Ultrastructure of the liver of the fingerling rainbow trout Salmo gairdneri Richardson

Portions of the livers of fingerling rainbow trout were studied by light and electron microscopy. The histology, cytology and ultrastructure of mesothelial cells, serosal fibroblasts, hepatocytes, sinusoidal endothelial cells, endothelial cells of central veins and blood cells were described. Mesothelial cells and fibroblasts constituted a very thin capsule. Hepatocytes contained extensive areas of rough surfaced endoplasmic reticulum, consisting mainly of parallel cisternae and pools of glycogen. One or two nuclei and numerous mitochondria occurred in the areas of endoplasmic reticulum, but never in the pools of glycogen. Hepatocyte surface possibilities included hepatocyte to hepatocyte, hepatocyte to bile canaliculus, hepatocyte to space of Disse and hepatocyte to serosa. The trout liver was compared compared to channel catfish liver and to rat liver. Functional implications of the structural features were discussed.     

The viscosity and glycoprotein biochemistry of salmonid mucus varies with species,salinity and the presence of amoebic gill disease

Fish mucus has previously been reported to change in appearance and composition among species and in response to changes in salinity and disease status. This study reports on the mucus viscosity and glycoprotein biochemistry of Atlantic salmon (Salmo salar L.), brown trout (Salmo trutta L.) and rainbow trout (Oncorhynchus mykiss Walbaum) in freshwater and seawater, both naïve to and affected by amoebic gill disease (AGD). Cutaneous mucus viscosity was measured over a range of shear rates (11.5, 23, 46 and 115 s^–1), and non-Newtonian behaviour was demonstrated for all three species. Mucus viscosity was significantly greater in seawater than in freshwater for all species, and significantly lower in AGD-affected Atlantic salmon and brown trout. Mucus glucose, total protein and osmolality data indicated that differences in viscosity due to salinity were mostly attributed to changes in mucus hydration, while differences due to disease were mostly attributed to changes in mucus composition. Trends in gill mucus cell histochemistry included shifts in glycoproteins from neutral mucins in freshwater to acidic mucins in seawater, and shifts towards neutral mucins, with an increase in mucus cell numbers, in response to AGD. Results suggested that Atlantic salmon and brown trout are more similar to one another in their mucus profile than to rainbow trout. Atlantic salmon and brown trout both exhibited a whole-body mucus response to AGD, whereas rainbow trout exhibited only a local gill response. Findings hold implications for fish physiology and pathology, and indicate that future fish-disease management strategies should be species and condition specific.Communicated by I.D. HumeThe word mucus has been used in its noun form throughout the paper for clarity

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An erratum to this article can be found at .     

Ultrastructural localization of ependymins in the endomeninx of the brain of the rainbow trout: possible association with collagen fibrils of the extracellular matrix

In the rainbow trout, ependymins represent the predominant protein constituents of the cerebrospinal fluid (CSF) and perimeningeal fluid (PMF). Synthesis of these glycoproteins occurs exclusively in the endomeninx. Generally, ependymins share characteristics with proteins mediating cell-contact phenomena. Here, we show that the endomeninx of the rainbow trout is composed of three different layers, viz. an outer layer, an arachnoid-like intermediate barrier layer and an inner layer. This structure is in agreement with a meningeal barrier concept separating the PMF from the CSF. Furthermore, by immuno-electron microscopy, we have localized the majority of intracellular ependymins to the rough endoplasmic reticulum of fibroblast-like cells of the inner layer and to cells to the intermediate barrier layer. This pattern is compatible with the observed distribution of ependymins in both the PMF and CSF. In addition to their intracellular localization, an extracellular association of ependymins with bundles of collagen fibrils is demonstrated; this is particularly pronounced around all blood vessels of the brain.     

Isolation and characterization of novel glycoproteins from fish epidermal mucus: correlation between their pore-forming properties and their antibacterial activities

In fish, a layer of mucus covers the external body surface contributing therefore, among other important biological functions, to the defense system of fish. The prevention of colonization by aquatic parasites, bacteria and fungi is mediated both by immune system compounds (IgM, lysozyme, etc.) and by antibacterial peptides and polypeptides. We have recently shown that only the hydrophobic components of crude epidermal mucus of fresh water and sea water fish exhibit strong pore-forming properties, which were well correlated with antibacterial activity [N. Ebran, S. Julien, N. Orange, P. Saglio, C. Lemaitre, G. Molle, Comp. Biochem. Physiol. 122 (1999)]. Here, we have isolated novel glycosylated proteins from the hydrophobic supernatant of tench (Tinca tinca), eel (Anguilla anguilla) and rainbow trout (Oncorhynchus mykiss) mucus. The study of their secondary structure was performed by circular dichroism and revealed structures in random coil and alpha-helix in the same proportions. When reconstituted in planar lipid bilayer, they induced the formation of ion channels. This pore-forming activity was well correlated with a strong antibacterial activity (minimal inhibitory concentration < 1 microM for the three proteins) against both gram-negative and gram-positive bacteria. Our results suggest that fish secrete antibacterial glycoproteins able to kill bacteria by forming large pores (several hundreds to thousands of pS) in the target membrane.     

Ultrastructural features of degeneration of the gallbladder during lamprey biliary atresia

Thin sections and freeze-fracture replicas were used to examine the fine structural features of degeneration of the gallbladder during lamprey biliary atresia. The cells of the epithelium undergo a progressive accumulation of dense bodies and vacuoles, loss of glycogen, condensation of the filamentous ectoplasm, fragmentation of microvilli, and dilation of cisternae of rough endoplasmic reticulum but eventually disappear by stage 4 of metamorphosis. Zonulae occludentes in the epithelium show a progressive increase in apical-basal depth as the junctional strands fragment. The possibility of an influence of transformed, subepithelial cells on degeneration of epithelial cells is suggested by close contact of the former with the thickened, highly pleated, epithelial basal lamina. The smooth muscle cells of the larval gallbladder are believed to transform during lamprey metamorphosis into these subepithelial cells which shed their external lamina, become intimately associated with collagen and other microfibrils, and which may be capable of phagocytosis. The events of gallbladder degeneration during lamprey metamorphosis show features of apoptosis.     

THE INFLUENCE OF TEMPERATURE ON THE SURVIVAL OF SEVERAL SPECIES OF FISH IN LOW TENSIONS OF DISSOLVED OXYGEN

The resistance to low tensions of dissolved oxygen over periods ranging from less than a day to a week was determined for rainbow trout ( Salmo gairdnerii Richardson), perch ( Perca fluviatilis L.), roach ( Rutilus rutilus (L.)), and mirror carp, a domestic form of the common carp ( Cyprinus carpio L.) at 10°, 16° and 20°C., tench ( Tinea tinea (L.)) at 10° and 16°C., dace ( Leuciscus leuciscus (L.)) at 16° and 20°C., chub ( Squalius cephalus (L.)) at 20°C., and bleak ( Alburnus alburnus (L.)) at 16°C.
At each temperature period of survival decreased with fall in oxygen tension.
Rise in temperature between 10° and 20°C. reduced resistance to lack of oxygen of all species except rainbow trout, in which there was no significant difference between resistance at 16° and 20°C. Rise in temperature between 10° and 16°C. did, however, lower resistance considerably.
Tench were the most resistant to lack of oxygen and, in general, trout were the most susceptible. At 20°C. mirror carp required a higher tension of oxygen to enable them to survive for a week than did rainbow trout, but for shorter periods could withstand much lower tensions than rainbow trout; at 10° and 16°C. their resistance was intermediate between that of tench and rainbow trout.     

Some histopathological effects of Aroclor 1254 on the liver and gonads of rainbow trout, Salmo gairdneri and carp, Cyprinus carpio

Sexually mature ♂ and ♀ rainbow trout ( Salmo gairdneri Richardson) and carp ( Cyprinus carpio L.) were injected intraperitoneally with Aroclor 1254 (25 mg kg⁻¹ body weight in 1 ml of arachis oil) once weekly for four weeks. Arachis oil was used as the control. At the end of the fourth week, samples of the liver, testis and ovary were taken from treated and control fish and examined by light and electron microscopy. The light microscope study indicated that there was general vacuolation of the hepatocytes of trout but not carp; fragmentation of the developing oocytes but no observable changes in the testis. Electron microscopy study showed that there was enlargement of the rough endoplasmic reticulum of the hepatocytes, some damage to spermatozoa and proliferation of the smooth endo- plasmic reticulum of the oocytes.     

Effect of a commercial trout diet on liver ultrastructure of fed and fasted yearling coho salmon, Oncorhynchus kisutch Walbaum

Yearling coho salmon were fed either a commercial trout (TC) diet or a diet consisting of homogenized adult Pacific Ocean coho salmon (PS), supplemented with vitamins and minerals. The hepatosomatic index of the TC-fed fish killed 12 h after the last feed or after 4 or 8 weeks of fasting were significantly larger ( P 0.05) than comparable PS-fed groups.
'Light' and'dark' hepatocyte cell types were evident in all groups although the dark cells were less numerous in the fasted fish. Hepatocytes of fasted fish contained markedly more endoplasmic reticulum than fed fish. Hepatocytic glycogen content of the TC-fed fish was higher than in PS-fed fish. Whereas in the TC-fed group hepatic glycogen was still evident in fish fasted for 8 weeks, the hepatocytes of the fasted PS-fed group contained little or no glycogen. The suitability of commercial fish diets for salmonids is discussed.     

STUDIES ON SMALL INTESTINAL CRYPT EPITHELIUM : I. The Fine Structure of the Crypt Epithelium of the Proximal Small Intestine of Fasting Humans

Small intestinal crypt epithelium obtained from normal fasting humans by peroral biopsy of the mucosa was studied with the electron microscope. Paneth cells were identified at the base of the crypts by their elaborate highly organized endoplasmic reticulum, large secretory granules, and small lysosome-like dense bodies within the cytoplasm. Undifferentiated cells were characterized by smaller cytoplasmic membrane-bounded granules which were presumed to be secretory in nature, a less elaborate endoplasmic reticulum, many unattached ribosomes and, in some cells, the presence of glycogen. Some undifferentiated cells at the base of the crypts contained lobulated nuclei and striking paranuclear accumulations of mitochondria. Membrane-bounded cytoplasmic fragments, probably originating from undifferentiated and Paneth cells, were frequently apparent within crypt lumina. Of the goblet cells, some were seen actively secreting mucus. In these, apical mucus appeared to exude into the crypt lumen between gaps in the microvilli. The membrane formerly surrounding the apical mucus appeared to fuse with and become part of the plasma membrane of the cell, suggesting a merocrine secretory mechanism. Enterochromaffin cells were identified by their location between the basal regions of other crypt cells and by their unique intracytoplasmic granules.     

Development of secretory activity in the seminal vesicle of the male migratory grasshopper,Melanoplus sanguinipes (fabr.) (Orthoptera : Acrididae)

This paper describes the ultrastructure of the seminal vesicle and the isoelectric focusing patterns of its secretion during sexual maturation and after allatectomy in Melanoplus sanguinipes (Fabr.) (Orthoptera : Acrididae). In epithelia from seminal vesicles of newly fledged males, the rough endoplasmic reticulum is well developed, and Golgi complexes are elaborate, which indicates the gland is metabolically active. The cells also contain large glycogen deposits and the lumen microvilli are well differentiated. These ultrastructural features are more dominant in 24-hr-old adults where the cytoplasm is clearly differentiated into basal and apical regions. Basally, the cytoplasm is dominated by rough endoplasmic reticulum, large Golgi complexes, glycogen deposits and numerous mitochondria, while the apical cytoplasm is filled with large secretory and/or lysosomal vesicles. Between days 3 and 7, the ultrastructural features change little other than the rough endoplasmic reticulum cisternae, which become vesicular. Analysis by isoelectric focusing shows that the amount of secretory protein increases with age until day 3, at which time the gland contains its full complement of secretion. In seminal vesicles from allatectomized insects, ultrastructural features of cells and isoelectric focusing patterns of the secretion arc identical to those from normal males.     

Heterogeneous distribution of glycosyltransferases in the endoplasmic reticulum of castor bean endosperm

Endoplasmic reticulum membranes stripped of attached ribosomes were isolated from homogenates of germinating castor bean (Ricinus communis L.) endosperm by sucrose density gradient centrifugation. The isolated endoplasmic reticulum fraction was further separated into two major membrane subfractions by centrifugation on a flotation gradient. Both subfractions appeared to be derived from the endoplasmic reticulum inasmuch as they share several enzymic markers including cholinephosphotransferase, NADH-cytochrome c reductase, and glycoprotein fucosyl-transferase and phase separation of membrane polypeptides using Triton X-114 revealed a striking similarity in both their hydrophilic and hydrophobic protein components. The endoplasmic reticulum membrane subfractions contain glycoproteins which were readily labeled by incubating intact endosperm tissue with radioactive sugars prior to fractionation.

Castor bean endosperm endoplasmic reticulum apparently exhibits a degree of enzymic heterogeneity, however, since the enzymes responsible for the synthesis of dolicholpyrophosphate N-acetylglucosamine and dolicholmonophosphate mannose together with their incorporation into the oligosaccharide-lipid precursor of protein N-glycosylation were largely recovered in a single endoplasmic reticulum subfraction.

     

Cytochemical demonstration of acid phosphatase activity in the pineal organ of the rainbow trout,Salmo gairdneri

Summary Activity of acid phosphatase (ACP) was investigated cytochemically in the pineal organ of the rainbow trout, Salmo gairdneri. Intense reaction product for ACP activity was observed (1) in lysosomes varying in size and shape and (2) in endoplasmic reticulum associated with the Golgi complex of (i) the pineal photoreceptor and supporting cells, (ii) vascular endothelial cells, and (iii) macrophages inhabiting pineal lumen, parenchymal epithelium and perivascular spaces. This localization of ACP is discussed with particular reference to the capacity for lysosomal digestion in a pineal organ combining photoreceptive and secretory functions, and lacking a blood-brain barrier, as holds true for the pineal of the rainbow trout. Taking advantage of its capacity for endocytotic uptake and lysosomal digestion, the pineal organ of the rainbow trout may serve as a barrier between the blood circulation and the cerebrospinal-fluid compartment. Furthermore, the macrophages may be considered as an essential component in pineal function of fish.Fellow of the Alexander von Humboldt Foundation.Fellow of the Alexander von Humboldt Foundation.     

Occurence and cytodifferentiation of mucopolysaccharide secreting cells in the pancreas of children with nesidioblastosis.

Large numbers of mucopolysaccharide secreting cells were found in the pancreatic tissue of children with nesidioblastosis. Ultrastructural studies showed that mucus cells contained secretion granules and a characteristic smooth endoplasmic reticulum composed of an array of anastomosed tubules. The periodic acid - thiocarbohydrazide - silver reaction demonstrated the presence of glycogen in the hyaloplasm and of polysaccharides in secretion granules, the Golgi apparatus and in vesicles. A hypothesis is proposed, according to which mucus cells differentiate from a pancreatic stem cell common to both endocrine and exocrine tissues, through a mitochondria-rich intermediate cell stage.     

Pale and dark bipolar cells in the chicken retina

Ultrastructurally, two different bipolar cell types can be distinguished in the retina of the chick embryo: one pale or electron-lucent and the other dark or electron-dense. The different electron density was seen over the whole cell, from its enclave in the outer limiting membrane to its termination in the inner plexiform layer. These observations prompted us to study the content and cytoplasmic variations of both cell types. The pale bipolar cell has a higher vacuole, vesicle and endoplasmic reticulum content and a lower number of microtubules and glycogen than the dark bipolar cell. The presence of these two cell types is probably due to a characteristic physiologic state, and the difference between the pale and dark bipolar cells can be attributed to the diverse number of gap unions which they establish with A II amacrine cells.     

Distribution and ultrastructure of taste buds in the oropharyngeal cavity of the rainbow trout, Salmo gairdneri Richardson

The distribution, external surface morphology and ultrastructure of taste buds in the oropharyngeal cavity of the rainbow trout, Salmo gairdneri Richardson, were studied using scanning and transmission electron microscopes (SEM and TEM). The SEM revealed three taste bud types, varying only in their degree of elevation from the general level of the epithelium. Types I and II were located on elevated papillae associated with teeth on the dentary, maxilla, palate, tongue and pharyngeal pads while the unelevated Type III were mainly found in the anterior (branchial) pharynx.
Each taste bud was composed of four cell types: basal, dark, intermediate and light cells, the apical processes of the last three filling the taste pores. The intermediate and light cells appeared similar in ultrastructure, varying only in the amount and organization of smooth endoplasmic reticulum (SER) in their cytoplasm. In addition to its contacts with the processes of intragemmal nerves distally, the basal cells established independent contacts with processes of extragemmal nerves basally. It is suggested that the distribution of the taste buds and their close association with teeth are adaptations to the predatory feeding habit of the rainbow trout. Age differences may account for the existence of two types of gustatory cells and the manner of innervation of the taste bud suggests the existence of two pathways for the transmission of gustatory sensation to the central nervous system (CNS).     

Effects of dietary Ergosan on cutaneous mucosal immune response in rainbow trout (Oncorhynchus mykiss)

The effects of dietary Ergosan on the growth performance and mucosal immunity in rainbow trout skin were investigated. 60 rainbow trout (100-110 g) were randomly assigned to 2 groups in triplicates and fed one of the experimental diet formulated with 5 g kg⁻¹ Ergosan or control diet for 50 days. Results showed that on the 45th day of feeding trial, Ergosan supplementation significantly enhanced the growth performance compared to control group. Various enzyme activities, namely lysozyme, protease, alkaline phosphatase and esterase in treatment group were also enhanced on the 45th and 50th day. Skin mucus in Ergosan-fed fish showed the agglutination of erythrocytes while in control group, no visible agglutination was shown. In addition, skin mucus in treatment group showed strong antibacterial activity against Yersinia ruckeri. In conclusion, the major immune components of rainbow trout mucus that are involved in the non-specific immunity were enhanced by administration of Ergosan in 5 g kg⁻¹.     

Morphometric analysis of fetal rat hepatocytes cultured in monolayer or following gyratory shaking

The stereological technique was used to quantify glycogen areas and endoplasmic reticulum in fetal rat hepatocytes cultured for 24 hr in monolayer (monolayer cells) or following shaking by gyratory rotation (shaken cells). The volume density and volume per cell of glycogen areas decreased in order of freshly isolated hepatocytes, monolayer cells, and shaken cells. The surface density and area per cell of smooth endoplasmic reticulum increased in order of freshly isolated cells, monolayer cells, and shaken cells. The results show that the decrease of glycogen areas and proliferation of the smooth endoplasmic reticulum are more prominent in shaken cells than in monolayer cells. Prominent proliferation of the smooth endoplasmic reticulum in shaken cells may be due to the consumption of glycogen for energy release as a result of gyratory rotation.     

Study of Vibrio anguillarum strains from different sources with emphasis on ecological and pathobiological properties.

A total of 317 Vibrio anguillarum strains were isolated from water, sediment, and diseased as well as healthy rainbow trout at a Danish mariculture farm and from feral fish caught close to the farm. All strains were examined serologically. Ten sera permitted determination of the O group in 66.7% of the strains from diseased rainbow trout. Furthermore, the O group could be determined in 45.1 to 65.4% of the strains from mucus, gills, and intestinal contents of healthy rainbow trout, while only 22.2 to 28.8% of the isolates from water, sediment, and gills or mucus of feral fish were groupable. Serogroup O1 and to some extent O2 appeared to be associated with trout. Strains from these serogroups were selected for analyses of hemagglutinating activity and surface hydrophobicity. Serogroup O1 comprised hemagglutinating as well as nonhemagglutinating strains; from cases of vibriosis, all O1 strains were nonhemagglutinating. The strains belonging to serogroup O2 were generally hemagglutinating. Examinations of surface hydrophobicity by salt aggregation and hydrophobic interaction chromatography suggested that the O1 strains were more hydrophobic than the O2 strains. In pathogenicity tests, O1 strains isolated from gills and mucus of healthy rainbow trout killed all trout in the test groups. A strain from the intestinal contents of healthy rainbow trout did not produce significant mortality. This strain could, however, be frequently reisolated from the pronephros of fish in the test group concerned. After challenge with strains from eel mucus and seawater, mortality was not produced, and furthermore, these strains could not be reisolated from the pronephros.