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  • Calcitonin  (1)
  • Morphogenesis  (1)
  • Rat kidney  (1)
  • 1970-1974  (3)
  • 1
    ISSN: 1432-0568
    Keywords: Calcitonin ; C-Cells of the thyroid and cells of the parathyroid glands ; Secondary hyperparathyroidism ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Im Verlauf ein- bis achtwöchiger Behandlung von Wistar-Ratten mit täglich 300 mMRC Einheiten Schweinecalcitonin kam es in den C-Zellen der Schilddrüse, verglichen mit denen der Kontrollserien (unbehandelte und mit Acetatpuffer allein behandelte Tiere), einerseits zu einer morphometrisch signifikanten Abahme der Zahl der Sekretgranula, während andererseits sämtliche Zellorganellen (Mitochondrie,, Golgi-Apparat und auch das granuläre endoplasmatische Reticulum) besser entwickelt waren. In den in gleichen Zeitabschnitten untersuchten Parathyroideazellen fanden wir bei mit Calcitonin behandelten Ratten Strukturveränderungen, die auf eine erhöhte Aktivität hinwiesen: Einfaltungen des Kerns, Erweiterung der Intercellularräume mit Vermehrung und Verlängerung der in diese hineinragenden Mikrovilli, bessere Ausbildung des Golgi-Apparates und des granulären endoplasmatischen Reticulums sowie eine größere Menge freier Ribosomen. Die Zahl der Sekretgranula war eindeutig höher als bei den Kontrolltieren. Der Ca ++- und Mg++-Blutspiegel zeigte während der ganzen Versuchsdauer bei allen Tieren keine statistisch faßbaren Änderungen. Die Autoren vertreten die Hypothese, daß die Aktivierung der C-Zellen durch das Auftreten eines durch die Calcitoninverabreichung hervorgerufenen sekundären Hyperparathyroidismus zustande kommt.
    Notes: Summary Male Wistar rats were injected for one to eight weeks with 300 mMRC units per day of porcine calcitonin. During this period C-cells (or “parafollicular” cells) of the thyroid gland and cells of the parathyroid glands were examined ultrastructurally. The C-cells were further studied morphometrically in animals treated with calcitonin dissolved in acetate buffer as well as in acetate buffer- and not-treated control animals. In the thyroid C cells the number of secretion granules significantly decreased following calcitonin administration, whereas the volume of all cell organelles (mitochondria, Golgi complex and granular endoplasmic reticulum) augmented. The cells of the parathyroid glands of the calcitonin-treated rats showed structural changes due to higher activity: invaginations of the nuclear envelope, enlargement of the intercellular spaces with increase in number and size of the microvilli, better development of the Golgi complex and the granular endoplasmic reticulum, larger population of free ribosomes and secretory granules. However, no significant differences in the blood calcium and magnesium levels were detected when a comparison was made of calcitonin-treated and control animals. All these observations support the hypothesis that the activation of the C-cells may result from a secondary hyperparathyroidism itself induced by the administration of moderate doses of calcitonin.
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  • 2
    ISSN: 1432-0568
    Keywords: Lysosome ; Autophagy ; Phagocytosis ; Acid phosphatase ; Morphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ultrastructure of the “physiological” cell death was studied in distal ventral bulbar cushions of 15 chick embryo hearts on the 4th and 5th day of incubation. Microperfusion fixation was performed. The ultracytochemistry of a lysosomal hydrolytic enzyme acid phosphatase was also investigated in another 15 embryonic hearts. In the course of the cell degeneration an increase in cellulr autophagy was observed without previous cytoplasmic or nuclear changes or phagocyte ingestion. A cytoplasmic diffusion of acid phosphatase outside of lysosomes was observed. Besides the cell death with the marked participation of the lysosomal system, another kind of dying cells was found, characterized by their nuclear pycnosis and cytoplasmic condensation. Starting from the 5th day of incubation the dying and dead cells were found phagocytized by some of their neighbouring viable mesenchymal cells. A formation of ribosomal crystals was not observed. The formation and fate of cytolysomes as well as the fate of phagocytes are discussed. The presence of pre-necrotic cells with important autophagy and of necrotic cells with nuclear changes was related to the possibility of a dual cause of the cell death. In the case of pre-necrotic cells the epigenetic factors like the biomechanic action of hemodynamics were considered, while the necrotic cells seem to be programmed to death by their genome. Finally the uniformity of cell death ultrastructure in different organs and species was noticed.
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  • 3
    ISSN: 1432-0568
    Keywords: Rat kidney ; Macula densa ; Dark and light cells ; Fixation procedure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Verfasser beschreiben die Ultrastruktur der dunklen Zellen in der Macula densa der Mittelstücke der Ratten-Niere nach Perfusionsfixierung in situ. In Vergleich mit den Resultaten aus einer früheren Versuchsreihe mit Immersionsfixierung ist der prozentuale Anteil der dunklen Zellen etwa viermal geringer, während ihre Ultrastruktur im Prinzip die gleiche geblieben ist. Die Verfasser vertreten die Auffassung, daß die dunklen Macula-Zellen nicht unbedingt Präparationsartefakte sind.
    Notes: Summary The authors describe the ultrastructure of the dark cells in the macula densa of the distal convoluted tubule of the rat kidney after fixation carried out by vascular perfusion in situ. In this case the frequency of the dark cells compared with that of the light cells is about four times lower than in previous investigations using the fixation procedure by immersion, whereas the ultrastructure remains essentially unchanged. However, the authors believe that the dark cells of the macula densa are not necessarily artifacts due to the preparation of the specimens for examination in the electron microscope. At present it is not yet possible to decide if the dark and the light cells are two specific cell types of the macula densa or if they represent two different functional stages of a single cell type.
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