Abstract Propylthiouracil (6‐propyl‐2‐thiouracil), an anti‐thyroid agent, was fed to mice in a concentration equal to 0.1% of their diet for periods of 10 and 15 weeks. The cells of the inner zone of the adrenal cortex were examined with the electron microscope. In animals receiving propylthiouracil for ten weeks mitochondria were altered and the smooth endoplasmic reticulum (SER) showed a marked focal proliferation. In contrast to control animals rough endoplasmic reticulum was abundant and was frequently associated with the hyperplastic SER. After 15 weeks these alterations were no longer present but had been replaced by a spectrum of “brown degeneration.” The less affected cells were characterized by increased numbers of liposomes and lysosomes and the more affected cells by liposomal and mitochondrial degeneration. These observations emphasize that “brown degeneration” is a true degenerative process and not a spontaneous proliferation of ceroid pigment. It is suggested that the changes described may be directly related to an alteration in cholesterol metabolism.
AbstractWeight gain is associated with an expanded renal medullary interstitium in humans and in animal models of obesity. In this study, the consequence of obesity and this expanded matrix on renal papillary structure was examined in 15 obese rabbits fed a high fat diet for 8-12 weeks compared to 21 rabbits fed a standard diet. When examined under a dissecting microscope, the tips of the renal papillae from formalin-fixed, methylene blue-stained kidneys showed patent ducts of Bellini in 5 of 5 instances from 2 lean rabbits, but in only 2 out of 12 ducts from 3 obese rabbits. The ostia of the remaining ducts were significantly distended (205+/- 42 mum versus 56+/- 8 mum) and occupied by lightly staining granular material. When examined with scanning electron microscopy, all ducts were patent in lean rabbits (6 ducts in 4 rabbits, averaging 104+/- 12 mum across), whereas only 6 of 11 ducts were patent in papillae from 4 obese rabbits. Renal medullary parenchymal tissue appeared at the openings of the remaining 5 ducts of Bellini in the 4 rabbits. Not only were these 5 ducts significantly distended by the interstitial material (with openings averaging 248+/- 56 mum across), but the associated collecting ducts were dilated relative to control (100+/- 15 mum versus 75 +/- 7 mum). Since the ducts of Bellini are the only renal openings that are not corsetted by a fibrous capsule, the authors speculate that the expanded medullary interstitium and increased renal sinus lipid partially obstruct renal outflow and elevate renal interstitial hydrostatic pressure in obesity, causing a prolapse of parenchymal contents, further obstructing urine outflow and leading to distention of the collecting ducts and ducts of Bellini.KeywordsCollecting Ducts Ducts Bellini Hypertension Kidney Obesity Rabbit
Abstract The effects of thyroxine and ACTH on the ultrastructure of cells of the adrenal zona fasciculata were studied by morphometric analysis and compared by two‐way analysis of variance. The results indicate that the effects of thyroxine and ACTH are different and independent. The statistically significant differences in effect of thyroxine and ACTH are: thyroxine causes an increase in the volume fraction of mitochondria and a decrease in the volume fraction of endoplasmic reticulum independent of ACTH; thyroxine causes a decrease in surface density of mitochondria and endoplasmic reticulum in the absence of ACTH, but in the presence of ACTH this effect is moderated by an interaction of thyroxine and ACTH. There were no statistically significant effects of either thyroxine or ACTH on volume fraction or surface density of liposomes.
