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  • 1
    ISSN: 1432-0827
    Keywords: Bone mineral analysis ; Hip strength analysis ; Age ; Femoral neck stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The greater hip fracture rate among elderly women is generally ascribed to differences in femoral neck strength between the sexes. Strength of a given bone is a function of both its material properties and the magnitudes of mechanical stresses within it. This study examined the hypothesis that these apparent strength differences between the sexes are due to dissimilarities in the restructuring of the femoral neck with age, which result in higher stresses in elderly women. Using Hip Strength Analysis, a computer program developed by the authors, femoral neck cross-sectional geometric properties for stress analyses were derived from bone mineral image data of 409 community living, white subjects ranging from 19 to 93 years of age. Though both sexes show declines in femoral neck bone mineral density (BMD) and cross-sectional area with age, only females show a decline in the cross-sectional moment of inertia (CSMI, a geometric index of bone rigidity). The lack of decline in male CSMI appears to be a result of a small but significant increase in femoral neck girth. Similar age-related changes have been observed in the femoral shaft by others. The net effect of these observed changes is that mechanical stresses in the femoral neck of females appear to increase at three times the rate per decade of those of males. These results lend support to the hypothesis that the higher fracture rate in elderly women is due, at least in part, to elevated levels of mechanical stress, resulting from a combination of greater bone loss and less compensatory geometric restructuring with age.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 369 (1977), S. 65-73 
    ISSN: 1432-2013
    Keywords: Carotid sinus nerve ; Primary afferent fibres ; Nucleus of the tractus solitarius ; C-fibres ; Antidromic potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Compound action potentials evoked by electrical stimulation in the brainstem of anaesthetized, paralyzed cats and rabbits were recorded distally in the carotid sinus nerve. The latencies of the components of the responses were indicative of fibres with conduction velocities between 0.5 and 32 m/s. These include both myelinated and unmyelinated fibres. Using histological reconstructions of the ‘responsive sites’, the termination of the primary afferent fibres of the sinus nerve within the medulla was mapped. In both cat and rabbit these responsive sites were restricted to thedorsomedial medulla in the vicinity of the NTS 0–3 mm rostral to the obex. Although in the cat the fast conducting myelinated fibres (conduction velocities 〉12.5 m/s) were discretely localized to the ventrolateral area of the NTS, the slower conducting myelinated and unmyelinated fibres were found more diffusely, spreading into areas dorsal and medial to the NTS. In the rabbit the terminals of all types of fibre were mainly confined to the NTS although some C fibres appeared to be grouped in the juxta-alar region. Responses were never evoked from the medial reticular formation or nucleus ambiguus in either cats or rabbits. The organization of the sinus nerve input to the medulla is discussed in the light of these results.
    Type of Medium: Electronic Resource
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