Microdissection studies of the structural alterations induced in rat kidneys by experimental postischemic acute renal failure.

A unique opportunity presented itself for a morphologic study of experimental unilateral acute renal failure (ARF) in male rats. The ARF had been induced in the rats by temporary occlusion (1h) of the left renal artery. Twenty-nine rats were divided into subsets as follows: 2-3 h, 24 h, 1 week, 2, 4, 8, and 12 weeks following release of occlusion. Microdissection showed a heterogeneous population of abnormally structured proximal tubules in which the regressive lesions of tubular necrosis were combined with the progressive reaction of repair. The lesions demonstrated are reminiscent of those which have been described in ARF in the human and in experimental animals. Many proximal tubules in the 2- to 3-hour subset presented 1-3 disruptive lesions (DLs) while greater numbers of proximal tubules from the 24-hour group presented 1-5 DLs. Many proximal tubules presented no DLs, but nearly all from the 24-hour subset (97-100%) displayed a squamate appearance which paralleled and was caused by acute tubular necrosis. At 1 week, a dilated pars recta was common, but by this time, the squamate pattern had disappeared. Many casts were present. At 2 weeks, many fewer casts were present in proximal tubules and none were seen at 4, 8 or 12 weeks. The nephrons, particularly the proximal tubules, presented a variety of structural alterations at 2, 4, 8 and 12 weeks. Changes of special interest include (1) the presence of swan-necks; (2) a distinctive squamate appearance of the proximal tubules in the animals killed at 24 h; (3) a spiral, curled appearance caused by differential hyperplasia in animals at 4, 8 and 12 weeks, and (4) a tendency for ischemic lesions to involve all layers of the renal cortex.

Hydrocortisone-induced cystic metanephric maldevelopment in serum-free organ culture.

To investigate the basic pathophysiology of renal cystic maldevelopment, the production of renal cysts was studied in a newly developed murine metanephric organ culture system. In this isolated, nonvascularized system, the addition of hydrocortisone (1.4 X 10(-5) M) to completely characterized, serum-free growth medium produced striking tubular cystic abnormalities. As nephron obstruction did not occur in the nonperfused organ culture system in which neither glomerular filtration nor urine flow were present, the model experimentally isolated the roles of tubular cell metabolism and tubular wall extracellular matrix development in the production of cystic alterations. Analysis with the techniques of intact nephron microdissection and light and electron microscopy demonstrated that organ culture cysts developed in proximal tubules amid a normal background of organotypic tubular differentiation and glomerular epithelial development. Frank cystic development in the system was regularly preceded by ultrastructural alterations in and around the walls of differentiating proximal tubules. Such changes consisted of basolateral intercellular spreading which increased with progressive tubular dilation and irregular thickening and lamellation of tubular basal laminae. The ultrastructural features of the model suggest roles for hydrocortisone-induced alterations in both tubular transport processes and basal lamina structure in the experimental production of cysts. We conclude that the production of cystic changes in organ culture by hydrocortisone permits highly controlled study of the roles of altered tubular cell and basal lamina metabolism in the pathogenesis of cystic metanephric maldevelopment.

Polycystic kidney and liver disease in Springbok: I. Morphology of the lesions.

Spontaneous polycystic kidney and liver disease in an inbred herd of Springbok (Antidorcas marsupialis) was studied by light microscopy, transmission electron microscopy, and microdissection. Springbok are a small species of gazelle of the family Bovidae native to South Africa. Since 1976, 18% of all live calves born have had nephromegaly and died within 2 weeks of birth. Examination of kidney and liver from ten calves which had died or were sacrifices since 1978 revealed bilateral, symmetrical nephromegaly due to moderate to marked focal dilatation of tubules predominately in the outer zone of the medulla. Microdissection of renal tissue from three affected calves indicated polycystic kidneys had cysts in all of the bends of Henle's loops, over half of the ascending limbs, and about one fourth of the collecting ducts. All of these calves had proliferation and cystic dilatation of bile ducts in most hepatic portal areas. The bile ducts were irregularly dilated and confluent with only a slight increase in periductular connective tissue. Ultrastructural studies revealed no consistent changes in the basement membranes of either the renal or hepatic cysts. This disease has several features similar to the autosomal recessive form of polycystic kidney disease in man and may prove a useful animal model.

Structural changes of experimental glomerulonephritis in rats as revealed by microdissection.

Microdissection revealed striking alterations in the nephrons of animal models AICN and anti-GBMN. The most severely damaged AICN kidney in the series presented marked heterogeneity in the size and deformity of the proximal tubules, corresponding to the diverse and variegated nephrons described by Oliver in chronic Bright's disease. The severely damaged anti-GBMN kidneys revealed widespread alterations in the proximal tubules, which, however, tended to be fairly uniform among the affected nephrons. This uniformity, perhaps, reflected the shorter duration of disease in the anti-GBMN animals. The most characteristic proximal tubular alteration in either the AICN or anti-GBMN animals was that combining atrophy of the pars convoluta and hypertrophy of the pars recta in same tubule. The largest and smallest nephrons encountered in the entire study were found in the most severly damaged kidney in the AICN. This finding reflected the simultaneous existence of regressive and progressive changes in this kidney, as certain nephrons underwent hypertrophy to compensate for the atrophy and disappearance of others. The remarkable functional glomerulotubular balance of single nephrons known to exist in both AICN and anti-GBMN was matched by the evidence presented here of structural glomerulotubular balance among the severely altered nephrons of a representative kidney from each group. Microdissection studies directed toward the characterization of the nephronic alterations in both membranous glomerulonephritis and proliferative glomerulonephritis of man should be of interest in relation to the findings in these experimental rat models of human disease.