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L A Tabak

Publications and source records attributed to L A Tabak.

At least 73 records · Page 4Linked to original sources
PubMed1987

Immunochemical quantitation of alpha-amylase and secretory IgA in parotid saliva from people of various ages.

The alpha-amylase (128 subjects) and secretory IgA (118 subjects) concentration in stimulated parotid saliva of healthy individuals aged 23-84 years, was determined. They were divided into three age groups: I, 23-39; II, 40-59; and III, 60-84 years old. The concentrations (microgram/ml) of alpha-amylase for group I = 803.6; II = 648.0; and III = 652.4; the concentrations for secretory IgA for group I = 96.2; II = 101.8; and III = 97.7. The Kruskal-Wallis test revealed no significant differences between groups for alpha-amylase or secretory IgA.

Adult↗
PubMed1987

Structural aspects of salivary glycoproteins.

The protective functions of saliva are attributed, in part, to its serous and mucous glycoproteins. We have studied, as representative molecules, the proline-rich glycoprotein (PRG) from human parotid saliva and the high (MG1) and low (MG2) molecular weight mucins from submandibular-sublingual saliva. PRG (38.9 kDa) contains 40% carbohydrate consisting of 6 triantennary N-linked units and a single peptide chain of 231 amino acids, 75% of which = PRO + GLY + GLN. PRG's secondary structure is comprised of 70% random coil (naked regions) and 30% beta-turns (glycosylated domains). MG1 (greater than 10(3) kDa) contains 15% protein (several disulfide linked subunits), 78% carbohydrate (290 units of 4-16 residues), 7% sulfate, and small amounts of covalently linked fatty acids. MG2 (200-250 kDa) contains 30% protein (single peptide chain), 68% carbohydrate (170 units of 2-7 residues), and 2% sulfate. The major carbohydrate units of MG2 are: NeuAc alpha 2,3Gal beta 1,3GalNAc,Gal beta 1,3GalNAc, and Fuc alpha 1,2Gal beta 1,3GalNAc. MG1 contains hydrophobic domains, as evidenced by its ability to bind fluorescent hydrophobic probes; MG2 does not. Collectively, the biochemical and biophysical comparisons between MG1 and MG2 indicate that these two mucins are structurally different. Several functional properties of MG1, MG2, and PRG have been examined, including their presence in two-hour in vivo enamel pellicle, binding to synthetic hydroxyapatite, lubricating properties, and interactions with oral streptococci. The data presented suggest that these glycoproteins may have multiple functions which are predicated, in part on their carbohydrate units. The potential significance of the structure-function relationships of these glycoproteins to the oral ecology is discussed.

Dental Pellicle↗
PubMed1987

Artificial salivas: present and future.

Modern technology has allowed us to understand better the functions of saliva and now provides a rationale for developing: (1) diagnostic reagents for monitoring oral and systemic health status and (2) replacement therapies for individuals with salivary dysfunctions. Several areas of dental research are directed at augmenting or enhancing both the quality and quantity of saliva for individuals with dry mouth. An "intrinsic" approach is being explored which utilizes medications such as pilocarpine and bromhexine to stimulate the salivary glands to produce more saliva. An "extrinsic" approach proposes to use topically applied artificial saliva. Studies in our laboratory have been directed toward developing artificial salivas which incorporate many of the protective features of "native" saliva. An ideal artificial saliva should be "long-lasting", provide lubrication, inhibit colonization of microflora responsible for dental caries and gingivitis, and coat the oral soft tissues for protection against environmental insult and desiccation. Studies are currently under way to determine the structural requirements of salivary molecules responsible for these protective functions. Composite salivary molecules consisting of multiple biologically active or "functional domains" could then be designed and synthesized based upon primary sequence and conformational analyses, computer-assisted structural predictions, and in vitro testing. These supersalivary substances could then be used as saliva substitutes for targeting to selected oral surfaces to promote mineralization, hydration, and/or regulate microbial-mediated disease.

Adult↗
PubMed1986

Preparation of a sialic acid-binding protein from Streptococcus mitis KS32AR.

A recent report has identified a lectin on the surfaces of several strains of Streptococcus mitis and Streptococcus sanguis with specificity for an N-acetylneuraminic acid alpha 2,3-galactose-beta 1,3-N-acetylgalactosamine sequence (P.A. Murray, M.J. Levine, L.A. Tabak, and M.S. Reddy, Biochem. Biophys. Res. Commun. 106:390-396, 1982). In the present study, purification and characterization of this sialic acid-binding protein (SABP) was begun. A clinical isolate of S. mitis was grown to mid stationary phase in synthetic FMC medium and then extracted with lithium 3,5-diiodosalicylate. Lyophilized extract was subjected to gel filtration on a Sephadex G-200 column, giving four protein peaks (A to D). Peak B, shown by hemagglutination assay to contain SABP, was next subjected to affinity chromatography on a Sepharose-4B matrix coupled to fetuin glycopeptides. After an extensive washing, peak B materials bound to the affinity matrix were eluted with buffered N-acetylneuraminic acid. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis with 2-mercaptoethanol on 7.5% gels of affinity-purified materials revealed components of 96, 70, and 65 kilodaltons (kDa). Without reducing agent, only the 65-kDa band and materials which did not penetrate the gel were visualized, suggesting that the 96- and 70-kDa components were disulfide linked. The chemical cross-linking agent, disuccinimidyl suberate, was used to demonstrate specific interactions between the SABP preparation and [14C]fetuin glycopeptides. After cross-linking, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography revealed the 96- and 70-kDa components, indicating that the SABP is at least bivalent. These findings support our previous suggestion that human salivary glycoproteins facilitate clearance of selected oral streptococci via specific interactions between sialic acid-containing oligosaccharides and a carbohydrate-binding protein on the bacterial cell surface.

Adhesiveness↗
PubMed1985

Isolation and characterization of a mucin-glycoprotein from rat submandibular glands.

A blood group A+ mucin-glycoprotein was purified from aqueous extracts of rat submandibular glands by sequential chromatography on columns of Sepharose CL-6B and Sephacryl S-300 in urea-containing buffers. Final purification was facilitated by reductive methylation which appeared to release contaminating (hydrophobic) peptides. Homogeneity of the purified mucin was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis at varying concentrations of acrylamide, lectin affinity chromatography, and Western blot analysis. In contrast to previously described preparations, the purified mucin contained only trace amounts of N-acetylglucosamine and aromatic amino acids. In addition, only low levels of basic amino acids were present.

ABO Blood-Group System↗
PubMed1985

Masticatory lubrication. The role of carbohydrate in the lubricating property of a salivary glycoprotein-albumin complex.

We report for the first time a masticatory-lubrication assay system to assess the lubricating properties of salivary constituents. The lubricating ability of the proline-rich glycoprotein (PRG) of parotid saliva was enhanced by human serum albumin. The interactive effect of albumin was abolished by chemically deglycosylating the glycoprotein. Fluorescence spectroscopy with a hydrophobic probe verified the existence of a PRG-albumin complex and demonstrated that deglycosylation of the PRG altered the nature of its interaction with albumin.

Adult↗
PubMed1985

Adsorption of human salivary mucins to hydroxyapatite.

The interactions between low (MG2) and high (MG1) molecular-weight human submandibular-sublingual mucin and hydroxyapatite (OHAp) were compared using a quantitative assay. Data obtained appeared to empirically fit the Langmuir adsorption isotherm. Apparent affinity constants derived from this isotherm indicated that MG1 had a greater affinity for OHAp than did MG2. Inhibition studies revealed that salivary glycolipids inhibited the interaction of MG1 and OHAp without influencing MG2 adsorption. In contrast, MG2 adsorption to OHAp was markedly inhibited by cysteine-containing salivary phosphoprotein fractions. Collectively, the data indicate MG1 and MG2 differ in their interaction with OHAp.

Adsorption↗
PubMed1985

Circular dichroism and fluorescence spectroscopic analyses of a proline-rich glycoprotein from human parotid saliva.

A proline-rich glycoprotein (PRG) was isolated from human parotid saliva and examined by circular dichroism and fluorescence spectroscopy. Addition of guanidine hydrochloride to PRG labeled with an extrinsic dansyl probe had no effect on the fluorescence spectra's 511 nm lambda-max location. Thermodynamic calculations supported the contention that PRG has no significant tertiary structure. Circular dichroism results for PRG were simulated by computer and a secondary structure composed of 70% random coil and 30% beta-form conformation was predicted. Circular dichroism of PRG failed to detect either poly-L-proline type I or II structures. Deglycosylation of PRG had no measurable effect on the circular dichroism spectrum, indicating that the carbohydrate side chains had little influence on PRG secondary structure. Based upon mathematical calculations, beta-turns were predicted around three glycosylated Asn residues of PRG. These collective data suggest that PRG is composed of a disordered polypeptide chain with at least three of the N-linked Asn residues participating in some type of beta-turn.

Adult↗
PubMed1984

Isolation and characterization of tracheobronchial mucin from a laryngectomee.

A tracheobronchial mucin was isolated from the tracheobronchial secretion of a laryngectomee. It was purified by gel filtration on Sepharose CL-6B in Tris-urea buffer and rechromatography of excluded materials through the same gel matrix. It was homogeneous in 0.7% agarose-2% polyacrylamide electrophoresis under nonreducing conditions. Comparable analysis with 2-mercaptoethanol revealed at least 3 subunits. Based upon recoverable weight, the mucin was composed of 75% carbohydrate, 21% protein, and 3% sulfate. Oligosaccharides obtained by alkaline beta-elimination indicated O-glycosyl linkage to the peptide component. Marked heterogeneity of the carbohydrate side-chains was reflected in the preparation of 20 distinct oligosaccharides ranging in size from 4 to 17 residues.

Aged↗
PubMed1984

Neuraminidase activity: a biochemical marker to distinguish Streptococcus mitis from Streptococcus sanguis.

Selected reference and freshly isolated strains of Streptococcus mitis (mitior) and Streptococcus sanguis were assayed for cell-associated neuraminidase activity by their ability to hydrolyze [3H-] sialyllactitol. A cell-associated neuraminidase was detected with S. mitis and S. sanguis serotype II (reclassified as S. mitis) but not with S. sanguis serotypes I and III. Neuraminidase activity of S. mitis correlated with this organism's inability to hydrolyze arginine, aesculin, and few, if any, sugars. The findings indicate that the presence of cell-associated neuraminidase activity is useful for the taxonomic classification of S. mitis.

Arginine↗
PubMed1983

Juvenile periodontitis as a model for neutrophil function: reduced binding of the complement chemotactic fragment, C5a.

The binding of the chemotactic complement fragment, C5a, to peripheral blood neutrophils of Localized Juvenile Periodontitis (LJP) patients and normal controls was quantitated using iodinated human C5a and a rapid centrifugation assay. There was a significant reduction in the number of binding sites per cell on neutrophils from the patient group, whereas the binding affinity remained the same as control values.

Binding Sites↗
PubMed1982

Purification of a low-molecular-weight, mucin-type glycoprotein from human submandibular-sublingual saliva.

A low-molecular-weight, monomeric, mucin-type glycoprotein (MG2) has been isolated from human submandibular-sublingual saliva. Initial purification involved sequential gel-filtration on Sephadex G-200 and Sepharose CL-2B, the latter in the presence of 6M urea. Fractions containing MG2 were next separated from contaminating secretory IgA by immunoaffinity chromatography or recycling through Sephadex G-200. Mucin fractions were 14C-labeled by reductive methylation, and then the final purification-step entailed recycling radiolabeled materials through Sephadex G-200. Radiolabeling aided in the assessment of purity, as judged by SDS-PAGE and ion-exchange chromatography. The carbohydrate portion accounted for 69.6% of the recovered weight and was composed of N-acetyl-glucosamine, N-acetylgalactosamine, galactose, fucose, and N-acetylneuraminic acid. Sulfate was also present. The protein comprised 30.4% of the recovered weight with threonine, serine, proline, and glycine accounting for 75.2% of the total amino acids. The oligosaccharides were alkali-labile, indicating an O-glycosyl linkage to the peptide. The mucin was weakly acidic and had an estimated mol. wt. of 200 000-250 000.

Amino Acids↗
PubMed1982

Characterization of a pentasaccharide in salivary mucin from the stumptail monkey, Macaca arctoides.

Oligosaccharides were prepared by alkaline cleavage and sodium borotritide reduction. Following gel filtration on Sephadex G-25, [3H]-oligosaccharides were further fractionated by anion-exchange and preparative paper chromatography. The principal neutral oligosaccharide contained GalNAcol: GlcNAc: Gal: Fuc (1:1:2:1). Using a combination of exoglycosidase digestion, periodate oxidation and methylation analysis by gas chromatography-mass spectrometry, it structure was determined to be: Gal beta 1 leads to 4 GlcNAc beta 1 leads to 3 (Fuc alpha 1 leads to 2 Gal 1 leads to 6)GalNAcol.

Animals↗
PubMed1982

Role of salivary mucins in the protection of the oral cavity.

Mucins are the principal organic constituents of mucus, the slimy visco-elastic material that coats all mucosal surfaces. Compelling evidence suggests that they play an integral role in non-immune protection of the oral cavity. Specific protective functions include: 1) protection against desiccation and environmental insult, 2) lubrication, and 3) antimicrobial effects against potential pathogens. Biosynthesis of mucin is regulated by both intrinsic ("cooperative sequential specificity") and extrinsic ("structural modulation") controls. These controls form the basis by which mucin's structure can be modified to meet a dynamically changing biological need.

Bacteria↗