Pathogenesis of Pituitary Tumors
Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA.Progress in brain research (Impact Factor: 2.83). 01/2010; 182:207-27. DOI: 10.1016/S0079-6123(10)82009-6
Pituitary tumors are common and mostly benign neoplasia which cause excess or deficiency of pituitary hormones and compressive damage to adjacent organs. Oncogene activation [e.g. PTTG (pituitary tumor-transforming gene) and HMGA2], tumor suppressor gene inactivation (e.g. MEN1 and PRKAR1A), epigenetic changes (e.g. methylation) and humoral factors (e.g. ectopic production of stimulating hormones) are all possible pituitary tumor initiators; the micro-environment of pituitary tumors including steroid milieu, angiogenesis and abnormal cell adhesion further promote tumor growth. Senescence, a cellular defence mechanism against malignant transformation, may explain the benign nature of at least some pituitary tumors. We suggest that future research on pituitary tumor pathogenesis should incorporate systems approaches, and address regulatory mechanisms for pituitary cell proliferation, development of new animal models of pituitary tumor and isolation of functional human pituitary tumor cell lines.
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ABSTRACT: By an unsophisticated experiment, published data on the anatomy of the eye, wave theory of light, and the laws of geometrical optics the author tries to prove that a spherical concave screen is the optimal variant of a screen on which spherical wave front is projected, formed by a single lens. The shape of the wave front and of the concave screen are in complete agreement. Such optical imperfections as the field curvature, distortion, coma (partially), and astigmatism of the oblique light beams are compensated for. These optical drawbacks are undetectable on a concave screen, and hence they are proposed to be the shortcomings of a flat screen. The author compares this to a spherical shape of the eye, the posterior wall of which represents a concave screen, an indisputable fact, and assumes that the before-named optic imperfections are completely compensated for in human eye due to concavity of the posterior optic wall. Based on the anatomy and practical results of using aspherical refracting surfaces in artificial optic devices, the author draws a parallel with the anatomical structures of the eye possessing aspherical refracting surfaces in order to demonstrate that higher and lower-order spherical aberrations (Zeidel's aberrations) are fully compensated for in human eye, as are the position and enlargement chromatism. Analysis of published data permitted the author to assert that the eye of man is characterized by a method for compensation of spherical aberrations, which has no analogs in man-made practice. Hence, the Nature has imparted the eye with such a collection of compact, universal, and highly effective methods for compensation of optic imperfections, which is not to be found in any of the man-made devices of today.Vestnik oftalmologii 01/1996; 112(4):28-30. DOI:10.1016/S1569-2590(05)10001-9
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ABSTRACT: Word count:Abstract: 212, Main text: 4128,Tables: 0,Figures: 6 Page 1 o Accepted Preprint first posted on 27 August 2008 as Manuscript JOE-08-0250 Copyright © 2008 by the Society for Endocrinology.
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