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Biomedical subjects

L L Huntsman

Publications and source records attributed to L L Huntsman.

33 records · Page 2Linked to original sources
PubMed1977

Nonuniform contraction in the isolated cat papillary muscle.

Microspheres infused into the coronary microcirculation were used as markers to define segments within isolated cat papillary muscles. Video recording and analysis provided measurements of the variations of segment lengths as the muscles contracted at lengths of 76-100% Lmax. In all muscles, segments in the center region were found to shorten during muscle isometric contraction while those in the end regions lengthened. Central shortening was typically 10-15%. In the passive state, segment lengths varied directly with muscle length over a broad range characterized by low force. Segments in the center region, however, displayed an abrupt transition to high stiffness at a certain length while end regions continued to stretch. Force-length relationships obtained for the presumably healthy center segment are significantly different from those obtained for the whole muscle. These results suggest that there may be major difficulties with the interpretation of mechanical measurements on papillary muscles unless contractile inhomogeneity is eliminated or taken into account.

Animals↗
PubMed1977

Estimation of stroke volume changes by ultrasonic doppler.

The purpose of this study was to conduct a controlled evaluation of the continuous-wave Doppler technique for the estimation of stroke volume changes. Six anesthetized dogs were studied. Aortic blood velocity was recorded from the suprasternal notch by a special continuous-wave Doppler unit. Cardiac output was varied by fluid infusion and exsanguination, and over 300 simultaneous records of aortic blood velocity and thermodilution cardiac output were taken. Average stroke volume and average systolic velocity integral (SVI), the area under the Doppler velocity curve were calculated. The relationship of SVI to stroke volume was evaluated for each animal using linear regression. Average results were: correlation coefficient 0.95 +/- 0.04 SD; y-intercept 0.38 +/- 0.14 cm(SD); standare error of fit 0.29 +/- 0.03 cm (SD). These data show that the systolic integral of aortic blood velocity was essentially directly proportional to stroke volume, even over a six-fold range. Thus, this technique will provide an accurate non-invasive estimate of changes in stroke volume.

Animals↗
PubMed1977

Length-dependent calcium inotropism in cat papillary muscle.

We studied changes in the relationship of isometric developed force to muscle length when extracellular calcium concentration was altered in isolated cat papillary muscles. In two series of experiments at temperatures of 30 degrees C and 32 degrees C, and rates of 12 and 30 beats/min, 21 muscles were exposed to calcium concentrations of 1.125, 2.25 and 4.5 mM. Muscle lengths were varied between 80% and 100% of the length at which maximum developed force occurred (Lmax). Peak developed force and the time from stimulus to peak were measured. The data indicate that force is not altered proportionately at all lengths when calcium concentration is changed. Rather, we found that a substantially greater modification of force occurs at short lengths than at long lengths. Similarly, the time to peak force increases with length at a rate which is more than 4 times greater at the low calcium concentration than it is at the high concentration. Small but consistent shifts of Lmax also are seen. We observed that Lmax is longer when inotropic changes reduce force and shorter when force is increased. These results indicate that the inotropic effect of extracellular calcium concentration changes is dependent on muscle length.

Animals↗
PubMed1975

Trancutaneous determination of aortic blood-flow velocities in man.

A transcutaneous ultrasonic Doppler technique for measurement of aortic blood-flow velocities has been developed and compared to more established techniques in order to evaluate its potential usefulness. It is possible by this method to quantitate blood velocity in both the ascending aorta and the aortic arch with ease and reliability. Ultrasonic access to the aorta from the suprasternal notch proved adequate in more than 90 per cent of the normal subjects examined. If further clinical trials prove as encouraging, this technique may be of significant value for patient monitoring and cardiac diagnosis.

Aorta↗
PubMed1975

Correlation of peak aortic and carotid flow acceleration during coronary occlusion in conscious baboons.

1. Peak blood flow acceleration measured in the common carotid artery was compared with peak flow acceleration measured in the ascending aorta of three baboons. 2. The response to occlusion for 60s of the circumflex branch or the anterior descending branch of the left coronary artery was investigated. 3. Both accelerations decreased approximately to the same extent. Peak aortic flow velocity, stroke volume and cardiac output also decreased but to a smaller extent. 4. It is concluded that peak aortic flow acceleration is a sensitive index of myocardial function during acute coronary occlusion in conscious primates and that peak carotid flow acceleration is an indirect measure of myocardial performance under the same conditions.

Animals↗
PubMedDate not supplied

Effect of ketamine on ventricular dynamics of unanesthetized baboons.

Ketamine hydrochloride is commonly employed to sedate or anesthetize laboratory primates but its cardiac actions have not been previously described in these animals. Four baboons, Papio cynocephalus, were chronically instrumented with electromagnetic flow detectors on the ascending aorta and common carotid artery. Cardiac output, peak aortic flow velocity and peak aortic flow acceleration are all depressed by Ketamine, 5 mg/kg i.m. Peak aortic flow acceleration and peak carotid flow acceleration were equally depressed. Thus, peak carotid flow acceleration is a useful indirect index of the left ventricular response to Ketamine in the baboon.

Animals↗