An Infrared Study of Fibril Formation in Insulin from Different Sources

A1thought the mechanisms of amyloidogenesis have not been entirely clarified, proteolysis of the parent proteins may be one of the important steps in the amyloid fibril formation. Recently, we reported that "dense fibrillar inclusions" (DFI), which had the characteristics of lysosomes and contained organized fibrillar profiles as well, were observed in the reticuloendothelial cells in close association with the foci of new amyloid deposits. We considered the findings as evidence for the involvement of lysosomal system in amyloid fibril formation (l). In the present study, we attempted to determine the identity of the contents of the DFI by the use of antisera against the amyloid protein (AA) and an immuno-electron microscopic technique.Amyloidosis was induced in CBA/J mice by daily injections of casein (l). AA was isolated from amyloid-laden spleens by gel filtration and antibody to it was produced in rabbits (2). For immunocytochemistry, the unlabeled antibody enzyme method (3) was employed.

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Ultrastructural analysis of collagen formation in the developing primate amnion

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100158078 ◽

1990 ◽

Vol 48 (3) ◽

pp. 106-107

Author(s):

Barry F. King ◽

Grete N. Fry

Keyword(s):

Golgi Apparatus ◽

Collagen Fibril ◽

Fibril Formation ◽

Amniotic Cavity ◽

Cytological Evidence ◽

Mammalian Embryo ◽

Intracellular Location ◽

Collagen Formation ◽

Amniotic Epithelium ◽

Extraembryonic Mesoderm

The amnion surrounding the mammalian embryo consists of the amniotic epithelium facing the amniotic cavity, a layer of extraembryonic mesoderm bordering the exocoelom and an intervening layer of extracellular matrix (Fig. 1). During gestation the amnion expands remarkably to acommodate the rapidly growing embryo. In this study we have examined the process of collagen fibril formation in the developing amnion of the rhesus monkey between 20 and 60 days of gestation.Most cytological evidence of collagen fibril formation was observed in association with the extraembryonic mesodermal cells rather than the amniotic epithelium. The mesodermal cells h ad abundant cisternae of rough endoplasmic reticulum and a prominent Golgi apparatus. Elongated secretory vacuoles were associated with the Golgi apparatus and often contained parallel aggregates of fine filaments (Fig. 2). In some secretory vacuoles, periodic densities also were observed. Some striated collagen fibrils were observed in an apparent intracellular location in long, membrane-limited compartments (Fig. 3). Still other striated fibrils were observed in dense bodies, presumably lysosomes (Fig. 4).

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