Efferent Filament Artery Research Articles

Localization of angiotensin‐converting enzyme in the trout gill

Angiotensin-converting enzyme (ACE) was localized in perfused trout gills by measuring gill extraction of two radiolabeled ACE inhibitors, 125I-351A (an iodinated derivative of lisinopril) and 3H-RAC-X-65, and by autoradiography of gills perfused with 125I-351A. A 125I-351A pulse was preferentially extracted by the arterio-arterial (AA) pathway (61.7% +/- 1.8% extraction; mean +/- SE, N = 4); the arteriovenous (AV) pathway extracted an additional 10%. Extraction by either pathway was reduced by simultaneous perfusion with 10(-5) M unlabeled lisinopril. AA extraction of RAC-X-65 during continuous perfusion was maximal (75% +/- 5%, N = 6) during the first few minutes of perfusion and decreased steadily to 38% +/- 9% by 20 min and to less than 10% by 40 min. AV extraction of RAC-X-65 was negligible. Autoradiography of gills continuously perfused with 125I-351A showed that the radiolabel was concentrated in the respiratory lamellae. The highest grain density was associated with the pillar cells nearest the medial (inner) lamellar margin. Afferent filamental arteries and afferent lamellar arterioles were labeled to a lesser extent. Relatively little label was found on the efferent lamellar arterioles or efferent filamental arteries. 125I-351A binding was not evident in AV vessels. These findings support the hypothesis that the gill is an important site for formation of plasma angiotensin II and they suggest that enzymes associated with mammalian endothelial cells are also common to gill pillar cells.

Neurons controlling the gill vasculature in five species of teleosts

A plexus of nerve fibers encompassing neuronal perikarya is present within the gill filament; it surrounds the proximal portion of the efferent filament artery and the efferent lamellar arterioles. This innervation resembles the pattern described for the area around the sphincter of the efferent filament artery: acetylcholinesterase-positive neurons and fibers, fast-fading yellow-fluorescent neurons and fibers, long-lasting green-fluorescent fibers. In addition, synaptic contacts between the different components suggest functional interrelationships. Nerves evidently control the efferent limb of the filament circulation including the sphincter of the efferent filament arteries, the proximal portion of the efferent filament arteries proper, and their corresponding efferent lamellar arterioles. However, the distal portion of this system is poorly innervated.

Comparative study of the adrenergic innervation of the teleost gill.

The adrenergic innervation of structures in the gills of six teleost species was studied with catecholamine fluorescence histochemistry. The species studied were the following: sand flathead, Platycephalus bassensis and blue-spot flathead Platycephalus caeuruleopunctatus (Platycephalidae); smooth toadfish, Tetractenos glaber (Tetraodontidae); Australian short-finned eel, Anguilla australis (Anguillidae); river blackfish, Gadopsis marmoratus (Gadopsidae); and common carp Cyprinus carpio (Cyprinidae). In all species except C. carpio fluorescent components were observed in the branchial nerves in the gill arch. In the arterio-arterial vascular pathway, the afferent and efferent branchial arteries were innervated only in Cyprinus. Fluorescent nerve fibres were found on afferent filamental arteries of all species except A. australis and on many afferent lamellar arterioles of all species except T. glaber. The secondary lamellae were devoid of fluorescent nerve fibres in all species. In Cyprinus and Anguilla, fluorescent nerve fibres were observed on occasional efferent lamellar arterioles. In Cyprinus, there was an additional innervation on the basal one-third of the efferent filamental artery. The innervation of the arteriovenous vascular pathway was similar in all species. Fluorescent nerve fibres were found on nutritive arterioles, and in the core of each filament between the surface epithelium and the wall of the filament venous sinus. Since most of the adrenergic innervation was found on afferent vessels of the arterio-arterial pathway, it is suggested that adrenergic nerves and circulating catecholamines may have distinct functions in the regulation of blood flow through the gills.

Gill microcirculation of the air-breathing climbing perch, Anabas testudineus (Bloch):relationships with the accessory respiratory organs and systemic circulation.

The general macrocirculation and branchial microcirculation of the air-breathing climbing perch, Anabas testudineus, was examined by light and scanning electron microscopy of vascular corrosion replicas. The ventral aorta arises from the heart as a short vessel that immediately bifurcates into a dorsal and a ventral branch. The ventral branch distributes blood to gill arches 1 and 2, the dorsal branch to arches 3 and 4. The vascular organization of arches 1 and 2 is similar to that described for aquatic breathing teleosts. The respiratory lamellae are well developed but lack a continuous inner marginal channel. The filaments contain an extensive nutritive and interlamellar network; the latter traverses the filament between, but in register with, the inner lamellar margins. Numerous small, tortuous vessels arise from the efferent filamental and branchial arteries and anastomose with each other to form the nutrient supply for the filament, adductor muscles, and arch supportive tissues. The efferent branchial arteries of arches 1 and 2 supply the accessory air-breathing organs. Arches 3 and 4 are modified to serve primarily as large-bore shunts between the dorsal branch of the ventral aorta and the dorsal aorta. In many filaments from arches 3 and 4, the respiratory lamellae are condensed and have only 1-3 large channels. In some instances in arch 4, shunt vessels arise from the afferent branchial artery and connect directly with the efferent filamental artery. The filamental nutrient and interlamellar systems are poorly developed or absent. The respiratory and systemic pathways in Anabas are arranged in parallel. Blood flows from the ventral branch of the ventral aorta, through gill arches 1 and 2, into the accessory respiratory organs, and then returns to the heart. Blood, after entering the dorsal branch of the ventral aorta, passes through gill arches 3 and 4 and proceeds to the systemic circulation. This arrangement optimizes oxygen delivery to the tissues and minimizes intravascular pressure in the branchial and air-breathing organs. The efficiency of this system is limited by the mixing of respiratory and systemic venous blood at the heart.

The sphincter of the efferent filament artery in teleost gills: I. Structure and parasympathetic innervation.

Previous studies have shown the existence of a sphincter in the efferent filament artery of the teleost gill and its constrictory response to acetylcholine (ACH) and vagal stimulation. This study deals with the muscular organization of this sphincter and the distribution of its innervation as elucidated by degeneration methods and cytochemistry. The sphincter innervation is supplied by the protrematic vagus nerves. Nerve endings filled with cholinergic-type vesicles are located in close association with the adventitial smooth muscle cells and display a strong acetylcholinesterase (ACHE) activity. Section of the protrematic vagus nerve induces a nearly complete degeneration of the sphincter innervation. ACHE-positive nerve cell bodies are present both in the sphincter area and in the protrematic vagus nerve. These results suggest that innervation of the sphincter in the efferent filament artery is cholinergic through the activity of postganglionic axons of the parasympathetic system.

The sphincter of the efferent filament artery in teleost gills: II. Sympathetic innervation.

In addition to the cholinergic innervation described in the sphincter of the efferent filament arteries (Bailly and Dunel-Erb, '86), an aminergic component has been demonstrated by specific techniques. The Falck fluorescence technique reveals a network of nerve fibers displaying a green fluorescence characteristic of catecholamines. At the ultrastructural level two types of fibers are present, one with clear vesicles and another with densecored vesicles. Axo-axonal synaptic relationships exist between the two types. Results of 5- and 6-OHDA (hydroxydopamine) treatments confirm the presence of an aminergic component. These observations support the notion of a dual innervation: cholinergic and adrenergic of, respectively, parasympathetic and sympathetic origin. The presence of presynaptic modulation is suggested. The aminergic component could inhibit or reduce the release of acetylcholine from cholinergic nerve endings. These results suggest that the sympathetic innervation modulates the vasoconstriction effect of the parasympathetic component.

Localization of 3H‐norepinephrine binding sites in the trout gill

AbstractTritiated norepinephrine (Nepi) or Epinephrine (Epi) was perfused through isolated gills of rainbow trout (Salmo gairdneri) and the affinity of vascular tissues for the amines examined by autoradiography. Pillar cells and certain endothelial cells in the filamental sinus accumulate 3H‐Nepi extensively. The afferent and efferent filamental arteries and filamental nutrient vessels did not bind 3H‐Nepi. Pillar cell and venous endothelial accumulation is selective for Nepi; Epi is not accumulated by these cells, and Nepi uptake can be inhibited by imipramine. These results suggest that pillar and venous endothelial cells are involved in regulation of plasma Nepi.

Adrenergic innervation of the gills of brown and rainbow trout, Salmo trutta and S. gairdneri.

The adrenergic innervation of structures in the gills of brown and rainbow trout was studied with catecholamine fluorescence histochemistry. In the arterio-arterial vascular pathway, there was an innervation of the afferent and efferent lamellar arterioles, but the afferent and efferent filamental arteries and the secondary lamellae were devoid of any fluorescent nerve fibres. In S. trutta only, there was an additional innervation of the afferent and efferent branchial arteries and the base of the efferent filamental artery. The innervation of the arterio-venous vascular pathway was similar in both trout species. Many fluorescent nerve fibres were found on nutritive arterioles in the gill arch and interbranchial septum, and in the core of each filament between the surface epithelium and the wall of the filament venous sinus. No fluorescent nerve fibres were observed at the origins of the capillaries arising from the efferent filamental artery. The sympathetic nerve supply is provided to the gills mainly through the posttrematic nerve, with an occasional small contribution through the pretrematic nerve. The presence of adrenergic nerves in the gills is discussed in relation to the regulation of blood flow through the arterio-arterial and arterio-venous pathways.

Vascular pathways in the gill filaments of the flounder, Platichthys flesus L.

This study is concerned with functional organization of some of the blood pathways in the gill filament of the flounder, Platichthys flesus L. The existence of two independent vascular pathways has been confirmed. The blood from the efferent filament artery (EFA) enters the central venous sinus (CVS) through very small blood vessels which are characterized by the presence of sphincter‐like structures. The existence of an independent chamber of the CVS mainly full of white blood cells provides evidence of an independent lymphatic system connected to the CVS. Gill rays support the afferent side of a gill filament whereas plasma and an extensive network of nutritive blood vessels in the CVS supports the efferent part.

The gill in the spiny dogfish, Squalus acanthias: respiratory and nonrespiratory function.

Aspects of functional anatomy with respect to water and blood flow through the gills of Squalus acanthias and one specimen of Mustelus mustelus are described. A reconstruction of an entire filament has been made. The cavernous body in the proximal segment of the filament is relatively small, contains a small amount of elastic tissue, and has no connections with the underlying afferent filament artery, except at its junction to the middle segment. In the middle segment of the filament, the wall and columns of the cavernous body are well supplied with elastic tissue. The size of the cavernous body increases gradually distally. The underlying afferent filament artery opens into it with numerous pores and eventually becomes incorporated in the cavernous body. The distal segment of the filament is characterized by the rapid increase in size of the cavernous body. Toward the free edge of the filament it almost reaches the efferent filament artery; toward the diaphragm it forms an anastomosing bridge with the neighboring filaments. Wall and columns in the distal segment of the cavernous body are richly supplied with elastic tissue. The afferent filament artery is no longer discernible. In living specimens the tips of opposite filaments are in close apposition during the whole respiratory cycle. Application of artificial ventral aortic pressure to freshly killed specimens evoked the same reaction in the filament tips. The cavernous bodies provide the hydrostatic skeleton, necessary to keep the gill sieve closed. Lamellae are equipped with finger-like appendages to facilitate adherence to the opposite filament tips. Lamellar appendages also reduce the dead space between lamellae of neighboring filaments. The whole of cavernous bodies may also serve as an elastic blood reservoir with a function similar to that of the bulbus arteriosus in teleost fish. Of all suitable places, only the lamellar streambed was clear and convincing in its response to perfusion with adrenalin or acetylcholine. Structural details of the nonrespiratory circulation within the gills are described.

Effects of perfusion pressure on the morphology of the central sinus in the trout gill filament.

The central sinus, a prominent component of the nonrespiratory, ionoregulatory vasculature of the fish gill has been variously described as a simple sack-like structure in the eel A. anguilla and as an intricate series of parallel vessels in the catfish I. punctatus. To resolve whether these differences are interspecific or methodological, corrosion replicas of the central sinus in the rainbow trout (Salmo gairdneri) were prepared at physiological and superphysiological perfusion pressures with a low-viscosity methyl methacrylate resin. At physiological perfusion pressure (30 mmHg, 4.0 kPa), the central sinus vasculature appears as a series of parallel vessels traversing the filament beneath, and in register with, the interlamellar filamental epithelium. At elevated perfusion pressure (55-65 mmHg, 7.3-8.7 kPa) the sinus becomes greatly distended and sack-like and the vessels appear to coalesce. These changes are most pronounced in the basal area of the filament and along the efferent filamental artery. The results show that the interpretation of the vascular organization of the central sinus is highly dependent on methodology. In addition, the sensitivity of the central sinus to changes in perfusion pressure suggests that the sinus plays a dynamic role in intrabranchial hemodynamics.

An electron microscopic study on the innervation of the gill filaments of a lamprey, Lampetra japonica.

This paper reports observations on the innervation of gill filaments of the lamprey, Lampetra japonica. Nerve fibers run on each side of the afferent filament artery (AFA nerve) and in the connective tissue compartment along the efferent filament artery (EFA nerve). The AFA nerve supplies vasomotor fibers to the afferent filament artery and arteriovenous anastomoses and special visceral motor fibers to branchial muscle fibers (musculus compressor branchialis circularis). Nerve endings of the vasomotor fibers contain large, cored vesicles (60-180 nm in diameter) with a variable number of small, clear vesicles (30-70 μm in diameter), whereas those of the visceral motor fibers have many small, clear vesicles with few large, cored vesicles. The EFA nerve supplies vasomotor fibers to the efferent filament artery. Their endings, containing mixtures of predominantly large, cored vesicles and small, clear vesicles make close synaptic contacts with reticular cells. The latter in turn are connected with each other or with smooth muscle cells in the wall of the efferent filament artery by nexuses. No nerves are found in the axial plate between the afferent and efferent filament arteries nor in the secondary lamellae of individual gill filaments. No afferent nerve supply to the gill filament has been found.

Microvascular pressures in gill filaments of lingcod (Ophiodon elongatus)

AbstractDynamic intravascular pressures were measured in the afferent and efferent filament arteries of Ophiodon elongatus using micropipettes. Measurements from anesthetized fish and from isolated, saline‐perfused preparations indicated that the major site of gill resistance was located in the lamellar complex (secondary lamella and associated arterioles). The presence of a postlamellar cholinergic constrictor site was also supported by efferent arterial pressure measurements during acetylcholine administration.

Short Communications: Blood-Flow Velocity in Microvessels of the Gill Filaments of the Goldfish (Carassius Auratus L.)

Short Communications: Blood-Flow Velocity in Microvessels of the Gill Filaments of the Goldfish (<i>Carassius Auratus L.</i>)

The microvasculature of the elasmobranch gill.

Corrosion replicas were made of the gill vasculature of the spiny dogfish shark (S. acanthias) and little skate (R. erinacea) by methylmethacrylate perfusion via the ventral or dorsal aorta at 2.0-5.3 kPa. After tissue maceration the replicas were examined by light and scanning electron microscopy. In both species 3 vascular pathways were found: (1) the major pathway subserving the respiratory function of the gill, consisting of the afferent filamental artery which feeds into a medial afferent sinus (MA) from which arise the prelamellar arterioles (AL) leading to the lamellae, the postlamellar arterioles and efferent filamental artery (EA); (2) a nutrient circulation arising from the EA, supplying oxygenated blood to the filamental tissue, and anastomosing with the interlamellar vessels (IL); (3) a collateral circulation consisting of ILs which drain through channels interdigitating with the ALs and which then form a collateral reticulum, beneath the water channel epithelium, with vessels from the adjacent filaments. In the dogfish, small prelamellar arteriovenous anastomoses (PA) connect the MAs to the ILs with the same frequency as the ALs. PAs have not been found in the skate, but the efferent nutrient circulation is much more extensively developed. Many similarities exist between the elasmobranchs and teleosts in regard to the microvascular organization of the gill.

The vascular anatomy of the gills of the smooth toadfishTorquiginer glaber (Teleostei: Tetraodontidae)

The branchial vasculature of the smooth toadfish,Torquiginer glaber, was studied by light microscopic examination of Microfil vascular casts, and scanning electron microscopy of critical point dried tissue and vascular corrosion casts. The anatomy of the respiratory vascular bed was similar to that described for other teleosts. An extensive non-respiratory vascular bed was also present in the gills. In each filament this comprised a series of capillaries arising mainly from the efferent side of the gill circulation (efferent filament artery, efferent lamellar arterioles, branches of the efferent branchial artery), but also from the afferent side (afferent filament artery, afferent lamellar arterioles, lamellar blood channels). The capillaries eventually connected to a system of broadly interconnected sinuses in the filament termed the central canal and the afferent and efferent companion vessels. The sinuses connected with a large subepithelial sinus and a pair of venolymphatic vessels in the gill arch. Connections between the subepithelial sinus of the arch and the anterior venous system were demonstrated. It is suggested that the non-respiratory capillaries serve a nutritive function, while the filament sinuses provide a combined venolymphatic drainage for the filament.

Functional aspects of the morphology and vascular anatomy of the gills of the endeavour dogfish,Centrophoms scalpratus (McCulloch) (Elasmobranchii:Squalidae)

The morphology and vascular anatomy of the gills of the Endeavour dogfish,Centrophorus scalpratus, were studied by light microscopic examination of Microfil vascular casts and scanning electron microscopy of vascular corrosion casts and critical point dried tissue. The anatomy of the respiratory vasculature was similar to that described for other elasmobranchs. How-ever, it was noted that approximately one-fifth of the total respiratory exchange area lay within a ventilatory deadspace, thus providing a potential respiratory by-pass shunt pathway. An extensive non-respiratory vascular bed was also present in the gills. In each gill filament there was a series of non-respiratory capillaries arising both from the afferent and efferent sides of the gill circulation (filament corpus cavernosum and efferent filament artery respectively). These capillaries eventually connected to a system of broadly interconnected sinuses in the filament termed the central canal and the afferent and efferent companion vessels. These sinuses connected with a large subepithelial sinus in the gill arch and a pair of large sinuses in the interbranchial septum. It is suggested that the non-respiratory capillaries serve a nutritive function, while the filament, septal and arch sinuses provide a venous and/or lymphatic drainage for the gills. The non-respiratory vascular bed of the gills would not function as a respiratory by-pass shunt pathway.

Vascular organization of the catfish gill filament

Light and scanning electron microscopic observations were made on methyl-methacrylate corrosion casts of the blood vessels in the gills of channel catfish (Ictalurus punctatus). The vasculature of the gill filament can be divided into three distinct pathways: 1. the well-known respiratory circulation which includes the afferent filamental artery (AF), afferent lamellar arteriole (AL), lamella (L), efferent lamellar arteriole (EL) and efferent filamental artery (EF), 2. a nutritive pathway from the EF through small nutritive capillaries (NC) and into one of several filamental veins (FV), and 3. an interlamellar circulation in which small prelamellar arterio-venous anastomoses (PAVA) connect the AL into a series of organized vascular spaces (interlamellar vessels, ILV's) that underlie the interlamellar filamental epithelium. Several sinus like spaces associated with AF, EF and the filamental cartilagenous support were also observed. The physiological significance of these vascular pathways is discussed.

An electron microscopic study of the cavernous bodies in the lamprey gill filaments.

The cavernous body in the lamprey gill filament was studied by electron microscopy. This body lies along the outer border of the axial plate of each gill filament and freely communicates with an afferent filament artery. Two series of blood channels run alternately, passing through the cavernous body, and lead to the marginal channels in the secondary lamellae. On the other hand, narrow blood spaces left in the cavernous body lead to the blood lacunae in the axial plate (osmoregulatory region) and to those in the secondary lamellae (respiratory region). All the blood in the cavernous body is finally collected by an efferent filament artery. The cavernous body is traversed by numerous trabeculae and collagenous columns which run diagonally in the blood spaces to connect the walls of the cavernous body. All the walls of the cavernous body, including trabeculae and collagenous columns, are completely surrounded by the cytoplasmic flanges of specialized cells called here "cavernous body cells." These cells are about 30 mu in diameter and characterized by (1) association with collagenous columns or trabeculae and also by the presence of (2) coated caveolae and vesicles, (3) vacuoles and (4) cytoplasmic granules in their cytoplasm. These cells are considered to be related to the pillar cells in origin because of their close association with collagenous columns or trabecule. The functional significance of the cavernous body and the cavernous body cells is discussed.

A study on the blood vascular system of the lamprey gill filament.

The blood vessels in the gill filaments of lamprey, Lampetra japonica, were studied with an electron microscope. Each gill filament is supplied by an afferent filament artery (afa) flanked by a pair of filament veins (fv), along the outer border of the axial plate, and an efferent filament artery (efa) along the inner, free border. Between these arteries are interposed the cavernous body and the blood lacunae. The marginal channel arises from the cavernous body, which leads to the afa, runs along the free border of the secondary lamella collecting oxygenated blood from the lamellar blood lacunae, and finally joins efa. This channel is considered to play an important role in the gill circulation as a bypass between afa and efa. Pillar cells were found only in the blood lacunae of the axial plate and the secondary lamellae. The basal lamina is generally absent on the vascular wall, but only a small amount of dense material could be seen on the basal surface of endothelial cells of afa and fv: this is regarded as an anchoring device between the cell and connective tissue fibrils. Fenestrations are generally absent in the endothelial layer but numerous gaps were seen in the wall of fv. Arterio-venus anastomoses were found between afa or the cavernous body and fv, and between efa or the collecting arteries of the efferent branchial artery and the peribranchial venous sinus. The anastomosing channel consists of the inner endothelial layer and the outer smooth muscle layer, which is thicker in the intermediate portion of the channel. The endothelial cells called "AVA cells" here are characterized by (1) dense cytoplasms, (2) apical microvilli and (3) basal cytoplasmic processes closely associated with smooth muscle cells.