Intussusceptive microvascular growth in the lung of larval Xenopus laevis Daudin: a light microscope, transmission electron microscope and SEM study of microvascular corrosion casts

Abstract

The remodeling of the uniform wide, plexus-like capillary bed of the lung of metamorphosing tadpoles of the South African clawed toad Xenopus laevis (Daudin) is studied from developmental stages 54 to 65 by scanning electron microscopy (SEM) of microvascular corrosion casts (VCCs), light microscopy (LM) and transmission electron microscopy (TEM). VCCs reveal that the remodeling of the existing uniform, plexus-like lung capillary bed into well-defined alveolar capillary meshworks starts in the caudal lung and then gradually proceeds cranially. Vascular remodeling is entirely by intussusceptive microvascular growth through insertion and enlargement of new and fusion of pre-existing capillary meshes. Analyses of lung tissue serial sections at the LM and TEM level confirm the presence of intracapillary cushions and tissue posts and correlate these structures in respect of size and location to the round to slit-like imprints and tiny "holes" found in VCCs. Additionally, SEM of VCCs give clear evidence that intussusceptive microvascular growth is also involved in the remodeling and maturation of alveolar arterioles and venules.

The subpleural pulmonary microvasculature in newborn yak (Bos grunniens)

“…Caduff observed the minute holes (about 1 μm) in the pulmonary microvasculature in 7 to 13 days old mice, implying that the holes might enlarge and form the new capillary network (Caduff et al 1986). Bartel also found the small holes in larval Xenopus laevis and hypothesized that these holes were related to the capillary fusions and new capillary network forming (Bartel and Lametschwandtner 2000). Therefore, our results suggested the subpleural capillary network was immature in newborn yak, consequently the sheetlike network would be changed into the weblike network with ages.…”

“…Arrow (↑) shows the imprint of endothelial nuclei on the cast of capillary. (2,500×,bar=10 μm) occurred in the vascular network in the postnatal mice and larval Xenopus laevis (Caduff et al 1986;Bartel and Lametschwandtner 2000). The sheetlike network would develop gradually to the weblike network with ages.…”

“…The pulmonary microvasculature has been thoroughly explored in the adult animals of amphibians (Bartel and Lametschwandtner 2000), reptiles (Yu 1997a), birds (West et al 1977;Fujii et al 1981;Nasu 2005;Yu et al 2006) and mammals (Kendall and Eissmann 1980;Ohtani 1980;Guntheroth et al 1982;Du et al 2006). A few studies have been done on the pulmonary microvascular architecture of new born animals, for example, Xenopus laevis (Bartel and Lametschwandtner 2000), rat (Caduff et al 1986;Burri and Tarek 1990), and human (Motta et al 1992).…”

“…A few studies have been done on the pulmonary microvascular architecture of new born animals, for example, Xenopus laevis (Bartel and Lametschwandtner 2000), rat (Caduff et al 1986;Burri and Tarek 1990), and human (Motta et al 1992). Anyhow, the detailed features of the pulmonary microvasculature on yak keep unknown, especially those of postnatal yak.…”

Correlating Micro-CT Imaging with Quantitative Histology

“…The Mercox II system combines excellent permeability through the entire vascular bed, excellent infiltration properties, short time of preparation and polymerization, minimal shrinkage and high chemical resistance. Although its price is rather high, it is a method of choice for the vascular corrosion casts (Bartel & Lametschwandtner, 2000;Minnich et al, 2002;Lametschwandtner et al, 2004;Kachlik & Baca, 2006, Kachlík & Hoch, 2008.…”