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Biomedical subjects

A Crowe

Publications and source records attributed to A Crowe.

71 records · Page 4Linked to original sources
PubMed1976

Effect of temperature of resistance to stretch of tortoise muscle.

The effects of temperature over the range 5-30 degrees on isometric contraction and resistance to mechanical stretches of the ramp and hold type applied to active muscle have been studied in isolated tortoise gastrocnemius muscles. The isometric tension decreases as the temperature is lowered but, when expressed as a proportion of the isometric tension, the change in tension at the end of the ramp phase of the stretch is increased at the lower temperatures. The proportionate tension change at the end of the hold phase of the stretch could not be directly related to the temperature. An attempt is made to interpret the results in terms of current opinions on the mechanism of the generation of muscular tension.

Animals↗
PubMedDate not supplied

The effect of controlled changes in volume on the active state of the rabbit isolated left ventricle.

The contractile properties of isovolumically contracting isolated rabbit left ventricles are studied under the influence of controlled rapid volume changes during systole and diastole. The time integral of the pressure curve (TTI), representing the active state, is used to quantify the energy consumption of the ventricle. Steady state conditions resulting from an introduced volume change show a TTI/EDV relation which represents the Starling curve. However, immediately after a quick volume increase (decrease) introduced in diastole, the TTI/EDV ratio has a higher (lower) value than indicated by the Starling relation. This shows a volume dependent activation (deactivation), related to changes in the inotropic state of the heart muscle cells within the ventricular wall. A volume increase at a later moment (in systole) always produces a lower rate of activation. Indeed, if the rapid volume change is introduced at moments later than 70% of time to peak pressure, TTI is less than observed from the Starling mechanism, indicating a deactivation. When comparing the decreasing effect on the active state introduced by volume decrease during systole, it is shown that this effect is not only a function of the amplitude of the decrease itself but is highly dependent upon the way EDV is reached.

Animals↗
PubMedDate not supplied

Recordings of the movement at the intervertebral segment L5-S1: a technique for the determination of the movement in the L5-S1 spinal segment by using three specified postural positions.

The pathomechanism of low-back pain generation is not understood very well. Functional disturbances of motion at the individual segmental level appear to play a role in many cases. In this study a technique of numeric analysis of radiographic observations of the lumbar spine is developed by which the authors are able to assess the displacement of the two components of the L5-S1 motion segment in the sagittal plane when the subject assumes three specified standard postural positions.

Adolescent↗
PubMedDate not supplied

Toward standards for posture. Postural characteristics of the lower back system in normal and pathologic conditions.

On theoretic grounds it can be assumed that aberrations of posture may play a role in the generation of low-back pain by creating concentrations of stress. However, this assumption remains speculative because of the absence of criteria for normal posture. This study considers some of these criteria, especially as they are related to the lumbar spine and pelvis. The relations between the angle of declivity of the sacrum and radius and inclination of the lordotic curvature of the lumbar spine show good correlation. Mean values of postural parameters in the group of spondylolysis patients differ significantly from those in the group of healthy volunteers.

Adolescent↗