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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 198 (1998), S. 53-61 
    ISSN: 1432-0568
    Keywords: Key words Regenerating spermatogonia ; Asymmetric divisions ; Cytoplasmic bridges ; Busulfan ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This study describes the morphological behaviour of spermatogonia following recovery from two doses of busulfan treatment in the rat. Twenty days after the second intraperitoneal injection of busulfan, the testes lost most of their spermatogenic cells and there were fewer dispersed singly surviving spermatogonia. These surviving cells were in close contact with the basal portions of adjacent Sertoli cells and the shrunken basal lamina, and were the source for repopulating the depleted seminiferous epithelium. During the initial stage of repopulation (48 days later), surviving spermatogonia underwent a phase of active proliferation: type A spermatogonia underwent symmetric and asymmetric divisions; type B spermatogonia underwent asynchronous differentiation. At day 96, normal spermatogenesis was fully recovered in many seminiferous tubules, represented by 80% of the rats regaining various degrees of fertility at day 120. These data provide an additional model for the study of self-renewal of stem spermatogonia and suggest that the asymmetric division of type A spermatogonia and their close contact with both the basal lamina and the Sertoli cells may be involved in regulating the number of stem spermatogonia and the delicate process of normal spermatogenesis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0568
    Keywords: Key words Marsupial ; Mitochondria ; Primordial germ cell migration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The primordial germ cells (PGCs) of tammar wallaby fetuses are large cells with large nuclei. The cytoplasm of the PGCs contains characteristic spherical mitochondria and abundant ribosomes that make the cyoplasm appear dense. No permanent junctional complexes between PGCs and somatic cells were observed, and there were few cytoplasmic inclusions. The majority of migrating PGCs were observed outside the gonad in the dorsal mesentery and in the tissues adjacent to the gonad. The migrating PGCs have many finger-like, blunt pseudopodia, within which microfilament bundles are observed. The numerous dumbell-like PGCs with polarised cytoplasm suggest that the PGCs of this marsupial move to the gonadal ridges by amoeboid movement, but once the PGCs reach the gonadal ridge, they assume their more characteristic ovoid shape.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 238 (1994), S. 191-198 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Postnatal development and differentiation of the rat epididymis was studied in the rat from 15 to 120 days of life using stereological techniques. Both the relative volume (volume density) and absolute volume of the epithelial, interstitial, and luminal compartments in the initial segment, caput, corpus, and cauda epididymides were determined. In all segments the volume density of the epithelial compartment increased between days 15 and 30 before falling to adult values at 45 days in the initial segment (0.476 ± 0.031), at 60 days in the caput (0.258 ± 0.028) and at 90 days in the corpus (0.245 ± 0.007) and cauda (0.140 ± 0.004). The relative volume of the interstitium decreased, whilst that of the lumen increased over the same period with adult values being achieved earlier in the proximal segments than in the distal segments. In contrast to volume fraction the absolute volume of all compartments in all segments increased from day 15 to day 90. Between 90 and 120 days the absolute volumes of compartments in the initial segment and caput showed little volume change. All compartments in the corpus and cauda showed significant increases in volume over the same period. A similar pattern of development was observed with respect to the surface area of both the luminal and basement membrane aspects of the epithelium; surface area per unit volume (surface density) in all segments reached adult values at approximately 60 days, whilst the increase in absolute area of the surfaces ceased at 90 days in the initial segment and caput and continued to 120 days in the corpus and cauda. The total length of the epididymal tubule showed the same pattern with no increase in length apparent in the initial segment and caput after 90 days. Length however continued to increase in the corpus and cauda between 90 and 120 days. Tubule and luminal diameter reached their definitive values in the initial segment on day 60 but continued to increase until day 90 in the distal segments. Epithelial height increased between 15 and 30 days in all segments; in the caput, epithelial height was greatest on day 30 before decreasing slightly; and in the corpus and cauda maximal epithelial height was observed on day 45 decreasing to stable values on day 60 and 90, respectively. All the data is consistent with a proximal to distal differentiation and development of the epididymis with growth continuing in all segments after the establishment of the definitive architecture. Growth of the distal segments continued after its cessation in the proximal segments. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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