Teleost chloride cell. II. Autoradiographic localization of gill Na,K-ATPase in killifish Fundulus heteroclitus adapted to low and high salinity environments

Ultrastructure of the main excretory duct epithelium of the female mouse submandibular gland with special reference to sexual dimorphism

The fine structure of the main excretory duct epithelium (MEDE) of female mouse submandibular gland was investigated by scanning and transmission electron microscopy and the results compared with the previously established structure of male mouse MEDE. A comparative analysis of the subepithelial capillaries of both sexes was also performed. In this pseudostratified epithelium, principal cell-types were observed: types-I, -II, -III and basal cells. This differed significantly from male MEDE, where type-II and -III are absent and type-I cells are the most numerous. The latter cell-type had abundant mitochondria, a few lipid-containing granules, lysosomes in the infra-nuclear cytoplasm and well-developed basal infoldings. These cells were also characterized by abundant glycogen granules throughout the cytoplasm, many profiles of strands of smooth endoplasmic reticulum in the apical region, and lysosomes in the infranuclear region. Type-II cells were the second most numerous. Their most characteristic features were the presence of tubular vesicles which appeared to be invaginated from the plasma membrane, RER, SER, free ribosomes, a few peroxisomes with nucleoids, and primary lysosomes in extremely light cytoplasm. They had many mitochondria throughout the cytoplasm, except in the apical region, a few lipid-containing granules and no basal infoldings. Type-III cells were very few and were characterized by well developed basal infoldings, abundant free ribosomes, RER, SER, vesicles containing moderately dense material, and many lipid-containing granules. They also had many mitochondria throughout the cytoplasm, except apically. Basal cells had a large nucleus and the cytoplasm had few organelles.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of lead loads on branchial osmoregulatory mechanisms in the rainbow trout Oncorhynchus mykiss

Exposure of rainbow trout to lead chloride (PbCl2, 1 ppm) in fresh water killed all animals within 16 days. Exposure to this lethal dose for 6 days only showed a significant increase in the haematocrit. Calcium, sodium and chloride concentrations in plasma were not notably modified. Both the influx and the net flux of sodium fluctuated much less than the diffusional water fluxes through secondary lamellae in gills. Branchial Na,K-ATPase, Ca-ATPase and HCO3-ATPase activities were not sensitive to lead toxicity. Lead caused a cellular 'wave-shaped' degeneration and renewal with modification in the number and morphology of chloride cells. Results are discussed in relation to the hydromineral balance of the trout.

Video-enhanced microscopy of organelle movement in an intact epithelium

Digitally enhanced video microscopy has provided improved optical resolution in the study of intracellular organelle/particle movement, particularly in extruded axoplasm and certain thin single cell systems. We report here, for the first time, particle movement in an intact, isolated epithelium, the killifish proximal convoluted tubule. Cytoplasmic particles exhibited predominantly unidirectional linear movement approaching several microns in length, sometimes with multiple turns. The velocities of 34 particles measured in 11 cells averaged 0.29 microns/sec (range, 0.007-3.1 microns/sec). Microtubules--the well-established basis for organelle movement in cells--were present but were sparsely represented in electron micrographs of these cells. Video-enhanced microscopic techniques can now be applied to the study of organelle/particle movement in an intact epithelium.

Assembly and sealing of tight junctions: possible participation of G-proteins, phospholipase C, protein kinase C and calmodulin

The making and sealing of a tight junction (TJ) requires cell-cell contacts and Ca2+, and can be gauged through the development of transepithelial electrical resistance (TER) and the accumulation of ZO-1 peptide at the cell borders. We observe that pertussis toxin increases TER, while AIF3 and carbamil choline (carbachol) inhibit it, and 5-guanylylimidodiphosphate (GTPTs) blocks the development of a cell border pattern of ZO-1, suggesting that G-proteins are involved. Phospholipase C (PLC) and protein kinase C (PKC) probably participate in these processes since (i) activation of PLC by thyrotropin-1 releasing hormone increases TER, and its inhibition by neomycin blocks the development of this resistance; (ii) 1,2-dioctanoylglycerol, an activator of PKC, stimulates TER development, while polymyxin B and 1-(5-isoquinoline sulfonyl)-2-methyl-piperazine dihydrochloride (H7), which inhibit this enzyme, abolish TER. Addition of 3-isobutyl-1-methyl-xanthine, dB-cAMP or forskolin do not enhance the value of TER, but have just the opposite effect. Trifluoperazine and calmidazoline inhibit TER development, suggesting that calmodulin (CaM) also plays a role in junction formation. These results indicate that junction formation may be controlled by a network of reactions where G-proteins, phospholipase C, adenylate cyclase, protein kinase C and CaM are involved.

Histochemical demonstration of carbonic anhydrase in gills and opercular epithelium of seawater- and freshwater-adapted killyfish (Fundulus heteroclitus)

Gills and operculum of seawater- and freshwater-adapted killyfish (Fundulus heteroclitus) were stained histochemically for carbonic anhydrase (CA). In the seawater-acclimatized specimens, CA was found predominantly in the chloride cells which were considerably larger than in the freshwater-adapted ones. Within these cells, the reaction products were concentrated in the apical parts of the cytoplasm. In contrast, chloride cells of freshwater-adapted fish were not, or only faintly, stained both in gills and opercular epithelium. Reaction products for CA were seen additionally in the cytoplasm of the outer respiratory cells lining the lamellae of gills both in seawater- and freshwater-adapted fish.

Fluorescent labelling of Na+, K(+)-ATPase in intact cells by use of a fluorescent derivative of ouabain: salinity and teleost chloride cells

Anthroylouabain, a fluorescent derivative of ouabain, was used to localize Na+, K(+)-ATPase in transport epithelia of two species of teleosts. Exposure of the opercular membrane of seawater-adapted tilapia (Oreochromis mossambicus) and the jaw skin of the long-jawed mudsucker (Gillichthys mirabilis) to a 2 microM anthroylouabain solution resulted in the appearance of cells stained bright blue. These were deemed to be chloride cells by their large size, distinct morphology and co-localization of DASPEI fluorescence, a mitochondrial stain. Addition of ouabain (1 mM final concentration) greatly decreased anthroylouabain fluorescent staining of chloride cells of seawater-adapted fish. Exposure of opercular membranes from freshwater tilapia to 2 microM anthroylouabain did not result in significant staining. Anthroylouabain is therefore a useful vital stain for localizing Na+,K(+)-ATPase in chloride cells of seawater-adapted teleosts, and may be useful for fluorescent labelling of ouabain-sensitive Na+,K(+)-ATPase in other tissues and species.

A study of the morphology of the gills of an extreme alkalinity and hyperosmotic adapted teleost Oreochromis alcalicus grahami (Boulenger) with particular emphasis on the ultrastructure of the chloride cells and their modifications with water dilution. A SEM and TEM study

The general gill morphology of Oreochromis alcalicus grahami, a teleost adapted to high salinity and hyperosmosis, is basically similar to that of other teleostean fish. The species has four pairs of gill arches, all of which have well developed filaments. Each of the arches (holobranchs) has two rows of filaments (hemibranchs). Bilaterally situated secondary lamellae branch from the central axis of the filaments. The lamellae reach their maximum size at the middle of the filament, gradually decrease in size and eventually disappear towards the tip of the filament, which is bare. The leading edge of the gill filament and the immediate interlamellar space is covered by a stratified epithelium consisting of pavement cells, mucous cells, chloride cells and undifferentiated cells. The surface of these cells is made up of concentric microridges. The chloride cells were found only on the primary epithelium (filamental epithelium) and very rarely on the secondary epithelium (lamellar epithelium). Two types of chloride cells were observed in the gills of Oreochromis. The superficial chloride cells have fewer mitochondria concentrated towards the basal aspect of the cell, and a network of tubules towards the apical surface and are less electron dense. These cells intercommunicate with the water through an apical pore. The deep chloride cells have numerous diffuse mitochondria intercalated between a fine profuse tubular network and are more electron dense. These cells are covered by one or more layers of pavement cells and thus do not have access to the external surface. After gradual dilution of the lake water in which the fish were kept, both types of chloride cells remained topographically and ultrastructurally distinct. However, in both kinds of cell the mitochondria decreased in number and size. Initially there was an increase in the diameter and the degree of interdigitation of the tubules followed by a gradual decrease. An increase in the quantity of rough endoplasmic reticulum, particularly at the perinuclear region of the cell, was noted. The morphometric analysis of the branchial system indicated that the gills of Oreochromis are well adapted for gas exchange by having numerous and relatively long gill filaments with a high lamellar density. These features provide a large surface for gas exchange which, when coupled with the notably thin water-blood barrier of an average thickness of only 0.83 micro, would facilitate efficient absorption of oxygen by the gills. Oreochromis alcalicus was observed to be incapable of adapting to freshwater. This may have been due to the progressive degeneration of the chloride cells.(ABSTRACT TRUNCATED AT 400 WORDS)

The natural history of liver glycogenosis due to phosphorylase kinase deficiency: a longitudinal study of 41 patients

We report a longitudinal study of 41 patients with liver glycogenosis due to phosphorylase kinase deficiency. In their youth, patients displayed hepatomegaly (92%), growth retardation (68%), delayed motor development (52%), hypercholesterolaemia (76%), hypertriglyceridaemia (70%), elevation of glutamate pyruvate transaminase (56%) and fasting hyperketosis (44%). With age, these clinical and biochemical abnormalities gradually disappeared and most adult patients were asymptomatic.

Accessory cells in the gill epithelium of the freshwater rainbow trout Salmo gairdneri

Two types of mitochondria-rich cells were identified in the gill epithelium of the freshwater-adapted rainbow trout, Salmo gairdneri, after selective impregnation of their tubular system with reduced osmium. A first type consisted of large cells with a poorly developed and loosely anastomosed tubular system; thus, that resembled the chloride cells commonly encountered in the gill epithelium of freshwater-adapted euryhaline fishes. A second type comprised smaller cells with an extensively developed and tightly anastomosed tubular system. These never reached the basal lamina of the gill epithelium and were adjacent to chloride cells, to which they were linked by shallow apical junctions (100-200 nm); thus, they resembled accessory cells, which are currently found in the gill epithelium of seawater-adapted fishes but are usually lacking in freshwater living fishes. Transfer of the freshwater-adapted trout into seawater induced the proliferation of the tubular system in the chloride cells and the formation of lateral plasma membrane interdigitations between accessory cells and the apical portion of the chloride cells. The length of the apical junction sealing off this extended intercellular space was reduced to 20-50 nm. The tubular system of the accessory cells was not modified. The extension of the tubular system in the chloride cells of the seawater-adapted fishes indicated that, as in most euryhaline fishes, these cells have a role in the adaptation of the rainbow trout to seawater. In contrast, the function of the presumptive accessory cells in freshwater trout remains to be established.

Ultrastructural features of chloride cells in the gill epithelium of the Atlantic salmon, Salmo salar, and their modifications during smoltification

To elucidate the ultrastructural modifications of the gill epithelium during smoltification, gills of the Atlantic salmon (Salmo salar) were examined by electron microscopy at three stages of this process, which were defined as follows: "parrs" were freshwater fish that had not yet started their transformation; "freshwater smolts" were freshwater fish that were ready to enter seawater; and "seawater smolts" were smolts that had been transferred from fresh water and maintained for 4 days in seawater (35%). In the gill epithelium of parrs, there were two types of chloride cells. The large chloride cells contained deeply stained mitochondria and numerous apical, irregular, dense, membrane-bound bodies that formed 77% of the chloride cell population and were distinguished easily from small chloride cells that have distinctly paler mitochondria and no dense bodies in their apical cytoplasm. In freshwater smolts, the large chloride cells formed 95% of the chloride-cell population. In contrast to the small chloride cells that were not modified, they almost doubled in size. Their tubular system developed extensively to form a tight network with regular meshes significantly smaller than those observed in parr chloride cells. Forty percent of the large chloride cells were associated with a new type of cell, the accessory cell, to which they were bound by shallow apical junctions. Half of these accessory cells were not seen to be in contact with the external medium. In seawater smolts, 80% of the large chloride cells were associated with accessory cells. Most accessory cells reached the external medium and sent numerous cytoplasmic interdigitations within the apical portion of the adjacent chloride cells. As a result, a section through the apical portion of the chloride cells and their associated accessory cells revealed a mosaic of interlocked cell processes bound together by an extended, shallow apical junction. It was concluded that the Atlantic salmon develops in fresh water most of the ultrastructural modifications of the gill epithelium which in most euryhaline fish are triggered by exposure to seawater. The effective transfer into seawater would act only as a final stimulus to achieve some adequacy between the freshwater smolt and its new environment.

Ammonia distribution and excretion in fish

This paper reviews the literature concerning ammonia production, storage and excretion in fish. Ammonia is the end product of protein catabolism and is stored in the body of fish in high concentrations relative to basal excretion rates. Ammonia, if allowed to accumulate, is toxic and is converted to less toxic compounds or excreted. Like other weak acids and bases, ammonia is distributed between tissue compartments in relation to transmembrane pH gradients. NH3 is generally equilibrated between compartments but NH4 (+) is distributed according to pH. Ammonia is eliminated from the blood upon passage through the gills. The mechanisms of branchial ammonia excretion vary between different species of fish and different environments, and primarily involves NH3 passive diffusion and NH4 (+)/Na(+) exchange. Water chemistry near the gill surface may also be important to ammonia excretion, but a more accurate measurement of the NH3 gradient across the gill epithelium is required before a more detailed analysis of NH3 and NH4 (+) excretion can be made.

Gill ultrastructure of the Pacific hagfish Eptatretus stouti

At the gross anatomical level, hagfish gills show unusual features not seen in any other fish gills. Our study was undertaken to determine if peculiarities also characterize the microscopic anatomy and ultrastructure of hagfish gills. To the contrary, branchial respiratory lamellae of Pacific hagfish were found to resemble the lamellae of lampreys, elasmobranchs, and teleosts, often down to the finest subcellular details. As in other fish, hagfish lamellae are lined by epithelium containing pavement cells with organelles indicative of a secretory function, basal cells showing undifferentiated cell features, and branchial ionocytes. The ionocytes are identical to chloride cells of teleosts in cytostructure, distribution, and abundance. There are pillar and marginal capillaries in hagfish gill lamellae. Pillar cells contain bundles of 5-nm microfilaments, and they associate with collagen columns as in other fish. Hagfish pillar cells do exhibit odd features, however: They cluster (groups of up to nine were seen), and their extracellular collagen columns are rarer than in other fish gills (averaging only two columns per three pillar cells). Other special features of hagfish gills are the following: lipid droplets and smooth endoplasmic reticulum are well developed in all cell types; pavement cells secrete a lipomucous product (stains with periodic acid-Schiff, Alcian blue, and Sudan black B); and goblet cells are absent. The presence of "chloride cells" in hagfish is puzzling, as hagfish body fluids are iso-osmotic to seawater and there is no need to osmoregulate for sodium chloride; the ionocytes contain carbonic anhydrase, suggesting a function in acid/base regulation.

Ultrastructural study of the liver in argininosuccinase deficiency

The liver of a 19-year-old woman with argininosuccinase deficiency was studied ultrastructurally under conditions for excellent tissue fixation. Dilated smooth endoplasmic reticulum and mitochondrial crystalloids were the most prominent abnormalities found. These features were compared to fine-structural abnormalities found in other disorders of the Krebs-Henseleit pathway. No change was considered specific or related to subcellular enzyme localization.

Surface ultrastructure of the gill arch of the killifish, Fundulus heteroclitus, from seawater and freshwater, with special reference to the morphology of apical crypts of chloride cells

The surface ultrastructure of the gill arches of the killifish, Fundulus heteroclitus, adapted to seawater or freshwater, was found to be similar to that reported for other euryhaline teleosts. Two rows of gill filaments (about 42 filaments per row) extended posterolaterally, and two rows of gill rakers (about 10 rakers per row) extended anteromedially from each arch. Leaf-like respiratory lamellae protruded along both sides of each filament, from its base to its apex. The distributions, sizes, and numbers of various surface cells and structures were also determined. All surfaces were covered by a mosaic of pavement cells, which measured about 7 X 4 microns and exhibited concentrically arranged surface ridges. Taste buds were especially prominent on the rakers and the pharyngeal surfaces of the first and second gill arches, but were often replaced by horny spines on the third and fourth gill arches. Apical crypts of chloride cells occurred mostly on the surfaces of the gill filaments adjacent to the afferent artery of the filament. In seawater adapted killifish, crypts resembled narrow, deep holes along the borders of adjacent pavement cells, had openings of about 2 microns2, and occurred at a frequency of about 1 per 70 microns2 of surface area. In freshwater fish, the crypts usually had larger openings (about 10 microns2), occurred less frequently (1 per 123 microns2), and exhibited many cellular projections in their interiors. Changes in crypt morphology may be related to the ion transport function of chloride cells.

The use of isolated fish opercular epithelium as a model tissue for studying intrinsic activities of loop diuretics

Isolated opercular epithelia of killifish (Fundulus heteroclitus) were mounted in an Ussing chamber. The epithelia displayed a transepithelial electrical potential difference (PD) of 10.6 +/- 0.3 mV (sea-water side negative) and a short-circuit current (SCC) of 72.1 +/- 2.1 microA cm-2. The electrical resistance was 160 +/- 3 omega cm2 (mean +/- SE, n = 269). The unidirectional flux of 36Cl from blood side to sea-water side compared well with the SCC. No net flux of 22Na or 24Na across the epithelium was observed. Raising of cyclic AMP levels by theophylline, 3-isobutyl-I-methyl-xanthine, isoprenaline and forskolin, increased SCC and PD. Prostaglandins PGE2 and to some extent PGF2 alpha inhibited SCC and PD. Inhibition of Na+-K+-ATPase by ouabain and orthovanadate reduced SCC and PD. Pretreatment of the epithelium with the stilbene disulphonic acid (DIDS) did not prevent the action of orthovanadate. Different types of diuretics were tested, but only the loop diuretics bumetanide, piretanide, and furosemide, rapidly and strongly inhibited PD and SCC and unidirectional 36Cl serosal to mucosal flux. Dose-response curves for these agents were parallel and EC50 values for effects on SCC were 40, 52, and 295 microM, respectively. The same relative activities of these diuretics have been seen in the renal thick ascending limb of Henle's loop (TALH). It is concluded that the killifish opercular skin responds to hormonal stimuli and various pharmacological agents in a manner similar to that of mammalian renal TALH. It should therefore be a useful model for studies of the modes of action and the structure-activity relationships of diuretics which act by inhibition of chloride transport or Na+-K+-ATPase activity.

The sodium pump in opossum vascular smooth muscle

Ouabain-sensitive Rb+ uptake and [3H]ouabain binding were used to measure rates of Na+ pumping and the number of pump sites, respectively, in thoracic aortae from opossums. From the number of Rb+ ions pumped per site per minute, estimates of pump turnover have been made. Values obtained are comparable to those of other species (see Table 1).

Morphology of the exocrine glands of the frog skin

Frog skin contains three distinct types of exocrine glands: granular (poison), mucous, and seromucous. The granular gland forms a syncytial secretory compartment within the acinus, which is surrounded by smooth muscle cells. The mucous and seromucous glands are easily identifiable as distinct glands. The serous and mucous secretory cells are arranged in a semilunar configuration opposite the ductal end and are filled with granules. Within the acinus, located at the ductal pole of the gland, are distinct groups of cells with few or no granules in the cytoplasm. In both the mucous and seromucous gland there is a cell type with abundant mitochondria; the one in the mucous gland is located in the region adjacent to the secretory cells. The duct of these glands is two-layered, with the individual cells appearing morphologically similar to the layers of the skin epithelium as the duct traverses the skin. The duct appears to be patent throughout its length. The morphological heterogeneity and distinct distribution of the cell types within the gland acinus may be indicative of a functional heterogeneity that allows the production of distinctly different types of secretion from the same gland type, depending on the type of stimulus.

Quantitative localization of Na-K pump site in frog inner ear dark cells

The Na-K pump site distribution within the dark cells of the frog inner ear was examined with quantitative freeze-dry [3H]ouabain autoradiography. Control experiments revealed that ouabain binding was specific. Na-K pumps were located in the basolateral dark cell plasma membrane and were distributed nonuniformly across the epithelial apical-basal axis. The highest concentration (sites per volume) was found over the basal region and the lowest over the apical region. The average pump site concentration for dark cells from four animals was 25 X 10(3) sites/micron3. Stereological analysis of conventionally fixed tissue revealed that the plasma membrane area per volume (Sv) was also nonuniform across the apical-basal axis with the highest surface to volume ratio in the basal region. The average Sv for two dark cell regions was 5.5 micron2/micron3. Combination of autoradiography and stereology revealed that the pump site density (sites per membrane area) was independent of position along the apical-basal axis and was equal to 4500 +/- 25%, a value close to the upper limit as determined by the diameter of the isolated Na-K-ATPase.

Reserpine-induced alterations in mucus production and calmodulin-binding proteins in a human epithelial cell line

The characterization of a mucus-producing human cell line (HC-84) derived from a colon carcinoma and its response to in vitro reserpine treatment is reported. Mucous granules were demonstrated within these cells on the basis of electron microscopic examination and incorporation of [3H]glucosamine with subsequent autoradiographic analysis. Fluorographic analysis of total HC-84 cell protein after incubation with [3H]glucosamine indicated that the majority of tritium was incorporated into two proteins with molecular weights of 115 and 120 kD. When total HC-84 protein was subjected to immuno-blot analysis utilizing rabbit antibody against human intestinal mucus, only these two proteins (115K and 120K) reacted positively, indicating a direct correlation between [3H]glucosamine incorporation and mucus production. Immunofluorescence localization of mucus within HC-84 cells utilizing this same antibody resulted in a punctate pattern of fluorescence within the cytoplasm. Treatment of HC-84 cells with 30 microM reserpine for 7 days resulted in a three-fold increase in mucus production compared with controls. There was also a concomitant loss of a 30K calmodulin-binding protein in cells treated with reserpine. These cells represent a useful system for studying the effect of reserpine on the processes of mucus synthesis and secretion.