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The vascular systems of epicolic and paracolic lymph nodes located in the vicinity of colon tumors resected from three patients were investigated by corrosion casting and scanning electron microscopy. Large vessels entered the nodes either at one site, not always corresponding with the anatomical hilus, or at 2-4 sites located along their perimeters. In the cortical zone of most examined nodes, the location of lymphoid nodules was marked by rosette-like capillary arrays drained by peripheral arcuate venules. The paracortex and medulla showed a dense capillary network with areas of tortuous capillaries, sometimes forming glomerular arrays suggesting nonsprouting angiogenesis by capillary elongation. Venules were abundant, especially in the paracortex and medulla, but high endothelial venules showing characteristic imprints of bulging endothelial cells in the casts were very rarely observed. Focal angiogenesis, abundance of venules and scarcity of high endothelial venules could result from remodeling of blood vessels induced by the tumor., (Copyright © 2012 Elsevier GmbH. All rights reserved.)

Vascular architecture of the human pancreas was investigated by corrosion casting combined with scanning electron microscopy in fetuses aged 20 and 25 gestational weeks. The general pattern of the microvascular system was similar to that of the postnatal pancreas, with an evident insulo-acinar portal system and with three types of capillary networks: capillaries of exocrine lobules, islet capillaries and periductal capillaries around large ducts located in the interlobular septa. All these capillary networks were supplied by arteriolar branches of the interlobular arteries. As compared with the postnatal pancreas, capillaries of exocrine lobules formed denser meshworks, had a more sinusoidal character and revealed morphological features indicative of angiogenesis (blind capillary sprouts). The number of efferent (portal) capillaries per islet was lower and the predominant pattern of islet vasculature was top to bottom rather than inner to outer, as observed in adults. These results show that in the second trimester the human pancreatic vascular architecture is almost completely developed and requires only minor remodeling to be fully functional in the postnatal period.

The microvascular architecture of developing lateral ventricle choroid plexus was investigated by corrosion casting and scanning electron microscopy in human fetuses aged 20 gestational weeks. The areas with different microvascular patterns corresponded to the particular parts of the mature plexus: anterior part, glomus, posterior part, the villous fringe and the free margin. In the posterior part, densely packed parallel arterioles and venules were surrounded by sheath-like capillary networks. Other areas contained compact capillary plexuses of the primary villi: the most prominent, protruding basket- and leaf-shaped plexuses were observed in the villous fringe, whilst less numerous and smaller plexuses occurred in the anterior part and glomus. The capillaries of the plexuses had a large diameter and sinusoidal dilations, and showed the presence of occasional short, blind sprouts indicative of angiogenesis. Short anastomoses between arterioles supplying the plexuses and venules draining them were only rarely observed. In the upper area of the choroid plexus, the superior choroidal vein was surrounded by a capillary network forming small, glomerular or rosette-shapes plexuses. The free margin of the choroid plexus was characterized by flat, multiple, arcade-like capillary loops. The general vascular architecture of the human choroid plexus at 20 gestational weeks seems to be similar to that of postnatal/mature plexus, still lacking, however, the complex vascular plexuses of the secondary villi. [ABSTRACT FROM AUTHOR]