Mechanoelectric transduction in bone

1989 ◽  
Vol 4 (4) ◽  
pp. 1034-1046 ◽  
Author(s):  
Dennis A. Chakkalakal
Keyword(s):  
Bone Cells ◽  
Ionic Composition ◽  
Solid Matrix ◽  
Specimen Preparation ◽  
Fluid Interfaces ◽  
Electromechanical Properties ◽  
Low Frequencies ◽  
Streaming Potentials ◽  
Mechanoelectric Transduction ◽  
Living Bone

The cells in living bone are embedded in a charged, organic-inorganic solid permeated by ionic fluids flowing through a complex network of channels (diameter ∼10−1–102 μm). The solid matrix, which has a high degree of composite material organization beginning at the macromolecular level, has even finer pores of diameter ≳10−3 μm containing extracellular fluids. Since bone cells are thus bathed in fluid environments of varying ionic composition and concentration, it is likely that the physiology of bone depends on its electrical and electromechanical properties. This hypothesis is supported by the known effects of externally applied mechanical and electrical signals on physiological functions. Contrary to the earlier perception of bone as an insulating material, it is now recognized that the fluid content of bone endows it with physiologically significant conductivity. Mechanoelectric transduction in bone, at low frequencies, is most likely an electrokinetic process associated with the solid-fluid interfaces in bone. Electromechanical properties of bone have been determined experimentally by measurements of stress-generated potentials and streaming potentials in wet bone specimens and electrophoretic mobility of bone particles. Interpretation of results has been difficult due to the complexity of the solid-fluid interfaces in bone and the often undefinable alterations of the pores and interfaces due to specimen preparation. This paper is a review of the present state of knowledge of mechanoelectric transduction in bone and its physiological significance.

The Role of Extracellular Fluid on the Electrical and Electromechanical Properties of Bone: A Review

1987 ◽  
Vol 110 ◽  
Author(s):  
Dennis A. Chakkalakal
Keyword(s):  
Extracellular Matrix ◽  
Blood Vessels ◽  
Weight Bearing ◽  
Extracellular Fluid ◽  
The Body ◽  
Solid Matrix ◽  
Long Bones ◽  
Electromechanical Properties ◽  
Living Bone ◽  
Pore Fraction

The cells in living bone – osteocytes, osteoblasts and osteoclasts – are embedded in a porous material consisting of an organic-inorganic composite solid containing a distribution of fixed charges, permeated by ionic fluids flowing through a complex network of channels. In the weight-bearing long bones of the body, the largest of these channels are up to a few hundred microns in diameter and contain blood vessels which are connected to the blood supply in the central canal of the long bones. These channels establish fluid connectivity with the cells (osteocytes) responsible for maintenance of the bone tissue through small canals (canaliculi) with diameters ranging down to a tenth of a micron. Outside the blood vessels, perivascular fluid permeates these channels. The solid matrix is itself porous with a high degree of composite material organization beginning at the macromolecular level. The internal connectivity of the pore fraction of the solid, which is not as extensive as the network of channels, and the connectivity of this pore fraction with the fluid channels may affect physiological functions, through its influence on mechanical, electrical and electromechanical properties of the extracellular matrix. It seems apparent that the structure and physical properties of the extracellular material of bone will largely determine the physicochemical environment of the cells. Thus, a materials characterization of the extracellular matrix of living bone has become an essential part of the efforts to advance our knowledge of bone physiology and pathology. This paper is a review of the present state of knowledge of the electrical and electromechanical properties of this material with emphasis on studies that appear to have the most physiological significance.

Tooth Movement

1991 ◽  
Vol 2 (4) ◽  
pp. 411-450 ◽  
Author(s):  
Zeev Davidovitch
Keyword(s):  
Alveolar Bone ◽  
Tooth Movement ◽  
Bone Cells ◽  
Biological Response ◽  
Mechanical Forces ◽  
Clinical Environment ◽  
Isolated Cells ◽  
Streaming Potentials ◽  
Pdl Cells ◽  
New Findings

This article reviews the evolution of concepts regarding the biological foundation of force-induced tooth movement. Nineteenth century hypotheses proposed two mechanisms: application of pressure and tension to the periodontal ligament (PDL), and bending of the alveolar bone. Histologic investigations in the early and middle years of the 20th century revealed that both phenomena actually occur concomitantly, and that cells, as well as extracellular components of the PDL and alveolar bone, participate in the response to applied mechanical forces, which ultimately results in remodeling activities. Experiments with isolated cells in culture demonstrated that shape distortion might lead to cellular activation, either by opening plasma membrane ion channels, or by crystallizing cytoskeletal filaments. Mechanical distortion of collagenous matrices, mineralized or non-mineralized, may, on the other hand, evoke the development of bioelectric phenomena (stress-generated potentials and streaming potentials) that are capable of stimulating cells by altering the electric charge on their membrane or their fluid envelope. In intact animals, mechanical perturbations on the order of about 1 min/d are apparently sufficient to cause profound osteogenic responses, perhaps due to matrix proteoglycan-related "strain memory". Enzymatically isolated human PDL cells respond biochemically to mechanical and chemical signals. The latter include endocrines, autocrines, and paracrines. Histochemical and immunohistochemical studies showed that during the early places of tooth movement, PDL fluids are shifted, and cells and matrix are distorted. Vasoactive neurotransmitters are released from periodontal nerve terminals, causing leukocytes to migrate out of adjacent capillaries. Cytokines and growth factors are secreted by these cells, stimulating PDL cells and alveolar bone lining cells to remodel their related matrices. This remodeling activity facilitates movement of teeth into areas in which bone had been resorbed. This emerging information suggests that in the living mammal, many cell types are involved in the biological response to applied mechanical stress to teeth, and thereby to bone. Essentially, cells of the nervous, immune, and endocrine systems become involved in the activation and response of PDL and alveolar bone cells to applied stresses. This fact implies that research in the area of the biological response to force application to teeth should be sufficiently broad to include explorations of possible associations between physical, cellular, and molecular phenomena. The goals of this investigative field should continue to expound on fundamental principles, particularly on extrapolating new findings to the clinical environment, where millions of patients are subjected annually to applications of mechanical forces to their teeth for long periods of time in an effort to improve their position in the oral cavity. Recently developed research tools such as cell culture techniques and immunologic probes, are the best hope for enhancing this development.

Microsurgical isolation of intact plant cell wall appositions for microanalyses

1979 ◽  
Vol 57 (12) ◽  
pp. 1349-1353 ◽  
Author(s):  
Hitoshi Kunoh ◽  
James R. Aist ◽  
Herbert W. Israel
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Plant Cell Wall ◽  
Analytical Techniques ◽  
Chemical Components ◽  
Specimen Preparation ◽  
Low Frequencies ◽  
Wall Appositions ◽  
Wall Apposition ◽  
Mother Cells

Little is known about the chemical components of the plant cell wall apposition as they relate to its structure and function. The small sizes (5–15 μm diameter) of the appositions, their low frequencies in the cells, and their intimate connections to the cell wall have almost precluded meaningful cytochemical and (or) biochemical analyses. With the development of analytical techniques using the electron microprobe it is now feasible to discover the elemental composition of minute cellular structures, such as the wall apposition, but problems in specimen preparation remain. As a necessary and critical first step in microprobe analysis we have found it best to microsurgically remove fresh wall appositions from their mother cells and then admit them directly into the scanning electron microscope (SEM) after air drying and gold coating. This paper describes the requisite technologies of specimen preparation, microtool fabrication, specimen selection and isolation which are involved. The technique described could find ready application in the microanalyses of many other subcellular structures.

Chondrocyte Translocation and Orientation to Applied DC Electric Fields

1999 ◽  
Author(s):  
Robert L. Mauck ◽  
Pen-hsiu G. Chao ◽  
Beth Gilbert ◽  
Wilmot B. Valhmu ◽  
Clark T. Hung
Keyword(s):  
Electric Fields ◽  
Bone Cells ◽  
Shape Change ◽  
Cell Types ◽  
Neural Cells ◽  
Similar Response ◽  
Mechanical Stimuli ◽  
Directed Movement ◽  
Streaming Potentials ◽  
Dc Electric Fields

Abstract Chemical and mechanical stimuli are known to cause directed movement in a number of different cell types. Less prominently studied, direct current (DC) electric fields are known to induce a similar response. In this study, we report on DC electric field-induced chondrocyte migration and re-orientation. Galvanotaxis and galvanotropism, migration and shape change in response to applied DC electric fields, respectively, have been demonstrated in many cells. For instance, field strengths of 1–10 V/cm have been reported to induce migration in keratinocytes. corneal epithelial cells, bone cells, fibroblasts and neural cells [1,7,8,11]. Recently, we have demonstrated for the first time that chondrocytes exhibit a galvanotactic response, realigning and migrating in response to applied DC electric fields (6 V/cm) [6]. In cartilage, chondrocytes may see electric fields associated with streaming potentials estimated to be up to 15 V/cm with current densities of up to 0.1A/cm2 [2]. The aim of this study was to explore basic science aspects of directed cell migration under applied DC electric fields and to investigate the potential application of this phenomena for tissue engineering, healing and repair of cartilage. The ability to direct cell growth and function will have significant implications on the bioengineering of replacement tissues.

Direct Observation of Heat Exchanger Deposits by Cross Sectioning

1967 ◽  
Vol 25 ◽  
pp. 364-365
Author(s):  
R. W. Anderson ◽  
D. L. Senecal
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Heat Exchanger ◽  
Direct Observation ◽  
Cross Sections ◽  
Preparation Method ◽  
Specimen Preparation ◽  
Flowing Water ◽  
Transmission Electron ◽  
Deposit Layer

A problem was presented to observe the packing densities of deposits of sub-micron corrosion product particles. The deposits were 5-100 mils thick and had formed on the inside surfaces of 3/8 inch diameter Zircaloy-2 heat exchanger tubes. The particles were iron oxides deposited from flowing water and consequently were only weakly bonded. Particular care was required during handling to preserve the original formations of the deposits. The specimen preparation method described below allowed direct observation of cross sections of the deposit layers by transmission electron microscopy.The specimens were short sections of the tubes (about 3 inches long) that were carefully cut from the systems. The insides of the tube sections were first coated with a thin layer of a fluid epoxy resin by dipping. This coating served to impregnate the deposit layer as well as to protect the layer if subsequent handling were required.

Enhancement of Contrast in the CEM and STEM Using Bumpy Specimens and Employing the “Dappled Field” Mode of Operation

1974 ◽  
Vol 32 ◽  
pp. 552-553 ◽  
Author(s):  
L. Gandolfi ◽  
J. Reiffel
Keyword(s):  
Operating Mode ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Specimen Preparation ◽  
Field Mode ◽  
Preparation Methods ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Mode Of Operation ◽  
Scanning Transmission

Calculations have been performed on the contrast obtainable, using the Scanning Transmission Electron Microscope, in the observation of thick specimens. Recent research indicates a revival of an earlier interest in the observation of thin specimens with the view of comparing the attainable contrast using both types of specimens.Potential for biological applications of scanning transmission electron microscopy has led to a proliferation of the literature concerning specimen preparation methods and the controversy over “to stain or not to stain” in combination with the use of the dark field operating mode and the same choice of technique using bright field mode of operation has not yet been resolved.

Pathology of Bone Cells in Pigs with Experimental Turbinate Osteoporosis (Atrophic Rhinitis)

1971 ◽  
Vol 29 ◽  
pp. 304-305
Author(s):  
A. W. Fetter ◽  
C. C. Capen
Keyword(s):  
Mucous Membrane ◽  
Bone Cells ◽  
Atrophic Rhinitis ◽  
Infectious Agents ◽  
Metabolic Disturbances ◽  
Progressive Reduction ◽  
Naturally Occurring ◽  
Fundamental Cause ◽  
Osteocytic Osteolysis ◽  
Uncertain Etiology

Atrophic rhinitis in swine is a disease of uncertain etiology in which infectious agents, hereditary predisposition, and metabolic disturbances have been reported to be of primary etiologic importance. It shares many similarities, both clinically and pathologically, with ozena in man. The disease is characterized by deformity and reduction in volume of the nasal turbinates. The fundamental cause for the localized lesion of bone in the nasal turbinates has not been established. Reduced osteogenesis, increased resorption related to inflammation of the nasal mucous membrane, and excessive resorption due to osteocytic osteolysis stimulated by hyperparathyroidism have been suggested as possible pathogenetic mechanisms.The objectives of this investigation were to evaluate ultrastructurally bone cells in the nasal turbinates of pigs with experimentally induced atrophic rhinitis, and to compare these findings to those in control pigs of the same age and pigs with the naturally occurring disease, in order to define the fundamental lesion responsible for the progressive reduction in volume of the osseous core.

Contrast from epitaxially sandwiched macromolecules

1978 ◽  
Vol 36 (2) ◽  
pp. 226-227
Author(s):  
M. Talianker ◽  
D.G. Brandon
Keyword(s):  
Gold Film ◽  
Lattice Defect ◽  
Gold Foil ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Resolution Limit ◽  
Transmission Electron ◽  
Crystal Lattice Defect ◽  
Void Effect ◽  
Lattice Resolution

A new specimen preparation technique for visualizing macromolecules by conventional transmission electron microscopy has been developed. In this technique the biopolymer-molecule is embedded in a thin monocrystalline gold foil. Such embedding can be performed in the following way: the biopolymer is deposited on an epitaxially-grown thin single-crystal gold film. The molecule is then occluded by further epitaxial growth. In such an epitaxial sandwich an occluded molecule is expected to behave as a crystal-lattice defect and give rise to contrast in the electron microscope.The resolution of the method should be limited only by the precision with which the epitaxially grown gold reflects the details of the molecular structure and, in favorable cases, can approach the lattice resolution limit.In order to estimate the strength of the contrast due to the void-effect arising from occlusion of the DNA-molecule in a gold crystal some calculations were performed.

The ionic strength dependence of chromatin folding

1978 ◽  
Vol 36 (2) ◽  
pp. 220-221
Author(s):  
F. Thoma ◽  
TH. Koller
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Ionic Strength ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Carbon Supports ◽  
Ionic Strength Dependence ◽  
Chromatin Folding ◽  
Strength Dependence ◽  
Preparation Techniques

Under a variety of electron microscope specimen preparation techniques different forms of chromatin appearance can be distinguished: beads-on-a-string, a 100 Å nucleofilament, a 250 Å fiber and a compact 300 to 500 Å fiber.Using a standardized specimen preparation technique we wanted to find out whether there is any relation between these different forms of chromatin or not. We show that with increasing ionic strength a chromatin fiber consisting of a row of nucleo- somes progressively folds up into a solenoid-like structure with a diameter of about 300 Å.For the preparation of chromatin for electron microscopy the avoidance of stretching artifacts during adsorption to the carbon supports is of utmost importance. The samples are fixed with 0.1% glutaraldehyde at 4°C for at least 12 hrs. The material was usually examined between 24 and 48 hrs after the onset of fixation.

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