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Biomedical subjects

R A Rodford

Publications and source records attributed to R A Rodford.

5 recordsLinked to original sources

The computational prediction of toxicity.

Recent developments in the prediction of toxicity from chemical structure have been reviewed. Attention has been drawn to some of the problems that can be encountered in the area of predictive toxicology, including the need for a multi-disciplinary approach and the need to address mechanisms of action. Progress has been hampered by the sparseness of good quality toxicological data. Perhaps too much effort has been devoted to exploring new statistical methods rather than to the creation of data sets for hitherto uninvestigated toxicological endpoints and/or classes of chemicals.

Carcinogens↗

A QSAR model for the eye irritation of cationic surfactants.

A QSAR model for the eye irritation of cationic surfactants has been constructed using a dataset consisting of the maximum average scores (MAS-accordance to Draize) for 29 in vivo rabbit eye irritation tests on 19 different cationic surfactants. The parameters used were logP (log [octanol/water partition coefficient]) and molecular volume (to model the partition of the surfactants into the membranes of the eye), logCMC (log critical micelle concentration-a measure of the reactivity of the surfactants with the eye) together with surfactant concentration. The model was constructed using neural network analysis. MAS showed strongly positive, non-linear correlations with surfactant concentration and logCMC and a strongly negative, non-linear correlation with logP. The Pearson correlation between the actual and predicted values of MAS was 0.838 showing that around 70% (r(2)=0.702) of the variance in the dataset is explained by the model. This value is consistent with levels of biological variability reported historically for the Draize rabbit eye test. The relationship provides a potentially useful prediction model for the eye irritation potential of new or untested cationic surfactants with physicochemical properties lying within the parameter space of the model.

Animals↗

Variation of Young's modulus with the test specimen's aspect ratio.

A study of Young's modulus in flexure of a number of methacrylate polymers indicated that the results were dependent on the test specimen thickness. The Young's modulus calculated from simple bending theory decreased with increased specimen thickness. This effect could not be accounted for either by the usual corrections for shear or corrections for the effect of the width/length ratio. It transpires that the effects noted experimentally are due to the combined effects of shear and the width/length ratio.

Denture Bases↗

Further observations on high impact strength denture-base materials.

Previous studies have shown that high impact strength can be conferred on denture-base poly(methyl methacrylate) polymers by modification with acrylic-terminated butadiene-styrene block copolymers, and that the acrylic end-group was necessary for effective reinforcement. It is now shown that, by solvent extraction studies, grafting of the copolymer occurs both with acrylic-terminated and non-terminated block copolymers. It is therefore concluded that the mode of grafting is different, and some possible mechanisms are discussed.

Acetone↗

Further development and evaluation of high impact strength denture base materials.

The further development of poly(methylmethacrylate) reinforced with low molecular weight polybutadiene-based rubbers previously studied is described. The materials produced have been optimized with respect to impact strength and Young's modulus, giving results up to 0.13 J for the former whilst maintaining the latter at about 2.3 G.Pa. Additionally, the systems have been evaluated with respect to viscoelastic properties, water absorption and the effect of the latter on mechanical properties. Further work on the underlying mechanisms should lead to a greater understanding of these systems which could, in turn, produce more superior materials.

Adsorption↗