Arteriovenous anastomoses in the afferent region of trout gill filaments (Salmo gairdneri richardson,teleostei)

Summary Arteriovenous anastomoses (AVAs) in the afferent region of trout gill filaments originate from two small filament arteries (Fromm's arteries), which parallel the main afferent filament vessel on either side. As in the efferent filament arteries the origin of AVAs is bordered by specialized endothelial cells. Fromm's arteries originate from efferent filament or branchial arteries. A few extremely narrow connections between the afferent filament artery and Fromm's arteries (= afferent shunts) do exist in some gill filaments. Nevertheless, the AVAs in the afferent filament region carry mainly arterialized blood, or blood plasma, to the central venous sinus of the filament.Supported by the Deutsche Forschungsgemeinschaft (Vo 229/1)     

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.     

Smooth muscles in relation to the gill skeleton of Perca fluviatilis: organization and innervation

Summary Two laminae composed of smooth muscles, elastic tissue and collagen have been described in relation with the gill skeleton in Perca fluviatilis. A transverse smoothmuscle lamina joins the base of the cartilage rods of the two opposite hemibranchs. A longitudinal smooth-muscle lamina runs parallel to the afferent branchial artery and joins the cartilage rods from one filament to the other. In both laminae, the formaldehyde-induced fluorescence technique (Falck-Hillarp) reveals a network of nerve fibers displaying a green fluorescence characteristic of catecholamines. At the ultrastructural level, the presence of nerve endings containing clear and granular vesicles, and the degeneration of these endings after 6-hydroxydopamine treatment confirm the aminergic nature and the sympathetic origin of this innervation. Surgical denervation brings evidence that the innervation of both laminae is supplied by the metatrematic branches of the branchial nerves. The role of these smooth-muscle laminae remains speculative.     

Vascular anatomy of the gills of the stingarees Urolophus mucosus and U. paucimaculatus (Urolophidae,Elasmobranchii)

The branchial vascular anatomy of Urolophus mucosus and U. paucimaculatus was studied by scanning electron microscopical examination of critical-point-dried tissue or of vascular corrosion casts. The vasculature could be divided into arterioarterial and arteriovenous pathways, which channel the flow of blood through the gills. The arterioarterial pathway consists of an afferent branchial artery which gives rise to afferent distributing arteries that run through the tissues of the interbranchial septum and supply the afferent filament arteries of several filaments. Afferent filament arteries open regularly into a corpus cavernosum in the core of the filament; unlike other elasmobranchs no septal corpora cavernosa are found. At the tip of the filament, channels of the corpus cavernosum connect to a channel which passes across the distal end of the filament from afferent to efferent side. This channel always connects to the afferent filament artery, and in many filaments it connects to the efferent filament artery as well. In addition, a vascular arcade connects all the afferent filament arteries along the entire length of each hemibranch. The filament corpus cavernosum supplies the secondary lamellae. The lamellae drain into efferent lamellar arterioles which in turn drain into the efferent filament artery and the efferent branchial artery. The vascular anatomy of the arteriovenous pathway is similar to that described in other elasmobranchs and consists of arteriovenous anastomoses, found only arising from efferent arterial circulation, and the venolymphatic system, which is composed of the central venous sinus and the companion vessels.     

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.     

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.     

Fine structure of nervous elements in the pancreas of some vertebrates

Summary The innervations of the exocrine and endocrine pancreas of some vertebrate animals were studied by electron microscopy. The pancreas of the bat and monkey contained ganglion cells in the interlobular connective tissue or between acinar cells. Unmyelinated nerve fibers ran through the interlobular connective tissue and reached the exocrine and endocrine parts, and terminated there as the endings. The nerve endings within the pancreas could be divided into four types: 1. Type 1-a of the nerve ending contained only agranular synaptic vesicles of about 500 Å in diameter. 2. Type 1-b characterized by containing agranular synaptic vesicles and some large cored vesicles (1,000 Å diameter). These two types of nerve endings might belong to the cholinergic (parasympathetic) endings. 3. Type 2-a contained small cored vesicles and agranular synaptic vesicles along with a few large cored vesicles. 4. Type 2-b was characterized by containing vesicles of the same size as those of agranular synaptic vesicles, and a majority of these vesicles contained bar-shaped crystalloids. This ending also contained a few large cored vesicles. These nerve endings of Type 2-a and 2-b might be the adrenergic (sympathetic) endings.     

Arterio-venous anastomoses in rainbow trout gill filaments

Summary The origin of arterio-venous anastomoses, connecting the efferent filament artery (EFA) with the central venous sinus (CVS) of gill filaments can be well discerned by scanning electron microscopy in the rainbow trout. Corresponding vessels between the afferent filament artery and the CVS could not be detected with the techniques applied. AVA-specific endothelial cells are characterized by their bulky shape and their microvillous surface. The general morphology of AVA's in Salmo gairdneri is very similar to that of AVA's in Tilapia mossambica (Vogel et al., 1974) but they are much longer in the trout. No filament whorls have been encountered in AVA endothelia of Salmo gairdneri.This study is dedicated to Prof. Dr. W. Graumann, Director of the Institute of Anatomy, University of Tübingen, on the occasion of his 60th birthday. It was supported by the Deutsche Forschungsgemeinschaft     

波纹唇鱼鳃丝的光镜、扫描和透射电镜观察

应用光学显微镜、扫描电镜和透射电镜对波纹唇鱼(Cheilinus undulatus)鳃的组织结构、表面形态特征及鳃小片超微结构进行了观察.结果表明,波纹唇鱼有3对全鳃,1对半鳃和1对伪鳃,鳃丝呈梳状紧密排列在鳃弓上,鳃小片紧密地镶嵌排列在鳃丝两侧,入鳃动脉、出鳃动脉和鳃小片毛细血管网组成鳃的血液系统.鳃丝非呼吸区分布...     

ULTRASTRUCTURE OF THE CAROTID BODY

An electron microscope investigation was made of the carotid body in the cat and the rabbit. In thin-walled blood vessels the endothelium was fenestrated. Larger vessels were surrounded by a layer of smooth muscle fibers. Among the numerous blood vessels lay groups of cells of two types covered by basement membranes. Aggregates of Type I cells were invested by Type II cells, though occasionally cytoplasmic extensions were covered by basement membrane only. Type I cells contained many electron-opaque cored vesicles (350 to 1900 A in diameter) resembling those in endocrine secretory cells. Type II cells covered nerve endings terminating on Type I cells and enclosed nerve fibers in much the same manner as Schwann cells. The nerve endings contained numerous microvesicles (~500 A in diameter), mitochondria, glycogen granules, and a few electron-opaque cored vesicles. Junctions between nerve endings and Type I cells were associated with regions of increased density in both intercellular spaces and the adjoining cytoplasm. Cilia of the 9 + 0 fibril pattern were observed in Type I and Type II cells and pericytes. Nonmyelinated nerve fibers, often containing microvesicles, mitochondria, and a few electron-opaque cored vesicles (650 to 1000 A in diameter) were present in Schwann cells, many of which were situated close to blood vessels Ganglion cells near the periphery of the gland, fibrocytes, and segments of unidentified cells were also seen. It was concluded that, according to present concepts of the structure of nerve endings, those endings related to Type I cells could be efferent or afferent.     

Neurons controlling the gill vasculature in five species of teleosts

Summary 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.     

Vascular anatomy of the gills in a high energy demand teleost,the skipjack tuna (Katsuwonus pelamis)

Tunas (family: Scombridae, Tribe: Thunnini) exhibit anatomical, physiological, and biochemical adaptations that dramatically increase the ability of their cardiorespiratory systems to transfer oxygen from the water to the tissues. In the present study the vascular anatomy of the skipjack tuna, Katsuwonus pelamis, gill was examined by light and scanning electron microscopic analysis of methyl methacrylate vascular corrosion replicas prepared under physiological pressure. The gill filament contains three distinct blood pathways, respiratory, interlamellar, and nutrient. The respiratory, or arterio-arterial (AA) pathway, is the site of gas exchange and consists of the afferent and efferent filamental arteries (AFA and EFA) and arterioles (ALA and ELA) and the lamellae. Each ALA in the basal filament supplies ten or more lamellae and they anastomose with their neighbor to form a continuous vascular arcade. Four modifications in the lamellar circulation appear to enhance gas exchange efficiency. 1) The ALA deliver blood directly to the outer margin of the lamellae where unstirred boundary layer effects are predicted to be minimal and water PO2 highest. 2) Pillar cells are closely aligned along the outer boundary of the inlet side and the inner boundary of the outlet side of the lamellae to form multiple distributing and receiving blood channels. 3) Elsewhere in the lamella, pillar cells are aligned to form diagonal channels that direct blood from the outer to the inner lamellar margins, thereby reducing vascular resistance. 4) The lamellar sinusoid is especially widened near the efferent end to augment oxygen saturation of blood flowing through the inner margin. These adaptations, plus the presence of a bow-shaped interlamellar septum, and a thinned filament core appear to decrease gill vascular resistance and maximize gas-exchange efficiency. The interlamellar (IL) and nutrient systems originate from post-lamellar vessels and are arterio-venous (AV) pathways. IL vessels form an extensive ladder-like lattice on both sides of the filamental cartilage and are supplied in part by narrow-bore vessels from the medial wall of the EFA. Their function is unknown. Nutrient vessels are formed from the confluence of a myriad of tortuous, narrow-bore vessels arising from the basal region of the EFA and from efferent branchial arteries. They re-enter the filament and eventually drain into the IL system or filamental veins. As these AV pathways are retained despite considerable reduction in filamental tissue, it is evident that they are integral components of other non-respiratory homeostatic activities of the gill.     

Innervation of mouse lymph nodes: nerve endings on muscular vessels and reticular cells

Lymph node nerve endings have been studied in 1- to 48-day-old mice. Serial sections of Epon-embedded lymph nodes were observed under the electron microscope to find the nerve endings. Most lymph node nerve fibers finally reach the smooth muscle cells of arterioles and muscular venules. Both kinds of vascular endings are similar, although endings are less numerous on venules. Nerve endings consist of one or more nerve processes surrounded by a usually incomplete Schwann cell sheath; frequently, axons show wide areas directly facing the muscle cells. The distance between such a naked axon and a myocyte ranges from 100 to 800 nm. Small granulated and clear vesicles are especially abundant in varicosities of nerve processes that are located very close to muscle cells. Nerve endings of lymph node vasculature probably correspond to vasomotor sympathetic adrenergic endings, regulating the degree of contraction of vessels which have a muscular layer. Other kinds of nerve endings also exist in lymph nodes: some axons appear free in the stroma and contact the surfaces of reticular cells; the latter also extend delicate cytoplasmic processes that surround the axons. The functional significance of nerve cell-reticular cell contacts is unknown.     

Fine structure and innervation of the avian adrenal gland

Summary Apart from cholinergic nerve fibers, which make up the main part of efferent fibers to the avian adrenal gland (Unsicker, 1973b), adrenergic, purinergic and afferent nerve fibers occur. Adrenergic nerve fibers are much more rare than cholinergic fibers. With the Falck-Hillarp fluorescence method they can be demonstrated in the capsule of the gland, in the pericapsular tissue and near blood vessels. By their green fluorescent varicosities they may be distinguished characteristically from undulating yellow fluorescent ramifications of small nerve cells which are found in the ganglia of the adrenal gland and below the capsule. The varicosities of adrenergic axons exhibit small (450 to 700 Å in diameter) and large (900 to 1300 Å in diameter) granular vesicles with a dense core which is usually situated excentrically. After the application of 6-hydroxydopamine degenerative changes appear in the varicosities. Adrenergic axons are not confined to blood vessels but can be found as well in close proximity of chromaffin cells. Probably adrenergic fibers are the axons of large ganglion cells which are situated mainly within the ganglia of the adrenal gland and in the periphery of the organ and whose dendritic endings show small granular vesicles after treatment with 6-OHDA.A third type of nerve fiber is characterized by varicosities containing dense-cored vesicles with a thin light halo, the mean diameter (1250 Å) of which exceeds that of the morphologically similar granular vesicles in cholinergic synapses. Those fibers resemble neurosecretory and purinergic axons and are therefore called p-type fibers. They cannot be stained with chromalum-hematoxyline-phloxine. Axon dilations showing aggregates of mitochondria, myelin bodies and dense-cored vesicles of different shape and diameter are considered to be afferent nerve endings. Blood vessels in the capsule of the gland are innervated by both cholinergic and adrenergic fibers.Supported by a grant from the Deutsche Forschungsgemeinschaft (Un 34/1).     

Electron microscopic observations on synapse-like contacts between pituicytes and different types of nerve fibers in the anuran pars nervosa

Summary Pituicytes of Rana pipiens could be classified into two types, pale and dense, according to their relative densities of cytoplasm and the populations of free ribosomes and cell organelles. An intermediate type of pituicyte was also recognized.Lipid droplet such as are typical in the cytoplasm of mammalian pituicytes, are not in the cytoplasm of either types of frog pituicyte. Both types have long cytoplasmic processes which run among the nerve fibers, and some of them end at the pericapillary space.Nerve endings making synapse-like contacts with the cell bodies or the processes of the pituicyte are frequent. According to the structures and sizes of granules and vesicles in the nerve endings, these endings are classified into one of three types: 1) A, which appears to be a peptidergic neuronal ending containing dense granules 1,200–2,000 Å in diameter and small clear vesicles 300–400 Å in diameter; 2) B, which appear to be monoaminergic endings containing cored vesicles 600–1,000 Å in diameter and small clear vesicles 300–500 Å in diameter; 3) C, which appear to be cholinergic endings containing only small clear vesicles. Type C endings are relatively rare. In the synaptic area the axonal membranes appose those of the pituicytes across a gap of about 200 Å and numerous presynaptic vesicles are clustered or accumulated near the presynaptic membranes.The author wish to express his hearty thanks Professor Dr. A. Gorbman, Zoology Department, University of Washington, Seattle, U.S.A. and Professor Dr. H. Fujita for their helpful advices and criticisms. The frog tissues were obtained and fixed in Professor A. Gorbman's laboratory supported by U.S.P.H.S. grant NS 04887.     

Demonstration and localization of synapsin I in vestibular receptors in the cat: immunocytochemical study

The presence and localization of synapsin I, a neuron-specific phosphoprotein, was investigated in the cat vestibular epithelium, using a rabbit antisynapsin I anti-serum. The staining was performed by immunofluorescence or by a peroxidase-antiperoxidase (PAP) technique. A strong immunoreactivity was observed with both methods. This immunoreactivity appeared as spherical patches distributed in the lower part of the epithelium. This distribution pattern is very similar to that of the efferent synaptic endings which form axodendritic synapses with the afferent nerve chalice of type I hair cells, or axosomatic synapses with type II hair cells. Some of the nerve chalices were also labelled; in this case, the immunoreactivity was more evident with PAP staining. These results thus suggest the presence of large amounts of synapsin I in the vestibular efferent nerve endings. These endings are known to be filled with numerous synaptic vesicles. This localization of synapsin I is well correlated with previous work that report a close association between synapsin I and small synaptic vesicles. The presence of synapsin I in sensory endings such as the afferent nerve chalices was unexpected and is under investigation.     

Arterial system of the gill of the lobster,Homarus americanus

Three-dimensional architecture of the branchial artery and venous vasculature of Homarus americanus was studied by the method of corrosion cast or styrene cracking and by scanning electron microscopy. Four arteries, the epibranchial (EA) and hypobranchial arteries (HA) on the septal wall of the afferent and efferent vessels, respectively, and two lateral canal arteries (LCA), each in one of the paired lateral canals, run parallel to the gill axis. The EA directs dendroid branches to the spongy tissue in the afferent vessel wall far from the efferent, supplying oxygen to the otherwise oxygen-depleted tissue. The HA distributes the filament arteriole (FA) into the central channel of individual middle filaments via the LCA. The FA opens halfway at a position where the channel narrows. Thus, it is likely that venous hemolymph in the central channel flows from base to tip in the direction in which arterial hemolymph from the FA flows. This and the anatomy of venous vasculature suggest three probable patterns of perfusion from afferent to efferent vessels: double serial circulation via the outer and inner filaments and novel routes both through the middle filament, i.e., single circulation via the afferent and efferent channels of this filament and double serial circulation via the outer filament and then the central channel of the middle. On the basis of the physics of flow and known physiological data, we propose that switching of these routes that involves independently functional multiple double serial circulations can play an important role in controlling efficiency of gas exchange, particularly during hypoxia. J Morphol. 233:165–181, 1997. © 1997 Wiley-Liss, Inc.     

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.     

Vascular anatomy of the fish gill

The fish gill is the most physiologically diversified vertebrate organ, and its vasculature the most intricate. Application of vascular corrosion techniques that couple high-fidelity resins, such as methyl methacrylate, with scanning electron microscopy yields three-dimensional replicas of the microcirculation that have fostered a better appreciate gill perfusion pathways. This is the focus of the present review. Three vascular networks can be identified within the gill filament. The arterioarterial (respiratory) pathway consists of the lamellae and afferent and efferent segments of the branchial and filamental arteries and lamellar arterioles. The body of the filament contains two post-lamellar pathways: the interlamellar and nutrient. The interlamellar system is an extensive ladder-like network of thin-walled, highly distensible vessels that traverses the filament between, and parallel to, the lamellae and continues around the afferent and efferent borders of the filament. Interlamellar vessels are supplied by short, narrow-bore feeder vessels from the medial wall of the efferent filamental artery. A myriad of narrow-bore, tortuous arterioles arise from the basal efferent filamental artery and efferent branchial artery and anastomose to form the nutrient circulation of the arch and filament. In the filament body, nutrient capillaries and interlamellar vessels are often closely associated, and the former may ultimately drain into the latter. Many of the anatomical characteristics of interlamellar vessels are strikingly similar to those of mammalian lymphatic capillaries, with the exception that interlamellar vessels are directly fed by arteriovenous-like anastomoses. It is likely that gill interlamellar and mammalian lymphatics are physiologically, if not embryologically, equivalent.     

Nitric oxide synthase in the glossopharyngeal and vagal afferent pathway of a teleost, Takifugu niphobles

To examine the presence of nitric oxide synthase (NOS) in the sensory system of the glossopharyngeal and vagus nerves of teleosts, nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) activity and immunoreactivity for NOS were examined in the puffer fish Takifugu niphobles. The nitrergic sensory neurons were located in the ganglia of both the glossopharyngeal and the vagal nerves. In the vagal ganglion, positive neurons were found in the subpopulations for the branchial rami and the coelomic visceral ramus, but not for the posterior ramus or the lateral line ramus. In the medulla, nitrergic afferent terminals were found in the glossopharyngeal lobe, the vagal lobe, and the commissural nucleus. In the gill structure, the nitrergic nerve fibers were seen in the nerve bundles running along the efferent branchial artery of all three gill arches. These fibers appeared to terminate in the proximal portion of the efferent filament arteries of three gill arches. On the other hand, autonomic neurons innervating the gill arches were unstained. These results suggest that nitrergic sensory neurons in the glossopharyngeal and vagal ganglia project their peripheral processes through the branchial rami to a specific portion of the branchial arteries, and they might play a role in baroreception of this fish. A possible role for nitric oxide (NO) in baroreception is also discussed.