bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluoride Distribution in Enamel after in vitro Caries-like Lesion Formation
Authors: Clarkson B.H. , Wefel J.S. , Feagin F.F.
Published: November 2010

Using a microdissection technique to obtain samples from carious and adjacent sound enamel, we compared the fluoride concentrations in surface and subsurface enamel. Undialyzed and dialyzed gels were used to create lesions with and without negatively birefringent surface zones, respectively. The fluoride concentration in the surface enamel of the lesions was always greater than that in the corresponding sound enamel, as was the subsurface fluoride concentrations of caries lesions compared with adjacent sound enamel at the same depth.
Enhancement of Tomosynthetic Images in Dental Radiology
Authors: van der Stelt P.F. , Ruttimann U.E. , Webber R.L.
Published: November 2010

In conventional projection radiography, anatomical structures superimposed on details of interest increase the difficulty of visual interpretation. Part of this problem can be resolved by tomographic reconstruction of specific "tissue" slices. Computer-aided tomosynthesis is one method which can reduce the superposition problem, but the reconstruction can benefit from further enhancement. In this investigation, we studied two such enhancement schemes: high-pass spatial-frequency filtration and iterative deconvolution. The performance of each technique was judged qualitatively in terms of the depiction of specific details of diagnostic interest, and quantitatively in terms of the degree of success afforded by each in rendering adjacent tissue slices independent. Both techniques demonstrated improved performance over the status quo.
Scanning and Transmission Electron Microscopy of Tubular Structures Presumed to be Human Odontoblast Processes
Authors: Weber D.F. , Zaki A.E.
Published: November 2010

Tubular structures interpreted as being odontoblast processes can be observed with the scanning electron microscope (SEM) on fractured dentin surfaces which have been demineralized and treated with collagenase. To confirm the nature of these structures, SEM preparations exhibiting similar tubular structures were subsequently examined with the transmission electron microscope (TEM). Newly-erupted human third molars were fractured buccolingually with heavy-gauge industrial nippers or sectioned mesiodistally with a Leitz saw microtome and fixed in glutaraldehyde. The exposed dentin surfaces were decalcified to a depth of approximately 500 μm and then treated with bacterial collagenase. Half of the specimens were critical-point-dried and coated for SEM. The other half were post-fixed and processed for TEM. After examination by SEM, the specimens were embedded and thin-sectioned for TEM. SEM observations of both the fractured and cut surfaces of dentin showed tubular structures running from the surface of the pulp to the dentino-enamel junction. When the SEM preparations were examined with TEM, the tubular structures were seen to be the inner sheath of the peritubular matrix, not odontoblast processes. In the specimens directly processed for TEM, the structures lying inside the sheath could be visualized clearly. In the outer two-thirds of the dentin, the tubules were essentially empty. Well-defined odontoblast processes were seen lying inside the sheath only in the inner dentin,
The Effect of Cross-linking Agents on the Impact Resistance of a Linear Poly(methyl methacrylate) Denture-base Polymer
Authors: Price C.A.
Published: November 2010

Eight different cross-linking agents were added to the monomer component of a linear poly(methyl methacrylate) denture-base resin in various concentrations, and their effect on the impact resistance of the cured polymer studied. The cross-linking agents were chosen to provide a range of cross-linking chain lengths and degrees of chain flexibility. When tested under oral conditions, the polymers cross-linked with long and flexible chains did not show the marked reduction in impact resistance found in polymers cross-linked with shorter and stiffer cross-linking chains. It seems likely that by replacing EGDMA in denture-base resins with a cross-linking agent such as PEG 600 DMA, one could use a higher concentration with a consequent improvement in solvent resistance.
A Comparison of the Potassium Content and Osmolality of Plaque Fluid and Saliva, and the Effects of Plaque Storage
Authors: Dibdin G.H. , Shellis R.P. , Dawes C.
Published: November 2010

Previous determinations of osmolality and potassium concentrations in plaque fluid, much higher than those in saliva, suggest a restricted exchange between the two, which must be reconciled with recent findings of quite rapid diffusion in plaque. Possible reasons for the high values were considered, and of these the effect of solute leakage from bacteria to the plaque fluid during typical periods of storage was investigated. It was also shown that the osmotic pressure of plaque fluid could be measured quite accurately by vapor pressure osmometry on whole plaque samples without the need for centrifugation. Samples of plaque, or plaque fluid prepared by centrifugation at 12,000 g, were compared for osmolality or potassium content with matched samples prepared from plaque stored chilled or in liquid nitrogen. Saliva samples obtained just prior to plaque collection were also analyzed. Freshly collected plaque from overnight-fasted subjects had a plaque fluid osmolality of 156 ± 35 as compared with 98 ± 23 mOs/kg for saliva. Potassium in plaque fluid from freshly collected "mature" plaque was 40.6 ± 5.1 as compared with 20.3 ± 5.3 mmol/L for saliva, but for 1-2-day-old plaque from fasted subjects it was significantly lower (30.4 ± 5.6 mmol/L). These values for plaque fluid are all much less than those previously found, and storage was found to cause a marked increase (range, 35-100%). Centrifugation at 12,000 g caused little change in plaque fluid osmolality but seemed to accelerate the rate of increase during subsequent storage.
Effects of Neutral Salts in a Bench-scale Caries Model
Authors: Brown W.E. , Chow L.C.
Published: November 2010

In an earlier paper on bench-scale simulation of the caries process, it was shown that the passage of ions through ion-permselective barriers could have profound effects on the composition of the solution within the "lesion" at steady state. As indicated in earlier papers, these changes are produced by unequal rates of diffusion of Ca and PO4 ions prior to reaching steady state. Comparable effects are attributable to F ions when present. Here, we used the same two-compartment diffusion apparatus and membranes, as described in the earlier paper, to show that a neutral salt, such as NaCl, disproportionates under the influence of membrane potential. Thus, although the Na and Cl concentrations are nearly equal in the "plaque-saliva" compartment, they become very different in the "lesion" solution. An excess of Na over Cl is equivalent to the presence of the component NaOH, and an excess of Clover Na is equivalent to the presence of HCI. With the highly permselective commercial membranes used in these experiments, the CalP ratio in the "lesion" solution changed from an initial value of 1.6 to a value as high as 53 or as low as 0.1 at steady state. These phenomena are relevant to the events taking place in a caries lesion and must be taken into account in devising physicochemical models of the caries process. A valid caries model, in turn, offers the possibility of identifying steps in the caries mechanism which might be blocked to prevent tooth decay.
Liposomes as Drug Carriers for Oral Ulcers
Authors: Harsanyi B.B. , Hilchie J.C. , Mezei M.
Published: November 2010

The aim of this study was to test the potential of liposomes as drug carriers to the ulcerated oral mucosa. Radioactive triamcinolone acetonide palmitate (3H-TRMAp) was encapsulated in large multilamellar lipid vesicles and served as the test lotion. 3H-TRMAp in solution served as control. Forty-six hamsters were divided into three groups. In group I, multiple confluent ulcers in both cheek pouches were treated by topical application. In group II, single ulcers on the cheeks were treated by intramucosal injection. In group III, multiple confluent ulcers were produced in the cheek pouch on one side, with a single ulcer in the contralateral cheek pouch; no drug was applied, and the tissues were prepared for histology. Hamsters were killed at three and 24 hours, respectively, after treatment. Pouches were divided into ulcerated and intact adjacent mucosa. Cheeks were divided into ulcerated mucosa and distant mucosa. Drug levels in the four mucosal portions as well as in the blood, liver, spleen, brain, and thalamic region were determined by radioactive tracer technique. At three hours, liposomal drug concentrations were lower than in control animals in the brain and the thalamic region. At 24 hours, liposomal drug values were higher than in control animals in the ulcerated mucosa and lower than in control animals in the thalamic region. Mean drug concentrations in the ulcerated mucosa were higher in group II than group I. The results parallel those of Mezei and Gulasekharam (1980, 1982); liposomes increase local and decrease systemic drug concentration. In addition, this study suggests that liposomes decrease drug diffusion into neighboring tissues and localize the drug in the area of inflammation. Liposomes may be useful in the treatment of oral ulcers.
Actinomyces Adsorption Mediated by Type-1 Fimbriae
Authors: Clark W.B. , Wheeler T.T. , Lane M.D. , Cisar J.O.
Published: November 2010

Monospecific antibody against the type-1 fimbriae of Actinomyces viscosus T14V reacted with 12 strains of A. viscosus (serotype 2), 12 strains of A. naeslundii (serotype 2 or serotype 3), but not with 11 serotype 1 strains of A. naeslundii. All strains positive for the type-1 fimbrial antigen adsorbed strongly to saliva-treated hydroxyapatite, and in many instances (18 of 24 strains) this interaction was inhibited by the monospecific antibody. These findings strongly suggest that only those strains of actinomyces which possess type-1 fimbriae adhere to the tooth surfaces, and that these fimbriae constitute the principal adhesin involved in this interaction.
Influence of Metal Thickness on Stress Distribution in Metal-Ceramic Crowns
Authors: Anusavice K.J. , Hojjatie B. , Dehoff P.H.
Published: November 2010

The objective of this study was to calculate the stress distribution induced in anterior metal-ceramic crowns fabricated with either gold-alloy or nickel-alloy copings of reduced thickness using plane stress analyses. Two-dimensional finite element models of three crown designs were subjected to a simulated biting force of 200 N which was distributed over porcelain near the lingual metal-ceramic junction. Based on plane stress analyses, the maximum tensile and compressive stresses in porcelain for the three cases were 29.5 MPa and 123.1 MPa, respectively. The highest tensile strains in porcelain for veneered Ni-Cr and Au-Pd copings with conventional dimensions were 0.016% and 0.014%, respectively. The maximum stresses and strains in porcelain for the crowns with a conventional coping thickness (0.3 mm) and a reduced coping thickness (0.1 mm) were not significantly different. All values were below the critical failure values of porcelain.
High-resolution Electron Microscopic Study of Age-hardening in a Commercial Dental Gold Alloy
Authors: Yasuda K. , Van Tendeloo G. , Van Landuyt J. , Amelinckx S.
Published: November 2010

High-resolution electron microscopy and electron diffraction were ap plied to elucidate the hardening mechanism in an 18-carat gold commercial dental alloy, Au-31.7 at.%,Cu-8.1 at.%,Pd-5.3 at.%,Ag-54.9 at.%. The interface between the AuCu-I ordered platelets and the surrounding Au3 Cu ordered phase was anilyzed down to the atomic scale. A geometric model for the interface was deduced directly from the high-resolution electron micrographs. No evidence was found for the presence of a FCC phase at the interface between AuCu-I and Au 3 Cu.
Fracture Toughness of Dental Composites Determined Using the Short-rod Fracture Toughness Test
Authors: Pilliar R.M. , Smith D.C. , Maric B.
Published: November 2010

Plane strainfracture toughness (KIC) has been evaluated for a number of commercially-available dental composites. A modified Short-rod Fracture Toughness (SRFT) specimen design has been used, enabling small specimens to be tested conveniently. The effect on KIC of aging in water at 37°C for seven days, one month, and six months has been determined for conventional, micro filled, and hybrid (coarse and fine filler particle-containing) composites. Our results suggest that aging for one month or more caused a reduction of KIC for the composites so aged. Comparison of the KIC values determined using the modified SRFT specimen with values obtained using more conventional specimen geometries gave good agreement, thereby suggesting the suitability of the small SRFT specimens for valid KIC determinations.
Water Sorption and Filler Characteristics of Composites for Use in Posterior Teeth
Authors: Øysæd H. , Ruyter I.E.
Published: November 2010

The purpose of this investigation was to determine the water sorption and solubility, as well as the filler composition and extent of chemical degradation in water, of eight different posterior composites. With one exception, the materials with the largest quantity of fillers had the least water sorption and solubility after three months in water at 37°C. The emission spectroscopy results showed that silicon was the major element in all the fillers except one, which had both silicon and strontium as major elements. Other components registered in quantities of 5-10 wt-% were barium, aluminum, zinc, and zirconium. The leaching of inorganic ions into water from the fillers varied depending on filler composition and filler treatment.
Prenatal Fluoride Exposure: Measurement of Plasma Levels and Enamel Uptake in the Guinea Pig
Authors: Parker P.R. , Bawden J.W.
Published: November 2010

This study measured the effects of variations in the maternal fluoride intake on changes in maternal plasma, fetal plasma, and fetal enamel fluoride levels of near-term guinea pig pups.

Pregnant sows were divided randomly into one of three groups whose drinking water was either de-ionized or contained 5 ppm or 20 ppm fluoride supplied ad libitum. At approximately 55 days' gestation, maternal and fetal plasma and fetal enamel samples were collected and assayed for fluoride. Results showed an increase in mean fluoride concentration for maternal plasma from the de-ionized to the 20-ppm group. Mean fetal plasma fluoride concentrations were lower at baseline and increased much less than did maternal plasma levels. Mean fetal enamel concentrations increased in a fashion similar to that of the maternal plasma levels and exhibited significant differences among all groups.
Interpreting the Correlation Coefficient when One of the Variables is Discrete
Authors: Appleton D.R. , Rugg-Gunn A.J. , Hackett A.F.
Published: November 2010

The effect on the correlation coefficient of discretizing data was investigated in two ways. First, the theoretical effect of dichotomizing data was calculated, and it was shown that the resulting correlation coefficient is considerably less than that between the underlying bi-variate normally distributed variables. Second, computer simulations were performed of a model in which a continuous variable (measured with some error) gives rise to a counting variable through a mechanism in which the count is zero below a certain threshold value for the continuous variable and then increases linearly as the continuous variable increases. It was shown that the correlation coefficient between the observed values of the continuous and counting variables decreased as (a) the measurement error increased, (b) the slope of the relationship decreased, and (c) the number of counts decreased. It is concluded that caution is required when interpreting correlation coefficients when one or both of the variables consist of a few (say only four or five) discrete scores.
In vivo Bovine Enamel Remineralization and Fluoride Uptake from two Dentifrices Containing Different Fluoride Concentrations
Authors: De Kloet H.J. , Exterkate R.A.M. , Rempt H.E. , Ten Cate J.M.
Published: November 2010

In this study, the differences in lesion remineralization and fluoride uptake after brushing with a 300 ppm F or a 1000 ppm F dentifrice (as NaF) were investigated.

Twenty volunteers with partial dentures in their lower jaws were divided into two groups. Bovine enamel slabs with artificial lesions were mounted in the dentures. After a test period of six weeks, the slabs were taken out and analyzed. There was no statistically significant difference between the two groups, in F-uptake and susceptibility of the enamel to demineralization, although the findings favored the 1000 ppm F toothpaste. The microradiograms in the 300 ppm F group showed lesions more pronounced than those in the 1000 ppm group.

The present study cannot support the presumption that the fluoride content of regular NaF dentifrices can be lowered to 300 ppm F without undesirable effects on lesion arrest and remineralization.
Estimation of Mercury Body Burden from Dental Amalgam: Computer Simulation of a Metabolic Compartmental Model
Authors: Vimy M.J. , Luft A.J. , Lorscheider F.L.
Published: November 2010

Estimated release rates of Hg vapor from dental amalgams permitted calculation of the potential Hg body burden by employing a four-compartment model for inorganic and elemental Hg distribution. A computer program, compatible with most personal computers, simulated the cumulative and incremental distribution in each compartment and total body accumulation between 1 and 10,000 days for different daily Hg dosages. For a given Hg dose of 30 μ g/day, metabolic compartments R1-R3 were close to equilibrium at 5, 100, and 300 days, respectively; whereas by 10,000 days, R4 closely approximated total body burden and had not yet attained equilibrium. Projected values obtained with the computer model were consistent with results obtained by another method using a standard tissue burden equation, which employed experimentally determined tissue half-lives for blood and CNS. The model predicted that continuous exposure to elemental Hg vapor, at 30 μ g/day for 10 years, would result in a total Hg body burden of 5.9 mg, of which 4.8 mg could be contained in R4. Assuming that the Hg in R4 displayed uniform distribution throughout the body, then the brain concentration was estimated to be 68 nglg wet weight. In contrast, if Hg in R4 reflected long-term preferential accumulation in brain and other neural tissue, then concentrations as high as 4.0 μ g/g could be attained. However, predictions of Hg concentrations in blood and urine were well within established ranges, and were unlikely to be of utility in assessing effects of chronic low-dose Hg exposure. It is concluded that the CNS could accumulate a substantial amount of Hg over extended time, based on low-dose elemental Hg vapor exposure via inhalation from dental amalgams.
A Measurement of Galvanic Current and Electrical Potential in Extracted Human Teeth
Authors: Momoi Y. , Asanuma A. , Kohno A. , Yanagisawa K.
Published: November 2010

When opposing teeth with amalgam and gold restoration are in contact, current flows in the mouth at the instant the dissimilar metals touch. In this study, this condition was simulated by use of resistors and extracted human teeth with amalgam and MOD gold inlay restorations.

When both teeth were in contact in a physiological saline solution, we measured current and electrical potential generated in each pulp chamber. Galvanic current generated in the tooth with amalgam was always larger (as much as 18.2 times at the instant of contact) than that in the tooth with gold. Electrical potential generated in the tooth with amalgam was always larger (as much as 9.7 times at the instant of contact) than that in the tooth with gold. It should be emphasized that the larger current generated in the tooth with amalgam was caused mainly by its larger electrical potential. These results correspond well with the clinical phenomenon of galvanic pain, which occurs in the tooth with amalgam rather than in the tooth with gold.
Dissolution of Mercury from Amalgam into Saline Solution
Authors: Okabe T. , Ferracane J. , Cooper C. , Matsumoto H. , Wagner M.
Published: November 2010

Dissolution of mercury from amalgams and some intermetallic compounds found in the amalgam structure, such as γ1, γ2, and β1, was examined during one week of aging in 0.9% NaCl solution at 37°C. The amount of mercury released from γ1(30.2 μg/cm2) was at least 13 times that released from amalgam (0.5 - 2.2 μg/cm2) and five times that released from β1(5.7 μg/cm2). γ 2 released the least amount of mercury (0.46 μg/cm2). The study revealed that as high as 55% of the mercury ions liberated from the amalgams and the amalgam phases was adsorbed onto the walls of the vials in which the specimens were aged.
A Simplified Diagnostic System for Cultural Detection and Enumeration of Streptococcus mutans
Authors: Jordan H.V. , Laraway R. , Snirch R. , Marmel M.
Published: November 2010

A simple dip-slide test (Cariescreen SM®) based on MSB selective agar was devised for detection and quantitation of Streptococcus mutans in oral samples. For this test, a bacitracin tablet is dissolved in a vial containing buffered saline diluent. Paraffin-stimulated saliva is collected in this diluent vial. A dip slide which incorporates a modified MSB agar (minus bacitracin) is immersed briefly in the diluted saliva. After addition of a CO2-generating tablet, the screw-cap dip slide is closed tightly in the vial and incubated for two days at 37°C and one day at room temperature. S. mutans populations in saliva are estimated by comparison with a colony density chart.

Growth of reference strains of S. mutans was equivalent on Cariescreen SM dip slides and on MSB agar plates. Reference strains of Streptococcus sanguis, Streptococcus salivarius, Streptococcus mitis, and Streptococcus milleri did not grow on Cariescreen SM dip slides. Aliquots of saliva from 50 schoolchildren and 51 adults were tested by the dip-slide method and by conventional plating methods in MSB agar. Very good correlation (0.93) between the two methods was obtained. This simplified S. mutans detection system is suitable for use by clinical personnel in dental clinics or other non-laboratory settings for identification of subjects potentially at risk for caries.
Proteolytic Activity of Bacteria Isolated from the Oral Cavities of BALB/c Mice Toward Salivary Proteins
Authors: Dumas C. , Champagne A. , Lavoie M.C.
Published: November 2010

The proteolytic activities of 350 bacterial isolates from different sites (saliva, tongue, teeth, and mucosa) of the oral cavities of BALB/c mice were tested against different proteins found in saliva (immunoglobulins A, M, G, albumin, lysozyme, mucin, lactoferrin, and lactoperoxidase), some of which are considered to possess antibacterial activity. The results indicate that: (1) lysozyme, lactoferrin, and lactoperoxidase are hydrolyzed by from 46 to 70% of the indigenous flora of the oral cavities of BALBlc mice; (2) IgA and IgM appeared less sensitive to the proteolytic activities of these strains than did the other proteins tested; (3) the colonization of the oral cavity does not seem to be correlated with the proteolytic activity; and (4) the presence of specific Ig proteases is relatively scarce within this population.
A Long-term Epidemiologic Study of the Relationship between Occlusal Factors and Mandibular Dysfunction in Children and Adolescents
Authors: Egermark-Eriksson I. , Carlsson G.E. , Magnusson T.
Published: November 2010

A longitudinal investigation of changes of signs and symptoms of man dibular dysfunction over four to five years was performed, by means of questionnaires and clinical examination, in 240 children, ages 7, 11, and 15 years at the first examination. The objective of this part of the study was to analyze correlations between some occlusal and other factors, and mandibular dysfunction. Signs and symptoms of mandibular dysfunction increased slightly in both frequency and severity but were judged to be mild in most cases. Several types of occlusal interference were frequently recorded at both examinations. Dental wear increased during the follow-up period, while the results of evaluations of motor activity and psychological traits were relatively constant. There were only a few significant correlations, most of which were weak, between the recorded variables and mandibular dysfunction, and those found were not consistent in all age groups. TMJ sounds were positively correlated with lateral deviation of the mandible between retruded contact and intercuspal position in all age groups. An attempt to analyze the longitudinal relationship of occlusal interference with signs and symptoms of mandibular dysfunction did not reveal any strong correlations. The results are interpreted as supporting the heterogeneous and multifactorial nature of functional disturbances of the masticatory system.
The Effect of Parathyroid Hormone (1-34) on Cyclic AMP Level, Ornithine Decarboxylase Activity, and Glycosaminoglycan Synthesis of Chondrocytes from Mandibular Condylar Cartilage, Nasal Septal Cartilage, and Spheno-occipital Synchondrosis in Culture
Authors: Takano T. , Takigawa M. , Shirai E. , Nakagawa K. , Sakuda M. , Suzuki F.
Published: November 2010

Previously, we reported methods for isolating chondrocytes from the craniofacial complex and their culture in vitro. The response of these chondrocyte cultures to bovine parathyroid hormone (1—34) (PTH) has now been investigated. PTH stimulated glycosaminoglycan (GAG) synthesis, a characteristic of the cartilage phenotype in cultured chondrocytes isolated from mandibular condylar cartilage (MCC), nasal septal cartilage (NSC), and spheno-occipital synchondrosis (SOS). These stimulations of GAG synthesis by PTH were dose-dependent. PTH also increased accumulation of cyclic AMP (cAMP) and the activity of ornithine decarboxylase (ODC), a rate-limiting enzyme in polyamine biosynthesis. However, PTH did not stimulate DNA synthesis. The increases in the cAMP level, ODC activity, and GAG synthesis after addition of PTH (10-7 mol/L) were greatest in MCCchondrocytes and least in NSC-chondrocytes. The difference in the responses to PTH of these three types of chondrocytes may reflect differences of the characteristics of these cells in vivo.
Endocytosis of Proteins by Salivary Gland Duct Cells
Authors: Hand A.R. , Coleman R. , Mazariegos M.R. , Lustmann J. , Lotti L.V.
Published: November 2010

The ability of the intralobular duct cells of the rat parotid gland to take up protein from the lumen was examined by retrograde infusion of exogenous proteins and by immunogold localization of endogenous secretory proteins. Small amounts of native horseradish peroxidase (HRP) were taken up by intercalated and striated duct cells, and were present in small vesicles, multi vesicular bodies, and lysosomes. In contrast, HRP modified by periodate oxidation was avidly internalized by the duct cells and was present in large apical vacuoles that acquired lysosomal hydrolase activity. Native and cationized ferritin were taken up in a similar manner when infused at a high concentration (up to 10 mg/mL). At lower concentrations (0.3-1.0 mg/mL), endocytosis of cationized ferritin occurred mainly in small apical tubules and vesicles in striated duct cells. Little native ferritin was taken up at these concentrations. After stimulation of acinar cell secretion by isoproterenol, similar vacuoles were occasionally observed in both intercalated and striated duct cells. Labeling of thin sections with antibodies to amylase and to a 26,000-dalton secretory protein (protein B1), followed by protein A-gold, revealed the presence of these proteins in the vacuoles, indicating endocytosis of acinar secretory proteins by the duct cells. Although uptake of acinar proteins by duct cells occurs at a low rate in normal animals, previous work suggests that extensive endocytosis may occur in certain pathological conditions. This may be a mechanism for removing abnormal or modified proteins from saliva before it reaches the oral cavity.
Genetic and Sex-related Differences in the Structure of Submandibular Glycoconjugates
Authors: Schulte B.A.
Published: November 2010

Structures of oligosaccharides in submandibular glycoproteins were evaluated in situ. Sections of fixed paraffin-embedded glands from rats, mice, hamsters, sheep, and man were stained with a battery of lectins conjugated to horseradish peroxidase in conjunction with other methods, such as digestion with sialidase with or without prior saponification and/or periodate oxidation. Secretory glycoproteins showed a characteristic lectin binding pattern for each genus. Sialoglycoconjugates were detected in acinar cell secretions in all genera except the rat but differed with respect to the linkage of sialic acid to penultimate β-galactose or α-N-acetylgalactosamine. Species and strains of mice showed minor differences in the structure of secretory glycoproteins. Sexes differed similarly in some but not other mouse species. Individual differences were seen in human glands, where oligosaccharide structure varied in relation to ABO blood group. In some species, heterogeneity in glycoprotein structure was observed among morphologically similar cells within a gland. Differences in the structure of salivary secretions between genera and between humans of different ABO blood type and secretor status substantiate biochemical and histochemical findings. The results showing species, sex, and individual differences in mice and heterogeneity in acinar cells in several species suggest a greater degree of genetic and perhaps hormonal influence on the synthesis of salivary glycoproteins than has previously been recognized.
Structural and Genetic Aspects of Proline-rich Proteins
Authors: Bennick A.
Published: November 2010

Considerable advances have been made in the genetics of salivary proline-rich proteins (PRP). The genes for acidic, basic, and glycosylated PRP have been cloned. They code for precursor proteins that all have an acidic N-terminal followed by proline-rich repeat sequences.

Structural studies on secreted proteins have demonstrated that not only acidic but also some basic PRPs have this general structure. It is possible that mRNA for different PRP may have originated from a single gene by differential mRNA splicing, but post-translational cleavages of the primary translation product apparently also occur. In vitro translation of salivary gland mRNA results in a single precursor protein for acidic PRP. Such in vitro translated protein can be cleaved by salivary kallikrein, giving rise to two commonly secreted acidic PRPs, and kallikrein or kallikrein-like enzymes may be responsible for other post-translational cleavages of PRPs. Acidic as well as some basic PRPs are phosphorylated. A protein kinase has been demonstrated in salivary glands which phosphorylates the PRPs and other secreted salivary proteins in a cAMP and Ca2+-calmodulinindependent manner. Knowledge of the conformation of PRPs is limited. There is no conclusive evidence of polyproline-like structure in the proline-rich part of PRPs. Ca2+ binding studies on acidic PRPs indicate that there is interaction between the Ca2+ binding N-terminal end and the proline-rich C-terminal part. This interaction is relieved by modification of arginine side-chains. 1H, 32P, and 43Ca NMR studies have further elucidated the conformation of acidic PRPs in solution.

Present evidence shows that salivary PRPs constitute a unique superfamily of proteins which pose a number of interesting questions concerning gene structure, pre- and post-translational modifications, and protein conformation.
Molecular Basis of Salivary Proline-rich Protein and Peptide Synthesis: Cell-free Translations and Processing of Human and Macaque Statherin mRNAs and Partial Amino Acid Sequence of their Signal Peptides
Authors: Oppenheim F.G. , Hay D.I. , Smith D.J. , Offner G.D. , Troxler R.F.
Published: November 2010

Acidic proline-rich phosphoproteins and phosphopeptides are abundant components of parotid and submandibular salivary secretions in man and in the subhuman primate, Macaca fascicularis. The major acidic proline-rich proteins and the proline-rich phosphopeptide, statherin, of man and macaques have been shown to be potent inhibitors of calcium phosphate precipitation and are thought to function in the oral environment by maintaining saliva supersaturated with respect to calcium phosphate salts. Little is known about the biosynthesis of these proline-rich phosphoproteins and peptides, and the aim of the present work was to determine the structural relationship between statherin precursors and native human and macaque statherin. RNA was isolated from human submandibular gland, and poly(A+) mRNA was selected by affinity chromatography on oligo(dT) cellulose and translated in a reticulocyte lysate. Electrophoretic analysis of the translation products revealed that this mRNA directed the synthesis of a large number of polypeptides with M,s ranging from 5000 to 70,000. Immunoprecipitates, prepared with an antiserum directed against human statherin, contained a single component with a Mr of 7800, approximately 2000 daltons larger than native statherin. Radiosequencing of the in vitro precursor of statherin in immunoprecipitates demonstrated the presence of a 19-residue signal peptide. These results suggest that statherin is derived from a unique structural gene, and does not result from proteolytic processing of a large polyprotein precursor.
Lysozyme-Protease-Inorganic Monovalent Anion Lysis of Oral Bacterial Strains in Buffers and Stimulated Whole Saliva
Authors: Pollock J.J. , Lotardo S. , Gavai R. , Grossbard B.L.
Published: November 2010

Similar to Streptococcus mutans, buffer suspensions of Lactobacillus casei, Lactobacillus plantarum, and Fusobacterium nucleatum all undergo cell lysis when treated with the lysozyme-protease-inorganic monovalent anion antibacterial system. For Lactobacillus species treated with lysozyme and proteases at pHs of 4 and 5.3, lysis resulted when a lytic activating concentration of bicarbonate anion followed enzyme treatment. Furthermore, synergistic lysis of these bacteria was noted when lysozyme-protease treatment was followed by bicarbonate anion used in combination with chloride or fluoride anions. Noteworthy, the halides were not active in promoting lysis when used by themselves in the absence of bicarbonate. For F. nucleatum suspended at pH 6.9, lysis was dependent upon the ionic strength of the buffer and resulted when lysozyme-protease treatment of the organism was followed by 100 mmol/L bicarbonate activation. When lysozyme and proteases were omitted from the incubation mixtures and replaced by stimulated whole saliva, pH 5.3, lysis was observed only with L. plantarum and S. mutans, but not with L. casei. The latter could be lysed, however, if suspended in saliva which was diluted several-fold with distilled water. In experiments where lysozyme was selectively depleted from whole saliva by immunoadsorption affinity chromatography, the great majority of the lysis capability of the saliva for L. plantarum was lost, although a significant degree of lysis appeared to be due to salivary factors other than lysozyme. F. nucleatum was also found to lyse in saliva at neutral pH, suggesting that both Gram-positive and Gram-negative oral bacteria may be susceptible to this antibacterial system in vivo.
Interference of IgA Protease with the Effect of Secretory IgA on Adherence of Oral Streptococci to Saliva-coated Hydroxyapatite
Authors: Reinholdt J. , Kilian M.
Published: November 2010

It has previously been shown that secretory immunoglobulin A (S-IgA) influences the sorption of oral streptococci to hydroxyapatite as well as to cell surfaces. The present experiments demonstrate that bacterial IgA proteases, which cleave S-IgA in the hinge region, are capable of interfering with this mechanism. This result was obtained with an IgAI specific protease from Hæmophilus influenzae and with a protease from Clostridium ramosum that cleaves IgAI as well as IgA2 of A2m(I) allotype. The modulation of S-IgA-mediated effects by IgA proteases were studied by means of an in vitro method which permits quantitative determination of the sorption of radiolabeled oral bacteria to hydroxyapatite beads. Other authors have suggested that IgA protease-mediated effects may be explained by a strongly reduced antigen-binding capacity of released Fabα fragments. Here we present evidence that streptococci, after exposure to specific S-IgA and IgA protease, are coated with Fabα fragments.
Molecular Mechanism of Mucin Secretion: I. The Role of Intragranular Charge Shielding
Authors: Verdugo P. , Deyrup-Olsen I. , Aitken M. , Villalon M. , Johnson D.
Published: November 2010

Mucus is an ubiquitous polymer hydrogel that functions as a protective coat on the surface of integument and mucosa of species ranging from simple animals (such as coelenterates) to mammals. The polymer matrix of mucus is made out of long-chain glycoproteins called mucins that are tangled together, forming a randomly woven, highly polyionic network (Lee et al., 1977; Verdugo et al., 1983). Mucin-containing granules, produced by mammalian goblet cells in vitro, undergo massive post-exocytotic swelling. Their swelling kinetics is similar to the swelling of condensed artificial polymer gels (Verdugo, 1984; Tanaka and Fillmore, 1979). We had proposed that mucins must be condensed in the secretory granule and expand by hydration during or after exocytosis (Verdugo, 1984; Tam and Verdugo, 1981). However, the polyionic charges of mucins prevents condensation unless they (the mucins) are appropriately shielded. The present experiments were designed to assert the presence of an intragranular shielding cation and its role in secretion.

Giant mucin granules of the slug (Ariolimax columbianus) are released intact from mucus-secreting cells of the slug's skin. They burst spontaneously outside the cell, forming, upon hydration, the typical slug mucus (Deyrup-Olsen et al., 1983). We report here that these granules contain from 2.5 to 3.6 moles calcium/kg dry material, and that calcium is released from the granules immediately before the burst that discharges their secretory product. Therefore, we propose that calcium functions as a shielding cation of poly ionic mucins, and that the bursting discharge of mucins from secretory granules must result from the release of calcium from the intragranular compartment. Calcium release would unshield the polyionic charges of mucins, driving the mutual repulsion of polymer chains and triggering a quick expansion of the mucin network (resembling a Jack-in-the-box mechanism).

The existence of a poly ion associated with a shielding cation seems to be a common feature in a large variety of secretory granules. Thus, the proposed spring-loaded release system based on the unshielding of a condensed polyion may serve as a general model for explaining the molecular mechanism of product release in secretion.
Neuropeptides and Secretion
Authors: Ekström J.
Published: November 2010

In the rat parotid gland, an atropine-resistant parasympathetic-nerve-evoked secretion was demonstrated in vivo. In the absence of atropine, the non-adrenergic, non-cholinergic transmitter release seemed to contribute to the fluid secretion and to be largely responsible for the secretion of amylase and acinar secretory granules. The gland was reached by nerve fibers containing substance P (SP), vasoactive intestinal peptide (VIP), and, to some extent, calcitonin-gene-related peptide (CGRP) via the parasympathetic auriculo-temporal nerve. Upon electrical stimulation of the nerve, these peptides were released. SP and substance K (SK), a novel tachykinin, induced a profuse watery secretion when injected i.v., while VIP caused a sparse but amylase-rich secretion. CGRP caused no secretion on its own. The tachykinin-evoked secretory response was enhanced by VIP and CGRP. A SPanalogue almost abolished the SP-evoked response, while the atropine-resistant parasympathetic response was only halved. None of the peptides under study can on its own account for the atropine-resistant parasympathetic secretion. The neuropeptides may play complementary roles in the regulation of the exocrine functions of the gland.
Intracellular Elemental Concentrations in Resting and Secreting Rat Parotid Glands
Authors: Izutsu K.T. , Johnson D.E. , Goddard M.
Published: November 2010

Electron probe x-ray micro-analysis was used to study the elemental concentration changes that occur during pilocarpine-stimulated saliva secretion. Quantitative x-ray micro-analysis of elemental concentrations in intracellular compartments of rat parotid glands stimulated in vivo with pilocarpine showed that Na concentration was significantly increased, while K concentration was significantly reduced. The magnitude of these changes was consistent with values obtained in other tissues with the x-ray micro-analysis method, and in the same tissue with other experimental methods. Comparisons with results from studies utilizing dispersed acini suggest that acinar dispersion procedures may affect intracellular elemental concentrations. Total electrolyte concentrations in cytoplasm and secretory granules were estimated to increase on a dry-weight basis following pilocarpine stimulation. The former change is consistent with the notion of a trans-cellular route of salivary fluid flow, while the latter change may be important in the exocytosis of secretory granules.
Mobilization of Intracellular Calcium by Methacholine and Inositol 1,4,5-Trisphosphate in Rat Parotid Acinar Cells
Authors: Aub D.L. , Putney J.W.
Published: November 2010

In the rat parotid acinar cell, methacholine caused an increase in [Ca2+]ias determined by quin-2 fluorescence. The increase in [Ca2+]iwas initially independent of, and subsequently dependent on, the presence of extracellular Ca2+, indicating mobilization of intracellular Ca2+, as well as activation of Ca2+entry. Methacholine mobilization of the internal Ca2+pool and stimulation of the initial transient phase of K+efflux have similar concentration dependencies; the EC50value for Ca2+mobilization is 80 nmollL, the EC50value for K+efflux is 200 nmol/L. In a permeable parotid cell preparation, inositol 1,4,5-trisphosphate, inositol 2,4,5-trisphosphate, and inositol 4,5-bisphosphate were able to release Ca2+from an ATP-dependent, oligomycininsensitive pool. These observations, when taken with the previous finding that methacholine stimulates Ca-independent inositol trisphosphate formation, support the view that inositol 1,4,5-trisphosphate acts as a second messenger mediating the release of an intracellular Ca2+pool following muscarinic receptor activation in the parotid gland.
Calcium-dependent Protein Kinase Reactions Associated with Parotid Gland Secretory Granule Membranes
Authors: Dowd F. , Watson E.L. , Lau Y.-S. , Justin J. , Pasieniuk J. , Jacobson K.L.
Published: November 2010

Rat parotid secretory granule membranes were examined for the presence of calcium-dependent protein kinase activities and kinase substrates. Protein kinase C (C-kinase), which is stimulated by certain phospholipids, was present in the membranes, as indicated by its ability to catalyze the phosphorylation of histone. Two substrates for protein kinase C were seen in the granule membranes. The cytosolic fraction from the cell contained kinase activity, which was stimulated by phosphatidylserine and which caused the phosphorylation of two granule membrane polypeptides. In addition, when both granule membranes and cytosol were incubated together, phosphorylation of the cytosolic substrates was inhibited, indicating that the granule membrane substrates were phosphorylated preferentially. The results indicate that the granule membranes may react with cytosolic protein kinase C activity in a way which would direct an intracellular calcium and diacylglycerol signal toward the granule membrane. Since these signals occur during stimulation by various agonists, the mechanism may contribute to secretion.
The Effect of Environmental Aging on the Fracture Toughness of Dental Composites
Authors: Pilliar R.M. , Vowles R. , Williams D.F.
Published: November 2010

The effect of aging four commercially-available dental composites in water or ethanol at 37°C for periods of up to 28 days was assessed by measuring changes in the materials' plane-strain fracture toughness (KIC) . The results, obtained by means of a mini Short Rod Fracture Toughness Test specimen design, suggest that while water aging does not produce significant changes in KIC, aging in ethanol does cause significant increases in fracture toughness for three of the four dental composites studied. In view of previously-reported loss of wear resistance for dental composites aged in ethanol solutions, the present study emphasizes the difficulties in using fracture toughness to predict wear properties.
The Effect of Taste Adaptation on Salivary Flow Rate and Salivary Sugar Clearance
Authors: Dawes C. , Watanabe S.
Published: November 2010

To provide an objective measure of the rate of taste adaptation, we measured changes in the flow rate of parotid saliva from 12 subjects while a tastant was infused continuously into their mouths. The tastants employed were sucrose, sodium chloride, and citric acid, each at two different concentrations. With all stimuli, the higher concentration elicited significantly higher initial flow rates, which declined exponentially with time. The half-time for adaptation of flow rate was independent of the nature or concentration of the stimulus and averaged 11.3 sec, which suggests that adaptation follows a single exponential curve.

The model of salivary sugar clearance developed by Dawes (1983) predicted that the rate of clearance would be independent of the initial sucrose concentration. However, this model did not take into account the effect of tast adaptation on salivary flow. This process was thus incorporated into the model, which then predicted that the time for clearance would be dependent on the initial sucrose concentration, as found experimentally by Goulet and Brudevold (1984). Hence the process of taste adaptation progressively reduces the stimulated salivary flow rate, which retards the rate of salivary clearance of sugar from the oral cavity.