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  • 1
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The localization of the neural cell adhesion molecule L1 in the male urogenital tract (including seminal vesicles and prostate) of the mouse and bull was investigated using immunocytochemical and immunochemical methods in order to better understand the function of this glycoprotein in non-neural tissues. L1 antibodies labeled non-myelinated nerves in all portions of the urogenital tract investigated. However, L1 immunoreactivity was also found between epithelial cells of several regions of the urogenital system including epididymal tail, deferent duct, ejaculatory duct and seminal vesicles. Some L1 immunoreactivity was also demonstrated between epithelial cells of murine urinary bladder and urethra. The specificity of the immunoreaction was verified by western blots. There was no correlation between L1 expression and proliferating activity as revealed by double immunocytochemistry using various markers of cell proliferation. This unexpected expression of L1 in nonneural tissue is mainly restricted to non-proliferating epithelia of those portions of the urogenital tract that are derived from the Wolffian duct. It is suggested that L1 in these epithelia could enhance the mechanical resistance and reduce transepithelial permeability.
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  • 2
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Stereologic techniques were used to analyse the density and distribution of Concanavalin—A (Con—A) receptor sites on the surface of isolated resting human peripheralblood T lymphocytes using. Con—A/colloidal-gold-labelled horseradish peroxidase. The T-lymphocyte surface appeared to be composed of microvilli, smooth areas and uncoated pits. Coated pits and coated vesicles, identified by the preferential staining of clathrin-containing membranes (tannic-acid/saponin fixation), were scarce. Quantitative analysis of the gold labelling on T lymphocytes after glutaraldehyde fixation indicated the presence of 2.13±0.46 gold particles per micron of cell surface and that these particles were preferentially located on uncoated pits. These results suggest the existence of cell-surface domains for these receptor sites in human resting T lymphocytes.
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  • 3
    ISSN: 1432-072X
    Keywords: Saccharomyces cerevisiae ; Mannoproteins ; Glucan ; Cell wall ; Population growth cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mannoproteins from cell walls of Saccharomyces cerevisiae synthesized at successive stages of the population growth cycle have been solubilized with Zymolyase and subsequently analyzed. The major change along the population cycle concerned a large size mannoprotein material; the size of the newly-synthesized molecules varied from 120,000–500,000 (mean of about 200,000) at early exponential phase to 250,000–350,000 (mean of about 300,000) at late exponential phase. These differences are due to modifications in the amount of N-glycosidically linked mannose residues, since the size of the peptide moiety was 90,000–100,000 at all growth stages and the level of O-glycosylation changed only slightly. After, incubation of the purified walls with concanavalin A-ferritin and subsequent analysis by electron microscopy, labelling was localized at the external and internal faces of the walls. The middle space of these was labelled after digestion of the glucan network with Zymolyase, which demonstrate the presence of mannoproteins in close contact with the structural glucan molecules throughout the wall.
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  • 4
    ISSN: 0012-1606
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0012-1606
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The olfactory border and the apical cell contacts of the organ of Masera (MO) of the mouse were investigated by freeze-fracture electron microscopy. The olfactory border is mainly composed of the terminals of receptor and supporting cells. Cells with thick microvillus-like projections, though less frequent than the other two cell types, also contribute to the border. Olfactory knobs show transitions between those displaying numerous cilia and those characterized by few or no cilia. The olfactory cilia have a typical necklace of 6–9 rows of particles. The eruption of developing cilia seems to be preceded by the formation of circular arrays of particles. The density of intramembranous particles (IMP) per μm2 in P- and E-faces of the ciliary membranes is 1095 ± 190 and 205 ± 65, respectively. In the microvilli of supporting cells, the density of IMP per μm2 is 1800 ± 270 for the P-face and 570 ± 135 for the E-face. At the base of the supporting cell microvilli, rod-shaped particles are observed. The lateral plasma membranes of these cells bear orthogonal arrays of particles. In the apical region of the MO neuroepithelium, extensive zonulae occludentes are present which seal the intercellular cleft. The zonulae occludentes between supporting and receptor cells are composed of 5–13 junctional strands, usually arranged in an elongate network. Zonulae occludentes between supporting cells are, in addition to the elongate network, also arranged in a mesh-like pattern. Gap junctions, both associated with the zonulae occludentes and independent of them, are occasionally found between supporting cells. The results obtained indicate that important similarities exist between the neuroepithelium of the MO and the olfactory epithelium proper, whereas remarkable differences exist between the MO and the vomeronasal neuroepithelium.
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  • 7
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Plasma membranes of sensory neurons from the olfactory and vomeronasal neuroepithelia of the male rat and olfactory neuroepithelium of the tiger salamander (Ambystoma tigrinum) have been examined, using the freeze-fracture technique, for the presence and morphology of orthogonal arrays of particles (OAP). Numerous OAP were scattered on the P-face of plasma membranes of the dendrites and cell bodies from rat vomeronasal sensory neurons. The OAP were 720 ± 200 nm2 in area and they consisted of 4 to 20 particles whose centre-to-centre distance was about 7 nm. On the E-face, complementary orthogonal arrays of pits were observed. No OAP were detected in the olfactory sensory neurons of the rat. In the dendritic and perikaryal plasma membranes of the tiger salamander olfactory sensory neurons, OAP 2230 ± 970 nm2 in area were observed on the P-face. The OAP consisted of 12 to 36 particles. The centre-to-centre distance of the particles was about 7 nm. In the olfactory receptor cell plasma membranes of this species, OAP formed complexes of 2 to 28 individual OAP, the longitudinal axes of which were usually arranged in parallel. Complementary complexes of orthogonal arrays of pits were observed on the E-face.
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  • 8
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To gain insight into the cellular and molecular mechanisms underlying neurogenesis in adult mouse olfactory bulb, several adhesion molecules expressed by glial cells and neurons were investigated. In the germinal zone of the olfactory bulb, the subependymal layer of the rostral region of the lateral ventricles, two adhesion molecules are detectable that are characteristic of early morphogenetic events: J1/tenascin and the polysialylated form, the so-called embryonic form, of N-CAM. The polysialylated form of N-CAM is expressed by most cells in the subependymal layer, and by some astrocytes and neurons in the granular layer adjacent to the subependymal layer. This suggests that bipotential precursor cells retain expression of the embryonic form during their migration from the subependymal layer and during the first stages of differentiation into neurons and glia. Expression of the polysialylated form of N-CAM is also retained in monolayer cultures of six-day-old olfactory bulbs, 55 days after seedingin vitro. J1/tenascin was detectable in the subependymal layer using two monoclonal antibodies. The immunostaining pattern was different between the two antibodies and more restricted to the subependymal layer than when staining with polyclonal J1 antibodies was performed, indicating that J1/tenascin exists in distinct isoforms. Finally, our observations suggest that, in the adult olfactory bulb, L1 is not only a neuron-neuron adhesion molecule, but it may also be involved in neuron-glia interactions, since it is found at contact sites between these two cell types. L1, therefore, may be a neuron-glia adhesion molecule in some parts of the CNS, while it is not in others.
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  • 9
    ISSN: 0147-5975
    Keywords: [idt] Calcofluor white ; [idt] Candida albicans ; [idt] cell wall ; [idt] stereology ; [idt] ultrastructure
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0878
    Keywords: Vomeronasal organ ; Membrane particles ; Cell contacts ; Freeze-etching ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The free surfaces and cell contacts in the epithelia of the vomeronasal organ of the rat were investigated by freeze-etching. The microvilli of receptor cells show a lower density of intramembranous particles (IMP) than the microvilli in the receptor-free epithelium. The ratio between the IMP on P and E-face is approximately 11∶1 in the receptor terminals, and 3.5∶1 in the cilia and microvilli of the receptor-free epithelium. Although atypical in length and only poorly equipped with rootlet fibers, the cilia of the receptor-free epithelium are furnished with typical ciliary necklace structures of up to 10 rows of membrane particles. Differences in the density of IMP on the P-faces of different cilia are probably due to continual ciliogenesis and also due to the different age of cilia in the receptor-free epithelium. Zonulae occludentes show different configurations in the neuroepithelium and in the receptor-free epithelium. In the former, they show a tendency to cross-link and form facet-like patterns, reflecting a constant morphology and relative stability for this apical region. In the receptor-free epithelium the junctional rows of zonulae occludentes display only loosely interconnected networks and a tendency to orient parallel to each other and to the free surface. In addition to zonulae occludentes, typical square aggregations of IMP are observed in the receptor-free epithelium. They are not exclusively restricted to the zone of intensive cell contacts by means of fine interdigitating cell processes, and their function has yet to be identified experimentally.
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