Search

A study was conducted on the excised, cross-circulated canine heart to examine the effects of myocardial temperature on left ventricular (LV) mechanoenergetics. The thermal effects were quantified using the framework of the LV contractility (Emax)-pressure-volume area (PVA)-myocardial oxygen consumption relationship. Emax was found to change reciprocally. Moreover, the oxygen cost of Emax proportionally changed with temperature, while that of PVA remained unchanged.

The synthesis of the first naturally occurring 1,4-disubstituted quinolizidine from the skin of poisonous frogs and toads has been carried out. 1,4-disubstituted quinolizidine is a new class of alkaloids with therapeutic uses. Mass and infrared spectroscopy have been used in studying the structure of the new compound which has been called quinolizidine 217A. Spectroscopic data reveal that quinolizidine 217A has the same structure as its natural counterpart.

A study was conducted to characterize a novel integrative technique for quantifying total Ca2+ handling and futile Ca2+ cycling in failing hearts. The model is supported by an equation to compute the amount of ATP consumed for total Ca2+ handling. Futile Ca2+ cycling was combined with Ca2+ handling O2 consumption to determine total Ca2+ handling in such hearts. Results indicated the applicability of the method to studying failing hearts supporting futile Ca2 cycling.

A comprehensive equation defining the force of restitution and potentiation in terms of two preceding beat intervals was used in a computer simulation approximating the contractilities of irregular arrhythmic beats. The relationship among the different parameters under investigation was similar to the results of an experimental procedure previously undertaken. This suggests that mechanical restitution and potentiation are responsible for the variable contractilities observed in arrhythmia.

A mathematical model has been devised to simulate cardiac cooling inotropy. Calcium and cross-bridge cycling kinetics techniques were used to simulate myocardial cooling mechanoenergetics in sarcoplasmic reticulum. Constant contractile efficiency in the presence of adjusted ATPase-dependent calcium uptake is achieved using the model.

The mechanoenergetic properties of left ventricular (LV) contraction were characterized in rat hearts during ascending aortic occlusion based on the analysis of systolic pressure-volume area (PVA) relationships. Analysis of LV pressure-volume (P-V) loops in rat hearts during the gradual occlusion of the ascending coronary artery indicated the presence of an upward convex curvilinear end-systolic P-V relationship (ESPVR). Furthermore, the linear ESPVR enveloping early P-V loops during aortic occlusion cannot be utilized for assessing LV contractility.

A volumetric conductance catheter was designed that can monitor diastolic processes in the left ventricles of rats. It measures stroke volume from an catheter descending to the left ventricle and an electromagnetic probe attached to the ascending aorta. The catheter was used to compare stroke volumes in six subject animals. The device was able to provide measurements for estimating end-systolic pressure-volume relationship at normal and occluded conditions in the aorta.

The reaction rates of cross-bridge formation and dissociation in cardiac muscle tissues can be represented as a function of contractile efficiency. A model was devised that factors in the calcium transient, calcium association rate constant and troponin C dissociation rate constant. The contractile efficiency was then evaluated from the relationship between force and length of contraction generated by one cross-bridge cycle.

Ventricular oxygen consumption of myocardial slices either in the resting or contracted state following electrical stimulation was measured in rats using a new approach. Myocardial slices contracting by electric stimulation with external load shortened and had increased oxygen consumption. Increases in extracellular concentration in myocardial slices with external load enhanced oxygen consumption to four times than normal.

The effect of cardiac infarction on the flow patterns in cardiac left ventricular ejection was studied using a realistic model which was made from the profile of the left ventricle of a dog heart in diastole. A coordinate measuring machine was used to measure the left ventricular coordinates, and these were input into a three-dimensional flow simulation package. The left ventricular wall motion was described by having the walls moved towards the center of the aortic outlet, and in the case of infarcted tissue, the ventricular wall movement was diminished to simulate infarction flow behavior. The final ventricular volume varied from 25 percent to 54.1 percent of the initial volume in cases without and with infarction, respectively. The maximum blood ejection velocities and ventricular pressure decreased significantly in the presence of infarction. Infarcted areas showed complex blood flow vortex formation not present in the healthy ventricles. The computational technique presented here predicts infarction flow effects which could be observed with measurement techniques such as ultrasound and magnetic resonance imaging, allowing a finer detail of understanding than using either simulation or experimental measurements alone.

The mechanism underlying vibration-induced depression of contraction of the left ventricular wall was investigated by examining the mechanoenergetics of various positive and negative inotropic interventions in isolated, cross-circulated dog heart preparations. Results showed that mechanical vibration applied to the ventricular wall suppresses cardiac contractility without affecting the excitation-contraction activities of dog heart.

The Huxley sliding filament cross-bridge muscle model was applied to myocardium isometric quick-release contractions to determine parameter variation and muscle fiber types effects on energy use predictions before and after peak systole. Results indicate about 15% of muscle fiber energy is used after peak systole, with about 30% of cross-bridge energy used. These results agree with researchers that more than 85% of total energy use occurs before peak systole onset.

The study of heart ventricular contractile failure reveals that the protocol stimulated left ventricular contractile failure is associated with the calcium ion concentration. The calcium ion concentration in the body is the primary cause for the mechanoenergetic effects that occur in the body

(3 + 2) cycloaddition reaction between 5-alkoyoxazole and chiral alpha-benzyloxy aldehydes produces optically pure 2-oxazoline-4-carboxylates in the presence of a tin(IV) chloride catalyst and the reaction exhibits high cis-selectivity with good yield. Chiral erythro-2-amino polyol derivatives are easily prepared from 5-(1'alkoxylalkyl)-substituted 2-oxazoline-4-carboxylate, which is synthetically prepared from cycloaddition reaction.

Left ventricle (LV) contractile dysfunction occurs along with an elevated oxygen cost of contractility in the dog due to hypercapnic acidosis. An elevated Ca2+ responsiveness of the contractile proteins during acidosis may explain this enhanced energy cost of the excitation contraction coupling. The oxygen cost of enhanced contractility was 1.53 plus or minus 0.40 times lower during preacidosis than during acidosis.