The effect of synthetic human parathyroid hormone (hPTH) on the formation of matrix vesicles (MV), and on the rate of cell division, production of cellular alkaline phosphatase (AP) and protein by ...primary cultures of chicken epiphyseal growth plate hypertrophic chondrocytes was investigated. Addition to serum-containing or serum-free media of physiological levels of hPTH, in a range from 0.1 to 10 nM, caused a progressive decrease in the formation of AP-rich MV. However, studies on incorporation of 3Hcholine into MV indicate that MV formation per se was not significantly decreased. hPTH was found to markedly decrease the expression of cellular AP, accompanied by an increase in cell division ( 3Hthymidine incorporation) and protein synthesis. Since these effects of hPTH were augmented by 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, and mimicked by the cAMP analogue N6,O2'-dibutyryl-adenosine 3',5'-cyclic-monophosphate (DBcAMP), the findings clearly indicate that hPTH was acting through the classic cAMP-mediated mechanism. Inasmuch as elevation of AP in growth plate chondrocytes coincides with MV formation, maturation and hypertrophy of the cells, and induction of mineralization, the stimulation of cell division and suppression of cellular AP indicates that hPTH would cause the cells to revert to a less differentiated state. Thus, elevation in PTH, which results from lowered circulating levels of Ca2+, should inhibit mineral deposition in the growth plate. This may be a physiological protective mechanism to prevent a further drain on serum Ca2+.
Provider: - Institution: - Data provided by Europeana Collections- In two studies we examined whether forging a psychological bond with a nation’s colonization past facilitates the experience of ...positive and negative group-based self-conscious emotions as a function of a positive or negative manipulation of this past. Because people need to belong, we hypothesized that stronger family involvement in a nation’s colonization past (i.e. involved ancestors) evokes stronger a positive self-conscious emotions after positive descriptions of the nation’s colonizing past, and stronger negative self-conscious emotions after negative descriptions. In Study 1, we found support for these hypotheses in a real-life setting in which Dutch people actually found out whether their ancestors were involved in the colonization of Indonesia or not. In Study 2, we manipulated family involvement and valence of the past. Results offered support for the tested hypotheses. Implications of the results are discussed in relation to theories on identity and emotion.- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
We analyze the main features of granular shear flow through experimental measurements in a Couette geometry and a comparison to a locally Newtonian, continuum model of granular flow. The model is ...based on earlier hydrodynamic models, adjusted to take into account the experimentally observed coupling between fluctuations in particle motion and mean-flow properties. Experimentally, the local velocity fluctuations are found to vary as a power of the local velocity gradient. This can be explained by an effective viscosity that diverges more rapidly as the random-close-packing density is approached than is predicted by Enskog theory for dense hard sphere systems. Experiment and theory are in good agreement, especially for the following key features of granular flow: The flow is confined to a small shear band, fluctuations decay approximately exponentially away from the sheared wall, and the shear stress is approximately independent of shear rate. The functional forms of the velocity and fluctuation profiles predicted by the model agree with the experimental results.
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