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Biomedical subjects

R Strang

Publications and source records attributed to R Strang.

At least 55 records · Page 3Linked to original sources
PubMed1989

Analysis of biogenic amines in the brain of the American cockroach (Periplaneta americana) by gas chromatography-negative ion chemical ionisation mass spectrometry.

Biogenic amines in the brain of the American cockroach have been identified and quantified by an extraction-derivatisation procedure involving their reaction with ditrifluoromethylbenzoyl chloride (DTFMB) in the aqueous phase followed by extraction into an organic solvent, hydrolysis of phenolic esters and conversion of free hydroxyl groups to trimethylsilyl (TMS) ethers and subsequent analysis by gas chromatography-negative ion chemical ionisation mass spectrometry. The molecular ion of these DTFMB-TMS derivatives carried most of the ion current which made the method highly specific and gave a potential limit of detection below the picogram level. This method establishes unequivocally that the principal amines in cockroach brain are tyramine, p-octopamine, dopamine, 5-hydroxytryptamine and noradrenaline. In contrast to mammalian nervous tissue, the other positional isomers of octopamine, together with the isomeric synephrines, are absent.

Animals↗
PubMed1988

In vitro temperature rises during visible-light curing of a lining material and a posterior composite.

The aim of this study was to measure the rise in temperature during: (i) a single cycle of a curing light unit, (ii) the polymerization of a layer of light-cured lining material, and (iii) the polymerization of a light-cured posterior composite material, and also during combinations of these individual procedures. Experimental work was undertaken in vitro and measurements were made using a thermocouple placed centrally in an insulated PTFE well. Large temperature rises occurred with the use of the curing light alone. The lining material itself did not contribute significantly to the rise in temperature during curing, nor did it provide thermal insulation from the output temperature emitted by the light guide. The presence of a layer of posterior composite reduced the temperature transmitted from the light but the residual temperature rise transmitted was still of such a magnitude as to cause concern regarding possible thermal injury to the pulp.

Calcium Hydroxide↗
PubMed1988

Comparison of solution- and gel-prepared enamel lesions--and in vitro pH-cycling study.

A variety of methods has been employed to produce artificial caries-like enamel lesions. The aim of this paper was to use a pH-cycling regime to compare the de-/remineralization behavior of lesions prepared by two methods. Lesions were produced by use of either an acidified undialyzed gelatin system or a buffered solution. Enamel sections, each containing four lesions, were allocated to four groups (A, B, C, D) and subjected to a daily pH-cycling regime of 16-hour demineralization and eight-hour remineralization. Groups A & B contained gelatin-prepared lesions, whereas Groups C & D contained solution-prepared lesions. To the remineralizing solutions used in Groups B & D, 2 ppm fluoride was added. The mineral content in the lesions was assessed, by means of microradiography/microdensitometry, at baseline and at intervals for six weeks. The lesions in all four groups exhibited net demineralization. In terms of the total mineral lost from the lesion (the delta z parameter), the demineralization rates of the solution-prepared lesions were significantly greater than those of the corresponding gelatin-prepared lesions. All sections in the non-fluoride groups showed subsurface demineralization in initially sound enamel, whereas only one section in the fluoride groups showed an area of mineral loss. Laminations in the mineral content profiles were apparent only in Group D. The results of this study indicate that the method of lesion preparation affects the subsequent behavior of lesions when exposed to de- and remineralizing protocols.

Bicuspid↗
PubMed1987

Evoked taste thresholds in a normal population and the application of electrogustometry to trigeminal nerve disease.

No standardised method for taste threshold measurement is available and therefore comparison between clinical studies is difficult. An electrogustometer was evaluated in normal subjects. No sex difference in taste threshold was noted; however, there was a significant elevation in detection threshold with age and smoking. Electrogustometric values both in patients before and after surgery for trigeminal neuralgia and in patients with trigeminal sensory neuropathy were determined. Many patients with trigeminal nerve disorders had abnormal electrogustometric detection thresholds suggesting that there is possibly an accessory taste pathway through the trigeminal nerve, although in some individuals the site of lesion may be in the brain stem. Electrogustometry is a convenient method for clinically assessing taste.

Adolescent↗
PubMed1987

The effect of baseline lesion mineral loss on in situ remineralization.

The effect of baseline lesion mineral loss on the remineralization of enamel lesions by a sodium fluoride dentifrice was studied in situ by means of an appliance carrying enamel sections. Artificial lesions of various sizes were created, by means of acidified gelatin, and were then mounted on the appliances of five volunteers. Each brushed twice daily for two min with a 1000 ppm F sodium fluoride dentifrice. Measurements of mineral content were made at baseline and at weekly intervals by microradiographic/microdensitometric techniques. Data from all five volunteers showed a linear increase in remineralization rate with increasing lesion size. Thus, in studies which compare the effects of different remineralizing formulations, care must be taken to ensure that initial lesion sizes are matched, or that the results are expressed as a percentage change in mineral content.

Cariostatic Agents↗