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Biomedical subjects

J S Duncan

Publications and source records attributed to J S Duncan.

At least 19 recordsLinked to original sources
PubMed1992

Lamotrigine-induced carbamazepine toxicity: an interaction with carbamazepine-10,11-epoxide.

We report an interaction between lamotrigine (LTG), a new antiepileptic drug (AED), and carbamazepine (CBZ) and its primary metabolite CBZ-10,11-epoxide (CBZ-E) in 9 consecutive patients (5 male, 4 female, aged 19-31 years). After introduction of LTG (median daily dose 200 mg, range 100-300 mg) the mean serum CBZ-E concentration increased by 45% (P less than 0.01) and the CBZ-E/CBZ ratio increased by 19% (P less than 0.02). In 4 patients these changes were associated with clinical toxicity (dizziness, nausea, diplopia). The possibility of an increase in serum CBZ-E concentrations needs to be considered if toxicity symptoms develop when LTG is added to CBZ therapy.

Adult↗
PubMed1991

The Chalfont Seizure Severity Scale.

Seizure severity has been largely neglected in studies of patients with epilepsy and the evaluations of treatment. A seizure severity scale, that measures the components of seizures that cause patients the most disturbance, is presented with an assessment of the scale's validity and reliability.

Anticonvulsants↗
PubMed1991

Modern treatment strategies for patients with epilepsy: a review.

Of patients who develop epilepsy 70-80% will become seizure free, the remaining 20% are the most difficult to treat satisfactorily. Eighty per cent of patients are best treated with a single drug. Stepwise treatment plans for the treatment of newly diagnosed patients and for the evaluation of patients with chronic epilepsy are suggested. There is a lack of consensus regarding the rate at which to taper antiepileptic drugs being discontinued in patients with active epilepsy. There are arguments for making drug changes rapidly; these arguments and strategies for managing the withdrawal of individual drugs are presented.

Anticonvulsants↗
PubMed1991

Reinforcement of linear structure using parametrized relaxation labeling.

An approach for reinforcing underlying linear structure while suppressing unwanted noise, useful for analysis of medical images, has been presented. The method utilizes principles previously presented with regard to relaxation labeling processes, but differ in that the label set is now considered to be continuous and the distribution of label preference values for each object (pixel) parametrized by a single vector. Due to this parametrization, the total number of computations per pixel in the new method is now dependent only on the number of neighbors used in the computation, and not on the number of labels as well, as in previous methods. Thus, for a general reinforcement problem with m labels and n neighbors being considered for each pixel, the time complexity per object (pixel) per iteration goes as O (nm2) for the prototypical algorithm (e.g. (Zucker, et. al., 1977)) and is reduced by the approach presented here to O (n). The method uses a new approach for deciding local neighborhood influence and making a decision between reinforced linear structure with some magnitude and orientation and a no-structure condition based on the nonlinear (sigmoidal) thresholding of a linear vector sum. It should be noted that there is a similarity between this sigmoidal thresholding function and similar functions used in artificial neural networks (Hopfield, 1984). Ongoing work is being performed to further investigate such overlap. Also, it is planned to extend the approach in several ways. These include the ability to reinforce co-circularity, as well as to reinforce underlying planar structure by updating surface normals in true three-dimensional diagnostic imagery.

Image Enhancement↗
PubMed1991

Measurement of left ventricular wall motion from contour shape deformation.

This paper has presented the formulation and initial results for a new algorithm aimed at estimating and quantifying the trajectories of points on the left ventricular wall of the heart based on two- dimensional image-derived shape information. The algorithm is based on first automatically estimating the LV contour for two frames and then sampling the contours and tracking the motion of each sample point. Work is currently in progress to evaluate and compare each of three shape-based matching criteria, and to extend the algorithm to multiple frames. Future work will extend the approach to three spatial dimensions, capitalizing on the idea that all of the basic concepts, including curvature measurement, can be readily adapted for the higher dimensional problem.

Algorithms↗
PubMed1990

Suppression of inter-ictal spikes by CM40907. A double-blind placebo-controlled investigation and review of spike counting as a methodology for assessing the antiepileptic effect of drugs.

To assess the efficacy of CM40907--a new antiepileptic drug--in suppressing inter-ictal spikes, 6 patients with severe intractable epilepsy and frequent spikes in their inter-ictal EEGs were entered in a double-blind placebo-controlled trial. The results show that CM40907 is efficacious in reducing spike counts in the first hour after oral administration. The results of the study are presented and inter-ictal spike counting as a method is discussed.

Adolescent↗
PubMed1989

Zonisamide usage.

Explore the source record for details and available documents.

Epilepsies, Myoclonic↗
PubMed1988

Effect of the removal of individual antiepileptic drugs on antipyrine kinetics, in patients taking polytherapy.

1. Antipyrine (AP) clearance, half-life and volume of distribution were determined in 52 patients, taking one or more antiepileptic drug (AED), before and 4 weeks after the complete removal of phenytoin (PHT, n = 20), carbamazepine (CBZ, n = 15) and sodium valproate (VPA, n = 17). 2. PHT removal was associated with a mean 13% fall in AP clearance and a mean 16% increase in AP half-life, in patients who were also taking CBZ with or without barbiturates. There was no significant difference between patients who did, and did not, take barbiturates, in addition to CBZ. 3. CBZ removal was associated with a mean 45% fall in AP clearance and a mean 69% increase in AP half-life, if there was no inducing AED comedication, but had no effect on AP clearance and half-life if PHT and/or barbiturates were also being taken. 4. Removal of VPA had no effect on AP clearance or half-life. 5. The removal of PHT, CBZ and VPA had no significant effect on AP volume of distribution. 6. PHT appears to be a more powerful inducer of hepatic enzyme activity, as measured by the AP test, than is CBZ.

Adolescent↗
PubMed1988

Withdrawal symptoms from phenytoin, carbamazepine and sodium valproate.

A prospective, double-blind, placebo-controlled investigation of possible withdrawal symptoms from phenytoin, carbamazepine and sodium valproate is reported in patients with active epilepsy, on combination therapy. There was an increase in seizures on reduction and withdrawal of carbamazepine, but there was no convincing evidence of withdrawal symptoms from any of these drugs.

Adolescent↗
PubMed1988

Frequent loss and restoration of antibiotic production by Streptomyces lasaliensis.

Antibiotic nonproducing variants of Streptomyces lasaliensis NRRL 3382R, which makes the polyether antibiotic lasalocid A (Las) and the quinoxaline antibiotic echinomycin (Ech), arose at a frequency of 3-11% after treatment with three different mutagens or regeneration of protoplasts compared with a spontaneous frequency of less than 0.1%. Cosynthesis of lasalocid A was not observed upon testing a large number of Las- mutants in different pair-wise combinations, nor did these mutants accumulate probable intermediates of lasalocid A biosynthesis. These results suggest that loss of the las genes or their expression is induced at a high frequency by mutagenic treatments. In fusions of protoplasts of a strain with the las+ ech+ spo+ nic-1 rif-3 markers with strains bearing the Las- LasS Ech- Bld- (or spo+) str-1 markers, Las+ Ech+ Spo+ StrR progeny were produced at a 61-89% frequency compared with a 1-9% frequency of StrR antibiotic producing progeny with the nic-1 or rif-3 genotypes. The more frequent restoration of antibiotic production than prototrophy or rifampicin sensitivity indicates that these antibiotic characters did not behave as normal chromosomal markers. Therefore the genetic instability might be due to the involvement of a plasmid in antibiotic production. The apparent lack of infectious transfer of the Las+ character to Las- parents in conjugal matings between the few strains tested and no correlation between the presence of a large plasmid, pKSL, and lasalocid A production in several strains of S. lasaliensis do not favor the latter hypothesis, but they do not conclusively disprove it. Consequently, we suggest that a plasmid or another mobile genetic element is controlling antibiotic production in S. lasaliensis.

4-Butyrolactone↗
PubMed1987

Seizure characteristics, pathology, and outcome after temporal lobectomy.

We analyzed the histories of 58 patients who had temporal lobectomy for seizure control. A good outcome was more likely if a definite lesion was removed. Unlike other pathologies, including nonspecific hippocampal sclerosis (NSHS), Ammon's horn sclerosis (AHS) was strongly related to a history of a prolonged childhood convulsion as the first epileptic event. Partial seizures developed at a younger age in patients with AHS than with NSHS or nonspecific changes. Epigastric rising sensations were associated with a greater chance of a good outcome than were other forms of simple partial seizure.

Adolescent↗
PubMed1986

Regional myocardial dysfunction during coronary angioplasty: evaluation by two-dimensional echocardiography and 12 lead electrocardiography.

Balloon inflation performed during percutaneous transluminal coronary angioplasty causes transient total occlusion of the coronary artery and thus provides a model for evaluation of the regional myocardial responses to transient ischemia. Twenty patients with normal left ventricular function undergoing angioplasty of isolated stenosis of the proximal left anterior descending coronary artery were studied. In group A (14 patients) analysis of one inflation-deflation sequence per patient was performed. Group B (six patients) had multiple (greater than 5) inflations; the first and last sequences were analyzed. Assessment included continuous two-dimensional echocardiography with computerized quantitative analysis of regional left ventricular wall motion, and continuous 12 lead electrocardiographic recordings. The mean duration of inflation in group A was 62 +/- 6 seconds (mean +/- SD). The onset of regional left ventricular dysfunction was 12 +/- 5 seconds after inflation. Profound dysfunction was noted in all patients. After 60 seconds of balloon occlusion of the coronary artery, 29% of patients had severe hypokinesia of the ischemic region and 71% had akinesia or dyskinesia. With deflation there was prompt recovery of regional function, with full recovery at 43 +/- 17 seconds. Comparison of data from first and last inflations in group B revealed no significant differences in time to onset of dysfunction, magnitude of dysfunction or time to complete recovery of function. The onset of ischemic electrocardiographic changes lagged behind the onset of wall motion abnormalities, with only 64% of patients showing evidence of ischemia on 12 lead electrocardiograms at 20 seconds of inflation. After 60 seconds, 86% had ischemia detectable by electrocardiography. Thus, balloon inflation during coronary angioplasty leads to profound but reversible regional left ventricular dysfunction. Repeated occlusions of the coronary artery during angioplasty do not have a cumulative ischemic effect. It may be hazardous to apply these findings to patients who have underlying major left ventricular dysfunction and in whom the reversibility of dysfunction and lack of cumulative ischemic effect may not be assured.

Adult↗