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Biomedical subjects

I Marshall

Publications and source records attributed to I Marshall.

139 records · Page 8Linked to original sources
PubMedDate not supplied

Human alpha- and beta-CGRP and rat alpha-CGRP are coronary vasodilators in the rat.

The effects of the recently described human alpha-calcitonin gene-related peptide (CGRP), human beta-CGRP and rat alpha-CGRP have been compared with those of the vasodilator sodium nitroprusside, on the rat and rabbit isolated heart. Hearts were perfused at constant flow and [Arg8]-vasopressin was used to increase coronary perfusion pressure. In the rat heart, the order of potency for evoking cumulative dose-dependent falls in perfusion pressure was human beta-CGRP greater than rat alpha-CGRP greater than human alpha-CGRP greater than sodium nitroprusside. In the same preparations the three CGRPs (but not sodium nitroprusside) elicited cumulative dose-related increases in heart rate. In the rabbit heart the order of potency for vasodilatation was rat alpha-CGRP greater than human alpha-CGRP greater than sodium nitroprusside. In marked contrast to results from the rat, neither rat alpha-CGRP nor human alpha-CGRP altered heart rate in the rabbit isolated heart. These results show that human alpha- and beta-CGRP and rat alpha-CGRP are vasodilators in the coronary vasculature, but that there is species variation as CGRP had a positive chronotropic effect in the rat heart but not in the rabbit heart.

Amino Acid Sequence↗
PubMedDate not supplied

The treatment of men with a learning disability convicted of exhibitionism.

This paper reviews work on the treatment of men convicted of exhibitionism or indecent exposure. Recidivism is extremely high after treatments, with true figures on recidivism unavailable until 4 years after conviction. It is extremely difficult to control for treatment effects because of the ethical issues surrounding withholding of treatment, but cognitive techniques provide a promising treatment approach. The present study attempted to address all these issues for men with a learning disability. A cognitive treatment is presented and data are available for at least 5 years after conviction. An AB design was used and treatment effects were monitored carefully. Treatment dealt with the issues of accepting that the offense took place, taking responsibility for the offense, accepting the intention of the offending behavior, victim awareness, and behavior consistent with offending for four offenders. All the men responded to treatment, although one offender with only 1 year of probation responded less convincingly than others. Beliefs relating to indecent exposure being fun or not causing harm to women seemed most open to alteration. The beliefs in which the perpetrator thought that the victim shared responsibility for the offense and that women may take a long while to recover from such an incident, seemed the most difficult to alter. Individual characteristics of the case examples are discussed in terms of these general trends.

Adult↗
PubMedDate not supplied

Reduction of electromagnetic interference from a commercially available MR-compatible flow simulator.

Electromagnetic interference (EMI) associated with the electronics of a commercially available computer controlled flow simulator substantially decreases the quality of the MR image. The effect of a custom-built radiofrequency shield on its spectral emission, and the corresponding signal-to-noise ratio measured for the image of a standard phantom, were determined. The results demonstrate the elimination of EMI and a significant improvement in image quality.

Electromagnetic Phenomena↗
PubMedDate not supplied

Flow in elliptical vessels calculated for a physiological waveform.

Understanding the nature of pulsatile flow is an important issue in haemodynamics, especially the initiation and progression of vascular disease. The geometry of a non-circular vessel was idealised to an elliptical cross-section, and the dynamic properties of the flow were calculated for a physiological waveform. The Fourier harmonics for a common carotid waveform were determined, and the velocity profile and wall shear stress were calculated from the superposition of the individual contributions from each harmonic. The effects of ellipticity on the flow pattern were found to be significant. The velocity profile along the major axis of the elliptical cross-section developed a flattened peak, which widened as the vessel became more elliptical. Wall shear stress demonstrated an angular dependence in elliptical vessels, where the point of minimum shear stress was located at the end of the major axis. Comparison with a cylindrical vessel demonstrated a 3% decrease in peak wall shear stress (tau = 2.96, N.m(-2)) at the end of the major axis, and 10% in the mean wall shear stress (tau = 0.44 N. m(-2)), for an elliptical vessel (epsilon = 0.8). The temporal average wall shear stress, which has been associated with atherogenic sites, also displayed a minimum at the end of the major axis that decreased with more elliptical cross-sections.

Blood Flow Velocity↗
PubMedDate not supplied

Mains interference in ECG recording.

Despite the increasing sophistication of ECG monitoring and recording equipment, the problem of mains interference and the techniques used to overcome it remain of fundamental importance. This paper presents simplified models of the instrumentation systems most commonly encountered in a hospital environment, concentrating on the ubiquitous isolated amplifier. Empirical values are given for the various parameters, and simple equations are developed to estimate the interference levels in practical situations.

Electrocardiography↗
PubMedDate not supplied

A diathermy suppression filter for external pacemakers.

Some patients undergoing cardiothoracic surgery require cardiac pacing. Surgical diathermy interferes with the operation of external pacemakers, and can cause a loss of cardiac output. The addition of a simple two-stage LC filter to the front end of the pacemaker enables cardiac output to be maintained during the use of surgical diathermy. (Although this article refers specifically to the Devices E4160 series pacemakers, the filter can, in principle, be used with any external pacemaker.

Diathermy↗
PubMedDate not supplied

Performance of angiographic catheters.

Simple methods of quantifying selected physical characteristics of angiographic catheters, which are likely to influence their in vivo performance, have been developed. The torsional stiffness ('torque') of catheters was measured, and tip control ('manoeuvrability') in an angiographic phantom was studied. Both braided and unbraided catheters were investigated all having the 'headhunter' tip shape. Significant differences between measurements made at 20 and 37 degrees C were found. Torsional stiffness was not a good predictor of performance in the angiographic phantom. Ethylene oxide re-sterilization has only a limited effect on the physical characteristics studied.

Angiography↗
PubMedDate not supplied

[Pharmacology of various aminosteroidal muscle relaxants].

A large number of analogues of pancuronium and vecuronium have been tested for neuromuscular blocking and other actions in anaesthetized cats, dogs, pigs and monkeys in an attempt to find a nondepolarizing substitute for succinylcholine. The results demonstrated an inverse relationship between dose and brevity of action; that is to say that grief duration was found only among compounds of relatively low potency. Two compounds given the code numbers Org 7617 and Org 9616 were found to possess promising properties. Both compounds are 17-butyrate analogues of vecuronium. Org 9616 also has an allyl group, in place of the methyl group, attached to the quaternary nitrogen at position 16. Both compounds have time courses similar to that of succinylcholine. They do not release histamine or produce ganglion block, and they are both considerably less potent than pancuronium in blocking the cardiac vagus. Both may produce a small fall in blood pressure. Electrophysiological analysis shows that neither compound is expected to occlude the receptor-operated ion channels of the motor endplate in concentrations likely to be achieved clinically.

Animals↗