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Biomedical subjects

C Dawes

Publications and source records attributed to C Dawes.

105 records · Page 6Linked to original sources
PubMed1966

The composition f human saliva secreted in response to a gustatory stimulus and to pilocaprine.

1. The composition of human saliva secreted in response to sour lemon drops (S.L.D.), and pilocarpine, was studied.2. At a given flow rate, pilocarpine-stimulated submandibular and parotid saliva contained less sodium and potassium and an equivalent amount of inorganic phosphate, and parotid saliva also contained more calcium and protein than did the corresponding types of S.L.D.-stimulated saliva.3. Prolonged S.L.D. stimulation did not cause a depletion in the protein concentration of either parotid or submandibular saliva and neither this procedure nor pilocarpine stimulation altered the proportions of the different proteins secreted.4. Pilocarpine was judged to be an inadequate substitute for more physiological, gustatory stimuli.

Calcium↗
PubMedDate not supplied

Salivary concentrations of urea released from a chewing gum containing urea and how these affect the urea content of gel-stabilized plaques and their pH after exposure to sucrose.

The objectives were to: (1) determine the salivary concentrations of urea during 20 min chewing of a sugar-free gum containing 30 mg of urea; (2) measure the degree to which this urea would diffuse into a gel-stabilized plaque; (3) study the effect of the urea on the fall and subsequent rise in pH (Stephan curve) on exposure to 10% sucrose for 1 min; (4) model the measurements 2 and 3 mathematically. In point 1, the salivary urea concentration of the 12 subjects peaked at 47 mmol/l in the first 2 min of gum chewing, falling within 15 min to the unstimulated salivary concentration of 3.4 mmol/l. Recovery of urea from the saliva averaged 81.5%. 'Plaques' of 1% agarose or 67% dead bacteria in agarose accumulated urea from the saliva roughly as expected, whereas those plaques containing 8% live and 59% dead Streptococcus vestibularis showed negligible accumulation. Computer modelling showed this difference to be due to urease of live bacteria breaking down the urea as rapidly as it entered the plaque. Simulation of the effect of gum chewing subsequent to initiation of a Stephan curve in the latter type of plaque showed a rapid rise in pH but then a fall again on return to unstimulated conditions. This fall had not been seen in previous studies, with Streptococcus oralis, nor was it predicted by the computer modelling. Neither experimental simulation nor computer modelling suggested that chewing urea-containing gum before exposure to sucrose would have any effect on a subsequent Stephan curve. Thus chewing gum is only likely to inhibit caries when it is chewed after consumption of fermentable carbohydrate, rather than before.

Adult↗
PubMedDate not supplied

How much saliva is enough for avoidance of xerostomia?

Xerostomia, the subjective sensation of dry mouth, occurs when the salivary flow rate is less than the rate of fluid loss from the mouth by evaporation and by absorption of water through the oral mucosa. Evaporation can only occur during mouth-breathing but could reach a maximum rate of about 0.21 ml/min at rest, although normally it would be much less. Water absorption through the mucosa can occur because saliva has one sixth the osmotic pressure of extracellular fluid, thus creating a water gradient across the mucosa. The maximum absorption rate is calculated to be about 0.19 ml/min, declining to zero as the saliva reaches isotonicity. A recent study found the residual saliva volume, the volume of saliva left in the mouth after swallowing, to be 71% of normal in patients with severe hyposalivation and whose mouths felt very dry. Saliva in the residual volume is present as a thin film which varies in thickness with site. The hard palate has the thinnest film and when this is <10 microm thick, evaporation during mouth-breathing and/or fluid absorption may rapidly decrease it to zero, resulting in xerostomia. This is also generally associated with reduced secretion from the soft palate minor glands, which may contribute to the film on the hard palate. Thus, xerostomia appears to be due, not to a complete absence of oral fluid, but to localized areas of mucosal dryness, notably in the palate. Unstimulated salivary flow rates >0.1-0.3 ml/min may be necessary for this condition to be avoided.

Absorption↗