Normal adaptation of pulmonary arterial intima to extrauterine life in the pig: Ultrastructural studies
ABSTRACT Adaptation of the pulmonary arterial intima was studied in injected lung specimens of 34 Large White pigs. Each type of pre- and intra-acinar artery was studied separately using transmission and scanning electron microscopy. Determination of the endothelial surface/volume ratio and volume densities of (1) endothelium and subendothelium. (2) endothelial cytoplasmic organelles and (3) subendothelial connective tissue elements yielded 6832 measurements which comprised a computerized database. At birth, endothelial cell morphology changed more rapidly and to a greater extent in peripheral than in proximal arteries. Endothelial surface/volume ratio increased (p < 0.0001). Fetal surface projections, junctional interdigitations and overlap became less evident. Adaptational changes were complete in three weeks. Between three weeks and adulthood a reduction in endothelial surface/volume ratio suggested cell growth. In the subendothelium the volume density of collagen and basement membrane and elastin increased (p<0.001). The internal elastic lamina, immature in all arteries at birth increased in thickness and integrity until in the adult, only in small muscular arteries did gaps between elastin profiles ensure frequent contact between endothelial and smooth muscle cells. At all ages regional differences in endothelial cell morphology were evident.
Article: The connective tissue of lung.The American review of respiratory disease 12/1975; 112(5):657-711. · 10.19 Impact Factor
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ABSTRACT: Endothelial cells isolated from bovine aorta synthesize and secrete type III procollagen in culture. The procollagen, which represents the major collagenous protein in culture medium, was specifically precipitated by antibodies to bovine type III procollagen and was purified by diethyl-aminoethylcellulose chromatography. Unequivocal identification of the pepsin-treated collagen was made by direct comparison with type III collagen isolated by pepsin digestion of bovine skin, utilizing peptide cleavage patterns generated by vertebrate collagenase, CNBr, and mast cell protease. The type III collagen was hydroxylated to a high degree, having a hydroxyproline/proline ratio of 1.5:1.0. Pulse-chase studies indicated that the procollagen was not processed to procollagen intermediates or to collagen. Pepsin treatment of cell layers, followed by salt fractionation at acidic and neutral pH, produced several components which were sensitive to bacterial collagenase and which comigrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with alpha A, alpha B, and type IV collagen chains purified from human placenta by similar techniques. Bovine aortic endothelial cells also secreted fibronectin and a bacterial collagenase-insensitive glycoprotein which, after reduction, had a molecular weight of 135,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (using procollagen molecular weight standards) and which was not precipitable by antibodies to cold-insoluble globulin or to alpha 2-macroglobulin. Collagen biosynthesis by these cells provides an interesting model system for studying the polarity of protein secretion and the attachment of cells to an extracellular matrix. The presence of type III collagen in the subendothelium and the specific interaction of this protein with fibronectin and platelets suggest the involvement of this collagen in thrombus formation following endothelial cell injury.Biochemistry 12/1979; 18(24):5433-42. · 3.38 Impact Factor
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ABSTRACT: Small vascular units consisting of an arteriole, its capillaries, and the emerging venule (ACV units) were identified in the rat omentum and mesentery. They were fixed in situ and processed for electron microscopy either as whole units or as dissected segments. Systematic examination of the latter (in thin sections, as well as in freeze-cleaved preparations) showed that the intercellular junctions of the vascular endothelium vary characteristically from one segment to another in the microvasculature. In arterioles, the endothelium has continuous and elaborate tight junctions with interpolated large gap junctions. The capillary endothelium is provided with tight junctions formed by either branching or staggered strands; gap junctions are absent at this level. The pericytic venules exhibit loosely organized endothelial junctions with discontinuous low-profile ridges and grooves, usually devoid of particles. No gap junctions were found in these vessels. The endothelium of muscular venules has the same type of junctions (discontinuous ridges and grooves of low profile); in addition, it displays isolated gap junctions of smaller size and lower frequency than in arterioles. The term communicating junction (macula communicans) is proposed as a substitute for gap junctions, since the latter is inappropriate, in general, and confusing in the special case of the vascular endothelium.The Journal of Cell Biology 01/1976; 67(3):863-85. · 10.82 Impact Factor