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  • 1
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: Online-Ressource (143 Seiten = 7 MB) , Illustrationen, Graphen
    Language: German
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 263 (1991), S. 253-263 
    ISSN: 1432-0878
    Keywords: Astrocytes ; Diencephalon ; Receptors, membrane ; Somatostatin (SRIF) ; Rat (Han: Wist)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Using a somatostatin-gold conjugate of known biological activity, high affinity binding sites for this neuropeptide were visualized at cellular resolution on cultured diencephalic astrocytes and on frozen sections of the rat diencephalon. Binding could be completely suppressed in competition experiments with surplus unlabeled somatostatin. On sections, the ligand was displaced from its binding sites by 10 μM guanosine triphosphate indicating a functional significance of the labeled structures. As with the native peptide, a surplus of the analog SMS 201–995 suppressed nearly all staining. The ligand was bound to distinct populations of astrocytes, namely to those in subependymal and perivascular positions, to astrocytes in somatostatin-innervated hypothalamic nuclei in the mid-sagittal plane and to borderline regions of circumventricular organs. A general mismatch between the distribution of somatostatin-immunoreactive terminals and the pattern of binding of the ligand does not exist. This, together with the competition experiments, suggests a functional relationship between the somatostatin-releasing neurons and associated astrocytes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 262 (1990), S. 431-443 
    ISSN: 1432-0878
    Keywords: Astrocytes ; Telencephalon ; Receptors, membrane ; Somatostatin (SRIF) ; Rat (Han: WIST)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Using a somatostatin-gold conjugate as ligand, high-affinity binding sites for this neuropeptide were demonstrated at three levels: (i) cultured astrocytes from rat cortex, (ii) hippocampal slice cultures, and (iii) frozen tissue sections of rat telencephalon. The conjugate proved as active as the native peptide in competing for the binding sites. Light-microscopic visualization of bound ligand was achieved by silver intensification of the colloidal gold. This method is faster and yields superior resolution compared with autoradiography. Cultured astrocytes from cortex and hippocampus could be labeled by the ligand. At the light- and electron-microscopic level, astrocytes could be double-labeled by the somatostatin-gold conjugate and immunostaining for glial fibrillary acidic protein (GFAP). In hippocampal slice cultures, the conjugate did not penetrate into the neuropil because of a covering glial layer. However, a portion of this completely GFAP-positive covering glia reacted with the somatostatin ligand. In frozen brain sections, apart from delicate punctate structures, two types of labeled glia cells were seen: single stellate astrocytes and perivascular glia cells.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0878
    Keywords: Somatostatin ; Cholecystokinin ; Binding sites ; Receptors ; Neurons ; Telencephalon ; Rat (Han: WIST)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The identification of high-affinity binding sites for neuropeptides on individual target cells is a prerequisite when studying the sites of action and the manner in which peptides act as neuromediators. In situ and in vitro, this can be achieved using newly synthesized, biologically active conjugates of somatostatin or cholecystokinin (sulphated octapeptide) with colloidal gold. Labelled neurons show a peptide-specific, non-overlapping distribution in rat telencephalic structures; i.e, whereas the somatostatin-gold conjugate labels binding sites on neurons and glial cells, cholecystokinin-binding sites are restricted to neurons. Binding of either gold-labelled ligand can be competitively suppressed by excess amounts of the native peptide or its analogues. Neuronal somatostatin-binding sites are visualized on neurons in lamina III and, in particular, in lamina V/VI of the primary somatosensory cortex and in the magnocellular nucleus of the telencephalic cholinergic system. Cholecystokinin-binding sites are localized in the main olfactory bulb, on neurons in the cortical “hindlimb” and “forelimb” region, in the hippocampus, and in the cingulate and visual cortex.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0878
    Keywords: Carcinus ; Ecdysone ; Hemigrapsus ; Mandibular organ ; Y-organ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the steroid producing Y-organ and the mandibular organ of the crustaceans Hemigrapsus nudus and Carcinus maenas has been studied with reference to the well investigated steroid secreting cells (SSC) of mammals. In accordance with the most important characteristic of mammalian SSC, abundant SER could be shown in the Y-organ, where it is unevenly distributed. The amount of SER seems to vary in correlation with the secretion of moulting hormone during the moult cycle. Most Y-organ cells contain a great number of mitochondria of the tubular type, another important characteristic of mammalian SSC. The ultrastructure of the mandibular organ of C. maenas differs considerably from that of the Y-organ. Some SER was found, mitochondria of unusual shape and size were conspicuous. No definite conclusion as to the function of the mandibular organ is yet to be drawn.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0878
    Keywords: Somatotropes, growth hormone cells ; Immunocytochemistry ; Growth hormone (GH) ; Receptors, membrane ; Somatostatin (SRIF) ; Growth hormone-releasing hormone (GRH) ; Rat (Han: WIST)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The synthetic peptides somatostatin (SRIF) and growth hormone-releasing hormone (GRH) were coupled directly to colloidal gold of different particle sizes. Both conjugates were biologically active in displacing the corresponding radiolabeled hormones from high affinity binding sites in pituitary membranes. Release of growth hormone (GH) from cultured anterior pituitary cells was modulated by both conjugates alone or in combination. Ultrastructural studies were performed with cells incubated at 4° C (2 h) and 37° C (2 min-2 h) with one of the labeled peptides or their combination. Somatotropes were identified by immunostaining with anti-rGH followed by protein A-ferritin, thus obtaining a triple labeling. Both hormone conjugates were internalized in different vesicles in the beginning but accumulated during longer incubation times in the same compartment. The secretory vesicles and the nucleus were not labeled by any hormone conjugate. In contrast to SRIF-gold, the uptake of GRH-gold conjugate decreased with longer incubation times. This effect could be neutralized by simulatenous incubation of the somatotropes with both regulating hormones. Hence, whereas the binding and internalization of SRIF by somatotropes do not seem to be influenced by GRH, the corresponding processes for GRH are stimulated by the presence of SRIF.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5176
    Keywords: blade discs ; Laminaria digitata ; kelp ; meristematic zone ; mariculture ; Phaeophyceae ; spore formation ; sorus formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Blade discs of vegetative thalli of Laminaria digitata (Huds.) Lamour. from Helgoland (North Sea) cut at 5–15 cm distance from the blade/stipe transition, formed sorus in the laboratory after 7–12weeks, 5 months earlier than whole fronds in the field. Sorus formation occurred in a broad range of daylength regimes or temperatures, at 8–16 h light pe rday and 6–12 °C. No sorus was developed during three months by meristematic blade discs cut from the lowermost 3 cm portion of the blade, nor from whole thalli cultured in parallel to isolated blade discs. These findings point to the possible existence of sporulation inhibitors produced by the laminarian meristem.
    Type of Medium: Electronic Resource
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  • 8
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    PANGAEA
    In:  Supplement to: Buchholz, Cornelia Maria; Wiencke, Christian (2015): Working on a baseline for the Kongsfjorden food web: production and properties of macroalgal particulate organic matter (POM). Polar Biology, 12 pp, https://doi.org/10.1007/s00300-015-1828-3
    Publication Date: 2023-05-12
    Description: Macroalgae, in particular kelps, produce a large amount of biomass in Kongsfjorden, which is to a great extent released into the water in an annual cycle. As an example, the brown alga Alaria esculenta loses its blade gradually, 3 ± 0.8 % of the blade area per day (August 2012), thereby adding to the pool of particulate organic matter (POM) in the fjord. Upon release small thallus pieces are “aging” in that they are prone to leaching and serving as substrate for microorganisms, thus turning into palatable food for suspension and bottom feeders. In order to define a macroalgal baseline for the Kongsfjorden food web, stable isotopes d14C and d15N were measured in individuals of A. esculenta, Saccharina latissima and Laminaria digitata directly sampled after collection and in artificially produced POM (aPOM) of A. esculenta that was allowed to age under experimental conditions. In aPOM from this species sampled in August 2012 the C/N ratios decreased between d1 and d8 of a 14-day culture period in parallel to the fading photosynthetic activity of the algal fragments as demonstrated by use of an Imaging-PAM. Microscopic observations of the aPOM in August 2012 and 2013 revealed the frequent occurrence of small brown algal endo- and epiphytes. First feeding experiments with Mysis oculata (Mysids) and Hiatella arctica (Bivalves) showed that these species can ingest macroalgal POM. The importance of kelp-derived POM for the food web is subject of the current research.
    Keywords: DIVER; Hansneset; Kongsfjorden, Spitsbergen, Arctic; Sampling by diver
    Type: Dataset
    Format: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet, 40.1 kBytes
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  • 9
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    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 135 pp
    Publication Date: 2018-03-14
    Type: Thesis , NonPeerReviewed
    Format: text
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  • 10
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    In:  EPIC317. Tagung der Sektion Phykologie in der Deutschen Botansichen Gesellschaft, Berchtesgarden, Haus der Berge, 2018-03-11-2018-03-14Berchtesgarden
    Publication Date: 2018-03-20
    Description: Kelp derived detritus is a potential food item at the base level of marine food webs. A good knowledge of the factors that influence stable isotope composition in kelps is essential for reliable food web models: The variation of stable isotope composition was analysed in three kelp species growing in Kongsfjorden, Svalbard. The parameters considered were depth, age, and algal anatomy: Between 15 and 2.5 m depth, towards higher photo fluence rate, Alaria esculenta was gradually enriched in δ13C while δ15N did not change. 2&3-year-old algae had significantly higher δ15N values in their blades than 5&6-year-old ones. A two factor analysis did not show any interactive effects between depth and age class. A. esculenta as well as Saccharina latissima and Laminaria digitata exhibited enrichment in heavy carbon isotopes in the blades.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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