Doppler evaluation of maternal and foetal vessels during normal gestation in queen

The aim of this work is to evaluate the haemodynamic characteristics of maternal and foetal vessels during normal pregnancy in queens, using colour Doppler and pulsed wave Doppler ultrasonography, in order to obtain information about maternal and foetal circulation. The blood waveforms of the uteroplacental arteries, aorta, caudal cava vein and umbilical cord of the fetuses were recorded weekly in seven healthy pregnant queens. Also, the measurements of peak systolic, end diastolic velocities, resistance and pulsatility indices were carried out. Uteroplacental blood flow was biphasic while the ones of the umbilical artery and aorta were first systolic and then diastolic. The caudal cava vein showed a typical waveform of venous vessels. During gestation the EDV and PSV of foetal vessels increased ( < 0.05) while the PI and RI of all vessels examined decreased ( < 0.05) except for the IP of the aorta. The Doppler ultrasonography, also in queens, can be used to evaluate the characteristics of maternal and foetal vessel flow and their progressive changes during pregnancy. This study can be considered the basis for further contribution in diagnosing and monitoring high-risk pregnancies in Veterinary Medicine.     

Doppler evaluation of maternal and fetal vessels during normal gestation in rabbits

The aim of this work was to evaluate the hemodynamic changes in the utero-placental arterial vessels in rabbits (Orictolagus cuniculus) throughout pregnancy as well as those in the umbilical cord, aorta, and caudal vena cava of fetuses to establish their normal reference ranges for systolic peak velocity (SPV), end diastolic velocity (EDV), pulsatility index (PI), and resistance index (RI). The blood flow waveforms were monitored every 4 d in 10 rabbits from Day 10 of pregnancy onward by means of color and pulsed wave Doppler ultrasonography using a 5.5-7.5 MHz microconvex transabdominal probe. The utero-placental blood flow was characterized by steep increases and decrease in the SPV with a slow diastolic wave and relatively high EDV, whereas that of the umbilical artery was discontinuous until Day 22 of pregnancy, when a diastolic waveform was also detectable. From Day 10 to 22 of pregnancy, the fetal aorta blood flow was discontinuous, but thereafter a diastolic peak was measurable. The blood flow of the fetal caudal vena cava was characterized by a systolic peak followed by a small diastolic peak. Throughout the gestation, the SPV and the EDV of maternal and fetal vessels increased (α < 0.05), whereas the PI and the RI decreased (α < 0.05), except for the utero-placental vessels. This work confirms that the rabbit could also be a valid experimental animal model to study, by Doppler ultrasonography, functional hemodynamic changes of the fetuses and placenta vessels in both normal and pathophysiologic conditions.     

Ultrastructure of gill bars of Branchiostoma lanceolatum with special reference to gill skeleton and blood vessels (Cephalochordata)

Summary The skeletal rods of the gill bars of Branchiostoma have been examined histochemically and electron microscopically. The rods are composed of 15-nm thick filaments which are interconnected by 10-nm thick and 15-nm long cross-linkages. The filaments appear to consist of structural proteins that are totally different from the proteins of the collagen fibrils. The cross-linkages between the filaments consist of acid mucopolysaccharides, and probably include chondroitin sulphate. The fine structure of blood vessels in the gill bars has been studied in uninjected specimens and in those intravascularly injected with either india ink or horseradish peroxidase. Blood vessels surrounded by basal laminae of delimiting epithelia or simply surrounded by connective tissue material are present in the gill bars. Very characteristic blood cells are normally found in these vessels. Furthermore, when either india ink or horseradish peroxidase is injected via the aorta and the endostylar vessel, irregular slitlike channels can be seen in the connective tissue. These channels are in open connection with the blood vessels and are thus a part of the vascular system.Supported by a grant from the Danish Natural Science Research Council     

The Circulatory System of Amphioxus (Branchiostoma lanceolatum (Pallas))

The morphology of the circulatory system of Amphioxus ( Branchiostoma lanceolatum (Pallas)) has been investigated using a new intravascular injection technique. A survey of the vessels of Amphioxus using this technique is given. The dorsal arteries and their ramifications are described in detail. The new injection technique brought to light myoseptal plexi, supplied from the dorsal arteries, between every two myomeres. Also the ventral parietal arteries have a much more complicated course than hitherto accepted. They are connected with an atrial plexus which is a continuous net of small vessels in the whole length of the dorso-lateral wall of the atrial cavity. It is postulated that this plexus has a supplementary function in respiration. Plexi of minute vessels in the gonads and a real blood circulation with afferent and efferent gonadal vessels have been demonstrated. Two vessels connecting the liver plexus with the cardinal vein (or the atrial plexi) have been noticed, the v. communicans accessoria anterior mentioned in 1900 by Burchardt, and a so-called oblique vessel never described before. The vessels of the caudal region are analyzed completely and also here a real blood circulation appears possible.     

Circulatory organs of abdominal appendages in primitive insects (Hexapoda: Archaeognatha, Zygentoma and Ephemeroptera)

The abdominal circulatory organs and the haemolymph supply of the terminal filament and the cerci were investigated in a total of nine species (serial semithin sections, TEM, in vivo observations). In all investigated species, the dorsal vessel features a bidirectional flow. In the 10th abdominal segment, there is an intracardiac valve preventing flow in the anterior direction. The posterior portion of the dorsal vessel differs significantly from the anterior portion in design and wall structure. Pumping actions and frequencies do not correspond with each other in the two portions. Vessels supply haemolymph to the long terminal appendages. The terminal filament vessel is connected to the dorsal vessel, the two cercal vessels originate from a transverse septum at the base of the terminal filament. All taxa show the same flow pattern through the caudal appendages. Ephemeroptera have a unique spherical body at the posterior end of the dorsal vessel functioning as a backflow valve. The results indicate that the plesiomorphic state of the circulatory organs in the abdomen of primitive insects differ distinctly from that of higher insects which serve as bases for generalized schemes common to entomological textbooks.     

Evaluation of dorsal aorta cannulation for immunological studies of grouper (Epinephelus malabaricus)

Blood is often withdrawn to study the immune responses of fish. However, netting, handling and anaesthetising the experimental fish, and drawing blood samples cause severe stress that may alter the effects of immune study protocols and treatments. We evaluated the effect of aorta cannulation, for use in immune studies, on grouper (Epinephelus malabaricus) plasma cortisol, total red and white blood cell counts and phagocytosis.Plasma cortisol increased from 30 to 88 ng/ml 1 day after insertion of the cannula, to a maximum of 951 ng/ml 3 to 5 days after surgery, indicating the groupers were stressed by cannulation and post-cannulation inflammation. Total RBC count decreased, and total WBC count increased after surgery. Following cannulation, the phagocytic index of peripheral blood leukocytes decreased from 100% to 46%. The adverse effects of cannulation were mitigated by continuously immersing groupers in oxytetracycline (OTC), which decreased the recovery period for treated fish. In contrast, OTC-treatment did not markedly improve the recovery of groupers subjected to caudal vessel puncture. Cortisol levels in OTC-treated grouper with caudal vessel puncture were significantly higher than in OTC-treated, cannulated grouper, and remained at a high level until day 13 of the experiment. From day 7 to 13, total RBC and WBC counts in OTC-treated, cannulated groupers were significantly different from those in OTC-treated groupers with caudal vessel puncture. OTC treatment improved the phagocytic index of groupers subjected to caudal vessel puncture, but the phagocytic index was lower than that of groupers subjected to cannulation. Cannulation minimises visual and handling disturbances, and facilitates standardisation of experimental conditions and quick and easy sampling via the dorsal aorta cannula. Therefore, dorsal aorta cannulation minimises the stress of blood sampling and should prove useful for immune studies in fish.     

Morphology and tyrosine-hydroxylase immunohistochemistry of the systemic secondary vessel system of the blue catfish,Arius graeffei

Fish have a secondary vessel system which emerges from the primary vasculature via large numbers of coiled origins. The precise role of this vessel system is unknown. Vascular casting techniques and scanning electron microscopy reveal that the secondary vessels of the blue catfish, Arius graeffei, originate from dorsal, lateral, and ventral segmental primary arteries and from the caudal dorsal aorta. These vessels anastomose with each other to form larger secondary arteries which parallel the primary vessels for their entire length. Secondary vessels do not appear to form a capillary bed in the skin in A. graeffei as they do in some fish species. Coiled secondary vessel origins are abundant within the tunica media and adventitia of the primary vessels from which they emerge. The origins of the secondary vessels are surrounded by the extensive cytoplasmic processes of specialized endothelial cells. These processes extend for up to 6 μm into the lumen of the primary vessel. Ultrastructurally the coiled secondary capillaries consist of an endothelial cell tube which is surrounded by a single layer of pericytes. These endothelial cells extend large numbers of microvilli into the lumen of the coiled secondary capillary. Nerve terminals are commonly associated with the coiled secondary capillaries. Immunohistochemistry has revealed the presence of tyrosine-hydroxylase, an enzyme involved in catecholamine synthesis in nerve varicosities close to secondary vessels in A. graeffei. This vessel system could therefore be regulated by adrenergic nerves. © 1996 Wiley-Liss, Inc.     

Functional morphology of the dorsal vessel in the adult fly Protophormia terraenovae (diptera,calliphoridae)

The morphology and ultrastructure of the contractile tubular vessel acting as the cardiac pump in Protophormia terraenovae flies were analyzed by means of light microscopy, SEM and TEM. The results provide a novel anatomical picture of the two vessel portions, the abdominal heart and the aorta, and lay the foundations for an interpretation of the cardiocirculatory function in the fly. In the thorax, the thin and unchambered aorta is without apertures, while the abdominal heart presents a very small caudal aperture and pairs of lateral ostia, one in each of the five chambers of which it is composed. The ostia of the four more distal chambers are of the incurrent type, which is to say that they act as valves ensuring that hemolymph flows only into the heart. Conversely, the ostia in the most proximal chamber allow hemolymph to flow both into and out of the heart. The entire vessel is composed of a single layer of myofibers that are oriented circularly around the lumen in the abdominal heart and longitudinally in the thoracic aorta. The abdominal heart has a thicker wall, a far more diffused and thick distribution of tracheoles, and a far greater number of mitochondria with respect to the aorta. This arrangement ensures a greater availability of oxygen and energy in the abdominal heart compared to the aorta and leads one to suppose that the high‐ and low‐frequency contractions of the cardiac cycle (Thon, [1982] J. Insect Physiol. 28:411–416) can be attributed to the abdominal heart and the aorta, respectively. J. Morphol. 240:15–31, 1999. © 1999 Wiley‐Liss, Inc.     

Vasculature of the head and respiratory organs in an obligate air-breathing fish,the swamp eel Monopterus (=Amphipnous) cuchia

Methyl methacrylate vascular corrosion replicas were used to examine the macrocirculation in the head region and the microcirculation of respiratory vessels in the air-breathing swamp eel Monopterus cuchia. Fixed respiratory tissue was also examined by SEM to verify capillary orientation. The respiratory and systemic circulations are only partially separated, presumably resulting in supply of mixed oxygenated and venous blood to the tissues. A long ventral aorta gives rise directly to the coronary and hypobranchial arteries. Two large shunt vessels connect the ventral aorta to the dorsal aorta, whereas the remaining ventral aortic flow goes to the respiratory islets and gills. Only two pairs of vestigial gill arches remain, equivalent to the second and third arches, yet five pairs of aortic arches were identified. Most aortic arches supply the respiratory islets. Respiratory islet capillaries are tightly coiled spirals with only a fraction of their total length in contact with the respiratory epithelium. Valve-like endothelial cells delimit the capillary spirals and are unlike endothelial cells in other vertebrates. The gills are highly modified in that the lamellae are reduced to a single-channel capillary with a characteristic three-dimensional zig-zag pathway. There are no arterio-arterial lamellar shunts, although the afferent branchial artery supplying the gill arches also supplies respiratory islets distally. A modified interlamellar filamental vasculature is present in gill tissue but absent or greatly reduced in the respiratory islets. The macro- and micro-circulatory systems of M. cuchia have been considerably modified presumably to accommodate aerial respiration. Some of these modifications involve retention of primitive vessel types, whereas others, especially in the microcirculation, incorporate new architectural designs some of whose functions are not readily apparent.     

Detection and Characterization of a Protein Isoaspartyl Methyltransferase Which Becomes Trapped in the Extracellular Space During Blood Vessel Injury

Injury to rat blood vessels in vivo was found to release intracellular pools of protein D-aspartyl/L-isoaspartyl carboxyl methyltransferase (PIMT) into the extracellular milieu, where it becomes trapped. This trapped cohort of PIMT is able to utilize radiolabeled S-adenosyl-L-methionine (AdoMet) introduced into the circulation to methylate blood vessel proteins containing altered aspartyl residues. As further shown in this study, methylated substrates are detected only at the specific site of injury. In vitro studies more fully characterized this endogenous PIMT activity in thoracic aorta and inferior vena cava. Methylation kinetics, immunoblotting, and the lability of methylated substrates at mild alkaline pH were used to demonstrate that both types of blood vessel contain an endogeneous protein D-aspartyl/L-isoaspartyl carboxyl methyltransferase (PIMT). At least 50% of the PIMT activity is resistant to nonionic detergent extraction, suggesting that the enzyme activity becomes trapped within or behind the extracellular matrix (ECM). Quantities of lactate dehydrogenase (LDH), another soluble enzyme of presumed intracellular origin, were found to be similarly trapped in the extracellular space of blood vessels.     

Study of normal and pathological blood vessel morphogenesis in Flt1-tdsRed BAC Tg mice

Blood vessel development and network patterning are controlled by several signaling molecules, including VEGF, FGF, TGF‐ß, and Ang‐1,2. Among these, the role of VEGF‐A signaling in vessel morphogenesis is best understood. The biological activity of VEGF‐A depends on its reaction with specific receptors Flt1 and Flk1. Roles of VEGF‐A signaling in endothelial cell proliferation, migration, survival, vascular permeability, and induction of tip cell filopodia have been reported. In this study, we have generated Flt1‐tdsRed BAC transgenic (Tg) mice to monitor Flt1 gene expression during vascular development. We show that tdsRed fluorescence is observed within blood vessels of adult mice and embryos, indicative of retinal angiogenesis and tumor angiogenesis. Flt1 expression recapitulated by Flt1‐tdsRed BAC Tg mice overlapped well with Flk1, while Flt1 was expressed more abundantly in endothelial cells of large blood vessels such as dorsal aorta and presumptive stalk cells in retina, providing a unique model to study blood vessel development. genesis 50:561–571, 2012. © 2012 Wiley Periodicals, Inc.     

Intrinsic Innervation of a Reptilian Esophagus (Podarcis hispanica)

We study the esophagus of Podarcis hispanica through different methods to clarify the structure and affinities of its wall innervation. The acetylcholinesterase method reveals cholinesterase activity in two submucosal nervous plexuses, with an increasing degree of structural complexity in the reptilian esophagus, compared with amphibians. Noradrenergic innervation, detected through fluorescence induced by formol, widely spreads its network in both the myenteric and submucosal plexuses (around the blood vessels in the external submucosal plexus, and to the glandular lamina propria in the inner submucosal plexus). Immunohistochemistry for vasoactive intestinal peptide shows a widespread innervation, with neurons clustered in ganglia and also scattered through the VIPergic network, only at the myenteric plexus. Immunohistochemistry for substance P shows a rich innervation along the entire wall of the esophagus, more concentrated in its caudal region, around the blood vessels. Electron microscopy shows the enteric neuronal ultrastructure and its relationship with the esophagus wall.     

Haemodynamic effects of adenosine on gills of the trout (Salmo gairdneri)

Summary The haemodynamic effects of adenosine on gills of the trout (Salmo gairdneri) were studied with in vitro and in vivo preparations.On the isolated head preparation, adenosine induced a decrease of the ventral aortic inflow and of the dorsal aortic outflow. Simultaneously the venous outflow increased. These effects were antagonized by theophylline. Adenosine induced a vasoconstriction in gill arches without filaments perfused by the afferent or the efferent branchial arteries. The efferent vessels were more sensitive to adenosine than afferent vessels. The whole systemic circulation of the isolated trunk did not show any response to adenosine. When adenosine was infused into the ventral aorta of living trout, the gill resistance to blood flow was greatly increased.These results suggest that adenosine is able to control the arterious and venous blood pathways in the trout gills by modulating their vascular resistance.     

Disruption of acvrl1 increases endothelial cell number in zebrafish cranial vessels

The zebrafish mutant violet beauregarde (vbg) can be identified at two days post-fertilization by an abnormal circulation pattern in which most blood cells flow through a limited number of dilated cranial vessels and fail to perfuse the trunk and tail. This phenotype cannot be explained by caudal vessel abnormalities or by a defect in cranial vessel patterning, but instead stems from an increase in endothelial cell number in specific cranial vessels. We show that vbg encodes activin receptor-like kinase 1 (Acvrl1; also known as Alk1), a TGFbeta type I receptor that is expressed predominantly in the endothelium of the vessels that become dilated in vbg mutants. Thus, vbg provides a model for the human autosomal dominant disorder, hereditary hemorrhagic telangiectasia type 2, in which disruption of ACVRL1 causes vessel malformations that may result in hemorrhage or stroke. Movies available on-line     

A constrained mixture model for developing mouse aorta

Mechanical stresses influence the structure and function of adult and developing blood vessels. When these stresses are perturbed, the vessel wall remodels to return the stresses to homeostatic levels. Constrained mixture models have been used to predict remodeling of adult vessels in response to step changes in blood pressure, axial length and blood flow, but have not yet been applied to developing vessels. Models of developing blood vessels are complicated by continuous and simultaneous changes in the mechanical forces. Understanding developmental growth and remodeling is important for treating human diseases and designing tissue-engineered blood vessels. This study presents a constrained mixture model for postnatal development of mouse aorta with multiple step increases in pressure, length and flow. The baseline model assumes that smooth muscle cells (SMCs) in the vessel wall immediately constrict or dilate the inner radius after a perturbation to maintain the shear stress and then remodel the wall thickness to maintain the circumferential stress. The elastin, collagen and SMCs have homeostatic stretch ratios and passive material constants that do not change with developmental age. The baseline model does not predict previously published experimental data. To approximate the experimental data, it must be assumed that the SMCs dilate a constant amount, regardless of the step change in mechanical forces. It must also be assumed that the homeostatic stretch ratios and passive material constants change with age. With these alterations, the model approximates experimental data on the mechanical properties and dimensions of aorta from 3- to 30-day-old mice.     

The anatomy of the blood vascular system of the giant vestimentiferan tubeworm Riftia pachyptila (Siboglinidae,Annelida)

The giant dimensions of vestimentiferan Riftia pachyptila (Jones, 1981 ) are achieved thanks to the well‐developed vascular system. In the vestimentum, there is a complicated net of lacunae, including the brain blood supply and the ventral lacuna underlying the ciliary field. The trunk region has an extensive network of blood vessels feeding the gonads («rete mirabile»). The thick muscular lining of the mesenterial vessels in the trunk and the dorsal vessel in the opisthosome serves as an additional pump, pushing blood into numerous vessels in the segments. It was hypothesized that the blood envelope of the ventral blood vessel in the trunk provides the blood supply to the trophosome. The 3D reconstruction has revealed that there are two vascular systems of the tentacular crown of R. pachyptila . Blood runs into the tentacles via axial afferent vessels, as described earlier only for Riftia , and also via basal ones, as described for other vestimentiferans except Riftia . The basal ones are poorly developed, and the number of lamellar blood vessels is small, indicating a lack of demand for these within huge R. pachyptila . It appears that the presence of these vessels is the preserved ancestral state of Vestimentifera. In different portions of the dorsal vessel, the morphology of the intravasal body varies, depending on function.     

Variability in the Presence of Elastic Fibre-like Structures in the Ventral Aorta of Agnathans (Hagfishes and Lampreys)

This paper investigates whether elastic fibre-like structures are present in the ventral aorta of hagfishes and lampreys. Fibres, which are morphologically similar to the elastic fibres of gnathostomatous (jawed) vertebrates, are shown to be present in the ventral aorta of the hagfish Paramyxine atami, and also, but to a lesser extent, the dorsal aorta of this species and the ventral aorta of another hagfish, Eptatretus stouti.The ‘elastic’ tissue formed irregular sheet-like aggregates, comprising well-defined amorphous material surrounded by tubular microfibrils, whose diameters ranged from 10 to 15 nm. While this tissue was most abundant in the same region of the aortae as that occupied by the elastica interna in the blood vessels of gnathostomes, it was also found deeper in the wall of these blood vessels. Although tubular microfibrils were found in the ventral aorta of the hagfish Myxine glutinosaand the lamprey Geotria australis, these were never associated with well–defined, amorphous material. This parallels the results of previous studies on Myxine glutinosaand another species of lamprey, Petromyzon marinus.Thus, the elastic fibre–like tissues found in the ventral aortae of P. atamiand E. stoutiprovide the first examples of such structures in this region in agnathan vertebrates.     

On the evolution of arterial vascular patterns of tetrapods

The factors that explain the diverse arrangement of the major arteries of tetrapods are not known. Here, I aim to illuminate some of the underpinnings of these patterns. I review the variation in the sauropsid left, right, and dorsal aortae regarding the origin of the gastrointestinal blood vessels and the relative diameters of left and right aortae where they join together to form the dorsal aorta. I focus on these features because the quality of blood that flows through these aortae can vary depending on the state of cardiac shunting and the size of the vessel can provide insight into the quantity of blood borne by the vessels. I then place the information in a phyletic, historical, and ecological context. The plesiomorphic pattern is for the gastrointestinal vessels to arise as segmental arteries from the dorsal aorta, which is formed from the confluence of left and right aortae with similar diameters. The pattern is well conserved with only two major variations. First, in several clades of reptiles (testudines, crocodilians, lizards of the genera Varanus and Hydrosaurus) a substantial portion of the gastrointestinal arteries arises from the left aorta, leaving the diameter of the left aorta smaller than the right at their confluence. I hypothesize that this vascular arrangement facilitates growth by allowing more alkaline blood to flow to the somatic (body wall) and appendicular circulations, which may promote bone deposition and inhibit resorption, whereas hypercapnic, acidic blood flows to the digestive viscera, which may provide CO₂ as a substrate for the synthesis of gastric acid, bicarbonate, fatty acids, glutamine, purine rings, as well as glucose from lactate. Second, in some snakes and lizards with snake‐like body forms, such as Amphisbaenidae, the diameters of left and right aortae are asymmetrical at their confluence with the left aorta exceeding the right, but in members of the amphibian order Gymnophiona the right generally exceeds the left. This condition is associated with asymmetrical development of the lungs. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Pulsatile blood flow effects on temperature distribution and heat transfer in rigid vessels

The effect of blood velocity pulsations on bioheat transfer is studied. A simple model of a straight rigid blood vessel with unsteady periodic flow is considered. A numerical solution that considers the fully coupled Navier-Stokes and energy equations is used for the simulations. The influence of the pulsation rate on the temperature distribution and energy transport is studied for four typical vessel sizes: aorta, large arteries, terminal arterial branches, and arterioles. The results show that: the pulsating axial velocity produces a pulsating temperature distribution; reversal of flow occurs in the aorta and in large vessels, which produces significant time variation in the temperature profile. Change of the pulsation rate yields a change of the energy transport between the vessel wall and fluid for the large vessels. For the thermally important terminal arteries (0.04-1 mm), velocity pulsations have a small influence on temperature distribution and on the energy transport out of the vessels (8 percent for the Womersley number corresponding to a normal heart rate). Given that there is a small difference between the time-averaged unsteady heat flux due to a pulsating blood velocity and an assumed nonpulsating blood velocity, it is reasonable to assume a nonpulsating blood velocity for the purposes of estimating bioheat transfer.