86 research outputs found
Towards quantitative 3D imaging of the osteocyte lacuno-canalicular network
No full textOsteocytes are the most abundant cells in bone and the only cells embedded in the bone mineral matrix. They form an extended, three-dimensional (3D) network, whose processes interconnecting the cell bodies reside in thin canals, the canaliculi. Together with the osteocyte lacunae, the canaliculi form the lacuno-canalicular network (LCN). As the negative imprint of the cellular network within bone tissue, the LCN morphology is considered to play a central role for bone mechanosensation and mechanotransduction. However, the LCN has neither been visualized nor quantified in an adequate way up to now. On this account, this article summarizes the current state of knowledge of the LCN morphology and then reviews different imaging methods regarding the quantitative 3D assessment of bone tissue in general and of the LCN in particular. These imaging methods will provide new insights in the field of bone mechanosensation and mechanotransduction and thus, into processes of strain sensation and transduction, which are tightly associated with osteocyte viability and bone quality
Serial FIB/SEM imaging for quantitative 3D assessment of the osteocyte lacuno-canalicular network
No full textUp to now, a quantitative three-dimensional (3D) assessment of the lacuno-canalicular network (LCN) within bone has not been achieved in a comprehensive way and the LCN has mostly been investigated using two-dimensional imaging methods only. First attempts for the 3D assessment of the osteocytes and their cell processes have been reported using different imaging techniques. Nevertheless, various experimental limitations allowed for assessment of isolated or incompletely interconnected osteocytes only. On the other hand, serial focused ion beam/scanning electron microscopy (FIB/SEM) currently seems to be a promising imaging method for quantitative 3D assessment of the LCN. However, combined 3D visualization and quantification of the LCN using serial FIB/SEM imaging has not been reported so far. The aim of this study was to provide a proof of concept that serial FIB/SEM meets all requirements for quantitative 3D imaging of the LCN. To this end, we developed a new bone sample preparation protocol for serial FIB/SEM imaging providing a resolution on the order of 30 nm. This technique was successfully applied to the mid-diaphysis of a mouse femur. Moreover, we devised and applied novel measures for subsequent quantitative 3D morphometry of the LCN. Briefly, serial FIB/SEM was shown to be an appropriate technique to quantify the morphology of the LCN truly in 3D. This will allow investigating bone matrix changes on an ultrastructural level, which result from aging, disease, and treatmen
An electron microscopy study of synapse densities during song learning in the zebra finch HVC
No full textPtychographic X-ray computed tomography at the nanoscale
No full textX-ray tomography is an invaluable tool in biomedical imaging. It can deliver the three-dimensional internal structure of entire organisms as well as that of single cells, and even gives access to quantitative information, crucially important both for medical applications and for basic research1, 2, 3, 4. Most frequently such information is based on X-ray attenuation. Phase contrast is sometimes used for improved visibility but remains significantly harder to quantify5, 6. Here we describe an X-ray computed tomography technique that generates quantitative high-contrast three-dimensional electron density maps from phase contrast information without reverting to assumptions of a weak phase object or negligible absorption. This method uses a ptychographic coherent imaging approach to record tomographic data sets, exploiting both the high penetration power of hard X-rays and the high sensitivity of lensless imaging7, 8, 9. As an example, we present images of a bone sample in which structures on the 100?nm length scale such as the osteocyte lacunae and the interconnective canalicular network are clearly resolved. The recovered electron density map provides a contrast high enough to estimate nanoscale bone density variations of less than one per cent. We expect this high-resolution tomography technique to provide invaluable information for both the life and materials science
From incompatible poly(aryl ether sulfone)/polyamide 4.6. blends to new impact resistant alloys by a synergistic combination of a block copolymer emulsifier and an impact modifier
No full textpeer reviewedThe compatibilization and impact modification of blends of a relatively new engineering plastic polyamide 4.6 (PA 4.6) and a poly(aryl ether sulfone) (PSU) are investigated. PSU‐b‐PA6 block copolymers, which can be easily synthesized by ring opening polymerization of ϵ‐caprolactam in the presence of a commercial PSU, were found to be very efficient emulsifiers for these incompatible blends. Small amounts (1–4%) of copolymer are sufficient to significantly reduce the particle size and to improve the tensile and impact properties. Combinations of the copolymer and an impact modifier (ethylene‐propylene rubber grafted with maleic anhydride) are synergistic and high impact PSU/PA 4.6 alloys are obtained in that way. Copyright © 1993 Hüthig & Wepf Verla
Study and control of polymer blends morphology and related properties
No full textpeer reviewedIt will be shown how a combination of techniques allows to gain a rather precise idea of the (un)miscibility situation in polymer blends at different size scales (i.e. from ca.20 A up to lμ); typical examples include simultaneous use of TEM, SEM, NRET and ss. NMR. On these bases, interesting blends have been studied and tailored, in which both morphology and interfacial adhesion have been controlled (in particular by the use of diblock copolymers) to provide for a better spectrum of properties. A number of situations will be described, implying commodity and engineering polymers, but also different types of fillers; their optimization has led to interesting applications in the field of better emulsion dispersions, very high impact resins, economical engineering plastics, controlled migration, filled materials,. Copyright © 1988 Hüthig & Wepf Verla
OMNY PIN-A versatile sample holder for tomographic measurements at room and cryogenic temperatures
No full textNowadays ptychographic tomography in the hard x-ray regime, i.e., at energies above about 2 keV, is a well-established measurement technique. At the Paul Scherrer Institut, currently two instruments are available: one is measuring at room temperature and atmospheric pressure, and the other, the socalled OMNY (tOMography Nano crYo) instrument, is operating at ultra-high vacuum and offering cryogenic sample temperatures down to 10 K. In this manuscript, we present the sample mounts that were developed for these instruments. Aside from excellent mechanical stability and thermal conductivity, they also offer highly reproducible mounting. Various types were developed for different kinds of samples and are presented in detail, including examples of how specimens can be mounted on these holders. We also show the first hard x-ray ptychographic tomography measurements of high-pressure frozen biological samples, in the present case Chlamydomonas cells, the related sample pins and preparation steps. For completeness, we present accessories such as transportation containers for both room temperature and cryogenic samples and a gripper mechanism for automatic sample changing. The sample mounts are not limited to x-ray tomography or hard x-ray energies, and we believe that they can be very useful for other instrumentation projects. (C) 2017 Author(s)
Stratum corneum: Structure and morphology of a highly efficient barrier Stratum corneum: Struktur und morphologie einer hoch effizienten barriere
No full textConfocal microscopy of skin in vitro and ex vivo
No full textConfocal laser scanning microscopy (CLSM) is a modern light microscopy technique that enables high-resolution three-dimensional imaging of biological and technical samples. The concept of a confocal microscope was first patented by Marvin Minsky in 1957; the first laser-scanning microscope was built in the early 1970s by Davidovits and Egger. In the mid-1980s, the commercialization of confocal laser scanning microscopes started, and during the last 15 years, instruments were improved especially regarding velocity and resolution, mainly due to faster computers and more effective optics and electronics. A detailed synopsis of the basics of confocal imaging as well as of various optical and technical aspects of microscope setups and image analysis is given by Pawley (1) or Diaspro (2)
Data underlying the publication: A cryogenic, coincident fluorescence, electron and ion beam microscope
No full textIntroduction
Data underlying the publication: A cryogenic, coincident fluorescence, electron and ion beam microscope.
Publication DOI: 10.7554/eLife.82891
Authors: D.B. Boltje, J.P. Hoogenboom, A.J. Jakobi, G.J. Jensen, C.T.H. Jonker, M.J. Kaag, A.J. Koster, M.G.F. Last, C. de Agrela Pinto, J.M. Plitzko, S. Raunser, S. Tacke, Z. Wang, E.B. van der Wee, R. Wepf, S. den Hoedt
Repository created by Daan Boltje
General description
All data underlying the manuscript figures is stored in this repository. Experiments have been carried out at the Department of Imaging Physics at Delft University of Technology (Delft, NL) in 2020 and 2021 and resulting data are presented in figures 1, 2, 3, 4, 7 and 8.
External validation experiments have been carried out at the Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, (Dortmund, DE) between March-May 2021. The data from these experiments are used in figure 5, 6 and video 1.</p
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