Transport: blood and circulation

The blood system transports nutrients, oxygen, carbon dioxide and nitrogenous wastes; other functions include defence. Fish have a closed, single circulation in which blood is pumped by a contractile heart via a ventral aorta to the gills, then via the dorsal aorta to vessels supplying the tissues and organs, with a venous return to the heart. Large venous sinuses occur in elasmobranchs. Air-breathing fish have modifications of the circulation. Complex networks of narrow blood vessels can occur as red patches, retia, maximizing transfer of nutrients, oxygen or heat. Most fish have nucleated red blood cells (erythrocytes) with haemoglobin. The types of white blood cells (leucocytes) are similar to those of other vertebrates but there are thrombocytes rather than platelets. Nutrient transport is in the plasma, the fluid component of the blood, which may also carry antifreeze agents and molecules (e.g. urea in elasmobranchs) which counteract deleterious osmotic effects

Case report of gross hematuria in the nutcracker syndrome resolved by renocaval reimplantation

Introduction. Nutcracker syndrome is defined as a set of signs and symptoms secondary to compression of the left renal vein (LRV) in the acute anatomic angle between the aorta and its superior mesenteric branch. Case report. A 38-year old woman with asymptomatic and ?idiopathic? gross hematuria came to the Clinic for Vascular and Endovascular Surgery, Clinical Center of Serbia in Belgrade. Hematuria was documented by cystoscopy and was found to be unilateral, located to the left urethral orifice. The contrast-enhanced multidetector computed tomography (MDCT) scan showed a stenotic LRV due to the extrinsic compression in the angle formed by the ventral aorta and superior mesenteric artery (MSA), with a jet of contrast through the lumen. Considering the negative investigations for more common causes of hematuria, its incapacitating nature, and above mentioned imaging findings suggestive of the nutcracker syndrome, an indication for the open surgical correction of the LRV entrapment was established. The patient underwent reimplantation of the LRV into the more distal inferior vena cava (IVC), to relocate it out of the constrictive aortomesenteric space. Intraoperative findings were notable for blood flow turbulence in the LRV and hypertrophy of its tributaries, which were ligated. We presented the first published case in the Serbian literature on nutcracker syndrome with hematuria resolved by renocaval reimplantation. Conclusion. This case report demonstrates that renocaval reimplantation, as the open surgery technique, could be the adequate method for resolving gross hematuria in patients with nutcracker syndrome.

Potent cardiovascular actions of homologous adrenomedullins in eels

Adrenomedullin (AM), known as a multifunctional hormone in mammals, forms a unique family of five paralogous peptides in teleost fish. To examine their cardiovascular effects using homologous AMs in eels, we isolated cDNAs encoding four eel AMs, and named AM1 (ortholog of mammalian AM), AM2, AM3 (paralog of AM2 generated only in teleost lineage), and AM5 according to the known teleost AM sequences. Unlike pufferfish, not only AM1 but AM2/3 and AM5 were expressed ubiquitously in various eel tissues. Synthetic mature AM1, AM2, and AM5 exhibited vasodepressor effects after intra-arterial injections, and the effects were more potent at dorsal aorta than at ventral aorta. This indicates that AMs preferentially act on peripheral resistance vessels rather than on branchial arterioles. The potency was in the order of AM2 = AM5 ≫ AM1 in both freshwater (FW) and seawater (SW) eels, which is different from the result of mammals in which AM1 is as potent as, or more potent than, AM2 when injected peripherally. The minimum effective dose of AM2 and AM5 in eels was 1/10 that of AM1 in mammals. The hypotension reached 50% at 1.0 nmol/kg of AM2 and AM5, which is much greater than atrial natriuretic peptide (20%), another potent vasodepressor hormone. Even with such hypotension, AMs did not change heart rate in eels. In addition, AM1 increased blood pressure at ventral aorta and dorsal aorta immediately after an initial hypotension at 5.0 nmol/kg, but not with AM2 and AM5. These data strongly suggest that specific receptors for AM2 and AM5 exist in eels, which differ from the AM1 receptors identified in mammals.

Myocardial Neovascularization by Adult Bone Marrow-Derived Angioblasts: Strategies for Improvement of Cardiomyocyte Function

In the pre-natal period hemangioblasts, derived from the human ventral aorta give rise to cellular elements involved in both hematopoiesis and vasculogenesis, resulting in formation of the primitive capillary network. Endothelial precursors with phenotypic and functional characteristics of embryonic hemangioblasts are also present in human adult bone marrow, and can be used to induce infarct bed vasculogenesis and angiogenesis after experimental myocardial infarction. The neovascularization results in decreased apoptosis of hypertrophied myocytes in the peri-infarct region, long-term salvage and survival of viable myocardium, reduction in collagen deposition, and sustained improvement in cardiac function. Autologous angioblasts may also be useful in cellular therapy strategies aiming to regenerate myocardial tissue after established heart failure. It is likely that protocols using cardiomyocyte/mesenchymal stem cells will require balanced co-administration of angioblasts to provide vascular structures for supply of oxygen and nutrients to both the chronically ischemic, endogenous myocardium and to the newly-implanted cardiomyocytes. Future studies will need to address the timing, relative concentrations, source and route of delivery of each of these cellular populations in animal models of acute and chronic myocardial ischemia.

Hypoxic vasoconstriction of cyclostome systemic vessels: the antecedent of hypoxic pulmonary vasoconstriction?

Hypoxic vasoconstriction (HV) is an intrinsic response of mammalian pulmonary vascular smooth muscle (VSM). In the present study, HV was examined by myography of vessel rings from three primitive vertebrates: New Zealand hagfish (NZH), Pacific hagfish (PH), and sea lamprey (SL). Hypoxia dilated pre-gill arteries (ventral aorta, afferent branchial) from all species, whereas it contracted systemic arteries [dorsal aorta (DA), efferent branchial, celiacomesenteric]. DA HV was reproducible over several days, and it could be sustained in NZH for 8 h without adverse effects. Tension was proportional to Po 2, and half-maximal HV was obtained at Po 2 (mmHg) of 4.7 ± 0.2 (NZH), 0.8 ± 0.1 (PH), and 10.7 ± 1.9 (SL). HV did not require preconditioning (preexisting contractile stimulus) and was unaffected by elevated extracellular potassium (200 mM NZH; 80 mM SL); removal of the endothelium (NZH); or inhibitors of cyclooxygenase, lipoxygenase, cytochrome P-450 or antagonists of α-adrenergic, muscarinic, nicotinic, purinergic, or serotoninergic receptors. These results show that HV is an intrinsic feature of systemic VSM in cyclostomes and suggest that HV has been in the repertoire of VSM responses, since the origin of vertebrates. The exceptionally hardy HV in cyclostome DA may provide a useful model with which to examine both the phylogeny and mechanisms of this response.