The diagnosis of osteoporosis is based on the measurement of bone mineral density (BMD). There are a number of clinical risk factors that provide information on fracture risk over and above that given by BMD. The assessment of fracture risk thus needs to be distinguished from diagnosis to take account of the independent value of the clinical risk factors. These include age, a prior fragility fracture, a parental history of hip fracture, smoking, use of systemic corticosteroids, excess alcohol intake and rheumatoid arthritis. The independent contribution of these risk factors can be integrated by the calculation of fracture probability with or without the use of BMD. Treatment can then be offered to those identified to have a fracture probability greater than an intervention threshold.
The influence of GABAA receptors on orientation selectivity of cat complex cells was tested by iontophoresis of the GABAA receptor blockers bicuculline and N-methyl-bicuculline while stimulating with drifting sinusoidal gratings. Reduction of orientation tuning was markedly less than reported in previous studies that used drifting bars as visual stimuli. Only 3/31 cells lost orientation selectivity, with an average increase in bandwidth of 33%, as opposed to half the cells losing selectivity and a bandwidth increase for the remainder of 47% as reported previously. Infusion of GABAA blockers revealed a prominent stimulus onset transient response, lasting about 120 ms, that showed a broadening of orientation selectivity comparable to that found using drifting bars under similar circumstances. We believe that drifting gratings emphasize a steady-state response component that retains, in the presence of GABAA blockers, significant orientation selectivity. Because the onset transient is initially unselective for orientation, we suggest that the steady-state, orientation-selective response component develops from an alternate inhibitory mechanism, possibly mediated by GABAB receptors.
The burden of osteoporosis in developing countries is increasing dramatically with the aging of the population and demographic trends; however, there is a lack of direct epidemiologic data. There are clear differences at present between and within populations that limits the validity of many estimates and more data is needed. Existing data and estimates are considered in terms of bone mass, bone structure, 10-year and lifetime probability of fracture, numbers sustaining fractures, the outcome of fracture, importance of differences in fracture management, and risk factors for their occurrence and outcome. Future trends are also considered.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.