indicated that a phosphotransfer between [3H]adenosine and AMP occurs. The phosphotransfer activity is inhibited by iodotubercidin, which suggests that it is performed by adenosine kinase acting in an ATP-independent manner. The existence of a similar phosphotransferase activity was demonstrated in membrane-free extracts from pig kidney. From the compounds tested it was shown that a variety of mononucleotides could act as phosphate donors. The results suggest that phosphotransfer reactions may be physiologically relevant in kidney. PMID:8110185

  10. Diabetes increases facilitative glucose uptake and GLUT2 expression at the rat proximal tubule brush border membrane

    PubMed Central

    Marks, Joanne; Carvou, Nicolas J C; Debnam, Edward S; Srai, Surjit K; Unwin, Robert J

    2003-01-01

    The mechanism of renal glucose transport involves the reabsorption of filtered glucose from the proximal tubule lumen across the brush border membrane (BBM) via a sodium-dependent transporter, SGLT, and exit across the basolateral membrane via facilitative, GLUT-mediated, transport. The aim of the present study was to determine the effect of streptozotocin-induced diabetes on BBM glucose transport. We found that diabetes increased facilitative glucose transport at the BBM by 67.5 % (P < 0.05) – an effect that was abolished by overnight fasting. Western blotting and immunohistochemistry demonstrated GLUT2 expression at the BBM during diabetes, but the protein was undetectable at the BBM of control animals or diabetic animals that had been fasted overnight. Our findings indicate that streptozotocin-induced diabetes causes the insertion of GLUT2 into the BBM and this may provide a low affinity/high capacity route of entry into proximal tubule cells during hyperglycaemia. PMID:12963802

  11. Diabetes increases facilitative glucose uptake and GLUT2 expression at the rat proximal tubule brush border membrane.

    PubMed

    Marks, Joanne; Carvou, Nicolas J C; Debnam, Edward S; Srai, Surjit K; Unwin, Robert J

    2003-11-15

    The mechanism of renal glucose transport involves the reabsorption of filtered glucose from the proximal tubule lumen across the brush border membrane (BBM) via a sodium-dependent transporter, SGLT, and exit across the basolateral membrane via facilitative, GLUT-mediated, transport. The aim of the present study was to determine the effect of streptozotocin-induced diabetes on BBM glucose transport. We found that diabetes increased facilitative glucose transport at the BBM by 67.5 % (P < 0.05)--an effect that was abolished by overnight fasting. Western blotting and immunohistochemistry demonstrated GLUT2 expression at the BBM during diabetes, but the protein was undetectable at the BBM of control animals or diabetic animals that had been fasted overnight. Our findings indicate that streptozotocin-induced diabetes causes the insertion of GLUT2 into the BBM and this may provide a low affinity/high capacity route of entry into proximal tubule cells during hyperglycaemia.

  12. A role for aminopeptidase N in Na(+)-dependent amino acid transport in bovine renal brush-border membranes.

    PubMed Central

    Plakidou-Dymock, S; Tanner, M J; McGivan, J D

    1993-01-01

    A monoclonal antibody FD19 which removes reconstitutable Na(+)-dependent amino acid transport activity from solubilized bovine renal brush-border membrane vesicles was found to react specifically with the enzyme aminopeptidase N. Cleavage of aminopeptidase N from the membranes with papain inhibited Na(+)-dependent amino acid transport activity without affecting that of alpha-methyl D-glucoside. Removal of aminopeptidase substantially increased the Km values for the Na(+)-dependent transport of alanine, glutamine, leucine and phenylalanine without affecting the Vmax. Both Na(+)-dependent amino acid transport and aminopeptidase activity in intact vesicles were competitively inhibited by amino acids with very similar specificity. These results suggest that the amino acid-binding sites of aminopeptidase N and the transporter interact in some way to increase the Km of the transport process for its substrates. However, independent direct inactivation of the transport system by papain cannot be ruled out. Images Figure 1 PMID:8094953

  13. Kinetics of Bacillus thuringiensis toxin binding with brush border membrane vesicles from susceptible and resistant larvae of Plutella xylostella.

    PubMed

    Masson, L; Mazza, A; Brousseau, R; Tabashnik, B

    1995-05-19

    An optical biosensor technology based on surface plasmon resonance was used to determine the kinetic rate constants for interactions between the CryIA(c) toxin from Bacillus thuringiensis and brush border membrane vesicles purified from susceptible and resistant larvae of diamondback moth (Plutella xylostella). CryIA(c) association and dissociation rate constants for vesicles from susceptible larvae were determined to be 4.5 x 10(3) M-1 s-1 and 3.2 x 10(-5) s-1, respectively, resulting in a calculated affinity constant of 7 nM. CryIE toxin did not kill susceptible or resistant larvae and did not bind to brush border vesicles. Contrary to expectations based on previous studies of binding in resistant P. xylostella, the binding kinetics for CryIA(c) did not differ significantly between susceptible larvae and those that were resistant to CryIA(c). Determination of the number of CryIA(c) receptors revealed an approximately 3-fold decrease in total CryIA(c) receptor numbers for resistant vesicles. These results suggest that factors other than binding may be altered in our resistant diamondback moth strain. They also support the view that binding is not sufficient for toxicity.

  14. Radiation-inactivation studies on brush-border-membrane vesicles. General considerations, and application to the glucose and phosphate carriers.

    PubMed Central

    Béliveau, R; Demeule, M; Ibnoul-Khatib, H; Bergeron, M; Beauregard, G; Potier, M

    1988-01-01

    Radiation-inactivation studies were performed on brush-border-membrane vesicles purified from rat kidney cortex. No alteration of the structural integrity of the vesicles was apparent in electron micrographs of irradiated and unirradiated vesicles. The size distributions of the vesicles were also similar for both populations. The molecular sizes of two-brush-border-membrane enzymes, alkaline phosphatase and 5'-nucleotidase, estimated by the radiation-inactivation technique, were 104800 +/- 3500 and 89,400 +/- 1800 Da respectively. Polyacrylamide-gel-electrophoresis patterns of membrane proteins remained unaltered by the radiation treatment, except in the region of higher-molecular-mass proteins, where destruction of the proteins was visible. The molecular size of two of these proteins was estimated from their mobilities in polyacrylamide gels and was similar to the target size, estimated from densitometric scanning of the gel. Intravesicular volume, estimated by the uptake of D-glucose at equilibrium, was unaffected by irradiation. Uptake of Na+, D-glucose and phosphate were measured in initial-rate conditions to avoid artifacts arising from a decrease in the driving force caused by a modification of membrane permeability. Na+-independent D-glucose and phosphate uptakes were totally unaffected in the dose range used (0-9 Mrad). The Na+-dependent uptake of D-glucose was studied in irradiated vesicles, and the molecular size of the transporter was found to be 288,000 Da. The size of the Na+-dependent phosphate carrier was also estimated, and a value of 234,000 Da was obtained. Images Fig. 1. Fig. 4. PMID:3421923

  15. A photoactivatable probe for the Na+/H+ exchanger cross-links a 66-kDa renal brush border membrane protein

    SciTech Connect

    Ross, W.; Bertrand, W.; Morrison, A. )

    1990-04-05

    Earlier studies on LLC-PK1 cells have demonstrated two pharmacologically distinct Na+/H+ exchangers in renal epithelia. In addition, the cDNA clone for the human Na+/H+ antiporter which is growth factor activatable has been isolated and expressed. We report here the synthesis of an amiloride analogue that can be photoactivated and labeled with 125I. This analogue covalently cross-links a 66-kDa protein of bovine renal brush border membranes. A rabbit polyclonal antibody that was directed against a 20-amino acid peptide of the cytoplasmic domain of its human Na+/H+ antiporter also gives a positive Western against 66-kDa protein of bovine brush border membranes. Thus, the photoactive probe may be helpful in the isolation and purification of the brush border Na+/H+ exchanger.

  16. A proton gradient is the driving force for uphill transport of lactate in human placental brush-border membrane vesicles.

    PubMed

    Balkovetz, D F; Leibach, F H; Mahesh, V B; Ganapathy, V

    1988-09-25

    The characteristics of lactate transport in brush-border membrane vesicles isolated from normal human full-term placentas were investigated. Lactate transport in these vesicles was Na+-independent, but was greatly stimulated when the extravesicular pH was made acidic. In the presence of an inwardly directed H+ gradient ([H+]o greater than [H+]i), transient uphill transport of lactate could be demonstrated. This H+ gradient-dependent stimulation was not a result of a H+ diffusion potential. Transport of lactate in the presence of the H+ gradient was not inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid or by furosemide, ruling out the participation of an anion exchanger in placental lactate transport. Many monocarboxylates strongly interacted with the lactate transport system, whereas, with the single exception of succinate, dicarboxylates did not. The monocarboxylates pyruvate and lactate, but not the dicarboxylate succinate, when present inside the vesicles, were able to exert a trans-stimulatory effect on the uptake of radiolabeled lactate. Kinetic analyses provided evidence for a single transport system with a Kt of 4.1 +/- 0.4 mM for lactate and a Vmax of 54.2 +/- 9.9 nmol/mg of protein/30 s. Pyruvate inhibited lactate transport competitively, by reducing the affinity of the system for lactate without altering the maximal velocity. It is concluded that human placental brush-border membranes possess a transport system specific for lactate and other monocarboxylates and that this transport system is Na+-independent and is energized by an inwardly directed H+ gradient. Lactate-H+ symport rather than lactate-OH- antiport appears to be the mechanism of the H+ gradient-dependent lactate transport in these membranes.

  17. Isolation and partial characterization of gypsy moth BTR-270, an anionic brush border membrane glycoconjugate that binds Bacillus thuringiensis Cry1A toxins with high affinity

    Treesearch

    Algimantas P. Valaitis; Jeremy L. Jenkins; Mi Kyong Lee; Donald H. Dean; Karen J. Garner

    2001-01-01

    BTR-270, a gypsy moth (Lymantria dispar) brush border membrane molecule that binds Bacillus thuringiensis (Bt) Cry1A toxins with high affinity, was purified by preparative gel electrophoresis. Rabbit antibodies specific for the Bt toxin-binding molecule were raised. Attempts to label BTR-270 by protein-directed techniques were...

  18. Effects of different Brush Border Membrane Vesicle isolation protocols on proteomic analysis of Cry1Ac binding proteins from the midgut of Helicoverpa armigera

    USDA-ARS?s Scientific Manuscript database

    The brush border membrane vesicles (BBMV) isolated from midgut cells of insect have been widely used for studying of the binding receptors and action mode of Cry proteins produced by Bacillus thuringiensis (Bt). There are several methods for isolating insect BBMV used in one-dimension electrophoresi...

  19. K⁺-dependent ³H-D-glucose transport by hepatopancreatic brush border membrane vesicles of a marine shrimp.

    PubMed

    Obi, Ijeoma E; Sterling, Kenneth M; Ahearn, Gregory A

    2013-01-01

    The effects of sodium, potassium, sugar inhibitors, and membrane potential on ³H-D-glucose uptake by hepatopancreatic epithelial brush border membrane vesicles (BBMV) of the Atlantic marine shrimp, Litopenaeus setiferus, were investigated. Brush border membrane vesicles were prepared using a MgCl₂/EGTA precipitation method and uptake experiments were conducted using a high speed filtration technique. ³H-D-Glucose uptake was stimulated by both sodium and potassium and these transport rates were almost doubled in the presence of an inside-negative-induced membrane potential. Kinetics of ³H-D-glucose influx were hyperbolic functions of both external Na⁺ or K⁺, and an induced membrane potential increased influx J(max) and lowered K(m) in both salts. ³H-D-Glucose influx versus [glucose] in both Na⁺ or K⁺ media also displayed Michaelis-Menten properties that were only slightly affected by induced membrane potential. Phloridzin was a poor inhibitor of 0.5 mM ³H-D-glucose influx, requiring at least 5 mM in NaCl and 10 mM in KCl to significantly reduce hexose transport. Several sugars (D-galactose, α-methyl-D-gluco-pyranoside, unlabeled D-glucose, D-fructose, and D-mannose) were used at 75 mM as potential inhibitors of 0.1 mM ³H-D-glucose influx. Only unlabeled D-glucose, D-fructose, and D-mannose significantly (p < 0.05) reduced labeled glucose transport. An additional experiment using increasing concentrations of D-mannose (0, 10, 25, 75, and 100 mM) showed this hexose to be an effective inhibitor of 0.1 mM ³H-D-glucose uptake at concentrations of 75 mM and higher. As a whole these results suggest that ³H-D-glucose transport by hepatopancreatic BBMV occurs by a carrier system that is able to use both Na⁺ and K⁺ as drivers, is enhanced by membrane potential, is relatively refractory to phloridzin, and is only inhibited by itself, D-fructose, and D-mannose. These properties are similar to those exhibited by the mammalian SLC5A9/SGLT4 transporter

  20. Molecular size of the Na+-H+ antiport in renal brush border membranes, as estimated by radiation inactivation

    SciTech Connect

    Beliveau, R.; Demeule, M.; Potier, M.

    1988-04-15

    The radiation inactivation method was applied to brush border membrane vesicles from rat kidney, in order to estimate the molecular size of the Na+-H+ antiporter. Sodium influx (1mM) driven by an acid intravesicular pH was unaffected by the high osmolarity of the cryoprotective solution. Initial rate of influx was estimated by linear regression performed on the first 10 seconds of transport: 0.512 pmol/micrograms protein/s. There was no binding component involved. Incubation performed in the presence of 1 mM amiloride, an inhibitor of the Na+-H+ antiport gave an initial rate of only 0.071 pmol/microgram/s, an 82% inhibition. Membrane vesicles were irradiated at -78 degrees C in a Gammacel Model 220. Sodium influx was reduced, as the dose of radiation increased, but the influx remained linear for the period of time (10s) during which the initial rate was estimated, indicating no alteration of the proton driving force during this time period. Amiloride-insensitive flux remained totally unaffected by the radiation dose, indicating that the passive permeability of the membrane towards sodium was unaffected. The amiloride-sensitive pathway presented a monoexponential profile of inactivation, allowing the molecular size to be estimated at 321 kDa. Based on DCCD-binding studies suggesting the molecular size of the monomer to be around 65 kDa for rat kidney, our results suggest that the functional transporter in the membrane to be a multimer.

  1. Binding of E. coli heat-stable enterotoxin to rat intestinal brush borders and to basolateral membranes

    SciTech Connect

    Guarino, A.; Cohen, M.B.; Overmann, G.; Thompson, M.R.; Giannella, R.A.

    1987-09-01

    We studied the binding of E. coli heat-stable enterotoxin (STa) to rat brush borders (BB) and to basolateral membranes (BLM) using a biologically active monoiodinated radioligand (( /sup 125/I)STa) and highly enriched BB and BLM preparations free of other significant organelle contamination. Binding of (/sup 125/I)STa to BB was specific; time-, temperature-, and pH-dependent; saturable; and partially reversible. Nonlabeled toxin competitively inhibited the binding of radioligand to BB in a dose-related manner. Scatchard analysis revealed a single class of receptors with an apparent affinity constant of 8.7 +/- 1.5 X 10(8) l/mol. Binding was not affected by amino acids, sugars, and lectins. Proteolytic enzymes significantly decreased binding, although several did so by modifying the radioligand. Trypsin inhibited binding without modifying the radioligand thus supporting the proteinaceous nature of the receptor. Since the enrichment in binding activity in the BB over the homogenate was significantly lower than the enrichment in sucrase activity, we concluded that binding activity is probably associated with other membranous domains, but direct examination revealed no binding activity on basolateral membranes.

  2. Na+-coupled D-glucose uptake and membrane order of enterocyte brush border membrane vesicles, under the effect of a series of N-phenylcarbamates.

    PubMed

    Fernandez, Y; Boigegrain, R A; Cambon-Gros, C; Deltour, P; Mitjavila, S

    1986-05-26

    The importance of the hydrophobic effect of exogenous substances and of modifications of membrane order on D-glucose uptake are still poorly defined. Our results show that the concentrative Na+ -coupled D-glucose uptake of rat enterocyte brush border membrane vesicles is inhibited by N-phenylcarbamates increase the membrane order. However, since the concentrations required for membrane order increase are much greater than those active on D-glucose uptake, the effects on lipid order cannot be responsible for the inhibition of D-glucose uptake. Measurements of D-glucose uptake under conditions of Na+ equilibrium show that these carbamates do not act directly on the carrier but indirectly by favouring the dissipation of the Na+ gradient.

  3. Postnatal ontogeny of kinetics of porcine jejunal brush border membrane-bound alkaline phosphatase, aminopeptidase N and sucrase activities.

    PubMed

    Fan, Ming Z; Adeola, Olayiwola; Asem, Elikplimi K; King, Dale

    2002-07-01

    Our objectives were to determine postnatal changes in the maximal enzyme activity (V(max)) and enzyme affinity (K(m)) of jejunal mucosal membrane-bound alkaline phosphatase, aminopeptidase N and sucrase using a porcine model which may more closely resemble the human intestine. Jejunal brush border membrane was prepared by Mg(2+)-precipitation and differential centrifugation from pigs of suckling (8 days), weaning (28 days), post-weaning (35 days) and adult (70 days) stages. p-Nitrophenyl phosphate (0-8 mM), L-alanine-p-nitroanilide hydrochloride (0-28 mM) and sucrose (0-100 mM) were used in alkaline phosphatase, aminopeptidase N and sucrase kinetic measurements. V(max) of alkaline phosphatase was the lowest in the adult (4.27 micromol.mg(-1) protein.min(-1)), intermediate in the suckling (9.75 micromol.mg(-l) protein.min(-l)) and the highest in the weaning and post-weaning stage (12.83 and 10.40 micromol.mg(-l) protein.min(-l)). K(m) of alkaline phosphatase was high in the suckling and weaning stages (5.14 and 9.93 mM) and low in the adult (0.66 mM). V(max) of aminopeptidase N was low in the suckling (7.04 micromol.mg protein(-1).min(-1)) and high in the post-weaning stage (13.36 micromol.mg(-l) protein.min(-l)). K(m) of aminopeptidase N was the highest in the two weaning stages (2.96 and 3.39 mM), intermediate in the adult (2.33 mM) and the lowest in the suckling stage (1.66 mM). V(max) of sucrase increased from the suckling to the adult (0.48-1.30 micromol.mg(-l) protein.min(-l)). K(m) of sucrase ranged from 11.19 to 16.57 mM. There are dramatic postnatal developmental changes in both the maximal enzyme activity and enzyme affinity of jejunal brush border membrane-bound alkaline phosphatase, aminopeptidase N and sucrase in the pig.

  4. Binding and degradation of /sup 125/I-insulin by isolated rat renal brush border membranes: evidence for low affinity, high capacity insulin recognition sites

    SciTech Connect

    Meezan, E.; Pillion, D.J.; Elgavish, A.

    1988-10-01

    The kidney plays a major role in the handling of circulating insulin in the blood, primarily via reuptake of filtered insulin at the luminal brush border membrane. 125I-insulin associated with rat renal brush border membrane vesicles (BBV) in a time- and temperature-dependent manner accompanied by degradation of the hormone to trichloroacetic acid (TCA)-soluble fragments. Both association and degradation of 125I-insulin were linearly proportional to membrane protein concentration with virtually all of the degradative activity being membrane associated. Insulin, proinsulin and desoctapeptide insulin all inhibited the association and degradation of 125I-insulin by BBV, but these processes were not appreciably affected by the insulin-like growth factors IGF-I and IGF-II or by cytochrome c and lysozyme, low molecular weight, filterable, proteins, which are known to be reabsorbed in the renal tubules by luminal endocytosis. When the interaction of 125I-insulin with BBV was studied at various medium osmolarities (300-1100 mosM) to alter intravesicular space, association of the ligand with the vesicles was unaffected, but degradation of the ligand by the vesicles decreased progressively with increasing medium osmolarity. Therefore, association of 125I-insulin to BBV represented binding of the ligand to the membrane surface and not uptake of the hormone or its degradation products into the vesicles. Attempts to crosslink 125I-insulin to a high-affinity insulin receptor using the bifunctional reagent disuccinimidyl suberate revealed only trace amounts of an 125I-insulin-receptor complex in brush border membrane vesicles in contrast to intact renal tubules where this complex was readily observed. Both binding and degradation of 125I-insulin by brush border membranes did not reach saturation even at concentrations of insulin approaching 10(-5) M.

  5. Binding of Bacillus thuringiensis Cry1 Toxins to the Midgut Brush Border Membrane Vesicles of Chilo suppressalis (Lepidoptera: Pyralidae): Evidence of Shared Binding Sites

    PubMed Central

    Fiuza, L.; Nielsen-Leroux, C.; Goze, E.; Frutos, R.; Charles, J.

    1996-01-01

    Binding and competition among Cry1Aa, Cry1Ac, and Cry1Ba toxins were analyzed quantitatively in vitro by using (sup125)I-labeled activated toxins and brush border membrane vesicles isolated from Chilo suppressalis larval midguts. The three toxins bound specifically to the midgut brush border membrane vesicles. Direct binding experiments showed that Cry1Aa and Cry1Ba recognized a single class of binding sites with different affinities, whereas Cry1Aa recognized two classes of binding sites, one with a high affinity and a low concentration and the other with a lower affinity but higher concentration. Competition experiments showed that toxins Cry1Ac and Cry1Ba shared a binding site in the C. suppressalis midgut membranes and that this site was also the low-affinity binding site for Cry1Aa. PMID:16535306

  6. Brush border membrane binding properties of Bacillus thuringiensis Vip3A toxin to Heliothis virescens and Helicoverpa zea midguts.

    PubMed

    Lee, Mi Kyong; Miles, Paul; Chen, Jeng-Shong

    2006-01-27

    The binding properties of Vip3A, a new family of Bacillus thuringiensis insecticidal toxins, have been examined in the major cotton pests, Heliothis virescens and Helicoverpa zea. Vip3A bound specifically to brush border membrane vesicles (BBMV) prepared from both insect larval midguts. In order to examine the cross-resistance potential of Vip3A to the commercially available Cry1Ac and Cry2Ab2 toxins, the membrane binding site relationship among these toxins was investigated. Competition binding assays demonstrated that Vip3A does not inhibit the binding of either Cry1Ac or Cry2Ab2 and vice versa. BBMV protein blotting experiments showed that Vip3A does not bind to the known Cry1Ac receptors. These distinct binding properties and the unique protein sequence of Vip3A support its use as a novel insecticidal agent. This study indicates a very low cross-resistance potential between Vip3A and currently deployed Cry toxins and hence supports its use in an effective resistance management strategy in cotton.

  7. Indirect coupling of urate and p-aminohippurate transport to sodium in human brush-border membrane vesicles.

    PubMed

    Roch-Ramel, F; Guisan, B; Schild, L

    1996-01-01

    [14C]urate and p-[14C]aminohippurate (PAH) uptake by human brush-border membrane vesicles (BBMV) were measured in the presence of an inwardly oriented sodium gradient. No direct sodium cotransport was observed. Indirect [14C]urate coupling to sodium transport was demonstrated by cis-stimulation of [14C]urate with nicotinate or pyrazinoate (PZA) in the extravesicular medium but not by adding lactate, alpha-ketoglutarate, or beta-hydroxybutyrate. Indirect sodium coupling of [14C]PAH uptake was observed only when alpha-ketoglutarate was added to the extravesicular medium, a mechanism similar to that of basolateral membranes. The ability for PZA (and nicotinate) to cis-stimulate urate uptake was correlated with a high apparent affinity for the urate/anion exchanger. In urate-loaded vesicles, for identical medium concentrations, [14C]PZA uptake via the urateanion exchanger was 10 times higher than [14C]lactate uptake. Such high PZA affinity for the urate exchanger, working in parallel with PZA sodium cotransport can account for the stimulation of urate reabsorption by PZA in vivo.

  8. Effect of uranyl nitrate on enzymes of carbohydrate metabolism and brush border membrane in different kidney tissues.

    PubMed

    Banday, Anees A; Priyamvada, Shubha; Farooq, Neelam; Yusufi, Ahad Noor Khan; Khan, Farah

    2008-06-01

    Uranium, the heaviest of the naturally occurring elements is widely present as environmental contaminant from natural deposits, industrial emissions and most importantly from modern weapons. Histopathological examinations revealed that uranyl nitrate (UN) exposure caused severe damage to pars recta of renal proximal tubule. However, biochemical events involved in cellular response to renal injury are not completely elucidated. We hypothesized that UN exposure would severely damage kidney tissues and alter their metabolic functions. Rats were treated with a single nephrotoxic dose of UN (0.5mg/kg body weight) i.p. After 5d, effect of UN was studied on the activities of various enzymes of carbohydrate metabolism, brush border membrane (BBM) and oxidative stress in different kidney tissues. Activity of lactate dehydrogenase increased whereas activities of isocitrate, succinate and malate dehydrogenases, glucose-6-phosphatase and fructose-1,6-bisphosphatase significantly decreased by UN exposure. Activity of glucose-6-phosphate dehydrogenase decreased whereas that of NADP-malic enzyme increased. The activities of BBM enzymes were significantly lowered and after dissociation from BBM excreted in urine. Lipid peroxidation and the activities of superoxide dismutase and glutathione peroxidase increased whereas catalase activity decreased by UN. UN treatment caused specific alterations in the activities of metabolic and membrane enzymes and perturbed antioxidant defenses.

  9. Uptake and binding of /sup 125/I-calmodulin by isolated rat renal brush border membrane vesicles

    SciTech Connect

    Meezan, E.; Elgavish, A.; Wallace, R.W.

    1986-05-01

    The authors have investigated the interaction of /sup 125/I-calmodulin with isolated rat renal brush border membrane vesicles (BBV) using an experimental protocol which allows us to distinguish between ligand binding to the outside of the vesicles vs. uptake and possible binding to the vesicle interior. By examining the association of /sup 125/I-calmodulin with BBV as a function of medium osmolarity (300-1100 mosm) to alter intravesicular space, virtually all ligand interaction with BBV was found to represent uptake of intact /sup 125/I-calmodulin into the intravesicular space. Uptake appeared specific by the following criteria: (1) it was largely calcium dependent (2) it was inhibited in a dose dependent fashion by calmodulin and the homologous protein troponin C, but not by unrelated proteins (lysozyme, cytochrome C, insulin) (3) it was inhibited by known calmodulin antagonists (calmidazolium, mellitin, trifluoperazine). Calmodulin uptake may be followed by binding of /sup 125/I-calmodulin to intravesicular BBV proteins; calmodulin-binding proteins in BBV with molecular weights of 143K, 118K, 50K, 47.5K, 46.5K and 35K were identified by Western blotting techniques. The specific association of /sup 125/I-calmodulin with isolated BBV is of interest in regard to the possible role of this calcium regulatory protein in the protein reabsorptive and ion transport functions of this renal tubular membrane fraction.

  10. Inositol lipid signalling occurs in brush-border membranes during initiation of compensatory renal growth in the rat.

    PubMed

    Banfić, H; Vuica, M; Knotek, M; Moslavac, S; Divecha, N

    1993-10-15

    Using highly specific mass assays, concentrations of inositol lipids and 1,2-diacylglycerol (DAG) were determined in plasma membranes isolated from rat kidney cortex. Significantly higher concentrations of inositol lipids were determined in brush-border (BBM) than in basal-lateral (BLM) plasma membranes, although DAG concentrations were similar in both. After unilateral nephrectomy, a decrease in PtdIns(4,5)P2 and PtdIns4P, with a concomitant increase in DAG and translocation of protein kinase C (PKC), were observed in BBM but not in BLM isolated from the remaining kidney. On the other hand, stimulation of renal cortical slices with insulin-like growth factor II (IGF-II) or phenylephrine caused similar effects in BLM but not in BBM. Stimulation of phospholipase C activity with translocation of PKC only to BBM in one kidney was also induced by occlusion of blood flow through the contralateral kidney for 15 min. At 30 min after the occlusion was removed and reflow established, DAG concentration and the amount of PKC in BBM returned to control values. These results suggest that an early signal after unilateral nephrectomy is transmitted to cells through BBM and can be switched on and off by blood occlusion and reflow through the contralateral kidney, while hormonal signals caused by IGF-II and phenylephrine are transmitted to cells through BLM.

  11. Restoring effect of selenium on the molecular content, structure and fluidity of diabetic rat kidney brush border cell membrane.

    PubMed

    Gurbanov, Rafig; Bilgin, Mehmet; Severcan, Feride

    2016-04-01

    Diabetic kidney disease (DKD) is a dominant factor standing for kidney impairments during diabetes. In this study, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to disclose the diabetes-induced structural changes in the kidney and evaluate the effects of selenium on diabetes. The increase in the area of the olefinic band indicated increased amount of lipid peroxidation end products in diabetic kidney brush border cell membrane. Moreover, saturated lipid content of this cell membrane considerably diminished. DKD was found to disrupt lipid order and cause a decrease in membrane dynamics. However, the administration of selenium at low and medium doses was shown to improve these conditions by changing the lipid contents toward control values, restoring the ordered structure of the lipids and membrane dynamics. Curve-fitting and artificial neural network (ANN) analyses of secondary structures of proteins demonstrated a relative increase in α-helix and reduction in the β-sheet during diabetes in comparison to the control group, which were ameliorated following selenium treatment at low and medium doses. These findings were further confirmed by applying hierarchical cluster analysis (HCA) and principal component analysis (PCA). A clear separation of the experimental groups was obtained with high heterogeneity in the lipid and protein regions. These chemometric analyses showed that the low and medium doses of selenium-treated diabetic groups are successfully segregated from the diabetic group and clustered closer to the control. The study suggests that medium and, more predominantly, low-dose selenium treatment can be efficient in eliminating diabetes-induced structural alterations.

  12. Phosphohydrolase activity of the isolated, brush-border membrane of Hymenolepis diminuta (Cestoda) following sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis.

    PubMed

    Pappas, P W

    1980-12-01

    Following electrophoresis of isolated, brush-border membranes of Hymenolepis diminuta on SDS-polyacrylamide gels, three distinct areas of alpha-naphthyl phosphate (NP) hydrolysis were detected; these corresponded to proteins with molecular weights of 106,800, 172,700, and greater than 340,000 Daltons. Hydrolysis of NP was inhibited by adenosine triphosphate, adenosine;5'-monophosphate, p-nitrophenyl-phosphate, glucose-1-phosphate, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-diphosphate, molybdate, ethylenediaminetetraacetate (EDTA), and ethyleneglycol-bis-(beta-amino-ethyl)-N,N'-tetraacetate (EGTA), but not by fluoride. Inhibition of NP hydrolysis by EDTA was relieved in the presence of Mg++ or Ca++. Heating the isolated, brush-border membrane in the presence of SDS for 5 min at 95 C destroyed all enzymatic activity. These characteristics indicated that the enzyme(s) responsible for NP hydrolysis (following separation of membrane proteins by SDS-polyacrylamide gel electrophoresis) were the same enzymes responsible for the phosphohydrolase activity associated with intact and solubilized, brush-border membrane preparations of H. diminuta.

  13. Specific binding of activated Vip3Aa10 to Helicoverpa armigera brush border membrane vesicles results in pore formation.

    PubMed

    Liu, Jing-Guo; Yang, Ai-Zhen; Shen, Xiao-Hong; Hua, Bao-Guang; Shi, Guang-Lu

    2011-10-01

    Helicoverpa armigera is one of the most harmful pests in China. Although it had been successfully controlled by Cry1A toxins, some H. armigera populations are building up resistance to Cry1A toxins in the laboratory. Vip3A, secreted by Bacillus thuringiensis, is another potential toxin against H. armigera. Previous reports showed that activated Vip3A performs its function by inserting into the midgut brush border membrane vesicles (BBMV) of susceptible insects. To further investigate the binding of Vip3A to BBMV of H. armigera, the full-length Vip3Aa10 toxin expressed in Escherichia coli was digested by trypsin or midgut juice extract, respectively. Among the fragments of digested Vip3Aa10, only a 62kDa fragment (Vip3Aa10-T) exhibited binding to BBMV of H. armigera and has insecticidal activity. Moreover, this interaction was specific and was not affected by the presence of Cry1Ab toxin. Binding of Vip3Aa10-T to BBMV resulted in the formation of an ion channel. Unlike Cry1A toxins, Vip3Aa10-T was just slightly associated with lipid rafts of BBMV. These data suggest that although activated Vip3Aa10 specifically interacts with BBMV of H. armigera and forms an ion channel, the mode of action of it may be different from that of Cry1A toxins.

  14. Exploring the Midgut Transcriptome and Brush Border Membrane Vesicle Proteome of the Rice Stem Borer, Chilo suppressalis (Walker)

    PubMed Central

    Peng, Chuanhua; Wang, Xiaoping; Li, Fei; Lin, Yongjun

    2012-01-01

    The rice stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), is one of the most detrimental pests affecting rice crops. The use of Bacillus thuringiensis (Bt) toxins has been explored as a means to control this pest, but the potential for C. suppressalis to develop resistance to Bt toxins makes this approach problematic. Few C. suppressalis gene sequences are known, which makes in-depth study of gene function difficult. Herein, we sequenced the midgut transcriptome of the rice stem borer. In total, 37,040 contigs were obtained, with a mean size of 497 bp. As expected, the transcripts of C. suppressalis shared high similarity with arthropod genes. Gene ontology and KEGG analysis were used to classify the gene functions in C. suppressalis. Using the midgut transcriptome data, we conducted a proteome analysis to identify proteins expressed abundantly in the brush border membrane vesicles (BBMV). Of the 100 top abundant proteins that were excised and subjected to mass spectrometry analysis, 74 share high similarity with known proteins. Among these proteins, Western blot analysis showed that Aminopeptidase N and EH domain-containing protein have the binding activities with Bt-toxin Cry1Ac. These data provide invaluable information about the gene sequences of C. suppressalis and the proteins that bind with Cry1Ac. PMID:22666467

  15. Exploring the midgut transcriptome and brush border membrane vesicle proteome of the rice stem borer, Chilo suppressalis (Walker).

    PubMed

    Ma, Weihua; Zhang, Zan; Peng, Chuanhua; Wang, Xiaoping; Li, Fei; Lin, Yongjun

    2012-01-01

    The rice stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), is one of the most detrimental pests affecting rice crops. The use of Bacillus thuringiensis (Bt) toxins has been explored as a means to control this pest, but the potential for C. suppressalis to develop resistance to Bt toxins makes this approach problematic. Few C. suppressalis gene sequences are known, which makes in-depth study of gene function difficult. Herein, we sequenced the midgut transcriptome of the rice stem borer. In total, 37,040 contigs were obtained, with a mean size of 497 bp. As expected, the transcripts of C. suppressalis shared high similarity with arthropod genes. Gene ontology and KEGG analysis were used to classify the gene functions in C. suppressalis. Using the midgut transcriptome data, we conducted a proteome analysis to identify proteins expressed abundantly in the brush border membrane vesicles (BBMV). Of the 100 top abundant proteins that were excised and subjected to mass spectrometry analysis, 74 share high similarity with known proteins. Among these proteins, Western blot analysis showed that Aminopeptidase N and EH domain-containing protein have the binding activities with Bt-toxin Cry1Ac. These data provide invaluable information about the gene sequences of C. suppressalis and the proteins that bind with Cry1Ac.

  16. Binding of Escherichia coli heat-stable toxin and rise of guanylyl cyclase activity in the brush-border membranes of rabbit intestinal epithelial cells.

    PubMed

    Bhattacharya, J; Chakrabarti, M K

    1999-03-01

    The study examines the age-related differences in the density of Escherichia coli heat-stable enterotoxin (STa) receptors in the small intestine of rabbits. The number of STa receptors was found to be 1.7 x 10(12) in 14-day old rabbits compared to 2.4 x 10(9) in 14-week old rabbits per milligram brush-border membrane protein. The STa-induced guanylyl cyclase activity in the intestinal brush-border membranes was found to be stimulated by 6.2 folds over the basal enzyme activity in 14-day old rabbits, whereas in the 14-week old rabbits, it was 4 folds over the basal activity. Moreover, the enzyme activity remained lower in the adult rabbits compared to the younger ones. Autoradiographic analysis of sodium dodecyl sulphate polyacrylamide gel electrophoresis showed two STa-binding proteins of apparent molecular weights of 140 and 38 kDa in the intestinal brush-border membranes of rabbits.

  17. Functional roles of Na+ and H+ in SO2-4 transport by rabbit ileal brush border membrane vesicles.

    PubMed

    Ahearn, G A; Murer, H

    1984-01-01

    Sulphate uptake by rabbit ileal brush border membrane vesicles was stimulated by a transmembrane sodium gradient [( Na+]o greater than [Na+]i), but not by a similar potassium gradient. 35SO4(-2) influx ( JSO4 oi ) from outside (o) to inside (i) these vesicles was a hyperbolic function of [SO4-2]o and the affinity constant for anion transport was strongly influenced by [Na+]o (100 mM Na+, KSO4 t = 0.52 mM SO4 -2; 10 mM Na+, KSO4 t = 4.32 mM SO4-2). JSO4 oi was a sigmoidal function of [Na+]o at pH 7.4 for both low (0.2 M) and high (4.0 mM) [SO4-2]o. The Na+-dependency of JSO4 oi was examined at pH 6.0, 7.4, and 8.0 (same pH inside and outside). At pH 6.0 and 7.4 sigmoidal Na+-dependent JSO4 oi exhibited nonlinear Eadie-Hofstee plots indicative of a transport mechanism capable of binding a variable number of sodium ions over the [Na+]o range used. Hill plots of anion transport under these conditions displayed slopes near unity at low [Na+]o and slopes approximating 2.0 at higher cation concentrations. At pH 8.0, Na+-dependent JSO4 oi was hyperbolic and showed linear Eadie-Hofstee and Hill plots, the latter with a single slope near 1.0. When a H+ gradient was imposed across the vesicle wall (pHi = 8.0, pHo = 6.0), Na+-dependent JSO4 oi was hyperbolic and significantly increased at each [Na+]o over values observed using bilateral pH 8.0. In contrast, a H+ gradient oriented in the opposite direction (pHi = 6.0, pHo = 8.0) led to Na+-dependent JSO4 oi that was sigmoidal and significantly lower at each [Na+]o than values found using bilateral pH 6.0. Electrogenicity of JSO4 oi at pH 8.0 for both high and low [Na+]o was demonstrated by using a valinomycin-induced transmembrane electrical potential difference. At pH 6.0, electrogenic JSO4 oi occurred only at low [Na+]o (5 mM); anion transfer was electroneutral at 50 mM Na+. A model is proposed for proton regulation of sodium sulphate cotransport where flux stoichiometry is controlled by [H+]i and sodium binding affinity is

  18. Effect of dietary fatty acids on jejunal and ileal oleic acid uptake by rat brush border membrane vesicles.

    PubMed

    Prieto, R M; Stremmel, W; Sales, C; Tur, J A

    1996-04-18

    To test the effect of dietary fatty acids on fatty acid uptake, the influx kinetics of a representative long-chain fatty acid, 3H-oleic acid, in both the jejunum and ileum of rats has been studied using brush border membrane vesicles (BBMV). Animals were fed with semipurified diets containing 5 g fat/100 g diet, as corn oil (control group), safflower oil (unsaturated group) and coconut oil hydrogenated (saturated group). With increasing unbound oleate concentration in the medium, the three dietary groups showed saturable kinetics in both jejunal and ileal BBMV (controls: Vmax = 0.15 +/- 0.01 nmol x mg protein-1 x 5 min-1 and Km = 136 +/- 29.1 nmol for jejunum, and Vmax = 0.23 +/- 0.03 nmol x mg protein-1 x 5 min-1 and Km = 196 +/- 50.3 nmol for ileum; unsaturated: Vmax = 0.28 +/- 0.05 nmol x mg protein-1 x 5 min-1 and Km = 242.7 +/- 91.8 nmol for jejunum, and Vmax = 1.29 +/- 0.06 nmol x mg protein-1 x 5 min-1 and Km = 509.8 +/- 97.5 nmol for ileum; saturated: Vmax = 0.03 +/- 0.01 nmol x mg protein-1 x 5 min-1 and Km = 124.5 +/- 72.6 nmol for jejunum, and Vmax = 0.04 +/- 0.01 nmol x mg protein -1.5 min-1 and Km = 205.6 +/- 85.3 nmol for ileum). These results support the theory that feeding an isocaloric diet containing only unsaturated fatty acids enhanced oleic acid uptake, and feeding an isocaloric diet containing only saturated fatty acids decreased oleic acid uptake. The results obtained in the present work also show the adaptative ability of jejunum and ileum to the type of dietary fat.

  19. Angiotensin 2 directly increases rabbit renal brush-border membrane sodium transport: Presence of local signal transduction system

    SciTech Connect

    Morduchowicz, G.A.; Sheikh-Hamad, D.; Dwyer, B.E.; Stern, N.; Jo, O.D.; Yanagawa, N. )

    1991-05-01

    In the present study, the authors have examined the direct actions of angiotensin II (AII) in rabbit renal brush border membrane (BBM) where binding sites for AII exist. Addition of AII (10(-11)-10(-7) M) was found to stimulate 22Na+ uptake by the isolated BBM vesicles directly. All did not affect the Na(+)-dependent BBM glucose uptake, and the effect of AII on BBM 22Na+ uptake was inhibited by amiloride, suggesting the involvement of Na+/H+ exchange mechanism. BBM proton permeability as assessed by acridine orange quenching was not affected by AII, indicating the direct effect of AII on Na+/H+ antiport system. In search of the signal transduction mechanism, it was found that AII activated BBM phospholipase A2 (PLA) and that BBM contains a 42-kDa guanine nucleotide-binding regulatory protein (G-protein) that underwent pertussis toxin (PTX)-catalyzed ADP-ribosylation. Addition of GTP potentiated, while GDP-beta S or PTX abolished, the effects of AII on BBM PLA and 22Na+ uptake, suggesting the involvement of G-protein in AII's actions. On the other hand, inhibition of PLA by mepacrine prevented AII's effect on BBM 22Na+ uptake, and activation of PLA by mellitin or addition of arachidonic acid similarly enhanced BBM 22Na+ uptake, suggesting the role of PLA activation in mediating AII's effect on BBM 22Na+ uptake. In summary, results of the present study show a direct stimulatory effect of AII on BBM Na+/H+ antiport system, and suggest the presence of a local signal transduction system involving G-protein mediated PLA activation.

  20. Effect of fluoride on the intestinal epithelial cell brush border membrane

    SciTech Connect

    Rastogi, R.; Upreti, R.K.; Kidwai, A.M.

    1987-07-01

    Fluoride consumed by man and animals is chiefly absorbed in the intestine. Chronic fluoride exposure causes mottled teeth and osteosclerosis. Over-fluoridation (126 mM) of drinking water have been reported to cause nausea, vomiting and diarrhea. Furthermore, the effect of acute and low concentrations of fluoride on gastric secretion, ion transport and other disorders have also been studied. Fluoride also causes alterations in the permeability of membranes and membrane bound enzymes. The intestinal cell lining plays an important role in digestion and absorption. It automatically becomes the most exposed site of contact to fluoride following ingestion. Earlier study have shown significant alterations in the formation of lipid peroxides in rat intestine following oral administration of fluoride. The present study was undertaken to investigate the damage of rat intestinal epithelium in situ caused by relatively high and low fluoride concentrations.

  1. Heterogeneity of L-alanine transport systems in brush-border membrane vesicles from rat placenta during late gestation.

    PubMed Central

    Alonso-Torre, S R; Serrano, M A; Medina, J M; Alvarado, F

    1992-01-01

    The placental uptake of L-alanine was studied by using purified brush-border membrane vesicles from rat trophoblasts. Saturation curves were carried out at 37 degrees C in buffers containing 100 mM (zero-trans)-NaSCN, -NaCl, -KSCN, -KCl, or -N-methyl-D-glucamine gluconate. The uncorrected uptake results were fitted by non-linear regression analysis to an equation involving one diffusional component either one or two saturable Michaelian transport terms. In the presence of NaCl, two distinct L-alanine transport systems were distinguished, named respectively System 1 (S-1; Vm1 about 760 pmol/s per mg of protein; KT1 = 0.5 mM) and System 2 (S-2; Vm2 about 1700 pmol/s per mg; KT2 = 9 mM). In contrast, in the presence of K+ (KCl = KSCN) or in the absence of any alkali-metal ions (N-methyl-D-glucamine gluconate), only one saturable system was apparent, which we identify as S-2. When Na+ is present, S-1, but not S-2, appears to be rheogenic, since its maximal transport capacity significantly increases in the presence of an inside-negative membrane potential, created either by replacing Cl- with the permeant anion thiocyanate (NaSCN > NaCl) or by applying an appropriate K+ gradient and valinomycin. alpha-(Methylamino)isobutyrate (methyl-AIB) appears to be a substrate of S-1, but not of S-2. For reasons that remain to be explained, however, methyl-AIB inhibits S-2. We conclude that S-1 represents a truly Na(+)-dependent mechanism, where Na+ behaves as an obligatory activator, whereas S-2 cannot discriminate between Na+ and K+, although its activity is higher in the presence of alkali-metal ions than in their absence (Na+ = K+ > N-methyl-D-glucammonium ion). S-2 appears to be fully developed 2 days before birth, whereas S-1 undergoes a capacity-type activation between days 19.5 and 21.5 of gestation, i.e. its apparent Vmax. nearly doubles, whereas its KT remains constant. PMID:1445280

  2. Hepatocyte growth factor activates phosphoinositide 3-kinase C2 beta in renal brush-border plasma membranes.

    PubMed Central

    Crljen, Vladiana; Volinia, Stefano; Banfic, Hrvoje

    2002-01-01

    Upon stimulation of renal cortical slices with hepatocyte growth factor (HGF), inositol lipid metabolism was studied in basal-lateral plasma membranes (BLM) and brush-border plasma membranes (BBM). Whereas in BLM rapid increases in 1,2-diacylglycerol, PtdIns(3,4,5)P(3) and PtdIns(3,4)P(2) were observed, suggesting that in BLM HGF activates both phospholipase C (PLC) and phosphoinositide 3-kinase (PI3K), in BBM only HGF-induced transient accumulation of PtdIns3P was seen, which was temporarily delayed from signalling events in BLM and could be blocked by the PtdIns-specific-PLC inhibitor ET-18-OCH(3) and the calpain inhibitor calpeptin, suggesting that 3-kinase activation in BBM lies downstream of PLC activation in BLM and is a calpain-mediated event. Moreover, the increase in immunoprecipitable PI3K-C2 beta activity, which is sensitive to wortmannin (10 nM) and shows strong preference for PtdIns over PtdIns4P as a substrate, was observed only in BBM upon stimulation of renal cortical slices with HGF and could be mimicked by the Ca(2+) ionophore A23187 and blocked by the cell-penetrant Ca(2+) chelator BAPTA-AM [1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid tetrakis(acetoxymethyl ester)]. On Western blots PI3K-C2 beta revealed a single immunoreactive band of 180 kDa in BLM and BBM, while after stimulation with HGF a gel shift of 18 kDa was noticed only in BBM, suggesting that the observed enzyme activation is achieved by proteolysis. When BBM were subjected to short-term (15 min) exposure to mu-calpain, a similar gel shift together with an increase in PI3K-C2 beta activity was observed, when compared with the BBM harvested after HGF stimulation. The above-mentioned gel shift and increase in PI3K-C2 beta activity could be prevented by the calpain inhibitor calpeptin. The data presented in this report show that in renal cells there is a spatial separation of the inositol lipid signalling system between BLM and BBM, and that HGF causes activation of PLC and

  3. Isolation and characterization of rabbit kidney brush borders

    PubMed Central

    Quirk, S. J.; Robinson, G. B.

    1972-01-01

    1. Brush borders were isolated from rabbit kidney-cortex homogenates by rate-zonal centrifugation through a sucrose density gradient in a B-XIV zonal rotor, followed by differential centrifugation. 2. The method of preparation gave brush borders of high purity with a reasonable yield. The morphological appearance supported the evidence from enzymic and chemical investigations, that the brush borders were only slightly contaminated with endoplasmic reticulum, mitochondria, lysosomes and nuclei. 3. The molar ratio of cholesterol to phospholipid lay within the range found in other plasma membranes, but the carbohydrate content was double that found in liver plasma membranes. 4. Alkaline phosphatase, maltase, trehalase and aminopeptidase were major enzymic constituents of the brush borders, and had an approximately equal yield and enrichment, but none of these enzymes fulfilled the criteria for marker enzymes. 5. Mg2+-dependent and Na+,K+-dependent adenosine triphosphatases, although found in brush borders, had low yields and low enrichments. ImagesPLATE 2PLATE 1 PMID:4264701

  4. Bacillus thuringiensis Cry1A toxin-binding glycoconjugates present on the brush border membrane and in the peritrophic membrane of the Douglas-fir tussock moth are peritrophins

    Treesearch

    Algimantas P. Valaitis; John D. Podgwaite

    2013-01-01

    Bacillus thuringiensis (Bt) Cry1A toxin-binding sites in the Douglas fir tussock moth (DFTM) larval gut were localized using immunofluorescence microscopy. Cry1Aa, Cry1Ab and Cry1Ac all bound strongly to the DFTM peritrophic membrane (PM); weaker binding of the Cry1A toxins was observed along the apical brush border of the midgut epithelium....

  5. Modulatory effect of thyroid hormones on uptake of phosphate and other solutes across luminal brush border membrane of kidney cortex

    SciTech Connect

    Yusufi, A.N.; Murayama, N.; Keller, M.J.; Dousa, T.P.

    1985-06-01

    The mechanism whereby thyroid hormones modulate the transport properties of luminal brush border membrane (BBM) of renal proximal tubules was studied in thyroparathyroidectomized rats. Administration of both T4 and T3 increased BBM capacity for Na/sup +/ gradient-dependent uptake of phosphate (P /sub i/) by BBM vesicles (BBMV). This effect of thyroid hormones was present in thyroparathyroidectomized and hypophysectomized rats, and it was not blocked by a saturating dose of propranolol. The stimulatory effect of T3 and T4 on BBM transport of P /sub i/ was dose dependent in the range of 5.2-520 nmol/100 g BW. Pretreatment of rats with inhibitors of 5'-monodeiodinase (5'-DI), iopanoic acid or ipodate, prevented the increase in serum T3 in rats injected with T4, but it did not diminish the increase in BBM transport of P /sub i/. Administration of iopanoic acid and ipodate also prevented a 5-fold increase in 5'-DI activity in renal cortical tissue elicited by T4 administration. Treatment with T3 resulted in an increase of Pi transport across BBM from kidneys of rats subjected to dietary P /sub i/ deprivation due either to total fasting or to feeding of a low P /sub i/ diet. Further, T3 administration enhanced amiloride-sensitive Na+-H+ countertransport across BBM, but the uptake of /sup 22/Na+ by BBMV in the absence of pH gradient was not changed. The Na+ gradient-dependent uptake of L-(/sup 3/H)proline by BBMV was slightly decreased, but the uptake of (/sup 14/C)citrate was not changed in response to T3. Administration of T3 increased P /sub i/ transport in BBMV prepared from juxtamedullary cortex, but not in BBMV from superficial cortex. Conversely, the rate of Na+-H+ countertransport was enhanced, and the enzymatic activity of alkaline phosphatase was decreased in BBMV from superficial cortex; no changes in these parameters were found in BBMV from juxtamedullary cortex.

  6. [Effect of natural or synthetic detergents on the transport of D-glucose in the membranes of vesicles of the brush border of the intestine of the rabbit].

    PubMed

    Favilli, F; Iantomasi, T; Stio, M; Treves, C; Vanni, P; Vincenzini, M T

    1988-01-01

    We describe here the effects of natural and synthetic detergents on the D-glucose transport into brush-border membranes of vesicles of rabbit's intestine. Two synthetic detergents: Triton X-100 and dodecyltrimethylammonium bromide have been found very strong inhibitors (more than 50 p. 100 of inhibition of maximal D-glucose uptake). Kinetic studies showed that these detergents behaved as mixed type inhibitors. The Na+-dependent transport of amino acids (aspartic acid, lysine, phenylalanine) is only poorly affected by dodecyltrimethylammonium bromide, while Triton X-100 inhibits unspecifically all the transport studied.

  7. Staphylococcus aureus enterotoxins A- and B: binding to the enterocyte brush border and uptake by perturbation of the apical endocytic membrane traffic.

    PubMed

    Danielsen, E Michael; Hansen, Gert H; Karlsdóttir, Edda

    2013-04-01

    Enterotoxins of Staphylococcus aureus are among the most common causes of food poisoning. Acting as superantigens they intoxicate the organism by causing a massive uncontrolled T cell activation that ultimately may lead to toxic shock and death. In contrast to our detailed knowledge regarding their interaction with the immune system, little is known about how they penetrate the epithelial barrier to gain access to their targets. We therefore studied the uptake of two staphylococcal enterotoxins (SEs), SEA and SEB, using organ cultured porcine jejunal explants as model system. Attachment of both toxins to the villus surface was scarce and patchy compared with that of cholera toxin B (CTB). SEA and SEB also bound to microvillus membrane vesicles in vitro, but less efficiently than CTB, and the binding was sensitive to treatment with endoglycoceramidase II, indicating that a glycolipid, possibly digalactosylceramide, acts as cell surface receptor at the brush border. Both SEs partitioned poorly with detergent resistant membranes (DRMs) of the microvillus, suggesting a weak association with lipid raft microdomains. Where attachment occurred, cellular uptake of SEA and SEB was also observed. In enterocytes, constitutive apical endocytosis normally proceeds only to subapical early endosomes present in the actomyosin-rich "terminal web" region. But, like CTB, both SEA and SEB penetrated deep into the cytoplasm. In conclusion, the data show that after binding to the enterocyte brush border SEA and SEB perturb the apical membrane trafficking, enabling them to engage in transcytosis to reach their target cells in the subepithelial lamina propria.

  8. The transmembrane pH gradient drives uphill folate transport in rabbit jejunum. Direct evidence for folate/hydroxyl exchange in brush border membrane vesicles.

    PubMed Central

    Schron, C M; Washington, C; Blitzer, B L

    1985-01-01

    In rabbit jejunal, but not ileal brush border membrane vesicles, an outwardly directed OH- gradient (pH 7.7 inside, pH 5.5 outside) markedly stimulated the initial velocity of folate (0.1 microM) uptake compared with uptake in the absence of a pH gradient. Under pH gradient conditions, folate was transiently accumulated at a concentration four times that found at equilibrium (over-shoot), implying uphill transport of the vitamin. Equilibrium folate uptake was inversely proportional to medium osmolality, suggesting uptake into an osmotically sensitive space. pH gradient-stimulated folate uptake was markedly reduced by inhibitors of anion exchange (4,4'-diisothiocyano-2,2'-disulfonic acid stilbene; 4-acetamido-4-isothiocyanostilbene-2,2'-disulfonic acid; furosemide), and was saturable (folate Km = 0.19 +/- 0.02 microM; Vmax = 12.8 +/- 0.4 pmol X mg protein-1 X min-1). Imposition of an inside-positive electrical potential did not stimulate folate uptake, suggesting that stimulation by a pH gradient was not due to an induced electrical potential. In contrast, an inwardly directed Na+ or K+ gradient did not stimulate folate uptake. These findings provide evidence for a carrier on the jejunal brush border membrane that mediates folate/OH- exchange (or H+/folate co-transport), and are consonant with the known presence of an outwardly directed OH- gradient in vivo (brush border acid microclimate), an acidic pH optimum for intestinal folate uptake, and the primary role of the jejunum in folate absorption. PMID:4056063

  9. Cloning and characterization of mouse brush border myosin-I in adult and embryonic intestine.

    PubMed

    Skowron, J F; Mooseker, M S

    1999-02-15

    Brush border myosin-I is a class I myosin with calmodulin light chains that has been identified in several vertebrate species. In chicken, it is exclusively expressed in intestinal epithelial cells where it forms spirally arrayed bridges that tether the microvillar actin bundle to the membrane. To facilitate future knockout strategies, we have isolated mouse brush border myosin-I cDNA and genomic clones. The deduced primary structure of mouse brush border myosin-I is homologous to other known brush border myosins-I. Northern blot, immunoblot, and immunolocalization studies indicate that the intestine-specific and subcellular localization profile of mouse brush border myosin-I are comparable to that determined for other brush border myosins-I. Northern analysis during embryogenesis revealed a 3.9-kb transcript first detected in 15-day embryos. This is in marked contrast to chicken, where brush border myosin-I expression begins early in embryogenesis. In situ localization in 17-day embryos indicated that RNA expression is restricted to the intestine. Protein expression is first detected in 16-day embryos with decreasing levels observed in a proximal to distal fashion. Immunolocalization in embryonic intestine revealed that brush border myosin-I is evenly distributed on both apical and basolateral membrane domains. There is also pronounced localization to a supranuclear region, presumably the Golgi apparatus. This suggests that brush border myosin-I may be targeted to the plasma membrane on Golgi-derived vesicles rather than by direct targeting to microvillar actin cores.

  10. Specificity of Bacillus thuringiensis endotoxins is correlated with the presence of high-affinity binding sites in the brush border membrane of target insect midguts

    SciTech Connect

    Hofmann, C.; Vanderbruggen, H.; Hoefte, H.; Van Rie, J.; Jansens, S.; Van Mellaert, H. )

    1988-11-01

    Binding studies were performed with two {sup 125}I-labeled Bacillus thuringiensis {delta}-endotoxins on brush border membrane vesicles prepared from the larval midgut of the tobacco hornworm Manduca sexta or the cabbage butterfly Pieris brassicae. One {delta}-endotoxin, Bt2-protoxin, is a 130-kDa recombinant crystalline protein from B. thuringiensis subsp. berliner. It kills larvae of both insect species. The active Bt2-toxin is a 60-kDa proteolytic fragment of the Bt2-protoxin. It binds saturably and with high affinity to brush border membrane vesicles from the midgut of both species. The other {delta}-endotoxin, Bt4412-protoxin, is a 136-kDa crystalline protein from B. thuringiensis subsp. thuringiensis, which is highly toxic for P. brassicae, but not for M. sexta larvae. Bt4412-toxin, obtained after proteolytic activation of Bt4412-protoxin, shows high-affinity saturable binding to P. brassicae vesicles but not to M. sexta vesicles. The correlation between toxicity and specific binding is further strengthened by competition studies. Other B. thuringiensis {delta}-endotoxins active against M. sexta compete for binding of {sup 125}I-labeled Bt2-toxin to M. sexta vesicles, whereas toxins active against dipteran or coleopteran larvae do not compete. Bt2-toxin and Bt4412-toxin bind to different sites on P. brassicae vesicles.

  11. Osmotic water permeability of rat intestinal brush border membrane vesicles: involvement of aquaporin-7 and aquaporin-8 and effect of metal ions.

    PubMed

    Tritto, Simona; Gastaldi, Giulia; Zelenin, Sergey; Grazioli, Monica; Orsenigo, Maria Novella; Ventura, Ulderico; Laforenza, Umberto; Zelenina, Marina

    2007-12-01

    Water channels AQP7 and AQP8 may be involved in transcellular water movement in the small intestine. We show that both AQP7 and AQP8 mRNA are expressed in rat small intestine. Immunoblot and immunohistochemistry experiments demonstrate that AQP7 and AQP8 proteins are present in the apical brush border membrane of intestinal epithelial cells. We investigated the effect of several metals and pH on the osmotic water permeability (Pf) of brush border membrane vesicles (BBMVs) and of AQP7 and AQP8 expressed in a cell line. Hg2+, Cu2+, and Zn2+ caused a significant decrease in the BBMV Pf, whereas Ni2+ and Li+ had no effect. AQP8-transfected cells showed a reduction in Pf in the presence of Hg2+ and Cu2+, whereas AQP7-transfected cells were insensitive to all tested metals. The Pf of both BBMVs and cells transfected with AQP7 and AQP8 was not affected by pH changes within the physiological range, and the Pf of BBMVs alone was not affected by phlorizin or amiloride. Our results indicate that AQP7 and AQP8 may play a role in water movement via the apical domain of small intestine epithelial cells. AQP8 may contribute to the water-imbalance-related clinical symptoms apparent after ingestion of high doses of Hg2+ and Cu2+.

  12. Design of a Photoreactive Analogue of the Escherichia coli Heat-Stable Enterotoxin STIb: Use in Identifying Its Receptor on Rat Brush Border Membranes

    NASA Astrophysics Data System (ADS)

    Gariepy, Jean; Schoolnik, Gary K.

    1986-01-01

    The Escherichia coli heat-stable enterotoxin, STIb was prepared by solid-phase peptide synthesis and purified to homogeneity by high-pressure liquid chromatography. This analogue was iodinated and shown to bind specifically to rat intestinal membranes. The radiolabeled peptide was derivatized at the amino terminus with the photoreactive heterobifunctional crosslinking agent N-hydroxysuccinimidyl p-benzoylbenzoate. This photoreactive probe also exhibited binding specificity. It was mixed with rat intestinal brush border membranes and photolyzed in the presence or absence of excess unlabeled STIb. Polyacrylamide gel electrophoresis performed in the presence of sodium dodecyl sulfate and 2-mercaptoethanol indicated that the peptide probe was cross-linked specifically to two molecular species of 57 and 75 kDa. One or both of these molecules appear to constitute the enterotoxin receptor or to be in close proximity to it.

  13. A Tenebrio molitor GPI-anchored alkaline phosphatase is involved in binding of Bacillus thuringiensis Cry3Aa to brush border membrane vesicles.

    PubMed

    Zúñiga-Navarrete, Fernando; Gómez, Isabel; Peña, Guadalupe; Bravo, Alejandra; Soberón, Mario

    2013-03-01

    Bacillus thuringiensis Cry toxins recognizes their target cells in part by the binding to glycosyl-phosphatidyl-inositol (GPI) anchored proteins such as aminopeptidase-N (APN) or alkaline phosphatases (ALP). Treatment of Tenebrio molitor brush border membrane vesicles (BBMV) with phospholipase C that cleaves out GPI-anchored proteins from the membranes, showed that GPI-anchored proteins are involved in binding of Cry3Aa toxin to BBMV. A 68 kDa GPI-anchored ALP was shown to bind Cry3Aa by toxin overlay assays. The 68 kDa GPI-anchored ALP was preferentially expressed in early instar larvae in comparison to late instar larvae. Our work shows for the first time that GPI-anchored ALP is important for Cry3Aa binding to T. molitor BBMV suggesting that the mode of action of Cry toxins is conserved in different insect orders. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. Chronic and selective inhibition of basolateral membrane Na-K-ATPase uniquely regulates brush border membrane Na absorption in intestinal epithelial cells

    PubMed Central

    Manoharan, Palanikumar; Gayam, Swapna; Arthur, Subha; Palaniappan, Balasubramanian; Singh, Soudamani; Dick, Gregory M.

    2015-01-01

    Na-K-ATPase, an integral membrane protein in mammalian cells, is responsible for maintaining the favorable intracellular Na gradient necessary to promote Na-coupled solute cotransport processes [e.g., Na-glucose cotransport (SGLT1)]. Inhibition of brush border membrane (BBM) SGLT1 is, at least in part, due to the diminished Na-K-ATPase in villus cells from chronically inflamed rabbit intestine. The aim of the present study was to determine the effect of Na-K-ATPase inhibition on the two major BBM Na absorptive pathways, specifically Na-glucose cotransport and Na/H exchange (NHE), in intestinal epithelial (IEC-18) cells. Na-K-ATPase was inhibited using 1 mM ouabain or siRNA for Na-K-ATPase-α1 in IEC-18 cells. SGLT1 activity was determined as 3-O-methyl-d-[3H]glucose uptake. Na-K-ATPase activity was measured as the amount of inorganic phosphate released. Treatment with ouabain resulted in SGLT1 inhibition at 1 h but stimulation at 24 h. To further characterize this unexpected stimulation of SGLT1, siRNA silencing was utilized to inhibit Na-K-ATPase-α1. SGLT1 activity was significantly upregulated by Na-K-ATPase silencing, while NHE3 activity remained unaltered. Kinetics showed that the mechanism of stimulation of SGLT1 activity was secondary to an increase in affinity of the cotransporter for glucose without a change in the number of cotransporters. Molecular studies demonstrated that the mechanism of stimulation was not secondary to altered BBM SGLT1 protein levels. Chronic and direct silencing of basolateral Na-K-ATPase uniquely regulates BBM Na absorptive pathways in intestinal epithelial cells. Specifically, while BBM NHE3 is unaffected, SGLT1 is stimulated secondary to enhanced affinity of the cotransporter. PMID:25652450

  15. Na+-independent and nonstereospecific transport of 2-hydroxy 4-methylthiobutanoic acid by brush border membrane vesicles from chick small intestine.

    PubMed

    Brachet, P; Puigserver, A

    1989-01-01

    1. The transport of L- and DL-2-hydroxy 4-methylthiobutanoic acid (HMB), the methionine hydroxy analogue, by brush border membrane vesicles (BBMV) from chick small intestine was the sum of a saturable Michaelian component and a diffusive term. 2. Unlike that of L- and DL-MET, uptake was Na+-independent and electroneutral. 3. The inhibition of L-HMB transport by L-lactate, a structural analogue, and D-HMB as well, was of the competitive type. 4. Preloading of BBMV with D-HMB but not with L-lactate or L-MET trans-stimulated the influx of labelled L-HMB. 5. HMB uptake by rat and chick intestinal BBMV exhibited similar characteristics but the chick nonstereospecific transport system appeared to be unable to carry out L-lactate translocation.

  16. Fast sampling, rapid filtration apparatus: principal characteristics and validation from studies of D-glucose transport in human jejunal brush-border membrane vesicles.

    PubMed

    Berteloot, A; Malo, C; Breton, S; Brunette, M

    1991-06-01

    Kinetic data in (brush-border) membrane vesicles which rely on the validity of the initial rate assumption for their interpretation and depend on tracer flux studies using the rapid filtration technique for their experimental measurement have been limited to some extent by the absence of techniques that would allow for real-time data analysis. In this paper, we report on our successful design of a fast sampling, rapid filtration apparatus (FSRFA) which seems to fill up this technical gap since showing the following characteristics: (i) rapid injection (5 msec) and mixing (less than 100 msec) of small amounts of vesicles (10-40 microliters) with an incubation medium (0.2-1.0 ml); (ii) fast (20 to 80 msec depending on the sample volume) and multiple (up to 18 samples at a maximal rate of 4 sec) sampling of the uptake mixture followed by rapid quenching in the stop solution (approximately 5 msec) according to a predetermined time schedule (any time combination from 0.25 to 9999 sec); and (iii) fast, automated, and sampling-synchronized filtration and washings of the quenched uptake medium (only 15-20 sec are necessary for the first filtration followed by two washings and extra filtrations). As demonstrated using adult human jejunal brush-border membrane vesicles and Na(+)-D-glucose cotransport as models, the FSRFA accurately reproduces the manual aspects of the rapid filtration technique while allowing for very precise initial rate determinations. Moreover, the FSRFA has also been designed to provide as much versatility as possible and, in its present version, allows for a very precise control of the incubation temperature and also permits a few efflux protocols to be performed. Finally, its modular design, which separates the fast sampling unit from the rapid filtration device, should help in extending its use to fields other than transport measurement.

  17. Calcium and glucose uptake in rat small intestinal brush-border membrane vesicles. Modulation by exogenous hypercortisolism and 1,25-dihydroxyvitamin D-3.

    PubMed

    Braun, H J; Birkenhäger, J C; De Jonge, H R

    1984-07-11

    The effect of exogenous hypercortisolism and 1,25-dihydroxyvitamin D-3 on small-intestinal calcium and glucose transport in the rat was studied at the level of brush-border membrane vesicles generated from isolated villous cells by a freeze-thaw procedure. At 5 X 10(-5) M extravesicular calcium, initial uptake rates in vesicles prepared from triamcinolone-treated adult rats were decreased by 30% after 5 days. Since calcium ionophore A23187 virtually abolished the difference in calcium uptake, triamcinolone appeared to affect calcium channel density or activity rather than intravesicular binding capacity. Kinetic analysis showed that a decrease in Vmax of a saturable calcium transport system could entirely account for the diminished rate of vesicular calcium uptake. Calcium transport rates could be partially restored by in vivo administration of 1,25-dihydroxyvitamin D-3 at a dosage which did not affect vesicular calcium uptake in control animals. Conversely, sodium-driven glucose accumulation in brush-border vesicles from triamcinolone-treated rats was stimulated by 50-70% after 36 h and appeared insensitive to vitamin D. A specific triamcinolone action on the glucose carrier itself rather than on the driving force of the sodium gradient was indicated by (i) a similar stimulation of glucose transport under equilibrium exchange conditions and (ii) an opposite effect of triamcinolone on sodium-driven alanine transport. The triamcinolone-induced changes in calcium and glucose uptake were not accompanied by a gross alteration of membrane integrity in vitro or by major alterations in vesicular protein composition, intravesicular glucose space and sucrase or alkaline phosphatase activity. The modification of vesicular transport properties is discussed in relation to the vitamin D-antagonized inhibition of intestinal calcium uptake and the stimulation of glucose absorption in response to supraphysiologic amounts of glucocorticoids observed in intact epithelium.

  18. Intestinal brush border assembly driven by protocadherin-based intermicrovillar adhesion

    PubMed Central

    Crawley, Scott W.; Shifrin, David A.; Grega-Larson, Nathan E.; McConnell, Russell E.; Benesh, Andrew E.; Mao, Suli; Zheng, Yuxi; Zheng, Qing Yin; Nam, Ki Taek; Millis, Bryan A.; Kachar, Bechara; Tyska, Matthew J.

    2014-01-01

    Transporting epithelial cells build apical microvilli to increase membrane surface area and enhance absorptive capacity. The intestinal brush border provides an elaborate example, with tightly packed microvilli that function in nutrient absorption and host defense. Although the brush border is essential for physiological homeostasis, its assembly is poorly understood. We found that brush border assembly is driven by the formation of Ca2+-dependent adhesion links between adjacent microvilli. Intermicrovillar links are composed of protocadherin-24 and mucin-like protocadherin, which target to microvillar tips and interact to form a trans heterophilic complex. The cytoplasmic domains of microvillar protocadherins interact with the scaffolding protein, harmonin, and myosin-7b, which promote localization to microvillar tips. Finally, a mouse model of Usher syndrome lacking harmonin exhibits microvillar protocadherin mislocalization and severe defects in brush border morphology. These data reveal an adhesion-based mechanism for brush border assembly and illuminate the basis of intestinal pathology in Usher syndrome patients. PMID:24725409

  19. Mechanism of cis- and trans-substrate interactions at the tetraethylammonium/H+ exchanger of rabbit renal brush-border membrane vesicles

    SciTech Connect

    Wright, S.H.; Wunz, T.M.

    1988-12-25

    The kinetic basis for trans-effects of intravesicular substrates on the uptake of the organic cation, tetraethylammonium (TEA), into rabbit renal brush-border membrane vesicles (BBMV) was studied. Preloading BBMV with 1, 2, or 4 mM TEA stimulated the initial rate of uptake and the total net accumulation of 0.1 mM (TH)TEA. The stimulatory effect of intravesicular TEA on the initial rate of uptake was a saturable function of the trans-TEA concentration, with a half-maximal effect noted at an intravesicular concentration of 0.28 mM. A 1 mM trans-concentration of TEA increased the Jmax of (TH)TEA uptake (from 4.3 to 6.8 nmol.mg-1.min-1) without affecting the apparent Kt. An outwardly directed H+ gradient also increased Jmax (to 10.7 nmol.mg-1.min-1), although the addition of an outwardly directed TEA gradient did not produce further increases in the rate of TEA uptake. External H+ acted as a competitive inhibitor of TEA uptake, and an increase in external (H+) (from 32 nM to 100 nM) produced an increase in the apparent Kt for TEA transport (from 0.12 to 0.26 mM) without affecting the Jmax. The results suggested that TEA and H+ compete for a common site or set of mutually exclusive sites on the cytoplasmic and luminal aspects of TEA/H+ exchanger in the renal brush border, and that these sites have a similar affinity for TEA.

  20. Contraction of isolated brush borders from the intestinal epithelium

    PubMed Central

    1976-01-01

    Brush borders isolated from epithelial cells from the small intestine of neonatal rats are able to contract in the presence of ATP and Mg2+; Ca2+ is not required. Contraction is characterized by a pinching-in of the plasma membrane in the region of the zonula adherens and a subsequent rounding of the brush borders. No movement or consistent shortening of the microvilli is observed. The contraction appears to involve the 5- to 7-nm diameter microfilaments in the terminal web which associate with the zonula adherens. These filaments bind heavy meromyosin as do the actin core filaments of the microvilli. A model for contraction is presented in which, in the intact cell, terminal web filaments and core filaments interact to produce shortening of the microvilli. PMID:783170

  1. Leucine transport is affected by Bacillus thuringiensis Cry1 toxins in brush border membrane vesicles from Ostrinia nubilalis Hb (Lepidoptera: Pyralidae) and Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae) midgut.

    PubMed

    Leonardi, M Giovanna; Caccia, Silvia; González-Cabrera, Joel; Ferré, Juan; Giordana, Barbara

    2006-01-01

    The pore-forming activity of Cry1Ab, Cry1Fa and Cry1Ca toxins and their interaction with leucine transport mediated by the K(+)/leucine cotransporter were studied in brush border membrane vesicles (BBMVs) isolated from the midgut of Ostrinia nubilalis and Sesamia nonagrioides. In both species, as in other Lepidoptera, leucine uptake by BBMVs can take place in the absence of cations, but it can also be driven by a K(+) gradient. Experiments with the voltage-sensitive fluorescent dye 3,3'-diethylthiacarbocyanine iodide proved that Cry1Ab, a Bacillus thuringiensis toxin active in vivo, enhanced the membrane permeability to potassium in O. nubilalis BBMVs. This result is in agreement with similar effects observed in S. nonagrioides BBMV incubated with various Cry1 toxins active in vivo. The effect of the above toxins was tested on the initial rate of 0.1 mM: leucine influx. Instead of an increase in leucine influx, a reduction was observed with the Cry1 toxins active in vivo. Cry1Ab and Cry1Fa, but not the inactive toxin Cry1Da, inhibited in a dose-dependent manner leucine uptake both in the absence and in the presence of a K(+) gradient, a clear indication that their effect is independent of the channel formed by the toxins and that this effect is exerted directly on the amino acid transport system.

  2. Effect of different non-steroidal anti-inflammatory drugs, aspirin, nimesulide and celecoxib on the disaccharide hydrolases and histoarchitecture of the rat intestinal brush border membrane.

    PubMed

    Sood, N; Kaushal, N; Sanyal, S N

    2008-01-01

    Non-steroidal anti-inflammatory drugs (NSAIDs) are known to cause gastrointestinal damage. New anti-inflammatory drugs have been developed in an attempt to improve their gastrointestinal side effect profile which however failed to do so. Therefore, the objective of the present study was to compare the effect of three different NSAIDs, aspirin, nimesulide and celecoxib on the intestinal brush border membrane (BBM) marker enzymes and correlate these alterations to the histoarchitecture of the intestine using electron microscopic study. Female Wistar rats were divided into four different groups viz: Group I (Control), Group II (aspirin treated), Group III (nimesulide treated) and Group IV (celecoxib treated). The Group II, III and IV received the corresponding drugs dissolved in water orally at a dose of 40 mg/kg body weight, while the control received the vehicle only. After 28 days, all the treatment groups demonstrated significant alterations in the activities of intestinal disaccharide hydrolases and alkaline phosphatase in both the crude homogenates and BBM preparations as well. The histopathological observations also showed considerable changes in the intestinal mucosa. It was suggested that NSAIDs like aspirin, nimesulide and celecoxib pose intestinal side effects due to initial changes in the enzymatic composition of the intestinal apical membranes. It was further concluded that newly discovered NSAIDs such as celecoxib has better safety profiles but studies are still required to comment decisively on the suitability of various NSAIDs depending upon their cyclooxygenase enzyme specificity.

  3. L-Carnitine transport in human placental brush-border membranes is mediated by the sodium-dependent organic cation transporter OCTN2.

    PubMed

    Lahjouji, Karim; Elimrani, Ihsan; Lafond, Julie; Leduc, Line; Qureshi, Ijaz A; Mitchell, Grant A

    2004-08-01

    Maternofetal transport of l-carnitine, a molecule that shuttles long-chain fatty acids to the mitochondria for oxidation, is thought to be important in preparing the fetus for its lipid-rich postnatal milk diet. Using brush-border membrane (BBM) vesicles from human term placentas, we showed that l-carnitine uptake was sodium and temperature dependent, showed high affinity for carnitine (apparent K(m) = 11.09 +/- 1.32 microM; V(max) = 41.75 +/- 0.94 pmol.mg protein(-1).min(-1)), and was unchanged over the pH range from 5.5 to 8.5. l-Carnitine uptake was inhibited in BBM vesicles by valproate, verapamil, tetraethylammonium, and pyrilamine and by structural analogs of l-carnitine, including d-carnitine, acetyl-d,l-carnitine, and propionyl-, butyryl-, octanoyl-, isovaleryl-, and palmitoyl-l-carnitine. Western blot analysis revealed that OCTN2, a high-affinity, Na(+)-dependent carnitine transporter, was present in placental BBM but not in isolated basal plasma membrane vesicles. The reported properties of OCTN2 resemble those observed for l-carnitine uptake in placental BBM vesicles, suggesting that OCTN2 may mediate most maternofetal carnitine transport in humans.

  4. Experimental type II diabetes and related models of impaired glucose metabolism differentially regulate glucose transporters at the proximal tubule brush border membrane.

    PubMed

    Chichger, Havovi; Cleasby, Mark E; Srai, Surjit K; Unwin, Robert J; Debnam, Edward S; Marks, Joanne

    2016-06-01

    What is the central question of this study? Although SGLT2 inhibitors represent a promising treatment for patients suffering from diabetic nephropathy, the influence of metabolic disruption on the expression and function of glucose transporters is largely unknown. What is the main finding and its importance? In vivo models of metabolic disruption (Goto-Kakizaki type II diabetic rat and junk-food diet) demonstrate increased expression of SGLT1, SGLT2 and GLUT2 in the proximal tubule brush border. In the type II diabetic model, this is accompanied by increased SGLT- and GLUT-mediated glucose uptake. A fasted model of metabolic disruption (high-fat diet) demonstrated increased GLUT2 expression only. The differential alterations of glucose transporters in response to varying metabolic stress offer insight into the therapeutic value of inhibitors. SGLT2 inhibitors are now in clinical use to reduce hyperglycaemia in type II diabetes. However, renal glucose reabsorption across the brush border membrane (BBM) is not completely understood in diabetes. Increased consumption of a Western diet is strongly linked to type II diabetes. This study aimed to investigate the adaptations that occur in renal glucose transporters in response to experimental models of diet-induced insulin resistance. The study used Goto-Kakizaki type II diabetic rats and normal rats rendered insulin resistant using junk-food or high-fat diets. Levels of protein kinase C-βI (PKC-βI), GLUT2, SGLT1 and SGLT2 were determined by Western blotting of purified renal BBM. GLUT- and SGLT-mediated d-[(3) H]glucose uptake by BBM vesicles was measured in the presence and absence of the SGLT inhibitor phlorizin. GLUT- and SGLT-mediated glucose transport was elevated in type II diabetic rats, accompanied by increased expression of GLUT2, its upstream regulator PKC-βI and SGLT1 protein. Junk-food and high-fat diet feeding also caused higher membrane expression of GLUT2 and its upstream regulator PKC

  5. Sodium chlorate, a major water disinfection byproduct, alters brush border membrane enzymes, carbohydrate metabolism and impairs antioxidant system of Wistar rat intestine.

    PubMed

    Ali, Shaikh Nisar; Ansari, Fariheen Aisha; Khan, Aijaz Ahmed; Mahmood, Riaz

    2017-05-01

    Sodium chlorate (NaClO3 ) is a widely used nonselective herbicide. It is also generated as a by-product during disinfection of drinking water by chlorine dioxide. The purpose of this study was to evaluate the effect of NaClO3 on rat intestine. Adult male rats were randomly divided into five groups: control and remaining four groups were administered orally different doses of NaClO3 and sacrificed 24 h after the treatment. The administration of NaClO3 produced acute oxidative stress in the intestine, which manifested in the form of markedly enhanced malondialdehyde levels and carbonyl content and lowered total sulfhydryl groups and glutathione levels. The activities of several brush border membrane (BBM) enzymes were greatly reduced as compared to control. There were alterations in the activities of various enzymes of carbohydrate metabolism and those involved in maintaining the antioxidant defense system. Histological studies support the biochemical results showing NaClO3 dose-dependent increase in tissue damage. Thus, the present study shows that oral administration of NaClO3 decreases the activities of BBM enzymes, induces oxidative stress, alters metabolic pathways, and impairs the antioxidant system of rat intestine. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1607-1616, 2017. © 2017 Wiley Periodicals, Inc.

  6. Influence of Ramadan-type fasting on carbohydrate metabolism, brush border membrane enzymes and phosphate transport in rat kidney used as a model.

    PubMed

    Salim, Samina; Farooq, Neelam; Priyamvada, Shubha; Asghar, Mohammad; Khundmiri, Syed Jalal; Khan, Samia; Khan, Farah; Yusufi, Ahad Noor Khan

    2007-11-01

    Ramadan fasting is a unique model of fasting in which Muslims the world over abstain from food and water from dawn to sunset for 1 month. We hypothesized that this model of prolonged intermittent fasting would result in specific adaptive alterations in rat kidney to keep a positive balance of metabolites and inorganic phosphate (Pi). The effect of Ramadan-type fasting was studied on enzymes of carbohydrate metabolism and brush border membrane (BBM) and BBM uptake of 32Pi in different renal tissue zones in the rat model. Rats were fasted (12 h) and then re-fed (12 h) daily for 30 d similar to human Ramadan fasting. Ramadan-type fasting resulted in increased serum Pi and phospholipids, whereas Pi clearance decreased. Serum creatinine and its clearance were not affected. Fasting caused a significant decrease in the activities of lactate and malate dehydrogenases, glucose-6-phosphatase and fructose-1,6-bisphosphatase, both in the renal cortex and medulla. However, the activity of glucose-6-phosphate dehydrogenase profoundly increased but that of malic enzyme decreased. The activities of alkaline phosphatase and gamma-glutamyl transpeptidase in BBM decreased, whereas transport of 32Pi significantly increased. The decrease in enzyme activities and increase in 32Pi transport were due to alterations of both maximal velocities and relative affinities. The results indicate that Ramadan-type fasting caused specific metabolic alterations with enhanced Pi conservation in different kidney tissues in a rat model used for Ramadan fasting in man.

  7. Polymer Brushes for Membrane Separations: A Review.

    PubMed

    Keating, John Joseph; Imbrogno, Joseph; Belfort, Georges

    2016-10-06

    The fundamentals and applications of polymer brush modified membranes are reviewed. This new class of synthetic membranes is explored with an emphasis on tuning the membrane performance through polymer brush grafting. This work highlights the intriguing performance characteristics of polymer brush modified membranes in a variety of separations. Polymer brushes are a versatile and effective means in designing membranes for applications in protein adsorption and purification, colloid stabilization, sensors, water purification, pervaporation of organic compounds, gas separations, and as stimuli responsive materials.

  8. Endocytic trafficking from the small intestinal brush border probed with FM dye.

    PubMed

    Hansen, Gert H; Rasmussen, Karina; Niels-Christiansen, Lise-Lotte; Danielsen, E Michael

    2009-10-01

    The small intestinal brush border functions as the body's main portal for uptake of dietary nutrients and simultaneously acts as the largest permeability barrier against pathogens. To enable this, the digestive enzymes of the brush border are organized in lipid raft microdomains stabilized by cross-linking galectins and intelectin, but little is known about the dynamic properties of this highly specialized membrane. Here, we probed the endocytic membrane trafficking from the brush border of organ-cultured pig intestinal mucosal explants by use of a fixable, lipophilic FM dye. The fluorescent dye readily incorporated into the brush border, and by 15 min faint but distinct punctae were detectable approximately 1 microm beneath the brush border, indicative of a constitutive endocytosis. The punctae represented a subpopulation of early endosomes confined to the actomyosin-rich terminal web region, and their number and intensity increased by 1 h, but trafficking further into the enterocyte was not observed except in immature epithelial cells of the crypts. A powerful ligand for receptor-mediated endocytosis, cholera toxin B subunit, increased apical endocytosis and caused membrane trafficking to proceed to compartments localized deeper into the cytoplasm of the enterocytes. Two major raft-associated brush border enzymes, alkaline phosphatase and aminopeptidase N, were excluded from endocytosis. We propose that the terminal web cytoskeleton, by inhibiting traffic from apical early endosomes further into the cell, contributes to the overall permeability barrier of the gut.

  9. Correction of enhanced Na(+)-H+ exchange of rat small intestinal brush-border membranes in streptozotocin-induced diabetes by insulin or 1,25-dihydroxycholecalciferol

    SciTech Connect

    Dudeja, P.K.; Wali, R.K.; Klitzke, A.; Sitrin, M.D.; Brasitus, T.A. )

    1991-05-01

    Diabetes was induced in rats by administration of a single i.p. injection of streptozotocin (50 mg/kg body wt). After 7 d, diabetic rats were further treated with insulin or 1,25-dihydroxycholecalciferol (1,25(OH)2D3) for an additional 5-7 d. Control, diabetic, diabetic + insulin, and diabetic + 1,25(OH)2D3 rats were then killed, their proximal small intestines were removed, and villus-tip epithelial cells were isolated and used to prepare brush-border membrane vesicles. Preparations from each of these groups were then analyzed and compared with respect to their amiloride-sensitive, electroneutral Na(+)-H+ exchange activity, using {sup 22}Na uptake as well as acridine orange techniques. The results of these experiments demonstrated that (a) H+ gradient-dependent {sup 22}Na uptake as well as Na+ gradient-dependent transmembrane H+ fluxes were significantly increased in diabetic vesicles compared to their control counterparts, (b) kinetic studies demonstrated that this enhanced {sup 22}Na uptake in diabetes was a result of increased maximal velocity (Vmax) of this exchanger with no change in apparent affinity (Km) for Na+, (c) serum levels of 1,25(OH)2D3 were significantly lower in diabetic animals compared with their control counterparts; and (d) insulin or 1,25(OH)2D3 treatment restored the Vmax alterations to control values, without any significant changes in Km, concomitant with significantly increasing the serum levels of 1,25(OH)2D3 in diabetic animals. These results indicate that Na(+)-H+ activity is significantly increased in proximal small intestinal luminal membranes of streptozotocin-induced diabetic rats. Moreover, alterations in the serum levels of 1,25(OH)2D3 may, at least in part, explain this enhanced antiporter activity and its correction by insulin.

  10. Domain III of the Bacillus thuringiensis delta-endotoxin Cry1Ac is involved in binding to Manduca sexta brush border membranes and to its purified aminopeptidase N.

    PubMed

    de Maagd, R A; Bakker, P L; Masson, L; Adang, M J; Sangadala, S; Stiekema, W; Bosch, D

    1999-01-01

    Three types of binding assays were used to study the binding of Bacillus thuringiensis delta-endotoxin Cry1Ac to brush border membrane vesicle (BBMV) membranes and a purified putative receptor of the target insect Manduca sexta. Using hybrid proteins consisting of Cry1Ac and the related Cry1C protein, it was shown that domain III of Cry1Ac is involved in specificity of binding as observed by all three techniques. In ligand blotting experiments using SDS-PAGE-separated BBMV proteins as well as the purified putative receptor aminopeptidase N (APN), the presence of domain III of Cry1Ac in a hybrid with Cry1C was necessary and sufficient for specific binding to APN. Using the surface plasmon resonance (SPR) technique with immobilized APN, it was shown that the presence of domain III of Cry1Ac in a hybrid is sufficient for binding to one of the two previously identified Cry1Ac binding sites, whereas the second site requires the full Cry1Ac toxin for binding. In addition, the role of domain III in the very specific inhibition of Cry1Ac binding by the amino sugar N-acetylgalactosamine (GalNac) was determined. Both in ligand blotting and in surface plasmon resonance experiments, as well as in binding assays using intact BBMVs, it was shown that the presence of domain III of Cry1Ac in a toxin molecule is sufficient for the inhibition of binding by GalNAc. These and other results strongly suggest that domain III of delta-endotoxins play a role in insect specificity through their involvement in specific binding to insect gut epithelial receptors.

  11. Aminopeptidase N purified from gypsy moth brush border membrane vesicles is a specific receptor for Bacillus thuringiensis CryIAc toxin.

    PubMed Central

    Lee, M K; You, T H; Young, B A; Cotrill, J A; Valaitis, A P; Dean, D H

    1996-01-01

    We have evaluated the binding of Bacillus thuringiensis Cry toxins to aminopeptidase N (APN) purified from Lymantria dispar (gypsy moth) brush border membrane vesicle (BBMV). CryIAc toxin bound strongly to APN, while either the structurally related CryIAa and CryIAb toxins or CryIC, CryIIA, and CryIIIA toxins showed weak binding to APN. An in vitro competition binding study demonstrated that the binding of CryIAc to L. dispar BBMV was inhibited by APN. Inhibition of short circuit current for CryIAc, measured by voltage clamping of whole L. dispar midgut, was substantially reduced by addition of phosphatidylinositol-specific phospholipase C, which is known to release APN from the midgut membrane. In contrast, addition of phosphatidylinositol-specific phospholipase C had only a marginal effect on the inhibition of short circuit current for CryIAa. These data suggest that APN is the major functional receptor for CryIAc in L. dispar BBMV. A ligand blotting experiment demonstrated that CryIAc recognized a 120-kDa peptide (APN), while CryIAa and CryIAb recognized a 210-kDa molecule in L. dispar BBMV. In contrast, CryIAa and CryIAb bound to both the 120- and 210-kDa molecules in Manduca sexta BBMV, while CryIAc recognized only the 120-kDa peptide. The 120-kDa peptide (APN) in L. dispar BBMV reacted with soybean agglutinin, indicating that N-acetylgalactosamine is a component of this glycoprotein. PMID:8702277

  12. Correction of enhanced Na(+)-H+ exchange of rat small intestinal brush-border membranes in streptozotocin-induced diabetes by insulin or 1,25-dihydroxycholecalciferol.

    PubMed Central

    Dudeja, P K; Wali, R K; Klitzke, A; Sitrin, M D; Brasitus, T A

    1991-01-01

    Diabetes was induced in rats by administration of a single i.p. injection of streptozotocin (50 mg/kg body wt). After 7 d, diabetic rats were further treated with insulin or 1,25-dihydroxycholecalciferol [1,25(OH)2D3] for an additional 5-7 d. Control, diabetic, diabetic + insulin, and diabetic + 1,25(OH)2D3 rats were then killed, their proximal small intestines were removed, and villus-tip epithelial cells were isolated and used to prepare brush-border membrane vesicles. Preparations from each of these groups were then analyzed and compared with respect to their amiloride-sensitive, electroneutral Na(+)-H+ exchange activity, using 22Na uptake as well as acridine orange techniques. The results of these experiments demonstrated that (a) H+ gradient-dependent 22Na uptake as well as Na+ gradient-dependent transmembrane H+ fluxes were significantly increased in diabetic vesicles compared to their control counterparts, (b) kinetic studies demonstrated that this enhanced 22Na uptake in diabetes was a result of increased maximal velocity (Vmax) of this exchanger with no change in apparent affinity (Km) for Na+, (c) serum levels of 1,25(OH)2D3 were significantly lower in diabetic animals compared with their control counterparts; and (d) insulin or 1,25(OH)2D3 treatment restored the Vmax alterations to control values, without any significant changes in Km, concomitant with significantly increasing the serum levels of 1,25(OH)2D3 in diabetic animals. These results indicate that Na(+)-H+ activity is significantly increased in proximal small intestinal luminal membranes of streptozotocin-induced diabetic rats. Moreover, alterations in the serum levels of 1,25(OH)2D3 may, at least in part, explain this enhanced antiporter activity and its correction by insulin. PMID:1850761

  13. Correction of enhanced Na(+)-H+ exchange of rat small intestinal brush-border membranes in streptozotocin-induced diabetes by insulin or 1,25-dihydroxycholecalciferol.

    PubMed

    Dudeja, P K; Wali, R K; Klitzke, A; Sitrin, M D; Brasitus, T A

    1991-05-01

    Diabetes was induced in rats by administration of a single i.p. injection of streptozotocin (50 mg/kg body wt). After 7 d, diabetic rats were further treated with insulin or 1,25-dihydroxycholecalciferol [1,25(OH)2D3] for an additional 5-7 d. Control, diabetic, diabetic + insulin, and diabetic + 1,25(OH)2D3 rats were then killed, their proximal small intestines were removed, and villus-tip epithelial cells were isolated and used to prepare brush-border membrane vesicles. Preparations from each of these groups were then analyzed and compared with respect to their amiloride-sensitive, electroneutral Na(+)-H+ exchange activity, using 22Na uptake as well as acridine orange techniques. The results of these experiments demonstrated that (a) H+ gradient-dependent 22Na uptake as well as Na+ gradient-dependent transmembrane H+ fluxes were significantly increased in diabetic vesicles compared to their control counterparts, (b) kinetic studies demonstrated that this enhanced 22Na uptake in diabetes was a result of increased maximal velocity (Vmax) of this exchanger with no change in apparent affinity (Km) for Na+, (c) serum levels of 1,25(OH)2D3 were significantly lower in diabetic animals compared with their control counterparts; and (d) insulin or 1,25(OH)2D3 treatment restored the Vmax alterations to control values, without any significant changes in Km, concomitant with significantly increasing the serum levels of 1,25(OH)2D3 in diabetic animals. These results indicate that Na(+)-H+ activity is significantly increased in proximal small intestinal luminal membranes of streptozotocin-induced diabetic rats. Moreover, alterations in the serum levels of 1,25(OH)2D3 may, at least in part, explain this enhanced antiporter activity and its correction by insulin.

  14. Functional Regulation of Sugar Assimilation by N-Glycan-specific Interaction of Pancreatic α-Amylase with Glycoproteins of Duodenal Brush Border Membrane*

    PubMed Central

    Asanuma-Date, Kimie; Hirano, Yuki; Le, Na; Sano, Kotone; Kawasaki, Nana; Hashii, Noritaka; Hiruta, Yoko; Nakayama, Ken-ichi; Umemura, Mariko; Ishikawa, Kazuhiko; Sakagami, Hiromi; Ogawa, Haruko

    2012-01-01

    Porcine pancreatic α-amylase (PPA) binds to N-linked glycans of glycoproteins (Matsushita, H., Takenaka, M., and Ogawa, H. (2002) J. Biol Chem., 277, 4680–4686). Immunostaining revealed that PPA is located at the brush-border membrane (BBM) of enterocytes in the duodenum and that the binding is inhibited by mannan but not galactan, indicating that PPA binds carbohydrate-specifically to BBM. The ligands for PPA in BBM were identified as glycoprotein N-glycans that are significantly involved in the assimilation of glucose, including sucrase-isomaltase (SI) and Na+/Glc cotransporter 1 (SGLT1). Binding of SI and SGLT1 in BBM to PPA was dose-dependent and inhibited by mannan. Using BBM vesicles, we found functional changes in PPA and its ligands in BBM due to the N-glycan-specific interaction. The starch-degrading activity of PPA and maltose-degrading activity of SI were enhanced to 240 and 175%, respectively, while Glc uptake by SGLT1 was markedly inhibited by PPA at high but physiologically possible concentrations, and the binding was attenuated by the addition of mannose-specific lectins, especially from Galanthus nivalis. Additionally, recombinant human pancreatic α-amylases expressed in yeast and purified by single-step affinity chromatography exhibited the same carbohydrate binding specificity as PPA in binding assays with sugar-biotinyl polymer probes. The results indicate that mammalian pancreatic α-amylases share a common carbohydrate binding activity and specifically bind to the intestinal BBM. Interaction with N-glycans in the BBM activated PPA and SI to produce much Glc on the one hand and to inhibit Glc absorption by enterocytes via SGLT1 in order to prevent a rapid increase in blood sugar on the other. PMID:22584580

  15. Role of N-linked oligosaccharides in the transport activity of the Na+/H+ antiporter in rat renal brush-border membrane

    SciTech Connect

    Yusufi, A.N.; Szczepanska-Konkel, M.; Dousa, T.P.

    1988-09-25

    The role of N-linked oligosaccharide side chains in the biogenesis and function of Na+-coupled transporters in renal luminal brush-border membrane (BBM) is not known. We examined the question of how in vivo inhibition by alkaloid swainsonine of alpha-mannosidase, a key enzyme in processing of glycoproteins in the Golgi apparatus, affects Na+/H+ antiport and Na+/Pi symport as well as activities of other transporters and enzymes in rat renal BBM. Administration of swainsonine to thyroparathyroidectomized rats, control or treated with 3,5,3'-triiodothyronine, markedly decreased the rate of Na+/H+ antiport, but had no effect on the rate of Na+/Pi symport across renal BBM vesicles (BBMV). Moreover, administration of swainsonine did not change activities of Na+ gradient, ((extravesicular Na+) greater than (intravesicular Na+))-dependent transport of D-glucose, L-proline, or the amiloride-insensitive 22Na+ uptake by BBMV; the activities of the BBM enzymes alkaline phosphatase, gamma-glutamyltransferase, or leucine aminopeptidase in BBMV were also not changed. The in vitro enzymatic deglycosylation of BBM by incubating freshly isolated BBMV with bacterial endoglycosidase F also resulted in a decreased rate of Na+/H+ antiport, but not Na+-coupled symports of Pi, L-proline, and D-glucose, or the activities of the BBM enzymes were not significantly affected. Similar incubation with endoglycosidase H was without effect on any of these parameters. Both the modification of BBMV glycoproteins by administration fo swainsonine in vivo as well as the in vitro incubation of BBMV with endoglycosidase F resulted in a decrease of the apparent Vmax of Na+/H+ antiport, but did not change the apparent Km of this antiporter for extravesicular Na+ and did not increase H+ conductance of BBM.

  16. Functional regulation of sugar assimilation by N-glycan-specific interaction of pancreatic α-amylase with glycoproteins of duodenal brush border membrane.

    PubMed

    Asanuma-Date, Kimie; Hirano, Yuki; Le, Na; Sano, Kotone; Kawasaki, Nana; Hashii, Noritaka; Hiruta, Yoko; Nakayama, Ken-ichi; Umemura, Mariko; Ishikawa, Kazuhiko; Sakagami, Hiromi; Ogawa, Haruko

    2012-06-29

    Porcine pancreatic α-amylase (PPA) binds to N-linked glycans of glycoproteins (Matsushita, H., Takenaka, M., and Ogawa, H. (2002) J. Biol Chem., 277, 4680-4686). Immunostaining revealed that PPA is located at the brush-border membrane (BBM) of enterocytes in the duodenum and that the binding is inhibited by mannan but not galactan, indicating that PPA binds carbohydrate-specifically to BBM. The ligands for PPA in BBM were identified as glycoprotein N-glycans that are significantly involved in the assimilation of glucose, including sucrase-isomaltase (SI) and Na(+)/Glc cotransporter 1 (SGLT1). Binding of SI and SGLT1 in BBM to PPA was dose-dependent and inhibited by mannan. Using BBM vesicles, we found functional changes in PPA and its ligands in BBM due to the N-glycan-specific interaction. The starch-degrading activity of PPA and maltose-degrading activity of SI were enhanced to 240 and 175%, respectively, while Glc uptake by SGLT1 was markedly inhibited by PPA at high but physiologically possible concentrations, and the binding was attenuated by the addition of mannose-specific lectins, especially from Galanthus nivalis. Additionally, recombinant human pancreatic α-amylases expressed in yeast and purified by single-step affinity chromatography exhibited the same carbohydrate binding specificity as PPA in binding assays with sugar-biotinyl polymer probes. The results indicate that mammalian pancreatic α-amylases share a common carbohydrate binding activity and specifically bind to the intestinal BBM. Interaction with N-glycans in the BBM activated PPA and SI to produce much Glc on the one hand and to inhibit Glc absorption by enterocytes via SGLT1 in order to prevent a rapid increase in blood sugar on the other.

  17. Carrier-mediated L-lactate transport in brush-border membrane vesicles from rat placenta during late gestation.

    PubMed Central

    Alonso de la Torre, S R; Serrano, M A; Alvarado, F; Medina, J M

    1991-01-01

    The mechanism for L-lactate transport across microvillous membrane vesicles prepared from rat placenta was examined. Uptake of L-lactate into these vesicles was mainly the result of transport into the intravesicular (osmotically active) space. The initial rate of L-lactate uptake was not affected by the presence of an inward gradient of either Na+ or K+. In the presence of an inward-directed proton gradient, L-lactate uptake was markedly stimulated, accumulating at concentrations 6-7-fold higher than the equilibrium. Lower transmembrane pH gradients were associated with slower initial uptakes and smaller overshoots. L-Lactate uptake determined under an inside-directed pH gradient was strongly inhibited by p-chloromercuriphenylsulphonic acid, a protein-thiol oxidizing agent. L-Lactate uptake was: (1) saturable as a function of the concentration of L-lactate, (2) inhibited by monocarboxylic acids such as pyruvate, D-lactate, beta-hydroxybutyrate and alpha-cyano-4-hydroxycinnamic acid, and (3) temperature-dependent. When present inside the vesicles, L-lactate, pyruvate and beta-hydroxybutyrate caused trans-stimulation of L-lactate uptake both in the presence and in the absence of an inside-directed pH gradient, indicating that L-lactate transport is a reversible process that can be shared by other monocarboxylic acids. There were no significant changes in maximal initial rate or in the kinetic parameters of L-lactate transport during the last 3 days of gestation. PMID:1654886

  18. Molecular Model of the Microvillar Cytoskeleton and Organization of the Brush Border

    PubMed Central

    Brown, Jeffrey W.; McKnight, C. James

    2010-01-01

    Background Brush border microvilli are ∼1-µm long finger-like projections emanating from the apical surfaces of certain, specialized absorptive epithelial cells. A highly symmetric hexagonal array of thousands of these uniformly sized structures form the brush border, which in addition to aiding in nutrient absorption also defends the large surface area against pathogens. Here, we present a molecular model of the protein cytoskeleton responsible for this dramatic cellular morphology. Methodology/Principal Findings The model is constructed from published crystallographic and microscopic structures reported by several groups over the last 30+ years. Our efforts resulted in a single, unique, self-consistent arrangement of actin, fimbrin, villin, brush border myosin (Myo1A), calmodulin, and brush border spectrin. The central actin core bundle that supports the microvillus is nearly saturated with fimbrin and villin cross-linkers and has a density similar to that found in protein crystals. The proposed model accounts for all major proteinaceous components, reproduces the experimentally determined stoichiometry, and is consistent with the size and morphology of the biological brush border membrane. Conclusions/Significance The model presented here will serve as a structural framework to explain many of the dynamic cellular processes occurring over several time scales, such as protein diffusion, association, and turnover, lipid raft sorting, membrane deformation, cytoskeletal-membrane interactions, and even effacement of the brush border by invading pathogens. In addition, this model provides a structural basis for evaluating the equilibrium processes that result in the uniform size and structure of the highly dynamic microvilli. PMID:20195380

  19. Interaction between Cry9Ca and two Cry1A delta-endotoxins from Bacillus thuringiensis in larval toxicity and binding to brush border membrane vesicles of the spruce budworm, Choristoneura fumiferana Clemens.

    PubMed

    Pang, Anthony S D; Gringorten, J Lawrence; van Frankenhuyzen, Kees

    2002-09-24

    A genetically altered variant of Cry9Ca from Bacillus thuringiensis shows high potency against the spruce budworm, Choristoneura fumiferana Clemens. Its activity, as measured by feeding inhibition in frass-failure assays, is estimated to be four to seven times greater than B. thuringiensis subsp. kurstaki HD-1, the strain currently used in commercial products to control this insect. Bioassays against budworm of mixtures of the modified Cry9Ca and two of the Cry1A endotoxin proteins produced by HD-1 show neither synergism nor antagonism. Experiments with brush border membrane vesicles from budworm midgut revealed that Cry9Ca and the Cry1A toxins share a common binding site and that bound Cry9Ca can be displaced from the membrane to some extent by the Cry1A toxins. However, it is uncertain whether the binding site is actually the receptor molecule or a membrane protein associated with pore formation.

  20. Lipid raft organization and function in the small intestinal brush border.

    PubMed

    Danielsen, E M; Hansen, G H

    2008-12-01

    The enterocyte brush border of the small intestine is a highly specialized membrane designed to function both as a high capacity digestive/absorptive surface of dietary nutrients and a permeability barrier towards lumenal pathogens. It is characterized by an unusually high content of glycolipids (approximately 30% of the total microvillar membrane lipid), enabling the formation of liquid ordered microdomains, better known as lipid rafts. The glycolipid rafts are stabilized by galectin-4, a 36 kDa divalent lectin that cross-links galactosyl (and other carbohydrate) residues present on membrane lipids and several brush border proteins, including some of the major hydrolases. These supramolecular complexes are further stabilized by intelectin, a 35 kDa trimeric lectin that also functions as an intestinal lactoferrin receptor. As a result, brush border hydrolases, otherwise sensitive to pancreatic proteinases, are protected from untimely release into the gut lumen. Finally, anti-glycosyl antibodies, synthesized by plasma cells locally in the gut, are deposited on the brush border glycolipid rafts, protecting the epithelium from lumenal pathogens that exploit lipid rafts as portals for entry to the organism.

  1. Brush-border tyrosine phosphorylation stimulates ileal neutral NaCl absorption and brush-border Na(+)-H+ exchange.

    PubMed

    Donowitz, M; Montgomery, J L; Walker, M S; Cohen, M E

    1994-04-01

    The drug genistein, a tyrosine (Tyr) kinase inhibitor, was used to define a role for Tyr phosphorylation in regulation of basal and stimulated neutral NaCl absorption in rabbit ileum. Brush-border vesicles contain Tyr-phosphorylated peptides. Genistein freeze-thawed into the vesicles caused a concentration-dependent inhibition of at least three peptides with M(r) 111,000, 83,000, and 80,000. Studied with the Ussing chamber-voltage clamp technique, genistein added to the ileal mucosal surface inhibited neutral NaCl absorption. Direct addition of genistein to brush-border vesicles made from ileal villus cells inhibited brush-border Na(+)-H+ exchange but not D-glucose-stimulated Na+ uptake. These effects were not duplicated by genistin, a drug with similar structure to genistein but lacking Tyr kinase inhibiting properties. Serosal but not mucosal epidermal growth factor (EGF) stimulated NaCl absorption. Mucosal genistein but not genistin also altered second-messenger regulation of neutral NaCl absorption, inhibiting the effect of Ca2+ ionophore A-23187 and of serosal EGF but not affecting the transport changes caused by 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP). In contrast, the Cl secretory effects indicated by the increase in short-circuit current for all three agents, A-23187, EGF, and 8-BrcAMP, were inhibited by mucosal genistein. These results suggest that 1) a Tyr kinase is involved in basally stimulating ileal neutral NaCl absorption and brush-border Na(+)-H+ exchange; 2) EGF stimulates NaCl absorption by an effect exerted from the serosal surface, but the effect also involves a brush-border Tyr kinase; 3) brush-border Tyr kinase is involved in the ability of Ca2+ ionophore A-23187 to inhibit neutral NaCl absorption but is not involved in the transport effects of cAMP. This study suggests that Tyr kinase(s) acting over short time periods is involved in stimulation of neutral NaCl absorption and brush-border Na(+)-H+ exchange and also in Ca(2

  2. Brush-border calmodulin. A major component of the isolated microvillus core

    PubMed Central

    1980-01-01

    Calmodulin is present in brush borders isolated from intestinal epithelial cells and is one of the major components of the microvillar filament bundle. Calmodulin was purified from either demembranated brush borders or microvilli by a simple boiling procedure. The boiled supernate derived from the microvillus cores contained one major polypeptide of 20,000 daltons.The supernate from the brush-border preparation contained the 20,000-dalton subunit and a second protein of 30,000 daltons. The 20,000-dalton subunit has been identified as calmodulin by several criteria: (a) heat resistance, (b) comigration with brain calmodulin on alkaline urea gels and SDS gels, both cases in which the 20,000-dalton protein, like calmodulin, exhibits a shift in electrophoretic mobility in the presence of Ca++, and (c) 4--5-fold activation of 3',5'-cyclic nucleotide phosphodiesterase in the presence but not the absence of Ca++. With a cosedimentation assay it was determined that brush-border calmodulin does not bind directly to actin. In the presence of Ca++ (greater than 5 x 10(-7) M) there was a partial release of calmodulin from the microvillus core, along with a substantial conversion of microvillus actin into a nonpelletable from. The dissociation of calmodulin was reversed by removal of Ca++. If microvillus cores were pretreated with phalloidin, the Ca++-induced solubilization of actin was prevented, but the partial dissociation of calmodulin still occurred. The molar ratio of calmodulin:actin is 1:10 in the demembranated brush border and 1:2-3 in the microvillus core. No calmodulin was detected in the detergent-solubilized brush-border membrane fraction. PMID:6893051

  3. Comparison of intestinal brush-border 95-Kdalton polypeptide and alpha- actinins

    PubMed Central

    1980-01-01

    To explore the suggestion that alpha-actinin cross-links actin filaments to the microvillar membrane (Mooseker and Tilney, 1975, J. Cell Biol. 67:725--743; Mooseker, 1976, J. Cell Biol. 71-417--433), we have assessed the possible relatedness of alpha-actinin and the brush- border 95-kdalton protein by four independent criteria: antigenicity, mobility on SDS gels, extractability in nonionic detergents, and peptide maps. We have found that anti-chicken gizzard alpha-actinin stains the junctional complex region of intact cells (Craig and Pardo, 1979, J. Cell Biol. 80:203--210) but does not stain isolated brush borders even though these structures contain a 95-kdalton polypeptide. Lack of staining is not caused by failure of the antibody to penetrate, as antiactin stains both the terminal web and the microvilli of isolated brush borders. By the antibody SDS gel overlay technique, we have established that anti-gizzard alpha-actinin recognizes homologous molecules in chicken skeletal and cardiac muscles, as well as in intestinal epithelial cells, but fails to recognize the brush-border 95- kdalton polypeptide. Conversely, anti-95-kdalton polypeptide does not recognize gizzard alpha-actinin. On high-resolution SDS polyacrylamide gel electrophoresis, alpha-actinin and brush-border 95-kdalton protein exhibit distinct mobilities. The two proteins also differ in their ability to be extracted in nonionic mobilities. The two proteins also differ in their ability to be extracted in nonionic detergent: epithelial cell immunoreactive alpha-actinin is soluble in NP-40, whereas 95-kdalton protein is insoluble. Finally, two-dimensional peptide mapping of iodinated tryptic peptides, as well as one- dimensional fingerprinting of partial tryptic, chymotryptic, papain, and S. aureus V8 protease digests, have revealed less than 5% homology between gizzard alpha-actinin and brush-border 95-kdalton polypeptide. The data suggest that there is no major structural homology between gizzard

  4. Galectin-2 at the enterocyte brush border of the small intestine.

    PubMed

    Thomsen, Martha Kampp; Hansen, Gert H; Danielsen, E Michael

    2009-08-01

    The brush border of pig small intestine is a local hotspot for beta-galactoside-recognizing lectins, as evidenced by its prominent labeling with fluorescent lectin PNA. Previously, galectins 3-4, intelectin, and lectin-like anti-glycosyl antibodies have been localized to this important body boundary. Together with the membrane glycolipids these lectins form stable lipid raft microdomains that also harbour several of the major digestive microvillar enzymes. In the present work, we identified a lactose-sensitive 14-kDa protein enriched in a microvillar detergent resistant fraction as galectin-2. Its release from closed, right-side-out microvillar membrane vesicles shows that at least some of the galectin-2 resides at the lumenal surface of the brush border, indicating that it plays a role in the organization/stabilization of the lipid raft domains. Galectin-2 was released more effectively from the membrane by lactose than was galectin-4, and surprisingly, it was also released by the noncanonical disaccharides sucrose and maltose. Furthermore, unlike galectin-4, galectin-2 was preferentially co-immunoisolated with sucrase-isomaltase rather than with aminopeptidase N. Together, these results show that the galectins are not simply redundant proteins competing for the same ligands but rather act in concert to ensure an optimal cross-linking of membrane glycolipids and glycoproteins. In this way, they offer a maximal protection of the brush border against exposure to bile, pancreatic enzymes and pathogens.

  5. Intelectin: a novel lipid raft-associated protein in the enterocyte brush border.

    PubMed

    Wrackmeyer, Uta; Hansen, Gert H; Seya, Tsukasa; Danielsen, E Michael

    2006-08-01

    Intelectin is a mammalian Ca2+-dependent, D-galactosyl-specific lectin expressed in Paneth and goblet cells of the small intestine and proposed to serve a protective role in the innate immune response to parasite infection. In addition, it is structurally identical to the intestinal lactoferrin receptor known to reside in the enterocyte brush border. To clarify this apparent discrepancy with regard to localization, the aim of this work was to study the cellular and subcellular distribution of small intestinal intelectin by immunofluorescence and immunogold electron microscopy. Secretory granules of lysozyme-positive Paneth cells in the bottom of the crypts as well as goblet cells along the crypt-villus axis were intensively labeled with intelectin antibodies, but quantitatively, the major site of intelectin deposition was the enterocyte brush border. This membrane is organized in stable glycolipid-based lipid raft microdomains, and like the divalent lectin galectin-4, intelectin was enriched in microvillar "superrafts", i.e., membranes that resist solubilization with Triton X-100 at 37 degrees C. This strategic localization suggests that the trimeric intelectin, like galectin-4, serves as an organizer and stabilizer of the brush border membrane, preventing loss of digestive enzymes to the gut lumen and protecting the glycolipid microdomains from pathogens.

  6. MYO1A (brush border myosin I) dynamics in the brush border of LLC-PK1-CL4 cells.

    PubMed Central

    Tyska, M J; Mooseker, M S

    2002-01-01

    The kidney epithelial cell line, LLC-PK1-CL4 (CL4), forms a well ordered brush border (BB) on its apical surface. CL4 cells were used to examine the dynamics of MYO1A (M1A; formerly BB myosin I) within the BB using GFP-tagged MIA (GFP-M1A), MIA motor domain (GFP-MDIQ), and tail domain (GFP-Tail). GFP-beta-actin (GFP-Actin) was used to assess actin dynamics within the BB. GFP-M1A, GFP-Tail, but not GFP-MDIQ localized to the BB, indicating that the tail is sufficient for apical targeting of M1A. GFP-Actin targeted to all the actin domains of the cell including the BB. Fluorescence recovery after photobleaching analysis revealed that GFP-M1A and GFP-Tail turnover in the BB is rapid, approximately 80% complete in <1 min. As expected for an actin-based motor, ATP depletion resulted in significant inhibition of GFP-M1A turnover yet had little effect on GFP-Tail exchange. Rapid turnover of GFP-M1A and GFP-Tail was not due to actin turnover as GFP-Actin turnover in the BB was much slower. These results indicate that the BB population of M1A turns over rapidly, while its head and tail domains interact transiently with the core actin and plasma membrane, respectively. This rapidly exchanging pool of M1A envelops an actin core bundle that, by comparison, is static in structure. PMID:11916846

  7. Breakdown of gliadin peptides by intestinal brush borders from coeliac patients.

    PubMed Central

    Bruce, G; Woodley, J F; Swan, C H

    1984-01-01

    The 'missing peptidase' hypothesis to explain the aetiology of coeliac disease has never been satisfactorily resolved and recent reports suggest that coeliac brush borders may have depressed levels of specific peptidase enzymes. It has been inferred from these studies that the subsequent brush border digestion of gliadin peptides may therefore be defective. In this present study a sensitive fluorometric assay was used to measure the hydrolysis of a peptic-tryptic digest of gliadin by both normal and coeliac brush borders. The coeliac brush borders were as efficient as the normals in hydrolysing gliadin peptides and showed no depression of any specific peptidase activity. PMID:6381246

  8. The Secretion and Action of Brush Border Enzymes in the Mammalian Small Intestine.

    PubMed

    Hooton, Diane; Lentle, Roger; Monro, John; Wickham, Martin; Simpson, Robert

    2015-01-01

    Microvilli are conventionally regarded as an extension of the small intestinal absorptive surface, but they are also, as latterly discovered, a launching pad for brush border digestive enzymes. Recent work has demonstrated that motor elements of the microvillus cytoskeleton operate to displace the apical membrane toward the apex of the microvillus, where it vesiculates and is shed into the periapical space. Catalytically active brush border digestive enzymes remain incorporated within the membranes of these vesicles, which shifts the site of BB digestion from the surface of the enterocyte to the periapical space. This process enables nutrient hydrolysis to occur adjacent to the membrane in a pre-absorptive step. The characterization of BB digestive enzymes is influenced by the way in which these enzymes are anchored to the apical membranes of microvilli, their subsequent shedding in membrane vesicles, and their differing susceptibilities to cleavage from the component membranes. In addition, the presence of active intracellular components of these enzymes complicates their quantitative assay and the elucidation of their dynamics. This review summarizes the ontogeny and regulation of BB digestive enzymes and what is known of their kinetics and their action in the peripheral and axial regions of the small intestinal lumen.

  9. Binding sites for Bacillus thuringiensis Cry2Ae toxin on heliothine brush border membrane vesicles are not shared with Cry1A, Cry1F, or Vip3A toxin.

    PubMed

    Gouffon, C; Van Vliet, A; Van Rie, J; Jansens, S; Jurat-Fuentes, J L

    2011-05-01

    The use of combinations of Bacillus thuringiensis (Bt) toxins with diverse modes of action for insect pest control has been proposed as the most efficient strategy to increase target range and delay the onset of insect resistance. Considering that most cases of cross-resistance to Bt toxins in laboratory-selected insect colonies are due to alteration of common toxin binding sites, independent modes of action can be defined as toxins sharing limited or no binding sites in brush border membrane vesicles (BBMV) prepared from the target insect larvae. In this paper, we report on the specific binding of Cry2Ae toxin to binding sites on BBMV from larvae of the three most commercially relevant heliothine species, Heliothis virescens, Helicoverpa zea, and Helicoverpa armigera. Using chromatographic purification under reducing conditions before labeling, we detected specific binding of radiolabeled Cry2Ae, which allowed us to perform competition assays using Cry1Ab, Cry1Ac, Cry1Fa, Vip3A, Cry2Ae, and Cry2Ab toxins as competitors. In these assays, Cry2Ae binding sites were shared with Cry2Ab but not with the tested Cry1 or Vip3A toxins. Our data support the use of Cry2Ae toxin in combination with Cry1 or Vip3A toxins in strategies to increase target range and delay the onset of heliothine resistance.

  10. Binding Sites for Bacillus thuringiensis Cry2Ae Toxin on Heliothine Brush Border Membrane Vesicles Are Not Shared with Cry1A, Cry1F, or Vip3A Toxin ▿

    PubMed Central

    Gouffon, C.; Van Vliet, A.; Van Rie, J.; Jansens, S.; Jurat-Fuentes, J. L.

    2011-01-01

    The use of combinations of Bacillus thuringiensis (Bt) toxins with diverse modes of action for insect pest control has been proposed as the most efficient strategy to increase target range and delay the onset of insect resistance. Considering that most cases of cross-resistance to Bt toxins in laboratory-selected insect colonies are due to alteration of common toxin binding sites, independent modes of action can be defined as toxins sharing limited or no binding sites in brush border membrane vesicles (BBMV) prepared from the target insect larvae. In this paper, we report on the specific binding of Cry2Ae toxin to binding sites on BBMV from larvae of the three most commercially relevant heliothine species, Heliothis virescens, Helicoverpa zea, and Helicoverpa armigera. Using chromatographic purification under reducing conditions before labeling, we detected specific binding of radiolabeled Cry2Ae, which allowed us to perform competition assays using Cry1Ab, Cry1Ac, Cry1Fa, Vip3A, Cry2Ae, and Cry2Ab toxins as competitors. In these assays, Cry2Ae binding sites were shared with Cry2Ab but not with the tested Cry1 or Vip3A toxins. Our data support the use of Cry2Ae toxin in combination with Cry1 or Vip3A toxins in strategies to increase target range and delay the onset of heliothine resistance. PMID:21441333

  11. Screening of the Bacillus thuringiensis Cry1Ac delta-endotoxin on the artificial phospholipid monolayer incorporated with brush border membrane vesicles of Plutella xylostella by optical biosensor technology.

    PubMed

    Okumura, S; Akao, T; Mizuki, E; Ohba, M; Inouye, K

    2001-02-26

    The binding of Cry1Ac, an insecticidal protein of Bacillus thuringiensis, to a brush border membrane (BBM) isolated from midguts of the diamondback moth Plutella xylostella was examined by surface plasmon resonance (SPR)-based biosensor. BBM was mixed with 1,3-ditetradecylglycero-2-phosphocholine (PC14), a neutral charged artificial lipid, and was reconstructed to a monolayer on a hydrophobic chip for the biosensor. The binding of Cry1Ac to the reconstructed monolayer was analyzed by a two-state binding model, and it was shown that Cry1Ac bound to the monolayer in the first step with an affinity constant (K(1)) of 508 nM, followed by the second uni-molecular step with an equilibrium constant (K(2)) of 0.472. The overall affinity constant K(d) was determined to be 240 nM. The binding was markedly inhibited by N-acetyl-D-galactosamine (K(i)=8 mM). The monolayer was shown to retain a high affinity to Cry1Ac, providing an insect-free system for rapid and large-scale screening of B. thuringiensis insecticidal proteins by the SPR-based biosensor technology.

  12. Effect of harmaline on rat intestinal brush border sucrase activity.

    PubMed

    Kaur, Navneet; Kaur, Jyotdeep; Mahmood, Akhtar

    2002-04-01

    The effect of harmaline, a plant alkaloid has been studied on rat intestinal brush border sucrase activity. Stimulation of sucrase activity by Na+ was found to be pH-dependent. At neutral pH, 20 mM Na+ stimulated sucrase activity by reducing K(m) by 30%, while at acidic pH (5.2), the activity increased 4-fold compared to Na+-free enzyme. At 1.0 mM, harmaline markedly inhibited (67%) the enzyme activity at pH 5.2 in the absence of Na+. However, inhibition was reduced in presence of 20 mM sodium, whereas 4.0 mM harmaline was required to inhibit the enzyme activity by 65%. In the absence of Na+ ions, harmaline inhibition of sucrase activity was of competitive type, but it changed to non-competitive type in presence of 20 mM Na+ at pH 5.2. Sucrase-harmaline interactions as a function of pH, both in presence and absence of Na+ revealed a shift in pH optima of the enzyme towards a higher pH in presence of 4 mM and 1 mM harmaline respectively. The observed inhibition was reversible in nature and was only partially overcome by sodium, lithium, potassium, cesium, rubidium and ammonium ions. These findings suggest that harmaline also inhibits rat brush border sucrase and that the presence of Na+ site is not a pre-requisite for the inhibition.

  13. The neurotoxins 1-methyl-4-phenylpyridinium and 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine are substrates for the organic cation transporter in renal brush border membrane vesicles.

    PubMed

    Sokol, P P; Holohan, P D; Ross, C R

    1987-07-01

    We examined the effects of the neurotoxins 1-methyl-4-phenyl-pyridinium (MPP+) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on the transport of the prototypic organic cation, N1-[3H]methylnicotinamide ([3H]NMN), in canine renal brush border membrane vesicles. A dose-response curve for MPTP and its oxidized metabolite, MPP+, revealed IC50 values of 160 and 16 microM, respectively. MPTP (5 mM) and MPP+ (5 mM), maximally inhibited H+-driven NMN (50 microM) uptake by 86.0 and 86.6%, respectively. Additionally, serotonin (0.5 mM) and harmaline (0.5 mM) inhibited NMN transport by 65.8 and 87.1%, respectively. Mepiperphenidol (Darstine) (0.5 mM), a classical organic cation competitor, inhibited NMN transport by 80.6%. However, dopamine (0.5 mM) was not as effective and resulted in only 24.9% inhibition. The cationic specificity was demonstrated by showing that MPP+ and MPTP had no effect on the transport of the organic anion, p-aminohippurate. Additionally, the effect of MPP+ on NMN was not due to either a voltage effect or vesicle disruption. In countertransport studies, MPTP acted as an elicitor of NMN counterflow and produced trans stimulation whereas MPP+ did not and resulted in trans inhibition. Inasmuch as transport involves both binding and translocation we speculate that MPTP binds and is translocated; in contrast MPP+ binds and is not translocated. These reagents may serve as a basis for elucidating the structure-activity requirements of the organic cation/H+ antiporter.

  14. Binding of diarrheagenic Escherichia coli to 32- to 33-kilodalton human intestinal brush border proteins.

    PubMed Central

    Manjarrez-Hernandez, A; Gavilanes-Parra, S; Chavez-Berrocal, M E; Molina-Lopez, J; Cravioto, A

    1997-01-01

    We have detected human intestinal brush border proteins to which Escherichia coli strains adhere by means of a blotting-nitrocellulose method in which the binding of radiolabeled bacteria to sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated intestinal cell membranes was evaluated. The brush border fraction contained several polypeptides that bound only adherent E. coli strains. The most prominent and consistent of these proteins had apparent molecular masses of 32 to 33 kDa. Additional polypeptides ranging from 50 to 70, from 105 to 130, and from 180 to 200 kDa were also recognized by adherent E. coli strains, although with less intensity (in accordance with the number of bound bacteria to these polypeptides). Independently of the pattern of adherence (localized [LA], diffuse [DA], or aggregative [AggA]) all HEp-2-adhering strains recognized, with different intensities, the 32- to 33-kDa brush border proteins, whereas nonadhesive strains did not. The relative avidity of an LA strain to bind to the 32- to 33-kDa proteins was approximately seven- and sixfold higher than the binding of strains with aggregative and diffuse adherence, respectively. Thus, it is reasonable to think that LA, DA, and AggA strains have a common adhesin that mediates binding to the 32- to 33-kDa bands. Inhibition experiments using HEp-2 cells demonstrated that isolated 32- to 33-kDa proteins or specific antiserum blocked preferentially bacterial adherence of the LA pattern. Delipidization and protein digestion of the human brush borders confirmed that E. coli bound to structures of a proteinaceous nature. Deglycosylation studies and sodium meta-periodate oxidation of the intestinal cell membranes decreased bacterial binding activity significantly, indicating that E. coli bound to carbohydrate moieties in the glycoproteins. These results suggest that binding of E. coli strains, mainly of the LA phenotype, to the 32- to 33-kDa proteins could play a role in colonization through

  15. Cloning of cDNAs encoding a rabbit renal brush border membrane protein immunologically related to band 3. Sequence similarity with microsomal dipeptidase.

    PubMed Central

    Igarashi, P; Karniski, L P

    1991-01-01

    Distinct anion transport processes have been identified in the mammalian renal proximal tubule, but none of the responsible proteins or genes have been isolated. A 43 kDa rabbit microvillus membrane protein that is immunologically related to the erythroid anion exchanger (band 3) was a candidate for a renal anion transporter. To examine the structural relationship with band 3, we cloned cDNAs encoding the 43 kDa protein. The 43 kDa band-3-like protein was purified, and a novel sequence of 24 amino acids was obtained from the N-terminus. Degenerate oligonucleotides were synthesized based on this sequence, and the polymerase chain reaction with single-sided specificity was used to amplify and clone a 1330 bp cDNA from rabbit renal cortex. Additional overlapping 272 bp and 1123 bp cDNAs were obtained by synthesizing and screening a rabbit renal cortical cDNA library. The composite sequence was 1483 bp, terminated with (A)16, and was similar in size to the principal transcript expressed in rabbit renal cortex. The single long open reading frame was predicted to encode a protein composed of 410 amino acids with a molecular mass of 45,193 Da; 15 amino acids predicted to reside at the N-terminus were absent in the mature protein and may constitute a signal peptide. There was only limited sequence similarity with human erythroid band 3. Rather, the sequence was highly similar to microsomal dipeptidase, including the presence of a signal peptide and a consensus sequence for covalent linkage to glycosylphosphatidylinositol. In summary, the 43 kDa protein from rabbit renal cortex that is recognized by a monospecific antibody to erythroid band 3 is most likely a microvillus membrane dipeptidase. Images Fig. 1. Fig. 5. Fig. 6. PMID:1741759

  16. Role of lysophosphatidylcholine in brush-border intestinal alkaline phosphatase release and restoration.

    PubMed

    Nakano, Takanari; Inoue, Ikuo; Alpers, David H; Akiba, Yasutada; Katayama, Shigehiro; Shinozaki, Rina; Kaunitz, Jonathan D; Ohshima, Susumu; Akita, Masumi; Takahashi, Seiichiro; Koyama, Iwao; Matsushita, Makoto; Komoda, Tsugikazu

    2009-07-01

    Intestinal alkaline phosphatase (IAP) is a brush-border membrane ectoenzyme (BBM-IAP) that is released into the lumen (L-IAP) after a high-fat diet. We examined the effects of oil feeding and the addition of mixed-lipid micelles on the formation of L-IAP in oil-fed rat intestine, Caco-2 cell monolayers, and mouse intestinal loops. We localized IAP in the duodenum of rats fed corn oil using fluorescence microscopy with enzyme-labeled fluorescence-97 as substrate. Four hours after oil feeding, L-IAP increased approximately 10-fold accompanied by the loss of BBM-IAP, consistent with BBM-IAP release. Rat IAP isozyme mRNAs progressively increased 4-6 h after oil feeding, followed by the increase of IAP activity in the subapical location at 6 h, consistent with the restoration of IAP protein. Postprandial lipid-micelle components, sodium taurocholate with or without oleic acid, mono-oleylglycerol, cholesterol, or lysophosphatidylcholine (lysoPC) were applied singly or as mixed-lipid micelles to the apical surface of polarized Caco-2 cell monolayers. LysoPC increased L-IAP >10-fold over basal release. LysoPC released IAP into the apical medium more than other intestinal brush-border enzymes, 5'-nucleotidase, sucrase, aminopeptidase N, and lactase, without comparable lactate dehydrogenase release or cell injury. LysoPC increased human IAP mRNA levels by 1.5-fold in Caco-2 cells. Luminally applied lysoPC also increased release of IAP preferentially in mouse intestinal loops. These data show that lysoPC accelerates the formation of L-IAP from BBM-IAP, followed by enhanced IAP synthesis, suggesting the role that lysoPC might play in the turnover of brush-border proteins.

  17. Inhibition of brush border sucrase by polyphenols in mouse intestine.

    PubMed

    Gupta, Shiffalli; Mahmood, Safrun; Khan, Rizwan H; Mahmood, Akhtar

    2009-11-23

    The interactions of gallic acid and tannic acid with purified brush border sucrase (EC 3.2.1.48) from mouse intestine have been studied. These findings indicate that both gallic acid and tannic acid inhibit sucrase activity, which is pH dependent. Kinetic analysis revealed that enzyme inhibition by gallic acid is a pure V effect at pH 5.0, which changes to mixed type at pH 7.2, and pure K effect at pH 8.5. In contrast, sucrase inhibition by tannic acid was a pure K effect at acidic pH and uncompetitive type in the alkaline pH range. Far-CD spectroscopic analysis revealed an increase in the helicity of the enzyme at acidic pH in the presence of tannic acid but no change at alkaline pH. Fluorescence spectra revealed a red shift in lambdamax of the enzyme, suggesting that tryptophan residues come to a more hydrophilic environment in the presence of polyphenols. These findings suggest that inhibition of mice sucrase by polyphenols is pH dependent, and is associated with conformational modifications of the enzyme.

  18. Quantitation of the Adherence of an Enteropathogenic Escherichia coli to Isolated Rabbit Intestinal Brush Borders

    PubMed Central

    Cheney, Christopher P.; Boedeker, Edgar C.; Formal, Samuel B.

    1979-01-01

    Two assays were developed to quantitate the adherence of an Escherichia coli strain (RDEC-1) known to colonize the mucosal surface of the small intestine of rabbits to brush borders isolated from rabbit intestinal epithelial cells. In the first assay, the mean adherence per rabbit brush border was determined by counting the number of organisms adhering to each of 40 brush borders under phase microscopy. The mean adherence of RDEC-1 (11.5 ± 0.7 per rabbit brush border) was significantly greater than adherence of two nonpathogenic strains: HS (2.7 ± 0.4 per rabbit brush border) and 640 (0.8 ± 0.1 per rabbit brush border). A similar distinction between the adherence of RDEC-1 and the control (nonadherent) organisms could be made more rapidly by determining the percentage of the total number of brush borders which had 10 or more adherent organisms; this second assay was used to define the optimum conditions for adherence. Maximum adherence was seen within 15 min. Adherence was temperature dependent, with adherence after 1 min at 37°C being fourfold greater than that at 4°C. The pH optimum for adherence was between 6.5 and 7.0, and adherence was abolished below pH 5.0. With the first, more sensitive assay, the effect of electrolytes and a number of hexoses and hexosamines on adherence was analyzed. RDEC-1 adherence was inhibited at high ionic strengths; however, adherence was not influenced at moderately high concentrations (20 mg/ml) by either d-mannose or l-fucose, in contrast to the case for other reported enteric pathogens. These two quantitative in vitro assays for adherence produce consistent results and have been used to partially characterize the adherence of RDEC-1 to rabbit brush borders. Images PMID:44705

  19. Glycine transport by intestinal brush border vesicles of the amphibian Discoglossus pictus.

    PubMed

    Saidane, D; Boge, G; Tritar, B; Peres, G

    1991-01-01

    1. In order to determine the different components of glycine uptake by the intestine of the frog, Discoglossus pictus, we have used brush border membrane vesicles isolated by a classical precipitation technique. 2. Enzymatic tests showed that a good purification was obtained. The concentration ratio of alkaline phosphatase was 14.8. 3. Glycine entry in vesicles as a function of time, in presence or absence of sodium, indicated an overshoot which decreased when incubation time was prolonged. The overshoot was dependent on the presence of sodium. 4. The nature of the anion associated to sodium had little effect on glycine uptake. Nevertheless, chloride and thiocyanate appeared more efficient than glutarate. 5. The effect of transmembrane potential was studied by using valinomycin associated with a potassium gradient. The addition of this substance stimulated glycine transport by 43%. 6. The transport at different glycine concentrations showed two components: one non-saturable with weak affinity and the other saturable with strong affinity (Kt = 0.338 mM). 7. In conclusion, glycine transport by the brush border of D. pictus intestine presents a saturable component depending on sodium and on transmembrane electrical potential.

  20. Location of a protein of the fodrin-spectrin-TW260/240 family in the mouse intestinal brush border.

    PubMed

    Hirokawa, N; Cheney, R E; Willard, M

    1983-03-01

    We have determined that a protein of the fodrin-spectrin-TW260/240 (FST) family is a component of the thin fibrils (approximately 5 nm wide, 100-200 nm long) that cross-link bundles of actin filaments to adjacent actin bundles and to the plasma membrane in the terminal web of the brush border of the intestinal epithelium. When isolated brush borders were incubated with anti-fodrin antibodies and prepared for electron microscopy by the quick-freeze, deep-etch technique, these approximately 5 nm fibrils were specifically decorated with the antibody. In addition, these cross-linking fibrils disappeared when the anti-fodrin-reactive proteins were extracted from the brush border. We conclude that FST is a component of a cross-linking system composed of approximately 5 nm fibrils that are morphologically distinct from the approximately 8 nm myosin-containing fibrils which were identified by anti-myosin decoration. In addition to linking actin bundles to adjacent actin bundles and to the plasma membrane, these FST fibrils may mediate actin-vesicle, actin-intermediate filament and vesicle-plasma membrane linkages.

  1. Intra Amniotic Administration of Raffinose and Stachyose Affects the Intestinal Brush Border Functionality and Alters Gut Microflora Populations.

    PubMed

    Pacifici, Sarina; Song, Jaehong; Zhang, Cathy; Wang, Qiaoye; Glahn, Raymond P; Kolba, Nikolai; Tako, Elad

    2017-03-19

    This study investigates the effectiveness of two types of prebiotics-stachyose and raffinose-which are present in staple food crops that are widely consumed in regions where dietary Fe deficiency is a health concern. The hypothesis is that these prebiotics will improve Fe status, intestinal functionality, and increase health-promoting bacterial populations in vivo (Gallus gallus). By using the intra-amniotic administration procedure, prebiotic treatment solutions were injected in ovo (day 17 of embryonic incubation) with varying concentrations of a 1.0 mL pure raffinose or stachyose in 18 MΩ H₂O. Four treatment groups (50, 100 mg·mL(-1) raffinose or stachyose) and two controls (18 MΩ H₂O and non-injected) were utilized. At hatch the cecum, small intestine, liver, and blood were collected for assessment of the relative abundance of the gut microflora, relative expression of Fe-related genes and brush border membrane functional genes, hepatic ferritin levels, and hemoglobin levels, respectively. The prebiotic treatments increased the relative expression of brush border membrane functionality proteins (p < 0.05), decreased the relative expression of Fe-related proteins (p < 0.05), and increased villus surface area. Raffinose and stachyose increased the relative abundance of probiotics (p < 0.05), and decreased that of pathogenic bacteria. Raffinose and stachyose beneficially affected the gut microflora, Fe bioavailability, and brush border membrane functionality. Our investigations have led to a greater understanding of these prebiotics' effects on intestinal health and mineral metabolism.

  2. Binding of Cyt1Aa and Cry11Aa toxins of Bacillus thuringiensis serovar israelensis to brush border membrane vesicles of Tipula paludosa (Diptera: Nematocera) and subsequent pore formation.

    PubMed

    Oestergaard, Jesko; Ehlers, Ralf-Udo; Martínez-Ramírez, Amparo C; Real, Maria Dolores

    2007-06-01

    Bacillus thuringiensis serovar israelensis (B. thuringiensis subsp. israelensis) produces four insecticidal crystal proteins (ICPs) (Cry4A, Cry4B, Cry11A, and Cyt1A). Toxicity of recombinant B. thuringiensis subsp. israelensis strains expressing only one of the toxins was determined with first instars of Tipula paludosa (Diptera: Nematocera). Cyt1A was the most toxic protein, whereas Cry4A, Cry4B, and Cry11A were virtually nontoxic. Synergistic effects were recorded when Cry4A and/or Cry4B was combined with Cyt1A but not with Cry11A. The binding and pore formation are key steps in the mode of action of B. thuringiensis subsp. israelensis ICPs. Binding and pore-forming activity of Cry11Aa, which is the most toxic protein against mosquitoes, and Cyt1Aa to brush border membrane vesicles (BBMVs) of T. paludosa were analyzed. Solubilization of Cry11Aa resulted in two fragments, with apparent molecular masses of 32 and 36 kDa. No binding of the 36-kDa fragment to T. paludosa BBMVs was detected, whereas the 32-kDa fragment bound to T. paludosa BBMVs. Only a partial reduction of binding of this fragment was observed in competition experiments, indicating a low specificity of the binding. In contrast to results for mosquitoes, the Cyt1Aa protein bound specifically to the BBMVs of T. paludosa, suggesting an insecticidal mechanism based on a receptor-mediated action, as described for Cry proteins. Cry11Aa and Cyt1Aa toxins were both able to produce pores in T. paludosa BBMVs. Protease treatment with trypsin and proteinase K, previously reported to activate Cry11Aa and Cyt1Aa toxins, respectively, had the opposite effect. A higher efficiency in pore formation was observed when Cyt1A was proteinase K treated, while the activity of trypsin-treated Cry11Aa was reduced. Results on binding and pore formation are consistent with results on ICP toxicity and synergistic effect with Cyt1Aa in T. paludosa.

  3. Phosphatase activities of rat intestinal enterocytes and their relation to diverse luminal pH, with special references to the possible localization of phytase along the brush border membrane.

    PubMed

    Nakano, Y; Kawamoto, T; Takano, Y

    2001-12-01

    Phosphatase activities associated with the intestinal brush border membrane (BBM) of the rat were examined histochemically in relation to the characteristic environment of the intestine, where luminal pH fluctuates drastically between alkaline and acid pH ranges. Special attention was given to intestinal alkaline phosphatase (IALP) and phytase on the BBM. Whole body fresh-frozen sections of young rats and their rapidly frozen and freeze-substituted small intestines, embedded in Technovit 7100, were processed for the histochemical demonstration of phosphatase activity at three different pH values (9.2, 7.3, and 5.2), representing the deviation of luminal pH in vivo. Either an azo-dye method or lead-salt method was employed using naphthol AS-MX phosphate and ATP as substrate, respectively. With the azo-dye method, intense phosphatase reactions were demonstrated along the BBM at all three pH ranges. Phosphatase reactions of the BBM at pH 9.2 and 7.3 were abolished by L(+)-phenylalanine, heat pre-treatment, and EDTA chelation although some reaction remained at pH 7.3 after the treatment with EDTA or L(+)-phenylalanine. Phosphatase reactions of the BBM at pH 5.2 were resistant to L(+)-phenylalanine, L(+)-tartrate, PCMB and EDTA chelation, implying that the characteristics of the enzyme responsible for phosphohydrolysis at acid pH values differed from those at higher pH values. The lead-salt method in which ATP was used as substrate revealed intense reactions--which were dependent on Mg++ and stimulated by Ca++ and resistant to L(+)phenylalanine--to be localized along the BBM at alkaline and neutral pH values, but not at acid pH values. In vitro experiments showed progressive hydrolysis of naphthol AS-MX phosphate by purified phytase at pH 5.2, in a dose-dependent manner, and suggested the possible involvement of phytase in the phosphatase reactions of the BBM at acid pH. These data indicate that the phosphatase reactions at alkaline and neutral pH values, associated

  4. Protein patterns of brush-border fragments in congenital lactose malabsorption and in specific hypolactasia of the adult.

    PubMed

    Freiburghaus, A U; Schmitz, J; Schindler, M; Rotthauwe, H W; Kuitunen, P; Launiala, K; Hadorn, B

    1976-05-06

    Brush-border membrane proteins of the small-bowel mucosa were separated on polyacrylamide gels from intestinal biopsy specimens obtained from four children with congenital lactose malabsorption and from two adults with specific hypolactasia. In three patients with the congenital type of lactase deficiency the protein band corresponding to brush-border lactase was reduced in intensity, but was never completely absent. No difference in gel patterns was detected when this pattern in congenital deficiency was compared to that obtained from the two patients with adult-type selective hypolactasia. In one patient with congenital lactose malabsorption the protein band corresponding to lactase activity was not detectable. The findings suggest that the mechanisms leading to low lactase activity in the congenital and adult forms of lactose intolerance are similar.

  5. BRUSH BORDER DEVELOPMENT IN THE INTESTINAL ABSORPTIVE CELLS OF XENOPUS DURING METAMORPHOSIS

    PubMed Central

    Bonneville, Mary A.; Weinstock, Melvyn

    1970-01-01

    The differentiation of the brush border which makes up the apical free surface of intestinal absorptive cells has been studied by electron microscopy. Specimens of Xenopus small intestine were fixed at various stages during metamorphosis, the time when a new intestinal epithelium forms. The interpretation of details described herein emphasizes the role of "surface-forming" vesicles. These vesicles are thought to provide membrane both for the initial expansion of the apical surface and for the later elongation of the microvilli. The latter are believed to be "molded" around filamentous cores that appear early in differentiation. The cores are attached to the apical membrane and extend vertically into the supranuclear cytoplasm. This interpretation rests chiefly on (a) the resemblance, both in morphology and in staining properties with colloidal thorium, between the membrane that limits the vesicles and that which limits the microvilli and (b) the distribution and time of appearance of the vesicles with respect to development of the microvilli. According to this view, the specific properties of surface membrane reside in preformed units that arise within the supranuclear cytoplasm. This morphogenetic process probably involves participation of the Golgi region as the site where the complex macromolecular architecture of the cell surface is assembled. PMID:4187705

  6. Evolutionary matches of enzyme and transporter capacities to dietary substrate loads in the intestinal brush border

    PubMed Central

    Weiss, Stacey L.; Lee, Eric A.; Diamond, Jared

    1998-01-01

    Safety factors of enzymes and transporters are defined as the ratio of Vmax (maximal reaction rates at high substrate concentrations) to the reaction rate under actual physiological conditions. Although corresponding safety factors have been measured for macroscopic biological structures and for human-engineered structures, safety factors have been little studied at the molecular level. Some evolutionary considerations suggest that safety factors should be modestly in excess of 1.0 (“enough but not too much”) and should tend to be similar for the various steps of a pathway consisting of two or more elements arranged in series. Hence we used a preparation of intact mouse small intestine to measure Vmax values (capacities) of brush-border sucrase (yielding glucose plus fructose) and of the brush-border glucose transporter, for comparison with each other and with dietary sucrose loads. Load was manipulated by varying dietary sucrose level or by studying lactating mice with increased energy requirements. Capacities both of sucrase and the glucose transporter increased with sucrose load (i.e., both proteins are inducible) and remained approximately matched to each other except on a carbohydrate-free diet. Their safety factors decreased from ca. 2.7 at low load to 1.0 at high load. Thus, neither sucrase nor the glucose transporter is the rate-limiting step for sucrose digestion; both steps are equally limiting. The modest safety factors and matched capacities must be genetically programmed through natural selection, with benefits of excess capacities being balanced against costs of biosynthetic energy and limited membrane space. PMID:9482848

  7. Studies on the enzymology of purified preparations of brush border from rabbit kidney

    PubMed Central

    George, S. G.; Kenny, A. J.

    1973-01-01

    1. A method for the preparation of brush border from rabbit kidneys is described. Contamination by other organelles was checked by electron microscopy and by the assay of marker enzymes and was low. 2. Seven enzymes, all hydrolases, were substantially enriched in the brush-border preparation and are considered to be primarily located in this structure. They are: alkaline phosphatase, maltase, trehalase, aminopeptidase A, aminopeptidase M, γ-glutamyl transpeptidase and a neutral peptidase assayed by its ability to hydrolyse [125I]iodoinsulin B chain. 3. Adenosine triphosphatases were also present in the preparation, but showed lower enrichments. 4. Alkaline phosphatase was the most active phosphatase present in the preparation. The weak hydrolysis of AMP may well have been due to this enzyme rather than a specific 5′-nucleotidase. 5. The two disaccharidases in brush border were distinguished by the relative heat-stability of trehalase compared with that of maltase. 6. The individuality of the four peptidases was established by several means. The neutral peptidase and aminopeptidase M, both of which can attack insulin B chain, differed not only in response to inhibitors and activators but also in the inhibitory effect of a guinea-pig antiserum raised to rabbit aminopeptidase M. This antiserum inhibited both the purified and the brush-border activities of aminopeptidase M. The neutral peptidase and γ-glutamyl transpeptidase were unaffected but aminopeptidase A was weakly inhibited. The characteristic responses to Ca2+ and serine with borate served to distinguish aminopeptidase A and γ-glutamyl transpeptidase from other peptidases. 7. No dipeptidases, tripeptidases or carboxypeptidases were identified as brush-border enzymes. 8. Incubation of brush border with papain released almost all the aminopeptidase M activity but only about half the activities of maltase, γ-glutamyl transpeptidase and aminopeptidase A. No release of alkaline phosphatase, trehalase or the

  8. Intra Amniotic Administration of Raffinose and Stachyose Affects the Intestinal Brush Border Functionality and Alters Gut Microflora Populations

    PubMed Central

    Pacifici, Sarina; Song, Jaehong; Zhang, Cathy; Wang, Qiaoye; Glahn, Raymond P.; Kolba, Nikolai; Tako, Elad

    2017-01-01

    This study investigates the effectiveness of two types of prebiotics—stachyose and raffinose—which are present in staple food crops that are widely consumed in regions where dietary Fe deficiency is a health concern. The hypothesis is that these prebiotics will improve Fe status, intestinal functionality, and increase health-promoting bacterial populations in vivo (Gallus gallus). By using the intra-amniotic administration procedure, prebiotic treatment solutions were injected in ovo (day 17 of embryonic incubation) with varying concentrations of a 1.0 mL pure raffinose or stachyose in 18 MΩ H2O. Four treatment groups (50, 100 mg·mL−1 raffinose or stachyose) and two controls (18 MΩ H2O and non-injected) were utilized. At hatch the cecum, small intestine, liver, and blood were collected for assessment of the relative abundance of the gut microflora, relative expression of Fe-related genes and brush border membrane functional genes, hepatic ferritin levels, and hemoglobin levels, respectively. The prebiotic treatments increased the relative expression of brush border membrane functionality proteins (p < 0.05), decreased the relative expression of Fe-related proteins (p < 0.05), and increased villus surface area. Raffinose and stachyose increased the relative abundance of probiotics (p < 0.05), and decreased that of pathogenic bacteria. Raffinose and stachyose beneficially affected the gut microflora, Fe bioavailability, and brush border membrane functionality. Our investigations have led to a greater understanding of these prebiotics’ effects on intestinal health and mineral metabolism. PMID:28335485

  9. Renal brush-border Na/sup +/-H/sup +/ exchange activity in the aging rat

    SciTech Connect

    Kinsella, J.L.; Sacktor, B.

    1987-04-01

    Amiloride-sensitive Na/sup +/-H/sup +/ exchange activity in brush-border membrane vesicles isolated from male rat proximal tubules was decreased in the senescent rat (24 mo) compared with the young adult (6 mo). There was no significant loss in Na/sup +/-H/sup +/ exchange activity in the kidneys of animals between 6 and 18 mo of age. Amiloride-insensitive /sup 22/Na/sup +/ uptake and the rate of pH gradient dissipation were not altered during aging. The decrease in sodium-dependent (/sup 32/P) phosphate transport preceded the decline in Na/sup +/-H/sup +/ exchange activity by at least 6 mo. Sodium-dependent D-(/sup 3/H) glucose transport was not significantly altered during aging. Thus various renal plasma membrane transport functions were affected differently in the aging rat. The decrease in Na/sup +/-H/sup +/ exchange activity during aging contrasted with the increase in exchange activity reported previously in acute ablation models of chronic renal failure.

  10. Radiation inactivation studies of renal brush border water and urea transport

    SciTech Connect

    Verkman, A.S.; Dix, J.A.; Seifter, J.L.; Skorecki, K.L.; Jung, C.Y.; Ausiello, D.A.

    1985-12-01

    Radiation inactivation was used to determine the nature and molecular weight of water and urea transport pathways in brush border membrane vesicles (BBMV) isolated from rabbit renal cortex. BBMV were frozen to -50 degrees C, irradiated with 1.5 MeV electrons, thawed, and assayed for transport or enzyme activity. The freezing process had no effect on enzyme or transport kinetics. BBMV alkaline phosphatase activity gave linear ln(activity) vs. radiation dose plots with a target size of 68 +/- 3 kDa, similar to previously reported values. Water and solute transport were measured using the stopped-flow light-scattering technique. The rates of acetamide and osmotic water transport did not depend on radiation dose (0-7 Mrad), suggesting that transport of these substances does not require a protein carrier. In contrast, urea and thiourea transport gave linear ln(activity) vs. dose curves with a target size of 125-150 kDa; 400 mM urea inhibited thiourea flux by -50% at 0 and 4.7 Mrad, showing that radiation does not affect inhibitor binding to surviving transporters. These studies suggest that BBMV urea transport requires a membrane protein, whereas osmotic water transport does not.

  11. Disruption of the C. elegans Intestinal Brush Border by the Fungal Lectin CCL2 Phenocopies Dietary Lectin Toxicity in Mammals

    PubMed Central

    Stutz, Katrin; Kaech, Andres; Aebi, Markus; Künzler, Markus; Hengartner, Michael O.

    2015-01-01

    Lectins are non-immunoglobulin carbohydrate-binding proteins without enzymatic activity towards the bound carbohydrates. Many lectins of e.g. plants or fungi have been suggested to act as toxins to defend the host against predators and parasites. We have previously shown that the Coprinopsis cinerea lectin 2 (CCL2), which binds to α1,3-fucosylated N-glycan cores, is toxic to Caenorhabditis elegans and results in developmental delay and premature death. In this study, we investigated the underlying toxicity phenotype at the cellular level by electron and confocal microscopy. We found that CCL2 directly binds to the intestinal apical surface and leads to a highly damaged brush border with loss of microvilli, actin filament depolymerization, and invaginations of the intestinal apical plasma membrane through gaps in the terminal web. We excluded several possible toxicity mechanisms such as internalization and pore-formation, suggesting that CCL2 acts directly on intestinal apical plasma membrane or glycocalyx proteins. A genetic screen for C. elegans mutants resistant to CCL2 generated over a dozen new alleles in bre 1, ger 1, and fut 1, three genes required for the synthesis of the sugar moiety recognized by CCL2. CCL2-induced intestinal brush border defects in C. elegans are similar to the damage observed previously in rats after feeding the dietary lectins wheat germ agglutinin or concanavalin A. The evolutionary conserved reaction of the brush border between mammals and nematodes might allow C. elegans to be exploited as model organism for the study of dietary lectin-induced intestinal pathology in mammals. PMID:26057124

  12. Role of intestinal brush border peptidases in the simulated digestion of milk proteins.

    PubMed

    Picariello, Gianluca; Miralles, Beatriz; Mamone, Gianfranco; Sánchez-Rivera, Laura; Recio, Isidra; Addeo, Francesco; Ferranti, Pasquale

    2015-05-01

    This study aimed to assess the impact of the "often neglected" intestinal brush border membranes (BBMs) hydrolases on dietary peptides, exploring the possibility that the disintegration of proteins progressed in the small intestine up to a "core" of intrinsically stable oligopeptides, persisting independently on the up-stream breakdown. Samples of sodium caseinate, skim milk powder, and whey protein isolate were submitted to in vitro simulated gastropancreatic digestion using two different procedures: (i) a simplified model involving the main compartmental specific proteases; (ii) a static digestion method based on a frameset of parameters inferred from in vivo. The gastroduodenal digesta were further hydrolyzed with peptidases from porcine jejunal BBM. The peptidomes arising from the two digestion models, characterized by combined HPLC and MS techniques, differed to some extent. However, only specific protein domains survived digestion, among which are potential bioactive or immunogenic (food allergy) peptides. The degree of hydrolysis (DH) after BBM digestion (70-77%) practically did not differ between the digestion models and significantly increased the DH after duodenal steps. Any in vitro digestion model should be supplemented with a jejunal phase to realistically determine the bioaccessibility and bioavailability of dietary peptides. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. In Vivo, Villin Is Required for Ca2+-Dependent F-Actin Disruption in Intestinal Brush Borders

    PubMed Central

    Ferrary, Evelyne; Cohen-Tannoudji, Michel; Pehau-Arnaudet, Gérard; Lapillonne, Alexandre; Athman, Rafika; Ruiz, Tereza; Boulouha, Lilia; El Marjou, Fatima; Doye, Anne; Fontaine, Jean-Jacques; Antony, Claude; Babinet, Charles; Louvard, Daniel; Jaisser, Frédéric; Robine, Sylvie

    1999-01-01

    Villin is an actin-binding protein localized in intestinal and kidney brush borders. In vitro, villin has been demonstrated to bundle and sever F-actin in a Ca2+-dependent manner. We generated knockout mice to study the role of villin in vivo. In villin-null mice, no noticeable changes were observed in the ultrastructure of the microvilli or in the localization and expression of the actin-binding and membrane proteins of the intestine. Interestingly, the response to elevated intracellular Ca2+ differed significantly between mutant and normal mice. In wild-type animals, isolated brush borders were disrupted by the addition of Ca2+, whereas Ca2+ had no effect in villin-null isolates. Moreover, increase in intracellular Ca2+ by serosal carbachol or mucosal Ca2+ ionophore A23187 application abolished the F-actin labeling only in the brush border of wild-type animals. This F-actin disruption was also observed in physiological fasting/refeeding experiments. Oral administration of dextran sulfate sodium, an agent that causes colonic epithelial injury, induced large mucosal lesions resulting in a higher death probability in mice lacking villin, 36 ± 9.6%, compared with wild-type mice, 70 ± 8.8%, at day 13. These results suggest that in vivo, villin is not necessary for the bundling of F-actin microfilaments, whereas it is necessary for the reorganization elicited by various signals. We postulate that this property might be involved in cellular plasticity related to cell injury. PMID:10459016

  14. Exposure to Engineered Nanomaterial Results in Disruption of Brush Borders in Epithelia Models in vitro

    NASA Astrophysics Data System (ADS)

    Faust, James J.

    Engineered nanoparticles (NP; 10-9 m) have found use in a variety of consumer goods and medical devices because of the unique changes in material properties that occur when synthesized on the nanoscale. Although many definitions for nanoparticle exist, from the perspective of size, nanoparticle is defined as particles with diameters less than 100 nm in any external dimension. Examples of their use include titanium dioxide added as a pigment in products intended to be ingested by humans, silicon dioxide NPs are used in foods as an anticaking agent, and gold or iron oxide NPs can be used as vectors for drug delivery or contrast agents for specialized medical imaging. Although the intended use of these NPs is often to improve human health, it has come to the attention of investigators that NPs can have unintended or even detrimental effects on the organism. This work describes one such unintended effect of NP exposure from the perspective of exposure via the oral route. First, this Dissertation will explain an event referred to as brush border disruption that occurred after nanoparticles interacted with an in vitro model of the human intestinal epithelium. Second, this Dissertation will identify and characterize several consumer goods that were shown to contain titanium dioxide that are intended to be ingested. Third, this Dissertation shows that sedimentation due to gravity does not artifactually result in disruption of brush borders as a consequence of exposure to food grade titanium dioxide in vitro. Finally, this Dissertation will demonstrate that iron oxide nanoparticles elicited similar effects after exposure to an in vitro brush border expressing model of the human placenta. Together, these data suggest that brush border disruption is not an artifact of the material/cell culture model, but instead represents a bona fide biological response as a result of exposure to nanomaterial.

  15. Angiotensin I Converting Enzyme (Kininase II) of the Brush Border of Human and Swine Intestine.

    DTIC Science & Technology

    1980-05-23

    demonstrated by bioassay. Captopril , the orally active specific inhibitor of ACE, inhibited tt6 enzyme: its I was 3 x 10_9M. Antibody to swine kidney ACE...interference in the functions of this enzyme may occur with chronic captopril therapy. K ngiotensir Iconverting enzyme (ACE; dipeptidyl carboxypeptidase; E.C...intestinal brush border (l0).+ These studies were also prompted by the use of the specific inhibitor of ACE, SQ 14225 or captopril , on a large scale in

  16. Kinetic characteristics of brush border sucrase activation by Na+ ions in mice intestine.

    PubMed

    Gupta, Shiffalli; Mahmood, Safrun; Mahmood, Akhtar

    2009-10-01

    The kinetics of Na+ activation of brush border sucrase (sucrose D-glucosidase E.C. 3.2.1.48) has been studied in mice intestine. At pH 5.0, 50 mM Na+ ions stimulated sucrase activity by 84%. At pH 7.2, enzyme stimulation was reduced to 16%, whereas, atpH 8.5, 10-100 mMNa+ ions produced 18-45% inhibition of enzyme activity. Kinetic studies revealed that at pH 5.0, the enzyme activation by Na+ ions was V-type, which changed to K-type atpH 7.2, whereas at alkaline pH (8.5), Na+ ions inhibited the enzyme activity non-competitively. Using the non-compulsory model of Na+ ion stimulation of brush border sucrase [Mahmood & Alvarado, Arch Bioch Biophys, 168 (1975) 585] various kinetic constants involved in activation of sucrase by Na ions were determined. It is apparent that Na+ stimulation of brush border sucrase is pH dependent, which is similar to that described for rat, rabbit and other mammalian species and conform to identical mechanisms, at least with reference to the affinity type effects, as observed in mice intestine.

  17. The cell adhesion molecule Fasciclin2 regulates brush border length and organization in Drosophila renal tubules

    PubMed Central

    Halberg, Kenneth A.; Rainey, Stephanie M.; Veland, Iben R.; Neuert, Helen; Dornan, Anthony J.; Klämbt, Christian; Davies, Shireen-Anne; Dow, Julian A. T.

    2016-01-01

    Multicellular organisms rely on cell adhesion molecules to coordinate cell–cell interactions, and to provide navigational cues during tissue formation. In Drosophila, Fasciclin 2 (Fas2) has been intensively studied due to its role in nervous system development and maintenance; yet, Fas2 is most abundantly expressed in the adult renal (Malpighian) tubule rather than in neuronal tissues. The role Fas2 serves in this epithelium is unknown. Here we show that Fas2 is essential to brush border maintenance in renal tubules of Drosophila. Fas2 is dynamically expressed during tubule morphogenesis, localizing to the brush border whenever the tissue is transport competent. Genetic manipulations of Fas2 expression levels impact on both microvilli length and organization, which in turn dramatically affect stimulated rates of fluid secretion by the tissue. Consequently, we demonstrate a radically different role for this well-known cell adhesion molecule, and propose that Fas2-mediated intermicrovillar homophilic adhesion complexes help stabilize the brush border. PMID:27072072

  18. Hormone induced expression of brush border lactase in suckling rat intestine.

    PubMed

    Chaudhry, Kamaljit Kaur; Mahmood, Safrun; Mahmood, Akhtar

    2008-05-01

    The postnatal development of intestine is associated with a decline in brush border lactase activity in rodents. This is similar to adulthood hypolactasia, a phenomenon prevalent in humans worldwide. In the present study, the effect of luminal proteases from adult rat intestine was studied in vitro on intestinal lactase activity in saline control, thyroxine, insulin and cortisone treated rat pups. Lactase levels were determined by enzyme analysis and Western blotting. mRNA levels encoding lactase were determined by Northern blotting. Administration of thyroxine for 4 days reduced (P<0.05) lactase activity, but insulin treatment had no effect in 8-day-old rat intestine. However, cortisone administration augmented (P<0.01) lactase activity, under these conditions. Western blot analysis showed decreased lactase signal corresponding to 220-kDa protein band in thyroxine treated animals. However, the intensity of lactase signal was high in cortisone treated animals compared to controls. mRNA levels encoding lactase showed a 6.8-kb mRNA transcript in saline and hormone treated rats. mRNA levels encoding lactase were increased in cortisone treated animals but were reduced in thyroxine injected pups compared to controls. Microvillus membranes from saline (P<0.01) and thyroxine (P<0.05) or insulin (P<0.01) treated rats upon incubation with luminal wash from adult rat intestine showed a significant decline in lactase activity. These findings suggest that thyroxine, insulin or cortisone induced changes in lactase expression in suckling rat intestine make it susceptible to luminal proteases, which may in part be responsible for observed maturational decline in lactase activity in adult rat intestine.

  19. Jejunal Brush Border Microvillous Alterations in Giardia muris-Infected Mice: Role of T Lymphocytes and Interleukin-6

    PubMed Central

    Scott, K. G.-E.; Logan, M. R.; Klammer, G. M.; Teoh, D. A.; Buret, A. G.

    2000-01-01

    Intestinal colonization with the protozoan Giardia causes diffuse brush border microvillous alterations and disaccharidase deficiencies, which in turn are responsible for intestinal malabsorption and maldigestion. The role of T cells and/or cytokines in the pathogenesis of Giardia-induced microvillous injury remains unclear. The aim of this study was to assess the role of T cells and interleukin-6 (IL-6) in the brush border pathophysiology of acute murine giardiasis in vivo. Athymic nude (nu−/nu−) CD-1 mice and isogenic immunocompetent (nu+/nu+) CD-1 mice (4 weeks old) received an axenic Giardia muris trophozoite inoculum or vehicle (control) via orogastric gavage. Weight gain and food intake were assessed daily. On day 6, segments of jejunum were assessed for parasite load, brush border ultrastructure, IL-6 content, maltase and sucrase activities, villus-crypt architecture, and intraepithelial lymphocyte (IEL) infiltration. Despite similar parasitic loads on day 6, infected immunocompetent animals, but not infected nude mice, showed a diffuse loss of brush border microvillous surface area, which was correlated with a significant reduction in maltase and sucrase activities and a decrease in jejunal IL-6 concentration. In both athymic control and infected mice, jejunal brush border surface area and disaccharidases were high, but levels of tissue IL-6 were low and comparable to the concentration measured in immunocompetent infected animals. In both immunocompetent and nude mice, infection caused a small but significant increase in the numbers of IELs. These findings suggest that the enterocyte brush border injury and malfunction seen in giardiasis is, at least in part, mediated by thymus-derived T lymphocytes and that suppressed jejunal IL-6 does not necessarily accompany microvillous shortening. PMID:10816492

  20. IgG trafficking in the adult pig small intestine: one- or bidirectional transfer across the enterocyte brush border?

    PubMed

    Möller, Rebecca; Hansen, Gert H; Danielsen, E Michael

    2017-03-01

    Immunoglobulin G (IgG) transfer in opposite directions across the small intestinal brush border serves different purposes in early life and in adulthood. In the neonate, maternal IgG is taken up from the gut lumen into the blood, conferring passive immunity to the offspring, whereas in the adult immunoglobulins, including IgG made by plasma cells in the lamina propria, are secreted via the brush border to the lumen as part of the mucosal defense. Here, IgG has been proposed to perform a luminal immune surveillance which eventually includes a reuptake through the brush border as pathogen-containing immune complexes. In the present work, we studied luminal uptake of FITC-conjugated and gold-conjugated IgG in cultured pig jejunal mucosal explants. After 1 h, binding to the brush border was seen in upper crypts and lower parts of the villi. However, no endocytotic uptake into EEA-1-positive compartments was detected, neither at neutral nor acidic pH, despite an ongoing constitutive endocytosis from the brush border, visualized by the polar tracer CF594. The 40-kDa neonatal Fc receptor, FcRn, was present in the microvillus fraction, but noteworthy, a 37 kDa band, most likely a proteolytic cleavage product, bound IgG in a pH-dependent manner more efficiently than did the full-length FcRn. In conclusion, our work does not support the theory that bidirectional transfer of IgG across the intestinal brush border is part of the luminal immune surveillance in the adult.

  1. Beneficial influence of dietary spices on the ultrastructure and fluidity of the intestinal brush border in rats.

    PubMed

    Prakash, Usha N S; Srinivasan, Krishnapura

    2010-07-01

    The beneficial influence of three common spices was examined in experimental rats on: (i) the membrane fluidity of intestinal brush-border membranes (BBM), (ii) the activity of intestinal membrane-bound enzymes, and (iii) ultrastructural alterations in the intestinal epithelium. Groups of male Wistar rats were maintained on dietary black pepper (0.5 %), red pepper (3.0 %), ginger (0.05 %) and spice bioactive compounds piperine (0.02 %) and capsaicin (0.01 %) for 8 weeks. A membrane fluidity study using an apolar fluorescent probe showed increased BBM fluidity in all the spice-fed animals. This was corroborated by a decreased cholesterol:phospholipid ratio in the jejunal and ileal regions of the intestine. These dietary spices stimulated the activities of BBM enzymes (glycyl-glycine dipeptidase, leucine amino peptidase and gamma-glutamyl transpeptidase) in the jejunal mucosa, suggesting a modulation in membrane dynamics due to the apolar spice bioactive compounds interacting with surrounding lipids and hydrophobic portions in the protein vicinity, which may decrease the tendency of membrane lipids to act as steric constraints to enzyme proteins and thus modify enzyme conformation. Scanning electronic microscopy of the intestinal villi in these spice treatments revealed alterations in the ultrastructure, especially an increase in microvilli length and perimeter which would mean a beneficial increase in the absorptive surface of the small intestine, providing for an increased bioavailability of micronutrients. Thus, dietary spices (black pepper, red pepper and ginger) were evidenced to induce alterations in BBM fluidity and passive permeability property, associated with the induction of an increased microvilli length and perimeter, resulting in an increased absorptive surface of the small intestine.

  2. Carbachol- and elevated Ca(2+)-induced translocation of functionally active protein kinase C to the brush border of rabbit ileal Na+ absorbing cells.

    PubMed Central

    Cohen, M E; Wesolek, J; McCullen, J; Rys-Sikora, K; Pandol, S; Rood, R P; Sharp, G W; Donowitz, M

    1991-01-01

    Protein kinase C is involved in mediating the effects of elevated Ca2+ in ileal villus Na+ absorbing cells to inhibit NaCl absorption. The present studies were undertaken to understand the mechanism by which this occurs. The effects of carbachol and the calcium ionophore A23187, agents which elevate intracellular Ca2+ and inhibit NaCl absorption in ileal villus cells, were studied. Carbachol treatment of villus cells caused a rapid decrease in protein kinase C activity in cytosol, with an accompanying increase in microvillus membrane C kinase. Exposure of the villus cells to calcium ionophore also caused a quantitatively similar decrease in cytosol C kinase and increase in C kinase activity in the microvillus membrane. This increase caused by carbachol and Ca2+ ionophore was specific for the microvillus membrane. In fact, 30 s and 10 min after exposure of the cells to carbachol, basolateral membrane protein kinase C decreased, in a time-dependent manner; whereas 10 min of Ca2+ ionophore exposure did not alter basolateral C kinase. Exposure of villus cells to Ca2+ ionophore or carbachol caused similar increases in microvillus membrane diacylglycerol content. As judged by the ability to inhibit Na+/H+ exchange measured in ileal villus cell brush border membrane vesicles, the protein kinase C which translocated to the microvillus membrane was functionally significant. Inhibition of Na+/H+ exchange required ATP and was reversed by the protein kinase C antagonist H-7. In conclusion, the effect of carbachol and Ca2+ ionophore in regulation of ileal NaCl absorption is associated with an increase in microvillus membrane diacylglycerol content and functionally active protein kinase C. The effects of both carbachol and Ca2+ ionophore are different on brush border and basolateral membrane distribution of protein kinase C. Images PMID:1885773

  3. Freeze-thaw and high-voltage discharge allow macromolecule uptake into ileal brush-border vesicles

    SciTech Connect

    Donowitz, M.; Emmer, E.; McCullen, J.; Reinlib, L.; Cohen, M.E.; Rood, R.P.; Madara, J.; Sharp, G.W.G.; Murer, H.; Malmstrom, K.

    1987-06-01

    High-voltage discharge or one cycle of freeze-thawing are shown to transiently permeabilize rabbit ileal brush-border membrane vesicles to macromolecules. Uptake of the radiolabeled macromolecule dextran, mol wt 70,000, used as a marker for vesicle permeability, was determined by a rapid filtration technique, with uptake defined as substrate associated with the vesicle and releasable after incubation of vesicles with 0.1% saponin. Dextran added immediately after electric shock (2000 V) or at the beginning of one cycle of freeze-thawing was taken up approximately eightfold compared with control. ATP also was taken up into freeze-thawed vesicles, whereas there was no significant uptake into control vesicles. The increase in vesicle permeability was reversible, based on Na-dependent D-glucose uptake being decreased when studied 5 but not 15 min after electric shock, and was not significantly decreased after completion of one cycle of freeze-thawing. In addition, adenosine 3',5'-cyclic monophosphate and Ca/sup 2 +/-calmodulin-dependent protein kinase activity were similar in control vesicles and vesicles exposed to high-voltage discharge or freeze-thawing. Also, vesicles freeze-thawed with (/sup 32/P)ATP demonstrated increased phosphorylation compared with nonfrozen vesicles, while freeze-thawing did not alter vesicle protein as judged by Coomassie blue staining. These techniques should allow intestinal membrane vesicles to be used for studies of intracellular control of transport processes, for instance, studies of protein kinase regulation of transport.

  4. Brush border Myosin Ia has tumor suppressor activity in the intestine

    PubMed Central

    Mazzolini, Rocco; Dopeso, Higinio; Mateo-Lozano, Silvia; Chang, Wakam; Rodrigues, Paulo; Bazzocco, Sarah; Alazzouzi, Hafid; Landolfi, Stefania; Hernández-Losa, Javier; Andretta, Elena; Alhopuro, Pia; Espín, Eloy; Armengol, Manel; Tabernero, Josep; Ramón y Cajal, Santiago; Kloor, Matthias; Gebert, Johannes; Mariadason, John M.; Schwartz, Simo; Aaltonen, Lauri A.; Mooseker, Mark S.; Arango, Diego

    2012-01-01

    The loss of the epithelial architecture and cell polarity/differentiation is known to be important during the tumorigenic process. Here we demonstrate that the brush border protein Myosin Ia (MYO1A) is important for polarization and differentiation of colon cancer cells and is frequently inactivated in colorectal tumors by genetic and epigenetic mechanisms. MYO1A frame-shift mutations were observed in 32% (37 of 116) of the colorectal tumors with microsatellite instability analyzed, and evidence of promoter methylation was observed in a significant proportion of colon cancer cell lines and primary colorectal tumors. The loss of polarization/differentiation resulting from MYO1A inactivation is associated with higher tumor growth in soft agar and in a xenograft model. In addition, the progression of genetically and carcinogen-initiated intestinal tumors was significantly accelerated in Myo1a knockout mice compared with Myo1a wild-type animals. Moreover, MYO1A tumor expression was found to be an independent prognostic factor for colorectal cancer patients. Patients with low MYO1A tumor protein levels had significantly shorter disease-free and overall survival compared with patients with high tumoral MYO1A (logrank test P = 0.004 and P = 0.009, respectively). The median time-to-disease recurrence in patients with low MYO1A was 1 y, compared with >9 y in the group of patients with high MYO1A. These results identify MYO1A as a unique tumor-suppressor gene in colorectal cancer and demonstrate that the loss of structural brush border proteins involved in cell polarity are important for tumor development. PMID:22307608

  5. [Design of radiolabeled antibody fragments for tumor-selective radioactivity localization--brush border enzyme-sensitive bond to decrease renal accumulation of radioactivity].

    PubMed

    Mukai, Takahiro; Fujioka, Yasushi; Arano, Yasushi; Saji, Hideo

    2003-08-01

    Nonspecific renal radioactivity localization constitutes a problem in targeted imaging and therapy with radiolabeled antibody fragments. Based on the idea that the renal radioactivity levels should be reduced if radiolabeled compounds excreted in the urine are released from antibody fragments by tubular brush border enzymes, 3'-iodohippuryl N epsilon-maleoyl-L-lysine (HML) was designed as a radioiodination reagent for antibody fragments; the glycyl-lysine sequence in HML is a substrate for a brush border enzyme and m-iodohippuric acid is released by cleavage of the linkage. In normal mice, HML-conjugated Fab demonstrated low renal radioactivity levels from early postinjection times. Directly radioiodinated Fab showed migration of radioactivity from the membrane to the lysosomal fraction of the renal cells from 10 to 30 min postinjection. On the other hand, the majority of the radioactivity was detected only in the membrane fraction after injection of HML-conjugated Fab. In tumor-bearing mice, HML-conjugated Fab showed a marked decrease in renal radioactivity localization without impairing the tumor accumulation. These findings indicate that HML is a useful reagent for reducing the renal radioactivity levels of antibody fragments.

  6. Induction of a Gradual, Reversible Morphogenesis of Its Host’s Epithelial Brush Border by Vibrio fischeri

    PubMed Central

    Lamarcq, Laurence H.; McFall-Ngai, Margaret J.

    1998-01-01

    Bacteria exert a variety of influences on the morphology and physiology of animal cells whether they are pathogens or cooperative partners. The association between the luminous bacterium Vibrio fischeri and the sepiolid squid Euprymna scolopes provides an experimental model for the study of the influence of extracellular bacteria on the development of host epithelia. In this study, we analyzed bacterium-induced changes in the brush borders of the light organ crypt epithelia during the initial hours following colonization of this tissue. Transmission electron microscopy of the brush border morphology in colonized and uncolonized hosts revealed that the bacteria effect a fourfold increase in microvillar density over the first 4 days of the association. Estimates of the proportions of bacterial cells in contact with host microvilli showed that the intimacy of the bacterial cells with animal cell surfaces increases significantly during this time. Antibiotic curing of the organ following colonization showed that sustained interaction with bacteria is essential for the retention of the induced morphological changes. Bacteria that are defective in either light production or colonization efficiency produced changes similar to those by the parent strain. Conventional fluorescence and confocal scanning laser microscopy revealed that the brush border is supported by abundant filamentous actin. However, in situ hybridization with β-actin probes did not show marked bacterium-induced increases in β-actin gene expression. These experiments demonstrate that the E. scolopes-V. fischeri system is a viable model for the experimental study of bacterium-induced changes in host brush border morphology. PMID:9453641

  7. Natural Selection at the Brush-Border: Adaptations to Carbohydrate Diets in Humans and Other Mammals.

    PubMed

    Pontremoli, Chiara; Mozzi, Alessandra; Forni, Diego; Cagliani, Rachele; Pozzoli, Uberto; Menozzi, Giorgia; Vertemara, Jacopo; Bresolin, Nereo; Clerici, Mario; Sironi, Manuela

    2015-08-28

    Dietary shifts can drive molecular evolution in mammals and a major transition in human history, the agricultural revolution, favored carbohydrate consumption. We investigated the evolutionary history of nine genes encoding brush-border proteins involved in carbohydrate digestion/absorption. Results indicated widespread adaptive evolution in mammals, with several branches experiencing episodic selection, particularly strong in bats. Many positively selected sites map to functional protein regions (e.g., within glucosidase catalytic crevices), with parallel evolution at SI (sucrase-isomaltase) and MGAM (maltase-glucoamylase). In human populations, five genes were targeted by positive selection acting on noncoding variants within regulatory elements. Analysis of ancient DNA samples indicated that most derived alleles were already present in the Paleolithic. Positively selected variants at SLC2A5 (fructose transporter) were an exception and possibly spread following the domestication of specific fruit crops. We conclude that agriculture determined no major selective event at carbohydrate metabolism genes in humans, with implications for susceptibility to metabolic disorders. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  8. A method for assaying intestinal brush-border sucrase in an intact intestinal preparation

    PubMed Central

    Lee, Eric A.; Weiss, Stacey L.; Lam, Mandy; Torres, Rosa; Diamond, Jared

    1998-01-01

    Small intestinal brush-border hydrolases usually are assayed in intestinal mucosal homogenates resuspended in solutions of unphysiological ionic composition. Thus, extrapolation of measured Vmax values (maximal reaction rates at high substrate concentrations) to in vivo conditions, hence comparison with physiological substrate loads, is uncertain. We therefore have developed a sucrase assay in an intact preparation of mouse small intestine, an everted intestinal sleeve incubated in a physiological Ringer’s solution. As in homogenate studies, sucrase is assayed by glucose production measured colorimetrically, but uptake of liberated glucose into the intestinal sleeve is prevented by the transport inhibitor phlorizin. The coefficient of variation of Vmax is 16% for sleeves from the same mouse and 8% for mean values from different mice. Sleeve sucrase activity is abolished by the inhibitor castanospermine. Activity in sleeves and homogenates proves to be the same when measured under identical solution conditions, but variations in assay conditions cause large activity changes from values measured in physiological solutions. PMID:9482847

  9. Natural Selection at the Brush-Border: Adaptations to Carbohydrate Diets in Humans and Other Mammals

    PubMed Central

    Pontremoli, Chiara; Mozzi, Alessandra; Forni, Diego; Cagliani, Rachele; Pozzoli, Uberto; Menozzi, Giorgia; Vertemara, Jacopo; Bresolin, Nereo; Clerici, Mario; Sironi, Manuela

    2015-01-01

    Dietary shifts can drive molecular evolution in mammals and a major transition in human history, the agricultural revolution, favored carbohydrate consumption. We investigated the evolutionary history of nine genes encoding brush-border proteins involved in carbohydrate digestion/absorption. Results indicated widespread adaptive evolution in mammals, with several branches experiencing episodic selection, particularly strong in bats. Many positively selected sites map to functional protein regions (e.g., within glucosidase catalytic crevices), with parallel evolution at SI (sucrase-isomaltase) and MGAM (maltase-glucoamylase). In human populations, five genes were targeted by positive selection acting on noncoding variants within regulatory elements. Analysis of ancient DNA samples indicated that most derived alleles were already present in the Paleolithic. Positively selected variants at SLC2A5 (fructose transporter) were an exception and possibly spread following the domestication of specific fruit crops. We conclude that agriculture determined no major selective event at carbohydrate metabolism genes in humans, with implications for susceptibility to metabolic disorders. PMID:26319403

  10. Freeze-thaw and high-voltage discharge allow macromolecule uptake into ileal brush-border vesicles.

    PubMed

    Donowitz, M; Emmer, E; McCullen, J; Reinlib, L; Cohen, M E; Rood, R P; Madara, J; Sharp, G W; Murer, H; Malmstrom, K

    1987-06-01

    High-voltage discharge or one cycle of freeze-thawing are shown to transiently permeabilize rabbit ileal brush-border membrane vesicles to macromolecules. Uptake of the radiolabeled macromolecule dextran, mol wt 70,000, used as a marker for vesicle permeability, was determined by a rapid filtration technique, with uptake defined as substrate associated with the vesicle and releasable after incubation of vesicles with 0.1% saponin. Dextran added immediately after electric shock (2,000 V) or at the beginning of one cycle of freeze-thawing was taken up approximately eightfold compared with control; with both techniques, the concentration of dextran after being taken up into the vesicles was similar to that in the incubation medium, suggesting attainment of equilibrium. ATP also was taken up into freeze-thawed vesicles, whereas there was no significant uptake into control vesicles. The increase in vesicle permeability was reversible, based on Na-dependent D-glucose uptake being decreased when studied 5 but not 15 min after electric shock, and was not significantly decreased after completion of one cycle of freeze-thawing. In addition, adenosine 3',5'-cyclic monophosphate and Ca2+-calmodulin-dependent protein kinase activity were similar in control vesicles and vesicles exposed to high-voltage discharge or freeze-thawing. Also, vesicles freeze-thawed with [32P]ATP demonstrated increased phosphorylation compared with nonfrozen vesicles, while freeze-thawing did not alter vesicle protein as judged by Coomassie blue staining. These techniques should allow intestinal membrane vesicles to be used for studies of intracellular control of transport processes, for instance, studies of protein kinase regulation of transport.

  11. Food grade titanium dioxide disrupts intestinal brush border microvilli in vitro independent of sedimentation.

    PubMed

    Faust, James J; Doudrick, Kyle; Yang, Yu; Westerhoff, Paul; Capco, David G

    2014-06-01

    Bulk- and nano-scale titanium dioxide (TiO2) has found use in human food products for controlling color, texture, and moisture. Once ingested, and because of their small size, nano-scale TiO2 can interact with a number of epithelia that line the human gastrointestinal tract. One such epithelium responsible for nutrient absorption is the small intestine, whose constituent cells contain microvilli to increase the total surface area of the gut. Using a combination of scanning and transmission electron microscopy it was found that food grade TiO2 (E171 food additive coded) included ∼25% of the TiO2 as nanoparticles (NPs; <100 nm), and disrupted the normal organization of the microvilli as a consequence of TiO2 sedimentation. It was found that TiO2 isolated from the candy coating of chewing gum and a commercially available TiO2 food grade additive samples were of the anatase crystal structure. Exposure to food grade TiO2 additives, containing nanoparticles, at the lowest concentration tested within this experimental paradigm to date at 350 ng/mL (i.e., 100 ng/cm(2) cell surface area) resulted in disruption of the brush border. Through the use of two independent techniques to remove the effects of gravity, and subsequent TiO2 sedimentation, it was found that disruption of the microvilli was independent of sedimentation. These data indicate that food grade TiO2 exposure resulted in the loss of microvilli from the Caco-2BBe1 cell system due to a biological response, and not simply a physical artifact of in vitro exposure.

  12. The Responses of Rat Intestinal Brush Border and Cytosol Peptide Hydrolase Activities to Variation in Dietary Protein Content DIETARY REGULATION OF INTESTINAL PEPTIDE HYDROLASES

    PubMed Central

    Nicholson, J. Alex; McCarthy, Denis M.; Kim, Young S.

    1974-01-01

    The effects of variation in dietary protein content on small intestinal brush border and cytosol peptide hydrolase activities have been investigated. One group of rats was fed a high protein diet (55% casein) and another group was fed a low protein diet (10% casein). After 1 wk, brush border peptide hydrolase activity (L-leucyl-β-naphthylamide as substrate) and cytosol peptide hydrolase activity (L-prolyl-L-leucine as substrate) were determined in mucosae taken from the proximal, middle, and distal small intestine. As judged by several parameters, brush border peptide hydrolase activity was significantly greater in rats fed the high protein diet when data for corresponding segments were compared. In contrast, no significant difference was seen in cytosol peptide hydrolase activity. In a second study, brush border and cytosol peptide hydrolase activities were determined in the proximal intestine by utilizing an additional three peptide substrates: L-leucyl-L-alanine, L-phenylalanylglycine, and glycyl-L-phenylalanine. Sucrase, maltase, and alkaline phosphatase activities were also determined. As before, brush border peptide hydrolase activities were significantly greater in rats fed the high protein diet. However, activities of the nonproteolytic brush border enzymes did not vary significantly with diet. In contrast to the results obtained with L-prolyl-L-leucine as substrate for the cytosol enzymes, cytosol activity against the three additional peptide substrates was greater in rats fed the high protein diet. It is suggested that the brush border peptide hydrolase response to variation in dietary protein content represents a functional adaptation analogous to the regulation of intestinal disaccharidases by dietary carbohydrates. The implication of the differential responses of the cytosol peptide hydrolases is uncertain, since little is known of the functional role of these nonorgan-specific enzymes. PMID:4430719

  13. Apolipoprotein A-1 (apoA-1) deposition in, and release from, the enterocyte brush border: a possible role in transintestinal cholesterol efflux (TICE)?

    PubMed

    Danielsen, E Michael; Hansen, Gert H; Rasmussen, Karina; Niels-Christiansen, Lise-Lotte; Frenzel, Franz

    2012-03-01

    Transintestinal cholesterol efflux (TICE) has been proposed to represent a non-hepatobiliary route of cholesterol secretion directly "from blood to gut" and to play a physiologically significant role in excretion of neutral sterols, but so far little is known about the proteins involved in the process. We have previously observed that apolipoprotein A-1 (apoA-1) synthesized by enterocytes of the small intestine is mainly secreted apically into the gut lumen during fasting where its assembly into chylomicrons and basolateral discharge is at a minimal level. In the present work we showed, both by immunomicroscopy and subcellular fractionation, that a fraction of the apically secreted apoA-1 in porcine small intestine was not released from the cell surface but instead deposited in the brush border. Cholesterol was detected in immunoisolated microvillar apoA-1, and it was partially associated with detergent resistant membranes (DRMs), indicative of localization in lipid raft microdomains. The apolipoprotein was not readily released from microvillar vesicles by high salt or by incubation with phosphatidylcholine-specific phospholipase C or trypsin, indicating a relatively firm attachment to the membrane bilayer. However, whole bile or taurocholate efficiently released apoA-1 at low concentrations that did not solubilize the transmembrane microvillar protein aminopeptidase N. Based on these findings and the well known role played by apoA-1 in extrahepatic cellular cholesterol removal and reverse cholesterol transport (RCT), we propose that brush border-deposited apoA-1 in the small intestine acts in TICE by mediating cholesterol efflux into the gut lumen.

  14. Ion induced changes in the structure of bordered pit membranes.

    PubMed

    Lee, Jinkee; Holbrook, N Michele; Zwieniecki, Maciej A

    2012-01-01

    Ion-mediated changes in xylem hydraulic resistance are hypothesized to result from hydrogel like properties of pectins located in the bordered pit membranes separating adjacent xylem vessels. Although the kinetics of the ion-mediated changes in hydraulic resistance are consistent with the swelling/deswelling behavior of pectins, there is no direct evidence of this activity. In this report we use atomic force microscopy (AFM) to investigate structural changes in bordered pit membranes associated with changes in the ionic concentration of the surrounding solution. When submerged in de-ionized water, AFM revealed bordered pit membranes as relatively smooth, soft, and lacking any sharp edges surface, in contrast to pictures from scanning electron microscope (SEM) or AFM performed on air-dry material. Exposure of the bordered pit membranes to 50 mM KCl solution resulted in significant changes in both surface physical properties and elevation features. Specifically, bordered pit membranes became harder and the fiber edges were clearly visible. In addition, the membrane contracted and appeared much rougher due to exposed microfibers. In neither solution was there any evidence of discrete pores through the membrane whose dimensions were altered in response to the ionic composition of the surrounding solution. Instead the variable hydraulic resistance appears to involve changes in the both the permeability and the thickness of the pit membrane.

  15. Antifouling Thin-Film Composite Membranes by Controlled Architecture of Zwitterionic Polymer Brush Layer.

    PubMed

    Liu, Caihong; Lee, Jongho; Ma, Jun; Elimelech, Menachem

    2017-02-21

    In this study, we demonstrate a highly antifouling thin-film composite (TFC) membrane by grafting a zwitterionic polymer brush via atom-transfer radical-polymerization (ATRP), a controlled, environmentally benign chemical process. Initiator molecules for polymerization were immobilized on the membrane surface by bioinspired catechol chemistry, leading to the grafting of a dense zwitterionic polymer brush layer. Surface characterization revealed that the modified membrane exhibits reduced surface roughness, enhanced hydrophilicity, and lower surface charge. Chemical force microscopy demonstrated that the modified membrane displayed foulant-membrane interaction forces that were 1 order of magnitude smaller than those of the pristine TFC membrane. The excellent fouling resistance imparted by the zwitterionic brush layer was further demonstrated by significantly reduced adsorption of proteins and bacteria. In addition, forward osmosis fouling experiments with a feed solution containing a mixture of organic foulants (bovine-serum albumin, alginate, and natural organic matter) indicated that the modified membrane exhibited significantly lower water flux decline compared to the pristine TFC membrane. The controlled architecture of the zwitterionic polymer brush via ATRP has the potential for a facile antifouling modification of a wide range of water treatment membranes without compromising intrinsic transport properties.

  16. Protein purification with polymeric affinity membranes containing functionalized poly(acid) brushes.

    PubMed

    Jain, Parul; Vyas, Mukesh Kumar; Geiger, James H; Baker, Gregory L; Bruening, Merlin L

    2010-04-12

    Porous nylon membranes modified with poly(acid) brushes and their derivatives can rapidly purify proteins via ion-exchange and metal-ion affinity interactions. Membranes containing poly(2-(methacryloyloxy)ethyl succinate) (poly(MES)) brushes bind 118 +/- 8 mg of lysozyme per cm(3) of membrane and facilitate purification of lysozyme from chicken egg white. Moreover, functionalization of the poly(MES) brushes with nitrilotriacetate (NTA)-Ni(2+) complexes yields membranes that bind poly(histidine)-tagged (His-tagged) ubiquitin with a capacity of 85 +/- 2 mg of protein per cm(3) of membrane. Most importantly, the membranes modified with poly(MES)-NTA-Ni(2+) allow isolation of His-tagged cellular retinaldehyde-binding protein directly from a cell extract in <10 min, and the protein purity is comparable to that achieved with commercial affinity columns. Therefore, porous nylon membranes containing functionalized poly(MES) brushes are attractive candidates for rapid, high-capacity purification of His-tagged proteins from cell extracts.

  17. Improving protein resistance of α-Al 2O 3 membranes by modification with POEGMA brushes

    NASA Astrophysics Data System (ADS)

    He, Huating; Jing, Wenheng; Xing, Weihong; Fan, Yiqun

    2011-11-01

    A kind of protein-resistant ceramic membrane is prepared by grafting poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) brushes onto the surfaces and pore walls of α-Al2O3 membrane (AM) by surface-initiated atom-transfer radical polymerization (SI-ATRP). Contact-angle, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and field-emission scanning electron microscopy (FESEM) were measured to confirm that the surfaces and pore walls of the ceramic porous membranes have been modified by the brushes with this method successfully. The protein interaction behavior with the POEGMA modified membranes (AM-POEGMA) was studied by the model protein of bovine serum albumin (BSA). A protein-resistant mechanism of AM-POEGMA was proposed to describe an interesting phenomenon discovered in the filtration experiment, in which the initial flux filtrating BSA solution is higher than the pure water flux. The fouling of AM-POEGMA was easier to remove than AM for the action of POEGMA brushes, indicated that the ceramic porous membranes modified with POEGMA brushes exhibit excellent protein resistance.

  18. Genetic evidence of an accessory activity required specifically for cubilin brush-border expression and intrinsic factor-cobalamin absorption.

    PubMed

    Xu, D; Kozyraki, R; Newman, T C; Fyfe, J C

    1999-11-15

    Cubilin is a high molecular weight multiligand receptor that mediates intestinal absorption of intrinsic factor-cobalamin and selective protein reabsorption in renal tubules. The genetic basis of selective intestinal cobalamin malabsorption with proteinuria was investigated in a canine model closely resembling human Imerslund-Gräsbeck syndrome caused by cubilin mutations. Canine CUBN cDNA was cloned and sequenced, showing high identity with human and rat CUBN cDNAs. An intragenic CUBN marker was identified in the canine family and used to test the hypothesis of genetic linkage of the disease and CUBN loci. Linkage was rejected, indicating that the canine disorder resembling Imerslund-Gräsbeck syndrome is caused by defect of a gene product other than cubilin. These results imply that there may be locus heterogeneity among human kindreds with selective intestinal cobalamin malabsorption and proteinuria and that normal brush-border expression of cubilin requires the activity of an accessory protein.

  19. Roles for Drosophila melanogaster Myosin IB in Maintenance of Enterocyte Brush-Border Structure and Resistance to the Bacterial Pathogen Pseudomonas entomophila

    PubMed Central

    Mermall, Valerie; Tilney, Lewis G.; Mooseker, Mark S.

    2007-01-01

    Drosophila myosin IB (Myo1B) is one of two class I myosins in the Drosophila genome. In the larval and adult midgut enterocyte, Myo1B is present within the microvillus (MV) of the apical brush border (BB) where it forms lateral tethers between the MV membrane and underlying actin filament core. Expression of green fluorescent protein-Myo1B tail domain in the larval gut showed that the tail domain is sufficient for localization of Myo1B to the BB. A Myo1B deletion mutation exhibited normal larval gut physiology with respect to food uptake, clearance, and pH regulation. However, there is a threefold increase in terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive enterocyte nuclei in the Myo1B mutant. Ultrastructural analysis of mutant midgut revealed many perturbations in the BB, including membrane tethering defects, MV vesiculation, and membrane shedding. The apical localization of both singed (fascin) and Dmoesin is impaired. BBs isolated from mutant and control midgut revealed that the loss of Myo1B causes the BB membrane and underlying cytoskeleton to become destabilized. Myo1B mutant larvae also exhibit enhanced sensitivity to oral infection by the bacterial pathogen Pseudomonas entomophila, and severe cytoskeletal defects are observed in the BB of proximal midgut epithelial cells soon after infection. Resistance to P. entomophila infection is restored in Myo1B mutant larvae expressing a Myo1B transgene. These results indicate that Myo1B may play a role in the local midgut response pathway of the Imd innate immune response to Gram-negative bacterial infection. PMID:17855510

  20. The NHE3 juxtamembrane cytoplasmic domain directly binds ezrin: dual role in NHE3 trafficking and mobility in the brush border.

    PubMed

    Cha, Boyoung; Tse, Ming; Yun, Chris; Kovbasnjuk, Olga; Mohan, Sachin; Hubbard, Ann; Arpin, Monique; Donowitz, Mark

    2006-06-01

    Based on physiological studies, the epithelial brush-border (BB) Na+/H+ antiporter3 (NHE3) seems to associate with the actin cytoskeleton both by binding to and independently of the PDZ domain containing proteins NHERF1 and NHERF2. We now show that NHE3 directly binds ezrin at a site in its C terminus between aa 475-589, which is separate from the PSD95/dlg/zonular occludens-1 (PDZ) interacting domain. This is an area predicted to be alpha-helical, with a positive aa cluster on one side (K516, R520, and R527). Point mutations of these positively charged aa reduced (NHE3 double mutant [R520F, R527F]) or abolished (NHE3 triple mutant [K516Q, R520F, R 527F]) ezrin binding. Functional consequences of these NHE3 point mutants included the following. 1) A marked decrease in surface amount with a greater decrease in NHE3 activity. 2) Decreased surface expression due to decreased rates of exocytosis and plasma membrane delivery of newly synthesized NHE3, with normal total expression levels and slightly reduced endocytosis rates. 3) A longer plasma membrane half-life of mutant NHE3 with normal total half-life. 4) Decreased BB mobile fraction of NHE3 double mutant. These results show that NHE3 binds ezrin directly as well as indirectly and suggest that the former is related to 1) the exocytic trafficking of and plasma membrane delivery of newly synthesized NHE3, which determines the amount of plasma membrane NHE3 and partially determines NHE3 activity, and 2) BB mobility of NHE3, which may increase its delivery from microvilli to the intervillus clefts, perhaps for NHE3-regulated endocytosis.

  1. The NHE3 Juxtamembrane Cytoplasmic Domain Directly Binds Ezrin: Dual Role in NHE3 Trafficking and Mobility in the Brush Border

    PubMed Central

    Cha, Boyoung; Tse, Ming; Yun, Chris; Kovbasnjuk, Olga; Mohan, Sachin; Hubbard, Ann; Arpin, Monique

    2006-01-01

    Based on physiological studies, the epithelial brush-border (BB) Na+/H+ antiporter3 (NHE3) seems to associate with the actin cytoskeleton both by binding to and independently of the PDZ domain containing proteins NHERF1 and NHERF2. We now show that NHE3 directly binds ezrin at a site in its C terminus between aa 475-589, which is separate from the PSD95/dlg/zonular occludens-1 (PDZ) interacting domain. This is an area predicted to be α-helical, with a positive aa cluster on one side (K516, R520, and R527). Point mutations of these positively charged aa reduced (NHE3 double mutant [R520F, R527F]) or abolished (NHE3 triple mutant [K516Q, R520F, R 527F]) ezrin binding. Functional consequences of these NHE3 point mutants included the following. 1) A marked decrease in surface amount with a greater decrease in NHE3 activity. 2) Decreased surface expression due to decreased rates of exocytosis and plasma membrane delivery of newly synthesized NHE3, with normal total expression levels and slightly reduced endocytosis rates. 3) A longer plasma membrane half-life of mutant NHE3 with normal total half-life. 4) Decreased BB mobile fraction of NHE3 double mutant. These results show that NHE3 binds ezrin directly as well as indirectly and suggest that the former is related to 1) the exocytic trafficking of and plasma membrane delivery of newly synthesized NHE3, which determines the amount of plasma membrane NHE3 and partially determines NHE3 activity, and 2) BB mobility of NHE3, which may increase its delivery from microvilli to the intervillus clefts, perhaps for NHE3-regulated endocytosis. PMID:16540524

  2. In vitro adhesion of K88ac+ Escherichia coli to Peyer's patch and peripheral blood lymphocytes, buccal and rectal epithelial cells or intestinal epithelial brush borders of weaned pigs.

    PubMed

    Valpotić, I; Runnels, P L; Moon, H W

    1989-08-01

    Escherichia coli adhesion assays were conducted using isolated porcine peripheral blood lymphocytes, Peyer's patch lymphocytes, rectal epithelial cells or brush borders, buccal epithelial cells and brush borders from small intestinal epithelial cells. The cells and brush borders were tested for their ability to bind K88-piliated enterotoxigenic E. coli Strain M1823B (K88ac) and E. coli Strain 1476 (K-12, K88ac). Comparison of adhesive phenotypes of 37 weaned pigs as determined by the adhesion assay with small intestinal brush borders and the adherence of K88ac+ enterotoxigenic E. coli to peripheral blood lymphocytes, Peyer's patch lymphocytes and rectal epithelial cells or brush borders, revealed no correlation. In vitro adhesion of K88ac-bearing E. coli was always negative with buccal epithelial cells. K88ac strains varied in their ability to adhere to lymphocytes and rectal epithelial cells or brush borders, indicating that the mechanism of adherence is unrelated to K88-mediated adhesion observed in animals that had the receptors on small-intestinal epithelial-cell brush borders. The non-piliated control E. coli Strain 123 adhered to fresh peripheral blood lymphocytes, and less intensively to frozen-thawed peripheral blood lymphocytes or Peyer's patch lymphocytes. It was concluded that none of the cell types or brush borders, except small-intestinal epithelial-cell brush borders, could be used as targets for phenotyping pigs for the presence of the K88 receptors that have been associated with adhesion and colonization of K88+ enterotoxigenic E. coli in the porcine small intestine.

  3. Borders as membranes :metaphors and models for improved policy in border regions.

    SciTech Connect

    Malczynski, Leonard A.; Passell, Howard David; Forster, Craig B.; Cockerill, Kristan

    2005-10-01

    Political borders are controversial and contested spaces. In an attempt to better understand movement along and through political borders, this project applied the metaphor of a membrane to look at how people, ideas, and things ''move'' through a border. More specifically, the research team employed this metaphor in a system dynamics framework to construct a computer model to assess legal and illegal migration on the US-Mexico border. Employing a metaphor can be helpful, as it was in this project, to gain different perspectives on a complex system. In addition to the metaphor, the multidisciplinary team utilized an array of methods to gather data including traditional literature searches, an experts workshop, a focus group, interviews, and culling expertise from the individuals on the research team. Results from the qualitative efforts revealed strong social as well as economic drivers that motivate individuals to cross the border legally. Based on the information gathered, the team concluded that legal migration dynamics were of a scope we did not want to consider hence, available demographic models sufficiently capture migration at the local level. Results from both the quantitative and qualitative data searches were used to modify a 1977 border model to demonstrate the dynamic nature of illegal migration. Model runs reveal that current US-policies based on neo-classic economic theory have proven ineffective in curbing illegal migration, and that proposed enforcement policies are also likely to be ineffective. We suggest, based on model results, that improvement in economic conditions within Mexico may have the biggest impact on illegal migration to the U.S. The modeling also supports the views expressed in the current literature suggesting that demographic and economic changes within Mexico are likely to slow illegal migration by 2060 with no special interventions made by either government.

  4. Regulation of the rabbit ileal brush-border Na+/H+ exchanger by an ATP-requiring Ca++/calmodulin-mediated process.

    PubMed Central

    Rood, R P; Emmer, E; Wesolek, J; McCullen, J; Husain, Z; Cohen, M E; Braithwaite, R S; Murer, H; Sharp, G W; Donowitz, M

    1988-01-01

    Brush-border vesicles purified from rabbit ileal villus cells were used to evaluate how Ca++/calmodulin (CaM) regulates the neutral linked NaCl absorptive process, part of which is a Na+/H+ exchanger. After freezing and thawing to allow incorporation of macromolecules into the vesicles, the effect of Ca++/CaM on brush-border Na+ uptake with an acid inside pH gradient, and on Na+/H+ exchange was determined. Freezing and thawing vesicles with 0.85 microM free Ca++ plus 5 microM exogenous CaM failed to alter Na+/H+ exchange as did the addition of exogenous ATP plus an ATP regenerating system, which was sufficient to elevate intravesicular ATP to 47 microM from a basal level of 0.4 microM. However, the combination of Ca++/CaM plus ATP inhibited Na+ uptake in the presence of an acid inside pH gradient and inhibited Na+/H+ exchange, while Na+ uptake in the absence of a pH gradient was not altered. This effect required a hydrolyzable form of ATP, and did not occur when the nonhydrolyzable ATP analogue, AMP-PNP, replaced ATP. Under the identical intravesicular conditions used for the transport studies, Ca++ (0.85 microM) plus exogenous CaM (5 microM), in the presence of magnesium plus ATP, increased phosphorylation of five brush-border peptides. These data are consistent with Ca++/CaM acting via phosphorylation to regulate the ileal brush-border Na+/H+ exchanger. PMID:2843567

  5. Loads, capacities and safety factors of maltase and the glucose transporter SGLT1 in mouse intestinal brush border

    PubMed Central

    Lam, Mandy M; O'Connor, Timothy P; Diamond, Jared

    2002-01-01

    Safety factors are defined as ratios of biological capacities to prevailing natural loads. We measured the safety factor of the mouse intestinal brush-border hydrolase maltase in series with the glucose transporter SGLT1, for comparison with previous studies of sucrase and lactase. Dietary maltose loads increased 4-fold from virgin to lactating mice. As in previous studies of intestinal adaptive regulation, that increase in load without change in dietary composition resulted in an increase in maltase and SGLT1 capacities mediated non-specifically by an increase in intestinal mass, without change in maltase or SGLT1 activities per milligram of tissue. Maltase and SGLT1 capacities increased only sublinearly with load during lactation, such that safety factors decreased with load: from 6.5 to 2.4 for maltase, and from 1.1 to 0.5 for SGLT1. The apparently high safety factor for maltase may be related to the multiple natural substrates hydrolysed by the multiple sites of maltase activity. The apparently low safety factor for SGLT1 is made possible by the contribution of hindgut fermentation to carbohydrate digestion. SGLT1 activity is paradoxically higher for mice consuming sucrose than for mice consuming maltose, despite maltose hydrolysis yielding double the glucose load yielded by sucrose hydrolysis, and despite glucose constituting the load upon SGLT1. PMID:12122147

  6. Intestinal morphology, brush border and digesta enzyme activities of broilers fed on a diet containing Cu2+-loaded montmorillonite.

    PubMed

    Ma, Y L; Guo, T

    2008-01-01

    1. A total of 320 1-d-old Arbor Acres broiler chicks were used to investigate the effect of Cu(2+)-loaded montmorillonite (CM) on the growth performance, intestinal morphology and activities of brush border enzyme in the intestinal mucosa and digestive enzyme in the intestinal digesta of broilers. 2. The chicks were assigned randomly into 4 groups with 80 chicks per treatment. The 4 dietary treatments were: basal diet only (control group), basal diet + 2 g montmorillonite/kg, basal diet + 1 g CM/kg, and basal diet + 2 g CM/kg. The chicks were raised in cages and feed and water were provided ad libitum for a period of 42 d. 3. The addition of CM to the diet of broilers significantly increased body weight and feed efficiency. Similarly, birds receiving montmorillonite had higher feed efficiency than the control after 42 d of feeding. 4. Data on villus height and crypt depth for duodenum, jejunum and ileum indicated that treating the diet of broilers with either CM or montmorillonite improved the mucosal morphology of the small intestine. 5. The presence of CM in the diet of broilers significantly increased the activities of maltase, aminopeptidase N and alkaline phosphatase in small intestinal mucosa. However, the activities of protease, trypsin, chymotrypsin, amylase and lipase in small intestinal digesta of broilers fed on the CM-supplemented diet were slightly higher than control values.

  7. An all-aqueous route to polymer brush-modified membranes with remarkable permeabilites and protein capture rates

    PubMed Central

    Anuraj, Nishotha; Bhattacharjee, Somnath; Geiger, James H.; Baker, Gregory L.; Bruening, Merlin L.

    2011-01-01

    Microporous membranes are attractive for protein purification because convection rapidly brings proteins to binding sites. However, the low binding capacity of such membranes limits their applications. This work reports a rapid, aqueous procedure to create highly permeable, polymer brush-modified membranes that bind large amounts of protein. The synthetic method includes a 10-min adsorption of a macroinitiator in a hydroxylated nylon membrane and a subsequent 5-min aqueous atom transfer radical polymerization of 2-(methacryloyloxy)ethyl succinate from the immobilized initiator to form poly(acid) brushes. This procedure likely leads to more swollen, less dense brushes than polymerization from silane initiators, and thus requires less polymer to achieve the same binding capacity. The hydraulic permeability of the poly(acid) membranes is 4-fold higher than that of similar membranes prepared by growing brushes from immobilized silane initiators. These brush-containing nylon membranes bind 120 mg/cm3 of lysozyme using solution residence times as short as 35 ms, and when functionalized with nitrilotriacetate (NTA)-Ni2+ complexes, they capture 85 mg/cm3 of histidine6-tagged (His-tagged) Ubiquitin. Additionally the NTA-Ni2+-functionalized membranes isolate His-tagged myo-inositol-1-phosphate synthase directly from cell extracts and show >90% recovery of His-tagged proteins. PMID:22287817

  8. Environmental cues and symbiont microbe-associated molecular patterns function in concert to drive the daily remodelling of the crypt-cell brush border of the Euprymna scolopes light organ.

    PubMed

    Heath-Heckman, Elizabeth A C; Foster, Jamie; Apicella, Michael A; Goldman, William E; McFall-Ngai, Margaret

    2016-11-01

    Recent research has shown that the microbiota affects the biology of associated host epithelial tissues, including their circadian rhythms, although few data are available on how such influences shape the microarchitecture of the brush border. The squid-vibrio system exhibits two modifications of the brush border that supports the symbionts: effacement and repolarization. Together these occur on a daily rhythm in adult animals, at the dawn expulsion of symbionts into the environment, and symbiont colonization of the juvenile host induces an increase in microvillar density. Here we sought to define how these processes are related and the roles of both symbiont colonization and environmental cues. Ultrastructural analyses showed that the juvenile-organ brush borders also efface concomitantly with daily dawn-cued expulsion of symbionts. Manipulation of the environmental light cue and juvenile symbiotic state demonstrated that this behaviour requires the light cue, but not colonization. In contrast, symbionts were required for the observed increase in microvillar density that accompanies post dawn brush-border repolarization; this increase was induced solely by host exposure to phosphorylated lipid A of symbiont cells. These data demonstrate that a partnering of environmental and symbiont cues shapes the brush border and that microbe-associated molecular patterns play a role in the regulation of brush-border microarchitecture. © 2016 John Wiley & Sons Ltd.

  9. Ultrathin, freestanding, stimuli-responsive, porous membranes from polymer hydrogel-brushes

    NASA Astrophysics Data System (ADS)

    Kang, Chengjun; Ramakrishna, Shivaprakash N.; Nelson, Adrienne; Cremmel, Clement V. M.; Vom Stein, Helena; Spencer, Nicholas D.; Isa, Lucio; Benetti, Edmondo M.

    2015-07-01

    The fabrication of freestanding, sub-100 nm-thick, pH-responsive hydrogel membranes with controlled nano-morphology, based on modified poly(hydroxyethyl methacrylate) (PHEMA) is presented. Polymer hydrogel-brush films were first synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequently detached from silicon substrates by UV-induced photo-cleavage of a specially designed linker within the initiator groups. The detachment was also assisted by pH-induced osmotic forces generated within the films in the swollen state. The mechanical properties and morphology of the freestanding films were studied by atomic force microscopy (AFM). Inclusion of nanopores of controlled diameter was accomplished by performing SI-ATRP from initiator-coated surfaces that had previously been patterned with polystyrene nanoparticles. Assembly parameters and particle sizes could be varied, in order to fabricate nanoporous hydrogel-brush membranes with tunable pore coverage and characteristics. Additionally, due to the presence of weak polyacid functions within the hydrogel, the membranes exhibited pH-dependent thickness in water and reversible opening/closing of the pores.The fabrication of freestanding, sub-100 nm-thick, pH-responsive hydrogel membranes with controlled nano-morphology, based on modified poly(hydroxyethyl methacrylate) (PHEMA) is presented. Polymer hydrogel-brush films were first synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequently detached from silicon substrates by UV-induced photo-cleavage of a specially designed linker within the initiator groups. The detachment was also assisted by pH-induced osmotic forces generated within the films in the swollen state. The mechanical properties and morphology of the freestanding films were studied by atomic force microscopy (AFM). Inclusion of nanopores of controlled diameter was accomplished by performing SI-ATRP from initiator-coated surfaces that had

  10. Effect of Na+ ions on pH-dependent conformational changes in brush border sucrase-isomaltase in mice intestine.

    PubMed

    Gupta, Shiffalli; Mahmood, Safrun; Khan, Rizwan Hasan; Mahmood, Akhtar

    2008-12-01

    Intestinal brush border sucrase-isomaltase (sucrose D-glucosidase E.C. 3.2.1.48, E.C. 3.2.1.10) exhibits pH-dependent stimulatory or inhibitory effects in response to Na+ ions. However, whether the enzyme undergoes conformational modulations as a function of pH and in the presence of alkali metal ions is not known. In this paper, we investigated the structural and functional relationship of purified murine sucrase in response to pH and Na+ ions using UV-CD fluorescence and spectroscopic studies. Kinetic studies revealed that at pH 5.0, the enzyme activation by Na+ ions was V-type, which changed to K-type at pH 7.2, whereas at alkaline pH (8.5), Na+ ions inhibited the enzyme activity and inhibition was uncompetitive in nature, affecting both the Km and Vmax components. Far UV-CD spectra of protein at pH 7.2 in the absence and presence of Na+ were almost overlapping, suggesting that secondary structure of protein was not affected upon addition of the salt. However, near UV-CD spectra indicated marked alterations in the tertiary structure of protein in presence of 50 mM Na+ ions. Increase in pH from 7.2 to 8.5 resulted in a marked rise in fluorescence intensity and red shift in lambda max due to tryptophan residues in the enzyme molecule. These findings suggested that alterations in enzyme activity as a function of pH and Na+ ions was associated with ionization of key amino acid residues together with structural modifications in the enzyme conformation around neutral or alkaline pH.

  11. Smart polymer brush nanostructures guide the self-assembly of pore-spanning lipid bilayers with integrated membrane proteins

    NASA Astrophysics Data System (ADS)

    Wilhelmina de Groot, G.; Demarche, Sophie; Santonicola, M. Gabriella; Tiefenauer, Louis; Vancso, G. Julius

    2014-01-01

    Nanopores in arrays on silicon chips are functionalized with pH-responsive poly(methacrylic acid) (PMAA) brushes and used as supports for pore-spanning lipid bilayers with integrated membrane proteins. Robust platforms are created by the covalent grafting of polymer brushes using surface-initiated atom transfer radical polymerization (ATRP), resulting in sensor chips that can be successfully reused over several assays. His-tagged proteins are selectively and reversibly bound to the nitrilotriacetic acid (NTA) functionalization of the PMAA brush, and consequently lipid bilayer membranes are formed. The enhanced membrane resistance as determined by electrochemical impedance spectroscopy and free diffusion of dyed lipids observed as fluorescence recovery after photobleaching confirmed the presence of lipid bilayers. Immobilization of the His-tagged membrane proteins on the NTA-modified PMAA brush near the pore edges is characterized by fluorescence microscopy. This system allows us to adjust the protein density in free-standing bilayers, which are stabilized by the polymer brush underneath. The potential application of the integrated platform for ion channel protein assays is demonstrated.

  12. Fabrication of cell outer membrane mimetic polymer brush on polysulfone surface via RAFT technique

    NASA Astrophysics Data System (ADS)

    Ma, Qian; Zhang, Hui; Zhao, Jiang; Gong, Yong-Kuan

    2012-10-01

    Cell membrane mimetic antifouling polymer brush was grown on polysulfone (PSF) membrane by surface-induced reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC). The RAFT agent immobilized PSF substrate was prepared by successive chloromethylation, amination with ethylenediamine (EDA) and amidation of the amine group of grafted EDA with the carboxylic group of 4-cyanopentanoic acid dithiobenzoate (CPAD). The surface RAFT polymerization of MPC was initiated in aqueous solution by 4,4‧-azobis-4-cyanopentanoic acid (ACPA). The formation of PMPC brush coating is evidenced by X-ray photoelectron spectroscopy and water contact angle measurements. The degree of polymerization of PMPC and the polymer grafting density were calculated from the high resolution XPS spectra. The platelet adhesion and protein adsorption results showed that the PMPC-grafted PSF surface has excellent antifouling ability to resist platelet adhesion completely and suppress protein adsorption significantly. This biomimetic and bio-friendly surface RAFT polymerization strategy could be promising for a variety of biomedical applications.

  13. Liquid Crystalline Block Copolymers with Brush Type Architecture: Toward Functional Membranes by Magnetic Field Alignment

    NASA Astrophysics Data System (ADS)

    Choo, Youngwoo; Gopinadhan, Manesh; Mahajan, Lalit; Kasi, Rajeswari; Osuji, Chinedum

    2015-03-01

    We introduce a novel liquid crystalline block copolymer with brush type architecture for membrane applications by magnetic field directed self-assembly. Ring-opening metathesis of n-alkyloxy cyanobiphenyl and polylactide (PLA) functionalized norbornene monomers provides efficient polymerization yielding low polydispersity block copolymers. The molecular weight of the PLA side chains, spacer length of the cyanobiphenyl mesogens are systematically varied to form well-ordered BCP morphologies at varying volume fractions. Interestingly, the system features morphology dependent anchoring condition where mesogens adopt planar anchoring on cylindrical interface while homeotropic anchoring was preferred on a planar block interface. The minority PLA domains from highly aligned materials can be readily degraded by hydrolysis to produce vertically aligned nanoporous polymer films which exhibit reversible thermal switching behavior. The polymers introduced here provide a versatile platform for scalable fabrication of aligned membranes and further functional materials based on such templates. This work was supported by NSF(CCMI-1246804).

  14. Constructing proton-conductive highways within an ionomer membrane by embedding sulfonated polymer brush modified graphene oxide

    NASA Astrophysics Data System (ADS)

    Zhao, Liping; Li, Yifan; Zhang, Haoqin; Wu, Wenjia; Liu, Jindun; Wang, Jingtao

    2015-07-01

    Sulfonated polymer brush modified graphene oxide (SP-GO) fillers with controllable brush length are synthesized via the facile distillation-precipitation polymerization, and then incorporated into sulfonated poly(ether ether ketone) (SPEEK) matrix to fabricate composite membranes. The influences of SP-GO upon the microstructures, including thermal and mechanical properties, water uptake/swelling, proton conduction, H2 permeability and single PEMFC performances of composite membranes are intensively investigated. It is found that the SP-GO fillers are uniformly dispersed and tend to lie perpendicularly to the cross-section surface of the whole membrane, which allow SP-GO fillers creating inter-connected and broad ionic pathways through the sulfonic acid groups in polymer brushes. Meanwhile, the SP-GO fillers connect the ionic clusters in SPEEK matrix via interfacial interactions. In such a way, proton-transfer highways are constructed along the SPEEK/SP-GO interface, which lower the proton transfer activation energy and enhance the proton conductivities of the composite membranes under both hydrated and anhydrous conditions. Furthermore, elevating the brush length on SP-GO could further enhance the proton conductivity. Compared to SPEEK control membrane, a 95.5% increase in hydrated conductivity, an 178% increase in anhydrous conductivity and a 37% increase in maximum power density are obtained for the optimal composite membrane.

  15. Structural and functional lesions in brush border of human polarized intestinal Caco-2/TC7 cells infected by members of the Afa/Dr diffusely adhering family of Escherichia coli.

    PubMed

    Peiffer, I; Guignot, J; Barbat, A; Carnoy, C; Moseley, S L; Nowicki, B J; Servin, A L; Bernet-Camard, M F

    2000-10-01

    Diffusely adhering Escherichia coli (DAEC) strains expressing F1845 fimbrial adhesin or Dr hemagglutinin belonging to the Afa/Dr family of adhesins infect cultured polarized human intestinal cells through recognition of the brush border-associated decay-accelerating factor (DAF; CD55) as a receptor. The wild-type Afa/Dr DAEC strain C1845 has been shown to induce brush border lesions by an adhesin-dependent mechanism triggering apical F-actin rearrangements. In the present study, we undertook to further characterize cell injuries following the interaction of wild-type Afa/Dr DAEC strains C1845 and IH11128 expressing fimbrial F1845 adhesin and Dr hemagglutinin, respectively, with polarized, fully differentiated Caco-2/TC7 cells. In both cases, bacterium-cell interaction was followed by rearrangement of the major brush border-associated cytoskeletal proteins F-actin, villin, and fimbrin, proteins which play a pivotal role in brush border assembly. In contrast, distribution of G-actin, actin-depolymerizing factor, and tubulin was not modified. Using draE mutants, we found that a mutant in which cysteine replaces aspartic acid at position 54 conserved binding capacity but failed to induce F-actin disassembly. Accompanying the cytoskeleton injuries, we found that the distribution of brush border-associated functional proteins sucrase-isomaltase (SI), dipeptidylpeptidase IV (DPPIV), glucose transporter SGLT1, and fructose transporter GLUT5 was dramatically altered. In parallel, SI and DPPIV enzyme activity decreased.

  16. Affinity Separation of Lectins Using Porous Membranes Immobilized with Glycopolymer Brushes Containing Mannose or N-Acetyl-d-Glucosamine

    PubMed Central

    Ogata, Yutaro; Seto, Hirokazu; Murakami, Tatsuya; Hoshino, Yu; Miura, Yoshiko

    2013-01-01

    Porous membranes with glycopolymer brushes were prepared as biomaterials for affinity separation. Glycopolymer brushes contained acrylic acid and D-mannose or N-acetyl-D-glucosamine, and were formed on substrates by surface-initiated atom transfer radical polymerization. The presence of glycopolymer brush was confirmed by X-ray photoelectron spectroscopy, contact angle, and ellipsometry measurements. The interaction between lectin and the glycopolymer immobilized on glass slides was confirmed using fluorescent-labeled proteins. Glycopolymer-immobilized surfaces exhibited specific adsorption of the corresponding lectin, compared with bovine serum albumin. Lectins were continuously rejected by the glycopolymer-immobilized membranes. When the protein solution was permeated through the glycopolymer-immobilized membrane, bovine serum albumin was not adsorbed on the membrane surface. In contrast, concanavalin A and wheat germ agglutinin were rejected by membranes incorporating D-mannose or N-acetyl-D-glucosamine, respectively. The amounts of adsorbed concanavalin A and wheat germ agglutinin was increased five- and two-fold that of adsorbed bovine serum albumin, respectively. PMID:24956944

  17. D-Glucose Acts via SGLTI to Increase NHE3 in Mouse Jejunal Brush Border by a NHERF2-Dependent Process

    PubMed Central

    Lin, Rong; Murtazina, Rakhilya; Cha, Boyoung; Chakraborty, Molee; Sarker, Rafiquel; Chen, Tian-e; Lin, Zhihong; Hogema, Boris M.; de Jonge, Hugo R.; Seidler, Ursula; Turner, Jerrold R.; Li, Xuhang; Kovbasnjuk, Olga; Donowitz, Mark

    2010-01-01

    Background & Aims Oral rehydration solutions (ORS) reduce diarrhea-associated mortality by unclear mechanisms. Sodium absorption is mediated by the Na+/H+ hydrogen exchanger NHE3 and is increased by Na+-glucose co-transport in vitro, but the mechanisms of this process are only partially understood and its in vivo relevance has not been determined. Methods Intracellular pH was measured in jejunal enterocytes of wild-type mice and mice with disrupted Na+/H+ exchange regulatory co-factor 2 (NHERF2−/− mice) by multi-photon microscopy. Diarrhea was induced by cholera toxin. Caco-2BBe cells that express NHE3 and the sodium/glucose cotransporter (SGLT)1 were studied by fluorometery, before and after siRNA-mediated knockdown of NHERF1 or NHERF2. NHE3 distribution was assessed by cell-surface biotinylation and confocal microscopy. Brush border mobility was determined by fluorescence recovery after photobleaching and confocal microscopy. Results The non-metabolized SGLT1 substrate α-methyl-D-Glu (α-MD-G) activated jejunal NHE3; this process required Akt and NHERF2. α-MD-G normalized NHE3 activity after cholera toxin-induced diarrhea. α-MD-G–stimulated jejunal NHE3 activity was: defective in NHERF2−/− mice and cells with NHERF2 knockdown, but occurred normally with NHERF1 knockdown; associated with increased NHE3 surface expression in Caco-2 cells, which was also NHERF2-dependent; associated with dissociation of NHE3 from NHERF2 and an increase in the NHE3 mobile fraction from the brush border; and accompanied by a NHERF2 ezrin-radixin-moesin–binding domain-dependent increase in co-precipitation of ezrin with NHE3. Conclusions SGLT1-mediated Na-glucose co-transport stimulates NHE3 activity in vivo by an Akt- and NHERF2-dependent signaling pathway. It is associated with increased brush border NHE3 and association between ezrin and NHE3. Activation of NHE3 corrects cholera toxin-induced defects in Na absorption and might mediate efficacy of ORS. PMID:20977906

  18. Grafting of carboxybetaine brush onto cellulose membranes via surface-initiated ARGET-ATRP for improving blood compatibility.

    PubMed

    Wang, Miao; Yuan, Jiang; Huang, Xiaobo; Cai, Xianmei; Li, Li; Shen, Jian

    2013-03-01

    Grafting-from has proven to be a very effective way to create high grafting densities and well-controlled polymer chains on different kinds of surfaces. In this work, we aim to graft zwitterionic brush from cellulose membrane (CM) via ARGET-ATRP (Activator Regenerated by Electron Transfer ATRP) method indirectly for blood compatibility improvement. Characterization of the CM substrates before and after modification was carried out by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements, X-ray photoelectron spectroscopy analysis, and atomic force microscopy, respectively. The results demonstrated zwitterionic brushes were successfully grafted on the CM surfaces, and the content of the grafted layer increased gradually with the polymerization time. The platelet adhesion, hemolytic test and plasma protein adsorption results indicated the cellulose membrane had significantly excellent blood compatibility featured on lower platelet adhesion and protein adsorption without causing hemolysis. The functionalized cellulose substrate could have a great potential usage for biomedical applications.

  19. High flux, positively charged loose nanofiltration membrane by blending with poly (ionic liquid) brushes grafted silica spheres.

    PubMed

    Yu, Liang; Zhang, Yatao; Wang, Yuanming; Zhang, Haoqin; Liu, Jindun

    2015-04-28

    Silica spheres modified by poly (ionic liquid) brushes, a novel positively charged nanomaterial is prepared by atom transfer radical polymerization (ATRP). A high flux positively charged loose nanofiltration membrane is fabricated via "blending-phase inversion" method. The morphology structures, hydrophilicity, thermal and mechanical properties, permeation performance of these membranes are investigated in detail. The results reveal that the hybrid membranes have enhanced surface hydrophilicity, water permeability, thermal stability, and mechanical properties. Characterization of membrane separation properties shows that the hybrid membranes possess higher salt permeability and relatively higher rejection for reactive dyes, which may open opportunities for the recycling of reactive dyes wastewater. Moreover, such hybrid membranes have an outstanding operational stability and salts concentration showed little effect on the separation properties.

  20. Calcium uptake by brush border membrane vesicles (BBMV): inhibition by magnesium (Mg) and strontium (Sr)

    SciTech Connect

    Wilson, H.D.; Christensen, K.; Schedl, H.P.

    1986-03-01

    The authors measured the effects of Mg and Sr on the uptake of Ca by BBMV prepared from proximal (P) and distal (D) small intestine of the rat. Compared to starting homogenate, BBMV showed 48-fold sucrase enrichment. The authors measured kinetics of ca uptake at 3 sec over the conc range of 0.03-1.00 mM by rapid filtration in the presence and absence of 5 mM Mg or Sr. Ca uptake comprised non-saturable and saturable components. Both inhibitors decreased mean rate of non-saturable Ca uptake (K/sub D/), but not significantly. Sr increased K/sub T/ for saturable transport in P, but under all other conditions K/sub T/ was the same in P and D in the presence or absence of Mg or Sr. Sr did not decrease V/sub max/ in P, but both Mg and Sr decreased V/sub max/ in all other comparisons. These findings suggest that (1) inhibition of Ca uptake in P BBMVs by Mg is non-competitive, while inhibition by Sr is competitive; and (2) inhibition by both Mg and Sr is non-competitive in D BBMV.

  1. Thiolation of polycarbophil enhances its inhibition of intestinal brush border membrane bound aminopeptidase N.

    PubMed

    Bernkop-Schnürch, A; Zarti, H; Walker, G F

    2001-11-01

    The purpose of this study was to evaluate the potential of polycarbophil-cysteine conjugates (PCP-Cys) as an oral excipient to protect leucine enkephalin (leu-enkp) from enzymatic degradation by the intestinal mucosa. Cysteine was covalently linked to polycarbophil by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC). Inhibitory activity was tested towards isolated aminopeptidase N and excised intact pig intestinal mucosa, with native mucus. Aminopeptidase N activity was assayed spectrophotometrically using L-leucine p-nitroanilide (leu-pNA) as a synthetic substrate and against the model peptide drug leu-enkp, by high-performance liquid chromatography (HPLC). Free cysteine at 6.3 and 63 microM (pH 6) significantly (p < 0.05) inhibited aminopeptidase N activity, and PCP-Cys (0.25% w/v, pH 6) had a significantly (p < 0.05) greater inhibitory effect than PCP on the aminopeptidase N activity towards both substrates. PCP-Cys completely protected leu-enkp against aminopeptidase N activity over a 2-h incubation period, whereas 83 +/- 4 and 60 +/- 7% remained stable in the presence of PCP and buffer only, respectively. Leu-enkp in the absence and presence of PCP (0.25% w/v) at pH 6 was completely digested by the intact intestinal mucosa at the 60- and 90-min incubation time points, respectively, whereas in the presence of PCP-Cys (0.25% w/v, pH 6) 11 +/- 3.5% of leu-enkp remained at the 120-min time point. Thiolation of PCP increased the stability of leu-enkp against the enzymatic degradation by aminopeptidase N and the intact intestinal mucosa, identifying a promising new excipient for peroral delivery of peptides.

  2. ZINC UPTAKE BY LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  3. FERRIREDUCTASE ACTIVITY IN LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES (BBMV). (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  4. CALCIUM TRANSPORT PROCESSES OF LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  5. Transport of thiamine by brush-border membrane vesicles from rat small intestine.

    PubMed Central

    Casirola, D; Ferrari, G; Gastaldi, G; Patrini, C; Rindi, G

    1988-01-01

    1. Microvillous vesicles obtained by a Ca2+ precipitation method from the intestine of adult Wistar albino rats were incubated at 25 degrees C with [35S]- or [3H]thiamine of high specific activity. 2. The time course of thiamine uptake was not influenced by the presence of Na+ or K+ nor by the absence of alkaline cations in the incubation medium. 3. At concentrations below 1.25 microM, thiamine was taken up mainly by a saturable mechanism with apparent Km = 0.8 microM and Vmax = 0.35 pmol mg protein-1 4 s-1. At higher concentrations, a non-saturable uptake mechanism prevailed. 4. The thiamine taken up was transferred to the intravesicular space. No thiamine phosphoesters could be detected in the vesicles. 5. The vesicular transport of thiamine was inhibited competitively by several thiamine derivatives and structural analogues, including: cold thiamine; thiamine monophosphate (inhibition constant, Ki = 33 microM); pyrithiamine (Ki = 1.7 microM); 2'-ethylthiamine (Ki = 27 microM); 5-chloroethylthiamine (Ki = 70 microM): Amprolium (Ki = 55 microM); 4'-oxythiamine (Ki = 510 microM). PMID:3392675

  6. Dicyclohexylcarbodiimide (DCCD) sensitive organic cation/H/sup +/ antiporter in renal brush border membrane vesicles (BBMV)

    SciTech Connect

    Sokol, P.P.; Holohan, P.D.; Ross, C.R.

    1986-03-01

    We tested the hypothesis that organic cation transport in BBMV is coupled to the countertransport of a H/sup +/ by employing a prototypic organic cation, N/sup 1/-methylnicotinamide (NMN), and a rapid filtration assay. Two H/sup +/ gradient uncouplers, carbonyl cyanide m-chlorophenylhydrazone (CCCP)/sub 3/ and gramicidin D were effective in dissipating H/sup +/ driven (/sup 3/H)NMN transport. Nigericin, a K/sup +//H/sup +/ exchanger, generated a H/sup +/ gradient in situ which drove the net accumulation of NMN. The molecular mechanism of H/sup +/ coupling was examined employing DCCD, a hydrophobic carbodiimide, which inactivates essential carboxylate groups, the putative H/sup +/ receptor. DCCD inactivated NMN transport irreversibly with an IC/sub 50/ of 2.6..mu..M whereas the hydrophilic carbodiimide, 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide, did not. DCCD inactivation followed pseudo-first-order kinetics and was not affected by NMN. A double logarithmic plot of the apparent rate constants vs. (DCCD) gave a slope of 0.8. The data are consistent with a simple bimolecular reaction mechanism and imply that one molecule of DCCD inactivates one carboxylate group per active transport unit. The results show that (1) the transport of organic cations is coupled to the countermovement of a H/sup +/ and (2) a carboxylate group is essential for H/sup +/ binding and translocation.

  7. FERRIREDUCTASE ACTIVITY IN LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES (BBMV). (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  8. CALCIUM TRANSPORT PROCESSES OF LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  9. ZINC UPTAKE BY LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  10. At the border: the plasma membrane-cell wall continuum.

    PubMed

    Liu, Zengyu; Persson, Staffan; Sánchez-Rodríguez, Clara

    2015-03-01

    Plant cells rely on their cell walls for directed growth and environmental adaptation. Synthesis and remodelling of the cell walls are membrane-related processes. During cell growth and exposure to external stimuli, there is a constant exchange of lipids, proteins, and other cell wall components between the cytosol and the plasma membrane/apoplast. This exchange of material and the localization of cell wall proteins at certain spots in the plasma membrane seem to rely on a particular membrane composition. In addition, sensors at the plasma membrane detect changes in the cell wall architecture, and activate cytoplasmic signalling schemes and ultimately cell wall remodelling. The apoplastic polysaccharide matrix is, on the other hand, crucial for preventing proteins diffusing uncontrollably in the membrane. Therefore, the cell wall-plasma membrane link is essential for plant development and responses to external stimuli. This review focuses on the relationship between the cell wall and plasma membrane, and its importance for plant tissue organization. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  11. New Poly(amino acid methacrylate) Brush Supports the Formation of Well-Defined Lipid Membranes

    PubMed Central

    2015-01-01

    A novel poly(amino acid methacrylate) brush comprising zwitterionic cysteine groups (PCysMA) was utilized as a support for lipid bilayers. The polymer brush provides a 12-nm-thick cushion between the underlying hard support and the aqueous phase. At neutral pH, the zeta potential of the PCysMA brush was ∼−10 mV. Cationic vesicles containing >25% DOTAP were found to form a homogeneous lipid bilayer, as determined by a combination of surface analytical techniques. The lipid mobility as measured by FRAP (fluorescence recovery after photobleaching) gave diffusion coefficients of ∼1.5 μm2 s–1, which are comparable to those observed for lipid bilayers on glass substrates. PMID:25746444

  12. Dose-dependence of the effects of corticosterone and the non-glucocorticoid, 18-hydroxycorticosterone, on the brush-border Na+/K+ exchanger.

    PubMed

    Igarreta, P; Lantos, C P; Calvo, J C; Paladini, A A; Damasco, M C

    1998-01-01

    Up to now, only glucocorticoids were thought to act on the renal proximal Na+/H+ exchanger. Using fluorimetric techniques we studied the kinetics of Na+/H+ exchange in brush border vesicles from ADX rats treated with increasing doses of corticosterone (B) and 18-hydroxycorticosterone (18OHB). Significant linear correlations were obtained when the Vmax of each treatment were plotted against log doses. 18OHB exhibits a slightly higher sensitivity than B and log-dose responses were steeper for 18OHB than for B treated rats. Differences between both treatments were highly significant at the 4.8 microg/100 g level, corresponding to the physiological blood level of 18OHB. Physiological doses of both steroids elicited equal Na+/H+ exchange-responses. 18OHB is not a glucocorticoid since even 88 microg/100 g did not promote hepatic glycogen deposition while the same dose of B increases glycogen deposits 3.5-fold. These results demonstrate the importance of the Na+/H+ exchanger as a mediator between corticoid action and H+ transport and that of the non-glucocorticoid 18OHB in this process.

  13. Border control--a membrane-linked interactome of Arabidopsis.

    PubMed

    Jones, Alexander M; Xuan, Yuanhu; Xu, Meng; Wang, Rui-Sheng; Ho, Cheng-Hsun; Lalonde, Sylvie; You, Chang Hun; Sardi, Maria I; Parsa, Saman A; Smith-Valle, Erika; Su, Tianying; Frazer, Keith A; Pilot, Guillaume; Pratelli, Réjane; Grossmann, Guido; Acharya, Biswa R; Hu, Heng-Cheng; Engineer, Cawas; Villiers, Florent; Ju, Chuanli; Takeda, Kouji; Su, Zhao; Dong, Qunfeng; Assmann, Sarah M; Chen, Jin; Kwak, June M; Schroeder, Julian I; Albert, Reka; Rhee, Seung Y; Frommer, Wolf B

    2014-05-16

    Cellular membranes act as signaling platforms and control solute transport. Membrane receptors, transporters, and enzymes communicate with intracellular processes through protein-protein interactions. Using a split-ubiquitin yeast two-hybrid screen that covers a test-space of 6.4 × 10(6) pairs, we identified 12,102 membrane/signaling protein interactions from Arabidopsis. Besides confirmation of expected interactions such as heterotrimeric G protein subunit interactions and aquaporin oligomerization, >99% of the interactions were previously unknown. Interactions were confirmed at a rate of 32% in orthogonal in planta split-green flourescent protein interaction assays, which was statistically indistinguishable from the confirmation rate for known interactions collected from literature (38%). Regulatory associations in membrane protein trafficking, turnover, and phosphorylation include regulation of potassium channel activity through abscisic acid signaling, transporter activity by a WNK kinase, and a brassinolide receptor kinase by trafficking-related proteins. These examples underscore the utility of the membrane/signaling protein interaction network for gene discovery and hypothesis generation in plants and other organisms. Copyright © 2014, American Association for the Advancement of Science.

  14. Alkali-metal-ion- and H+-dependent activation and/or inhibition of intestinal brush-border sucrase. A model involving three functionally distinct key prototropic groups.

    PubMed Central

    Vasseur, M; Van Melle, G; Frangne, R; Alvarado, F

    1988-01-01

    For rabbit intestinal brush-border sucrase, a model based on classical Michaelis-Dixon theory cannot fully explain the peculiar antagonistic relationship existing between the substrate and one key proton, Hx, which at acid pH values behaves as a fully competitive inhibitor. In the same pH range, a second proton, Hy, is responsible for changes in catalytic activity and behaves as a mixed-type partially non-competitive inhibitor [Vasseur, Tellier & Alvarado (1982) Arch. Biochem. Biophys. 218, 263-274]. Although involved in the same ionization reaction, these two protons have different kinetic functions, since they are responsible for affinity-type and capacity-type effects respectively. Depending on whether Hx is bound or not, we postulate the enzyme to alternate between two distinct forms differing in their binding properties. The alkali-metal ions Na+ and Li+ have a concentration-dependent biphasic effect on this equilibrium. At low concentrations they facilitate the release of Hx, resulting in K-type activation. At higher concentrations they favour enzyme reprotonation, causing K-type inhibition. On the basic side of the pH spectrum, our results confirm the existence of separate non-competitive effects of the alkali-metal ions, particularly Li+ [Alvarado & Mahmood (1979) J. Biol. Chem. 254, 9534-9541]. To explain the molecular mechanisms underlying the alkali-metal-ion- and H+-dependent effects, we formulate a sucrase model, the three-protons model, in which the acid and basic ionization constants involve respectively two and one key prototropic groups that are functionally distinguishable. A global iterative fit of the relevant general equation to our whole set of data has permitted us to estimate the numerical value of each of the constants constituting the model. PMID:2843163

  15. Controlled Architecture of Dual-Functional Block Copolymer Brushes on Thin-Film Composite Membranes for Integrated "Defending" and "Attacking" Strategies against Biofouling.

    PubMed

    Ye, Gang; Lee, Jongho; Perreault, François; Elimelech, Menachem

    2015-10-21

    We report a new macromolecular architecture of dual functional block copolymer brushes on commercial thin-film composite (TFC) membranes for integrated "defending" and "attacking" strategies against biofouling. Mussel-inspired catechol chemistry is used for a convenient immobilization of initiator molecules to the membrane surface with the aid of polydopamine (PDA). Zwitterionic polymer brushes with strong hydration capacity and quaternary ammonium salt (QAS) polymer brushes with bactericidal ability are sequentially grafted on TFC membranes via activators regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP), an environmentally benign and controlled polymerization method. Measurement of membrane intrinsic transport properties in reverse osmosis experiments shows that the modified TFC membrane maintains the same water permeability and salt selectivity as the pristine TFC membrane. Chemical force microscopy and protein/bacterial adhesion studies are carried out for a comprehensive evaluation of the biofouling resistance and antimicrobial ability, demonstrating low biofouling propensity and excellent bacterial inactivation for the modified TFC membrane. We conclude that this polymer architecture, with complementary "defending" and "attacking" capabilities, can effectively prevent the attachment of biofoulants and formation of biofilms and thereby significantly mitigate biofouling on TFC membranes.

  16. Proper Brushing

    MedlinePlus

    ... 3 teeth using a vibrating back & forth rolling motion. A rolling motion is when the brush makes contact with the ... gumline. Gently brush using back, forth, and rolling motion along all of the inner tooth surfaces. Tilt ...

  17. Humic acid removal and easy-cleanability using temperature-responsive ZrO2 tubular membranes grafted with poly(N-isopropylacrylamide) brush chains.

    PubMed

    Zhao, Yijiang; Zhou, Shouyong; Li, Meisheng; Xue, Ailian; Zhang, Yan; Wang, Jingang; Xing, Weihong

    2013-05-01

    New poly(N-isopropylacrylamide) brushes grafted with ZrO2 (PNIPAAm-g-ZrO2) composite membranes, which had been prepared in our laboratory, were used for humic acid (HA) removal. We found that the fluxes associated with such membranes, when compared to those obtained from unmodified ZrO2 membranes, declined slightly at both 25 °C and 35 °C. The PNIPAAm-g-ZrO2 membrane achieved a high rejection, of 98.0%, at a suitable steady flux of 111.9 L m(-2) h(-1) at 25 °C. This membrane exhibited good anti-fouling properties as well as improved membrane performance during filtration of HA. The important role of pH and Ca(2+) concentration in HA removal was also investigated. Lower adsorption fouling and a higher rejection were obtained at higher pH levels. The Ca(2+) ions reduced the electrostatic exclusion and played a cross-linking role between HA and the PNIPAAm-g-ZrO2 membrane surface. Fouling was severe in the presence of Ca(2+). These tests led to the development of an environment-friendly membrane cleaning method, by means of temperature-change water elution around LCST of PNIPAAm-brushes. After the alternate temperature-change (25 °C/35 °C) cleaning, a flux recovery of 98.2% was obtained for the PNIPAAm-g-ZrO2 membrane. Moreover, after four repeated experiments, the anti-fouling and easy-cleaning properties were still maintained. It is implied that PNIPAAm-brushes were firmly "stuck" to the membrane surface, and could not easily be removed by water cleaning or HA filtration. The PNIPAAm-g-ZrO2 membranes exhibited good stability and great potential for HA removal.

  18. Endothelial Src kinase regulates membrane recycling from the lateral border recycling compartment during leukocyte transendothelial migration.

    PubMed

    Dasgupta, Bidisha; Muller, William A

    2008-12-01

    When leukocytes cross endothelial cells during the inflammatory response, membrane from the recently described lateral border recycling compartment (LBRC) is selectively targeted around diapedesing leukocytes. This "targeted recycling" is critical for leukocyte transendothelial migration. Blocking homophilic PECAM interactions between leukocytes and endothelial cells blocks targeted recycling from the LBRC and blocks diapedesis. However, the cellular signaling pathways that trigger targeted recycling are not known. We show that targeted recycling from the LBRC is dependent on Src kinase. The selective Src kinase inhibitor PP2 blocked targeted recycling and blocked diapedesis by over 70%. However, Src kinase inhibition did not affect the structure or normal constitutive recycling of membrane from the LBRC in the absence of leukocytes. PECAM, a Src kinase substrate, traffics between the LBRC and the endothelial surface at the cell border. However, virtually all of the PECAM in the cell that was phosphorylated on tyrosine residues was found in the LBRC. These findings demonstrate that Src kinase activity is critical for the targeted recycling of membrane from the LBRC to the site of transendothelial migration and that the PECAM in the LBRC is qualitatively different from the PECAM on the surface of endothelial cells.

  19. Temperature-controlled flow switching in nanocapillary array membranes mediated by poly(N-isopropylacrylamide) polymer brushes grafted by atom transfer radical polymerization.

    PubMed

    Lokuge, Ishika; Wang, Xuejun; Bohn, Paul W

    2007-01-02

    We report actively controlled transport that is thermally switchable and size-selective in a nanocapillary array membrane (NCAM) prepared by grafting poly(N-isopropylacrylamide) (PNIPAAm) brushes onto the exterior surface of a Au-coated polycarbonate track-etched membrane. A smooth Au layer on the membrane surface, which is key to obtaining a uniform polymer film, was prepared by thermal evaporation of approximately 50 nm Au on both exterior surfaces. After evaporation, the inner diameter of the pore is reduced slightly, but the NCAM retains a narrow pore size distribution. PNIPPAm brushes with 10-30 nm (dry film) thickness were grafted onto the Au surface through surface-initiated atom transfer radical polymerization (ATRP) using a disulfide initiator, (BrC(CH3)2COO(CH2)11S)2. Molecular transport through the PNIPAAm polymer brush-modified NCAMs was investigated by real-time fluorescence measurements using fluorescein isothiocyanate (FITC)-labeled dextrans ranging from 4.4 to 282 kDa in membranes with variable initial pore diameters (80, 100, and 200 nm) and different PNIPAAm thicknesses. Manipulating the temperature of the NCAM through the PNIPAAm lower critical solution temperature (LCST) causes large, size-dependent changes in the transport rates. Over specific ranges of probe size, transport is completely blocked below the LCST but strongly allowed above the LCST. The combination of the highly uniform PNIPAAm brush and the monodisperse pore size distribution is critical in producing highly reproducible switching behavior. Furthermore, the reversible nature of the switching raises the possibility of using them as actively controlled filtration devices.

  20. Organization of an actin filament-membrane complex. Filament polarity and membrane attachment in the microvilli of intestinal epithelial cells

    PubMed Central

    1975-01-01

    The association of actin filaments with membranes is now recognized as an important parameter in the motility of nonmuscle cells. We have investigated the organization of one of the most extensive and highly ordered actin filament-membrane complexes in nature, the brush border of intestinal epithelial cells. Through the analysis of isolated, demembranated brush borders decorated with the myosin subfragment, S1, we have determined that all the microvillar actin filaments have the same polarity. The S1 arrowhead complexes point away from the site of attachment of actin filaments at the apical tip of the microvillar membrane. In addition to the end-on attachment of actin filaments at the tip of the microvillus, these filaments are also connected to the plasma membrane all along their lengths by periodic (33 nm) cross bridges. These bridges were best observed in isolated brush borders incubated in high concentrations of Mg++. Their visibility is attributed to the induction of actin paracrystals in the filament bundles of the microvilli. Finally, we present evidence for the presence of myosinlike filaments in the terminal web region of the brush border. A model for the functional organization of actin and myosin in the brush border is presented. PMID:1202021

  1. Hemocompatibility of poly(vinylidene fluoride) membrane grafted with network-like and brush-like antifouling layer controlled via plasma-induced surface PEGylation.

    PubMed

    Chang, Yung; Shih, Yu-Ju; Ko, Chao-Yin; Jhong, Jheng-Fong; Liu, Ying-Ling; Wei, Ta-Chin

    2011-05-03

    In this work, the hemocompatibility of PEGylated poly(vinylidene fluoride) (PVDF) microporous membranes with varying grafting coverage and structures via plasma-induced surface PEGylation was studied. Network-like and brush-like PEGylated layers on PVDF membrane surfaces were achieved by low-pressure and atmospheric plasma treatment. The chemical composition, physical morphology, grafting structure, surface hydrophilicity, and hydration capability of prepared membranes were determined to illustrate the correlations between grafting qualities and hemocompatibility of PEGylated PVDF membranes in contact with human blood. Plasma protein adsorption onto different PEGylated PVDF membranes from single-protein solutions and the complex medium of 100% human plasma were measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. Hemocompatibility of the PEGylated membranes was evaluated by the antifouling property of platelet adhesion observed by scanning electron microscopy (SEM) and the anticoagulant activity of the blood coagulant determined by testing plasma-clotting time. The control of grafting structures of PEGylated layers highly regulates the PVDF membrane to resist the adsorption of plasma proteins, the adhesion of platelets, and the coagulation of human plasma. It was found that PVDF membranes grafted with brush-like PEGylated layers presented higher hydration capability with binding water molecules than with network-like PEGylated layers to improve the hemocompatible character of plasma protein and blood platelet resistance in human blood. This work suggests that the hemocompatible nature of grafted PEGylated polymers by controlling grafting structures gives them great potential in the molecular design of antithrombogenic membranes for use in human blood.

  2. Impairments in enzyme activity and biosynthesis of brush border-associated hydrolases in human intestinal Caco-2/TC7 cells infected by members of the Afa/Dr family of diffusely adhering Escherichia coli.

    PubMed

    Peiffer, I; Bernet-Camard, M F; Rousset, M; Servin, A L

    2001-05-01

    Wild-type diffusely adhering Escherichia coli (DAEC) harbouring afimbrial adhesin (Afa) or fimbrial Dr and F1845 adhesins (Afa/Dr DAEC) apically infecting the human intestinal epithelial cells promote injuries in the brush border of the cells. We report here that infection by Afa/Dr DAEC wild-type strains C1845 and IH11128 in polarized human fully differentiated Caco-2/TC7 cells dramatically impaired the enzyme activity of functional brush border-associated proteins sucrase-isomaltase (SI) and dipeptidylpeptidase IV (DPP IV). Blockers of the transduction signal molecules, previously found to be active against the Afa/Dr DAEC-induced cytoskeleton injury, were inactive against the Afa/Dr-induced decrease in sucrase enzyme activity. In parallel, Afa/Dr DAEC infection promotes the blockade of the biosynthesis of SI and DPP IV without affection enzyme stability. The observation that no changes occurred in mRNA levels of SI and DPP IV upon infection suggested that the decrease in biosynthesis probably resulted from a decrease in the translation rate. When the cells were infected with recombinant E. coli strains expressing homologous adhesins of the wild-type strains, neither a decrease in sucrase and DPP IV enzyme activities nor an inhibition of enzyme biosynthesis were observed. In conclusion, taken together, these data give new insights into the mechanisms by which the wild-type Afa/Dr DAEC strains induce functional injuries in polarized fully differentiated human intestinal cells. Moreover, the results revealed that other pathogenic factor(s) distinct from the Afa/Dr adhesins may play(s) a crucial role in this mechanism of pathogenicity.

  3. Binding of Bacillus thuringiensis Cry1A toxins with brush border membrane vesicles of maize stem borer (Chilo partellus Swinhoe).

    PubMed

    Sharma, Priyanka; Nain, Vikrant; Lakhanpaul, Suman; Kumar, P A

    2011-02-01

    Maize stem borer (Chilo partellus) is a major insect pest of maize and sorghum in Asia and Africa. Bacillus thuringiensis (Bt) δ-endotoxins have been found effective against C. partellus, both in diet-overlay assay and in transgenic plants. Gene stacking as one of the resistance management strategies in Bt maize requires an understanding of receptor sharing and binding affinity of δ-endotoxins. In the present study, binding affinity of three fluorescein isothiocyanate labeled Cry1A toxins showed high correlation with the toxicity of respective δ-endotoxins. Competitive binding studies showed that Cry1Ab toxins share some of the binding sites with Cry1Aa and Cry1Ac with low affinity and that Cry1Ab may have additional binding sites that are unavailable to the other two toxins tested.

  4. CD2+ AND H+ STIMULATE UPTAKE OF 59FE2+ IN LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  5. ZINC STIMULATES L-PROLINE TRANSPORT BY THE IMINO SYSTEM IN LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  6. CD2+ AND H+ STIMULATE UPTAKE OF 59FE2+ IN LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  7. ZINC STIMULATES L-PROLINE TRANSPORT BY THE IMINO SYSTEM IN LOBSTER HEPATOPANCREATIC BRUSH BORDER MEMBRANE VESICLES. (R823068)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  8. Impact of electroviscosity on the hydraulic conductance of the bordered pit membrane: a theoretical investigation.

    PubMed

    Santiago, Michael; Pagay, Vinay; Stroock, Abraham D

    2013-10-01

    In perfusion experiments, the hydraulic conductance of stem segments ( ) responds to changes in the properties of the perfusate, such as the ionic strength ( ), pH, and cationic identity. We review the experimental and theoretical work on this phenomenon. We then proceed to explore the hypothesis that electrokinetic effects in the bordered pit membrane (BPM) contribute to this response. In particular, we develop a model based on electroviscosity in which hydraulic conductance of an electrically charged porous membrane varies with the properties of the electrolyte. We use standard electrokinetic theory, coupled with measurements of electrokinetic properties of plant materials from the literature, to determine how the conductance of BPMs, and therefore , may change due to electroviscosity. We predict a nonmonotonic variation of with with a maximum reduction of 18%. We explore how this reduction depends on the characteristics of the sap and features of the BPM, such as pore size, density of chargeable sites, and their dissociation constant. Our predictions are consistent with changes in observed for physiological values of sap and pH. We conclude that electroviscosity is likely responsible, at least partially, for the electrolyte dependence of conductance through pits and that electroviscosity may be strong enough to play an important role in other transport processes in xylem. We conclude by proposing experiments to differentiate the impact of electroviscosity on from that of other proposed mechanisms.

  9. Recruitment of CD55 and CD66e brush border-associated glycosylphosphatidylinositol-anchored proteins by members of the Afa/Dr diffusely adhering family of Escherichia coli that infect the human polarized intestinal Caco-2/TC7 cells.

    PubMed

    Guignot, J; Peiffer, I; Bernet-Camard, M F; Lublin, D M; Carnoy, C; Moseley, S L; Servin, A L

    2000-06-01

    The Afa/Dr family of diffusely adhering Escherichia coli (Afa/Dr DAEC) includes bacteria expressing afimbrial adhesins (AFA), Dr hemagglutinin, and fimbrial F1845 adhesin. We show that infection of human intestinal Caco-2/TC7 cells by the Afa/Dr DAEC strains C1845 and IH11128 is followed by clustering of CD55 around adhering bacteria. Mapping of CD55 epitopes involved in CD55 clustering by Afa/Dr DAEC was conducted using CD55 deletion mutants expressed by stable transfection in CHO cells. Deletion in the short consensus repeat 1 (SCR1) domain abolished Afa/Dr DAEC-induced CD55 clustering. In contrast, deletion in the SCR4 domain does not modify Afa/Dr DAEC-induced CD55 clustering. We show that the brush border-associated glycosylphosphatidylinositol (GPI)-anchored protein CD66e (carcinoembryonic antigen) is recruited by the Afa/Dr DAEC strains C1845 and IH11128. This conclusion is based on the observations that (i) infection of Caco-2/TC7 cells by Afa/Dr DAEC strains is followed by clustering of CD66e around adhering bacteria and (ii) Afa/Dr DAEC strains bound efficiently to stably transfected HeLa cells expressing CD66e, accompanied by CD66e clustering around adhering bacteria. Inhibition assay using monoclonal antibodies directed against CD55 SCR domains, and polyclonal anti-CD55 and anti-CD66e antibodies demonstrate that CD55 and CD66e function as a receptors for the C1845 and IH11128 bacteria. Moreover, using structural draE gene mutants, we found that a mutant in which cysteine replaced aspartic acid at position 54 displayed conserved binding capacity but failed to induce CD55 and CD66e clustering. Taken together, these data give new insights into the mechanisms by which Afa/Dr DAEC induces adhesin-dependent cross talk in the human polarized intestinal epithelial cells by mobilizing brush border-associated GPI-anchored proteins known to function as transducing molecules.

  10. Bacterial biodegradation of extractives and patterns of bordered pit membrane attack in pine wood.

    PubMed

    Burnes, T A; Blanchette, R A; Farrell, R L

    2000-12-01

    Wood extractives, commonly referred to as pitch, cause major problems in the manufacturing of pulp and paper. Treatment of nonsterile southern yellow pine chips for 14 days with Pseudomonas fluorescens, Pseudomonas sp., Xanthomonas campestris, and Serratia marcescens reduced wood extractives by as much as 40%. Control treatments receiving only water lost 11% of extractives due to the growth of naturally occurring microorganisms. Control treatments were visually discolored after the 14-day incubation, whereas bacterium-treated wood chips were free of dark staining. Investigations using P. fluorescens NRRL B21432 showed that all individual resin and fatty acid components of the pine wood extractives were substantially reduced. Micromorphological observations showed that bacteria were able to colonize resin canals, ray parenchyma cells, and tracheids. Tracheid pit membranes within bordered pit chambers were degraded after treatment with P. fluorescens NRRL B21432. P. fluorescens and the other bacteria tested appear to have the potential for biological processing to substantially reduce wood extractives in pine wood chips prior to the paper making process so that problems associated with pitch in pulp mills can be controlled.

  11. Secreted maltase-glucoamylase is upregulated in membrane maltase-glucoamylase null mice

    USDA-ARS?s Scientific Manuscript database

    The known mammalian brush-border glucohydrolases are membrane-bound, small intestine lumenal enzymes that digest dietary starches and sugars into monosaccharides for absorption. The phenotype of maltase-glucoamylase deficiency is not understood. To address this, we ablated membrane-bound maltase-gl...

  12. Electrospun regenerated cellulose nanofibrous membranes surface-grafted with polymer chains/brushes via the atom transfer radical polymerization method for catalase immobilization.

    PubMed

    Feng, Quan; Hou, Dayin; Zhao, Yong; Xu, Tao; Menkhaus, Todd J; Fong, Hao

    2014-12-10

    In this study, an electrospun regenerated cellulose (RC) nanofibrous membrane with fiber diameters of ∼200-400 nm was prepared first; subsequently, 2-hydroxyethyl methacrylate (HEMA), 2-dimethylaminoethyl methacrylate (DMAEMA), and acrylic acid (AA) were selected as the monomers for surface grafting of polymer chains/brushes via the atom transfer radical polymerization (ATRP) method. Thereafter, four nanofibrous membranes (i.e., RC, RC-poly(HEMA), RC-poly(DMAEMA), and RC-poly(AA)) were explored as innovative supports for immobilization of an enzyme of bovine liver catalase (CAT). The amount/capacity, activity, stability, and reusability of immobilized catalase were evaluated, and the kinetic parameters (Vmax and Km) for immobilized and free catalase were determined. The results indicated that the respective amounts/capacities of immobilized catalase on RC-poly(HEMA) and RC-poly(DMAEMA) nanofibrous membranes reached 78 ± 3.5 and 67 ± 2.7 mg g(-1), which were considerably higher than the previously reported values. Meanwhile, compared to that of free CAT (i.e., 18 days), the half-life periods of RC-CAT, RC-poly(HEMA)-CAT, RC-poly(DMAEMA)-CAT, and RC-poly(AA)-CAT were 49, 58, 56, and 60 days, respectively, indicating that the storage stability of immobilized catalase was also significantly improved. Furthermore, the immobilized catalase exhibited substantially higher resistance to temperature variation (tested from 5 to 70 °C) and lower degree of sensitivity to pH value (tested from 4.0 and 10.0) than the free catalase. In particular, according to the kinetic parameters of Vmax and Km, the nanofibrous membranes of RC-poly(HEMA) (i.e., 5102 μmol mg(-1) min(-1) and 44.89 mM) and RC-poly(DMAEMA) (i.e., 4651 μmol mg(-1) min(-1) and 46.98 mM) had the most satisfactory biocompatibility with immobilized catalase. It was therefore concluded that the electrospun RC nanofibrous membranes surface-grafted with 3-dimensional nanolayers of polymer chains/brushes would be

  13. Modelling the mechanical behaviour of pit membranes in bordered pits with respect to cavitation resistance in angiosperms.

    PubMed

    Tixier, Aude; Herbette, Stephane; Jansen, Steven; Capron, Marie; Tordjeman, Philippe; Cochard, Hervé; Badel, Eric

    2014-08-01

    Various correlations have been identified between anatomical features of bordered pits in angiosperm xylem and vulnerability to cavitation, suggesting that the mechanical behaviour of the pits may play a role. Theoretical modelling of the membrane behaviour has been undertaken, but it requires input of parameters at the nanoscale level. However, to date, no experimental data have indicated clearly that pit membranes experience strain at high levels during cavitation events. Transmission electron microscopy (TEM) was used in order to quantify the pit micromorphology of four tree species that show contrasting differences in vulnerability to cavitation, namely Sorbus aria, Carpinus betulus, Fagus sylvatica and Populus tremula. This allowed anatomical characters to be included in a mechanical model that was based on the Kirchhoff-Love thin plate theory. A mechanistic model was developed that included the geometric features of the pits that could be measured, with the purpose of evaluating the pit membrane strain that results from a pressure difference being applied across the membrane. This approach allowed an assessment to be made of the impact of the geometry of a pit on its mechanical behaviour, and provided an estimate of the impact on air-seeding resistance. The TEM observations showed evidence of residual strains on the pit membranes, thus demonstrating that this membrane may experience a large degree of strain during cavitation. The mechanical modelling revealed the interspecific variability of the strains experienced by the pit membrane, which varied according to the pit geometry and the pressure experienced. The modelling output combined with the TEM observations suggests that cavitation occurs after the pit membrane has been deflected against the pit border. Interspecific variability of the strains experienced was correlated with vulnerability to cavitation. Assuming that air-seeding occurs at a given pit membrane strain, the pressure predicted by the model

  14. Effects of Protease, Phytase and a Bacillus sp. Direct-Fed Microbial on Nutrient and Energy Digestibility, Ileal Brush Border Digestive Enzyme Activity and Cecal Short-Chain Fatty Acid Concentration in Broiler Chickens

    PubMed Central

    Murugesan, Ganapathi R.; Romero, Luis F.; Persia, Michael E.

    2014-01-01

    Two experiments were conducted to determine the effects of protease and phytase (PP) and a Bacillus sp. direct-fed microbial (DFM) on dietary energy and nutrient utilization in broiler chickens. In the first experiment, Ross 308 broiler chicks were fed diets supplemented with PP and DFM in a 2×2 factorial arrangement. The 4 diets (control (CON), CON + PP, CON + DFM, and CON + PP + DFM) were fed from 15–21 days of age. In Experiment 1, significant interaction (P≤0.01) between PP and DFM on the apparent ileal digestibility coefficient for starch, crude protein, and amino acid indicated that both additives increased the digestibility. Both additives increased the nitrogen retention coefficient with a significant interaction (P≤0.01). Although no interaction was observed, significant main effects (P≤0.01) for nitrogen-corrected apparent ME (AMEn) for PP or DFM indicated an additive response. In a follow-up experiment, Ross 308 broiler chicks were fed the same experimental diets from 1–21 days of age. Activities of ileal brush border maltase, sucrase, and L-alanine aminopeptidase were increased (P≤0.01) by PP addition, while a trend (P = 0.07) for increased sucrase activity was observed in chickens fed DFM, in Experiment 2. The proportion of cecal butyrate was increased (P≤0.01) by DFM addition. Increased nutrient utilization and nitrogen retention appear to involve separate but complementary mechanisms for PP and DFM, however AMEn responses appear to have separate and additive mechanisms. PMID:25013936

  15. Amnionless function is required for cubilin brush-border expression and intrinsic factor-cobalamin (vitamin B12) absorption in vivo.

    PubMed

    He, Qianchuan; Madsen, Mette; Kilkenney, Adam; Gregory, Brittany; Christensen, Erik I; Vorum, Henrik; Højrup, Peter; Schäffer, Alejandro A; Kirkness, Ewen F; Tanner, Stephan M; de la Chapelle, Albert; Giger, Urs; Moestrup, Søren K; Fyfe, John C

    2005-08-15

    Amnionless (AMN) and cubilin gene products appear to be essential functional subunits of an endocytic receptor called cubam. Mutation of either gene causes autosomal recessive Imerslund-Gräsbeck syndrome (I-GS, OMIM no. 261100) in humans, a disorder characterized by selective intestinal malabsorption of cobalamin (vitamin B12) and urinary loss of several specific low-molecular-weight proteins. Vital insight into the molecular pathology of I-GS has been obtained from studies of dogs with a similar syndrome. In this work, we show that I-GS segregates in a large canine kindred due to an in-frame deletion of 33 nucleotides in exon 10 of AMN. In a second, unrelated I-GS kindred, affected dogs exhibit a homozygous substitution in the AMN translation initiation codon. Studies in vivo demonstrated that both mutations abrogate AMN expression and block cubilin processing and targeting to the apical membrane. The essential features of AMN dysfunction observed in vivo are recapitulated in a heterologous cell-transfection system, thus validating the system for analysis of AMN-cubilin interactions. Characterization of canine AMN mutations that cause I-GS establishes the canine model as an ortholog of the human disorder well suited to studies of AMN function and coevolution with cubilin.

  16. Life at the border: Adaptation of proteins to anisotropic membrane environment

    PubMed Central

    Pogozheva, Irina D; Mosberg, Henry I; Lomize, Andrei L

    2014-01-01

    This review discusses main features of transmembrane (TM) proteins which distinguish them from water-soluble proteins and allow their adaptation to the anisotropic membrane environment. We overview the structural limitations on membrane protein architecture, spatial arrangement of proteins in membranes and their intrinsic hydrophobic thickness, co-translational and post-translational folding and insertion into lipid bilayers, topogenesis, high propensity to form oligomers, and large-scale conformational transitions during membrane insertion and transport function. Special attention is paid to the polarity of TM protein surfaces described by profiles of dipolarity/polarizability and hydrogen-bonding capacity parameters that match polarity of the lipid environment. Analysis of distributions of Trp resides on surfaces of TM proteins from different biological membranes indicates that interfacial membrane regions with preferential accumulation of Trp indole rings correspond to the outer part of the lipid acyl chain region—between double bonds and carbonyl groups of lipids. These “midpolar” regions are not always symmetric in proteins from natural membranes. We also examined the hydrophobic effect that drives insertion of proteins into lipid bilayer and different free energy contributions to TM protein stability, including attractive van der Waals forces and hydrogen bonds, side-chain conformational entropy, the hydrophobic mismatch, membrane deformations, and specific protein–lipid binding. PMID:24947665

  17. Distribution of IGF receptors in the plasma membrane of proximal tubular cells

    SciTech Connect

    Hammerman, M.R.; Rogers, S. )

    1987-11-01

    To characterize the distribution of receptors for insulin-like growth factors I and II (IGF I and II) in the plasma membrane of the renal proximal tubular cell, the authors measured binding of {sup 125}I-labeled IGF I and {sup 125}I-labeled IGF II to proximal tubular basolateral and brush-border membranes and characterized IGF I-stimulated phosphorylation of detergent-solubilized membranes. {sup 125}I-IGF bound primarily to a 135,000 relative molecular weight (M{sub r}) protein and IGF II to a 260,000 M{sub r} protein in isolated membranes. Binding of {sup 125}I-IGF I was severalfold greater in basolateral than in brush-border membranes. IGF I-stimulated phosphorylation of the 92,000 M{sub r} {beta}-subunit of its receptors could be demonstrated only in basolateral membranes. These findings are consistent with an asymmetrical distribution of receptors for IGF I in the plasma membrane of the renal proximal tubular cell, localization being primary on the basolateral side. In contrast, binding of {sup 125}I-IGF II to isolated basolateral and brush-border membranes was equivalent, suggesting that receptors for this peptide are distributed more symmetrically in the plasma membrane. The findings suggest that the action of IGF I in proximal tubule are mediated via interaction of circulating peptide with specific receptors in the basolateral membrane. However, the findings established the potential for actions of IGF II to be exerted in proximal tubule via interaction with both basolateral and/or brush-border membrane receptors.

  18. Impact of Electroviscosity on the Hydraulic Conductance of the Bordered Pit Membrane: A Theoretical Investigation1[C

    PubMed Central

    Santiago, Michael; Pagay, Vinay; Stroock, Abraham D.

    2013-01-01

    In perfusion experiments, the hydraulic conductance of stem segments () responds to changes in the properties of the perfusate, such as the ionic strength (), pH, and cationic identity. We review the experimental and theoretical work on this phenomenon. We then proceed to explore the hypothesis that electrokinetic effects in the bordered pit membrane (BPM) contribute to this response. In particular, we develop a model based on electroviscosity in which hydraulic conductance of an electrically charged porous membrane varies with the properties of the electrolyte. We use standard electrokinetic theory, coupled with measurements of electrokinetic properties of plant materials from the literature, to determine how the conductance of BPMs, and therefore , may change due to electroviscosity. We predict a nonmonotonic variation of with with a maximum reduction of 18%. We explore how this reduction depends on the characteristics of the sap and features of the BPM, such as pore size, density of chargeable sites, and their dissociation constant. Our predictions are consistent with changes in observed for physiological values of sap and pH. We conclude that electroviscosity is likely responsible, at least partially, for the electrolyte dependence of conductance through pits and that electroviscosity may be strong enough to play an important role in other transport processes in xylem. We conclude by proposing experiments to differentiate the impact of electroviscosity on from that of other proposed mechanisms. PMID:24014573

  19. Insulated Fiber Brush.

    DTIC Science & Technology

    An insulated-strand fiber brush is provided for a DC motor /generator. The brush is comprised of a plurality of fiber segments which are insulated from one another near the contact surface of a rotor bar. In one embodiment, insulating spacers are fixed to a brush assembly and wear with the fibers, and in another embodiment insulation is provided by a separate shell. (Author)

  20. Correlative light and scanning electron microscopy of the same sections gives new insights into the effects of pectin lyase on bordered pit membranes in Pinus radiata wood.

    PubMed

    West, Mark; Vaidya, Alankar; Singh, Adya P

    2012-08-01

    Bordered pits are structures in the cell walls of softwood tracheids which permit the movement of water between adjacent cells. These structures contain a central pit membrane composed of an outer porous ring (margo) and an inner dense and pectin-rich disc (torus). The membrane is overarched on each side by pit borders. Pits may be aspirated, a condition where the torus seals against the pit border, effectively blocking the pathway between cells. In living trees this maintains overall continuity of water conduction in xylem by sealing off tracheids containing air. Drying of timber results in further pit aspiration, which reduces wood permeability to liquid treatment agents such as antifungal chemicals. One possible way to increase permeability is by treating wood with pectin lyase to modify or remove the torus. The effectiveness of this treatment was initially evaluated using light microscopy (LM) of toluidine blue stained wood. Pectic material is coloured pink-magenta with this stain, and loss of this colour after treatment has been interpreted as indicating destruction of the torus. However, correlative light (LM) and scanning electron (SEM) microscopic observations of identical areas of toluidine blue stained sections revealed that many unstained pits had intact but modified tori when viewed with SEM. These observations indicate that LM alone is not sufficient to evaluate the effects of pectin lyase on pit membranes in wood. Combining LM and SEM gives more complete information.

  1. Lack of Cry1Fa Binding to the Midgut Brush Border Membrane in a Resistant Colony of Plutella xylostella Moths with a Mutation in the ABCC2 Locus

    PubMed Central

    Hernández-Martínez, Patricia; Hernández-Rodríguez, Carmen Sara; Krishnan, Vidisha; Crickmore, Neil; Escriche, Baltasar

    2012-01-01

    Previous studies reported “mode 1” Bacillus thuringiensis resistance in a colony of diamondback moths (NO-QA), and recently, this resistance has been mapped to an ABC transporter (ABCC2) locus. We report the lack of binding of Cry1Fa to insects derived from this colony and compare our data with those from other insects with ABCC2-associated resistance. PMID:22773634

  2. Genetic diversity of the Plasmodium falciparum apical membrane antigen I gene in parasite population from the China-Myanmar border area.

    PubMed

    Zhu, Xiaotong; Zhao, Zhenjun; Feng, Yonghui; Li, Peipei; Liu, Fei; Liu, Jun; Yang, Zhaoqing; Yan, Guiyun; Fan, Qi; Cao, Yaming; Cui, Liwang

    2016-04-01

    To investigate the genetic diversity of the Plasmodium falciparum apical membrane antigen 1 (PfAMA1) gene in Southeast Asia, we determined PfAMA1 sequences from 135 field isolates collected from the China-Myanmar border area and compared them with 956 publically available PfAMA1 sequences from seven global P. falciparum populations. This analysis revealed high genetic diversity of PfAMA1 in global P. falciparum populations with a total of 229 haplotypes identified. The genetic diversity of PfAMA1 gene from the China-Myanmar border is not evenly distributed in the different domains of this gene. Sequence diversity in PfAMA1 from the China-Myanmar border is lower than that observed in Thai, African and Oceanian populations, but higher than that in the South American population. This appeared to correlate well with the levels of endemicity of different malaria-endemic regions, where hyperendemic regions favor genetic cross of the parasite isolates and generation of higher genetic diversity. Neutrality tests show significant departure from neutrality in the entire ectodomain and Domain I of PfAMA1 in the China-Myanmar border parasite population. We found evidence supporting a substantial continent-wise genetic structure among P. falciparum populations, with the highest genetic differentiation detected between the China-Myanmar border and the South American populations. Whereas no alleles were unique to a specific region, there were considerable geographical differences in major alleles and their frequencies, highlighting further necessity to include more PfAMA1 alleles in vaccine designs.

  3. Brushing Your Child's Teeth

    MedlinePlus

    ... the toothpaste rather than swallowing it. For children under age 3, use just a small amount of toothpaste ... floss and brush your teeth every day. Children under age 6 may be able to handle a toothbrush ...

  4. Almond brush module cutter

    SciTech Connect

    Zohns, M.A.; Jenkins, B.M.; Mehlschau, J.J.; Morrison, D.

    1983-06-01

    This paper addresses the design, construction, and evaluation of an almond brush module cutter. The module cutter is one link in a system which processes tree prunings for fuel and fiber. This system includes a modified cotton module builder, a module mover, the cutter, and a tub grinder. An economic analysis of the cutter is presented along with the problems involved in cutting brush modules.

  5. Cavitation during wire brushing

    NASA Astrophysics Data System (ADS)

    Li, Bo; Zou, Jun; Ji, Chen

    2016-11-01

    In our daily life, brush is often used to scrub the surface of objects, for example, teeth, pots, shoes, pool, etc. And cleaning rust and stripping paint are accomplished using wire brush. Wire brushes also can be used to clean the teeth for large animals, such as horses, crocodiles. By observing brushing process in water, we capture the cavitation phenomenon on the track of moving brush wire. It shows that the cavitation also can affect the surface. In order to take clear and entire pictures of cavity, a simplified model of one stainless steel wire brushing a boss is adopted in our experiment. A transparent organic tank filled with deionized water is used as a view box. And a high speed video camera is used to record the sequences. In experiment, ambient pressure is atmospheric pressure and deionized water temperature is kept at home temperature. An obvious beautiful flabellate cavity zone appears behind the moving steel wire. The fluctuation of pressure near cavity is recorded by a hydrophone. More movies and pictures are used to show the behaviors of cavitation bubble following a restoring wire. Beautiful tracking cavitation bubble cluster is captured and recorded to show.

  6. [Involvement of tissue interaction between cranial neural crest cells, their pathways lateral to the midbrain hindbrain border and the buccopharyngeal membrane in Meckel's cartilage formation in avian embryos].

    PubMed

    Imai, Hajime

    2012-03-01

    Cranial neural crest cells migrate to the craniofacial primordia and differentiate into skeletal tissues of the jaw such as Meckel's cartilage. It has not been clearly demonstrated how neural crest cells are committed to differentiate into these tissues. In this study, the conditions that are required for the formation of Meckel's cartilage were investigated. In situ hybridization in chick embryos indicated that Fgf8 and Shh involved in the pattern formation of limb cartilages were expressed in the neural tube of the midbrain-hindbrain border, the buccopharyngeal membrane and the oro-proximal site of the 1st branchial arch (oro-proximal BA1). Cell-tracing with DiI confirmed that the neural crest cells derived from both the posterior midbrain and rhombomere 1 migrated to the buccopharyngeal membrane, which subsequently forms oro-proximal BA1, by passing through the mesenchyme lateral to the midbrain-hindbrain boundary. Based on the above results, we carried out two types of ectopic transplantation experiments by chick-quail chimera The graft of oro-proximal BA1, the complex of epithelium and mesenchyme, formed a Meckel's cartilage-like structure in a self-differentiation manner, whereas neither epithelium only nor mesenchyme formed any elongated cartilage. The ectopic transplant of the buccopharyngeal membrane into the mesenchyme lateral to the neural tube of the mid-hindbrain border in which neural crest cells were migrating formed a Meckel's cartilage-like structure. These results suggest that the cranial neural crest cells derived from the mid-hindbrain region are committed to the cell fate during migration, and receive further signaling to differentiate into Meckel's cartilage in their destination.

  7. Bidirectional Brush Seals

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Wilson, Jack; Wu, Tom; Flower, Ralph

    1997-01-01

    Presented is a study of the use of a set of I.D./O.D. bidirectional press seals to reduce the leakage losses in a wave rotor. Relative to the baseline configuration, data indicate the use of brush seals enhanced wave rotor efficiency from 36 to 45 percent at low leakages (small rotor endwall gap spacings) and from 15 to 33 percent at high leakages (larger endwall gap spacings). These brush seals are capable of sealing positive or negative pressure drops with respect to the axial direction. Surface tribology for these tests suggested little evidence of grooving although the bristles appeared polished.

  8. Friction between Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Sokoloff, Jeffrey

    2006-03-01

    A polymer brush consists of a surface with a fairly concentrated coating of polymer chains, each one of which has one of its ends tightly bound to the surface. They serve as extremely effective lubricant, producing friction coefficients as low as 0.001 or less! Polymer brushes are a promising way to reduce friction to extremely low values. They have the disadvantage, however, that they must be immersed in a liquid solvent in order to function as a lubricant. The presence of a solvent is believed to result in osmotic pressure which partially supports the load. The density profile of a polymer brush (i.e., the density of monomers as a function of distance from the surface to which the polymers are attached) is well established. What is not understood is how the interaction of polymer brush coated surfaces in contact with each other is able to account for the details of the observed low friction. For example, molecular dynamics studies generally do not predict static friction, whereas surface force apparatus measurements due to Tadmor, et. al., find that there is static friction. This is the topic of the present presentation.

  9. Brush potential curve tracer

    DOEpatents

    Finch, H.A.

    1985-06-21

    A device for analyzing commutating characteristics of a motor or generator includes a holder for supporting a plurality of probes adjacent a brush of the motor or generator. Measurements of electrical current characteristics of the probes provides information useful in analyzing operation of the machine. Methods for employing a device in accordance with the invention are also disclosed.

  10. Smart photonic carbon brush

    NASA Astrophysics Data System (ADS)

    Morozov, Oleg G.; Kuznetsov, Artem A.; Morozov, Gennady A.; Nureev, Ilnur I.; Sakhabutdinov, Airat Z.; Faskhutdinov, Lenar M.; Artemev, Vadim I.

    2016-03-01

    Aspects of the paper relate to a wear monitoring system for smart photonic carbon brush. There are many applications in which regular inspection is not feasible because of a number of factors including, for example, time, labor, cost and disruptions due to down time. Thus, there is a need for a system that can monitor the wear of a component while the component is in operation or without having to remove the component from its operational position. We propose a new smart photonic method for characterization of carbon brush wear. It is based on the usage of advantages of the multiplicative response of FBG and LPFG sensors and its double-frequency probing. Additional measuring parameters are the wear rate, the brush temperature, the engine rotation speed, the hangs control, and rotor speed. Sensor is embedded in brush. Firstly the change of sensor length is used to measure wear value and its central wavelength shift for temperature ones. The results of modeling and experiments are presented.

  11. Ureteral retrograde brush biopsy

    MedlinePlus

    ... is inserted over or next to the guide wire. The ureteroscope is a longer, thinner telescope with a small camera. The surgeon can see the inside of the ureter or kidney through the camera. A nylon or steel brush is placed through the ureteroscope. ...

  12. Analysis of tooth brushing cycles.

    PubMed

    Tosaka, Yuki; Nakakura-Ohshima, Kuniko; Murakami, Nozomi; Ishii, Rikako; Saitoh, Issei; Iwase, Yoko; Yoshihara, Akihiro; Ohuchi, Akitsugu; Hayasaki, Haruaki

    2014-11-01

    The aim of this study was to demonstrate the effectiveness of an analysis of tooth brushing cycles using a system that measures tooth brushing motion and brushing force with an accelerometer and strain tension gage attached to a toothbrush. Mechanical plaque removal with a manual toothbrush remains the primary method of maintaining good oral hygiene for the majority of the population. Because toothbrush motion has not been fully understood, it should be clarified by analysis of tooth brushing cycles. Twenty healthy female dental hygienists participated in this study. Their tooth brushing motions were measured and analyzed using an American Dental Association-approved manual toothbrush to which a three-dimensional (3-D) accelerometer and strain tension gage were attached. 3-D motion and brushing force on the labial surface of the mandibular right central incisor and the lingual surface of the mandibular left first molar were measured, analyzed, and compared. Multilevel linear model analysis was applied to estimate variables and compare motion and forces related to the two tooth surfaces. The analysis of tooth brushing cycles was feasible, and significant differences were detected for durations and 3-D ranges of toothbrush motion as well as brushing force between the two tooth surfaces. The analysis used in this study demonstrated an ability to detect characteristics of tooth brushing motion, showing tooth brushing motion to change depending on the brushed location. These results also suggest that more detailed instructions might be required according to patient's oral condition.

  13. Wire brush fastening device

    SciTech Connect

    Meigs, R.A.

    1993-08-31

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus.

  14. Wire brush fastening device

    DOEpatents

    Meigs, R.A.

    1995-09-19

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus. 13 figs.

  15. Wire brush fastening device

    DOEpatents

    Meigs, Richard A.

    1995-01-01

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus.

  16. DNA decontamination of fingerprint brushes.

    PubMed

    Szkuta, Bianca; Oorschot, Roland A H van; Ballantyne, Kaye N

    2017-08-01

    Genetic profiling of DNA collected from fingerprints that have been exposed to various enhancement techniques is routine in many forensic laboratories. As a result of direct contact with fingermark residues during treatment, there is concern around the DNA contamination risk of dusting fingermarks with fingerprint brushes. Previous studies have demonstrated the potential for cross-contamination between evidentiary items through various mechanisms, highlighting the risk of using the same fingerprint brush to powder multiple surfaces within and between crime-scenes. Experiments were performed to assess the contamination risk of reused fingerprint brushes through the transfer of dried saliva and skin deposits from and to glass surfaces with new unused squirrel hair and fiberglass brushes. Additional new unused brushes and brushes previously used in casework were also tested for their ability to contaminate samples. In addition, the ability to eradicate DNA from used squirrel hair and fiberglass fingerprint brushes was assessed using a 1% sodium hypochlorite solution and a 5% solution of a commercially available alternative, Virkon. DNA profiling results from surfaces contacted by treated and untreated brushes were compared to determine the effectiveness of the devised cleaning protocol. Brush durability was also assessed over multiple wash/rinse/dry cycles with both agents. Varying amounts of DNA-containing material were collected and transferred by squirrel hair and fiberglass brushes, with detectability on the secondary surface dependent on the biological nature of the material being transferred. The impact of DNA contamination from dirty fingerprint brushes was most apparent in simulations involving the transfer of dried saliva and brushes previously used in casework, while minimal transfer of touch DNA was observed. Alarmingly, large quantities of DNA were found to reside on new unused squirrel hair brushes, while no DNA was detected on new unused fiberglass

  17. Brush seals for cryogenic applications

    NASA Astrophysics Data System (ADS)

    Proctor, Margaret P.

    1994-07-01

    This viewgraph presentation presents test results of brush seals for cryogenic applications. Leakage for a single brush seal was two to three times less than for a 12-tooth labyrinth seal. The maximum temperature rise for a single brush seal was less than 50 R and occurred at 25 psid across the seal and 35,000 rpm. A static blowout test demonstrated sealing capability up to 550 psid. The seal limit was not obtained. The power loss for a single brush at 35,000 rpm and 175 psid was 2.45 hp. Two brushes far apart leak less than two brushes tight packed. Rotor wear was approximately 0.00075 mils and bristle wear was 1-3 mils after 4-1/2 hours.

  18. Biomolecule-functionalized polymer brushes.

    PubMed

    Jiang, Hui; Xu, Fu-Jian

    2013-04-21

    Functional polymer brushes have been utilized extensively for the immobilization of biomolecules, which is of crucial importance for the development of biosensors and biotechnology. Recent progress in polymerization methods, in particular surface-initiated atom transfer radical polymerization (ATRP), has provided a unique means for the design and synthesis of new biomolecule-functionalized polymer brushes. This current review summarizes such recent research activities. The different preparation strategies for biomolecule immobilization through polymer brush spacers are described in detail. The functional groups of the polymer brushes used for biomolecule immobilization include epoxide, carboxylic acid, hydroxyl, aldehyde, and amine groups. The recent research activities indicate that functional polymer brushes become versatile and powerful spacers for immobilization of various biomolecules to maximize their functionalities. This review also demonstrates that surface-initiated ATRP is used more frequently than other polymerization methods in the designs of new biomolecule-functionalized polymer brushes.

  19. Trans-Membrane Area Asymmetry Controls the Shape of Cellular Organelles

    PubMed Central

    Beznoussenko, Galina V.; Pilyugin, Sergei S.; Geerts, Willie J. C.; Kozlov, Michael M.; Burger, Koert N. J.; Luini, Alberto; Derganc, Jure; Mironov, Alexander A.

    2015-01-01

    Membrane organelles often have complicated shapes and differ in their volume, surface area and membrane curvature. The ratio between the surface area of the cytosolic and luminal leaflets (trans-membrane area asymmetry (TAA)) determines the membrane curvature within different sites of the organelle. Thus, the shape of the organelle could be critically dependent on TAA. Here, using mathematical modeling and stereological measurements of TAA during fast transformation of organelle shapes, we present evidence that suggests that when organelle volume and surface area are constant, TAA can regulate transformation of the shape of the Golgi apparatus, endosomal multivesicular bodies, and microvilli of brush borders of kidney epithelial cells. Extraction of membrane curvature by small spheres, such as COPI-dependent vesicles within the Golgi (extraction of positive curvature), or by intraluminal vesicles within endosomes (extraction of negative curvature) controls the shape of these organelles. For instance, Golgi tubulation is critically dependent on the fusion of COPI vesicles with Golgi cisternae, and vice versa, for the extraction of membrane curvature into 50–60 nm vesicles, to induce transformation of Golgi tubules into cisternae. Also, formation of intraluminal ultra-small vesicles after fusion of endosomes allows equilibration of their TAA, volume and surface area. Finally, when microvilli of the brush border are broken into vesicles and microvilli fragments, TAA of these membranes remains the same as TAA of the microvilli. Thus, TAA has a significant role in transformation of organelle shape when other factors remain constant. PMID:25761238

  20. Role of intracellular membranes in transcellular calcium transport

    SciTech Connect

    Coleman, J.R.; Young, L.B.; Wade, P.C.

    1981-01-01

    Models can be tested through the use of various agents that affect different portions of the overall mechanism. The calcium ionophore A23187 can be used to increase the rate of calcium entry through the brush border, effectively removing diffusion through the brush border as a rate-limiting step. It would be expected that treatment with A23187 would thus increase the overall rate of calcium transcellular transport. In contrast, chlorpromazine has been shown to inhibit in vitro calcium uptake by Golgi membranes. Consequently if the model is correct, treatment with A23187 and chlorpromazine would tend to raise the cytoplasmic calcium concentration, since the Golgi membrane uptake mechanism would be inhibited, and calcium would accumulate in mitochondria with little or no increase in transcellular transport. Finally, Golgi membranes have been shown to release calcium in response to ATP. Sodium azide inhibits ATP generation and calcium uptake by mitochondria. Thus, treatment with A23187 and soidum azide should cause accumulation of calcium in the Golgi membranes, if the proposed model is correct. The purpose of this investigation was to use coordinated electron probe x-ray microanalysis and transmission electron microscopy to test the response of the intestinal absorptive cells to the agents mentioned.

  1. Developmental organization of the intestinal brush-border cytoskeleton.

    PubMed

    Takemura, R; Masaki, T; Hirokawa, N

    1988-01-01

    At the terminal web of chicken intestinal epithelial cell, the actin bundles are cross-linked by a fine filamentous network of actin-associated cross-linkers. Myosin, fodrin, and TW 260/240 have been identified as major components of the cross-linkers. We studied the development of the cross-linkers by quick-freeze, deep-etch electron microscopy, and the expression of cross-linker proteins (myosin, fodrin 240, and TW 260) by immunofluorescence and immunoblotting analysis during the embryogenesis. Microvilli start to form at 5-7 days, and the rootlets begin to elongate at 10 days. At an early stage of the development of the terminal web (13 days), fodrin 240 and a small amount of myosin are expressed, and a few actin-associated cross-linkers are present between the rootlets. However, TW 260 is not expressed at this stage. At an intermediate stage (19 days), the amount of myosin increases, and TW 260 begins to be expressed. The number of cross-linkers associated with the unit length of the rootlets is 24/microns. At the final stage of the terminal web formation (2 days after hatching), the amount of fodrin 240, myosin, and TW 260 is similar to the adult level, and the number of the actin-associated cross-linkers per unit length of the rootlet is 27/microns (approximately 85% of the adult). These results suggest that the synthesis of cross-linker proteins may be intricately regulated to achieve the desired density of cross-linkages at each developmental stage: at early and intermediate stages, sufficient and not an excess of cross-linkages are formed; and at a final stage, a higher complexity of cross-linkages is achieved. In addition, there is a differential expression of the components of the actin-associated cross-linkers: myosin and fodrin could be early components of the cross-linkers involved in the basic stabilization of the terminal web structure, whereas TW 260/240 becomes incorporated later, possibly involved in the stabilization preparatory to the rapid elongation of microvilli, which occurs after the formation of the terminal web.

  2. 'King George Island' Brushed

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Annotated Version

    This mosaic was made from frames acquired by the microscopic imager on NASA's Mars Exploration Rover Spirit during Spirit's 1,031 Martian day, or sol, on the red planet (Nov. 27, 2006). It shows a rock target called 'King George Island' after the target was brushed by the rover's rock abrasion tool. The mosaic covers approximately 6 centimeters (2.4 inches) across and shows the granular nature of the rock exposure. The grains are typically about 1 millimeter (.04 inches) wide. Data from the rover's Moessbauer spectrometer provides evidence that they have an enhanced amount of the mineral hematite relative to surrounding soils.

  3. Current developments in brush seals

    NASA Technical Reports Server (NTRS)

    Loewenthal, Bob

    1994-01-01

    The objective of the brush seal development program is to develop a comprehensive design methodology for brush seals using application requirements from engine manufacturers and experimental characterization of seal design and tribological pairs. The goals are to substantially lower leakage compared to labyrinth seals, seal life consistent with man-rated mission requirements, to investigate single and multiple staged brush seals, temperature up to 1200 F and surface speed up to 900 fps, and pressure drop across the seal of 50 psid. Test results are presented in viewgraph format.

  4. Current developments in brush seals

    NASA Astrophysics Data System (ADS)

    Loewenthal, Bob

    1994-07-01

    The objective of the brush seal development program is to develop a comprehensive design methodology for brush seals using application requirements from engine manufacturers and experimental characterization of seal design and tribological pairs. The goals are to substantially lower leakage compared to labyrinth seals, seal life consistent with man-rated mission requirements, to investigate single and multiple staged brush seals, temperature up to 1200 F and surface speed up to 900 fps, and pressure drop across the seal of 50 psid. Test results are presented in viewgraph format.

  5. Interaction between two polyelectrolyte brushes.

    PubMed

    Kumar, N Arun; Seidel, Christian

    2007-08-01

    We report molecular dynamics simulations on completely charged polyelectrolyte brushes grafted to two parallel surfaces. The pressure Pi is evaluated as a function of separation D between the two grafting planes. For decreasing separation, Pi shows several regimes distinguished by their scaling with D which reflects the different physical nature of the various regimes. At weak compression the pressure obeys the 1D power law predicted by scaling theory of an ideal gas of counterions in the osmotic brush regime. In addition we find that the brushes shrink as they approach each other trying to avoid interpenetration. At higher compressions where excluded volume interactions become important, we obtain scaling exponents between -2 at small grafting density rho(a) and -3 at large rho(a). This behavior indicates a transition from a brush under good solvent condition to the melt regime with increasing grafting density.

  6. Structures of Bordered Pits Potentially Contributing to Isolation of a Refilled Vessel from Negative Xylem Pressure in Stems of Morus australis Poir.: Testing of the Pit Membrane Osmosis and Pit Valve Hypotheses.

    PubMed

    Ooeda, Hiroki; Terashima, Ichiro; Taneda, Haruhiko

    2017-02-01

    Two hypotheses have been proposed to explain the mechanism preventing the refilling vessel water from being drained to the neighboring functional vessels under negative pressure. The pit membrane osmosis hypothesis proposes that the xylem parenchyma cells release polysaccharides that are impermeable to the intervessel pit membranes into the refilling vessel; this osmotically counteracts the negative pressure, thereby allowing the vessel to refill. The pit valve hypothesis proposes that gas trapped within intervessel bordered pits isolates the refilling vessel water from the surrounding functional vessels. Here, using the single-vessel method, we assessed these hypotheses in shoots of mulberry (Morus australis Poir.). First, we confirmed the occurrence of xylem refilling under negative pressure in the potted mulberry saplings. To examine the pit membrane osmosis hypothesis, we estimated the semi-permeability of pit membranes for molecules of various sizes and found that the pit membranes were not semi-permeable to polyethylene glycol of molecular mass <20,000. For the pit valve hypothesis, we formed pit valves in the intervessel pits in the short stem segments and measured the maximum liquid pressure up to which gases in bordered pits were retained. The threshold pressure ranged from 0.025 to 0.10 MPa. These values matched the theoretical value calculated from the geometry of the pit chamber (0.0692-0.101 MPa). Our results suggest that gas in the pits is retained by surface tension, even under substantial positive pressure to resolve gases in the refilling vessel, whereas the molecule size required for the pit membrane osmosis mechanism in mulberry would be unrealistically large. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  7. Iraq Border

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In an area north of the city of Al-Basrah, Iraq, which borders Iran, a former wetland has been drained and walled off. Now littered with minefields and gun emplacments, it is a staging area for military exercises. This image was acquired by Landsat 7's Enhanced Thematic Mapper plus (ETM+) sensor on January 24, 2001. This is a false-color composite image made using near-infrared, red, and green wavelengths. The image has also been sharpened using the sensor's panchromatic band. Image provided by the USGS EROS Data Center Satellite Systems Branch

  8. Osmotic and Salted Brush Phase of Polyelectrolyte Brushes

    NASA Astrophysics Data System (ADS)

    Helm, Christane A.; Ahrens, Heiko; Förster, Stephan

    2004-03-01

    Amphiphilic block copolymers consisting of a fluid hydrophobic Poly(ethyletylene) (PEE), and a Poly(styrenesulfonate) (PSS) part form monolayers at the air/water interface. With x-ray reflectivity it is shown that the hydrophobic blocks of PEE_114PSS_83 and PEE_144PSS_136 constitute a nm-thick melt, while the polyelectrolyte forms an osmotically swollen brush with counterion incorporation. A slight thickness increase on monolayer compression is found which can be explained by the strong stretching of the brushes. Only at high salt conditions (above 0.1 M), the brush shrinks and the thickness scales with the molecular area (exponent -1/3), and with the salt concentration (exponent ca. -1/5). With Grazing Incidence Diffraction, the lateral order of the polyelectrolyte chains can be detected.

  9. Distribution of Chains in Polymer Brushes Produced by a “Grafting From” Mechanism

    SciTech Connect

    Martinez, Andre P.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.; Adamson, Douglas H.

    2016-01-11

    The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. We synthesized the brushes with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were more polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. Moreover, the origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.

  10. Distribution of Chains in Polymer Brushes Produced by a “Grafting From” Mechanism

    DOE PAGES

    Martinez, Andre P.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.; ...

    2016-01-11

    The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. We synthesized the brushes with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were moremore » polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. Moreover, the origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.« less

  11. Cryogenic Brush Seal Test Results

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.; Walker, James F.

    1996-01-01

    Brush seals are compliant, contact seals that have long-life, low-leakage characteristics desirable for use in rocket engine turbopumps. 50.8-mm (2.0 inch) diameter brush seals with a nominal initial radial interference of 0.127-mm (0.005 inch) were tested in liquid nitrogen at shaft speeds up to 35,000 rpm and differential pressure loads up to 1.21 MPa (175 psi) per brush. The measured leakage rate of a single brush was 2-3 times less than that measured for a 12-tooth, 0.127-mm (0.005 inch) radial clearance labyrinth seal used as a baseline. Stage effects were studied and it was found that two brush seals with a large separation distance leaked less than two brushes tightly packed together. The maximum measured groove depth on the Inconel 718 rotor was 25.4 (mu)m (0.001 inch) after 4.31 hours of shaft rotation. The Haynes-25 bristles wore approximately 25.4-76.2 (mu)m (0.001-0.003 inch) under the same conditions. Three seal runner coatings, chromium carbide, Teflon impregnated chromium, and zirconium oxide, were tested in liquid hydrogen at 35,000 and 65,000 rpm with separate 50.8 mm diameter brush seals made of Haynes-25 bristles and having a nominal initial radial interference of 129 rpm. Two bare Inconel-718 rotors were also tested as a baseline. The test results revealed significant differences between the wear characteristics of the uncoated and coated seal runners. At both speeds the brush seal with the bare Inconel-718 seal runner exhibited significant bristle wear with excessive material transferring to the runner surface. In contrast, the coated seal runners inhibited the transfer and deposit of bristle material. The chromium carbide coating showed only small quantities of bristle material transferring to its surface. The Teflon impregnated chromium coating also inhibited material transfer and provided some lubrication. This coating, however, is self-sacrificing. The Teflon remained present on the low speed runner, but it was completely removed from the

  12. Effect of mechanical stimulation by tooth brushing on oxygen tension in dog gingiva.

    PubMed

    Tanaka, M; Hanioka, T; Ojima, M; Hori, T; Shizukuishi, S

    1994-11-01

    To determine oxygen tension (pO2) in gingival tissue, an oxygen micro-electrode with a membrane-coated Pt needle was inserted into the gingiva of 12 dogs. Teeth were brushed using a modified Bass technique for 10 s under 200 g pressure. pO2 increased and reached a maximum 15 min after brushing, then gradually returned to the baseline. A significant increase in pO2 persisted for approx. 1 h. These findings suggest that short-term stimulation by tooth brushing increases oxygen tension in the gingiva.

  13. Brush/Fin Thermal Interfaces

    NASA Technical Reports Server (NTRS)

    Knowles, Timothy R.; Seaman, Christopher L.; Ellman, Brett M.

    2004-01-01

    Brush/fin thermal interfaces are being developed to increase heat-transfer efficiency and thereby enhance the thermal management of orbital replaceable units (ORUs) of electronic and other equipment aboard the International Space Station. Brush/fin thermal interfaces could also be used to increase heat-transfer efficiency in terrestrial electronic and power systems. In a typical application according to conventional practice, a replaceable heat-generating unit includes a mounting surface with black-anodized metal fins that mesh with the matching fins of a heat sink or radiator on which the unit is mounted. The fins do not contact each other, but transfer heat via radiation exchange. A brush/fin interface also includes intermeshing fins, the difference being that the gaps between the fins are filled with brushes made of carbon or other fibers. The fibers span the gap between intermeshed fins, allowing heat transfer by conduction through the fibers. The fibers are attached to the metal surfaces as velvet-like coats in the manner of the carbon fiber brush heat exchangers described in the preceding article. The fiber brushes provide both mechanical compliance and thermal contact, thereby ensuring low contact thermal resistance. A certain amount of force is required to intermesh the fins due to sliding friction of the brush s fiber tips against the fins. This force increases linearly with penetration distance, reaching 1 psi (6.9 kPa) for full 2-in. (5.1 cm) penetration for the conventional radiant fin interface. Removal forces can be greater due to fiber buckling upon reversing the sliding direction. This buckling force can be greatly reduced by biasing the fibers at an angle perpendicularly to the sliding direction. Means of containing potentially harmful carbon fiber debris, which is electrically conductive, have been developed. Small prototype brush/fin thermal interfaces have been tested and found to exhibit temperature drops about onesixth of that of conventional

  14. Brush seals for cryogenic applications

    NASA Astrophysics Data System (ADS)

    Proctor, Margaret P.

    1993-11-01

    Brush seals are compliant, contacting seals and have significantly lower leakage than labyrinth seals in gas turbine applications. Their characteristics of long life and low leakage make them candidates for use in rocket engine turbopumps. Two-inch diameter brush seals with a nominal 0.005 inch radial interference were tested in liquid nitrogen at shaft speeds up to 35,000 rpm and pressure drops up to 175 psid per seal. A labyrinth seal was also tested to provide a baseline. Performance, staging effects, and wear results are presented.

  15. Charge transferred in brush discharges

    NASA Astrophysics Data System (ADS)

    Talarek, M.; Kacprzyk, R.

    2015-10-01

    Electrostatic discharges from surfaces of plastic materials can be a source of ignition, when appear in explosive atmospheres. Incendivity of electrostatic discharges can be estimated using the transferred charge test. In the case of brush discharges not all the energy stored at the tested sample is released and the effective surface charge density (or surface potential) crater is observed after the discharge. Simplified model, enabling calculation of a charge transferred during electrostatic brush discharge, was presented. Comparison of the results obtained from the simplified model and from direct measurements of transferred charge are presented in the paper.

  16. Mesoscale modeling of polyelectrolyte brushes with salt.

    PubMed

    Ibergay, Cyrille; Malfreyt, Patrice; Tildesley, Dominic J

    2010-06-03

    We report dissipative particle dynamics (DPD) simulations of a polyelectrolyte brush under athermal solvent conditions. The electrostatic interactions are calculated using the particle-particle particle-mesh (PPPM) method with charges distributed over the particles. The polymer beads, counterions, co-ions, and solvent particles are modeled explicitly. The DPD simulations show a dependence of the brush height on the grafting density and the charge fraction that is typical of the nonlinear osmotic brush regime. We report the effect of the addition of salt on the structural properties of the brush. In the case of a polyelectrolyte brush with a high surface coverage, the simulations reproduce the transition between the nonlinear osmotic brush regime where the thickness of the brush is independent of the salt concentration and the salted regime where the brush height decreases weakly with the salt concentration.

  17. Target Wernecke After Brushing by Curiosity

    NASA Image and Video Library

    2013-03-18

    The gray area in center of this image is where the Dust Removal Tool on NASA Mars rover Curiosity brushed a rock target called Wernecke. The brushing revealed dark nodules and white veins crisscrossing the light gray rock.

  18. Macroion Interaction at Polyelectrolyte Brush Interfaces

    NASA Astrophysics Data System (ADS)

    Qu, Chen

    2015-03-01

    The effect of macroions, including synthetic polyelectrolytes, DNA and proteins, on the structure and surface properties of charged polymer thin films remains inadequately understood partially due to the complexity involving the hydrophobic effect and the conformational change of polymeric macroions. In this work, we explore a group of inorganic nanocluster based macroions, hydrophilic polyoxometalates (POMs) of robust nanocluster structure and carrying high surface charges (~ 2-42 negative charges) to investigate their interaction with surface tethered poly-2-vinylpyridine (P2VP) brush-like thin films immersed in aqueous solution. We observe the collapse of swollen P2VP chains by adding POM macroions of increased concentration by AFM, QCM and contact goniometer measurements, in sharp contrast to the increased chain stretching by adding monovalent salts. A careful comparison is made between distinct POMs based on their charge, size and chemical nature. These findings serve as a good reference for theoretical model modification and design of new mesoporous composite membranes.

  19. Fabrication of protein-resistant blend based on PVDF-HFP and amphiphilic brush copolymer made from PMMA and PEGMA

    NASA Astrophysics Data System (ADS)

    Hwangbo, Kyung-Hee; Kim, Yu-Jeong; Cho, Kuk Young

    2012-12-01

    Polymeric blends provide a facile route to obtaining materials with various synergistic properties arising from the individual components. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), a hydrophobic polymer, is finding new applications in polymer electrolytes, membranes, and heat-resistant structural materials owing to its high thermal stability, mechanical strength, and weatherability. In this report, blends of PVDF-HFP and polymer brush were prepared with enhanced water uptake and protein resistance, which are important requirements for membranes used in food and biological applications. Polymer brush is composed of poly(methyl methacrylate) main chains, which are miscible with PVDF-HFP, and hydrophilic poly(ethylene glycol) (PEG) brush chains. Incorporation of PEG chains through the polymer brush structure not only enhanced water uptake and protein adsorption resistance but also produced a well-distributed morphology of the blending components through the matrix as evidenced by observation of the morphology after selective extraction of polymer brush from the matrix.

  20. 75 FR 13489 - Natural Bristle Paint Brushes and Brush Heads from the People's Republic of China: Final Results...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-22

    ... International Trade Administration (A-570-501) Natural Bristle Paint Brushes and Brush Heads from the People's... order on natural bristle paint brushes and brush heads from the People's Republic of China (``PRC...; Natural Bristle Paint Brushes and Brush Heads From the People's Republic of China, 51 FR 5580 (February...

  1. 75 FR 44939 - Natural Bristle Paint Brushes and Brush Heads from the People's Republic of China: Final Results...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-30

    ... Bristle Paint Brushes and Brush Heads from the People's Republic of China: Final Results of Changed... duty order on natural bristle paint brushes and brush heads from the People's Republic of China (``PRC... antidumping duty order on natural paint brushes and brush head in March 1986. See Antidumping Duty...

  2. Turbine-Driven Pipe-Cleaning Brush

    NASA Technical Reports Server (NTRS)

    Werlink, Rudy J.; Rowell, David E.

    1994-01-01

    Simple pipe-cleaning device includes small turbine wheel axially connected, by standoff, to circular brush. Turbine wheel turns on hub bearing attached to end of upstream cable. Turbine-and-brush assembly inserted in pipe with cable trailing upstream and brush facing downstream. Water or cleaning solution pumped through pipe. Cable held at upstream end, so it holds turbine and brush in pipe at location to be cleaned. Flow in pipe turns turbine, which turns wheel, producing desired cleaning action. In addition to brushing action, device provides even mixing of cleaning solution in pipe.

  3. Brush Seals for Improved Steam Turbine Performance

    NASA Technical Reports Server (NTRS)

    Turnquist, Norman; Chupp, Ray; Baily, Fred; Burnett, Mark; Rivas, Flor; Bowsher, Aaron; Crudgington, Peter

    2006-01-01

    GE Energy has retrofitted brush seals into more than 19 operating steam turbines. Brush seals offer superior leakage control compared to labyrinth seals, owing to their compliant nature and ability to maintain very tight clearances to the rotating shaft. Seal designs have been established for steam turbines ranging in size from 12 MW to over 1200 MW, including fossil, nuclear, combined-cycle and industrial applications. Steam turbines present unique design challenges that must be addressed to ensure that the potential performance benefits of brush seals are realized. Brush seals can have important effects on the overall turbine system that must be taken into account to assure reliable operation. Subscale rig tests are instrumental to understanding seal behavior under simulated steam-turbine operating conditions, prior to installing brush seals in the field. This presentation discusses the technical challenges of designing brush seals for steam turbines; subscale testing; performance benefits of brush seals; overall system effects; and field applications.

  4. Planar dipolar polymer brush: field theoretical investigations

    NASA Astrophysics Data System (ADS)

    Mahalik, Jyoti; Kumar, Rajeev; Sumpter, Bobby

    2015-03-01

    Physical properties of polymer brushes bearing monomers with permanent dipole moments and immersed in a polar solvent are investigated using self-consistent field theory (SCFT). It is found that mismatch between the permanent dipole moments of the monomer and the solvent plays a significant role in determining the height of the polymer brush. Sign as well as magnitude of the mismatch determines the extent of collapse of the polymer brush. The mismatch in the dipole moments also affects the force-distance relations and interpenetration of polymers in opposing planar brushes. In particular, an attractive force between the opposing dipolar brushes is predicted for stronger mismatch parameter. Furthermore, effects of added monovalent salt on the structure of dipolar brushes will also be presented. This investigation highlights the significance of dipolar interactions in affecting the physical properties of polymer brushes. Csmd division, Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37831, USA.

  5. Explicit Solvent Simulations of Friction between Brush Layers of Charged and Neutral Bottle-Brush Macromolecules

    SciTech Connect

    Carrillo, Jan-Michael; Brown, W Michael; Dobrynin, Andrey

    2012-01-01

    We study friction between charged and neutral brush layers of bottle-brush macromolecules using molecular dynamics simulations. In our simulations the solvent molecules were treated explicitly. The deformation of the bottle-brush macromolecules under the shear were studied as a function of the substrate separation and shear stress. For charged bottle-brush layers we study effect of the added salt on the brush lubricating properties to elucidate factors responsible for energy dissipation in charged and neutral brush systems. Our simulations have shown that for both charged and neutral brush systems the main deformation mode of the bottle-brush macromolecule is associated with the backbone deformation. This deformation mode manifests itself in the backbone deformation ratio, , and shear viscosity, , to be universal functions of the Weissenberg number W. The value of the friction coefficient, , and viscosity, , are larger for the charged bottle-brush coatings in comparison with those for neutral brushes at the same separation distance, D, between substrates. The additional energy dissipation generated by brush sliding in charged bottle-brush systems is due to electrostatic coupling between bottle-brush and counterion motion. This coupling weakens as salt concentration, cs, increases resulting in values of the viscosity, , and friction coefficient, , approaching corresponding values obtained for neutral brush systems.

  6. Nanotribology of charged polymer brushes

    NASA Astrophysics Data System (ADS)

    Klein, Jacob

    Polymers at surfaces, whose modern understanding may be traced back to early work by Sam Edwards1, have become a paradigm for modification of surface properties, both as steric stabilizers and as remarkable boundary lubricants2. Charged polymer brushes are of particular interest, with both technological implications and especially biological relevance where most macromolecules are charged. In the context of biolubrication, relevant in areas from dry eye syndrome to osteoarthritis, charged polymer surface phases and their complexes with other macromolecules may play a central role. The hydration lubrication paradigm, where tenaciously-held yet fluid hydration shells surrounding ions or zwitterions serve as highly-efficient friction-reducing elements, has been invoked to understand the excellent lubrication provided both by ionized3 and by zwitterionic4 brushes. In this talk we describe recent advances in our understanding of the nanotribology of such charged brush systems. We consider interactions between charged end-grafted polymers, and how one may disentangle the steric from the electrostatic surface forces5. We examine the limits of lubrication by ionized brushes, both synthetic and of biological origins, and how highly-hydrated zwitterionic chains may provide extremely effective boundary lubrication6. Finally we describe how the lubrication of articular cartilage in the major joints, a tribosystem presenting some of the greatest challenges and opportunities, may be understood in terms of a supramolecular synergy between charged surface-attached polymers and zwitterionic groups7. Work supported by European Research Council (HydrationLube), Israel Science Foundation (ISF), Petroleum Research Fund of the American Chemical Society, ISF-NSF China Joint Program.

  7. Examining lysozyme structures on polyzwitterionic brush surfaces.

    PubMed

    Wang, Haoyu; Akcora, Pinar

    2017-09-18

    Conformational structures of lysozyme at the interfaces of hydrophilic polymer poly[2-(methacryloyloxy)ethyl dimethyl-(3-sulfopropyl)ammonium hydroxide] (PMEDSAH), are examined to understand the role of protein-polymer interactions on the stability of lysozyme. This work underpins the effect of hydration layer on the structures of physically adsorbed lysozyme on PMEDSAH brushes. Hydrophilic nature and strength of hydration layers around brushes are controlled by varying the brush thickness and temperature. We measured that lysozyme is structurally less stable on 15nm thick hydrophilic PMEDSAH brushes at 75°C than at room temperature. To the contrary, 5-8nm thick brushes stretch in hydrated state by heating, hence yield higher structural stability of lysozyme. These results suggest that short polyzwitterionic brushes can facilitate improved biomaterial interactions that are essential for biosensors performing at elevated temperatures. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Stimuli-sensitive intrinsically disordered protein brushes

    NASA Astrophysics Data System (ADS)

    Srinivasan, Nithya; Bhagawati, Maniraj; Ananthanarayanan, Badriprasad; Kumar, Sanjay

    2014-10-01

    Grafting polymers onto surfaces at high density to yield polymer brush coatings is a widely employed strategy to reduce biofouling and interfacial friction. These brushes almost universally feature synthetic polymers, which are often heterogeneous and do not readily allow incorporation of chemical functionalities at precise sites along the constituent chains. To complement these synthetic systems, we introduce a biomimetic, recombinant intrinsically disordered protein that can assemble into an environment-sensitive brush. This macromolecule adopts an extended conformation and can be grafted to solid supports to form oriented protein brushes that swell and collapse dramatically with changes in solution pH and ionic strength. We illustrate the value of sequence specificity by using proteases with mutually orthogonal recognition sites to modulate brush height in situ to predictable values. This study demonstrates that stimuli-responsive brushes can be fabricated from proteins and introduces them as a new class of smart biomaterial building blocks.

  9. Phase behavior of ternary polymer brushes

    DOE PAGES

    Simocko, Chester K.; Frischknecht, Amalie L.; Huber, Dale L.

    2016-01-07

    Ternary polymer brushes consisting of polystyrene, poly(methyl methacrylate), and poly(4-vinylpyridine) have been synthesized. These brushes laterally phase separate into several distinct phases and can be tailored by altering the relative polymer composition. Self-consistent field theory has been used to predict the phase diagram and model both the horizontal and vertical phase behavior of the polymer brushes. As a result, all phase behaviors observed experimentally correlate well with the theoretical model.

  10. Design and Testing of High Performance Brushes.

    DTIC Science & Technology

    1982-03-01

    with the development of compact homopolar motors and generators, in that no known electrical brushes were capable of meeting the design requirements...seems that unlubricated metal to metal contact brushes, lightly loaded and with a large number of a-spots, will be used not only in the homopolar ...serviceable and quite versatile, brush testing apparatus is alike, since The major goal in designing the apparatus they basically consist of a motor and axle

  11. Myosin 1b Regulates Amino Acid Transport by Associating Transporters with the Apical Plasma Membrane of Kidney Cells.

    PubMed

    Komaba, Shigeru; Coluccio, Lynne M

    2015-01-01

    Amino acid transporters (AATers) in the brush border of the apical plasma membrane (APM) of renal proximal tubule (PT) cells mediate amino acid transport (AAT). We found that the membrane-associated class I myosin myosin 1b (Myo1b) localized at the apical brush border membrane of PTs. In opossum kidney (OK) 3B/2 epithelial cells, which are derived from PTs, expressed rat Myo1b-GFP colocalized in patched microvilli with expressed mouse V5-tagged SIT1 (SIT1-V5), which mediates neutral amino acid transport in OK cells. Lentivirus-mediated delivery of opossum Myo1b-specific shRNA resulted in knockdown (kd) of Myo1b expression, less SIT1-V5 at the APM as determined by localization studies, and a decrease in neutral AAT as determined by radioactive uptake assays. Myo1b kd had no effect on Pi transport or noticeable change in microvilli structure as determined by rhodamine phalloidin staining. The studies are the first to define a physiological role for Myo1b, that of regulating renal AAT by modulating the association of AATers with the APM.

  12. Resisting protein adsorption on biodegradable polyester brushes.

    PubMed

    Hu, Xinfang; Gorman, Christopher B

    2014-08-01

    The protein adsorption and degradation behaviors of poly(lactic acid), poly(glycolic acid) (PGA) and poly(ε-caprolactone) (PCL) brushes and their co-polymer brushes with oligo(ethylene glycol) (OEG) were studied. Both brush structure and relative amount of OEG and polyester were found to be important to the protein resistance of the brushes. A protein-resisting surface can be fabricated either by using OEG as the top layer of a copolymer brush or by increasing the amount of OEG relative to polyester when using a hydroxyl terminated OEG (OEG-OH) and a methoxy terminated OEG (OEG-OMe) mixture as the substrate layer. The degradation of single polyester brushes and their co-polymer brushes using OEG-OH as a substrate layer or using OEG as a top layer was hindered. This phenomenon was rationalized by the inhibition of the proposed back-biting process as the hydroxy end groups of polyester were blocked by OEG molecules. Among these brushes tested, PGA co-polymer brushes using the methoxy/hydroxyl OEG mixture as the substrate layer proved to be both protein-resistant and degradable due to the relatively large amount of OEG moieties and the good biodegradability of PGA.

  13. Nanopatterned polymer brushes: conformation, fabrication and applications

    NASA Astrophysics Data System (ADS)

    Yu, Qian; Ista, Linnea K.; Gu, Renpeng; Zauscher, Stefan; López, Gabriel P.

    2015-12-01

    Surfaces with end-grafted, nanopatterned polymer brushes that exhibit well-defined feature dimensions and controlled chemical and physical properties provide versatile platforms not only for investigation of nanoscale phenomena at biointerfaces, but also for the development of advanced devices relevant to biotechnology and electronics applications. In this review, we first give a brief introduction of scaling behavior of nanopatterned polymer brushes and then summarize recent progress in fabrication and application of nanopatterned polymer brushes. Specifically, we highlight applications of nanopatterned stimuli-responsive polymer brushes in the areas of biomedicine and biotechnology.

  14. Tooth brushing inhibits oral bacteria in dogs.

    PubMed

    Watanabe, Kazuhiro; Hayashi, Kotaro; Kijima, Saku; Nonaka, Chie; Yamazoe, Kazuaki

    2015-10-01

    In this study, scaling, polishing and daily tooth brushing were performed in 20 beagle dogs, and the number of oral bacteria was determined using a bacterial counter. The dogs were randomized into the scaling (S), scaling + polishing (SP), scaling + tooth daily brushing (SB) and scaling + polishing + tooth daily brushing (SPB) groups. Samples were collected from the buccal surface of the maxillary fourth premolars of the dogs immediately after scaling and every week thereafter from weeks 1 to 8. Throughout the study, the number of bacteria was significantly lower in the SB and SPB groups compared with the S group. The findings suggest that daily tooth brushing inhibited oral bacterial growth in the dogs.

  15. Brush seals for turbine engine fuel conservation

    NASA Astrophysics Data System (ADS)

    Sousa, Mike

    1994-07-01

    The program objective is to demonstrate brush seals for replacing labyrinth seals in turboprop engines. The approach taken was to design and procure brush seals with assistance from Sealol, modify and instrument an existing T407 low pressure turbine test rig, replace inner balance piston and outer balance piston labyrinth seals with brush seals, conduct cyclic tests to evaluate seal leakage at operating pressures and temperatures, and evaluate effect of seal pack width and rotor eccentricity. Results are presented in viewgraph format and show that brush seals offer performance advantages over labyrinth seals.

  16. Development of a Brush Seals Program Leading to Ceramic Brush Seals

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Flower, Ralph; Howe, Harold

    1994-01-01

    Some events of a U.S. Army/NASA Lewis Research Center brush seals program are reviewed, and the development of ceramic brush seals is described. Some preliminary room-temperature flow data are given, and the results of testing metallic brushes in cryogenic nitrogen are discussed.

  17. Bundle Formation in Polyelectrolyte Brushes

    NASA Astrophysics Data System (ADS)

    Günther, J. U.; Ahrens, H.; Förster, S.; Helm, C. A.

    2008-12-01

    Bundle formation of the vertically oriented polyelectrolytes within polyelectrolyte brushes is studied with x-ray reflectivity and grazing-incidence diffraction as a function of grafting density and ion concentration. At 0.8 Molar monomer concentration and without added salt, a bundle consists of two chains and is 50 Å long. On the addition of up to 1M CsCl, the aggregation number increases up to 15 whereas the bundle length approaches a limiting value, 20 Å. We suggest that the bundle formation is determined by a balance between long-ranged electrostatic repulsion, whose range and amplitude is decreased on salt addition, and short-ranged attraction.

  18. Brush seal numerical simulation: Concepts and advances

    NASA Technical Reports Server (NTRS)

    Braun, M. J.; Kudriavtsev, V. V.

    1994-01-01

    The development of the brush seal is considered to be most promising among the advanced type seals that are presently in use in the high speed turbomachinery. The brush is usually mounted on the stationary portions of the engine and has direct contact with the rotating element, in the process of limiting the 'unwanted' leakage flows between stages, or various engine cavities. This type of sealing technology is providing high (in comparison with conventional seals) pressure drops due mainly to the high packing density (around 100 bristles/sq mm), and brush compliance with the rotor motions. In the design of modern aerospace turbomachinery leakage flows between the stages must be minimal, thus contributing to the higher efficiency of the engine. Use of the brush seal instead of the labyrinth seal reduces the leakage flow by one order of magnitude. Brush seals also have been found to enhance dynamic performance, cost less, and are lighter than labyrinth seals. Even though industrial brush seals have been successfully developed through extensive experimentation, there is no comprehensive numerical methodology for the design or prediction of their performance. The existing analytical/numerical approaches are based on bulk flow models and do not allow the investigation of the effects of brush morphology (bristle arrangement), or brushes arrangement (number of brushes, spacing between them), on the pressure drops and flow leakage. An increase in the brush seal efficiency is clearly a complex problem that is closely related to the brush geometry and arrangement, and can be solved most likely only by means of a numerically distributed model.

  19. Brush seal numerical simulation: Concepts and advances

    NASA Astrophysics Data System (ADS)

    Braun, M. J.; Kudriavtsev, V. V.

    1994-07-01

    The development of the brush seal is considered to be most promising among the advanced type seals that are presently in use in the high speed turbomachinery. The brush is usually mounted on the stationary portions of the engine and has direct contact with the rotating element, in the process of limiting the 'unwanted' leakage flows between stages, or various engine cavities. This type of sealing technology is providing high (in comparison with conventional seals) pressure drops due mainly to the high packing density (around 100 bristles/sq mm), and brush compliance with the rotor motions. In the design of modern aerospace turbomachinery leakage flows between the stages must be minimal, thus contributing to the higher efficiency of the engine. Use of the brush seal instead of the labyrinth seal reduces the leakage flow by one order of magnitude. Brush seals also have been found to enhance dynamic performance, cost less, and are lighter than labyrinth seals. Even though industrial brush seals have been successfully developed through extensive experimentation, there is no comprehensive numerical methodology for the design or prediction of their performance. The existing analytical/numerical approaches are based on bulk flow models and do not allow the investigation of the effects of brush morphology (bristle arrangement), or brushes arrangement (number of brushes, spacing between them), on the pressure drops and flow leakage. An increase in the brush seal efficiency is clearly a complex problem that is closely related to the brush geometry and arrangement, and can be solved most likely only by means of a numerically distributed model.

  20. Polyethyleneimine brushes effectively inhibit encrustation on polyurethane ureteral stents both in dynamic bioreactor and in vivo.

    PubMed

    Gultekinoglu, Merve; Kurum, Barış; Karahan, Siyami; Kart, Didem; Sagiroglu, Meral; Ertaş, Nusret; Haluk Ozen, A; Ulubayram, Kezban

    2017-02-01

    Polyurethane (PU) ureteral stents have been widely used as biomedical devices to aid the flow of the urine. Due to the biofilm formation and encrustation complications it has been hindered their long term clinical usage. To overcome these complications, in this study, cationic polyethyleneimine (PEI) brushes grafted on PU stents and their performances were tested both in a dynamic biofilm reactor system (in vitro) and in a rat model (in vivo). Thus, we hypothesized that PEI brushes inhibit bacterial adhesion owing to the dynamic motion of brushes in liquid environment. In addition, cationic structure of PEI disrupts the membrane and so kills the bacteria on time of contact. Cationic PEI brushes decreased the biofilm formation up to 2 orders of magnitude and approximately 50% of encrustation amount in respect to unmodified PU, in vitro. In addition, according to Atomic Absorption Spectroscopy (AAS) results, approximately 90% of encrustation was inhibited on in vivo animal models. Decrease in encrustation was clearly observed on the stents obtained from rat model, by Scanning Electron Microscopy (SEM). Also, histological evaluations showed that; PEI brush grafting decreased host tissue inflammation in close relation to decrease in biofilm formation and encrustation. As a results; dual effect of anti-adhesive and contact-killing antibacterial strategy showed high efficiency on PEI brushes grafted PU stents both in vitro and in vivo. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Chemopreventive effects of nonsteroidal anti-inflammatory drugs in the membrane lipid composition and fluidity parameters of the 1,2-dimethylhydrazine-induced colon carcinogenesis in rats.

    PubMed

    Kanwar, Shailender Singh; Vaiphei, Kim; Nehru, Bimla; Sanyal, Sankar N

    2007-01-01

    Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, celecoxib, and etoricoxib are reported to act as chemopreventive agents in experimental colon cancer induced by 1,2-dimethylhydrazine (DMH) as they are known cyclooxygenase (COX) enzyme inhibitors. To determine whether NSAIDs can also effectively modulate the membrane lipid compositions and the fluidity parameters of colonic brush border membrane, rats were injected subcutaneously (s.c.) with DMH 30 mg/kg body weight per week for 6 weeks. The animals were simultaneously treated with NSAIDs orally at the dose of aspirin, 60 mg/kg body weight; celecoxib, 6 mg/kg body weight; and etoricoxib, 0.6 mg/kg body weight. The animals were sacrificed after 6 weeks of treatments. Brush border membrane was isolated from proximal and distal portions of the colon. Membrane lipids were extracted and analyzed while the fluidity parameters were assessed by steady-state fluorescence polarization technique using the membrane extrinsic fluorophore 1,6-diphenyl-1,3,5-hexatriene (DPH). The translational diffusion was measured by using the excimer formation of pyrene incorporated in the membrane. Colonic mucosal changes in DMH alone and DMH+NSAID treated animals were assessed histologically. The results demonstrate that (a) there is a distinct occurrence of premalignant alterations in DMH-induced colon in the form of multiple plaque lesions (MPLs), which were greatly reduced by the NSAIDs used, (b) the membrane lipid changes in DMH-induced colon were completely restored back, (c) the alterations in membrane fluorescence polarization and the fluidity parameters are partially recovered, particularly with etoricoxib, and (d) the pyrene excimer formation process was completely restored. It may be concluded that the NSAIDs, particularly the coxib group of the drugs (COX-2 selective), are effective in chemoprevention in the DMH-induced colon carcinogenesis and membrane alterations.

  2. Dual wound dc brush motor gearhead

    NASA Technical Reports Server (NTRS)

    Henson, Barrie W.

    1986-01-01

    The design requirements, the design, development tests and problems, the qualification and life test and the findings of the strip examination of a dual wound DC brushed motor gearhead are described. It is the only space qualified dual wound dc brushed motor gearhead in Europe.

  3. Brush-Wheel Samplers for Planetary Exploration

    NASA Technical Reports Server (NTRS)

    Rivellini, Tommaso

    2003-01-01

    A report proposes brush-wheel mechanisms for acquiring samples of soils from remote planets. In simplest terms, such a mechanism would contain brush wheels that would be counter-rotated at relatively high speed. The mechanism would be lowered to the ground from a spacecraft or other exploratory vehicle. Upon contact with the ground, the counter-rotating brush wheels would kick soil up into a collection chamber. Thus, in form and function, the mechanism would partly resemble traditional street and carpet sweepers. The main advantage of using of brush wheels (in contradistinction to cutting wheels or other, more complex mechanisms) is that upon encountering soil harder than expected, the brushes could simply deflect and the motor(s) could continue to turn. That is, sufficiently flexible brushes would afford resistance to jamming and to overloading of the motors used to rotate the brushes, and so the motors could be made correspondingly lighter and less power hungry. Of course, one could select the brush stiffnesses and motor torques and speeds for greatest effectiveness in sampling soil of a specific anticipated degree of hardness.

  4. A Brush Seals Program Modeling and Developments

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Flower, Ralph; Howe, Harold

    1996-01-01

    Some events of a U.S. Army/NASA Lewis Research Center brush seals program are reviewed, and the development of ceramic brush seals is described. Some preliminary room-temperature flow data are modeled and compare favorably to the results of Ergun.

  5. Brush cells of rodent gallbladder and stomach epithelia express neurofilaments.

    PubMed

    Luciano, Liliana; Groos, Stephanie; Reale, Enrico

    2003-02-01

    It has been suggested that brush cells (BCs), a distinct type of cell occurring in various epithelia of the respiratory and gastrointestinal tracts, may function as receptor cells. The major characteristics of BCs are a prominent brush border and an unusually highly ordered arrangement of cytoskeletal elements (F-actin, microtubules, and intermediate filaments). In this study we aimed to characterize the nature of the intermediate filaments in BCs by light and electron microscopic immunostaining. Gallbladder and stomach specimens from mice and rats, respectively, were fixed in various solutions, embedded either in paraffin or epoxy resin, and processed for immunodetection. Commercially available, well-characterized antibodies against neurofilaments, peripherin, and cytokeratin peptide 18 were used. The polyclonal antiserum cocktail to neurofilaments was applied as a supplement in a double-labeling procedure with anti-actin and anti-cytokeratin 18 antibodies. The results demonstrate that the BCs of both organs express two types of intermediate filaments, i.e., neurofilaments and cytokeratin 18 filaments, and that these have a compartmentalized distribution in the cytoplasm. BCs do not express peripherin. The immunodetection of intermediate filaments distinctive for mature neurons in BCs supports their putative receptor function. The co-expression of neurofilaments and cytokeratins is shown for the first time in healthy tissues.

  6. Glucose monitoring using a polymer brush modified polypropylene hollow fiber-based hydraulic flow sensor.

    PubMed

    Fortin, Nicolas; Klok, Harm-Anton

    2015-03-04

    Tight regulation of blood glucose levels of diabetic patients requires durable and robust continuous glucose sensing schemes. This manuscript reports the fabrication of ultrathin, phenylboronic acid (PBA) functionalized polymer brushes that swell upon glucose binding and which were integrated as the sensing interface in a new polypropylene hollow fiber (PPHF)-based hydraulic flow glucose sensor prototype. The polymer brushes were prepared via surface-initiated atom transfer radical polymerization of sodium methacrylate followed by postpolymerization modification with 3-aminophenyl boronic acid. In a first series of experiments, the glucose-response of PBA-functionalized poly(methacrylic acid) (PMAA) brushes grafted from planar silicon surfaces was investigated by quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM) experiments. The QCM-D experiments revealed a more or less linear change of the frequency shift for glucose concentrations up to ∼10 mM and demonstrated that glucose binding was completely reversible for up to seven switching cycles. The AFM experiments indicated that glucose binding was accompanied by an increase in the film thickness of the PBA functionalized PMAA brushes. The PBA functionalized PMAA brushes were subsequently grafted from the surface of PPHF membranes. The hydraulic permeability of these porous fibers depends on the thickness and swelling of the PMAA brush coating. PBA functionalized brush-coated PPHFs showed a decrease in flux upon exposure to glucose, which is consistent with swelling of the brush coating. Because they avoid the use of enzymes and do not rely on an electrochemical transduction scheme, these PPHF-based hydraulic flow sensors could represent an interesting alternative class of continuous glucose sensors.

  7. Liquid Crystalline Phases of Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Amini, Kiana; Abukhdeir, Nasser; Matsen, Mark

    The phase behavior of liquid-crystal polymeric brushes in solvent are investigated using self-consistent field theory. The polymers are modeled as freely-jointed chain consisting of N rigid segments. The isotropic interactions between the polymer and the solvent are treated using the standard Flory-Huggins theory, while the anisotropic liquid-crystalline (LC) interactions between rigid segments are taken into account using the Mayer-Saupe theory. For weak LC interactions, the brush exhibits the conventional parabolic-like profile, while for strong LC interactions, the polymers crystallize into a dense brush with a step-like profile. At intermediate interaction strengths, we find the microphase-segregated phase observed previously for lattice-model calculations. In this phase, the brush exhibits a crystalline layer next to the grafting surface with an external layer similar to the conventional brush. This work was supported by NSERC of Canada.

  8. Macroion induced dehydration of weak polyelectrolyte brushes

    NASA Astrophysics Data System (ADS)

    Zheng, Zhongli; Zhu, Y. Elaine

    2014-03-01

    The interaction of macroions, including polyelectrolytes, DNAs, and proteins, with polymer and cellular surfaces is critically related to many biomolecular activities, such as protein adsorption and DNA hybridization at probe surfaces. In an experimental approach to examine the macroion electrostatic interaction with a polymer surface while minimizing the long-debated hydrophobic interaction, we study the interaction of molybdenum-based inorganic polyoxometalate (POM) nanoclusters carrying 42 negative charges as model hydrophilic macroions with surface-tethered poly-2-vinylpyridine (P2VP) brushes immersed in aqueous solutions. By AFM, QCM, and contact goniometer, we have observed the collapse of P2VP chains by adding POM macroions at a constant pH. Surprisingly, added POM macroions can cause the shift of swollen-to-collapse transition pH to a lower value, in contrast to the shift to high pH value by adding simple monovalent salts. At sufficiently high POM concentration, a stable POM-P2VP composite layer, showing little dependence on solution pH and additional salts, can be formed, suggesting a simple route to construct meso-porous polymer membranes.

  9. Proton conduction of polyAMPS brushes on titanate nanotubes

    PubMed Central

    Feng, Jun; Huang, Yaqin; Tu, Zhengkai; Zhang, Haining; Pan, Mu; Tang, Haolin

    2014-01-01

    Proton conducting materials having reasonable proton conductivity at low humidification conditions are critical for decrease in system complexity and improvement of power density for polymer electrolyte membrane fuel cells. This study shows that polyelectrolyte brushes on titanate nanotubes formed through surface-initiated free radical polymerization exhibit less humidity-dependent proton conduction because of the high grafting density of polymer electrolyte chains and well-distribution of ionic groups. The results described in this study provide an idea for design of new proton conductors with effective ion transport served at relatively low humidification levels. PMID:25169431

  10. Construction of 3D micropatterned surfaces with wormlike and superhydrophilic PEG brushes to detect dysfunctional cells.

    PubMed

    Hou, Jianwen; Shi, Qiang; Ye, Wei; Fan, Qunfu; Shi, Hengchong; Wong, Shing-Chung; Xu, Xiaodong; Yin, Jinghua

    2014-12-10

    Detection of dysfunctional and apoptotic cells plays an important role in clinical diagnosis and therapy. To develop a portable and user-friendly platform for dysfunctional and aging cell detection, we present a facile method to construct 3D patterns on the surface of styrene-b-(ethylene-co-butylene)-b-styrene elastomer (SEBS) with poly(ethylene glycol) brushes. Normal red blood cells (RBCs) and lysed RBCs (dysfunctional cells) are used as model cells. The strategy is based on the fact that poly(ethylene glycol) brushes tend to interact with phosphatidylserine, which is in the inner leaflet of normal cell membranes but becomes exposed in abnormal or apoptotic cell membranes. We demonstrate that varied patterned surfaces can be obtained by selectively patterning atom transfer radical polymerization (ATRP) initiators on the SEBS surface via an aqueous-based method and growing PEG brushes through surface-initiated atom transfer radical polymerization. The relatively high initiator density and polymerization temperature facilitate formation of PEG brushes in high density, which gives brushes worm-like morphology and superhydrophilic property; the tendency of dysfunctional cells adhered on the patterned surfaces is completely different from well-defined arrays of normal cells on the patterned surfaces, providing a facile method to detect dysfunctional cells effectively. The PEG-patterned surfaces are also applicable to detect apoptotic HeLa cells. The simplicity and easy handling of the described technique shows the potential application in microdiagnostic devices.

  11. Resistance to the Bacillus thuringiensis bioinsecticide in a field population of Plutella xylostella is due to a change in a midgut membrane receptor.

    PubMed

    Ferré, J; Real, M D; Van Rie, J; Jansens, S; Peferoen, M

    1991-06-15

    The biochemical mechanism for resistance to Bacillus thuringiensis crystal proteins was studied in a field population of diamondback moths (Plutella xylostella) with a reduced susceptibility to the bioinsecticidal spray. The toxicity and binding characteristics of three crystal proteins [CryIA(b), CryIB, and CryIC] were compared between the field population and a laboratory strain. The field population proved resistant (greater than 200-fold compared with the laboratory strain) to CryIA(b), one of the crystal proteins in the insecticidal formulation. Binding studies showed that the two strains differ in a membrane receptor that recognizes CryIA(b). This crystal protein did not bind to the brush-border membrane of the midgut epithelial cells of the field population, either because of strongly reduced binding affinity or because of the complete absence of the receptor molecule. Both strains proved fully susceptible to the CryIB and CryIC crystal proteins, which were not present in the B. thuringiensis formulation used in the field. Characteristics of CryIB and CryIC binding to brush-border membranes of midgut epithelial cells were virtually identical in the laboratory and the field population.

  12. Resistance to the Bacillus thuringiensis bioinsecticide in a field population of Plutella xylostella is due to a change in a midgut membrane receptor.

    PubMed Central

    Ferré, J; Real, M D; Van Rie, J; Jansens, S; Peferoen, M

    1991-01-01

    The biochemical mechanism for resistance to Bacillus thuringiensis crystal proteins was studied in a field population of diamondback moths (Plutella xylostella) with a reduced susceptibility to the bioinsecticidal spray. The toxicity and binding characteristics of three crystal proteins [CryIA(b), CryIB, and CryIC] were compared between the field population and a laboratory strain. The field population proved resistant (greater than 200-fold compared with the laboratory strain) to CryIA(b), one of the crystal proteins in the insecticidal formulation. Binding studies showed that the two strains differ in a membrane receptor that recognizes CryIA(b). This crystal protein did not bind to the brush-border membrane of the midgut epithelial cells of the field population, either because of strongly reduced binding affinity or because of the complete absence of the receptor molecule. Both strains proved fully susceptible to the CryIB and CryIC crystal proteins, which were not present in the B. thuringiensis formulation used in the field. Characteristics of CryIB and CryIC binding to brush-border membranes of midgut epithelial cells were virtually identical in the laboratory and the field population. PMID:2052591

  13. Binary Polymer Brushes of Strongly Immiscible Polymers.

    PubMed

    Chu, Elza; Babar, Tashnia; Bruist, Michael F; Sidorenko, Alexander

    2015-06-17

    The phenomenon of microphase separation is an example of self-assembly in soft matter and has been observed in block copolymers (BCPs) and similar materials (i.e., supramolecular assemblies (SMAs) and homo/block copolymer blends (HBCs)). In this study, we use microphase separation to construct responsive polymer brushes that collapse to generate periodic surfaces. This is achieved by a chemical reaction between the minor block (10%, poly(4-vinylpyridine)) of the block copolymer and a substrate. The major block of polystyrene (PS) forms mosaic-like arrays of grafted patches that are 10-20 nm in size. Depending on the nature of the assembly (SMA, HBC, or neat BCP) and annealing method (exposure to vapors of different solvents or heating above the glass transition temperature), a range of "mosaic" brushes with different parameters can be obtained. Successive grafting of a secondary polymer (polyacrylamide, PAAm) results in the fabrication of binary polymer brushes (BPBs). Upon being exposed to specific selective solvents, BPBs may adopt different conformations. The surface tension and adhesion of the binary brush are governed by the polymer occupying the top stratum. The "mosaic" brush approach allows for a combination of strongly immiscible polymers in one brush. This facilitates substantial contrast in the surface properties upon switching, previously only possible for substrates composed of predetermined nanostructures. We also demonstrate a possible application of such PS/PAAm brushes in a tunable bioadhesion-bioadhesive (PS on top) or nonbioadhesive (PAAm on top) surface as revealed by Escherichia coli bacterial seeding.

  14. BSA adsorption on bimodal PEO brushes.

    PubMed

    Bosker, W T E; Iakovlev, P A; Norde, W; Cohen Stuart, M A

    2005-06-15

    BSA adsorption onto bimodal PEO brushes at a solid surface was measured using optical reflectometry. Bimodal brushes consist of long (N=770) and short (N=48) PEO chains and were prepared on PS surfaces, applying mixtures of PS(29)-PEO(48) and PS(37)-PEO(770) block copolymers and using the Langmuir-Blodgett technique. Pi-A isotherms of (mixtures of) the block copolymers were measured to establish the brush regime. The isotherms of PS(29)-PEO(48) show hysteresis between compression and expansion cycles, indicating aggregation of the PS(29)-PEO(48) upon compression. Mixtures of PS(29)-PEO(48) and PS(37)-PEO(770) demonstrate a similar hysteresis effect, which eventually vanishes when the ratio of PS(37)-PEO(770) to PS(29)-PEO(48) is increased. The adsorption of BSA was determined at brushes for which the grafting density of the long PEO chains was varied, while the total grafting density was kept constant. BSA adsorption onto monomodal PEO(48) and PEO(770) brushes was determined for comparison. The BSA adsorption behavior of the bimodal brushes is similar to the adsorption of BSA at PEO(770) monomodal brushes. The maximum of BSA adsorption at low grafting density of PEO(770) can be explained by ternary adsorption, implying an attraction between BSA and PEO. The contribution of primary adsorption to the total adsorbed amount is negligible.

  15. Zwitterionic Poly(amino acid methacrylate) Brushes

    PubMed Central

    2014-01-01

    A new cysteine-based methacrylic monomer (CysMA) was conveniently synthesized via selective thia-Michael addition of a commercially available methacrylate-acrylate precursor in aqueous solution without recourse to protecting group chemistry. Poly(cysteine methacrylate) (PCysMA) brushes were grown from the surface of silicon wafers by atom-transfer radical polymerization. Brush thicknesses of ca. 27 nm were achieved within 270 min at 20 °C. Each CysMA residue comprises a primary amine and a carboxylic acid. Surface zeta potential and atomic force microscopy (AFM) studies of the pH-responsive PCysMA brushes confirm that they are highly extended either below pH 2 or above pH 9.5, since they possess either cationic or anionic character, respectively. At intermediate pH, PCysMA brushes are zwitterionic. At physiological pH, they exhibit excellent resistance to biofouling and negligible cytotoxicity. PCysMA brushes undergo photodegradation: AFM topographical imaging indicates significant mass loss from the brush layer, while XPS studies confirm that exposure to UV radiation produces surface aldehyde sites that can be subsequently derivatized with amines. UV exposure using a photomask yielded sharp, well-defined micropatterned PCysMA brushes functionalized with aldehyde groups that enable conjugation to green fluorescent protein (GFP). Nanopatterned PCysMA brushes were obtained using interference lithography, and confocal microscopy again confirmed the selective conjugation of GFP. Finally, PCysMA undergoes complex base-catalyzed degradation in alkaline solution, leading to the elimination of several small molecules. However, good long-term chemical stability was observed when PCysMA brushes were immersed in aqueous solution at physiological pH. PMID:24884533

  16. Density Profile of Spherical Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Förster, S.; Wenz, E.; Lindner, P.

    1996-07-01

    Small angle neutron scattering measurements were made on a series of block copolymer micelles that represent model systems for spherical polymer brushes. We find hyperbolic density profiles of the form r-α with values of α between 1.05 and 1.35. This as well as the scaling of the brush height with the aggregation number f are in agreement with the model proposed by Daoud and Cotton [J. Phys. (Paris) 43, 531 (1982)] for unswollen and swollen spherical polymer brushes.

  17. Functional significance of membrane associated proteolysis in the toxicity of Bacillus thuringiensis Cry3Aa toxin against Colorado potato beetle.

    PubMed

    García-Robles, Inmaculada; Ochoa-Campuzano, Camila; Sánchez, Jorge; Contreras, Estefanía; Real, M Dolores; Rausell, Carolina

    2012-11-01

    Bacillus thuringiensis Cry toxins are widely used as biocontrol agents in bioinsecticides and transgenic plants. In the three domain-Cry toxins, domain II has been identified as an important determinant of their highly specific activity against insects. In this work, we assessed the role in membrane associated proteolysis and toxicity in Colorado potato beetle (CPB) of a previously reported ADAM recognition motif present in Cry3Aa toxin domain II. We used site-directed mutagenesis to modify the Bacillus thuringiensis cry3A gene in amino acid residues 344, 346, 347, 351 and 353 of the ADAM recognition motif in Cry3Aa toxin. Cry3Aa toxin mutants displayed decreased toxicity when compared to the wild type toxin and impaired ability to compete CPB brush border membrane associated cleavage of an ADAM fluorogenic substrate. Although the proteolytic profile of Cry3Aa toxin mutants generated by brush border membrane associated proteases was similar to that of Cry3Aa toxin, the metalloprotease inhibitor 1,10-phenanthroline was less efficient on the proteolysis of mutants than on that of the wild type toxin. The relevance of the Cry3Aa-ADAM interaction through the predicted recognition sequence was further confirmed by analyzing the effect of membrane integrity disturbance on Cry3Aa toxin membrane associated proteolysis and CPB larvae toxicity. Data support that Cry3Aa proteolysis, as a result of the interaction with ADAM through the Cry3Aa recognition motif, is essential for Cry3Aa toxic action in CPB. Detailed knowledge of Cry3Aa interaction with CPB midgut membrane should facilitate the development of more effective Bt based products against this devastating pest and other Coleoptera. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...

  19. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...

  20. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...

  1. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...

  2. 21 CFR 868.5795 - Tracheal tube cleaning brush.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Tracheal tube cleaning brush. 868.5795 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5795 Tracheal tube cleaning brush. (a) Identification. A tracheal tube cleaning brush is a device consisting of a brush with plastic bristles...

  3. Effectiveness of oscillatory gutter brushes in removing street sweeping waste.

    PubMed

    Vanegas-Useche, Libardo V; Abdel-Wahab, Magd M; Parker, Graham A

    2015-09-01

    In this paper, the novel concept of oscillatory gutter brushes of road sweepers is studied experimentally. Their effectiveness in removing different debris types is studied by means of a brushing test rig. The debris types dealt with are medium-size gravel, small and fine particles, wet thin debris, and compacted debris. The performance of two types of brushes, cutting and F128, under diverse operating conditions is investigated. The purpose of the tests is to ascertain whether brush oscillations superimposed onto brush rotation improve sweeping effectiveness. According to the results, brush oscillations seem to be useful for increasing brushing effectiveness in the case of bonded particles and wet thin debris, especially for bonded debris, but they seem to be of no value for other loosed debris. Also, appropriate values of brush penetration, sweeper speed, brush angle of attack, rotational speed, and frequency of brush speed oscillations, for the debris types studied are provided.

  4. Vaccination of sheep against haemonchosis with H11, a gut membrane-derived protective antigen from the adult parasite: prevention of the periparturient rise and colostral transfer of protective immunity.

    PubMed

    Andrews, S J; Hole, N J; Munn, E A; Rolph, T P

    1995-07-01

    Pregnant ewes were immunised with a fraction highly enriched in the membrane glycoprotein antigen H11, isolated from the intestinal brush border of adult Haemonchus contortus. Immunity induced by immunisation was able to abolish almost completely (98-99%) the worm egg output from pregnant ewes challenged with ca. 10,000 infective larvae of H. contortus during the last trimester. Furthermore, lambs born and reared on vaccinated ewes had substantial antibody levels to H11 derived from maternal transfer. This antibody conferred moderate protection against a bolus challenge of ca. 3000 infective larvae of H. contortus in 5-week-old lambs.

  5. Plaque removing effect of a convex-shaped brush compared with a conventional flat brush.

    PubMed

    Thevissen, E; Quirynen, M; van Steenberghe, D

    1987-12-01

    The plaque-removing effect of a convex-shaped multitufted brush was compared with that of a conventional flat multitufted brush. Two group (five and seven dental students, respectively), well instructed in the modified Bass technique, participated in a blind, splitmouth, crossover study during two consecutive experimental periods of 96 hours of undisturbed plaque growth. After each of these periods, a supervised brushing session was performed, followed by toothpick utilization. Plaque removal was evaluated using the modified Navy Plaque Index (MNPI) and planimetry. A 4% erythrosin solution was used as a disclosing agent. Planimetrically, the flat Oral B brush appeared significantly more effective than the convex shaped Ph brush (P less than 0.001). This superiority was even enhanced after the use of toothpicks (P less than 0.0005). The differences between the brushes, however, were too small to be detected by the less discriminating MNPI. Although it has been claimed that the convex brush could assure approximal plaque control, the results indicate that for the convex-shaped, as well as for the flat brush, an approximal aid is essential for good plaque control. The hypothesis that the design of the convex-shaped brush could facilitate the modified Bass technique for the average patient could not be proven in this study.

  6. 75 FR 34097 - Natural Bristle Paint Brushes and Brush Heads From the People's Republic of China: Notice of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-16

    ... International Trade Administration Natural Bristle Paint Brushes and Brush Heads From the People's Republic of... circumstances review to revoke the antidumping duty order on natural bristle paint brushes and brush heads from the People's Republic of China (``PRC''). See generally, Antidumping Duty Order: Natural Bristle...

  7. Flow visualization in a simulated brush seal

    NASA Technical Reports Server (NTRS)

    Braun, M. J.; Canacci, V.; Hendricks, R. C.

    1990-01-01

    A method to visualize and characterize the complex flow fields in simulated brush seals is presented. The brush seal configuration was tested in a water and then in an oil tunnel. The visualization procedure revealed typical regions that are rivering, jetting, vortical or lateral flows and exist upstream, downstream or within the seal. Such flows are engendered by variations in fiber void that are spatial and temporal and affect changes in seal leakage and stability. While the effects of interface motion for linear or cylindrical configurations have not been considered herein, it is believed that the observed flow fields characterize flow phenomenology in both circular and linear brush seals. The axial pressure profiles upstream, across and downstream of the brush in the oil tunnel have been measured under a variety of inlet pressure conditions and the ensuing pressure maps are presented and discussed.

  8. Tooth brushing inhibits oral bacteria in dogs

    PubMed Central

    WATANABE, Kazuhiro; HAYASHI, Kotaro; KIJIMA, Saku; NONAKA, Chie; YAMAZOE, Kazuaki

    2015-01-01

    In this study, scaling, polishing and daily tooth brushing were performed in 20 beagle dogs, and the number of oral bacteria was determined using a bacterial counter. The dogs were randomized into the scaling (S), scaling + polishing (SP), scaling + tooth daily brushing (SB) and scaling + polishing + tooth daily brushing (SPB) groups. Samples were collected from the buccal surface of the maxillary fourth premolars of the dogs immediately after scaling and every week thereafter from weeks 1 to 8. Throughout the study, the number of bacteria was significantly lower in the SB and SPB groups compared with the S group. The findings suggest that daily tooth brushing inhibited oral bacterial growth in the dogs. PMID:25994486

  9. Preparation of gradient polyacrylate brushes in microchannels.

    PubMed

    Lee, Seongyeol; Youm, Sang Gil; Song, Yeari; Yi, Whikum; Sohn, Daewon

    2012-05-01

    Gradient poly(2-hydroxyethyl methacrylate) brushes were synthesized by surface-initiated atom transfer radical polymerization (ATRP) confined within a microfluidic system on a silicon wafer. For ATRP, surface initiator, 11-((2-bromo, 2-methyl) propionyloxy) undecyltrichlorosilane (BUC), was synthesized, and allowed to self-assemble in a monolayer on the Si wafer, as analyzed by XPS to confirm the presence of an ester group of BUC. A solution containing 2-hydroxyethylmethacrylate, Cu catalyst, and bipyridin was allowed to flow in a microchannel and polymerize, resulting in the brushes with a gradient of thickness on the Si wafer. Using ellipsometry and ATR-IR, we verified the gradients of well established brushes on the Si wafer. AFM and contact angle data showed that wettability of the brushes did not exhibit a linear relationship with hydrophilicity.

  10. Three-Wheel Brush-Wheel Sampler

    NASA Technical Reports Server (NTRS)

    Duckworth, Geoffrey A.; Liu, Jun; Brown, Mark G.

    2010-01-01

    A new sampler is similar to a common snow blower, but is robust and effective in sample collection. The brush wheels are arranged in a triangle shape, each driven by a brushless DC motor and planetary gearhead embedded in the wheel shaft. Its speed can be varied from 800 - 2,000 rpm, depending on the surface regolith resistance. The sample-collecting flow path, and internal features, are designed based on flow dynamics, and the sample-collecting rates have consistently exceeded the requirement under various conditions that span the range of expected surface properties. The brush-wheel sampler (BWS) is designed so that the flow channel is the main body of the apparatus, and links the brush-wheel assembly to the sample canister. The combination of the three brush wheels, the sample flow path, and the canister location make sample collection, storage, and transfer an easier task.

  11. Antialgal activity of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes against the marine alga Ulva.

    PubMed

    Yandi, Wetra; Mieszkin, Sophie; Callow, Maureen E; Callow, James A; Finlay, John A; Liedberg, Bo; Ederth, Thomas

    2017-02-01

    Marine biofouling has detrimental effects on the environment and economy, and current antifouling coatings research is aimed at environmentally benign, non-toxic materials. The possibility of using contact-active coatings is explored, by considering the antialgal activity of cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. The antialgal activity was investigated via zoospore settlement and sporeling growth assays of the marine algae Ulva linza and U. lactuca. The assay results for PDMAEMA brushes were compared to those for anionic and neutral surfaces. It was found that only PDMAEMA could disrupt zoospores that come into contact with it, and that it also inhibits the subsequent growth of normally settled spores. Based on the spore membrane properties, and characterization of the PDMAEMA brushes over a wide pH range, it is hypothesized that the algicidal mechanisms are similar to the bactericidal mechanisms of cationic polymers, and that further development could lead to successful contact-active antialgal coatings.

  12. Design and Testing of High Performance Brushes.

    DTIC Science & Technology

    1983-05-01

    shows an example. What ordinarily serves as a ’brush’. applitations such as homopolar motors / generators and in transmitting current across an interface...speed current collection bricating layer of silver and graphite debris. systems for homopolar electrical machines. Use The other, associated with the...performantc hornopolar by examining the origin of the power losses when electrical motors and generators, based either on superconducting or brushes

  13. Homopolar Motor and Brush Development Studies

    DTIC Science & Technology

    2005-08-01

    FUNDING NUMBERS Final Report- Homopolar Motor and Brush Development Studies Office of Naval Research Contract #N0001 4-04-1-0064 Contract # N00014-04-1-0064...superconducting homopolar motors . This report surveys prior data, reports, papers, and other studies that relate to superconducting homopolar motors . It also...subject. 14. SUBJECT TERMS 15. NUMBER OF PAGES Homopolar motors , generators, electric ship, brush polarity, superconducting materials, 72 unipolar or

  14. Carrier-mediated concentrative urate transport in rat renal membrane vesicles.

    PubMed

    Abramson, R G; Lipkowitz, M S

    1985-04-01

    [2-14C]Urate uptake and efflux were studied in brush border and basolateral membrane vesicles of rat renal cortex that were exposed to 20 microM copper chloride. In the presence of inwardly directed NaCl gradients urate uptake was maintained at levels in excess of chemical equilibrium. Comparison of glucose and chloride uptakes revealed that equilibrium glucose uptake was not affected by copper, but chloride failed to reach equilibrium in copper-exposed vesicles. It is suggested that the persistence of an electrolyte gradient could provide a driving force to raise the concentration of free intravesicular urate above that in the media. Preincubation of vesicles with unlabeled urate failed to diminish uptake of added urate; rather, urate uptake was trans stimulated. Uptake of labeled urate was also significantly accelerated when an outward gradient for unlabeled urate was created. Pyrazinoic and oxonic acids also trans stimulated urate uptake. The demonstration of accelerated homeo- and heteroexchange diffusion indicates that transport is carrier mediated in both brush border and basolateral vesicles. Outwardly directed hydroxyl gradients failed to influence urate uptake in either the presence or absence of copper or NaCl. Thus, this carrier, which is active only in the presence of trace amounts of copper, is distinct from a urate/anion exchanger.

  15. Water driven turbine/brush pipe cleaner

    NASA Technical Reports Server (NTRS)

    Werlink, Rudy J. (Inventor)

    1995-01-01

    Assemblies are disclosed for cleaning the inside walls of pipes and tubes. A first embodiment includes a small turbine with angled blades axially mounted on one end of a standoff support. An O-ring for stabilizing the assembly within the pipe is mounted in a groove within the outer ring. A replaceable circular brush is fixedly mounted on the opposite end of the standoff support and can be used for cleaning tubes and pipes of various diameters, lengths and configurations. The turbine, standoff support, and brush spin in unison relative to a hub bearing that is fixedly attached to a wire upstream of the assembly. The nonrotating wire is for retaining the assembly in tension and enabling return of the assembly to the pipe entrance. The assembly is initially placed in the pipe or tube to be cleaned. A pressurized water or solution source is provided at a required flow-rate to propel the assembly through the pipe or tube. The upstream water pressure propels and spins the turbine, standoff support and brush. The rotating brush combined with the solution cleans the inside of the pipe. The solution flows out of the other end of the pipe with the brush rotation controlled by the flow-rate. A second embodiment is similar to the first embodiment but instead includes a circular shaped brush with ring backing mounted in the groove of the exterior ring of the turbine, and also reduces the size of the standoff support or eliminates the standoff support.

  16. Cytohistological discordance on gastrointestinal brushings: Facts unfolded

    PubMed Central

    Tyagi, Ruchita; Kaur, Jagpal; Kaur, Gursheen; Selhi, Pavneet Kaur; Puri, Harpreet Kaur; Sood, Neena

    2016-01-01

    Introduction: Brush cytology is a rapid, cost-effective, and reliable tool to diagnose gastrointestinal tract (GIT) lesions in low-resource settings. Most of the studies on GIT brushings have focused on upper GI lesions. We have studied the diagnostic accuracy of brush cytology in the entire length of GIT and correlated the cytological diagnosis with histopathology. The aim of this study is to study diagnostic utility of brush cytology of GIT lesions in the context of correlation with biopsy and study the factors responsible for cytohistological discordance. Materials and Methods: A retrospective analysis of 101 cases of prebiopsy brush cytology samples of GIT lesions was done over a period of 1 year (June 2014 to May 2015). The cytological diagnosis was compared with histopathological diagnosis and percentage of correlation was calculated. The reasons for discordance were noted and studied. Results: The cytological diagnosis of 79 (78.2%) correlated with histopathological diagnosis. There was discordance in cytological and histological diagnosis in 22 cases (21.8%). Inadequacy of cytological sample and overlap of nuclear atypia caused by regenerative changes and malignancy were significant factors for cytohistological discordance. Conclusion: The diagnostic accuracy of brush cytology can be improved by taking appropriate measures to eliminate factors responsible for fallacies in cytological diagnosis. PMID:27833250

  17. Mechanism of organic anion transport across the apical membrane of choroid plexus.

    PubMed

    Pritchard, J B; Sweet, D H; Miller, D S; Walden, R

    1999-11-19

    The mechanism and membrane localization of choroid plexus (CP) organic anion transport were determined in apical (or brush border) membrane vesicles isolated from bovine choroid plexus and in intact CP tissue from cow and rat. Brush border membrane vesicles were enriched in Na(+),K(+)-ATPase (20-fold; an apical marker in CP) and demonstrated specific, sodium-coupled transport of proline, glucose, and glutarate. Vesicular uptake of the anionic herbicide 2, 4-dichlorophenoxyacetic acid (2,4-D) was markedly stimulated by an inward sodium gradient but only in the presence of glutarate, indicating the presence of apical dicarboxylate/organic anion exchange. Consistent with this interpretation, an imposed outward glutarate gradient stimulated 2,4-D uptake in the absence of sodium. Under both conditions, uptake was dramatically slowed and overshoot was abolished by probenecid. Likewise, apical accumulation of 2,4-D by intact bovine choroid plexus tissue in vitro was stimulated by external glutarate in the presence of sodium. Glutarate stimulation was abolished by 5 mM LiCl. Identical findings were obtained using rat CP tissue, which showed both sodium/glutarate-stimulated 2,4-D (tissue/medium (T/M) approximately 8) and p-aminohippurate (T/M = 2) transport. Finally, since the renal exchanger (rROAT1) has been cloned in rat kidney, a rROAT1-green fluorescent protein construct was used to analyze exchanger distribution directly in transiently transfected rat CP. As predicted by the functional studies, the fluorescently tagged transporter was seen in apical but not basolateral membranes of the CP.

  18. Designing of dynamic polyethyleneimine (PEI) brushes on polyurethane (PU) ureteral stents to prevent infections.

    PubMed

    Gultekinoglu, Merve; Tunc Sarisozen, Yeliz; Erdogdu, Ceren; Sagiroglu, Meral; Aksoy, Eda Ayse; Oh, Yoo Jin; Hinterdorfer, Peter; Ulubayram, Kezban

    2015-07-01

    Permanent antibacterial coatings have been developed by brush-like polyethyleneimine (PEI) on polyurethane (PU) ureteral stents since bacterial adhesion and biofilm formation with the following encrustation on stent surface limit their long term usage. In order to control or prevent bacterial infections; PEI chains with two different molecular weights (Mn: 1800 or 60,000 Da) were covalently attached on the polyurethane (PU) surface by "grafting to" approach to obtain a brush-like structure. Then, PEI brushes were alkylated with bromohexane to enhance the disruption of bacterial membranes with increasing polycationic character. X-ray Photoelectron and Infrared Spectroscopy investigations confirmed that PEI grafting and alkylation steps were performed successfully. Surface roughness in dry state increased dramatically from 65.8 nm to 277.7 nm and 145.2 nm for short chain PEI and long chain PEI grafted samples, respectively. Both low and high molecular weight PEI grafts exhibited a brush-like structure and potent antibacterial activity by lowering the adherence of Klebsiella pneumonia, Escherichia coli and Proteus mirabilis species up to two orders of magnitude without any cytotoxic effect on L929 and G/G cells. Thus, permanent bactericidal activity was achieved by the contact-active strategy of dynamic PEI brush-like structures on polyurethane ureteral stent.

  19. Brushing up on oil recovery

    SciTech Connect

    Mackey, J.

    1995-12-01

    To be prepared for a range of oil spills, emergency response organizations must have an arsenal of powerful and adaptable equipment. Around the coastal United States, a network of oil spill cooperatives and emergency response organizations stand ready with the technology and the know-how to respond to the first sign of an oil spill. When the telephone rings, they may be required to mop up 200 gallons of oil that leaked off the deck of a ship or to contain and skim 2,000 gallons of oil from a broken hose at a loading terminal. In a few cases each year, they may find themselves responding to a major pollution incident, one that involves hundreds of people and tons of equipment. To clean an oil spill at a New Jersey marine terminal, the local cooperative used the Lundin Oil Recovery Inc. (LORI) skimming system to separate the oil and water and the lift the oil out of the river. The LORI skimming technology is based on sound principles of fluid management - using the natural movement of water instead of trying to fight against it. A natural feeding mechanism delivers oily water through the separation process, and a simple mechanical separation and recovery device - a brush conveyor - removes the pollutants from the water.

  20. The Border Pedagogy Revisited

    ERIC Educational Resources Information Center

    Kazanjian, Christopher John

    2011-01-01

    Border pedagogy is a multicultural educational approach utilized in multicultural settings to help students understand their histories and experiences and how it affects their identities and cultures. The approach seeks to produce intellectuals that transcend physical and metaphysical boundaries. The goal of border pedagogy is to remove cultural…

  1. The Border Pedagogy Revisited

    ERIC Educational Resources Information Center

    Kazanjian, Christopher John

    2011-01-01

    Border pedagogy is a multicultural educational approach utilized in multicultural settings to help students understand their histories and experiences and how it affects their identities and cultures. The approach seeks to produce intellectuals that transcend physical and metaphysical boundaries. The goal of border pedagogy is to remove cultural…

  2. Why Border Enforcement Backfired

    PubMed Central

    Massey, Douglas S.; Durand, Jorge; Pren, Karen A.

    2016-01-01

    In this article we undertake a systematic analysis of why border enforcement backfired as a strategy of immigration control in the United States. We argue theoretically that border enforcement emerged as a policy response to a moral panic about the perceived threat of Latino immigration to the United States propounded by self-interested bureaucrats, politicians, and pundits who sought to mobilize political and material resources for their own benefit. The end result was a self-perpetuating cycle of rising enforcement and increased apprehensions that resulted in the militarization of the border in a way that was disconnected from the actual size of the undocumented flow. Using an instrumental variable approach, we show how border militarization affected the behavior of unauthorized migrants and border outcomes to transform undocumented Mexican migration from a circular flow of male workers going to three states into an eleven-million person population of settled families living in 50 states. PMID:27721512

  3. Thermoresponsive PDMAEMA Brushes: Effect of Gold Nanoparticle Deposition.

    PubMed

    Yenice, Zuleyha; Schön, Sebastian; Bildirir, Hakan; Genzer, Jan; von Klitzing, Regine

    2015-08-13

    The paper addresses the effect of gold nanoparticle (Au-NP) deposition on the thermoresponsive volume phase transition of the weak polyelectrolyte poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. PDMAEMA brushes were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP). The PDMAEMA/Au-NP composite brushes were fabricated by immersing the brush modified wafer in the Au-NP suspension. Atomic force microscopy (AFM), ellipsometry, and scanning electron microscopy (SEM) have been employed to characterize the neat PDMAEMA brushes and PDMAEMA/Au-NP composite brushes. All neat PDMAEMA brushes swelled below the volume phase transition temperature and collapsed with increasing temperature over a broad temperature range independent of the initial brush thickness. Water uptake of the brushes is also independent of initial brush thickness. The adsorption of the charged Au-NPs significantly affects the degree of swelling and the thermoresponsive properties of the brushes. PDMAEMA/Au-NP composite brushes do not exhibit any noticeable phase transition at the experimental temperature range irrespective of the initial brush thickness. The reason for this behavior is attributed to a combination of the following: the decreased conformational entropy of the Au-NP adsorbed polymer chains, the increased hydrophilicity of the system due to the charged Au-NPs, and the ≈13 nm diameter Au-NPs causing steric hindrance. We have also shown that the AFM full-indentation method can be successfully applied to determine the polymer brush thicknesses.

  4. Cold plasma brush generated at atmospheric pressure

    SciTech Connect

    Duan Yixiang; Huang, C.; Yu, Q. S.

    2007-01-15

    A cold plasma brush is generated at atmospheric pressure with low power consumption in the level of several watts (as low as 4 W) up to tens of watts (up to 45 W). The plasma can be ignited and sustained in both continuous and pulsed modes with different plasma gases such as argon or helium, but argon was selected as a primary gas for use in this work. The brush-shaped plasma is formed and extended outside of the discharge chamber with typical dimension of 10-15 mm in width and less than 1.0 mm in thickness, which are adjustable by changing the discharge chamber design and operating conditions. The brush-shaped plasma provides some unique features and distinct nonequilibrium plasma characteristics. Temperature measurements using a thermocouple thermometer showed that the gas phase temperatures of the plasma brush are close to room temperature (as low as 42 deg. C) when running with a relatively high gas flow rate of about 3500 ml/min. For an argon plasma brush, the operating voltage from less than 500 V to about 2500 V was tested, with an argon gas flow rate varied from less than 1000 to 3500 ml/min. The cold plasma brush can most efficiently use the discharge power as well as the plasma gas for material and surface treatment. The very low power consumption of such an atmospheric argon plasma brush provides many unique advantages in practical applications including battery-powered operation and use in large-scale applications. Several polymer film samples were tested for surface treatment with the newly developed device, and successful changes of the wettability property from hydrophobic to hydrophilic were achieved within a few seconds.

  5. Cold plasma brush generated at atmospheric pressure.

    PubMed

    Duan, Yixiang; Huang, C; Yu, Q S

    2007-01-01

    A cold plasma brush is generated at atmospheric pressure with low power consumption in the level of several watts (as low as 4 W) up to tens of watts (up to 45 W). The plasma can be ignited and sustained in both continuous and pulsed modes with different plasma gases such as argon or helium, but argon was selected as a primary gas for use in this work. The brush-shaped plasma is formed and extended outside of the discharge chamber with typical dimension of 10-15 mm in width and less than 1.0 mm in thickness, which are adjustable by changing the discharge chamber design and operating conditions. The brush-shaped plasma provides some unique features and distinct nonequilibrium plasma characteristics. Temperature measurements using a thermocouple thermometer showed that the gas phase temperatures of the plasma brush are close to room temperature (as low as 42 degrees C) when running with a relatively high gas flow rate of about 3500 ml/min. For an argon plasma brush, the operating voltage from less than 500 V to about 2500 V was tested, with an argon gas flow rate varied from less than 1000 to 3500 ml/min. The cold plasma brush can most efficiently use the discharge power as well as the plasma gas for material and surface treatment. The very low power consumption of such an atmospheric argon plasma brush provides many unique advantages in practical applications including battery-powered operation and use in large-scale applications. Several polymer film samples were tested for surface treatment with the newly developed device, and successful changes of the wettability property from hydrophobic to hydrophilic were achieved within a few seconds.

  6. Stratified polymer brushes from microcontact printing of polydopamine initiator on polymer brush surfaces.

    PubMed

    Wei, Qiangbing; Yu, Bo; Wang, Xiaolong; Zhou, Feng

    2014-06-01

    Stratified polymer brushes are fabricated using microcontact printing (μCP) of initiator integrated polydopamine (PDOPBr) on polymer brush surfaces and the following surface initiated atom transfer radical polymerization (SI-ATRP). It is found that the surface energy, chemically active groups, and the antifouling ability of the polymer brushes affect transfer efficiency and adhesive stability of the polydopamine film. The stickiness of the PDOPBr pattern on polymer brush surfaces is stable enough to perform continuous μCP and SI-ATRP to prepare stratified polymer brushes with a 3D topography, which have broad applications in cell and protein patterning, biosensors, and hybrid surfaces. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Performance characteristics of brush seals for limited-life engines

    SciTech Connect

    Chupp, R.E. ); Dowler, C.A. )

    1993-04-01

    Brush seals are potential replacements for air-to-air labyrinth seals in gas turbine engines. An investigation has been conducted to determine the performance characteristics of brush seals for application in limited-life gas turbine engines. An elevated temperature, rotating test rig was designed and built to test labyrinth and brush seals in simulated subsonic and supersonic engine conditions. Results from initial tests for subsonic applications demonstrated that brush seals exhibit appreciably lower leakage compared to labyrinth seals, and thus offer significant engine performance improvements. Performance results have been obtained showing the effect of various brush seal parameters, including: initial interference, backplate gap, and multiple brush seals in series.

  8. Bidirectional Brush Seals: Post-Test Analysis

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C.; Wilson, Jack; Wu, Tom Y.; Flower, Ralph; Mullen, Robert L.

    1997-01-01

    A post-test analysis of a set of inside-diameter/outside-diameter (ID/OD) bidirectional brush seals used in three-port wave rotor tests was undertaken to determine brush bristle and configuration wear, pullout, and rotor coating wear. The results suggest that sharp changes in the pressure profiles were not well reflected in bristle tip configuration patterns or wear. Also, positive-to-negative changes in axial pressure gradients appeared to have little effect on the backing plates. Although the brushes had similar porosities, they had very different unpacked arrays. This difference could explain the departure of experimental data from computational fluid dynamics flow predictions for well-packed arrays at higher pressure drops. The rotor wear led to "car-track" scars (upper and lower wear bands) with a whipped surface between the bands. Those bands may have resulted from bristle stiffening at the fence and gap plates during alternate portions of the rotor cycle. Within the bristle response range the wear surface reflected the pressure distribution effect on bristle motion. No sacrificial metallurgical data were taken. The bristles did wear, with correspondingly more wear on the ID brush configurations than on the OD configurations; the complexity in constructing the ID brush was a factor.

  9. Bordering on environmental disaster.

    PubMed Central

    Schmidt, C W

    2000-01-01

    Millions of people live on the U.S.-Mexico border, drawn by employment opportunities from industry and agriculture, and booming growth is expected to continue in the coming decades. But the influx of people has long outstripped the capacity of border towns and cities to provide for their citizens, and a large percentage of the population lives in sprawling, underserviced shantytowns. Although investment in environmental infrastructure on both sides has led to improvements, shortages among necessities such as drinking water, wastewater treatment, and solid waste disposal are at crisis levels. In addition, a host of diseases including gastrointestinal infections, asthma, tuberculosis, multiple myeloma, systemic lupus erythematosus, hepatitis A, neural tube defects, and lead poisoning have been linked to environmental conditions on the border. Ongoing binational studies are attempting to define the breadth of the public and environmental health crisis and find ways to help make the border a healthier place. PMID:10903625

  10. Brazil-Bolivia Border

    NASA Image and Video Library

    2013-04-16

    This image of the river-delineated border between western Brazil Acre province, and northwestern Bolivia Pando Department, demarcates a remarkable difference in land use and development practices as seen by NASA Terra spacecraft.

  11. Bordering on environmental disaster.

    PubMed

    Schmidt, C W

    2000-07-01

    Millions of people live on the U.S.-Mexico border, drawn by employment opportunities from industry and agriculture, and booming growth is expected to continue in the coming decades. But the influx of people has long outstripped the capacity of border towns and cities to provide for their citizens, and a large percentage of the population lives in sprawling, underserviced shantytowns. Although investment in environmental infrastructure on both sides has led to improvements, shortages among necessities such as drinking water, wastewater treatment, and solid waste disposal are at crisis levels. In addition, a host of diseases including gastrointestinal infections, asthma, tuberculosis, multiple myeloma, systemic lupus erythematosus, hepatitis A, neural tube defects, and lead poisoning have been linked to environmental conditions on the border. Ongoing binational studies are attempting to define the breadth of the public and environmental health crisis and find ways to help make the border a healthier place.

  12. Two-stage eutectic metal brushes

    SciTech Connect

    Hsu, John S

    2009-07-14

    A two-stage eutectic metal brush assembly having a slip ring rigidly coupled to a shaft, the slip ring being electrically coupled to first voltage polarity. At least one brush is rigidly coupled to a second ring and slidingly engaged to the slip ring. Eutectic metal at least partially fills an annulus between the second ring and a stationary ring. At least one conductor is rigidly coupled to the stationary ring and electrically coupled to a second voltage polarity. Electrical continuity is maintained between the first voltage polarity and the second voltage polarity. Periodic rotational motion is present between the stationary ring and the second ring. Periodic rotational motion is also present between the brush and the slip ring.

  13. LM2500+ Brush Seal Case Study

    NASA Technical Reports Server (NTRS)

    Haaser, Fred G.

    2006-01-01

    The LM2500+ industrial aeroderivative gas turbine, a 25% enhanced power derivative of the LM2500 gas turbine, recently completed its development test program during the period 5/96 - 10/96. Early in the engine program a Quality Function Deployment (QFD) process was used to determine customer needs for this project.The feedback obtained from the QFD process showed without doubt that gas turbine customers now emphasize product reliability and availability at the top of their needs. One area of development on the LM2500+ was to investigate the use of a brush seal as a means to reduce undesirable turbine cooling leakages within the turbine mid frame in order to enhance part life. This presentation presents a case study on the factors that went into evaluating a brush seal during engine test, test results, and the ultimate decision not to implement the brush seal for cost and other reasons.

  14. Angiotensin-converting enzyme of the human small intestine. Subunit and quaternary structure, biosynthesis and membrane association.

    PubMed Central

    Naim, H Y

    1992-01-01

    Angiotensin-converting enzyme (ACE) was isolated from detergent-derived extracts of human intestinal brush-border membranes (BBMs) by immunoprecipitation using a monoclonal antibody. Analysis of the immunoprecipitates by SDS/PAGE revealed a polypeptide of apparent M(r) 184,000 under reducing and non-reducing conditions, indicating that ACE does not contain intermolecular disulphide bridges. The quaternary structure of ACE was examined using cross-linking experiments with dithiobis[succinimidylpropionate] (DSP) and density gradient centrifugation on sucrose gradients. Both approaches demonstrated that ACE is assembled in the membrane as a monomer. By contrast, the control glycoprotein aminopeptidase N (ApN) exists as a dimer. Biosynthetic labelling experiments in intestinal tissue explants demonstrated that the 184,000-M(r) protein is generated from a single-polypeptide, mannose-rich precursor of ACE (M(r) 175,000) by modification of the carbohydrate side-chains in the Golgi apparatus. The mode of association of the mature form of the enzyme with BBMs was investigated by hydrophobic labelling of right-side-out brush-border vesicles with the photoactivatable carbene-generating reagent 125I-labelled 3-(trifluoromethyl)-3-(m[formylamino]phenyl)diazirine (125I-labelled TID), followed by treatment with trypsin at dilutions that do not cause substantial degradation of ACE. These studies demonstrated that ACE is associated with the membrane via a hydrophobic segment. Furthermore, treatment of 35S-labelled inside-out membrane vesicles with trypsin revealed that ACE possesses a cytoplasmic tail, and therefore has a transmembraneous orientation. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. PMID:1326943

  15. Design and Testing of High Performance Brushes.

    DTIC Science & Technology

    1979-06-01

    contact drop of anode silver brush during current decrease . Three graphite brush during current decrease contact spota assumed...urn~ aici~ ~‘IL~ ‘Till lAst’ GA.D cTIss lI~ II 1310 295 ~ ~O~IIMI 19-52 ~95* COA~~U 913•IM~ ~~~~~~ 29 ~~ 3.5 ~ lUI oi~~AT,. 10 .c .~~ ~0LT S 9313 ,” I

  16. Polymer brushes: routes toward mechanosensitive surfaces.

    PubMed

    Bünsow, Johanna; Kelby, Tim S; Huck, Wilhelm T S

    2010-03-16

    Soft nanotechnology involves both understanding the behavior of soft matter and using these components to build useful nanoscale structures and devices. However, molecular scale properties such as Brownian motion, diffusion, surface forces, and conformational flexibility dominate the chemistry and physics in soft nanotechnology, and therefore the design rules for generating functional structures from soft, self-assembled materials are still developing. Biological motors illustrate how wet nanoscale machines differ from their macroscopic counterparts. These molecular machines convert chemical energy into mechanical motion through an isothermal process: chemical reactions generate chemical potential and diffusion of ions, leading to conformational changes in proteins and the production of mechanical force. Because the actuation steps form a thermodynamic cycle that is reversible, the application of mechanical forces can also generate a chemical potential. This reverse process of mechanotransduction is the underlying sensing and signaling mechanism for a wide range of physiological phenomena such as hearing, touch, and growth of bone. Many of the biological systems that respond to mechanical stimuli do this via complex stress-activated ion channels or remodeling of the actin cytoskeleton. These biological actuation and mechanosensing processes are rather different from nano- and microelectromechanical systems (NEMS and MEMS) produced via semiconductor fabrication technologies. In our group, we are working to emulate biological mechanotransduction by systematically developing building blocks based on polymer brushes. In this soft nanotechnology approach to mechanotransduction, the chemical building blocks are polymer chains whose conformational changes and actuation can be investigated at a very basic level in polymer brushes, particularly polyelectrolyte brushes. Because these polymer brushes are easily accessible synthetically with control over parameters such as

  17. Conductive Nanowires Templated by Molecular Brushes.

    PubMed

    Raguzin, Ivan; Stamm, Manfred; Ionov, Leonid

    2015-10-21

    In this paper, we report the fabrication of conductive nanowires using polymer bottle brushes as templates. In our approach, we synthesized poly(2-dimethylamino)ethyl methacrylate methyl iodide quaternary salt brushes by two-step atom transfer radical polymerization, loaded them with palladium salt, and reduced them in order to form metallic nanowires with average lengths and widths of 300 and 20 nm, respectively. The obtained nanowires were deposited between conductive gold pads and were connected to them by sputtering of additional pads to form an electric circuit. We connected the nanowires in an electric circuit and demonstrated that the conductivity of these nanowires is around 100 S·m(-1).

  18. Improved molybdenum disulfide-silver motor brushes have extended life

    NASA Technical Reports Server (NTRS)

    Horton, J. C.; King, H. M.

    1964-01-01

    Motor brushes of proper quantities of molybdenum disulfide and copper or silver are manufactured by sintering techniques. Graphite molds are used. These brushes operate satisfactorily for long periods in normal atmosphere or in a high-vacuum environment.

  19. Oral Health: Brush Up on Dental Care Basics

    MedlinePlus

    ... help you stave off cavities. Consider these brushing basics from the American Dental Association: Brush your teeth twice a day . When ... opportunities Reprint Permissions A single copy of these ... for Medical Education and Research (MFMER). All rights reserved.

  20. Synthesis and antibacterial properties of ZnO brush pens

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Zhang, Rong; Li, Yilin; Weng, Yuan; Liang, Weiquan; Zhang, Wenfeng; Zheng, Weitao; Hu, Haimei

    2015-12-01

    In this paper, ZnO with a novel hierarchical nanostructure has been synthesized by a new solution method. The novel hierarchical structure is named a ‘brush pen’. The biocompatibility and antibacterial properties of ZnO brush pens have been evaluated. The results demonstrate that ZnO brush pens show good antibacterial activity against Staphylococcus aureus.

  1. [Process of the tooth brushing habit formation in children. 2. Factors forming the behavior of tooth brushing in children].

    PubMed

    Suzuki, Y

    1990-06-01

    The purpose of this study was to find in the factors forming the habit of tooth brushing in children. Questionnaires about the habit of tooth brushing were collected in Nagoya and the suburbs from mothers of kindergarten pupils aged from one to six. These data were analysed by the second class of Hayashi's quantifying theory. The results of this study were summarised as follows: 1. Habit of tooth brushing: 1) A high correlation ratio was obtained in the discriminatory efficiency of the habit of tooth brushing, at ages one to three this was 0.44 and for ages four to six it was 0.47. 2) The following six items were chosen in relation to the habit formation of tooth brushing at ages one to three, "motive for starting tooth brushing", "frequency of tooth brushing per day on the average", "co-operative of the child towards its mother's help", "positive attitude towards tooth brushing", "experienced guidance in tooth brushing from its mother", "experienced guidance in tooth brushing from a dentist or dental hygienist". 3) Similarly for ages four to six, the following four items were chosen, "frequency of tooth brushing per day on the average", "persons who actually brush the children's teeth at night", "attitude of the child towards tooth brushing", "experienced guidance in tooth brushing from a dentist or dental hygienist". 2. Ability of tooth brushing: 1) A comparative high correlation ratio was obtained in the discriminatory efficiency of the ability of tooth brushing, at ages one to three this was 0.37 and for ages four to six it was 0.20. 2) The following five items were chosen in relation to the ability of tooth brushing at ages one to three, "age", "motive for the start of tooth brushing", "mother's attitude to child not brushing its teeth", "frequency of using tooth paste", "experienced guidance in tooth brushing from a dentist or dental hygienist". 3) Similarly for ages four to six, the following five items were chosen, "age", "persons who actually brush the

  2. Attraction between Opposing Planar Dipolar Polymer Brushes

    DOE PAGES

    Mahalik, J. P.; Sumpter, Bobby G.; Kumar, Rajeev

    2017-08-01

    In this paper, we use a field theory approach to study the effects of permanent dipoles on interpenetration and free energy changes as a function of distance between two identical planar polymer brushes. Melts (i.e., solvent-free) and solvated brushes made up of polymers grafted on nonadsorbing substrates are studied. In particular, the weak coupling limit of the dipolar interactions is considered, which leads to concentration-dependent pairwise interactions, and the effects of orientational order are neglected. It is predicted that a gradual increase in the dipole moment of the polymer segments can lead to attractive interactions between the brushes at intermediatemore » separation distances. Finally, because classical theory of polymer brushes based on the strong stretching limit (SSL) and the standard self-consistent field theory (SCFT) simulations using the Flory’s χ parameter always predicts repulsive interactions at all separations, our work highlights the importance of dipolar interactions in tailoring and accurately predicting forces between polar polymeric interfaces in contact with each other.« less

  3. Soil slippage increased by brush conversion

    Treesearch

    Edward S. Corbett; Raymond M. Rice

    1966-01-01

    After 8 fire burned the San Dimas Experimental Forest, near Glendora Calif., in 1960, about 350 acres of brushland were converted to grass. Six years later, the frequency and extent of soil slips - a form of gravitational mass movement - on this acreage was compared with those on comparable sites where brush cover was recovering naturally after the fire. Both the area...

  4. Solvent response of mixed polymer brushes

    NASA Astrophysics Data System (ADS)

    Gong, Kai; Chapman, Walter G.

    2011-12-01

    We have performed classical density functional theory calculations to study the behavior of mixed polymer brushes tethered to a planar surface. We assume no lateral segregation of the polymer at the grafting density studied and consider an implicit solvent. For a binary mixture of short and long athermal polymer chains, the short chain is compressed while the long chain is stretched compared with corresponding pure polymer chains at the same grafting density, which is consistent with simulation. This results from configurational entropy effects. Furthermore, we add a mean-field interaction for each polymer brush to simulate their different response towards a solvent. The long chain is forced to dislike the solvent more than the short chain. Through the interplay between the solvent effects and configurational entropy effects, a switch of the polymer brush surface (or outer) layer is found with increasing chain length of the long chain. The transition chain length (long chain) increases with increasing the solvent selectivity, and decreases with increasing the grafting density of the long chain. These results can provide guidance for the design of smart materials based on mixed polymer brushes.

  5. Charge Transport Properties in Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Moog, Mark; Tsui, Frank; Vonwald, Ian; You, Wei

    Electrical transport properties in poly(3-methyl)thiophene (P3MT) brushes have been studied. The P3MT brushes correspond to a new type of surface-tethered, vertically oriented conjugated molecular wires, sandwiched between two metallic electrodes to form the electrode-molecule-electrode (EME) devices. P3MT is a highly conjugated polymer, a ''workhorse'' material for organic electronics and photonics. The P3MT brushes were grown on ITO surfaces with controlled length (between 2 and 100 nm). The top electrodes were transfer-printed Au films with lateral dimensions between 200 nm and 50 μm. I-V and differential conductance measurements were performed using conductive AFM and 4-terminal techniques. Tunneling and field-emission measurements in EME devices with molecular lengths < 5 nm show HOMO mediated direct hole tunneling with energy barriers of 0.3 and 0.5 eV at the respective interfaces with ITO and Au. The transport properties in longer brushes are indicative of the two quasi-Ohmic interfaces with a characteristic offset in the conductance minimum of 0.12 V biased toward the ITO. Temperature dependent parameters have been examined at various molecular lengths. The drift mobility and the interplay between intra- and intermolecular transport have been investigated.

  6. 21 CFR 884.1100 - Endometrial brush.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... endometrium (the mucosal lining of the uterus) by brushing its surface. This device is used to study...'s: (i) “Use of International Standard ISO 10993 ‘Biological Evaluation of Medical Devices—Part I: Evaluation and Testing,’ ” and (ii) “510(k) Sterility Review Guidance of 2/12/90 (K90-1),” (2) Labeling:...

  7. Chinese Brush Calligraphy Character Retrieval and Learning

    ERIC Educational Resources Information Center

    Zhuang, Yueting; Zhang, Xiafen; Lu, Weiming; Wu, Fei

    2007-01-01

    Chinese brush calligraphy is a valuable civilization legacy and a high art of scholarship. It is still popular in Chinese banners, newspaper mastheads, university names, and celebration gifts. There are Web sites that try to help people enjoy and learn Chinese calligraphy. However, there lacks advanced services such as content-based retrieval or…

  8. Multifunctional brushes made from carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Cao, Anyuan; Veedu, Vinod P.; Li, Xuesong; Yao, Zhaoling; Ghasemi-Nejhad, Mehrdad N.; Ajayan, Pulickel M.

    2005-07-01

    Brushes are common tools for use in industry and our daily life, performing a variety of tasks such as cleaning, scraping, applying and electrical contacts. Typical materials for constructing brush bristles include animal hairs, synthetic polymer fibres and metal wires (see, for example, ref. 1). The performance of these bristles has been limited by the oxidation and degradation of metal wires, poor strength of natural hairs, and low thermal stability of synthetic fibres. Carbon nanotubes, having a typical one-dimensional nanostructure, have excellent mechanical properties, such as high modulus and strength, high elasticity and resilience, thermal conductivity and large surface area (50-200 m2 g-1). Here we construct multifunctional, conductive brushes with carbon nanotube bristles grafted on fibre handles, and demonstrate their several unique tasks such as cleaning of nanoparticles from narrow spaces, coating of the inside of holes, selective chemical adsorption, and as movable electromechanical brush contacts and switches. The nanotube bristles can also be chemically functionalized for selective removal of heavy metal ions.

  9. Chinese Brush Calligraphy Character Retrieval and Learning

    ERIC Educational Resources Information Center

    Zhuang, Yueting; Zhang, Xiafen; Lu, Weiming; Wu, Fei

    2007-01-01

    Chinese brush calligraphy is a valuable civilization legacy and a high art of scholarship. It is still popular in Chinese banners, newspaper mastheads, university names, and celebration gifts. There are Web sites that try to help people enjoy and learn Chinese calligraphy. However, there lacks advanced services such as content-based retrieval or…

  10. Degrafting of polymer brushes from substrates enables insight about the brush structure and facilitates surface patterning

    NASA Astrophysics Data System (ADS)

    Patil, Rohan; Turgman-Cohen, Salomon; Srogl, Jiri; Kiserow, Douglas; Genzer, Jan

    Polymers end-grafted to surfaces or interfaces, commonly referred to as polymer brushes, enable tailoring physico-chemical properties of material surfaces. Many applications of polymer brushes require information about the molecular weight (MW) and grafting density (GD) of polymer brushes. For brushes synthesized by surface initiated polymerization (SIP) determining these attributes was always a challenge. We have developed a simple method of measuring MW and GD of these systems by degrafting SIP from silica-based surfaces by using tetrabutyl ammonium fluoride (TBAF), which attacks selectively Si-O bonds and enables complete degrafting of poly(methyl methacrylate) (PMMA) brushes from silica based substrates without damaging the backbone. The rate of PMMA degrafting decreases with reaction time and depends on the concentration of TBAF, temperature, and the initial GD of the system. The molecular weight distribution of the degrafted PMMA was measured using size exclusion chromatography. The GD was calculated from known MW and dry thickness of the PMMA brush. Spatial patterns of degrafted regions on the substrate can be prepared by either localizing the TBAF to certain regions or by gradually immersing homogeneous samples into TBAF solution.

  11. Degrafting of polymer brushes from substrates enables insight about the brush structure and facilitates surface patterning

    NASA Astrophysics Data System (ADS)

    Patil, Rohan; Turgman-Cohen, Salomon; Srogl, Jiri; Kiserow, Douglas; Genzer, Jan

    Polymers end-grafted to surfaces or interfaces, commonly referred to as polymer brushes, enable tailoring physico-chemical properties of material surfaces. Many applications of polymer brushes require information about the molecular weight (MW) and grafting density (GD) of polymer brushes. For brushes synthesized by surface initiated polymerization (SIP) determining these attributes was always a challenge. We have developed a simple method of measuring MW and GD of these systems by degrafting SIP from silica-based surfaces by using tetrabutyl ammonium fluoride (TBAF), which attacks selectively Si-O bonds and enables complete degrafting of poly(methyl methacrylate) (PMMA) brushes from silica based substrates without damaging the backbone. The rate of PMMA degrafting decreases with reaction time and depends on the concentration of TBAF, temperature, and the initial GD of the system. The molecular weight distribution of the degrafted PMMA was measured using size exclusion chromatography. The GD was calculated from known MW and dry thickness of the PMMA brush. Spatial patterns of degrafted regions on the substrate can be prepared by either localizing the TBAF to certain regions or by gradually immersing homogeneous samples into TBAF solution.

  12. Measurements of experimental plasma brush behavior in hybrid armatures

    NASA Astrophysics Data System (ADS)

    Hawke, R. S.; Morrison, J. J.; Susoeff, A. R.

    1993-01-01

    Hybrid armatures used in railguns, consist of a conducting link which is commutated to the rails by plasma brushes. The formation, properties and stability of plasma brushes is important to the performance of the armature. This paper describes a set of experiments in which the effects of varying plasma brush parameters including the initial mass of metal foil used to form the plasma as well as the current were studied. The evolution of the plasma brush from a solid metal foil through its melt, vapor and plasma phase were observed. The resulting brush length and voltage drop were measured. The results of these tests are presented, discussed and compared to numerical simulations.

  13. Anthrax Cases Associated with Animal-Hair Shaving Brushes.

    PubMed

    Szablewski, Christine M; Hendricks, Kate; Bower, William A; Shadomy, Sean V; Hupert, Nathaniel

    2017-05-01

    During the First World War, anthrax cases in the United States and England increased greatly and seemed to be associated with use of new shaving brushes. Further investigation revealed that the source material and origin of shaving brushes had changed during the war. Cheap brushes of imported horsehair were being made to look like the preferred badger-hair brushes. Unfortunately, some of these brushes were not effectively disinfected and brought with them a nasty stowaway: Bacillus anthracis. A review of outbreak summaries, surveillance data, and case reports indicated that these cases originated from the use of ineffectively disinfected animal-hair shaving brushes. This historical information is relevant to current public health practice because renewed interest in vintage and animal-hair shaving brushes has been seen in popular culture. This information should help healthcare providers and public health officials answer questions on this topic.

  14. Sugar uptake by intestinal basolateral membrane vesicles.

    PubMed

    Wright, E M; van Os, C H; Mircheff, A K

    1980-03-27

    A high yield of membrane vesicles was prepared from the basolateral surface of rat intestinal cells using an N2 cavitation bomb and density gradient centrifugation. The membranes were enriched 10-fold and were free of significatn contamination by brush border membranes and mitochondria. The rate of D-E114C]glucose and L-E13H]glucose uptake into the vesicle was measured using a rapid filtration technique. D-Glucose equilibrated within the vesicles with a half-time 1/25th that for L-glucose. The stereospecific uptake exhibited saturation kinetics with a Km of approx. 44 mM and a V of approx. 110 nmol . mg-1 min-1 at 10 degrees C. The activation energy for the process was 14 kcal . mol-1 below 15 degrees C and it approached 3 kcal . mol-1 above 22 degrees C. Carrier-mediated uptake was eliminated in the presence of 1 mM HgCl2 and 0.5 mM phloretin. The rate of transport was unaffected by the absence or presence of sodium concentration gradients. Competition studies demonstrated that all sugars with the D-glucose pyranose ring chair conformation shared the transport system, and that, with the possible exception of the -OH group at carbon No. 1, there were no specific requirements for an equatorial -OH group at any position in the pyranose ring. In the case of alpha-methyl-D-glucoside its inability to share the D-glucose transport system may be due to steric hindrance posed by the -OCH3 group rather than by a specific requirement for a free hydroxyl group at the position in the ring. It is concluded that sugars are transported across the basolateral membrane of the intestinal epithelium by a facilitated diffusion system reminiscent of that in human red blood cells.

  15. Adsorbed gels versus brushes: viscoelastic differences.

    PubMed

    Dutta, Amit K; Belfort, Georges

    2007-03-13

    It is of fundamental importance to be able to easily distinguish between the viscoelastic properties of a molecular gel (noncovalent cross-linked three-dimensional polymer structure) and a brush (polymer structure that emanates from a surface in three dimensions without cross-linking). This has relevance in biology and in designing surfaces with desired chemical and viscoelastic properties for nano and genomic technology applications. Agarose and thiol-tagged poly(ethylene glycol) were chosen as model systems, as they are known, on adsorption, to behave like a molecular gel and brush, respectively. Here, we focus on their viscoelastic differences using a quartz crystal microbalance with dissipation monitoring (QCM-D). Changes in resonance frequency and dissipation for three overtones using QCM-D were fitted with the Voigt viscoelastic model to calculate the shear viscosity and shear modulus for the adsorbed agarose gel and the PEG brush. At a surface coverage of 500 ng/cm2, the shear viscosities and shear moduli were 0.0025 +/- 0.0002 Pa-s and 2.0 +/- 0.17 x 105 Pa and 0.0010 +/- 0.0001 Pa-s and 5.0 +/- 0.3 x 104 Pa for the gel and brush, respectively. Thus, the adsorbed agarose gel layer was far more rigid than that of the covalently bound PEG brush due to its cross-linked network. Also, the diffusivity of agarose and PEG in solution was compared during adsorption onto a bare gold surface. The estimated value for the effective diffusivity of the PEG (without a thiol tag) and of the agarose gel was on the order of 10(-11) and 10(-15) m2/s, respectively. This low diffusivity for agarose supports the contention that it exists as a molecular gel with a H-bonded cross-linked network in aqueous solution. With the methods used here, it is relatively easy to distinguish the differences in viscoelastic properties between an adsorbed gel and brush.

  16. Hands across the Border.

    ERIC Educational Resources Information Center

    Langston, Diane

    1990-01-01

    Describes the Hands across the Border Cultural Exchange Program between the communities of Palominas, Arizona, and Arizpe, Sonora, Mexico. An Arizona fifth/sixth grader studies Mexico prior to hosting a visitor from Mexico and enjoying a reciprocal visit to the Arizpe student's home. Highlights the program's unique features and benefits. (DMM)

  17. Virtual sea border

    NASA Astrophysics Data System (ADS)

    Ferriere, D.; Rucinski, A.; Jankowski, T.

    2007-04-01

    Establishing a Virtual Sea Border by performing a real-time, satellite-accessible Internet-based bio-metric supported threat assessment of arriving foreign-flagged cargo ships, their management and ownership, their arrival terminal operator and owner, and rewarding proven legitimate operators with an economic incentive for their transparency will simultaneously improve port security and maritime transportation efficiencies.

  18. "Border Sexualities, Border Families in Schools": Queering Education

    ERIC Educational Resources Information Center

    Ryan, John

    2012-01-01

    This essay reviews Maria Pallotta-Chiarolli's (2010) Lambda Award-winning monograph "Border Sexualities, Border Families in Schools", in which queer and mestizage pedagogies frame a groundbreaking and highly accessible exploration of the issues that sexual border dwellers experience. Her particular focus areas are bisexual "sexually fluid"…

  19. "Border Sexualities, Border Families in Schools": Queering Education

    ERIC Educational Resources Information Center

    Ryan, John

    2012-01-01

    This essay reviews Maria Pallotta-Chiarolli's (2010) Lambda Award-winning monograph "Border Sexualities, Border Families in Schools", in which queer and mestizage pedagogies frame a groundbreaking and highly accessible exploration of the issues that sexual border dwellers experience. Her particular focus areas are bisexual "sexually fluid"…

  20. Toward Infection-Resistant Surfaces: Achieving High Antimicrobial Peptide Potency by Modulating the Functionality of Polymer Brush and Peptide.

    PubMed

    Yu, Kai; Lo, Joey C Y; Mei, Yan; Haney, Evan F; Siren, Erika; Kalathottukaren, Manu Thomas; Hancock, Robert E W; Lange, Dirk; Kizhakkedathu, Jayachandran N

    2015-12-30

    Bacterial infection associated with indwelling medical devices and implants is a major clinical issue, and the prevention or treatment of such infections is challenging. Antimicrobial coatings offer a significant step toward addressing this important clinical problem. Antimicrobial coatings based on tethered antimicrobial peptides (AMPs) on hydrophilic polymer brushes have been shown to be one of the most promising strategies to avoid bacterial colonization and have demonstrated broad spectrum activity. Optimal combinations of the functionality of the polymer-brush-tethered AMPs are essential to maintaining long-term AMP activity on the surface. However, there is limited knowledge currently available on this topic. Here we report the development of potent antimicrobial coatings on implant surfaces by elucidating the roles of polymer brush chemistry and peptide structure on the overall antimicrobial activity of the coatings. We screened several combinations of polymer brush coatings and AMPs constructed on nanoparticles, titanium surfaces, and quartz slides on their antimicrobial activity and bacterial adhesion against Gram-positive and Gram-negative bacteria. Highly efficient killing of planktonic bacteria by the antimicrobial coatings on nanoparticle surfaces, as well as potent killing of adhered bacteria in the case of coatings on titanium surfaces, was observed. Remarkably, the antimicrobial activity of AMP-conjugated brush coatings demonstrated a clear dependence on the polymer brush chemistry and peptide structure, and optimization of these parameters is critical to achieving infection-resistant surfaces. By analyzing the interaction of polymer-brush-tethered AMPs with model lipid membranes using circular dichroism spectroscopy, we determined that the polymer brush chemistry has an influence on the extent of secondary structure change of tethered peptides before and after interaction with biomembranes. The peptide structure also has an influence on the density

  1. Effect of polymer brushes on the Self Assembly of 3D Poly(Styrene-Methylmethacrylate) thin films

    NASA Astrophysics Data System (ADS)

    Lwoya, Baraka; Albert, Julie

    2015-03-01

    It would be instrumental to understand the self-assembly capabilities of polymers especially given their industrial capabilities of templating and membrane application .The ability of block copolymers to self assemble into different morphologies is determined by several factor including type of polymer blocks, volume fraction, substrate preference to a polymer and chain architecture . In this paper Poly(Styrene-Methylmethacrylate) (PS-PMMA) was chosen was chosen to further understand the effect polymer brushes on the substrate had on the self assembly of 3D structured PS-PMMA spin coated thin films (30-150 nm). The polymer brushes were grown using surface initiated atomic transfer radical polymerization (SI-ATRP) with the optimal chain length being confirmed by gel permeation chromatography. By using ellipsometer and contact angle measurement the uniformity of the polymer brushes are characterized, while the morphology of the spin coated thin films after thermal annealing would be characterized using atomic force microscopy (AFM).

  2. Lubrication at Physiological Pressures by Polyzwitterionic Brushes

    NASA Astrophysics Data System (ADS)

    Chen, Meng; Briscoe, Wuge H.; Armes, Steven P.; Klein, Jacob

    2009-03-01

    The very low sliding friction at natural synovial joints, which have friction coefficients of μ < 0.002 at pressures up to 5 megapascals or more, has to date not been attained in any human-made joints or between model surfaces in aqueous environments. We found that surfaces in water bearing polyzwitterionic brushes that were polymerized directly from the surface can have μ values as low as 0.0004 at pressures as high as 7.5 megapascals. This extreme lubrication is attributed primarily to the strong hydration of the phosphorylcholine-like monomers that make up the robustly attached brushes, and may have relevance to a wide range of human-made aqueous lubrication situations.

  3. Application of amorphous brush-plated

    NASA Astrophysics Data System (ADS)

    Zheng, M.; Zhu, Y.; Zheng, Z.

    1994-02-01

    The results obtained during industrial trials have shown that the service life of hot work dies can be increased by 33 to 180% using the brush plating technique to prepare amorphous coatings. The coatings possess a much higher hardness, lower friction coefficient at room and elevated temperatures, good scale resistance in addition to higher surface finish, compared to uncoated dies, and thus improve the tribological performance of the dies. In this work, a study of the crystallization process, its kinetics, and the hardness variations of the coatings has been made. According to the data obtained, it can be considered that the main reason for the success of amorphous brush-plated coatings is that, during the operation, crystallization and precipitation takes place instantaneously, which results in a strong secondary hardening effect, thus leading to an increase in the red hardness of the surface layers of dies, therefore ensuring higher thermal wear resistance of the dies.

  4. Lubrication at physiological pressures by polyzwitterionic brushes.

    PubMed

    Chen, Meng; Briscoe, Wuge H; Armes, Steven P; Klein, Jacob

    2009-03-27

    The very low sliding friction at natural synovial joints, which have friction coefficients of mu < 0.002 at pressures up to 5 megapascals or more, has to date not been attained in any human-made joints or between model surfaces in aqueous environments. We found that surfaces in water bearing polyzwitterionic brushes that were polymerized directly from the surface can have mu values as low as 0.0004 at pressures as high as 7.5 megapascals. This extreme lubrication is attributed primarily to the strong hydration of the phosphorylcholine-like monomers that make up the robustly attached brushes, and may have relevance to a wide range of human-made aqueous lubrication situations.

  5. Vision, healing brush, and fiber bundles

    NASA Astrophysics Data System (ADS)

    Georgiev, Todor

    2005-03-01

    The Healing Brush is a tool introduced for the first time in Adobe Photoshop (2002) that removes defects in images by seamless cloning (gradient domain fusion). The Healing Brush algorithms are built on a new mathematical approach that uses Fibre Bundles and Connections to model the representation of images in the visual system. Our mathematical results are derived from first principles of human vision, related to adaptation transforms of von Kries type and Retinex theory. In this paper we present the new result of Healing in arbitrary color space. In addition to supporting image repair and seamless cloning, our approach also produces the exact solution to the problem of high dynamic range compression of17 and can be applied to other image processing algorithms.

  6. Effect of brushing on fluoride release from 3 bracket adhesives.

    PubMed

    Staley, Robert N; Mack, Steven J; Wefel, James S; Vargas, Marcos A; Jakobsen, Jane R

    2004-09-01

    The purpose of this in vitro study was to compare fluoride ion release from 3 orthodontic bracket adhesives with and without brushing the bracketed teeth with a fluoridated dentifrice. The bracket adhesives included a light-cured composite resin (Transbond; 3M Unitek, Monrovia, Calif), a fluoride-releasing composite resin (Advance; L D Caulk Division, Dentsply International, Milford, Del), and a resin-modified glass ionomer (Fuji Ortho LC; GC America, Alsip, Ill). The teeth in the control group were not bonded with brackets. Sixty extracted human teeth were randomly assigned to 6 groups of 10 each: (1) Transbond, brushed; (2) Advance, brushed; (3) Advance, not brushed; (4) Fuji, brushed; (5) Fuji, not brushed; and (6) control, brushed. After bonding, each tooth was placed in a sealed plastic test tube containing 4 ml of deionized water. The toothpaste used in brushing contained 0.15% weight per volume sodium fluoride, 1500 parts per million parts fluoride (Winter-fresh gel; Colgate-Palmolive Co., New York, NY). Brushing began 24 hours after the teeth were bonded and placed in deionized water. After brushing, the teeth were thoroughly rinsed with deionized water and returned to a sealed test tube. Fluoride measurements were taken before brushing began, at intervals of 72 hours for 22 days, and 90 and 93 days after bonding. Findings included: (1) brushing significantly increased the release of fluoride ions from the teeth in the composite resin and control groups, (2) the enamel crowns of the unbonded control teeth absorbed and re-released a substantial amount of fluoride ions obtained from the toothpaste, (3) the brushed group of teeth bonded with the fluoride-releasing composite resin released significantly more fluoride on the last 4 days that measurements were taken after brushing than the nonbrushed group bonded with the same adhesive, (4) the brushed group of teeth bonded with the resin-modified glass ionomer released significantly more fluoride on the last 4

  7. Uses of the Westrup brush machine

    Treesearch

    Jill Barbour

    2002-01-01

    The Westrup brush machine can be used as the first step in the conditioning process of seeds. Even though there are various sizes of the machine, only the laboratory model (LA-H) is described. The machine is designed to separate seed from pods or flowers, dewing tree seed, remove appendages or hairs from seed, split twin seed, de-lint cotton seed, scarify hard coated...

  8. Polyelectrolyte brushes: a novel stable lubrication system in aqueous conditions.

    PubMed

    Kobayashi, Motoyasu; Terada, Masami; Takahara, Atsushi

    2012-01-01

    Surface-initiated controlled radical copolymerizations of 2-dimethylaminoethyl methacrylate (DMAEMA), 2-(methacryloyloxy)ethyl phosphorylcholine (MPC), 2-(methacryloyloxy)ethyltrimethylammonium chloride) (MTAC), and 3-sulfopropyl methacrylate potassium salt (SPMK) were carried out on a silicon wafer and glass ball to prepare polyelectrolyte brushes with excellent water wettability. The frictional coefficient of the polymer brushes was recorded on a ball-on-plate type tribometer by linear reciprocating motion of the brush specimen at a selected velocity of 1.5 x 10(-3) m s-1 under a normal load of 0.49 N applied to the stationary glass ball (d = 10 mm) at 298 K. The poly(DMAEMA-co-MPC) brush partially cross-linked by bis(2-iodoethoxy)ethane maintained a relatively low friction coefficient around 0.13 under humid air (RH > 75%) even after 200 friction cycles. The poly(SPMK) brush revealed an extremely low friction coefficient around 0.01 even after 450 friction cycles. We supposed that the abrasion of the brush was prevented owing to the good affinity of the poly(SPMK) brush for water forming a water lubrication layer, and electrostatic repulsive interactions among the brushes bearing sulfonic acid groups. Furthermore, the poly(SPMK-co-MTAC) brush with a chemically cross-linked structure showed a stable low friction coefficient in water even after 1400 friction cycles under a normal load of 139 MPa, indicating that the cross-linking structure improved the wear resistance of the brush layer.

  9. Mechanisms for nano particle removal in brush scrubber cleaning

    NASA Astrophysics Data System (ADS)

    Huang, Yating; Guo, Dan; Lu, Xinchun; Luo, Jianbin

    2011-01-01

    A model describing the nano particle (<100 nm) removal behavior in brush scrubber cleaning is presented based on experiment results and theoretical analysis. The forces on the particles in different situations are analyzed and discussed. The adhesion forces of the van der Waals force, the electrostatic force, the brush load and the static friction between the particle and the wafer are calculated. The contact elastic force, hydrodynamic drag force and friction between the brush and the particle are considered as removal forces and are evaluated. The porous structure and roughness surface of brush material are considered in the hydrodynamic model to describe the brush deformation and the flow field in the cleaning process. The porous structure will result in decrease of hydrodynamic drag force. There are four situations of the particles relative to the brush roughness asperities for which the forces on the particle are different. When the particle is in contact with a brush asperity or on the wafer surface and in a semi-infinite fluid flow field, the particle may be removed by hydrodynamic force and elastic force in the presence of surfactant. When the particle is embedded in the brush asperity, the remove will realized when the friction caused by adhesion between the brush and the particle overcome the adhesion force between particle and wafer surface. The removed particles will be in the flow field or adhered on the brush surface and may redeposit on the wafer surface.

  10. Dynamic Polymer Brush at Polymer/Water Interface

    NASA Astrophysics Data System (ADS)

    Yokoyama, Hideaki; Inoue, Kazuma; Ito, Kohzo; Inutsuka, Manabu; Tanaka, Keiji; Yamada, Norifumi

    2015-03-01

    A layer of polymer chains tethered by one end to a surface is called polymer brush and known to show various unique properties such as anti-fouling. The surface segregation phenomena of copolymers with surface-active blocks should be useful for preparing such a brush layer in spontaneous process. We report hydrophilic polymer brushes formed at the interface between water and polymer by the segregation of amphiphilic diblock copolymers blended in a crosslinked rubbery matrix and call it ``dynamic polymer brush.'' In this system, the hydrophilic block with high surface energy avoids air surface, but segregates to cover the interface between hydrophobic elastomer and water. The structures of the brush layers at D2O/polymer interfaces were measured by neutron reflectivity. The dynamic polymer brush layer surprisingly reached 75% of the contour length of the chain and 2.7 chains/nm2. The brush density was surprisingly comparable to the polymer brush fabricated by the ``grafting-from'' method. We will discuss the dependence of the brush structure on molecular weight and block fraction of amphiphilic block copolymers. Such a surprisingly thick and dense polymer brush were induced by the large enthalpy gain of hydration of hydrophilic block.

  11. Structure of Polyelectrolyte Brushes in the Presence of Multivalent Counterions

    DOE PAGES

    Yu, Jing; Mao, Jun; Yuan, Guangcui; ...

    2016-07-20

    Polyelectrolyte brushes are of great importance to a wide range of fields, ranging from colloidal stabilization to responsive and tunable materials to lubrication. Here, we synthesized high-density polystyrenesulfonate (PSS) brushes using surface initiated atom transfer radical polymerization and performed neutron reflectivity (NR) and surface force measurements using a surface forces apparatus (SFA) to investigate the effect of monovalent Na+, divalent Ca2+, Mg2+, and Ba2+, and trivalent Y3+ counterions on the structure of the PSS brushes. NR and SFA results demonstrate that in monovalent salt solution the behavior of the PSS brushes agrees with scaling theory well, exhibiting two distinct regimes:more » the osmotic and salted brush regimes. Introducing trivalent Y3+ cations causes an abrupt shrinkage of the PSS brush due to the uptake of Y3+ counterions. The uptake of Y3+ counterions and shrinkage of the brush are reversible upon increasing the concentration of monovalent salt. Divalent cations, Mg2+, Ca2+, and Ba2+, while all significantly affecting the structure of PSS brushes, show strong ion specific effects that are related to the specific interactions between the divalent cations and the sulfonate groups. Our results demonstrate that the presence of multivalent counterions, even at relatively low concentrations, can strongly affect the structure of polyelectrolyte brushes. Finally, the results also highlight the importance of ion specificity to the structure of polyelectrolyte brushes in solution.« less

  12. Healthy Border 2020 Embassy Launch

    Cancer.gov

    The U.S.-Mexico Border Health Commission launched the Healthy Border 2020 at the Mexican Embassy in the United States on June 24, 2015. This new initiative aims to strengthening what was accomplished on the previous plan of action entitled Healthy Border 2010.

  13. Steric interactions between two grafted polymer brushes

    NASA Astrophysics Data System (ADS)

    Ruckenstein, Eli; Li, Buqiang

    1997-07-01

    A lattice model and a generator-matrix method are employed to calculate the interaction force profile between two grafted polymer brushes. The correlation between neighboring bonds and the interdigitation between the two brushes are taken into account. The calculations show that the effect of incorporating the bond correlations is equivalent to an increase in the value of the polymer-solvent interaction parameter when the bond correlations are ignored. The interdigitation between the two brushes decreases the free energy of the system and consequently results in a smaller steric repulsion. A complete interdigitation occurs at a separation close to half the separation between the two plates for which the interaction force is zero. The model is compared with the experimental interaction force profiles for ten systems which involve poly(2-vinylpyridine)-polyisoprene (PVP-PI), poly(2-vinylpyridine)-polystyrene (PVP-PS) block copolymers as well as end-functionalized polystyrenes (PS-X). For most of the systems, the theoretical predictions are in good agreement with experiment. In addition, the present results are compared with the equations proposed by de Gennes, based on the assumption of a step distribution function for the segment density, and by Milner et al., based on the parabolic distribution of the segment density. Both equations neglected interdigitation. It is shown in this paper that the interdigitation is not negligible and that it can decrease by an order of magnitude the repulsive force.

  14. Optical brush: Imaging through permuted probes

    PubMed Central

    Heshmat, Barmak; Lee, Ik Hyun; Raskar, Ramesh

    2016-01-01

    The combination of computational techniques and ultrafast imaging have enabled sensing through unconventional settings such as around corners, and through diffusive media. We exploit time of flight (ToF) measurements to enable a flexible interface for imaging through permuted set of fibers. The fibers are randomly distributed in the scene and are packed on the camera end, thus making a brush-like structure. The scene is illuminated by two off-axis optical pulses. Temporal signatures of fiber tips in the scene are used to localize each fiber. Finally, by combining the position and measured intensity of each fiber, the original input is reconstructed. Unlike conventional fiber bundles with packed set of fibers that are limited by a narrow field of view (FOV), lack of flexibility, and extended coaxial precalibration, the proposed optical brush is flexible and uses off-axis calibration method based on ToF. The enabled brush form can couple to other types of ToF imaging systems. This can impact probe-based applications such as, endoscopy, tomography, and industrial imaging and sensing. PMID:26868954

  15. Belize-Guatemala Border

    NASA Image and Video Library

    2017-08-29

    The border between Belize and Guatemala illustrates striking differences in land use practices. In a study of deforestation published in 2016, Chicas and co-authors found that in their study area between 1991 and 2014, on the Guatemalan side of the border forested land declined 32%; in Belize, forested area declined 11%. In part of their study area shown in this image, the difference is more dramatic: near-pristine forest in Belize on the right, and agricultural fields in Guatemala on the left. The image was acquired May 10, 2016, covers an area of 27 by 41 km, and is located at 16.7 degrees north, 89.2 degrees west. https://photojournal.jpl.nasa.gov/catalog/PIA21826

  16. Astronomers without borders

    NASA Astrophysics Data System (ADS)

    Simmons, Mike

    2011-06-01

    ``Astronomers Without Borders'' is a new global organisational dedicated to furthering understanding and goodwill across national and cultural boundaries using the universal appeal of astronomy and space science. A growing network of affiliate organisations brings together clubs, magazines and other organizations involved in astronomy and space science. Forums, galleries, video conferences and other interactive technologies are used to connect participants around the world. Sharing of resources and direct connections through travel programs are also planned. One project, ``The World at Night'' (TWAN), has become an Special Project of IYA2009. TWAN creates wide-angle images of the night sky in important natural and historic settings around the world, dramatically demonstrating the universal nature and appeal of the night sky. ``Astronomers Without Borders'' is also a leader of the 100 Hours of Astronomy IYA2009 Global Cornerstone Project.

  17. Metrics for border management systems.

    SciTech Connect

    Duggan, Ruth Ann

    2009-07-01

    There are as many unique and disparate manifestations of border systems as there are borders to protect. Border Security is a highly complex system analysis problem with global, regional, national, sector, and border element dimensions for land, water, and air domains. The complexity increases with the multiple, and sometimes conflicting, missions for regulating the flow of people and goods across borders, while securing them for national security. These systems include frontier border surveillance, immigration management and customs functions that must operate in a variety of weather, terrain, operational conditions, cultural constraints, and geopolitical contexts. As part of a Laboratory Directed Research and Development Project 08-684 (Year 1), the team developed a reference framework to decompose this complex system into international/regional, national, and border elements levels covering customs, immigration, and border policing functions. This generalized architecture is relevant to both domestic and international borders. As part of year two of this project (09-1204), the team determined relevant relative measures to better understand border management performance. This paper describes those relative metrics and how they can be used to improve border management systems.

  18. Alterations in gut microflora populations and brush border functionality following intra-amniotic daidzein administration

    USDA-ARS?s Scientific Manuscript database

    Daidzein is an isoflavone found primarily in soybean and various soy-based products such as tofu. In the intestines, daidzein is reductively transformed to its constituent metabolites equol and O-desmethylangolensin. Although the ingestion of daidzein has been associated with marked physiological im...

  19. The effect of prostaglandin synthase inhibitor, aspirin on the rat intestinal membrane structure and function.

    PubMed

    Kaur, G; Kaur, J; Mittal, N; Nath Sanyal, S

    2010-01-01

    Aspirin at a dose of 50 mg/kg body weight was found to decrease the activity of the rat intestinal brush border membrane (BBM) - associated enzymes such as the sucrase, lactase, maltase and alkaline phosphatase. Aspirin treatment also led to a decrease in the microviscosity in the native as well as the benzyl alcohol treated membrane which might be due to the lipid peroxidative damage in the membrane. Physical correlation of the membrane oxidative damage was evident as the Fourier Transformation Infra Red (FTIR) study of the Aspirin treated membrane, which include an increased proportion of gauche to trans conformer, shift in the methylene C-H asymmetric and symmetric stretching frequencies, C = O double bond stretching, NH bending, antisymmetric (N)-CH3 bending, C-N stretching and antisymmetric CNC stretching while there was no change in the CH2 wagging and twisting as well as in NH-bending amide bond I and II. Aspirin treatment also caused an alteration in the glucose and histidine transport, as evident by a decreased Vmax value while the apparent Km remaining unchanged in the control and Aspirin-treated animals confirming that there was no change in the substrate affinity constant of the membrane transport proteins for the glucose and the basic amino acid, although the rate of transport decreased considerably. There was a decrease noted in the energy of activation of glucose and histidine transport when studied at different temperature but no change in the temperature of phase transition in the BBM with Aspirin treatment, thus implying that perhaps the thermotropic phase transition in the membrane may have relatively little effect on the transport processes. The result suggests an underlying molecular mechanism indicating the implied membrane damage by Aspirin, an important member of the non-steroidal antiinflammatory drug (NSAID) family which could possibly through an oxidative damage may lead to an altered molecular structure, physical state and biological

  20. Rotordynamic and Leakage Characteristics of a 4-Stage Brush Seal

    DTIC Science & Technology

    1992-12-01

    AD-A266 012 WL-TR-92-2125 .AP ROTORDYNAMIC AND LEAKAGE CHARACTERISTICS OF A 4-STAGE BRUSH SEAL K. J. CONNER D. W. CHILDS TURBOMACHINERY LABORATORIES...pre-rotation, and seal spacing. Direct damping is shown to increase with running speed; otherwise, the rotordynamic coefficients are relatively...test results for the 4-stage brush seal with an 8-cavity labyrinth showed superior rotordynamics performance for the brush seal; viz., larger values for

  1. Magnetically Activated Self-Cleaning Membranes

    DTIC Science & Technology

    2010-06-01

    available nanofiltration membranes were modified by growing polymer brushes from the surface of the membrane. Two different polymerization methods have been...dimethylaminopyridine DMF: n,n-dimethylformamide EDC: 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide HEMA: 2-hydroxyethylmethacrylate NF: Nanofiltration NHS... nanofiltration , oily wastewaters, rejection, superparamagnetic nanoparticles Acknowledgements The financial support of the Strategic Environmental Research

  2. Morphological transformations in polymer brushes in binary mixtures: DPD study.

    PubMed

    Cheng, Jianli; Vishnyakov, Aleksey; Neimark, Alexander V

    2014-11-04

    Morphological transformations in polymer brushes in a binary mixture of good and bad solvents are studied using dissipative particle dynamics simulations drawing on a characteristic example of polyisoprene natural rubber in an acetone-benzene mixture. A coarse-grained DPD model of this system is built based on the experimental data in the literature. We focus on the transformation of dense, collapsed brush in bad solvent (acetone) to expanded brush solvated in good solvent (benzene) as the concentration of benzene increases. Compared to a sharp globule-to-coil transition observed in individual tethered chains, the collapsed-to-expanded transformation in brushes is found to be gradual without a prominent transition point. The transformation becomes more leveled as the brush density increases. At low densities, the collapsed brush is highly inhomogeneous and patterned into bunches composed of neighboring chains due to favorable polymer-polymer interaction. At high densities, the brush is expanded even in bad solvent due to steric restrictions. In addition, we considered a model system similar to the PINR-acetone-benzene system, but with the interactions between the solvent components worsened to the limit of miscibility. Enhanced contrast between good and bad solvents facilitates absorption of the good solvent by the brush, shifting the collapsed-to-expanded transformation to lower concentrations of good solvent. This effect is especially pronounced for higher brush densities.

  3. Carbazole functionalized isocyanide brushes in heterojunction photovoltaic devices.

    PubMed

    Lim, Eunhee; Gao, Feng; Schwartz, Erik; Cornelissen, Jeroen J L M; Nolte, Roeland J M; Rowan, Alan E; Greenham, Neil C; Do, Lee-Mi

    2012-01-01

    In this work, carbazole-containing polyisocyanide (PIACz) brushes were used for photovoltaic devices. A photovoltaic device was fabricated on top of the brushes by spin-coating a suitable acceptor and evaporating an Al cathode. Devices with a poly(N-vinylcarbazole) (PVK) bulk polymer were also prepared for comparison. Interestingly, the brushes showed better photovoltaic characteristics as compared to the blended PVK system. This is attributed to the specific morphologies of the polyisocyanide brushes, which provide a large interfacial area between the donor and acceptor for efficient photogeneration. It was found that the device performance varied according to the molecular size of the incorporated acceptors.

  4. Thermally controlled permeation of ionic molecules through synthetic nanopores functionalized with amine-terminated polymer brushes

    NASA Astrophysics Data System (ADS)

    Nasir, Saima; Ali, Mubarak; Ensinger, Wolfgang

    2012-06-01

    We present temperature-dependent ionic transport through an array of nanopores (cylindrical and conical) and a single conical nanopore functionalized with amine-terminated poly(N-isopropylacrylamide) [PNIPAAM-NH2] brushes. For this purpose, nanopores are fabricated in heavy ion irradiated polyethylene terephthlate (PET) membranes by a controlled chemical track-etching technique, which leads to the generation of carboxyl (COOH) groups on the pore surface. End-functionalized polymer chains are immobilized onto the inner pore walls via a ‘grafting-to’ approach through the covalent linkage of surface COOH moieties with the terminal amine groups of the PNIPAAM molecules by using carbodiimide coupling chemistry. The success of the chemical modification reaction is corroborated by measuring the permeation flux of charged analytes across the multipore membranes in an aqueous solution, and for the case of single conical pore by measuring the current-voltage (I-V) characteristics, which are dictated by the electrostatic interaction of the charged pore surface with the mobile ions in an electrolyte solution. The effective nanopore diameter is tuned by manipulating the environmental temperature due to the swelling/shrinking behaviour of polymer brushes attached to the inner nanopore walls, leading to a decrease/increase in the ionic transport across the membrane. This process should permit the thermal gating and controlled release of ionic drug molecules through the nanopores modified with thermoresponsive polymer chains across the membrane.

  5. LLC-PK sub 1 cells express Na sup + -lactate cotransport in apical membranes after confluency

    SciTech Connect

    Poustis-Delpont, C.; Mengual, R.; Sudaka, P. )

    1988-12-01

    L-({sup 3}H)lactate uptake was characterized in LLC-PK{sub 1} cell apical membrane vesicles obtained by intensive culture on microcarrier beads. The apical membrane preparation technique involved MgCl{sub 2} precipitation. Na{sup +}-dependent L-({sup 3}H)lactate uptake was present only after confluency; its appearance paralleled the subcellular localization of aminopeptidase in apical membranes. L-({sup 3}H)lactate uptake was Na{sup +}-dependent and electrogenic. Only the Na{sup +}-dependent component of L({sup 3}H)lactate uptake was saturable with one family of independent carriers. The apparent affinity constant was 1.1 {plus minus} 0.25 mM and the apparent maximal velocity was 29 {plus minus} 3 nmol{center dot}mg{sup {minus}1}{center dot}min{sup {minus}1}. The Na{sup +}-lactate cotransport stoichiometry was 2 Na{sup +} for 1 lactate. The specificity of the L-lactate transport system was compatible with that of the monocarboxylic acid pathway described previously brush-border membranes of kidney cortex and discrete from the tricarboxylic acid carrier, the D-glucose transporter, and the general pathway for anions. The LLC-PK{sub 1} cell line appears to be a useful tool for study of the regulation of L-lactate uptake and biosynthesis of the renal monocarboxylic acid transporter.

  6. Impact of glycosylation and detergent-resistant membranes on the function of intestinal sucrase-isomaltase.

    PubMed

    Wetzel, Gabi; Heine, Martin; Rohwedder, Arndt; Naim, Hassan Y

    2009-07-01

    Sucrase-isomaltase (SI) is a highly N- and O-glycosylated intestinal brush border membrane protein. SI is sorted with high fidelity to the apical membrane via O-linked glycans that mediate its association with lipid rafts or detergent-resistant membranes (DRMs). Here, we show that N- and O-glycosylation and DRMs are implicated in the regulation of the function of SI in intestinal Caco-2 cells. The activities of sucrase (SUC) and isomaltase (IM) increase substantially in DRMs when N- and O-glycosylation patterns are intact. Disruption of DRMs by solubilization with Triton X-100 at 37 degrees C substantially reduces the activities of SUC and IM. Furthermore, modulation of O-glycosylation by benzyl-2-acetamido-2-deoxy-alpha-d-galactopyranoside and N-glycosylation by deoxymannojirimycin is linked to a decreased capacity of SI to associate with DRMs, with a subsequent reduction of the enzymatic activities of SUC and IM. This is the first report that reveals a direct role of N- and O-glycans in association with DRMs in regulating the function of a membrane glycoprotein.

  7. Domain III substitution in Bacillus thuringiensis delta-endotoxin CryIA(b) results in superior toxicity for Spodoptera exigua and altered membrane protein recognition.

    PubMed Central

    de Maagd, R A; Kwa, M S; van der Klei, H; Yamamoto, T; Schipper, B; Vlak, J M; Stiekema, W J; Bosch, D

    1996-01-01

    To test our hypothesis that substitution of domain III of Bacillus thuringiensis delta-endotoxin (Cry) proteins might improve toxicity to pest insects, e.g., Spodoptera exigua, in vivo recombination was used to produce a number of cryIA(b)-cryIC hybrid genes. A rapid screening assay was subsequently exploited to select hybrid genes encoding soluble protoxins. Screening of 120 recombinants yielded two different hybrid genes encoding soluble proteins with domains I and II of CryIA(b) and domain III of CryIC. These proteins differed by only one amino acid residue. Both hybrid protoxins gave a protease-resistant toxin upon in vitro activation by trypsin. Bioassays showed that one of these CryIA(b)-CryIC hybrid proteins (H04) was highly toxic to S. exigua compared with the parental CryIA(b) protein and significantly more toxic than CryIC. In semiquantitative binding studies with biotin-labelled toxins and intact brush border membrane vesicles of S. exigua, this domain III substitution appeared not to affect binding-site specificity. However, binding to a 200-kDa protein by CryIA(b) in preparations of solubilized and blotted brush border membrane vesicle proteins was completely abolished by the domain III substitution. A reciprocal hybrid containing domains I and II of CryIC and domain III of CryIA(b) did bind to the 200-kDa protein, confirming that domain III of CryIA(b) was essential for this reaction. These results show that domain III of CryIC protein plays an important role in the level of toxicity to S. exigua, that substitution of domain III may be a powerful tool to increase the repertoire of available active toxins for pest insects, and that domain III is involved in binding to gut epithelium membrane proteins of S. exigua. PMID:8633853

  8. Effect of Frequency of Brushing Teeth on Plaque and Calculus Accumulation, and Gingivitis in Dogs.

    PubMed

    Harvey, Colin; Serfilippi, Laurie; Barnvos, Donald

    2015-01-01

    The efficacy of brushing the teeth of beagle dogs in a randomized, controlled, blinded study design using a clearly-defined brushing technique was evaluated for 4 brushing frequencies: brushing daily, brushing every other day, brushing weekly and brushing every other week, compared with no brushing in a control group of dogs. All dogs were fed a standard dry kibble diet during the study. Standard plaque, calculus, and gingivitis indices were used to score the teeth. A 'clean tooth' model was used. No gingival or non-gingival lacerations or other signs of injury to oral tissues were found at the end of the 28 day trial period. Brushing more frequently had greater effectiveness in retarding accumulation of plaque and calculus, and reducing the severity of pre-existing gingivitis. Brushing daily or every other day produced statistically significant improved results compared with brushing weekly or every other week. Based on the results of this study, daily brushing is recommended.

  9. Atmospheric Science Without Borders

    NASA Astrophysics Data System (ADS)

    Panday, Arnico; Praveen, Ps; Adhikary, Bhupesh; Bhave, Prakash; Surapipith, Vanisa; Pradhan, Bidya; Karki, Anita; Ghimire, Shreta; Thapa, Alpha; Shrestha, Sujan

    2016-04-01

    The Indo-Gangetic Plains (IGP) in northern South Asia are among the most polluted and most densely populated places in the world, and they are upwind of vulnerable ecosystems in the Himalaya mountains. They are also fragmented across 5 countries between which movement of people, data, instruments and scientific understanding have been very limited. ICIMOD's Atmosphere Initiative has for the past three years been working on filling data gaps in the region, while facilitating collaborations across borders. It has established several atmospheric observatories at low and mid elevations in Bhutan and Nepal that provide new data on the inflow of pollutants from the IGP towards the mountains, as well as quantify the effects of local emissions on air quality in mountain cities. EGU will be the first international conference where these data will be presented. ICIMOD is in the process of setting up data servers through which data from the region will be shared with scientists and the general public across borders. Meanwhile, to promote cross-border collaboration among scientists in the region, while addressing an atmospheric phenomenon that affects the lives of the several hundred million people, ICIMOD' Atmosphere Initiative has been coordinating an interdisciplinary multi-year study of persistent winter fog over the Indo-Gangetic Plains, with participation by researchers from Pakistan, India, China, Nepal, Bhutan and Bangladesh. Using a combination of in-situ measurements and sample collection, remote sensing, modeling and community based research, the researchers are studying how changing moisture availability and air pollution have led to increases in fog frequency and duration, as well as the fog's impacts on local communities and energy demand that may affect air pollution emissions. Preliminary results of the Winter 2015-2016 field campaign will be shown.

  10. Collaborating Across Borders

    NASA Astrophysics Data System (ADS)

    Flatten, Amy

    Physicists transcend national boundaries, ethnic differences, and scientific disciplines to address globally shared problems and questions. This talk will highlight how scientists have collaborated across borders - both geographic and scientific - to achieve ground-breaking discoveries through international scientific cooperation. The speaker also will address how international collaborations will be even more crucial for addressing future challenges faced by the physics community, such as building large-scale research facilities, strengthening scientific capacity in developing countries, fostering ''science for diplomacy'' in times of political tensions and other critical issues.

  11. Degradative inactivation of cyclic AMP-dependent protein kinase by a membranal proteinase is restricted to the free catalytic subunit in its native conformation.

    PubMed Central

    Alhanaty, E; Patinkin, J; Tauber-Finkelstein, M; Shaltiel, S

    1981-01-01

    A membranal proteinase from brush-border epithelial cells of the rat small intestine was shown to bring about a restricted and limited degradation of the free catalytic subunit (C) of cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) with concomitant inactivation of the kinase. This membranal proteinase exhibits a remarkable specificity. (i) It degrades C in its native conformation, but not after it has been heat-denatured. (ii) The degradation of C (Mr 40,000) does not proceed further, once a distinct clipped product (Mr 34,000) is formed. (iii) The undissociated ("stored") form of the enzyme (R2C2) is not attacked by the membranal proteinase, preserving both its potential catalytic activity and its molecular integrity. Only upon addition of cyclic AMP to release free C does the proteinase attack it. (iv) The membranal proteinase does not degrade the regulatory subunit (R), released by cyclic AMP from R2C2, although R is quite susceptible to degradation by other proteolytic enzymes. None of these features of the membranal proteinase could be reproduced with trypsin, chymotrypsin, clostripain, or papain. The specific, restricted, and limited action of this membranal enzyme raises the possibility that it may have a distinct physiological assignment associated with the bioregulation of cyclic AMP-dependent protein kinase. Images PMID:6267595

  12. Degradative inactivation of cyclic AMP-dependent protein kinase by a membranal proteinase is restricted to the free catalytic subunit in its native conformation.

    PubMed

    Alhanaty, E; Patinkin, J; Tauber-Finkelstein, M; Shaltiel, S

    1981-06-01

    A membranal proteinase from brush-border epithelial cells of the rat small intestine was shown to bring about a restricted and limited degradation of the free catalytic subunit (C) of cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) with concomitant inactivation of the kinase. This membranal proteinase exhibits a remarkable specificity. (i) It degrades C in its native conformation, but not after it has been heat-denatured. (ii) The degradation of C (Mr 40,000) does not proceed further, once a distinct clipped product (Mr 34,000) is formed. (iii) The undissociated ("stored") form of the enzyme (R2C2) is not attacked by the membranal proteinase, preserving both its potential catalytic activity and its molecular integrity. Only upon addition of cyclic AMP to release free C does the proteinase attack it. (iv) The membranal proteinase does not degrade the regulatory subunit (R), released by cyclic AMP from R2C2, although R is quite susceptible to degradation by other proteolytic enzymes. None of these features of the membranal proteinase could be reproduced with trypsin, chymotrypsin, clostripain, or papain. The specific, restricted, and limited action of this membranal enzyme raises the possibility that it may have a distinct physiological assignment associated with the bioregulation of cyclic AMP-dependent protein kinase.

  13. Nuclear Pore Complex Protein Sequences Determine Overall Copolymer Brush Structure and Function?

    NASA Astrophysics Data System (ADS)

    Ando, David; Kim, Yongwoon; Zandi, Roya; Colvin, Michael; Rexach, Michael; Gopinathan, Ajay

    2015-03-01

    Disordered proteins are an interesting class of unfolded protein biopolymers which are functionally versatile. Their sequences are unconstrained by a sequence-structure relationship, and allow for a wide range of chemical and physical polymer properties. The Nuclear Pore Complex (NPC) contains over one hundred of such proteins (FG nups), which collectively function to regulate the exchange of all materials between the nucleus and cytoplasm. We perform coarse grained simulations of both individual FG nups and grafted rings of nups mimicking the in vivo geometry of the NPC, supplemented with polymer brush modeling. Our results indicate that different regions or ``blocks'' of an individual FG nup can have distinctly different forms of disorder, and that this property appears to be a conserved feature across eukarya. Furthermore, this block structure at the individual protein level is critical to the formation of a unique higher-order polymer brush architecture. Because the interactions between FG nups may be modulated by certain forms of transport factors, our results indicate that transitions between brush morphologies could play an important role in regulating transport across the NPC, suggesting novel forms of gated transport across membrane pores with wide biomimetic applicability.

  14. JTAGG II Brush Seal Test Results

    NASA Technical Reports Server (NTRS)

    Arora, Gul K.; Proctor, Margaret P.

    1997-01-01

    The Tri-services JTAGG 2 engine uses two identical brush seals, in tandem, located aft of the high pressure compressor. The engine operating conditions, at intermediate rated power (IRP), for this seal are estimated to be 50,000 rpm (899 ft/sec) speed, 175 psid air to air pressure differential and 1200 F air temperature. The testing was comprised of static air leakage, performance, seal offset, rotor run out tests and a 50 hr endurance test in the NASA Lewis seal rig. Based on the test results, it is concluded that the brush seal design should be able to meet the air leakage flow factor goal of less than 0.004 for the engine IRP operating conditions. For the 4.12 in. i.d. labyrinth seal, 0.005 in. typical radial clearance, at the JTAGG 2 operating conditions, the leakage flow factor is 0.007. The long term seal life can not be predicted accurately due to the limited endurance testing of 50 hr. However, based on the excellent condition of the test seal and rotor after 50 hr of testing, it is anticipated that the seals should easily meet the JTAGG 2 engine test requirement.

  15. The hydration properties of carboxybetaine zwitterion brushes.

    PubMed

    Du, Hongbo; Qian, Xianghong

    2016-04-15

    Combined quantum mechanical calculations and classical molecular dynamics simulations were conducted to investigate the hydration properties of carboxybetaine zwitterion brushes with varying separation distances between the quaternary ammonium cation and carboxylic anion. The brushes consist of zwitterion trimers and are investigated to mimic interacting zwitterion chains grafted on a substrate as well as polymers with interacting zwitterion side chains. Our results show that the values of both positive and negative charges, their separation distances as well as chain interactions appear to play a critical role in the hydration properties of the zwitterions. The overall hydration property of these zwitterions is dictated by the competition between the strong hydration of the charged groups and the dehydration of the hydrocarbon chains. The strongest hydration occurs when the -CH2- unit in the hydrocarbon chain reaches 6-8 for these trimers. Further increase in the hydrocarbon chain length to 10-14 leads to significant and sudden dehydration of the trimers. The water structure and the water residence time surrounding the zwitterions also demonstrate substantial alteration at this length scale. This hydrophilic-to-hydrophobic transition is induced by the hydrophobic interactions of the trimer chains. Our hydration results could explain the observed trend of the superiority of the methylated carbohydrates and poly(ethylene glycol) as antifouling materials compared to corresponding hydroxyl-terminated compounds.

  16. EUV mask black border evolution

    NASA Astrophysics Data System (ADS)

    Turley, Christina; Bonam, Ravi; Gallagher, Emily; Grohs, Jonathan; Kagawa, Masayuki; Kindt, Louis; Narita, Eisuke; Nash, Steven; Sakamoto, Yoshifumi

    2014-10-01

    The black border is a frame created by removing all the multilayers on the EUV mask in the region around the chip. It is created to prevent exposure of adjacent fields when printing an EUV mask on a wafer. Papers have documented its effectiveness. As the technology transitions into manufacturing, the black border must be optimized from the initial mask making process through its life. In this work, the black border is evaluated in three stages: the black border during fabrication, the final sidewall profile, and extended lifetime studies. This work evaluates the black border through simulations and physical experiments. The simulations address concerns for defects and sidewall profiles. The physical experiments test the current black border process. Three masks are used: one mask to test how black border affects the image placement of features on mask and two masks to test how the multilayers change through extended cleans. Data incorporated in this study includes: registration, reflectivity, multilayer structure images and simulated wafer effects. By evaluating the black border from both a mask making perspective and a lifetime perspective, we are able to characterize how the structure evolves. The mask data and simulations together predict the performance of the black border and its ability to maintain critical dimensions on wafer. In this paper we explore what mask changes occur and how they will affect mask use.

  17. The Effects of a Brushing Procedure on Stereotypical Behavior

    ERIC Educational Resources Information Center

    Davis, Tonya N.; Durand, Shannon; Chan, Jeffrey M.

    2011-01-01

    In this study we analyzed the effects of a brushing protocol on stereotyped behavior of a young boy with autism. First, a functional analysis was conducted which showed that the participant's stereotypy was maintained by automatic reinforcement. Next, the Wilbarger Protocol, a brushing intervention, was implemented. An ABA design was implemented…

  18. Using goats to control brush regrowth on fuelbreaks

    Treesearch

    Lisle R. Green; Leonard A. Newell

    1982-01-01

    On fuelbreaks, herbicides have been the primary tool for controlling brush regrowth. Vegetation of low volume and low growth is maintained on these wide strips as an aid to firefighting safety. Goats are a promising alternative to herbicides, and may be the best tool available for controlling brush regrowth on fuelbreaks. They eat a wider variety of plants, and more...

  19. Shear and normal forces in charged polymer brushes

    NASA Astrophysics Data System (ADS)

    Liao, Qi; Rubinstein, Michael

    2015-03-01

    We present the results of molecular dynamics simulations of steady shear between a pair of opposing charged polymer brushes in the osmotic-brush regime and compare the results with predictions of scaling models. Using the monomer and counterion density profiles, we have verified different regimes in the diagram of states of compressed polyelectrolyte brushes predicted by the scaling model of Zhulina et al[Macromolecules, 2014]. Our simulation results for the normal forces of compressed polyelectrolyte brushes are in excellent agreement with predictions of the scaling model. However, our results for the dependence of the shear forces on the separation between brushes are only in qualitative agreement with the predictions of the scaling model. The dependence of the interpenetration length on the separation of polyelectrolyte brushes exhibits a maximum instead of the plateau predicted by the scaling model for the partially interpenetrated brushes. Our simulation results confirm that our implicit solvent simulations of polyelectrolyte brushes that ignore hydrodynamics interaction are in agreement with the scaling predictions that include hydrodynamic interaction because of screening of hydrodynamic interaction and long range electrostatic interactions on the correlation length scale.

  20. 16 CFR Figure 9 to Part 1610 - Brushing Device Template

    Code of Federal Regulations, 2012 CFR

    2012-01-01

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  1. 16 CFR Figure 7 to Part 1610 - Brushing Device

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...

  2. 16 CFR Figure 7 to Part 1610 - Brushing Device

    Code of Federal Regulations, 2010 CFR

    2010-01-01

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  3. 16 CFR Figure 7 to Part 1610 - Brushing Device

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...

  4. 16 CFR Figure 9 to Part 1610 - Brushing Device Template

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 9 Figure 9 to Part 1610—Brushing...

  5. 16 CFR Figure 7 to Part 1610 - Brushing Device

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...

  6. 16 CFR Figure 8 to Part 1610 - Brush

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...

  7. 16 CFR Figure 9 to Part 1610 - Brushing Device Template

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 9 Figure 9 to Part 1610—Brushing...

  8. 16 CFR Figure 9 to Part 1610 - Brushing Device Template

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 9 Figure 9 to Part 1610—Brushing...

  9. 16 CFR Figure 8 to Part 1610 - Brush

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...

  10. 16 CFR Figure 8 to Part 1610 - Brush

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...

  11. 16 CFR Figure 8 to Part 1610 - Brush

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt. 1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...

  12. 16 CFR Figure 9 to Part 1610 - Brushing Device Template

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Brushing Device Template 9 Figure 9 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 9 Figure 9 to Part 1610—Brushing...

  13. 16 CFR Figure 7 to Part 1610 - Brushing Device

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Brushing Device 7 Figure 7 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 7 Figure 7 to Part 1610—Brushing Device ER25MR08.006...

  14. 16 CFR Figure 8 to Part 1610 - Brush

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Brush 8 Figure 8 to Part 1610 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS STANDARD FOR THE FLAMMABILITY OF CLOTHING TEXTILES Pt.1610, Fig. 8 Figure 8 to Part 1610—Brush ER25MR08.007...

  15. 75 FR 21347 - Natural Bristle Paint Brushes From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-23

    ... COMMISSION Natural Bristle Paint Brushes From China AGENCY: United States International Trade Commission. ACTION: Scheduling of a full five-year review concerning the antidumping duty order on natural bristle... whether revocation of the antidumping duty order on natural bristle paint brushes from China would be...

  16. 75 FR 39706 - Natural Bristle Paint Brushes From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-12

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Natural Bristle Paint Brushes From China AGENCY: United States International Trade Commission... the antidumping duty order on natural bristle paint brushes from China (75 FR 21347, April 23, 2010...

  17. 75 FR 18237 - Natural Bristle Paint Brushes From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-09

    ... COMMISSION Natural Bristle Paint Brushes From China AGENCY: United States International Trade Commission... duty order on natural bristle paint brushes from China. SUMMARY: The Commission hereby gives notice....C. 1675(c)(5)) to determine whether revocation of the antidumping duty order on natural bristle...

  18. Physical characteristics of some northern California brush fuels

    Treesearch

    Clive M. Countryman

    1982-01-01

    Brush species make up much of the fuel load in forested wildlands. Basic physical and chemical characteristics of these species influence ease of ignition, rate of fire spread, burning time, and fire intensity. Quantitative knowledge of the variations in brush characteristics is essential to progress in fire control and effective use of fire in wildland management....

  19. A Critique of the Brushing for Life Programme

    ERIC Educational Resources Information Center

    Downer, Martin C.; Drugan, Caroline S.; Blinkhorn, Anthony S.

    2006-01-01

    Background and objective: Brushing for Life is intended to promote regular brushing of children's teeth with fluoride toothpaste. The programme is delivered by health visitors who provide toothbrushes, toothpaste and dental health education material at children's 8, 18 and 36 month development checks. The purpose of the present paper was to…

  20. The Effects of a Brushing Procedure on Stereotypical Behavior

    ERIC Educational Resources Information Center

    Davis, Tonya N.; Durand, Shannon; Chan, Jeffrey M.

    2011-01-01

    In this study we analyzed the effects of a brushing protocol on stereotyped behavior of a young boy with autism. First, a functional analysis was conducted which showed that the participant's stereotypy was maintained by automatic reinforcement. Next, the Wilbarger Protocol, a brushing intervention, was implemented. An ABA design was implemented…

  1. Effects of material choices on brush seal performance

    NASA Astrophysics Data System (ADS)

    Atkinson, Edward; Bristol, Brent

    1992-09-01

    This paper discusses some of the initial hot and cold material testing undertaken in a brush seal development program. It describes the effects of material selection on relative wear and leakage of brush seals. Criteria for ranking wear couples are addressed.

  2. Wildlife response to brush management: a contemporary evaluation

    USDA-ARS?s Scientific Manuscript database

    Brush management has been widely practiced with the general intent of curtailing or reversing the proliferation of shrubs and trees in grasslands and savannas. The traditional aim of brush management has been to increase livestock forage or to improve water yield. Its potential role for restoring h...

  3. A Critique of the Brushing for Life Programme

    ERIC Educational Resources Information Center

    Downer, Martin C.; Drugan, Caroline S.; Blinkhorn, Anthony S.

    2006-01-01

    Background and objective: Brushing for Life is intended to promote regular brushing of children's teeth with fluoride toothpaste. The programme is delivered by health visitors who provide toothbrushes, toothpaste and dental health education material at children's 8, 18 and 36 month development checks. The purpose of the present paper was to…

  4. Method for making a high current fiber brush collector

    NASA Astrophysics Data System (ADS)

    Scuro, S. J.

    1986-05-01

    An axial-type homopolar motor having high density, high current fiber brush collectors affording efficient, low contact resistance and low operating temperatures is discussed. The collectors include a ring of concentric row of brushes in equally spaced beveled holes soldered in place using a fixture for heating the ring to just below the solder melting point at a soldering iron for the local application of additional heat at each brush. Prior to soldering, an oxide film is formed on the surfaces of the brushes and ring, and the bevels are burnished to form a wetting surface. Flux applied with the solder at each bevel removes to an effective soldering depth the oxide film on the brushes and the holes.

  5. Simple effective thickness model for circular brush seals

    NASA Astrophysics Data System (ADS)

    Dowler, Constance A.; Chupp, Raymond E.; Holle, Glenn F.

    1992-07-01

    Brush seals are being investigated as replacements for some of the labyrinth seals in gas turbine engines. A relatively simple flow model approach has been presented to generalize brush seal leakage throughout the range of test and application environments. The model uses a single parameter, effective brush thickness, to correlate flow through the seal. A revision to the flow model is presented in this paper to account for seal curvature, which is especially important for smaller diameter brush seals. The revised model has been applied to leakage flow data from five sources. The results demonstrate the utility of the flow model approach in correlating the performance of brush seals having different design geometries. The revised model is shown to effectively account for the effect of seal curvature.

  6. Surface Fluctuations of Polymer Brushes Swollen in Good Solvent Vapor

    SciTech Connect

    Sun, Liang; Akgun, Bulent; Narayanan, Suresh; Jiang, Zhang; Mark, Foster

    2016-10-11

    Swollen polymer brushes are found in many systems where the brush is intended to mediate interactions with the surroundings. The surface height fluctuations of planar polystyrene brushes (0.04 – 0.63 chains/nm2) highly swollen in toluene vapor are so strongly slowed by the tethering of the chains that they are unobservable in the current experimental window of length and time. This is the case despite the fact that the segmental dynamics of the brush chains should be very fast due to the substantial plasticization by the solvent. With respect to thermally stimulated fluctuations, the surfaces of these swollen brushes are solid-like on time scales and length scales pertinent to many practical applications.

  7. Computer Simulations of Bottle Brushes: From Melts to Soft Networks

    SciTech Connect

    Cao, Zhen; Carrillo, Jan-Michael Y.; Sheiko, Sergei S.; Dobrynin, Andrey V.

    2015-07-13

    We use a combination of Molecular dynamics simulations and analytical calculations, and study dens bottle-brush systems in a melt and network State. Analysis of our simulation results shows that bottle-brush macromolecules in melt behave as ideal chains with effective Kuhn length bK. Simulations show that the bottle-brush-induced bending rigidity is due to an entropy decrease caused by redistribution of the side chains upon backbone bending. The Kuhn length of the bottle:brushes increases with increasing the side-chain degree of polymerization nsc as bK proportional to nsc0.46. Moreover, this model of bottle brush macromolecules is extended to describe mechanical properties of bottle brush networks in linear and nonlinear deformation regimes. In the linear deformation regime, the network shear modulus scales with the degree of polymerization of the side chains as G0 proportional to (nsc + 1)-1 as long as the ratio of the Kuhn length, bK, to the size of the fully extended bottle-brush backbone between cross-links, R-max, is smaller than unity, bK/Rmax << 1. Bottle-brush networks With bK/Rmax proportional to 1 demonstrate behavior similar to that of networks Of semiflexible chains with G0 proportional to nsc-0.5. Finally, in the nonlinear network deformation regime, the deformation-dependent shear modulus is a universal function of the first strain invariant I1 and bottle-brush backbone deformation ratio beta describing stretching ability of the bottle-brush backbone between cross-links.

  8. Computer Simulations of Bottle Brushes: From Melts to Soft Networks

    DOE PAGES

    Cao, Zhen; Carrillo, Jan-Michael Y.; Sheiko, Sergei S.; ...

    2015-07-13

    We use a combination of Molecular dynamics simulations and analytical calculations, and study dens bottle-brush systems in a melt and network State. Analysis of our simulation results shows that bottle-brush macromolecules in melt behave as ideal chains with effective Kuhn length bK. Simulations show that the bottle-brush-induced bending rigidity is due to an entropy decrease caused by redistribution of the side chains upon backbone bending. The Kuhn length of the bottle:brushes increases with increasing the side-chain degree of polymerization nsc as bK proportional to nsc0.46. Moreover, this model of bottle brush macromolecules is extended to describe mechanical properties of bottlemore » brush networks in linear and nonlinear deformation regimes. In the linear deformation regime, the network shear modulus scales with the degree of polymerization of the side chains as G0 proportional to (nsc + 1)-1 as long as the ratio of the Kuhn length, bK, to the size of the fully extended bottle-brush backbone between cross-links, R-max, is smaller than unity, bK/Rmax << 1. Bottle-brush networks With bK/Rmax proportional to 1 demonstrate behavior similar to that of networks Of semiflexible chains with G0 proportional to nsc-0.5. Finally, in the nonlinear network deformation regime, the deformation-dependent shear modulus is a universal function of the first strain invariant I1 and bottle-brush backbone deformation ratio beta describing stretching ability of the bottle-brush backbone between cross-links.« less

  9. Structure of Polyelectrolyte Brushes in the Presence of Multivalent Counterions

    SciTech Connect

    Yu, Jing; Mao, Jun; Yuan, Guangcui; Satija, Sushil; Jiang, Zhang; Chen, Wei; Tirrell, Matthew

    2016-07-20

    Polyelectrolyte brushes are of great importance to a wide range of fields, ranging from colloidal stabilization to responsive and tunable materials to lubrication. Here, we synthesized high-density polystyrenesulfonate (PSS) brushes using surface initiated atom transfer radical polymerization and performed neutron reflectivity (NR) and surface force measurements using a surface forces apparatus (SFA) to investigate the effect of monovalent Na+, divalent Ca2+, Mg2+, and Ba2+, and trivalent Y3+ counterions on the structure of the PSS brushes. NR and SFA results demonstrate that in monovalent salt solution the behavior of the PSS brushes agrees with scaling theory well, exhibiting two distinct regimes: the osmotic and salted brush regimes. Introducing trivalent Y3+ cations causes an abrupt shrinkage of the PSS brush due to the uptake of Y3+ counterions. The uptake of Y3+ counterions and shrinkage of the brush are reversible upon increasing the concentration of monovalent salt. Divalent cations, Mg2+, Ca2+, and Ba2+, while all significantly affecting the structure of PSS brushes, show strong ion specific effects that are related to the specific interactions between the divalent cations and the sulfonate groups. Our results demonstrate that the presence of multivalent counterions, even at relatively low concentrations, can strongly affect the structure of polyelectrolyte brushes. Finally, the results also highlight the importance of ion specificity to the structure of polyelectrolyte brushes in solution.

  10. Potential applications of oral brush cytology with liquid-based technology: results from a cohort of normal oral mucosa.

    PubMed

    Kujan, Omar; Desai, Mina; Sargent, Alexandra; Bailey, Andrew; Turner, Andrew; Sloan, Philip

    2006-09-01

    Fifty healthy volunteers were studied to assess the potential applications of oral brush sampling using liquid-based cytology. Three specimens from the buccal mucosa and lateral border of tongue were collected from each subject by using cervical brushes and brooms. The brush was immersed in a preservative fluid. The sample in the preservative fluid was processed according to the manufacturer's directions (SurePath, UK). Slides were stained by the Papanicolaou method and assessed for squamous cell adequacy by the same criteria used for cervical cytology screening. Immunocytochemical staining for FHIT (Fragile Histidine Triad) was applied in liquid-based preparations following the streptavidin-biotin-peroxidase method. Human papillomavirus (HPV) detection was performed using the Hybrid Capture 2 assay (Digene) and the PCR-based Roche AMPLICOR HPV Test. LBC preparation slides showed good sample preservation, specimen adequacy and visualization of cell morphology. Interestingly, nine cases showed borderline cytological abnormalities from apparently normal oral mucosa. All cases showed good quality positive FHIT immunoreactivity staining. All studied cases were high-risk HPV negative using HC2 assay method. However, the AMPLICOR Roche Test detected four samples with positive results for high-risk HPVs. Liquid-based cytology has potential as a screening tool for oral cancer and precancer. The method may also have applications for research and practice in the field of oral cancer and precancer. However a special custom-designed oral cytobrush is required.

  11. Anesthesia education across borders.

    PubMed

    Dohlman, Lena E

    2013-12-01

    Changing attitudes toward global health are affecting medical education programs at all levels in the USA and abroad. This review describes some of these changes, and how these affect the educational aspects of US global health programs and anesthesia training in developing countries. Interest in global health has surged in the past decade, and support for programs has increased in medical schools, university hospitals and from the US government. Recognition of the surgical burden of disease as a global public health problem has been slow but is also increasing. Anesthesia involvement in building healthcare education infrastructure and workforce in low-resource countries is needed and important, and benefits can be had on both sides of the border. The past 5 years have brought a new global focus on workforce development and education in anesthesia. Programs need to be supported by all stakeholders and monitored for safety, quality and outcomes.

  12. Life on the Hardened Border

    ERIC Educational Resources Information Center

    Miller, Bruce Granville

    2012-01-01

    The many Coast Salish groups distributed on both sides of the United States-Canada border on the Pacific coast today face significant obstacles to cross the international border, and in some cases are denied passage or intimidated into not attempting to cross. The current situation regarding travel by Aboriginal people reflects the…

  13. Life on the Hardened Border

    ERIC Educational Resources Information Center

    Miller, Bruce Granville

    2012-01-01

    The many Coast Salish groups distributed on both sides of the United States-Canada border on the Pacific coast today face significant obstacles to cross the international border, and in some cases are denied passage or intimidated into not attempting to cross. The current situation regarding travel by Aboriginal people reflects the…

  14. Effect of alcohols on gastric and small intestinal apical membrane integrity and fluidity.

    PubMed Central

    Ballard, H J; Wilkes, J M; Hirst, B H

    1988-01-01

    Duodenal and jejunal brush border membrane vesicle integrity was studied after in vitro treatment of rabbit tissue with ethyl, benzyl or octyl alcohol. The effects of the alcohols on gastric parietal cell apical and microsomal membrane vesicle integrity was also studied. Membrane vesicle integrity was determined from the enclosed volume of the vesicle preparations, measured as [14C]glucose space at equilibrium. Exposure of vesicles to the three alcohols caused concentration dependent decreases in enclosed volume. The rank order of potency of the alcohol was octyl greater than benzyl greater than ethyl. Concentrations greater than or equal to 10 mM benzyl alcohol significantly reduced the enclosed volume of duodenal or jejunal vesicles; jejunal vesicles were disrupted by 625 mM ethanol, whereas 2 M ethanol was required to disrupt the duodenal vesicles. Gastric apical membrane integrity was reduced with 0.25 M ethanol, the vesicles being approximately an order of magnitude more sensitive to ethanol than gross estimates of gastric mucosal damage, but 1 M ethanol was required to significantly damage gastric microsomes. All concentrations of benzyl or octyl alcohol tested (greater than or equal to 5 mM) reduced the enclosed volume of both gastric apical membrane vesicles and gastric microsomes. As determined by shrink-swell techniques, benzyl alcohol permeated duodenal vesicles at a faster rate than NH4Cl (apparent rate constant of 9.89 (0.71) X 10(-3)s-1 compared with 4.48 (0.23) X 10(-3)s-1). Therefore, reductions in enclosed volume in response to alcohol treatment could not be explained by alcohol induced osmotic shrinkage. The enclosed volume of the vesicles after alcohol treatment was negatively correlated with membrane fluidity suggesting a common causal effect, the increased fluidity increasing membrane fragility. Duodenal vesicles were more resistant to disruption by the alcohols compared with gastric and jejunal vesicles. PMID:3220304

  15. A Comparison of the Sensitivity of Brush Allodynia and Semmes-Weinstein Monofilament Testing in the Detection of Allodynia Within Regions of Secondary Hyperalgesia in Humans.

    PubMed

    Maracle, Emmalee C; Hung, Laurie Y; Fell, Sabrina I; Osmond, Michael R; Brown, Stephen H M; Srbely, John Z

    2017-01-01

    Two of the most common Quantitative Sensory Techniques (QST) employed to detect allodynia include mechanical brush allodynia and Semmes-Weinstein monofilaments. However, their relative sensitivity at detecting allodynia is poorly understood. The purpose of this study was to compare the sensitivity of brush allodynia against Semmes-Weinstein monofilament technique for detecting allodynia within regions of secondary hyperalgesia in humans. Twenty subjects (10 males, 10 females; 21.1 ± 0.9 years) were recruited and randomly allocated to allodynia or monofilament groups. Topical capsaicin (Zostrix 0.075%) was applied to a target region defined by C4-C7 dermatomes. Allodynia testing was performed at 0- (baseline) and 10 minutes postcapsaicin. The Semmes-Weinstein group assessed changes in skin sensitivity 8 cm inferior to target region and 2 cm lateral to the spinous process, while brush allodynia was employed to detect the point inferior to the target region where subjects reported changes in skin sensitivity. The distance (cm) from this point to the inferior border of the target region was termed the Allodynia Score. Statistically significant increases in the Allodynia Score were observed at 10 minutes postcapsaicin compared to baseline (P < 0.001). No differences in monofilament scores were observed between 10 minutes postcapsaicin and baseline (P = 0.125). Brush allodynia also demonstrated superior sensitivity, detecting allodynia in 100% of cases compared to 60% in the Semmes-Weinstein group. Brush allodynia is more sensitive than Semmes-Weinstein monofilaments for detecting mechanical allodynia in regions of secondary hyperalgesia. Brush allodynia may be preferred over Semmes-Weinstein monofilaments for clinical applications requiring reliable detection of allodynia. © 2016 World Institute of Pain.

  16. Microsensors for border patrol applications

    NASA Astrophysics Data System (ADS)

    Falkofske, Dwight; Krantz, Brian; Shimazu, Ron; Berglund, Victor

    2005-05-01

    A top concern in homeland security efforts is the lack of ability to monitor the thousands of miles of open border with our neighbors. It is not currently feasible to continually monitor the borders for illegal intrusions. The MicroSensor System (MSS) seeks to achieve a low-cost monitoring solution that can be efficiently deployed for border patrol applications. The modifications and issues regarding the unique requirements of this application will be discussed and presented. The MicroSensor System was developed by the Defense Microelectronics Activity (DMEA) for military applications, but border patrol applications, with their unique sensor requirements, demand careful adaptation and modification from the military application. Adaptation of the existing sensor design for border applications has been initiated. Coverage issues, communications needs, and other requirements need to be explored for the border patrol application. Currently, border patrol has a number of deficiencies that can be addressed with a microsensor network. First, a distributed networked sensor field could mitigate the porous border intruder detection problem. Second, a unified database needs to be available to identify aliens attempting to cross into the United States. This database needs to take unique characteristics (e.g. biometrics, fingerprints) recovered from a specialized field unit to reliably identify intruders. Finally, this sensor network needs to provide a communication ability to allow border patrol officers to have quick access to intrusion information as well as equipment tracking and voice communication. MSS already addresses the sensing portion of the solution, including detection of acoustic, infrared, magnetic, and seismic events. MSS also includes a low-power networking protocol to lengthen the battery life. In addition to current military requirements, MSS needs a solar panel solution to extend its battery life to 5 years, and an additional backbone communication link

  17. Dispersing brush mice prefer habitat like home

    PubMed Central

    Mabry, Karen E; Stamps, Judy A

    2007-01-01

    During natal dispersal, young animals leave their natal area and search for a new area to live. In species in which individuals inhabit different types of habitat, experience with a natal habitat may increase the probability that a disperser will select the same type of habitat post-dispersal (natal habitat preference induction or NHPI). Despite considerable interest in the ecological and the evolutionary implications of NHPI, we lack empirical evidence that it occurs in nature. Here we show that dispersing brush mice (Peromyscus boylii) are more likely to search and settle within their natal habitat type than expected based on habitat availability. These results document the occurrence of NHPI in nature and highlight the relevance of experience-generated habitat preferences for ecological and evolutionary processes. PMID:18077253

  18. Sterilization effects of atmospheric cold plasma brush

    NASA Astrophysics Data System (ADS)

    Yu, Q. S.; Huang, C.; Hsieh, F.-H.; Huff, H.; Duan, Yixiang

    2006-01-01

    This study investigated the sterilization effects of a brush-shaped plasma created at one atmospheric pressure. A population of 1.0×104-1.0×105 Escherichia coli or Micrococcus luteus bacteria was seeded in filter paper media and then subjected to Ar and/or Ar +O2 plasmas. A complete kill of the Micrococcus luteus required about 3 min argon plasma exposures. With oxygen addition into the argon plasma gas streams, a complete kill of the bacteria needed only less than 1 min plasma exposure for Micrococcus luteus and about 2 min exposure for Escherichia coli. The plasma treatment effects on the different bacteria cell structures were examined using scanning electron microscopy.

  19. Sterilization effects of atmospheric cold plasma brush

    SciTech Connect

    Yu, Q.S.; Huang, C.; Hsieh, F.-H.; Huff, H.; Duan Yixiang

    2006-01-02

    This study investigated the sterilization effects of a brush-shaped plasma created at one atmospheric pressure. A population of 1.0x10{sup 4}-1.0x10{sup 5} Escherichia coli or Micrococcus luteus bacteria was seeded in filter paper media and then subjected to Ar and/or Ar+O{sub 2} plasmas. A complete kill of the Micrococcus luteus required about 3 min argon plasma exposures. With oxygen addition into the argon plasma gas streams, a complete kill of the bacteria needed only less than 1 min plasma exposure for Micrococcus luteus and about 2 min exposure for Escherichia coli. The plasma treatment effects on the different bacteria cell structures were examined using scanning electron microscopy.

  20. CO₂-lased enamel microhardness after brushing and cariogenic challenge.

    PubMed

    Corrêa-Afonso, Alessandra Marques; Bachmann, Luciano; de Almeida, Cíntia Guimarães; Dibb, Regina Guenka Palma; Corona, Silmara Aparecida Milori; Borsatto, Maria Cristina

    2013-10-01

    This study aimed to assess how the wear that brushing promotes affects CO₂ laser-irradiated enamel microhardness after cariogenic challenge in vitro. Forty fragments measuring 4 × 4 mm were randomly assigned to four groups according to the enamel surface treatment: G1-control, G2-CO₂-laser irradiation, G3-brushing, and G4-CO₂ laser irradiation + brushing. A laser device emitting at 10.6 μm was used (power=0.5 W, energy per pulse=0.05 mJ, and frequency=10 kHz). Specimens belonging to groups G3 and G4 were brushed (80,000 strokes) with a brushing simulator using toothpaste. Next, the samples were challenged with acid: the specimens were immersed in demineralizing and remineralizing solutions for 8 days. The acid resistance of enamel was evaluated by cross-sectional microhardness tests. The area under the curve (KHN × μm) was calculated. Analysis of variance (ANOVA) one-away and Fisher's test were performed for the statistical analysis (p<0.05). Group G2 specimens (31,185 ± 4706) were statistically different from specimens belonging to groups G1 (26,723 ± 2446), G3 (28,194 ± 1376), and G4 (28,207 ± 2234), which were statistically similar. The brushing time used in the present study probably wore the CO₂-lased enamel, so demineralization could not be prevented in the brushed group.

  1. Comparing solvophobic and multivalent induced collapse in polyelectrolyte brushes

    DOE PAGES

    Jackson, Nicholas E.; Brettmann, Blair K.; Vishwanath, Venkatram; ...

    2017-02-03

    Here, coarse-grained molecular dynamics enhanced by free-energy sampling methods is used to examine the roles of solvophobicity and multivalent salts on polyelectrolyte brush collapse. Specifically, we demonstrate that while ostensibly similar, solvophobic collapsed brushes and multivalent-ion collapsed brushes exhibit distinct mechanistic and structural features. Notably, multivalent-induced heterogeneous brush collapse is observed under good solvent polymer backbone conditions, demonstrating that the mechanism of multivalent collapse is not contingent upon a solvophobic backbone. Umbrella sampling of the potential of mean-force (PMF) between two individual brush strands confirms this analysis, revealing starkly different PMFs under solvophobic and multivalent conditions, suggesting the role ofmore » multivalent “bridging” as the discriminating feature in trivalent collapse. Structurally, multivalent ions show a propensity for nucleating order within collapsed brushes, whereas poor-solvent collapsed brushes are more disordered; this difference is traced to the existence of a metastable PMF minimum for poor solvent conditions, and a global PMF minimum for trivalent systems, under experimentally relevant conditions.« less

  2. Ezrin, a membrane cytoskeletal cross-linker, is essential for the regulation of phosphate and calcium homeostasis.

    PubMed

    Hatano, Ryo; Fujii, Eiko; Segawa, Hiroko; Mukaisho, Kenichi; Matsubara, Mitsunobu; Miyamoto, Ken-Ichi; Hattori, Takanori; Sugihara, Hiroyuki; Asano, Shinji

    2013-01-01

    Ezrin cross-links plasma membrane proteins with the actin cytoskeleton. In the kidney, ezrin mainly localizes at the brush border membrane of proximal tubules with the scaffolding protein, Na(+)/H(+) exchanger regulatory factor (NHERF) 1. NHERF1 interacts with the sodium/phosphate cotransporter, Npt2a. Defects in NHERF1 or Npt2a in mice cause hypophosphatemia. Here we studied the physiological role of ezrin in renal phosphate reabsorption using ezrin knockdown mice (Vil2). These mice exhibit hypophosphatemia, hypocalcemia, and osteomalacia. The reduced plasma phosphate concentrations were ascribed to defects in urinary phosphate reabsorption. Immunofluorescence and immunoblotting indicated a marked reduction in renal Npt2a and NHERF1 expression at the apical membrane of proximal tubules in the knockdown mice. On the other hand, urinary loss of calcium was not found in Vil2 mice. Plasma concentrations of 1,25-dihydroxyvitamin D were elevated following reduced plasma phosphate levels, and mRNA of the vitamin D-dependent TRPV6 calcium channel were significantly increased in the duodenum of knockdown mice. Expression of TRPV6 at the apical membrane, however, was significantly decreased. Furthermore, tibial bone mineral density was significantly lower in both the adult and young Vil2 mice. These results suggest that ezrin is required for the regulation of systemic phosphate and calcium homeostasis in vivo.

  3. Brushing abrasion of luting cements under neutral and acidic conditions.

    PubMed

    Buchalla, W; Attin, T; Hellwig, E

    2000-01-01

    Four resin based materials (Compolute Aplicap, ESPE; Variolink Ultra, Vivadent; C&B Metabond, Parkell and Panavia 21, Kuraray), two carboxylate cements (Poly-F Plus, Dentsply DeTrey and Durelon Maxicap, ESPE), two glass-ionomer cements (Fuji I, GC and Ketac-Cem Aplicap, ESPE), one resin-modified glass ionomer cement (Vitremer, 3M) one polyacid-modified resin composite (Dyract Cem, Dentsply DeTrey) and one zinc phosphate cement (Harvard, Richter & Hoffmann) were investigated according to their brushing resistance after storage in neutral and acidic buffer solutions. For this purpose 24 cylindrical acrylic molds were each filled with the materials. After hardening, the samples were stored for seven days in 100% relative humidity and at 37 degrees C. Subsequently, they were ground flat and polished. Then each specimen was covered with an adhesive tape leaving a 4 mm wide window on the cement surface. Twelve samples of each material were stored for 24 hours in a buffer solution with a pH of 6.8. The remaining 12 samples were placed in a buffer with a pH of 3.0. All specimens were then subjected to a three media brushing abrasion (2,000 strokes) in an automatic brushing machine. Storage and brushing were performed three times. After 6,000 brushing strokes per specimen, the tape was removed. Brushing abrasion was measured with a computerized laser profilometer and statistically analyzed with ANOVA and Tukey's Standardized Range Test (p < or = 0.05). The highest brushing abrasion was found for the two carboxylate cements. The lowest brushing abrasion was found for one resin based material, Compolute Aplicap. With the exception of three resin-based materials, a lower pH led to a higher brushing abrasion.

  4. Effect of dielectric discontinuity on a spherical polyelectrolyte brush.

    PubMed

    Tergolina, Vinicius B; Dos Santos, Alexandre P

    2017-09-21

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

  5. Flow visualization in a single simulated brush seal

    NASA Technical Reports Server (NTRS)

    Braun, M. J.; Canacci, V. A.; Kazmierchak, M.; Hendricks, R. C.

    1992-01-01

    A method to visualize and characterize the complex flow fields in brush seals is presented. A configuration characteristic of the brush seal confined in a two-dimensional tunnel with water as the working fluid was studied. Visualization of the flow field revealed regions that are characteristically jetting, vortical, and crossflow and exist upstream, downstream or within the seal. Such flows are engendered by variations in fiber void that are spatial and temporal and affect changes in seal leakage and stability. While the effects of interface motion and cylindrical configuration have not been considered herein, it is believed that the observed flow fields characterize flow phenomenology in brush seals.

  6. Brush Lettering II; Commercial and Advertising Art--Intermediate: 9185.01.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    This course outline has been prepared as a guide to help the student gain mastery in the proper brush techniques required for proficiency in brush lettering. The skills of Brush Lettering 1 are a prerequisite. Consisting of 135 clock hours, the course prepares the student to understand brush lettering for poster production and advertising layout.…

  7. The border-to-border distribution method for analysis of cytoplasmic particles and organelles.

    PubMed

    Yacovone, Shalane K; Ornelles, David A; Lyles, Douglas S

    2016-02-01

    Comparing the distribution of cytoplasmic particles and organelles between different experimental conditions can be challenging due to the heterogeneous nature of cell morphologies. The border-to-border distribution method was created to enable the quantitative analysis of fluorescently labeled cytoplasmic particles and organelles of multiple cells from images obtained by confocal microscopy. The method consists of four steps: (1) imaging of fluorescently labeled cells, (2) division of the image of the cytoplasm into radial segments, (3) selection of segments of interest, and (4) population analysis of fluorescence intensities at the pixel level either as a function of distance along the selected radial segments or as a function of angle around an annulus. The method was validated using the well-characterized effect of brefeldin A (BFA) on the distribution of the vesicular stomatitis virus G protein, in which intensely labeled Golgi membranes are redistributed within the cytoplasm. Surprisingly, in untreated cells, the distribution of fluorescence in Golgi membrane-containing radial segments was similar to the distribution of fluorescence in other G protein-containing segments, indicating that the presence of Golgi membranes did not shift the distribution of G protein towards the nucleus compared to the distribution of G protein in other regions of the cell. Treatment with BFA caused only a slight shift in the distribution of the brightest G protein-containing segments which had a distribution similar to that in untreated cells. Instead, the major effect of BFA was to alter the annular distribution of G protein in the perinuclear region.

  8. Border Security: Barriers Along the U.S. International Border

    DTIC Science & Technology

    2009-03-16

    Border Fence Construction Process and Funding................................................................. 18 Types of Fences and Barriers...33 Figures Figure 1. Imperial Beach Station Apprehensions...13 Figure 3. Apprehensions at San Diego Sector Stations, Excluding Imperial Beach and Chula Vista

  9. [Vesicular intracellular transport in the digestive organs. Membrane vesicle--the universal mechanism of the functional transport].

    PubMed

    Morozov, I A

    2014-01-01

    On the basis of long-term research of the morpho-functional characteristics of the cells of the stomach, small intestine and gallbladder the mechanism and function of membrane vesicles in the implementation of the main functions of these organs sets out in this article: the secretion of hydrochloric acid by parietal cells, the absorption of nutrients in the small intestine and the fluid at a concentration of bile epitheliocytes of gallbladder. Proofs of the intracellular formation of hydrochloric acid in tubulovesicles of the parietal cells and turnover of its secretory membranes in the process of secretory cycle, that has ensured the re-use and explained the extraordinary life of these unique cells are presented. The credible mechanism of HCl output oppression by H(+)-K(+)-ATPase activity blockers has set out on this basis. The article provides detailed endocytosis mechanism of the ions and nutrients absorption by enterocytes. The mechanism of participation of the apical contractile complex of brush border of epithelial cells in the initiation of endocytosis and cytoplasmic microtubules in transport of membrane vesicles in the cytoplasm was analyzed. Based on our research and numerous of the world scientific proceedings the conclusion was done about the existence of two energy dependent types of transport in the absorptive epithelium of the digestive--transmembrane (ionic and nutritive) homeostatic type which is realized by the ATP-system of the basal plasmalemma, and vesicular (endocytosis) type which is impltmented by apical contractile complex of brush border and cytoplasmic microtubules. Both types of transport are interrelated and are under constant cellular control. This observation is relevant to the majority of cells, including those involved in the secretion of various substances: hydrochloric acid by parietal cells, enzymes by main cells of the gastric glands and exocrinocytes of the pancreas, hormone by endocrine cells of the APUD system and, finally

  10. Brush/gold nanoparticle hybrids: effect of grafting density on the particle uptake and distribution within weak polyelectrolyte brushes.

    PubMed

    Christau, Stephanie; Möller, Tim; Yenice, Zuleyha; Genzer, Jan; von Klitzing, Regine

    2014-11-04

    The effect of the brush grafting density on the loading of 13 nm gold nanoparticles (AuNPs) into stimuli-responsive poly(N,N-(dimethylamino ethyl) methacrylate) (PDMAEMA) brushes anchored to flat impenetrable substrates is reported. Atom-transfer radical polymerization (ATRP) is used to grow polymer brushes via a "grafting from" approach from a 2-bromo-2-methyl-N-(3-(triethoxysilyl) propyl) propanamide (BTPAm)-covered silicon substrate. The grafting density is varied by using mixtures of initiator and a "dummy" molecule that is not able to initiate polymerization. A systematic study is carried out by varying the brush grafting density while keeping all of the other parameters constant. X-ray reflectivity is a suitable tool for investigating the spatial structure of the hybrid, and it is combined with scanning electron microscopy and UV/vis spectroscopy to study the particle loading and interpenetration of the particles within the polymer brush matrix. The particle uptake increases with decreasing grafting density and is highest for an intermediate grafting density because more space between the polymer chains is available. For very low grafting densities of PDMAEMA brushes, the particle uptake decreases because of a lack of the polymer matrix for the attachment of particles. The structure of the surface-grafted polymer chains changes after particle attachment. More water is incorporated into the brush matrix after particle immobilization, which leads to a swelling of the polymer chains in the hybrid material. Water can be removed from the brush by decreasing the relative humidity, which leads to brush shrinking and forces the AuNPs to get closer to each other.

  11. Membrane fluidity and surface changes during initiation of 1,2 dimethylhydrazine-induced colon carcinogenesis: protection by zinc.

    PubMed

    Chadha, Vijayta Dani; Dhawan, D K

    2009-01-01

    The present study evaluated the modulatory effects of zinc on colonic membrane fluidity and surface abnormalities following 1,2 dimethylhydrazine (DMH)-induced colon carcinogenesis. Rats were segregated into four groups: normal control, DMH treated, zinc treated, DMH + zinc treated. Colon carcinogenesis was initiated through weekly subcutaneous injections of DMH (30 mg/kg body weight) for 8 weeks. Zinc (in the form of zinc sulphate) was supplemented to rats at a dose level of 227 mg/L in drinking water, ad libitum, for the entire duration of the study. Brush border membranes (BBM) were isolated from the colon of rats and the fluidity parameters were assessed by steady-state fluorescence polarization technique using the membrane extrinsic fluorophore 1,6-diphenyl-1,3,5-hexatriene (DPH). The translational diffusion was measured by using the excimer formation of pyrene incorporated in the membrane. The results demonstrated a significant increase in the polarization and anisotropy, accompanied by an increase in order parameter in the membrane preparations from the colon of DMH-injected rats. Further, studies with pyrene fluorophore indicated a marked decrease in membrane microviscosity following DMH treatment. However, the alterations in membrane fluorescence polarization and the fluidity parameters were completely restored following zinc treatment. Drastic alterations in colon surface were noticed after 8 weeks of DMH treatment. However, zinc treatment to DMH-treated rats greatly restored normalcy in the colonic surface. The study concludes that zinc has a strong membrane stabilizing effect and thus has a positive beneficial effect against chemically induced colonic preneoplastic progression in rats.

  12. Astronauts Culbertson and Bursch brush their teeth on Discovery's middeck

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Astronauts Frank L. Culbertson (right), mission commander, and Daniel W. Bursch, mission specialist, brush their teeth on Discovery's middeck. Two sleep restraints form part of the backdrop for the photograph.

  13. Surface wave excitations and backflow effect over dense polymer brushes

    PubMed Central

    Biagi, Sofia; Rovigatti, Lorenzo; Sciortino, Francesco; Misbah, Chaouqi

    2016-01-01

    Polymer brushes are being increasingly used to tailor surface physicochemistry for diverse applications such as wetting, adhesion of biological objects, implantable devices and much more. Here we perform Dissipative Particle Dynamics simulations to study the behaviour of dense polymer brushes under flow in a slit-pore channel. We discover that the system displays flow inversion at the brush interface for several disconnected ranges of the imposed flow. We associate such phenomenon to collective polymer dynamics: a wave propagating on the brush surface. The relation between the wavelength, the amplitude and the propagation speed of the flow-generated wave is consistent with the solution of the Stokes equations when an imposed traveling wave is assumed as the boundary condition (the famous Taylor’s swimmer). PMID:26975329

  14. Martian Sandstone Target Windjana Before and After Brushing

    NASA Image and Video Library

    2014-04-29

    This image from an animation shows a patch of sandstone scrubbed with the Dust Removal Tool, a wire-bristle brush, on NASA Curiosity Mars rover. This rock target is called Windjana, after a gorge in Western Australia.

  15. Dendron brushes and dendronized polymers: a theoretical outlook.

    PubMed

    Borisov, O V; Polotsky, A A; Rud, O V; Zhulina, E B; Leermakers, F A M; Birshtein, T M

    2014-04-07

    Dendron brushes are molecular structures built up of treelike macromolecules, with multiple generations of branches, grafted with a root segment to a surface (particle) or to a backbone chain (dendronized polymer) with a sufficiently high grafting density so that the dendrons interact laterally. Recent advances in the theory of dendron brushes are highlighted and complemented by insights from numerical self-consistent field modelling. Our focus is on controversial issues, which are still under debate, such as, the strain distribution in individual dendrons and the appearance of distinct populations with a different extent of stretching for dendrons in planar brushes. We anticipate that dendritic brushes (i) show a strong resistance against bending, which may manifest in a high apparent persistence length of dendronized polymers, and (ii) have an unusually large beneficial effect on the colloidal stability due to the sharp steric repulsive interaction observed when these surface layers are pushed towards the overlap.

  16. Astronauts Culbertson and Bursch brush their teeth on Discovery's middeck

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Astronauts Frank L. Culbertson (right), mission commander, and Daniel W. Bursch, mission specialist, brush their teeth on Discovery's middeck. Two sleep restraints form part of the backdrop for the photograph.

  17. Dense brushes of stiff polymers or filaments in fluid flow

    NASA Astrophysics Data System (ADS)

    Römer, F.; Fedosov, D. A.

    2015-03-01

    Dense filamentous brush-like structures are present in many biological interfacial systems (e.g., glycocalyx layer in blood vessels) to control their surface properties. Such structures can regulate the softness of a surface and modify fluid flow. In this letter, we propose a theoretical model which predicts quantitatively flow-induced deformation of a dense brush of stiff polymers or filaments, whose persistence length is larger or comparable to their contour length. The model is validated by detailed mesoscopic simulations and characterizes different contributions to brush deformation including hydrodynamic friction due to flow and steric excluded-volume interactions between grafted filaments. This theoretical model can be used to describe the effect of a stiff-polymer brush on fluid flow and to aid in the quantification of experiments.

  18. Unique Tuft Test Facility Dramatically Reduces Brush Seal Development Costs

    NASA Technical Reports Server (NTRS)

    Fellenstein, James A.

    1997-01-01

    Brush seals have been incorporated in the latest turbine engines to reduce leakage and improve efficiency. However, the life of these seals is limited by wear. Studies have shown that optimal sealing characteristics for a brush seal occur before the interference fit between the brush and shaft is excessively worn. Research to develop improved tribopairs (brush and coating) with reduced wear and lower friction has been hindered by the lack of an accurate, low-cost, efficient test methodology. Estimated costs for evaluating a new material combination in an engine company seal test program are on the order of $100,000. To address this need, the NASA Lewis Research Center designed, built, and validated a unique, innovative brush seal tuft tester that slides a single tuft of brush seal wire against a rotating shaft under controlled loads, speeds, and temperatures comparable to those in turbine engines. As an initial screening tool, the brush seal tuft tester can tribologicaly evaluate candidate seal materials for 1/10th the cost of full-scale seal tests. Previous to the development of the brush seal tuft tester facility, most relevant tribological data had been obtained from full-scale seal tests conducted primarily to determine seal leakage characteristics. However, from a tribological point of view, these tests included the confounding effects of varying contact pressures, bristle flaring, high-temperature oxidation, and varying bristle contact angles. These confounding effects are overcome in tuft testing. The interface contact pressures can be either constant or varying depending on the tuft mounting device, and bristle wear can be measured optically with inscribed witness marks. In a recent cooperative program with a U.S. turbine engine manufacturer, five metallic wire candidates were tested against a plasma-sprayed Nichrome-bonded chrome carbide. The wire materials used during this collaboration were either nickel-chrome- or cobaltchrome-based superalloys. These

  19. Border Sovereignty and Protection Act

    THOMAS, 111th Congress

    Rep. Hunter, Duncan D. [R-CA-52

    2009-04-23

    05/26/2009 Referred to the Subcommittee on Immigration, Citizenship, Refugees, Border Security, and International Law. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

  20. Border Sovereignty and Protection Act

    THOMAS, 111th Congress

    Rep. Hunter, Duncan D. [R-CA-52

    2009-04-23

    House - 05/26/2009 Referred to the Subcommittee on Immigration, Citizenship, Refugees, Border Security, and International Law. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation: