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  • 1
    Electronic Resource
    Electronic Resource
    Effects of combined and separate intermittent administration of low-dose human parathyroid hormone fragment (1–34) and 17β-estradiol on bone histomorphometry in ovariectomized rats with established osteopenia (1992)
    Springer
    Calcified tissue international 50 (1992), S. 214-220 
    Details
    ISSN: 1432-0827
    Keywords: Ovariectomy ; Osteopenia ; PTH ; Estradiol ; Bone turnover ; Quantitive bone histomorphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary To evaluate the potential use of a combination of parathyroid hormone (PTH) and estrogen as therapy for osteoporosis, we examined the effects of combined and separate administration of low-dose PTH and estradiol in ovariectomized rats with established osteopenia. Ovariectomized rats were untreated for 5 weeks after surgery and then injected s.c. with vehicle (Ovx+V), 1–34 hPTH (2.5 μg/kg/day) (Ovx+P), 17β-estradiol (50 μg/kg/day) (Ovx+E), or a combination of these (Ovx+P+E), for a further 4 weeks. We found no differences in serum calcium, tubular reabsorption of phosphate, or 25OHD. 1,25(OH)2D levels were significantly higher in Ovx+P and lower in Ovx+E, when compared with Ovx+V. Though there was no change in bone mineral density (BMD) in the diaphysis region of femurs, reduction of BMD in the distal region of the femurs in Ovx+V was reversed in Ovx+E and Ovx+P+E. Compared with Ovx+V, Ovx+P and Ovx+P+E had significantly higher cancellous bone volume (Cn-BV/TV) whereas Ovx+E showed a nonsignificant increase. When indices of bone turnover were examined, PTH alone showed a small but not significant improvement in bone formation rate (BFR). Increased osteoclast surface (OCS), as the result of ovariectomy, was inhibited in Ovx+E and Ovx+P+E. Estrogen alone (Ovx+E) severely inhibited BFR, but co-administration of PTH and estrogen (Ovx+P+E) showed an impressive reversal of such inhibition. The changes in BFR were mainly derived from changes in double-labeled surface (dLS), except a small increase in mineral apposition rate was also observed in Ovx+P+E. These results suggest that, after extensive cancellous bone loss in the rat tibia, low doses of PTH function anabolically, especially in situations where the bone formation rate is low. A combination of both estrogen and PTH may provide the best treatment for improving bone mass by decreasing resorption and maintaining a high bone formation rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296285
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  • 2
    Electronic Resource
    Electronic Resource
    A high affinity, calmodulin-responsive (Ca^2^+ + Mg^2^+)-ATPase in isolated bone cells
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 727 (1983), S. 230-238 
    Details
    ISSN: 0005-2736
    Keywords: (Ca^2^+ + Mg^2^+)-ATPase ; (Rat bone cell) ; Ca^2^+ flux ; Calmodulin response
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2736(83)90408-X
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  • 3
    Electronic Resource
    Electronic Resource
    Cyclic AMP-dependent and calcium-dependent signals in parathyroid hormone function
    Amsterdam : Elsevier
    Experimental Gerontology 25 (1990), S. 223-231 
    Details
    ISSN: 0531-5565
    Keywords: DNA synthesis ; bone resorption ; cAMP ; intracellular calcium ; parathyroid hormone ; protein kinase C ; signal transduction
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0531-5565(90)90056-8
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of the dark current in doped-well multiple quantum well AlGaAs infrared photodetectors (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5656-5658 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the origin of the dark current in λ=8 μm peak wavelength 40-A(ring) GaAs/300-A(ring) Al0.3 Ga0.7 As multiple quantum well photodetectors. By carefully controlling the experimental conditions we have measured the dark current for temperatures in the range 4–120 K. The experimental characteristics are explained by thermionic emission for low biases and tunneling for high biases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343630
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  • 5
    Electronic Resource
    Electronic Resource
    Tunable long-wavelength detectors using graded barrier quantum wells grown by electron beam source molecular beam epitaxy (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 383-385 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We discuss a new design for a voltage tunable graded barrier multiquantum well infrared detector. The tunability of this detector is significantly better than previous designs. It has large shifts in peak position, spectral width, and long-wavelength cutoff.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103699
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  • 6
    Electronic Resource
    Electronic Resource
    High sensitivity low dark current 10 μm GaAs quantum well infrared photodetectors (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 851-853 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By increasing the quantum well barrier width, we have dramatically reduced the tunneling dark current by an order of magnitude and thereby significantly increased the blackbody detectivity D@B|BB. For a GaAs quantum well infrared detector having a cutoff wavelength of λc=10.7 μm, we have achieved D*BB =1.0×1010 cm (Hz)1/2/W at T=68 K, a temperature which is readily achievable with a cryogenic cooler.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102682
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  • 7
    Electronic Resource
    Electronic Resource
    Absence of isochromosome 12p in a pineal region malignant germ cell tumor
    Amsterdam : Elsevier
    Cancer Genetics and Cytogenetics 50 (1990), S. 153-160 
    Details
    ISSN: 0165-4608
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0165-4608(90)90249-A
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  • 8
    Electronic Resource
    Electronic Resource
    Parathyroid Hormone Secretory Response to EDTA-Induced Hypocalcemia in Black and White Premenopausal Women (1999)
    Springer
    Calcified tissue international 65 (1999), S. 257-261 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Parathyroid responsivity — EDTA hypocalcemia — Racial differences — Black women.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. One consistent racial difference in mineral homeostasis is increased efficiency of renal calcium conservation in blacks which could account, in part, for differences in bone density and fracture risk. Since parathyroid hormone (PTH) is the major regulator of calcium homeostasis, we investigated its secretion in black and white women in response to hypocalcemia. Two hour EDTA infusions (50 mg/kg) were performed in 34 premenopausal women (17 black, 17 white). Blood was sampled at 30-minute intervals during the infusion, at 60-minute intervals for 3 more hours, and at 24 hours. Serum ionized calcium decreased identically in both groups with a nadir at 2 hours and returned to baseline within 24 hours. Serum 1-84 PTH levels rose similarly in both groups with a peak PTH level that was slightly higher in black women, and on average, slightly earlier than that in white women. Serum PTH levels remained elevated in both groups at 24 hours with no overall group differences in PTH response. In black, but not white women, serum 25OHD levels correlated negatively with both basal PTH and peak PTH level, achieved with infusion. Serum 1,25(OH)2D levels rose and osteocalcin levels decreased, with no group differences. We conclude that overall, premenopausal black women show no clear differences in PTH secretory activity to an EDTA-induced hypocalcemic stimulus. Basal vitamin D status appeared to be a determinant of the degree of the PTH response in black women, with the peak PTH level being inversely correlated with levels of 25OHD. Since we have previously shown that the skeleton contributes less to acute calcium needs in blacks than in whites, the lack of a racial difference in PTH secretory responsivity suggests that calcium homeostasis is more likely maintained in blacks through greater PTH sensitivity at extraskeletal sites, such as the kidney.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900694
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  • 9
    Electronic Resource
    Electronic Resource
    Biochemical Responses of Bone Metabolism to 1,25-Dihydroxyvitamin D Administration in Black and White Women (2000)
    Springer
    Osteoporosis international 11 (2000), S. 271-277 
    Details
    ISSN: 1433-2965
    Keywords: Key words:1,25(OH)2D – Bone metabolism – Bone turnover – Calcium conservation – Dynamic tests – Racial differences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: The basis for the racial difference in bone mass between black and white women is not known. Lower bone turnover, better renal calcium conservation, and decreased sensitivity to parathyroid hormone (PTH) have been proposed as explanations. A dynamic comparison of osteoblast function, utilizing stimulation by 1,25-dihydroxyvitamin D [1,25(OH)2D], has not been tested between these two ethnic groups. We compared well-matched black (n= 15) and white (n= 15) premenopausal women, before and during 5 days of 1,25(OH)2D administration (1.0 μg/day) in order to assess dynamic indices of bone metabolism. As expected, at baseline, black women had lower levels of serum 25-hydroxyvitamin D and biochemical markers of bone turnover with slightly higher levels of PTH. Black women also had superior renal calcium conservation than white women at baseline. In response to 1,25(OH)2D administration, black women had a slightly greater increase in serum calcium and greater decrement in PTH. Moreover, black women showed a lesser increment in urinary calcium than white women and a more robust increase in two markers of bone formation – osteocalcin and carboxyterminal propeptide of type 1 procollagen – than white women. There were no changes in bone resorption indices in either race upon 1,25(OH)2D administration. These data provide preliminary evidence that black women conserve calcium more efficiently under both static and dynamic conditions, and also appear to have better osteoblastic functional reserve than white women.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001980050292
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