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Effect of incubation temperature on growth of the working and conducting myocardium in the embryonic chick
Skuhrová, Kristýna ; Sedmera, David (advisor) ; Gregorovičová, Martina (referee)
It was shown almost 50 years ago that hypothermic incubation of chicken embryos results in a reduction in the size of embryos and an increase in the heart weight, presumably by hypertrophy (increase in cell volume). The chicken embryos were incubated in normothermia (37.5 ř C) and hypothermia (33.5 ř C) from the eleventh embryonic day. On the 17th day, the embryos were weighed and then their hearts were weighed. In agreement with the previous results, hypothermic embryos were 29% smaller and their hearts 18% heavier. The heart-to-body weight ratio was 67% higher in the hypothermic group. The measured cell size was very similar in the target areas and it was also between the two groups. The left ventricle width was twofold that the right one and the difference was not significantly higher in the hypothermia model. Purkinje fibers, the terminal part of the conduction system, were smaller than the working cardiomyocytes. Purkinje fibers were slightly enlarged after hypothermic incubation. The proliferation rate was measured by immunohistochemical labeling of anti-phospho histone H3. The experimental group showed much higher proliferation rate; it reached statistical significance in the right ventricle. Thus, hypothermic incubation resulted in increased growth of embryonic heart based on hyperplasia...
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Mechanisms of growth of the cardiac conduction system
Skuhrová, Kristýna ; Sedmera, David (advisor) ; Elsnicová, Barbara (referee)
The ability to produce regular rhythm and independence of nervous system and are some of the features of the cardiac conduction system. The conduction system comprises the sinoatrial node, internodal tracts, the atrioventricular node, the atrioventricular (His) bundle, its right and left branches, and the terminal network of Purkinje fibers. However, this system is frequently the cause of the cardiac rhythm disorders, i.e., arrhythmias. There are many unanswered questions about the conduction system, even though its development is closely connected to the growth of the whole heart. The heart undergoes many dramatic changes during its development, such as modification of linear heart tube into the mature four-chamber organ. Looping and forming chambers cause change of localization first "pacemaker" from the caudal end of the heart tube to the area of the right atrium. Prenatal growth of the heart is based upon cell proliferation or hyperplasia. The cell divisions are rapidly stopped soon after birth and the cells start to grow by increase in volume, i.e., hypertrophy. The cells of some species can expand hyperplasia or hypertrophy in early postnatal period. The mouse is one of the organisms with the cell expansion provided by combination of proliferation and hypertrophy. Most of the adult...
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