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P Gastineau

Publications and source records attributed to P Gastineau.

5 recordsLinked to original sources
PubMed1983

Force-velocity-length relationship during cardiac hypertrophy. Time course of activation.

Basic mechanical properties observed during cardiac hypertrophy were studied in left ventricular rat papillary muscles after exposure to chronic pressure and/or volume overloading. It is always possible, during such overloading conditions, to define the level of contractility in terms of a force-velocity-length (F-V-L) relationship regardless of time and initial length. Thus, during a determined period of the contraction phase and for a given total load, shortening velocity remained an univocal time-invariant function of shortening length, involving a time-independent maximum intensity of activation. The onset of this precise phase was reached relatively soon after stimulus. The time-independent F-V-L relation was observed both in controls and in hypertrophied heart muscles, whatever the degree and the type of induced hypertrophy, and even during the latest phases of congestive heart failure.

Animals↗
PubMed1982

Load dependence of mammalian heart relaxation during cardiac hypertrophy and heart failure.

Mechanical properties of relaxation were studied in left ventricular rat papillary muscle during cardiac hypertrophy induced by chronic pressure and/or volume overload. Maximum velocity of isotonic lengthening was linearly related to total extent of isotonic shortening and to maximum velocity of isotonic contraction and depended on the type of chronic overloading without correlation with the degree of cardiac hypertrophy. Time to peak shortening was significantly increased in each group of hypertrophied heart muscles as compared to controls. The sensitivity of cardiac relaxation to the loading conditions was determined by the time course of relaxation. To quantify the degree of load sensitivity, we measured the ratio of isotonic area to isometric area, which was the area limited by the afterloaded force vs. time at 50% of the isometric peak tension divided by the area of the force vs. time trace in the isometric twitch below the same level of load. The value of this ratio was about 0.81 in normal rat and did not show any significant differences in hypertrophied heart muscles even at the terminal stage of congestive heart failure. During acute hypoxia the load sensitivity of relaxation disappeared both in normal and in hypertrophied hearts. Thus inadequacy in oxygen supply has more drastic effects, as compared with those induced by chronic overload, probably by affecting the sarcoplasmic reticulum uptake of activating calcium.

Animals↗
PubMedDate not supplied

Degree of granulation of atrial cardiocytes: its decrease after aorto-caval fistula in the rat.

The experimental creation of an aorto-caval fistula in the rat leads to a decrease of the degree of granulation of atrial cardiocytes. This decrease is significant for granules distal to the nucleus and not for paranuclear granules. This partial degranulation reinforces the hypothesis according to which atrial cardiocytes participate in some sensitivity to local changes in blood pressure and flow.

Aorta, Abdominal↗
PubMedDate not supplied

Aorto-caval fistula in the rat. An experimental model of heart volume overloading.

Abdominal aorto-caval fistula was experimentally induced in rats, and animals were sacrificed 5 days, 1 month, and 6 months later. Cardiac weight almost doubled the normal weight during the first month. Cell length increased to the same extent as the cell width, indicating harmonious growth. Increase in cell volume, as well as the amount of degenerative changes, were more pronounced in subendocardium than in midwall and subepicardium. Cytological features of active cellular growth was found not only in the early stages (5 days and 1 month) but also 6 months after the operation. This finding is consonant with proteosynthesis stimulation not only in the early period of constitution of hypertrophy but also in the later stages.

Animals↗