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Biomedical subjects

C Fyfe

Publications and source records attributed to C Fyfe.

6 recordsLinked to original sources
PubMed1995

Introducing asymmetry into interneuron learning.

A review is given of a new artificial neural network architecture in which the weights converge to the principal component subspace. The weights learn by only simple Hebbian learning yet require no clipping, normalization or weight decay. The net self-organizes using negative feedback of activation from a set of "interneurons" to the input neurons. By allowing this negative feedback from the interneurons to act on other interneurons we can introduce the necessary asymmetry to cause convergence to the actual principal components. Simulations and analysis confirm such convergence.

Interneurons↗
PubMed1994

Serum lipid profile determines platelet reactivity to native and modified LDL-cholesterol in humans.

The effects of thrombin (0.2 U/ml) and native (n-LDL), malondialdehyde-modified (MDA-LDL) and auto-oxidized (ox-LDL) low-density lipoproteins (20 micrograms of protein/ml) on platelet activation were evaluated in seven hyperlipidemic patients and compared to seven controls (fasting serum cholesterol 8.49 +/- 0.5 and 4.61 +/- 0.4 mM, respectively). Basal and thrombin-induced increases in platelet intracellular free calcium ion concentration ([Ca2+]i; fura-2) were similar in hyperlipidemic patients and controls (45 +/- 5 vs 42 +/- 3 and 635 +/- 51 vs 599 +/- 69 mM, respectively). n-LDL, MDA-LDL and ox-LDL increased basal [Ca2+]i (16, 36 and 81 percent, p < 0.01 between LDL-types), increases were consistently smaller in patients. There was an inverse relationship between LDL-induced responses and fasting serum LDL cholesterol as well as LDL/HDL ratio. In conclusion, modified LDL activated platelets to a greater extent than n-LDL, suggesting different types of LDL-receptors. Their agonistic effect was inversely related to the fasting serum lipid profile, suggesting that blunting of platelet responses to LDL could represent a protective mechanism in hyperlipidemic patients.

Adult↗
PubMed1990

Investigations of the horse conceptus via magnetic resonance imaging (MRI) and nitroxide spin labels as contrast agents.

Results are presented which illustrate the usefulness of Magnetic Resonance Imaging as applied to the study of living embryos. Nitroxide spin labels were employed as contrast agents to study the structure and properties of the embryos. These spin labels offer the additional advantage that they may potentially be bound to biologically important molecules thereby imparting the ability to produce contrast in the MR images to these new molecules. The horse conceptus was chosen over other embryos due to its large size. Whereas the embryos of cattle and swine are sub-millimetre in size, the horse conceptus is on the order of 10 millimetres in diameter. The availability of microscopic imaging gradient coils will allow the techniques developed in this study to be applied to the smaller embryos of other species.

Animals↗
PubMed1986

A simple adjustable functional brace for tibial fractures.

The use of an adjustable functional brace for fractures of the tibia has several practical and theoretical advantages. The high cost of commercially available braces has limited their use until now. We describe a simple, inexpensive orthosis which has given good results in a clinical study for 32 unselected fractures. The fractures' alignment was well maintained. The brace was comfortable to wear and there were few complications. It is hoped that the low cost of this simple custom-made brace will encourage more widespread use of this technique.

Adolescent↗
PubMed1982

An integrative approach to the electrophoresis of the reductase and dehydrogenase isozymes in respiring and fermenting yeasts.

A method is described for qualitatively monitoring changes in the starch gel electrophoresis isozyme patterns of key yeast dehydrogenase and reductase activities involved in the transition from aerobic to anaerobic conditions during batch fermentations. The hypoxic transition was accompanied by the disappearance of catalase, superoxide dismutase, mitochondrial dehydrogenases and the appearance of a novel 6-phosphogluconic acid dehydrogenase activity. Significant genetic differences were noted in the banding patterns of wine yeasts, baker's yeast and a commonly used laboratory yeast strain.

Alcohol Oxidoreductases↗