724 research outputs found
Activation of the bone-derived latent TGF beta complex by isolated osteoclasts
No full textAlthough TGF beta is unquestionably an important growth regulatory polypeptide with effects on many cell types, the cellular mechanisms which release it from the binding proteins which mask its biological activity are not well understood. Here we show that when isolated osteoclasts are activated, they release active TGF beta from the latent TGF beta complex produced by bone organ cultures. Since active TGF beta has powerful inhibitory effects on osteoclast formation and bone resorption and stimulates osteoblast activity, is present in abundant amounts in the bone matrix and is released during hormone-stimulated osteoclastic bone resorption, the activation of TGF beta by stimulated osteoclasts may be an important regulatory step in normal bone remodeling
sj-docx-1-jdr-10.1177_00220345231195765 – Supplemental material for Force-Loaded Cementocytes Regulate Osteoclastogenesis via S1P/S1PR1/Rac1 Axis
No full textSupplemental material, sj-docx-1-jdr-10.1177_00220345231195765 for Force-Loaded Cementocytes Regulate Osteoclastogenesis via S1P/S1PR1/Rac1 Axis by H. Wang, T. Li, Y. Jiang, S. Chen, S. Zou, L.F. Bonewald and P. Duan in Journal of Dental Research</p
Effects of retinol on activation of latent transforming growth factor-? by isolated osteoclasts
No full textThe multifunctional cytokine, transforming growth factor-beta (TGF?), is found in many tissues in a latent or inactive form. The nature and composition of the latent complex can vary depending on tissue type. The release of active TGF? from its latent complex is a potentially important mechanism for regulation of TGF? activity. We have shown previously that osteoclasts activate latent TGF? produced by bone and that bone cells produce a 100-kDa latent complex that lacks the latent TGF?-binding protein. Here we investigated the effects of retinol on osteoclast activation of various forms of latent TGF?. Two sources of osteoclasts were used that provide either mature avian osteoclasts or avian osteoclast precursors. Whereas both cell populations activate latent TGF beta, only mature osteoclasts respond to retinol with an increase in activation of latent TGF? over basal levels. Activation could not be ascribed to pH changes in conditioned medium. Nonacid-dissociable 100-kDa latent complex, which is also produced by bone cells, was added to mature osteoclasts and to osteoclast precursors, but no activation was observed. Platelet latent TGF?, which contains the 130-kDa latent TGF?-binding protein, was activated by both osteoclast populations. Conditioned medium from the precursor population activated latent complex, whereas conditioned medium from mature cells did not. Activation of latent TGF? by retinol-treated mature cells was not blocked by inhibitors of plasmin, nor was activation by conditioned medium from precursor cells. These data suggest that retinol-induced activation of latent TGF? by osteoclasts is dependent on the stage of differentiation of these cells and the presence of other cell types, and that unlike other cell systems, the plasmin-plasminogen activator mechanism is not involved
Latent forms of transforming growth factor-? (TGF?) derived from bone cultures: identification of a naturally occurring 100-kDa complex with similarity to recombinant latent TGF?
No full textTransforming growth factor-? (TGF?) is produced by most tissues, including bone, as a complex that is biologically inert. Release of TGF? homodimer from this latent complex is necessary for TGF? to exert effects on target cells. Thus, the nature of the latent complex and the mechanisms responsible for TGF? release are the key to understanding TGF? actions. We have found that murine calvarial bone cultures secrete multiple latent forms of TGF?. Using analytical chromatography and Western blot analysis, we have compared bone latent TGF? with the previously characterized latent complex present in platelets and with simian TGF? precursor, which is stably expressed in a latent form by Chinese hamster ovarian (CHO) cells. A major component of the bone material appears to be a latent complex of 100 kDa, consisting of mature TGF? (25-kDa homodimer). Like the recombinant TGF? precursor, it elutes from a Mono-Q fast pressure liquid chromatography anion exchange column at 0.2 M NaCl and shows a very similar banding pattern on Western blots. Thus, this bone complex closely resembles recombinant TGF? precursor expressed in a latent form by CHO cells and differs from the naturally occurring platelet complex, which has an additional 135-kDa binding protein that is bound through disulfide bonds to the precursor proregion. Western blot analysis also indicates that, like CHO cells, which express recombinant TGF? precursor, but unlike other cell types, the bone cultures secrete detectable amounts of uncleaved TGF? precursor. The bone calvarial culture is the first example of a naturally occurring system that expresses the 100-kDa latent TGF? complex
Characterization of a cell line derived from a human giant cell tumor that stimulates osteoclastic bone resorption
No full textGiant cell tumors of bone are common but unusual tumors that are comprised of multiple cell types. Most attention has been focused on the giant cells, which resemble osteoclasts morphologically and functionally. This study examines the properties of a cell line derived from mononuclear cells from one of these tumors, since it appears likely that these cells may be able to influence the activities of cells with the osteoclast phenotype. This cell line, C433, has the following characteristics: (1) it represents undifferentiated cells, not recognized by any known antigenic markers for leukocytes; (2) it contains tartrate-resistant acid phosphatase; (3) it responds to the osteotropic factors 1,25 dihydroxyvitamin D3, insulin-like growth factor I and II, but not to parathyroid hormone; (4) it forms sarcomas in nude mice; and (5) it produces an activity that stimulates isolated avian and rat osteoclasts to resorb bone. This cell line may be useful in examining interactions between osteoclasts and accessory cells involved in bone resorption
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Association of genotype with bone metabolism, skeletal adaptation and stress fracture injury occurrence
No full textPositive changes in bone metabolism, structural characteristics, size and mass are commonly associated with weight-bearing exercise. Despite this, negative effects of exercise on bone phenotypes, such as stress fracture injuries have been reported. Little is known about the extent of the genetic mediation of changes in bone characteristics, stress fracture injury and bone resorption in response to exercise. Accordingly, this thesis investigated: the genotype dependent changes in bone phenotypes in academy footballers before and after an increase in training volume; genetic associations with stress fracture injury in elite athletes and a preliminary investigation into genetic associations with bone resorption following 120 min of treadmill running. The tibial bone characteristics of 80, full-time academy footballers was determined using pQCT before and after 12 weeks of increased volume football training. Genetic associations with baseline, post increased training and change in bone characteristics were then determined. Secondly, radiologically confirmed stress fracture history was reported in 518 elite athletes, forming the Stress Fracture Elite Athlete (SFEA) cohort. Genetic associations were analysed for the whole group, and were also sub-stratified. Finally, recreationally active healthy male participants (n=42) performed a 120 min run at 70% O2max. Genetic associations with bone resorption at baseline, immediately, 24, 48 and 72 hours post run were investigated
Removing Love waves from shallow seismic SH-wave data
No full textGeophysical exploration measurements are used to obtain an image of the geological structures of the subsurface, as detailed as possible. To this end, a wavefield is generated by a seismic source. This wavefield propagates through the subsurface, and will partly reflect on boundaries between layers with contrasting properties, and it will partly propagate further into the subsurface. De wavefields that have propagated back to the surface are measured with receivers. When this experiment is repeated several times on different locations, the measured data can be used to obtain the desired image. There are two kinds of seismic waves that can propagate through the subsurface. The ones that are generally used are the pressure waves, or P-waves, where the movement of the particles is parallel to the propagation direction of the wave. The other ones are the shear waves, or S-waves, where the movement of the particles is perpendicular to the propagation direction of the wave. When the particle movement is horizontally polarized (perpendicular to the plane of propagation), this wave type is often decoupled, or in other words, it propagates independently of other wave types. These waves are also called SH-waves. The surface of the Earth behaves as a perfect reflector for SH-waves. This means that all SH-waves that reach the surface will be completely reflected back into the subsurface. When the top layer of the subsurface is thin (smaller than the wavelength of the SH-wave), and when this top layer has a lower wave velocity than deeper layers, then the presence of the surface leads to a kind of surface waves, which were first described by A.E.H. Love, and are therefore called 'Love waves'. Love wave characteristics are: their group velocity is almost equal to the shear wave velocity; since they propagate solely along the surface, they attenuate slowly and are thus often stronger than reflected waves; and they are dispersive. The presence of Love waves deteriorates the quality of the final picture (or seismogram), because they obscure the desired reflections. Existing techniques to remove Love waves from seismic data often perform insufficient, or require certain knowledge about the subsurface. This knowledge is generally not available. Therefore, the ideal method should be one where the measured data alone is sufficient to separate the Love waves from the desired reflection information. The method we describe in this thesis uses the Betti-Rayleigh reciprocity theorem for elastic media. Reciprocity is a mathematical tool to relate two different states to each other. Here, one state is the actual situation, where the medium is bounded by a stress-free surface. The other state is an ideal situation, where there is no surface, and the top layer is extended to infinity. When there is no surface, there are also no surface waves. By applying the reciprocity theorem, we derive an integral equation, from which the Love wave free wavefield can be solved as a function of the data that do contain these surface waves. Other input parameters are the (shear-) wave velocity and the mass density of the top layer, and the source wavelet. When the data are discrete, the integral equation becomes a matrix equation. This can be solved using conventional numerical methods, such as matrix inversion. When the medium is horizontally layered (a so called 1-D medium), the kernel of the matrix equation becomes diagonal in the wave-number domain. Then the matrix equation reduces to a scalar expression. We tested the method on several synthetic datasets. In all cases, the Love waves were completely removed. Even other noise in the form of scattered Love waves was removed, in the cases where it was present. The method also had no problems when the input parameters were chosen wrongly. And when distortions were introduced into the data (distortions like random noise, or the effects of anelastic attenuation), the method still performed well. To test the method on field data, we performed a seismic experiment on the site of the Sofia tunnel (before it was drilled) near Hendrik Ido Ambacht in the Netherlands. The dataset that was the result seemed all right at first. Strong Love waves were indeed present in the data. However, we could not succeed in removing these Love waves with the method. Even worse, the method added noise to the data, to such an extent, that it completely obscured the original data. Although we searched extensively for possible reasons, we were not able to find the exact cause of the bad results. In the final chapter, we made a start to remove the surface waves from coupled P- and SV-wave systems, using the same method as we did for SH-waves. Because P- and SV-waves are coupled, the resulting equations are also coupled. This means that we need all possible source and receiver combinations to remove the surface waves. But it appeared that the equations could be solved independently with regard to the source direction. We validated the theory with an example where we removed the Rayleigh wave from the response of a homogeneousCivil Engineering and Geoscience
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