The rodlet cells of teleostean fish: their potential role in host defence in relation to the role of mast cells/eosinophilic granule cells

The distribution and potential function of the rodlet cells of teleosts were studied by microscopic observations on tissue samples from the digestive tract and adjacent tissues, including the bulbus arteriosus. Fish representing 3-5 genera from each of the families Salmonidae, Cyprinidae, Gadidae and Labridae were included in the study. Great individual variations in the distribution of rodlet cells were found in all species of salmonids, gadids and labrids. The cells seemed to be absent in some individuals of a species and were associated with different epithelial tissues in others, but were not found in vascular endothelia. Their occurrence was common in all salmonids caught in their natural environment, whereas those in aquaculture, kept under controlled conditions with respect to water quality, showed extremely few rodlet cells. In species of the cyprinid family, the picture was different. Rodlet cells were consistently present under the endothelium of the bulbus arteriosus, and were very numerous at this location in individuals infected with blood flukes. In other epithelial tissues of cyprinids, rodlet cells were encountered in fairly high numbers, but in some tissues of individuals from all species they were occasionally absent. In all of the studied families rodlet cells seemed to be recruited when helminths affected epithelial tissues. Mast cells/eosinophilic granule cells were consistently very numerous in tissues of the intestine of cyprinids and labrids. In gadids, mast cells/eosinophilic granule cells seemed to be absent. Present evidence points to a role for the rodlet cells in defence functions, e.g. in combating helminths, and the suggestion earlier made for mast cells/eosinophilic granule cells, that evolution has created a "standing force" in particular tissues of teleosts consistently exposed to pathogens, whereas an efficient "mobilization force" has been an advantage in those living in more pathogen-free environments, may also be applied to rodlet cells, explaining the differences between teleostean families with respect to their distribution pattern.     

Alteration of rodlet cells in chub caused by the herbicide Stam® M-4 (Propanil)

Handling stress and exposure to the herbicide Stam® M-4 (Propanil) were associated with an exponential depletion of the rodlet cells (RC) in the bulbus arteriosus of chub Leuciscus cephalus . Structural changes of the RC in herbicide-exposed fish were encountered, including the occurrence of myeloid bodies in the cytoplasm of the RC of the intestine, various degrees of rodlet degeneration and high vacuolization in the cytoplasm of RC in almost all examined organs of exposed chub.     

The effect of dexamethasone on the occurrence and ultrastructure of rodlet cells in goldfish

In the bulbus arteriosus of goldfish Carassius auratus a subendothelial 'reticular space' was comprised of reticular-like cells, neutrophils, medium-sized granular leucocytes, phagocytes, endothelial cells and reticulo-endothelial cells; herein, rodlet cells (RCs) accumulated and probably matured. Four classes of RCs were identified: (1) Those occurring in the reticular space and contacting reticular-like cells; (2) those present in the reticular space contacting reticular-like and endothelial cells; here the RCs were discharging; (3) those occurring in the bulbar lumen anchored to lining endothelial cells or other RCs; (4) those free in the bulbar lumen. There was no significant difference in the number of RCs among control and saline- and dexamethasone-treated fish, but significant differences were found in RCs' class partition and in their discharge modality. In dexamethasone-treated goldfish class (3) RCs were almost absent (2% v. 10% of the other experimental groups), moreover 35% of the RCs developed a 'bleb' discharge modality rather than the most typical 'koronenartigen konfiguration' which developed in the vast majority (90%) of the other experimental groups.     

Observations on rodlet cells found in the vascular system and extravascular space of angelfish (Pterophyllum scalare scalare)

In the angelfish ( Pterophyllum scalare scalare ) numerous rodlet cells were found in the large post-orbital blood vessel caudal to the eye and in the surrounding extravascular space. Within the vessel the rodlet cells formed striking regular arrays, along the inner aspect of the wall. The rodlets within the cells were positive to PAS but negative to Sudan Black B, Masson's, and the Fuelgen stain. The capsule around the cells was negative for all these stains. These rodlet cells appeared to be traversing the vessel endothelium, and to be pushing the endothelium aside without damaging it. Some discharged their contents into the vessel, but we never observed the release of intact rodlets. The nuclei of rodlet cells in actual contact with the vessel were at the end of the cell more distant from the endothelial wall. Cell-to-cell adhesion structures or communications junctions between rodlet cells and the endothelium were not evident. A putative rodlet cell precursor in the extravascular space contained large electron-dense granules, and extended pseudopodia that contacted nearby rodlet cells. Based on their morphology, tissue distribution, and their behaviour, we conclude that the rodlet cell is an endogeneous teleost cell type, and possibly represents a form of matured granulocyte.     

Ultrastructural and ultrahistochemical studies on ventricular endocardial cells in teleosts (Pisces)

The ultrastructure of the ventricular endocardial cells in 17 bony-fish species representing eight families, is described. In species of Characidae, Cobitidae, Cyprinidae, and Gyrinocheilidae these cells are flat (1–2 µm at nucleus) and contain numerous ribosomes, some few bristle-coated vesicles (BCV) and small (0.243 pm) electron dense inclusion bodies. However, in species of Cichlidae, Gadidae, and Poeciliidae most endocardial cells appear relatively thicker (2–5 µm at nucleus) and contain numerous BCV, tubules of agranular endoplasmic reticulum, and large (0.5-1.5 µm) moderately electron dense bodies (MDB). In the MDB occur a number of small (20–150 nm) electron dense granules. Within the family Anabantidae, most endocardial cells seem to be of the first type in Colisa laliu and Trichogaster leeri. whereas in Helosioma iemmincki there are numerous cells of the second type. When glutaraldehyde/tannic acid fixed heart tissue of Pollachius virens is treated with ferrous chloride, ferric chloride, or osmium tetroxide, and grid stained by uranyl and lead solutions, damaged endocardial cells appear highly electron dense, whereas undamaged ones are electron lucent. Further, when glutaraldehyde fixed tissue is treated with osmium tetroxide/potassium ferrocyanide the subendocardial space is filled by a highly electron dense material. The methods described in this study make it possible to distinguish between those endocardial vacuoles having structural contact with the cell membrane, and those lacking such contact, and also to determine whether the lumen of the former is continuous with the subendocardial space, or with the intertrabecular lumen.     

Histological, histochemical and ultrastructural studies on the bulbus arteriosus of the sticklebacks, Gasterosteus aculeatus and Pungitius pungitius (Pisces: Teleostei)

The bulbar wall has three layers. Its lining consists of squamous-columnar endothelial cells that store neutral mucopolysaccharides and are PAS-positive. They do not contain large amounts of acid phosphatase, acid mucopolysaccharides, glycogen or lipids. A morphometric analysis shows that 32% of the cell volume in Pungitius and 12% in Gasterosteus is occupied by specific granules, 100–600 nm in diameter. According to X-ray probe micro-analysis, these granules bind chromium ions, even though the endothelial cells do not contain catecholamines. Rootlets, packed with plasmalemmal vesicles, extend from the endothelial cells into the middle layer of the bulbus. Here, smooth muscle cells alternate with elastic fibres. The staining reactions of bulbar elastica are compared with those in the mammalian aorta and the ligamentum nuchae. The outer layer of the bulbus is visceral pericardium and beneath its covering mesothelial cells are numerous collagen fibres, non-myelinated nerves, occasional fibroblasts and melanocytes. Scanning electron microscopy shows that the bulbar lining is thrown into longitudinal folds, but that there are no trabeculae subdividing the lumen.
Many features of the bulbus arteriosus may be related to the low systolic pressures of teleosts and to the proximity of their heart and gills. In contrast to mammals, only a small part of the arterial system can act as a windkessel. The bulbus is thus more distensible than the mammalian aorta and must lie within the pericardial cavity so that its greater excursions can be accommodated. Perhaps because the bulbus is so distensible, it has elastic fibres rather than lamellae. This in turn may affect the organization of the smooth muscle cells which do not form "span muscles" as in some mammalian aortae. Like most cells in the bulbus, they are joined to others by desmosomes. Evidently, firm cohesion is important in highly distensible vessels.     

Structural and histochemical characterization of the cotyledon storage organelles of jojoba (Simmondsia chinensis)

Summary Jojoba cotyledon cells are isodiametric and 44 m in diameter. They contain two prominent storage organelles—wax bodies and protein bodies. Isolated and intact wax bodies react positively with several lipid histochemical stains; they are spherical and 1.5 m in diameter. Protein bodies are irregular in shape, but usually appear spherical. They range in diameter from 7–15 m, are unit membrane bound, have an irregular grainy matrix and do not contain a globoid inclusion. Protein bodies stain positively for both protein and lipid. The possible composition and role of this protein/lipid body complex is discussed.     

AP-1 Membrane–Cytoplasm Recycling Regulated by μ1A-Adaptin

The adaptor protein complex AP-1 mediates vesicular protein sorting between the trans Golgi network and endosomes. AP-1 recycles between membranes and the cytoplasm together with clathrin during transport vesicle formation and vesicle uncoating. AP-1 recycles independent of clathrin, indicating binding to unproductive membrane domains and premature termination of vesicle budding. Membrane recruitment requires ADP ribosylation factor-1-GTP, a transmembrane protein containing an AP-1-binding motif and phosphatidyl-inositol phosphate (PI-4-P). Little is known about the regulation of AP-1 membrane–cytoplasm recycling. We identified the N-terminal domain of μ1A-adaptin as being involved in the regulation of AP-1 membrane–cytoplasm recycling by constructing chimeras of μ1A and its homologue μ2. The AP-1* complex containing this μ2–μ1A chimera had slowed down recycling kinetics, resulting in missorting of mannose 6-phosphate receptors. The N-terminal domain is only accessible from the cytoplasmic AP-1 surface. None of the proteins known to influence AP-1 membrane recycling bound to this μ1A domain, indicating the regulation of AP-1 membrane–cytoplasm recycling by an yet unidentified cytoplasmic protein.     

Description of the Oocysts of Two New Species of Eimeria (Apicomplexa: Eimerüdae) from the Florida Manatee, Trichechus manatus (Sirenia: Trichechidae)

Two new species of Eimeria (Apicomplexa: Eimerüdae) are described from the feces of the Florida manatee, Trichechus manatus latirostrts (Sirenia: Trichechidae). Oocysts of Eimeria manatus n. sp. are spherical to subsphencal, 11.8 × 10.7 (10.5–13.5 × 9.0–13.5) μ m , with a smooth, thin, bilayered wall; shape index (length/width) 1.1 (1.0–1.3). Micropyle and oocyst residuum absent; polar granule(s) usually present. Sporocysts are ovoid, 8.6 × 5.1 (8.0–9.5 × 5.0–5.5) μm, with thin, membrane–like walls and a knoblike Stieda body; shape index 1.7 (1.4–1.8). Sporozoites elongate, each with a large posterior refractile body. The sporocyst residuum consists of a small cluster or row of few to many small granules. Oocysts of Eimeria nodulosa n. sp. are spherical to subspherical, 15.6 × 14.7 (14.5–17.5 × 13.0–16.0) μm, with a distinctly bilayered wall; shape index 1.1 (1.0–1.2). Unsporulated and freshly sporulated oocysts often possess large, knob–like structures on the external surface of the oocyst wall that support a thin membrane or filament. Micropyle, oocyst residuum and polar granule absent. Sporocysts are ovoid, 10.6 × 5.9 (9.5–12.0 × 5.0–6.5) μm, with a smooth, thin wall and knob–like Stieda body; shape index 1.8 (1.5–2.1). Sporozoites granular and elongate, each with a large posterior refractile body. The sporocyst residuum consists of a loose aggregate or scattered mass of moderately sized granules.     

Ultrastructural study on the intestine of Senegal sole, Solea senegalensis

The intestinal epithelium of Senegal sole, Solea senegalensis Kaup is composed of three main cell types: epithelial, goblet and rodlet. The cytoplasm of columnar epithelial cells – enterocytes – has spherical lipid droplets. The dominant feature throughout the intestinal mucosa was goblet cells filled with numerous mucous droplets of high density. The cytoplasm of the rodlet cells contained peripheral filamentous, pycnotic nuclei, and numerous cytoplasmic inclusions (rodlets), with a very dense cylindrical core surrounded by flocculent material. Some physiological implications related to ultrastructural features of the intestine are also discussed.     

Endogenous Stages of the Life Cycle of Isospora rivolta in the Dog

SYNOPSIS. Coccidia-free beagle puppies were experimentally infected with a cloned culture of Isospora rivolta oocysts. The endogenous stages were found in the posterior 1/2 of the small intestine, and rarely in the cecum and colon. Maximum numbers of all stages occurred just anterior to the ileocecal valve. Endogenous stages were found in the distal third of the villi, predominantly parasitizing subepithelial cells of the lamina propria; however, stages were occasionally present in epithelial cells. The number of asexual generations could not be determined from their structure, but evidence based on oocyst production suggested that there were at least 2 asexual generations. The schizonts were 17–24 by 12–25 μ and contained 4–24 merozoites, the most common number being 4 or 8. Schizonts with mature merozoites were found as early as 72 hr, but were present in maximum numbers at 96 hr. Merozoites had slender curved bodies and were 10.5–13.4 by 2.3–3.0 μ. Mature gamonts were found by 144 hr. Mature microgametocytes were 13.4 by 8.7 μ and contained 50–70 microgametes. Microgametes had slightly curved tapering bodies (5.8–6.4 by 0.6 μ) with 2 posteriorly directed flagella 11–14 μ long. Mature macrogametes had reticular cytoplasm and a uniformly large nucleus and nucleolus.
The prepatent period was 142–146 hr. The patent period was 13–23 days with an average of 19 days.     

Eimeria procyonis sp. n., an Isospora sp., and a Redescription of E. nuttalli Yakimoff and Matikaschwili, 1932 (Protozoa: Eimeriidae) from the American Raccoon (Procyon lotor)

SYNOPSIS. Thirty-two of 48 raccoons examined were infected with a previously undescribed species of Eimeria which is herein named E. procyonis. Of the 32 infected animals, 10 also harbored E. nuttalli and 1 had Isospora sp. oocysts.
The ellipsoid to ovoid oocysts of E. procyonis measured 23.4 × 18.0 (16–29 × 13–24) μm; its sporocysts measured 12.1 × 9.3 (11.5–15 × 7–10) μm, each containing a slightly flattened substiedal body. The sporocyst residuum consisted of numerous scattered granules each ∼1 μm in diameter. The oocyst wall was double-layered. The outer layer appeared rough and pitted, measuring 1.5 μm, except at the micropyle where it was 1 μm thick.
The oocysts of the Isospora sp. measured 16.8 × 13.7 (16–18.5 × 12.5–15.5) μm. The wall consisted of a single layer ∼0.5 μm thick. The sporocysts measured 11.2 × 9.1 (9.5–11.5 × 8–10) μm, and each contained 4 elongate sporozoites. The oocysts of E. nuttalli measured 17.5 × 13.6 (12-21 × 11-15) μm, with a smooth single-layered wall approximately 0.7 μm thick. The sporocysts measured 12.2 × 7.1 (9-13 × 5.5–11) μm. Each sporocyst had a thin, dark, Stieda body and the sporocyst residuum consisted of many fine granules.     

Fine structure of the respiratory organs of the Climbing perch, Anabas testudineus (Pisces: Anabantidae)

An electron microscopic study has been made of the three respiratory organs of climbing perch. The gill structure is similar to that of the other telcosts but the thickness of the water/blood barrier is much greater, being as great as 20 μm in some specimens. The increased thickness is due to a multilayered epithelium which is thinner (3.5–7 μm) over the marginal channel of the secondary lamellae. The other two main layers, basement membrane and pillar cell flange, are relatively thin (about 1 μm).
The pillar cells have a typical structure, but in certain regions they are contiguous with one another and line well-defined blood channels. Some of the columns of basement membrane material in such regions may be common to adjacent pillar cells.
The air-breathing organs are (a) the lining of the suprabranchial chambers , and (b) the labyrinthine plates attached to the dorsal region of branchial arches. Electron microscopy showed that their structure is well adapted for gas exchange, the air/blood barriers being only 0.12–0.3 μm, comprising an epithelial layer, basement membrane, and thin capillary endothelium. The many parallel blood channels of the respiratory islets of both organs are separated by pillar-like structures which differ from the pillar cells of the secondary lamellae. Thus the hypothesis that the air-breathing organs represent modified gills is not supported by this study.
The fine structure of the non-respiratory region of the air-breathing organs is similar to that of the skin, and includes chemoreceptor-like cells. Evidence concerning the possible homology of pillar cells with plain muscle cells is discussed.     

Some aspects of the infrastructure of the ‘Stäbchendrüscnzellen’, a peculiar cell associated with the endothelium of the bulbus arteriosus and with other fish tissues*

The fine structure of an unusual cell, the ‘Stäbchendriisenzellen’ (the so-called foliaceous or rodlet cells of several authors), associated with the endothelium of the vascular system of marine and freshwater fishes was studied in the goldfish Carassius auratus (L.). The bulbus arteriosus was fixed with either a 6 % solution of buffered glutaraldehyde or with one part of a 3 % solution of lanthanum nitrate plus two parts of a 3 % solution of buffered glutaraldehyde and then post-fixed in a 1.2% solution of osmium tetroxide. Electron micrographs of the vascular tissue show four cell forms which appear to be phases in the life cycle of the endothelium-associated cell. Two of the phases are not encased and are characterized by their inclusions: in one cell these are crystalline, while in the second, they are amorphous and granular. In the other phases the cell is encased partially or completely within an apparently contractile fibrous wall surrounded by the plasmalemma. In the encased phases, the arrangement and condition of the cell organelles appears to have been changed, and in the fully-encased phase mitochondrial activity seems to have decreased. This apparent change in the mitochondrial activity is accompanied by a thickening of the mitochondrial membrane from 48 to 109 Å. The micrographs seem to indicate that this cell in question behaves as a foreign body and, in some way, may be interacting with the epithelial tissue of the bulbus arteriosus.     

The Structure of the Oocyst and the Excystation Process of Isospora marquardti sp. n. from the Colorado pika, Ochotona princeps

SYNOPSIS. Oocysts of Isospora marquardti sp. n. from the Colorado pika, Ochotona princeps , have spheroid oocysts, 30.5 (23–36) μm in diameter, and ovoid sporocysts, measuring 19.3 × 12.0 (17–22 × 10–14) μm. A polar body, 2 × 4 μm, a spheroid sporocyst residuum (8.3 μm in diameter), a Stieda body, and a distinct substiedal body (3 × 3 μm) are present. A micropyle and an oocyst residuum are absent. Excysted sporozoites, averaging 3.0 × 18.5 (2–4 × 15–20) μm, contain 2 refractile globules, 1 on each side of the nucleus with a prominent nucleolus.
The sporozoite excystation process using a trypsin-sodium taurocholate fluid is described.     

Carbohydrate-containing endothelial cells lining the bulbus arteriosus of teleosts and the conus arteriosus of elasmobranchs (Pisces)

The study is a survey of the shape and carbohydrate histochemistry of the endothelial cells lining the conus arteriosus of 10 species of elasmobranchs and the bulbus arteriosus of 80 species of teleosts. Intensely PAS-positive cells that were often tall, were found in many teleosts and were typical of phylogenetically advanced species. They were not seen in any elasmobranch. Most of the teleosts with strongly PAS-positive cells were marine fish or euryhaline animals that were caught in freshwater. Beyond this, it is difficult to generalize on their life-style or habitat, for they included small fish, large fish, fast swimmers, bottom-living forms, deep-water fish, littoral species and Antarctic "bloodless" forms. It is likely that the PAS-positivity of the endothelial cells can be attributed to the moderately-dense granules revealed by E.M., but as yet the significance of these is unclear.     

The Fine Structure of the Paralabial Organelle in the Rumen Ciliate Ophryoscolex purkinjei Stein, 1858

The paralabial organelle of the rumen ciliate Ophryoscolex purkinjei , located on the ventral side of the ciliophor, is a highly specialized part of the somatic cortex. It consists of alternating rows of short modified cilia and thin pellicular folds which form a ridge-like structure. The central "top kinety" is composed of monokinetids which bear cilia with 9 + 2 axonemes and 2 μm in length. The top kinety is accompanied by a comb-shaped fold on its distal side and by a broad wedge-shaped fold on its proximal side. To both sides there follow two or three lateral kineties made of dikinetids. The anterior kinetosome of each pair bears a clavate cilium, only 0.5–0.7 μm in length and with a 9 + 0 axoneme while the cilium of the posterior kinetosome is even shorter. Lateral folds with numerous microtubules cover these lateral kineties and rows of barren basal bodies. The fine structure of this supposed sensory organelle show a basic pattern in four other ophryoscolecids, and its increasing complexity parallels the suggested phylogenetic line of evolution of these ciliates.     

Eimeria saudiensis N. Sp. (Apicomplexa: Eimeriidae) from the Arabian Oryx (Oryx leucoryx) in Saudi Arabia

Oocysts of Eimeria saudiensis n. sp. (Apicomplexa: Eimeriidae) are described from the feces of the Arabian oryx, Oryx leucoryx , from the Riyadh Zoo, Saudi Arabia. The oocysts were ellipsoidal or slightly ovoid, 31.2 times 24.5 (24.3–36.5 times 20.0–27.6) μm with a bilayered wall about 1.7 μm thick. The micropyle was covered by a dome-shaped cap. The oocyst residuum was absent, but tiny polar granules were present. The sporocysts were elongate ovoid, 14.3 times 7.2 (11.5–18.5 times 6.0–9.0) μm, had a Stieda body, but lacked a substiedal body. The sporocyst residuum was present, composed of numerous small granules. The sporozoites were elongate club-shaped, and contained two prominent refractile bodies.     

Sphaerospora epinepheli N. Sp. (Myxosporea: Sphaerosporidae) Observed in Grouper (Epinephelus malabaricus)

Sphaerospora epinepheli n. sp. is described from grouper, Epinephelus malabaricus , in cage-cultured and wild fish collected from both coastal lines of southern Thailand. Subspherical to spherical spores and mono- or disporous pseudoplasmodia were observed in the lumen of kidney tubules. Pseudoplasmodia were round to elongate, size range 15.6–22.9 μm (length) × 8.4–21.6 μm (width). Spores were 7.8–10.0 μm (length) × 12.3–14.5 μm (thickness), and 7.0–9.5 μm (width) with two spherical polar capsules of equal size measuring 2.9–4.4 μm in diameter and containing polar filaments with six or seven windings. Two uninucleate sporoplasms showed iodine vacuoles. Blood stages, similar to C-blood protozoans observed from freshwater fish in Europe, were found from peripheral blood smears of grouper. Ultrastructural studies of blood stages showed a similar structure to unidentified mobile protozoans from the blood of carp. Electron dense bodies were observed in the cytoplasm of the primary cell blood stages. Infected proximal-tubular epithelial cells showed highly vacuolated cytoplasm and pycnotic nuclei.     

Differentiation of the cardiac outflow tract components in alevins of the sturgeon Acipenser naccarii (Osteichthyes, Acipenseriformes): implications for heart evolution

Previous work showed that in the adult sturgeon an intrapericardial, nonmyocardial segment is interposed between the conus arteriosus of the heart and the ventral aorta. The present report illustrates the ontogeny of this intermediate segment in Acipenser naccarii. The sample studied consisted of 178 alevins between 1 and 24 days posthatching. They were examined using light and electron microscopy. Our observations indicate that the entire cardiac outflow tract displays a myocardial character during early development. Between the fourth and sixth days posthatching, the distal portion of the cardiac outflow tract undergoes a phenotypical transition, from a myocardial to a smooth muscle-like phenotype. The length of this region with regard to the whole outflow tract increases only moderately during subsequent developmental stages, becoming more and more cellularized. The cells soon organize into a pattern that resembles that of the arterial wall. Elastin appears at this site by the seventh day posthatching. Therefore, two distinct components, proximal and distal, can be recognized from the fourth day posthatching in the cardiac outflow tract of A. naccarii. The proximal component is the conus arteriosus, characterized by its myocardial nature and the presence of endocardial cushions. The distal component transforms into the intrapericardial, nonmyocardial segment mentioned above, which is unequivocally of cardiac origin. We propose to designate this segment the "bulbus arteriosus" because it is morphogenetically equivalent to the bulbus arteriosus of teleosts. The present findings, together with data from the literature, point to the possibility that cells from the cardiac neural crest are involved in the phenotypical transition that takes place at the distal portion of the cardiac outflow tract, resulting in the appearance of the bulbus arteriosus. Moreover, they suggest that the cardiac outflow tract came to be formed by a bulbus arteriosus and a conus arteriosus from an early period of the vertebrate evolutionary story. Finally, we hypothesize that the embryonic truncus of birds and mammals is homologous to the bulbus arteriosus of fish.