The aim of this study was to quantitatively clarify the c-axis alignment of biological apatite (BAp) crystallites (hereafter referred to as BAp alignment) in the cortical bone of the human mandible first molar. Six mandible specimens were collected from the cadavers of six dentulous Japanese adults (mean age, 63.0 +/- 12.1 years) held at the Department of Anatomy, Tokyo Dental College. A microbeam x-ray diffraction system was used to determine BAp alignment in the mesiodistal direction. Bone mineral density (BMD) was also measured using 3-dimensional trabecular structure measurement software. The results showed that the degree of BAp alignment in the mesiodistal direction was low in the alveolar area and high at the base of the mandible, suggesting that BAp alignment in the alveolar area is affected by occlusal force. Moreover, it was observed that the correlation between BAp alignment and BMD was small, indicating that BAp alignment and BMD could be independent factors. Therefore, determining BAp alignment was important in the evaluation of bone quality, including bone strength.
We studied the effects of hypoxia on the electrical activity and ultrastructure of pacemaker cells of sinoatrial nodal tissue excised from rabbit heart. The slope of slow diastolic depolarization was markedly reduced within 15-20 minutes after gassing Tyrode's solution with nitrogen, whereas other action potential parameters were not much affected. At 60-90 minutes in the hypoxic solution, the maximum diastolic potential decreased by 13 mV, and the peak potential decreased to -5 mV, but abbreviated action potentials continued to occur for another 30-60 minutes. After 60-90 minutes of hypoxia, reoxygenation did not produce complete recovery of the action potential. In glucose-free solution, action potentials ceased within 40 minutes of hypoxia, but reoxygenation restored electrical activity. A good correlation was found between the duration of hypoxia and the extent of ultrastructural change in sinoatrial nodal cells. After 15-20 minutes of hypoxia, mitochondria showed decreased electron density of their matrix and loss of intramitochondrial particles. The glycogen content was reduced. After 60-90 minutes of hypoxia, further changes in the mitochondria occurred: clearing of the matrix, fragmentation of cristae, rupture of the outer membrane, and formation of myelin figures. Glycogen had almost completely depleted after reoxygenation. These changes were partly reversible except for the glycogen content. Our results provide electrophysiological evidence that cells in the sinoatrial nodal tissue can withstand long exposure to hypoxia, using energy produced by the anaerobic glycolytic pathway. MethodsAlbino rabbits of either sex, weighing about 2 kg, were anesthetized with ether, and the heart was by guest on March 22, 2015 http://circres.ahajournals.org/ Downloaded from by guest on March 22, 2015 http://circres.ahajournals.org/ Downloaded from K Nishi, Y Yoshikawa, K Sugahara and T Morioka exposed to hypoxic solution. Changes in electrical activity and ultrastructure of sinoatrial nodal cells of the rabbit's heart
The importance of considering bone quality during oral implant treatment is increasingly being recognized. Assessment of bone quality in response to changes in the jaw bone is extremely important when planning treatment. The present study analyzed biological apatite (BAp) crystallites, a bone quality factor, in order to investigate crystallographic anisotropy in dentate and edentulous human mandibles. Using mandibular samples from Japanese adult cadavers, a region of interest was established comprising cortical bone in the central incisors. Samples were classified into five morphological categories based on the extent of bone resorption. Bone mineral density (BMD) was measured and diffraction intensity ratios were calculated using a microbeam X‐ray diffraction system. While no differences were observed in BMD, differences were observed in BAp crystallite alignment between the measurement points. In the alveolar region, samples with residual alveolar bone showed strong alignment in the occlusal direction, while samples with marked alveolar bone resorption had preferential alignment in the mesiodistal direction. The present findings suggest that tooth loss and the extent of alveolar bone resorption affects bone quality in the mandible. © 2018 Wiley Periodicals, Inc. J. Biomed. Mater. Res. Part B: 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 838–846, 2019.
Biological apatite (BAp) crystallite c-axis alignment is known to one of the factor in mechanical function in bone. The purpose of this study was to investigate BAp crystallite alignment as a potential factor in the evaluation of bone strength in clinical practice by evaluating the relationship between BAp alignment and bone mineral density (BMD) using an experimental hemi-occlusion model in rabbit mandibular cortical bone.A higher degree of BAp crystallite c-axis alignment was observed in the mesiodistal direction on the nonocclusion than on the occlusion side in the alveolar area, a tendency that was not seen in the base of the mandible. No significant differences were observed in BMD between the alveolar area and the base of the mandible or between the occlusion and non-occlusion sides. No correlation was observed between BAp crystallite alignment and BMD.These results demonstrate that removal of occlusal force caused change in BAp crystallite alignment in the alveolar area in mandibular cortical bone. This indicates the importance of evaluating BAp crystallite alignment in addition to BMD in clinical practice. Moreover, clarification of BAp crystallite alignment in the jawbone would allow direction of occlusal load to be taken into account in orthodontic treatment involving tooth alignment.
The aim of this study was clarify the effects of reducing various functional pressures essential for the maintenance of bone homeostasis. Femoral bone mineral density (BMD) and biological apatite (BAp) crystallite alignment were measured in conventionally reared and hindlimb-unloaded mice. The femur was divided into 10 equal segments perpendicular to the longitudinal axis of the bone and measurements were performed on the cortical bone in the five segments closest to the midpoint of the femur. Significantly lower BMD and BAp alignment in the longitudinal (Z-axis) direction were observed in the hindlimb-unloaded group. The present findings suggest that unloading by tail suspension significantly decreases not only mouse femoral bone mass but also BAp crystallite alignment, although minimal uniaxial preferential alignment is retained.
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