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  • Cell & Developmental Biology  (1)
  • Intercellular spaces  (1)
  • 1990-1994  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 272 (1993), S. 533-543 
    ISSN: 1432-0878
    Keywords: Mucocytes ; Calcification ; Intercellular spaces ; Zooxanthellae ; Calicoblastic ectoderm ; Confocal laser scanning microscopy ; Freeze-substitution ; Corals: Galaxea fascicularis, Acropora formosa, Tubastrea faulkneri (Cnidaria)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The extra-thecal epithelia of cryofixed undecalcified, freeze-substituted polyps of the scleractinian corals Galaxea fascicularis and Tubastrea faulkneri and axial and basal polyps of Acropora formosa have been examined, in anhydrously prepared thick slices, by confocal laser scanning light microscopy. The avoidance of chemical fixation and decalcification makes it possible to determine whether previously seen structures are real or artefactual products of swelling, shrinkage and distortion. All of the epithelia of all the corals examined are characterised by well defined intercellular spaces. Mucocytes are present in all cell layers in Galaxea and Tubastrea but are not present in any cell layers in the axial polyp of Acropora although they are abundant in the oral ectoderm of the basal polyps in this coral. Zooxanthellae are absent in Tubastrea, the epithelia of the exert septa of Galaxea and the axial polyp of Acropora. The calicoblastic ectoderm is generally composed of thin squamous cells with large intercellular spaces. At rapidly calcifying regions such as the tips of the exert septa of Galaxea, the calicoblastic cells are elongated with extensive arborisation of the basal regions of the cells. They are separated by large intercellular spaces and contain numerous fluorescent granules. The apical regions of these cells appear to be closely applied to the surface of the skeleton. There is no evidence of a space between the apical region of the calicoblastic cells and the skeleton.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Changes in intracellular ionized free calcium ([Ca]i), inositol triphosphate (IP3), and-sn-1,2-diacylglycerol (DAG) were determined in relation to agonist-induced human neutrophil superoxide (O2-) production. With 0.1 μM N-formyl-methionyl-leucyl-phenylalanine (fMLP) stimulation, generation of IP3 and a peak rise in [Cai] occurred at 30 sec, preceding maximal O2- production (1.5 min) and the maximal rise in DAG mass (4 min). FMLP-induced O2 production was inhibited by pertussis toxin. In cytochalasin B-primed, concanavalin A (Con A) stimulated neutrophils, a peak rise in [Ca], but not IP3 proceeded O2 production, and pertussis toxin did not inhibit O2- production. EGTA inhibited the cytochalasin B/fMLP-induced increment in [Ca]i and O2- production by 75% and 50% respectively, and completely ablated the response to cytochalasin B/Con A, suggesting a role for extracellular as well as intracellular calcium in the respiratory burst. However, three types of experiments indicate that an increase in [Ca]i is neither sufficient nor always required for O2 - production. First, treatment with ionomycin resulted in a marked increase in [Ca]i but did not cause O2- production. Second, pertussis toxin inhibited both fMLP-induced IP3 generation and O2- production but did not inhibit the rise in [Ca]i Third, following neutrophil priming with dioctanoylglycerol (diC8), maximal O2- production occurred in response to 0.015 μM fMLP or Con A without a rise in [Ca]i, and diC8/fMLP-induced O2- production was not inhibited by EGTA. Taken together, these data suggest that (1) an increment in [Ca]i is not strictly essential for neutrophil O2- production, (2) unlike fMLP, Con A-induced O2- production does not proceed through a pathway involving the pertussis toxin-sensitive G protein, and (3) regulation of neutrophil [Ca]i involves mechanisms independent of IP3 concentration.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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