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  • Cell & Developmental Biology  (2)
  • 1
    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 median eminence of neonatal (newborn, 1-, 3-, 5-, and 10-day old) and adult guinea pigs was studied to determine the dynamic changes occurring in this structure during early life. At birth the portal vasculature consists of the Mantelplexus and a few, non-fenestrated capillary loops. The number of ansae and the degree of fenestration increase rapidly after birth. The abundance of cytoplasmic and ciliary projections into the ventricular recess and the large numbers of organelles indicate that the ependymal cells are more active in the neonatal period than in the adult male. Moreover, the ependymal endfeet cover most of the surface area of the primary portal plexus during this time. The neuronal layers of the median eminence are difficult to distinguish at birth due to the lack of myelinated fibers in the zona interna. Significant myelination appears on day 3 but is not complete until day 10. There is a progressive increase in the numbers of Herring bodies and large neurosecretory granules (1,500-1,700 Å) during this same time period. In the zona externa, few nerve terminals abut on the perivascular space until day 3. Increases in numbers of granules per axon profile were noted for each day after birth. Despite the relatively long gestation period of the guinea pig (68-72 days), the morphologic appearance of the median eminence at birth suggests that the neurovascular link controlling anterior pituitary function is not yet complete.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 231 (1991), S. 457-466 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The decapeptide gonadotropin-releasing hormone (GnRH) stimulates release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary. In the present study we used a 51-base oligonucleotide probe and in situ hybridization to study the neuronal content of GnRH mRNA at several time points in the estrous cycle and 7 days after castration of male rats. GnRH mRNA containing cells were found in the medial septum (SEPT), the vertical and horizontal limbs of the diagonal band of Broca (DBB), and throughout the preoptic area (POA) from the organum vasculosum of the lamina terminalis (OVLT) to its caudal merger with the anterior hypothalamus.The number of neurons producing detectable quantities of GnRH mRNA was not different either among females killed at 0700 h proestrus, 1000 h estrus, or 1900 h of diestrus 1 or between intact male rats and male rats killed 1 week after castration. We did, however, detect a significant difference in the number of GnRH mRNA producing neurons between males and females (P 〈 0.05), where females had 20% more labeled cells.We detected no significant difference in the relative copy number of GnRH mRNA molecules (grains per labeled cell) either over the estrous cycle or between intact and castrate males. However, females overall had 24% more grains per labeled cell than males (P 〈 0.05). These results suggest that gonadal steroid regulation of GnRH both over the estrous cycle and after short-term castration of males is mediated primarily by cellular processes subsequent to GnRH gene regulation. Furthermore, these results suggest that biosynthetic activity of GnRH is higher in females than in males.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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