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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Spontaneously hypertensive rats (SHR) and two strains of normotensive rats were compared with respect to enzymatic activities and calcium accumulation of plasma membrane and endoplasmic reticulum enriched fractions from their mesenteric arteries. Increased specific activities of alkaline phosphatase, 5'-nucleotidase and Mg2+-ATPase, and increased ATP-dependent calcium accumulation were found in 5- to 6-month-old SHR as compared to both strains fo age-matched normotensive rats. Alkaline phosphatase was increased in 33-day-old "early hypertensive" and 3- to 4-month-old SHR, but 5'-nucleotidase, Mg2+-ATPase, and calcium accumulation were not. Hydralazine treatment of young SHR partially prevented the increase of both alkaline phosphatase activity and blood pressure that develops with age. The relationship between alkaline phosphatase activity and the alterations in vascular reactivity associated with hypertension remains to be determined.
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PMID:Relationship between blood pressure of spontaneously hypertensive rats and alterations in membrane properties of mesenteric arteries. 13 88

The left ventricular myocardium of normal and hypertensive rats has been characterized morphometrically in the endocardial and epicardial zones. Compared to the epicardial regions, the normal endocardial regions contain 30 per cent more myocytes, 27 per cent less interstitial space, 48 per cent less capillary volume, 17 per cent less capillary surface, and the same capillary length per unit tissue volume. In terms of both the relative and absolute volumes and surface areas of their organelles, the cytoplasmic composition of normal endocardial and epicardial myocytes is nearly identical. After 14 weeks of hypertension, induced by constriction of the left renal artery, left ventricular weight is increased by 30 per cent, wall thickness by 42 per cent. The number of myocytes and the total length of capillaries remain constant. The epicardial region enlarged 37 per cent with proportional increases of myocyte and interstitial volumes. In contrast, the endocardial enlargement was only 26 per cent, comprised of 21 per cent hypertrophy of myocytes and a 55 per cent increase in interstitial components. Expansion of capillary lumina accounted for much of the interstitial enlargement throughout the myocardium. Hypertrophy of myocytes is 76 per cent greater in the epicardial region and is accompanied by a reduced mitochondria to myofibril ratio and disproportionately large increases (2- to 3-fold) in both smooth endoplasmic reticulum and T-system volume and surface area. On a cellular basis the absolute morphometric characteristics of myocytes from hypertensive rats are significantly different from normal, and significant differences occur between the inner and outer layers of the myocardium for practically every cytoplasmic component.
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PMID:Absolute morphometric study of myocardial hypertrophy in experimental hypertension. II. Ultrastructure of myocytes and interstitium. 14 63

The morphology and permeability to horseradish peroxidase of the rat aortic intima have been investigated in three experimental models of hypertension having different values of plasma renin content and plasma aldosterone level. During hypertension the aortic endothelium shows three main changes: 1) increased arithmetic mean thickness, with prominent rough endoplasmic reticulum and polyribosomes; 2) the appearance of actin microfilament bundles; and 3) increased permeability to horseradish peroxidase. These changes are not present in all models, do not appear to depend on hypertension per se, and are independent of each other. The subendothelial layer of hypertensive animals shows an increased thickness that appears to be correlated with an increase of endothelial cell volume. Our results suggest that: 1) the aortic intima reacts differently to different types of hypertension, and 2) factors other than hypertension per se play a role in the development of vascular changes observed in animals with elevated blood pressure.
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PMID:Morphologic and functional changes of the aortic intima during experimental hypertension. 57 70

The ultrastructure of SHR (Spontaneously Hypertensive Rats) fasciculata cells was compared descriptively and quantitatively with that of nonstimulated fasciculata cells of Wistar rats using sterological methods. The volume and surface densities are expressed per cm3 of cytoplasm. The smooth endoplasmic reticulum in the SHR was significantly increased compared to the control animals (surface density : 28%, volume density: 35%). Mitochondria volume remained unchanged although the inner mitochondrial membranes were significantly reduced (37%). An attempt was made to draw up a relation between sterological and biochemical data of steroid synthesis within the fasciculata cell. A genetically determined enzymatic defect in the early steps of the transformation of cholesterol to pregnenolone may exist at the level of the inner mitochondrial membrane. Whether this altered steroid metabolism is important to the etiology of hypertension in the SHR requires further investigation.
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PMID:A stereological study of adrenocortical cells in spontaneously hypertensive rats (shr). 68 2

Investigation of the behaviour of the renal juxtaglomerular apparatus in 19 patients with malignant hypertension has shown that in kidneys fixed immediately after operation the juxtaglomerular granulation index is twice as high as in autopsy kidneys. The formation of renin by the epitheloid cells begins with the appearance of osmiophilic substances in the region of the endoplasmic reticulum. The first stages of granule formation are small rhomboid particles in the Golgi cisternes, which aggregate to form bigger round or polymorphic granules in the Golgi area. In pathological conditions the substances synthesized may be set free and become active locally as a result of fibrinoid necrosis of the vascular wall. The rate of production is increased firstly by forcing the production of active agents in the preexistent epitheloid cells, secondly by transformation of the so-called bivalent cells and finally, by cell division. In accelerated hypertension the production of renin also takes place in nephrons whose glomeruli, tubules and macula densa, are damaged. There is a correlation between blood pressure elevation and the juxtaglomerular granulation index.
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PMID:The juxtaglomerular apparatus in malignant hypertension of man. 82 80

The response of the intima-media of the thoracic aorta to 1 to 4 weeks of two-kidney renal hypertension in the rat has been analyzed by morphometric techniques at light and electron microscopic levels. The increased thickness of the aorta that ensues is the result of an increase in the size but not the number of smooth muscle cell layers. The volume fractions of intima occupied by endothelium (26%), internal elastic lamina (37%), and subendothelial space (37%) in normotensive animals are not significantly altered by the hypertension. The percent increases in muscle cross-sectional area is greatest (58 to 60%) in the two innermost layers (M1 and M2). M1 is composed of nearly equal compartments of smooth muscle cells and interstitial space that expand 69% and 50%, respectively, with hypertension. Analysis of the subcellular constituents of the M1 smooth muscle cells indicates that significant changes in absolute volume include increases of caveolae (45%), myofibrils (59%), mitochondria (81%), glycogen (163%), and rough endoplasmic reticulum (221%). Factors contributing to these alterations are discussed.
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PMID:Morphometric analysis of hypertension-induced hypertrophy of rat thoracic aorta. 88 10

Electron microscopic studies of interstitial cells (IC) of the renal medulla inspontaneously hypertensive rats (SHR) were carried out. Morphometric analysis revealed no differences in the total volume of the lipid granules of IC in the 1 1/2-month-old SHR and control Wistar rats; one-year-old SHR showed an increased volume of granules, IC of SHR displayed hypertrophy and hyperplasia of both the rough and the smooth endoplasmic reticulum and the Golgi complex, especially marked at the early stage of hypertension. Apparently the state of ultrastructures of the synthesis and secretion should be accepted as a criterion for the assessment of the IC function, at least in arterial hypertension, but not the degree of decreased lipid granularity as supposed formerly.
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PMID:[Interstitial cells of the renal medulla in rats with genetic spontaneous hypertension]. 95 21

Unilaterally nephrectomized rats treated with deoxycorticosterone and 1% sodium chloride in their drinking water developed severe systemic hypertension with marked cardiac and renal lesions. No pathologic changes could be detected in the retinal vasculature by light microscopy, but electron microscopy revealed inconstant alterations in the pericytes of retinal capillaries: these cells showed hyaloplasmic edema, margination of chromatin, dilatation of rough endoplasmic reticulum, and swelling of mitochondria. Injection of lanthanum into control rats confirmed that this 40-A tracer cannot pass the interendothelial tight junctions. In hypertensive animals, however, it penetrated these junctions and could be visualized in capillary basement membranes and between cells of the retina. The results indicate that an increase in permeability is probably the first pathologic change to occur in the retinal capillaries of hypertensive rats.
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PMID:The retinal capillaries of the rat in deoxycorticosterone hypertension. An ultrastructural study with the diffusion tracer lanthanum. 99 22

Cerebral biopsies were obtained for electron microscopy 48 and 72 hours after the onset of encephalopathy from a child with severe Reye's syndrome. Gravely ill at the time of craniectomy to relieve cerebral hypertension, the child survived and recovered good brain function; therefore, the biopsy findings appear to reflect the organelle pathology of the brain at a severe yet reversible stage in the disease process. The cardinal ultrastructural changes in the brain in Reye's syndrome are astrocyte swelling and partial deglycogenation, myelin bleb formation and universal injury of neuron mitochondria. The mitochondrial injury consists of matrix disruption with moderate but not massive swelling. Dilatation of rough endoplasmic reticulum and nuclear changes occurred only in neurons with severely altered mitochondria. The organelle pathology of the brain in this case did not resemble the organelle pathology of the brain in human "hepatic encephalopathy" or in experimental ammonia intoxication in primates. The mitochondrial ultrastructure of the cerebral neurons resembled the unique mitochondrial ultrastructural changes seen in the liver parenchyma in Reye's syndrome.
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PMID:Brain ultrastructure in Reye's syndrome. 117 96

Hypertension was induced in young rats by latex encapsulation of both kidneys. By the fourth week, 85% of the renal-encapsulated (RE) rats became hypertensive. Varying degrees of cardiovascular involvement were evident in the moderately to severely hypertensive rats. The level of systolic blood pressure was directly correlated with the width and the volume of zona glomerulosa of the adrenal cortex. Electron microscopy combined with morphometric-stereologic techniques was employed to quantitate change in the adrenal cortex. The cells of both zona glomerulosa and zona fasciculata of RE rats showed significant increases in the volume of the cell, nucleus, smooth endoplasmic reticulum, and lipid droplets; only in the zona glomerulosa cells was the increase in surface area of the smooth endoplasmic reticulum statistically significant. It is suggested that these structural changes associated with renal-encapsulation hypertension are related at least in part to stress of the hypertensive cardiovascular disease.
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PMID:Quantitative ultrastructural study of the rat adrenal cortex in renal encapsulation-induced hypertension. 124 82


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