Biomedical subjects

W H Bowen

Publications and source records attributed to W H Bowen.

At least 19 recordsLinked to original sources

PubMed1992

The effect of delmopinol on glucosyltransferase adsorbed on to saliva-coated hydroxyapatite.

The aim was to explore the effects of delmopinol, a substituted amino-alcohol compound recently reported as a potential antiplaque agent, on GTF activity in solution and when adsorbed on to sHA. Delmopinol was without a significant effect on GTF activity in solution. In contrast, a reduction in the bound glucans synthesized by the adsorbed GTF was found in the presence of delmopinol. Delmopinol did not displace the adsorbed GTF from the sHA, nor was there significant desorption of glucans from sHA. The total glucan synthesis (bound and unbound) was reduced in the presence of delmopinol. Inhibition of GTF was not reversed by sucrose. Inhibition of GTF activity by delmopinol apparently results from drug-enzyme interaction on the surface of sHA beads. These observations provide further support for the important differences in the properties of adsorbed GTF and GTF in solution, illustrating that GTF-drug interaction differs between enzyme adsorbed to surfaces and enzyme in solution.

Adsorption↗

PubMed1992

Glucans synthesized in situ in experimental salivary pellicle function as specific binding sites for Streptococcus mutans.

Many researchers have suggested that the role of glucan-mediated interactions in the adherence of Streptococcus mutans is restricted to accumulation of this cariogenic bacterium following its sucrose (i.e., glucan)-independent binding to saliva-coated tooth surfaces. However, the presence of enzymatically active glucosyltransferase in salivary pellicle suggests that glucans could also promote the initial adherence of S. mutans to the teeth. In the present study, the commonly used hydroxyapatite adherence assay was modified to include the incorporation of glucosyltransferase and the synthesis of glucans in situ on saliva-coated hydroxyapatite beads. Several laboratory strains and clinical isolates of S. mutans were examined for their ability to adhere to experimental pellicles, either with or without the prior formation of glucans in situ. Results showed that most strains of S. mutans bound stereospecifically to glucans synthesized in pellicle. Inhibition studies with various polysaccharides and fungal dextranase indicated that alpha 1,6-linked glucose residues were of primary importance in the glucan binding observed. Scanning electron microscopic analysis showed direct binding of S. mutans to hydroxyapatite surface-associated polysaccharide and revealed no evidence of trapping or cell-to-cell binding. S. mutans strains also attached to host-derived structures in experimental pellicles, and the data suggest that the bacterial adhesins which recognize salivary binding sites were distinct from glucan-binding adhesins. Furthermore, glucans formed in experimental pellicles appeared to mask the host-derived components. These results support the concept that glucans synthesized in salivary pellicle can promote the selective adherence of the cariogenic streptococci which colonize human teeth.

Bacterial Adhesion↗

PubMed1992

Molecular analysis of a Streptococcus mutans strain exhibiting polymorphism in the tandem gtfB and gtfC genes.

Streptococcus mutans UA101, which was previously demonstrated to be highly cariogenic in gnotobiotic rats, exhibited much lower water-insoluble glucan (IG) synthetic activity compared with that of S. mutans GS5 and was unable to express sucrose-dependent colonization of smooth surfaces in vitro. On the basis of Southern and Western blot (immunoblot) analyses, it was demonstrated that, unlike most S. mutans strains, strain UA101 contained a single copy of a gene coding for IG synthesis. The gene was isolated from a clone bank constructed with the plasmid pTH10 clone bank in Escherichia coli and had apparently evolved after homologous recombination of the gtfB and gtfC genes present on the chromosome of a recent ancestor of strain UA101. The enzyme expressed from the gene, gtfBC, was purified to near homogeneity by utilizing a single-step preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis system and was characterized. A derivative of strain UA101, UA101LBS, containing a chromosomal insertion of the GS5 gtfC gene was constructed after transformation. UA101LBS exhibited high IG synthetic activity and colonized smooth surfaces in vitro. By utilizing a conventional rat model system involving animals fed a high-sucrose diet, strain UA101 exhibited low levels of smooth surface caries activity relative to Streptococcus sobrinus 6715. By contrast, UA101LBS was as cariogenic as strain 6715. However, sulcal caries occurred equally well with all of the strains tested. These results are evaluated relative to the role of gtf gene products in cariogenicity.

Animals↗

PubMed1992

Characteristics and cariogenicity of a fructanase-defective Streptococcus mutants strain.

Polymers of D-fructose produced by a variety of oral bacteria are believed to function as extracellular carbohydrate reserves. Degradation of these polysaccharides in plaque following exhaustion of dietary carbohydrates is thought to contribute to the extent and duration of the acid challenge to the tooth surface and thus to the initiation and progression of dental caries. Streptococcus mutans produces a fructanase, the product of the fruA gene, which is capable of degrading beta(2,6)- and beta(2,1)-linked fructans that are commonly synthesized by dental plaque microorganisms. To evaluate the role of the FruA protein in exopolysaccharide metabolism and to assess the contribution of this enzyme to the pathogenic potential of S. mutans, a fructanase-deficient strain of S. mutans was constructed. Inactivation of a cloned fruA gene was accomplished in Escherichia coli by using a mini-Mu dE transposon, and then an isogenic mutant of S. mutans UA159 was constructed by allelic exchange. Successful inactivation of fruA was confirmed through the use of biochemical assays, Western blotting (immunoblotting) with anti-recombinant FruA antisera, and Southern hybridization. The data indicated that FruA was the only fructan hydrolase produced by S. mutans UA159. Inactivation of fruA had no significant effects on glucosyltransferase or fructosyltransferase activity. In the rat caries model using animals fed a high-sucrose diet and ad libitum, there were no significant differences in the number or severity of smooth surface, sulcal, or root caries elicited by the fruA mutant and the wild-type organism.

Animals↗

PubMed1992

The effects of sucralose, xylitol, and sorbitol on remineralization of caries lesions in rats.

The purpose of this study was to determine whether ingestion of sucralose, xylitol, sorbitol, or distilled water alone could enhance remineralization of early caries lesions in rats. Rats were infected by Streptococcus sobrinus, fed diet 2000 (Ziegler Brothers, Gardners, PA) ad libitum for two weeks, and, in addition, were offered drinking water sweetened by sucrose (10% w/v). A group of rats terminated at this time displayed significant levels of sulcal and smooth-surface caries. The remaining animals, for the ensuing three weeks, either continued on the same cariogenic challenge or received their essential nutrition by gavage and drank water, sweetened by one of the agents listed above, ad libitum. At the end of the additional three-week period, animals receiving sucralose, xylitol, sorbitol, or distilled water had fewer lesions than did the animals terminated after the two-week cariogenic challenge. The results show that removal of the cariogenic challenge allowed remineralization to occur and that no sweetening agent was superior to another in this respect.

Animals↗

PubMed1992

Interactions of delmopinol with constituents of experimental pellicle.

The prolonged retention of an effective chemotherapeutic agent on oral surfaces and in dental plaque aids in plaque control. The objective of this study was to investigate interactions between delmopinol, a morpholinoethanol derivative, and experimental pellicle. Hydroxyapatite beads were coated with different constituents of pellicle (e.g., saliva, carbohydrates, cell-free enzymes, and bacteria). Delmopinol demonstrated a higher affinity for saliva-coated hydroxyapatite (sHA) and for experimental pellicle coated with in situ-synthesized glucans than for untreated hydroxyapatite. High-molecular-weight (MW) dextran but not low-MW dextran interfered with the adsorption of delmopinol to sHA. Delmopinol did not compete with dextran for the same binding sites on sHA, nor did it compete with saliva for the same binding sites on untreated hydroxyapatite. Delmopinol inhibited the activity of cell-free fructosyltransferase adsorbed onto sHA. In addition, synthesis of glucans by Streptococcus mutans adsorbed onto sHA was significantly reduced in the presence of delmopinol.

Adsorption↗

PubMed1991

Agonist-induced Ca2+ mobilization in the rat submandibular gland during aging and subsequent to chronic propranolol treatment.

The effects of age and chronic propranolol treatment on the agonist-induced rise in intracellular free Ca2+ ([Ca2+]i), an index for the coupling of receptor-second messenger generation, was studied using a dispersed rat submandibular gland preparation. Muscarinic stimulation (10 microns carbachol) caused a rapid (T1/2 less than 2 s) and dramatic (approximately 4.5-fold) rise in [Ca2+]i followed by a lower sustained increase (approximately 3-fold) in [Ca2+]i as measured directly with the Ca(2+)-sensitive fluorescent probe, fura-2. The magnitude and the rate of increase of the initial rise in [Ca2+]i and the level of the sustained increase in [Ca2+]i were not different between 2- an 21-month-old rats. Stimulation in a Ca(2+)-free medium reduced the initial agonist-induced increase in [Ca2+]i by approximately 35-40%, while the sustained increase was abolished by the removal of extracellular Ca2+ from cells in both young and old rats. Chronic treatment for 30 days with 20 mg/kg propranolol, a beta-adrenergic antagonist, did not significantly alter the ability of dispersed submandibular cells in old rats to mobilize Ca2+ during agonist stimulation or influence the in vivo stimulated gland output. These results suggest that the agonist-induced rise in [Ca2+]i is not altered by aging or by chronic treatment of aged rats with propranolol and, therefore, receptor-second messenger coupling remains intact.

Aging↗

PubMed1991

Combined effects of Zn(2+)-chlorhexidine and Zn(2+)-cetylpyridinium chloride on caries incidence in partially desalivated rats.

The effects of Zn2+ combined with either chlorhexidine or cetylpyridinium chloride (CPC) on caries incidence in partially desalivated rats were investigated. Seven groups of 12 animals each received topical applications for 20 s with a saturated swab (0.2 ml) of the following aqueous solutions twice daily on weekdays (10 a.m. and 3 p.m.) and once daily during weekends (12 a.m.) for 5 wk: deionized water (placebo); 40 mM zinc acetate; 2.2 mM chlorhexidine diacetate; 4.4 mM CPC; 40 mM zinc acetate and 2.2 mM chlorhexidine diacetate; 40 mM zinc acetate and 4.4 mM CPC; and 20 mM NaF (positive control). Coronal caries was scored by the method of Keyes. All treatments except CPC alone resulted in significantly (P less than 0.05, ANOVA) less smooth-surface caries than did the placebo. NaF treatment resulted in significantly less smooth-surface caries than did Zn2+, chlorhexidine, CPC, and Zn(2+)-CPC. The inclusion of zinc ions did not significantly increase the caries-inhibitory efficacy of chlorhexidine (CH). The combination of Zn(2+)-CPC decreased smooth-surface scores significantly more than did CPC alone. Significant differences in sulcal-surface caries were not observed among the groups. Zn(2+)-CPC suppressed the Streptococcus sobrinus counts significantly more than did the separate agents. Animals treated with Zn(2+)-CH harbored the lowest populations of S. sobrinus.

Acetates↗

PubMed1991

Role of a cell surface-associated protein in adherence and dental caries.

Insertional inactivation of the Streptococcus mutans spaP gene was used to construct an isogenic mutant (834) of strain NG8 (serotype c) which lacked the major cell surface-associated protein referred to as P1 (15). Results of several studies suggest that P1 is involved in the adherence of S. mutans to saliva-coated apatite surfaces. With an in vitro model system of hydroxyapatite (HA) beads coated with parotid saliva (PS) and additional HA surfaces coated with PS and in situ-formed glucan, it was observed that mutant 834 adhered poorly to the PS/HA surfaces. In contrast, both parent and mutant strains bound to the PS-glucan/HA surface. Groups of intact and desalivated rats were infected with each strain to determine relative capacities to induce dental caries. Rats were fed a highly cariogenic diet containing 56% sucrose for 3 to 5 weeks. Each strain colonized the rodent model and caused similar levels of smooth-surface caries under these dietary conditions. It was concluded that P1 influences the ability of organisms to adhere to saliva-coated surfaces and possibly affects primary colonization of the oral cavity in the absence of a glucan surface but has no effect on glucan-mediated adherence in vitro or in vivo.

Animals↗

PubMed1991

A computer program designed for the analysis of data from rat caries studies.

The Keyes method for scoring dental caries in the rat animal model has been used as the basis for a computer-assisted scoring system on the Apple Macintosh personal computer that is described here. The program provides the ability to draw on diagrams of the rat molar dentition and to enter enamel lesion scores (L, E) and dentinal lesion scores (Ds, Dm, and Dx) for all aspects of the molars. The scores and drawings may be changed at any time. Total carious teeth and totals of L, E, Ds, Dm, and Dx are automatically calculated and presented upon user command. Error trapping for typographical errors is provided. In addition, the program provides automatic storage of the collected information, searching and sorting on any of the experimental parameters and on-disk help files that can be accessed from any place within the program. The capacity to obtain printed copy of any or all of the stored information is provided in the program. The program also enables the creation of external data files containing totals for carious teeth, in addition to L, E, Ds, Dm, and Dx totals for each animal of each group represented in the data base. These files are suitable for the transfer of data to commercially available programs for graphical and statistical analyses. The programming technique we describe could be extended to other model systems with standardized scoring for oral disease.

Animals↗

PubMed1991

Influence of milk, lactose-reduced milk, and lactose on caries in desalivated rats.

There is a growing population who suffer from hyposalivation. These patients frequently sip liquids to alleviate their discomfort. Milk appears to have many of the physical properties of a good saliva substitute. Desalivated rats given 2% milk or lactose-reduced milk remained essentially caries-free. In contrast, animals given sucrose or lactose to drink developed caries. In addition, animals given sucrose or lactose harbored significantly higher populations of Streptococcus sobrinus than did other groups. Results showed that milk and lactose-reduced milk can be used safely by hyposalivatory patients as a saliva substitute.

Animals↗

PubMed1991

Enhancing the virulence of Streptococcus sobrinus in rats.

The purpose of this study was to explore the virulence of strains of Streptococcus sobrinus that had been re-isolated from a desalivated rat. Furthermore, we wished to determine the influence of desalivation on the acidogenicity of fasting and sucrose-pulsed dental plaque in rats infected by strains of S. sorbrinus. Experimental groups were formed and infected as follows: Group 1, desalivated animals, S. sorbrinus ATCC27352; Group 2, intact animals, infected as in Group 1; Group 3, desalivated animals, S. sorbrinus re-isolated from a desalivated animal that had been infected with the ATCC 27352 strain for five weeks; Group 4, intact animals, infected as in Group 3; Group 5, desalivated animals, S. sobrinus re-isolated from a desalivated animal that had been infected with the ATCC27352 strain for ten weeks; Group 6, intact animals, infected as in Group 5; Group 7, intact animals, no infection. All animals were fed cariogenic diet 2000 and sucrose-sweetened drinking water ad libitum. After five weeks, desalivated and intact animals that had been infected with isolates obtained from desalivated animals had significantly higher (p less than 0.05) smooth-surface-caries scores than did intact and desalivated animals infected with cultures of the original stock ATCC strain. Moreover, fasting plaque pH values were statistically lower in desalivated animals (Groups 1 and 3) than in intact animals (Groups 2, 6, and 7) (Turkey analysis, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Caries prevention--fluoride: reaction paper.

Although the prevalence of caries has declined in young persons in developed countries, there is still a need for water fluoridation. The effectiveness of fluoride is dependent on the ambient levels of fluoride in the oral cavity. Fluoride appears to exert the bulk of its protective effect locally by promoting remineralization of early carious lesions. Nevertheless, fluoride tablets continue to be prescribed as if the action of fluoride is expressed systemically. There is an urgent need to explore the clearance of fluoride from the mouth and to develop methods to ensure constant levels of fluoride in the oral cavity, thereby reducing both the need for frequent exposure and the amount necessary for clinical effect.

Dental Caries↗

PubMed1991

Dental caries: is it an extinct disease?

Although almost half of U.S. children aged 5 to 17 years are caries-free, less than 5 percent of adults 18 to 65 years have no tooth decay. It appears that caries attacks persist unrelentingly throughout life. Continuous caries prevention, therefore, is essential, especially in an aging population.

Adolescent↗

PubMed1990

Influence of sweetening agents in solution on dental caries in desalivated rats.

Sucralose (trichlorogalactosucrose), sorbitol and aspartame in drinking water induced little or no caries in desalivated rats infected with Streptococcus sobrinus and Actinomyces viscosus and receiving their essential nutrition by gastric gavage. In contrast, sucrose and fructose induced extensive decay. Only sucrose could sustain implantation of Strep. sobrinus in these animals. The populations of A. viscosus were sparse (0.3-0.5%) in the animals given fructose and sucrose. Large populations of A. viscosus occurred in the controls and in those given sucralose, sorbitol and aspartame. In a second experiment, where animals were also desalivated and receive diet 2000 ad libitum, sucrose in solution promoted caries whereas sucralose, aspartame and saccharin were without effect. Addition of 10 parts/10(6) F overcame the caries-promoting effect of sucrose in solution. There was no interaction between fluoride and other sweetening agents that affected the incidence of caries.

Actinomyces↗

PubMed1990

Immunochemical studies on levans from several strains of Actinomyces viscosus.

High molecular-weight levans elaborated by 8 separate strains of Actinomyces viscosus were purified: the inteactions of these levans with concanavalin A and anti-fructan myeloma immunoglobulins UPC-10 and J606 were examined by the quantitative precipitin method. Oligosaccharides released from the levans by partial acid hydrolysis were separated by partition chromatography on paper and characterized in situ by selective spray reagents. The liberated oligomers were compared with oligomers of known structure released from levans of Aerobacter levanicum and Leuconostoc mesenteriodes B512 as well as with plant inulin. The fragmentation analysis indicated a structure for Actinomyces levans comprising chains of beta (2----6)-linked fructofuranosyl units joined through multiple (1,2,6)-linked fructosyl branch units.

Actinomyces↗

PubMed1990

The effect of chronic propranolol treatment on salivary composition and caries in the rat.

Many drugs are known to affect salivary secretion. The purpose of this study was to explore the chronic effects of a commonly used beta-adrenergic blocker, propranolol. Adult rats were desalivated or treated for 28 days with propranolol HCl (10 or 20 mg/kg, daily) or sterile buffer (sham-operated control) using osmotic pumps for delivery. The parotid and submandibular glands of each rat were cannulated and secretion elicited by pilocarpine (10 mg/kg, intravenous). There were no statistical differences in salivary protein content (Lowry) or output among the groups (ANOVA, p greater than 0.05). Analysis of salivary proteins by SDS-PAGE revealed a constant profile for submandibular secretions, but peak A and SP-3 proline-rich proteins were not detectable in parotid saliva of animals treated with propranolol for the entire experiment. Significantly increased smooth-surface (p = 0.0003) and sulcal (p = 0.0011) caries scores were found within these propranolol groups (ANOVA). The findings provide further evidence that chronic administration of propranolol alters salivary composition by decreasing proline-rich proteins and concurrently enhances susceptibility to caries.

Analysis of Variance↗

PubMed1990

Phenotypic characterization of Streptococcus sanguis virulence factors associated with bacterial endocarditis.

Certain strains of Streptococcus sanguis adhere (Adh+) selectively to human platelets and, in plasma, induce them to aggregate (Agg+) into in vitro thrombi. In this study, we examined 18 recent endocarditis and dental plaque isolates of microorganisms that were biotyped as S. sanguis for coexpression of platelet interactivity phenotypes with another possible virulence factor in bacterial endocarditis, dextran synthesis. Detectable production of extracellular glucosyltransferase ranged from 0.2 to 66 mU/mg of culture fluid for 10 representative strains tested. Production of extracellular or cell-associated glucosyltransferase, fructosyltransferase, and soluble or insoluble dextrans was not necessarily coexpressed with platelet interactivity phenotypes, since the levels of production of soluble and insoluble dextrans varied among representative Adh+ Agg+ and Adh- Agg- strains. Analysis of a second panel of 38 fresh dental plaque isolates showed that S. sanguis distributes in a reproducible manner into the possible phenotype groups. Strains with different platelet interactivity phenotypes were distinguished with a panel of four murine monoclonal antibodies (MAbs) raised against Adh+ Agg+ strain 133-79 and screened to rule out artifactual reactions with antigenic components in culture media. The MAbs reacted selectively with Adh+ Agg+ strains in a direct-binding, whole-cell, enzyme-linked immunosorbent assay and also inhibited their interactions with platelets. Analysis of minimal tryptic digests of many strains, including variants that failed to bind the MAbs, suggested that some noninteractivity phenotypes possess cryptic surface determinants. Since the ability to adhere to platelets and induce them to aggregate is relatively stable, these traits may be useful in a phenotyping scheme for these Lancefield nontypeable streptococci.

Animals↗