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.
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ABSTRACT: The pulmonary vasculature is comprised of three anatomic compartments connected in series: the arterial tree, an extensive capillary bed, and the venular tree. Although in general this vasculature is thin-walled, structure is nonetheless complex. Contributions to structure (and thus potentially to function) from cells other than endothelial and smooth muscle cells as well as those from the extracellular matrix should be considered. This review is multifaceted, bringing together information regarding 1) classification of pulmonary vessels, 2) branching geometry in the pulmonary vascular tree, 3) a quantitative view of structure based on morphometry of the vascular wall, 4) the relationship of nerves, a variety of interstitial cells, matrix proteins, and striated myocytes to smooth muscle and endothelium in the vascular wall, 5) heterogeneity within cell populations and between vascular compartments, 6) homo- and heterotypic cell-cell junctional complexes, and 7) the relation of the pulmonary vasculature to that of airways. These issues for pulmonary vascular structure are compared, when data is available, across species from human to mouse and shrew. Data from studies utilizing vascular casting, light and electron microscopy, as well as models developed from those data, are discussed. Finally, the need for rigorous quantitative approaches to study of vascular structure in lung is highlighted.01/2012; 2(1):675-709. DOI:10.1002/cphy.c100081
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ABSTRACT: This chapter focuses on the central significance of the pulmonary endothelium in the control of pulmonary vascular tone in pulmonary development, homeostasis, and pathophysiological processes. We review the upstream stimuli known to regulate the expression and activity of endothelium-specific mediators of vascular tone. Subsequently, we focus on the known actions of the endothelium-derived vasoactive effectors most important for the balance of control of vasomotor tone – vasodilators (nitric oxide and prostacyclin) and vasoconstrictors (thromoboxane A2 and endothelin). Additional mediators that may affect pulmonary vasomotor tone and endothelium-derived hyperpolarizing factor related activity are discussed, along with more poorly characterized effectors. Finally, the complex balance of these vasoactive factors and the intersection of their downstream signaling pathways is presented in the context of prototypical in vivo physiological and pathophysiological processes in the pulmonary circulation.
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ABSTRACT: Hypoxemic respiratory failure in the term newborn is still an important cause of morbidity and mortality during the first month of extrau - terine life. The most common causes are meconium aspiration syndrome (MAS), hyaline membrane syndrome, pneumonia/sepsis and pulmonary hypoplasia with or without congenital diaphragmatic hernia. Most of these diseases can become complicated with persistent pulmonary hypertension, making their treatment difficult. The echocardiographic findings for the diagnosis of pulmonary hypertension include an elevated pressure of the pulmonary artery and extrapulmonary right -to-left shunting of blood at the foramen ovale and/or the ductus arteriosus. We made a review about prenatal growth and development of the pulmonary circulation and the differences between hypoxia and hypoxemia.