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A double membrane surrounds organelles such as mitochondria (A) during autophagy.
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; @4 l, k+ j1 f" dPORTER
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Thus the molecular description of autophagy is a relatively recent phenomenon (Klionsky and Emr, 2000). But the morphology came early. Autophagy is the destructive process in which a double membrane envelops cytoplasm and organelles before targeting them to lysosomes for destruction. It was first spotted in differentiating kidney cells as they redirected their metabolic energies (Clark, 1957).
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A robust model was established by Ashford and Porter (1962), who spotted autophagy when glucagon was perfused into rat livers. Glucagon is made in response to low blood sugar levels, so autophagy may be the cell's way of scaling back operations in hard times. In the words of Ashford and Porter (1962), the hydrolysis may be "providing the protoplast with breakdown products for use in a reoriented physiology," with the membrane "shield the rest of the cell from the general spread of the degradative process."& D, }! b2 O" r9 q! e% a! k( b5 z
" j$ X' `8 C0 ]- p3 D& nThe word autophagy crept into the literature in the 1960s (Deter et al., 1967) as it became clear that the process intersected with but was distinct from other forms of lysosomal degradation. The endoplasmic reticulum was proposed as the source of the autophagic membranes (Dunn, 1990), although uncertainties about this and other details of autophagy remain.
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; O& t( {7 Y+ E0 D( PAshford, T.P., and K.R. Porter. 1962. J. Cell Biol. 12:198–202.4 a g# N- e, l8 C: m/ ^7 s% ^( m: S
1 R: A# `* T$ A' W; k+ C/ FClark, S.L. 1957. J. Biophys. Biochem. Cytol. 3:349–361.
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8 T- O0 z6 _* U- }# v/ TDeter, R.L., et al. 1967. J. Cell Biol. 35:C11–C16.
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5 y9 f% a* A' Z. Y' e+ {- oDunn, W.A. 1990. J. Cell Biol. 110:1923–1933.9 }+ l) T' D9 P+ V
. |9 f* g- B; CKlionsky, D.J., and S.D. Emr. 2000. Science. 290:1717–1721.(In cell biology research it seems that b) |
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发表于 2009-3-6 08:57
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