Release and interconversion of P2 receptor agonists by human osteoblast-like cells.

Nucleotides, acting as agonists at P2 receptors, are important extracellular signaling molecules in many tissues. In bone they affect both bone-forming osteoblast and bone-resorbing osteoclast cell activity. The presence of nucleotides in the extracellular microenvironment is largely determined by their release from cells and metabolism by ecto-enzymes, both of which have scarcely been studied in bone. We have investigated adenosine 5'-triphosphate (ATP) release from SaOS-2 osteoblastic cells and the activities of cell surface ecto-enzymes on ATP metabolism. ATP, but not LDH, was detected in SaOS-2 cell conditioned medium, suggesting these cells were actively releasing ATP. Introduction of ADP resulted in increased ATP concentrations in the medium, which was found not to be receptor mediated. Nucleotide inhibition and substrate specificity studies revealed an ecto-nucleoside diphosphokinase (ecto-NDPK) was responsible for the ADP-->ATP conversion; PCR and immunocytochemistry confirmed its presence. Analysis of ATP metabolism over time demonstrated overall ATP degradation was increased by inhibiting ecto-NDPK activity; confirming that the combined action of multiple osteoblast-expressed ecto-enzymes affected extracellular nucleotide concentration. The data establish the coexistence of ATP-consuming, and for the first time, ATP-generating activities on the osteoblast cell surface, the discovery of which has significant implications for studies involving P2 receptor subtypes in bone.

Logic and reliability of evaluations of competence to stand trial.

Because the trier of fact determines the weight to be assigned to an examiner's opinion by assessing the strength and persuasiveness of his or her analysis of the data, it is essential that forensic reports communicate the examiner's reasoning process. This study analyzes community examiners' reports on competence to stand trial (CST), emphasizing the nature of examiners' (1) expressed conceptualizations of CST and (2) reasoning establishing a nexus between CST impairments and symptoms of psychopathology. Expert raters coded 100 randomly selected CST reports with respect to a variety of issues, including the examiners' description of the defendant's psycholegal deficits, provision of specific reasoning to link these deficits to psychopathology, and agreement with a paired examiner's global and specific opinions about the defendant's impairments. CST reports were found to (1) reflect basic operationalizations of competence that fail to incorporate legally relevant facets such as a defendant's decisional capacities and (2) adequately document clinical findings, but fail to describe the reasoning underlying psycholegal conclusions. Examiners demonstrated moderately high levels of agreement on defendant's global CST, but expressed radically divergent bases for this opinion. These findings are discussed in light of legal, ethical, and professional standards of practice.

Interpersonal perception and mode of resolution in marital conflict.

The present study examined the relationship between changes in couples' perceptions of each other during a conflictual interaction and their mode of conflict resolution. Thirty-three volunteer married couples were videotaped while recreating a conflictual interaction that had occurred previously. During a subsequent replaying of the videotape, husbands' and wives' verbal descriptions of perceptions of self and spouse were elicited at three different stages of the conflict, using a method for eliciting perceptions derived from Laing. Phillipson, and Lee's multiperspective interpersonal perception technique. The interpersonal perceptions of couples who resolved the conflict by engaging the issue at hand were contrasted with those of couples who resolved the conflict via avoidance. Statistically significant differences were found between the groups, suggesting that engaging the issue was associated with an increase in spouses' access to one another's interpersonal perceptions, whereas avoidance was associated with decreases in consensually valid perceptions. Substantive and methodological implications of the study are discussed.

Method Variance, Inadequate Constructs, Or Things That Go Bump In The Night?

Jackson's (1975) revised method for multimethod factor analysis and his critique of Golding and Seidman's (1974) similar "two step principal components" procedure are critically examined. While Jackson's revised method is more empirically defensible, the conceptual assumptions upon which it is based may not be warranted, and his critique of the Golding-Seidman method may be misleading. It is argued that "method variance" is properly viewed as a hidden facet of nomologicals underlying a construct, and that multimethod investigations that fail to specify the nomological, assumptions surrounding particular trait-method units are conceptually and empirically unsound.

Multivariable-Multimethod Convergence in the Domain of Interpersonal Behavior.

While empirical studies of the domain of interpersonal behavior indicate a great deal of conceptual convergence, there are few data bearing on the convergent validity of indices of interpersonal behavior across modes of measurement within the same population of subjects. As part of a larger study of the assessment of interpersonal behavior, 64 Ss participated in a multivariable-multimethod investigation, and completed a variety of self-report assessment devices, direct self ratings, and peer ratings. Substantial convergence for three dimensions of interpersonal behavior, Aggressive Dominance, Affiliation-Sociability, and Autonomy, was obtained across all modes of measurement. The results have implications for the assessment of interpersonal behavior, the individual differences versus situational variance controversy, and associated theoretical and methodological problems in multivariable-multimethod-multisituational designs.

ANALYSIS OF MULTITRAIT-MULTIMETHOD MATRICES: A TWO STEP PRINCIPAL COMPONENTS PROCEDURE.

A relatively simple technique for .assessing the convergence of sets of variables across method domains is presented. The technique, two-step principal components analysis, empirically orthogonalizes each method domain into sets of components, and then analyzes convergence among components across domains. The proposed technique is directly compared with Jackson's (1969) multi-method factor analysis (which involves an a priori orthogonalization) in the analysis of data from personality, vocational interest and aptitude domains. While Jackson's technique focuses on individual variables, and the two-step procedure focuses on the components of variable domains, both techniques produced evidence of cross-domain convergence. However, Jackson's method was found t o have several undesirable mathematical and interpretational consequences, while the two-step procedure appears to be a promising technique for the systematic, empirical analysis of multitrait-multimethod matrices.