Biomedical subjects

C Lagrasta

Publications and source records attributed to C Lagrasta.

24 records · Page 2Linked to original sources

PubMed1992

Myocyte cellular hypertrophy and hyperplasia contribute to ventricular wall remodeling in anemia-induced cardiac hypertrophy in rats.

To determine the effects of chronic anemia on the functional and structural characteristics of the heart, 1-month-old male rats were fed a diet deficient in iron and copper, which led to a hemoglobin concentration of 4.63 g/dl, for 8 weeks. At sacrifice, under fentanyl citrate and droperidol anesthesia, systolic, diastolic, and mean arterial blood pressures were decreased, whereas differential pressure was increased. Left ventricular systolic pressure and the ventricular rate of pressure rise (mmHg/s) were reduced by 9% and 14%, respectively. Moreover, developed peak systolic ventricular pressure and maximal dP/dt diminished 14% and 12%. After perfusion fixation of the coronary vasculature and the myocardium, at a left ventricular intracavitary pressure equal to the in vivo measured end diastolic pressure, a 10% thickening of the left ventricular wall was measured in association with a 13% increase in the equatorial cavitary diameter and a 44% augmentation in ventricular mass. The 52% hypertrophy of the right ventricle was characterized by an 11% thicker wall and a 37% larger ventricular area. The 33% expansion in the aggregate myocyte volume of the left ventricle was found to be due to a 14% myocyte cellular hypertrophy and a 17% myocyte cellular hyperplasia. These cellular parameters were calculated from the estimation of the number of myocyte nuclei per unit volume of myocardium in situ and the evaluation of the distribution of nuclei per cell in enzymatically dissociated myocytes. Myocyte cellular hyperplasia provoked a 9% increase in the absolute number of cells across the left ventricular wall. In contrast, myocyte cellular hypertrophy (42%) was responsible for the increase in myocyte volume of the right ventricle. The proliferative response of left ventricular myocytes was not capable of restoring diastolic cell stress, which was enhanced by the changes in ventricular anatomy with anemia. In conclusion, chronic anemia induced an unbalanced load on the left ventricle, which evoked a hyperplastic reaction of preexisting myocytes, in an attempt to normalize diastolic wall and myocyte stress.

Anemia↗

PubMed1991

Enalapril prevents cardiac fibrosis and arrhythmias in hypertensive rats.

To evaluate the effects of hypertension on cardiac hypertrophy, on myocardial structure, and on ventricular arrhythmias, 27 3-month-old spontaneously hypertensive rats were treated with enalapril (10 mg/kg) daily for 11 months and compared with 26 untreated control rats. Systolic arterial pressure was significantly decreased in treated rats, and at the end of the experiment, it was 199 +/- 3 mm Hg (treated) versus 237 +/- 3 mm Hg (controls) (p less than 0.001). At this time, spontaneous arrhythmias and induced arrhythmias either by programmed electrical stimulation (train of stimuli +1 or 2 extrastimuli) or by trains of eight stimuli at decreasing coupling intervals were observed in isolated heart preparations. Comparing enalapril-treated and control rats, spontaneous arrhythmias (9 of 27 versus 20 of 26, respectively; p less than 0.01), programmed stimulation-induced arrhythmias (3 of 26 versus 12 of 23, respectively; p less than 0.01), and trains of stimuli-induced arrhythmias (4 of 26 versus 14 of 19, respectively, p less than 0.001) were less frequent in the enalapril group. Left ventricular weight was decreased in treated rats by 18% (p less than 0.001). Enalapril administration diminished the fraction of myocardium occupied by foci of replacement fibrosis normally occurring in control rats by 59% (p less than 0.001). Finally, a significant correlation was found between left ventricular weight, the extent of myocardial fibrosis, and the occurrence of ventricular fibrillation. It was concluded that chronic treatment with enalapril, which resulted in attenuation of systemic arterial pressure by limiting cardiac hypertrophy and myocardial fibrosis, decreases the propensity of the heart of hypertensive rats to arrhythmogenesis.

Analysis of Variance↗

PubMed1989

Long-term pressure-induced cardiac hypertrophy: capillary and mast cell proliferation.

To determine whether a prolonged duration of mechanical load on the ventricular myocardium leads to capillary proliferation, constriction of the pulmonary artery was produced in rats at 3 mo of age, and the hearts were examined 200 days later. Functionally, elevations of right ventricular systolic pressure, from 30 +/- 12 to 67 +/- 11 mmHg, and right ventricular end-diastolic pressure, from 2.4 +/- 1.4 to 8.6 +/- 2.4 mmHg, were found. Anatomically, a 69% enlargement in right ventricular mass was observed, and this hypertrophic growth was characterized by a 78% thickening of the wall with no change in ventricular wall area, the latter calculated from the quotient of ventricular volume and wall thickness. Morphometric data showed a 44% increase in the capillary-to-myocyte ratio, a 66% augmentation of the total length of capillaries in the whole ventricle, and a 77% greater number of capillaries across the ventricular wall. Furthermore, these indexes of neogenesis of capillary units were associated with a more than three fold increase in the numerical density of mast cell profiles in the myocardium. In conclusion, capillary proliferation occurs in the adult rat heart, and this process appears to be coupled with mast cell hyperplasia.

Animals↗

PubMed1989

Capillary growth in anemia-induced ventricular wall remodeling in the rat heart.

To determine whether anemia-induced cardiac hypertrophy affects ventricular size and shape and the component structures of the capillary network of the left and right ventricles, young male rats were fed an iron- and copper-deficient diet for 7 weeks. By that time, blood hemoglobin content fell to 5 +/- 1 g/dl, and packed cell volume fell to 18 +/- 3%. To further characterize the implications of anemia, red blood cell number, hemoglobin corpuscular content, systemic arterial pressure, heart rate, and blood viscosity were measured. Moreover, the changes in ventricular weights were analyzed in terms of the alterations in ventricular wall area and ventricular wall thickness to establish the impact of the elevation in load associated with a high cardiac output state on ventricular remodeling. The quantitative properties of the capillary circulation were also examined biventricularly by low power electron microscopic morphometry to evaluate the adaptive growth potential of the coronary microcirculation in this form of cardiac hypertrophy. Anemia was found to interfere with the production of red blood cells and their mean corpuscular hemoglobin content and resulted in a 40% reduction in blood viscosity and a 12% and 27% decrease in systolic and diastolic blood pressure, respectively. The changes in heart rate were not statistically significant. In comparison with control animals, heart weight increased by 50%, but the enlargement in right ventricular mass (65%) was greater than that of the left ventricle (47%). Ventricular hypertrophy occurred with increases in wall area and wall thickness although the former increased consistently more than the latter in either ventricle. Tissue growth was accompanied by a 60% lengthening of the capillary network, which in combination with an increase in capillary diameter resulted in a 65% and 34% expansion in capillary luminal volume and 56% and 20% larger luminal surface density in the left and right sides of the heart, respectively. In conclusion, hypochromic microcytic anemia leads to eccentric ventricular hypertrophy with a significant amount of capillary proliferation that may tend to protect the myocardium from the increased potential for ischemic injury.

Adaptation, Physiological↗

PubMed1988

Cellular basis of wall remodeling in long-term pressure overload-induced right ventricular hypertrophy in rats.

To determine the effects of long-term pressure overload on the structural mechanisms implicated in wall remodeling of the right ventricle, a mild pulmonary artery banding was applied to rats approximately 2 months old, and the animals were killed 150 days later. The surgical procedure resulted in a 60% reduction in the cross-sectional area of the constricted vessel and a 52% increase in the weight of the right ventricle. The hypertrophic myocardial response was associated with an elevation in right ventricular systolic pressure (from 33 +/- 11 mm Hg to 71 +/- 12 mm Hg), right ventricular end-diastolic pressure (from 3 +/- 1 mm Hg to 10 +/- 3 mm Hg), and central venous pressure (from 2 +/- 0.2 mm Hg to 10 +/- 3 mm Hg). The 76% increase in wall thickness after pulmonary artery stenosis was the result of a 24% lateral expansion of cardiac muscle cells and a 44% increase in the number of myocytes across the ventricular wall. The intermyocyte distance was also increased by 22%. These cellular adaptations occurred with no alterations in total myocyte length, average sarcomere length, and volume composition of the myocardium. Ventricular wall area was decreased by 14%, which suggests a small reduction in chamber volume. Myocyte growth was accompanied by proportional expansions of mitochondrial and myofibrillar components, so that the ratio of mitochondria to myofibrils in the cytoplasm remained essentially constant. In conclusion, ventricular remodeling in this model of chronic pressure hypertrophy is characterized by increases in cellular diameter and number that would both tend to decrease the magnitude of systolic and diastolic stresses on a per cell basis and thus improve the myocardial response to a prolonged and sustained mechanical load.

Animals↗

PubMedDate not supplied

Effect of long-term administration of two beta-blocking agents on myocardial structure in spontaneously hypertensive rats.

Two vasodilating beta-blockers, dilevalol and pindolol, were studied for their effects on the development of hypertension and left ventricular hypertrophy in spontaneously hypertensive rats. Dilevalol has agonist activity at beta 2-, whereas pindolol interacts with both beta 1- and beta 2-receptor subtypes. Groups of 7-week old spontaneously hypertensive rats were given dilevalol (30 mg/kg) or pindolol (3 mg/kg) in the drinking water for 3 months. A control group of spontaneously hypertensive rats and age-matched normotensive Wistar Kyoto rats were also used. Systolic blood pressure and heart rate were recorded weekly. Cardiac structural changes were determined by morphometric analysis. Control spontaneously hypertensive rats developed hypertension and left ventricular hypertrophy as compared with normotensive rats. Dilevalol and pindolol prevented the rise in blood pressure, but only dilevalol lowered heart rate. However, neither of the compounds prevented the development of left ventricular hypertrophy, but they differently influenced myocardial structure as measured by the volume fraction of fibrotic tissue in the left ventricle. Dilevalol markedly prevented the amount of fibrosis to a level comparable to that found in normotensive rats, whereas pindolol had a weaker effect. The data suggest that individual pharmacologic characteristics, such as partial agonist activity of each beta-blocker examined, may account for differential effects on the myocardial structure.

Analysis of Variance↗