No abstract

1 We have examined the generation of intracellular reactive oxygen species (ROS) and release of histamine by rat peritoneal mast cells (RPMC) in response to stimulation with antigen (ovalbumin), compound 48/80, nerve growth factor (NGF) and substance P (SP). 2 We have also examined the eects of the non-speci®c nitric oxide synthase inhibitor, L-NAME (100 mM) upon the release of histamine and generation of intracellular ROS in response to the named secretagogues. 3 Ovalbumin (100 ± 1000 mg ml 71 ), compound 48/80 (0.1 ± 100 mg ml 71 ), NGF (0.1 ± 100 mg ml 71 ), and SP (5 ± 50 mM), caused a concentration-dependent release of histamine from RPMC. 4 Ovalbumin (1 ng ml 71 ± 0.1 mg ml 71), compound 48/80 (1 ± 100 mg ml 71 ), NGF (1 pg ml 71 ± 1 mg ml 71 ), and SP (0.005 ± 50 mM) caused a concentration-dependent generation of intracellular ROS by RPMC. 5 Pre-incubation of RPMC with L-NAME (100 mM) caused a signi®cant enhancement of both histamine release and intracellular ROS from RPMC in response to ovalbumin, compound 48/80, NGF and SP. 6 Our data demonstrate that NGF, SP and ovalbumin are capable of causing intracellular ROS generation by RPMC at lower concentrations than those causing signi®cant histamine release and we speculate that this may contribute to the activation of cytokine production. 7 The data also show that NO modulates histamine release, and ROS generation in response to the secretagogues used. This may have signi®cance in pathologies where NO synthesis is decreased, leading to an increased activation of mast cells.

The single crystal X-ray structure of the all-axial conformer of the (R,R,R,R) enantiomer of the chiral donor tetramethyl-BEDT-TTF (TM-BEDT-TTF) was described and compared to the all-equatorial conformer. (S,S,S,S)-Tetramethyl-BEDT-TTF formed crystalline 1 : 1 complexes with TCNQ and TCNQ-F 4 , as well as a THF solvate of the TCNQ complex. Donors bis((2S,4S)-pentane-2,4-dithio)tetrathiafulvalene and (ethylenedithio)((2S,4S)-pentane-2,4-dithio)tetrathiafulvalene, which contain seven-membered rings bearing chirally oriented methyl groups, only formed complexes with TCNQ-F 4. The TCNQ-F 4 complexes contain planar organosulfur systems, in contrast to the TCNQ complexes in which there is minimal charge transfer. A variety of crystal packing modes were observed. Electrocrystallization experiments with both enantiomers and the racemic form of tetramethyl-BEDT-TTF afforded mixed valence radical cation salts with the AsF 6 and SbF 6 anions formulated as (TM-BEDT-TTF) 2 XF 6 (X = As, Sb). Electrical conductivity was only found in one charge transfer complex, while the radical cation salts are all semiconducting.

In vivo, LPS stimulates TxA2 production and p38 MAPK phosphorylation in equine platelets and leukocytes at a concentration within a similar range to those reported in clinical endotoxaemia. These data suggest that LPS-induced eicosanoid production in the early phase of clinical endotoxaemia may involve direct effects of LPS upon platelets, mediated via activation of p38 MAPK.