Vitamin D: two dihydroxylated metabolites are required for normal chicken egg hatchability

When hens are raised to sexual maturity from hatching with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] as their sole source of cholecalciferol (vitamin D3), fertile eggs appear to develop normally but fail to hatch. When hens receive a combination of 1,25(OH)2D3 and 24R,25-dihydroxyvitamin D3 [24,25(OH)2D3], hatchability equivalent to that with hens given vitamin D3 is obtained. These results suggest a biological role for 24,25(OH)2D3 not previously recognized.

1alpha,25-dihydroxyvitamin D3-like component present in the plant Solanum glaucophyllum

The ability of an aqueous extract prepared from dried leaves of the South American shrub Solanum glaucophyllum to interact with a chick intestinal receptor system highly specific for the biologically active form of vitamin D, 1alpha, 25-dihydroxyvitamin D3 (1alpha,25-(OH)2D3), was monitored under both in vivo and in vitro conditions. The pretreatment of chicks with the S. glaucophyllum extract reduced the amount of subsequently administered radioactive 1alpha, 25-dihydroxyvitamin D3 localized in the intestinal chromatin fraction by 90% when compared with vitamin D-deficient controls. In addition, the active principle in the aqueous extract was found to compete effectively with 1alpha, 25-(OH)2D3 in a reconstituted intestinal receptor system in vitro. The plant factor(s) was found to be as effective as 1alpha, 25-(OH)2D3 in decreasing the renal 25-hydroxycholecalciferol-1alpha hydroxylase activity levels when administered to vitamin D-deficient chicks. By means of the in vitro intestinal receptor assay, it was possible to estimate that there are approximately 10 to 60 mg of the biologically active material in one kilogram of dries S. glaucophyllum leaves. These data indicate that the plant factor(s) may be a structural analog of 1alpha, 25-(OH)2D3 and suggest the feasibility of its isolation.

Biological activity of 24,25-dihydroxycholecalciferol in chicks and rats

The ability of 24R, 25- and 24S, 25-dihydroxycholecalciferol to stimulate intestinal calcium transport and bone calcium mobilization in chicks was measured. Enhancement of intestinal calcium transport by 325 or 130 nmoles of either compound was maximal by 24 hours. The effects of these compounds on bone calcium mobilization were also maximal by 24 to 36 hours. When lower doses were tested, 2 nmoles of the 24R, 25-dihydroxycholecalciferol significantly stimulated intestinal calcium transport, whereas 130 nmoles of the S isomer were required for a significant response. Neither steroid had a significant effect on bone calcium mobilization when doses of less than 130 nmoles were given. When chicks received orally 32.5, 325 or 1,625 pmoles of 24R, 25-dihydroxycholecalciferol daily from hatching for 4 weeks, several parameters showed a dose-related response. These included growth, serum calcium, bone ash, renal 25-hydroxycholecalciferol-1-hydroxylase and intestinal vitamin D-dependent calcium binding protein. Rats given 32.5 to 1,625 pmoles of 24R, 25-dihydroxycholecalciferol for 3 or 6 weeks were equivalent to vitamin D-treated controls in terms of growth and serum calcium levels. It is concluded that within the lower dose ranges (2 to 30 pmoles) the R isomer of 24,25-dihydroxycholecalciferol is more active in stimulating intestinal calcium transport than the S isomer but that neither compound increases bone calcium mobilization at these dose levels. Also, the rat is more responsive in terms of growth and serum calcium, to small dialy doses of 24R, 25-dihydroxycholecalciferol than is the chick.

Radiographic cephalometric method of assessment of craniofacial growth in monkeys

A method for reorientation of a monkey in a cephalostat was refined and the accuracy of the procedure was determined.