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  • 1970-1974  (3)
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  • 1
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The developing oocytes of the crab Cancer pagurus L. were studied with the light and electron microscope. Protein yolk formation was found to take place in two different ways. Yolk precursors of type 1 accumulate within the cisternae of an extensively developed granular endoplasmic reticulum. Also further growth and transformation into the definite yolk body occur within the reticular membranes. There is no structural indication that any other cell organelle contributes to the synthesis of this type of yolk building. Protein yolk formation of type 2 involves accumulation and transformation of material within a limiting membrane of the smooth type. The enclosed material is presumably derived from micropinocytosis, enclosed cellular elements and vesicles originating from the Golgi complex. It thus appears that the cell organelles play an important role in the process of drotein yolk formation in the growing oocytes of Cancer pagurus.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Neural lobe ; Mouse ; Growth and development ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Nerve fibres of the neurosecretory hypothalamo-hypophyseal tract were studied in embryonic C3H mouse neural lobes; at least four glands at each gestational day 15–19 were examined. Single axons and small bundles of fibres are visible at gestational days 15 and 16. By day 17 large fibre bundles penetrate between glial cells. They increase in number during the next two days. Electron-lucent and electron-dense vesicles are seen in the fibres of the 15th and 16th gestational days. In the 17–19 day-old embryos development is characterized by a successive rise in the number of the two types of vesicles. The mean diameter of the electron-lucent vesicles is approximately unchanged in all the stages examined (50 nm). The electron-dense vesicles increase in size from approximately 80–90 nm at days 15–16 to 140 nm at the 19th gestational day. By day 19 contacts between neurosecretory fibre terminals and the outer basement membrane of internal and peripheral capillaries are occasionally observed. The possibly adrenergic nature of a few terminals contacting peripheral vascular structures in 17 and 18 day-old embryos is suggested.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0878
    Keywords: Median eminence ; Mouse ; Growth and development ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The development of the external zone of the median eminence of the mouse was studied in the electron microscope. The examination follows the development of the embryo from the 15th day of the gestation period and the juvenile growth until 24 days of age. Single terminals of the tubero-infundibular neurons of the external zone were found to extend to the outer basement membrane of the perivascular space of the portal primary capillary plexus in the 16 day-old embryo. In the 18 day-old embryo a narrow external zone has developed. Organization of the external zone into the adult pattern is accomplished at the age of three to four weeks. Small agranular as well as large granular vesicles are present in the tubero-infundibular nerve terminals even in the 16 day-old embryo. Changes in the organization of the nerve endings along the outer perivascular basement membrane in relation to the ependymal vascular feet were considered.
    Type of Medium: Electronic Resource
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