The elastic fiber. I. The separation and partial characterization of its macromolecular components

Chronic actinic keratopathy--a condition associated with conjunctival elastosis (pingueculae) and typified by characteristic extracellular concretions

Morphologic observations on a peculiar type of corneal reaction with a predisposition for the superficial stroma of the interpalpebral portion of the cornea are reviewed. Histochemical evidence is provided which indicates that the corneal concretions, though not homogenous, are proteinaceous in nature and contain amino acids not normally detectable in the cornea. The corneal concretions were associated with conjunctival elastosis (pingueculae) in all 22 instances in which the eyes were sectioned in the horizontal plane. Identical concretions were identified within these associated pingueculae, as well as in a large percentage of other pingueculae and cutaneous lesions with actinic elastosis. The findings suggest that the abnormal material arises in the pericorneal conjunctival connective tissue from whence it diffuses into, and deposits in, the superficial corneal stroma. The data also raise the possibility that the concretions may be derived, at least in part, from altered elastic tissue. Morphologic and epidemiologic observations on the condition taken together strongly suggest that this unique reaction is a sequel to the cumulative effect of chronic actinic irradiation. Further observations on this keratopathy are needed to establish whether this unique response can be provoked by other noxious stimuli.

The subendothelium and thrombogenesis

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Elastogenesis in the developing chick lung: a light and electron microscopical study

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Contact-inhibited revertant cell lines isolated from SV40-transformed cells. II. Ultrastructural study

The ultrastructural appearances of normal 3T3, SV40-transformed 3T3 (SV-3T3), and F1A revertant cell lines are compared. Both confluent and subconfluent cultures are described after in situ embedding of the cells for electron microscopy. There is striking nuclear pleomorphism in F1A revertant cells, with many cells having large nuclei compared to the less variable nuclear morphology of both normal 3T3 and SV-3T3 cells. Under the culture conditions used, deep infoldings of the nuclear envelope are prominent in growing cells, e.g., subconfluent normal 3T3 and confluent SV-3T3 cells. Such infoldings are infrequently seen in cultures which display contact inhibition of growth, e.g., normal 3T3 or F1A revertant cells grown just to confluence. In confluent cultures, the cytoplasmic organelles in revertant cells closely resemble those of normal 3T3 cells. In both normal and revertant cells in confluent culture, the peripheral cytoplasm (ectoplasm) has many 70 A filaments (alpha filaments), which are frequently aggregated into bundles. Alpha filaments are also abundant in the ectoplasm near regions of cell-to-cell apposition and in the motile cell processes (filopodia). The abundance and state of aggregation of alpha filaments correlates with contact inhibition of movement and growth in these cell lines since fewer bundles of alpha filaments are seen in growing cells than in contact-inhibited cells. This observation suggests that these filaments may be an important secondary component in the regulation of contact inhibition of movement and, possibly, of growth in normal and revertant cells.

The smooth muscle cell. II. Growth of smooth muscle in culture and formation of elastic fibers

Smooth muscle derived from the inner media and intima of immature guinea pig aorta were grown for up to 8 wk in cell culture. The cells maintained the morphology of smooth muscle at all phases of their growth in culture. After growing to confluency, they grew in multiple overlapping layers. By 4 wk in culture, microfibrils (110 A) appeared within the spaces between the layers of cells. Basement membrane-like material also appeared adjacent to the cells. Analysis of the microfibrils showed that they have an amino acid composition similar to that of the microfibrillar protein of the intact elastic fiber. These investigations coupled with the radioautographic observations of the ability of aortic smooth muscle to synthesize and secrete extracellular proteins demonstrate that this cell is a connective tissue synthetic cell.

The smooth muscle cell. I. In vivo synthesis of connective tissue proteins

These studies have examined the ability of smooth muscle cells from developing aorta of the prepubertal rat to utilize amino acids in the synthesis and secretion of connective tissue proteins. Prepubertal rats, previously given either an alcohol carrier or estradiol-17-beta, were each given an intravenous injection of proline-(3)H. The animals were sacrificed after 15 and 30 min, and 4 hr. Light and electron microscope radioautographs of the aortic smooth muscle and of the myometrial cells demonstrated that the aortic cells, in both groups of animals, and the myometrial cells, in the estrogen-stimulated animals, took up the proline and rapidly secreted it in both collagen and elastic fibers within 4 hr. In contrast, the myometrial cells of the nonstimulated animal took up relatively small amounts of proline and retained most of the amino acid within the cells. Electron microscope radioautographs demonstrated that the organelles involved in this activity were the rough endoplasmic reticulum and Golgi complex together with peripheral elements, presumed to be small vesicles. These studies have demonstrated that the smooth muscle cells of the developing aorta and of the estrogen-stimulated myometrium have a capacity to synthesize and secrete proteins associated with the extracellular connective tissue matrix.

Behavior of smooth muscle cells and formation of extracellular structures in the reaction of arterial walls to injury

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Platelet adhesion to subendothelial components in experimental aortic injury. Role of fine fibrils and basement membrane

The intact intima of the rabbit abdominal aorta contained a well-defined, fairly continuous endothelial basement membrane and a network fo fine fibrils, which branched from both sides of the basement membrane. Partial ligation of the abdominal aorta of the rabbit resulted in endothelial desquamation, but left a layer of subendothelial fine fibrils and occasionally, segments of endothelial basement membrane. Platelets adhered to exposed fine fibrils including those extending from basement membrane fragments. Adhesion to occasionally exposed collagen fibres occurred but there was no direct adhesion to exposed internal elastic lamina or elastin fragments, for these elements were always covered by a thin layer of fine fibrils.