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Biomedical subjects

D Beighton

Publications and source records attributed to D Beighton.

At least 127 records · Page 7Linked to original sources
PubMed1990

Proteolytic activity of oral streptococci.

Streptococcus mutans and Streptococcus sobrinus were the least proteolytic of 8 species of oral streptococci while Streptococcus oralis and Streptococcus sanguis were the most proteolytic. Degradation of FITC-BSA was significantly correlated with the hydrolysis of synthetic endopeptidase substrates. As S. oralis strains proliferate in dental plaque in the absence of dietary food their success, in vivo, might be due partially to their greater proteolytic activity compared to other oral streptococci.

Caseins↗
PubMed1990

Sialidase activity of the "Streptococcus milleri group" and other viridans group streptococci.

Viridans group streptococci were examined for the production of sialidase (neuraminidase) activity, using the fluorescent substrate 4-methylumbelliferyl-alpha-D-N-acetylneuraminic acid in a simple and rapid (15-min) assay. Sialidase was produced by all strains of Streptococcus oralis and S. intermedius and by a majority of S. mitis strains. S. mutans, S. sobrinus, S. gordonii, S. sanguis, S. vestibularis, S. salivarius, S. anginosus, S. constellatus, "S. parasanguis," and the "tufted fibril group" were uniformly negative. Sialidase production may be a useful characteristic to assist in the identification of viridans group streptococci.

Humans↗
PubMed1990

Phenotypic differentiation of Streptococcus intermedius, Streptococcus constellatus, and Streptococcus anginosus strains within the "Streptococcus milleri group".

A biochemical scheme was developed by which strains of Streptococcus constellatus, Streptococcus intermedius, and Streptococcus anginosus can reliably be distinguished from within the "Streptococcus milleri group." Strains identified as S. intermedius were differentiated by the ability to produce detectable levels of alpha-glucosidase, beta-galactosidase, beta-D-fucosidase, beta-N-acetylgalactosaminidase, beta-N-acetylglucosaminidase, and sialidase with 4-methylumbelliferyl-linked fluorogenic substrates in microdilution trays after 3 h of incubation at 37 degrees C, together with the production of hyaluronidase. Strains of S. constellatus and S. anginosus were differentiated by the production of alpha-glucosidase and hyaluronidase by the former and the production of beta-glucosidase by the latter. The majority of strains of the S. milleri group obtained from dental plaque were identified as S. intermedius, as were most strains isolated from abscesses of the brain and liver. Strains of S. constellatus and S. anginosus were from a wider variety of infections, both oral and nonoral, than were strains of S. intermedius, with the majority of strains from urogenital infections being identified as S. anginosus.

Dental Plaque↗
PubMed1989

Trypsin-like, chymotrypsin-like and glycylprolyl dipeptidase activities in gingival crevicular fluid from human periodontal sites with gingivitis.

These activities were measured simultaneously, using synthetic fluorescent protease substrates, in gingival crevicular fluid collected at 6 pre-determined sites from 10 individuals with mild to moderate gingivitis. The three enzyme activities were detected in 85, 18 and 93% of the sites, respectively. The volume of fluid collected from discrete sites was significantly correlated with the total amount of substrate hydrolysed, but not with the specific rate of substrate hydrolysis. Log10 (total trypsin-like activity) was significantly correlated with the Gingival Index, Plaque Index and probing depth (r = 0.319, 0.423 and 0.336), while total glycylprolyl dipeptidase activity was significantly correlated with probing depth (r = 0.381). These findings add to knowledge of the biochemistry of gingival crevicular fluid, but the usefulness of such assays for diagnostic or monitoring purposes in periodontal diseases needs to be determined.

Adult↗
PubMed1989

Intra-oral colonization of macaque monkeys by Actinobacillus actinomycetemcomitans.

Actinobacillus actinomycetemcomitans was acquired by captive Macaca fascicularis 3 to 6 months after birth, and all monkeys aged over 6 months harbored detectable levels. This microorganism was most frequently isolated from the gingival plaque of the incisor (and other) teeth compared with other oral sites. Strains were leukotoxic by bioassay and Western blot analysis. Antibodies in macaque serum contained neutralized the leukotoxin of a human A. actinomycetemcomitans strain. High titres of maternal neutralizing anti-leukotoxin antibodies were detected in neonates; the titre then fell rapidly so that by 6 months the antibody titer was zero. Antileukotoxin antibody production was detected after 6 months of age, rapidly reaching a high level within 2 years after birth. The presence of leukotoxic strains of A. actinomycetemcomitans in the gingival region did not appear to be correlated with an increase in susceptibility to periodontal disease.

Actinobacillus↗
PubMed1989

Associations between salivary levels of Streptococcus mutans, Streptococcus sobrinus, lactobacilli, and caries experience in Kenyan adolescents.

Salivary levels of mutans streptococci (S. mutans and S. sobrinus) and lactobacilli were determined in a random sample of rural Kenyans between 15 and 19 years of age (n = 149). It is possible for the natural history of dental caries in this population to be studied since it is characterized by a limited access to conventional dental treatment. Using a short set of biochemical tests, we identified from seven to ten presumptive mutans streptococcus colonies--cultured from the saliva of each individual--to differentiate between S. mutans and S. sobrinus. No colonies resembling S. rattus (S. mutans serotype b) were isolated. Lactobacilli were identified as Gram-positive, catalase-negative rods. The mean D1-4MFS and D3-4MFS were 7.03 +/- 6.43 and 1.46 +/- 3.44, respectively. The mean mutans streptococcus and lactobacillus levels were 8.7 x 10(4) and 6.7 x 10(4), respectively. The salivary mutans streptococcus and lactobacillus levels were significantly correlated (p less than 0.01). Of the subjects, 64% harbored only S. mutans, 4% only S. sobrinus, 30% both species, and 2% neither. Lactobacilli were ubiquitous. The caries experience of the group was significantly (p less than 0.001) correlated with both the total salivary level of mutans streptococci and the salivary S. mutans levels, but not with the salivary S. sobrinus level.

Adolescent↗
PubMed1987

Proteolytic activities in the supragingival plaque of monkeys (Macaca fascicularis).

Thirteen peptidase substrates were hydrolysed by this plaque. After fasting the monkeys for 24 h, the rates of hydrolysis of N-leucyl-, N-alanyl-, N-isoleucyl- and N-tyrosyl-2-naphthylamines, glycyl-L-proline 4-nitroanilide, N alpha-benzoyl-DL-arginine-2-naphthylamine and L-leucyglycine were significantly increased. Changes in these peptidase activities may serve to enhance the mobilization of amino acids and peptides, and they may explain why the growth rates of dental-plaque bacteria in vivo are generally unaffected by the availability of the host's diet.

Animals↗
PubMed1986

The influence of diet on the growth of streptococcal bacteria on the molar teeth of monkeys (Macaca fascicularis).

The rates of regrowth of bacteria in developmental grooves on these teeth were determined. Plaque was removed from palatal grooves up to 96 h after cleaning and the number of bacteria and of individual streptococcal species were determined; Streptococcus sanguis, Streptococcus mutans and Streptococcus mitior were the major ones. In monkeys fed one of three different diets, the numbers of each species reached stable levels 18-24 h after tooth cleaning. The median doubling times of the streptococcal population were 4.69, 3.82 and 4.25 h for two maintenance diets and a sucrose diet, respectively. The median doubling times of individual species ranged from 2.01 to 4.38 h and appeared to be independent of the composition of the various diets. There was no difference in the number of bacteria in 18 h-old plaque from discrete sites in fed or fasted monkeys, nor in the numbers of streptococci, except that the size of the Strep. mitior population increased significantly with fasting. Thus host-derived substrates, possibly salivary components, may be used by plaque bacteria and support their on growth in developmental grooves in the absence of food.

Animals↗
PubMed1986

The growth of bacteria and the production of exoglycosidic enzymes in the dental plaque of macaque monkeys.

The rate of growth of the predominant bacterial strains of plaque from the developmental grooves of first deciduous molar teeth was determined. Median doubling times were 3.32, 3.45, 2.88 and 4.54 h for streptococci, lactobacilli, actinomyces and Neisseria mucosa respectively. Withdrawal of dietary food did not greatly influence the number of bacteria found in the grooves 18 h after they had been cleaned when compared to the number in fed monkeys; exceptions were significant increases in Streptococcus mitior and N. mucosa. Addition of 0.5 per cent (w/v) glucose to the drinking water of fasted monkeys also did not influence the size of this bacterial population 18 h after cleaning, so bacteria growing in cleaned grooves must gain a major part of their nutritional needs from their immediate environment, most likely salivary constituents. The ability of oral bacteria to use the oligosaccharide side-chains of salivary glycoproteins was then explored. Exoglycosidases for the preferred anomeric linkages of the principal monosaccharide units of salivary glycoproteins were produced both by oral bacteria in vitro and by dental plaque in vivo. Thus plaque flora has the potential to degrade glycoproteins and this may explain how bacteria in the grooves grow in the absence of dietary food.

Actinomyces↗
PubMed1986

The effects of the availability of diet on the levels of exoglycosidases in the supragingival plaque of macaque monkeys.

Supragingival plaque from macaque monkeys was assayed for 13 exoglycosidase enzymes, with appropriate p-nitrophenylglycosides and N-acetylneuramin-lactose used as substrates. Protein in each plaque sample was quantitated with a Coomassie Brilliant Blue dye binding assay, and the specific activity of each enzyme was calculated. In monkeys fed a starch-based diet, fasting resulted in significant increases in the levels of alpha-L-fucosidase, beta-N-acetyl-D-glucosaminidase, beta-N-acetyl-D-galactosaminidase, and neuraminidase. Such changes are consistent with the hypothesis that plaque bacteria degrade salivary glycoproteins for their growth and maintenance in both the presence and especially the absence of dietary food. In contrast, fasting monkeys previously fed a sucrose-rich diet showed no significant alterations in the specific activities of those enzymes whose levels were increased in the starch-based diet group. It is considered likely that, under the conditions prevailing when the sucrose-rich diet is fed, the effective and maximal utilization of sucrose by plaque bacteria necessitates the increased mobilization of nitrogen sources, including the amino sugars of glycoproteins.

Animals↗
PubMed1985

The relationship between the number of the bacterium Streptococcus mutans at discrete sites on the dentition of macaque monkeys (Macaca fascicularis) and the subsequent development of dental caries.

Sixteen consecutively-born monkeys were used in a longitudinal study to determine the changes occurring in the total number of bacteria in the palatal grooves of the upper left first deciduous molar teeth, following the introduction of a sucrose-based diet. The total number of bacteria recovered from the grooves increased significantly following the diet change. Twenty-nine days after the diet change, the number of Streptococcus mutans had increased from a median value of less than 10(2) to approx. 10(7) per groove, and the number of Streptococcus sanguis decreased. These changes in the number of Strep. mutans occurred prior to the detection of dental caries. Grooves that became carious harboured significantly more bacteria and more Strep. mutans than did grooves remaining caries-free six months after the diet change.

Animals↗
PubMed1985

Establishment and distribution of the bacteria Actinomyces viscosus and Actinomyces naeslundii in the mouths of monkeys (Macaca fascicularis).

The colonization of the mouth by the two Actinomyces species, postulated to be members of a basic plaque flora, was studied in 27 consecutively-born neonatal monkeys. Bacteria adherent to the tongue and cheek surfaces were sampled from each monkey soon after birth (mean age = 3.2 days). The tongue and cheek surfaces and the labial surfaces of the incisor teeth were sampled at 4, 8 and 12 weeks of age. From only one neonatal sample were Actinomyces species isolated. By 4 weeks of age, the incisor teeth are partially erupted and, from teeth erupted more than 1 mm, A. naeslundii was frequently isolated and its proportion increased between 4 and 8 weeks on all surfaces sampled. At 4, 8 and 12 weeks, the proportion of A. naeslundii on the incisor teeth was greater than on the mucosal surfaces. The isolation rate of A. viscosus was low in these neonates, but it was isolated from each of 6 juvenile monkeys fed a starch diet. In the 6 juvenile monkeys, the proportion of A. viscosus decreased following the introduction of a sucrose-containing diet, whereas the proportion of A. naeslundii on the teeth increased. The early establishment of A. naeslundii and, to a lesser extent, A. viscosus in the dental plaque of neonatal monkeys fed exclusively by their mothers suggests that members of a basic plaque flora may be those bacteria establishing in the plaque during the period of breast-feeding.

Actinomyces↗
PubMed1984

The establishment of the bacterium Streptococcus mutans in dental plaque and the induction of caries in macaque monkeys (Macaca fascicularis) fed a diet containing cooked-wheat flour.

A diet containing 50.7 per cent cooked wheat flour (78 per cent starches and dextrin) was fed to 82 monkeys from weaning for up to 407 days. Streptococcus mutans became established naturally and remained at a high level (25-40 per cent of the total anaerobic colony count) in the dental plaque of the majority of animals but in only 2 were carious lesions detected. The predominant Strep. mutans serotypes isolated from plaque were c, e and h, which produced acid when incubated with the diet in vitro. Twenty-five monkeys were switched to a cariogenic high sucrose diet, and 6 months later 72 per cent of them had carious lesions (mean +/- SD = 6.5 +/- 6.6 carious lesions per monkey). The failure of the starch diet to promote tooth decay in monkeys supports the general conclusion that starch and starch products are virtually non-cariogenic for man.

Animals↗
PubMed1983

Light- and electron-microscopic study of the microbial deposits present on the tongue and dentition of macropods.

The dental deposits in the kangaroos and wallabies were similar to human calculus with lysed bacterial cell remnants embedded in previously mineralized areas. The surface of the microbial deposits in contact with the enamel showed: (a) triangular structures 3-5 micron deep and 4-5 micron wide at their base repeating every 4 or 5 micron which probably occupied the remnants of Tomes processes which in macropods do not flatten out; (b) irregular, short (1 micron) projections that probably occupied the inter-prismatic areas. Few organisms were observed on the anterior or dorsal surfaces of the tongues but on the posterior region there was abundant microbial colonization. Large amounts of extracellular matrix were preserved using a fixation technique designed to minimize the loss of water-soluble material. Bacteria were arranged perpendicular to the epithelial cell surfaces and were present on either surface of desquamating epithelial cells. Aqueous fixation erroneously suggested that inter-bacterial and bacterial-epithelial cell adhesion was primarily by fine fibrillar strands.

Animals↗