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Biomedical subjects

K Myhre

Publications and source records attributed to K Myhre.

53 records · Page 3Linked to original sources
PubMed1978

Effects of physical training in intermittent claudication.

Mechanisms for increased claudication distance following physical training were studied in ten patients with peripheral arterial insufficiency. The exercise capacity on a bicycle ergometer increased by an average of 26% after 3--4 months of training (P less than 0.05). Neither maximum lower leg blood flow during the exercise test nor oxygen uptake at exhaustion changed significantly after training (-8% and +5%, respectively), whereas popliteal-venous O2-saturation was lower at exhaustion after the training than before (8.5 +/- 3.2 and 11.4 +/- 4.6, respectively, P less than 0.05). Anaerobic glycolysis, as evidenced by the lactate release, was also lowered after the training (P less than 0.05). In conclusion, the present study shows that the increased exercise capacity following physical training in claudicants is associated with an increased local aerobic working capacity despite a virtually unchanged blood flow. This increased aerobic exercise capacity might partly be explained by an increased O2 extraction in the lower leg during exercise.

Aged↗
PubMed1977

Fever and behavioural temperature regulation in the frog Rana esculenta.

The skin and colonic temperatures were recorded in frogs (Rana esculenta) which had selected a suitable microenvironment in a box filled with 2-3 cm water. The water temperatures ranged from 0 degrees C to + 40 degrees C. Such measurements were performed before and after intraperitoneal injections of killed pathogenic bacteria (M. xenopi and M. range), killed non-pathogenic bacteria (M. aquae II) and 0.9% sterile saline, intraperitoneal injections of blood plasma from frogs pre-injected with killed M. ranae, injections of PGE1 into the brain. The injections of pathogenic bacterial endotoxin caused, after latencies of 5-120 min, higher preferred water temperatures, which produced an average maximum colonic temperature increase of 6.5 degrees C +/- 1.0 degrees C (S.E.) (p less than 0.001). The non-pathogenic bacteria and sterile saline caused no temperature change. Monophasic hyperthermia of shorter latency was caused by injections of blood plasma from frog preinjected with M. ranae. Monophasic hyperthermia of the shortest latency was observed after diencephalic injections of PGE1. Based on their similarity we suggest that ectothermic and endothermic fever have a common phylogenetic origin.

Animals↗
PubMed1977

The effect of plasma proteins on the capillary permeability in the rete mirabile of the eel (Anguilla vulgaris L.).

Measurements of transcapillary exchange of high-molecular dextrans, K+ and THO in the rete mirabile of the eel (Anguilla vulgaris L.) have been made under steady-state conditions while varying the amounts of plasma proteins in the perfusates. When the perfusates contained 20% or less horse serum the permeabilities of D-75 000, K% and THO increased significantly. The effect on the K+ permeability was irreversible while that on D-75 000 and THO was not. The permeability was unaffected when the perfusate contained 30% serum or more. Adding 1.3 g/100 ml bovine albumin to the perfusate maintained the D-75 000 and THO permeabilities unchanged while that of K+ appeared to increase. At an albumin content of 0.33 g/100 ml the effect was similar to that produced by low serum perfusates. Our main conclusion is that lack of the albumin fraction of the plasma proteins reversibly increases the intercellular pore area and irreversibly changes the K+ permeability of the cell membrane.

Air Sacs↗
PubMed1976

The effect of serotonin and transcapillary pressure on the capillary permeability in the rete mirabile of the eel (Anguilla vulgaris l.).

Measurements of transcapillary exchange of high-molecular dextrans, K+ and THO in the rete mirabile of eel (Anguilla vulgaris L.) have been made under steady-state conditions while the transcapillary pressure was varied and pharmaca added to the perfusates. Raising the transcapillary input pressure increased the exchange of dextrans and K+ but lowered that of THO. Histamine and ouabain had no effect on the transcapillary exchange of the test molecules. The highest dose (100 mug/ml) of serotonin reversibly increased the capillary permeability of D-75 000, K+ and THO while the medium dose (50 mug/ml) only raised the transcapillary exchange of K+ and THO. The lowest dose (10 mug/ml) had no permeability effect. Our main conclusion is that serotonin reversibly increases the area of the intercellular pores by affecting the capillary wall directly.

Air Sacs↗
PubMed1975

Thermoregulatory behavior and body temperature in chicks of willow grouse (Lagopus lagopus lagopus).

Clocal temperatures (Tcl) of outdoor living captive willow grouse chicks (Lagopus lagopus lagopus) were found to increase from 39.4 +/- 0.5 degrees C. the first day to 40.3 +/- 0.5 degrees C. the twelfth day after hatching. Average Tcl of adults was 40.7 +/- 0.3 degrees C. When left alone for 30 min. in a controlled test environment providing temperatures ranging from 21 degrees C. to 46 degrees C., the one day old chicks preferred significantly higher ambient temperatures than eight day old birds. Tcl was significantly lower in the chicks tested the day after hatching than in the older chicks. It is concluded that the chicks' thermoregulatory behavior is essential for maintaining homeothermia, and that the birds' thermoregulatory set-point is low the day after hatching and climbs to adult level during the first week.

Animals↗
PubMed1968

The maximum oxygen intake. An international reference standard of cardiorespiratory fitness.

Lack of cardiorespiratory fitness may well contribute to the increasing prevalence of degenerative cardiovascular disease throughout the world. As a first step towards co-ordinated and internationally comparable investigation of this problem, methods of measuring the reference standard of cardiorespiratory fitness-the maximum oxygen intake, (Vo(2))(max)-were compared by an international working party that met in Toronto in the summer of 1967.Repeated testing of 24 subjects showed that the (Vo(2))(max) was greatest on the treadmill, 3.4% smaller in a stepping test, and 6.6% smaller during use of a bicycle ergometer. There were also parallel differences in cardiac stroke volume. Uphill treadmill running was recommended for the laboratory measurement of (Vo(2))(max), and stepping or bicycle exercise for field studies. A discontinuous series of maximum tests caused some improvement in the fitness of subjects, and a "continuous" test (with small increases in load at 2-min intervals) was preferred.

Adult↗
PubMed1968

Standardization of submaximal exercise tests.

It is often impossible to measure the reference standard of cardiorespiratory fitness (the maximum oxygen intake) directly, and there is thus a need for subsidiary standard procedures based on body responses to submaximal exercise. In order to reach agreement on such procedures, a recent international working party has compared a variety of possible tests involving step, bicycle, and treadmill exercise; criteria of comparison included the extent of habituation and learning with each procedure, the physiological responses, and practical considerations. There was little to commend submaximal exercise on the treadmill. Anxiety and learning were least on the bicycle ergometer, but significant anaerobic metabolism developed at loads of more than 55% of aerobic power; the main role of the bicycle was thus in laboratory tests requiring arm immobilization. The step test was cheap and portable, subjects showed relatively little anxiety or learning, and good-quality electrocardiograms were obtained: it thus seemed the procedure of choice for field tests. The results of all forms of submaximal test should be extrapolated to maximum oxygen intake in order to overcome difficulties arising from differences in the age and fitness of subjects. Four common extrapolation procedures, based respectively on one to four measurements of oxygen consumption and pulse rate, yielded similar predictions of maximum oxygen intake. A single progressive test, in which the exercise load was increased at the end of every third minute, gave an identical prediction of maximum oxygen intake to that obtained from a series of 4 discontinuous tests. The progressive test was thus the preferred procedure; however, in subjects with some circulatory delay, it might be necessary to replace the four 3-min loads by three 4-min loads.

Adult↗