[Does food affect tartar deposition?] / Heeft voeding invloed op de vorming van tandsteen?

Tartar is formed by the precipitation of calcium phosphate on dental plaque, particularly in an alkaline environment. Fruit is acidic and contains a lot of carbohydrates besides, leading to acidification in dental plaque. In a large-scale population study, fruit consumption was therefore associated with a reduced risk of tartar build-up. Protein degradation does create an alkaline environment. However, consumption of dairy products, which are rich in protein and calcium ions, does not lead to increased formation of tartar. Oral care products containing the amino acid arginine or urea, both generating an alkaline environment, do not lead to increased tartar formation either. These studies suggest that the effect of diet on the metabolism in dental plaque is insufficient to cause an increase in tartar formation.

[What are the differences between the various covid-19 vaccines?] / Wat zijn de verschillen tussen diverse vaccins tegen COVID-19?

The coronavirus pandemic is caused by the SARS-CoV-2. Vaccination appears to offer the way out of this pandemic. Vaccines against this virus make use of the SARS-CoV-2's spike protein, an essential protein on the surface of the virus that it uses to attach itself to the host cells. In viral vector vaccines (AstraZeneca, Sputnik, Johnson & Johnson) the gene for the spike protein is introduced into an adenovirus. Following vaccination, the modified adenovirus will infect cells of the host, which will subsequently start to produce the spike protein, causing an immune response. RNA vaccines (Pfizer, Moderna) only introduce messenger RNA for the spike protein into host cells, which the messenger RNA uses to produce spike protein. Viral vector vaccines and RNA vaccines are not only faster to develop and safer to produce than traditional vaccines, they are also easier to modify to new viruses and virus variants. The latter may be of great importance for future pandemics.

LFchimera: a synthetic mimic of the two antimicrobial domains of bovine lactoferrin.

Saliva is essential for the maintenance of oral health. When salivary flow is impaired, the risk of various oral diseases such as caries and candidiasis increases drastically. Under healthy conditions, saliva provides effective protection against microbial colonization by the collaborative action of numerous host-defense molecules. This review describes how saliva has been the guideline for the design and characterization of a heterodimeric antimicrobial construct called LFchimera. This construct mimics the helical parts of two antimicrobial domains in the crystal structure of bovine lactoferrin. It shows high antimicrobial activity against a broad spectrum of Gram-positive and Gram-negative bacteria, fungi, and parasites including biowarfare agents such as Bacillus anthracis, Burkholderia pseudomallei, and Yersinia pestis. Further, sublethal concentrations of LFchimera inhibited biofilm formation, the invasiveness of HeLa cells by Yersinia spp., and prevented haemolysis of enteropathogenic Escherichia coli, demonstrating the versatility of these peptides.

[Saliva diagnostics: a summary of the expanded possibilities]. / Speekseldiagnostiek: een overzicht van de toegenomen mogelijkheden.

In hospitals, blood is still the gold standard in diagnostics, but outside hospitals saliva is used more and more. Collecting saliva is not invasive and is therefore easier, safer and cheaper than drawing blood. Saliva secretion itself is also a diagnostic parameter. A low saliva secretion rate may indicate an underlying disease such as Sjögren syndrome and is a risk factor for the occurrence of caries, dental erosion, Candida infections and is associated with upper respiratory tract infections in athletes. Unlike blood, saliva can be collected independently of qualified staff. Saliva can then be sent to laboratories where it can be screened for inherited diseases or virus infections like Covid-19. Tests for which saliva does not need to be sent away but can be processed on site, like pregnancy tests or HIV tests, which are already commercially available, are even easier. The rapid development of biosensors in combination with mobile phone based health apps will lead to new possibilities for saliva diagnostics.

[The relationship between xerostomia and saliva secretion in young adults]. / De relatie tussen xerostomie en speekselsecretie bij jongvolwassenen.

The relationship between xerostomia and reduced saliva secretion is known to occur in patients suffering from dry mouth. These are mainly (frail) older people experiencing reduced saliva secretion as a result of the use of medication. In the current research, we investigated whether the severity of xerostomia could be used as predictor for saliva secretion in young adults. 369 dentistry students participated in this study, of whom 33.4% were male and 66.6% were female, with an average age of 20.2 ± 2.4 years. It was found that the severity of xerostomia in the young adult students had a weak correlation with the unstimulated saliva secretion rate. This indicates that dry mouth complaints in this age group are not a good predictor for saliva secretion. In addition, it is concluded that hyposalivation is not restricted to older people or to specific patient groups, but that even among a trial population of young adults, individuals can suffer from dry mouth and/or reduced saliva secretion.

Effects of environmental temperature on saliva flow rate and secretion of protein, amylase and mucin 5B.

OBJECTIVE: The aim of this study is to evaluate the short term effects of environmental temperature on saliva flow rate and composition. METHODS: In a cross-over study design 20 subjects (18-25 years old, 14 women, 6 men) were exposed in randomized order at different days to three temperatures (4 °C, 21 °C and 37 °C). Five minutes after a subject was exposed to the test temperature, collection of resting saliva was started for 5 min at the same temperature. Saliva flow rate, pH, viscosity, protein concentration, mucin 5B concentration and amylase activity were measured. RESULTS: Exposure to 4 °C resulted in an increase of the saliva flow rate (p < 0.01), protein output and amylase output (p < 0.001) compared to exposure to 21 °C or 37 °C. Although the figures for mucin 5B output at 4 °C were higher than at higher temperatures, this was not significant. There were no significant differences in the salivary mucin 5B concentration and viscosity between saliva samples collected at the indicated temperatures. CONCLUSIONS: Lowering of the temperature induces an increase in saliva flow rate, as well as protein and amylase output.

[Dissertation 25 years after date 48. The effect of saliva on the -colonisation of oral bacteria]. / Proefschriften 25 jaar na dato 48. Effect van speeksel op de kolonisatie van mondbacteriën.

In the research that formed the basis of the dissertation 'Intervention of saliva in the colonization process of oral bacteria' from 1992, the aggregation or clustering of oral bacteria by saliva was investigated. This prevents bacterial colonisation in the mouth. Major individual differences in aggregation activity of different saliva samples were found to exist, partly determined by the blood group of the saliva donor. As well as being found in red blood cells, AB0 blood group antigens also appear on salivary glycoproteins. This does, however, not hold true for all individuals: this is only the case for so-called secretors. Non-secretors aggregated fewer bacteria than secretors. Later research showed that this was associated with a higher risk of caries. Subsequent research revealed that the complement system, a defence system in blood, was activated by saliva of secretors, but not of non-secretors. This shows that the oral defence systems are influenced by blood group and secretor status, but in a different way than we originally thought.

REDD+ and climate smart agriculture in landscapes: A case study in Vietnam using companion modelling.

Finding land use strategies that merge land-based climate change mitigation measures and adaptation strategies is still an open issue in climate discourse. This article explores synergies and trade-offs between REDD+, a scheme that focuses mainly on mitigation through forest conservation, with "Climate Smart Agriculture", an approach that emphasizes adaptive agriculture. We introduce a framework for ex-ante assessment of the impact of land management policies and interventions and for quantifying their impacts on land-based mitigation and adaptation goals. The framework includes a companion modelling (ComMod) process informed by interviews with policymakers, local experts and local farmers. The ComMod process consists of a Role-Playing Game with local farmers and an Agent Based Model. The game provided a participatory means to develop policy and climate change scenarios. These scenarios were then used as inputs to the Agent Based Model, a spatially explicit model to simulate landscape dynamics and the associated carbon emissions over decades. We applied the framework using as case study a community in central Vietnam, characterized by deforestation for subsistence agriculture and cultivation of acacias as a cash crop. The main findings show that the framework is useful in guiding consideration of local stakeholders' goals, needs and constraints. Additionally the framework provided beneficial information to policymakers, pointing to ways that policies might be re-designed to make them better tailored to local circumstances and therefore more effective in addressing synergistically climate change mitigation and adaptation objectives.

Bacillus globigii cell size is influenced by variants of the quorum sensing peptide extracellular death factor.

Toxin-antitoxin modules are necessary for the mode of action of several antibiotics. One of the most studied toxin-antitoxin modules is the quorum sensing-dependent MazEF system in Escherichia coli. The quorum sensing factor in this system is called the extracellular death factor (EDF), a linear pentapeptide with the sequence NNWNN. In spite of the extensive research on the mazEF system and the involvement of the quorum sensing factor EDF, the effect of EDF itself on bacteria has not yet been studied. In this research, we determined the effect of EDF and variants on cell growth in the Gram-negative bacterium E. coli and the Gram-positive Bacillus globigii. By aligning the zwf gene (from where EDF originates) of different bacterial species, we found 27 new theoretical variants of the peptide. By evaluating growth curves and light microscopy we found that three EDF variants reduced bacterial cell size in B. globigii, but not in E. coli. The D-peptides did not affect cell size, indicating that the effect is stereospecific. Peptides wherein tryptophan was substituted by alanine also did not affect cell size, which indicates that the effect seen is mediated by an intracellular target.

Effect of salivary factors on the susceptibility of hydroxyapatite to early erosion.

OBJECTIVE: Salivary pellicle is known to reduce the erosion of enamel and differences in the level of protection exist between individual saliva sources, but which parameters or components are important is not known. The focus of this study was to investigate the relationship between saliva parameters and early erosion of hydroxyapatite (HAp) with an in situ grown saliva film. METHODS: Twenty-eight volunteers carried two HAp and one porcelain discs in their buccal sulcus for 1.5 h. Next, the discs covered with pellicle and the attached saliva film were exposed extraorally to 50 mM (pH = 3) citric acid for 2 min and unstimulated and stimulated saliva was collected. Calcium loss from HAp after erosive challenge was measured, corrected for calcium loss from pellicle on porcelain discs and averaged. Several salivary parameters were analysed. Pearson's linear correlation and multiple regression analysis were used to study the relation between saliva parameters and HAp erosion. RESULTS: Significant correlations were found between HAp erosion and the concentration of phosphorus in unstimulated saliva (r = 0.40, p = 0.03) and between HAp erosion and the concentration of sodium (r = -0.40, p = 0.03), chloride (r = -0.47, p = 0.01), phosphorus (r = 0.45, p = 0.01) and flow (r = -0.39, p = 0.04) of stimulated saliva. Multivariate analysis revealed a significant role in the HAp erosion for sodium, urea, total protein, albumin, pH and flow of unstimulated saliva and for sodium, potassium, urea, and phosphorus of stimulated saliva. CONCLUSIONS: Several salivary parameters are associated with the susceptibility of HAp to erosion.

Application of MLST and pilus gene sequence comparisons to investigate the population structures of Actinomyces naeslundii and Actinomyces oris.

Actinomyces naeslundii and Actinomyces oris are members of the oral biofilm. Their identification using 16S rRNA sequencing is problematic and better achieved by comparison of metG partial sequences. A. oris is more abundant and more frequently isolated than A. naeslundii. We used a multi-locus sequence typing approach to investigate the genotypic diversity of these species and assigned A. naeslundii (n = 37) and A. oris (n = 68) isolates to 32 and 68 sequence types (ST), respectively. Neighbor-joining and ClonalFrame dendrograms derived from the concatenated partial sequences of 7 house-keeping genes identified at least 4 significant subclusters within A. oris and 3 within A. naeslundii. The strain collection we had investigated was an under-representation of the total population since at least 3 STs composed of single strains may represent discrete clusters of strains not well represented in the collection. The integrity of these sub-clusters was supported by the sequence analysis of fimP and fimA, genes coding for the type 1 and 2 fimbriae, respectively. An A. naeslundii subcluster was identified with both fimA and fimP genes and these strains were able to bind to MUC7 and statherin while all other A. naeslundii strains possessed only fimA and did not bind to statherin. An A. oris subcluster harboured a fimA gene similar to that of Actinomyces odontolyticus but no detectable fimP failed to bind significantly to either MUC7 or statherin. These data are evidence of extensive genotypic and phenotypic diversity within the species A. oris and A. naeslundii but the status of the subclusters identified here will require genome comparisons before their phylogenic position can be unequivocally established.

Multiple components contribute to ability of saliva to inhibit influenza viruses.

INTRODUCTION: Saliva is a potentially important barrier against respiratory viral infection but its mechanism of action is not well studied. METHODS: We tested the antiviral activities of whole saliva, specific salivary gland secretions, and purified salivary proteins against strains of influenza A virus (IAV) in vitro. RESULTS: Whole saliva or parotid or submandibular/sublingual secretions from healthy donors inhibited IAV based on hemagglutination inhibition and neutralization assays. This differs from human immunodeficiency virus (HIV), for which only submandibular/sublingual secretions are reported to be inhibitory. Among purified salivary proteins, MUC5B, scavenger receptor cysteine-rich glycoprotein 340 (salivary gp-340), histatins, and human neutrophil defensins (HNPs) inhibited IAV at the concentrations present in whole saliva. In contrast, some abundant salivary proteins (acidic proline-rich proteins and amylase) had no activity, nor did several other less abundant salivary proteins with known activity against HIV (e.g. thrombospondin or serum leukocyte protease inhibitor). Whole saliva and MUC5B did not inhibit neuraminidase activity of IAV and viral neutralizing and aggregating activity of MUC5B was potentiated by the neuraminidase inhibitor oseltamivir. Hence, MUC5B inhibits IAV by presenting a sialic acid ligand for the viral hemagglutinin. The mechanism of action of histatins requires further study. CONCLUSIONS: These findings indicate that saliva represents an important initial barrier to IAV infection and underline the complexity of host defense activity of oral secretions. Of interest, antiviral activity of saliva against IAV and HIV differs in terms of specific glandular secretions and proteins that are inhibitory.

Salivary agglutinin/DMBT1SAG expression is up-regulated in the presence of salivary gland tumors.

Salivary agglutinin (SAG) is encoded by the gene Deleted in Malignant Brain Tumors 1 (DMBT1) and represents the salivary variant of DMBT1 (DMBT1(SAG)). While SAG is a bona fide anti-caries factor, DMBT1 was proposed as a candidate tumor-suppressor for brain, digestive tract, and lung cancer. Though DMBT1(SAG) is expressed in the salivary glands, its expression in salivary gland tumors is unknown. Here we analyzed DMBT1(SAG) expression in 20 salivary gland tumors and 14 tumor-flanking tissues by immunohistochemistry. DMBT1(SAG) in salivary gland tumors resembles the changes of expression levels known from DMBT1 in tumors in other cancer types. Particularly, DMBT1(SAG) was up-regulated in 10/14 tumor-flanking tissues, and a strong staining of the luminal content in the tumor and/or the tumor-flanking tissue was observed in 14/20 cases. This suggests that, in addition to its role in caries defense, SAG may serve as a potential tumor indicator and/or tumor suppressor in salivary gland tissue.

Immunohistochemical detection of salivary agglutinin/gp-340 in human parotid, submandibular, and labial salivary glands.

Salivary agglutinin is a Streptococcus mutans binding protein and a member of the scavenger receptor cysteine-rich superfamily. It is identical to lung gp-340 and brain DMBT1, which possibly play a role in innate immunity and tumor suppression, respectively. The goal of this study was to localize salivary agglutinin in human salivary glands. Two monoclonal antibodies, directed against gp-340, were characterized. mAb 213-1 reacted with sialic acid epitopes and cross-reacted with MUC7. The reaction with mAb 213-6 disappeared after reduction, suggesting that a protein epitope was recognized. In the parotid gland, immunohistochemical labeling with mAb 213-6 was found in the duct cells. In the submandibular gland and labial gland, both serous acini and demilune cells were labeled. In the labial gland, labeling was found at the luminal side of the duct cells. Salivary agglutinin was distinctly localized in salivary glands, but in distinct glandular secretions, no differences in electrophoretic behavior were observed.

A role for Lewis a antigens on salivary agglutinin in binding to Streptococcus mutans.

Streptococcus mutans is a major etiological agent in dental caries. Salivary agglutinin is one of the main salivary components binding to S. mutans. To learn more about the interaction of salivary agglutinin with S. mutans, parotid, submandibular, sublingual and palatal saliva samples were incubated with S. mutans suspension. Both depleted saliva samples and bacterial extracts were analyzed by SDS-PAGE and immunoblotting. Salivary agglutinin was present in all types of glandular saliva and in all cases bound to S. mutans, also to PC337C, a P1 mutant of S. mutans. Agglutinin was separated by SDS-PAGE under reducing and non-reducing conditions and then transferred to nitrocellulose. Non-reduced agglutinin bound S. mutans, but reduced agglutinin did not. Adhesion of S. mutans to agglutinin-coated microplates was inhibited by amine-containing components, 1 M NaCl or KCl and EDTA. Adhesion decreased with decreasing pH with no adhesion below pH 5.0. These data suggest that calcium-dependent electrostatic interactions play a role in binding. By immunoblotting was demonstrated that blood group antigens and Lewis antigens were present on agglutinin. Synthetic blood group antigens and Lewis antigens covalently coupled to polyacrylamide were tested for binding to S. mutans. Only Le(a)(Gal beta 1,3(Fuc alpha 1,4)GlcNAc) bound to S. mutans, whereas the blood group antigens Le(b), Le(x), Le(y), H1, H2, A, B and sialylated Le(a) did not. Lea without galactose (Fuc alpha 1,4GlcNAc) still bound to S. mutans, but Le(a) without fucose (Gal beta 1,3GlcNAc) did not. Binding of agglutinin to S. mutans was not inhibited by Le(a). In conclusion, S. mutans can bind to Le(a) carbohydrate epitopes in which the fucose is an essential residue. Le(a) carbohydrate epitopes are present on salivary agglutinin but play no major role in binding.

Interaction of the salivary low-molecular-weight mucin (MG2) with Actinobacillus actinomycetemcomitans.

Periodontitis is associated with the presence of certain Gram-negative bacteria in the oral cavity, among these Actinobacillus actinomycetemcomitans. In order to determine which types of salivary components interact with A. actinomycetemcomitans two strains (HG 1175 and FDC Y4) were incubated with whole saliva and individual glandular secretions, viz. parotid, submandibular, and sublingual saliva. Immunochemical analysis by immunoblotting of bacteria-bound salivary proteins showed that IgA, the low-molecular mucin MG2, parotid agglutinin, and a 300 kDa sublingual and submandibular glycoprotein, were bound to the bacterial strains tested. In addition, adherence of A. actinomycetemcomitans to salivary proteins in a solid-phase was studied. After electrophoresis and transfer of salivary proteins to nitrocellulose membranes A. actinomycetemcomitans adhered only to MG2. In this assay periodate treatment, mild acid hydrolysis or neuraminidase digestion of the saliva glycoproteins abolished binding of two clinical isolates (HG 1175 and NY 664), suggesting that sialic acid residues on MG2 are involved in the binding. In contrast, adherence of the smooth laboratory strain Y4 was not affected by removal of sialic acid residues or even periodate treatment of MG2.

Binding of human high-molecular-weight salivary mucins (MG1) to Hemophilus parainfluenzae.

In human saliva, two different mucin populations can be distinguished, viz., high-molecular-weight mucins (MG1, mol. wt > 1 x 10(6)) and low-molecular-weight mucins (MG2, mol. wt approximately 125 kD). The carbohydrate moiety of MG1 displays a wide spectrum of oligosaccharide structures, varying in composition, length, branching, and acidity. The biological significance of the heterogeneity in carbohydrate structures of mucins is unclear. The present investigation focused on the question whether MG1, because of its diverse carbohydrate side-chain population, can bind to a large variety of oral micro-organisms. A replica plate technique, in combination with immunochemical detection with monoclonal antibodies against MG1, was used to screen in vivo human oral microflora for the presence of micro-organisms which could bind the high-molecular-weight salivary mucin MG1. Binding to purified MG1 was established for Hemophilus (para)influenzae species, whereas other species, including Streptococcus and Staphylococcus, were negative. MG1 binding to Hemophilus parainfluenzae could be abolished by protease treatment of MG1. In contrast, periodate acid treatment, partial deglycosylation, or addition of monosaccharides did not affect MG1 binding to H. parainfluenzae, indicating that MG1 carbohydrate side-chains were not directly involved in the binding. The binding was pH-dependent, showing an increase when the pH was lowered from 8.0 to 4.0. These data indicate that MG1 can be bound in a selective manner by Hemophilus spp. and suggest that the 'naked' unglycosylated polypeptide moiety of MG1 is involved in its binding to Hemophilus parainfluenzae.

Interaction of the salivary glycoprotein EP-GP with the bacterium Streptococcus salivarius HB.

The interaction of the human salivary glycoprotein EP-GP with a number of oral bacterial species, following incubation with human whole saliva, has been investigated. EP-GP could be detected with a specific monoclonal antibody, by means of ELISA or by electrophoresis in combination with Western Transfer. The results indicated that EP-GP is bound only by Streptococcus salivarius, and not by the other tested strains of bacteria, Actinomyces viscosus, A. naeslundii, Actinobacillus actinomycetemcomitans, Bacteroides fragilis, S. gordonii, S. oralis, S. sanguis, S. mitis, S. mutans, S. sobrinus, S. rattus, S. constellatus, and S. anginosus. Binding of EP-GP to S. salivarius is mediated by a protein-protein interaction, which was found to be pH-dependent with a maximum binding between pH 5 and 6. For further characterization of the binding of EP-GP to S. salivarius, four mutants were tested, each of them lacking different cell wall antigens. EP-GP was bound to all mutants in amounts comparable with the wildtype, in spite of the different surface antigen compositions. We were able to identify a 27-kD EP-GP binding protein, by extraction of S. salivarius-cell wall antigens and electrophoretic techniques. In addition to EP-GP, S. salivarius also bound two other salivary proteins, namely, secretory IgA and low-molecular-weight mucin (MG-2).