2,3-Dehydro-4-epi-N-acetylneuraminic acid; a neuraminidase inhibitor

Treatment of N-acetylneuraminic acid methyl ester with sulfuric acid and acetic anhydride at 50 degrees followed by deacetylation gave 2,3-dehydro-2-deoxy-N-acetylneuraminic acid methyl ester and methyl 5-acetamido-2,6-anhydro-2,3,5-trideoxy-D-glycero-D-talo-non-2-enonate (2,3-dehydro-4-epi-NeuAc methyl ester) in equal yields (approximately 40% each). The structure of the latter was ascertained primarily from analysis of its mass spectrum and 1H- and 13C-nuclear magnetic resonance spectra. The relative proportions of these two glycals in the foregoing reaction was dependent on temperature, as at 0 degrees, the yield of 2,3-dehydro-4-epi-NeuAc was markedly diminished. A minor by-product of this acetylation reaction was 2-methyl-(methyl 7,8,9-tri-O-acetyl-2,6-anhydro-2,3,5-trideoxy-D-glycero-D-talo-non-2-enonate)-[ 4,5-d]-2-oxazoline. Based upon this finding and additional interconversion experiments, a mechanism involving the intermediacy of the latter oxazoline to account for the epimerization is proposed. These glycals and their methyl esters are competitive inhibitors of Arthrobacter sialophilus, neuraminidase, suggesting that the 4-hydroxyl group must be equatorially oriented for maximal enzyme inhibition.

Properties of human thyroidal and extrathyroidal TSH receptors

The presence of high affinity receptor sites for thyroid-stimulating hormone (TSH) in the human is not limited to the thyroid gland. In this report, the properties of thyroidal and extrathyroidal TSH binding have been explored through the effect of various agents (TSI of Graves' disease, propranolol, hCG, N-acetylneuraminic acid, ACTH, insulin and L-thyroxine) on the receptors.

Statistically significant inhibition of [125I]TSH binding occurred with all immunoglobulin preparations (TSI) of Graves' disease on thyroid cell membrane receptors. Thirty-three per cent of the same immunoglobulins showed significant inhibition of [125I]TSH binding when testicular cell membranes were used, while there was no such inhibition when renal cell membranes were utilized. D or L-propranolol at least doubled the [125I]TSH initial binding (Bo) to the thyroid membranes but had no effect on the testicular or fat cell binding. Human chorionic gonadotrophin (hCG) at concentrations of 400 USP units per 350 μl totally inhibited the [125I]TSH from binding to testicular membranes but not to thryroid or fat cell membranes. Conversely, the binding of [125I]hCG to human testicular membrane was inhibited by both stable hCG and TSH, but with human thyroid membrane, only TSH could inhibit binding of [125I]hCG. These data suggest that the TSH receptors in extrathyroidal tissues may not be identical to TSH receptors within the thyroid. TSH binding to thyroidal tissue was significantly suppressed by N-acetylneuraminic acid, was increased by D and L-propranolol and was unaffected by ACTH and insulin. L-thyroxine had a dose-related suppressive effect on the TSH binding, commencing at 50 μg/ml. While these effects were observed in vitro, it is possible that some of the above agents may also interfere with thyroid gland function in vivo. They suggest further that a number of interactions may take place at the TSH binding sites which could alter TSH binding and/or function.

[Selective anti-aggregation--a new concept for inhibitors of the platelet function (author's transl)]

Activation and aggregation of platelets, as to their biochemical nature, are two distinct partial mechanisms of platelet reaction. The known inhibitors of platelet aggregation such as acetylsalicylic acid or prostacyclin interfere in metabolic pathways involved in the activation of platelets. In contrast, selective inhibitors of aggregation inhibit the interactions between the surfaces of activated platelets. N-acetylneuraminic acid is an example of a selectively anti-aggregating substance in vitro. Besides its inhibitory effect on the primary aggregation, a platelet-specific inhibition of prostaglandin synthesis belongs to its pattern of effects. By inhibiting the mechanism of aggregation, N-acetylneuraminic acid also inhibits one of the most important trigger of prostaglandin synthesis in platelets. This results in an interruption of the feedback amplification in activation which is mediated by prostaglandin and thromboxane synthesis in human platelets. These properties of anti-aggregating agents combine a favorable pattern of effects with a platelet-specific point of attack.

The distribution of Helix pomatia lectin receptors on mouse lymphoid cells and other tissues

The distribution of receptors for the Helix pomatia lectin on mouse lymphoid cells and other tissues was investigated. Using a sensitive rosetting assay combined with immunofluorescence, lectin receptors were found on the membrane of approximately 90% of peripheral T lymphocytes, 75% of thymocytes, 30% of bone marrow cells, 20% of nude spleen cells, 15-50% of peritoneal exudate macrophages, and a subpopulation of peritoneal exudate mast cells. The Thy-1-positive nude spleen cells were predominantly Helix lectin receptor-negative. Approximately 5% of B lymphocytes were weakly positive, and neutrophils were negative. Receptors were present also on a subpopulation of cells of a fibroblast cell line and in acetone powder from the liver and, at a lower level, from the kidney and brain. Membrane receptors on all cell types were partially detectable without neuraminidase treatment of the cells. Two methods of fractionating Helix lextin-positive cells were employed, which gave significantly different results. By rosetting and depletion using density fractionation, T cell mitogen responses were abolished, while B cell mitogen responses, T cell cytotoxicity, and natural killer cytotoxicity were only slightly affected, if at all, Helix lectin-agarose column fractionation seemed more sensitive, in that essentially all natural kill cells bound to the column, as well as considerable number of B lymphocytes. Cytotoxic T cells were heterogeneous; roughly half were not bound, but the remainder were bound and eluted.

Lymphocyte transformation induced by autologous splenocytes incorporated with the tetrasialoganglioside GQ1b

Incorporation of the tetrasialoganglioside GQ1b into membranes of mouse splenocytes rendered these cells effective triggers in an autologous mixed lymphocyte reaction. Whereas GQ1b-incorporated cells increased mitogenic responses of thymocytes by 10 to 13-fold over untreated cultures, the trisialoganglioside GT1b was only partially effective, and the di- and monosialogangliosides tested had no effect. The mixed lymphocyte reaction generated in the autologous system by highly glycosylated gangliosides is abolished by neuraminidase or mile formic acid treatment prior to their insertion into target cell membranes suggesting a role for the extra sialic acid residues in imparting additional antigenic specificity to the modified cells.

Anti-self receptors. IV. H-2-restricted receptors on thymocytes recognize carbohydrate structures on target cells

Rosetting between thymocytes and autologous erythrocytes in mediated by receptors on thymocytes that primarily recognize self H-2L molecules on erythrocytes. This paper describes preliminary attempts to chemically characterize the receptor and acceptor molecules involved in this H-2-restricted interaction. On the basis of sugar inhibition studies and the sensitivity of the receptors to protease and glycosidase treatments it appears that a protein receptor on thymocytes recognizes the carbohydrate portion of a glycoprotein on erythrocytes. Furthermore, the thymocyte receptor appears to recognize terminal D-galactose, D-mannose and sialic acid residues on a branched-chain carbohydrate structure on erythrocytes, with mouse strains of different H-2 haplotype expressing carbohydrate structures that differ in the linkage of these three terminal sugars. These findings indicate that H-2-restricted carbohydrate-protein interactions can occur between cells, a conclusion with important theoretical implications.

Cytotoxicity of pyocin S2 to tumor and normal cells and its interaction with cell surfaces

Cytotoxicity and adsorption of pyocin S2 produced by Pseudomonas aeruginosa M47 (PAO 3047) to virally transformed mammalian cells, human malignant cells and normal cells in the same species were studied. Pyocin S2 inhibited the growth of not only tumor cells (XC, TSV-5, mKS-A TU-7, HeLa-S3 and AS-II cells) but also normal cells (BALB/3T3 and BHK 21 cells). The inhibitory effects on the cells increased with an increase of pyocin S2 activity. On the other hand, there were some tumor cells (155-4 T2 and HCG-27 cells) and normal cells (normal rat kidney and human embryo lung cells) which were resistant to pyocin S2. The pyocin S2 activity was neutralized by the cell membrane preparations from pyocin S2-sensitive cells, but not by those from pyocin-resistant cells. This neutralization ability was inhibited by high concentrations of D-galactose, N-acetyl-D-galactosamine and N-acetyl neuraminic acid and completely destroyed by periodate and neuraminidase. The inhibition by the saccharides was concentration dependent. These results suggest that the toxicity of pyocin S2 in the cell membrane and further, that the carbohydrate moiety, especially of D-galactose, N-acetyl-D-galactosamine and sialic acid, may play an important role as an initial binding site for pyocin S2.

Suppression of the intravascular adherence of granulocytes by N-acetyl neuraminic (sialic) acid

Adherence of granulocytes to the endothelium of small veins in different microvascular beds was quantified by visual counting of the adherent cells. Increased adherence of granulocytes induced by the stress of preparation or by ultraviolet light irradiation of the microvasculature was greatly reduced by i.v. administration of sialic acid. In the rabbit ear chamber laser irradiation induced increased granulocyte stickiness which was similarly prevented by intra-arterial infusion of sialic acid. In normal rats, sialic acid treatment induced granulocytosis and the effect was more striking on Busulphan-induced leucopenia in rats. Glucuronic acid applied under identical conditions had no effect on granulocyte adhesiveness in vivo or on the peripheral blood granulocyte count. According to these findings exogenous sialic acid greatly reduces the effect different pathogenic stimuli have of inducing adherence of granulocytes to blood vessel walls and induces granulocytosis by mobilizing cells from the "marginating" and reserve pools.

Marine biopolymers with cell specificity. II. Purification and characterization of agglutinins from mucus of windowpane flounder Lophopsetta maculata

The windowpane flounder, Lophopsetta maculata, was found to have proteins in the body mucus which agglutinate mouse leukemia cells, L5784Y but not L1210. They also agglutinate rabbit and mouse erythrocytes, a marine yeast and a bacterium, and have weak activity against mouse sarcoma 180 cells, human B, guinea pig, and horse erythrocytes. The hemagglutinating activity was not affected by the treatment with 2-mercaptoethanol, trypsin, or pronase, but was inhibited by a high concentration of N-acetylneuraminic acid. The major active component was purified and found to be a protein having a molecular weight of 68 000 which dissociates into subunits of equal size (16 000). Isoelectrofocusing gave two sharp bands, close together, at pI 4.7 +/- 0.1. The protein contains high amounts of aspartic acid, glutamic acid and glycine, and very little histidine and half-cystine.

Role of sialic acid in the macrophage glycolipid receptor for MIF

Acidic glycolipids from guinea pig macrophages enhance the response of macrophages to migration inhibitory factor (MIF), suggesting a role of glycolipid receptors for this lymphocyte mediator. Neuraminidase treatment of these glycolipids results in the loss of their biologic activity. This activity remains intact after incubation of the glycolipids with beta-galactosidase. In order to investigate whether sialic acid is essential for the macrophage's response to MIF, macrophages were incubated with neuraminidase. Neuraminidase treatment of peritoneal exudate cells results in the abrogation of macrophage responsiveness to MIF. Other exoglycosidases such as beta-galactosidase and beta-glucosidase had no effect upon the macrophage response. The effect of neuraminidase was found to be reversible within 18 hr. These experiments suggest that macrophage glycolipids containing sialic acid are components of the macrophage receptor for MIF.

Effects of administration of N-acetylneuraminic acid (NANA) on brain NANA content and behavior

Rat pups were malnourished during the first 3 weeks after birth. Experimental rats were injected intraperitoneally with 1 mg N-acetylneuraminic acid (NANA) per 50 g body weight daily from 14 to 21 days postnatally. Control animals were similarly injected with 1 mg glucose per 50 g body weight. At 21 days of age, the rats were tested in an open field and their brains analyzed for protein, DNA, ganglioside NANA and glycoprotein NANA. The administration of NANA was associated with an increase in cerebral and cerebellar ganglioside and glycoprotein NANA concentrations. However, it had no effects on brain weight, cell size and number. There was also a reduction in the expected behavioral abnormalities secondary to malnutrition. At 21 days of age, similarly treated littermates of the experimental animals were weaned to a stock diet and tested in a Y maze at 6 months of age. Rats treated with NANA learned the maze quicker than controls and the previously noted changes in brain biochemistry were found to have persisted. Intraperitoneal injection of [14C]NANA into malnourished rats during the same period showed that it was readily incorporated into brain glycoproteins and gangliosides. The possibility that the brain concentration of NANA has an effect on behavior is discussed.

Inhibition by N-acetyl neuraminic (sialic) acid of platelet aggregation induced by different stimuli

Addition of N-acetyl neuraminic acid (sialic acid, NANA) to citrated rat platelet-rich plasma significantly inhibited aggregation induced by near-threshold concentration of ADP, collagen or thrombin. In heparinized rat platelet-rich plasma aggregation of platelets induced by endotoxin or tumour cells of various origins was also inhibited by sialic acid. It is suggested that exogenous or endogenous sialic acid may act against various aggregating stimuli on the platelet membrane by masking a common factor through which various aggregating agents exert their effect.

Neuraminidase-dependent hamagglutination of human erythrocytes by human strains of Actinomyces viscosus and Actinomyces naeslundii

Human A, B, and O erythrocytes (RBC) were agglutinated by many human strains of Actinomyces viscosus and A. naeslundii. At 37 degrees C, these bacterium-mediated hemagglutination reactions required the action of bacterial neuraminidase upon the RBC; however, at 4 degrees C, the requirement for neuraminidase was not as striking. Bacterial cell suspensions which caused hemagglutination at 37 degrees C contained both soluble extracellular and cell-associated neuraminidase activities as shown by enzyme assays using a soluble substrate (i.e., alpha 1-acid glycoprotein). Bacterium-mediated hemagglutination occurred only in the presence of soluble neuraminidase activity, and the rate of hemagglutination could be inhibited by 2-deoxy-2,3-dehydro-N-acetylneuraminic acid, a competitive inhibitor of purified soluble neuraminidase from A. viscosus T14V. Suspensions of bacteria which contained only cell-associated neuraminidase activity were unable to initiate hemagglutination, but they caused immediate hemagglutination when mixed with neuraminidase-treated RBC. All hemagglutination reactions were reversible in the presence of 0.02 M lactose and were abolished by heating (85 degrees C for 30 min) the actinomycete cells but not the RBC. The proposed mechanism of hemagglutination involves two sequential steps: (i) the action of neuraminidase to unmask galactose-containing receptors on the RBC and (ii) the multivalent binding of these receptors by many low-affinity lection sites on the bacterial surface.

Factors influencing adherence of group B streptococci to human vaginal epithelial cells

Factors affecting the adherence of group B streptococci to human vaginal epithelial cells in vitro were examined. Maximal adherence was achieved within 15 min of incubation of bacteria with epithelial cells. Adherence was temperature and pH dependent; maximal adherence occurred at 37 degrees C and pH 5.5. Killing of streptococci with ultraviolet light or penicillin did not affect adherence. Similarly, adherence was not altered by preincubating epithelial cells at 65 degrees C for 30 min. Thus neither bacterial nor epithelial cell viability appears to be a prerequisite for adherence. Preincubation of streptococci at 65 degrees C for 30 min resulted in a marked decrease in adherence, whereas preincubation of group B streptococci with neuraminidase was associated with a significant increase in adherence. The adherence of strains belonging to five different group B streptococcal serotypes was not altered by group-specific or type-specific rabbit antisera. These findings suggest that the site for adherence on the bacterial cell wall is heat sensitive and is marked by sialic acid, but is not related to either group-specific or type-specific antigens.

Inhibition of platelet aggregation by native and desialised alpha-1 acid glycoprotein

The alpha-1 acid glycoprotein (orosomucoid; AAG) is a normal constituent of human plasma (650+/-215 microgram ml(-1)) which increases in concentration as much as fivefold in associations with acute inflammation and cancer, and thus is recognized as an acute phase protein. AAG consists of a single polypeptide chain, has a molecular weight of 44,100, and contains approximately 45% carbohydrate including 12% sialic acid; it is the most negatively charged of the plasma proteins. Certain of the biological properties of AAG are related to its sialic acid content; thus, clearance and immunogenicity of AAG are markedly increased on desialisation. The biological functions of AAG are largely unknown. AAG has the ability to inhibit certain lymphocyte re-activities including blastogenesis in response to concanavalin A, phytohaemagglutinin and allogeneic cells, and these inhibitory effects are enhanced in association with desialisation. In view of these observations, a report that unphysiologically large (5--15 mg ml(-1)) amounts of AAG inhibit the platelet aggregation induced by ADP and adrenaline, and evidence that a sialic acid-deficient species of AAG appears elevated in several chronic disease states, we compared the effects of AAG and its desialised counterpart (AAG-D) on platelet aggregation. We report that desialisation of AAG is associated with increased expression of activity inhibitory to the platelet aggregation otherwise observed on stimulation with ADP, collagen or thrombin.

Purification and characterization of the CFA/I antigen of enterotoxigenic Escherichia coli

The fimbral colonization factor antigen CFA/I of enterotoxigenic Escherichia coli was purified and characterized. The initial purification step was release of these fimbriae from the bacterial cells by homogenization with a Waring blender. Common fimbriae and flagellar antigen were avoided by careful control of growth conditions and the use of a nonmotile (H-) mutant of the prototype strain H-10407 (O78:H11). The essential purification steps were membrane filtration (Millipore Corp.), ammonium sulfate fractionation, and negative diethylaminoethyl-Sephadex column chromatography. Yields were approximately 4.0 mg of CFA/I protein per g (wet weight) of bacteria. Purified CFA/I is a fimbrial molecule 7.0 nm in diameter and has an average molecular weight of 1.6 X 10(6), as determined by sedimentation equilibrium. CFA/I is a polymer of identical subunits of molecular weight 23,800 with an N-terminal valine, 37% hydrophobic amino acid residues, and 11 residues of proline per mol. The purified antigen retains its morphology, antigenicity, and biological activity. Purified antigen retains its morphology, antigenicity, and biological activity. Purified CFA/I exhibits mannose-resistant hemagglutination of human group A, bovine, and chicken erythrocytes, as do CFA/I-positive bacteria. This was demonstrated by sensitizing latex microbeads with the purified antigen since cell-free CFA/I fimbriae do not hemagglutinate erythrocytes. Thus, CFA/I detached from the bacteria are monovalent; however, purified CFA/I antigen retains an affinity for the epithelial cells of rabbit small intestine and blocks adhesion of CFA/I-positive bacteria. These results demonstrate that purified CFA/I is a good candidate for use in an oral vaccine for immunoprotection against diarrhea caused by CFA/I-positive enterotoxigenic E. coli.

Adherence of erythrocytes to Mycoplasma pneumoniae

The human pathogen Mycoplasma pneumoniae adheres to a variety of cells, including erythrocytes. A hemadsorption technique was developed to quantitate adherence by photometric measurement of lysates of erythrocytes that attached to sheets of M. pneumoniae grown in cups of Linbro plates. Attachment of sheep erythrocytes (SE) increased with higher ionic strength, was unaffected by minor pH variations (6 to 9), and was blocked by anti-M. pneumoniae antiserum, but was not inhibited by a variety of sugars, amino acids, and bovine serum albumin. The reaction was time and temperature dependent. The temperature curve showed peaks at 14 and 28 degrees C with untreated SE but only one peak at about 38 degrees C with glutaraldehyde-treated SE. The temperature dependence indicated involvement of either metabolic or membrane activities in the binding process. Trypsin treatment of the M. pneumoniae sheet abolished adherence of SE but was only partially effective with human erythrocytes and noneffective with rabbit erythrocytes. The binding capacity of the mycoplasma cells for SE was restored by incubation in growth medium for 3 to 4 h; this restoration was inhibited by 10 mug of chloramphenicol per ml. Neuraminidase treatment of SE removed their attachment capacity but had no effect on attachment of rabbit erythrocytes and only a slight effect on attachment of human erythrocytes. Pretreatment of M. pneumoniae with neuraminic acid partially blocked the adherence of SE, whereas rabbit erythrocyte attachment was not affected. Attached SE could be detached by trypsin, but not by neuraminidase. For human and rabbit erythrocytes, the results suggest binding mechanisms other than the interaction between neuraminidase-sensitive receptors and protein-containing binding sites shown for SE.

Interaction of Mycoplasma pneumoniae with human lung fibroblasts: role of receptor sites

The biochemical nature of the neuraminidase-sensitive Mycoplasma pneumoniae receptor site on human lung fibroblast cells was studied. Purified, mixed sialoglycolipid (ganglioside) preparations from human and bovine tissues did not bind to M. pneumoniae organisms and block their subsequent attachment to fibroblasts. Fibroblasts incubated for 24 h in sialoglycolipid solutions to increase the ganglioside content of their membranes did not show increased pathogen attachment when later incubated with mycoplasmas. HeLa cells grown in the presence of sodium butyrate to increase GM3 ganglioside levels likewise did not have significantly increased uptake of M. pneumoniae organisms. Treatment of fibroblasts with enzymes indicated that the mycoplasma receptor site is trypsin and papain resistant but Pronase sensitive. Pronase digests of fibroblast membranes contained a product(s) which combined with M. pneumoniae cellls and cosedimented with them during centrifugation. Glycoproteins, purified from fibroblast membranes by a lithium diiodosalicylate solubilization technique, similarly bound to M. pneumoniae organisms. Collectively, these data suggest that the major component of the M. pneumoniae receptor site is a sialoglycoprotein with little or no lipid.

The absence of a role for the carbohydrate moiety in the binding of apolipoprotein B to the low density lipoprotein receptor

The binding of low density lipoprotein (LDL) to fibroblasts occurs through apolipoprotein B, a glycoprotein. The role of the carbohydrate in binding was assessed in two ways: (1) LDL, freed of sialic acid and most of the glucosamine and hexoses by digestion with a mixture of glycosidases, bound to fibroblasts as does native LDL. (2) The glycopeptides liberated from apoprotein B by trypsin and pronase failed to inhibit LDL binding to fibroblasts. Apparently the carbohydrate moiety of LDL does not interact with the plasma membrane receptor.

Correlation of activation and aggregation of platelets. Discrimination between anti-activating and anti-aggregating agents

Shape change and release reaction indicate different degrees of the complex platelet response termed activation. Aggregation is a variable consequence of activation. Aggregation shows a temperature dependency opposite to that shown by the preceding shape change. Aggregation increases at lower temperature and requires, in contrast to activation, extracellular Ca2+, stirring, and at a low degree of activation the presence of fibrinogen. Aggregation can enhance activation by triggering prostaglandin endoperoxide-thromboxane synthesis. If activation reaches a high level associated with the release reaction, activation is further amplified by prostaglandin endoperoxide-thromboxane synthesis emerging independent of aggregation. These mechanisms of amplification of activation are blocked by indomethacin, an inhibitor of prostaglandin endoperoxide-thromboxane synthesis=anti-activating agent. In contrast, anti-aggregating agents, exemplified here with n-acetyl neuraminic acid, attack the aggregation of activated platelets but neither activation nor prostaglandin endoperoxide-thromboxane synthesis. Its anti-aggregating effect, in addition, enables n-acetyl neuraminic acid to imitate the inhibitory effect of indomethacin on the feedback amplification which results from aggregation. Anti-aggregating agents as characterized here may open a new valuable concept for anti-aggregation in vivo.

Characterization of sialytransferase in noncancerous and neoplastic human liver tissue

When compared to uninvolved adjacent tissue, metastatic tumors in human liver appear to have significantly reduced sialytransferase activity. No significant kinetic differences (Michaelis constants, thermostability, and pH optima) between noncancerous and cancerous tissue sialytransferase were found. Mixing experiments between cancerous and noncancerous tissues indicated that inhibitors of sialytransferase activity were present in cancerous tissue. Subsequent experiments demonstrated increased levels of bound sialic acid in the tumor tissues. Inasmuch as futuin, a sialoglycoprotein, inhibits sialyltransferase activity, the increased levels of bound sialic acid in tumor tissue may be responsible for the reduced enzyme activity in these tissues.

Autosomal locus regulates inverse relationship between sialic acid content and capacity of mouse erythrocytes to activate human alternative complement pathway

The observation that mouse erythrocytes (E(m)) from 21 inbred strains had variable capabilities to activate the human alternative complement pathway permitted the demonstration that membrane sialic acid content was inversely related to activating capacity and was regulated by codominant alleles of a single autosomal locus. Linear regression analysis also demonstrated a significant inverse correlation between the sialic acid content of E(m) from four inbred strains and the concentration of beta1H required for decay-dissociation of the properdin-stabilized amplification convertase on the E(m). E(m) from F(1) hybrids derived from strains with high and low alternative pathway activating capacities and from their backcrosses exhibited the alternative pathway activating capacities expected if the activity were regulated by alleles of a single autosomal locus. That this same locus predominantly regulated the sialic acid content of E(m) was established by the significant inverse correlation between the sialic acid content and the alternative pathway activating capacity of E(m) from mice of the F(1) and backcross generations. Although the fluid phase interaction of C3, B, and [unk]D continuously generates C3b in a reaction augmented by properdin, it is the covalent attachment of C3b to bystander surfaces deficient in sialic acid that activates the alternative complement pathway at that site because of impaired binding of beta1H to C3b on such surfaces. Thus, discrimination between activating and nonactivating surfaces occurs after C3b deposition, and sialic acid deficiency represents the molecular basis for our earlier finding that activating particles circumvent the regulatory actions of the control proteins of the alternative pathway.

Inhibition by N-acetyl neuraminic acid of platelet thrombogenesis induced by laser injury to rat and hamster venules

1 In rats and hamsters under barbiturate anaesthesia, laser radiation to venules about 50 micrometer in diameter in mesoappendix and cheek pouch respectively caused the formation of platelet thrombi which occluded the vessels in about 9 min. 2 This occlusion time was significantly prolonged by the intravenous injection of N-acetyl neuraminic acid (NANA) but not by D-glucuronic acid or beta-methoxyneuraminic acid, in doses which had no effect on blood pH or on the condition of the animals. 3 The results confirm the anti-thrombotic effect of NANA previously demonstrated with another technique.

Anti-inflammatory effect of sialic acid

Sialic acid was shown to possess anti-inflammatory properties as measured by carrageenan-induced rat paw oedema and pleurisy tests. As the number of leukocytes mobilized was significantly reduced it was concluded that the inhibitory effect of sialic acid on leukocyte accumulation is responsible for the inhibition of exudate/oedema formation.

Adherence of Mycoplasma gallisepticum to human erythrocytes

Pathogenic mycoplasmas adhere to and colonize the epithelial lining of the respiratory and genital tracts of infected animals. An experimental system suitable for the quantitative study of mycoplasma adherence has been developed by us. The system consists of human erythrocytes (RBC) and the avian pathogen Mycoplasma gallisepticum, in which membrane lipids were labeled. The amount of mycoplasma cells attached to the RBC, which was determined according to radioactivity measurements, decreased on increasing the pH or ionic strength of the attachment mixture. Attachment followed first-order kinetics and depended on temperature. The mycoplasma cell population remaining in the supernatant fluid after exposure to RBC showed a much poorer ability to attach to RBC during a second attachment test, indicating an unequal distribution of binding sites among cells within a given population. The gradual removal of sialic acid residues from the RBC by neuraminidase was accompanied by a decrease in mycoplasma attachment. Isolated glycophorin, the RBC membrane glycoprotein carrying almost all the sialic acid moieties of the RBC, inhibited M. gallisepticum attachment, whereas asialoglycophorin and sialic acid itself were very poor inhibitors of attachment. Only part of the (125)I-labeled glycophorin bound to mycoplasmas could be removed by neuraminidase or by exchange with unlabeled glycophorin. It is suggested that glycophorin, representing the isolated major RBC receptor for M. gallisepticum, binds to the mycoplasmas both specifically, through its sialic acid moieties, and nonspecifically, through its exposed hydrophobic polypeptide moiety.

[Study of the role of sialic acids in the formation of bound form of insulin]

In studying the formation of insulin complexes with transferrin the role played by sialic acids in this process was ascertained. The role of terminal sialic acids, included into the glycoprotein composition, in the formation of complexes of these glycoproteins with a number of components circulating in the blood was noted earlier. To study the role played by sialic acids of transferrin molecule in the formation of complexes with insulin the author used transferrin untreated and treated with neuraminidase, an enzyme splitting the sialic acid molecules from grycoprotein specifically. The influence of these preparations on the biological activity of insulin was studied. Transferrin devoid of sialic acid lost its capacity to form complexes with insulin. Control experiments demonstrated that by itself neuraminidase treatment of preparations of transferrin and insulin failed to influence their biological activity. The results of experiments with the use of neuraminidase demonstrated that sialic acid in donor transferrin molecule could be of great significance in the formation of an insulin-transferrin complex.

Inhibition of alkaline phosphatase by sialic acid

The interaction of human organ alkaline phosphatases (orthophosphoric-monoester phosphohydrolases (alkaline optimum), EC 3.1.3.1) with sugars was studied. Hexosamines, N-acetylneuraminic acid (NANA or sialic acid), N-acetylmuramic acid and N-acetylglycolylneuraminic acid inhibited human organ alkaline phosphatase activities. Of these, sialic acid was the most effective inhibitor. The pH profiles for the enzymes in the absence and presence of sialic acid were similar. The sialic acid - enzyme complex was more heat stable than the free enzyme between 20 and 45 degrees C. Lineweaver-Burk plots of 1/v versus 1/S at various concentrations of sialic acid showed intersecting straight lines indicating that the mechanism of inhibition was a mixed type. The Ki value obtained from the plots of 1/v versus the square of sialic acid concentration was 0.07 mM for the hepatic, sialidase-treated hepatic, and intestinal alkaline phosphatases. The respective Hill coefficients varied somewhat with the alkaline phosphatase isoenzyme. Hyperbolic curves were obtained when the percentage of remaining activity was plotted against the substrate concentration at different concentrations of sialic acid. The Hill coefficient was lowered in the presence of sialic acid. The sialidase-treated hepatic enzymes used gave the most effective conversion. Partial denaturation of the enzyme with urea, or pronase digestion had a little if any effect on the sialic acid inhibition with constant time.

'VA', a new type of erythrocyte polyagglutination characterized by depressed H receptors and associated with hemolytic anemia. II. Observations by immunofluorescence, electron microscopy, cell electrophoresis and Biochemistry

With help of immunoflorescence, best with anti-AHP from Helix pomatia, a stippled structure could be demonstrated on the patient"s red blood cells. Thus an "A-like" receptor could be detected on the erythrocyte membrane of this group O patient. The reactive antigen was proved not to be a crypt antigen exposed by the action of neuraminidase. The same stippled fluorescence with antiAhp was observed on the red blood cells of a patient suffering from hemolytic anemia induced by influnza A2 virus. In this case this virus was shown not to be responsible for polyagglutination. No virus or microorganism could be isolated from the patient"s blood. Also by immunofluorescence the weak expression of the H antigen could be demonstrated with an extract of Evonymus europaeus. Electron microscopy of erythrocytes was normal. The neuraminic acid content and the electrophoretic mobility were found to be decreased to a minor degree. No distinct cell populations could be observed.

Specificity and possible origin of anti-N antibodies developed by patients undergoing chronic haemodialysis

Studies were performed on two anti-N sera from patients who had formed anti-N antibodies during their period of haemodialysis. No specific inhibition of these antibodies was obtained by extracts prepared from a new and a used dialysis unit, and it was concluded that there was no evidence of a compound in the units which would stimulate production of the anti-N. The specificity of the anti-N's was shown to be against a precursor of MN antigens, since all activity in the sera could be removed by neuraminidase-treated M cells, which expressed MN precursor. Since the anti-N's would react with untreated N cells only at 4 degrees C, but with formaldehyde-treated cells at 4, 25 and 37 degrees C, it was concluded that the specificity of the anti-N's was directed against an antigen developed by red cells after formaldehyde treatment. It is proposed that the production of the anti-N antibodies is stimulated by formaldehyde-treated red cells passing into the patient during re-use of a dialysis unit sterilized with formaldehyde.

Inhibition of influenza virus replication in tissue culture by 2-deoxy-2,3-dehydro-N-trifluoroacetylneuraminic acid (FANA): mechanism of action

The neuraminidase inhibitor 2-deoxy-2,3-dehydro-N-trifluoroacetylneuraminic acid (FANA) inhibits the mutlicycle replication of influenza viruses in tissue culture. Influenza virus grown in the presence of FANA contains neuraminic acid on its envelope which then serves as receptor for other virus particles causing extensive aggregation. Thus, FANA inhibits influenza virus replication by preventing the enzymatic removal of neuraminic acid from the virus envelope.

Responses of Megalodiscus temperatus miracidia to amino and sialic acids found in snail-conditioned water

Analysis of snail-conditioned water (SCW) from Helisoma trivolvis revealed 17 free amino acids. Those in great concentration were glycine, serine, and alanine. The concentration of sialic acid was found to be twice that of the most abundant amino acid. The behavior of miracidia of Megalodiscus temperatus, measured by the contact with return method, to agar cylinders containing single amino acids and sialic acid indicated greater responses to polar molecules charged either positively or negatively at neutral pH. The molecules elicting the greatest response were aspartic, glutamic, and sialic acid. No correlation was found between concentration of amino acids in H. trivolvis SCW and response of M. temperatus miracidia.

Thyroid-stimulating hormone binding to beef thyroid membranes. Role of N-acetylneuraminic acid

The effect of sugars on 125I-thyroid-stimulating hormone binding to beef thyroid membranes was studied to determine their role in thyroid-stimulating hormone (TSH) binding. At 0.1 M concentration, N-acetylneuraminic acid produced a 3- to 7-fold increase in TSH binding, was the only sugar to enhance TSH binding, and did so whether binding was determined in the cyclase medium or under conditions of optimum binding. The enhanced TSH binding remained after the membranes were removed from the high NeuAc concentration and an effect was observed at concentrations of 10 mM NeuAc. NeuAc did not alter the kinetics of TSH binding but the pH optimum for TSH binding shifted from pH 5.5 to 7.5 in the presence of NeuAc. Incubation of the membranes with increasing concentrations of NeuAc resulted in increased sialic acid content of the membranes. The NeuAc concentration curve of membrane sialic acid and TSH binding were roughly parallel. The capacity of the low affinity site increased from 0.74 to 2.5 nmol/mg of protein in the presence of NeuAc. The apparent affinity (0.88 X 10(6) M-1) of this site was unaffected by NeuAc. With the high affinity site, NeuAc increased both the apparent affinity and capacity from 2.2 X 10(8)M-1 to 5.5 X 10(8) M-1 and 1.6 to 3.1 pmol/mg of protein, respectively. Neuraminidase or neuraminidase plus beta-galactosidase incubation of the membranes removed approximately 60% of the sialic acid from the membranes within 15 to 30 min but did not affect TSH binding. Large quantities of sialic acid were detected in the soluble fractions during isolation of the membranes, 4 to 5% of which was ultrafilterable and not associated with high molecular weight proteins. It is concluded that among the sugars tested, NeuAc exhibits an unique effect on TSH binding that may have physiological significance. The inability to alter TSH binding by enzymatic removal of endogenous sialic acid suggests that either NeuAc resistant to hydrolysis is sufficient to maintain TSH binding or that NeuAc important in TSH binding is removed during membrane preparation but is replaced by incubation with exogenous NeuAc.

Humoral reactions in syngeneic hosts against tumor cell surface incomplete saccharide moieties

Components on the surface of MM2 ascites mammary carcinoma cells induce agglutination factors in the serum of syngeneic host C3H/He mice, and bind the factors in vitro. These components have been classified into three groups: MM2-specific substances, mammary tumor virus (MTV)-associated substances and tumor-associated embryonic materials. The substances contained saccharide moieties and their terminal sugar residues were essential for the binding of the serum factors. These terminal saccharides were exposed during cell proliferation,but masked in stationary cells, at least partly, due to elongation of the saccahride moieits. The terminal structures of these polysaccharide moities of growing and stationary cells were studied by semiquantitative tumor cell agglutination using the agglutinating activities against MM2 cells of MM2-regressor serum and of FMA/R- and Ehrlich-regressor sera which had partial cross-agglutination activities. Agglutination by phytohemagglutinins, inhibition of the agglutination by saccharides or with isolated cell surface components and treatment of the cells with glycosidases were also used for this purpose.

Transformation of human peripheral lymphocytes by galactose oxidase

Human peripheral lymphocytes can be transformed by treatment with galactose oxidase alone. Prior treatment with neuraminidase enhances this effect. The aldehyde blocking agents thiocarbohydrazide, hydroxylamine, dimedone, and sodium borohydride block transformation when they follow, but not when they precede, galactose oxidase treatment. Thus, as is the case for periodate-induced lymphocyte transformation, the formation of free aldehyde at the cell surface would seem to be a critical event in the triggering of transformation by this agent. The degree of transformation is highly variable from individual to individual, and also for the same donor at different times. However, the lymphocytes of some people give a consistently poor response to galactose oxidase. Similar results have been obtained for periodate-induced transformation of human lymphocytes, but to this date this is unexplained.