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Results for “NEURAMINIDASE”

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PubMed1976

[Practical interest of a micromethod for neuraminidase treatment of lymphocytes in transplantation immunology (author's transl)].

Vibrio cholerae neuraminidase treatment increases the cell sensitivity to complement and antibodies cytotoxic action. This property can be applied to the microlymphocytotoxicity technic for antibodies study in dialysed and kidney transplanted patients and for pretransplantation cross-matches. The enzymatic treatment usually employed needs a great deal of lymphocytes submitted in a second step to antibodies cytotoxic action. But this method appeared difficult to be routinely applied. We developed a simpler method consisting in treating only the lymphocytes needed to perform the test, on the reaction plate itself. This method gives the same results as the classical enzymatic treatment: the intensity of the weakly positive reaction is strongly increased, after pretreatment of cells; in certain cases, it allows one to detect cytotoxic antibodies not revealed without neuraminidase. These antibodies can be related (or not) to HLA system but practically the more important fact is the ability of this method to reveal an eventual incompatibility.

Antibodies↗

PubMed1975

[The effect of neuraminidase of C. diphtheriae on the functional capacity of the peritoneal exudate cells of guinea pigs to diphtheria bacilli].

A study was made of the effect of neuraminidase preparation containing no diphtheria toxin admixtures and hyaluronidase on the phagocytic activity of macrophages. Neuraminidase produced a stimulating effect on the cells of the developing macrophage culture. The macrophages treated with the enzyme increased their capacity to digestion of nontoxigenic diphtheria bacilli.

Animals↗

PubMed1993

[Effect of neuraminidase on the adherence of S. mutans to salivary pellicle].

The salivary glycoproteins have been showing to play a receptor role in the adherence of bacteria to surface of teeth. Sialic acid is believed to be an important component of the salivary glycoprotein which adsorb selectively on tooth surface. The purpose of this study was to investigate the effect of neuraminidase on the adherence of S. mutans to saliva-coated hydroxyapatite, and concomitantly to determine the content of free sialic acid. The results show significantly lower adherence of S. mutans to neuraminidase treated versus untreated salivary pellicle. Results from these studies suggested that sialic acid receptors may mediate adherence of S. mutans.

Bacterial Adhesion↗

PubMed1976

[Neuraminidase activity of N. meningitidis].

The work was aimed at the study of the neuraminidase activity of meningococci. The optimal conditions for detection of this enzyme in meningococci were chosen preliminarily. In experiments carried out with the observance of these conditions it was shown that meningococci of the main serological groups possessed neuraminidase activity revealed in the exponential growth phase of the microorganisms and was apparently of great pathogenetic significance providing a possibility of overcoming the physiological barrier of the host organism by the microbes.

Neisseria meningitidis↗

PubMed1993

Simple purification and secondary structure evaluation of Sendai virus neuraminidase water soluble fragment.

We have developed a quick and simple method to purify the water soluble fragment of Sendai virus neuraminidase (cHN). We used the trifluoperazine (TFP) as detergent because of its ability to selectively solubilize the HN (Baiocchi et al., (1988) FEBS Lett. 238, 171-174). Here we describe conditions by which trypsin produces the cHN from the TFP treated virions. The cHN is further purified by size exclusion chromatography and it fully retains the neuraminidase activity and the allosteric inhibitory site as described in (Dallocchio et al., (1991) Biochem. Int. 25, 663-668). Both circular dichroism (CD) spectra, analyzed by deconvolution methods and secondary structure prediction were used to assess the secondary structure of cHN.

Amino Acid Sequence↗

PubMed1993

Production of mucinase and neuraminidase and binding of Shigella to intestinal mucin.

Production of mucinase and neuraminidase by Shigella spp. and their ability to bind to mucin was investigated. All four species of Shigella produced these enzymes. Virulent and avirulent pairs of Shigella did not differ in their ability to produce the enzymes after 18 h of growth. However, a significant difference in neuraminidase production was noted in Shigella dysenteriae type 1 and S. boydii (12-15) at 10 h growth. Avirulent strains of S. dysenteriae type 1, S. flexneri 2a, and S. boydii bound significantly more amounts of mucin than their virulent counterparts.

Animals↗

PubMed1977

[The occurrence of neuraminidase and N-acylneuraminate pyruvate lyase in Haemophilus paragallinarum and Haemophilus paravium n.sp (author's transl)].

14 strains of H. paragallinarum, isolated from fowls suffering from infectious coryza or received from other investigators for comparison, and a collective consisting of 9 strains of the new species H. paravium nova species, also isolated from fowls, were shown to possess both enzymes, neuraminidase (EC 3.2.1.18) and N-Acylneuraminate-pyruvate lyase (EC 4.1.3.3). The detection of the enzymes was made initially by paper chromatography using N-acetyl-neuraminyllactose as substrate and secondly by the colorimetric assay of Warren's thiobarbituric acid method using N-acetylneuraminyllactose, colomic acid, Na salt, bovine submaxillary mucin, human serum and furthermore N-acetyl-neuraminate as substrates for neuraminidase and N-acylneuraminate pyruvate lyase respectively. The enzyme activities of the strains of H. paravium are stronger than those of H. paragallinarum.

Animals↗

PubMed1977

Inhibition studies on Vibrio cholerae neuraminidase.

A series of viral neuraminidase inhibitors showing no structural analogy to neuraminic acids have been tested to find whether they are effective inhibitors of V. cholerae neuraminidase, too. Here we report the results obtained with the N-phenyloxamic acid derivatives 2 to 6 (R-NH-CO-COOR'; R = -C6H5NO2, -C6H5OH, -C6H5NH2; R' = -H, -C2H5; see Table 1) and with simple aromatic compounds structurally related to R, i.e. 4-nitroaniline (7), N-acetyl-4-nitroaniline (8), 4-nitrophenol (9), 2,4-dinitrophenol (10), and 4-aminophenol (11) (see Table 2). The inhibitory effects of 2 to 11 were studied according to the method of Dixon[19] in 0.1m sodium acetate buffer, pH 5.5, 2mM CaCl2, at 37 degrees C using the benzyl-alpha-ketoside of N-acetyl-D-neuraminic acid (1) as a substrate. The compounds 2 to 11 are shown to be competitive inhibitors of the enzymatic hydrolysis of the alpha-ketoside 1. The competitive inhibition kinetics are supported by the method of Lineweaver and Burk[20]. The inhibition constants (Ki) are found to be in the range of 0.03 to 5.7 mM. The simple aromatic compounds 7 to 11 show higher inhibitory activities than the phenyloxamic acid derivatives 2 to 6. In addition, significant differences in the Ki values were observed within the two series of inhibitors, whereby those containing a nitro group were most effective.

Aniline Compounds↗

PubMed1995

Modulation of the neuraminidase activity of HN protein from Newcastle disease virus by substrate binding and conformational change: kinetic and thermal denaturation studies.

A statistical study of the enzyme kinetics of the soluble fraction of Haemagglutinin-Neuraminidase (HN) protein from Newcastle Disease virus reveals that a high substrate concentrations its neuraminidase activity follows substrate-inhibition kinetics, in which the binding of a second molecule of substrate to the protein inhibits its enzymatic activity. Results show that the enzymatic activity is modulated by the second substrate to a different extent when the protein is in different environments. Taken together with results obtained by thermal denaturation studies of HN under varying conditions the data show that conformational changes leading to a loss of rigidity of HN are concomitant with the loss of catalytic activity. Also, electrophoretic and sucrose gradient analyses show that the soluble domain of HN behaves as a monomer.

Kinetics↗

PubMed1997

Histological evidence of neuraminidase involvement in acute nephritis: desialized leukocytes infiltrate the kidney in acute post-streptococcal glomerulonephritis.

Serum neuraminidase (NA, sialidase) activity has been demonstrated in acute poststreptococcal glomerulonephritis (APSGN) and implicated in the pathogenesis of the disease. Recent investigations show that neuraminidase-treated leukocytes accumulate preferentially in kidneys; therefore, we were interested in knowing if desialized cells infiltrate the kidney in APSGN. We first tested the capacity of peanut agglutinin lectin (PNA) to detect injected NA-treated leukocytes in the kidney of rats. NA-treated leukocytes were transfused and desialized cells were identified with fluorescein-conjugated peanut lectin (FITC-PNA) in renal tissue. PNA positive cells were identified in rat kidneys 3 hours after injection (glomeruli: 1.67 +/- 0.19 cells/g.c.s.; interstitium: 0.50 +/- 0.12 cells/int). Sections from available renal biopsy material of APSGN (n = 11), other glomerulonephritis (n = 28) and normal kidneys (n = 5) were double-stained with FITC-PNA and with monoclonal antibody to the CD11b molecule, which is expressed on polymorphonuclear and monocytes the main types of infiltrating cells during APSGN. Desialized (FITC-PNA positive) cells were found in the glomeruli (2.17 +/- SEM 0.22 cells per glomerular cross section, g.c.s.) and interstitium (0.61 +/- 0.15 cells per 0.0625 mm2, int) in all biopsies of APSGN. Only in 2 of 28 other glomerulonephritis showed desialized cells. More than 80% of the PNA positive cells in APSGN expressed the CD11b molecule and the infiltration was more intense in early biopsies. In conclusion, desialized leukocytes represent a significant part of the inflammatory infiltrate in APSGN. This finding gives support for a role of NA in the disease and provides clinical validation for a mechanism of renal cellular infiltration suggested by experimental observations.

Animals↗

PubMedDate not supplied

[Effect of neuraminidase treatment of chick embryo fibroblasts on the adsorption and reproduction of the fowl plague virus].

Treatment with neuraminidase (100 units/ml) of chick embryo fibroblasts in vitro only partially inhibits adsorption of fowl plague virus on these cells. Cultivation of chick embryo fibroblasts in the presence of 50 units/ml neuraminidase had no effect on the sensitivity of these cells to fowl plague virus and on the extent of virus reproductions. It is suggested that neuraminic acid which is a component of the external cell membrane is not only substance responsible for adsorption of orthomyxoviruses.

Adsorption↗

PubMed1997

[Changes in cell membrane fluidity evoked by removal of influenza virus receptors with neuraminidase].

The effect of the removal of the influenza virus receptor (N-acetylneuraminic acid) from the erythrocyte membrane by neuraminidase (RDE = receptor destroying enzyme) on the biophysical properties of the cell membrane has been examined using a fluorescent polarization technique. Diphenylhexatriene (DPH) was used as a fluorescent probe for structural ordering in the core of the membrane. A statistically significant decrease in the steady state values of DPH anisotropy was observed in membranes treated with RDE as compared to control. The anisotropy decrease reflected a reduced ordering of the hydrocarbon region of the erythrocyte membrane as well as an increase of its fluidity. An increase of membrane fluidity evoked by the action of influenza virus neuraminidase may play a significant role in the process of influenza virus penetration into the susceptible cell by endocytosis.

Anisotropy↗

PubMedDate not supplied

[Speed and intensity of the immune response to the administration of inactivated influenza vaccine in relation to neuraminidase activity].

A comparative study of the rate of appearance of specific virus antigen in immune competent organs of mice immunized with inactivated influenza vaccine with active neuraminidase or a vaccine devoid of the neuraminidase activity was carried out by means of the immunofluorescence test and the serological tests. A considerable delay in the time (by 16--18 hours) of detection of virus antigen in cells of lymph nodes of mice as well as later (1--2 days) and less intensive (2--4-fold) production of specific virus antibody was demonstrated after immunization of mice with the vaccine without the active enzyme.

Animals↗

PubMed1997

[Prognostic value of neuraminidase activity in mammary gland secretion in fetal death].

Neuraminidase activity and levels of sialic acids and some hormones were measured in mammary secretion of women with induced pregnancy with a history of endocrine sterility. The activity of neuraminidase in the breast milk of pregnant women with galactorrhea may serve an informative prognostic test indicating intrauterine fetal death for 8-10 days.

Breast↗

PubMedDate not supplied

[A mechanism for limiting reproduction influenza A virus reassortants with incomplete functional compatibility of hemagglutinin and neuraminidase gene products].

The mechanism of decrease in the level of virus accumulation in reassortants with hemagglutinin (HA) and neuraminidase (NA) genes from different parents is studied. The reassortant viruses and their passage variants do not differ by the rate of virus protein production or their stability in infected cells. Electron microscopy and titration of infectious virus in culture fluid and cell-associated virus showed that the variants selected by serial passages accumulated mainly in the culture fluid, whereas the initial reassortant virions were predominantly cell-associated. These data suggest that incomplete removal of sialic acid residues by viral neuraminidase N1 in some reassortants results in re-attachment of virions to the infected cells and thus impairs the virus dissemination, which may be regarded as a reassortant-limiting factor probably significant for virus evolution.

Animals↗

PubMed1976

Deficit in neuraminidase associated with mucolipidosis II (I-cell disease).

Using a tritiated sialyloligosaccharide as a substrate, the authors showed that mucolipidosis II is characterized by a lack of neuraminidase activity in leucocytes, while the other acidic hydrolases activities are normal. According to Ashwell, terminal galactose is the required signal for glycoproteins uptake by the cells. Thus, a neuraminidase deficit may explain the increase of sialylated hydrolases activities in the plasma and the non-recognition of these enzymes by cultured fibroblasts.

Humans↗

PubMed1976

The influence of trypsin and neuraminidase on content of serotonin in rat blood platelets.

Trypsin produced phasic changes (increase or decrease) in the serotonin levels in blood platelets depending on the initial concentration of serotonin in the platelets. The lowest concentration of trypsin that was used raised the content of serotonin in unloaded platelets, while all tested concentrations of trypsin lowered content of serotonin when the platelets were loaded with serotonin. Prolongation of time of incubation from 6 to 12 minutes revealed an action of some of the concentrations of trypsin that were previously inactive. Neuraminidase lowered serotonin levels in rat platelets. The effect of the highest concentration of neuraminidase was enhanced in presence of some of the concentrations of trypsin.

Animals↗

PubMed1994

Regions on the hemagglutinin-neuraminidase proteins of human parainfluenza virus type-1 and Sendai virus important for membrane fusion.

To study the contributions of the hemagglutinin-neuraminidase (HN) and the fusion (F) glycoproteins in virus-induced membrane fusion, the HN and F proteins of human parainfluenza virus type-1 (hPIV-1) and Sendai virus (SV) were expressed in HeLa T4+ cells using the vaccinia virus-T7 RNA polymerase transient expression system. Expression of F protein alone did not induce cell fusion. However, coexpression of homologous F and HN proteins resulted in extensive syncytium formation by hPIV-1 or SV glycoproteins, which supports the proposal that both the F and HN glycoproteins are necessary for membrane fusion. To investigate the function of HN in membrane fusion, we coexpressed heterologous combinations of the HN and F proteins of hPIV-1 and SV. No fusion was observed when SV HN and hPIV-1 F proteins were coexpressed. In contrast, the coexpression of hPIV-1 HN and SV F induced extensive cell fusion. These results suggest that specific interaction between HN and F is required to induce membrane fusion. To locate regions that are essential to the fusion promoting activity, chimeric HN proteins of SV and hPIV-1 were constructed. The chimeric proteins coexpressed with the SV or hPIV-1 F proteins indicated that some regions in the middle 62% of HN contribute to the fusion-promoting activity. To determine the role of the transmembrane region of HN on fusion-promoting activity, mutant HN proteins were expressed and their biological activities examined. Mutation of hPIV-1 HN at residue 55 from cysteine to tryptophan did not affect cell binding, neuraminidase activities, or homooligomer formation, but did result in the loss of cell fusion activity. The mutation of the same cysteine residue to glycine retained the fusion-promoting activity, suggesting that a sulfhydryl moiety is not specifically required at position 55, but the structure of the residue that occupies the position is important in fusion-promoting activity.

HN Protein↗