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  • Articles  (14,148)
  • General Chemistry  (11,315)
  • Humans  (2,074)
  • Rats  (936)
  • Fluid Mechanics and Heat Transfer
  • 1980-1984  (6,771)
  • 1975-1979  (4,990)
  • 1955-1959  (2,387)
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  • 1
    Electronic Resource
    Electronic Resource
    Immobilization osteoporosis and active vitamin D: Effect of active vitamin D analogs on the development of immobilization osteoporosis in rats (1981)
    Springer
    Calcified tissue international 33 (1981), S. 623-630 
    Details
    ISSN: 1432-0827
    Keywords: Osteoporosis ; Immobilization ; Rats ; Vitamin D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The therapeutic effects of vitamin D analogs, 1,24(R)-dihydroxycholecalciferol [1,24(R)(OH)2D3], 1,24(S)-dihydroxycholecalciferol [1,24(S)(OH)2D3], and 1,25-dihydroxycholecalciferol [1,25(OH)2D3] on immobilization osteoporosis were studied in rats. The right hind limb was immobilized through application of a plaster cast following the section of the sciatic nerve. The left hind limb was intact. Vitamin D analogs were orally administered for 6 weeks at dose levels of 0.02 and 0.10µg/kg/day, respectively. The mean lengths of the immobilized femurs were not significantly different from those of the intact femurs in all the experimental groups. In the immobilized femur of animals treated with 1,24(R)(OH)2D3, 0.10µg/kg, dry and ash weights were heavier and calcium and phosphorus contents greater than those in the nontreated group. Furthermore, the amount of calcified bone mass and the cortical thickness of the femurs of the immobilized limb in 1,24(R)(OH)2D3-treated animals were greater than those in the nontreated animals. Treatment with 1,25(OH)2D3 at 0.10µg/kg caused an increase of the bone mass in both immobilized and intact femurs when compared with those of the control group. It was concluded that the administration of 1,24(R)(OH)2D3 diminished the effect of immobilization in the development of osteoporosis without any side effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02409500
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  • 2
    Electronic Resource
    Electronic Resource
    Maintenance of a calcemic response to parathyroid hormone in D-deficient rats by the prevention of severe hyperparathyroidism (1977)
    Springer
    Calcified tissue international 23 (1977), S. 277-281 
    Details
    ISSN: 1432-0827
    Keywords: PTH ; Vitamin D ; Pituitary ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Parathyroid gland transplanted rats and hypophysectomized rats were raised from weaning on a diet without vitamin D and low in calcium (0.02%) for 4 weeks. At the end of this period the animals of both experimental groups, when compared to their respective controls (i.e., sham-operated animals for parathyroid-transplanted ones, and hypophysectomized plus bovine growth hormone-supplemented ones for hypophysectomized rats) were characterized by (a) moderate or absent secondary hyperparathyroidism; (b) near normal bone calcium content; and (c) a maintained responsiveness to the calcemic effect of parathyroid extract (PTE). The PTE action is a bone effect that does not require the presence of the kidneys and is not related to changes in serum calcium and/or phosphorus concentrations. These results indicate that when severe hyperparathyroidism is prevented, the sensitivity of bone to the calcemic action of PTE can be maintained in D-deficient calcium-deprived rats. They also suggest that in these animals the main factor leading to resistance to PTH is the state of severe chronic hyperparathyroidism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02012797
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  • 3
    Electronic Resource
    Electronic Resource
    Dissociation of renal cyclic AMP and phosphate responses to parathyroid hormone in uremia (1979)
    Springer
    Calcified tissue international 29 (1979), S. 147-154 
    Details
    ISSN: 1432-0827
    Keywords: Vitamin D ; Chronic uremia ; Rats ; Renal responsivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Various investigators have shown that chronic uremia is associated with a normal or exaggerated phosphaturic response to parathyroid hormone (PTH). To explore the relationship between progressive uremia, renal tubular cyclic AMP (cAMP), and inorganic phosphate (Pi) response to PTH and acidosis, in vivo and in vitro experiments were designed in rats with experimental uremia of 4–6 weeks’ duration. Both uremic and pair-fed control rats were treated with 1,25-dihydroxycholecalciferol (1,25(OH)2D3) and/or chronic NH4Cl feeding. Urinary Pi and cAMP and plasma immunoreactive PTH (iPTH) were measured as well as PTH- and NaF-stimulated cAMP from isolated renal tubules. Excretion of cAMP decreased by 30% in uremic as compared to control rats despite a 3-fold rise in Pi excretion. Acidosis superimposed on uremia did not further decrease cAMP excretion, nor did it significantly alter the elevated Pi excretion. 1,25(OH)2D3 treatment of uremic rats further lowered cAMP excretion although Pi excretion rose, hypercalcemia occurred, and plasma iPTH fell. In nonuremic control rats, 1,25(OH)2D3 treatment led to hypercalcemia, a progressive decrease in cAMP, and increase in Pi excretion. Isolated renal tubules from uremic or acidotic uremic rats revealed a 50% reduction in both PTH- and NaF-stimulated cAMP generation compared to control rat renal tubules. This observation was unchanged by 1,25(OH)2D3 treatment. Renal tubules of 1,25(OH)2D3-treated control rats demonstrated a decreased cAMP production in response to both PTH and NaF which was inversely related to the calcium content of the renal tubules. Renal tubular calcium levels of uremic rats, initially 3-fold elevated, also increased during 1,25(OH)2D3 treatment. These results are consistent with the hypothesis that progressive uremia results in a dissociation between PTH, urinary cAMP, and Pi excretion which cannot be explained by either metabolic acidosis or 1,25(OH)2D3 deficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408070
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  • 4
    Electronic Resource
    Electronic Resource
    Scanning electron microscopy of castrate rat bone (1982)
    Springer
    Calcified tissue international 34 (1982), S. 547-552 
    Details
    ISSN: 1432-0827
    Keywords: Rats ; Osteoporosis ; Anorganic ; Femur ; Castrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The study describes the SEM appearances of endosteal and periosteal surfaces of anorganic femoral diaphyses from 16-month-old normal and castrate male rats. Different types of surfaces could be recognized in both groups. Percentage areas occupied by each surface type were analyzed with a Ladd Data Analyzing Digitizer. Endosteal surfaces were composed of significantly more (P〈0.05) incompletely mineralized, forming surface and significantly less (P〈0.05) completely mineralized, resting surface in castrates than in controls. Both endosteal and periosteal surfaces from experimental bone demonstrated significantly more (P〈0.05) osteoblast lucunae than did control surfaces, and vascular canal entrances were significantly wider (P〈0.001) on castrate endosteal surfaces than on control endosteal surfaces. There was a greater proportion of small nodule forming surface/large nodule forming surface in castrate endosteal bone than in control, and a greater proportion prolonged resting surface/fibrous resting surface in control periosteal bone than in castrate. The results indicate that, when viewed in the SEM, anorganic endosteal and periosteal bone surfaces from femoral diaphyses of old castrate male rats demonstrate appearances characteristic of changes in bone turnover that occur with osteoporosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411302
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  • 5
    Electronic Resource
    Electronic Resource
    The reversibility of disuse osteoporosis (1977)
    Springer
    Calcified tissue international 23 (1977), S. 179-184 
    Details
    ISSN: 1432-0827
    Keywords: Immobilization ; Osteoporosis ; Reversibility ; Rats ; 3H-Thymidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary One hind leg of 80 adult rats of the Sprague-Dawley strain was made osteoporotic by immobilization for 9 weeks. Osteoporosis was noted in both the femur and the tibia when the hydrated gross bone density and the bone surface areas were measured. No signs of reversibility were observed during 10 weeks after the period of immobilization. Tetracycline and DCAF labelling failed to show significant signs of increased bone formation during the 10 weeks after remobilization. At the moment of remobilization and for some weeks thereafter, there were signs of depressed mitotic activity in the bone cells when expressed as the3H-thymidine/DNA ratio. The conclusion was that neither the cell-proliferation rate nor the cellular activity increases sufficiently for restitution of the disuse osteoporosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02012784
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  • 6
    Electronic Resource
    Electronic Resource
    Acute effects ofSolanum malacoxylon on bone formation rates in growing rats (1979)
    Springer
    Calcified tissue international 28 (1979), S. 239-243 
    Details
    ISSN: 1432-0827
    Keywords: Solanum malacoxylon ; Bone formation ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The plantSolanum malacoxylon is responsible for a syndrome of hypercalcemia, soft tissue mineralization, and progressive wasting in South American cattle known asenteque seco orespichamento. There is evidence that a glycoside of 1,25-dihydroxycholecalciferol is the active principle in the plant. The basis for the hyperostosis seen in the disease is unclear. To study the acute effects on bone formation rates, 8-week-old rats were given an aqueous extract equivalent to 250 or 1000 mg ofSolanum daily per os for 7 days. Bones were labeled by injection of fluochrome 2 days before the start of treatment and 2 days prior to sacrifice. Morphometric evaluation of undecalcified sections of caudal vertebrae revealed an increased amount of trabecular bone in bothSolanum treated groups with no difference due to dose level. This was associated with an increase in the bone apposition rate on trabecular surfaces. No differences were found in the amount of osteoid or osteoid seam width. Periosteal apposition rate and endochondral bone formation were also measured and no significant differences found. The findings indicate that acute stimulation of cell level bone formation on trabecular surfaces may play a role in the hyperostosis seen in the naturally occurring condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441242
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  • 7
    Electronic Resource
    Electronic Resource
    Use of dermestid beetles for cleaning bones (1980)
    Springer
    Calcified tissue international 31 (1980), S. 45-47 
    Details
    ISSN: 1432-0827
    Keywords: Dermestid beetles ; Cleaning bones ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Various parts of the skeleton of normal and osteoporotic rats were compared with respect to their dry weight, ash weight, and calcium content when the bones were cleaned byDermestes maculatus beetles or manually. Both techniques gave similar results. This was also true when whole body calcium measured by neutron activation and total skeletal calcium from bones cleaned by the beetles were compared. Thus dermestid beetles are useful as a technique to clean bones, especially for the parts of the skeleton which are difficult to dissect by hand.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407166
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of castration on the bone structure of male rats: A model of osteoporosis (1980)
    Springer
    Calcified tissue international 32 (1980), S. 77-82 
    Details
    ISSN: 1432-0827
    Keywords: Osteoporosis ; Castration ; Density ; Femur ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Forty young (23-day-old) and thirty old (1-year-old) male rats were castrated and sacrificed with controls at intervals up to 18 months of age. No differences were observed between femurs or mandibles of rats castrated at 23 days and those of controls. Year-old castrate rats developed femoral osteoporosis after 2 months, which became more pronounced 4 months after castration. This was characterized by reductions in femoral density, dry weight, dry weight per unit length, and ash weight, and by the appearance of resorption cavities in diaphyseal walls and a sparsity of trabeculae in metaphyses and epiphyses of castrate femurs. These results indicate that the year-old castrate male rat may be a valuable experimental model for studies of the treatment of osteoporosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408524
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  • 9
    Electronic Resource
    Electronic Resource
    Role of parathyroid hormone and 1,25-dihydroxyvitamin D3 in the development of osteopenia in oophorectomized rats (1982)
    Springer
    Calcified tissue international 34 (1982), S. 510-514 
    Details
    ISSN: 1432-0827
    Keywords: Rats ; Osteopenia of oophorectomy ; 1,25-Dihydroxyvitamin D3 ; Parathyroid hormone ; Osteoporosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The effect of ovarian insufficiency on calcium metabolism has been thought to involve an increased bone resorptive effect of parathyroid hormone and possible impaired synthesis of 1,25-dihydroxyvitamin D3. In the present study a rat model allowing for controlled serum levels of parathyroid hormone and 1,25-dihydroxyvitamin D3 was used. Oophorectomy in this species is associated with increased serum levels of 1,25-dihydroxyvitamin D3 and decreased bone mass. Although thyroparathyroidectomy increased bone mass, an increased sensitivity of bone to parathyroid hormone in oophorectomized rats was not observed. Thus the development of the osteopenia did not seem to be related to increased parathyroid hormone sensitivity or to reduced levels of 1,25-dihydroxyvitamin D3. Exogenous 1,25-dihydroxyvitamin D3 increased bone mass in oophorectomized as well as intact rats. Intestinal calcium transport was increased by moderate doses of 1,25-dihydroxyvitamin D3. Intestinal calcium transport was also reduced by thyroparathyroidectomy and increased by the administration of parathyroid extract. A tendency for increased accumulation of 1,25-dihydroxyvitamin D3 in blood in oophorectomized rats has been noted. It is suggested that the tendency to hypercalcemia in ovarian-insufficient females given 1-hydroxylated vitamin D compounds may be related to a diminished metabolism of 1,25-dihydroxyvitamin D3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411294
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  • 10
    Electronic Resource
    Electronic Resource
    A comparative study on the occurrence and activity of extracellular matrix vesicles in young and adult rat maxillary bone (1981)
    Springer
    Calcified tissue international 33 (1981), S. 129-134 
    Details
    ISSN: 1432-0827
    Keywords: Matrix vesicles ; Young/adult ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The occurrence of matrix vesicles in the maxillary bone of normal young and adult rats was demonstrated by both ultrastructural and enzymatic studies. Transmission electron microscopy revealed that the vesicles are invested in trilaminar membranes. Occasionally, crystals were found both within the vesicles and in the surrounding matrix. Separated fractions of vesicles, membranes, and cells were studied biochemically. The amounts of vesicular protein and enzymatic activity per gram bone in the adult rats were significantly lower than in the young. This coincides with the higher number of vesicles observed in the TEM specimens of young rats when compared to that in the old ones. The specific activities of all enzymes examined in the three bone fractions obtained from both young and adult rats were similar. This indicates that no significant difference exists in the enzymatic characteristics of matrix vesicles from the maxillary bone of young and adult rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02409425
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