A scanning and transmission electron microscopy study of the parabronchial unit in quail (Coturnix coturnix) and town pigeons (Columba livia)

Abstract

Summary:A combined scanning electron (SEM) and transmission electron microscopy (TEM) investigation was undertaken to gain insight into the complex structural pattern of the atrial compartment and the gas exchange tissue of parabronchial units in quail and town pigeons. The aim was also to depict the changes taking place in the parabronchial unit in the late prehatching and early posthatching periods in quail. The standard SEM and TEM investigation was carried out in 13 mature quail and 8 town pigeons. The developmental study involved embryonic quail (Days 15, 16, 17), newly hatched quail, quail 24 h after hatching, and quail aged 2, 10, 19, and 25 days (3 individuals per group). The luminal relief of the parabronchus is formed by anastomosing interatrial septa delineating the atrial pits, which are thinner and shallower in pigeons. The atrial bottom opens in mature individuals into 3-6 infundibula. The extracellular material represented by trilaminar substance, which does not appear until hatching, veils the surface relief of the parabronchial epithelium, which is consequently hardly accessible to three-dimensional visualization. Only in town pigeons with fewer discontinuous layers of extracellular material was it possible to visualize the surface of the atrial epithelium, that is, of the granular and squamous atrial cells. The SEM analysis has convincingly shown the intricate spatial organization of atria, infundibula, and air and blood capillaries of the gas exchange tissue. The retinacula, that is, parallelly arranged processes of squamous respiratory cells bridging the air-capillary lumina, were evidenced by SEM and TEM. The complex structure of the avian parabronchus has been successfully demonstrated in the present SEM and TEM study.

Immunohistochemical localization of epidermal growth factor system in the lung of the Japanese quail (Coturnix coturnix japonica) during the post-hatching period

“…Atria, infundibula, and air capillaries are lined with the parabronchial epithelium that contains of granular cells, squamous atrial cells, and squamous respiratory cells (reviewed in Maina, 2006b). The morphological similarity between the granular atrial cells in bird species with type II pneumocytes of the mammalian lung has been reported (Klika et al, 1999;Scheuermann et al, 1997). Squamous atrial and squa-mous respiratory cells are not observed in the pulmonary epithelium of any other vertebrate (Scheuermann et al, 1997).…”

“…The avian lung is inherently, structurally mature and it is potentially functionally competent at hatching (Bayram and Liman, ; Klika et al, ; Maina, ). Before hatching, the parabronchi have reached their final number and position.…”

A novel chicken lung epithelial cell line: Characterization and response to low pathogenicity avian influenza virus

“…in the atria of bird lung airways (Scheuermann et al, 1997). These (Klika et al, 1999;Scheuermann et al, 2000).…”

Effect of Short-term Space Flight on Structure of Liver, Lungs, Bone and Bone arrow of Japanese Quail Hatched on Orbital Station Mir

“…Avian lungs have air capillaries instead of alveoli as in mammals; granular pneumocytes (the type II pneumocytes) and dust cells -(macrophages) are not present at the site of gaseous exchange in the air capillaries but both granular cells and macrophages are found at the level of conductive portion of lungs (Abdalla et al 1982;Klika et al 1996;Scheuermann et al 1997). Taking into account these structural and functional characteristics of avian lung (Abdalla et al 1982;Maina 1988;Klika et al 1999;Bernhard et al 2001), substantial no differences in the structure/ultrastructure of lungs between experimental and control chicks were found by LM and TEM in this experiment. Morphometry of the lungs revealed no significant difference between the lungs of control and flight chicks.…”