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Biomedical subjects

D J Livingstone

Publications and source records attributed to D J Livingstone.

34 records · Page 2Linked to original sources
PubMed1989

Pattern recognition display methods for the analysis of computed molecular properties.

Pattern recognition methods, particularly the 'unsupervised learning' techniques, are well suited for the preliminary analysis of the large data sets produced by computer chemistry. The use of linear and non-linear display methods for such exploratory analysis are exemplified with the aid of two data sets of biologically active molecules. Advantages and disadvantages of these techniques are discussed.

Computer Simulation↗
PubMed1988

Perspectives in QSAR: computer chemistry and pattern recognition.

Computer chemistry allows a detailed description of properties for a wide range of molecular environments. In these respects it offers substantial benefits to the QSAR (Quantitative Structure Activity Relationship) analyst. Problems associated with the resulting wide data matrices are, it is proposed, amenable to solution through multivariate 'pattern recognition' techniques.

Chemical Phenomena↗
PubMed1988

Effect of whole-bowel irrigation on the antidotal efficacy of oral activated charcoal.

Whole-bowel irrigation was studied in three volunteer subjects and compared with oral activated charcoal as a gastrointestinal decontamination procedure for acute drug overdose. The volunteer subjects were given 650 mg aspirin and were assigned randomly to the following treatment groups: 24-hour urine collection only; immediate whole-bowel irrigation with a polyethylene glycol solution; 50 g oral activated charcoal followed by whole-bowel irrigation; and oral activated charcoal alone. The cumulative 24-hour urinary salicylate excretion was measured in each trial. Catharsis was achieved rapidly with whole-bowel irrigation. Oral activated charcoal without catharsis was most effective in decreasing aspirin absorption (P = .011). These results do not support the routine use of a cathartic in combination with oral activated charcoal.

Adult↗
PubMed1983

Microbial classification of seawaters. The case against arbitrary health standards.

Various microbial health standards for recreational bathing waters obtain in many parts of the world, including Europe and America. These criteria appear to be a product of water laboratory scientists and legislators, bypassing the person most concerned--the local medical officer with his experience and knowledge of parochial epidemiology. In Natal we have a sophisticated and stringent system of grading bathing beaches which includes pathogenic microorganisms. The system functions as a measuring device for assessing changes in water quality, not as an arbitrary health standard. It is hoped that the practice of setting capricious so-called health standards for marine recreational waters does not spread to this country.

Escherichia coli↗
PubMed1976

An appraisal of sewage pollution along a section of the Natal coast after the introduction of submarine outfalls.

A bacteriological survey on the distribution and occurrence of coliforms and pathogenic indicators of pollution within the surf-zone and near-shore waters along a section of the Natal coast before the use of submarine outfalls with reported previously. In that report more than half the beaches in the region were found to be of Class IV or III quality. After the submarine outfalls became operational, ten further sampling runs were made. A considerable improvement in the sea-water quality was apparent, most of the beaches being regarded to Class II or I, notably in the bathing areas.

Bathing Beaches↗
PubMedDate not supplied

Unsupervised forward selection: a method for eliminating redundant variables.

An unsupervised learning method is proposed for variable selection and its performance assessed using three typical QSAR data sets. The aims of this procedure are to generate a subset of descriptors from any given data set in which the resultant variables are relevant, redundancy is eliminated, and multicollinearity is reduced. Continuum regression, an algorithm encompassing ordinary least squares regression, regression on principal components, and partial least squares regression, was used to construct models from the selected variables. The variable selection routine is shown to produce simple, robust, and easily interpreted models for the chosen data sets.

Algorithms↗
PubMedDate not supplied

Neural network studies. 2. Variable selection.

Quantitative structure-activity relationship (QSAR) studies usually require an estimation of the relevance of a very large set of initial variables. Determination of the most important variables allows theoretically a better generalization by all pattern recognition methods. This study introduces and investigates five pruning algorithms designed to estimate the importance of input variables in feed-forward artificial neural network trained by back propagation algorithm (ANN) applications and to prune nonrelevant ones in a statistically reliable way. The analyzed algorithms performed similar variable estimations for simulated data sets, but differences were detected for real QSAR examples. Improvement of ANN prediction ability was shown after the pruning of redundant input variables. The statistical coefficients computed by ANNs for QSAR examples were better than those of multiple linear regression. Restrictions of the proposed algorithms and the potential use of ANNs are discussed.

Databases, Factual↗
PubMedDate not supplied

[Application of neural networks using the volume learning algorithm for the study of structure-activity relationship in chemical compounds].

A volume learning algorithm for artificial neural networks was developed to quantitatively describe the three-dimensional structure-activity relationships using as an example N-benzylpiperidine derivatives. The new algorithm combines two types of neural networks, the Kohonen and the feed-forward artificial neural networks, which are used to analyze the input grid data generated by the comparative molecular field approach. Selection of the most informative parameters using the algorithm helped to reveal the most important spatial properties of the molecules, which affect their biological activities. Cluster regions determined using the new algorithm adequately predicted the activity of molecules from a control data set.

Algorithms↗
PubMedDate not supplied

Xanthone additives for blood storage that maintain its potential for oxygen delivery. I. 2-Hydroxyethoxy- and 2-ethoxy-6-(5-tetrazoyl) xanthones in citrate-phosphate-dextrose-adenine (CPDA-1) blood.

Two xanthones, 2-hydroxyethoxy-6-(5-tetrazoyl) (BW A440C) and 2-ethoxy-6-(5-tetraozyl) (BW A827C), are members of a chemical series tested in vitro as potential additives to citrate-phosphate-dextrose-adenine (CPDA-1) medium for blood storage. P50 was maintained in the presence of these compounds during 42 days' storage by a partial maintenance of 2,3 diphosphoglycerate (2,3 DPG) and by a direct effect on hemoglobin previously reported for BW A827C. Red cell 2,3 DPG levels for BW A440C (n = 5), BW A827C (n = 5), and control (n = 6), respectively, were 3.38 +/- 0.47, 3.44 +/- 0.25, and 1.20 +/- 0.10 mM +/- SEM on day 7; 1.16 +/- 0.13, 1.52 +/- 0.37, and 0.16 +/- 0.02 mM on day 21; and 0.67 +/- 0.09, 0.61 +/- 0.08, and 0.06 +/- 0.006 mM on day 42. Red cell adenine triphosphate levels at the same time intervals were 1.84 +/- 0.09, 1.46 +/- 0.18, and 2.11 +/- 0.04 mM; 2.10 +/- 0.05, 2.07 +/- 0.17, and 2.13 +/- 0.05 mM; and 1.42 +/- 0.13, 1.37 +/- 0.13, and 1.38 +/- 0.06 mM, respectively. The degree of hemolysis was less with the addition of the compounds, and the methemoglobin formation, plasma Na+ and K+, and lactate production were unaffected by the compounds.

2,3-Diphosphoglycerate↗