Presence Of Neuraminic Acid Research Articles

N1 neuraminidase of influenza virus A/FPV/Rostock/34 has haemadsorbing activity.

The neuraminidase (NA) gene of influenza virus A/FPV/Rostock/34 virus (H7N1) was cloned and expressed in Sf9 cells using a baculovirus vector. The expression product had the expected molecular mass and showed neuraminidase activity. NA expressed in Sf9 cells also showed haemagglutinating activity as indicated by its ability to induce haemadsorption of chicken red blood cells. Haemadsorption depended on the presence of neuraminic acid on the erythrocytes, but was not blocked by 2-deoxy-2,3-dehydro-N-acetylneuraminic acid, a specific inhibitor of the enzymatic activity. These observations suggest that the N1 neuraminidase has two distinct reactive sites: a catalytic site and a receptor binding site. This concept was confirmed by site-directed mutagenesis which showed that the haemadsorbing activity of FPV NA was abolished when amino acids located on two surface loops at the putative binding site were exchanged. Substitutions on either of the two loops were sufficient for this effect. The mutated NAs retained full neuraminidase activity. In contrast, a mutated NA lacking neuraminidase activity still had haemadsorbing activity.

Fusion of Sendai virus with liposomes: Dependence on the viral fusion protein (F) and the lipid composition of liposomes

The characteristics of fusion of the membrane of Sendai virus with that of liposomes has been investigated using two different methods to monitor the fusion reaction. The first method, which permits quantitation of lipid fused with virus, dependes on separation by centrifugation of unfused liposomes from those fused with virus. The second involves the digestion after fusion of internal viral proteins by trypsin contained in liposomes; this assay is completely independent of exchange of lipid between liposomal and viral membranes in the absence of fusion. A fusion-inactive mutant virus, pa-cl, with an uncleaved F protein served as the appropriate control in these experiments. It was found that fusion of the virus with liposomes that contained no protein required cleavage of the F protein; such cleavage was previously shown to be required for fusion of the virus with cell membranes. This indicates the relevance of this model system for studies on fusion. Kinetic studies indicated that at neutral pH fusion was 88% complete in 10 min at 37°. Investigation of the effects of liposomal lipid composition indicated that the presence of cholesterol in the liposomal membrane was required for fusion; a 0.3 – 0.4-mole fraction of cholesterol was optimal. The presence of neuraminic acid in the membrane was not essential for fusion. The results obtained are compatible with previous evidence suggesting a hydrophobic interaction between the cleaved F protein and the target membrane during fusion.

REMOVAL OF PAS POSITIVE SURFACE SUGARS IN TUMOR CELLS BY GLYCOSIDASES.

SummaryStructural components of the coat of fixed TA3 tumor cells are stained both by the Hale and the PAS procedures. The Hale positive material can be removed by active neuramidase, indicating the presence of neuraminic acid. The PAS positive component is not influenced by lipid extraction or by diastase digestion and is only slightly affected by neuramidase. However, it is strongly affected by an enzyme preparation from Clostridium perfringens, containing a mixture of glycosidases. By specific blocking of individual glycosidases in the incubation medium, it was determined that galactose and acetyl-galactosamine are important components for the PAS positivity of the cell coat. Fucose is of less significance and perhaps less abundant than other PAS positive sugar units. N-acetyl-hexosaminidase from fungi of Genus Chalaropsis was also active against the PAS positive cell coat but differed from the glycosidases of CI. perfringens in that it did not require the previous removal of the Hale positive componen...

The neuraminic acid content of cerebrospinal fluid as affected by neurological diseases.

Interest in the presence of neuraminic acid in human cerebrospinal fluid (CSF) and the variations in its concentration is derived from the possibility that these may reflect some aspect of central nervous metabolic activity. This, in turn, is based on the fact that neuraminic acid constitutes a part of the molecular structure of those water soluble glycolipids of brain that are generally referred to as gangliosides (1). However, the ubiquitous nature of neuraminic acid in all tissue fluids and structures renders any inquiry based on analysis of CSF for neuraminic acid alone of doubtful significance. It need only be pointed out that neuraminic acid is found in many tissues either as part of the tissue gangliosides or else in

Cerebrospinal fluid neuraminic acid deficiency in schizophrenia.

With the thought that metabolic disturbances nuclear to the schizophrenic process might best be studied in the central nervous system itself, the attention of this laboratory has been directed to certain little-known chemical constituents of the brain and cerebrospinal fluid. 1-7 The presence of neuraminic acid as a normal constituent of the macromolecular brain gangliosides suggested that its study in cerebrospinal fluid might afford a ready and repeatable source of pertinent information. The mean neuraminic acid content of cerebrospinal fluid in schizophrenic patients is here shown to be considerably below that of nonschizophrenic adults and comparable only to values found in some children under 7 years of age. 7 The present report describes the preparation of neuraminic acid standard from bovine brain ganglioside, the detailed procedure for the estimation of neuraminic acid in cerebrospinal fluid, and the values found in what is now a total of 195 subjects. A later