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  • 1990-1994  (2)
  • 1992  (2)
  • Immunocytochemistry  (1)
  • Intraclass correlation  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 85 (1992), S. 79-88 
    ISSN: 1432-2242
    Keywords: Intraclass correlation ; Negative estimate ; Restricted maximum likelihood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary At least two common practices exist when a negative variance component estimate is obtained, either setting it to zero or not reporting the estimate. The consequences of these practices are investigated in the context of the intraclass correlation estimation in terms of bias, variance and mean squared error (MSE). For the one-way analysis of variance random effects model and its extension to the common correlation model, we compare five estimators: analysis of variance (ANOVA), concentrated ANOVA, truncated ANOVA and two maximum likelihood-like (ML) estimators. For the balanced case, the exact bias and MSE are calculated via numerical integration of the exact sample distributions, while a Monte Carlo simulation study is conducted for the unbalanced case. The results indicate that the ANOVA estimator performs well except for designs with family size n = 2. The two ML estimators are generally poor, and the concentrated and truncated ANOVA estimators have some advantages over the ANOVA in terms of MSE. However, the large biases may make the concentrated and truncated ANOVA estimators objectionable when intraclass correlation (ϱ) is small. Bias should be a concern when a pooled estimate is obtained from the literature since ϱ〈0.05 in many genetic studies.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 193 (1992), S. 152-163 
    ISSN: 0002-9106
    Keywords: Cerebral endothelium ; Development ; Immunocytochemistry ; Rat ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A constant supply of blood-borne glucose is vital to cerebral metabolism. Although transport of glucose into the nervous tissue, effectively separated from the blood by a functional barrier (the blood-brain barrier, BBB), is one of the essential properties of the cerebral endothelium, little is known about its metabolic regulation and developmental expression in the BBB. In this study we provide evidence by immunocytochemistry that the pattern of the brain endothelial glucose transporter in rat brains (BBB-GT), immunologically homologous with the human hepatoma (G2), human erythrocyte transporter (Glut 1), changes with BBB maturation. While the neuroepithelium at embryonic days 12 and 13 shows a high incidence of immuno-detectable BBB-GT, vascularisation of the cerebral anlage and subsequent development of vascular tightness, as evidenced by intravascularly applied horseradish peroxidase and fluorescinated dextrans, is accompanied by a significant reduction BBB-GT expression in neuroepithelial cells and confinement of BBB-GT expression to the cerebral endothelium. Immunoblots and Northern blots of embryonic brain homogenates corroborate this change in BBB-GT expression in the brain anlage at the time of BBB maturation. However, low molecular weight glucose transporters, presumed to be of non-endothelial origin, are less dramatically reduced. The development of BBB tightness, therefore, seems to play a pivotal role in the pattern of BBB-GT expression during brain differentiation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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