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     

Periclase solid solutions containing Li+1 and R+3 ions

Recent work on phase equilibria diagrams has shown that periclase can take R⁺³ (Cr⁺³, Al⁺³, and Fe⁺³) in solid solution at elevated temperatures. In order to retain electrical neutrality, 2R⁺³ and a vacancy replaces 3Mg⁺² in the periclase lattices. When Li⁺¹ is added to MgO/R₂O₃ compositions, one Li⁺¹ and one R⁺³ replaces 2 Mg⁺² to form a solid solution which is stable at room temperature. These periclase solid solutions are more stable under conditions of temperature fluctuations and hydration than periclase/R₂O₃ solid solutions without lithia.     

Monitoring of stress reduction in shallow trench isolation CMOS structures via synchrotron X-ray topography, electrical data and raman spectroscopy

Local oxidation of silicon (LOCOS) isolation technology is becoming increasingly unusable for critical dimensions of 0.25 m and below, due to the intolerably large dimension of the oxide bird'sbeak. Therefore, this technique has been replaced by a process called shallow trench isolation (STI) which uses deposited dielectrics to fill trenches etched in the silicon between the active areas. One of the chief drawbacks to STI is the tendency of such structures to be highly stressed, especially after the oxide/dielectric backfill, which can have a deleterious impact on the electrical performance of fabricated devices. It is essential to monitor the stress/strain fields generated by shallow trench isolation structures. Synchrotron X-ray topography (SXRT), a genuinely non-destructive technique, has been employed to provide in situ stress evaluation during the development of an STI-based complimentary metal oxide semiconductor (CMOS) integrated circuit process. Various process options were evaluated and the data was compared with electrical n⁺/p diode leakage and micro-Raman spectroscopy data.     

Altered vulnerability to acute opiate withdrawal following stress: Roles of N-methyl-{d}-aspartate and glucocorticoid receptors.

Five experiments studied the modulation of acute opiate withdrawal by restraint stress. Rats were subjected to a 2-hr restraint stress, and 1, 3, or 7 days later they received a single injection of morphine followed by injection of naloxone. Naloxone precipitated a withdrawal syndrome. This syndrome was enhanced when it occurred 1 day after stress but was reduced when it occurred 7 days after stress. The enhancement of withdrawal by restraint stress was prevented by treatment with the N-methyl-{d}-aspartate (NMDA) receptor antagonist MK801 or the glucocorticoid receptor antagonist RU486 prior to stress. Together these experiments show that restraint stress alters vulnerability to opiate withdrawal and identify activation of NMDA and glucocorticoid receptors as causal to this vulnerability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stereoselective Alkylations of Enolates Derived from Ligands Attached to the Indenyl Iron Chiral Auxiliary [(η5-C9H7)Fe(CO)(PPh3)]: X-ray Crystal Structure and Conformational Analysis of [(η5-C9H7)Fe(CO)(PPh3)COCH3]

The preparation, X-ray crystal structure, and conformational analysis of the acetyl complex [(η⁵ - C₉H₇)Fe(CO)(PPh₃)COCH₃] ( 5 ) are described. Deprotonation and alkylation of complex 5 generates the corresponding propanoyl ( 6 ) and butanoyl ( 7 ) complexes. Deprotonation and alkylation of complexes 6 and 7 to generate complementary diastereoisomers of the corresponding 2-methylbutanoyl complex occur with high stereoselectivities. The aldol reaction of the diethylaluminium enolate derived from 5 with acetaldehyde also shows a high stereoselectivity (95:5). The reactions of the indenyl complex 5 clearly parallel those for the cyclopentadienyl analogue and this is rationalised in terms of the conformational analysis.