Walls Of Postcapillary Venules Research Articles

Oxidatively modified human low-density lipoprotein stimulates leukocyte adherence to the microvascular endothelium in vivo

In vitro studies indicate that oxidatively modified low-density lipoprotein (oxLDL) promotes leukocyte sticking to the vascular endothelium, a constant feature of early atherogenesis. Using intravital fluorescence microscopy in the dorsal skinfold chamber model in hamsters, we investigated whether systemic administration of human LDL, oxidized by Cu2+, elicited leukocyte/endothelium interaction in vivo. While no effect was seen after injection of native LDL, oxLDL administration resulted in an immediate induction of leukocyte rolling along the microvascular endothelium and subsequent firm sticking to the wall of postcapillary venules as well as arterioles. The presented model may provide an alternative experimental approach to long-term feeding studies with atherogenic diets for the in vivo investigation of leukocyte/endothelium interaction in early atherogenesis.

Involvement of autonomic nervous system in gastric mucosal defense mechanism.

This article describes the histochemical, immunohistochemical, radioautographic, and ultrastructural localizations of aminergic and peptidergic nerves, neurotransmitter receptors, and their binding sites in the stomach wall. Cholinergic and vasoactive intestinal polypeptide (VIP)-ergic nerve fibers are distributed along the gastric microvasculature, within the myenteric and submucosal plexuses, and in the muscularis mucosae and circular muscle layer. In the mucosa, both nerve fibers evenly extend along the capillaries in association with the epithelial cells up to the mucosal surface. In particular, cholinergic nerves are proved to doubly innervate the mucosal capillaries and nonmuscular venules as well as the parietal cells. Adrenergic and neuropeptide Y (NPY)-containing nerves are distributed primarily along the arterioles of the gastric microvasculature, within the myenteric plexuses, and in the circular muscle layer. These nerve fibers extend up to the basal portion of the mucosa in close association with small arterioles, capillaries, and epithelial cells. Some of the adrenergic nerve axons are coexistent with the cholinergic nerve axons within the Schwann cell. Histamine H1 receptors are widely located on the walls of arterioles, capillaries and venules, while H2 receptors are evident not only on the parietal cells but also on the walls of the collecting venules and surrounding capillaries in the mucosa. Dopamine D1 receptors are predominantly located on the smooth muscle cells of the arterioles near the muscularis mucosae, while D2 receptors are present on the walls of postcapillary venules and collecting venules. Functional coordination of both intramural peptidergic nerves as intrinsic origin and aminergic nerves as extrinsic origin is considered to be essential for maintaining the gastric mucosal defense mechanism against a variety of aggressive factors.

Ultrastructural observations in port wine stains.

The cause for the progressive vascular dilatation in port wine stains remains unclear. We compared the histology and ultrastructure of lesional and adjacent normal skin in paired biopsy specimens of 12 and 8 patients, respectively (age range, 6 to 53 years). In semithin sections, the lesions of all patients showed ectatic vessels and a fine-fibrous or hyaline thickening of the walls of postcapillary venules, as well as in some instances a loosening of the surrounding connective tissue. Ultrastructurally, the wall material consisted predominantly of peripheral deposits of amorphous material interspersed with collagen fibrils (diameter, 35 +/- 4 nm); occasionally the number of basal laminae in the inner part was also increased. Cross-banded filamentous aggregates with a periodicity of 95 nm were observed in and around the walls. The endothelium of many patients displayed fenestrations and/or small gaps. Various kinds of alterations of the intervascular connective tissue were found. We conclude that structural alterations of the vascular and later also of the intervascular connective tissue are related to the dilatation of the vessels. These findings are in agreement with the immunopathologically demonstrated increase of basement membrane components in the same biopsy specimens, but are interpreted as secondary phenomena. Endothelial stability and permeability may also be affected.

Treatment of rats with hCG induces inflammation-like changes in the testicular microcirculation.

Adult rats were injected subcutaneously with 50 i.u. hCG and vascular permeability was compared to that in saline-treated control rats by two independent methods. At 4 h after hCG treatment the rats were injected intra-arterially (i.a.) with FITC-labelled macromolecular dextran (Mr 150,000) and the testicular microcirculation was studied in vivo by using a fluorescence microscope. Other rats were injected i.a. with a suspension of colloidal carbon and the location of leaking blood vessels was recorded in sections from the testes by light and electron microscopy. In hCG-treated animals leucocytes were found adhering to the endothelium in post-capillary venules and in these venular segments dextran was leaking into the interstitium. Carbon particles were deposited in the walls of post-capillary venules and leucocytes migrated through open interendothelial cell gaps in hCG-treated animals. In control animals leucocyte adhesion and migration were not observed, the injected dextran remained in the circulation and the blood vessels were not labelled by carbon. It is suggested that the hCG-induced increase in testicular interstitial fluid volume, like the tissue oedema in inflammation, is caused by a leucocyte-mediated increase in venular permeability.

Studies in Cutaneous Aging II. The Microvasculature

We studied by light and electron microscopy the microcirculatory vessels in the sun exposed and sun protected skin of normal and psoriatic individuals in order to separate the features of actinic damage from those of chronological aging. In actinically damaged skin, the vascular walls of postcapillary venules and of arterial and venous capillaries were thickened by the peripheral addition of a layer of basement membrane-like material. The veil cells which were intimately related to these layers often had dilated cisternae of rough endoplasmic reticulum containing electron dense material. In 3 of 8 individuals, 70, 70 and 72 yr old, the buttock skin showed mold vascular wall thickening. In 5 other patients, 59-88 yr old the vessels of the buttock skin were normal. In 4 individuals 80-93 yr old, the vessels were abnormally thin (0.5-1.0 micrometer). The veil cells were either absent or decreased in number in these specimens. We propose that (1) the veil cell is responsible for the synthesis and maintenance of the peripheral portion of the vascular wall of the dermal microcirculatory vessels; (2) the veil cell is stimulated to produce excessive basement membrane-like material in response to UV light, factors associated with diabetes mellitus, and possibly to factors associated with the early phase of chronological aging; and (3) with progressive aging there is a decrease in the number and synthetic activity of veil cells which correlates with the appearance of abnormally thin walled vessels.

The structure of the hemolymph node—a light, transmission, and scanning electron microscopic study

In the rat, hemolymph nodes have been studied by light, transmission, and scanning electron microscopy. Their basic structure is similar to that of the normal lymph node. Both have afferent and efferent lymphatics, lymphatic sinuses with macrophages and trabeculae, and lymphoid tissue separable into three distinct zones. The hemolymph node, however, possesses very few afferent lymphatics. It is very vascular and contains capillaries with an attenuated basement membrane. A large number of red blood cells are present focally in the lymphoid parenchyma and diffusely in the lymphatic sinuses, where red blood cells are trapped and subsequently phagocytosed by macrophages. These red blood cells cross the wall of postcapillary venules and that of dilated capillaries between endothelial cells and a narrow gap in the basement membrane. Direct anastomoses between blood vessels and lymphatic sinuses have not been demonstrated.

Lymphocytosis Induced in Mice by Supernatant Fluids of Bordetella pertussis Cultures: A Histopathological Study

Abstract Intravenous injection into mice of phase I Bordetella pertussis culture supernatants produces a marked lymphocytosis. The evolution of lymphocytosis was correlated with histopathological alterations in the lymphoid organs. The early phase, 17 hr to day 3, was associated with massive depletion of both lymphocytes from the white pulp of the spleen and of cortical thymocytes. There was a corresponding profound decrease of splenic and thymic weights. The later phase was associated with a marked decrease in lymphocytes of lymph nodes while concomitantly the spleen and thymus appeared to be repopulating. Both thymic-dependent and thymic-independent lymphocyte populations were mobilized from spleen and lymph nodes. There was a striking diminution in the number of lymphocytes contained within the walls of postcapillary venules (PCVS) of all lymph nodes between 2 and 7 days. The data suggest that initially the lymphocytosis is due predominantly to release of splenic lymphocytes and to a lesser extent of thymocytes into the circulation. Subsequently, the lymphocytosis is sustained by the depopulation of the lymph nodes. Lymph node depopulation is maintained by the failure of circulating lymphocytes to emigrate from the blood through the PCVS.