LUMENating blood vessels

The acquisition of a lumen is an essential step in vascular morphogenesis. In this issue of Developmental Cell, Xu et?al. (2011) show that the small GTPase Rasip is a critical regulator of cytoskeleton dynamics and cell adhesion, which together drive the emergence of vascular lumens.     

Potassium and blood vessels.

Intraarterial infusion of potassium causes vasodilation whereas reduction of the potassium concentration in the inflowing blood causes vasoconstriction. These responses have always been puzzling since the predicted effects from the Nernst equation are just the reverse. Recent evidence suggests that they result form effects on the activity of sarcolemmal Na, K ATPase in the vascular smooth muscle cell which influence the electrogenic NaK pump. The possible relevance of these findings is discussed.     

The effect of VEGF on blood vessels and blood cells during Xenopus development

Vascular endothelial growth factor (VEGF) is known to play an essential role in vascular development. We have overexpressed VEGF122 or VEGF170, which are equivalent to mouse VEGF120 and VEGF164, in developing Xenopus embryos. Overexpression of VEGF170 but not VEGF122 demonstrated an absence of expression of hematopoietic markers alpha-globin and GATA-1 but only in the posterior portion of the blood island. Interestingly, strong signals of endothelial markers, msr, fli-1, and tie-2, were detectable in those regions, instead of hematopoietic markers. These results suggested both that injection of VEGF170 resulted in disturbance of vasculogenesis in the posterior portion of the blood island, with excessive production of endothelial cells at the expense of blood cells, and that the anterior and posterior portions of the VBI may have distinct characteristics.     

The fine structure of cephalopod blood vessels II. The vessels of the nervous system

Summary Blood vessels of the perioesophageal nerve ganglia (brain) of Octopus vulgaris and the stellate ganglia of Sepia officinalis are described. The vessels have an incomplete endothelium, a complete basement membrane and a complete investment of pericytes. The pericytes are joined by specialised membrane junctions but these are not tight junctions. The main type of neuron/vessel arrangement is one where there is a collagen-filled space between the pericytes and the surrounding glial cells. Axons or neurons are sometimes applied directly to the vessel pericytes and in the neuropil, pericytes contact glial cells that ensheath bundles of axons. Blood spaces between neurons are also present.We would like thank Professor J. Z. Young and Dr. E. G. Gray for encouragement and advice, Mrs. Jane Astafiev for drawing Fig. 11, Mr. S. Waterman for photographic assistance and Miss Cheryl Martin for secretarial and other assistance.     

The collagen of the gingiva and of its blood vessels

The collagen of the gingiva and that of its blood vessels of several animal species and of man were studied with the scanning electron microscope following corrosion with pancreatin at 0.3%. The gingival collagen forms fundamental cells or fasciculi that are distributed throughout the entire territory. In the interior of the cells there are small balls either detached or in clusters. Because of the contact and the fusion of these balls with the collagenic fasciculi, and due to their resistance to the pancreatin corrosion procedure, we believe them to be condensations of collagen. The approximate size of these balls was 2 micrometer. The fasciculi that surround these cells have either the form of bundles or are united in bands. There is an abundance of blood vessels in the gingiva and they are surrounded by collagen. This collagen can assume any of varied positions. The relations that exist between the vascular collagen and that of the gingiva are different in every case.     

Cryopreservation of isolated blood vessels

Canine saphenous veins were immersed in fetal calf serum (FCS) containing various cryoprotective agents, slowly frozen and stored for several weeks at subzero temperatures. Pharmacological investigations of frozen/thawed tissues revealed considerable attenuation of the contractile force of frozen stored veins as compared to unfrozen veins. The best recovery after thawing of frozen stored canine veins was obtained on tissues which had been frozen slowly to -70 degrees C and stored in liquid nitrogen while being immersed in FCS containing 1.8 mol/l dimethyl sulfoxide (DMSO). Though the maximum response to noradranline of helical strips prepared from these veins was diminished to about 60% the evidence suggests that there may be a very good preservation of the main biochemical properties, such as monoamine oxidase activity, endogenous prostaglandin synthesis and neuronal uptake mechanism in veins stored under these conditions. The same method of cryopreservation was applied to store samples of human veins. Comparison of the pD2 values for various agonists and of the blocking activities of various antagonists of both 5-HT receptors and alpha-adrenoceptors yielded an excellent correlation between the parameters determined on frozen/thawed and unfrozen human veins. It is concluded that freezing isolated blood vessels may be considered an effective means of preserving and storing vascular tissues for pharmacological investigations.     

Interdependent development of blood vessels and organs

The cardiovascular system is the first functional organ in the vertebrate embryo, and many organs start to develop adjacent to cells of the cardiovascular system. Endothelial cells (EC) form the inner cell lining of blood vessels and represent the major cell type that interacts with developing organs. On the one hand, EC provide organs with signals. These signals determine the location, differentiation and morphology of an organ. On the other hand, EC receive signals from the organ-specific cell types. Such signals give EC organ-specific features that the organ needs to interact with the circulatory system. This review provides the reader with specific examples of an interdependent development of organs and blood vessels.Eckhard Lammert and Ganka Nikolova were supported by the Deutsche Forschungsgemeinschaft DFG (La1216/2–1)