Prolonged low-dose infusion of human parathyroid hormone does not increase femoral cancellous bone volume in ovariectomized rats.
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OBJECTIVE: Daily injections of human parathyroid hormone (hPTH) increase bone volume in various animal species and in osteoporotic women. For hPTH to be widely accepted as an anabolic therapy for treating postmenopausal osteoporosis alternative delivery options need to be explored to replace the need for daily patient subcutaneous self-injection. Among these are inhalation, oral delivery and the use of programmable implanted minipumps to deliver the peptide. While infusion of high doses of PTH causes bone loss and hypercalcemia, no studies have assessed the effects of prolonged infusion of low doses of PTH on bone growth. DESIGN AND METHODS: [Leu(27)]-cyclo(Glu(22)-Lys(26))-hPTH-(1--31)NH(2) was delivered by Alzet minipumps to ovariectomized rats for 6 weeks after which histomorphometric indices (cancellous bone volume, trabecular thickness, mean trabecular number) of bone formation were measured in distal femurs. RESULTS: Infusing low doses (0.05 and 0.1 nmole/100g body weight/day) of the hPTH analog, [Leu(27)]-cyclo(Glu(22)-Lys(26))-hPTH-(1--31)NH(2), for 6 weeks does not prevent the ovariectomy-induced loss of rat femoral cancellous bone volume, trabecular thickness or trabecular number. CONCLUSION: These results support the absolute requirement of daily injections for the osteogenic action of hPTH on bone. (+info)
Bone response to orthodontic loading of endosseous implants in the rabbit calvaria: early continuous distalizing forces.
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The purpose of this experimental study was to evaluate the effect of early orthodontic loading on the stability and bone-implant interface of titanium implants in a rabbit model. Twenty-four short threaded titanium fixtures were inserted in the calvarial mid-sagittal suture of 10 rabbits. Two weeks following insertion, 20 implants (test group) were subjected to continuous distalization forces of 150 g for a period of 8 weeks. The remaining four implants (control group) were left unloaded for the same follow-up interval. Clinically, all implants except for one test fixture were stable, and exhibited no mobility or displacement throughout the experimental loading period. Histologically, all stable implants were well-integrated into bone. No differences could be found between the pressure and tension surfaces of the test implants relative to bone quality and density within a range of 1000 microns from the fixture surface. Similarly, qualitative differences were not observed between the apical and coronal portions of test fixtures. Morphometrically, a mean percentage bone-to-implant contact of 76.00 +/- 18.73 per cent was found at the test pressure sides, 75.00 +/- 11.54 per cent at the test tension sides, and 68.00 +/- 15.55 per cent at the control unloaded surfaces. No statistically significant differences in the percentage of bone-to-metal contact length fraction were found between test pressure surfaces, test tension surfaces, and unloaded control surfaces. Marginal bone resorption around the implant collar or immediately beneath it was found in roughly the same percentage of analysed sites in the test and control fixtures. In contrast, slight bone apposition was demonstrated at the implant collar of the test pressure surfaces, while no apposition or resorption were observed in the test tension zones. This study suggests that short endosseous implants can be used as anchoring units for orthodontic tooth movement early in the post-insertion healing period. (+info)
Mechanical loading attenuates bone loss due to immobilization and calcium deficiency.
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Our purpose was to determine the effects of a mechanical loading intervention on mass, geometry, and strength of rat cortical bone during a period of disuse concurrent with calcium deficiency (CD). Adult female rats were assigned to unilateral hindlimb immobilization, immobilized-loaded, or control (standard chow, 1.85% calcium) treatments. Both immobilized groups were fed a CD rat chow (0.01% calcium) to induce high bone turnover. Three times weekly, immobilized-loaded rats were subjected to 36 cycles of 4-point bending of the immobilized lower leg. After 6 wk, the immobilized rats exhibited decreased tibial shaft bone mineral density (-12%), ultimate load (-19%), and stiffness (-20%; tested in 3-point bending to failure) vs. control rats. Loading prevented this decline in bone density and attenuated decreases in ultimate load and stiffness. Elastic modulus was unaffected by disuse or loading. Bone cross-sectional area in the immobilized-loaded rats was equivalent to that of control animals, even though endocortical resorption continued unabated. On the medial periosteum, percent mineralizing surface doubled vs. that in immobilized rats. This loading regimen stimulated periosteal mineralization and maintained bone mineral density, thereby attenuating the loss in bone strength incurred with disuse and concurrent calcium deficiency. (+info)
Fat mass deposition during pregnancy using a four-component model.
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Estimates of body fat mass gained during human pregnancy are necessary to assess the composition of gestational weight gained and in studying energy requirements of reproduction. However, commonly used methods of measuring body composition are not valid during pregnancy. We used measurements of total body water (TBW), body density, and bone mineral content (BMC) to apply a four-component model to measure body fat gained in nine pregnant women. Measurements were made longitudinally from before conception; at 8-10, 24-26, and 34-36 wk gestation; and at 4-6 wk postpartum. TBW was measured by deuterium dilution, body density by hydrodensitometry, and BMC by dual-energy X-ray absorptiometry. Body protein was estimated by subtracting TBW and BMC from fat-free mass. By 36 wk of gestation, body weight increased 11.2 +/- 4.4 kg, TBW increased 5.6 +/- 3.3 kg, fat-free mass increased 6.5 +/- 3.4 kg, and fat mass increased 4.1 +/- 3.5 kg. The estimated energy cost of fat mass gained averaged 44,608 kcal (95% confidence interval, -31, 552-120,768 kcal). The large variability in the composition of gestational weight gained among the women was not explained by prepregnancy body composition or by energy intake. This variability makes it impossible to derive a single value for the energy cost of fat deposition to use in estimating the energy requirement of pregnancy. (+info)
Prevention of osteoporosis and fractures.
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Osteoporosis and low bone density are associated with a risk of fracture as a result of even minimally traumatic events. The estimated lifetime risk of osteoporotic fracture is as high as 50 percent, especially in white and Asian women. The use of caffeine, tobacco and steroids is associated with a decrease in bone density. Cognitive impairment, vision problems and postural instability increase the risk of falling and sustaining a fracture. Medications such as long-acting sedative hypnotics, anticonvulsants and tricyclic antidepressants also increase this risk. Combinations of clinical and radiographic findings can predict fracture risk more effectively than bone densitometry, but often only after the first fracture has occurred. The addition of dietary calcium and/or vitamin D is clearly both cost-effective and significant in reducing the likelihood of fractures. Bisphosphonates reduce fracture risk but at a cost that may be prohibitive for some patients. Estrogen and estrogen-receptor modulators have not been well studied in randomized trials evaluating the reduction of fractures, but they are known to increase bone density. Pharmacologic therapy and the reduction of sensory and environmental hazards can prevent osteoporotic fractures in some patients. (+info)
Bone mineral density of the proximal femur after unilateral cementless total hip replacement.
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It was the aim of this study to examine bone mineral density changes in the non-operated contralateral femur of patients undergoing total hip replacement. Bone density in the contralateral femur of 45 patients with an average age of 54 years was measured with the aid of the DEXA technique at one week, 3 and 6 months after total hip replacement. Within the first 3 months there was an average reduction of bone density of 3.9% (3.0%-5.9%). After a further 3 months the average difference was 2.5%. (+info)
The 4A syndrome association with osteoporosis.
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4A syndrome is characterised by adrenocortical insufficiency, achalasia, alacrima, autonomic and other neurological abnormalities. We report an 18-year-old boy with 4 A syndrome and having all classical features of the disease including sensorimotor neuropathy. In addition, the patient had low aldosterone levels and signs of osteoporosis, which apparently developed without glucocorticoid replacement therapy. Although it is speculated that the lack of local growth factors, nutritional deficiency secondary to achalasia or receptor abnormalities regarding bone metabolism contribute to osteoporosis, its etiopathogenesis still needs to be clarified. (+info)
Decreased bone area, bone mineral content, formative markers, and increased bone resorptive markers in endogenous Cushing's syndrome.
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It is well established that chronic excess of glucocorticoids has negative effects on bone and collagen turnover, and that secondary osteoporosis is a known clinical complication of endogenous Cushing's syndrome (CS). The aim of the present study was to evaluate bone dimension and bone mineral content in relation to biochemical markers of bone and collagen turnover, in a consecutive series of 23 patients with endogenous CS (18 with pituitary adenoma and 5 with adrenal tumor; 17 women, 6 men; mean age 39.7+/-2.8 (S.E. M.) and 44.3+/-3.1 years respectively), compared with 23 age-, sex- and body mass index-matched healthy controls. Bone mineral densities were uniformly reduced in the different regions analyzed: lumbar spine (16.1%, P<0.001), femoral neck (15.2%, P<0.001), total body (11.5%, P<0.001), and the subregions of arms (8.4%, P<0.05), legs (10.1%, P<0.05) and trunk (15.8%, P<0.001). Similar results were observed for bone mineral content, although these were less prominent. The calculated area was significantly decreased in trunk (13.8%, P<0.01) and total body (11.6%, P<0.05). Serum levels of osteocalcin were significantly decreased (28%, P<0.03) in patients with CS. No significant differences were observed for the formative markers carboxyterminal propeptide of type I procollagen and aminoterminal propeptide of type I procollagen. Markers of bone resorption, serum Crosslaps and carboxyterminal cross-linked telopeptide of type I collagen were increased in patients compared with controls, although only significantly for Crosslaps (P<0.02). No correlations between formative and resorptive markers were found in the patients, but in controls, the formative markers were positively correlated with resorptive markers. In conclusion, bone dimension and bone mineral content of the entire skeleton are found to be decreased in endogenous CS. As judged by biochemical markers of bone remodeling, this is caused by decreased bone formation and an increased bone resorption. (+info)