On P2X receptors in the brain: microvessels. Dedicated to the memory of the late Professor Geoffrey Burnstock (1929-2020)

This tribute article presents selected immunocytochemical and transmission electron microscope data on the location of ATP-gated P2X receptor in the rat brain, as studied in the 1990s in Prof G. Burnstock’s laboratory at University College London. There are examples of immuno-ultrastructural findings and introductory information about pre- and post-synaptic location of P2X receptors in the rat cerebellum and endocrine hypothalamus to support the concept of purinergic transmission in the central nervous system. Then findings of diverse immunoreactivity for P2X1, P2X2, P2X4, and P2X6 receptors associated with brain microvessels are shown, including vascular endothelium and pericytes as well as perivascular astrocytes and neuronal components. These findings imply the involvement of P2X receptors and hence purinergic signalling in the neurovascular unit, at least in microvessels in the rat cerebellum and hypothalamic paraventricular and supraoptic nuclei examined here. Various aspects of P2X receptors in brain microvessels are discussed

Nerve-perivascular fat communication as a potential influence on the performance of blood vessels used as coronary artery bypass grafts.

Perivascular fat, the cushion of adipose tissue surrounding blood vessels, possesses dilator, anti-contractile and constrictor actions. The majority of these effects have been demonstrated in vitro and may depend on the vessel and/or the experimental method or species used. In general, the relaxant effect of perivascular adipose tissue is local and may be either endothelium-dependent or endothelium-independent. However, nerve stimulation studies show that, in general, perivascular adipose tissue (PVAT) has an anti-contractile vascular effect likely to involve an action of the autonomic vascular nerves. Apart from a direct effect of perivascular fat-derived factors on bypass conduits, an interaction with a number of neurotransmitters and other agents may play an important role in graft performance. Although the vascular effects of PVAT are now well-established there is a lack of information regarding the role and/or involvement of peripheral nerves including autonomic nerves. For example, are perivascular adipocytes innervated and does PVAT affect neuronal control of vessels used as grafts? To date there is a paucity of electrophysiological studies into nerve-perivascular fat control. This review provides an overview of the vascular actions of PVAT, focussing on its potential relevance on blood vessels used as bypass grafts. In particular, the anatomical relationship between the perivascular nerves and fat are considered and the role of the perivascular-nerve/fat axis in the performance of bypass grafts is also discussed

Sympathetic innervation of the kidney in health and disease: Emphasis on the role of purinergic cotransmission

There is introductory information about non-synaptic transmission at sympathetic neuroeffector junctions and sympathetic nerve cotransmission utilizing noradrenaline and ATP as cotransmitters. Then the organzation and location of sympathetic nerves in different sites in the kidney are described, including renal arteries, juxtaglomerular arterioles and renal tubules. Sympathetic nervous control of glomerular filtration rate and of renin secretion are discussed. Evidence, obtained largely from experiments on animals, for sympathetic nerve modulation of the transport of water, sodium and other ions in the collecting duct of the nephron is described. Finally, there is coverage of the roles of sympathetic nerves in renal diseases, including hypertension, diabetes, hypothyroidism and ischaemia

A Brief Comment on Vasa Vasorum of Human Saphenous Vein: relevance for Coronary Artery Bypass Surgery

The importance of the vasa vasorum and blood supply to the wall of human saphenous vein (hSV) used for coronary artery bypass grafting (CABG) is briefly discussed. This is in the context of the possible physical link of the vasa vasorum connecting with the lumen of hSV and the anti-ischaemic impact of this microvessel network in the hSV used for CABG

Saphenous Vein Vasa Vasorum as a Potential Target for Perivascular Fat-Derived Factors

Perivascular adipose tissue (PVAT) is a source of factors affecting vasomotor tone with the potential to play a role in the performance of saphenous vein (SV) bypass grafts. As these factors have been described as having constrictor or relaxant effects, they may be considered either beneficial or detrimental. The close proximity of PVAT to the adventitia provides an environment whereby adipose tissue-derived factors may affect the vasa vasorum, a microvascular network providing the vessel wall with oxygen and nutrients. Since medial ischaemia promotes aspects of graft occlusion the involvement of the PVAT/vasa vasorum axis in vein graft patency should be considered

Endothelin-1, endothelin receptor antagonists, and vein graft occlusion in coronary artery bypass surgery: 20 years on and still no journey from bench to bedside

The saphenous vein is the most commonly used bypass graft in patients with coronary artery disease. During routine coronary artery bypass, grafting the vascular damage inflicted on the vein is likely to stimulate the release of endothelin-1, a potent endothelium-derived vasoconstrictor that also possesses cell proliferation and inflammatory properties, conditions associated with vein graft failure. In both in vitro and in vivo studies, endothelin receptor antagonists reduce neointimal thickening. The mechanisms underlying these observations are multifactorial and include an effect on cell proliferation and cell/tissue damage. Much of the data supporting the beneficial action of endothelin-1 receptor antagonism at reducing intimal thickening and occlusion in experimental vein grafts were published over 20 years ago. The theme of the recent ET-16 conference in Kobe was “Visiting Old and Learning New”. This short review article provides an overview of studies showing the potential of endothelin receptor antagonists to offer an adjuvant therapeutic approach for reducing saphenous vein graft failure and poses the question why this important area of research has not been translated from bench to bedside given the potential benefit for coronary artery bypass patients

A Stock Assessment Program for Chesapeake Bay Fisheries: Development of an Alosa Juvenile Index of Abundance: Annual Report 1990

This presentation is the annual report for Contract No. NA90AA-H-SF671 A Stock Assessment Program for Chesapeake Bay Fisheries: Development of an Alosa Juvenile Index of Abundance, for the period 15 June 1990 to 31 July 1991. The fishes of concern were the alewife (Alosa pseudoharengus), American shad (A. sapidissima), and the blueback herring (A. aestivalis). The abundance of the Alosa stocks, once an important component of the landings of Virginia fisheries, have dramatically decreased in the last decade. The 1981 landings of Alosa species in Virginia were the lowest ever recorded. American shad and river herring are also pursued by recreational fisherman in Virginia, however, the extent and success of this activity is largely unknown. Additionally, these species have a vital ecological role. Young-of-the-year Alosa are the dominant pelagic prey species in their extensive freshwater and upper estuarine nursery grounds. After spawning, adults return to the sea and are prey of many marine piscivores. It is important that studies of the Alosa stocks in Virginia be continued. Current data, as well as historical data, are needed in order that data analyses may make constructive contributions to rational management strategies

Quantifying Seasonal-Variation In Somatic Tissue - Surfclam Spisula-Solidissima (Dillwyn, 1817) - A Case-Study

Condition indexes are commonly derived from bivalve species. Usable meat yields (UMY, in l/bu) from 181 daily landings of Atlantic surfclams, Spisula solidissima (Dellwyn, 1817), at a Virginia processing plant in 1974 and 160 landings in 1975 were used as an index in our analysis. The data were fitted to a basic sinusoidal model and a two-compartment sinusoidal model to demonstrate the utility of these models for quantifying cyclic events. The basic model, x = x(0) + A cos2 pi t + B sin2 pi t, is linear in its independent variables and fitted by multiple regression, with x = UMY, 1 = time in years, where x(0), A, and B are constants determined by the regression procedure (x(0) = mean UMY). Its alternate form is x = x(0) + r cos2 pi(t - t(0)), with x, x(0), and t as before, r = amplitude of the sinusoidal variation, and t, = time when the maximal UMY occurs; r and t, are related to A and B as r = root A(2) + B-2, and t(0) = (1/2 pi)tan(-1) (B/A). The sinusoidal fit to the 1974 data was highly significant (p \u3c 0.0005); therefore, the null hypothesis that the data are not a function of time was rejected. The annual mean yield, x(0), was 5.93 l/bu, t(0) was 0.45 (i.e., the maximal UMY occurred about mid-June), and the amplitude r was 0.730; thus, the difference between the lowest and highest yields, 2r, was almost 1.5 l/bu. Similar estimates were determined from the 1975 data and the combined data. The fit was recalculated for both data sets after excluding apparent outliers. As expected, the root-mean-square residual (RMS,,,) decreased, whereas the coefficient of determination (R(2)) increased with the removal of the apparent outliers, but the fitted parameters were inconsequentially affected. A fit of the data to a two-component sinusoidal model, x = x(0) + A(1) cos2 pi t + B-1 sin2 pi t + A(2) cos4 pi t + B-2 sin4 pi t, modeled an annual variation with an asymmetric rise and fall. As a demonstration, the data were also fitted to a parabolic model, x = a, + a(1)t + a(2)t(2). Although this model produced fits comparably as close as the sinusoidal models, the coefficients are not interpretable in a simple manner, as is the case with the sinusoidal fits, and it does not allow asymmetric behavior