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Biomedical subjects

T C Donald

Publications and source records attributed to T C Donald.

7 recordsLinked to original sources
PubMed1980

Effect of damaged ends in papillary muscle preparations.

The mechanical characteristics of the central segment of isolated cat papillary muscle were determined with recently developed equipment. Two small sharpened stainless steel pins, inserted transversely through the muscle, were used to mark the ends of a segment not damaged by attachments. Installation of the pins did not affect the performance of the muscle. The distance between the pins was measured and controlled to produce isometric and afterloaded isotonic contractions of the segment of the muscle between the pins. Data from such contractions were compared with traditional whole muscle measurements made on the same preparation. The isometric length-tension curve of the central segment was significantly higher than that of the whole muscle, and there was no plateau of developed force at long lengths in five of six muscles studied. In the resting state, the segment was more compliant than the whole muscle for physiologic lengths and much stiffer for longer lengths. Segment velocity and shortening were significantly higher than whole muscle velocity and shortening at comparable loads.

Animals↗
PubMed1977

An analog approach to measuring O2 uptake on-line.

An analog circuit has been designed to provide a solution to the Haldane transformation that yields true O2 fraction. Incoming signals proportional to fractional concentration of CO2 and O2 in mixed expired gas are utilized in the circuit and the results are multiplied by a value proportional to ventilation. The final products are analog signals proportional to O2 uptake and CO2 output. The system is applicable to the anesthetized and paralyzed animal kept at a known constant ventilation. The final products are analog signals proportional to O2 uptake and CO2 output. The system is applicable to the anesthetized and paralyzed animal kept at a known constant ventilation. Diagrams of the circuit and expired gas collection and analysis arrangements are provided.

Animals↗
PubMed1976

Afterload-induced homeometric autoregulation in isolated cardiac muscle.

Pressure-induced homeometric autoregulation (HAR) has been demonstrated by many investigators in the mammalian ventricle; In isolated cardiac muscle, however, several investigators have reported the opposite effect (anti-HAR); namely, that the first beat after a transition from isotonic to isometric contraction is the most forceful, with a decline over several beats to a steady state. In the present study we find that trabeculae from the canine right ventricle demonstrate either HAR or anti-HAR, depending on the rate of stimulation, the calcium level, and the temperature. Higher calcium, higher temperature, and lower rate of stimulation produce either less HAR or more anti-HAR. When only temperature and rate of stimulation are varied, in each muscle there is a unique rate for each temperature above which HAR occurs and below which anti-HAR occurs.

Animals↗