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Biomedical subjects

S J Cox

Publications and source records attributed to S J Cox.

At least 19 recordsLinked to original sources
PubMed2001

Adaptive mesh refinement techniques for electrical impedance tomography.

Adaptive mesh refinement techniques can be applied to increase the efficiency of electrical impedance tomography reconstruction algorithms by reducing computational and storage cost as well as providing problem-dependent solution structures. A self-adaptive refinement algorithm based on an a posteriori error estimate has been developed and its results are shown in comparison with uniform mesh refinement for a simple head model.

Algorithms↗
PubMed2000

The ecological cost of sex.

Why sex prevails in nature remains one of the great puzzles of evolution. Sexual reproduction has an immediate cost relative to asexual reproduction, as males only express their contribution to population growth through females. With no males to sustain, an asexual mutant can double its relative representation in the population in successive generations. This is the widely accepted 'twofold cost of males'. Many studies have attempted to explain how sex can recoup this cost from fitness benefits associated with the recombination of parental genotypes, but these require complex biological environments that cycle over evolutionary timescales. In contrast, we have considered the ecological dynamics that govern asexual invasion. Here we show the existence of a threshold growth rate for the sexual population, above which the invasion is halted by intraspecific competition. The asexual population then exerts a weaker inhibitory effect on the carrying capacity of the sexual population than on its own carrying capacity. The stable outcome of this is coexistence on a depleted resource base. Under these ecological circumstances, longer-term benefits of sex may eventually drive out the asexual competitor.

Animals↗
PubMed2000

Identification of the cable parameters in the somatic shunt model.

We show that the first five moments of the soma potential and soma current uniquely and stably determine the soma conductance and capacitance and the dendritic electrotonic length, conductance, and capacitance in the so-called somatic shunt model of the passive behavior of a neuron. We test our resulting input admittance algorithm on synthetic data and demonstrate the regularizing effect of knowledge of the ratio of soma to dendrite surface areas.

Computer Simulation↗
PubMed2000

High fidelity imaging and high performance computing in nonlinear EIT.

We show that nonlinear EIT provides images with well defined characteristics when smoothness of the image is used as a constraint in the reconstruction process. We use the gradient of the logarithm of resistivity as an effective measure of image smoothness, which has the advantage that resistivity and conductivity are treated with equal weight. We suggest that a measure of the fidelity of the image to the object requires the explicit definition and application of such a constraint. The algorithm is applied to the simulation of intra-ventricular haemorrhaging (IVH) in a simple head model. The results indicate that a 5% increase in the blood content of the ventricles would be easily detectable with the noise performance of contemporary instrumentation. The possible implementation of the algorithm in real time via high performance computing is discussed.

Algorithms↗
PubMed1999

Emergency vaccination of sheep against foot-and-mouth disease: protection against disease and reduction in contact transmission.

The ability of several emergency FMD vaccine formulations to elicit early protective immunity in sheep was examined. All vaccine formulations were shown to protect sheep against airborne challenge with homologous FMDV within 4 days of vaccination. Protection was associated in part with the induction of serum antibody responses but was also demonstrated in the absence of any detectable antibody response at the time of challenge. Aqueous Al(OH)3/saponin vaccine formulations and oil emulsion vaccines based on Montanide ISA 206 adjuvant reduced virus replication and the numbers of animals subclinically infected up to 28 days post-challenge, when compared with non-vaccinated animals, consequently limiting transmission of the disease or infection to in-contact susceptible animals.

Adjuvants, Immunologic↗
PubMed1999

The role of small ruminants in the epidemiology and transmission of foot-and-mouth disease.

Despite representing the largest part of the world's foot-and-mouth disease (FMD)-susceptible domestic livestock, sheep and goats have generally been neglected with regard to their epidemiological role. This is partly due to the often inapparent nature of the disease in these hosts. Nevertheless, their ability to become carriers represents a reservoir for further infection and spread of disease, and so trade of live sheep and goats present a major risk of entry of FMD to disease-free countries. Research and epidemiological studies continue to be necessary in order both to prevent the entry of the virus and to assist in control should the disease reoccur. This review concentrates primarily on more recent studies relating to sheep and goats and, in particular, considers the importance of these hosts in the overall epidemiology of FMD.

Animals↗
PubMed1999

Evidence of partial protection against foot-and-mouth disease in cattle immunized with a recombinant adenovirus vector expressing the precursor polypeptide (P1) of foot-and-mouth disease virus capsid proteins.

A recombinant live vector vaccine was produced by insertion of cDNA encoding the structural proteins (P1) of foot-and-mouth disease virus (FMDV) into a replication-competent human adenovirus type 5 vaccine strain (Ad5 wt). Groups of cattle (n = 3) were immunized twice, by the subcutaneous and/or intranasal routes, with either the Ad5 wt vaccine or with the recombinant FMDV Ad5-P1 vaccine. All animals were challenged by intranasal instillation of FMDV 4 weeks after the second immunizations. In the absence of a detectable antibody response to FMDV, significant protection against viral challenge was seen in all of the animals immunized twice by the subcutaneous route with the recombinant vaccine. The observed partial protection against clinical disease was not associated with a reduction in titre of persistent FMDV infections in the oropharynx of challenged cattle.

Adenoviruses, Human↗
PubMed1999

Ethnicity, bioethics, and prenatal diagnosis: the amniocentesis decisions of Mexican-origin women and their partners.

Bioethical standards and counseling techniques that regulate prenatal diagnosis in the United States were developed at a time when the principal constituency for fetal testing was a self-selected group of White, well-informed, middle-class women. The routine use of alpha-fetoprotein (AFP) testing, which has become widespread since the mid-1980s, introduced new constituencies to prenatal diagnosis. These new constituencies include ethnic minority women, who, with the exception of women from certain Asian groups, refuse amniocentesis at significantly higher rates than others. This study examines the considerations taken into account by a group of Mexican-origin women who had screened positive for AFP and were deciding whether to undergo amniocentesis. We reviewed 379 charts and interviewed 147 women and 120 partners to test a number of factors that might explain why some women accept amniocentesis and some refuse. A woman's attitudes toward doctors, medicine, and prenatal care and her assessment of the risk and uncertainty associated with the procedure were found to be most significant. Case summaries demonstrate the indeterminacy of the decision-making process. We concluded that established bioethical principles and counseling techniques need to be more sensitive to the way ethnic minority clients make their amniocentesis choices.

Adolescent↗
PubMed1998

A new method for extracting cable parameters from input impedance data.

We establish conditions under which the input impedance and its first two derivatives, evaluated at the origin, uniquely determine the axial resistance, membrane capacitance, and membrane conductance of a finite uniform cable with one sealed end. We argue that these impedance data are readily available to the experimentalist and we demonstrate the recovery of a cable's electrical parameters from synthetic noisy measurements.

Algorithms↗
PubMed1998

Stereotactic pallidotomy for the treatment of Parkinson's disease. Efficacy and adverse effects at 6 months in 26 patients.

We evaluated the safety and efficacy of microelectrode-guided stereotactic pallidotomy in patients with advanced Parkinson's disease (PD). Using diagnostic criteria and evaluations outlined in the Core Assessment Programme in Transplantation (CAPIT) protocol, we studied unilateral pallidotomy in 26 patients with advanced idiophatic PD, motor fluctuations, and peak dose dyskinesias. All underwent unilateral stereotactic pallidotomy. Assessments conducted in the "practically defined off" and "best on" states at baseline and at 1 and 6 months postoperatively included Unified Parkinson's Disease Rating Scale (UPDRS) parts II, III, and IV and timed motor testing as outlined in CAPIT. Motor UPDRS in the "off" state improved at 1 and 6 months after surgery (p = 0.002, p = 0.008) Likewise, the sum of individual "off" contralateral motor UPDRS items improved (p = 0.0002, p = 0.0005). The duration (p = 0.0001 at 1 and p = 0.001 at 6 months) and severity (p = 0.003 at 1 and p = 0.0005 at 6 months) of dyskinesia improved, but other aspects of the "on" function were unchanged. Serious adverse effects occurred in eight patients and included one fatal deep and three nonfatal frontal lobe hemorrhages with resultant language or behavioral deficits. Nonhemorrhagic complications included one hemiparesis and three frontal lobe syndromes. Pallidotomy improves PD motor disability in the "off" state. Peak dose dyskinesias are reduced, although other aspects of "on" motor function are unchanged. Although morbidity may limit its use, pallidotomy is effective in targeting particular symptoms such as unremitting dyskinesia and severe "off" motor disability in advanced PD.

Activities of Daily Living↗
PubMed1992

The solid phase attachment of fungal hyphae in an ELISA to screen for antifungal antibodies.

A method to immobilize fungal hyphae onto the wells of 96-well microplates for use in an in-direct ELISA to screen for antifungal antibodies in sera and cell culture supernatants is described. The hyphae from three genera (Penicillium, Eurotium and Fusarium) were successfully attached by overnight drying onto wells precoated with poly-L-lysine and glutaraldehyde. Microscopy revealed that the hyphae remained attached to the wells throughout the ELISA and antiserum titrations showed that the attached hyphae were uniformly coated and remained reactive. Background absorbances were low and the plates could be stored at -20 degrees C without loss of reactivity.

Antibodies, Fungal↗
PubMed1991

Spontaneous external biliary fistula uncomplicated by gallstones.

External biliary fistulae are rare. Only 65 cases have been reported in the literature and in each instance gallstones were a complicating factor. We report in this paper the first case of spontaneous external (cholecystocutaneous) biliary fistula uncomplicated by gallstones.

Aged↗
PubMed1991

Verapamil in major (psychotic) depression.

Dramatic response of major (psychotic) depression to verapamil in an 82-year-old woman suggests that further study of the use of the drug in affective disorders is required, particularly in the light of a possible aetiological role for calcium.

Aged↗
PubMed1980

Ultra-low dose intravenous heparin in the prevention of postoperative deep-vein thrombosis.

Heparin (1 IU kg-1 h-1) given intravenously for 3-5 days during and after operation in a double-blind randomised study, significantly reduced the frequency of deep-vein thrombosis detected by 125I-fibrinogen uptake, and pulmonary embolism. 22% (11/50) control patients and 4% (2/45) patients receiving heparin had deep-vein thrombosis or pulmonary embolism. Heparin administration was not associated with any increase in preoperative or postoperative bleeding.

Aged↗
PubMed1974

Saphenous nerve injury caused by stripping of the long saphenous vein.

Sensory impairment in the cutaneous distribution of the saphenous nerve was measured in 30 patients after bilateral stripping of the long saphenous vein. The vein was stripped upwards in one leg and downwards in the other. Three months after operation a significantly greater incidence of sensory loss was found in those legs in which the vein was stripped upwards (13 out of 26) compared with those which had been stripped downwards (6 out of 26).We recommend that the long saphenous vein should be stripped downwards.

Adult↗