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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 60 (1963), S. 276-292 
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electron microscopic observations have been made on the structure of guinea-pig spermatozoa in successive segments of the epididymal duct. Marked changes are observed in the shape and internal structure of the acrosome as the sperm move through the epididymis. The morphological basis for this continuing differentiation of the sperm is traced back to certain unusual features of acrosome formation in the early spermatids of this species. The possible relation of the progressive development of the acrosome to the known increase in fertilizing capacity of the spermatozoa during their passage through the epididymis is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The marginal band of nucleated erythrocytes in the toadfish is found, in electron micrographs, to be composed of about twenty-five microtubules approximately 200 Å in diameter. These form a bundle that encircles the erythrocyte just beneath the plasma membrane. These observations support the interpretation of Meves 1904, that this relatively stiff equatorial band may contribute to the maintenance of the discoid shape of nucleated erythrocytes in fish, amphibians, reptiles and birds. Similar microtubules form an annular bundle encircling the nucleus in fish thrombocytes. The number of tubular elements involved here is in excess of one hundred and they are located deep to the ectoplasmic layer instead of immediately beneath the plasmalemma. The term endoplasmic ring is therefore proposed for this structure. Comparative observations on nucleated erythrocytes of various species are presented showing that the density and fine structure of the material occupying the interchromosomal areas of the nucleus, always matches the cytoplasm and is related to the hemoglobin concentration of the species. These ultrastructural observations are consistent with the optical absorption and biochemical findings of other investigators indicating the presence of intranuclear hemoglobin in nucleated erythrocytes. Crystalline order is occasionally found in electron micrographs of the hemoglobin rich areas of the nucleus in toadfish erythrocytes but is not found in the cytoplasm.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 70 (1966), S. 347-363 
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structure of the crystalline inclusions found in Batrachoseps liver cells is described and it is shown that the most symmetric unit cell upon which the crystal lattice is built is a face-centered cube. Taking into consideration the physical properties of a face-centered cubic structure, an attempt is made to determine the nature of the macromolecules that comprise the crystal. It is concluded on the basis of available evidence that the macromolecules probably represent serum lipoproteins. The intracellular synthesis of the crystals and the possible functions they may subserve in the animal are discussed. A comparison is made between the crystals and granules in rat hepatocytes discussed by Bruni and Porter (1965).
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 67 (1965), S. 279-296 
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A description of the guinea pig spermatozoon has been presented using descriptive terms that are applicable to mammalian spermatozoa in general. The spermatozoon consists of two principal parts, the head and the tail. The tail is further subdivided into four regions, the neck, middle-piece, principal-piece and end-piece. The principal components of the head are the acrosomal cap and the nucleus. On its posterior surface, the nucleus bears a shallow implantation fossa lined by the nuclear envelope which is locally specialized to form the basal plate. The neck contains a connecting-piece bearing an articular surface that attaches to the basal plate lining the implantation fossa. The connecting-piece is formed by the convergence and fusion of nine longitudinal segmented columns which merge caudally with nine outer dense fibers that surround the axial filament complex throughout the major part of the length of the flagellum. In the middle-piece, the core of longitudinal fibers is surrounded by a mitochondrial sheath. The end of the middle-piece is marked by the annulus, a thin dense ring to which the flagellar membrane is firmly adherent. In the principal-piece, the core of longitudinal fibers is enclosed in a fibrous sheath composed of closely spaced circumferential ribs that attach to two longitudinal columns running along opposite sides of the sheath for its entire length. It is suggested that accurate communication would be facilitated by abandonment of the terms “galea capitis”, “head cap”, “post-nuclear cap”, “implantation plates”, “thin laminated fibers”, “protoplasmic bead”, “middle-piece bead”, “ring-centriole”, “Jensen's ring”, “spiral sheath”, “tail helix”, and “tail sheath”.
    Type of Medium: Electronic Resource
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  • 5
    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 principal cells and intraepithelial leucocytes in the initial segment of the rat caput epididymidis was examined with the electron microscope. Specializations of the principal cells associated with absorption include numerous endocytic invaginations of the cell surface, numerous coated vesicles and multivesicular bodies in the apical cytoplasm. It was demonstrated that particulate tracers are taken into the cells and sequestered in secondary lysosomes and multivesicular bodies. Morphological features consistent with secretory activity are also found in the principal cells and include numerous cisternae of rough endoplasmic reticulum with a flocculent grey content and an extremely well-developed Golgi apparatus. The speculation that the principal cells are actively secretory despite the absence of secretory granules formed in the Golgi and of a visible mechanism for release of the product at the cell surface is discussed.The “halo cells” in the epididymal epithelium were also examined and it is shown that many of these cells are not typical migratory lymphocytes. Chief among the differences are their granule-containing multivesicular bodies and more abundant endoplasmic reticulum. Nonetheless, it is conceivable that the halo cells are lymphocytes and that the conditions they encounter as they leave the circulation and enter the epididymal epithelium may stimulate morphological changes. The possible immunological significance of these observations is discussed.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The ultrastructural pathology of the initial segment of the rat caput epididymidis was examined after oral administration of a single high dose of the antifertility compound α-chlorhydrin (U-5897) at time intervals ranging from two hours to nine days after treatment. At doses in excess of 30 mg/kg this compound produces a lesion specifically localized in the initial segment of the epididymis characterized by sloughing of the epithelium, which leads to obstruction of the lumen of the epididymal duct, spermatocoel and sperm granuloma formation and an ultimate occlusive fibrosis. In rats fed 140 mg/kg of U-5897 the first effects can be seen as early as two hours after treatment. Within 48 hours after treatment, the lumen of the greater part of the initial segment is filled with degenerating cells and debris which block further passage of sperm along the duct. The present study provides insight into the nature of the early events in the evolution of this epididymal lesion. Possible mechanisms of action of α-chlorhydrin are discussed.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Attention is directed to an unusual type of junctional complex between Sertoli cells in the seminiferous epithelium. The space between the membranes of adjoining cells is narrowed to 70-90 Å over large areas of their contact surfaces. In the superficial cytoplasm of each cell is an extensive cisterna of the endoplasmic reticulum, parallel to the membrane and 400-600 Å from it. Spaced at more or less regular intervals in the thin layer of cytoplasm between the cisterna and the cell membrane are periodic densities that appear to be band-like aggregations of fine filaments. The sub-surface cisternae are smooth-contoured on the side toward the cell membrane but bear ribosomes on the side facing the cytoplasm. The possible significance of these distinctive junctions is discussed in relation to the support of the germ cells and the coordination of the developmental events in the cycle of the seminiferous epithelium.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Previous work with electron opaque intercellular markers has indicated that in adults occluding junctions between adjacent Sertoli cells are the principal morphological basis of the blood-testis barrier (Dym and Fawcett, '70). Since the barrier of not present at birth this study was undertaken to determine when it is established during postnatal development of the rat and to correlate its appearance with other developmental events in the seminiferous epithelium. From birth to 16 days of age interstitially injected tracers, such as horseradish peroxidase, freely entered the seminiferous epithelium and permeated the 200 Å intercellular clefts between presumptive Sertoli cells and germ cells, reaching the center of the seminiferous cords and site of the future tubule lumen. Between day 16 and 19 occluding junctions between Sertoli cells appear and thenceforth interstitially injected electron opaque tracers were effectively prevented from reaching the tubule lumen. Therefore, in rats, the blood-testis barrier is established between 16 and 19 days of age.In an attempt to determine whether the development of the Sertoli cell junctions and the blood-testis barrier is under hormonal control circulating gonadotropins were suppressed using daily injections of clomiphene or estrogens from birth. The appearance of blood-testis barrier was delayed approximately seven days in the absence of gonadotropins. However, by day 26 the Sertoli cell junctions did appear and interstitially injected tracers were prevented from reaching the tubule lumen. Thus the development of the occluding junctions between Sertoli cells that constitute the permeability barrier does not appear to be directly dependent upon gonadotropins.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An intensive search has failed to locate a proximal centriole in the neck of the rat spermatozoon. This centriole is present in late spermatids but disappears before spermiation. The distal centriole also degenerates during spermiogenesis, though more gradually; it is no longer demonstrable by the time the spermatozoa reach the cauda epididymidis (except as a few remnants in a small minority of the cells). The rat spermatozoon is thus exceptional among mammals in being effectively acentriolate. The implications of this are discussed. Since there are no centrioles, the activity and control of the flagellum cannot depend on a centriole as a kinetic center. Furthermore, since no centrioles are introduced by the rat spermatozoon at fertilization, there can be no paternal inheritance of a formed centriole through the cytoplasm. And, in this species at least, paternal centrioles have no role in the first cleavage of the fertilized egg.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: During a study on the fine structure of different regions of the reproductive tract of the ground squirrel, Citellus lateralis, cells possessing cytological features associated with steroid production were observed among the ductuli efferentes. Comparison of the morphology of these cells with that of Leydig and adrenocortical cells, demonstrated that they resembled Leydig cells in many anatomical details. Further evidence for the similarity of the cells associated with the ductuli efferentes to Leydig cells emerged during sexual regression, when both types of cells underwent the same regressive changes in organization and morphology. This suggests that the cells present among the ductuli efferentes are active in the synthesis of androgenic hormones, and possibly play a role in the endocrine control of reproduction in this species of ground squirrel.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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