A study by scanning (SEM) and transmission (TEM) electron microscopy of the glomerular capillaries in developing rat kidney

Abstract

Kidneys of 2 to 10 day-old rats of Wistar and Sprague-Dawley strains were fixed with glutaraldehyde by retrograde vascular perfusion and then prepared for observation in TEM and SEM. In addition methacrylate casts of differentiating glomerular capillaries were examined by SEM. Although the glomerular vascular pattern differs from one glomerulus to another, its differentiation proceeds according to the following general plan. First the glomerular capillary splits longitudinally, finally to form 3 to 5 lobules consisting of a capillary network, sustained centrally by the mesangium. In the present study the differentiation of glomerular capillaries is described in five successive arbitrarily selected stages. At Stage I a capilllary loop penetrates between the lower limb and the middle segment of the S-shaped body, the rudimentary nephron. At Stage II the capillary undergoes a first subdivision, establishing the primitive lobulation of the glomerulus. At Stage III the vascular and urinary poles differentiate. At Stage IV the glomerulus assumes the aspect of a spherical body, and the capillaries in each lobule undergo subdivision. In Stage V the glomerular vascular pattern approaches its adult appearance, although the maturation processes continue for an extended period of time. Hence in the 10 day-old rat the best-differentiated glomeruli are half the size of adult glomeruli, and their capillary loops are proportionally less well-developed. The capillaries of adjacent lobules may communicate with each other, but a direct vascular shunt between the afferent and efferent vessels cannot be demonstrated.

Renal microvasculature of the rainbow trout, Salmo gairdneri: Scanning electron microscopy of corrosion casts of glomeruli

“…Teleosts show renal growth and glomerulogenesis as body weight increases (Nash, 1931;Ford, 19581, and hence small simple glomeruli are likely to be recently formed, while the larger more complex glomeruli of three or four lobules are fully developed. A similar pattern of development has been noted in postmetamorphous and adult bullfrog kidney (Naito, 1984); and in the neonatal rat, during the first few days after birth, glomeruli increase in complexity and the number of lobules (Kazimierczak, 1980). In this study the major concern was the microvasculature associated with the glomeruli.…”

“…In trout, as in other species, the glomerular capillaries tend to form lobules. Inter-and intralobular anastomoses between capillary loops of the glomerulus have been described (Rouiller, 1969;Shea, 1979;Kazimierczak, 1980;Naito, 1984), and there is now evidence that the glomerular capillary network is nonplanar (Wahl et al, 1984). Microdissection and repeated SEM of glomerular casts at various stages of dissection (Murakami et al, 1971;Murakami, 1971), and glomerular reconstructions mang and Morrison, 1980) do, however, suggest that in the rat, glomerular lobules are more or less functionally independent.…”

The elasmobranch renal corpuscle: Fine structure of Bowman's capsule and the glomerular capillary wall

“…The endothelial cells of these latter capillaries are initially relatively thick and devoid of pores; later, the thickness of the cells decreases and the number of pores gradually increases until the cells are similar to the endothelium of the adult (Bergelin and Karlsson, 1975;Reeves et al, 1978;Reeves and Farquhar, 1982;Schaeverbeke and Cheignon, 1980;Kazimierczak, 1980). Larsson and Maunsbach (1982) reported an increase of about 600 times the number of pores from stage I11 (filtering glomerular anlagen containing few capillary loops) to the adult.…”

Effects of maternal bilateral ureteral ligation on fetal development of kidney in rats: Morphometrical changes in glomerular components

“…This idea is supported by several lines of evidence as follows. Kazimierczak (1980) has shown that in the development of the kidney in newborn rat, the epithelial part of the nephron is formed by metanephric blastema; Endothelial cells form from angioblasts in early stage, indicating that the origin of glomerular epithelium is quite different from that of glomerular capillary. Bernstein et al (1981) reported that in metanephric culture, the maturation of visceral epithelial cells is performed without capillary ingrowth.…”