No description available.

The principal objective of the research was to model the outflow results of multiple tracer outflow dilution (M.T.O.D.) techniques from the canine tibia so as to obtain a more precise understanding of the physiological mechanisms underlying mineral exchange in bone. To date, M.T.O.D. techniques have been performed on the tibiae of greyhound dogs but the subsequent outflow results have produced information mainly at the capillary level for the diffusible tracers concerned such as capillary permeability-surface area PSC products from the widely used Crone-Renkin formulation. Back diffusion and heterogeneous capillary flow rates lacking from the formulation, however, have impaired the accuracy of PS(C). Outflow results from two series of previously performed M.T.O.D. experiments were modelled. In the first experimental series, outflow results from the ipsilateral femoral vein concerning l25l-albumin reference and 85Sr (Ca analogue), 86Rb (K analogue) diffusible tracers were used ; the tracers having being injected into the tibial nutrient arteries. In the second experimental series, 125l-albumin and 85Sr outflow results were used from parathyroidectomised dogs in which both tracers had been injected together before and after a dose of 0.0005 mg bovine parathyroid hormone (PTH). The problem of back diffusion was alleviated by optimising a homogeneous flow model to M.T.O.D. data. The model produced informative parameter estimates for 85Sr and 86Rb concerning fluid spaces and associated boundaries in Haversian systems largely comprising the diaphyseal cortex. Exchange was assumed to take place there by virtue of injecting the tracers into the tibial nutrient artery. Blood flow rates, known to be influential in governing the extent of tracer exchange in the diaphysis, were investigated using the microsphere technique. Flow rate heterogeneity was found to be substantial, as adjudged by distributions of relative deposition densities of microspheres in 40 pieces of cortex and 10 marrow samples in 6 tibiae. For the cortex, the distributions were positively skewed with a relative dispersion of around 40%. Additional work involving light microscopy suggested that the distribution of cortical flow rates were not attributable to particular changes in capillary density, which were relatively uniform at 2682 + 510 capillaries/cm2 (4 tibiae ; 240 observations). The findings concerning flow rate heterogeneity, together with the deduction that the cortex and marrow respectively received 65% and 35% of tibial nutrient artery flow, prompted the development of a parallel multicapillary model in which 4 capillary systems were alloted to the cortex and 1 such system to the marrow. Input to the model was a suitable form of the reference tracer outflow profile which describes the large vessel transport behaviour assumed identical for all tracers concerned. Parameter estimates (mean + s.d.) found by optimisation for 85Sr and 86Rb (n=6) were PSC = 0.045 + 0.021 and 0.047 + 0.022 ml/s respectively. Apparent volumes of distribution (n=5) for the interstitial fluid were 0.90 + 0.36 (85Sr) and 0.69 + 0.22 ml of diaphysis (86Rb). Additional studies involving gamma variates showed that model inputs were robust in terms of varying degrees of large vessel dispersion. Furthermore, simulation studies involving the effect of asymmetric transport on the resulting parameter estimates in the context of modelling the PTH data provided speculative evidence for the concept of a bone-lining cell membrane controlling uptake to bone surfaces.

The purpose of this study was to determine whether there are differences in bone mineral content and density between paralyzed and nonparalyzed sides of patients who had sustained strokes associated with unilateral muscle weakness, to determine the relationship between duration of stroke and degree of demineralization and to compare the degree of demineralization in upper and lower limbs. The bone mineral content and density were measured by dual photon absorptiometry (high resolution scanning mode, Lunar DP4) in ambulant patients with a history of single completed strokes associated with unilateral weakness. The bone mineral content and density of each limb was determined by the region of interest analysis program. In the 30 patients included in this study, the bone mineral content and density were significantly less on the paralyzed than on the nonparalyzed side. The degree of demineralization was more pronounced in the upper than in the lower limbs. The mean percentage differences in bone mineral content and density between paralyzed and nonparalyzed arms were 13.8% (P < 0.00001) and 7.95% (P = 0.0003), respectively, and between paralyzed and nonparalyzed legs the differences were 4.5% (P = 0.0012) and 3.42% (P = 0.0028), respectively. A better correlation was noted between the time elapsed since the stroke and the degree of demineralization in the upper limbs (r = 0.75, P < 0.0001), than in the lower limbs (r = 0.60, P = 0.0004). In conclusion, patients who have strokes associated with muscle weakness are at an increased risk of developing osteoporosis on the paralyzed side and particularly in the upper limbs.

There is a need for an improved bone mineral density measurement procedure for neonates. Currently, measurements are made using single photon absorptiometry (SPA). The poor reproducibility of this method means that it has little direct clinical diagnostic application and is therefore not suitable for diagnosing disease in individual patients. A technique using digital radiography has been developed to measure bone mineral density. Digital images of phantoms and chicken bones were acquired at two kvp settings of a digital angiographic unit. Digital information from water, aluminum and lucite phantoms were used to calculate effective mass attenuation coefficients of the phantom materials. These values were subsequently used in bone mineral density calculations of sections of the chicken bones. The bone mineral densities of the chicken bones obtained from the digital radiography method were compared to SPA measurements. The digital radiography method gave consistently higher bone mineral densities for the bones than SPA. This could be due to the differences in measurement technique as SPA scans a single slice whereas digital radiography images a large area of the bone. / Thesis / Master of Science (MSc)

No description available.

The purpose of the study was to examine the relationship and comparisons of athletic amenorrhea and bone mineral density in adolescent, cross-country runners. Subjects: Twenty-eight female adolescent cross-country runners (Mean Age + SD = 15.0 + 1.3 years); consisting of seventeen eumenorrheics & eleven amenorrheics. Design: The design consisted of a sixmonth longitudinal design in which the subjects were measured before and after cross-country season for height, weight, and lean tissue (LT), body fat (BF), bone mineral content (BMC), and bone mineral density (BMD) using whole-body scan densitiometry with a Lunar Dual-energy X-ray Absorptiometer (DXA). Run performance, weekly training volumes, menstrual dysfunction, menarchal age, nutritional information, and stress fractures were reported by the subjects. Statistical analyses consisted of Pearson product-moment and partial correlations to examine the associations of the variables, paired t-tests to measure seasonal body composition changes, multivariate analysis (MANOVA & MANCOVA) to investigate the subgroup differences of variables, and simple linear regression to determine the best body composition predictor variable for BMD. Results: The eumenorrheic subgroup's BMD was significantly greater than the amenorrheic subgroup's BMD (F(1, 54) = 16.22, p<.05, partial h² =.231). The eumenorrheic subgroup's bodyweight (F(1, 54) = 7.65, p<.05, partial h² =.124), BF (F(1, 54) = 8.56, p<.05, partial h² =.137), and BMC (F(1, 54) = 8.52, p<.05, partial h² =.136) were significantly greater than the amenorrheic subgroup. There was also a significant seasonal increase in BMD (t(27) = -4.01, p <.05) for the overall group. Bodyweight was the body composition component that best predicted BMD (F(1, 26) = 46.434, p<.05, R² =.641). There were no significant subgroup differences with respect to run performance, stress fractures, and nutritional supplementation. Conclusions: Athletic amenorrhea was highly associated with lower levels of BMD in adolescent, cross-country runners. Athletic amenorrhea was also highly associated with lower levels of bodyweight, BF, and BMC in adolescent cross-country runners. Finally, cross-country running was highly associated with increased BMD in adolescent athletes. Implications: The long-term implication of the study is that subjects with lower levels of BMD may be at a greater risk of osteoporosis. Recommendations: Educate and instruct runners to utilize proper training methods so the healthful benefits of crosscountry running, as well as improved performance, are obtained.

Development of peak bone mass during childhood to early adulthood has been considered as a major determinate of risk of fracture and osteoporosis later in life. The purpose of this project was to determine the impact of food and nutrient intake on bone from childhood to early adulthood using mixed longitudinal data from the University of Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS). <p>To determine the role of consumption of milk products and vegetable and fruit on the total body-bone mineral content (TB-BMC) accrual in boys and girls from childhood to late adolescence, seven-year longitudinal data were used. Using a multilevel modeling statistical approach containing major biological and environmental factors, vegetables and fruit intake, calcium intake and physical activity were significant independent environmental predictors of TB-BMC in boys. <p>Change in the pattern of beverage intake of adolescents as a major component of nutrition transition has aroused health concerns such as obesity, tooth decay, and inadequate bone accrual. Beverage consumption and its relationship with calcium intake of grade 9 students from 1991 to 2004 was evaluated. Percent contribution of milk to total beverage intake was significantly decreased in boys and girls. A significant negative association between milk intake and consumption of non-carbonated soft drinks was observed in both genders. In girls only, a significant negative trend in calcium intake was observed over time. <p>Milk products, specifically fluid milk, were the major source of dietary calcium from childhood to early adulthood in both genders. There was a substitution of fluid milk by cheese, a decrease in vegetable and fruit intake, and the low intake of vitamin D in young adults, specifically females. <p>The effect of food and nutrient intake, measured at young adult age and previously in peri-adolescence, on bone mass was investigated. In males, the intake of calcium from peri-adolescence to early adulthood was sustained, whereas in females, there was a significant decrease. Height, weight, protein intake, physical activity and gender were the significant predictors of bone measures only in young adults who had consistent calcium intake from peri-adolescence. Collectively, the results of this study present the bone protective nutrients and food groups from childhood to early adulthood in our cohort. The food choices and dietary habits of the cohort change by age, but not in the favour of bones, with females more at risk. To prevent risk of osteoporosis, there should be promotion of a healthy dietary plan, not a single food group or nutrient, accompanied with an adequate level of physical activity.

Development of peak bone mass during childhood to early adulthood has been considered as a major determinate of risk of fracture and osteoporosis later in life. The purpose of this project was to determine the impact of food and nutrient intake on bone from childhood to early adulthood using mixed longitudinal data from the University of Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS). <p>To determine the role of consumption of milk products and vegetable and fruit on the total body-bone mineral content (TB-BMC) accrual in boys and girls from childhood to late adolescence, seven-year longitudinal data were used. Using a multilevel modeling statistical approach containing major biological and environmental factors, vegetables and fruit intake, calcium intake and physical activity were significant independent environmental predictors of TB-BMC in boys. <p>Change in the pattern of beverage intake of adolescents as a major component of nutrition transition has aroused health concerns such as obesity, tooth decay, and inadequate bone accrual. Beverage consumption and its relationship with calcium intake of grade 9 students from 1991 to 2004 was evaluated. Percent contribution of milk to total beverage intake was significantly decreased in boys and girls. A significant negative association between milk intake and consumption of non-carbonated soft drinks was observed in both genders. In girls only, a significant negative trend in calcium intake was observed over time. <p>Milk products, specifically fluid milk, were the major source of dietary calcium from childhood to early adulthood in both genders. There was a substitution of fluid milk by cheese, a decrease in vegetable and fruit intake, and the low intake of vitamin D in young adults, specifically females. <p>The effect of food and nutrient intake, measured at young adult age and previously in peri-adolescence, on bone mass was investigated. In males, the intake of calcium from peri-adolescence to early adulthood was sustained, whereas in females, there was a significant decrease. Height, weight, protein intake, physical activity and gender were the significant predictors of bone measures only in young adults who had consistent calcium intake from peri-adolescence. Collectively, the results of this study present the bone protective nutrients and food groups from childhood to early adulthood in our cohort. The food choices and dietary habits of the cohort change by age, but not in the favour of bones, with females more at risk. To prevent risk of osteoporosis, there should be promotion of a healthy dietary plan, not a single food group or nutrient, accompanied with an adequate level of physical activity.

No description available.

No description available.