Myocardial function during chronic food restriction in isolated hypertrophied cardiac muscle

Background: the effect of food restriction (FR) on myocardial performance has been studied in normal hearts. Few experiments analyzed the effects of undernutrition on hearts subjected to cardiac overload. The aim of this study was to determine whether chronic FR promotes more significant changes in hypertrophied hearts than in normal hearts. Methods: Myocardial performance was studied in isolated left ventricular papillary muscle from young male spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto rats (WKY) submitted to FR or to control diet. The animals subjected to FR were fed 50% of the amount of food consumed by control groups for 60 days. Isolated muscles were studied while contracting isometrically and isotonically. Results: FR decreased the body weight and the left ventricular weight in both groups. FR increased the left ventricular weight-to-body weight ratio in the WKY rats and tended to decrease this ratio in SHR (P = 0.055). The arterial systolic pressure was greater in SHR than in WKY groups and did not change with FR. In the animals with normal diet, myocardial performance was better in SHR than in WKY. FR increased time to tension to fall from peak to 50% of peak tension and time to peak tension in the WKY rats and time to peak tension in the SHR. Conclusions: FR for 60 days has a trend to attenuate the development of cardiac hypertrophy and does not promote more mechanical functional changes in the hypertrophied myocardium than in the normal cardiac muscle.

Heat exchangers for cardioplegia systems: In vitro study of four different concepts

The aim of this work is the evaluation of four different heat exchangers used for myocardium during cardioplegic system in cardiac surgeries. Four types of shell and tube heat exchangers made of different exchange elements were constructed, as follows: stainless steel tubes, aluminium tubes, polypropylene hollow fiber, and bellows type. The evaluation was performed by in vitro tests of parameters such as heat transfer, pressure drop, and hemolysis tendency. The result has shown that all four systems tested were able to achieve the heat performance, and to offer low resistance to flow, and safety, as well as have low tendency to hemolysis. However, we can emphasize that the bellows type heat exchanger has a significant difference with regard to the other three types.

Cardiac benefits of exercise training in aging spontaneously hypertensive rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Is gender crucial for cardiovascular adjustments induced by exercise training in female spontaneously hypertensive rats?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Collagen and reticular fibers in left ventricular muscle in diabetic rats: Physical exercise prevents its changes?

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Evaluation of Vmax as an index of myocardial contractility during afterload and preload elevations

In order to test if the maximal velocity of shortening (V(max)TP) reflects the level of inotropism and is affected by preload and afterload, the behavior of this index was compared in two groups of anesthetized, atropinized dogs when preload and afterload were raised with an angiotensin II infusion. In seven dogs (group I), the arterial pressure elevation was allowed to inhibit reflectively the sympathetic tone and depress contractility. In eleven dogs (group II), the adrenergic activity was abolished by previous administration of reserpine. In group I, there was a significant decrease in V(max)TP during the angiotensin infusion. In group II, there was no significant change in the value of this index when the drug was infused. In six animals of this group, a further increase of arterial pressure was induced, but the values of V(max)TP remained similar to control. These results suggest that this index reflects the inotropic state of the myocardium and does not suffer significantly from the influence of preload and afterload elevations within our experimental limits.

Effect of non-steroidal anti-inflammatory drugs (NSAID) on the histamine release induced by compound 48/80 and cardiac anaphylaxis in guinea-pig isolated heart

Histamine release from guinea pig heart treated with compound 48/80 was potentiated by the cyclooxygenase inhibitors indomethacin and piroxicam but not by aspirin or phenylbutazone. This differential effect suggests that the potentiation is not merely due to an inhibition of prostaglandin synthesis. Piroxicam potentiated the histamine release induced by cardiac anaphylaxis whereas indomethacin reduced this effect. The SRS-A antagonist FPL 55712 inhibited histamine release induced by cardiac anaphylaxis, but not that evoked by compound 48/80, and also prevented the potentiation due to indomethacin and piroxicam. In total, these data suggest that the potentiation of histamine release by piroxicam and indomethacin is probably due to a diversion of arachidonic acid metabolism from the cyclooxygenase to the lipoxygenase pathways. The resulting lipoxygenase products may then regulate histamine release, with the secretion due to antigen being more sensitive to such modulation than that evoked by compound 48/80.

Is coronary sinus blood oxygen tension behavior determined by myocardial oxygen tension variation during cardiac reperfusion?

The relationship between coronary sinus blood oxygen tension (CSPO 2) and myocardial oxygen tension (MPO 2) variations during cardiac ischemia and reperfusion was studied in anesthetized open-chest dogs. Oxygen tension was measured by a polarographic method. Ischemia resulted in a slightly decreased CSPO 2 and a more pronounced reduction of MPO 2. After reperfusion the CSPO 2 rose rapidly and transiently before it returned gradually to the control level. By contrast, during the recovery period, the MPO 2 increased slowly, with recovery occurring long after the peak of CSPO 2. These data suggest that during the reperfusion phase, the CSPO 2 variation is probably due to opening of the myocardial arteriovenous shunts instead of an increase of flow through the myocardial capillary bed.

Anatomic data of the human coronary sinus

The authors studied the formation, tributaries, lenght and the ostium of the coronary sinus, as well as the relationship of the venous walls to the myocardium and to the epicardium. The observations were made out of 143 hearts of subjects of different ages, and it was found that the most frequent display of the coronary sinus valve was a semilunar form (52 adults, 15 youngsters, 2 children, 3 newborn); it was also found valves in a cribiform or septal form. The absence of the valve of coronary sinus was noted in 53 cases (42 adults, 9 youngsters, 2 newborn). The valve of Vieussens was found, in some cases, at the level of the transition between the great cardiac vein and the coronary sinus, as well as others single or double parietal venous valves. The action of the valve of coronary sinus is also discussed by the authors.

Nickel chloride: potential accumulation from the airway. Toxicokinetics in rats.

The rate removal of nickel from the airway was measured in vivo. Removal in vivo was studied by intratracheal injection of nickel chloride solutions. Regardless of time after injection, the lungs and heart retained the greatest concentration of nickel and 40 days after 1.68 mumol administration they were the organs where nickel was still significantly measurable. The slow removal of nickel may indicate the presence of high affinity binding sites in the lung. Nickel can interact with others metals, such as copper and zinc, so that nickel exposure may have public health implications.

Efeito do envelhecimento sobre o comportamento mecânico dos músculos papilares de ratos Wistar.

PURPOSE--To evaluate the effects of age on mechanical performance of rat myocardium. METHODS--Left ventricular papillary muscles were isolated from male Wistar rats at 1, 3, 6 and 12 months of age. Muscles were studied isometrically and isotonically, stimulated at 0.2 Hz, perfused with Krebs-Henseleit solution having an external calcium concentration of 2.52 mM, and maintained at 28 degrees C. RESULTS--Peak isometric developed tension was significantly higher in 1 month than 3, 6 and 12 months. Peak rate of isometric tension rise decreased substantially between 1, 3 and 12 months. Time to peak isometric developed tension showed a significant increase of both 3 and 12 months of age. Time to half relaxation increased significantly from 3 to 6 and from 3 to 12 months. Maximum rate of tension decline decreased from 3 to 6 and from 3 to 12 months. No difference in resting tension was noted among any group. Isotonically, peak shortening and time to peak shortening increased from 1 to 3 months of age. Time to half re-lengthening increased from 3 to 6 and from 3 to 12 months of age. No difference in peak shortening velocity, peak relaxation velocity and relative change in muscle length was noted among any groups. CONCLUSION--The maturation affects the mechanical performance of cardiac muscle.