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  • 1
    Electronic Resource
    Electronic Resource
    Reversible suppression by ionophore A23187 of retinoic acid-induced cartilage resorption in cultured fetal rat bones (1984)
    Springer
    Development genes and evolution 193 (1984), S. 121-126 
    Details
    ISSN: 1432-041X
    Keywords: Retinoic acid ; Cartilage resorption ; Bone culture ; Ionophore A23187
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In fetal rat bones in culture the divalent cation ionophore A23187 inhibited in a dose-dependent manner both the release of proteoglycans and the subsequent degradation of cartilage induced by retinoic acid, indicating that calcium was involved in its action. A23187 had to be present continuously to manifest its inhibitory effect; retrieval of the ionophore abolished the suppression, demonstrating that the effect was reversible and not due to toxicity. A23187 at 1.0 μM, which completely blocked the retinoic acid-induced cartilage resorption, markedly suppressed3H-leucine,3H-mannose and3H-thymidine incorporation in control and retinoic acid-treated cultures. Reduced3H-thymidine incorporation did not appear to be responsible for the inhibition by A23187 of retinoic acid-induced cartilage resorption because inhibitors of DNA synthesis did not affect the retinoic acid response. In the presence of retinoic acid the ionophore at 0.3 μM had no effect on the incorporation of3H-leucine and3H-mannose, but suppressed the retinoic acid-induced proteoglycan release. This suggests that reduced protein and glycoprotein synthesis were not the main causes for the inhibitory effect of A23187. In conclusion, retinoic acid-induced cartilage degradation required calcium at some crucial points.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848886
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  • 2
    Electronic Resource
    Electronic Resource
    Structure-activity relationship of retinoids on the differentiation of cultured chick foot skin (1984)
    Springer
    Development genes and evolution 194 (1984), S. 9-17 
    Details
    ISSN: 1432-041X
    Keywords: Retinoic acid ; Retinoids ; Chick embryo ; Skin differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The influence of retinoids (vitamin A and its analogues) on epithelial differentiation was examined in explants of foot skin from chick embryos. In the presence of retinoic acid (10 μM) keratinization and differentiation of scale-like structures, which occurred in tarsometatarsal skin explants, was inhibited and a mucous metaplasia developed. Retinoic acid caused club-shaped feathers in skin explants taken from the anterior surface of the tibia — skin which was determined to differentiate into feathers. In skin explants taken from a breed with feathered feet, the differentiation of tarsometatarsal skin was completely blocked; in tibial skin, club-shaped feathers resulted in response to retinoic acid. These findings indicated that skin of the two origins reacted differently to the retinoid, as was noted in the breed with scaly feet. The structure-activity relationship of 22 retinoids with marked differences in their biological activity was investigated in tarsometatarsal skin explants. Comparing the concentration of various retinoids needed to completely inhibit the differentiation of scale-like structures, retinoids containing tetramethylated indane or tetraline were 100 and 1,000 times more active than retinoic acid. Retinoids with a sulphur-containing end group were also active but less so than the corresponding compound with a carboxylic acid end group. The inactive ethyl, ester analogue, etretinate, was activated in the presence of esterase, indicating that the free carboxylic acid group was important for the activity of retinoids. The retinoid-induced inhibition of keratinization followed by mucous metaplasia in cultured chick embryo skin is a simple and useful model system to test new retinoids which may be helpful in the treatment of dermatological and oncological diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848948
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  • 3
    Electronic Resource
    Electronic Resource
    Inhibition and reversion of chondrogenesis by retinoic acid in rat limb bud cell cultures (1980)
    Springer
    Development genes and evolution 189 (1980), S. 25-33 
    Details
    ISSN: 1432-041X
    Keywords: Chondrogenesis ; Retinoic acid ; Cartilage resorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mesenchyme cells derived from embryonic rat limb buds cultured at high density differentiated into chondrocytes. The degree of chondrogenesis was assessed by alcian blue staining, a stain specific for cartilage matrix. The addition of retinoic acid on day 1 of culture inhibited chondrogenesis in a dose-dependent fashion. When retinoic acid was added to the cultures on day 5, the cartilage nodules, consisting of newly differentiated cartilage cells, disappeared during the following 6 days. Coinciding with this process the histochemically demonstrable alkaline phosphatase activity, localized in the internodular areas, also disappeared. This indicated that retinoic acid not only inhibited chondrogenesis but also induced resorption of cartilage cells and that at least two cell types were affected, the cartilage cells and the cells bearing alkaline phosphatase. Actinomycin D and cycloheximide, inhibitors of RNA and protein synthesis, suppressed the retinoic acid effect in day 5 limb bud cell cultures. This result indicated that the effect of retinoic acid required RNA and protein synthesis and is compatible with the view that vitamin A may act in a hormone-like way.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848564
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  • 4
    Electronic Resource
    Electronic Resource
    Retinoic acid-induced cartilage degradation is caused by cartilage cells (1991)
    Springer
    Development genes and evolution 199 (1991), S. 377-386 
    Details
    ISSN: 1432-041X
    Keywords: Retinoic acid ; Cartilage degradation ; Tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cartilage cubes, prepared from the proximal epiphyses of neonatal rat humeri and consisting of cartilage tissue only, were cultured in the presence of retinoic acid. The retinoid induced the loss of metachromatic staining with toluidine blue, which correlates with the loss of proteoglycan, followed by tissue degradation processes resulting in a distinct reduction of the cartilage mass. Histologically, fibroblast-like cells appeared within chondrones, indicating a transformation of chondroblasts. Focal tissue degradation was observed after only 2 days. Electron microscopically, the clustered cells within the zone of tissue degradation were rich in various lysosomal structures indicating their lytic activity. Cycloheximide and EDTA completely blocked the retinoic acid effects suggesting that protein synthesis was required and that metalloproteinases may be involved in the degradation processes. In conclusion, with the new test system described here we demonstrated that cartilage cells themselves performed the tissue degradation induced by retinoic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01705847
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  • 5
    Electronic Resource
    Electronic Resource
    Retinoic acid induced proteoglycan release and cartilage resorption in rat bone cultures are age dependent and inhibited by EDTA (1979)
    Springer
    Development genes and evolution 187 (1979), S. 59-71 
    Details
    ISSN: 1432-041X
    Keywords: Retinoic acid ; Cartilage resorption ; Bone culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In explanted humeri of late fetal rats, retinoic acid was found to induce the release of proteoglycan followed by cartilage resorption. Tissue breakdown, which was demonstrated by losses of DNA, RNA, and protein, coincided with the appearance of necrotic cells. In control humeri chondrocytes were the main cell type, but in humeri treated for 4 days with retinoic acid the surviving cells were chondroblastlike. Sensitivity of proteoglycan release and tissue breakdown to retinoic acid decreased with age. The proteinase inhibitors cysteine, Trasylol, and soya and lima bean trypsin inhibitors did not antagonize the effects of retinoic acid. Phenylmethanesulfonyl fluoride suppressed cartilage resorption more effectively than proteoglycan release, while pepstatin merely suppressed cartilage resorption. The inhibition by EDTA of both the release of proteoglycan and cartilage resorption induced by retinoic acid was dose dependent. Zn2+ abolished these effects, whereas Mn2+ only relieved the release of proteoglycan induced by retinoic acid; this indicates that these two effects of retinoic acid are not necessarily linked. In view of our recent demonstration that the release of proteoglycan induced by retinoic acid requires RNA and protein synthesis, we suggest that the degradation of proteoglycans in response to retinoic acid is dependent upon continued synthesis of metalloproteinases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848167
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  • 6
    Electronic Resource
    Electronic Resource
    Calmodulin antagonists inhibit retinoic acid-induced cartilage degradation in vitro (1985)
    Springer
    Development genes and evolution 194 (1985), S. 224-227 
    Details
    ISSN: 1432-041X
    Keywords: Retinoic acid ; Cartilage resorption ; Bone culture ; Trifluoperazine ; Calmodulin antagonists
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In cultured fetal rat bones retinoic acid induces the release of proteoglycan, followed by cartilage tissue breakdown. This correlates with a shortening of the bone of up to 40%. The calmodulin antagonists trifluoperazine, chlorpromazine, diazepam and the naphthalenesulphonamide W-7 inhibited the retinoic acid-induced bone shortening. Inhibition by trifluoperazine and W-7 was noted at 40 and 75 μM, respectively, concentrations which were not cytotoxic as judged from3H-leucine incorporation into protein. Trifluoperazine and W-7 at the above concentrations did not affect the release of proteoglycan induced by retinoic acid, indicating that bone shortening is not necessarily linked with the release of proteoglycan. In consideration of our previous and present demonstrations that retinoic acid-induced cartilage resorption was inhibited by the ionophore A23187 and by calmodulin antagonists, we suggest that Ca2+ and calmodulin may be involved in the mediation of retinoic acid action in cartilage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848250
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  • 7
    Electronic Resource
    Electronic Resource
    Ro 15-1570, a new sulfur-containing retinoid devoid of bone toxicity in rats (1984)
    Springer
    Archives of toxicology 56 (1984), S. 117-122 
    Details
    ISSN: 1432-0738
    Keywords: Rat ; Retinoids ; Bone alterations ; Adverse effects ; Arotinoid ethylsulfone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Repeated ingestion of high doses of retinoids cause the so-called hypervitaminosis A syndrome. In rats the main symptoms are weight loss, alopecia, erythema, desquamation of the skin, and alterations of the skeletal system, including bone fractures. In the present study, three retinoids (Ro 15-1570, arotinoid ethylsulfone, 6 mg/kg; retinoic acid, 100 mg/kg and etretinate, 50 mg/kg) were administered orally to rats for 1 and 2 weeks, respectively, to six male and six female rats/group. All the above changes were induced by all three retinoids, with the exception that the arotinoid ethylsulfone Ro 15-1570 did not cause bone alterations. The absence of toxic effects on the bones by Ro 15-1570 was confirmed by X-ray-film examinations, densitometry of the X-rayed femora and tibiae, examination of the thickness of the femoral and tibial compacta in histological slides plus the determination of the femoral ash weight and its main inorganic constituents (calcium, magnesium, sodium, and potassium). The present demonstration that the arotinoid ethylsulfone Ro 15-1570 was devoid of bone toxicity constitutes major progress in the pharmacologic development of retinoids with a better balance between therapeutic and adverse effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349083
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  • 8
    Electronic Resource
    Electronic Resource
    Teratogenicity of arotinoids (retinoids) in vivo and in vitro (1990)
    Springer
    Archives of toxicology 64 (1990), S. 616-622 
    Details
    ISSN: 1432-0738
    Keywords: Teratogenicity in vivo ; Teratogenicity in vitro ; Retinoids ; Arotinoids ; Micromass culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of structural modifications on the arotinoid molecule, a new class of retinoids, on their teratogenicity in mice was studied. Animals were treated on days 8 and 9 of gestation, the most susceptible stages to retinoid-induced malformations in rodents. The teratogenic potency of the 13 arotinoids tested varied over a dose range of more than five orders of magnitude. Next, we tested whether the quantitative differences in the teratogenicity of these arotinoids correlates with their activity in high density (micromass) cultures of rat embryonic limb bud and midbrain cells. There was a good quantitative correlation between the in vivo teratogenicity and the in vitro activity in limb bud cells but no correlation was found in midbrain cells. Thus, the limb bud cell culture system may be useful for a preliminary testing to select non-teratogenic retinoids. For the risk assessment in humans, however, the in vitro results should be verified in animals studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01974689
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  • 9
    Electronic Resource
    Electronic Resource
    Prolactin lowering activity of the retinoid Ro 14-9706 affecting lactation and pup survival (1994)
    Springer
    Archives of toxicology 68 (1994), S. 385-393 
    Details
    ISSN: 1432-0738
    Keywords: Key words: Retinoid – Arotinoid – Endocrine and neurochemical effects – Cross fostering – Adrenocortical degeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The arotinoid Ro 14-9706, though devoid of any teratogenic potential, was found to reduce dose dependently the survival of pups when their mothers were treated with toxic doses during days 6 – 15 of gestation. The increased mortality was primarily seen during early lactation. When pups derived from treated mothers were nursed by control foster mothers unexposed to the drug, their survival was significantly improved indicating that the increased mortality was not solely due to fetal drug exposure. When pups derived from untreated mothers were fostered by dams that were exposed to the arotinoid during pregnancy, a significant pup mortality (p 〈0.01) was observed, suggesting that the nursing behaviour of lactating dams was seriously affected. This impairment could be linked to a prolactin-suppressive activity of the arotinoid during lactation which was also seen during pregnancy. Other pituitary hormones, however, were not affected by the compound. Although the drug induced pronounced structural alterations in mitochondria of adrenocortical cells, visualized by light microscopy as extended vacuolization in the zona fasciculata and reticularis, this pathological finding did not translate into functional impairment of steroidogenesis. Thus, the arotinoid Ro 14-9706 exhibits in rats a prolactin-suppressive activity which affects lactation and subsequently pup survival. This particular endocrinological interference is a new phenomenon and uncommon for retinoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050086
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of vitamin D derivatives on soft tissue calcification in neonatal and calcium mobilization in adult rats (1989)
    Springer
    Archives of toxicology 63 (1989), S. 394-400 
    Details
    ISSN: 1432-0738
    Keywords: Vitamin D analogs ; 1,25-Dihydroxyvitamin D3 ; Hypercalcemia ; HL-60 cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The activity of 18 vitamin D analogs on soft tissue calcification and growth impairment in neonatal rats and their effect on bone calcium mobilization, intestinal calcium absorption and binding to intestinal 1,25-dihydroxyvitamin D3 receptors in adult rats were compared. Depending on the chemical modification of the vitamin D parent compounds, they could be separated into active and inactive analogs. Cholecalciferol and ergocalciferol were similarly active, but epimerization of ergocalciferol at carbon 23 caused loss of activity. Hexafluorination at carbon 26 and 27 and the introduction of a double bond at carbon 22 or 23 had no or little effect on the activity. The loss of activity was caused by the introduction of a triple bond at carbon 23 and by hydroxylation at carbon 23, 26 or 28. The differentiation of human promyelocytic leukemia cells (HL-60) induced by these derivatives was used as a parameter for antitumour activity. All six analogs, which markedly affected calcium metabolism, were highly active in HL-60 cells. However, at least three derivatives were highly active in the antitumour test but failed to induce hypercalcemia. Thus, these results indicate that it could be possible to develop medically useful vitamin D derivatives devoid of hypercalcemic side-effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00303129
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