The three-dimensional architecture of the elastic-fiber network in canine hepatic portal system

The architectural arrangement of the elastic-fiber network in the wall of canine hepatic portal veins was observed with the scanning electron microscope (SEM). Selective NaOH sonication digestion and autoclaving were used to expose and isolate the networks of elastic fibers from six selected regions of the hepatic portal vessels from seven healthy dogs. Elastic stains of adjacent segments prepared for light microscopy demonstrated that the elastic fibers were concentrated in two areas within the intact portal wall. The innermost area corresponded to the internal elastic lamina (IEL) of the tunica intima, the internal muscular layer, and the connective tissue layer of the tunica media. The second area was in the tunica adventitia. SEM specimens revealed two sleeves of elastic fiber networks which corresponded to the above regions. Small scattered bundles of radially oriented elastic fibers spanned the gap between the two sleeves. Each tunica had a different architectural arrangement of elastic fibers. The IEL had circumferentially oriented fibers which branched and anastomosed to form a continuous network on the innermost surface. The architecture of the IEL was the most variable between the different regions. The network of the IEL was the most "open" in the caudal region (splenic vein) and became "denser" toward the liver. The large elastic fibers in the tunica media were oriented at approximately right angles to the primary fibers of the IEL. These longitudinally oriented fibers anastomosed with adjacent longitudinal fibers to form a continuous network. In the tunica adventitia, thick, longitudinally oriented fibers of the continuous network fused together to form incomplete layers of fibers. The architecture of the elastic-fiber network in the canine hepatic portal vein was compared to that previously described in the systemic canine saphenous vein.     

Electron microscopic structure and innervation of the carotid baroreceptor region in the rock hyrax (Procavia capensis).

Semi-thin plastic sections reveal that the carotid baroreceptor region in the rock hyrax comprising the origin of the internal carotid artery has a preponderantly elastic structure and a thick tunica adventitia. In contrast, the common carotid artery has a musculoelastic structure, whereas the cranial segment of the internal carotid artery (immediately distal to the baroreceptor areas) shows the features of a muscular artery. Electron microscopy discloses the presence of sensory nerve endings within the parts of the tunica adventitia adjoining the preponderantly elastic zone of the internal carotid artery. These nerve endings are characterized by varicose regions containing a large quantity of mitochondria. Bundles of collagen fibers in the tunica adventitia form convolutions or whorls around the nerve terminals and often terminate on the surface of the elastic fibers or into the basement membranes of the neuronal profiles. The large content of elastic tissue in the tunica media of the baroreceptor region may render the vessel wall highly distensible to intraluminal pressure changes. This, in turn, would facilitate the transmission of the stimulus intensity to the sensory nerve terminals located in the tunica adventitia. It is suggested that the stretching of elastic fibers may form the main mechanical event leading to the distortion of the associated nerve terminals. However, a change in the geometrical configuration of the bundles of collagen under the influence of the elastic fibers may provide a better insight into the mechanisms of distortion of the baroreceptors related to and/or in contact with collagen fibers.     

Postnatal alterations in elastic fiber organization precede resistance artery narrowing in SHR

Resistance artery narrowing and stiffening are key elements in the pathogenesis of essential hypertension, but their origin is not completely understood. In mesenteric resistance arteries (MRA) from spontaneously hypertensive rats (SHR), we have shown that inward remodeling is associated with abnormal elastic fiber organization, leading to smaller fenestrae in the internal elastic lamina. Our current aim is to determine whether this alteration is an early event that precedes vessel narrowing, or if elastic fiber reorganization in SHR arteries occurs because of the remodeling process itself. Using MRA from 10-day-old, 30-day-old, and 6-mo-old SHR and normotensive Wistar Kyoto rats, we investigated the time course of the development of structural and mechanical alterations (pressure myography), elastic fiber organization (confocal microscopy), and amount of elastin (radioimmunoassay for desmosine) and collagen (picrosirius red). SHR MRA had an impairment of fenestrae enlargement during the first month of life. In 30-day-old SHR, smaller fenestrae and more packed elastic fibers in the internal elastic lamina were paralleled by increased wall stiffness. Collagen and elastin levels were unaltered at this age. MRA from 6-mo-old SHR also had smaller fenestrae and a denser network of adventitial elastic fibers, accompanied by increased collagen content and vessel narrowing. At this age, elastase digestion was less effective in SHR MRA, suggesting a lower susceptibility of elastic fibers to enzymatic degradation. These data suggest that abnormal elastic fiber deposition in SHR increases resistance artery stiffness at an early age, which might participate in vessel narrowing later in life.     

Interstitial flow through the internal elastic lamina affects shear stress on arterial smooth muscle cells

Interstitial flow through the tunica media of an artery wall in the presence of the internal elastic lamina (IEL), which separates it from the subendothelial intima, has been studied numerically. A two-dimensional analysis applying the Brinkman model as the governing equation for the porous media flow field was performed. In the numerical simulation, the IEL was modeled as an impermeable barrier to water flux, except for the fenestral pores, which were uniformly distributed over the IEL. The tunica media was modeled as a heterogeneous medium composed of a periodic array of cylindrical smooth muscle cells (SMCs) embedded in a fiber matrix simulating the interstitial proteoglycan and collagen fibers. A series of calculations was conducted by varying the physical parameters describing the problem: the area fraction of the fenestral pore (0. 001-0.036), the diameter of the fenestral pore (0.4-4.0 microm), and the distance between the IEL and the nearest SMC (0.2-0.8 microm). The results indicate that the value of the average shear stress around the circumference of the SMC in the immediate vicinity of the fenestral pore could be as much as 100 times greater than that around an SMC in the fully developed interstitial flow region away from the IEL. These high shear stresses can affect SMC physiological function.     

Elastic fibers in the anulus fibrosus of the dog intervertebral disc

A light microscopic investigation of the anulus fibrosus in cervical intervertebral discs of the dog was conducted to ascertain the arrangement and distribution of elastic fibers. Elastic fibers were observed in all lamellae of the anulus fibrosus. However, collagenous fibers were the predominant type of connective tissue fiber, and elastic fibers were randomly dispersed among them. Intralamellar (collagenous and elastic) fibers were vertically and obliquely oriented in both superficial and deep lamellae of the anulus fibrosus. All intralamellar fibers were densely and regularly arranged in superficial lamellae, but they were more loosely organized in deep lamellae. A narrow border of interlamellar, elastic fibers was observed between broader, contiguous lamellae in the superficial zone of the anulus fibrosus. Interlamellar elastic fibers wer vertically and obliquely arranged in superficial lamellae; however, they were radially oriented in deep lamellae. The deepest lamella of the anulus fibrosus consisted of a loose, three-dimensional network of intermeshing collagenous and elastic fibers. These observations suggest that elastic fibers are integral components of the articular and shock absorption mechanisms of the anulus fibrosus, and the cervical intervertebral disc of the dog is a suitable model for experimental investigation of the role of elastic fibers in intervertebral disc herniation.     

Microscopic studies on the transition between the sigmoid sinus, the superior bulb of the jugular vein and the first portion of the internal jugular vein

The author studied the structure of the tissue components of the tunicae of the terminal segment of the sigmoid sinus, particularly at the level of the transition between the sigmoid sinus, the superior bulb of the jugular vein and the first portion of the human internal jugular vein; it was established that the transition between the sigmoid sinus and the first portion of the internal jugular vein occupies the whole extension of the superior bulb of the jugular vein up to the inferior third of the first portion of this vessel. These vascular walls exhibit a structure similar to that of the dura, i.e. the tunica adventitia is formed by fascicles of collagenic fibers which describe discontinuous spirals, more open proximal to the beginning of the first portion of the internal jugular vein. Approximately in the inferior third of the first portion of the internal jugular vein, there appear fascicles of smooth muscle fibers which are arranged similarly to those of the venous walls. The tunica intima of these vascular segments exhibits an endothelium resting on a network of elastic fibers which may play the role of an internal elastic lamina. From the bony border of the jugular foramen there originates a connective system whose fascicles of collagenic and elastic fibers incorporate to the wall of the internal jugular vein after describing a stretch in spiral around the vascular lumen.     

Natural incidence of interruptions in the internal elastic lamina of caudal and renal arteries of the rat

Interruptions in the internal elastic lamina (IEL) have been quantified by light microscopy in the caudal arteries of different strains of rats and in caudal and renal arteries of (i) male and female virgin rats up until 2 years of age, (ii) repeatedly bred rats and (ii) hypertensive rats. Results showed that gaps in the IEL exist in caudal arteries of adult males in all strains studied, but to a lesser extent in the hairless mutant. In the virgin Wistar rat these interruptions in the IEL form with age in both caudal and renal arteries, and are more numerous (i) in the male than in the female in both arteries, and (ii) in the caudal than in the renal artery in both sexes. Repeated breeding in the Wistar rat abolishes the sex difference in incidence of IEL gaps in both renal and caudal arteries. The Sprague-Dawley breeder rat is more susceptible than the Wistar breeder to their formation in the renal artery. Hypertension in the male consistently increases the formation of IEL gaps in the renal but not in the caudal artery. The importance of local factors, e.g. hemodynamics, in the formation of these defects in the IEL, and their possible relationship with the development of arteriosclerosis is discussed.     

An investigation of a sympathetic innervation of the vertebral artery in primates: is there a neurogenic substrate for vasoconstriction?

Vasoconstriction of the vertebral artery may be neurogenic in origin. Although the existence of a perivascular sympathetic plexus of the vertebral artery is not in doubt, no method used to date has conclusively demonstrated a direct sympathetic innervation of the vascular smooth muscle cells and, hence, vasomotor function. It was the aim of this study, therefore, to visualise and localise noradrenergic fibres in the wall of the vertebral artery. Intracranial vertebral artery specimens (10 vervet monkeys and 10 baboon vessels) were sectioned (40 mm serial sections) and treated with anti-tyrosine hydroxylase, anti-dopamine b-hydroxylase, and anti-chromogranin-A antibodies. Some evidence of catecholaminergic fibres in the tunica adventitia but not penetrating the external elastic lamina or tunica media of the vertebral artery wall was seen. These findings were confirmed by electron microscopy. It was concluded that although a perivascular sympathetic plexus exists, the vertebral artery of primates was not shown to have a direct sympathetic innervation and a neurogenic vasoconstrictor function is unlikely.     

Development of terminal filaments and ovariole envelopes in Thermobia domestica (Insecta, Zygentoma) larvae

The 3rd instar female larvae of Thermobia domestica have five pairs of gonad primordia, each enclosed within a basal lamina (tunica propria). At the end of the 3rd instar some somatic cells scattered on the outer surface of the lamina are seen. During the 4th larval instar the gonad primordia start to form the ovarioles. Each ovariole is elongated and polarized, having anterior and posterior ends. The anterior group of outer somatic cells proliferate to form the terminal filament. At the 6th larval stage the ovarioles are already formed. The terminal filament is separated from the germarium by a thick basal lamina (transverse septum). There are three types of cell building the terminal filament. 1/Basal cells with numerous fingerlike projections; 2/Cells with electron lucent cytoplasm and large nuclei, and 3/Cells with darker cytoplasm containing bundles of fibers and more compact nuclei. The outer surface of the filament is covered by a thick, fibrous basal lamina. The somatic cells that in the previous stages were scattered on the tunica propria as distinct cells, in the 6th larval stage form a cellular envelope (tunica externa). This envelope is formed by a layer of flat cells, and contains numerous tracheae.     

A histological study on the coronary artery of the indigenous black Bengal goat in Bangladesh.

The coronary artery of the black Bengal goat was studied by light microscopy. The wall of the coronary artery consisted of the tunica intima, tunica media and tunica externa. The tunica intima consisted of a single layer of flattened endothelium. The tunica media was well-developed and composed of mainly of smooth muscle cells together with some fine elastic fibers. The tunica externa consisted of predominant collagen fibers, and some elastic fibers and smooth muscle cells. Elastic fibers in the tunica externa formed a circular arrangement around the tunica media. Sex differences were not observed. The media with well-developed smooth muscle cells may be responsible for changes in functional physiological conditions of the heart.     

Electron microscopic observations on the formation of elastic fibres in cultures of aortic medial cells and adventitial cells

The formation of elastic fibres was observed in the cultured cells derived from the tunica media and the tunica adventitia of mouse aorta. Bundles of myofilaments with dense bodies were abundantly observed in the cytoplasm of the cultured medial cells, and numerous bundles of microfibrillar components were present in the intercellular spaces. Fine granules of approximately 50 nm in diameter were observed in the bundles of microfibrillar components. It was supposed that these fine granules of elastin fused with each other and formed elastic aggregates and then formed large elastic clumps. Numerous bundles of microfibrillar components were also present in the intercellular spaces of the cultured adventitial cells. Elastic aggregates were scarcely observed in the bundles of microfibrillar components. However, large elastic clumps as observed in the medial cell culture could not be found in the adventitial cell culture. It is suggested that the formation of large elastic clumps might be related to the sheet structures or lamellae of elastic fibres in the tunica media.     

Histological and histochemical studies of the gall bladder of the graylag goose (Anser anser)

ABSTRACT

We investigated the histological structure of the graylag goose (Anser anser) gall bladder. Sections of the gall bladder were stained with hematoxylin and eosin (H & E), Alcian blue (pH 2.5) for acid mucopolysaccharides, Gomori’s method for reticular fibers, Masson’s trichrome, periodic acid-Schiff (PAS) and Verhoeff’s elastin stain. The goose gall bladder was composed of a tunica mucosa, tunica muscularis and tunica adventitia or tunica serosa. The tunica mucosa formed regularly distributed simple isometric folds plus larger, less numerous, branched folds. The luminal surface was lined by tall columnar epithelial cells that stained for both acid and neutral mucopolysaccharides. The epithelial cells formed a discontinuous striated border of interdigitating microvilli on the luminal surface. Neither a lamina muscularis nor goblet cells were observed in the tunica mucosa. Unusual findings included branched mucosal folds, discontinuous microvilli and absence of an outer longitudinal layer in the tunica muscularis. No marked sex-associated differences were found. The general histochemical and histological structures of the graylag goose gall bladder are similar to those of birds such as chukar partridge and quail, but with some unique elements that may reflect differences in organ function.     

Coronary Injury Score Correlates with Proliferating Cells and Alpha-Smooth Muscle Actin Expression in Stented Porcine Coronary Arteries

Neointimal formation and cell proliferation resulting into in-stent restenosis is a major pathophysiological event following the deployment of stents in the coronary arteries. In this study, we assessed the degree of injury, based on damage to internal elastic lamina, media, external elastic lamina, and adventitia following the intravascular stenting, and its relationship with the degree of smooth muscle cell proliferation. We examined the smooth muscle cell proliferation and their phenotype at different levels of stent injury in the coronary arteries of domestic swine fed a normal swine diet. Five weeks after stent implantation, swine with and without stents were euthanized and coronaries were excised. Arteries were embedded in methyl methacrylate and sections were stained with H&E, trichrome, and Movat’s pentachrome. The expression of Ki67, α-smooth muscle actin (SMA), vimentin, and HMGB1 was evaluated by immunofluorescence. There was a positive correlation between percent area stenosis and injury score. The distribution of SMA and vimentin was correlated with the degree of arterial injury such that arteries that had an injury score >2 did not have immunoreactivity to SMA in the neointimal cells near the stent struts, but these neointimal cells were positive for vimentin, suggesting a change in the smooth muscle cell phenotype. The Ki67 and HMGB1 immunoreactivity was highly correlated with the fragmentation of the IEL and injury in the tunica media. Thus, the extent of coronary arterial injury during interventional procedure will dictate the degree of neointimal hyperplasia, in-stent restenosis, and smooth muscle cell phenotype.     

A scanning electron microscope study of human cerebral arteries.

Human cerebral arteries were obtained from autopsy, fixed under pressure, cut open, and tacked onto pieces of cork. For one artery the intima was partly teased away, exposing the media, and treated with a silver nitrate process. For another artery the adventitia was exposed. Both arteries were processed through graded ethanols and coated with gold paladium for the scanning electron microscope. The collagen fibers of the adventitia were approximately 5 mum in diameter and consisted of a bundle of microfilaments, each of which had a diameter of 800-1000 A (1 A = 10(-10) m). The collagen fibers were oriented parallel to the long axis of the artery. The muscle cells of the media had a diameter of 2-5 mum and were arranged circumferentially with a pitch of approximately 20 degrees. The collagen fibers of the media travel perpendicular to the muscle cells, and parallel to the long axis of the artery. The fibrillar components of the elastin in the intima had a diameter of approximately 700-1000 A and were arranged parallel to the long axis of the artery. It was postulated that the fibrillar part of the elastin was the elastic component of the elastin.     

A morphological comparison of aortic elastin from five species as seen with the scanning electron microscope

The elastic laminae were extracted from thoracic aortas of adult animals including sheep, dogs, rabbits, cats and rats by treating them in hot alkaline solution (0.1 N NaOH at 75 degrees C) and observed with a scanning electron microscope. The elastic laminae are comprised of sheet-like internal elastic lamina, fibrous and membraneous elastin in tunica media, interlamellar fibers and hollow spaces which we presume were formerly filled with smooth muscle cells in the tunica media. These structures are the same in all five species except that the number of layers and the total thickness of the wall differs.     

Observations on the fine structure of the baroreceptors and adrenergic innervation of the guinea-pig carotid sinus

We examined the fine structure of the baroreceptors and the adrenergic innervation of the guinea-pig carotid sinus. The tunica adventitia contained many nerve bundles whose perineuria enclosed unmyelinated nerve fibers, alone or together with myelinated nerve fibers. Baroreceptors, which lay close to elastic and collagen fibers in the adventitia and media, were surrounded by “terminal” cells with ultrastructural features characteristic of Schwann cells and contained inclusions of various types. Morphologic features of the baroreceptors included densely packed mitochondria, osmiophilic lamellated and homogeneous bodies, clear and granular vesicles, lamellar systems, glycogen granules, neurofilaments, neurotubuli, and vacuolated mitochondria. In animals that had been treated with 6-hydroxydopamine, occasional electrondense endings (or fibers) were observed in the adventitial layer. The baroreceptors in the guinea-pig carotid sinus appear to have most of the morphologic features reported for other species.     

Localization of dopamine D1 and D2 receptor mRNAs in the rat systemic and pulmonary vasculatures.

The present study was designed to evaluate the expression of dopamine D1 and D2 receptor mRNAs in systemic and pulmonary vasculatures. Using specific antisense riboprobes for dopamine D1 and D2 receptor cDNAs, in situ hybridization histochemistry was performed in the aorta, common carotid artery, vertebral artery, pulmonary artery, and superior vena cava of the adult male Sprague Dawley rat. In the case of the aorta, common carotid artery, and vertebral artery, dopamine D1 receptor mRNAs localized mainly in the smooth muscle cells of the tunica media. However, the signals of dopamine D2 receptor mRNAs were found in the endothelium and subendothelial layer of tunica intima, and interstitial cells of tunica adventitia. In the case of the pulmonary artery, signals of dopamine D1 receptor mRNAs were detected within the tunica intima, media, and adventitia. Expression of D2 receptor mRNAs was detected in the walls of small blood vessels within the tunica adventitia of the pulmonary artery. There were no detectable signals of dopamine D1 and D2 receptor mRNAs in the vein. The uneven distribution of dopamine D1 and D2 receptor mRNAs in the rat systemic vasculatures and pulmonary artery suggests that dopamine differentially regulates the vasodilation of the systemic and pulmonary arteries through the differential stimulation of dopamine D1 and D2 receptor.     

Zur Wandstruktur der großen Arterien der Vögel

Zusammenfassung Die Wandstruktur der großen Arterien des Schwans, der Drossel und des Stars wurde licht- und elektronenoptisch untersucht und eine Einteilung in elastische, muskuläre und Übergangsgefäße getroffen.Die Media der elastischen Gefäße besteht aus muskulo-elastischen Zylindersegmenten, die mit breiten Bindegewebslagen alternieren. Die Zylindersegmente bestehen aus plattenförmigen Lagen glatter Muskelzellen, die von elastischen Fasernetzen flankiert werden. Diese Zylindersegmente beginnen und enden in den Bindegewebslagen stark gegeneinander versetzt, so daß ein kulissenartig einander überlappendes Plattensystem entsteht. Die Bindegewebslagen bestehen neben kollagenen Fasern und Fibrozyten aus mehreren konzentrischen Lagen elastischer Fasernetze. Die elastischen Netze sind durch Verbindungsfasern zu einem dreidimensionalem, die ganze Gefäßwand durchsetzenden elastischen System verknüpft. In den Übergangsgefäßen sind die Bindegewebslagen zwischen den muskulo-elastischen Systemen weitgehend reduziert.Bindegewebige und muskuläre Wandbestandteile sind im muskulären Vogelgefäß weitgehend voneinander getrennt. Die Media besteht aus glatten Muskelzellen, die von elastischen Netzen zu Schichten zusammengefaßt werden, die Adventitia aus kollagenen Fasern, Fibrozyten und konzentrischen Lagen elastischer Fasernetze. Die glatten Gefäßmuskelzellen sind durch elastische Fasernetze zu muskulo-elastischen Einheiten zusammengefaßt. Die mechanischen Verknüpfungspunkte zwischen Muskelzellen und elastischen Fasern sind über die ganze Zelloberfläche verteilt.Die Gefäßbautypen sind durch eine Wandstärken-Lumenrelation gekennzeichnet. Sie beträgt im elastischen Gefäß 1:5 bis 1:6, im muskulären Gefäß 1:14 bis 1:16.

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The wall structure of large arteries in birds

Summary A classification of large arteries (elastic, muscular and intermediate type) in mute swan, trush and starling was undertaken with light and electron microscopy.The tunica media of elastic arteries consists of musculo-elastic cylindrical segments alternating with wide connective tissue layers. The former consists of smooth muscle cell layers, which are adjoined by a network of elastic fibers. These musculo-elastic cylinder segments overlap incompletely. The connective tissue layers consist of networks of elastic fibers concentrically arranged in addition to collagen fibers and fibrocytes. The elastic networks are joined by connecting elastic fibers, thus forming a three-dimensionalsystem. In the intermediate type of arteries the connective tissue layers between the musculo-elastic systems are greatly reduced.Connective tissue and muscular components of the wall of muscular arteries are almost completely separated. The tunica media is composed of smooth muscle cells sandwiched by networks of elastic fibers. The tunica adventitia is formed by concentric networks of elastic fibers, collagen fibers and fibrocytes.The arterial smooth muscle cells, together with networks of elastic fibers, form a musculoelastic unit. The points of mechanical attachment between smooth muscle cells and elastic fibers are scattered all over the cellular surface. The arterial types described above are characterized by a well-defined wall thickness/lumen ratio. This ratio is of the order of 1:5 to 1:6 for elastic arteries and 1:14 to 1:16 for muscular arteries.

Medizinische Dissertation unter Anleitung von Prof. Dr. Dr. H.-R. Duncker.     

Functional medial thickening and folding of the internal elastic lamina in coronary spasm

Although there are a number of studies on vasospastic angina, the structural changes at the cellular level that occur in the coronary arterial wall during spasm are not well known. Coronary spasm was induced by brushing the coronary adventitia in nine anesthetized beagles, and structural changes in the spastic coronary segments were examined by light and electron microscopy, making comparisons with the adjacent nonspastic segments. The % diameter stenosis of the spastic segments as measured angiographically was 79.4±12% (mean±SD). Light microscopic changes in the spastic and nonspastic segments were as follows: medial thickness 1,512 vs. 392 μm (P<0.0001) and % diameter and % area stenoses of spastic segment 81.0% and 96.5%, respectively, indicating that spasm was induced by medial thickening. Circular smooth muscle cells (SMCs) in the media were arranged in parallel with the internal (IEL) and external (EEL) elastic lamina in nonspastic segments but radially rearranged in spastic segments. SMCs were classified by their patterns of connection to IEL into six types by electron microscopy. Of these, three contracted and pulled the IEL toward the EEL, causing folding of the IEL and waving of EEL resulting in thickening of the media and narrowing of the lumen. We conclude that coronary spasm was elicited by radial rearrangement of the medial SMCs due to their own contraction and resultant medial thickening and folding of IEL, creating a piston effect to narrow the lumen, i.e., spasm.     

Heightened aberrant deposition of hard-wearing elastin in conduit arteries of prehypertensive SHR is associated with increased stiffness and inward remodeling

Elastin is a major component of conduit arteries and a key determinant of vascular viscoelastic properties. Aberrant organization of elastic lamellae has been reported in resistance vessels from spontaneously hypertensive rats (SHR) before the development of hypertension. Hence, we have characterized the content and organization of elastic lamellae in conduit vessels of neonatal SHR in detail, comparing the carotid arteries from 1-wk-old SHR with those from Wistar-Kyoto (WKY) and Sprague Dawley (SD) rats. The general structure and mechanics were studied by pressure myography, and the internal elastic lamina organization was determined by confocal microscopy. Cyanide bromide-insoluble elastin scaffolds were also prepared from 1-mo-old SHR and WKY aortas to assess their weight, amino acid composition, three-dimensional lamellar organization, and mechanical characteristics. Carotid arteries from 1-wk-old SHR exhibited narrower lumen and greater intrinsic stiffness than those from their WKY and SD counterparts. These aberrations were associated with heightened elastin content and with a striking reduction in the size of the fenestrae present in the elastic lamellae. The elastin scaffolds isolated from SHR aortas also exhibited increased relative weight and stiffness, as well as the presence of peculiar trabeculae inside the fenestra that reduced their size. We suggest that the excessive and aberrant elastin deposited in SHR vessels during perinatal development alters their mechanical properties. Such abnormalities are likely to compromise vessel expansion during a critical period of growth and, at later stages, they could compromise hemodynamic function and participate in the development of systemic hypertension.