Gap junctional intercellular communication contributes to the contraction of rat osteoblast populated collagen lattices

The contraction of native collagen lattices by resident mesenchymal cells mimics the organization of collagen during development and repair. Lattice contraction is cell density dependent, suggesting that cell-to-cell communications may contribute to the process. This possibility was investigated by comparing lattice contraction by four rat osteoblastic cell lines: ROS 17/2.8 cells (ROS); ROS transfected with an antisense cDNA sequence of the gap junctional protein connexin 43 (RCx16); ROS transfected with connexin 45 cDNA, a connexin not normally expressed in ROS cells (ROS/Cx45); and ROS transfected with cDNA encoding carboxy-terminal truncated Cx45 (ROS/Cx45tr). The cell coupling indices, which reflect gap junctional communication, were quantitated by the fluorescent dye scrape loading. ROS cells were well coupled (index 3.0), ROS/Cx45tr were better coupled (index 4.2), ROS/Cx45 were poorly coupled (index 1.7), and RCx16 showed no coupling (index 1.1). As determined by immunoblotting, the level of connexin 43 protein was increased in both ROS/Cx45tr and ROS/Cx45 cell lines compared with ROS cells, while the level in RCx16 cells was reduced. ROS populated collagen lattices (PCLs) contracted significantly more at day 5 (177 mm2 to 67 mm2) than ROS/Cx45tr (84 mm2), ROS/Cx45 (108 mm2), or RCx16 (114 mm2). Myosin ATPase activity, which is required for lattice contraction, was equivalent in all four cell lines, indicating that it was not responsible for inhibiting PCL contraction. ROS cells in collagen appeared elongated compared with the other cell lines which were more rounded. These experiments suggest gap junctional communication contributes to PCL contraction by resident osteoblasts.     

Note on the interpretation of powder shear test data

Powder shear testing has been used to assess flowability of powders for at least 48 years [A.W. Jenike, Storage and Flow of Solids, Bull., Eng. Exp. Station, Univ. Utah, vol. 123, 1964]. A fundamental part of the data interpretation involves construction of Mohr’s circles such that they are tangent to the experimental locus; a set of powder shear strengths, τ_m, measured at variable applied compressive normal stresses, σ_N. Despite the customary application of this tangency criterion, we have found justifications for it to be scant.In this work, we revisit the Mohr’s circle construction and find that proper construction would require measurement of reactionary lateral powder stresses, σ_r. We further provide reasoning to support placement of the experimental locus passing through the apex (top) of Mohr’s circles for isotropic or orthotropic powders and not tangentially to them. This placement is not unexpectedly in agreement with the results of a recent numerical simulation [C. Thornton, L. Zhang, Numerical simulations of the direct shear test, Chem. Eng. Technol. 26 (2) (2003) 153-156], and reveals errors in subsequently calculated constants on the order of 20%.     

Effects of dihydrotestosterone alone and combined with estrogen on bone mineral density, bone growth, and formation rates in ovariectomized rats

The combination of fast MR sequences and rapid i.v. injection of paramagnetic contrast media provides information on cerebral perfusion. MR-perfusion imaging primarily depicts the relative cerebral blood volume. The aim of this study was to test whether MR-perfusion imaging with a clinical MR scanner using a standard 2D-FLASH sequence provides clinically relevant information on patients with cerebrovascular diseases and brain tumors. Brain infarctions, lesions in cerebral microangiopathy and occlusions of the carotid artery with very poor collateralization showed definite differences in perfusion imaging compared with normal controls. However, our results show that acceleration of the imaging sequence and optimization of the contrast bolus and data processing are prerequisites for the clinical use of this method, which in principle may provide information on the absolute cerebral blood volume and even blood flow.     

Definitely not a breeze: Extending an operant model of effective supervision to teams.

To identify what leaders ought to do to orchestrate optimal team performance, an expanded model of effective supervision was tested in a setting combining realism, control, and clear-cut outcomes. The components of the empirically based operant model—monitoring and consequences—were extended to tasks requiring the integration of team efforts. A sailboat regatta was arranged, with series standings as the primary measure of supervisory effectiveness. Using the Operant Supervisory Team Taxonomy and Index, trained observers recorded skippers' (N?=?19) actions. As predicted, racing success correlated significantly (p?r?=?–.51 and –.47, respectively) during the actual races. The relationship between the model's two critical behaviors and an unfiltered measure of effectiveness has implications for the group and leadership literatures as well as for management practices. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

History of bioceramics

The history of bioceramics is reviewed and the current status of the use of nearly inert, surface reactive, and resorbable bioceramics discussed.     

Thin film ferroelectrics for capacitor applications

Pulsed laser deposition (PLD) has been used to fabricate simple thin film capacitor structures with a variety of ferroelectric materials. Thin film capacitors using the conventional ferroelectric material BaxSr1-xTiO3(BSTO) have been made across the entire compositional series. Electrical characterization shows that in thin film form these ferroelectrics display Curie point behaviour which is largely independent of composition. This contrasts sharply with bulk behaviour. The thin film fabrication and characterization of relaxor ferroelectric ceramics, such as Pb(Mg1/3Nb2/3)O3 (PMN) and Pb(Zn1/3Nb2/3)O3-BaTiO3(PZN-BT), is also reported. © 1998 Chapman & Hall     

Efficacy of self-examination therapy in the treatment of generalized anxiety disorder.

To determine the efficacy of self-examination therapy in the treatment of generalized anxiety disorder, 38 adults volunteered for a study in which they were randomly assigned to self-examination therapy or to a delayed-treatment group. Analyses indicated that participants in self-examination therapy had significantly fewer symptoms of anxiety than did participants in the delayed-treatment group on the outcome measures of this study, which included ratings by trained clinicians and participants. The reduction in anxiety for people receiving self-examination therapy was maintained 3 months after treatment ended. The delayed-treatment group also showed significant improvement in anxiety symptoms after receiving self-examination therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Peer model and experimenter expectancies about appropriate response as determinants of behavior in the hypnotic setting.

Conducted 2 studies with undergraduates (N = 180) to analyze the behavioral effects of the variables "peer model behavior" and the "E's statement of his own expectancy" on the application of hypnosis. The 2 sources of social influence were established prior to induction of hypnosis. The sources were studied for their effects within the framework of a factorial design in which model and hypnotist expectancies about appropriate hypnotic response were manipulated simultaneously, in harmony and in opposition to each other. Exp I established the accuracy of the expectancy manipulations. Exp II analyzed the consequent effects of such manipulations and predicted a positive relationship between hypnotist-expectancy effect and Ss' susceptibility to hypnosis. As predicted, both variables effectively shaped Ss' hypnotic response. The level of susceptibility of Ss to hypnosis was significantly related to the strength of influence of the hypnotist's expressed expectancy. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)