The Fine Structure of Capillaries and Small Arteries

Abstract

Details of capillary endothelia of the mammalian heart are described and compared with capillaries of other organs and tissues. Continuous invagination and pinching off of the plasma membrane to form small vesicles which move across the cytoplasm are suggested as constituting a means of active and selective transmission through capillary walls (12). This might be designated as cytopempsis (transmission by cell). The fine structure of the different layers in the walls of small heart arteries is demonstrated. Endothelial protrusions extend through windows of the elestica interna to make direct contact with smooth muscle plasma membranes. The elastica interna appears to vary greatly in both thickness and density, and probably restricts filtration, diffusion, and osmosis to such an extent that windows and the transport mechanisms described (cytopempsis) are necessary for the functional integrity of the smooth muscle layer. The contractile material consists of very fine, poorly oriented filaments.

Regulation of Cellular Communication by Signaling Microdomains in the Blood Vessel Wall

“…Compartmentalized Nitric Oxide Signaling at the Myoendothelial Junction. The MEJ is a distinct anatomic structure in the blood vessel wall where (predominantly) ECs send cellular projections through small holes in the internal elastic lamina separating the intima and media that allow for direct cell-to-cell contact with the overlying smooth muscle cell layer (Moore and Ruska, 1957; for review, see Heberlein et al, 2009). In small resistance arteries, MEJs are numerous compared with larger conduit arteries and coordinate signal transduction between the smooth muscle and endothelium by facilitating intercellular transport of small molecules and ions as well as harboring polarized proteins involved in vascular cell crosstalk (Sandow and Hill, 2000;Dora et al, 2003a;Isakson and Duling, 2005;Isakson et al, 2007;Isakson, 2008;Straub et al, 2011).…”

Molecular determinants of endothelial transcytosis and their role in endothelial permeability

“…The term transcytosis was introduced by Simionescu (207) to define a transcellular transport pathway that couples endocytosis to exocytosis on the opposite plasma membranes. Other names, such as cytopempis (109) or diacytosis (77), have been suggested but never generally applied. Depending on the mechanism involved-fluid phase, adsorptive, and receptormediated-PVs take a bulk of plasma, or molecules that have been attached on vesicle membrane either electrostatically or receptor mediated, to carry them on the abluminal front of the endothelium (201).…”

Study progress of homocellular and heterocellular gap junctions in vessel wall

“…The myoendothelial junction (MEJ) was first described in 1957 in a transmission electron microscopy (TEM) study of small arteries in the dog heart (Moore and Ruska, 1957). It was the place that endothelial protrusions extended through windows of the elastica interna to make direct contact with smooth muscle plasma membranes (Moore and Ruska, 1957).…”

“…It was the place that endothelial protrusions extended through windows of the elastica interna to make direct contact with smooth muscle plasma membranes (Moore and Ruska, 1957). In fact, there are three distinct "types" of MEJs: (1) endothelial cell (EC) extensions through the internal elastic lamina (IEL) that make contact with the VSMC, (2) VSMC extensions through the IEL that make contact with the EC, or (3) both EC and VSMC extensions into the IEL (Michel et al, 1995).…”