Biomedical subjects

E Hexeberg

Publications and source records attributed to E Hexeberg.

43 records · Page 3Linked to original sources

PubMed1990

[Research training--the work situation of research trainees at the School of Medicine, University of Bergen].

In an investigation in spring 1989 on research training at the Medical Faculty, University of Bergen, 111 questionnaires were returned of a total of 180 distributed. 35% of the trainees were satisfied with the training, 31% not, while 30% did not know as yet. Trainees who had been full-time research fellows for two years or more (n = 33), were split in two groups with different opinions. Half of them were satisfied with the training programme, and the other half were not. The most important factor linked with the trainees' opinion of the training was personal supervision. The satisfied ones were content with supervision they had received, whereas the unsatisfied ones were not. By and large, office and laboratory conditions were adequate for the trainees, but data equipment had been supplied by many of the trainees themselves. The overall impression of this investigation is that the research training programme is working fairly well, but there is remove for improvement in the supervision of the individual trainee.

Curriculum↗

PubMed1990

[Research training--what trainees think about future research education].

A research training programme should have a clearly defined aim and a framework for accomplishment and contents. In Norway no such programme exists for the medical PhD. Present research training depends to a large extent on the individual student. The aim of this paper is to contribute to a discussion on the goals for a research programme and to report what research trainees and research fellows at the Medical Faculty, University of Bergen think is necessary as regards framework and content. 111 of 180 questionnaires were returned. On the average, the students preferred a research programme to last 4.0 years. 91 persons wanted the programme to contain a compulsory part lasting, on average, 5.5 months. The majority preferred no examination during this part of the programme. Most students wanted to maintain the present Norwegian standard for the medical PhD.

Curriculum↗

PubMed1990

Gradual reduction of coronary perfusion pressure in cats: changes in transmural distribution of blood flow.

We evaluated a model for regional myocardial hypoperfusion in cats with an extracorporeal shunt line to the left main coronary artery, and investigated the effects of reduced coronary perfusion pressure on the transmural distribution of left ventricular blood flow measured with radioactive microspheres. Shunt establishment did not alter cardiac function, myocardial tissue blood flow, or its transmural distribution. An artificial shunt stenosis, which clearly reduced coronary perfusion pressure without changing cardiac function, caused reduced endocardial blood flow, slight flow reduction in mid-myocardium, and no flow change in the epicardium. When a severe stenosis was applied, causing increased end-diastolic pressure and reduced shunt flow, endocardial and mid-myocardial flow further decreased whereas epicardial blood flow remained essentially unchanged. These results demonstrate a transmural profile of the coronary autoregulation capacity.

Animals↗

PubMed1989

Nonuniform shortening of the anterior wall of feline left ventricles.

Recorded performance of segments between implanted ultrasonic crystals placed at midwall position of the left ventricle reportedly depends almost exclusively on midwall function and alignment with fibers. Accordingly, one would expect the ratio between performance of a segment perpendicular to midwall fiber direction (transverse) and a parallel segment (longitudinal) to be constant and independent of changes in preload, afterload, and the inotropic state. We tested this hypothesis by implanting cross-oriented crystal pairs in nine open-chest cats and studied their performance during preload and afterload changes with and without isoproterenol infusion. Fiber orientation across the ventricular wall was determined by serial histological sectioning. The ratio between performance of transverse and longitudinal segments (trans/long) changed with interventions. Increased end-diastolic pressure leads to increased segment performances as well as trans/long. Inotropic stimulation produced increased sensitivity to preload changes both for individual segment performances and for trans/long. These results suggest that longitudinal segments represent the function of midwall fibers, whereas transverse segments may well represent the function of sub-endocardial fibers, which run closer to this orientation. Thus trans/long provides a way to quantify nonuniformity of local myocardial contraction.

Animals↗

PubMed1987

Local myocardial function following coronary occlusion in cats. Effect on non-ischaemic regions.

The mechanical function and perfusion in ischaemic and non-ischaemic myocardium after coronary occlusion was studied in 10 cats using pressure-length loop analysis and radiolabelled microspheres. Measurements in three regions--ischaemic, adjacent normal and remote normal myocardium--all showed different responses to coronary occlusion. In the ischaemic region loop area, segment shortening and tissue flow were markedly reduced. In the adjacent normal region, both loop area and segment shortening as well as flow increased. In the remote normal region, neither loop area, segment shortening nor flow showed consistent changes. End-diastolic segment length increased in all regions, most in the ischaemic region and least in the remote region. The increased end-diastolic segment length in all regions after coronary occlusion indicates activation of the Frank-Starling mechanism as an attempt to maintain stroke volume. However, the end-diastolic segment length did not increase uniformly for all normal myocardium: it depended on the proximity to the ischaemic region. Increased contractile function in the adjacent normal myocardium due to non-uniform distribution of the Frank-Starling effect is the most likely mechanism behind the left ventricle's ability to partially compensate for loss of contractile mass during acute regional ischaemia in anaesthetized cats.

Animals↗

PubMed1986

Fibre orientation in the left ventricle and its influence on local pressure-length loop analysis in cats.

Deviation from local fibre orientation may seriously affect quantification of myocardial segment work, as measured by implanted ultrasound crystals. Crystal pairs were positioned in mid-wall layers with known directions to the long axis of the heart. One transmitter and four receiving crystals covered a sector on the anterior ventricular wall of 100 degrees. The results show a strong influence of alignment to fibre direction on the pressure-length loop area; the relation followed a cos2 psi function where psi denotes the angle between the crystal pair direction and fibre direction established by microscopy. The angle between the mid-wall muscle fibres on the anterior aspect of the left ventricle and the long axis of the heart varied between 62 degrees and 90 degrees with a mean value of 76 degrees. This study shows that pressure-length loop quantitation depends strongly on crystal alignment to cardiac muscle fibres through which the ultrasound passes.

Animals↗

PubMed1985

Interpretation of myocardial contraction recorded from local segments.

An attempt to quantify the influence of extra-segmental contraction upon external mechanical work of a segment was made in cat hearts. By placing four ultrasound crystals across a borderline between normal and ischaemic myocardium, the pressure-length loop area of segments with different ischaemic contents were recorded. The relation between a normalised segment work index and the amount of ischaemic tissue within the segment showed a negative correlation. Assuming that the contributions to the segment work index from ischaemic and normal tissue coupled in series within the segment add up by cancelling each other, the extra-segmental influence of adjacent fibre contraction could be established. In six cats the extra-segmental influence which affected a typical segment of 10.0 mm corresponded to 1.5 to 3.7 mm of adjacent myocardial musculature on either side of the segment.

Animals↗