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  • Springer  (158)
  • Taylor & Francis  (9)
  • 1980-1984  (167)
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  • 1
    Digitale Medien
    Digitale Medien
    Inhibition of active bone resorption by copper (1981)
    Springer
    Calcified tissue international 33 (1981), S. 35-39 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Copper ; Resorption ; Bone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary An investigation of the role of copper in bone metabolism was undertaken. Explanted calvaria from 6-day-old mice were grown for 48 h in medium with and without the addition of copper sulfate. Active resorption was found to be significantly inhibited in the presence of copper sulfate concentrations of 10−6M and above. Copper sulfate concentrations of 10−5M and above inhibited hydroxyproline, protein, and DNA synthesis. Lower concentrations were ineffective. The effect of 5 × 10−6M copper sulfate on resorption was reversible. Several other compounds were tested for similar effects and at 5 × 10−6M were found to inhibit bone resorption in the order: copper sulfate 〉 brown gold chloride 〉 sodium aurothiomalate 〉 zinc sulfate 〉 sodium sulfate. The copper sulfate effect was twice that of sodium aurothiomalate, and sodium sulfate was not significantly inhibitory. The results suggest that the high serum copper levels associated with rheumatoid arthritis may reflect the activity of a hypothetical control mechanism of bone resorption. In the diseased state this would act to restore the normal rate of bone resorption.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02409410
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Regulation of plasma 1,25-(OH)2-D3 by phosphate: Evidence against a role for total or acid-soluble renal phosphate content (1983)
    Springer
    Calcified tissue international 35 (1983), S. 773-777 
    Details
    ISSN: 1432-0827
    Schlagwort(e): 1,25-(OH)2-D3 ; Hypophysectomy ; Growth hormone ; Phosphorus ; 31P NMR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary In order to evaluate a possible role for tissue phosphate or phosphorylated compounds in mediating the increase in plasma 1,25-(OH)2-D3 levels during dietary phosphate deprivation, measurements of total and acid-soluble renal cortical phosphate content have been made in both intact and hypophysectomized (hypox) rats eating a normal diet and also after four days of dietary phosphate deprivation. Similar measurements were also made in phosphate-deprived hypophysectomized rats replaced with growth hormone (GH). Total and acid-soluble renal cortical phosphate content averaged 81±8 µmol/g and 4.1±0.6 µmol/g, respectively, in intact rats eating the normal diet and were not significantly altered after phosphate deprivation despite a fall in plasma phosphate of about 40% and a fourfold increase in plasma 1,25-(OH)2-D3 levels. Total and acid-soluble renal cortical phosphate content levels were higher in hypox rats, averaging 92±8 µmol/g and 4.9±0.7 µmol/g, respectively, but also did not change after phosphate deprivation. Replacement of phosphate-deprived hypox rats with GH resulted in a further fall in plasma phosphate and a significant increase in plasma 1,25-(OH)2-D3 levels, but there was no change in either total or acid-soluble renal cortical phosphate content. The distribution of organophosphorus compounds in the acid-soluble phosphate fraction in these experiments was also evaluated using31P NMR spectroscopy. Although there appeared to be an increase in the total concentration of organophosphorus compounds after phosphate deprivation, this effect was not altered by hypophysectomy or by replacement of phosphate-deprived hypox rats with GH. These data suggest that unless phosphate deprivation affects only a small or specific cellular phosphate pool, some factor other than renal cell inorganic phosphate content must initiate the increase in renal 1,25-(OH)2-D3 synthesis that occurs during phosphate deprivation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02405122
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Growth hormone and triiodothyronine permit an increase in plasma 1,25(OH)2D concentrations in response to dietary phosphate deprivation in hypophysectomized rats (1983)
    Springer
    Calcified tissue international 35 (1983), S. 100-106 
    Details
    ISSN: 1432-0827
    Schlagwort(e): 1,25(OH)2D ; Hypophysectomy ; GH ; T3 ; Phosphorus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Hypophysectomy abolishes the four- to fivefold increase in plasma 1,25(OH)2D levels that normally accompanies dietary phosphate deprivation in rats despite a smaller but significant decrease in plasma phosphate in these animals. This effect appears within 1 week of hypophysectomy and may be the result of a lack of GH, T3, or some other pituitary hormone. In hypothyroid rats (2 weeks after TPTX) not given replacement T3, plasma 1,25(OH)2D levels rose threefold from 148±57 pmol/l to 402±96 pmol/l (mean±SD) after 4 days of dietary phosphate deprivation. However, in hypophysectomized animals given replacement T3 alone, plasma 1,25(OH)2D levels rose fourfold from 82±13 to 333±230 pmol/l after 4 days of phosphate deprivation. In addition, in hypophysectomized animals replaced with GH alone, plasma 1,25(OH)2D levels rose from 243±86 to 525±85 pmol/l during phosphate deprivation. These results would suggest that both GH and T3 must be absent to prevent enhanced renal 1,25(OH)2D synthesis during phosphate deprivation. GH and T3 appear to play a permissive role since plasma levels of these hormones do not increase when intact rats are deprived of phosphate. Furthermore, bioassayable somatomedin levels are also not increased in intact rats during phosphate deprivation as well as plasma levels of prolactin. As observed previously, plasma 1,25(OH)2D levels were inversely correlated to plasma phosphate concentrations (r=0.46,P〈0.025), despite the inclusion of data points for unreplaced hypophysectomized animals who were hypophosphatemic but showed no increase in plasma 1,25(OH)2D. Thus the possibility remains that GH and T3 may exert their effect by permitting the renal 25OHD-1α-hydroxylase to respond to a change in phosphate concentrations during dietary phosphate deprivation, that, in turn, may ultimately increase renal 1,25(OH)2D synthesis and plasma levels of this hormone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02405013
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Control of plasma 1,25-(OH)2-vitamin D concentrations by calcium and phosphorus in the rat: Effects of hypophysectomy (1981)
    Springer
    Calcified tissue international 33 (1981), S. 485-488 
    Details
    ISSN: 1432-0827
    Schlagwort(e): 1,25-(OH)2-D ; Hypophysectomy ; Calcium ; Phosphorus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The mechanism by which dietary phosphate deprivation elevates plasma 1,25-(OH)2-D levels is not known. To evaluate the role of the pituitary in regulating plasma 1,25-(OH)2-D concentrations, the responses of plasma 1,25-(OH)2-D to dietary phosphate deprivation and, separately, to dietary calcium deprivation were evaluated in intact and hypophysectomized male rats. Among intact and hypophysectomized rats eating normal diets, plasma 1,25-(OH)2-D levels averaged 228±76 and 148±62 pmol/1, respectively (P〈0.01). During dietary phosphate deprivation, plasma 1,25-(OH)2-D levels rose to 1160±260 in intact rats and fell to 90±26 pmol/l in hypophysectomized rats (P〈0.001). By contrast, during dietary calcium deprivation, plasma 1,25-(OH)2-D levels rose in both intact and hypophysectomized animals to 856±107 and 742±279 pmol/l, respectively (NS). In response to dietary phosphate deprivation, serum calcium concentrations rose as 1,25-(OH)2-D concentrations rose in intact rats but remained at control levels in hypophysectomized rats. These results support the hypothesis that a pituitary hormone acting either directly or indirectly on the kidney mediates the increase in plasma 1,25-(OH)2-D during dietary phosphate deprivation. The hypercalcemia that occurs in rats during dietary phosphate deprivation appears to depend on the elevation of plasma 1,25-(OH)2-D.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02409478
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Local leukocyte mobilization in irradiated or cyclophosphamide-treated rats (1980)
    Springer
    Cellular and molecular life sciences 36 (1980), S. 1221-1222 
    Details
    ISSN: 1420-9071
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Sprague-Dawley rats made neutropenic by60Co irradiation or cyclophosphamide treatment retained a limited capacity for mounting a local leukocyte mobilization (LLM) response. Rats irradiated with 700 rad60Co lacked an LLM. Rats treated with 100 mg/kg cyclophosphamide showed no LLM following an initial low response when assayed originally.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01976141
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    A comment on the estimation of times required for the attainment of equilibrium by noncooperative, single site ligand-receptor systems (1982)
    Springer
    Cellular and molecular life sciences 38 (1982), S. 648-650 
    Details
    ISSN: 1420-9071
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary A table presents the number of hours required for binding to reach 80% and 95% of the equilibrium value for a noncooperative, single site ligand binding system. A 2nd table provides the fraction of binding sites occupied and the fraction of the total ligand bound at equilibrium under the same conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01964070
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Cytochemical studies of metaphase chromosomes by flow cytometry (1980)
    Springer
    Chromosoma 77 (1980), S. 229-251 
    Details
    ISSN: 1432-0886
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The cytochemical properties of metaphase chromosomes from Chinese hamster and human cells were studied by flow cytometry. This technique allows precise quantitation of the fluorescence properties of individual stained chromosome types. Chromosomes were stained with the following fluorescent DNA stains: Hoechst 33258, DAPI, chromomycin A3, ethidium bromide, and propidium iodide. The relative fluorescence of individual chromosome types varied depending on the stain used, demonstrating that individual chromosome types differ in chemical properties. Flow measurements were performed as a function of stain and chromosome concentration to characterize the number and distribution of stain binding sites. Flow analysis of double stained chromosomes show that bound stains interact by energy transfer with little or no binding competition. For most hamster chromosomes, there is a strong correlation between relative fluorescence and stain base preference suggesting that staining differences may be determined primarily by differences in average base composition. A few hamster chromosome types exhibit anomalous staining which suggests that some other property, such as repetitive DNA sequences, also may be an important determinant of chromosomal staining.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00286050
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Effects of age and sex on the regulation of plasma 1,25-(OH)2-D by phosphorus in the rat (1981)
    Springer
    Calcified tissue international 33 (1981), S. 477-484 
    Details
    ISSN: 1432-0827
    Schlagwort(e): 1,25-(OH)2-D ; Calcium ; Phosphorus ; Sex ; Age
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Dietary phosphate deprivation in women, but not men, is accompanied by a fall in plasma PO4 and a rise in plasma 1,25-(OH)2-vitamin D concentrations. In contrast, young male rats exhibit a fall in plasma PO4 and a rise in plasma 1,25-(OH)2-D concentrations in response to PO4 deprivation. To evaluate whether age and sex influence basal plasma 1,25-(OH)2-D levels and their regulation by PO4 deprivation, plasma 1,25-(OH)2-D, PO4, and Ca levels were measured in male and female rats ranging in age from 6 weeks to 6 months while they were eating normal or low PO4 diets for 1 to 16 days. Similar observations were also made in 6-week-old castrated male and female rats, males replaced with testosterone, and females replaced with estradiol. Basal plasma 1,25-(OH)2-D levels were higher in 6-week-old males (228±76 pmol/l) than in 6-week-old females (148±62 pmol/l;P〈0.01) and declined by age 11 weeks to stable levels averaging about 100 pmol/l without sex difference. Dietary PO4 deprivation resulted in a three-to fourfold increase in plasma 1,25-(OH)2-D concentrations regardless of age and sex, accompanied by a correlated rise in serum Ca concentrations. Castration of 6-week-old males and females eliminated the sex difference in basal plasma 1,25-(OH)2-D levels and appeared to enhance the elevation of plasma 1,25-(OH)2-D concentrations in response to PO4 deprivation in females. Although gonadal hormones may modify basal plasma 1,25-(OH)2-D levels, they are not required for the augmentation of plasma 1,25-(OH)2-D levels in response to PO4 deprivation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02409477
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Effects of weight loss on serum 1,25-(OH)2-vitamin D concentrations in adults: A preliminary report (1984)
    Springer
    Calcified tissue international 36 (1984), S. 139-144 
    Details
    ISSN: 1432-0827
    Schlagwort(e): 1,25(OH)2-vitamin D ; Weight loss ; Phosphate ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary During a review of 42 metabolic studies in healthy women and men we observed that serum 1,25-(OH)2-D concentrations were directly correlated to the observed daily changes in body weight (r=0.68;P〈0.001) and to caloric intake/kg/day (r=0.39;P=0.01). These relationships could not be accounted for by related and physiologically expected changes in serum Ca or iPTH concentrations. However, serum 1,25-(OH)2-D concentrations were observed to be inversely correlated to serum PO4 levels (r=−0.44;P=0.004). In addition, serum PO4 levels were inversely correlated to the daily changes in body weight (r=−0.40;P=0.009). Since dietary sodium intake averaged 142 mmol/day, it is unlikely that the observed changes in weight were the result of changes in salt and water balance. Thus it seems reasonable to speculate that serum 1,25-(OH)2-D concentrations may vary directly with energy balance, as reflected by changes in body weight. This effect may be mediated by alterations in PO4 metabolism. The accurate assessment of serum 1,25-(OH)2-D levels thus appears to require several measurements over time periods during which body weight is stable.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02405309
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Metabolites of vitamin D in normal and X-linked hypophosphatemic mice (1984)
    Springer
    Calcified tissue international 36 (1984), S. 662-667 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Vitamin D ; Hyp ; X-linked hypophosphatemia ; Metabolic bone disease ; Mice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Hyp mice are a model for human X-linked hypophosphatemia (vitamin D-resistant rickets.) To determine whether an abnormality of vitamin D metabolism exists in this disease, the profiles of the metabolites of vitamin D were determined in normal andHyp mouse plasma.Hyp and normal mice were fed a vitamin D-deficient diet and received 1,23H-vitamin D3 at 16 Ci/mmol by stomach tube at 5 ng/g body weight (0.21 µCi/g b.w.) on alternate days for 14 days. The dose of vitamin D given maintained near normal plasma 25-OH-vitamin D. Thus the mice were in a vitamin D-replete state with all metabolite pools labeled with3H. Plasma was collected from 4 normal and 4Hyp mice. The plasma was extracted, and the extracts were chromatographed separately for each mouse on an LH-20 column. Each major peak of radioactivity was rechromatographed using high performance liquid chromatography on a Zorbax-Sil column using solvent systems known to resolve several vitamin D metabolites. Twenty-one radioactive peaks were identified. The disintegrations per minute of3H in each peak were quantified and converted to plasma concentration using the known specific activity of the administered vitamin D. The 25-OH-vitamin D accounted for 55% of the circulating radioactivity, and 24,25-(OH)2-vitamin D accounted for 22%. The plasma levels of 24,25-(OH)2-vitamin D were similar to levels previously reported by us using protein binding assays. No peaks of radioactivity were missing in the plasma extracts of theHyp mice. Also there was no evidence that plasma 24,25-(OH)2-vitamin D was elevated in theHyp mice.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02405387
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