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Biomedical subjects

J E Tyler

Publications and source records attributed to J E Tyler.

At least 19 recordsLinked to original sources
PubMed1990

Rapid monitoring of fluoride (F-) levels in blood plasma.

Evidence exists that plasma F- concentrations of 1.0 part/10(6) are nephrotoxic and that much lower levels disturb enamel mineralization. Ingested F(-)-containing gels, tablets and toothpastes all raise plasma F- levels significantly, as does prolonged exposure to fluorine-containing anaesthetic gases. There is, therefore, a continuing need to determine the total F- burden accruing in any given individual from multiple sources, as well as the average plasma F- burden which could be carried without risk to kidneys or teeth. To meet this need by facilitating fast and accurate monitoring of plasma F- levels, a new method has been devised and tested. A specific ion F- electrode in conjunction with a combination pH electrode forms a differential cell very sensitive to low concentrations of F-. When compared with the performance of a single F- electrode plus Ag/AgCl reference electrode, the differential cell is not only as consistent and accurate but also has a much shorter response time (2 vs. 20 min) and requires a much smaller sample volume (0.05 vs. 1.0 ml). In healthy subjects the mean plasma F- level was 0.044 (+/- 0.001) parts/10(6); in three patients undergoing prolonged (24 h) sedation with the fluorine-containing gas isoflurane, mean plasma F- rose to 0.275 (+/- 0.025) parts/10(6). No binding of F- to plasma components occurred at the operating pH (1.2) of the differential cell and plasma could be stored for at least 40 days at low temperature (4 degrees C) without alteration to measured F- values.

Blood Chemical Analysis↗
PubMed1990

Isoflurane sedation for patients undergoing mechanical ventilation: metabolism to inorganic fluoride and renal effects.

The metabolism and renal effects of isoflurane sedation were studied for 24 h in patients undergoing mechanical ventilation. Forty-six patients admitted to our intensive therapy unit were allocated randomly to receive either 0.1-0.6% isoflurane or midazolam 0.01-0.2 mg kg-1 h-1 for sedation. In 26 patients sedated with isoflurane, plasma inorganic fluoride increased from a mean concentration of 4.03 mumol litre-1 to 13.57 mumol litre-1 12 h after stopping sedation. Plasma inorganic fluoride concentrations in 20 patients sedated with midazolam were unchanged from baseline values (mean 5.32 mumol litre-1). Serum electrolyte, urea and creatinine concentrations, and urine output rates during and after sedation in patients who received isoflurane were similar to those who received midazolam. We conclude that, following isoflurane sedation for up to 24 h, metabolism to inorganic fluoride is insufficient to cause clinical renal dysfunction.

Aged↗
PubMed1989

The rapid measurement of fluoride concentrations in stored human saliva by means of a differential electrode cell.

For the purpose of rapid measurement, the performance of a differential cell, consisting of a combination pH electrode and a F- electrode and used at low pH (1.2), was compared with the use of a single F- electrode at pH 5.0. The differential cell proved to be as accurate and consistent as the single electrode: its response time was 2 min for a saliva volume of 50 microliters; the response time of the single electrode was 20 min with a saliva volume of 1000 microliters. Analysis of salivary supernatant fluid provided an unreliable guide to the original salivary F- concentrations but if fresh whole saliva was acidified to pH 1.2 immediately upon collection, the original baseline values were repeatedly obtained when measurements were made at intervals over a storage period of 14 days at 4 degrees C. Immediate acidification thus provides a satisfactory method for collecting samples from separate populations and then transporting them at leisure to a laboratory for direct measurement at pH 1.2 with the differential cell.

Calcium↗
PubMed1989

Simulation of natural enamel caries in vitro with methylcellulose acid gels: effect of addition of calcium and phosphate ions.

A modified acid gel technique for producing caries-like lesions in dental enamel has been developed. The decalcifying medium consists of a 10% (w/v) methylcellulose gel acidified with 0.1 M lactic acid-sodium lactate at pH 4.5 and having a hydroxyapatite content of 0.05% (w/v). This medium can produce caries-like lesions in vitro at a slow rate, which are indistinguishable from natural enamel caries when examined by polarised light microscopy and contact microradiography.

Adolescent↗
PubMed1987

Widespread Legionella pneumophila contamination of dental stations in a dental school without apparent human infection.

Following isolation of Legionella pneumophila from a special dental station water circuit, used primarily to cool high-speed dental drills which produce fine aerosols, a case finding and environmental survey was undertaken. Widespread colonization of the dental stations was found and the results suggested that amplification of the background levels of L. pneumophila was taking place within the stations. However there was no evidence for transmission causing human infection.

Antibodies, Bacterial↗
PubMed1986

Superficial fluoride levels and response to in-vitro caries-like lesion induction of enamel from Bristol (U.K.) and Birmingham (U.K.) human deciduous teeth.

Surface enamel fluoride levels were measured in deciduous canine teeth from Bristol, with non-fluoridated water supplies, and Birmingham, with fluoridated water supplies. Three populations studied were from Bristol (teeth shed before 1960), Bristol (after 1975) and Birmingham (after 1975). Up to 75 micron from the enamel surface, fluoride concentrations of post-1975 Bristol and Birmingham teeth were, respectively, X 1.3 and 3.4 greater than those of pre-1960 Bristol teeth. The increase in the Bristol teeth is presumably due mainly to the increased use of fluoride-containing toothpastes, that in Birmingham to fluoridated water plus the use of fluoride toothpastes. No difference in the rates of penetration into enamel of acid-gel induced, caries-like lesions were found between the two Bristol populations; Birmingham teeth showed a reduction of 10 per cent in penetration rate. It is suggested that raised fluoride levels in surface enamel do not reduce solubility sufficiently to account, by themselves, for the recent nationwide marked reduction in caries in children. Possibly, the raising of plaque fluoride levels is a more important factor, affecting demineralization, remineralization and bacterial activity.

Acid Etching, Dental↗
PubMed1984

Uptake of fluoride by human surface enamel from ammonium bifluoride and consequent reduction in the penetration in vitro by caries-like lesions.

In-vitro fluoride uptake by mid-coronal, premolar enamel surfaces from topically-applied solutions of NH4HF2 was determined using a multi-electrode system for fluoride and calcium analyses. In tooth surfaces dehydrated with 100 per cent ethanol before the topical application of 1 per cent aqueous NH4HF2, there was a 2-3-fold increase in fluoride concentration up to a depth of 50 microns and fluoride enhancement to a total depth of 100 microns into the enamel. Caries-like lesions were induced in vitro in both treated and untreated enamel by the use of acidified, 6 per cent hydroxymethyl-cellulose gel containing 0.04 per cent hydroxyapatite at pH 4.5. After 120 days exposure, the mean depth of lesion penetration in the controls was 149 (+/- 34) microns. No lesions occurred in half the treated specimens; in specimens with lesions, the mean depth of penetration was 19 (+/- 3) microns. Thus, NH4HF2 was a potent inhibitor of caries-like lesion formation in vitro.

Acid Etching, Dental↗
PubMed1978

Discrimination between oral streptococci by pyrolysis gas-liquid chromatography.

Washed organisms, including strains of Streptococcus mitior, S. mutans, and S. sanguis, were examined by curie-point pyrolysis gas-liquid chromatography. A linear discriminant function based upon three items from the output data was adequate for segregating the strains according to species. Strains with intermediate properties were also encountered. Sources of variability in cultures were evaluated, chromatographic performance was maintained throughout the investigation, and matching performance from a duplicate pair of chromatographic columns was demonstrated.

Dental Plaque↗
PubMed1975

Gas chromatography of volatile fatty acids. Method involving separation from biological material by vacuum distillation.

A method is described for the quantitation of C2-C5 volatile fatty acids present in biological tissues. It involved recovery of the acids from their biological matrix by vacuum micro-distillation at room temperature, followed by gas phase separation of aqueous solutions on orthophosphoric acid-modified Phasepak Q columns. The subsequent gas chromatographic procedure resolved iso from normal isomers and showed a linear response for each volatile acid over the range 10-400 ng. There was no evidence of ghosting, isomer peak broadening, or peak tailing. Relative molar response values were shown to be linear with carbon number for all the volatile fatty acids studied.

Carbon↗
PubMed1974

Growth rates of a pseudomonad on 2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenol.

The growth of a pseudomonad on 2,4-D (2,4-dichlorophenoxyacetic acid) and 2,4-DCP (2,4-dichlorophenol) was studied in batch and continuous culture. The optimum growth rate using 2,4-D was 0.14/h at 25 C in a pH range from 6.2 to 6.9. Highest specific growth rate using 2,4-DCP was 0.12/h at 25 C in a pH range from 7.1 to 7.8. Growth was strongly inhibited by 2,4-DCP above a concentration of 25 mg/liter whereas no appreciable inhibition was observed with 2,4-D at concentrations up to 2,000 mg per liter. Growth on 2,4-DCP was described by Monod kinetics at subinhibitory concentrations but the inhibition by 2,4-DCP exhibited an unusual linear response to substrate concentration, and did not fit a model based on noncompetitive inhibition. The lag phase of batch cultures was found to depend on both 2,4-DCP concentration and prior adaptation of the inoculum. A study such as this on the kinetics of growth on related substrates may be useful as a method of finding the rate-limiting step in a metabolic sequence.

2,4-Dichlorophenoxyacetic Acid↗