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Biomedical subjects

W J Simpson

Publications and source records attributed to W J Simpson.

86 records · Page 5Linked to original sources
PubMed1965

Total body scanning with strontium-85 in the diagnosis of metastatic bone disease.

To demonstrate skeletal metastases before radiographic changes were apparent, Sr(85) scans were carried out on 46 patients who complained of sketetal pain but whose radiographs were negative. Positive scans were obtained in 34 patients, 20 of whom were subsequently shown to have metastases; three did not have skeletal metastases a year or more later; the outcome is unknown in 11 patients. Twelve patients had negative scans: three ultimately developed metastases, six did not, and three were inconclusive. Autoradiographs demonstrated Sr(85) concentrations in areas of reactive osteogenesis.Although not specific for skeletal metastases, Sr(85) scans are most helpful in substantiating this diagnosis when radiographic changes are absent.

Autoradiography↗
PubMedDate not supplied

An evaluation of the performance of ten commercial luminometers.

An assessment has been carried out of the relative performance of ten instruments for quantification of adenosine triphosphate (ATP) by the firefly luciferase assay. The instruments evaluated were Amersham Amerlite Analyser, Dynatech Tube Luminometer, Dynatech Multiplate Luminometer, Dynatech Camera Luminometer, Hamilton Lumicon, LKB 1250 Luminometer, LKB 1251 Luminometer, Lumac Biocounter M2010A, Turner 20 TD Luminometer and a prototype version of the CLEAR SpeedTech 2000. An 800-fold difference in sensitivity was found between the most sensitive (Lumac, Turner) and the least sensitive (Dynatech Tube) of the conventional instruments. The Dynatech Camera Luminometer which worked on a completely different principle to the other instruments was about 5000 times less sensitive than the best of the photomultiplier tube instruments. The relative sensitivity of the instruments was maintained regardless of whether solutions of ATP in water or trichloroacetic acid extracts of bacteria were analysed. An analysis of 960 ATP bioluminescence assays showed that data obtained from such measurements are normally distributed.

Adenosine Triphosphate↗
PubMedDate not supplied

The effect of detergents on firefly luciferase reactions.

The reaction rate of ATP-limited firefly luciferase-catalysed reactions, is affected by the presence of detergents. Anionic detergents inhibit luciferase activity without causing significant enzyme inactivation during the reaction. Cationic detergents increase reaction rate several-fold with a sharply defined optimum concentration of detergent for the effect. However, cationic detergents inactivate firefly luciferase during the reaction, resulting in a continuously decreasing reaction rate. Under such conditions, peak light intensity must be used as an indication of initial reaction rate. The inactivation rate increases with increasing detergent concentration. Non-ionic and zwitterionic detergents increase reaction rate over a broad range of detergent concentrations. Enzyme stability during the reaction is not affected by non-ionic detergents and only affected by zwitterionic detergents at high detergent concentration. Cyclodextrins, which can increase reaction rates of some chemiluminescent reactions, have little effect on firefly luciferase activity. Assays for ATP using firefly luciferase must be internally standardized by the constant addition technique in which a known amount of ATP is added to the test sample, since external calibration of such assays, by reference to a previously prepared standard curve, can lead to imprecision when detergents are present.

Adenosine Triphosphate↗
PubMedDate not supplied

Influence of intracellular pH on light emission from a luxA/B derivative of Lactococcus lactis subsp. diacetylactis.

High levels of constitutive aldehyde-dependent light emission were obtained from nongrowing cells of Lactococcus lactis subsp. diacetylactis F712 transformed with IuxA/B when they were suspended in buffered solutions. Inductions of light emission was time-dependent and was not due to growth, synthesis of luciferase or stimulation of metabolism by fermentable carbohydrate. The major factor controlling light emission in such cells appears to be the intracellular pH value. Experiments with ionophores indicated that a transmembrane pH gradient was not essential for light emission.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMedDate not supplied

Application of in vivo bioluminescence to the study of ionophoretic action.

Ionophores (carbonyl cyanide m-chlorophenylhydrazone; valinomycin; and the hop-derived compounds colupulone, trans-isohumulone and trans-humulinic acid) reduced the rate of dodecanal-dependent light emission from IuxA/B-transformed cells of Lactococcus lactis subsp. diacetylactis F712 when the cells were suspended in a buffered medium (pH 6.4) containing glucose. This allowed an assay for ionophores to be devised and permitted measurement of the effects of such compounds on the test organism by the use of a non-destructive technique in real time.

Anti-Bacterial Agents↗