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Biomedical subjects

E Urbánek

Publications and source records attributed to E Urbánek.

At least 19 recordsLinked to original sources

Control and driving of pneumatic total artificial hearts TNS-BRNO-II and -III in long-term experiments.

Hemodynamic analysis was carried out during long-term experiments with the pneumatic total artificial hearts TNS-BRNO-II and TNS-BRNO-III to determine standard methods of starting artificial hearts and criteria for their long-term operation in vivo. In long-term experiments, regulatory mechanisms automatically regulating the systole length and diastolic aspiration pressure have also been verified. Comparison of hemodynamic variables obtained from invasive measurements with pneumatic pressure curves permitted the control and monitoring of the experiment in its entirety by noninvasive methods only. The control of the artificial heart using the Chirasist TN 3 and Chirasist TN 4 was adapted to specific properties of the pumps, above all to the functions of the atypical inlet valves. The terminal stages of the experiments have shown that a 100-ml pump can ensure survival of experimental calves up to 210 kg body weight.

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[Comparative study on myocardial damage in irradiated for a long time and nonirradiated rats after administration of FCOL].

The trials were made to assess the effect of FCOL (9-alpha-fluorocortisol + Na2HPO4) and the effect of K and Mg asparaginates and their mixtures on the modifications of Ca2+, Na+, and K+ ions and of the K/Na ratio in the myocardium of rats not irradiated or submitted to permanent whole-body irradiation (gamma irradiation with 0.57 Gy per day during 25 days, total accumulated dose 14.25 Gy; the trials were performed 25 days after the irradiation). The totality of reversible and irreversible functional modifications of the myocardium, expressed by the quantitative assessment of the K/Na ratio and the concentration of Ca2+ ions, was evaluated in order to determine the cardiotoxicity or cardioprotection. It was demonstrated that irradiation alone causes a slight irreversible modification in the myocardium which is not found in non-irradiated rats. FCOL itself increases the rate of Ca2+ and Na+ ions in irradiated and non-irradiated rats, but does not influence the quantity of K+ ions. Severe irreversible myocardial damages are caused by FCOL, but these damages are considerably lower in irradiated rats. Neither in irradiated nor in non-irradiated rats, the isomers of Mg asparaginate show any protective action against the cardiotoxic effect of FCOL. The isomers of K asparaginate, also combined with Mg asparaginates, as well as the preparation Inzolen exert a demonstrable protective effect against myocardial ion modifications following to application of FCOL. The protection is more efficient in irradiated rats.

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Innervation of atrial stumps in calves living with the TNS-Brno II artificial heart.

The remnant stumps of the atria in six calves surviving with the artificial TNS-Brno II methacrylate heart for up to 5 months were examined by means of the Bodian silver-impregnating technique and by the formalin-induced fluorescence technique visualizing noradrenaline in monoaminergic nerve terminals. The degeneration of the nerve terminal system detected in animals surviving for 2 days and 1 week was followed by regeneration of the vegetative nerve system in four animals surviving for greater than 1 month. Moreover, thick myelinated nerves afferent in character were detected within the atrium of one animal surviving for 5 months.

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Mechanisms causing the death of 8 calves surviving with implanted artificial heart from 31 to 173 days.

Causes of the death of four animals from the total of eight were technical failures (diaphragm perforations, disconnection of the quick-connector, and a failure of the supply of electric current which could not be prevented). Causes of the death of the remaining four animals were embolisation in the brain stem, embolisation in the superior mesenteric artery leading to diffuse peritonitis, ruptures of aorta and hemocoagulation disorder causing fatal gastrointestinal bleeding.

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A comparative study of a group of eight calves, surviving longer than 1 month with the total artificial heart.

Over the last 2 1/2 years, eight calves with implanted total artificial hearts (from experimental group IV) have survived for greater than 1 month. In this group two subgroups were further differentiated, subgroup IVa, including three calves surviving 31, 35, and 75 days, and subgroup IVb, with five calves surviving 104, 142, 150, and 155 days and one calf still surviving greater than 160 days. Mean survival in the fourth group was greater than 106.5 days. The artificial ventricles used were the TNS-BRNO-II made of polymethylmethacrylate (seven calves) and the TNS-BRNO-III, made of segmented polyetherurethane (one calf). The controller and driving units were of our own design. The Chirasist-TN-3 and TN-4 worked without trouble over the total duration of the studies in all calves. Autoregulation of suction was used in three of these calves. All calves survived in good physiological condition; however, some common changes were observed in all of them, such as a gradual central venous pressure increase and liver enlargement. Anticoagulation therapy was used in all calves. Causes of death were technical in three cases and biological in four. Body weight gains were normal in the majority of these calves, with slight individual differences observed. Diaphragm mineralization of various degrees was observed in three cases. In one of them it was directly related to the cause of death. These results are very encouraging for further development of the total artificial heart research in our center.

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BRNO-I, an implantable, diaphragm-type total artificial heart: technical aspects of design.

The technical aspects of artificialheart design for experiments on calves are presented in this paper. The object of the design was to verify the basic anatomic and hemodynamic criteria for the design of more perfect cardiac prostheses. Each of the ventricles has a 100-ml stroke volume and is dismountable. Rigid parts are made of polymethylmethacrylate. The inlet valve has the shape of a flap. The outlet valve has two polyurethane reinforcing leaves. The diaphragm is also made of polyurethane. During tests using artificial circulation, a maximum cardiac output of 14.6 L/min was achieved. Typical sensitivity of flow on the atrial pressure is 0.3 L/min/torr at a frequency of 90 pulses per minute.

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Determination of cardiac output of the artificial heart from the drive air flow.

An indication chamber, inserted between the right heart drive and the pump proper, was designed to provide continual measurement of the quantity of blood pumped by the pneumatic artificial heart. The flow is evaluated from the motion of a piston provided with a photoelectric transducer. The effect of compressibility of the drive gas on measurement accuracy is eliminated. The indication chamber provides for automatic replenishment of gas that escapes by diffusion and through minor leakage. During testing in an artificial circulation within the range of physiological conditions, measurement in accuracies did not exceed 5%.

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The effect of preirradiation application of aspartic acid salts on hemopoietic recovery in X-irradiated mice.

The possibility of radioprotective action of K and Mg aspartate administered in tap water for ten days prior to X-irradiation was investigated in male mice of the strain C 57 Bl/10. In normal animals, thymus weight was found to be increased by 10-day treatment with K and Mg aspartate. The postirradiation regeneration of spleen weight and incorporation of radioactive iron into the spleen and femoral marrow following sublethal irradiation was favorably modified by the treatment used. Pretreatment of mice with K and Mg aspartate delays the onset of early deaths at irradiation with an absolutely lethal X-ray exposure and raises the percentage of surviving animals after nearly lethal exposures.

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The effect of postirradiation application of aspartic acid salts on hemopoietic recovery in sublethally X-irradiated mice.

The effect of aspartic acid salts, especially of K and Mg aspartates, on certain hematological changes in the peripheral blood and hemopoietic organs of sublethally X-irradiated male mice of the strain C57Bl/10 was investigated. Salts of aspartic acid were administered in tap water after irradiation. A favorable effect of aspartic acid salts on erythropoietic recovery and on regeneration of thymus weight was found during the first two weeks after irradiation.

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Mechanical combined heart supporting system for prevention of irreversible ventricular fibrillation after experimental cardiogenic shock.

To determine whether haemodynamic effective support of the failing heart can prevent spontaneous irreversible ventricular fibrillation (IVF) after experimental cardiogenic shock, 63 open chest dogs were assigned randomly into four groups--two control groups (combined heart failure--CHF) and two MCHSS-treated (combined heart failure and non-pulsatile bypass with intraaortic counterpulsation). The CHF was produced by occlusion of the anterior descending coronary artery (group I) or the left circumflex coronary artery (group II) and by an artificial shunt between the pulmonary artery and right atrium. IVF were observed in 10 out of 22 control dogs (group I) and im 17 out of 21 control dogs (group II). In the 20 dogs with the CHF (10 animals in each group) the MCHSS was performed in the course of two hours. During the heart support no IVF were observed in any of the dogs. The difference between the incidence of IVF in the control and treated animals is statistically significant (Chi square = 21.9767 greater than Chi square 0.005).

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Electrolyte changes in myocardial injury.

The shifts in the myocardial electrolyte metabolism during secondary or primary cardiopathies in dogs and rats, respectively, are described. Major attention is paid to the changes of Ca in the myocardial tissue. The increase in the Ca level after ligation of ramus circumflex of the left coronary artery, or after F-COL + Na2HPO4, and vitamin D2 administration, is regarded as a triggering process for more profound successive changes in the metabolism of the myocardial cell, which eventually lead to depletion of the high energy phosphate reserves. In the dogs with experimental coronary occlusion, the normalization of the myocardial ionogram, i.e., the ratio of K, Na, Ca, and Mg, was achieved by means of the mechanical heart assist, using the original design of the blood pump, where bypass and counterpulsation principles work simultaneously. The normalization of the Ca level in this case was achieved on the basis of a marked reduction of the volume work of the left ventricle, which is secured by the bypass component; on the other hand, the counterpulsation component of the combined pump secures the reduction of pressure work placed upon the left ventricle (represented by the decrease fo the end-diastolic pressure) and helps in the opening of the collaterals in the infarcted area during early diastole. Thus, the oxygen supply to the ischemic zone is improved. On the basis of our experiments with the combined blood pump, the failing heart is supported, not only hemodynamically, but also from the metabolic point of view. A similar effect is achieved by the administration of K-Mg-aspartate, and K-L- or K-DL-aspartate in dogs with experimental infarction. In primary electrolyte steroid cardiopathies characterized by necrosis, K-Mg-aspartate or K-aspartate only prevents the Ca increase in the myocardial tissue, whereas Mg-L- or Mg-DL-aspartate remains without andy effect. The necrotic changes observed after vitamin D2 administration are always accompanied by extremely high Ca levels in the myocardium. It shown in our experiments that administration of K-Mg-aspartate or Fe-dextran decreases the Ca level and reduces the necrotic and myolytic changes in the cardiac tissue. The authors recommend as an effective means in the therapy of acute heart failure the combination of mechanical heart support with the causative pharmacological therapy.

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