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  • 1
    Electronic Resource
    Electronic Resource
    Freeze-fracture and morphometric analysis of occluding junctions in rectal glands of elasmobranch fish (1981)
    Springer
    The journal of membrane biology 58 (1981), S. 101-114 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The structure of occluding junctions in secretory and ductal epithelium of salt-secreting rectal glands from two species of elasmobranch fish, the spiny dogfishSqualus acanthias and the stingrayDasyatis sabina, was examined by thin-section and freeze-fracture electron microscopy. In both species, occluding junctions between secretory cells are shallow in their apical to basal extent and are characterized by closely juxtaposed parallel strands. Average strand number in the dogfish was 3.5±0.2 with a mean depth of 56±5 nm; in the stingray a mean of 2.0±0.2 strands encompassed an average depth of 18±3 nm. In contrast, the linear extent of these junctions was remarkably large due to the intermeshing of the narrow apices of the secretory cells to form the tubular lumen. Morphometric analysis gave values of 66.8±2.5 and 74.9±4.6 m/cm2 for the length of junction per unit of luminal surface area in the dogfish and stingray, respectively. This junctional morphology is similar to that generally described for “leaky” epithelia. In comparison, the stratified ductal epithelium which carries the NaCl-rich secretion to the intestine is characterized by extensive occluding junctions which extend 0.6–0.8 μm in depth and consist of a mean of 12 strands arranged in an anastomosing network, an architectural pattern typical of “tight” epithelia. The length density of these junctions in the dogfish rectal gland was 7.6±0.1 m/cm2. The junctional architecture of the rectal gland secretory epithelium (few strands, large junctional length densities) is similar to that described for several other hypertonic secretory epithelia [20, 34] and is compatible with the recent model for salt secretion in rectal glands [39] and in other Cl− secretory epithelia which posits a conductive paracellular pathway for transepithelial Na+ secretion from intercellular space to the lumen to form the NaCl-rich secretory product.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870973
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  • 2
    Electronic Resource
    Electronic Resource
    Secretagogue effects on intracellular calcium in pancreatic duct cells (1990)
    Springer
    Pflügers Archiv 416 (1990), S. 652-658 
    Details
    ISSN: 1432-2013
    Keywords: Pancreatic ducts ; Intracellular calcium ; Carbachol ; Secretin ; Cholecystokinin ; Acetylcholine ; Bicarbonate secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Regulation of intracellular free calcium ([Ca2+]i) in single epithelial duct cells of isolated rat and guinea pig pancreatic interlobular ducts by secretin, carbachol and cholecystokinin was studied by microspectrofluorometry using the Ca2+-sensitive, fluorescent probe Fura-2. Rat and guinea pig duct cells exhibited mean resting [Ca2+]i of 84 nM and 61 nM, respectively, which increased by 50%–100% in response to carbachol stimulation, thus demonstrating the presence of physiologically responsive cholinergic receptors in pancreatic ducts of both species. The carbachol-induced increase in [Ca2+]i involved both mobilization of Ca2+ from intracellular stores and stimulation of influx of extracellular Ca2+. In contrast, neither cholecystokinin nor secretin showed reproducible or sizeable increses in [Ca2+]i. Both rat and guinea pig duct cells showed considerable resting Ca2+ permeability. Lowering or raising the extracellular [Ca2+]i led, respectively, to a decrease or increase in the resting [Ca2+]i. Application of Mn2+ resulted in a quenching of the fluorescence signal indicating its entry into the cell. The resting Ca2+ and Mn2+ permeability could be blocked by La3+ suggesting that it is mediated by a Ca2+ channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370610
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  • 3
    Electronic Resource
    Electronic Resource
    Microscopical methods for the localization of Na+, K+-ATPase (1981)
    Springer
    Journal of molecular histology 13 (1981), S. 397-418 
    Details
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Na+, K+-ATPase plays a central role in the ionic and osmotic homeostasis of cells and in the movements of electrolytes and water across epithelial boundaries. Microscopic localization of the enzyme is, therefore, of crucial importance in establishing the subcellular routes of electrolyte flow across structurally complex and functionally polarized epithelia. Recently developed approaches to the localization of Na+, K+-ATPase are reviewed. These methods rely on different properties of the enzyme and encompass cytochemical localization of the K+-dependent nitrophenylphosphatase component of the enzyme, autoradiographic localization of tritiated ouabain binding sites, and immunocytochemical localization of the holoenzyme and of its catalytic subunit. The rationales for each of these techniques are outlined as are the critieria that have been established to validate each method. The observed localization of Na+, K+-ATPase in various tissues is discussed, particularly as it relates to putative and hypothetical mechanisms that are currently thought to mediate reabsorptive and secretory electrolyte transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01005056
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  • 4
    Electronic Resource
    Electronic Resource
    Ultracytochemical localization of Na+,K+-activated ATPase in chloride cells from the gills of a euryhaline teleostThis Research was Supported by Grant P4B 3634 from the National Science Foundation. The Authors thank Ms Natalia Raphael for her contributions to this study (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 193 (1979), S. 99-129 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The activity of the electrolyte transport enzyme, sodium, potassium-activated adenosine triphosphatase (Na+,K+-ATPase), in the gills of the pinfish, Lagodon rhomboides, increased markedly following transfer of fish from brackish water to seawater. Cytochemical localization of Na+,K+-ATPase via its potassium-dependent phosphatase (K+-NPPase) activity in the branchial epithelium of pinfish adapted to seawater demonstrated that chloride cells are the major sites for the enzyme. Subcellularly, the heaviest depositions of reaction product were observed lining the cytoplasmic membrane surfaces of the labyrinth of anastomosing plasma membrane tubules that ramifies throughout the chloride cell cytoplasm. Enzyme activity was demonstrated also on the cytoplasmic surface of the apical crypt membrane and on the cytoplasmic surfaces of vesicles in the cytoplasm subjacent to the crypt. Deletion of potassium from the cytochemical incubation medium or inclusion of 10 mM ouabain abolished the reaction products associated with these membranes. The significance of these cytochemical results is discussed with reference to current hypotheses of chloride cell function.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1091930107
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  • 5
    Electronic Resource
    Electronic Resource
    Rapid isolation of chloride cells from pinfish gillThis work was supported by Grant P4B3634 from the National Science Foundation. (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 190 (1978), S. 687-702 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Enriched fractions of chloride cells with good ultrastructural integrity have been obtained from gill filaments of the euryhaline teleost, Lagodon rhomboides. The branchial epithelium from seawater-adapted fish was dissociated by gentle mechanical means in a Ca++, Mg++ -free balanced salt solution. Density gradient centrifugation of the mixed cell suspensions through a Ficoll gradient yielded a fraction containing between 50 and 70% chloride cells. This fraction showed a 3- to 4-fold enrichment over comparable gill homogenate values for sodium plus potassium-activated adenosinetriphosphatase, (Na+, K+-ATPase), an enzyme concentrated in chloride cells. Isolation of chloride cells from fish adapted to one-third seawater was less successful, due to the smaller size and reduced number of these cells, although fractions with at least a 2-fold enrichment of the enzyme were obtained. These results continue to support the belief that chloride cells are responsible for the osmoregulatory activity associated with the branchial epithelium of teleosts and that this vital function is mediated through the activity of the transport associated enzyme, Na+, K+ -ATPase, the specific activity of which increases with osmotic stress.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1091900306
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  • 6
    Electronic Resource
    Electronic Resource
    Fine structure and function of the alimentary epithelium in Artemia salina Nauplii (1974)
    Springer
    Cell & tissue research 155 (1974), S. 423-436 
    Details
    ISSN: 1432-0878
    Keywords: Brine shrimp ; Artemia salina ; Alimentary tract ; Fine structure, function ; Salt and water absorption ; Osmoregulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The fine structure of the alimentary tract in the second instar nauplius of the brine shrimp, Artemia salina, has been described. The foregut and hindgut of the larva are composed of cuboidal epithelium which is cuticularized. The epithelium of the midgut and gastric caeca is columnar and is characterized by apical microvilli, basal membrane infolds, and abundant mitochondria. The structural characteristics of the midgut cells correlate with previous physiological and biochemical evidence on both adult and larval brine shrimp which indicates that the midgut plays an important role in absorption and osmoregulation in these animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227006
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  • 7
    Electronic Resource
    Electronic Resource
    Functional morphology of the neck organ in Artemia salina nauplii (1975)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 145 (1975), S. 371-385 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fine structure of the ion transporting epithelium of the neck organ in the brine shrimp (Artemia salina) nauplius is described. The neck organ is a dome-like gland situated atop the cephalothorax of the larva and is composed of 50 to 60 cuboidal epithelial cells. These cells possess many of the characteristics of salt-secretory cells from other tissues. They contain many mitochondria and exhibit a high degree of plasma membrane elaboration. This membrane amplification takes two forms; the apical plasmalemma is infolded into irregular loops, while the basal and lateral membranes penetrate the cytoplasm in the form of branching sinusoids. The labyrinth of tubular reticulum thus formed fills most of the cell volume. Mitochondria in the labyrinth are often in intimate contact with these tubular membranes and regular arrays of parallel mitochondria with constricted intervening sinusoids are often observed. Other organelles including Golgi complexes, multivesicular bodies, and rough endoplasmic reticulum are also numerous, particularly in the narrow rim of cytoplasm which lies between the apical infolds and the labyrinth. Yolk platelets and glycogen fields are conspicuous in the basal perinuclear regions of the cells.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051450309
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