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Correlative scanning-transmission electron microscopic examination of the perinatal rat brain
Authors:Dr. D. E. Scott  W. K. Paull
Affiliation:(1) Department of Anatomy, University of Rochester, School of Medicine & Dentistry Rochester, New York, USA;(2) Medical College of Georgia Augusta, Georgia, USA;(3) Department of Anatomy, University of Rochester, School of Medicine & Dentistry, 601 Elmwood Avenue, 14642 Rochester, New York, USA
Abstract:Summary The ultrastructural organization of the perinatal hypothalamus and the dynamics of neuronal and ependymal growth and plasticity were examined in this investigation. The brains of fetal rats 16, 17 and 18 days in utero and those of postnatal rats 1–16 days post partum were fixed with aldehyde fixatives and prepared for combined SEM/TEM analysis. By day 17 in utero the ventricular (ependymal) surfaces of the fetal thalamic wall, cerebral vesicle and rhomboid fossa were relatively well differentiated with cilia and microvilli. Type II histiocytes were the first supraependymal cell to appear upon the ventricular lumen and were evident by day 17 in utero. In contrast, the apical surfaces of tanycytes of the infundibular recess as well as those of most other circumventricular organs were poorly differentiated and unremarkable. Tanycytes of the infundibular recess exhibited a simple hexagonal mosaic pattern of apposed plasmalemmata and even by day 1 post partum few cilia or microvilli were evident.By day 5–6 post partum Type I supraependymal neurons and axonal processes began to make their appearance with some emerging from the underlying parenchyma of the median eminence. By day 16 post partum the ventricular surface of the infundibular recess was comparable with that of the adult.The Type I supraependymal neurons are remarkably similar in their ultrastructural organization with parvicellular neurosecretory neurons elsewhere in the endocrine hypothalamus. Their emergence at day 5–6 post partum suggests a possible correlation with the critical period of sexual differentiation and a potential receptor role for this cell line. On the contrary this phenomenon may simply be a developmental anomaly. Nonetheless, the mergence of such elements upon the lumen of the third cerebral ventricle underscores a remarkable degree of neuronal plasticity in the perinatal hypothalamus.Supported by USPHS Program Project Grant NS 11642-04 and USPHS-BRSG Grant RR-05403.The authors wish to thank N. Kutryeff for her excellent technical assistance
Keywords:Third ventricle (Rat)  Hypothalamus  Perinatal  Supraependymal neurons  Median eminence  SEM-TEM
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