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Morphometry of right ventricular hypertrophy induced by strenuous exercise in rat.
No full textEffects on the myocardium, particularly those structural properties of the capillary network relevant to tissue oxygenation, were studied morphometrically in rats subjected to a severe running program. Physical conditioning produced a 31% increase in right ventricular weight and only a 12% increase in the weight of the left ventricle. Quantitative analysis of right ventricular myocardium demonstrated relative decreases in capillary luminal volume density (-27%) and capillary luminal surface density (-20%) and an increase in the average maximum distance from the capillary wall to the mitochondria of myocytes (14%). In contrast, the contractile mass expanded in proportion to the growth of the ventricle through augmentation of the cross-sectional area (17%) and length (19%) of the average myocyte. Evaluation of the subcellular constituents of myocytes showed no change in the mitochondria-to-myofibril volume ratio. In conclusion, the capillary bed controlling oxygen availability, diffusion, and transport suggests that excessive physical activity may be detrimental to the myocardium
Morphometry of right ventricular hypertrophy induced by strenuous exercise in rat.
No full textEffects on the myocardium, particularly those structural properties of the capillary network relevant to tissue oxygenation, were studied morphometrically in rats subjected to a severe running program. Physical conditioning produced a 31% increase in right ventricular weight and only a 12% increase in the weight of the left ventricle. Quantitative analysis of right ventricular myocardium demonstrated relative decreases in capillary luminal volume density (-27%) and capillary luminal surface density (-20%) and an increase in the average maximum distance from the capillary wall to the mitochondria of myocytes (14%). In contrast, the contractile mass expanded in proportion to the growth of the ventricle through augmentation of the cross-sectional area (17%) and length (19%) of the average myocyte. Evaluation of the subcellular constituents of myocytes showed no change in the mitochondria-to-myofibril volume ratio. In conclusion, the capillary bed controlling oxygen availability, diffusion, and transport suggests that excessive physical activity may be detrimental to the myocardium
Morphometry of exercise-induced right ventricular hypertrophy in the rat.
No full textIn our morphometric study of the effects of exercise on the heart, male Wistar-Kyoto rats at 5 weeks of age were subjected daily to a moderate treadmill running program that lasted for 7 weeks. The heart responded to physical conditioning by different magnitudes of tissue growth of the right (22%) and left (7%) ventricular myocardium, the latter change not statistically significant. The increase in right volume was associated with a 25% enlargement of ventricular area, a 26% average lengthening of the myocytes, and no change in sarcomere length and in ventricular midwall thickness. Exercise produced significant alterations in the quantitative parameters of the microvasculature of the right ventricle, but no appreciable changes in the left ventricle. Right ventricular hypertrophy was characterized by an absolute 44% growth of the endothelial luminal surface brought about through a 16% increase in capillary numerical density, and a 41% augmentation of the total length of the capillary network. Maximum diffusion distance from the capillary wall to the mitochondria of myocytes decreased 10% as a result of capillary proliferation and the lack of lateral expansion of myocyte cross-sectional area. Evaluation of the subcellular constituents of myocytes showed no change in the mitochondria:myofibrils volume ratio indicating a growth of these components proportional to each other and to the growth of the myocyte population as a whole. It was concluded that, as a result of running exercise, right ventricular growth is nalogous to eccentric hypertrophy in which the structural adaptations of the capillary bed can be expected to improve the diffusion and transport of oxygen within the tissue
Morphometry of exercise-induced right ventricular hypertrophy in the rat.
No full textIn our morphometric study of the effects of exercise on the heart, male Wistar-Kyoto rats at 5 weeks of age were subjected daily to a moderate treadmill running program that lasted for 7 weeks. The heart responded to physical conditioning by different magnitudes of tissue growth of the right (22%) and left (7%) ventricular myocardium, the latter change not statistically significant. The increase in right volume was associated with a 25% enlargement of ventricular area, a 26% average lengthening of the myocytes, and no change in sarcomere length and in ventricular midwall thickness. Exercise produced significant alterations in the quantitative parameters of the microvasculature of the right ventricle, but no appreciable changes in the left ventricle. Right ventricular hypertrophy was characterized by an absolute 44% growth of the endothelial luminal surface brought about through a 16% increase in capillary numerical density, and a 41% augmentation of the total length of the capillary network. Maximum diffusion distance from the capillary wall to the mitochondria of myocytes decreased 10% as a result of capillary proliferation and the lack of lateral expansion of myocyte cross-sectional area. Evaluation of the subcellular constituents of myocytes showed no change in the mitochondria:myofibrils volume ratio indicating a growth of these components proportional to each other and to the growth of the myocyte population as a whole. It was concluded that, as a result of running exercise, right ventricular growth is nalogous to eccentric hypertrophy in which the structural adaptations of the capillary bed can be expected to improve the diffusion and transport of oxygen within the tissue
Effects of strenuous exercise on the quantitative morphology of left ventricular myocardium in the rat
No full textThe adaptation of the structural components in the myocardium of the left ventricle to strenuous exercise was studied morphometrically in rats following a treadmill running program. The response of the left ventricle was evaluated separately in the interventricular septum and in the left ventricular free wall. Exercise produced a 24% growth of the septum without altering free wall volume. The hypertrophic expansion of the septum was characterized by a decrease in the volume fraction of capillary lumen in the myocardium (-20%), a reduction in the capillary luminal surface per unit volume of myocytes (-17%) and by an increase in the maximum distance from the capillary wall to the mitochondria of myocytes (9%). Although none of these changes were demonstrable on a statistical basis in the left ventricular free wall, similar results were obtained in the whole left ventricle by combining the data from the septum and free wall. Since the septum constitutes a functional unit with the free wall, it was concluded that the effect of excessive physical activity on the capillary parameters responsible for oxygen availability and diffusion could lead to a local reduction in the oxygenation potential of ventricular myocardium
Morphometry of right ventricular hypertrophy induced by myocardial infarction in the rat
No full textThe growth response of the right ventricle was studied in rats following ligation of the left coronary artery, which produced infarcts comprising approximately 40% of the left ventricle. A month after surgery the weight of the right ventricle was increased 30%, and this hypertrophic change was characterized by a 17% wall thickening, consistent with the 13% greater diameter of myocytes. Myocardial hypertrophy was accompanied by an inadequate growth of the microvasculature that supports tissue oxygenation. This was seen by relative decreases in capillary luminal volume density (-27%) and capillary luminal surface density (-21%) and by an increase in the average maximum distance from the capillary wall to the mitochondria of myocytes (19%). In contrast, measurements of the mean myocyte volume per nucleus showed a proportional enlargement of these cells (32%), from 16,300 cu μ in control animals to 21,500 cu μ in experimental rats. Quantitative analysis of the right coronary artery revealed a 33% increase in its luminal area, commensurate with the magnitude of ventricular hypertrophy
Effects of strenuous exercise on the quantitative morphology of left ventricular myocardium in the rat
No full textThe adaptation of the structural components in the myocardium of the left ventricle to strenuous exercise was studied morphometrically in rats following a treadmill running program. The response of the left ventricle was evaluated separately in the interventricular septum and in the left ventricular free wall. Exercise produced a 24% growth of the septum without altering free wall volume. The hypertrophic expansion of the septum was characterized by a decrease in the volume fraction of capillary lumen in the myocardium (-20%), a reduction in the capillary luminal surface per unit volume of myocytes (-17%) and by an increase in the maximum distance from the capillary wall to the mitochondria of myocytes (9%). Although none of these changes were demonstrable on a statistical basis in the left ventricular free wall, similar results were obtained in the whole left ventricle by combining the data from the septum and free wall. Since the septum constitutes a functional unit with the free wall, it was concluded that the effect of excessive physical activity on the capillary parameters responsible for oxygen availability and diffusion could lead to a local reduction in the oxygenation potential of ventricular myocardium
Morphometry of right ventricular hypertrophy induced by myocardial infarction in the rat.
No full textThe growth response of the right ventricle was studied in rats following ligation of the left coronary artery, which produced infarcts comprising approximately 40% of the left ventricle. A month after surgery the weight of the right ventricle was increased 30%, and this hypertrophic change was characterized by a 17% wall thickening, consistent with the 13% greater diameter of myocytes. Myocardial hypertrophy was accompanied by an inadequate growth of the microvasculature that supports tissue oxygenation. This was seen by relative decreases in capillary luminal volume density (-27%) and capillary luminal surface density (-21%) and by an increase in the average maximum distance from the capillary wall to the mitochondria of myocytes (19%). In contrast, measurements of the mean myocyte volume per nucleus showed a proportional enlargement of these cells (32%), from 16,300 cu μ in control animals to 21,500 cu μ in experimental rats. Quantitative analysis of the right coronary artery revealed a 33% increase in its luminal area, commensurate with the magnitude of ventricular hypertrophy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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