The O2 diffusion constants D and K of tumor tissue (DS-Carcinosarcoma in the rat kidney) were determined at temperatures of 20, 30, 37, and 40 degrees C. The following mean values were obtained for the conditions of 37 degrees C: D = 1.75-10(-5) cm2/s and K = 1.9-10(-5) mlO2/cm-min-atm. Within the range of 20-40 degrees C, temperature variations in tumor tissue cause changes in the O2 diffusion coefficient D of 2.0-2.5%/C and in the Krogh O2 diffusion constant K of 0.5-1.5%/C. The measured O2 diffusion constants for tumor tissue correspond to values of normal tissue with similar water content. This indicates that the insufficient O2 supply in DS-Carcinosarcoma is due not to unfavorable O2 diffusivity of the tumor tissue but rather to a decreased convective O2 transport and to insufficient capillarization. An analysis of O2 diffusion in DS-Carcinosarcoma tissue using the determined O2 diffusion constants lead to the result that, under the conditions of arterial normoxia and normocapnia, critical O2 supply conditions are to be expected when the intercapillary distance exceeds approximately 120 micrometer.

We have previously shown that the pteridine compound neopterin stimulates inducible nitric oxide synthase (iNOS) gene expression in vascular smooth muscle cells in vitro. The mechanisms whereby neopterin exhibits these effects remained unclear. The present study demonstrates that neopterin induces the translocation of the transcription factor nuclear factor-w~B (NF-~B) to the nucleus. Pretreatment of cells with the antioxidant pyrrolidine dithiocarbamate completely suppressed the effects of neopterin on NF-r,~B activation, iNOS gene expression, and nitric oxide release. From these data we conclude that neopterin activates the translocation of NF-r,B suhunits to the nucleus by modulating the intracellular redox state. This is one possible explanation for the impact of neopterin on iNOS gene expression.

Fiir die Berechnung des Sauerstoffaustausches in der Lunge und die Beurteilung yon Sauerstoffdruckverteilungen und damit der Q-Versorgung im Gewebe naeh den Gesetzm/~gigkeiten der Diffusion ist die Kennthis der diffusionsbestimmenden Konstanten der untersuchten Gewebe eine wichtige Voraussetzung. Es handelt sich um den Sauerstoffdiffusionskoeffizienten D mit der Dimension [em2/see], der ben6tigt wird, wenn bei bekannten O~-Konzentrationsuntersehieden die diffundierende Sauerstoffmenge bereehnet werden soll, oder um den Kroghschen Diffusionskoeffizienten K mit der Dimension [ml O2/cm • min • Arm]. Der Kroghsehe Diffusionskoeffizient, auch Diffusionsleitf/~higkeit genannt, entslol~eht 18 Pflfigers Arch. ges. Physiol., Bd. 295

No abstract

The tamoxifen-induced reduction of cell viability in HepG2 cells depends on drug concentration and cell density and is due to cytostatic and cytocide effects. The latter may be mediated by a down-regulation of telomerase activity.