Studies of diffusion in calvaria

Neuman, W. F.; Neuman, M.W.

doi:10.1007/bf02409468

Cited by 13 publications

(8 citation statements)

References 10 publications

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“…48 Finally, Wu et al demonstrated the feasibility of 3-D projectionreconstruction imaging of bone in situ with 31 P and 1 H images of intact porcine tibia. 47 Proton vs. 31 …”

Section: P Nmr Spectroscopy and Imaging Of Bone In Situmentioning

confidence: 98%

“…The prospects of noninvasively imaging matrix and mineral constituents in solid bone by NMR is addressed as well. 31 P NMR is arguably the only nondestructive and potentially noninvasive method for measuring mineral content either in bulk 8,7,29,49 or in a spatially resolved manner by imaging. 1,27,47,48 Measurements of mineral content using 31 P spectroscopy rely on the notion that bone mineral content is proportional to phosphorus concentration.…”

Section: Role Of Bone Watermentioning

confidence: 99%

“…2,40 Quantitative information thus is scarce. 14,31 NMR is ideally suited for measurement of self-diffusion in tissues and the subject has been widely studied ever since the pulsed gradient spin-echo experiment was first conceived. 37 However, this method is not applicable to calcified tissues where diffusion can be several orders of magnitude slower and further, the lifetime of the signal typically exceeds the time required to play out the gradient pulses.…”

Section: One-dimensional Box Modelmentioning

confidence: 99%

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Nuclear Magnetic Resonance Studies of Bone Water

Wehrli

Fernández‐Seara²

2005

Ann Biomed Eng

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Mineralized bone tissue has a significant water component. Bone water is associated with the collagen fibers or mineral fraction or occurring as pore water of the Haversian and lacunocanalicular system. Among the multiple physiologic functions that include signaling and providing to bone its viscoelastic properties, bone water enables the transport of ions and nutrients to and waste products from the cells. In addition, it plays a key role during mineralization whereby collagen-bound water is gradually replaced by calcium apatite-like mineral. In this review it is shown how nuclear magnetic resonance (NMR) allows the study of various physiologically relevant properties of bone water nondestructively. Isotope exchange experiments are described from which the apparent water diffusion coefficient can be calculated. The method is based on monitoring the migration of H2O into the D2O after immersion of the specimen in heavy water. Data obtained from rabbit cortical bone in the normal and mineral-depleted skeleton provide evidence for the hypothesized reciprocal relationship between bone water and mineral. Further, from the diffusion coefficient (Da = (7.8+/-1.5) x 10(-7) cm2/s) measured at 40 degrees C it can be inferred that diffusive transport of small molecules from the bone's microvascular system to the osteocytes occurs within minutes. Finally, whereas isotope exchange is not feasible in vivo, it is shown that bone water can be imaged by proton MRI.

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“…48 Finally, Wu et al demonstrated the feasibility of 3-D projectionreconstruction imaging of bone in situ with 31 P and 1 H images of intact porcine tibia. 47 Proton vs. 31 …”

Section: P Nmr Spectroscopy and Imaging Of Bone In Situmentioning

confidence: 98%

Section: Role Of Bone Watermentioning

confidence: 99%

Section: One-dimensional Box Modelmentioning

confidence: 99%

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Nuclear Magnetic Resonance Studies of Bone Water

Wehrli

Fernández‐Seara²

2005

Ann Biomed Eng

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“…The difficulty of the OCP crystal detection in the body lies in the fact of the elevated solubility compared to the HAP phase, whereas the extracellular solution in bone is not heavily supersaturated. 13 It has been shown recently in model experiments 5 that the formation of the OCP crystals at the early stage of precipitation and their vanishing with time (a few minutes) at simultaneous solution homogenization and HAP nucleation and growth.…”

Section: Biological Samples: Bone and Cardiac Valvementioning

confidence: 99%

Model of the mechanism of Ca loss by bones under microgravity and earth conditions

Suvorova

Buffat

2002

J. Biomed. Mater. Res.

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A comparative characterization of crystal structure, morphology, sizes, and orientation in Ca phosphate precipitation from aqueous solutions, the mineral phase in bones, and mineral deposits on cardiac valves has been performed by high-resolution transmission electron microscopy to model possible mechanisms of Ca loss by bones. Physiological changes occurring in organisms can lead to deep perturbations of the natural calcium phosphate supersaturation and its local distribution, which in turn influences the phase composition, morphology, and organization of the mineral phase. Formation of crystals with larger size or of two distinct phases instead of the single hydroxyapatite one can result in the deterioration of the Ca balance in bone and tissue destruction as well as the possible misorientation (or spread of orientation) between HAP crystals newly formed in the bone.

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“…The values presented above are based on the assumption that the diffusivity of oxygen across the osteon is governed by the diffusivity of oxygen in connective tissues. However, the diffusion of molecules such as glucose is ϳ50% greater in connective tissue than in the bone (30), and hence, the connective tissue value represents an upper limit of oxygen diffusion. As a lower limit, we have chosen the diffusion coefficient of oxygen in bone to be equal to that of water in bone.…”

Section: C925 Numerical Modeling Of Oxygen In Bonementioning

confidence: 99%

Numerical modeling of oxygen distributions in cortical and cancellous bone: oxygen availability governs osteonal and trabecular dimensions

Zahm

Bucaro

Ayyaswamy

et al. 2010

American Journal of Physiology-Cell Physiology

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has demonstrated the role of oxygen tension in the regulation of skeletal cell function and viability, the microenvironmental oxemic status of bone cells remains unknown. In this study, we have employed the Krogh cylinder model of oxygen diffusion to predict the oxygen distribution profiles in cortical and cancellous bone. Under the assumption of saturation-type Michaelis-Menten kinetics, our numerical modeling has indicated that, under steady-state conditions, there would be oxygen gradients across mature osteons and trabeculae. In Haversian bone, the calculated oxygen tension decrement ranges from 15 to 60%. For trabecular bone, a much shallower gradient is predicted. We note that, in Haversian bone, the gradient is largely dependent on osteocyte oxygen utilization and tissue oxygen diffusivity; in trabecular bone, the gradient is dependent on oxygen utilization by cells lining the bone surface. The Krogh model also predicts dramatic differences in oxygen availability during bone development. Thus, during osteon formation, the modeling equations predict a steep oxygen gradient at the initial stage of development, with the gradient becoming lesser as osteonal layers are added. In contrast, during trabeculum formation, the oxygen gradient is steepest when the diameter of the trabeculum is maximal. Based on these results, it is concluded that significant oxygen gradients exist within cortical and cancellous bone and that the oxygen tension may regulate the physical dimensions of both osteons and bone trabeculae. osteon; bone trabeculum; kinetics; Krogh; H; aversian OXYGEN DELIVERY governs the form and function of both soft and hard tissues (25). In the bone, a decrease in the rate of oxygen transport can severely impact skeletal health causing delays in bone healing, a change in the rate of bone turnover, and a raised incidence of vertebral and cranial malformations (7,26,31,33,40). Most commonly, oxemic stress is thought to be caused by a decrease in fluid flow during biomechanical unloading (8,13,22,34); when this occurs, there is a reduction in the oxygen transport rate in the lacunocanalicular system and impaired osteocyte function (29). While it is clear that the local oxygen tension (PO 2 ) is a potent regulator of skeletal cell metabolism and viability (1, 38, 41, 43), the oxygen distribution profile in the bone is currently unknown.The viability and function of cells in complex tissues is dependent on the delivery of oxygen and nutrients. Several numerical studies have attempted to model nutrient exchange by stress-induced fluid flow and diffusion within the lacunocanalicular system of the bone (22,29,34,45). While these studies have provided values for low-molecular-weight solutes, oxygen transport in the bone has not been addressed. In an earlier investigation, we have employed the Krogh cylinder assumption to model the oxygen supply to avian femoral growth cartilage (16); this same model has been used to predict the oxygen tension in skeletal muscle (24), brain (21), and bone marrow (3, 4).The Krogh cy...

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Studies of diffusion in calvaria

Cited by 13 publications

References 10 publications

Nuclear Magnetic Resonance Studies of Bone Water

Nuclear Magnetic Resonance Studies of Bone Water

Model of the mechanism of Ca loss by bones under microgravity and earth conditions

Numerical modeling of oxygen distributions in cortical and cancellous bone: oxygen availability governs osteonal and trabecular dimensions

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