Flattened Endothelial Cells Research Articles

Blue rubber‐bleb nevus syndrome with Masson's vegetant intravascular hemangioendothelioma

A 14-year-old Japanese male showed numerous small cutaneous hemangiomas and severe anemia produced by internal hemorrhages from intestinal hemangiomas. Histological studies revealed ectatic vessels lined by a single layer of endothelial cells. Six hemangiomas, with fibrous walls of variable thickness, showed characteristics of vegetant intravascular hemangioendothelioma (Masson) in an organizing thrombus. Electron microscopy confirmed that the dilated cavities, were lined by a layer of flattened endothelial cells, surrounded by a few pericytes and/or smooth muscle cells. No appreciable abnormalities were found in the blood vessels located in the clinically normal skin. A few amyloid deposits in the subepidermal connective tissue were also observed.

The pulmonary arteriole

The terminal branches of the mammalian pulmonary arterial tree are called arterioles despite statements that these vessels in the adult have no smooth muscle. We examined these vessels in the cat (8 hr to 11 years) and man (24 hr to 76 years) by light microscopy and special staining to clarify the terminology problem. In both cat and man, the changes in arterioles from the newborn to the aged individual are similar and differ only in time course. At and shortly after birth, fetal pulmonary arterioles are found throughout the lung: Endothelial cells are polygonal and somewhat thickened, the smooth muscle of the media has plump nuclei with blunt ends and fine chromatin; the cytoplasm is pale and periodic acid-Schiff (PAS) negative; internal and external elastic laminae are present. Mixed in with these fetal vessels are a few arterioles which show occasional areas of PAS-positive material and nuclei which are elongating. Occasional arterioles are more strongly PAS positive and show further elongation of nuclei and increased condensation of chromatin. After weeks to months (species variation) almost all arterioles show wall thinning, flattened endothelial cells, smooth muscle cells which occupy most of the media with deeply stained elongated nuclei and scant but persistent cytoplasm which is deeply PAS positive, and persistence of an internal and external elastic layer. Such vessels persist in the aged cat and human. We have called these sequential changes in the pulmonary arteriole maturation changes. The functional correlates of these arteriolar alterations for the adult mammal are discussed.

Organic fragmentation in pulmonary thrombo-emboli.

Organic fragmentation is a cell-mediated process whereby the periphery of thrombo-emboli is broken up into multiple tiny fragments lined by flat cells and separated by endothelialised clefts and spaces. The process was looked for in 238 lung emboli from 107 subjects and was observed in 45 emboli (41 subjects). The true incidence is much higher since fragmentation is preceded by the surfacing of emboli by flat endothelial cells. Among such emboli its frequency was 41%. Fragmentation can involve emboli of all sizes though it is most frequent and extensive in small ones. The process is important for the resolution of emboli and helps the canalisation of the embolised arteries. It reduces the size of emboli and may also undermine mural attachments and thereby lessen the extent of anchoring to the vessel wall. The mechanism of fragmentation and the origin of the cells responsible are discussed.

Electron microscopic localization of adenosine triphosphatase (NaK-ATPase) activity in the rat cornea

Sodium-potassium-activated adenosine triphosphatase (NaK-ATPase) activity was investigated histochemically in the rat cornea. The enzyme was localized in all epithelial cell membranes and in the nerve fibres of the stroma. The intercellular membranes of the flat endothelial cells were also active. When 3 × 10 −4 m-ouabain was added to the preincubation and incubation solutions, a clear inhibition of the reaction was observed. The presence of 70 m m-Na + and 30 m m-K + in the incubation solution stimulated the histochemical enzyme reaction to a marked extent. When the substrate (ATP) was replaced by ADP or by glycerophosphates, there was no reaction as was also the case in the absence of Pb 2+. These findings were regarded as a proof for the specificity of the technique. Methodological problems of ATPase histochemistry and the physiological role of NaK-ATPase activity in the different structures of the cornea are discussed.

The ultrastructure of lymphatic valves in the adult rabbit lung.

An electron microscopic investigation has revealed that the pulmonary lymphatic valves of adult rabbits are not simple duplicatures of the lymphatic vessel wall. They consist of an uninterrupted central connective tissue core, covered on both sides with a single layer of flattened endothelial cells. Near their insertion in the lymphatic vessel wall, the connective tissue core reveals a distinct thickening being composed mainly of collagen bundles. In the other parts it contains mainly elastic fibers and fine filaments, enclosing also some rather peculiar connective tissue cells. Nervous and muscular elements were not observed. The endothelium is continuous and exhibits no open junctions. The valvular basement membrane is better developed than in lymphatic capillaries. The endothelial cells contain numerous cytoplasmic filaments which might be endowed with contractile properties. The nuclei of the endothelial and the connective tissue cells are irregularly spaced and frequently clustered near the free edge of the valve.

コウライエビの研究-VIII

As a lymphoid organ was found in the vascular system, its anatomical and histological structure was studied. 1. The position of this organ differs slightly in the male and female. In the female, it is pressed by the ovary onto the upper anterior part of the liver. 2. An afferent and many efferent vessels led in and out are observed. The former is connected with the antennal artery and runs along the anterior edge of the liver to be led ultimately into the organ. In the female, the afferent vessel passes through the ovary. It is composed of an endothelial cell layer and surrounding loose fibrous tissue. Mesodermal reticular cells are scattered in this fibrous tissue. The efferent vessels emerging from several places of this organ usually expand to form cysts but those emerging from the anterior external edge and from the interior edge are tubiform. The former are connected to the upper part of the leucopoietic organ, dorsal epidermis, gonads, etc. The latter are linked with the lymphoid vessels below the cardiac stomach. The cystiform vessels complicatedly bending around the organ are linked with the lymphoid vessels, but the one linked with the liver tunica penetrates the small openings of the tunica into the liver. The efferent vessels are composed of adventitia of longitudinally running fibers and the intima of endothelial cells. 3. The afferent vessel is bifurcated progressively immediately after entering the organ, and each becomes the central artery of the sheath which is a structural unit of this organ. The spaces between the peri-arterial sheaths take the form of winding, interconnected sinuses. The wall of sinus is made up of sporadical endothelial cells and argyrophil lattice fibers. 4. The pulp of this organ is the peri-arterial sheath which surrounds the bifurcated artery in the organ. The wall of the central artery is made up of a layer of flat endothelial cells in which interstices are found. The peri-arterial sheath is composed of free cells and interstitial tissues which consist of reticular tissue and fibrous tissues. In fibrous tissues, argyrophil fibers are distributed in flagments and concentrically within the peri-arterial sheath, and collagenous fibers are distributed outside this layer of argyrophil fibers. 5. The greater part of the free cells in the peri-arterial sheath are lymph-like cells and distributed mainly in the argyrophil fiber layer. In this fibrous layer, there are observed certain cells which are believed to he their young cells. Moreover, these free cells are extruding into the arterial lumen through interstices in the endothelial cell layer. Lymph-like cells measure 2.5-4.0 μ in diameter and they have very thin cytoplasm, and nuclei which are stained well by haematoxylin especially at the peripheries. Discoid free cells, measuring 6.0-8.0 μ in diameter and poorly stained by the haematoxylin can also be recognized in the sinuses. Comparing these free cells with the lymphocyte-type cells produced in leucopoietic organ, which resemble each other most closely, the lymph-like cells are clearly distinguishable from the lymphocyte-types, but free cells in the sinuses can not be distinguished from them. 6. The lymph-like cells of the peri-arterial sheath frequently vary in quantity with the abnormal changes in the body. The peri-arterial sheath, as well as the central artery, is filled with lymph-like cells and their young cells. Besides this, the reticular cells of the peri-arterial sheath degeneratively fibers and a large amount of granules appear in the fibers. It can be further confirmed that those cells are released into the central artery.

Ultrastructure of retinal capillaries of the rat

The retinal capillaries of normal, albino rats were studied with the electron microscope. The capillaries are lined by flat endothelial cells which rest upon a homogeneous basement membrane. Mitochondria were rare. Spherical vesicles, referred to as pinooytic vesicles by some authors, were found distributed throughout the endothelial cytoplasm but more often aligned along the free border of the cell. In addition to the vesicles, fine structures, appearing as discontinuous pairs of parallel lines and interpreted as portions of endoplasmic reticulum, were also dispersed in the endothelial cytoplasm. Microvilli of various lengths projected from the endothelial cytoplasm into the lumen of the capillaries. There was considerable variation in the width of the basement membrane which encircles the endothelial layer of the vessel. Pericytes were embedded in the basement membrane and lay in a plane parallel to the longitudinal axis of the capillary. Although the capillaries were not, as a rule, completely surrounded by pericytes, the latter cells were often superimposed upon one another, adding significantly to the over-all thickness of the capillary. In all specimens examined, the capillaries were invested by glial elements of the retina. There was no contiguity of capillary and neuronal tissue.

Epidural Hemorrhage Secondary to Cavernous Hemangioma of the Petrous Portion of the Temporal Bone

Hemangiomas of the bone are rare. They constitute from 1 to ~ per cent of all bone tumors. The most common site of hemangiomas is in the vertebrae, those of the skull being second in frequency. In the skull they are usually found in the calvarium, involving the parietal and frontal lobes, m There are two types of hemangiomas. The capillary variety is made up of closely packed capillaries which are lined by a single layer of nearly cuboidal endothelial cells. The more common cavernous type is composed of larger blood-filled spaces which are lined by a single layer of flattened endothelial cells. Elastic fibers and smooth muscle are usually not present in the walls of these tumors and the amount and character of the fibrous supporting stroma vary greatly? CASE REPORT

The Origin and Development of the Anterior Lymph-Sacs in the Sea-Turtle (Thalassochelys caretta)

1. In the lymph-sac area of embryos at the end of the second week of development the mesenchyme is very compact, showing slight signs of vacuolation. The area is bounded by the anterior cardinal vein and its dorsal branches, the wide meshed superficial plexus and the ventro-lateral branches of the cardinal vein. Within this area the lymph-sac anlagen first appear, lying in the angle between the dorso-lateral branches and the cardinal vein itself. 2. The dorsal tributaries of the pre-cardinals are concerned in the development of the lymph-sacs. In the mesenchyme surrounding these tributaries isolated spaces develop in direct connexion with the veins. 3. The development of the anterior lymph-sacs in the seaturtle is initiated by vacuolation of the mesenchyme in the region of the cardinal tributaries during the middle part of the third week of development. 4. A series of channels is formed from the anterior cardinal tributaries and isolated spaces which in their greatest development exist as plexuses of vessels connected with the cardinal veins. 5. These channels enlarge and fuse with each other, the remnants of their walls appearing as protoplasmic fibres in the lumen, producing a system of cavities very irregular in size and shape. They inter-communicate and connect at the same time with the dorsal tributaries of the pre-cardinal veins. The mesenchyme cells surrounding these cavities are gradually transformed to the flattened endothelial cells which later line the sacs. 6. The lymph-sac is well developed at twenty-four days. Fusion and enlargement of individual cavities has continued up to this time. 7. As the development of the lymph-sacs proceeds they lose connexion with the cardinal veins except for the opening at the posterior end of the sac. 8. The development of the anterior lymph-sacs in the turtle shows two distinct anlagen, one from the mesenchyme and the other from the venous tributaries, which unite to form the veno-lymphatics. The increase in size and confluence of the veno-lymphatics determines the development of the anterior lymph-sacs.