Assessment of cellular oxygen gradients with a panel of phosphorescent oxygen-sensitive probes

The supply of oxygen (O(2)) to respiring tissue, cells, and mitochondria regulates metabolism, gene expression, and cell fate. Depending on the cell type and mitochondrial function, O(2) gradients between extra- and intracellular compartments may vary and play important physiological roles such as the regulation of activity of prolyl hydroxylases and adaptive responses to hypoxia. Here we present a new methodology for the analysis of localized O(2) gradients in cultures of adherent cells, using three phosphorescent Pt-porphyrin based probes with different localization. One new O(2) probe targeted to the cell membrane was developed and used together with existing MitoXpress and Nano2 probes to monitor mean pericellular (PC), extracellular (EC), and intracellular (IC) O(2) concentrations, respectively. Mouse fibroblasts and neuronal PC12 cells cultured in standard microplates were stained with probes and measured on a commercial time-resolved fluorescence reader in phosphorescence lifetime mode. Respiring cells exposed to various levels of atmospheric O(2) showed differences in oxygenation of their IC, PC, and EC compartments. Experiments with different cell numbers and modulation of respiration activity demonstrated that these gradients are dynamic and regulated by the O(2) diffusion and consumption rate. The new method facilitates the assessment of such gradients.     

Smelting of high-carbon ferrochrome from chromium agglomerate produced with alumina-silica flux

In a test melts, high-carbon ferrochrome is produced from chrome sinter and chrome-ore fines in an arc electrofurnace. Two types of sinter with the best performance—the best sintering rate, strength, and product yield—are studied. It is demonstrated by experimental melts that high-carbon ferrochrome can be produced from proposed agglomerates. An estimation of smelting parameters for production of high-carbon ferrochrome is made.     

Heating of slabs in continuous furnaces equipped with “hot” riders

Orskh-Khalilovo Metallurgical Combine. Translated from Metallurg, No. 10, pp. 46–47, October, 1988.