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  • 1
    Electronic Resource
    Electronic Resource
    Effect of 1,25-dihydroxyvitamin D3 on osteopenia induced by prednisolone in adult rats (1982)
    Springer
    Calcified tissue international 34 (1982), S. 253-257 
    Details
    ISSN: 1432-0827
    Keywords: Prednisolone ; Calcium ; Bone ; Corticoid osteopenia ; Vitamin D metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Adult male rats were fed a diet containing 0.15% calcium, 0.3% phosphorus, and either 100, 50, or 20 mg of prednisolone per kg of diet. All these levels of prednisolone led to osteopenia, decreased intestinal absorption of calcium, slightly lower serum calcium and phosphorus, and a decreased level of serum 1,25-dihydroxyvitamin D3. Exogenous parenteral 1,25-dihydroxyvitamin D3 corrected steroid-induced changes in serum calcium and phosphorus, but could not completely correct the low intestinal calcium transport; nor did it prevent the development of osteopenia. The prednisolone-induced osteopenia seems at least in part to be caused by impaired intestinal calcium transport. The impaired calcium transport may be the result of low levels of 1,25-dihydroxyvitamin D3 and a direct effect of presnisolone on the intestine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411246
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of 1,25(OH)2D3 on bone tissue in the rabbit: Studies on fracture healing, disuse osteoporosis, and prednisone osteoporosis (1984)
    Springer
    Calcified tissue international 36 (1984), S. 591-595 
    Details
    ISSN: 1432-0827
    Keywords: Fracture ; (Glucocorticoid ; 1,25(OH)2D3 ; Osteoporosis ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A closed tibial fracture, which was controlled by an intramedullary stainless steel pin, was created in 16 rabbits. Eight rabbits were treated with 75 ng of 1,25(OH)2D3 daily as subcutaneous (s.c.) injections. After three weeks, the fractured tibia resisted a force of 101,7±21.0 Newtons in the control group and 57.3±8.0 Newtons in animals given 1,25(OH)2D3 (m±SE,P〈0.05). In another group of eight rabbits, the left hindleg was immobilized in a plastic splint. Four rabbits were given 75 ng of 1,25(OH)2D3/day s.c. and the effect of immobilization was studied on the calcaneus. Bone ash/cm3 of the calcaneus on the immobilized side was decreased by 11±2% in control rabbits and by 20±2% in the group treated with 1,25(OH)2D3 indicating a more advanced immobilization osteoporosis (m±SE,P〈0.05), which was also demonstrated by studies of bone density. Eighteen rabbits were used in a study of the effects of 1,25(OH)2D3 on the development of prednisolone osteoporosis. The dose of prednisolone was 2.5 mg per day, given by the oral route. After four months, the density of the femur was 1.53±0.02 g/cm2 in control rabbits and 1.42±0.01 in prednisolonetreated animals (P〈0.01). In rabbits additionally given 1,25(OH)2D3, the mean value for bone density was further lowered (n.s.). It appears that 1,25(OH)2D3 exaggerates disuse osteoporosis and prednisolone osteoporosis and impairs fracture healing in rabbits. These results differ from what has been shown earlier with 1,25(OH)2D3 treatment in the rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405372
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  • 3
    Electronic Resource
    Electronic Resource
    Oral 1,25(OH)2D3: An effective prophylactic treatment for glucocorticoid osteopenia in rats (1983)
    Springer
    Calcified tissue international 35 (1983), S. 107-110 
    Details
    ISSN: 1432-0827
    Keywords: Calcium ; Glucocorticoid ; Vitamin D ; Osteoporosis ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Eighty-eight adult male Sprague-Dawley rats were given a diet with either (a) 0.5% Ca and 0.6% P or (b) 0.01% Ca and 0.6% P. Osteopenia was created by adding prednisolone to the diet. The prophylactic effect of oral 1,25(OH)2D3 on the osteopenia was studied. It was found that prednisolone osteopenia in the rat was associated with defective Ca absorption. By giving an oral dose of 1,25(OH)2D3, it was possible to maintain normal Ca absorption during prednisolone treatment and to prevent the bone loss. No significant hypercalcemia or any kidney calcifications were seen. These results are in contrast to earlier findings, in which subcutaneous administration of 1,25(OH)2D3 failed to prevent prednisolone osteopenia because of its tendency to increase bone resorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405014
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of Vitamin D Receptor Genotypes on Calcium Absorption, Duodenal Vitamin D Receptor Concentration, and Serum 1,25 Dihydroxyvitamin D Levels in Normal Women (1997)
    Springer
    Calcified tissue international 60 (1997), S. 491 -495 
    Details
    ISSN: 1432-0827
    Keywords: Key words: VDR genotypes — Calcium absorption — Duodenal VDR — 1,25 dihydroxyvitamin D.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. It is well established that bone mineral density is under strong genetic control. Recently it was reported that the Bsm I restriction fragment length polymorphism of the vitamin D receptor (VDR) gene could account for up to 75% of the genetic variance in bone mineral density. However, the physiological basis for such an effect has not been established. The VDR gene codes for the vitamin D receptor protein which regulates intestinal calcium absorption. In order to assess the biochemical basis we studied the effect of common allelic variation of the VDR gene on intestinal VDR protein concentration, calcium absorption, and serum 1,25 dihydroxyvitamin D (1,25(OH)2D). Ninety-two Caucasian women were genotyped for Bsm I and Taq I polymorphism at the VDR gene locus. From these we compared 49 young women aged 25–35 years and 43 elderly women aged 65–83 years, who had all three measurements performed. There were no significant differences in intestinal VDR protein concentration, serum 1,25(OH)2D, or radioactive calcium absorption among VDR genotype groups. Therefore, the small intestine does not seem to be a target for VDR gene polymorphism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900269
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  • 5
    Electronic Resource
    Electronic Resource
    Autoradiographic localization of target cells for 1α, 25-dihydroxyvitamin D3 in bones from fetal rats (1983)
    Springer
    Calcified tissue international 35 (1983), S. 177-182 
    Details
    ISSN: 1432-0827
    Keywords: Vitamin D ; Bone ; Osteoblasts ; Receptors ; 1,25-dihydroxyvitamin D3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Thaw-mount autoradiographic studies after injection of3H-1,25-D3 were conducted on 18-and 20-day-old rat fetuses. In maxillary bones, ribs, and tibia, nuclear concentration of radioactivity was found in osteoprogenitor cells and osteoblasts. Osteocytes and chondrocytes in epiphyseal plates were either unlabeled or weakly labeled. In competition experiments, nuclear concentration of radioactivity was blocked by the injection of a high dose of nonradioactive 1,25-D3 prior to the administration of the labeled hormone, but not by a similar dose of nonradioactive 25-D3. The results are interpreted as indicating that osteoprogenitor cells and osteoblasts are target cells for the direct action of 1,25-D3 on fetal bone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405028
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  • 6
    Electronic Resource
    Electronic Resource
    Metabolism and biological activity of vitamin D (1970)
    Springer
    Calcified tissue international 4 (1970), S. 43-44 
    Details
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02152345
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  • 7
    Electronic Resource
    Electronic Resource
    Studies on the role of 24-hydroxylation of vitamin D in the mineralization of cartilage and bone of vitamin D-deficient rats (1981)
    Springer
    Calcified tissue international 33 (1981), S. 489-497 
    Details
    ISSN: 1432-0827
    Keywords: Vitamin D ; Vitamin D deficiency ; Cartilage ; Bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary To test the importance of 24-hydroxylation of vitamin D3 on bone mineralization, rat pups born to vitamin D-deficient females were given either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3 for 16 days beginning at the time of weaning. Following such treatment analysis of blood samples revealed no detectable 24R,25-(OH)2D3 and 1,25-(OH)2D3 in the rats given the difluoro compound while revealing the expected 24,24-difluoro-25-hydroxyvitamin D3 and 24,24-difluoro-1,25-dihydroxyvitamin D3. The rats given 25-hydroxyvitamin D3 had the expected levels of 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3, and 1,25-dihydroxyvitamin D3. Following sacrifice at day 17, postweaning bone mineralization and modeling were studied in long bones using histological methods. Bones taken from vitamin D-deficient rats at the beginning and end of the experimental period had lesions typical of rickets. These included wide growth plates, excessive amounts of osteoid, and metaphyseal fibrosis. Following treatment with either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3, bone mineralization returned to normal. Growth plate widths and the amount of osteoid on bone surfaces were both substantially reduced and to a similar degree in both treatment groups. Normal cartilage core formation and trabecularization of the metaphyseal primary spongiosa were also restored to a similar degree in both groups. In effect, no difference was observed in any bone parameter studied between the 25-hydroxyvitamin D3- and the 24,24-difluoro-25-hydroxyvitamin D3-treated animals. These results provide strong evidence that 24-hydroxylation of the vitamin D molecule plays little or no role in the modeling and mineralization of bone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02409479
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  • 8
    Electronic Resource
    Electronic Resource
    The effects of vitamin D analogues on bone resorption (1974)
    Springer
    Calcified tissue international 15 (1974), S. 333-339 
    Details
    ISSN: 1432-0827
    Keywords: Vitamin D ; Bone ; Resorption ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract A series of analogues of vitamin D have been tested for their ability to stimulate bone resorption in two test systems used previously to investigate the metabolites of vitamine D. These analogues were tested (a) by directly comparing their action on bone explants of mouse half-calvariain vitro, and (b) by injecting them into young mice and measuring the degree of resorptionin vitro when explants were prepared 18 hours after the injection. It is concluded that the key functional groups concerned with enhancing the activity of vitamin D3 are the 1α- and the 25-hydroxyl,both together; the cis ring structure for ring A appears necessary. 1α-Hydroxycholecalciferol (1α-OHD3) is about as active as 25-OHD3 in the direct test, but its potency is much nearer to that of 1,25-(OH)2D3 when tested by the second (indirect) method; it seems likely that 1α-OHD3 is converted into 1,25-(OH)2D3 in vivo. The results are discussed in relation to the designing of analogues for clinical and experimental use.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02059069
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  • 9
    Electronic Resource
    Electronic Resource
    Vitamin D receptor gene polymorphism, bone mass, body size, and vitamin D receptor density (1995)
    Springer
    Calcified tissue international 57 (1995), S. 161-162 
    Details
    ISSN: 1432-0827
    Keywords: Bone mass ; Vitamin D receptor ; Body size ; VDR gene polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract We determined vitamin D receptor (VDR) gene alleles (based on the BsmI restriction site polymorphism), duodenal mucosal receptor density, bone mass at spine and total body, and body size in 32 healthy premenopausal females. While we found no relationship between allele and receptor density in duodenal mucosa, bone mineral content (BMC) at both spine and total body was significantly associated with VDR gene alleles. BMC was highest for the bb allele, lowest for BB, and intermediate for Bb. A similar association was noted between allele and body size variables, particularly weight. When BMC was adjusted for body weight, the association with VDR polymorphism disappeared. The VDR gene polymorphism may be affecting bone mass not through classical nutritional mechanisms (e.g., intestinal calcium absorption), but through an influence on body size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298438
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  • 10
    Electronic Resource
    Electronic Resource
    The action of various vitamin D3 metabolites on calcium and phosphorus metabolism in chick embryo calvariae (1986)
    Springer
    Cellular and molecular life sciences 42 (1986), S. 553-554 
    Details
    ISSN: 1420-9071
    Keywords: Embryonic development ; bone ; vitamin D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Chick embryos from vitamin D-deficient hens given physiological doses of 1,25-dihydroxyvitamin D3 or 24,25-dihydroxyvitamin D3 or both become severely hypocalcemic, hyperphosphatemic and fail to hatch as compared to those derived from hens given 25-hydroxyvitamin D3 or 24,25-difluoro-25-hydroxyvitamin D3. Calvariae from the former contain less mineral and on incubation in vitro produce significantly lower calcium and higher phosphate concentration in the medium than do the calvariae derived from the embryos of hens supported on 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01946699
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