From 133 to 615 glomeruli were examined in sections of kidneys from each of 60 animals, representing six rodent models of proteinuria. Particular attention was paid to the position of segmental lesions. Lewis rats given sheep anti-rat glomerular basement membrane antibodies had lesions almost exclusively at the glomerulo-tubular junction. Wistar rats on a diet of 24 per cent casein or with subtotal nephrectomy and a diet of 24 per cent soya had lesions mainly at the hilum. Wistar rats given bovine serum albumin had global lesions but virtually no segmental lesions. Wistar rats given puromycin aminonucleoside had lesions at the glomerulo-tubular junction and global mesangial abnormalities shortly after the treatment but later developed segmental lesions at all parts of the glomerulus. Untreated BUF/Mna rats had lesions at the glomerulo-tubular junction early in life but later had lesions at all parts of the glomerulus. Untreated NZB/NZW hybrid mice had various types of glomerulonephritis and also had lesions at the glomerulo-tubular junction. These findings showed that (1) segmental lesions at the glomerulo-tubular junction, or glomerular tip, occur in experimental animals, a fact not previously reported, and these tip changes are a common feature in several different models of proteinuria; (2) hilar segmental lesions are seen in conditions with hyperfiltration of protein; and (3) segmental lesions at various parts of the glomerulus are seen in some models of proteinuria and probably indicate late effects of random toxic damage to the glomerulus. Thus, there are at least three different types of segmental glomerular lesions in experimental animals--tip, hilar, and random--with different morphology and pathogenesis. It is likely that these findings can be extended to human renal diseases with segmental glomerular lesions. This will help to clarify the controversial and unsatisfactory term focal segmental glomerulosclerosis.

As measurement of absolute glomerular size is difficult we developed a method of assessing glomerular size that was simple and practical and could be used to compare the kidneys in different groups of patients. Using a semi-automatic image analyser, the cross-sectional area of 100 randomly-selected glomeruli, outlined by Bowman's capsule, was measured on sections of kidneys taken at necropsy. The mean of the logarithms of the largest 25 areas was calculated. The method was applied to compare control kidneys (53) with the kidneys in acromegalics (20), in patients with one kidney (10) and in patients with asymmetrical kidneys (12). Kidneys were heavier in the three test groups than in controls. Glomerular sizes were similar in controls and in acromegalics but were larger in single and disparate kidneys. There was a relationship between glomerular size and kidney weight within the control group and across the four groups taken together. This only partly accounted for the observed differences in glomerular size between the groups. Histological comparison of the acromegalic and single kidneys showed more global glomerulosclerosis in single kidneys and also segmental lesions, mainly at the glomerular hilum, only in the single kidneys. These findings show that renal enlargement occurs in acromegaly and in single and disparate kidneys but is accompanied by markedly different glomerular features. This implies different mechanisms for the renal enlargement. The method of assessing glomerular size is useful in the study of these and other conditions affecting the kidney.

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mRNA coding for pre-pro-PTH, a precursor of PTH, was sought in an apparently nonfunctioning parathyroid carcinoma that had transformed from one that was previously functioning. Total poly(A+) RNA was prepared by phenol-chloroform-isoamyl alcohol extraction and oligo-dT-cellulose affinity chromatography from the tumor tissue and bovine parathyroid glands. In the rabbit reticulocyte lysate cell-free translation system, total poly(A+) RNA from the tumor as well as that from bovine parathyroid glands directed the translation of a product which was specifically precipitated by an anti-PTH serum and which migrated at the same position as pre-pro-PTH on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results indicated the presence of mRNA coding for pre-pro-PTH (PTH mRNA) in an apparently nonfunctioning parathyroid carcinoma, suggesting that PTH synthesis is not always absent in parathyroid carcinomas which are not accompanied by hyperparathyroidism.