Peptidergic control of the heart of the stick insect, Baculum extradentatum

The dorsal vessel of the Vietnamese stick insect, Baculum extradentatum, consists of a tubular heart and an aorta that extends anteriorly into the head. Alary muscles, associated with the heart, are anchored to the body wall with attachments to the dorsal diaphragm. Alary muscle contraction draws haemolymph into the heart through incurrent ostia. Excurrent ostia lie on the dorsal vessel in the last thoracic and in each of the first two abdominal segments. Muscle fibers are associated with these excurrent ostia. Crustacean cardioactive peptide (CCAP)- and proctolin-like immunoreactivity is present in axons of the segmental nerves that project to the dorsal vessel, and in processes extending over the heart and alary muscles. Proctolin-like immunoreactive processes are also localized to the valves of the incurrent ostia and to the excurrent ostia. Neither the link nerve neurons, nor the lateral cardiac neurons, stain positively for these peptides. Physiological assays reveal dose-dependent increases in heart beat frequency in response to CCAP and proctolin. Isolating the dorsal vessel from the ventral nerve cord led to a change in the pattern of heart contractions, from a tonic, stable heart beat, to one which was phasic. The tonic nature was restored by the application of CCAP.     

Scanning electron microscopy of the dorsal vessel of Panstrongylus megistus (Burmeister, 1835) (Hemiptera: Reduviidae).

In this study we analyzed the microanatomy of the dorsal vessel of the triatomine Panstrongylus megistus. The organ is a tubule anatomically divided into an anterior aorta and a posterior heart, connected to the body wall through 8 pairs of alary muscles. The heart is divided in 3 chambers by means of 2 pairs of cardiac valves. A pair of ostia can be observed in the lateral wall of each chamber. A bundle of nerve fibers was found outside the organ, running dorsally along its major axis. A group of longitudinal muscular fibers was found in the ventral portion of the vessel. The vessel was found to be lined both internally and externally by pericardial cells covered by a thin laminar membrane. Inside the vessel the pericardial cells were disposed in layers and on the outside they formed clusters or rows.     

Contraction of the ventral abdomen potentiates extracardiac retrograde hemolymph propulsion in the mosquito hemocoel

Background

Hemolymph circulation in mosquitoes is primarily controlled by the contractile action of a dorsal vessel that runs underneath the dorsal midline and is subdivided into a thoracic aorta and an abdominal heart. Wave-like peristaltic contractions of the heart alternate in propelling hemolymph in anterograde and retrograde directions, where it empties into the hemocoel at the terminal ends of the insect. During our analyses of hemolymph propulsion in Anopheles gambiae, we observed periodic ventral abdominal contractions and hypothesized that they promote extracardiac hemolymph circulation in the abdominal hemocoel.

Methodology/Principal Findings

We devised methods to simultaneously analyze both heart and abdominal contractions, as well as to measure hemolymph flow in the abdominal hemocoel. Qualitative and quantitative analyses revealed that ventral abdominal contractions occur as series of bursts that propagate in the retrograde direction. Periods of ventral abdominal contraction begin only during periods of anterograde heart contraction and end immediately following a heartbeat directional reversal, suggesting that ventral abdominal contractions function to propel extracardiac hemolymph in the retrograde direction. To test this functional role, fluorescent microspheres were intrathoracically injected and their trajectory tracked throughout the hemocoel. Quantitative measurements of microsphere movement in extracardiac regions of the abdominal cavity showed that during periods of abdominal contractions hemolymph flows in dorsal and retrograde directions at a higher velocity and with greater acceleration than during periods of abdominal rest. Histochemical staining of the abdominal musculature then revealed that ventral abdominal contractions result from the contraction of intrasegmental lateral muscle fibers, intersegmental ventral muscle bands, and the ventral transverse muscles that form the ventral diaphragm.

Conclusions/Significance

These data show that abdominal contractions potentiate extracardiac retrograde hemolymph propulsion in the abdominal hemocoel during periods of anterograde heart flow.     

Homeotic genes autonomously specify the anteroposterior subdivision of the Drosophila dorsal vessel into aorta and heart

The embryonic dorsal vessel in Drosophila possesses anteroposterior polarity and is subdivided into two chamber-like portions, the aorta in the anterior and the heart in the posterior. The heart portion features a wider bore as compared with the aorta and develops inflow valves (ostia) that allow the pumping of hemolymph from posterior toward the anterior. Here, we demonstrate that homeotic selector genes provide positional information that determines the anteroposterior subdivision of the dorsal vessel. Antennapedia (Antp), Ultrabithorax (Ubx), abdominal-A (abd-A), and Abdominal-B (Abd-B) are expressed in distinct domains along the anteroposterior axis within the dorsal vessel, and, in particular, the domain of abd-A expression in cardioblasts and pericardial cells coincides with the heart portion. We provide evidence that loss of abd-A function causes a transformation of the heart into aorta, whereas ectopic expression of abd-A in more anterior cardioblasts causes the aorta to assume heart-like features. These observations suggest that the spatially restricted expression and activity of abd-A determine heart identities in cells of the posterior portion of the dorsal vessel. We also show that Abd-B, which at earlier stages is expressed posteriorly to the cardiogenic mesoderm, represses cardiogenesis. In light of the developmental and morphological similarities between the Drosophila dorsal vessel and the primitive heart tube in early vertebrate embryos, these data suggest that Hox genes may also provide important anteroposterior cues during chamber specification in the developing vertebrate heart.     

The circulatory system in Mysidacea--implications for the phylogenetic position of Lophogastrida and Mysida (Malacostraca, Crustacea)

The morphology of the circulatory organs in Mysida and Lophogastrida (traditionally combined as Mysidacea) is revisited investigating species so far unstudied. In addition to classical morphological methods, a newly developed combination of corrosion casting with micro computer tomography (MicroCT) and computer aided 3D reconstructions is used. Lophogastrida and Mysida show a highly developed arterial system. The tubular heart extends through the greater part of the thorax and is connected with the ventral vessel via an unpaired descending artery. It is suggested that a distinct ostia pattern supports the monophyly of Mysidacea. The cardiac artery system is more complex in Lophogastrida than in Mysida, consisting of up to 10 pairs of arteries that supply the viscera. In both taxa, an anterior and posterior aorta leads off the heart. In the anterior part of the cephalothorax the anterior aorta forms dilations into which muscles are internalized; these structures are called myoarterial formations. One of these myoarterial formations can also be found in all the other peracarid taxa but not in other Malacostraca.     

Functional morphology of the heart and of a new cephalic pulsatile organ in the blowfly Calliphora vicina (Diptera: Calliphoridae) and their roles in hemolymph transport and tracheal ventilation

In the blowfly Calliphora vicina (Diptera: Calliphoridae), the morphology of the dorsal vessel and of a new cephalic accessory pulsatile organ (CPO) were analysed with light-microscopic, SEM and TEM techniques. The CPO and neck aorta are reconstructed 3-dimensionally by computer-aided design. The pulse activity of the CPO and of the heart was measured in intact flies over periods of several hours or days using contact-thermography with laser beam heat-marking. The intratracheal pressure was simultaneously measured at the anterior thoracic spiracle. The dorsal vessel is constructed of pairs of left–right alternating cells. Its enlarged chamber in the anterior abdomen contains two pairs of incurrent ostia, its posterior narrower heart tube possesses three pairs of incurrent ostia and paired caudal excurrent openings. The aorta opens with a funnel-like opening in the neck. Proportions, arrangement and ultrastructure of the aorta, heart cells and pericardial muscles are described. Cushionlike sarcoplasmic protrusions of heart cells (pair no. 17) probably function as internal valves. The neck aorta is constructed of a cuticular ‘roof’ deviating from the dorsal neck membrane and a ventral longitudinal muscle ‘floor’. The aorta is not kept open because of missing muscle or connective tissue strands. The underside of the CPO is fused with air sacs that function as antagonists to the muscles. The heart reverses its beat periodically in resting and active flies. During the longer forward-pulse periods, mean frequency is lower (about 3.0 Hz at Ta 20°C), during the shorter backward periods mean frequency is higher (4.6 Hz). The CPO beats only during forward-pulse periods of the heart with an independent and slower pulse rate (1.8 Hz). The CPO-pulses produce positive pressure pulses at the anterior thoracic spiracle. During backward-pulse periods of the heart and pulse pause of the CPO, a continuous negative pressure arises at the thoracic spiracle instead of pressure pulses. The intimate connection of an accessory pulsatile organ with tracheal air sacs makes it work as a bifunctional pump for hemolymph distribution and tracheal ventilation. Neurosecretory and synapsing innervation of the CPO in connection with aorta, heart and pericardial septum muscle innervation suggest that both organs are regulated and that the duration of their periods is neuronally coordinated.     

Ostia, the inflow tracts of the Drosophila heart, develop from a genetically distinct subset of cardial cells.

The homeobox gene tinman and the nuclear receptor gene seven-up are expressed in mutually exclusive dorsal vessel cells in Drosophila, however, the physiological reason for this distinction is not known. We demonstrate that tin and svp-lacZ expression persists through the larval stage to the adult stage in the same pattern of cells expressing these genes in the embryo. In the larva, six pairs of Svp-expressing cells form muscular ostia, which permit hemolymph to enter the heart for circulation, however, more anterior Svp-expressing cells form the wall of the dorsal vessel. During pupation, the adult heart forms from a chimera of larval and imaginal muscle fibers. The portion of the dorsal vessel containing the larval ostia is histolyzed and the anterior Svp-expressing cells metamorphose into imaginal ostia. This is the first demonstration that the significant molecular diversity of cardial cells identified in the embryonic heart correlates with the formation of physiologically and functionally distinct muscle cells in the animal. Furthermore, our experiments define the cellular changes that occur as the larval heart is remodeled into an imaginal structure in an important model organism.     

Morphology of the pupal heart,adult heart,and associated tissues in the fruit fly,Drosophila melanogaster

The early pupal heart of the fruit fly Drosophila melanogaster has recently been the subject of intense physiological and molecular work, yet it has not been well described, nor has it been compared with the heart of the adult fly. In the work reported here, the hearts of adults and early pupae of D. melanogaster were studied by scanning and transmission electron microscopy and by light microscopy. The hearts of adults and early pupae both consist of a tube of circular striated muscle one cell in thickness. The alary muscles, which suspend the heart, are more delicate in the adult compared to the early pupa. The pericardial cells in both early pupae and adults are connected to the heart by connective tissue radiating from the alary muscles or dorsal diaphragm. We confirm that four major changes occur in the heart during metamorphosis: 1) a conical chamber is formed de novo in the first and second abdominal segments; 2) the adult heart curves to conform to the contour of the abdomen; 3) a layer of longitudinal striated muscle appears on the ventral surface of the heart; 4) a fourth pair of ostia is added to the three already present in the early pupa; and note additionally that 5) the ostia appear as simple openings in the heart of the early pupa but are valve‐like in the adult. J. Morphol. 240:225–235, 1999. © 1999 Wiley‐Liss, Inc.     

The circulatory system in Phreatoicidea: implications for the isopod ground pattern and peracarid phylogeny

The circulatory systems of four species of Phreatoicidea and two species of Oniscidea were studied on the basis of serial semi-thin sections and a corrosion cast method. A 3D computer reconstruction was used to visualize the circulatory organs in the head of the Phreatoicidea. In the Phreatoicidea, the circulatory system consists of a longitudinal dorsal heart extending from the third thoracic to the border between the fourth and fifth pleonal segments. It is equipped with two pairs of asymmetrically arranged ostia, while five pairs of lateral cardiac arteries and an unpaired anterior aorta extend from the heart. Entering the head, the aorta is accompanied by the two first lateral arteries, which supply the muscles of the mandibles. Four pairs of arteries branch off the aorta to supply both pairs of antennae, the eyes, and sinuses in the head. In addition, several minute capillaries extend from the aorta to supply the brain. The two oniscidean species were re-investigated with regard to some characters which have been controversially discussed. In these species, the heart extends from the border between the fifth and sixth thoracic segments to the fifth pleonal segment. Five pairs of lateral cardiac arteries and the unpaired anterior aorta lead off the heart. A ventral vessel was not observed. The ground pattern of the circulatory system in isopods is reconstructed with greater reliability through optimisation of its characters based on proposed phylogenetic relationships. The results do not support a phylogenetic position of the Isopoda as basal Peracarida or even basal Eumalacostraca.     

Comparative analysis of the circulatory system in Amphipoda (Malacostraca, Crustacea)

We present data on the haemolymph vascular system (HVS) in four representatives of the major amphipod lineages Gammaridea, Hyperiidea and Caprellidea based on corrosion casting and three‐dimensional reconstructions of histological semi‐thin sections. In all these species the HVS comprises a dorsal pulsatile heart, which is continued in the body axis by the anterior and posterior aortae. The heart is equipped with three pairs of incurrent ostia. The number of cardiac arteries that lead off the heart varies among species: in the studied Gammaridea four pairs occur, in Hyperia galba only the three posterior pairs of cardiac arteries occur, while in Caprella mutica cardiac arteries are absent. In all the studied species the posterior aorta leads as a simple tube into the pleon attached to the dorsal diaphragm. The anterior aorta runs from its origin in the anterior part of the second thoracic segment into the cephalothorax. Both pairs of antennae have an arterial supply off the anterior aorta. An overview of previously studied species including our present findings shows the amphipod HVS to be relatively uniform and the gammarid form is discussed as being closest to the ground pattern of Amphipoda.     

An Angiocardiographic Analysis of the Central Circulation in the Air Breathing Teleost Channa argus

The unique anatomy of the double ventral aorta outflow system in the air breathing teleost Channa argus (Ophiocephalus) showing an anterior and posterior ventral aorta is described. The marked trabeculation of the ventricle and bulbus arteriosus and the arrangement of central veins are used as a basis for the hypothesis that Channa may selectively channel the well oxygenated blood draining the air breathing organs via the anterior cardinal vein to the posterior ventral aorta, which forms the systemic arterial circulation. An angiocardiographic technique was used to test this hypothesis, as well as to delineate the functional role of the heart chambers in the cardiac cycle. No reflux of contrast to the sinus venosus during atrial filling and no ventricular filling before atrial contraction were apparent, which makes the atrium the main determinant of the ventricular end-diastolic volume. Ventricular contraction left a small or no residual volume. The ventricular ejectate was initially nearly completely absorbed by the very elastic bulbus arteriosus, acting as a pressure chamber (Windkessel) stabilizing and prolonging ventral aortic blood flow. Contrast medium was not selectively passed from the anterior cardinal vein to the posterior ventral aorta. However, the diameter of this vessel and its density of contrast were greater than in the anterior aorta, suggesting a preference for a greater blood flow from the air breathing organ through the heart to the posterior aorta.     

The insect abdomen--a heartbeat manager in insects?

Different possibilities of coordination between circulation, respiration and abdominal movements were found in pupae of Pieris brassicae, Tenebrio molitor, Galleria mellonella and Leptinotarsa decemlineata. Coordination principles depend on metabolic rate: the need to support circulation with abdominal movements appears only at higher metabolic rates. Integration between different abdominal movements and circulation depends on species, on physiological state and, supposedly, on internal morphology. At low metabolic rates, there is no need for a very intensive hemolymph flow, and the dorsal vessel is capable of initiating and/or maintaining necessary hemolymph flow. Starting from a certain metabolic level, it is possible that the abdomen is used to accelerate hemolymph flow in the case of a large amount of hemolymph. When the necessary flow speed has been reached, relatively weak pulsation of the dorsal vessel with accessory pulsatile organs and diaphragms can easily maintain the necessary flow intensity. Heart activity may sometimes be initiated by abdominal movements via cardiac reflex or mechanical excitation. Sometimes, when heart function is weakened by histolysis, the abdomen may temporarily take over the main circulatory function or occasionally contribute to acceleration of low-speed hemolymph flow. In this case the functions are simultaneous and may be triggered by some mediator(s). In active adult insects the whole body is moving, and hence hemolymph circulates and the tracheal system is effectively ventilated by a whole body ensemble consisting of the dorsal vessel, moving organs, body appendages and accessory pulsatile organs. The mechanism of autocirculation (analogous to autoventilation in gas exchange) is a probable mechanism in circulation in adult insects.     

The Hox gene abdominal-A specifies heart cell fate in the Drosophila dorsal vessel

The Drosophila melanogaster dorsal vessel is a linear organ that pumps blood through the body. Blood enters the dorsal vessel in a posterior chamber termed the heart, and is pumped in an anterior direction through a region of the dorsal vessel termed the aorta. Although the genes that specify dorsal vessel cell fate are well understood, there is still much to be learned concerning how cell fate in this linear tube is determined in an anteroposterior manner, either in Drosophila or in any other animal. We demonstrate that the formation of a morphologically and molecularly distinct heart depends crucially upon the homeotic segmentation gene abdominal-A (abd-A). abd-A expression in the dorsal vessel was detected only in the heart, and overexpression of abd-A induced heart fate in the aorta in a cell-autonomous manner. Mutation of abd-A resulted in a loss of heart-specific markers. We also demonstrate that abd-A and sevenup co-expression in cardial cells defined the location of ostia, or inflow tracts. Other genes of the Bithorax Complex do not appear to participate in heart specification, although high level expression of Ultrabithorax is capable of inducing a partial heart fate in the aorta. These findings for the first time demonstrate a specific involvement for Hox genes in patterning the muscular circulatory system, and suggest a mechanism of broad relevance for animal heart patterning.     

Homeotic selector genes control the patterning of seven-up expressing cells in the Drosophila dorsal vessel

The linear cardiac tube of Drosophila, the dorsal vessel, is an important model organ for the study of cardiac specification and patterning in vertebrates. In Drosophila, the Hox segmentation gene abdominal-A (abd-A) is required for the specification of a functionally distinct heart region at the posterior of the dorsal vessel, from which blood is pumped anteriorly through a tube termed the aorta. Since we have previously shown that the posterior part of the aorta is specified during embryogenesis to form the adult heart during metamorphosis, we determined if the embryonic aorta is also patterned by the function of Hox segmentation genes. Using gain- and loss-of-function experiments, we demonstrate that the three Hox genes expressed in the posterior aorta and heart are sufficient to confer heart or posterior aorta fate throughout the dorsal vessel. Additionally, we demonstrate that Ultrabithorax and abd-A, but not Antennapedia, function to control cell number in the dorsal vessel. These studies add robustness to the model that homeotic selector genes pattern the Drosophila dorsal vessel, and further extend our understanding of how the cardiac tube is patterned in animal models.     

Topographical mapping of sites of enhanced HRP permeability in the normal rabbit aorta.

The spatial distribution of sites of enhanced permeability to the macromolecule horseradish peroxidase (HRP) in the normal rabbit aorta after one min circulation was studied using image analysis. These sites, referred to as "HRP spots," exhibit a nonuniform distribution that is qualitatively similar in all rabbits studied. The density of HRP spots is highest in the aortic arch, decreases distally, reaches a minimum in the lower descending thoracic aorta, and then increases again in the abdominal aorta. The region of highest spot density follows a clockwise helical pattern in the aortic arch and outside the arch occurs in streaks largely oriented in the bulk flow direction. The streaks in the abdominal aorta localize along the anatomical right lateral wall and occasionally along the left lateral wall proximal to the celiac artery and along the ventral wall between the celiac and superior mesenteric arteries. The density of spots is high in the immediate vicinity of aortic ostia with the most elevated density being distal to ostia in most cases. At a short distance from the ostium edge of the celiac and superior mesenteric branches the proximal density is comparably high, and no preferred spot orientation is observed around the brachiocephalic vessel. These results are consistent with an influence of localizing factors such as detailed hemodynamic phenomena and/or arterial wall structural and/or functional variations.     

Morphology of the haemolymph vascular system in Tanaidacea and Cumacea: - implications for the relationships of "core group" Peracarida (Malacostraca; Crustacea)

Tanaidacea and Cumacea are crucial for understanding the phylogenetic relationships of "core group" peracarids. Here, the haemolymph vascular system in three tanaidacean and four cumacean species was studied on the basis of histological sections and 3D reconstruction. The circulatory organs in Tanaidacea include a tubular heart which extends through most of the thorax. It is extended into the cephalothorax by an anterior aorta. Haemolymph enters the heart through one to two pairs of incurrent ostia. Up to five pairs of cardiac arteries emanate from the heart to supply viscera in the body cavity. In the anterior cephalothorax, the aorta forms a pericerebral ring from which the arteries for the brain and the antennae branch off. In Cumacea, the heart is shorter but more voluminous. In all cumaceans studied, five pairs of cardiac arteries supply the thoracopods and the pleon. The single pair of ostia is situated in the centre of the heart. The anterior aorta runs into the anterior cephalothorax where it supplies the brain and antennae. This paper provides a general comparative discussion of all available data from the literature and the data provided herein. In certain details, the haemolymph vascular system of the Tanaidacea resembles that of Amphipoda, and some correspondences between Cumacea and Isopoda are pointed out. These findings might support a closer relationship between the latter two taxa while they show no support for an amphipod/isopod clade.     

A change of heart: cardiovascular development in the shrimp Metapenaeus ensis

The larval development of penaeid shrimp is among the most complicated in crustaceans. In Metapenaeus ensis, there are six naupliar, three protozoeal and three mysid larval instars, followed by postlarval development. Irregular heartbeat begins late in naupliar instar 6. Co-ordinated beating at 400-600 beats min(-1) commences in the first protozoeal instar and continues throughout larval life. Initially, the contractile region is located more posteriorly in the cephalothorax and has a single pair of ostia, and the arterial distribution is limited to a single anterior vessel. In later mysid instars, a second cardiac pumping site develops posterior to, but connected with, the original site. This extension is more muscular, contains additional ostia and develops additional distribution vessels supplying the cephalothorax and abdominal areas. The original site is gradually merged into the new extension and only small refinements in the circulation occur in postlarval and juvenile life. Changes in physiological responses of the heart also occur throughout development. Responses to intra-pericardial microinjection of 5-hydroxytryptamine change drastically during development, as do cardiac responses to ambient hypoxia. Similarly, heartbeat of later juvenile instars is inhibited by injection of tetrodotoxin, while heartbeat of larval and early juvenile instars is not, suggesting that neurogenic regulation via the cardiac ganglion arises later in development. Our present studies attempt to integrate the anatomical and physiological changes in the development of the crustacean heart.     

两种早期心衰大鼠模型的建立和心功能的比较

目的比较两种不同方法建立大鼠心衰模型心功能的特点,寻找大鼠模型早期心衰阶段。方法用冠脉结扎法及腹主动脉结扎法建立不同的心衰模型,用血流动力学及心脏称重的方法比较其心功能的各项指标。结果冠脉结扎组术后2周没有心功能的改变,2周后收缩和舒张功能均下降,4周达最低。腹主动脉结扎组术后14周没有心功能的下降,16周出现了舒张功能的衰竭。结论冠脉结扎法及腹主动脉结扎法均可以造成早期心衰,冠脉结扎法术后2周为早期心衰阶段,2周后同时出现收缩和舒张功能衰竭,腹主动脉结扎法术后14周为早期心衰阶段,14周后出现了舒张功能衰竭。