Biomedical subjects

S M Higham

Publications and source records attributed to S M Higham.

61 records · Page 4Linked to original sources

PubMed1991

Extracellular administration of lactate dehydrogenase and its effects on human plaque pH and acid anion concentrations.

The effect of lactate dehydrogenase (LDH) on human plaque pH and acid anion concentrations in vivo was investigated. Rinsing with sucrose solutions supplemented with LDH (1 or 2 U/ml) gave rise to reduced pH fall, decreased cH area and an increase in the mean minimum pH when compared with rinsing with sucrose only (p less than 0.05). Mean acid anion estimations showed that plaque fluid concentrations of lactate, acetate and proprionate significantly decrease (p less than 0.05) following rinsing with sucrose containing LDH at both levels and decreases in succinate when 1 U/ml LDH was present, whereas formate concentrations were only significantly lower when 2 U/ml LDH was added to sucrose rinses. It is thought that the ability of LDH to produce an alteration in the acid end-products of plaque metabolism may provide some protection against dental caries.

Acetates↗

PubMed1990

Effects of lactate dehydrogenase on fissure caries in rats.

The effect of supplementing the diet or drinking water with lactate dehydrogenase (LDH) on the formation of caries lesions in rats was investigated. Addition of LDH [20 and 5 mg/kg in the high-sucrose (65%) diet, 2 and 1 U/ml in the drinking water (LDH-specific activity 735 U/mg solid)] resulted in significant reductions (p less than 0.01) in the number and severity of caries lesions when the enzyme was administered to rats for 4 or 7 days, although no significant differences were found after 14 or 21 days. No differences were observed between effects of addition to water or diet. Fissure caries failed to develop when rats were fed a low sucrose diet (5%) containing LDH (20 mg/kg diet), whereas 50% of the animals in the control group developed lesions. The findings indicate that LDH may play an important role in delaying the onset of caries lesion formation in rats, and that the protection observed may be inversely related to the intensity of the cariogenic challenge.

Animals↗

PubMed1990

Plaque fluid as a bacterial milieu.

Studies of the extracellular, free concentrations of substrates, growth factors, inhibitors, and end-products of metabolism to which the intact plaque microflora is exposed in situ can assist in the understanding of factors controlling plaque pathogenicity. Information is becoming increasingly available from analysis of fluid separated by centrifugation of plaques collected at various intervals after an intra-oral pulse of dietary or experimental substrate, or different procedures or treatments having cariostatic potential. Such analytical results give more information than those obtained by analysis of aqueous or other extracts, because they yield values of substrate concentration representing those occurring at the bacterial cell surface. The largest body of information concerns extracellular levels of acid end-products of sugar catabolism in relation to food quality or sequence, and of amino acids and other products of nitrogen metabolism, in relation to studies of the detailed metabolic events of the Stephan curve, and of the demineralizing effect of the plaque environment. Areas where little information is available and which merit further study include plaque clearance of salivary and other components with anti-caries activity (e.g., antibodies, enzymes, fluorides, cations, other antimicrobials, etc.), and substrate concentrations to determine gradients for diffusion into and out of plaque.

Amino Acids↗

PubMed1989

Human dental plaque pH, and the organic acid and free amino acid profiles in plaque fluid, after sucrose rinsing.

The relationship between these factors was studied in plaque and plaque fluid samples taken at intervals during the Stephan pH curve following a sucrose mouth rinse. Levels of lactate rose after the rinse, then fell during the pH recovery phase. Levels of acetate, propionate and phosphate fell after rinsing, then rose again. Amino acid concentrations also changed, with many showing a fall followed by a rise; others rising then falling; and some showing a more variable or complex pattern. In resting plaque fluid, only alanine, proline, glutamic acid, glycine and ammonia were present at concentrations above 1 mmol/l. Delta-aminovaleric acid was detected at levels below those that have been found in monkeys. Hydroxyproline and hydroxylysine were consistently detected, levels of arginine were generally low, and those of cystine consistently very low. The results may provide a basis for understanding the complex metabolic interrelations that occur in the course of the Stephan curve and which may reflect or produce the observed pH changes. They suggest that besides the amount of acid produced, the type of acid, buffering power and base production should be considered as determinants of plaque pH.

Acetates↗

PubMed1989

Effects of Parafilm and cheese chewing on human dental plaque pH and metabolism.

The effects of chewing Parafilm and cheese following sucrose rinsing on human dental plaque pH and plaque fluid organic and amino acid concentrations were investigated. Immediate increases in plaque pH were observed following chewing with concomitant decreases in lactate and acetate concentrations and increases in the concentration of formate and many amino acids. Chewing with cheese when compared with Parafilm resulted in significantly higher (p less than 0.05) plaque fluid concentrations of most amino acids, although significant decreases (p less than 0.05) in phosphate, succinate, and acetate concentrations were observed. However, no significant difference in the levels of formate, lactate, and propionate were found between the two chewing treatments.

Adolescent↗

PubMedDate not supplied

Acid anion profiles in dental plaque following consumption of cereal-based foods and fruits.

The aim of this study was to investigate the acid anions produced in plaque after chewing various cereal-based foods and fruits for one minute. Test foods were oranges, apples, bananas, Cornflakes, Branflakes, Weetabix, Alpen, white bread, wholemeal bread, rice and spaghetti, plus positive and negative controls of 10% sucrose and 10% sorbitol. 4 males and 3 females, aged 22-37 years, participated in the study .7 min from the start of chewing, 48-h plaque was collected from all accessible smooth surfaces, with no attempt to collect interproximal plaque, and centrifuged. Plaque fluid was withdrawn and analyzed by isotachophoresis for formate, succinate, lactate, acetate and propionate. At rest, acetate was the major anion present in plaque fluid, whereas following carbohydrate consumption, highest levels of lactate were detected followed by acetate. The amount of lactate only, detected in plaque fluid, was significantly correlated to the carbohydrate present in the food. It was concluded that important information regarding the acidogenicity of test foods is gained by studying the acid anion profile of plaque fluid.

Acetates↗

PubMedDate not supplied

The effect of chewing urea-containing gum on plaque acidogenic and alkaligenic parameters.

The aim of this double-blind crossover study was to determine the effect of chewing urea-containing gum on selected microbiological plaque properties. Eleven subjects chewed either urea-containing or urea-free placebo gum 3 times daily, each for 4 weeks, with at least a 4-week separation between regimes. After each chewing regime, plaque was sampled from all available surfaces, and inoculated into media indicative of acid or base production. In addition, interdental pH measurements were taken using touch Beetrode electrodes following sucrose and sorbitol mouthrinses, and sucrose mouthrinses followed by urea rinse, urea gum, or placebo gum. No significant differences in plaque acidogenic and alkaligenic properties were found between the urea and placebo gum regimes. Urea rinsing, urea gum and placebo gum all reduced the depth and duration of the pH fall following a sucrose mouthrinse. They also enhanced a rise in pH above the resting pH, but although urea gum produced a larger increase than placebo gum, the difference was not significant.

Acids↗