Factors inducing a loss of net negative surface charge on spleen cells of mice grafted with a slow-growing tumour.

The mean electrophoretic mobility (EPM) of splenic cells was determined in 4 different host-tumour systems. In splenic cells harvested from mice bearing slow-growing tumours, a significant EPM decrease was observed (12%) and in increase in the proportion of cells with slow mobility. Moreover, after 1 h incubation in RPMI medium at 37 degrees C and 2 washings, spleen cells showed a marked increase in their EPM (average 30%). Finally, the supernatant from incubation medium after contact with normal spleen cells (1 h at 37 degrees C) produced a significant decrease in their EPM (approximately 12%). On the other hand, no significant EPM variations were found between control spleen cells and cells from fast-growing tumours, before or after 1h incubation. The existence of factors which induce a loss of negative surface charge on spleen cells of some tumour-grafted mice is discussed

The F0F1-ATP Synthase Complex Contains Novel Subunits and Is Essential for Procyclic Trypanosoma brucei

The mitochondrial F0F1 ATP synthase is an essential multi-subunit protein complex in the vast majority of eukaryotes but little is known about its composition and role in Trypanosoma brucei, an early diverged eukaryotic pathogen. We purified the F0F1 ATP synthase by a combination of affinity purification, immunoprecipitation and blue-native gel electrophoresis and characterized its composition and function. We identified 22 proteins of which five are related to F1 subunits, three to F0 subunits, and 14 which have no obvious homology to proteins outside the kinetoplastids. RNAi silencing of expression of the F1 α subunit or either of the two novel proteins showed that they are each essential for the viability of procyclic (insect stage) cells and are important for the structural integrity of the F0F1-ATP synthase complex. We also observed a dramatic decrease in ATP production by oxidative phosphorylation after silencing expression of each of these proteins while substrate phosphorylation was not severely affected. Our procyclic T. brucei cells were sensitive to the ATP synthase inhibitor oligomycin even in the presence of glucose contrary to earlier reports. Hence, the two novel proteins appear essential for the structural organization of the functional complex and regulation of mitochondrial energy generation in these organisms is more complicated than previously thought

Characterization of cell subpopulations of the thymus by a hydrophobic fluorescent probe: 1-anilino-8-naphthalene sulphonate.

1-anilino-8-naphthalene sulphonate (ANS) is a hydrophobic fluorescent probe. ANS is not fluorescent in water or in RPMI 1640 medium, but it becomes fluorescent when bound to hydrophobic components of cells. The binding of ANS to mouse thymocytes shows that two cell subpopulations are identified, which differ in their emission wave-lengths, as reflected by their distinct 'blue' and 'green' fluorescence. This difference correlates with the DNA content of cells and this technique may characterize thymic cells in the G1 or in the S-G2 phases of the cell cycle in a quick and simple way