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  • 1
    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
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  • 2
    ISSN: 1432-0649
    Keywords: PACS: 42.55R; 42.60B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 3+ :LiSrAlF6 (Cr:LiSAF) regenerative amplifier, seeded by a diode-pumped Cr:LiSAF femtosecond oscillator. The amplifier produced pulses of less than 200 fs duration and greater than 1 μJ energy at repetition rates of up to 25 kHz.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1433-2965
    Keywords: Bone histomorphometry ; Bone mass ; Cancellous bone structure ; Cancellous bone strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to examine the relationship between histomorphometric variables of cancellous bone structure and ultimate compressive strength (UCS) in the second lumbar vertebra (L2) and to determine whether structural variables in the iliac crest are predictive of the same variables and of UCS in L2. At autopsy, 7.5 mm diameter cores were removed from the iliac crest and from L2 of 29 subjects who had died suddenly without bone disease. Cancellous bone volume (BV/TV, %) was significantly lower in L2 than in iliac crest due to lower trabecular number (Tb.N, per mm) and thickness (Tb.Th, µm). There were significant correlations between iliac crest and L2 for BV/TV, Tb.N and trabecular separation (Tb.Sp, µm), but not for Tb.Th. BV/TV was negatively correlated, and Tb.Sp was positively correlated with age at both sites. Tb.Th was not significantly correlated with age in the iliac crest, but a significant negative correlation was observed in L2. The UCS of vertebral cores was negatively correlated with age. BV/TV and Tb.Th in L2 were positively correlated with UCS in L2. Cortical width and BV/TV in iliac crest were positively correlated with UCS in L2. We conclude that: (1) cancellous bone volume in the iliac crest is higher than in the lumbar spine due to thicker, more closely spaced trabecular plates, (2) the changes in structural variables with age are generally similar in the iliac crest and lumbar vertebra, but trabecular thinning with age is more evident in the spine than in the ilium, and (3) the compressive strength of cancellous bone in the lumbar spine is correlated with histomorphometric variables of bone structure, as measured both in the lumbar spine and in the iliac crest.
    Type of Medium: Electronic Resource
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