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Biomedical subjects

M J Kirby

Publications and source records attributed to M J Kirby.

At least 19 recordsLinked to original sources
PubMed2001

Comparison of bioassays and laboratory assays for apple stem grooving virus.

The standard field double-budding assay with the indicator Virginia Crab and the glasshouse test with the indicator Malus micromalus, were compared with ELISA and immunocapture PCR for the detection of Apple stem grooving virus (ASGV) in 102 apple trees and three oriental pear. Twenty-two trees were positive for ASGV by both ELISA and IC-PCR but three of these trees were negative by Virginia Crab, three were negative by M. micromalus and one was negative by both these bioassays. The infected trees were re-tested by IC-PCR and ELISA in a second year; the IC-PCR results were confirmed but two of the 22 infected trees were negative by ELISA. On this evidence, IC-PCR is a more reliable assay for ASGV than the slow and expensive bioassays.

Base Sequence↗
PubMed2001

The Whitney reduction network: a method for computing autoassociative graphs.

This article introduces a new architecture and associated algorithms ideal for implementing the dimensionality reduction of an m-dimensional manifold initially residing in an n-dimensional Euclidean space where n >> m. Motivated by Whitney's embedding theorem, the network is capable of training the identity mapping employing the idea of the graph of a function. In theory, a reduction to a dimension d that retains the differential structure of the original data may be achieved for some d < or = 2m + 1. To implement this network, we propose the idea of a good-projection, which enhances the generalization capabilities of the network, and an adaptive secant basis algorithm to achieve it. The effect of noise on this procedure is also considered. The approach is illustrated with several examples.

Journal Article↗
PubMed1996

Circular nodes in neural networks.

In the usual construction of a neural network, the individual nodes store and transmit real numbers that lie in an interval on the real line; the values are often envisioned as amplitudes. In this article we present a design for a circular node, which is capable of storing and transmitting angular information. We develop the forward and backward propagation formulas for a network containing circular nodes. We show how the use of circular nodes may facilitate the characterization and parameterization of periodic phenomena in general. We describe applications to constructing circular self-maps, periodic compression, and one-dimensional manifold decomposition. We show that a circular node may be used to construct a homeomorphism between a trefoil knot in R3 and a unit circle. We give an application with a network that encodes the dynamic system on the limit cycle of the Kuramoto-Sivashinsky equation. This is achieved by incorporating a circular node in the bottleneck layer of a three-hidden-layer bottleneck network architecture. Exploiting circular nodes systematically offers a neural network alternative to Fourier series decomposition in approximating periodic or almost periodic functions.

Neural Networks, Computer↗
PubMed1980

The effect of viloxazine on drug-induced inhibition of food intake in the rat.

In male Wistar rats trained to eat their normal daily dietary requirement in a restricted 2 h period, dose-dependent decreases in food consumption were produced by fenfluramine, tiflorex, mazindol and amphetamine. The antidepressant drug viloxazine (Vivalan) alone did not alter food intake significantly, nor did the drug prevent the inhibitory effects of either mazindol or amphetamine. However, complete prevention of the inhibitory effect of fenfluramine was achieved with 7.5 mg kg-1 viloxazine, while 40 mg kg-1 viloxazine similarly prevented the anorectic action of tiflorex. An interaction involving 5-hydroxytryptaminergic mechanisms is suggested, and since viloxazine given after fenfluramine or tiflorex produced no reversal of the inhibition of food intake, it is suggested that viloxazine prevents access of the anorectic agents to their site of action. The clinical significance of these interactions is discussed.

Amphetamine↗
PubMed1979

Influence of ciclazindol on monoamine uptake and CNS function in normal subjects.

The potential antidepressant drug ciclazindol inhibited dopamine uptake into human platelets without affecting 5-hydroxytryptamine uptake as compared with a control. It inhibited the tyramine pressor response less than desipramine after single 50-mg oral doses in 6 healthy volunteers under double-blind conditions. Compared with tandamine in a double-blind placebo-controlled study in nine healthy subjects, ciclazindol 50 mg orally caused no significant anticholinergic effects but reduced appetite according to an analysis of variance. Nonparametric analysis did not confirm the anorectic effect. Previous studies had shown that ciclazindol increased glucose uptake into isolated human skeletal muscle independently of insulin. Overall, ciclazindol resembles the antiobesity drug mazindol in molecular structure and pharmacological effects in man. Interactions with sympathomimetic amines and adrenergic neurone-blocking drugs cannot be excluded on the basis of these studies.

Adult↗
PubMed1977

Clinical pharmacological studies of tandamine, a potential antidepressive drug.

Tandamine hydrochloride, a thiopyranoindole, was more active than desmethylimipramine in inhibiting the tyramine pressor response after single oral doses in human volunteers. When compared with a placebo, tandamine was found to possess significant anticholinergic activity, to reduce appetite and to produce sedation. Compared with clomipramine, it caused a smaller inhibition of 5-HT but a more marked inhibition of dopamine uptake into human platelets. Further clinical and pharmacological studies with tandamine may help to elucidate the respective roles of different monoamines in depression, sedation and appetite.

Adult↗
PubMed1977

The effect of methysergide and other receptor antagonists on fenfluramine-induced glucose uptake into the isolated rat hemidiaphragm.

Fenfluramine in therapeutic concentrations causes a significant and dose related increase in glucose uptake into isolated rat and human skeletal muscle in the presence of insulin. Using fenfluramine, 100 ng/ml, on the rat hemidiaphragm preparation the effects of the following receptor blocking drugs in concentrations up to 250 ng/ml were investigated on this phenomenon: atropine, haloperidol, mepyramine, methysergide, propranolol and thymoxamine. Only methysergide, the 5-HT antagonist, reduced the action of fenfluramine in relatively low concentrations of the drug which were dose related (10 ng/ml causing approximately 40% inhibition). This suggests that the peripheral as well as the central actions of fenfluramine are mediated through 5-HT receptors.

Animals↗
PubMed1976

Do "anorectic" drugs produce weight loss by appetite suppression?

A peripheral action on glucose metabolism may play an improtant part in the weight loss associated with treatment with some antiobesity drugs such as fenfluramine and mazindol. In therapeutic concentrations these agents increase glucose uptake into animal and human skeletal muscle. This action is distinct from their effects on central transmitters and from the reduction in food intake in animals.

Animals↗
PubMed1976

The influence of premedication, anaesthesia, age and weight on glucose uptake into human isolated skeletal muscle.

The effect of the anaesthetic procedures and of the sex, age and weight of each patient on glucose uptake and glycogen content of human skeletal muscle has been studied in vitro in the presence and absence of insulin. Statistical analysis indicated that the relationships between age and both glucose uptake and the response to insulin were significant, older patients in general having higher uptakes. The blucose uptake was highly correlated with the three obesity indices (ponderal index, body mass index and percentage of the ideal weight). The anaesthetic agents had no significant effect on glucose uptake. The choice of premedication appeared to have a small effect on the basal glucose uptake level, but as the choice of premedication was also age related and age itself was a significant factor, this effect may not be of importance. It is concluded that the age and the degree of obesity of the patients ought to be taken into account when studying samples of human muscle.

Adult↗