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Mary C Farachcarson - One of the best experts on this subject based on the ideXlab platform.

  • perlecan hspg2 deficiency alters the pericellular space of the lacunocanalicular system surrounding osteocytic processes in cortical bone
    Journal of Bone and Mineral Research, 2011
    Co-Authors: William R Thompson, Shannon Modla, Brian J Grindel, Kirk J Czymmek, Catherine B Kirnsafran, Liyun Wang, Randall L Duncan, Mary C Farachcarson
    Abstract:

    Osteocytes project long, slender processes throughout the mineralized matrix of bone, where they connect and communicate with effector cells. The interconnected cellular projections form the functional lacunocanalicular system, allowing Fluid to pass for cell-to-cell communication and nutrient and waste exchange. Prevention of mineralization in the pericellular space of the lacunocanalicular pericellular space is crucial for uninhibited interstitial Fluid Movement. Factors contributing to the ability of the pericellular space of the lacunocanalicular system to remain open and unmineralized are unclear. Immunofluorescence and immunogold localization by transmission electron microscopy demonstrated perlecan/Hspg2 signal localized to the osteocyte lacunocanalicular system of cortical bone, and this proteoglycan was found in the pericellular space of the lacunocanalicular system. In this study we examined osteocyte lacunocanalicular morphology in mice deficient in the large heparan sulfate proteoglycan perlecan/Hspg2 in this tissue. Ultrastructural measurements with electron microscopy of perlecan/Hspg2-deficient mice demonstrated diminished osteocyte canalicular pericellular area, resulting from a reduction in the total canalicular area. Additionally, perlecan/Hspg2-deficient mice showed decreased canalicular density and a reduced number of transverse tethering elements per canaliculus. These data indicated that perlecan/Hspg2 contributed to the integrity of the osteocyte lacunocanalicular system by maintaining the size of the pericellular space, an essential task to promote uninhibited interstitial Fluid Movement in this mechanosensitive environment. This work thus identified a new barrier function for perlecan/Hspg2 in murine cortical bone. © 2011 American Society for Bone and Mineral Research.

Ronald F Zernicke - One of the best experts on this subject based on the ideXlab platform.

  • poroelastic evaluation of Fluid Movement through the lacunocanalicular system
    Annals of Biomedical Engineering, 2009
    Co-Authors: Grant C Goulet, D Coombe, Robert J Martinuzzi, Ronald F Zernicke
    Abstract:

    A poroelastic lacunocanalicular model was developed for the quantification of physiologically relevant parameters related to bone Fluid flow. The canalicular and lacunar microstructures were explicitly represented by a dual-continuum poroelastic model. Effective material properties were calculated using the theory of composite materials. Porosity and permeability values were determined using capillaric and spherical-shell models for the canalicular and lacunar microstructures, respectively. Pore Fluid pressure and Fluid shear stress were calculated in response to simulated mechanical loading applied over a range of frequencies. Species transport was simulated with convective and diffusive flow, and osteocyte consumption of nutrients was incorporated. With the calculated parameter values, realistic pore Fluid pressure and Fluid shear stress responses were predicted and shown to be consistent with previous experimental and theoretical studies. Stress-induced Fluid flow was highlighted as a potent means of species transport, and the importance of high-magnitude low-frequency loading on osteocyte nutrition was demonstrated. This new model can serve as the foundation for future hierarchical modeling efforts that may provide insight into the underlying mechanisms of mechanotransduction and functional adaptation of bone.

A Schwab - One of the best experts on this subject based on the ideXlab platform.

  • pressure threshold for Fluid loss from the peritoneal cavity
    American Journal of Physiology-renal Physiology, 1996
    Co-Authors: Michael F Flessner, A Schwab
    Abstract:

    Ascites or dialysis Fluid in the peritoneal cavity causes Fluid loss from the cavity to the body. Experiments in animals and in humans have shown that the Fluid loss rate increases with large increments in the intraperitoneal hydrostatic pressure (Pip). We hypothesized that there is a low-threshold Pip above which this Fluid loss occurs. Because the full Pip force is exerted across the abdominal wall (AW), we further hypothesized that Fluid Movement into the abdominal wall would vary directly with the Pip. To address these questions, we dialyzed rats for 3 h in the supine position at constant levels of Pip with isotonic and hypertonic dialysis solutions containing a protein marker of Fluid Movement. We measured total Fluid loss, AW Fluid-marker concentration, and lymph flow. With variation of Pip from 0 to 8 cmH2O, we found that 1) lymph flows (0.61 +/- 0.03 ml/h) were not dependent on Pip, 2) measured isotonic Fluid loss rate varied from 0.29 +/- 0.06 ml/h at 0 cmH2O to 0.62 +/- 0.02 at 2 cmH2O and then rose in a linear fashion to 5.06 +/- 0.10 ml/h at 8 cmH2O, 3) Fluid Movement into the AW paralleled the measured Fluid loss rate, and 4) protein clearance from the cavity overestimated the true Fluid loss because of adsorption of the marker to the peritoneal surface. We conclude that, although peritoneal lymph flow is not dependent on intraperitoneal hydrostatic or osmotic pressure, Fluid loss from the cavity and Fluid loss to the abdominal wall are directly proportional to Pip > 2 cmH2O. We also note that protein markers of Fluid Movement require correction for tissue surface adsorption for accurate results.

  • pressure threshold for Fluid loss from the peritoneal cavity
    American Journal of Physiology-renal Physiology, 1996
    Co-Authors: Michael F Flessner, A Schwab
    Abstract:

    Ascites or dialysis Fluid in the peritoneal cavity causes Fluid loss from the cavity to the body. Experiments in animals and in humans have shown that the Fluid loss rate increases with large increments in the intraperitoneal hydrostatic pressure (Pip). We hypothesized that there is a low-threshold Pip above which this Fluid loss occurs. Because the full Pip force is exerted across the abdominal wall (AW), we further hypothesized that Fluid Movement into the abdominal wall would vary directly with the Pip. To address these questions, we dialyzed rats for 3 h in the supine position at constant levels of Pip with isotonic and hypertonic dialysis solutions containing a protein marker of Fluid Movement. We measured total Fluid loss, AW Fluid-marker concentration, and lymph flow. With variation of Pip from 0 to 8 cmH2O, we found that 1) lymph flows (0.61 +/- 0.03 ml/h) were not dependent on Pip, 2) measured isotonic Fluid loss rate varied from 0.29 +/- 0.06 ml/h at 0 cmH2O to 0.62 +/- 0.02 at 2 cmH2O and then ...

Agnes Remond - One of the best experts on this subject based on the ideXlab platform.

  • study of the influence of fibrous pericellular matrix in the cortical interstitial Fluid Movement with hydroelectrochemical effects
    Journal of Biomechanical Engineering-transactions of The Asme, 2008
    Co-Authors: Thibault Lemaire, Salah Naili, Agnes Remond
    Abstract:

    Fluid flow within cortical bone tissue is modeled through an upscaling approach of a local description of the Fluid Movement. At the pore scale, the coupled phenomena (Poiseuille effect, osmosis, and electro-osmosis) governing the interstitial Fluid Movement are considered. Thus, actions of electro-osmotic and osmotic motions, in addition to the classical Poiseuille flow, are studied at the canaliculus scale by deriving a coupled Darcy law. The addition of a Brinkman-like term in this macroscopic result helps us to take into account the influence of the pericellular matrix on the coupled transport phenomena. At the canaliculus scale, the general trends that can be drawn from this study are as follows: (i) The presence of the fibrous matrix tends to reduce the Fluid flow considerably; (ii) the role of osmotic and electro-osmotic effects is no longer negligible for dense fibrous media.

  • Multiscale analysis of the coupled effects governing the Movement of interstitial Fluid in cortical bone
    Biomechanics and Modeling in Mechanobiology, 2006
    Co-Authors: Thibault Lemaire, Salah Naili, Agnes Remond
    Abstract:

    A multiscale approach (periodic homogenization) is carried out to model osteon’s behaviour, and especially the coupled phenomena that govern its interstitial Fluid Movement. Actions of electro-osmotic and osmotic motions in addition to the classical Poiseuille flow are studied at the mesoscale of the canaliculus and within the micropores of the collagen-apatite matrix. Use of this fully coupled modelling leads to a comparison of these different effects. Limitation of a classical Darcian description of the Fluid flow at the two scales is so studied. For each of these studies a special attention is given to the pore’s geometry influence and to their electrical and hydraulic properties

Shinya Yamada - One of the best experts on this subject based on the ideXlab platform.

  • influence of respiration on cerebrospinal Fluid Movement using magnetic resonance spin labeling
    Fluids and Barriers of the CNS, 2013
    Co-Authors: Shinya Yamada, Mitsue Miyazaki, Yuichi Yamashita, Cheng Ouyang, Masao Yui, Masao Nakahashi, Seiko Shimizu, Ikuo Aoki, Yukuo Morohoshi, James Gordon Mccomb
    Abstract:

    Background Magnetic resonance imaging (MRI) cardiac gated phase contrast (PC) cine techniques have non-invasively shown the effect of the cardiac pulse on cerebrospinal Fluid (CSF) Movement. Echo planar imaging (EPI) has shown CSF Movement as influenced by both cardiac pulsation and respiration. Previously, it has not been possible to visualize CSF Movement in response to respiration non-invasively. The present study was undertaken to do so.

  • visualization of cerebrospinal Fluid Movement with spin labeling at mr imaging preliminary results in normal and pathophysiologic conditions
    Radiology, 2008
    Co-Authors: Shinya Yamada, Mitsue Miyazaki, Yukuo Morohoshi, Hitoshi Kanazawa, Minako Higashi, Stefan Bluml, Gordon J Mccomb
    Abstract:

    Institutional review board approval and informed consent were obtained for this study. This study was HIPAA compliant. The purpose of this study was to visualize the Movement of cerebrospinal Fluid (CSF) noninvasively by using an unenhanced magnetic resonance imaging technique. A time-spatial labeling inversion pulse (SLIP) technique was applied to label, or tag, CSF in a region of interest. The tagged CSF was clearly visualized at inversion times of 1500-4500 msec after pulse labeling in both intracranial and intraspinal compartments. Noninvasive visualization of CSF Movement, including bulk and turbulent flow, in normal (n = 7) and altered (n = 2) physiologic conditions was possible by using the unenhanced time-SLIP technique.