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  • Articles: DFG German National Licenses  (11)
  • 1980-1984  (11)
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  • Articles: DFG German National Licenses  (11)
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  • 1
    Electronic Resource
    Electronic Resource
    Quantitative analysis of rough endoplasmic reticulum approaches to the cell membrane in the secretory ameloblast of the rat incisor (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 209 (1984), S. 289-295 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The distribution of approaches of rough endoplasmic reticulum to the cell membrane within the supranuclear region of the secretory ameloblast of the rat incisor was quantitated using a Zeiss MOP-3. In ameloblasts cut in cross section, most of these approaches appear as circular profiles representing cross sections of elongated cisternae, which are aligned parallel to the long axis of the cell. Because of their position, orientation, and distribution of ribosomes, these approaches were consistent with the appearance of subsurface cisternae. Using cross-sectioned ameloblasts, the lengths of apposed plasma membranes either between or within rows of cells were measured from electron micrographs. Along these lengths, matched approaches of rough endoplasmic reticulum from opposite sides of the apposed plasma membranes were counted. Approaches from either side that were unmatched were also counted. Thirteen percent of the approaches were matched between rows of ameloblasts, and 13.5% of the approaches were matched within rows, demonstrating no significant difference between the two sites. Furthermore, mathematical analysis showed that the theoretical probability of two approaches coinciding is 17%. The experimental values are not statistically different from the theoretical probability, and it is concluded that the matching of rough endoplasmic reticulum approaches to the plasma membrane, or subsurface cisternae, occurs at random.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092090305
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Knife chatter during thin sectioning of rat incisor enamel can cause periodicities resembling cross-striations (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 207 (1983), S. 533-538 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Cross-striations are traditionally associated with the enamel rods in many species including man. Although these striations are obvious with light microscopy, their exact nature has been difficult to determine with the transmission electron microscope on thin sections of enamel. Thin section microscopy either reveals no structures that can be called cross-striations, or shows periodic light and dark bands across the rods. Superficially, these bands resemble chatter artifact. To test this possibility, rat incisor enamel was used because cross-striations have not been demonstrated on these enamel rods. Thin sections were prepared of enamel blocks oriented in various ways with respect to the cutting edge of the diamond knife. The sections showed either uniform enamel or light and dark bands over rod profiles or interrod enamel. Since these bands could be produced artifactually it is concluded that similar bands seen on enamel rods of other species may also be artifacts.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092070315
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Relationship between the quality of fixation and the presence of stippled material in newly formed enamel of the rat incisor (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 208 (1984), S. 15-31 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Extracellular accumulation of a granular material that is presumed to be an organic “precursor” to mineralized enamel has been reported. This material, generally referred to as “stippled material,” was observed mainly after immersion fixation with osmium tetroxide. In studies with perfusion fixation, the presence of stippled material was inconsistent. Therefore, it appeared that the occurrence of stippled material was dependent on the method of fixation. To test this assumption, tissues were fixed by immersion in either osmium tetroxide or glutaraldehyde and by perfusion with either glutaraldehyde or a mixture of acrolein, glutaradehyde, and formaldehyde. It was found that as the quality of cellular preservation improved, the occurrence of stippled material decreased. Since no stippled material could be found in material judged to be well fixed, it was concluded that stippled material is not an extracellular precursor to mineralized enamel, but is a breakdown product resulting from poor fixation.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092080104
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of osmium postfixation and uranyl and lead staining on the ultrastrucure of young enamel in the rat incisor (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 207 (1983), S. 1-16 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Enamel crystallites are electron opaque without osmium or heavy metal staining and give a crystalline electron diffraction pattern. Since the opacity and diffraction pattern are abolished from ultrathin sections of young enamel by floating on distilled water (Bishop and Warshawsky, 1982), the possibility that aqueous staining may also remove crystallites was tested. In addition, the effect of osmium postifixation on crystallite structure was examined.Rat incisors fixed by perfusion with a mixture of aldehydes were either nonosmicated or osmicated prior to dehydration. Incisor segments in the region of inner enamel secretion were embedded in the same Epon block to ensure reliable comparison. Osmicated enamel was more intensely stained with toluidine blue and more electron opaque than nonosmicated enamel. No other structural differences were seen. However, crystallites in osmicated enamel were more resistant to grid demineralization and electron beam damage. Routine staining was done by floating sections on solutions of uranyl acetate and lead citrate; sections were also floated on similar solutions from which the heavy metals were omitted. These solutions removed the electron opaque crystallites from the youngest enamel. Stained sections showed electron opaque crystallite-like structure similar to unstained enamel. When sections that were extracted by the solutions from which the metals were omitted were restained, they appeared identical to routinely stained enamel. It was conclud that staining of young enamel removes the crystallites and reveals only the organic matrix.
    Additional Material: 38 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092070102
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    The behavior of substances labeled with 3H-proline and 3H-fucose in the cellular processes of odontoblasts and ameloblasts (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 200 (1981), S. 1-10 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Odontoblasts are cells with single cytoplasmic processes that grow longer as more dentin is elaborated. Ameloblasts also have single processes and it has been postulated that they too grow longer as more enamel is made. Support for this hypothesis was obtained using rat incisors to investigate the behavior of substances labeled with 3H-proline and 3H-fucose. A comparison was made between odontoblasts, which have processes known to grow and remain within the dentin, and the ameloblasts whose Tomes' processes are hypothesized to grow and leave remnants in the completed enamel. With 3H-proline, the odontoblast bodies are labeled at the early time intervals. They synthesize and secrete a layer of intensely labeled predentin, which by 1 and 2 days is converted to mineralized dentin. Matrix deposited after the main pulse is weakly labeled. Odontoblast processes are never labeled in dentin formed prior to injection. With 3H-fucose, the cell bodies are labeled at the early intervals and the newly formed glycoproteins are deposited into the predentin. Almost immediately, these are progressively added to the dentin at the calcification front. With time a gradient of labeling extends from the unlabeled dentin toward the odontoblast bodies. Unlike the behavior of labeled proteins, by 1 and 2 days labeled glycoproteins appear along the entire length of the odontoblast processes. In the enamel, no Tomes' processes are present during maturation. With 3H-proline, reactions are adjacent to the cells and diffuse toward, but do not reach the dentino-enamel junction by 1 and 2 days. With 3H-fucose, reactions appear over the enamel near the cells. By 1 and 2 days no diffusive pattern is seen, but grains are concentrated near the dentino-enamel junction, in a region containing holes known to be the beginning of Tomes' processes. Since odontoblast glycoproteins migrate along odontoblast processes, it was postulated that cytoplasmic remnants were present in enamel along which ameloblast glycoproteins could also migrate to reach the holes at the dentino-enamel junction.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092000102
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Electron microscopic studies on the potential loss of crystallites from routinely processed sections of young enamel in the rat incisor (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 202 (1982), S. 177-186 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Newly formed rat incisor enamel was fixed aqueously by perfusion with glutaraldehyde and anhydrously by immersion in ethylene glycol. Ultrathin sections were studied using transmission electron microscopy and electron diffraction. Aqueously processed enamel was shown to lose its mineral content when sectioned on distilled water. This mineral loss was minimized by limiting the exposure of sections to the water. In such preparations, enamel crystallites were seen by virtue of their intrinsic electron density only. Selected area electron diffraction provided corroborative evidence for the presence or absence of crystallites in the sections. Observations on mineralized sections and on stained mineralized and distilled-water-demineralized sections revealed organic material apparently in the same location as the crystallites. Anhydrously processed enamel which was sectioned on ethylene glycol showed a similar appearance of the crystallites. This appearance was not obviously altered after staining despite evidence that organelles in the ameloblasts were stained. In view of the observations that both methods yielded similar crystallite morphology, it was concluded that aqueous techniques can be used to study the relationship between organic and inorganic components. However, valid description of crystallites in such preparations requires minimal exposure of ultrathin sections to water.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092020202
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    In vivo experimentation on rat incisor enamel organs through a surgical window (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 210 (1984), S. 693-705 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Experimental agents administered systemically are costly and often toxic to animals. An in vivo technique has been developed whereby a surgical window in the alveolar bone allows selected areas of the rat incisor enamel organ and underlying enamel to be exposed to various drugs, radiolabeled molecules, and molecular weight markers. Sherman rats weighing 100 gm were anesthetized and the inferior surface of each hemimandible was surgically exposed. A slow-speed dental hand drill was used to drill a small hole through the alveolar bone overlying the secretion or maturation zones of the enamel organ. The wound was closed and during recovery the mechanical trauma to the underlying tissue moved away from the hole due to the continuous eruption of the tooth. Two to 5 days later the hole was reexposed and microinjections of 3H-proline, 125I-salmon calcitonin, vinblastine sulphate, and normal saline (as control) were administered through the hole with a micro-manipulator and a microliter syringe. Radioautographic detection of 3H-proline incorporation in secretory ameloblasts and enamel at 10 minutes, 30 minutes, 1 hour, 4 hours, 1 day, and 2 days after microinjection was identical to that obtained previously by systemic injection. Two hours after microinjection of vinblastine sulphate the cellular response was again identical to that following systemic injection; 125I-salmon calcitonin (M.W. ∼ 3,600D) was used as a molecular weight marker and was seen to diffuse into the enamel of the maturation zone at 10 minutes after microinjection. This study has demonstrated the feasibility of this new technique for experimentation on rat incisor enamel organs.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092100417
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  • 8
    Electronic Resource
    Electronic Resource
    The development of enamel structure in rat incisors as compared to the teeth of monkey and man (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 200 (1981), S. 371-399 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The rat incisor is an excellent model system in which to study amelogenesis. However, the information obtained has not been extrapolated to the human because of alleged structural differences between the teeth. The obvious differences include continuous eruption in rat incisors and an enamel rod pattern in rats which seemingly differs from the keyhole pattern of human enamel. A comprehensive analysis was made of those features of enamel structure considered fundamental to the understanding of its formation. This was done by applying the knowledge of amelogenesis obtained in rat incisors to the teeth of monkey and man. The following points of basic similarity were established between these species: (1) Interrod enamel is secreted first. It forms the side walls of cavities which are initially occupied by Tomes' processes. (2) The formation of interrod cavities is followed by deposition of enamel rods within these spaces. (3) The rods conform to the shape of the cavities and are secreted from one surface of Tomes' process. (4) At the initial site of rod deposition its enamel is continuous with the interrod enamel wall. (5) Growth of the rod compresses the process to one side of the cavity resulting in an arcade-shaped “space” between the rod and the remaining interrod walls. This study demonstrates that it is no longer necessary to postulate a keyhole structure for primate enamel, and it has established that a fundamental similarity exists in the basic structure and in the mode of formation of enamel in all three species.
    Additional Material: 37 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092000402
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of 3H-labeled proline and tyrosine (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 164 (1982), S. 45-56 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: After injection of labeled precursors such as 3H-proline or 3H-tyrosine into rats, the incisor dentin contains a continuous and stable record of precursor incorporation into labeled proteins. This record was visualized and quantitated with radioautography in order to evaluate the quantitative changes in enamel where newly secreted proteins randomize with older proteins and both are eventually lost. Up to 4 hours after injection, the pulse-dose was incorporated as a highly labeled band of predentin. The band was entirely within calcified dentin at 2 days and was further removed from new predentin by 4 and 8 days. Dentin which formed proximal to the heavily labeled band contained an amount of radioactivity reflecting the level of labeled precursor available at that time. A standardizing factor for experimental error was obtained by quantitating the reaction in the heavily labeled band, and a post-pulse incorporation factor was determined from the amount of radioactivity added per day as weakly labeled dentin. The variation within the heavily labeled band was assumed to reflect experimental error. The number of grains in the bands were averaged from 4 hours to 8 days to give the standardizing factor. This was multiplied by the ratio of enamel to dentin counts in the same section to obtain a corrected enamel count. In this way the coefficient of variation was improved from a high of 17.2% in uncorrected enamel counts to 2.4% in corrected counts. The post-pulse incorporation factor was higher with tyrosine than with proline. With proline it amounted to 5% increase per day from 1 to 4 days and 2.5% per day from 4 to 8 days after injection. In addition, with 3H-proline the incorporation into predentin increased from 30 minutes to 4 hours. With tyrosine, the counts increased from 30 minutes to 1 hour, but decreased by nearly one third from 1 to 4 hours. This was interpreted as a loss of short-lived matrix proteins including procollagen peptides produced during conversion from procollagen to tropocollagen in the predentin.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001640105
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of putative secretory sites on ameloblasts of the rat incisor (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 171 (1984), S. 163-189 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The distribution and structure of the putative sites where enamel matrix is secreted from the ameloblast were studied by correlating the external topography with the distribution of organelles in Tomes' process cut in various planes of section. Both the interrod and rod secretion sites are associated with deep membrane infoldings. It was found that the interrod secretion site completely surrounds each ameloblast, and the marked interdigitation of adjacent cells results in a cooperative growth front for interrod enamel. In contrast, the rod secretion site is present on only one surface of the interdigitating portion of Tomes' process. Numerous granules were observed adjacent to the membrane infoldings associated with both sites, and granules were seen fused to membrane infoldings suggesting that the matrix of enamel is a merocrine secretion product.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001710204
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