Kinetics of circulating TNF-alpha and TNF soluble receptors following surgery in a clinical model of sepsis

The interrelationship between cytokines and their natural antagonists in patients with systemic sepsis are incompletely understood. We have followed the changes in serum levels of TNF-alpha and the two soluble receptors (TNF-sr) in a clinical model of post-operative sepsis. Serial blood samples were taken in patients undergoing percutaneous nephrolithotomy (PCNL) starting pre-operatively and continuing for 24 h thereafter. The levels of TNF-alpha and TNF-sr were raised in patients who became clinically septic and correlated well with the severity of sepsis (using the APACHE III score). In septic patients there was no difference in the pattern of changes in the two types of receptor (TNF-sr55 and TNF-sr75). However, in non-septic patients TNF-sr75 was higher in those with endotoxaemia than those without. This difference was not observed with TNF-sr55 which suggests a different mechanism of release or degree of sensitivity for the two soluble receptors. Regardless of severity of illness, the levels of all three molecules (TNF-alpha and the two receptors) appeared to start rising at about the same time point. The peak TNF-alpha level was reached earlier (2-4 h) than that of the two TNF-sr (4-8 h). The relative rise in TNF-alpha was greater than that of the soluble receptors and this difference was even more marked in those with more severe sepsis. The relationship between peak TNF-alpha and peak TNF-sr was non-linear and the concentration of each TNF-sr appeared to plateau at the higher levels of TNF-alpha. This suggests the exhaustion of a limited pool or saturation of the rate of release. Taken together, these results suggest sepsis develops because of delayed and insufficient secretion of TNF-sr compared with TNF-alpha.     

Continuous analysis in extracorporeally circulating blood--a rat model applying flow-through ion-selective electrodes for the measurement of Ca2+, K+, Na+ and pH

A rat model is introduced which enables investigations in anticoagulated blood with continuous measurements by a flow-through electrode system. In the present study, a potentiometric ion-selective electrode (ISE)-system was used for measuring Ca2+, K+, Na+ and pH in rats. The setup was adjusted to an extracorporeal blood-volume of 0.750 ml. This permits indirect measurements of the analytes via a dialysis membrane, with electrical separation of the ISE's and the animal. The flow-rates of blood and dialysis-solution were adjusted in such a way that water diffusing from the aqueous dialysis solution into the blood, across the dialysis membrane, does not alter the haematocrit. Polyethyleneglycol-hirudin was used for anticoagulation, since it was superior to heparin. The assembly enables continuous measurements in the living anaesthetized rat over a time period of at least 3 hours.     

Fly's eye: a counting camera for thermal neutrons-some applications, problems, and prospects

An area detector for thermal neutrons based on image intensification techniques has been described. Some capabilities and limitations of the detection system have been discussed. Among the former are high spatial resolution, high instantaneous counting rate, electronic zoom, time-gating, and integration. The detector is limited in that the maximum counting rate for a resolution element is 60 regularly spaced counts per second. Also, the nonuniformity of response over the detector puts a limit on the useful size and necessitates point-by-point calibration. In addition, a higher efficiency for neutron detection would be desirable. Some typical applications of the system are crystal inspection, neutron magnetic diffraction topography, and searches for temperature-induced changes in diffraction patterns. The future application of solid-state television sensors and microchannel-plate intensifiers to improve the system were briefly mentioned.