Biomedical subjects

G Olivetti

Publications and source records attributed to G Olivetti.

At least 109 records · Page 6Linked to original sources

PubMed1987

Effects of exercise on the capillary vasculature of the rat heart.

Effects on the myocardium, particularly those structural properties of the capillary network relevant to tissue oxygenation, were studied morphometrically in rats subjected to moderate exercise, strenuous exercise, and strenuous exercise preceded by a preconditioning period of moderate exercise. These different modalities of exercise were used to test the hypothesis that endurance training leads to capillary proliferation in the heart. The findings indicate that treadmill running produces right ventricular hypertrophy exclusively, which is accompanied by lengthening of the myocytes. Furthermore, a moderate running program results in an increase in the numerical density, luminal surface, and total length of capillaries in the right ventricle. In contrast, strenuous exercise with or without a preconditioning period produces a relative decrease in capillary luminal volume, surface, and numerical density. In the former case the diffusion distance for oxygen is decreased and in the latter it is increased. These data suggest that moderate exercise affects the microvasculature in ways that improve the efficiency of tissue oxygenation in the myocardium, whereas strenuous exercise has the opposite effect.

Adaptation, Physiological↗

PubMed1986

Quantitative structural analysis of the myocardium during physiologic growth and induced cardiac hypertrophy: a review.

The quantitative structural properties of the ventricular myocardium during postnatal physiologic growth are compared with those accompanying an increased load in the adult rat heart to determine whether induced cardiac hypertrophy is a pathologic condition or simply a form of well compensated accelerated growth. The expansion of the ventricular myocardium during maturation shows a remarkable degree of well balanced compensatory response, because the capillary microvasculature, parenchymal cells and subcellular components of myocytes all grow in proportion to the increase in cardiac mass. In contrast, the increases in myocyte diameter and length caused by pressure hypertrophy, volume hypertrophy and infarction-induced hypertrophy are consistent with concentric, eccentric and a combination of concentric and eccentric hypertrophic growth of the whole ventricle, respectively. These cellular shape changes may represent a compensatory response of the myocardium at the cellular level of organization that tends to minimize the effects of an increased pressure or volume load, or both, on the heart. Cardiac hypertrophy, however, may also show alterations affecting capillary luminal volume and surface and the mitochondrial to myofibril volume ratio, which indicate an inadequate growth adaptation of the component structures responsible for tissue oxygenation and energy production. Thus, hypertrophy of the adult heart differs from that during physiologic growth, and the hypertrophied myocardium may exhibit structural abnormalities that can be expected to increase its vulnerability to ischemia.

Blood Pressure↗

PubMed1986

Myocyte cell loss and myocyte hypertrophy in the aging rat heart.

To determine the effects of age on the myocardium, the functional and structural characteristics of the heart were studied in rats at 3, 10 to 12 and 19 to 21 months of age. Systemic arterial pressure, left ventricular pressure and its first derivative (dP/dt) and heart rate were comparable in the three animal groups. In the interval between 3 and 10 to 12 months, mean myocyte cell volume per nucleus increased 53 and 26% in the left and the right ventricle, respectively. The total number of myocyte nuclei remained constant in either ventricle. In the following period, between 10 to 12 and 19 to 21 months, a 39% further cellular hypertrophy on the left side of the heart was found in association with an 18% loss of cells in the ventricle. Cell loss was accompanied by discrete areas of interstitial and replacement fibrosis in the subendocardium. In contrast, no myocardial damage was observed in the right ventricle, and the measured 35% additional enlargement of myocytes occurred without a change in cell number. Thus, the aging left ventricle is composed of a smaller number of hypertrophied cells. Cellular hypertrophy may explain the unaltered cardiac function of the aged myocardium.

Aging↗

PubMed1986

Myocardial infarction in rats. Infarct size, myocyte hypertrophy, and capillary growth.

To determine the compensatory reserve capacity of the ventricular myocardium following infarction, the left coronary artery in rats was ligated, and the animals were killed 40 days later. Infarcts affecting an average 23% of the left ventricle were characterized by a 27% hypertrophic growth of the remaining myocardium that produced a complete replacement of the necrotic tissue. In contrast, infarcts with an average 50% loss of mass resulted in 83% expansion of the spared myocardium that was inadequate for a complete restoration of ventricular tissue. Myocyte hypertrophy was 26% and 78% in small and large infarcts, respectively. Cellular hypertrophy in both cases involved significant increases in myocyte transverse area and myocyte length. After large infarcts, there was an 18% reduction in capillary surface and a 16% increase in the diffusion distance. Corresponding values for small infarcts were -10% and 9%. These alterations combined with the deficient reconstitution of myocardial mass following large infarcts resulted in 25%, 29%, and 30% deficits in the absolute amounts of capillary lumen, surface, and length per ventricle respectively. Even with small infarcts, a deficit was seen in capillary luminal surface (-16%), and length (-19%). In conclusion, we have demonstrated that cardiac hypertrophy following myocardial infarction is consistent with cellular shape changes characteristic of a combination of concentric and eccentric hypertrophic growth. However, cardiac muscle cells appear to be unable to compensate for the loss of mass induced by a 50% infarct. The inadequate adaptation of the capillary vasculature in the infarcted hearts suggests that the injured ventricle is more vulnerable to additional ischemic episodes.

Animals↗

PubMed1986

Response of the border zone to myocardial infarction in rats.

The response of the surviving myocardium 30 days after coronary artery occlusion was measured morphometrically in the regions bordering and remote from infarcts of different sizes. Mean cell volume per nucleus increased with infarct size in both zones, but the rate of change was greater in the border than in the remote portion of the unaffected myocardium. Capillary numerical density within the uninjured tissue progressively decreased with infarct size leading to an increased diffusion distance for oxygen. Although the magnitude of changes in capillary density was similar in the two regions of the ventricle, the analysis of the individual values in each heart showed that in infarcts comprising more than 11% of the ventricular wall capillary concentration and the path length for oxygen supply to the myocytes were affected more in the border zone than in the myocardium remote from the scar. In conclusion, the border zone participates in the hypertrophic recovery process after infarction, but the inadequate growth of the capillary microvasculature suggests that this region is more susceptible to additional ischemic episodes.

Animals↗

PubMed1985

Effects of strenuous exercise on the quantitative morphology of left ventricular myocardium in the rat.

The 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.

Animals↗

PubMed1985

Morphometry of superficial glomeruli in acute hypertension in the rat.

Pressor doses of angiotensin II (AII) were infused intravenously in Munich-Wistar rats to study the effects of acute hypertension on the structural components of the superficial renal corpuscles and urinary protein excretion. All administration raises arterial blood pressure by 38% and increases 13-fold the normal rate of urinary excretion of proteins that contain albumin and IgG. Morphometric analysis of the quantitative characteristics of the glomerular capillaries reveals a 24% increase in the mean cross-sectional area of the capillary profiles and a 33% expansion of the capillary luminal volume. The amount of extracellular material present in the mesangium is also increased by 76%. The surface area of basement membrane available for ultrafiltration remains constant. However, the length density and the total length of the filtration slit diaphragms are reduced by 35 and 24%, respectively. Thus, the major findings of this investigation are as follows: The presence of IgG in the urine suggests a size defect in the glomerular filter with AII-induced hypertension; the dilatation of capillary loops may result in mechanical stretching of the basement membrane, altering the size-selective properties of the glomerular filter in acute hypertension; and the reduced pore area of the filtration slit diaphragms implies a lower hydraulic conductivity of the glomerular filter that may be responsible for the decreased glomerular capillary ultrafiltration coefficient present in this model of hypertension.

Acute Disease↗

PubMed1985

Myocardial response to infarction in the rat. Morphometric measurement of infarct size and myocyte cellular hypertrophy.

For determination of the effects of myocardial infarction on the recovery potential of muscle mass in the surviving tissue, ligation of the left coronary artery was performed in 3-month-old rats, and the infarcted ventricles were analyzed morphometrically a month after surgery. Comparisons were made with 4-month-old control rats that underwent sham operations and with 3-month-old control rats that were not operated upon for evaluation of the magnitude of infarct size and discrimination of the relative contribution of tissue growth that occurred in the surviving myocardium solely as a result of the change in age, from 3 to 4 months (postoperative tissue growth, or POTG), from the additional growth induced by infarction (hypertrophic growth, or HG). Coronary occlusion induced a 276-cu mm loss of ventricular tissue volume that corresponded to 43% of the total left ventricular mass, 648 cu mm. Over a 30-day period the remaining 372 cu mm of viable tissue expanded by 90% with an overall volume gain of 334 cu mm. This tissue augmentation consisted of 20% POTG, 67 cu mm, and 80% HG, 267 cu mm. Total myocyte volume increased 89%, from 302 cu mm to 571 cu mm, and average myocyte cell volume per nucleus increased 92%, from 16,500 cu mu to 31,600 cu mu. The expansion of the myocyte mass was the result of a 21% POTG and a 79% HG. Corresponding values for the myocyte population were 19% and 81%.

Age Factors↗

PubMed1984

Characterization of glomerular permeability and proteinuria in acute hypertension in the rat.

The effects of acute angiotensin II (AII) induced hypertension on renal hemodynamics, urinary excretory rates, and clearances of endogenous proteins, together with colloidal iron staining and numerical density of differently charged ferritins in glomerular basement membrane (GBM) have been studied. AII decreases para-aminohippurate clearance (63%) more than glomerular filtration rate (GFR) (42%), resulting in an increased filtration fraction (54%). Simultaneously, large increments in the excretory rates and clearances of albumin and IgG2a occur. The number of native ferritin particles per unit volume of GBM and its different layers increases significantly in both superficial and juxtamedullary glomeruli as a result of acute hypertension. In contrast, the number of cationized ferritin particles per unit volume of GBM as well as colloidal iron staining of GBM and adjacent cell membranes remain unchanged, irrespective of AII treatment. The results demonstrate that acute AII-induced hypertension enhances glomerular permeability to proteins of different size and shape in the absence of detectable alterations in the fixed negative charges of the GBM. Since both RBF and GFR are decreased, the increased transglomerular passage of proteins in acute hypertension appears to be due to an increase in the pore size of the glomerular filter, induced possibly by either high intracapillary pressure and/or a direct action of AII on GBM constituents.

Acute Disease↗

PubMed1984

Structural compensatory mechanisms in rat heart in early spontaneous hypertension.

The response of the left ventricle (LV) during the development of spontaneous hypertension (SH) in rats was studied morphometrically at 21, 28, 35, and 45 days after birth and compared with that of normotensive (WK) controls. LV hypertrophy, varying from 24 to 27%, was characterized by the preservation of the volume fraction of capillary lumen and capillary luminal surface in the myocardium, as a result of capillary proliferation. From 21 to 45 days the number of capillaries per unit area of myocardium increased 68% in SH rats by the insertion in parallel of new capillary elements among the myocytes. This estimation was obtained by correcting the value of capillary density at 45 days for the amount of spreading produced by myocyte growth during this interval. On a similar basis capillary proliferation was only 24% in WK rats. Myocyte growth in experimental animals (151%) was achieved by a 77% enlargement in myocyte cross-sectional area (MCSA) and by a 42% lengthening of the cells. In controls myocyte expansion (124%) was the result of comparable increments in MCSA (47%) and myocyte length (53%).

Aging↗

PubMed1984

Morphometry of right ventricular hypertrophy induced by myocardial infarction in the rat.

The 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 mu in control animals to 21,500 cu mu 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.

Animals↗

PubMed1984

Glomerular permeability in acute hypertension.

Acute hypertension induced by intravenous infusion of angiotensin II (AII) leads to enhanced transglomerular passage of albumin and IgG, as demonstrated by electronmicroscopic immunoperoxidase techniques. Although no morphological damage of the capillary wall was detected, significant amounts of macromolecules were present in the mesangial region. On a functional basis, a 42% decrease in glomerular filtration rate and a 63% decline in p-aminohippurate clearance were seen, resulting in a 54% increase in the filtration fraction. Quantitative measurements of albumin and IgG2a clearances showed a 90- and 15-fold increase, respectively. Similarly, the concentration of native ferritin particles in the glomerular basement membrane (GBM) increased 11-fold. On the other hand, the number of cationized ferritin particles and the staining properties of GBM to colloidal iron were not altered. These observations indicate that acute AII-induced hypertension affects glomerular permeability to proteins of different size and shape, possibly by increasing the pore size of the glomerular filter by either high intracapillary pressure and/or a direct action of AII on GBM constituents.

Albumins↗

PubMed1984

Morphometry of right and left ventricular myocardium after strenuous exercise in preconditioned rats.

Young male rats were exposed to a biphasic training program in which a 7-week preconditioning period of moderate treadmill exercise was followed by 8 weeks of strenuous endurance running. In comparison with sedentary control animals, the trained rats at 20 weeks of age had developed myocardial hypertrophy of the right ventricle (20%) and interventricular septum (23%), but there was no difference in the weight of the left ventricular free wall. Myocyte hypertrophy (26%) in the right ventricle was achieved through an increase in mean cell length (24%) and the addition of new sarcomere units in series. Exercise induced no acceleration of capillary growth in either ventricle, leading to significant decreases in the capillary luminal volume density (-21%) and surface density (-16%) in the right ventricle. Such alterations in the structural properties of the microvasculature implicated in oxygen availability and diffusion suggest that vigorous exercise, even after a preconditioning period, may still be detrimental to the myocardium. The techniques of myocardial morphometry were examined with respect to potential errors associated with oblique tissue sections and the use of light versus electron microscopy for cell counting. It was shown that the practical effects of obliquity are negligible and that electron microscopic resolution is essential.

Animals↗

PubMed1983

[Immunodiffusion of non-histone chromosomal proteins from human skin tumors].

A previously unpublished reaction of precipitation in agarose between histone and non-histone proteins extracted in saline buffer from nuclei of human skin tumors, is reported. Two bands of precipitation similar to those in an immunodiffusion reaction between NHP and specific antisera, were observed. The reaction described is very similar to the affinodiffusion reaction of glycoproteins and lectins in agarose.

Agar↗

PubMed1983

Morphometric measurement of cellular hypertrophy.

This study is a comparison of two morphometric methods for measuring mean cellular hypertrophy. One method, based on the relatively simple point-counting technique used to determine nuclear to cytoplasmic ratios, measures increases in mean cell volume per nuclear volume. The second method, involving nuclear profile counting in tissue sections of different known thicknesses, evaluates the increase in mean cell volume per nucleus. The latter method is considered more accurate because of the significantly greater amount of tissue sampling utilized. Furthermore, cellular hypertrophy is better defined by the increase in cell size per nucleus than by a change in the cell to nucleus volume ratio, values that can be numerically equal only if mean nuclear volume remains constant. Thus, comparison of these methods is a way to evaluate either the reliability of the point-counting technique or the equivalent hypothesis that mean nuclear volumes do not vary significantly during periods of growth. Cellular hypertrophy has been measured in 18 examples of normal tissue growth and 18 examples of induced growth. Five cell types are included: cardiac myocytes, aortic smooth muscle cells, capillary endothelium, and glomerular mesangial and epithelial cells. Little agreement was found between the two methods of measurement. Mean nuclear hypertrophy varied widely and unpredictably, more than +/- 20% in the majority of cell populations. It is concluded that the point-counting method alone is unreliable as a quantitative measure of cellular hypertrophy.

Animals↗

PubMed1982

Quantitative structural changes of the rat thoracic aorta in early spontaneous hypertension. Tissue composition, and hypertrophy and hyperplasia of smooth muscle cells.

The thoracic aorta of 21-, 28-, 35-, and 45-day-old spontaneously hypertensive (SH) and Wistar Kyoto (WK) rats was analyzed morphometrically to evaluate the cellular hypertrophy and proliferation of medial smooth muscle cells during the development of genetically determined hypertension. The absolute increase in volume of collagen and ground substance, and elastic tissue was also measured. In SH animals, cellular hypertrophy was found to be the dominant mechanism of muscle growth in the 21- to 28-day and 35- to 45-day intervals, resulting in an overall 68% enlargement of the mean cell volume from 21 to 45 days. The total number of smooth muscle cells increased only 21% (not statistically significant) and the tendency toward hyperplasia was restricted to the 28- to 35-day period. Normotensive controls showed cell proliferation mainly from 21 to 28 days and cellular hypertrophy from 35 to 45 days with an absolute 33% increase in the number of cells and a 26% larger volume of the mean smooth muscle cell at 45 days of age. from 21 to 45 days, the above changes in cell size and number provoked an overall 104% and 67% growth of the muscle mass in SH and WK rats, respectively. The initial response phase of spontaneous hypertension was also characterized by an increase of collagen and ground substance, 184%, which was slightly greater than that of the elastic component, 168%. Changes in mural concentration of fibrous proteins that were similar to but of less magnitude than those of controls, were seen. These results demonstrate that short-term spontaneous hypertension determines a simultaneous growth adaptation in every component structure of the media of the thoracic aorta leading to a disproportionate accumulation of scleroproteins that markedly exceeds that of the contractile component of the vessel wall. At a cellular level, smooth muscle cell hypertrophy is the prevailing process that underlies the tissue response of the aorta in early hypertension.

Aging↗

PubMed1981

Postnatal development of the M-band in rat cardiac myofibrils.

Cardiac muscle fibers in rats at 1 and 5 days after birth showed little evidence of M-bands. An ultrastructural analysis of myofibrils failed to demonstrate dense M-band material in longitudinal sections or M-bridges in transverse sections of sarcomeres. M-bands began to increase in number after 5 days of postnatal life and were present in 60% of all sarcomeres at 11 days of age. Polypeptides with molecular weights of 190,000 (Ma) and 175,000 (Mb) were obtained by polyacrylamide-sodium dodecyl sulfate (SDS) gel electrophoresis of myofibril preparations. These two proteins were found in both 1- and 11-day-old rats and were considered to be specific components of the M-band. The densitometric analysis demonstrated that Ma and mb polypeptides increased approximately 2-fold during the interval from 1 to 11 days after birth. These structural and biochemical changes of the M-band material in myocytes appear to be related to the maturation of contractile function in the young heart.

Animals↗

PubMed1981

Glomerular permeability to endogenous proteins in the rat: effects of acute hypertension.

The distribution of endogenous albumin and immunoglobulin G (IgG) has been studied by the immunoperoxidase technique in the superficial glomeruli of both normotensive and hypertensive (acute angiotensin II-induced) Munich-Wistar rats. Endogenous IgG has also been detected in rats immunized with horseradish peroxidase. Labeled antibodies have been applied to sections on a conventional manner as well as by an electrophoretic technique. The immunization of animals with horseradish peroxidase, as well as application of the electrophoretic technique, both result in a greater yield of labeled glomeruli. Albumin is present within the capillary lumina of control animals, penetrates the capillary walls, and extends into the urinary space. Endogenous IgG is mainly confined to lumina of glomerular capillaries, with only small amounts visible in the laminae rarae of the basement membrane. After acute hypertension induced by angiotensin II, there is increased staining of albumin and IgG in the basement membrane and of albumin in the urinary space. There is also penetration of IgG into Bowman's space. Both macromolecules are found in dilated mesangial channels. These modifications of glomerular permselectivity in hypertension are not accompanied by discernible ultrastructural changes in the peripheral capillary wall. It is suggested that the transcapillary passage of albumin and IgG is dependent upon hemodynamic factors and/or subtle changes in the filtering membrane.

Animals↗