The actin-based cytoskeleton of endothelial cells plays an important role in regulating cell function. Both thrombin and phorbol 12-myristate 13-acetate (PMA) (an activator of protein kinase C; PKC) cause rearrangement of actin and increased permeability of endothelial monolayers. Conversely, thrombin, but not PMA, induces phosphorylation of myosin light chains (MLC), a process considered essential for cellular contraction. We, therefore, decided to investigate which signaling pathways are involved in thrombin-induced actin reorganization in pulmonary artery endothelial cells. Thrombin induced a rapid and transient increase in cytoskeletal actin that paralleled MLC phosphorylation. Antagonism of the Ca(2+)-binding protein, calmodulix (CaM), or inhibition of the CaM-dependent MLC kinase (MLCK) abolished the elevation in cytoskeletal actin whereas inhibition of PKC did not. In contrast, PMA decreased cytoskeleton-associated actin without affecting phosphorylation of MLC. A23187, a Ca(2+)- ionophore, or thapsigargin, an inhibitor of endoplasmic Ca(2+)-ATPase, either in the presence or absence of PMA, did not increase cytoskeletal actin. Therefore, increased intracellular Ca2+, even with concurrent activation of PKC, is insufficient for redistribution of actin to the cytoskeleton, indicating that thrombin recruits yet another signaling pathway. Both thrombin and PMA caused extensive rearrangement of filamentous actin with a disappearance of the dense peripheral band and an increase in stress fibers, but each agent induced a distinct morphology. Thrombin-induced rearrangement of actin filaments was attenuated by inhibitors of either PKC or MLCK. These data suggest that both PKC- and MLCK-dependent pathways are involved in thrombin-induced endothelial cell actin rearrangement, but that recruitment of actin to the cytoskeleton is not necessary for this rearrangement. Recruitment of actin and myosin to the cytoskeleton does not require PKC but does involve MLCK-catalyzed phosphorylation of MLC.

Actins↗

PubMedDate not supplied

Parental attitude and adjustment to childhood epilepsy.

Parenteral attitudes and adjustment to epilepsy were assessed for 50 parents of children aged 6 to 14 with epilepsy. Fishbein's Expectancy-Value Model of Attitude was used to assess parental attitudes. Parental adjustment was measured both by a self-report instrument and by an independent psychosocial assessment conducted by a psychiatric social worker. The major finding was a strong positive relationship (R = .67, p less than .001) between parental attitude and adjustment for the mothers. The attitude-adjustment relationship was not significant for the fathers. In addition, parental attitudes and perception of seizure control accounted for 60% of the variance in the mothers' adjustment scores. Seizure control was significantly positively related (p less than .05) to parental adjustment.

Adaptation, Psychological↗