Lattice Boltzmann method for simulating the viscous flow in large distensible blood vessels

A lattice Boltzmann method for simulating the viscous flow in large distensible blood vessels is presented by introducing a boundary condition for elastic and moving boundaries. The mass conservation for the boundary condition is tested in detail. The viscous flow in elastic vessels is simulated with a pressure-radius relationship similar to that of the Pulmonary blood vessels. The numerical results for steady flow agree with the analytical prediction to very high accuracy, and the simulation results for pulsatile flow are comparable with those of the aortic flows observed experimentally. The model is expected to find many applications for studying blood flows in large distensible arteries, especially in those suffering from atherosclerosis. stenosis. aneurysm, etc.

Fractal structures in stenoses and aneurysms in blood vessels

Recent advances in the field of chaotic advection provide the impetus to revisit the dynamics of particles transported by blood flow in the presence of vessel wall irregularities. The irregularity, being either a narrowing or expansion of the vessel, mimicking stenoses or aneurysms, generates abnormal flow patterns that lead to a peculiar filamentary distribution of advected particles, which, in the blood, would include platelets. Using a simple model, we show how the filamentary distribution depends on the size of the vessel wall irregularity, and how it varies under resting or exercise conditions. The particles transported by blood flow that spend a long time around a disturbance either stick to the vessel wall or reside on fractal filaments. We show that the faster flow associated with exercise creates widespread filaments where particles can get trapped for a longer time, thus allowing for the possible activation of such particles. We argue, based on previous results in the field of active processes in flows, that the non-trivial long-time distribution of transported particles has the potential to have major effects on biochemical processes occurring in blood flow, including the activation and deposition of platelets. One aspect of the generality of our approach is that it also applies to other relevant biological processes, an example being the coexistence of plankton species investigated previously.

Nitric oxide control of lower vertebrate blood vessels by vasomotor nerves

In mammals, much is understood about the endothelial and neural NO control mechanisms in the vasculature. In contrast, NO control of blood vessels in lower vertebrates is poorly understood, with the majority of research focusing on the presence of an endothelial NO system; however, its presence remains controversial. This study examined the mechanisms by which NO regulates the large blood vessels of non-mammalian vertebrates. In all species examined, the arteries and veins contained a plexus of NOS-positive perivascular nerves that included nerve bundles and fine, varicose nerve terminals. However, in the large arteries and veins of various species of fishes and amphibians, no anatomical evidence was found for endothelial NOS using both NADPH-diaphorase and eNOS immunohistochemistry. In contrast, perinuclear NOS staining was readily apparent in blue-tongue lizard, pigeon and rat, which suggested that eNOS first appeared in reptiles. Physiological analysis of NO signalling in the vascular smooth muscle of short-finned eel and cane toad could not find any evidence for endothelial NO signalling. In contrast, it appears that activation of the nitrergic vasomotor nerves is responsible for NO control of the blood vessels.

Nitric oxide control of lower vertebrate blood vessels

The gas, nitric oxide, plays a critical role in the control of the cardiovascular system of animals, and in particular blood pressure. This thesis demonstrated unique mechanisms by which nitric oxide regulates the blood vessels of various animals, which will alter our understanding of vascular regulation by peripheral nerves.

The natriuretic peptide system of the heart and central blood vessels of the toad, Bufo marinus

This research has established the presence of a natriuretic peptide system in the cardiovascular system of the toad, Bufo marinus. The presence of atrial natriuretic peptide mRNA and the peptide itself were shown in the heart which does not contain natriuretic peptide receptors in contrast to the large arteries and veins. In arteries these receptors mediated vasodilation. Atrial natriuretic peptide released from the heart may act on large arteries to regulate blood flow, but the action does not target the heart.

The evolution of nitric oxide signalling in vertebrate blood vessels

Nitric oxide is one of the most important signalling molecules involved in the regulation of physiological function. It first came to prominence when it was discovered that the vascular endothelium of mammals synthesises and releases nitric oxide (NO) to mediate a potent vasodilation. Subsequently, it was shown that NO is synthesised in the endothelium by a specific isoform of nitric oxide synthase (NOS) called NOS3. Following this discovery, it was assumed that an endothelial NO/NOS3 system would be present in all vertebrate blood vessels. This review will discuss the latest genomic, anatomical and physiological evidence which demonstrates that an endothelial NO/NOS3 signalling is not ubiquitous in non-mammalian vertebrates, and that there have been key evolutionary steps that have led to the endothelial NO signalling system being a regulatory system found only in reptiles, birds and mammals. Furthermore, the emerging role of nitrite as an endocrine source of NO for vascular regulation is discussed.

Vasodilatory effects of homologous adrenomedullin 2 and adrenomedullin 5 on isolated blood vessels of two species of eel

In mammals, adrenomedullin (AM) is a potent vasodilator through signalling pathways that involve the endothelium. In teleost fishes, a family of five AMs are present (AM1/4, AM2/3 and AM5) with four homologous AMs (AM1, AM2/3 and AM5) recently cloned from the Japanese eel, Anguilla japonica. Both AM2 and AM5 have been shown to be strong in vivo vasodepressors in eel, but the mechanism of action of homologous AMs on isolated blood vessels has not been examined in teleost fish. In this study, both eel AM2 and AM5 caused a marked vasodilation of the dorsal aorta. However, only AM5 consistently dilated the small gonadal artery in contrast to AM2 that had no effect in most preparations. Neither AM2 nor AM5 had any effect when applied to the first afferent branchial artery; in contrast, eel ANP always caused a large vasodilation of the branchial artery. In the dorsal aorta, indomethacin significantly reduced the AM2 vasodilation, but had no effect on the AM5 vasodilation. In contrast, removal of the endothelium significantly enhanced the AM5 vasodilation only. In the gonadal artery, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ) significantly reduced the AM5 vasodilation suggesting a role for soluble guanylyl cyclase in the dilation, but l-NNA and removal of the endothelium had no effect. The results of this study indicate that AM2 and AM5 have distinct vasodilatory effects that may be due to the peptides signalling via different receptors to regulate vascular tone in eel.

Disturbance and repair of solitary waves in blood vessels with aneurysm

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

About the arterial blood vessels pelvic opossum's (Didelphis albiventris) behaviour

The work consists of the study of 20 opossums (Didelphis albiventris); 7 females and 13 males, adults, natives of Jaboticabal county proceeding to a canulation and injection of the arterial system with neoprene latex-650 in the aorta artery (full-blooded). Right away the preparations were fixed by a 10% formaldehyde aqueous solution and afterwards dissected and formed a scheme. The analysis of the pieces showed that in the opossum, the end of the aorta always divides in the common iliac artery, right and left sides, both originating the external and internal iliac artery, on the right and left sides. The medium sacral artery results, medianly, from the aorta division's angle in 2 common iliac arteries in 8 cases (40% - 6 males and 2 females); this vessel comes from the left common iliac artery in 7 animals (35% - 5 males and 2 females) or comes from the right common iliac artery, in 5 preparations (25% - 3 females and 2 males). The deep iliac circumflex artery is born by the common iliac artery from the right side in 10 preparations (50% - 6 males and 4 females), can appear as well, concomitantly with the external and internal iliac artery, from the right side in 9 pieces (45% - 6 males and 3 females) and further from the right this vessels can emerge from the external iliac artery, in 1 case only (5% - 1 male).

Topography of the blood vessels in the hilum of the kidney of Myrmecophaga tridactyla

The study was undertaken in 10 formol-imbibed kidneys of great anteater (Myrmecophaga tridactyla). After the dissection the following characteristics were showed: kidney blood vessels are distributed in 2 different sites, namely hilar and extrahilar, amounting 3 to 6 in the right side 3 to 7 in the left side. Arterial branches in extrahilar region range from 1 to 2 in both sides and in hilar region they present from 1 to 4 in the right and 1 to 2 in the left. Venous roots occur in 1 to 2 vessels in the right and 1 to 3 vessels in the left, occupying only the hilar region, except one case where it was present in the right side.