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PubMed2002

Supplementation of conventional trivalent influenza vaccine with purified viral N1 and N2 neuraminidases induces a balanced immune response without antigenic competition.

Influenza viruses neuraminidase (NA) were chromatographically extracted from influenza viruses A/Nanchang/933/95 H3(NC)N2(NC) [R] and A/Johannesburg/82/96 H1(JH)N1(JH) [R] and used to supplement conventional inactivated trivalent influenza vaccine. Immunization of mice with this preparation resulted in high titers of antibodies to both hemagglutinins (HA) and neuraminidases (NA); there were no significant differences in the anti-HA antibody titers between the conventional and the supplemented vaccine preparation. Likewise, there were no significant differences in anti-NA antibody titers between the supplemented vaccine and titers from mice immunized with a neuraminidase vaccine containing a mixture of N1-NA and N2-NA. There was no evidence of a diminution of the immune response to the HA components of the vaccine despite the presence of antigenically equivalent amounts of both N1-NA and N2-NAs. Homotypic and distantly related heterotypic infections for both H1, N1 and H3N2 subtypes were suppressed and greater reduction in pulmonary virus titers (PVT) were observed in the trivalent vaccine supplemented with purified neuraminidase from each subtype, N1 and N2. Effects on the influenza B viral components were not studied. Previous studies on supplementation of conventional influenza vaccine focused only on monovalent H3N2 vaccine preparations; this study demonstrates in a mouse model system that supplementation of trivalent influenza vaccine with both influenza A subtype neuraminidases, N1 and N2 is highly immunogenic for HA and NA of each subtype and efficacious in protecting against influenza from homotypic and heterotypic infectious challenges of either subtype.

Animals↗
PubMed1977

Effects of neuraminidase on lectin binding by wild-type and ricin-resistant strains of hamster fibroblasts.

The nature of cell surface receptors for ricin on wild-type and ricin-resistant variants of baby hamster kidney fibroblasts has been studied. Neuraminidase stimulated ricin binding threefold by wild-type cells, and increased their susceptibility to ricin toxicity as measured by inhibition of [3H]leucine uptake (LD30 fell from 5.0 to 0.5 microgram/mL). Basal ricin binding by ricin-resistant variants (10-300% that of wild type) was also stimulated (2- to 17-fold) by neuraminidase in all seven clonal strains examined; susceptibility to ricin was greatly increased by neuraminidase in these variants. Neuraminidase did not affect the binding of concanavalin A by wild type or a ricin-resistant variant, but decreased the binding of wheat-germ agglutinin by 90% in both cell types. The trivial binding of peanut agglutinin by wild type and a ricin-resistant variant was markedly enhanced (14- to 22-fold) by neuraminidase. Neither collagenase (50 U/mL) nor Pronase (0.0001%) affected ricin binding by wild type or a ricin-resistant variant. These data suggest the existence of "exposed" and "cryptic" oligosaccharide receptors for ricin on the cell membrane glycoproteins of baby hamster kidney fibroblasts. The cryptic ricin receptors probably include at least the sequence D-galactosyl-beta-(1 replaced by 3)-N-acetylhexosamine substituted by sialic acid residues. Exposed and cryptic ricin receptors appear to be different and under separate genetic control.

Carrier Proteins↗
PubMed2003

Investigation of neuraminidase-substrate recognition using molecular dynamics and free energy calculations.

Development of the new generation of therapeutics against the influenza viral coat protein neuraminidase is a response to the continuing threat of influenza epidemics. A variety of structurally similar compounds have been reported that vary greatly in their ability to inhibit neuraminidase, a critical enzyme that cleaves sialic acid and promotes virion release. To determine how neuraminidase exhibits this wide range of affinities with structurally similar compounds, molecular dynamic simulations, coupled with free energy calculations, were used to determine the binding components of a series of neuraminidase inhibitors. Using four cocrystal structures of neuraminidase-inhibitor complexes, we examined the structural and energetic components of ligand potency and selectivity. An in-depth energetic analysis, including internal energy, entropy, and nonbonded interactions, reveals that potency of ligand binding is governed by nonpolar contacts. Electrostatic components generally oppose binding, although two of the best inhibitors use electrostatic interactions to orient the ligand. This investigation suggests that the enhanced selectivity and potency of the better ligands may arise from an improved positioning of their ligand atoms in the active site due to polar and hydrophobic functionalities. Simulations that included crystal water molecules in the active site indicate that the more potent ligands make less use of water-mediated interactions.

Alanine↗
PubMed2004

Syntheses and neuraminidase inhibitory activity of multisubstituted cyclopentane amide derivatives.

In further studies aimed toward identifying effective and safe inhibitors of influenza neuraminidases, we synthesized a series of multisubstituted cyclopentane amide derivatives. Amides prepared were 14 examples of N-substituted alkyl or aralkyl types from primary amines, 13 examples of the N,N-disubstituted alkyl, aralkyl, or substituted-alkyl type from secondary amines, and 12 examples from cycloaliphatic or substituted cycloaliphatic secondary amines. These compounds bearing two chiral centers, at position-1 in the ring and position-1' in the side chain attached at position 3, were tested for their ability to inhibit A and B forms of influenza neuraminidase. The 1-ethylpropylamide, diethylamide, dipropylamide, and 4-morpholinylamide showed very good inhibitory activity (IC(50) = 0.015-0.080 microM) vs the neuraminidase A form, but modest activity (IC(50) = 3.0-9.2 microM) vs the neuraminidase B form. Since the parent amides bear two chiral centers (C-1 and C-1'), three of the better inhibitors were tested at higher levels of diastereomeric purity. The diastereomers corresponding to the active forms of the 1-(ethyl)propylamide, the diethylamide, and the dipropylamide (all of the same configuration at the C-1' chiral center), and the diastereomer of the diethylamide representing the active form at both C-1' and C-1 were isolated or synthesized from precursors that were isolated as diastereomers. These diastereomers showed some improvement in neuraminidase inhibition over the parent diastereomeric mixtures. 1-Carboxy-1-hydroxy derivatives of the best active compounds, the diethylamide and the dipropylamide, were also prepared. These compounds were not as active as the compounds without the 1-hydroxy group. In an in vivo study, the C-1' active isomer of the diethylamide from the 1-carboxy series was tested in influenza-infected mice by oral and intranasal administration and found to be very effective only intranasally in preventing weight loss at doses as low as 0.1 (mg/kg)/day.

Administration, Intranasal↗
PubMed1974

Rat brain microsomal gangliosides. Accessibility to a neuraminidase preparation and the possible existence of different pools in relation to their biosynthesis.

1. Treatment of rat brain microsomal membranes with a neuraminidase preparation from Clostridium perfringens resulted in an almost complete conversion of polysialogangliosides into monosialogangliosides. 2. Neuraminidase treatment of the membranes did not increase the incorporation of N-[(3)H]acetylneuraminic acid from CMP-N-[(3)H]acetylneuraminic acid into the gangliosidic fraction, indicating that a monosialoganglioside is an acceptor of N-acetylneuraminic acid in these membranes only if, in addition to having the right chemical structure, it is in a proper position, probably in relation to the endogenous sialyltransferases. 3. These experiments also indicated that no independent turnover of the neuraminidase-labile N-acetylneuraminyl groups of gangliosides occurred in vitro. 4. N-[(3)H]Acetylneuraminic acid from endogenous polysialogangliosides labelled in vitro was released by neuraminidase at a slower rate than N-acetylneuraminic acid from unlabelled gangliosides of the same membranes. From this it was concluded that recently synthesized polysialogangliosides (completed in vitro) are in the membranes in a position less accessible to neuraminidase than are those synthesized earlier which were present in the membranes at the start of the labelling experiment.

Animals↗
PubMed1974

Comparative effect and fate of non-entrapped and liposome-entrapped neuraminidase injected into rats.

Non-entrapped and liposome-entrapped Clostridium perfringens neuraminidase (0.5-0.6 unit) was injected into rats and its fate as well as its effect on plasma and erythrocyte N-acetylneuraminic acid was investigated. The following observations were made. (1) Although removal of both non-entrapped and liposome-entrapped neuraminidase from the circulation was completed within 5h after injection, their recovery in tissues was distinctly different; 7-10% of the injected non-entrapped enzyme was found in the liver and none in the liver lysosomal fraction or the spleen. In contrast, 20-26% of the liposome-entrapped enzyme was found in the liver of which 60-69% was in the lysosomal fraction. Spleen contained 3.6-5.0% of the enzyme. (2) The presence of the non-entrapped neuraminidase in blood led to the extensive desialylation of plasma and to a decrease in the concentration or total removal from the circulation of some of the plasma glycoproteins. (3) Injection of non-entrapped neuraminidase also led to the partial desialylation of erythrocytes the life span of which was diminished and their uptake by the liver and spleen augmented. (4) Entrapment of neuraminidase in liposomes before its injection prevented the enzyme from acting on its substrate in plasma or on the erythrocyte surface, and values obtained for plasma glycoproteins and erythrocyte survival were similar to those observed in control rats. (5) Entrapment in liposomes of therapeutic hydrolases intended for the degradation of substances stored within the tissue lysosomes of patients with storage diseases could prevent the potentially hazardous enzymic action of hydrolases in blood and at the same time direct the enzymes to the intracellular sites where they are needed.

Animals↗
PubMed1978

Intestinal neuraminidase activity of suckling rats and other mammals. Relationship to the sialic acid content of milk.

1. The neuraminidase activity of homogenates of the mucosa of the middle and distal thirds of the small intestine of rats increased about 5-fold between birth and 4 to 8 days of age, and then gradually declined to the much lower adult activity by 24 days. No comparable changes occurred in the proximal third. 2. In 8-day-old rats, the neuraminidase activity of the middle and distal thirds of the small intestine was about 10 times greater than that of the proximal third, 20 times greater than that of the colon and at least 100 times greater than that of the liver, brain, gastric mucosa or pancreas. 3. In all other species investigated (mice, rabbits, cats and guinea pigs), the neuraminidase activity of the middle and distal thirds of the small intestine was greater in suckling animals than in adults. 4. The sialic acid content of rat milk increased about 2-fold between birth and 8 days post partum and then declined. 5. There was a highly significant positive correlation between the intestinal neuraminidase activity of suckling animals of various species and ages and the sialic acid content of milk obtained from the corresponding species and stage of lactation. 6. It is suggested that the intestinal neuraminidase of suckling mammals functions primarily to remove sialic acid from various components of milk, thus providing sialic acid for the synthesis of sialoglycoproteins and gangliosides by the young.

Aging↗
PubMed1984

Developmental regulation of neuraminidase-sensitive lectin-binding glycoproteins during myogenesis of rat L6 myoblasts.

Intact monolayers of L6 myoblasts were treated with neuraminidase, with the aim of selectively removing sialic acid residues of cell-surface glycoproteins. Neuraminidase treatment unmasked binding sites for Ricinus communis agglutinin I and peanut agglutinin, thus allowing the identification of the major binding proteins for these lectins. For Ricinus communis agglutinin I these neuraminidase-sensitive glycoproteins had apparent Mr values of 136000, 115000, 87000, 83000 and 49000. For peanut agglutinin the major neuraminidase-sensitive glycoproteins had apparent Mr values of 200000, 136000, 87000 and 83000. We found highly reproducible, developmentally regulated, changes in the lectin-binding capacity of certain of these glycoproteins as L6 myoblasts differentiated into myotubes. Coincident with myoblast fusion there was a co-ordinate decrease in Ricinus communis agglutinin I binding by glycoproteins of apparent Mr of 136000 and 49000. There was also a co-ordinate shift in mobility of the broad band of glycoprotein, centred at an apparent Mr of 115000 in myoblasts, to a new average apparent Mr of 107000 in mid-fusion cultures and myotube cultures. Peanut agglutinin binding by the major protein of apparent Mr 136000 also decreased at the mid-fusion stage of myogenesis, and was barely detectable in 7-day-old fused cultures. These developmentally regulated changes in neuraminidase-sensitive glycoproteins were all inhibited by growth of myoblasts in 6.4 microM-5-bromo-2'-deoxyuridine, indicating that they are associated with myoblast differentiation. In contrast, an increase in fibronectin was seen in mid-fusion cultures, which was not inhibited by growth of myoblasts in 5-bromo-2'-deoxyuridine. This initial increase in fibronectin is, therefore, unlikely to be directly related to myoblast fusion or differentiation.

Animals↗
PubMed2000

Neuraminidase-producing ability of intestinal bacteria isolated from coastal fish.

The neuraminidase-producing ability of bacteria from coastal fish intestines and their environments was determined using a fluorogenic substrate, 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid. Of 836 isolates examined, 758 (90.7%) produced little or no neuraminidase (< 0.0002 U ml-1) while 78 (9.3%) produced >/= 0.0002 U neuraminidase ml-1. Of note, 10% of vibrios from fish intestines could produce neuraminidases, and 9% did it efficiently. This result suggests that the vibrios capable of producing neuraminidases are able to colonize and establish in the intestinal tract of coastal fish to some extent. Additionally, as many as 58% of the Vibrio isolates with high abilities were tentatively identified as Vibrio damsela.

Animals↗
PubMed1981

Neuraminidase activity and free sialic acid levels in the serum of patients with acute poststreptococcal glomerulonephritis.

It has been suggested that in acute poststreptococcal glomerulonephritis, streptococcal neuraminidase may remove sialic acid from some normal plasma or tissue components, thus rendering it antigenic. We therefore investigated serum neuraminidase activity and serum and urinary free neuraminic acid levels, using the thiobarbituric acid method, in 39 patients with acute poststreptococcal nephritis. Serum neuraminidase activity was found in eight patients, and increased thiobarbituric acid-reactive material (presumed to be free neuraminic acid on the basis of absorption-spectrum similarity) was found in 28 patients. Serial determinations in 21 patients indicated that neuraminidase activity was present only initially and that free neuraminic acid levels decreased with time, usually becoming undetectable after four weeks. Determinations in patients with other renal and nonrenal diseases suggested that the findings were characteristic of poststreptococcal nephritis. Urinary neuraminic acid levels were unrelated to serum levels and were not markedly different between patients and normal subjects. These data suggest a role for neuraminidase activity in acute poststreptococcal nephritis, but they do not indicate whether it is primary or secondary.

Acute Disease↗
PubMed1972

Regeneration of the surface glycoproteins of a transplantable mouse tumor cell after treatment with neuraminidase.

Strain A mouse ascites tumor cells that were treated with neuraminidase (EC 3.2.1.18) (these cells show decreased tumor-forming ability in allogeneic C3H mice) rapidly regenerate sialoglycoproteins at the cell surface during culture. The incorporation of labeled D-glucosamine into membrane glycoproteins of cells that were treated or untreated with neuraminidase proceeds at similar rates. Surface glycoproteins that contain sialic acid are synthesized de novo during culture of neuraminidase-treated cells, and in nondividing cells, synthesis is accompanied by turnover of the membrane glycoproteins. The rate of turnover of membrane glycoproteins that lack sialic acid residues is the same as that occurring in non-dividing cells that are not treated with neuraminidase and that are cultured under identical conditions. Turnover of the surface membrane of nondividing cells leads to the accumulation of glycoproteins in the supernatant medium of cell cultures. The rapid regeneration of cell surfaces that contain sialic acid by TA3 cells that were treated with neuraminidase, makes it unlikely that the rejection of these cells in vivo, in C3H mice, is due solely to the induction of a primary immune response to new or to previously concealed antigenic specificities that would be expressed on the surface of the sialic acid-depleted cell.

Animals↗
PubMed1987

Neuraminidase from Trypanosoma cruzi: analysis of enhanced expression of the enzyme in infectious forms.

We purified the neuraminidase (sialidase, acylneuraminyl hydrolase, EC 3.2.1.18) from the protozoan parasite Trypanosoma cruzi, strain Y, and examined the developmental regulation of the enzyme. The detectable amount of enzyme activity increased 10- to 20-fold upon conversion of the parasite from the noninfectious epimastigote form to the infectious trypomastigote form. The enzyme was purified from membranes of trypomastigotes greater than 5000-fold to apparent homogeneity and migrated as an entity of Mr 60,000 under denaturing conditions. Antibodies produced in rabbits against the denatured protein recognized the neuraminidase in membrane extracts from the infectious stage but not from the noninfectious stage. Sera from a patient with acute chagasic disease also reacted strongly with the neuraminidase. Other T. cruzi strains exhibited similar neuraminidase activities and induction rates. The coincidence of infectivity and enhanced expression of neuraminidase in trypomastigotes suggests that this enzyme constitutes a virulence factor in T. cruzi.

Animals↗
PubMed1962

Studies on the transferrins of adult serum, cord serum, and cerebrospinal fluid. The effect of neuraminidase.

Nine of the twelve known variants of human transferrin have been resolved by the action of neuraminidase into stepwise patterns of four additional slower moving components whose relative intensities depended upon the concentration of enzyme. These components appeared to represent the stepwise removal of the four sialic acid residues from the transferrin molecule, and at large enzyme concentrations, almost all of the transferrin was reduced to the position of the slowest moving component. In contrast, the electrophoretic mobilities of haptoglobin, ceruloplasmin, and alpha(2)-macroglobulin showed a gradual decrease with increasing neuraminidase concentration. The transferrins of chimpanzees, rhesus and cynomolgus monkeys, and cattle were resolved by neuraminidase into two slower moving components. These experiments suggested that the primate and cattle transferrins contained only two sialic acid residues accessible to the enzyme. Transferrins C, B(2), and D(1) and a cynomolgus monkey transferrin were purified from serum by starch block electrophoresis and cellulose chromatography. Ultracentrifugal analysis could detect no difference in sedimentation rate between transferrin C, the primate transferrin, and neuraminidase-treated transferrin C. The human transferrins showed no variation in amino acid composition, but the cynomolgus transferrin was approximately 20 per cent higher in serine content and 50 per cent lower in glucosamine than human transferrin C. Reactions of antigenic identity were obtained among five human transferrin variants but a reaction of only partial identity was obtained between transferrin C and the cynomolgus transferrin. The transferrin pattern of cord blood showed a prominent band in the position of transferrin C, accompanied by four faint slower moving bands which coincided with the four transferrin components produced by the action of neuraminidase on transferrin C. The transferrin pattern of cerebrospinal fluid in individuals homozygous for serum transferrin C showed two principal components, one of which appeared to contain no sialic acid. Haptoglobin, ceruloplasmin, and alpha(2)-macroglobulin were also present in cerebrospinal fluid.

Adult↗
PubMed1992

Desialylation of lysosomal membrane glycoproteins by Trypanosoma cruzi: a role for the surface neuraminidase in facilitating parasite entry into the host cell cytoplasm.

Trypanosoma cruzi enters host cells via formation of an acidic vacuole which is subsequently disrupted, allowing the parasite access to the cytoplasm. We show that in an acid environment, release of the parasite surface neuraminidase is enhanced, and this release is likely mediated by a phosphatidylinositol-specific phospholipase C (PIPLC), since antibodies to a carbohydrate epitope (CRD) revealed in glycosylphosphatidylinositol (GPI)-anchored proteins after PIPLC cleavage remove the great majority of the soluble neuraminidase activity from culture supernatants. The neuraminidase is active at acidic pH, and is capable of desialylating known vacuolar constituents, i.e., lysosomal membrane glycoproteins. Parasite escape into the cytoplasm is significantly facilitated in terminal sialylation-defective mutant Lec 2 cells, and enzymatically desialylated membranes are more susceptible to lysis by a parasite hemolysin previously implicated in vacuole membrane rupture. These findings provide evidence that terminal sialylation on carbohydrate moieties contributes to maintaining lysosomal membrane integrity, and indicate a role for a protozoan-derived neuraminidase in facilitating parasite entry into host cells. These observations raise the possibility that other microbial neuraminidases may serve a similar function in acidic intracellular compartments.

Animals↗
PubMed1988

Agarose gel patterns of alkaline phosphatase isoenzymes before and after treatment with neuraminidase.

The clinical value of alkaline phosphatase isoenzyme analysis is limited by the inability of most electrophoretic methods to resolve the liver and bone isoenzymes. The authors attacked this problem by treating serum samples with neuraminidase, then running treated and untreated samples side-by-side on specially prepared agarose gels. Each isoenzyme showed a characteristic mobility before and after neuraminidase treatment that allowed its identification. The mobility of the bone isoenzyme was most affected, whereas the intestinal isoenzyme was resistant to the action of neuraminidase. In samples with both liver and bone isoenzymes, pretreatment with neuraminidase clearly distinguished the bands, allowing quantitation by densitometry. Using this method, the authors discovered 22 liver isoenzymes in 54 samples that were interpreted as only bone isoenzyme before neuraminidase treatment. They also detected two bone isoenzymes in 35 samples that appeared to contain only liver +/- biliary isoenzymes. In addition, this procedure enabled them to characterize several unusual isoenzymes with respect to mobility, thus avoiding confusion with the other isoenzymes.

Alkaline Phosphatase↗
PubMed1984

Delayed afterdepolarisations and triggered activity in canine Purkinje fibres treated with neuraminidase.

We investigated the electrophysiological alterations induced by the removal of sialic acid from the sarcolemma in canine Purkinje fibres. About 70% of total sialic acid content of Purkinje fibres was removed by 120 min of exposure to neuraminidase (1 U X ml-1). The treatment with neuraminidase did not change any of the action potential characteristics at normal Ca2+ concentration (2.7 mmol X litre-1). However, action potential duration and maximum upstroke velocity of phase zero of the action potential were reduced to a greater degree in neuraminidase-treated Purkinje fibres than in non-treated controls at high Ca2+ concentration (8.1 mmol X litre-1). At high Ca2+ concentration, delayed afterdepolarisations were induced in five out of nine neuraminidase-treated Purkinje fibres and triggered activity was observed in two, when driven in trains of 20 stimuli of different cycle length (1000 to 180 ms). No discernible delayed afterdepolarisations were observed in nine non-treated control Purkinje fibres. In addition, the amplitude of delayed afterdepolarisations induced by ouabain (0.2 mumol X litre-1) in neuraminidase-treated Purkinje fibres was larger than non-treated controls. These findings suggest that sialic acid residues of glycocalyx function as a kind of barrier to Ca2+ influx.

Action Potentials↗
PubMed1998

A point mutation in the neu-1 locus causes the neuraminidase defect in the SM/J mouse.

Lysosomal neuraminidase (sialidase) occurs in a high molecular weight complex with the glycosidase beta-galactosidase and the serine carboxypeptidase protective protein/cathepsin A (PPCA). Association of the enzyme with PPCA is crucial for its correct targeting and lysosomal activation. In man two genetically distinct storage disorders are associated with either a primary or a secondary deficiency of lysosomal neuraminidase: sialidosis and galactosialidosis. In the mouse the naturally occurring inbred strain SM/J presents with a number of phenotypic abnormalities that have been attributed to reduced neuraminidase activity. SM/J mice were originally characterized by their altered sialylation of several lysosomal glycoproteins. This defect was linked to a single gene, neu-1 , on chromosome 17, which was mapped by linkage analysis to the H-2 locus. In addition, these mice have an altered immune response that has also been coupled to a deficiency of the Neu-1 neuraminidase. Here we report the identification in SM/J mice of a single amino acid substitution (L209I) in the Neu-1 protein which is responsible for the partial deficiency of lysosomal neuraminidase. We propose that the reduced activity is caused by the enzyme's altered affinity for its substrate, rather than a change in substrate specificity or turnover rate. The mutant enzyme is correctly compartmentalized in lysosomes and maintains the ability to associate with its activating protein, PPCA. We propose that it is this mutation that is responsible for the SM/J phenotype.

Adenosine Diphosphate↗
PubMed1989

Changes in the membrane surface charge density and/or membrane potential of the porcine intestinal brush-border membrane vesicles induced by treatment with neuraminidase.

The effects of neuraminidase treatment on the membrane surface charge density and/or membrane potential of the porcine intestinal brush-border membrane vesicles were studied by using three fluorescent dyes, 1,6-diphenyl-1,3,5-hexatriene (DPH), 1-anilino-8-naphthalene sulfonate (ANS), and 3,3'-dipropyl-2,2'-thiadicarbocyanine iodide (DiS-C3(5]. The results of quenching studies of DPH-labeled membranes using cationic (T1+) and anionic (I-) quenchers suggested an increase of negative charge on the membrane surface by desialylation upon neuraminidase treatment. This interpretation was further supported by a decrease of ANS-binding affinity of the membranes after treatment with the enzyme. In addition, the degree of valinomycin-induced fluorescence change of DiS-C3(5)-probed membranes in the presence of various concentrations of KCl was reduced by treatment of the membranes with neuraminidase. This suggests that penetration of the dye molecules into the vesicle interior is facilitated by the treatment. The membrane potentials estimated from the null point of valinomycin-induced changes in the DiS-C3(5) fluorescence of the control and neuraminidase-treated membranes were -25 to -29.7 and -40 to -48.8 mV, respectively. From these results, it is suggested that the membrane surface charge density and/or membrane potential of the intestinal brush-border membranes are susceptible to modification of carbohydrate moieties on the membrane surface by neuraminidase treatment.

Animals↗