Search

The term aneurysm is used to indicate a permanent and irreversible localized vascular dilatation that involves all three layers of the blood vessel wall. It may develop in any part of the circulatory system, including veins, and its history, presentation, and management differ depending on the location. A venous aneurysm is defined as a solitary area of fusiform or saccular dilatation occurring in the course of a major vein or connected by a single channel to a major venous structure. The lower extremities are the most frequently affected, with the popliteal vein being the most common site. Although different theories have been advanced, the etiology of the disease remains uncertain. Mechanical stress and/or degenerative changes within the vein wall are believed to represent the most likely causes of venous aneurysm. To date, there are only a few publications dealing with the histological appearance of popliteal vein aneurysm, and no studies that specifically describe its ultrastructural details have been published to our knowledge. In an attempt to fill this gap and to provide better insights into the pathophysiological mechanisms possibly involved in aneurysmal venous disease, we describe the fine structure of popliteal vein wall and valve in health and disease using both scanning and transmission electron microscopy.

During diverse pathological conditions, vascular smooth muscle cells (SMCs) characteristically change from a quiescent, contractile phenotype to a proliferative, synthetic state, migrate toward the intima, and synthesize excess extracellular matrix. Although reactive oxygen species (ROS) are generally considered to be toxic to cells, recent evidence suggests that they may also modulate multiple signaling pathways. The vascular system contains several sources of ROS, among which NADPH oxidases (NOXes) have been shown to take an important part in the regulation of cell function, with effects on growth and proliferation. In the present study, the authors investigate the ultrastructural features of SMCs and the expression profile of Nox4 in healthy and atherosclerotic human aorta to explore the possibility of a relationship between Nox4 and SMCs differentiation state. The data extend at the level of immunoelectron microscopy previous observations, demonstrating for the first time the precise distribution and the differential expression of Nox4 in the morphologically distinct SMC types of healthy and diseased human aorta.

Spermiogenesis in Caiman crocodylus was examined by electron microscopy. The acrosomal complex, the perforatorium and the growing axoneme of young spermatids are described. During the nuclear elongation of intermediate spermatids, two ≪manchettes≫ of microtubules were observed in addition to the acrosomal complex, perforatorium growth and chromatin condensation. At the onset of spermatid elongation, there is a set of microtubules around the nucleus and, at the end of elongation, a second set of microtubules parallel to the main axis of the cell appears. Both circular and longitudinal manchettes were observed together. In the neck‐region a striated structure of electron‐dense material is found on one side of the distal centriole. The descent of the mitochondria into che middle‐piece of the tail occurs only in the last stage of differentiation. The mitochondria are small, their cristae are irregularly arranged and the centres of the mitochondria consist of an electrondense material. Unlike most oth...