The administration of vita-min D(3) to rachitic chicks induces in intestinal mucosal tissue the formation or elaboration of a calcium-binding factor which is found in the supernatant of the mucosal homogenate. The enhanced binding of Ca by the "vitanmin D" supernatant (in contrast to "rachitic" supernatant) was indicated by a slower rate of diffusion of Ca(45) across a cellophane dialyzing membrane and by a lesser amount of Ca(45) being bound to an ion-exchange resin (Chelex-100) in the presence of vitamiiin D(3) supernatant. The binding activity was only associated with the protein fraction from a Sephadex G-25 column and was destroyed by trypsin digestion. This and other evidence suggest that the soluble factor is a protein. The vitamin D(3)-enhanced duodenal absorption of Ca(47) in rachitic chicks occurred almost simultaneously with the appearance of the vitamin D(3)-induced factor, and there was good correlation between the concentration of binding factor and the rate of absorption of Ca(47).
Hydrogen peroxide and heat are two components of a technique commonly used to bleach human teeth. The effects of these two components on pulp tissue of dog teeth were evaluated histologically. Hydrogen peroxide alone or with heat caused obliteration of odontoblasts, hemorrhage, resorption, and inflammatory infiltration, while heat alone was not detrimental. Pulpal changes demonstrated evidence of reversibility after 60 d.
Vitamin D-dependent calcium-binding protein (CaBP) was localized in tissue sections of kidneys from rabbits, rats, and chicks using antiserum specific for chick intestinal CaBP. In rabbit kidney, CaBP was present in all cells of the distal convoluted tubule and most cells of the connecting tubule. Fewer, but still a majority, of the cells of cortical collecting ducts contained CaBP. The intensity of immunochemical staining and the number of stained cells decreased markedly in medullary collecting ducts, and only a few collecting duct cells contained CaBP at the junction of the inner and outer medulla. In the rat kidney, CaBP was present in all distal convoluted tubule cells, but the immunochemical staining was less intense than in the rabbit. The protein also was found in most connecting tubule cells of the rat; however, only a few collecting duct cells in the superficial corte of the rat contained CaBP. CaBP was essentially absent from mid- to deep-cortical collecting duct cells, while a very few collecting duct cells always contained CaBP at the junction of the inner and outer stripes of the outer medulla. In the chick, CaBP was present in distal convoluted tubule cells as the distal convoluted tubule coursed adjacent to the central vein. CaBP was absent from chick collecting duct cells. In all three species CaBP was not detected in the other portions of the nephron.
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