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Elastin fiber defect in copper deficiency
Micron, 1980, Vol.: 11, pp. 199-200. Pergamon Press Ltd. Printed in Great Britain.
ELASTIN FIBER DEFECT IN COPPERDEFICIENCY
M.L. Hart, S.A. Beydler and W.H. Carries Department of Pathology, University of California Los Angeles, California, 90024, U.S.A.
Vascular elastin has been shown by scanning electron microscopy to have d i s t i n c t i v e fiber forms (Hart, Beydler and Carnes, 1978). Elastin fiber formation is impaired in copper deficiency due to i n h i b i t i o n of crosslinkage, i n i t i a t e d by the copper-dependent enzyme, lysyl oxidase. As a consequence of t h i s there is reduction of tensile strength and spontaneous rupture of arteries. A study of aortic elastin in copper-deficient swine was undertaken to further characterize this defect in fibrillogenesis. Newborn pigs were reared on a copper-deficient diet supplemented with iron, and controls on the same diet received 0.5 mg/kg body weight per day of copper as the sulfate. After two months, when serum coppers were reduced to less than 5% of the normal value (150 u g/ ml), the animals were sacrificed. The aortic elastin was isolated by a modified Lansing procedure and prepared for scanning electron microscopy by osmium and thiocarbohydrazide ligand-binding without metal coating. Specimens were examined at primary magnifications of lO-IO,OOO. The elastin laminae of the normal aortic media are composed of fused smaller fibers that form tapering interlaminar connections (Fib. l ) . In the copper-deficient the laminae are thin and the interlaminar fibers are misshapen (Fig. 2). Higher magnification reveals fine axial furrows on the surfaces of the normal fibers (Fig. 3). This conformation is markedly altered in the copper-deficient. Bulbous protuberances of elastin cover the surfaces of the altered fibers (Fig. 4) at the expense of f i n e r connecting f i b r i l s . Similar alterations occur in the intimal and adventitial elastin fibers. These observations suggest that alignment of elastin subunits in fibrillogenesis is dependent upon the same mechanism that i n i t i a t e s crosslinkage of t h e i r peptide chains. (Supported by U.S. Public Health Service Research Grant HL 12561)
Hart, M.L., S.A. Beydler and W.H. Carnes (1978). The f i b r i l l a r structure of aortic elastin. In R.P. Becker and O. Johari (Eds.) Scanning Electron Microscopy, Vol. I I , Chicago, pp.21-27.
199
200
M. 1 . Hart, S. A. Beydler and W. H. Carnes
Fig. 1 Medial e l a s t i n of control aorta, showing p a r a l l e l laminae with tapered interlaminar fibers.
Fig. 2 Medial e l a s t i n of copper-deficient aorta, showing attenuated, misshapen fibers
Fig. 3 Medial e l a s t i n of control aorta, showing furrowed surfaces of f i b e r s ,
Fig. 4 Medial e l a s t i n of copper-deficient aorta, showing bulbous deformities of f i b e r s
ELASTIN FIBER DEFECT IN COPPERDEFICIENCY
M.L. Hart, S.A. Beydler and W.H. Carries Department of Pathology, University of California Los Angeles, California, 90024, U.S.A.
Vascular elastin has been shown by scanning electron microscopy to have d i s t i n c t i v e fiber forms (Hart, Beydler and Carnes, 1978). Elastin fiber formation is impaired in copper deficiency due to i n h i b i t i o n of crosslinkage, i n i t i a t e d by the copper-dependent enzyme, lysyl oxidase. As a consequence of t h i s there is reduction of tensile strength and spontaneous rupture of arteries. A study of aortic elastin in copper-deficient swine was undertaken to further characterize this defect in fibrillogenesis. Newborn pigs were reared on a copper-deficient diet supplemented with iron, and controls on the same diet received 0.5 mg/kg body weight per day of copper as the sulfate. After two months, when serum coppers were reduced to less than 5% of the normal value (150 u g/ ml), the animals were sacrificed. The aortic elastin was isolated by a modified Lansing procedure and prepared for scanning electron microscopy by osmium and thiocarbohydrazide ligand-binding without metal coating. Specimens were examined at primary magnifications of lO-IO,OOO. The elastin laminae of the normal aortic media are composed of fused smaller fibers that form tapering interlaminar connections (Fib. l ) . In the copper-deficient the laminae are thin and the interlaminar fibers are misshapen (Fig. 2). Higher magnification reveals fine axial furrows on the surfaces of the normal fibers (Fig. 3). This conformation is markedly altered in the copper-deficient. Bulbous protuberances of elastin cover the surfaces of the altered fibers (Fig. 4) at the expense of f i n e r connecting f i b r i l s . Similar alterations occur in the intimal and adventitial elastin fibers. These observations suggest that alignment of elastin subunits in fibrillogenesis is dependent upon the same mechanism that i n i t i a t e s crosslinkage of t h e i r peptide chains. (Supported by U.S. Public Health Service Research Grant HL 12561)
Hart, M.L., S.A. Beydler and W.H. Carnes (1978). The f i b r i l l a r structure of aortic elastin. In R.P. Becker and O. Johari (Eds.) Scanning Electron Microscopy, Vol. I I , Chicago, pp.21-27.
199
200
M. 1 . Hart, S. A. Beydler and W. H. Carnes
Fig. 1 Medial e l a s t i n of control aorta, showing p a r a l l e l laminae with tapered interlaminar fibers.
Fig. 2 Medial e l a s t i n of copper-deficient aorta, showing attenuated, misshapen fibers
Fig. 3 Medial e l a s t i n of control aorta, showing furrowed surfaces of f i b e r s ,
Fig. 4 Medial e l a s t i n of copper-deficient aorta, showing bulbous deformities of f i b e r s