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

Scavenger endothelial cells of fish, a review

The definition of scavenger endothelial cells (SEC) is exclusively based on functional and structural characteristics. The following characteristics are common hallmarks for the vertebrate SEC: (a) All vertebrates examined are furnished with a population of special SEC that plays a role in the catabolism of physiologic and non-physiologic soluble waste macromolecules. (b) From the ligands that are endocytosed, SEC in all seven vertebrate classes appear to express the collagen α-chain receptor and the scavenger receptors. In addition, the hyaluronan and the mannose receptors are present on SEC of mammalia (several species) and osteichthyes (e.g., salmon and cod). It is likely that all four receptor types are present in all vertebrate classes. (c) Like liver endothelial cells (LEC) in mammals, SEC in all vertebrate classes are geared to endocytosis of soluble macromolecules, but phagocytic uptake of particles is taken care of mainly by macrophages. (d) The most primitive vertebrates (hagfish, lamprey and ray) carry their SEC in gill vessels, whereas phylogenetically younger fishes (salmon, carp, cod and plaice) carry their SEC in either kidney or heart and in all terrestrial vertebrates-SEC are found exclusively in the liver. (e) SEC of all vertebrates are localized in blood sinusoids or trabeculae that carry large amounts of slowly flowing and O₂ poor blood. (f) SEC differs functionally and structurally from what is normally associated with "conventional vascular endothelium."

The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and Excretion of Nitrogenous Waste

The fish gill is a multipurpose organ that, in addition to providing for aquatic gas exchange, plays dominant roles in osmotic and ionic regulation, acid-base regulation, and excretion of nitrogenous wastes. Thus, despite the fact that all fish groups have functional kidneys, the gill epithelium is the site of many processes that are mediated by renal epithelia in terrestrial vertebrates. Indeed, many of the pathways that mediate these processes in mammalian renal epithelial are expressed in the gill, and many of the extrinsic and intrinsic modulators of these processes are also found in fish endocrine tissues and the gill itself. The basic patterns of gill physiology were outlined over a half century ago, but modern immunological and molecular techniques are bringing new insights into this complicated system. Nevertheless, substantial questions about the evolution of these mechanisms and control remain.

Morphological changes in hepatic Ito cells after parenteral treatment with carmellose sodium in rats

Carmellose sodium (1.5%), dissolved in physiological saline, was given for 4 days via oral, subcutaneous or intraperitoneal routes. In the rats treated with carmellose sodium by the parenteral route, hepatic sinusoidal component cells and free macrophages were swollen. The degree of the swelling was more severe in the rats treated by the intraperitoneal route than by the subcutaneous route. The swollen sinusoidal component cells which engulfed the carmellose sodium-related substance were classified as Kupffer's cells or Ito cells by immunohistochemical reaction. Ito cells were isolated from a 5-week-old rat and were cultured in Dulbecco's modified Eagle's medium (DMEM). Some of the Ito cells which were cultured in DMEM containing 0.3% carmellose sodium showed phagocytic properties; vesicles in their cytoplasm and other Ito cells which were cultured in DMEM containing India ink contained some carbon particles.

The branchial circulation and the gill epithelia in the Atlantic hagfish, Myxine glutinosa L

The vessels of the branchial circulation of the Atlantic hagfish, Myxine glutinosa, and their relationship with the gill epithelia have been studied by light and electron microscopy. The inner surface of the pouch wall (containing the interconnected radial arteries) and the afferent and efferent unbranched portions (cavernous tissues) of the radially oriented gill folds are covered by a multilayered epithelium. The lamellar portion that is characterized by pillar cells is lined by a thin bilayered epithelium. The thin-walled sinusoid system is part of an arterio-venous circulation. This is demonstrated by the presence of arterio-venous anastomoses and by the connection to the peribranchial sinus. The sinusoid system has a close spatial relationship to the multilayered epithelium. The multilayered epithelium consists of pavement cells, cells of the medial layer and basal cells. Granulated cells are often found in the basal half of the epithelium. The pavement cells are characterized by large vesicles in close apposition to the apical plasma membrane. Ionocytes, which display a cytoplasmic tubular system that is continuous with the intercellular space, a high number of mitochondria, and small apical vesicles, are present. The occurence of the ionocytes in the afferent multilayered epithelium as well as the bilayered lamellar epithelium, the morphology of the ionocyte, and the absence of accessory cells is reminiscent of the freshwater teleost gill, and in part the elasmobranch gill, and is discussed in relation to osmo- and ion regulation.

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.

Antibody-enhanced phagocytosis of lamprey polymorphonuclear leucocytes against sheep erythrocytes

Centrifugation on Ficoll-Paque of the blood from the Arctic lamprey, Lampetra japonica, yielded a uniform population of leucocytes containing about 90% polymorphonuclear leucocytes (PMNs). The PMNs showed a significantly enhanced phagocytic activity in vitro against sheep erythrocytes (ES), provided they were opsonized with the specific lamprey antibody (AL) against ES. This enhanced phagocytosis by PMN was more active at 4 degrees C than 15 degrees C, being dependent on Ca++; the opsonic activity of lamprey antibody was not replaced by bullfrog antibody. By the use of electron microscopy, it was found that the PMNs possess a well developed Golgi complex and rough ER, as well as highly variable cytoplasmic granules. Observations by both SEM and TEm revealed the formation of prominent pseudopodia, lamellipodia and phagosomes by the PMN during the process of engulfing erythrocytes.