Acute effects of hemodialysis on salivary flow rate and composition.

AIMS: To evaluate acute effects of hemodialysis (HD) on the salivary flow rate, pH and biochemical composition before, during and after completion of a dialysis session. MATERIAL AND METHODS: Unstimulated whole saliva (UWS) and chewing-stimulated whole saliva (CH-SWS) were collected in 94 HD patients. Salivary flow rate, pH, concentrations of total protein, albumin, cystatin C, secretory immunoglobulin A (S-IgA) and of sodium, potassium and urea were measured. RESULTS: HD had an acute stimulating effect on the salivary flow rate (UWSbefore = 0.30+/-0.22 ml/min, UWSduring = 0.39+/-0.25 ml/min, p < 0.005). The mean pH of UWS showed a small but significant increase during HD mainly due to an increased watery secretion from the salivary glands. The salivary biochemical constituents changed markedly, but no significant difference in output was found. The electrolyte concentration did not change significantly during dialysis. The level of urea in CH-SWS declined to 40% (Ureabefore = 25.+/-6.4 mmol/l, Ureaduring = 15.3+/-4.5 mmol/1). CONCLUSIONS: This study shows that HD has significant acute effects on both salivary secretion rate and protein concentrations in saliva. We conclude that the observed changes in salivary concentrations and proteins are mainly due to an increased watery secretion from the salivary glands.

Oral and salivary changes in patients with end stage renal disease (ESRD): a two year follow-up study.

OBJECTIVES: To compare oral health, salivary flow rate, xerostomia and thirst in end stage renal disease (ESRD) patients remaining on dialysis treatment and after renal transplantation. DESIGN: Longitudinal observation. SETTING: ESRD patients recruited from dialysis centres in Amsterdam, The Hague and Utrecht, The Netherlands. METHOD: At baseline and after two years, salivary flow rates, xerostomia and thirst were determined in 43 ESRD patients. The number of decayed missing filled teeth/surfaces (DMFT/DMFS) was recorded, and periodontal status assessed. RESULTS: After renal transplantation (n = 20), the salivary flow rate increased significantly from UWS = 0.30 +/- 0.21 ml/min to 0.44 +/- 0.29 ml/min (p <0.001) and the level of xerostomia and thirst decreased. After two years, the percentage of bleeding on probing in dialysis patients (n = 23) decreased from 29.5 +/- 25.4% to 10.3 +/- 12.3%, (p <0.05). No differences in DMFT and DMFS were observed between dialysis and renal transplant patients. CONCLUSIONS: DMFT, dental plaque, gingival bleeding and periodontal indices did not change remarkably after two years, comparing dialysis and renal transplant patients. Renal transplantation enhances salivary flow and decreases symptoms of xerostomia and thirst, and hence enhances the potential to improve the quality of life of affected individuals.

Isolation of different high-Mr mucin species from human whole saliva.

By using CsCl-density-gradient ultracentrifugation, two high-Mr mucin species were isolated from human whole saliva, having buoyant densities in 0.2 M-guanidinium chloride of approx. 1.56 g/ml (pool IA) and 1.48 g/ml (pool IIA). Analytical density-gradient centrifugation of submandibular, sublingual, labial and palatal saliva, followed by immunochemical analysis with anti-mucin monoclonal antibodies, indicated immunochemical and physicochemical similarities between the high-density mucins of pool IA and mucins from palatal salivary glands. Chemical analysis indicated that the putative palatal mucin was rich in sulphate, but poor in sialic acid. The lower-density mucins of pool IIA equated with the high-Mr mucins of submandibular-sublingual saliva, both immunochemically and physicochemically (buoyant density).

Immunochemical analysis of high molecular-weight human salivary mucins (MG1) using monoclonal antibodies.

Using four Mabs with different specificities for salivary mucins, an ELISA has been developed in which human whole saliva, glandular salivas, salivary protein fractions and purified, high molecular-weight, mucin fractions (MG1) isolated from human submandibular and sublingual glandular tissues have been immunochemically analysed. All four Mabs reacted with MG1s. Three of them reacted with the purified, low molecular-weight salivary mucins (MG2). None was reactive with parotid saliva. MG1 preparations isolated from submandibular and sublingual glandular tissues of one and the same individual displayed different patterns of reactivity with these Mabs, indicating that they differ immunochemically. Analysis of the MG1s in salivas derived from individual salivary glands showed differences in immunochemical composition. These results indicate that the MG1 fraction in human whole saliva consists of several immunochemically different species.

Aggregation of oral bacteria by human salivary mucins in comparison to salivary and gastric mucins of animal origin.

Seventeen strains of oral bacteria of the genera Actinomyces (5), Bacteroides (3), and Streptococcus (9) were tested for aggregation by the human whole salivary mucin fraction (HWSM) in comparison to three types of animal mucin preparations from submandibular glands of cow (BSM) and sheep (OSM), and from the stomach of pig (PGM). Considerable variation was seen with respect to the rate and titer of aggregation induced by these mucins. The aggregating activity of HWSM varied widely among the different bacterial strains. The Bacteroides group showed hardly any induced aggregation, whereas the final aggregation titers varied for S. sanguis (3 strains) between 12 and 48, for S. oralis (3 strains) between 6 and 48, for the S. mutans group (3 strains) between 6 and 96, and for the five Actinomyces strains even between 6 and 192. For a particular strain, similar differences in titer were seen between the four mucins. For a human salivary mucin (MG-2) it has been described that sialic acid in the sequence NeuAc (alpha 2,3)Gal(beta 1,3)GalNac- was specifically involved in the interaction with S. sanguis strains, in contrast to S. rattus BHT. Our results, however, indicate that this sugar sequence is not a prerequisite for the aggregation of S. sanguis, as animal mucins, devoid of this structure, were equally well or even better capable of inducing aggregation. On the other hand, desialization of BSM and OSM largely abolished their aggregating capability towards S. rattus BHT. Moreover, it was found that BSM and OSM, which are comparable with respect to their major oligosaccharide structure, show considerable differences in aggregating activity towards the same bacterial strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Involvement of human mucous saliva and salivary mucins in the aggregation of the oral bacteria Streptococcus sanguis, Streptococcus oralis, and Streptococcus rattus.

The contribution of human parotid (Par) and submandibular/sublingual (SM/SL) saliva and of the human whole salivary mucin fraction (HWSM) to saliva-induced bacterial aggregation was studied for S. sanguis C476, S. oralis I581, and S. rattus HG 59. The mucous SM/SL saliva showed a much higher aggregation potency towards the S. sanguis and S. oralis strain than did the serous Par saliva. The SM/SL saliva-induced aggregation was observed after 30 min, at 60 min followed by the Par saliva-induced aggregation, and showed a 4-fold higher aggregation titer of 128 for S. sanguis, and an 8-fold higher titer of 516 for S. oralis. In contrast, the Par saliva showed a slightly higher aggregation activity than the SM/SL saliva towards S. rattus as judged by a twofold higher titer of 64. Morphologically, however, the SM/SL saliva-induced aggregation of S. rattus was far more pronounced as was also found for S. sanguis. Finally, the HWSM-induced aggregation showed a 4 to 8-fold higher titer than the originating salivary source, measuring 2048 for S. oralis and 128 for S. rattus. Moreover, no difference was observed in aggregation activity between the HWSM from whole saliva of a blood group O donor and the HWSM from SM/SL saliva of a blood group A donor. All the data point to an important, though not exclusive role of the human salivary mucin fraction in the saliva-induced aggregation of these strains.

Viscosity of human salivary mucins: effect of pH and ionic strength and role of sialic acid.

The viscosity of isolated human salivary mucins has been studied as a function of shear rate, mucin concentration, pH, and ionic strength. At neutral pH, viscosity increased proportionally with mucin concentrations between 0 and 14 mg/ml. Increasing the ionic strength from 35 to 235 mM resulted in an approximately 50% decrease in specific viscosity. A part from the ionic strength effect, no specific effect of calcium ions was observed. Under low ionic strength conditions, viscosity of mucin solutions reached a maximum value at pH 4.2. The extent of the viscosity increase was dependent on ionic strength, mucin concentration and shear rate. Increase of the ionic strength up to 200 mM almost completely abolished the pH-optimum, suggesting that electrostatic interactions underlie the pH-dependent behaviour. The position of the pH-optimum was not changed upon desialization of the mucin, indicating that terminal sialic acid residues do not determine the pH-dependence of human salivary mucin viscosity.

Isolation of high molecular weight mucins from human whole saliva by ultracentrifugation.

A high molecular weight mucin fraction was prepared from human whole saliva using relatively mild conditions. The method involves ultracentrifugation of human whole saliva in the presence of 7.2 M urea and 0.5 M sodium chloride. The resulting preparation consists of a highly purified salivary mucin fraction, as judged by several purity criteria: molecular weight analysis of the final preparation by gel electrophoresis and analytical gel filtration indicated an apparent molecular weight greater than 10(6). Analytical isopycnic density centrifugation demonstrated that the preparation consisted of a mucin fraction with a buoyant density of approximately 1.47 g/ml. The final preparation comprised 12.8% protein, 31.8% N-acetylglucosamine, 11.5% N-acetylgalactosamine, 9.5% fucose, 21.4% galactose, 0.8% mannose, 10.3% N-acetylneuraminic acid, 1.7% sulphate and 0.16% fatty acids.

Aggregation of 27 oral bacteria by human whole saliva. Influence of culture medium, calcium, and bacterial cell concentration, and interference by autoaggregation.

Twenty-seven oral strains of the genera Actinomyces (5), Bacteroides (3), and Streptococcus (19) were tested for aggregation by human whole saliva, as well as the effect of culture medium, Ca-ions, and bacteria concentration thereupon. Of the media tested, GF-broth gave rise to less interference by autoaggregation or higher aggregation titers than BHI and TSB, and was used throughout this study. In most cases, Ca-ions (1 mM) only enhanced the rate of induced aggregation, whereas raising the bacteria concentration increased the rate of both induced- and autoaggregation. The final titers, ranging from 1-64, were hardly affected by these parameters, except those of S. rattus HG 59 and S. mutans HG 199, which were respectively increased and decreased by Ca-ions. Saliva-induced aggregation was observed for 21 strains of A. viscosus, A. naeslundii, A. israelii, B. gingivalis, B. intermedius, S. cricetus, S. mutans, S. rattus, S. sanguis, and S. sobrinus, mostly within 15 min to 3 h. Seventeen of these strains also showed autoaggregation, usually well after the onset of induced aggregation. Any potential induced aggregation of B. gingivalis HG 91 was always masked by autoaggregation, as well as that of the S. mutans strains under a particular set of conditions. The aggregation rate and titer varied considerably in a mutually unrelated and strain-dependent way. These microtiterplate data were matched by the 5 spectrophotometric patterns observed for saliva-bacterial interaction, which moreover, gave the better differentiation between induced and autoaggregation. In conclusion, most strains tested can show rapid saliva-induced aggregation in a strain-dependent way, yet strongly affected by the experimental conditions and interference from autoaggregation.

Comparison of different assays for the aggregation of oral bacteria by human whole saliva.

For comparison, human whole saliva-induced aggregation was studied by phase-contrast microscopy, spectrophotometry combined with macroscopic observations, and in microtiterplate assay under identical experimental conditions for Actinomyces viscosus HG 85 (T14-V) and HG 380 (T14-AV), Bacteroides gingivalis HG 66 (W 83), Streptococcus rattus HG 59 (BHT), and Streptococcus sanguis I HG 169. The entire process of formation, extension, and sedimentation of aggregates could merely be observed by the combination of these assays. The very first stages of aggregation could only be detected and quantitated by phase-contrast microscopy. Within 2 1/2 min, 50% of the A. viscosus, S. rattus, and S. sanguis cells were aggregated, denoted as T50. In microtiterplates, however, aggregates were observed in general only after sedimentation at 30-45 min of incubation, expressed as TA. For interpretation of the spectrophotometric curves, additional microscopic and macroscopic data were a prerequisite. The small decline in absorbance during the first 30-45 min (phase 1) corresponded to the formation and extension of nonsedimenting aggregates, whereas the subsequent pronounced fall in absorbance (phase 2) was caused by the massive sedimentation of aggregates. The moment of inflexion between both phases, TI, marked the onset of sedimentation of aggregates and corresponded very well with TA, at which time already 92-98% of the cells were aggregated as quantitated by microscopy. In conclusion, only by microscopy the formation and extension of aggregates could be observed within a few minutes and quantitated in terms of aggregation rate. From 30-45 min, merely the sedimentation of aggregates was visualized in microtiterplates, whereas the time course of the overall process was recorded indirectly by spectrophotometry.