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  • 1
    Electronic Resource
    Electronic Resource
    DNA localization in nuclear fragments of apoptotic ameloblasts using anti-DNA immunoelectron microscopy: Programmed cell death of ameloblasts (1995)
    Springer
    Histochemistry and cell biology 104 (1995), S. 151-159 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Ameloblasts responsible for tooth enamel formation are classified into two different phases: secretion and maturation. At the transition between these secretion and maturation stages, a considerable number of cells die. In this study, we examined the morphology of degenerating ameloblasts by conventional electron microscopy, and DNA cleavage in degenerating ameloblast nuclei by the in situ terminal transferase assay. The results suggest that apoptosis (programmed cell death) in ameloblasts, including DNA ligation is induced at the transitional stage. The nuclear fragments, chromatin condensation and DNA relocation in apoptotic nuclei were examined quantitatively by post-embedding anti-DNA immunogold electron microscopy and the in situ terminal transferase assay combined with electron microscopy. Numerical analysis revealed that immunogold labeling density in the condensed chromatin of apoptotic nuclei was comparable on the average to that in the perinuclear heterochromatin of normal nuclei, and that individual apoptotic nuclear fragments exhibited highly variable gold particle density, from fragments with lower density to that of normal heterochromatin, to fragments with densities twice as high as that of normal heterochromatin. The in situ terminal transferase assay combined with electron microscopy detected DNA ends exposed by ultrathin sectioning as well as DNA cleavage by a putative endonuclease. In conclusion, the state of the DNA, including its ligation and degeneration, changes gradually during chromatin condensation and nuclear fragmentation of apoptosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01451574
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructural changes in the tail muscles of anuran tadpoles during metamorphosis (1974)
    Springer
    Cell & tissue research 155 (1974), S. 321-336 
    Details
    ISSN: 1432-0878
    Keywords: Muscle fibres (Tadpole tail) ; Degeneration ; Macrophages ; Autophagic vacuoles ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This report describes histochemical and ultrastructural studies of tail muscles in tadpoles of Rana japonica and Rana catesbeiana during metamorphosis, this process being accompanied by degeneration of the tail. Degeneration of individual tail muscles does not occur at the same time; this is true for both the red and white muscle fibres. The initial phase of degeneration showed mesenchymal macrophages first invading the muscle fibres and then sending out many long cytoplasmic processes which split the fibres apart. The disappearance of myofibrils during degeneration proceeds along at least two different mechanisms even within a single muscle fibre. In one type, the Z-band becomes diffuse and then disappears, resulting in fragmentation of the myofibrils at the sites previously occupied by the Z-bands. The second pattern of degeneration is characterized by disappearance of the Z-band followed by a fanning out of the myofilaments not associated with fragmentation of myofibrils. As atrophy of muscle fibres proceeds, acid phosphatase activity is localized in the perinuclear sarcoplasm. Macrophages show more intense acid phosphatase activity than do the muscle fibres. The formation of autophagic vacuoles is described and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222809
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  • 3
    Electronic Resource
    Electronic Resource
    Autolysis and heterolysis of the epidermal cells in anuran tadpole tail regression (1985)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 185 (1985), S. 269-275 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Autolysis and heterolysis of the degenerating epidermis of the tail fin of Rana japonica tadpoles during spontaneous metamorphosis were observed by transmission and scanning electron microscopy. In the early climactic stages of metamorphosis (st. 19-20), the outermost epidermal cells developed vacuoles that were acid phosphatase positive and showed apparent breakdown of the cell membrane. The cells shrunk, perhaps due to the rupture of the cell membrane, and sloughed off without typical cornification. As tail resorption proceeded, autolysis of the epidermal cells spread towards the inner layers, in which some epidermal cells lost desmosomal junctions. They also displayed atrophic figures with condensed cytoplasm, breakdown of the cell membrane, and pycnotic nuclei. Lymphocytes, neutrophils and macrophages were already present in the basal layers of the premetamorphic epidermis (st. 10). Based on ultrastructural observation, blood cells could be distinguished from autolysing epidermal cells. Only a few blood cells were found in the early climactic stages of metamorphosis (st. 19-20), but the number of the blood cells, especially macrophages, greatly increased during the final stages of metamorphosis (st. 23-24). During the final stages, many macrophages were observed to phagocytose the autolysing epidermal cells by projecting slender pseudopodia into the inner epidermis. Macrophages also were observed to pass through the degraded basal lamella. These results suggest that not only autophagy but also heterophagy of the epidermal cells by the macrophages is a major process in the regression of the tail fin epidermis.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051850211
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  • 4
    Electronic Resource
    Electronic Resource
    Scanning electron microscopy of macrophages in the tail musculature of the metamorphosing anuran tadpole, Rana japonica (1985)
    Springer
    Cell & tissue research 241 (1985), S. 545-550 
    Details
    ISSN: 1432-0878
    Keywords: Macrophage ; Muscle ; Metamorphosis ; Back-scattered electron ; Tadpole (Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Scanning electron microscopy was used to investigate the morphological changes of the tail musculature of the metamorphosing anuran tadpole, attention being focused on phagocytosis by macrophages. Muscle fibers were stained en bloc with silver and freeze-fractured during dehydration, or torn after drying. Samples were sputter-coated with gold-palladium and observed in both secondary electron- and back-scattered electron modes with a scanning electron microscope. Various cells were identified by the methods of secondary electron- and back-scattered electron images. Some macrophages lying between muscle fibers at prometamorphic stages possessed numerous finger-like projections and well-developed ruffles. During degeneration of muscle fibers macrophages collected in the degenerating region and invaded the space between the disordering myofibrils. In advanced stages the numbers of macrophages clearly increased on or around the degenerating muscle fibers. At the climactic stage fragmented muscles were entrapped and then engulfed by the macrophages. With the completion of phagocytosis, the macrophages became globular with reduction of the ridge-like ruffles. Macrophages may play a role not only in scavenging the fragmented muscle fibers, but also using their long processes in active formation of the fragments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214574
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  • 5
    Electronic Resource
    Electronic Resource
    Network and lamellar structures in the tail muscle fibers of the metamorphosing anuran tadpole (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 211 (1985), S. 369-375 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Networks of regularly arranged tubular units and lamellar structures were observed in the degenerating tail muscle fibers of spontaneously metamorphosing anuran tadpoles. These networks appeared to be similar to those previously found in the skeletal muscle of other animals under abnormal conditions. They stained clearly with ruthenium red (RR) and a continuity with the transverse tubular system (T tubules) of triads was clearly observed. The diameter of the tubular unit, 20-25 nm, was almost equal to that of the T tubules of the intact tail muscle fibers, indicating the network structures were probably formed by T tubules connecting together. In the early stages of metamorphosis, networks in the tetragonal configuration were observed within the end region of the muscle fibers. At the climax of metamorphosis, well-developed networks in which the tubular units were arranged in a hexagonal pattern were seen in various regions of the fibers. Other observed lamellar structures may originate from lateral elements of the triads. The formation of the network structure is discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092110402
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  • 6
    Electronic Resource
    Electronic Resource
    The ultrastructure of oral (buccopharyngeal) membrane formation and rupture in the anuran embryo (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 210 (1984), S. 513-524 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The ultrastructure of the oral (buccopharyngeal) membrane was examined by transmission and electron microscopy in the anuran, Rana japonica, embryo. The stomodeum is recognizable on the ventral surface anterior to the neural folds as the neural folds are beginning to close (neural tube stage). The stomodeum is gradually enlarged and deepened as development proceeds. At the neural tube stage, the oral membrane is 5-7 cell layers thick and the stomodeal ectodermal cells are cuboidal and the foregut endodermal cells are cuboidal or columnar. Desmosomes and basal lamina could not be found between the ectodermal and endodermal epithelia. The oral membrane gradually thins between the neural tube and hatching stages. At the hatching stage, the oral membrane becomes two or three cell layers thick and each cell is flattened. Many perforations of the oral membrane occur after hatching and the oral membrane appears “net-like.” Necrotic cells occur in the oral membrane and these cells contain many autophagic vacuoles. ACPase-positive lysosomes, Golgi regions, and autophagic vacuoles were present in the oral membrane. At the asymmetrical trunk stage, a large part of the oral membrane disappears and only remnants are left.
    Additional Material: 33 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092100312
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  • 7
    Electronic Resource
    Electronic Resource
    Satellite cells in the tail muscles of the urodelan larvae during development (1984)
    Springer
    Cell & tissue research 236 (1984), S. 431-438 
    Details
    ISSN: 1432-0878
    Keywords: Satellite cells ; Satellite fibres ; Tail muscle ; Urodela ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The incidence and ultrastructure of satellite cells in the tail muscles of urodelan larvae were examined during development during which the number of satellite cells is gradually reduced. They are found more frequently in red than in the white fibres in all four stages examined (stage 53, 64, 66+ and juvenile). As development proceeds, intercellular space between satellite cell and muscle fibre is in general gradually extended and is mostly filled with basal lamina. Small muscle cells, satellite fibres, which are situated under the basal lamina of the parent fibre, are morphologically similar to satellite cells but contain a small amount of myofibrils. Three types of satellite fibres are distinguishable on the basis of differences in K2-EDTA-treated ATPase activity, width of Z line, and parent fibre type. Neuromuscular junctions are visible in satellite fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214247
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  • 8
    Electronic Resource
    Electronic Resource
    Regional specificity of anuran larval skin during metamorphosis: dermal specificity in development and histolysis of recombined skin grafts (1986)
    Springer
    Cell & tissue research 245 (1986), S. 297-304 
    Details
    ISSN: 1432-0878
    Keywords: Anuran tadpole ; Skin ; Regional specificity ; Epithelio-mesenchymal interaction ; Metamorphosis ; Rana japonica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Skins from back and tail were dissected from tadpoles of Rana japonica prior to resorption of the tail and separated into epidermis and dermis by treatment with neutral protease. Homotypically and heterotypically recombined skins were constructed from the separated epidermis and dermis and transplanted into the tail of the original tadpole. Skin grafts using dermis from tail region degenerated simultaneously with resorption of the tail. However, skin grafts containing dermis from back region survived on the posterior part of the juvenile frog beyond metamorphosis. Furthermore, all epidermis underlaid with dermis from back region formed secretory glands and became flattened epithelia characteristic of adult back skin, regardless of region from which the epidermis came. Even when epidermis isolated from tail skin was cultured inside a back skin graft, the tail epidermis survived forming an epithelial cyst and developed secretory glands. These results suggest that regional specificities of anuran larval skin, i.e., development of back skin and even histolysis of tail skin, are determined by regionally specific dermis. The results also suggest that some of epidermal cells of tail skin are able to differentiate into epithelial cells similar to back skin of the adult under the influence of back dermis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213935
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  • 9
    Electronic Resource
    Electronic Resource
    Morphological changes in the oral (Buccopharyngeal) membrane in urodelan embryos: Development of the mouth opening (1988)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 195 (1988), S. 59-69 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ultrastructure of the oral (buccopharyngeal) membrane in the embryo of the urodelan, Hynobius tokyoensis, was examined by transmission (TEM) and scanning electron microscopy (SEM). The oral membrane consists of the stomodeal ectoderm and foregut endoderm, and is three to five cell layers thick at stage 24. The oral membrane gradually thickens as development proceeds. The stomodeal collar, derived from the ectoderm, is folded inward along the foregut endoderm. Tooth germs are formed partly by cells of the stomodeal collar and partly by mesenchymal cells and calcification takes place before hatching. Secretory granules, which are markers of epithelial differentiation, appear in some cells of the foregut endoderm. Within the oral membrane, the cells of the stomodeal collar become the basal cells, and the endodermal cells of the foregut become the apical cells of the future oral epithelium. Gaps are formed by the epithelial differentiation of the endodermal cells of the foregut in the oral membrane. The gaps connect with each other, with the stomodeum, and with the foregut. As a result of these events, the mouth opens at stage 43, just after hatching.
    Additional Material: 29 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051950106
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  • 10
    Electronic Resource
    Electronic Resource
    Fine structure of the spermatophores and their ejaculated forms, sperm reservoirs, of the Japanese common squid, Todarodes pacificus (1991)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 207 (1991), S. 241-251 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Spermatophores in a squid, Todarodes pacificus, were observed by light and electron microscopy and were further analyzed by X-ray microanalysis (XMA) of frozen thin sections. Each spermatophore consists of a sperm mass, a cement body, an ejaculatory apparatus, and some fluid materials, all of which are covered by an outer tunic. The outer tunic consists of about 20 membranous layers, each containing straight, parallel microgrooves. Each layer's microgroove pattern is roughly in an orthogonal arrangement with respect to the next layer's pattern. The sperm mass, which is the only cellular component, consists of a sperm rope which is coiled more than 500 times. Most of the spermatozoa in the rope are arranged regularly and are enveloped in materials which are well-stained by Alcian blue. The cement body is located between the sperm mass and ejaculatory apparatus and has a hard outer shell with an arrowhead-like structure, presumably for penetration into the tissue of the female. Calcium and phosphorus are present in the shell of the cement body, which also has an affinity for alizarin red. The ejaculatory apparatus consists of two tubes, designated as the inner tunic and the inner membrane.After the spermatophoric reaction, a sperm reservoir is formed at the anterior end of the extruded and inverted ejaculatory apparatus. The sperm reservoir, which encases the sperm mass, is composed of the cement body at the anterior end and the inner tunic of the ejaculatory apparatus at the posterior end.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052070303
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