Ultrastructural aspects of functional interest in the ventricular myocardial wall of the antarctic icefish Chaenocephalus aceratus

Tota, Bruno; F, Farina; Zummo, Giovanni

doi:10.1016/0305-0491(88)90296-9

Cited by 7 publications

(8 citation statements)

References 10 publications

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“…Recent studies on carps acclimated to cold have shown a shift in the synthetic activity of the heart cells from myofibrillar components to structural proteoglycans (Pelouch and Vornanen, 1996). Also, some especial distribution of amorphous material and microfibrils has been described in the ventricle of the icefish Chaenocephalus aceratus (Tota et al, 1988; Harrison et al, 1991).…”

Section: Discussionmentioning

confidence: 99%

Bulbus arteriosus of the antarctic teleosts. I. The white-bloodedChionodraco hamatus

et al. 1999

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The bulbus arteriosus of teleost fish is a thick-walled chamber that extends between the single ventricle and the ventral aorta. The functional importance of the bulbus resides in the fact that it maintains a steady blood flow into the gill system through heart contraction. Despite of this, a thorough study of the structure of the bulbus in teleost fish is still lacking. We have undertaken a morphologic study of the bulbus arteriosus in the stenothermal teleosts of the Antarctic sea. The structural organization of the bulbus arteriosus of the icefish Chionodraco hamatus has been studied here by conventional light, scanning, and transmission electron microscopy.The inner surface of the bulbus shows a festooned appearance due to the presence of longitudinal, unbranched ridges that extend between the ventricle and the arterial trunk. The wall of the bulbus is divided into endocardial, subendocardial, middle, and external layers. Endocardial cells show a large number of moderately-dense bodies. The endocardium invaginates into the subendocardium forming solid epithelial cords that contain numerous secretory vacuoles. Cells in the subendocardium group into small domains, have some of the morphological characteristics of smooth muscle cells, and appear enmeshed in a three-dimensional network of matrix filaments. Cells in the middle layer are typical smooth muscle cells. They appear arranged into layers and are surrounded by a filamentous meshwork that excludes collagen fibers. Orientation of this meshwork occurs in the vicinity of the smooth muscle cells. Elastin fibers are never observed. The external layer is formed by wavy collagen bundles and fibroblast-like cells. This layer lacks blood vessels and nerve fibers.The endocardium and the endocardium-derived cords are secretory epithelia that may be involved in the formation of mucins or glycosaminoglycans. These mucins may have a protecting effect on the endocardium. The subendocardium and the middle layer appear to be formed by the same cell type, smooth muscle, with a gradient of differentiation from the secretory (subendocardium) to the contractile (middle layer) phenotype. Despite the absence of elastin fibers, the filamentous matrix could maintain the elastic properties of the bulbus wall. Smooth muscle cells appear to be actively involved in bulbus wall dynamics. The restriction of collagen to the external layer suggests that it may control wall dilatation and bulbus compliance.

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Section: Discussionmentioning

confidence: 99%

Bulbus arteriosus of the antarctic teleosts. I. The white-bloodedChionodraco hamatus

et al. 1999

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“…The net result is a greatly elevated cardiac stroke work (see Axelsson, 2006), which is exactly the situation produced by hypoxic bradycardia (but to a lesser degree). Given this parallel, perhaps some Antarctic fish hearts should be considered to be in an 'adapted hypoxic state', especially since they can have negligible myoglobin in their hearts (Sidell and O'Brien, 2006) and lack a coronary circulation (Tota et al, 1988;Axelsson, 2006). The finding that myocytes of the haemoglobinless icefish have low myofibrilar and high mitochondrial contents (Tota et al, 1988) points to a low oxygen demand and a poor oxygen supply.…”

Section: Temperaturementioning

confidence: 99%

“…Given this parallel, perhaps some Antarctic fish hearts should be considered to be in an 'adapted hypoxic state', especially since they can have negligible myoglobin in their hearts (Sidell and O'Brien, 2006) and lack a coronary circulation (Tota et al, 1988;Axelsson, 2006). The finding that myocytes of the haemoglobinless icefish have low myofibrilar and high mitochondrial contents (Tota et al, 1988) points to a low oxygen demand and a poor oxygen supply. Furthermore, the reduced oxygen carrying capacity of their blood raises the possibility that oxygen extraction by the myocardium can significantly decrease the oxygen content of blood passing through the heart, unlike temperate species with their high haemoglobin concentration.…”

Section: Temperaturementioning

confidence: 99%

Tribute to P. L. Lutz: a message from the heart – why hypoxic bradycardia in fishes?

Farrell

2007

Journal of Experimental Biology

139

109

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SUMMARY The sensing and processing of hypoxic signals, the responses to these signals and the modulation of these responses by other physical and physiological factors are an immense topic filled with numerous novel and exciting discoveries. Nestled among these discoveries, and in contrast to mammals, is the unusual cardiac response of many fish to environmental hypoxia– a reflex slowing of heart rate. The afferent and efferent arms of this reflex have been characterised, but the benefits of the hypoxic bradycardia remain enigmatic since equivocal results have emerged from experiments examining the benefit to oxygen transfer across the gills. The main thesis developed here is that hypoxic bradycardia could afford a number of direct benefits to the fish heart, largely because the oxygen supply to the spongy myocardium is precarious (i.e. it is determined primarily by the partial pressure of oxygen in venous blood, PvO2) and,secondarily, because the fish heart has an unusual ability to produce large increases in cardiac stroke volume (VSH) that allow cardiac output to be maintained during hypoxic bradycardia. Among the putative benefits of hypoxic bradycardia is an increase in the diastolic residence time of blood in the lumen of the heart, which offers an advantage of increased time for diffusion, and improved cardiac contractility through the negative force–frequency effect. The increase in VSH will stretch the cardiac chambers, potentially reducing the diffusion distance for oxygen. Hypoxic bradycardia could also reduce cardiac oxygen demand by reducing cardiac dP/dt and cardiac power output, something that could be masked at cold temperature because of a reduced myocardial work load. While the presence of a coronary circulation in certain fishes decreases the reliance of the heart on PvO2, hypoxic bradycardia could still benefit oxygen delivery via an extended diastolic period during which peak coronary blood flow occurs. The notable absence of hypoxic bradycardia among fishes that breathe air during aquatic hypoxia and thereby raise their PvO2, opens the possibility that that the evolutionary loss of hypoxic bradycardia may have coincided with some forms of air breathing in fishes. Experiments are needed to test some of these possibilities. Ultimately, any potential benefit of hypoxic bradycardia must be placed in the proper context of myocardial oxygen supply and demand, and must consider the ability of the fish heart to support its routine cardiac power output through glycolysis.

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Section: Discussionmentioning

confidence: 99%

“…The myocardial layer of many teleosts is composed of myocytes, granulated non-contractile cells, interstitial spaces with electron-dense material and lacunary spaces that contain amorphous material and collagen fibres (Midttun 1980;Tota et al 1988;Harrison et al 1990). The mechanical role of the collagen bundles scattered throughout the extracellular matrix is suggested to be of major importance in maintaining the integrity of the ventricular wall in the working heart (Tota et al 1988). Fish myocytes are usually long cells that consist of peripherally located myofibrils and centrally located mitochondria, with the nucleus occupying the longitudinal space within the peripheral ring of myofibrils (Tota 1989;Satchell 1991).…”

Section: Discussionmentioning

confidence: 99%

Copper sulfate affects Nile tilapia (Oreochromis niloticus) cardiomyocytes structure and contractile function

et al. 2011

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Copper sulfate (CuSO(4))is an inorganic chemical product worldwide used as an algaecide and a fungicide in aquaculture and agriculture and being discharged into freshwater environments where it can affect the freshwater fauna, especially fishes. The impact of copper on fish cardiac function was analyzed in two groups of Nile tilapias, Oreochromis niloticus (control group and group exposed to 1 mg l(-1) of CuSO(4) for 96 h). Structural and ultra-structural changes were studied and related to perturbations of the inotropic and chronotropic responses of ventricle strips. Fish of Cu exposed group did not show significant alterations in the medium diameter and in the percentage of collagen in the cardiac myocytes when evaluated through the light microscope. However, the ultrastructural analysis revealed cellular swelling followed by mitochondrial swelling. The myofibrils did not show significant variations among groups. Force contraction was significantly decreased, and rates of time to tension increase (contraction) and decrease (relaxation) were significantly augmented after copper exposure. The results suggest that the copper sulfate impairs the oxidative mitochondrial function and consequently alters the cardiac performance of this species.

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Ultrastructural aspects of functional interest in the ventricular myocardial wall of the antarctic icefish Chaenocephalus aceratus

Cited by 7 publications

References 10 publications

Bulbus arteriosus of the antarctic teleosts. I. The white-bloodedChionodraco hamatus

Bulbus arteriosus of the antarctic teleosts. I. The white-bloodedChionodraco hamatus

Tribute to P. L. Lutz: a message from the heart – why hypoxic bradycardia in fishes?

Copper sulfate affects Nile tilapia (Oreochromis niloticus) cardiomyocytes structure and contractile function

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