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  • 1
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. A rat epidermal keratinocyte (REK) line which exhibits histodifferentiation nearly identical to the native epidermis when cultured at an air–liquid interface was used to study the metabolism of hyaluronan, the major intercellular macromolecule present in basal and spinous cell layers. Two different support matrices were used: reconstituted collagen fibrils with and without a covering basal lamina previously deposited by canine kidney cells. REKs formed a stratified squamous, keratinized epithelium on both support matrices. Hyaluronan and its receptor, CD44, colocalized in the basal and spinous layers similar to their distribution in the native epidermis. Most (approximately 75%) of the hyaluronan was retained in the epithelium when a basal lamina was present while most (approximately 80%) diffused out of the epithelium in its absence. While REKs on the two matrices synthesized hyaluronan at essentially the same rate, catabolism of this macromolecule was much higher in the epithelium on the basal lamina (half-life approximately 1 day, similar to its half-life in native human epidermis). The formation of a true epidermal compartment in culture bounded by the cornified layer on the surface and the basal lamina subjacent to the basal cells provides a good model within which to study epidermal metabolism.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 147 (1974), S. 479-490 
    ISSN: 1432-0878
    Keywords: Proline ; Keratohyalin ; Basal lamina ; Epithelium ; Autoradiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mouse lingual epithelium incorporates significant amounts of L-proline-2, 3-H3 one hour after intraperitoneal injection of the tritiated amino acid. All viable cell strata incorporated approximately equal amounts of proline as assessed by autoradiographic techniques. Grain counts at 30 minutes, 1 hour, 4 hours and 24 hours, the four time periods studied, indicated a progressive incorporation of proline up to 4 hours following injection. Preferential incorporation of proline into any one cell structure or group of structures was not observed. Keratohyalin granules (KHG's) demonstrated incorporated proline; however, usually only one silver grain appeared over each granule, and, based on grain counts, the amount of proline incorporated by KHG's appeared slightly less than the general labeling observed in KHG-containing cells. This finding supports recent biochemical studies which have indicated a considerably lower proline content of keratohyalin than had previously been reported. Significant proline incorporation into the epithelial basal lamina was not observed during the 24 hours of this study. Thus, while recent recombination experiments have conclusively demonstrated that epithelial basal cells synthesize considerable quantities of basal lamina in a 24 hour period; it would appear that epithelial basal cells contribute little to a formed, intact basal lamina. This finding lends credence to the concept of a long basal lamina turnover time.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 211 (1985), S. 142-148 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Samples of human plantar and palmar skin were excised and incubated in 20 mM EDTA after which the epidermis was gently separated from the dermis with the plane of separation occurring in the lamina lucida. Scanning electron microscopic examination of the dermal component revealed the classically described series of regularly spaced grooves and papillae that characterize the epidermal-dermal junction in thick skin. Primary dermal grooves exhibited evenly spaced tunnels that were originally occupied by sweat gland ducts. The basement membrane (basal lamina) in the primary grooves was relatively smooth but did exhibit a flattened, reticulated pattern at high magnifications. The basement membrane of secondary dermal grooves and papillae was in the form of numerous, elevated microridges off of which septae arose at roughly right angles. The surface appearance of the basement membrane in these areas was that of a honeycomb owing to the numerous compartments and recesses formed by the ridges and septae. Degradation of the basement membrane by trypsin demonstrated that the foundation for the highly folded and compartmentalized basement membrane was composed of dermal collagen fibrils, 60-70 nm in diameter, that were arranged in a series of variably sized, interconnected collagen bundles or walls. Epidermal basal cells extended cytoplasmic (foot) processes into two or more compartments, formed by the ridges and septae, which considerably amplified the basement membrane surface available for epidermal attachment. Scanning electron microscopic studies of the epidermal-dermal junction confirm the variable surface character of this interface previously reported by others using sectioned material. This regional variation in surface architecture apparently distinguishes between areas in which epidermal basal cells are specialized for attachment (papillae, secondary dermal grooves) and regions occupied by slow cycling epidermal stem cells from which mitotically active keratinocytes arise.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 140 (1974), S. 383-403 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Incubation of human oral mucosa in physiological solutions containing proteolytic enzymes permits separation of the preparation into its epithelial and connective tissue components. Trypsin, collagenase and elastase were utilized to effect epithelium-connective tissue separation. Elastase was the most suitable in that a reliable separation of the epithelium from the connective tissue occurred at the lamina lucida (the electron-lucent zone between the basal cell and basal lamina) with only minimal alteration of the epithelium. The most common change observed in separated epithelium was the formation of cytoplasmic protrusions or blebs on the inferior surface of the epithelial basal cell. Bleb formation was quite extensive when preparations were incubated one to two hours beyond the point where the epithelium could be separated from the connective tissue. With prolonged incubations inferior aspects of epithelial basal cells demonstrated the formation of an entirely new cytoplasmic front apparently resulting from fusion of membranes and subsequent confluence of the cytoplasm contained within the blebs. Individual hemidesmosomes or small lengths of the original inferior epithelial basal cell membrane became enclosed in membrane-bound vacuoles within the cytoplasm of the epithelial basal cell. These vacuoles were shown to have been interiorized by the absence of a ruthenium red reaction product within the vacuolar spaces. Bleb formation was shown to be strictly enzyme-induced since intact specimens demonstrated extensive basal cell blebbing following prolonged incubation. Occasional desmosomes were broken and the component halves interiorized in membrane-bound vacuoles within the cell cytoplasm. Alterations observed in epithelial basal cells as a consequence of exposure to exogenous proteolytic enzymes mimic alterations observed in many disease processes and during certain stages of development.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 133 (1972), S. 431-453 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Following incubation in an isotonic saline solution containing 20 mM EDTA, human oral mucosa may be separated into its epithelial and connective tissue components. Ultrastructural study of the separated tissues reveals that the plane of separation is through the lamina lucida. Hemidesmosomal structure is altered by the separation process: the peripheral density is absent but a fine, generally filamentous material remains associated with the outer membrane leaflet of the hemidesmosome. Desmosome structure is not altered. An intact lamina densa remains attached to the connective tissue fragment. Oral mucosa incubated in EDTA-saline containing calcium, or its return to a divalent cation-supplemented medium after treatment with EDTA, prevents separation. By maintaining the structural integrity of the hemidesmosome, divalent cations appear to play a principal role in uniting oral mucosal epithelium to the lamina propria.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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