Monocyte, macrophage and foreign body giant cell interactions with molecularly engineered surfaces

To elucidate the mechanisms involved in monocyte/macrophage adhesion and fusion to form foreign body giant cells on molecularly engineered surfaces, we have utilized our in vitro culture system to examine surface chemistry effects, cytoskeletal reorganization and adhesive structure development, and cell receptor-ligand interactions in in vitro foreign body giant cell formation. Utilizing silane-modified surfaces, monocyte/macrophage adhesion was essentially unaffected by surface chemistry, however the density of foreign body giant cells (FBGCs) was correlated with surface carbon content. An exception to the surface-independent macrophage adhesion were the alkyl-silane modified surfaces which exhibited reduced adhesion and FBGC formation. Utilizing confocal immunofluorescent techniques, cytoskeletal reorganization and adhesive structure development in in vitro FBGC formation was studied. Podosomes were identified as the adhesive structures in macrophages and FBGCs based on the presence of characteristic cytoplasmic proteins and F-actin at the ventral cell surface. Focal adhesion kinase (FAK) and focal adhesions were not identified as the adhesive structures in macrophages and FBGCs. In studying the effect of preadsorbed proteins on FBGC formation, fibronectin or vitronectin do not play major roles in initial monocyte/macrophage adhesion, whereas polystyrene surfaces modified with RGD exhibited significant FBGC formation. These studies identify the potential importance of surface chemistry-dependent conformational alterations which may occur in proteins adsorbed to surfaces and their potential involvement in receptor-ligand interactions. Significantly, preadsorption of α₂-macroglobulin facilitated macrophage fusion and FBGC formation readily on the RGD surface in the absence of any additional serum proteins. As α₂-macroglobulin receptors are not found on blood monocytes but are expressed only with macrophage development, these results point to a potential interaction between adsorbed α₂-macroglobulin and its receptors on macrophages during macrophage development and fusion. These studies identify important surface independent and dependent effects in foreign body reaction development that may be important in the identification of biological design criteria for molecularly engineered surfaces and tissue engineered devices. © 1999 Kluwer Academic Publishers     

Psychotherapy appointment no-shows: Rates and reasons.

Patients who frequently miss or do not show for their scheduled psychotherapy appointments create administrative and clinical difficulties, and may not be receiving effective treatment. Prior research has predominately focused on either identifying demographic and administrative factors related to patient no-show rates or evaluating the effectiveness of administrative procedures for reducing no-shows. This paper attempts to identify rates of missed appointments in clinical practice and explore more specific clinical process factors related to patient no-shows. Psychotherapists (N = 24) and their patients (N = 542) in the outpatient department of a public safety-net hospital were surveyed to examine how frequently patients missed scheduled psychotherapy appointments and for what reasons. Findings indicate that the majority of missed appointments were accounted for by patients with occasional absences (approx. 1 per month), while only a small percentage of patients missed appointments with high frequency. Patients missed their psychotherapy appointments for a number of reasons, including clinical symptoms, practical matters, motivational concerns, and negative treatment reactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Air release in PVC plastisols

The ability of a PVC plastisol to liberate entrapped air during mixing and processing is an important factor to the processors. This property, known as air release, is affected by several variables such as resin, plastisol viscosity, surface tension, surfactant system and plasticizer type. A study was conducted to obtain a more fundamental understanding of the effects of these variables on air release. Complicating the accurate study of a plastisol's air release properties is the fact that current test procedures such as the vacuum rise, syringe test and Huff or ring test each have limitations imposed by either plastisol properties or by testing technique. Any one of these procedures alone may not adequately measure air release. This paper, in addition to studying the factors affecting air release, discusses these testing limitations and makes recommendations as to the best methods for evaluating air release properties in the laboratory.