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  • 1
    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.
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  • 2
    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.
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  • 3
    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.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 34 (1982), S. 547-552 
    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.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 9 (1972), S. 17-27 
    ISSN: 1432-0827
    Keywords: Periosteal Hyperplasia ; Osteomyelosclerosis ; Magnesium ; Parathyroid ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Un régime contenant 0.8 à 2 mg de Mg pour 100 g, administré à des rats jeunes ou adultes pendant 18 à 21 jours, provoque une croissance généralisée d'os médullaire (ostéomyélosclérose), ainsi que des tumeurs périostées de type desmoide, au niveau de la linea aspera du fémur. Ces modifications s'accompagnent d'une décroissance du magnésium osseux de 52 à 71%, déterminée par spectrophotométrie d'absorption atomique. Au niveau des tumeurs périostées, la parathyroidectomie favorise la formation de cartilage. L'administration d'extrait parathyroidien inhibe la formation de cartilage en faveur de la formation de tissue fibreux et d'os. L'adjonction de magnésium au régime restitue rapidement l'apparence normale des tissus.
    Abstract: Zusammenfassung Eine Nahrung mit 0,8–2 mg Mg per 100 g wurde jungen oder ausgewachsenen Ratten während 18–21 Tagen verfüttert; sie verursachte ein generalisiertes medulläres Knochenwachstum (Osteomyelosklerose) und ebenso desmoidartige Tumoren, des Periosts an der femoralen Linea aspera. Diese Veränderungen waren von einer Abnahme von 52–71% der Magnesium-Konzentration im Knochen begleitet (Bestimmung am Atomabsorptions-Spektrophotometer). Bei Tumoren des Periosts wurde die Knorpelbildung durch Parathyreoidektomie begünstigt. Durch Verabreichung von Parathyreoidea-Extrakt wurde die Knorpelbildung gehemmt und an deren Stell fibröses Gewebe und Knochen gebildet. Wurde der Nahrung Magnesium zugesetzt, so bekamen die Gewebe rasch ein normales Aussehen.
    Notes: Abstract A diet containing from 0.8 to 2 mg Mg/100 g, fed to young or adult rats for 18 to 21 days produced generalized medullary bone growth (osteomyelosclerosis) and also periosteal tumours of the desmoid type, at the femoral linea aspera. These changes were accompanied by decreases in bone magnesium concentration of 52 to 71% as measured by atomic absorption spectrophotometry. In the periosteal tumours, parathyroidectomy favoured cartilage formation. The administration of parathyroid extract inhibited cartilage formation in favour of fibrous tissue and bone production. The addition of magnesium to the diet quickly restored the normal appearance of the tissues.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 23 (1977), S. 179-184 
    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.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 50 (1992), S. 80-87 
    ISSN: 1432-0827
    Keywords: PGE2 ; Ovariectomy ; Rats ; New bone trabeculae ; Positive balance ; Accelerated bone turnover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Serum chemistry and bone morphometry of the proximal tibial metaphysis were performed in 3-month-old double fluorescent-labeled, female Sprague-Dawley rats subjected to bilateral ovariectomy or sham surgery for 4 months prior to treatment with 0, 0.3, 1, 3, or 6 mg of prostaglandin E2 (PGE2)/kg/day subcutaneously for 30 days. The 4-month postovariectomized rats possessed an osteopenic proximal tibial metaphysis with 7% trabecular area compared with controls (19%). PGE2 treatment elevated osteocalcin levels and augmented proximal tibial metaphyseal bone area in ovariectomized and sham-operated rats. Osteopenic, ovariectomized rats treated with 6 mg PGE2/kg/day for 30 days restored bone area to levels of agematched sham-operated rats. Morphometric analyses showed increased woven and lamellar bone area, fluorescent-labeled perimeter (osteoblastic recruitment), mineral apposition rate (osteoblastic activity), bone formation rate (BFR/BV), and longitudinal bone growth. These dramatic bone changes were all significantly increased at the doseresponse manner. This study showed that in vivo PGE2 is a powerful activator of bone remodeling, it increases both bone resorption and bone formation, and produces an anabolic effect by shifting bone balance to the positive direction. Furthermore, PGE2-induced augmentation of metaphyseal bone area in ovariectomized rats was at least two times greater than in sham-operated rats.
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  • 8
    ISSN: 1432-0827
    Keywords: Insulinlike growth factor I ; Interleukin 1 ; Oophorectomy ; Estrogen ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Oophorectomy (OOX) has been known to increase bone turnover, but its precise mechanism is not fully understood. In order to further investigate the mechanism, we determined insulinlike growth factor I (IGF-I) concentrations in serum and bone tissue and interleukin 1 (IL-1) release from spleen macrophages in oophorectomized rats because it has been demonstrated that IGF-I stimulates bone formation and IL-1 stimulates bone resorption. Female 8-week-old Wistar rats were divided into four groups: (1) control, (2) OOX, (3) OOX given estradiol, and (4) control given estradiol. Ten μg/kg of 17β-estradiol was given daily by subcutaneous injection. After 5 weeks of treatment, IGF-I concentrations in the extract from right femur and in serum were determined by specific radioimmunoassay. IL-1 activity released from lipopolysaccharide (LPS)-stimulated spleen macrophages was determined by bioassay. IGF-I contents in the femur and IGF-I concentrations in serum in oophorectomized rats were significantly higher than those in control rats. Treatment by estradiol inhibited the increase in IGF-I concentrations both in femur and in serum. IL-1 release from LPS-stimulated spleen macrophages in oophorectomized rats was increased, and treatment by estradiol also inhibited the stimulated IL-1 release. The ash weights and the calcium contents of left femur in oophorectomized rats were lower than those in control rats. These results suggest that both IGF-I and IL-1 may be involved in the mechanism of the regulation of bone turnover in oophorectomized rats.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 56 (1995), S. 549-553 
    ISSN: 1432-0827
    Keywords: Bone development ; Bone morphogenetic protein ; Artificial membrane ; Polytetrafluoroethylene ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract It has been shown earlier that it is possible to improve bone healing, to regenerate previously existing bone, and to create new bone by means of an osteopromotive membrane technique. The present study addresses the question of whether it is possible to combine this technique with a locally applied factor, stimulatory to osteogenesis. Circular transosseous ‘critical size’ defects in mandibles of rats were either implanted with recombinant human bone morphogenetic protein type 2 (rhBMP-2) or were left empty; half the number of implanted and half the number of empty defects were covered with an expanded polytetrafluoroethylene (e-PTFE) membrane (GORE-TEX®). Results were evaluated after 12 and 24 days of healing by a histomorphological scoring system. Implantation of rhBMP-2 alone resulted in bony bridging of the defect after only 12 days, but also in voluminous amounts of new bone outside the original defect area. When rhBMP-2 was combined with membrane, newly formed woven bone bridged the defect and the bone contour was maintained by the membrane. The combined treatment with membrane and rhBMP-2 demonstrated a significantly better bone healing than with e-PTFE membrane alone at both 12 days and 24 days of healing. It was concluded that rhBMP-2 has a strong osteoinductive potential and, in contrast to what was found earlier with other types of BMP preparations, this potential was retained when combining the rhBMP-2 with the osteopromotive membrane technique, yielding better bone healing than with the membrane alone, and at the same time maintaining the bone contour. This combination may have important therapeutic applications for osseous healing and in reconstructive surgery. The study also shows the importance of an appropriate carrier material when applying stimulatory substances to enhance bone formation in combination with a membrane.
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  • 10
    ISSN: 1432-0827
    Keywords: Boen ; Metabolism ; Rats ; Strontium ; Tooth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé L'on a procédé à une étude approfondie sur l'incorporation et l'enlèvement du strontium des os et des dents de rats dans les cas de régimes alimentaires à forte et faible teneur en strontium. Dans le cas d'un régime par ailleurs en tous points satisfaisant, l'adjonction d'une quantité de strontium de masse égale à celle du calcium provoque un phénomene débilitant très severe chez le jeune rat en pleine croissance, et peut même conduire à la mort du sujet. Les effets pathogéniques du strontium ont été découverts par des méthodes utilisées seulement en recherche dans les tissus durs. L'excédent de cellules osseuses, formées à l'origine du fait de la présence de grandes quantités de strontium dans l'alimentation, se résorbe si l'on passe à un regime à faible teneur en strontium. Il apparait qu'il y a deux types d'élimination dustrontium de l'organisme: a) par excrétion, et b) par assimilation dans les tissus durs. L'on n'a plus à démontrer que le strontium s'intègre par transfert dans les incisives. L'on a également observé, chez les sujets expérimentaux aussi bien que chez ceux du groupe de vérification, que des différences dans le taux de sodium et de potassium apparaissent dans les semi-mandibules.
    Abstract: Zusammenfassung Die Einlagerung sowie die Resorption von Strontium wurde an Rattenknochen und-zähnen mittels Zugabe von niedrigen und hohen Strontiumdosen zu der Diät untersucht. Wird bei einer sonst befriedigenden Diät Calcium durch äquimolare Strontiummengen ersetzt, so entsteht eine Schwächung bei jungen wachsenden Ratten, die bis zum Tode führen kann. Die pathologischen, durch Strontium entstandenen Veränderungen wurden nur mit denjenigen Methoden verfolgt, die zur Untersuchung der harten Gewebe angewendet werden. Das Übermaß an osteoidem Gewebe, welches ursprünglich bei Zugabe großer Strontiummengen zu der Nahrung entsteht, wird in einer darauffolgenden strontiumarmen Diätperiode resorbiert. Die Resorption des Strontiums scheint an zwei physiologische Prozesse gebunden zu sein: a) Ausscheidung aus dem Organismus; b) Eingliederung in die harten Gewebe. Der Strontiumtransport in den Schneidezähnen ist bewiesen worden. Es wurden auch Unterschiede im Natrium- und Kaliumgehalt des halben Unterkiefers bei Experiment- und Kontrollgruppen beobachtet.
    Notes: Abstract The incorporation and removal of strontium from the bones and teeth of rats under conditions of low and high dietary levels of strontium were investigated. In an otherwise satisfactory diet, an amount of strontium equimolar to that of calcium seriously debilitates the young growing rat and may culminate in death. The pathology due to strontium was found by the methods used only in the hard tissues. The excess osteoid formed originally in the presence of large amounts of dietary strontium is removed during a subsequent period of feeding on a low strontium regimen. Strontium removal from participation in physiologic processes appears to be of two types, (a) excretion from the body, and (b) incarceration within the hard tissues. The translocation of strontium to the incisor teeth has been demonstrated. Differences of sodium and potassium contents of the hemi-mandibulae of the experimental and control groups were also observed.
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