Smooth Muscle Cell Nuclei Research Articles

Polyploid nuclei in human artery wall smooth muscle cells.

Although polyploid nuclei have long been known to be present in many adult human tissues, the ploidy of smooth muscle cells in human artery wall has never been determined. We measured DNA content in individual smooth muscle cell nuclei of artery wall specimens by two means: Feulgen microdensitometry and flow microfluorimetry. A significant percentage of nuclei were polyploid; most of these were tetraploid, although higher levels were also found. The frequency of polyploidy varied with age from less than 1% at birth to a mean of 7% in adult aortic, carotid, and iliac vessels. Atherosclerotic plaques had a lower tetraploid content than the underlying media, whereas normal intima was similar to the corresponding media. The increase in frequency of hyperploid smooth muscle cell nuclei correlates with the normal growth, development, and aging of human artery wall. We suggest that the regular existence of a subset of polyploid smooth muscle cells may indicate an important functional role for this phenotype.

Quantitative morphology of arterioles from the hamster cheek pouch related to mechanical analysis

The structure of 20 second-order arterioles from the hamster cheek pouch was quantitated after histological fixation at physiological pressures. Dilated and contracted vessels with respective internal diameters of 66 ± 9.2 and 30 ± 9.1 μm (SD) were studied. Electron microscopy of four dialted arterioles revealed a combined intima-media thickness of 3.2 ± 1.5 μm with the following composition determined by stereological point counting: endothelial cells (20%), endothelial basement membrane (3%), a continuous elastic lamina (8%), smooth muscle cells (49%), and medial extracellular space (20%). Light microscopy of whole mounts of cheek pouches and isolated arterioles stained with hematoxylin was used to measure orientation and lengths of both smooth muscle and endothelial cell nuclei. The smooth muscle orientation was not significantly different in dilated or contracted arterioles. For all of the muscle orientation measurements combined, the mean pitch angle was 1.1 ± 5.9° ( N = 1000) with respect to the circumferential axis of the vessel. Comparison of dilated and contracted arterioles indicated a significant decrease in the muscle cell and nuclear length, but no detectable change in either orientation or nuclear length of the longitudinally oriented endothelial cells. Wall areas measured from transverse sections of dilated and contracted vessels did not change upon contraction. Stereological estimates of relaxed smooth muscle cell length averaged approximately 60 μm. The manner in which structural parameters affect arteriolar mechanical properties is discussed, and it is concluded that, in hamster pouch arterioles, over 99% of the developed smooth muscle force is transmitted circumferentially.

A study of rat intracerebral arterioles: methods, morphology, and reactivity.

Penetrating, intracerebral arterioles from rat were isolated, cannulated, and studied in vitro. Vessel wall elements were found to consist of an endothelial cell layer, one smooth muscle cell layer, and a thin adventitial layer or leptomeningeal sheath. Smooth muscle cell nuclei were oriented perpendicular to the vessel's longitudinal axis; endothelial cell nuclei were parallel to the axis. Mean vessel diameter with the smooth muscle inactivated (passive diameter) was 36.7 +/- 1.6 (SE) micrometer. Spontaneous smooth muscle tone developed at 37 degrees C and reduced vessel diameter to 70 +/- 4% of passive diameter. Vessels were activated by the extraluminal application of 140 mM KCl solution at pH 8.00, which produced a transient contraction that decayed within 30 s to a steady contraction of somewhat less intensity. Changes in intravascular pressure were used to alter wall tension of the vessels. Tension in the vessel wall was computed, and length-tension curves for the arteriolar smooth muscle were approximated. Length-tension relationships similar to those seen in other smooth-muscle preparations were found with maximal estimated force development of 1.29 x 10(-5) N . m-2. Alterations of bath pH caused changes in vessel diameter that were inversely related to extraluminal pH and varied by approximately 77% in the range from pH 6.85 to 8.00. Adenosine dilated vessels to 140 +/- 6% of control diameter at a concentration of 10(-5) M. The mechanical characteristics and the reactivity to H+, K+, and adenosine of these vessels were quantitatively consistent with in vitro data from larger cerebral vessels and in vivo data from pial arteries.

Morphometric investigation of hypertrophy in the arteries of DOCA-hypertensive rats.

The increase in peripheral resistance of the vascular bed in hypertension has been attributed to adaptive hypertrophy of the media or a so-called contracture of the arterial wall due to altered reactivity of smooth muscle cells. We have measured medial cross-sectional area, numbers of smooth muscle cell nuclei and the relative proportions of scleroproteins present in the media in hypertensive rats. The results show that hyperplasia of smooth muscle cells and an increase in medial area occur in hypertension, a change most marked in the peripheral branches of the renal artery.

Feulgen-deoxyribonucleic acid analysis of rabbit aortic smooth muscle cells using scanning- integrating microdensitometry.

A procedure entailing the use of the Feulgen reaction is described for precise quantification of nuclear DNA levels in smooth muscle cells (SMC) of paraffin-processed microtome sections of the rabbit aorta. It was established that maximal, stable, and reproducible Feulgen-DNA (F-DNA) staining of SMC nuclei is achieved using 3.5 N HCl hydrolysis of 30-50 min prior to staining of aortic sections in Schiff reagent for 60 min at 22 degrees C. Scanning-integrating microdensitometry of Feulgen-stained SMC revealed that the tunica media is comprised of a relatively homogeneous population of cells with between 0.3 and 1% of the SMC nuclei yielding 3C or 4C (tetraploid) F-DNA levels, depending on location within the aortic wall. The nuclear chromatin in inner medial SMC was found to be in a more dispersed state than that of outer SMC (using nuclear area and nuclear susceptibility to acid hydrolysis as indices of chromatin dispersion). A linear correspondence was evidenced between nuclear area and nuclear F-DNA stainability throughout the tunica media. The observation that the lumenal portion of the tunica media contains a greater abundance of SMC with large, vesicular nuclei is interpreted as reflecting a greater metabolic reactivity of this compartment relative to that of SMC bordering the tunica adventitia.

Hormone receptors of the baboon cardiovascular system. Biochemical characterization of aortic cytoplasmic androgen receptors.

Cytoplasmic androgen receptors were identified in the aorta of the baboon (Papio sp.). Using the synthetic androgen R1881 (17 beta-hydroxy-17 alpha-methyl-estra-4,9,11-trien-3-one) as probe, androgen receptors were demonstrated only when the incubation mixtures contained 1.0 microM triamcinolone acetonide (TA). The relative binding affinity of selected steroids for the aortic androgen receptor was R1881, 100%; 5 alpha-dihydrotestosterone, 46.1%; testosterone, 60.7% progesterone, 9.1%; R5020, 3.1%; and estradiol-17 beta, 7.5%. THe androgen receptor migrated on low-ionic-strength linear sucrose density gradients as a macromolecule with a sedimentation coefficient of 8.0S. Saturation analysis performed at 2 degrees C (available sites) showed that the androgen receptor content a baboon aortic cytoplasmic extracts was 12.9 +/- 2.4 fmoles/mg protein and that the dissociation constant for R1881 was 1.47 +/- 0.07 nM. The observation that TA was required in the cytoplasmic extracts in order to identify androgen receptors indicates the presence of progesterone receptor-like binding components. These aortic cytoplasmic androgen receptors are indicated to be physiologically functional by previous autoradiographic studies that showed localization of radioisotope in the nuclei of aortic smooth muscle cells following injection of baboons with 5 alpha-dihydrotestosterone.

EXPERIMENTAL STUDIES ON HYPERTENSIVE CEREBRAL ARTERIAL LESIONS, ESPECIALLY ON THE HEALING OF MEDIAL SMOOTH MUSCLE CELL NECROSIS AS THEIR EARLIEST LESION

It is thought that the morphogenesis of plasmatic arterionecrosis as the direct cause of hypertensive intracerebral hemorrhage is initiated by medial smooth muscle necrosis, and hypertension is believed to be the cause of medial smooth muscle cell necrosis.Hypertension in rats with bilaterally constricted renal arteries can be normalized by removing the constricting clips from the renal arteries. Using this method, healing process of hypertensive medial smooth muscle cell necrosis in proximal and distal segments, especially in the former of the middle cerebral arteries was studied by light and electron microscopy.After the removal of clips in hypertensive rats with severe systolic hypertension over 200 mm Hg, blood pressure dropped remarkably. In these rats, mortality and incidence of brain lesions such as softening, edema and bleeding decreased compared with the same aged hypertensive rats.Electron microscopy showed that in the media of the proximal middle cerebral arteries, occurrence and progression of smooth muscle cell necrosis were suppressed and cell debris which had increased in the media of hypertensive rats diminished after the removal of clips. Basement membrane-like substances and collagen fibers were slightly increased in the medial extracellular space which decreased in width. The ratio of the total area of the media occupied by smooth muscle cells to the whole medial area became larger after the removal of clips as compared with that of hypertensive rats not only just before the removal of clips but also in the same experimental period.On the other hand, autoradiographic study revealed that no 3H-thymidine was incorporated into the nuclei of medial smooth muscle cells at any time till 21 days after the removal of clips.These facts indicate that total smooth muscle cell dimension in the media increased due to hypertrophy of the medial smooth muscle cells after the removal of clips.Thickness of the media of the proximal segments of the middle cerebral arteries was measured by Suwa's method. There was on difference in the thickness of the media of the animals with the constricted renal arteries between before and 4 weeks after the removal of clips from the arteries. But the thickness of the media in these animals was thicker than that of normotensive rats.Reaction products of intravenously injected horseradish peroxidase were seen in the vesicles of endothelial cells, but massive insudation of them by junctional transport into the subendothelial space was not observed before and after the removal of the clips. lt was the same in the untreated normotensive rats. So it can be said that increased vascular permeability did not play any role both in the occurrence and healing of the smooth muscle cell necrosis in this experimental study.In conclusion, necrosis of the medial smooth muscle cells in th cerebral arteries, considered to be a trigger for the development of plasmatic arterionecrosis in hypertensive patients may be healed with hypertrophy of the remained medial muscle cells after normalization of high blood pressure.

Electron microscopy of pulmonary vasculature after application of fulvine.

<b>Wagenvoort, C. A., Dingemans, K. P., and Lotgering, G. G. (1974).</b><i>Thorax</i>, <b>29</b>, 511-521. <b>Electron microscopy of pulmonary vasculature after application of fulvine.</b> This is an electron microscopic study of the effect of fulvine on the pulmonary arteries and veins of the rat. Marked constriction of the arteries was evident from excessive crenation of the internal elastic membrane, resulting in squeezing of nuclei of both smooth muscle cells and endothelial cells between the folds on either side of this lamina. Four weeks after fulvine administration fibrin deposits were found in the arterial media followed by necrosis of muscle cells. In the adventitia there was a new development of smooth muscle fibres, probably derived from fibroblasts. In pulmonary veins and venules there was also constriction and hyperplasia of smooth muscle. The muscle cells showed pronounced cytoplasmic excrescences protruding into the endothelial layer. This probably reflects constriction of the muscle cells. As in the arteries, fibrin deposits and necrosis of muscle cells were observed from the fourth week onward.